10,960 research outputs found
Anomalous reaction-transport processes: the dynamics beyond the Mass Action Law
In this paper we reconsider the Mass Action Law (MAL) for the anomalous
reversible reaction with diffusion. We provide a
mesoscopic description of this reaction when the transitions between two states
and are governed by anomalous (heavy-tailed) waiting-time
distributions. We derive the set of mesoscopic integro-differential equations
for the mean densities of reacting and diffusing particles in both states. We
show that the effective reaction rate memory kernels in these equations and the
uniform asymptotic states depend on transport characteristics such as jumping
rates. This is in contradiction with the classical picture of MAL. We find that
transport can even induce an extinction of the particles such that the density
of particles or tends asymptotically to zero. We verify analytical
results by Monte Carlo simulations and show that the mesoscopic densities
exhibit a transient growth before decay.Comment: 4 pages, 3 figure
Animal Transport: Developing optimum animal handling procedures and effective transport strategies in the food production chain to improve animal welfare and food quality
End of project reportA series of studies were performed to investigate the effect of transport on liveweight, physiological and haematological responses of cattle. The first study was carried out over a 6 week period in the Spring of 2004. Eighty-four continental x bulls (mean weight (s.d.) 367 (35) kg), naïve to transport, were randomly assigned to one of six journey (J) times of 0, 6, 9, 12, 18 and 24h transport at a stocking density of 1.02m2/bull. Blood samples were collected by jugular venipuncture before, immediately after and at 1, 2, 4, 6, 8, 12 and 24h and bulls were weighed before, immediately after, and at 4, 12 and 24h. Bulls travelling for 6h (280 km), 9h (435 km), 12h (582 km), 18h (902 km) and 24h (1192 km) lost 4.7, 4.5, 5.7 (P=0.05), 6.6 (P=0.05) and 7.5 (P=0.05) percentage liveweight compared with baseline. During the 24h recovery period liveweight was regained to pre-transport levels. Lymphocyte percentages were lower (P=0.001) and neutrophil percentages were higher (P=0.05) in all animals. Blood protein and creatine kinase, glucose and NEFA concentrations were higher (P=0.05) in the bulls following transport and returned to baseline within 24h. In conclusion, liveweight and some physiological and haematological responses of bulls returned to pre-transport levels within 24h having had access to feed and water. Transport of bulls from 6 – 24hours did not impact negatively on animal welfare
Synchronization of globally coupled two-state stochastic oscillators with a state dependent refractory period
We present a model of identical coupled two-state stochastic units each of
which in isolation is governed by a fixed refractory period. The nonlinear
coupling between units directly affects the refractory period, which now
depends on the global state of the system and can therefore itself become time
dependent. At weak coupling the array settles into a quiescent stationary
state. Increasing coupling strength leads to a saddle node bifurcation, beyond
which the quiescent state coexists with a stable limit cycle of nonlinear
coherent oscillations. We explicitly determine the critical coupling constant
for this transition
The Mass-Metallicity Relation for Giant Planets
Exoplanet discoveries of recent years have provided a great deal of new data
for studying the bulk compositions of giant planets. Here we identify 47
transiting giant planets () whose stellar
insolation is low enough (, or roughly ) that they are not affected
by the hot Jupiter radius inflation mechanism(s). We compute a set of new
thermal and structural evolution models and use these models in comparison with
properties of the 47 transiting planets (mass, radius, age) to determine their
heavy element masses. A clear correlation emerges between the planetary heavy
element mass and the total planet mass, approximately of the form . This finding is consistent with the core accretion model of
planet formation. We also study how stellar metallicity [Fe/H] affects
planetary metal-enrichment and find a weaker correlation than has been
previously reported from studies with smaller sample sizes. We confirm a strong
relationship between the planetary metal-enrichment relative to the parent star
and the planetary mass, but see no relation in
with planet orbital properties or stellar mass.
The large heavy element masses of many planets ( ) suggest
significant amounts of heavy elements in H/He envelopes, rather than cores,
such that metal-enriched giant planet atmospheres should be the rule. We also
discuss a model of core-accretion planet formation in a one-dimensional disk
and show that it agrees well with our derived relation between mass and .Comment: Accepted to The Astrophysical Journal. This revision adds a
substantial amount of discussion; the results are the sam
Physiological and behavioural aspects of housing stress in cattle
End of project reportThe effect of various space allowances on pituitary, adrenal, immune responses and performance was investigated in 72 Holstein x Friesian bulls. Bulls (403 ± 3.5 kg) were blocked by weight and randomly assigned into two groups (familiar, F and unfamiliar, UF) x three (1.2, 2.7 and 4.2 m2 per bull; n = 24 bulls per space allowance) treatments and housed for 83 days in 18 pens (n = 4 per pen). Blood samples were collected on day –1, 0, 3, 14, 36 and 77 with respect to mixing and housing on day 0. The bulls were administered with adrenocorticotrophic hormone (ACTH) on day 3 and corticotrophin-releasing hormone (CRH) on days 14, 36 and 77. The basal cortisol concentrations were not affected (P>0.05) by mixing of familiar and unfamiliar bulls. On day 3, basal cortisol was greater (P0.05) of treatment and treatment x time on ACTH. On day 14, interferon-? production was lower (P0.05) different for those housed at 1.2 m2. Bulls housed at either space allowances had (P<0.05) neutrophilia, lymphopenia, eosinopenia and decreased haemoglobin on day 3 compared with day 0. The liveweight gain from days 0 to 83 was lower (P< 0.05) in bulls housed at 1.2 compared with those at 2.7 and 4.2 m2. Housing bulls at 1.2 m2 space allowance had a detrimental effect on their growth and was associated with an acute rise in plasma cortisol concentration (on day 3) compared with space allowances of 2.7 and 4.2 m2/bull.European Union Structural Funds (EAGGF
Evolution and impact of defects in a p-channel CCD after cryogenic proton-irradiation
P-channel CCDs have been shown to display improved tolerance to radiation-induced charge transfer inefficiency (CTI) when compared to n-channel CCDs. However, the defect distribution formed during irradiation is expected to be temperature dependent due to the differences in lattice energy caused by a temperature change. This has been tested through defect analysis of two p-channel e2v CCD204 devices, one irradiated at room temperature and one at a cryogenic temperature (153K). Analysis is performed using the method of single trap pumping. The dominant charge trapping defects at these conditions have been identified as the donor level of the silicon divacancy and the carbon interstitial defect. The defect parameters are analysed both immediately post irradiation and following several subsequent room-temperature anneal phases up until a cumulative anneal time of approximately 10 months. We have also simulated charge transfer in an irradiated CCD pixel using the defect distribution from both the room-temperature and cryogenic case, to study how the changes affect imaging performance. The results demonstrate the importance of cryogenic irradiation and annealing studies, with large variations seen in the defect distribution when compared to a device irradiated at room-temperature, which is the current standard procedure for radiation-tolerance testing
Postirradiation behavior of p-channel charge-coupled devices irradiated at 153 K
The displacement damage hardness that can be achieved using p-channel charge-coupled devices (CCD) was originally demonstrated in 1997, and since then a number of other studies have demonstrated an improved tolerance to radiation-induced CTI when compared to n-channel CCDs. A number of recent studies have also shown that the temperature history of the device after the irradiation impacts the performance of the detector, linked to the mobility of defects at different temperatures. This study describes the initial results from an e2v technologies p-channel CCD204 irradiated at 153 K with a 10 MeV equivalent proton fluences of 1.24×109 and 1.24×1011 protons cm-2. The dark current, cosmetic quality and the number of defects identified using trap pumping immediately were monitored after the irradiation for a period of 150 hours with the device held at 153 K and then after different periods of time at room temperature. The device also exhibited a flatband voltage shift of around 30 mV / krad, determined by the reduction in full well capacity
Spreading of Persistent Infections in Heterogeneous Populations
Up to now, the effects of having heterogeneous networks of contacts have been
studied mostly for diseases which are not persistent in time, i.e., for
diseases where the infectious period can be considered very small compared to
the lifetime of an individual. Moreover, all these previous results have been
obtained for closed populations, where the number of individuals does not
change during the whole duration of the epidemics. Here, we go one step further
and analyze, both analytically and numerically, a radically different kind of
diseases: those that are persistent and can last for an individual's lifetime.
To be more specific, we particularize to the case of Tuberculosis' (TB)
infection dynamics, where the infection remains latent for a period of time
before showing up and spreading to other individuals. We introduce an
epidemiological model for TB-like persistent infections taking into account the
heterogeneity inherent to the population structure. This sort of dynamics
introduces new analytical and numerical challenges that we are able to sort
out. Our results show that also for persistent diseases the epidemic threshold
depends on the ratio of the first two moments of the degree distribution so
that it goes to zero in a class of scale-free networks when the system
approaches the thermodynamic limit.Comment: 12 pages and 2 figures. Revtex format. Submitted for publication
The Broadband X-Ray Spectrum of the X-Ray-obscured Type 1 AGN 2MASX J193013.80+341049.5
We present results from modeling the broadband X-ray spectrum of the Type 1 active galactic nucleus (AGN) 2MASX J193013.80+341049.5 using NuSTAR, Swift, and archival XMM-Newton observations. We find this source to be highly X-ray obscured, with column densities exceeding 10²³ cm⁻² across all epochs of X-ray observations, spanning an 8 yr period. However, the source exhibits prominent broad optical emission lines, consistent with an unobscured Type 1 AGN classification. We fit the X-ray spectra with both phenomenological reflection models and physically motivated torus models to model the X-ray absorption. We examine the spectral energy distribution of this source and investigate some possible scenarios to explain the mismatch between X-ray and optical classifications. We compare the ratio of reddening to X-ray absorbing column density (E_(B−V)/N_H) and find that 2MASX J193013.80+341049.5 likely has a much lower dust-to-gas ratio relative to the Galactic interstellar medium, suggesting that the broad line region itself could provide the source of extra X-ray obscuration, being composed of low-ionization, dust-free gas
Improved costs and outcomes with conscious sedation vs general anesthesia in TAVR patients: Time to wake up?
BackgroundTranscatheter aortic valve replacement (TAVR) has become a commonplace procedure for the treatment of aortic stenosis in higher risk surgical patients. With the high cost and steadily increasing number of patients receiving TAVR, emphasis has been placed on optimizing outcomes as well as resource utilization. Recently, studies have demonstrated the feasibility of conscious sedation in lieu of general anesthesia for TAVR. This study aimed to investigate the clinical as well as cost outcomes associated with conscious sedation in comparison to general anesthesia in TAVR.MethodsRecords for all adult patients undergoing TAVR at our institution between August 2012 and June 2016 were included using our institutional Society of Thoracic Surgeons (STS) and American College of Cardiology (ACC) registries. Cost data was gathered using the BIOME database. Patients were stratified into two groups according to whether they received general anesthesia (GA) or conscious sedation (CS) during the procedure. No-replacement propensity score matching was done using the validated STS predicted risk of mortality (PROM) as a propensity score. Primary outcome measure with survival to discharge and several secondary outcome measures were also included in analysis. According to our institution's data reporting guidelines, all cost data is presented as a percentage of the general anesthesia control group cost.ResultsOf the 231 patients initially identified, 225 (157 GA, 68 CS) were included for analysis. After no-replacement propensity score matching, 196 patients (147 GA, 49 CS) remained. Overall mortality was 1.5% in the matched population with a trend towards lower mortality in the CS group. Conscious sedation was associated with significantly fewer ICU hours (30 vs 96 hours, p = <0.001) and total hospital days (4.9 vs 10.4, p<0.001). Additionally, there was a 28% decrease in direct cost (p<0.001) as well as significant decreases in all individual all cost categories associated with the use of conscious sedation. There was no difference in composite major adverse events between groups. These trends remained on all subsequent subgroup analyses.ConclusionConscious sedation is emerging as a safe and viable option for anesthesia in patients undergoing transcatheter aortic valve replacement. The use of conscious sedation was not only associated with similar rates of adverse events, but also shortened ICU and overall hospital stays. Finally, there were significant decreases in all cost categories when compared to a propensity matched cohort receiving general anesthesia
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