3,463 research outputs found
Unraveling the Helix Nebula: Its Structure and Knots
Through HST imaging of the inner part of the main-ring of the Helix Nebula
together with CTIO 4-m images of the fainter outer parts, we have an
unprecedented-quality view of the nearest bright planetary nebula. These images
have allowed determination that the main-ring of the nebula is composed of an
inner-disk of about 499\arcsec diameter (0.52 pc) surrounded by an outer-ring
(in reality a torus) of 742\arcsec diameter (0.77 pc) whose plane is highly
inclined to the plane of the disk. This outer-ring is surrounded by an
outermost-ring of 1500\arcsec (1.76 pc) diameter which is flattened on the side
colliding with the ambient interstellar medium. The inner-disk has an extended
distribution of low density gas along its rotational axis of symmetry and the
disk is optically thick to ionizing radiation, as is the outer-ring.
Published radial velocities of the knots provides support for the
two-component structure of the main-ring of the nebula and to the idea that the
knots found there are expanding along with the nebular material from which it
recently originated. There is a change in the morphology of the knots as a
function of the distance from the local ionization front. This supports a
scenario in which the knots are formed in or near the ionization front and are
then sculpted by the stellar radiation from the central star as the ionization
front advances beyond them.Comment: 30 pages, 20 figures, many figures have reduce fidelity for astroph
preprint. Note: URLs in preprint were change
Age structure and disturbance legacy of North American forests
Most forests of the world are recovering from a past disturbance. It is well known that forest disturbances profoundly affect carbon stocks and fluxes in forest ecosystems, yet it has been a great challenge to assess disturbance impacts in estimates of forest carbon budgets. Net sequestration or loss of CO<sub>2</sub> by forests after disturbance follows a predictable pattern with forest recovery. Forest age, which is related to time since disturbance, is a useful surrogate variable for analyses of the impact of disturbance on forest carbon. In this study, we compiled the first continental forest age map of North America by combining forest inventory data, historical fire data, optical satellite data and the dataset from NASA's Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS) project. A companion map of the standard deviations for age estimates was developed for quantifying uncertainty. We discuss the significance of the disturbance legacy from the past, as represented by current forest age structure in different regions of the US and Canada, by analyzing the causes of disturbances from land management and nature over centuries and at various scales. We also show how such information can be used with inventory data for analyzing carbon management opportunities. By combining geographic information about forest age with estimated C dynamics by forest type, it is possible to conduct a simple but powerful analysis of the net CO<sub>2</sub> uptake by forests, and the potential for increasing (or decreasing) this rate as a result of direct human intervention in the disturbance/age status. Finally, we describe how the forest age data can be used in large-scale carbon modeling, both for land-based biogeochemistry models and atmosphere-based inversion models, in order to improve the spatial accuracy of carbon cycle simulations
Effects of Dehydration on Resistance Training: An Ongoing Study
Introduction: Dehydration via hot bath has been shown to impair resistance training performance when performed the same day. The performance decrements in this instance could potentially be due to a combination of the dehydration and residual effects of the heat exposure and not of the dehydration alone. To date, no research has examined the effects of previous night dehydration on resistance training performance. Purpose: The purpose of this ongoing study was to determine the effects of previous night dehydration on performance and perceptual measures during a full-body resistance training protocol. Methods: Healthy, resistance trained males (n = 4) completed two bouts of a full body resistance training protocol (three sets to failure for bench press, lat pull, overhead press, bicep curl, triceps push down, and leg press), dehydrated (~3% body weight) (DT), or heat exposed with fluid replacement (HT). Heart rate (HR) was taken after every set, and participants estimated ratings of perceived exertion (RPE) after each exercise. Session RPE (SRPE) was estimated 5 minutes following completion of the protocol and estimations for feelings of recovery (PRS), perceived readiness to exercise (PR), thirst, and sleep quality. Results: Analysis revealed a significantly less (p = \u3c 0.001) total reps were completed for DT (163.0 ± 4.8) compared to HT (191.3 ± 10.3), though no differences were found for reps per exercise. No significant differences were found for HR (DT vs HT) at any time point. RPE was significantly higher for DT following bicep curl (p = 0.03) (DT: 7.8 ± 0.96, HT: 6.0 ± 0.82) and triceps push down (p = 0.03) (DT: 7.5 ± 0.58, HT: 6.0 ± 0.82). SRPE was significantly higher (p = 0.003) for DT (8.0 ± 0.0) vs HT (6.3 ± 0.5). Significant differences for PRS (p = 0.004) (DT: 5.0 ± 1.4, HT: 7.5 ± 0.58) and PR (p = \u3c 0.001) (DT: 5.0 ± 0.0, HT: 2.5 ± 0.58) indicate participants expected impaired performance during DT. Feelings of thirst were significantly higher (p = 0.001) for DT (7.98 ± 0.94) vs HT (2.73 ± 1.11). No differences were found for estimations of sleep quality (p = 0.59). Conclusion: Even though only preliminary data from a study presently ongoing, the present results suggest that previous night dehydration has a negative influence on both performance and perceptual measures
Kidney and Pancreas Transplantation in the United States, 1998â2007: Access for Patients with Diabetes and End-Stage Renal Disease
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73092/1/j.1600-6143.2009.02566.x.pd
Mind the Gap: Experimental Tests to Improve Efficacy of Fladry for Nonlethal Management of Coyotes
Coyotes (Canis latrans) are the top predator of livestock in the contiguous United States. Developing more effective nonlethal tools to prevent coyote depredation will facilitate coexistence between livestock producers and coyotes. Fladry is a nonlethal deterrent designed to defend livestock by creating a visual barrier to wolves (C. lupus). Fladry may also be effective with coyotes, but large gap spacing between flags may reduce its efficacy. To address this issue, we performed 2 experiments on captive coyotes using fladry modified to reduce gap spacing at the U.S. Department of Agriculture, Predator Research Facility in Millville, Utah, USA, during 2015â2016 and 2017â2018. In 2015â2016, we tested 2 styles for attaching flags (topâknot and showerâcurtain) to the ropeâline that reduce gaps by preventing coiling of individual flags. In 2017â2018, we tested the efficacy of gap spacing (27.9âcm vs. 45.7âcm) between flags for preventing coyote crossings. For both tests, we compared the time until coyotes crossed the fladry between treatment types. We found no differences in time to crossing between the 2 attachment designs. In our second experiment, fladry with smaller gaps between flags had greater efficacy of preventing coyote crossings than did fladry with larger gaps. Our results also indicated that for each additional minute coyotes spent interacting with fladry overall (i.e., increased persistent behavior), survival of the barrier decreased. These results suggest that persistent coyotes may overcome neophobia more rapidly than coyotes that do not exhibit persistent behaviors. Furthermore, use of topâknot fladry and coyoteâwidth spacing will increase protection of livestock from coyotes
An Acoustic Survey of Beaked Whales and Kogia spp. in the Mariana Archipelago Using Drifting Recorders
The distribution, abundance, and habitat of cryptic cetacean species such as beaked whales and dwarf/pygmy sperm whales (Kogia spp.) are challenging to study due to their long dive times and/or very limited surface behavior. Even less is known in minimally studied and remote regions, including the Mariana Archipelago and parts of the broader western Pacific. In 2018, we deployed a network of eight Drifting Acoustic Spar Buoy Recorders (DASBRs) on the west side of the Mariana Archipelago with the goal of examining the distribution and habitat of beaked whales and Kogia spp. in this region using passive acoustic monitoring. Concurrently, conductivity-temperature-depth (CTD) data were collected within the drift area and combined with satellite oceanographic data to build Ensemble Random Forest Models to identify specific oceanographic features that determine the distribution of these species. DASBRs deployed at locations ranging from 13°N to 18°N generally drifted from east to west between the Mariana Archipelago and the West Mariana Ridge. Spectral and temporal characteristics of echolocation signals were used to identify the presence of beaked whales and Kogia spp. species. This dataset contained frequency modulated (FM) pulses characteristic of Longmanâs (Indopacetus pacificus), Cuvierâs (Ziphius cavirostris), and Blainvilleâs (Mesoplodon densirostris) beaked whales, as well as the unidentified beaked whale FM pulse known as the âBWC,â along with narrow-band high frequency clicks from Kogia spp. The detection rate was substantially higher for all species on the five tracks in the region north of 15.5°N than for those drifts occurring farther south. Species distribution models suggest that differences in the oceanographic characteristics between the northern and southern regions may impact foraging opportunities, possibly explaining the specific ecological niche for these species within this water mass. This is the first study of the distribution of cryptic cetacean species within the wider Mariana Archipelago region. We demonstrate that autonomous drifting acoustic recorders, combined with environmental sampling and remote satellite data are a powerful tool for studying the habitat dependent distribution of cryptic cetacean species
Dynamics of Quasi-ordered Structure in a Regio-regulated pi-Conjugated Polymer:Poly(4-methylthiazole-2,5-diyl)
Dynamics of regio-regulated Poly(4-methylthiazole-2,5-diyl) [HH-P4MeTz] was
inves tigated by solid-state 1H, 2D, 13C NMR spectroscopies, and differential
scanning calorimetry(DSC) measurements. DSC, 2D quadrupolar echo NMR, 13C
cross-polarization and magic-angle spinning(CPMAS) NMR, and 2D spin-echo(2DSE)
CPMAS NMR spectroscopy suggest existence of a quasi-ordered phase in which
backbone twists take place with weakened pi-stackings. Two-dimensional exchange
2D NMR(2DEX) detected slow dynamics with a rate of an order of 10^2Hz for the
CD_3 group in d_3-HH-P4MeTz at 288K. The frequency dependence of proton
longitudinal relaxation rate at 288K shows a omega^-1/2 dependence, which is
due to the one-dimensional diffusion-like motion of backbone conformational
modulation waves. The diffusion rate was estimated as 3+/-2 GHz, which was
approximately 10^7 times larger than that estimated by 2DEX NMR measurements.
These results suggest that there exists anomalous dispersion of modulation
waves in HH-P4MeTz. The one-dimensional group velocity of the wave packet is
responsible for the behavior of proton longitudinal relaxation time. On the
other hand, the 2DEX NMR is sensitive to phase velocity of the nutation of
methyl groups that is associated with backbone twists. From proton T_1 and T_2
measurements, the activation energy was estimated as 2.9 and 3.4 kcal/mol,
respectively. These were in agreement with 3.0 kcal/mol determined by
Moller-Plesset(MP2) molecular orbital(MO) calculation. We also performed
chemical shielding calculation of the methyl-carbon in order to understand
chemical shift tensor behavior, leading to the fact that a quasi-ordered phase
coexist with the crystalline phase.Comment: 14 pages, 11 figures, to appear in Phys.Rev.
Defining forgiveness: Christian clergy and general population perspectives.
The lack of any consensual definition of forgiveness is a serious weakness in the research literature (McCullough, Pargament & Thoresen, 2000). As forgiveness is at the core of Christianity, this study returns to the Christian source of the concept to explore the meaning of forgiveness for practicing Christian clergy. Comparisons are made with a general population sample and social science definitions of forgiveness to ensure that a shared meaning of forgiveness is articulated. Anglican and Roman Catholic clergy (N = 209) and a general population sample (N = 159) completed a postal questionnaire about forgiveness. There is agreement on the existence of individual differences in forgiveness. Clergy and the general population perceive reconciliation as necessary for forgiveness while there is no consensus within psychology. The clergy suggests that forgiveness is limitless and that repentance is unnecessary while the general population suggests that there are limits and that repentance is necessary. Psychological definitions do not conceptualize repentance as necessary for forgiveness and the question of limits has not been addressed although within therapy the implicit assumption is that forgiveness is limitless.</p
XO-5b: A Transiting Jupiter-sized Planet With A Four Day Period
The star XO-5 (GSC 02959-00729, V=12.1, G8V) hosts a Jupiter-sized,
Rp=1.15+/-0.12 Rjup, transiting extrasolar planet, XO-5b, with an orbital
period of P=4.187732+/-0.00002 days. The planet mass (Mp=1.15+/-0.08 Mjup) and
surface gravity (gp=22+/-5 m/s^2) are significantly larger than expected by
empirical Mp-P and Mp-P-[Fe/H] relationships. However, the deviation from the
Mp-P relationship for XO-5b is not large enough to suggest a distinct type of
planet as is suggested for GJ 436b, HAT-P-2b, and XO-3b. By coincidence XO-5
overlies the extreme H I plume that emanates from the interacting galaxy pair
NGC 2444/NGC 2445 (Arp 143).Comment: 10 pages, 9 Figures, Submitted to Ap
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