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Suspension Design, Modeling, and Testing of a Thermo-Acoustic-Driven Linear Alternator
The Score-Stove™ generates electricity from a wood-burning cooking stove using a thermo-acoustic engine (TAE) that converts heat to sound through a linear alternator (LA). This paper introduces a prototype hemitoroidal suspension that was refined into a segmented trapezoidal shape that gave a higher cyclic life for the LA and includes a critical evaluation that compares a theoretical analysis with experimental results. The results show an improvement from the 40% efficiency of a standard loudspeaker used in reverse as an LA to 70–80% efficiency with the new suspension and a double Halbach array magnetic topology
Nonlinear Spinor Fields and its role in Cosmology
Different characteristic of matter influencing the evolution of the Universe
has been simulated by means of a nonlinear spinor field. Exploiting the spinor
description of perfect fluid and dark energy evolution of the Universe given by
an anisotropic Bianchi type-VI, VI, V, III, I or isotropic
Friedmann-Robertson-Walker (FRW) one has been studied. It is shown that due to
some restrictions on metric functions, initial anisotropy in the models Bianchi
type-VI, VI, V and III does not die away, while the anisotropic Bianchi
type-I models evolves into the isotropic one.Comment: 22 pages, 12 Figure
Determining physical properties of the cell cortex
Actin and myosin assemble into a thin layer of a highly dynamic network
underneath the membrane of eukaryotic cells. This network generates the forces
that drive cell and tissue-scale morphogenetic processes. The effective
material properties of this active network determine large-scale deformations
and other morphogenetic events. For example,the characteristic time of stress
relaxation (the Maxwell time)in the actomyosin sets the time scale of
large-scale deformation of the cortex. Similarly, the characteristic length of
stress propagation (the hydrodynamic length) sets the length scale of slow
deformations, and a large hydrodynamic length is a prerequisite for long-ranged
cortical flows. Here we introduce a method to determine physical parameters of
the actomyosin cortical layer (in vivo). For this we investigate the relaxation
dynamics of the cortex in response to laser ablation in the one-cell-stage {\it
C. elegans} embryo and in the gastrulating zebrafish embryo. These responses
can be interpreted using a coarse grained physical description of the cortex in
terms of a two dimensional thin film of an active viscoelastic gel. To
determine the Maxwell time, the hydrodynamic length and the ratio of active
stress and per-area friction, we evaluated the response to laser ablation in
two different ways: by quantifying flow and density fields as a function of
space and time, and by determining the time evolution of the shape of the
ablated region. Importantly, both methods provide best fit physical parameters
that are in close agreement with each other and that are similar to previous
estimates in the two systems. We provide an accurate and robust means for
measuring physical parameters of the actomyosin cortical layer.It can be useful
for investigations of actomyosin mechanics at the cellular-scale, but also for
providing insights in the active mechanics processes that govern tissue-scale
morphogenesis.Comment: 17 pages, 4 figure
Interacting spinor and scalar fields in Bianchi type-I Universe filled with viscous fluid: exact and numerical solutions
We consider a self-consistent system of spinor and scalar fields within the
framework of a Bianchi type I gravitational field filled with viscous fluid in
presence of a term. Exact self-consistent solutions to the
corresponding spinor, scalar and BI gravitational field equations are obtained
in terms of , where is the volume scale of BI universe. System of
equations for and \ve, where \ve is the energy of the viscous fluid,
is deduced. Some special cases allowing exact solutions are thoroughly studied.Comment: 18 pages, 6 figure
Scalar field in cosmology: Potential for isotropization and inflation
The important role of scalar field in cosmology was noticed by a number of
authors. Due to the fact that the scalar field possesses zero spin, it was
basically considered in isotropic cosmological models. If considered in an
anisotropic model, the linear scalar field does not lead to isotropization of
expansion process. One needs to introduce scalar field with nonlinear potential
for the isotropization process to take place. In this paper the general form of
scalar field potentials leading to the asymptotic isotropization in case of
Bianchi type-I cosmological model, and inflationary regime in case of isotropic
space-time is obtained. In doing so we solved both direct and inverse problem,
where by direct problem we mean to find metric functions and scalar field for
the given potential, whereas, the inverse problem means to find the potential
and scalar field for the given metric function. The scalar field potentials
leading to the inflation and isotropization were found both for harmonic and
proper synchronic time.Comment: 10 page
Probability for Primordial Black Holes in Higher Derivative Theories
The probability for quantum creation of an inflationary universe with a pair
of black holes in higher derivative theories has been studied. Considering a
gravitational action which includes quadratic () and/or cubic
term () in scalar curvature in addition to a cosmological constant
() in semiclassical approximation with Hartle-Hawking boundary
condition, the probability has been evaluated. The action of the instanton
responsible for creating such a universe, with spatial section with
topology, is found to be less than that with a spatial
topology, unless in -theory. In the
theory, however, there exists a set of solutions without a cosmological
constant when and which admit
primordial black holes (PBH) pair in an inflationary universe scenario. We note
further that when , one gets PBH pairs in the two cases :
(i) with and both positive and (ii) with positive
and negative satisfying a constraint .
However, the relative probability for creation of an inflationary universe with
a pair of black holes in the -theory suppresses when or . However, if the above
constraints are relaxed one derives interesting results leading to a universe
with PBH in -theory without cosmological constant. PACS No(s). :
04.20.Jb, 04.60.+n, 98.80.HwComment: 15 pages, No figures. accepted in Int. J. Mod. Phys. D (2001
Application of Molecular Diversity in a Forage Grass Breeding Program
Little or no genotypic information is available for many forage grass populations. The degree of genetic similarity within and among populations greatly influences the choice of breeding strategies and germplasm for developing improved cultivars. Molecular markers have proven effective in classifying genetic diversity of a number of perennial grasses (e.g. Fu et al., 2004; Kubik et al., 2001). We present here an overview of our efforts to integrate molecular diversity data into our breeding program
Natural Convection Flow with Combined Buoyancy Effects Due to Thermal and Mass Diffusion in a Thermally Stratified Media
We present here a numerical study of laminar doubly diffusive free convection flows adjacent to a vertical surface in a stable thermally stratified medium. The governing equations of mass, momentum, energy and species are non-dimensionalized. These equations have been solved by using an implicit finite difference method and local non-similarity method. The results show many interesting aspects of complex interaction of the two buoyant mechanisms that have been shown in both the tabular as well as graphical form
Agronomic Traits in Tall Fescue Populations under Irrigated and Rain-Fed Conditions
Grasslands and native rangelands are the predominant land-use all over the world. Tall fescue [Schedonorus arundinaceus (Schreb.) Dumort] is a cool-season perennial grass widely grown throughout the temperate regions of the world and an important component of the grasslands. Drought can have serious consequences on performance of agriculture, soil and plant health, and economics. Developing drought tolerant plants that can maintain productivity during drought, will have great environmental and economic benefits to farmers. A tall fescue population was developed by crossing a drought tolerant genotype to a susceptible genotype. The population was evaluated for different morphological and yield traits under irrigated and rain-fed conditions at the University of Wyoming, USA. Large variations among the 252 tall fescue genotypes for several traits of interest have been observed. Plants under irrigated conditions were about 1.5 times more vigorous and 1.9 times taller than those grown in rain-fed conditions. Rain-fed conditions greatly reduced the tillering ability (\u3c 2.6 fold) of tall fescue plants. Plants under irrigated conditions were 2.9 times more productive than those grown in rain-fed condition. The largest difference in a year for water content (WC) between the plants grown in the two conditions was 8.06%. Genotypes with better tolerance to drought have been identified in the population which could be useful to develop drought tolerant tall fescue cultivars
Simulated Heatwaves Lead to Upregulated Chemical Defense of a Marine Foundation Macrophyte Against Microbial Colonizers
Climate change is characterized not only by an increase in mean temperature, but also an increase in the variability around the means causing extreme events like marine heatwaves. These events are expected to have strong influence on the ecology of marine foundation species such as the eelgrass Zostera marina. Bacterial and macroscopicfoulersareubiquitousinthemarineenvironment;theycanhavedetrimental impacts on macrophytes and warming is known to enhance bacterial fouling. Thus, to investigate the consequence of heatwaves on the chemical defense of eelgrass against microbial colonizers, we incubated Z. marina plants in the Kiel Outdoor Benthocosm system under ambient control conditions and two different heatwave treatments: a treatment experiencing two spring heatwaves followed by a summer heatwave, and a treatment only experiencing just the summer heatwave. The capacity to deter microbial colonizers was found to be significantly up-regulated in Z. marina from both heatwave treatments in comparison to Z. marina under control conditions, suggesting defense regulation of Z. marina in response to marine heatwaves. We conclude climate extremes such as heatwaves can trigger a regulation in the defense capacity, which could be necessary for resilience against climate change scenarios. Such dynamics in rapid regulation of defense capacity as found in this study could also apply to other host plant – microbe interactions under scenarios of ongoing climate change or extreme climate events like heatwaves
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