Self‐diffusion coefficient of ring polymers in semidilute solution

In a topologically constraining environment the size of a flexible nonconcatenated ring polymer (macrocycles) and its dynamics are known to differ from that of linear polymers. Hence, the diffusion coefficient of ring polymers can be expected to be different from linear chains. We present here scaling arguments for the concentration and molecular weight dependence of self‐diffusion coefficient of ring polymers in semidilute solutions, and show that contrary to expectations these scaling relations are identical to what is known for linear polymers. At higher concentrations excluded volume interactions arising from possibilities of segmental overlap can become effective for large ring polymers. In this regime the diffusion coefficient of large ring polymers shows a relatively weaker dependence on concentration and molecular weight. ©2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2370–2379, 2008     

From dispersed nanodiscs to thin films of layered organic material via reversible swelling

We show that nanodiscs stabilized with polymers order and pile up on a surface upon drying. The resulting surface films with an average thickness of one micron are made of collapsed cohesive layers with smectic long-range order. This occurs with and without plastifying stabilizing polymer and produces crevasses. The stacked discs undergo a two-to-three-dimensional crystallization while bottom layers close to the surface fuse and produce infinite bilayers. Small angle X-ray scattering experiments demonstrate that excess polymer is segregated from the crystalline stack. Water adsorption isotherms show that reversible swelling of the excess polymer does not destroy the compact stack of partially fused nanodiscs collapsed parallel to the surface. In the absence of chemical binding, the stacks of layered nanodiscs can be removed by simple washing with pure water. AFM, TEM and SEM experiments demonstrate that presence of crevasses is quenched by the presence of a plastifying polymer.     

Solution of the differential equation (∂2∂x∂y + ax∂∂x + by∂∂y + cxy + ∂∂t) P(x,y, t) = 0 and the Bogoliubov transformation

An eigen function expansion for the solution of the Lambropolous partial differential equation is obtained by the use of a transformation similar to the Bugolubov transformation familiar in Bose gas theory. Also the technique of normal ordering of operators is employed. The orthogonality properties of such solutions are also analysed.     

Properties and applications of forests of quadtrees for pictorial data representation

Region representation as a quadtree data structure is a rich field in computer science with many different approaches. Forests of quadtrees offer space savings over regular quadtrees by concentrating the vital information [4, 5, 6]. They scavenge unused and unneeded space (i.e., node containing no information). This paper investigates several properties of forests of quadtrees which can be used to design manipulation algorithms for forest-quadtree data structure. In addition, the paper discusses the space saving and shows how the basic operations that can be performed on a quadtree can also be done on the more space efficient representation (a forest of quadtrees).     

Trapping and reactivity of electrons in methanol-isopropanol glasses irradiated at 77 K

Mixtures of methanol and isopropanol in a ratio (v/v) varying from 91 to 19 have been gamma-irradiated at 77 K and relative yields of trapped electrons have been measured. The reactivity of the trapped electrons towards acetone and uranyl nitrate has been studied at various methanol isopropanol ratios. On the basis of the results, an attempt has been made to assess the relative importance of the reaction of the electron with the solute prior to trapping with respect to the tunnelling reaction of the trapped electron with the solute.     

Storage problems in continuous time with random inputs,random outputs,and deterministic release

The subject of study here is the model of a dam, with random inputs and outputs along with a deterministic release. The amounts of the Poisson jumps, either up or down, are independently and identically distributed. Closed form solutions are obtained for the Laplace transforms of first passage densities to different situations of overflow or emptiness. These results can throw insights regarding different threshold studies in storage, inventory, biological, and environmental problems. The closed form solutions are obtained by applying imbedding methods for different types of densities conceptualized in novel ways.     

Pes study of spin-state transitions in d6 transition metal complexes and oxides

Transitions from the low-to the high-spin state in Fe²⁺ and Co³⁺ compounds have been examined by X-ray and UV photoelectron spectroscopy. It has been shown that the core-level bands in XPES, in particular the metal 3s band, as well as the valence bands, are diagnosis in the study of spin-state transitions.     

Accretion onto a Kerr black hole in the presence of a dipole magnetic field

We analyze the accretion of charged matter onto a rotating black hole immersed in an aligned dipolar magnetic field. We specialize to motion in the equatorial plane and calculate the ‘Keplerian’ angular momentum distribution, the marginally stable and marginally bound orbits, and the efficiency of mass-to-energy conversion as functions of the angular momentum of the black hole and of the product of the dipole moment and the charge of the infalling matter. Although the detailed results are quite different from those previously obtained in the case of an uniform magnetic field, the astrophysically relevant results are very similar; when hydrodynamical accretion is considered, these effects of the magnetic field are always very small. But for test particles the efficiency can be significantly increased for limited ranges of the parameters.