All-optical 3D atomic loops generated with Bessel light fields

The propagation invariance of Bessel beams as well as their transversal structure are used to perform a comparative analysis of their effect on cold atoms for four different configurations and combinations thereof. We show that, even at temperatures for which the classical description of the atom center of mass motion is valid, the interchange of momentum, energy and orbital angular momentum between light and atoms yields efficient tools for all-optical trapping, transporting and, in general, manipulating the state of motion of cold atoms.Comment: 13 pages, 9 figure

Piecewise contracting maps on the interval: Hausdorff dimension, entropy and attractors

We consider the attractor $\Lambda$ of a piecewise contracting map $f$ defined on a compact interval. If $f$ is injective, we show that it is possible to estimate the topological entropy of $f$ (according to Bowen's formula) and the Hausdorff dimension of $\Lambda$ via the complexity associated with the orbits of the system. Specifically, we prove that both numbers are zero.Comment: 8 page

Ensambles de arqueas y bacterias en la Zona de Mínimo Oxígeno del ecosistema de surgencia de Chile central determinados mediante biomarcadores orgánicos

Indexación: Web of Science; Scielo.Organic biomarkers were used to investigate the influence of seasonal changes in oxygenation and water chemistry on the distribution of archaea and bacteria in the water column and surface sediments of the continental shelf off central Chile (ca. 36°S), an area influenced by seasonal upwelling and the development of an oxygen minimum zone. We were interested in establishing if occurrence of archaea and bacteria responds to oxygenation and water chemistry for which we analyzed archaeal isoprenoid (i) and bacterial branched (br) glycerol dialkyl glycerol tetraethers (GDGTs). Our results combined with molecular data from a year round observational program at the same sampling site and depths indicatives the occurrence and dominance of the marine pelagic group Thaumarchaeota. Changes in the distribution of iGDGTs might be explained by (i) the presence of archaeal populations in sub-oxic waters, phylogenetically different from those in surface water, (ii) changes in the relative contribution of Euryarchaeota with depth, and (iii) a relationship between Thaumarchaeota and environmental factors other than temperature. Branched GDGTs were more abundant in the upper, oxic layer during the non-upwelling season, may be a result of higher river runoff, whereas their diversity was higher within sub-oxic waters. Our results indicate a vertical segregation of iGDGTs and brGDGTs, with predominance of archaeal biomarkers during the low productivity season.Se utilizaron biomarcadores orgánicos en para investigar la influencia de cambios estacionales en los niveles de oxigenación y la química del agua sobre la distribución de arqueas y bacterias en la columna de agua y los sedimentos superficiales de la plataforma continental frente a Chile central, un área influenciada por surgencia estacional asociada al desarrollo de una zona de mínimo oxígeno. Nuestro interés es establecer si la ocurrencia de arquea y bacteria responde a la oxigenación y química del agua para lo cual analizamos gliceroles dialquil gliceroles tetra-éteres (GDGTs) isoprenoides arqueanos (i) y ramificados bacterianos (r). Nuestros resultados, combinados con datos moleculares de observaciones durante un año en el mismo lugar y profundidades del sitio de estudio indican la presencia y dominancia del grupo arqueano marino- pelágico Thaumarchaeota. Los cambios observados en la distribución de iGDGTs podrían explicarse por (i) la presencia de poblaciones de arqueas marinas en la capa de agua sub-óxica, filogenéticamente diferentes a las de aguas superficiales, (ii) cambio en la contribución relativa de Euryarchaeota con profundidad, y (iii) una relación entre Thaumarchaeota y factores ambientales distintos a la temperatura. Los GDGTs ramificados fueron más abundantes en la capa óxica superior durante el periodo de no-surgencia, tal vez influenciado por la alta descarga de ríos, mientras que su diversidad fue más alta en el agua sub-óxica. Nuestros resultados indican una segregación vertical de los GDGTs isoprenoides y ramificados, con el predominio de biomarcadores arqueanos durante el periodo de baja productividad.http://ref.scielo.org/vq5y7

Depicting #fatherhood involvement on Instagram: Caregiving, affection, and stimulation

This article aims to analyze how fatherhood is performed on Instagram by examining the domains of involvement. Parental roles and behaviors have changed in the last years and are currently a relevant social and scientific topic. The way that fatherhood is performed is also a frequent subject on social media, spreading the ideal of a new fatherhood and portraying the father as committed to childcare duties. The hashtag “fatherhood” was used to identify posts on Instagram representing father involvement. A final sample of 121 posts was identified. Results depicted three main domains in fatherhood’s online representations of involvement: (1) child caregiving; (2) fathers as a source of the child’s affection; and (3) fathers involved in play, committed to the child’s interests and offering new opportunities of stimulation. The display of fatherhood as a role requiring dedication and effort also emerged, but to a lesser extent. Nevertheless, only positive emotions were shared, depicting pleasure in the performed role, and communicating an ideal and self-enhancing profile. Moreover, posts seemed to disseminate an ideal of fatherhood rather than raise questions or discuss the challenges related to it. Findings uncover how media social representations of fatherhood are still an unfinished process, failing to capture diversity and challenges in contemporary families

Subharmonic Generation in Quantum Systems

We show how the classical-quantum correspondence permits long-lived subharmonic motion in a quantum system driven by a periodic force. Exponentially small deviations from exact subharmonicity are due to coherent tunneling between quantized vortex tubes which surround classical elliptic periodic orbits.Comment: 11 pages + 5 figures (available upon request), Revtex 3.0, NSF-ITP-93-4

Uso de 7Be para cuantificar el impacto de un evento de precipitación intensa sobre la redistribución del suelo en un sitio sometido a cero labranza

Durante muchos años el sitio de estudio, ubicado en el centro-sur de Chile (38°37´S 73°04´O), fue cultivado bajo cero labranza sin quema de residuos. A comienzos del 2005, después de la cosecha y previo al inicio de las lluvias de otoño se sometieron a quema los residuos del cultivo, dejando el suelo desnudo sin cobertura vegetal hasta el inicio de un período de precipitaciones intensas ocurrido en Mayo de 2005. Para estimar los montos y distribución espacial de la erosión y sedimentación asociados al periodo de precipitación intensa se utilizaron mediciones de 7Be asociadas a un modelo de conversión de los inventarios de 7Be en montos de redistribución de suelo. La erosión neta y fracción de pérdida de sedimentos desde el sitio de estudio (1.2±0.2 kg m-2 y 88% respectivamente) asociadas al periodo de precipitación intensa fueron considerablemente mayores que las estimadas para el mismo sitio durante el período previo de cero labranza sin quema (16 años) utilizando la técnica del 137Cs (0.14±0.2 kg m-2 a-1 y 19%respectivamente)

Language development disorder in Fetal Alcohol Spectrum Disorders (FASD), a case study

Prenatal alcohol exposure can cause developmental damage in children. There are different types and ranges of alterations that fall under the name of fetal alcohol spectrum disorders (FASD). Disabilities in learning, cognition, and behavior are observed. Environmental conditions are an influencing factor in this population since they are generally adverse and are either not diagnosed at an early stage or given the appropriate support and approach. We present a case study of a 9-year-old child, in which all the variables affecting his development (FASD diagnosis and socioenvironmental conditions) were observed and analyzed. His early childhood under institutional care, the move to a foster home at the age of 6, and several measures of evaluation from foster care to the present are described. Difficulties in vocabulary, access to vocabulary, morphology, syntax, grammar, oral narrative, pragmatics, speech, and communication were observed, along with cognitive difficulties in memory, perception and executive functioning, social adaptation, learning, and behavior. An early diagnosis and approach enable this population to develop skills in different dimensions to address early adversity despite their neurological and behavioral commitment. Speech-language pathologist services are crucial for the diagnosis and treatment of the language and communication difficulties that characterize this syndrom

Changes in soil erosion associated with the shift from conventional tillage to a no-tillage system, documented using 137Cs measurements

Caesium-137 measurements have been used to document changes in the rate and extent of soil erosion associated with the shift from conventional tillage to a no-till system on a farm in south-central Chile. The study site is located in the Coastal Mountains of the 9th Region (38°37′S 73°04′W), and is characterized by Araucano series Ultisols (Typic Hapludult), a temperate climate and a mean annual precipitation of 1100 mm year-1. A field, which was under conventional tillage until May 1986 and which was subsequently managed using a no-till system, was selected for the study. An approach for using 137Cs measurements to quantify the medium-term erosion and deposition rates associated with the periods of contrasting land management documented previously was employed. This approach involves both a standard method and a simplified method, which permits a larger number of sampling points to be used. In this study, emphasis was placed on application of the simplified method, which has the important advantage of requiring only two 137Cs measurements per sampling point. The results obtained for the study field showed that the implementation of no-till practices, including crop residue management, coincided with a reduction in the net erosion rate by about 87% and the proportion of the study area subject to erosion from 100% to 57%, and therefore significantly decreased soil and nutrient loss. Reduced soil and nutrient loss has important on-site benefits, in terms of sustainable management of the soil resource and maintaining crop productivity, as well as reducing off-site problems associated with the degradation of river water quality

Documentos para la historia de la medicina en Chile: la obra de Eduardo Cruz Coke: "Procurar curar y alimentar al niño antes de que nazca"

Sin lugar a dudas, las obras de grande mujeres y hombres trascienden fronteras. Y no existe mayor frontera a trascender que la de la salud humana y primordialmente la de los niños, niñas y jóvenes: he ahí el porvenir. En la vida y obra del Doctor Eduardo Cruz Coke podemos apreciar dicha preocupación por los más desvalidos. Durante su corta -y fructífera- estadía en el Ministerio de Salud de Chile, logró colocar los cimientos de lo que podríamos llamar la Salud Materno-Infantil y la Salud y Bienestar Colectivo. No solamente él observa que el cuerpo humano debe estar sano, sino que, la sociedad en su conjunto. Un claro ejemplo de su labor médica y política la encontramos en la presentación al Congreso Nacional de la Ley de protección de la Infancia, la cual también abarcaba a la madre del infante. Por primera vez se da a conocer un documento inédito que descansa en el Archivo Nacional de Chile y que era necesario entregar a la academia para su estudio