氧气含量对射频磁控溅射方法制备的NiO∶Cu/ZnO异质pn结的光电性能的影响

利用磁控溅射方法改变氧气含量制备了一系列NiO∶Cu/ZnO异质pn结。实验结果表明,氧含量对NiO∶Cu/ZnO异质pn结电学影响很大。相对于纯氩溅射,引入一定氧气(O2/(Ar+O2)比例为30%)后,NiO∶Cu/ZnO异质pn结的整流特性明显得到改善。与此同时,NiO∶Cu/ZnO异质pn结的光透过率也从40%增大到80%。这可能是由于氧气的轻量引入致使NiO∶Cu/ZnO异质pn结的结晶得到改善,薄膜内缺陷减少所致。进一步提高氧气含量,直到O2/(Ar+O2)比例至80%后,异质结的整流特性有所削弱,这可能是由于过多氧气的引入造成薄膜缺陷再次增多,进而影响到异质结的整流特性。这一结论得到了EDS、XRD、AFM和UV结果的支持。     

Millisecond kinetics of nanocrystal cation exchange using microfluidic X-ray absorption spectroscopy

We describe the use of a flow-focusing microfluidic reactor to measure the kinetics of the CdSe-to-Ag2Se nanocrystal cation exchange reaction using micro-X-ray absorption spectroscopy (microXAS). The small microreactor dimensions facilitate the millisecond mixing of CdSe nanocrystals and Ag+ reactant solutions, and the transposition of the reaction time onto spatial coordinates enables the in situ observation of the millisecond reaction using microXAS. Selenium K-edge absorption spectra show the progression of CdSe nanocrystals to Ag2Se over the course of 100 ms without the presence of long-lived intermediates. These results, along with supporting stopped-flow absorption experiments, suggest that this nanocrystal cation exchange reaction is highly efficient and provide insight into how the reaction progresses in individual particles. This experiment illustrates the value and potential of in situ microfluidic X-ray synchrotron techniques for detailed studies of the millisecond structural transformations of nanoparticles and other solution-phase reactions in which diffusive mixing initiates changes in local bond structures or oxidation states.     

Structural, vibrational and ab initio studies of L-histidine oxalate

Single crystals of L-histidine oxalate were obtained by slow evaporation of an aqueous solution at room temperature. The grown crystals have been subjected to X-ray diffraction (XRD), Infrared, and Raman spectroscopy. The title compound crystallises in the non-centrosymmetric space group P2(1)2(1)2(1,) the crystal cohesion is achieved by relatively strong hydrogen bonds, so that the NH3 groups show significant distortion with respect to the tetrahedral symmetry. Raman and infrared spectra of the title compound were recorded in the frequency range 300-3200 and 400-4000 cm-1, respectively. To obtain a reliable assignment of the observed spectral lines, we have calculated the geometry and the frequencies of the vibrational modes of histidine cation and the oxalate anion using the semi empirical PM3 method.     

Synthesis of bis‐pyrrole tetra esters and alcohols as novel mimetics of the anticancer mitomycin

Open‐chain bis‐Reissert compounds 1 were converted to the corresponding bis‐oxazolium intermediates via acid‐catalyzed intramolecular cyclization. These oxazolium compounds exist in a variety of tautomeric structures in which the meso‐ionic form can be intercepted by reaction with dipolarophiles in a 1,3‐dipolar‐cycloaddition reaction to produce a variety of highly functionalized bis‐pyrrole esters 2 . In turn, the bis‐pyrrole esters could be converted to the corresponding bis‐pyrrole tetrols 3 in high yields. J. Heterocyclic Chem., 2011.     

Direct sampling and analysis from solid-phase extraction cards using an automated liquid extraction surface analysis nanoelectrospray mass spectrometry system

Direct liquid extraction based surface sampling, a technique previously demonstrated with continuous flow and autonomous pipette liquid microjunction surface sampling probes, has recently been implemented as a liquid extraction surface analysis (LESA) mode on a commercially available chip‐based infusion nanoelectrospray ionization (nanoESI) system. In the present paper, the LESA mode was applied to the analysis of 96‐well format custom‐made solid‐phase extraction (SPE) cards, with each well consisting of either a 1 or a 2 mm diameter monolithic hydrophobic stationary phase. These substrate wells were conditioned, loaded with either single or multi‐component aqueous mixtures, and read out using the commercial nanoESI system coupled to a hybrid triple quadrupole/linear ion trap mass spectrometer or a linear ion trap mass spectrometer. The extraction conditions, including extraction/nanoESI solvent composition, volume, and dwell times, were optimized in the analysis of targeted compounds. Limit of detection and quantitation as well as analysis reproducibility figures of merit were measured. Calibration data was obtained for propranolol using a deuterated internal standard which demonstrated linearity and reproducibility. A 10× increase in signal and cleanup of micromolar angiotensin II from a concentrated salt solution was demonstrated. In addition, a multicomponent herbicide mixture at ppb concentration levels was analyzed using MS³ spectra for compound identification in the presence of isobaric interferences. Published in 2011 by John Wiley & Sons, Ltd.     

HNF4α Antagonists Discovered by a High-Throughput Screen for Modulators of the Human Insulin Promoter

Hepatocyte nuclear factor (HNF)4α is a central regulator of gene expression in cell types that play a critical role in metabolic homeostasis, including hepatocytes, enterocytes, and pancreatic β cells. Although fatty acids were found to occupy the HNF4α ligand-binding pocket and were proposed to act as ligands, there is controversy about both the nature of HNF4α ligands as well as the physiological role of the binding.?Here, we report the discovery of potent synthetic HNF4α antagonists through a high-throughput screen for effectors of the human insulin promoter. These molecules bound to HNF4α with high affinity and modulated the expression of known HNF4α target genes. Notably, they were found to be selectively cytotoxic to cancer cell lines in?vitro and in?vivo, although in?vivo potency was limited by suboptimal pharmacokinetic properties. The discovery of bioactive modulators for HNF4α raises the possibility that diseases involving HNF4α, such as diabetes and cancer, might be amenable to pharmacologic intervention by modulation of HNF4α activity.     

A single-step, mild, neutral, catalyst-free method for cyanohydrin synthesis

Abstract  

A wide variety of carbonyl compounds can be transformed to their corresponding cyanohydrins in a single step using a dimethyl sulfoxide (DMSO)–water system in excellent yields (75–94%). The major advantages of this system are that the reaction conditions are mild and neutral; the reaction proceeds without catalyst and gives the corresponding cyanohydrins in short time (15–120 min).     

Stability indicating HPLC method for the simultaneous determination of moxifloxacin and prednisolone in pharmaceutical formulations

Background

Obtaining new pharmaceutical materials with enhanced properties by using natural compounds and environment-friendly methods is a continuous goal for scientists. Ficaria verna Huds. is a widespread perennial plant with applications in the treat of haemorrhoids and to cure piles; it has also anti-inflammatory, astringent, and antibiotic properties. The goal of the present study is the obtaining and characterization of new F. verna extract/??-cyclodextrin complexes by using only natural compounds, solvents, and environment-friendly methods in order to increase the quality and acceptability versus toxicity indicator. Thus, the flavonoid content (as quercetin) of Ficaria verna Huds. flowers and leaves from the West side of Romania was determined and correlated with their antioxidant activity. Further, the possibility of obtaining ??-cyclodextrin supramolecular systems was studied.

Results

F. verna flowers and leaves extracts were obtained by semi-continuous solid-liquid extraction. The raw concentrated extract was spectrophotometrically analyzed in order to quantify the flavonoids from plant parts and to evaluate the antioxidant activity of these extracts. The F. verna extracts were used for obtaining ??-cyclodextrin complexes; these were analyzed by scanning electron microscopy and Karl Fischer water titration; spectrophotometry was used in order to quantifying the flavonoids and evaluates the antioxidant activity. A higher concentration of flavonoids of 0.5% was determined in complexes obtained by crystallisation method, while only a half of this value was calculated for kneading method. The antioxidant activity of these complexes was correlated with the flavonoid content and this parameter reveals possible controlled release properties.

Conclusions

The flavonoid content of F. verna Huds. from the West side of Romania (Banat county) is approximately the same in flowers and leaves, being situated at a medium value among other studies. ??-Cyclodextrin complexes of F. verna extracts are obtained with lower yields by crystallisation than kneading methods, but the flavonoids (as quercetin) are better encapsulated in the first case most probably due to the possibility to attain the host-guest equilibrium in the slower crystallisation process. F. verna extracts and their ??-cyclodextrin complexes have antioxidant activity even at very low concentrations and could be used in proper and valuable pharmaceutical formulations with enhanced bioactivity.     

Effects of mass transfer on MHD second grade fluid towards stretching cylinder: A novel perspective of Cattaneo–Christov heat flux model

The aim of this research is to analyze the effects of mass transfer on second grade fluid flow subjected to the heat transfer incorporated with the relaxation time to reach the state of equilibrium on or after the state of upheaval. A new heat model namely Cattaneo–Christov heat flux comprising the relaxation time is employed instead of very commonly used mundane model based on classical theory of heat flux. Flow is considered towards stretching cylinder in the existence of external magnetic field. Suitable transformations are first used to deduce the momentum, heat and concentration equations and are then solved analytically. The effects of physical quantities such as fluid parameter, magnetic field, Schmidt number, relaxation time, curvature parameter, Prandtl number and chemical reaction on momentum, temperature and concentration profile are examined graphically whereas for validation of results convergence analysis along with residual error are obtained numerically. A comparison of obtained results is also given with the existing literature as a limiting case of reported problem and are found an excellent agreement. The temperature profile indicates thinning effect for higher values of Prandtl number and relaxation time. It is also noted that the velocity increases with increasing values of fluid parameter whereas it declines for the case of magnetic field. This study can be used an application of central heating system and to measure the fast chemical reactions rates.     

Microbial Natural Products with Antiviral Activities,Including Anti-SARS-CoV-2: A Review

The SARS-CoV-2 virus, which caused the COVID-19 infection, was discovered two and a half years ago. It caused a global pandemic, resulting in millions of deaths and substantial damage to the worldwide economy. Currently, only a few vaccines and antiviral drugs are available to combat SARS-CoV-2. However, there has been an increase in virus-related research, including exploring new drugs and their repurposing. Since discovering penicillin, natural products, particularly those derived from microbes, have been viewed as an abundant source of lead compounds for drug discovery. These compounds treat bacterial, fungal, parasitic, and viral infections. This review incorporates evidence from the available research publications on isolated and identified natural products derived from microbes with anti-hepatitis, anti-herpes simplex, anti-HIV, anti-influenza, anti-respiratory syncytial virus, and anti-SARS-CoV-2 properties. About 131 compounds with in vitro antiviral activity and 1 compound with both in vitro and in vivo activity have been isolated from microorganisms, and the mechanism of action for some of these compounds has been described. Recent reports have shown that natural products produced by the microbes, such as aurasperone A, neochinulin A and B, and aspulvinone D, M, and R, have potent in vitro anti-SARS-CoV-2 activity, targeting the main protease (M^pro). In the near and distant future, these molecules could be used to develop antiviral drugs for treating infections and preventing the spread of disease.