460 research outputs found
On the complexity of finding multi-constrained spanning trees
No full textAbstractIn this paper we present some new results concerning the classification of undirected spanning tree problems from the viewpoint of their computational complexity. Specifically, we study some problems asking for the existence in an undirected, unweighted graph, of a spanning tree satisfying one or several constraints. Thus we extend to the multi-constrained, unweighted case, the analysis that we have already made in a previous work for the one-constrained, weighted case. The problems are classified as solvable in polynomial time or NP-complete
Heuristically guided algorithm for k-parity matroid problems
No full textAbstractIt is known that a large class of “hard” combinatorial optimization problems can be put in the form of a k-parity (weighted) matroid problem. In this paper we describe a heuristically guided algorithm for solving the above class of problems, which utilizes the information obtainable from the problem domain by computing, at each step, a possibly tight lower bound to the solution
TeV astronomy of millisecond pulsars
No full textThis thesis is concerned with the detection of pulsed TeV γ-rays from millisecond pulsars. These stars appear to include some very efficient producers of high energy particles, but the mechanisms by which they produce TeV γ-rays are still a matter of debate. After an introductory section, there is a brief description of the principles used in the atmospheric Cerenkov technique. The design and operation of the University of Durham atmospheric Cerenkov telescopes are reviewed. The main analysis techniques used to search for periodic signals are then described. The effects on periodic signals of binary motion of a source are discussed. These are a particularly important consideration for observations of millisecond pulsars, where high timing accuracy is required. One of the problems of detecting TeV sources is the cosmic ray background. A means of rejecting background events in TeV γ -ray telescopes is considered in chapter 5. The technique is developed for the Durham Mark III telescope. Substantial rejection of the cosmic ray background is achieved, with minimal loss of source events. The evolutionary scenarios which lead to the formation of millisecond pulsars are outlined. Two models for 7-ray emission are discussed briefly and applied to six known millisecond pulsars. Empirical results on these and two other pulsars are also presented. In particular, a detection of PSR 1855+09 is reported, and an upper limit to the flux from PSR 1957+20 is derived. All the empirical fluxes are compatible with the emission models, but the 'polar gap' model may be favoured. The final chapter summarises the results obtained and suggests some directions for future work on the 7-ray emission from millisecond pulsars
Chronic Effects of Subcutaneous Interleukin-2 Therapy on Soluble Interleukin-2 Receptors in Advanced Small Cell Lung Cancer
No full text The increase in IL-2 receptor serum levels is one of the most typical changes in immune parameters during IL-2 cancer immunotherapy. To better define the effects of prolonged IL-2 injection on SIL-2R levels, we evaluated 7 advanced small cell lung cancer patients who received IL-2 subcutaneously at a daily dose of 9x106 IU/m2/12h for two days followed by 3x106 IU/m2/12h for 18 days (5 days/week for 4 weeks). Moreover, four patients were also evaluated during the second IL-2 cycle. Venous blood samples were drawn before and at weekly intervals during IL-2 therapy. Mean SIL-2R serum levels rapidly increased with the start of IL-2 injection, and they were signicantly higher than the baseline levels throughout the immunotherapy cycle. The increase in mean SIL-2R levels was higher in patients with progressive disease than in those with response or stable disease, but the difference was not significant. Finally, the increase in mean SIL-2R concentrations during the second IL-2 cycle was not significantly different from that seen during the first one. The present study confirms that IL-2 administration determines an evident increase in SIL-2R levels; moreover, it would demonstrate that re-exposure to IL-2 after a rest period does not induce a more pronounced SIL-2R release. </jats:p
Very high energy gamma ray astronomy and non pulsating low mass x-ray binaries
No full textThis thesis is concerned with non pulsating Low Mass X-Ray Binaries as Very High Energy γ-ray sources, in particular Scorpius X-1; the brightest of these objects in X-rays, and the most likely to be detectable at energies above 250 GeV. After a first introductory chapter, experimental techniques presently used in Very High Energy γ-ray Astronomy are reviewed. In the third chapter statistical techniques used to quantify count rate excesses and orbital modulations are described and applied to data from Scorpius X-1. Data taken in 1988 and 1989 showing a 3cr count excess, reported previously elsewhere, are found to show orbital modulation at the 3% statistical level. The analysis of data taken on 1990 shows no signal. Periodicity tests, in particular the Rayleigh test, are also described. The principles of a segmented fast algorithm for period searches in Cerenkov data using memory limited, but relatively fast, micro-computers are shown in the fourth chapter. Various of these machines can be used simultaneously in order to achieve a large efficiency. A method to perform various trials per independent frequency is also presented. The results of period searches in data from three selected objects (Scorpius X-1, GX 5-1 and Supernova 1987A) are presented. No periodicity is found at significant level in these data. The complete power spectrum of four segments of data from Cygnus X-3 showing a signal near to 12.59 ms are also shown. The final chapter considers theoretical models developed previously for more massive systems accounting for the different physical scenario of these low mass systems. The process of pair production between high energy photons and the radiation field of the accretion disc appears as the tightest constraint on how close to the neutron star high energy photons can be produced
Integrated On-Chip Microfluidic Immunoassay for Rapid Biomarker Detection
No full textAbstractInfectious diseases remain a major health concern in many parts of the developing world, where access to adequate health care and modern diagnostic tools are absent. Current diagnostic technologies like ELISA and PCR require large sample volumes, bulky, expensive instrumentation, highly trained personnel, long experimental time, and a modern infrastructure that developing countries lack. Hence, portable, low cost tools would be a huge first step towards making accurate diagnostics available to a wider range of patients worldwide. In this work, we present a portable, microfluidic platform, controlled via a smartphone application, that requires no external pumping and is capable of rapid (within 18minutes) 6-step colorimetric detection of an array of vaccinia virus proteins spotted on a nitrocellulose pad. We envision this platform as a first step to a fully integrated, portable immunoassay that can be used to expand global healthcare
Unexpected correlations between gene expression and codon usage bias from microarray data for the whole Escherichia coli K-12 genome
No full textEscherichia coli has long been regarded as a model organism in the study of codon usage bias (CUB). However, most studies in this organism regarding this topic have been computational or, when experimental, restricted to small datasets; particularly poor attention has been given to genes with low CUB. In this work, correspondence analysis on codon usage is used to classify E.coli genes into three groups, and the relationship between them and expression levels from microarray experiments is studied. These groups are: group 1, highly biased genes; group 2, moderately biased genes; and group 3, AT-rich genes with low CUB. It is shown that, surprisingly, there is a negative correlation between codon bias and expression levels for group 3 genes, i.e. genes with extremely low codon adaptation index (CAI) values are highly expressed, while group 2 show the lowest average expression levels and group 1 show the usual expected positive correlation between CAI and expression. This trend is maintained over all functional gene groups, seeming to contradict the E.coli–yeast paradigm on CUB. It is argued that these findings are still compatible with the mutation–selection balance hypothesis of codon usage and that E.coli genes form a dynamic system shaped by these factors
Emilio Ghione and the Mask of Za La Mort
No full textThis study aims to examine the cultural impact of Emilio Ghione's Za La Mort films (1914-1924) on Italian culture. These films constitute a significant Italian combination of several early cinema genres and sub-genres, such as the apache film, the traces of which have almost entirely disappeared. More broadly, the changing interpretations of Za La Mort figure allow us to understand wider shifts in Italian and European popular culture.
The first chapter of the study considers the wealth of influences from European popular culture that Emilio Ghione merged into the apache films, such as the apache sub-culture in Paris. The second chapter of the study then reconstructs the Za La Mort filmography, most of which has now been lost, from film viewings and archival documents. The third chapter considers Emilio Ghione's Za La Mort novels and theatrical productions in the years 1922-1930, and Ghione's attempts to make Za La Mort a more Fascist and nationalistic figure. The fourth chapter considers the enduring figure of Za La Mort in Italian popular culture, especially in Raffaele Matarazzo's Fumeria D'Oppio and a 1940's fumetti series. The fifth chapter considers the audience reception of the Za La Mort films from the limited remaining evidence and, positioning the series between the Cinema of Attractions of the 1900s and the Classical Cinema of the mid-1920's, analyses how the Za La Mort films were constructed to please a predominantly working class audience that valued spectacular thrills and great acting performances over narrative consistency and stable characterisation.
This research re-establishes the importance of one of Italian cinema's most important film-makers of the silent period, and his enduring importance as a popular cultural figure in Italy
The scale of mutational variability in the murid genome.
No full textMutation rates vary across mammalian genomes, but little is known about the scale over which this variation occurs. Knowledge of the magnitude and scale of mutational variation is required to understand the processes that drive mutation, and is essential in formulating a robust null hypothesis for comparative genomics studies. Here we estimate the scale of mutational variation in the murid genome by calculating the spatial autocorrelation of nucleotide substitution rates in ancestral repeats. Such transposable elements are good candidates for neutrally evolving sequence and therefore well suited for the study of mutation rate variation. We find that the autocorrelation coefficient decays to a value close to zero by ∼15 Mb, with little apparent variation in mutation rate under 100 kb. We conclude that the primary scale over which mutation rates vary is subchromosomal. Furthermore, our analysis shows that within-chromosome mutational variability exceeds variation among chromosomes by approximately one order of magnitude. Thus, differences in mutation rate between different regions of the same chromosome frequently exceed differences both between whole autosomes and between autosomes and the X-chromosome. Our results indicate that factors other than the time spent in the male germ line are important in driving mutation rates. This raises questions about the biological mechanism(s) that produce new mutations and has implications for the study of male-driven evolution
Subgradient Techniques for Passivity Enforcement of Linear Device and Interconnect Macromodels
No full textThis paper presents a class of nonsmooth convex optimization methods for the passivity enforcement of reduced-order macromodels of electrical interconnects, packages, and linear passive devices. Model passivity can be lost during model extraction or identification from numerical field solutions or direct measurements. Nonpassive models may cause instabilities in transient system-level simulation, therefore a suitable postprocessing is necessary in order to eliminate any passivity violations. Different from leading numerical schemes on the subject, passivity enforcement is formulated here as a direct frequency-domain norm minimization through perturbation of the model state-space parameters. Since the dependence of this norm on the parameters is nonsmooth, but continuous and convex, we resort to the use of subdifferentials and subgradients, which are used to devise two different algorithms. We provide a theoretical proof of the global optimality for the solution computed via both schemes. Numerical results confirm that these algorithms achieve the global optimum in a finite number of iterations within a prescribed accuracy leve
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