1,448 research outputs found
Brain edema : a valid endpoint for measuring hepatic encephalopathy?
Hepatic encephalopathy (HE) is a major complication of liver failure/disease which frequently develops during the progression of end-stage liver disease. This metabolic neuropsychiatric syndrome involves a spectrum of symptoms, including cognition impairment, attention deficits and motor dysfunction which eventually can progress to coma and death. Pathologically, HE is characterized by swelling of the astrocytes which consequently leads to brain edema, a common feature found in patients with acute liver failure (ALF) as well as in cirrhotic patients suffering from HE. The pathogenic factors involved in the onset of astrocyte swelling and brain edema in HE are unresolved. However, the role of astrocyte swelling/brain edema in the development of HE remains ambiguous and therefore measuring brain edema as an endpoint to evaluate HE is questioned. The following review will determine the effect of astrocyte swelling and brain edema on neurological function, discuss the various possible techniques to measure brain edema and lastly to propose a number of neurobehavioral tests to evaluate HE
Photoinjector-generation of a flat electron beam with transverse emittance ratio of 100
The generation of a flat electron beam directly from a photoinjector is an
attractive alternative to the electron damping ring as envisioned for linear
colliders. It also has potential applications to light sources such as the
generation of ultra-short x-ray pulses or Smith-Purcell free electron lasers.
In this Letter, we report on the experimental generation of a flat-beam with a
measured transverse emittance ratio of for a bunch charge of
nC; the smaller measured normalized root-mean-square emittance is
m and is limited by the resolution of our experimental setup.
The experimental data, obtained at the Fermilab/NICADD Photoinjector
Laboratory, are compared with numerical simulations and the expected scaling
laws.Comment: 5 pages, 3 figure
Treatment of calibration uncertainty in multi-baseline cross-correlation searches for gravitational waves
Uncertainty in the calibration of gravitational wave (GW) detector data leads to systematic errors, which must be accounted for in setting limits on the strength of GW signals. When cross-correlation measurements are made using data from a pair of instruments, as in searches for a stochastic GW background, the calibration uncertainties of the individual instruments can be combined into an uncertainty associated with the pair. With the advent of multi-baseline GW observation (e.g., networks consisting of multiple detectors such as the LIGO observatories and Virgo), a more sophisticated treatment is called for. We have described how the correlations between calibration factors associated with different pairs can be taken into account by marginalizing over the uncertainty associated with each instrument
Gravitational waves from Sco X-1: A comparison of search methods and prospects for detection with advanced detectors
The low-mass X-ray binary Scorpius X-1 (Sco X-1) is potentially the most
luminous source of continuous gravitational-wave radiation for interferometers
such as LIGO and Virgo. For low-mass X-ray binaries this radiation would be
sustained by active accretion of matter from its binary companion. With the
Advanced Detector Era fast approaching, work is underway to develop an array of
robust tools for maximizing the science and detection potential of Sco X-1. We
describe the plans and progress of a project designed to compare the numerous
independent search algorithms currently available. We employ a mock-data
challenge in which the search pipelines are tested for their relative
proficiencies in parameter estimation, computational efficiency, robust- ness,
and most importantly, search sensitivity. The mock-data challenge data contains
an ensemble of 50 Scorpius X-1 (Sco X-1) type signals, simulated within a
frequency band of 50-1500 Hz. Simulated detector noise was generated assuming
the expected best strain sensitivity of Advanced LIGO and Advanced VIRGO ( Hz). A distribution of signal amplitudes was then
chosen so as to allow a useful comparison of search methodologies. A factor of
2 in strain separates the quietest detected signal, at
strain, from the torque-balance limit at a spin frequency of 300 Hz, although
this limit could range from (25 Hz) to (750 Hz) depending on the unknown frequency of Sco X-1. With future
improvements to the search algorithms and using advanced detector data, our
expectations for probing below the theoretical torque-balance strain limit are
optimistic.Comment: 33 pages, 11 figure
Turbulent small-scale neutral and ion density fluctuations as measured during MAC/Epsilon
During the MAC/Epsilon campaign (Fall 1987, from Andoya, Northern Norway, 69 N, 16 E) a total of four altitude profiles of neutral gas number densities and six profiles of ion number densities were measured with high spatial resolution in the height range from 60 to 120 km. First results of these rocket-borne experiments are presented with emphasis on small scale turbulent density variations and related turbulent parameter as structure function constants and energy dissipation rates
Generation of angular-momentum-dominated electron beams from a photoinjector
Various projects under study require an angular-momentum-dominated electron
beam generated by a photoinjector. Some of the proposals directly use the
angular-momentum-dominated beams (e.g. electron cooling of heavy ions), while
others require the beam to be transformed into a flat beam (e.g. possible
electron injectors for light sources and linear colliders). In this paper, we
report our experimental study of an angular-momentum-dominated beam produced in
a photoinjector, addressing the dependencies of angular momentum on initial
conditions. We also briefly discuss the removal of angular momentum. The
results of the experiment, carried out at the Fermilab/NICADD Photoinjector
Laboratory, are found to be in good agreement with theoretical and numerical
models.Comment: 8 pages, 7 figures, submitted to Phys. Rev. ST Accel. Beam
Multi-messenger astronomy with a Southern-Hemisphere gravitational-wave observatory
Joint observations of gravitational waves and electromagnetic counterparts
will answer questions about cosmology, gamma-ray bursts, and the behaviour of
matter at supranuclear densities. The addition of a Southern-Hemisphere
gravitational-wave observatory to proposed global networks creates a longer
baseline, which is beneficial for sky localisation. We analyse how an
observatory in Australia can enhance the multi-messenger astronomy capabilities
of future networks. We estimate the number of binary neutron star mergers with
joint observations of gravitational waves and kilonova counterparts detectable
by the Vera C. Rubin Observatory. First, we consider a network of upgrades to
current observatories. Adding an Australian observatory to a three-observatory
network (comprising two observatories in the USA and one in Europe) boosts the
rate of joint observations from per year to
per year (a factor of two improvement). Then, we consider a
network of next-generation observatories. Adding a km Australian
observatory to a global network of a Cosmic Explorer km in the USA and an
Einstein Telescope in Europe only marginally increases the rate from
per year to per year (a factor of 1.1
improvement). The addition of an Australian observatory, however, ensures that
at least two observatories are online far more often. When the Cosmic Explorer
km is offline for a major upgrade, the Australian observatory increases
the joint observation rate from per year to
per year (a factor of 82 improvement). When the Einstein
Telescope is offline, the joint observation rate increases from
per year to per year (a factor of 113
improvement). We sketch out the broader science case for a Southern-Hemisphere
gravitational-wave observatory.Comment: v1, 13 pages, 7 figures. Submitted to PRD on August 24 202
A Bacteriophage-Acquired O-Antigen Polymerase (Wzy<sub>β</sub>) from <i>P. aeruginosa </i>Serotype O16 Performs a Varied Mechanism Compared to Its Cognate Wzy<sub>α</sub>
Pseudomonas aeruginosa is a Gram-negative bacterium that produces highly varied lipopolysaccharide (LPS) structures. The O antigen (O-Ag) in the LPS is synthesized through the Wzx/Wzy-dependent pathway where lipid-linked O-Ag repeats are polymerized by Wzy. Horizontal-gene transfer has been associated with O-Ag diversity. The O-Ag present on the surface of serotypes O5 and O16, differ in the intra-molecular bonds, α and β, respectively; the latter arose from the action of three genes in a seroconverting unit acquired from bacteriophage D3, including a β-polymerase (Wzyβ). To further our understanding of O-polymerases, the inner membrane (IM) topology of Wzyβ was determined using a dual phoA-lacZα reporter system wherein random 3’ gene truncations were localized to specific loci with respect to the IM by normalized reporter activities as determined through the ratio of alkaline phosphate activity to β-galactosidase activity. The topology of Wzyβ developed through this approach was shown to contain two predominant periplasmic loops, PL3 (containing an RX10G motif) and PL4 (having an O-Ag ligase superfamily motif), associated with inverting glycosyltransferase reaction. Through site-directed mutagenesis and complementation assays, residues Arg254, Arg270, Arg272 and His300 were found to be essential for Wzyβ function. Additionally, like-charge substitutions, R254K and R270K, could not complement the wzyβ knockout, highlighting the essential guanidium side group of Arg residues. The O-Ag ligase domain is conserved among heterologous Wzy proteins that produce β-linked O-Ag repeat units. Taking advantage of the recently obtained whole-genome sequence of serotype O16 a candidate promoter was identified. Wzyβ under its native promoter was integrated in the PAO1 genome, which resulted in simultaneous production of α- and β-linked O-Ag. These observations established that members of Wzy-like family consistently exhibit a dual-periplasmic loops topology, and identifies motifs that are plausible to be involved in enzymatic activities. Based on these results, the phage-derived Wzyβ utilizes a different reaction mechanism in the P. aeruginosa host to avoid self-inhibition during serotype conversion
Why igneous wollastonite is so rare in CAIs
Primary wollastonite (wo) thought to have crystallized
from a liquid is quite rare in CAIs, having been reported in only two igneous
inclusions, White Angel and KT-1 [1, 2]. Both of these CAIs exhibit
significant mass fractionations in multiple elements and KT-1 is a FUN
inclusion, so it is highly desirable to place as many constraints as possible on
their formation. Since phase diagrams previously developed for CAIs do not
involve wo [3], we use literature data on wo-saturated and wo-free phase
diagrams in the system CaO-MgO-Al_2O_3-SiO_2 (CMAS) to establish a basic
framework for describing crystallization of wo-bearing CAIs
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