2,409 research outputs found
Evidence for Two Exponent Scaling in the Random Field Ising Model
Novel methods were used to generate and analyze new 15 term high temperature series for both the (connected) susceptibility χ and the structure factor (disconnected susceptibility) χd for the random field Ising model with dimensionless coupling K=J/kT, in general dimension d. For both the bimodal and the Gaussian field distributions, with mean square field J2g, we find that (χd-χ)/K2gχ2=1 as T→Tc(g), for a range of [h2]=J2g and d=3,4,5. This confirms the exponent relation γ¯=2γ (where χd~t−γ¯, χ~t−γ, t=T-Tc) providing that random field exponents are determined by two (and not three) independent exponents. We also present new accurate values for γ
From Current to Constituent Quarks: a Renormalization Group Improved Hamiltonian-based Description of Hadrons
A model which combines the perturbative behavior of QCD with low energy
phenomenology in a unified framework is developed. This is achieved by applying
a similarity transformation to the QCD Hamiltonian which removes interactions
between the ultraviolet cutoff and an arbitrary lower scale. Iteration then
yields a renormalization group improved effective Hamiltonian at the hadronic
energy scale. The procedure preserves the standard ultraviolet behavior of QCD.
Furthermore, the Hamiltonian evolves smoothly to a phenomenological low energy
behavior below the hadronic scale. This method has the benefit of allowing
radiative corrections to be directly incorporated into nonperturbative
many-body techniques. It is applied to Coulomb gauge QCD supplemented with a
low energy linear confinement interaction. A nontrivial vacuum is included in
the analysis via a Bogoliubov-Valatin transformation. Finally, the formalism is
applied to the vacuum gap equation, the quark condensate, and the dynamical
quark mass.Comment: 36 pages, RevTeX, 5 ps figures include
The atmospheric charged kaon/pion ratio using seasonal variation methods
Observed since the 1950's, the seasonal effect on underground muons is a well
studied phenomenon. The interaction height of incident cosmic rays changes as
the temperature of the atmosphere changes, which affects the production height
of mesons (mostly pions and kaons). The decay of these mesons produces muons
that can be detected underground. The production of muons is dominated by pion
decay, and previous work did not include the effect of kaons. In this work, the
methods of Barrett and MACRO are extended to include the effect of kaons. These
efforts give rise to a new method to measure the atmospheric K/ ratio at
energies beyond the reach of current fixed target experiments. These methods
were applied to data from the MINOS far detector. A method is developed for
making these measurements at other underground detectors, including OPERA,
Super-K, IceCube, Baksan and the MINOS near detector.Comment: 15 pages, 4 figures, submitted to Astropart. Phy
Bacterial Artificial Chromosome Clones of Viruses Comprising the Towne Cytomegalovirus Vaccine
Bacterial artificial chromosome (BAC) clones have proven invaluable for genetic manipulation of herpesvirus genomes. BAC cloning can also be useful for capturing representative genomes that comprise a viral stock or mixture. The Towne live attenuated cytomegalovirus vaccine was developed in the 1970s by serial passage in cultured fibroblasts. Although its safety, immunogenicity, and efficacy have been evaluated in nearly a thousand human subjects, the vaccine itself has been little studied. Instead, genetic composition and in vitro growth properties have been inferred from studies of laboratory stocks that may not always accurately represent the viruses that comprise the vaccine. Here we describe the use of BAC cloning to define the genotypic and phenotypic properties of viruses from the Towne vaccine. Given the extensive safety history of the Towne vaccine, these BACs provide a logical starting point for the development of next-generation rationally engineered cytomegalovirus vaccines
Occam's Higgs: A Phenomenological Solution to the Electroweak Hierarchy Problem
We propose a phenomenological solution to the Electroweak hierarchy problem.
It predicts no new particles beyond those in the Standard Model. The Higgs is
arbitrarily massive and slow-roll inflation can be implemented naturally. Loop
corrections will be negligible even for large cutoffs.Comment: 7 pp., 2 figs., LaTeX. Slight rewordin
Glueball Spectroscopy in a Relativistic Many-Body Approach to Hadron Structure
A comprehensive, relativistic many-body approach to hadron structure is
advanced based on the Coulomb gauge QCD Hamiltonian. Our method incorporates
standard many-body techniques which render the approximations amenable to
systematic improvement. Using BCS variational methods, dynamic chiral symmetry
breaking naturally emerges and both quarks and gluons acquire constituent
masses. Gluonia are studied both in the valence and in the collective, random
phase approximations. Using representative values for the strong coupling
constant and string tension, calculated quenched glueball masses are found to
be in remarkable agreement with lattice gauge theory.Comment: 12 pages, 1 uuencoded ps figure, RevTe
Neutralization of Diverse Human Cytomegalovirus Strains Conferred by Antibodies Targeting Viral gH/gL/pUL128-131 Pentameric Complex
Human cytomegalovirus (HCMV) is the leading cause of congenital viral infection, and developing a prophylactic vaccine is of high priority to public health. We recently reported a replication-defective human cytomegalovirus with restored pentameric complex glycoprotein H (gH)/gL/pUL128-131 for prevention of congenital HCMV infection. While the quantity of vaccine-induced antibody responses can be measured in a viral neutralization assay, assessing the quality of such responses, including the ability of vaccine-induced antibodies to cross-neutralize the field strains of HCMV, remains a challenge. In this study, with a panel of neutralizing antibodies from three healthy human donors with natural HCMV infection or a vaccinated animal, we mapped eight sites on the dominant virus-neutralizing antigen-the pentameric complex of glycoprotein H (gH), gL, and pUL128, pUL130, and pUL131. By evaluating the site-specific antibodies in vaccine immune sera, we demonstrated that vaccination elicited functional antiviral antibodies to multiple neutralizing sites in rhesus macaques, with quality attributes comparable to those of CMV hyperimmune globulin. Furthermore, these immune sera showed antiviral activities against a panel of genetically distinct HCMV clinical isolates. These results highlighted the importance of understanding the quality of vaccine-induced antibody responses, which includes not only the neutralizing potency in key cell types but also the ability to protect against the genetically diverse field strains. IMPORTANCE HCMV is the leading cause of congenital viral infection, and development of a preventive vaccine is a high public health priority. To understand the strain coverage of vaccine-induced immune responses in comparison with natural immunity, we used a panel of broadly neutralizing antibodies to identify the immunogenic sites of a dominant viral antigen-the pentameric complex. We further demonstrated that following vaccination of a replication-defective virus with the restored pentameric complex, rhesus macaques can develop broadly neutralizing antibodies targeting multiple immunogenic sites of the pentameric complex. Such analyses of site-specific antibody responses are imperative to our assessment of the quality of vaccine-induced immunity in clinical studies
Biomass Yield of Switchgrass Cultivars under High- versus Low-Input Conditions
Switchgrass (Panicum virgatum L.) is undergoing development as a biomass crop to support conversion of cellulosic biomass to energy. To avoid the competition of biomass with food or feed crops, most commercialization proposals suggest that switchgrass should be grown exclusively on marginal lands that are not fit for food or feed production. The objective of this study was to investigate the potential for cultivar x environment interactions that would affect the methods and approaches for breeding and evaluating switchgrass cultivars, including both upland and lowland types, for high-input versus low-input types of environments. Biomass yield was measured on 14 cultivars that were present in 28 replicated field experiments representing seven regions, ranging from 75 to 100° W and spanning USDA Hardiness Zones 4 through 7. Region was the most important environmental factor interacting with cultivars, supporting the idea that the north-central and northeastern United States should have independent switchgrass breeding programs. Cultivars interacted with soil phosphorus concentration in New Jersey and with depth of the A and B horizons in New York and showed mild interactions with rate of nitrogen fertilizer at several locations. Cultivar rank correlation coefficients between the two rates of nitrogen fertilization (100 vs. 0 kg N ha−1) ranged from 0.23 to 0.88, suggesting a possible benefit to breeding and selection without applied nitrogen fertilizer
Multigrid Monte Carlo Algorithms for SU(2) Lattice Gauge Theory: Two versus Four Dimensions
We study a multigrid method for nonabelian lattice gauge theory, the time
slice blocking, in two and four dimensions. For SU(2) gauge fields in two
dimensions, critical slowing down is almost completely eliminated by this
method. This result is in accordance with theoretical arguments based on the
analysis of the scale dependence of acceptance rates for nonlocal Metropolis
updates. The generalization of the time slice blocking to SU(2) in four
dimensions is investigated analytically and by numerical simulations. Compared
to two dimensions, the local disorder in the four dimensional gauge field leads
to kinematical problems.Comment: 24 pages, PostScript file (compressed and uuencoded), preprint
MS-TPI-94-
The Minimum Backlog Problem
We study the minimum backlog problem (MBP). This online problem arises, e.g.,
in the context of sensor networks. We focus on two main variants of MBP.
The discrete MBP is a 2-person game played on a graph . The player
is initially located at a vertex of the graph. In each time step, the adversary
pours a total of one unit of water into cups that are located on the vertices
of the graph, arbitrarily distributing the water among the cups. The player
then moves from her current vertex to an adjacent vertex and empties the cup at
that vertex. The player's objective is to minimize the backlog, i.e., the
maximum amount of water in any cup at any time.
The geometric MBP is a continuous-time version of the MBP: the cups are
points in the two-dimensional plane, the adversary pours water continuously at
a constant rate, and the player moves in the plane with unit speed. Again, the
player's objective is to minimize the backlog.
We show that the competitive ratio of any algorithm for the MBP has a lower
bound of , where is the diameter of the graph (for the discrete
MBP) or the diameter of the point set (for the geometric MBP). Therefore we
focus on determining a strategy for the player that guarantees a uniform upper
bound on the absolute value of the backlog.
For the absolute value of the backlog there is a trivial lower bound of
, and the deamortization analysis of Dietz and Sleator gives an
upper bound of for cups. Our main result is a tight upper
bound for the geometric MBP: we show that there is a strategy for the player
that guarantees a backlog of , independently of the number of cups.Comment: 1+16 pages, 3 figure
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