oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 594 )

2018 ( 817 )

2017 ( 752 )

2016 ( 1105 )

Custom range...

Search Results: 1 - 10 of 462039 matches for " A. Riquelme "
All listed articles are free for downloading (OA Articles)
Page 1 /462039
Display every page Item
Pie bot
RUBEN ACU?A RIQUELME
Revista chilena de pediatría , 1953,
Abstract:
Hernia inguinal estrangulada en el ni o menor de dos a os
RUBEN ACU?A RIQUELME
Revista chilena de pediatría , 1953,
Abstract:
Crossover from Weak to Strong Nonlinear Disorder in the Viscoelasticity of Glucose Incubated Erythrocytes  [PDF]
A. M. Korol, B. D. Riquelme, M. D’Arrigo
Open Journal of Biophysics (OJBIPHY) , 2013, DOI: 10.4236/ojbiphy.2013.33022
Abstract:

Biomechanics is a wide interdisciplinary field, which includes all mechanical aspects from living organisms. As traditional erythrocytes viscoelastic analysis is mostly qualitative, the development of new quantitative methods capable of analyzing at the same time biological and mechanical aspects of the cells in flow, when changing from healthy controls to glucose incubated at different concentrations, is crucial for restricting the subjectivity in the study of the cell behaviour. On the other hand, it is important to appreciate the role of mathematics in the analysis of tissues and cells. Recent developed non linear mathematical methods are particularly fruitful when they are strongly correlated with cells sensitivity to initial conditions. An optic system called Erythrodeformeter has been developed and constructed in our laboratory, in order to evaluate the erythrocytes viscoelastic properties. To analyze the erythrocytes viscoelastic dynamics we used the technique of Time Delay Coordinates suggested by Takens, False Nearest Neighbours proposed by Abarbanel and co-workers, and the forecasting procedure proposed by Sugihara and May, the so called Correlation Coefficient. The results suggest that through this random walk analysis, apparent noise associated with deterministic chaos can be used not only to distinguish but also to characterize at the same time biological and mechanical aspects of the cells in flow, when changing from healthy controls to glucose incubated at different concentrations.


Magnetic Amplification by Magnetized Cosmic Rays in SNR Shocks
Mario A. Riquelme,Anatoly Spitkovsky
Physics , 2009, DOI: 10.1088/0004-637X/717/2/1054
Abstract: (Abridged) X-ray observations of synchrotron rims in supernova remnant (SNR) shocks show evidence of strong magnetic field amplification (a factor of ~100 between the upstream and downstream medium). This amplification may be due to plasma instabilities driven by shock-accelerated cosmic rays (CRs). One candidate is the cosmic ray current-driven (CRCD) instability (Bell 2004), caused by the electric current of large Larmor radii CRs propagating parallel to the upstream magnetic field. Particle-in-cell (PIC) simulations have shown that the back-reaction of the amplified field on CRs would limit the amplification factor of this instability to less than ~10 in galactic SNRs. In this paper, we study the possibility of further amplification driven near shocks by "magnetized" CRs, whose Larmor radii are smaller than the length scale of the field that was previously amplified by the CRCD instability. We find that additional amplification can occur due to a new instability, driven by the CR current perpendicular to the field, which we term the "perpendicular current-driven instability" (PCDI). We derive the growth rate of this instability, and, using PIC simulations, study its non-linear evolution and saturation. We find that PCDI increases the amplification of the field (amplification factor up to ~45, not including the shock compression) and discuss its observational signatures. Our results strengthen the idea of CRs driving a significant part of the magnetic field amplification observed in SNR shocks.
Electron Injection by Whistler Waves in Non-relativistic Shocks
Mario A. Riquelme,Anatoly Spitkovsky
Physics , 2010, DOI: 10.1088/0004-637X/733/1/63
Abstract: Electron acceleration to non-thermal, ultra-relativistic energies (~ 10-100 TeV) is revealed by radio and X-ray observations of shocks in young supernova remnants (SNRs). The diffusive shock acceleration (DSA) mechanism is usually invoked to explain this acceleration, but the way in which electrons are initially energized or 'injected' into this acceleration process starting from thermal energies is an unresolved problem. In this paper we study the initial acceleration of electrons in non-relativistic shocks from first principles, using two- and three-dimensional particle-in-cell (PIC) plasma simulations. We systematically explore the space of shock parameters (the Alfv\'enic Mach number, M_A, the shock velocity, v_{sh}, the angle between the upstream magnetic field and the shock normal, theta_{Bn}, and the ion to electron mass ratio, m_i/m_e). We find that significant non-thermal acceleration occurs due to the growth of oblique whistler waves in the foot of quasi-perpendicular shocks. The obtained electron energy distributions show power law tails with spectral indices up to alpha ~ 3-4. The maximum energies of the accelerated particles are consistent with the electron Larmor radii being comparable to that of the ions, indicating potential injection into the subsequent DSA process. This injection mechanism, however, requires the shock waves to have fairly low Alf\'enic Mach numbers, M_A <~ 20, which is consistent with the theoretical conditions for the growth of whistler waves in the shock foot (M_A <~ (m_i/m_e)^{1/2}). Thus, if the whistler mechanism is the only robust electron injection process at work in SNR shocks, then SNRs that display non-thermal emission must have significantly amplified upstream magnetic fields. Such field amplification is likely achieved by the escaping cosmic rays, so electron and proton acceleration in SNR shocks must be interconnected.
Cambios latitudinales en la pesquería pelágica de merluza de cola (Macruronus magellanicus) de la zona centro-sur (1986-2003)
Cubillos,Luis A; Riquelme,Katty; Ernst,Billy;
Latin american journal of aquatic research , 2009,
Abstract: we analyzed spatio-temporal changes in patagonian grenadier catches by the purse-seine fleet off central-southern chile (34°-41°30's) in order to check the hypothesis that the juvenile fraction of the population migrates northward in spring. log-book data from 1986 to 2003 were used to calculate the center of gravity of and variance of each catch. we proposed that, if the fleet follows the migratory behavior of the juvenile fraction, the centers of gravity of the catches will migrate from south to north as the fishing season progresses. nevertheless, the centers of gravity migrated northward in only four cases. unexpectedly, the centers of gravity remained stationary within each fishing season. now we propose that, in spring, a resident juvenile fraction of patagonian grenadier increases its accessibility and vulnerability in the surface waters due to the environmental conditions, characterized by the dominance of upwelling events, and rather than a northward migration.
Problemática Laboral de la Mujer en Cargos Directivos de los Servicios Públicos en Chile
Julio García del Junco,Adriana Riquelme
Economic Analysis Working Papers , 2008,
Abstract: A pesar de una mejor formación y participación en el mundo laboral, la mayoría de las mujeres, continúan enfrentadas al denominado "techo de cristal": la barrera invisible que les impide el acceso a los puestos de alta dirección en las organizaciones. Esta investigación analiza las distintas barreras o problemáticas laborales a las que se ven enfrentadas las mujeres directivas de los servicios públicos, ya sea para acceder y/o desempe ar dicho cargo. Para efectuar un análisis diferenciado, las distintas barreras citadas por las directivas se clasifican en factores sociales, organizacionales y actitudinales.
Cambios latitudinales en la pesquería pelágica de merluza de cola (Macruronus magellanicus) de la zona centro-sur (1986-2003) Latitudinal changes in the Patagonian grenadier (Macruronus magellanicus) pelagic fishery off central-southern Chile (1986-2003)
Luis A Cubillos,Katty Riquelme,Billy Ernst
Latin american journal of aquatic research , 2009,
Abstract: Se analizaron los cambios espacio-temporales de las capturas de merluza de cola obtenidas por la flota industrial de cerco en la zona centro-sur de Chile (34°-41°30'S), para revisar la hipótesis de migración hacia el norte de la fracción juvenil de merluza de cola en primavera. Se utilizaron datos de bitácoras de pesca del periodo 1986-2003, y a partir de éstos se calcularon centros de gravedad de las capturas y su varianza. Se postula que si la flota sigue el comportamiento migratorio de la fracción juvenil, se esperaría que los centros de gravedad de las capturas migren latitudinalmente de sur a norte conforme la estación de pesca avanza. No obstante, sólo se encontró cuatro casos en que ocurrió una migración hacia el norte de los centroides. Más bien, los centros de gravedad se presentan estacionarios, al interior de cada temporada de pesca. Se postula que existe una fracción juvenil residente que sólo incrementa su accesibilidad y vulnerabilidad en aguas superficiales en primavera debido al régimen ambiental, que se caracteriza por la dominancia de eventos de surgencia y no a una migración de sur a norte. We analyzed spatio-temporal changes in Patagonian grenadier catches by the purse-seine fleet off central-southern Chile (34°-41°30'S) in order to check the hypothesis that the juvenile fraction of the population migrates northward in spring. Log-book data from 1986 to 2003 were used to calculate the center of gravity of and variance of each catch. We proposed that, if the fleet follows the migratory behavior of the juvenile fraction, the centers of gravity of the catches will migrate from south to north as the fishing season progresses. Nevertheless, the centers of gravity migrated northward in only four cases. Unexpectedly, the centers of gravity remained stationary within each fishing season. Now we propose that, in spring, a resident juvenile fraction of Patagonian grenadier increases its accessibility and vulnerability in the surface waters due to the environmental conditions, characterized by the dominance of upwelling events, and rather than a northward migration.
Etiologíay factores pronósticos de la neumonía adquirida en la comunidad en el adulto hospitalizado, Puerto Montt, Chile Etiology and prognostics factors of community-acquired pneumonia among adults patients admitted to a regional hospital in Chile
Raúl Riquelme O,Mauricio Riquelme O,María Luisa Rioseco Z,Valeria Gómez M
Revista médica de Chile , 2006,
Abstract: Background: Community-acquired pneumonia (CAP) is a common and serious illness in Chile. Aim: To evaluate the etiology, severity, prognostic factors and blood culture yield of CAP requiring hospitalization in Puerto Montt in Southern, Chile. Patients and methods: All non immunocompromised adults with CAP admitted at Puerto Montt Hospital during one year, were prospectively studied. Clinical and radiological assessment was done in all patients. Blood and sputum cultures were obtained and serology for atypical agents was determined. Results: We studied 200 patients, aged 63±19 years (109 males). The prognostic factors associated with mortality were an age over 65 years, an altered mental status, shock and acute renal failure. Etiology was demonstrated in 29% of patients. The most frequent pathogens were Streptococcus pneumoniae (40.7%), Haemophilus influenzae (23.7%) and Chlamydia pneumoniae (16.9%). Mixed infections were found in 17%. Fifteen atypical pathogens were identified in 12 patients. Of these only two received a specific treatment but no one died and their length hospital stay was similar than in the rest of the patients. Overall, blood cultures were positive in 12.5% of patients, but among alcoholics, 58% were positive. In only one percent of cases, positive cultures motivated therapeutic changes among clinicians. Eight percent of S pneumoniae strains were penicillin resistant. Conclusions: Atypical agents were a common cause of CAP in this group of patients, but their pathogenic role and treatment requirements are debatable. Focusing blood cultures on specific groups could improve their yield. The rate of Penicillin resistance for S pneumoniae was
Neumonía adquirida en la comunidad en el anciano hospitalizado: Aspectos clínicos y nutricionales Community-acquired pneumonia in the elderly: Clinical and nutritional aspects
Raúl Riquelme O,Mauricio Riquelme O,María Luisa Rioseco Z,Valeria Gómez M
Revista médica de Chile , 2008,
Abstract: Community acquired pneumonia (CAP) in the elderly has unique features and there is little information about the effects of nutrition status on its outcome. Aim: To assess the clinical manifestations and prognostic factors of CAP in immunocompetent elderly patients requiring hospitalization. Patients and methods: Prospective study of all patients with CAP, admitted to Puerto Montt Hospital, Chile over one year. Epidemiológica! and clinical information and laboratory results were recorded. A nutritional assessment was also performed. Outcomes of elderly (>65 years) and young patients were compared. Results: Two hundred patients aged 63± 19 years were studied. Of these, 109 were older than 65 years (78.4±8 years) and 91 were younger than 65years (45.5±11 years). Multiple associated diseases, altered mental status, absence of fever, malnutrition and mortality were more common in the older group. Suspected aspiration pneumonia was more common in younger patients, probably related to alcoholism. Malnutrition was associated with longer hospital stay and mortality at any age. An univariate analysis showed that a low serum albumin (<3.4 g/dl) and a mid arm muscle circumference below the 25th percentile were associated with higher mortality. Conclusions: CAP in the elderly has specific features and malnutrition is associated with a worse prognosis in young and elderly patients
Page 1 /462039
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.