A generalized drift-diffusion model for rectifying Schottky contact simulation

We present a discussion on the modeling of Schottky barrier rectifying contacts (diodes) within the framework of partial-differential-equation-based physical simulations. We propose a physically consistent generalization of the drift-diffusion model to describe the boundary layer close to the Schottky barrier where thermionic emission leads to a non-Maxwellian carrier distribution, including a novel boundary condition at the contact. The modified drift-diffusion model is validated against Monte Carlo simulations of a GaAs device. The proposed model is in agreement with the Monte Carlo simulations not only in the current value but also in the spatial distributions of microscopic quantities like the electron velocity and concentratio

Changes in olfactory bulb volume following lateralized olfactory training.

Repeated exposure to odors modifies olfactory function. Consequently, "olfactory training" plays a significant role in hyposmia treatment. In addition, numerous studies show that the olfactory bulb (OB) volume changes in disorders associated with olfactory dysfunction. Aim of this study was to investigate whether and how olfactory bulb volume changes in relation to lateralized olfactory training in healthy people. Over a period of 4 months, 97 healthy participants (63 females and 34 males, mean age: 23.74 ± 4.16 years, age range: 19-43 years) performed olfactory training by exposing the same nostril twice a day to 4 odors (lemon, rose, eucalyptus and cloves) while closing the other nostril. Before and after olfactory training, magnetic resonance imaging (MRI) scans were performed to measure OB volume. Furthermore, participants underwent lateralized odor threshold and odor identification testing using the "Sniffin' Sticks" test battery.OB volume increased significantly after olfactory training (11.3 % and 13.1 % respectively) for both trained and untrained nostril. No significant effects of sex, duration and frequency of training or age of the subjects were seen. Interestingly, PEA odor thresholds worsened after training, while olfactory identification remained unchanged.These data show for the first time in humans that olfactory training may involve top-down process, which ultimately lead to a bilateral increase in olfactory bulb volume

Involvement of sperm acetylated histones and the nuclear isoform of Glutathione peroxidase 4 in fertilization

We previously demonstrated that the nuclear form of Glutathione peroxidase 4 (nGPx4) has a peculiar distribution in sperm head, being localized to nuclear matrix and acrosome and that sperm lacking nGPx4 are more prone to decondensation in vitro. In this study we have hypothesized that sperm retained acetylated histones and nGPx4 are implicated in paternal chromatin decondensation and male pronucleus formation at fertilization. Indeed, significant higher amounts of acetylated histone H4 and acetylated histone H3 were observed by both immunofluorescence and western blotting in nGPx4-KO sperm vs WT ones. In vitro fertilization of zona pellucida- deprived oocytes by WT sperm in the presence of trichostatin (TSA) also demonstrated that paternal histone acetylation was inversely related to the timing of sperm nucleus decondensation at fertilization. In contrast, TSA had no effect on nGPx4-KO sperm, indicating they had a maximal level of histone acetylation. Moreover the paternally imprinted gene Igf2/H19 was hypomethylated in KO sperm compared to WT ones. The lack of nGPx4 negatively affected male fertility, causing a marked decrease in total pups and pregnancies with delivery, a significant reduction in pronuclei (PN) embryos in in vitro fertilization assays and an approximately 2 h delay in egg fertilization in vivo. Because the zona pellucida binding and fusion to oolemma of nGPx4-KO and WT sperm were similar, the subfertility of nGPx4 sperm reflected a decreased sperm progression through egg cumulus/zona pellucida, pinpointing a defective acrosome in line with acrosomal nGPx4 localization. We conclude that paternal acetylated histones and acrosomal nGPx4 are directly involved in fertilization

“Life at the River is a Living Hell:” a qualitative study of trauma, mental health, substance use and HIV risk behavior among female fish traders from the Kafue Flatlands in Zambia

Abstract Background In Western settings, the relationship between trauma history, posttraumatic stress disorder, substance use, and HIV risk behavior, is well established. Although female fish traders in Zambia are affected by HIV at rates estimated to be 4–14 times higher than the national prevalence, no studies have examined the co-occurring issues of trauma, substance use and HIV risk behavior among this vulnerable population. The current study examined: 1) trauma history, trauma symptoms and HIV risk behaviors and 2) the relationship between these co-occurring issues among female fish traders from the Kafue Flatlands in Zambia. Methods Twenty individual semi-structured qualitative interviews and a focus group discussion (n = 12 participants) were conducted with female fish traders in the Kafue Flatlands of Zambia. Template analysis was used to examine the data. Results The findings indicate that female fish traders in Zambia are at risk of multiple and ongoing traumatic events and daily stressors, severe mental health symptoms (including western conceptualizations of disorders such as anxiety, depression, post-traumatic stress disorder (PTSD) and complicated grief, as well as local idioms of distress), substance abuse, and HIV sexual risk behaviors. The results suggest a relationship between trauma and HIV sexual risk behavior in this population. Conclusions The indication of these co-occurring issues demonstrates the need for HIV prevention intervention efforts, which account for trauma, mobility, and psychosocial outcomes in order to reduce HIV sexual risk behavior among female fish traders in Zambia.http://deepblue.lib.umich.edu/bitstream/2027.42/136165/1/12905_2017_Article_369.pd

Determination of pyrrolizidine alkaloids in dietary sources using a spectrophotometric method

Pyrrolizidine alkaloids (PAs) are a class of toxic compounds found in the composition of more than 6000 plants. People can be exposed to PAs by consuming phytotherapeutic products, food from crops contaminated with seeds of some species with high content of PAs, and/ or contaminated animal products like bee products. For this reason we developed and validated a method for quantitative determination of PAs, from the most frequently contaminated food sources, honey and flour. Colorimetric Ehrlich reagent method was used with standard addition (1mg/kg senecionine). The extraction solvent was methanol 50% acidified with citric acid to pH 2-3, as this solvent can be used for alkaloids and N-oxides. We found that, in extracting the alkaloid only once from the dietary sources, the percent of recovery is low (52.5% for honey, and 45.75% for flour). Using successive extractions, three times with the same solvent, the senecionine retrieval percentage increased to 86.0% for honey and 76.0% for flour. The method was validated using the following parameters: selectivity, linearity (0,25- 20 mg/ mL senecionine), accuracy (average recovery 93.5 - 107.93%) and precision (RSD 3,26-4.55%.). The calculated limit of quantification (0.174 mg/ mL) makes this method applicable for determining Pas occurring at toxic levels for consumers

Trajectories in phase diagrams, growth processes and computational complexity: how search algorithms solve the 3-Satisfiability problem

Most decision and optimization problems encountered in practice fall into one of two categories with respect to any particular solving method or algorithm: either the problem is solved quickly (easy) or else demands an impractically long computational effort (hard). Recent investigations on model classes of problems have shown that some global parameters, such as the ratio between the constraints to be satisfied and the adjustable variables, are good predictors of problem hardness and, moreover, have an effect analogous to thermodynamical parameters, e.g. temperature, in predicting phases in condensed matter physics [Monasson et al., Nature 400 (1999) 133-137]. Here we show that changes in the values of such parameters can be tracked during a run of the algorithm defining a trajectory through the parameter space. Focusing on 3-Satisfiability, a recognized representative of hard problems, we analyze trajectories generated by search algorithms using growth processes statistical physics. These trajectories can cross well defined phases, corresponding to domains of easy or hard instances, and allow to successfully predict the times of resolution.Comment: Revtex file + 4 eps figure