Direct determination of the ambipolar diffusion length in strained InxGa1−xAs/InP quantum wells by cathodoluminescence

The ambipolar diffusion length is measured in strained InxGa1−xAs/InP quantum wells for several mole fractions in the interval 0.3<x<0.8 by cathodoluminescence. The ambipolar diffusion length is found to have a significantly higher value in the lower indium mole fraction samples corresponding to tensile-strained wells. This longer diffusion length for the tensile samples is consistent with results of carrier lifetime experiments by M. C. Wang, K. Kash, C. E. Zah, R. Bhat, and S. L. Chuang [Appl. Phys. Lett. 62, 166 (1993)]

Failure assessment of lightly reinforced floor slabs. I: Experimental investigation

This paper is concerned with the ultimate behavior of lightly reinforced concrete floor slabs under extreme loading conditions. Particular emphasis is given to examining the failure conditions of idealized composite slabs which become lightly reinforced in a fire situation as a result of the early loss of the steel deck. An experimental study is described which focuses on the response of two-way spanning floor slabs with various materials and geometric configurations. The tests enable direct assessment of the influence of a number of key parameters such as the reinforcement type, properties, and ratio on the ultimate response. The results also permit the development of simplified expressions that capture the influence of salient factors such as bond characteristics and reinforcement properties for predicting the ductility of lightly reinforced floor slabs. The companion paper complements the experimental observations with detailed numerical assessments of the ultimate response and proposes analytical models that predict failure of slab members by either reinforcement fracture or compressive crushing of concrete. © 2011 American Society of Civil Engineers

Petrography and geochemistry of ferricrete near Shire, northern Ethiopia

A detailed petrographic and geochemical study was conducted on ferricrete (laterite) developed on Mesozoic (?) ferruginous sandstone near Shire, Tigray region, northern Ethiopia. 30 rock samples were analyzed for major and minor elements and studied for petrographic details. Ferruginous sandstone overlying the Neoproterozoic low grade basement rocks dominantly contains quartz followed by orthoclase feldspar and iron oxides/hydroxides as cement. Residual enrichment process has resulted in the development 2-3m thick ferricrete horizon and also sub-horizons: mottled, mixed nodular and psuedo-pisolitic. Mineralogy of the ferricrete includes limonite, goethite and hematite. Arid conditions and dehydration reactions seem to have produced hematite from goethite. The ore minerals show replacement, cavity and fracture filling, remobilization and colloform textures. Si&gt;Al&gt;Fe is the mobility pattern observed in the ferricrete horizon though presence of secondary quartz and kaolinite are also common. Development of ferricrete is related to the climatic condition that existed during Eocene and is comparable with similar deposits in Arabian Nubian Shield (ANS).Key words: Ferricrete, Laterite, Ferruginous sandstone, Shire, Tigray, Northern Ethiopia, AN

Self-harm with suicidal and non-suicidal intent in young people in sub-Saharan Africa: a systematic review

Background: Self-harm, whether attributed to suicidal or non-suicidal motives, is associated with several poor outcomes in young people, including eventual suicide. Much of our understanding of self-harm in young people is based on literature from Europe (particularly, the UK), North America, and Australia. We aimed to synthesise the available evidence on prevalence, the commonly reported self-harm methods, correlates, risk and protective factors, and reasons for self-harm, in adolescents (aged 10–25 years) in sub-Saharan Africa. Method: We searched MEDLINE, PsycINFO, PubMed, African Journals OnLine, and African Index Medicus for records from 1950 through August 2019, without language restrictions. We supplemented the database searches by searching relevant portals for postgraduate theses, reference harvesting, contacting authors for unpublished studies, and hand searching relevant print sources. We applied narrative synthesis to the evidence. Results: Seventy-four studies from 18 sub-Saharan African countries met the inclusion criteria. The median lifetime prevalence estimate was 10·3% (interquartile range [IQR] 4·6% – 16·1%); median 12-month prevalence estimate was 16·9% (IQR: 11·5% – 25·5%); median 6-month prevalence estimate was 18·2% (IQR: 12·7% – 21·8%); and the median 1-month prevalence estimate was 3·2% (IQR: 2·5–14·8%). Studies from Western sub-Saharan Africa reported the highest 12-month prevalence estimates (median = 24·3%; IQR = 16·9% – 27·9%). Clinical samples commonly reported overdose, whereas self-cutting was most commonly reported in non-clinical samples. Academic failure, sexual, emotional, and physical abuse, romantic relationship problems, family conflict, depression, and previous self-harm were identified as key correlates of self-harm. No study reported protective factors against self-harm. Conclusion: Variation in estimates was explained by small sample sizes and variation in definitions and measures used. Exploration of associations, risks and protective factors was based upon concepts and measures derived from high income countries. More detailed and culturally sensitive research is needed to understand the context-specific risks and protective factors for self-harm in adolescents in sub-Saharan Africa

Linking dwarf galaxies to halo building blocks with the most metal-poor star in Sculptor

Current cosmological models indicate that the Milky Way's stellar halo was assembled from many smaller systems. Based on the apparent absence of the most metal-poor stars in present-day dwarf galaxies, recent studies claimed that the true Galactic building blocks must have been vastly different from the surviving dwarfs. The discovery of an extremely iron-poor star (S1020549) in the Sculptor dwarf galaxy based on a medium-resolution spectrum cast some doubt on this conclusion. However, verification of the iron-deficiency and measurements of additional elements, such as the alpha-element Mg, are mandatory for demonstrating that the same type of stars produced the metals found in dwarf galaxies and the Galactic halo. Only then can dwarf galaxy stars be conclusively linked to early stellar halo assembly. Here we report high-resolution spectroscopic abundances for 11 elements in S1020549, confirming the iron abundance of less than 1/4000th that of the Sun, and showing that the overall abundance pattern mirrors that seen in low-metallicity halo stars, including the alpha-elements. Such chemical similarity indicates that the systems destroyed to form the halo billions of years ago were not fundamentally different from the progenitors of present-day dwarfs, and suggests that the early chemical enrichment of all galaxies may be nearly identical.Comment: 16 pages, including 2 figures. Accepted for publication in Nature. It is embargoed for discussion in the press until formal publication in Natur

Coordinate-space calculation of the window observable for the hadronic vacuum polarization contribution to (g−2)μ(g-2)_\mu

The `intermediate window quantity' of the hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon allows for a high-precision comparison between the data-driven approach and lattice QCD. The existing lattice results, which presently show good consistency among each other, are in strong tension with the data-driven determination. In order to check for a potentially common source of systematic error of the lattice calculations, which are all based on the time-momentum representation (TMR), we perform a calculation using a Lorentz-covariant coordinate-space (CCS) representation. We present results for the isovector and the connected strange-quark contributions to the intermediate window quantity at a reference point in the $(m_\pi,m_K)$ plane, in the continuum and infinite-volume limit, based on four different lattice spacings. Our results are in good agreement with those of the recent TMR-based Mainz-CLS publication.Comment: 35 pages, 6 figures, 6 table

Coordinate-space calculation of QED corrections to the hadronic vacuum polarization contribution to (g−2)μ(g-2)_\mu

As several lattice collaborations agree on the result for the window quantity of the hadronic vacuum polarization (HVP) contribution to $(g-2)_\mu$, whilst being in tension with the calculation using the dispersive approach, further effort is needed in order to pin down the cause for this difference. Here we want to focus on the isospin breaking corrections to the leading order HVP. In many lattice applications, the photon propagator is treated stochastically; however, by analogy with the hadronic light-by-light contribution (HLbL) to $(g-2)_\mu$, we suggest a coordinate-space approach to the HVP at next-to-leading order. We present a calculation of the two diagrams of the (2+2) topology at unphysical pion mass, where we apply a Pauli-Villars regularization for the extra photon propagator in the diagram that is UV-divergent. We compare the UV-finite diagram to the pseudoscalar exchange contributions calculated from a vector-meson dominance model.Comment: 8 pages, 3 figures, 2 tables, Proceedings of the The 40th International Symposium on Lattice Field Theory (Lattice 2023), July 31st - August 4th, 2023, Fermi National Accelerator Laborator

Engaging currently available tested and proven strategies to tackle hepatitis B viral epidemic: the HBV-4-pronged approach (HBV4PA)

Hepatitis B viral (HBV) infection is a major world problem and is a key contributing factor to the worldwide incidence of hepatocelullar carcinoma, especially in sub-Saharan Africa. However, although hepatitis B treatment is available and effective, it is out of the reach of the common person. Many have, because of cost of treatment, succumbed to the chronic effects of HBV infection, such as liver cirrhosis and primary liver cancer. In this article, we make a case for the provision of free antiviral drugs to chronically-infected HBV patients by expanding the current HIV services to HBV-infected individuals using the PMTCT model. This, when implemented, will save lives, prevent unnecessary and escalating health expenditure and ensure sustainable development

Dust Reddening in SDSS Quasars

We explore the form of extragalactic reddening toward quasars using a sample of 9566 quasars with redshifts 0<z<2.2, and accurate optical colors from the Sloan Digital Sky Survey (SDSS). We confirm that dust reddening is the primary explanation for the red ``tail'' of the color distribution of SDSS quasars. Our fitting to 5-band photometry normalized by the modal quasar color as a function of redshift shows that this ``tail'' is well described by SMC-like reddening but not by LMC-like, Galactic, or Gaskell et al. (2004) reddening. Extension to longer wavelengths using a subset of 1886 SDSS-2MASS matches confirms these results at high significance. We carry out Monte-Carlo simulations that match the observed distribution of quasar spectral energy distributions using a Lorentzian dust reddening distribution; 2% of quasars selected by the main SDSS targeting algorithm (i.e., which are not extincted out of the sample) have E_{B-V} > 0.1; less than 1% have E_{B-V} > 0.2, where the extinction is relative to quasars with modal colors. Reddening is uncorrelated with the presence of intervening narrow-line absorption systems, but reddened quasars are much more likely to show narrow absorption at the redshift of the quasar than are unreddened quasars. Thus the reddening towards quasars is dominated by SMC-like dust at the quasar redshift.Comment: 29 pages including 8 figures. AJ, September 2004 issu

Volunteerism in a Health Care Delivery System in Nigeria: A Cottage Hospital Experience

Introduction: The need for volunteerism in the implementation of National Programmes is becoming more obvious now than before, especially in resource poor countries. The activities of volunteers are required in all aspects of life, especially in the developed countries, and they cut across age groups, gender, occupation and geographical barriers. Unfortunately there is paucity of information on the activities and constraints of volunteers in developing countries.Aim: To evaluate the contribution of volunteer staff involved in implementing the Community Health Insurance Scheme of a cottage hospital in Southern Nigeria.Method: The study design involved a descriptive analysis of all volunteering activities at Obio Cottage Hospital in Port Harcourt, Rivers State South-south Nigeria, from January 1, 2011 till December 31, 2011. Primary and secondary sources of data were used.Results: The total number of applicants who wished to volunteer during the period was 131, thirty-four of these were selected as 'Participants' in the programme. Women were more likely to volunteer than men, and highly educated Nigerians, including medical doctors and degree holders participated. Obio Cottage Hospital benefitted from the scheme in financial terms to the tune of more than 4 million Naira. (about 27 thousand US Dollars) within the one year of study while the participants all agreed that the scheme assisted them in actualizing their career and positioned them to getting paid jobs. The clinical output of the hospital more than doubled during the period.Conclusion: Organized volunteerism is of great benefit to the participants, institution, community and country and should be encouraged.Keywords: Volunteer, Obio Cottage Hospital, Participants, Nigeri