The break quantity rule in a 1-warehouse, N-retailers distribution system

In this paper the effect of the break quantity rule on the inventory costs in a 1-warehouse, N-retailers distribution system is analyzed. The break quantity rule is to deliver large orders from the warehouse, and small orders from the nearest retailer, where a so--called break quantity determines whether an order is small or large. Under the assumptions that the stock at the warehouse can only be used to satisfy large orders, and that demand during the leadtimes is normally distributed, an expression for the inventory costs is derived. The objective of this paper is to provide insight into the effect of the break quantity rule on the inventory holding costs, and therefore we present extensive computational results, showing that in many cases the rule leads to a significant cost reduction

On the newsboy model with a cutoff transaction size

In this paper we analyse the effect of satisfying in a different way customers with an order larger than a prespecified cutoff transaction size, in a simple newsboy setting. For compound Poisson demand with discrete order sizes, we show how to determine the expected costs and the optimal cutoff transaction size. Moreover, by approximating the distribution of the total demand during a period by the normal distribution one can determine an expression for the average cost function that depends on the cutoff transaction size only. A main advantage of this approximation is that the computational effort is much less. The quality of using the normal approximation is evaluated through a number of numerical experiments, which show that the approximative results are satisfactory

On the use of break quantities in multi--echelon distribution systems

In multi-echelon distribution systems it is usually assumed that demand is only satisfied from the lowest echelon. In this paper we will consider the case where demand can be satisfied from any level in the system. However, then the problem arises of how to allocate orders from customers to the different locations. A possible way of dealing with this problem consists of using a so-called break quantity rule. This easy implementable rule is to deliver every order with a size exceeding the break quantity from a higher echelon. The use of the break quantity rule now results in a reduction of the demand variability at the retailer and hence less safety stocks need to be held. The concept is studied for a two-echelon distribution system, consisting of one warehouse and one retailer, where the inventory at the retailer is controlled by an order up to level policy, and where at the warehouse there is enough inventory to satisfy all orders from the retailer and the customers. For this system an approximation for the long run average costs as a function of the break quantity is derived, and an algorithm is presented to determine the cost-optimal break quantity. Computational results indicate that the break quantity rule can lead to significant cost reductions

IgM antibody level against proinflammatory bacterial peptidoglycan is inversely correlated with extent of atherosclerotic disease

Objective: Atherosclerosis may lead to acute clinical events by rupture of a vulnerable atherosclerotic plaque. Previously, we demonstrated that peptidoglycan (PGN), a major cell wall component of gram-positive bacteria that induces production of proinflammatory cytokines through TLR2 and CD14, is prevalent in atherosclerotic lesions with histological features associated with plaque vulnerability. We hypothesized that in atherosclerotic patients antibody levels against PGN may differ compared with matched controls. Methods and results: ELISA was performed to measure immunoglobulin levels against PGN in sera of 80 atherosclerotic patients versus 77 control patients with an increased cardiovascular risk, frequency-matched for age, sex and risk factors for atherosclerotic disease. In all patients and controls, intima-media (IMT) thickness was assessed using an array transducer. Significantly lower levels of IgM directed against PGN were found in atherosclerotic patients compared with the control patients without clinically manifested disease (P=0.02). The IgM levels against PGN decreased with increasing mean common carotid IMT thickness (P=0.006). Conclusions: These results show that patients suffering from atherosclerotic disease have decreased IgM levels against PGN. The data suggest that an antibody response against PGN could have a protective effect against the development or activity of atherosclerotic disease

Shear-stress and wall-stress regulation of vascular remodeling after balloon angioplasty: effect of matrix metalloproteinase inhibition

BACKGROUND: Constrictive vascular remodeling (VR) is the most significant component of restenosis after balloon angioplasty (PTA). Whereas in physiologi

Associations of autozygosity with a broad range of human phenotypes

In many species, the offspring of related parents suffer reduced reproductive success, a phenomenon known as inbreeding depression. In humans, the importance of this effect has remained unclear, partly because reproduction between close relatives is both rare and frequently associated with confounding social factors. Here, using genomic inbreeding coefficients (F-ROH) for >1.4 million individuals, we show that F-ROH is significantly associated (p <0.0005) with apparently deleterious changes in 32 out of 100 traits analysed. These changes are associated with runs of homozygosity (ROH), but not with common variant homozygosity, suggesting that genetic variants associated with inbreeding depression are predominantly rare. The effect on fertility is striking: F-ROH equivalent to the offspring of first cousins is associated with a 55% decrease [95% CI 44-66%] in the odds of having children. Finally, the effects of F-ROH are confirmed within full-sibling pairs, where the variation in F-ROH is independent of all environmental confounding.Peer reviewe

Stock rationing in a continuous review two-echelon inventory model

In this paper we consider a 1-warehouse, N-retailer inventory system where demand occurs at all locations. We introduce an inventory model which allows us to set different service levels for retailers and direct customer demand at the warehouse. For each retailer a critical level is defined, such that a retailer replenishment order is delivered from warehouse stock if and only if the stock level exceeds this critical level. It is assumed that retailer replenishment orders, which are not satisfied from warehouse stock, are delivered directly from the outside supplier, instead of being backlogged. We present an analytical upper bound on the total cost of the system, and develop a heuristic method to optimize the policy parameters. Numerical experiments indicate that our technique provides a very close approximation of the exact cost. Also, we show that differentiating among the retailers and direct customer demand can yield significant cost reductions

The break quantity rule in a 1-warehouse, N-retailers distribution system

In this paper the effect of the break quantity rule on the inventory costs in a 1-warehouse, N-retailers distribution system is analyzed. The break quantity rule is to deliver large orders from the warehouse, and small orders from the nearest retailer, where a so--called break quantity determines whether an order is small or large. Under the assumptions that the stock at the warehouse can only be used to satisfy large orders, and that demand during the leadtimes is normally distributed, an expression for the inventory costs is derived. The objective of this paper is to provide insight into the effect of the break quantity rule on the inventory holding costs, and therefore we present extensive computational results, showing that in many cases the rule leads to a significant cost reduction.inventory;break quantity rule;multi-echelon distribution systems