5,451 research outputs found
Derivation of Non-isotropic Phase Equations from a General Reaction-Diffusion Equation
A non-isotropic version of phase equations such as the Burgers equation, the
K-dV-Burgers equation, the Kuramoto-Sivashinsky equation and the Benney
equation in the three-dimensional space is systematically derived from a
general reaction-diffusion system by means of the renormalization group method.Comment: 21pages,no figure
Direct observation of a hydrophobic bond in loop-closure of a capped (-OCH2CH2-)n oligomer in water
The small r variation of the probability density P(r) for end-to-end
separations of a -CH2CH3 capped (-OCH2CH2-)n oligomer in water is computed to
be closely similar to the CH4 ... CH4 potential of mean force under the same
circumstances. Since the aqueous solution CH4 ... CH4 potential of mean force
is the natural physical definition of a primitive hydrophobic bond, the present
result identifies an experimentally accessible circumstance for direct
observation of a hydrophobic bond which has not been observed previously
because of the low solubility of CH4 in water. The physical picture is that the
soluble chain molecule carries the capping groups into aqueous solution, and
permits them to find one another with reasonable frequency. Comparison with the
corresponding results without the solvent shows that hydration of the solute
oxygen atoms swells the chain molecule globule. This supports the view that the
chain molecule globule might have a secondary effect on the hydrophobic
interaction which is of first interest here. The volume of the chain molecule
globule is important for comparing the probabilities with and without solvent
because it characterizes the local concentration of capping groups. Study of
other capping groups to enable X-ray and neutron diffraction measurements of
P(r) is discussed.Comment: 4 pages, 3 figure
Derivation of Amplitude Equations by Renormalization Group Method
A proper formulation in the perturbative renormalization group method is
presented to deduce amplitude equations. The formulation makes it possible not
only avoiding a serious difficulty in the previous reduction to amplitude
equations by eliminating all of the secular terms but also consistent
derivation of higher-order correction to amplitude equations.Comment: 6 page, revte
Hydrophobic and hydrophilic interactions in aqueous mixtures of alcohols at a hydrophobic surface
Aqueous solutions of alcohols are interesting because of their anomalous behavior that is believed
to be due to the molecular structuring of water and alcohol around each other in solution. The interfacial
structuring and properties are significant for application in alcohol purification processes
and biomolecular structure. Here we study aqueous mixtures of short alcohols (methanol, ethanol,
1-propanol, and 2-propanol) at a hydrophobic surface using interfacial statistical associating fluid
theory which is a perturbation density functional theory. The addition of a small amount of alcohol
decreases the interfacial tension of water drastically. This trend in interfacial tension can be
explained by the structure of water and alcohol next to the surface. The hydrophobic group of an
added alcohol preferentially goes to the surface preserving the structure of water in the bulk. For
a given bulk alcohol concentration, water mixed with the different alcohols has different interfacial
tensions with propanol having a lower interfacial tension than methanol and ethanol. 2-propanol is
not as effective in decreasing the interfacial tension as 1-propanol because it partitions poorly to
the surface due to its larger excluded volume. But for a given surface alcohol mole fraction, all the
alcohol mixtures give similar values for interfacial tension. For separation of alcohol from water,
methods that take advantage of the high surface mole fraction of alcohol have advantages compared
to separation using the vapor in equilibrium with a water-alcohol liquid
Renormalization group approach to vibrational energy transfer in protein
Renormalization group method is applied to the study of vibrational energy
transfer in protein molecule. An effective Lagrangian and associated equations
of motion to describe the resonant energy transfer are analyzed in terms of the
first-order perturbative renormalization group theory that has been developed
as a unified tool for global asymptotic analysis. After the elimination of
singular terms associated with the Fermi resonance, amplitude equations to
describe the slow dynamics of vibrational energy transfer are derived, which
recover the result obtained by a technique developed in nonlinear optics [S.J.
Lade, Y.S. Kivshar, Phys. Lett. A 372 (2008) 1077].Comment: 11 page
Stable Control of Pulse Speed in Parametric Three-Wave Solitons
We analyze the control of the propagation speed of three wave packets
interacting in a medium with quadratic nonlinearity and dispersion. We found
analytical expressions for mutually trapped pulses with a common velocity in
the form of a three-parameter family of solutions of the three-wave resonant
interaction. The stability of these novel parametric solitons is simply related
to the value of their common group velocity
A Diagnostic of Laser-imploded Target at Fast Ignition by Uniformly Redundant Penumbral Array Camera
RF amplification property of the MgO-based magnetic tunnel junction using field-induced ferromagnetic resonance
The radio-frequency (RF) voltage amplification property of a tunnel
magnetoresistance device driven by an RF external-magnetic-field-induced
ferromagnetic resonance was studied. The proposed device consists of a magnetic
tunnel junction (MTJ) and an electrically isolated coplanar waveguide. The
input RF voltage applied to the waveguide can excite the resonant dynamics in
the free layer magnetization, leading to the generation of an output RF voltage
under a DC bias current. The dependences of the RF voltage gain on the static
external magnetic field strength and angle were systematically investigated.
The design principles for the enhancement of the gain factor are also
discussed.Comment: 12 pages, 3 figure
Lithium Diffusion & Magnetism in Battery Cathode Material LixNi1/3Co1/3Mn1/3O2
We have studied low-temperature magnetic properties as well as
high-temperature lithium ion diffusion in the battery cathode materials
LixNi1/3Co1/3Mn1/3O2 by the use of muon spin rotation/relaxation. Our data
reveal that the samples enter into a 2D spin-glass state below TSG=12 K. We
further show that lithium diffusion channels become active for T>Tdiff=125 K
where the Li-ion hopping-rate [nu(T)] starts to increase exponentially.
Further, nu(T) is found to fit very well to an Arrhenius type equation and the
activation energy for the diffusion process is extracted as Ea=100 meV.Comment: Submitted to Journal of Physics: Conference Series (2014
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