298 research outputs found
Comment on ``Adsorption of Polyelectrolyte onto a Colloid of Opposite Charge''
In a recent Letter, Gurovitch and Sens studied the adsorption of a weakly
charged polyelectrolyte chain onto an oppositely charged colloidal particle. By
using a variational technique they found that the colloidal particle can adsorb
a polymer of higher charge than its own, and thus be ``overcharged.'' I argue
that the observed overcharging by a factor of 16/5 is indeed an artifact of the
approximations involved in the study. Moreover, I show that the existence of
overcharging depends crucially on the choice of the trial wave function,
contrary to their claim.Comment: A comment on: E. Gurovitch and P. Sens, Phys. Rev. Lett. 82, 339
(1999
Reply to: Comment on `Long-range electrostatic interactions between like-charged colloids: steric and confinement effects'
In his Comment (cond-mat/0104060) to [Phys. Rev. E 60, 6530 (1999)], Mateescu
shows that while the effective interactions remain repulsive when the specific
size of the micro-ions is taken into account via a Modified Poisson-Boltzmann
equation, a similar conclusion cannot be reached for the situation of complete
lateral confinement. This point is correct but has already been considered in a
more general study [Phys. Rev. E 62, R1465 (2000), where repulsion is
generically obtained]; moreover, we argue that it illustrates the irrelevancy
of the notion of pair potential in completely confined configurations, as shown
on a simple example
Urinary bladder melanosis with complete resolution case report
Background
Melanosis of the bladder is a rare condition characterized by multifocal, diffuse melanin pigmentation of the urothelial mucosa or lamina propria without any proliferation of melanocytes. Less than 25 cases have been reported so far of which only four patients had concurrent urothelial carcinoma.
Case presentation
We are reporting a case of melanosis of the bladder in a 58-year-old female associated with pTaG1 transitional urothelial cell carcinoma (TCC) of the bladder who presented with symptoms of recurrent urinary tract infection (UTI). Cystoscopy and biopsy results confirmed benign melanosis.
Conclusion
Our case is unique because bladder melanosis associated low grade TCC with complete resolution of both conditions within one year
Organized condensation of worm-like chains
We present results relevant to the equilibrium organization of DNA strands of
arbitrary length interacting with a spherical organizing center, suggestive of
DNA-histone complexation in nucleosomes. We obtain a rich phase diagram in
which a wrapping state is transformed into a complex multi-leafed, rosette
structure as the adhesion energy is reduced. The statistical mechanics of the
"melting" of a rosette can be mapped into an exactly soluble one-dimensional
many-body problem.Comment: 15 pages, 2 figures in a pdf fil
USE OF AN INNOVATIVE METHOD FOR STRUCTURAL ANALYSIS OF THE DISTRIBUTION DEVICE USED IN PNEUMATIC MACHINES FOR WEEDING PLANT SOWING
The topic addressed is a computer-aided design (CAD) method combined with computer-aided engineering (CAE) used in the analysis of choosing the optimal constructive variant of the distribution device used in pneumatic machines for weeding plant sowing. The CAD configurations, realized by the 3D parametric modeling using the SolidWorks program, were subjected to structural analysis (von Mises equivalent stress distribution, relative displacement field distribution and safety factor). Based on the resulting data, the mass/resistance coefficient for the 3 analyzed configurations were determined. The comparison of these indicators led to the choice of the optimal constructive variant, namely the most efficient one
CAD-CAE METHOD FOR STRUCTURAL ANALYSIS OF THE WELDED FRAME WITHIN THE COMPONENT OF A SEED DRILL USED FORDIRECTLY SOWING STRAW CEREALS
This paper presents a Computer Assisted Design (CAD) method combined with computer-aided engineering (CAE) used in the analysis of choosing the constructive variant of the welded frame from within the component of a seed drill used fordirectly sowing straw cereals, so that the ratio between the consumption of material for the construction structure per unit of safety coefficient to be minimal and the carrying capacity to be maximal. For this purpose 3D modeling with SolidWorks software has effectively managed three dimensional configurations of the welded frame using Design Table. The three configurations were subjected to structural analysis (the von Mises equivalent of the tension field distribution, the relative displacement of field distribution and the safety coefficient). Based on the resulting data, the mass / resistance ratios for the three configurations analyzed were determined. The comparison of these indicators led to the choice of the optimal constructive variant in the most efficient way. The presented method contributes to reducing the design validation time by eliminating physical performance and testing
Comment on "Long-range electrostatic interactions between like-charged colloids: Steric and confinement effects"
In a recent study [Phys. Rev. E 60, 6530 (1999)], Trizac and Raimbault showed
that the effective pair interaction between like charged colloids immersed in a
cylindrically confined electrolyte remains repulsive even when the size of the
micro-ions or the finite longitudinal extension of the confining cylinder are
taken into account. Contrary to their claim, we argue that the case of finite
longitudinal confinement doesn't always generate repulsive interactions and to
illustrate this point we also provide a simple example.Comment: 3 pages, 1 figure. Accepted for publication in Phys. Rev. E 200
Synchronizing automata with a letter of deficiency 2
AbstractWe present two infinite series of synchronizing automata with a letter of deficiency 2 whose shortest reset words are longer than those for synchronizing automata obtained by a straightforward modification of Černý’s construction
Conformation of a Polyelectrolyte Complexed to a Like-Charged Colloid
We report results from a molecular dynamics (MD) simulation on the
conformations of a long flexible polyelectrolyte complexed to a charged sphere,
\textit{both negatively charged}, in the presence of neutralizing counterions
in the strong Coulomb coupling regime. The structure of this complex is very
sensitive to the charge density of the polyelectrolyte. For a fully charged
polyelectrolyte the polymer forms a dense two-dimensional "disk", whereas for a
partially charged polyelectrolyte the monomers are spread over the colloidal
surface. A mechanism involving the \textit{overcharging} of the polyelectrolyte
by counterions is proposed to explain the observed conformations.Comment: 4 pages, 4 figures (6 EPS files
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