Hard Spheres: Crystallization and Glass Formation

Motivated by old experiments on colloidal suspensions, we report molecular dynamics simulations of assemblies of hard spheres, addressing crystallization and glass formation. The simulations cover wide ranges of polydispersity s (standard deviation of the particle size distribution divided by its mean) and particle concentration. No crystallization is observed for s > 0.07. For 0.02 < s < 0.07, we find that increasing the polydispersity at a given concentration slows down crystal nucleation. The main effect here is that polydispersity reduces the supersaturation since it tends to stabilise the fluid but to destabilise the crystal. At a given polydispersity (< 0.07) we find three regimes of nucleation: standard nucleation and growth at concentrations in and slightly above the coexistence region; "spinodal nucleation", where the free energy barrier to nucleation appears to be negligible, at intermediate concentrations; and, at the highest concentrations, a new mechanism, still to be fully understood, which only requires small re-arrangement of the particle positions. The cross-over between the second and third regimes occurs at a concentration, around 58% by volume, where the colloid experiments show a marked change in the nature of the crystals formed and the particle dynamics indicate an "ideal" glass transition

GCA in 2d

We make a detailed study of the infinite dimensional Galilean Conformal Algebra (GCA) in the case of two spacetime dimensions. Classically, this algebra is precisely obtained from a contraction of the generators of the relativistic conformal symmetry in 2d. Here we find quantum mechanical realisations of the (centrally extended) GCA by considering scaling limits of certain 2d CFTs. These parent CFTs are non-unitary and have their left and right central charges become large in magnitude and opposite in sign. We therefore develop, in parallel to the usual machinery for 2d CFT, many of the tools for the analysis of the quantum mechanical GCA. These include the representation theory based on GCA primaries, Ward identities for their correlation functions and a nonrelativistic Kac table. In particular, the null vectors of the GCA lead to differential equations for the four point function. The solution to these equations in the simplest case is explicitly obtained and checked to be consistent with various requirements.Comment: 45 pages; v2: 47 pages. Restructured introduction, minor corrections, added references. Journal versio

Enhanced Ionic Conductivity of Monovalent Cation Halide (AgBr, AgI, LiI) in Mesoporous Alumina

Monovalent ionic conductors (AgI, AgBr and LiI) impregnated in mesoporous alumina were studied in the context of heterogeneous ionic conductors. The crystalline structure and local structure of the ionic conductors were investigated by XRD, DSC and NMR. Enhancement of ionic conductivity strongly depended on the ionic conductors, which was attributed to local structure as well as space charge layer.Nagasaki Symposium on Nano-Dynamics 2008 (NSND2008) 平成20年1月29日(火)於長崎大学 Poster Presentatio

The ideal porous structure of EDLC carbon electrodes with extremely high capacitance

We propose an ideal porous structure of carbon electrodes for electric double-layer capacitors (EDLCs). The porous carbon successfully improved the gravimetric capacitance above ?200 F g?1 even in an organic electrolyte by utilizing the carbon nanopore surface more effectively. High-resolution transmission electron microscopy images and X-ray diffraction patterns classified 15 different porous carbon electrodes into slit-shape and worm-like-shape, and the pore size distributions of the carbons were carefully determined applying the grand canonical Monte Carlo method to N2 adsorption isotherms at 77 K. The ratio of pores where solvated ions and/or desolvated ions can penetrate also has a significant effect on the EDL capacitance as well as the pore shape. The detailed study on the effect of porous morphologies on the EDLC performance indicates that a hierarchical porous structure with a worm-like shaped surface and a pore size ranging from a solvated ion to a solvent molecule is an ideal electrode structure

Sub-millimeter Observations of Giant Molecular Clouds in the Large Magellanic Cloud: Temperature and Density as Determined from J=3-2 and J=1-0 transitions of CO

We have carried out sub-mm 12CO(J=3-2) observations of 6 giant molecular clouds (GMCs) in the Large Magellanic Cloud (LMC) with the ASTE 10m sub-mm telescope at a spatial resolution of 5 pc and very high sensitivity. We have identified 32 molecular clumps in the GMCs and revealed significant details of the warm and dense molecular gas with n(H2) $\sim$ 10$^{3-5}$ cm$^{-3}$ and Tkin $\sim$ 60 K. These data are combined with 12CO(J=1-0) and 13CO(J=1-0) results and compared with LVG calculations. We found that the ratio of 12CO(J=3-2) to 12CO(J=1-0) emission is sensitive to and is well correlated with the local Halpha flux. We interpret that differences of clump propeties represent an evolutionary sequence of GMCs in terms of density increase leading to star formation.Type I and II GMCs (starless GMCs and GMCs with HII regions only, respectively) are at the young phase of star formation where density does not yet become high enough to show active star formation and Type III GMCs (GMCs with HII regions and young star clusters) represents the later phase where the average density is increased and the GMCs are forming massive stars. The high kinetic temperature correlated with \Halpha flux suggests that FUV heating is dominant in the molecular gas of the LMC.Comment: 74 pages, including 41 figures, accepted for publication in ApJ

3 to 12 millimetre studies of dense gas towards the western rim of supernova remnant RX J1713.7-3946

The young X-ray and gamma-ray-bright supernova remnant RXJ1713.7-3946 (SNR G347.3-0.5) is believed to be associated with molecular cores that lie within regions of the most intense TeV emission. Using the Mopra telescope, four of the densest cores were observed using high-critical density tracers such as CS(J=1-0,J=2-1) and its isotopologue counterparts, NH3(1,1) and (2,2) inversion transitions and N2H+(J=1-0) emission, confirming the presence of dense gas >10^4cm^-3 in the region. The mass estimates for Core C range from 40M_{\odot} (from CS(J=1-0)) to 80M_{\odot} (from NH3 and N2H+), an order of magnitude smaller than published mass estimates from CO(J=1-0) observations. We also modelled the energy-dependent diffusion of cosmic-ray protons accelerated by RXJ1713.7-3946 into Core C, approximating the core with average density and magnetic field values. We find that for considerably suppressed diffusion coefficients (factors \chi=10^{-3} down to 10^{-5} the galactic average), low energy cosmic-rays can be prevented from entering the inner core region. Such an effect could lead to characteristic spectral behaviour in the GeV to TeV gamma-ray and multi-keV X-ray fluxes across the core. These features may be measurable with future gamma-ray and multi-keV telescopes offering arcminute or better angular resolution, and can be a novel way to understand the level of cosmic-ray acceleration in RXJ1713.7-3946 and the transport properties of cosmic-rays in the dense molecular cores.Comment: 17 pages, 13 figures and 5 tables. Accepted for publication in MNRAS 2012 February 1

An unusual association of diffuse adenomyomatosis with dysplastic adenoma in chronic calculous cholecystitis: case presentation

<p>Abstract</p> <p>Background</p> <p>Gallbladder adenomyomatosis is an epithelial proliferation and hypertrophy of the muscularis mucosae of the gallbladder. Rokitansky-Aschoff sinuses are a characteristic of this condition. The segmental adenomyomatosis has a higher risk of developing into gallbladder carcinoma, especially in the fundal region of elderly patients.</p> <p>We report the case of a patient affected by chronic calculous cholecystitis with diffuse adenomyomatosis associated with dysplastic adenoma.</p> <p>Case presentation</p> <p>An 81-year-old woman presented at our hospital with a 1-year history of intermittent pain localized at the right upper abdominal quadrant, without diffusion to any other body part. On physical examination the abdomen was soft, not distended, and tender to palpation in the right upper quadrant. Murphy sign was negative. Laboratory tests were normal. The patient was scheduled for a laparoscopic cholecystectomy, and neither endoscopic ultrasonographic scan nor magnetic resonance imaging was performed. The operation, performed after obtaining informed consent, was uncomplicated and the intra-operative pathological examination showed no malignancy. The definitive pathological examination of the gallbladder showed: multiple stones of cholesterol origin; diffuse mucosal adenomyomatosis; and a 1.1 cm pedunculated mass localized at the fundus, whose surface was lumpy. This mass was diagnosed as an adenoma with multiple areas of severe dysplasia.</p> <p>Conclusions</p> <p>The adenoma of the gallbladder, together with the dysplasia, represents a biological carcinogenetic model. Carcinoma has rarely been reported in adenomyomatosis. Degenerative risk suggests surgery should be mandatory when there is a concomitant presence of large adenoma and adenomyomatosis.</p

Search for coherent charged pion production in neutrino-carbon interactions

We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed and an upper limit of $0.60 \times 10^{-2}$ is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV.Comment: 5 pages, 4 figure

Experimental study of the atmospheric neutrino backgrounds for proton decay to positron and neutral pion searches in water Cherenkov detectors

The atmospheric neutrino background for proton decay to positron and neutral pion in ring imaging water Cherenkov detectors is studied with an artificial accelerator neutrino beam for the first time. In total, about 314,000 neutrino events corresponding to about 10 megaton-years of atmospheric neutrino interactions were collected by a 1,000 ton water Cherenkov detector (KT). The KT charged-current single neutral pion production data are well reproduced by simulation programs of neutrino and secondary hadronic interactions used in the Super-Kamiokande (SK) proton decay search. The obtained proton to positron and neutral pion background rate by the KT data for SK from the atmospheric neutrinos whose energies are below 3 GeV is about two per megaton-year. This result is also relevant to possible future, megaton-scale water Cherenkov detectors.Comment: 13 pages, 16 figure