323,139 research outputs found
L’Archivio della Fabbrica di San Pietro in Vaticano come fonte per la storia di Roma
No full textQuesto volume raccoglie i frutti di alcuni dei più recenti studi condotti sui
documenti dell’Archivio Storico della Fabbrica di San Pietro da un gruppo di
ricercatori provenienti da ambiti scientifici e accademici diversi; si tratta di studi
selezionati con il triplice obiettivo di evidenziare il carattere fortemente
interdisciplinare delle ricerche, di diffonderne i risultati e di mettere in luce
l’influenza che le attività della Fabbrica hanno esercitato nel corso dei secoli sullo
sviluppo culturale, tecnico-edilizio, economico e sociale della città di Roma.
I dieci saggi che compongono l’opera, infatti, tratteggiano in modo inequivocabile
un legame indissolubile con la città eterna: la vicenda plurisecolare della Fabbrica
di San Pietro si radica profondamente in quella di Roma, che a sua volta trova
nelle carte dell’Archivio della Fabbrica una fonte di conoscenza storica unica,
preziosa, insostituibile
Ensemble X-ray variability of active galactic nuclei from serendipitous source catalogues
No full textThe X-ray variability of the Active Galactic Nuclei (AGN) has been most often investigated with studies of individual, nearby, sources, and only a few ensemble analyses have been applied to large samples in wide ranges of luminosity and redshift. We want to determine the ensemble variability properties of two serendipitously selected AGN samples extracted from the catalogs of XMM-Newton and Swift, with redshift between ~0.2 and ~4.5, and X-ray luminosities, in the 0.5-4.5 keV band, between ~10^43 erg/s and ~10^46 erg/s. We use the structure function (SF), which operates in the time domain, and allows for an ensemble analysis even when only a few observations are available for individual sources and the power spectral density (PSD) cannot be derived. SF is also more appropriate than fractional variability and excess variance, because such parameters are biased by the duration of the monitoring time interval in the rest-frame, and thus by cosmological time dilation. We find statistically consistent results for the two samples, with the SF described by a power law of the time lag, approximately as SF ~ tau^0.1. We do not find evidence of the break in the SF, at variance with the case of lower luminosity AGNs. We confirm a strong anti-correlation of the variability with X-ray luminosity, accompanied by a change of the slope of the SF. We find evidence in support of a weak, intrinsic, average increase of X-ray variability with redshift. The change of amplitude and slope of the SF with X-ray luminosity provides new constraints on both single oscillator models and multiple subunits models of variability
A multi-epoch spectroscopic study of the BAL quasar APM 08279+5255: I. C IV absorption variability
No full textContext. Broad absorption lines indicate gas outflows with velocities from thousands of km s-1 to about 0.2 the speed of light, which may be present in all quasars and may play a major role in the evolution of the host galaxy. The variability of absorption patterns can provide information on changes in the density and velocity distributions of the absorbing gas and its ionisation status. Aims. We want to accurately follow the evolution in time of the luminosity and both the broad and narrow C IV absorption features of an individual object, the quasar APM 08279+5255, and analyse the correlations among these quantities. Methods. We have collected 23 photometrical and spectro-photometrical observations at the 1.82 m Telescope of the Asiago Observatory since 2003, plus 5 other spectra from the literature. We analysed the evolution in time of the equivalent width of the broad absorption feature and two narrow absorption systems, the correlation among them and with the R band magnitude. We performed a structure function analysis of the equivalent width variations. Results. We present an unprecedented monitoring of a broad absorption line quasar based on 28 epochs during 14 years. The shape of broad absorption feature shows relative stability, while its equivalent width slowly declines until it sharply increases during 2011. At the same time, the R magnitude stays almost constant until it sharply increases during 2011. The equivalent width of the narrow absorption redwards of the systemic redshift only shows a decline. Conclusions. The broad absorption behaviour suggests changes in the ionisation status as the main cause of variability. We show for the first time a correlation of this variability with the R band flux. The different behaviour of the narrow absorption system might be due to recombination time delay. The structure function of the absorption variability has a slope comparable with typical optical variability of quasars. This is consistent with variations of the 200 Å ionising flux originating in the inner part of the accretion disk
Developmental dissociation between visual and auditory repetition priming: the role of input lexicons
No full textContrasting theories posit the source of verbal repetition priming in the activation of preexisting memory representations in the input lexicons or, alternatively, in the formation of new episodic memory traces. The two hypotheses predict different outcomes from the comparison of developmental rates of visual and auditory verbal repetition priming. The activation theory predicts a developmental dissociation between the early maturation of auditory priming and the later maturation of visuo-verbal priming, contingent upon the discrepant acquisition rates of the auditory and visual input lexicons. The episodic theory, instead, does not make such an assumption. We administered visual and auditory implicit Stem Completion to 40 reading beginners (first-graders), 40 third-graders and 20 fifth-graders. Consistent with previous reports, auditory priming was stable across different age groups. Visual priming and a measure of lexicality in reading, instead, showed a parallel developmental increase passing from reading beginners to third-graders and to fifth-graders. In the overall group, visual priming and the measure of lexicality in reading were significantly associated. These data describe a new developmental dissociation in the memory abilities of normal children and provide further support for the hypothesis that repetition priming for words reflects facilitated access to previously established memory representations
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Combined effect of temozolomide and hyperthermia on human melanoma cell growth and O-6-methylguanine-DNA methyltransferase activity
No full textHyperthermic isolated limb perfusion (HILP) with L-phenylalanine mustard (L-PAM) represents an effective treatment for locally advanced melanoma of the limbs. However. regional chemotherapy of melanoma still needs to be improved. Temozolomide (TMZ) is a methylating agent that spontaneously decomposes into the active metabolite of dacarbazine. the most effective agent for the systemic treatment of melanoma. Tumor cells with high levels of O-6-methylouanine-DNA methyltransferase (MGMT) and/or with a defective DNA mismatch repair (MMR) are resistant to TMZ. Inhibition of MGMT activity increases TMZ sensitivity of MMR-proficient, but not of MMR-deficient cells, while inhibition of base excision repair (BER) potentiates TMZ cytotoxicity in both cell types. Recent studies, performed in an animal model, have shown that TMZ is more effective than L-PAM when applied regionally and that hyperthermia can increase the antitumor activity of TMZ. In this study, three thermoresistant human melanoma cell lines, endowed with different MGMT activity and functional status of the MMR system. were treated with TMZ at 37 degrees C or 41.5 degrees C for 90 min, and then analyzed for cell growth and MGMT activity. Hyperthermia significantly enhanced TMZ cytotoxicity in MMR-proficient cells, either endowed or not with MGMT activity, and in MMR-deficient cells. Endogenous MGMT activity was not affected by hyperthermia that, however, enhanced the enzyme depletion induced by TMZ treatment. Moreover, MGMT recovery after drug removal was delayed in cells that had been treated at 41.5 degrees C. Taken together, these findings confirm the therapeutic potential of a combined treatment of hyperthermia and TMZ. They also suggest that inhibition of BER and/or increased DNA methylation may be involved in the thermal enhancement of TMZ cytotoxicity. Additional studies are necessary to better clarify the mechanisms underlying hyperthermia-induced potentiation of TMZ activity. However, the present investigation provides further support to the development of clinical trials of HILP with TMZ
Overestimation of numerical distances in the left space
No full textNormal subjects presented with a middle number and two left- and right-sided outer numbers overestimate the numerical distance between the middle number and that positioned at its left side. Repetitive transcranial magnetic stimulation (rTMS) of the right posterior parietal cortex specifically counteracts this bias, suggesting that the mental representation of space defined by numbers is shifted toward the left side depending on a greater activity of the right hemisphere
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