Synthesis of high molecular weight copolymer of styrene and butadiene bearing high 1,4‐cis butadiene unit from copolymerization with CpTiCl3/methylaluminoxane catalyst

Copolymerization of styrene (St) and butadiene (Bd) with CpTiCl₃/methylaluminoxane (MAO) catalyst in the presence or absence of chloranil (CA) was investigated. The CpTiCl₃/MAO catalyst showed a high activity for the copolymerization of St with Bd. The 1,4‐cis contents in the Bd units for the copolymerization of St and Bd with the CpTiCl₃/MAO catalyst was observed, and the 1,4‐cis content was optimum at a MAO/Ti mole ratio of around 225. The effect of the polymerization temperature on the copolymerization was noted, as was the effect of the 1,4‐cis microstructure in the Bd units for the copolymerization of St and Bd. The addition of CA to the CpTiCl₃/MAO catalyst was found to influence the molecular weight of the copolymer. The high weight‐average molecular weight copolymer (M_w = ca. 50 × 10⁴) consisting of mainly a 1,4‐cis microstructure of Bd units (1,4‐cis = 80.0%) was obtained from the copolymerization with the CpTiCl₃/MAO catalyst in the presence of CA (CA/Ti mole ratio = 1) at 0°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2942–2946, 2003     

Defect structures in cosputtered thin films of transition-metal disilicides with C11<Subscript><Emphasis Type="Italic">b</Emphasis></Subscript>, C40 and C54 structures

Defect structures in crystallites of the stable phases in thin films of transition-metal (TM) disilicides (C11 _b MoSi₂, C40 TaSi₂, and C54 TiSi₂) produced by cosputtering and subsequent annealing have been investigated by transmission electron microscopy (TEM). Crystallites in thin films of MoSi₂, TaSi₂, and TiSi₂ all contain planar faults parallel to hexagonally arranged TMSi₂ planes, which are a characteristic feature commonly observed in all three crystal structures. These planar faults are twin boundaries in all cases. Twins in thin films of these disilicides, thus, have a common characteristic that the twin habit plane is parallel to hexagonally arranged TMSi₂ stoichiometric planes. For twins in thin films of C11 _b MoSi₂, and C54 TiSi₂, the twining elements can be deduced and the twin habit plane is found not to be parallel to the twinning (K ₁) plane, but to be perpendicular to it. Twins formed in C40 TaSi₂ thin films are different from those formed in C11 _b MoSi₂ and C54 TiSi₂ thin films, in that the crystal orientation of the twin is exactly the same as that of the matrix, since they are racemic twins that are only enantiomorphically (space groups of P6₂22 or P6₄22) related to each other. This article is based on a presentation in the symposium “Terence E. Mitchell Symposium on the Magic of Materials: Structures and Properties” from the TMS Annual Meeting in San Diego, CA in March 2003.     

Bone marrow-impregnated collagen matrix for wound healing: experimental evaluation in a microcirculatory model of angiogenesis, and clinical experience

Objectives

This study aims to investigate the effect of collagen matrix impregnated with bone marrow on wound healing angiogenesis in an effective microcirculatory model and to describe our clinical experience.

Methods

We used a skinfold chamber of original design which visualises microcirculation following wound creation on the dorsal skin of the mouse to establish an in vivo experimental model to estimate angiogenesis. Animals were divided into two groups: a bone marrow group (n=6) in which bone marrow-impregnated collagen matrix was applied to the wound; and a control group (n=7), in which collagen immersed in saline was applied, and functional capillary density was quantified during the repair process.

Results

The increase rate in functional capillary density during wound healing significantly increased in the bone marrow group on days 3, 5 and 7 after creation of the wound but no significant difference was detected on day 10. A patient with a chronic leg ulcer that had not responded to conventional therapy for 1 year was treated with autogenous bone marrow-impregnated collagen matrix and successful wound closure was obtained.

Conclusion

The present study suggested that collagen matrix impregnated with bone marrow significantly promoted the repair process, especially in the early stage. The features of the treatment, including the possible use of a patient's own cells, simple method, immediate application without any processing procedure and preservation of the inclusive potentiality of bone marrow suspension, offer significant advantages in terms of the anticipated routine clinical use.     

Effect of solvents on the degradation of polymers by high-speed stirring

The effect of solvents on the degradation of poly(methyl methacrylate), polystyrene, and polyisobutylene by high-speed stirring (30,000 rpm) at 30°C was studied. From the intrinsic viscosities of polymers stirred for given times, the viscosity-average degree of polymerization, P?_v was obtained and the number of scissions per molecule, B/n₀. was calculated. Ovenall's equation could be applied to the results, where dB_i/dl is the rate of breakage of molecules of ith degree of polymerization, n_i is the number of molecules present, P_I is the limiting degree of polymerization, and k_i is a rate constant; k and P_I were changed with solvents, and were found to have no relation to the physical properties of the solvents but to the intrinsic viscosities the polymers showed in the solvents used for the stirring. k was smaller and P_I larger for solvents where polymers had larger intrinsic viscosities. This relation implies that the degree of expansion of a polymer coil in a solvent is closely related to the rate constant of scission and to the limiting degree of polymerization.     

Sensitization of nano-porous ZnO photo-anode by a conjugated conducting polymer

Hybrid ZnO films are prepared via one-step electrochemical process. Extraction of organic component from hybrid films results tiny wires like ZnO columns perpendicular to the substrate. Visible light sensitive-conjugated polymer poly(2-methoxy-5-[2 ethylhexyloxy]-1-4-phenylenevinylene, MEH–PPV) was embedded in highly porous ZnO ceramic by a solvent vaporization technique. An attempt was made to fabricate polymer sensitized photovoltaic cell by coupling polymer embedded ZnO electrodes with an electrolyte. Maximum photovoltage of 490 mV is observed for the cell with the configuration of ZnO|MEH–PPV|I^?/I₃^? cell.     

The Safety and Anti-Tumor Effects of Ozonated Water in Vivo

Ozonated water is easier to handle than ozone gas. However, there have been no previous reports on the biological effects of ozonated water. We conducted a study on the safety of ozonated water and its anti-tumor effects using a tumor-bearing mouse model and normal controls. Local administration of ozonated water (208 mM) was not associated with any detrimental effects in normal tissues. On the other hand, local administration of ozonated water (20.8, 41.6, 104, or 208 mM) directly into the tumor tissue induced necrosis and inhibited proliferation of tumor cells. There was no significant difference in the number of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling (TUNEL)-positive cells following administration of ozonated water. The size of the necrotic areas was dependent on the concentration of ozonated water. These results indicate that ozonated water does not affect normal tissue and damages only the tumor tissue by selectively inducing necrosis. There is a possibility that it exerts through the production of reaction oxygen species (ROS). In addition, the induction of necrosis rather than apoptosis is very useful in tumor immunity. Based on these results, we believe that administration of ozonated water is a safe and potentially simple adjunct or alternative to existing antineoplastic treatments.     

Proper acquisition and handling of scanning electron microscopy images using a high-performance personal computer

The modern high-performance personal computer (PC) has very recently expanded the range of utilization of digital scanning electron microscopy (SEM) images, and the PC will be used increasingly with SEMs. However, the image quality of digital SEM images may be considerably influenced by scanning and digitization conditions. In particular, the effects of the aliasing error peculiar to digital data are often serious in the low-magnification acquisition (undersampling) of SEM images, and moreover even a high-magnification image (oversampling) is disturbed by the undersampled noise (a sort of aliasing error). Furthermore, the signal-to-noise ratio of a digitized SEM image is closely related to the performance of the analog-to-digital converter. To prevent a flood of low-quality digital images with artifacts by the aliasing and additional noise, we propose a method using very high-density sampling (scanning). In addition, we will discuss how to handle digital SEM images from the point of view of the sampling and quantization.     

Recognition of amino acids by membrane potential and circular dichroism of immobilized albumin membranes

The shifts in membrane potential, caused by the injection of some amino acids into a permeation cell, were measured using immobilized serum albumin membranes at isoelectric points of the amino acids. The effective fixed charge density was estimated to decrease after the injection of alamine, phenylalanine, and tryptophan and to increase after the injection of serine. The change in the fixed charge density originated from the conformational change of the immobilized albumin membranes induced by the binding between the albumin and amino acids in the membranes, since the conformational change of the immobilized albumin membranes induced by the binding of the amino acids to the serum albumin was observed from circular dichroism measurements. There was found, however, some discrepancy between the conformational change of the serum albumin in the albumin membranes detected by the membrane potential measurements and the circular dichroism measurements. This is explained by the fact that the circular dichroism measurements detect the increase or decrease in the α-helix, β sheet, and random coil contents; however, they do not always contribute to the detection of the change in the charge density due to the presence of the amino acid in the albumin membranes. © 1995 John Wiley & Sons, Inc.     

Development of Heterojunction Diode-Type Gamma Ray Detectors Based on Epitaxially Grown Thick CdTe on$hboxn^+$-Si Substrates

Room temperature nuclear radiation detectors with energy discrimination capability developed by growing thick cadmium telluride (CdTe) epitaxial layers directly on n⁺-Si substrates in a metal-organic vapor phase epitaxy system is reported for the first time. The CdTe/n⁺-Si heterojunction diode detector exhibited good rectification and charge collection properties. The reverse leakage currents were typically 1times10^-7 to 5times10^-7 A/cm² at 50-V bias. The detector clearly demonstrated its energy discrimination capability by resolving gamma peak from the ²⁴¹Am radioisotope during radiation detection test at room temperature