Disseminated Mycobacterium avium complex infection as a differential diagnosis of tuberculosis in HIV patients

BACKGROUND: Disseminated Mycobacterium avium complex infection (DMAC) has symptoms and microscopic findings similar to those of TB in HIV patients. To inform a clinical algorithm-based differential diagnosis, we aimed to characterise the clinical features of DMAC.METHODS: This was a retrospective cohort study of 192 HIV-positive patients with culture-confirmed mycobacterial infections hospitalised during 1996-2016 at a major HIV/AIDS treatment centre in Taiwan.RESULTS: HIV patients with DMAC (n = 58) had a three times higher 1-year mortality than those with TB (n = 98) (48.3% vs. 16.3%, P < 0.001). DMAC and TB were not distinguishable by the WHO TB screening criteria (fever, cough, night sweats or weight loss). Nevertheless, DMAC was characterised by a lower median CD4 count (5.0 cells/µL vs. 38.5 cells/µL, P < 0.001), lower median body mass index (BMI) (17.7 kg/m² vs. 19.7 kg/m², P = 0.002) and the absence of chest radiographic findings (P < 0.001). Simultaneous presence of CD4 <20 cells/µl, BMI <18.5 kg/m² and negative chest radiographic finding had a 98% specificity for diagnosing DMAC against TB or other types of mycobacterial infections.CONCLUSION: DMAC is an important differential diagnosis of TB in HIV patients. A simple rule based on CD4, BMI and chest radiography may inform the decision to start anti-DMAC treatment in patients with mycobacterial infection.

In-situ atomic layer deposition of tri-methylaluminum and water on pristine single-crystal (In)GaAs surfaces: electronic and electric structures

The electronic structure of single-crystal (In)GaAs deposited with tri-methylaluminum (TMA) and water via atomic layer deposition (ALD) is presented with high-resolution synchrotron radiation core-level photoemission and capacitance-voltage (CV) characteristics. The interaction of the precursor atoms with (In)GaAs is confined at the topmost surface layer. The Ga-vacant site on the GaAs(111)A-2 × 2 surface is filled with Al, thereby effectively passivating the As dangling bonds. The As-As dimers on the GaAs(001)-2 × 4 surface are entirely passivated by one cycle of TMA and water. The presumed layerwise deposition fails to happen in GaAs(001)-4 × 6. In In0.20Ga0.80As(001)-2 × 4, the edge row As atoms are partially bonded with the Al, and one released methyl then bonds with the In. It is suggested that the unpassivated surface and subsurface atoms cause large frequency dispersions in CV characteristics under the gate bias. We also found that the (In)GaAs surface is immune to water in ALD. However, the momentary exposure of it to air (less than one minute) introduces significant signals of native oxides. This indicates the necessity of in situ works of high κ/(In)GaAs-related experiments in order to know the precise interfacial atomic bonding and thus know the electronic characteristics. The electric CV measurements of the ALD-Al2O3 on these (In)GaAs surfaces are correlated with their electronic properties.

The closing velocity of mechanical heart valve leaflets

The closing motion of the occluder leaflets in bileaflet type mechanical heart valves (MHV) was monitored with a laser sweeping technique. The angular displacements of the leaflets were registered with precision of 0.2 microsecond steps. Experimental measurements were made using five 29 mm Edwards-Duromedics including three original specification (EDOS) and two modified specification (EDMS), and two 29 mm St Jude Medical MHVs. The testing valve was installed in the mitral position of a physiologic pulsatile mock circulatory flow loop using water-glycerine solution as the testing fluid. Each valve was tested by: (1) direct mounting the valve on metal washers, and (2) mounting the valve with its sewing ring. Experiments were carried out at pulse rates of 70, 90, and 120 beats min-1, with the corresponding cardiac output of 5, 6, and 7.5 litres min-1, and maximum left ventricular pressure gradients (dp/dt) of 1,800, 3,000 and 5,600 mm Hg s-1, respectively. The maximum leaflet closing velocity of each of the tested valve types are presented. The difference in leaflet closing movements between the direct rigid mounting and the sewing ring mounting are discussed. The details of the laser sweeping technique are presented.

Static and dynamic stresses during valve closure of a bileaflet mechanical heart valve prosthesis

The effect of contact geometry and component compliance on the magnitude, distribution, and state of various types of stresses on a bileaflet mechanical heart valve prosthesis during valve closure was analyzed using an Edwards-Duromedics mitral valve as example. Static and dynamic stresses developing on both the leaflet and pivot ball during valve closure were modeled using finite element analysis (FEA). Uniform contact between the leaflet and housing as well as between the pivot ball and pivot slot can significantly reduce both static and dynamic stresses around the contact area. The level of the dynamic flexural stresses can be an order of magnitude higher than that of the static stresses. When both the radial and axial compliance of the housing are taken into consideration, peak dynamic stress was more than 40% less than that generated through the impact between a moving leaflet and a non-compliant rigid housing.