Queue Length Asymptotics for Generalized Max-Weight Scheduling in the presence of Heavy-Tailed Traffic

We investigate the asymptotic behavior of the steady-state queue length distribution under generalized max-weight scheduling in the presence of heavy-tailed traffic. We consider a system consisting of two parallel queues, served by a single server. One of the queues receives heavy-tailed traffic, and the other receives light-tailed traffic. We study the class of throughput optimal max-weight-alpha scheduling policies, and derive an exact asymptotic characterization of the steady-state queue length distributions. In particular, we show that the tail of the light queue distribution is heavier than a power-law curve, whose tail coefficient we obtain explicitly. Our asymptotic characterization also contains an intuitively surprising result - the celebrated max-weight scheduling policy leads to the worst possible tail of the light queue distribution, among all non-idling policies. Motivated by the above negative result regarding the max-weight-alpha policy, we analyze a log-max-weight (LMW) scheduling policy. We show that the LMW policy guarantees an exponentially decaying light queue tail, while still being throughput optimal

Role of magnetic resonance imaging and in vivo MR spectroscopy in clinical, experimental and biological research

Magnetic resonance imaging, a noninvasive imaging modality in clinical medicine produces soft tissue anatomical pictures in any desired plane that are exquisite representation of the spatial distribution of mobile protons present in human/animal tissues. In vivo magnetic resonance spectroscopy, on the other hand, is a useful technique for studying metabolic processes in biological systems. In the last decade, magnetic resonance imaging and in vivo spectroscopy methods have become an established tool in many areas of biomedical research for example, in understanding the physiology of several disease processes, tumor metabolism, and drug discovery process. In fact, in vivo magnetic resonance spectroscopy can be used for diagnosis of a specific disease pattern with biochemical/metabolic signature (marker), assessment of tumor response to different treatment regimens, drug concentrations in tissues, drug efficacy and metabolism. The advantage of in vivo magnetic resonance is its versatility and comprehensive characterization of normal and diseased tissues. In this article, a few examples of in vivo magnetic resonance methods and their utility in clinical, experimental and biological research are presented

Water in the Arab World

This volume is intended to serve as a water handbook. It represents the collective knowledge about water resources management acquired over recent years, both within the World Bank water team and with counterparts working in the Arab countries of North Africa and the Middle East (MNA). The chapters offer a cornucopia of ideas and themes. Some chapters are based on background papers prepared for the 2007 "MNA Development Report on Water." Others draw on sector work prepared at the request of client countries. Yet others summarize observations based on study tours or other learning events sponsored by the World Bank. Upon reviewing this lodestone of embedded knowledge, we realized that bringing together our observations and analyses could serve a useful purpose for public officials, other practitioners, academics, and students who are interested in learning more about the complexities of managing water resources management in one of the driest parts of the world

Adaptive Critic-Based Neural Network Controller for Uncertain Nonlinear Systems with Unknown Deadzones

A multilayer neural network (NN) controller in discrete-time is designed to deliver a desired tracking performance for a class of nonlinear systems with input deadzones. This multilayer NN controller has an adaptive critic NN architecture with two NNs for compensating the deadzone nonlinearity and a third NN for approximating the dynamics of the nonlinear system. A reinforcement learning scheme in discrete-time is proposed for the adaptive critic NN deadzone compensator, where the learning is performed based on a certain performance measure, which is supplied from a critic. The adaptive generating NN rejects the errors induced by the deadzone whereas a second NN based critic generates a signal, which is used to tune the weights of the action generating NN so that the deadzone compensation scheme becomes adaptive whereas a third multilayer NN simultaneously approximate the nonlinear dynamics of the system. Using the Lyapunov approach, the uniform ultimately boundedness (UUB) of the closed-loop tracking error and weight estimates of action generating NN, critic NN and the third NN are shown by using a novel weight update

Secondary bacterial flora in patients with pulmonary tuberculosis - a preliminary report

Sputum samples from 100 smear positive or skiagram positive pulmonary tuberculosis patients were cultured for superinfecting or co-injecting bacteria. These patients were equally divided into five groups. This included Croup-I who are not treated; Group-II who are treated up to three months; Group-III who are treated for more than three but less than six months; Group-IV treated more than six months and lastly Group-V who have completed the prescribed treatment schedule of varying durations. Neisseria catarrhalis and Strep. viridans predominated in all patients irrespective of group, other organisms isolated, were Micrococci, E.Coli, Serratia, Proteus and Pseudomonas. There was no significant difference in the pattern of organisms isolated from different group of patients. The antibiogram showed the usual susceptibility pattern

Hypocholesteremic effect of phenoxybenzamine (Dibenzyline), an adrenergic blocking agent: experimental studies with monkeys and human volunteers

The effect of an orally effective adrenergic blocking agent, Dibenzyline, on serum cholesterol levels was studied in human subjects and in monkeys on high-fat diets. In addition, the effect of the phenoxyethyl analogue of Dibenzyline, G-D 131, was also investigated in monkeys. The studies showed that the increase in serum cholesterol level brought about by a high-fat diet in monkeys could be considerably reduced by supplementation with Dibenzyline. This hypocholesteremic action was also observed with the analogue of Dibenzyline, G-D 131, which does not possess the adrenergic blocking property. It appears, therefore, that the hypocholesteremic action of Dibenzyline is independent of its adrenergic blocking activity. When a high-fat diet which also contained a high amount of cholesterol was used, Dibenzyline retarded the increase in serum cholesterol of monkeys for a considerable length of time. Administration of Dibenzyline, 10 mg. daily for 11 days, brought about a fall in serum cholesterol in two of the three human subjects and arrested the further increase in serum cholesterol in the third subject on a high-butterfat diet. All the subjects showed increased fecal elimination of cholic and dihydroxycholanic acids during the Dibenzyline-supplemented period, suggesting that the hypocholesteremic effect of the drug is at least partly mediated through increased elimination of cholesterol as bile acids