195 research outputs found
Dose-Response Relationships Following Oral Administration of DuP 753 to Normal Humans
We assessed the inhibitory effect of DuP 753, an orally active angiotensin II receptor antagonist, on the pressor action of exogenous angiotensin I and II in healthy volunteers. In a single dose study, doses of 2.5, 5, 10, 20, and 40 mg of DuP 753 or placebo were tested serially at one week intervals. In the multiple dose study, the administration of placebo or DuP 753 (5, 10, 20, or 40 mg, per os once daily) for eight consecutive days was evaluated. The blood pressure response to angiotensin I and II was inhibited in a dose-dependent fashion with a blocking effect still present 24 h post drug. DuP 753 also induced a dose-dependent compensatory rise in plasma renin. This new compound was well tolerated by these normal volunteers. Thus, DuP 753 appears to be a well tolerated, orally active, potent and long-lasting antagonist of angiotensin II in humans. Am J Hypertens 1991;4:350S-354
PyCOOL - a Cosmological Object-Oriented Lattice code written in Python
There are a number of different phenomena in the early universe that have to
be studied numerically with lattice simulations. This paper presents a graphics
processing unit (GPU) accelerated Python program called PyCOOL that solves the
evolution of scalar fields in a lattice with very precise symplectic
integrators. The program has been written with the intention to hit a sweet
spot of speed, accuracy and user friendliness. This has been achieved by using
the Python language with the PyCUDA interface to make a program that is easy to
adapt to different scalar field models. In this paper we derive the symplectic
dynamics that govern the evolution of the system and then present the
implementation of the program in Python and PyCUDA. The functionality of the
program is tested in a chaotic inflation preheating model, a single field
oscillon case and in a supersymmetric curvaton model which leads to Q-ball
production. We have also compared the performance of a consumer graphics card
to a professional Tesla compute card in these simulations. We find that the
program is not only accurate but also very fast. To further increase the
usefulness of the program we have equipped it with numerous post-processing
functions that provide useful information about the cosmological model. These
include various spectra and statistics of the fields. The program can be
additionally used to calculate the generated curvature perturbation. The
program is publicly available under GNU General Public License at
https://github.com/jtksai/PyCOOL . Some additional information can be found
from http://www.physics.utu.fi/tiedostot/theory/particlecosmology/pycool/ .Comment: 23 pages, 12 figures; some typos correcte
Geometric K-Homology of Flat D-Branes
We use the Baum-Douglas construction of K-homology to explicitly describe
various aspects of D-branes in Type II superstring theory in the absence of
background supergravity form fields. We rigorously derive various stability
criteria for states of D-branes and show how standard bound state constructions
are naturally realized directly in terms of topological K-cycles. We formulate
the mechanism of flux stabilization in terms of the K-homology of non-trivial
fibre bundles. Along the way we derive a number of new mathematical results in
topological K-homology of independent interest.Comment: 45 pages; v2: References added; v3: Some substantial revision and
corrections, main results unchanged but presentation improved, references
added; to be published in Communications in Mathematical Physic
The Missing Link in the Pathophysiology of Vascular Cognitive Impairment: Design of the Heart-Brain Study
Background: Hemodynamic balance in the heart-brain axis is increasingly recognized as a crucial factor in maintaining functional and structural integrity of the brain and thereby cognitive functioning. Patients with heart failure (HF), carotid occlusive disease (COD), and vascular cognitive impairment (VCI) present themselves with complaints attributed to specific parts of the heart-brain axis, but hemodynamic changes often go beyond the part of the axis for which they primarily seek medical advice. The Heart-Brain Study hypothesizes that t
Data challenges of time domain astronomy
Astronomy has been at the forefront of the development of the techniques and
methodologies of data intensive science for over a decade with large sky
surveys and distributed efforts such as the Virtual Observatory. However, it
faces a new data deluge with the next generation of synoptic sky surveys which
are opening up the time domain for discovery and exploration. This brings both
new scientific opportunities and fresh challenges, in terms of data rates from
robotic telescopes and exponential complexity in linked data, but also for data
mining algorithms used in classification and decision making. In this paper, we
describe how an informatics-based approach-part of the so-called "fourth
paradigm" of scientific discovery-is emerging to deal with these. We review our
experiences with the Palomar-Quest and Catalina Real-Time Transient Sky
Surveys; in particular, addressing the issue of the heterogeneity of data
associated with transient astronomical events (and other sensor networks) and
how to manage and analyze it.Comment: 15 pages, 3 figures, to appear in special issue of Distributed and
Parallel Databases on Data Intensive eScienc
Fitting the integrated Spectral Energy Distributions of Galaxies
Fitting the spectral energy distributions (SEDs) of galaxies is an almost
universally used technique that has matured significantly in the last decade.
Model predictions and fitting procedures have improved significantly over this
time, attempting to keep up with the vastly increased volume and quality of
available data. We review here the field of SED fitting, describing the
modelling of ultraviolet to infrared galaxy SEDs, the creation of
multiwavelength data sets, and the methods used to fit model SEDs to observed
galaxy data sets. We touch upon the achievements and challenges in the major
ingredients of SED fitting, with a special emphasis on describing the interplay
between the quality of the available data, the quality of the available models,
and the best fitting technique to use in order to obtain a realistic
measurement as well as realistic uncertainties. We conclude that SED fitting
can be used effectively to derive a range of physical properties of galaxies,
such as redshift, stellar masses, star formation rates, dust masses, and
metallicities, with care taken not to over-interpret the available data. Yet
there still exist many issues such as estimating the age of the oldest stars in
a galaxy, finer details ofdust properties and dust-star geometry, and the
influences of poorly understood, luminous stellar types and phases. The
challenge for the coming years will be to improve both the models and the
observational data sets to resolve these uncertainties. The present review will
be made available on an interactive, moderated web page (sedfitting.org), where
the community can access and change the text. The intention is to expand the
text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics &
Space Scienc
Characteristics and Evolution of sill-driven off-axis hydrothermalism in Guaymas Basin – the Ringvent site
The Guaymas Basin spreading center, at 2000 m depth in the Gulf of California, is overlain by a thick sedimentary cover. Across the basin, localized temperature anomalies, with active methane venting and seep fauna exist in response to magma emplacement into sediments. These sites evolve over thousands of years as magma freezes into doleritic sills and the system cools. Although several cool sites resembling cold seeps have been characterized, the hydrothermally active stage of an off-axis site was lacking good examples. Here, we present a multidisciplinary characterization of Ringvent, an ~1 km wide circular mound where hydrothermal activity persists ~28 km northwest of the spreading center. Ringvent provides a new type of intermediate-stage hydrothermal system where off-axis hydrothermal activity has attenuated since its formation, but remains evident in thermal anomalies, hydrothermal biota coexisting with seep fauna, and porewater biogeochemical signatures indicative of hydrothermal circulation. Due to their broad potential distribution, small size and limited life span, such sites are hard to find and characterize, but they provide critical missing links to understand the complex evolution of hydrothermal systems
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