21 research outputs found
Henri Temianka Correspondence; (kaper)
No full textThis collection contains material pertaining to the life, career, and activities of Henri Temianka, violin virtuoso, conductor, music teacher, and author. Materials include correspondence, concert programs and flyers, music scores, photographs, and books.https://digitalcommons.chapman.edu/temianka_correspondence/3819/thumbnail.jp
Metingen aan een lekke coaxiale kabel
No full textUitgaande van twee zwak gekoppelde transmissieljnen is een rekenmodel opgesteld voor de “lekke" coaxiale kabel Om dit model te testen is een tachtig meter lange meetbaan geconstrueerd waarbij is getracht een uniform uitwendig circuit zo goed mogeljk te benaderen. De resultaten hiervan zijn in een aantal metingen vastgelegd. Daarna is nagegaan wat de gevolgen zjn van een verstoring in het uitwendig circuit op het veld buiten de kabel. Tevens wordt nagegaan op welke wijze verdere verbetering verkregen kan worden verkregen.Electrical Engineering, Mathematics and Computer ScienceTransmissie van Informati
On uniqueness of semi-wavefronts
No full textTrofimchuk, S (reprint author), Univ Talca, Inst Matemat & Fis, Casilla 747, Talca, Chile.Motivated by the uniqueness problem for monostable semi-wave-fronts, we propose a revised version of the Diekmann and Kaper theory of a nonlinear convolution equation. Our version of the Diekmann-Kaper theory allows (1) to consider new types of models which include nonlocal KPP type equations (with either symmetric or anisotropic dispersal), nonlocal lattice equations and delayed reaction-diffusion equations; (2) to incorporate the critical case (which corresponds to the slowest wavefronts) into the consideration; (3) to weaken or to remove various restrictions on kernels and nonlinearities. The results are compared with those of Schumacher (J Reine Angew Math 316: 54-70, 1980), Carr and Chmaj (Proc Am Math Soc 132: 2433-2439, 2004), and other more recent studies
Single entities. Emigration of Polish jazz and pop musicians
No full textJazz and pop music representatives are a particularly mobile group of musicians. This is mainly due to the fact of pop music market being dependent on financial factors, channels of distributions and technology. The hybridization of popular music faces it with the migrating, creative human element, and the migration itself undergoes numerous changes in the reality of global, digital world. The author focuses on the tendency of Polish jazz and pop musicians to emigrate. The phenomenon is analysed in the changing cultural, social and political contexts. By interpreting the different fates of musicians representing various generations (B. Kaper, H. Wars, Z. Seifert, M. Urbaniak, T. Stańko), the author distinguishes different waves of emigration and individual motivations, as well as more universal reasons for emigration
Existence and stability analysis of spiky solutions for the Gierer-Meinhardt system with large reaction rates
No full textWe study the Gierer-Meinhardt system in one dimension in the limit of large reaction rates. First we construct three types of solutions: (i) an interior spike; (ii) a boundary spike and (iii) two boundary spikes. Second we prove results on their stability. It is found that an interior spike is always unstable; a boundary spike is always stable. The two boundary spike configuration can be either stable or unstable, depending on the parameters. We fully classify the stability in this case. We characterise the destabilizing eigenfunctions in all cases. Numerical simulations are shown which are in full agreement with the analytical results
Echoes from the companion star in Sco X-1
No full textWe present simultaneous X-ray (RXTE) and optical (ULTRACAM) narrow-band ( Bowen blend/He II and nearby continuum) observations of Sco X-1 at 2-10 Hz time resolution. We find that the Bowen/He II emission lags the X-ray light curves with a light traveltime of similar to 11-16 s which is consistent with reprocessing in the companion star. The echo from the donor is detected at orbital phase similar to 0.5 when Sco X-1 is at the top of the flaring branch (FB). Evidence of echoes is also seen at the bottom of the FB but with time-lags of 5-10 s which are consistent with reprocessing in an accretion disc with a radial temperature profile. We discuss the implication of our results for the orbital parameters of Sco X-1
Detailed optical and near-infrared polarimetry, spectroscopy and broad-band photometry of the afterglow of GRB 091018 : polarization evolution
No full textFollow-up observations of large numbers of gamma-ray burst (GRB) afterglows, facilitated by the Swift satellite, have produced a large sample of spectral energy distributions and light curves, from which their basic micro- and macro-physical parameters can in principle be derived. However, a number of phenomena have been observed that defy explanation by simple versions of the standard fireball model, leading to a variety of new models. Polarimetry can be a major independent diagnostic of afterglow physics, probing the magnetic field properties and internal structure of the GRB jets. In this paper we present the first high-quality multi-night polarimetric light curve of a Swift GRB afterglow, aimed at providing a well-calibrated data set of a typical afterglow to serve as a benchmark system for modelling afterglow polarization behaviour. In particular, our data set of the afterglow of GRB 091018 (at redshift z = 0.971) comprises optical linear polarimetry (R band, 0.13-2.3d after burst); circular polarimetry (R band) and near-infrared linear polarimetry (Ks band). We add to that high-quality optical and near-infrared broad-band light curves and spectral energy distributions as well as afterglow spectroscopy. The linear polarization varies between 0 and 3per cent, with both long and short time-scale variability visible. We find an achromatic break in the afterglow light curve, which corresponds to features in the polarimetric curve. We find that the data can be reproduced by jet break models only if an additional polarized component of unknown nature is present in the polarimetric curve. We probe the ordered magnetic field component in the afterglow through our deep circular polarimetry, finding P circ < 0.15per cent (2σ), the deepest limit yet for a GRB afterglow, suggesting ordered fields are weak, if at all present. Our simultaneous R- and Ks-band polarimetry shows that dust-induced polarization in the host galaxy is likely negligible
A polyethylene glycol functionalized hyaluronic acid coating for cardiovascular catheter lubrication
No full textCatheterization is a common medical operation for cardiovascular disease diagnosis and treatment, where low friction is attained through hydrophilic lubricious coatings. But these coatings can cause iatrogenic complications when particles become lose and float freely in the blood stream. Here we present an ultra-thin coating based on polyethylene glycol (PEG) functionalized hyaluronic acid (HA). The mussel-inspired biopolymer hyaluronic acid was first conjugated to dopamine (DN) to get HADN and then poly (ethylene glycol) bis (3-amino-propyl) terminated (PBA) was used to functionalize the HADN with PEG. The reciprocating sliding ball-on-flat ex vivo model based on PU ball and porcine aorta was used to evaluate the lubrication performance and the results suggest coating of HADN with best lubrication enhancement. After 40 min friction test, the surface of aorta remained intact for HADN-PBA coated PU as compared to HADN coating and positive control (sliding against bare PU). The amount of glycocalyx, number of endothelial nuclei and intima surface of aorta for coated PU were similar to negative control (without rubbing). Besides lubrication, the high biocompatibility suggests the coating of HADN-PBA is safe and lubrication benefits to the cardiovascular catheter. (c) 2020 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).</p
UvA-DARE (Digital Academic Repository) Link to publication Citation for published version (APA): VLT SPECTROSCOPY OF GRB 990510 AND GRB 990712 : PROBING THE FAINT AND BRIGHT ENDS OF THE GAMMA-RAY BURST HOST GALAXY POPULATION1
No full textGeneral rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. ABSTRACT We present time-resolved optical spectroscopy of the afterglows of the gamma-ray bursts GRB 990510 and GRB 990712. Through the identiÐcation of several absorption lines in the Ðrst-epoch GRB 990510 spectrum, we determine the redshift for this burst at z º 1.619. No clear emission lines are detected. The strength of the Mg I feature is indicative of a dense environment, most likely the host galaxy of GRB 990510. Although the host is extremely faint the GRB afterglow allows us to probe its inter-(V Z 28), stellar medium andÈin principleÈto measure its metallicity. The optical spectrum of GRB 990712 (whose host galaxy is the brightest of the known GRB hosts at cosmological redshifts) shows clear features both in emission and absorption, at a redshift of z \ 0.4331^0.0004. On the basis of several line emission diagnostic diagrams, we conclude that the host galaxy of GRB 990712 is most likely an H II galaxy. We derive an unreddened [O II] star formation rate of 2.7^0.8 yr~1. Correcting for the M _ measured extinction intrinsic to the host galaxy this value increases to yr~1. width, compared to that of Ðeld galaxies at z ¹ 1, also suggests that the host of GRB 990712 is vigorously forming stars. We employ the oxygen and Hb emission-line intensities to estimate the global oxygen abundance for the host of GRB 990712 : log (O/H) \ [3.7^0.4, which is slightly below the lowest metallicity one Ðnds in nearby spiral galaxies. For both GRBs we study the time evolution of the absorption lines, whose equivalent width might be expected to change with time if the burst resides in a dense compact medium. We Ðnd no evidence for a signiÐcant change in the Mg II width
Conceptual metaphor meets conceptual change
No full textThis paper argues that the metaphorical representation of concepts and the appropriation of language-based construals can be hypothesized as additional sources of conceptual change alongside those previously proposed. Analyses of construals implicit in the lay and scientific use of the noun energy from the perspective of the theory of conceptual metaphor are summarized. The experientially grounded metaphorical construals identified in both uses help conceptualize the shift from the concrete, naïve to the abstract, scientific understanding of energy. The case of the concept of energy motivates the more general hypothesis that an important part of learning a highly abstract (even mathematical) concept is the appropriation of experientially grounded metaphorical construals implicit in scientific discourse. Pedagogical implications of this proposal are discussed. © 2009 S. 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