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Showing papers by "Charles University in Prague published in 1996"


Journal ArticleDOI
TL;DR: A simple randomized algorithm which solves linear programs withn constraints andd variables in expected time, and computes the lexicographically smallest nonnegative point satisfyingn given linear inequalities ind variables.
Abstract: We present a simple randomized algorithm which solves linear programs withn constraints andd variables in expected $$\min \{ O(d^2 2^d n),e^{2\sqrt {dIn({n \mathord{\left/ {\vphantom {n {\sqrt d }}} \right. \kern- ulldelimiterspace} {\sqrt d }})} + O(\sqrt d + Inn)} \}$$ time in the unit cost model (where we count the number of arithmetic operations on the numbers in the input); to be precise, the algorithm computes the lexicographically smallest nonnegative point satisfyingn given linear inequalities ind variables. The expectation is over the internal randomizations performed by the algorithm, and holds for any input. In conjunction with Clarkson's linear programming algorithm, this gives an expected bound of $$O(d^2 n + e^{O(\sqrt {dInd} )} ).$$ The algorithm is presented in an abstract framework, which facilitates its application to several other related problems like computing the smallest enclosing ball (smallest volume enclosing ellipsoid) ofn points ind-space, computing the distance of twon-vertex (orn-facet) polytopes ind-space, and others. The subexponential running time can also be established for some of these problems (this relies on some recent results due to Gartner).

411 citations


Journal ArticleDOI
TL;DR: Controversy regarding the relative efficacy of treatments for the relief of the symptoms of benign prostatic hyperplasia (BPH) is investigated.
Abstract: BACKGROUND Controversy regarding the relative efficacy of treatments for the relief of the symptoms of benign prostatic hyperplasia (BPH). METHODS This was a 6-month double-blind randomized equivalence study that compared the effects of a plant extract (320 mg Permixon®) with those of a 5α-reductase inhibitor (5 mg finasteride) in 1,098 men with moderate BPH using the International Prostate Symptom Score (IPSS) as the primary end-point. RESULTS Both Permixon® and finasteride decreased the IPSS (−37% and −39%, respectively), improved quality of life (by 38 and 41%), and increased peak urinary flow rate (+25% and +30%, P = 0.035), with no statistical difference in the percent of responders with a 3 ml/sec improvement. Finasteride markedly decreased prostate volume (−18%) and serum PSA levels (−41%); Permixon® improved symptoms with little effect on volume (−6%) and no change in PSA levels. Permixon® fared better than finasteride in a sexual function questionnaire and gave rise to less complaints of decreased libido and impotence. CONCLUSIONS Both treatments relieve the symptoms of BPH in about two-thirds of patients but, unlike finasteride, Permixon® has little effect on so-called androgen-dependent parameters. This suggests that other pathways might also be involved in the symptomatology of BPH. © 1996 Wiley-Liss, Inc.

324 citations




Journal ArticleDOI
P. Abreu, Wolfgang Adam, Tim Adye1, E. Agasi  +548 moreInstitutions (36)
TL;DR: The DEtector with Lepton, Photon and Hadron Identification (DELPHI) is a detector for particle identification at the Large Electron-Positron (LEP) collider at CERN.
Abstract: DELPHI (DEtector with Lepton, Photon and Hadron Identification) is a detector for e^+e^- physics, designed to provide high granularity over a 4\pi solid angle, allowing an effective particle identification. It has been operating at the LEP (Large Electron-Positron) collider at CERN since 1989. This article reviews its performance.

274 citations


Journal ArticleDOI
TL;DR: Dynamic changes in the ADC of water and in the energy status were measured at postnatal day 8 or 9 in neonatal rat brains after cardiac arrest using 1H MRS/MRI and 31P MRS, indicating that cell swelling is an important cause for the ADC decrease of water.
Abstract: To obtain a better understanding of the mechanisms underlying early changes in the brain water apparent diffusion coefficient (ADC) observed in cerebral ischemia, dynamic changes in the ADC of water and in the energy status were measured at postnatal day 8 or 9 in neonatal rat brains after cardiac arrest using 1H MRS/MRI and 31P MRS, respectively. The time courses of the MR parameters were compared with changes in the extracellular space (ECS) volume fraction (alpha) and tortuosity (lambda), determined from concentration-time profiles of tetramethylammonium applied by iontophoresis. The data show a decrease of the ADC of tissue water after induction of global ischemia of which the time course strongly correlates with the time course of the decrease in the ECS volume fraction and the increase in ECS tortuosity. This indicates that cell swelling is an important cause for the ADC decrease of water.

262 citations


Journal ArticleDOI
TL;DR: In this article, a duality invariant first order action is constructed on the loop group of a Drinfeld double, which gives at the same time the description of both σ-models in a pair related by Poisson-Lie T-duality.

260 citations


Journal ArticleDOI
P. Abreu1, Wolfgang Adam2, Tim Adye3, I. V. Ajinenko  +578 moreInstitutions (46)
TL;DR: In this article, improved tunings of the JETSET, ARIADNE and HERWIG parton shower models were obtained by fitting the models to these DELPHI data as well as to identified particle distributions from all LEP experiments.
Abstract: Event shape and charged particle inclusive distributions are measured using 750000 decays of the Z to hadrons from the DELPHI detector at LEP. These precise data allow a decisive confrontation with models of the hadronization process. Improved tunings of the JETSET, ARIADNE and HERWIG parton shower models and the JETSET matrix element model are obtained by fitting the models to these DELPHI data as well as to identified particle distributions from all LEP experiments. The description of the data distributions by the models is critically reviewed with special importance attributed to identified particles.

224 citations


Journal ArticleDOI
S. Aid1, V. Andreev2, B. Andrieu3, R. D. Appuhn  +413 moreInstitutions (25)
TL;DR: In this paper, a new measurement of the proton structure function F 2 ( x, Q 2 ) is reported for momentum transfers squared Q 2 between ].5 GeV 2 and 5000 GeV2 and for Bjorken x between 3 · 10 −5 and 0.32 using data collected by the HERA experiment H1 in 1994.

192 citations


Journal ArticleDOI
TL;DR: Whether toxoplasmosis induces personality factor-shifts or whether certain combinations of personality factors influence the probability of acquiring Toxoplasma infection, is examined using the personality profiles of 164 male patients diagnosed with acute toxoplasms during the past 13 years.
Abstract: Toxoplasma gondii, the coccidian parasite, is known to induce changes in the behaviour of its intermediate hosts. The high prevalence of this parasite in the human population (20-80%) offers the opportunity of studying the influence of the parasite on human behaviour by screening of a normal population. A total of 224 men and 170 women were tested for toxoplasmosis and their personality profiles were measured by Cattell's questionnaire. Highly significant differences between Toxoplasma-infected and uninfected subjects were observed (P < 0.01). For men the factors G (low superego strength), L (protension), O (guilt proneness), and Q2 (group dependency) were positively influenced in infected subjects. For women the prevailing factors were A (affectothymia, P < 0.01), L (alaxia), O (untroubled adequacy) and Q2 (self-sufficiency). To reveal whether toxoplasmosis induces personality factor-shifts or whether certain combinations of personality factors influence the probability of acquiring Toxoplasma infection, we examined the personality profiles of 164 male patients diagnosed with acute toxoplasmosis during the past 13 years. The existence of a positive correlation between the duration of latent toxoplasmosis and the intensity of superego strength decrease (P < 0.02) suggested that the decrease of superego strength (the willingness to accept group moral standards) was induced by T. gondii infection.

170 citations


Journal ArticleDOI
TL;DR: In this paper, laser kinetic spectroscopy was used to determine the photophysical parameters (fluorescence and triplet-triplet (T-T) spectra, lifetimes of the triplet and singlet states, bimolecular constant for oxygen quenching, fluorescence quantum yield and quantum yield of formation of the triplet state.
Abstract: Laser kinetic spectroscopy was used to determine the photophysical parameters (fluorescence and triplet-triplet (T-T) spectra, lifetimes of the triplet and singlet states, bimolecular constant for oxygen quenching, fluorescence quantum yield and quantum yield of formation of the triplet state) of the water-soluble complexes of Ag(II), Cd(II), Co(II), Cu(II), Mg(II), Ni(II), Pd(II), Pt(II) and Zn(II) with the tetrasodium salt of meso-tetrakis(4-sulphonatophenyl)porphyrin (H 2 TPPS 4 ). The complexes of metals with d 0 and d 10 electron configurations (Cd(II), Mg(II) and Zn(II)) are characterized by high triplet quantum yields and strong fluorescence in the red spectral region and are thus more efficient photosensitizers than the ligand alone.

Journal ArticleDOI
TL;DR: Observations support the hypothesis of a causal relation between the loading mode and the dominant osteonal direction and the organization of the haversian bone seems a typical example of functional adaptation.

Journal ArticleDOI
TL;DR: Basic tenets related to the use of three main classes of potentiometric redistribution fluorescent dyes (carbocyanines, oxonols, and rhodamines) are discussed in detail and possible artifacts or puzzling results stemming from faulty experimental protocol are pointed out.
Abstract: Basic tenets related to the use of three main classes of potentiometric redistribution fluorescent dyes (carbocyanines, oxonols, and rhodamines) are discussed in detail. They include the structure/function relationship, formation of nonfluorescent (H-type) and fluorescent (J-type) dimers and higher aggregates, probe partitioning between membranes and medium and binding to membranes and intracellular components (with attendant changes in absorption and emission spectra, fluorescence quantum yield and lifetime). The crucial importance of suitable probe-to-cell concentration ratio and selection of optimum monitored fluorescence wavelength is illustrated in schematic diagrams and possible artifacts or puzzling results stemming from faulty experimental protocol are pointed out. Special attention is paid to procedures used for probe-response calibration (potential clamping by potassium in the presence of valinomycin, use of gramicidin D in combination with N-methylglucamine, activation of Ca-dependent K-channels by A23187, the null-point technique). Among other problems treated are dye toxicity, interaction with mitochondria and other organelles, and possible effects of intracellular pH and the quantity of cytosolic proteins and/or RNA on probe response. Individual techniques using redistribution dyes (fluorescence measurements in cuvettes, flow cytometry and microfluorimetry of individual cells including fluorescence confocal microscopy) are discussed in terms of reliability, limitations and drawbacks, and selection of suitable probes. Up-to-date examples of application of slow dyes illustrate the broad range of problems in which these probes can be used.

Journal ArticleDOI
01 May 1996
TL;DR: A number of problems with the existing expiration mechanism are discussed, and several extensions to it are presented which solve these problems, reduce user wait times and decrease the staleness of returned Web pages.
Abstract: All Web caches must try to keep cached pages up to date with the master copies of those pages, to avoid returning stale pages to users. In traditional distributed systems terminology, the problem of keeping cached pages up to date is called coherence. We discuss the coherence problem for Web caches, and argue that coherence techniques used for distributed file system caches may not be satisfactory for Web caches. We survey techniques used by popular Web caches for maintaining coherence, including the popular “expiration mechanism” which probably originated in CERN's proxy http server. We discuss a number of problems with the existing expiration mechanism, and present several extensions to it which solve these problems, reduce user wait times and decrease the staleness of returned Web pages. We also discuss pre-fetching and replication, more speculative techniques for keeping Web caches up to date.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the minimum dimensionk such that any n-point metric spaceM can be D-embedded into somek-dimensional normed spaceX (possibly depending on M), that is, there exists a mappingf: M→X with====== ¯¯\frac{1}{D}dist_M (x,y) \leqslant \left| {f(x) - f(y)} \right| \leqi-slant dist_M [m,y] for any
Abstract: We investigate the minimum dimensionk such that anyn-point metric spaceM can beD-embedded into somek-dimensional normed spaceX (possibly depending onM), that is, there exists a mappingf: M→X with $$\frac{1}{D}dist_M (x,y) \leqslant \left| {f(x) - f(y)} \right| \leqslant dist_M (x,y) for any$$ Extending a technique of Arias-de-Reyna and Rodriguez-Piazza, we prove that, for any fixedD≥1,k≥c(D)n 1/2D for somec(D)>0. For aD-embedding of alln-point metric spaces into the samek-dimensional normed spaceX we find an upper boundk≤12Dn 1/[(D+1)/2]lnn (using thel ∞ space forX), and a lower bound showing that the exponent ofn cannot be decreased at least forD∃[1,7)∪[9,11), thus the exponent is in fact a jumping function of the (continuously varied) parameterD.

Journal ArticleDOI
TL;DR: In this paper, a potential hybrid phosphine ligand with heteroannular soft and hard donor groups was synthesized in 71% yield from 1-phenyl-1-phospha[1]ferrocenophane by ring opening with phenyllithium, followed by reaction with carbon dioxide and acidification.

Journal ArticleDOI
TL;DR: Both methods using data for proteins in H2O are somewhat better predictors than amide I' VCD alone and, for helix, worse than ECD alone, and predictions are improved by combining both with ECD data, indicating that the improvement is due to using their very different structural sensitivities.

Journal ArticleDOI
TL;DR: This work summarizes and extends known enumeriative results for the patternp=ababand to give an explicit formula for the number of p(abab, n, l, k) of partitions of such partitions.
Abstract: These are partitions of[l]={1, 2, . . . , l}intonblocks such that no four-term subsequence of [l]induces the mentioned pattern and eachkconsecutive numbers of[l]fall into different blocks. These structures are motivated by Davenport–Schinzel sequences. We summarize and extend known enumeriative results for the patternp=ababand give an explicit formula for the numberp(abab, n, l, k)of such partitions. Our main tools are generating functions. We determine the corresponding generating function forp=abbaandk=1, 2, 3.Fork=2there is a connection with the number of directed animals. We solve exactly two related extremal problems.

Journal ArticleDOI
TL;DR: By including a variety of morphologic, biochemical, immunogenetic, and molecular markers, the current map integrates and extends existing linkage data and should facilitate rat gene mapping and genetic studies of hypertension and other complex phenotypes of interest in the HXB and BXH recombinant inbred strains.
Abstract: We have constructed a genetic linkage map in the rat by analyzing the strain distribution patterns of 500 genetic markers in a large set of recombinant inbred strains derived from the spontaneously hypertensive rat and the Brown-Norway rat (HXB and BXH recombinant inbred strains). 454 of the markers could be assigned to specific chromosomes, and the amount of genome covered by the mapped markers was estimated to be 1151 centimorgans. By including a variety of morphologic, biochemical, immunogenetic, and molecular markers, the current map integrates and extends existing linkage data and should facilitate rat gene mapping and genetic studies of hypertension and other complex phenotypes of interest in the HXB and BXH recombinant inbred strains.

Journal ArticleDOI
TL;DR: It was concluded that the stress-inducing noninfectious stimuli, such as repeated cold water immersions, which increased metabolic rate due to shivering the elevated blood concentrations of catecholamines, activated the immune system to a slight extent.
Abstract: The aim of this study was to investigate whether or not the human immune system can be activated by a noninfectious stimulus, thereby improving the physiological status of the individual. The effect of a single cold water immersion (14° C for 1 h) on the immune system of athletic young men, monitored immediately after immersion, was minimal. With the continuation of the cold water immersions (three times a week for a duration of 6 weeks) a small, but significant, increase in the proportions of monocytes, lymphocytes with expressed IL2 receptors (CD25) and in plasma tumour necrosis factor alpha content was induced. An increase in the plasma concentrations of some acute phase proteins, such as haptoglobin and haemopexin, was also observed. After 6 weeks of repeated immersions a trend towards an increase in the plasma concentrations of IL6 and the amount of total T lymphocytes (CD3), T helper cells (CD4), T suppressor cells (CD8), activated T and B lymphocytes (HLA-DR) and a decrease in the plasma concentration of α1-antitrypsin was observed. Concentrations of IL1β, neopterin, C-reactive protein, orosomucoid, ceruloplasmin, macroglobulin, immunoglobulins (IgG, IgM, IgA) and C3, C4 components of the complement, as well as the total number of erythrocytes, leucocytes, granulocytes and neutrophils showed no significant changes after the repeated cold water immersions. It was concluded that the stress-inducing noninfectious stimuli, such as repeated cold water immersions, which increased metabolic rate due to shivering the elevated blood concentrations of catecholamines, activated the immune system to a slight extent. The biological significance of the changes observed remains to be elucidated.

Journal ArticleDOI
TL;DR: In this article, it was shown that the H-colouring problem for fixed digraphs admits a homomorphism if and only if there exists an oriented tree which is homomorphic to the digraph but not to H.
Abstract: Let H be a fixed digraph. We consider the H-colouring problem, i.e., the problem of deciding which digraphs G admit a homomorphism to H. We are interested in a characterization in terms of the absence in G of certain tree-like obstructions. Specifically, we say that H has tree duality if, for all digraphs G, G is not homomorphic to H if and only if there is an oriented tree which is homomorphic to G but not to H. We prove that if H has tree duality then the H-colouring problem is polynomial. We also generalize tree duality to bounded treewidth duality and prove a similar result. We relate these duality concepts to the notion of the X-property studied by Gutjahr, Welzl, and Woeginger. We then focus on the case when H itself is an oriented tree. In fact, we are particularly interested in those trees that have exactly one vertex of degree three and all other vertices of degree one or two. Such trees are called triads. We have shown in a companion paper that there exist oriented triads H for which the H-colouring problem is NP -complete. We contrast these with several families of oriented triads H which have tree duality, or bounded treewidth duality, and hence polynomial H-colouring problems. If P 6= NP , then no oriented triad H with an NP -complete H-colouring problem can have bounded treewidth duality; however no proof of this is known, for any oriented triad H. We prove that none of the oriented triads H with NP -complete Hcolouring problems given in the companion paper has tree duality.

Journal ArticleDOI
TL;DR: In this article, the hydration properties of linear segmented polyurethane copolymers were investigated with various fractions of hard and soft block segments, based on polyethylene adipate (PEA), 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO).
Abstract: Equilibrium and dynamic sorption isotherm measurements, differential scanning calorimetry (DSC) measurements, and, mainly, dielectric relaxation spectroscopy (DRS) measurements by means of the thermally stimulated depolarization currents (TSDC) method were used to investigate the hydration properties of linear segmented polyurethane copolymers. Three types of samples were investigated with various fractions of hard and soft block segments. They were based on polyethylene adipate (PEA), 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO). At 20°C the water content h of the samples at various values of relative humidity rh increases in proportion to the weight fraction of soft block segments phase. At saturation (rh = 100%) the ratio of sorbed water molecules to polar carbonyl polyester groups is 0.13. At saturation at 20°C there is no fraction of freezable water. The glass transition temperature, Tg, measured by DSC and by TSDC, shifts to lower temperature with increasing h by about 8–10 K at saturation at 20°C. A dielectric relaxation mechanism related to interfacial polarization in the phase-separated morphology is also plasticized by water in a way similar to that observed for the main (α) relaxation. © 1996 John Wiley & Sons, Inc.

Journal ArticleDOI
TL;DR: The overrepresentation of the variant allele, a guanine to adenine polymorphism in the SCAD gene at position 625, and biochemical studies indicate that the A625 allele confers susceptibility to the development of ethylmalonic aciduria are indicated.
Abstract: Ethylmalonic aciduria is a common biochemical finding in patients with inborn errors of short chain fatty acid β-oxidation. The urinary excretion of ethylmalonic acid (EMA) may stem from decreased oxidation by short chain acyl-CoA dehydrogenase (SCAD) of butyryl-CoA, which is alternatively metabolized by propionyl-CoA carboxylase to EMA. We have recently detected a guanine to adenine polymorphism in the SCAD gene at position 625 in the SCAD cDNA, which changes glycine 209 to serine (G209S). The variant allele (A625) is present in homozygous and in heterozygous form in 7 and 34.8% of the general population, respectively. One hundred and thirty-five patients from Germany, Denmark, the Czech Republic, Spain, and the United Sates were selected for this study on the basis of abnormal EMA excretion ranging from 18 to 1185 mmol/mol of creatinine (controls <18 mmol/mol of creatinine). Among them, we found a significant overrepresentation of the variant allele. Eighty-one patients (60%) were homozygous for the A625 allele, 40 (30%) were heterozygous, and only 14 (10%) harbored the wild-type allele (G625) in homozygous form. By overexpressing the wild-type and variant protein (G209S) in Escherichia coli and COS cells, we showed that the folding of the variant protein was slightly compromised in comparison to the wild-type and that the temperature stability of the tetrameric variant enzyme was lower than that of the wild type. Taken together, the overrepresentation and the biochemical studies indicate that the A625 allele confers susceptibility to the development of ethylmalonic aciduria.

Journal ArticleDOI
TL;DR: In this article, a six-step sequential extraction technique and statistical factor analysis were used to identify three dominant types of components of sediments, i.e., Ag, As, Be, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn.

Journal ArticleDOI
TL;DR: The present state of analysis for triazine herbicides and their residues is critically surveyed in this paper, where the authors summarize the properties of triazines and the history of the determination of the parent compounds and their residue.

Journal ArticleDOI
TL;DR: Comparison of killing data on S. cerevisiae S6/1 with those on the smaller-celled Kluyveramyces lactis showed the killing pulse amplitude to be roughly proportional to cell size except for low pulse amplitudes, at which smaller cells are much more killing-prone.

Journal ArticleDOI
TL;DR: In this paper, the asymptotic behavior of the flow for a system of the Navier-Stokes type is investigated and the existence of a global attractor with a finite fractal dimension is proved.

Journal ArticleDOI
S. Aid1, J. Zsembery2, K. Zuber3, M. zurNedden4  +423 moreInstitutions (28)
TL;DR: In this article, the authors presented results on J/ψ mesons in ep interactions in the H1 experiment at HERA and showed that the cross-section of diffractive Jψ production with proton dissociation is of similar magnitude as the elastic cross-sectional area.

Journal ArticleDOI
TL;DR: Five primary malignant tumours of the major salivary glands are presented, composed largely of a single population of clear cells, but displaying histological and immunohistochemical features of myoepithelial differentiation, such as the formation of collagenous spherules and expression of S‐100 protein and actin.
Abstract: Previous reports of monomorphic clear cell carcinoma of the salivary glands have shown inconsistent results with immunohistochemistry, especially for S-100 protein, and this has led to uncertainty about the nature of these tumours. We believe that much can be explained by considering this group as comprising not one but two separate neoplasms, one epithelial and the other myoepithelial. The former has been described as hyalinizing clear cell carcinoma--it generally occurs in the minor salivary glands, and strongly expresses cytokeratins but not S-100 protein or alpha smooth muscle actin. In contrast, this study presents five primary malignant tumours of the major salivary glands also composed largely of a single population of clear cells, but displaying histological and immunohistochemical features of myoepithelial differentiation, such as the formation of collagenous spherules and expression of S-100 protein and actin. A small number of similar tumours have been reported previously. We, therefore, believe that these neoplasms represent a clear cell variant of malignant myoepithelioma (myoepithelial carcinoma).