Interfacial Chemical Effects of Amorphous Zinc Oxide/Graphene

Research on the preparation and performance of graphene composite materials has become a hotspot due to the excellent electrical and mechanical properties of graphene. Among such composite materials, zinc oxide/graphene (ZnO/graphene) composite films are an active research topic. Therefore, in this study, we used the vacuum thermal evaporation technique at different evaporation voltages to fabricate an amorphous ZnO/graphene composite film on a flexible polyethylene terephthalate (PET). The amorphous ZnO/graphene composite film inherited the great transparency of the graphene within the visible spectrum. Moreover, its electrical properties were better than those of pure ZnO but less than those of graphene, which is not consistent with the original theoretical research (wherein the performance of the composite films was better than that of ZnO film and slightly lower than that of graphene). For example, the bulk free charge carrier concentrations of the composite films (0.13, 1.36, and 0.47 × 1018 cm−3 corresponding to composite films with thicknesses of 40, 75, and 160 nm) were remarkably lower than that of the bare graphene (964 × 1018 cm−3) and better than that of the ZnO (0.10 × 1018 cm−3). The underlying mechanism for the abnormal electrical performance was further demonstrated by X-ray photoelectron spectroscopy (XPS) detection and first-principles calculations. The analysis found that chemical bonds were formed between the oxide (O) of amorphous ZnO and the carbon (C) of graphene and that the transfer of the π electrons was restricted by C=O and C-O-C bonds. Given the above, this study further clarifies the mechanism affecting the photoelectric properties of amorphous composite films

Fluorine ion induced phase evolution of tin-based perovskite thin films: structure and properties

To study the effect of fluorine ions on the phase transformation of a tin-based perovskite, CsSnI3 x(F)x films were deposited by using thermal vacuum evaporation from a mixed powder of SnI2, SnF2 and CsI, followed by rapid vacuum annealing. The color evolution, structure, and properties of CsSnI3 xFx films aged in air were observed and analyzed. The results showed that the colors of the films changed from black to yellow, and finally presented as black again over time; the unstable B-g-CsSnI3 xFx phase transformed into the Y-CsSnI3 xFx phase, which is then recombined into the Cs2SnI6 xFx phase with the generation of SnO2 in air. Fluorine dopant inhibited the oxidation process. The postponement of the phase transformation is due to the stronger bonds between F and Sn than that between I and Sn. The color changing process of the CsSnI3 xFx films slowed that the hole concentrations increased and the resistivities decreased with the increase of the F dopant ratio. With the addition of SnF2, light harvesting within the visible light region was significantly enhanced. Comparison of the optical and electrical properties of the fresh annealed CsSnI3 xFx films showed that the band gaps of the aged films widened, the hole concentrations kept the same order, the hole mobilities reduced and therefore, the resistivities increased. The double layer Cs2SnI6 xFx phase also showed ‘p’ type semi-conductor properties, which might be due to the incomplete transition of Sn2+ to Sn4+, i.e. Sn2+ provides holes as the acceptor

Protection effect of kallistatin on carbon tetrachloride-induced liver fibrosis in rats via antioxidative stress.

Prolonged inflammation and oxidative stress are emerging as key causes of pathological wound healing and the development of liver fibrosis. We have investigated the effects of recombinant human kallistatin, produced in Pichia. pastoris, on preventing carbon tetrachloride (CCl4)-induced liver fibrosis in rats. Daily administration of kallistatin prevented development of CCl4-induced liver fibrosis, which was evidenced by histological study. In all kallistatin treated rats, activation of hepatic stellate cells (HSC) as assessed by s-smooth muscle actin staining was attenuated, TGF- β1 expression was inhibited, class I serum biomarkers associated with the process of fibrogenesis, such as hyaluronic acid, laminin, and procollagen III, were lowered, compared with that in the model control group. Furthermore, residual hepatic functional reserve was improved by kallistatin treatment. CCl4 induced elevation of malondialdehyde level and reduced superoxide dismutase activity in the liver, while kallistatin reduced these oxidative parameters. We also investigated the effects of kallistatin on rat primary HSC and LX-2, the human HSC cell line. Kallistatin scavenged H2O2-induced ROS in the LX-2 cells, and suppressed the activation of primary HSC. These results suggest recombinant human kallistatin might be a promising drug candidate for therapeutic intervention of liver fibrosis

Experimental and numerical studies on the influence of centrifugal casting parameters on the solidification structure of Al-Cu alloy

A horizontal centrifugal casting experiment was designed to determine the change in the solidification structure of Al-Cu alloy casting and the underlying variation in temperature, then obtained interface heat transfer coefficient by inverse calculation. The continuous simulation of metal melt filling from the gate to copper mold cavity is realized. The influence of centrifugal speed, pouring temperature, and mold preheating temperature on the solidified structure was analyzed. Simulation results showed that increasing the centrifugal speed mainly enhance the solidification rate of the molten metal and then refined the solidified structure of the Al-Cu alloy. Increasing the pouring temperature and mold preheating temperatures coarsen the grain size of the casting, but the range of change is small

Surgical site infections after elective craniotomy for brain tumor: a study on potential risk factors and related treatments

Abstract Background Surgical site infection (SSI) is a common complication following craniotomy that increases morbidity, mortality, and medical expenses. The objectives of this study were to determine the relevant risk factors associated with SSI after elective craniotomy for brain tumor and analyse the treatments for SSI. Methods A retrospective nested case‒control study was conducted using data from patients who underwent craniotomy for brain tumor resection at the Neurosurgical Oncology Department No. 6 of Beijing Tiantan Hospital, Capital Medical University, between January 2019 and December 2021. Risk factors for SSI were determined using multivariate logistic regression analysis. We analyzed microbiological and related treatment data for different SSI types. Results Among 2061 patients who underwent craniotomy for brain tumor, 31 had SSI (1.50%). In the multivariate logistic regression analysis, body mass index (BMI) and operative duration were identified as independent risk factors for SSI. The most common microorganism isolated from SSIs was Staphylococcus epidermidis (22.9%), and drug sensitivity results showed that gram-positive bacteria were sensitive to linezolid, vancomycin and tigecycline, whereas gram-negative bacteria were sensitive to meropenem, cefepime and ceftazidime. Six of the seven patients who underwent bone flap removal due to osteomyelitis were infected with gram-negative bacteria. Conclusions BMI and operative duration were identified as independent risk factors for SSI. Diabetes mellitus, previous ratio therapy, type of incision, recurrence tumor and other risk factors were not found to be associated with the occurrence of SSI in this study

Porous Ni-Cr-Mo-Cu alloys fabricated by elemental powder reactive synthesis

Fabrication of porous Ni-Cr-Mo-Cu alloys is available through Ni, Cr, Mo and Cu elemental powder reactive synthesis at the sintering temperature of 1150 °C. The pore structures, including swelling behavior, open porosity, pore size and viscous permeability of the porous Ni-Cr-Mo-Cu alloys are systematically investigated. The results revealed that the parameters of pore structure firstly increased, and then decreased with the increase of the sintering temperature. When the sintering temperature rose to 1000 °C, the volume expansion, open porosity and viscous permeability of porous Ni-Cr-Mo-Cu alloys reached the peak value of 8.0%, 41.6% and 17.2 μ m ^2 , respectively. In addition, it was confirmed that the pore structure evolution was based on three stages, that is, in the low temperature section before stearic acid decomposition, the formation of pores was initiated by the volatilization of pore-forming agent and the interstitial pores of green compact; when the temperature was lower than 1083 °C, the increase of open porosity was mainly due to the Kirkendall effect caused by solid partial diffusion; while, when the temperature is within the range of 1083 ∼ 1150 °C, the shrinkage behavior at high temperature and a small amount of metal solution formed by the unreacted Cu led to decrease in pore structure parameters

Effects of Cr content on the corrosion behavior of porous Ni–Cr–Mo–Cu alloys in H3PO4 solution

Porous Ni–Cr–Mo–Cu alloys were prepared via reaction synthesis of mixed powders. Electrochemical performance test and weight-loss method were used to evaluate the effects of chromium content in the range of 10 ∼ 30 wt% on the alloys corrosion performance in 30 wt% H _3 PO _4 solution. The microstructure, element valence and phase composition of the porous Ni–Cr–Mo–Cu alloys were characterized via scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and x-ray diffraction analysis (XRD), respectively. And the results show that the alloys exhibited serviceable corrosion performance and the corrosion behavior was better than that of pure Ni and Cu. Incremental changes in the chromium contents within a certain range enhanced the corrosion resistance of the alloys. These alloys with 30 wt% chromium exhibited excellent anti-corrosion ability in the H _3 PO _4 solution. The electrochemical test displayed that the double capacitive loops of the alloys in the H _3 PO _4 solution increased with the chromium content; at chromium content of 30 wt%, the charge transfer resistance and activation energy were 1123 Ω and 74.10 kJ mol ^−1 , respectively. The possible corrosion-inhibition mechanism was examined by XPS, which may be owing to the formation of MoO _x (x = 1, 2, 3) and Cr _2 O _3 passivation layers in the H _3 PO _4 solution, which prevent further corrosion in acid environments

Effects of kallistatin on serum AST, ALT and Albumin in CCl₄-induced liver fibrosis rats (n = 8).

<p>The results are showed as mean±SD.</p>##<p><i>p</i><0.01 <i>vs.</i> negative control;</p><p>*<i>p</i><0.05 <i>vs.</i> model control;</p><p>**<i>p</i><0.01 <i>vs.</i> model control.</p

Effects of kallistatin on MDA and SOD in CCl₄-induced liver fibrosis rats (n = 8).

<p>The results are showed as the mean±SD (n = 8).</p>##<p><i>p</i><0.01 <i>vs.</i> negative control;</p><p>*<i>p</i><0.05 <i>vs.</i> model control group;</p><p>**<i>p</i><0.01 <i>vs.</i> model control group.</p