The spin-S Blume-Capel RG flow diagram

Using the finite-size scaling renormalization group, we obtain the two-dimensional flow diagram of the Blume-Capel model forS=1 andS=3/2. In the first case our results are similar to those of mean-field theory, which predicts the existence of first- and second-order transitions with a tricritical point. In the second case, however, our results are different. While we obtain in theS=1 case a phase diagram presenting a multicritical point, the mean-field approach predicts only a second-order transition and a critical endpoint.     

A Self-Similar Dynamics in Viscous Spheres

We study the evolution of radiating and viscous fluid spheres assuming an additional homothetic symmetry on the spherically symmetric space-time. We match a very simple solution to the symmetry equations with the exterior one (Vaidya). We then obtain a system of two ordinary differential equations which rule the dynamics, and find a self-similar collapse which is shear-free and with a barotropic equation of state. Considering a huge set of initial self-similar dynamics states, we work out a model with an acceptable physical behavior.     

Gravitational collapse of a charged and radiating fluid ball in the diffusion limit

The collapse of a charged and radiating ball in the diffusion limit is studied using a method reported by Herrera and collaborators. The interior solution is matched with the exterior Reissner-Nordström-Vaidya metric to obtain a system of differential equations at the surface of the distribution, which can be integrated numerically for some set of initial data. For one model, the profiles of the physical variables are obtained at any piece of the material in terms of Schwarzschild-like coordinates.     

Accurate Gaussian basis sets for the H2O molecule generated with the molecular improved generator coordinate Hartree–Fock method

The molecular improved generator coordinate Hartree–Fock (MIGCHF) method is used to generate accurate basis sets of primitive Gaussian-type functions for the H₂O molecule. Sequences of increasing size atom centered basis sets are employed to explore the accuracy that can be achieved with this method. Using the O(24s14p8d5f2g1h);H(22s9p5d2f1g) basis set, the HF and second-order electron correlation energies of the H₂O ground state at the experimental geometry are computed as −76.0674680 and −0.3491935 hartree, respectively. The HF energy is in error by 20 μhartree and the second-order correlation energy corresponds to 96.5% of an estimate of the limiting value. The relevance of the present calculations is to show the accuracy that can be achieved in studies of small polyatomic molecules with the MIGCHF method.     

Applications of thermal analysis in some solid-state reactions

TG-DTG-DTA has been used to characterize various isomers of CoCl₂·2(CH₃C₆H₄NH₂). Thermal analysis is further used to analyse the binary mixtures of these isomers. DTA recorded after different elapsed times follows the progress of reaction between cobalt chloride and benzocaine where progressively small endotherms are associated with starting materials. The application of thermal analysis to following the solid-solid reactions between metal acetates and 8-hydroxyquinoline was highlighted. The stoichiometry of such reactions was confirmed from the decrease in intensity of an endotherm as one increases the stoichiometry.Thanks are due to Drs. Keshav Chander, K. Kaur, Rajinder Singh and G. S. Chopra for helpful discussions and experimental work.     

Excitation decay pathways of Lhca proteins: a time-resolved fluorescence study

Light-harvesting complex I (LHCI), which serves as a peripheral antenna for photosystem I (PSI) in green plants, consists mainly of four polypeptides, Lhca1-4. We report room temperature emission properties of individual reconstituted monomeric Lhca proteins (Lhca1, -2, -3, and -4) and dimeric Lhca1/4, performed by steady-state and time-resolved fluorescence techniques. The emission quantum yields of the samples are approximately 0.12, 0.085, 0.081, 0.041, and 0.063 for Lhca1, -2, -3, -4, and the -1/4 dimer, respectively, which is considerably lower than the value of 0.22 found for light-harvesting complex II (LHCII), the main peripheral antenna complex of photosystem II in green plants. The decay components of LHCI proteins can be divided in two categories: Lhca1 and Lhca3 have decay times of 1.1-1.6 ns and 3.3-3.6 ns, and Lhca2 and Lhca4 have decay times of 0.7-0.9 ns and 3.1-3.2 ns. These categories seem to correlate with the pigment composition of the samples. All decay times are faster than that observed previously for LHCII. When the absolute emission yields and the lifetimes of the Lhca samples are combined, the overall emission properties of the individual Lhca proteins are expressed in terms of their emitting dipole moment strength. In the samples without extreme red states, that is, Lhca1 and Lhca2, the emitting dipole moment has a value close to unity (relative to monomeric chlorophyll in acetone), which is similar to that for LHCII, whereas, in the samples with the red-most state (F-730), that is, Lhca3, -4, and the -1/4 dimer, the emitting dipole moment has a value less than unity (0.6-0.8), which can be explained by mixing the red-most (exciton) state with a dark charge-transfer state, as suggested in previous PSI red pigment studies. In addition, we find a lifetime component of approximately 50-150 ps in all red-pigment-containing samples, which cannot be due to "slow" energy transfer, but is instead assigned to an unrelaxed state of the pigment-protein, which, on this time-scale, is converted into the final emitting state.     

Thermal decomposition of Cu(II) Malonate

The isothermal decomposition of anhydrous Cu(II) malonate of uniform particle size has been studied at 170, 180 and 190°. Decomposition to cupric oxide takes place via the intermediate formation of 2CuCO₃.Cu(OH)₂. X-ray diffraction has been employed to identify the decomposition products. The experimental kinetic data for Cu(II) malonate decomposition are best fitted by two stages: (i) a linear process and (ii) a first-order expression. The activation energies for the two kinetic stages have been found to be 45.7 and 57.2 kcal/mole, respectively. A DTA study of Cu(II) malonate decomposition has also been made. Activation energies have been determined via analysis of the DTA curve using the Borchardt and Piloyan equations.

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Zusammenfassung Die isotherme Zersetzung von wasserfreiem Cu(II)-malonat einheitlicher Partikelgröße wurde bei Temperaturen von 170°, 180° und 190° untersucht. Die Zersetzung von Cu(II)-malonat zu Kupfer(II)-oxid erfolgt über die intermediäre Bildung von 2CuCO₃.Cu(OH)₂. Die Röntgendiffraktionstechnik wurde zur Identifizierung der Zersetzungsprodukte eingesetzt. Die Versuchsergebnisse von Cu(II)-malonat können am besten zwei kinetischen Zuständen angepaßt werden: (1) einem linearen Prozeß und (2) einem Ausdruck erster Ordnung. Die entsprechenden Aktivierungsenergien für die zwei kinetischen Zustände waren 45.7 Kcal/Mol bzw. 57.2 Kcal/Mol. Eine DTA-Untersuchung von Cu(II)-malonat wurde ebenfalls durchgeführt. Die Aktivierungsenergien wurden aus der Analyse der DTA-Kurve mittels der Gleichungen von Borchardt und Piloyan bestimmt.

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Résumé On a étudié la décomposition thermique du malonate de cuivre(II) anhydre à 170, 180 et 190°. La décomposition du malonate en CuO se produit avec formation intermédiaire de 2CuCO₃.Cu(OH)₂. Les produits de décomposition ont été identifiés par diffraction des rayons X. Les données expérimentales correspondent à deux étapes de cinétique différente: (i) un processus linéaire et (ii) une expression du premier ordre. Les énergies d'activation respectives des deux étapes cinétiques s'élèvent à 45.7 et 57.2 kcal.mol^/s-1. Le malonate de cuivre(II) a aussi été étudié par ATD. Les énergies d'activation ont été déterminées à partir de la courbe ATD en appliquant les équations de Borchardt et de Piloyan.

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(II) 170°, 180° 190°. (II) 2CuCO₃. Cu(H)₂. . (II) : (1) (2) . , , , 45,7 / 57,2 /. (II). , , .

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One of the authors (P.C.K.) is grateful to the University Grants Comission, New Delhi, for the award of a junior research fellowship. The authors are grateful to Dr. K. N. Goswami of the Physics Department, University of Jammu, for his help in the X-ray studies of the products.     

Comparative study of solid state reactivity between ferrous oxalate dihydrate and unsubstituted/substituted aniline hydrochlorides

The solid state reactions between ferrous oxalate dihydrate i.e. FeC₂O₄.2H₂O and unsubstituted/ substituted aniline hydrochlorides have been studied. The products [FeCl/oxH/. AN-Cl] have been characterized by elemental analysis, infrared and Mössbauer spectroscopic techniques. The kinetic studies for the reactions have been performed at various temperatures for fixed particle sizes at constant compaction. The following order of reactivity has been observed: unsubstituted > p-substituted > m-substituted o-substituted.