Abrasive effects of sediments on impellers of pumps used for catching raw water.

This study presents an analysis of the abrasive effects of sediments from the bed of the Acre River, Brazil, on the wear of three different ferrous materials employed in the manufacture of impellers of centrifuge pumps used to catch raw water. In order to evaluate the abrasive wear and specific wear coefficient (k) as a function of sediment concentration, tests were conducted in samples of SAE 8620 steel, nodular cast iron and gray cast iron by using a rotary-ball abrasion meter. These tests employed abrasive slurry with concentration of 1, 2, 3, 5 and 10 g L-1 of sediments in distilled water. The volume of worn material as a function of the relative velocity of water flow in relation to the impeller blades was mathematically estimated. The experimental results showed that: i) The semi-angular and semi-rounded shapes of the sediments from the Acre River produced evidence of micro-grooving and plastic deformation in the three metallic alloys; ii) SAE 8620 steel showed higher resistance to abrasive wear than samples of gray and nodular cast iron; iii) the increase in the volume of worn material due to increment in sediment concentration and the relative velocity of the mixture (water + sediment) to the rotor pads.Neste estudo analisou-se a capacidade abrasiva dos sedimentos do leito do Rio Acre, Brasil, no desgaste de 3 materiais ferrosos diferentes utilizados na fabrica??o de rotores de bombas centr?fugas, utilizados na capta??o de ?gua bruta. Para determinar o modo de desgaste e a rela??o do coeficiente de desgaste espec?fico do material (k), em fun??o da concentra??o de sedimentos, foram realizados ensaios em abras?metro de esfera rotativa em amostras de a?o SAE 8620, ferro fundido nodular e em ferro fundido cinzento, usando como suspens?es abrasivas as concentra??es de 1, 2, 3, 5 e 10 g L-1 de sedimento em ?gua destilada. O volume de desgaste em fun??o da velocidade relativa do fluxo da ?gua em rela??o ?s p?s do rotor foi estimado matematicamente. Os resultados mostraram que: i) As formas semiangulares e semiarredondadas dos sedimentos do Rio Acre produziram evidencias de microssulcamento e deforma??o pl?stica nas tr?s ligas met?licas; ii) O a?o SAE 8620 mostrou maior resist?ncia ao desgaste abrasivo do que as amostras de ferros fundidos cinzento e nodular; e iii) O aumento do volume de desgaste decorrente da aumento da concentra??o de sedimento e da velocidade relativa que a mistura (?gua + sedimento) para pelas p?s do rotor

Why Are Outcomes Different for Registry Patients Enrolled Prospectively and Retrospectively? Insights from the Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF).

Background: Retrospective and prospective observational studies are designed to reflect real-world evidence on clinical practice, but can yield conflicting results. The GARFIELD-AF Registry includes both methods of enrolment and allows analysis of differences in patient characteristics and outcomes that may result. Methods and Results: Patients with atrial fibrillation (AF) and ≥1 risk factor for stroke at diagnosis of AF were recruited either retrospectively (n = 5069) or prospectively (n = 5501) from 19 countries and then followed prospectively. The retrospectively enrolled cohort comprised patients with established AF (for a least 6, and up to 24 months before enrolment), who were identified retrospectively (and baseline and partial follow-up data were collected from the emedical records) and then followed prospectively between 0-18 months (such that the total time of follow-up was 24 months; data collection Dec-2009 and Oct-2010). In the prospectively enrolled cohort, patients with newly diagnosed AF (≤6 weeks after diagnosis) were recruited between Mar-2010 and Oct-2011 and were followed for 24 months after enrolment. Differences between the cohorts were observed in clinical characteristics, including type of AF, stroke prevention strategies, and event rates. More patients in the retrospectively identified cohort received vitamin K antagonists (62.1% vs. 53.2%) and fewer received non-vitamin K oral anticoagulants (1.8% vs . 4.2%). All-cause mortality rates per 100 person-years during the prospective follow-up (starting the first study visit up to 1 year) were significantly lower in the retrospective than prospectively identified cohort (3.04 [95% CI 2.51 to 3.67] vs . 4.05 [95% CI 3.53 to 4.63]; p = 0.016). Conclusions: Interpretations of data from registries that aim to evaluate the characteristics and outcomes of patients with AF must take account of differences in registry design and the impact of recall bias and survivorship bias that is incurred with retrospective enrolment. Clinical Trial Registration: - URL: http://www.clinicaltrials.gov . Unique identifier for GARFIELD-AF (NCT01090362)

Risk profiles and one-year outcomes of patients with newly diagnosed atrial fibrillation in India: Insights from the GARFIELD-AF Registry.

BACKGROUND: The Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF) is an ongoing prospective noninterventional registry, which is providing important information on the baseline characteristics, treatment patterns, and 1-year outcomes in patients with newly diagnosed non-valvular atrial fibrillation (NVAF). This report describes data from Indian patients recruited in this registry. METHODS AND RESULTS: A total of 52,014 patients with newly diagnosed AF were enrolled globally; of these, 1388 patients were recruited from 26 sites within India (2012-2016). In India, the mean age was 65.8 years at diagnosis of NVAF. Hypertension was the most prevalent risk factor for AF, present in 68.5% of patients from India and in 76.3% of patients globally (P < 0.001). Diabetes and coronary artery disease (CAD) were prevalent in 36.2% and 28.1% of patients as compared with global prevalence of 22.2% and 21.6%, respectively (P < 0.001 for both). Antiplatelet therapy was the most common antithrombotic treatment in India. With increasing stroke risk, however, patients were more likely to receive oral anticoagulant therapy [mainly vitamin K antagonist (VKA)], but average international normalized ratio (INR) was lower among Indian patients [median INR value 1.6 (interquartile range {IQR}: 1.3-2.3) versus 2.3 (IQR 1.8-2.8) (P < 0.001)]. Compared with other countries, patients from India had markedly higher rates of all-cause mortality [7.68 per 100 person-years (95% confidence interval 6.32-9.35) vs 4.34 (4.16-4.53), P < 0.0001], while rates of stroke/systemic embolism and major bleeding were lower after 1 year of follow-up. CONCLUSION: Compared to previously published registries from India, the GARFIELD-AF registry describes clinical profiles and outcomes in Indian patients with AF of a different etiology. The registry data show that compared to the rest of the world, Indian AF patients are younger in age and have more diabetes and CAD. Patients with a higher stroke risk are more likely to receive anticoagulation therapy with VKA but are underdosed compared with the global average in the GARFIELD-AF. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01090362

Stratospheric ozone intrusions during the passage of cold fronts over central Chile

This study analyzes tropospheric column ozone variability in the southern hemisphere as a function of ozone transport from the stratosphere to the troposphere and photochemical formation. Geographically, the study area was located in the mid-latitudes in South America (33 degrees S), to the west of the Andes mountain range, in an area highly susceptible to stratospheric intrusions. Monthly ozonesonde measurements were recorded in Colina to ascertain seasonal vertical ozone distribution from the surface to the stratosphere between September 2010 and May 2012. Vertical distribution of the tropospheric ozone was measured in Talagante for fronts crossing from west to east in central Chile, during two periods in September 2014 and March 2015. These periods were significantly different in terms of the stratospheric ozone annual cycle and height of the tropopause. Our results showed rapid increases of approximately 50% in the tropospheric column ozone at time intervals shorter than 1 week. At the surface level, unusually enhanced ozone levels up to 10 parts per billion volume (ppbv) were observed during nighttime. Additionally, stratosphere-troposphere exchange (STE) preferentially occurred in spring and winter, with higher contribution during spring when the tropospheric column ozone attained its maximum concentration. These results provide valuable information regarding tropospheric ozone, a major local and global climate pollutant, to decision makers. In addition, they provide the research community with experimental data from the southern hemisphere, which helps bridge knowledge gaps in a region that has been rarely studied by national and international scientific communities.FONDECYT Program 1113017

Taller de estrategias de investigación

Los textos que se presentan a continuación son resultado del trabajo realizado por estudiantes de sociología que cursaron el taller de Estrategias de Investigación, durante el primer semestre de 1999. El primer trabajo que presentamos es el de Lídice Tobar, que aborda el fenómeno comunicacional de Omar Gárate a partir de sus programa radial: El rinconcito ranchero. El segundo trabajo es el realizado por Rodrigo Gallardo, Manuel Hadjiconstantis y Alberto Horno. Ellos se propusieron indagar en las expectativas de los jóvenes respecto de los programas culturales, para esto elaboraron y aplicaron una encuesta entre alumnos secundarios. Sigue luego el trabajo de Joao da Silva Forttes y Francisco Mancilla, los que desarrollan una investigación que indaga históricamente en torno de la emergencia y desarrollo del mundo punk. El último trabajo de esta publicación es el de Pablo Pérez Wilson, el que tras largas estadías bajo el suelo santiaguino, elabora un trabajo de investigación que interroga críticamente el mural de Mario Toral, Memoria Visual de una Nación. El autor intenta hacer visible la mirada que propone la obra, reflexionando acerca de la administración de la memoria en el Chile de la transición.Presentación, Pabla Avila F. 4; Omar Gárate, el hombre de los once poderes, Lídice Tobar 5; Explorando los programas culturales de la televisión chilena: Hacia una relación con la juventud actual, Rodrigo Gallardo, Manuel Hadjiconstantis, Alberto Horno 11; El movimiento punk: ¿contracultura o estereotipo?, Joao Da Silva Forttes, Francisco Mancilla Vega 23; Memoria Visual de una Nación, Pablo Pérez Wilson 4

Vitamin C and oxidative stress in the seminiferous epithelium

In this article, we focus on the fundamental role of vitamin C transporters for the normal delivery of vitamin C to germ cells in the adluminal compartment of seminiferous tubules. We argue that the redox status within spermatozoa or in semen is partly responsible for the etiology of infertility. In this context, antioxidant defence plays a critical role in male fertility. Vitamin C, a micronutrient required for a wide variety of metabolic functions, has long been associated with male reproduction. Two systems for vitamin C transport have been described in mammals. Facilitative hexose transporters (GLUTs), with 14 known isoforms to date, GLUT1-GLUT14, transport the oxidized form of vitamin C (dehydroascorbic acid) into the cells. Sodium ascorbic acid co-transporters (SVCTs), SVCT1 and SVCT2 transport the reduced form of vitamin C (ascorbic acid). Sertoli cells control germ cell proliferation and differentiation through cell-cell communication and form the blood-testis barrier. Because the blood-testis barrier limits direct access of molecules from the plasma into the adluminal compartment of the seminiferous tubule, one important question is the method by which germ cells obtain vitamin C. Some interesting results have thrown light on this matter. Expression of SVCT2 and some isoforms of GLUT transporters in the testis have previously been described. Our group has demonstrated that Sertoli cells express functionally active vitamin C transporters. Kinetic characteristics were described for both transport systems (SVCT and GLUT systems). Sertoli cells are able to transport both forms of vitamin C. These findings are extremely relevant, because Sertoli cells may control the amount of vitamin C in the adluminal compartment, as well as regulating the availability of this metabolite throughout spermatogenesis