Optical studies of some impact phenomena and surface hardness measurements

An introduction to the phenomena of pressure crack figures is given with special reference to static-impact figures produced on glass and diamond. The optical techniques and the apparatus used are described, including the Inter-ferometric technique used for the detection and measurement of the surface distortions for crack figures obtained first on glass, and then on diamond. The spherical impactors used were of steel (for glass), tungsten carbide and diamond (mainly for diamond). A study is made of the fracture strength properties of ten different types of optical glass and the results are compared with other properties of the glasses, including measurements of their surface hardnesses obtained by an abrading method described in the Appendix. Orientated crack figures have been produced on three different faces of diamond, the shapes being hexagonal on the octahedral and the dodecahedral faces, and square on the cubic face. For the octahedral and a cubic face, the development of these figures is studied as the load is gradually increased; and the mechanism of the crack formation and the accompanying cracking effects within the body of the crystal are discussed in terms of easy cleavage and shattering, respectively. It is found that the octahedral face is definitely the least resistant to fracture by this method, the cubic face appearing to be most resistant: also the critical stresses involved are found to be considerably less than a theoretically calculated value which indicates some form of flaw distribution over the surface analogous to the Griffith cracks for glass. It has also been seen that the octahedral face of diamond can be cracked in this way by using Tungsten Carbide or Sapphire balls, although in the latter case the tip of the ball was shattered by the occurrence of multiple slip. Both for glass and diamond, the observations obtained from the interferograms of the surface distortions is considered to offer strong evidence for the existence of micro plastic flow. No signs of micro slip could be detected in the studies on diamond except possibly in connection with the crystallo-graphic shattering which occurred internally for one test on the octahedral stone.<p

30 Years on: How the Neurodevelopmental Hypothesis of Schizophrenia Morphed into the Developmental Risk Factor Model of Psychosis

At its re-birth 30 years ago, the neurodevelopment hypothesis of schizophrenia focussed on aberrant genes and early neural hazards, but then it grew to include ideas concerning aberrant synaptic pruning in adolescence. The hypothesis had its own stormy development and it endured some difficult teenage years when a resurgence of interest in neurodegeneration threatened its survival. In early adult life, it over-reached itself with some reductionists claiming that schizophrenia was simply a neurodevelopmental disease. However, by age 30, the hypothesis has matured sufficiently to incorporated childhood and adult adversity, urban living and migration, as well as heavy cannabis use, as important risk factors. Thus, it morphed into the developmental risk factor model of psychosis and integrated new evidence concerning dysregulated striatal dopamine as the final step on the pathway linking risk factors to psychotic symptoms

Kinetic Turbulence

The weak collisionality typical of turbulence in many diffuse astrophysical plasmas invalidates an MHD description of the turbulent dynamics, motivating the development of a more comprehensive theory of kinetic turbulence. In particular, a kinetic approach is essential for the investigation of the physical mechanisms responsible for the dissipation of astrophysical turbulence and the resulting heating of the plasma. This chapter reviews the limitations of MHD turbulence theory and explains how kinetic considerations may be incorporated to obtain a kinetic theory for astrophysical plasma turbulence. Key questions about the nature of kinetic turbulence that drive current research efforts are identified. A comprehensive model of the kinetic turbulent cascade is presented, with a detailed discussion of each component of the model and a review of supporting and conflicting theoretical, numerical, and observational evidence.Comment: 31 pages, 3 figures, 99 references, Chapter 6 in A. Lazarian et al. (eds.), Magnetic Fields in Diffuse Media, Astrophysics and Space Science Library 407, Springer-Verlag Berlin Heidelberg (2015

The order parameter of the chiral Potts model

An outstanding problem in statistical mechanics is the order parameter of the chiral Potts model. An elegant conjecture for this was made in 1983. It has since been successfully tested against series expansions, but as far as the author is aware there is as yet no proof of the conjecture. Here we show that if one makes a certain analyticity assumption similar to that used to derive the free energy, then one can indeed verify the conjecture. The method is based on the ``broken rapidity line'' approach pioneered by Jimbo, Miwa and Nakayashiki.Comment: 29 pages, 7 figures. Citations made more explicit and some typos correcte

Solar Wind Turbulence and the Role of Ion Instabilities

International audienc

Who will care for the women?

Over 20 million people today, including children, working-age disabled, and elderly persons, require some sort of assistance to live safely. Largely because women live longer than men, well into the ages when the probability of needing care increases, 70 percent of elderly people who need long-term care are women. Furthermore, most long-term care is provided by women, mainly as unpaid care in the home, or as low-paid care in institutions and community settings (Stone & Weiner 2001). The United States faces a severe long-term care crisis because of the nation\u27s inability to plan for the changing demographic balance. The crisis in long term care has two problems: a) that we are putting too many resources into institutional care relative to home- and community-based care and relying too heavily on unpaid care in the home to meet the real needs of the aging population, and b) that we do not, and increasingly will not, have enough people to provide for the volume of care that will be needed in the coming decades. This chapter begins with a description of the long-term care system in the United States – what long-term care is, who needs it, in what settings it is provided, and who pays for it. Using the author\u27s analysis of a national survey of caregivers conducted by the National Alliance for Caregiving and the AARP in 2003 along with other sources, this section shows that a substantial portion of the people who need long-term care rely on unpaid care from family and friends, mainly women. When people do receive paid care, almost half – mostly women -- receive it in institutional settings. The discussion demonstrates that women are far more likely to end up in institutions than men, even controlling for age and level of impairment. It then argues that, for a number of reasons, states and the federal government will have to respond to the preferences of consumers for home- and community-based care

Spin operator matrix elements in the superintegrable chiral Potts quantum chain

We derive spin operator matrix elements between general eigenstates of the superintegrable Z_N-symmetric chiral Potts quantum chain of finite length. Our starting point is the extended Onsager algebra recently proposed by R.Baxter. For each pair of spaces (Onsager sectors) of the irreducible representations of the Onsager algebra, we calculate the spin matrix elements between the eigenstates of the Hamiltonian of the quantum chain in factorized form, up to an overall scalar factor. This factor is known for the ground state Onsager sectors. For the matrix elements between the ground states of these sectors we perform the thermodynamic limit and obtain the formula for the order parameters. For the Ising quantum chain in a transverse field (N=2 case) the factorized form for the matrix elements coincides with the corresponding expressions obtained recently by the Separation of Variables Method.Comment: 24 pages, 1 figur

The Gaia-ESO Survey: the most metal-poor stars in the Galactic bulge

We present the first results of the EMBLA survey (Extremely Metal-poor BuLge stars with AAOmega), aimed at finding metal-poor stars in the Milky Way bulge, where the oldest stars should now preferentially reside. EMBLA utilises SkyMapper photometry to pre-select metal-poor candidates, which are subsequently confirmed using AAOmega spectroscopy. We describe the discovery and analysis of four bulge giants with -2.72<=[Fe/H]<=-2.48, the lowest metallicity bulge stars studied with high-resolution spectroscopy to date. Using FLAMES/UVES spectra through the Gaia-ESO Survey we have derived abundances of twelve elements. Given the uncertainties, we find a chemical similarity between these bulge stars and halo stars of the same metallicity, although the abundance scatter may be larger, with some of the stars showing unusual [{\alpha}/Fe] ratios.Comment: 7 pages, 5 figures. Accepted for publication by MNRA

Sensory ways to indigenous multimodal literacies : Hands and feet tell the story

This chapter reports original research that asks the question: What are the ways of knowing, being, and communicating that are valued and practiced in Indigenous communities? Literacy curricula, internationally and nationally, typically do not take into account the multi-sensorial dimensions of non-Western forms of representation that go beyond narrow conceptions of print. For example, literacies are often conceived as drawing on print, visual, spatial, gestural, and audio modes, but the role of haptics and locomotion has typically received little attention. This chapter highlights examples of the multi-sensoriality of Indigenous literacies observed in participatory community research with an Indigenous school. It extends recent theories of sensory studies in the history and cultural anthropology of the senses, applying these principles to literacy education. Sensory literacies is a theoretical perspective that gives priority to the sensorial dimensions of the body and its role in communication in literacy practice, because without a sensing body, we cannot know about or communicate with the world. The data demonstrates how the forgotten role of the hands and feet in dominant theories of communication is central to Indigenous identity and literacies. Written by a white academic with an Indigenous researcher, the chapter problematises the privileging of narrow, logocentric, and Western forms of literacy and its implications for rethinking the role of the whole body in literacy and the literacy curriculum for Indigenous students