74,825 research outputs found
The Polarization of Drifting Subpulses
Using new techniques based on the polarimetric fluctuation spectrum, the
fluctuation behaviour of the polarization of individual pulses is examined in
three pulsars that show drifting subpulses, allowing various aspects of the
fluctuations to be quantified for the first time. Of the three pulsars studied,
only PSR B0809+74 shows behaviour completely consistent with the superposition
of orthogonal polarization modes (OPMs), and this only at 328 MHz and in
superposition with an apparently randomly polarized component. The observed
periodic pattern is decomposed into the sum of two orthogonally polarized,
out-of-phase drift patterns, one of which shows a dramatic jump in subpulse
phase near the leading edge of the pulse window. For PSR B0320+39 and PSR
B081813, considerable periodic fluctuations away from OPM orientations are
seen, a condition that also occurs in the trailing half of the pulse in PSR
B0809+74 at 1380 MHz. In some cases the deviation is so strong that the
periodic locus of the polarization vector in the Poincar\'{e} sphere is almost
circular, in contrast to the strictly colinear states of superposed OPMs.
Several possibilities are discussed for the physical origin of these patterns.
The similarity between the subpulse patterns in one of the OPMs of PSR B0809+74
at 328 MHz to that of the total intensity signal at 1380 MHz supports a picture
of superposed, out of phase drift patterns. To explain the full range of
behaviour seen in the three pulsars, it must be possible to produce at least
three arbitrarily polarized superposed patterns. While the data do not suggest
a particular approach for the empirical decomposition of patterns into
non-orthogonally polarized components, the specific, quantitative nature of the
results should provide strong constraints for theoretically driven modelling.Comment: 11 pages, 6 figures (1 colour), accepted for publication in A&A.
Abstract abridge
Is China ‘Crowding Out’ South African Exports of Manufactures?
This article analyses the impact of Chinese competition on South African manufacturing exports to its major markets in Europe, the United States and Sub-Saharan Africa. The article considers five related research questions. First, are China and South Africa competing with each other in export markets, how extensive is such competition and how is this changing over time? Second, to what extent has Chinese competition led to the displacement of South African exports? Third, in which countries have South African exports been most affected? Fourth, which South African export sectors face the greatest threat from Chinese competition? Finally, how does South Africa's experience compare to that of Brazil, another middle-income country and regional power. We find that competition between South Africa and China increased significantly over the past decade, particularly in African markets. All types of manufactured exports lost ground to China, but the impact is strongest in low-technology products. South African exports have nevertheless increased from 2001 so that ‘crowding out’ should be interpreted in relative terms
Development of electrical switchgear for space nuclear electrical systems Quarterly progress report, 4 Dec. 1964 - 4 Mar. 1965
Alternating current circuit breakers and direct current engine contactors for space nuclear electrical system
Time-of-flight anemometer for hot section applications
The design, construction and testing of laser anemometer configurations for Hot Section velocity measurements is considered. Optimizing the laser anemometer system necessarily included the data processing algorithms used. It is felt that the requirements here are too demanding for standard laser anemometer systems
A functional genomic screen in vivo identifies CEACAM5 as a clinically relevant driver of breast cancer metastasis
Mosses of Mt. Trus Madi, Sabah, Malaysia
A species list of mosses collected in Mt. Trus Madi, Sabah, between 10 September and 10 October 1996 is presented. A total of 153 taxa were collected, of which 11 are new to Borneo and five new to Sabah
Inter-dependence of the volume and stress ensembles and equipartition in statistical mechanics of granular systems
We discuss the statistical mechanics of granular matter and derive several
significant results. First, we show that, contrary to common belief, the volume
and stress ensembles are inter-dependent, necessitating the use of both. We use
the combined ensemble to calculate explicitly expectation values of structural
and stress-related quantities for two-dimensional systems. We thence
demonstrate that structural properties may depend on the angoricity tensor and
that stress-based quantities may depend on the compactivity. This calls into
question previous statistical mechanical analyses of static granular systems
and related derivations of expectation values. Second, we establish the
existence of an intriguing equipartition principle - the total volume is shared
equally amongst both structural and stress-related degrees of freedom. Third,
we derive an expression for the compactivity that makes it possible to quantify
it from macroscopic measurements.Comment: 5 pages, including 2 figures, To appear in Phys. Rev. Let
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