Biotechnology and Plant Productivity

Author Institution: Dept. of Biology, Case Western Reserve UniversityThere is considerable potential for the application of biotechnology and genetic engineering to plant productivity. The basic manipulations for the isolation of genes and their transfer between species are well documented in model systems. However, more information is required concerning the basic processes governing plant productivity at the molecular level before practical applications can be achieved. In this paper, detailed consideration is given to (1) the use of restriction fragment polymorphisms as genetic markers, and (2) the molecular basis of hybrid vigor. In both cases it is clear that these techniques will be adjuncts to the already established methods for plant improvement but with far reaching potential for the future

The Morphology and Misfit Dislocation Formation Characteristics of Strained Heteroepitaxial Layers: Ex Situ and In Situ Growth Studies

Under certain regimes of heteroepitaxial layer growth, misfit stresses can lead to very significant distortions in interface morphology, which can influence strain relief and subsequent misfit dislocation introduction. These phenomena have been clearly demonstrated in the case of SiGe/Si heteroepitaxy and the way in which surface SiGe growth ripples are accompanied by strain waves has been established. The ripples provide partial elastic relief of the layer misfit stress in a manner which has been correlated with theoretical expectations. The local stress variations ultimately may influence the formation and disposition of misfit dislocations in the strained layer structures. The present paper reviews primarily our understanding of these growth characteristics. It also outlines current in situ synchrotron growth studies which exploit real-time X-ray topography and diffraction to probe heteroepitaxial strain-relief processes

Anisotropic matern correlation and spatial prediction using REML

The Mat´ern correlation function provides great flexibility for modeling spatially correlated random processes in two dimensions, in particular via a smoothness parameter, whose estimation allows data to determine the degree of smoothness of a spatial process. The extension to include anisotropy provides a very general and flexible class of spatial covariance functions that can be used in a model-based approach to geostatistics, in which parameter estimation is achieved via REML and prediction is within the E-BLUP framework. In this article we develop a general class of linear mixed models using an anisotropic Mat´ern class with an extended metric. The approach is illustrated by application to soil salinity data in a rice-growing field in Australia, and to fine-scale soil pH data. It is found that anisotropy is an important aspect of both datasets, emphasizing the value of a straightforward and accessible approach to modeling anisotropy

Long excursion to the Auvergne

n/

Seventy years of sex education in Health Education Journal: a critical review

This paper examines key debates and perspectives on sex education in Health Education Journal (HEJ), from the date of the journal’s first publication in March 1943 to the present day. Matters relating to sexuality and sexual health are revealed to be integral to HEJ’s history. First published as Health and Empire (1921 – 1942), a key purpose of the journal since its inception has been to share information on venereal disease and its prevention within the UK and across the former British Empire. From 1943 to the present day, discussions on sex education in the newly-christened HEJ both reflect and respond to evolving socio-cultural attitudes towards sexuality in the UK. Changing definitions of sex education across the decades are examined, from the prevention of venereal disease and moral decline in war-time Britain in the 1940s, to a range of responses to sexual liberation in the 1960s and 1970s; from a focus on preventing sexually-transmitted infections, teenage pregnancy and HIV in the 1980s, to the provision of sexual health services alongside sex education in the 2000s. Over the past 70 years, a shift from prevention of pre-marital sexual activity to the management of its outcomes is apparent; however, while these changes over time are notable, perhaps the most striking findings of this review are the continuities in arguments for and against the discussion of sexual issues. After more than 70 years of debate, it would seem that there is little consensus concerning motivations for and the content of sex education

Interwell relaxation times in p-Si/SiGe asymmetric quantum well structures: the role of interface roughness

We report the direct determination of nonradiative lifetimes in Si∕SiGe asymmetric quantum well structures designed to access spatially indirect (diagonal) interwell transitions between heavy-hole ground states, at photon energies below the optical phonon energy. We show both experimentally and theoretically, using a six-band k∙p model and a time-domain rate equation scheme, that, for the interface quality currently achievable experimentally (with an average step height ⩾1 Å), interface roughness will dominate all other scattering processes up to about 200 K. By comparing our results obtained for two different structures we deduce that in this regime both barrier and well widths play an important role in the determination of the carrier lifetime. Comparison with recently published experimental and theoretical data obtained for mid-infrared GaAs∕AlxGa1−xAs multiple quantum well systems leads us to the conclusion that the dominant role of interface roughness scattering at low temperature is a general feature of a wide range of semiconductor heterostructures not limited to IV-IV material

Global impacts of energy demand on the freshwater resources of nations

The growing geographic disconnect between consumption of goods, the extraction and processing of resources, and the environmental impacts associated with production activities makes it crucial to factor global trade into sustainability assessments. Using an empirically validated environmentally extended global trade model, we examine the relationship between two key resources underpinning economies and human well-being—energy and freshwater. A comparison of three energy sectors (petroleum, gas, and electricity) reveals that freshwater consumption associated with gas and electricity production is largely confined within the territorial boundaries where demand originates. This finding contrasts with petroleum, which exhibits a varying ratio of territorial to international freshwater consumption, depending on the origin of demand. For example, although the United States and China have similar demand associated with the petroleum sector, international freshwater consumption is three times higher for the former than the latter. Based on mapping patterns of freshwater consumption associated with energy sectors at subnational scales, our analysis also reveals concordance between pressure on freshwater resources associated with energy production and freshwater scarcity in a number of river basins globally. These energy-driven pressures on freshwater resources in areas distant from the origin of energy demand complicate the design of policy to ensure security of fresh water and energy supply. Although much of the debate around energy is focused on greenhouse gas emissions, our findings highlight the need to consider the full range of consequences of energy production when designing policy