38,100 research outputs found
Hydrogen adsorption on Pd(133) surface
In this study used is an approach based on measurements of the total energy
distribution (TED) of field emitted electrons in order to examine the
properties of Pd (133) from the aspect of both hydrogen adsorption and surface
hydrides formation. The most favourable sites offered to a hydrogen atom to be
adsorbed have been indicated and an attempt to describe the peaks of the
enhancement factor R spectrum to the specific adsorption sites has also been
made.Comment: to be submitted to the Centr. Eur. J. Phy
A High-Precision Micropipette Sensor for Cellular-Level Real-Time Thermal Characterization
We report herein development of a novel glass micropipette thermal sensor fabricated in a cost-effective manner, which is capable of measuring steady thermal fluctuation at spatial resolution of similar to 2 mu m with an accuracy of +/- 0.01 degrees C. We produced and tested various micrometer-sized sensors, ranging from 2 mu m to 30 mu m. The sensor comprises unleaded low-melting-point solder alloy (Sn-based) as a core metal inside a pulled borosilicate glass pipette and a thin film of nickel coating outside, creating a thermocouple junction at the tip. The sensor was calibrated using a thermally insulated calibration chamber, the temperature of which can be controlled with an accuracy of +/- 0.01 degrees C, and the thermoelectric power (Seebeck coefficient) of the sensor was recorded from 8.46 to 8.86 mu V/degrees C. We have demonstrated the capability of measuring temperatures at a cellular level by inserting our temperature sensor into the membrane of a live retinal pigment epithelium cell subjected to a laser beam with a focal spot of 6 mu m. We measured transient temperature profiles and the maximum temperatures were in the range of 38-55 +/- 0.5 degrees C.open111212sciescopu
Z-graded weak modules and regularity
It is proved that if any Z-graded weak module for vertex operator algebra V
is completely reducible, then V is rational and C_2-cofinite. That is, V is
regular. This gives a natural characterization of regular vertex operator
algebras.Comment: 9 page
Modeling quark-hadron duality in polarization observables
We apply a model for the study of quark-hadron duality in inclusive electron
scattering to the calculation of spin observables. The model is based on
solving the Dirac equation numerically for a scalar confining linear potential
and a vector color Coulomb potential. We qualitatively reproduce the features
of quark-hadron duality for all potentials considered, and discuss the onset of
scaling and duality for the responses, spin structure functions, and
polarization asymmetries. Duality may be applied to gain access to kinematic
regions which are hard to access in deep inelastic scattering, namely for
, and we discuss which observables are most suitable for this
application of duality
Unitarity potentials and neutron matter at the unitary limit
We study the equation of state of neutron matter using a family of unitarity
potentials all of which are constructed to have infinite scattering
lengths . For such system, a quantity of much interest is the ratio
where is the true ground-state energy of the system,
and is that for the non-interacting system. In the limit of
, often referred to as the unitary limit, this ratio is
expected to approach a universal constant, namely . In the
present work we calculate this ratio using a family of hard-core
square-well potentials whose can be exactly obtained, thus enabling us to
have many potentials of different ranges and strengths, all with infinite
. We have also calculated using a unitarity CDBonn potential
obtained by slightly scaling its meson parameters. The ratios given by
these different unitarity potentials are all close to each other and also
remarkably close to 0.44, suggesting that the above ratio is indifferent
to the details of the underlying interactions as long as they have infinite
scattering length. A sum-rule and scaling constraint for the renormalized
low-momentum interaction in neutron matter at the unitary limit is discussed.Comment: 7.5 pages, 7 figure
Systematic analysis of group identification in stock markets
We propose improved methods to identify stock groups using the correlation
matrix of stock price changes. By filtering out the marketwide effect and the
random noise, we construct the correlation matrix of stock groups in which
nontrivial high correlations between stocks are found. Using the filtered
correlation matrix, we successfully identify the multiple stock groups without
any extra knowledge of the stocks by the optimization of the matrix
representation and the percolation approach to the correlation-based network of
stocks. These methods drastically reduce the ambiguities while finding stock
groups using the eigenvectors of the correlation matrix.Comment: 9 pages, 7 figure
The nucleon's strange electromagnetic and scalar matrix elements
Quenched lattice QCD simulations and quenched chiral perturbation theory are
used together for this study of strangeness in the nucleon. Dependences of the
matrix elements on strange quark mass, valence quark mass and momentum transfer
are discussed in both the lattice and chiral frameworks. The combined results
of this study are in good agreement with existing experimental data and
predictions are made for upcoming experiments. Possible future refinements of
the theoretical method are suggested.Comment: 24 pages, 9 figure
The structure of parafermion vertex operator algebras
It is proved that the parafermion vertex operator algebra associated to the
irreducible highest weight module for the affine Kac-Moody algebra A_1^{(1)} of
level k coincides with a certain W-algebra. In particular, a set of generators
for the parafermion vertex operator algebra is determined.Comment: 12 page
Relationship between the gamma-ray burst pulse width and energy due to the Doppler effect of fireballs
We study in details how the pulse width of gamma-ray bursts is related with
energy under the assumption that the sources concerned are in the stage of
fireballs. Due to the Doppler effect of fireballs, there exists a power law
relationship between the two quantities within a limited range of frequency.
The power law range and the power law index depend strongly on the observed
peak energy as well as the rest frame radiation form, and the upper and
lower limits of the power law range can be determined by . It is found
that, within the same power law range, the ratio of the of the rising
portion to that of the decaying phase of the pulses is also related with energy
in the form of power laws. A platform-power-law-platform feature could be
observed in the two relationships. In the case of an obvious softening of the
rest frame spectrum, the two power law relationships also exist, but the
feature would evolve to a peaked one. Predictions on the relationships in the
energy range covering both the BATSE and Swift bands for a typical hard burst
and a typical soft one are made. A sample of FRED (fast rise and exponential
decay) pulse bursts shows that 27 out of the 28 sources belong to either the
platform-power-law-platform feature class or the peaked feature group,
suggesting that the effect concerned is indeed important for most of the
sources of the sample. Among these bursts, many might undergo an obvious
softening evolution of the rest frame spectrum.Comment: Accepted for publication in The Astrophysical Journa
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