Quasi-affine symmetric designs

A symmetric design with parameters v = q ²(q + 2), k = q(q + 1), λ = q, q ≥ 2, is called a quasi-affine design if its point set can be partitioned into q + 2 subsets P ₀, P ₁,..., P _q , P _q+1 such that the induced structure in every point neighborhood is an affine plane of order q (repeated q times). A quasi-affine design with q ≥ 3 determines its point neighborhoods uniquely and dual of such a design is also a quasi-affine design. These structural properties pave way for definition of a strongly quasi-affine design and it is also shown that associated with every quasi-affine design is a unique strongly quasi-affine design from which the given quasi-affine design is obtained by certain unique cutting and pasting operation. This investigation also enables us to associate a unique 2-regular graph with q + 2 vertices and in turn, a unique colored partition of the integer q + 2. These combinatorial consequences are finally used to obtain an exponential lower bound on the number of non-isomorphic solutions of such symmetric designs improving the earlier lower bound of 2. Work of Sanjeevani Gharge is supported by Faculty Improvement Programme of U.G.C., India.     

Room temperature synthesis of water repellent silica coatings by the dip coat technique

The present paper describes the room temperature synthesis of dip coated water repellent silica coatings onto stainless steel substrates using 1,1,1,3,3,3-hexamethyldisilazane as a surface modifying agent. The hydrophobic property of the silica coating was enhanced by increasing its surface roughness, which was achieved by a proper control over the MeOH/TMOS molar ratio (S) during the synthesis. The contact angle of a water droplet (10 μl) increased from 72° to 145° with an increase in the S value from 9.1 to 36.4. The silica coating showed a minimum sliding angle of 15° for a water droplet of 10 μl. The water repellent silica coatings are thermally stable up to a temperature of 340 °C. The results have been discussed by taking into consideration the contact angle measurements, surface morphology and sol-gel parameters.     

The Binomial k‐Clique

A finite collection C of k‐sets, where is called a k‐clique if every two k‐sets (called lines) in C have a nonempty intersection and a k‐clique is a called a maximal k‐clique if and C is maximal with respect to this property. That is, every two lines in C have a nonempty intersection and there does not exist A such that , and for all . An elementary example of a maximal k‐clique is furnished by the family of all the k‐subsets of a ‐set. This k‐clique will be called the binomial k‐clique. This paper is intended to give some combinatorial characterizations of the binomial k‐clique as a maximal k‐clique. The techniques developed are then used to provide a large number of examples of mutually nonisomorphic maximal k‐cliques for a fixed value of k.     

Asymmetric Hybrid Polyoxometalates: A Platform for Multifunctional Redox‐Active Nanomaterials

Access to asymmetrically functionalized polyoxometalates is a grand challenge as it could lead to new molecular nanomaterials with multiple or modular functionality. Now, a simple one‐pot synthetic approach to the isolation of an asymmetrically functionalized organic–inorganic hybrid Wells–Dawson polyoxometalate in good yield is presented. The cluster bears two organophosphonate moieties with contrasting physical properties: a chelating metal‐binding group, and a long aliphatic chain that facilitates solvent‐dependent self‐assembly into soft nanostructures. The orthogonal properties of the modular system are effectively demonstrated by controlled assembly of POM‐based redox‐active nanoparticles. This simple, high‐yielding synthetic method is a promising new approach to the preparation of multi‐functional hybrid metal oxide clusters, supermolecular systems, and soft‐nanomaterials.     

RLIP76, a non-ABC transporter,and drug resistance in epilepsy

Background  

Permeability of the blood-brain barrier is one of the factors determining the bioavailability of therapeutic drugs and resistance to chemically different antiepileptic drugs is a consequence of decreased intracerebral accumulation. The ABC transporters, particularly P-glycoprotein, are known to play a role in antiepileptic drug extrusion, but are not by themselves sufficient to fully explain the phenomenon of drug-resistant epilepsy. Proteomic analyses of membrane protein differentially expressed in epileptic foci brain tissue revealed the frequently increased expression of RLIP76/RALBP1, a recently described non-ABC multi-specific transporter. Because of a significant overlap in substrates between P-glycoprotein and RLIP76, present studies were carried out to determine the potential role of RLIP76 in AED transport in the brain.     

A successful algorithm for solving directed Hamiltonian path problems

In this paper we present a graph-theoretic polynomial algorithm which has positive probability of finding a Hamiltonian path in a given graph, if there is one; if the algorithm fails, it can be rerun with a randomly chosen starting solution, and there is again a positive probability it will find an answer. If there is no Hamiltonian path, the algorithm will always terminate with failure. We call this a Successful Algorithm because it has high (close to 1) empirical probability of success and it works in polynomial time. Some basic theoretical results concerning spanning arborescences of a graph are given. The concept of a ramification index is defined and it is shown that ramification index of a Hamiltonian path is zero. The algorithm starts with finding any spanning arborescence and by suitable pivots it endeavors to reduce the ramification index to zero. Probabilistic properties of the algorithm are discussed. Computational experience with graphs up to 30 000 nodes is included.     

Rapid synthesis of water-glass based aerogels by in situ surface modification of the hydrogels

The objective of the present research was to reduce the processing time of water-glass based aerogels synthesized via an ambient pressure drying. For this purpose we employed a co-precursor method for the surface modification in hydrogels using trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDS). The surface modification resulted in the displacement of pore water from the hydrogels and thereby absolutely avoiding the time-consuming solvent exchange step. The attachment of trymethylsilyl (Si(CH₃)₃) groups to the silica surface was confirmed by the presence of SiCH₃ peaks at 2900, 1400, 1255 and 845 cm⁻¹ in the Fourier Transform Infrared (FTIR) spectra. The differential thermal analysis (DTA) revealed that the aerogels maintain their hydrophobic behavior up to a maximum temperature of 500 °C above which they become hydrophilic. The physical and textural properties of the silica aerogels have been reported and the results have been discussed by taking into account the surface modification and the amounts of the pore water displaced out from the hydrogels.     

Diphosphoryl-functionalized Polyoxometalates: Structurally and Electronically Tunable Hybrid Molecular Materials

Herein, we report the synthesis and characterization of a new class of hybrid Wells–Dawson polyoxometalate (POM) containing a diphosphoryl group (P₂O₆X) of the general formula [P₂W₁₇O₅₇(P₂O₆X)]⁶⁻ (X=O, NH, or CR¹R²). Modifying the bridging unit X was found to impact the redox potentials of the POM. The ease with which a range of α-functionalized diphosphonic acids (X=CR¹R²) can be prepared provides possibilities to access diverse functionalized hybrid POMs. Compared to existing phosphonate hybrid Wells–Dawson POMs, diphosphoryl-substituted POMs offer a wider tunable redox window and enhanced hydrolytic stability. This study provides a basis for the rational design and synthesis of next-generation hybrid Wells–Dawson POMs.     

Influence of phosphorylation on the foamability and stability of bovine serum albumin and citrus peel pectin mixed foams

We study the influence of phosphorylation on the foamability and stability of bovine serum albumin (BSA), phosphorylated BSA (pBSA), and citrus peel pectin (CPP) mixed foams as a function of BSA–CPP, pBSA–CPP mixing ratios, at a fixed solution pH of 4.5. Our results show that pBSA solutions result in more stable foams as compared with their BSA counterparts. We further show that the addition of CPP leads to BSA–CPP and pBSA–CPP complexation which increases the foamability and stability of foams as compared with protein-only foams. Also, foam stability is highest for pBSA–CPP mixed foams with mixing ratio pBSA:CPP?=?1:1 due to the combined effect of pBSA–pBSA and pBSA–CPP interactions.