557 research outputs found
Travel routes to remote ocean targets reveal the map sense resolution for a marine migrant
How animals navigate across the ocean to isolated targets remains perplexing greater than 150 years since this question was considered by Charles Darwin. To help solve this long-standing enigma, we considered the likely resolution of any map sense used in migration, based on the navigational performance across different scales (tens to thousands of kilometres). We assessed navigational performance using a unique high-resolution Fastloc-GPS tracking dataset for post-breeding hawksbill turtles (Eretmochelys imbricata) migrating relatively short distances to remote, isolated targets on submerged banks in the Indian Ocean. Individuals often followed circuitous paths (mean straightness index = 0.54, range 0.14-0.93, s.d. = 0.23, n = 22), when migrating short distances (mean beeline distance to target = 106 km, range 68.7-178.2 km). For example, one turtle travelled 1306.2 km when the beeline distance to the target was only 176.4 km. When off the beeline to their target, turtles sometimes corrected their course both in the open ocean and when encountering shallow water. Our results provide compelling evidence that hawksbill turtles only have a relatively crude map sense in the open ocean. The existence of widespread foraging and breeding areas on isolated oceanic sites points to target searching in the final stages of migration being common in sea turtles
Cross-sections for nuclide production in 56Fe target irradiated by 300, 500,750, 1000, 1500, and 2600 MeV protons compared with data on hydrogen target irradiation by 300, 500, 750, 1000, and 1500 MeV/nucleon 56Fe ions
Cross-sections for radioactive nuclide production in 56Fe(p,x) reactions at
300, 500, 750, 1000, 1500, and 2600 MeV were measured using the ITEP U-10
proton accelerator. In total, 221 independent and cumulative yields of products
of half-lives from 6.6 min to 312 days have been obtained via the
direct-spectrometry method. The measured data have been compared with the
experimental data obtained elsewhere by the direct and inverse kinematics
methods and with calculations by 15 codes, namely: MCNPX (INCL, CEM2k, BERTINI,
ISABEL), LAHET (BERTINI, ISABEL), CEM03 (.01, .G1, .S1), LAQGSM03 (.01, .G1,
>.S1), CASCADE-2004, LAHETO, and BRIEFF. Most of our data are in a good
agreement with the inverse kinematics results and disprove the results of some
earlier activation measurements that were quite different from the inverse
kinematics measurements. The most significant calculation-to-experiment
differences are observed in the yields of the A<30 light nuclei, indicating
that further improvements in nuclear reaction models are needed, and pointing
out as well to a necessity of more complete measurements of such reactions.Comment: 53 pages, 9 figures, 6 tables, only pdf file, submitted to Phys. Rev.
Ciliary muscle dimension changes with accommodation vary in myopia and emmetropia
Purpose: The purpose of this study was to determine whether accommodation-induced changes in ciliary muscle dimensions vary between emmetropes and myopes, and the effect of the image analysis method. Methods: Seventy adults aged 18 to 27 years consisted of 25 people with emmetropia (spherical equivalent refraction [SER] +0.21 ± 0.36 diopters [D]) and 45 people with myopia (-2.84 ± 1.72 D). There were 23 people with low myopia (>-3 D) and 22 people with moderate myopia (-3 to -6 D). Right eye ciliary muscles were imaged (Visante OCT; Carl Zeiss Meditec) at 0 D and 6 D demands. Measures included ciliary muscle length (CML), ciliary muscle curved length (CMLarc), maximum ciliary muscle thickness (CMTmax), CMT1, CMT2, and CMT3 (fixed distances 1-3 mm from the scleral spur), CM25, CM50, and CM75 (proportional distances 25%-75%). Linear mixed model analysis determined effects of refractive groups, race, and demand on dimensions. Significance was set at P < 0.05. Results: Myopic eyes had greater CML and CMLarc nasally than emmetropic eyes. Myopic eyes had thicker muscles than emmetropic eyes at nasal positions, except CM25 and CMT3, and at CM75 temporally. During accommodation and only nasally, CML reduced in emmetropic and myopic eyes, and CMLarc reduced in myopic eyes only. During accommodation, both nasally and temporally, muscles thickened anteriorly (CMT1 and CM25) and thinned posteriorly (CMT3 and CM75) except for temporal CM75. Moderate myopic eyes had greater temporal CMLarc than low myopic eyes, and the moderate myopes had thicker muscles both nasally and temporally using fixed and proportional distances. Conclusions: People with myopia had longer and thicker ciliary muscles than people with emmetropia. During accommodation, the anterior muscle thickened and the curved nasal muscle length shortened, more in myopic than in emmetropic eyes. The fixed distance method is recommended for repeat measures in the same individual. The proportional distance method is recommended for comparisons between refractive groups
Does transient increase in axial length during accommodation attenuate with age?
Background: The aim was to profile transient accommodative axial length (AXL) changes from early adulthood to advanced presbyopia and to determine whether any differences exist between the responses of myopic and emmetropic individuals. Methods: Ocular biometry was measured by the LenStar biometer (Haag-Streit, Switzerland) in response to 0.00, 3.00 and 4.50 D accommodative stimuli in 35 emmetropes and 37 myopes, aged 18 to 60 years. All results were corrected to reduce errors arising from the increase in crystalline lens thickness with accommodation. Accommodative responses were measured sequentially by the WAM 5500 Auto Ref/Keratometer (Grand Seiko, Japan). Results: AXL increased significantly with accommodation (p<0.001), with a mean corrected AXL elongation of 2 ± 18 ”m and 8 ± 16 ”m observed at 3.00 D and 4.50 D, respectively. The magnitude of accommodative AXL change was not dependent on refractive error classification (p=0.959), however a significant reduction in the magnitude and variance of AXL change was evident after 43-44 years of age (p<0.002). Conclusion: The negative association between transient AXL elongation and age, in combination with reduced variance of data after age 43-44 years, is consistent with a significant increase in posterior ocular rigidity, which may be influential in the development of presbyopia
Inequalities and identity processes in crises: recommendations for facilitating safe response to the COVID-19 pandemic
Structural inequalities and identity processes are pivotal to understanding public response to COVIDâ19. We discuss how identity processes can be used to promote communityâlevel support, safe normative behaviour, and increase compliance with guidance. However, we caution how government failure to account for structural inequalities can alienate vulnerable groups, inhibit groups from being able to follow guidance, and lead to the creation of new groups in response to illegitimate treatment. Moreover, we look ahead to the longitudinal impacts of inequalities during pandemics and advise government bodies should address identityâbased inequalities to mitigate negative relations with the public and subsequent collective protest
CEM03 and LAQGSM03 - new modeling tools for nuclear applications
An improved version of the Cascade-Exciton Model (CEM) of nuclear reactions
realized in the code CEM2k and the Los Alamos version of the Quark-Gluon String
Model (LAQGSM) have been developed recently at LANL to describe reactions
induced by particles and nuclei for a number of applications. Our CEM2k and
LAQGSM merged with the GEM2 evaporation/fission code by Furihata have
predictive powers comparable to other modern codes and describe many reactions
better than other codes; therefore both our codes can be used as reliable event
generators in transport codes for applications. During the last year, we have
made a significant improvements to the intranuclear cascade parts of CEM2k and
LAQGSM, and have extended LAQGSM to describe photonuclear reactions at energies
to 10 GeV and higher. We have produced in this way improved versions of our
codes, CEM03.01 and LAQGSM03.01. We present a brief description of our codes
and show illustrative results obtained with CEM03.01 and LAQGSM03.01 for
different reactions compared with predictions by other models, as well as
examples of using our codes as modeling tools for nuclear applications.Comment: 12 pages, 10 figures, to be published in Journal of Physics:
Conference Series: Proc. Europhysics Conf. on New Trends in Nuclear Physics
Applications and Technologies (NPDC19), Pavia, Italy, September 5-9, 200
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Towards a more-than-human approach to tree health
New ways of working and thinking in relation to tree health and plant biosecurity are required. The climate is changing and the number of pests and diseases is increasing. A review of the social science literature on plant health reveals that scholars are not quite sure what this ânew thinkingâ might entail. In this chapter, we begin the process of re-imagining tree health by starting with the trees and our research engagement with them. Trees are acknowledged in this chapter as never static, but rather fluid, shape-shifters, translated across time and space. Health and disease are revealed as relational, and a fixed approach to tree health management wonât work. In a world of rapid change, this way of working is not just relevant for trees
Spallation Residues in the Reaction 56Fe + p at 0.3, 0.5, 0.75, 1.0 and 1.5 A GeV
The spallation residues produced in the bombardment of 56}Fe at 1.5, 1.0,
0.75, 0.5 and 0.3 A GeV on a liquid-hydrogen target have been measured using
the reverse kinematics technique and the Fragment Separator at GSI (Darmstadt).
This technique has permitted the full identification in charge and mass of all
isotopes produced with cross-sections larger than 10^{-2} mb down to Z=8. Their
individual production cross-sections and recoil velocities at the five energies
are presented. Production cross-sections are compared to previously existing
data and to empirical parametric formulas, often used in cosmic-ray
astrophysics. The experimental data are also extensively compared to different
combinations of intra-nuclear cascade and de-excitation models. It is shown
that the yields of the lightest isotopes cannot be accounted for by standard
evaporation models. The GEMINI model, which includes an asymmetric fission
decay mode, gives an overall good agreement with the data. These experimental
data can be directly used for the estimation of composition modifications and
damages in materials containing iron in spallation sources. They are also
useful for improving high precision cosmic-ray measurements.Comment: Submited to Phys. Rev. C (10/2006
Green Plants in the Red: A Baseline Global Assessment for the IUCN Sampled Red List Index for Plants
Plants provide fundamental support systems for life on Earth and are the basis for all terrestrial ecosystems; a decline in plant diversity will be detrimental to all other groups of organisms including humans. Decline in plant diversity has been hard to quantify, due to the huge numbers of known and yet to be discovered species and the lack of an adequate baseline assessment of extinction risk against which to track changes. The biodiversity of many remote parts of the world remains poorly known, and the rate of new assessments of extinction risk for individual plant species approximates the rate at which new plant species are described. Thus the question âHow threatened are plants?â is still very difficult to answer accurately. While completing assessments for each species of plant remains a distant prospect, by assessing a randomly selected sample of species the Sampled Red List Index for Plants gives, for the first time, an accurate view of how threatened plants are across the world. It represents the first key phase of ongoing efforts to monitor the status of the worldâs plants. More than 20% of plant species assessed are threatened with extinction, and the habitat with the most threatened species is overwhelmingly tropical rain forest, where the greatest threat to plants is anthropogenic habitat conversion, for arable and livestock agriculture, and harvesting of natural resources. Gymnosperms (e.g. conifers and cycads) are the most threatened group, while a third of plant species included in this study have yet to receive an assessment or are so poorly known that we cannot yet ascertain whether they are threatened or not. This study provides a baseline assessment from which trends in the status of plant biodiversity can be measured and periodically reassessed
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