Inventory Policy Implications of On-Line Customer Purchase Behavior

In this paper we will examine some implications of online data for a classical operations management model, vis. the Economic Order Quantity model. Customer waiting behavior on individual orders (which occur during stockouts) forms the basis for evaluating the potential backorders. The potential attraction of reducing inventory holding costs must be balanced with the loss due to lost sales. We clearly delineate the conditions under which it is profitable to stock out every ordering cycle, and the conditions under which the traditional economic order quantity model still holds. In order to allow practical application of the model, we develop a number of different approaches to the problem of estimating the backorder function from available on-line transaction data

On the impact of electronic commerce on logistics operations

This paper formulates and analyzes a model to integrate inventory management and promotion decisions in a multi-product environment. The model assumes that actual demands for the items depend on both item availability and the level of promotion used for the item. A notable feature of the model is that customer demand is partially backordered, where the fraction of demand backordered depends on how long a customer has to wait for delivery. The firm is assumed to have a limited promotion budget. The effect of a promotion is modeled through an increase in the demand rate of the item being promoted. We formulate a general, non-stationary, finite horizon version of the problem. However this problem is very difficult to solve optimally. In order to develop insights into the nature of the solution we formulate a stationary version of the general problem with the additional restriction that only one item can be promoted at a time. An efficient solution approach is developed for this stationary version, and limited numerical results are provided. These numerical results indicate that a coordinated approach to promotions and logistics decisions can lead to significantly higher profit for the firm

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Information about delays can enhance service quality in many industries. Delay in-formation can take many forms, with different degrees of precision. Different levels of information have different effects on customers and so on the overall system. The goal of this research is to explore these effects. We first consider a queue with balk-ing under three levels of delay information: No information, partial information (the system occupancy) and full information (the exact waiting time). We assume Pois-son arrivals, independent, exponential service times, and a single server. Customers decide whether to stay or balk based on their expected waiting costs, conditional on the information provided. By comparing the three systems, we identify some important cases where more accurate delay information improves performance. In other cases, however, information can actually hurt the provider or the customers. We then investigate the impacts on the system of different cost functions and weight distributions. Specifically, we compare systems where these parameters are related by various stochastic orders, under different information scenarios. We also explor

A novel endonuclease from kinetoplastid hemoflagellated protozoan parasite Leishmania

A nuclease activity has been purified from the nuclei-kinetoplast fraction of Leishmania. This enzyme, termed endonuclease M (Endo M), is shown by electrophoresis in a denaturing polyacrylamide gel to be associated with a single polypeptide of molecular mass 52 kDa. Physical analysis of the enzyme indicates that it has a sedimentation coefficient S20,w of 4.5S, a Stoke's radius of 32.5 A, and a native molecular mass of 53 kDa. The final Mono Q purified Endo M possesses both DNase and RNase activities. It acts as an endonuclease by introducing random single-stranded nicks into the supercolled DNA molecules, that often leads to its linearization due to nicking at the opposite strands, and subsequent degradation of the DNA with further incubation. Single-stranded DNA is twice preferred to double-stranded DNA as substrate. Single-stranded RNA is also degraded rapidly and is competitive as a substrate with single-stranded DNA. RNA: DNA hybrids, however, are largely resistant to the Endo M digestion

Chromatographic Separation of DNA Dependent RNA Polymerases and Molecular Properties of RNA Polymerase II from a Leishmania Spp

Multiple forms of DNA-dependent RNA polymerases have been isolated and characterized from Leishmania strain UR6 promastigotes. RNA polymerases from this organism fail to resolve into multiple forms by conventional chromatography on DEAE-Sephadex A25, but could be separated by a modification of the method using CM-Sephadex C25. The CM-Sephadex bound enzyme is resistant to a-amanitin even up to a concentration of 250 µg/ml. The activity which flows through CM-Sephadex further resolves into two forms upon chromatography on DEAE-Sephadex A25. These forms are sensitive to a-amanitin to different extent. Enzyme activity in peak I is 50% inhibited by 3 µg/ml and in peak II by 50 µg/ml of the drug respectively. The enzyme in peak I has been further purified by heparin agarose and fast performance liquid chromatography (FPLC) on MonoQ. The enzyme has Stoke’s radius of 70Å, a sedimentation coefficient of 17.6S and an f/fo of 1.35. Analysis of ammonium sulfate and metal ion optima of the enzyme in peak I, relative activities with Mn+2 versus Mg+2 and template specificities gave results similar to those reported for other type II RNA polymerases in eukaryotes. The MonoQ purified enzyme resolves into 16 polypeptides on denaturing polyacrylamide gel and densitometric analysis suggests that 9 major bands are present in the stoichiometry expected of RNA polymerase subunits having molecular weights: 154000; 104000; 77000; 64000; 52000; 48000; 46000; 45000 and 39000 respectively

Dual inhibition of DNA topoisomerases of Leishmania donovaniby novel indolyl quinolines

A wide variety of biologically active compounds contain indole and quinoline nuclei. A one step synthesis of some novel indolyl quinoline analogs e.g.2-(2" - Dichloro - acetamidobenzyl) - 3 - (3' - indolyl)-quinoline [1], 2-(2"-Dichloroacetamido-5"-bromo- benzyl)-3'-[3'-(5'-bromoindolyl)]-6-bromo quinoline [2], and 2-(2"-acetamido benzyl)-3-(3'-indolyl)-quinoline [3] has been developed under Friedel-Crafts acylation conditions. The compounds inhibit the relaxation and decatenation reactions catalysed by type I and type II DNA topoisomerases ofLeishmania donovani.Among the three synthetic indolyl quinolines, the Br-derivative [2] is most active. The results reported here concerning the inhibition of type I and type II DNA topoisomerases indicate that the compounds act as "dual inhibitors" of the enzymes and can be exploited for rational drug design in human leishmaniasis