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Congenital and acquired heart diseases are highly prevalent in developing countries despite limited specialised care. Namibia established a paediatric cardiac service in 2009 with significant human resource and infrastructural constraints. Therefore, patients are referred for cardiac interventions to South Africa.
To describe the diagnoses, clinical characteristics, interventions, post-operative morbidity and mortality, and follow-up of patients referred for care.
Demographics, diagnoses, interventions, intra- and post-operative morbidity and mortality, as well as longitudinal follow-up data of all patients referred to South Africa, were recorded and analysed.
The total cohort constituted 193 patients of which 179 (93%) had CHD and 7% acquired heart disease. The majority of patients (78.8%) travelled more than 400 km to Windhoek before transfer. There were 28 percutaneous interventions. Palliative and definitive surgery was performed in 27 and 129 patients, respectively. Out of 156 patients, 80 (51.3%) had post-operative complications, of which 15 (9.6%) were a direct complication of surgery. Surgical mortality was 8/156 (5.1%, 95% confidence interval 2.2–9.8), with a 30-day mortality of 3.2%. Prolonged ICU stay was associated with a 5% increased risk of death with hazard ratio 1.05, 95% confidence interval 1.02–1.08, p=0.001. Follow-up was complete in 151 (78%) patients for more than 7 years.
Despite the challenges associated with a cardiac programme for referring patients seeking intervention in a neighbouring country and the adverse characteristics of multiple lesions and complexity associated with late presentation, we report good surgical and interventional outcomes. Our goal remains to develop a comprehensive sustainable cardiac service in Namibia.
Based on the data from the Next Generation Virgo cluster Survey (NGVS), we statistically study the photometric properties of globular clusters (GCs), ultra-compact dwarfs (UCDs) and dwarf nuclei in the Virgo core (M87) region. We found an obvious negative color (g - z) gradient in GC system associate with M87, i.e. GCs in the outer regions are bluer. However, such color gradient does not exist in UCD system, neither in dwarf nuclei system around M87. In addition, we found that many UCDs are surrounded by extended, low surface brightness envelopes. The dwarf nuclei and UCDs show different spatial distributions from GCs, with dwarf nuclei and UCDs (especially for the UCDs with visible envelopes) lying at larger distances to the Virgo center. These results support the view that UCDs (at least for a fraction of UCDs) are more tied to dwarf nuclei than to GCs.
This paper describes a research programme recently initiated at Utrecht University that aims to contribute new, fundamental physical understanding and quantitative descriptions of rock and fault behaviour needed to advance understanding of reservoir compaction and fault behaviour in the context of induced seismicity and subsidence in the Groningen gas field. The NAM-funded programme involves experimental rock and fault mechanics work, microscale observational studies to determine the processes that control reservoir rock deformation and fault slip, modelling and experimental work aimed at establishing upscaling rules between laboratory and field scales, and geomechanical modelling of fault rupture and earthquake generation at the reservoir scale. Here, we focus on describing the programme and its intended contribution to understanding the response of the Groningen field to gas production. The key knowledge gaps that drive the programme are discussed and the approaches employed to address them are highlighted. Some of the first results emerging from the work in progress are also reported briefly and are providing important new insights.
Recent archaeological investigations at Tipan Chen Uitz, Belize, yielded two remarkable Classic Maya ballplayer panels. Iconographic and glyphic analysis of these panels within a regional context provides new insights into large-scale socio-political relationships, demonstrating that the ballgame was an important means and mechanism for macro-political affiliation in the Maya Lowlands. The panels suggest that Tipan was part of a wider system of vassalage that tied it to other Maya centres, including Naranjo, a regional capital under the dominion of Calakmul where the Snake-Head dynasty held sway. The data presented here underpin a more general discussion of archaeological approaches to ancient interaction spheres.
We present an exceptional data set acquired with the Vacuum Tower Telescope (Tenerife, Spain) covering the pre-flare, flare, and post-flare stages of an M3.2 flare. The full Stokes spectropolarimetric observations were recorded with the Tenerife Infrared Polarimeter in the He i 1083.0 nm spectral region. The object under study was active region NOAA 11748 on 2013 May 17. During the flare the chomospheric He i 1083.0 nm intensity goes strongly into emission. However, the nearby photospheric Si i 1082.7 nm spectral line profile only gets shallower and stays in absorption. Linear polarization (Stokes Q and U) is detected in all lines of the He i triplet during the flare. Moreover, the circular polarization (Stokes V) is dominant during the flare, being the blue component of the He i triplet much stronger than the red component, and both are stronger than the Si i Stokes V profile. The Si i inversions reveal enormous changes of the photospheric magnetic field during the flare. Before the flare magnetic field concentrations of up to ~1500 G are inferred. During the flare the magnetic field strength globally decreases and in some cases it is even absent. After the flare the magnetic field recovers its strength and initial configuration.
The 2011 investigations of the Caves Branch Archaeological Survey at the large and recently documented Maya site of Tipan Chen Uitz resulted in the discovery of the site's first monument with a glyphic inscription. Prior to this discovery, the site's glyphic corpus was limited to a small collection of texts rendered on fragmentary ceramics. In this paper, we describe these sherds as well as the monument (Monument 1), report on their archaeological contexts, provide an epigraphic analysis of the texts, and consider these written sources relative to our growing understanding of Tipan and its place in the ancient political landscape. The discovery of Monument 1 is important, for it stands to contribute to sociopolitical reconstructions in this part of the central Maya Lowlands and has significant implications for the possible presence of other, as yet undiscovered, Late Classic period (A.D. 550-830) monuments at Tipan.
The microstructural and phase evolution of silicon films (Si:H) prepared by low temperature (200°C) rf plasma-enhanced chemical vapor deposition (PECVD) with hydrogen dilution of silane has been studied using real time spectroscopic ellipsometry (RTSE) and atomic force microscopy (AFM). Both RTSE and AFM support the concept of an evolutionary phase diagram that describes different regimes of bulk layer thickness and H2-dilution ratio R within which predominantly amorphous silicon (a-Si:H) and microcrystalline silicon (μc-Si:H) films are obtained. In this study, the evolutionary phase diagram has been extended to identify four separate growth regimes: (i) a-Si:H with a smooth surface and a stable roughness layer thickness, (ii) a-Si:H with a rougher surface and an unstable roughness layer thickness, (iii) mixed-phase (a+μc)-Si:H, and (iv) fully-coalesced (single-phase) μc-Si:H. Based on this framework, the effect of increased rf power to achieve higher deposition rates in the rf PECVD process was investigated.
In this study, we optimize the plasma-enhanced chemical vapor deposition (PECVD) process to achieve high-density nucleation of single-phase microcrystalline silicon (µc-Si:H) p-type layers on zinc oxide (ZnO) surfaces at 200 °C for applications in amorphous silicon (a-Si:H) based p-i-n solar cells. The phase evolution of the Si:H p-layers on specular ZnO-coated glass substrates is characterized using real time spectroscopic ellipsometry (RTSE). The resulting evolutionary phase diagram depicts the accumulated film thickness at which the amorphous-to- microcrystalline (→µc) transition occurs versus the H2-dilution ratio, with all other parameters fixed. Guided by this diagram, we find that high-density microcrystallite nucleation and fully- coalesced µc-Si:H p-layers ∼100 Å thick can be obtained on specular ZnO at 200 Å using a B(CH3)3 doping gas flow ratio of D=[B(CH3)3]/[SiH4]=0.02 and an optimized H2-dilution ratio of R=[H2]/SiH4]=200. Lower H2-dilution levels (R<160) generate purely amorphous or mixed (a+µc) phases, and higher dilution levels (R>200) generate longer induction periods, low-density nucleation, and incomplete coalescence of microcrystallites even after ∼100 Å. The time evolution of the microstructure and the resulting dielectric functions as determined by RTSE are similar for optimized µc-Si:H p-layers ∼200 Å thick prepared on specular and textured ZnO surfaces, indicating that the substrate texturing does not necessitate process reoptimization.
Spectroscopic ellipsometry (SE) analysis of so-called “specular” (macroscopically smooth) and “textured” (macroscopically rough) thin film amorphous silicon (a-Si:H) based solar cell structures demonstrates the need to incorporate interface layers into the multilayer stack in order to simulate the observed Stokes vector of the specularly-reflected beam. In most cases, these layers can be attributed to microscopic roughness (e.g., at the SnO2/p-layer/i-layer interface in a-Si:H p-i-n solar cells), as verified by atomic force microscopy (AFM). In limited cases, the layers may include regions wherein chemical intermixing also occurs (e.g., at the ZnO/Ag interface in back-reflectors), particularly for overlying films prepared by sputtering. In spite of the clear evidence for the existence of interface layers, they have been neglected in previous simulations of the optical quantum efficiency (QE) of the solar cells. In this study, we incorporate the experimentally- observed characteristics of interface layers as input into optical models for the p-i-n solar cell structure. In this way, we demonstrate the beneficial effects of SnO2/p/i interface microroughness as an anti-reflector and the detrimental effects of the ZnO/Ag interlayer as a parasitic absorber.