3,350 research outputs found

    Correlates of Smoking Cessation Among Filipino Immigrant Men

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    A survey on tobacco use among 318 Filipino immigrant men aged 40–75 years was conducted in Los Angeles, California. Those who reported more English language use with their family, friends and neighbors (OR = 1.31) and who lived in households with complete smoking prohibition (OR = 3.82) were more likely to be successful in quitting smoking. Those who endorsed more positive beliefs on physical and social consequences of smoking (OR = 0.69) and who had mostly smoking friends (OR = 0.37) were less likely to be successful in quitting smoking. Our findings suggest that prohibiting smoking in households, creating social networks of non-smokers, and education or counseling are important components of a smoking cessation intervention for Filipino immigrant men

    Wire Harness Assembly Process Supported by Collaborative Robots: Literature Review and Call for R&D

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    The wire harness assembly process is a complicated manufacturing activity, which is becoming more complex because of the evolving nature of mechatronic and electronic products that require more connectors, sensors, controllers, communication networking, etc. Furthermore, the demand for wire harnesses continues to grow in all industries worldwide as the majority of equipment, appliances, machinery, vehicles, etc., are becoming "smart" (i.e., more mechatronic or electronic). Moreover, most of the wire harness assembly process tasks are done manually, and most of these are considered non-ergonomic for human assembly workers. Hence, the wire harness manufacturing industry is faced with the challenge of increasing productivity while improving the occupational health of its human assembly workers. The purpose of this paper is to conduct a literature review exploring the state of the use of collaborative robots in the wire harness assembly process due to their potential to reduce current occupational health problems for human assembly workers and increase the throughput of wire harness assembly lines, and to provide main findings, discussion, and further research directions for collaborative robotics in this application domain. Eleven papers were found in the scientific literature. All papers demonstrated the potential of collaborative robots to improve the productivity of wire harness assembly lines, and two of these in particular on the ergonomics of the wire harness assembly process. None of the papers reviewed presented a cost-benefit or a cycle time analysis to qualitatively and/or quantitatively measure the impact of the incorporation of collaborative robots in the wire harness assembly process. This represents an important area of opportunity for research with relevance to industry. Three papers remark on the importance of the integration of computer vision systems into a collaborative wire harness assembly process to make this more versatile as many types of wire harnesses exist. The literature review findings call for further research and technological developments in support of the wire harness manufacturing industry and its workers in four main categories: (i) Collaborative Robotics and Grippers, (ii) Ergonomics, (iii) Computer Vision Systems, and (iv) Implementation Methodologies

    Hot C-rich white dwarfs: Testing the DB-DQ transition through pulsations

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    Context. Hot DQ white dwarfs are a new class of white dwarf stars that were discovered recently within the framework of the SDSS project. There are nine known hot DQ stars, out of a total of several thousands white dwarfs spectroscopically identified. Three hot DQ white dwarfs have been reported to exhibit photometric variability with periods compatible with pulsation g-modes. Aims. We present a nonadiabatic pulsation analysis of carbon-rich hot DQ white dwarf stars. One of our main aims is to test the convective-mixing scenario for the origin of hot DQs by studying their pulsational properties. Methods. Our pulsation study is based on the full evolutionary models of hot DQ white dwarfs developed by Althaus and collaborators, which consistently cover the entire evolution from the born-again stage to the white dwarf cooling track. Specifically, we present a stability analysis of white dwarf models from stages before the blue edge of the DBV instability strip (Teff ≈ 30 000 K), until the domain of the hot DQ white dwarfs (18 000-24 000 K), including the transition DBhot DQ white dwarf. We explore evolutionary models with M* = 0.585 M⊙ and M* = 0.87 M⊙, and two values of the thickness of the He-rich envelope (MHe = 2x10-7 M* and = 10-8 M*). These envelopes are 4–5 orders of magnitude thinner than those of standard DB white dwarf models resulting from canonical stellar evolution computations. Results. We found that at evolutionary phases in which the models are characterized by He-dominated atmospheres, they exhibit unstable g-mode pulsations typical of DBV stars, and when the models become DQ white dwarfs with carbon-dominated atmospheres, they continue being pulsationally unstable with characteristics similar to DB models, and in agreement with the periods detected in variable hot DQ white dwarfs. In particular, for models with MHe = 10-8 M*, a narrow gap exists separating the DB from the DQ instability domains. Conclusions. Our calculations provide strong support for the convective-mixing picture of the formation of hot DQs. In particular, our results suggest the existence of pulsating DB white dwarfs with very thin He-rich envelopes, which after passing the DBV instability strip become variable hot DQ stars. The existence of these DB stars with very thin envelopes should be investigated by asteroseismology.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

    Hot C-rich white dwarfs: Testing the DB-DQ transition through pulsations

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    Context. Hot DQ white dwarfs are a new class of white dwarf stars that were discovered recently within the framework of the SDSS project. There are nine known hot DQ stars, out of a total of several thousands white dwarfs spectroscopically identified. Three hot DQ white dwarfs have been reported to exhibit photometric variability with periods compatible with pulsation g-modes. Aims. We present a nonadiabatic pulsation analysis of carbon-rich hot DQ white dwarf stars. One of our main aims is to test the convective-mixing scenario for the origin of hot DQs by studying their pulsational properties. Methods. Our pulsation study is based on the full evolutionary models of hot DQ white dwarfs developed by Althaus and collaborators, which consistently cover the entire evolution from the born-again stage to the white dwarf cooling track. Specifically, we present a stability analysis of white dwarf models from stages before the blue edge of the DBV instability strip (Teff ≈ 30 000 K), until the domain of the hot DQ white dwarfs (18 000-24 000 K), including the transition DBhot DQ white dwarf. We explore evolutionary models with M* = 0.585 M⊙ and M* = 0.87 M⊙, and two values of the thickness of the He-rich envelope (MHe = 2x10-7 M* and = 10-8 M*). These envelopes are 4–5 orders of magnitude thinner than those of standard DB white dwarf models resulting from canonical stellar evolution computations. Results. We found that at evolutionary phases in which the models are characterized by He-dominated atmospheres, they exhibit unstable g-mode pulsations typical of DBV stars, and when the models become DQ white dwarfs with carbon-dominated atmospheres, they continue being pulsationally unstable with characteristics similar to DB models, and in agreement with the periods detected in variable hot DQ white dwarfs. In particular, for models with MHe = 10-8 M*, a narrow gap exists separating the DB from the DQ instability domains. Conclusions. Our calculations provide strong support for the convective-mixing picture of the formation of hot DQs. In particular, our results suggest the existence of pulsating DB white dwarfs with very thin He-rich envelopes, which after passing the DBV instability strip become variable hot DQ stars. The existence of these DB stars with very thin envelopes should be investigated by asteroseismology.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

    Wire Harness Assembly Process Supported by a Collaborative Robot: A Case Study Focus on Ergonomics

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    Products and assets are becoming increasingly “smart”, e.g., mechatronic, electronic, or cyber-physical. In the lack of fully reliable wireless solutions, extensive wiring and wire bundling into wire harnesses are needed. This has manufacturing implications, leading to increasingly complex wire harness assembly processes, where numerous components, connectors, and cables are assembled, connecting critical and non-critical electric and electronic systems in smart products and assets. Thus, wire harnesses demand is rapidly rising in most industries, requiring human or robotic work. Often, required work tasks are repetitive and physically demanding, while still needing people for quality reasons. An attractive solution would therefore be humans collaborating with robots. Unfortunately, there are very few scientific studies on automation solutions using collaborative robots (cobots) for wire harness assembly process tasks to increase process productivity and improve work ergonomics. Furthermore, wire harness assembly process tasks are presently carried out 90% manually in this industry, causing serious ergonomic problems for assembly workers who perform such tasks daily. The challenge is reducing the ergonomic risks currently present in many established wire harness assembly processes while improving production time and quality. This paper presents an early prototype and simulation to integrate a cobot into a wire harness assembly process, primarily for work ergonomic improvements. The use of a cobot is specifically proposed to reduce ergonomic risks for wire harness assembly workers. Two methodologies: RULA and JSI were used to evaluate the ergonomics of the task of cable tie collocation. The real-world case study results illustrate the validation of a cobot which significantly reduced non-ergonomic postures in the task of placing cable ties in the wire harnesses assembly process studied. An ergonomic analysis without the cobot (the actual process) was conducted, based on RULA and JSI methodologies, presenting the highest possible scores in both evaluations, which calls for urgent changes in the current wire harness assembly process task studied. Then, the same analysis was performed with the cobot, obtaining significant reductions in the ergonomic risks of the task at hand to acceptable values

    New chemical profiles for the asteroseismology of ZZ CETI stars

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    We compute new chemical profiles for the core and envelope of white dwarfs appropriate for pulsational studies of ZZ Ceti stars. These profiles are extracted from the complete evolution of progenitor stars, evolved through the main sequence and the thermally pulsing asymptotic giant branch (AGB) stages, and from time-dependent element diffusion during white dwarf evolution. We discuss the importance of the initial-final mass relationship for the white dwarf carbon-oxygen composition. In particular, we find that the central oxygen abundance may be underestimated by about 15% if the white dwarf mass is assumed to be the hydrogen-free core mass before the first thermal pulse. We also discuss the importance for the chemical profiles expected in the outermost layers of ZZ Ceti stars of the computation of the thermally pulsing AGB phase and of the phase in which element diffusion is relevant. We find a strong dependence of the outer layer chemical stratification on the stellar mass. In particular, in the less massive models, the double-layered structure in the helium layer built up during the thermally pulsing AGB phase is not removed by diffusion by the time the ZZ Ceti stage is reached. Finally, we perform adiabatic pulsation calculations and discuss the implications of our new chemical profiles for the pulsational properties of ZZ Ceti stars. We find that the whole g-mode period spectrum and the mode-trapping properties of these pulsating white dwarfs as derived from our new chemical profiles are substantially different from those based on chemical profiles widely used in existing asteroseismological studies. Thus, we expect the asteroseismological models derived from our chemical profiles to be significantly different from those found thus far.Facultad de Ciencias Astronómicas y Geofísica

    New cooling sequences for old white dwarfs

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    We present full evolutionary calculations appropriate for the study of hydrogen-rich DA white dwarfs. This is done by evolving white dwarf progenitors from the zero-age main sequence, through the core hydrogen-burning phase, the helium-burning phase, and the thermally pulsing asymptotic giant branch phase to the white dwarf stage. Complete evolutionary sequences are computed for a wide range of stellar masses and for two different metallicities, Z = 0.01, which is representative of the solar neighborhood, and Z = 0.001, which is appropriate for the study of old stellar systems, like globular clusters. During the white dwarf cooling stage, we self-consistently compute the phase in which nuclear reactions are still important, the diffusive evolution of the elements in the outer layers and, finally, we also take into account all the relevant energy sources in the deep interior of the white dwarf, such as the release of latent heat and the release of gravitational energy due to carbon-oxygen phase separation upon crystallization. We also provide colors and magnitudes for these sequences, based on a new set of improved non-gray white dwarf model atmospheres, which include the most up-to-date physical inputs like the Lyα quasi-molecular opacity. The calculations are extended down to an effective temperature of 2500 K. Our calculations provide a homogeneous set of evolutionary cooling tracks appropriate for mass and age determinations of old DA white dwarfs and for white dwarf cosmochronology of the different Galactic populations.Facultad de Ciencias Astronómicas y Geofísica

    Comportamiento de tres sistemas de almacenamiento de maíz (Zea mays L.) comparado con un sistema tradicional

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    An experiment was conducted to test a variety of corn storage systems. In conducting the study three types of deposits were used: A) Silo: a cylindrical container constructed with metal screen which bottom was placed 50 centimeters above ground surface. A metal protection was provided around each column to avoid rodents entrance - B) Granary: a container made out of bomboo and placed on a wood structure 50 centimeters above ground surface. As in system A), the same kind of protection was provided against rodents. C) Conventional: the local farmer has been utilizing a room for grain storage purposes, so comparisons with this traditional method were made. Corn was stored in various ways as follows: 220 kilograms of shelled corn (S), for the silo; 275 kilograms of cobs with husks (TCC), for one of the two granaries tested; 350 kilograms of cobs without husks for the other; 800 kilograms of cobs with husks (T), for the conventional system. Before storing the corn, all deposits, except the conventional one, were properly cleaned and sprinkled with an insecticide to provide the same initial conditions from an environmental point of view. The corn to be stored was sprinkled in like manner, keeping it from getting too wet. In order to determine changes in the state of conservation with time of storage, corn samples were taken every week. The following could be observed in system T: a. The highest temperature troughout the experiment. b. Spoiled corn and a decrease in the germination percentage. c. Damage by rodents in amount which was not possible to determine. System S showed the best storage conditions as well as least percentage of losses far as spoiled grains and decrease in germination percentage in concern. None of the treatments showed growth of microorganisms.Se llevó a cabo un ensayo para probar diferentes sistemas de almacenamiento de maíz. Se utilizaron 3 tipos de depósitos denominados así: A) Silo: recipiente cilíndrico, construido en malla metálica, cuyo fondo quedo a 50 cm del suelo. Para evitar la entrada de roedores, en cada columna se colocó un protector metálico. B) Troje:: recipiente de guadua colocado sobre una estructura de madera. El fondo del recipiente quedo a 50 cm del suelo. Como en el sistema A) se utilizó la misma clase de protección contra los roedores. C) Tradicional: Consistió en una de las formas como normalmente el agricultor almacena su cosecha, en este caso una pieza servía para tal fin. Este sistema sirvió como punto de comparación con los demás sistemas. En el silo se almacenaron 220 kg de maíz desgranado (S). En una troje se almacenaron 275 kg de maíz en mazorcas con capacho (TCC) y en la otra se almacenaron 350 kg de maíz en mazorca sin capacho (TSC). En la pieza se almacenaron 800 kg de maíz en mazorca con capacho (T). Antes de almacenar el maíz, los depósitos mencionados a excepción del tradicional, fueron aseados y asperjados con un insecticida para evitar infestaciones iniciales y colocar a todos en igualdad de condiciones en lo referente a este aspecto. Luego se asperjó el maíz (almacenado) con el mismo insecticida, evitando humedecerlo. Cada 8 días se tomaron muestras para analizar el estado en que se encontraba el producto y así Ilevar el control. El sistema T, presentó a través del ensayo la mayor temperatura, daño y disminución del porcentaje de germinación. No se presentó desarrollo de microorganismos en ninguno de los tratamientos. El ataque de roedores se presentó solamente en 1, pero el daño no se pudo cuantificar. El sistema S, presento las mejores condiciones de almacenamiento ya que el porcentaje de grano dañado y disminución del porcentaje de germinación fueron los más bajos.Maíz-Zea may

    Arabidopsis HAP2/GCS1 is a gamete fusion protein homologous to somatic and viral fusogens

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    Cell–cell fusion is inherent to sexual reproduction. Loss of HAPLESS 2/GENERATIVE CELL SPECIFIC 1 (HAP2/GCS1) proteins results in gamete fusion failure in diverse organisms, but their exact role is unclear. In this study, we show that Arabidopsis thaliana HAP2/GCS1 is sufficient to promote mammalian cell–cell fusion. Hemifusion and complete fusion depend on HAP2/GCS1 presence in both fusing cells. Furthermore, expression of HAP2 on the surface of pseudotyped vesicular stomatitis virus results in homotypic virus–cell fusion. We demonstrate that the Caenorhabditis elegans Epithelial Fusion Failure 1 (EFF-1) somatic cell fusogen can replace HAP2/GCS1 in one of the fusing membranes, indicating that HAP2/GCS1 and EFF-1 share a similar fusion mechanism. Structural modeling of the HAP2/GCS1 protein family predicts that they are homologous to EFF-1 and viral class II fusion proteins (e.g., Zika virus). We name this superfamily Fusexins: fusion proteins essential for sexual reproduction and exoplasmic merger of plasma membranes. We suggest a common origin and evolution of sexual reproduction, enveloped virus entry into cells, and somatic cell fusion

    Hot C-rich white dwarfs: Testing the DB-DQ transition through pulsations

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    Context. Hot DQ white dwarfs are a new class of white dwarf stars that were discovered recently within the framework of the SDSS project. There are nine known hot DQ stars, out of a total of several thousands white dwarfs spectroscopically identified. Three hot DQ white dwarfs have been reported to exhibit photometric variability with periods compatible with pulsation g-modes. Aims. We present a nonadiabatic pulsation analysis of carbon-rich hot DQ white dwarf stars. One of our main aims is to test the convective-mixing scenario for the origin of hot DQs by studying their pulsational properties. Methods. Our pulsation study is based on the full evolutionary models of hot DQ white dwarfs developed by Althaus and collaborators, which consistently cover the entire evolution from the born-again stage to the white dwarf cooling track. Specifically, we present a stability analysis of white dwarf models from stages before the blue edge of the DBV instability strip (Teff ≈ 30 000 K), until the domain of the hot DQ white dwarfs (18 000-24 000 K), including the transition DBhot DQ white dwarf. We explore evolutionary models with M* = 0.585 M⊙ and M* = 0.87 M⊙, and two values of the thickness of the He-rich envelope (MHe = 2x10-7 M* and = 10-8 M*). These envelopes are 4–5 orders of magnitude thinner than those of standard DB white dwarf models resulting from canonical stellar evolution computations. Results. We found that at evolutionary phases in which the models are characterized by He-dominated atmospheres, they exhibit unstable g-mode pulsations typical of DBV stars, and when the models become DQ white dwarfs with carbon-dominated atmospheres, they continue being pulsationally unstable with characteristics similar to DB models, and in agreement with the periods detected in variable hot DQ white dwarfs. In particular, for models with MHe = 10-8 M*, a narrow gap exists separating the DB from the DQ instability domains. Conclusions. Our calculations provide strong support for the convective-mixing picture of the formation of hot DQs. In particular, our results suggest the existence of pulsating DB white dwarfs with very thin He-rich envelopes, which after passing the DBV instability strip become variable hot DQ stars. The existence of these DB stars with very thin envelopes should be investigated by asteroseismology.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat
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