4,502 research outputs found
PDF and scale uncertainties of various DY distributions in ADD and RS models at hadron colliders
In the extra dimension models of ADD and RS we study the dependence of the
various parton distribution functions on observable of Drell-Yan process to NLO
in QCD at LHC and Tevatron energies. Uncertainties at LHC due to factorisation
scales in going from leading to next-to-leading order in QCD for the various
distributions get reduced by about 2.75 times for a range . Further uncertainties arising from the error on experimental
data are estimated using the MRST parton distribution functions.Comment: 27 pages, 11 figures, the version to appear in European Physical
Journal
A minimax approach for the joint design of acoustic crosstalk cancellation filters
Journal ArticleAbstract-This paper presents a method for jointly designing immersive audio rendering filters for a single listener using loudspeakers. The filters for crosstalk cancellation are assumed to have finite impulse responses and are designed using the minimax criterion. In addition to the traditional Atal-Schroeder crosstalk canceler structure, this paper explores an alternate topology that requires the approximation of a single filter. In general, the minimax approach provides improved low-frequency performance leading to a better overall separation of the direct-path and cross-path transfer functions than least-squares designs. The performance of the single-filter structure is better than that of the traditional crosstalk cancellation structure
Analytic calculation of energies and wave functions of the quartic and pure quartic oscillators
Ground state energies and wave functions of quartic and pure quartic
oscillators are calculated by first casting the Schr\"{o}dinger equation into a
nonlinear Riccati form and then solving that nonlinear equation analytically in
the first iteration of the quasilinearization method (QLM). In the QLM the
nonlinear differential equation is solved by approximating the nonlinear terms
by a sequence of linear expressions. The QLM is iterative but not perturbative
and gives stable solutions to nonlinear problems without depending on the
existence of a smallness parameter. Our explicit analytic results are then
compared with exact numerical and also with WKB solutions and it is found that
our ground state wave functions, using a range of small to large coupling
constants, yield a precision of between 0.1 and 1 percent and are more accurate
than WKB solutions by two to three orders of magnitude. In addition, our QLM
wave functions are devoid of unphysical turning point singularities and thus
allow one to make analytical estimates of how variation of the oscillator
parameters affects physical systems that can be described by the quartic and
pure quartic oscillators.Comment: 8 pages, 12 figures, 1 tabl
DCO, DCN and ND reveal three different deuteration regimes in the disk around the Herbig Ae star HD163296
The formation pathways of deuterated species trace different regions of
protoplanetary disks and may shed light into their physical structure. We aim
to constrain the radial extent of main deuterated species; we are particularly
interested in spatially characterizing the high and low temperature pathways
for enhancing deuteration of these species. We observed the disk surrounding
the Herbig Ae star HD 163296 using ALMA in Band 6 and obtained resolved
spectral imaging data of DCO (=3-2), DCN (=3-2) and ND
(=3-2). We model the radial emission profiles of DCO, DCN and
ND, assuming their emission is optically thin, using a parametric model
of their abundances and radial excitation temperature estimates. DCO can be
described by a three-region model, with constant-abundance rings centered at 70
AU, 150 AU and 260 AU. The DCN radial profile peaks at about ~60 AU and
ND is seen in a ring at ~160 AU. Simple models of both molecules using
constant abundances reproduce the data. Assuming reasonable average excitation
temperatures for the whole disk, their disk-averaged column densities (and
deuterium fractionation ratios) are 1.6-2.6 cm
(0.04-0.07), 2.9-5.2 cm (0.02) and 1.6-2.5 cm (0.34-0.45) for DCO, DCN and ND, respectively.
Our simple best-fit models show a correlation between the radial location of
the first two rings in DCO and the DCN and ND abundance
distributions that can be interpreted as the high and low temperature
deuteration pathways regimes. The origin of the third DCO ring at 260 AU is
unknown but may be due to a local decrease of ultraviolet opacity allowing the
photodesorption of CO or due to thermal desorption of CO as a consequence of
radial drift and settlement of dust grains
Coherent States for the Non-Linear Harmonic Oscillator
Wave packets for the Quantum Non-Linear Oscillator are considered in the
Generalized Coherent State framerwork. To first order in the non-linearity
parameter the Coherent State behaves very similarly to its classical
counterpart. The position expectation value oscillates in a simple harmonic
manner. The energy-momentum uncertainty relation is time independent as in a
harmonic oscillator. Various features, (such as the Squeezed State nature), of
the Coherent State have been discussed
Late life depression with cognitive impairment: Evaluation and treatment
Older adults with depression often present with signs and symptoms indicative of functional or cognitive impairment. These somatic symptoms make evaluating and treating depression in older adults more complex. Late life depression (LLD), depression in adults over the age of 65, is more frequently associated with cognitive changes. Cognitive impairment in LLD may be a result of the depressive disorder or an underlying dementing condition. Memory complaints are also common in older adults with depression. There is a wide range of cognitive impairment in LLD including decreased central processing speed, executive dysfunction, and impaired short-term memory. The etiology of cognitive impairment in LLD may include cerebrovascular disease, a significant risk factor for LLD, which likely interrupts key pathways between frontal white matter and subcortical structures important in mood regulation. Because depressive symptoms often coexist with dementia, it is important to determine the temporal relationship between depressive symptoms and cognitive change. If depressive symptoms pre-date the cognitive impairment and cognitive symptoms are mild and temporary, LLD is the likely etiology of the cognitive impairment. If cognitive changes appear prior to depressive symptoms and persist after LLD is successfully treated, an underlying dementia is more likely. Clinicians should be exclude common conditions such as thyroid disease which can contribute to depressive symptoms and cognitive impairment prior to treating LLD. Both antidepressants and psychotherapy can be effective in treating LLD. Subsequent evaluations following treatment should also reassess cognition
Being More Realistic about the Public Health Impact of Genomic Medicine
Wayne Hall and colleagues discuss the limitations of genomic risk prediction for population-level preventive health care
- …