5,550 research outputs found
Are CSCL and Learning Sciences research relevant to large-scale educational reform?
This Symposium includes 4 papers: Paper 1 - From e-Learning Pilot Scheme to Scalable e-Learning Innovations: Wishful thinking or reality? (pp. 573-574 Nancy Law and Yeung Lee, University of Hong Kong)
Paper 2: Restoring “how people learn” as the core of educational reform in Japanese classrooms (pp. 574-575 Naomi Miyake, University of Tokyo)
Paper 3: Scaling up rapid collaborative practices in Singapore schools (pp. 575-577 Chee-Kit Looi, National Institute of Education, Nanyang Technological University
Paper 4: eTwinning: a European Network Community for Teachers to support cross-border school collaboration (pp. 577-579 Riina Vuorikari, European Schoolnet)CSCL 2013 Proceedings: v. 1 - Full Papers & Symposia - http://www.isls.org/cscl2013/Volume%201%20Final%20CSCL%202013%20Proceedings.pdf ; v. 2 - Short Papers, Panels, Posters, Demos, & Community Events - http://www.isls.org/cscl2013/Volume%202%20Final%20CSCL%202013%20Proceedings.pdfConference Theme: To see the world and a grain of sand: Learning across levels of space, time, and scaleMany scholars have contributed efforts to improve education in schools. A major motivation for learning scientists to develop design research as a methodology is to contribute to theory and educational practice through rigorous research without avoiding the complexities and messiness in authentic educational settings. There are many examples of successful implementation of collaborative, knowledge-construction oriented pedagogies using socio-cognitive and socio-metacognitive tools in formal and informal educational settings as well as in teacher professional development. However, there are many challenges to scaling up such innovations beyond small-scale implementation, including that of developing into “fatal mutations” (Brown, 1992). This symposium provides an opportunity for discussion and reflection on the impact that CSCL and Learning Sciences researchers have made on large-scale education reform and what, if any, may be done to extend this impact by bringing together a set of papers describing some large-scale education innovation initiatives in Asia and Europe.published_or_final_versio
Cubierta Hiperbólico-parabólica
Spokane Church in the State of Washington has been attractively roofed with a parabolic-hyperbolic pre-stressed concrete shell. According to the author, this type of shell structure, normally accepted to be of simple analysis, can present certain difficulties as regards stability. Theories deriving from the study of a membrane are not enough because, if the shell is large enough certain secondary stresses appear which quickly affect stability.
In this case the shell, which is symmetrical along one axis only, has two overhangs of 15 and 31 meters respectively, which required a special study.
In an attempt to smooth out the difficulties of an exact calculation the author tried as far as possible to even up the bending moments of the whole shell, thus allowing the indétermination conditions to be lessened. To do this he gave the shell a 7.5 centimeter thick overhang of light concrete at the back and a 12 centimeter thickness of ordinary concrete at the front.
The front walls are strengthened by the shell, which they support. The light supports at the back will not take any load over the normal design load.
To calculate the stress of the shell and around the rim, the membrane theory was applied, and it was assumed that the shell was symmetrical about two axes; this analysis gave a maximum stress of 14 kg/cm2.
Considering that the boundary area was subject to axial compressive stresses, in principle, it was thought that only normal reinforcement would be needed over the whole shell, without needing it to be pre-stressed; but it was realised that the secondary stresses would be decisive in the general behaviour of the shell.
The shrinkage of the concrete would be another cause of these secondary stresses, and likewise the differential shrinkage and elastic shortening of several parts of the structure.
The object of the pre-stressing was to apply uniform pressure on the whole shell. To achieve this a stress of 16 tons was applied on each 1-meter wide band of the shell. In the direction of the two stirrups the pre-stress was 10 tons per meter, to avoid the possibility of cracks.La iglesia de Spokane, del Estado de Washington, se ha cubierto, graciosamente, con una, lámina parabólico-hiperbólica, de hormigón pretensado. Este tipo de láminas, dice el autor, de análisis corrientemente admitido sencillo, puede presentar ciertas dificultades en su estabilidad. No son suficientes las teorías que el estudio de una membrana proporciona, ya que, si las dimensiones de estas láminas alcanzan ciertas proporciones, aparecen esfuerzos secundarios que rápidamente surgen al intervenir en la estabilidad de la lámina.
En este caso la lámina, simétrica solamente según un eje, presenta dos voladizos de 15 y 31 m, respectivamente, lo que ha constituido un estudio particular.
El autor, con objeto de al lanar dificultades de un cálculo exacto, intentó igualar, en la medida de lo posible, los momentos flectores en toda la lámina, admitiendo, con ello, que las condiciones de indeterminación se verían reducidas. Para proceder asi se le dio a la lámina un espesor de 7,5 cm de hormigón ligero en la parte posterior formando ménsula y de 13 cm en la parte anterior de hormigón del tipo ordinario.
Los muros frontales se han solidarizado con la lámina, a la que le sirven de apoyo. Los soportes, ligeros, de la parte posterior, no permiten sobrecargas superiores a las normales previstas.
Para el cálculo de las tensiones de la lámina y de los elementos de borde se aplicó la teoría de membrana y se supuso que la lámina era simétrica respecto de los dos ejes, de cuyo análisis resultó una tensión máxima de 14 kg/cm2.
Por creer que los elementos del borde estaban sometidos a esfuerzos axiles de compresión, en un principio todo hacía resumir que sólo se necesitarían armaduras nominales en toda la lámina, sin que fuera necesario el pretensado; sin embargo, se pudo apreciar que los esfuerzos secundarios dominarían el comportamiento general de la lámina.
La retracción del hormigón sería otra de las causas de dichos esfuerzos secundarios. También influían en estos esfuerzos secundarios la retracción diferencial y acortamiento elástico de varias partes de la estructura.
El pretensado tenía por objeto introducir una presión uniforme en toda, la lámina. Para lograrlo se aplicó una tensión de 16 toneladas por banda de un metro de anchura de lámina. En la dirección de los dos estribos, la tensión de pretensado ha sido de 10 toneladas por metro, para evitar la fisuración
Design approaches in technology enhanced learning
Design is a critical to the successful development of any interactive learning environment (ILE). Moreover, in technology enhanced learning (TEL), the design process requires input from many diverse areas of expertise. As such, anyone undertaking tool development is required to directly address the design challenge from multiple perspectives. We provide a motivation and rationale for design approaches for learning technologies that draws upon Simon's seminal proposition of Design Science (Simon, 1969). We then review the application of Design Experiments (Brown, 1992) and Design Patterns (Alexander et al., 1977) and argue that a patterns approach has the potential to address many of the critical challenges faced by learning technologists
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ESTABLISHING A LOCAL BANK AND COMPARING EFFICACIES OF THIRD PARTY VIRUS-SPECIFIC CYTOTOXIC T CELLS (VST) AND CYTOKINE INDUCED KILLER CELLS (VSCIK)
EUS-guided verteporfin photodynamic therapy for pancreatic cancer
BACKGROUND AND AIMS: Locally advanced pancreatic cancer (LAPC) often causes obstruction. Verteporfin photodynamic therapy (PDT) can feasibly "debulk" tumor more safely than noncurative surgery and has multiple advantages over older PDT agents. We aimed to assess the feasibility of EUS-guided verteporfin PDT in ablating nonresectable LAPC. METHODS: Adults with LAPC with adequate biliary drainage were prospectively enrolled. Exclusion criteria included significant metastatic disease burden, disease involving >50% duodenal or major artery circumference, and recent treatment with curative intent. CT was obtained between day -28 to 0. On day 0, verteporfin 0.4 mg/kg was infused 60 to 90 minutes before EUS, during which a diffuser was positioned in the tumor and delivered light at 50 J/cm for 333 seconds. CT was obtained on day 2, with adverse event monitoring occurring on days 1, 2, and 14. Primary outcome was presence of necrosis. RESULTS: Of 8 patients (62.5% male, mean age 65±7.9 y) included in the study, 5 were staged at T3, 2 at T2, and 1 at T1. Most (4) had primary lesions in the pancreatic head. Mean pretrial tumor diameter was 33.3±13.4 mm. On day 2 CT, 5 lesions demonstrated a zone of necrosis measuring a mean diameter of 15.7±5.5 mm; 3 cases did not develop necrosis. No adverse events were noted during the procedure or postprocedure observation period (day 1-3), and no changes in patient reported outcomes were noted. CONCLUSIONS: In this pilot study, EUS-guided verteporfin PDT is feasible and shows promise as a minimally invasive ablative therapy for LAPC in select patients. Tumor necrosis is visible within 48 hours after treatment. Patient enrollment and data collection are ongoing
Short- and long-term conditioning of a temperate marine diatom community to acidification and warming
Ocean acidification and greenhouse warming will interactively influence competitive success of key phytoplankton groups such as diatoms, but how long-term responses to global change will affect community structure is unknown. We incubated a mixed natural diatom community from coastal New Zealand waters in a short-term (two-week) incubation experiment using a factorial matrix of warming and/or elevated pCO2 and measured effects on community structure. We then isolated the dominant diatoms in clonal cultures and conditioned them for 1 year under the same temperature and pCO2 conditions from which they were isolated, in order to allow for extended selection or acclimation by these abiotic environmental change factors in the absence of interspecific interactions. These conditioned isolates were then recombined into ‘artificial’ communities modelled after the original natural assemblage and allowed to compete under conditions identical to those in the short-term natural community experiment. In general, the resulting structure of both the unconditioned natural community and conditioned ‘artificial’ community experiments was similar, despite differences such as the loss of two species in the latter. pCO2 and temperature had both individual and interactive effects on community structure, but temperature was more influential, as warming significantly reduced species richness. In this case, our short-term manipulative experiment with a mixed natural assemblage spanning weeks served as a reasonable proxy to predict the effects of global change forcing on diatom community structure after the component species were conditioned in isolation over an extended timescale. Future studies will be required to assess whether or not this is also the case for other types of algal communities from other marine regimes
Dynamics of a Vortex in a Trapped Bose-Einstein Condensate
We consider a large condensate in a rotating anisotropic harmonic trap. Using
the method of matched asymptotic expansions, we derive the velocity of an
element of vortex line as a function of the local gradient of the trap
potential, the line curvature and the angular velocity of the trap rotation.
This velocity yields small-amplitude normal modes of the vortex for 2D and 3D
condensates. For an axisymmetric trap, the motion of the vortex line is a
superposition of plane-polarized standing-wave modes. In a 2D condensate, the
planar normal modes are degenerate, and their superposition can result in
helical traveling waves, which differs from a 3D condensate. Including the
effects of trap rotation allows us to find the angular velocity that makes the
vortex locally stable. For a cigar-shape condensate, the vortex curvature makes
a significant contribution to the frequency of the lowest unstable normal mode;
furthermore, additional modes with negative frequencies appear. As a result, it
is considerably more difficult to stabilize a central vortex in a cigar-shape
condensate than in a disc-shape one. Normal modes with imaginary frequencies
can occur for a nonaxisymmetric condensate (in both 2D and 3D). In connection
with recent JILA experiments, we consider the motion of a straight vortex line
in a slightly nonspherical condensate. The vortex line changes its orientation
in space at the rate proportional to the degree of trap anisotropy and can
exhibit periodic recurrences.Comment: 19 pages, 6 eps figures, REVTE
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