Green pH- and magnetic-responsive hybrid hydrogels based on poly(methacrylic acid) and Eucalyptus wood nanocellulose for controlled release of ibuprofen

Cellulose - pH- and magnetic-sensitive hybrid hydrogels based on poly(methacrylic acid) (PMAA), nanocellulose (NC), carboxymethyl cellulose (CMC) and magnetite particles (MN) were prepared as...     

Synthesis and Stereochemistry of Some new Derivatives of 1,2-O-Cyclohexylidene-α-D-Xylofuranuronic Acid

Abstract

1,2-O-Cyclohexylidene-α-d-xylofuranuronic acid (2) has been converted into its 3-O-acetyl derivative and consecutively to the corresponding acid chloride and ethyl ester. Direct reaction of 2 with ethanol in the presence of p-to-luene sulphonic acid gave the ethyl ester. Reaction of 2 with phosphorus pentachloride in dry ether gave the acid chloride of 1,2-O-cyclohexylidene-3-O-dichlorophosphoryl–α-d-xylofuranuronic acid. Conformational data have been obtained from ¹H and ¹³C NMR measurements.     

Spectrophotometric Study of Catechol Oxidation by Aerial O2 in Alkaline Aqueous Solutions Containing Mg(II) Ions.

Electronic absorption spectroscopy was employed to study the aerial oxidation of catechol (1,2-benzenediol) in alkaline aqueous solution containing an excess of Mg(II) ions. Graphical analysis by the matrix method of UV spectra recorded at regular time intervals gave a good fit for two absorbing species in solution. Based on this result and our earlier ESR spectroscopic investigations we concluded that two main absorbing species in this system are Mg(II)-spin stabilized o-benzosemiquinone anion radical and C-C dimer formed by the nucleophilic attack of catecholate anion on o-benzoquinone. Although the formation of 1,2,4-benzenetriol during the catechol oxidation has been detected in some ESR studies its presence was not indicated by this analysis probably because of the low and/or stable steady state concentration throughout the experiment.     

Structural evidence for the arc-shaped topology of hetero[5]polynorbornanes

Two novel polarofacial-[5]-polynorbornanes, O ² N ₂ O ²– and COCOC–, were synthesized by cycloaddition reactions and their molecular and crystal structures were determined. These hetero[5]polynorbornanes posses heteroatoms at the norbornene bridges located at the outer convex surface, whereas functionalities are positioned on the inner concave surface. Molecular structures attest the extent of the curvature of their polycyclic backbone, and established that the COCOC-[5]-polynorbornane possesses more curved topology due to larger steric repulsion of 7-norbornane bridges. These experimental results are in good agreement with computational predictions of geometry. Quantum chemical study has identified lone pair repulsive interactions and steric repulsions of bridges as important factors for determining curvature.     

Limit Theorems for the Maximum Terms of a Sequence of Random Variables with Marginal Geometric Distributions

Let X _n1 ^* , ... X _nn ^* be a sequence of n independent random variables which have a geometric distribution with the parameter p _n = 1/n, and M _n ^* = \max\{X _n1 ^* , ... X _nn ^* }. Let Z ₁, Z₂, Z₃, ... be a sequence of independent random variables with the uniform distribution over the set N _n = {1, 2, ... n}. For each j N _n let us denote X _nj = min{k : Z_k = j}, M _n = max{X_n1, ... X_nn}, and let S _n be the 2nd largest among X _n1, X_n2, ... X_nn. Using the methodology of verifying D(u_n) and D'(u_n) mixing conditions we prove herein that the maximum M _n has the same type I limiting distribution as the maximum M _n ^* and estimate the rate of convergence. The limiting bivariate distribution of (S_n, M_n) is also obtained. Let _n, _n N_n, , and T _n = min{M(A_n), M(B_n)}. We determine herein the limiting distribution of random variable T _n in the case _n , _n/_n > 0, as n .     

Dirac Cohomology for Lie Superalgebras

Dirac cohomology is a new tool to study representations of semisimple Lie groups and Lie algebras. The aim of this paper is to define a Dirac operator for a Lie superalgebra of Riemannian type and show that this Dirac operator has similar nature as the one for semisimple Lie algebras. As a consequence, we show how to determine the infinitesimal character of a representation by the infinitesimal character of its Dirac cohomology.     

Superconducting microwave cavity towards controlling the motion of polar molecules

We propose the use of superconducting microwave cavities for the focusing and deceleration of cold polar molecular beams. A superconducting cavity with a high quality factor produces a large ac Stark shift in polar molecules, which allow us to efficiently control molecular motion. Our discussion is based on the experimental characterization of a prototype cavity: a lead–tin-coated cylindrical copper cavity, which has a quality factor of 10⁶ and tolerates several watts of input power. Such a microwave device provides a powerful way to control molecules not only in low-field-seeking states, but also in high-field-seeking states such as the ground rotational state.     

On classifying unitary modules by their Dirac cohomology

Let G be a connected real reductive group with maximal compact subgroup K of the same rank as G. Dirac cohomology of an A_q(λ) module can be identified with a geometric object—the k-dominant part of a face of the convex hull of the Weyl group orbit of the parameter λ + ρ. We show how Dirac cohomology can be used as a parameter to classify the A_q(λ) modules.     

A tight colored Tverberg theorem for maps to manifolds

We prove that any continuous map of an N-dimensional simplex ΔN with colored vertices to a d-dimensional manifold M must map r points from disjoint rainbow faces of ΔN to the same point in M: For this we have to assume that N?(r−1)(d+1), no r vertices of ΔN get the same color, and our proof needs that r is a prime. A face of ΔN is a rainbow face if all vertices have different colors.This result is an extension of our recent “new colored Tverberg theorem”, the special case of M=Rd. It is also a generalization of Volovikov?s 1996 topological Tverberg theorem for maps to manifolds, which arises when all color classes have size 1 (i.e., without color constraints); for this special case Volovikov?s proof, as well as ours, works when r is a prime power.     

Colloidal gallium indium oxide nanocrystals: a multifunctional light-emitting phosphor broadly tunable by alloy composition

We demonstrate compositionally tunable photoluminescence in complex transparent conducting oxide nanocrystals. Alloyed gallium indium oxide (GIO) nanocrystals with variable crystal structures are prepared by a colloidal method throughout the full composition range and studied by different structural and spectroscopic methods, including photoluminescence and X-ray absorption. The structures and sizes of the GIO nanocrystals can be simultaneously controlled, owing to the difference in the growth kinetics of In(2)O(3) and Ga(2)O(3) nanocrystals and the polymorphic nature of both materials. Using the synthesized nanocrystal series, we demonstrate the structural and compositional dependences of the photoluminescence of GIO nanocrystals. These dependences, induced by the interactions between specific defect sites acting as electron donors and acceptors, are used to achieve broad emission tunability in the visible spectral range at room temperature. The nature of the photoluminescence is identified as donor-acceptor pair recombination and changes with increasing indium content owing to the changes in the energy states of, and interactions between, donors and acceptors. Structural analysis of GIO nanocrystals by extended X-ray absorption fine structure spectroscopy reveals that In(3+) occupies only octahedral, rather than tetrahedral, sites in the spinel-type γ-Ga(2)O(3) nanocrystal host lattice, until reaching the substitutional incorporation limit of ca. 25%. The emission decay dynamics is also strongly influenced by the nanocrystal structure and composition. The oxygen vacancy defects, responsible for the observed photoluminescence properties, are also implicated in other functional properties, particularly conductivity, enabling the application of colloidal GIO nanocrystals as integrated optoelectronic materials.