6,582 research outputs found
Representaciones de la fÃsica, su enseñanza y aprendizaje. Un estudio con estudiantes de nivel secundario y universitario
Se describe un estudio exploratorio cuyo objetivo fue identificar, caracterizar y describir las representaciones sociales sobre la fÃsica, su enseñanza y aprendizaje en alumnos de diferentes niveles de escolaridad de modo de obtener indicadores para la construcción de los instrumentos a utilizar en las fases siguientes de la investigación. Se empleó una metodologÃa cualitativa con un enfoque descriptivo e interpretativo. Cinco grupos de alumnos de nivel secundario y universitario básico (n=172) respondieron a una prueba individual de evocación libre. Las producciones se analizaron empleando una técnica de análisis de contenido. Se identificaron representaciones relativas a las dimensiones cognitiva, pedagógica, afectiva y sociocultural
Seismic Ground Motion Amplifications Estimated by Means of Spectral Ratio Techniques: Examples for Different Geological and Morphological Settings
One of the most important issue in seismic hazard and microzonation studies is the
evaluation of local site response (i.e. the tendency of a site to experience during an
earthquake greater or lower levels of ground shacking with respect to another). In general
site effects reflect all modifications (in amplitude, frequency content and duration) of a
wave-field produced by a seismic source during the propagation near the surface, due to
particular geologic (stratigraphy and morphology), geotechnical (mechanical properties of
deposits) and physical (e.g. coupling of incident, diffracted and reflected seismic waves)
conditions of a particular site.
Actually local seismic amplification represents one of the main factors responsible for
building damage during earthquakes: this statement is supported by well documented
evidences of structural damages during past moderate to high energy events occurred both
in Italy (e.g. 23th November 1980, Mw 6.9, Irpinia earthquake, Faccioli, 1986; 26th September
1997, Mw 6.0, Umbria-Marche earthquake, Caserta et al., 2000; the 31th October 2002, Mw
5.7, Molise earthquake, Strollo et al., 2007; 6th April 2009, Mw 6.3, L’Aquila earthquake,
Cultrera et al., 2009) and in other worldwide countries (e.g. 3rd March 1985, Mw 7.8, Chile
earthquake, Celebi, 1987; 17th August 1999, Mw 7.6, Izmit earthquake, Sadik Bakir et al.,
2002). For this reason the site effects evaluation, performed by experimental methods but
also through numerical simulations, has attracted the attention of engineering seismology
and earthquake engineering communities. Of consequence, in the last decade many
experiments were performed in correspondence of different setting such as alluvial basins
(Parolai et al., 2001 and 2004; Ferretti et al., 2007; Massa et al., 2009; Bindi et al., 2009) or
topographies (e.g. Pischiutta et al., 2010; Massa et al., 2010; Buech et al., 2010; Marzorati et
al., 2011; Lovati et al., 2011).
The present work has the aim to evaluate the capabilities of the most common passive
methods at present used in seismology to evaluate the site response: HVSR (Horizontal to
Vertical Spectral Ratio technique on seismic noise, Nakamura, 1989, or earthquakes, Lermo
& Chavez Garcia, 1993) and SSR (Standard Spectral Ratio, Borcherdt, 1970).Published195-2184.1. Metodologie sismologiche per l'ingegneria sismicaope
Semi-Teleparallel Theories of Gravitation
A class of theories of gravitation that naturally incorporates preferred
frames of reference is presented. The underlying space-time geometry consists
of a partial parallelization of space-time and has properties of Riemann-Cartan
as well as teleparallel geometry. Within this geometry, the kinematic
quantities of preferred frames are associated with torsion fields. Using a
variational method, it is shown in which way action functionals for this
geometry can be constructed. For a special action the field equations are
derived and the coupling to spinor fields is discussed.Comment: 14 pages, LaTe
The waveform similarity approach to identify dependent events in instrumental seismic catalogues
In this paper, waveform similarity analysis is adapted and implemented in a declustering
procedure to identify foreshocks and aftershocks, to obtain instrumental catalogues that are
cleaned of dependent events and to perform an independent check of the results of traditional
declustering techniques.
Unlike other traditional declustering methods (i.e. windowing techniques), the application
of cross-correlation analysis allows definition of groups of dependent events (multiplets) characterized
by similar location, fault mechanism and propagation pattern. In this way the chain of
intervening related events is led by the seismogenetic features of earthquakes. Furthermore, a
time-selection criterion is used to define time-independent seismic episodes eventually joined
(on the basis of waveform similarity) into a single multiplet. The results, obtained applying
our procedure to a test data set, show that the declustered catalogue is drawn by the Poisson
distribution with a degree of confidence higher than using the Gardner and Knopoff method.
The declustered catalogues, applying these two approaches, are similar with respect to the
frequency–magnitude distribution and the number of earthquakes.
Nevertheless, the application of our approach leads to declustered catalogues properly related
to the seismotectonic background and the reology of the investigated area and the success of
the procedure is ensured by the independence of the results on estimated location errors of the
events collected in the raw catalogue
Determining the Physical Properties of the B Stars I. Methodology and First Results
We describe a new approach to fitting the UV-to-optical spectra of B stars to
model atmospheres and present initial results. Using a sample of lightly
reddened stars, we demonstrate that the Kurucz model atmospheres can produce
excellent fits to either combined low dispersion IUE and optical photometry or
HST FOS spectrophotometry, as long as the following conditions are fulfilled:
1) an extended grid of Kurucz models is employed,
2) the IUE NEWSIPS data are placed on the FOS absolute flux system using the
Massa & Fitzpatrick (1999) transformation, and
3) all of the model parameters and the effects of interstellar extinction are
solved for simultaneously.
When these steps are taken, the temperatures, gravities, abundances and
microturbulence velocities of lightly reddened B0-A0 V stars are determined to
high precision. We also demonstrate that the same procedure can be used to fit
the energy distributions of stars which are reddened by any UV extinction curve
which can be expressed by the Fitzpatrick & Massa (1990) parameterization
scheme.
We present an initial set of results and verify our approach through
comparisons with angular diameter measurements and the parameters derived for
an eclipsing B star binary. We demonstrate that the metallicity derived from
the ATLAS 9 fits to main sequence B stars is essentially the Fe abundance. We
find that a near zero microturbulence velocity provides the best-fit to all but
the hottest or most luminous stars (where it may become a surrogate for
atmospheric expansion), and that the use of white dwarfs to calibrate UV
spectrophotometry is valid.Comment: 17 pages, including 2 pages of Tables and 6 pages of Figures.
Astrophysical Jounral, in pres
Cutaneous necrobiotic xanthogranuloma (NXG)--successfully treated with low dose chlorambucil.
Eur J Dermatol. 2001 Sep-Oct;11(5):458-62.
Cutaneous necrobiotic xanthogranuloma (NXG)--successfully treated with low dose chlorambucil.
Machado S, Alves R, Lima M, Leal I, Massa A.
SourceService of Dermatology, Hospital Geral Santo António, Rua D. Manuel II, EdifÃcio ex: Cicap, 4099-001 Porto, Portugal. [email protected]
Abstract
We report a case of necrobiotic xanthogranuloma in a 51 year-old white male patient presenting with a 6-year history of multiple indurated violaceous nodules and plaques involving the eyelids, trunk and extremities. He had an associated paraproteinemia (Ig G lambda), elevated sedimentation rate, cryoglobulinemia and hypocomplementemia. No extracutaneous involvement was detected. He was successfully treated with chlorambucil (2 mg/d for 7 months), leading to disappearance of all skin lesions
Calcolo automatico dei valori di picco in velocità , accelerazione e spostamento a partire da dati velocimetrici
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