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In the 2015 review paper ‘Petawatt Class Lasers Worldwide’ a comprehensive overview of the current status of high-power facilities of
was presented. This was largely based on facility specifications, with some description of their uses, for instance in fundamental ultra-high-intensity interactions, secondary source generation, and inertial confinement fusion (ICF). With the 2018 Nobel Prize in Physics being awarded to Professors Donna Strickland and Gerard Mourou for the development of the technique of chirped pulse amplification (CPA), which made these lasers possible, we celebrate by providing a comprehensive update of the current status of ultra-high-power lasers and demonstrate how the technology has developed. We are now in the era of multi-petawatt facilities coming online, with 100 PW lasers being proposed and even under construction. In addition to this there is a pull towards development of industrial and multi-disciplinary applications, which demands much higher repetition rates, delivering high-average powers with higher efficiencies and the use of alternative wavelengths: mid-IR facilities. So apart from a comprehensive update of the current global status, we want to look at what technologies are to be deployed to get to these new regimes, and some of the critical issues facing their development.
The number of tests performed is an important surveillance indicator. We illustrate this point using HIV surveillance data, focusing on Tokyo and Okinawa, two prefectures with high HIV notification rates in Japan. Restricting to data reported from local public health centres and affiliate centres where testing data are accessible, we assessed HIV surveillance data during 2007–2014, based on the annual HIV notification rate (per 100 000 population), HIV testing rate (per 100 000 population) and proportion testing HIV-positive (positivity). Nationally, testing activity and positivity showed an inverse relationship; in 2008, the testing rate peaked, but positivity was lowest. While notification rates were higher for Tokyo (median = 0.98, range = 0.89–1.33) than Okinawa (median = 0.61, range = 0.42–1.09), Okinawa had slightly higher testing rates (median = 187, range = 158–274) relative to Tokyo (median = 172, range = 163–210). Positivity was substantially lower in Okinawa (median = 0.34%, range = 0.24–0.45%) compared with Tokyo (median = 0.57%, range = 0.46–0.67%). Relative to the national testing rate (median = 85, range = 80–115) and positivity (median = 0.34%, range = 0.28–0.36%), Tokyo had higher positivity, despite more testing. In 2014 in Okinawa, all three indicators increased, providing a strong reason to be concerned as positivity increased despite more testing. Together with other information, accounting for testing and positivity improve interpretation of surveillance data to guide public health assessments.
Root rots are one of the main biotic constraints to common bean (Phaseolus vulgaris L.) production, causing losses estimated at 221 000 metric tons a year in sub-Saharan Africa. Until recently, root rots in Ugandan common bean agroecologies were mostly caused by Pythium and Fusarium spp., especially in high altitude areas. But now, severe root rots are observed in low and medium altitude agroecologies characterized by dry and warm conditions. The objective of our study was therefore to ascertain the current prevalence and incidence of common bean root rot diseases in Ugandan common bean agroecologies. Our results show that root rots were present in all seven agroecologies surveyed. Overall, the most rampant root rot was southern blight caused by Sclerotium rolfsii Sacc., followed by root rots caused by Fusarium spp., Pythium spp. and Rhizoctonia solani, respectively. Our study clearly showed the influence of environmental conditions on the prevalence and incidence of common bean root rots. While Fusarium and Pythium root rots are favoured under low air temperature and high air humidity in highland areas, high incidence of southern blight is favoured by warm and moist conditions of lowland areas. The prevalence and incidence of common bean root rots was mapped, providing a reliable baseline for future studies. Similarly, hotspots identified for common bean root rots will be a very useful resource for evaluation of germplasm and breeding lines for resistance to root rots.
Ice pile-up and ride-up are common occurrences along beaches in the sub-Arctic and Arctic. An understanding of the factors which lead to pile-up is important for design of a defensive strategy to prevent damage to coastal installations.
Since ice action on a sloping beach is complex, an experimental model study was undertaken to determine the factors which promote ice pile-up. The factors varied in this study were the freeboard, slope, and roughness of the beach. One experiment was performed to observe the effectiveness of a shore defense structure against ice ride-up.
Experiments were performed to determine the forces required to buckle a floating ice sheet pushing against structures of different widths. The characteristic length of each ice sheet was determined to enable a comparison to be made between the theoretical and experimental results.
Most of the experimental data points are within the range of the theoretical values of normalized buckling loads for frictionless and hinged boundary conditions, which represent the extreme situations for ice-structure contact. Thus, the agreement between the theoretical and experimental buckling loads is considered to be good. Photographs of the buckled ice sheets show a resemblance to the theoretical mode of buckling.
Polarization measurements of the radio Arc were made with the VLA at 15 GHz. High frequency polarimetry made with high spatial resolution minimizes Faraday depolarization and reveals polarized filaments which correspond to the predominant filaments of the radio Arc. We notice a peculiar linear feature in the polarization map (“thorns”) which suggests the presence of a second magnetic field system. The total intensity maps show no evidence for an interaction between the two field systems, so the thorns may be foreground magnetized structures. However, if the two magnetic field systems do interact, it would allow a model in which the acceleration of relativistic particles takes place at their intersection. The accelerated particles would flow toward both ends of the radio Arc, and account for the intrinsic polarization observed along the entire length of the system. Thermal electrons responsible for the Faraday depolarization occuring at longer wavelengths may be supplied by the interaction of the streams of relativistic particles with relatively dense, ambient thermal clouds.
More than 4000 stars observed in both MOA and DENIS projects showing periodic or quasi-periodic light curves are studied. Almost all Mira stars are located on the classical period-luminosity relation, and the multiplicity of the period-luminosity relation is confirmed for small-amplitude stars. The colour-magnitude diagrams based on the MOA red band, Rm, and Ks constructed for the sequences, form a single strip with small successive shifts.
The innermost region of slim accretion disks with standard α viscosity is unstable against axisymmetric radial inertial acoustic perturbations under certain conditions. Numerical simulations are performed in order to demonstrate behaviors of such unstable disks. It is shown that oscillations with the period of ~ 10−3(MBH/M⊙) s can be excited near the inner edge of the disks, where MBH is the mass of the central object. This kind of unstable disks is a possible origin of the periodic X-ray time variabilities with period of ~ 104s observed in a Seyfert galaxy NGC 6814.
Cosmic X-rays were observed with three sets of proportional counters covering the energy range between 0.15 and 20 keV. The detector born on a spinning rocket scanned a celestial region in which the galactic latitude bII changed from 30° to −55° across the galactic plane in the Cygnus-Cassiopeia region. The spectrum of Cyg XR-2 thus obtained is represented by a thermal bremsstrahlung of temperature 3.4 keV modified by the interstellar absorption for the hydrogen column density of 3 × 1021 cm−2. The diffuse component showed an interstellar absorption effect, which was however found much weaker than one would expect if the diffuse component were due entirely to be of extragalactic origin. The spectrum obtained in the highest latitude region is represented approximately by a power law E−1.8 but shows a possible trough at about 1 keV.
Surface-induced aromatic stabilization (SIAS), a recently proposed mechanism leading to a formation of charge-transfer (CT) states at organic/metal (O/M) interfaces [G. Heimel, et al., Nat. Chem.5, 187 (2013)], was investigated for an aromatic hydrocarbon, diindenoperylene (DIP), by means of synchrotron radiation-based ultraviolet photoelectron spectroscopy (UPS). By employing DIP and noble metal substrates (Ag and Cu), we confirmed the formation of CT states, indicating that an inclusion of a specific functional group with a hetero-atom within adsorbate molecules as suggested before is not necessarily required for the formation of CT states mediated by the SIAS. With a comparison of the mother and analogue molecules, perylene and PTCDA, we discuss the structural requirement for the realization of the SIAS.
In order to study the oriented aggregation of BaTiO3nanocrystals in the ultrasound-assisted synthesis in an aqueous solution [F.Dang et al., Jpn.J.Appl.Phys. 48, 09KC02 (2009)], the electric dipole-dipole interaction model has been studied by numerical simulations. The results of the numerical simulations are consistent with the experimental ones if the electric dipole moment of a primary particle (a nanocrystal) of 5 nm in diameter is about 10 D =3.3 x 10-29 (C m). It suggests that a 5-10 nm BaTiO3 nanocrystal synthesized in an aqueous solution with ultrasound has spontaneous polarization.
Emission light from Ag/ Rhodamine-B (RB) Langmuir-Blodgett (LB) films due to surface plasmon (SP) excitations has been investigated using the Kretschmann configuration of the attenuated total reflection (ATR) method and the reverse irradiation of laser beam from air to the samples. The conventional photoluminescence (PL) of the RB LB films showed a broad spectrum and the peak wavelength was about 600 nm. In the reverse irradiation, emission light was observed through the prism, and the intensities and the spectra strongly depended upon the emission angle where the light was observed. The wavelengths of the emission light became shorter as the emission angles increased. The relation between the wavelength and the emission angle agreed with the resonant condition of excitations of SPs in the Kretschmann configuration of ATR method. It was concluded that the emission light was caused by excitations of multiple SPs at the Ag/RB LB films.
n-type 3C-SiC was heteroepitaxially grown on n-type Si(100) substrates using HMDS (hexamethyldisilane) and characterized by DLTS (deep level transient spectroscopy) measurements. In order to investigate relationship of defect density with epilayer thickness, epilayers with various thicknesses were grown. Relatively thin (<1.0μm thick) epilayers were found to contain defects with energy levels distributed in a wide energy range, while relatively thick (>2.2μm thick) epilayers contain a defect with an activation energy of 0.25eV. This defect level is slightly shallower than that in 3C-SiC grown by SiH4 and C3H8 (∼0.3eV).
Organic light emitting diodes (OLEDs) containing cathode buffer layers of nanometer thickness were fabricated and their electrical and emitting properties were investigated. The OLEDs have an indium tin oxide (ITO) anode/ copper phthalocyanine (CuPc) / N, N'-dephenyl-N,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine (TPD) / 8- hydroxyquinoline aluminum (Alq3) / buffer layer / Al cathode structure with the buffer layers made from alternating thin films of Alq3 and Al with nanometer thickness. Improvement of driving voltage and the efficiency for the devices were observed by insertion of the buffer layer. It was estimated that some modulations of the Schottky barrier at the Alq3 and the Al cathode interface were induced due to the insertion of the buffer layer and it caused an enhancement of electron injection from the Al cathode. A model of the band structure at the buffer layer was proposed.
A direction to increasing photovoltaic performances of dye sensitized solar cells (DSC) is proposed. An interface between TiO2/dye and an electrolyte layer is focused on. It is proved that better coverage of TiO2 layers with dye molecules increases photovoltaic performances, where dye staining is carried out in pressurized CO2 atmosphere. This is explained by decreases in the amount of surface traps on TiO2 nano-particles, which is discussed by thermally stimulated current (TSC). The decrease in the surface trap density increases electron diffusion coefficient and improves electron lifetime in TiO2 layers. In addition, the TiO2-staining with dye molecules having the larger dipole moment seems to leave less amount of electron trap. Another crucial research item is solidification. Quasi-solidification is carried out by using surface modified anodically-oxidized Al2O3 films filled with ionic liquids, where ion paths are fabricated on the surface-modified Al2O3 walls by concentrating iodine and iodide molecules on the walls. Because of the fabrication of the ion path, photovoltaic performances increased even after solidification. Grötthuss type mechanism is introduced to explain the increase in the photovoltaic performances after the solidification.
We report a reduction in the contact resistance between pentacene and Au source/drain electrodes of organic field effect transistors (OFETs) with bottom-contact structure. By immersing the Au electrodes in a sulfuric acid and hydrogen peroxide mixture (SPM), the injection barrier between the Au electrodes and pentacene was lowered by approximately 0.2 eV and the contact resistance significantly decreased. The fabricated bottom-contact OFETs revealed a field-effect mobility of more than 0.66 cm2/Vs at a channel length ranging from 3 to 30 μm, which is comparable to that of top-contact OFETs with a 50 μm channel length. The transfer characteristics of the OFET with the SPM treatment were stable even after 44days storage in air under room illumination without any passivation. Moreover, the drain current reduction due to threshold voltage (Vth) shift under continuous application of gate voltage quickly recovered toward the original value with unloading of gate voltage.
Two heterophase interfaces formed in the joining of α-SiC were investigated using high-resolution electron microscopy coupled with a multi-slice structural image simulation. A reaction product TiC was formed epitaxially on the basal plane of α-SiC single crystal when SiC was brazed with a Ag-Cu alloy containing small amount of Ti. A coherent interface with Si-C and Ti-C bonding was found between the SIC(0001) and TiC(111). Al4C3 was grown also epitaxially on the basal plane of SiC when it was brazed with AL. A semicoherent interface including interfacial dislocations and intermediate' transition phase was observed between the SIC(0001) and Al4C3(0001). It was estimated that the carbon atom sublattice was maintained through those crystals.
Photoelectrochemical properties of Ga- and N-face GaN grown by hydride vapor phase epitaxy (HVPE) were investigated. The properties were also compared with Ga-face GaN grown by metal-organic vapor phase epitaxy (MOVPE). The flatband potentials were in order of Ga-face GaN grown by MOVPE < N-face GaN < Ga-face GaN. The highest photocurrent density at zero bias was obtained from the N-face GaN. The photocurrent density was over 3 times larger than that of Ga-face GaN.
We have demonstrated enhancement-mode n-channel gallium nitride (GaN) MOSFETs on Si (111) substrates with high-temperature operation up to 300 °C. The GaN MOSFETs have good normally-off operation with the threshold voltages of +2.7 V. The MOSFET exhibits good output characteristics from room temperature to 300 °C. The leakage current at 300°C is less than 100 pA/mm at the drain-to-source voltage of 0.1 V. The on-state resistance of MOSFET at 300°C is about 1.5 times as high as that at room temperature. These results indicate that GaN MOSFET is suitable for high-temperature operation compared with AlGaN/GaN HFET.
This work presents some observations during the period of the Whole Heliosphere Interval (WHI) of the effects of interplanetary (IP) structures on the near-Earth space using three sets of observations: magnetic field and plasma from the Advanced Composition Explorer (ACE) satellite, ground-based cosmic ray data from the Global Muon Detection Network (GMDN) and geomagnetic indices (Disturbance storm-time, Dst, and auroral electrojet index, AE). Since WHI was near minimum solar activity, high speed streams and corotating interaction regions (CIRs) were the dominant structures observed in the interplanetary space surrounding Earth. Very pronounced geomagnetic effects are shown to be correlated to CIRs, especially because they can cause the so-called High-Intensity Long-Duration Continuous AE Activity (HILDCAAs) - Tsurutani and Gonzalez (1987). At least a few high speed streams can be identified during the period of WHI. The focus here is to characterize these IP structures and their geospace consequences.