EFFECTS OF ULTRAVIOLET RADIATION ON THE MITOTIC CYCLE AND DNA, RNA AND PROTEIN SYNTHESIS IN MAMMALIAN EPIDERMIS IN VIVO

Abstract— Acute effects of ultraviolet radiation on the mitotic cycle and macromolecular synthesis were investigated on hairless mouse epidermis in vivo. Colcemid was used to arrest mitoses in metaphase and thus allow more accurate mitotic counts. The radioactive tracers, TdR-³H, cytidine-³H, and the amino acids, histidine-³H and methionine-³H were used to examine DNA, RNA and protein synthesis, respectively. Using these techniques, we found that wavelengths shorter than 320 nm markedly inhibited mitosis, increased the basal cell turnover time and depressed DNA, RNA and protein synthesis within the first few hours post-irradiation. By 24hr, recovery and acceleration of these functions were in progress, reaching a peak by 48–72 hr and persisting though to a lesser degree for 7 days. This stage of acceleration was associated with epidermal hyperplasia and most likely represented post-injury cell renewal.     

Determination of organophosphate and carbamate pesticides based on enzyme inhibition using a pH-sensitive fluorescence probe

A flow injection system for the determination of organophosphate and carbamate pesticides is described. A sensitive fluorescence probe was synthesized and used as the pH indicator to detect the inhibition of the enzyme acetylcholinesterase (AChE). The percentage inhibition of enzyme activity is correlated to the pesticide concentration. Several parameters influencing the performance of the system are discussed. The detection limits of 3.5, 50, 12 and 25 μg/l for carbofuran, carbaryl, paraoxon and dichlorvos, in pure water, respectively were achieved with an incubation time of 10 min. A complete cycle of analysis, including incubation time, took 14 min. The detection system has been applied to the determination of carbofuran in spiked vegetable juices (Chinese cabbage and cole), achieving recovery values between 93.2 and 107% for Chinese cabbage juice and 108 and 118% for cole juice at the different concentration levels assayed.     

A Challenge: Can Mathematics Aid Development of the Process of Operational Research?

Some of the structures developed by operational researchersto help clients explore a problem-situation and design a wayforward are described briefly. The difficulty of getting appropriatemathematical support for the analysis, interpretation, and developmentof these structures is discussed.     

Carrier dynamics in CsPbI3 perovskite microcrystals synthesized in solution phase

Carrier diffusion and recombination kinetics in all-inorganic CsPbI₃ perovskite microcrystals directly synthesized in solution phase are reported.     

Anomalous Charge Transfer from Organic Ligands to Metal Halides in Zero-Dimensional [(C6H5)4P]2SbCl5 Enabled by Pressure-Induced Lone Pair-π Interaction

Low-dimensional (low-D) organic metal halide hybrids (OMHHs) have emerged as fascinating candidates for optoelectronics due to their integrated properties from both organic and inorganic components. However, for most of low-D OMHHs, especially the zero-D (0D) compounds, the inferior electronic coupling between organic ligands and inorganic metal halides prevents efficient charge transfer at the hybrid interfaces and thus limits their further tunability of optical and electronic properties. Here, using pressure to regulate the interfacial interactions, efficient charge transfer from organic ligands to metal halides is achieved, which leads to a near-unity photoluminescence quantum yield (PLQY) at around 6.0 GPa in a 0D OMHH, [(C₆H₅)₄P]₂SbCl₅. In situ experimental characterizations and theoretical simulations reveal that the pressure-induced electronic coupling between the lone-pair electrons of Sb³⁺ and the π electrons of benzene ring (lp-π interaction) serves as an unexpected “bridge” for the charge transfer. Our work opens a versatile strategy for the new materials design by manipulating the lp-π interactions in organic–inorganic hybrid systems.     

Intermittent electron transfer activity from single CdSe/ZnS quantum dots

Electron transfer activity from excited single CdSe/ZnS core/shell quantum dots (QDs) to adsorbed Fluorescein 27 was studied by single QD fluorescence spectroscopy. In comparison with QDs, the QD-acceptor complexes showed a shorter average and broader distribution of QD emission lifetimes due to electron transfer to adsorbates. Large fluctuation of lifetimes in single QD/dye complexes was observed, indicating intermittent electron transfer activity from QDs.     

(La1-xCex)2/3Ca1/3MnO3体系的输运性质和反常磁特性研究

本文报告了对Ce掺杂锰氧化物(La1-xCex)2/3Ca1/3MnO3 (x=0～1.0)系列样品的输运特性和反常磁特性的研究结果.实验表明,Ce掺杂对Tc有明显的抑制作用,整体上电阻率随Ce掺杂含量增加而上升,在外加磁场时表现出极大的磁电阻效应.磁化强度随温度变化的曲线出现了两个转变,高温处对应于Mn离子磁矩的铁磁金属转变,低温处的转变则对应于Ce离子磁矩自旋有序排列的形成.表明Ce掺杂引起样品中铁磁双交换作用和反铁磁超交换作用之间的竞争,Ce离子与Mn离子有很强的相互作用.随Ce掺杂含量的增加,铁磁有序转变温度下降,而反铁磁有序转变温度则向高温处移动,铁磁区域明显减小.     

New global exponential stability result to a general Cohen–Grossberg neural networks with multiple delays

In this paper, we first discuss the existence of an equilibrium point to a general Cohen–Grossberg neural networks with multiple delays by means of using degree theory and linear matrix inequality (LMI) technique. Then by applying the existence result of an equilibrium point, linear matrix inequality technique and constructing a Lyapunov functional, we study the global exponential stability of equilibrium solution to the Cohen–Grossberg neural networks. Compared with known results, our results of global exponential stability of equilibrium point are new. In our results, the hypothesis for differentiability in existing papers on the behaved functions is removed and the hypotheses for boundedness and monotonicity in existing papers on the activation functions are also removed.     

加拿大一枝黄花的研究及应用现状

加拿大一枝黄花(Solidago Canadensis L.),是原产于北美的一种菊科多年生草本植物,20世纪30年代开始进入我国,现在这种植物已成为我国大部分境内迅速扩散传播的恶性杂草。目前,国内外的很多研究者已经利用各种方法从加拿大一枝黄花中提取出了倍半萜烯类、氨基酸、醇类等化学物质,对其生物性能进行了研究,并且对于控制这种植物的生长提出了各种解决方案。同时,加拿大一枝黄花已经在提炼精油、医学制药等方面得到广泛的应用。     

A STUDY OF ULTRA-HIGH ENERGY γ-RAYS BY EMULSION CHAMBERS

Ultra-high energy γ-rays have been observed by emulsion chambers exposed at Yunnan Station （3200m, 700g/cm² atmospheric depth）. The integral spectrum, the vertical intensity and the attenuation length in air of the gamma rays in the energy region 2 TeV to 30 TeV are presented. The results of gamma ray families with total observed energies ranging from 5 TeV to 70 TeV are discussed.