454 research outputs found
Recommended from our members
In Search of the Solar Wind Nitrogen Isotope Composition: Analysis of a Gold Plate from the Genesis Spacecraft Concentrator
We report N isotope analysis of a gold plate from the Genesis spacecraft concentrator. We did not find evidence for a light N component in the solar wind
Understanding the threats posed by non-native species: public vs. conservation managers.
Public perception is a key factor influencing current conservation policy. Therefore, it is important to determine the influence of the public, end-users and scientists on the prioritisation of conservation issues and the direct implications for policy makers. Here, we assessed public attitudes and the perception of conservation managers to five non-native species in the UK, with these supplemented by those of an ecosystem user, freshwater anglers. We found that threat perception was not influenced by the volume of scientific research or by the actual threats posed by the specific non-native species. Media interest also reflected public perception and vice versa. Anglers were most concerned with perceived threats to their recreational activities but their concerns did not correspond to the greatest demonstrated ecological threat. The perception of conservation managers was an amalgamation of public and angler opinions but was mismatched to quantified ecological risks of the species. As this suggests that invasive species management in the UK is vulnerable to a knowledge gap, researchers must consider the intrinsic characteristics of their study species to determine whether raising public perception will be effective. The case study of the topmouth gudgeon Pseudorasbora parva reveals that media pressure and political debate has greater capacity to ignite policy changes and impact studies on non-native species than scientific evidence alone
Discovery of a flux-related change of the cyclotron line energy in Her X-1
We present the results of ten years of repeated measurements of the Cyclotron
Resonance Scattering Feature (CRSF) in the spectrum of the binary X-ray pulsar
Her X-1 and report the discovery of a positive correlation of the centroid
energy of this absorption feature in pulse phase averaged spectra with source
luminosity.Our results are based on a uniform analysis of observations bythe
RXTE satellite from 1996 to 2005, using sufficiently long observations of 12
individual 35-day Main-On states of the source. The mean centroid energy E_c of
the CRSF in pulse phase averaged spectra of Her X-1 during this time is around
40 keV, with significant variations from one Main-On state to the next. We find
that the centroid energy of the CRSF in Her X-1 changes by ~5% in energy for a
factor of 2 in luminosity. The correlation is positive, contrary to what is
observed in some high luminosity transient pulsars. Our finding is the first
significant measurement of a positive correlation between E_c and luminosity in
any X-ray pulsar. We suggest that this behaviour is expected in the case of
sub-Eddington accretion and present a calculation of a quantitative estimate,
which is very consistent with the effect observed in Her X-1.We urge that Her
X-1 is regularly monitored further and that other X-ray pulsars are
investigated for a similar behaviour.Comment: 4 pages, 2 figures, accepted by A&A Letter
Cloacal and Ocular Microbiota of the Endangered Australian Northern Quoll
The Australian northern quoll is an important predatory marsupial carnivore that is currently endangered due to inappropriate fire regimes, predation, and the spread of invasive cane toads. The microbiota of Australian marsupials has not been extensively studied, but is thought to play a role in their health. This study provides an initial characterization of the cloacal microbiota of the northern quoll, as well as other marsupials including possums and kangaroos which were opportunistically sampled. The northern quoll cloaca microbiota was dominated by Enterococcus and Lactobacillus and had a relatively high proportion of members of the Proteobacteria phylum, which has been observed in other carnivorous marsupials. The diversity and structure of the microbiota was not influenced by presence of Chlamydiales which are intracellular bacteria and potential pathogens. The microbiota of the other marsupials was quite varied, which may be related to their health status. Characterization of the northern quoll microbiota will help to better understand the biology of this endangered animal
Molecular evidence of Chlamydia pecorum and arthropod-associated Chlamydiae in an expanded range of marsupials
© 2017 The Author(s). The order Chlamydiales are biphasic intracellular bacterial pathogens infecting humans and domesticated animals. Wildlife infections have also been reported, with the most studied example being Chlamydia pecorum infections in the koala, an iconic Australian marsupial. In koalas, molecular evidence suggests that spill-over from C. pecorum infected livestock imported into Australia may have had a historical or contemporary role. Despite preliminary evidence that other native Australian marsupials also carry C. pecorum, their potential as reservoirs of this pathogen and other Chlamydia-related bacteria (CRBs) has been understudied. Mucosal epithelial samples collected from over 200 native Australian marsupials of different species and geographic regions across Australia were PCR screened for Chlamydiales. Previously described and genetically distinct C. pecorum genotypes and a range of 16S rRNA genotypes sharing similarity to different CRBs in the broader Chlamydiales order were present. One 16S rRNA Chlamydiales genotype recently described in Australian ticks that parasitise native Australian marsupials was also identified. This study provides further evidence that chlamydial infections are widespread in native fauna and that detailed investigations are required to understand the influence these infections have on host species conservation, but also whether infection spill-over plays a role in their epidemiology
Patients' experiences of illness, operation and outcome with reference to gastro-oesophageal reflux disease.
Background. Describing the illness-story from a patient perspective could increase understanding of living with a chronic disease for health professionals and others, facilitate decision-making about treatment and enhance information about the outcome from a patient perspective. Aim. To illuminate patients' illness experiences of having a gastro-oesophageal reflux disease (GORD), going through surgery and the outcome. Methods. Twelve patients were interviewed 5 years after having had the operation; six patients had had fundoplication via laparoscopy and six via open surgery. Each patient was asked to talk openly about their experiences, thoughts, feelings and consequences of living with the illness, going through surgery and the period from surgery to the day of interview. A qualitative content analysis was performed concerning the context of the data and its meaning. Findings. Three central categories were identified and nine subcategories: living with GORD- symptoms of the disease affecting daily living, taking medicines, work, family and social life; concerns related to surgery- decision-making about the operation, influence by physicians; life after the operation- outcomes and consequences, side-effects and complications of the operation, sick leave, information and sharing experiences with future patients. All patients were free from symptoms of the illness after surgery independent of type of surgery, but side-effects from surgical treatment varied individually. Interviewees would have liked information concerning side-effects after surgery from previous patients. Conclusions. This study contributes to knowledge about patients' long-term suffering, their control of symptoms and how they have tried to cure themselves, but also about their concerns about surgery and the importance of surgical treatment to their quality of life. They wanted information about treatment, outcome and consequences, not only from a health care perspective but also from previous patients having had the same treatment
Spectral Formation in Accreting X-Ray Pulsars: Bimodal Variation of the Cyclotron Energy with Luminosity
Accretion-powered X-ray pulsars exhibit significant variability of the
Cyclotron Resonance Scattering Feature (CRSF) centroid energy on pulse-to-pulse
timescales, and also on much longer timescales. Two types of spectral
variability are observed. For sources in group 1, the CRSF energy is negatively
correlated with the variable source luminosity, and for sources in group 2, the
opposite behavior is observed. The physical basis for this bimodal behavior is
currently not understood. We explore the hypothesis that the accretion dynamics
in the group 1 sources is dominated by radiation pressure near the stellar
surface, and that Coulomb interactions decelerate the gas to rest in the group
2 sources. We derive a new expression for the critical luminosity such that
radiation pressure decelerates the matter to rest in the supercritical sources.
The formula for the critical luminosity is evaluated for 5 sources, using the
maximum value of the CRSF centroid energy to estimate the surface magnetic
field strength. The results confirm that the group 1 sources are supercritical
and the group 2 sources are subcritical, although the situation is less clear
for those highly variable sources that cross over the critical line. We also
explain the variation of the CRSF energy with luminosity as a consequence of
the variation of the characteristic emission height. The sign of the height
variation is opposite in the supercritical and subcritical cases, hence
creating the observed bimodal behavior.Comment: Accepted for publication in Astronomy & Astrophysic
Argon, krypton, and xenon abundances in the solar wind measured in silicon from the genesis mission
Up to now solar wind (SW) abundances of Kr and Xe
have been exclusively determined using SW irradiated regolith [1]. Hence,
one of Genesis’s major objectives is to obtain the heavy noble gas
composition of the present-day SW using artificial targets exposed to the SW
for 2.5 years. SW abundances will allow to study fractionation processes
upon SW formation, e.g., due to the first ionization potential (FIP-effect) [2].
This is of importance to deduce solar abundances of noble gases and other
elements from SW data. Solar, i.e., photospheric, abundances of noble gases
are indirectly determined due to the lack of suitable lines in the spectrum.
Recently, solar abundance estimates for Ne and Ar were strongly reduced
whereas Kr and Xe changed only slightly [3]. This led to a dramatic decrease
of the solar Ar/Kr ratio by a factor of ~3 from the earlier value [4] of 2140. If
true, this change would invalidate theories of heavy noble gas fractionation in
the SW identified with regolith data [1, 5]. The Kr and Xe composition in
present-day SW will enable us to reassess solar abundances and fractionation
theories. Thus, we concentrate here on abundances of Ar, Kr and Xe in the
bulk SW
Entrepreneurship education as human capital: implications for youth self-employment and conflict mitigation in sub-Saharan Africa
Previous research has focused on stable developed economies to predict that human capital and entrepreneurship education (EE) provision at the higher education (HE) level will positively affect entrepreneurial success. This article draws on the outcome of recent EE projects in two HE institutions in a conflict-torn northern Nigeria as a proxy to advocate the introduction of entrepreneurship as a compulsory component into the secondary school curriculum in Sub-Saharan Africa. Using semi-structured interview data, it is found that the provision of EE at secondary education level could help to facilitate human capital development and assist efforts to curb youth unemployment. Specifically, the study suggests that EE comprises both generic and specific human capital that increases an individual’s ability to identify and exploit opportunities, particularly for young people, and in doing so helps to reduce their vulnerability to poverty and involvement in armed conflict. Suggestions for future research and policy considerations are provided
- …