Underlying SUSY in a generalized Jaynes-Cummings model.

We present a general qubit-boson interaction Hamiltonian that describes the Jaynes-Cummings model and its extensions as a single Hamiltonian class. Our model includes non-linear processes for both the free qubit and boson field as well as non-linear, multi-boson excitation exchange between them. It shows an underlying algebra with supersymmetric quantum mechanics features allowing an operator based diagonalization that simplifies the calculations of observables. As a practical example, we show the evolution of the population inversion and the boson quadratures for an initial state consisting of the qubit in the ground state interacting with a coherent field for a selection of cases covering the standard Jaynes-Cummings model and some of its extensions including Stark shift, Kerr-like, intensity dependent coupling, multi-boson exchange and algebraic deformations.

Study of the heavily p-type doping of cubic GaN with Mg.

We have studied the Mg doping of cubic GaN grown by plasma-assisted Molecular Beam Epitaxy (PA-MBE) over GaAs (001) substrates. In particular, we concentrated on conditions to obtain heavy p-type doping to achieve low resistance films which can be used in bipolar devices. We simulated the Mg-doped GaN transport properties by density functional theory (DFT) to compare with the experimental data. Mg-doped GaN cubic epitaxial layers grown under optimized conditions show a free hole carrier concentration with a maximum value of 6 × 1019 cm-3 and mobility of 3 cm2/Vs. Deep level transient spectroscopy shows the presence of a trap with an activation energy of 114 meV presumably associated with nitrogen vacancies, which could be the cause for the observed self-compensation behavior in heavily Mg-doped GaN involving Mg-VN complexes. Furthermore, valence band analysis by X-ray photoelectron spectroscopy and photoluminescence spectroscopy revealed an Mg ionization energy of about 100 meV, which agrees quite well with the value of 99.6 meV obtained by DFT. Our results show that the cubic phase is a suitable alternative to generate a high free hole carrier concentration for GaN.

The Influence of Lifestyle Behaviors on the Incidence of Frailty.

BACKGROUND: Frailty is a clinical state defined as an increase in an individual's vulnerability to developing adverse health-related outcomes. OBJECTIVES: We propose that healthy behaviors could lower the incidence of frailty. The aim is to describe the association between healthy behaviors (physical activity, vaccination, tobacco use, and cancer screening) and the incidence of frailty. DESIGN: This is a secondary longitudinal analysis of the Mexican Health and Aging Study (MHAS) cohort. SETTING: MHAS is a population-based cohort, of community-dwelling Mexican older adults. With five assessments currently available, for purposes of this work, 2012 and 2015 waves were used. PARTICIPANTS: A total of 6,087 individuals 50-year or older were included. MEASUREMENTS: Frailty was defined using a 39-item frailty index. Healthy behaviors were assessed with questions available in MHAS. Individuals without frailty in 2012 were followed-up three years in order to determine their frailty incidence, and its association with healthy behaviors. Multivariate logistic regression models were used to assess the odds of frailty occurring according to the four health-related behaviors mentioned above. RESULTS: At baseline (2012), 55.2% of the subjects were male, the mean age was 62.2 (SD ± 8.5) years old. The overall incidence (2015) of frailty was 37.8%. Older adults physically active had a lower incidence of frailty (48.9% vs. 42.2%, p< 0.0001). Of the activities assessed in the adjusted multivariate models, physical activity was the only variable that was independently associated with a lower risk of frailty (odds ratio: 0.79, 95% confidence interval 0.71-0.88, p< 0.001). CONCLUSIONS: Physically active older adults had a lower 3-year incidence of frailty even after adjusting for confounding variables. Increasing physical activity could therefore represent a strategy for reducing the incidence of frailty. Other so-called healthy behaviors were not associated with incident frailty, however there is still uncertainty on the interpretation of those results.

TWO-WAY Bridge between Muscular Dysfunction and Cognitive Impairment: Secondary Analyses of SABE - Bogota Study.

BACKGROUND AND OBJECTIVE: Muscular dysfunction and cognitive impairment are both disabling states, affecting especially the elderly. Thus, are important subjects of research. Our goal is to describe the association between these two entities in the elderly. METHODS: This is a secondary analysis from the SABE 2012 Bogota survey, which is a cross-sectional study. We define muscular dysfunction as an abnormal result in gait speed and/or handgrip strength tasks. Cognitive impairment was defined as an abnormal result in Mini Mental State Examination. Other independent variables were measured. RESULTS: A total of 1,564 older adults were included in the analysis. Cognitive impairment showed statistically significant association with both low handgrip strength (OR: 2.25; CI 1.52 - 3.33) and low gait speed (OR: 2.76; CI 1.83 - 4.15) in the adjusted model. CONCLUSION: In older adults, muscular dysfunction is associated with cognitive impairment. New studies should address the causality and temporality of this relationship.

Estudio de patrones capilaroscópicos en población sana / Capillarroscopic patterns in healthy population

La capilaroscopia es un método no invasivo y seguro que permite la visualización de los capilares a nivel del lecho periungueal de los dedos de las manos. Es útil en la evaluación del Fenómeno de Raynaud y de las colagenopatías, principalmente de la esclerodermia; sin embargo, se conoce poco acerca de la prevalencia y distribución de los cambios capilaroscópicos en sujetos sanos, siendo el objetivo de este estudio evaluar y describir las alteraciones capilaroscópicas en este grupo. A 100 participantes seleccionados por criterios de inclusión y exclusión se les realizó una videocapilaroscopia del lecho ungueal del cuarto y quinto dedo de la mano no dominante; el 86% de la población estudiada presentó hallazgos capilaroscópicos como: capilares tortuosos, entrecruzados y arborificados. Además, las alteraciones capilaroscópicas fueron más frecuentes en sujetos que consumían tabaco, se encontró una relación significativa entre el tabaco y la presencia de arborificaciones. Este es el primer estudio descriptivo de alteraciones capilaroscópicas en sujetos sanos en el Ecuador.

Capillaroscopy is a noninvasive and safe method that allows visualizationof capillaries in the nailbed. It is useful in the assesment ofRaynaud’s phenomenon and collagen diseases, especially scleroderma;however, little is known about the prevalence and distributionof capillaroscopic changes in healthy subjects, hence the aim ofthis study was to assess and describe the microvascular alterationsin this group. 100 participants selected by inclusion and exclusioncriteria underwent videocapillaroscopy of the nailfold of the fourthand fifth fingers of the nondominant hand; 86% of the study populationpresented capillaroscopic findings such as tortuous capillaries,crisscrossing and arborifications. Also, the microvascular alterationswere more frequent in subjects who had history of tobaccosmoking: a significant relationship between smoking and the presenceof arborifications was found. This is the first descriptive studyof microvascular alterations in healthy subjects in Ecuador.

Degradation of Al/SiCp composites produced with rice-hull ash and aluminum cans.

The use of recycling aluminum from beverage containers and rice-hull ash (RHA) offers to be an attractive alternative for the economic production of Al/SiCp composites. However, corrosion phenomena in the composites represent technological barriers yet to be resolved before they can be exploited to their full potential. A simple methodology involving characterization by XRD, SEM, EDX, FTIR and ICP was designed in order to investigate the causes of the rapid degradation in a humid environment of Al/SiCp composites produced with RHA and aluminum cans. Results reveal that the use of RHA was beneficial to avoid degradation through the formation and subsequent hydration of the Al4C3 phase. However with condensed moisture acting as an electrolyte, localized corrosion took place with aggressive damage manifested by the disintegration of the composite into a powdery mixture. The relevant corrosion mechanism was mainly attributed to microgalvanic coupling between the Mg2Si intermetallic compound and the matrix (although other phases such as SiC, Si, MgAl2O4 could also work as microcathodes).

¿Son útiles los trabajos de investigación que se realizan como requisito de grado? Un análisis de los estudios de intervención en la Facultad de Odontología de la Universidad Nacional de Colombia / Utility of clinical research studies in pregraduate level in Faculty of Dentistry in National University 1996-2000

Objetivo: Evaluar la calidad y utilidad de los estudios de investigación clínica relacionados con intervenciones en salud oral, efectuados por estudiantes de la Facultad de Odontología de la Universidad Nacional de Colombia como requisito de grado durante el período 1996 - 2000. Diseño del estudio: Observacional, analítico, transversal. Fuente de los datos: 26 reportes finales de trabajos de investigación disponibles en la biblioteca local de la Facultad de Odontología. Medidas principales de desenlace: Calidad del estudio teniendo en cuenta su contribución para la toma de decisiones clínicas. Utilidad del estudio considerando tanto su calidad como la accesibilidad de los resultados para aplicarlos en la práctica clínica. Resultados: Se encontró baja calidad en un 79 por ciento de los estudios. La baja calidad se asoció al tipo de estudio (revisiones) y a la vinculación a pregrado de los autores. Los sistemas de registro de utilización en la biblioteca local no permiten evaluar tasas de utilización de los documentos resultantes de las investigaciones. Conclusiones: La utilidad de los estudios a nivel de pregrado es cuestionable. La investigación se debe fortalecer mediante políticas relacionadas con entrenamiento en aspectos de investigación y disponibilidad de recursos para publicación de resultados

CFTR mutations in three Latin American countries.

We analyzed 192 cystic fibrosis (CF) alleles in three Latin American countries: Mexico, Colombia, and Venezuela. Mutation screening was performed by polymerase chain reaction (PCR) and a reverse dot blot detection kit that enables determination of 16 of the most common CF mutations worldwide. Mutations were detected in 47.9% of the screened CF alleles. The most prevalent CF allele was DeltaF508 (39. 6%). The remaining 16 non-DeltaF508 detectable mutations represented 8.3% of the CF alleles. Among them, the G542X, N1303K, and 3849+10kb C>T were the most common. Although the frequency of DeltaF508 described here is lower than that reported for Caucasian populations, including in Spain, it is remarkable that mutation prevalences found in this study resemble those observed in Spain. Two of these mutations, G542X and 3849+10kb C>T, that were relevant in this analysis, have a particularly high incidence in Spanish communities. The low frequency of DeltaF508 described here may be explained by the Amerindian, Caucasian, and Black admixture that occurred in Latin America after the discovery of the New World, and also by the probable occurrence of mutations contributed by the original natives, which were undetectable in this analysis.

Trends in asthma mortality in young people in southern Brazil.

BACKGROUND: Mortality from asthma increased and is now declining in some countries, but little is known about these trends in South America. OBJECTIVE: We aimed to assess trends in mortality from asthma in southern Brazil in children and young adults. METHODS: Death certificates of 425 people in the state of Rio Grande do Sul aged between 5 and 39 years in whom asthma was reported to be the underlying cause of death during the period 1970 to 1992 were reviewed. Population data were available in 10-year age groups. Testing for trends in mortality rates was conducted using linear and log-linear regression procedures. RESULTS: Asthma mortality rates in the age groups 5 to 19 and 20 to 39 years ranged between 0.04 and 0.39/100,000 and 0.28 to 0.75/100,000, respectively, and were nonuniformly distributed over the study period. The mean annual increase in rate in 5- to 19-year olds was +0.01 (95% CI 0.003 to 0.016), an average annual percentage increase of +6.8% (95% CI 3% to 11%), with a total increase of 352% between 1970 and 1992. This increase was not due to a shift in labeling from bronchitis to asthma. In the 20 to 39-year age group, asthma and bronchitis mortality rates showed no trend to increase or decrease. CONCLUSIONS: Asthma mortality in southern Brazil is low, but rose significantly between 1970 and 1992 in the 5 to 19-year age group. This trend differs from that found in other states of Brazil and several other Latin American countries. Reasons for this difference remain unclear.

PIP: Levels of mortality due to asthma are declining in some countries. To measure trends in mortality from asthma in southern Brazil among children and young adults, the death certificates of 425 people in the state of Rio Grande do Sul aged 5-39 years in whom asthma was reported to be the underlying cause of death during the period 1970-92 were reviewed. Asthma mortality rates among people aged 5-19 and 20-39 years were 0.04-0.39/100,000 and 0.28-0.75/100,000, respectively, and were nonuniformly distributed over the study period. The mean annual increase in mortality rate among 5-19 year olds was 0.01, an average annual percentage increase of 6.8%, with a total increase of 352% during 1970-92. This increase was not due to a shift in labeling from bronchitis to asthma. Among people aged 20-39 years, asthma and bronchitis mortality rates showed no trend of increase or decrease. Reasons for the dramatic increase in asthma-related mortality among 5-19 year olds are unclear.