Characteristic Potentials for Mesoscopic Rings Threaded by an Aharonov-Bohm Flux

Electro-static potentials for samples with the topology of a ring and penetrated by an Aharonov-Bohm flux are discussed. The sensitivity of the electron-density distribution to small variations in the flux generates an effective electro-static potential which is itself a periodic function of flux. We investigate a simple model in which the flux sensitive potential leads to a persistent current which is enhanced compared to that of a loop of non-interacting electrons. For sample geometries with contacts the sensitivity of the electro-static potential to flux leads to a flux-induced capacitance. This capacitance gives the variation in charge due to an increment in flux. The flux-induced capacitance is contrasted with the electro-chemical capacitance which gives the variation in charge due to an increment in an electro-chemical potential. The discussion is formulated in terms of characteristic functions which give the variation of the electro-static potential in the interior of the conductor due to an increment in the external control parameters (flux, electro-chemical potentials). Paper submitted to the 16th Nordic Semiconductor Meeting, Laugarvatan, Iceland, June 12-15, 1994. The proceedings will be published in Physica Scripta.Comment: 23 pages + 4 figures, revtex, IBM-RC1955

Association Between Smoking and Tuberculosis Infection: A Population Survey in a High Tuberculosis Incidence Area

Associations between smoking and tuberculosis disease including death from tuberculosis have been reported, but there are few reports on the influence of smoking on the risk of developing Mycobacterium tuberculosis infection. The aim of this study was to determine the association between smoking and M tuberculosis infection. In a cross sectional population survey, data on smoking and tuberculin skin test (TST) results of 2401 adults aged >15 years were compared. A total of 1832 (76%) subjects had a positive TST (>10 mm induration). Of 1309 current smokers or ex-smokers, 1070 (82%) had a positive TST. This was significantly higher than for never smokers (unadjusted OR 1.99, 95% confidence interval (CI) 1.62 to 2.45). A positive relationship with pack-years was observed, with those smoking more than 15 pack-years having the highest risk (adjusted OR 1.90,95% CI 1.28 to 2.81). Smoking may increase the risk of M tuberculosis infection.\u

Missed opportunities in the diagnosis of pulmonary tuberculosis in children

In 52% of children with confirmed and probable tuberculosis the diagnosis could have been made earlier than it was. The main clinical clues which should have led to suspicion of tuberculosis were close adult contacts and previous recurrent respiratory tract infections

Symptom screening rules to identify active pulmonary tuberculosis: Findings from the Zambian South African Tuberculosis and HIV/AIDS Reduction (ZAMSTAR) trial prevalence surveys.

BACKGROUND: High tuberculosis (TB) burden countries should consider systematic screening among adults in the general population. We identified symptom screening rules to be used in addition to cough ≥2 weeks, in a context where X-ray screening is not feasible, aiming to increase the sensitivity of screening while achieving a specificity of ≥85%. METHODS: We used 2010 Zambia South Africa Tuberculosis and HIV/AIDS Reduction (ZAMSTAR) survey data: a South African (SA) training dataset, a SA testing dataset for internal validation and a Zambian dataset for external validation. Regression analyses investigated relationships between symptoms or combinations of symptoms and active disease. Sensitivity and specificity were calculated for candidate rules. RESULTS: Among all participants, the sensitivity of using only cough ≥2 weeks as a screening rule was less than 25% in both SA and Zambia. The addition of any three of six TB symptoms (cough <2 weeks, night sweats, weight loss, fever, chest pain, shortness of breath), or 2 or more of cough <2 weeks, night sweats, and weight loss, increased the sensitivity to ~38%, while reducing specificity from ~95% to ~85% in SA and ~97% to ~92% in Zambia. Among HIV-negative adults, findings were similar in SA, whereas in Zambia the increase in sensitivity was relatively small (15% to 22%). CONCLUSION: High TB burden countries should investigate cost-effective strategies for systematic screening: one such strategy could be to use our rule in addition to cough ≥2 weeks

TB or not TB?

Object: The aim of the study was to identify diagnoses that are confused with pulmonary tuberculosis in children. Design: Prospective, investigative clinical study. Setting: Tertiary care teaching hospital and an urban tuberculosis clinic in an area with a very high incidence of pulmonary tuberculosis (&gt; 800 new cases/100 ODD/year). Patients: Children suspected of having tuberculosis, children followed up for pulmonary infiltrates with eosinophilia and children with congenital pulmonjiry anomalies were investigated. Intervention(s): None. Outcome measure: Pulmonary tuberculosis was diagnosed using modified World Health Organisation criteria and the diagnoses of those children not suffering from pulmonary tuberculosis were analysed. Results: Of the 354 children initially suspected of suffering from tuberculosis 71 (20%) were found to be suffering from other pulmonary disease, viz. pneumonia or bronchopneumonia (29%), bronchopneumonia with Wheezing (18%), and asthma with lobar or segmental collapse (12%). Of 14 children suffering from pulmonary infiltrates with peripheral eosinophilia 6 (43%) were initially incorrectly diagnosed and treated for tuberculosis. Of 54 children with congenital pulmonary anomalies, 8 (15%) were treated for tuberculosis before the correct diagnosis was made. Congenital anomalies most often confused with tuberculosis were unilateral lung hypoplasia, bronchogenic cyst and tracheal bronchus with an anomalous lobe. Conclusions: The criteria for diagnosing tuberculosis in children is complicated in areas with a high incidence of tuberculosis and poor socio-economic circumstances where many children presenting with conditions other than tuberculosis will be in contact with an adult case of pulmonary tuberculosis. The commonest conditions confused with tuberculosis are pneumonia, bronchopneumonia and asthma. Pulmonary infiltrates with  peripheral eosinophilia and congenital lung abnormalities should be considered especially if the children have an atypical clinical picture or do not respond to tuberculosis treatment.S Afr Med J 1995; 85: 658-66

Comparing multidrug-resistant tuberculosis patient costs under molecular diagnostic algorithms in South Africa

SETTING: Ten primary health care facilities in Cape Town, South Africa, 2010–2013. OBJECTIVE: A comparison of costs incurred by patients in GenoType® MDRTBplus line-probe assay (LPA) and Xpert® MTB/RIF-based diagnostic algorithms from symptom onset until treatment initiation for multidrug-resistant tuberculosis (MDR-TB). METHODS: Eligible patients identified from laboratory and facility records were interviewed 3–6 months after treatment initiation and a cost questionnaire completed. Direct and indirect costs, individual and household income, loss of individual income and change in household income were recorded in local currency, adjusted to 2013 costs and converted to $US. RESULTS: Median number of visits to initiation of MDR-TB treatment was reduced from 20 to 7 (P < 0.001) and median costs fell from US$68.1 to US$38.3 (P = 0.004) in the Xpert group. From symptom onset to being interviewed, the proportion of unemployed increased from 39% to 73% in the LPA group (P < 0.001) and from 53% to 89% in the Xpert group (P < 0.001). Median household income decreased by 16% in the LPA group and by 13% in the Xpert group. CONCLUSION: The introduction of an Xpert-based algorithm brought relief by reducing the costs incurred by patients, but loss of employment and income persist. Patients require support to mitigate this impact

Comparing laboratory costs of smear/culture and Xpert(®) MTB/RIF-based tuberculosis diagnostic algorithms

SETTING: Cape Town, South Africa, where Xpert® MTB/RIF was introduced as a screening test for all presumptive tuberculosis (TB) cases. OBJECTIVE: To compare laboratory costs of smear/culture- and Xpert-based tuberculosis (TB) diagnostic algorithms in routine operational conditions. METHODS: Economic costing was undertaken from a laboratory perspective, using an ingredients-based costing approach. Cost allocation was based on reviews of standard operating procedures and laboratory records, timing of test procedures, measurement of laboratory areas and manager interviews. We analysed laboratory test data to assess overall costs and cost per pulmonary TB and multidrug-resistant TB (MDR-TB) case diagnosed. Costs were expressed as 2013 Consumer Price Index-adjusted values. RESULTS: Total TB diagnostic costs increased by 43%, from US$440 967 in the smear/culture-based algorithm (April–June 2011) to US$632 262 in the Xpert-based algorithm (April–June 2013). The cost per TB case diagnosed increased by 157%, from US$48.77 (n = 1601) to US$125.32 (n = 1281). The total cost per MDR-TB case diagnosed was similar, at US$190.14 and US$183.86, with 95 and 107 cases diagnosed in the respective algorithms. CONCLUSION: The introduction of the Xpert-based algorithm resulted in substantial cost increases. This was not matched by the expected increase in TB diagnostic efficacy, calling into question the sustainability of this expensive new technology

Transport Properties of a One-Dimensional Two-Component Quantum Liquid with Hyperbolic Interactions

We present an investigation of the sinh-cosh (SC) interaction model with twisted boundary conditions. We argue that, when unlike particles repel, the SC model may be usefully viewed as a Heisenberg-Ising fluid with moving Heisenberg-Ising spins. We derive the Luttinger liquid relation for the stiffness and the susceptibility, both from conformal arguments, and directly from the integral equations. Finally, we investigate the opening and closing of the ground state gaps for both SC and Heisenberg-Ising models, as the interaction strength is varied.Comment: 10 REVTeX pages + 4 uuencoded figures, UoU-002029

Shockwave synthesis of a thallium-based superconductor with a novel defect microstructure

We report the shock-wave synthesis at a yield ≳80% by volume of the single copper layer thalliumsuperconductor of composition Tl2Ba2CuO6. The as-synthesized material displays zero resistance near 55 K and a diamagnetic onset to bulk superconductivity at 70 K. Lattice imaging indicates that the superconducting microcrystals consist of a novel defect microstructure involving an intergrowth of two copper-oxygen layers probably interleaved by partial thallium and barium occupancy

Integration of TB and ART services fails to improve TB treatment outcomes: Comparison of ART/TB primary healthcare services in Cape Town, South Africa

BACKGROUND: The combined tuberculosis (TB) and HIV epidemics in South Africa (SA) have created enormous operational challenges for a health service that has traditionally run vertical programmes for TB treatment and antiretroviral therapy (ART) in separate facilities. This is particularly problematic for TB/HIV co-infected patients who need to access both services. OBJECTIVE: To determine whether integrated TB facilities had better TB treatment outcomes than single-service facilities in Cape Town, SA. METHODS: TB treatment outcomes were determined for newly registered, adult TB patients (aged > or = 18 years) at 13 integrated ART/TB primary healthcare (PHC) facilities and four single-service PHC facilities from 1 January 2009 to 30 June 2010. A chi2 test adjusted for a cluster sample design was used to compare outcomes by type of facility. RESULTS: Of 13,542 newly registered patients, 10,030 received TB treatment in integrated facilities and 3,512 in single-service facilities. There was no difference in baseline characteristics between the two groups with HIV status determined for 9,351 (93.2%) and 3,227 (91.9%) patients, of whom 6 649 (66.3%) and 2,213 (63%) were HIV-positive in integrated facilities and single-service facilities, respectively. The median CD4+ count of HIV-positive patients was 152 cells/microl (interquartile range (IQR) 71-277) for integrated facilities and 148 cells/microl (IQR 67-260) for single-service facilities. There was no statistical difference in the TB treatment outcome profile between integrated and single-service facilities for all TB patients (p = 0.56) or for the sub-set of HIV-positive TB patients (p = 0.58) CONCLUSION: This study did not demonstrate improved TB treatment outcomes in integrated PHC facilities and showed that the provision of ART in the same facility as TB services was not associated with lower TB death and default rates