3,806 research outputs found
Do You Ever Miss Me, Dearest?
https://digitalcommons.library.umaine.edu/mmb-vp/3948/thumbnail.jp
Bromethalin toxicosis--evaluation of aminophylline treatment and an epidemiolgic assessment
The compound bromethalin is described and characterized in terms of mode of action when used as a rodenticide. It is hypothesized that an antimetabolite which inhibits the conversion of bromethalin to its desmethylbromethalin metabolite could represent a potential treatment for bromethalin toxicosis. An ideal antimetabolite of bromethalin is described, and based on these considerations, aminophylline (theophylline ethylenediamine) was chosen as a potential antimetabolite. In lab trials, aminophylline was administered to rats given a lethal dose of bromethalin, but it was not effective in prolonging rat survival. However, it did result in mean survival time being increase to nearly double. Further studies aminophylline or similar drugs may results in identifying a suitable treatment for bromethalin-induced toxic syndrome
Gravity-induced vacuum dominance
It has been widely believed that, except in very extreme situations, the
influence of gravity on quantum fields should amount to just small,
sub-dominant contributions. This view seemed to be endorsed by the seminal
results obtained over the last decades in the context of renormalization of
quantum fields in curved spacetimes. Here, however, we argue that this belief
is false by showing that there exist well-behaved spacetime evolutions where
the vacuum energy density of free quantum fields is forced, by the very same
background spacetime, to become dominant over any classical energy-density
component. This semiclassical gravity effect finds its roots in the infrared
behavior of fields on curved spacetimes. By estimating the time scale for the
vacuum energy density to become dominant, and therefore for backreaction on the
background spacetime to become important, we argue that this vacuum dominance
may bear unexpected astrophysical and cosmological implications.Comment: To appear in Phys. Rev. Lett
A high-density relativistic reflection origin for the soft and hard X-ray excess emission from Mrk 1044
We present the first results from a detailed spectral-timing analysis of a
long (130 ks) XMM-Newton observation and quasi-simultaneous NuSTAR and
Swift observations of the highly-accreting narrow-line Seyfert 1 galaxy Mrk
1044. The broadband (0.350 keV) spectrum reveals the presence of a strong
soft X-ray excess emission below 1.5 keV, iron K emission
complex at 67 keV and a `Compton hump' at 1530 keV. We find
that the relativistic reflection from a high-density accretion disc with a
broken power-law emissivity profile can simultaneously explain the soft X-ray
excess, highly ionized broad iron line and the Compton hump. At low frequencies
( Hz), the power-law continuum dominated 1.55 keV band
lags behind the reflection dominated 0.31 keV band, which is explained with
a combination of propagation fluctuation and Comptonization processes, while at
higher frequencies ( Hz), we detect a soft lag which is
interpreted as a signature of X-ray reverberation from the accretion disc. The
fractional root-mean-squared (rms) variability of the source decreases with
energy and is well described by two variable components: a less variable
relativistic disc reflection and a more variable direct coronal emission. Our
combined spectral-timing analyses suggest that the observed broadband X-ray
variability of Mrk~1044 is mainly driven by variations in the location or
geometry of the optically thin, hot corona.Comment: 23 pages, 19 figures, 4 tables, Published in MNRA
Awaking the vacuum in relativistic stars
Void of any inherent structure in classical physics, the vacuum has revealed
to be incredibly crowded with all sorts of processes in relativistic quantum
physics. Yet, its direct effects are usually so subtle that its structure
remains almost as evasive as in classical physics. Here, in contrast, we report
on the discovery of a novel effect according to which the vacuum is compelled
to play an unexpected central role in an astrophysical context. We show that
the formation of relativistic stars may lead the vacuum energy density of a
quantum field to an exponential growth. The vacuum-driven evolution which would
then follow may lead to unexpected implications for astrophysics, while the
observation of stable neutron-star configurations may teach us much on the
field content of our Universe.Comment: To appear in Phys. Rev. Let
Creating functional autogenous vascular access in older patients
ObjectiveArteriovenous fistulas (AVFs) are the preferred choice for hemodialysis vascular access (AV access); however, there is debate over the utility of AVFs in older patients, particularly concerning access maturation and functionality. We reviewed our AV access experience in patients ≥65 years of age.MethodsWe analyzed consecutive AV access patients ≥65 years old with access operations between March 2003 and December 2009. All patients had ultrasound vessel mapping. In addition to overall outcomes review, the data for patients ≥65 years old were stratified into three 10-year increments by age for further analysis. We compared functional patency data for our older patients with those of our non-elderly patients aged 21 to 64 years treated during the same time period.ResultsFour hundred sixty-one consecutive AV access patients new to our practice were included in this study. Ages were 65 to 94 years (mean, 73 years). Two hundred thirty-six (51.2%) were female, 276 (59.9%) patients were diabetic, and 103 (22.3%) were obese. One hundred seven (23.2%) patients had previous access operations. Radiocephalic AVFs were constructed in 29 (6.3%) patients, 99 (21.5%) patients had brachial artery inflow AVFs, 330 (71.6%) had proximal radial artery AVFs, and three were based on the femoral artery. Transposition AVFs were used in 124 (26.9%) patients. No grafts were used for AV access in any patient during the study period. Time to AVF use was 0.5 to 6 months (mean, 1.5 months). Primary, primary assisted, and cumulative patency for patients aged 65 to 94 years were 59.9%, 93.7%, and 96.9% at 12 months and 45.3%, 90.1%, and 94.6% at 24 months, respectively. Follow-up was 1.5 to 77 months (mean, 17.0 months). Subgroup age stratification (65-74 [n = 268], 75-84 [n = 167], 85-94 [n = 26] years) found no statistical difference in functional access outcomes. Primary, primary assisted, and cumulative patency rates were not statistically different in the elderly and non-elderly populations (P = .29, .27, and .37, respectively). One hundred fifty-six patients died during the study period, 1.3 to 61 months (mean, 20 months) after access creation. No deaths were related to access operations.ConclusionsAVFs are feasible and offer functional and timely AV access in older patients. There was no difference in functional access outcomes for older patients with subgroup age stratification. AVF patency rates were not statistically different in the elderly and non-elderly populations. Cumulative AVF patency for patients ≥65 years of age was 96.9% at 12 months and 94.6% at 24 months
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