1,721,427 research outputs found
PET imaging in endocrine disorders PET clinics
No full textThis issue of PET Clinics reviews the latest advances in the issue of PET imaging for the diagnosis, assesment, and follow up of cancencer of endocrine system. Cancers of the thyroid gland and adrenal glands are discussed with special empasis on medullary thyroid cancer. Also covered in this issue are PET and the parathyroid, PET and pheochromocytoma, and PET and hyperinsulinism
Electrical-conductivity calculation in ab initio simulations of metals: Application to liquid sodium
No full textWe describe a calculation of the electrical conductivity in ab initio simulations of liquid sodium, using the Kubo-Greenwood formula for the optical conductivity and the molecular-dynamics scheme;based on finite-temperature density functional theory. The effect of different Brillouin-zone samplings and that of the finite size of the system have been extensively studied at different temperatures. Close to the melting point, even with an adequate sampling of the Brillouin zone, our results exhibit a large discrepancy between theory and experiment. This is much reduced at higher temperatures. The possible reasons for this behavior are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
PET/CT in Neuroendocrine Tumors: evaluation of receptor status and metabolism
No full textDiagnosis of neuroendocrine tumors: Histopatology, biochemical investigation, structural imaging.
Positron emission tomografy radiopharmaceutical: Receptor-targeting radiopharmaceuticals, metavolism-targeted radiopharmaceuticals, imaging protocols.
Indications for positron emission tomografy/CT: diagnosis, stating and restating; detection of unknown primary tumor, therapy stratification, evaluation of therapy response.
Role of metabolic positron emission tomografy/CT
Ab initio molecular dynamics simulation of laser melting of silicon
No full textThe method of ab initio molecular dynamics, based on finite temperature density functional theory, is used to simulate laser heating of crystal silicon. We have found that a high concentration of excited electrons dramatically weakens the covalent bond. As a result, the system undergoes a melting transition to a metallic state. In contrast to ordinary liquid silicon, the new liquid is characterized by a high coordination number and a strong reduction of covalent bonding effects
Structural, dynamical, electronic, and bonding properties of laser-heated silicon: An ab initio molecular-dynamics study
No full textThe method of ab initio molecular dynamics, based on finite-temperature density-functional theory, is used to simulate laser heating of crystalline silicon. We found that a high concentration of excited electrons dramatically weakens the covalent bonding. As a result the system undergoes a melting transition to a metallic state. We studied several structural, dynamical, electronic, and bonding properties of this phase of silicon. In contrast to ordinary liquid silicon, this liquid is characterized by a high coordination number and a strong reduction of covalent-bonding effects. However this phase is transient. In fact, by strongly reducing the level of electronic excitation, liquid silicon reverts very rapidly to its usual properties
Nonmetal-metal transition in metal–molten-salt solutions
No full textThe method of ab initio molecular dynamics, based on finite-temperature density-functional theory, is used to study the nonmetal-metal transition in two different metal–molten-salt solutions, Kx(KCl)1-x and Nax(NaBr)1-x. As the excess metal concentration is increased the electronic density becomes delocalized and percolating conducting paths are formed, making a significant dc electrical conductivity possible. This marks the onset of the metallic regime. By calculating several electronic and structural properties, remarkable differences between the two solutions are observed. The anomalous behavior of Nax(NaBr)1-x, typical of all the Na-NaX solutions, is found to be related to the strong attractive interaction between the sodium ions and the excess electrons
Hot electrons and the approach to metallic behavior in Kx(KCl)1-x
No full textThe approach to the metallic phase of molten Kx(KCl)1-x mixtures is studied using ab initio molecular dynamics based on finite-temperature density functional theory. The finite electronic temperature is found to result in new and unexpected effects. In particular, we observe a thermally induced lowering of the predicted DC conductivity, which greatly improves the agreement with the experiment, and a widening of the HOMO-LUMO energy gap. We expect that these are genuinely new physical effects which could be observed also in other systems
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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