The rising need for crop diversification to mitigate the impacts of climate change on food security urges the exploration of crop wild relatives (CWR) as potential genetic resources for crop improvement. This study aimed at assessing the diversity of CWR of the Indian Ocean islands of Mauritius and Rodrigues and proposing cost-effective conservation measures for their sustainable use. A comprehensive list of the native species was collated from The Mauritius Herbarium and published literature. Each species was assessed for the economic value of its related crop, utilization potential for crop improvement, relative distribution, occurrence status and Red List conservation status, using a standard scoring method for prioritization. The occurrence data of the priority species were collected, verified, geo-referenced and mapped. A total of 43 crop-related species were identified for both islands and 21 species were prioritized for active conservation. The CWR diversity hotspots in Mauritius included Mondrain, followed by Florin and Le Pouce Mountain. Although a wide diversity of CWR has been recorded on both islands, most do not relate to major economic crops in use, therefore only a few species may be gene donors to economic crops at the regional and global level. For example, coffee, a major global beverage crop, has three wild relatives on Mauritius, which could potentially be of interest for future predictive characterization.

The meridional circulation of the Sun is observationally found to vary with the solar cycle, becoming slower during the solar maxima. We explain this by constructing a theoretical model in which the equation of the meridional circulation (the φ component of the vorticity equation) is coupled with the equations of the flux transport dynamo model. We find that the Lorentz force of the dynamo-generated magnetic fields can slow down the meridional circulation during the solar maxima in broad conformity with the observations.

The observed convective flows on the photosphere (e.g., supergranulation, granulation) play a key role in the Babcock-Leighton (BL) process to generate large scale polar fields from sunspots fields. In most surface flux transport (SFT) and BL dynamo models, the dispersal and migration of surface fields is modeled as an effective turbulent diffusion. We present the first kinematic 3D FT/BL model to explicitly incorporate realistic convective flows based on solar observations. The results obtained are generally in good agreement with the observed surface flux evolution and with non-convective models that have a turbulent diffusivity on the order of 3 × 1012 cm2 s−1 (300 km2 s−1). However, we find that the use of a turbulent diffusivity underestimates the dynamo efficiency, producing weaker mean fields and shorter cycle.

Aiming at a physical interpretation of the cosmological evolution of radio galaxies, we extend to a high redshift our analytical model for the propagation of relativistic beams first through a hot gaseous halo of the parent elliptical galaxy and then through an even hotter, but less dense, diffuse IGM, after crossing a pressure-matched interface between the two media1–5. This model, verified by quasi-hydrodynamical numerical simulations5 has earlier explained: (1) the current mean size of classical double radio sources (D ∼350 kpc), (2) their steep linear-size evolution with redshift, z: D α (1+z)−3, (3). The correlation between size and radio luminosity (at fixed z): D α P0.3, (4) the number and <P> of giant radio galaxies, and (5) the break in the local radio luminosity function (LRLF), occurring near P ∼1024W.Hz−1 at 1 GHz (Ho = 50 kms−1 Mpc−1). Inputs to the model are observationally based average parameters of the halo1 {kTh ∼1 keV, n(r) ∼10−2cm−3[1+(r/2kpc)2]−3/4}, IGM7 {kTIGM ∼18 keV (1+z)2, nIGM ∼7.10−7cm−3(1+z)3} and the beam4 {opening angle θ (radian) = 0.02 + 0.03 [29 - log P(t=0)]}. We assume a reasonable value of ∊ = 0.1 for the initial efficiency of conversion of the beam power, Lb (Watts) into (total) radio output Pt ∼1010. P(W.Hz−1). A gradual weakening of magnetic field within the expanding source raises the significance of inverse Compton losses against the Cosmic Microwave Background (CMB), leading to a reduced radio efficiency (RRE)3,2.

Laboratory studies have been made on molecules of astrophysical interest such as AlO, CO, CrO, SiS, NH+ and OH. Vibrational and rotational constants have been determined more accurately in the various electronic states.

We have observed 11 radio quiet QSOs (RQQSOs) to see if they exhibit intranight variability in the optical. The detection of such microvariability would support models in which fluctuations on accretion disks are dominant, while if it is never present, models based on relativistic jets would be favored. Although several of these RQQSOs show hints of microvariability, we cannot claim to have discovered this phenomenon in this class of objects. Several of the comparison stars have clearly shown rapid variability.

Discovery of a diffuse ultra-steep spectrum radio source of size ∼ 0.3 Mpc, possibly a radio halo, in a cluster of galaxies at z = 0.13 is reported hilighting the presence of a giant radio spiral within the halo.

Optical components such as lenses, glass windows, and prisms are subject to Fresnel reflection due to the mismatch between the refractive indices of the air and glass. An optical interface layer, i.e., antireflection (AR) layer, is needed to eliminate this unwanted reflection at the air/glass interface. Nanostructured broadband and wide-angle AR structures have been developed using a scalable self-assembly process. Ultra-high performance of the nanostructured AR coatings has been demonstrated on various substrates such as quartz, sapphire, polymer, and other materials typically employed in optical lenses. AR coatings on polycarbonate lead to optical transmittance enhancement from approximately 90% to almost 100% for the entire visible, and part of the near-infrared (NIR), band. The AR coatings have also been demonstrated on curved surfaces. AR coatings on n-BK7 lenses enable ultra-high light transmittance for the entire visible, and most of the NIR, spectrum. Nanostructured oxide layers with step-graded index profiles, deposited onto the optical elements of an optical system, can significantly increase sensitivity, and hence improve the overall performance of the system.

This research consists mainly of introducing the hydroarchaeological method, especially as related to issues of drought. The article outlines how this multidisciplinary method can provide insights into the success and failures of an archaeological site, in this case the Maya site of Palenque. We also detail convincing evidence that shows that the Maya of Palenque did not leave their city because of deficiencies of water, as some paleoclimatologists and archaeologists have asserted. The first logical step toward understanding any settlement’s water system is to use basic hydrologic methods and theory and to understand the local watershed. There is great potential for watershed-climate modeling in developing plausible scenarios of water use and supply and of the effect of extreme conditions (flood and drought), all of which cannot be fully represented by atmosphere-based climate and weather projections. The research demonstrates how the local watershed, land-use, and ecological conditions interact with regional climate changes. The archaeological implications for this noninvasive “virtual” method are many, including detecting periods of stress within a community, estimating population by developing caps based on the availability of water, and understanding settlement patterns, as well as assisting present local populations in understanding their water cycle.

We present a model for dislocation array image effects during epilayer island growth. Misfit dislocations often appear at an interface between phases, to accommodate a lattice mismatch. In many situations, such as early film growth, one of the phases may be discontinuous, leaving the interface region clearly bounded. The structure of such a finite interface differs from the normally-modeled infinite boundary because of end effects near the edges of the islands. We have modeled the dislocation structure of such a finite interface in MBE-grown InAs islands on GaP, and compare our results to high-resolution images of the same structure. The 11% misfit causes dislocation introduction from the outset of growth. Islands containing between 4 and 14 dislocations were examined, and dislocation spacings were found to be enlarged near the island perimeters. The model provides a clear understanding of this and other effects.

Wafer bonding is an emerging technology for fabrication of complex three-dimensional (3D) structures; particularly it enables monolithic wafer-level 3D integration of high performance, multi-function microelectronic systems. For such a 3D integrated circuits, low-temperature wafer bonding is required to be compatible with the back-end-of-the-line processing conditions. Recently our investigation on surface melting characteristics of copper nanorod arrays showed that the threshold of the morphological changes of the nano-rod arrays occurs at a temperature significantly below the copper bulk melting point. With this unique property of the copper nanorod arrays, wafer bonding using copper nanorod arrays as a bonding intermediate layer was investigated at low temperatures (400 °C and lower). 200 mm Wafers, each with a copper nanorod array layer, were bonded at 200 – 400 °C and with a bonding down-force of 10 kN in a vacuum chamber. Bonding results were evaluated by razor blade test, mechanical grinding and polishing, and cross-section imaging using a focus ion beam/scanning electron microscope (FIB/SEM). The FIB/SEM images show that the copper nanorod arrays fused together accompanying by a grain growth at a bonding temperature of as low as 200 °C. A dense copper bonding layer was achieved at 400 °C where copper grains grew throughout the copper structure and the original bonding interface was eliminated. The sintering of such nanostructures depends not only on their feature size, but also significantly influenced by the bonding pressure. These two factors both contribute to the mass transport in the nanostructure, leading to the formation of a dense bonding layer.

(2-Methoxy)ethoxy substituted anilines have been polymerized by chemical and electrochemical methods in hydrochloric acid (HC1) and p-toluenesulphonic acid(TsOH). Electrical conductivity, optical properties, solubility and charge capacity of these polymers are discussed.

A modification of the jogged-screw model has been adopted recently by the authors to explain observations of 1/2[110]-type jogged-screw dislocations in equiaxed Ti-48Al under creep conditions. The aim of this study has been to verify and validate the parameters and functional dependencies that have been assumed in this previous work. The original solution has been reformulated to take into account the finite length of the moving jog. This is a better approximation of the tall jog. The substructural model parameters have been further investigated in light of the Finite Length Moving Line (FLML) source approximation. The original model assumes that the critical jog height (beyond which the jog is not dragged) is inversely proportional to the applied stress. By accounting for the fact that there are three competing mechanisms (jog dragging, dipole dragging, dipole bypass) possible, we can arrive at a modified critical jog height. The critical jog height was found to be more strongly stress dependent than assumed previously. The original model assumes the jog spacing to be invariant over the stress range. However, dynamic simulation using a line tension model has shown that the jog spacing is inversely proportional to the applied stress. This has also been confirmed by TEM measurements of jog spacings over a range of stresses. Taylor's expression assumed previously to provide the dependence of dislocation density on the applied stress, has now been confirmed by actual dislocation density measurements. Combining all of these parameters and dependencies, derived both from experiment and theory, leads to an excellent prediction of creep rates and stress exponents. The further application of this model to other materials, and the important role of atomistic and dislocation dynamics simulations in its continued development is also discussed.

A modification of the classic jogged-screw model has been previously adopted to explain observations of 1/2[110]-type jogged-screw dislocations in equiaxed Ti-48Al under creep conditions. The aim of this study has been to verify and validate the parameters and functional dependencies that have been assumed in that model. The original solution has been reformulated to take into account the finite length of the moving jog. This is a better approximation of the tall jog. The substructural model parameters have been further investigated in light of the Finite Length Moving Line (FLML) source approximation. The original model assumes that the critical jog height (beyond which the jog is not dragged) is inversely proportional to the applied stress. By accounting for the fact that there are three competing mechanisms (jog dragging, dipole dragging, dipole bypass) possible, we can arrive at a modified critical jog height. The critical jog height was found to be more strongly stress dependent than assumed previously. The original model assumes the jog spacing to be invariant over the stress range. However, dynamic simulation using a line tension model has shown that the jog spacing is inversely proportional to the applied stress. This has also been confirmed by TEM measurements of jog spacings over a range of stresses. Taylor's expression assumed previously to provide the dependence of dislocation density on the applied stress, has now been confirmed by actual dislocation density measurements. Combining all of these parameters and dependencies, derived both from experiment and theory, leads to an excellent prediction of creep rates and stress exponents.

We have investigated the direct growth of narrow-gap InAs on wide-gap GaP by Molecular Beam Epitaxy. InAs and GaP have the largest mismatch among all the III-arsenides and the III-phosphides – 11%. A perfect epitaxial relationship is maintained between the InAs and the GaP despite the large lattice mismatch. Moreover, a reproducible defect structure with unique electronic properties is developed at the heterointerface. A point defect associated with the intersection of 90° misfit dislocations may act as an ordered, structural dopant. This dopant is fully ionized with a constant, high sheet carrier density of 1013 cm−2, independent of InAs layer thickness, and exhibits no freeze out even at 5 K. Device applications for such a system include temperature insensitive Hall sensors. We have also demonstrated high electron mobilities (over 10000 cm2/V-sec) in nominally undoped thick InAs layers grown on GaP. The explanation of this effect is presented to emphasize the exciting possibilities of band gap engineering in this system.

InAs is a narrow band gap semiconductor with potential for such applications as IR detectors, low temperature transistors, etc‥ However, the lack of suitable substrates has hampered progress in the development of InAs based devices. In the present study, InAs was grown by Molecular Beam Epitaxy on (001) GaP substrates. Though this system has a high lattice mismatch, (∼11%), certain MBE growth conditions result in 80% relaxed InAs layers on GaP with the mismatch accommodated predominantly by 90° pure edge dislocations. Misfit dislocation microstructures were studied using Transmission Electron Microscopy. Electrical characterization using lateral conductance and Hall effect measurements were also performed. Preliminary results indicate the possibility of misfit dislocation related conductivity. The possible correlation between interface structure and electrical properties is discussed.

Mismatch stress relaxation mechanisms in bilayer films of (In, Al)As on InAs on GaP have been examined. Initial edge (90°) misfit dislocations at the InAs/GaP interface appear to be introduced directly at island edges during initial stages of growth. The incomplete mismatch compensation is taken up by later introduction of glissile (60°) dislocations, usually in pairs which combine to form edge dislocations. The edge dislocations in the interface then move laterally to equalize their spacings. The upper (In, Al)As capping layer, which is tensile strained to match the relaxed InAs, exhibits a different mechanism of misfit dislocation introduction. Threading dislocations move by climb, directly introducing sessile edge dislocations at the buried interface. It is believed this is the first time that this mechanism has been observed.