Oxygen Transfer Model for a Flow-Through Hollow-Fiber Membrane Biofilm Reactor

A mechanistic oxygen transfer model was developed and applied to a flow-through hollow-fiber membrane-aerated biofilm reactor. Model results are compared to conventional clean water test results as well as performance data obtained when an actively nitrifying biofilm was present on the fibers. With the biofilm present, oxygen transfer efficiencies between 30 and 55% were calculated from the measured data including the outlet gas oxygen concentration, ammonia consumption stoichiometry, and oxidized nitrogen production stoichiometry, all of which were in reasonable agreement. The mechanistic model overpredicted the oxygen transfer by a factor of 1.3 relative to the result calculated from the outlet gas oxygen concentration, which was considered the most accurate of the measured benchmarks. A mass transfer coefficient derived from the clean water testing with oxygen sensors at the membrane-liquid interface was the most accurate of the predictive models (overpredicted by a factor of 1.1) while a coefficient determined by measuring bulk liquid dissolved oxygen underpredicted the oxygen transfer by a factor of 3. The mechanistic model was found to be an adequate tool for design because it used the published diffusion and partition coefficients rather than requiring small-scale testing to determine the system-specific mass transfer coefficients.     

Deposition and characterization of MgO/Si gate stacks grown by molecular beam epitaxy

In this article, the deposition and characterization of amorphous MgO films grown on Si (001) using molecular beam epitaxy is reported. In order to ensure amorphous films, low substrate temperatures (200 °C) and high oxygen pressures were used (up to 5 × 10^− 3 Pa). Both atomic and molecular oxygen species were used at different pressures. Films ranging in thickness from 3 nm till 30 nm were grown and characterized using structural and electrical methods.The dielectric constant deduced from this thickness series corresponds to 8.74 close to the bulk value of 9.8. The best equivalent oxide thickness value observed for this series - grown under high oxygen pressure - corresponds to 1.2 nm for a current density measured at V_FB − 1 V of 0.1 A/cm². The films grown with atomic oxygen display a lower capacitance and lower leakage compared to the films grown using molecular oxygen. This is due to the appearance of a thin SiO₂ interface layer which is also responsible for the high defect density observed in the capacitance-voltage measurements. Upon annealing both types of films in forming gas for 15 min at 450 °C, the capacitance decreases further while the leakage increases. This change is assigned to the appearance of the lower bandgap (6.6 eV), lower dielectric constant (6.6) phase of silicate, MgSiO₃. Furthermore a V_FB shift of − 0.6 V is observed and is related to the appearance of oxygen vacancies as Mg diffuses into the SiO₂ interface layer.     

Tenure mix: apart or together? Home-making practices and belonging in a Dutch street

This paper discusses home-making practices and senses of belonging in a street in a disadvantaged neighbourhood in the south of the Netherlands. The local tenure mix of tenants and owner-occupiers offers insight into the role class and ethnicity play in social mixing. Therefore, attention is paid to narratives and the informal organisation of different living spaces and territory-making practices. Here, the domestic space could be experienced as a vehicle of intimacy and sociability, or conversely as encouraging alienation. Such practices, in combination with length of stay result in mechanisms of inclusion and exclusion. The insights derived from this study will contribute to the theoretical discussion on home-making practices and belonging.     

Highly transparent modulated surface textured front electrodes for high‐efficiency multijunction thin‐film silicon solar cells

To further increase the efficiency of multijunction thin‐film silicon (TF‐Si) solar cells, it is crucial for the front electrode to have a good transparency and conduction, to provide efficient light trapping for each subcell, and to ensure a suitable morphology for the growth of high‐quality silicon layers. Here, we present the implementation of highly transparent modulated surface textured (MST) front electrodes as light‐trapping structures in multijunction TF‐Si solar cells. The MST substrates comprise a micro‐textured glass, a thin layer of hydrogenated indium oxide (IOH), and a sub‐micron nano‐textured ZnO layer grown by low‐pressure chemical vapor deposition (LPCVD ZnO). The bilayer IOH/LPCVD ZnO stack guarantees efficient light in‐coupling and light trapping for the top amorphous silicon (a‐Si:H) solar cell while minimizing the parasitic absorption losses. The crater‐shaped micro‐textured glass provides both efficient light trapping in the red and infrared wavelength range and a suitable morphology for the growth of high‐quality nanocrystalline silicon (nc‐Si:H) layers. Thanks to the efficient light trapping for the individual subcells and suitable morphology for the growth of high‐quality silicon layers, multijunction solar cells deposited on MST substrates have a higher efficiency than those on single‐textured state‐of‐the‐art LPCVD ZnO substrates. Efficiencies of 14.8% (initial) and 12.5% (stable) have been achieved for a‐Si:H/nc‐Si:H tandem solar cells with the MST front electrode, surpassing efficiencies obtained on state‐of‐the‐art LPCVD ZnO, thereby highlighting the high potential of MST front electrodes for high‐efficiency multijunction solar cells. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of nickel and cadmium speciation on nitrification inhibition

Heavy metals have been postulated to cause significant nitrification inhibition. Using biomass from a well-controlled continuously operated lab-scale nitrifying bioreactor, the effect of nickel and cadmium on ammonium and nitrite oxidation was quantified. The extent of inhibition was calculated from the kinetics of ammonium oxidation and nitrite oxidation, inferred from maximum specific oxygen uptake rates (SOUR) measured in batch respirometric assays. Nickel and cadmium inhibited ammonium oxidation but not nitrite oxidation up to total analytical concentrations of approximately 1.0 mM. Metal fractions (total and free ion) were correlated with the extent of ammonium oxidation inhibition in the presence of various metal complexing agents (EDTA, NTA, citrate, SO4(2-)). Inhibition was not a function of the total analytical metal concentration but strongly correlated with free cation concentration, [Ni2+] or [Cd2+]. This relationship could be described by either an empirical noncompetitive inhibition model for [Ni2+] or a linear model in the case of [Cd2+]. Furthermore, the free Ni2+ or Cd2+ concentrations could be modulated by the addition of a strong chelating agent (e.g., EDTA), resulting in reduced deleterious effects. However, at elevated doses, EDTA itself impaired nitrification. In sum, predictions and mandatory strategies of nitrification inhibition by heavy metals should be based on free cation concentrations and not on total metal concentrations.     

Pancreatitis-associated protein: a putative marker for pancreas graft rejection

BACKGROUND: Graft rejection is one of the major causes of graft loss after pancreas transplantation. Pancreatitis-associated protein (PAP) is synthesized by the pancreas due to pancreatic inflammation and has shown to be a good serum marker for injury of the pancreas. It may also be potentially useful in the early recognition of rejection and may thus improve pancreas survival. METHODS: We retrospectively evaluated PAP as an early serum marker of pancreas graft rejection in a cross-sectional study in which immunohistochemical analysis of pancreas biopsies was undertaken using antibodies against PAP. PAP concentrations were also measured in sera of blood donors and in patients with renal failure, renal replacement therapy, kidney transplantation alone, and simultaneous pancreas-kidney transplantation. RESULTS: All patients had elevated PAP serum levels compared with blood donors (median PAP: 22 ng/ml, range: 5-75 ng/ml; P<0.0001). Patients on renal replacement therapy had higher values than patients with renal failure (median: 420 ng/ml and 150 ng/ml, respectively). There was a strong inverse correlation between PAP levels and creatinine clearance (P<0.001). PAP values in simultaneous pancreas-kidney transplantation patients with histological rejection were significantly higher than values in those who were clinically stable (median: 925 ng/ml and 322 ng/ml, respectively; P=0.006). Rejection was significantly associated with PAP staining of acinar cell surface. There was also a significant correlation between surface positivity of staining and serum PAP levels (P=0.008). No positive PAP staining was observed in concurrently collected biopsies of renal allografts undergoing rejection. CONCLUSIONS: Serum PAP levels appear to strongly correlate with creatinine clearance measurements. In patients with a pancreas-kidney transplantation, PAP may prove to be a useful biological and histological marker of pancreatic graft rejection.     

What do cancer patients mean when they complain of concentration and memory problems?

Cognitive function items are increasingly included in quality of life measures, and complaints of concentration and memory difficulties are often reported by cancer patients. The aim of this study was to examine the factors influencing patients' level of complaint by comparing subjective reports with objective test performance of a sample of adult lymphoma patients, disease-free and > or = 6 months after treatment. There was no significant difference between complainers and non-complainers in sociodemographic or clinical characteristics or in their performance on standard neuropsychometric tests of concentration and memory. Those reporting concentration and memory difficulties had significantly higher scores on measures of anxiety, depression and fatigue. This calls into question the validity of including cognitive function items in self-report quality of life measures. Patients who report concentration and memory difficulties should be screened for clinically significant and potentially remediable mood disorder. Objective testing remains the method of choice for assessing higher mental function.     

Rectovaginal septum adenomyotic nodules: a series of 500 cases

PURPOSE: Selective mesenteric angiography is an expensive, invasive, diagnostic, and therapeutic tool for lower gastrointestinal hemorrhage. Some institutions have required a positive nuclear medicine bleeding scan before angiography. We have attempted to determine if this is a valid screening test for mesenteric angiography. Are there any other factors to predict which patients are actively bleeding and who will benefit from angiography? METHODS: All cases of mesenteric angiography for hemorrhage performed during a 12-year period were reviewed. RESULTS: A total of 131 angiograms were performed during a 12-year period with 45 patients demonstrating active bleeding; 54 patients had a bleeding scan before angiography. A positive bleeding scan did not increase the percentage of positive angiograms. A history of prior gastrointestinal bleeding, transfusions, orthostatic hypotension, or tachycardia were not predictors for a positive angiogram. DISCUSSION: This study could not identify any single useful predictor that will increase the likelihood of obtaining a positive angiogram. Nuclear medicine scans should not be used routinely as a screening test for angiography.     

Successful islet autotransplantation in humans: functional insulin secretory reserve as an estimate of surviving islet cell mass

Bafilomycin A1, a specific inhibitor of vacuolar type H(+)-ATPase, can inhibit the growth of a variety of cultured cells in a dose-dependent manner, but its mechanism is unclear. The aim of this study was to examine whether bafilomycin A1 inhibits the growth of Capan-1 human pancreatic cancer cells through apoptosis. The effect of bafilomycin A1 on tumour growth in vitro and in vivo was examined using an MTT assay and an in vivo tumour model. The presence or absence of apoptosis was determined by morphology and DNA analysis of tumour cells. The concentration of bafilomycin A1 for 50 per cent inhibition of cell viability during 72 h by the MTT assay was 5 nm. In DNA analysis, a ladder of fragmented DNA was detected in Capan-1 cells treated with bafilomycin A1 at concentrations greater than 10 nm for 24 h. Nude mice bearing a xenografted Capan-1 cell line tumour received 4 weeks of bafilomycin A1 (1.0 mg/kg per day). This treatment significantly inhibited tumour growth compared with controls after 21 days (P < 0.05). Histopathological examination of tumour cells in the treated group demonstrated signs of apoptosis with chromatin condensation and cell shrinkage. These observations suggest that bafilomycin A1 inhibits the growth of Capan-1 human pancreatic cancer cells through apoptosis.     

Comparison of nitrification inhibition by metals in batch and continuous flow reactors

Stringent effluent discharge limits for nitrogen require development of assays to accurately and rapidly determine whether a wastewater stream will inhibit nitrification. The suitability of a short-term extant batch respirometric assay to predict nitrification inhibition by metals (Cu, Zn, Ni and Cd) in continuous flow reactors was evaluated. Linear metal partition coefficients were determined to be 78.42+/-2.46, 0.54+/-0.04, 0.05+/-0.01 and 0.60+/-0.01 L/g biomass COD in batch experiments (pH=7.5) for Cu, Zn, Ni and Cd, respectively. A mass-balance model, incorporating metal partitioning, adequately fit the metal concentration profiles in the continuous flow reactor during and after a 24-hour shock load. However, the short-term batch assays significantly underestimated observed inhibition in the continuous flow reactor. The underestimation was, most likely, due to slow kinetics of Zn, Ni and Cd internalization and an exacerbation effect due to continued metal exposure in the continuous flow reactor. The discrepancy in inhibition between batch and continuous systems was the largest for Cu, presumably due to its unique mode of action, which involves loss of cell membrane integrity. Hence, using results from short-term batch respirometric assays to infer responses in continuous flow reactors with longer exposure should be done with caution and must accommodate partitioning behavior and internalization kinetics.