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We introduce a new model of gamma ray burst (GRB) that explains its observed prompt
signals, namely, its primary quasi-thermal spectrum and high energy tail. This mechanism
can be applied to either assumption of GRB progenitor: coalescence of compact objects or
hypernova explosion. The key ingredients of our model are: (1) The initial stage of a GRB
is in the form of a relativistic quark-gluon plasma lava; (2) The expansion and cooling of
this lava results in a QCD phase transition that induces a sudden gravitational stoppage
of the condensed non-relativistic baryons and form a hadrosphere; (3) Acoustic shocks and
Alfven waves (magnetoquakes) that erupt in episodes from the epicenter efficiently
transport the thermal energy to the hadrospheric surface and induce a rapid detachment of
leptons and photons from the hadrons; (4) The detached
e + e − and γ
form an opaque, relativistically hot leptosphere, which expands and cools to
T ~ mc2, or 0.5 MeV,
e + e − → 2γ
and its reverse process becomes unbalanced, and the GRB photons are finally released; (5)
The mode-conversion of Alfven waves into electromagnetic waves in the leptosphere provides
a snowplow acceleration and deceleration that gives rise to both the high energy spectrum
of GRB and the erosion of its thermal spectrum down to a quasi-thermal distribution.
According to this model, the observed GRB photons should have a redshifted peak frequency
Ep ~ Γ(1 + β/2)mc2/(1 + z),
where Γ ~ O(1) is the Lorentz factor of the bulk flow of the lava,
which may be determined from the existing GRB data.
Advancement of ion acceleration by intense laser pulses is studied with ultra-thin nanometer-thick diamond like carbon and micrometer-thick Titanium target foils. Both investigations aim at optimizing the electron density distribution which is the key for efficient laser driven ion acceleration. While recently found maximum ion energies achieved with ultra-thin foils mark record values micrometer thick foils are flexible in terms of atomic constituents. Electron recirculation is one prerequisite for the validity of a very simple model that can approximate the dependence of ion energies of nanometer-thick targets when all electrons of the irradiated target area interact coherently with the laser pulse and Coherent Acceleration of Ions by Laser pulses (CAIL) becomes dominant. Complementary experiments, an analytical model and particle in cell computer simulations show, that with regard to ultra-short laser pulses (duration ~45 fs at intensities up to 5 × 1019 W/cm2) and a micrometer-thick target foil with higher atomic number a close to linear increase of ion energies manifests in a certain range of laser intensities.
In this paper we report on an experimental study of high harmonic radiation generated in nanometer-scale foil targets irradiated under normal incidence. The experiments constitute the first unambiguous observation of odd-numbered relativistic harmonics generated by the v × B component of the Lorentz force verifying a long predicted property of solid target harmonics. Simultaneously the observed harmonic spectra allow in-situ extraction of the target density in an experimental scenario which is of utmost interest for applications such as ion acceleration by the radiation pressure of an ultraintense laser.
Experiments on ion acceleration by irradiation of ultra-thin diamond-like carbon (DLC) foils, with thicknesses well below the skin depth, irradiated with laser pulses of ultra-high contrast and linear polarization, are presented. A maximum energy of 13 MeV for protons and 71 MeV for carbon ions is observed with a conversion efficiency of ~10%. Two-dimensional particle-in-cell (PIC) simulations reveal that the increase in ion energies can be attributed to a dominantly collective rather than thermal motion of the foil electrons, when the target becomes transparent for the incident laser pulse.
An experimental method is proposed for detecting the effects of positive natural selection on DNA polymorphisms. Since beneficial mutations are expected to increase in frequency faster than neutral mutations, variants which have reached high frequencies in a relatively short period could be linked to some beneficial mutation. D. melanogaster has a cosmopolitan polymorphic inversion -In(2L)t - whose age in some local populations has been estimated. Setting the age of In(2L)t as the upper limit for the age of variants, we searched for variants whose frequencies were possibly influenced by positive natural selection. We detected a single candidate whose frequency and distribution met the requirements imposed by our method.
Using the ion-temperature-gradient-driven drift waves as a paradigm for drift-wave anomalous transport, we explore the structure of the linear and nonlinear modes. Two phases of transport are shown to exist: (i) Bohm-like transport for parameters close to marginal stability; (ii) gyro-Bohm transport for turbulent convection cells in systems driven away from marginal stability. Nonlinear relaxation to large-scale coherent convective structures is observed in three-dimensional toroidal particle simulations.
The theory of ion heating in a Q-machine Barium plasma by the electrostatic ion cyclotron instability is considered in some detail. Linear and quasi-linear theories are considered. The effect on resistivity of the instability is also considered. The ion temperature was observed, optically, to increase to a value in excess of 25 000°K by a mechanism attributable to a collisionless process. Energy transfer from the drifting electron current to the ions is analyzed explicitly. Detailed comparisons with experiments are presented.
Relativistic electron beam heating of a dense plasma through the two-stream instability is studied. A large amplitude beam-plasma wave excited by the instability induces waves of wide wavenumber spectrum at low phase velocities through secondary parametric instability processes. In some cases such a complicated mode coupling of the beam-plasma wave into low phase velocity waves and their saturation may be described in terms of soliton formation. A beam stopping length associated with this process is obtained.
Plasma effects on the emission of synchrotron radiation are investigated using a two-dimensional electromagnetic relativistic simulation code. Results are compared with those for a vacuum; it is found that the emission lies between the vacuum emission for nc and nc + 1 where nc is the critical harmonic for EM wave propagation (nc = ωp/Ω0).
We study plasma-beam injection into transverse magnetic fields using both electrostatic and electromagnetic particle-in-cell (PIC) codes. In the case of small beam momentum or energy (low drift kinetic β) we study both large- and small-ion-gyroradius beams. Large-ion-gyroradius beams with a large dielectric constant ε ≫ (M/m)½ are found to propagate across the magnetic field via E × B drifts at nearly the initial injection velocity, where and M/m is the ion-to-electron mass ratio. Beam degradation and undulations are observed, in agreement with previous experimental and analytical results. When ε is of order (M/m)½ the plasma beam propagates across field lines at only half its initial velocity and loses its coherent structure. When ε is much less than (M/m)½ the beam particles decouple at the magnetic field boundary, scattering the electrons and slightly deflecting the ions. For small-ion-gyroradius beam injection a flute-type instability is observed at the beam-magnetic-field interface. In the case of large beam momentum or energy (high drift kinetic β) we observe good penetration of a plasma beam by shielding the magnetic field from the interior of the beam (diamagnetism). However, we observe anomalously fast penetration of the magnetic field into the beam and find that the diffusion rate depends on the electron gyroradius of the beam.
CYP2C19 polymorphisms and smoking influence the efficacy of H. pylori eradication therapy, but interaction between the two have hitherto not been examined. A total of 142 H. pylori-positive patients who received triple drug therapy with lansoprazole, amoxicillin and clarithromycin were categorized into three groups with regard to diplotypes of CYP2C19: homozygous extensive metabolizer (homEM), heterozygous EM (hetEM), and poor metabolizer (PM). The overall success rate was 61·3%. Smoking was an independent risk factor of eradication failure (OR 2·81, 95% CI 1·14–6·91), whereas CYP2C19 polymorphisms were less influential. Among non-smokers, the homEM and hetEM groups showed worse eradication rates (58·5 and 67·3%) relative to PM (76·2%) as expected; however, an opposite trend was observed among smokers (homEM 50·0%, hetEM 46·7%, PM 20·0%), indicating possible interactions with CYP2C19 polymorphisms. Smoking has a greater influence on H. pylori eradication than the CYP2C19 genotype. Interaction between smoking and CYP2C19 should be examined in the future.
Energetic ion beams are produced during the interaction of
ultrahigh-intensity, short laser pulses with plasmas. These
laser-produced ion beams have important applications ranging from the
fast ignition of thermonuclear targets to proton imaging, deep proton
lithography, medical physics, and injectors for conventional
accelerators. Although the basic physical mechanisms of ion beam
generation in the plasma produced by the laser pulse interaction with
the target are common to all these applications, each application
requires a specific optimization of the ion beam properties, that is,
an appropriate choice of the target design and of the laser pulse
intensity, shape, and duration.
Identification of factors influencing success of Helicobacter pylori (HP) eradication is important for clinical practice. We have prospectively conducted an HP eradication study in the Aichi Cancer Center with a total of 142 patients available for analysis. The overall success rate was 61·3% (95% confidence interval 52·7–69·3%). Smoking during the medication for eradication significantly decreased the success rate (42·9%), whereas smoking cessation during the treatment was associated with a similar rate as for non-smokers (66·7%). We also examined links between an eradication outcome and polymorphisms of Le, Se, IL1A, IL1B, IL1RN and MPO genes, but with one exception none showed any association. The non-functional le allele of Le polymorphisms, leading to decreased expression of Leb antigen to which HP attaches with adhesin, showed a beneficial effect for success. Although further clarification is necessary, our study indicated that smoking cessation and Le gene polymorphisms may affect the success rate of HP eradication.
Three types of shape memory ceramics were introduced. They were the irreversible shape memory silica glass, the reversible shape memory bi-ceramics glass and reversible shape memory silica and Si-C-O glassy fiber samples (the small size change) induced by thermal expansion.
Black hole candidates sometimes show a transition between the high (or soft) state and the low (or hard) state. In the low state, low frequency time variations are much larger than the high state. A possible mechanism of the large-amplitude, sporadic time variabilities in the low-state is the magnetic energy release in low-β (β = Pgas/Pmag < 1) disks (Mineshige, Kusunose & Matsumoto 1995). It had been thought that low-β disks cannot exist because buoyant escape of magnetic flux due to the Parker instability may set the lower limit for β inside the disk. Shibata, Tajima & Matsumoto (1990), however, pointed out that in accretion disks, once a low-β disk is formed, it can stay in low-β state partly because the growth rate of the Parker instability decreases when β < 1. They suggested that magnetic accretion disks fall into two types; high-β disks and low-β disks.
We propose a mechanism of amplification of magnetic fields and plasma heating in clusters of galaxies. Recent observations indicate the existence of ~ μG magnetic fields in clusters of galaxies (e.g., Kronberg 1994). There should be some mechanism which locally amplify magnetic fields. In clusters of galaxies, individual motions of galaxies may create locally strong field region by stretching and tangling the magnetic fields threading the galaxies. Magnetic reconnection taking place in the tangled magnetic fields may convert the kinetic energy of the galaxy motion into the inter-galactic plasma heating (Makishima 1996).
Since cementitious materials used in repositories will be in contact with water, one of the most important tasks is to assess their long-term performance while they are being degraded very slowly by leaching. The authors have proposed an electrochemical acceleration test method and clarified its applicability. In this method, a specimen is placed between two glass vessels containing water. An anode and a cathode connected to a DC power source provide a potential gradient across the specimen. Ca2+ ions in the pore solution move rapidly to the cathode side, and thus hasten cement hydrate dissolution.
In this study, we obtained two types of almost homogeneously degraded specimens by controlling cumulative quantity of dissolved Ca2+ ions. In the first type, there was no Ca(OH)2and the C-S-H phases underwent insignificant alteration, whereas in the second type, degradation of the C-S-H phases occurred.
As a preliminary evaluation of cementitious materials, diffusion coefficients of tritiated water were measured for nondegraded and degraded specimens. Diffusion coefficients were increased by degradation and closely corresponded to changes in porosity.
Nonlinear growth of the Parker instability (PI) and the Balbus & Hawley instability (BHI) in accretion disks have been studied by local three-dimensional magnetohydrodynamic (MHD) simulations. In high-β disks (β = Pgas/Pmag > 1), the PI has only minor effects on the saturation level of BHI. In low β disks (β ≤ 1), the disk stays in a low-β state because magnetic flux cannot escape fast enough to convert the disk into a high-β state. We found that even in low-β disk the BHI generates fluctuating magnetic fields. The effective magnetic viscosity αB(= –⟨BrBΦ/4πP0⟩) is O(0.1) when β ~ 1.
Complete and dissociated edge dislocations were created near the center of the surface (101) of aluminum small crystals whose surfaces are (111), (111), (101), (101). (121) and (121). Molecular dynamics with N-body embedded atom potentials were used. Higher stress is needed to create a complete edge dislocation than to create a dissociated dislocation.
Observations of Shubnikov-de Haas(SdH) and de Haas-van Alphen(dHvA) oscillations in organic metals (BEDT-TTF)2X, with X=KHg(SCN)4, θ-I3 and β″-AuBr2. are reported. In KHg(SCN)4 salt, in addition to the SdH oscillations with fundamental frequency of 670 T corresponding to about 16% of the first Brillouin zone(FBZ), we observed splitting of each SdH peak which we ascribed to “spin-splitting” We have also found that the ground state of this salt is not a simple metal but has some magnetic character. In θ-l3 salt we have succeeded in an observation of dHvA oscillations for the first time. We observed a “saw-tooth” dHvA oscillation characteristic to a highly two-dimensional and extraordinary clean electronic system. In addition to the fundamental frequency of 4170 T corresponding to 50.4 % of the FBZ and its higher harmonics, we observed an oscillation with lower frequency of 730 T corresponding to about 8.8 % of the FBZ. A new Fermi surface topology for θ-l3 salt is proposed based on the analysis of the dHvA effect. In β″-AuBr2, we observed complex dHvA oscillations, which can be explained in terms of the mixing of two fundamental frequencies of 47 and 268 T, suggesting the presence of very small pockets corresponding to 0.6 and 2.9 % of the FBZ.