Anaerobic membrane bioreactors: Are membranes really necessary?

Membranes themselves represent a significant cost for the full scale application of anaerobic membrane bioreactors (AnMBR). The possibility of operating an AnMBR with a self-forming dynamic membrane generated by the substances present in the reactor liquor would translate into an important saving. A self-forming dynamic membrane only requires a support material over which a cake layer is formed, which determines the rejection properties of the system. The present research studies the application of self-forming dynamic membranes in AnMBRs. An AnMBR was operated under thermophilic and mesophilic conditions, using woven and non woven materials as support for the dynamic membranes. Results showed that the formation of a cake layer over the support materials enables the retention of more than 99% of the solids present in the reactor. However, only low levels of flux were achieved, up to 3 L/m2 x h, and reactor operation was unstable, with sudden increases in filtration resistance, due to excessive cake layer formation. Further fine-tuning of the proposed technology involves looking for conditions that can control effectively cake layer formatio

Influence of Peri-duodenal Non-constrictive Cuff on the Body Weight of Rats

Background Weight loss has been found to improve or re- solve cardiovascular comorbidities. There is a significant need for reversible device approaches to weight loss. Methods Non-constrictive cuff (NCC) is made of implantable silicone rubber with an internal diameter greater than the duodenum. Ten or 11 NCC were individually mounted along the duodenum from the pyloric sphincter toward the distal duodenum to cover ~22 mm in the length. Twelve Wistar rats were implanted with NCC, and six served as sham, and both groups were observed over 4 months. Six rats with implant had their NCC removed and were observed for additional 4weeks. Results The food intake decreased from 40.1 to 28.1 g/day after 4 months of NCC implant. The body weight gain decreased from 1.76 to 0.46 g/day after 4 months of NCC implant. The fasting glucose decreased from 87.7 to 75.3 mg/ dl at terminal day. The duodenal muscle layer covered by the NCC increased from 0.133 to 0.334 mm. After 4 weeks of NCC removal, the food intake, body weight gain, and fasting glucose recovered to 36.2, 2.51 g/day, and 83.9 mg/dl. The duodenal muscle layer covered by the NCC decreased to 0.217 mm. Conclusion The NCC implant placed on the proximal duode- num is safe in rats for a 4-month period. The efficacy of the NCC implant is significant for decrease in food intake, body weight gain, and fasting glucose in a normal rat model. The removal of NCC implant confirmed a cause-effect relation with food intake and hence body weight

Meshless 2D direct numerical simulation and heat transfer in a backward-facing step with heat conduction in the step

A meshless direct pressure-velocity coupling procedure is presented to perform Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES) of turbulent incompressible flows in regular and irregular geometries. The proposed method is a combination of several efficient techniques found in different Computational Fluid Dynamic (CFD) procedures. With this new procedure, preliminary calculations with 2D steady state flows show that viscous effects become negligible faster that ever predicted numerically. The fundamental idea of this method lays on several important inconsistencies found in three of the most popular techniques used in CFD, segregated procedures, as well as in other formulations. The inconsistencies found become important in elliptic flows and they might lead to some wrong solutions. Preliminary calculations done in 2D laminar flows, suggest that the numerical diffusion and interpolation error are much important at low speeds, mainly when both, viscous and inertia forces are present. With this competitive and efficient procedure, the solution of the 2D Direct Numerical Simulation of turbulent flow with heat transfer on a backward-facing step is presented. The thermal energy is going to be transferred to the fluid through conduction on the step, with both constant temperature and heat flux conditions in the back wall of the step. The variation of the local Nusselt Number through the wall will be studied and its corresponding effect in the energy transfer to the fluid

A Cost Benefit Calculator for RFID Implementations in the Apparel Retail Industry

The apparel retail industry is on the one hand facing challenges from increasing competition, consolidations, and thus increasing pressure to reduce costs. On the other hand, customers are getting more demanding, resulting in shorter fashion cycles, and demands for new customer experience. RFID technology is supposed to raise efficiency and to enable innovative customer service offerings. Besides cost savings, benefits are expected to arise from newly designed RFID applications and customer insights from analyses of shop floor data. Recently, apparel retailers started to investigate this technology, resulting in several trials and pilots world-wide. However, the business case of RFID in the apparel retail industry is not clear. Based on the findings of a real-world deployment, our contribution presents a cost-benefit calculator that is specifically designed to meet the requirements of apparel retail industry RFID implementations

Measuring sociocultural engagement of health professions education students:a psychometric study

Background: Sociocultural engagement of students refers to broadening viewpoints and providing awareness of, and respect for, diverse backgrounds and perspectives. However, there are no existing validated instruments in the literature for measuring sociocultural engagement of health professions education (HPE) students. Therefore, the aim of this study is to develop and validate a questionnaire designed to assess sociocultural engagement among HPE students. Methods: The study included undergraduate HPE students (n = 683) at Gulf Medical University. The initial version of the sociocultural engagement of students’ questionnaire (SESQ) was developed after extensive literature review and guided by the Global Learning Qualifications Framework. We then tested the content validity of the questionnaire by using focus group discussion with subject experts (n = 16) and pilot testing with students (n = 20). We distributed the content-validated version of the SESQ (16 items) to undergraduate students in six HPE colleges. To examine the construct validity and construct reliability of the questionnaire, we conducted exploratory factor analysis, followed by confirmatory factor analysis. Results: Confirmatory factor analysis supported the two-factor structure which consists of 13 items with good fitness indices (χ2 = 214.35, df = 61, χ 2/df = 3.51, CFI = 0.98, RMSEA = 0.06, SRMR = 0.025, and AIC = 208.00). The two factors were sociocultural interactions (8 items) and sociocultural adaptation (5 items). The construct reliability of the total questionnaire is 0.97 and the two factors were 0.93 and 0.92 for sociocultural interactions and sociocultural adaptation, respectively. In addition, there were significant weak correlations between both factors of sociocultural engagement scores and student satisfaction with the university experience (r =.19 for each, P =.01). Conclusions: The sociocultural engagement of students’ questionnaire exhibits good evidence of construct validity and reliability. Further studies will be required to test the validity of this questionnaire in other contexts.</p

Measuring sociocultural engagement of health professions education students:a psychometric study

Background: Sociocultural engagement of students refers to broadening viewpoints and providing awareness of, and respect for, diverse backgrounds and perspectives. However, there are no existing validated instruments in the literature for measuring sociocultural engagement of health professions education (HPE) students. Therefore, the aim of this study is to develop and validate a questionnaire designed to assess sociocultural engagement among HPE students. Methods: The study included undergraduate HPE students (n = 683) at Gulf Medical University. The initial version of the sociocultural engagement of students’ questionnaire (SESQ) was developed after extensive literature review and guided by the Global Learning Qualifications Framework. We then tested the content validity of the questionnaire by using focus group discussion with subject experts (n = 16) and pilot testing with students (n = 20). We distributed the content-validated version of the SESQ (16 items) to undergraduate students in six HPE colleges. To examine the construct validity and construct reliability of the questionnaire, we conducted exploratory factor analysis, followed by confirmatory factor analysis. Results: Confirmatory factor analysis supported the two-factor structure which consists of 13 items with good fitness indices (χ2 = 214.35, df = 61, χ 2/df = 3.51, CFI = 0.98, RMSEA = 0.06, SRMR = 0.025, and AIC = 208.00). The two factors were sociocultural interactions (8 items) and sociocultural adaptation (5 items). The construct reliability of the total questionnaire is 0.97 and the two factors were 0.93 and 0.92 for sociocultural interactions and sociocultural adaptation, respectively. In addition, there were significant weak correlations between both factors of sociocultural engagement scores and student satisfaction with the university experience (r =.19 for each, P =.01). Conclusions: The sociocultural engagement of students’ questionnaire exhibits good evidence of construct validity and reliability. Further studies will be required to test the validity of this questionnaire in other contexts.</p

Exploring the use of zircon geochronology as an indicator of Laurentide Ice Sheet till provenance, Indiana, USA

A pilot study was designed to evaluate the potential of zircon geochronology as a provenance indicator of till from the Lake Michigan, Saginaw, and Huron-Erie Lobes of the Laurentide Ice Sheet. Based on existing ice flow-path models, we hypothesized that till from each lobe would have different zircon age population distributions because the lobes originated from regions of the Canadian Shield with different bedrock ages. After correcting for zircon fertility, the majority of grains in all till samples are 1600–950 Ma, with ~30 % of ages >2500 Ma. This similarity means that till from the three lobes cannot be clearly differentiated based on their zircon populations. The dominant ages found and the homogeneity of distributions in the till indicates a non-Shield source and, instead, reflect an origin from some combination of underlying till and sedimentary bedrock in the Great Lakes region. Even though the datasets are small, the tills have similarities to zircon distributions in Michigan Basin rocks. This implies that a substantial fraction of zircon in till was not transported long distances from the Canadian Shield. Although zircon ages are not distinct between tills, the method provides a novel application to understand Laurentide Ice Sheet glacial erosion and transport

Distension-Induced Gastric Contraction is Attenuated in an Experimental Model of Gastric Restraint

Background Gastric distension has important implications for motility and satiety. The hypothesis of this study was that distension affects the amplitude and duration of gastric contraction and that these parameters are largely mediated by efferent vagus stimulation. Methods A novel isovolumic myograph was introduced to test these hypotheses. The isovolumic myograph isolates the stomach and records the pressure generated by the gastric contraction under isovolumic conditions. Accordingly, the phasic changes of gastric contractility can be documented. A group of 12 rats were used under in vivo conditions and isolated ex vivo conditions and with two different gastric restraints (small and large) to determine the effect of degree of restraint. Results The comparison of the in vivo and ex vivo contractility provided information on the efferent vagus mediation of gastric contraction, i.e., the in vivo amplitude and duration reached maximum of 12.6±2.7 mmHg and 19.8±5.6 s in contrast to maximum of 5.7±0.9 mmHg and 7.3±1.3 s in ex vivo amplitude and duration, respectively. The comparison of gastric restraint and control groups highlights the role of distension on in vivo gastric contractility. The limitation of gastric distension by restraint drastically reduced the maximal amplitude to below 2.9±0.2 mmHg. Conclusions The results show that distension-induced gastric contractility is regulated by both central nervous system and local mechanisms with the former being more substantial. Furthermore, the gastric restraint significantly attenuates gastric contractility (decreased amplitude and shortened duration of contraction) which is mediated by the efferent vagus activation. These findings have important implications for gastric motility and physiology and may improve our understanding of satiety

Geometry of River Networks II: Distributions of Component Size and Number

The structure of a river network may be seen as a discrete set of nested sub-networks built out of individual stream segments. These network components are assigned an integral stream order via a hierarchical and discrete ordering method. Exponential relationships, known as Horton's laws, between stream order and ensemble-averaged quantities pertaining to network components are observed. We extend these observations to incorporate fluctuations and all higher moments by developing functional relationships between distributions. The relationships determined are drawn from a combination of theoretical analysis, analysis of real river networks including the Mississippi, Amazon and Nile, and numerical simulations on a model of directed, random networks. Underlying distributions of stream segment lengths are identified as exponential. Combinations of these distributions form single-humped distributions with exponential tails, the sums of which are in turn shown to give power law distributions of stream lengths. Distributions of basin area and stream segment frequency are also addressed. The calculations identify a single length-scale as a measure of size fluctuations in network components. This article is the second in a series of three addressing the geometry of river networks.Comment: 16 pages, 13 figures, 4 tables, Revtex4, submitted to PR

Construct validity of a questionnaire for measuring student engagement in problem-based learning tutorials

Background: Student engagement is student investment of time and energy in academic and non-academic experiences that include learning, teaching, research, governance, and community activities. Although previous studies provided some evidence of measuring student engagement in PBL tutorials, there are no existing quantitative studies in which cognitive, behavioral, and emotional engagement of students in PBL tutorials is measured. Therefore, this study aims to develop and examine the construct validity of a questionnaire for measuring cognitive, behavioral, and emotional engagement of students in PBL tutorials. Methods: A 15-item questionnaire was developed guided by a previously published conceptual framework of student engagement. Focus group discussion (n = 12) with medical education experts was then conducted and the questionnaire was piloted with medical students. The questionnaire was then distributed to year 2 and 3 medical students (n = 176) in problem-based tutorial groups at the end of an integrated course, where PBL is the main strategy of learning. The validity of the internal structure of the questionnaire was tested by confirmatory factor analysis using structural equation modeling assuming five different models. Predictive validity evidence of the questionnaire was studied by examining the correlations between students’ engagement and academic achievement. Results: Confirmatory factor analysis indicates a good fit between the measurement and structural model of an 11-item questionnaire composed of a three-factor structure: behavioral engagement (3 items), emotional engagement (4 items), and cognitive engagement (4 items). Models in which the three latent factors were considered semi-independent provided the best fit. The construct reliabilities of behavioral, cognitive, and emotional factors were 0.82, 0.82, and 0.76, respectively. We failed however to find significant relationships between academic achievement and engagement. Conclusions: We found a strong evidence to support the construct validity of a three-factor structure of student engagement in PBL tutorial questionnaire. Further studies are required to test the validity of this instrument in other educational settings. The predictive validity is another area needing further scrutiny.</p