332 research outputs found
About Bianchi I with VSL
In this paper we study how to attack, through different techniques, a perfect
fluid Bianchi I model with variable G,c and Lambda, but taking into account the
effects of a -variable into the curvature tensor. We study the model under
the assumption,div(T)=0. These tactics are: Lie groups method (LM), imposing a
particular symmetry, self-similarity (SS), matter collineations (MC) and
kinematical self-similarity (KSS). We compare both tactics since they are quite
similar (symmetry principles). We arrive to the conclusion that the LM is too
restrictive and brings us to get only the flat FRW solution. The SS, MC and KSS
approaches bring us to obtain all the quantities depending on \int c(t)dt.
Therefore, in order to study their behavior we impose some physical
restrictions like for example the condition q<0 (accelerating universe). In
this way we find that is a growing time function and Lambda is a decreasing
time function whose sing depends on the equation of state, w, while the
exponents of the scale factor must satisfy the conditions
and
, i.e. for all equation of state relaxing in this way the
Kasner conditions. The behavior of depends on two parameters, the equation
of state and a parameter that controls the behavior of
therefore may be growing or decreasing.We also show that through
the Lie method, there is no difference between to study the field equations
under the assumption of a var affecting to the curvature tensor which the
other one where it is not considered such effects.Nevertheless, it is essential
to consider such effects in the cases studied under the SS, MC, and KSS
hypotheses.Comment: 29 pages, Revtex4, Accepted for publication in Astrophysics & Space
Scienc
Asia-Pacific working group consensus on non-variceal upper gastrointestinal bleeding: An update 2018
Non-variceal upper gastrointestinal bleeding remains an important emergency condition, leading to significant morbidity and mortality. As endoscopic therapy is the 'gold standard' of management, treatment of these patients can be considered in three stages: pre-endoscopic treatment, endoscopic haemostasis and post-endoscopic management. Since publication of the Asia-Pacific consensus on non-variceal upper gastrointestinal bleeding (NVUGIB) 7 years ago, there have been significant advancements in the clinical management of patients in all three stages. These include pre-endoscopy risk stratification scores, blood and platelet transfusion, use of proton pump inhibitors; during endoscopy new haemostasis techniques (haemostatic powder spray and over-the-scope clips); and post-endoscopy management by second-look endoscopy and medication strategies. Emerging techniques, including capsule endoscopy and Doppler endoscopic probe in assessing adequacy of endoscopic therapy, and the pre-emptive use of angiographic embolisation, are attracting new attention. An emerging problem is the increasing use of dual antiplatelet agents and direct oral anticoagulants in patients with cardiac and cerebrovascular diseases. Guidelines on the discontinuation and then resumption of these agents in patients presenting with NVUGIB are very much needed. The Asia-Pacific Working Group examined recent evidence and recommends practical management guidelines in this updated consensus statement
Alcohol Use Patterns and Subsequent Sexual Behaviors Among Women, Men who have Sex with Men and Men who have Sex with Women Engaged in Routine HIV Care in the United States
Among people with HIV, alcohol use is associated with increased prevalence of sexual transmission behaviors. We examined associations between alcohol use in the prior year and sexual behaviors approximately six months later among 1857 women, 6752 men who have sex with men (MSM) and 2685 men who have sex with women (MSW). Any alcohol use was associated with increased risk of unsafe vaginal sex among women; anal sex and =>2 anal sex partners among MSM; and anal sex, =>2 anal or vaginal sex partners, and unsafe vaginal sex among MSW. In particular, among women >7 alcoholic drinks/week and among MSW =>5 alcoholic drinks/drinking day increased the likelihood of certain subsequent sexual behaviors. For all groups, especially women, the risk of sex under the influence of drugs/alcohol markedly increased with increases in quantity and frequency of alcohol consumption. These different patterns of drinking and sexual behaviors indicate the importance of tailored counseling messages to women, MSM and MSW
Do Symptoms of Depression Interact with Substance Use to Affect HIV Continuum of Care Outcomes?
Few studies examine how depression and substance use interact to affect HIV control. In 14,380 persons with HIV (PWH), we used logistic regression and generalized estimating equations to evaluate how symptoms of depression interact with alcohol, cocaine, opioid, and methamphetamine use to affect subsequent retention in care, maintaining an active prescription for ART, and consistent virologic suppression. Among PWH with no or mild depressive symptoms, heavy alcohol use had no association with virologic suppression (OR 1.00 [0.95–1.06]); among those with moderate or severe symptoms, it was associated with reduced viral suppression (OR 0.80 [0.74–0.87]). We found no interactions with heavy alcohol use on retention in care or maintaining ART prescription or with other substances for any outcome. These results highlight the importance of treating moderate or severe depression in PWH, especially with comorbid heavy alcohol use, and support multifaceted interventions targeting alcohol use and depression
Bianchi II with time varying constants. Self-similar approach
We study a perfect fluid Bianchi II models with time varying constants under
the self-similarity approach. In the first of the studied model, we consider
that only vary and The obtained solution is more general that
the obtained one for the classical solution since it is valid for an equation
of state while in the classical solution
Taking into account the current observations, we conclude
that must be a growing time function while is a positive
decreasing function. In the second of the studied models we consider a variable
speed of light (VSL). We obtain a similar solution as in the first model
arriving to the conclusions that must be a growing time function if
is a positive decreasing function.Comment: 10 pages. RevTeX
A place-based approach to payments for ecosystem services
Payment for Ecosystem Services (PES) schemes are proliferating but are challenged by insufficient attention to spatial and temporal inter-dependencies, interactions between different ecosystems and their services, and the need for multi-level governance. To address these challenges, this paper develops a place-based approach to the development and implementation of PES schemes that incorporates multi-level governance, bundling or layering of services across multiple scales, and shared values for ecosystem services. The approach is evaluated and illustrated using case study research to develop an explicitly place-based PES scheme, the Peatland Code, owned and managed by the International Union for the Conservation of Nature’s UK Peatland Programme and designed to pay for restoration of peatland habitats. Buyers preferred bundled schemes with premium pricing of a primary service, contrasting with sellers’ preferences for quantifying and marketing services separately in a layered scheme. There was limited awareness among key business sectors of dependencies on ecosystem services, or the risks and opportunities arising from their management. Companies with financial links to peatlands or a strong environmental sustainability focus were interested in the scheme, particularly in relation to climate regulation, water quality, biodiversity and flood risk mitigation benefits. Visitors were most interested in donating to projects that benefited wildlife and were willing to donate around £2 on-site during a visit. Sellers agreed a deliberated fair price per tonne of CO2 equivalent from £11.18 to £15.65 across four sites in Scotland, with this range primarily driven by spatial variation in habitat degradation. In the Peak District, perceived declines in sheep and grouse productivity arising from ditch blocking led to substantially higher prices, but in other regions ditch blocking was viewed more positively. The Peatland Code was developed in close collaboration with stakeholders at catchment, landscape and national scales, enabling multi-level governance of the management and delivery of ecosystem services across these scales. Place-based PES schemes can mitigate negative trade-offs between ecosystem services, more effectively include cultural ecosystem services and engage with and empower diverse stakeholders in scheme design and governance
2022 Upgrade and Improved Low Frequency Camera Sensitivity for CMB Observation at the South Pole
Constraining the Galactic foregrounds with multi-frequency Cosmic Microwave
Background (CMB) observations is an essential step towards ultimately reaching
the sensitivity to measure primordial gravitational waves (PGWs), the sign of
inflation after the Big-Bang that would be imprinted on the CMB. The BICEP
Array telescope is a set of multi-frequency cameras designed to constrain the
energy scale of inflation through CMB B-mode searches while also controlling
the polarized galactic foregrounds. The lowest frequency BICEP Array receiver
(BA1) has been observing from the South Pole since 2020 and provides 30 GHz and
40 GHz data to characterize the Galactic synchrotron in our CMB maps. In this
paper, we present the design of the BA1 detectors and the full optical
characterization of the camera including the on-sky performance at the South
Pole. The paper also introduces the design challenges during the first
observing season including the effect of out-of-band photons on detectors
performance. It also describes the tests done to diagnose that effect and the
new upgrade to minimize these photons, as well as installing more dichroic
detectors during the 2022 deployment season to improve the BA1 sensitivity. We
finally report background noise measurements of the detectors with the goal of
having photon noise dominated detectors in both optical channels. BA1 achieves
an improvement in mapping speed compared to the previous deployment season.Comment: Proceedings of SPIE Astronomical Telescopes + Instrumentation 2022
(AS22
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