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941.
The issues involved in teaching English language learners mathematics while they are learning English pose many challenges for mathematics teachers and highlight the need to focus on language-processing issues related to teaching mathematical content. Two realistic-type problems from high-stakes tests are used to illustrate the complex interactions between culture, language, and mathematical learning. The analyses focus on aspects of the problems that potentially increase cognitive demands for second-language learners. An analytical framework is presented that is designed to enable mathematics teachers to identify critical elements in problems and the learning environment that contribute to increased cognitive demands for students of English as a second language. The framework is proposed as a cycle of teacher reflection that would extend a constructivist model of teaching to include broader linguistic, cultural, and cognitive processing issues of mathematics teaching, as well as enable teachers to develop more accurate mental models of student learning. 相似文献
942.
E. Chikoidze Y. Dumont H.J. von Bardeleben J. Gleize F. Jomard E. Rzepka G. Berrerar D. Ferrand O. Gorochov 《Applied Physics A: Materials Science & Processing》2007,88(1):167-171
ZnO:Mn thin films are grown by the metal organic chemical vapor deposition technique. Mn (x) varies in the 0<x<0.44 range.
Vegard’s law has been verified for the lattice parameters. Electron paramagnetic resonance (EPR) measurements prove the substitutional
incorporation of Mn2+ on zinc sites. The behavior of the EPR line width regarding temperature is discussed. All ZnO:Mn layers show antiferromagnetic
interaction and a J1/kB=-15 K effective exchange constant. The optical band gap of ZnO:Mn increases with the manganese concentration. Raman spectroscopy
reveals a Mn-related scattering band.
PACS 71.55.Gs; 75.50.Pp; 61.10.Nz; 76.30.Fc; 75.30.Et; 78.40.-q 相似文献
943.
944.
B. Savo P. Romano A. Nigro R. Di Leo 《Physica C: Superconductivity and its Applications》2002,370(4):275-280
The flat voltage noise component of current biased, high-transparency Nb/AlOx/Nb superconducting tunnel junctions has been investigated at frequencies up to 70 kHz. Several aspects of the analyzed phenomena suggest the presence of current noise effects induced by the discreteness of the charge carriers. At subgap voltages, where excess currents occur, a behavior coherent with a multiple Andreev reflection-assisted transport through the tunnel barrier has been found. However, the measured charge values exceed any theoretical prediction. 相似文献
945.
F.Oner R.A.Mamedoy 《理论物理通讯》2002,37(3):327-330
Behavior of the Coulomb energy difference for light nuclei is explained in terms of the different values of the average Coulomb interaction between two particles.Coulomb energy difference according to shell model of light mirror nuclei in the Coulomb and exchange integrals in the formula can be explained with exponential-type wavefunctions.In this study,using the one-center expansion of exponential-type wavefunctions in terms of Slater-type orbitals with the same center,we derived formula for Coulomb energy difference of light mirror nuclei. 相似文献
946.
Frank H.G.M. Wijnands Charles G. Crookes Paul M. Charles Richard M. Ash Ian F. Lealman Michael J. Robertson Anthony E. Kelly Kevin A. Williams Aeneas B. Massara Richard V. Penty Ian H. White 《Optical and Quantum Electronics》2002,34(10):959-973
An anomalous modulation in the wavelength spectrum has been observed in lasers with spot-size converters. This intensity modulation is shown to be caused by beating between the fundamental lasing mode and radiation modes in the taper. This results in a periodic modulation in the net gain spectrum, which causes wavelength jumps between adjacent net gain maxima, and a drive current dependent spectral width that is expected to affect system performance. The amplitude of this spectral modulation is reduced significantly by either using an angled rear-facet which reflects the beating radiation modes away from the laser axis, or by using a nonlinear, adiabatic taper. 相似文献
947.
Alp E. E. Sturhahn W. Toellner T. S. Zhao J. Hu M. Brown D. E. 《Hyperfine Interactions》2002,144(1-4):3-20
Nuclear resonant inelastic X-ray scattering of synchrotron radiation is being applied to ever widening areas ranging from
geophysics to biophysics and materials science. Since its first demonstration in 1995 using the 57Fe resonance, the technique has now been applied to materials containing 83Kr, 151Eu, 119Sn, and 161Dy isotopes. The energy resolution has been reduced to under a millielectronvolt. This, in turn, has enabled new types of
measurements like Debye velocity of sound, as well as the study of origins of non-Debye behavior in presence of other low-energy
excitations. The effect of atomic disorder on phonon density of states has been studied in detail. The flux increase due to
the improved X-ray sources, crystal monochromators, and time-resolved detectors has been exploited for reducing sample sizes
to nano-gram levels, or using samples with dilute resonant nuclei like myoglobin, or even monolayers. Incorporation of micro-focusing
optics to the existing experimental setup enables experiments under high pressure using diamond-anvil cells. In this article,
we will review these developments.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
948.
E. Goering M. Justen J. Geissler U. Rüdiger M. Rabe G. Güntherodt G. Schütz 《Applied Physics A: Materials Science & Processing》2002,74(6):747-753
Highly a-axis-textured CrO2 films have been deposited on Al2O3 (0001) substrates by chemical vapor deposition. CrO2 has been found to have highly a-axis (010)-oriented columnar growth on a Cr2O3 (0001) initial layer. The six-fold surface symmetry of the Cr2O3 initial layer leads to three equivalent in-plane orientations of the a-axis-oriented CrO2 unit cell. We report Cr L2,3 X-ray magnetic circular dichroism data along the surface normal and at 60° off-normal sample orientation. For a 60° sample
alignment, a strong increase of the projected orbital moment could be observed for unoccupied majority t2g states using moment analysis. Therefore, the c axis is identified as the intrinsic magnetic easy axis of CrO2. In addition, a small spin moment and a very strong magnetic dipole term Tz have been found.
Received: 8 January 2002 / Accepted: 8 January 2002 相似文献
949.
A. Cavallini B. Fraboni W. Dusi N. Auricchio M. Zanarini P. Chirco 《Applied Physics A: Materials Science & Processing》2002,75(3):427-429
The time recovery of the spectroscopic capabilities of CdZnTe and CdTe detectors, irradiated with increasing doses of high-
and low-energy neutrons, as well as electrons, has been investigated by studying their spectroscopic behavior at different
photon energies using leakage current measurements and PICTS (photo-induced current transient spectroscopy) analysis. The
detectors were stored at room temperature for up to one year to study the time evolution of their spectroscopic performance
and to correlate it with the presence of defective states in the material. We have observed a clear improvement in the material’s
detection properties with time, though only in those detectors which have not been severely degraded by the irradiation. The
recovery can be associated with a decrease in the concentration of some defective states, thus allowing the assessment of
the crucial role these play in determining the charge collection processes in the material and its spectroscopic capabilities.
Received: 1 August 2001 / Accepted: 3 August 2001 / Published online: 20 December 2001 相似文献
950.