Optical properties of structurally-relaxed Si/SiO2_2 superlattices: the role of bonding at interfaces

We have constructed microscopic, structurally-relaxed atomistic models of Si/SiO$_2$ superlattices. The structural distortion and oxidation-state characteristics of the interface Si atoms are examined in detail. The role played by the interface Si suboxides in raising the band gap and producing dispersionless energy bands is established. The suboxide atoms are shown to generate an abrupt interface layer about 1.60 \AA thick. Bandstructure and optical-absorption calculations at the Fermi Golden rule level are used to demonstrate that increasing confinement leads to (a) direct bandgaps (b) a blue shift in the spectrum, and (c) an enhancement of the absorption intensity in the threshold-energy region. Some aspects of this behaviour appear not only in the symmetry direction associated with the superlattice axis, but also in the orthogonal plane directions. We conclude that, in contrast to Si/Ge, Si/SiO$_2$ superlattices show clear optical enhancement and a shift of the optical spectrum into the region useful for many opto-electronic applications.Comment: 11 pages, 10 figures (submitted to Phys. Rev. B

Les analysis on cylinder cascade flow based on energy ratio coefficient

The flow field around the cylinder cascade is widely used to analyze the interaction of vortex shedding and the information on heat transfer. Large eddy simulation (LES) can be used to get the turbulent flow information in detail. The resolved largescale structures are determined by the size of the grid, and the turbulent vortex dissipation is modeled with a subgrid scale model. Whereas there is no accurate criterion to provide the subgrid scale with the physical meaning. Based on turbulent energy ratio coefficient and numerical simulation results with turbulent model, the subgrid was generated for the incompressible fluid flowing around a column of cylinder cascade with a gap-to-diameter ratio of 2. Smagorinsky-Lily (SM) model was applied to LES analysis. The turbulent flow information was compared with the experimental data by PIV. Two cases with different Reynolds numbers were studied. When the turbulent energy ratio coefficient reached to 30%- 40%, the turbulent dissipation could be captured by LES method with less grid number. The large scale vortex interaction behind the cylinder cascade was analyzed further. It is verified that LES method can be used for engineering based on the turbulent energy ratio coefficient with acceptable computational cost.papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

New Non-invasive Techniques to Quantify Skin Surface Strain and Sub-surface Layer Deformation of Finger-pad during Sliding

Studies on the variation of skin properties with gender, age and anatomical region, with regards to interaction with different materials have resulted in significant research output. Investigations on skin surface strain and sub-surface layer deformation during sliding, however, have not received as much attention. This novel study uses two non-invasive techniques, optical coherence tomography (OCT) and digital image correlation (DIC), to measure properties of the index finger of a 25. year old female when under normal and shear loading. Measurements were taken during static, and for the first time, dynamic phases.It was observed that the number of ridges in contact with a Quartz glass surface, observed under OCT, reduced when the finger started sliding. The sliding also resulted in deformation at the stratum corneum junction. The surface strain, analysed using DIC was higher nearer to the distal interphalangeal joint compared to the fingertip. This newly developed approach provides a powerful and non-invasive method to study the structural changes of finger-pad skin during loading and sliding. This approach can now be repeated at different anatomical locations for medical, bioengineering and consumer applications

A description of patients with recurrence of pulmonary tuberculosis in TB hospital, Ermelo

Thesis (MMed)--Stellenbosch University, 2015.South Africa is one of the high burden countries for TB in Sub Sahara in Africa with Mpumalanga as one of the provinces with a high burden of disease. Data available on tuberculosis in Msukaligwa indicate the following: Cure Rate 40%; Smear conversion at the end of intensive phase 35% and Defaulter Rate 27.5%. The problem of TB is made worse by the twin epidemic of HIV, with a prevalence of 38.9% in our district -the highest among the 3 districts in the province. Retreatment TB carries the risk of developing TB drug resistance with severe consequences for the patient and the population. Understanding the characteristics of these patients will help in designing interventions to prevent the problem, promote a high cure rate for patients with TB in our health care system and reduce to minimum the burden of re-treatment pulmonary TB on our health care facilities and community. One critical precondition for Retreatment TB is non adherence to TB treatment. Factors responsible for non adherence could be classified as individual patient factors; Co-morbid conditions; Health system; treatment related and Community factors. The outcomes of Retreatment TB could be, cure, and death and failure of treatment leading to drug resistance. The Setting of this study is the 58-bedded TB hospital in Ermelo. The Aim of the study was to describe the occurrence, characteristics and management outcome of Retreatment Pulmonary Tuberculosis in patients in the Ermelo TB hospital. The specific Objectives were to describe the socio-demographic, behavioural and clinical factors related to recurrence of the TB in patients; to determine the contribution of non adherence to treatment on recurrence of TB in the study population; to identify the prevalence of resistance to TB medication among patients with Retreatment TB ; to identify treatment outcomes in patients who have been followed up for the duration of Retreatment TB and finally to make recommendations to the Department of Health, Mpumalanga towards minimizing Retreatment TB and improving the overall TB programme. The Study design is cross sectional and descriptive; the study population comprised of patients admitted with TB at Ermelo TB hospital aged 15 years and older between 1 January 2005 and 31 December 2007.No specific probability sampling was applied in the selection of the patients. Data Collection involved visits to the TB hospital during the period and extracting the relevant information from the patient medical records and the TB register using a predesigned data collection form. Data analysis was done by the statistician from the Centre for Statistical Consultation, University of Stellenbosch. Being a descriptive study, the data analysis expresses the prevalence of various factors associated with retreatment TB. This study met the Ethical approval of the University of Stellenbosch as well as the Research Ethics Committee of the Department of Health & Social Services, Mpumalanga. Findings All the three hundred and eighty eight patient records with retreatment TB forming 19.6% of TB patients admitted between 2005 and 2007 were reviewed. The distributions of the patients were: males 66%; mean age of 41.4 years; females 34%; mean age 35.3 years. They were mostly unemployed; primary education 93%; unmarried 43% and married 34%.Retreatment TB was diagnosed with sputum smear microscopy in 71% with bacilli load of 3+ in 45%.The sources of referral to TB hospital were: public hospital 71 %; private doctors 2%. 74% of the patients have had TB 1-3 years before the episode under study. Retreatment TB categories were: after treatment completed 69%; default 19%; after cure 8% and treatment failure 4%. 98% of patients tested had +ve HIV status; the median CD4 cell count was 106 cells/µl at the time of retreatment; very few (5%) were on ART. Drug resistance to primary TB drugs was as follows: Rifampicin 16%; Isoniazid 29%; Ethambutol 19% and Streptomycin 23%. The treatment outcomes for those whom data were available were: successful 49.1%, death 23.8%; treatment default 22.9%. MDR-TB complicated 3.3% of the patients. Conclusion: Majority of the retreatment TB patients were males with an average age of 41years and unemployed. More than two thirds of the patient had completed TB treatment previously and default on treatment accounted for less than one quarter of retreatment categories. The process of care was better in terms of diagnosis of TB with sputum smear. Improvement in the documentation of key factors like smoking, alcohol, drug use among patients and co-morbidity as well as counselling and testing for HIV and provision of ARTs is required. Treatment outcomes with regards to successful outcome need to be monitored and improved upon.AFRIKAANSE OPSOMMING: Geen opsomming beskikbaa

Strain-specific copy number variation in the intelectin locus on the 129 mouse chromosome 1

<p>Abstract</p> <p>Background</p> <p>C57BL/6J mice possess a single <it>intelectin (Itln) </it>gene on chromosome 1. The function of intelectins is not well understood, but roles have been postulated in insulin sensitivity, bacterial recognition, intestinal lactoferrin uptake and response to parasites and allergens. In contrast to C57BL/6J mice, there is evidence for expansion of the <it>Itln </it>locus in other strains and at least one additional mouse <it>Itln </it>gene product has been described. The aim of this study was to sequence and characterise the <it>Itln </it>locus in the 129S7 strain, to determine the nature of the chromosomal expansion and to inform possible future gene deletion strategies.</p> <p>Results</p> <p>Six 129S7 BAC clones were sequenced and assembled to generate 600 kbp of chromosomal sequence, including the entire <it>Itln </it>locus of approximately 500 kbp. The locus contained six distinct <it>Itln </it>genes, two <it>CD244 </it>genes and several <it>Itln</it>- and <it>CD244</it>-related pseudogenes. It was approximately 433 kbp larger than the corresponding C57BL/6J locus. The expansion of the <it>Itln </it>locus appears to have occurred through multiple duplications of a segment consisting of a full-length <it>Itln </it>gene, a <it>CD244 </it>(pseudo)gene and an <it>Itln </it>pseudogene fragment. Strong evidence for tissue-specific distribution of <it>Itln </it>variants was found, indicating that <it>Itln </it>duplication contributes more than a simple gene dosage effect.</p> <p>Conclusions</p> <p>We have characterised the <it>Itln </it>locus in 129S7 mice to reveal six <it>Itln </it>genes with distinct sequence and expression characteristics. Since C57BL/6J mice possess only a single <it>Itln </it>gene, this is likely to contribute to functional differences between C57BL/6J and other mouse strains.</p

Tunneling conductance in strained graphene-based superconductor: Effect of asymmetric Weyl-Dirac fermions

Based on the BTK theory, we investigate the tunneling conductance in a uniaxially strained graphene-based normal metal (NG)/ barrier (I)/superconductor (SG) junctions. In the present model, we assume that depositing the conventional superconductor on the top of the uniaxially strained graphene, normal graphene may turn to superconducting graphene with the Cooper pairs formed by the asymmetric Weyl-Dirac electrons, the massless fermions with direction-dependent velocity. The highly asymmetrical velocity, vy/vx>>1, may be created by strain in the zigzag direction near the transition point between gapless and gapped graphene. In the case of the highly asymmetrical velocity, we find that the Andreev reflection strongly depends on the direction and the current perpendicular to the direction of strain can flow in the junction as if there was no barrier. Also, the current parallel to the direction of strain anomalously oscillates as a function of the gate voltage with very high frequency. Our predicted result is found as quite different from the feature of the quasiparticle tunneling in the unstrained graphene-based NG/I/SG conventional junction. This is because of the presence of the direction-dependent-velocity quasiparticles in the highly strained graphene system.Comment: 18 pages, 7 Figures; Eq.13 and 14 are correcte

1S0 Proton and Neutron Superfluidity in beta-stable Neutron Star Matter

We investigate the effect of a microscopic three-body force on the proton and neutron superfluidity in the $^1S_0$ channel in $\beta$-stable neutron star matter. It is found that the three-body force has only a small effect on the neutron $^1S_0$ pairing gap, but it suppresses strongly the proton $^1S_0$ superfluidity in $\beta$-stable neutron star matter.Comment: 12 pages, 2 figure

Theoretical study of the two-proton halo candidate 17^{17}Ne including contributions from resonant continuum and pairing correlations

With the relativistic Coulomb wave function boundary condition, the energies, widths and wave functions of the single proton resonant orbitals for $^{17}$Ne are studied by the analytical continuation of the coupling constant (ACCC) approach within the framework of the relativistic mean field (RMF) theory. Pairing correlations and contributions from the single-particle resonant orbitals in the continuum are taken into consideration by the resonant Bardeen-Cooper-Schrieffer (BCS) approach, in which constant pairing strength is used. It can be seen that the fully self-consistent calculations with NL3 and NLSH effective interactions mostly agree with the latest experimental measurements, such as binding energies, matter radii, charge radii and densities. The energy of $\pi$2s$_{1/2}$ orbital is slightly higher than that of $\pi1d_{5/2}$ orbital, and the occupation probability of the $(\pi$2s$_{1/2})^2$ orbital is about 20%, which are in accordance with the shell model calculation and three-body model estimation

Combined constraints on modified Chaplygin gas model from cosmological observed data: Markov Chain Monte Carlo approach

We use the Markov Chain Monte Carlo method to investigate a global constraints on the modified Chaplygin gas (MCG) model as the unification of dark matter and dark energy from the latest observational data: the Union2 dataset of type supernovae Ia (SNIa), the observational Hubble data (OHD), the cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and the cosmic microwave background (CMB) data. In a flat universe, the constraint results for MCG model are, $\Omega_{b}h^{2}=0.02263^{+0.00184}_{-0.00162}$ ($1\sigma$) $^{+0.00213}_{-0.00195}$ $(2\sigma)$, $B_{s}=0.7788^{+0.0736}_{-0.0723}$ ($1\sigma$) $^{+0.0918}_{-0.0904}$ $(2\sigma)$, $\alpha=0.1079^{+0.3397}_{-0.2539}$ ($1\sigma$) $^{+0.4678}_{-0.2911}$ $(2\sigma)$, $B=0.00189^{+0.00583}_{-0.00756}$ ($1\sigma$) $^{+0.00660}_{-0.00915}$ $(2\sigma)$, and $H_{0}=70.711^{+4.188}_{-3.142}$ ($1\sigma$) $^{+5.281}_{-4.149}$ $(2\sigma)$.Comment: 12 pages, 1figur

Observational constraint on generalized Chaplygin gas model

We investigate observational constraints on the generalized Chaplygin gas (GCG) model as the unification of dark matter and dark energy from the latest observational data: the Union SNe Ia data, the observational Hubble data, the SDSS baryon acoustic peak and the five-year WMAP shift parameter. It is obtained that the best fit values of the GCG model parameters with their confidence level are $A_{s}=0.73^{+0.06}_{-0.06}$ ($1\sigma$) $^{+0.09}_{-0.09}$ $(2\sigma)$, $\alpha=-0.09^{+0.15}_{-0.12}$ ($1\sigma$) $^{+0.26}_{-0.19}$ $(2\sigma)$. Furthermore in this model, we can see that the evolution of equation of state (EOS) for dark energy is similar to quiessence, and its current best-fit value is $w_{0de}=-0.96$ with the $1\sigma$ confidence level $-0.91\geq w_{0de}\geq-1.00$.Comment: 9 pages, 5 figure