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HCWs in laboratory departments were more likely than those in the medical department to want HIV patients to be admitted on separate wards. HCWs in the laboratory departments are frequently involved in handling of specimens of BBFs and have a high level of perceived risk of contracting HIV. This may be the reason why they have this unfavorable attitude. This is a discriminatory attitude that could affect patient’s attendance at health centers for obtaining ARV and regular medical check-ups or adherence of patients to treatment plans (Famoroti et al., 2013; Omosanya et al., 2013). Though majority of HCWs will not refuse to treat PLWHA, 90% of them would want patients to be screened prior to surgical and obstetric procedures. This is similar to findings among HCWs in India where 90% of HCWs endorsed the practice of conducting mandatory HIV testing prior to surgery (Mahindra et al., 2007).
|
study
| 99.94 |
A higher proportion of nurses believed all patients should be routinely screened for HIV. Nurses have been reported to have a less favorable attitude to PLWHA. Similarly, in India, doctors were reported to be less prejudiced when compared to nurses in their attitude towards PWLHA (Mahindra et al., 2007).
|
study
| 99.7 |
Trained nurses and auxiliary nurses compared with physicians in Nigeria were reported to be more likely to deny patient services based on HIV sero-status (Sadoh et al., 2006). Similarly, a higher proportion of nurses than other HCWs in China tended to avoid contact with PLWHA and more than two-thirds of Jordanian nurses (84%) refused to provide care to patients who tested positive for HIV/AIDS (Hassen & Wahsheh, 2011; Lin, Li, Wan, Wu, & Yan, 2012). This unfavorable attitude to PLWHA could be because nurses are more involved in the direct care of and contact with patients and their perceived risk of contracting HIV at work is high (Famoroti et al., 2013). Health care providers have been reported to perceive HIV testing of patients as a self-protection strategy out of fear of infection risk at work. Furthermore, fear of contracting HIV and death from HIV infection has been reported as factors related to HIV stigma in health care (Li et al., 2007). Mandatory HIV testing of patients is controversial. Proponents of mandatory HIV testing believe it ensures early detection and treatment of infected individuals which is beneficial while some believe it is ethically wrong as it infringes on patients’ confidentiality if they are not informed that results will be shared (Li et al., 2007). In addition, patients at risk of HIV may not seek medical care in the hospital if they know they would be routinely screened which may lead to other public health problems. Presently in UCH, routine HIV testing is only done for patients going for surgical or gynecological operations.
|
review
| 99.9 |
Two-thirds of respondents believe HCT should be part of pre-employment medical examination for all prospective health care workers and that they should submit to mandatory HCT, at least once a year. Mandatory HIV testing has been introduced for a large number of HCWs in the developed world (Salkeld & McGeehan, 2010). Salkeld, McGeehan, Chaudhuri, and Kerslake (2009) reported that junior doctors who were offered an HIV test as part of their pre-employment occupational health checks by National Health Service Trusts in the United Kingdom were highly critical of the manner the HIV test was offered. In UCH, HCT is prohibited for recruitment and employment purposes (University College Hospital/College of Medicine, 2005)
|
other
| 99.06 |
In this study, majority of respondents had heard of HCT and were aware of an HCT center in UCH but only half had gone for HCT at the time of this study. HCWs in the medical departments were twice more likely to have gone for HCT than those in the laboratory departments. Though HCWs in the laboratory departments reported lowest direct contact with patients they are at risk of exposure to BBFs and should therefore be encouraged to go for HCT. Majority of respondents had also provided HCT information to patients and some had referred patients for HCT. It is imperative for HCWs to be role models. They should not only provide information on HCT to patients but also undergo the test themselves.
|
study
| 99.94 |
A selection bias could have occurred in the participation of the HCWs entering the study with more educated respondents being more willing to participate. However, efforts were made to follow up and retrieve questionnaires from all cadres of HCWs. It is possible that respondents could have copied other HCWs’ questionnaires but this would have happened mainly within departments and would not affect the results significantly. This study did not assess knowledge and training of HCWs on HIV/AIDS which could have influenced their attitude to PLWHA. Studies have shown that HCWs with knowledge and training of HCWs on HIV/AIDS were less likely to stigmatize and discriminate PLWHA (Adetoyeje, Bashir, & Ibrahim, 2007; Famoroti et al., 2013).
|
study
| 99.94 |
The study concludes that splash of BBFs on intact skin was the most commonly reported exposure among HCWs in this tertiary hospital. HCWs in surgical departments reported they were least protected. Majority of HCWs had positive attitude towards PLWHA. However, a large proportion of nurses believed that all patients should be routinely screened for HIV. Half of HCWs had accessed HCT service. There is need to ensure that workers are well protected in the workplace. All aspects of Standard Precautions should be employed in all patient care whether the patient is HIV positive or not and protective equipment required to practice Standard Precaution should always be available to reduce the risk of exposure to BBFs. The University College Hospital workplace policy on HIV/AIDS should be made available to HCWs so they can be aware of what is expected of them in their care of PLWHA. HCWs should be encouraged to go for HCT in order to be effective role models in the prevention of HIV/AIDS.
|
study
| 95.1 |
The study by Richter et al. (2017) found significant electrophysiological communication between gastric pacemaker activity and the alpha rhythm within certain regions of the cerebral cortex including the right anterior insula. In other words, they found a role for interstitial cells of Cajal in interoception, the sensory system responsible for detecting internal regulation responses. The communication between ICC and the insular cortex occurred through phase amplitude coupling, the phase of the lower frequency gastric pacemaker modulated the amplitude of alpha waves in the anterior insula. Although phase amplitude coupling has almost exclusively been shown to occur within the brain, this study discovered that it also facilitates gut—brain communication. Interestingly, phase amplitude coupling was also observed within the gut; the amplitude of the higher frequency dominant intestinal pacemaker [the “slow wave” generated by interstitial cells of Cajal associated with the myenteric plexus (ICC-MP; Huizinga et al., 1995; Thomsen et al., 1998)] was seen to be modulated by the phase of a lower frequency induced rhythmic depolarization likely originating in the network of ICC associated with the deep muscular plexus (ICC-DMP) (Huizinga et al., 2014). This interaction changed propulsive activity into the classical segmentation pattern of the intestine associated with absorption of nutrients. The study from Richter et al. (2017) is highly significant since it demonstrates the ongoing monitoring of gastric pacemaker activity by the right anterior insula. In the stomach, the three-cycles/min pacemaker activity responsible for the orchestration of its dominant peristaltic activity, is generated by a network of ICC-MP and ICC-IM (the intramuscular ICC) (Edwards and Hirst, 2006). The communication between gastric ICC and the brain involves the intramuscular array (IMA)-ICC-complexes which incorporate ICC-IM, nerve endings of the vagal afferents and varicosities of motor neurons (Powley et al., 2008, 2016), ideally suited for bi-directional communication with the brain (Figure 1). The vagal afferents connect to the insular cortex via the nucleus tractus solitarius (Shipley, 1982) and the insular cortex innervates the dorsal motor nucleus, which, in turn, provides innervation to enteric nerves of the stomach (Berthoud et al., 1990). The insular cortex was activated during gastric balloon distention and deactivated during ingestion of a meal, indicating a detailed monitoring of stomach conditions (Geeraerts et al., 2011). Vagal afferents are all connected to ICC (Powley et al., 2016) indicating that the vagus will not monitor individual ICC but the features of the interconnected network of ICC (Huizinga et al., 2015; Pawelka and Huizinga, 2015; Wei et al., 2016). How detailed information from this network is conveyed to the brain should be a topic for future research. This information will contain signals from several slow waves propagating over the stomach at the same time. This information will contain changes in ICC network properties that occur in response to a meal (Chen and McCallum, 1992) (Berthoud, 2008), which may relate to satiety (Andrews and Sanger, 2002). There is the potential that detailed information regarding meal quality and/or quantity, or even types of nutrients ingested could be signaled via alterations in ICC signaling. Detailed information is now emerging how ICC network properties change in patients with gastroparesis (O'Grady et al., 2012; O'Grady and Abell, 2015) and diabetes (He et al., 2001). Dyspepsia may relate to abnormal vago-vagal reflexes, including efferent innervation and abnormal signaling from the stomach to the insula or abnormal processing of such signals (Page and Blackshaw, 2009; Lee et al., 2016). Abnormalities in initiation and conduction were observed in patients with gastroparesis in the presence of a normal 3 cpm frequency (O'Grady et al., 2012) suggesting that in certain conditions, the recorded ICC pacemaker frequency may be normal but that it is the injury to the ICC network that is related to gastroparesis, which may relate to delayed gastric emptying and/or the initiation of nausea and vomiting through vagal afferents. Gastric dysmotilities are also related to depression indicating the myriad of ways that different regions of the brain can influence each other (Ruhland et al., 2008). Gastric slow wave activity changes markedly in response to neurotransmitters and hormones (El-Sharkawy and Szurszewski, 1978; El-Sharkawy et al., 1978), hence it is likely that the insular cortex monitors such changes. Vagal stretch and tension receptors are always incorporated in mechanistic explanations as to how the stomach signals to the brain (Young et al., 2008; Kentish et al., 2013). The study of Richter et al. (2017) suggests that the ICC-IMA complexes are a sensorimotor unit and that sensations might be primarily integrated by and expressed by ICC activity and as such monitored by the insular cortex, where, in conjunction with other regions of the brain, conscious and subconscious decisions are made how to react to these stimuli. Monitoring of slow wave activity, even at rest (Richter et al., 2017), ensures an exquisitely sensitive system that is instantly available to inform the brain of any activity, change in activity or abnormal conditions. Further investigations into the role of ICC will be essential to unravel this gut brain communication pathway, including the sensitivity of ICC to inflammation, the remarkable ability of ICC to recover from severe injury and loss (Wang et al., 2002; Bettolli et al., 2012) and the molecular basis of ICC network regeneration (Hayashi et al., 2013).
|
review
| 99.7 |
Branches of IMAs (brown, 3,3′-diaminobenzadine stained) run in tight apposition with ICC-IM (blue-gray, c-Kit immuno-labeled with peroxidase). Branches of IMA arrays vary in their degree of varicosity and in the tightness of apposition. (A) Four neighboring principal branches of an IMA array coursing in tight apposition with a network of neighboring ICC-IM intercalated among smooth muscle bundles (unstained). In this example, the IMA branches express modest swellings or varicosities, most of which are in close proximity to the somata and processes of ICC-IM. (B) Two neighboring principal branches of an IMA array course near to, and appear to contact intermittently, the local ICC-IM network. In contrast to the array branches shown in (A), those shown in (B) are more lamelliform, the apparent contacts with the ICC-IM are more intermittent, and many of the IMA lamellae appear to lie on the smooth muscle bundles (unstained) adjacent to the ICC-IM network. (C,D) Two examples of principal IMA branches that course in tight conjunction with ICC-IM and form swellings or varicosities on both ICC-IM somata and fibers. Scale bar = 10 μm. Reproduced with permission from Powley et al. (2016).
|
study
| 99.94 |
Chronic obstructive pulmonary disease (COPD) is characterized by progressive airflow obstruction that is not fully reversible. It is associated with inhaling particles or toxic gases which causes an abnormal inflammatory response in the lungs; it is primarily induced by smoking [1, 2].
|
review
| 98.44 |
Exacerbation events are relatively common in disease progression. About 70% of exacerbations are caused by respiratory infection from bacteria or virus. Exacerbation is associated with increased disease symptoms and worse lung function, quality of life, and physical capacity. Literature states that mean period to recover previous functional characteristics is three months [3–6].
|
review
| 99.8 |
Hospitalization may be necessary in patients with rapidly deteriorating respiratory symptoms and treatment includes mechanical ventilation which is associated with a higher mortality risk. To reduce functional exercise capacity loss during a severe exacerbation, studies have been performed to evaluate the effects of lower limb muscle training [3, 7, 8]. Most have assessed the influence of anaerobic training. Troosters et al. (2010) showed improved lower limb muscle strength without increased systemic inflammation after muscle training in hospitalized COPD patients with exacerbation; the authors did not identify adverse clinical events during muscle training. Similarly, in a randomized study of 46 hospitalized COPD patients, Borges and Carvalho (2014) found improved leg strength and quality of life 30 days after discharge in the group who received upper and lower limb anaerobic training during hospitalization and did not observe adverse clinical effects during the training program. However, studies evaluating the adverse effects of aerobic activity in hospitalized patients with exacerbated COPD are scarce in literature. Tang et al. (2012) showed that combined aerobic anaerobic training in exacerbated COPD patients presented 13 adverse events, one with a serious arrhythmia event. However, we found no other studies that had investigated adverse effects related to aerobic training during hospitalization in exacerbated COPD patients.
|
review
| 98.25 |
This clinical study is part of a randomized controlled trial including 11 hospitalized patients with exacerbation COPD from March 2012 to October 2014. Exacerbation was considered according to the GOLD (Global Initiative for Chronic Obstructive Lung Disease) criteria. COPD was confirmed prior to hospitalization by spirometry using a bronchodilator where forced expiratory volume in one second/forced vital capacity was less than 0.70 (FEV1/FVC < 0.70) and severe exacerbation was considered when hospitalization was needed and changes in maintenance medication or the introduction of corticosteroids and/or antibiotics was needed. The exclusion criteria were a Glasgow score < 15, Borg dyspnea score > 7 , instable heart disease, limited mobility, hemodynamic instability, and mechanical ventilation.
|
other
| 98.44 |
All patients were evaluated 24 hours after hospitalization for demographic characteristics (age, gender, occupation, education, and monthly income), smoking history (pack year calculation, smoking status), Charlson index , and body composition. After 48 hours of hospitalization, all patients performed a 6-minute walk test (6MWT) and a new spirometry test, and BODE index was calculated . Finally, after 72 hours of hospitalization patients underwent aerobic exercise on a treadmill for 15 minutes.
|
study
| 99.94 |
Spirometry was performed using a portable computerized pulmonary function system (FERRARIS KOKO, Louisville, CO, USA), according to the American Thoracic Society . FVC and FEV1 were measured in litres (L), and the FEV1/FVC calculated. Measurements were obtained before and 20 minutes after being given a metered 400 μg dose of fenoterol as a bronchodilator. The FVC and FEV1 values were also expressed as a percentage of reference values .
|
study
| 99.94 |
Body composition was assessed by anthropometry and bioelectrical impedance. Anthropometry: height and weight were determined using a Filizola® balance with the patient barefoot and wearing light clothes, and body mass index (BMI) was calculated [BMI = weight (kg)/height (m)2]. Bioelectrical impedance: patients were instructed to empty their bladder, rest for thirty minutes, and remove all metal objects before measurements. Resistance was measured in the right side of the body according to Kyle et al., (2004) (BIA 101, RJL Systems, Detroit, MI, USA). Fat Free Mass (FFM) was estimated from an equation developed for patients with respiratory failure and FFM index T [FFMI = FFM (kg)/height (m)2] was calculated. Nutritional depletion was defined when FFMI < 15 kg/m2 for women and <16 kg/m2 for men .
|
study
| 100.0 |
The six-minute walk test was performed according to the American Thoracic Society . Patients with hypoxemia or who presented with pulse oximetry < 85% during the test were supplemented with oxygen according to medical prescription . In this case, the physical therapist walked beside the patient pulling the portable cylinder trolley.
|
other
| 99.9 |
Aerobic exercise was performed using a treadmill (Inbramed Master) with the patient walking for 15 minutes. Speed was obtained from the 6MWD with distance divided by 360 s (6 minutes × 60 seconds) and the value obtained in m/s was transformed into km/h by multiplying by 3.6. The slope was increased by one point according to the Borg dyspnea scale ≤ 3 (moderate dyspnea) which was evaluated every five minutes during the exercise. Pulse oximeter (SpO2) and heart rate (HR) were monitored throughout the exercise. ECG was used to evaluate arrhythmia. The Borg scale for dyspnea and the legs and respiratory rate and blood pressure were monitored at the beginning and end of the exercise. There were two-minute warm-up and recovery using a lower speed and no inclination. Patients with hypoxemia SpO2 < 85% during training were supplemented with O2 according to medical prescription. Aerobic exercise will be considered safe if patients did not present with any clinical adverse event during or after exercise.
|
other
| 99.6 |
Descriptive analysis of data was performed using Sigmaplot 12.0 (Systat Software, Inc., San Jose, CA, USA). The data are presented in tables, and continuous variables with normal distribution are expressed as mean values with standard deviations and continuous variables with nonnormal distribution as medians and quartiles.
|
study
| 99.8 |
For the composition of this study, we identified 59 hospitalized patients with a diagnosis of exacerbated COPD. Of these, 48 (69%) were excluded for reasons already detailed above (Figure 1). Thus, eleven patients were included in the study. Table 1 shows spirometry for included and excluded patients. We did not identify statistically significant differences in relation to spirometry values (Table 1).
|
study
| 100.0 |
Eleven patients were included in this protocol. All patients were receiving oral corticosteroids, inhaled bronchodilators, and antibiotics. According to FEV1 values, 18.1% were classified as moderate, 45.4% severe, and 36.3% very severe COPD. The BODE index showed that 27.2% were in class II, 27.2% in class III, and 45.4% in class IV. Nutritional depletion was identified in 27.3% of patients. Table 2 shows patient characteristics.
|
study
| 99.94 |
Table 3 shows patient characteristics before and after aerobic exercise. All patients completed 15 minutes of aerobic exercise. We observed a significant increase in systolic blood pressure (125.2 ± 13.6 versus 135.8 ± 15.0; p = 0.004) and respiratory rate (20.9 ± 4.4 versus 25.2 ± 4.5; p = 0.008), but neither of those parameters was considered clinically significant. There was a statistically significant decrease in SpO2 (93.8 ± 2.3 versus 88.5 ± 5.7; p = 0.001) even with supplemental O2, offered to all patients during exercise, and increased dyspnea index after the activity. Mean speed was 1.9 km/h with 0.7° slope during aerobic exercise. None of the patients showed arrhythmia or thoracic or leg pain (Table 3).
|
study
| 99.94 |
Most patients (54.5%) had severe dyspnea according to the Borg scale and none felt fatigue in the legs. Our results agree with those of Troosters et al. (2010) who performed anaerobic training with 17 hospitalized COPD patients and did not observe adverse clinical events. However, a randomized study of hospitalized COPD patients was performed by Tang et al. (2012) using three groups: control (n = 11), low-intensity exercise (n = 11), and moderate-high intensity exercise (n = 10). The low-intensity training group performed aerobic training each day for 7.5 minutes at 40% of the 6-minute walk test speed associated with muscle training at a load of 40% of one maximum repetition. The moderate-high intensity training group performed the same activities, but with a load of 70%. The authors identified 13 adverse events; one was a serious arrhythmia event in patients during mild training. The most frequently reported adverse event in the study was the feeling of fatigue or malaise which was more frequent in the moderate-high intensity group, but without significant difference .
|
study
| 91.06 |
Another point related to adverse clinical events was the beginning of exercise training after hospitalization. Our study showed no negative clinical effects beginning after 72 hours of hospitalization. We did not find any recommendations in literature about the right time to initiate aerobic training during hospitalization . There are careful recommendations for initiating training in the 48 hours after admission. For instance, Greening et al. evaluated the muscular rehabilitation associated with aerobic exercise and early neuromuscular stimulation in hospitalized COPD patients. They found no difference between intervention and control groups in hospital readmission rate. However, there was an increased mortality risk after 12 months in patients who received intervention during hospitalization. On the other hand, other studies which began exercise after 48 hours hospitalization showed no negative outcomes, but those studies did not follow patients for more than one month [21, 22].
|
study
| 99.44 |
Our patients presented more severe obstruction (FEV1 34%) than those in literature. In Troosters et al. (2010), FEV1 values were on average 50% in the control group and 40% in the intervention group, similar to Ali et al. , whose FEV1 values were 44% in the control group and 46% in the intervention group. The mean 6MWD for our patients was lower than in literature; Troosters et al. (2010) and Borges and Carvalho (2014) showed that patients walked almost 100 metres more than our patients. Our patients presented more severity than those in literature hospitalized with exacerbated COPD.
|
study
| 99.8 |
The aerobic exercise protocol performed in this study is clinically safe for hospitalized COPD patients with the same characteristics. The predominant exclusion criteria were the presence of a comorbidity that limited mobility and high dyspnea score. Therefore, the safety of aerobic exercise cannot be generalized for all COPD patients with exacerbation.
|
study
| 99.94 |
Bone marrow metastasis (BMM) of solid tumors is a rather rare but a relatively early phenomenon. Stem cells expressing CD44, a hyaluronic acid cell surface receptor, has been accused for the early deposition of malignant cells in the bone marrow BMM poses a clinical challenge to the oncologist in tailoring chemotherapy options and dosing especially when complete blood counts are compromised. Therefore, early diagnosis of BMM of solid tumors is of utmost importance depending on the primary solid tumor. For decades, conventional methods such as bone scintigraphy, MR, CT and also FDG PET and FDG PET/CT have been used to show bone and bone marrow metastasis. These imaging modalities can be divided into two groups based on the differences in physical and biological principles as those which detect disease site at bone marrow and osteoblastic reaction after invasion of surrounding bone by the pathologic process. The former one was further subclassified into two groups as those that visualize lesions as negative focal marrow defects seen on BMS or MR and those that directly visualize abnormal tissue such as with FDG PET/CT . In addition to imaging modalities other methods such as low mean platelet volume (MPV) and meticulously prepared touch imprint smears or circulating tumor cells (CTCs) have been studied in demonstrating BMM. FDG PET/CT has the advantage of giving information about primary tumor site, lymph node status, and other organ metastasis in a single study, which has been regarded as a “quantum jump” in nuclear medicine. In addition, it has directed attention to the bone marrow not only to search for unsuspected deposits but also to perform high yield bone marrow biopsies at least in lymphomas and multiple myeloma [4, 5].
|
review
| 99.9 |
Skeletal metastasis usually happens by seeding of tumor emboli through bloodstream and also via retrograde venous blood flow or direct extension . Bone remodeling due to osteolytic and osteoblastic reactions form the basis of indirect evidence of skeletal metastasis in solid tumors. Whereas, the superiority of the FDG PET/CT in detecting bone marrow metastasis comes from the fact that it visualizes the metabolic activity of disseminated tumor cells directly in the bone marrow unlike bone marrow scintigraphy or other radiological methods which provides indirect evidence of skeletal metastasis .
|
review
| 92.06 |
In this retrospective cohort study, the study sample consisted of 68 subsequent patients presented to our institution’s pathology department with bone marrow metastases of solid tumors from January 2006 to March 2010. We searched the patient files to detect which patients had undergone FDG-PET/CT analysis. PET/CT was found to have been ordered in 10 out of 68 patients (6.8%) for various purposes. These patients were included in the final analysis. The interval between the PET/CT examination and bone marrow biopsy was approximately 2 weeks. Seven of 10 patients were chemotherapy naive at the time of analysis whereas 3 patients had received chemotherapy. All patients gave informed consent about the PET/CT examinations and bone marrow biopsies. The detailed excerpts of the patients are as follows.
|
study
| 100.0 |
A 46-year-old male patient presented with fatigue, weight loss, anemia and dyspeptic complaints for the last 2 months. Gastric cancer was diagnosed with upper endoscopic biopsy. FDG-PET/CT was ordered in order to initial staging. PET/CT images not only demonstrated increased FDG accumulation at the primary tumor site but also revealed multiple metastatic intraabdominal lymphadenopathies and left supraclavicular lymph node. Heterogeneous widespread FDG uptake in the axial skeleton suggested bone marrow involvement (Fig. 1). Hgb was 9.5 g/dL; WBC, 4,100 and PLT, 33,000 per µL. Bone marrow biopsy showed metastatic gastric cancer.
|
clinical case
| 100.0 |
A 24-year-old female patient was diagnosed with embryonal rhabdomyosarcoma of the perineum. FDG PET/CT which was ordered for restaging showed hypermetabolic mass at the perineal region consistent with recurrence and bilateral inguinal metastatic lymph nodes. Additionally, there was left iliac lytic lesion with increased FDG uptake consistent with bone-bone marrow metastases and moderately heterogenous disseminated intense FDG accumulation in the axial skeleton suggestive of bone marrow involvement. Supported by prolonged cytopenia PET/CT findings prompted us to do a bone marrow biopsy which proved to have metastatic rhabdomyosarcoma.
|
clinical case
| 100.0 |
A 59-year-old female patient having a history of right modified radical mastectomy 16 years previously due to breast cancer had developed bone metastases and 6 cycles of chemotherapy were administered. After the completion of chemotherapy, FDG-PET/CT was ordered to evaluate prolonged thrombocytopenia. PET/CT showed moderately heterogenous increased FDG uptake in the axial skeleton suspicious of bone marrow involvement. Bone marrow biopsy proved solid metastasis with carcinoma consistent with breast cancer. Her Hgb was 9.6 g/dL, WBC 7,400 and platelets 78,000 per µL at the time of biopsy.
|
clinical case
| 100.0 |
A 67-year-old man with sigmoid colon cancer was referred for PET/CT for the evaluation of increased tumor marker after one year of diagnosis. FDG-PET/CT revealed tumoral wall thickening with intense FDG uptake at the sigmoid colon consistent with recurrence and metastatic mesenteric and paraaortocaval lymph nodes. In addition, there was widespread heterogeneously increased FDG uptake in the skeleton consistent with bone marrow involvement (Fig. 2). Bone marrow biopsy proved mucinous tumor involvement despite a platelet count of 179,000 per µL.
|
clinical case
| 100.0 |
A 68-year-old male presented with right shoulder pain for the last 4 weeks. Thorax CT revealed a mass at the level of right upper lobar bronchus in the lung. Bronchoscopic biopsy showed small cell lung cancer. FDG-PET/CT was ordered in order to stage the tumor. PET/CT images demonstrated increased FDG metabolism at the primary tumor with multiple metastatic lymphadenopathies and liver metastases. Additionally, there was widespread heterogenous FDG uptake in the axial skeleton reminiscent of bone marrow metastases. Complete blood count was consistent with mild thrombocytopenia (101,000 per microliter). A trephine biopsy from the posterior iliac crest done when the thrombocyte count dropped to 49,000 after one week proved that there was bone marrow involvement with small cell lung cancer. This case beautifully illustrates that PET/CT heralded bone marrow involvement before we suspected from complete blood count.
|
clinical case
| 100.0 |
A 44-year-old male surgeon was presented to the neurology clinic with headache. After searching for possible causes of headache, pseudotumor cerebri was diagnosed. Mild anemia, decreased albumin, increased alkaline phosphatase and lactate dehydrogenase prompted to search for malignancy. Low platelet value together with anemia, decreased fibrinogen and increased D-dimer levels were consistent with microangiopathic hemolytic anemia and disseminated intravascular coagulation. Abdominal and pelvic CT revealed left adrenal mass, gastrohepatic lymphadenomegaly and a left iliac lytic lesion. FDG-PET/CT which was ordered for detection of primary site revealed moderately hypermetabolic lesion at the left upper abdomen suggestive of primary gastric tumor, in addition to widespread axial bone and bone marrow metastases, celiac, paraaortocaval and mesenteric lymphadenopaties with increased FDG enhancements. Upper endoscopic study proved gastric signet-ring cell carcinoma. A bone marrow trephine biopsy showed infiltration of the marrow with signet-ring cancer cells. He passed away without having chance for a chemotherapy challenge due to high level of bilirubinemia.
|
clinical case
| 100.0 |
A 56-year-old male patient who was on follow-up for rectosigmoid colon cancer revelaed a pelvic mass on abdominal CT. FDG-PET/CT performed for staging showed hypermetabolic mass consistent with recurrence and metastatic lymphadenopaties at the left inguinal, right external iliac and promontorial region. PET/CT also revealed metastatic lesion in the liver and multipl lesions at the bones as well as in the bone marrow (Fig. 3). Bone marrow biopsy was done with absolutely normal blood count directed by PET/CT findings. Bone marrow metastasis was found consistent with poorly differentiated mucinous adenocarcinoma secondary to colon cancer.
|
clinical case
| 100.0 |
A 69-year-old woman with nasopharyngeal cancer was referred to PET/CT in order to detect a suspected local recurrence. FDG PET/CT images demonstrated increased FDG uptake at the left nasopharyngeal region suggestive of locally recurrent tumor (Fig. 4). Also, there were multiple bone and bone marrow involvement at the vertebral column and manubrium sterni. Bone marrow biopsy proved sinonasal tumor involvement despite a thrombocyte count of 180,000 per µL.
|
clinical case
| 100.0 |
In a 52-year-old man with gastric signet-ring cell tumor FDG PET/CT was performed for initial staging purposes. PET/CT study showed slightly increased FDG uptake at the gastric wall as well as diffuse lytic lesions with slightly heterogeneous increased FDG uptake suggestive of metastases. Despite normal complete blood count indices bone marrow biopsy revealed signet-ring cell carcinoma infiltration.
|
clinical case
| 100.0 |
A 62-year-old male patient with history of chronic lymphocytic leukemia presented with cough, shortness of breath, cervical lymphadenopathy and sweating for the last 3 months. A cervical excisional biopsy showed undifferentiated carcinoma and infiltration with small lymphocytes consistent with chronic lymphocytic leukemia. A PET/CT which was ordered for staging and detection of primary tumor revealed hypermetabolic mass at the right hilar region. Also, metastatic bilateral cervical, supraclavicular, bilateral axillary, abdominal, pelvic lymphadenopathies in addition to multiple liver and widespread bone marrow metastasis were detected (Fig. 5). Although complete blood count was normal, diffuse bone marrow involvement prompted us to attempt a bone marrow biopsy. Biopsy showed poorly differentiated large cell carcinoma of the lung.
|
clinical case
| 100.0 |
FDG-PET/CT was ordered in 10 out of 68 solid tumor patients with pathologically proven BMM. Of these 10 patients, 3 were female and 7 were male; mean age was 54.7 years (range 24 - 69). While FDG PET/CT showed bone and BMM in 4 of 10 patients (40%), the rest of the patients had BMM without bone involvement. In other words BMMs were detected in all of our patients. There was a wide variation of tumor types. The characteristics of the patients are presented in Table 1. Five patients (50%) who had probable bone marrow involvement on their FDG PET/CT scans had unsuspected complete blood counts with regard to BMM. Bone marrow biopsies showed 5 adenocarcinoma, 4 of which were mucinous in type, 1 sinonasal cancer, 1 rhabdomyosarcoma, 1 small cell lung cancer, 1 large cell lung cancer and 1 breast carcinoma.
|
study
| 99.9 |
Bone metastases are a frequent complication of cancer, occurring in up to 70 percent of patients with advanced breast or prostate cancer and in approximately 15 to 30 percent of patients with carcinoma of the lung, colon, stomach, bladder, uterus, rectum, thyroid, or kidney . By applying sensitive immunocytochemical and molecular assays, disseminated tumor cells (DTC) in bone marrow (BM) can be detected in 20-40% of cancer patients without any clinical or even histopathological signs of metastasis . Detection of overt bone marrow metastasis in adult patients with solid tumors might change the approach to the patient especially without any symptoms and signs of marrow infiltration as there is evidence, at least from patients with breast and gastric cancer , even micrometastatic disease in bone marrow is associated with a poor prognosis.
|
review
| 99.8 |
FDG-PET has emerged as a powerful modality for evaluating skeletal metastasis and revolutionized the diagnosis and staging of patients with solid tumors especially when other diagnostic imaging methods such as bone scintigraphy, CT or MRI results are equivocal. Because tumor cells have increased rate of glucose metabolism metastatic lesions can be detected by FDG-PET/CT earlier than the time of altered anatomy.
|
review
| 99.8 |
Although bone scintigraphy has traditionally been accepted as the diagnostic modality of choice to assess bone metastasis, it has the disadvantage of missing early bone marrow metastasis due to absence or minimal reactive bone formation. For example in one recent study, 20% of patients with NSCLC had absolutely normal Tc-99m bone scintigraphy while PET/CT showed involvement. In addition, lytic lesions are not detected by bone scintigraphy due to the absence of osteoblastic reaction in some solid tumors . Attempts to overcome this problem have resulted in the utilization of bone marrow scintigraphy in addition to bone scanning has not also been gained popularity because of relatively high false positive and false negative results. CT has also a similar drawback with bone scintigraphy in delineating bone marrow metastases because of the absence of reactive bone formation or cortical destruction in lesions confined to bone marrow. MRI has recently been regarded as a very sensitive modality in detecting BM metastasis compared to bone scintigraphy due to fact that it has the ability to show malignant deposits directly before reactive changes have occurred . Daldrup-Link et al demonstrated that whole-body MRI, FDG PET and skeletal scintigraphy has a sensitivity of 82%, 90% and 71%, respectively in detecting skeletal metastases . On the other hand, MRI has been considered to be not specific enough in delineating bone marrow metastases due to some benign entities such as hemangiomas, inflammatory processes, and post-therapy changes and also impractical for various reasons such as absence of widespread availability or claustrophobia of the patients [16, 17]. The superiority of FDG-PET/CT lies in the fact that it has the ability to evaluate not only the entire skeleton but also the other organs in a single examination. Many studies have confirmed that FDG-PET/CT has comparable sensitivities in the ability of detecting bone marrow metastases in solid tumors [18, 19]. It has also shown efficacy for the detection of BM metastases from lung and breast carcinoma [20, 21]. The diagnostic accuracy, sensitivity and specificity of FDG-PET in detecting bone marrow metastasis in lung cancer were 94%, 91% and 96%, respectively, compared to bone scintigraphy in one study . FDG-PET is also superior to other modalities in identifying unsuspected disease involving the bone at an earlier stage when only the bone marrow has been involved before bone remodeling has occurred. This might pose many clinical implications. Some solid tumors such as prostate and breast have predilection to metastasize to bone relatively early to their course of disease. Early detection of bone and BM metastasis may change the treatment plan dramatically both for bone directed therapies such as zoledronic acid or denosumab and radiotherapy and for systemic therapies. For example, detecting bone and BM metastasis in otherwise early stage hormone positive breast cancer may obviate the need for combination chemotherapy or establishing osteoclast inhibiting (zoledronic acid, ibandronic acid) or RANK ligand inhibiting (donesumab) therapies earlier than overt metastases. Instead, we can put the patient on hormonotherapy which is far less toxic than chemotherapy. In our patients, after ordering PET/CT for other reasons bone and bone marrow metastases were detected unexpectedly, despite normal complete blood count indices in 5 patients (patient 4, 7, 8, 9, and 10). This prompted us to modify the management plan as follows: In patient 4, 7 and 10, finding of bone marrow metastasis led to a decrease in the initial chemotherapy doses to avoid severe bone marrow toxicity. In patient 8 and 9, detecting bone and bone marrow metastasis obviated the need of local therapy. Instead, we planned bisphosphonate and tailored chemotherapy for this patient.
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review
| 99.9 |
At sites where there is increased FDG accumulation relative to other sites the diagnostic yield of BM biopsies can increase dramatically at least theoretically. Many studies such as that of Moog’s et al point out that FDG-PET facilitates detecting accurate biopsy sites in lymphomas which have metastasized to the bone marrow . However, standardized biopsies from the posterior iliac crest were done in all of our patients.
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| 99.9 |
Despite the advantages of FDG PET/CT, it has some drawbacks that need to be born in mind. Granulocyte colony stimulating factor (G-CSF) for BM stimulation may result in diffusely increased FDG accumulation in the BM which can cause misinterpretation as generalized marrow metastases. In addition, small metastatic lesion in the marrow can be missed due to benign bone marrow hyperplasia (such as G-CSF or presence of anemia) or inherent resolution limits of PET/CT. We found that all of our cases had increased FDG uptake in their bone marrows suggesting bone marrow involvement. FDG-PET/CT, furthermore, has a lower sensitivity in detecting sclerotic metastases seen particularly in prostate cancer probably because of hypocellularity although we did not have any case of prostate cancer to exemplify this fact . Osteoblastic metastases of breast cancer have a low or undetectable FDG uptake .
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| 99.94 |
Finding of bone marrow metastases might have many clinical implications as we depicted in our patients summaries. PET/CT has the ability to detect a substantial number of metabolically active tumor cells in the bone marrow in all of our patients which we proved by bone marrow biopsies. We think that this cohort of patients with solid tumors is hypothesis-generating with regard to detecting early bone marrow metastases by FDG PET/CT.
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| 97.44 |
The Utah State University owned Caine Dairy Teaching and Research Center is among the nation's leading dairy production research centers. Research at the Caine Dairy focuses on animal nutrition and reproduction, waste-handling, animal health, and irrigated pasture for intensive rotational grazing. The center also houses three-hundred head of cattle used for dairy production. The Caine Dairy is equipped with a traditional flush system to clean the feed stations for the cattle, and 2000 gallons of water are used to flush twice daily. The flushed waste is directed through a coarse filter grate and the large solids are removed and dried. The liquid phase is pumped into a one acre settling lagoon, which empties into a one acre evaporation pond, where the wastewater is held until it is pumped to the feed stations to be used for flushing stalls. Recycling used wastewater to flush stalls is a common practice in agriculture . However, recycling water creates a closed system for the liquid waste, where solid waste is the only stream leaving the system. The result is a buildup of water soluble nutrients, such as phosphorus and nitrogen, and turbid wastewater.
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| 99.9 |
One strategy that can be employed with agricultural wastes is land application . However many dairy wastewaters, such as the wastewater at the Caine Dairy, contain high concentrations of nitrogen and phosphorus that are not appropriate for land application, and must undergo costly pretreatment solutions if they are to be land applied . These same compounds can serve as a nutrient source for the production of algal biomass that can be used as a feedstock for downstream processing into bioproducts [4, 5].
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other
| 76.3 |
The Rotating Algal Biofilm Reactor (RABR) is a biofilm-based reactor system using a partially submerged rotating cylinder with growth substratum attached to the outside of the cylinder and with a novel harvesting mechanism . Biofilm growth is possible even in turbid wastewater systems, because the RABR rotates the biofilm in and out of the water, thereby exposing it to both light and a nutrient source. The RABR provides the possibility for wastewater nutrient sources to be utilized for algae-based systems that could not support suspended algal growth due to turbidity, color, or water depth limitations. Applications of biofilm engineering compared with suspended growth systems offer additional benefits by eliminating the need for polymers, sedimentation, and centrifugation when harvesting , and therefore reduce the costs associated with harvesting when compared to traditional suspended growth systems . The harvested biofilms can be used to generate bioproducts through downstream processing including bioplastics, biofuel feedstock, high value pharmaceutical compounds, and nutrient rich animal feed [4, 9–12]. Other biofilm systems, such as the Algal Turf Scrubber, have been investigated as possible algal production strategies; however these biofilm systems are limited by turbidity .
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review
| 99.6 |
Previous studies have been conducted using dairy wastewater as a nutrient source in algae systems [13, 14], and it has been suggested that an algae-based alternative could provide a more cost effective treatment process for dairy and other livestock wastewater sources [15, 16]. In some other algal growth systems, organic carbon has been shown to be antagonistic to phototrophic growth often due to nutrient competition with heterotrophic bacteria [17, 18]. However there is a lack of information in the literature regarding the effect of temperature and organic carbon content on algae growth in dairy wastewater systems. There is also a lack of published information concerning the potential for biofilms to be used to remove nutrients from dairy wastewater and create a renewable source of bioproducts. The objective of this study was to determine the effect of temperature and organic carbon concentration on biofilm biomass productivity and on associated nutrient uptake into algae-based biomass cultivated on dairy wastewater.
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| 99.94 |
Wastewater was collected from the Utah State University Caine Dairy Farm evaporation pond. Characteristics of the water and the produced algae-based biofilm are summarized in Table 1. Turbidity of the water was measured at 890 NTU (Hach 2100Q turbidimeter). Algae biomass inoculum for the laboratory RABRs was collected from the pilot scale RABR systems currently operating at the Logan City wastewater treatment facility, a 460 acre (1.86 km2) open lagoons system . Visual microscopy of the pilot scale RABR based biofilm indicated that the collected algae biomass contained a variety of algae species, with Pseudanabaena, Oscillatoria, and Chroococcus as the predominant species. The biomass was then cultivated on a cotton rope substratum in shaker flasks using dairy wastewater as the nutrient source before application to the RABR system to allow the culture to adapt to the nutrient source. The carbon:nitrogen:phosphorus molar ratio of the adapted biofilm was measured to be 85:16:1, which is comparable to other algae-based systems .Table 1Composition of influent Caine Dairy wastewater and cultivated biomass from the RABR system. (Analysis by Chemtech-Ford Laboratories – Sandy, UT)Chemical compositionWatera (mg L-1)Biomassb (mg kg-1 dry wt.)Total organic carbon1200648500Total nitrogen155c 140400Total phosphorus1219100Aluminum7.67776Boron1.73132Barium0.6375.7Cobalt0.031.96Chromium0.4245.3Copper3.0585.2Iron6.80624Manganese0.67107Molybdenum0.0927Sodium46023455Nickel0.2524.1Lead0.056.41Silica1065572Strontium1.18125Zinc1.15116 aDairy wastewater influent stream bProduced algae-based biofilm cTotal Kjeldahl Nitrogen (Organic nitrogen, ammonia, and ammonium)
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| 100.0 |
Rotating Algal Biofilm Reactors of 1-Liter volume were constructed and operated according to Christenson and Sims , and the biofilm reactors were wrapped with premeasured lengths of 3/16 in. dia. (0.476 cm dia.) solid braid cotton rope (Fig. 1). In order to test the effect of organic carbon concentration on biomass productivity, the reactors were filled with different dilutions of wastewater and balanced to match the total nitrogen and phosphorus concentrations in the undiluted dairy wastewater influent stream using sodium nitrate (Thermo Fischer, Pittsburgh, PA) and potassium phosphate (Thermo Fischer, Pittsburgh, PA). The final organic carbon content of the wastewater dilutions was set to 1200, 600, and 300 mg L-1 of total organic carbon. The N:P ratio was balanced weekly to the same 155 mg:12 mg ratio to accommodate for the uptake of nutrients by the biofilm. This experiment was conducted utilizing a semi-batch system, with a hydraulic retention time (HRT) of 7 days.Fig. 1Laboratory scale RABRs. Each set of three RABRs represents a different organic carbon concentration, and all reactors are held at a constant temperature. This experimental design was replicated at three different temperatures, for a total of 27 different reactors. The rectangular base of each RABR contains 1 L of wastewater and the cylindrical portion of the reactors (76 mm diameter, 200 mm length) rotates at approximately 8 rpm. Biofilm accumulates on the cotton rope surface of the cylinder
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study
| 100.0 |
Laboratory scale RABRs. Each set of three RABRs represents a different organic carbon concentration, and all reactors are held at a constant temperature. This experimental design was replicated at three different temperatures, for a total of 27 different reactors. The rectangular base of each RABR contains 1 L of wastewater and the cylindrical portion of the reactors (76 mm diameter, 200 mm length) rotates at approximately 8 rpm. Biofilm accumulates on the cotton rope surface of the cylinder
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study
| 99.9 |
A water bath (VWR) with ¼ in. dia. (0.635 cm dia.) stainless steel tubing was used to maintain the water temperature of the reactors at 7, 17, or 27 ° C (±0.5 ° C). This range of temperatures was chosen as a representative range of seasonal water temperatures in Northern Utah . Constant light was provided from eight 40 W fluorescent lamps that provided a total of 200 μmol photons m-2 s-1 of continuous photosynthetically active radiation to the upper surface of the RABR systems. Two grams of centrifuged wet weight of adapted inoculum were added to the cotton rope growth substratum upon initiating rotation of the reactors.
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study
| 99.94 |
Biomass was harvested from the rope substrata weekly by mechanical scraping and lyophilized for biomass determination, ash free dry weight (AFDW) measurements, and chemical composition. AFDW calculation was determined using lyophilized biomass at 550 ° C. Biomass productivity was calculated using the AFDW of the biofilm divided by the areal footprint of the reactor (0.0338 m2). Growth rates were calculated, and an Arrhenius plot of the data was used to obtain the temperature correction coefficient. ANOVA calculations were based on using biomass productivity as the dependent variable. Total theoretical productivity for the reactor was also calculated using measured growth rates. The Arrhenius equation was used to model the effect of temperature on the biofilm growth rate.
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study
| 100.0 |
Triplicate RABR trials for each combination of organic carbon concentration and temperature were conducted for statistical analysis. Each temperature was evaluated by testing three levels of organic carbon in triplicate for a total of nine reactors at each temperature and each organic carbon level. The total number of RABRs was 27, three for each combination of organic loading and temperature. Error bars show 95% confidence intervals from the mean in all figures. ANOVA was performed using triplicate data points in each trial.
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| 100.0 |
In this study, biofilm productivity was the quantitative outcome, and temperature and organic loading were the explanatory variables. The advantage of performing ANOVA is that it not only provides a means to see how both of the independent variables, temperature and concentration of organic carbon, impact the dependent variable, biomass productivity, but also how the interaction of the two independent variables impacts the dependent variable .
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| 100.0 |
Results of ANOVA can be seen in Table 2. With p-values of less than 0.005, both increasing temperature and increasing organic carbon concentration were correlated with an increase in biofilm productivity. However the interaction of temperature and organic loading did not contribute to a statistically significant increase in productivity (p-value 0.8871).Table 2Summary of the Analysis of Variance (ANOVA) results for the effect of temperature and organic carbon concentration on productivity of RABR based algae biofilmSourceSum of squared deviationsDegrees of freedomMean squareF-Statistic P-ValueTemperature14.1227.068.87 0.0021 TOC Concentration30.2215.118.98 <0.0001 Interaction0.8840.220.28 0.8871 Error14.32180.8Total59.5226
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| 100.0 |
Because ANOVA results indicate that temperature was a contributing factor to biomass productivity, biofilm productivity rates at the three specified temperatures were applied to the Arrhenius equation in order to obtain the activation energy (E a). The equation used was1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ K=A*{e}^{\frac{-{E}_a}{RT}} $$\end{document}K=A*e−EaRTwhere K is the biomass productivity, E a is the activation energy of the reaction, and R is the universal gas constant (8.314 J K-1 mol-1). Equation 1 was then linearized by taking the natural log of both sides.2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ lnK=\frac{-{E}_a}{RT}+ ln\;A $$\end{document}lnK=−EaRT+lnA
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| 100.0 |
The slope of the line formed after plotting lnK vs. - \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \frac{1}{T} $$\end{document}1T provides the activation energy (E a) (Fig. 2). Using the Van’t Hoff-Arrhenius equation, it was possible to apply the activation energy to derive the equationFig. 2Arrhenius plot of RABR productivity (g · m-2 day-1) as a function of temperature (K). The slope of the best fit line for each concentration represents \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \frac{-{E}_a}{R} $$\end{document}−EaR where R = 8.314 J K − 1 mol − 1 and E a was calculated (Table 3) 3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \frac{K_2}{K_1}={\theta}^{T_2-{T}_1} $$\end{document}K2K1=θT2−T1in order to find the temperature correction coefficient; theta (Θ) . The activation energies and temperature correction coefficients are reported in Table 3, and were observed to be consistent with values seen in other biological systems [24–26].Table 3Temperature correction coefficients, activation energies, and constants of biofilm productivity and nutrient uptake at three levels of organic loading (TOC)Level of TOC (mg/L)Symbol1200600300Biomass Productivity (g m-2 day-1)K8.696.445.15Activation Energy (J K-1 mol-1)Ea 647397395440Temperature Correction Coefficient (unitless)Θ1.00961.01451.0081Nitrogen Uptake Rate (mg m-2 day-1)KN 1.220.910.723Nitrogen Correction Coefficient (unitless)ΘN 1.00981.01511.0078Phosphorus Uptake Rate (mg m-2 day-1)KP 0.170.120.1Phosphorus Correction Coefficient (unitless)ΘP 1.01011.01491.0116
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| 100.0 |
Arrhenius plot of RABR productivity (g · m-2 day-1) as a function of temperature (K). The slope of the best fit line for each concentration represents \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \frac{-{E}_a}{R} $$\end{document}−EaR where R = 8.314 J K − 1 mol − 1 and E a was calculated (Table 3)
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study
| 100.0 |
ANOVA results indicated that increasing the concentration of organic carbon had a positive correlation with biofilm productivity, and the effect of organic carbon concentration on biofilm productivity is presented in Fig. 3. Application of an algae-based biofilm system for nutrient uptake in dairy wastewater requires that the biofilm be capable of growth in the presence of high levels of organic carbon. The positive correlation between productivity and organic carbon concentration indicates that a biofilm system could be used to remove nutrients from a waste stream with elevated levels of organic carbon. This positive correlation could be due to a symbiotic effect of natural bacteria providing carbon dioxide for phototrophic growth. In a dairy waste stream of similar elemental composition to that of the Caine Dairy, which produces 4000 gal day-1, the theoretical yield for AFDW biomass is 9.5 kg day-1 of algae-based biofilm.Fig. 3Areal biofilm productivity as a function of organic carbon concentration at three different temperatures. Error bars represent ± 95% confidence interval. n = 3 for each data point. n = 27 for entire system
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| 100.0 |
Because ANOVA calculations indicate that temperature and organic loading did not interact to contribute to growth rate, an Arrhenius linearization of the data is advantageous. Application of biomass productivity (K) to Eq. 2 yields values of E a. Both K and E a values are reported in Table 3. These values allow productivity to be compared directly to temperature, creating a predictive system that can be used to estimate biofilm productivity at a given temperature.
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study
| 100.0 |
At a known concentration of organic carbon, the temperature correction coefficient (Θ), derived from Eq. 3, allows for prediction of biofilm productivity at any temperature within the range evaluated, i.e. 7–27 ° C. At a given water temperature and concentration of organic carbon, the Θ-values from Table 3 can be applied to the equation4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {K}_{prediction}=5.152*{\theta}^{T_{water}-280} $$\end{document}Kprediction=5.152*θTwater−280to predict algal biofilm productivity. A larger Θ value indicates a more significant increase in growth rate as temperature increases.
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| 100.0 |
Using molar ratios of the algae-based biofilm, it was also possible to derive a temperature correction coefficient from the biofilm productivity values in order to predict nitrogen and phosphorus uptake by the system. Rates of nitrogen and phosphorus uptake are reported in Table 3 as K N and K P respectively, and the temperature correction coefficients for nitrogen and phosphorus, Θ N and Θ P, are also reported in Table 3. At a known water temperature and concentration of organic carbon, the Θ N-values from Table 3 can be applied to the equation5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {K}_{N, prediction}=0.723*{\theta_N}^{T_{water}-280} $$\end{document}KN,prediction=0.723*θNTwater−280to predict rate of nitrogen uptake (mg m-2 day-1), and the Θ P-values from Table 3 can be applied to the equation6\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {K}_{P,\ prediction}=0.098*{\theta_P}^{T_{water}-280} $$\end{document}KP,prediction=0.098*θPTwater−280to predict rate of phosphorus uptake (mg m-2 day-1) by the biofilm.
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| 100.0 |
After harvesting the produced biofilm, the productivity of the system was calculated. Temperature was made to be a limiting factor for the growth of algae by providing nutrients in excess under constant light [27, 28]. Controlling temperature as the limiting factor allows for the evaluation of the effect of temperature on biofilm productivity, as shown in Fig. 4.Fig. 4Areal biofilm productivity (AFDW) as a function of temperature at three levels of organic loading. Error bars represent ± 95% confidence interval. n = 3 for each data point. n = 27 for entire system
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study
| 100.0 |
Results of this research are the first in the refereed literature that the authors are aware of that determined growth rates of algae-based biofilm on dairy wastewater at different temperatures for different strengths of the wastewater. Equations 4, 5 and 6 can be used for a waste stream with known organic carbon concentration and water temperature to predict biofilm productivity and nutrient uptake; where Θ is the value taken from Table 3 and T water is water temperature in degrees Kelvin from 280 to 300. The relationships among temperature, productivity, and TOC developed in this study can be applied to the design of dairy wastewater remediation systems and algae-based biomass production systems using biofilm reactors.
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study
| 100.0 |
The material properties: permittivity and permeability, can be used to classify all materials including metamaterials (MTMs)1. MTMs are engineered materials composed of sub-wavelength unit cells with unique properties that may not usually be available in nature2–6. Modification of the MTM geometry can be used to tune its electric and or magnetic response thereby producing tailored values of permittivity or permeability. The resulting modification of the effective material properties may also affect the MTM’s transmission, reflection, absorption, and coupling capabilities7. MTM applications include negative index materials8–11, near zero index materials12,13, gradient index materials14, and electromagnetic cloaking15–17.
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review
| 88.44 |
Due to the thickness and weight required to achieve the desired MTM properties, researchers have realized the efficacy of planar, two-dimensional equivalents known as metasurfaces (MSs). Metasurfaces are usually planar, easier to fabricate, and weigh much less when compared to 3D MTM structures. They are also less lossy due to their reduced size18. Some applications of MSs include: angular-independent surfaces19–21, absorbers22–24, radar cross section reduction surfaces25, wave front shapers26, ultra-thin transmission-type metalenses27–30, and wide angle impedance matching layers (WAIMs)31,32. WAIMs are usually employed to minimize the amount of scan loss in phased array antennas. This scan loss is caused by the variations in the array’s active impedance that arise from changes in the mutual coupling between the radiating elements as the scan angle and frequency change33.
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other
| 72.44 |
Several WAIM schemes have been introduced and used over the years. The earliest techniques involved using thin high-dielectric-constant superstrates in front of an array aperture34 or dielectric slabs adjacent to the array aperture35,36. The above WAIM schemes either improve scanning in one plane at the expense of the others34, or increase the chance of array blindness35,36. These WAIM techniques were also limited to single frequency or narrow bandwidth operations.
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other
| 99.8 |
To improve the bandwidth of WAIM structures, multi-layered MTM37,38 structures and dielectrics39 have been used. Unfortunately, the overall volume and weight of the array is also increased. To enable wide angle scanning without increasing the volume and weight of antenna arrays, MSs have been employed. The anisotropic MS-WAIM (henceforth referred to as MS only for brevity) in ref.31 provided an improved match for an array of open-ended circular waveguides to free space over several angles. However, only the scanning results for the H-plane were presented; the associated E-plane and D-plane (diagonal plane of a radiating aperture) results were not reported. Moreover, wide angle scanning over a narrow bandwidth was the focus of the design, which was achieved over a 3.3% bandwidth. The works reported in ref.34 and ref.31 were extended in ref.32. The dielectric slab was replaced with an ultra-thin metasurface composed of subwavelength split-ring resonators (SRRs) for an improved scan in the H and D-planes. Simulation results showed that wide angle scanning was achieved over a 20% impedance bandwidth.
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study
| 99.94 |
While there has been some advancement on WAIM metasurfaces, most of the past work was focused on wide angle scanning over narrow bandwidths31,32. In this paper, we propose a new ultra-thin MS that can achieve both wideband operation and wide angle scanning. The MS is composed of strongly-coupled (termed tightly-coupled in the antenna literature) unequal arm Jerusalem cross (TC-UAJC) elements. The TC-UAJC is an evolved version of the Jerusalem cross40 and its derivatives41,42. The wide bandwidth is obtained by taking advantage of the tight coupling within and between the multi-resonant elements. The band of operation is located much lower than the MS’s resonance frequency to avoid the associated highly dispersive and lossy regions31. These losses are due to the total power absorbed by the MS near its resonance frequency. At frequencies near its resonance, the field concentration per unit cell in the metallic layers of the structure is increased, which in turn leads to an increase in the resistive heating43. This MS is fairly insensitive to the changing phases of the signals incident upon it over a wide bandwidth. As a result, it is able to maintain its performance for scanning angles of up to 70ο from the normal to the MS for both transverse magnetic (TM) and transverse electric (TE) polarized incident waves. The metasurface is integrated with a tightly coupled antenna array to validate its feasibility. It is shown that the metasurface-array combination provides improved scanning along the E (72ο), Η (80ο), and D (79ο) planes over a 6:1 impedance bandwidth without the need for bulky dielectrics or multi-layered structures, resulting in a light-weight antenna system with reduced profiles.
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study
| 100.0 |
The unit cell configuration of the MS is depicted in Fig. 1. The metallic pieces (in yellow) are etched on the top surface of a dielectric substrate. The TC-UAJC element consists of two orthogonal, bent-arm capacitively-loaded-strips. They are tuned for the desired operating frequencies. These arm segments provide inductance; the gaps between the extremities of its bent arms provide capacitance.Figure 1Top view of the MS unit cell geometry. The optimized unit cell dimensions for the MS are: w = 0.2 mm, Hsub = 0.254 mm, g1 = 1.5 mm, g2 = 0.1 mm, L1 = 4.8 mm, L2 = 3.0 mm, L3 = 0.35 mm, L4 = 0.4 mm, L5 = 0.15 mm, L6 = 0.3 mm, and r1 = 1.0 mm.
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study
| 99.9 |
In order to minimize the variation of the array active reflection coefficients at wider scan angles, the MS introduces a capacitive reactance below its resonance frequency point to counteract the effects of the array’s inductively reactive ground plane. The MS serves as a wideband impedance transformer between the array aperture and free space. To ensure a low loss MS, its operational bandwidth is located way below its resonance frequency.
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other
| 99.9 |
The TC-UAJC element presented in this paper uses three main techniques to achieve optimal transmission and minimal reflection over a wide bandwidth below its resonance frequencies. Firstly, tightly coupled elements are used to increase their inter-element capacitance. It should be noted that smaller inter-element spacing produces large bandwidths but can lower the resonance frequency if the resulting capacitance is excessive44. The smaller inter element spacing combined with the subwavelength nature of the MS elements allows field propagation to neighbouring elements and the elimination of impedance variations to give rise to large bandwidths40. In the extreme case when the elements are very small and tightly packed, the current distribution across the MS approaches the Wheeler uniform current sheet concept45. The reduction in resonance frequency comes as a result of the well-known relationship, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\omega =1/\sqrt{LC}$$\end{document}ω=1/LC. Secondly, the horizontal and vertical arms of the TC-UAJC element are tightly coupled to each other for increased intra-element capacitance and thin traces are used for increased inductance, thereby enabling both compactness and an inherently wideband element46. Thirdly, the constituent parts of the element provide closely spaced multiple resonances47 which combine to produce a wide bandwidth.
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study
| 99.94 |
The proposed MS is designed using the commercially available ANSYS High Frequency Structure Simulator, ANSYS-HFSS48. A single-sided MS was simulated and an initial optimization was carried out to obtain the optimum transmission and reflection values. A prototype of the optimized MS was fabricated based on these optimized values and was tested to verify its operation. The effective medium parameters of the MS were also extracted from the MS S-parameters using MATLAB49 and the method described in ref.50. To demonstrate the WAIM capability of this MS across a wide frequency range, it is then integrated with a tightly coupled antenna array (TCAA) in an HFSS model for a final optimization. The antenna array consists of a set of tightly coupled dipole antennas39 with less than 0.4 λ spacing between them.
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study
| 100.0 |
The single sided MS was modeled using master-slave periodic boundary conditions in the x and y directions of the unit cell of Fig. 1. The periodic boundaries enforce a linearly progressive phase shift between the master and slave boundary pairs with uniform amplitude to enable beam scanning in the required directions. Two Floquet ports were used to illuminate both sides of the MS, one located at the top face and the other at the bottom face of the model’s air box. The length of the airbox was chosen to ensure that all higher order modes other than the two propagating zeroth-order Floquet modes experience at least 70 dB of attenuation.
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study
| 97.44 |
The copper-cladded Rogers RT/DuroidTM 5880 substrate with a relative dielectric constant of 2.2 and a height of Hsub = 0.254 mm was selected. The TC-UAJC element was etched on the 17 μm thick copper sheet on its upper surface. The HFSS solution frequency was selected to be 20 GHz for a (0.5–20) GHz frequency sweep. The maximum scan volume was θ = 70°. To minimize the simulation time and the amount of discretization, the metals in the HFSS model were taken to be perfect electric conductors (PECs). The zeroth-order Floquet modes, TM00 and TE00, were used for scanning in the y-z and x-z planes respectively as shown in Fig. 2. The electric field of the TM00 Floquet mode is parallel to the plane of incidence (along the y-direction) and the electric field of the TE00 Floquet mode is perpendicular to the plane of incidence (along the x-direction).Figure 2Top view of the unit cell. (a) The TM00 floquet mode fields. (b) The TE00 Floquet mode fields at the face of the top Floquet port.
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study
| 100.0 |
To determine the orientation of an antenna with respect to the MS element, the surface current distribution on the element is studied. The resulting surface current densities on the MS element for the corresponding TE and TM reflection (i.e., |S11|→0) and transmission (i.e., |S21|→0) resonances for normal incidence are shown in Fig. 3. For the TE reflection and transmission resonance cases, the MS is only weakly excited. For the TM reflection resonance case on the other hand, the MS is strongly excited with opposite sense circulating current loops. The circulating surface currents flow in equal and opposite directions in adjacent regions of the MS indicating that the magnetic fields created cancel out each other leaving no net magnetic response. Current flow is maximum along the y-direction suggesting that the optimum radiator-MS coupling is achieved when a radiator’s E-plane is aligned with the y-axis of the MS.Figure 3The surface current densities on the MS for normal incidence showing circulating current loops. (a) TM reflection resonance at 15.8 GHz. (b) TE reflection resonance at 19.5 GHz. (c) TE transmission resonance at 19.7 GHz.
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study
| 100.0 |
For a MS to act as an efficient wideband WAIM, it must be able to fulfil certain basic criteria. Firstly, the intended operational frequencies of the antenna array should be considerably lower than the resonance frequencies of the MS to avoid the highly dispersive and lossy regions31. Secondly, it should have little effect on the phases of the signals incident upon it during scan across the whole band of interest in order to facilitate the same output response. Thirdly, it should be thin and light weight to help reduce the volume and profile of the antenna array.
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other
| 99.9 |
In Fig. 4, we show with the simulated scattering parameters (S-parameters) at broadside, that the reflection resonance frequencies of the MS are above 15.8 GHz, which is much higher than the intended operational frequencies of the antenna array (below 5.0 GHz). The return loss for both the TE and TM polarizations is greater than 20 dB across the frequency band of interest and, hence, the insertion loss is virtually zero. Due to the unequal lengths of the two arms of the TC-UAJC element, they exhibit slightly different reflection resonance frequencies when illuminated by the TM and TE incident waves. Each resonance frequency is directly proportional to the unwound length, L, of the TC-UAJC element51.The first reflection resonance occurs at 15.8 GHz for the TM excitation when the electric field is along the longer arm; the second one occurs at 19.5 GHz for the TE excitation when it is along the shorter arm.Figure 4Magnitudes of the S-parameters for normal incidence. (a) TE and TM excitations of the MS. (b) An expanded view showing the first TM reflection resonance at 15.8 GHz and the first TE reflection resonance at 19.5 GHz. A TE transmission resonance can also be seen at 19.7 GHz.
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study
| 100.0 |
Magnitudes of the S-parameters for normal incidence. (a) TE and TM excitations of the MS. (b) An expanded view showing the first TM reflection resonance at 15.8 GHz and the first TE reflection resonance at 19.5 GHz. A TE transmission resonance can also be seen at 19.7 GHz.
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other
| 98.5 |
The transmission phase variation with frequency for the TM polarized incident fields for various angles of incidence is shown in Fig. 5. The phase varies by only 3° for a 0°–70° change in the incident angle. This small change in phase implies that the MS will hardly alter the phase of electromagnetic waves traversing it22. The resulting MS is very thin and light weight. It is only 0.254 mm thick.Figure 5Transmission phase variation with frequency for the TM polarized incident fields for various angles of incidence.
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study
| 99.94 |
One of the major goals was to make the reflection magnitude and transmission phase across the frequency band of interest as small as possible without having an adverse impact on the bandwidth of the MS. Consequently, several of the design parameters were studied to determine the values that produced the minimum reflection magnitude and transmission phase. It was found that the parameters g1, g2, r1, and Hsub have the most impact on the MS performance.
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study
| 99.94 |
The effects of g1 on the reflection magnitude and transmission phase values are shown in Fig. 6a,e, respectively. Increasing g1 reduces both the reflection magnitude and transmission phase values. However, further increase beyond 1 mm has negligible impact. The effects of g2 are shown in Fig. 6b,f. Decreasing g2 gives decreasing values for both the magnitude and phase. The value of g2 is limited by manufacturing tolerances so it has been confined to a minimum value of 0.1 mm. The parameters g1 and g2 control the amount of intra-element coupling. Smaller values of g2 indicate a tighter coupling between the horizontal and vertical arms of the TC-UAJC resulting in a large coupling capacitance. When this coupling capacitance is combined with the high loop inductance produced by the thin traces of the structure, the element bandwidth is enhanced.Figure 6The effects of various MS design parameters on the reflection magnitude (a–d) and transmission phase (e–h) as functions of the excitation frequency for the TM incidence case. (a) and (e) g1. (b) and (f) g2. (c) and (g) r1. (d) and (h) Hsub.
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study
| 100.0 |
Figure 6c,g show the effects of r1. Decreasing r1 gives decreasing values for both the magnitude and phase. The minimum value of r1 has been restricted to 1 mm for ease of fabrication. The resonance frequency of the unit cell is essentially determined by r1. Smaller values of r1 lead to smaller elements with correspondingly higher resonance frequencies, creating a wider separation between the frequency band of interest and the element resonance frequency. The result from this wide separation is a smaller transmission phase variation with respect to the scan angle. The inter-element coupling is controlled by the values of r1.
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study
| 100.0 |
The effects of Hsub are shown in Fig. 6d,h. Decreasing Hsub gives decreasing values for both the magnitude and phase of the S-parameters. Thinner substrates, i.e., smaller Hsub, ensure higher transmission and minimal reflection of the incident signal. From all of these reflection magnitude and transmission phase plots given in Fig. 6, the optimum values are: g1 = 1.5 mm, g2 = 0.1 mm, r1 = 1.0 mm and Hsub = 0.254 mm.
|
study
| 100.0 |
To further characterize the MS’s response, it is of interest to determine its effective material and wave parameters. The method described in ref.50 was used to extract the effective wave impedance Zeff, the effective dielectric constant εeff, and the effective permeability μeff from the S-parameters. These wave and medium parameters are shown in Fig. 7. During the extraction process, the MS was assumed to be homogeneous with an effective thickness equal to that of the substrate upon which the TC-UAJC element resides. Homogenization is justified due to the sub-wavelength nature of the MS inclusions. Owing to the MS’s very thin nature in the direction of propagation, the extraction process was expected to proceed smoothly. Moreover, its thinness led to virtually the same results relative to each port of the unit cell. In order to obtain more complete extraction results, the MS was simulated up to 30 GHz for the TM excitation, well above its TM reflection resonance frequency of 15.8 GHz.Figure 7Extracted parameters of the MS for the TM excitation. (a) Effective impedance. (b) Effective permittivity and effective permeability at the frequencies of interest and (c) across the whole band showing TM resonance at 15.8 GHz.
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study
| 100.0 |
Referring to the frequency range of interest, 0 to 5.0 GHz, the extracted parameters reveal the following. The effective wave impedance Zeff shows that the MS itself is not matched to free space. As will be demonstrated with its integration with the driven array, it acts as a low loss impedance matching facilitator between the array and free space. The composite antenna and MS system are found to be well matched to free space over a wide bandwidth.
|
other
| 99.3 |
The extracted value of the effective permeability μeff is equal to one; i.e., the MS acts as a purely electric surface with no bianisotropic behaviour. The value of εeff changes by less than 4%, 8.545–8.882, over the entire frequency range of interest. These results further illustrate that by working well below the resonances, the lossy regions of the MS are avoided.
|
study
| 99.94 |
To verify the simulation results, a 40×40 unit cell MS was fabricated and measured in an anechoic chamber. The test setup was in both reflection and transmission modes. As shown in Fig. 8(a), the reflection mode included two horn antennas for transmit and receive on the same side of the MS. An expanded view of the fabricated MS is also given in Fig. 8(b). The simulated and measured transmission and reflection results for the MS are shown in Fig. 9. It is noted that the measurements were carried out only up to 18.0 GHz again to due to the chamber limitations. Consequently, only the TM reflection resonance at 15.8 GHz could be verified experimentally. The simulated results show very good scanning up to 70° with acceptable transmission and reflection losses for both the TE and TM excitations. Measurements were carried out for broadside and for 30° incidence; those results show good agreement with the simulated results. For the reflection measurements, the simulated and measured results agree very well except below 3.0 GHz. These discrepancies have been determined to be mainly a consequence of the limited functional frequency range of the absorbers available in the anechoic chamber. The transmission measurements on the other hand, agree well with the simulated results across the whole measured band.Figure 8Measurement setup. (a) The reflection measurement and (b) an expanded view of the MS under test.Figure 9Simulated and measured transmission and reflection results for the MS. (a) Return loss - TE incidence. (b) Return loss - TM incidence. (c) Insertion loss - TE incidence. (d) Insertion loss - TM incidence.
|
study
| 100.0 |
In order to demonstrate the scanning advantages of including a MS with a driving antenna array, an infinite TCAA was simulated with both an infinite dielectric slab WAIM31,32 and then with an infinite version of the TC-UAJC based MS. The infinite nature of the geometries allowed us to simulate a unit cell of the corresponding finite TCAA-WAIM system. While this choice neglected some minor edge effects, it captures the essence of the performance of the realistic structure given the large extent of the fabricated MS sample. The TCAA is a wideband array and, hence, was selected to test appropriately the wideband performance of the MS. To analyze the reference dielectric slab WAIM, it was placed directly above the antenna array with the optimized parameters: the relative permittivity εr = 2.5 and thickness of dielectric slab hdi = 12.0 mm.
|
study
| 100.0 |
Figure 10(a) shows a side view of one unit cell of the TCAA integrated with the MS structure. The TCAA is made up of an infinite dipole array with overlapping arms and fed with lumped ports. It is oriented vertically along the y-z plane with arms printed on opposite sides of a thin printed circuit board (PCB) substrate. The blue colored arm of the dipole is on the top layer of the substrate and the orange colored arm is on its bottom layer. The purple region, indicated by y3, represents the amount of overlap with the arms of the adjacent elements. The arms were assumed to be perfect electric conductors (to significantly reduce the computational overhead) mounted on a Rogers RT/Duroid 6010 substrate with a dielectric constant of 10.2 and a thickness of 1.016 mm. Each element was driven with a lumped port whose active input impedance was (170 − j38) \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\rm{\Omega }}$$\end{document}Ω. Figure 10(b) shows the top view of the MS which is made up of a 5×5 array of the TC-UAJC MS elements within the TCAA unit cell. The dimensions of the MS were adjusted to account for the interactions between it and the antenna. The new optimized dimensions were: r1 = 1.59 mm, g1 = 0.9774 mm, g2 = 0.2384 mm, L2 = 4.4568 mm. All other dimensions remained the same.Figure 10TCAA integrated with the MS. (a) Side view of a unit cell with vertically oriented dipole arms printed on opposite sides of the PCB. Blue = top layer, orange = bottom layer, purple = overlap with adjacent elements. (b) Expanded top view of the modified MS within one unit cell. The dimensions of the various parameters of the TCAA-WAIM unit cell are: z1 = y1 = 4.0 mm, y2 = 8.0 mm, y3 = 1.0 mm, hair = 6.76 mm, hgnd = 28.25 mm, h = 1.016 mm, and dx = dy = 24.0 mm. (c) Perspective view of the unit cell.
|
study
| 100.0 |
TCAA integrated with the MS. (a) Side view of a unit cell with vertically oriented dipole arms printed on opposite sides of the PCB. Blue = top layer, orange = bottom layer, purple = overlap with adjacent elements. (b) Expanded top view of the modified MS within one unit cell. The dimensions of the various parameters of the TCAA-WAIM unit cell are: z1 = y1 = 4.0 mm, y2 = 8.0 mm, y3 = 1.0 mm, hair = 6.76 mm, hgnd = 28.25 mm, h = 1.016 mm, and dx = dy = 24.0 mm. (c) Perspective view of the unit cell.
|
other
| 97.6 |
The scanning abilities of the MS and dielectric WAIM systems are compared in Fig. 11 across the E, H, and D (diagonal) planes over a wide bandwidth. The dashed lines represent the dielectric WAIM results and the solid lines represent the MS results. At broadside, the simulated performance characteristics of the TCAA integrated with the dielectric and MS WAIMs are virtually identical. However, the MS system has the added advantage of more degrees of freedom with the potential to provide a better impedance match to the assumed 50-Ω source. Across the E-Plane, both the MS and dielectric WAIMs can scan to 60°, however, the MS can do so with a lower VSWR at wider scan angles. Across the H- and D-Planes, the two systems have very similar performance with the dielectric slab system being slightly better over the lower frequency band while the MS performs better over the higher frequency band. Nevertheless, both the dielectric and MS-based WAIM systems scan well out to 70° across their D-planes. Moreover, it can be observed that the MS system covers a wider bandwidth for all scan angles. The MS-array combination (37.264 mm) is also of a lower profile compared to the dielectric array combination (42.25 mm).Figure 11Scanning of the MS (solid lines) and dielectric WAIM (dashed lines) systems. (a) E-plane. (b) H-plane and (c) D-planes.
|
study
| 100.0 |
The transmittance values of the MS and dielectric WAIMs for all scan angles across the E, H, and D planes are compared in Fig. 12 at 4.0 GHz. It is interesting to find that the MS outperforms the dielectric WAIM across both the E and D planes and performs the same as the dielectric WAIM in the H plane. Previous works on single layer WAIMs based purely on the modification of the free space region above the array aperture are overwhelmingly carried out at a single frequency of operation. Therefore, to make a direct comparison to them, we compare in Table 1 the performance of the MS at 4.0 GHz to those reported in two key works in this area. The work in ref.31 only presents scanning across the H-plane for two designs. One scans up to 55° and another scans between 40° and 80°. It is shown here that the MS achieves wider scanning in both the E and H planes in comparison to the results reported in both ref.31,32. Moreover, it falls only 2° short of the D-plane scan in ref.32.Figure 12Comparison of the MS (solid lines) and dielectric WAIM (dashed lines) across the E, H, and D planes at a minimum of 80% transmittance (equivalent to VSWR < 3) at 4.0 GHz.Table 1Maximum Scan Range at a Single Frequency.Previous workThis workRef.31Ref.32DielectricMSE-PlaneN/A45°64°72°H-Plane55°65°80°80°D-PlaneN/A81°72°79°
|
study
| 99.94 |
A wideband MS to be used as a WAIM layer has been systematically designed and its characteristics were experimentally validated. Its effective material parameters were extracted to show the constancy of ε and μ over the desired, very wide operational band of frequencies. The optimized MS was used as a superstrate over a TCAA of simple printed dipoles to reduce the impedance mismatch of the system to its source when the array is scanning. It was shown that the MS provides improved scanning along the E and D planes over its wide bandwidth without the use of bulky isotropic dielectrics or multi-layered structures. Furthermore, it maintained the scanning performance in the H plane. An MS-TCAA prototype integrated with a realistic feed network will be reported in the near future.
|
study
| 99.94 |
The proposed MS was simulated and optimized in ANSYS-HFSS using master-slave periodic boundary conditions and two Floquet ports to illuminate both sides of the MS. The copper-cladded Rogers RT/DuroidTM 5880 with a relative dielectric constant of 2.2 and a height of Hsub = 0.254 mm was selected as the substrate. The TC-UAJC elements were etched on the 17 μm thick copper sheet on the top surface of the dielectric substrate. To minimize the simulation time and the amount of discretization, the metals in the HFSS model were taken to be perfect electric conductors (PECs). To verify the MS simulation results, a 40×40 unit cell array was fabricated and measured in an anechoic chamber. Measurements were carried out using an Agilent vector network analyzer and two horn antennas to obtain the transmission and reflection coefficients for both TE and TM polarizations by rotating the horns through 90°. In the transmission case, the horn antennas are place equidistant on opposite sides of the MS and the signal received from the transmitting horn is measured for both broadside and 30° incidence. For the reflection measurements, the transmit and receive horns were on the same side of the MS as shown in Fig. 8. The effective medium parameters of the MS were extracted from the MSs S-parameters using MATLAB and the method described in ref.50.
|
study
| 100.0 |
With a median age of 64 years, glioblastoma (GBM) patients are in nearly half of cases at an age, that frequently defines them as “aged” or “elderly” [1, 2]. Generally, the present standard of care for GBM patients includes involved field radiotherapy (RT) as well as concomitant as well as 6 cycles of adjuvant chemotherapy with temozolomide (TMZ) and goes back to the study from Stupp et al. in 2005 . The patient cohort, however, was limited to an age of equal or less than 70 years and a post-hoc analysis of this cohort found a negative correlation between the patient’s age and the benefit from a combined regimen [3, 4]. An anticipated increased likelihood of adverse events of TMZ in elderly patients might be one explanation for this finding . Notably, several mono-institutional reports as well as data-base-studies have demonstrated that elderly GBM patients treated with standard-RT plus TMZ do have a longer survival compared to patients treated with alternative or reduced regimens, especially after extensive resection of the tumor [6–8].
|
review
| 99.9 |
As the positive effect of RT in elderly patients is not a matter of debate anymore , several alternative dosing-regimens have been tested in prospective trials. Exemplary, Roa and colleagues demonstrated non-inferiority of a 3 week regimen compared to the 6 week standard regimen of radiotherapy . Recently, Roa and colleagues demonstrated, that also an even more hypofractionated one-week-regimen is equal-effective in elderly and frail patients compared to the formerly described mildly hypofractionated 3 week course . Of note, neither of these two regimens were tested together with concomitant chemotherapy.
|
review
| 99.9 |
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