4,398 research outputs found
Chaotic and pseudochaotic attractors of perturbed fractional oscillator
We consider a nonlinear oscillator with fractional derivative of the order
alpha. Perturbed by a periodic force, the system exhibits chaotic motion called
fractional chaotic attractor (FCA). The FCA is compared to the ``regular''
chaotic attractor. The properties of the FCA are discussed and the
``pseudochaotic'' case is demonstrated.Comment: 20 pages, 7 figure
B-T phase diagram of CoCr2O4 in magnetic fields up to 14 T
We have measured the magnetization and specific heat of multiferroic CoCr2O4
in magnetic fields up to 14 T. The high-field magnetization measurements
indicate a new phase transition at T* = 5 - 6 K. The phase between T* and the
lock-in transition at 15 K is characterized by magnetic irreversibility. At
higher magnetic fields, the irreversibility increases. Specific-heat
measurements confirm the transition at T*, and also show irreversible behavior.
We construct a field-temperature phase diagram of CoCr2O4.Comment: 4 page
On-Orbit Performance of the Helioseismic and Magnetic Imager Instrument onboard the Solar Dynamics Observatory
The Helioseismic and Magnetic Imager (HMI) instrument is a major component of
NASA's Solar Dynamics Observatory (SDO) spacecraft. Since beginning normal
science operations on 1 May 2010, HMI has operated with remarkable continuity,
e.g. during the more than five years of the SDO prime mission that ended 30
September 2015, HMI collected 98.4% of all possible 45-second velocity maps;
minimizing gaps in these full-disk Dopplergrams is crucial for helioseismology.
HMI velocity, intensity, and magnetic-field measurements are used in numerous
investigations, so understanding the quality of the data is important. We
describe the calibration measurements used to track HMI performance and detail
trends in important instrument parameters during the mission. Regular
calibration sequences provide information used to improve and update the HMI
data calibration. The set-point temperature of the instrument front window and
optical bench is adjusted regularly to maintain instrument focus, and changes
in the temperature-control scheme have been made to improve stability in the
observable quantities. The exposure time has been changed to compensate for a
15% decrease in instrument throughput. Measurements of the performance of the
shutter and tuning mechanisms show that they are aging as expected and continue
to perform according to specification. Parameters of the tunable-optical-filter
elements are regularly adjusted to account for drifts in the central
wavelength. Frequent measurements of changing CCD-camera characteristics, such
as gain and flat field, are used to calibrate the observations. Infrequent
expected events, such as eclipses, transits, and spacecraft off-points,
interrupt regular instrument operations and provide the opportunity to perform
additional calibration. Onboard instrument anomalies are rare and seem to occur
quite uniformly in time. The instrument continues to perform very well.Comment: 50 pages, 18 figures, 20 table
Relationship between Tibial conformation, cage size and advancement achieved in TTA procedure
Previous studies have suggested that there is a theoretical discrepancy between the cage size and the resultant tibial tuberosity advancement, with the cage size consistently providing less tibial tuberosity advancement than predicted. The purpose of this study was to test and quantify this in clinical cases. The hypothesis was that the advancement of the tibial tuberosity as measured by the widening of the proximal tibia at the tibial tuberosity level after a standard TTA, will be less than the cage sized used, with no particular cage size providing a relative smaller or higher under-advancement, and that the conformation of the proximal tibia will have an influence on the amount of advancement achieved
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Assessing the effect of reducing agents on the selective catalytic reduction of NO<inf>x</inf> over Ag/Al<inf>2</inf>O<inf>3</inf> catalysts
The selective catalytic reduction (SCR) of NOx in the presence of different reducing agents over Ag/Al2O3 prepared by wet impregnation was investigated by probing catalyst activity and using NMR relaxation time analysis.We gratefully acknowledge funding for this work from the EPSRC CASTech grant (EP/G012156/1). Carmine D’Agostino would like to acknowledge Wolfson College, Cambridge, for supporting his research activities. The authors would also like to thank Dr Jonathan Mitchell for useful discussions.This is the final version of the article. It first appeared from RSC via http://dx.doi.org/10.1039/C5CY01508
Alkaloid quantities in endophyte-infected tall fescue are affected by the plant-fungus combination and environment
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An unusual presentation of sclerosing mesenteritis mimicking inflammatory bowel disease in a teenager
Quantitative elemental bio-imaging of Mn, Fe, Cu and Zn in 6-hydroxydopamine induced Parkinsonism mouse models
This study demonstrates the application of quantitative elemental bio-imaging for the determination of the distribution Cu, Mn, Fe and Zn in Parkinsonism mouse model brains. Elevated concentrations of these metals within the substantia nigra (SN) are suspected to play a role on the development of Parkinson's disease. Elemental bio-imaging employs laser ablation inductively coupled mass spectrometry (LA-ICP-MS) to construct images of trace element distribution. Quantitative data was produced by ablating the standard tissue sections and recording the mean signal intensity calibrated against multi level matrix matched tissue standards. The concentrations of Fe within the substantia nigra of the lesioned animals increased significantly when compared against control animals. Furthermore, the data was compared against solution nebulisation ICP-MS in which the whole substantia nigra was excised. The trends were the same for both methods; however the elemental bio-imaging method returned significantly higher concentrations. This was caused by dilution from inclusion of surrounding tissue of the SN during the excision procedure. © The Royal Society of Chemistry 2009
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