8,230 research outputs found
Enhanced conversion efficiency for harmonic generation with double resonance
Conversion efficiency for cw harmonic generation is calculated for the situation in which both fundamental and harmonic waves are resonant. Compared with the situation of a singly resonant cavity at the fundamental, the doubly resonant geometry can lead to an increase of the effective nonlinear coefficient. High conversion efficiency can thus be achieved with nonlinear crystals of relatively low nonlinear coefficient. and with modest pump power for the fundamental input
From first-order magneto-elastic to magneto-structural transition in (Mn,Fe)1.95P0.50Si0.50 compounds
We report on structural, magnetic and magnetocaloric properties of
MnxFe1.95-xP0.50Si0.50 (x > 1.10) compounds. With increasing the Mn:Fe ratio, a
first-order magneto-elastic transition gradually changes into a first-order
magneto-structural transition via a second-order magnetic transition. The study
also shows that thermal hysteresis can be tuned by varying the Mn:Fe ratio.
Small thermal hysteresis (less than 1 K) can be obtained while maintaining a
giant magnetocaloric effect. This achievement paves the way for real
refrigeration applications using magnetic refrigerants.Comment: 4 pages, 3 figures, Supplemental Materia
Capture on High Curvature Region: Aggregation of Colloidal Particle Bound to Giant Phospholipid Vesicles
A very recent observation on the membrane mediated attraction and ordered
aggregation of colloidal particles bound to giant phospholipid vesicles (I.
Koltover, J. O. R\"{a}dler, C. R. Safinya, Phys. Rev. Lett. {\bf 82},
1991(1999)) is investigated theoretically within the frame of Helfrich
curvature elasticity theory of lipid bilayer fluid membrane. Since the concave
or waist regions of the vesicle possess the highest local bending energy
density, the aggregation of colloidal beads on these places can reduce the
elastic energy in maximum. Our calculation shows that a bead in the concave
region lowers its energy . For an axisymmetrical dumbbell
vesicle, the local curvature energy density along the waist is equally of
maximum, the beads can thus be distributed freely with varying separation
distance.Comment: 12 pages, 2 figures. REVte
Spheres and Prolate and Oblate Ellipsoids from an Analytical Solution of Spontaneous Curvature Fluid Membrane Model
An analytic solution for Helfrich spontaneous curvature membrane model (H.
Naito, M.Okuda and Ou-Yang Zhong-Can, Phys. Rev. E {\bf 48}, 2304 (1993); {\bf
54}, 2816 (1996)), which has a conspicuous feature of representing the circular
biconcave shape, is studied. Results show that the solution in fact describes a
family of shapes, which can be classified as: i) the flat plane (trivial case),
ii) the sphere, iii) the prolate ellipsoid, iv) the capped cylinder, v) the
oblate ellipsoid, vi) the circular biconcave shape, vii) the self-intersecting
inverted circular biconcave shape, and viii) the self-intersecting nodoidlike
cylinder. Among the closed shapes (ii)-(vii), a circular biconcave shape is the
one with the minimum of local curvature energy.Comment: 11 pages, 11 figures. Phys. Rev. E (to appear in Sept. 1999
Large deformation of spherical vesicle studied by perturbation theory and Surface evolver
With tangent angle perturbation approach the axial symmetry deformation of a
spherical vesicle in large under the pressure changes is studied by the
elasticity theory of Helfrich spontaneous curvature model.Three main results in
axial symmetry shape: biconcave shape, peanut shape, and one type of myelin are
obtained. These axial symmetry morphology deformations are in agreement with
those observed in lipsome experiments by dark-field light microscopy [Hotani,
J. Mol. Biol. 178, (1984) 113] and in the red blood cell with two thin
filaments (myelin) observed in living state (see, Bessis, Living Blood Cells
and Their Ultrastructure, Springer-Verlag, 1973). Furthermore, the biconcave
shape and peanut shape can be simulated with the help of a powerful software,
Surface Evolver [Brakke, Exp. Math. 1, 141 (1992) 141], in which the
spontaneous curvature can be easy taken into account.Comment: 16 pages, 6 EPS figures and 2 PS figure
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