1,912 research outputs found
A non-invasive approach to estimate the energetic requirements of an increasing seabird population in a perturbed marine ecosystem
This is the author accepted manuscript. The final version is available from Springer Nature via the DOI in this record.There is a growing desire to integrate the food requirements of predators living in marine
ecosystems impacted by humans into sustainable fisheries management. We used non-
invasive video-recording, photography and focal observations to build time-energy budget
models and to directly estimate the fish mass delivered to chicks by adult greater crested terns
Thalasseus bergii breeding in the Benguela ecosystem. Mean modelled adult daily food
intake increased from 140.9 g·d−1 of anchovy Engraulis capensis during incubation to 171.7g·d−1
and 189.2 g·d−1 when provisioning small and large chicks, respectively. Modelled prey
intake expected to be returned to chicks was 58.3 g·d−1 (95% credible intervals: 44.9–75.8 g·d−1)
over the entire growth period. Based on our observations, chicks were fed 19.9 g·d−1
(17.2–23.0 g·d−1) to 45.1 g·d−1 (34.6–58.7 g·d−1 25 ) of anchovy during early and late
provisioning, respectively. Greater crested terns have lower energetic requirements at the
individual (range: 15–34%) and population level (range: 1–7%) than the other Benguela
endemic seabirds that feed on forage fish. These modest requirements – based on a small
body size and low flight costs – coupled with foraging plasticity have allowed greater crested
terns to cope with changing prey availability, unlike the other seabirds species using the same
exploited prey base.Our research was supported by a Department of Science and Technology-National Research
Foundation Centre of Excellence grant to the FitzPatrick Institute of African Ornithology, the
Leiden Conservation Foundation (RBS) and our institutes. Robben Island Museum provided
logistical support and access to the tern colonies
The costs of kleptoparasitism: a study of mixed-species seabird breeding colonies
This is the author accepted manuscript. The final version is available from OUP via the DOI in this record.Mixed-species assemblages are common in nature, providing mutual benefits to associating species including anti-predator advantages or resource facilitation. However, associating with other species may also impose costs through kleptoparasitism (food theft). Identification of these costs, and how they vary when different species breed alongside one another, is essential to understand the payoffs of mixed-species assemblages. We explore the costs of kleptoparasitism for greater crested terns Thalasseus bergii provisioning offspring at a single-species colony, where individuals suffer kleptoparasitism from conspecifics, and at a mixed colony where terns breed alongside Hartlaub’s gulls Chroicocephalus hartlaubii and are vulnerable to both intra and interspecific kleptoparasitism. Gull presence likely contributes to increases in both kleptoparasitic attacks and the proportion of prey lost or stolen during provisioning, relative to the single-species colony. Provisioning adults suffered additional energetic costs in response to gull kleptoparasitism, requiring more attempts to deliver prey, taking longer to do so, and swallowing more prey (to the detriment of their offspring). Gulls also appear to increase the duration of tern vulnerability to kleptoparasitism, because they continued to steal food from adults and chicks after precocial chicks left the nest, when intraspecific kleptoparasitism is negligible. Terns breeding in a mixed colony, therefore, suffer direct and indirect costs through decreased provisioning and increased provisioning effort, which may ultimately affect reproductive success, resulting in colony decline where kleptoparasitism is frequent. This study illustrates how forming a mixed-species seabird breeding assemblage has costs as well as benefits, potentially fluctuating between a parasitic and a mutualistic relationship.This work was supported by a Department of Science and TechnologyCentre
of Excellence grant to the FitzPatrick Institute of African
Ornithology. R.B.S. was supported by a fellowship from the Leiden
Conservation Foundation. This research was approved by SANParks
(CONM1182), the Department of Environmental Affairs (RES2013/24,
RES2014/83, and RES2015/65) and the animal ethics committee of the
University of Cape Town (2013/V3/TC)
Self-reported Needs of Youth and Families: Informing System Change and Advocacy Efforts
This study sought to explore caregiver-reported needs of youth and families receiving services within a System of Care (SOC). Data were collected to augment the in-depth, standardized interview protocols that are part of the National Evaluation of SOCs in order to identify gaps in the local delivery of services and supports to youth with severe emotional and/or behavioral disorders and their families. Primary caregivers of youth receiving services within the SOC were asked to report on the current need(s) of the youth and the current need(s) of the family. These open-ended responses were coded and examined for themes. The most common needs of the youth were Services and Life Management, while the most common needs of the family were Services and Financial. Focus groups conducted with youth and caregivers confirmed these themes. Findings from this study shed light on the diverse needs of these families, indicate that families believe they are not receiving adequate supports and services, underscore that youth have distinct views, and highlight that providing a way for the typically disenfranchised youth and families to express their perspective is central to the functioning of SOCs. Study findings were used by a local nonprofit organization to inform their advocacy efforts, and were incorporated into an enrollment process at a local mental health agency are part of a programmatic change pilot effort
Self-reported Needs of Youth and Families: Informing System Change and Advocacy Efforts
This study sought to explore caregiver-reported needs of youth and families receiving services within a System of Care (SOC). Data were collected to augment the in-depth, standardized interview protocols that are part of the National Evaluation of SOCs in order to identify gaps in the local delivery of services and supports to youth with severe emotional and/or behavioral disorders and their families. Primary caregivers of youth receiving services within the SOC were asked to report on the current need(s) of the youth and the current need(s) of the family. These open-ended responses were coded and examined for themes. The most common needs of the youth were Services and Life Management, while the most common needs of the family were Services and Financial. Focus groups conducted with youth and caregivers confirmed these themes. Findings from this study shed light on the diverse needs of these families, indicate that families believe they are not receiving adequate supports and services, underscore that youth have distinct views, and highlight that providing a way for the typically disenfranchised youth and families to express their perspective is central to the functioning of SOCs. Study findings were used by a local nonprofit organization to inform their advocacy efforts, and were incorporated into an enrollment process at a local mental health agency are part of a programmatic change pilot effort
Innermost stable circular orbits around relativistic rotating stars
We investigate the innermost stable circular orbit (ISCO) of a test particle
moving on the equatorial plane around rotating relativistic stars such as
neutron stars. First, we derive approximate analytic formulas for the angular
velocity and circumferential radius at the ISCO making use of an approximate
relativistic solution which is characterized by arbitrary mass, spin, mass
quadrupole, current octapole and mass -pole moments. Then, we show that
the analytic formulas are accurate enough by comparing them with numerical
results, which are obtained by analyzing the vacuum exterior around numerically
computed geometries for rotating stars of polytropic equation of state. We
demonstrate that contribution of mass quadrupole moment for determining the
angular velocity and, in particular, the circumferential radius at the ISCO
around a rapidly rotating star is as important as that of spin.Comment: 12 pages, 2 figures, accepted for publication in Phys. Rev.
Recommended from our members
Alterations to the Gastrointestinal Microbiome Associated with Methamphetamine Use among Young Men who have Sex with Men.
Methamphetamine (MA) use is a major public health problem in the United States, especially among people living with HIV (PLWH). Many MA-induced neurotoxic effects are mediated by inflammation and gut microbiota may play a role in this process, yet the effects of MA on the microbiome have not been adequately explored. Therefore, we performed 16S rRNA gene sequencing on rectal swab samples from 381 men who have sex with men, 48% of whom were PLWH and 41% of whom used MA. We compared microbiome composition between MA users and non-users while testing for potential interactions with HIV and controlling for numerous confounders using inverse probability of treatment weighting. We found that MA use explained significant variation in overall composition (R2 = 0.005, p = 0.008) and was associated with elevated Finegoldia, Parvimonas, Peptoniphilus, and Porphyromonas and reduced Butyricicoccus and Faecalibacterium, among others. Genera including Actinomyces and Streptobacillus interacted with HIV status, such that they were increased in HIV+ MA users. Finegoldia and Peptoniphilus increased with increasing frequency of MA use, among others. In summary, MA use was associated with a microbial imbalance favoring pro-inflammatory bacteria, including some with neuroactive potential and others that have previously been associated with poor HIV outcomes
Safety of the Deferral of Coronary Revascularization on the Basis of Instantaneous Wave-Free Ratio and Fractional Flow Reserve Measurements in Stable Coronary Artery Disease and Acute Coronary Syndromes.
OBJECTIVES:
The aim of this study was to investigate the clinical outcomes of patients deferred from coronary revascularization on the basis of instantaneous wave-free ratio (iFR) or fractional flow reserve (FFR) measurements in stable angina pectoris (SAP) and acute coronary syndromes (ACS).
BACKGROUND:
Assessment of coronary stenosis severity with pressure guidewires is recommended to determine the need for myocardial revascularization.
METHODS:
The safety of deferral of coronary revascularization in the pooled per-protocol population (n = 4,486) of the DEFINE-FLAIR (Functional Lesion Assessment of Intermediate Stenosis to Guide Revascularisation) and iFR-SWEDEHEART (Instantaneous Wave-Free Ratio Versus Fractional Flow Reserve in Patients With Stable Angina Pectoris or Acute Coronary Syndrome) randomized clinical trials was investigated. Patients were stratified according to revascularization decision making on the basis of iFR or FFR and to clinical presentation (SAP or ACS). The primary endpoint was major adverse cardiac events (MACE), defined as the composite of all-cause death, nonfatal myocardial infarction, or unplanned revascularization at 1 year.
RESULTS:
Coronary revascularization was deferred in 2,130 patients. Deferral was performed in 1,117 patients (50%) in the iFR group and 1,013 patients (45%) in the FFR group (p < 0.01). At 1 year, the MACE rate in the deferred population was similar between the iFR and FFR groups (4.12% vs. 4.05%; fully adjusted hazard ratio: 1.13; 95% confidence interval: 0.72 to 1.79; p = 0.60). A clinical presentation with ACS was associated with a higher MACE rate compared with SAP in deferred patients (5.91% vs. 3.64% in ACS and SAP, respectively; fully adjusted hazard ratio: 0.61 in favor of SAP; 95% confidence interval: 0.38 to 0.99; p = 0.04).
CONCLUSIONS:
Overall, deferral of revascularization is equally safe with both iFR and FFR, with a low MACE rate of about 4%. Lesions were more frequently deferred when iFR was used to assess physiological significance. In deferred patients presenting with ACS, the event rate was significantly increased compared with SAP at 1 year.info:eu-repo/semantics/publishedVersio
Quadrupole moments of rotating neutron stars
Numerical models of rotating neutron stars are constructed for four equations
of state using the computer code RNS written by Stergioulas. For five selected
values of the star's gravitational mass (in the interval between 1.0 and 1.8
solar masses) and for each equation of state, the star's angular momentum is
varied from J=0 to the Keplerian limit J=J_{max}. For each neutron-star
configuration we compute Q, the quadrupole moment of the mass distribution. We
show that for given values of M and J, |Q| increases with the stiffness of the
equation of state. For fixed mass and equation of state, the dependence on J is
well reproduced with a simple quadratic fit, Q \simeq - aJ^2/M c^2, where c is
the speed of light, and a is a parameter of order unity depending on the mass
and the equation of state.Comment: ReVTeX, 7 pages, 5 figures, additional material, and references adde
Parenting in a warming world: thermoregulatory responses to heat stress in an endangered seabird
This is the final version. Available on open access from Oxford University Press via the DOI in this recordThe frequency of extreme weather events, including heat waves, is increasing with climate change. The thermoregulatory demands resulting from hotter weather can have catastrophic impacts on animals, leading to mass mortalities. Although less dramatic, animals also experience physiological costs below, but approaching, critical temperature thresholds. These costs may be particularly constraining during reproduction, when parents must balance thermoregulation against breeding activities. Such challenges should be acute among seabirds, which often nest in locations exposed to high solar radiation and predation risk. The globally endangered bank cormorant Phalacrocorax neglectus breeds in southern Africa in the winter, giving little scope for poleward or phenological shifts in the face of increasing temperatures. Physiological studies of endangered species sensitive to human disturbance, like the bank cormorant, are challenging, because individuals cannot be captured for experimental research. Using a novel, non-invasive, videographic approach, we investigated the thermoregulatory responses of this seabird across a range of environmental temperatures at three nesting colonies. The time birds spent gular fluttering, a behaviour enhancing evaporative heat loss, increased with temperature. Crouching or standing birds spent considerably less time gular fluttering than birds sitting on nests (ca 30% less at 22°C), showing that postural adjustments mediate exposure to heat stress and enhance water conservation. Crouching or standing, however, increases the vulnerability of eggs and chicks to suboptimal temperatures and/or expose nest contents to predation, suggesting that parents may trade-off thermoregulatory demands against offspring survival. We modelled thermoregulatory responses under future climate scenarios and found that nest-bound bank cormorants will gular flutter almost continuously for several hours a day by 2100. The associated increase in water loss may lead to dehydration, forcing birds to prioritize survival over breeding, a trade-off that would ultimately deteriorate the conservation status of this species.National Research FoundationDST-NRF Centre of Excellence fund at the FitzPatrick Institute of African OrnithologyLeiden Conservation Foundatio
Generation and Suppression of Decoherence in Artificial Environment for Qubit System
It is known that a quantum system with finite degrees of freedom can simulate
a composite of a system and an environment if the state of the hypothetical
environment is randomized by external manipulation. We show theoretically that
any phase decoherence phenomena of a single qubit can be simulated with a
two-qubit system and demonstrate experimentally two examples: one is phase
decoherence of a single qubit in a transmission line, and the other is that in
a quantum memory. We perform NMR experiments employing a two-spin molecule and
clearly measure decoherence for both cases. We also prove experimentally that
the bang-bang control efficiently suppresses decoherence.Comment: 25 pages, 7 figures; added reference
- …