Fourier transform infrared studies on the thermal degradation of polyacrylonitrile

Fourier transform infrared studies of the thermal degradation of polyacrylonitrile (PAN) conducted at 200°C in air and under reduced pressure are presented. The spectra are markedly superior to those published previously. A mechanism consistent with the infrared results obtained under reduced pressure is advanced, and assignments for the infrared bands occuring in the spectrum of both the reduced pressure and air degraded PAN are given.     

Exclusive 1,2-Reduction of Functionalised Conjugated Aldehydes with Sodium Triacetoxyborohydride

Functionalised α, β-unsaturated aldehydes were exclusively reduced to allylic alcohols with sodium-triacetoxyborohydride. Neither saturated alcohol nor saturated aldehydes are obtained. Conjugated ketones are not reduced.     

Stability of reduced molybdosilicic acids

The effect of reduction on the stability of molybdosilicic acids (MSA) has been investigated. It has been found that when two or more of the 12 Mo(VI) atoms in alpha or beta-MSA are reduced to Mo(V), the products are stable in alkaline medium. Also, beta-MSA reduced to this extent is stable at higher temperature and is not transformed into alpha-MSA. Solutions in which the apparent degree of reduction is less than 2 Mo(V) per MSA ion should be treated as a mixture of unreduced MSA and MSA reduced exactly to 2 Mo(V) per MSA ion. A mixture of unreduced MSA and MSA reduced to contain 4 Mo(V) per MSA ion is not a stable system. The yellow unreduced MSA is reduced by the reduced form to give the product with 2 Mo(V) per MSA ion. The consequences for determining silicon as MSA are given, as well as a method of obtaining pure beta-MSA from a mixture of alpha-MSA and beta-MSA.     

Density dependences of long-range fluctuations and short-range correlation lengths of CHF3 and CH2F2 in supercritical states

Small-angle x-ray scattering (SAXS) measurements are carried out for supercritical polar fluorocarbons, CHF3 and CH2F2, along the isotherm of 1.04 in reduced temperatures with the density range from 0.3 to 1.5 in reduced units. A novel apparatus for determination of absorption factors of the sample fluids is used in the present measurements. The apparatus enables us to detect simultaneously the accurate factors during the observation of the SAXS signals. Long-range fluctuations such as density fluctuations and correlation lengths are evaluated from the obtained SAXS data. The reduced correlation lengths are obtained by normalization by each molecular size, in order to discuss the fluctuations independent of the difference of the individual molecular size. The density fluctuations and the reduced correlation lengths of CHF3 and CH2F2 are compared with those of CO2 and H2O. The results are as follows: H2O>CH2F2>CHF3 approximately CO2 in the order of magnitude. The fluctuations of CH2F2 are significantly distinguishable from those of CHF3 and show intermediate aspect between H2O and a group of CO2 and CHF3. In addition, the short-range correlation lengths, i.e., the Ornstein-Zernike direct correlation lengths, are firstly discussed from both viewpoints of density and substance dependences. The reduced short-range correlation lengths normalized by individual molecular size are found to trace a universal curve as a function of the reduced density.     

Wick’s theorem and reconstruction schemes for reduced density matrices

We first obtained a closed form of the Wick’s theorem expressed in Grassman wedge product, which is similar to a binomial expansion. With this new expansion, new reconstruction schemes for reduced density matrices are derived rigorously. The higher order reduced density matrices are systematically decomposed into a sum of the lower order reduced density matrices which could be used to solve the contracted Schr?dinger equation.     

Epoxide composites with thermally reduced graphite oxide and their properties

The properties of epoxide composites modified by thermal reduced graphite oxide are studied. The dielectric permittivities of epoxide composites with additives of up to 1.5 wt % of reduced graphite oxide are studied at a frequency of 9.8 GHz. It is shown that despite its low electrical conductivity, the large specific surface area of reduced graphite oxide allows us to create epoxide composites with high complex dielectric permittivities and dielectric loss tangents.     

Further development of reduced graphs for identifying bioactive compounds

Reduced graphs provide summary representations of chemical structures. Here, a variety of different types of reduced graphs are compared in similarity searches. The reduced graphs are found to give comparable performance to Daylight fingerprints in terms of the number of active compounds retrieved. However, no one type of reduced graph is found to be consistently superior across a variety of different data sets. Consequently, a representative set of reduced graphs was chosen and used together with Daylight fingerprints in data fusion experiments. The results show improved performance in 10 out of 11 data sets compared to using Daylight fingerprints alone. Finally, the potential of using reduced graphs to build SAR models is demonstrated using recursive partitioning. An SAR model consistent with a published model is found following just two splits in the decision tree.     

Charge density distributions derived from smoothed electrostatic potential functions: design of protein reduced point charge models

To generate reduced point charge models of proteins, we developed an original approach to hierarchically locate extrema in charge density distribution functions built from the Poisson equation applied to smoothed molecular electrostatic potential (MEP) functions. A charge fitting program was used to assign charge values to the so-obtained reduced representations. In continuation to a previous work, the Amber99 force field was selected. To easily generate reduced point charge models for protein structures, a library of amino acid templates was designed. Applications to four small peptides, a set of 53 protein structures, and four KcsA ion channel models, are presented. Electrostatic potential and solvation free energy values generated by the reduced models are compared with the corresponding values obtained using the original set of atomic charges. Results are in closer agreement with the original all-atom electrostatic properties than those obtained with a previous reduced model that was directly built from the smoothed MEP functions [Leherte and Vercauteren in J Chem Theory Comput 5:3279–3298, 2009].     

Arylthiols as highly chemoselective and environmentally benign radical reducing agents

Arylthiols serve as excellent environmentally benign reducing agents for organotellurium, organostibine, and organobismuthine compounds under radical conditions. Both small molecules and macromolecules possessing these heteroatom groups are reduced under moderate thermal conditions to give near quantitative yields in most cases. The reduction shows high chemoselectivity with respect to the heteroatom compounds; the reactivity decreases in the order alkylbismuthines, alkylstibines, and alkyltellurides, while simple alkyl iodides could not be reduced. Alkyltellurides are selectively reduced in the presence of alkyl iodides even when an excess amount of arylthiol is used. Furthermore, alkylstibines are also selectively reduced in the presence of alkyltellurides. Moreover, the reduction conditions are compatible with the presence of a variety of polar functional groups in the substrates, products, and solvents, which are not tolerant under ionic and metal-catalyzed conditions. Carbon-carbon bond formation is possible with use of the carbon-centered radicals that are generated. The results clearly reveal the synthetic utility of arylthiols in organic synthesis.     

Feature selection for hierarchical clustering

Feature selection is a valuable technique in data analysis for information-preserving data reduction. This paper describes a feature selection approach for hierarchical clustering based on genetic algorithms using a fitness function that tries to minimize the difference between the dissimilarity matrix of the original feature set and the one of the reduced feature sets. Clustering trees based on reduced feature sets are comparable with those based on the complete feature set. Special measures to favor small reduced feature sets are discussed.     

Ungesättigte endgruppen in PVC—V reduktionsreaktion der modelle von ungesättigten endgruppen des PVC

Models for unsaturated endgroups in PVC (viz 3-chloropentene-1, 1-chloropentene-2, 2,3-dichloropentene-1, 1,3-dichloropentene-1, 1,2-dichloropentene-2 and 2,4-dichloropentene-1) were reduced with LiAlH₄ in THF. Gas chromatographic, i.r. and NMR analyses of the products showed that the chlorine atoms attached to saturated carbon atoms are substituted by hydrogen atoms during the reduction, while those attached to carbon atoms linked by double bonds are not changed. By Cotman's reduction method, the double bonds are not reduced. Therefore the branching degree determined by methods based on measurement of CH₃ groups in reduced PVC must be corrected so that the nature and number of unsaturated end-groups are taken into account. Some of these groups can be determined by measurements on the reduced polymer.     

Similarity searching using reduced graphs

Reduced graphs provide summary representations of chemical structures. In this work, the effectiveness of reduced graphs for similarity searching is investigated. Different types of reduced graphs are introduced that aim to summarize features of structures that have the potential to form interactions with receptors while retaining the topology between the features. Similarity searches have been carried out across a variety of different activity classes. The effectiveness of the reduced graphs at retrieving compounds with the same activity as known target compounds is compared with searching using Daylight fingerprints. The reduced graphs are shown to be effective for similarity searching and to retrieve more diverse active compounds than those found using Daylight fingerprints; they thus represent a complementary similarity searching tool.     

Rieke zinc as a reducing agent for common organic functional groups

The ability of Rieke zinc to reduce common organic functional groups has been studied. Nitrobenzene, conjugated aldehydes, arylacetylenes, and phenylpropiolates are readily reduced under mild conditions. Benzonitrile, alkylacetylenes, ketones, unconjugated aldehydes, and alkenes are not reduced.     

Ground state reduced potential curves (RPC) of metal hydrides of the IIb group and of PtH

Ground state reduced potential curves calculated from the RKR (Rydberg-Klein-Rees) potentials of IIb-metal hydrides are shown to represent the most salient exception as yet encountered in the scheme of reduced potentials; the anomalous behavior of the ground state reduced potential curve is most stiking for HgH as compared with the ground state reduced potentials of the heavy metal hydrides TlH and PtH. This is in line with the well known anomalies of metal hydrides of the llb group.     

Corresponding states theory and thermodynamic properties of liquid alkali metals

According to phenomenological scaling and the law of corresponding states, reduced coordinates F ^*-T ^*, where F* represents the reduced thermodynamic properties (enthalpy of vaporization, speed of sound, surface tension, saturated liquid density) and T ^* is the reduced temperature, are introduced for the prediction of the thermodynamic properties of alkali metals. Values of the thermodynamic properties from the melting point up to boiling point are correlated. It has been shown that the correlation between reduced thermodynamic properties, as well as with the reduced temperature, can be expressed as a unique straight-line plot with a linear correlation coefficient of 0.9998. The proposed correlation has a simple form for easy calculation, requires only the melting and boiling point parameters, which are usually easy to acquire, and can predict the thermodynamic properties from the melting temperature up to the boiling temperature accurately.     

New techniques in radiochemical determinations using polarographic methods

This work was undertaken as part of a research program on the development of new radio-chemical procedures. The techniques used are those of standard polarographic practices. Radio-isotopes that can be polarographically reduced to the zero oxidation state amalgamate with the mercury, are removed from the solution, and the radioactivity determined. Reproducible curves of activity vs. Ede are found to be in every way analogous to polarograms obtained under the same experimental condition. The requirements necessary for any radio-ihotope to be determined quantitatively by this method are that the radio-isotope be polarographically reduced to the zero oxidation state and that no other radio-isotope be polarographically reduced at the same potential. This type of analysis has been successfully applied to several radio-isotopes and mixtures of radio-isotopes.     

Reduced cycle indices and their applications in enumeration of NMR signals and equivalence classes

An efficient technique is formulated based on a polynomial structure which we call the reduced cycle index for the enumeration of equivalence classes and NMR signals under group action. The reduced cycle indices are shown to be the cycle index polynomials of a subset of significantly smaller order of the point group of the molecule. Thus, the reduced cycle indices are much simpler and their use leads to a considerable reduction in tile computation of the generating functions from the cycle indices and irreducible representations contained in a set.Alfred P. Sloan Fellow; Camille and Henry Dreyfus Teacher-Scholar.     

Adsorption, diffusion and desorption of chlorine on and from rutile TiO2{110}: a theoretical investigation.

The adsorption, diffusion and desorption of chlorine on and from stoichiometric, reduced and partially reduced (defective) rutile TiO2{110} are investigated using ab initio density functional theory (DFT) calculations. Theoretical results are compared with experimental investigations, and microkinetic simulations based on DFT values are then used to verify the diffusion mechanisms assumed in the experimental investigations.     

Application of the Wilson—Wegner expansion to represent vapor—liquid equilibrium surfaces of binary and ternary systems from the critical locus to the vapor pressure of the heavier component

The Torquato—Stell modification of the Wilson—Wegner expansion has been used to present and to represent the vapor—liquid equilibrium surfaces of several binary methane—alkane mixtures and one ternary system from the critical locus to the heavier component's vapor pressure within the experimental accuracy of the data. Inconsistent phase compositions are revealed without recourse to equations of state computations. Since the critical point of the mixtures are not precisely known, an isothermal regression analysis of the data is first used to obtain an improved estimate of the critical point of mixtures using the scaled expressions. Then, along isotherms, the phase compositions are analyzed in terms of the reduced proximity to the critical pressure. Subsequently, the entire compositional surfaces are presented in terms of both the reduced proximity to the critical pressure of the mixture and the reduced proximity to the critical temperature of the heavier component.