17,911 research outputs found
Prompt J/psi production from Tevatron to LHC
Models with essential non-perturbative QCD dynamics and describing Tevatron
data on high- charmonium are extrapolated to give predictions of
prompt J/psi production at the LHC. Differences of up to an order of magnitude
occurs. An important point is here the treatment of higher order perturbative
QCD effects.Comment: Presented at the VIII International Workshop on Hadron Physics
(Hadrons 2002), Bento Goncalves, Brazil, 14 - 19 April 200
Global mean sea surface computation based upon a combination of SEASAT and GEOS-3 satellite altimeter data
A mean sea surface map was computed for the global ocean areas between 70 deg N latitude and 62 deg S latitude based upon the 70 day SEASAT and 3.5 year GEOS-3 altimeter data sets. The mean sea surface is presented in the form of a global contour map and a 0.25 deg x 0.25 deg grid. A combination of regional adjustments based upon crossover techniques and the subsequent adjustment of the regional solutions into a global reference system was employed in order to minimize the effects of radial orbit error. A global map of the crossover residuals after the crossover adjustments are made is in good agreement with earlier mesoscale variability contour maps based upon the last month of SEASAT collinear data. This high level of agreement provides good evidence that relative orbit error was removed to the decimeter level on a regional basis. This represents a significant improvement over our previous maps which contained patterns, particularly in the central Pacific, which were due to radial orbit error. Long wavelength, basin scale errors are still present with a submeter amplitude due to errors in the PGS-S4 gravity model. Such errors can only be removed through the improvement of the Earth's gravity model and associated geodetic parameters
Northern Saw-whet Owl Autumn Migration in Eastern Nebraska: Results from a Three-year Banding Study
Prior to 2019, records of NSWOs in Nebraska during fall were limited. There were fewer than five accepted reports in eastern Nebraska since the 1950s (Silcock and Jorgensen, 2021). The Hitchcock banding station along the Missouri River bluffs in nearby western Iowa has captured, banded, and released 20-50 birds during autumn migration for a number of years (J. Toll, personal communication). Furthermore, a single season banding study in central Nebraska during fall 2004 captured 14 NSWOs (Kim 2005), suggesting the species may migrate annually over much of the state in fall, or at least in more years than previously thought. This is despite the relative lack of continuous forested habitat in the eastern and central part of the state and extensive areas of agricultural land cover. However, the absence of any systematic effort to detect this species over multiple years, especially away from the Missouri River, renders such conclusions speculative. To address information gaps, we conducted targeted NSWO banding efforts in the vicinity of Lincoln, Nebraska, for three consecutive years in 2019, 2020, and 2021. Our objectives were to determine 1) whether NSWOs migrate through this area regularly in fall, 2) the phenology of migration through our area, and 3) whether NSWO age classes vary by year. Our results should clarify and define the status of NSWOs’ fall movements in eastern Nebraska
Generalized Incremental Mechanisms for Scheduling Games
We study the problem of devising truthful mechanisms for cooperative cost sharing
games that realize (approximate) budget balance and social cost. Recent negative
results show that group-strategyproof mechanisms can only achieve very poor approximation
guarantees for several fundamental cost sharing games. Driven by these limitations,
we consider cost sharing mechanisms that realize the weaker notion of weak groupstrategyproofness.
Mehta et al. [Games and Economic Behavior, 67:125–155, 2009] recently
introduced the broad class of weakly group-strategyproof acyclic mechanisms and
show that several primal-dual approximation algorithms naturally give rise to such mechanisms
with attractive approximation guarantees. In this paper, we provide a simple yet
powerful approach that enables us to turn any r-approximation algorithm into a r-budget
balanced acyclic mechanism. We demonstrate the applicability of our approach by deriving
weakly group-strategyproof mechanisms for several fundamental scheduling problems
that outperform the best possible approximation guarantees of Moulin mechanisms.
The mechanisms that we develop for completion time scheduling problems are the first
mechanisms that achieve constant budget balance and social cost approximation factors.
Interestingly, our mechanisms belong to the class of generalized incremental mechanisms
proposed by Moulin [Social Choice and Welfare, 16:279–320, 1999]
Damped finite-time-singularity driven by noise
We consider the combined influence of linear damping and noise on a dynamical
finite-time-singularity model for a single degree of freedom. We find that the
noise effectively resolves the finite-time-singularity and replaces it by a
first-passage-time or absorbing state distribution with a peak at the
singularity and a long time tail. The damping introduces a characteristic
cross-over time. In the early time regime the probability distribution and
first-passage-time distribution show a power law behavior with scaling exponent
depending on the ratio of the non linear coupling strength to the noise
strength. In the late time regime the behavior is controlled by the damping.
The study might be of relevance in the context of hydrodynamics on a nanometer
scale, in material physics, and in biophysics.Comment: 9 pages, 4 eps-figures, revtex4 fil
High resolution Ge/Li/ spectrometer reduces rate-dependent distortions at high counting rates
Modified spectrometer system with a low-noise preamplifier reduces rate-dependent distortions at high counting rates, 25,000 counts per second. Pole-zero cancellation minimizes pulse undershoots due to multiple time constants, baseline restoration improves resolution and prevents spectral shifts
Encapsulation of phosphorus dopants in silicon for the fabrication of a quantum computer
The incorporation of phosphorus in silicon is studied by analyzing phosphorus
delta-doped layers using a combination of scanning tunneling microscopy,
secondary ion mass spectrometry and Hall effect measurements. The samples are
prepared by phosphine saturation dosing of a Si(100) surface at room
temperature, a critical annealing step to incorporate phosphorus atoms, and
subsequent epitaxial silicon overgrowth. We observe minimal dopant segregation
(5 nm), complete electrical activation at a silicon growth temperature of 250
degrees C and a high two-dimensional electron mobility of 100 cm2/Vs at a
temperature of 4.2 K. These results, along with preliminary studies aimed at
further minimizing dopant diffusion, bode well for the fabrication of
atomically precise dopant arrays in silicon such as those found in recent
solid-state quantum computer architectures.Comment: 3 pages, 4 figure
Motility of small nematodes in disordered wet granular media
The motility of the worm nematode \textit{Caenorhabditis elegans} is
investigated in shallow, wet granular media as a function of particle size
dispersity and area density (). Surprisingly, we find that the nematode's
propulsion speed is enhanced by the presence of particles in a fluid and is
nearly independent of area density. The undulation speed, often used to
differentiate locomotion gaits, is significantly affected by the bulk material
properties of wet mono- and polydisperse granular media for .
This difference is characterized by a change in the nematode's waveform from
swimming to crawling in dense polydisperse media \textit{only}. This change
highlights the organism's adaptability to subtle differences in local structure
and response between monodisperse and polydisperse media
Consequences of wall stiffness for a beta-soft potential
Modifications of the infinite square well E(5) and X(5) descriptions of
transitional nuclear structure are considered. The eigenproblem for a potential
with linear sloped walls is solved. The consequences of the introduction of
sloped walls and of a quadratic transition operator are investigated.Comment: RevTeX 4, 8 pages, as published in Phys. Rev.
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