End-group analysis of polymacromonomer formed in the radical polymerization of styrene-type PMMA macromonomers by using 2H NMR spectroscopy

Summary Isotactic (iso-) and syndiotactic (syn-) poly(methyl methacrylate) (PMMA) macromonomers having styrene group as a polymerizable function were polymerized with perdeuterated 2,2-azobisisobutyronitrile in toluene at 60°C. The resultant polymacromonomers were analyzed by ²H NMR spectroscopy to determine the number of initiator fragment in a polymacromonomer chain (N) and initiator efficiency (f). The N values were less than unity (0.500.72), indicating the chain transfer reaction to occur in the radical polymerization of macromonomer. The f values were 0.180.28 and much smaller than that for styrene polymerization (0.50.7). Iso-macromonomer gave larger N and f values than syn- one, suggesting that the tacticity of macromonomer affects the reaction pathway probably owing to the difference in chain mobility between iso- and syn-PMMA chains.     

Learning from Cluster Examples

Learning from cluster examples (LCE) is a hybrid task combining features of two common grouping tasks: learning from examples and clustering. In LCE, each training example is a partition of objects. The task is then to learn from a training set, a rule for partitioning unseen object sets. A general method for learning such partitioning rules is useful in any situation where explicit algorithms for deriving partitions are hard to formalize, while individual examples of correct partitions are easy to specify. In the past, clustering techniques have been applied to such problems, despite being essentially unsuited to the task. We present a technique that has qualitative advantages over standard clustering approaches. We demonstrate these advantages by applying our method to problems in two domains; one with dot patterns and one with more realistic vector-data images.     

Distribution of carbon in polycrystalline copper surfaces treated by methane plasma immersion ion implantation

Copper substrates with rather large grains (dimensions of some mm) treated by pulsed methane plasma immersion ion implantation exhibit a laterally inhomogeneous carbon distribution. Areas with high carbon X-ray intensity in electron probe microanalysis coincide with thicker carbon containing layers as seen in sputter depth profiling via secondary ion mass spectrometry. The distribution of carbon within the surface depends not only on the treatment time and pulse repetition rate but also on the orientation of the individual copper grains.     

Dynamic structures of motor proteins myosin and kinesin, and switch protein troponin as detected by SDSL-ESR

We have studied biological nano-machines, motor and switch proteins operating as supramolecular complexes by electron spin resonance (ESR) and found key features of their molecular movements. In all the systems, the specific movements of elements or domains were detected and quite dynamic at nanometer scale. We have observed two broad but distinct orientations, separated by a 25 degrees axial rotation, of a spin label attached specifically to the light chain (LC) domain of myosin motor in the muscle fibers. The distribution became only narrower upon muscle activation. ESR spectrum from the spin label of the neck-linker of dimeric kinesin motor consisted of immobilized and mobilized components and did not exhibit nucleotide-dependent mobility change. The distance between two labels of kinesin dimer was also measured by spin dipole-dipole interaction, showing a broad distribution and a nucleotide-dependent change on the nanometer scale (>1.5 nm). These results suggest that two LC domains of myosin and two neck linkers of kinesin play a similar role for sliding movement using two conformations. The spin label of the skeletal (Tn)-I regulatory domain (TnIreg) showed a large mobility change by Ca2+ ion suggesting a Ca-induced switch movement of TnIreg. Spin dipole-dipole interaction showed that in reconstituted muscle fibers both skeletal and cardiac TnC undergo Ca2+-induced structural change that is thought to be essential for TnIreg movement. We also succeeded in fixing the newly-synthesized bifunctional spin label rigidly on the TnC molecule in solution, indicating that we can determine the precise coordinate of the spin principal axis of troponin on the oriented filament.     

Analysis of poly(ethyl methacrylate)s by on-line hyphenation of liquid chromatography at the critical adsorption point and nuclear magnetic resonance spectroscopy

Liquid chromatography at the critical adsorption point (LC CAP) with on-line NMR detection (on-line LC CAP NMR) was utilized for analysis of tacticity distribution of stereo-regular poly(ethyl methacrylate)s (PEMAs). The separation of a model PEMA sample composed of four constituents with similar molar masses (Mw = (14-16) x 10(3) g mol-1) differing in their tacticity (rr triad content = 0, 33, 68, and 89%) was achieved by LC CAP with a mixed eluent composed of acetone, acetone-d6, and cyclohexane. The tacticity composition within each peak eluted from the LC CAP column was directly determined by a 750-MHz 1H NMR spectrometer that was used as a real-time detector in the continuous-flow mode. Tacticity distribution in a particular PEMA sample with mm/mr/rr = 2/45/53 and narrow molar mass distribution of Mw/Mn = 1.05 has been revealed by the LC CAP NMR technique.     

Visual response saturation to orientation contrast in the perception of texture boundary

We analyzed how the visual response to orientation modulation in texture patterns varied as a function of the magnitude of orientation contrast. Using a contrast-discrimination technique, we measured threshold increments of orientation contrast (the orientation contrast required for discriminating between two textures) at various pedestal-orientation contrasts. The orientation-contrast-response function estimated for a step-orientation contrast, which produces a vivid percept of surface boundaries, saturated at approximately 30 degrees (experiment 1). The saturation was still evident even when the strength of the step-orientation contrast was reduced by orientation noise (experiment 2), but no strong saturation was found for textures that did not produce a vivid percept of surface boundaries (experiment 3). These results are consistent with the notion that orientation-based texture segregation involves the generation of a neural representation of the surface boundary whose strength is nearly independent of the magnitude of orientation contrast.     

Altered mitochondrial gene expression in a maternal distorted leaf mutant of Arabidopsis induced by chloroplast mutator

Chloroplast mutator (chm) of Arabidopsis is a recessive nuclear mutation that causes green and white variegation in leaves and is inherited in a non-Mendelian fashion. In this study, we have identified and characterized a mutant observed in F1 and backcrossed BC1 populations from a cross between chm1-3 and ecotype Columbia. This mutant, maternal distorted leaf (MDL), grows very poorly and is distinguished by distorted rough leaves and aborted flowering organs. Electron microscopic observation showed that in MDL plants, a significant portion of mitochondria are abnormal and appear to be nonfunctional. DNA gel blot and sequence analysis of the MDL mitochondrial DNA (mtDNA) revealed rearrangements in two mtDNA fragments associated with rps3-rpl16 genes (encoding ribosomal proteins S3 and L16, respectively). One rearrangement resulted in the insertion of the rps3-rpl16 operon downstream of atp9. An independent deletion in this region had eliminated the majority of rps3. In contrast, another rearrangement deleted part of rpl16, whereas rps3 remained intact. RNA gel blot analysis indicated that expression of these genes is also altered as a consequence of the mtDNA rearrangements. Thus, a mutation at the CHM locus affects mitochondrial gene expression, and impaired mitochondrial function may result in the distorted phenotype.     

A simple method for predicting the performance of a heat exchanger mounted in an air conditioner (1st report,proposed reduced‐mesh analysis modeling method)

To analyze the performance of a heat exchanger (HEX) used in air conditioners within a realistic time frame, a simple method—based on a reduced‐mesh calculation model—was developed. The pressure loss caused by the HEX is given by a momentum source term, and the heat‐transfer performance of the HEX is approximated by using a wall function as the boundary condition. The analytical results from this simple analysis model (under a fin‐pitch range of 1.0 to 1.6 mm) were compared with experimental measurements of pressure loss and heat‐transfer performance. This comparison showed that the pressure loss from the simple analysis model agrees with the experimentally measured loss (within 3% error) and that the heating capacity determined by the simple model agrees with the experimentally measured one (within a 1% error). © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(1): 12–23, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10130     

Seroprevalence against Toxoplasma gondii in domiciled cats in Japan

A serological survey with latex agglutination test to detect anti-Toxoplasma gondii antibodies was conducted on 800 serum samples collected from domiciled cats at animal hospitals in various areas of Japan. The overall prevalence was 6.0% (48/800). Among 48 positive individuals, there was no specific distribution of strength of antibody titers; the titers were 1:64 in 8 cats, 1:128 in 12, 1:256 in 8, 1:512 in 10, 1:1,024 in 8 and 1:2,048 in 2. The maximum prevalence was 15.4% in 13 cats at 17-23 yrs old group, whereas all were negative in 58 cats aged 12-16 yrs. The age groups in the order of higher prevalence were 8, 4, 10, 5, 3, and 7 yrs, showing no aging effect to the prevalence. In terms of rearing conditions of those cats, they were classified into 4 groups, i.e., indoor, free, outdoor, and others. The prevalence in the outdoor group (11.1%) was significantly higher (p < 0.05) than that in the free group (4.8%). Epidemiological aspects observed in the domiciled cats were different from those reported in the stray cats.