3,541 research outputs found
Baryon Junction Stopping at the SPS and RHIC via HIJING/B
Baryon stopping at the SPS and RHIC energies is calculated by introducing a
new baryon junction mechanism into HIJING. The exchange of a baryon junction,
according to Regge phenomenology, leads to a cosh(y/2) rapidity dependence and
an s^(-1/4) energy dependence of the inclusive baryon cross section. This
baryon junction dynamics also leads naturally to enhanced p_T broadening in pA
and AA together with enhanced mid-rapidity hyperon production.Comment: Proceedings for Quark Matter 97; 4 pages, 1 eps-figur
Climate warming, euxinia and carbon isotope perturbations during the Carnian (Triassic) Crisis in South China
The Carnian Humid Episode (CHE), also known as the Carnian Pluvial Event, and associated biotic changes are major enigmas of the Mesozoic record in western Tethys. We show that the CHE also occurred in eastern Tethys (South China), suggestive of a much more widespread and probably global climate perturbation. Oxygen isotope records from conodont apatite indicate a double-pulse warming event. The CHE coincided with an initial warming of 4 °C. This was followed by a transient cooling period and then a prolonged ~7 °C warming in the later Carnian (Tuvalian 2). Carbon isotope perturbations associated with the CHE of western Tethys occurred contemporaneously in South China, and mark the start of a prolonged period of carbon cycle instability that persisted until the late Carnian. The dry-wet transition during the CHE coincides with the negative carbon isotope excursion and the temperature rise, pointing to an intensification of hydrologic cycle activities due to climatic warming. While carbonate platform shutdown in western Tethys is associated with an influx of siliciclastic sediment, the eastern Tethyan carbonate platforms are overlain by deep-water anoxic facies. The transition from oxygenated to euxinic facies was via a condensed, manganiferous carbonate (MnO content up to 15.1 wt%), that records an intense Mn shuttle operating in the basin. Significant siliciclastic influx in South China only occurred after the CHE climatic changes and was probably due to foreland basin development at the onset of the Indosinian Orogeny. The mid-Carnian biotic crisis thus coincided with several phenomena associated with major extinction events: a carbonate production crisis, climate warming, Ύ 13 C oscillations, marine anoxia, biotic turnover and flood basalt eruptions (of the Wrangellia Large Igneous Province)
Complete genome sequence of Mesorhizobium sophorae ICMP 19535T, a highly specific, nitrogen-fixing symbiont of New Zealand endemic Sophora spp
We report here the complete genome sequence of Mesorhizobium sophorae ICMP 19535T. This strain was isolated from Sophora microphylla root nodules and can nodulate and fix nitrogen with this host and also with Sophora prostrata, Sophora longicarinata, and Clianthus puniceus. The genome consists of 8.05 Mb
On the Adaptive Real-Time Detection of Fast-Propagating Network Worms
We present two light-weight worm detection algorithms thatoffer significant advantages over fixed-threshold methods.The first algorithm, RBS (rate-based sequential hypothesis testing)aims at the large class of worms that attempts to quickly propagate, thusexhibiting abnormal levels of the rate at which hosts initiateconnections to new destinations. The foundation of RBS derives fromthe theory of sequential hypothesis testing, the use of which fordetecting randomly scanning hosts was first introduced by our previouswork with the TRW (Threshold Random Walk) scan detection algorithm. The sequential hypothesistesting methodology enables engineering the detectors to meet falsepositives and false negatives targets, rather than triggering whenfixed thresholds are crossed. In this sense, the detectors that weintroduce are truly adaptive.We then introduce RBS+TRW, an algorithm that combines fan-out rate (RBS)and probability of failure (TRW) of connections to new destinations.RBS+TRW provides a unified framework that at one end acts as a pure RBSand at the other end as pure TRW, and extends RBS's power in detectingworms that scan randomly selected IP addresses
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Precipitation and latent heating distributions from satellite passive microwave radiometry. Part I: improved method and uncertainties
A revised Bayesian algorithm for estimating surface rain rate, convective rain proportion, and latent heating profiles from satellite-borne passive microwave radiometer observations over ocean backgrounds is described. The algorithm searches a large database of cloud-radiative model simulations to find cloud profiles that are radiatively consistent with a given set of microwave radiance measurements. The properties of these radiatively consistent profiles are then composited to obtain best estimates of the observed properties. The revised algorithm is supported by an expanded and more physically consistent database of cloud-radiative model simulations. The algorithm also features a better quantification of the convective and nonconvective contributions to total rainfall, a new geographic database, and an improved representation of background radiances in rain-free regions. Bias and random error estimates are derived from applications of the algorithm to synthetic radiance data, based upon a subset of cloud-resolving model simulations, and from the Bayesian formulation itself. Synthetic rain-rate and latent heating estimates exhibit a trend of high (low) bias for low (high) retrieved values. The Bayesian estimates of random error are propagated to represent errors at coarser time and space resolutions, based upon applications of the algorithm to TRMM Microwave Imager (TMI) data. Errors in TMI instantaneous rain-rate estimates at 0.5°-resolution range from approximately 50% at 1 mm hâ1 to 20% at 14 mm hâ1. Errors in collocated spaceborne radar rain-rate estimates are roughly 50%â80% of the TMI errors at this resolution. The estimated algorithm random error in TMI rain rates at monthly, 2.5° resolution is relatively small (less than 6% at 5 mm dayâ1) in comparison with the random error resulting from infrequent satellite temporal sampling (8%â35% at the same rain rate). Percentage errors resulting from sampling decrease with increasing rain rate, and sampling errors in latent heating rates follow the same trend. Averaging over 3 months reduces sampling errors in rain rates to 6%â15% at 5 mm dayâ1, with proportionate reductions in latent heating sampling errors
A Knob for Changing Light Propagation from Subluminal to Superluminal
We show how the application of a coupling field connecting the two lower
metastable states of a lambda-system can produce a variety of new results on
the propagation of a weak electromagnetic pulse. In principle the light
propagation can be changed from subluminal to superluminal. The negative group
index results from the regions of anomalous dispersion and gain in
susceptibility.Comment: 6 pages,5 figures, typed in RevTeX, accepted in Phys. Rev.
A Study of Parton Energy Loss in Au+Au Collisions at RHIC using Transport Theory
Parton energy loss in Au+Au collisions at RHIC energies is studied by
numerically solving the relativistic Boltzmann equation for the partons
including and collision
processes. Final particle spectra are obtained using two hadronization models;
the Lund string fragmentation and independent fragmentation models. Recent,
preliminary transverse momentum distributions from central Au+Au
collisions at RHIC are reproduced using gluon-gluon scattering cross sections
of 5-12 mb, depending upon the hadronization model. Comparisons with the HIJING
jet quenching algorithm are made.Comment: 6 pages, 6 figures, attached files are replaced (wrong files were
uploaded in version 1
Two-loop approximation in the Coulomb blockade problem
We study Coulomb blockade (CB) oscillations in the thermodynamics of a
metallic grain which is connected to a lead by a tunneling contact with a large
conductance in a wide temperature range, ,
where is the charging energy. Using the instanton analysis and the
renormalization group we obtain the temperature dependence of the amplitude of
CB oscillations which differs from the previously obtained results. Assuming
that at the oscillation amplitude weakly depends on
temperature we estimate the magnitude of CB oscillations in the ground state
energy as .Comment: 10 pages, 3 figure
Simplified amino acid alphabets based on deviation of conditional probability from random background
The primitive data for deducing the Miyazawa-Jernigan contact energy or
BLOSUM score matrix consists of pair frequency counts. Each amino acid
corresponds to a conditional probability distribution. Based on the deviation
of such conditional probability from random background, a scheme for reduction
of amino acid alphabet is proposed. It is observed that evident discrepancy
exists between reduced alphabets obtained from raw data of the
Miyazawa-Jernigan's and BLOSUM's residue pair counts. Taking homologous
sequence database SCOP40 as a test set, we detect homology with the obtained
coarse-grained substitution matrices. It is verified that the reduced alphabets
obtained well preserve information contained in the original 20-letter
alphabet.Comment: 9 pages,3figure
Superluminal optical pulse propagation in nonlinear coherent media
The propagation of light-pulse with negative group-velocity in a nonlinear
medium is studied theoretically. We show that the necessary conditions for
these effects to be observable are realized in a three-level -system
interacting with a linearly polarized laser beam in the presence of a static
magnetic field. In low power regime, when all other nonlinear processes are
negligible, the light-induced Zeeman coherence cancels the resonant absorption
of the medium almost completely, but preserves the dispersion anomalous and
very high. As a result, a superluminal light pulse propagation can be observed
in the sense that the peak of the transmitted pulse exits the medium before the
peak of the incident pulse enters. There is no violation of causality and
energy conservation. Moreover, the superluminal effects are prominently
manifested in the reshaping of pulse, which is caused by the
intensity-dependent pulse velocity. Unlike the shock wave formation in a
nonlinear medium with normal dispersion, here, the self-steepening of the pulse
trailing edge takes place due to the fact that the more intense parts of the
pulse travel slower. The predicted effect can be easily observed in the well
known schemes employed for studying of nonlinear magneto-optical rotation. The
upper bound of sample length is found from the criterion that the pulse
self-steepening and group-advance time are observable without pulse distortion
caused by the group-velocity dispersion.Comment: 16 pages, 7 figure
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