Energy levels and far-infrared spectroscopy for two electrons in a semiconductor nanoring

The effects of electron-electron interaction of a two-electron nanoring on the energy levels and far-infrared (FIR) spectroscopy have been investigated based on a model calculation which is performed within the exactly numerical diagonalization. It is found that the interaction changes the energy spectra dramatically, and also shows significant influence on the FIR spectroscopy. The crossings between the lowest spin-singlet and triplet states induced by the coulomb interaction are clearly revealed. Our results are related to the experiment recently carried out by A. Lorke et al. [Phys. Rev. Lett. 84, 2223 (2000)].Comment: 17 pages, 6 figures, revised and accepted by Phys. Rev. B (Dec. 15

Influence of shape of quantum dots on their far-infrared absorption

We investigate the effects of the shape of quantum dots on their far-infrared absorption in an external magnetic field by a model calculation. We focus our attention on dots with a parabolic confinement potential deviating from the common circular symmetry, and dots having circular doughnut shape. For a confinement where the generalized Kohn theorem does not hold we are able to interprete the results in terms of a mixture of a center-of-mass mode and collective modes reflecting an excitation of relative motion of the electrons. The calculations are performed within the time-dependent Hartree approximation and the results are compared to available experimental results.Comment: RevTeX, 16 pages with 10 postscript figures included. Submitted to Phys. Rev.

Magnetization of noncircular quantum dots

We calculate the magnetization of quantum dots deviating from circular symmetry for noninteracting electrons or electrons interacting according to the Hartree approximation. For few electrons the magnetization is found to depend on their number, and the shape of the dot. The magnetization is an ideal probe into the many-electron state of a quantum dot.Comment: 11 RevTeX pages with 6 included Postscript figure

Non-adiabatic current generation in a finite width semiconductor ring

We consider a model of a semiconductor quantum ring of finite width in a constant perpendicular magnetic field. We show how a current of the same order as the persistent current can be generated non-adiabatically by a short intensive pulse in the Tera-Hertz regime.Comment: LaTeX, 4 pages with included eps figure

Effects of sustained electrical stimulation on spasticity assessed by the pendulum test

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked DownloadNeuromodulation using electrical stimulation is able to enhance motor control of individuals suffering an upper motor neuron disorder. This work examined the effect of sustained electrical stimulation to modify spasticity in the leg muscles. We applied transcutaneous spinal cord stimulation with a pulse rate of 50 Hz for 30 min. The subjects were assessed before and after the intervention using in a pendulum test setup. The motion of the free swinging leg was acquired through video tracking and goniometer measurements. The quantification was done through the R2n index which shows consistency identifying the spasticity levels. In all incomplete SCI subjects having severe spasticity, the results show that electrical stimulation is effective to modify the increased muscle tone.Consejo Nacional de Ciencia y Tecnologí

Corrigendum to “Environmental and life-history factors influence inter-colony multidimensional niche metrics of a breeding Arctic marine bird” [Sci. Total Environ. 796 (2021) 148935] (Science of the Total Environment (2021) 796, (S0048969721040079), (10.1016/j.scitotenv.2021.148935))

The authors regret that the printed version of the above article contained an omission of an individual deserving of co-authorship. The correct and final version follows. The authors would like to apologise for any inconvenience caused. \u3c Reyd A. Smith1⁎, David J. Yurkowski2, Kyle J.L. Parkinson1, Jérôme Fort3, Holly L. Hennin4, H. Grant Gilchrist4, Keith A. Hobson5, Mark L. Mallory6, Paco Bustamante3, Jóhannis Danielsen7, Svend E. Garbus8, Sveinn A. Hanssen9, Jón Einar Jónsson10, Christopher J. Latty11, Ellen Magnúsdóttir10, Børge Moe9, Glen J. Parsons12, Christian Sonne8, Grigori Tertitski13, and Oliver P. Love1\u3e Windsor, Windsor, Ontario, Canada, N9B 3P4 2 Fisheries and Oceans Canada, Winnipeg, Manitoba, Canada, R3T 2N6 3 Littoral, Environnement et Sociétés (LIENSs), UMR 7266 CNRS – La Rochelle University, La Rochelle, France, FR-17000 4 Environment and Climate Change Canada, Ottawa, Ontario, Canada, K0A 1H0. 5 Western University, London, Ontario, Canada, N6A 3K7 6Acadia University, Wolfville, Nova Scotia, Canada, B4P 2R6 7 Faroe Marine Research Institute, Tórshavn, Faroe Islands, FO-110 8 Aarhus University, Roskilde, Denmark, DK-4000 9 Norwegian Institute for Nature Research, Tromsø, Norway, N-9296 10 University of Iceland\u27s Research Centre at Snæfellsnes, Hafnargata 3, 340, Stykkishólmur, Iceland 11 Arctic National Wildlife Refuge, U.S. Fish and Wildlife Service, Fairbanks, Alaska, United States, 99701 12 Nova Scotia Department of Lands and Forestry, Kentville, Nova Scotia, Canada, B4N 4E5 13 Institute of Geography of the Russian Academy of Sciences, Moscow, Russia, 119017\u3

Eigenvalue Problem in Two Dimensions for an Irregular Boundary II: Neumann Condition

We formulate a systematic elegant perturbative scheme for determining the eigenvalues of the Helmholtz equation (\bigtriangledown^{2} + k^{2}){\psi} = 0 in two dimensions when the normal derivative of {\psi} vanishes on an irregular closed curve. Unique feature of this method, unlike other perturbation schemes, is that it does not require a separate formalism to treat degeneracies. Degenerate states are handled equally elegantly as the non-degenerate ones. A real parameter, extracted from the parameters defining the irregular boundary, serves as a perturbation parameter in this scheme as opposed to earlier schemes where the perturbation parameter is an artificial one. The efficacy of the proposed scheme is gauged by calculating the eigenvalues for elliptical and supercircular boundaries and comparing with the results obtained numerically. We also present a simple and interesting semi-empirical formula, determining the eigenspectrum of the 2D Helmholtz equation with the Dirichlet or the Neumann condition for a supercircular boundary. A comparison of the eigenspectrum for several low-lying modes obtained by employing the formula with the corresponding numerical estimates shows good agreement for a wide range of the supercircular exponent.Comment: 26 pages, 12 figure

NANOG alone induces germ cells in primed epiblast in vitro by activation of enhancers.

Nanog, a core pluripotency factor in the inner cell mass of blastocysts, is also expressed in unipotent primordial germ cells (PGCs) in mice, where its precise role is yet unclear. We investigated this in an in vitro model, in which naive pluripotent embryonic stem (ES) cells cultured in basic fibroblast growth factor (bFGF) and activin A develop as epiblast-like cells (EpiLCs) and gain competence for a PGC-like fate. Consequently, bone morphogenetic protein 4 (BMP4), or ectopic expression of key germline transcription factors Prdm1, Prdm14 and Tfap2c, directly induce PGC-like cells (PGCLCs) in EpiLCs, but not in ES cells. Here we report an unexpected discovery that Nanog alone can induce PGCLCs in EpiLCs, independently of BMP4. We propose that after the dissolution of the naive ES-cell pluripotency network during establishment of EpiLCs, the epigenome is reset for cell fate determination. Indeed, we found genome-wide changes in NANOG-binding patterns between ES cells and EpiLCs, indicating epigenetic resetting of regulatory elements. Accordingly, we show that NANOG can bind and activate enhancers of Prdm1 and Prdm14 in EpiLCs in vitro; BLIMP1 (encoded by Prdm1) then directly induces Tfap2c. Furthermore, while SOX2 and NANOG promote the pluripotent state in ES cells, they show contrasting roles in EpiLCs, as Sox2 specifically represses PGCLC induction by Nanog. This study demonstrates a broadly applicable mechanistic principle for how cells acquire competence for cell fate determination, resulting in the context-dependent roles of key transcription factors during development.This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nature1648

Deregulation, Privatisation and Marketisation of Nordic Comprehensive Education : Social Changes Reflected in Schooling

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