Intrinsic limits governing MBE growth of Ga-assisted GaAs nanowires on Si(111)

Diffusion-enhanced and desorption-limited growth regimes of Ga-assisted GaAs nanowires were identified. In the latter regime, the number of vertical NWs with a narrow length distribution was increased by raising the growth temperature. The maximum axial growth rate; which can be quantified by the supplied rate of As atoms, is achieved when a dynamical equilibrium state is maintained in Ga droplets i.e. the number of impinging As atoms on the droplet surface is equivalent to that of direct deposited Ga atoms combining with the diffusing ones. The contribution of Ga diffusion to the wire growth was evidenced by the diameter-dependent NW axial growth rate

Space Biosciences Division

In the Space Biosciences Division at NASA's Ames Research Center, we perform the biological research and technology development necessary to tackle the challenges of living in the extreme environments of space and to enable NASA's long-term human exploration mission. This brochure provides a broad overview for our research and development capabilities, several case study examples, and finally real-world applications and collaborative partnerships

Velocity dominated singularities in the cheese slice universe

We investigate the properties of spacetimes resulting from matching together exact solutions using the Darmois matching conditions. In particular we focus on the asymptotically velocity term dominated property (AVTD). We propose a criterion that can be used to test if a spacetime constructed from a matching can be considered AVTD. Using the Cheese Slice universe as an example, we show that a spacetime constructed from a such a matching can inherit the AVTD property from the original spacetimes. Furthermore the singularity resulting from this particular matching is an AVTD singularity.Comment: 11 pages, 3 figures, accepted for publication in the International Journal of Modern Physics

Peningkatan Aktivitas Pembelajaran dan Hasil Belajar Pendidikan Kewarganegaraan dengan Metode Diskusi Kelompok pada Siswa Kelas IV S Ekolah Dasar Negeri 03 Semayang Kabupaten Sanggau

The pourpose of the research iis to know the improving studeng activity of civics at grade IV student of SD 03 Semayang by using group discussion method. The method of this research is descriptive method using qualitative way in which the data or evidence is analyzed after collecting the data from the field. The subject of the research is 22 students of grade IV at elementary school 03 Semayang. The result of data analyzing show that after using group discussion method for 2 cycles, the student learning activity improves 19% at first cycles become 59 at second cycles. Increasing the presentage of student learning activity influences the improving students outcome in achiving KKM of Civic at school that is 60. In wich, the research shows that the student can achive KKm about 41% at first cycle increase 91% at the second cycle. So that, it can be conduded that by improving student learning activity using group discussion method can influence the improving student aoutcome at grade IV student of elementary school 03 Semayang

Low-Noise GaAs Quantum Dots for Quantum Photonics

Quantum dots are both excellent single-photon sources and hosts for single spins. This combination enables the deterministic generation of Raman-photons -- bandwidth-matched to an atomic quantum-memory -- and the generation of photon cluster states, a resource in quantum communication and measurement-based quantum computing. GaAs quantum dots in AlGaAs can be matched in frequency to a rubidium-based photon memory, and have potentially improved electron spin coherence compared to the widely used InGaAs quantum dots. However, their charge stability and optical linewidths are typically much worse than for their InGaAs counterparts. Here, we embed GaAs quantum dots into an $n$-$i$-$p$-diode specially designed for low-temperature operation. We demonstrate ultra-low noise behaviour: charge control via Coulomb blockade, close-to lifetime-limited linewidths, and no blinking. We observe high-fidelity optical electron-spin initialisation and long electron-spin lifetimes for these quantum dots. Our work establishes a materials platform for low-noise quantum photonics close to the red part of the spectrum.Comment: (19 pages, 12 figures, 1 table

The Cenozoic Song Hong and Beibuwan Basins, Vietnam

The Vietnamese offshore margin holds a substantially underexplored petroleum potential. The key to unravelling this potential lies in understanding the tectono-stratigraphic framework of the region including the Cenozoic mechanisms governing syn-rift and source rock deposition. This is essential for prediction of, for instance the presence and nature of source rocks in South-East Asia and possible reservoir intervals in the syn-rift packages. The Vietnamese part of the Song Hong and Beibuwan Basins (Fig. 1) differs from other basins along the western margin of the South China Sea in that the Palaeogene syn-rift succession is sporadically exposed due to uplift and inversion. These exposures provide a unique glimpse into the Cenozoic syn-rift succession of the basin