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High-quality data from appropriate archives are needed for the continuing improvement of radiocarbon calibration curves. We discuss here the basic assumptions behind 14C dating that necessitate calibration and the relative strengths and weaknesses of archives from which calibration data are obtained. We also highlight the procedures, problems, and uncertainties involved in determining atmospheric and surface ocean 14C/12C in these archives, including a discussion of the various methods used to derive an independent absolute timescale and uncertainty. The types of data required for the current IntCal database and calibration curve model are tabulated with examples.
The IntCal09 and Marine09 radiocarbon calibration curves have been revised utilizing newly available and updated data sets from 14C measurements on tree rings, plant macrofossils, speleothems, corals, and foraminifera. The calibration curves were derived from the data using the random walk model (RWM) used to generate IntCal09 and Marine09, which has been revised to account for additional uncertainties and error structures. The new curves were ratified at the 21st International Radiocarbon conference in July 2012 and are available as Supplemental Material at www.radiocarbon.org. The database can be accessed at http://intcal.qub.ac.uk/intcal13/.
Reducing the delay of backend interconnects is critical in delivering improved performance in next generation computer chips. One option is to implement interlayer dielectric (ILD) materials with increasingly lower dielectric constant (k) values. Despite industry need, there has been a recent decrease in study and production of these materials in academia and business communities. We have generated a backbone and porogen system that allows us to control porosity from 0 to 60% volume, achieve k-values from 3.4 to 1.6, maintain high chemical stability to various wet cleans, and deliver uniquely high mechanical strength at a given porosity. Finite element modeling and experimental results demonstrate that further improvements can be achieved through control of the pore volume into an ordered network. With hopes to spur more materials development, this paper discusses some molecular design and nanoscale hierarchical principles relevant to making next generation low-k ILD materials.
Geothermal energy has the potential to provide long-term, secure base-load energy and greenhouse gas (GHG) emissions reductions. Accessible geothermal energy from the Earth's interior supplies heat for direct use and to generate electric energy. Climate change is not expected to have any major impacts on the effectiveness of geothermal energy utilization, but the widespread deployment of geothermal energy could play a meaningful role in mitigating climate change. In electricity applications, the commercialization and use of engineered (or enhanced) geothermal systems (EGS) may play a central role in establishing the size of the contribution of geothermal energy to long-term GHG emissions reductions.
The natural replenishment of heat from earth processes and modern reservoir management techniques enable the sustainable use of geothermal energy as a low-emission, renewable resource. With appropriate resource management, the tapped heat from an active reservoir is continuously restored by natural heat production, conduction and convection from surrounding hotter regions, and the extracted geothermal fluids are replenished by natural recharge and by injection of the depleted (cooled) fluids.
Global geothermal technical potential is comparable to global primary energy supply in 2008. For electricity generation, the technical potential of geothermal energy is estimated to be between 118 EJ/yr (to 3 km depth) and 1,109 EJ/yr (to 10 km depth). For direct thermal uses, the technical potential is estimated to range from 10 to 312 EJ/yr. The heat extracted to achieve these technical potentials can be fully or partially replenished over the long term by the continental terrestrial heat flow of 315 EJ/yr at an average flux of 65 mW/m2.
In this book, first published in 2006, seven internationally renowned writers address the theme of Power from the perspective of their own disciplines. Energy expert Mary Archer begins with an exploration of the power sources of our future. Astronomer Neil Tyson leads a tour of the orders of magnitude in the cosmos. Mathematician and inventor of the Game of Life John Conway demonstrates the power of simple ideas in mathematics. Screenwriter Maureen Thomas explains the mechanisms of narrative power in the media of film and videogames, Elisabeth Bronfen the emotional power carried by representations of life and death, and Derek Scott the power of patriotic music and the mysterious Mozart effect. Finally, celebrated parliamentarian Tony Benn critically assesses the reality of power and democracy in society.
Space, time and power are fundamentals of physics that determine the dynamic structure of our lives. Recent publications from the Darwin College Lecture Series have addressed two of these topics: Space in the 2001 lecture series and Time in 2000. Each of those volumes included a range of perspectives that span the arts, humanities and sciences. Now, in this new volume, we have invited seven international authorities to analyse and interpret the theme of Power as it is understood in their different fields of learning. The subjects that they consider include not only the sources of power that humanity has at its disposal, but also the forms of power that are exerted over us by cultural products and societies.
Life on earth, and of course all human activity, depends on the availability of sufficient power to support that activity. Mary Archer starts our exploration of power by considering where this power comes from. Drawing both on her academic work as a researcher in chemistry and Professor of Energy Policy, and on her public life including presidency of the National Energy Foundation, Archer reviews and forecasts human power usage and supply. Her chapter on the future of sustainable power sources addresses the rate with which we consume fossil fuel resources, and the alternatives that might supply the hundreds of exajoules we consume each year.
We isolated over 650 yeasts over a three year period from the gut of a variety of beetles and characterized them on the basis of LSU rDNA sequences and morphological and metabolic traits. Of these, at least 200 were undescribed taxa, a number equivalent to almost 30% of all currently recognized yeast species. A Bayesian analysis of species discovery rates predicts further sampling of previously sampled habitats could easily produce another 100 species. The sampled habitat is, thereby, estimated to contain well over half as many more species as are currently known worldwide. The beetle gut yeasts occur in 45 independent lineages scattered across the yeast phylogenetic tree, often in clusters. The distribution suggests that the some of the yeasts diversified by a process of horizontal transmission in the habitats and subsequent specialization in association with insect hosts. Evidence of specialization comes from consistent associations over time and broad geographical ranges of certain yeast and beetle species. The discovery of high yeast diversity in a previously unexplored habitat is a first step toward investigating the basis of the interactions and their impact in relation to ecology and evolution.
Information concerning parasite genomes will be
fundamental to the future directions of parasitology
research in the new millennium. Already the complete
sequences of numerous pathogenic bacteria
are available to the scientific community. These
sequences contain essential information and clues
on drug targets and vaccine candidates and will
eventually help to unravel the mechanisms whereby
pathogens succeed in their often complex and
intricate life cycles. The void between a complete
genome sequence of a pathogenic organism and the
tools for its control might be truly enormous but the
sequence provides the essential foundation for future
study. Considerable progress has been made over the
last five years to transfer genome technologies to
eukaryotic pathogens and it was timely for the
British Society for Parasitology to consider parasite
genome research at the Autumn Symposium in
September 1998. The meeting provided the opportunity to
consider the rapid progress being made
in various parasite genome projects, bioinformatics
of genome analysis (including availability and access)
and the exciting possibilities for research in the post-genomic era.
Critics argue that shelf registration greatly reduces the ability of underwriters to perform adequate due diligence. This argument suggests underwriters will demand greater compensation for shelf issues compared to such traditional issues as an insurance premium for protection against potential litigation or loss of reputation caused by inadequate due diligence. Our findings suggest the presence of such a premium, that the premium is higher for firms with higher expected due diligence liabilities, and that underwriters perceive that shelf registration erodes due diligence and, subsequently, price the due diligence erosion accordingly. This pricing behavior is consistent with our findings that firms with higher expected due diligence liabilities are more likely to choose traditional registration.
1. In 1923 Eggenberger and Pólya introduced the following ‘urn scheme’ as a model for the development of a contagious phenomenon. A box contains b black and r red balls, and a ball is drawn from it at random with ‘double replacement’ (i.e. whatever ball is drawn, it is returned to the box together with a fresh ball of the same colour); the procedure is then continued indefinitely. A slightly more complicated version with m-fold replacement is sometimes discussed, but it will be sufficient for our purposes to keep m = 2 and it will be convenient further to simplify the scheme by taking b = r = 1 as the initial condition. We shall however generalise the scheme in another direction by allowing an arbitrary number k(≧2) of colours. Thus initially the box will contain k differently coloured balls and successive random drawings will be followed by double replacement as before. We write sn (a k-vector with jth component ) for the numerical composition of the box immediately after the nth replacement, so that and we observe that is a Markov process for which the state-space consists of all ordered k-ads of positive integers, the (constant) transition-probability matrix having elements determined by
where Sn is the sum of the components of sn and (e(i))j = δij. We shall calculate the Martin boundary for this Markov process, and point out some applications to stochastic models for population growth.
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