4,746 research outputs found
Controlling the partial coalescence of a droplet on a vertically vibrated bath
A new method is proposed to stop the cascade of partial coalescences of a
droplet laid on a liquid bath. The strategy consists in vibrating the bath in
the vertical direction in order to keep small droplets bouncing. Since large
droplets are not able to bounce, they partially coalesce until they reach a
critical size. The system behaves as a low pass filter : droplets smaller than
the critical size are selected. This size has been investigated as a function
of the acceleration and the frequency of the bath vibration. Results suggest
that the limit size for bouncing is related to the first mode of the droplet
deformation.Comment: 4 pages, 3 figures, accepted in Phys. Rev.
Asymmetry-Driven Structure Formation in Pair Plasmas
The nonlinear propagation of electromagnetic waves in pair plasmas, in which
the electrostatic potential plays a very important but subdominant role of a
"binding glue" is investigated. Several mechanisms for structure formation are
investigated, in particular, the "asymmetry" in the initial temperatures of the
constituent species. It is shown that the temperature asymmetry leads to a
(localizing) nonlinearity that is new and qualitatively different from the ones
originating in ambient mass or density difference. The temperature asymmetry
driven focusing-defocusing nonlinearity supports stable localized wave
structures in 1-3 dimensions, which, for certain parameters, may have flat-top
shapes.Comment: 23 pages, 6 figures, introduction revised, edited typos, accepted for
publication in Phys. Rev.
Acceleration of Plasma Flows Due to Reverse Dynamo Mechanism
The "reverse-dynamo" mechanism - the amplification/generation of fast plasma
flows by micro scale (turbulent) magnetic fields via magneto-fluid coupling is
recognized and explored. It is shown that macro-scale magnetic fields and flows
are generated simultaneously and proportionately from micro scale fields and
flows. The stronger the micro-scale driver, the stronger are the macro-scale
products. Stellar and astrophysical applications are suggested.Comment: 16 pages including 3 figures. The Astrophys. J. (accepted);
additional material is given for clarification; terminology is change
Vortex Bubble Formation in Pair Plasmas
It is shown that delocalized vortex solitons in relativistic pair plasmas
with small temperature asymmetries can be unstable for intermediate intensities
of the background electromagnetic field. Instability leads to the generation of
ever-expanding cavitating bubbles in which the electromagnetic fields are zero.
The existence of such electromagnetic bubbles is demonstrated by qualitative
arguments based on a hydrodynamic analogy, and by numerical solutions of the
appropriate Nonlinear Schr\"odinger equation with a saturating nonlinearity.Comment: 4 pages of two-column text, 2 figure
Microscopic origin of local moments in a zinc-doped high- superconductor
The formation of a local moment around a zinc impurity in the high-
cuprate superconductors is studied within the framework of the bosonic
resonating-valence-bond (RVB) description of the model. A topological
origin of the local moment has been shown based on the phase string effect in
the bosonic RVB theory. It is found that such an moment distributes
near the zinc in a form of staggered magnetic moments at the copper sites. The
corresponding magnetic properties, including NMR spin relaxation rate, uniform
spin susceptibility, and dynamic spin susceptibility, etc., calculated based on
the theory, are consistent with the experimental measurements. Our work
suggests that the zinc substitution in the cuprates provide an important
experimental evidence for the RVB nature of local physics in the original (zinc
free) state.Comment: The topological reason of local moment formation is given. One figure
is adde
A case of multiple fibroid uterus, complete placenta praevia, antepartum haemorrhage, myomectomy and obstetric hysterectomy: a near miss
An interesting case of young unbooked, unregistered, primigravida with multiple fibroid uterus, placenta praevia type IV, presented with APH in haemorrhagic Shock, impacted large fibroid in Lower Uterine Segment and Multiple fibroids on Anterior wall, fundus for which myomectomy was performed. Preterm Caesarean Section with extremely low birth weight infant delivered followed by life-saving Emergency Obstetric hysterectomy. She had uneventful recovery without any complications of massive transfusion or surgery. Case is being reported as an obstetric near miss
Local structure of REFeAsO (RE=La, Pr, Nd, Sm) oxypnictides studied by Fe K-edge EXAFS
Local structure of REOFeAs (RE=La, Pr, Nd, Sm) system has been studied as a
function of chemical pressure varied due to different rare-earth size. Fe
K-edge extended X-ray absorption fine structure (EXAFS) measurements in the
fluorescence mode has permitted to compare systematically the inter-atomic
distances and their mean square relative displacements (MSRD). We find that the
Fe-As bond length and the corresponding MSRD hardly show any change, suggesting
the strongly covalent nature of this bond, while the Fe-Fe and Fe-RE bond
lengths decrease with decreasing rare earth size. The results provide important
information on the atomic correlations that could have direct implication on
the superconductivity and magnetism of REOFeAs system, with the chemical
pressure being a key ingredient
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