Classifying spaces and homotopy sets of axes of pairings

We consider the maps between classifying spaces of the form . The main theorem shows that if the restriction map on is a weak epimorphism, then the restriction on should factor through the classifying spaces of the center of the compact Lie group . An application implies that is an H-space (Hopf space) if and only if is abelian.

     

Complex formation of hydronium ion with several crown ethers in 1,2-dichloroethane,acetonitrile, and nitrobenzene solutions

A conductance study concerning the interaction between hydronium ion and several crown ethers in acetonitrile, nitrobenzene and 1,2-dichloroethane solutions has been carried out at 25°C. The stability constants of the resulting 1:1 complexes in acetonitrile and nitrobenzene solutions were determined from the molar conductance-mole ratio data and found to vary in the order 18C6>DB30C10>DC18C6>DB18C6>DB21C7>DB24C8>B15C5. In 1,2-dichloroethane solution, the complexation process results in the dissociation of ion pairs. There is an inverse relationship between the stabilities of the complexes and the Gutmann donicity of the solvents. In nitrobenzene solution, some evidence for the formation of a 2:1 sandwich adduct between the smaller crowns (i.e., B15C5 and 18-crowns) are observed from the molar conductance-mole ratio data which is supported by the¹H NMR data.     

Remarks on the correlation function implied by the Bjerrum theory of ion pairing

The Friedman theory of correlation functions implied by the Bjerrum theory is generalized by taking into account additional terms and by improving the basic expression for the free energy. By combining the mean spherical approximation (MSA) and the mass action law (MAL) good agreement with HNC and MC data is reached.     

Dissociation constants: NH4OH as a standard

It is proposed that NH₄OH be used as a standard for determining dissociation constants on a standard basis. Ultrasonic absorption and electrical conductance measurements as a function of pressure provide the basis for quantitative evaluation of all parameters except activity coefficients. It is shown how the weak ionization of NH₄OH can be used to minimize uncertainty due to activity coefficients. Density data at atmospheric pressure confirm the values used to provide quantitative explanations of the acoustic and conductance data. Application of the differential sound absorption technique should extend the method dissociation constants of other classes of salts, in particular the 1–2, 2–2, and 3–2 sulfates.     

Asymmetric Counteranion‐Directed Catalysis: Concept,Definition, and Applications

Recently, the use of enantiomerically pure counteranions for the induction of asymmetry in reactions proceeding through cationic intermediates has emerged as an exciting new concept, which has been termed asymmetric counteranion‐directed catalysis (ACDC). Despite its success, the concept has not been fully defined and systematically discussed to date. This Review closes this gap by providing a clear definition of ACDC and by examining both clear cases as well as more ambiguous examples to illustrate the differences and overlaps with other catalysis concepts.     

Ground State Structure of Hs Super-heavy Isotopes

The ground state properties of Hs nuclei studied in the framework of the relativistic mean field theory revealed that more stable isotopes are located on the proton abundant side of the chain.The last stable nucleus to the proton drip line is ~(256)Hs.The most stable unknown Hs nucleus may be ~(268)Hs.The density dependent delta interaction pairing is used to improve the BCS pairing correction,which results in more reasonable single-particle energy level distributions and nucleon occupation,and it is shown to be available to describe the properties of nuclei in the superheavy region.     

Analysis of questioned documents: A review

During the last years (2000–2014), many publications concerning the forensic analysis of questioned documents have been published, and new techniques and methodologies are nowadays employed to overcome forensic caseworks. This article reviews a comprehensive collection of the works focused on this issue, including dating studies, the analysis of inks from pens and printers, the analysis of paper, the analysis of other samples related to questioned documents and studies on intersecting lines. These sections highlight the most relevant analytical studies by a wide range of analytical techniques. Separation and spectrometric techniques are critically discussed and compared, emphasizing the advantages and disadvantages of each one. Finally, concluding remarks on the research published are included.     

Ne wtonian-Rie mannian时空中的动力学(Ⅰ)

根据现代微分几何的理论 ,力学原理及现代微积分把Newtonian_Galilean时空中的动力学推广到Newtonian_Riemannian时空中 ,建立N_R时空中的动力学 ,分几个部分 ,(Ⅰ )是其中之一 ,余后续·     

Oligonucleotide Analogues with Integrated Bases and Backbones. Part 23

The sulfone 2 , and the sulfoxides (S)‐ 3 and (R)‐ 3 were obtained by oxidation of the thiomethylene‐linked A*[s ]U dinucleoside 1 . Conformational analysis and association studies of 2 , (S)‐ 3 , and (R)‐ 3 reveal a strong influence of the configuration on the conformation of the linking unit and on the self‐association of the dinucleosides.