1,721,394 research outputs found
The cosmic rays flux from the Pierre Auger Observatory data
Full text linkL'Osservatorio Pierre Auger sta esplorando i misteri dei raggi cosmici di altissima energia. Questo esperimento è stato concepito da più di dieci anni per esplorare le proprietà dei raggi cosmici più energetici, come il flusso, la distribuzione e la direzione di arrivo, la composizione in massa, il tutto con una elevata significatività statistica e studiando l'intero cielo.
Pochi anni dopo che Penzias e Wilson hanno stabilito l'esistenza del fondo cosmico di radiazione che ha una temperatura media di 2,7 K, Greisen, Zatsepin e Kuzmin previsero la soppressione del flusso dei raggi cosmici di alta energia dovuta alla loro interazione con questo fondo cosmico.
Prima dell’Osservatorio Pierre Auger gli esperimenti AGASA ed Hires hanno ottenuto risultati contrastanti per quanto riguarda questa soppressione. Questi esperimenti utilizzano tecniche di rilevamento differenti. L'esperimento Auger è un rivelatore “ibridio”, nel senso che utilizza per la prima volta entrambe le tecniche. È costituito da due rivelatori progettati per osservare, in coincidenza, lo sciame di particelle che si può sviluppare lungo diversi chilometri quando raggiunge la superficie terrestre. Il rivelatore di superficie (SD) è composto di 1600 stazioni di Cherenkov che campionano il fronte dello sciame a terra. Il rivelatore a fluorescenza (FD) è dotato di 24 telescopi di fluorescenza che rilevano la luce emessa dalle molecole di azoto atmosferico eccitate dallo sciame, mentre attraversa l'atmosfera. Il FD misura il profilo longitudinale dello sciame.
L’Osservatorio nell’emisfero Sud è in Argentina vicino la città di Malargüe ed è stato completato nel Maggio 2008 ed inaugurato nel Novembre 2008. L’Osservatorio è in presa dati in modo stabile dal Gennaio 2004. Durante questo tempo l'esperimento ha accumulato una quantità di dati senza precedenti ed i primi risultati sono stati pubblicati. L'Osservatorio nell’emisfero Nord sarà costruito in Colorado, negli Stati Uniti d'America. Gli osservatori insieme consentiranno una completa copertura del cielo.
L'obiettivo principale di questa tesi è la misurazione dello spettro dei raggi cosmici di energia superiore ai 3 EeV sulla base dei dati registrati presso l'Osservatorio Pierre Auger.The Pierre Auger Observatory is exploring the mysteries of the highest-energy cosmic rays. This experiment was conceived more than ten years ago to explore the properties of the most energetic cosmic rays such as the flux, arrival direction distribution and mass composition, with high statistical significance and covering the whole sky.
A few years after Penzias and Wilson established the existence of the cosmic microwave background with a mean temperature of 2.7 K , Greisen, Zatsepin and Kuzmin predicted that a cutoff of the cosmic ray flux at the highest energies is expected due to the interaction of the ultra high energy cosmic rays with the cosmic microwave background photons.
Before the Pierre Auger Observatory the AGASA and Hires experiments have obtained differents results about this cutoff. Those experiments use different detection techniques. The Auger experiment is an “hybrid” detector in the sense that uses for the first time both techniques. It consists of two complementary detectors designed to observe, in coincidence, the shower of particles which can be spread along several kilometres when they reach the earth surface. A Surface Detector (SD) composed of 1600 Cherenkov stations samples the front of the shower at ground. A Fluorescence Detector (FD) equipped with 24 telescopes collects the fluorescence light emitted by atmospheric nitrogen molecules excited as the shower is crossing the atmosphere. The FD measure the longitudinal profile of the shower.
The Southern Observatory in Argentina near the Malargüe village was completed in May 2008 and inaugurated in November 2008. It is taking data in stable manner since January 2004. During this time the experiment has accumulated an unprecedented statistics and the first results are pubblished.
The Northern Observatory will be built in Colorado, USA. Both observatories allow a full sky coverage. The main objective of this thesis is the measurement of the cosmic ray energy spectrum above 3 EeV based on the data recorded at the Pierre Auger Observatory
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
p53 and p66 proteins compete for hypoxia-inducible factor 1 alpha stabilization in young and old rat hearts exposed to intermittent hypoxia
No full textBACKGROUND:
During development and aging, as well as under hypoxia, many cells can adapt to a stressful environment, while others are damaged and die by apoptosis. In particular, intermittent hypoxia, i.e., hypoxia followed by reoxygenation, determines different responses in young and adult myocardia.
OBJECTIVE:
In the rat myocardium exposed to hypoxia, the roles played by p53 and p66 Shc proteins in matching, in an age-dependent mode, in stabilizing hypoxia-inducible factor-1alpha (HIF-1alpha), and in preventing its biological activity, which usually induces synthesis of rescue proteins against this stress, were investigated.
METHODS:
Five animals from three groups, each consisting of 10 male Wistar rats, 8 days and 3 and 24 months old, were kept under physiological conditions; 5 young and 5 old rats were exposed to intermittent hypoxic challenges (12 h at 10% O2 followed by 12 h at 21% O2) for 8 days. Pregnant rats were kept for 3 days under hypoxic conditions before delivery, and 5 neonate rats were kept in intermittent hypoxia for 8 days. Left ventricles were excised and processed for TUNEL and Western blotting analyses.
RESULTS:
HIF-1alpha stabilization by p53 along with decline in Bcl2, substantial caspase-3 expression, and a large number of apoptotic events make the hypoxic young myocardium the most damaged when compared to the neonatal one, in which HIF-1alpha is not stabilized. Moreover, high expression and activation of p66 in hypoxic young and in normoxic old myocardia suggests a pathological increase of the response to oxidative stress in the former and a physiological progressive increase in the latter.
CONCLUSIONS:
The different responses to hypoxic challenge during life show that the young seem the most reactive and damaged, as is well documented by p53-mediated HIF-1alpha stabilization. The neonate, not showing any modification in terms of HIF-1alpha expression and activation, seems 'adapted' to such an environment, since it was maintained in hypoxia 3 days before and 8 days after birth. In the old, increasing p66 expression and tyrosine phosphorylation, probably exerting a slight HIF-1alpha stabilization in the two experimental conditions, provide evidence of longevity and oxidative stress resistance, as suggested by the low number of apoptotic events seen upon hypoxic challenge, and this fact could be due to impairment of oxygen-sensing mechanisms or to adaptation of the cells to apoptosis
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Effects of Hypoxia on Nocturnal Erection Quality: A Case Report from the Manaslu Expedition
No full textINTRODUCTION:
High altitude environment represents a fine model to study physiological and pathophysiological effects of oxygen availability on sleep-related erections (SREs).
AIM:
To describe altitude-dependent effects on quality of SREs in order to estimate the role of hypoxia in erection physiology.
METHODS:
A healthy 37-year-old male mountain climber underwent a chronic high altitude-related hypoxia experience during the 43 days of the Manaslu expedition (Nepal). SREs were recorded by RigiScan (Timm Medical Technologies, Inc., Eden Prairie, MN, USA) at altitudes ranging from 0 to 5,800 m above sea level. The erection-related parameters assessed were: number, duration, event duration (% of session), event rigidity %, time rigidity %, tumescence and rigidity activated unit, and event tum % > bline (%).
MAIN OUTCOMES MEASURES:
SREs were recorded by RigiScan at altitudes ranging from 0 to 5,800 m above sea level.
RESULTS:
Erectile parameters showed an altitude-related reduction during the hypoxic exposure, although all functional alterations were reverted by the return to sea level.
CONCLUSIONS:
Our case report supports the hypothesis that oxygen availability and delivery could play an important role in the regulation of local penile erection-related mechanisms and that low oxygen levels might be considered an etiological cofactor in erectile dysfunction
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