Determinants of World Demand for U.S. Corn Seeds: The Role of Trade Costs

The United States is a large net exporter of corn seeds. Seed trade, including that of corn, has been expanding, but its determinants are not well understood. This paper econometrically investigates the determinants of world demand for U.S. corn seeds with a detailed analysis of trade costs impeding export flows to various markets, including costs associated with distance, tariffs, and sanitary and phytosanitary (SPS) regulations. The analysis relies on a gravity-like model based on an explicit specification of derived demand for seed by foreign corn producers, estimated based on data from 48 countries and for the years 1989 to 2004. An SPS count variable is incorporated as a shifter in the unit cost of seeds faced by foreign users. A sample selection framework is used to account for the determination of which trade flows are positive. All trade costs matter and have had a negative impact on U.S. corn seed exports. Tariffs matter most, followed by distance and SPS measures. �

Multiband Detectors and Application of Nanostructured Anti-Reflection Coatings for Improved Efficiency

This work describes multiband photon detection techniques based on novel semiconductor device concepts and detector designs with simultaneous detection of dierent wavelength radiation such as UV and IR. One aim of this investigation is to examine UV and IR detection concepts with a view to resolve some of the issues of existing IR detectors such as high dark current, non uniformity, and low operating temperature and to avoid having additional optical components such as filters in multiband detection. Structures were fabricated to demonstrate the UV and IR detection concepts and determine detector parameters: (i) UV/IR detection based on GaN/AlGaN heterostructures, (ii) Optical characterization of p-type InP thin films were carried out with the idea of developing InP based detectors, (iii) Intervalence band transitions in InGaAsP/InP heterojunction interfacial workfunction internal photoemission (HEIWIP) detectors. Device concepts, detector structures, and experimental results are discussed. In order to reduce reflection, TiO2 and SiO2 nanostructured thin film characterization and application of these as anti-reflection coatings on above mentioned detectors is also discussed

Sustainable road construction with compressed stabilized Earth

Heat island effect has been given significant recognition in LEED certification process. The idea is to reduce the heat island effect to minimize impacts on micro climates and human and wild life habitats. In this context, it is useful to have roads with Solar Reflectance Index of more than 29% and also less than 50% impervious. Cement stabilized earth has the potential to satisfy this requirement as an alternative to asphalt paved roads. This paper describes some field experience gained while constructing a cement stabilized earth road with adequate strength and durability

Bio-electrosprayed human neural stem cells are viable and maintain their differentiation potential [version 2; peer review: 2 approved, 1 approved with reservations]

BACKGROUND: Bio-electrospray (BES) is a jet-based delivery system driven by an electric field that has the ability to form micro to nano-sized droplets. It holds great potential as a tissue engineering tool as it can be used to place cells into specific patterns. As the human central nervous system (CNS) cannot be studied in vivo at the cellular and molecular level, in vitro CNS models are needed. Human neural stem cells (hNSCs) are the CNS building block as they can generate both neurones and glial cells. METHODS: Here we assessed for the first time how hNSCs respond to BES. To this purpose, different hNSC lines were sprayed at 10 kV and their ability to survive, grow and differentiate was assessed at different time points. RESULTS: BES induced only a small and transient decrease in hNSC metabolic activity, from which the cells recovered by day 6, and no significant increase in cell death was observed, as assessed by flow cytometry. Furthermore, bio-electrosprayed hNSCs differentiated as efficiently as controls into neurones, astrocytes and oligodendrocytes, as shown by morphological, protein and gene expression analysis. CONCLUSIONS: This study highlights the robustness of hNSCs and identifies BES as a suitable technology that could be developed for the direct deposition of these cells in specific locations and configurations

Strategies for Planning Mould Free Air Conditioned Buildings in Tropical Climates

Buildings constructed in tropical climatic conditions must be designed to have a very low carbon foot print that will need the buildings to be used as free running while ensuring adequate thermal comfort with passive means. However, there could be certain instances when the use of active means of thermal comfort like air conditioning will be inevitable due to special requirements. Hospital buildings or buildings with special equipment would need lower indoor temperature like 15 - 18 °C compared to the ambient temperature in tropical climates. Thus, the growth of mould on the building elements such as walls and floors of the surrounding areas will be inevitable unless special planning provisions have been used with strategically placed buffer zones that will have normal air conditioning which maintains indoors with relatively lower levels of moisture content. Mould created on various building elements can produce spores, air-bome particles and gases which are harmful to the humans and built environments. In order to identify the magnitude and the causes for mould growth, a comprehensive research was carried out with a case study in a hospital building planned without attention to much detail and hence led to a severe growth of mould, where several concerns were raised by the occupants of the building, related to sick building syndrome. This will shed light on special planning precautions that must be taken by the architects and engineers who plan buildings with specially air conditioned spaces in large buildings located in countries with tropical climatic conditions

Embodied energy of alternative building materials and their impact on life cycle cost parameters

House construction all over the world is in need of many alternative building materials since the conventional materials are in short supply and also cause degradation of the environment as in clay, sand and coral mining. For popularization of alternative materials, it is necessary to ensure that they are generally cost effective. However, the cost effectiveness should not only be based on initial capital cost but the whole life cycle costing. This will include the cost of energy used in the production stage of such building materials, cost of casting and the energy used in the life span of the building usage. This research has investigated and developed the embodied energy of different building materials. This study also included the performance of different materials on operational energy. It is shown that the alternative building materials and systems would have either reduced or similar impact on life cycle cost, compared to the conventional building materials

Effect of masonry bond pattern on indoor thermal comfort

In order to make the houses aesthetically more appealing, different bond patterns are used in bonded masonry. This is mainly done in brick masonry. In some cases, walls are left unplastered to expose the brickwork bonded with different patterns. This paper presents a study on performance of commonly used bond patterns in Sri Lanka such as English, Flemish and Rat-trap. Indoor thermal performance of different bond patterns was assessed by measuring indoor and outdoor temperature using physical models. Rat-trap bond shows better thermal performance compared to the others. Computer models were validated with the results achieved from the experimental program. With all these findings, now the house builders, architects and engineers can select the masonry bond pattern suitable for their structures with the proper understanding of its performance.Senate Research Grant, University of Moratuw