362 research outputs found
Effects of Low-Level Artificial Light at Night on Kentucky Bluegrass and Introduced Herbivore
Increasing evidence suggests that artificial light at night (ALAN) can negatively impact organisms. However, most studies examine the impacts of ALAN on a single species or under high levels of artificial light that are infrequent or unrealistic in urban environments. We currently have little information on how low levels of artificial light emanating from urban skyglow affect plants and their interactions with herbivores. We examined how low levels of ALAN affect grass and insects, including growth rate, photosynthesis, and stomatal conductance in grass, and foraging behavior and survival in crickets. We compared growth and leaf-level gas exchange of Kentucky Bluegrass (Poa pratensis) under low-levels of ALAN (0.3 lux) and starlight conditions (night light at 0.001 lux). Furthermore, each light treatment was divided into treatments with and without house crickets (Acheta domesticus). Without crickets present, bluegrass grown under artificial light at night for three weeks grew taller than plants grown under natural night light levels. Once crickets were introduced at the end of week three, grass height decreased resulting in no measurable effects of light treatment. There were no measurable differences in grass physiology among treatments. Our results indicate that low levels of light resulting from skyglow affect plant growth initially. However, with herbivory, ALAN effects on grass may be inconsequential. Gaining an understanding of how ALAN affects plant-insect interactions is critical to predicting ecological and evolutionary consequences of anthropogenic disturbance
The âMirageâ Sensor in a Industrial Environment: Optical and Thermal Losses Determinations
Since the first âMirageâ experiment run in the laboratory of ESPCI in 1979 [1], this method has been used by many other laboratories for the determination of optical and thermal properties and for non destructive evaluation [2] [3] [4]
The Corley-Jacobson dispersion relation and trans-Planckian inflation
In this Letter we study the dependence of the spectrum of fluctuations in
inflationary cosmology on possible effects of trans-Planckian physics, using
the Corley/Jacobson dispersion relations as an example. We compare the methods
used in previous work [1] with the WKB approximation, give a new exact
analytical result, and study the dependence of the spectrum obtained using the
approximate method of Ref. [1] on the choice of the matching time between
different time intervals. We also comment on recent work subsequent to Ref. [1]
on the trans-Planckian problem for inflationary cosmology.Comment: 6 pages, Revtex
On Signatures of Short Distance Physics in the Cosmic Microwave Background
Following a self-contained review of the basics of the theory of cosmological
perturbations, we discuss why the conclusions reached in the recent paper by
Kaloper et al are too pessimistic estimates of the amplitude of possible
imprints of trans-Planckian (string) physics on the spectrum of cosmic
microwave anisotropies in an inflationary Universe. It is shown that the likely
origin of large trans-Planckian effects on late time cosmological fluctuations
comes from nonadiabatic evolution of the state of fluctuations while the
wavelength is smaller than the Planck (string) scale, resulting in an excited
state at the time that the wavelength crosses the Hubble radius during
inflation.Comment: 11 pages, 4 figure
Trans-Planckian Physics and the Spectrum of Fluctuations in a Bouncing Universe
In this paper, we calculate the spectrum of scalar field fluctuations in a
bouncing, asymptotically flat Universe, and investigate the dependence of the
result on changes in the physics on length scales shorter than the Planck
length which are introduced via modifications of the dispersion relation. In
this model, there are no ambiguities concerning the choice of the initial
vacuum state. We study an example in which the final spectrum of fluctuations
depends sensitively on the modifications of the dispersion relation without
needing to invoke complex frequencies. Changes in the amplitude and in the
spectral index are possible, in addition to modulations of the spectrum. This
strengthens the conclusions of previous work in which the spectrum of
cosmological perturbations in expanding inflationary cosmologies was studied,
and it was found that, for dispersion relations for which the evolution is not
adiabatic, the spectrum changes from the standard prediction of
scale-invariance.Comment: 10 pages, 6 figures, RevTeX4. Analytical determination of the
spectrum, corrected some typos, conclusions unchange
Monocyte-macrophage activation is associated with nonalcoholic fatty liver disease and liver fibrosis in HIV monoinfection independently of the gut microbiome and bacterial translocation
Background: Nonalcoholic fatty liver disease (NAFLD) is common among people
living with HIV. There are limited data available on the pathophysiology of NAFLD
and the development of fibrosis in this population.
Objectives: The aim of this study was to investigate the association of bacterial
translocation, adipose tissue dysfunction, monocyte activation and gut dysbiosis in
patients with HIV monoinfection and NAFLD.
Methods: Cases with biopsy-proven NAFLD and HIV monoinfection were age and sexmatched
to HIV-positive and HIV-negative controls. Markers of bacterial translocation
[lipopolysaccharide-binding protein (LBP), bacterialDNAand lipopolysaccharide (LPS)],
adipose tissue dysfunction (leptin, adiponectin) and monocyte activation (sCD14 and
sCD163) were measured by ELISA. Hepatic patterns of macrophage activation were
explored with immunohistochemistry. 16 s rRNA sequencing was performed with stool.
Results: Thirty-three cases were included (F2 fibrosis nŒ16), matched to HIV-positive
(nŒ29) and HIV-negative (nŒ17) controls. Cases with NAFLD were more obese (BMI
31.04.4 vs. 24.12.8 kg/m2, P<0.001) and had significantly increased levels of sCD14,
sCD163 and higher leptin to adiponectin ratio vs. HIV-positive controls. Cases with F2
verse
Interstellar abundances in the neutral and ionized gas of NGC604
We present FUSE spectra of the giant HII region NGC604 in the spiral galaxy
M33. Chemical abundances are derived from far-UV absorption lines and are
compared to those derived from optical emission lines. We derived the column
densities of HI, NI, OI, SiII, PII, ArI, and FeII, fitting the line profiles
with either a single component or several components. Our net results, assuming
a single component, show that N, O, Si, and Ar are apparently underabundant in
the neutral phase by a factor of 10 or more with respect to the ionized phase,
while Fe is the same. However, we discuss the possibility that the absorption
lines are made of individual unresolved components, and find that only PII,
ArI, and FeII lines should not be affected by the presence of hidden saturated
components, while NI, OI, and SiII might be much more affected. If N, O, and Si
are actually underabundant in the neutral gas of NGC604 with respect to the
ionized gas, this would confirm earlier results obtained for the blue compact
dwarfs. However, a deeper analysis focused on P, Ar, and Fe mitigates the above
conclusion and indicates that the neutral gas and ionized gas could have
similar abundances.Comment: Accepted for publication in A&
High star formation rates as the origin of turbulence in early and modern disk galaxies
High spatial and spectral resolution observations of star formation and
kinematics in early galaxies have shown that two-thirds are massive rotating
disk galaxies with the remainder being less massive non-rotating objects. The
line of sight averaged velocity dispersions are typically five times higher
than in today's disk galaxies. This has suggested that
gravitationally-unstable, gas-rich disks in the early Universe are fuelled by
cold, dense accreting gas flowing along cosmic filaments and penetrating hot
galactic gas halos. However these accreting flows have not been observed, and
cosmic accretion cannot power the observed level of turbulence. Here we report
on a new sample of rare high-velocity-dispersion disk galaxies we have
discovered in the nearby Universe where cold accretion is unlikely to drive
their high star-formation rates. We find that the velocity dispersion is most
fundamentally correlated with their star-formation rates, and not their mass
nor gas fraction, which leads to a new picture where star formation itself is
the energetic driver of galaxy disk turbulence at all cosmic epochs.Comment: 9 pages, 2 figures, Supplimentary Info available at:
http://pulsar.swin.edu.au/~agreen/nature/sigma_mean_arXiv.pdf. Accepted for
publication in Natur
Board examination for anatomical pathology in Switzerland: two intense days to verify professional competence
About 15years ago, the Swiss Society of Pathology has developed and implemented a board examination in anatomical pathology. We describe herein the contents covered by this 2-day exam (autopsy pathology, cytology, histopathology, molecular pathology, and basic knowledge about mechanisms of disease) and its exact modalities, sketch a brief history of the exam, and finish with a concise discussion about the possible objectives and putative benefits weighed against the hardship that it imposes on the candidate
Metal enrichment of the neutral gas of blue compact dwarf galaxies: the compelling case of Pox 36
We present the analysis of the interstellar spectrum of Pox 36 with the Far
Ultraviolet Spectroscopic Explorer (FUSE). Pox 36 was selected because of the
relatively low foreground gas content that makes it possible to detect
absorption-lines weak enough that unseen components should not be saturated.
Interstellar lines of HI, NI, OI, SiII, PII, ArI, and FeII are detected. Column
densities are derived directly from the observed line profiles except for HI,
whose lines are contaminated by stellar absorption. We used the TLUSTY models
to remove the stellar continuum and isolate the interstellar component. The
best fit indicates that the dominant stellar population is B0. The fit of the
interstellar HI line gives a column density of 10^{20.3\pm0.4} cm-2. Chemical
abundances were then computed from the column densities using the dominant
ionization stage in the neutral gas. Our abundances are compared to those
measured from emission-line spectra in the optical. Our results suggest that
the neutral gas of Pox 36 is metal-deficient by a factor ~7 as compared to the
ionized gas, and they agree with a metallicity of ~1/35 Z. Conclusions:
The abundance discontinuity between the neutral and ionized phases implies that
most of the metals released by consecutive star-formation episodes mixes with
the HI gas. The volume extent of the enrichment is so large that the
metallicity of the neutral gas increases only slightly. The star-forming
regions could be enriched only by a small fraction (~1%), but it would greatly
enhance its metallicity. Our results are compared to those of other BCDs. We
confirm the overall underabundance of metals in their neutral gas, with perhaps
only the lowest metallicity BCDs showing no discontinuity.Comment: Accepted for publication in A&
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