Development and long-term in vivo evaluation of a biodegradable urethane-doped polyester elastomer

We have recently reported upon the development of crosslinked urethane-doped polyester (CUPE) network elastomers, which was motivated by the desire to overcome the drawbacks presented by crosslinked network polyesters and biodegradable polyurethanes for soft tissue engineering applications. Although the effect of the isocyanate content and post-polymerization conditions on the material structure-property relationship was examined in detail, the ability of the diol component to modulate the material properties was only studied briefly. Herein, we present a detailed report on the development of CUPE polymers synthesized using diols 4, 6, 8, 10, or 12 methylene units in length in order to investigate what role the diol component plays on the resulting material's physical properties, and assess their long-term biological performance in vivo. An increase in the diol length was shown to affect the physical properties of the CUPE polymers primarily through lowered polymeric crosslinking densities and elevated material hydrophobicity. The use of longer chain diols resulted in CUPE polymers with increased molecular weights resulting in higher tensile strength and elasticity, while also increasing the material hydrophobicity to lower bulk swelling and prolong the polymer degradation rates. Although the number of methylene units largely affected the physical properties of CUPE, the choice of diol did not affect the overall polymer cell/tissue-compatibility both in vitro and in vivo. In conclusion, we have established the diol component as an important parameter in controlling the structure-property relationship of the polymer in addition to diisocyanate concentration and post-polymerization conditions. Expanding the family of CUPE polymers increases the choices of biodegradable elastomers for tissue engineering applications.     

HAMMER: hierarchical attribute matching mechanism for elastic registration

A new approach is presented for elastic registration of medical images, and is applied to magnetic resonance images of the brain. Experimental results demonstrate very high accuracy in superposition of images from different subjects. There are two major novelties in the proposed algorithm. First, it uses an attribute vector, i.e., a set of geometric moment invariants (GMIs) that are defined on each voxel in an image and are calculated from the tissue maps, to reflect the underlying anatomy at different scales. The attribute vector, if rich enough, can distinguish between different parts of an image, which helps establish anatomical correspondences in the deformation procedure; it also helps reduce local minima, by reducing ambiguity in potential matches. This is a fundamental deviation of our method, referred to as the hierarchical attribute matching mechanism for elastic registration (HAMMER), from other volumetric deformation methods, which are typically based on maximizing image similarity. Second, in order to avoid being trapped by local minima, i.e., suboptimal poor matches, HAMMER uses a successive approximation of the energy function being optimized by lower dimensional smooth energy functions, which are constructed to have significantly fewer local minima. This is achieved by hierarchically selecting the driving features that have distinct attribute vectors, thus, drastically reducing ambiguity in finding correspondence. A number of experiments demonstrate that the proposed algorithm results in accurate superposition of image data from individuals with significant anatomical differences.     

Effects of heat shock on the thermotolerance, protein composition, and toxin production of Vibrio parahaemolyticus

Vibrio parahaemolyticus, an important seafood-associated enteropathogen, usually encounters different adverse conditions in its native or food-processing environment, and the stresses resulting from these conditions may affect the survival of this pathogen and thus change its risk with regard to food hygiene. In this study, we investigated the thermotolerance of V. parahaemolyticus under sublethal heat shock and characterized this response by examining the changes in protein profiles and toxin production. Logarithmically grown cells heat shocked at 42 degrees C for 30 min were more resistant to thermal inactivation at 47 degrees C than were unshocked cells. After the 25 degrees C culture was heat shocked, 24 species of proteins were induced, while 13 species were inhibited, as indicated by polyacrylamide gel electrophoresis. DnaJ-, GroEL-, and GroES-like proteins with molecular sizes of 47, 62, and 12 kDa, respectively, were detected by immunoblotting with antibodies raised against the Escherichia coli proteins. During 1 to 8 h of heat shock, GroEL-like protein was produced in substantial amounts and was present in the periplasmic and extracellular fractions, while DnaJ- and GroES-like proteins were present mainly in the total cellular fraction. DnaK-like protein was not detected; nevertheless, the presence of the dnaK-like genetic element was revealed by Southern blotting. Production of thermostable direct hemolysin, the major virulence factor in V. parahaemolyticus, was enhanced in the cells heat shocked at 42 degrees C but not in those heat shocked at 37 degrees C.     

Nanocrystalline alpha-Ni(OH)2 prepared by ultrasonic precipitation

Nanocrystalline alpha-Ni(OH)2 was prepared by an ultrasonic precipitation/stirring method. Results of X-ray diffraction, transmission electron microscopy, infrared, and thermogravimetric measurements confirm that the sample obtained is alpha phase. Compared with the sample prepared without ultrasonic stirring, the crystal structure of the alpha phase sample has been changed from beta phase. The crystalline size of the sample is about 20 nm, which is smaller than the sample produced without ultrasonic stirring (70 nm).     

Photon absorption in resonant-cavity-enhanced gaas far-infrared detectors

Interface reflection has been demonstrated to play an important role in GaAs multilayer homojunction far-infrared (FIR) detectors. A transfer matrix method that is able to provide a true optical field distribution within an FIR detector has been employed to optimize photon absorption and structure. The dependence of photon absorption on the reflectivity and the phase shift of the bottom mirror in a resonant-cavity-enhanced GaAs FIR detector has been investigated. Weak wavelength selectivity has been observed for both resonant and off-resonant FIR, which is a unique advantage for detector application. In comparison with the experimental result, a 20.8% increase in quantum efficiency was found in an optimized FIR detector.     

Relaxed alignment tolerance of monolithic ring lasers

An investigation of relaxed alignment tolerance in monolithic ring lasers is presented. It was found that the relaxed alignment tolerance is strongly dependent on the out-of-plane angle. A preferred region for the out-of-plane angle is proposed. In this region the resonator has greatly relaxed alignment tolerances, and the unidirectional operation can be obtained under a much-lower magnetic field. Two lasers have been constructed in the region, and satisfactory performance was found, in good agreement with the theoretical analysis.     

Effects of Subchronic Samarium Exposure on Testicle Tissue of Mice

Effects of Subchronic Samarium Exposure on Testicle Tissue of Mice     

Design and Implement of Personalized Distance Education System Based on Web Usage Mining

Modern distance education essentially differs from traditional pattern of education in providing personalized education support service. This paper analyzes the status in which distance education provides personalized education support service nowadays. A distance education system is put forward based on Web usage mining techniques. Through analyzing the access behavior, the frequency, the browsing contents and the staying time of the students, get the general pattern of students＇ access behaviors, and than provide personalized education support service comprehensively according to these analysis.     

Tm(3+)-Doped Tellurite Glass for a Broadband Amplifier at 1.47 num

Tm(3+)-doped tellurite glass is investigated as a host for a broadband amplifier at 1.47 mum. The Tm(3+) fluorescence spectrum, lifetime, and cross section in tellurite glass are compared with those in fluorozirconate glasses. The advantages of a Tm(3+)-tellurite amplifier, especially when it is employed in combination with an Er(3+)-tellurite 1.55-mum amplifier, are discussed.