9,229 research outputs found
Ionic Capillary Evaporation in Weakly Charged Nanopores
Using a variational field theory, we show that an electrolyte confined to a
neutral cylindrical nanopore traversing a low dielectric membrane exhibits a
first-order ionic liquid-vapor pseudo-phase-transition from an
ionic-penetration "liquid" phase to an ionic-exclusion "vapor" phase,
controlled by nanopore-modified ionic correlations and dielectric repulsion.
For weakly charged nanopores, this pseudotransition survives and may shed light
on the mechanism behind the rapid switching of nanopore conductivity observed
in experiments.Comment: This version is accepted for publication in PR
Theoretical investigation of finite size effects at DNA melting
We investigated how the finiteness of the length of the sequence affects the
phase transition that takes place at DNA melting temperature. For this purpose,
we modified the Transfer Integral method to adapt it to the calculation of both
extensive (partition function, entropy, specific heat, etc) and non-extensive
(order parameter and correlation length) thermodynamic quantities of finite
sequences with open boundary conditions, and applied the modified procedure to
two different dynamical models. We showed that rounding of the transition
clearly takes place when the length of the sequence is decreased. We also
performed a finite-size scaling analysis of the two models and showed that the
singular part of the free energy can indeed be expressed in terms of an
homogeneous function. However, both the correlation length and the average
separation between paired bases diverge at the melting transition, so that it
is no longer clear to which of these two quantities the length of the system
should be compared. Moreover, Josephson's identity is satisfied for none of the
investigated models, so that the derivation of the characteristic exponents
which appear, for example, in the expression of the specific heat, requires
some care
Optical implementations of two-dimensional fractional Fourier transforms and linear canonical transforms with arbitrary parameters
Cataloged from PDF version of article.We provide a general treatment of optical two-dimensional fractional Fourier transforming systems. We
not only allow the fractional Fourier transform orders to be specified independently for the two dimensions
but also allow the input and output scale parameters and the residual spherical phase factors to be
controlled. We further discuss systems that do not allow all these parameters to be controlled at the
same time but are simpler and employ a fewer number of lenses. The variety of systems discussed and
the design equations provided should be useful in practical applications for which an optical fractional
Fourier transforming stage is to be employed. © 1998 Optical Society of Americ
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Bubbly cavitating flow generation and investigation of its erosional nature for biomedical applications
This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.The paper presents a study of the generation of hydrodynamic bubbly cavitation in microchannels to investigate the destructive energy output resulting from this phenomenon and its potential use in biomedical applications. The research performed in this study includes the experimental results from bubbly cavitation experiments and the findings showing the destructive effects of bubbly cavitating flow on selected specimens and cells. The bubbles caused by hydrodynamic cavitation are highly destructive at the surfaces of the target medium on which they are carefully focused. The resulting destructive energy output could be effectively used for good means such as destroying kidney stones or killing infected cancer cells. Motivated by this potential, the cavitation damage (material removal) to cancerous cells and chalk pieces having similar material properties as calcium phosphate in human bones was investigated. Also the potential of hydrodynamic bubbly cavitation generated at the microscale for biomedical treatments was revealed using the microchannel configuration of a microorifice (with an inner diameter of 0.147 mm and a length of 1.52cm).This work was supported by Sabancı University Internal Grant for Research Program under Grant FRG-C47004
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