Do changes of pen and penmate affect the behaviour of heifers?

We wanted to investigate if relocation affects behaviour of dairy heifers. In the study 32 Holstein heifers were housed in pairs until they were 13 months old. 16 heifers stayed in the same pen with the same penmate (control). The pen and penmates of 16 heifers were changed 16 times between 11 and 13 months of age

Emulsions stabilised by whey protein microgel particles: Towards food-grade Pickering emulsions

We have investigated a new class of food-grade particles, whey protein microgels, as stabilisers of triglyceride-water emulsions. The sub-micron particles stabilized oil-in-water emulsions at all pH with and without salt. All emulsions creamed but exhibited exceptional resistance to coalescence. Clear correlations exist between the properties of the microgels in aqueous dispersion and the resulting emulsion characteristics. For conditions in which the particles were uncharged, fluid emulsions with relatively large drops were stabilised, whereas emulsions stabilized by charged particles contained smaller flocculated drops. A combination of optical microscopy of the drops and spectrophotometry of the resolved aqueous phase allowed us to estimate the interfacial adsorption densities of the particles using the phenomenon of limited coalescence. We deduce two classes of particle arrangement. Complete adsorption of the particles was obtained when they were neutral or when their charges were screened by salt resulting in at least one particle monolayer at the interface. By contrast, only around 50% of the particles adsorbed when they were charged with emulsion drops being covered by less than half a monolayer. These findings were supported by direct visualization of drop interfaces using cryo-scanning electron microscopy. Uncharged particles were highly aggregated and formed a continuous 2-D network at the interface. Otherwise particles organized as individual aggregates separated by particle-free regions. In this case, we suggest that some particles spread at the interface leading to the formation of a continuous protein membrane. Charged particles displayed the ability to bridge opposing interfaces of neighbouring drops to form dense particle disks protecting drops against coalescence; this is the main reason for the flocculation and stability of emulsions containing sparsely covered drops. © 2014 the Partner Organisations

The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: implications for the lifetime of atmospheric ice particles

International audienceUsing a multidiagnostic approach the rate Rev [ molec cm-3 s-1] or flux Jev [ molec cm-2 s-1] of evaporation of H2O and its corresponding rate constant for condensation, kcond [s-1 ], on a 1 µm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions for pure ice are Jev = 1.6 · 10 28 ± 1 · exp (- 10.3 ± 1.2/ RT) [ molec cm-2 s-1] , kcond = 1.7 · 10 - 2 ± 1 · exp (+ 1.6 ± 1.5/ RT ) [s -1], in the presence of a HCl mole fraction in the range 3.2 · 10 - 5 - 6.4 · 10 - 3 : Jev = 6.4 · 10 26 ± 1 · exp (- 9.7 ± 1.2/ RT) [ molec cm-2 s-1] , kcond = 2.8 · 10 - 2 ± 1 · exp ( + 1.5 ± 1.6 /RT) [s -1], and a HBr mole fraction smaller than 6.4 · 10 - 3 : Jev = 7.4 · 10 25 ± 1 · exp ( - 9.1 ± 1.2 /RT) [ molec cm-2 s-1] , kcond = 7.1 · 10 - 5 ± 1 · exp (+ 2.6 ± 1.5/ RT) [s -1]. The small negative activation energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl = Eev - Econd = 11.9 ± 2.7 kcal mol-1 , DHsubl = 11.2 ± 2.8 kcal mol-1, and DHsubl = 11.7 ± 2.8 kcal mol-1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol-1 . Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3?6 and 10?20, respectively, for submonolayer coverages of HX once the fraction of the ice not contaminated by HX has evaporated

La memoria y el aprendizaje escolar

Desde finales del siglo XIX, y quizá desde antes, una serie de autores han venido criticando que la actividad escolar consista fundamentalmente en aprender de memoria una serie de hechos y de datos. Las voces contra ese aprendizaje memorístico han sido muy numerosas, pero en muchas escuelas de multitud de países se sigue teniendo que aprender de memoria una gran cantidad de cosas. Frente a ello un número creciente de autores han defendido que la escuela no puede limitarse hoy en día a transmitir informaciones y valores (Delval y Lomelí, 2013), sino que se debe aprender sobre todo a resolver problemas y que los sujetos desempeñan un papel activo en su aprendizaje, que el conocimiento no se recibe ya hecho, sino que hay que construirlo, y que lo que se aprende tiene que tener un significado y relacionarse con el resto de los conocimientos y acciones que realizan los sujetos.Since the late nineteenth century, and perhaps before, a number of authors have been criticizing that the school activity consists mainly of memorizing a series of facts and data. Voices against that rote learning have been very numerous, but in many schools from many different countries it’s usual still to memorize a lot of things. Faced with this growing number of authors have argued that the school can not be limited today to transmit information and values (Delval and Lomeli, 2013), but is due primarily to learn and solve problems and that individuals play an active role in their learning, that knowledge is not received already done, but you have to build it, and what you learn has to have a meaning and be related to the rest of the knowledge and actions performed by the subjects

Aspects of the construction of knowledge about society

El niño tiene que construir modelos o representaciones de la realidad social en la que vive, para tratar de dar un sentido al mundo que le rodea y además esas representaciones sirven de marco para su acción. La mayor parte de esas representaciones mentales no son simples copias de las de los adultos, sino que constituyen una construcción personal y difieren cualitativamente de las de los mayores. El estudio del desarrollo del conocimiento sobre la sociedad en el niño atrae cada vez más atención por parte de los investigadores. Tres son los enfoques teóricos principales. La posición constructivista, según la cual el niño tiene que realizar su propia construcción de los conocimientos con ayuda de los instrumentos intelectuales de que dispone. La tradición del estudio de las representaciones sociales originada en la sociología francesa y renovada por Moscovici, y la psicología histórico-cultural de tradición vygotskiana. La primera posición pone el acento sobre la actividad del sujeto, mientras que las otra dos enfatizan las influencias ambientales y constituyen un necesario contrapunto de la posición constructivista. Sin embargo, la existencia de creencias infantiles diferentes de las de los adultos y del contexto social, y la universalidad de algunas de estas creencias nos obligan a no olvidar la labor personal de construcción que tiene que realizar el sujeto.The child has to construct models or representations about the reality of thesociety where he or she lives in order to give a meaning to the surroundingworld and, furthermore, taking into consideration that these representationsserve as landmarks to his action. Most of the mental representationsconstructed by the child are not simple copies of the adult representations;instead, they are personal constructions and differ qualitatively from thoseof the older people. The study of the development of knowledge aboutsociety in children is attracting the attention of many investigators. Thereare three main theoretical approaches to this subject: the constructivistposition says that the child has to construct their own knowledge countingon their personal intellectual instruments; the traditional study aboutsocial representations originated in the French School of Sociology, thathas been renewed by Moscovici; and the Historical Cultural Psychologyof vygotskyan approach. The first position emphasizes the activity of thesubject, while the others put the emphasis on the environmental influencesand so hold a counterpoint to the constructivist position. However, theexistence of children beliefs different from those from adults’ as wellas from the social context, and the universality of some of these beliefs,compel us not to forget the personal work of construction made by the subject

Vygotski, Piaget: a formação do conhecimento e a cultura

O velho problema da influência da cultura sobre a formação do conhecimento voltou a chamar muito a atenção dos psicólogos. O interesse pela cultura está ligado à defesa de posições que se atribuem a Vygotski, cuja obra contrapõe-se à de Piaget, que é criticado pela sua falta de atenção à influência social e à cultura. Analisa-se neste artigo a pretendida separação entre desenvolvimento natural e cultura, que Vygotski estabelece, e defende-se que essa separação não pode ser estabelecida. Examinam-se, também, as idéias do autor soviético sobre a formação de conceitos científicos e sobre as funções psicológicas superiores. Mostra-se que a posição de Vygotski tem muitos traços empiristas, pois enfatiza enormemente a influência do meio, o que entraria em contradição com seu pretendido caráter marxista. Além disso, ele não consegue dar conta das transformações que acontecem no interior do sujeito por ocasião da construção de novos conhecimentos; aliás, é este o principal problema que os psicólogos precisam enfrentar. Sinaliza-se, ainda, que a posição de Piaget possui elementos para explicar essas transformações

LA CONSTRUCCIÓN DEL CONOCIMIENTO SOBRE LA SOCIEDAD

El conocimiento sobre la sociedad no se transmite directamente en el medio social y es asimilado sin más por los sujetos, sino que requiere de una construcción. Si estudiamos la génesis de esos conocimientos sobre la sociedad tal y como se produce en los sujetos en desarrollo encontramos que tiene lugar un proceso lento de construcción que depende mucho también del desarrollo cognitivo de los sujetos. Ya se trate de las ideas sobre el funcionamiento económico o político de una sociedad, sobre la organización social, sobre la nación, sobre la guerra y la paz, o incluso sobre la idea de dios, podemos ver que las ideas de los sujetos en desarrollo no son una copia de las concepciones dominantes en la sociedad, que los sujetos incorporarían, sino que estos realizan un trabajo de construcción muy personal que depende mucho de sus capacidades cognitivas. Por ello, si estudiamos la génesis de las ideas sobre cualquier aspecto de la realidad social podemos asistir a un lento proceso de construcción en el que los sujetos desempeñan un papel muy activo, que refleja claramente la actividad constructiva de los sujetos. Tomar en cuenta la génesis de esas ideas y las diversas concepciones que los sujetos elaboran resulta esencial para proporcionar una educación adecuada y una formación democrática, cosa que no suele realizarse en la actividad escolar