4,525 research outputs found
From single steps to mass migration: the problem of scale in the movement ecology of the Serengeti wildebeest
A central question in ecology is how to link processes that occur over
different scales. The daily interactions of individual organisms ultimately
determine community dynamics, population fluctuations and the functioning
of entire ecosystems. Observations of these multiscale ecological
processes are constrained by various technological, biological or logistical
issues, and there are often vast discrepancies between the scale at which
observation is possible and the scale of the question of interest. Animal
movement is characterized by processes that act over multiple spatial and
temporal scales. Second-by-second decisions accumulate to produce
annual movement patterns. Individuals influence, and are influenced by,
collective movement decisions, which then govern the spatial distribution
of populations and the connectivity of meta-populations. While the
field of movement ecology is experiencing unprecedented growth in the
availability of movement data, there remain challenges in integrating
observations with questions of ecological interest. In this article, we present
the major challenges of addressing these issues within the context of the
Serengeti wildebeest migration, a keystone ecological phenomena that
crosses multiple scales of space, time and biological complexity.
This article is part of the theme issue ’Collective movement ecology’
A multi-method approach to delineate and validate migratory corridors
Context:
Managers are faced with numerous methods for delineating wildlife movement corridors, and often must make decisions with limited data. Delineated corridors should be robust to different data and models.
Objectives:
We present a multi-method approach for delineating and validating wildlife corridors using multiple data sources, which can be used conserve landscape connectivity. We used this approach to delineate and validate migration corridors for wildebeest (Connochaetes taurinus) in the Tarangire Ecosystem of northern Tanzania.
Methods:
We used two types of locational data (distance sampling detections and GPS collar locations), and three modeling methods (negative binomial regression, logistic regression, and Maxent), to generate resource selection functions (RSFs) and define resistance surfaces. We compared two corridor detection algorithms (cost-distance and circuit theory), to delineate corridors. We validated corridors by comparing random and wildebeest locations that fell within corridors, and cross-validated by data type.
Results:
Both data types produced similar RSFs. Wildebeest consistently selected migration habitat in flatter terrain farther from human settlements. Validation indicated three of the combinations of data type, modeling, and corridor detection algorithms (detection data with Maxent modeling, GPS collar data with logistic regression modeling, and GPS collar data with Maxent modeling, all using cost-distance) far outperformed the other seven. We merged the predictive corridors from these three data-method combinations to reveal habitat with highest probability of use.
Conclusions:
The use of multiple methods ensures that planning is able to prioritize conservation of migration corridors based on all available information
Findings from a pilot randomised trial of an asthma internet self-management intervention (RAISIN)
<b>Objective </b>To evaluate the feasibility of a phase 3
randomised controlled trial (RCT) of a website (Living
Well with Asthma) to support self-management.<p></p>
<b>Design and setting</b> Phase 2, parallel group, RCT,
participants recruited from 20 general practices across
Glasgow, UK. Randomisation through automated voice
response, after baseline data collection, to website
access for minimum 12 weeks or usual care.<p></p>
<b>Participants </b>Adults (age≥16 years) with physician
diagnosed, symptomatic asthma (Asthma Control
Questionnaire (ACQ) score ≥1). People with unstable
asthma or other lung disease were excluded.<p></p>
<b>Intervention</b> Living Well with Asthma’ is a desktop/
laptop compatible interactive website designed with
input from asthma/ behaviour change specialists, and
adults with asthma. It aims to support optimal
medication management, promote use of action plans,
encourage attendance at asthma reviews and increase
physical activity.<p></p>
<b>Outcome measures</b> Primary outcomes were
recruitment/retention, website use, ACQ and mini-
Asthma Quality of Life Questionnaire (AQLQ).
Secondary outcomes included patient activation,
prescribing, adherence, spirometry, lung inflammation
and health service contacts after 12 weeks. Blinding
postrandomisation was not possible.<p></p>
<b>Results </b>Recruitment target met. 51 participants
randomised (25 intervention group). Age range
16–78 years; 75% female; 28% from most deprived
quintile. 45/51 (88%; 20 intervention group) followed
up. 19 (76% of the intervention group) used the
website, for a mean of 18 min (range 0–49). 17 went
beyond the 2 ‘core’ modules. Median number of logins
was 1 (IQR 1–2, range 0–7). No significant difference
in the prespecified primary efficacy measures of ACQ
scores (−0.36; 95% CI −0.96 to 0.23; p=0.225), and
mini-AQLQ scores (0.38; −0.13 to 0.89; p=0.136). No
adverse events.<p></p>
<b>Conclusions</b> Recruitment and retention confirmed
feasibility; trends to improved outcomes suggest use of
Living Well with Asthma may improve self-management
in adults with asthma and merits further development
followed by investigation in a phase 3 trial
Effect of Differential Rotation on the Maximum Mass of Neutron Stars: Realistic Nuclear Equations of State
The merger of binary neutron stars is likely to lead to differentially
rotating remnants. In this paper, we survey several cold nuclear equations of
state (EOSs) and numerically construct models of differentially rotating
neutron stars in general relativity. For each EOS we tabulate maximum allowed
masses as a function of the degree of differential rotation. We also determine
effective polytropic indices, and compare the maximum allowed masses with those
for the corresponding polytropes. We consistently find larger mass increases
for the polytropes, but even for the nuclear EOSs we typically find maximum
masses 50% higher than the corresponding values for nonrotating (TOV) stars. We
evaluate our findings for the six observed binary neutron star (pulsar)
systems, including the recently discovered binary pulsar J0737-3039. For each
EOS we determine whether their merger will automatically lead to prompt
collapse to a black hole, or whether the remnant can be supported against
collapse by uniform rotation (possibly as a supramassive star) or differential
rotation (possibly as a hypermassive star). For hypermassive stars, delayed
collapse to a black hole is likely. For the most recent EOSs we survey the
merger remnants can all be supported by rotation against prompt collapse, but
their actual fate will depend on the nonequilibrium dynamics of the coalescence
event. Gravitational wave observations of coalescing binary neutron stars may
be able to distinguish these outcomes -- no, delayed or prompt collapse -- and
thereby constrain possible EOSs.Comment: 8 pages, 3 figures, submitted to Ap
Lunar drill footplate and casing
To prevent hole collapse during lunar drilling operations, a casing has been devised of a graphite reinforced polyimide composite which will be able to withstand the lunar environment. Additionally, this casing will be inserted into the ground in segments two meters long which will penetrate the regolith simultaneously with the auger. The vertical action of the mobile platform will provide a downward force to the casing string through a special adaptor, giving the casing the needed impetus to sink the anticipated depth of ten meters. Casing segments will be connected with a simple snap arrangement. Excess casing will be cut off by a cylindrical cutting tool which will also transport the excess casing away from the hole. A footplate will be incorporated to grasp the auger rod string during rod segment additions or removals. The footplate grasping mechanism will consist of a set of vice-like arms, one end of each bearing threaded to a common power screw. The power screw will be threaded such that one end's thread pitch opposes that of the other end. The weight of the auger and rod string will be transmitted through the arms to the power screw and absorbed by a set of three ball bearing assemblies. The power screw will be driven by a one-half horsepower brushless motor actuated by radio control. The footplate will rest on four short legs and be anchored with pins that are an integral part of each leg
Mutations in the E2 glycoprotein and the 3\u27 untranslated region enhance chikungunya virus virulence in mice
Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that causes debilitating musculoskeletal pain and inflammation and can persist for months to years after acute infection. Although studies of humans and experimentally infected animals suggest that CHIKV infection persists in musculoskeletal tissues, the mechanisms for this remain poorly understood. To evaluate this further, we isolated CHIKV from the serum of persistently infected Rag1 -/- mice at day 28. When inoculated into naive wild-type (WT) mice, this persistently circulating CHIKV strain displayed a capacity for earlier dissemination and greater pathogenicity than the parental virus. Sequence analysis revealed a nonsynonymous mutation in the E2 glycoprotein (E2 K200R) and a deletion within the 3' untranslated region (3'-UTR). The introduction of these changes into the parental virus conferred enhanced virulence in mice, although primary tropism for musculoskeletal tissues was maintained. The E2 K200R mutation was largely responsible for enhanced viral dissemination and pathogenicity, although these effects were augmented by the 3'- UTR deletion. Finally, studies with Irf3/Irf7 -/- and Ifnar1 -/- mice suggest that the E2 K200R mutation enhances viral dissemination from the site of inoculation independently of interferon regulatory factor 3 (IRF3)-, IRF7-, and IFNAR1-mediated responses. As our findings reveal viral determinants of CHIKV dissemination and pathogenicity, their further study should help to elucidate host-virus interactions that determine acute and chronic CHIKV infection
Measurements of the Diffuse Ultraviolet Background and the Terrestrial Airglow with the Space Telescope Imaging Spectrograph
Far-UV observations in and near the Hubble Deep Fields demonstrate that the
Space Telescope Imaging Spectrograph (STIS) can potentially obtain unique and
precise measurements of the diffuse far-ultraviolet background. Although STIS
is not the ideal instrument for such measurements, high-resolution images allow
Galactic and extragalactic objects to be masked to very faint magnitudes, thus
ensuring a measurement of the truly diffuse UV signal. The programs we have
analyzed were not designed for this scientific purpose, but would be sufficient
to obtain a very sensitive measurement if it were not for a weak but
larger-than-expected signal from airglow in the STIS 1450-1900 A bandpass. Our
analysis shows that STIS far-UV crystal quartz observations taken near the limb
during orbital day can detect a faint airglow signal, most likely from NI\1493,
that is comparable to the dark rate and inseparable from the far-UV background.
Discarding all but the night data from these datasets gives a diffuse
far-ultraviolet background measurement of 501 +/- 103 ph/cm2/sec/ster/A, along
a line of sight with very low Galactic neutral hydrogen column (N_HI = 1.5E20
cm-2) and extinction (E(B-V)=0.01 mag). This result is in good agreement with
earlier measurements of the far-UV background, and should not include any
significant contribution from airglow. We present our findings as a warning to
other groups who may use the STIS far-UV camera to observe faint extended
targets, and to demonstrate how this measurement may be properly obtained with
STIS.Comment: 7 pages, Latex. 4 figures. Uses corrected version of emulateapj.sty
and apjfonts.sty (included). Accepted for publication in A
Informing aerial total counts with demographic models: population growth of Serengeti elephants not explained purely by demography
Conservation management is strongly shaped by the interpretation of population trends. In the Serengeti ecosystem, Tanzania, aerial total counts indicate a striking increase in elephant abundance compared to all previous censuses. We developed a simple age-structured population model to guide interpretation of this reported increase, focusing on three possible causes: (1) in situ population growth, (2) immigration from Kenya, and (3) differences in counting methodologies over time. No single cause, nor the combination of two causes, adequately explained the observed population growth. Under the assumptions of maximum in situ growth and detection bias of 12.7% in previous censuses, conservative estimates of immigration from Kenya were between 250 and 1,450 individuals. Our results highlight the value of considering demography when drawing conclusions about the causes of population trends. The issues we illustrate apply to other species that have undergone dramatic changes in abundance, as well as many elephant populations
Evaluating the crystalline orbital hierarchy and high pressure structure property response of an extended-ligand platinum(II) bis(1,2 dioximato) complex
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