Pointing the way to the products? Comparison of the stress tensor and the second-derivative tensor of the electron density

The eigenvectors of the electronic stress tensor can be used to identify where new bond paths form in a chemical reaction. In cases where the eigenvectors of the stress tensor are not available, the gradient-expansion-approximation suggests using the eigenvalues of the second derivative tensor of the electron density instead; this approximation can be made quantitatively accurate by scaling and shifting the second-derivative tensor, but it has a weaker physical basis and less predictive power for chemical reactivity than the stress tensor. These tools provide an extension of the quantum theory of atoms and molecules from the characterization of molecular electronic structure to the prediction of chemical reactivity.     

Is the ion-linear quadrupole capture rate constant anisotropic with respect to the sign of the product of the charge on the ion and the quadrupole moment of the molecule?

The sign of the charge-quadrupole moment product is shown to affect the rate of ion-linear quadrupole capture.

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Does the Temperature of the prise de mousse Affect the Effervescence and the Foam of Sparkling Wines?

The persistence of effervescence and foam collar during a Champagne or sparkling wine tasting constitute one, among others, specific consumer preference for these products. Many different factors related to the product or to the tasting conditions might influence their behavior in the glass. However, the underlying factor behind the fizziness of these wines involves a second in-bottle alcoholic fermentation, also well known as the prise de mousse. The aim of this study was to assess whether a low temperature (13 °C) or a high temperature (20 °C) during the in-bottle fermentation might have an impact on the effervescence and the foaming properties (i.e., collar height and bubble size) of three French sparkling wines (a Crémant de Loire and two Champagne wines), under standard tasting conditions. Our results showed that sparkling wines elaborated at 13 °C and served in standard tasting conditions (i.e., 100 mL, 18 °C) had better ability to keep the dissolved CO₂ (between 0.09 and 0.30 g/L) in the liquid phase than those elaborated at 20 °C (with P < 0.05). Most interestingly, we also observed, for the Crémant de Loire and for one Champagne wine, that the lower the temperature of the prise de mousse, the smaller (with P < 0.05) the bubbles in the foam collar throughout the wine tasting.     

Is the dynamical polarization a significant part of the contribution of the triples to the correlation energy?

One may call dynamical polarization of doubly excited configurations the energy lowering of these configurations under the response of the other electrons to the so-created fluctuation of the electric field. This contribution of triply excited configurations may be identified and calculated through a computation that only requires a computation time proportional to the sixth power of the number of molecular orbitals (MOs), instead of the seventh power for the total contribution of the triples. Its amplitude depends on the choice of the MOs and becomes important when localized MOs are used.     

Self-sorting: the exception or the rule?

In this paper, we pose the question of whether self-sorting in designed systems is exceptional behavior or whether it is likely to become a more general phenomenon governing molecular recognition and self-assembly. To address this question we prepared a mixture comprising two of Davis' self-assembled ionophores, Rebek's tennis ball and calixarene tetraurea capsule, Meijer's ureidopyrimidinone, Reinhoudt's calixarene bis(rosette), and two molecular clips in CDCl(3) solution and observed the behavior of this ensemble by (1)H NMR. As hypothesized, high-fidelity self-sorting behavior was observed. The influence of several key variables-temperature, concentration, equilibrium constants, and the presence of competitors-on the fidelity of self-sorting is described. These results show that self-sorting is neither the exception nor the rule. They suggest, however, that the subset of known molecular aggregates that exceed the criteria required for thermodynamic self-sorting is larger than previously appreciated and potentially quite broad.     

Micellar Copolymerization: the State of the Arts

Over the past two decades, hydrophobically modified water-soluble polymers (HMWSPs), particularly hydrophobically associating polyacrylamides (HAPAMs), have attracted increased interest owing to their practical and fundamental importance[1]. This system usually consists of a hydrophilic backbone with a small proportion (generally less than 2 mol %) of hydrophobic pendent groups. When dissolved in aqueous solutions, the apolar moieties tend to exclude water and are held together by intra- a…     

Correlation Analysis of the Runoff of the Rivers and the Seisms in China

In recent hundred years the annual discharge variations of the Changjiang River (represented by the Yichang station) and the Huanghe River (represented by Shanxian and Tangnaihe, respectively) have closely related to the geographical distribution of the earthquakes coming about in China in the same year, Both the occurrence of the destructive seism or seismic swarm in the river basins and the disappearance of the shocks in the east and south of the basins are the conditions that the Changjiang and Huanghe Rivers are the high flow while that the strong earthquake of magnitude 7 or more occurred in North China is the condition for the Changjiang low flow year and that of 6 or more in the Qilian Mountains area is for the Huanghe River. In the latter part of this paper, a 2-year sample is given to explain that the conditions of the 2 rivers being high flow years are that the north-south seismic belt is active and in the meanwhile no seism occurred in South China, and those of the low flow year are that the     

Exploration on the Biotechnological Aspect of the Ureolytic Bacteria for the Production of the Cementitious Materials—a Review

Biomineralization is a process that leads to the formation of minerals using the biologically or biotechnologically mediated route. Calcium carbonate is one such biomineral that is secreted by the ureolytic bacteria which contributes for the strengthening and improvement of cementitious and sandy materials. It is a new and innovative area in the geotechnological engineering and structural engineering due to its wide range of implications in strengthening of soil, sand, stone, and cementitious materials. The shape and size of the calcium carbonate particle vary with the strain of the bacterium used, and it is species specific. This paper aims in the critical review of the mechanism of calcium carbonate precipitation by the bacterium, various bacteria involved, and the useful outputs of the technique of biomineralization. Based on the critical review, it also recommends the future development and research in the field to develop a technology that can strengthen the existing and the proposed structures.     

Noninvasive Detection of the Gases Inside the Sealed Batteries by the On-line Mass Spectrometry

Mass spectrometer is connected through an adaptor to a sealed small battery to probe the gas phase changes inside the battery. The factors influencing the response time are analyzed with a simplified model. The feasibility of the new technique is demonstrated with a Ni-Cd battery, showing different profiles of MS intensities for O2 and H2. Compared with gas chromatography, this technique has the advantage of being noninvasive and should be useful for the study and diagnostic examination of small sealed batteries.     

Synthesis of two peptides of α-bungarotoxin and the participation of the amino acid residue Trp-28 of the neurotoxin in the antigenicity of the molecule

Using the method of solid-phase peptide synthesis, two peptides have been synthesized, one of which corresponds to the central ring structure of -bungarotoxin (-BTX), while the second has in position 28 a Gly residue in place of the Trp in the first peptide, and their interrelationship with antitoxin antibodies has been investigated. It has been shown that the amino acid residue Trp-28 of -BTX, which is the contact residue in binding with the acetylcholine receptor, also participates directly in binding with the active centers of antibodies to -BTX.Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 628–631, July–August, 1997.     

How to explain the difficulties in the coffinite synthesis from the study of uranothorite?

The preparation of Th(1-x)U(x)SiO(4) uranothorite solid solutions was successfully undertaken under hydrothermal conditions (T = 250 °C). From XRD and EDS characterization, the formation of a complete solid solution between x = 0 (thorite) and x = 0.8 was evidenced. Nevertheless, additional (Th,U)O(2) dioxide and amorphous silica were systematically observed for the highest uranium mole loadings. The influence of kinetics parameters was then studied to avoid the formation of such side products. The variation of the synthesis duration allowed us to point out the initial formation of oxide phases then their evolution to a silicate phase through a dissolution/precipitation process close to that already described as coffinitization. Also, the uranium mole loading initially considered was found to significantly influence the kinetics of reaction, as this latter strongly slows down for x > 0.3. Under these conditions, the difficulties frequently reported in the literature for the synthesis of pure USiO(4) coffinite were assigned to a kinetic hindering associated with the coffinitization reaction.     

Studies on the Kinetics of the FO CO Reaction

IntroductionAproposedcycleinvolvingtheFOradicalsisl:ThecontributionofthiscycletothecatalyticdestrUctionofozoneisdeterndnedbythefirststep.Thereaction(l)isalsothoughttobeapossiblesinkforatInosphericCO2.Baueretal.3gavearateconstantofl.24.lO-i3cm3/sforreaction(l),whichwasbelievedtobecorrectwithinafactorof2at9(X)-l4(X)K.Theactivationenergywasestimatedtobe46.OkJ/mol.Bedzhanyanetal.4reportedk<4xlO-"and<5xlO-l6cm3/sat3ooand55OK,respectively.Alowerbarrierofl3.8kJ/molcanbeextrapoIated.Francisco…     

On the Nature of the Cherdyntsev–Chalov Effect

It is shown that the Cherdyntsev–Chalov effect, usually presented as the separation of even isotopes of uranium upon their transition from the solid to the liquid phase, can include initiated acceleration of the radioactive decay of uranium-238 nuclei during the formation of cracks in geologically (seismic and volcanically) active zones of the Earth’s crust. The fissuring of the solid-phase medium leads to an increase in mechanical tensile stress and the emergence of strong local electric fields, resulting in the injection of chemical-scale high-energy electrons into the aqueous phase of the cracks. Under these conditions, the e^? catalytic decay of uranium-238 nucleus studied earlier can occur during the formation of metastable protactinium-238 nuclei with locally distorted nucleon structure, which subequently undergo β^–decay with the formation of thorium-234 and helium-4 nuclei as products of the fission of the initial uranium-238 nucleus with a characteristic period of several years. The observed increased activity of uranium-234 nuclei that form during the subsequent β-decay of thorium and then protactinium is associated with the initiated fission of uranium-238. The possibility is discussed of developing thermal power by using existing wastes from uranium production that contain uranium-238 to activate this isotope through the mechanochemical processing of these wastes in aqueous media with the formation of ₉₁ ²³⁸ Pa _isu , the half-life of which is several years.     

A Novel Oligosaccharide from the Mucus of the Loach

A novel oligosaccharide was isolated and purified from the mucus of the loach, Misgurnus anguillicaudatus. Its was identified by several qualitative tests and characterized by elementary analysis,UV and IR spectrum. Its average molecular weight(Mw=1539.4) was determined by gel permeation chromatography. The major structural monomers of Misgurnus anguillicaudatus oligosaccharide were identified to be D-galactose and L-fucose by paper chromatography and gas chromatography.     

Revisiting the Corey-Chaykovsky reaction: the solvent effect and the formation of β-hydroxy methylthioethers

The classical Corey-Chaykovsky (CC) reaction of ketones in ethereal solvents (i.e., THF or Et₂O) resulted in the production of a significant amount of β-hydroxy methylthioether 2 along with normal epoxide product 1. Some interesting and synthetically useful transformations of the CC reaction product of cyclopropyl ketones were also described.     

What is the structure of the RecA-DNA filament?

The bacterial RecA protein has been a model system for understanding how a protein can catalyze homologous genetic recombination. RecA-like proteins have now been characterized from many organisms, from bacteriophage to humans. Some of the RecA-like proteins, including human RAD51, appear to function as helical filaments formed on DNA. However, we currently have high resolution structures of inactive forms of the protein, and low resolution structures of the active complexes formed by RecA-like proteins on DNA in the presence of ATP or ATP analogs. Within a crystal of the E. coli RecA protein, a helical polymer exists, and it has been widely assumed that this polymer is quite similar to the active helical filament formed on DNA. Recent developments have suggested that this may not be the case.     

Does the topological approach characterize the hydrogen bond?

 The topological analysis of the electron localization function has been applied to complexes representative of the weak, medium and strong hydrogen bond. For both the weak and the medium hydrogen bonds, the number of basins in the complexes is the sum of those of the moieties. In this case, the formation of a weak or a medium hydrogen-bonded complex does not involve a chemical reaction. In the weak hydrogen bond case, the reduction of the localization domain yields two domains in the first step, which can be partitioned afterwards into valence and core domains. In contrast, for medium complexes the core–valence separation is the first event which occurs during the reduction process and therefore the complex should be considered as a single molecular species. Moreover, the analysis of the basin population variance indicates in this case a noticeable delocalization between the V(A, H) and V(B) basins. Finally, the symmetrical strong hydrogen bond has a protonated basin V(H) at the bond midpoint. Such a topology corresponds to an incomplete proton transfer and to a rather covalent bond. Received: 19 April 1999 / Accepted: 22 July 1999 / Published online: 17 January 2000     

Studies of the dissociation and the protonation of TB-chlorosulphophenol

The dissociation constant of each step for TB-chlorosulphophenol has been determined by potentiometric method, and the thermodynamic constants, △G°, △H° and △S°, of the dissociation process have been calculated. The protonation constants were measured by the spectrophotometric method. The pH values of various forms of anions of the chromogenic reagent at their concentrations were also calculated.