Kinetics of chain collapse in dilute polymer solutions: Molecular weight and solvent dependences

The molecular weight and solvent dependences of the characteristic time of chain collapse were studied for poly(methyl methacrylate) (PMMA) of the molecular weight Mw =6.4× 106 and 1.14× 107 in pure acetonitrile (AcN) and in the mixed solvent of AcN+water (10 vol %). The size of PMMA chains was measured as a function of the time after the quench by static light scattering and the chain collapse processes were expressed by the plot of the expansion factor α2 vs ln t. The chain collapse in the mixed solvent AcN+water (10 vol %) was found to occur much faster than that in pure AcN, though the measurement of the former collapse process required several hours. In order to make a comparison between the rates of chain collapses, the fast chain collapse process was superposed on the slow one by scaling the time of the fast process as γt. The scale factor γ was determined by comparing the chain collapse processes of nearly the same equilibrium expansion factor with each other. Accordingly, the superposition of the collapse for Mw =6.4× 106 on that for Mw =1.14× 107 yielded γm =4.0±0.6 for the process in AcN+water and 5.5±0.6 in AcN. The superposition of the chain collapse process in AcN+water on that in AcN yielded γs =9.5±1.4 for Mw =6.4× 106 and 12.0±1.8 for Mw =1.14× 107. This analysis suggests that γm and γs are constant independent of each other. Thus, by assuming the molecular weight dependence of γm ∼ Mz, the characteristic time τexp of chain collapse was conjectured as τexp ∼κ Mz, where κ reflects the nature of solvent species. The ratio of κ for PMMA in AcN to that in AcN+water is given by γs. The exponent was estimated to be z=2.4±0.7 for AcN+water and 3.0±0.7 for AcN. These values are compatible with the theoretical prediction z=3 based on a phenomenological model, though the observed characteristic times are longer by several orders of magnitude than those of the theoretical prediction

The relationship between free-throw accuracy and performance variables in male wheelchair basketball players

We investigated the relationship between the free-throw accuracy and performance variables among fourteen elite male wheelchair basketball players. Participants performed 20 basketball free-throws. Basketball performance variables were the phases of the pre-shoot routine: (a) time taken, (b) minimum angle when taking the ball back, (c) angle at ball release, (d) angular displacement during the forward arm swing, and (e) angular velocity at ball release on the elbow, shoulder, and hip. A significant negative correlation was observed between the free-throw accuracy and mean pre-shot time, suggesting that participants with a shorter pre-shot time showed a higher free-throw accuracy. In addition, a significant negative correlation was found between the free-throw accuracy and variability of angular velocity of the hip at the time of ball release, indicating that the consistency of hip movement is an important factor in free-throw accuracy. In contrast, there were no relationship between the free-throw accuracy and player’s classification point defined as International Wheelchair Basketball Federation, and experience of wheelchair basketball. These data suggest that the routine duration and trunk movement are related to free-throw accuracy in wheelchair basketball

Magnetized Fast Isochoric Laser Heating for Efficient Creation of Ultra-High-Energy-Density States

The quest for the inertial confinement fusion (ICF) ignition is a grand challenge, as exemplified by extraordinary large laser facilities. Fast isochoric heating of a pre-compressed plasma core with a high-intensity short-pulse laser is an attractive and alternative approach to create ultra-high-energy-density states like those found in ICF ignition sparks. This avoids the ignition quench caused by the hot spark mixing with the surrounding cold fuel, which is the crucial problem of the currently pursued ignition scheme. High-intensity lasers efficiently produce relativistic electron beams (REB). A part of the REB kinetic energy is deposited in the core, and then the heated region becomes the hot spark to trigger the ignition. However, only a small portion of the REB collides with the core because of its large divergence. Here we have demonstrated enhanced laser-to-core energy coupling with the magnetized fast isochoric heating. The method employs a kilo-tesla-level magnetic field that is applied to the transport region from the REB generation point to the core which results in guiding the REB along the magnetic field lines to the core. 7.7 $\pm$ 1.3 % of the maximum coupling was achieved even with a relatively small radial area density core ($\rho R$ $\sim$ 0.1 g/cm$^2$). The guided REB transport was clearly visualized in a pre-compressed core by using Cu-$K_\alpha$ imaging technique. A simplified model coupled with the comprehensive diagnostics yields 6.2\% of the coupling that agrees fairly with the measured coupling. This model also reveals that an ignition-scale areal density core ($\rho R$ $\sim$ 0.4 g/cm$^2$) leads to much higher laser-to-core coupling ($>$ 15%), this is much higher than that achieved by the current scheme

SORL1 Is Genetically Associated with Late-Onset Alzheimer’s Disease in Japanese, Koreans and Caucasians

To discover susceptibility genes of late-onset Alzheimer’s disease (LOAD), we conducted a 3-stage genome-wide association study (GWAS) using three populations: Japanese from the Japanese Genetic Consortium for Alzheimer Disease (JGSCAD), Koreans, and Caucasians from the Alzheimer Disease Genetic Consortium (ADGC). In Stage 1, we evaluated data for 5,877,918 genotyped and imputed SNPs in Japanese cases (n = 1,008) and controls (n = 1,016). Genome-wide significance was observed with 12 SNPs in the APOE region. Seven SNPs from other distinct regions with p-values ,261025 were genotyped in a second Japanese sample (885 cases, 985 controls), and evidence of association was confirmed for one SORL1 SNP (rs3781834, P=7.3361027 in the combined sample). Subsequent analysis combining results for several SORL1 SNPs in the Japanese, Korean (339 cases, 1,129 controls) and Caucasians (11,840 AD cases, 10,931 controls) revealed genome wide significance with rs11218343 (P=1.7761029) and rs3781834 (P=1.0461028). SNPs in previously established AD loci in Caucasians showed strong evidence of association in Japanese including rs3851179 near PICALM (P=1.7161025) and rs744373 near BIN1 (P = 1.3961024). The associated allele for each of these SNPs was the same as in Caucasians. These data demonstrate for the first time genome-wide significance of LOAD with SORL1 and confirm the role of other known loci for LOAD in Japanese. Our study highlights the importance of examining associations in multiple ethnic populations

Coil-globule transition of poly(methyl methacrylate) in a mixed solvent

From light scattering measurements the coil-globule transition has been observed for poly(methyl methacrylate) in the mixed solvent water+tert-butyl alcohol with molecular weight Mw=2.38×106. Since the phase separation occurred very slowly for this system, the mean square radius of gyration 〈s2〉 and the second virial coefficient A2 were determined reliably even far below the phase-separation temperature. A comparison of the observed 〈s2〉 with a theory for a contracted coil confirmed the coil-globule transition. The observed second virial coefficient had a minimum in the temperature region where 〈s2〉 approaches the value for the globule state

Kinetics of nucleation in a dilute polymer solution

To determine the time evolution of the droplet size distribution in the nucleation process, we have made light-scattering measurements on supercooled dilute solutions of poly(methyl methacrylate) in 1-chlorobutane, which showed extremely slow phase separation. The observed scattered intensities were analyzed by the Guinier plot and represented in a scaled form. The time evolution of the mean radius R¯(t), total density N(t), and droplet-size distribution N(R,t) of droplets of minority phase was given by the relations R¯(t)~t, N(t)∼t0.6, and N(R,t)=N(t)h(R/R¯)/R¯, independent of quench depth and concentration