1,721,267 research outputs found
Geometry and physics of pseudodifferential operators on manifolds
No full textA review is made of the basic tools used in mathematics to define a
calculus for pseudodifferential operators on Riemannian manifolds endowed with a
connection: existence theorem for the function that generalizes the phase; analogue
of Taylor’s theorem; torsion and curvature terms in the symbolic calculus; the two
kinds of derivative acting on smooth sections of the cotangent bundle of the Riemannian
manifold; the concept of symbol as an equivalence class. Physical motivations
and applications are then outlined, with emphasis on Green functions of quantum
field theory and Parker’s evaluation of Hawking radiation
Towards obtaining Green functions for a Casimir cavity in de Sitter spacetime
No full textRecent work in the literature has studied rigid Casimir cavities in a weak gravitational field, or in
de Sitter spacetime, or yet other spacetime models. The present review paper studies the difficult
problem of direct evaluation of scalar Green functions for a Casimir-type apparatus in de Sitter
spacetime. Working to first order in the small parameter of the problem, i.e. twice the gravity
acceleration times the plates’ separation divided by the speed of light in vacuum, suitable
coordinates are considered for which the differential equations obeyed by the zeroth- and firstorder
Green functions can be solved in terms of special functions. This result can be used, in
turn, to obtain, via the point-split method, the regularized and renormalized energy–momentum
tensor both in the scalar case and in the physically more relevant electromagnetic case
Physiological and Pathological Role of ROS: Benefits and Limitations of Antioxidant Treatment.
No full textROS were long considered one of the key players in tissue injury. Indeed, overproduction of ROS results in oxidative stress, a process leading to the development of many pathological conditions, for the treatment of which, the use of antioxidants was proposed.
Over time, it was shown that ROS at low concentrations act as signaling molecules leading to the regulation of physiological functions. Moreover, several interventions that increase ROS generation activate stress-adaptive responses that extend the lifespan. It was also shown that excessive use of antioxidants can counter the beneficial effects of ROS.
Currently, much progress has been made in understanding the role of ROS in human diseases and aging as well as in the regulation of physiological functions, and in identifying the signaling pathways involved in ROS. However, much remains to be understood about the mutual interactions among signaling pathways underlying organism-adaptive responses, their modifications (which occur during aging), and some disease states. The aim of this special issue is underlines the effects of ROS production and antioxidant treatment in living organisms, focusing on their impact on health, diseases, and aging
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
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
The TRbeta-selective agonist, GC-1, stimulates mitochondrial oxidative processes to a lesser extent than triiodothyronine
No full textJ Endocrinol. 2010 Jun;205(3):279-89. Epub 2010 Apr 1.
The TRbeta-selective agonist, GC-1, stimulates mitochondrial oxidative processes to a lesser extent than triiodothyronine.
Venditti P, Chiellini G, Di Stefano L, Napolitano G, Zucchi R, Columbano A, Scanlan TS, Di Meo S.
SourceDipartimento delle Scienze Biologiche, Sezione di Fisiologia, Università di Napoli Federico II, Via Mezzocannone 8, I-80134 Napoli, Italy. [email protected]
Abstract
Specific tissue responses to thyroid hormone are mediated by the hormone binding to two subtypes of nuclear receptors, TRalpha and TRbeta. We investigated the relationship between TRbeta activation and liver oxidative metabolism in hypothyroid rats treated with equimolar doses of triiodothyronine (T(3)) and GC-1, a TRbeta agonist. T(3) treatment produces increases in O(2) consumption and H(2)O(2) production higher than those elicited by GC-1. The greater effects of T(3) on oxidative processes are linked to the higher hormonal stimulation of the content of respiratory chain components including autoxidizable electron carriers as demonstrated by the measurement of activities of respiratory complexes and H(2)O(2) generation in the presence of respiratory inhibitors. It is conceivable that these differential effects are dependent on the inability of GC-1 to stimulate TRalpha receptors that are likely involved in the expression of some components of the respiratory chain. The greater increases in reactive oxygen species production and susceptibility to oxidants exhibited by mitochondria from T(3)-treated rats are consistent with their higher lipid and protein oxidative damage and lower resistance to Ca(2)(+) load. The T(3) and GC-1 effects on the expression levels of nuclear respiratory factor-1 and -2 and peroxisome proliferator-activated receptor-gamma coactivator-1alpha suggest the involvement of respiratory factors in the agonist-linked changes in mitochondrial respiratory capacities and H(2)O(2) production.
PMID:20360308[PubMed - indexed for MEDLINE
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