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P Vargas

Publications and source records attributed to P Vargas.

At least 19 recordsLinked to original sources
PubMed2002

Scaling approach to the magnetic phase diagram of nanosized systems.

Based on the discovery of a simple scaling relation, a new technique for the investigation of the phase diagram of nanosized magnetic systems is proposed. By scaling the exchange interaction between magnetic moments, the magnetic phase diagram of currently lithographically produced particles can be obtained from those corresponding to much smaller systems. Such a technique reduces the computation time by several orders of magnitude, and provides a new approach to the investigation of the relative stability of distinct internal magnetic configurations of nanosized systems. The technique is illustrated by the determination of the phase diagram of cylindrically shaped Co particles.

Journal Article↗
PubMed2002

[Present perspectives on Creutzfeldt-Jakob disease: pathogenesis, diagnosis and treatment].

In recent years, interest in the group of diseases generically known as "transmissible spongiform encephalopathies" has reemerged, mainly due to the socioeconomic implications of one of its variants: bovine spongiform encephalopathy. Transmissible spongiform encephalopathies seem to be caused by proteinaceous particles called prions, isoforms of a membrane protein which can be found in humans as well as in several animal species. Their precise function is still unknown. Although investigation into transmissible spongiform encephalopathies has clarified some uncertainties about its pathogenesis and epidemiology, many important questions remain. This is especially true or treatment, since no effective curative therapy exists as yet.

Creutzfeldt-Jakob Syndrome↗
PubMed2001

Children with asthma and nebulizer use: parental asthma self-care practices and beliefs.

We examined demographic characteristics, patterns of medication use, asthma morbidity, and asthma self-management practices and beliefs among inner-city children currently using a nebulizer. We also describe the relationship between asthma self-management practices and beliefs and anti-inflammatory (AI) therapy. We observed a high rate of morbidity, including frequent emergency room visits, hospitalizations, symptom days and nights, and school absences in this group of school-aged children with asthma. More than three-quarters (81%) reported asthma symptoms consistent with mild persistent or greater severity of asthma, and therefore these subjects should be taking AI medications. Another 16% (36 of 231) of these children reported symptoms consistent with mild intermittent asthma. Only 1 out of 7 children in this study reported taking AI medications. We found that parents of children taking daily AI medications were more likely to agree with the belief that children should use asthma medications daily even when the child is not reporting any symptoms.

Administration, Inhalation↗
PubMed2000

Energy losses of muons, pions, protons, and deuterons channeled in Si

The energy loss of positive muons, pions, protons, and deuterons channeled in Si crystals has been investigated by computer simulation. The model considers the individual trajectories of particles inside the target and calculates the electronic energy loss for each particle history. The results show important differences in the energy loss distributions, stopping powers, and straggling values for low and intermediate energies, as a consequence of channeling effects.

Journal Article↗
PubMed2000

The colonization history of Olea europaea L. in Macaronesia based on internal transcribed spacer 1 (ITS-1) sequences, randomly amplified polymorphic DNAs (RAPD), and intersimple sequence repeats (ISSR).

Phylogenetic relationships in the Olea europaea complex and the phylogeography of 24 populations of the Macaronesian olive (O. europaea ssp. cerasiformis) were assessed by using three molecular markers: nuclear ribosomal internal transcribed spacer 1 (ITS-1) sequences, randomly amplified polymorphic DNAs (RAPD), and intersimple sequence repeats (ISSR). Parsimony analysis of the ITS-1 sequences and Neighbour-joining (NJ) analyses of RAPD and ISSR banding variation revealed four major lineages in the O. europaea complex: (1) ssp. cuspidata; (2) ssp. cerasiformis from Madeira; (3) ssp. laperrinei; and (4) ssp. cerasiformis from the Canary Islands plus ssp. europaea. These results provide unequivocal support for two independent dispersal events of Olea to the Madeira and Canary Islands. Molecular and morphological evidence led to recognition of two separate olive taxa in Macaronesia, to date included in ssp. cerasiformis. NJ analyses of the combined RAPD and ISSR data suggest that the colonization of the Canaries by O. europaea may have followed an east to west stepping-stone model. An interisland dispersal sequence can be recognized, starting from the continent to Fuerteventura, Gran Canaria, Tenerife, La Gomera, and finally La Palma. High dispersal activity of the lipid-rich Olea fruits by birds in the Mediterranean region is congruent with multiple dispersal of olives to Macaronesia and successive colonization of the archipelagos. The observation of strong genetic isolation between populations of different islands of the Canary Islands suggests, however, that subsequent interisland dispersal and establishment has been very rare or may not have occurred at all.

DNA, Ribosomal↗
PubMed2000

Reverse flow in the umbilical vein in a case of trisomy 9.

This report describes a case of reverse flow in the umbilical vein and ductus venosus during atrial contraction of a fetus at 12 weeks of gestation with increased nuchal translucency (9.1 mm). In addition, Doppler velocimetry detected high retrograde flow in the inferior vena cava. Cytogenetic analysis of chorionic villi revealed trisomy 9. We suggest that these findings may be a first trimester sign of chromosomal and cardiac abnormalities in the fetus.

Adult↗
PubMed2000

Factors associated with medication self-administration in children with asthma.

This study investigated factors associated with early self-administration of inhaled asthma medications by minority children. Specifically, the study evaluated: (1) the reasons parents allow early administration of inhaled medications, (2) childhood activities associated with early medication administration, (3) parent's perception of the child's ability to use a metered-dose inhaler (MDI), (4) the child's actual ability to use an MDI, and (5) concordance/discordance between physician-parent reports and parent-child reports of asthma medications. Study results indicated that 93% of the children were taking inhaled asthma medications without adult supervision. Early self-administration of asthma medications was related to the parent's employment status and the performance of other childhood behaviors such as completion of homework independently and crossing the street alone. Only 7% of the children had effective MDI skills, but 60% of the parents rated their child's MDI skills as excellent. Twenty percent, 67%, and 50%, respectively, of the parents' reports of beta-agonists, daily inhaled steroids, and cromolyn were discordant with the physician's actual prescriptions. Sixty-two percent, 57%, and 79%, respectively, of the children's reports for inhaled beta-agonists, daily inhaled steroids, and cromolyn were discordant with their parents' reports. Implications for anticipatory guidance, future educational strategies, and supervision of MDI technique are provided.

Adolescent↗
PubMed1999

Biogeographic patterns in Mediterranean and Macaronesian species of Saxifraga (Saxifragaceae) inferred from phylogenetic analyses of ITS sequences.

A biogeographic study of Saxifraga section Saxifraga was performed based on phylogenetic analyses of ITS (internal transcribed spacer) sequences of nuclear ribosomal DNA. ITS sequences from 21 species and 31 populations were examined to identify colonization patterns for the two species of Saxifraga occurring in Macaronesia and for S. globulifera in the west Mediterranean basin. Phylogenetic analysis of the sequence data yield a single most parsimonious tree with many of the major clades well supported by bootstrap and decay values. The ITS tree provided resolution at specific and populational levels that points to two biogeographic patterns within the genus. In contrast to the molecular evidence provided by other authors for a Mediterranean origin of several Macaronesian genera of angiosperms, our results indicate that the Madeiran archipelago was colonized a single time by a species of Saxifraga originating from the Eurosiberian region. On the other hand, the molecular evidence also suggests that populations of S. globulifera from North Africa have been isolated for a long time from populations occurring in the Iberian Peninsula, and that the endemic S. reuteriana has evolved from the Iberian populations of S. globulifera. The Mediterranean Sea has probably been an effective isolating barrier for some plant groups that occur in Europe and North Africa.

Journal Article↗
PubMed1998

Nuclear ribosomal DNA evidence for a western North American origin of Hawaiian and South American species of Sanicula (Apiaceae).

Results from phylogenetic analysis of nuclear rDNA internal transcribed spacer (ITS) sequences from a worldwide sample of Sanicula indicate that Hawaiian sanicles (Sanicula sect. Sandwicenses) constitute a monophyletic group that descended from a western North American ancestor in Sanicula sect. Sanicoria, a paraphyletic assemblage of mostly Californian species. A monophyletic group comprising representatives of all 15 species of S. sect. Sanicoria and the three sampled species of S. sect. Sandwicenses was resolved in all maximally parsimonious trees, rooted with sequences from species of Astrantia and Eryngium. All sequences sampled from eastern North American, European, and Asian species of Sanicula fell outside the ITS clade comprising S. sect. Sanicoria and S. sect. Sandwicenses. A lineage comprising the Hawaiian taxa and three species endemic to coastal or near-coastal habitats in western North America (Sanicula arctopoides, Sanicula arguta, and Sanicula laciniata) is diagnosed by nucleotide substitutions and a 24-bp deletion in ITS2. The hooked fruits in Sanicula lead us to conclude that the ancestor of Hawaiian sanicles arrived from North America by external bird dispersal; similar transport has been hypothesized for the North American tarweed ancestor of the Hawaiian silversword alliance (Asteraceae). Two additional long-distance dispersal events involving members of S. sect. Sanicoria can be concluded from the ITS phylogeny: dispersal of Sanicula crassicaulis and Sanicula graveolens from western North America to southern South America.

Apiaceae↗
PubMed1996

Adherence enhancers in pill-related clinical trials: a health behavior in cancer prevention model-based approach.

Preventing non-adherence and treating adherence failure are important to consider in designing community-based clinical trials. The approach and methods for managing adherence are vital. This paper describes a practical and theoretically-based strategy for managing adherence in a small cancer prevention trial with subjects (n = 40) taking a non-steroidal anti-inflammatory drug, piroxicam. Average daily pill intake adherence was exceptionally high (97.4%) as measured by self-report calendar. Thus, the generalized adherence enhancement approach used in this study may have been a related factor, although statistical model-testing was not possible in this small trial. The generalized intervention took into account factors such as the potential barriers and benefits of being in the study, self-efficacy and satisfaction with the participant/staff relationship. These and other theoretical variables were incorporated into an overall adherence strategy that is discussed.

Aged↗
PubMed1992

Teaching community oriented primary care in a traditional medical school: a two year progress report.

Efforts are being made to extend the practice of Community Oriented Primary Care by reorienting existing health services or restructuring medical education curricula. Nevertheless, changes in education must be simultaneous to changes in health services so that health professionals trained in COPC will find areas to practice COPC. The experience described in this article presents an effort in these two directions. A teaching program was introduced in a traditional medical school curriculum and was extended to six health services by training the directors of the health service as teaching instructors of COPC or closely coordinating actions with the director of the health service. The results of the program show fulfillment of learning objectives and student satisfaction with the program. Evaluations of the development of COPC in the health services involved show modifications in health programs to meet community needs and stronger community leadership and organization.

Colombia↗
PubMed1984

The effect of stimulant medication on academic performance, in the context of multimodal treatment, in attention deficit disorders with hyperactivity: two case reports.

Stimulant medications enhance performance on attentional, memory, and perceptual laboratory tasks and improve behavior in the majority of children with attention deficit disorder with hyperactivity. Most investigators, however, fail to find academic improvement. This report presents two cases in which stimulant medication in the context of multimodal treatment led to considerable gain in academic performance. One case was diagnosed as a combination of attention deficit disorder with hyperactivity and overanxious disorder of childhood. In the other case, disordered conduct was the complicating factor. The necessity of using a multimodal approach in children who suffer from multiple behavioral impairments is emphasized.

Achievement↗
PubMed1981

Infant of the diabetic mother: review of 225 cases.

The maternal and neonatal data on 225 infants of diabetic mothers (IDM) are presented. The incidence of maternal and neonatal complications confirms previous reports, indicating improved survival rates and decreasing neonatal morbidity for the IDM. The observed incidence of hyaline membrane disease was 2.8%, perhaps reflecting attempts to prolong pregnancy when possible to 39 weeks' gestation with judicious use of primary cesarean section. Further, from analysis of neonatal growth, the head circumference of the large-for-gestational-age infant was found to be significantly increased after 37 weeks' gestation. Whether or not this observation represents increased brain growth in these infants is not known.

Birth Weight↗