6,756 research outputs found
Moving NRQCD for B Form Factors at High Recoil
We derive the continuum and lattice tree-level moving NRQCD (mNRQCD) through
order 1/m^2. mNRQCD is a generalization of NRQCD for dealing with hadrons with
nonzero velocity u_mu. The quark's total momentum is written as P^mu=Mu^mu+k^mu
where k^mu << Mu^mu is discretized and Mu^mu is treated exactly. Radiative
corrections to couplings on the lattice are discussed. mNRQCD is particularly
useful for calculating B->pi and B->D form factors since errors are similar at
low and high recoil.Comment: 3 pages, 1 figure, Lattice2002(heavyquark
Force and energy dissipation variations in non-contact atomic force spectroscopy on composite carbon nanotube systems
UHV dynamic force and energy dissipation spectroscopy in non-contact atomic
force microscopy were used to probe specific interactions with composite
systems formed by encapsulating inorganic compounds inside single-walled carbon
nanotubes. It is found that forces due to nano-scale van der Waals interaction
can be made to decrease by combining an Ag core and a carbon nanotube shell in
the Ag@SWNT system. This specific behaviour was attributed to a significantly
different effective dielectric function compared to the individual
constituents, evaluated using a simple core-shell optical model. Energy
dissipation measurements showed that by filling dissipation increases,
explained here by softening of C-C bonds resulting in a more deformable
nanotube cage. Thus, filled and unfilled nanotubes can be discriminated based
on force and dissipation measurements. These findings have two different
implications for potential applications: tuning the effective optical
properties and tuning the interaction force for molecular absorption by
appropriately choosing the filling with respect to the nanotube.Comment: 22 pages, 6 figure
Development of a composite model derived from cardiopulmonary exercise tests to predict mortality risk in patients with mild-to-moderate heart failure
Objective: Cardiopulmonary exercise testing (CPET) is used to predict outcome in patients with mild-to-moderate heart failure (HF). Single CPET-derived variables are often used, but we wanted to see if a composite score achieved better predictive power. Methods: Retrospective analysis of patient records at the Department of Cardiology, Castle Hill Hospital, Kingston-upon-Hull. 387 patients [median (25th-75th percentile)] [age 65 (56-72) years; 79% males; LVEF 34 (31-37) %] were included. Patients underwent a symptomlimited, maximal CPET on a treadmill. During a median follow up of 8.6 ± 2.1 years in survivors, 107 patients died. Survival models were built and validated using a hybrid approach between the bootstrap and Cox regression. Nine CPET-derived variables were included. Z-score defined each variable's predictive strength. Model coefficients were converted to a risk score. Results: Four CPET-related variables were independent predictors of all-cause mortality in the survival model: the presence of exertional oscillatory ventilation (EOV), increasing slope of the relation between ventilation and carbon dioxide production (VE/VCO2 slope), decreasing oxygen uptake efficiency slope (OUES), and an increase in the lowest ventilatory equivalent for carbon dioxide (VEqCO2 nadir). Individual predictors of mortality ranged from 0.60 to 0.71 using Harrell’s C-statistic, but the optimal combination of EOV + VE/VCO2 slope + OUES + VEqCO2 nadir reached 0.75. The Hull CPET risk score had a significantly higher area under the curve (0.78) when compared to the Heart Failure Survival Score (AUC=0.70;
Comparing Wilson and Clover Quenched Spectroscopy with an Improved Gauge Action
We present results of quenched hadron spectroscopy comparing
\order(a) improved Wilson (Clover) fermions with conventional Wilson
fermions. The configurations were generated using an \order(a^2) improved
6-link pure gauge action at 's corresponding to lattice spacings
of , , , , and fm. We find evidence that
fermionic scaling violations are consistent with \order(a^2) for Clover and
\order(a) with a nonnegligible \order(a^2) term for standard Wilson
fermions. This latter mixed ansatz makes a reliable continuum extrapolation
problematic for Wilson fermions. We also find that the slope of the scaling
violations is roughly for both Wilson and Clover fermions.Comment: 3 pages latex with 2 postscript figures. Talk presented at
LATTICE96(spectrum
Stringent Phenomenological Investigation into Heterotic String Optical Unification
For the weakly coupled heterotic string (WCHS) there is a well-known factor
of twenty conflict between the minimum string coupling unification scale,
Lambda_H ~5x10^(17) GeV, and the projected MSSM unification scale, Lambda_U ~
2.5x10^(16) GeV, assuming an intermediate scale desert (ISD). Renormalization
effects of intermediate scale MSSM-charged exotics (ISME) (endemic to
quasi-realistic string models) can resolve this issue, pushing the MSSM scale
up to the string scale. However, for a generic string model, this implies that
the projected Lambda_U unification under ISD is accidental. If the true
unification scale is 5.0x10^(17) GeV, is it possible that illusionary
unification at 2.5x10^(17) GeV in the ISD scenario is not accidental? If it is
not, then under what conditions would the assumption of ISME in a WCHS model
imply apparent unification at Lambda_U when ISD is falsely assumed? Geidt's
"optical unification" suggests that Lambda_U is not accidental, by offering a
mechanism whereby a generic MSSM scale Lambda_U < Lambda_H is guaranteed. A
WCHS model was constructed that offers the possibility of optical unification,
depending on the availability of anomaly-cancelling flat directions meeting
certain requirements. This paper reports on the systematic investigation of the
optical unification properties of the set of stringent flat directions of this
model. Stringent flat directions can be guaranteed to be F-flat to all finite
order (or to at least a given finite order consistent with electroweak scale
supersymmetry breaking) and can be viewed as the likely roots of more general
flat directions. Analysis of the phenomenology of stringent flat directions
gives an indication of the remaining optical unification phenomenology that
must be garnered by flat directions developed from them.Comment: standard latex, 18 pages of tex
Quenched hadron spectroscopy using improved fermionic and gauge actions
We present results of quenched hadron spectroscopy using \order(a)
improved Wilson fermions. The configurations were generated using an
\order(a^2) improved 6-link pure gauge action at 's
corresponding to lattice spacings of , , , , and
fm. We find evidence that fermionic scaling violations are consistent with
\order(a^2) errors.Comment: 4 pages latex with 3 postscript figures. Corrected column heading in
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