2,336 research outputs found

    Assessing movements of three buoy line types using DSTmilli Loggers: Implications for entanglements of bottlenose dolphins in the crab pot fishery

    Get PDF
    A study was conducted in October 2006 in the Charleston, South Carolina area to test the movements of three different buoy line types to determine which produced a preferred profile that could reduce the risk of dolphin entanglement. Tests on diamond-braided nylon commonly used in the crab pot fishery were compared with stiffened line of Esterpro and calf types in both shallow and deep water environments using DSTmilli data loggers. Loggers were placed at intervals along the lines to record depth, and thus movements, over a 24 hour period. Three observers viewed video animations and charts created for each of the six trial days from the collected logger data and provided their opinions on the most desirable line type that fit set criteria. A quantitative analysis (ANCOVA) of the data was conducted taking into consideration daily tidal fluctuations and logger movements. Loggers tracking the tides had an r2 value approaching 1.00 and produced little movement other than with the tides. Conversely, r2 values approaching 0.00 were less affected by tidal movement and influenced by currents that cause more erratic movement. Results from this study showed that stiffened line, in particular the medium lay Esterpro type, produced the more desirable profiles that could reduce risk of dolphin entanglement. Combining the observer’s results with the ANCOVA results, Esterpro was chosen nearly 60% of the time as opposed to the nylon line which was only chosen 10% of the time. ANCOVA results showed that the stiffened lines performed better in both the shallow and deep water environments, while the nylon line only performed better during one trial in a deep water set, most probably due to the increased current velocities experienced that day. (58pp.)(PDF contains 68 pages

    Interpretation of Nuclear Quadrupole Resonance Spectra in Doped La2_2CuO4_4

    Full text link
    The nuclear quadrupole resonance (NQR) spectrum of strontium doped La2_2CuO4_4 surprisingly resembles the NQR spectrum of La2_2CuO4_4 doped with excess oxygen, both spectra being dominated by a main peak and one principal satellite peak at similar frequencies. Using first-principles cluster calculations this is investigated here by calculating the electric field gradient (EFG) at the central copper site of the cluster after replacing a lanthanum atom in the cluster with a strontium atom or adding an interstitial oxygen to the cluster. In each case the EFG was increased by approximately 10 % leading unexpectedly to the explanation that the NQR spectra are only accidentally similar and the origins are quite different. Additionally the widths of the peaks in the NQR spectra are explained by the different EFG of copper centres remote from the impurity. A model, based on holes moving rapidly across the planar oxygen atoms, is proposed to explain the observed increase in frequency of both the main and satellite peaks in the NQR spectrum as the doping concentration is increased

    Phase diagram of YBa2_2Cu3_3O7y_{7-y} at T<<Tc_c based on Cu(2) transverse nuclear relaxation

    Full text link
    Two maxima in transverse relaxation rate of Cu(2) nuclei in YBa2_2Cu3_3O7y_{7-y} are observed, at T = 35 K and T = 47 K. Comparison of the 63^{63}Cu(2) and 65^{65}Cu(2) rates at T = 47 K indicates the magnetic character of relaxation. The enhancement at T = 47 K of fluctuating local magnetic fields perpendicular to the CuO2_2 planes is connected with the critical fluctuations of orbital currents. Maximum at T = 35 K is connected with the appearance of inhomogeneous supeconducting phase. Together with data published to date, our experimental results allow to suggest a qualitatively new phase diagram of the superconducting phase.Comment: 4 LaTEX pages + 3 figures in *.ps forma

    The physics of the B Factories

    Get PDF
    “The Physics of the B Factories” describes a decade long effort of physicists in the quest for the precise determination of asymmetry — broken symmetry — between particles and anti-particles. We now recognize that the matter we see around us is the residue — one part in a billion — of the matter and antimatter that existed in the early universe, most of which annihilated into the cosmic background radiation that bathes us. But the question remains: how did the baryonic matter-antimatter asymmetry arise? This book describes the work done by some 1000 physicists and engineers from around the globe on two experimental facilities built to test our understanding of this phenomenon, one at the SLAC National Accelerator Laboratory in California, USA, and a second at the KEK Laboratory, Tsukuba, Japan, and what we have learned from them in broadening our understanding of nature. Why is our universe dominated by the matter of which we are made rather than equal parts of matter and antimatter? This question has puzzled physicists for decades. However, this was not the question we addressed when we wrote the paper on CP violation in 1972. Our question was whether we can explain the CP violation observed in the K meson decay within the framework of the renormalizable gauge theory. At that time, Sakharov’s seminal paper was already published, but it did not attract our attention. If we were aware of the paper, we would have been misled into seeking a model satisfying Sakharov’s conditions and our paper might not have appeared. In our paper, we discussed that we need new particles in order to accommodate CP violation into the renormalizable electroweak theory, and proposed the six-quark scheme as one of the possible ways introducing new particles. We thought that the six-quark scheme is very interesting, but it was just a possibility. The situation changed when the tau-lepton was found and it was followed by the discovery of the Upsilon particle. The existence of the third generation became reality. However, it was still uncertain whether the mixing of the six quarks is a real origin of the observed CP violation. Theoretical calculation of CP asymmetries in the neutral K meson system contains uncertainty from strong interaction effects. What settled this problem were the B Factories built at SLAC and KEK. These B Factories are extraordinary in many ways. In order to fulfill the requirements of special experiments, the beam energies of the colliding electron and positron are asymmetric, and the luminosity is unprecedentedly high. It is also remarkable that severe competition between the two laboratories boosted their performance. One of us (M. Kobayashi) has been watching the development at KEK very closely as the director of the Institute of Particle and Nuclear Studies of KEK for a period of time. As witnesses, we appreciate the amazing achievement of those who participated in these projects at both laboratories. The B Factories have contributed a great deal to our understanding of particle physics, as documented in this book. In particular, thanks to the high luminosity far exceeding the design value, experimental groups measured mixing angles precisely and verified that the dominant source of CP violation observed in the laboratory experiments is flavor mixing among the three generations of quarks. Obviously we owe our Nobel Prize to this result. Now we are awaiting the operation of the next generation Super B Factories. In spite of its great success, the Standard Model is not an ultimate theory. For example, it is not thought to be possible for the matter dominance of the universe to be explained by the Standard Model. This means that there will still be unknown particles and unknown interactions. We have a lot of theoretical speculations but experimental means are rather limited. There are great expectations for the Super B Factories to reveal a clue to the world beyond the Standard Model

    Variation with mass of \boldmath{B(E3; 0_1^+ \to 3_1^-)} transition rates in A=124134A=124-134 even-mass xenon nuclei

    Full text link
    B(E3;01+31)B(E3; 0_1^+ \to 3_1^-) transition matrix elements have been measured for even-mass 124134^{124-134}Xe nuclei using sub-barrier Coulomb excitation in inverse kinematics. The trends in energy E(3)E(3^-) and B(E3;01+31)B(E3; 0_1^+ \to 3_1^-) excitation strengths are well reproduced using phenomenological models based on a strong coupling picture with a soft quadrupole mode and an increasing occupation of the intruder h11/2h_{11/2} orbital.Comment: 5 pages, 4 figures, PRC in pres

    Coulomb suppression of NMR coherence peak in fullerene superconductors

    Full text link
    The suppressed NMR coherence peak in the fullerene superconductors is explained in terms of the dampings in the superconducting state induced by the Coulomb interaction between conduction electrons. The Coulomb interaction, modelled in terms of the onsite Hubbard repulsion, is incorporated into the Eliashberg theory of superconductivity with its frequency dependence considered self-consistently at all temperatures. The vertex correction is also included via the method of Nambu. The frequency dependent Coulomb interaction induces the substantial dampings in the superconducting state and, consequently, suppresses the anticipated NMR coherence peak of fullerene superconductors as found experimentally.Comment: 4 pages, Revtex, and 2 figures. Revised and final version to appear in Phys. Rev. Lett. (1998

    Where is the pseudoscalar glueball ?

    Full text link
    The pseudoscalar mesons with the masses higher than 1 GeV are assumed to belong to the meson decuplet including the glueball as the basis state supplementing the standard SU(3)FSU(3)_F nonet of light qqˉq\bar{q} states (u,d,s)(u,d,s). The decuplet is investigated by means of an algebraic approach based on hypothesis of vanishing the exotic SU(3)FSU(3)_F commutators of "charges" and their time derivatives. These commutators result in a system of equations determining contents of the isoscalar octet state in the physical isoscalar mesons as well as the mass formula including all masses of the decuplet: π(1300)\pi(1300), K(1460), η(1295)\eta(1295), η(1405)\eta(1405) and η(1475)\eta(1475). The physical isoscalar mesons ηi\eta_i, are expressed as superpositions of the "ideal" qqˉq\bar{q} states (NN and SS) and the glueball GG with the mixing coefficient matrix following from the exotic commutator restrictions. Among four one-parameter families of the calculated mixing matrix (numerous solutions result from bad quality of data on the π(1300)\pi(1300) and K(1460) masses) there is one family attributing the glueball-dominant composition to the η(1405)\eta(1405) meson. Similarity between the pseudoscalar and scalar decuplets, analogy between the whole spectra of the 0+0^{-+} and 0++0^{++} mesons and affinity of the glueball with excited qqˉq\bar{q} states are also noticed.Comment: 18 pp., 2. figs., 2 tabs.; Published version. One of the authors withdraws his nam

    On the precision of chiral-dispersive calculations of ππ\pi\pi scattering

    Get PDF
    We calculate the combination 2a0(0)5a0(2)2a_0^{(0)}-5a_0^{(2)} (the Olsson sum rule) and the scattering lengths and effective ranges a1a_1, a2(I)a_2^{(I)} and b1b_1, b2(I)b_2^{(I)} dispersively (with the Froissart--Gribov representation) using, at low energy, the phase shifts for ππ\pi\pi scattering obtained by Colangelo, Gasser and Leutwyler (CGL) from the Roy equations and chiral perturbation theory, plus experiment and Regge behaviour at high energy, or directly, using the CGL parameters for aas and bbs. We find mismatch, both among the CGL phases themselves and with the results obtained from the pion form factor. This reaches the level of several (2 to 5) standard deviations, and is essentially independent of the details of the intermediate energy region (0.82E1.420.82\leq E\leq 1.42 GeV) and, in some cases, of the high energy behaviour assumed. We discuss possible reasons for this mismatch, in particular in connection with an alternate set of phase shifts.Comment: Version to appear in Phys. Rev. D. Graphs and sum rule added. Plain TeX fil

    Genome-wide screening for DNA variants associated with reading and language traits

    Get PDF
    This research was funded by: Max Planck Society, the University of St Andrews - Grant Number: 018696, US National Institutes of Health - Grant Number: P50 HD027802, Wellcome Trust - Grant Number: 090532/Z/09/Z, and Medical Research Council Hub Grant Grant Number: G0900747 91070Reading and language abilities are heritable traits that are likely to share some genetic influences with each other. To identify pleiotropic genetic variants affecting these traits, we first performed a genome‐wide association scan (GWAS) meta‐analysis using three richly characterized datasets comprising individuals with histories of reading or language problems, and their siblings. GWAS was performed in a total of 1862 participants using the first principal component computed from several quantitative measures of reading‐ and language‐related abilities, both before and after adjustment for performance IQ. We identified novel suggestive associations at the SNPs rs59197085 and rs5995177 (uncorrected P ≈ 10–7 for each SNP), located respectively at the CCDC136/FLNC and RBFOX2 genes. Each of these SNPs then showed evidence for effects across multiple reading and language traits in univariate association testing against the individual traits. FLNC encodes a structural protein involved in cytoskeleton remodelling, while RBFOX2 is an important regulator of alternative splicing in neurons. The CCDC136/FLNC locus showed association with a comparable reading/language measure in an independent sample of 6434 participants from the general population, although involving distinct alleles of the associated SNP. Our datasets will form an important part of on‐going international efforts to identify genes contributing to reading and language skills.Publisher PDFPeer reviewe
    corecore