键函数法与Be2体系的稳定性1: Be2的基态

采用价电子全CI(FCI)方法对Be2的基态(X^1∑g^+)进行了研究, 仔细考察了键函数在弱键体系计算中的作用。对引入键函数的不同方式分别按Boys方法计算了基组重叠误差(BSSE)。键函数的运用使得Be2基态性质的计算结果大为改善。研究结果表明键函数方法在相互作用能小的体系的计算中十分可取。     

键函数法与Be2体系的稳定性1: Be2的基态

采用价电子全CI(FCI)方法对Be2的基态(X^1∑g^+)进行了研究, 仔细考察了键函数在弱键体系计算中的作用。对引入键函数的不同方式分别按Boys方法计算了基组重叠误差(BSSE)。键函数的运用使得Be2基态性质的计算结果大为改善。研究结果表明键函数方法在相互作用能小的体系的计算中十分可取。     

Can Counter-Intuitive Halogen Bonding Be Coulombic?

We use the term “counter-intuitive” to describe an intermolecular interaction in which the electrostatic potentials of the interacting regions of the ground-state molecules have the same sign, both positive or both negative. In the present work, we consider counter-intuitive halogen bonding with nitrogen bases, in which both the halogen σ-hole and the nitrogen lone pair have negative potentials on their molecular surfaces. We show that these interactions can be treated as Coulombic despite the apparent repulsion between the ground-state molecules, provided that both electrostatics and polarization are explicitly taken into account. We demonstrate first that the energies of 20 counter-intuitive interactions with four nitrogen bases can be expressed very well in terms of just two molecular properties: the electrostatic potential of the halogen σ-hole and the average polarizability of the nitrogen base. Then we show that the same two properties can also represent the energies of an expanded data base that includes the 20 counter-intuitive plus an additional 20 weak and moderately-strong intuitive halogen bonding interactions (in which the σ-hole potentials are now positive).     

Spectra and dose with ANN of 252Cf, 241Am–Be, and 239Pu–Be

Artificial neural networks have been applied to unfold the neutron spectra and to calculate the effective dose, the ambient equivalent dose, and the personal dose equivalent for ²⁵²Cf, ²⁴¹Am–Be, and ²³⁹Pu–Be neutron sources. The count rates that these neutron sources produce in a Bonner Sphere Spectrometer with a ⁶LiI(Eu) were utilized as input in both artificial neural networks. Spectra and the ambient dose equivalent were also obtained with BUNKIUT code and the UTA4 response matrix. With both procedures spectra and ambient dose equivalent agrees in less than 10%. The Artificial neural network technology is an alternative procedure to unfold neutron spectra and to perform neutron dosimetry.     

Could Polyphenols Really Be a Good Radioprotective Strategy?

Currently, radiotherapy is one of the most effective strategies to treat cancer. However, deleterious toxicity against normal cells indicate for the need to selectively protect them. Reactive oxygen and nitrogen species reinforce ionizing radiation cytotoxicity, and compounds able to scavenge these species or enhance antioxidant enzymes (e.g., superoxide dismutase, catalase, and glutathione peroxidase) should be properly investigated. Antioxidant plant-derived compounds, such as phenols and polyphenols, could represent a valuable alternative to synthetic compounds to be used as radio-protective agents. In fact, their dose-dependent antioxidant/pro-oxidant efficacy could provide a high degree of protection to normal tissues, with little or no protection to tumor cells. The present review provides an update of the current scientific knowledge of polyphenols in pure forms or in plant extracts with good evidence concerning their possible radiomodulating action. Indeed, with few exceptions, to date, the fragmentary data available mostly derive from in vitro studies, which do not find comfort in preclinical and/or clinical studies. On the contrary, when preclinical studies are reported, especially regarding the bioactivity of a plant extract, its chemical composition is not taken into account, avoiding any standardization and compromising data reproducibility.     

~(10)Be与黄土的堆积演化

本文报道了0.75Ma以来中国洛川和西峰黄土剖面的~(10)Be测量结果。黄土~(10)Be记录与深海钻孔沉积物δ~(18)O之间有着极好的相关性。根据这种相关性,建立了0.75Ma以来洛川和西峰剖面的地层时标,进而计算了黄土堆积速率和~(10)Be通量,给出黄土风成沉积的简单定性模式。     

How Many Networks Can Be Made from Four-Coordinate Atoms?

In how many ways can three-dimensional space be divided into tiles such that four edges meet at every vertex? A procedure to calculate the number of possibilities was recently presented by the mathematician A. Dress. Some of the tilings correspond to the structures of zeolites and other networks.     

VOLTAMMETRIC BEHAVIORS OF ADRENALINE AND ITS Be(Ⅱ)COMPLEX

The electrochemical oxidation behaviors of adrenaline(AD)and itsBe(Ⅱ)complex have been studied by voltammetric method with a carbon pasteworking electrode.On the bases of calculation of the atomic net electroniccharges of AD molecule by INDO approximate method and results ofcomparative experiment with dopamine the possible coordination site ofBe(Ⅱ)-AD complex is proposed.     

B2Be2簇的结构与成键性质的研究

用HF／6-31Gabinitio法对B2Be2簇9种异构体27个电子态的结构进行了全构型优化,再用大基组二次组态相互作用QCISD（T）／6-311G方法进行单点计算，9种异构体的稳定性顺序是：h＞i＞g＞e＞f＞c＞a＞d＞b.通过结构转变中的Walsh图、能量间隙、键数参数（BNP）和键电荷的研究，揭示了B2Be2的成键特征.     

中国黄土石英中的~(10)Be研究——Ⅰ.“自身成因~(10)Be”与黄土源区侵蚀速率

对于0.2Ma以来的黄土堆积物,其石英“自身成因~(10)Be”主要来源于源区初始~(10)Be,载带着源区侵蚀速率变化信息。中国洛川黄土剖面GL 47(L_1),GL83(L_2)两样品石英“自身成因~(10)Be”浓度分别为5×10~5原子/g,2.2×10~6原子/g。据此计算的源区侵蚀速率为:L_1期(10—90ka),ε_(BeL_1)=1.5×10~(-3)cm/a;L_2期(130—190k a),ε_(BeL_2)=3.8×10~(-4)cm/a。更深层位黄土石英“自身成因~(10)Be”研究可望用于黄土地层测年。     

地质化探样品中痕量Be,B的发射光谱测定

近年来有关利用电极中的氯化反应来提高发射光谱分析灵敏度的报道较多,但均未提出利用热化学反应测定痕量Be、B的反应条件和测试方法。本法选用AlCl_3+NaF作反应剂,以大比例(9∶1)稀释试样,Be、B的直接测定下限分别达到0.12ppm和0.52ppm,相对标准偏差Be<11.6％,B<13.5％。经选择AlCl_3、AgCl、CdCl_2、NH_4Cl、NaCl、     

Be在富勒烯C74笼内稳定位置的理论研究

为了研究富勒烯金属包合物Be@C74的结构和电子性质,本文采用密度泛函理论B3LYP方法优化了Be@C74的结构,计算了它的势能面、LUMO-HOMO、电子亲和势、电子化能以及Mulliken集居数。结果表明:Be原子位于C74笼中心并且近似保持基态的电子构型;Be原子和C74笼之间是相互排斥作用;Be原子包入C74笼中心后,C74笼只有微小的变形;包合物Be@C74笼的给予和得到电力的能力与C74空笼几乎不变;Be与C74笼之间只有微小的杂化。     

Can Artemisia herba-alba Be Useful for Managing COVID-19 and Comorbidities?

The focus of this roadmap is to evaluate the possible efficacy of Artemisia herba-alba Asso. (Asteraceae) for the treatment of COVID-19 and some of its symptoms and several comorbidities using a combination of in silico (molecular docking) studies, reported ethnic uses, and pharmacological activity studies of this plant. In this exploratory study, we show that various phytochemicals from Artemisia herba-alba can be useful against COVID-19 (in silico studies) and for its associated comorbidities. COVID-19 is a new disease, so reports of any therapeutic treatments against it (traditional or conventional) are scanty. On the other hand, we demonstrate, using Artemisia herba-alba as an example, that through a proper search and identification of medicinal plant(s) and their phytochemicals identification using secondary data (published reports) on the plant’s ethnic uses, phytochemical constituents, and pharmacological activities against COVID-19 comorbidities and symptoms coupled with the use of primary data obtained from in silico (molecular docking and molecular dynamics) studies on the binding of the selected plant’s phytochemicals (such as: rutin, 4,5-di-O-caffeoylquinic acid, and schaftoside) with various vital components of SARS-CoV-2, it may be possible to rapidly identify plants that are suitable for further research regarding therapeutic use against COVID-19 and its associated symptoms and comorbidities.     

Can Fluorinated Molecular Cages Be Utilized as Building Blocks of Hyperhalogens?

Based on the density functional theory for exchange‐correlation potential, fluorocarbon molecular cages are investigated as building blocks of hyperhalogens. By utilizing C₈F₇ as a ligand, a series of hyperhalogen anions, that is, M(C₈F₇)₂^? (M=Li, Na, and K) and M(C₈F₇)₃^? (M=Be, Mg, and Ca), are modeled. Calculations show that all the C₈F₇ moieties preserve their geometric and electronic integrity in these anions. These anionic molecules possess larger vertical electron detachment energies (5.11–6.45 eV) than that of C₈F₇^?, verifying their hyperhalogen nature. Moreover, it is also revealed that using larger fluorinated cage C₁₀F₉ as ligands can bring about hyperhalogen anions with larger vertical electron detachment energies. The stability of these studied anions is determined by their large HOMO–LUMO gaps and positive dissociation energies of predetermined possible fragmentation pathways. It is hoped this study will provide an approach for the construction of new types of hyperhalogens and stimulate more research in superatom chemistry.     

Microcalorimetric Evaluation of Precipitation in Cu–2Be–0.2Mg

Beryllium precipitation from the Cu-rich matrix in a Cu–2 mass% Be–0.2 mass% Mg alloy homogenized and quenched from 1073 K was studied by differential scanning calorimetry (DSC). The DSC traces showed two main exothermic effects, A and B, each comprising two subeffects: A₁ and A₂ , and B₁ and B₂ respectively. Effects A₁ and A₂ correspond to the precipitation of GP zones and subsequent overlapping and independent precipitation of the phase. Only at very low heating rates can be inherited from GP zones. Effects B₁ and B₂ correspond to heat evolved during transitions to the states with and phases, respectively. Heat effect A can be quantitatively described in terms of solid solubilities before and after precipitation, and of the precipitation heats of the phases involved. The heat content of the combined GP zone/ phase precipitation effect was proportional to the number of beryllium atoms precipitated, yielding an average value of 21 kJ mol^–1 beryllium for beryllium precipitation. It was shown that the phase arises from the combined transition from states with GP zones and phases, whereas arises from the transition of states with and phases. The apparent activation energies associated with GP zones and , and phases are 1.16±0.08, 1.18±0.07, 1.37±0.08 and 1.74±0.09 eV, respectively. These values are discussed in terms of the mobility of dissolved atoms related to the concentrations of excess vacancies and solute-vacancy complexes, and the direction of plate-like precipitate growth (either normal or perpendicular to the plate). It is inferred that the main roles of magnesium are to decrease the amount and rate of GP formation, to enhance the volume fraction of and to suppress the discontinuous precipitation of .This revised version was published online in November 2005 with corrections to the Cover Date.     

What Is Chromatography, and Can It Be a Single-Phase Process?

The appropriateness of the existence of several definitions of chromatography (as a phenomenon, a science, a process, a separation technique, etc.) is asserted. It is shown that new examples of column-free single-phase versions of field chromatography proposed by Prof. V.G. Berezkin have no relation to chromatography.     

Be和B的几个小分子及其离子的电子结构

B和Be化合物的电子结构研究可以为~(10)Be质谱检测中~(10)B干扰的消除提供 理论依据。用B3LYP/6-311 + + G（3df, 3pd）方法和G3方法计算了BF(~1∑~+)， BeF~(~2∑~+)，HBO(~1A')，HBeO(~2∑~+)，HBeF(~1∑~+)，BBeB(~1A_1)，H_2BO (~2B_2)和H_3BO(~1A')等分子及其负离子BF~- (~2∏)，BeF~- (~1∑~+)，HBO~- (~2A')，HBeO~- (~1∑~+)，HBeF~- (~2A')，BBeB~- (~2A_1)，H_2BO~- (~1A_1) ，H_3BO~-(~2A')的电子结构，并利用CASSCF-MRCISD方法计算了BeF(2~∑~+) /BeF~-(~1∑~+)，BF(~1∑~+)/BF~-(~2∏)和BF(~3∏)/BF~-(~4∑~-)的热能曲线。 探讨了这些体系的稳定性。解释了~(10)Be质变测量方法中的有关结果。     

氢原子在Be(0001)表面吸附的密度泛函理论研究

采用第一性原理的密度泛函理论研究单个氢原子和多个氢原子在Be(0001)表面吸附性质.给出了氢吸附Be(0001)薄膜表面的原子结构、吸附能、饱和度、功函数、偶极修正等特性参数.同时也讨论了相关吸附性质与氢原子覆盖度(0.06-1.33ML)的关系.计算结果表明:氢原子的吸附位置与覆盖度之间有强烈的依赖关系,覆盖度低于0.67ML时,氢原子能量上易于占据fcc或hcp的中空位置;覆盖度为0.78ML时,中空位与桥位为氢原子的最佳吸附位;覆盖度在0.89到1.00ML时,桥位是氢原子吸附能量最有利的位置;以上覆盖度中Be(0001)表面最外层铍原子的结构均没有发生明显变化.当覆盖度为1.11-1.33ML,高覆盖度下Be(0001)表面的最外层铍原子部分发生膨胀,近邻氢原子渗入到铍表面次层,氢原子易于占据在hcp和桥位.吸附结构中的氢原子比氢分子中的原子稳定.当覆盖度大1.33ML时,计算结果没有发现相对于氢分子更稳定的吸氢结构.同时从分析偶极修正和氢原子吸附垂直高度随覆盖度的变化关系判断氢覆盖度为1.33ML时,在Be(0001)表面吸附达到饱和.