“前因后果”说简析

在我国哲学教材中,“前因后果”说是一种传统的观点,如说因果联系是“由先行现象引起后续现象的一种必然联系”;“因果关系是包括时间先后秩序在内的由一种现象必然引起另一种现象的本质的内在的联系”,基本含义都是把时间当做因果关系的必要条件。笔者认为,如果人们对原因和结果的认识仅仅停留在前因后果上,那只是反映了事物之间的表面特征,还不能揭示它们之间的内在的本质联系。 人们在同外界事物的交往中,往往会看到一种现象之后跟随着另一种现象,这种现象间的依次交替,就在人们的头脑中形成了因果观念。因此,原因和结果作为产生者和被产生者,确实存在着先行后继的特点。在一定范围内,“前因后果”说有它的合理之处。然而,熟知并非真知,“前因后果”说仅仅反映了现象之间的外在联系,人们的认识如果停留在这种水平上,还不能从辩证法的高度进一步揭示它们之间的本质联系。 首先,“前因后果”说仅仅说明了由某一现象向另一现象的过渡,尽管一些教科书把这种过渡解释为一种必然的联系,但是并没有揭示这种必然联系的内在发生和发展。恩格斯指出:“当我们把事物看做是静止而没有生命的,各自独立、相互并列或先后相继的时候,我们在事物中确实碰不到任何矛盾。我们在这里看到某些特性,这些特性。

Theoretical Study on Dissociation Mechanisms of Di-ethyl Berylliums and Di-t-butyl Berylliums

The potential energy surfaces （PES） of unimolecular dissociation reactions for di-ethyl beryl- lium and di-t-butyl beryllium are investigated by B3LYP, CCSD（T）, and G3B3 approaches. Possible reaction pathways through either the radical or transition state （TS） of the molecules are considered. The geometries, vibrational frequencies and relative energies for various sta- tionary points are determined. From the study of energetics, the TS pathways arising from concerted molecular eliminations are indicated to be the main dissociation pathways for both molecules. The PES differences of the dissociation reactions are investigated. The activation energies and rate constants will be helpful for investigating the predictive ability of the reaction in further theoretical and experimental research.

MXenes as noble-metal-alternative co-catalysts in photocatalysis

Photocatalysis has become a focal point in research as a clean and sustainable technology with the potential to solve environmental problems and energy crises.The loading of noble-metal co-catalysts can substantially improve the photocatalytic efficiency of semiconductors.Because the high cost and scarcity of noble metals markedly limit their large-scale applications,finding a noble-metal-alternative co-catalyst is crucial.MXene,a novel 2D transition metal material,has attracted considerable attention as a promising substitute for noble metal co-catalysts owing to its cost-efficiency,unique 2D layered structure,and excellent electrical,optical,and thermodynamic properties.This review focuses on the latest advancements in research on MXenes as co-catalysts in relatively popular photocatalytic applications(hydrogen production,CO2 reduction,nitrogen fixation,and organic pollutant oxidation).The synthesis methods and photocatalytic mechanisms of MXenes as co-catalysts are also summarized according to the type of MXene-based material.Finally,the crucial opportunities and challenges in the prospective development of MXene-based photocatalysts are outlined.We emphasize that modern techniques should be used to demonstrate the effects of MXenes on photocatalysis and that the photocatalytic activity of MXene-based photocatalysts can be further improved using defective engineering and recent phenomena such as the localized surface plasmon resonance effect and single-atom catalysis.

Application of Thermal Cracking Mechanism of Chrysene Molecule Using Density Functional Theory

Density functional theory calculations were carried out to study the thermal cracking for chrysene molecule to estimate the bond energies for breaking C 10b-C 11, C 11-H 11 and C4a-C 12a bonds as well as the activation energies. It was found that for C 10b-C 11 C11-HI 1 and C4a-C12a reactions, it is often possible to identify one pathway for bond breakage through the singlet or triplet states. Thus, the C 11-H11 and C11-C10b bonds ruptured in triplet state whilst the C12a-C4a in singlet state. Also, it was fond that the activation energy value for C4a-C12a bond breakage is lower than required for C10b-C11 and C11-H11 bonds that enquired the C4a-C12a bond ＂bridge bond＂ is a weaker and ruptured firstly in thermal cracking process. It seems that the characteristic planarity for polyaromatic hydrocarbons is an important factor to acquire the molecule structure the required stability along the reaction paths as well as the full octet rule and Clar＇s n-sextet structure, especially when chrysene molecular lose the property of planarity. The atomic charges supported the observation that the breaking bonds C10b-C11, CI1-H11 and C4a-C12a in triplet or singlet states. The configurations in transition state and the conformation for the end products reaction were explained and discussed.

Theoretical Study of Isoprene Dissociative Photoionization

Theoretical calculations have been carried out to investigate the possible dissociation channels of isoprene. We focus on the major fragment ions of C5H7＋, C5H5＋, C4H5＋, C3H6＋, C3H5＋, C3H4＋, C3H3＋ and C2H3＋, which were observed experimentally from the isoprene dissociative photoionization. The energy calculations were performed with the CBS-QB3 model. All the geometries and energies of the fragments, intermediates and transition states involved in the dissociations channels were determined. Finally, the mechanisms of the dissociation pathways were discussed on the comparison of theoretical and experimental results.

Infrared Spectra,Structures and Bonding of Binuclear Transition Metal Carbonyl Cluster Ions

Binuclear transition metal carbonyl clusters serve as the simplest models in understand- ing metal-metal and ligand bonding that are important organometallic chemistry catalysis. Binuclear first row transition metal carbonyl ions are produced via a pulsed laser vaporiza- tion/supersonic expansion cluster ion source in the gas phase. These ions are studied by mass-selected infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Density functional theory calculations have been performed on the geometric struc- tures and vibrational spectra of the carbonyl ions. Their geometric and electronic structures are determined by comparison of the experimental IR spectra with the simulated spectra. The structure and the metM-metal and metal-CO bonding of both saturated and unsaturated homonuclear as well as heteronuclear carbonyl cluster cations and anions are discussed.

Numerical Simulation of Multicomponent Alloy Solidification

A non-equilibrium model of multicomponent melt solidification has been developed in which a Stefan problem with two boundaries is solved numerically, the boundaries being between the solid phase and the two-phase transition zone and between the two-phase transition zone and the liquid phase. The two-phase zone is represented as a porous medium with variable porosity. The additional force resisting the melt flow due to porosity and introduced by analogy with Darcy＇s law is taken into account. Computer simulation has been performed of the experiment on Sn-20 wt.%Pb binary alloy solidification by the method of downward-directed crystallization along the gravity vector. The paper shows the results of a quasi two-dimensional benchmark experiment on horizontal （i.e., at the right angle to the gravity vector） directional solidification of a binary Sn-3 wt.%Pb alloy. The calculations were done using two crystallization models： the equilibrium model and the non-equilibrium one. It is shown that the non-equilibrium model gives a better description of the thermal field evolution and solute distribution caused by natural convection.

不良贷款清收中的政治经济学分析:张家界案例研究

当前 ,金融部门不良资产抓降工作已经成为提高金融部门质量、面对入世后更为激烈的金融业竞争的关键手段。本文通过对湖南省张家界金融系统不良资产清收的个案研究 ,得出的基本结论在于 ,银行与外部债务人的“关系”问题是制约不良资产清收的关键性约束条件。在理论上 ,涉及利益集团、交易中的权力问题都属于政治经济学的范畴。本文认为 ,正是由于该约束条件 ,形成了现实运行中银行信贷操作中的一系列问题 :信贷操作有规不循、党政部门竞相瓜分、债务人主权与支配地位的形成与巩固 (所谓的信用危机 )。基于该结论 ,本文提出从制度上引进党政部门参与的“反市场过渡性解”。

Pt embedded Ni3Se2@NiOOH core-shell dendrite-like nanoarrays on nickel foam as bifunctional electrocatalysts for overall water splitting

Developing high-performance bifunctional catalysts toward hydrogen evolution reaction(HER) and oxygen evolution reaction(OER) is essential to enhance water splitting efficiency for large-scale hydrogen production. Neither noble metal Pt nor transition metal compounds show satisfactory performances for both HER and OER simultaneously. Here, we prepared a three-dimensional Pt-Ni3 Se2@NiOOH/NF(PNOF) hybrid catalyst via in-situ growth strategy. Benefitting from the self-supported structure and oxygen vacancies on the surface of NiOOH nanosheets, the PNOF electrode shows remarkably catalytic performance for dual HER and OER. The overall water electrolyzer using PNOF as anode and cathode can achieve a current density of10 mA cm^-2 at a low voltage of 1.52 V with excellent long-term stability, which is superior to precious metal catalysts of Pt/C and Ir/C. This study provides a promising strategy for preparing bifunctional catalysts with high performance.

Temperature-sensitive molecularly imprinted microgels with esterase activity

Temperature-sensitive molecularly imprinted microgels(MIGs)exhibiting esterase activity were prepared by a reverse emulsion method using dialdehyde dextran-histidine conjugate(PAD-His)as the functional macromonomer and p-nitrophenyl phosphate(NPP)as the stable transition state analogue(TSA)as well as Co2+as the coordination center.The catalytic activity of MIGs was greatly influenced by the amount of the template,and could be modulated by temperature.The hydrolysis kinetics of p-nitrophenyl acetate(NPA)in the presence of MIGs could be described by the Michaelis-Menten equation.The MichaelisMenten constant and maximum velocity were found to be 2.2×105mol/L and 2.04×10 -8mol/h,respectively.In addition,the MIGs were found to have a high catalytic selectivity to NPA.