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A system is described whereby X-ray fluorescence analysis of elements below atomic number 19 (potassium) is undertaken with a “windowless” demountable X-ray tube. Comparison is made with 100-μ- and 30-μ-thick beryllium windows- Deflection plates are required before or behind the sample to eliminate scattered electrons. A high-resolution X-ray diffractometer is also described by making use of a fine focal line on the target. Burn-through due to localized heating on the target is eliminated by using a thermocouple arrangement.
The powder diffraction x-ray technique commonly used to measure strain in polycrystalline materials requires a knowledge of the elastic constants in order to convert the strain into a stress value. For many materials, these constants are not always known. Another technique to measure strain is the x-ray lattice curvature (substrate bending) method which requires no knowledge of the film elastic constants. The strain is measured in the substrate and requires only the elastic constants of the substrate to convert the measured strain into stress. Using a combination of the powder diffraction technique and a double crystal lattice curvature technique, the elastic constants of TaSi2 and WSi2 have been determined for various crystallographic directions.
We report major new insights from recent research at the Powars II Paleoindian red ocher quarry (48PL330). We salvaged more than 7,000 artifacts from Powars II between 2014 and 2016 by screening redeposited sediment from the talus slope below the intact portion of the site. Clovis artifacts dominate the diagnostic artifact assemblage, including 53 Clovis points, 33 preforms, and artifacts associated with a previously unrecognized blade core industry. We report the first radiocarbon dates from the site, determined from dating bone tools, which indicate Cody-aged use (ca. >10,000 cal BP). Further, salvage efforts discovered a previously unknown toolstone source from which many of the Clovis artifacts were produced. The Powars II Clovis points most resemble early Paleoindian points from the far Northern Plains and were likely both produced and discarded in the red ocher quarry after hunting, as evidenced by preform production and the presence of impact fractures on many used points. Given these production and discard patterns, Powars II holds some of the best evidence archaeologists currently have for Paleoindian ritualism related to hunting.
In 2012 Ghana passed a new Mental Health Act, which aimed to create a new system of mental healthcare in Ghana. The Act includes provisions for the creation of a modern, community-based mental health system and for the protection of the rights of persons with mental disorders. This article discusses the implications of the Act and the progress which has been made towards its implementation.
The concept of information has penetrated almost all areas of human inquiry, from physics, chemistry, and engineering through biology to the social sciences. And yet its status as a physical entity remains obscure. Traditionally, information has been treated as a derived or secondary concept. In physics especially, the fundamental bedrock of reality is normally vested in the material building blocks of the universe, be they particles, strings, or fields. Because bits of information are always instantiated in material degrees of freedom, the properties of information could, it seems, always be reduced to those of the material substrate. Nevertheless, over several decades there have been attempts to invert this interdependence and root reality in information rather than matter. This contrarian perspective is most famously associated with the name of John Archibald Wheeler, who encapsulated his proposal in the pithy dictum ‘it from bit?’ (Wheeler, 1999).
In a practical, everyday sense, information is often treated as a primary entity, as a ‘thing in its own right’ with a measure of autonomy; indeed, it is bought and sold as a commodity alongside gas and steel. In the life sciences, informational narratives are indispensable: biologists talk about the genetic code, about translation and transcription, about chemical signals and sensory data processing, all of which treat information as the currency of activity, the ‘oil’ that makes the ‘biological wheels go round’. The burgeoning fields of genomic and metagenomic sequencing and bioinformatics are based on the notion that informational bits are literally vital. But beneath this familiar practicality lies a stark paradox. If information makes a difference in the physical world, which it surely does, then should we not attribute to it causal powers? However, in physics causation is invariably understood at the level of particle and field interactions, not in the realm of abstract bits (or qubits, their quantum counterparts). Can we have both? Can two causal chains coexist compatibly? Are the twin narratives of material causation and informational causation comfortable bedfellows? If so, what are the laws and principles governing informational dynamics to place alongside the laws of material dynamics?
Recent advances suggest that the concept of information might hold the key to unravelling the mystery of life's nature and origin. Fresh insights from a broad and authoritative range of articulate and respected experts focus on the transition from matter to life, and hence reconcile the deep conceptual schism between the way we describe physical and biological systems. A unique cross-disciplinary perspective, drawing on expertise from philosophy, biology, chemistry, physics, and cognitive and social sciences, provides a new way to look at the deepest questions of our existence. This book addresses the role of information in life, and how it can make a difference to what we know about the world. Students, researchers, and all those interested in what life is and how it began will gain insights into the nature of life and its origins that touch on nearly every domain of science.