1,608 research outputs found
Do Binary Hard Disks Exhibit an Ideal Glass Transition?
We demonstrate that there is no ideal glass transition in a binary hard-disk
mixture by explicitly constructing an exponential number of jammed packings
with densities spanning the spectrum from the accepted ``amorphous'' glassy
state to the phase-separated crystal. Thus the configurational entropy cannot
be zero for an ideal amorphous glass, presumed distinct from the crystal in
numerous theoretical and numerical estimates in the literature. This objection
parallels our previous critique of the idea that there is a most-dense random
(close) packing for hard spheres [Torquato et al, Phys. Rev. Lett., 84, 2064
(2000)].Comment: Submitted for publicatio
Charge Fluctuations on Membrane Surfaces in Water
We generalize the predictions for attractions between over-all neutral
surfaces induced by charge fluctuations/correlations to non-uniform systems
that include dielectric discontinuities, as is the case for mixed charged lipid
membranes in an aqueous solution. We show that the induced interactions depend
in a non-trivial way on the dielectric constants of membrane and water and show
different scaling with distance depending on these properties. The generality
of the calculations also allows us to predict under which dielectric conditions
the interaction will change sign and become repulsive
The field theoretic derivation of the contact value theorem in planar geometries and its modification by the Casimir effect
The contact value theorem for Coulomb gases in planar or film-like geometries
is derived using a Hamiltonian field theoretic representation of the system.
The case where the film is enclosed by a material of different dielectric
constant to that of the film is shown to contain an additional Casimir-like
term which is generated by fluctuations of the electric potential about its
mean-field value.Comment: Link between Sine-Gordon and Coulomb gas pressures via subtraction of
self interaction terms included. Discussion of results within Debye-Huckel
approximation included. Added reference
Morphological effects induced by Cucurbitacin E on ovarian cancer cells in vitro
Objective: To study the effects of Cucurbitacin E, extracted from Ecballium elaterium L. A.Rich. on ovarian cancer cell lines in vitro. Materials and Methods: Human ovarian cancer cells (OV_95_CC3) and human lymphocytes were treated with Cucurbitacin E (CuE), a tetracyclic triterpenoid. Morphological changes were examined under the microscope, using the Papanicolau staining procedure, after one and twenty-four hours incubation. Results: Marked effects were observed in treated ovarian cancer cells. With previously studied cell lines, reversible budding of cells and thread formation were observed. In the present study, cells treated with CuE demonstrated more dramatic changes, which were irreversible and more pronounced after twenty-four hours. These changes were not observed in untreated ovarian cells and normal lymphocytes treated with the same compound. Conclusion: From these results obtained, it can be observed that Cucurbitacin E is toxic to ovarian cancer cells but not to normal peripheral lymphocytes.peer-reviewe
Visualization of Spin Polarized States in Biologically-Produced Ensembles of Ferromagnetic Palladium Nanoparticles
We report visualization of spin polarized states in macroscopic ensembles of biologically-produced
ferromagnetic palladium nanoparticles using the Faraday effect-based technique of magneto-optical
imaging. The ferromagnetic palladium only exists in the form of nanoparticles. Large quantities of
palladium nanoparticles may be synthesized via biomineralization from a Pd2+ solution. The ferromagnetic
Pd nanoparticles are formed in the periplasmic space of bacteria during the hydrogen-assisted reduction of
Pd2+ ions by hydrogenases. The ferromagnetism in Pd comes from itinerant electrons. A high Curie
temperature of ferromagnetic palladium, about 200 degrees centigrade above room temperature, would
allow for a range of room-temperature magnetic applications. The processes of the isolation of electron
spins in separate nanoparticles, spin hopping, spin transport and spin correlations may even form a basis
of quantum computing. So far, measurements of the magnetic properties of Pd nanoparticles (PdNP) have
been limited by integral techniques such as SQUID magnetometry, magnetic circular dihroism and muon
spin rotation spectroscopy ( SR). In the present study, ferromagnetic Pd nanoparticles are characterized
using the technique of magneto-optical imaging. This allows visualization of the spin polarization by the
variations in the intensity of polarized light. To perform measurements at relatively low magnetic fields, a
spin injection from a colossal magnetoresistive material has been used.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3533
Consequences of anisotropy in electrical charge storage: application to the characterization by the mirror method of TiO2 rutile
This article is devoted first to anisotropic distributions of stored electric
charges in isotropic materials, second to charge trapping and induced
electrostatic potential in anisotropic dielectrics. On the one hand, we examine
the case of anisotropic trapped charge distributions in linear homogeneous
isotropic (LHI) insulators, obtained after an electron irradiation in a
scanning electron microscope. This injection leads to the formation of a mirror
image
Magnetic Field Structure around Low-Mass Class 0 Protostars: B335, L1527 and IC348-SMM2
We report new 350 micron polarization observations of the thermal dust
emission from the cores surrounding the low-mass, Class 0 YSOs L1527,
IC348-SMM2 and B335. We have inferred magnetic field directions from these
observations, and have used them together with results in the literature to
determine whether magnetically regulated core-collapse and star-formation
models are consistent with the observations. These models predict a pseudo-disk
with its symmetry axis aligned with the core magnetic field. The models also
predict a magnetic field pinch structure on a scale less than or comparable to
the infall radii for these sources. In addition, if the core magnetic field
aligns (or nearly aligns) the core rotation axis with the magnetic field before
core collapse, then the models predict the alignment (or near alignment) of the
overall pinch field structure with the bipolar outflows in these sources. We
show that if one includes the distorting effects of bipolar outflows on
magnetic fields, then in general the observational results for L1527 and
IC348-SMM2 are consistent with these magnetically regulated models. We can say
the same for B335 only if we assume the distorting effects of the bipolar
outflow on the magnetic fields within the B335 core are much greater than for
L1527 and IC348-SMM2. We show that the energy densities of the outflows in all
three sources are large enough to distort the magnetic fields predicted by
magnetically regulated models.Comment: Accepted for publication in The Astrophysical Journa
Charge-Fluctuation-Induced Non-analytic Bending Rigidity
In this Letter, we consider a neutral system of mobile positive and negative
charges confined on the surface of curved films. This may be an appropriate
model for: i) a highly charged membrane whose counterions are confined to a
sheath near its surface; ii) a membrane composed of an equimolar mixture of
anionic and cationic surfactants in aqueous solution. We find that the charge
fluctuations contribute a non-analytic term to the bending rigidity that varies
logarithmically with the radius of curvature. This may lead to spontaneous
vesicle formation, which is indeed observed in similar systems.Comment: Revtex, 9 pages, no figures, submitted to PR
Simple physics of the partly pinned fluid systems
In this paper, we consider some aspects of the physics of the partly pinned
(PP) systems obtained by freezing in place particles in equilibrium bulk fluid
configurations in the normal (nonglassy) state. We first discuss the
configurational overlap and the disconnected density correlation functions,
both in the homogeneous and heterogeneous cases, using the tools of the theory
of adsorption in disordered porous solids. The relevant Ornstein-Zernike
equations are derived, and asymptotic results valid in the regime where the
perturbation due to the pinning process is small are obtained. Second, we
consider the homogeneous PP lattice gas as a means to make contact between
pinning processes in particle and spin systems and show that it can be
straightforwardly mapped onto a random field Ising model with a strongly
asymmetric bimodal distribution of the field. Possible implications of these
results for studies of the glass transition based on PP systems are also
discussed.Comment: 13 pages, 4 figures; v2 to appear in J. Chem. Phy
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