171 research outputs found
The angular distribution of the reaction
The reaction is very important for low-energy
( MeV) antineutrino experiments. In this paper we calculate
the positron angular distribution, which at low energies is slightly backward.
We show that weak magnetism and recoil corrections have a large effect on the
angular distribution, making it isotropic at about 15 MeV and slightly forward
at higher energies. We also show that the behavior of the cross section and the
angular distribution can be well-understood analytically for MeV by calculating to , where is the nucleon mass. The
correct angular distribution is useful for separating events from other reactions and detector backgrounds, as well as for
possible localization of the source (e.g., a supernova) direction. We comment
on how similar corrections appear for the lepton angular distributions in the
deuteron breakup reactions and . Finally, in the reaction , the
angular distribution of the outgoing neutrons is strongly forward-peaked,
leading to a measurable separation in positron and neutron detection points,
also potentially useful for rejecting backgrounds or locating the source
direction.Comment: 10 pages, including 5 figure
VERITAS Search for VHE Gamma-ray Emission from Dwarf Spheroidal Galaxies
Indirect dark matter searches with ground-based gamma-ray observatories
provide an alternative for identifying the particle nature of dark matter that
is complementary to that of direct search or accelerator production
experiments. We present the results of observations of the dwarf spheroidal
galaxies Draco, Ursa Minor, Bootes 1, and Willman 1 conducted by VERITAS. These
galaxies are nearby dark matter dominated objects located at a typical distance
of several tens of kiloparsecs for which there are good measurements of the
dark matter density profile from stellar velocity measurements. Since the
conventional astrophysical background of very high energy gamma rays from these
objects appears to be negligible, they are good targets to search for the
secondary gamma-ray photons produced by interacting or decaying dark matter
particles. No significant gamma-ray flux above 200 GeV was detected from these
four dwarf galaxies for a typical exposure of ~20 hours. The 95% confidence
upper limits on the integral gamma-ray flux are in the range 0.4-2.2x10^-12
photons cm^-2s^-1. We interpret this limiting flux in the context of pair
annihilation of weakly interacting massive particles and derive constraints on
the thermally averaged product of the total self-annihilation cross section and
the relative velocity of the WIMPs. The limits are obtained under conservative
assumptions regarding the dark matter distribution in dwarf galaxies and are
approximately three orders of magnitude above the generic theoretical
prediction for WIMPs in the minimal supersymmetric standard model framework.
However significant uncertainty exists in the dark matter distribution as well
as the neutralino cross sections which under favorable assumptions could
further lower the limits.Comment: 21 pages, 2 figures, updated to reflect version published in ApJ.
NOTE: M.D. Wood added as autho
Effect of early vasopressin vs norepinephrine on kidney failure in patients with septic shock. The VANISH Randomized Clinical Trial
IMPORTANCE: Norepinephrine is currently recommended as the first-line vasopressor in septic shock; however, early vasopressin use has been proposed as an alternative. OBJECTIVE: To compare the effect of early vasopressin vs norepinephrine on kidney failure in patients with septic shock. DESIGN, SETTING, AND PARTICIPANTS: A factorial (2×2), double-blind, randomized clinical trial conducted in 18 general adult intensive care units in the United Kingdom between February 2013 and May 2015, enrolling adult patients who had septic shock requiring vasopressors despite fluid resuscitation within a maximum of 6 hours after the onset of shock. INTERVENTIONS: Patients were randomly allocated to vasopressin (titrated up to 0.06 U/min) and hydrocortisone (n = 101), vasopressin and placebo (n = 104), norepinephrine and hydrocortisone (n = 101), or norepinephrine and placebo (n = 103). MAIN OUTCOMES AND MEASURES: The primary outcome was kidney failure-free days during the 28-day period after randomization, measured as (1) the proportion of patients who never developed kidney failure and (2) median number of days alive and free of kidney failure for patients who did not survive, who experienced kidney failure, or both. Rates of renal replacement therapy, mortality, and serious adverse events were secondary outcomes. RESULTS: A total of 409 patients (median age, 66 years; men, 58.2%) were included in the study, with a median time to study drug administration of 3.5 hours after diagnosis of shock. The number of survivors who never developed kidney failure was 94 of 165 patients (57.0%) in the vasopressin group and 93 of 157 patients (59.2%) in the norepinephrine group (difference, -2.3% [95% CI, -13.0% to 8.5%]). The median number of kidney failure-free days for patients who did not survive, who experienced kidney failure, or both was 9 days (interquartile range [IQR], 1 to -24) in the vasopressin group and 13 days (IQR, 1 to -25) in the norepinephrine group (difference, -4 days [95% CI, -11 to 5]). There was less use of renal replacement therapy in the vasopressin group than in the norepinephrine group (25.4% for vasopressin vs 35.3% for norepinephrine; difference, -9.9% [95% CI, -19.3% to -0.6%]). There was no significant difference in mortality rates between groups. In total, 22 of 205 patients (10.7%) had a serious adverse event in the vasopressin group vs 17 of 204 patients (8.3%) in the norepinephrine group (difference, 2.5% [95% CI, -3.3% to 8.2%]). CONCLUSIONS AND RELEVANCE: Among adults with septic shock, the early use of vasopressin compared with norepinephrine did not improve the number of kidney failure-free days. Although these findings do not support the use of vasopressin to replace norepinephrine as initial treatment in this situation, the confidence interval included a potential clinically important benefit for vasopressin, and larger trials may be warranted to assess this further. TRIAL REGISTRATION: clinicaltrials.gov Identifier: ISRCTN 20769191
A literature review of the disruptive effects of user fee exemption policies on health systems
BACKGROUND: Several low- and middle-income countries have exempted patients from user fees in certain categories of population or of services. These exemptions are very effective in lifting part of the financial barrier to access to services, but they have been organized within unstable health systems where there are sometimes numerous dysfunctions. The objective of this article is to bring to light the disruptions triggered by exemption policies in health systems of low- and middle-income countries. METHODS: Scoping review of 23 scientific articles. The data were synthesized according to the six essential functions of health systems. RESULTS: The disruptions included specifically: 1) immediate and significant increases in service utilization; 2) perceived heavier workloads for health workers, feelings of being exploited and overworked, and decline in morale; 3) lack of information about free services provided and their reimbursement; 4) unavailability of drugs and delays in the distribution of consumables; 5) unpredictable and insufficient funding, revenue losses for health centres, reimbursement delays; 6) the multiplicity of actors and the difficulty of identifying who is responsible ('no blame' game), and deficiencies in planning and communication. CONCLUSIONS: These disruptive elements give us an idea of what is to be expected if exemption policies do not put in place all the required conditions in terms of preparation, planning and complementary measures. There is a lack of knowledge on the effects of exemptions on all the functions of health systems because so few studies have been carried out from this perspective
New Foundations: Pseudo-pacification and special liberty as potential cornerstones of a multi-level theory of homicide and serial murder
Over the past 30 years the industrialized West has witnessed a move towards space, heterogeneity and subjectivity in the criminological study of violence and homicide. Although large-scale quantitative studies of the temporal and spatial distribution of homicide continue to provide a broad empirical context, aetiological explanations tend to be based on analyses of the heterogeneous psychological interactions and experiences of individual subjects at the micro-level. However, mid-range studies of the temporal and spatial distribution of perpetrators and victims of homicide between unrelated adults have provided a useful link between the micro- and macro-levels. Focusing primarily on British homicide and serial murder, this article attempts to strengthen this link by combining contemporary micro-analyses of the subjective motives of perpetrators with mid-range analyses of space, which can therefore be seen as part of the structural tradition of theorizing about homicide and serial murder. Placing these analyses in a broad underlying context constituted by major historical shifts in political economy and the cultural forms of ‘pseudo-pacification’ and ‘special liberty’ will lay the initial cornerstones for an integrated multi-level theory. © The Author(s) 2014
Care and communication between health professionals and patients affected by severe or chronic illness in community care settings: a qualitative study of care at the end of life
Background: Advance care planning (ACP) enables patients to consider, discuss and, if they wish, document their wishes and preferences for future care, including decisions to refuse treatment, in the event that they lose capacity to make decisions for themselves. ACP is a key component of UK health policy to improve the experience of death and dying for patients and their families. There is limited evidence about how patients and health professionals understand ACP, or when and how this is initiated. It is evident that many people find discussion of and planning for end of life care difficult, and tend to avoid the topic.
Aim: To investigate how patients, their relatives and health professionals initiate and experience discussion of ACP and the outcomes of advance discussions in shaping care at the end of life.
Design and data collection: Qualitative study with two workstreams: (1) interviews with 37 health professionals (general practitioners, specialist nurses and community nurses) about their experiences of ACP; and (2) longitudinal case studies of 21 patients with 6-month follow-up. Cases included a patient and, where possible, a nominated key relative and/or health professional as well as a review of medical records. Complete case triads were obtained for 11 patients. Four cases comprised the patient alone, where respondents were unable or unwilling to nominate either a family member or a professional carer they wished to include in the study. Patients were identified as likely to be within the last 6 months of life. Ninety-seven interviews were completed in total.
Setting: General practices and community care settings in the East Midlands of England.
Findings: The study found ACP to be uncommon and focused primarily on specific documented tasks involving decisions about preferred place of death and cardiopulmonary resuscitation, supporting earlier research. There was no evidence of ACP in nearly half (9 of 21) of patient cases. Professionals reported ACP discussions to be challenging. It was difficult to recognise when patients had entered the last year of life, or to identify their readiness to consider future planning. Patients often did not wish to do so before they had become gravely ill. Consequently, ACP discussions tended to be reactive, rather than pre-emptive, occurring in response to critical events or evidence of marked deterioration. ACP discussions intersected two parallel strands of planning: professional organisation and co-ordination of care; and the practical and emotional preparatory work that patients and families undertook to prepare themselves for death. Reference to ACP as a means of guiding decisions for patients who had lost capacity was rare.
Conclusions: Advance care planning remains uncommon, is often limited to documentation of a few key decisions, is reported to be challenging by many health professionals, is not welcomed by a substantial number of patients and tends to be postponed until death is clearly imminent. Current implementation largely ignores the purpose of ACP as a means of extending personal autonomy in the event of lost capacity.
Future work: Attention should be paid to public attitudes to death and dying (including those of culturally diverse and ethnic minority groups), place of death, resuscitation and the value of anticipatory planning. In addition the experiences and needs of two under-researched groups should be explored: the frail elderly, including those who manage complex comorbid conditions, unrecognised as vulnerable cases; and those patients affected by stigmatised conditions, such as substance abuse or serious mental illness who fail to engage constructively with services and are not recognised as suitable referrals for palliative and end of life care.
Funding: The National Institute for Health Research Health Services and Delivery Research programme
Altering the Motivational Function of Nicotine through Conditioning Processes
The collection of chapters in this 55th Nebraska Symposium on Motivation Volume clearly highlights that effective strategies for reducing compulsive tobacco use will require a multifaceted approach in which genetic, neurobiological, individual, and cultural factors are considered. It is difficult, if not impossible, to predict where the next important breakthrough will come from (Bevins & Bardo, 2004; Dethier, 1966; Laidler, 1998). Accordingly, further research that extends and challenges current theory and practice at each of these levels of analysis is needed. The continuing focus of our research program, and the topic of the present chapter, is on the role of Pavlovian conditioning processes involving nicotine. Theoretical and empirical approaches to nicotine dependence that include Pavlovian conditioning processes have lead to important advances in our understanding and treatment of chronic tobacco use (e.g., see Rose, Chapter 8 and Tiffany, Warthen, & Goedecker, Chapter 10 in current Volume). These approaches conceptualize the drug as an unconditioned stimulus (US) or reinforcer. That is, the pharmacological effects of the drug (e.g., reward, analgesia, psychomotor stimulation) enter into an association with stimuli that reliably co-occur with these effects (e.g., paraphernalia, situational cues). Later exposure to these conditioned stimuli (CSs) can evoke conditioned responses (CRs) that increase the chances an individual will seek drug.
More recently, we have suggested that the interoceptive stimulus effects of nicotine might also serve as a CS for other appetitive non-drug outcomes (i.e., USs) and/or a stimulus that occasions whether other CS-US associations will or will not occur (i.e., an occasion setter or facilitator; see Bevins & Palmatier, 2004). We have further suggested that such an associative learning history could impact the tenacity of nicotine addiction—e.g., shorten the time between experimentation and dependence, increase the difficulty of quitting, make sustaining abstinence more difficult, etc. At the current time these suggestions are speculative. With this in mind, the present chapter will review the research in this area, as well as highlight some of its historical precursors and suggest some possible future directions for research. In doing so, hopefully the reader will gain an appreciation for how this approach might lead to further insight into how Pavlovian conditioning processes can alter the motivational function of nicotine in a manner that contributes to chronic tobacco use
Embrapa and the Construction of Scientific Heritage in Brazilian Agriculture: Sowing Memory
The Brazilian Agricultural Research Corporation, Embrapa, is well renowned for incorporating the Cerrado into Braziltry’s modern agriculture through its discoveries of how to improve infertile soils and to develop soybean seeds adapted to the Tropics. Known as the Tropical Revolution, Brazil’s own Green Revolution, this past episode continues to define Embrapa’s identity and Brazil’s agricultural science and technology, reinforcing a view of agricultural development while neglecting alternatives.
Purpose: This article seeks to understand how Embrapa has carved its name in Brazil’s agricultural history, creating a powerful national brand with global recognition. It explores what constitutes Embrapa’s ‘organizational heritage’. how this has been built within the organization, and to what effect
Antiinflammatory Therapy with Canakinumab for Atherosclerotic Disease
Background: Experimental and clinical data suggest that reducing inflammation without affecting lipid levels may reduce the risk of cardiovascular disease. Yet, the inflammatory hypothesis of atherothrombosis has remained unproved. Methods: We conducted a randomized, double-blind trial of canakinumab, a therapeutic monoclonal antibody targeting interleukin-1β, involving 10,061 patients with previous myocardial infarction and a high-sensitivity C-reactive protein level of 2 mg or more per liter. The trial compared three doses of canakinumab (50 mg, 150 mg, and 300 mg, administered subcutaneously every 3 months) with placebo. The primary efficacy end point was nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death. RESULTS: At 48 months, the median reduction from baseline in the high-sensitivity C-reactive protein level was 26 percentage points greater in the group that received the 50-mg dose of canakinumab, 37 percentage points greater in the 150-mg group, and 41 percentage points greater in the 300-mg group than in the placebo group. Canakinumab did not reduce lipid levels from baseline. At a median follow-up of 3.7 years, the incidence rate for the primary end point was 4.50 events per 100 person-years in the placebo group, 4.11 events per 100 person-years in the 50-mg group, 3.86 events per 100 person-years in the 150-mg group, and 3.90 events per 100 person-years in the 300-mg group. The hazard ratios as compared with placebo were as follows: in the 50-mg group, 0.93 (95% confidence interval [CI], 0.80 to 1.07; P = 0.30); in the 150-mg group, 0.85 (95% CI, 0.74 to 0.98; P = 0.021); and in the 300-mg group, 0.86 (95% CI, 0.75 to 0.99; P = 0.031). The 150-mg dose, but not the other doses, met the prespecified multiplicity-adjusted threshold for statistical significance for the primary end point and the secondary end point that additionally included hospitalization for unstable angina that led to urgent revascularization (hazard ratio vs. placebo, 0.83; 95% CI, 0.73 to 0.95; P = 0.005). Canakinumab was associated with a higher incidence of fatal infection than was placebo. There was no significant difference in all-cause mortality (hazard ratio for all canakinumab doses vs. placebo, 0.94; 95% CI, 0.83 to 1.06; P = 0.31). Conclusions: Antiinflammatory therapy targeting the interleukin-1β innate immunity pathway with canakinumab at a dose of 150 mg every 3 months led to a significantly lower rate of recurrent cardiovascular events than placebo, independent of lipid-level lowering. (Funded by Novartis; CANTOS ClinicalTrials.gov number, NCT01327846.
- …