3D printing of cement composites

The aims of this study were to investigate the feasibility of generating 3D structures directly in rapid-hardening Portland cement (RHPC) using 3D Printing (3DP) technology. 3DP is a Additive Layer Manufacturing (ALM) process that generates parts directly from CAD in a layer-wise manner. 3D structures were successfully printed using a polyvinylalcohol: RHPC ratio of 3:97 w/w, with print resolutions of better than 1mm. The test components demonstrated the manufacture of features, including off-axis holes, overhangs / undercuts etc that would not be manufacturable using simple mould tools. Samples hardened by 1 day post-build immersion in water at RT offered Modulus of Rupture (MOR) values of up to 0.8±0.1MPa, and, after 26 days immersion in water at RT, offered MOR values of 2.2±0.2MPa, similar to bassanite-based materials more typically used in 3DP (1-3 MPa). Post-curing by water immersion restructured the structure, removing the layering typical of ALM processes, and infilling porosity

Directionally asymmetric self-assembly of cadmium sulfide nanotubes using porous alumina nanoreactors: Need for chemohydrodynamic instability at the nanoscale

We explore nanoscale hydrodynamical effects on synthesis and self-assembly of cadmium sulfide nanotubes oriented along one direction. These nanotubes are synthesized by horizontal capillary flow of two different chemical reagents from opposite directions through nanochannels of porous anodic alumina which are used primarily as nanoreactors. We show that uneven flow of different chemical precursors is responsible for directionally asymmetric growth of these nanotubes. On the basis of structural observations using scanning electron microscopy, we argue that chemohydrodynamic convective interfacial instability of multicomponent liquid-liquid reactive interface is necessary for sustained nucleation of these CdS nanotubes at the edges of these porous nanochannels over several hours. However, our estimates clearly suggest that classical hydrodynamics cannot account for the occurrence of such instabilities at these small length scales. Therefore, we present a case which necessitates further investigation and understanding of chemohydrodynamic fluid flow through nanoconfined channels in order to explain the occurrence of such interfacial instabilities at nanometer length scales.Comment: 26 pages, 6 figures; http://www.iiserpune.ac.in/researchhighlight

Determining the prevalence of malnutrition in hospitalised paediatric patients

No Abstract. South African Medical Journal Vol. 96(9) (Part 2) 2006: 993-99

Determining the prevalence of malnutrition in hospitalised paediatric patients

No Abstract

Excitonic ferromagnetism in the hexaborides

A ferromagnet with a small spontaneous moment but with a high Curie temperature can be obtained by doping an excitonic insulator made from a spin triplet exciton condensate. Such a condensate can occur in a semimetal with a small overlap or a semiconductor with a small bandgap. We propose that it is responsible for the unexpected ferromagnetism in the doped hexaboride material Ca_{1-x}La_xB_6.Comment: 4 pages, 3 figure

Anomalous violation of the local constant field approximation in colliding laser beams

It is commonly assumed that in ultrastrong laser fields, when the strong field parameter of the laser field $\xi$ is larger than one, the electron radiation is well described by the local constant field approximation (LCFA). We discuss the failure of this conjecture, considering radiation of an ultrarelativistic electron interacting with strong counterpropagating laser waves. A deviation from LCFA, in particular in the high-frequency domain, is shown to occur even at $\xi\gg 1$ because of the appearance of an additional small time scale in the trajectory. Moreover, we identify a new class of LCFA violation, when the radiation formation length becomes smaller than the one via LCFA. It is characterized by a broad and smooth spectrum rather than an harmonic structure. A similar phenomenon is also demonstrated in the scenario of an electron colliding with an ultrashort laser pulse. The relevance to laser-plasma kinetic simulations is discussed

One country, many industries: Heterogeneity of Chinese OFDI motivations at meso level

Research on the stimulants for Chinese Foreign Direct Investment (FDI) is extensive. However most analysis incorporates theoretical models based on the Institution-Based View or, to a lesser extent, the Resource-Based View (RBV). These highlight the importance of the macro (country) and micro (firm) level, while largely ignoring the meso (industry) level. In addition, although investments are known to have several different motivations, stimulated by quite different factors, analysis tends to focus on aggregate FDI flows. We contribute to the literature by proposing an ‘industry-based view’ of FDI which takes account of heterogeneity across industries and FDI motivation. We apply this framework to Chinese OFDI in Europe, differentiating both in terms of investment motivations and sectoral characteristics at (meso) industry level and at (micro) firm level, in home and host countries. Using logistic and multinomial logistic models, our analysis confirms that different types of Chinese FDI (in terms of motivation) are stimulated by different industry-level characteristics in both home and host countries

Marker-assisted Screening of Cotton Cultivars for Bacterial Blight Resistance Gene

Bacterial blight or leaf blight is a common disease of cotton in almost all cotton growing countries, including Tanzania. Bacterial blight is caused by infection of plants with the bacteria (Xanthomonas axonopodis pv. malvacearum) and the use of resistant cultivars is the most effective long-term strategy to manage the disease. The strategy starts with identification of resistant individuals, which can be identified either phenotypically by inoculation or by use of molecular markers linked to genes that confer resistance. The B12 gene is known to confer a high level of resistance to all Xanthomonas axonopodis pv. malvacearum races found in USA and Africa. Four Brazilian and three local cultivars were screened for the presence of SSR (CIR246) and SNP NG0207155 markers linked to B12. The SNP marker showed the greatest frequency of resistance-linked alleles in the cultivar UK08 (85.71%) followed by UK91 (75%),UKM08 and Ipê (25%), Araça(8.33%),Aroeira (7.1%) and the least in Cedro (0%). Comparable results were recorded for SSR marker where the cultivar UK08 presented relatively higher frequency of resistance alleles (85.71%) of samples tested followed by UK91 (68.75%), UKM08 (25%), Ipê, Aroeira and Araça (8%) and the last was Cedro (0%). The results suggest the potential utility of Tanzanian germplasm in breeding for resistance to Xanthomonas axonopodis pv. malvacearum race 18 and the need to purify the same germplasm by marker assisted selection.Key words: Bacterial Blight, Cotton, Resistant cultivars, Tanzania

Influence of temperature on extreme rainfall intensity in Sicily (Italy)

Some climate model experiments suggest an intensification of short-duration extreme precipitation in many parts of the world associated with a warming climate. This behavior could have a physical motivation due to the fact that warmer air has the potential to hold more atmospheric moisture and, then, to provide more water to rainfall events. The theoretical basis of the relationship that links air temperature and atmospheric humidity is provided by the Clausius-Clapeyron relation, according to which, if the relative humidity remains constant, then atmospheric humidity will increase with temperature at a rate (often referred to as CC-rate) in the order of 6-7% C-1, following the saturation vapour pressure curve as a function of temperature. The study of the relationship between extreme rainfall events and surface temperature could be of capital importance for evaluating the effects of global warming on future precipitation, since it may have important impacts on society with relevant fallouts on several aspects (e.g. flooding, risk protection, etc.). Different approaches have been proposed for the study at different locations of the scaling relationship between extreme rainfall intensity and surface temperature. In some cases, it has been observed a rate consistent with the thermodynamic Clausius-Clapeyron relation (CC-rate). Nevertheless, in many cases, the existence of scaling rate between temperature and extreme precipitation has been demonstrated with significantly different values with respect to the theoretical CC-rate, being in some cases sensibly higher (super-CC) and in other relevantly lower (sub-CC). In this work, an analysis of the scaling relationship between sub-daily extreme rainfall and surface temperature in a semi-arid region (Sicily, Italy) is carried out, also investigating the role of different factors, such as the duration of maximum rainfall depths for fixed duration (i.e. 10, 30 and 60 minutes), the type of adopted regression models (exponential regression, two-segments piecewise regression and LOESS - Locally-weighted scatterplot smoothing - regression), and the climate seasonality (unique season for the entire hydrological year; dry season from April to September and wet season for the remaining part of the year). The original dataset is constituted by hourly temperature and 10-minutes rainfall data collected from 2003 to 2015 by the regional agency SIAS (Servizio Informativo Agrometeorologico Siciliano) through 107 weather stations spread over the region. The results demonstrate that in Sicily the scaling rates are generally lower than the CC-rate; however, the observed tendency towards sub-CC rates is smoothed by the consideration of shorter duration for rainfall maximum depths (higher rates for 10-minutes durations) and under wetter periods (higher rates considering only wet season values), demonstrating how such factors play a fundamental role