118 research outputs found
The Chivay Obsidian Source and the Geological Origin of Titicaca Basin Type Obsidian Artifacts
Instabilities in crystal growth by atomic or molecular beams
The planar front of a growing a crystal is often destroyed by instabilities.
In the case of growth from a condensed phase, the most frequent ones are
diffusion instabilities, which will be but briefly discussed in simple terms in
chapter II. The present review is mainly devoted to instabilities which arise
in ballistic growth, especially Molecular Beam Epitaxy (MBE). The reasons of
the instabilities can be geometric (shadowing effect), but they are mostly
kinetic or thermodynamic. The kinetic instabilities which will be studied in
detail in chapters IV and V result from the fact that adatoms diffusing on a
surface do not easily cross steps (Ehrlich-Schwoebel or ES effect). When the
growth front is a high symmetry surface, the ES effect produces mounds which
often coarsen in time according to power laws. When the growth front is a
stepped surface, the ES effect initially produces a meandering of the steps,
which eventually may also give rise to mounds. Kinetic instabilities can
usually be avoided by raising the temperature, but this favours thermodynamic
instabilities. Concerning these ones, the attention will be focussed on the
instabilities resulting from slightly different lattice constants of the
substrate and the adsorbate. They can take the following forms. i) Formation of
misfit dislocations (chapter VIII). ii) Formation of isolated epitaxial
clusters which, at least in their earliest form, are `coherent' with the
substrate, i.e. dislocation-free (chapter X). iii) Wavy deformation of the
surface, which is presumably the incipient stage of (ii) (chapter IX). The
theories and the experiments are critically reviewed and their comparison is
qualitatively satisfactory although some important questions have not yet
received a complete answer.Comment: 90 pages in revtex, 45 figures mainly in gif format. Review paper to
be published in Physics Reports. Postscript versions for all the figures can
be found at http://www.theo-phys.uni-essen.de/tp/u/politi
The management of acute venous thromboembolism in clinical practice. Results from the European PREFER in VTE Registry
Venous thromboembolism (VTE) is a significant cause of morbidity and mortality in Europe. Data from real-world registries are necessary, as clinical trials do not represent the full spectrum of VTE patients seen in clinical practice. We aimed to document the epidemiology, management and outcomes of VTE using data from a large, observational database. PREFER in VTE was an international, non-interventional disease registry conducted between January 2013 and July 2015 in primary and secondary care across seven European countries. Consecutive patients with acute VTE were documented and followed up over 12 months. PREFER in VTE included 3,455 patients with a mean age of 60.8 ± 17.0 years. Overall, 53.0 % were male. The majority of patients were assessed in the hospital setting as inpatients or outpatients (78.5 %). The diagnosis was deep-vein thrombosis (DVT) in 59.5 % and pulmonary embolism (PE) in 40.5 %. The most common comorbidities were the various types of cardiovascular disease (excluding hypertension; 45.5 %), hypertension (42.3 %) and dyslipidaemia (21.1 %). Following the index VTE, a large proportion of patients received initial therapy with heparin (73.2 %), almost half received a vitamin K antagonist (48.7 %) and nearly a quarter received a DOAC (24.5 %). Almost a quarter of all presentations were for recurrent VTE, with >80 % of previous episodes having occurred more than 12 months prior to baseline. In conclusion, PREFER in VTE has provided contemporary insights into VTE patients and their real-world management, including their baseline characteristics, risk factors, disease history, symptoms and signs, initial therapy and outcomes
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RESULTS OF A DATING ATTEMPT -CHEMICAL AND PHYSICAL MEASUREMENTS RELEVANT TO THE CASE OF THE CRETACEOUS TERTIARY EXTINCTIONS
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University of California Radiation Laboratory Report UCRL-9524
Figures 1 and 2 summarize total decay energies for the four radioactive series. The alpha-decay energy obtained by measuring the energy of the alpha particle leading to the ground state includes the energy of the recoil nucleus. The curve shown in figure 3 defines in broad outline the conditions and regions of alpha instability. A great deal more is to be learned from a more detailed examination of the region where alpha radioactivity is prominent. Of great value to the experimentalist is that he is able to predict alpha energies, and the agreement between predicted and measured values often serves as a criterion for isotopic assignment. A number of systems for correlating alpha decay energies have been employed, and that perhaps most widely used is illustrated in figure 4. Here the isotopes of each element on a mass number vs. energy plot are joined, resulting in a family of curves which over a wide region comprise a series of nearly parallel lines
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DECAY PROPERTIES OF Am243 AND POSSIBLE ROTATIONAL BANDS IN THE ALPHA SPECTRA OF ODD-EVEN NUCLEI
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