Mediación semiótica en pro de la construcción de significado de rayo al hacer operativa su definición

El significado de un objeto geométrico se va consolidando en el uso que se hace de su definición y de los enunciados que establecen sus propiedades; también, en el uso que se hace del objeto mismo como herramienta. Así, entender un objeto geométrico involucra, entre otras cosas, hacer operativa su definición. Es decir, el estudiante debe poder llegar a usar de manera pertinente la definición, en calidad de garantía, en el marco de la producción de demostraciones. En este artículo se analizan aspectos de la construcción del significado de rayo asociados al uso de la definición como garantía. Este análisis tiene sus raíces en el signo triádico de Peirce y en la evolución de los interpretantes del profesor y de los estudiantes mientras se esfuerzan por hacer operativa tal definición. Además, ilustra la articulación de las nociones «construcción de significado» y «mediación semiótica del profesor».El significat d'un objecte geomètric es va consolidant en l'ús que es fa de la seva definició i dels enunciats que estableixen les seves propietats; també, en l'ús que es fa de l'objecte mateix com a eina. Així, entendre un objecte geomètric involucra, entre altres coses, fer operativa la seva definició. És a dir, l'estudiant ha de poder arribar a usar de manera pertinent la definició, en qualitat de garantia, en el marc de la producció de demostracions. En aquest article s'analitzen aspectes de la construcció del significat de raig associats a l'ús de la definició com a garantia. Aquesta anàlisi té les seves arrels en el signe triádico de Peirce i en l'evolució dels interpretants del professor i dels estudiants mentre s'esforcen per fer operativa tal definició. A més, il·lustra l'articulació de les nocions «construcció de significat» i «mediació semiòtica del professor».The meaning of a geometric object is consolidated through the use of its definition and of the statements that establish its properties; also in the use of the object itself as a tool. So, understanding a geometric object involves, among other things, operationalizing its definition. That is, the learner should be able to pertinently use the definition as a warrant for statements when producing a proof. This article analyzes aspects of meaning-making of ray associated to the use of the definition as warrant. This analysis is rooted in the Peircean triadic sign and in the evolution of the teacher and learners' interpretants while they made the effort to operationalize such definition. Also, it illustrates the articulation of the notions «meaning-making» and «teacher semiotic mediation»

Changes in children’s television and computer time according to parental education, parental income and ethnicity: A 6-year longitudinal EYHS study

Objectives : To investigate changes in children's television and computer time according to three socioeconomic status (SES) indicators. Design : Prospective cohort study. Methods : Data were drawn from the European Youth Heart Study and included longitudinal data collected in 1997 and 2003 in Denmark. Television and computer time were self-reported by children. Parental education, income and ethnicity were parent-reported. Baseline data were available for 549 children (47.0% boys, 9.6 years). Generalized linear mixed models analyzed whether changes in television and computer time from baseline to follow-up differed according to the SES-indicators. Result : TV viewing time increased with 25% over time (ExpB = 1.25, 95% CI = 1.04-1.50). At both time points, children with two higher educated parents viewed 25% less hours of television than children with no higher educated parents (ExpB = 0.75, 95% CI = 0.60-0.94) and one higher educated parent (ExpB = 0.75, 95% CI = 0.59-0.97). Among children with no higher educated parents the odds of being in a higher category of computer time increased with 80% over time (OR = 1.80, 95% CI = 1.24-2.60). Among children with two higher educated parents the odds of being in a higher category of computer time decreased with 45% over time (OR = 0.55, 95% CI = 0.32-0.94). The association with ethnicity showed that white children had 42% lower odds (OR = 0.58; 95% CI = 0.34-1.00) of being in a higher category of computer time than non-white children. No significant associations were found for parental income. Conclusions : The most important SES measure of screen-based behaviors in children was parental education. Ethnicity was only associated with computer time. Financial resources were less relevant for changes in television viewing and computer use

Thickness-Dependent Differential Reflectance Spectra of Monolayer and Few-Layer MoS2, MoSe2, WS2 and WSe2

The research field of two dimensional (2D) materials strongly relies on optical microscopy characterization tools to identify atomically thin materials and to determine their number of layers. Moreover, optical microscopy-based techniques opened the door to study the optical properties of these nanomaterials. We presented a comprehensive study of the differential reflectance spectra of 2D semiconducting transition metal dichalcogenides (TMDCs), MoS2, MoSe2, WS2, and WSe2, with thickness ranging from one layer up to six layers. We analyzed the thickness-dependent energy of the different excitonic features, indicating the change in the band structure of the different TMDC materials with the number of layers. Our work provided a route to employ differential reflectance spectroscopy for determining the number of layers of MoS2, MoSe2, WS2, and WSe2.Comment: Main text (3 Figures) and Supp. Info. (23 Figures

Gender- and hydration-associated differences in the physiological response to spinning

UniveIntroduction: There is scarce and inconsistent information about gender-related differences in the hydration of sports persons, as well as about the effects of hydration on performance, especially during indoor sports. Objective: To determine the physiological differences between genders during in indoor physical exercise, with and without hydration. Methods: 21 spinning sportspeople (12 men and 9 women) participated in three controlled, randomly assigned and non-sequential hydration protocols, including no fluid intake and hydration with plain water or a sports drink (volume adjusted to each individual every 15 min), during 90 min of spinning exercise. The response variables included body mass, body temperature, heart rate and blood pressure. Results: During exercise without hydration, men and women lost ~2% of body mass, and showed higher body temperature (~0.2°C), blood pressure (~4 mmHg) and heart rate (~7 beats/min) compared to exercises with hydration. Body temperature and blood pressure were higher for men than for women during exercise without hydration, differences not observed during exercise with hydration. Between 42-99% of variance in body temperature, blood pressure and heart rate could be explained by the physical characteristics of subjects and the work done. Conclusions: During exercise with hydration (either with water or sport drink), the physiological response was similar for both genders. Exercise without hydration produced physical stress, which could be prevented with either of the fluids (plain water was sufficient). Gender differences in the physiological response to spinning (body temperature, mean blood pressure and heart rate) can be explained in part by the distinct physical characteristics of each individual. (Nutr Hosp. 2014;29:644-651) DOI:10.3305/nh.2014.29.3.701

Inhibition of bacterial and fungal plant pathogens by thionins of types I and II

Thionins are cysteine-rich, 5 kDa polypeptides which are active against plant pathogens. Thionins of type I, from the endosperms of wheat (Wα1, Wα2, Wβ) and barley (Bα, Bβ), and of type II, from barley (BLa, BLb, BLc), have been purified to apparent homogeneity. For a given pathogen, the effective concentration giving 50% inhibition (EC-50) determined for the different thionins varied over a less than fivefold range. The ranking of the variants according to their activity differed among different pathogens, but certain variants, such as Wα1, Wβ or Bβ, tended to be more active than the others. Strains of some bacterial species, such as Clavibacter michiganensis subsp. sepedonicus or Pseudomonas solanacearum were sensitive in the 2–3 × 10−7M concentration rangem whereas the most sensitive fungal pathogens, such as Rosellinia necatrix, Colletotrichum lagenarium and Fusarium solani, had EC-50 values in the 1−4 × 10−6M range. Thionins, which were not particularly effective in liquid medium against Phytophthora infestans (EC-50=3.9 × 10−5M) were more effective than the fungicide Ridomil on a molar basis in a drop application assay on leaf discs from potato

Tocopherol composition and antioxidant activity of Spanish wild vegetables

Traditional use of noncultivated vegetables has decreased with the development of agriculture and global supply chains. However, some species are still consumed as part of our traditional Mediterranean diet. Plants are among the most important sources of natural antioxidants for retarding lipid oxidative rancidity in foods or for pharmaceutical applications against chronic diseases related to free radicals production. The present study reports tocopherols composition and antioxidant activity of eight wild greens traditionally used in Spain. According to the edible part consumed, two groups were differentiated. Leafy vegetables whose young stems with leaves are consumed (Apium nodiflorum (L.) Lag., Foeniculum vulgare Mill., Montia fontana L. and Silene vulgaris (Moench) Garcke), and wild asparagus whose young shoots with leaf buds scarcely developed are eaten (Asparagus acutifolius L., Bryonia dioica Jacq., Humulus lupulus L. and Tamus communis L.). Among the leafy vegetables, Silene vulgaris and Apium nodiflorum presented the highest antioxidant capacity and antioxidants contents. Among the wild asparagus, the highest antioxidant capacity was obtained in Humulus lupulus

Central venous-catheter related bacteremia: incidence and risk factors in a hospital in western Mexico

AbstractBackgroundCentral venous catheters (CVC) are needed for monitoring and treatment of critically ill patients; however, their use increases the risk of bacteremia. The aim of the study was to quantify the incidence of central venous catheter-related bacteremia (CVCRB) and to identify factors associated with this infection.MethodsA prospective cohort study was conducted in a concentration hospital of western Mexico. The association of CVCRB and study variables was investigated using multivariate Cox regression analysis.ResultsTwo hundred and four patients with CVC were studied. The mean age was 4.6 years; 66.2% were male. Insertion sites of the catheters were subclavian vein 72.5% (n = 148), jugular vein 20.1% (n = 41) and femoral vein 7.4% (n = 15). CVCRB incidence was 6.5 events/1,000 catheter-days; microorganisms identified were gram-positive cocci 37.5% (n = 6), gram-negative bacilli 37.5% (n = 6) and Candida albicans 25% (n = 4). It was observed that the increase in catheter manipulations per day was associated with bacteremia (HR 1.14, 95% CI 1.06–1.23), whereas the use of intravenous antibiotics showed a protective effect (HR 0.84, 95% CI 0.76–0.92).ConclusionsIn addition to the strategies of maximum caution when placing or manipulating the catheter, we recommend decreasing, as much as possible, disconnects between the CVC and the infusion line. Antibiotics showed a protective effect, but the outcome is uncertain and the promotion of antimicrobial resistance should be considered