16,257 research outputs found
Why teach unix?
This paper examines computing academics' conceptions of the Unix operating system, and the purpose of teaching Unix. Interview transcripts from nine academics were analysed phenomenographically. A small number of qualitatively different conceptions of Unix were identified, within two broad categories. The first broad category manifested a technical approach to Unix. Within this broad category, the conceptions of Unix were, from the least to most sophisticated ! (1) Unix as a set of unrelated commands; (2) Unix as a command line interface superior to GUIs; and (3) Unix as a problem solving tool. The second broad category was a non technical conception of Unix, in which Unix was seen as a resource that is cheap, secure and robust. With regard to teaching Unix, two broad categories of reasons were identified ! practical and pedagogical. These results for teachers are broadly consistent with an earlier phenomenographic study of student conceptions of Unix. © 2007, Australian Computer Society, Inc
Large spin relaxation rates in trapped submerged-shell atoms
Spin relaxation due to atom-atom collisions is measured for magnetically
trapped erbium and thulium atoms at a temperature near 500 mK. The rate
constants for Er-Er and Tm-Tm collisions are 3.0 times 10^-10 cm^3 s^-1 and 1.1
times 10^-10 cm^3 s^-1, respectively, 2-3 orders of magnitude larger than those
observed for highly magnetic S-state atoms. This is strong evidence for an
additional, dominant, spin relaxation mechanism, electrostatic anisotropy, in
collisions between these "submerged-shell" L > 0 atoms. These large spin
relaxation rates imply that evaporative cooling of these atoms in a magnetic
trap will be highly inefficient.Comment: 10 pages, 3 figure
Valence and magnetic instabilities in Sm compounds at high pressures
We report on the study of the response to high pressures of the electronic
and magnetic properties of several Sm-based compounds, which span at ambient
pressure the whole range of stable charge states between the divalent and the
trivalent. Our nuclear forward scattering of synchrotron radiation and specific
heat investigations show that in both golden SmS and SmB6 the pressure-induced
insulator to metal transitions (at 2 and about 4-7 GPa, respectively) are
associated with the onset of long-range magnetic order, stable up to at least
19 and 26 GPa, respectively. This long-range magnetic order, which is
characteristic of Sm(3+), appears already for a Sm valence near 2.7. Contrary
to these compounds, metallic Sm, which is trivalent at ambient pressure,
undergoes a series of pressure-induced structural phase transitions which are
associated with a progressive decrease of the ordered 4f moment.Comment: 15 pages (including 7 figures) submitted to J. Phys.: Condens. Matte
Import, export, and recycling of dissolved nutrients in the Ogeechee River estuary (Georgia, USA)
We constructed an empirical mass balance model of nutrient fluxes in the Ogeechee River estuary (Georgia, USA) from eight surveys of seasonal estuarine nutrient concentrations during 2015 and 2016. The model results indicated a net removal of dissolved phosphorus and a net production of dissolved nitrogen (N) within the estuary over an annual cycle. During summer and autumn low flow periods, much of the dissolved N discharged to the ocean seems to be recycled into the estuary in the form of phytoplankton biomass. As a result, the outwelled N is not new nitrogen fueling coastal production but is nitrogen trapped within a recycling loop across the ocean–estuarine boundary. Higher flows in the fall and winter lead to direct discharge of nutrients with minimal recycling. A balanced N budget for the Ogeechee River estuary requires that estuarine N-fixation must exceed burial and denitrification losses within the estuary
A Simple But Highly Selective Electrochemical Sensor for Dopamine
A modified platinum electrode was fabricated by the electropolymerization of pyrrole using a sodium p-sulphonatocalix[6]arene as the supporting electrolyte. The
modified electrode acts as a reasonably sensitive electrochemical sensor for dopamine giving a linear calibration curve in the range 0.075 – 1.00 mM dopamine. The sensor shows no ability to sense the common interferent ascorbic acid, therefore the concentration
for dopamine can be directly sensed in a large excess of ascorbic acid with no need to make adjustments for the signal for ascorbic acid. Investigations are included to study the mode of sensing of the modified electrode
The Coulomb Sum and Proton-Proton Correlations in Few-Body Nuclei
In simple models of the nuclear charge operator, measurements of the Coulomb
sum and the charge form factor of a nucleus directly determine the
proton-proton correlations. We examine experimental results obtained for
few-body nuclei at Bates and Saclay using models of the charge operator that
include both one- and two-body terms. Previous analyses using one-body terms
only have failed to reproduce experimental results. However, we find that the
same operators which have been used to successfully describe the charge form
factors also produce substantial agreement with measurements of the Coulomb
sum.Comment: 11 pages, Revtex version 3.0 with 3 Postscript figures appended, ANL
preprint PHY-7473-TH-9
Influence of low-level Pr substitution on the superconducting properties of YBa2Cu3O7-delta single crystals
We report on measurements on Y1-xPrxBa2Cu3O7-delta single crystals, with x
varying from 0 to 2.4%. The upper and the lower critical fields, Hc2 and Hc1,
the Ginzburg-Landau parameter and the critical current density, Jc(B), were
determined from magnetization measurements and the effective media approach
scaling method. We present the influence of Pr substitution on the pinning
force density as well as on the trapped field profiles analyzed by Hall probe
scanning.Comment: 4 pages, 5 figures, accepted for publication in J. Phys. Conf. Se
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