4,558 research outputs found
Magnon scattering processes and low temperature resistivity in CMR manganites
Low temperature resistivity of CMR manganites is investigated. At the ground
state, conduction electrons are perfectly spin polarized, which is called
half-metallic. From one-magnon scattering processes, it is discussed that the
resistivity of a half metal as a function of temperature scales as rho(T) -
rho(0) propto T^3. We take (Nd,Tb,Sr)MnO_3 as an example to compare theory and
experiments. The result is in a good agreement.Comment: To appear in Proc. ICM 200
Tokyo Axion Helioscope
A new search result of the Tokyo axion helioscope is presented. The axion
helioscope consists of a dedicated cryogen-free 4T superconducting magnet with
an effective length of 2.3 m and PIN photodiodes as x-ray detectors. Solar
axions, if exist, would be converted into X-ray photons through the inverse
Primakoff process in the magnetic field. Conversion is coherently enhanced even
for massive axions by filling the conversion region with helium gas. The
present third phase measurement sets a new limit of
g_{a\gamma\gamma}<(5.6--13.4)\times10^{-10} GeV^{-1} for the axion mass of
0.84<m_a<1.0 eV at 95% confidence level.Comment: 4th Patras Workshop on Axions, WIMPs and WISP
Generalized Arcsine Law and Stable Law in an Infinite Measure Dynamical System
Limit theorems for the time average of some observation functions in an
infinite measure dynamical system are studied. It is known that intermittent
phenomena, such as the Rayleigh-Benard convection and Belousov-Zhabotinsky
reaction, are described by infinite measure dynamical systems.We show that the
time average of the observation function which is not the function,
whose average with respect to the invariant measure is finite, converges to
the generalized arcsine distribution. This result leads to the novel view that
the correlation function is intrinsically random and does not decay. Moreover,
it is also numerically shown that the time average of the observation function
converges to the stable distribution when the observation function has the
infinite mean.Comment: 8 pages, 8 figure
Seasonal cycles of ozone and oxidized nitrogen species in northeast Asia - 2:A model analysis of the roles of chemistry and transport
[1] The dominant factors controlling the seasonal variations of ozone (O-3) and three major oxidized nitrogen species, peroxyacetyl nitrate (PAN), nitrogen oxides (NOx), and nitric acid (HNO3), in northeast Asia are investigated by using a three-dimensional global chemical transport model to analyze surface observations made at Rishiri Island, a remote island in northern Japan. The model was evaluated by comparing with observed seasonal variations, and with the relationships between O-3, CO, and PAN. We show that the model reproduces the chemical environment at Rishiri Island reasonably well, and that the seasonal cycles of O-3, CO, NOy species, and VOCs are well predicted. The impact of local emissions on some of these constituents is significant, but is not the dominant factor affecting the seasonal cycles. The seasonal roles of chemistry and transport in controlling O-3 and PAN are revealed by examining production/ destruction and import/ export/deposition fluxes in the boundary layer over the Rishiri region. For O-3, transport plays a key role throughout the year, and the regional photochemical contribution is at most 10% in summer. For PAN, in contrast, transport dominates in winter, while in-situ chemistry contributes as much as 75% in summer. It is suggested that the relative contribution of transport and in-situ chemistry is significantly different for O-3 and PAN, but that the wintertime dominance of transport due to the long chemical lifetimes of these species is sufficient to drive the seasonal cycles of springtime maximum and summertime minimum characteristic of remote sites
Relationship between reaction Time And Onset of The Muscle Activation During Drop Landing
Quickness is one of very important factors for athletes in sporting activities. Measuring reaction time reflects how quickly they can move by contracting associated muscles. Reaction time consists of the pre-motor time, as the time from stimulus input to the onset of the muscle activation, and the motor time, as the time from the onset of the muscle activation to the point of body motion begun. In 2004, Demont et al. were reported that a neuromuscular feed forward process as measured by preactivation of the muscle to stabilize joints dynamically during drop landing. This contributed to prevent injuries. Both time of pre-motor and preactivation were the muscle activities that occur before the body motion begins. The purpose of this study was to clarify the relationship between reaction time and onset of the muscle activity during drop landing
Measurement of the thickness of an insensitive surface layer of a PIN photodiode
We measured the thickness of an insensitive surface layer of a PIN
photodiode, Hamamatsu S3590-06, used in the Tokyo Axion Helioscope. We made
alpha-particles impinge on the PIN photodiode in various incidence angles and
measured the pulse height to estimate the thickness of the insensitive surface
layer. This measurement showed its thickness was on the
assumption that the insensitive layer consisted of Si. We calculated the peak
detection efficiency for low energy x-rays in consideration of the insensitive
layer and escape of x-rays and Auger electrons. This result showed the
efficiency for 4-10keV x-rays was more than 95%.Comment: 7 pages, 7 figure
A box model study on photochemical interactions between VOCs and reactive halogen species in the marine boundary layer
International audienceA new chemical scheme is developed for the multiphase photochemical box model SEAMAC (size-SEgregated Aerosol model for Marine Air Chemistry) to investigate photochemical interactions between volatile organic compounds (VOCs) and reactive halogen species in the marine boundary layer (MBL). Based primarily on critically evaluated kinetic and photochemical rate parameters as well as a protocol for chemical mechanism development, the new scheme has achieved a near-explicit description of oxidative degradation of up to C3-hydrocarbons (CH4, C2H6, C3H8, C2H4, C3H6, and C2H2) initiated by reactions with OH radicals, Cl- and Br-atoms, and O3. Rate constants and product yields for reactions involving halogen species are taken from the literature where available, but the majority of them need to be estimated. In particular, addition reactions of halogen atoms with alkenes will result in forming halogenated organic intermediates, whose photochemical loss rates are carefully evaluated in the present work. Model calculations with the new chemical scheme reveal that the oceanic emissions of acetaldehyde (CH3CHO) and alkenes (especially C3H6) are important factors for regulating reactive halogen chemistry in the MBL by promoting the conversion of Br atoms into HBr or more stable brominated intermediates in the organic form. The latter include brominated hydroperoxides, bromoacetaldehyde, and bromoacetone, which sequester bromine from a reactive inorganic pool. The total mixing ratio of brominated organic species thus produced is likely to reach 10-20% or more of that of inorganic gaseous bromine species over wide regions over the ocean. The reaction between Br atoms and C2H2 is shown to be unimportant for determining the degree of bromine activation in the remote MBL. These results imply that reactive halogen chemistry can mediate a link between the oceanic emissions of VOCs and the behaviors of compounds that are sensitive to halogen chemistry such as dimethyl sulfide, NOx, and O3 in the MBL
RELATIONSHIP BETWEEN REDUCED OF MEDIAL LONGITUDINAL ARCH HEIGHT AND KNEE VALGUS
Knee valgus during jump landing is considered to be one of the situations that may cause injury to the anterior cruciate ligament (ACL). Decreased muscle torque during hip abduction is also reported to be a causative factor for knee valgus, as is pronation of the ankle joint (Joseph M et al. 2008). Further, knee valgus may occur when a reduction in the height of the medial longitudinal arch causes ankle pronation, leading to tibial inclination angle to the inside. In this study, motion analysis was performed to investigate the relationship between a reduction in the height of the medial longitudinal arch and knee valgus
- …