3,240 research outputs found
Status, distribution and use of threatened tree species in the walnut-fruit forests of Kyrgyzstan
Information is lacking on the status of threatened tree species in Central Asia. This paper aims to provide preliminary information for 10 fruit and nut tree species of Kyrgyzstan. A field survey was conducted throughout the range of walnut-fruit forests in this country, supported by a socio-economic survey. Results indicated that species differed markedly in abundance. Whereas Malus sieversii was found in all locations, four species (Crataegus pontica,Pistacia vera,Pyrus korshinskyi and Sorbus persica) were only found in a minority (≤ 30%) of sites. Four species showed evidence of a bimodal distribution of stem diameters, which could be attributed to fuelwood harvesting, as indicated by the socio-economic survey. A majority of respondents reported a decline in the available grazing resource, a decline in the availability of harvested fruits and an increase in time required to collect fuelwood over the past decade. These results suggest that unsustainable land-use practices may be impacting negatively on populations of threatened fruit tree species. These results highlight the need to regulate local forest use to ensure that threatened fruit and nut tree species are effectively conserved, and the need for targeted actions to conserve the most threatened species, such as P. korshinskyi. © 2014 © 2014 Taylor & Francis
Maximum n-times Coverage for Vaccine Design
We introduce the maximum -times coverage problem that selects overlays
to maximize the summed coverage of weighted elements, where each element must
be covered at least times. We also define the min-cost -times coverage
problem where the objective is to select the minimum set of overlays such that
the sum of the weights of elements that are covered at least times is at
least . Maximum -times coverage is a generalization of the multi-set
multi-cover problem, is NP-complete, and is not submodular. We introduce two
new practical solutions for -times coverage based on integer linear
programming and sequential greedy optimization. We show that maximum -times
coverage is a natural way to frame peptide vaccine design, and find that it
produces a pan-strain COVID-19 vaccine design that is superior to 29 other
published designs in predicted population coverage and the expected number of
peptides displayed by each individual's HLA molecules.Comment: 10 pages, 5 figure
Population Synthesis of Hot Subdwarfs: A Parameter Study
Binaries that contain a hot subdwarf (sdB) star and a main sequence companion
may have interacted in the past. This binary population has historically helped
determine our understanding of binary stellar evolution. We have computed a
grid of binary population synthesis models using different assumptions about
the minimum core mass for helium ignition, the envelope binding energy, the
common envelope ejection efficiency, the amount of mass and angular momentum
lost during stable mass transfer, and the criteria for stable mass transfer on
the red giant branch and in the Hertzsprung gap. These parameters separately
and together can significantly change the entire predicted population of sdBs.
Nonetheless, several different parameter sets can reproduce the observed
subpopulation of sdB + white dwarf and sdB + M dwarf binaries, which has been
used to constrain these parameters in previous studies. The period distribution
of sdB + early F dwarf binaries offers a better test of different mass transfer
scenarios for stars that fill their Roche lobes on the red giant branch.Comment: 21 pages, 15 figures, accepted for publication in Ap
Visual function due to regeneration of optic nerve or optic tract through peripheral nerve homografts
Segments of sciatic nerve from one leg were used to induce regeneration of transected optic nerve (ON) or tract in Syrian hamsters. In the first group, the nerve graft was sutured to the stump of the transected ON of the right eye in young adult animals, and the other end was placed below the surface of the ipsilateral superior colliculus (SC); the opposite eye was removed. In one animal, orienting movements in the wrong direction were elicited and recorded on videotape, beginning when the animal was more than 1.5 yr old, over 1 yr after surgery. In the second group, a similar procedure was used but with the nerve going to the contralateral SC. In 3 of 4 long-term survivors, visually elicited turning was obtained and recorded, most reliably in the final 4 mo of their 2-yr life. Regenerating retinofugal axons were traced and their terminations in SC reconstructed using a CT-B procedure and immunohistochemistry (secondary AB conjugated to Alexa-488) and fluorescence microscopy. The visually unresponsive animal had no regeneration, and the most responsive animal had the greatest amount of regeneration. In a 3rd procedure, the right brachium of SC was transected, and 2 or 3 segments of sciatic nerve were implanted as bridges to elicit optic tract regeneration. The first 3 of these animals were operated at age 13-19 days; considerable regeneration was verified anatomically in each case, after behavioral demonstration of visual orienting.
Supported by NIH grant EY00126.published_or_final_versio
Pattern-Sensitive Epilepsy. I: A Demonstration of a Spatial Frequency Selective Epileptic Response to Gratings
Rare individuals suffer epileptic seizures when they view certain images, particularly stripes. Contrast-threshold functions (the ability to see faint stripes of various widths) were determined for two pattern-sensitive brothers, and the epileptogenicity of various patterns was assessed for one of them. Sine wave grating contrast-detection thresholds for the two subjects were essentially normal, with lowest thresholds at approximately 2 cycles/ degree (c/deg). Epileptiform discharges occurred maximally at 5 c/deg with a 1-octave 50% bandwidth. Pattern epileptogenicity was increased by the addition of a third harmonic sine wave grating to its fundamental, but was unaffected by the phase relation of the two gratings. The frequency selectivity of epileptic responsiveness was quantitatively similar to a “spatial frequency channel.” Inhibitory interactions were not present. The findings suggest relations between the phenomena of pattern-sensitive epilepsy and hypothesized spatial frequency channels which merit further exploration. RESUMEN De manera excepcional, hay personas que pueden tener ataques epilÉpticos cuando ven ciertas imÁgenes, particularmente rayas. Se determinaron los umbrales para contrastes (la capacidad de ver rayas de diversas anchuras y muy tenues) en dos hermanos sensibles a patrones y se estableciÓ la epileptogeneidad de di versos patrones en uno de ellos. Los umbrales para contrastes fueron esencialmente normales en los dos sujetos cuando se utilizeÓ una rejilla hecha con ondas sinusoidales, siendo el umbral inferior unos 2 ciclos/ grado (c/deg). Descargas epileptiformes tuvieron lugar de modo mÁximo a 5 c/deg con una amplitud de banda del 50% de una octava. la capacidad epileptogÉnica del partÓn aumentÓ cuando se aÑadiÓ una tercera sinusoide armÓnica a la rejilla base pero esa capacidad no se viÓ alterada por la relaciÓn de fase entre las dos rejillas. La selectividad de la frecuencia de la respuesta epileptogÉnica fue cuantitativamente similar al “canal de frecuencia espacial”. No se observaron interacciones inhibitorias. Los hallazgos sugieren que hay relaciones entre la epilepsyÍa secundaria a patrones visuales y los hipotÉticos canales de frecuencia espacial, lo cual merece mÁs investigaciÓn.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65270/1/j.1528-1157.1980.tb04075.x.pd
Associations between reliable changes in depression and changes in BMI, total body fatness and visceral adiposity during a 12-month weight loss trial.
We investigated associations between changes in depression and body composition over a 12-month weight loss trial. Of the 298 adults (BMI > 27 m/kg2), 219 with complete depression and body composition data were included. A 10-item Center for Epidemiologic Studies Depression Scale measured depression; dual-energy X-ray absorptiometry measured body composition. Multinomial logistic regression predicted reliable changes in depression by BMI, body fat (BF) and visceral adiposity (VAT). Multiplicative interaction terms tested modification by sex and ethnicity. Participants with increases in body composition were less likely to experience improvements in depression (BMI: RRR = 0.79 (0.68-0.91), p < 0.01; BF: RRR = 0.97 (0.94 - 0.99), p = 0.01; VAT: RRR = 0.99 (0.98-1.00), p = 0.02), but not worsening of depression (BMI: RRR = 1.29 (0.96-1.73), p = 0.10; BF: RRR = 1.04 (0.99-1.09), p = 0.15; VAT: RRR = 1.01 (1.00-1.03), p = 0.18). Sex and ethnicity interaction terms were not significant. However, the relationship was only significant among females, among non-Latinos for BMI and BF, and among Latinos for VAT. Our study supports the association between depression and obesity and highlights the need for longitudinal studies investigating VAT and depression in diverse ethnic groups
Towards Improved Quantum Simulations and Sensing with Trapped 2D Ion Crystals via Parametric Amplification
Improving coherence is a fundamental challenge in quantum simulation and
sensing experiments with trapped ions. Here we discuss, experimentally
demonstrate, and estimate the potential impacts of two different protocols that
enhance, through motional parametric excitation, the coherent spin-motion
coupling of ions obtained with a spin-dependent force. The experiments are
performed on 2D crystal arrays of approximately one hundred Be ions
confined in a Penning trap. By modulating the trapping potential at close to
twice the center-of-mass mode frequency, we squeeze the motional mode and
enhance the spin-motion coupling while maintaining spin coherence. With a
stroboscopic protocol, we measure dB of motional squeezing below
the ground-state motion, from which theory predicts a dB enhancement in
the sensitivity for measuring small displacements using a recently demonstrated
protocol [Science , 673 (2021)]. With a continuous squeezing
protocol, we measure and accurately calibrate the parametric coupling strength.
Theory suggests this protocol can be used to improve quantum spin squeezing,
limited in our system by off-resonant light scatter. We illustrate numerically
the trade-offs between strong parametric amplification and motional dephasing
in the form of center-of-mass frequency fluctuations for improving quantum spin
squeezing in our set-up.Comment: 11 pages, 6 figure
Chandra observations of Abell 2199
We present results from an analysis of two Chandra observations of the rich,
nearby galaxy cluster Abell 2199. We find evidence (having corrected for
projection effects) for radial gradients in temperature and metallicity in the
X-ray emitting gas: the temperature drops from kT~4.2 keV at R=200 kpc to 1.6
keV within R=5 kpc of the centre. The metallicity rises from ~0.3 solar at
R=200 kpc to ~0.7 solar at R=30 kpc before dropping to 0.3 solar within the
central 5 kpc. We find evidence for structure in the surface brightness
distribution associated with the central radio source 3C338. No evidence is
found for the gas having a large spread in temperature at any particular
location despite the cooling time being short (<10**9yr) within the central ~15
kpc. Heating and mass cooling rates are calculated for various assumptions
about the state of the gas.Comment: 10 pages, 12 figures. Accepted by MNRAS. Minor changes following
referee's comment
The Complete transmission spectrum of WASP-39b with a precise water constraint
This is the author accepted manuscript. The final version is available from American Astronomical Society via the DOI in this record.WASP-39b is a hot Saturn-mass exoplanet with a predicted clear atmosphere based on observations in the optical and infrared. Here we complete the transmission spectrum of the atmosphere with observations in the near-infrared (NIR) over three water absorption features with the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) G102 (0.8-1.1 microns) and G141 (1.1-1.7 microns) spectroscopic grisms. We measure the predicted high amplitude H2O feature centered at 1.4 microns, and the smaller amplitude features at 0.95 and 1.2 microns, with a maximum water absorption amplitude of 2.4 planetary scale heights. We incorporate these new NIR measurements into previously published observational measurements to complete the transmission spectrum from 0.3-5 microns. From these observed water features, combined with features in the optical and IR, we retrieve a well constrained temperature Teq = 1030(+30,-20) K, and atmospheric metallicity 151 (+48,-46)x solar which is relatively high with respect to the currently established mass-metallicity trends. This new measurement in the Saturn-mass range hints at further diversity in the planet formation process relative to our solar system giants.This work is based on observations made with the NASA/ESA Hubble Space Telescope that were
obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. These observations are associated with programs GO-14169 (PI. HR Wakeford) and GO-14260 (PI. D Deming). D.K.S., H.R.W., T.E., B.D., and N.N.,
acknowledge funding from the European Research Council (ERC) under the European Unions Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no. 336792. J.G. acknowledges support from Leverhulme Trust. A.L.C. acknowledges support from the STFC. H.R.W. also acknowledges support from the Giacconi Fellowship at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc
Beyond Volume: The Impact of Complex Healthcare Data on the Machine Learning Pipeline
From medical charts to national census, healthcare has traditionally operated
under a paper-based paradigm. However, the past decade has marked a long and
arduous transformation bringing healthcare into the digital age. Ranging from
electronic health records, to digitized imaging and laboratory reports, to
public health datasets, today, healthcare now generates an incredible amount of
digital information. Such a wealth of data presents an exciting opportunity for
integrated machine learning solutions to address problems across multiple
facets of healthcare practice and administration. Unfortunately, the ability to
derive accurate and informative insights requires more than the ability to
execute machine learning models. Rather, a deeper understanding of the data on
which the models are run is imperative for their success. While a significant
effort has been undertaken to develop models able to process the volume of data
obtained during the analysis of millions of digitalized patient records, it is
important to remember that volume represents only one aspect of the data. In
fact, drawing on data from an increasingly diverse set of sources, healthcare
data presents an incredibly complex set of attributes that must be accounted
for throughout the machine learning pipeline. This chapter focuses on
highlighting such challenges, and is broken down into three distinct
components, each representing a phase of the pipeline. We begin with attributes
of the data accounted for during preprocessing, then move to considerations
during model building, and end with challenges to the interpretation of model
output. For each component, we present a discussion around data as it relates
to the healthcare domain and offer insight into the challenges each may impose
on the efficiency of machine learning techniques.Comment: Healthcare Informatics, Machine Learning, Knowledge Discovery: 20
Pages, 1 Figur
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