3,761 research outputs found
Worsening of cerebral hyperemia by the administration of terlipressin in acute liver failure with severe hepatic encephalopathy
There is increasing evidence that terlipressin is useful in patients with cirrhosis and
hepatorenal syndrome, but there are no data of its use in patients with acute liver
failure (ALF) in whom hepatorenal syndrome is common. Although terlipressin
produces systemic vasoconstriction, it produces cerebral vasodilatation and may
increase cerebral blood flow (CBF). Increased CBF contributes to intracranial
hypertension in patients with ALF. The aim of this study was to evaluate the safety of
terlipressin in patients with ALF with respect to cerebral haemodynamics. Six
successive patients with ALF were electively ventilated for grade IV hepatic
encephalopathy. Patients were monitored invasively and CBF was measured (Kety-
Schmidt technique). Measurements were made before, at 1, 3 hour and 5 hours after
intravenous (single bolus) administration of terlipressin (0.005 mg/kg) )intravenously
(single bolus), median 0.25mg (range 0.2-0.3). There was no significant change in
heart rate, mean arterial pressure or cardiac output. CBF and jugular venous oxygen
saturation both increased significantly at 1 hour (p<0.0=0.016) respectively.
Intracranial pressure increased significantly at 21 hours (p<0=.0.031), returning back
to baseline values at 42 hours. This study shows that administration of terlipressin, at
a dose that did not alter systemic haemodynamicshemodynamics, resulted in
worsening of cerebral hyperemia and intracranial hypertension in patients with ALF
and severe hepatic encephalopathy. These data suggest the need to exercise extreme
caution in the use of terlipressin in these patients in view of its potentially deleterious
consequences on cerebral haemodynamics
The One Loop Effective Action of QED for a General Class of Electric Fields
We compute the effective action of QED at one loop order for an electric
field which points in the direction and depends arbitrarily upon the
light cone time coordinate, . This calculation
generalizes Schwinger's formula for the vacuum persistence probability in the
presence of a constant electric field.Comment: 9 pages, LaTeX 2 epsilo
ANALYSIS OF THE PRESSURE DISTRIBUTION PATTERN AND THE CONTROLLING BALANCE DURING KICK MOVEMENT OF TAI-CHI CHUAN
The purpose of this study was to compare the pressure distribution patterns of the stable kick and unstable kick from the kick movement of a Tai-Chi Chuan athlete. A national elite female Tai-Chi Chuan athlete was the subject for this study. The Tekscan HR Mat Pressure Measurement System was used to collect the vertical ground reaction force and the pressure history of the standing foot in right kicking movement and left kicking movement. All the data of the standing foot were divided into metatarsals, tarsals and phalanges to calculate the partial force and partial pressure. The pressure-time diagram of the phalanges, metatarsals and tarsals indicated that the pressure histories trended to be stable in each time as the lefl kick completed, and the phalanges produced 'snatchy' and larger pressures acting on the ground
Owl and Lizard: Patterns of Head Pose and Eye Pose in Driver Gaze Classification
Accurate, robust, inexpensive gaze tracking in the car can help keep a driver
safe by facilitating the more effective study of how to improve (1) vehicle
interfaces and (2) the design of future Advanced Driver Assistance Systems. In
this paper, we estimate head pose and eye pose from monocular video using
methods developed extensively in prior work and ask two new interesting
questions. First, how much better can we classify driver gaze using head and
eye pose versus just using head pose? Second, are there individual-specific
gaze strategies that strongly correlate with how much gaze classification
improves with the addition of eye pose information? We answer these questions
by evaluating data drawn from an on-road study of 40 drivers. The main insight
of the paper is conveyed through the analogy of an "owl" and "lizard" which
describes the degree to which the eyes and the head move when shifting gaze.
When the head moves a lot ("owl"), not much classification improvement is
attained by estimating eye pose on top of head pose. On the other hand, when
the head stays still and only the eyes move ("lizard"), classification accuracy
increases significantly from adding in eye pose. We characterize how that
accuracy varies between people, gaze strategies, and gaze regions.Comment: Accepted for Publication in IET Computer Vision. arXiv admin note:
text overlap with arXiv:1507.0476
Lyapunov and Wirtinger inequalities
AbstractIn this paper, we prove the Lyapunov inequality for the second-order linear differential equation (r(t)φ(y′(t)))′+p(t)φ(y(t))=0, where(i)φ(s) = |s|αt-2s, α > 1 is a fixed real number(ii)r(t) and p(t) are integrable on [a, b] with r(t) > 0 on [a, b].On the other hand, a generalized Wirtinger inequality is also given
The State of Self-Organized Criticality of the Sun During the Last 3 Solar Cycles. I. Observations
We analyze the occurrence frequency distributions of peak fluxes , total
fluxes , and durations of solar flares over the last three solar cycles
(during 1980--2010) from hard X-ray data of HXRBS/SMM, BATSE/CGRO, and RHESSI.
From the synthesized data we find powerlaw slopes with mean values of
for the peak flux, for the total
flux, and for flare durations. We find a systematic
anti-correlation of the powerlaw slope of peak fluxes as a function of the
solar cycle, varying with an approximate sinusoidal variation
, with a
mean of , a variation of , a solar cycle
period yrs, and a cycle minimum time . The
powerlaw slope is flattest during the maximum of a solar cycle, which indicates
a higher magnetic complexity of the solar corona that leads to an
overproportional rate of powerful flares.Comment: subm. to Solar Physic
Soluble `Supersymmetric' Quantum XY Model
We present a `supersymmetric' modification of the -dimensional quantum
rotor model whose ground state is exactly soluble. The model undergoes a
vortex-binding transition from insulator to metal as the rotor coupling is
varied. The Hamiltonian contains three-site terms which are relevant: they
change the universality class of the transition from that of the ()--- to
the -dimensional classical XY model. The metallic phase has algebraic ODLRO
but the superfluid density is identically zero. Variational wave functions for
single-particle and collective excitations are presented.Comment: 12 pages, REVTEX 3.0, IUCM93-00
Sputter grown Fe and Fe/Cr multilayers with fourfold magnetic anisotropy on GaAs
Thin films of Fe have been epitaxially sputtered on GaAs substrates with native oxide removal prior to the deposition carried out by an Ar ion milling. Films grown at substrate temperatures above 100 °C show well-defined fourfold anisotropies. The onset of epitaxial growth is accompanied by an increase in the surface roughness with growth occurring in a distinct island-like pattern. The Fe layers show significantly reduced moments, which decrease with increasing temperature. Antiferromagnetic coupling between Fe layers with Cr spacers was measured in a multilayer with a Cr thickness of 2.7 nm, around the second antiferromagnetic peak. The magnetic properties of the films are discussed in the context of multilayer storage applications
Nonlocal Yang-Mills
We present a very simple and explicit procedure for nonlocalizing the action
of any theory which can be formulated perturbatively. When the resulting
nonlocal field theory is quantized using the functional formalism --- with unit
measure factor --- its Green's functions are finite to all orders. The
construction also ensures perturbative unitarity to all orders for scalars with
nonderivative interactions, however, decoupling is lost at one loop when vector
and tensor quanta are present. Decoupling can be restored (again, to all
orders) if a suitable measure factor exists. We compute the required measure
factor for pure Yang-Mills at order and then use it to evaluate the
vacuum polarization at one loop. A peculiar feature of our regularization
scheme is that the on-shell tree amplitudes are completely unaffected. This
implies that the nonlocal field theory can be viewed as a highly noncanonical
quantization of the original, local field equations.Comment: 38 pages, figures available upon request. No macro neede
On the dynamics of Extrasolar Planetary Systems under dissipation. Migration of planets
We study the dynamics of planetary systems with two planets moving in the
same plane, when frictional forces act on the two planets, in addition to the
gravitational forces. The model of the general three-body problem is used.
Different laws of friction are considered. The topology of the phase space is
essential in understanding the evolution of the system. The topology is
determined by the families of stable and unstable periodic orbits, both
symmetric and non symmetric. It is along the stable families, or close to them,
that the planets migrate when dissipative forces act. At the critical points
where the stability along the family changes, there is a bifurcation of a new
family of stable periodic orbits and the migration process changes route and
follows the new stable family up to large eccentricities or to a chaotic
region. We consider both resonant and non resonant planetary systems. The 2/1,
3/1 and 3/2 resonances are studied. The migration to larger or smaller
eccentricities depends on the particular law of friction. Also, in some cases
the semimajor axes increase and in other cases they are stabilized. For
particular laws of friction and for special values of the parameters of the
frictional forces, it is possible to have partially stationary solutions, where
the eccentricities and the semimajor axes are fixed.Comment: Accepted in Celestial Mechanics and Dynamical Astronom
- …