1,818 research outputs found
Asymmetry of jets, lobe size and spectral index in radio galaxies and quasars
We investigate the correlations between spectral index, jet side and extent
of the radio lobes for a sample of nearby FRII radio galaxies. In
Dennett-Thorpe et al. (1997) we studied a sample of quasars and found that the
high surface brightness regions had flatter spectra on the jet side (explicable
as a result of Doppler beaming) whilst the extended regions had spectral
asymmetries dependent on lobe length. Unified schemes predict that asymmetries
due to beaming will be much smaller in narrow-line radio galaxies than in
quasars: we therefore investigate in a similar manner, a sample of radio
galaxies with detected jets. We find that spectral asymmetries in these objects
are uncorrelated with jet sidedness at all brightness levels, but depend on
relative lobe volume. Our results are not in conflict with unified schemes, but
suggest that the differences between the two samples are due primarily to power
or redshift, rather than to orientation. We also show directly that hotspot
spectra steepen as a function of radio power or redshift. Whilst a shift in
observed frequency due to the redshift may account for some of the steepening,
it cannot account for all of it, and a dependence on radio power is required.Comment: accepted for publication in MNRAS, 10 pages; typos/minor correctio
Aerosol chemical composition in Asian continental outflow during the TRACE-P campaign: Comparison with PEM-West B
Aerosol associated soluble ions and the radionuclide tracers 7Be and 210Pb were quantified in 414 filter samples collected in spring 2001 from the DC-8 during the Transport and Chemical Evolution over the Pacific (TRACE-P) campaign. Binning the data into near Asia (flights from Hong Kong and Japan) and remote Pacific (all other flights) revealed large enhancements of NO3â, SO4=, C2O4=, NH4+, K+, Mg2+, and Ca2+ near Asia. The boundary layer and lower troposphere were most strongly influenced by continental outflow, and the largest enhancements were seen in Ca2+ (a dust tracer) and NO3â (reflecting uptake of HNO3 onto the dust). Comparing the TRACE P near Asia bin with earlier results from the same region during PEM-West B (in 1994) shows at least twofold enhancements during TRACE P in most of the ions listed above. Calcium and NO3â were most enhanced in this comparison as well (more than sevenfold higher in the boundary layer and threefold higher in the lower troposphere). Independent estimation of Asian emissions of gaseous precursors of the aerosol-associated ions suggest only small changes between the two missions, and precipitation fields do not suggest any significant difference in the efficiency of the primary sink, precipitation scavenging. It thus appears that with the possible exception of dust, the enhancements of aerosol-associated species during TRACE P cannot be explained by stronger sources or weaker sinks. We argue that the enhancements largely reflect the fact that TRACE P focused on characterizing Asian outflow, and thus the DC-8 was more frequently flown into regions that were influenced by well-organized flow off the continent
Influence of rice straw and calcium cyanamide on microbiological activity in two portuguese alluvial soils
Usaram-se dois aluviossolos portugueses (um arenoso outro franco) em experiĂȘncias destinadas a estudar a influĂȘncia da cianamida cĂĄlcica na actividade microbiolĂłgica, sob condiçÔes controladas. Ensaiaram-se modalidades com palha de arroz, palha de trigo e sem palha. Em algumas experiĂȘncias utilizou-se para comparação um solo de loess colhido na Alemanha. A aplicação de palha conduziu a um aumento nĂtido da activi- dade da dehidrogenase nos dois solos, tendo-se verificado a superioridade da palha de trigo no solo arenoso. A influĂȘncia da cianamida foi pequenainfo:eu-repo/semantics/publishedVersio
Counts and Sizes of Galaxies in the Hubble Deep Field - South: Implications for the Next Generation Space Telescope
Science objectives for the Next Generation Space Telescope (NGST) include a
large component of galaxy surveys, both imaging and spectroscopy. The Hubble
Deep Field datasets include the deepest observations ever made in the
ultraviolet, optical and near infrared, reaching depths comparable to that
expected for NGST spectroscopy. We present the source counts, galaxy sizes and
isophotal filling factors of the HDF-South images. The observed integrated
galaxy counts reach >500 galaxies per square arcminute at AB<30. We extend
these counts to faint levels in the infrared using models. The trend previously
seen that fainter galaxies are smaller, continues to AB=29 in the high
resolution HDF-S STIS image, where galaxies have a typical half-light radius of
0.1 arcseconds. Extensive Monte Carlo simulations show that the small measured
sizes are not due to selection effects until >29mag. Using the HDF-S NICMOS
image, we show that galaxies are smaller in the near infrared than they are in
the optical. We analyze the isophotal filling factor of the HDF-S STIS image,
and show that this image is mostly empty sky even at the limits of galaxy
detection, a conclusion we expect to hold true for NGST spectroscopy. At the
surface brightness limits expected for NGST imaging, however, about a quarter
of the sky is occupied by the outer isophotes of AB<30 galaxies. We discuss the
implications of these data on several design concepts of the NGST near-infrared
spectrograph. We compare the effects of resolution and the confusion limit of
various designs, as well as the multiplexing advantages of either multi-object
or full-field spectroscopy. We argue that the optimal choice for NGST
spectroscopy of high redshift galaxies is a multi-object spectrograph (MOS)
with target selection by a micro electro mechanical system (MEMS) device.Comment: 27 pages including 10 figures, accepted for publication in the
Astronomical Journal, June 2000, abridged abstrac
Interactions of a Light Hypersonic Jet with a Non-Uniform Interstellar Medium
We present three dimensional simulations of the interaction of a light
hypersonic jet with an inhomogeneous thermal and turbulently supported disk in
an elliptical galaxy. We model the jet as a light, supersonic non-relativistic
flow with parameters selected to be consistent with a relativistic jet with
kinetic power just above the FR1/FR2 break.
We identify four generic phases in the evolution of such a jet with the
inhomogeneous interstellar medium: 1) an initial ``flood and channel'' phase,
where progress is characterized by high pressure gas finding changing weak
points in the ISM, flowing through channels that form and re-form over time, 2)
a spherical, energy-driven bubble phase, were the bubble is larger than the
disk scale, but the jet remains fully disrupted close to the nucleus, 3) a
rapid, jet break--out phase the where jet breaks free of the last dense clouds,
becomes collimated and pierces the spherical bubble, and 4) a classical phase,
the jet propagates in a momentum-dominated fashion leading to the classical jet
+ cocoon + bow-shock structure.
Mass transport in the simulations is investigated, and we propose a model for
the morphology and component proper motions in the well-studied Compact
Symmetric Object 4C31.04.Comment: 66 pages, 22 figures, PDFLaTeX, aastex macros, graphicx and amssymb
packages, Accepted, to be published 2007 ApJ
Combinatorial functions of two chimeric antibodies directed to human CD4 and one directed to the a-chain of the human interleukin-2 receptor
The general feasibility of chimerization of monoclonal antibodies (mAbs) has already been shown for a large number of
them. In order to evaluate in vitro parameters relevant to immunosuppressive therapy, we have chimerized and synthesized
two anti-CD4 mAbs recognizing two different epitopes on the human T-lymphocyte antigen, CD4. The chimerized mAbs
are produced at levels corresponding to those of the original hybridoma cell lines. With respect to activation of human
complement, the individual Abs are negative; however, when used in combination, complement activation was performed.
When applied in combination, they were found to modulate the CD4 antigen, whereas the individual mAb do not display
this property. Individually they mediate an up to 60% inhibition of the mixed lymphocyte reaction (MLR). However, by
combination of an anti-CD4 mAb with one directed against the a-chain of the human IL2 receptor, nearly 100% inhibition
of the MLR was achieved, even with reduced dosage of the mAbs. Our data suggest that the combination of an anti-CD4
mAb and an anti-IL2Rcc chain mAb is more effective with respect to immunosuppression than each mAb by itself, indicating
that this mAb cocktail could be a new strategy for immunosuppressive therapy
Ethnic disparities in quality of diabetes care in Scotland:a national cohort study
Aims: The aim of this study is to compare quality of diabetes care in people with type 2 diabetes by ethnicity, in Scotland. Methods: Using a linked national diabetes registry, we included 162,122 people newly diagnosed with type 2 diabetes between 2009 and 2018. We compared receipt of nine guideline indicated processes of care in the first-year post-diabetes diagnosis using logistic regression, comparing eight ethnicity groups to the White group. We compared annual receipt of HbA1c and eye screening during the entire follow-up using generalised linear mixed effects. All analyses adjusted for confounders. Results: Receipt of diabetes care was lower in other ethnic groups compared to White people in the first-year post-diagnosis. Differences were most pronounced for people in the: African, Caribbean or Black; Indian; and other ethnicity groups for almost all processes of care. For example, compared to White people, odds of HbA1c monitoring were: 44% lower in African, Caribbean or Black people (OR 0.56 [95% CI 0.48, 0.66]); 47% lower in Indian people (OR 0.53 [95% CI 0.47, 0.61]); and 50% lower in people in the other ethnicity group (OR 0.50 [95% CI 0.46, 0.58]). Odds of receipt of eye screening were 30%â40% lower in most ethnic groups compared to the White group. During median 5 year follow-up, differences in HbA1c monitoring and eye screening largely persisted, but attenuated slightly for the former. Conclusions: There are marked ethnic disparities in routine diabetes care in Scotland in the short- and medium-term following diabetes diagnosis. Further investigation is needed to establish and effectively address the underlying reasons.</p
Expansion of pinched hypersurfaces of the Euclidean and hyperbolic space by high powers of curvature
We prove convergence results for expanding curvature flows in the Euclidean
and hyperbolic space. The flow speeds have the form , where and
is a positive, strictly monotone and 1-homogeneous curvature function. In
particular this class includes the mean curvature . We prove that a
certain initial pinching condition is preserved and the properly rescaled
hypersurfaces converge smoothly to the unit sphere. We show that an example due
to Andrews-McCoy-Zheng can be used to construct strictly convex initial
hypersurfaces, for which the inverse mean curvature flow to the power
loses convexity, justifying the necessity to impose a certain pinching
condition on the initial hypersurface.Comment: 18 pages. We included an example for the loss of convexity and
pinching. In the third version we dropped the concavity assumption on F.
Comments are welcom
The Sagnac effect in Coupled-Resonator Slow-Light Waveguide Structures
We study the effect of rotation on the propagation of electromagnetic waves
in slow-light waveguide structures consisting of coupled micro-ring resonators.
We show that such configurations exhibit new a type of the Sagnac effect which
can be used for the realization of highly-compact integrated rotation sensors
and gyroscopes
A General Formulation of the Source Confusion Statistics and Application to Infrared Galaxy Surveys
Source confusion has been a long-standing problem in the astronomical
history. In the previous formulation, sources are assumed to be distributed
homogeneously on the sky. This fundamental assumption is not realistic in many
applications. In this work, by making use of the point field theory, we derive
general analytic formulae for the confusion problems with arbitrary
distribution and correlation functions. As a typical example, we apply these
new formulae to the source confusion of infrared galaxies. We first calculate
the confusion statistics for power-law galaxy number counts as a test case.
When the slope of differential number counts, \gamma, is steep, the confusion
limits becomes much brighter and the probability distribution function (PDF) of
the fluctuation field is strongly distorted. Then we estimate the PDF and
confusion limits based on the realistic number count model for infrared
galaxies. The gradual flattening of the slope of the source counts makes the
clustering effect rather mild. Clustering effects result in an increase of the
limiting flux density with \sim 10%. In this case, the peak probability of the
PDF decreases up to \sim 15% and its tail becomes heavier.Comment: ApJ in press, 21 pages, 9 figures, using aastex.cls, emulateapj5.sty.
Abstract abridge
- âŠ