Density Functional Theory for Block Copolymer Melts and Blends

We derive an expression for the free energy of the blends of block copolymers expressed as a functional of the density distribution of the monomer of each block. The expression is a generalization of the Flory-Huggins-de Gennes theory for homo polymer blends, and also a generalization of the Ohta-Kawasaki theory for the melts of diblock copolymers. The expression can be used for any blends of homopolymers and block copolymers of any topological structure. The expression gives a fast and stable computational method to calculate the micro and macro phase separation of the blends of homopolymers and block copolymers.Comment: 25 pages, 9 figures, will appear in Macromolecule

Crossover Time in Relative Fluctuations Characterizes the Longest Relaxation Time of Entangled Polymers

In entangled polymer systems, there are several characteristic time scales, such as the entanglement time and the disengagement time. In molecular simulations, the longest relaxation time (the disengagement time) can be determined by the mean square displacement (MSD) of a segment or by the shear relaxation modulus. Here, we propose the relative fluctuation analysis method, which is originally developed for characterizing large fluctuations, to determine the longest relaxation time from the center of mass trajectories of polymer chains (the time-averaged MSDs). Applying the method to simulation data of entangled polymers (by the slip-spring model and the simple reptation model), we provide a clear evidence that the longest relaxation time is estimated as the crossover time in the relative fluctuations.Comment: 17 pages, 9 figures, to appear in J. Chem. Phy

Early childhood exposure to maternal smoking and Kawasaki Disease: A longitudinal survey in Japan

Kawasaki disease is the leading cause of acquired childhood heart disease in most developed countries, but the etiology of the disease is unknown. An aberrant immune response to some environmental triggers may play a role and involuntary exposure to tobacco smoke can alter immune functions. We thus prospectively examined the association between early childhood exposure to maternal smoking and the incidence of Kawasaki disease. We used a large, nationwide population-based longitudinal survey ongoing since 2010 and restricted participants to a total of 38,444 children for whom information on maternal smoking was available. Maternal smoking status was ascertained at 6months of age, and responses to questions about hospital admission for Kawasaki disease between the ages of 6 and 30months were used as outcome. We conducted binomial log-linear regression analyses adjusting for children's, parental, and residential factors with children of non-smoking mothers as our reference group. Maternal smoking increased the risk of admission, in particular for the period between 6 and 18months of age, in a dose-dependent manner. Compared with children of non-smoking mothers, the children of mothers who smoked had a risk ratio of 1.83 (95% confidence interval: 1.06, 3.35) for hospital admissions between 6 and 30months of age and a risk ratio of 2.69 (95% confidence interval: 1.56, 4.64) for hospital admissions between 6 and 18months of age. Early childhood exposure to maternal smoking may increase the risk of Kawasaki disease hospitalizations in childhood

Searching for a Companion Star of Tycho's Type Ia Supernova with Optical Spectroscopic Observations

We report our first results of photometric and spectroscopic observations for Tycho's supernova remnant (SNR Tycho) to search for the companion star of a type Ia supernova (SN Ia). From photometric observations using Suprime-Cam on the Subaru Telescope, we have picked up stars brighter than 22 mag (in $V$-band) for spectroscopy, which are located within a circular region with the radius of 30" around the center of SNR Tycho. If the ejecta of young supernova remnants, such as SNR Tycho, have a sufficient amount of Fe I, we should be able to detect absorption lines at 3720 \AA and 3860 \AA associated with transitions from the ground state of Fe I in the spectrum of the companion star. To identify the companion star of a SN Ia using these characteristic absorption lines of Fe I, we made optical low-resolution spectroscopy of their targets using FOCAS on the Subaru Telescope. In our spectroscopic observations, we obtained spectra of 17 stars in the SNR Tycho region and compare them with template stellar spectra. We detect significant absorption lines from two stars at 3720 \AA. Since widths of their absorption lines are broad, it is likely that the detected absorptions are due to Fe I in the expanding ejecta of SNR Tycho. However, none of stars exhibits a clear red wing in the observed profiles of the absorption, though a star in the background of the SNR should show it. Hence, we suggest another interpretation that the detected absorption lines might be caused by the peculiarity of stars. A star named Tycho(E) has the absorption line at 3720 \AA and its projected position is close to the center of SNR Tycho. Based on our observations, Tycho(E) is a new candidate as the companion star of Tycho's supernova.Comment: 17 pages, 28 figures, accepted for publication in PAS