Effect of elevated CO2 and high temperature on seed-set and grain quality of rice

Hybrid vigour may help overcome the negative effects of climate change in rice. A popular rice hybrid (IR75217H), a heat-tolerant check (N22), and a mega-variety (IR64) were tested for tolerance of seed-set and grain quality to high-temperature stress at anthesis at ambient and elevated [CO2]. Under an ambient air temperature of 29 °C (tissue temperature 28.3 °C), elevated [CO2] increased vegetative and reproductive growth, including seed yield in all three genotypes. Seed-set was reduced by high temperature in all three genotypes, with the hybrid and IR64 equally affected and twice as sensitive as the tolerant cultivar N22. No interaction occurred between temperature and [CO2] for seed-set. The hybrid had significantly more anthesed spikelets at all temperatures than IR64 and at 29 °C this resulted in a large yield advantage. At 35 °C (tissue temperature 32.9 °C) the hybrid had a higher seed yield than IR64 due to the higher spikelet number, but at 38 °C (tissue temperature 34–35 °C) there was no yield advantage. Grain gel consistency in the hybrid and IR64 was reduced by high temperatures only at elevated [CO2], while the percentage of broken grains increased from 10% at 29 °C to 35% at 38 °C in the hybrid. It is concluded that seed-set of hybrids is susceptible to short episodes of high temperature during anthesis, but that at intermediate tissue temperatures of 32.9 °C higher spikelet number (yield potential) of the hybrid can compensate to some extent. If the heat tolerance from N22 or other tolerant donors could be transferred into hybrids, yield could be maintained under the higher temperatures predicted with climate change

Study of intermixing in a GaAs/AlGaAs quantum-well structure using doped spin-on silica layers

The effect of two different dopants, P and Ga, in spin-on glass (SOG) films on impurity-free vacancy disordering (IFVD) in GaAs/AlGaAs quantum-well structures has been investigated. It is observed that by varying the annealing and baking temperatures, P-doped SOG films created a similar amount of intermixing as the undoped SOG films. This is different from the results of other studies of P-doped SiO₂ and is ascribed to the low doping concentration of P, indicating that the doping concentration of P in the SiO₂ layer is one of the key parameters that may control intermixing. On the other hand, for all the samples encapsulated with Ga-doped SOG layers, significant suppression of the intermixing was observed, making them very promising candidates with which to achieve the selective-area defect engineering that is required for any successful application of IFVD.One of the authors (H.H.T.) acknowledges a fellowship awarded to him by the Australian Research Council

IoT enabled communication device with mixer less low complex QPSK based transmitter architecture for low frequency applications

echnological development in the area of wireless communications lead to the requirement of tight integration of both the digital and analog functional units. Integrating mixers is a challenging task, especially in mixed signal design. IoT communication devices require low design complexity as we expect millions of devices connected. In this paper we propose a mixer less low complex QPSK based transmitter architecture targeting low frequency applications which reduced the complexity in transmitter design. A prototype has been developed using Bipolar Junction Transistors (BJTs) and FPGA as the base band controller. The design can easily be adapted to MOSFET technology and modulation is achieved without the need of generating the carrier externally. The prototype developed was tested successfully by generating frequencies of range varying from 1 KHz to 120 MHz. The proposed architecture can also be used for any other digital modulation scheme such as BPSK, FSK etc

Observation of enhanced defect emission and excitonic quenching from spherically indented ZnO

The influence of spherical nanoindentation on the band edge and deep level emission of single crystal c-axis ZnO has been studied by cathodoluminescence(CL) spectroscopy and monochromatic imaging. Excitonic emission is quenched at the indent site and defect emission in the range of 450–720nm is enhanced.The authors wish to acknowledge the Australian Research Council for its financial support

Suppression of interdiffusion in GaAs/AlGaAs quantum-well structure capped with dielectric films by deposition of gallium oxide

In this work, different dielectric caps were deposited on the GaAs/AlGaAs quantum well(QW) structures followed by rapid thermal annealing to generate different degrees of interdiffusion. Deposition of a layer of GaxOy on top of these dielectric caps resulted in significant suppression of interdiffusion. In these samples, it was found that although the deposition of GaxOy and subsequent annealing caused additional injection of Ga into the SiO₂ layer, Ga atoms were still able to outdiffuse from the GaAsQW structure during annealing, to generate excess Ga vacancies. The suppression of interdiffusion with the presence of Ga vacancies was explained by the thermal stress effect which suppressed Ga vacancydiffusion during annealing. It suggests that GaxOy may therefore be used as a mask material in conjunction with other dielectric capping layers in order to control and selectively achieve impurity-free vacancy disordering.J. Wong-Leung, P. N. K. Deenapanray, and H. H. Tan acknowledge the fellowships awarded by the Australian Research Council

Effects of excitation density on cathodoluminescence from GaN

Wurtzite GaN epilayers are studied by cathodoluminescence(CL)spectroscopy. Results show that the intensities of donor–acceptor pair (DAP) and yellow luminescence (YL) peaks sublinearly depend on excitation density, presumably, due to saturation effects. The intensity of near-gap emission, however, exhibits a superlinear dependence on electron-beam excitation. In contrast to photoluminescence measurements, CL studies of GaN are usually performed in a regime with a strongly nonlinear dependence of luminescence intensities on excitation due to a large difference in carrier generation rates for these two techniques. As a result, the ratios of near-gap to YL and DAP emission intensities strongly depend on electron-beam current. Moreover, electron-beam spot size (i.e., beam focusing) dramatically affects CL intensity. An understanding of such saturation effects is necessary for a correct interpretation of CL spectra from GaN

XML Reconstruction View Selection in XML Databases: Complexity Analysis and Approximation Scheme

Query evaluation in an XML database requires reconstructing XML subtrees rooted at nodes found by an XML query. Since XML subtree reconstruction can be expensive, one approach to improve query response time is to use reconstruction views - materialized XML subtrees of an XML document, whose nodes are frequently accessed by XML queries. For this approach to be efficient, the principal requirement is a framework for view selection. In this work, we are the first to formalize and study the problem of XML reconstruction view selection. The input is a tree $T$, in which every node $i$ has a size $c_i$ and profit $p_i$, and the size limitation $C$. The target is to find a subset of subtrees rooted at nodes $i_1,\cdots, i_k$ respectively such that $c_{i_1}+\cdots +c_{i_k}\le C$, and $p_{i_1}+\cdots +p_{i_k}$ is maximal. Furthermore, there is no overlap between any two subtrees selected in the solution. We prove that this problem is NP-hard and present a fully polynomial-time approximation scheme (FPTAS) as a solution

Cathodoluminescence depth profiling of ion-implanted GaN

Cathodoluminescence(CL)spectroscopy shows that even relatively low-dose keV light-ion bombardment (corresponding to the generation of ∼5×10¹⁹ vacancies/cm³) of wurtzite GaN results in a dramatic quenching of visible CL emission. Postimplantation annealing at temperatures up to 1050 °C generally causes a partial recovery of measured CL intensities. However, CL depth profiles indicate that, in most cases, such a recovery results from CL emission from virgin GaN, beyond the implanted layer due to a reduction in the extent of light absorption within the implanted layer. In this case, CL emission from the implanted layer remains completely quenched even after such an annealing. These results show that an understanding of the effects of ion bombardment and postimplantation annealing on luminescence generation and light absorption is required for a correct interpretation of luminescencespectra of GaN optically doped by keV ion implantation

Comparative assessment of floristic structure, diversity and regeneration status of tropical rain forests of Western Ghats of Karnataka, India

Tropical forests are one of the richest landscapes in terms of its richness, diversity and endemicity. The present study was carried out in the Central Western Ghats: one of the hottest hotspot of biodiversity. The aim of the study was to compare floristic diversity in tropical wet evergreen forest between northern and southern parts of Western Ghats of Karnataka. Kodagu district in southern part and Uttara Kannada district in northern part was chosen to assess the same, as these two districts cover highest forest cover in the Western Ghats of Karnataka. In each district all the evergreen forests were sampled with 1000 m X 5 belt transacts. Totally 22 such samplings were done both southern and northern part of Western Ghats. In each of these transacts all the trees measuring e” 30 gbh were enumerated and botanically identified to the species level and the same was used for computation of diversity indices. The richness and diversity was comparatively higher in southern part compared to northern part of Western Ghats, where as the richness of threatened tree species was comparatively higher in northern part of Western Ghats. In addition to the species richness and diversity, the paper also deals with the dominant tree species and families in both the region

CULTIVATION PROSPECTS OF DENDROCALAMUS ASPER BACKER.FOR EDIBLE SHOOTS IN SEMIARID AND HUMID TROPICS OF PENINSULAR INDIA

ABSTRACT: Dendrocalamus asper also known as 'Sweet Bamboo' is the most widely accepted species globally for edible shoots. The prospects of cultivation of D.asper in humid tropics and semiarid conditions of peninsular India was assessed using various financial indicators and through quantitative and qualitative analysis of juvenile shoots. Growth parameters in on-farm field trials by IWST, Bangalore suggest that this species grows well in humid tropical conditions as compared to semi-arid conditions in Peninsular India. In semiarid conditions in Hosakote, Bangalore on an average 16 shoots were produced in a five year old clump with the average shoot diameter of 18±1.1mm and extractable volume of > 0.75 kg. In humid tropical conditions in Thithimathi, Kodagu, D. asper clumps of same age produced around 25 shoots. The average shoot diameter was 55±2mm at the end of fifth year which translated into higher volume (> 2kg) of edible portion in harvested shoots. In D.asper, 30% extraction of the total new shoots emerging from the fifth year was ideal. There was no difference in nutritional composition of the species between semiarid and humid tropics in terms of protein, carbohydrates, crude fibre and fat.Financial indicators at different discount rates (10%, 12% and 15%) suggest that cultivation of D.asper for shoot production may be a profitable venture in humid tropics with a high equivalent annual net income (EAI) around 7.6 -9 lakhs as compared to a lower EAI in semiarid conditions (0.22 to 0.59 lakhs)