Structure analysis of the Ga-stabilized GaAs(001)-c(8x2) surface at high temperatures

Structure of the Ga-stabilized GaAs(001)-c(8x2) surface has been studied using rocking-curve analysis of reflection high-energy electron diffraction (RHEED). The c(8x2) structure emerges at temperatures higher than 600C, but is unstable with respect to the change to the (2x6)/(3x6) structure at lower temperatures. Our RHEED rocking-curve analysis at high temperatures revealed that the c(8x2) surface has the structure which is basically the same as that recently proposed by Kumpf et al. [Phys. Rev. Lett. 86, 3586 (2001)]. We found that the surface atomic configurations are locally fluctuated at high temperatures without disturbing the c(8x2) periodicity.Comment: 14 pages, 4 figures, 1 tabl

Size dependent line broadening in the emission spectra of single GaAs quantum dots: Impact of surface charges on spectral diffusion

Making use of droplet epitaxy, we systematically controlled the height of self-assembled GaAs quantum dots by more than one order of magnitude. The photoluminescence spectra of single quantum dots revealed the strong dependence of the spectral linewidth on the dot height. Tall dots with a height of ~30 nm showed broad spectral peaks with an average width as large as ~5 meV, but shallow dots with a height of ~2 nm showed resolution-limited spectral lines (<120 micro eV). The measured height dependence of the linewidths is in good agreement with Stark coefficients calculated for the experimental shape variation. We attribute the microscopic source of fluctuating electric fields to the random motion of surface charges at the vacuum-semiconductor interface. Our results offer guidelines for creating frequency-locked photon sources, which will serve as key devices for long-distance quantum key distribution.Comment: 6 pages, 6 figures; updated figs and their description

A novel type of proximity focusing RICH counter with multiple refractive index aerogel radiator

A proximity focusing ring imaging Cherenkov detector, with the radiator consisting of two or more aerogel layers of different refractive indices, has been tested in 1-4 GeV/c pion beams at KEK. Essentially, a multiple refractive index aerogel radiator allows for an increase in Cherenkov photon yield on account of the increase in overall radiator thickness, while avoiding the simultaneous degradation in single photon angular resolution associated with the increased uncertainty of the emission point. With the refractive index of consecutive layers suitably increasing in the downstream direction, one may achieve overlapping of the Cherenkov rings from a single charged particle. In the opposite case of decreasing refractive index, one may obtain well separated rings. In the former combination an approximately 40% increase in photon yield is accompanied with just a minor degradation in single photon angular resolution. The impact of this improvement on the pion/kaon separation at the upgraded Belle detector is discussed.Comment: submitted to Nucl. Instr. Meth.

Precise determination of mini railway track with ground based laser scanning

In order to determine the relative or absolute railway track and foundation deformation, ground-based laser scanning technology is utilised in this study to attain a precise 3D track reference. Located at the University of Nottingham’s Innovation Park, the newly built Nottingham Geospatial Building, where the Nottingham Geospatial Institute is based, has a roof laboratory that has unique testing facilities. This includes a mini railway track of 120m in length and other long-term monitoring monuments. A test was performed to precisely determine the ground-truth location of the railway track using a phase-based laser scanner for the formation of a standard reference. A real three dimensional mesh of the laser scanning data forms the basis for the line extraction. The compactly supported radial basis function (CS-RBF) was employed to determine the track features based on a 3D mesh approach. To verify the achievable accuracy of laser scanning technology, ground truth points measured with geodetic methods are compared with the extracted sample points and the results are presented in this paper

Mineral Chemistry and Reflectance Spectra for the Anorthosite Clast in Lunar Meteorite Dhofar 489 with Reference to Lunar Farside Crust.

第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月18日（金） 国立国語研究所 2階講

Lunar Crustal Mineralogy inferred from Lunar Meteorites and Kaguya Data.

第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月18日（金） 国立国語研究所 2階講

Comparisons of Mineralogy Between Cumulate Eucrites and Lunar Meteorites Possibly from the Farside Anorsothitic Crust

Anorthosites composed of nearly pure anorthite (PAN) at many locations in the farside highlands have been observed by the Kaguya multiband imager and spectral profiler [1]. Mineralogical studies of lunar meteorites of the Dhofar 489 group [2,3] and Yamato (Y-) 86032 [4], all possibly from the farside highlands, showed some aspects of the farside crust. Nyquist et al. [5] performed Sm-Nd and Ar-Ar studies of pristine ferroan anorthosites (FANs) of the returned Apollo samples and of Dhofar 908 and 489, and discussed implications for lunar crustal history. Nyquist et al. [6] reported initial results of a combined mineralogical/chronological study of the Yamato (Y-) 980318 cumulate eucrite with a conventional Sm-Nd age of 4567 24 Ma and suggested that all eucrites, including cumulate eucrites, crystallized from parental magmas within a short interval following differentiation of their parent body, and most eucrites participated in an event or events in the time interval ~4400- 4560 Ma in which many isotopic systems were partially reset. During the foregoing studies, we recognized that variations in mineralogy and chronology of lunar anorthosites are more complex than those of the crustal materials of the HED parent body. In this study, we compared the mineralogies and reflectance spectra of the cumulate eucrites, Y-980433 and 980318, to those of the Dhofar 307 lunar meteorite of the Dhofar 489 group [2]. Here we consider information from these samples to gain a better understanding of the feldspathic farside highlands and the Vesta-like body

Feature Lines for Illustrating Medical Surface Models: Mathematical Background and Survey

This paper provides a tutorial and survey for a specific kind of illustrative visualization technique: feature lines. We examine different feature line methods. For this, we provide the differential geometry behind these concepts and adapt this mathematical field to the discrete differential geometry. All discrete differential geometry terms are explained for triangulated surface meshes. These utilities serve as basis for the feature line methods. We provide the reader with all knowledge to re-implement every feature line method. Furthermore, we summarize the methods and suggest a guideline for which kind of surface which feature line algorithm is best suited. Our work is motivated by, but not restricted to, medical and biological surface models.Comment: 33 page

Structural and magnetic properties of Fe/ZnSe(001) interfaces

We have performed first principles electronic structure calculations to investigate the structural and magnetic properties of Fe/ZnSe(001) interfaces. Calculations involving full geometry optimizations have been carried out for a broad range of thickness of Fe layers(0.5 monolayer to 10 monolayers) on top of a ZnSe(001) substrate. Both Zn and Se terminated interfaces have been explored. Total energy calculations show that Se segregates at the surface which is in agreement with recent experiments. For both Zn and Se terminations, the interface Fe magnetic moments are higher than the bulk bcc Fe moment. We have also investigated the effect of adding Fe atoms on top of a reconstructed ZnSe surface to explore the role of reconstruction of semiconductor surfaces in determining properties of metal-semiconductor interfaces. Fe breaks the Se dimer bond formed for a Se-rich (2x1) reconstructed surface. Finally, we looked at the reverse growth i.e. growth of Zn and Se atoms on a bcc Fe(001) substrate to investigate the properties of the second interface of a magnetotunnel junction. The results are in good agreement with the theoretical and experimental results, wherever available.Comment: 7 pages, 8 figures, accepted for publication in PR

Spectroscopy of 32Ne and the Island of Inversion

We report on the first spectroscopic study of the N=22 nucleus 32Ne at the newly completed RIKEN Radioactive Ion Beam Factory. A single gamma-ray line with an energy of 722(9) keV was observed in both inelastic scattering of a 226 MeV/u 32Ne beam on a Carbon target and proton removal from 33Na at 245 MeV/u. This transition is assigned to the de-excitation of the first J^pi = 2+ state in 32Ne to the 0+ ground state. Interpreted through comparison with state-of-the-art shell model calculations, the low excitation energy demonstrates that the Island of Inversion extends to at least N=22 for the Ne isotopes.Comment: Accepted for publication in Phys. Rev. Lett. 11 pages, 3 figure