2,536 research outputs found

    Capacity Reservation under Spot Market Price Uncertainty

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    The traditional way of procurement, using long-term contract and capacity reservation, is competing with the escalating global spot market. Considering the variability of the spot prices, the flexibility of combined sourcing can be used to benefit from occasional low short-term spot price levels while the long-term contract is a means to hedge the risk of high spot market price incidents. This contribution focuses on the cost-effective management of the combined use of the above two procurement options. The structure of the optimal combined purchasing policy is complex. In this paper we consider the capacity reservation - base stock policy to provide a simple implementation and comparison to single sourcing options. Our analysis shows that in case of large spot market price variability the combined sourcing is superior over spot market sourcing even in case of low average spot market price and also superior over long-term sourcing even in case of high average spot market price.Capacity reservation; spot market; purchasing policy; supply chain contracts; stochastic inventory control

    The structure of the optimal combined sourcing policy using capacity reservation and spot market with price uncertainty

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    This contribution focuses on the cost-effective management of the combined use of two procurement options: the short-term option is given by a spot-market with random price, whereas the long-term alternative is characterized by a multi period capacity reservation contract with fixed purchase price, reservation level and capacity reservation cost. Considering a multiperiod problem with stochastic demand, the structure of the optimal combined purchasing policy is derived using stochastic dynamic programming.Capacity reservation, spot market, purchasing policy, supply contracts, stochastic inventory control

    The Effects of Anticholinesterase Drugs on Bethanechol-İnduced Contractile Responses in Rat Ileum Smooth Muscle

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    At present, anticholinesterase drugs are valuable as therapeutic agents when cholinergic activity decreased in cases such as glokom, myastenia gravis and postoperative period which induces atony in bladder and intestinal smooth muscles. In these conditions anticholinesterases are expected to increase the levels of acetylcholine by inhibiting the enzyme acetylcholinesterase, thus they can exhibit both muscarinic and nicotinic effects indirectly rather than constituting a direct effect on muscarinic receptors. But recently, it has been shown that anticholinesterase drugs may exhibit a dose-dependent antimuscarinic effect by interacting with muscarinic receptors directly. According to these results, we investigated the dose-dependent effects of anticholinesterases on bethanechol-induced contractile responses at ileum smooth muscle preparations. Our results show that none of the three anticholinesterases did cause any potentialization on contractile responses for bethanechol at their first three concentrations (p > 0,05; paired samples t test). But at their highest concentration such as 1000 M, neostigmine, edrophonium and piridostigmine attenuated the bethanechol induced contractile responses (p 0,05; paired samples t test). These results suggest that anticholinesterases do not have dual effects on bethanechol induced contractile responses in rat ileum smooth muscle preparations. Larger doses of anticholinesterases may evoke antimuscarinic effects on ileum smooth muscle contractions

    Radioprotective Agents

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    Since1949, a great deal of research has been carried out on the radioprotective activity of various chemical substances. Thiol compounds, compounds which contain –SH radical, different classes of pharmacological agents and other compounds such as vitamine C and WR-2721 have been shown to reduce mortality when administered prior to exposure to a lethal dose of radiation. Recently, honey bee venom as well as that of its components melittin and histamine have shown to be valuable in reduction of radiation-induced damage and also provide prophylactic alternative treatment for serious side effects related with radiotherapy. It has been suggested that the radioprotective activity of bee venom components is related with the stimulation of the hematopoetic system

    Therapeutical Potential of Venom Peptides

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    The term of pharmazooticals is known as a few amount of drugs derived from natural sources such as plants, venomous species of snakes, spiders, scorpions, frogs, lizards and cone snails. Peptide components of venoms are directed against wide variety of pharmacological targets such as ion channels and receptors. At the beginning, a number of these peptides have been used in experimental studies for defining the physiological, biochemical and immunological activities of organisms like mammalians. In recent studies, it has been shown that venom peptides can be valuable in treatment of acute and chronic pain, autoimmune and cardiovascular diseases, neurological disorders and chronic inflammatory and tumoral processes. Therefore particularly in clinical approaches, these peptide molecules or their synthetic analogues are considered as alternative agents that can be used instead of classical drugs for many clinical disorders due to their potent activity besides very few side effects

    Alternative Drugs in Pain Therapy

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    Various treatment modalities of acute and chronic pain have been an area of interest of medicine and investigators for centuries. There are two major classes of drugs that are used to control pain: opioid and non-opioid analgesics. They could be used in the case of monotherapy or combination therapy in pain management. However, these agents are not accepted as ideal drugs in clinical approaches against pain because of their serious side effects such as development of tolerance and addiction, renal failure and gastrointestinal bleeding. As a consequent, developing new forms of pain relievers that are more safe and effective without any other side effects has became the main goal of researchers. In recent studies, it has been shown that conotoxin therapies are not addictive, and have tolerable indexes unlike opioids. In addition, conotoxins side effects are much milder and easier to manage than those of opioids. In this regard, it has been emphasized that biotoxins such as conotoxins obtained from marine creatures can be better choices in pain management for future prospects

    Connecting the Dots: Low-Mass Stars, Brown Dwarfs, and Planets

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    The lowest mass object that Mother Nature makes through the process of “star formation” is currently unknown. While numerous very low mass stars, brown dwarfs, and planets have been found, their relation to each other remains unclear. Here I describe how the study of brown dwarfs has the potential to help us understand both star and planet formation mechanisms. I describe the physical traits attributed to stars, brown dwarfs, and planets; compare the mass functions of brown dwarfs and planets; and discuss how studies of brown dwarfs in both young clusters and in the field can be used to challenge and constrain star and planet formation theories

    Interactive Mobile Sculpture System

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