Showing papers by "Japan Atomic Energy Agency published in 2014"

Quantum error correction in a solid-state hybrid spin register

Abstract: Error correction is important in classical and quantum computation Decoherence caused by the inevitable interaction of quantum bits with their environment leads to dephasing or even relaxation Correction of the concomitant errors is therefore a fundamental requirement for scalable quantum computation Although algorithms for error correction have been known for some time, experimental realizations are scarce Here we show quantum error correction in a heterogeneous, solid-state spin system We demonstrate that joint initialization, projective readout and fast local and non-local gate operations can all be achieved in diamond spin systems, even under ambient conditions High-fidelity initialization of a whole spin register (99 per cent) and single-shot readout of multiple individual nuclear spins are achieved by using the ancillary electron spin of a nitrogen-vacancy defect Implementation of a novel non-local gate generic to our electron-nuclear quantum register allows the preparation of entangled states of three nuclear spins, with fidelities exceeding 85 per cent With these techniques, we demonstrate three-qubit phase-flip error correction Using optimal control, all of the above operations achieve fidelities approaching those needed for fault-tolerant quantum operation, thus paving the way to large-scale quantum computation Besides their use with diamond spin systems, our techniques can be used to improve scaling of quantum networks relying on phosphorus in silicon, quantum dots, silicon carbide or rare-earth ions in solids

Conceptual design of the International Axion Observatory (IAXO)

Abstract: The International Axion Observatory (IAXO) will be a forth generation axion helioscope. As its primary physics goal, IAXO will look for axions or axion-like particles (ALPs) originating in the Sun via the Primakoff conversion of the solar plasma photons. In terms of signal-to-noise ratio, IAXO will be about 4–5 orders of magnitude more sensitive than CAST, currently the most powerful axion helioscope, reaching sensitivity to axion-photon couplings down to a few × 10−12 GeV−1 and thus probing a large fraction of the currently unexplored axion and ALP parameter space. IAXO will also be sensitive to solar axions produced by mechanisms mediated by the axion-electron coupling gae with sensitivity — for the first time — to values of gae not previously excluded by astrophysics. With several other possible physics cases, IAXO has the potential to serve as a multi-purpose facility for generic axion and ALP research in the next decade. In this paper we present the conceptual design of IAXO, which follows the layout of an enhanced axion helioscope, based on a purpose-built 20 m-long 8-coils toroidal superconducting magnet. All the eight 60cm-diameter magnet bores are equipped with focusing x-ray optics, able to focus the signal photons into ~ 0.2 cm2 spots that are imaged by ultra-low-background Micromegas x-ray detectors. The magnet is built into a structure with elevation and azimuth drives that will allow for solar tracking for ~ 12 h each day.

Active Sites and Mechanisms for Oxygen Reduction Reaction on Nitrogen-Doped Carbon Alloy Catalysts: Stone–Wales Defect and Curvature Effect

Abstract: Carbon alloy catalysts (CACs) are promising oxygen reduction reaction (ORR) catalysts to substitute platinum. However, despite extensive studies on CACs, the reaction sites and mechanisms for ORR are still in controversy. Herein, we present rather general consideration on possible ORR mechanisms for various structures in nitrogen doped CACs based on the first-principles calculations. Our study indicates that only a particular structure of a nitrogen pair doped Stone–Wales defect provides a good active site. The ORR activity of this structure can be tuned by the curvature around the active site, which makes its limiting potential approaching the maximum limiting potential (0.80 V) in the volcano plot for the ORR activity of CACs. The calculated results can be compared with the recent experimental ones of the half-wave potential for CAC systems that range from 0.60 to 0.80 V in the reversible-hydrogen-electrode (RHE) scale.

Laser ion acceleration for hadron therapy

Abstract: The paper examines the prospects of using laser plasma as a source of high-energy ions for the purpose of hadron beam therapy — an approach which is based on both theory and experimental results (ions are routinely observed to be accelerated in the interaction of high-power laser radiation with matter). Compared to therapy accelerators like synchrotrons and cyclotrons, laser technology is advantageous in that it is more compact and is simpler in delivering ions from the accelerator to the treatment room. Special target designs allow radiation therapy requirements for ion beam quality to be satisfied. (reviews of topical problems)

A novel fine-tuning mesoporous adsorbent for simultaneous lead(II) detection and removal from wastewater

Abstract: The functionalized mesoporous silica based fine-tuning mesoporous adsorbent was developed for ultra-trace lead (Pb(II)) detection and removal from wastewater. The mesoporous adsorbent was fabricated by direct immobilization of 1E,1‘E,1“E,1“‘E(tetrakis(3-carboxysalicylidene)) naphthalene–1,2,5,5–tetramine (TSNT) onto mesoporous silica monoliths. The design of the ligand into ordered pore-based mesoporous adsorbent transformed the Pb(II) detection and removal systems into smart and stable assemblies. The ability of the mesoporous adsorbent to detect and remove Pb(II) from aqueous solutions has been studied and discussed with different optimized conditions of concentrations, the amount of mesoporous adsorbent, concentration of coexisting electrolyte and pH. The design of such a tunable mesoporous adsorbent offered a simple procedure in such toxic Pb(II) ions removal without using high-tech, sophisticated instruments. The mesoporous adsorbent was able to detect the ultra-trace Pb(II) ions with high sensitivity and selectivity based on charge transfer ((intense π–π transition) transduction. Therefore, the mesoporous adsorbent proved to have an efficient ability for continuous monitoring of toxic Pb(II) ions even on-site and in situ chemical analyses. The removal data revealed that mesoporous adsorbent has high sorption capacity (184.32 mg/g) based on sorption isotherms measurements. The major advantage of the tunable design mesoporous adsorbent was that the mesoporous adsorbent retained highly efficient sensitive selectivity without a significant kinetic hindrance, despite the slight decrease of sorption after several regeneration/reuse cycles. Uptake of Pb(II) onto mesoporous adsorbent to equilibrium occurred quickly and the mesoporous adsorbent could be regenerated for reuse with diluted HCl. Therefore, the mesoporous adsorbent has been shown to have the potential to be used as an effective adsorbent for ultra–trace Pb(II) ions detection and removal from wastewater.

Polaron spin current transport in organic semiconductors

Abstract: The transport and relaxation mechanisms in organic semiconductors are still insufficiently understood, but measurements now show that in these materials polarons carry pure spin currents over extended distances with long relaxation times, and uncover the role of spin-orbit coupling in this process.

A novel ligand based dual conjugate adsorbent for cobalt(II) and copper(II) ions capturing from water

Abstract: Organic–inorganic based conjugate materials are important in nanotechnology based on the high functionality and stable complex formation with target metal ions at optimum conditions. In this study, a new ligand immobilization based dual and tunable conjugate adsorbent was investigated under specific solution acidity for detection and removal of Co(II) and Cu(II) ions. In this detection system, notable color changes (intense π–π transition) and absorbance spectral intensity of the conjugate adsorbent for Co(II) and Cu(II) were observed at pH 8.0 and 5.2, respectively. Under the optimum conditions, the calibration graphs were the linear and detection limit which were 0.52 and 0.41 μg/L for Co(II) and Cu(II), respectively. The removal efficiency was carried out as a function of solution pH, initial metal ions concentration, and co-existing diverse ions. Sorption equilibrium was well fitted to Langmuir isotherms and determined sorption capacity was 205.33 and 199.20 mg/g for Co(II) and Cu(II), respectively. The adsorbent proved to have an efficient ability for continuous monitoring and removal of Co(II) and Cu(II) ions, even on-site and in situ chemical analyses. The adsorbent was eluted with dilute HCl acid and simultaneously regenerated into its original form. However, several cycles were reused with slight decrease in sorption capacity compared with the initial capacity. Therefore the conjugate adsorbent can be used as cost-effective materials and is a potential candidate for the selective detection and removal of Co(II) and Cu(II) ions from wastewater. The proposed adsorbent was compared with other materials and applied to the analysis and removal of Co(II) and Cu(II) ions from several water samples with satisfactory results.

Functionalized novel mesoporous adsorbent for selective lead(II) ions monitoring and removal from wastewater

Abstract: An efficient material is needed to develop selective and effective sensing/removal systems with high flexibility, and low capital cost for control the capturing of toxic ions. In this study, we designed ligand immobilized mesoporous adsorbent for ultra-trace Pb(II) monitoring and removal from wastewater. The adsorbent was synthesized by indirect immobilization of 4-tert-octyl-4-((phenyl)diazenyl)phenol onto inorganic mesoporous silica. This adsorbent exhibited the large surface area-to-volume ratios and uniformly shaped pores in case cavities, and its active sites kept open functionality to taking up Pb(II). The applicability of the adsorbent for Pb(II) detection and removal was assessed, and the efficient parameters such as solution pH, contacting time, initial Pb(II) concentration and ionic strength of competing ions were measured. The effective pH range for detection and removal systems was at the neutral region. The data revealed that the adsorbent was able to detect the ultra-trace Pb(II) ions with high sensitivity and selectivity by charge transfer (intense π–π transition) transduction mechanism. Then the adsorbent proved to have an efficient ability for continuous Pb(II) monitoring and removal even on-site and in situ chemical analyses. The maximum sorption capacity and limit of detection were 200.80 mg/g and 0.12 μg/L, respectively. The adsorbent was reused in several cycles without significant deterioration after elution with a suitable eluent (0.10 M HCl). Therefore, the design of mesoporous adsorbent has a great potentiality to be used in selective Pb(II) detection/removal from wastewater. Large-scale studies are recommended to confirm these promising results from the laboratory scale.

48Ca+249Bk Fusion Reaction Leading to Element Z=117: Long-Lived α-Decaying 270Db and Discovery of 266Lr

Abstract: The superheavy element with atomic number Z=117 was produced as an evaporation residue in the 48Ca+249Bk fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The radioactive decay of evaporation residues and their α-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-μs and a few days. Two decay chains comprising seven α decays and a spontaneous fission each were identified and are assigned to the isotope 294-117 and its decay products. A hitherto unknown α-decay branch in 270Db (Z=105) was observed, which populated the new isotope 266Lr (Z=103). The identification of the long-lived (T1/2=1.0+1.9−0.4 h) α-emitter 270Db marks an important step towards the observation of even more long-lived nuclei of superheavy elements located on an “island of stability.” (Less)

Efficient detection and extraction of cobalt(II) from lithium ion batteries and wastewater by novel composite adsorbent

Abstract: a b s t r a c t This study developed a novel composite adsorbent for highly selective and sensitive detection and extrac- tion of cobalt (Co(II)) from lithium-ion batteries (LIBs) and wastewater. The composite adsorbent was prepared by indirect immobilization of 6-((2-(2-hydroxy-1-naphthoyl)hydrazono)methyl)benzoic acid (HMBA) onto mesoporous silica monoliths. The composite adsorbent enhanced the color formation by stable complexation as (Co(II)-HMBA) n+ complexes during detection and sorption operations. The data evident the one-step detection of wide range Co(II) concentrations into interior pore surface coverage of the composite adsorbent from solutions without using high tech instruments, which was unique fea- ture of this adsorbent. The influence of different sorption parameters, such as: initial Co(II) concentration, equilibration time, solution pH and the presence of competing ions and reuses were studied and discussed systematically. The effective pH range for Co(II) ions detection and sorption was neutral pH region and the maximum sorption capacity of the adsorbent was as high as 189.37 mg/g. The adsorbed Co(II) was eluted with stripping agent (0.3 M HCl) and simultaneously regenerated into initial form for the next capturing operations after rinsing with water. The data also clarified that the composite adsorbent was selectively extracted Co(II) from LIBs even in the presence of high concentration diverse ions. Impor- tantly, the composite adsorbent was retaining functionality in spite of many chemical treatments during sorption-elution-recovery/regeneration cycles. Therefore, the present study revealed that such a low- cost material could be used as potential adsorbent for the selective detection and recovery of Co(II) ions from LIBs and wastewater streams.

Abundance Profiling of Extremely Metal-poor Stars and Supernova Properties in the Early Universe

Abstract: After the big bang nucleosynthesis, the first heavy element enrichment in the universe was made by a supernova (SN) explosion of a population (Pop) III star (Pop III SN). The abundance ratios of elements produced from Pop III SNe are recorded in abundance patterns of extremely metal-poor (EMP) stars. The observations of the increasing number of EMP stars have made it possible to statistically constrain the explosion properties of Pop III SNe. We present Pop III SN models whose nucleosynthesis yields well reproduce, individually, the abundance patterns of 48 such metal-poor stars as [Fe/H] ≲ – 3.5. We then derive relations between the abundance ratios of EMP stars and certain explosion properties of Pop III SNe: the higher [(C + N)/Fe] and [(C + N)/Mg] ratios correspond to the smaller ejected Fe mass and the larger compact remnant mass, respectively. Using these relations, the distributions of the abundance ratios of EMP stars are converted to those of the explosion properties of Pop III SNe. Such distributions are compared with those of the explosion properties of present day SNe: the distribution of the ejected Fe mass of Pop III SNe has the same peak as that of the present day SNemore » but shows an extended tail down to ∼10{sup –2}-10{sup –5} M {sub ☉}, and the distribution of the mass of the compact remnant of Pop III SNe is as wide as that of the present-day, stellar-mass black holes. Our results demonstrate the importance of large samples of EMP stars obtained by ongoing and future EMP star surveys and subsequent high-dispersion spectroscopic observations in clarifying the nature of Pop III SNe in the early universe.« less

Efficient gold(III) detection, separation and recovery from urban mining waste using a facial conjugate adsorbent

Abstract: This study developed an efficient fine-tuning conjugate adsorbent for simultaneous gold (Au(III)) detection and recovery from urban mining waste. The adsorbent was prepared by indirect and dense immobilization of 6-((2-(2-hydroxy-1-naphthoyl)hydrazono)methyl) benzoic acid (HMBA) onto fine-tuned surface patterning of nanostructure inorganic silica. This adsorbent has the large surface area-to-volume ratios and uniformly shaped pores in nanostructures in its cage cavities. Therefore, the conjugate adsorbent permitted to fast and specific Au(III) ions capturing via a colorimetric naked-eye visualization based on the stable complexation [Au(III)–HMBA] n + mechanism. The small energy gap for the complex compared with the HMBA suggested the easily excitation of electrons according to the electron transfer or energy transferred mechanism, which results in the intense color of the stable complexation mechanism. The influence of several variables such as solution acidity, initial concentrations and the addition of diverse ions for Au(III) detection and recovery has also been considered and evaluated. The detection limit of the conjugate adsorbent at optimum conditions was 0.11 μg/L. The Au(III) sorption forms a monolayer on the interior pore surfaces of the conjugate adsorbent and showed high sorption capacity (203.42 mg/g). In addition, the sorption uptake on the adsorbent reaching equilibrium was rapid and adsorbent was also exhibited high Au(III) ion selectivity in ionic competition. Acidified thiourea was used in the elution of the Au(III) and conjugate adsorbent exhibited in terms of reproducibility and versatility over a number of analysis/regeneration cycles. Therefore, the present conjugate adsorbent offered a low-cost material for potential application of ultra-trace Au(III) detection and recovery from urban mining waste scraps.

Novel shape evolution in exotic Ni isotopes and configuration-dependent shell structure

Abstract: model space.Experimental energy levels are reproduced well by a single fixed Hamiltonian. Intrinsic shapesare analyzed for MCSM eigenstates. Intriguing interplays among spherical, oblate, prolate and γ-unstable shapes are seen, including shape fluctuations, E(5)-like situation, the magicity of doubly-magic

Speciation of Radioactive Soil Particles in the Fukushima Contaminated Area by IP Autoradiography and Microanalyses

Abstract: Radioactive soil particles several tens of micrometers in size were collected from litter soil in the radiation contaminated area by the Fukushima nuclear plant accident and characterized using electron and X-ray microanalyses. The radioactive particles were discriminated by autoradiography using imaging plates (IP) on which microgrids were formed by laser ablation in order to find the particles under microscopy. Fifty radioactive particles were identified and classified into three types from their morphology and chemical composition, namely: (1) aggregates of clay minerals, (2) organic matter containing clay mineral particulates, and (3) weathered biotite originating from local granite. With respect to the second type, dissolution of the organic matter did not reduce the radiation, suggesting that the radionuclides were also fixed by the clay minerals. The weathered biotite grains have a plate-like shape with well-developed cleavages inside the grains, and kaolin group minerals and goethite filling the c...

Enhanced dc spin pumping into a fluctuating ferromagnet near T C

Abstract: A linear-response formulation of the dc spin pumping, i.e., a spin injection from a precessing ferromagnet into an adjacent spin sink, is developed in view of describing many-body effects caused by spin fluctuations in the spin sink. It is shown that when an itinerant ferromagnet near ${T}_{\mathrm{C}}$ is used as the spin sink, the spin pumping is largely increased owing to the fluctuation enhancement of the spin conductance across the precessing ferromagnet/spin sink interface. As an example, the enhanced spin pumping from yttrium iron garnet into nickel palladium alloy (${T}_{C}\ensuremath{\simeq}20$ K) is analyzed by means of a self-consistent renormalization scheme, and it is predicted that the enhancement can be as large as tenfold.