3,130 research outputs found

    Martel in the Slovene Karst in 1893

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    E.A. Martel (1859-1938) is rightly regarded as one of the most important people in the history of cave study. Writing in French, as he did, his work was little known in those parts of central Europe that were in the Austrian empire. Thus much of what he wrote about the Classical Karst was not readily accessible to those now living in that area. It is for that reason that this English translation of his 1894 publication has been made. Martel had been in Slovenia from 14 September 1893 to mid October. He was shown the principal caves and karst features of the region by Wilhelm Putick who had been exploring these places from 1886 onwards. This assistance had been authorised by Count Falkenhayn, the Minister of Agriculture in Wien. Such was the importance with which Martel was regarded internationally

    Finite size effects near the onset of the oscillatory instability

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    A system of two complex Ginzburg - Landau equations is considered that applies at the onset of the oscillatory instability in spatial domains whose size is large (but finite) in one direction; the dependent variables are the slowly modulated complex amplitudes of two counterpropagating wavetrains. In order to obtain a well posed problem, four boundary conditions must be imposed at the boundaries. Two of them were already known, and the other two are first derived in this paper. In the generic case when the group velocity is of order unity, the resulting problem has terms that are not of the same order of magnitude. This fact allows us to consider two distinguished limits and to derive two associated (simpler) sub-models, that are briefly discussed. Our results predict quite a rich variety of complex dynamics that is due to both the modulational instability and finite size effects

    Macrolide resistance in porcine streptococci: a human health hazard?

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    In order to obtain better insights into the possible exchange of resistance genes between human and porcine streptococci, macrolide and lincosamide resistant streptococci from tonsillar and colon swabs from pigs and pork carcass swabs were isolated and their resistance phenotypes and genotypes were determined. The sequences of the erm(B) genes of 21 human streptococci, 22 porcine streptococci and 15 streptococci isolated from pork carcasses were compared. From each of the 33 pigs and from 88 of 99 carcass swabs, at least one resistant streptococcal strain was isolated. The predominant phenotype was the constitutively expressed MLSB phenotype, mostly encoded by the erm(B) gene. Identical erm(B) gene sequences were present in strains from humans, pigs and pork carcasses

    Positron-neutrino correlations in 32Ar and 33Ar Decays: Probes of Scalar weak currents and nuclear isospin mixing

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    The positron-neutrino correlation in the 0^+ \to 0^+ \beta decay of ^{32}Ar was measured at ISOLDE by analyzing the effect of lepton recoil on the shape of the narrow proton group following the superallowed decay. Our result is consistent with the Standard Model prediction; for vanishing Fierz interference we find a=0.9989 \pm 0.0052 \pm 0.0036. Our result leads to improved constraints on scalar weak interactions. The positron-neutrino correlation in ^{33}Ar decay was measured in the same experiment; for vanishing Fierz interference we find a=0.944 \pm 0.002 \pm 0.003. The ^{32}Ar and ^{33}Ar correlations, in combination with precision measurements of the half-lives, superallowed branching ratios and beta endpoint energies, will determine the isospin impurities of the superallowed transitions. These will provide useful tests of isospin-violation corrections used in deducing |V_{\rm ud}| which currently indicates non-unitarity of the KM matrix.Comment: 15 pages, 6 figure

    ODD Symptom Network During Preschool

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    Several different conceptualizations of Oppositional Defiant Disorder (ODD) symptoms have been proposed, including one undivided set of symptoms (DSM-IV-TR; APA 2000); two domains of symptoms subdivided into affective and behavioral; and three domains of symptoms subdivided as angry/irritable, argumentative/defiant, and spiteful. The current study utilizes a novel approach to examining the division of ODD symptoms through use of network analysis. Participants were 109 preschoolers (64 male) between the ages of three and six (M = 4.34 years, SD = 1.08) and their parents and teachers/caregivers, who provided ratings of ODD symptoms. Results are consistent with one-, two-, and three- cluster solutions of ODD, but perhaps provide most support for the three-cluster solution. In addition, results support the idea that negative affect, particularly anger, forms the core of the ODD symptom network during preschool. These results suggest the importance of targeting anger in preschool interventions for ODD

    Impulsivity Symptoms as Core to the Developmental Externalizing Spectrum

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    Impulsivity is posited to be a key part of the externalizing spectrum during childhood, but this idea has received minimal empirical attention. The goal of the present investigation was to utilize network analysis to determine whether behavioral impulsivity symptoms are key components of the externalizing network across several developmental periods from preschool into adolescence. Participants were 109 preschoolers (64 % male) ages 3 to 6, 237 children (59 % male) ages 6 to 9, 372 children (59 % male) ages 10 to 13, and 357 adolescents (59 % male) ages 13 to 17 and their parents. Parents completed ratings of Attention-Deficit/Hyperactivity Disorder (ADHD) and Oppositional Defiant Disorder (ODD) symptoms on a well-validated rating scale. Network analyses indicated that ADHD and ODD were somewhat differentiated in preschool, becoming united by behavioral impulsivity symptoms during early childhood, and then differentiating into inattention versus externalizing clusters later during childhood and in adolescence. Behavioral impulsivity symptoms were core to the externalizing spectrum across most developmental periods, but core inattentive and ODD symptoms were also identified in line with progressive differentiation. These results suggest the increasing importance of impulsivity symptoms across development, explaining externalizing comorbidity and potentially serving as a viable target for childhood interventions for externalizing problems

    Experimental study of a liquid Xenon PET prototype module

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    A detector using liquid Xenon in the scintillation mode is studied for Positron Emission Tomography (PET). The specific design aims at taking full advantage of the liquid Xenon properties. It does feature a promising insensitive to any parallax effect. This work reports on the performances of the first LXe prototype module, equipped with a position sensitive PMT operating in the VUV range (178 nm).Comment: Proc. of the 7th International Workshops on Radiation Imaging Detectors (IWORID-7), Grenoble, France 4-7 July 200

    Instability of two interacting, quasi-monochromatic waves in shallow water

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    We study the nonlinear interactions of waves with a doubled-peaked power spectrum in shallow water. The starting point is the prototypical equation for nonlinear uni-directional waves in shallow water, i.e. the Korteweg de Vries equation. Using a multiple-scale technique two defocusing coupled Nonlinear Schr\"odinger equations are derived. We show analytically that plane wave solutions of such a system can be unstable to small perturbations. This surprising result suggests the existence of a new energy exchange mechanism which could influence the behaviour of ocean waves in shallow water.Comment: 4 pages, 2 figure

    Non-volatile molecular memory elements based on ambipolar nanotube field effect transistors

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    We have fabricated air-stable n-type, ambipolar carbon nanotube field effect transistors (CNFETs), and used them in nanoscale memory cells. N-type transistors are achieved by annealing of nanotubes in hydrogen gas and contacting them by cobalt electrodes. Scanning gate microscopy reveals that the bulk response of these devices is similar to gold-contacted p-CNFETs, confirming that Schottky barrier formation at the contact interface determines accessibility of electron and hole transport regimes. The transfer characteristics and Coulomb Blockade (CB) spectroscopy in ambipolar devices show strongly enhanced gate coupling, most likely due to reduction of defect density at the silicon/silicon-dioxide interface during hydrogen anneal. The CB data in the ``on''-state indicates that these CNFETs are nearly ballistic conductors at high electrostatic doping. Due to their nanoscale capacitance, CNFETs are extremely sensitive to presence of individual charge around the channel. We demonstrate that this property can be harnessed to construct data storage elements that operate at the few-electron level.Comment: 6 pages text, 3 figures and 1 table of content graphic; available as NanoLetters ASAP article on the we
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