42,849 research outputs found
Spectroscopic Evidence for the Specific Na+ and K+ Interactions with the Hydrogen-bonded Water Molecules at the Electrolyte Aqueous Solution Surfaces
Sum frequency generation vibrational spectra of the water molecules at the
NaF and KF aqueous solution surfaces showed significantly different spectral
features and different concentration dependence. This result is the first
direct observation of the cation effects of the simple alkali cations, which
have been believed to be depleted from the aqueous surface, on the hydrogen
bonding structure of the water molecules at the electrolyte solution surfaces.
These observations may provide important clue to understand the fundamental
phenomenon of ions at the air/water interface.Comment: 15 pages, 2 figure
Molecular biology on a microfluidic chip
We have developed microfluidic chips for automating molecular biology processes such as gene ligation and gene transformation from nanolitre sample volumes with parallel architecture. Unlike conventional tube methods with cumbersome pipetting procedures, all processes, including metering of samples, ligation and transformation, were carried out in the microfluidic chips through pneumatic control of the nanofluid. The microfluidic devices presented here offer an illustration of some of the basic physics that arises when trying to miniaturize and automate biological techniques
New Method for Numerically Solving the Chemical Potential Dependence of the Dressed Quark Propagator
Based on the rainbow approximation of Dyson-Schwinger equation and the
assumption that the inverse dressed quark propagator at finite chemical
potential is analytic in the neighborhood of , a new method for
obtaining the dressed quark propagator at finite chemical potential from
the one at zero chemical potential is developed. Using this method the dressed
quark propagator at finite chemical potential can be obtained directly from the
one at zero chemical potential without the necessity of numerically solving the
corresponding coupled integral equations by iteration methods. A comparison
with previous results is given.Comment: Revtex, 14 pages, 5 figure
Extended Optical Model Analyses of Elastic Scattering, Direct Reaction, and Fusion Cross Sections for the 9Be + 208Pb System at Near-Coulomb-Barrier Energies
Based on the extended optical model approach in which the polarization
potential is decomposed into direct reaction (DR) and fusion parts,
simultaneous analyses are performed for elastic scattering, DR, and
fusion cross section data for the Be+Pb system at
near-Coulomb-barrier energies. Similar analyses are also performed
by only taking into account the elastic scattering and fusion data as was
previously done by the present authors, and the results are compared with those
of the full analysis including the DR cross section data as well. We find that
the analyses using only elastic scattering and fusion data can produce very
consistent and reliable predictions of cross sections particularly when the DR
cross section data are not complete. Discussions are also given on the results
obtained from similar analyses made earlier for the Be+Bi system.Comment: 5 figure
model with Hopf term and fractional spin statistics
We reconsider the model with the Hopf term by using the
Batalin-Fradkin-Tyutin (BFT) scheme, which is an improved version of the Dirac
quantization method. We also perform a semi-classical quantization of the
topological charge Q sector by exploiting the collective coordinates to
explicitly show the fractional spin statistics.Comment: 15 page
Symbolic computation of exact solutions expressible in hyperbolic and elliptic functions for nonlinear PDEs
Algorithms are presented for the tanh- and sech-methods, which lead to
closed-form solutions of nonlinear ordinary and partial differential equations
(ODEs and PDEs). New algorithms are given to find exact polynomial solutions of
ODEs and PDEs in terms of Jacobi's elliptic functions.
For systems with parameters, the algorithms determine the conditions on the
parameters so that the differential equations admit polynomial solutions in
tanh, sech, combinations thereof, Jacobi's sn or cn functions. Examples
illustrate key steps of the algorithms.
The new algorithms are implemented in Mathematica. The package
DDESpecialSolutions.m can be used to automatically compute new special
solutions of nonlinear PDEs. Use of the package, implementation issues, scope,
limitations, and future extensions of the software are addressed.
A survey is given of related algorithms and symbolic software to compute
exact solutions of nonlinear differential equations.Comment: 39 pages. Software available from Willy Hereman's home page at
http://www.mines.edu/fs_home/whereman
Detector and Telescope Development for ProtoEXIST and Fine Beam Measurements of Spectral Response of CZT Detectors
We outline our plan to develop ProtoEXIST, a balloon-borne prototype
experiment for the Energetic X-ray Imaging Survey Telescope (EXIST) for the
Black Hole Finder Probe. EXIST will consist of multiple wide-field hard X-ray
coded-aperture telescopes. The current design of the EXIST mission employs two
types of telescope systems: high energy telescopes (HETs) using CZT detectors,
and low energy telescopes (LETs) using Si detectors. With ProtoEXIST, we will
develop and demonstrate the technologies required for the EXIST HETs. As part
of our development efforts, we also present recent laboratory measurements of
the spectral response and efficiency variation of imaging CZT detectors on a
fine scale (~0.5 mm). The preliminary results confirm the need for multi-pixel
readouts and small inter-pixel gaps to achieve uniform spectral response and
high detection efficiency across detectors.Comment: 9 pages, 12 figures, 1 table, appears in SPIE 2005 proceedings (5898:
UV, X-ray, and Gamma-ray Space Instrumentation for Astronomy XIV
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