Modelación de ún móvil sobre una trayectoria en espiral, modulando la amplitud de modelos senosoidales

Este trabajo reporta el análisis de las producciones de estudiantes que participan en un diseño de aprendizaje basado en la modelación del movimiento de un móvil sobre una trayectoria espiral con velocidad constante por modelos senosoidales modulados por exponenciales. Se monta un arreglo experimental donde se filma el móvil y a partir de los datos recogidos con el software Tracker se ajustan gráficamente con el software LDM. Interesa analizar argumentos, herramientas y procedimientos de los estudiantes con la intención de caracterizar procedimientos para la modulación de la amplitud de modelos senosoidales. La metodología de esta investigación es la ingeniería didáctica y la perspectiva teórica en que sustentamos nuestro trabajo es la socioepistemología

¿La modelación sirve como herramienta para establecer comportamientos de gráficos senosoidales modulados por exponenciales?

Este trabajo pretende como objetivo responder a la interrogante planteada, y es que si la modelación sirve como herramienta para establecer comportamientos de gráficos senosoidales modulados por exponenciales. Se monta un arreglo experimental donde se filma el móvil y a partir de los datos recogidos con el software Tracker se ajustan gráficamente con el software LDM. Interesa analizar argumentos, herramientas y procedimientos de los estudiantes con la intención de establecer la modelación como herramienta para visualizar gráficos senosoidales y ver como paso a paso la modelación le abre paso al objetivo planeado. La metodología de esta investigación es la ingeniería didáctica y la perspectiva teórica en que sustentamos nuestro trabajo es la socioepistemología. Este punto es tratado de un punto de vista socioepistemológico por Montiel, que establece en su tesis doctoral (estudio socioepistemológico de la función trigonométrica, 2005), un análisis histórico de corte socioepistemológico, identificando tres prácticas de referencia que considera fundamentales, las cuales son “la matematización de la astronomía, la matematización de la física y la matematización de la transferencia del calor”, donde cita lo siguiente: “todas ellas reguladas por las prácticas sociales de anticipación, predicción y formalización, respectivamente. Llamaremos a estos tres momentos de construcción social de la función trigonométrica, de donde reconocemos dos cambios en el paradigma que rige la actividad matemática y que son necesarios para estudiar el movimiento y la transferencia de calor...” (Montiel 2005, página 104). De esto, y para el fenómeno que se analiza y se modela, se desprende el punto a estudiar con respecto al movimiento (la matematización de la física), buscando que los estudiantes anticipen, predigan y formalicen la función trigonométrica presente

Dutch parallel corpus: a balanced parallel corpus for Dutch-English and Dutch-French

status: publishe

Potential for Increased Human Foodborne Exposure to PCDD/F When Recycling Sewage Sludge on Agricultural Land

Sewage sludge from municipal wastewater treatment is used in agriculture as a nutrient source and to aid in moisture retention. To examine the potential impact of sludge-amended soil on exposures to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from plant and animal foods, we conducted a review of published empirical data from international sources. Levels of PCDD/F in municipal sewage sludge ranged from 0.0005 to 8,300 pg toxic equivalents (TEQ)/g. Background levels in soil ranged from 0.003 to 186 pg TEQ/g. In sludge-amended soils, levels of PCDD/F ranged from 1.4 to 15 pg TEQ/g. Studies that measured levels before and after sludge treatment showed an increase in soil concentration after treatment. Relationships between PCDD/F levels in soil and resulting concentrations in plants were very weakly positive for unpeeled root crops, leafy vegetables, tree fruits, hay, and herbs. Somewhat stronger relationships were observed for plants of the cucumber family. In all cases, large increases in soil concentration were required to achieve a measurable increase in plant contamination. A considerably stronger positive relationship was observed between PCDD/F in feed and resulting levels in cattle tissue, suggesting bioaccumulation. Although PCDD/Fs are excreted in milk, no association was found between feed contamination and levels of PCDD/Fs measured in milk. There is a paucity of realistic data describing the potential for entry of PCDD/Fs into the food supply via sewage sludge. Currently available data suggest that sewage sludge application to land used for most crops would not increase human exposure. However, the use of sludge on land used to graze animals appears likely to result in increased human exposure to PCDD/F

Writing skills, knowledge, motivation, and strategic behavior predict students’ persuasive writing performance in the context of robust writing instruction

This study tested whether writing skills, knowledge, motivation, and strategic behaviors (within the context of robust writing instruction) each made a statistically unique contribution to predicting fifth-grade students’ (123 girls, 104 boys) composition quality and length on a persuasive writing task involving source material, after variance due to other predictors and control variables (reading comprehension, gender, class, and school effects) were controlled. With one exception, writing skills, knowledge, motivation, and strategic behaviors each accounted for statistically unique variance in predicting compositional quality. The exception involved writing knowledge, which did not make a unique contribution in the fall but did in the spring, when a topic knowledge measure was added. In addition, writing motivation, and strategic behaviors accounted for unique variance in composition length in the fall, and writing knowledge did so in the spring

Underdeveloped RPE Apical Domain Underlies Lesion Formation in Canine Bestrophinopathies

Canine bestrophinopathy (cBest) is an important translational model for BEST1-associated maculopathies in man that recapitulates the broad spectrum of clinical and molecular disease aspects observed in patients. Both human and canine bestrophinopathies are characterized by focal to multifocal separations of the retina from the RPE. The lesions can be macular or extramacular, and the specific pathomechanism leading to formation of these lesions remains unclear. We used the naturally occurring canine BEST1 model to examine factors that underlie formation of vitelliform lesions and addressed the susceptibility of the macula to its primary detachment in BEST1-linked maculopathies

Preliminary Findings of the High Quantity of Microplastics in Faeces of Hong Kong Residents

Microplastics are recognised as a ubiquitous and hazardous pollutant worldwide. These small-sized particles have been detected in human faeces collected from a number of cities, providing evidence of human ingestion of microplastics and their presence in the gastrointestinal tract. Here, using Raman spectroscopy, we identified an average of 50 particles g−1 (20.4–138.9 particles g−1 wet weight) in faeces collected from a healthy cohort in Hong Kong. This quantity was about five times higher than the values reported in other places in Asia and Europe. Polystyrene was the most abundant polymer type found in the faeces, followed by polypropylene and polyethylene. These particles were primarily fragments, but about two-thirds of the detected polyethylene terephthalate were fibres. More than 88% of the microplastics were smaller than 300 µm in size. Our study provides the first data on the faecal level, and thus the extent of ingestion, of microplastics in Hong Kong’s population. This timely assessment is crucial and supports the recently estimated ingestion rate of microplastics by Hong Kong residents through seafood consumption, which is one of the highest worldwide. These findings may be applicable to other coastal populations in South China with similar eating habits

In vivo imaging and quantitative analysis of leukocyte directional migration and polarization in inflamed tissue

Directional migration of transmigrated leukocytes to the site of injury is a central event in the inflammatory response. Here, we present an in vivo chemotaxis assay enabling the visualization and quantitative analysis of subtype-specific directional motility and polarization of leukocytes in their natural 3D microenvironment. Our technique comprises the combination of i) semi-automated in situ microinjection of chemoattractants or bacteria as local chemotactic stimulus, ii) in vivo near-infrared reflected-light oblique transillumination (RLOT) microscopy for the visualization of leukocyte motility and morphology, and iii) in vivo fluorescence microscopy for the visualization of different leukocyte subpopulations or fluorescence-labeled bacteria. Leukocyte motility parameters are quantified off-line in digitized video sequences using computer-assisted single cell tracking. Here, we show that perivenular microinjection of chemoattractants [macrophage inflammatory protein-1alpha (MIP-1alpha/Ccl3), platelet-activating factor (PAF)] or E. coli into the murine cremaster muscle induces target-oriented intravascular adhesion and transmigration as well as polarization and directional interstitial migration of leukocytes towards the locally administered stimuli. Moreover, we describe a crucial role of Rho kinase for the regulation of directional motility and polarization of transmigrated leukocytes in vivo. Finally, combining in vivo RLOT and fluorescence microscopy in Cx3CR1(gfp/gfp) mice (mice exhibiting green fluorescent protein-labeled monocytes), we are able to demonstrate differences in the migratory behavior of monocytes and neutrophils.Taken together, we propose a novel approach for investigating the mechanisms and spatiotemporal dynamics of subtype-specific motility and polarization of leukocytes during their directional interstitial migration in vivo

Acute renal impairment in coronavirus-associated severe acute respiratory syndrome

Acute renal impairment in coronavirus-associated severe acute respiratory syndrome.BackgroundSevere acute respiratory syndrome (SARS) is a newly emerged infection from a novel coronavirus (SARS-CoV). Apart from fever and respiratory complications, acute renal impairment has been observed in some patients with SARS. Herein, we describe the clinical, pathologic, and laboratory features of the acute renal impairment complicating this new viral infection.MethodsWe conducted a retrospective analysis of the plasma creatinine concentration and other clinical parameters of the 536 SARS patients with normal plasma creatinine at first clinical presentation, admitted to two regional hospitals following a major outbreak in Hong Kong in March 2003. Kidney tissues from seven other patients with postmortem examinations were studied by light microscopy and electron microscopy.ResultsAmong these 536 patients with SARS, 36 (6.7%) developed acute renal impairment occurring at a median duration of 20 days (range 5–48 days) after the onset of viral infection despite a normal plasma creatinine level at first clinical presentation. The acute renal impairment reflected the different prerenal and renal factors that exerted renal insult occurring in the context of multiorgan failure. Eventually, 33 SARS patients (91.7%) with acute renal impairment died. The mortality rate was significantly higher among patients with SARS and acute renal impairment compared with those with SARS and no renal impairment (91.7% vs. 8.8%) (P < 0.0001). Renal tissues revealed predominantly acute tubular necrosis with no evidence of glomerular pathology. The adjusted relative risk of mortality associated with the development of acute renal impairment was 4.057 (P < 0.001). By multivariate analysis, acute respiratory distress syndrome and age were the most significant independent risk factors predicting the development of acute renal impairment in SARS.ConclusionAcute renal impairment is uncommon in SARS but carries a high mortality. The acute renal impairment is likely to be related to multi-organ failure rather than the kidney tropism of the virus. The development of acute renal impairment is an important negative prognostic indicator for survival with SARS