Biomedical subjects

L Primavera

Publications and source records attributed to L Primavera.

5 recordsLinked to original sources

PubMed2006

Periodic and aperiodic traveling pulses in population dynamics: an example from the occurrence of epidemic infections.

The dynamics of the occurrence of the dengue hemorrhagic fever in the 72 provinces of Thailand is investigated by performing a proper orthogonal decomposition (POD) on spatiotemporal data. Using this technique, we are able to identify and select the contribution of different modes, selected according to the energy content, to the evolution of the epidemic during 14 years. We found that the phenomenon is characterized by periodic cycles of yearly occurrence characterized by spatial scales of about 420 km. Superimposed on this basic mode, POD analysis is able to reveal the presence of high-energetic aperiodic traveling pulses of the epidemic, which extend spatially for about 510 km from Bangkok.

Communicable Diseases↗

PubMed2005

Proper orthogonal decomposition of solar photospheric motions.

The spatiotemporal dynamics of the solar photosphere is studied by performing a proper orthogonal decomposition (POD) of line of sight velocity fields computed from high resolution data coming from the MDI/SOHO instrument. Using this technique, we are able to identify and characterize the different dynamical regimes acting in the system. Low-frequency oscillations, with frequencies in the range 20-130 microHz, dominate the most energetic POD modes (excluding solar rotation), and are characterized by spatial patterns with typical scales of about 3 Mm. Patterns with larger typical scales of approximately 10 Mm, are associated to p-modes oscillations at frequencies of about 3000 microHz.

Journal Article↗

PubMed1999

Effects of entropy inhomogeneity on density-temperature correlation in solar wind.

Compressive fluctuations in solar wind slow speed streams are studied by means of a magnetohydrodynamics (MHD) model, which represents the plasma in the vicinity of the heliospheric current sheet. The model contains a current sheet, as well as density and temperature variations, corresponding to a large scale modulation of the specific entropy. Alfvénic fluctuations are initially superimposed on the background equilibrium and compressive fluctuations are consequently generated during the time evolution. The resulting correlation between density and temperature fluctuations at various spatial scales is interpreted in terms of both generation of magnetosonic fluctuations and of an "entropy cascade." The latter phenomenon arises as a consequence of the interaction between the MHD turbulence and the underlying large scale entropy structure. In particular, it is responsible for anticorrelated density and temperature fluctuations detected at various scales. The results of the model are compared with the proton density-temperature correlation calculated during several crossings of solar wind slow speed streams by the Helios spacecraft. The model reproduces to a good extent the main observed features, in particular the dependence of the correlation coefficient on location (close to or far from the current sheet) and on the fluctuation scale. The results show that large scale inhomogeneities, in particular, that of specific entropy, are important ingredients in the dynamics of the MHD turbulence in slow speed streams.

Journal Article↗

PubMed1986

Learning style and intelligence of reading disabled students.

This study examined the relationship between elements of the Learning Style Inventory and various scales of the WISC-R for reading disabled students. Previous research generally suggests that reading disabled students have preferences that tap the visual-spatial domain and have higher WISC-R Performance Scale and subtest scores than Verbal Scale and subtest scores. Subjects with IQs of 90 or better on either the Verbal or Performance Scales of the WISC-R and a consistency score of 75 or better on the inventory were selected. Contrary to what might be expected, data generally showed a nonmeaningful pattern of correlations between scales of the Learning Style Inventory and WISC-R Performance-type functioning. However, as an important part of the validation of the inventory, lack of association between the two can be interpreted as support for its construct validity.

Arousal↗

PubMed1981

Object manipulation: an interactional strategy with autistic children.

The present research compared the effect of three play procedures upon the frequency and duration of object manipulation by six autistic children. The three interaction play procedures varied in the degree of similarity between the adult's and the child's performances. In procedure 1, the experimenter imitated the subject's movements with her duplicate object. In procedure 2, the experimenter performed a different movement with her duplicate object. In procedure 3, the experimenter performed a different action on a different object. The interaction procedure, in which the experimenter imitated both the material and the method of play chosen by the autistic child, resulted in greater frequency and duration of object manipulation.

Autistic Disorder↗