27,590 research outputs found
Erosion and deposition in interplain channels of the Maury channel system
Large turbidity currents originating on the insular margin of southern lceland have flowed clown a 2 500 km-long pathway comprising rise valleys, unchanneled plains and segments of erosional and depositional deep-sea channels that are collectively called the Maury Channel system. Two steep interplain reaches of the channel have been eut up to 100 m through volcanogenic turbidites of probable La te Pleistocene age. Near-bottom observations with side-scan sonars and profllers across the upper channels (at 59°24\u27N, 18°50\u27W, 2 750 m depth) and at the lower interplain channel (around 56°23\u27N, 24°25\u27W, 3 340 m depth) defmed their structure and morphology. The upper channels, and a tributary to the lower channel, start as broad, shallow depressions that deepen and narrow downstream. The lower channel bas a pattern of anastomosing branches that probably evolved by head ward extension of low-angle tribu taries to the original sinuous channel, and its branches are at different stages of development. Several hundred bottom photographs show well-indurated rocks on channel walls and floors, with such flysch-like characteristics as cyclic graded bedding, clastic dikes, and syndepositional deformation. The lower-channel branches have been eut by turbidity currents with speeds of 5- 12 rn/sec., and combined discharges exceeding 1 x 106 m3 /sec. Bedrock erosion in and around the channels bas proceeded by intense corrasion and fluid stressing, and is marked by such small-scale effects as rock polishing, fluting, pot-holing and ledge recession. Rockfalls have caused retreat of steep channel walls, and conglomerate or pcbbly mudstone deposits suggest that debris flows have been locally active. Sorne coarse debris delivered by these processes and clay halls torn from semi-lithifled outcrops remain in the channels, but the channel f1ll is generally thin, with a patch y veneer of pelagie mud that bas accumulated since the last major turbidity current event. The surfaces of the unconsolidated s~diment have been smoothed and lineated, or moulded into seo ur moats and occasional fields of ripples, by thermohaline currents
Microstrip resonator for microwaves with controllable polarization
In this work the authors implemented a resonator based upon microstrip
cavities that permits the generation of microwaves with arbitrary polarization.
Design, simulation, and implementation of the resonators were performed using
standard printed circuit boards. The electric field distribution was mapped
using a scanning probe cavity perturbation technique. Electron spin resonance
using a standard marker was carried out in order to verify the polarization
control from linear to circular.Comment: 3 pages, 3 figures, submitted to Appl. Phys. Let
Dynamic heterogeneities in critical coarsening: Exact results for correlation and response fluctuations in finite-sized spherical models
We study dynamic heterogeneities in the out-of-equilibrium coarsening
dynamics of the spherical ferromagnet after a quench from infinite temperature
to its critical point. A standard way of probing such heterogeneities is by
monitoring the fluctuations of correlation and susceptibility, coarse-grained
over mesoscopic regions. We discuss how to define fluctuating coarse-grained
correlations (C) and susceptibilities (Chi) in models where no quenched
disorder is present. Our focus for the spherical model is on coarse-graining
over the whole volume of spins, which requires accounting for N^{-1/2}
non-Gaussian fluctuations of the spin. The latter are treated as a perturbation
about the leading order Gaussian statistics. We obtain exact results for these
quantities, which enable us to characterise the joint distribution of C and Chi
fluctuations. We find that this distribution is qualitatively different, even
for equilibrium above criticality, from the spin-glass scenario where C and Chi
fluctuations are linked in a manner akin to the fluctuation-dissipation
relation between the average C and Chi. Our results show that coarsening at
criticality is clearly heterogeneous for d>4 and suggest that, as in other
glassy systems, there is a well-defined timescale on which fluctuations across
thermal histories are largest. Surprisingly, however, neither this timescale
nor the amplitude of the heterogeneities increase with the age of the system,
as would be expected from the growing correlation length. For d<4, the strength
of the fluctuations varies on a timescale proportional to the age of the
system; the corresponding amplitude also grows with age, but does not scale
with the correlation volume as might have been expected naively.Comment: 39 pages, 9 figures, version for publication in J. Stat. Mech.
Shortened by cutting all technical details in section 6, with minor
corrections elsewher
Bulges or Bars from Secular Evolution?
We use high resolution collisionless -body simulations to study the
secular evolution of disk galaxies and in particular the final properties of
disks that suffer a bar and perhaps a bar-buckling instability. Although we
find that bars are not destroyed by the buckling instability, when we decompose
the radial density profiles of the secularly-evolved disks into inner S\'ersic
and outer exponential components, for favorable viewing angles, the resulting
structural parameters, scaling relations and global kinematics of the bar
components are in good agreement with those obtained for bulges of late-type
galaxies. Round bulges may require a different formation channel or
dissipational processes.Comment: Accepted to ApJL. 4 figures, 2 in color Corrected minor typos and
reference lis
Long term variability of the cosmic ray intensity
In a previous paper Bhat, et al., assess the evidence for the continuing acceleration of cosmic rays in the Loop I supernova remnant. The enhanced gamma-ray emission is found consistent with the Blandford and Cowie model for particle acceleration at the remnant shock wave. The contributions of other supernovae remnants to the galactic cosmic ray energy density are now considered, paying anisotropy of cosmic rays accelerated by local supernovae ( 100 pc). The results are compared with geophysical data on the fluctuations in the cosmic ray intensity over the previous one billion years
On the spectrum of Farey and Gauss maps
In this paper we introduce Hilbert spaces of holomorphic functions given by
generalized Borel and Laplace transforms which are left invariant by the
transfer operators of the Farey map and its induced version, the Gauss map,
respectively. By means of a suitable operator-valued power series we are able
to study simultaneously the spectrum of both these operators along with the
analytic properties of the associated dynamical zeta functions.Comment: 23 page
Venture Capital in Japan: A Financial Instrument Supporting the Innovativeness of the Japanese Economy
Two factors: First, the relatively small number of new companies as well as the number of companies subject to liquidation over the year ("firm turnover") in Japan, and second, the insignificant prestige associated with the profession of entrepreneur do not foster growth in the dynamics of this form of financing ventures. The cited indicator for Japan in among the lowest in comparison with other highly developed countries1, while the profession of entrepreneur is not the foremost dream of college graduates. They would much rather prefer realizing their professional careers as members of the government bureaucracy or employees of a major corporation2. However, this mindset is slowly changing, if for no other reason then, in spite of popular conviction, because most small companies are not established during periods of prosperity, but near the end of the downward phase of the economic cycle. That is exactly the phase Japan has been dealing with for several years now. Young, creative people, recruited from the unemployed, are seeking self-employment, using all possible opportunities embedded in the "again starting up" machinery of the economy.Dwa czynniki: pierwszy - stosunkowo mała liczba nowych firm, a także firm likwidowanych w skali roku ("firm turnover") w Japonii oraz drugi - niewielki prestiż, jakim cieszy się zawód przedsiębiorcy, nie sprzyjają dynamizacji omawianej formy finansowania przedsięwzięć. Cytowany wskaźnik, dla Japonii należy do najniższych w porównaniu z innymi krajami wysoko rozwiniętymi (Grabowiecki 2000), zaś profesja przedsiębiorcy nie jest szczytem marzeń ludzi po studiach. Znacznie bardziej chcieliby oni swoją karierę zawodową realizować jako członkowie rządowej biurokracji lub pracownicy dużej korporacji (Corver 2008, s. 2). Ta świadomość ulega jednak stopniowej zmianie, chociażby dlatego, że wbrew popularnym przekonaniom, większość niewielkich przedsiębiorstw, powstaje nie w okresie prosperity, lecz pod koniec spadkowej fazy cyklu koniunkturalnego. Z taką fazą mamy do czynienia w Japonii od paru lat. Młodzi, kreatywni ludzie, rekrutujący się z bezrobotnych, poszukują samozatrudnienia, wykorzystują wszelakie szanse, tkwiące w "ruszającej na powrót" maszynerii gospodark (Yonekura, Lynskey 2003, s. 11)
Aging in One-Dimensional Coagulation-Diffusion Processes and the Fredrickson-Andersen Model
We analyse the aging dynamics of the one-dimensional Fredrickson-Andersen
(FA) model in the nonequilibrium regime following a low temperature quench.
Relaxation then effectively proceeds via diffusion limited pair coagulation
(DLPC) of mobility excitations. By employing a familiar stochastic similarity
transformation, we map exact results from the free fermion case of diffusion
limited pair annihilation to DLPC. Crucially, we are able to adapt the mapping
technique to averages involving multiple time quantities. This relies on
knowledge of the explicit form of the evolution operators involved. Exact
results are obtained for two-time correlation and response functions in the
free fermion DLPC process. The corresponding long-time scaling forms apply to a
wider class of DLPC processes, including the FA model. We are thus able to
exactly characterise the violations of the fluctuation-dissipation theorem
(FDT) in the aging regime of the FA model. We find nontrivial scaling forms for
the fluctuation-dissipation ratio (FDR) X = X(tw/t), but with a negative
asymptotic value X = -3*pi/(6*pi - 16) = -3.307. While this prevents a
thermodynamic interpretation in terms of an effective temperature, it is a
direct consequence of probing FDT with observables that couple to activated
dynamics. The existence of negative FDRs should therefore be a widespread
feature in non mean-field systems.Comment: 39 pages, 4 figure
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