480 research outputs found
Behavior of steel-concrete-steel sandwich structures with lightweight cement composite and novel shear connectors
10.1016/j.compstruct.2012.05.023Composite Structures94123500-350
On the effective velocity created by a point vortex in two-dimensional hydrodynamics
We complete previous investigations on the statistics of velocity
fluctuations arising from a random distribution of point vortices in
two-dimensional hydrodynamics. We show that, on a statistical sense, the
velocity created by a point vortex is shielded by cooperative effects on a
distance , the inter-vortex separation. For , the ``effective'' velocity decays as instead of the ordinary
law recovered for . These results are similar to those
obtained by Agekyan [Sov. Astron. 5 (1962) 809] in his investigations on the
fluctuations of the gravitational field. They give further support to our
previous observation that the statistics of velocity fluctuations are
(marginally) dominated by the contribution of the nearest neighbor.Comment: Submitted to Phys. Rev.
Improved Copper Circularity as a Result of Increased Material Efficiency in the U.S. Housing Stock
Material efficiency (ME) can support rapid climate change mitigation and circular economy. Here, we comprehensively assess the circularity of ME strategies for copper use in the U.S. housing services (including residential buildings and major household appliances) by integrating use-phase material and energy demand. Although the ME strategies of more intensive floor space use and extended lifetime of appliances and buildings reduce the primary copper demand, employing these strategies increases the commonly neglected use-phase share of total copper requirements during the century from 23–28 to 22–42%. Use-phase copper requirements for home improvements have remained larger than the demand gap (copper demand minus scrap availability) for much of the century, limiting copper circularity in the U.S. housing services. Further, use-phase energy consumption can negate the benefits of ME strategies. For instance, the lifetime extension of lower-efficiency refrigerators increases the copper use and net environmental impact by increased electricity use despite reductions from less production. This suggests a need for more attention to the use phase when assessing circularity, especially for products that are material and energy intensive during use. To avoid burden shifting, policymakers should consider the entire life cycle of products supporting services when pursuing circular economy goals
On the Entropy of a Quantum Field in the Rotating Black Holes
By using the brick wall method we calculate the free energy and the entropy
of the scalar field in the rotating black holes. As one approaches the
stationary limit surface rather than the event horizon in comoving frame, those
become divergent. Only when the field is comoving with the black hole (i.e.
) those become divergent at the event horizon. In the
Hartle-Hawking state the leading terms of the entropy are , where is the cut-off in the radial coordnate near the
horizon. In term of the proper distance cut-off it is written as . The origin of the divergence is that the density of state
on the stationary surface and beyond it diverges.Comment: Latex, 23 pages, 7 eps figure
The mouse deafness locus (dn) is associated with an inversion on chromosome 19
Recombination data for the mouse deafness locus (dn) on chromosome 19 are consistent with the presence of an inversion for which one of the breakpoints is between D19Mit14 and D19Mit96, a distance of less than 226 kb. Fluorescence in situ hybridization studies using a bacterial artificial chromosome on interphase (G1) nuclei provide additional support for the presence of an inversion. The dn gene is probably the orthologue of the human DFNB7/DFNB11 gene on chromosome 9. Copyright (C) 1998 Elsevier Science B.V
Kinetic theory of point vortices: diffusion coefficient and systematic drift
We develop a kinetic theory for point vortices in two-dimensional
hydrodynamics. Using standard projection operator technics, we derive a
Fokker-Planck equation describing the relaxation of a ``test'' vortex in a bath
of ``field'' vortices at statistical equilibrium. The relaxation is due to the
combined effect of a diffusion and a drift. The drift is shown to be
responsible for the organization of point vortices at negative temperatures. A
description that goes beyond the thermal bath approximation is attempted. A new
kinetic equation is obtained which respects all conservation laws of the point
vortex system and satisfies a H-theorem. Close to equilibrium this equation
reduces to the ordinary Fokker-Planck equation.Comment: 50 pages. To appear in Phys. Rev.
Current reversal with type-I intermittency in deterministic inertia ratchets
The intermittency is investigated when the current reversal occurs in a
deterministic inertia ratchet system. To determine which type the intermittency
belongs to, we obtain the return map of velocities of particle using
stroboscopic recording, and numerically calculate the distribution of average
laminar length . The distribution follows the scaling law of , the characteristic relation of type-I
intermittency.Comment: 4 pages, 7 figure
Multiple post-domestication origins of kabuli chickpea through allelic variation in a diversification-associated transcription factor
Chickpea (Cicer arietinum) is among the founder crops domesticated in the Fertile Crescent. One of two major forms of chickpea, the so-called kabuli type, has white flowers and light-colored seed coats, properties not known to exist in the wild progenitor. The origin of the kabuli form has been enigmatic. We genotyped a collection of wild and cultivated chickpea genotypes with 538 single nucleotide polymorphisms (SNPs) and examined patterns of molecular diversity relative to geographical sources and market types. In addition, we examined sequence and expression variation in candidate anthocyanin biosynthetic pathway genes. A reduction in genetic diversity and extensive genetic admixture distinguish cultivated chickpea from its wild progenitor species. Among germplasm, the kabuli form is polyphyletic. We identified a basic helix-loop-helix (bHLH) transcription factor at chickpea\u27s B locus that conditions flower and seed colors, orthologous to Mendel\u27s A gene of garden pea, whose loss of function is associated invariantly with the kabuli type of chickpea. From the polyphyletic distribution of the kabuli form in germplasm, an absence of nested variation within the bHLH gene and invariant association of loss of function of bHLH among the kabuli type, we conclude that the kabuli form arose multiple times during the phase of phenotypic diversification after initial domestication of cultivated chickpea
Optical nanofibers and spectroscopy
We review our recent progress in the production and characterization of
tapered optical fibers with a sub-wavelength diameter waist. Such fibers
exhibit a pronounced evanescent field and are therefore a useful tool for
highly sensitive evanescent wave spectroscopy of adsorbates on the fiber waist
or of the medium surrounding. We use a carefully designed flame pulling process
that allows us to realize preset fiber diameter profiles. In order to determine
the waist diameter and to verify the fiber profile, we employ scanning electron
microscope measurements and a novel accurate in situ optical method based on
harmonic generation. We use our fibers for linear and non-linear absorption and
fluorescence spectroscopy of surface-adsorbed organic molecules and investigate
their agglomeration dynamics. Furthermore, we apply our spectroscopic method to
quantum dots on the surface of the fiber waist and to caesium vapor surrounding
the fiber. Finally, towards dispersive measurements, we present our first
results on building and testing a single-fiber bi-modal interferometer.Comment: 13 pages, 18 figures. Accepted for publication in Applied Physics B.
Changes according to referee suggestions: changed title, clarification of
some points in the text, added references, replacement of Figure 13
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