4,827 research outputs found
Objective measurement of therapeutic response in breast cancer using tumour markers.
In 65 patients with systemic breast cancer, a biochemical response index using three tumour markers in combination, carcinoembryonic antigen (CEA), carbohydrate antigen 15-3 (CA 15-3) and erythrocyte sedimentation rate (ESR), allowed objective biochemical assessment of response to endocrine therapy. Changes in these three markers at 2, 4 and 6 months showed a highly significant correlation with UICC assessed response at 6 months. At 4 months, changes in these three markers resulted in a selectivity of 93%, with a sensitivity of 92% and a specificity of 82%. Survival of groups of patients assessed biochemically or by UICC criteria for non-progression or progression showed no significant difference. The advantage of the biochemical assessment are that it is objective and reproducible. The assessment gives similar information to the UICC assessment but can be carried out earlier. Changes in the three markers appears to reflect the dynamics of change in tumour mass in response to systemic therapy in contrast to the UICC criteria which reflect structural change
Hydrodynamic capabilities of an SPH code incorporating an artificial conductivity term with a gravity-based signal velocity
This paper investigates the hydrodynamic performances of an SPH code
incorporating an artificial heat conductivity term in which the adopted signal
velocity is applicable when gravity is present. In accordance with previous
findings it is shown that the performances of SPH to describe the development
of Kelvin-Helmholtz instabilities depend strongly on the consistency of the
initial condition set-up and on the leading error in the momentum equation due
to incomplete kernel sampling. An error and stability analysis shows that the
quartic B-spline kernel (M_5) possesses very good stability properties and we
propose its use with a large neighbor number, between ~50 (2D) to ~ 100 (3D),
to improve convergence in simulation results without being affected by the
so-called clumping instability. SPH simulations of the blob test show that in
the regime of strong supersonic flows an appropriate limiting condition, which
depends on the Prandtl number, must be imposed on the artificial conductivity
SPH coefficients in order to avoid an unphysical amount of heat diffusion.
Results from hydrodynamic simulations that include self-gravity show profiles
of hydrodynamic variables that are in much better agreement with those produced
using mesh-based codes. In particular, the final levels of core entropies in
cosmological simulations of galaxy clusters are consistent with those found
using AMR codes. Finally, results of the Rayleigh-Taylor instability test
demonstrate that in the regime of very subsonic flows the code has still
several difficulties in the treatment of hydrodynamic instabilities. These
problems being intrinsically due to the way in which in standard SPH gradients
are calculated and not to the implementation of the artificial conductivity
term.Comment: 26 pages, 15 figures, accepted for publication in A&
Evaluation of the performance of a lateral flow device for quantitative detection of anti-SARS-CoV-2 IgG
Introduction: The AbC-19™ lateral flow immunoassay (LFIA) performance was evaluated on plasma samples from a SARS-CoV-2 vaccination cohort, WHO international standards for anti-SARS-CoV-2 IgG (human), individuals ≥2 weeks from infection of RT-PCR confirmed SARS-CoV-2 genetic variants, as well as microorganism serology. Methods: Pre-vaccination to three weeks post-booster samples were collected from a cohort of 111 patients (including clinically extremely vulnerable patients) from Northern Ireland. All patients received Oxford-AstraZeneca COVID-19 vaccination for the first and second dose, and Pfizer-BioNTech for the third (first booster). WHO international standards, 15 samples from 2 variants of concern (Delta and Omicron) and cross-reactivity with plasma samples from other microorganism infections were also assessed on AbC-19™. Results: All 80 (100%) participants sampled post-booster had high positive IgG responses, compared to 38/95 (40%) participants at 6 months post-first vaccination. WHO standard results correlated with information from corresponding biological data sheets, and antibodies to all genetic variants were detected by LFIA. No cross-reactivity was found with exception of one (of five) Dengue virus samples. Conclusion: These findings suggest BNT162b2 booster vaccination enhanced humoral immunity to SARS-CoV-2 from pre-booster levels, and that this antibody response was detectable by the LFIA. In combination with cross-reactivity, standards and genetic variant results would suggest LFIA may be a cost-effective measure to assess SARS-CoV-2 antibody status
Improving smoothed particle hydrodynamics with an integral approach to calculating gradients
In this paper we develop and test a fully conservative SPH scheme based on a
tensor formulation that can be applied to simulate astrophysical systems. In
the proposed scheme, derivatives are calculated from an integral expression
that leads to a tensor (instead of a vectorial) estimation of gradients and
reduces to the standard formulation in the continuum limit. The new formulation
improves the interpolation of physical magnitudes, leading to a set of
conservative equations that resembles those of standard SPH. The resulting
scheme is verified using a variety of well-known tests, all of them simulated
in two dimensions. We also discuss an application of the proposed tensor method
to astrophysics by simulating the stability of a Sun-like polytrope calculated
in three dimensions.Comment: 15 pages, 12 figures, accepted for publication in Astronomy and
Astrophysics; minor changes due to language editin
G313.3+00.3: A New Planetary Nebula discovered by the Australia Telescope Compact Array and the Spitzer Space Telescope
We present a new planetary nebula, first identified in images from the
Australia Telescope Compact Array, although not recognized at that time. Recent
observations with the Spitzer Space Telescope during the GLIMPSE Legacy program
have rediscovered the object. The high-resolution radio and infrared images
enable the identification of the central star or its wind, the recognition of
the radio emission as thermal, and the probable presence of polycylic aromatic
hydrocarbons in and around the source. These lead to the conclusion that
G313.3+00.3 is a planetary nebula. This object is of particular interest
because it was discovered solely through radio and mid-infrared imaging,
without any optical (or near-infrared) confirmation, and acts as a proof of
concept for the discovery of many more highly extinguished planetary nebulae.
G313.3+00.3 is well-resolved by both the instruments with which it was
identified, and suffers extreme reddening due to its location in the
Scutum-Crux spiral arm.Comment: 18 pages, LaTeX (aastex), incl. 8 PostScript (eps) figures and 1
table. Accepted by ApJ (Part 1
Hydrodynamic simulations with the Godunov SPH
We present results based on an implementation of the Godunov Smoothed
Particle Hydrodynamics (GSPH), originally developed by Inutsuka (2002), in the
GADGET-3 hydrodynamic code. We first review the derivation of the GSPH
discretization of the equations of moment and energy conservation, starting
from the convolution of these equations with the interpolating kernel. The two
most important aspects of the numerical implementation of these equations are
(a) the appearance of fluid velocity and pressure obtained from the solution of
the Riemann problem between each pair of particles, and (b the absence of an
artificial viscosity term. We carry out three different controlled
hydrodynamical three-dimensional tests, namely the Sod shock tube, the
development of Kelvin-Helmholtz instabilities in a shear flow test, and the
"blob" test describing the evolution of a cold cloud moving against a hot wind.
The results of our tests confirm and extend in a number of aspects those
recently obtained by Cha (2010): (i) GSPH provides a much improved description
of contact discontinuities, with respect to SPH, thus avoiding the appearance
of spurious pressure forces; (ii) GSPH is able to follow the development of
gas-dynamical instabilities, such as the Kevin--Helmholtz and the
Rayleigh-Taylor ones; (iii) as a result, GSPH describes the development of curl
structures in the shear-flow test and the dissolution of the cold cloud in the
"blob" test.
We also discuss in detail the effect on the performances of GSPH of changing
different aspects of its implementation. The results of our tests demonstrate
that GSPH is in fact a highly promising hydrodynamic scheme, also to be coupled
to an N-body solver, for astrophysical and cosmological applications.
[abridged]Comment: 19 pages, 13 figures, MNRAS accepted, high resolution version can be
obtained at
http://adlibitum.oats.inaf.it/borgani/html/papers/gsph_hydrosim.pd
Simulations of the grand design galaxy M51: a case study for analysing tidally induced spiral structure
We present hydrodynamical models of the grand design spiral M51 (NGC 5194),
and its interaction with its companion NGC 5195. Despite the simplicity of our
models, our simulations capture the present day spiral structure of M51
remarkably well, and even reproduce details such as a kink along one spiral
arm, and spiral arm bifurcations. We investigate the offset between the stellar
and gaseous spiral arms, and find at most times (including the present day)
there is no offset between the stars and gas to within our error bars. We also
compare our simulations with recent observational analysis of M51. We compute
the pattern speed versus radius, and like the observations, find no single
global pattern speed. We also show that the spiral arms cannot be fitted well
by logarithmic spirals. We interpret these findings as evidence that M51 does
not exhibit a quasi-steady density wave, as would be predicted by density wave
theory. The internal structure of M51 derives from the complicated and
dynamical interaction with its companion, resulting in spiral arms showing
considerable structure in the form of short-lived kinks and bifurcations.
Rather than trying to model such galaxies in terms of global spiral modes with
fixed pattern speeds, it is more realistic to start from a picture in which the
spiral arms, while not being simple material arms, are the result of tidally
induced kinematic density `waves' or density patterns, which wind up slowly
over time.Comment: 23 pages, 20 figures, accepted for publication in MNRA
Morning Increase in Onset of Ischemic Stroke
The Time of Onset of Ischemic Stroke Was Determined for 1,167 of 1,273 Patients during the Collection of Data by Four Academic Hospital Centers between June 30, 1983, and June 30, 1986. More Strokes Occurred in Awake Patients from 10:00 Am to Noon Than during Any Other 2-Hour Interval. the Incidence of Stroke Onset Declined Steadily during the Remainder of the Day and Early Evening. the Onset of Stroke is Least Likely to Occur in the Late Evening, Before Midnight. © 1989 American Heart Association, Inc
The ISM in spiral galaxies: can cooling in spiral shocks produce molecular clouds?
We investigate the thermodynamics of the ISM and the formation of molecular
hydrogen through numerical simulations of spiral galaxies. The model follows
the chemical, thermal and dynamical response of the disc to an external spiral
potential. Self-gravity and magnetic fields are not included. The calculations
demonstrate that gas can cool rapidly when subject to a spiral shock. Molecular
clouds in the spiral arms arise through a combination of compression of the ISM
by the spiral shock and orbit crowding. These results highlight that local
self-gravity is not required to form molecular clouds. Self-shielding provides
a sharp transition density, below which gas is essentially atomic, and above
which the molecular gas fraction is >0.001. The timescale for gas to move
between these regimes is very rapid (<~1 Myr). From this stage, the majority of
gas generally takes between 10 to 20 Myr to obtain high H fractions (>50
%). Although our calculations are unable to resolve turbulent motions on scales
smaller than the spiral arm and do not include self-gravity. True cloud
formation timescales are therefore expected to be even shorter.
The mass budget of the disc is dominated by cold gas residing in the spiral
arms. Between 50 and 75 % of this gas is in the atomic phase. When this gas
leaves the spiral arm and drops below the self-shielding limit it is heated by
the galactic radiation field. Consequently, most of the volume in the interarm
regions is filled with warm atomic gas. However, some cold spurs and clumps can
survive in interarm regions for periods comparable to the interarm passage
timescale. Altogether between 7 and 40% of the gas in our disc is molecular,
depending on the surface density of the calculation, with approximately 20%
molecular for a surface density comparable to the solar neighbourhood.Comment: 16 pages, 19 figures, accepted for publication in MNRA
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