Conceptually driven and visually rich tasks in texts and teaching practice: the case of infinite series

The study we report here examines parts of what Chevallard calls the institutional dimension of the students’ learning experience of a relatively under-researched, yet crucial, concept in Analysis, the concept of infinite series. In particular, we examine how the concept is introduced to students in texts and in teaching practice. To this purpose, we employ Duval's Theory of Registers of Semiotic Representation towards the analysis of 22 texts used in Canada and UK post-compulsory courses. We also draw on interviews with in-service teachers and university lecturers in order to discuss briefly teaching practice and some of their teaching suggestions. Our analysis of the texts highlights that the presentation of the concept is largely a-historical, with few graphical representations, few opportunities to work across different registers (algebraic, graphical, verbal), few applications or intra-mathematical references to the concept's significance and few conceptually driven tasks that go beyond practising with the application of convergence tests and prepare students for the complex topics in which the concept of series is implicated. Our preliminary analysis of the teacher interviews suggests that pedagogical practice often reflects the tendencies in the texts. Furthermore, the interviews with the university lecturers point at the pedagogical potential of: illustrative examples and evocative visual representations in teaching; and, student engagement with systematic guesswork and writing explanatory accounts of their choices and applications of convergence tests

Remote man-machine control system evaluation Final report

Remote-controlled man-machine system for space exploration analyzed in Mars spacecraft system stud

Coherent Control of Isotope Separation in HD+ Photodissociation by Strong Fields

The photodissociation of the HD+ molecular ion in intense short- pulsed linearly polarized laser fields is studied using a time- dependent wave-packet approach where molecular rotation is fully included. We show that applying a coherent superposition of the fundamental radiation with its second harmonic can lead to asymmetries in the fragment angular distributions, with significant differences between the hydrogen and deuterium distributions in the long wavelength domain where the permanent dipole is most efficient. This effect is used to induce an appreciable isotope separation.Comment: Physical Review Letters, 1995 (in press). 4 pages in revtex format, 3 uuencoded figures. Full postcript version available at: http://chemphys.weizmann.ac.il/~charron/prl.ps or ftp://scipion.ppm.u-psud.fr/coherent.control/prl.p

Laser induced electron diffraction: a tool for molecular orbital imaging

We explore the laser-induced ionization dynamics of N2 and CO2 molecules subjected to a few-cycle, linearly polarized, 800\,nm laser pulse using effective two-dimensional single active electron time-dependent quantum simulations. We show that the electron recollision process taking place after an initial tunnel ionization stage results in quantum interference patterns in the energy resolved photo-electron signals. If the molecule is initially aligned perpendicular to the field polarization, the position and relative heights of the associated fringes can be related to the molecular geometrical and orbital structure, using a simple inversion algorithm which takes into account the symmetry of the initial molecular orbital from which the ionized electron is produced. We show that it is possible to extract inter-atomic distances in the molecule from an averaged photon-electron signal with an accuracy of a few percents

Expression and signal transduction of the glucagon receptor in βTC3 cells

AbstractThe expression and signal transduction of the glucagon receptor (GR) have been studied in βTC3 cells. Northern blot and RT-PCR analysis indicated the expression of the GR gene in βTC3 cells. One-5 nM glucagon stimulated a 2.5-fold increase in the IPs production. At glucagon concentrations higher than 5 nM, the production of IPs was blunted but not abolished. The accumulation of intracellular cAMP was observed following the stimulation with 5 nM of glucagon. A maximal 4.5-fold increase in cAMP was observed using 250 nM glucagon and higher. Comparative studies using a glucagon anatogonist, des-His1[Glu]9glucagon, showed no effect on intracellular cAMP and IPs in βTC3 cells. Our data shows that the GR gene is expressed in βTC3 cells. The GR in βTC3 cells transmits its intracellular signal by causing the accumulation of both IPs and cAMP

Crystallization and preliminary X-ray diffraction studies of D-glyceraldehyde-3-phosphate dehydrogenase from the hyperthermophilic archaeon Methanothermus fervidus.

Journal ArticleThe homotetrameric holo-D-glyceraldehyde-3-phosphate dehydrogenase from the hyperthermophilic archaeon Methanothermus fervidus has been crystallized in the presence of NADP+ using the hanging-drop vapour-diffusion method. Crystals grew from a solution containing 2-methyl-2,4-pentanediol and magnesium acetate. A native data set has been collected to 2.1 A using synchrotron radiation and cryocooling. Diffraction data have been processed in the orthorhombic system (space group P21212) with unit-cell dimensions a = 136.7, b = 153.3, c = 74.9 A and one tetramer per asymmetric unit

Citizens' perception of the Cohesion Policy and support for the European Union

Using a novel database, this study assesses the impact of the perception of the personal benefits of the EU Cohesion Policy on support for the European project. The results show that the gap in support between people who claim to have benefited from the Cohesion Policy and those who feel they have not vanished once differences in individual traits and reverse causality are taken into account. This means that, despite the significant positive effect that the intensity of the Cohesion Policy in the region exerts on the perception of the policy, it does not stimulate support for the EU

Cultured Human Epidermal Cells Do Not Synthesize HLA-DR

All nucleated cells express HLA-A, B, and C antigens. However, only a few cells, including epidermal cells, demonstrate HLA-DR antigens which are potent transplantation immunogens in man. The current study was undertaken to determine if epidermal cells continue to synthesize and/or express HLA-DR antigens after prolonged in vitro culture. Epidermal cells cultured for 7days or more no longer stimulated allogeneic lymphocytes in the epidermal cell-lymphocyte reaction. Indirect immunofluorescence light microscopy of cultured cells using mouse monoclonal antibody to HLA-DR antigen confirmed that these cells do not express HLA-DR antigens whereas they retain β2-microglobulin. Detergent extracts of 12-day cultured epidermal cells biosynthetically labeled with 35S-methionine were immunoprecipitated with monoclonal anti-DR antibody and analyzed by the method of two-dimensional polyacrylamide gel electrophoresis. No radiolabeled proteins were found on these gels in the regions where HLA-DR molecules are known to migrate. These data indicate that HLA-DR antigen is absent from cultured epidermal cells. Finally, we describe a technique for growing epidermal cells on a gelatin membrane which allows subsequent removal of intact cell monolayers from the culture dish. Such monolayers may be useful for purposes of transplantation

The propensity of molecules to spatially align in intense light fields

The propensity of molecules to spatially align along the polarization vector of intense, pulsed light fields is related to readily-accessible parameters (molecular polarizabilities, moment of inertia, peak intensity of the light and its pulse duration). Predictions can now be made of which molecules can be spatially aligned, and under what circumstances, upon irradiation by intense light. Accounting for both enhanced ionization and hyperpolarizability, it is shown that {\it all} molecules can be aligned, even those with the smallest static polarizability, when subjected to the shortest available laser pulses (of sufficient intensity).Comment: 8 pages, 4 figures, to be submitted to PR