9,350 research outputs found
Range Constraints for Introduced Elk in Southwest Yukon, Canada
Forage availability, snow depths, and winter temperatures were assessed to determine if they might impose range constraints on introduced elk (Cervus elaphus) that voluntarily colonized a 95 km2 area of southwest Yukon (Canada) in 1959. Parkland-like vegetation of stunted aspen (Populus tremuloides) and nonforest upland plant communities, which is atypical vegetation for a boreal forest environment, composed 30% of the colonized area. About 95% of the area produced less than 300 kg/ha of forage, which represents poor productivity compared to more southern elk ranges. In the remaining 5%, indigenous graminoid communities produced (average ± SD) 408 ± 131 kg/ha of forage, exceeded only by nonindigenous roadside vegetation with 652 ± 115 kg/ha. Data from radio-collared animals indicated that most elk occurrences (38% year-round) were associated with parkland-like vegetation, and fecal pellet groups were six times as frequent in indigenous graminoid vegetation as in forest vegetation. Late February 2011 snow depths of 41 ± 7 cm, during a year with a below-normal snowfall, suggested a potential for reduced winter access to forage. Meteorological data from 1981 â 2010 indicate that one-third of winter daily minima in the study area were likely lower than â20ËC, a threshold below which the metabolism of an elk calf must increase to maintain its body temperature. Each assessed habitat variable was unfavorable to elk compared with other western North American winter ranges, which may have limited the development of a more robust population in the southwestern Yukon.La disponibilitĂ© des fourrages, lâĂ©paisseur de couche de neige et les tempĂ©ratures hivernales ont Ă©tĂ© Ă©valuĂ©es afin de dĂ©terminer si elles sont susceptibles dâimposer des contraintes Ă lâaire de rĂ©partition du wapiti (Cervus elaphus) introduit en 1959 en vue de la colonisation volontaire dâune aire de 95 km2 du sud-ouest du Yukon (Canada). La vĂ©gĂ©tation de type forĂȘt-parc composĂ©e de trembles rabougris (Populus tremuloides) et les communautĂ©s de plantes non forestiĂšres en montagne, soit une vĂ©gĂ©tation atypique en milieu de forĂȘt borĂ©ale, composent 30 % de la zone colonisĂ©e. Environ 95 % de la zone visĂ©e produisait moins de 300 kg de fourrage par hectare, ce qui constitue une productivitĂ© mĂ©diocre comparativement aux aires de rĂ©partition de wapitis se trouvant plus au sud. Dans le 5 % qui reste, les communautĂ©s graminoĂŻdes indigĂšnes produisaient (moyenne ± Ă©cart-type) 408 ± 131 kg/ha de fourrage, ce qui Ă©tait dĂ©passĂ© seulement par la vĂ©gĂ©tation non indigĂšne en bordure de route de 652 ± 115 kg/ha. Les donnĂ©es obtenues grĂące aux bĂȘtes dotĂ©es de colliers Ă©metteurs ont indiquĂ© que la plupart des occurrences de wapitis (38 % Ă lâannĂ©e) survenaient dans la vĂ©gĂ©tation de type forĂȘt-parc. Par ailleurs, les groupements de pelotes fĂ©cales se retrouvaient six fois plus souvent dans la vĂ©gĂ©tation graminoĂŻde indigĂšne que dans la vĂ©gĂ©tation forestiĂšre. LâĂ©paisseur de couche de neige de 41 ± 7 cm enregistrĂ©e Ă la fin fĂ©vrier 2011, une annĂ©e oĂč les chutes de neige ont Ă©tĂ© infĂ©rieures Ă la normale, suggĂšrent que lâaccĂšs au fourrage pourrait ĂȘtre rĂ©duit lâhiver. Les donnĂ©es mĂ©tĂ©orologiques prĂ©levĂ©es de 1981 Ă 2010 indiquent que le tiers des tempĂ©ratures minimales quotidiennes hivernales dans la zone Ă lâĂ©tude Ă©taient vraisemblaÂblement infĂ©rieures Ă â20 ËC, un seuil en dessous duquel le mĂ©tabolisme dâun jeune wapiti doit sâĂ©lever pour maintenir sa tempĂ©rature corporelle. Chacune des variables de lâhabitat qui a Ă©tĂ© Ă©valuĂ©e nâĂ©tait pas favorable au wapiti, comparativement Ă dâautres aires de rĂ©partition dâhiver de lâOuest nord-amĂ©ricain, ce qui pourrait avoir eu pour effet de restreindre la formation dâune population plus robuste dans le sud-ouest du Yukon
The Transition Between Quantum Coherence and Incoherence
We show that a transformed Caldeira-Leggett Hamltonian has two distinct
families of fixed points, rather than a single unique fixed point as often
conjectured based on its connection to the anisotropic Kondo model. The two
families are distinguished by a sharp qualitative difference in their quantum
coherence properties and we argue that this distinction is best understood as
the result of a transition in the model between degeneracy and non-degeneracy
in the spectral function of the ``spin-flip'' operator.Comment: some typos corrected and a reference adde
Discovery of Molecular Gas in the Outflow and Tidal Arms around M82
We present the first fully sampled map of 12CO (1-0) emission from M82
covering the entire galaxy. Our map contains a 12 x 15 kpc^2 area. We find that
extraplanar CO emission, previously reported at short distances above the
galactic plane, extends to heights of up to 6 kpc above the disk. Some of this
emission is associated with tidal arms seen in HI, implying either that M82
contained substantial amounts of molecular gas in the outer disk, or that
molecular gas formed after the tidal features. CO emission along the direction
of the outflow extends to distances of 3 kpc above and below the disk. At this
distance, the line is shifted in velocity about 100 km/s, and has the same
sense as the galactic outflow from the central starburst. This implies that
molecular gas may be entrained into the outflow.Comment: 4 pages, 6 figures. Uses emulateapj5. Accepted by ApJ Letter
Cosmic-Ray Nuclei, Antiprotons and Gamma-rays in the Galaxy: a New Diffusion Model
We model the transport of cosmic ray nuclei in the Galaxy by means of a new
numerical code. Differently from previous numerical models we account for a
generic spatial distribution of the diffusion coefficient. We found that in the
case of radially uniform diffusion, the main secondary/primary ratios (B/C, N/O
and sub-Fe/Fe) and the modulated antiproton spectrum match consistently the
available observations. Convection and re-acceleration do not seem to be
required in the energy range we consider: GeV/nucleon. We
generalize these results accounting for radial dependence of the diffusion
coefficient, which is assumed to trace that of the cosmic ray sources. While
this does not affect the prediction of secondary/primary ratios, the simulated
longitude profile of the diffuse -ray emission is significantly
different from the uniform case and may agree with EGRET measurements without
invoking ad hoc assumptions on the galactic gas density distribution.Comment: 17 pages, 6 figures. v3: Added detailed references to nuclear
cross-section networ
Interprofessional Learning during an International Fieldwork Placement
The need for competent interprofessional health care professionals is well recognised. Various educational activities have been developed to facilitate the development of interprofessional competence. In this paper we describe an interprofessional, fieldwork experience conducted in a developing country, and the learning gained by the first cohort of students who completed the five week immersion. Eight final year students from Medicine, Occupational Therapy, Physiotherapy and Speech Pathology were interviewed pre- and post-placement by an independent researcher. The transcribed interviews were analysed thematically. Findings indicated that over the placement students gained an appreciation of the skills of the other disciplines and were able to move beyond a textbook definition of what a certain profession did to acquire a real understanding of interprofessional practice. However, students reported that this understanding was predicated on their first clarifying the extent to which they were working in a transdisciplinary or interdisciplinary team, and becoming more confident in their own disciplinary contribution without reliance on formal documentation or standardised assessments. Using daily team discussions, self-reflections and discussions with clinical educators, the students learned to prioritise their busy caseload, share resources and skills, and facilitate team members to achieve therapeutic goals. The interprofessional learning took place in an intercultural context where the students learned to work with children with severe disabilities, with staff with different classroom approaches, and with interpreters, while adjusting emotionally to the level of unmet need of many of the children. Based on the students' experiences, immersion in an intercultural fieldwork experience is a useful way to facilitate interprofessional learning
The HTA risk analysis chart: visualising the need for and potential value of managed entry agreements in health technology assessment
Background
Recent changes to the regulatory landscape of pharmaceuticals may sometimes require reimbursement authorities to issue guidance on technologies that have a less mature evidence base. Decision makers need to be aware of risks associated with such health technology assessment (HTA) decisions and the potential to manage this risk through managed entry agreements (MEAs).
Objective
This work develops methods for quantifying risk associated with specific MEAs and for clearly communicating this to decision makers.
Methods
We develop the âHTA risk analysis chartâ, in which we present the payer strategy and uncertainty burden (P-SUB) as a measure of overall risk. The P-SUB consists of the payer uncertainty burden (PUB), the risk stemming from decision uncertainty as to which is the truly optimal technology from the relevant set of technologies, and the payer strategy burden (PSB), the additional risk of approving a technology that is not expected to be optimal. We demonstrate the approach using three recent technology appraisals from the UK National Institute for Health and Clinical Excellence (NICE), each of which considered a price-based MEA.
Results
The HTA risk analysis chart was calculated using results from standard probabilistic sensitivity analyses. In all three HTAs, the new interventions were associated with substantial risk as measured by the P-SUB. For one of these technologies, the P-SUB was reduced to zero with the proposed price reduction, making this intervention cost effective with near complete certainty. For the other two, the risk reduced substantially with a much reduced PSB and a slightly increased PUB.
Conclusions
The HTA risk analysis chart shows the risk that the healthcare payer incurs under unresolved decision uncertainty and when considering recommending a technology that is not expected to be optimal given current evidence. This allows the simultaneous consideration of financial and data-collection MEA schemes in an easily understood format. The use of HTA risk analysis charts will help to ensure that MEAs are considered within a standard utility-maximising health economic decision-making framework
The Mass Function of Super Giant Molecular Complexes and Implications for Forming Young Massive Star Clusters in the Antennae (NGC 4038/39)
We have used previously published observations of the CO emission from the
Antennae (NGC 4038/39) to study the detailed properties of the super giant
molecular complexes with the goal of understanding the formation of young
massive star clusters. Over a mass range from 5E6 to 9E8 solar masses, the
molecular complexes follow a power-law mass function with a slope of -1.4 +/-
0.1, which is very similar to the slope seen at lower masses in molecular
clouds and cloud cores in the Galaxy. Compared to the spiral galaxy M51, which
has a similar surface density and total mass of molecular gas, the Antennae
contain clouds that are an order of magnitude more massive. Many of the
youngest star clusters lie in the gas-rich overlap region, where extinctions as
high as Av~100 imply that the clusters must lie in front of the gas. Combining
data on the young clusters, thermal and nonthermal radio sources, and the
molecular gas suggests that young massive clusters could have formed at a
constant rate in the Antennae over the last 160 Myr and that sufficient gas
exists to sustain this cluster formation rate well into the future. However,
this conclusion requires that a very high fraction of the massive clusters that
form initially in the Antennae do not survive as long as 100 Myr. Finally, we
compare our data with two models for massive star cluster formation and
conclude that the model where young massive star clusters form from dense cores
within the observed super giant molecular complexes is most consistent with our
current understanding of this merging system. (abbreviated)Comment: 40 pages, four figures; accepted for publication in Ap
Positrons from particle dark-matter annihilation in the Galactic halo: propagation Green's functions
We have made a calculation of the propagation of positrons from dark-matter
particle annihilation in the Galactic halo in different models of the dark
matter halo distribution using our 3D code, and present fits to our numerical
propagation Green's functions. We show that the Green's functions are not very
sensitive to the dark matter distribution for the same local dark matter energy
density. We compare our predictions with computed cosmic ray positron spectra
(``background'') for the ``conventional'' CR nucleon spectrum which matches the
local measurements, and a modified spectrum which respects the limits imposed
by measurements of diffuse Galactic gamma-rays, antiprotons, and positrons. We
conclude that significant detection of a dark matter signal requires favourable
conditions and precise measurements unless the dark matter is clumpy which
would produce a stronger signal. Although our conclusion qualitatively agrees
with that of previous authors, it is based on a more realistic model of
particle propagation and thus reduces the scope for future speculations.
Reliable background evaluation requires new accurate positron measurements and
further developments in modelling production and propagation of cosmic ray
species in the Galaxy.Comment: 8 pages, 6 ps-figures, 3 tables, uses revtex. Accepted for
publication in Physical Review D. More details can be found at
http://www.gamma.mpe-garching.mpg.de/~aws/aws.htm
First Interferometric Observations of Molecular Gas in a Polar Ring: The Helix Galaxy NGC 2685
We have detected four Giant Molecular cloud Associations (GMAs) (sizes <
6.6'' ~ 430 pc) in the western and eastern region of the polar ring in NGC2685
(the Helix galaxy) using the Owens Valley Radio Observatory (OVRO) millimeter
interferometer. Emission from molecular gas is found close to the brightest
Halpha and HI peaks in the polar ring and is confirmed by new IRAM 30m single
dish observations. The CO and HI line velocities are very similar, providing
additional kinematic confirmation that the CO emission emerges from the polar
ring. For the first time, the total molecular mass within a polar ring is
determined (M_H2~(8-11)x10^6 M_sol, using the standard Galactic conversion
factor). We detect about M_H2~4.4x10^6 M_sol in the nuclear region with the
single dish. Our upper limit derived from the interferometric data is lower
(M_H2<0.7x10^6 M_sol) suggesting that the molecular gas is distributed in an
extended (< 1.3 kpc) diffuse disk. These new values are an order of magnitude
lower than in previous reports. The total amount of molecular gas and the
atomic gas content of the polar ring are consistent with formation due to
accretion of a small gas-rich object, such as a dwarf irregular. The properties
of the NGC2685 system suggest that the polar ring and the host galaxy have been
in a stable configuration for a considerable time (few Gyr). The second (outer)
HI ring within the disk of NGC2685 is very likely at the outer Lindblad
resonance (OLR) of the ~ 11 kpc long stellar bar.Comment: 8 pages, 4 figures, accepted by ApJ Letter
- âŠ