New phytoactive polymers prepared by polycondensation

Some new poly(ether-ester)s (PEEs) and poly(ether-amide)s (PEAs) with polyether sequences linked by tartrate units have been synthesized. Derivatives bearing residues from the synthetic plant-growth regulator 1-naphthylacetic acid (NAA) as pendent groups and end-groups have been prepared by esterification of PEEs and PEAs with NAA. Polymers bearing residues from pyridine-2, 6-dicarboxylic acid (a herbicide) in the main chain have been prepared. The hydrolysis has been found to depend on the structure of the polymer carrier, on pH of the medium and on the ability of the polymers to form complexes with polyacids. The phytosanitary activity of the new polymers has been related to the particular features of their hydrolysis behaviour.     

Novel,Complex Flavonoids from Mallotus philippensis (Kamala Tree)

One new flavanone, 4′‐hydroxyisorottlerin ( 2 ), and two new chalcone derivatives, kamalachalcones C ( 3 ) and D ( 4 ), were isolated from Mallotus philippensis (kamala tree). The largest compound ( 4 ; M_r 1098 g/mol) was shown to possess a unique, fused‐ring system made of two hydroxy‐chalcone units, giving rise to eight fused benzene/pyran units. From the same plant, the following six known compounds were also isolated: kamalachalcone A ( 5 ) and B ( 6 ), isoallorottlerin ( 7 ), isorottlerin ( 8 ), 5,7‐dihydroxy‐8‐methyl‐6‐prenylflavanone ( 9 ); 6,6‐dimethylpyrano(2″,3″: 7,6)‐5‐hydroxy‐8‐methylflavanone ( 10 ), and rottlerin ( 1 ). The structures of the new compounds were confirmed by in‐depth spectral analyses, including 2D‐NMR techniques, and the full ¹³C‐NMR assignments of the known flavanones 1 and 7 – 10 are published for the first time.     

Discotic liquid crystals of cucurbit[7]uril (CB[7])-functionalised Laponite clays

ABSTRACT

Here we demonstrate that in the presence of the small, barrel-shaped molecule cucurbit[7]uril (CB[7]) Laponite clay particles undergo a phase transition into a birefringent gel with lamellar structure and a fluid, Laponite-poor aqueous solution. We employ various characterisation methods and polarised light microscopy to study this transition and the system's structural and optical properties. Furthermore, when dried completely we obtain a layered, transparent composite film, still retaining some liquid-crystalline structure that can be rehydrated reversibly. We argue that this new system may be a model system for anisotropic patchy particles.     

Balanced Incomplete Block Designs with Block Size 9 and λ=2,4,8

The necessary conditions for the existence of a balanced incomplete block design on v points, with index λ and block size k, are that: $$\begin{gathered} {\text{ }}\lambda (v - 1) \equiv 0{\text{ mod (}}k - 1{\text{)}} \hfill \\ \lambda v(v - 1) \equiv 0{\text{ mod (}}k - 1{\text{)}} \hfill \\ \end{gathered} $$ In this paper we study k=9 with λ=2,4 or 8. For λ=8, we show these conditions on v are sufficient, and for λ=2, 4 respectively there are 8 and 3 possible exceptions the largest of which are v=1845 and 783. We also give some examples of group divisible designs derived from balanced ternary designs.     

Upper bounds on the general covering number Cλ(v,k, t,m)

A collection of k‐subsets (called blocks) of a v‐set X (v) = {1, 2,…, v} (with elements called points) is called a t‐(v, k, m, λ) covering if for every m‐subset M of X (v) there is a subcollection of with such that every block K ∈ has at least t points in common with M. It is required that v ≥ k ≥ t and v ≥ m ≥ t. The minimum number of blocks in a t‐(v, k, m, λ) covering is denoted by C_λ(v, k, t, m). We present some constructions producing the best known upper bounds on C_λ(v, k, t, m) for k = 6, a parameter of interest to lottery players. © 2004 Wiley Periodicals, Inc.     

Thermodynamic theory of incompressible hydrodynamics

The grand potential for open systems describes thermodynamics of fluid flows at low Mach numbers. A new system of reduced equations for the grand potential and the fluid momentum is derived from the compressible Navier-Stokes equations. The incompressible Navier-Stokes equations are the quasistationary solution to the new system. It is argued that the grand canonical ensemble is the unifying concept for the derivation of models and numerical methods for incompressible fluids, illustrated here with a simulation of a minimal Boltzmann model in a microflow setup.     

Balanced incomplete block designs with block size 8

The necessary conditions for the existence of a balanced incomplete block design on υ ≥ k points, with index λ and block size k, are that: For k = 8, these conditions are known to be sufficient when λ = 1, with 38 possible exceptions, the largest of which is υ = 3,753. For these 38 values of υ, we show (υ, 8, λ ) BIBDs exist whenever λ > 1 for all but five possible values of υ, the largest of which is υ = 1,177, and these five υ's are the only values for which more than one value of λ is open. For λ>1, we show the necessary conditions are sufficient with the definite exception of two further values of υ, and the possible exception of 7 further values of υ, the largest of which is υ=589. In particular, we show the necessary conditions are sufficient for all λ> 5 and for λ = 4 when υ ≠ 22. We also look at (8, λ) GDDs of type 7^m. Our grouplet divisible design construction is also refined, and we construct and exploit α ‐ frames in constructing several other BIBDs. In addition, we give a PBD basis result for {n: n ≡ 0, 1; mod 8, n ≥ 8}, and construct a few new TDs with index > 1. © 2001 John Wiley & Sons, Inc. J Combin Designs 9: 233–268, 2001     

The preparata codes and a class of 4-designs

An extension theorem for t-designs is proved. As an application, a class of 4-(4^m + 1,5,2) designs is constructed by extending designs related to the 3-designs formed by the minimum weight vectors in the Preparata code of length n = 4^m, m ≥ 2. © 1994 John Wiley & Sons, Inc.     

Multifunctional Hybrid Materials From Poly(3‐Hydroxybutyrate), TiO2 Nanoparticles,and Chitosan Oligomers by Combining Electrospinning/Electrospraying and Impregnation

Several types of fibrous material containing poly(3‐hydroxybutyrate) (PHB), nanosized TiO₂‐anatase (nanoTiO₂), and chitosan oligomers are prepared by combining the electrospinning, electrospraying, and impregnation techniques. Simultaneous electrospinning/electrospraying provides uniform distribution of electrosprayed nanoTiO₂ along the PHB fibers and throughout the mat. Hybrid materials of different design manifest excellent photocatalytic activity, even after repeated use. They exhibit high bactericidal activity against Escherichia coli. In addition, the fibrous scaffolds are compatible with human mesenchymal stem cells and provide a favorable environment for their development.

     

Synthesis of polymer-stabilized magnetic nanoparticles and fabrication of nanocomposite fibers thereof using electrospinning

Polymer-stabilized magnetic nanoparticles were obtained using two biocompatible polyelectrolytes: N-carboxyethylchitosan (CECh) and poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS). The size of the particles (mean diameter 10 or 30 nm, respectively) and the stability of the dispersions could be effectively controlled depending on the polyelectrolyte nature. The presence of polyelectrolyte shell was proved by transmission electron microscopy (TEM) studies and confirmed by thermogravimetric analyses. Depending on the polyelectrolyte nature the magnetic nanoparticles existed in different magnetic states - superparamagnetic or intermediate state between superparamagnetic and ferrimagnetic one, as evidenced by the measurements of the magnetization and Mössbauer analyses. Fabrication of nanocomposite magnetic fibers with mean diameter in the range 100-500 nm was achieved using electrospinning of the system CECh/ferrofluid/non-ionogenic polymer.