467 research outputs found
The Erpenbeck high frequency instability theorem for ZND detonations
The rigorous study of spectral stability for strong detonations was begun by
J.J. Erpenbeck in [Er1]. Working with the Zeldovitch-von Neumann-D\"oring (ZND)
model, which assumes a finite reaction rate but ignores effects like viscosity
corresponding to second order derivatives, he used a normal mode analysis to
define a stability function V(\tau,\eps) whose zeros in
correspond to multidimensional perturbations of a steady detonation profile
that grow exponentially in time. Later in a remarkable paper [Er3] he provided
strong evidence, by a combination of formal and rigorous arguments, that for
certain classes of steady ZND profiles, unstable zeros of exist for
perturbations of sufficiently large transverse wavenumber \eps, even when the
von Neumann shock, regarded as a gas dynamical shock, is uniformly stable in
the sense defined (nearly twenty years later) by Majda. In spite of a great
deal of later numerical work devoted to computing the zeros of V(\tau,\eps),
the paper \cite{Er3} remains the only work we know of that presents a detailed
and convincing theoretical argument for detecting them.
The analysis in [Er3] points the way toward, but does not constitute, a
mathematical proof that such unstable zeros exist. In this paper we identify
the mathematical issues left unresolved in [Er3] and provide proofs, together
with certain simplifications and extensions, of the main conclusions about
stability and instability of detonations contained in that paper.
The main mathematical problem, and our principal focus here, is to determine
the precise asymptotic behavior as \eps\to \infty of solutions to a linear
system of ODEs in , depending on \eps and a complex frequency as
parameters, with turning points on the half-line
Search for sterile neutrino oscillation using RENO and NEOS data
We present a reactor model independent search for sterile neutrino
oscillation using 2\,509\,days of RENO near detector data and 180 days of NEOS
data. The reactor related systematic uncertainties are significantly suppressed
as both detectors are located at the same reactor complex of Hanbit Nuclear
Power Plant. The search is performed by electron
antineutrino\,() disappearance between six reactors and two
detectors with baselines of 294\,m\,(RENO) and 24\,m\,(NEOS). A spectral
comparison of the NEOS prompt-energy spectrum with a no-oscillation prediction
from the RENO measurement can explore reactor oscillations
to sterile neutrino. Based on the comparison, we obtain a 95\% C.L. excluded
region of \,eV. We also obtain a 68\% C.L. allowed
region with the best fit of \,eV and
=0.080.03 with a p-value of 8.2\%. Comparisons of
obtained reactor antineutrino spectra at reactor sources are made among RENO,
NEOS, and Daya Bay to find a possible spectral variation.Comment: 6 pages, 5 figures: This manuscript has been significantly revised by
the joint reanalysis by RENO and NEOS Collaborations. (In the previous
edition, the RENO collaboration used publicly available NEOS data to evaluate
the expected neutrino spectrum at NEOS.
Deriving the mass of particles from Extended Theories of Gravity in LHC era
We derive a geometrical approach to produce the mass of particles that could
be suitably tested at LHC. Starting from a 5D unification scheme, we show that
all the known interactions could be suitably deduced as an induced symmetry
breaking of the non-unitary GL(4)-group of diffeomorphisms. The deformations
inducing such a breaking act as vector bosons that, depending on the
gravitational mass states, can assume the role of interaction bosons like
gluons, electroweak bosons or photon. The further gravitational degrees of
freedom, emerging from the reduction mechanism in 4D, eliminate the hierarchy
problem since generate a cut-off comparable with electroweak one at TeV scales.
In this "economic" scheme, gravity should induce the other interactions in a
non-perturbative way.Comment: 30 pages, 1 figur
Goat health and management for improved smallholdersâ livelihoods in central Malawi â a socioeconomic analysis of rural households
DATA AVAILABILITY : Anonymized tabulated data are available in S1 File, additional
anonymised survey files are available upon request.The true value of goats, their management systems, and the limitations of smallholdings have not been fully
explored in the context of sustainable livelihoods among rural smallholders in central Malawi. However, goats
are an essential part of rural livelihoods as transferable assets and sources of household nutrition, especially at
times of food insecurity aligned to an ever more variable climate. To study the impact and limitations of goat
ownership in Malawiâs Lilongwe district, surveys were performed across four villages covering 148 households
from October-November 2019. Surveys were designed to identify linkages between household demographics,
livelihoods, goat ownership, and management practices. Findings revealed goats are highly valued compared to
other livestock. However, herds were small (median = 3) with only 62% reported kidding in the last year, while
50% reported deaths due to diseases, predation (such as by hyenas), and dog bites. Odds-ratio analyses identified
farmers (as a primary occupation) were more likely to successfully breed goats to increase their herd size. Larger
herds were associated with those who could accumulate wealth and utilise goats for ceremonies. However,
diseases were a major contributor to losses and increased the risk of household food insecurity. Limiting disease
impacts through anthelmintics and supplementation were correlated to an increased likelihood of sustainable
offtake from smallholdings and improved livelihoods. With limited access to veterinary services, smallholders
utilise a diversity of medicinal plants and ash to treat diarrhoea in their herd. The results highlight that goat
security and health is fundamental to realising smallholding livelihood gains. Future efforts should aim to
empower smallholders through providing tools to monitor goat health and to assess the effects of local practices,
including the use of medicinal plants, for goat health.The Biotechnology and Biological Sciences Research Council,https://www.elsevier.com/locate/smallrumresam2024Veterinary Tropical DiseasesSDG-02:Zero Hunge
Grain refinement of magnesium alloys: a review of recent research, theoretical developments and their application
This paper builds on the ââGrain Refinement of Mg Alloysââ published in 2005 and reviews the grain refinement research onMg alloys that has been undertaken since then with an emphasis on the theoretical and analytical methods that have been developed. Consideration of recent research results and current theoretical knowledge has highlighted two important factors that affect an alloyâs as-cast grain size. The first factor applies to commercial Mg-Al alloys where it is concluded that impurity and minor elements such as Fe and Mn have a substantially negative impact on grain size because, in combination with Al, intermetallic phases can be formed that tend to poison the more potent native or deliberately added nucleant particles present in the melt. This factor appears to explain the contradictory experimental outcomes reported in the literature and suggests that the search for a more potent and reliable grain refining technology may need to take a different approach. The second factor applies to all alloys and is related to the role of constitutional supercooling which, on the one hand, promotes grain nucleation and, on the other hand, forms a nucleation-free zone preventing further nucleation within this zone, consequently limiting the grain refinement achievable, particularly in low solute-containing alloys. Strategies to reduce the negative impact of these two factors are discussed. Further, the Interdependence model has been shown to apply to a broad range of casting methods from slow cooling gravity die casting to fast cooling high pressure die casting and dynamic methods such as ultrasonic treatment
Serum magnesium and calcium levels in relation to ischemic stroke : Mendelian randomization study
ObjectiveTo determine whether serum magnesium and calcium concentrations are causally associated with ischemic stroke or any of its subtypes using the mendelian randomization approach.MethodsAnalyses were conducted using summary statistics data for 13 single-nucleotide polymorphisms robustly associated with serum magnesium (n = 6) or serum calcium (n = 7) concentrations. The corresponding data for ischemic stroke were obtained from the MEGASTROKE consortium (34,217 cases and 404,630 noncases).ResultsIn standard mendelian randomization analysis, the odds ratios for each 0.1 mmol/L (about 1 SD) increase in genetically predicted serum magnesium concentrations were 0.78 (95% confidence interval [CI] 0.69-0.89; p = 1.3
7 10-4) for all ischemic stroke, 0.63 (95% CI 0.50-0.80; p = 1.6
7 10-4) for cardioembolic stroke, and 0.60 (95% CI 0.44-0.82; p = 0.001) for large artery stroke; there was no association with small vessel stroke (odds ratio 0.90, 95% CI 0.67-1.20; p = 0.46). Only the association with cardioembolic stroke was robust in sensitivity analyses. There was no association of genetically predicted serum calcium concentrations with all ischemic stroke (per 0.5 mg/dL [about 1 SD] increase in serum calcium: odds ratio 1.03, 95% CI 0.88-1.21) or with any subtype.ConclusionsThis study found that genetically higher serum magnesium concentrations are associated with a reduced risk of cardioembolic stroke but found no significant association of genetically higher serum calcium concentrations with any ischemic stroke subtype
EPIdemiology of Surgery-Associated Acute Kidney Injury (EPIS-AKI) : Study protocol for a multicentre, observational trial
More than 300 million surgical procedures are performed each year. Acute kidney injury (AKI) is a common complication after major surgery and is associated with adverse short-term and long-term outcomes. However, there is a large variation in the incidence of reported AKI rates. The establishment of an accurate epidemiology of surgery-associated AKI is important for healthcare policy, quality initiatives, clinical trials, as well as for improving guidelines. The objective of the Epidemiology of Surgery-associated Acute Kidney Injury (EPIS-AKI) trial is to prospectively evaluate the epidemiology of AKI after major surgery using the latest Kidney Disease: Improving Global Outcomes (KDIGO) consensus definition of AKI. EPIS-AKI is an international prospective, observational, multicentre cohort study including 10 000 patients undergoing major surgery who are subsequently admitted to the ICU or a similar high dependency unit. The primary endpoint is the incidence of AKI within 72 hours after surgery according to the KDIGO criteria. Secondary endpoints include use of renal replacement therapy (RRT), mortality during ICU and hospital stay, length of ICU and hospital stay and major adverse kidney events (combined endpoint consisting of persistent renal dysfunction, RRT and mortality) at day 90. Further, we will evaluate preoperative and intraoperative risk factors affecting the incidence of postoperative AKI. In an add-on analysis, we will assess urinary biomarkers for early detection of AKI. EPIS-AKI has been approved by the leading Ethics Committee of the Medical Council North Rhine-Westphalia, of the Westphalian Wilhelms-University MĂŒnster and the corresponding Ethics Committee at each participating site. Results will be disseminated widely and published in peer-reviewed journals, presented at conferences and used to design further AKI-related trials. Trial registration number NCT04165369
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