791 research outputs found
The evolution of a national research plan for computers in education in The Netherlands
This paper describes the evolution of a national research plan for computers and education in The Netherlands. This approach was initiated in 1983 and includes two phases: one from 1984 until 1988 and one from 1989 until 1992. The paper describes the research plans for the second phase, based upon the experiences of the first, and draws some general conclusions about the development of national research plans for computers in education
On totally geodesic submanifolds in the Jacobian locus
We study submanifolds of A_g that are totally geodesic for the locally
symmetric metric and which are contained in the closure of the Jacobian locus
but not in its boundary. In the first section we recall a formula for the
second fundamental form of the period map due to Pirola, Tortora and the first
author. We show that this result can be stated quite neatly using a line bundle
over the product of the curve with itself. We give an upper bound for the
dimension of a germ of a totally geodesic submanifold passing through [C] in
M_g in terms of the gonality of C. This yields an upper bound for the dimension
of a germ of a totally geodesic submanifold contained in the Jacobian locus,
which only depends on the genus. We also study the submanifolds of A_g obtained
from cyclic covers of the projective line. These have been studied by various
authors. Moonen determined which of them are Shimura varieties using deep
results in positive characteristic. Using our methods we show that many of the
submanifolds which are not Shimura varieties are not even totally geodesic.Comment: To appear on International Journal of Mathematic
Building with materials from demolition projects
Students of Eindhoven University of Technology have developed a sustainable and innovative hikers’ cabin, called "Trek-In" for SNK, a Dutch coordinating organization of natural campsites. By now, three Trek-Ins are in commercial use, while SNK intends to exploit over 100 Trek-Ins in the coming years. This case study shows current possibilities of recycling in an architectural context, because nearly all materials used are derived from demolition waste materials. The structure as well as inner and outer finishing, but also plumbing, wash hand basin, toilet bowl, light switches, wall sockets, kitchen, et cetera, are all reclaimed from demolitions. A Trek-In exists of two modules that are fully assembled in a factory. The two modules are brought together on-site, where a simple foundation will do. This foundation is also made out of demolition waste materials. Making the foundation and placing the two modules can be done in just one day. The paper describes this exciting students’ project from start until realization of a prototypes. Principles of the way demolition waste is applied are also described, as well as the way Trek-Ins are constructe
A challenging practical experience, The Trek-in; a durable and innovative hikers’ cabin
Small buildings pop up everywhere across our natural environment. Their purpose is a place where people can stay the night. Unfortunately, together they give a disorganized impression of the landscape. Students of the Eindhoven University of Technology were asked to design a durable and innovative hikers’ cabin, to change that tendency. A competition led to the concept for a new hikers’ cabin. This competition was won by two architectural master students and after that developed in a multidisciplinary project of six students who subscribed for a challenging practical experience within their education. These six students had different educational backgrounds, were from different disciplines within the Department of the Built Environment, were at different stages in their education and had to cope with the different interests of all the other participants. Nevertheless, they were able to develop an integrated design, the Trek-in
On some differential-geometric aspects of the Torelli map
In this note we survey recent results on the extrinsic geometry of the
Jacobian locus inside . We describe the second fundamental form
of the Torelli map as a multiplication map, recall the relation between totally
geodesic subvarieties and Hodge loci and survey various results related to
totally geodesic subvarieties and the Jacobian locus.Comment: To appear on Boll. UMI, special volume in memory of Paolo de
Bartolomei
Cleavage of the Oxanorbornene Oxygen Bridge with Lewis Acids: Computation and Experiment
Since the discovery of the biological activity of aminophosphonates, research started on the synthesis of more constraint azaheterocyclic phosphonates. We developed a route via an intramolecular Diels-Alder reaction towards α-aminophosphonates 1. [1] The obtained oxanorbornene skeleton is a valuable synthetic intermediate that has been used in various natural product syntheses. [2] An important synthetic transformation involves the cleavage of the oxygen bridge, used to construct substituted arenes and cyclohexenes. We wanted to investigate the ring opening of adducts 1 using different Lewis acids experimentally and get more insight in the reaction pathways towards the different products via computational experiments. In this presentation the results obtained with TiCl4 and FeCl3 catalyst are shown.
The computational study started with the catalysts and their multiplicity. Next, the complexation energy with different binding sites was calculated. Therefore, a level of theory study was done using an ONIOM QM/QM approach. This shows the importance of the inclusion of electron correlation effects. B3LYP geometries and energies can be used as a good approximation. Bidentate coordination towards the most electronegative phosphonate oxygen and the oxygen bridge is favoured for both catalysts. Then, different reaction pathways were investigated via a static, gas-phase approach. The energy barrier towards the transition state using the TiCl4 catalyst, shown in Figure 1, is much lower than for the FeCl3 catalyst and very different products are formed. The computational results were compared with the experiments
On the canonical degrees of curves in varieties of general type
A widely believed conjecture predicts that curves of bounded geometric genus
lying on a variety of general type form a bounded family. One may even ask
whether the canonical degree of a curve in a variety of general type is
bounded from above by some expression , where and are
positive constants, with the possible exceptions corresponding to curves lying
in a strict closed subset (depending on and ). A theorem of Miyaoka
proves this for smooth curves in minimal surfaces, with . A conjecture
of Vojta claims in essence that any constant is possible provided one
restricts oneself to curves of bounded gonality.
We show by explicit examples coming from the theory of Shimura varieties that
in general, the constant has to be at least equal to the dimension of the
ambient variety.
We also prove the desired inequality in the case of compact Shimura
varieties.Comment: 10 pages, to appear in Geometric and Functional Analysi
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