Well Diversified Efficient Portfolios

Investors scarcely use mean-variance optimization when deciding on their actual portfolios. One of the main reasons they give is that efficient portfolios are systematically concentrated in a few assets. This article shows that such an allocation is achieved when portfolio risk and return are seen as infinitely accurate magnitudes. However, if the frontier is considered within some infinitesimal tolerance, as in a one-hundredth neighborhood, there are thousands of efficient portfolios and, indeed, many of them are well diversified.

Infecciones y alteraciones epigenéticas en cáncer

ResumenLa participación de mecanismos epigenéticos, junto con infecciones en etapas tempranas de la vida, moldean lesiones premalignas del cáncer, en particular el cáncer gástrico, uno de los tumores más frecuentes en Chile, Latinoamérica y el mundo. El principal objetivo de este artículo, como parte de la serie de revisiones en torno a mecanismos epigenéticos en el desarrollo de enfermedades crónicas, es actualizar el rol de alteraciones epigenéticas (i.e. metilación del ADN) en el contexto de la infección crónica por H. pylori en las etapas precursoras del cáncer gástrico. Las investigaciones desarrolladas en esta área permiten delinear desafíos e interrogantes, en los cuales la pediatría tiene un papel preponderante en el desarrollo de estrategias de prevención y detección temprana de esta enfermedad.AbstractThe role of epigenetics and infectious diseases at early stages of life influence pre-malignant lesions of cancer, in particular, gastric cancer, one of the most frequent tumours in Chile, Latin America, and worldwide. This article examines the role of H.pylori and epigenetic alterations (i.e. DNA methylation) at early stages of gastric cancer and proposes, from the paediatric point of view, strategies for prevention and early detection

Baseline assessment of prevalence and geographical distribution of HPV types in Chile using self-collected vaginal samples

<p>Abstract</p> <p>Background</p> <p>Chile has broad variations in weather, economics and population from the far desert north (Region 1) to the cold, icy south (Region 12). A home-based self-collected vaginal sampling was nested in the 2003 Chilean population-based health survey in order to explore the possibility of a type-specific geographical variation for human papillomavirus</p> <p>Methods</p> <p>The population was a national probability sample of people 17 years of age and over. Consenting women provided self-collected cervicovaginal swabs in universal collection media (UCM). DNA was extracted and typed to 37 HPV genotypes using PGMY consensus PCR and line blot assay. Weighted prevalence rates and adjusted OR were calculated.</p> <p>Results</p> <p>Of the 1,883 women participating in the health survey, 1,219 (64.7%) provided a cervicovaginal sample and in 1,110 (56.2% of participants and 66.5% of those eligible) the samples were adequate for analysis. Refusal rate was 16.9%. HPV prevalence was 29.2% (15.1% high-risk HPV and 14.1% low-risk HPV). Predominant high-risk types were HPV 16, 52, 51, 56 and 58. Predominant low-risk HPVs were HPV 84, CP6108, 62, 53 and 61. High-risk and low-risk HPV rates were inversely correlated between the regions. High-risk HPV prevalence was highest among the youngest women, whereas low-risk HPV increased slightly with age.</p> <p>Conclusion</p> <p>Self-obtained vaginal sampling is adequate for monitoring HPV in the community, for identifying high-risk areas, and for surveying the long term impact of interventions.</p

Functional Interaction between Human Papillomavirus Type 16 E6 and E7 Oncoproteins and Cigarette Smoke Components in Lung Epithelial Cells

The smoking habit is the most important, but not a sufficient cause for lung cancer development. Several studies have reported the human papillomavirus type 16 (HPV16) presence and E6 and E7 transcripts expression in lung carcinoma cases from different geographical regions. The possible interaction between HPV infection and smoke carcinogens, however, remains unclear. In this study we address a potential cooperation between tobacco smoke and HPV16 E6 and E7 oncoproteins for alterations in proliferative and tumorigenic properties of lung epithelial cells. A549 (alveolar, tumoral) and BEAS-2B (bronchial, non-tumoral) cell lines were stably transfected with recombinant pLXSN vectors expressing HPV16 E6 and E7 oncoproteins and exposed to cigarette smoke condensate (CSC) at different concentrations. HPV16 E6 and E7 expression was associated with loss of p53 stability, telomerase (hTERT) and p16INK4A overexpression in BEAS-2B cells as demonstrated by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting (WB). In A549 cells we observed downregulation of p53 but not a significant increase of hTERT transcripts. In addition, the HPV16 E6/E7 transfected cell lines showed an increased proliferation rate and anchorage-independent growth in a HPV16 E6 and E7 expression-dependent manner. Moreover, both HPV16 E6/E7 and mock transfected cells showed an increased proliferation rate and anchorage-independent growth in the presence of 0.1 and 10 µg/mL CSC. However, this increase was significantly greater in HPV16 E6/E7 transfected cells (p<0.001). Data were confirmed by FCSE proliferation assay. The results obtained in this study are suggestive of a functional interaction between tobacco smoke and HPV16 E6/E7 oncoproteins for malignant transformation and tumorigenesis of lung epithelial cells. More studies are warranted in order to dissect the molecular mechanisms involved in this cooperation

Enseñanza virtual durante la pandemia, un curso de Física elemental

El contexto de la pandemia mundial de COVID-19 ocasionó un cambio abrupto y repentino de la modalidad de trabajo y estudio en la mayoría de los países. En particular, a nivel educativo fue necesario rápidamente pasar a una modalidad virtual para poder sostener la continuidad pedagógica. En este trabajo se exponen las estrategias utilizadas en tres comisiones de Introducción a la Física de la Universidad Nacional de General Sarmiento. Para ello, se ofrecieron clases virtuales, tanto sincrónicas como asincrónicas, y todas ellas se subieron a YouTube para la utilización de los estudiantes. El uso de esta plataforma permitió tener un registro detallado de la actividad de los usuarios relacionada con estos videos, los cuales pudieron ser contrastados y comparados con los registros de asistencia de las actividades de evaluación. La experiencia fue exitosa por la rápida adaptación de contenidos, siendo bien recibida por los estudiantes logrando un grado de interacción satisfactorio entre docentes y estudiantes y obteniendo resultados similares a los de la cursada presencial histórica.The context of the global COVID-19 pandemic caused an abrupt and sudden change in the modality of work and study in most countries. Specifically, at an educational level, it was necessary to quickly move to a virtual modality in order to sustain pedagogical continuity. In this work the strategies used in three commissions of Introduction to Physics of the National University of General Sarmiento are exposed. For this, virtual classes were held, both synchronous and asynchronous, and all of them were uploaded to YouTube for the use of the students. The use of this platform allowed to have a detailed record of activity of the users related to these videos, which could be contrasted and compared with the attendance records of the evaluation activities. The experience was successful due to the rapid adaptation of content, being well received by students, achieving a satisfactory degree of interaction between teachers and students and obtaining results similar with the historical face-to-face course.Fil: Bortule, María Victoria. Universidad Nacional de General Sarmiento. Instituto de Industria; ArgentinaFil: Scagliotti, Ariel Fabricio. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Frisco, Adriana. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Corvalán, Darío. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Cuch, Daniel Alejandro. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Vigh, Carlos Donato. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; Argentin

EL SOLAR MAYA-CH’OL Y SUS SABERES ETNOBOTÁNICOS EN COMUNIDADES AL NORTE DE CHIAPAS, MÉXICO

El agroecosistema denominado solar presenta un papel fundamental en el sistema de vida del pueblo ch’ol en el sureste de México; la conservación del conocimiento tradicional de especies vegetales, ha permitido obtener diversos recursos para la subsistencia y han contribuido en los ingresos económicos de las familias. Por ello, los objetivos de esta investigación fueron describir el agroecosistema denominado “solar”, identificar las especies vegetales que las familias choles utilizan y determinar las categorías antropocéntricas del uso de estas especies, con base a sus conocimientos tradicionales. Esta investigación se realizó en comunidades maya-ch’ol del Valle de Tulijá, al norte de Chiapas, México; para la obtención de la información, se implementó el proceso metodológico SIV (Sistemas de Vida), se aplicaron herramientas participativas y técnicas tradicionales de muestreo etnobotánico, en el periodo agosto 2016 a agosto 2017; el análisis de la información fue desarrollado mediante métodos descriptivos. El solar maya-ch’ol se caracteriza por presentar cuatro espacios zonificados destinados para el aprovechamiento de sus recursos, los cuales son traspatio, hortaliza, jardín y reserva forestal; en los cuales se registran 131 especies útiles, agrupadas en 58 familias, sobre todo representadas por Fabaceae (11 especies), Malvaceae y Rutaceae (8 especies); de todas las especies destaca el registro de 65 nombres de plantas en lengua ch’ol. Del total de especies, se presenta una clasificación de 19 categorías de usos antropocéntricos, representados en su mayoría por uso comestible, medicinal y ornamental; asimismo, los biotipos usados con mayor frecuencia son los árboles, y las partes más utilizadas son los frutos y las hojas. Bajo tal contexto, este estudio permitió revalorizar los saberes etnobotánicos en relación al manejo de los componentes del solar; además, se hace evidente la importancia de este espacio en el ámbito del sistema de vida del pueblo maya-ch’ol

A single bout of whole-body vibration improves hamstring flexibility in university athletes: A randomized controlled trial

Hamstring muscle injuries are one of most frequent injuries in team sports. Whole-body vibration (WBV) has an important effect on flexibility that could prevent shortening of the hamstrings. To investigate both acute and residual effect of a single bout of WBV on hamstring flexibility in a group of university athletes from team sports 70 athletes (81% men, age 21 ± 1.9 years old) were separated into three groups; control group (CG; n=24), hamstring flexibility group without vibration (-V; n=23), and hamstring flexibility group with vibration (+V; n=23). Both -V and +V groups performed the same experimental protocol, composed of 6 sets of 30 seconds of passive hamstring flexibility over a vibration platform with both legs alternately (full-length 6 minutes; 3 minutes per leg). A high-magnitude vibration loading was applied only in +V group (40 Hz and 4 mm). Hamstring flexibility was evaluated through the Modified Sit and Reach (MSR) and Passive Straight Leg Raise (PSLR) test before (baseline), immediately after (acute effect), and after 72 h (residual effect) intervention. Both experimental groups showed a significant improvement in flexibility compared to CG in all measures (p<0.05). No statistical differences were found between +V and –V, however, MSR, right PSLR, and left PSLR residual effect size (Cohen's d) were greater in +V. In conclusion, adding a WBV stimulus to flexibility training improves acute and residual hamstring flexibility in university athletes from team sports

High-risk HPV infection after five years in a population-based cohort of Chilean women

<p>Abstract</p> <p>Background</p> <p>The need to review cervical cancer prevention strategies has been triggered by the availability of new prevention tools linked to human papillomavirus (HPV): vaccines and screening tests. To consider these innovations, information on HPV type distribution and natural history is necessary. This is a five-year follow-up study of gynecological high-risk (HR) HPV infection among a Chilean population-based cohort of women.</p> <p>Findings</p> <p>A population-based random sample of 969 women from Santiago, Chile aged 17 years or older was enrolled in 2001 and revisited in 2006. At both visits they answered a survey on demographics and sexual history and provided a cervical sample for HPV DNA detection (GP5+/6+ primer-mediated PCR and Reverse line blot genotyping). Follow-up was completed by 576 (59.4%) women; 45 (4.6%) refused participation; most losses to follow-up were women who were unreachable, no longer eligible or had missing samples. HR-HPV prevalence increased by 43%. Incidence was highest in women < 20 years of age (19.4%) and lowest in women > 70 (0%); it was three times higher among women HR-HPV positive versus HPV negative at baseline (25.5% and 8.3%; OR 3.8, 95% CI 1.8-8.0). Type-specific persistence was 35.3%; it increased with age, from 0% in women < 30 years of age to 100% in women > 70. An enrollment Pap result ASCUS or worse was the only risk factor for being HR-HPV positive at both visits.</p> <p>Conclusions</p> <p>HR-HPV prevalence increased in the study population. All HR-HPV infections in women < 30 years old cleared, supporting the current recommendation of HR-HPV screening for women > 30 years.</p