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Since the real Universe is clumpy and inhomogeneous even at rather large scale such as 100 Mpc, we may wonder whether the isotropic and homogeneous Friedmann model is valid when we compare some cosmological parameters with the observed values. The observed Hubble parameter H0 or the density parameter Ω0 might be deviated from the theoretically expected ones from the Friedmann model. In fact, the density parameter Ω0 seems to vary depending on the observational methods and the distance scales. Furthermore, our Universe seems to possess a fractal property in the galaxy distributions at least at scale up to 10 Mpc.
The adsorption of Al, Ga and Si on the Si(001) surface is studied by the ab initio molecular dynamics (Car-Parrinello) method based on the norm-conserving pseudopotential. In the stable structures obtained for half mono-layer coverage( ө = 1/2), these ad-atoms form dimers, but the dimer configurations are different. Al and Ga atoms form parallel dimers whose dimerization direction is parallel to that of substrate Si-dimers, while adsorbed Si atoms form (dense) orthogonal dimers. The electronic origin of the difference in the stable configurations among Al, Ga and Si ad-atoms is analyzed by calculating the local density of states (LDOS) of each atom.
Heterostructures of a Pb(Zr,Ti)O3 (PZT) waveguide/(Pb,La)(Zr,Ti)O3 (PLZT) system buffer layer were grown on a Nb-doped SrTiO3 (Nb:ST) substrate by solid-phase epitaxy. The propagation loss in the PLZT heterostructure waveguides was on the order of I dB/cm. An electro-optic beam deflection device with an ITO prism electrode on the surface of the PLZT heterostructure waveguide presented efficient deflection of the coupled laser beam by applying a voltage between the electrode and the substrate. A beam deflection greater than 10 mrad at 5 V and frequency response as fast as 13 MHz were observed. An apparent electro-optic coefficient as large as 39 pmJV was estimated from the deflection characteristics for the TE mode and TM mode suggesting the polarization independent nature of the PZT waveguide. For integrating the electrooptic PLZT heterostructure waveguides, channel waveguides were fabricated in the PZT waveguides using a simple wet-etching process. Based on a low-voltage drive structure, lowloss waveguide process, and fine patterning process, a fabricated digital matrix switch showed a – 10 dB cross-talk at a voltage as low as 7.5 V.
Phase-change memory is promising because it has a simple structure and has scalability that originates from its unique operating mechanism. However, the programming current should be reduced in accordance with the scaling of cell size [1,2]. We previously reported PCM (Phase Change Memory) cells that operate under 1.5-V/100-μA writing pulses [3, 4]. This PCM had a cell structure composed of 180-nm-W (tungsten) bottom contact to an O-GST (Oxygen-doped GeSbTe) film. Its low-power characteristic is suitable for 0.13-μm generation embedded applications. In the present study, we introduced a new W/O-GST/TaO/W cell structure and found further decrease of programming current the improved stability in the fabrication process. We analyzed the mechanism by which oxygen in GST and the additional TaO layer reduce the power consumption during SET/RESET operations.
A new cosmology based on the Bose-Einstein condensation is proposed. This is
a unified model of Dark Energy and Dark Matter, and predicts several
collapses of BEC, followed by the final acceleration which successfully
describes the recent observational results. Furthermore, this model can be
extended to the early inflationary regime, and explains natural initiation
of the inflation, autonomous termination of the inflation, inevitable
initiation of the reheating process, autonomous adjustment of the
cosmological constant to zero, and acceptable generation of density
Many scaling relations have been observed for
self-gravitating systems (SGS) in the universe. We explore a consistent
understanding of them from a simple principle based on the proposal that the
collision-less dark matter (DM) fluid terns into a turbulent state, i.e. dark
turbulence, after crossing the caustic surface in the non-linear stage.
After deriving Kolmogorov scaling laws from Navier-Stokes and Jeans equations by the method used in solving the Smoluchowski coagulation equation, we apply this to several
observations such as the scale-dependent velocity dispersion,
mass-luminosity ratio, and mass-angular momentum relation. They all point
the concordant value for the constant energy flow per mass: 0.3 cm2/s3, which may be understood as the speed of the hierarchical
coalescence process in the cosmic structure formation.
In order to compare the bubble dynamics of various quantum liquids, we performed the visual observation of a sound-induced bubble in a normal liquid 4He, pure superfluid 4He, and superfluid 3He–4He liquid mixtures of saturated and unsaturated 3He concentrations. When an acoustic wave pulse was applied to these liquids under saturated vapour pressure, a macroscopic bubble was generated on the surface of a piezoelectric transducer. For all liquids, the size of the bubble increased, as a higher voltage was applied to the transducer at a fixed temperature. In the normal 4He we observed a primary bubble surrounded with many small bubbles which ascended upward together. In contrast to normal phase, only one bubble was generated in the superfluid 4He, and its shape proved to be highly irregular with an ill-defined surface. In the 3He saturated superfluid mixture, we also observed a solitary bubble but with a nearly perfect spherical shape. The bubble in this mixture expanded on the transducer surface, grew to a maximum size of the order of 1 mm and then started shrinking. As the bubble detached from the transducer with shrinking, we clearly detected an origination of the upward jet flow which penetrated the bubble. The jet velocity in the liquid mixture was approximately 102–103 times smaller than in water. At the final stage of the process we could sometimes observe a vortex ring generation. It is interesting that, though the bubble size and time scale of the phenomenon differ from those in water, the behaviour in the collapsing process had much in common with the simulation study of the vortex ring generation in water. In addition, for the mixture with the unsaturated 3He concentration of about 25% at 600 mK, the shape of the upward jet was observed distinctly, using more precise measurement with shadowgraph method.
We have studied the heteroepitaxial growth of 3C–SiC film on an Si(100) substrate by plasma chemical vapor deposition using monomethylsilane, a single-molecule gas containing both Si and C atoms. We have tried to introduce an interval process, in which we decrease the substrate temperature for a few minutes at a suitable stage of film growth. It was expected that, during the interval process, stabilization such as desorption of nonreacted precursors and lateral diffusion of species produced at the initial stage of film growth would occur. From the results, it appears that the interval process using a substrate temperature of 800 °C effectively suppresses polycrystallization of 3C–SiC growth on the Si(100) surface
We developed an immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA), using partial recombinant nucleoproteins (rNP) of Reston Ebola virus (EBO-R) and Zaire Ebola virus (EBO-Z). We examined the reaction of 10 sera from cynomolgus macaques naturally infected with EBO-R to each of the partial rNP in the IgG ELISA. All the sera reacted to the C-terminal halves of the rNP of both EBO-R and EBO-Z. Most of the sera reacted to the RΔC (amino acid (aa) 360–739), and RΔ6 (aa 451–551) and/or RΔ8 (aa 631–739) at a higher dilution than to the corresponding truncated rNPs of EBO-Z. The results indicate that this IgG ELISA is useful for detecting EBO-R specific antibody, and may have a potential to discriminate EBO-R infection from other subtypes.
In 1985, Dashidaira Dam, equipped with a flushing gate, was built on the Kurobe River in Toyama, Japan. Since the dam sediments were first flushed out in December 1991, benthic fish counts have decreased year by year due to repeated flushing of clay-rich dam sediments.
In June 2001, the flushed dam water contained a low oxygen concentration (1 to 2 mg/l) and high concentrations of smectite and vermiculite. To establish the cause of the death of the benthic fish, living flatfish were collected from Toyama Bay in order to examine their gills, which showed tissue damage and chemical changes caused by adherent expandable clays, derived from the flushed dam sediments. For comparison, exposure experiments on rainbow trout were carried out using smectite suspensions. Examination by optical microscopy revealed that the gills had shrunk because of the smectite concentrations. Low oxygen concentrations and large amounts of expanding clays have a significant effect on downstream benthic life.
The nonlinear dynamics and structure of plasmas with
tightly twisted magnetic
field lines have been studied using a toroidal plasma device. Stepwise
magnetohydrodynamic (MHD) relaxation occurs, resulting in a discontinuous
change in the pitch of magnetic field lines. This discrete
nature of the pitch
stems from the instability of kink (torsional) modes. The MHD relaxation
stabilizes kink modes by selecting (self-organizing) appropriate
pitches. The self-organized state displays the characteristic of a
‘dissipative structure’ in
that it is accompanied by enhanced energy dissipation; the global
the plasma current is substantially enhanced. The magnetic energy, which is
generated by the internal plasma current, first changes into
through the kink instability, and then it goes mainly to ion thermal energy
through viscous dissipation of the fluctuating flow. The
viscosity dissipates the
fluctuation energy with conservation of helicity. The self-organization
of the stabilized magnetic field is characterized by the
preferential conservation of the helicity.
We review here the results on gene delivery into pollen grains and transformation by particle bombardment. Most of the studies that have been done up to date on bombardment-mediated transformation of pollen are still confined to transient expression of several pollen- or anther-specific promoters. However, these studies do provide evidence that pollen grains can be transformed at least transiently, and suggest the potential use of these “transformed” pollen grains or those bearing foreign DNA for direct pollination to obtain transgenic seeds via natural reproduction system. The alternative way of using pollen transformation for crop improvement is to develop haploid plants via in vitro culture of bombarded immature pollen grains. Included here are the authors' own recent results on successful production of transgenic haploid plants derived from in vitro culture of bombarded pollen. These results provide a basis for a discussion of the usefulness of pollen transformation for crop improvement.
Significance of pollen transformation for crop improvement
Pollen transformation is an attractive approach for plant breeding and crop improvement. There have been reports of various techniques for gene delivery into pollen or microspores, including imbibition of pollen with DNA (Hess 1980), Agrobacterium-mediated transformation (Hess 1987; Pechan 1989), electroporation of pollen (Matthews et al. 1990; Fennell and Hauptmann 1992; Jardinaud et al. 1993), and polyethylene glycol-mediated transformation (Fennell and Hauptmann 1992).
However, all these techniques are problematic in their applicability or reproducibility. Electroporation is useful for introducing foreign DNA into germinating pollen (Matthews et al. 1990), but it is not applicable to plant species in which in vitro pollen germination is difficult.
We use computer simulation to identify a process by which cooperation evolves without iteration, and evolves better in large than in small societies. It is based on an empirically supported heuristic for deciding whether to enter noniterated prisoner's dilemma games, namely, Expect others to have the same dispositions as yourself. Players are assigned a probability of cooperating that also defines their expectations about others' behavior and thus their willingness to play. The carrying capacity of the ecology is 10,000. Players multiply by 2 if their aggregate payoff in a given round (1) places them among the more successful 5,000 and (2) is more than zero. We find that the most adaptive disposition is toward the mean of the population. That is where individuals have the optimal mix of consummated plays with more cooperative players and unconsummated plays with less cooperative ones. When encounters occur by proximity, fortuitous clusters toward the cooperative tail will grow and dominate the society. Such clusters are more likely in large societies.
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