Minimum-Cost Load-Balancing Partitions

We consider the problem of balancing the load among several service-providing facilities, while keeping the total cost low. Let D be the underlying demand region, and let p ₁,…,p _m be m points representing m facilities. We consider the following problem: Subdivide D into m equal-area regions R ₁,…,R _m , so that region R _i is served by facility p _i , and the average distance between a point q in D and the facility that serves q is minimal. We present constant-factor approximation algorithms for this problem, with the additional requirement that the resulting regions must be convex. As an intermediate result we show how to partition a convex polygon into m equal-area convex subregions so that the fatness of the resulting regions is within a constant factor of the fatness of the original polygon. In fact, we prove that our partition is, up to a constant factor, the best one can get if one’s goal is to maximize the fatness of the least fat subregion. We also discuss the structure of the optimal partition for the aforementioned load balancing problem: indeed, we argue that it is always induced by an additive-weighted Voronoi diagram for an appropriate choice of weights. An earlier version of this paper appeared in the Proceedings of the 22nd Annual ACM Symposium on Computational Geometry, pp. 301–308, 2006. B. Aronov’s research supported in part by NSF grant ITR-0081964 and by a grant from the US-Israel Binational Science Foundation. P. Carmi partially supported by the Lynn and William Frankel Center for Computer Sciences. M.J. Katz partially supported by grant no. 2000160 from the US-Israel Binational Science Foundation.     

Birth order effects: A reply to Breland.

Answers H. M. Breland's assertions concerning birth order effects in verbal achievement. It is argued that if birth order differences in intellectual functioning exist in childhood, they are very slight and exert at most minimal effects on adult functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Use of isolated inbred human populations for identification of disease genes

The genetic mapping of disease loci involves the use of patient phenotype and genotype data in the search for genetic markers that segregate, or are associated with, a trait or disorder. Genetically isolated populations offer many advantages for such studies. The high degree of inbreeding and/or founder effects in some small population isolates result in an increased incidence of recessive disorders. Monogenic disorders are less likely to show non-allelic heterogeneity in isolated populations than in more diverse populations. The use of isolated populations also reduces the complexity of polygenic disorders by reducing the number of loci probably involved in the disorder. Finally, a variety of strategies can be used with particular efficacy for the mapping of disease genes in isolated populations.     

Power Assignment in Radio Networks with Two Power Levels

We study the power-assignment problem in radio networks, where each radio station can transmit in one of two possible power levels, corresponding to two ranges—short and long. We show that this problem is NP-hard, and we present an O(n²)-time assignment algorithm such that the number of transmitters that are assigned long range by the algorithm is at most (11/6) times the number of transmitters that are assigned long range by an optimal algorithm. We also present a (9/5)-approximation algorithm for this problem whose running time is considerably higher.     

Numerical simulation of the effect of LPG blending on the characteristics of a diesel engine

The present work aims to investigate numerically the effect of LPG blending on the characteristics of diesel engines subjected to variable compression ratio, injection timing, and engine speed. Three blends of LPG are used, which are 10% LPG + 90% diesel, 20% LPG + 80% diesel, and 30% LPG + 70% diesel. The numerical investigation is carried out using the simulation software Diesel-RK. Increasing the percentage of LPG in diesel starts combustion early where the lowest delay period is recorded for a blend of 30% LPG + 70% diesel 6.36 deg. The combustion pressure and heat release are decreased due to the difference in the heating values of blended fuels. Although the peak energy release for diesel is 0.05458 (1/deg.) at 375 deg. BTDC, it was 0.0542, 0.05424, and 0.0537 (1/deg.) at 375 deg. BTDC for 10%, 20%, 30% LPG, respectively. Diesel with 30% LPG has a higher spray penetration followed by 20% LPG then 10% LPG and diesel come last. The diesel with 10% LPG gives a 5.35% reduction in NOx, while diesel with 20% and 30% LPG emit less NOx emission by 9.05% and 16.5%, respectively. Increasing the percentage of LPG in diesel yields to reduce soot concentration because LPG has lower carbon to hydrogen ratio. The lowest ability to emit smoke is detected for fuel with 30% LPG where a 7.4% reduction is obtained. It is worth noting that blending LPG with diesel can fight the trade-off relation between Soot-NOx as a reduction in both of them is obtained. Based on the results obtained, the blending ratio is 30% LPG. The obtained results are validated with the results of other researchers.     

A time course analysis of Stroop interference and facilitation: Comparing normal individuals and individuals with schizophrenia.

Using randomized stimulus onset asynchrony (SOAs), the authors traced the time course of Stroop interference and facilitation in normal participants and participants with schizophrenia. Unlike earlier findings using blocked SOAs, singular peaks in interference, facilitation, or both occurred at particular SOAs. The peaks of normal participants and participants with schizophrenia differed. Findings are congruent with a model of Stroop performance that posits individual differences in processing speeds of target and nontarget stimulus dimensions, coupled with critical points in response selection. Participants with schizophrenia also showed more overall interference than normal control participants. A second experiment that added a temporal gap between the distractor word and target color obliterated Stroop effects only for individuals with schizophrenia. These findings provide a new empirical basis for models of Stroop effects. They are also consistent with hypotheses about the importance of the prefrontal cortex for working memory and prefrontal dysfunction in schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Model-free dynamic contrast-enhanced MRI analysis: differentiation between active tumor and necrotic tissue in patients with glioblastoma

Magnetic Resonance Materials in Physics, Biology and Medicine - Treatment response assessment in patients with high-grade gliomas (HGG) is heavily dependent on changes in lesion size on MRI....