Velocity distributions in a gas-gun microparticle accelerator.

Here, we build and characterize a single-stage gas-gun microparticle accelerator, where a pressurized gas expands and launches particles on a target. The microparticles in the range of 60-250 µm are accelerated by the expansion of pressurized nitrogen. By using a high-speed camera, we study how the velocity distribution of accelerated particles is modified by particle size, pressure in the gas reservoir, valve's opening time, and diaphragm's thickness and composition. We employ this microparticle accelerator to study the impact of glass particles with diameters of (69 ± 6) µm accelerated at moderate velocities ∼ (10-25) m/s, using films of poly-dimethylsiloxane as targets.

Nanotribological behavior of deep cryogenically treated martensitic stainless steel.

Cryogenic treatments are increasingly used to improve the wear resistance of various steel alloys by means of transformation of retained austenite, deformation of virgin martensite and carbide refinement. In this work the nanotribological behavior and mechanical properties at the nano-scale of cryogenically and conventionally treated AISI 420 martensitic stainless steel were evaluated. Conventionally treated specimens were subjected to quenching and annealing, while the deep cryogenically treated samples were quenched, soaked in liquid nitrogen for 2 h and annealed. The elastic-plastic parameters of the materials were assessed by nanoindentation tests under displacement control, while the friction behavior and wear rate were evaluated by a nanoscratch testing methodology that it is used for the first time in steels. It was found that cryogenic treatments increased both hardness and elastic limit of a low-carbon martensitic stainless steel, while its tribological performance was enhanced marginally.

Earthquake rupture below the brittle-ductile transition in continental lithospheric mantle.

Earthquakes deep in the continental lithosphere are rare and hard to interpret in our current understanding of temperature control on brittle failure. The recent lithospheric mantle earthquake with a moment magnitude of 4.8 at a depth of ~75 km in the Wyoming Craton was exceptionally well recorded and thus enabled us to probe the cause of these unusual earthquakes. On the basis of complete earthquake energy balance estimates using broadband waveforms and temperature estimates using surface heat flow and shear wave velocities, we argue that this earthquake occurred in response to ductile deformation at temperatures above 750°C. The high stress drop, low rupture velocity, and low radiation efficiency are all consistent with a dissipative mechanism. Our results imply that earthquake nucleation in the lithospheric mantle is not exclusively limited to the brittle regime; weakening mechanisms in the ductile regime can allow earthquakes to initiate and propagate. This finding has significant implications for understanding deep earthquake rupture mechanics and rheology of the continental lithosphere.

Monitoring southwest Greenland's ice sheet melt with ambient seismic noise.

The Greenland ice sheet presently accounts for ~70% of global ice sheet mass loss. Because this mass loss is associated with sea-level rise at a rate of 0.7 mm/year, the development of improved monitoring techniques to observe ongoing changes in ice sheet mass balance is of paramount concern. Spaceborne mass balance techniques are commonly used; however, they are inadequate for many purposes because of their low spatial and/or temporal resolution. We demonstrate that small variations in seismic wave speed in Earth's crust, as measured with the correlation of seismic noise, may be used to infer seasonal ice sheet mass balance. Seasonal loading and unloading of glacial mass induces strain in the crust, and these strains then result in seismic velocity changes due to poroelastic processes. Our method provides a new and independent way of monitoring (in near real time) ice sheet mass balance, yielding new constraints on ice sheet evolution and its contribution to global sea-level changes. An increased number of seismic stations in the vicinity of ice sheets will enhance our ability to create detailed space-time records of ice mass variations.

Social, health and consumption profiles and perceptions of treatment in a group recovering alcoholics, Medellín, Colombia / Perfil social, de saúde, de consumo e percepção do tratamento de um grupo de alcoólicos em processo de recuperação, Medellín, Colombia / Perfil social, de salud, de consumo y percepción del tratamiento de un grupo de alcohólicos en proceso de recuperación, Medellín, Colombia

Alcohol is responsible for 2.5 million deaths annually and is a risk factor in certain communicable diseases. The negative of its consumption can be felt in all areas of life. The object of this descriptive study was to determine the social, health and consumption characteristics and the perceptions of rehabilitation treatment in alcoholics. The information was collected using a questionnaire for the social and health variables and a semi-structured interview to determine perceptions of treatment. The majority were male, middle class and had begun consuming alcohol at 11 years of age, with depression being the most common psychological comorbidity. They perceived treatment as welfare.(AU)

O álcool causa 2,5 milhões de mortes anualmente, é fator de risco para quem sofre alguma enfermidade transmissível, seu consumo traz consequências negativas em todos os âmbitos. O objetivo deste estudo descritivo foi determinar as características sociais, de saúde, de consumo e a percepção sobre o tratamento de reabilitação em pessoas alcoólicas. A informação foi coletada através de um questionário para conhecer variáveis sociais e de saúde, e uma entrevista semiestruturada para determinar a percepção do tratamento. O perfil da maioria das pessoas era homens de classe média que começaram a consumir aos 11 anos de idade e que apresentavam a depressão como comorbidade psiquiátrica mais frequente. Viam o tratamento como uma questão de bem-estar.(AU)

El alcohol causa anualmente 2.5 millones de muertes, es factor de riesgo para sufrir alguna enfermedad trasmisible, su consumo trae consecuencias negativas en todos los ámbitos. En este estudio descriptivo, el objetivo fue determinar las características sociales, de salud, de consumo y la percepción sobre el tratamiento de rehabilitación en personas alcohólicas. La información se recolecto a través de una encuesta para conocer variables sociales y de salud y una entrevista semiestructurada para determinar la percepción del tratamiento. La mayoría de las personas fueron hombres, de clase media que iniciaron el consumo a los 11 años de edad y cuya comorbilidad psiquiátrica más frecuente fue la depresión. Percibían el tratamiento como un bienestar.(AU)

Social, health and consumption profiles and perceptions of treatment in a group recovering alcoholics, Medellín, Colombia / Perfil social, de salud, de consumo y percepción del tratamiento de un grupo de alcohólicos en proceso de recuperación, Medellín, Colombia

Alcohol is responsible for 2.5 million deaths annually and is a risk factor in certain communicable diseases. The negative of its consumption can be felt in all areas of life. The object of this descriptive study was to determine the social, health and consumption characteristics and the perceptions of rehabilitation treatment in alcoholics. The information was collected using a questionnaire for the social and health variables and a semi-structured interview to determine perceptions of treatment. The majority were male, middle class and had begun consuming alcohol at 11 years of age, with depression being the most common psychological comorbidity. They perceived treatment as welfare.

O álcool causa 2,5 milhões de mortes anualmente, é fator de risco para quem sofre alguma enfermidade transmissível, seu consumo traz consequências negativas em todos os âmbitos. O objetivo deste estudo descritivo foi determinar as características sociais, de saúde, de consumo e a percepção sobre o tratamento de reabilitação em pessoas alcoólicas. A informação foi coletada através de um questionário para conhecer variáveis sociais e de saúde, e uma entrevista semiestruturada para determinar a percepção do tratamento. O perfil da maioria das pessoas era homens de classe média que começaram a consumir aos 11 anos de idade e que apresentavam a depressão como comorbidade psiquiátrica mais frequente. Viam o tratamento como uma questão de bem-estar.

El alcohol causa anualmente 2.5 millones de muertes, es factor de riesgo para sufrir alguna enfermedad trasmisible, su consumo trae consecuencias negativas en todos los ámbitos. En este estudio descriptivo, el objetivo fue determinar las características sociales, de salud, de consumo y la percepción sobre el tratamiento de rehabilitación en personas alcohólicas. La información se recolecto a través de una encuesta para conocer variables sociales y de salud y una entrevista semiestructurada para determinar la percepción del tratamiento. La mayoría de las personas fueron hombres, de clase media que iniciaron el consumo a los 11 años de edad y cuya comorbilidad psiquiátrica más frecuente fue la depresión. Percibían el tratamiento como un bienestar.

Prevalencia de sintomatología depresiva y ansiosa en estudiantes de 14 a 18 años de un colegio privado de Medellín / Prevalence of Depressive and Anxious Symptomatology in 14-18 ys-old Students from a Private School in Medellin

Introducción: Este estudio busca determinar la prevalencia de los síntomas depresivos, ansiosos y factores de riesgo familiares, medioambientales y personales, en una población de adolescentes entre 14 y 18 años de edad de un colegio privado de Medellín. Métodos: Estudio observacional analítico de corte. Se aplicó una encuesta sociodemográfica, y las escalas de BAI (inventario de ansiedad de Beck) y BDI- II (inventario de depresión de Beck-II), para detectar la presencia de sintomatología ansiosa y depresiva. Resultados: Se encuestaron 152 adolescentes, el promedio de edad fue de 15,4 ± 0,9 años, la prevalencia de síntomas ansiosos fue de 25%, y de síntomas depresivos, de 25,7%. De los 38 (25%) estudiantes que tuvieron puntajes positivos en el BAI, 26 (68,4%) presentaron puntajes positivos en el BDI, y de los 39 (25,6%) alumnos que tuvieron puntajes positivos para BDI, en 26 (66,7%) se hallaron puntajes positivos para el BAI. Conclusiones: Los factores de riesgo para sintomatología ansiosa y depresiva fueron: ser mujer, ser víctima de matoneo y el maltrato. Tener amigos fue factor protector para sintomatología depresiva. Se encontró asociación estadística entre el autorreporte de sintomatología depresiva en el adolescente y sintomatología de ansiedad; entre el autorreporte de ansiedad con sintomatología depresiva; de igual manera, entre la sintomatología de depresión y ansiedad y la percepción de los padres para dichos síntomas.

Objective: This study describes prevalence of depressive and anxious symptoms together with family, environmental and personal risk factors in a group of adolescents between 14 and 18 years of age in a private school of Medellín. Methods: An analytic observational cross sectional study was performed in 152 adolescents, evaluating sociodemographic aspects and prevalence of depressive and anxious symptomatology, as established through BDI-II and BAI. Results: Average age was 15.4 ± 0.9 years old, with a 25% prevalence of anxiety symptoms and 25.7% of depressive symptoms. From the 38 (25%) students with BAI positive, 26 (68.4%) were BDI positive, and from the 39 (25.6%) students with BDI positive, 26 (66.7%) were BAI positive. Conclusions: the risk factors for anxiety and depressive symptomatology were: being a woman, being a victim of bullying and abuse. Having friends was the protective factors for depressive symptomatology. There was a statistical association between self-report of depressive and anxiety symptomatology; between the anxiety self-report and the depressive symptomatology; as well as between depressive and anxiety symptomatology and parents' perception of such symptoms.

[Prevalence of Depressive and Anxious Symptomatology in 14-18 ys-old Students from a Private School in Medellin]. / Prevalencia de sintomatología depresiva y ansiosa en estudiantes de 14 a 18 años de un colegio privado de Medellín.

OBJECTIVE: This study describes prevalence of depressive and anxious symptoms together with family, environmental and personal risk factors in a group of adolescents between 14 and 18 years of age in a private school of Medellín. METHODS: An analytic observational cross sectional study was performed in 152 adolescents, evaluating sociodemographic aspects and prevalence of depressive and anxious symptomatology, as established through BDI-II and BAI. RESULTS: Average age was 15.4 ± 0.9 years old, with a 25% prevalence of anxiety symptoms and 25.7% of depressive symptoms. From the 38 (25%) students with BAI positive, 26 (68.4%) were BDI positive, and from the 39 (25.6%) students with BDI positive, 26 (66.7%) were BAI positive. CONCLUSIONS: the risk factors for anxiety and depressive symptomatology were: being a woman, being a victim of bullying and abuse. Having friends was the protective factors for depressive symptomatology. There was a statistical association between self-report of depressive and anxiety symptomatology; between the anxiety self-report and the depressive symptomatology; as well as between depressive and anxiety symptomatology and parents' perception of such symptoms.