The increasing burden of tuberculosis in rural South Africa - impact of the HIV epidemic

Objective. To determine the impact of the HIV epidemic on tuberculosis caseload in rural South Africa.Setting. Hlabisa health district, Kwazulu-Natal.Methods. Demographic and clinical data were extracted from the tuberculosis database for the period, May 1991 June 1995. The attributable fraction of HIV-infected tuberculosis cases was estimated from the prevalence of HIV infection in tuberculosis cases and the prevalence of HIV infection in women attending antenatal clinics.Results. Between 1991 and 1995, the annual tuberculosis caseload increased from 301 to 839 cases. Tuberculosis accounted for 4.7% of all admissions in 1989 and 8.3% in 1995 (P < 0.0001). The incidence of tuberculosis increased from 154/1 00 000 in 1991, to 413/100 000 in 1995. The proportion with smear-positive pulmonary disease fell from 65% to 56% (P = 0.04), and pleural tuberculosis accounted for 7.5% of disease in 1991 and 18% in 1995 (P = 0.002). The minimum HIV prevalence in patients with tuberculosis increased from 8.7% in 1991 to 28.3% in 1995, and the proportion of tuberculosis cases attributable to HIV infection was estimated to be at least 44% in 1995.Conclusion. The burden of HIV-related tuberculosis is increasing rapidly in rural South Africa and is exerting a negative impact. Innovative approaches to control will be needed to cope with it effectively

Magnetically dilute metallic glasses. II. 4\u3ci\u3ef\u3c/i\u3e moments

Magnetic-susceptibility and high-field magnetization measurements are presented for amorphous Zr40Cu600-xMx (M denoting Gd and Tb), with x ranging from zero to ten. Effective moments of magnetic solutes were determined by fitting susceptibility data to the Curie-Weiss expression. The moments of Gd and Tb are very close to those expected for trivalent ions and the paramagnetic Weiss temperatures are positive. Saturation did not occur in any of the samples, even at 80 kOe and 1.3 K; however, the alloys containing Gd approached normalized magnetization values of unity. High-field hysteresis loops were used to obtain the temperature dependence of the coercive fields Hc and to determine ordering temperatures, defined as those temperatures for which Hc vanishes. The zero-field susceptibility for both the Gd and Tb alloys shows sharp peaks at low temperatures. The magnetically ordered state of the Gd alloys is characterized as spin-glass-like; that is, the spins are frozen in random directions and there are both ferromagnetic and antiferromagnetic exchange interactions, with the former dominant. The Tb alloys also have low-temperature magnetic states characterized as spin-glass-like in this sense. However, in the Tb alloys, the presence of local random anisotropy affects the high-field magnetization considerably. Attempts to fit the high-field magnetization of the Tb alloys to the local-random-anisotropy theory of Harris et al. are described

Remote lab experiments: Opening possibilities for distance learning in engineering fields

Remote experimentation laboratories are systems based on real equipment, allowing students to perform practical work through a computer connected to the internet. In engineering fields lab activities play a fundamental role. Distance learning has not demonstrated good results in engineering fields because traditional lab activities cannot be covered by this paradigm. These activities can be set for one or for a group of students who work from different locations. All these configurations lead to considering a flexible model that covers all possibilities (for an individual or a group). An inter-continental network of remote laboratories supported by both European and Latin American institutions of higher education has been formed. In this network context, a learning collaborative model for students working from different locations has been defined. The first considerations are presented

Distinctive dielectric properties of nematic liquid crystal dimers

We provide an overview of the effect of the molecular structure on the dielectric properties of dimers exhibiting nematic and twist-bend nematic phases with special focus on how the conformational distribution changes are reflected by the dielectric behaviour. Nematic dimers show distinctive dielectric properties which differ from those of archetypical nematic liquid crystals, as for example, unusual temperature dependence of the static permittivity or dielectric spectra characterised by two low-frequency relaxation processes with correlated strengths. The interpretation of such characteristic behaviour requires that account is taken of the effect of molecular flexibility on the energetically favoured molecular shapes. The anisotropic nematic interactions greatly influence the conformational distribution. Dielectric behaviour can be used to track those conformational changes due to dependence of the averaged molecular dipole moment on the averaged molecular shape. Results for a number of dimers are compared and analysed on the basis of the influence of details of the molecular structure, using a recently developed theory for the dielectric properties of dimers.Postprint (author's final draft

Excited D-brane decay in Cubic String Field Theory and in Bosonic String Theory

In the cubic string field theory, using the gauge invariant operators corresponding to the on-shell closed string vertex operators, we have explicitly evaluated the decay amplitudes of two open string tachyons or gauge fields to one closed string tachyon or graviton up to level two. We then evaluated the same amplitudes in the bosonic string theory, and shown that the amplitudes in both theories have exactly the same pole structure. We have also expanded the decay amplitudes in the bosonic string theory around the Mandelstam variable s=0, and shown that their leading contact terms are fully consistent with a tachyonic Dirac-Born-Infeld action which includes both open string and closed string tachyon.Comment: 19 pages, Latex, v3; references added, some words about contact terms are adde

D-Branes in Field Theory

Certain gauge theories in four dimensions are known to admit semi-classical D-brane solitons. These are domain walls on which vortex flux tubes may end. The purpose of this paper is to develop an open-string description of these D-branes. The dynamics of the domain walls is shown to be governed by a Chern-Simons-Higgs theory which, at the quantum level, captures the classical "closed string" scattering of domain wall solitons.Comment: 23 Pages, 3 figures. v2: reference adde

Bayesian parameter estimation of ligament properties based on tibio-femoral kinematics during squatting

The objective of this study is to estimate the, probably correlated, ligament material properties and attachment sites in a highly non-linear, musculoskeletal knee model based on kinematic data of a knee rig experiment for seven specific specimens. Bayesian parameter estimation is used to account for uncertainty in the limited experimental data by optimization of a high dimensional input parameter space (50 parameters) consistent with all probable solutions. The set of solutions accounts for physiologically relevant ligament strain (ϵ&lt;6%). The transitional Markov Chain Monte Carlo algorithm was used. Alterations to the algorithm were introduced in order to avoid premature convergence. To perform the parameter estimation with feasible computational cost, a surrogate model of the knee model was trained. Results show that there is a large intra- and inter-specimen variability in ligament properties, and that multiple sets of ligament properties fit the experimentally measured tibio-femoral kinematics. Although all parameters were allowed to vary significantly, large interdependence is only found between the reference strain and attachment sites. The large variation between specimens and interdependence between reference strain and attachment sites within one specimen, show the inability to identify a small range of ligament properties representative for the patient population. To limit ligament properties uncertainty in clinical applications, research will need to invest in establishing patient-specific uncertainty ranges and/or accurate in vivo measuring methods of the attachment sites and reference strain and/or alternative (combinations of) movements that would allow identifying a unique solution.</p

Weldability of polycrystalline aluminides. Final report

When gas-tungsten arc welded, iron aluminides form a coarse fusion zone microstructure which is susceptible to hydrogen cracking. Magnetic arc oscillation and weld pool inoculation were implemented to refine the fusion zone microstructure in iron aluminide alloy FA-129 weldments. Magnetic arc oscillation effectively refined the fusion zone microstructure, and slow strain rate tensile tests showed fine-grained microstructures to be less susceptible to hydrogen cracking. However, magnetic arc oscillation was found to be suitable only for well-controlled fabrication environments. Weld pool inoculation offers a potentially more robust refinement method. Titanium inoculation was also shown to effectively refined the fusion zone microstructure, but weldment properties were not improved using this refinement method. The effect of titanium on the size, shape and distribution of the second phase particles in the fusion zone appears to be the cause of the observed decrease in weldment properties

Molecular dynamics of a binary mixture of twist-bend nematic liquid crystal dimers studied by dielectric spectroscopy

We report a comprehensive dielectric characterization of a liquid crystalline binary mixture composed of the symmetric mesogenic dimer CB7CB and the nonsymmetric mesogenic dimer FFO9OCB. In addition to the high-temperature nematic phase, such a binary mixture shows a twist-bend nematic phase at room temperature which readily vitrifies on slow cooling. Changes in the conformational distribution of the dimers are reflected in the dielectric permittivity and successfully analyzed by means of an appropriate theoretical model. It is shown that the dielectric spectra of the mixture reflect the different molecular dipole properties of the components, resembling in the present case the characteristic dielectric spectra of nonsymmetric dimers. Comparison of the nematic and twist-bend nematic phases reveals that molecular dynamics are similar despite the difference in the molecular environment.Postprint (author's final draft

Miscibility studies of two twist-bend nematic liquid crystal dimers with different average molecular curvatures. A comparison between experimental data and predictions of a Landau mean-field theory for the NTB-N phase transition

We report a calorimetric study of a series of mixtures of two twist-bend liquid crystal dimers, the 1'',7''-bis(4-cyanobiphenyl)-4'-yl heptane (CB7CB) and 1''-(2',4-difluorobiphenyl-4'-yloxy)-9''-(4-cyanobiphenyl-4'-yloxy) nonane (FFO9OCB), the molecules of which have different effective molecular curvatures. High-resolution heat capacity measurements in the vicinity of the NTB-N phase transition for a selected number of binary mixtures clearly indicate a first order NTB-N phase transition for all the investigated mixtures, the strength of which decreases when the nematic range increases. Published theories predict a second order NTB-N phase transition, but we have developed a self-consistent mean field Landau model using two key order parameters: A symmetric and traceless tensor for the orientational order and a short-range vector field which is orthogonal to the helix axis and rotates around of the heliconical structure with an extremely short periodicity. The theory, in its simplified form, depends on two effective elastic constants and explains satisfactorily our heat capacity measurements and also predicts a first-order NTB-N phase transition. In addition, as a complementary source of experimental measurements, the splay (K1) and bend (K3) elastic constants in the conventional nematic phase for the pure compounds and some selected mixtures have been determined.Postprint (author's final draft