Stability Prediction of cefazolin sodium and Cephaloridine in solid state

The stability of commercially-available solid pharmaceutical preparations containing cephaloridine and cefazolin sodium was evaluated with an accelerated isothermal degradation method at three different temperatures (37°, 45° and 60°C). A specific and sensitive differential pulse polarographic method was used for cephalosporin determination. Data obtained from high-temperature studies were processed using Arrhenius relation to predict shelf-life. The greater thermal stability of cephaloridine than cefazolin sodium was found, in contrast to what can be deduced from official monographs. Differential scanning calorimetry and X-ray diffraction were used to characterize the solid state of cephalosporin antibiotics.     

Diclofenac sodium: oxidative degradation in solution and solid state

The formation of two oxidative degradates of diclofenac in solution and the solid state was demonstrated.     

Stability study of flutamide in solid state and in aqueous solution

A high-performance liquid chromatography (HPLC) assay has been developed for the determination of flutamide and its degradation products. Using this method, the influence of important formulation factors on the stability of flutamide has been estimated. The stability studies have been carried out in solid state as well as in aqueous solution. The results obtained have shown a good stability for flutamide in solid state. This drug remained practically unchanged after a four-month assay in adverse temperature and humidity conditions. On the other hand, the results obtained from the stability study in solution during 12 days have shown that flutamide in aqueous solution underwent a clear degradation at mean or high temperature (22°C, 37°C) and acidic pH conditions (1.1). With respect to the influence of ionic strength, it has been found that the presence of sodium chloride prevents the degradation of flutamide in aqueous solution. The second-order kinetics model provides the best fit for highly degraded solutions.     

Relevance of liquid state to solid state properties

We outline in this talk the beginning of a new programme to study physical properties of crystalline solids. It is based on considering the latter, a broken symmetry phase, in terms of the higher symmetry liquid phase. The solid is a calculable perturbation on the fluid. This is exactly opposite to the standard approach which relates mechanical properties to the behaviour of defects (mainly dislocations) etc., in an otherwise perfect crystalline solid. However, most other broken symmetry phases (e.g. ferromagnets) are discussed starting from a symmetric Hamiltonian or a free energy functional, and earlier work by one of the authors shows that the liquid-solid transition is well described, qualitatively and quantitatively, by this approach. On the other hand, defect theories of melting have a long record of nonsuccess. In the first part of the talk, the density wave theory of freezing will be outlined, and it will be shown how properties such as Debye Waller factor, entropy change of freezing etc. can be calculated with no or one free parameter. The problem of calculating shear elastic constants and dislocation core structures as well as energies in terms only of observable liquid state properties will be set up, and results presented. The method will be contrasted with zero temperature ‘atomistic’ models which obscure the essential dependence on structure and flounder in a mass of detail. The concluding part will describe further proposed applications, some suggestive experimental results extant in the literature, and some speculations. Only a summary is presented.     

Stability of thin solid films

A small amplitude perturbation analysis is used to determine the conditions under which a solid film several hundred ångströms thick on a substrate will rupture. If the perturbation grows with time the film is unstable and rupture may occur, whereas if the perturbation decays the film is stable. Film rupture is caused essentially by diffusion of atoms along the free interface of the film which can, under certain conditions, amplify a perturbation applied to the film-gas interface. This surface diffusion is generated by a gradient of the chemical potential along the free interface. The chemical potential is affected by the curvature of the interface, by the pre-existing internal stresses normally found in thin films (they generate a strain energy term in the chemical potential) and by interaction forces between the atoms at the gas-solid interface with those of the film and substrate. The thin film is assumed to behave like an elastic body. The difference in the forces which act on a volume element in a film thinner than the range of interaction forces between the atoms of the film and substrate and the forces in a bulk solid is accounted for by introducing a body force into the equations of displacement of an elastic solid. Because of the difficulties in writing boundary conditions at the film-substrate interface, two limiting situations are considered: (1) a thin film on a rigid substrate and (2) a thin free film. A critical internal stress necessary for rupture is identified. The time of rupture is estimated from the inverse of the maximum growth coefficient of the perturbation. The dominant wavelength corresponding to the maximum growth coefficient gives an idea as to the size of the islands formed through rupture.     

Rheology of polypropylene in the solid state

The tensile behaviour of a commercial grade of isotactic polypropylene was tested in a temperature range between 20 and 150 °C with a video-controlled testing system which is capable of imposing a constant true strain-rate within the neck automatically. The results are displayed in the form of effective stress-strain curves and modelled by a constitutive equation in a multiplicative form. It is thus shown that, for each temperature, the plastic response can be described up to very large strains ( 2.0) by a set of four parameters. The assumptions introduced in this modelling are critically discussed in order to check the validity of the simplifying hypotheses (strain homogeneity, isochoric deformation, etc.). The constitutive equation thus obtained was utilized in a finite difference code in order to predict the development of stretching instabilities of polypropylene. The simulation gives access to the engineering stress-strain response of the stretched test piece and to the detailed kinetics of the incipient neck. It is found that the severity of the instabilities is less at room temperature than near the melting point because of the decrease of the strain-hardening and of the strain-rate sensitivity with temperature.     

组元配比对球磨固态燃烧式反应和扩散型反应的影响

采用搅拌式高能球磨机研究了不同铝含量的Al/CuO球磨固态燃烧反应和Al-Cu及Al-Cu-Al2O3扩散型反应。结果表明：理想配比的Al/CuO的反应孕育期最短,偏离这一配比,孕育期延长,反应由整体燃烧式逐渐过渡到渐进燃烧式完成;球磨强度扩大以燃烧式进行的组元配比范围;当铝含量超过理想配比中的比例,随Al含量增加,反应由单一的还原反应向还原＋合成复合反应模式转化,反应产物为平衡组织,依次为Cu Al2O3、CuoAl4 Al2O3、CuAl2 Al2O3、Al(Cu) Al2O3;而球磨Al-Cu和Al-Cu-Al2O3体系的反应以扩散方式进行,产物是非平衡组织。     

Combinatorial solid state materials science and technology

Conventional ‘one by one’ synthesis approach has been a major rate limiting step in the systematic exploration of increasingly complex materials for the demanding new technologies. New concepts of ‘combinatorial chemistry’ are presented for the substantially efficient and cost-effective parallel synthesis and optimization of variety of multicomponent compounds as well as artificially designed lattices and devices. Effectiveness of variety of application areas developed by us is discussed with typical examples and brief review of the merits, challenges, current status and the future directions.     

Material state remapping in computational solid mechanics

A computational procedure for remapping material state information from one finite element mesh to another is described. The procedure is useful in connection with evolving meshes for inelastic problems, as for example occur in the context of fracture simulation and adaptive mesh refinement. The proposed method is based on weak enforcement of equality between corresponding fields on the two meshes, where piecewise‐constant fields on both meshes are generalized from the quadrature‐point values. The essential algorithmic problem is that of calculating the volume partition of an arbitrary convex region with respect to a covering set of disjoint convex regions. Instead of geometrically resolving the associated intersections, the problem is herein approximated by a constrained optimization problem, which may be readily and efficiently solved computationally. This formulation is a main contribution of the paper. Computational examples are given that illustrate the effectiveness of the proposed procedure. Copyright © 2002 John Wiley & Sons, Ltd.     

Stress-strain state of solid railway wheels

A method for the design of railway wheels, which is based on use of the semianalytical finite-element method and which makes it possible to account for both the forces of contact interaction between the wheel and rail and negative production clearance during the press fitting of wheels, is developed.Translated from Problemy Prochnosti, No. 10, pp. 75–78, October, 1990.     

Role of stacking faults in solid state transformations

This article illustrates the two different roles played by stacking faults in solid state transformations viz. (i) in accommodating part of the transformation strains as observed in the noble metal-based alloys undergoing martensitic transformations, and (ii) in providing a mechanism for changing the stacking sequence of layers in a variety of materials like SiC, ZnS, Co and its alloys, and certain steels. Diffraction patterns taken from the martensitic phases of noble-metal-based alloys as well as from SiC and ZnS crystals undergoing transformation from one close-packed modification to another reveal the presence of characteristic diffuse streaks. It is shown that from a theoretical analysis of the observed intensity distribution along streaked reciprocal lattice rows in terms of physically plausible models for the geometry and distribution of faults, one can make a choice between various possible routes for transformation. From simple computer simulation studies, it is shown that the observed arrest of transformations in SiC is essentially due to the insertion of stacking faults in a random space and time sequence leading to an irregular distribution of solitons.     

Study of omeprazole-gamma-cyclodextrin complexation in the solid state

The possibility of obtaining inclusion complexes between omeprazole (OME) and γ-cyclodextrin (γ-CD) by kneading, spray-drying, coprecipitation, and freeze-drying was evaluated. All these methods lead to the isolation of a true inclusion compound, as evidenced by differential scanning calorimetry (DSC), infrared spectroscopy, and X-ray diffractometry on powder (PXRD). Moreover, PXRD and scanning electron microscopy (SEM) afforded data concerning crystallinity and surface characteristics of the solid phases obtained. In all cases, a significant increase of the release rate with respect to the drug alone was found, and it was attributed to the formation of an inclusion compound. Among the solid phases obtained, the coprecipitated product presented the highest dissolution rate.     

Four decades of research in solid state chemistry

Solid state chemistry was in its infancy when the author got interested in the subject. In this article, the author outlines the manner in which the subject has grown over the last four decades, citing representative examples from his own contributions to the different facets of the subject. The various aspects covered include synthesis, structure, defects, phase transitions, transition metal oxides, catalysts, superconductors, metal clusters and fullerenes. In an effort to demonstrate the breadth and vitality of the subject, the author shares his own experiences and aspirations and gives expression to the agony and ecstacy in carrying out experimental research in such a frontier area in India. Distinguished Materials Scientist Award Lecture presented at the MRSI meeting, Trivandrum on February 9, 1993. Professor C N R Rao, born on June 30, 1934 in Bangalore, received the M. Sc. degree in Physical Chemistry from Banaras Hindu University in 1953, the Ph.D degree from Purdue University, USA in 1958 and the D.Sc. degree from the University of Mysore in 1960. He was a research scholar at IIT, Kharagpur (1953–54), Lecturer at the Indian Institute of Science (1959–63), Associate Professor (1963–64) and Professor (1964–76) at the Indian Institute of Technology, Kanpur. He was the first Head of the Chemistry Department as well as the first Dean of Research at IIT, Kanpur. He moved back to the Indian Institute of Science in 1976 where he was founder Chairman of the Solid State and Structural Chemistry Unit and the Materials Research Laboratory till 1984, when he became the Director of the Institute. He has been President of the Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore since its founding in 1989. He was President of the Indian National Science Academy and the Indian Academy of Sciences as well as the International Union of Pure and Applied Chemistry. He was Commonwealth Professor at the University of Oxford and Nehru Professor at the University of Cambridge. He is the author of over 800 research papers and has authored/edited 30 books pertaining to solid state chemistry, spectroscopy, molecular structure, surface science and chemical education. He is a member of the editorial boards of over 15 international journals and is the founder-editor of the Bulletin of Materials Science. He is Honorary Professor at the University of Wales, Cardiff (UK) and Adjunct Professor at the Pennsylvania State University. Of the many honours received by Professor Rao, mention may be made of the Marlow Medal of the Faraday Society, London (1967), Bhatnagar Prize (1968), Jawaharlal Nehru Fellowship (1973), Padma Shri (1974), Sir C V Raman Award of the University Grants Commission (1975), Centennial Foreign Fellowship of the American Chemical Society (1976), Federation of the Indian Chambers of Commerce and Industry Prize (1977), S N Bose Medal of the Indian National Science Academy (1980), Royal Society of Chemistry (London) Medal (1981), P C Ray Medal of the Indian Chemical Society (1984), Padma Vibhushan (1985), Nehru Award for Science (1988), Modi Award for innovative science (1989), Hevrovsky Gold Medal of the Czechoslovak Academy (1989), Honorary Fellowship of the Royal Society of Chemistry, London (1989), Meghnad Saha Medal of INSA (1990), CSIR Golden Jubilee Prize in physical sciences (1991), Blackett Lectureship of the Royal Society (1991), K K Barooah Foundation Award for Science (1992) and Goyal Prize in Chemistry (1993). Professor Rao is a Fellow of the Science Academies in India and of the Royal Society, London. He is a Foreign Associate of the US National Academy of Sciences and a Foreign Member of the American Academy of Science and Arts, the Russian Academy of Science as well as the Czech, Polish, Serbian and Slovenian Science Academies. He is a member of the Pontifical Academy of Sciences and a founder fellow of Third World Academy of Sciences (of which he is now Vice President). He is an honorary member of the Materials Research Societies of Japan and South Korea and of the International Academy of Ceramics and honorary fellow of Institution of Engineers and IETE. He has received D.Sc. (honoris Causa) from 22 Universities. He was a member of the first National Committee on Science and Technology and later of the Scientific Advisory Committee to the Union Cabinet. He was Chairman of the Science Advisory Council to Prime Minister Rajiv Gandhi.     

Ionic space-charge effects in solid state organic photovoltaics

The effect of mobile ions on the operation of donor-acceptor bilayer solar cells is studied. We demonstrate the large effect ions can have on the energetics of the solar cells, illustrated by (for instance) changing the output voltage of a cell in situ from 0.35 to 0.74 V. More importantly, it is shown ionic species do not obstruct the charge generating properties of the photovoltaic devices and ionic space charge can be used in situ to improve their efficiencies. The results obtained are explained by taking into account energetic changes at the donor-acceptor interface as well as built-in potentials, giving clear guidelines on how ionic species can offer many new and exciting functionalities to organic photovoltaics.