A Self Consistent Field Formulation of Excited State Mean Field Theory

We show that, as in Hartree Fock theory, the orbitals for excited state mean field theory can be optimized via a self-consistent one-electron equation in which electron-electron repulsion is accounted for through mean field operators. In addition to showing that this excited state ansatz is sufficiently close to a mean field product state to admit a one-electron formulation, this approach brings the orbital optimization speed to within roughly a factor of two of ground state mean field theory. The approach parallels Hartree Fock theory in multiple ways, including the presence of a commutator condition, a one-electron mean-field working equation, and acceleration via direct inversion in the iterative subspace. When combined with a configuration interaction singles Davidson solver for the excitation coefficients, the self consistent field formulation dramatically reduces the cost of the theory compared to previous approaches based on quasi-Newton descent.Comment: 6 pages, 3 tables, 1 figure, plus supplementary materia

OPTIMIZATION OF FORMULATION OF SOLID DISPERSION OF FUROSEMIDE BY FACTORIAL DESIGN

Objective: The present study aimed to improve the rate of dissolution of furosemide by solid dispersion technique. Methods: Solid dispersion of furosemide was prepared by using hydrogel isolated from the seeds of Lepidium sativum as a novel carrier by the solvent evaporation method. Solid dispersion was evaluated to study the improvement in the rate of dissolution. Molecular dispersion of furosemide in the novel carrier was studied by DSC and FTIR studies. Solid dispersion was filled in capsules after stability studies and the formulation was optimized by adopting factorial design. Results: Solid dispersion of furosemide exhibited dissolution improvement from 13.54 % (plain furosemide) to 69.12% (solid dispersion) in the first 60 min. Improvement in dissolution efficiency was found to be retained after stability studies. Capsules were filled with the formulation of solid dispersion using two different grades of lactose-α lactose monohydrate and anhydrous lactose and were found stable after stabilization studies. Conclusion: The dissolution improvement of furosemide was attributed to its molecular dispersion in the novel carrier selected for this study. The recrystallization of furosemide was prevented due to intermolecular interaction between the novel carrier and furosemide. This was confirmed by FTIR. Evaluation of the dissolution data of factorial batches was analyzed by ANOVA. Analysis of the data revealed that selected levels of α lactose monohydrate and anhydrous lactose would be useful to navigate design space

STUDY OF THE FUNCTIONALITY OF A NOVEL SOLUTION BINDER OBTAINED FROM OCIMUM BASILICUM SEEDS: A MECHANISTIC APPROACH

Objective: The aim of the present study was to investigate the functionality of the hydrogel isolated from the seeds of Ocimum basilicum (Gel) as a novel solution binder. Methods: Paracetamol is known to possess poor manufacturability. Therefore it was selected as a model drug to study the efficiency of Gel as a solution binder. Paracetamol tablets were prepared at gradually increasing compression pressure from the granules prepared by using Gel of various viscosities as a solution binder. Compactibility parameter was calculated to assess the utility of Gel as a novel tablet binder. Optimization of the formulation was done by adopting factorial design as an appropriate DOE. Tablets of factorial batches were evaluated for disintegration time and crushing strength. The effect of viscosity of binder solution used to prepare granulation and compression pressure applied on granulation on the performance of the tablets was confirmed by analyzing the data using ANOVA. Results: The addition of binder solution to prepare granulation with the viscosity ≥ 19.33 centipoises was found to be suitable to attain desired degree of agglomeration. The crushing strength of the tablets was found to be increased with an increase in compression pressure and an increase in viscosity of binder solution. Conclusion: The compatibility parameter was observed to be increased as the viscosity of the binder solution added in the formulation was gradually increased. The Gel as a binder material was found to deform plastically at compression pressures 34.48 to 75.85 MPa. This confirmed its functionality as a solution binder in Paracetamol tablet preparation

Temperature-driven transition from the Wigner Crystal to the Bond-Charge-Density Wave in the Quasi-One-Dimensional Quarter-Filled band

It is known that within the interacting electron model Hamiltonian for the one-dimensional 1/4-filled band, the singlet ground state is a Wigner crystal only if the nearest neighbor electron-electron repulsion is larger than a critical value. We show that this critical nearest neighbor Coulomb interaction is different for each spin subspace, with the critical value decreasing with increasing spin. As a consequence, with the lowering of temperature, there can occur a transition from a Wigner crystal charge-ordered state to a spin-Peierls state that is a Bond-Charge-Density Wave with charge occupancies different from the Wigner crystal. This transition is possible because spin excitations from the spin-Peierls state in the 1/4-filled band are necessarily accompanied by changes in site charge densities. We apply our theory to the 1/4-filled band quasi-one-dimensional organic charge-transfer solids in general and to 2:1 tetramethyltetrathiafulvalene (TMTTF) and tetramethyltetraselenafulvalene (TMTSF) cationic salts in particular. We believe that many recent experiments strongly indicate the Wigner crystal to Bond-Charge-Density Wave transition in several members of the TMTTF family. We explain the occurrence of two different antiferromagnetic phases but a single spin-Peierls state in the generic phase diagram for the 2:1 cationic solids. The antiferromagnetic phases can have either the Wigner crystal or the Bond-Charge-Spin-Density Wave charge occupancies. The spin-Peierls state is always a Bond-Charge-Density Wave.Comment: 12 pages, 8 EPS figures. Longer version of previous manuscript. Contains new numerical data as well as greatly expanded discussio

Temperature-driven transition from the Wigner crystal to the bond-charge-density wave in the quasi-one-dimensional quarter-filled band

It is known that within the interacting electron model Hamiltonian for the one-dimensional 1/4-filled band, the singlet ground state is a Wigner crystal only if the nearest-neighbor electron-electron repulsion is larger than a critical value. We show that this critical nearest-neighbor Coulomb interaction is different for each spin subspace, with the critical value decreasing with increasing spin. As a consequence, with the lowering of temperature, there can occur a transition from a Wigner crystal charge-ordered state to a spin-Peierls state that is a bond-charge-density wave with charge occupancies different from the Wigner crystal. This transition is possible because spin excitations from the spin-Peierls state in the 1/4-filled band are necessarily accompanied by changes in site charge densities. We apply our theory to the 1/4-filled band quasi-one-dimensional organic charge-transfer solids, in general, and to 2:1 tetramethyltetrathiafulvalene (TMTTF) and tetramethyltetraselenafulvalene cationic salts, in particular. We believe that many recent experiments strongly indicate the Wigner crystal to bond-charge-density Wave transition in several members of the TMTTF family. We explain the occurrence of two different antiferromagnetic phases but a single spin-Peierls state in the generic phase diagram for the 2:1 cationic solids. The antiferromagnetic phases can have either the Wigner crystal or the bond-charge-spin-density wave charge occupancies. The spin-Peierls state is always a bond-charge-density wave

Management of intra-articular fractures of distal end radius in adults

Background: Incidence of intra articular fracture L/3rd radius is significantly on rise due to high velocity accidents in young and adults. Painless wrist function is of vital importance for functioning of upper extremity in almost all activities of daily living and precise function of hand. Intra articular fracture of L/3rd radius has generally gross comminution and so also small articular fragments. Orthopaedic community differ about specific implants to fix this complex injury. The present study was undertaken to know efficacy of different modalities of treatment for different fracture pattern. Comminuted intra articular fracture geometry varies widely, to fix these small fragments to achieve stable anatomical reduction is a challenging task.   Methods: It is a combined i.e. retrospective and prospective study conducted at Hardikar Hospital, Pune, India from 1999 to December 2000. Patients of intra-articular fracture of distal end radius by different modes of treatment are included in the study. 1 patient with unilateral fracture was lost for follow-up. Thus 50 fractures, in 49 patients. were included in study. Clinico-radiological assessment was carried out by Lidstrom's (1959) criteria.Results: Satisfactory early functional end results with plaster treatment is 72.2% whereas with other modality of treatment it rises to 87.5%, indicating superiority of other modalities of treatment as far as early functional end results are concerned.Conclusions: Manipulation and plaster cast method continues to be the treatment of choice in the stable intra articular distal radial fractures. Hence there is a need for a "differentiated therapy for distal radial fractures". The treatment plan for patients must be based not only on fracture pattern identified on plain radiographs but also on factors such as bone quality, bone comminution, energy of injury and associated soft tissue damage. Additional factors to be considered in individual patient are-life style associated medical conditions and compliance

Formulation and Evaluation of Solid Dispersions of Furosemide in Sodium Starch Glycolate

Purpose: This investigation was carried out to determine if a solid dispersion of furosemide in sodium starch glycolate (SSG) would enhance the dissolution properties of the drug. Methods: Solid dispersion of furosemide in SSG was prepared in ratios of 1:1 and 1 (furosemide):2 (SSG) by kneading method. In each case, the solid dispersion was characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and X-ray diffraction (XRD) to ascertain if there were any physicochemical interactions between drug and carrier that could affect dissolution. Tablets containing the solid dispersion were formulated and their dissolution characteristics compared with commercial furosemide tablets. The dissolution studies were performed at 37 ± 0.5oC and 50 rpm in simulated gastric fluid (pH 1.2). Results: FTIR spectroscopy, DSC, and XRD showed a change in crystal structure toward an amorphous form of furosemide. Dissolution data indicated that furosemide dissolution was enhanced. XRD, DSC, FTIR spectroscopy and dissolution studies indicated that the solid dispersion formulated in 1:2 ratio showed a 5.40-fold increase in dissolution and also exhibited superior dissolution characteristics to commercial furosemide tablets. Conclusion: Solid dispersion technique can be used to improve the dissolution of furosemide Keywords: Solid dispersion, Furosemide, Sodium starch glycolate, Dissolution enhancement, physicochemical characterisationTropical Journal of Pharmaceutical Research Vol. 8 (1) 2009: pp. 43-5

Anomalous current transport in Au/low-doped n-GaAs Schottky barrier diodes at low temperatures

The current-voltage characteristics of Au=low doped n-GaAs Schottky diodes were determined at various temperatures in the range of 77-300 K. The estimated zero-bias barrier height and the ideality factor assuming thermionic emission (TE) show a temperature dependence of these parameters. While the ideality factor was found to show the T0 effect, the zero-bias barrier height was found to exhibit two different trends in the temperature ranges of 77-160 K and 160-300 K. The variation in the flat-band barrier height with temperature was found to be -(4.7±0.2)× 104 eVK-1, approximately equal to that of the energy band gap. The value of the Richardson constant, A∗∗, was found to be 0.27 Acm-2K-2 after considering the temperature dependence of the barrier height. The estimated value of this constant suggested the possibility of an interfacial oxide between the metal and the semiconductor. Investigations suggested the possibility of a thermionic field-emission-dominated current transport with a higher characteristic energy than that predicted by the theory. The observed variation in the zero-bias barrier height and the ideality factor could be explained in terms of barrier height inhomogenities in the Schottky diode