1,831 research outputs found
Two-step phase changes in cubic relaxor ferroelectrics
The field-driven conversion between the zero-field-cooled frozen relaxor
state and a ferroelectric state of several cubic relaxors is found to occur in
at least two distinct steps, after a period of creep, as a function of time.
The relaxation of this state back to a relaxor state under warming in zero
field also occurs via two or more sharp steps, in contrast to a one-step
relaxation of the ferroelectric state formed by field-cooling. An intermediate
state can be trapped by interrupting the polarization. Giant pyroelectric noise
appears in some of the non-equilibrium regimes. It is suggested that two
coupled types of order, one ferroelectric and the other glassy, may be required
to account for these data.Comment: 27 pages with 8 figures to appear in Phys. Rev.
Beyond school-related learning : parent-child homework talk as a morality building activity
Family interactions constitute an arena for children's moral development: it is indeed through ordinary talk, and shared, task-oriented activities that children are socialized into moral orders and culturally informed ways of thinking and acting. Drawing on a video-based study on the everyday life of 19 middle-class families and adopting a discourse analytic approach, the paper sheds light on the socializing function of a domestic activity: homework. We illustrate that, when it unfolds as a family activity, the issues at stake go far beyond its school-oriented goals: homework provides ‘ethical affordances’ that make relevant moral talk whereby parents introduce children to some unquestioned principles such as homework must be done neatly and it is part of the child's duties. We contend that, by participating in morally loaded homework interactions, children are socialized not only into a school-aligned cultural list concerning what is right and what is wrong about homework, but moreover into a constitutive, taken-for-granted pillar of human sociality: the moral assessability of human conduct, i.e., its being subject to evaluations informed by the ‘right vs. wrong’ category. Implications for teacher training and parent education programs are discussed in the conclusion
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Experimental and numerical investigation on forced convection in circular tubes with nanofluids
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.In this paper an experimental and numerical study to investigate the convective heat transfer
characteristics of fully developed turbulent flow of a water–Al2O3 nanofluid in a circular tube is presented.
The numerical simulations are accomplished on the experimental test section configuration. In the analysis,
the fluid flow and the thermal field are assumed axial-symmetric, two-dimensional and steady state. The
single-phase model is employed to model the nanofluid mixture and k-ε model is used to describe the
turbulent fluid flow. Experimental and numerical results are carried out for different volumetric flow rates
and nanoparticles concentration values. Heat transfer convective coefficients as a function of flow rates and
Reynolds numbers are presented. The results indicate that the heat transfer coefficients increase for all
nanofluids concentrations compared to pure water at increasing volumetric flow rate. Heat transfer
coefficient increases are observed at assigned volumetric flow rate for nanofluid mixture with higher
concentrations whereas Nusselt numbers present lower values than the ones for pure water
Aging in the Relaxor Ferroelectric PMN/PT
The relaxor ferroelectric
(PbMnNbO)(PbTiO), ,
(PMN/PT(90/10)) is found to exhibit several regimes of complicated aging
behavior. Just below the susceptibility peak there is a regime exhibiting
rejuvenation but little memory. At lower temperature, there is a regime with
mainly cumulative aging, expected for simple domain-growth. At still lower
temperature, there is a regime with both rejuvenation and memory, reminiscent
of spin glasses. PMN/PT (88/12) is also found to exhibit some of these aging
regimes. This qualitative aging behavior is reminiscent of that seen in
reentrant ferromagnets, which exhibit a crossover from a domain-growth
ferromagnetic regime into a reentrant spin glass regime at lower temperatures.
These striking parallels suggest a picture of competition in PMN/PT (90/10)
between ferroelectric correlations formed in the domain-growth regime with
glassy correlations formed in the spin glass regime. PMN/PT (90/10) is also
found to exhibit frequency-aging time scaling of the time-dependent part of the
out-of-phase susceptibility for temperatures 260 K and below. The stability of
aging effects to thermal cycles and field perturbations is also reported.Comment: 8 pages RevTeX4, 11 figures; submitted to Phys. Rev.
When school language and culture enter the home : testing children as a ‘school-aligned’ parental activity
Since Bronfenbrenner’s claims on the ecology of human development, an
impressive amount of research has explored the ways in which children’s
primary social worlds (i.e., family and school) connect and potentially create an osmotic ecological milieu. In the building of the so-called ‘familyschool partnership’, homework plays a crucial role. Being a school activity
carried out inside the home, it is a key site for implementing parental involvement and a crucial occasion where cultural models of ‘good parent’ and
‘good pupil’ are instantiated. This video-based, conversation analytic study
shows a specific activity taking place while parents assist their children with
homework: testing. The analysis shows that parents deploy a ‘school-like’
interactive conduct by reproducing the standards, morality, and linguistic
practices of the school. In so doing, they comply with the contemporary
model of ‘good parent as school partner’ and socialize their children into
the culture of the school by turning them into ‘good pupils’.
Keywords: homework; family-school partnership; test; parental involvement; ethnography-informed conversation analysis
Insetos bentônicos do Rio El Tala (Catamarca, Argentina): Variação longitudinal de sua estrutura e seu uso para avaliar a qualidade da água
The aim of this work was to determine the structure of the benthic entomofauna and its variation along the El Tala River (Catamarca, Argentina). Five sampling stations were established, considering the location of nearby housing with respect to the watercourse. The following variables were determined in situ: altitude, latitude and longitude, bedstream width, river depth, river-current speed, water and air temperatures. Benthic insects were collected with a square parcel sampler of 0.09-m2 area and 300-μm net opening and identified to the family level. Faunal density, richness, and diversity exhibited a longitudinal variation. From sampling Stations 1 (reference site) to 3, the number of orders and families decreased, whereas in sampling Station 4 those values increased and continued to do so through to Station 5 (downstream station). Station 5 showed the highest family richness (17) and the highest value for the Shannon-Wiener index (2.74) and the lowest value in Simpson's Dominance index (D = 0.22). These values could be explained because of the self-cleansing capabilities of the river downstream. The water quality of El Tala River is Class I (very clean and non-impacted), according to the results obtained from the application of the biotic Biological-Monitoring-Working-Party and Average-Store-per-Taxon indices.O objetivo deste trabalho foi determinar a estrutura da entomofauna bentônica do Rio El Tala (Catamarca, Argentina) e sua variação longitudinal. Cinco estações de amostragem foram estabelecidas considerando-se a localização da habitação em relação ao curso de água. As seguintes variáveis foram determinadas in situ: altitude, latitude e longitude; largura do leito; profundidade do rio; velocidade da correnteza, e temperatura da água e do ar. Insetos bentônicos foram coletados em cinco estações de amostragem, utilizando-se um coletor tipo Surber de 0,09 m2 , com rede de malha 300 μm, tendo sido identificados em laboratório até o nível de Família. Densidade, riqueza e diversidade da fauna exibiram variação longitudinal. Da estação de amostragem 1 (site de referência) à 3, uma tendência decrescente no número de ordens e famílias foi observada, enquanto que as estações de amostragem 4 e 5 apresentaram uma tendência crescente. As amostras da estação 5 (estação rio abaixo) apresentaram a maior riqueza de famílias (17), o valor mais elevado do Índice de Shannon (2,74) e o menor valor de Dominância de Simpson (D = 0,22). Estes valores podem ser explicados pela capacidade de autopurificação de rio a jusante. A qualidade da água do Rio El Tala é Classe I (muito limpo e água sem impacto), de acordo com os resultados obtidos pela aplicação de índices bióticos BMWP’ e ASPT’.Facultad de Ciencias Naturales y Muse
Insetos bentônicos do Rio El Tala (Catamarca, Argentina): Variação longitudinal de sua estrutura e seu uso para avaliar a qualidade da água
The aim of this work was to determine the structure of the benthic entomofauna and its variation along the El Tala River (Catamarca, Argentina). Five sampling stations were established, considering the location of nearby housing with respect to the watercourse. The following variables were determined in situ: altitude, latitude and longitude, bedstream width, river depth, river-current speed, water and air temperatures. Benthic insects were collected with a square parcel sampler of 0.09-m2 area and 300-μm net opening and identified to the family level. Faunal density, richness, and diversity exhibited a longitudinal variation. From sampling Stations 1 (reference site) to 3, the number of orders and families decreased, whereas in sampling Station 4 those values increased and continued to do so through to Station 5 (downstream station). Station 5 showed the highest family richness (17) and the highest value for the Shannon-Wiener index (2.74) and the lowest value in Simpson's Dominance index (D = 0.22). These values could be explained because of the self-cleansing capabilities of the river downstream. The water quality of El Tala River is Class I (very clean and non-impacted), according to the results obtained from the application of the biotic Biological-Monitoring-Working-Party and Average-Store-per-Taxon indices.O objetivo deste trabalho foi determinar a estrutura da entomofauna bentônica do Rio El Tala (Catamarca, Argentina) e sua variação longitudinal. Cinco estações de amostragem foram estabelecidas considerando-se a localização da habitação em relação ao curso de água. As seguintes variáveis foram determinadas in situ: altitude, latitude e longitude; largura do leito; profundidade do rio; velocidade da correnteza, e temperatura da água e do ar. Insetos bentônicos foram coletados em cinco estações de amostragem, utilizando-se um coletor tipo Surber de 0,09 m2 , com rede de malha 300 μm, tendo sido identificados em laboratório até o nível de Família. Densidade, riqueza e diversidade da fauna exibiram variação longitudinal. Da estação de amostragem 1 (site de referência) à 3, uma tendência decrescente no número de ordens e famílias foi observada, enquanto que as estações de amostragem 4 e 5 apresentaram uma tendência crescente. As amostras da estação 5 (estação rio abaixo) apresentaram a maior riqueza de famílias (17), o valor mais elevado do Índice de Shannon (2,74) e o menor valor de Dominância de Simpson (D = 0,22). Estes valores podem ser explicados pela capacidade de autopurificação de rio a jusante. A qualidade da água do Rio El Tala é Classe I (muito limpo e água sem impacto), de acordo com os resultados obtidos pela aplicação de índices bióticos BMWP’ e ASPT’.Facultad de Ciencias Naturales y Muse
Reply to Comment on "Quantum dense key distribution"
In this Reply we propose a modified security proof of the Quantum Dense Key
Distribution protocol detecting also the eavesdropping attack proposed by
Wojcik in his Comment.Comment: To appear on PRA with minor change
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