Dithioester functionalization of poly(cyclohexene oxide) and its application to obtain block copolymers

A new method of introducing dithioester groups into the polymer chain of poly(cyclohexene oxide) is reported. It includes the use of diaryliodonium salt and an aromatic dithioacid as a redox couple to initiate the cationic polymerization of cyclohexene oxide. It was found that the dithioacid by itself cannot start the polymerization of cationic polymerizable monomers; however, in combination with a diaryliodonium salt, an exothermic reaction was produced, yielding a thiocarbonylthio‐functionalized polyether. Thermal profiles of the redox polymerizations were determined by means of optical pyrometry. A preliminary study showed that when the poly(cyclohexene oxide) functionalized with dithioester groups was introduced into the radical polymerization of styrene, the polystyryl growing radicals reacted with the dithioester‐functionalized polyether to form a block polymer. The amount of polyether actually incorporated into the block copolymer was calculated to be 70% of the initial amount of poly(cyclohexene oxide)/dithiobenzoic acid charged into the reactor. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Time-Domain Simulation of Power Combining in a Chain of THz Gunn Diodes in a Transmission Line

Solid-state THz devices usually suffer from low power output. This, however, can be overcome by efficient power combining. In this paper, the power combining of a chain of active devices (longitudinal array of N Gunn diodes) in a semi-infinite transmission line has been simulated. Superlinear growth of power P is found in a line with inductive-capacitive elements: P is quadratic in N when P is small and becomes linear when P is large. Intricate auto-modulation due to coupling between the devices is shown to accompany power combining.     

Latex allergens: review of current knowledge

Both health care workers and spina bifida patients are at risk to develop type I latex allergy since allergenic proteins of natural rubber latex are present in a variety of latex products. Natural latex contains more than 250 polypeptides and approximately 60 of them show IgE-binding characteristics. A multitude of these latex allergens has been identified, and their sensitization potency for both risk groups has been determined. While hevein (Hev b 6.02) is the major allergen in latex-allergic health care workers, 80% of latex sensitized-spina bifida children have IgE antibodies to the "rubber elongation factor" (Hev b 1). Almost all relevant latex allergens have been identified in natural latex products: however, no data on the allergen profiles of individual latex products exist. The knowledge of the major latex allergens enables improved diagnosis and to monitor the success of prevention strategies for decreasing the high prevalence of latex allergies.     

On mixing rules for the hydraulic permeability of fiber mixtures

We perform numerical simulations of Stokes flow through ordered arrays of fibers of square cross-section. The results for the permeability of single-size-fiber arrays are in very good agreement with the well-known correlation of Jackson and James, provided that an effective radius of equivalent cylindrical fibers is used with the same cross-sectional area. Then, we consider arrays of mixtures of different-sized fibers and test several mixing rules, proposed for estimating the composite permeability. The two most well-known, namely, the unweighted- and the volume-averaged resistivity rules give good predictions for not too large size-ratios, yet they systematically overestimate and underestimate the numerical results, respectively. Then, it appears almost self-evident that a combination of the above two mixing rules would provide a better prediction. Indeed, the geometric mean gives excellent agreement with the numerical results over an extended range of size ratios and relative volume fractions.     

使用生物反应器酶促合成酸酐（英）

用装有固定化脂肪酶的生物反应器系统对有效地合成蓖麻油酸酐进行了尝试。合成酸酐试图证明：通过控制反应混合物的最适含水量,反应是否能达到目标的缩合度。结果表明,使用生物反应器,反应能迅速地进行,在生物反应器内进行重复间歇反应是可行的,这样与不同脂肪酶相比较,每次脂肪酶的用量均能大大减少。     

Growth and characterization of bis thiourea cadmium iodide: A semiorganic single crystal

Single crystals of bis thiourea cadmium iodide[CdI₂(CH₄N₂S)₂], abbreviated as BTCI, a semiorganic material has been successfully grown by both slow evaporation and slow cooling methods. Crystal of dimensions up to 3.3 × 1.0 × 1.5 cm³ is reported. Single crystal X-ray diffraction analysis has been carried out to confirm monoclinic system and etching studies for their perfection. The morphology of the grown crystal was also identified by single crystal X-ray diffraction analysis. The powder X-ray diffractogram of the crystal has been recorded and the various planes of reflection are identified. The presence of functional groups and the coordination of metal ions to thiourea were confirmed by FTIR analysis. Transmission spectra reveals that the crystal has low UV cutoff of 324 nm and has a good transmittance in the entire visible region enabling its use in optical applications. The thermal behaviour of the crystal has been investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA), which indicates that the material does not decompose before melting. Studies of dielectric properties (dielectric constant and dielectric loss) both as function of frequencies (100 Hz to 5 MHz) for varying temperatures in the range 308–348 K suggests good candidate for electro optic modulators.     

Epigenetic Regulation of Optic Nerve Development,Protection, and Repair

Epigenetic factors are known to influence tissue development, functionality, and their response to pathophysiology. This review will focus on different types of epigenetic regulators and their associated molecular apparatus that affect the optic nerve. A comprehensive understanding of epigenetic regulation in optic nerve development and homeostasis will help us unravel novel molecular pathways and pave the way to design blueprints for effective therapeutics to address optic nerve protection, repair, and regeneration.     

Theoretical Equation of State for Highly Anharmonic Solids

Thermodynamic properties of Lennard–Jones (LJ) face-centered cubic crystals are calculated in a wide range of temperatures along sublimation and melting lines on the basis of statistical mechanical theory which accounts for anharmonicity, pair and triple correlations in the displacements of atoms. Results are compared with the most accurate Monte Carlo data available. Excellent agreement was found. Anharmonic and correlation contributions to entropy, internal energy, and the compressibility factor of LJ solids are computed and their relative importance analyzed. An analytical equation of state approximating the theoretical results is developed.