2,317 research outputs found
Matching of analytical and numerical solutions for neutron stars of arbitrary rotation
We demonstrate the results of an attempt to match the two-soliton analytical
solution with the numerically produced solutions of the Einstein field
equations, that describe the spacetime exterior of rotating neutron stars, for
arbitrary rotation. The matching procedure is performed by equating the first
four multipole moments of the analytical solution to the multipole moments of
the numerical one. We then argue that in order to check the effectiveness of
the matching of the analytical with the numerical solution we should compare
the metric components, the radius of the innermost stable circular orbit
(), the rotation frequency and the
epicyclic frequencies . Finally we present some
results of the comparison.Comment: Contribution at the 13th Conference on Recent Developments in Gravity
(NEB XIII), corrected typo in of eq. 5 of the published versio
Faithful transformation of quasi-isotropic to Weyl-Papapetrou coordinates: A prerequisite to compare metrics
We demonstrate how one should transform correctly quasi-isotropic coordinates
to Weyl-Papapetrou coordinates in order to compare the metric around a rotating
star that has been constructed numerically in the former coordinates with an
axially symmetric stationary metric that is given through an analytical form in
the latter coordinates. Since a stationary metric associated with an isolated
object that is built numerically partly refers to a non-vacuum solution
(interior of the star) the transformation of its coordinates to Weyl-Papapetrou
coordinates, which are usually used to describe vacuum axisymmetric and
stationary solutions of Einstein equations, is not straightforward in the
non-vacuum region. If this point is \textit{not} taken into consideration, one
may end up to erroneous conclusions about how well a specific analytical metric
matches the metric around the star, due to fallacious coordinate
transformations.Comment: 18 pages, 2 figure
Extending Sibgatullin's ansatz for the Ernst potential to generate a richer family of axially symmetric solutions of Einstein's equations
The scope of this talk is to present some preliminary results on an effort,
currently in progress, to generate an exact solution of Einstein's equation,
suitable for describing spacetime around a rotating compact object.
Specifically, the form of the Ernst potential on the symmetry axis and its
connection with the multipole moments is discussed thoroughly. The way to
calculate the multipole moments of spacetime directly from the value of the
Ernst potential on the symmetry axis is presented. Finally, a mixed ansatz is
formed for the Ernst potential including parameters additional to the ones
dictated by Sibgatullin. Thus, we believe that this talk can also serve as a
comment on choosing the appropriate ansatz for the Ernst potential.Comment: Talk given in the 11th Conference on Recent Developments in Gravity,
2-5 June 2004, Lesbos, Greec
An ecohydrological journey of 4500 years reveals a stable but threatened precipitation–groundwater recharge relation around Jerusalem
Groundwater is a key water resource in semiarid and seasonally dry regions around the world, which is replenished
by intermittent precipitation events and mediated by vegetation, soil, and regolith properties. Here, a climate
reconstruction of 4500 years for the Jerusalem region was used to determine the relation between climate, vegetation,
and groundwater recharge. Despite changes in air temperature and vegetation characteristics, simulated recharge
remained linearly related to precipitation over the entire analyzed period, with drier decades having lower rates
of recharge for a given annual precipitation due to soil memory effects. We show that in recent decades, the lack of
changes in the precipitation–groundwater recharge relation results from the compensating responses of vegetation
to increasing CO2, i.e., increased leaf area and reduced stomatal conductance. This multicentury relation is
expected to be modified by climate change, with changes up to −20% in recharge for unchanged precipitation,
potentially jeopardizing water resource availability
Lack of evidence for MHC-unrestricted (atypical) recognition of mucin by mucinous pancreatic tumour-reactive T-cells
Cytotoxic T-cells generated against heterologous, mucinous pancreatic tumour cells were shown to recognize mucin in a major histocombatibility complex (MHC)-unrestricted fashion. In contrast, the present study demonstrates a typical allogeneic response of heterologous cytotoxic T-cells established against mucin-expressing pancreatic tumour cells. Heterologous cytotoxic T cells lysed targets that were used as stimulators and other targets that shared human leucocyte antigen (HLA) with the stimulator. These cytotoxic T-cells lysed mucin-expressing stimulator cells but not autologous tumour cells in spite of expressing mucin on their surface. Likewise, tumour-infiltrating CD4+T-cells proliferated against its own tumour cell target, while such T-cells did not respond to heterologous, mucin-expressing pancreatic tumour cells. Culturing heterologous tumour-specific cytotoxic T-cells with purified pancreatic tumour cell-mucin rendered them unresponsive to their target cells. Furthermore, purified mucin did not produce a mucin-specific response in mucinous pancreatic tumour patients' primary T-cells even in the presence of antigen-presenting cells. Our study finds no evidence for MHC-unrestricted recognition of mucin by pancreatic cancer patients' T-cells. © 2000 Cancer Research Campaig
SentiBench - a benchmark comparison of state-of-the-practice sentiment analysis methods
In the last few years thousands of scientific papers have investigated
sentiment analysis, several startups that measure opinions on real data have
emerged and a number of innovative products related to this theme have been
developed. There are multiple methods for measuring sentiments, including
lexical-based and supervised machine learning methods. Despite the vast
interest on the theme and wide popularity of some methods, it is unclear which
one is better for identifying the polarity (i.e., positive or negative) of a
message. Accordingly, there is a strong need to conduct a thorough
apple-to-apple comparison of sentiment analysis methods, \textit{as they are
used in practice}, across multiple datasets originated from different data
sources. Such a comparison is key for understanding the potential limitations,
advantages, and disadvantages of popular methods. This article aims at filling
this gap by presenting a benchmark comparison of twenty-four popular sentiment
analysis methods (which we call the state-of-the-practice methods). Our
evaluation is based on a benchmark of eighteen labeled datasets, covering
messages posted on social networks, movie and product reviews, as well as
opinions and comments in news articles. Our results highlight the extent to
which the prediction performance of these methods varies considerably across
datasets. Aiming at boosting the development of this research area, we open the
methods' codes and datasets used in this article, deploying them in a benchmark
system, which provides an open API for accessing and comparing sentence-level
sentiment analysis methods
The Pathophysiology of Inhalational Brucellosis in Balb/c Mice
To characterize the clinical presentation and pathophysiology of inhalational brucellosis, Balb/c mice were challenged with Brucella melitensis 16M in a nose-only aerosol exposure chamber. A low dose of 1000 cfu/animal of B. melitensis resulted in 45% of mice with tissue burdens eight weeks post-challenge. The natural history of brucellosis in mice challenged by higher aerosol doses was examined by serial euthanizing mice over an eight week period. Higher challenge doses of 1.00E+05 and 5.00E+05 cfu resulted in positive blood cultures 14 days post-challenge and bacterial burdens were observed in the lung, liver and/or spleens 14 days post-challenge. In addition, the progression of brucellosis was similar between mice challenged by the intranasal and aerosol routes. The results from this study support the use of the Balb/c aerosol nose-only brucellosis mouse model for the evaluation of therapeutics against inhalational brucellosis
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