Controlled copolymerization of vinyl acetate with 1‐alkenes and their fluoro derivatives by degenerative transfer

The degenerative transfer copolymerization of vinyl acetate with ethene and higher 1‐alkenes, as well as their fluoro derivatives (R_fCH?CH₂), under mild conditions was carried out using AIBN as the initiator and ethyl iodoacetate as the control agent. The obtained random copolymers were fairly high in alkene content, with high molecular weights and relatively narrow polydispersities. The quasi‐living nature of the copolymerization allowed the synthesis of a block terpolymer by sequential addition of two different 1‐alkene comonomers to a vinyl acetate copolymerization system. The fluorinated side chains of vinyl acetate/fluoro alkene copolymers segregate toward the air‐side of thin films, resulting in advancing water contact angle as high as 114°. 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3728–3736, 2005     

Alternating polyester/fluoroalkene copolymers: Combining high hydrophobicity with degradability

2‐Methylene‐1,3‐dioxepane (MDO) was copolymerized with fluoroalkenes (R_fCH?CH₂) using azobis(isobutyronitrile) AIBN as an initiator. NMR spectroscopy confirmed that the obtained polymers are effectively alternating copolymers of caprolactone and fluoroalkene. Angle resolved XPS of copolymer films revealed that the outer layers have higher CF_x:COO ratio relative to the subsurface, indicating that the perfluoroalkyl tails segregate to the air‐side, thereby presenting a hydrophobic surface with water contact angle as high as 130°. Blends of this material with polycaprolactone and polycarbonate polymers also form hydrophobic films. In the presence of trifluoroacetic acid, the copolymer undergoes complete degradation through hydrolysis. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1225–1232, 2006     

DNA vaccine containing the mycobacterial hsp65 gene prevented insulitis in MLD-STZ diabetes

Background  

Our group previously demonstrated that a DNA plasmid encoding the mycobacterial 65-kDa heat shock protein (DNA-HSP65) displayed prophylactic and therapeutic effect in a mice model for tuberculosis. This protection was attributed to induction of a strong cellular immunity against HSP65. As specific immunity to HSP60 family has been detected in arthritis, multiple sclerosis and diabetes, the vaccination procedure with DNA-HSP65 could induce a cross-reactive immune response that could trigger or worsen these autoimmune diseases.     

Experimental calibration and field investigation of the oxygen isotopic fractionation between biogenic aragonite and water

Marine molluscs have long been recognised as potential records of palaeoclimate change using the patterns and differences in the stable isotopic composition of the carbonate shells. The aim of this study is to improve the robustness of this approach for aragonitic molluscs by completing the first experimental calibration of the fractionation between water and biogenic aragonite. Fractionation factors were calibrated by growing specimens of the freshwater mollusc Lymnaea peregra under controlled conditions of water temperature and isotopic composition. Fifteen populations of L. peregra were maintained at constant temperature and isotopic conditions for five months (at five different temperatures and using three different water compositions). Water samples and temperature measurements were taken regularly throughout the experiment. The temperature dependence of the fractionation factor, between 8 and 24 degrees C, is given by: 1000 ln alpha=16.74x(1000T(-1))-26.39 (T in Kelvin) and the relationship between temperature (T), delta(18)O(carb) and delta(18)O(wat) is given by: T=21.36-4.83xdelta(+ degrees )O(carb)-delta(+ degrees )O(wat) (T is in degrees C, delta(18)O(carb) is with respect to Vienna Pee Dee Belemnite (PDB), the International Atomic Energy Agency (IAEA) replacement standard for PDB, and delta(18)O(wat) is with respect to Vienna standard mean ocean water (VSMOW)) The outcome of the controlled experiment is compared with previous studies on synthetic, and biogenic, calcite and aragonite from field and laboratory investigations. These comparisons suggest that although a vital offset exists between the fractionation of isotopes in synthetic and biogenic aragonite for molluscs in general, there is no vital effect that is specific either to freshwater, or to individual, genera. Therefore, the calibrated relationship may be used for any freshwater or marine mollusc to derive palaeotemperatures providing the isotopic composition of the environmental water can be reliably constrained. Copyright 1999 John Wiley & Sons, Ltd.     

Optimal Control of a Stochastic Hybrid System with Discounted Cost

We address the optimal control problem of a very general stochastic hybrid system with both autonomous and impulsive jumps. The planning horizon is infinite and we use the discounted-cost criterion for performance evaluation. Under certain assumptions, we show the existence of an optimal control. We then derive the quasivariational inequalities satisfied by the value function and establish well-posedness. Finally, we prove the usual verification theorem of dynamic programming.     

The probabilistic structure of controlled diffusion processes

This paper surveys those aspects of controlled diffusion processes wherein the control problem is treated as an optimization problem on a set of probability measures on the path space. This includes: (i) existence results for optimal admissible or Markov controls (both in nondegenerate and degenerate cases), (ii) a probabilistic treatment of the dynamic programming principle, (iii) the corresponding results for control under partial observations, (iv) a probabilistic approach to the ergodic control problem. The paper is expository in nature and aims at giving a unified treatment of several old and new results that evolve around certain central ideas.     

A topology for Markov controls

For a controlled nondegenerate diffusion, a topology is defined on the set of all Markov relaxed controls, which is compact metrizable and with respect to which the resultant law of the diffusion with prescribed initial law is a continuous function of the control.     

InCl3-promoted a novel Prins cyclization for the synthesis of hexahydro-1H-furo[3,4-c]pyran derivatives

(2-(4-Methoxyphenyl)-4-methylenetetrahydrofuran-3-yl)methanol reacts smoothly with different aldehydes in the presence of InCl₃ at an ambient temperature to afford a novel series of cis-fused 7a,3,6-trisubstituted hexahydro-1H-furo[3,4-c]pyran derivatives in good yields with high selectivity. This is the first Letter on the synthesis of cis-fused hexahydro-1H-furo[3,4-c]pyran derivatives via the Prins cyclization.     

Small noise asymptotics for invariant densities for a class of diffusions: A control theoretic view

We consider multi-dimensional nondegenerate diffusions with invariant densities, with the diffusion matrix scaled by a small >0. The o.d.e. limit corresponding to =0 is assumed to have the origin as its unique globally asymptotically stable equilibrium. Using control theoretic methods, we show that in the ↓0 limit, the invariant density has the form ≈exp(−W(x)/²), where the W is characterized as the optimal cost of a deterministic control problem. This generalizes an earlier work of Sheu. Extension to multiple equilibria is also given.     

Addition of aryl cuprates to azides: a novel approach for the synthesis of unsymmetrical diaryl amines

Aryl and benzyl azides react smoothly with aryl cuprates, generated in situ from aryl magnesium bromide and CuCN in THF to furnish a variety of unsymmetrical diaryl amines in good yields. This is the first report on the synthesis of diarylamines from aryl azides and aryl bromides via an organometallic approach.