Theoretical Study on the Activity of a-COOH and b-COOH of N-Phosphoryl Aspartic Acids

The bio-mimic reactions of N-phosphoryl amino acids are very important in the study of many biochemical processes. The difference of reactivity between a-COOH and b-COOH in phosphoryl aspartic acid was studied by theoretical study (Hartree-Fock and Density Functional methods) in this paper. The intermediates II containing five-membered ring were more stable than III with six-membered ring. While for intermediates III, the isomers with six-membered ring in apical-equatorial spanning arrangement were more stable than those with di-equatorial spanning arrangement. At B3LYP/6-31G** level, it was shown that transition states IV and V involving a-COOH or b-COOH group had energy barriers of DE = 58.67 kJmol-1 and 103.94 kJmol-1, respectively. These results were in agreement with the experimental data. So the a-COOH group was involved in form of the intramolecular penta-coordinate phosphoric-carboxylic mixed anhydride intermediates, but not b-COOH group.

Theoretical Study on the Reaction Mechanism between Dichlorocarbene and Armchair Single-walled Carbon Nanotubes

The reaction mechanism between CCl2 and armchair single-walled carbon nanotu- bes (ASWCNTs) (3,3) and (4,4) has been studied by semiempirical AM1 and ab initio methods. The activation barriers of CCl2 adding to ASWCNT (3,3) and (4,4) are computed and compared. The lower barrier of CCl2 forms cycloaddition isomer on (3,3) maybe because the strain energy of (3,3) is larger than that of (4,4). Our theoretical results are consistent with the experimental results.

Theoretical Study on the Structures, Vibrational Spectra, and the Nature of the Intermediate Hydrogen Bond of Schiff Bases

Semi-empirical method PM3 was used to study the geometry and vibrational spectrum of N-(2-hydroxy-1- naphthyl-methylene)-1-pyrenamine (NPY) with the intermediate hydrogen bond.Results are comparable to experimentations. Based on results of both NPY and its model, N(2-hydroxy-1-naphthyl-methylene)aniline, it was found that the N-(2-hydroxy-1-naphthyl-methylene)group is principally responsible for the special hydrogen bonding through conjugation

A Theoretical Study of the Pressure for Liquid Metal Infiltration of a Fiber Preform

A theoretical model has been established for calculating the infiltration pressure of metal melt into the preform of ceramic fibers according to the basic principle of hydromechanics. There are three forces acting on the infiltration process in the model, i.e. viscous friction, capillary force, and gravity The effects of the volume fraction of fibers (Vf) and infiltrating depth on the infiltration pressure are discussed. The results show that the infiltration pressure increases with the increase of fiber volume fraction and infiltration depth. There is a linear relationship between infiltration pressure and infiltiation depth. The effect of gravity on the infiltration pressure can be

AB INTIO THEORETICAL STUDY OF MIXED CLUSTER AICB

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Strengthen Theoretical Study of Prisoners' Human Rights

The following are excerpts of a speech made by Jin Jian, President of the China Penology Society and Vice-President of the China Society for Human Rights Studies at a seminar on prisoners’ human rights organized by the China Penology Society and the China Society for Human Rights Studies.

Theoretical study of tunable chirality from graphene integrated achiral metasurfaces

Control of chirality using metamaterials plays a critical role in a diverse set of advanced photonics applications,such as polarization control, bio-sensing, and polarization-sensitive imaging devices. However, this poses a major challenge, as it primarily involves the geometrical reconfiguration of metamolecules that cannot be adjusted dynamically. Real-world applications require active tuning of the chirality, which can easily manipulate the magnitude, handedness, and spectral range of chiroptical response. Here, enabled by graphene, we theoretically reveal a tunable/switchable achiral metasurface in the near-infrared region. In the model, the achiral metasurface consists of an array of circular holes embedded through a metal/dielectric/metal trilayer incorporated with the graphene sheet, where holes occupy the sites of a rectangular lattice. Circular conversion dichroism(CCD) originates from the mutual orientation between the achiral metasurface and oblique incident wave.The achiral metasurface possesses dual-band sharp features in the CCD spectra, which are tuned over a broad bandwidth by electrically modulating the graphene's Fermi level. By selecting aluminium as the metal materials,we numerically achieved strong CCD and considerably reduced materials costs with our nanostructures compared with the typically used noble metals such as gold and silver.

Theoretical study of stimulated Raman scattering in long tapered fiber amplifier

A model that is based on the propagation equation and coupled mode theory is introduced in order to describe stimulated Raman scattering(SRS) effects in long tapered fiber amplifiers.Based on the presented model,fiber amplifiers with uniform and long tapered fibers are theoretically and numerically simulated.It can be drawn from the results of our simulations that the long tapered fiber has the advantage in suppressing SRS when applied in fiber laser amplifiers.Our results can provide guidance in the designing of system configuration in long tapered-fiber-based fiber laser systems.

A Review Study of Experimental and Theoretical Humidification Dehumidification Solar Desalination Technology

Most of the desalination technologies consume a huge quantity of energy resulting from petroleum products in the form of heat or electrical energy. Solar desalination is a promisingly sustainable freshwater production technology. Solar desalination humidification dehumidification process showed the best approach as it is of the highest overall energy efficiency. In this review paper, a detailed study of the previous work is performed on solar humidification dehumidification desalination techniques experimentally and theoretically. Also in this review, different types of HDH systems were mentioned. The review showed that the humidification dehumidification desalination systems are suitable for decentralized demand. On the other hand, capacity of HDH units is not as large as conventional methods or small as solar stills. Finally, this study threw light on the scope of the parameters which have a considerable influence on increasing the freshwater output of the HDH systems as feed water flow rate, air flow rate, and design of the evaporator, condenser, and packing material. A brief economical study and a comparison of the costs per liter are performed for various humidification dehumidification desalination systems presented in this study.

Progress in octahedral spherical hohlraum study

In this paper,we give a review of our theoretical and experimental progress in octahedral spherical hohlraum study.From our theoretical study,the octahedral spherical hohlraums with 6 Laser Entrance Holes(LEHs)of octahedral symmetry have robust high symmetry during the capsule implosion at hohlraum-to-capsule radius ratio larger than 3.7.In addition,the octahedral spherical hohlraums also have potential superiority on low backscattering without supplementary technology.We studied the laser arrangement and constraints of the octahedral spherical hohlraums,and gave a design on the laser arrangement for ignition octahedral hohlraums.As a result,the injection angle of laser beams of 50°-60°was proposed as the optimum candidate range for the octahedral spherical hohlraums.We proposed a novel octahedral spherical hohlraum with cylindrical LEHs and LEH shields,in order to increase the laser coupling efficiency and improve the capsule symmetry and to mitigate the influence of the wall blowoff on laser transport.We studied on the sensitivity of the octahedral spherical hohlraums to random errors and compared the sensitivity among the octahedral spherical hohlraums,the rugby hohlraums and the cylindrical hohlraums,and the results show that the octahedral spherical hohlraums are robust to these random errors while the cylindrical hohlraums are the most sensitive.Up till to now,we have carried out three experiments on the spherical hohlraum with 2 LEHs on Shenguang(SG)laser facilities,including demonstration of improving laser transport by using the cylindrical LEHs in the spherical hohlraums,spherical hohlraum energetics on the SGIII prototype laser facility,and comparisons of laser plasma instabilities between the spherical hohlraums and the cylindrical hohlraums on the SGIII laser facility.

Development of family resilience models

Family resilience is not the sum of the individual psychological resilience of each of the family members,but the family itself as a unit of resilience research.The representative models of family stress tolerance theory mainly include Mc Cubbin's series of family stress tolerance models and Walsh's family stress tolerance framework,which are widely used in the practice of family therapy.In the future,empirical studies on family resilience should be strengthened,measurement tools with high reliability and validity should be established,and the combination of family resilience theory and community-based practice should be promoted.

从认知心理学的角度谈知识管理

How to understand knowledge management correctly?This article tries to discuss knowledge management in terms of cognitive psychology.It expounds the concept of cognition,discusses the essence of knowledge in terms of cognitive psychology,and puts forward the concept of knowledge net.The significance of the research on knowledge net to knowledge innovation,and the types of knowledge net and knowledge innovation are also expounded.

对潜在信息资源的认识研究

Based on a description of the implication,character and type of information resources,this article analyzes the potential information resourecs which are seldom noticed by people.Emphases are put on their specific properties.The necessity and urgency of developing potential information resources are elaborated.The possibility of developing and utilizing potential information resources are predicted.

Removal Effect of Fluoride Ions by Aluminum Salt in Wastewater

To study a kind of high-efficiency fluoride removal agent based on aluminum salt,through theoretical and experimental research,the influence of different factors(dosage of agent,concentration of fluoride ions,pH,TDS,hardness and alkalinity,etc.)on the removal effect of fluoride ions by fluoride removal agent in industrial wastewater,especially mine water was analyzed.The results show that the fluoride ion removal agent based on aluminum salt could achieve efficient removal of fluoride ions,and the optimal mass ratio of fluoride ion concentration and compound reagent was 1∶130.The concentration of fluoride ions in the water produced after precipitation was≤1 mg/L under the optimal pH condition.As the pH of the solution was 6.5-7.5,the effect of fluoride removal by the agent was the highest.When the pH of the solution was>10.5 or<5,there was no effect of fluoride removal.Under the conditions of optimal pH and reagent dosage,the removal rate of fluoride ions rose with the increase of fluoride ion concentration in wastewater,up to 87.4%.It is also verified that TDS had no obvious effect on fluoride removal,and the smaller the hardness and alkalinity,the better the effect of fluoride removal.

Theoretical Analysis of Structural Characteristics of Morin Rearrangement for Cephalosporins Prepared from Penicillin Sulfoxide

The structure of penicillin sulfoxide is rearranged to cephalosporins by the Morin rearrangement. It is a unit reaction for the preparation of various types of cephalosporins. In order to make better use of the reaction and in view of the shortage of the reaction theory, this study used m062x/6-311++G(d, p) to explore the possible ring-opening reaction of the penicillin sulfoxide. It is found that the isomer of(S)-sulfoxide is a necessary structure. At the same time, the intramolecular hydrogen bonding effect between the side-chain amide proton(-CONH-) and the sulfinyl oxygen(-SO) is the decisive structure factor for the formation of alkenyl in ring-opening reaction, and the best reaction path is S0-> TS2-> IN1 channel. The main effect of acid catalysis is to catalyze the dehydration reaction of sulfenic acid to form sulfur cations for subsequently ring closing reaction.

Antifouling nanocomposite polymer coatings for marine applications:A review on experiments,mechanisms,and theoretical studies

Marine fouling is a worldwide challenge with huge damages on industrial structures,side effects on economics of industries,and environmental and safety-related hazards.Different approaches have been used for combating fouling in the marine environment.Meanwhile,nanocomposite polymer coatings are a novel generation of antifouling coatings with merits of toxin-free chemical composition and ease of large-scale application.Nanomaterials such as nano-metals,nano-metal oxides,metal-organic frameworks,carbon-based nanostructures,MXene,and nanoclays have antibacterial and antifouling properties in the polymer coatings.Besides,these nanomaterials can improve the corrosion resistance,mechanical strength,weathering stability,and thermal resistance of the polymer coatings.Therefore,in this review paper,the antifouling nanocomposite coatings are introduced and antifouling mechanisms are discussed.This review explicitly indicates that the antifouling efficiency of the nanocomposite coatings depends on the properties of the polymer matrix,the inherent properties of the nanomaterials,the weight percent and the dispersion method of the nanomaterials within the coating matrix,and the chemicals used for modifying the surface of the nanomaterials;meanwhile,the hybrids of different nanomaterials and appropriate chemical agents could be used to improve the antifouling behavior of the prepared nanocomposites.Moreover,the theoretical studies are introduced to pave the way of researchers working on theantifouling coatings,and the importance of the theoretical studies and computational modeling along with the experimental research is notified to develop antifouling coatings with high efficiency.

From thermal conductive to thermal insulating:Effect of carbon vacancy content on lattice thermal conductivity of ZrC_(x)

Lattice thermal conductivities of zirconium carbide(ZrC_(x),x=1,0.75 and 0.5)ceramics with different carbon vacancy concentrations were calculated using a combination of first-principles calculations and the Debye-Callaway model.The Gruneisen parameters,Debye temperatures,and phonon group velocities were deduced from phonon dispersions of ZrC_(x) determined using first-principles calculations.In addition,the effects of average atomic mass,grain size,average atomic volume and Zr isotopes on the lattice thermal conductivities of ZrC_(x) were analyzed using phonon scattering models.The lattice thermal conductivity decreased as temperature increased for ZrC,ZrC_(0.75) and ZrC_(0.5)(Zr2 C),and decreased as carbon vacancy concentration increased.Intriguingly,ZrC_(x) can be tailored from a thermal conducting material for ZrC with high lattice thermal conductivity to a thermal insulating material for ZrC_(0.5) with low lattice thermal conductivity.Thus,it opens a window to tune the thermal properties of ZrC_(x) by controlling the carbon vacancy content.

Geometry, stability and aromaticity of β-diketiminate-coordinated alkaline-earth compounds

Alkaline-earth(Ae) metals have attracted a wealth of interdependent research from synthetic chemists.In Ae-catalyzed organometallic reactions,β-diketiminate is a typical ligand used to stabilize Ae catalysts by forming six-membered rings comprising Ae metals.Herein,studies focusing on the configuration of β-diketiminate-coordinated Ae compounds observed that the C-C and C-N bonds are homogeneous and unchanged.Furthermore,energetic studies observed that the formation of the Ae-incorporated sixmembered rings results in enhanced stability of>20 kcal/mol.The nucleus-independent chemical shifts,anisotropy of the induced current density,and molecular orbital analyses demonstrated the nonaromaticity of the β-diketiminate-coordinated Ae compounds.The improved stability of these compounds can be explained by the delocalization of the π electrons derived from the β-diketiminate moiety.

Synthesis of mono and bis-4-methylpiperidiniummethyl-urea as corrosion inhibitors for steel in acidic media

Mono and bis-4-methylpiperidiniummethyl urea were synthesized,characterized and used as new corrosion inhibitors of mild steel in the acidic media.Inhibitory effect of two compounds on mild steel surface in the 1 mol·L^(–1 )sulphuric acid has been studied by a series of techniques,such as potentiodynamic polarization,weight loss and quantum chemical calculation methods.Potentiodynamic polarization measurements showed that two inhibitors are mixed type.All measurements showed that inhibition efficiencies enhanced with increase of inhibitor concentration.This reveals that inhibitive actions of inhibitors were mainly due to adsorption on mild steel surface.Density functional(DFT)calculations have been carried out for the title compounds by performing HF and DFT levels of theory using the standard 6-31G*basis set.