Barrier-free subsurface incorporation of 3d metal atoms into Bi(111) films

By combining scanning tunneling microscopy with density functional theory it is shown that the Bi(111) surface provides a well-defined incorporation site in the first bilayer that traps highly coordinating atoms such as transition metals (TMs) or noble metals. All deposited atoms assume exactly the same specific sevenfold coordinated subsurface interstitial site while the surface topography remains nearly unchanged. Notably, 3d TMs show a barrier-free incorporation. The observed surface modification by barrier-free subsorption helps to suppress aggregation in clusters. It allows a tuning of the electronic properties not only for the pure Bi(111) surface, but may also be observed for topological insulators formed by substrate-stabilized Bi bilayers. © 2015 American Physical Society.DFG/SFB/616DFG/SPP/1601DFG/Pf238/3

Exploring the band structure of Wurtzite InAs nanowires using photocurrent spectroscopy

We use polarized photocurrent spectroscopy in a nanowire device to investigate the band structure of hexagonal Wurtzite InAs. Signatures of optical transitions between four valence bands and two conduction bands are observed which are consistent with the symmetries expected from group theory. The ground state transition energy identified from photocurrent spectra is seen to be consistent with photoluminescence emitted from a cluster of nanowires from the same growth substrate. From the energies of the observed bands we determine the spin orbit and crystal field energies in Wurtzite InAs. This information is vital to the development of crystal phase engineering of this important III-V semiconductor.ER

Quantum states and linear response in dc and electromagnetic fields for charge current and spin polarization of electrons at Bi/Si interface with giant spin-orbit coupling

An expansion of the nearly free-electron model constructed by Frantzeskakis, Pons and Grioni [Phys. Rev. B {\bf 82}, 085440 (2010)] describing quantum states at Bi/Si(111) interface with giant spin-orbit coupling is developed and applied for the band structure and spin polarization calculation, as well as for the linear response analysis for charge current and induced spin caused by dc field and by electromagnetic radiation. It is found that the large spin-orbit coupling in this system may allow resolving the spin-dependent properties even at room temperature and at realistic collision rate. The geometry of the atomic lattice combined with spin-orbit coupling leads to an anisotropic response both for current and spin components related to the orientation of the external field. The in-plane dc electric field produces only the in-plane components of spin in the sample while both the in-plane and out-of-plane spin components can be excited by normally propagating electromagnetic wave with different polarizations.Comment: 10 pages, 9 figure

Competing Ultrafast Energy Relaxation Pathways in Photoexcited Graphene

For most optoelectronic applications of graphene a thorough understanding of the processes that govern energy relaxation of photoexcited carriers is essential. The ultrafast energy relaxation in graphene occurs through two competing pathways: carrier-carrier scattering -- creating an elevated carrier temperature -- and optical phonon emission. At present, it is not clear what determines the dominating relaxation pathway. Here we reach a unifying picture of the ultrafast energy relaxation by investigating the terahertz photoconductivity, while varying the Fermi energy, photon energy, and fluence over a wide range. We find that sufficiently low fluence ($\lesssim$ 4 $\mu$J/cm$^2$) in conjunction with sufficiently high Fermi energy ($\gtrsim$ 0.1 eV) gives rise to energy relaxation that is dominated by carrier-carrier scattering, which leads to efficient carrier heating. Upon increasing the fluence or decreasing the Fermi energy, the carrier heating efficiency decreases, presumably due to energy relaxation that becomes increasingly dominated by phonon emission. Carrier heating through carrier-carrier scattering accounts for the negative photoconductivity for doped graphene observed at terahertz frequencies. We present a simple model that reproduces the data for a wide range of Fermi levels and excitation energies, and allows us to qualitatively assess how the branching ratio between the two distinct relaxation pathways depends on excitation fluence and Fermi energy.Comment: Nano Letters 201

Knowledge and practices on maternal health care among mothers: A Cross sectional study from rural areas of mid-western development region Nepal

Background: Safe motherhood is a priority program in Nepal, aiming to restrain maternal deaths. Meanwhile, knowledge, practices, accessibility, and service quality are considered keys to improve service utilization. This study was conducted to identify knowledge and practices of maternal health care among mothers having < 1-year-old child in the Mid-western Development Region, Nepal. Materials and Methods: A community-based cross-sectional study was conducted during January-April 2011 in rural, Mid-western Development Region, Nepal. Three Village Development Committees (VDC) from Bardiya (plain) and two VDCs from each of the Salyan and Pyuthan (hill) and Jumla (mountain) districts were selected randomly. Hence, there were 81 clusters (1VDC = 9 clusters) and 7-8 participants were selected randomly from each cluster. Data were collected by interview using structured questionnaire and Focus Group Discussion Guideline (18 FGDs), analyzed by SPSS (16.0). CD recorded qualitative data were transcribed and narrated. Percent mean and standard deviation were calculated. Results: Three quarters of the participants had correct knowledge regarding minimum numbers of antenatal visits to be done by a pregnant woman (WHO guideline). Nearly two-fifth participants knew schedule of antenatal care (ANC) visits. Almost 60% had done ≥ 4 ANC visits during last pregnancy. Majority visited Sub Health Post/Health Post/Primary Health Care Centre for ANC Checkup. About 90% had taken Iron and folic acid tablets. About 57% were home deliveries (last childbirth), 40% deliveries were assisted by relatives/husband, and only 32% did postnatal health checkup. Conclusions: There were gaps in the knowledge and practices for health care during pregnancy, childbirth and in the postpartum period. A high rate of home deliveries with the low postnatal service utilization was prevalent. Intensive awareness progam and behavioral change interventions, regular pregnancy monitoring may promote the health service utilization

Effect of maturation on physico-chemical and sensory quality characteristics of custard apple wine

Recently, researchers have taken a shift to utilize the custard apple for wine preparation besides its major use in ice cream, confectionary and milk products. In the present study, an attempt has been made to study the effect of maturation on physico-chemical and sensory quality characteristics of custard apple wine. Custard apple wine was prepared as per the earlier standardized method. The wine so prepared was matured for six months. The physico-chemical analysis was conducted at every three months interval for six months and sensory evaluation was performed after six months of storage. With the maturation, a decrease in total soluble solids, total sugars, titratable acidity, ethanol, total phenols and tannins was observed, whereas, an increase in reducing sugars and pH was observed. All the sensory quality characteristics of custard apple wine increased with advancement of the maturation period except astringency. Cluster analysis of the data obtained from physico-chemical analysis revealed that there was no difference between three months and six months of storage. Physico-chemical characteristics of custard apple wine were reduced to two principal components using principal component analysis which accounted for 100% variation. In general, maturation for six months improved the quality of custard apple wine considerably

Effects of livestock on occurrence of the Vulnerable red panda Ailurus fulgens

The Vulnerable red panda Ailurus fulgens is endemic to the Himalayas. Anthropogenic activities, including deforestation, have degraded the species’ habitat but the effects of livestock have not been examined. We assessed the effects of illegal livestock activity on the presence of the red panda in Rara National Park, Nepal. The probability of detecting red panda faecal pellets decreased with livestock occurrence but not with elevation or aspect. The presence of bamboo and proximity to water are important to red pandas but did not influence their habitat use at the spatial resolution evaluated. Livestock grazing in Rara National Park appears to adversely affect the presence of the red panda within its habitat. To reduce illegal livestock grazing we recommend enforcement of existing regulations, that training workshops be held for herders, and awareness-raising and dialogue with residents.publishedVersio

Exploring the band structure of Wurtzite InAs nanowires using photocurrent spectroscopy

We use polarized photocurrent spectroscopy in a nanowire device to investigate the band structure of hexagonal Wurtzite InAs. Signatures of optical transitions between four valence bands and two conduction bands are observed which are consistent with the symmetries expected from group theory. The ground state transition energy identified from photocurrent spectra is seen to be consistent with photoluminescence emitted from a cluster of nanowires from the same growth substrate. From the energies of the observed bands we determine the spin orbit and crystal field energies in Wurtzite InAs. This information is vital to the development of crystal phase engineering of this important III-V semiconductor