201 research outputs found
Assessing the sensitivity of multi-distance hsNIRS for measuring changes in oxCCO in the brain
A hybrid multi-distance hyperspectral near-infrared spectroscopy (hsNIRS) and diffuse correlation spectroscopy (DCS) optical system was used to test transient changes in cytochrome c oxidase (oxCCO) in the brain during carotid compressions (CC) and hypercapnia
Stratorotational instability in MHD Taylor-Couette flows
The stability of dissipative Taylor-Couette flows with an axial stable
density stratification and a prescribed azimuthal magnetic field is considered.
Global nonaxisymmetric solutions of the linearized MHD equations with toroidal
magnetic field, axial density stratification and differential rotation are
found for both insulating and conducting cylinder walls. Flat rotation laws
such as the quasi-Kepler law are unstable against the nonaxisymmetric
stratorotational instability (SRI). The influence of a current-free toroidal
magnetic field depends on the magnetic Prandtl number Pm: SRI is supported by
Pm > 1 and it is suppressed by Pm \lsim 1. For too flat rotation laws a smooth
transition exists to the instability which the toroidal magnetic field produces
in combination with the differential rotation. This nonaxisymmetric azimuthal
magnetorotational instability (AMRI) has been computed under the presence of an
axial density gradient. If the magnetic field between the cylinders is not
current-free then also the Tayler instability occurs and the transition from
the hydrodynamic SRI to the magnetic Tayler instability proves to be rather
complex. Most spectacular is the `ballooning' of the stability domain by the
density stratification: already a rather small rotation stabilizes magnetic
fields against the Tayler instability. An azimuthal component of the resulting
electromotive force only exists for density-stratified flows. The related
alpha-effect for magnetic SRI of Kepler rotation appears to be positive for
negative d\rho/dz <0.Comment: 10 pages, 13 figures, submitted to Astron. Astrophy
Melting of a 2D Quantum Electron Solid in High Magnetic Field
The melting temperature () of a solid is generally determined by the
pressure applied to it, or indirectly by its density () through the equation
of state. This remains true even for helium solids\cite{wilk:67}, where quantum
effects often lead to unusual properties\cite{ekim:04}. In this letter we
present experimental evidence to show that for a two dimensional (2D) solid
formed by electrons in a semiconductor sample under a strong perpendicular
magnetic field\cite{shay:97} (), the is not controlled by , but
effectively by the \textit{quantum correlation} between the electrons through
the Landau level filling factor =. Such melting behavior, different
from that of all other known solids (including a classical 2D electron solid at
zero magnetic field\cite{grim:79}), attests to the quantum nature of the
magnetic field induced electron solid. Moreover, we found the to increase
with the strength of the sample-dependent disorder that pins the electron
solid.Comment: Some typos corrected and 2 references added. Final version with minor
editoriol revisions published in Nature Physic
The Shapes of Cooperatively Rearranging Regions in Glass Forming Liquids
The shapes of cooperatively rearranging regions in glassy liquids change from
being compact at low temperatures to fractal or ``stringy'' as the dynamical
crossover temperature from activated to collisional transport is approached
from below. We present a quantitative microscopic treatment of this change of
morphology within the framework of the random first order transition theory of
glasses. We predict a correlation of the ratio of the dynamical crossover
temperature to the laboratory glass transition temperature, and the heat
capacity discontinuity at the glass transition, Delta C_p. The predicted
correlation agrees with experimental results for the 21 materials compiled by
Novikov and Sokolov.Comment: 9 pages, 6 figure
Spatial and Spectral Coherent Control with Frequency Combs
Quantum coherent control (1-3) is a powerful tool for steering the outcome of
quantum processes towards a desired final state, by accurate manipulation of
quantum interference between multiple pathways. Although coherent control
techniques have found applications in many fields of science (4-9), the
possibilities for spatial and high-resolution frequency control have remained
limited. Here, we show that the use of counter-propagating broadband pulses
enables the generation of fully controlled spatial excitation patterns. This
spatial control approach also provides decoherence reduction, which allows the
use of the high frequency resolution of an optical frequency comb (10,11). We
exploit the counter-propagating geometry to perform spatially selective
excitation of individual species in a multi-component gas mixture, as well as
frequency determination of hyperfine constants of atomic rubidium with
unprecedented accuracy. The combination of spectral and spatial coherent
control adds a new dimension to coherent control with applications in e.g
nonlinear spectroscopy, microscopy and high-precision frequency metrology.Comment: 12 page
DER OKONOMISCHE EFFEKT EINER ERHOHUNG DER ARBEITSLOSENLEISTUNGEN : NEUBETRACHT UNTER VERWENDUNG DES ATKINSON MODELLS
In der zweiten Halfte der 1970er begannen sich wirtschaftliche Kennziffern industrialisierter Staaten rapide zu verschlechtern. Gleichzeitig ruckte der Wohlfahrtsstaat als Ursache in das Zentrum der Kritik. Einige Wirtschaftswissenschaftler, insbesondere die deutschen Neo- Liberalisten, hatten bereits seit den 1950ern eine kritische Haltung zum wohlfahrtsstaatlichen Konzept eingenommen. Seit den 1970ern gesellten sich zu diesen Liberalisten auch viele Wirtschaftswissenschaftler, die zuvor den Wohlfahrtsstaat unterstutzt hatten. A.B. Atkinson wies jedoch daraufhin, daB viele der verwandten okonomischen Analysen auf un- fundierten theoretischen Modellen basierten, die die eigentlichen Merkmale des sozialen Wohlfahrtsprogramms auBer Acht lieBen. In der vorliegenden Arbeit gehen wir daher, den wirtschaftlichen Auswirkungen der Arbeitslosenversicherung in Einklang mit Atkinsons Kritik nach. Es gelang ihm gegenteilige Ergebnisse zu dem popularen Shapiro und Stiglitz Shirking Modell, durch Einfuhrung zweier Annahmen, d.h. Arbeitslosenleistungen werden identifizierten Shirkern vorenthalten und Arbeitslosenleistungen werden generell nur fur einen bestimmten Zeitraum angeboten, nachzuweisen. In der vorliegenden Arbeit zeigen wir, daB Gehalt basierende Arbeitslosenleistungen sich positiv auf Produktivitat und Beschaftigung auswirken. Zeitliche Begrenzung und eine ansteigende Sockelleistung alleine haben nicht die gleichen Ergebnisse im Shapiro und Stiglitz Modell
α-thalassaemia
Alpha-thalassaemia is inherited as an autosomal recessive disorder characterised by a microcytic hypochromic anaemia, and a clinical phenotype varying from almost asymptomatic to a lethal haemolytic anaemia
The Mathematical Theory of Wavelets
ABSTRACT. We present an overview of some aspects of the mathematical theory of wavelets. These notes are addressed to an audience of mathematicians familiar with only the most basic elements of Fourier Analysis. The material discussed is quite broad and covers several topics involving wavelets. Though most of the larger and more involved proofs are not included, complete references to them are provided. We do, however, present complete proofs for results that are new (in particular, this applies to a recently obtained characterization of “all ” wavelets in section 4). 1
Geographic variation in breeding system and environment predicts melanin-based plumage ornamentation of male and female Kentish plovers
Sexual selection determines the elaboration of morphological and behavioural traits and thus drives the evolution of phenotypes. Sexual selection on males and females can differ between populations, especially when populations exhibit different breeding systems. A substantial body of literature describes how breeding systems shape ornamentation across species, with a strong emphasis on male ornamentation and female preference. However, whether breeding system predicts ornamentation within species and whether similar mechanisms as in males also shape the phenotype of females remains unclear. Here, we investigate how different breeding systems are associated with male and female ornamentation in five geographically distinct populations of Kentish plovers Charadrius alexandrinus. We predicted that polygamous populations would exhibit more elaborate ornaments and stronger sexual dimorphism than monogamous populations. By estimating the size and intensity of male (n = 162) and female (n = 174) melanin-based plumage ornaments, i.e. breast bands and ear coverts, we show that plumage ornamentation is predicted by breeding system in both sexes. A difference in especially male ornamentation between polygamous (darker and smaller ornaments) and monogamous (lighter and larger) populations causes the greatest sexual dimorphism to be associated with polygamy. The non-social environment, however, may also influence the degree of ornamentation, for instance through availability of food. We found that, in addition to breeding system, a key environmental parameter, rainfall, predicted a seasonal change of ornamentation in a sex-specific manner. Our results emphasise that to understand the phenotype of animals, it is important to consider both natural and sexual selection acting on both males and females
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