9,197 research outputs found
Sputum Induction in Children Is Feasible and Useful in a Bustling General Hospital Practice
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The Jeroen Bosch Hospital funded this study.Peer reviewedPublisher PD
Relativistic Beaming and the Intrinsic Properties of Extragalactic Radio Jets
Relations between the observed quantities for a beamed radio jet, apparent
transverse speed and apparent luminosity (beta_app,L), and the intrinsic
quantities, Lorentz factor and intrinsic luminosity (gamma,L_o), are
investigated. The inversion from measured to intrinsic values is not unique,
but approximate limits to gamma and L_o can be found using probability
arguments. Roughly half the sources in a flux density--limited, beamed sample
have a value of gamma close to the measured beta_app. The methods are applied
to observations of 119 AGN jets made with the VLBA at 15 GHz during 1994-2002.
The results strongly support the common relativistic beam model for an
extragalactic radio jet. The (beta_app,L) data are closely bounded by a
theoretical envelope, an aspect curve for gamma=32, L_o= 10^25 W/Hz. This gives
limits to the maximum values of gamma and L_o in the sample: gamma_max about
32, and L_o,max ~ 10^26 W/Hz. No sources with both high beta_app and low L are
observed. This is not the result of selection effects due to the observing
limits, which are flux density S>0.5 Jy, and angular velocity mu<4 mas/yr. Many
of the fastest quasars have a pattern Lorentz factor gamma_p close to that of
the beam, gamma_b, but some of the slow quasars must have gamma_p<<gamma_b.
Three of the 10 galaxies in the sample have a superluminal feature, with speeds
up to beta_app about 6. The others are at most mildly relativistic. The
galaxies are not off-axis versions of the powerful quasars, but Cygnus A might
be an exception.Comment: 12 pages, 9 figures, 1 table, accepted for publication in the
Astrophysical Journa
Cantor type functions in non-integer bases
Cantor's ternary function is generalized to arbitrary base-change functions
in non-integer bases. Some of them share the curious properties of Cantor's
function, while others behave quite differently
Testing the Gaussian Copula Hypothesis for Financial Assets Dependences
Using one of the key property of copulas that they remain invariant under an
arbitrary monotonous change of variable, we investigate the null hypothesis
that the dependence between financial assets can be modeled by the Gaussian
copula. We find that most pairs of currencies and pairs of major stocks are
compatible with the Gaussian copula hypothesis, while this hypothesis can be
rejected for the dependence between pairs of commodities (metals).
Notwithstanding the apparent qualification of the Gaussian copula hypothesis
for most of the currencies and the stocks, a non-Gaussian copula, such as the
Student's copula, cannot be rejected if it has sufficiently many ``degrees of
freedom''. As a consequence, it may be very dangerous to embrace blindly the
Gaussian copula hypothesis, especially when the correlation coefficient between
the pair of asset is too high as the tail dependence neglected by the Gaussian
copula can be as large as 0.6, i.e., three out five extreme events which occur
in unison are missed.Comment: Latex document of 43 pages including 14 eps figure
Inheritance of physico-chemical properties and ROS generation by carbon quantum dots derived from pyrolytically carbonized bacterial sources
Bacteria are frequently used in industrial processes and nutrient supplementation to restore a healthy human microflora, but use of live bacteria is often troublesome. Here, we hypothesize that bacterially-derived carbon-quantum-dots obtained through pyrolytic carbonization inherit physico-chemical properties from probiotic and pathogenic source-bacteria. Carbon-quantum-dots carbonized at reaction-temperatures below 200 °C had negligible quantum-yields, while temperatures above 220 °C yielded poor water-suspendability. Fourier-transform infrared-spectroscopy demonstrated preservation of amide absorption bands in carbon-quantum-dots derived at intermediate temperatures. X-ray photoelectron-spectroscopy indicated that the at%N in carbon-quantum-dots increased with increasing amounts of protein in source-bacterial surfaces. Carbonization transformed hydrocarbon-like bacterial surface compounds into heterocyclic aromatic-carbon structures, evidenced by a broad infrared absorption band (920-900 cm−1) and the presence of carbon in C–C functionalities of carbon-quantum-dots. The chemical composition of bacterially-derived carbon-quantum-dots could be explained by the degradation temperatures of main bacterial cell surface compounds. All carbon-quantum-dots generated reactive-oxygen-species, most notably those derived from probiotic lactobacilli, carrying a high amount of surface protein. Concluding, amide functionalities in carbon-quantum-dots are inherited from surface proteins of source-bacteria, controlling reactive-oxygen-species generation. This paves the way for applications of bacterially-derived carbon-quantum-dots in which reactive-oxygen-species generation is essential, instead of hard-to-use live bacteria, such as in food supplementation or probiotic-assisted antibiotic therapy
Star Formation in Bright Rimmed Clouds. I. Millimeter and Submillimeter Molecular Line Surveys
We present the results of the first detailed millimeter and submillimeter
molecular line survey of bright rimmed clouds, observed at FCRAO in the CO
(J=1-0), C18O (J=1-0), HCO+ (J=1-0), H13CO+ (J=1-0), and N2H+ (J=1-0)
transitions, and at the HHT in the CO (J=2-1), HCO+ (J=3-2), HCO+ (J=4-3),
H13CO+ (J=3-2), and H13CO+ (J=4-3) molecular line transitions. The source list
is composed of a selection of bright rimmed clouds from the catalog of such
objects compiled by Sugitani et al. (1991). We also present observations of
three Bok globules done for comparison with the bright rimmed clouds. We find
that the appearance of the millimeter CO and HCO+ emission is dominated by the
morphology of the shock front in the bright rimmed clouds. The HCO+ (J=1-0)
emission tends to trace the swept up gas ridge and overdense regions which may
be triggered to collapse as a result of sequential star formation. Five of the
seven bright rimmed clouds we observe seem to have an outflow, however only one
shows the spectral line blue-asymmetric signature that is indicative of infall,
in the optically thick HCO+ emission. We also present evidence that in bright
rimmed clouds the nearby shock front may heat the core from outside-in thereby
washing out the normally observed line infall signatures seen in isolated star
forming regions. We find that the derived core masses of these bright rimmed
clouds are similar to other low and intermediate mass star forming regions.Comment: 67 pages, including 35 figures and 6 tables. Accepted for publication
in ApJ. Version with embedded full-resolution figures available at
http://www.astro.umass.edu/~devries/brc1
The thermal equation of state of FeTiO_3 ilmenite based on in situ X-ray diffraction at high pressures and temperatures
We present in situ measurements of the unit-cell volume of a natural terrestrial ilmenite (Jagersfontein mine, South Africa) and a synthetic reduced ilmenite (FeTiO_3) at simultaneous high pressure and high temperature up to 16 GPa and 1273 K. Unit-cell volumes were determined using energy-dispersive synchrotron X-ray diffraction in a multi-anvil press. Mössbauer analyses show that the synthetic sample contained insignificant amounts of Fe^(3+) both before and after the experiment. Results were fit to Birch-Murnaghan thermal equations of state, which reproduce the experimental data to within 0.5 and 0.7 GPa for the synthetic and natural samples, respectively. At ambient conditions, the unit-cell volume of the natural sample [V_0 = 314.75 ± 0.23 (1 ) Å^3] is significantly smaller than that of the synthetic sample [V_0 = 319.12 ± 0.26 Å^3]. The difference can be attributed to the presence of impurities and Fe^(3+) in the natural sample. The 1 bar isothermal bulk moduli K_(T0) for the reduced ilmenite is slightly larger than for the natural ilmenite (181 ± 7 and 165 ± 6 GPa, respectively), with pressure derivatives K_0' = 3 ± 1. Our results, combined with literature data, suggest that the unit-cell volume of reduced ilmenite is significantly larger than that of oxidized ilmenite, whereas their thermoelastic parameters are similar. Our data provide more appropriate input parameters for thermo-chemical models of lunar interior evolution, in which reduced ilmenite plays a critical role
Survey of Pasture Species and Management, Manure Management, Milk Production and Reproduction on Pasture-Based Dairy Farms in Florida and Georgia, USA
Traditionally, most dairy farms in the south-eastern United States confine cows to barns or on pasture lots year-round and feed stored forages and concentrated feeds (Fontaneli et al. 2005). Often, much of the feed is purchased, however, the cost of purchased feed and fuel has risen rapidly in the last 5 years (NASS 2009). In addition, a significant amount of capital is tied up in buildings, machinery and manure management systems on the farms. For these reasons, many dairy farmers have shown an interest in or started transitioning to pasture-based dairy systems (Ricks and Hardee 2012). The management practices and production results of pasture-based dairy farms in the south-east appear to vary widely (Macoon et al. 2011), but have not been described.
The objective of this study was to document pasture and crop management, manure management and milk production on pasture-based dairy farms in Florida and Georgia
Properties of Be and C deduced from the folding--potential model
The -- differential cross sections are analyzed in the
optical model using a double--folded potential. With the knowledge of this
potential bound and resonance--state properties of --cluster states in
Be and C as well as astrophysical S--factors of
He(,)Be and Be(,)C are
calculated. --widths and B(E2)--values are deduced.Comment: 2 pages LaTeX, 2 figures can be obtained from the author
The Presence and Distribution of HI Absorbing Gas in Sub-galactic Sized Radio Sources
We consider the incidence of HI absorption in intrinsically small
sub-galactic sized extragalactic sources selected from sources classified as
Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources. We
find that the smaller sources (<0.5 kpc) have larger HI column densities than
the larger sources (>0.5 kpc). Both a spherical and an axi-symmetric gas
distribution, with a radial power law density profile, can be used to explain
this anti-correlation between projected linear size and HI column density.
Since most detections occur in objects classified as galaxies, we argue that if
the unified schemes apply to GPS/CSSs a disk distribution for the HI is more
likely. The most favoured explanation for the compact sizes of the GPS/CSSs is
that they are young sources evolving in a power law density medium. For the
GPSs with measured expansion velocities, our derived densities are within an
order of magnitude of those estimated from ram-pressure confinement of the
lobes assuming equipartition. Our results therefore support the youth model.Comment: 12 pages, 8 figures, accepted for publication in A&
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