2,343 research outputs found
Predicting the Impact of Climate Change on Cheat Grass (Bromus tectorum) Invasibility for Northern Utah: A GIS and Remote Sensing Approach
Cheat grass (Bromus tectorum) invasibility represents a serious threat to natural ecosystems dominated by sagebrush (Artemisia tridentata). Ecosystem susceptibility to annual grass invasion seems to be driven by specific biophysical conditions. The study was conducted in Rich County, Utah, where cheat grass invasion is not yet an apparent problem, but an imminent invasion might be just a matter of time (temporal scale) to meet spatial variations in environmental conditions (spatial scale). Literature review and expert knowledge were used to define biophysical variables and their respective suitability ranges of where cheat grass takeover might occur. GIS, remote sensing and logistic regression-statistical analyses were employed to estimate probability of cheat grass invasion along environmental gradients. GIS procedures were used to spatially predict areas prone to be invaded by cheat grass under present climatic conditions (model prediction power was 47 percent). Afterwards, simulated climatic change projections (for 2099 year) from the Community Climatic System Model (CCSM-3) were used to model the invasibility risk of cheat grass. The 2099 cheat grass prediction map showed a favorable reduction of around 25 percent in the areas affected by cheat grass invasion, assuming that climate changes occurred as predicted by the CCSM model. The location of highly predisposed areas can be useful to alert managers and define where resources might be allocated to reduce a potential invasion and preserve native rangeland ecosystems
Comparison of the Pade Approximation Method to Perturbative QCD Calculations
We present a method of estimating perturbative coefficients in Quantum Field
Theory using Pade Approximants. We test this method on various known QCD
results, and find that the method works very well.Comment: 14 pages (phyzzx macropackage) + 1 postscript figure encoded through
uufiles, appended at the end of the tex file. Additional relevant references
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Synchronous and opponent thermosensors use flexible cross-inhibition to orchestrate thermal homeostasis.
Body temperature homeostasis is essential and reliant upon the integration of outputs from multiple classes of cooling- and warming-responsive cells. The computations that integrate these outputs are not understood. Here, we discover a set of warming cells (WCs) and show that the outputs of these WCs combine with previously described cooling cells (CCs) in a cross-inhibition computation to drive thermal homeostasis in larval Drosophila WCs and CCs detect temperature changes using overlapping combinations of ionotropic receptors: Ir68a, Ir93a, and Ir25a for WCs and Ir21a, Ir93a, and Ir25a for CCs. WCs mediate avoidance to warming while cross-inhibiting avoidance to cooling, and CCs mediate avoidance to cooling while cross-inhibiting avoidance to warming. Ambient temperature-dependent regulation of the strength of WC- and CC-mediated cross-inhibition keeps larvae near their homeostatic set point. Using neurophysiology, quantitative behavioral analysis, and connectomics, we demonstrate how flexible integration between warming and cooling pathways can orchestrate homeostatic thermoregulation
Layered topological semimetal GaGeTe: New polytype with non-centrosymmetric structure
[EN]
GaGeTe is a layered van der Waals material composed of germanene and GaTe sublayers that has been recently predicted to be a basic Z2 topological semimetal. To date, only one polytype of GaGeTe is known with trigonal centrosymmetric structure (a phase, space group R-3m, No. 166). Here we show that asgrown samples of GaGeTe show traces of at least another polytype with hexagonal noncentrosymmetric structure (f3 phase, space group P63mc, No. 186). Moreover, we suggest that another bulk hexagonal polytype (g phase, space group P-3m1, No. 164) could also be found near room conditions. Both a and f3 polytypes have been identified and characterized by means of X-ray diffraction and Raman scattering measurements with the support of ab initio calculations. We provide the vibrational properties of both polytypes and show that the Raman spectrum reported for GaGeTe almost forty years ago and attributed to the a phase, was, in fact, that of the secondary f3 phase. Additionally, we show that a Fermi resonance occurs in a-GaGeTe under non-resonant excitation conditions, but not under resonant excitation conditions. Theoretical calculations show that bulk f3-GaGeTe is a non-centrosymmetric weak topological semimetal with even smaller lattice thermal conductivity than centrosymmetric bulk aGaGeTe. In perspective, our work paves the way for the control and engineering of GaGeTe polytypes to design and implement complex van der Waals heterostructures formed by a combination of centrosymmetric and non-centrosymmetric layers of up to three different polytypes in a single material, suitable for a number of fundamental studies and technological applications.This publication is part of the project MALTA Consolider Team network (RED2018-102612-T) , financed by MINECO/AEI/10.13039/501100003329; by I ? D ? i projects PID2019-106383 GB -41/42/43 financed by MCIN/AEI/10.13039/501100011033; and by project PROMETEO/2018/123 (EFIMAT) financed by Generalitat Valenciana. E.B. would like to thank the Universitat Politecnica de Valencia for his postdoctoral contract (Ref. PAID -10-21) . AHR was supported by the U.S. Department of Energy (DOE) , Office of Science, Basic Energy Sciences under award DE-SC0021375. We also acknowledge the computational resources awarded by XSEDE, a project supported by National Science Foundation grant number ACI-1053575. The authors also acknowledge the support from the Texas Advances Computer Center (with the Stampede2 and Bridges supercom- puters) . E.L.d.S would like to acknowledge the Network of Extreme Conditions Laboratories (NECL) , financed by FCT and co -financed by NORTE 2020, through the program Portugal 2020 and FEDER; the High Performance Computing Chair-a R & D infrastructure (based at the University of ? Evora; PI: M. Avillez) ; and for the computational support provided by the HPC center OBLIVION -U. ? Evora to perform the lattice thermal conductivity calculations. A.L. and D.E. would like to thank the Generalitat Valenciana for the Ph.D. Fellowship no. GRISOLIAP/2019/025.Gallego-Parra, S.; Bandiello, E.; Liang, A.; Da Silva, EL.; Rodriguez-Hernandez, P.; Muñoz, A.; Radescu, S.... (2022). Layered topological semimetal GaGeTe: New polytype with non-centrosymmetric structure. Materials Today Advances. 16:1-16. https://doi.org/10.1016/j.mtadv.2022.1003091161
Cancer testis antigen and interleukin expression correlates with survival in small bowel neuroendocrine tumors
View full abstracthttps://openworks.mdanderson.org/leading-edge/1042/thumbnail.jp
Quantum field theoretic approach to neutrino oscillations in matter
We consider neutrino oscillations in non-uniform matter in a quantum field
theoretic (QFT) approach, in which neutrino production, propagation and
detection are considered as a single process. We find the conditions under
which the oscillation probability can be sensibly defined and demonstrate how
the properly normalized oscillation probability can be obtained in the QFT
framework. We derive the evolution equation for the oscillation amplitude and
discuss the conditions under which it reduces to the standard
Schr\"odinger-like evolution equation. It is shown that, contrary to the common
usage, the Schr\"odinger-like evolution equation is not applicable in certain
cases, such as oscillations of neutrinos produced in decays of free pions
provided that sterile neutrinos with eV exist.Comment: LaTeX, 24 pages + 16 pages of appendices, 1 figure. V2: typos
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A study of open strings ending on giant gravitons, spin chains and integrability
We systematically study the spectrum of open strings attached to half BPS
giant gravitons in the N=4 SYM AdS/CFT setup. We find that some null
trajectories along the giant graviton are actually null geodesics of AdS_5x
S^5, so that we can study the problem in a plane wave limit setup. We also find
the description of these states at weak 't Hooft coupling in the dual CFT. We
show how the dual description is given by an open spin chain with variable
number of sites. We analyze this system in detail and find numerical evidence
for integrability. We also discover an interesting instability of long open
strings in Ramond-Ramond backgrounds that is characterized by having a
continuum spectrum of the string, which is separated from the ground state by a
gap. This instability arises from accelerating the D-brane on which the strings
end via the Ramond-Ramond field. From the integrable spin chain point of view,
this instability prevents us from formulating the integrable structure in terms
of a Bethe Ansatz construction.Comment: 38 pages+appendices, 9 figures. Uses JHEP3. v2: added reference
Use of Intravenous Peramivir for Treatment of Severe Influenza A(H1N1)pdm09
Oral antiviral agents to treat influenza are challenging to administer in the intensive care unit (ICU). We describe 57 critically ill patients treated with the investigational intravenous neuraminidase inhibitor drug peramivir for influenza A (H1N1)pdm09 [pH1N1]. Most received late peramivir treatment following clinical deterioration in the ICU on enterically-administered oseltamivir therapy. The median age was 40 years (range 5 months-81 years). Common clinical complications included pneumonia or acute respiratory distress syndrome requiring mechanical ventilation (54; 95%), sepsis requiring vasopressor support (34/53; 64%), acute renal failure requiring hemodialysis (19/53; 36%) and secondary bacterial infection (14; 25%). Over half (29; 51%) died. When comparing the 57 peramivir-treated cases with 1627 critically ill cases who did not receive peramivir, peramivir recipients were more likely to be diagnosed with pneumonia/acute respiratory distress syndrome (pâ=â0.0002) or sepsis (pâ=â<0.0001), require mechanical ventilation (pâ=â<0.0001) or die (pâ=â<0.0001). The high mortality could be due to the pre-existing clinical severity of cases prior to request for peramivir, but also raises questions about peramivir safety and effectiveness in hospitalized and critically ill patients. The use of peramivir merits further study in randomized controlled trials, or by use of methods such as propensity scoring and matching, to assess clinical effectiveness and safety
The Genetic contribution to solving the cocktail-party problem
Communicating in everyday situations requires solving the cocktail-party problem, or segregating the acoustic mixture into its constituent sounds and attending to those of most interest. Humans show dramatic variation in this ability, leading some to experience real-world problems irrespective of whether they meet criteria for clinical hearing loss. Here, we estimated the genetic contribution to cocktail-party listening by measuring speech-reception thresholds (SRTs) in 425 people from large families and ranging in age from 18 to 91 years. Roughly half the variance of SRTs was explained by genes (h 2 = 0.567). The genetic correlation between SRTs and hearing thresholds (HTs) was medium (Ï G = 0.392), suggesting that the genetic factors influencing cocktail-party listening were partially distinct from those influencing sound sensitivity. Aging and socioeconomic status also strongly influenced SRTs. These findings may represent a first step toward identifying genes for hidden hearing loss, or hearing problems in people with normal HTs
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