12,142 research outputs found
Improved (e,e') response functions at intermediate momentum transfers: the 3He case
A possibility of extending the applicability range of non-relativistic
calculations of electronuclear response functions in the quasielasic peak
region is studied. We show that adopting a particular model for determining the
kinematical inputs of the non-relativistic calculations can extend this range
considerably, almost eliminating the reference frame dependence of the results.
We also show that there exists one reference frame, where essentially the same
result can be obtained with no need of adopting the particular kinematical
model. The calculation is carried out with the Argonne V18 potential and the
Urbana IX three-nucleon interaction. A comparison of these improved
calculations with experimental data shows a very good agreement for the
quasielastic peak positions at 600, 700 MeV/c and for the peak heights
at the two lower --values, while for the peak height at MeV/c one
finds differences of about 20%.Comment: 10 pages, 4 figure
Characteristic spatial scale of vesicle pair interactions in a plane linear flow
We report the experimental studies on interaction of two vesicles trapped in
a microfluidic analog of four-roll mill, where a plane linear flow is realized.
We found that the dynamics of a single vesicle is significantly altered by the
presence of another vesicle at separation distances up to about 3.2 \div 3.7
times of effective radius of the vesicles. This is supported by direct
measurements of a single vesicle back-reaction on the velocity field. Thus, the
experiment provides the lower bound for the interaction scale of vesicles and
so the corresponding upper bound for the volume fraction \phi=0.08 \div 0.13 of
non-interacting vesicle suspensions.Comment: 5 pages, 8 figures, PRE accepted for publicatio
Chemotaxis of Arbacia punctulata spermatozoa to resact, a peptide from the egg jelly layer
Resact, a peptide of known sequence isolated from the jelly layer of Arbacia punctulata eggs, is a potent chemoattractant for A. punctulata spermatozoa. The chemotactic response is concentration dependent, is abolished by pretreatment of the spermatozoa with resact, and shows an absolute requirement for millimolar external calcium. A. punctulata spermatozoa do not respond to speract, a peptide isolated from the jelly layer of Strongylocentrotus purpuratus eggs. This is the first report of animal sperm chemotaxis in response to a defined egg-derived molecule
Sedeonic relativistic quantum mechanics
We represent sixteen-component values "sedeons", generating associative
noncommutative space-time algebra. We demonstrate a generalization of
relativistic quantum mechanics using sedeonic wave functions and sedeonic
space-time operators. It is shown that the sedeonic second-order equation for
the sedeonic wave function, obtained from the Einstein relation for energy and
momentum, describes particles with spin 1/2. We show that for the special types
of wave functions the sedeonic second-order equation can be reduced to the set
of sedeonic first-order equations analogous to the Dirac equation. At the same
time it is shown that these sedeonic equations differ in space-time properties
and describe several types of massive and corresponding massless particles. In
particular we proposed four different equations, which could describe four
types of neutrinos.Comment: 22 pages, 3 table
Two-fluid behavior of the Kondo lattice in the 1/N slave boson approach
It has been recently shown by Nakatsuji, Pines, and Fisk [S. Nakatsuji, D.
Pines, and Z. Fisk, Phys. Rev. Lett. 92, 016401 (2004)] from the
phenomenological analysis of experiments in Ce1-xLaxCoIn5 and CeIrIn5 that
thermodynamic and transport properties of Kondo lattices below coherence
temperature can be very successfully described in terms of a two-fluid model,
with Kondo impurity and heavy electron Fermi liquid contributions. We analyze
thermodynamic properties of Kondo lattices using 1/N slave boson treatment of
the periodic Anderson model and show that these two contributions indeed arise
below the coherence temperature. We find that the Kondo impurity contribution
to thermodynamics corresponds to thermal excitations into the flat portion of
the energy spectrum.Comment: 7 pages, 2 figure
Octonic Electrodynamics
In this paper we present eight-component values "octons", generating
associative noncommutative algebra. It is shown that the electromagnetic field
in a vacuum can be described by a generalized octonic equation, which leads
both to the wave equations for potentials and fields and to the system of
Maxwell's equations. The octonic algebra allows one to perform compact combined
calculations simultaneously with scalars, vectors, pseudoscalars and
pseudovectors. Examples of such calculations are demonstrated by deriving the
relations for energy, momentum and Lorentz invariants of the electromagnetic
field. The generalized octonic equation for electromagnetic field in a matter
is formulated.Comment: 12 pages, 1 figur
Electrodynamics of Media
Contains reports on one research project.Joint Services Electronics Programs (U.S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E)U. S. Air Force Cambridge Research Laboratories Contract F19628-70-C-006
Direct Confirmation of Two Pattern Speeds in the Double Barred Galaxy NGC 2950
We present surface photometry and stellar kinematics of NGC 2950, which is a
nearby and undisturbed SB0 galaxy hosting two nested stellar bars. We use the
Tremaine-Weinberg method to measure the pattern speed of the primary bar. This
also permits us to establish directly and for the first time that the two
nested bars are rotating with different pattern speeds, and in particular that
the rotation frequency of the secondary bar is higher than that of the primary
one.Comment: 12 pages, 4 figures. To appear in ApJ Letter
Canonical-grandcanonical ensemble in-equivalence in Fermi systems?
I discuss the effects of fermionic condensation in systems of constant
density of states. I show that the condensation leads to a correction of the
chemical potential and of the Fermi distribution in canonical Fermi systems at
low temperatures. This implies that the canonical and grandcanonical ensembles
are not equivalent even for Fermi systems.Comment: 4 pages and 1 figur
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