Accelerated development of CuSbS2 thin film photovoltaic device prototypes

Development of alternative thin film photovoltaic technologies is an important research topic because of the potential of low‐cost, high‐efficiency solar cells to produce terawatt levels of clean power. However, this development of unexplored yet promising absorbers can be hindered by complications that arise during solar cell fabrication. Here, a high‐throughput combinatorial method is applied to accelerate development of photovoltaic devices, in this case, using the novel CuSbS₂ absorber via a newly developed three‐stage self‐regulated growth process to control absorber purity and orientation. Photovoltaic performance of the absorber, using the typical substrate CuIn_xGa_{1 − x}Se₂ (CIGS) device architecture, is explored as a function of absorber quality and thickness using a variety of back contacts. This study yields CuSbS₂ device prototypes with ~1% conversion efficiency, suggesting that the optimal CuSbS₂ device fabrication parameters and contact selection criteria are quite different than for CIGS, despite the similarity of these two absorbers. The CuSbS₂ device efficiency is at present limited by low short‐circuit current because of bulk recombination related to defects, and a small open‐circuit voltage because of a theoretically predicted cliff‐type conduction band offset between CuSbS₂ and CdS. Overall, these results illustrate both the potential and limits of combinatorial methods to accelerate the development of thin film photovoltaic devices using novel absorbers. Copyright © 2016 John Wiley & Sons, Ltd.     

Assessment of iron bioavailability from twenty elite late‐maturing tropical maize varieties using an in vitro digestion/Caco‐2 cell model

An in vitro digestion/Caco‐2 cell model was used to assess iron bioavailability of twenty elite late‐maturing tropical maize varieties grown in three diverse agroecologies in West and Central Africa (WCA). Kernel‐iron concentration of the varieties, averaged across locations, varied from 19.2 to 24.4 mg kg^?1, while mean kernel‐zinc concentration ranged between 19.4 and 24.6 mg kg^?1. Significant differences in iron bioavailability were observed among varieties, but the environment had no significant effect. Mean bioavailable iron ranged between 14% below and 43% above the reference control variety, TZB‐SR. Variety DMR‐LSR‐Y with the highest concentrations of kernel‐iron and ‐zinc of 24–25 mg kg^?1 across the three locations had a similar quantity of bioavailable iron as the reference control, TZB‐SR. In the long run this variety could be potentially effective in reducing iron deficiency because of its high kernel‐iron. The most promising varieties were Mid‐altitude STR synthetic and ACR91SUWAN‐1‐SRC1. They had kernel‐iron and ‐zinc levels of 22–24 mg kg^?1 and bioavailable iron 24–36% higher than the reference control, TZB‐SR. Additional research is necessary to determine if the increases in kernel‐iron concentration and bioavailable iron observed in this study can significantly improve the iron status of individuals in WCA at risk for iron deficiency. Copyright © 2004 Society of Chemical Industry     

Physical parameters of fiber affecting passage from the rumen

Our objective was to review the factors that affect fiber passage from the rumen. Rumen residence time and passage from the rumen are important in control of intake, digestibility, protein metabolism, and protein escape. Physical factors associated with particle size and particle specific gravity affect passage from the rumen. Although particles of 5 cm may pass through the reticulo-omasal orifice, most particles leaving the rumen are smaller than 1 mm. Polypropylene ribbon cut into 7-cm lengths, introduced into the rumen, markedly reduced intake and were ruminated to fine particle size before being passed. Materials with specific gravity less than 1.0 are ruminated extensively and are passed slowly. As specific gravity of plastic particles increase, rumination of particles is decreased and passage is increased. Particles with specific gravities between 1.17 and 1.42 pass most rapidly. Increasing specific gravities further results in a decline in passage and a further lowering of rumination of particles. Natural hay and fresh forages are hydrated in the rumen, which causes functional specific gravity to increase. Some factors that affect rate of change of functional specific gravity of forages have been investigated. Small particle size, autoclaved rumen fluid, buffer solutions, and specific salts increased the rate of change of functional specific gravity of particles. Understanding of these factors may enable us to make better decisions in managing ruminant productions systems.     

Real-time gaseous, PM and ultrafine particle emissions from a modern marine engine operating on biodiesel

Emissions from harbor-craft significantly affect air quality in populated regions near ports and inland waterways. This research measured regulated and unregulated emissions from an in-use EPA Tier 2 marine propulsion engine on a ferry operating in a bay following standard methods. A special effort was made to monitor continuously both the total Particulate Mass (PM) mass emissions and the real-time Particle Size Distribution (PSD). The engine was operated following the loads in ISO 8178-4 E3 cycle for comparison with the certification standards and across biodiesel blends. Real-time measurements were also made during a typical cruise in the bay. Results showed the in-use nitrogen oxide (NOx) and PM(2.5) emission factors were within the not to exceed standard for Tier 2 marine engines. Comparing across fuels we observed the following: a) no statistically significant change in NO(x) emissions with biodiesel blends (B20, B50); b) ～ 16% and ～ 25% reduction of PM(2.5) mass emissions with B20 and B50 respectively; c) a larger organic carbon (OC) to elemental carbon (EC) ratio and organic mass (OM) to OC ratio with B50 compared to B20 and B0; d) a significant number of ultrafine nuclei and a smaller mass mean diameter with increasing blend-levels of biodiesel. The real-time monitoring of gaseous and particulate emissions during a typical cruise in the San Francisco Bay (in-use cycle) revealed important effects of ocean/bay currents on emissions: NO(x) and CO(2) increased 3-fold; PM(2.5) mass increased 6-fold; and ultrafine particles disappeared due to the effect of bay currents. This finding has implications on the use of certification values instead of actual in-use emission values when developing inventories. Emission factors for some volatile organic compounds (VOCs), carbonyls, and poly aromatic hydrocarbons (PAHs) are reported as supplemental data.     

Benefits of two mitigation strategies for container vessels: cleaner engines and cleaner fuels

Emissions from ocean-going vessels (OGVs) are a significant health concern for people near port communities. This paper reports the emission benefits for two mitigation strategies, cleaner engines and cleaner fuels, for a 2010 container vessel. In-use emissions were measured following International Organization for Standardization (ISO) protocols. The overall in-use nitrogen oxide (NO(x)) emission factor was 16.1 ± 0.1 gkW(-1) h(-1), lower than the Tier 1 certification (17 gkW(-1) h(-1)) and significantly lower than the benchmark value of 18.7 gkW(-1) h(-1) commonly used for estimating emission inventories. The in-use particulate matter (PM(2.5)) emission was 1.42 ± 0.04 gkW(-1) h(-1) for heavy fuel oil (HFO) containing 2.51 wt % sulfur. Unimodal (～30 nm) and bimodal (～35 nm; ～75 nm) particle number size distributions (NSDs) were observed when the vessel operated on marine gas oil (MGO) and HFO, respectively. First-time emission measurements during fuel switching (required 24 nautical miles from coastline) showed that concentrations of sulfur dioxide (SO(2)) and particle NSD took ～55 min to reach steady-state when switching from MGO to HFO and ～84 min in the opposite direction. Therefore, if OGVs commence fuel change at the regulated boundary, then vessels can travel up to 90% of the distance to the port before steady-state values are re-established. The transient behavior follows a classic, nonlinear mixing function driven by the amount of fuel in day tank and the fuel consumption rate. Hence, to achieve the maximum benefits from a fuel change regulation, fuel switch boundary should be further increased to provide the intended benefits for the people living near the ports.     

Does Bisphenol A Confer Risk of Neurodevelopmental Disorders? What We Have Learned from Developmental Neurotoxicity Studies in Animal Models

Substantial evidence indicates that bisphenol A (BPA), a ubiquitous environmental chemical used in the synthesis of polycarbonate plastics and epoxy resins, can impair brain development. Clinical and epidemiological studies exploring potential connections between BPA and neurodevelopmental disorders in humans have repeatedly identified correlations between early BPA exposure and developmental disorders, such as attention deficit/hyperactivity disorder and autism spectrum disorder. Investigations using invertebrate and vertebrate animal models have revealed that developmental exposure to BPA can impair multiple aspects of neuronal development, including neural stem cell proliferation and differentiation, synapse formation, and synaptic plasticity—neuronal phenotypes that are thought to underpin the fundamental changes in behavior-associated neurodevelopmental disorders. Consistent with neuronal phenotypes caused by BPA, behavioral analyses of BPA-treated animals have shown significant impacts on behavioral endophenotypes related to neurodevelopmental disorders, including altered locomotor activity, learning and memory deficits, and anxiety-like behavior. To contextualize the correlations between BPA and neurodevelopmental disorders in humans, this review summarizes the current literature on the developmental neurotoxicity of BPA in laboratory animals with an emphasis on neuronal phenotypes, molecular mechanisms, and behavioral outcomes. The collective works described here predominantly support the notion that gestational exposure to BPA should be regarded as a risk factor for neurodevelopmental disorders.     

A 40 keV cyclotron for radioisotope dating

We have built and begun testing a small low energy negative ion cyclotron for direct detection of ¹⁴C. At present, the cyclotron is operated in a high resolution mode at the 31st harmonic, with 1–2 kV on the dees. The high harmonic and a minimum number of turns of approximately 100, should give a fwhm mass resolution of about $\text{1}\text{30000}$ — sufficient to suppress the background from molecular ions such as ¹³CH^?. Background such as scattered ions of ¹²C^? and ¹³C^? should be totally suppressed by the cyclotron acceleration process. (At the 88″ cyclotron at LBL we found that ions only 1% off-resonance are suppressed by more than a factor of 10¹⁷.) A miniature Cs sputter source located at the center of the cyclotron is expected to provide more than 1 μA of negative carbon ions. Negative ions are used in order to eliminate the interference from ¹⁴N. Unlike high energy cyclotrons, focussing is obtained solely from the axial components of the accelerating electric field. The magnetic field is kept flat to within 1 part in 10⁴ in order to maintain exact isochronism throughout the several thousand accelerating rf cycles. The low final energy of 40 keV eliminates any danger from radiation or need for shielding, and the final orbit radius of only 10.5 cm, reduce the size and cost of the machine to that of conventional mass spectrometers.     

Anodic behaviour of oxidised Ni–Fe alloys in cryolite–alumina melts

Nickel-iron alloys have been identified as promising inert anode candidates for the Hall–Héroult process. In this study, binary Ni–Fe alloys of various compositions were subjected to short-term galvanostatic electrolysis in a cryolite–alumina bath at 960 °C. Prior to electrolysis, the anodes were oxidised at 800 °C for 48 h, forming a protective scale. Fe₂O₃, Ni_xFe_3−xO₄ and Ni_xFe_{1 − x}O were identified as the major scale components using a combination of X-ray diffraction (XRD) analysis and energy dispersive X-ray spectroscopy (EDX). Anodes having Ni content of 50–65 wt% performed adequately during short-term electrolysis, operating at a steady potential of 3–3.5 V vs. AlF₃/Al. Overall, it was found that the pre-formed oxide scale was effective in reducing anode wear and fluoridation. In the absence of a pre-formed scale, anodes were shown to undergo appreciable internal corrosion and/or passivation due to metal fluoride formation. Analysis of the anodes following electrolysis was performed using XRD and electron microprobe analysis (EPMA).     

Divergent Synthesis of Novel Cylindrocyclophanes that Inhibit Methicillin-Resistant Staphylococcus aureus (MRSA)

The cylindrocyclophanes are a family of macrocyclic natural products reported to exhibit antibacterial activity. Little is known about the structural basis of this activity due to the challenges associated with their synthesis or isolation. We hypothesised that structural modification of the cylindrocyclophane scaffold could streamline their synthesis without significant loss of activity. Herein, we report a divergent synthesis of the cylindrocyclophane core enabling access to symmetrical macrocycles by means of a catalytic, domino cross-metathesis-ring-closing metathesis cascade, followed by late-stage diversification. Phenotypic screening identified several novel inhibitors of methicillin-resistant Staphylococcus aureus. The most potent inhibitor has a unique tetrabrominated [7,7]paracyclophane core with no known counterpart in nature. Together these illustrate the potential of divergent synthesis using catalysis and unbiased screening methods in modern antibacterial discovery.     

Influence of Phenological Stage on Swainsonine and Endophyte Concentrations in Oxytropis sericea

Locoweeds are defined as Astragalus and Oxytropis species that cause intoxication due to the alkaloid swainsonine. Swainsonine concentrations in Oxytropis sericea were influenced by location, plant part, and the developmental stage of the plant. Concentrations followed similar trends at each location, generally increasing over the growing season in above-ground parts until the plant reaches maturity with no change in concentration in the crowns. At the onset of senescence, swainsonine decreased in floral parts to less than half of the peak concentration. Similar to swainsonine concentrations, endophyte amounts were influenced by location, plant part, and the developmental stage of the plant. Likewise, endophyte amounts generally increased over the growing season in above ground parts and remained static in the crowns at all four locations. Swainsonine in Oxytropis sericea was positively associated with the endophyte Undifilum, which is responsible for swainsonine biosynthesis.