Tracking Mobile Users with Uncertain Parameters

A method of reducing the wireless cost of tracking mobile users with uncertain parameters is developed in this paper. Such uncertainty arises naturally in wireless networks, since an efficient user tracking is based on a prediction of its future call and mobility parameters. The conventional approach based on dynamic tracking is not reliable in the sense that inaccurate prediction of the user mobility parameters may significantly reduce the tracking efficiency. Unfortunately, such uncertainty is unavoidable for mobile users, especially for a bursty mobility pattern. The two main contributions of this study are a novel method for topology-independent distance tracking, and a combination of a distance-based tracking with a distance-sensitive timer that guarantees both efficiency and robustness. The expected wireless cost of tracking under the proposed method is significantly reduced, in comparison to the existing methods currently used in cellular networks. Furthermore, as opposed to other tracking methods, the worst case tracking cost is bounded from above and governed by the system, such that it outperforms the existing methods. The proposed strategy can be easily implemented, and it does not require a significant computational power from the user.     

The hardness of decoding linear codes with preprocessing

The problem of maximum-likelihood decoding of linear block codes is known to be hard. The fact that the problem remains hard even if the code is known in advance, and can be preprocessed for as long as desired in order to device a decoding algorithm, is shown. The hardness is based on the fact that existence of a polynomial-time algorithm implies that the polynomial hierarchy collapses. Thus, some linear block codes probably do not have an efficient decoder. The proof is based on results in complexity theory that relate uniform and nonuniform complexity classes     

Studies on the mass spectra of 6-methylthiopurine and its C-and N-methyl derivatives

6-Methylthiopurines which bear a 9-NH- or a 9-NCH₃-group (class A) form an [M—1]-ion with much higher abundance than do the 1-, 3-, or 7-methyl derivatives (class B). The higher stability of the [M—1]-ion in class A may be explained by ring closure to N-7. Methyl radicals are cleaved from N-, but not from S- or C-methyl groups, with the exception of the 7-methyl derivative, in which the S-CH₃-group can also split off a methyl radical. The methylthio group may lose all of the following fragments: S, SH, SCH, SCH₂ and SCH₃. In the remaining purine skeleton, in general first the pyrimidine and subsequently the imidazole ring breaks down with elimination of HCN.     

Euclidean distortion and the sparsest cut

We prove that every -point metric space of negative type (and, in particular, every -point subset of ) embeds into a Euclidean space with distortion , a result which is tight up to the iterated logarithm factor. As a consequence, we obtain the best known polynomial-time approximation algorithm for the Sparsest Cut problem with general demands. If the demand is supported on a subset of size , we achieve an approximation ratio of .

     

Elementary Theory of Optimal Silo Storage Design

This study indicates a method for calculating an economic division of warehouses into compartments when different varieties have to be stored simultaneously and separately. The study deals with cases where the total storage capacity demand and the number of varieties are known and fixed, but where the storage capacity demand of each variety is unknown. Problems of this nature exist in the preliminary designing of grain silos, fleets of transport vehicles, utensils in public kitchens, etc. If the warehouse capacity can cope with the total storage capacity demand, but the number of compartments is insufficient, it is possible that part of the material to be stored cannot be accommodated, although certain compartments may only be partly filled; this will be due to the impossibility of storing different varieties together. The materials will have to be stored in other warehouses, at a higher charge per capacity unit than that of the warehouse in question.The division of the warehouse into a large number of compartments will assure storage of most, if not all, the material. On the other hand, increase in the number of compartments (and installations) makes for increased investment in transport installation, partitions and additional storage capacity to compensate for space taken up by these partitions and installations.The object of this study is to introduce a method for calculating the optimal division of a warehouse into compartments, so that the annual costs of storage and capital investment are minimized.It is possible-by introducing not very restrictive statistical assumptions-to calculate the annual costs of storing excluded material elsewhere for different modes of partitioning a warehouse into compartments. The annual building cost of the warehouse is calculated in the ordinary way.In this study a solution is offered for the partitioning of a warehouse into equal compartments. It is to be expected that the extension of this solution to cases of the partition into compartments, differing from each other as to storage capacity, will tend to lower costs.     

Acceleration of the corrosion reaction of magnesium by Fenton reagents

Abstract

Magnesium alloys have attracted increased attention for a variety of applications, chief among which are alternative energy and medical implants. The use of biodegradable implants in the complex system of the human body, in which myriad reactions occur, must consider the potential effects of the body’s natural chemical reactions on implant corrosion rates. The aim of this study was to elucidate the synergistic effects of pure Mg and Mg alloys on the Mg corrosion reaction with reagents that participate in the Fenton reaction. We corroborated our results with six different measurement methods (hydrogen evolution rate [HER], gas chromatography [GC], potentiodynamic polarization, inductively coupled plasma [ICP] spectrometry, Auger electron spectroscopy [AES], and scanning electron microscope [SEM]). The results point out that the corrosion and hydrogen evaluation rates of Mg were elevated by the addition of Fenton reagents, divalent iron and hydrogen peroxide, to a saline solution. In the context of Mg-based alloy medical implant development and use, this observation is significant.     

Intrinsic Fluorescence of Metabolite Amyloids Allows Label‐Free Monitoring of Their Formation and Dynamics in Live Cells

The formation of apoptosis‐inducing amyloidal structures by metabolites has significantly extended the “amyloid hypothesis” to include non‐proteinaceous, single metabolite building blocks. However, detection of metabolite assemblies is restricted compared to their larger protein‐based counterparts owing to the hindrance of external labelling and limited immunohistochemical detection tools. Herein, we present the detection of the formation, dynamics, and cellular distribution of metabolite amyloid‐like structures and provide mechanistic insights into the generation of supramolecular chromophores. Moreover, the intrinsic fluorescence properties allow the detection of metabolite assemblies in living cells without the use of external dyes. Altogether, this intrinsic fluorescence of metabolite assemblies further verifies their amyloidal nature, while providing an important tool for further investigation of their pathological role in inborn error of metabolism disorders.     

Approximating Probability Distributions Using Small Sample Spaces

We formulate the notion of a "good approximation" to a probability distribution over a finite abelian group ?. The quality of the approximating distribution is characterized by a parameter ɛ which is a bound on the difference between corresponding Fourier coefficients of the two distributions. It is also required that the sample space of the approximating distribution be of size polynomial in and 1/ɛ. Such approximations are useful in reducing or eliminating the use of randomness in certain randomized algorithms. We demonstrate the existence of such good approximations to arbitrary distributions. In the case of n random variables distributed uniformly and independently over the range , we provide an efficient construction of a good approximation. The approximation constructed has the property that any linear combination of the random variables (modulo d) has essentially the same behavior under the approximating distribution as it does under the uniform distribution over . Our analysis is based on Weil's character sum estimates. We apply this result to the construction of a non-binary linear code where the alphabet symbols appear almost uniformly in each non-zero code-word. Received: September 22, 1990/Revised: First revision November 11, 1990; last revision November 10, 1997     

Online time-constrained scheduling in linear and ring networks

We consider the problem of scheduling a sequence of packets over a linear network, where every packet has a source and a target, as well as a release time and a deadline by which it must arrive at its target. The model we consider is bufferless, where packets are not allowed to be buffered in nodes along their paths other than at their source. This model applies to optical networks where opto-electronic conversion is costly, and packets mostly travel through bufferless hops. The offline version of this problem was previously studied in M. Adler et al. (2002) [3]. In this paper we study the online version of the problem, where we are required to schedule the packets without knowledge of future packet arrivals. We use competitive analysis to evaluate the performance of our algorithms. We present the first online algorithms for several versions of the problem. For the problem of throughput maximization, where all packets have uniform weights, we give an algorithm with a logarithmic competitive ratio, and present some lower bounds. For other weight functions, we show algorithms that achieve optimal competitive ratios.     

New resonant cavity-enhanced absorber structures for mid-infrared detector applications

A new dielectric Fabry–Perot cavity was designed for a resonant enhancing optical absorption by a thin absorber layer embedded into the cavity. In this cavity, the front mirror is a subwavelength grating with ~ 100% retroreflection. For a HgCdTe absorber in a matching cavity of the new type, the design is shown to meet the combined challenges of increasing the absorbing efficiency of the entire device up to ~ 100?% and reducing its size and overall complexity, compared to a conventional resonant cavity enhanced HgCdTe absorber, while maintaining a fairly good tolerance against the grating’s fabrication errors.