37,426 research outputs found
Computer program calculates the effective temperature for a crystalline solid /DETS/
Computer program computes and prints out both the Debye and resulting effective temperatures for each Debye model-dependent average energy per vibrational mode, Debye-Waller factor, and specific heat. The program calculates by the trapezodial rule and then Simpsons rule
What role does the right side of the heart play in circulation?
Right ventricular failure (RVF) is an underestimated problem in intensive care. This review explores the physiology and pathophysiology of right ventricular function and the pulmonary circulation. When RVF is secondary to an acute increase in afterload, the picture is one of acute cor pulmonale, as occurs in the context of acute respiratory distress syndrome, pulmonary embolism and sepsis. RVF can also be caused by right myocardial dysfunction. Pulmonary arterial catheterization and echocardiography are discussed in terms of their roles in diagnosis and treatment. Treatments include options to reduce right ventricular afterload, specific pulmonary vasodilators and inotropes
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Macroeconomic Shocks, Job Security and Health: Evidence from the Mining Industry
How do exogenous changes in the macroeconomic environment affect workers’ perceived job security, and consequently, their mental and physical health? To answer this question, we exploit variation in world commodity prices over the period 2001-17 and analyse panel data that includes detailed classifications of mining workers. We find that commodity price increases cause increases in perceived job security, which in turn, significantly and substantively improve the mental health of workers. In contrast, we find no effects on physical health. Our results imply that the estimated welfare costs of recessions are much larger when the effects of job insecurity, and not only unemployment, are considered
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Multiple environmental controls explain global patterns in soil animal communities
Soil animals play important roles in ecosystem functioning and stability, but the environmental controls on their communities are not fully understood. In this study, we compiled a dataset of soil animal communities for which the abundance and body mass of multiple soil animal groups were recorded. The mass–abundance scaling relationships were then used to investigate multiple environmental controls on soil animal community composition. The data reveal latitudinal shifts from high abundances of small soil animals at high latitudes to greater relative abundances of large soil animals at low latitudes. A hierarchical linear mixed effects model was applied to reveal the environmental variables shaping these latitudinal trends. The final hierarchical model identified mean annual temperature, soil pH and soil organic carbon content as key environmental controls explaining global mass–abundance scaling relationships in soil animal communities (R2c = 0.828, Ngroup = 117). Such relationships between soil biota with climate and edaphic conditions have been previously identified for soil microbial, but not soil animal, communities at a global scale. More comprehensive global soil community datasets are needed to better understand the generality of these relationships over a broader range of global ecosystems and soil animal groups
Origin of the transient unpulsed radio emission from the PSR B1259-63 binary system
We discuss the interpretation of transient, unpulsed radio emission detected
from the unique pulsar/Be-star binary system PSR B1259-63. Extensive monitoring
of the 1994 and 1997 periastron passages has shown that the source flares over
a 100-day interval around periastron, varying on time-scales as short as a day
and peaking at 60 mJy (~100 times the apastron flux density) at 1.4 GHz.
Interpreting the emission as synchrotron radiation, we show that (i) the
observed variations in flux density are too large to be caused by the shock
interaction between the pulsar wind and an isotropic, radiatively driven,
Be-star wind, and (ii) the radio emitting electrons do not originate from the
pulsar wind. We argue instead that the radio electrons originate from the
circumstellar disk of the Be star and are accelerated at two epochs, one before
and one after periastron, when the pulsar passes through the disk. A simple
model incorporating two epochs of impulsive acceleration followed by
synchrotron cooling reproduces the essential features of the radio light curve
and spectrum and is consistent with the system geometry inferred from pulsed
radio data.Comment: To be published in Astrophysical Journal Letters 7 pages, 1
postscript figur
On the detectability of extragalactic fast radio transients
Recent discoveries of highly dispersed millisecond radio bursts by Thornton
et al. in a survey with the Parkes radio telescope at 1.4 GHz point towards an
emerging population of sources at cosmological distances whose origin is
currently unclear. Here we demonstrate that the scattering effects at lower
radio frequencies are less than previously thought, and that the bursts could
be detectable at redshifts out to about in surveys below 1 GHz. Using a
source model in which the bursts are standard candles with bolometric
luminosities ergs/s uniformly distributed per unit
comoving volume, we derive an expression for the observed peak flux density as
a function of redshift and use this, together with the rate estimates found by
Thornton et al. to find an empirical relationship between event rate and
redshift probed by a given survey. The non-detection of any such events in
Arecibo 1.4 GHz survey data by Deneva et al., and the Allen Telescope Array
survey by Simeon et al. is consistent with our model. Ongoing surveys in the
1--2 GHz band should result in further discoveries. At lower frequencies,
assuming a typical radio spectral index , the predicted peak flux
densities are 10s of Jy. As a result, surveys of such a population with current
facilities would not necessarily be sensitivity limited and could be carried
out with small arrays to maximize the sky coverage. We predict that sources may
already be present in 350-MHz surveys with the Green Bank Telescope. Surveys at
150 MHz with 30 deg fields of view could detect one source per hour above
30 Jy.Comment: 5 pages, 2 figures, Accepted for publication in MNRAS on 2013 July
25. Received 2013 July 24; in original form 2013 May 3
XMM-Newton observations of PSr B1259-63 near the 2004 periastron passage
PSR B1259-63 is in a highly eccentric 3.4 year orbit with a Be star and
crosses the Be star disc twice per orbit, just prior to and just after
periastron. Unpulsed radio, X-ray and gamma-ray emission observed from the
binary system is thought to be due to the collision of pulsar wind with the
wind of Be star. We present here the results of new XMM-Newton observations of
the PSR B1259-63 system during the beginning of 2004 as the pulsar approached
the disc of Be star.We combine these results with earlier unpublished X-ray
data from BeppoSAX and XMM-Newton as well as with ASCA data. The detailed X-ray
lightcurve of the system shows that the pulsar passes (twice per orbit) through
a well-defined gaussian-profile disk with the half-opening angle (projected on
the pulsar orbit plane) ~18.5 deg. The intersection of the disk middle plane
with the pulsar orbital plane is inclined at ~70 deg to the major axis of the
pulsar orbit. Comparing the X-ray lightcurve to the TeV lightcurve of the
system we find that the increase of the TeV flux some 10--100 days after the
periastron passage is unambiguously related to the disk passage. At the moment
of entrance to the disk the X-ray photon index hardens from 1.8 up to 1.2
before returning to the steeper value 1.5. Such behaviour is not easily
accounted for by the model in which the X-ray emission is synchrotron emission
from the shocked pulsar wind. We argue that the observed hardening of the X-ray
spectrum is due to the inverse Compton or bremsstrahlung emission from 10-100
MeV electrons responsible for the radio synchrotron emission.Comment: 9 pages, accepted to MNRA
The clustering of radio galaxies at z~0.55 from the 2SLAQ LRG survey
We examine the clustering properties of low-power radio galaxies at redshift
0.4<z<0.8, using data from the 2SLAQ Luminous Red Galaxy (LRG) survey. We find
that radio-detected LRGs (with optical luminosities of 3-5L* and 1.4GHz radio
powers between 1e24 and 1e26 W/Hz) are significantly more clustered than a
matched sample of radio-quiet LRGs with the same distribution in optical
luminosity and colour. The measured scale length of the 2pt auto-correlation
function, r0, is 12.3+/-1.2 1/h Mpc and 9.02+/-0.52 1/h Mpc for the
radio-detected and radio-quiet samples respectively. Using the halo model
framework we demonstrate that the radio-loud LRGs have typical halo masses of
10.1+/-1.4 x10^13 1/h M_sun compared to 6.44+/-0.32 x10^13 1/h M_sun for the
radio-quiet sample. A model in which the radio-detected LRGs are almost all
central galaxies within haloes provides the best fit, and we estimate that at
least 30% of LRGs with the same clustering amplitude as the radio-detected LRGs
are currently radio-loud. Our results imply that radio-loud LRGs typically
occupy more massive haloes than other LRGs of the same optical luminosity, so
the probability of finding a radio-loud AGN in a massive galaxy at z~0.55 is
influenced by the halo mass in addition to the dependence on optical
luminosity. If we model the radio-loud fraction of LRGs, F_rad, as a function
of halo mass M, then the data are well-fitted by a power law of the form F_rad
\propto M^(0.65+/-0.23). The relationship between radio emission and clustering
strength could arise either through a higher fuelling rate of gas onto the
central black holes of galaxies in the most massive haloes (producing more
powerful radio jets) or through the presence of a denser IGM (providing a more
efficient working surface for the jets, thus boosting their radio luminosity).Comment: Accepted for publication in MNRA
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