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This paper characterizes the dark current development of p-on-n type HgCdTe multi-layer heterojunction long wavelength infrared (LWIR) and very long wavelength infrared (VLWIR) photodiodes. Four devices that operate at different wavelengths are fabricated by employing a multi-layer structure. The results demonstrate the favorable dark current which is close to the “Rule 07” limitation is obtained with a 50% cutoff wavelength of $16.6~\mu $ m. Besides, the influence mechanisms on the device are extracted by analyzing the temperature-dependent dark current from 40 K to 130 K. The results suggest that the proposed devices perform comparable to those of conventional double-layer heterojunction devices. Furthermore, it can be noted that by precisely controlling the composition distribution and depletion region positions as well as improving the process, we can further achieve superior LWIR and VLWIR devices.

This paper applies sign restrictions to identify oil structural shocks by imposing nonzero restrictions on the short-term price elasticity of oil supply. With the help of oil inventory data, flow supply, flow demand and speculative demand shocks in the global oil market are identified. Then, the impact of different kinds of oil price shocks on fluctuations of the U.S. and Chinese stock markets is examined and some insights from the perspective of frequency domain are provided. We observe that the U.S. and Chinese stock markets are extensively influenced by the three types of oil structural shocks. In particular, oil price shocks induced by speculation can significantly affect the performance of stock markets in both countries. Under the frequency domain, we notice that the flow demand shock is the most important driver of the variance in U.S. and Chinese stock returns and volatility, particularly at low and business cycle frequencies. Meanwhile, we note that short-term fluctuations in Chinese stock market returns and volatility are more vulnerable to speculative demand shocks. These analysis results are not only useful for policymakers to take targeted measures to deal with the impact of oil price shocks on the stock market, but also useful for investors to adjust their stock portfolios to achieve excess returns.

Developing microbial consortiums is necessary for microbial enhanced oil recovery (MEOR) in heavy crude oil production. The aqueous phase of produced fluid has long been considered an ideal source of microorganisms for MEOR. However, it is recently found that rich microorganisms (including hydrocarbon-degrading bacteria) are present in the crude oil phase, which is completely different from the aqueous phase of produced fluid. So, in this study, the microbial consortia from the crude oil phase of produced fluids derived from four wells were enriched, respectively. The microbial community structure during passage was dynamically tracked, and the response of enriched consortia to successive disturbance of environmental factors was investigated. The results showed the crude oil phase had high microbial diversity, and the original microbial community structure from four wells was significantly different. After ten generations of consecutive enrichment, different genera were observed in the four enriched microbial consortia, namely, Geobacillus, Bacillus, Brevibacillus, Chelativorans, Ureibacillus, and Ornithinicoccus. In addition, two enriched consortia (eG1614 and eP30) exhibited robustness to temperature and oxygen perturbations. These results further suggested that the crude oil phase of produced fluids can serve as a potential microbial source for MEOR.

Mercury (Hg) is a toxic heavy-metal element, which can be enriched in fauna and flora and transformed into methylmercury (MeHg). MeHg is a widely distributed environmental pollutant that may be harmful to fish-eating populations through enrichment of aquatic food chains. The central nervous system is a primary target of MeHg. Embryos and infants are more sensitive to MeHg, and exposure to MeHg during gestational feeding can significantly impair the homeostasis of offspring, leading to long-term neurodevelopmental defects. At present, MeHg-induced neurodevelopmental toxicity has become a hotspot in the field of neurotoxicology, but its mechanisms are not fully understood. Some evidence point to oxidative damage, excitotoxicity, calcium ion imbalance, mitochondrial dysfunction, epigenetic changes, and other molecular mechanisms that play important roles in MeHg-induced neurodevelopmental toxicity. In this review, advances in the study of neurodevelopmental toxicity of MeHg exposure during pregnancy and the molecular mechanisms of related pathways are summarized, in order to provide more scientific basis for the study of neurodevelopmental toxicity of MeHg.

•Methylmercury can induces neurodevelopmental toxicity.•Oxidative stress plays important roles in methylmercury neurodevelopmental toxicity.•Notch1, PI3K, and PKC pathways may be regulated by oxidative stress.•Natural antioxidants may attenuate methylmercury neurodevelopmental toxicity.

Three cross-linked porphyrin-based polyimides (PPBPI-H-CR, PPBPI-Mn-CR, and PPBPI-Fe-CR) were synthesized from 5,10,15,20-tetra(4-aminophenyl)porphyrin (TAPP) and 2,5-bis(3,4-dicarboxyphenoxy)-4′-phenylethynyl-biphenyl dianhydride (PEPHQDA) via polymerization and thermal cross-linking reactions. Their chemical structures were confirmed by FTIR and 13C CP/MAS NMR. SEM, XRD, and TEM analyses were used to observe their surface and nature characteristic morphologies as well as pore channels. DSC and TGA were carried out to confirm their cross-linking behaviors and thermal stabilities. PPBPI-H-CR showed the largest specific surface area (733 m2g–1) and the highest CO2uptake (2.26 mmol g–1at 273 K and 1 bar) among the PPBPI-CRs. PPBPI-Mn-CR and PPBPI-Fe-CR compared to PPBPI-H-CR exhibited smaller specific surface areas, more uniform pore sizes around 1.2 nm, and larger isosteric heats of adsorption due to the presence of coordination sites for manganese and iron. PPBPI-CRs exhibited separation factors of CO2/N2(31.48, 35.09, and 45.34) and CO2/CH4(13.17, 9.06, and 12.99).

The HgCdTe layers (x_Cd∼0.285 and 0.225) were grown by molecular beam epitaxy and liquid phase epitaxy, respectively, followed by the deposition of CdTe and ZnS films as barrier layers by thermal evaporation. Then, the p-on-n photodiodes were fabricated by AS ion implantation, Hg overpressure annealing, passivation, and metallization. The secondary ion mass spectrometry and transmission electron microscopy results indicate that the evaporated CdTe layer with a column structure induces the channeling effect of As ion implantation causing the device performance degradation. This effect could be suppressed by depositing a CdTe film with a layered structure through E-beam evaporation. Finally, the current–voltage (I–V) and capacitance–voltage (C–V) characteristics of these p–n junctions were estimated and analyzed.

The Zn 1− x Mg x Se alloys for x up to 0.72 have been grown on GaAs(0 0 1) substrates by molecular beam epitaxy. For Zn-rich samples, the pure zincblende (0 0 1) structure is obtained. For Mg-rich films, however, both (1 1 1) and (0 0 1) domains coexist with the former having a lower x value as compared to the latter. Despite its very low content, the (1 1 1) domain has a profound contribution to the optical spectra, suggesting that the (1 1 1) structure is more stable and has higher crystal quality in the Mg-rich films when grown on GaAs(0 0 1) substrates. The measured infrared reflection and photoluminescence spectra can only be understood well when the different structural phases in the films are properly considered.

The power of the frequency domain causality test proposed by Breitung and Candelon (2006) is analyzed. We show that the power of the test is closely related to the root of the VAR model. When the root of the VAR model is near 1 or − 1 , the test may have a maximal power at the frequencies close to 0 or π. [ABSTRACT FROM AUTHOR]

Dislocation cell structures in CdZnTe substrates and its behavior of threading into HgCdTe LPE epilayers were studied. A kind of dislocation cell structure of which dislocations linearly pile up to three <1 1 0> orientations on the (1 1 1) B face of CdZnTe crystal was found. The formation of this cell structure can be demonstrated by the enrichment of the dislocations through slip during the growth or cooling process. By comparing the dislocation densities and distributions of HgCdTe LPE epilayers with it of CdZnTe substrates at the constant region using an optical microscopy system, the behavior of cell structures of CdZnTe substrates threading into HgCdTe LPE epilayers were also discussed. The results show that the stored dislocation densities at the dislocation walls can significantly affect the behavior of dislocation cell structures threading into HgCdTe LPE epilayers. Dislocation cell structures of which dislocation walls have higher stored dislocation densities can appear in constant region of HgCdTe epilayers. But the dislocations of HgCdTe epilayers growth on CdZnTe substrate with lower stored dislocation densities at the dislocation walls are almost uniformly distributed.