7,658 research outputs found
Flare magnetic reconnection and relativistic particles in the 2003 October 28 event
An X17.2 solar flare occurred on 2003 October 28, accompanied by
multi-wavelength emissions and a high flux of relativistic particles observed
at 1AU. We present the analytic results of the TRACE, SOHO, RHESSI, ACE, GOES,
hard X-ray (INTEGRAL satellite), radio (Onderejov radio telescope), and neutron
monitor data. It is found that the inferred magnetic reconnection electric
field correlates well with the hard X-ray, gamma-ray, and neutron emission at
the Sun. Thus the flare's magnetic reconnection probably makes a crucial
contribution to the prompt relativistic particles, which could be detected at 1
AU. Since the neutrons were emitted a few minutes before the injection of
protons and electrons, we propose a magnetic-field evolution configuration to
explain this delay. We do not exclude the effect of CME-driven shock, which
probably plays an important role in the delayed gradual phase of solar
energetic particles.Comment: 5 pages, 7 figures, accepted by A&
Quantum diffusion on a cyclic one dimensional lattice
The quantum diffusion of a particle in an initially localized state on a
cyclic lattice with N sites is studied. Diffusion and reconstruction time are
calculated. Strong differences are found for even or odd number of sites and
the limit N->infinit is studied. The predictions of the model could be tested
with micro - and nanotechnology devices.Comment: 17 pages, 5 figure
Vibration effects on heat transfer in cryogenic systems Quarterly progress report no. 1, Jun. 1 - Aug. 31, 1966
Vibration effects on natural convection and fluid transport properties in cryogenic system
Investigating the driving mechanisms of coronal mass ejections
The objective of this investigation was to first examine the kinematics of
coronal mass ejections (CMEs) using EUV and coronagraph images, and then to
make a comparison with theoretical models in the hope to identify the driving
mechanisms of the CMEs. We have studied two CMEs which occurred on 2006 Dec. 17
(CME06) and 2007 Dec. 31 (CME07). The models studied in this work were
catastrophe, breakout, and toroidal instability models. We found that after the
eruption, the accelerations of both events exhibited a drop before increasing
again. Our comparisons with the theories suggested that CME06 can be best
described by a hybrid of the catastrophe and breakout models while CME07 is
most consistent with the breakout model.Comment: 9 pages 7 figure
Dynamical Evolution of Globular Cluster Systems formed in Galaxy Mergers: Deep HST/ACS Imaging of Old and Intermediate-Age Globular Clusters in NGC 3610
(ABRIDGED) The ACS camera on board the Hubble Space Telescope has been used
to obtain deep images of the giant elliptical galaxy NGC 3610, a
well-established dissipative galaxy merger remnant. These observations
supersede previous WFPC2 images which revealed the presence of a population of
metal-rich globular clusters (GCs) of intermediate age (~1.5-4 Gyr). We detect
a total of 580 GC candidates, 46% more than from the previous WFPC2 images. The
new photometry strengthens the significance of the previously found bimodality
of the color distribution of GCs. Peak colors in V-I are 0.93 +/-0.01 and 1.09
+/- 0.01 for the blue and red subpopulations, respectively. The luminosity
function (LF) of the inner 50% of the metal-rich (`red') population of GCs
differs markedly from that of the outer 50%. In particular, the LF of the inner
50% of the red GCs shows a flattening consistent with a turnover that is about
1.0 mag fainter than the turnover of the blue GC LF. This is consistent with
predictions of recent models of GC disruption for the age range mentioned above
and for metallicities that are consistent with the peak color of the red GCs as
predicted by population synthesis models. We determine the specific frequency
of GCs in NGC 3610 and find a present-day value of S_N = 1.4 +/- 0.6. We
estimate that this value will increase to S_N = 3.8 +/- 1.7 at an age of 10
Gyr, which is consistent with typical S_N values for `normal' ellipticals. Our
findings constitute further evidence in support of the notion that metal-rich
GC populations formed during major mergers involving gas-rich galaxies can
evolve dynamically (through disruption processes) into the red, metal-rich GC
populations that are ubiquitous in `normal' giant ellipticals.Comment: 15 pages, 14 figures, 4 tables. Accepted for publication in The
Astronomical Journal. Figure 6 somewhat degraded to adhere to astro-ph rule
Viral load and antibody boosting following herpes zoster diagnosis
BACKGROUND: Acute varicella zoster virus (VZV) replication in shingles is accompanied by VZV antibody boosting. It is unclear whether persisting virus shedding affects antibody levels. OBJECTIVES: To investigate the relationship between VZV viral load and antibody titres in shingles patients during six months following diagnosis and assess whether VZV antibody titre could discriminate patients with recent shingles from healthy population controls. STUDY DESIGN: A prospective study of 63 patients with active zoster. Blood samples were collected at baseline, one, three and six months to measure VZV DNA and IgG antibody titre. We compared VZV antibody titres of zoster patients and 441 controls. RESULTS: In acute zoster, viral load was highest at baseline and declined gradually over the following six months. Mean antibody titres rose fourfold, peaking at one month and remaining above baseline levels throughout the study. Antibody levels at one, three and six months after zoster were moderately correlated with baseline but not subsequent viral load. Regarding use of antibody titres to identify recent shingles, to achieve 80% sensitivity, specificity would be 23.4%, 67.7%, 64.8% and 52.6%, at baseline, visit 2, 3 and 4 respectively, whilst to achieve 80% specificity, sensitivity would be 28.3%, 66.1%, 52.6%, 38.6%, at baseline, visit 2, 3 and 4 respectively. CONCLUSIONS: Clinical VZV reactivation boosted VZV antibody levels and the level of boosting was dependent upon baseline viral replication. While antibody titres could discriminate patients with shingles 1-6 months earlier from blood donor controls, there was a large trade-off between sensitivity and specificity
Preliminary archaeoentomological analyses of permafrost-preserved cultural layers from the pre-contact Yup’ik Eskimo site of Nunalleq, Alaska : implications, potential and methodological considerations
Acknowledgements Site excavation and samples collection were conducted by archaeologists from the University of Aberdeen, with the help of archaeologists and student excavators from the University of Aberdeen University of Alaska Fairbanks and Bryn Mawr College, Kuskokwim Campus, College of Rural Alaska and residents of Quinhagak and Mekoryuk. This study is funded through AHRC grant to the project ‘Understanding Cultural Resilience and Climate Change on the Bering Sea through Yup’ik Ecological Knowledge, Lifeways, Learning and Archaeology’ to Rick Knecht, Kate Britton and Charlotta Hillderal (University of Aberdeen; AH/K006029/1). Thanks are due to Qanirtuuq Inc. and Quinhagak, Alaska for sampling permissions and to entomologists working at the CNC in Ottawa for allowing access to reference collections of beetles, lice and fleas. Yves Bousquet, Ales Smetana and Anthony E. Davies are specially acknowledged for their help with the identification of coleopteran specimens. Finally, we would also like to thank Scott Elias for useful comments on the original manuscript.Peer reviewedPublisher PD
Measuring the Non-Separability of Optical Fields
Across various areas in the optical world, there has been a growing interest in exploiting the properties of non-separable optical fields. A class of non-separable fields, known as vector modes, exhibit a coupling between the spatial and polarisation degrees of freedom that is akin of entanglement in quantum mechanics. These vector modes, however, are typically characterized using qualitative measurements which are inadequate in determining to what extent an optical field is non-separable. Here, we present tools to characterize the degree of non-separability of an arbitrary optical field, exploiting the similarities between vector modes and quantum entangled states. As an example, we use vector modes carrying orbital angular momentum to demonstrate the effectiveness of our scheme, and note that the approach can be generalized to vector modes as a whole
Structural and magnetic properties of E-Fe_{1-x}Co_xSi thin films deposited via pulsed laser deposition
We report pulsed laser deposition synthesis and characterization of
polycrystalline Fe1-xCox Si thin films on Si (111). X-ray diffraction,
transmission electron, and atomic force microscopies reveal films to be dense,
very smooth, and single phase with a cubic B20 crystal structure.
Ferromagnetism with significant magnetic hysteresis is found for all films
including nominally pure FeSi films in contrast to the very weak paramagnetism
of bulk FeSi. For Fe1-xCoxSi this signifies a change from helimagnetism in
bulk, to ferromagnetism in thin films. These ferromagnetic thin films are
promising as a magnetic-silicide/silicon system for polarized current
production, manipulation, and detection.Comment: 12 pages, 4 figures accepted in the Applied Physics Letter
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