Quantum fluctuation induced ordered phase in the Blume-Capel model

We consider the Blume-Capel model with the quantum tunneling between the excited states. We find a magnetically ordered phase transition induced by quantum fluctuation in a model. The model has no phase transition in the corresponding classical case. Usually, quantum fluctuation breaks ordered phase as in the case of the transverse field Ising model. However, in present case, an ordered phase is induced by quantum fluctuation. Moreover, we find a phase transition between a quantum paramagnetic phase and a classical diamagnetic phase at zero temperature. We study the properties of the phase transition by using a mean field approximation (MFA), and then, by a quantum Monte Carlo method to confirm the result of the MFA.Comment: 7 pages, 6 figures, corrected some typo

Development and operational experience of magnetic horn system for T2K experiment

A magnetic horn system to be operated at a pulsed current of 320 kA and to survive high-power proton beam operation at 750 kW was developed for the T2K experiment. The first set of T2K magnetic horns was operated for over 12 million pulses during the four years of operation from 2010 to 2013, under a maximum beam power of 230 kW, and $6.63\times10^{20}$ protons were exposed to the production target. No significant damage was observed throughout this period. This successful operation of the T2K magnetic horns led to the discovery of the $\nu_{\mu}\rightarrow\nu_e$ oscillation phenomenon in 2013 by the T2K experiment. In this paper, details of the design, construction, and operation experience of the T2K magnetic horns are described.Comment: 22 pages, 40 figures, also submitted to Nuclear Instrument and Methods in Physics Research,

Dynamic Reprogramming of DNA Methylation at an Epigenetically Sensitive Allele in Mice

There is increasing evidence in both plants and animals that epigenetic marks are not always cleared between generations. Incomplete erasure at genes associated with a measurable phenotype results in unusual patterns of inheritance from one generation to the next, termed transgenerational epigenetic inheritance. The Agouti viable yellow (A(vy)) allele is the best-studied example of this phenomenon in mice. The A(vy) allele is the result of a retrotransposon insertion upstream of the Agouti gene. Expression at this locus is controlled by the long terminal repeat (LTR) of the retrotransposon, and expression results in a yellow coat and correlates with hypomethylation of the LTR. Isogenic mice display variable expressivity, resulting in mice with a range of coat colours, from yellow through to agouti. Agouti mice have a methylated LTR. The locus displays epigenetic inheritance following maternal but not paternal transmission; yellow mothers produce more yellow offspring than agouti mothers. We have analysed the DNA methylation in mature gametes, zygotes, and blastocysts and found that the paternally and maternally inherited alleles are treated differently. The paternally inherited allele is demethylated rapidly, and the maternal allele is demethylated more slowly, in a manner similar to that of nonimprinted single-copy genes. Interestingly, following maternal transmission of the allele, there is no DNA methylation in the blastocyst, suggesting that DNA methylation is not the inherited mark. We have independent support for this conclusion from studies that do not involve direct analysis of DNA methylation. Haplo-insufficiency for Mel18, a polycomb group protein, introduces epigenetic inheritance at a paternally derived A(vy) allele, and the pedigrees reveal that this occurs after zygotic genome activation and, therefore, despite the rapid demethylation of the locus

Frontogenesis of the Angola–Benguela Frontal Zone

A diagnostic analysis of the climatological annual mean and seasonal cycle of the Angola–Benguela Frontal Zone (ABFZ) is performed by applying an ocean frontogenetic function (OFGF) to the ocean mixing layer (OML). The OFGF reveals that the meridional confluence and vertical tilting terms are the most dominant contributors to the frontogenesis of the ABFZ. The ABFZ shows a well-pronounced semiannual cycle with two maximum (minimum) peaks in April–May and November–December (February–March and July–August). The development of the two maxima of frontogenesis is due to two different physical processes: enhanced tilting from March to April and meridional confluence from September to October. The strong meridional confluence in September to October is closely related to the seasonal southward intrusion of tropical warm water to the ABFZ that seems to be associated with the development of the Angola Dome northwest of the ABFZ. The strong tilting effect from March to April is attributed to the meridional gradient of vertical velocities, whose effect is amplified in this period due to increasing stratification and shallow OML depth. The proposed OFGF can be viewed as a tool to diagnose the performance of coupled general circulation models (CGCMs) that generally fail at realistically simulating the position of the ABFZ, which leading to huge warm biases in the southeastern Atlantic.</p

Self-Diffusion of a Polymer Chain in a Melt

Self-diffusion of a polymer chain in a melt is studied by Monte Carlo simulations of the bond fluctuation model, where only the excluded volume interaction is taken into account. Polymer chains, each of which consists of $N$ segments, are located on an $L \times L \times L$ simple cubic lattice under periodic boundary conditions, where each segment occupies $2 \times 2 \times 2$ unit cells. The results for $N=32, 48, 64, 96, 128, 192, 256, 384$ and 512 at the volume fraction $\phi \simeq 0.5$ are reported, where $L = 128$ for $N \leq 256$ and L=192 for $N \geq 384$. The $N$-dependence of the self-diffusion constant $D$ is examined. Here, $D$ is estimated from the mean square displacements of the center of mass of a single polymer chain at the times larger than the longest relaxation time. From the data for $N = 256$, 384 and 512, the apparent exponent $x_{\rm d}$, which describes the apparent power law dependence of $D$ on $N$ as $D \propto N^{- x_{\rm d}}$, is estimated as $x_{\rm d} \simeq 2.4$. The ratio $D \tau /$ seems to be a constant for $N = 192, 256, 384$ and 512, where $\tau$ and $$ denote the longest relaxation time and the mean square end-to-end distance, respectively.Comment: 4 pages, 3 figures, submitted to J. Phys. Soc. Jp

Relaxation of a Single Knotted Ring Polymer

The relaxation of a single knotted ring polymer is studied by Brownian dynamics simulations. The relaxation rate lambda_q for the wave number q is estimated by the least square fit of the equilibrium time-displaced correlation function to a double exponential decay at long times. The relaxation rate distribution of a single ring polymer with the trefoil knot appears to behave as lambda_q=A(1/N^)x for q=1 and lambda_q=A'(q/N)^x' for q=2 and 3, where x=2.61, x'=2.02 and A>A'. The wave number q of the slowest relaxation rate for each N is given by q=2 for small values of N, while it is given by q=1 for large values of N. This crossover corresponds to the change of the structure of the ring polymer caused by the localization of the knotted part to a part of the ring polymer.Comment: 13 pages, 5 figures, uses jpsj2.cl