36,260 research outputs found
Truth and Probability
Contains two other essays as well: Further Considerations & Last Papers: Probability and Partial Belief.
Do methanethiol adsorbates on the Au(111) surface dissociate?
The interaction of methanethiol molecules CHSH with the Au(111) surface
is investigated, and it is found for the first time that the S-H bond remains
intact when the methanethiol molecules are adsorbed on the regular Au(111)
surface. However, it breaks if defects are present in the Au(111) surface. At
low coverage, the fcc region is favored for S atom adsorption, but at saturated
coverage the adsorption energies at various sites are almost iso-energetic. The
presented calculations show that a methanethiol layer on the regular Au(111)
surface does not dimerize.Comment: 4 pages, 2 figures, 4 tables, submitted to Phys. Rev. Let
Changes in yield and composition of barley, wheat and triticale grains harvested during advancing stages of ripening
peer-reviewedThis study involved an evaluation of the changes in grain yield, nutritive value, ensilability
and harvesting losses of intensively managed winter cereals harvested during
the advancing stages of ripening. Five cereal crops (barley cv. Regina and wheat cv.
Madrigal in 2001; barley cv. Regina, wheat cv. Falstaff and triticale cv. Fidelio in 2002)
were assessed. Twenty plots per crop were arranged in a randomised complete block
design, with five times of harvest (four for barley in 2002) and four replicate blocks
per harvest. Dry matter (DM) yields changed relatively little between harvest dates,
but fresh yields declined (P < 0.001) over time due to the moisture loss associated with
ripening. Time-course changes in indices of nutritive value, such as concentrations of
crude protein, starch and ash, and organic matter digestibility, were relatively small
and did not follow a consistent pattern. Ensilability indices, such as DM and watersoluble
carbohydrate concentrations and buffering capacity, indicated that satisfactory
fermentations were likely if such crops were ensiled; buffering capacity, generally
declining with advancing maturity. Harvesting losses were not clearly related to growth
stage at harvest. It is concluded that winter cereal grain (barley, wheat and triticale)
DM yields and quality were relatively constant as ripening progressed from DM concentrations
of around 550 to >800 g/kg.One of the authors (P.S.) was in receipt
of a Teagasc Walsh Fellowship
Development and flight test of an experimental maneuver autopilot for a highly maneuverable aircraft
This report presents the development of an experimental flight test maneuver autopilot (FTMAP) for a highly maneuverable aircraft. The essence of this technique is the application of an autopilot to provide precise control during required flight test maneuvers. This newly developed flight test technique is being applied at the Dryden Flight Research Facility of NASA Ames Research Center. The FTMAP is designed to increase the quantity and quality of data obtained in test flight. The technique was developed and demonstrated on the highly maneuverable aircraft technology (HiMAT) vehicle. This report describes the HiMAT vehicle systems, maneuver requirements, FTMAP development process, and flight results
Electroweak gauge boson production at hadron colliders through O(alpha_s^2)
We describe a calculation of the O(alpha_s^2) QCD corrections to the fully
differential cross section for W and Z boson production in hadronic collisions.
The result is fully realistic in that it includes spin correlations, finite
width effects, gamma-Z interference and allows for the application of arbitrary
cuts on the leptonic decay products of the W and Z. We have implemented this
calculation into a numerical program. We demonstrate the use of this code by
presenting phenomenological results for several future LHC analyses and recent
Tevatron measurements, including the W cross section in the forward rapidity
region and the central over forward cross section ratio.Comment: 11 pages, 4 figure
Self-Interacting Dark Matter Halos and the Gravothermal Catastrophe
We study the evolution of an isolated, spherical halo of self-interacting
dark matter (SIDM) in the gravothermal fluid formalism. We show that the
thermal relaxation time, , of a SIDM halo with a central density and
velocity dispersion of a typical dwarf galaxy is significantly shorter than its
age. We find a self-similar solution for the evolution of a SIDM halo in the
limit where the mean free path between collisions, , is everywhere
longer than the gravitational scale height, . Typical halos formed in this
long mean free path regime relax to a quasistationary gravothermal density
profile characterized by a nearly homogeneous core and a power-law halo where
. We solve the more general time-dependent problem and
show that the contracting core evolves to sufficiently high density that
inevitably becomes smaller than in the innermost region. The core
undergoes secular collapse to a singular state (the ``gravothermal
catastrophe'') in a time , which is longer than the
Hubble time for a typical dark matter-dominated galaxy core at the present
epoch. Our model calculations are consistent with previous, more detailed,
N-body simulations for SIDM, providing a simple physical interpretation of
their results and extending them to higher spatial resolution and longer
evolution times. At late times, mass loss from the contracting, dense inner
core to the ambient halo is significantly moderated, so that the final mass of
the inner core may be appreciable when it becomes relativistic and radially
unstable to dynamical collapse to a black hole.Comment: ApJ in press (to appear in April), 12 pages. Extremely minor changes
to agree with published versio
Propulsion system-flight control integration and optimization: Flight evaluation and technology transition
Integration of propulsion and flight control systems and their optimization offers significant performance improvements. Research programs were conducted which have developed new propulsion and flight control integration concepts, implemented designs on high-performance airplanes, demonstrated these designs in flight, and measured the performance improvements. These programs, first on the YF-12 airplane, and later on the F-15, demonstrated increased thrust, reduced fuel consumption, increased engine life, and improved airplane performance; with improvements in the 5 to 10 percent range achieved with integration and with no changes to hardware. The design, software and hardware developments, and testing requirements were shown to be practical
Transient dynamics of a superconducting nonlinear oscillator
We investigate the transient dynamics of a lumped-element oscillator based on
a dc superconducting quantum interference device (SQUID). The SQUID is shunted
with a capacitor forming a nonlinear oscillator with resonance frequency in the
range of several GHz. The resonance frequency is varied by tuning the Josephson
inductance of the SQUID with on-chip flux lines. We report measurements of
decaying oscillations in the time domain following a brief excitation with a
microwave pulse. The nonlinearity of the SQUID oscillator is probed by
observing the ringdown response for different excitation amplitudes while the
SQUID potential is varied by adjusting the flux bias. Simulations are performed
on a model circuit by numerically solving the corresponding Langevin equations
incorporating the SQUID potential at the experimental temperature and using
parameters obtained from separate measurements characterizing the SQUID
oscillator. Simulations are in good agreement with the experimental
observations of the ringdowns as a function of applied magnetic flux and pulse
amplitude. We observe a crossover between the occurrence of ringdowns close to
resonance and adiabatic following at larger detuning from the resonance. We
also discuss the occurrence of phase jumps at large amplitude drive. Finally,
we briefly outline prospects for a readout scheme for superconducting flux
qubits based on the discrimination between ringdown signals for different
levels of magnetic flux coupled to the SQUID.Comment: 15 pages, 9 figure
Weighted Supermembrane Toy Model
A weighted Hilbert space approach to the study of zero-energy states of
supersymmetric matrix models is introduced. Applied to a related but
technically simpler model, it is shown that the spectrum of the corresponding
weighted Hamiltonian simplifies to become purely discrete for sufficient
weights. This follows from a bound for the number of negative eigenvalues of an
associated matrix-valued Schr\"odinger operator.Comment: 18 pages, 2 figures; to appear in Lett. Math. Phys
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