Design and Optimization of Thermal Field for PVT Method 8-Inch SiC Crystal Growth.

As a wide bandgap semiconductor material, silicon carbide has promising prospects for application. However, its commercial production size is currently 6 inches, and the difficulty in preparing larger single crystals increases exponentially with size increasing. Large-size single crystal growth is faced with the enormous problem of radial growth conditions deteriorating. Based on simulation tools, the physical field of 8-inch crystal growth is modeled and studied. By introducing the design of the seed cavity, the radial temperature difference in the seed crystal surface is reduced by 88% from 93 K of a basic scheme to 11 K, and the thermal field conditions with uniform radial temperature and moderate temperature gradient are obtained. Meanwhile, the effects of different processing conditions and relative positions of key structures on the surface temperature and axial temperature gradients of the seed crystals are analyzed in terms of new thermal field design, including induction power, frequency, diameter and height of coils, the distance between raw materials and the seed crystal. Meanwhiles, better process conditions and relative positions under experimental conditions are obtained. Based on the optimized conditions, the thermal field verification under seedless conditions is carried out, discovering that the single crystal deposition rate is 90% of that of polycrystalline deposition under the experimental conditions. Meanwhile, an 8-inch polycrystalline with 9.6 mm uniform deposition was successfully obtained after 120 h crystal growth, whose convexity is reduced from 13 mm to 6.4 mm compared with the original scheme. The results indicate that the optimized conditions can be used for single-crystal growth.

High-Dose Acetaminophen Alters the Integrity of the Blood-Brain Barrier and Leads to Increased CNS Uptake of Codeine in Rats.

The consumption of acetaminophen (APAP) can induce neurological changes in human subjects; however, effects of APAP on blood-brain barrier (BBB) integrity are unknown. BBB changes by APAP can have profound consequences for brain delivery of co-administered drugs. To study APAP effects, female Sprague-Dawley rats (12-16 weeks old) were administered vehicle (i.e., 100% dimethyl sulfoxide (DMSO), intraperitoneally (i.p.)) or APAP (80 mg/kg or 500 mg/kg in DMSO, i.p.; equivalent to a 900 mg or 5600 mg daily dose for a 70 kg human subject). BBB permeability was measured via in situ brain perfusion using [14C]sucrose and [3H]codeine, an opioid analgesic drug that is co-administered with APAP (i.e., Tylenol #3). Localization and protein expression of tight junction proteins (i.e., claudin-5, occludin, ZO-1) were studied in rat brain microvessels using Western blot analysis and confocal microscopy, respectively. Paracellular [14C]sucrose "leak" and brain [3H]codeine accumulation were significantly enhanced in rats treated with 500 mg/kg APAP only. Additionally, claudin-5 localization and protein expression were altered in brain microvessels isolated from rats administered 500 mg/kg APAP. Our novel and translational data show that BBB integrity is altered following a single high APAP dose, results that are relevant to patients abusing or misusing APAP and/or APAP/opioid combination products.

Structure, Function, and Regulation of the Blood-Brain Barrier Tight Junction in Central Nervous System Disorders.

The blood-brain barrier (BBB) allows the brain to selectively import nutrients and energy critical to neuronal function while simultaneously excluding neurotoxic substances from the peripheral circulation. In contrast to the highly permeable vasculature present in most organs that reside outside of the central nervous system (CNS), the BBB exhibits a high transendothelial electrical resistance (TEER) along with a low rate of transcytosis and greatly restricted paracellular permeability. The property of low paracellular permeability is controlled by tight junction (TJ) protein complexes that seal the paracellular route between apposing brain microvascular endothelial cells. Although tight junction protein complexes are principal contributors to physical barrier properties, they are not static in nature. Rather, tight junction protein complexes are highly dynamic structures, where expression and/or localization of individual constituent proteins can be modified in response to pathophysiological stressors. These stressors induce modifications to tight junction protein complexes that involve de novo synthesis of new protein or discrete trafficking mechanisms. Such responsiveness of BBB tight junctions to diseases indicates that these protein complexes are critical for maintenance of CNS homeostasis. In fulfillment of this vital role, BBB tight junctions are also a major obstacle to therapeutic drug delivery to the brain. There is an opportunity to overcome this substantial obstacle and optimize neuropharmacology via acquisition of a detailed understanding of BBB tight junction structure, function, and regulation. In this review, we discuss physiological characteristics of tight junction protein complexes and how these properties regulate delivery of therapeutics to the CNS for treatment of neurological diseases. Specifically, we will discuss modulation of tight junction structure, function, and regulation both in the context of disease states and in the setting of pharmacotherapy. In particular, we will highlight how these properties can be potentially manipulated at the molecular level to increase CNS drug levels via paracellular transport to the brain.

Modulation of Opioid Transport at the Blood-Brain Barrier by Altered ATP-Binding Cassette (ABC) Transporter Expression and Activity.

Opioids are highly effective analgesics that have a serious potential for adverse drug reactions and for development of addiction and tolerance. Since the use of opioids has escalated in recent years, it is increasingly important to understand biological mechanisms that can increase the probability of opioid-associated adverse events occurring in patient populations. This is emphasized by the current opioid epidemic in the United States where opioid analgesics are frequently abused and misused. It has been established that the effectiveness of opioids is maximized when these drugs readily access opioid receptors in the central nervous system (CNS). Indeed, opioid delivery to the brain is significantly influenced by the blood-brain barrier (BBB). In particular, ATP-binding cassette (ABC) transporters that are endogenously expressed at the BBB are critical determinants of CNS opioid penetration. In this review, we will discuss current knowledge on the transport of opioid analgesic drugs by ABC transporters at the BBB. We will also examine how expression and trafficking of ABC transporters can be modified by pain and/or opioid pharmacotherapy, a novel mechanism that can promote opioid-associated adverse drug events and development of addiction and tolerance.

Transcriptome profiling reveals specific patterns of paclitaxel synthesis in a new Taxus yunnanensis cultivar.

The difference in contents of paclitaxel and 10-deacetylbaccatin III (10-DABIII) in needles between wildtype (WT) and a new cultivar (Zhongdayihao, ZD1) of Taxus yunnanensis was examined. Transcriptome profiling was conducted for different tissues of the ZD1 and WT to illustrate the regulation mechanism of paclitaxel biosynthesis. It was observed that average contents of paclitaxel and 10-DABIII in ZD1 were 4 folds and 32 folds higher than those in WT, respectively. More significant elevations of differential expressed genes (DEGs) from paclitaxel biosynthesis pathway were revealed in ZD1 rather than WT, which should be responsible for the higher contents of paclitaxel and 10-DABIII in the ZD1. Special tissues-dependent expression patterns of paclitaxel biosynthesis DEGs in ZD1 compared to WT were unraveled. The relative higher expressions of paclitaxel biosynthesis genes in needles than other tissues supported the higher content of paclitaxel and 10-DABIII content in needles of ZD1. Attenuation of plant hormone signal transduction pathway led to the lower expression of TFs in ZD1 rather than WT. Besides, the significant negative correlations between differential expressed TFs and DEGs from paclitaxel biosynthesis pathway displayed a possibly negative regulation pattern of these TFs on paclitaxel biosynthesis pathway genes. These results provided new insights into the molecular process of paclitaxel synthesis in Taxus.

Effects of phosphorus on chemical forms of Cd in plants of four spinach (Spinacia oleracea L.) cultivars differing in Cd accumulation.

In order to clarify how cadmium (Cd) chemical forms in planta relate to the genotype difference in Cd accumulation of spinach (Spinacia oleracea L.), two low-Cd and two high-Cd cultivars were compared under a hydroponic experiment with two concentrations of Cd (8.98 or 44.71 µmol Cd L(-1)). The concentrations of phosphorus in the hydroponic system were also adjusted to two levels (0.5 and 1.0 mmol L(-1)) to investigate the influence of phosphorus on the forms and accumulation of Cd in the tested cultivars. Average Cd concentrations in shoots were 8.50-10.06 mg kg(-1) for high-Cd cultivars and 6.11-6.64 mg kg(-1) for low-Cd cultivars a under lower Cd treatment and were as high as 24.41-31.35 mg kg(-1) and 19.65-25.76 mg kg(-1), respectively, under a higher treatment. Phosphorus significantly decreased Cd accumulation in the tested cultivars, and the effect had superiority over the cultivar alternation under higher Cd stress. Cadmium in the NaCl-extractable fraction of the plant tissues showed the greatest relationship to genotype difference of Cd accumulation. The difference in the capacity to binding Cd into F HAc, F HCl, or F Residue was another important mechanism involving in the genotype difference in Cd accumulation of spinach. Among them, average proportion of Cd in F HAc in low-Cd cultivars was higher than that in high-Cd cultivars in association with the effect of phosphorus.

Occurrence of organophosphorus flame retardants in indoor dust in multiple microenvironments of southern China and implications for human exposure.

Organophosphorus flame retardants (OPFRs) are important alternatives to brominated flame retardants (BFRs), but information on their contamination of the environment in China is rare. We examined the occurrence of 12 OPFRs in indoor dust in four microenvironments of southern China, including a rural electronic waste (e-waste) recycling area, a rural non-e-waste area, urban homes, and urban college dormitory rooms. The OPFR concentrations (with a median of 25.0 µg g(-1)) were highest in the e-waste area, and the concentrations in other three areas were lower and comparable (7.48-11.0 µg g(-1)). The levels of OPFRs in the present study were generally relatively lower than the levels of OPFRs found in Europe, Canada, and Japan because BFRs are still widely used as the major FRs in China. The composition profile of OPFRs in the e-waste area was dominated by tricresyl phosphate (TCP) (accounting for 40.7%, on average), while tris(2-chloroethyl) phosphate (TCEP) was the most abundant OPFR (64.4%) in the urban areas (homes and college dormitories). These two distribution patterns represent two OPFR sources (i.e., emissions from past e-waste and from current household products and building materials). The difference in the OPFR profiles in the rural area relative to the OPFR profiles in the urban and e-waste areas suggests that the occurrence of OPFRs is due mainly to emissions from characteristic household products in rural homes. Although human exposures to all the OPFRs were under the reference doses, the health risk for residents in the e-waste area is a concern, considering the poor sanitary conditions in this area and exposure from other sources.

Preparation and dehydrogenation properties of lithium hydrazidobis(borane) (LiNH(BH3)NH2BH3).

LiNH(BH3)NH2BH3, the first example of metal-substituted hydrazine bisborane (HBB), is synthesized via the reaction between HBB and n-butyllithium in ether solution. (11)B NMR and Fourier transform infrared spectroscopy indicate a new structure, in which one of the N-H bonds is replaced by a N-Li bond. The X-ray diffraction pattern of the product also indicates the formation of a new crystal structure. This compound releases hydrogen at 126 and 170 °C with satisfactory purity and exhibits superior hydrogen storage properties compared with HBB. Differential scanning calorimetry measurement suggests the dehydrogenation reaction of this compound is less exothermic than that of HBB.

Dechlorane Plus in serum from e-waste recycling workers: influence of gender and potential isomer-specific metabolism.

Dechlorane Plus (DP) and its dechlorinated product, anti-Cl11-DP, were measured in serum of 70 occupationally exposed workers in an e-waste recycling region and 13 residents of an urban area in South China. The DP levels were significantly higher in the workers (22-2200 ng/g with median of 150 ng/g lipid) than in the urban residents (2.7-91 ng/g with median of 4.6 ng/g lipid). The DP concentrations in females were found to be associated with their age but such relation was not found for males. Significant differences in DP levels and DP isomer composition were found between genders. The females had remarkably higher DP levels and f(anti) values (fraction of anti-DP to total DPs) in serum than the males. Anti-Cl11-DP was significantly correlated with anti-DP for both genders but with different slope of regression line. The ratios of anti-Cl11-DP to anti-DP (mean of 0.017) in males were significantly higher than those (mean of 0.010) in females. Combining with the lower f(anti) values in males, it is likely that males have higher metabolic potential for DPs than females which resulted in the lower DP loading in serum. However, the different patterns of selective uptake and/or excretion of different compounds between genders cannot be eliminated as a possible reason for the observed gender differences. This study is the first to report on the gender difference in DP accumulation in human, and its mechanism is worth further investigation.

Promising hydrogen storage properties and potential applications of Mg-Al-Pd trilayer films under mild conditions.

We prepared a series of nano-sized Mg-Al-Pd trilayer films and investigated their hydrogen storage properties under mild conditions. Results showed that Al 1 nm sample had the best absorption kinetics and excellent optical properties at room temperature, making it a promising candidate for hydrogen sensors and smart windows.

Superior (de)hydrogenation properties of Mg-Ti-Pd trilayer films at room temperature.

In this paper, a series of Mg-Ti-Pd trilayer films with various thicknesses of the Ti interlayer were prepared by magnetron sputtering. The trilayer films could be reversibly (de)hydrogenated at room temperature. The relationship between structure and properties of Mg-Ti-Pd trilayer films was comprehensively investigated. Our studies showed that the hydrogen storage properties of Mg-Pd films were significantly improved with the addition of a Ti interlayer. The optimal hydrogenation properties were obtained when the Ti interlayer was 1 nm. The superior hydrogenation properties achieved by introduction of the Ti interlayer could be attributed to several aspects: prevention of Mg-Pd alloying; catalytic dissociation of H(2) molecules and provision of heterogeneous nucleation sites. These results were elucidative for the development of high performance intermetallic hydrogen storage materials and thin film based functional devices.

In situ hybridization of LiNH2-LiH-Mg(BH4)2 nano-composites: intermediate and optimized hydrogenation properties.

Nano-composites of LiNH(2)-LiH-xMg(BH(4))(2) (0 ≤ x ≤ 2) were prepared by plasma metal reaction followed by a nucleation growth method. Highly reactive LiNH(2)-LiH hollow nanoparticles offered a favorable nucleus during a precipitation process of liquid Mg(BH(4))(2)·OEt(2). The electron microscopy results suggested that more than 90% of the obtained nano-composites were in the range 200-400 nm. Because of the short diffusion distance and ternary mixture self-catalyzing effect, this material possesses enhanced hydrogen (de)sorption attributes, including facile low-temperature kinetics, impure gases attenuation and partial reversibility. The optimal hydrogen storage properties were found at the composition of LiNH(2)-LiH-0.5Mg(BH(4))(2), which was tentatively attributed to a Li(4)(NH(2))(2)(BH(4))(2) intermediate. 5.3 wt% hydrogen desorption could be recorded at 150 °C, with the first 2.2 wt% release being reversible. This work suggests that controlled in situ hybridization combined with formula optimization can improve hydrogen storage properties.

Low-temperature mass production of superconducting MgB2 nanofibers from Mg(BH4)2 decomposition and recombination.

Massive superconducting MgB(2) nanofibers are obtained for the first time from Mg(BH(4))(2). The technique optimizes reaction conditions to only 1 h at 460 °C and provides nanofibers which exhibited satisfying superconducting properties. The morphology transformation according to temperature changes and the special mechanism of precursor inductive synthesis are discussed.