Ensino e aprendizaxe das Ciencias Experimentais: a coeducacion como meta. 'Enseñanza y aprendizaje de las Ciencias Experimentales : la coeducación como meta'.

1. Poner de manifiesto algunos elementos de currículum oculto, en lo referente a actitudes y expectativas diferentes del profesorado, respecto de las alumnas/os. 2. Elaborar propuestas susceptibles de ser incorporadas al Diseño Curricular Base de Ciencias de la Naturaleza para la Enseñanza Secundaria Obligatoria. 3. Conocer la imagen de la Ciencia y de las personas científicas que tiene el alumnado de segundo de BUP. 4. Hipótesis general: persisten elementos de sexismo que actúan en el Sistema Educativo, en la enseñanza y en el aprendizaje de las Ciencias. Su existencia constituye un elemento de discriminación para las alumnas. 482 profesores de cursos de formación de las cuatro provincias de Galicia, Asturias, Badajoz, Euzkadi, Murcia, Andalucía y Valencia. Población observada: 96 alumnos de segundo de BUP de dos IB de Vigo. 16 libros de texto y suplementos relacionados con la Ciencia y la Tecnología de los periódicos 'El País' y 'La Voz de Galicia'. 747 estudiantes de segundo de BUP de 14 IB de La Coruña, Vigo, Santiago, Lugo y Orense. El presente trabajo se enmarca dentro de la corriente de convergencia entre los estudios sociales de la Ciencia y los estudios sobre género y Ciencia. La metodología empleada es la constatación de 6 subhipótesis: las 3 primeras (1.A, 1.B, 1.C) pasan cuestionarios al profesorado y realizan observación de aulas. La cuarta (2.A) analiza una muestra de libros de texto y de suplementos científicos. Las dos últimas (3.A, 3.B) pasan cuestionarios al alumnado, donde tienen en cuenta las siguientes variables: sexo, procedencia rural o urbana, nivel económico de las familias y nivel de estudios de las madres y de los padres. Profesorado: plantilla de análisis de textos, vaciado de suplementos científicos, cuestionarios. Para los estudiantes: C-T-G-S para observar la interacción en las aulas. Correlaciones. 1. Persisten los estereotipos en el profesorado. 2. Claro protagonismo en las aulas. 3. Mayor interacción de los alumnos varones con el profesorado. 4. No se observan diferencias en los comportamientos del alumnado en las clases impartidas por profesores/as. 5. Los libros de texto reproducen una situación que está muy por detrás de la realidad social y científica. 6. Los suplementos científicos transmiten una imagen de la Ciencia menos estereotipada. 7. La concepción que el alumnado de segundo de BUP posee acerca de la Ciencia y de las personas que la ejercen, es menos estereotipada que la que transmiten los textos. 8. Existen diferencias significativas entre mujeres y varones a la hora de percibir la igualdad de unas y otros ante la Ciencia. 1. Necesidad de establecer cambios en la enseñanza de las Ciencias, hacia una presentación de ella más humana, contextualizada, con relación con la vida y las necesidades de las personas que tenga en cuenta que en las aulas coexisten niñas y niños con intereses, habilidades y destrezas diferentes. 2. El profesorado ha de adquirir instrumentos para huir del pensamiento dicotómico y para utilizar el género como categoría de análisis.

Estrategias de enseñanza de comprensión lectora y expresión escrita con alumnos de ESO.

Diseñar, aplicar y comprobar el grado de validez de 3 programas dirigidos al desarrollo y mejora de las estrategias necesarias para una adecuada comprensión y producción de textos. La investigación se propone los siguientes objetivos : 1.- Revisar las estrategias de comprensión y expresión escrita empleadas por alumnos del segundo ciclo de secundaria (3 ESO), con anterioridad a la aplicación de los 3 tratamientos. 2.- Analizar la influencia de una instrucción directa en estrategias dirigidas a construir la representación textual sobre la comprensión lectora de los alumnos. 3.- Estudiar la influencia de una instrucción directa en estrategias dirigidas a construir la representación textual sobre la calidad de la producción escrita de los alumnos. 4.- Examinar el efecto de una instrucción directa en los procesos y estrategias de composición sobre la calidad de la producción escrita de los alumnos. 5.- Estudiar el efecto que puede tener una instrucción directa en los procesos y estrategias de composición escrita sobre la construcción de la representación textual implicada en la comprensión lectora. 6.- Comprobar los efectos que puede tener una instrucción conjunta en ambos tipos de estrategias (comprensión lectora y composición escrita) sobre la calidad de las producciones escritas (elementos creativos, mecanismos de cohesión, y coherencia textual) y sobre el modo de elaborar la representación textual implicada en la comprensión lectora. 7.- Contrastar la influencia que puede tener la instrucción directa en estrategias de comprensión lectora sobre el rendimiento académico de los alumnos. 8.- Analizar la influencia que puede tener la instrucción directa en estrategias de composición escrita sobre el rendimiento académico de los alumnos. 9.- Analizar la influencia que puede tener una instrucción integrada por estrategias de comprensión lectora y composición escrita sobre el rendimiento académico de los alumnos participantes en el programa.. La muestra está compuesta por 86 alumnos de tercero de ESO, del IES Rodríguez Fabrés.. Diseño de grupos de control no equivalentes con medidas pretratamiento y postratamiento; parte de grupos formados de manera natural en el IES; aplica una metodología cuasiexperimental. Se eligen aleatoriamente los grupos experimentales y control. Se determina el nivel de comprensión lectora y expresión escrita que poseen los alumnos, realizando para ellos en todos los grupos una estimación inicial (fase pretest). Se realiza una estimación del rendimiento académico de los alumnos durante la primera evaluación a través de las calificaciones obtenidas en 4 áreas: Lengua y Literatura, Matemáticas, Ciencias Sociales y Ciencias Naturales; mediante la puntuación otorgada por el profesorado en cuatro capacidades concretas de los alumnos: Interés, comprensión, expresión y autonomía. Realizada la medición inicial, procede a la aplicación de los diferentes programas en cada uno de los grupos experimentales Aplicados los programas, realiza las mediones postest de las variables anteriormente mencionadas, para comprobar los efectos del tratamiento en los grupos experiementales. Grupo 1: Control. No intervienen en ningún programa, se les aplican pruebas pretest y postest, constituido por 28 sujetos. Grupo 2: Grupo experimental que trabajó el programa 'Mejorar nuestra forma de expresarnos cuando escribimos'. 13 sujetos. Grupo 3: Grupo experimental que trabajó el programa 'Mejorar nuestra comprensión de los textos expositivos', integrado por 19 sujetos. Grupo 4: Grupo experimental donde se desarrolló el programa: 'Mejorar nuestra comprensión y expresión de textos', integrado por 26 sujetos. Clasificación de las variables : A.-Variables dependientes: Pueden haberse modificado como consecuencia de la aplicación de las variables dependientes : A.1.- Rendimiento en comprensión lectora. A.2.- Rendimiento en expresión escrita. A.3.- Rendimiento escala de estrategias cognitivas y actitudes hacia la expresión escrita. A.4.- Rendimiento académico general. B.-Variables independientes : Manipuladas deliberadamente : B.1.- Programa: 'Mejorar nuestra forma de expresarnos cuando escribimos'. B.2.- Programa: 'Mejorar nuestra comprensión de los textos expositivos'. B.3.- Programa: : 'Mejorar nuestra comprensión y expresión de textos'.. Informes del Instituto, Test del factor G de Cattel (TEA), Test de actitudes escolares (TEA 2), 4 pruebas de medición de comprensión lectora (ad hoc), 4 pruebas de medición en expresión escrita (ad hoc), escala de estrategias cognitivas y actitudes hacia la exposición escrita (ad hoc), actas de calificaciones y capacidades del IES y cuestionario de estudio y trabajo intelectual (C.E.T.I.).. Análisis estadístico con el paquete SPSS; análisis de varianza.. Analiza los efectos diferenciales que la implementación de los 3 programas tienen en la mejora de las capacidades comprensivas y expresivas de los alumnos de 3õ ESO en su rendimiento escolar, analizando las diferentes variables. La investigación subraya la validez que cada uno de los programas ha tenido a la hora de mejorar aquellos aspectos en los que se pretendía incidir en el diseño e implementación de la investigación. verificado a través del contraste de hipótesis. Respecto a los programas empleados, la investigación ha demostrado que el programa 'mejor comprensión de textos expositivos' como el programa más potente para mejorar las competencias de los alumnos, verificándose en la mejora de rendimiento logrado por los alumnos.. Una intervención específica orientada al desarrollo y empleo de los procesos y estrategias implicados en la composición de los textos variados potencian la calidad de la expresión escrita de los alumnos. Una intervención específica orientada al desarrollo y empleo de las estrategias necesarias para construir una representación coherente del contenido del texto, contribuye a mejorar la comprensión lectora. Una intervención específica y conjunta en estrategias de comprensión lectora y expresión escrita, mejora el desempeño de ambas competencias , aunque no de forma generalizada para todos los alumnos.

In situ degradability of dry matter and neutral-detergent fibre of thorn scrubland forage consumed by goats in the semi-arid region of north Mexico

Three goats provided with oesophageal and ruminal cannulae were used to determine variations in dry matter (DM) and neutral-detergent fibre (NDF) degradability of the forage consumed when grazing thorn scrubland in the semi-arid region of north Mexico, during two consecutive dry and wet periods. Ingesta samples were incubated intraruminally, the data were fitted to the exponential equation P = a + b (1-e(-ct)) and statistically analysed using a randomized-block design. Organic matter and crude protein (CP) contents were higher (P < 0.05) in the wet seasons. Values of NDF were similar in dry and wet season of both years whereas higher numerical values of acid-detergent fibre (ADF), lignin and cellulose were registered in the dry seasons. DM and NDF degradabilities after 24 and 48 h of ruminal incubation were higher (P < 0.05) in the wet seasons. Higher values (P < 0.05) in DM and NDF bag losses at zero time (A fraction) were registered in the two wet seasons. The insoluble but fermentable DM and NDF (B fractions) were higher (P < 0.05) in the 1999 wet season and variable in the rest of the studied period. Numerically higher values of DM and NDF c fraction were found in wet periods, whereas DM and NDF potential degradabilities were higher (P < 0.05) in the wet season in 1999 and similar across seasons in 2000. Lowest (P < 0.05) contents of CP in grazed forage, DM and NDF degradabilities after 48 h of ruminal incubation, and A, and B, and c fractions were observed in the dry seasons. Thus, these results may be related to both the lower feeding value of forage consumed by the animals and lower performance of livestock during this period. Then, the DM and NDF degradability after 48 h, together with the insoluble but fermentable matter and the c fraction permit the nutritive value of the forage consumed by grazing goats to be accurately described.

A sparse parallel hybrid Monte Carlo algorithm for matrix computations

In this paper we introduce a new algorithm, based on the successful work of Fathi and Alexandrov, on hybrid Monte Carlo algorithms for matrix inversion and solving systems of linear algebraic equations. This algorithm consists of two parts, approximate inversion by Monte Carlo and iterative refinement using a deterministic method. Here we present a parallel hybrid Monte Carlo algorithm, which uses Monte Carlo to generate an approximate inverse and that improves the accuracy of the inverse with an iterative refinement. The new algorithm is applied efficiently to sparse non-singular matrices. When we are solving a system of linear algebraic equations, Bx = b, the inverse matrix is used to compute the solution vector x = B(-1)b. We present results that show the efficiency of the parallel hybrid Monte Carlo algorithm in the case of sparse matrices.

Global asymptotic stability in a class of Putnam-type equations

In this paper, we initiate the study of a class of Putnam-type equation of the form x(n-1) = A(1)x(n) + A(2)x(n-1) + A(3)x(n-2)x(n-3) + A(4)/B(1)x(n)x(n-1) + B(2)x(n-2) + B(3)x(n-3) + B-4 n = 0, 1, 2,..., where A(1), A(2), A(3), A(4), B-1, B-2, B-3, B-4 are positive constants with A(1) + A(2) + A(3) + A(4) = B-1 + B-2 + B-3 + B-4, x(-3), x(-2), x(-1), x(0) are positive numbers. A sufficient condition is given for the global asymptotic stability of the equilibrium point c = 1 of such equations. (c) 2005 Elsevier Ltd. All rights reserved.

The asymptotic behavior of densities related to the supremum of a stable process

If X is a stable process of index α∈(0, 2) whose Lévy measure has density cx−α−1 on (0, ∞), and S1=sup0x)∽Aα−1x−α as x→∞ and P(S1≤x)∽Bα−1ρ−1xαρ as x↓0. [Here ρ=P(X1>0) and A and B are known constants.] It is also known that S1 has a continuous density, m say. The main point of this note is to show that m(x)∽Ax−(α+1) as x→∞ and m(x)∽Bxαρ−1 as x↓0. Similar results are obtained for related densities.

Layer-by-layer coating of alginate matrices with chitosan–alginate for the improved survival and targeted delivery of probiotic bacteria after oral administration

The oral administration of probiotic bacteria has shown potential in clinical trials for the alleviation of specific disorders of the gastrointestinal tract. However, cells must be alive in order to exert these benefits. The low pH of the stomach can greatly reduce the number of viable microorganisms that reach the intestine, thereby reducing the efficacy of the administration. Herein, a model probiotic, Bifidobacterium breve, has been encapsulated into an alginate matrix before coating in multilayers of alternating alginate and chitosan. The intention of this formulation was to improve the survival of B. breve during exposure to low pH and to target the delivery of the cells to the intestine. The material properties were first characterized before in vitro testing. Biacore™ experiments allowed for the polymer interactions to be confirmed; additionally, the stability of these multilayers to buffers simulating the pH of the gastrointestinal tract was demonstrated. Texture analysis was used to monitor changes in the gel strength during preparation, showing a weakening of the matrices during coating as a result of calcium ion sequestration. The build-up of multilayers was confirmed by confocal laser-scanning microscopy, which also showed the increase in the thickness of coat over time. During exposure to in vitro gastric conditions, an increase in viability from <3 log(CFU) per mL, seen in free cells, up to a maximum of 8.84 ± 0.17 log(CFU) per mL was noted in a 3-layer coated matrix. Multilayer-coated alginate matrices also showed a targeting of delivery to the intestine, with a gradual release of their loads over 240 min.

Solvability and spectral properties of integral equations on the real line: I. Weighted spaces of continuous functions

We consider in this paper the solvability of linear integral equations on the real line, in operator form (λ−K)φ=ψ, where and K is an integral operator. We impose conditions on the kernel, k, of K which ensure that K is bounded as an operator on . Let Xa denote the weighted space as |s|→∞}. Our first result is that if, additionally, |k(s,t)|⩽κ(s−t), with and κ(s)=O(|s|−b) as |s|→∞, for some b>1, then the spectrum of K is the same on Xa as on X, for 01. As an example where kernels of this latter form occur we discuss a boundary integral equation formulation of an impedance boundary value problem for the Helmholtz equation in a half-plane.

Superhumps, magnetic fields and the mass ratio in AM Canum Venaticorum

We show that the observed K velocities and periodicities of AM CVn can be reconciled given a mass ratio q~0.22 and a secondary star with a modest magnetic field of surface strength B~1 T. We see that the new mass ratio implies that the secondary is most likely semidegenerate. The effect of the field on the accretion disc structure is examined. The theory of precessing discs and resonant orbits is generalized to encompass higher order resonances than 3:2 and shown to retain consistency with the new mass ratio.

Bioactive films produced from self-assembling peptide amphiphiles as versatile substrates for tuning cell adhesion and tissue architecture in serum-free conditions

The development of versatile bioactive surfaces able to emulate in vivo conditions is of enormous importance to the future of cell and tissue therapy. Tuning cell behaviour on two-dimensional surfaces so that the cells perform as if they were in a natural three-dimensional tissue represents a significant challenge, but one that must be met if the early promise of cell and tissue therapy is to be fully realised. Due to the inherent complexities involved in the manufacture of biomimetic three-dimensional substrates, the scaling up of engineered tissue-based therapies may be simpler if based upon proven two-dimensional culture systems. In this work, we developed new coating materials composed of the self-assembling peptide amphiphiles (PAs) C16G3RGD (RGD) and C16G3RGDS (RGDS) shown to control cell adhesion and tissue architecture while avoiding the use of serum. When mixed with the C16ETTES diluent PA at 13 : 87 (mol mol-1) ratio at 1.25 times 10-3 M, the bioactive {PAs} were shown to support optimal adhesion, maximal proliferation, and prolonged viability of human corneal stromal fibroblasts ({hCSFs)}, while improving the cell phenotype. These {PAs} also provided stable adhesive coatings on highly-hydrophobic surfaces composed of striated polytetrafluoroethylene ({PTFE)}, significantly enhancing proliferation of aligned cells and increasing the complexity of the produced tissue. The thickness and structure of this highly-organised tissue were similar to those observed in vivo, comprising aligned newly-deposited extracellular matrix. As such, the developed coatings can constitute a versatile biomaterial for applications in cell biology, tissue engineering, and regenerative medicine requiring serum-free conditions.

Aflatoxins and cyclopiazonic acid in feed and milk from dairy farms in Sao Paulo, Brazil

The occurrence of aflatoxins (AF) B(1), B(2), G(1), G(2) and cyclopiazonic acid (CPA) in feeds, and AFM(1) and CPA in milk was determined in dairy farms located in the northeastern region of Sao Paulo state, Brazil, between October 2005 and February 2006. AF and CPA determinations were performed by HPLC. AFB(1) was found in 42% of feed at levels or 1.0-26.4 mu g kg(-1) (mean: 7.1 +/- 7.2 mu g kg(-1)). The concentrations of AFM(1) in raw milk varied between 0.010 and 0.645 mu g l(-1) (mean: 0.104 +/- 0.138 mu g l(-1)). Only one sample was above the tolerance limit adopted in Brazil (0.50 mu g l(-1)) for AFM(1) in milk. Regarding CPA in feed, six (12%) samples showed concentrations of 12.5-1533 mu g kg(-1) (mean: 57.6 +/- 48.7 mu g kg(-1)). CPA was detected in only three milk samples (6%) at levels of 6.4, 8.8 and 9.1 mu g l(-1). Concentrations of aflatoxins and CPA in feed and milk were relatively low, although the high frequency of both mycotoxins indicates the necessity to continuously monitor dairy farms to prevent contamination of feed ingredients.

Dietary copper absorption and excretion in three semi-terrestrial grapsoid crabs with different levels of terrestrial adaptation

Three species of phylogenetically related semi-terrestrial crabs (Superfamily Grapsoidea - Sesarma rectum, Goniopsis cruentata and Neohelice granulata (formerly: Chasmagnathus granulatus) with different degrees of terrestriality were studied to quantify the accumulation of copper (Cu) in hemolymph, gills, hepatopancreas and antennal gland, and its excretion through the faeces. These crabs were fed for 15 days practical diets containing 0 (A), 0.5 (B), 1.0 (C), and 1.5% (D) of added CuCl2 (corresponding to 0, 0.2, 0.5 and 0.7% of Cu2+, respectively). The amount of food ingested was directly proportional to the degree of terrestriality: S. rectum, the most terrestrial species, ate around 2-3 times more than the other crabs, whereas G. cruentata ate 1.5-2 times more than N. granulata, the least terrestrial. The amount of Cu excreted in the feces was proportional to Cu ingestion, and was 76.8% and 64.2% higher for Sesarma fed diet D compared to G. cruentata and N. granulata, respectively. Sesarma also displayed higher Cu concentration in the haemolymph, gills and antennal glands, but not in the hepatopancreas. A detoxifying mechanism followed by elimination was probably present at this last organ, preventing Cu accumulation. More terrestrial crabs, such as Sesarma, may accumulate more Cu in hemolymph and tissues, showing a correlation between metal accumulation and increased terrestriality. In this aspect, contaminated feed sources with Cu may have more impact in conservation of terrestrial crabs. (C) 2008 Elsevier Inc. All rights reserved.

Characterization of the mechanisms underlying the inflammatory response to Polistes lanio lanio (paper wasp) venom in mouse dorsal skin

Stings by Polistes wasps can cause life-threatening allergic reactions, pain and inflammation. We examined the changes in microvascular permeability and neutrophil influx caused by the venom of Polistes lanio a paper wasp found in southeastern Brazil. The intradermal injection of wasp venom caused long-lasting paw oedema and dose-dependently increased microvascular permeability in mouse dorsal skin. SR140333, an NK(1) receptor antagonist, markedly inhibited the response, but the NK(2) receptor antagonist SR48968 was ineffective. The oedema was reduced in capsaicin-treated rats, indicating a direct activation of sensory fibres. Dialysis of the venom partially reduced the oedema and the remaining response was further inhibited by SR140333. Mass spectrometric analysis of the venom revealed two peptides (QPPTPPEHRFPGLM and ASEPTALGLPRIFPGLM) with sequence similarities to the C-terminal region of tachykinin-like peptides found in Phoneutria nigniventer spider venom and vertebrates. Wasp venom failed to release histamine from mast cells in vitro and spectrofluorometric assay of the venom revealed a negligible content of histamine in the usual dose of P.l. lanio venom (1 nmol of histamine/7 mu g of venom)that was removed by dialysis. The histamine H(1) receptor antagonist pyrilamine, but not bradykinin B(1) or B(2) receptor antagonists, inhibited venom-induced oedema. In conclusion, P. l. lanio venom induces potent oedema and increases vascular permeability in mice, primarily through activation of tachykinin NK(1) receptors by substance P released from sensory C fibres, which in turn releases histamine from dermal mast cells. This is the first description of a neurovascular mechanism for P. l. lanio venom-mediated inflammation. The extent to which the two tachykinin-like peptides identified here contribute to this neurogenic inflammatory response remains to be elucidated. (c) 2008 Elsevier Ltd. All rights reserved.

Relative populations and toxin production by Aspergillus flavus and Fusarium verticillioides in artificially inoculated corn at various stages of development under field conditions

The presence, development and production of mycotoxins by Aspergillus flavus and Fusarium verticillioides were studied in corn ears under field conditions after artificial contamination of corn silks. The planted area was divided into five treatments: T1, inoculated with A.flavus solution containing 1 x 10(8) spores, ears covered; T2, inoculated with F. verticillioides solution containing 1 X 10(8) spores, ears covered; T3, inoculated with E verticillioides plus A. flavus solution containing 1 x 10(8) spores of each, ears covered; T4, sprayed with sterile phosphate-buffered saline, ears covered; TS, non-sprayed silks, uncovered ears. Soil and air samples were also collected and analysed for the occurrence of fungi. Water activity, relative air humidity, rainfall and temperature were determined to assess the correlation between abiotic factors and the presence of fungi in the samples. Contamination with the inoculated fungus predominated in T1 and T2. In the other treatments, F. verticillioides was the most frequently isolated contaminant irrespective of treatment. Considering the production of mycotoxins, a positive relation between the production of fumonisins B-1 and B-2 and the frequency of F. verticillioides was statistically verified in all treatments. (C) 2007 Society of Chemical Industry.

Use of PCR for detecting Aspergillus flavus in maize treated by gamma radiation process

The aim of this study was to verify the effects of gamma radiation process on the fungal DNA and the application of PCR in the detection of Aspergillus flavus in irradiated maize grains. The samples were inoculated with a toxigenic strain and incubated under controlled conditions of relative humidity, water activity, and temperature for 15 days. After incubation, the samples were treated with gamma radiation with doses of 5 and 10 kGy and individually analyzed. The use of PCR technique showed the presence of DNA bands of Aspergillus flavus in all irradiated samples that showed no fungal growth in agar medium.