3,403 research outputs found
Variability in broods of the seastar \u3ci\u3eLeptasterias aequalis\u3c/i\u3e
Enormous variation exists in the reproductive output of marine invertebrates (e.g., in the numbers of em¬bryos produced, the volumes of embryos, and the energy that they contain). It is not clear why there is such great variability or what the population-level consequences are. We sampled a population of the brooding seastar Leptasterias aequalis (Stimpson, 1862) to collect basic information on brood sizes, embryo volume, and embryo energy content with a goal to better understand the reproductive ecology of this species. We collected brooding females in February and again in April. We measured the size of their broods and sampled the broods to estimate volume and energy con¬tent of the embryos. There was great variability in the volume and energy content of embryos produced by individual females and among the embryos in a single female\u27s brood. Larger adults produced larger embryos, which generally had greater energy content and may be of a higher quality. The average energy content of embryos appeared to in¬crease during the brooding period. Larger females produced larger broods but lost a greater proportion of the embryos. The net result is that larger individuals may not produce any more juveniles than smaller individuals, but those that they do produce may be of a higher quality.
Originally published in Canadian Journal of Zoologyand used with permission
Modulational instability of spatially broadband nonlinear optical pulses in four-state atomic systems
The modulational instability of broadband optical pulses in a four-state
atomic system is investigated. In particular, starting from a recently derived
generalized nonlinear Schr\"odinger equation, a wave-kinetic equation is
derived. A comparison between coherent and random phase wave states is made. It
is found that the spatial spectral broadening can contribute to the nonlinear
stability of ultra-short optical pulses. In practical terms, this could be
achieved by using random phase plate techniques.Comment: 9 pages, 3 figures, to appear in Phys. Rev.
Instabilities in neutrino-plasma density waves
One examines the interaction and possible resonances between supernova
neutrinos and electron plasma waves. The neutrino phase space distribution and
its boundary regions are analyzed in detail. It is shown that the boundary
regions are too wide to produce non-linear resonant effects. The growth or
damping rates induced by neutrinos are always proportional to the neutrino flux
and .Comment: 9 pages, a few words modified to match PRD publicatio
Fabrication of Large Size Ex Vivo-Produced Oral Mucosal Equivalents for Clinical Application
The soft tissue reconstruction of significant avulsed and/or surgically created tissue defects requires the ability to manufacture substantial soft tissue constructs for repair of the resulting wounds. In this study, we detail the issues that need to be addressed in upsizing the manufacture of larger tissue-engineered devices (ex vivo-produced oral mucosa equivalent [EVPOME]) in vitro from a methodology previously used for smaller constructs. The larger-sized EVPOME, consisting of autologous human oral keratinocytes and a dermal substitute, AlloDerm?, was fabricated for the purpose of reconstructing large clinical defects. Regulated as an autologous somatic cell therapy product, the fabrication process abided by current Good Manufacturing Practices and current Good Tissue Practices as required by the Center for Biologics Evaluation and Research (CBER) of the United States Food and Drug Administration (FDA). Successful fabrication of large EVPOMEs utilized a higher cell seeding density (5.3?105 cells/cm2) with a relatively thinner AlloDerm, ranging from 356.6 to 508.0??m in thickness. During the air?liquid interface culture, the thickness of the scaffold affected the medium diffusion rate, which, in turn, resulted in changes of epithelial stratification. Histologically, keratinocyte progenitor (p63), proliferation (Ki-67), and late differentiation marker (filaggrin) expression showed differences correlating with the expression of glucose transporter-1 (GLUT1) in the EVPOMEs from the thickest (550?1020??m) to the thinnest (228.6?330.2??m) AlloDerm scaffold. Glucose consumption and 2-deoxyglucose (2DG) uptake showed direct correlation with scaffold thickness. The scaffold size and thickness have an impact on the cellular phenotype and epithelial maturation in the manufacturing process of the EVPOME due to the glucose accessibility influenced by the diffusion rate. These outcomes provide basic strategies to manufacture a large-sized, healthy EVPOME graft for reconstructing large mucosa defects.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140251/1/ten.tec.2014.0600.pd
From Navas to Kaltoft: The European Court of Justice’s evolving definition of disability and the implications for HIV-positive individuals
This article will examine the definition of disability developed by the European Court of Justice for the purposes of the Employment Equality Directive and examine whether it is sufficient for the purpose of bringing People Living with HIV/AIDS within its scope. The article will argue that in order to adequately protect People Living with HIV/AIDS within the EU from discrimination, the European Court of Justice needs to ensure that a coherent EU wide definition of disability, based fully upon the social model of disability, is adopted. This is necessary in order to ensure adequate protection not only for People Living with HIV/AIDS but for all individuals with disabilities from discrimination throughout the EU. In addition to this central argument, this paper will argue that the lack of a coherent definition of disability grounded in the social model fragments protection for People Living with HIV/AIDS across the EU leading to a number of possible unintended consequences
Numerical simulation of unconstrained cyclotron resonant maser emission
When a mainly rectilinear electron beam is subject to significant magnetic compression, conservation of magnetic moment results in the formation of a horseshoe shaped velocity distribution. It has been shown that such a distribution is unstable to cyclotron emission and may be responsible for the generation of Auroral Kilometric Radiation (AKR) an intense rf emission sourced at high altitudes in the terrestrial auroral magnetosphere. PiC code simulations have been undertaken to investigate the dynamics of the cyclotron emission process in the absence of cavity boundaries with particular consideration of the spatial growth rate, spectral output and rf conversion efficiency. Computations reveal that a well-defined cyclotron emission process occurs albeit with a low spatial growth rate compared to waveguide bounded simulations. The rf output is near perpendicular to the electron beam with a slight backward-wave character reflected in the spectral output with a well defined peak at 2.68GHz, just below the relativistic electron cyclotron frequency. The corresponding rf conversion efficiency of 1.1% is comparable to waveguide bounded simulations and consistent with the predictions of kinetic theory that suggest efficient, spectrally well defined radiation emission can be obtained from an electron horseshoe distribution in the absence of radiation boundaries.Publisher PD
Mini-magnetospheres above the lunar surface and the formation of lunar swirls
In this paper we present in-situ satellite data, theory and laboratory
validation that show how small scale collisionless shocks and
mini-magnetospheres can form on the electron inertial scale length. The
resulting retardation and deflection of the solar wind ions could be
responsible for the unusual "lunar swirl" patterns seen on the surface of the
Moon.Comment: 5 pages, 5 figure
Metric fluctuations and decoherence
Recently a model of metric fluctuations has been proposed which yields an
effective Schr\"odinger equation for a quantum particle with a modified
inertial mass, leading to a violation of the weak equivalence principle. The
renormalization of the inertial mass tensor results from a local space average
over the fluctuations of the metric over a fixed background metric. Here, we
demonstrate that the metric fluctuations of this model lead to a further
physical effect, namely to an effective decoherence of the quantum particle. We
derive a quantum master equation for the particle's density matrix, discuss in
detail its dissipation and decoherence properties, and estimate the
corresponding decoherence time scales. By contrast to other models discussed in
the literature, in the present approach the metric fluctuations give rise to a
decay of the coherences in the energy representation, i. e., to a localization
in energy space.Comment: 7 page
Consolidated science and user requirements for a next generation gravity field mission
In an internationally coordinated initiative among the main user communities of gravity field products the science and user requirements for a future gravity field mission constellation (beyond GRACE-FO) have been reviewed and defined. This activity was realized as a joint initiative of the IAG (International Association of Geodesy) Sub-Commissions 2.3 and 2.6, the GGOS (Global Geodetic Observing System) Working Group on Satellite Missions, and the IUGG (International Union of Geodesy and Geophysics). After about one year of preparation, in a user workshop that was held in September 2014 consensus among the user communities of hydrology, ocean, cryosphere, solid Earth and atmosphere on consolidated science requirements could be achieved. The consolidation of the user requirements became necessary, because several future gravity field studies
have resulted in quite different performance numbers as a target for a future gravity mission (2025+). Based on limited number of mission scenarios which took also technical feasibility into account, a consolidated view on the science requirements among the international user communities was derived, research fields that could not be tackled by current gravity missions have been identified, and the added value (qualitatively and quantitatively) of these scenarios with respect to science return has been evaluated. The resulting document shall form the basis for further programmatic and technological developments. In this contribution, the main results of this initiative will be presented. An overview of the specific requirements of the individual user groups, the consensus on consolidated requirements as well as the new research fields that have been identified during this process will be discussed
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