992 research outputs found
Complexation of a polyelectrolyte with oppositely charged spherical macroions: Giant inversion of charge
Complexation of a long flexible polyelectrolyte (PE) molecule with oppositely
charged spherical particles such as colloids, micelles, or globular proteins in
a salty water solution is studied. PE binds spheres winding around them, while
spheres repel each other and form almost periodic necklace. If the total charge
of PE is larger than the total charge of spheres, repulsive correlations of PE
turns on a sphere lead to inversion of the net charge of each sphere. In the
opposite case, we predict another correlation effect: under-screened by PE
spheres bind to PE in such a great number that they invert charge of PE. The
inverted charge by absolute value can be larger than the bare charge of PE even
when screening by monovalent salt is weak. At larger concentrations of
monovalent salt, the inverted charge can reach giant proportions. Our theory is
in qualitative agreement with recent experiments on micelles-PE systems.Comment: Various additions and corrections to the text, Figures and
references. Accepted for publication in J. Chem. Phys. 200
On the Szeged Index of Unbranched Catacondensed Benzenoid Molecules
The Szeged index (Sz) of unbranched catacondensed benzenoid
(UBCB) hydrocarbons is examined. An efficient method for the calculations of their Sz is put forward. Among the UBCB molecules
with a fixed number of hexagons, the linear polyacene has a rnaximal
and the helicene a minimal Sz
Glassy phases in Random Heteropolymers with correlated sequences
We develop a new analytic approach for the study of lattice heteropolymers,
and apply it to copolymers with correlated Markovian sequences. According to
our analysis, heteropolymers present three different dense phases depending
upon the temperature, the nature of the monomer interactions, and the sequence
correlations: (i) a liquid phase, (ii) a ``soft glass'' phase, and (iii) a
``frozen glass'' phase. The presence of the new intermediate ``soft glass''
phase is predicted for instance in the case of polyampholytes with sequences
that favor the alternation of monomers.
Our approach is based on the cavity method, a refined Bethe Peierls
approximation adapted to frustrated systems. It amounts to a mean field
treatment in which the nearest neighbor correlations, which are crucial in the
dense phases of heteropolymers, are handled exactly. This approach is powerful
and versatile, it can be improved systematically and generalized to other
polymeric systems
Current trends in internet marketing
In article the task to consider tools which are used by tourist operators to promote the tourist product on a social networking. The social network promptly develops and it is very important to be able to use competently them to reach positive result.В статье ставится задача рассмотреть инструменты, которые используют туристические операторы для продвижения своего туристского продукта в социальной сети. Социальная сеть стремительно развивается и очень важно уметь их грамотно использовать, чтобы достичь положительного результата
Some results on the Wiener index related to the \v{S}olt\'{e}s problem of graphs
The Wiener index, , of a connected graph is the sum of distances
between its vertices. In 2021, Akhmejanova et al. posed the problem of finding
graphs with large . It is shown that there is a graph with for any
integer . In particular, there is a regular graph of even degree with
this property for any odd . The proposed approach allows to construct
new families of graphs with when the order of
increases.Comment: 9 pages, 3 tables, 7 figure
Renormalized One-loop Theory of Correlations in Disordered Diblock Copolymers
A renormalized one-loop theory (ROL) is used to calculate corrections to the
random phase approximation (RPA) for the structure factor \Sc(q) in
disordered diblock copolymer melts. Predictions are given for the peak
intensity , peak position , and single-chain
statistics for symmetric and asymmetric copolymers as functions of ,
where is the Flory-Huggins interaction parameter and is the degree
of polymerization. The ROL and Fredrickson-Helfand (FH) theories are found to
yield asymptotically equivalent results for the dependence of the peak
intensity upon for symmetric diblock copolymers in the
limit of strong scattering, or large , but yield qualitatively
different predictions for symmetric copolymers far from the ODT and for
asymmetric copolymers. The ROL theory predicts a suppression of
and a decrease of for large values of , relative to the RPA
predictions, but an enhancement of and an increase in
for small (). By separating intra- and
inter-molecular contributions to , we show that the decrease in
near the ODT is caused by the dependence of the intermolecular
direct correlation function, and is unrelated to any change in single-chain
statistics, but that the increase in at small values of is
a result of non-Gaussian single-chain statistics.Comment: 16 pages, 13 figures, submitted to J. Chem. Phy
Chemical modification of extracellular matrix by cold atmospheric plasma-generated reactive species affects chondrogenesis and bone formation.
The goal of this study was to investigate whether cold plasma generated by dielectric barrier discharge (DBD) modifies extracellular matrices (ECM) to influence chondrogenesis and endochondral ossification. Replacement of cartilage by bone during endochondral ossification is essential in fetal skeletal development, bone growth and fracture healing. Regulation of this process by the ECM occurs through matrix remodelling, involving a variety of cell attachment molecules and growth factors, which influence cell morphology and protein expression. The commercially available ECM, Matrigel, was treated with microsecond or nanosecond pulsed (μsp or nsp, respectively) DBD frequencies conditions at the equivalent frequencies (1 kHz) or power (~1 W). Recombinant human bone morphogenetic protein-2 was added and the mixture subcutaneously injected into mice to simulate ectopic endochondral ossification. Two weeks later, the masses were extracted and analysed by microcomputed tomography. A significant increase in bone formation was observed in Matrigel treated with μsp DBD compared with control, while a significant decrease in bone formation was observed for both nsp treatments. Histological and immunohistochemical analysis showed Matrigel treated with μsp plasma increased the number of invading cells, the amount of vascular endothelial growth factor and chondrogenesis while the opposite was true for Matrigel treated with nsp plasma. In support of the in vivo Matrigel study, 10 T1/2 cells cultured in vitro on μsp DBD-treated type I collagen showed increased expression of adhesion proteins and activation of survival pathways, which decreased with nsp plasma treatments. These results indicate DBD modification of ECM can influence cellular behaviours to accelerate or inhibit chondrogenesis and endochondral ossification. Copyright © 2016 John Wiley & Sons, Ltd
Trees, Quadratic Line Graphs and the Wiener Index
The Wiener index is a topological index defined as the sum of distances between all pairs of vertices in a tree. It was introduced as a structural descriptor for molecular graphs of alkanes, which are trees with vertex degrees of four at the most (chemical trees). The line graph L(G) of a graph G has the vertex set V(L(G)) = E(G) and two distinct vertices of L(G) are adjacent if the corresponding edges of G have a common endvertex. It is known that the Wiener indices of a tree and of its line graph are always distinct. An infinite two-parameter family of growing chemical trees T with the property W(T) = W(L(L(T))) has been constructed
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