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Solar water splitting is one of the key steps in artificial photosynthesis for future carbon-neutral, storable and sustainable source of energy. Here we show that one of the major obstacles for achieving efficient and stable overall water splitting over the emerging nanostructured photocatalyst is directly related to the uncontrolled surface charge properties. By tuning the Fermi level on the nonpolar surfaces of gallium nitride nanowire arrays, we demonstrate that the quantum efficiency can be enhanced by more than two orders of magnitude. The internal quantum efficiency and activity on p -type gallium nitride nanowires can reach ~51% and ~4.0 mol hydrogen h −1  g −1 , respectively. The nanowires remain virtually unchanged after over 50,000 μmol gas (hydrogen and oxygen) is produced, which is more than 10,000 times the amount of photocatalyst itself (~4.6 μmol). The essential role of Fermi-level tuning in balancing redox reactions and in enhancing the efficiency and stability is also elucidated. One of the obstacles in implementing solar water splitting is the requirement for materials with high internal quantum efficiency. Here, the authors investigate the effects of magnesium doping on the Fermi levels of gallium nitride nanowires, and tune this value to maximize redox efficiency.

Fetal growth restriction (FGR) affects up to 5 % of pregnancies worldwide, and trophoblast function plays a significant role on the outcome. An epidemiological study has linked vitamin D deficiency to adverse perinatal outcomes, which include decreased birth weight. The placenta as an important source of vitamin D regulates its metabolism through the vitamin D receptor (VDR), but the mechanism by which VDR regulates trophoblast function is poorly understood. Our study aimed at determining placental VDR expression in FGR and gestation-matched control (GMC) pregnancies and identifying the actions of VDR in trophoblast differentiation and apoptosis. Placentae were collected from a well-defined cohort of idiopathic FGR and GMC pregnancies. VDR mRNA and protein expressions were determined by PCR, immunohistochemistry and immunoblotting, while functional consequences of VDR inactivation in vitro were determined on BeWo cells by determining changes in differentiation, attachment and apoptosis. Significant decreases in VDR mRNA expression ( p  = 0.0005) and protein expression ( p  = 0.0003) were observed in the FGR samples, while VDR inactivation, which showed markers for differentiation, cell attachment and apoptosis, was significantly increased. Thus, decreased placental VDR may contribute to uncontrolled premature differentiation and apoptosis of trophoblasts that are characteristics of idiopathic FGR pregnancies. Key message Fetal growth restriction (FGR) affects up to 5 % of all pregnancies worldwide. FGR is the second highest cause of perinatal mortality and morbidity. The placenta plays a pivotal role in vitamin D metabolism during pregnancy. Vitamin D deficiency is associated with adverse pregnancy outcomes. Placental vitamin D receptor expression is decreased in FGR.

The increase of bias-dependent source access resistance, rs, with high gate bias is attributed to a sharp drop in transconductance, gm, and current gain cut-off frequency, fT, of high-electron-mobility transistors (HEMTs). Consequently, source and drain implant regions (n++ cap regions) are commonly used to obtain expected results in experimental devices as predicted theoretically. This paper investigates the effect of different doping profiles in n++ cap regions using a finite space in access regions on gm and fT with increasing bias. The device under test (DUT) is a beta-gallium oxide (β-Ga2O3)-based HEMT using an AlN barrier to create polarization-induced two-dimensional electron gas (2DEG). Dynamic access resistance is optimized by lateral Gaussian n++ doping characteristics using a finite gap between the ohmic contacts and barrier layer, which ensures high RF device performance. The technology computer-aided design (TCAD) simulation results for source access resistance are validated with an appropriate analytical model. It is observed that the peak electric field in the source access region can be controlled to delay electron velocity saturation, which yields higher mobility and reduced access resistance.

AimsTo assess the association between physical activity (PA) during pregnancy and the prevalence of gestational diabetes mellitus (GDM) accounting for sitting time.MethodsThe study used data from a cohort study of 2030 pregnant women in Vietnam. Women were recruited from six hospitals in Ha Noi, Hai Phong, and Ho Chi Minh City. Baseline measurements including PA and GDM were taken at 24–28 weeks of gestation. PA was assessed during the past 3 months before the interview using the interviewer-administered Pregnancy Physical Activity Questionnaire. GDM was diagnosed at 24–28 weeks of gestation using the 2013 World Health Organization criteria.Results1987 out of 2030 pregnant women were included in the final analysis, of which 432 had GDM (21.7%). Women undertaking the highest level (upper tertile) of PA during pregnancy appeared to have a lower risk of GDM [odds ratio (OR) 0.70, 95% confidence interval (CI) 0.53–0.94, Ptrend 0.017] when compared to those at the lowest tertile of PA. Similarly, women with increased levels of moderate-intensive activity and household/caregiving activity during pregnancy were associated with reduced risks of GDM (OR 0.66, 95% CI 0.50–0.86, Ptrend 0.002 and OR 0.72, 95% CI 0.55–0.95, Ptrend 0.020, respectively). These apparent inverse associations were not attenuated by their sitting time. There were no significant associations between sitting time, light-intensity activity, vigorous-intensity activity, occupation, sports/exercise, commuting, or meeting exercise guidelines and GDM risk.ConclusionsHigh levels of PA, particularly moderate-intensity and household/caregiving activities during pregnancy were associated with a lower prevalence of GDM independent of sitting time.

This paper studies various sub-optimal versions of BCJR demodulator to examine the possibility of computational reduction. BCJR demodulator is used to deal with intentional intersymbol interference in bandwidth efficient systems. The complexity of BCJR demodulator can be reduced by using the approximation in the logarithm domain and by considering less number of trellis states instead of full states. To estimate the performance of different types of BCJR demodulator, we proposed the partial response signalling system with finite shaping pulse providing 10% gain of bandwidth efficiency. The simulation results of this study show that in the case without error correction coding the complexity of BCJR demodulator can be significantly decreased without energy losses. When low-density parity-check coding is used, it is possible to use these sub-optimal versions of BCJR demodulator, but the system may suffer additional energy losses.

The current study aims at exploring the beneficial effect of silica fume (SF) and acrylic emulsion polymer (PR) on the enhanced properties of polypropylene fiber reinforced concrete (FRC) with the supplementary cementitious binder comprised of the Portland cement, slag, silica fume and fly ash. The compressive strength and impact-abrasion resistance were used for the estimation of engineering properties while the water absorption performance, surface electricity resistance, and rapid chloride penetration resistance were used for estimation of durability. Experimental results showed that a sole addition of SF increased the compressive strengths but decreased the abrasion-impact resistances of modified FRCs, which was just opposite to the influence of a sole addition of PR. A sole addition of either the SF or PR could moderately improve the durability of modified FRCs, respectively. However, due to the beneficial effect of the complementary interaction between SF and the optimal amount of PR, the mechanical properties and durability of modified FRCs seemed to become significantly improved.

We report on the design and fabrication of high performance AlxGa1−xN nanowire ultraviolet (UV) light-emitting diodes (LEDs) on silicon substrate by molecular beam epitaxy. The emission wavelength and surface morphology of nanowires can be controlled by varying the growth parameters that include substrate temperatures and/or Aluminum/Gallium flux ratios. The devices exhibit excellent current-voltage characteristics with relatively low resistance. Such nanowire LEDs generate strong emission in the UV-B band tuning from 290 nm to 330 nm. The electroluminescence spectra show virtually invariant blue-shift under injection current from 50 mA to 400 mA, suggesting the presence of a negligible quantum-confined Stark effect. Moreover, we have shown that, the AlGaN nanowire LEDs using periodic structures, can achieve high light extraction efficiency of ~ 89% and 92% for emissions at 290nm and 320nm, respectively. The randomly arranged nanowire 290 nm UV LEDs exhibit light extraction efficiency of ~ 56% which is higher compared to current AlGaN based thin-film UV LEDs.