Conceptual Design of a Fast-Ignition Laser Fusion Reactor FALCON-D

A new conceptual design of the laser fusion power plant FALCON-D (Fast ignition Advanced Laser fusion reactor CONcept with a Dry wall chamber) has been proposed. The fast ignition method can achieve the sufficient fusion gain for a commercial operation (~100) with about 10 times smaller fusion yield than the conventional central ignition method. FALCON-D makes full use of this property and aims at designing with a compact dry wall chamber (5~6m radius). 1-D/2-D hydrodynamic simulations showed the possibility of the sufficient gain achievement with a 40 MJ target yield. The design feasibility of the compact dry wall chamber and solid breeder blanket system was shown through the thermomecanical analysis of the dry wall and neutronics analysis of the blanket system. A moderate electric output (~400MWe) can be achieved with a high repetition (30Hz) laser. This dry wall concept not only reduces some difficulties accompanied with a liquid wall but also enables a simple cask maintenance method for the replacement of the blanket system, which can shorten the maintenance time. The basic idea of the maintenance method for the final optics system has also been proposed. Some critical R&D issues required for this design are also discussed

Shape-independent scaling of excitonic confinement in realistic quantum wires

The scaling of exciton binding energy in semiconductor quantum wires is investigated theoretically through a non-variational, fully three-dimensional approach for a wide set of realistic state-of-the-art structures. We find that in the strong confinement limit the same potential-to-kinetic energy ratio holds for quite different wire cross-sections and compositions. As a consequence, a universal (shape- and composition-independent) parameter can be identified that governs the scaling of the binding energy with size. Previous indications that the shape of the wire cross-section may have important effects on exciton binding are discussed in the light of the present results.Comment: To appear in Phys. Rev. Lett. (12 pages + 2 figures in postscript

Suzaku X-Ray Imaging and Spectroscopy of Cassiopeia A

Suzaku X-ray observations of a young supernova remnant, Cassiopeia A, were carried out. K-shell transition lines from highly ionized ions of various elements were detected, including Chromium (Cr-Kalpha at 5.61 keV). The X-ray continuum spectra were modeled in the 3.4--40 keV band, summed over the entire remnant, and were fitted with a simplest combination of the thermal bremsstrahlung and the non-thermal cut-off power-law models. The spectral fits with this assumption indicate that the continuum emission is likely to be dominated by the non-thermal emission with a cut-off energy at > 1 keV. The thermal-to-nonthermal fraction of the continuum flux in the 4-10 keV band is best estimated as ~0.1. Non-thermal-dominated continuum images in the 4--14 keV band were made. The peak of the non-thermal X-rays appears at the western part. The peak position of the TeV gamma-rays measured with HEGRA and MAGIC is also shifted at the western part with the 1-sigma confidence. Since the location of the X-ray continuum emission was known to be presumably identified with the reverse shock region, the possible keV-TeV correlations give a hint that the accelerated multi-TeV hadrons in Cassiopeia A are dominated by heavy elements in the reverse shock region.Comment: Publ. Astron. Soc. Japan 61, pp.1217-1228 (2009

Excitons in T-shaped quantum wires

We calculate energies, oscillator strengths for radiative recombination, and two-particle wave functions for the ground state exciton and around 100 excited states in a T-shaped quantum wire. We include the single-particle potential and the Coulomb interaction between the electron and hole on an equal footing, and perform exact diagonalisation of the two-particle problem within a finite basis set. We calculate spectra for all of the experimentally studied cases of T-shaped wires including symmetric and asymmetric GaAs/Al$_{x}$Ga$_{1-x}$As and In$_{y}$Ga$_{1-y}$As/Al$_{x}$Ga$_{1-x}$As structures. We study in detail the shape of the wave functions to gain insight into the nature of the various states for selected symmetric and asymmetric wires in which laser emission has been experimentally observed. We also calculate the binding energy of the ground state exciton and the confinement energy of the 1D quantum-wire-exciton state with respect to the 2D quantum-well exciton for a wide range of structures, varying the well width and the Al molar fraction $x$. We find that the largest binding energy of any wire constructed to date is 16.5 meV. We also notice that in asymmetric structures, the confinement energy is enhanced with respect to the symmetric forms with comparable parameters but the binding energy of the exciton is then lower than in the symmetric structures. For GaAs/Al$_{x}$Ga$_{1-x}$As wires we obtain an upper limit for the binding energy of around 25 meV in a 10 {\AA} wide GaAs/AlAs structure which suggests that other materials must be explored in order to achieve room temperature applications. There are some indications that In$_{y}$Ga$_{1-y}$As/Al$_{x}$Ga$_{1-x}$As might be a good candidate.Comment: 20 pages, 10 figures, uses RevTeX and psfig, submitted to Physical Review

PICK1 is not a susceptibility gene for schizophrenia in a Japanese population: Association study in a large case–control population

The protein interacting with C-kinase 1 (PICK1) has been implicated in thesusceptibility to schizophrenia. PICK1 interacts with enzymes and receptors that playroles in the pathogenesis of schizophrenia via glutamatergic dysfunction. Recently, twostudies reported associations between schizophrenia and two PICK1 genepolymorphisms, rs3952 in Chinese and Japanese populations and rs2076369 in aJapanese population. We attempted to confirm these associations in a case-control studyof 1765 Japanese patients with schizophrenia and 1851 Japanese control subjects.Neither polymorphism was associated with schizophrenia (rs3952, p = 0.755;rs2076369, p = 0.997). A haplotype block with these polymorphisms spanning the 5’region of the PICK1 gene showed high linkage disequilibrium in the Japanesepopulation (D’ = 0.98, r2 = 0.34); however, neither haplotype was significantlyassociated with schizophrenia. We conclude that the common haplotypes andpolymorphisms of the PICK1 gene identified thus far are unlikely to contribute togenetic susceptibility to schizophrenia in the Japanese population

Gain in a quantum wire laser of high uniformity

A multi-quantum wire laser operating in the 1-D ground state has been achieved in a very high uniformity structure that shows free exciton emission with unprecedented narrow width and low lasing threshold. Under optical pumping the spontaneous emission evolves from a sharp free exciton peak to a red-shifted broad band. The lasing photon energy occurs about 5 meV below the free exciton. The observed shift excludes free excitons in lasing and our results show that Coulomb interactions in the 1-D electron-hole system shift the spontaneous emission and play significant roles in laser gain.Comment: 4 pages, 4 figures, prepared by RevTe

Nickel-Catalyzed Carbon–Carbon Bond-Forming Reactions of Unactivated Tertiary Alkyl Halides: Suzuki Arylations

The first Suzuki cross-couplings of unactivated tertiary alkyl electrophiles are described. The method employs a readily accessible catalyst (NiBr[subscript 2]·diglyme/4,4′-di-tert-butyl-2,2′-bipyridine, both commercially available) and represents the initial example of the use of a group 10 catalyst to cross-couple unactivated tertiary electrophiles to form C–C bonds. This approach to the synthesis of all-carbon quaternary carbon centers does not suffer from isomerization of the alkyl group, in contrast with the umpolung strategy for this bond construction (cross-coupling of a tertiary alkylmetal with an aryl electrophile). Preliminary mechanistic studies are consistent with the generation of a radical intermediate along the reaction pathway.National Institute of General Medical Sciences (U.S.) (R01-GM62871)Merck Research Laboratories (Summer Fellowship

Transient four-wave mixing in T-shaped GaAs quantum wires

The binding energy of excitons and biexcitons and the exciton dephasing in T-shaped GaAs quantum wires is investigated by transient four-wave mixing. The T-shaped structure is fabricated by cleaved-edge overgrowth, and its geometry is engineered to optimize the one-dimensional confinement. In this wire of 6.6×24 nm2 size, we find a one-dimensional confinement of more than 20 meV, an inhomogeneous broadening of 3.4 meV, an exciton binding energy of 12 meV, and a biexciton binding energy of 2.0 meV. A dispersion of the homogeneous linewidth within the inhomogeneous broadening due to phonon-assisted relaxation is observed. The exciton acoustic-phonon-scattering coefficient of 6.1±0.5 μeV/K is larger than in comparable quantum-well structures