Synthesis and Some Properties of Some Sulfonium Polyelectrolytes: Polymers and Copolymers Derived from Methylthioethyl Acrylate

Methylthioethyl acrylate, prepared by ester exchange from methylthioethanol and methyl acrylate, behaves in copolymerization like a typical acrylate ester such as butyl acrylate. This monomer can be alkylated to yield corresponding sulfonium monomers. With dimethyl sulfate, (2-acryloxyethyl) dimenthylsulfonium methyl sulfate is obtained. This latter monomer has a predictable lower relative copolymerization rate with alkyl acrylates than methylthioethyl acrylate. Water-soluble sulfonium polymers are polymeric cations and can act effectively as flocculants.     

Recent Advances in Free-Radical Ring-Opening Polymerization

Although cyclic ketene acetals, such as 2-methylene-1, 3-dioxepane, undergo quantitative free-radical ring-opening polymerization, their reactivity in copolymerization is rather low. In order to find a series of monomers that have high reactivities in copolymerization and still undergo free radical ring-opening polymerization, a series of cyclic acrylates was synthesized and polymerized. For example, β-bromolactic acid condensed with benzaldehyde to give a cyclic acetal lactone which on treatment with base gave the cyclic acrylate. Free-radical solution polymerization at 140°C of the cyclic acrylate, which produced a benzyl radical upon ring opening, gave quantitative ring opening. However, in bulk at 120°C, only 20% of the rings were opened during poiymerization. The resulting polymers containing the pyruvate ester units were shown to be highly biodegradable with microorganisms. Vesicles containing these cyclic acrylates on the end of one of the hydrophobic chains of the lipidlike molecules were shown to undergo free-radical ring-opening polymerization to give polymerized vesicles which were biodegradable. In order to discover groups other than carbonyl groups and strained rings that would promote free-radical ring-opening polymerization, a series of spiromethylenecyclohexadienes were prepared and polymerized. Thus, 3-methylenespiro [5,5] undeca-1,4-diene in bulk at 130°C gave a polymer in which 79% of the rings had opened and in solution at 130°C gave a polymer in which nearly all of the rings had opened. A benzo derivative, 3-methylene-8,9-benzo [5,5] undeca-1,4,8-triene, gave a polymer that is essentially an alternating copolymer of p-xylylene and o-xylylene and has a very high thermal decomposition temperature. A tricyclic dispirocyclohexadiene derivative was shown to undergo double free-radical ring-opening polymerization to give a polymer with expansion in volume containing a p-phenylene group in the backbone.     

The Heusler phases LiRh2Si and LiRh2Ge: Synthesis, structure and properties

The isostructural Heusler phases LiRh₂Si and LiRh₂Ge have been synthesized from the elements and an excess of lithium at 1000 °C. Both materials adopt the CuMn₂Al crystal structure, space group Fm−3m (No. 225) with the room temperature lattice parameter a=5.747(1) Å [Vol=189.866(1) Å³] and a=5.847(1) Å [Vol=199.88(6) Å³] for LiRh₂Si and LiRh₂Ge, respectively. X-ray analyses suggest mixed site occupancy of the form Li_1−xRh₂Si_1+x (x<0.4), but not for LiRh₂Ge. Both materials are diamagnetic, χ_mol(LiRh₂Si)=−6×10⁻⁵ cm³(mole)⁻¹ and χ_mol(LiRh₂Ge)=−10×10⁻⁵ cm³(mole)⁻¹ and metallic with room temperature resistivities of approximately 19 and 32 μΩ cm, respectively. These properties are consistent with the calculated electronic structure.     

Pure insulin nanoparticle agglomerates for pulmonary delivery

Diabetes is a set of diseases characterized by defects in insulin utilization, either through autoimmune destruction of insulin-producing cells (Type I) or insulin resistance (Type II). Treatment options can include regular injections of insulin, which can be painful and inconvenient, often leading to low patient compliance. To overcome this problem, novel formulations of insulin are being investigated, such as inhaled aerosols. Sufficient deposition of powder in the peripheral lung to maximize systemic absorption requires precise control over particle size and density, with particles between 1 and 5 microm in aerodynamic diameter being within the respirable range. Insulin nanoparticles were produced by titrating insulin dissolved at low pH up to the pI of the native protein, and were then further processed into microparticles using solvent displacement. Particle size, crystallinity, dissolution properties, structural stability, and bulk powder density were characterized. We have demonstrated that pure drug insulin microparticles can be produced from nanosuspensions with minimal processing steps without excipients, and with suitable properties for deposition in the peripheral lung.     

Concise routes to pyrazolo[1,5-a]pyridin-3-yl pyridazin-3-ones

Cycloaddition of pyridine N-imine with 6-alkyl-4-oxohex-5-ynoates followed by condensation with hydrazine provides concise access to pharmacologically active 6-(pyrazolo[1,5-a]pyridin-3-yl)pyridazinones. For the first time alkynyl heterocycles are also shown to be effective dipolarophiles for pyridine N-imine, and analogous compounds can be accessed directly in modest yields through the reaction of 6-(alkyn-1-yl)pyridazin-3-one derivatives.     

Multivariate polynomial interpolation and sampling in Paley–Wiener spaces

In this paper, an equivalence between existence of particular exponential Riesz bases for spaces of multivariate bandlimited functions and existence of certain polynomial interpolants for functions in these spaces is given. Namely, polynomials are constructed which, in the limiting case, interpolate ${\left\{({\tau }_n,f\left({\tau }_n\right))\right\}}_n$ for certain classes of unequally spaced data nodes ${\left\{{\tau }_n\right\}}_n$ and corresponding ${?}_2$ sampled data ${\left\{f\left({\tau }_n\right)\right\}}_n$. Existence of these polynomials allows one to construct a simple sequence of approximants for an arbitrary multivariate bandlimited function $f$ which demonstrates $L_2$ and uniform convergence on ${\mathbb{R}}^d$ to $f$. A simpler computational version of this recovery formula is also given at the cost of replacing $L_2$ and uniform convergence on ${\mathbb{R}}^d$ with $L_2$ and uniform convergence on increasingly large subsets of ${\mathbb{R}}^d$. As a special case, the polynomial interpolants of given ${?}_2$ data converge in the same fashion to the multivariate bandlimited interpolant of that same data. Concrete examples of pertinent Riesz bases and unequally spaced data nodes are also given.     

The Effect of a Modified Moore Method on Attitudes and Beliefs in Precalculus

As part of a study on the effects of teaching with a Modified Moore Method (MMM), a survey containing 20 items from Schoenfeld's (1989 ) investigation of attitudes and beliefs about mathematics was administered to students in undergraduate precalculus classes. The study included one section of precalculus taught with an MMM, a student‐centered and inquiry‐based teaching method, and two sections taught using traditional lecture methods. The survey was administered one week into the semester, following the drop/add date, and during the last week of classes. In this paper, we discuss the findings of the attitudes and beliefs portions of the survey and correlations with scores on a common final exam. We looked for differences between the MMM and traditional sections as well as gender differences. There were only a few differences in the attitudes and beliefs among the students, although there were more changes for females than males and all the significant differences were positive. The correlation between attitudes and beliefs and final exam scores was much stronger in the traditionally taught classes than in the MMM class. When separated by gender, only the reported attitudes and beliefs of the females in the traditional class significantly correlated with final exam scores.     

Luminescence temperature sensing using poly(vinyl alcohol)-encapsulated Ru(bpy)3 2+ films

The ruthenium(II) diimine complexes, such as ruthenium(II) tris(bipyridyl), Ru(bpy)3 2+, possess highly luminescent excited states that are not only readily quenched by oxygen but also by an increase in temperature. The former effect can be rendered insignificant by encapsulating the complex in an oxygen impermeable polymer, although encapsulation often leads also to a loss of temperature sensitivity. The luminescence properties of Ru(bpy)3 2+ encapsulated in PVA were studied as a function of oxygen concentration and temperature and found to be independent of the former, but still very sensitive towards the latter. The results were fitted to an established Arrhenius-type equation, based on thermal quenching of the emitting state by a slightly higher (DeltaE= 3100 cm(-1))3d-d state that deactivates very rapidly (10(-13) s)via a non-radiative process.