A comparison of average and discounted cost models for the dynamic lot size inventory problem

It is a common practice in the inventory literature to use average cost models as approximations to the theoretically correct discounted cost models. An average cost model minimizes the average undiscounted cost per period, while a discounted cost model minimizes the total discounted cost over the problem horizon. This paper attempts to answer an important question: How good are the results (the total discounted costs) for the average cost models compared to those for the discounted cost models? This question has been conclusively answered for the simplest inventory model where the demand rate and other parameters are assumed to remain constant in time. This paper addresses this issue for the first time for the case where demand rates are allowed to be nonstationary in time.A discounted cost model has been developed in the paper to carry out this comparison. It is shown that a simple dynamic programming algorithm can be used to find optimal order policies for the discounted cost model.The effect of the varying interest rates and other parameters on the relative performance of the average cost model has been studied by developing an insightful analysis and also by doing a computational study. The results show that, while the average cost model can cost as much as about 26% more than the discounted cost model in extreme cases, this increase is not significant for the parameter values in the range of the common interest.     

Raman scattering study of the phase sequence in A2BX4 halides

Raman spectra of Cs₂ZnI₄ single crystal have been measured in different scattering orientations covering the successive phase transitions down to 68 K. Two second order anomalies at around ice temperature (270 K) and at ～ 92 K are observed. The anomaly around ice temperature exhibits the features of a normal-incommensurate transition evidenced by softening of a low-lying lattice phonon whose frequency decreases as the transition temperature is approached from below whereas the latter one appears to arise from usual structural distortions.     

Biopolymer based nanomaterials in drug delivery systems: A review

Drug delivery systems (DDS) are used to achieve a higher therapeutic effects of a pharmaceutical drug or natural compound in a specific diseased site with minimal toxicological effect and these systems consists of liposomes, microspheres, gels, prodrugs and many. Nanotechnology is a rapidly developing multi-disciplinary science that ensures the fabrication of the polymers to nanometer scale for various medical applications. Uses of biopolymers in DDS ensure the biocompatibility, biodegradability and low immunogenicity over the synthetic ones. Biopolymers such as silk fibroins, collagen, gelatin, albumin, starch, cellulose and chitosan can be easily made into suspension that serve as delivery vehicles for both macro and mini drug molecules. There are various methods such as supercritical fluid extraction, desolvation, electrospraying, spray-drying, layer-by-layer self-assembly, freeze-drying and microemulsion introduced to make these DDS. This drug carrier systems enhance the drug delivery actively and can be used in ocular, transdermal, dental or intranasal delivery systems. This review describes the new trends in nanomaterials based drug delivery systems mainly using biopolymers such as proteins (silk fibroin, collagen, gelatin and albumin) and polysaccharides (chitosan, alginate, cellulose and starch).     

High spin states in102Ag

High spin states are populated in¹⁰²Ag using the reaction¹⁶O+⁸⁹Y with projectile energies in the energy range 60–80 MeV. Gamma multipolarities are inferred from DCO ratios and coincidence relationships are established among the gamma rays assigned to¹⁰²Ag. A comprehensive level scheme is constructed with four band systems, two of positive parity and the other two of negative parity. The present study extended spins upto 19^– in the main negative parity band. A new band is populated in the present work and is similar to the one observed in¹⁰⁶Ag.The authors wish to thank and record their appreciation to Dr. S.K. Parthasaradhi, VECC, Calcutta for preparing the target used in this experiment. The authors gratefully acknowledge useful discussions with Dr. Rakhesh Popli. The authors record their grateful thanks to Prof. A.P. Patro and Prof. G.K. Mehta, former and present directors of the Nuclear Science Centre, for their interest in this work, helpful discussions and providing excellent facilities. The authors also thank Dr. S.K. Datta of the Nuclear Science Centre for his continued interest and helpful discussions and accelerator staff of N.S.C. for their efficient services in delivering the beam. Grateful thanks are also due to the University Grants Commission for providing financial support.     

Cage‐to‐Cage Cascade Transformations

A series of Pd₂ L ₄‐type binuclear self‐assembled coordination cages ( 1 – 4 ), where L stands for a nonchelating bidentate ligand, were prepared. The strategies adopted for the synthesis of the cages were: combination of Pd^II with 1) a selected ligand or 2) subcomponents of the ligand. Highly efficient cage‐to‐cage transformation reactions are demonstrated by suitable covalent modification (from 1 to 2 or 3 or 4 ) or ligand‐exchange reactions (from 1 to 2 or 3 or 4 ; from 2 to 3 or 4 ). Thus, new cascade transformations (from 1 to 2 to 3 ; from 1 to 2 to 4 ) are achieved beautifully.     

A new oxo-sterol derivative from the rhizomes of Costus speciosus

Chemical investigation of the rhizomes of Costus speciosus led to the isolation of a new compound, 22-ketocholesteryl palmitate (1) along with four known compounds, 24-methylenecycloartanol (2), cycloartanol (3), stigmasterol (4) and linoleic acid (5). The structure of new compound was characterised by extensive 1D-, 2D-NMR and mass spectrometry (GC-MS and HR-ESI-MS) techniques.