3,394 research outputs found
Iridescence in Meat Caused by Surface Gratings
The photonic structure of cut muscle tissues reveals that the well-ordered gratings diffract light, producing iridescent colours. Cut fibrils protruding from the muscle surface create a two-dimensional periodic array, which diffract light at specific wavelengths upon illumination. However, this photonic effect misleads consumers in a negative way to relate the optical phenomenon with the quality of the product. Here we discuss the fundamentals of this optical phenomenon and demonstrate a methodology for quantitatively measuring iridescence caused by diffraction gratings of muscle tissue surface of pork (Sus scrofa domesticus) using reflection spectrophotometry. Iridescence was discussed theoretically as a light phenomenon and spectral measurements were taken from the gratings and monitored in real time during controlled drying. The findings show that the intensity of diffraction diminishes as the surface grating was dried with an air flow at 50 °C for 2 min while the diffracted light wavelength was at 585 ± 9 nm. Our findings indicate that the diffraction may be caused by a blazed surface grating. The implications of the study include providing guidelines to minimise the iridescence by altering the surface microstructure, and in consequence, removing the optical effect
Overestimation in angular path integration precedes Alzheimer's dementia
Path integration (PI) is impaired early in Alzheimer's disease (AD) but reflects multiple sub-processes that may be differentially sensitive to AD. To characterize these sub-processes, we developed a novel generative linear-angular model of PI (GLAMPI) to fit the inbound paths of healthy elderly participants performing triangle completion, a popular PI task, in immersive virtual reality with real movement. The model fits seven parameters reflecting the encoding, calculation, and production errors associated with inaccuracies in PI. We compared these parameters across younger and older participants and patients with mild cognitive impairment (MCI), including those with (MCI+) and without (MCI-) cerebrospinal fluid biomarkers of AD neuropathology. MCI patients showed overestimation of the angular turn in the outbound path and more variable inbound distances and directions compared with healthy elderly. MCI+ were best distinguished from MCI- patients by overestimation of outbound turns and more variable inbound directions. Our results suggest that overestimation of turning underlies the PI errors seen in patients with early AD, indicating specific neural pathways and diagnostic behaviors for further research
Spectroscopy of soft modes and quantum phase transitions in coupled electron bilayers
Strongly-correlated two-dimensional electrons in coupled semiconductor
bilayers display remarkable broken symmetry many-body states under accessible
and controllable experimental conditions. In the cases of continuous quantum
phase transitions soft collective modes drive the transformations that link
distinct ground states of the electron double layers. In this paper we consider
results showing that resonant inelastic light scattering methods detect soft
collective modes of the double layers and probe their evolution with
temperature and magnetic field. The light scattering experiments offer venues
of research of fundamental interactions and continuous quantum phase
transitions in low-dimensional electron liquids.Comment: 10 pages, 7 figure
Topological Properties of Spatial Coherence Function
Topology of the spatial coherence function is considered in details. The
phase singularity (coherence vortices) structures of coherence function are
classified by Hopf index and Brouwer degree in topology. The coherence flux
quantization and the linking of the closed coherence vortices are also studied
from the topological properties of the spatial coherence function.Comment: 9 page
Isolation and characterization of Streptococcus sp. from diseased flounder (Paralichthys olivaceus) in Jeju Island
Streptococcus sp. is gram-positive coccus that causes streptococcal infections in fish due to intensification of aquaculture and caused significant economic losses in fish farm industry. A streptococcal infection occurred from cultured diseased olive flounder (Paralichthys olivaceus) in May, 2005 at a fish farm in Jeju Island, Korea. The diseased flounder exhibited bilateral exophthalmic eyes and rotten gills; water temperature was 16~18℃ when samples were collected. Of the 22 fish samples collected, 3 samples were identified as Lactococcus garvieae and 18 samples were identified as Streptococcus parauberis by culture-based, biochemical test. Serological methods such as slide agglutination, hemolysis and antimicrobial susceptibility test were also used as well as multiplex PCR-based method to simultaneously detect and confirm the pathogens involved in the infection. S. parauberis and L. garvieae have a target region of 700 and 1100 bp., respectively. One fish sample was not identified because of the difference in the different biochemical and serological tests and was negative in PCR assay. In the present study, it showed that S. parauberis was the dominant species that caused streptococcosis in the cultured diseased flounder
Conjugate Hard X-ray Footpoints in the 2003 October 29 X10 Flare: Unshearing Motions, Correlations, and Asymmetries
We present a detailed imaging and spectroscopic study of the conjugate hard
X-ray (HXR) footpoints (FPs) observed with RHESSI in the 2003 October 29 X10
flare. The double FPs first move toward and then away from each other, mainly
parallel and perpendicular to the magnetic neutral line, respectively. The
transition of these two phases of FP unshearing motions coincides with the
direction reversal of the motion of the loop-top (LT) source, and with the
minima of the estimated loop length and LT height. The FPs show temporal
correlations between HXR flux, spectral index, and magnetic field strength. The
HXR flux exponentially correlates with the magnetic field strength, which also
anti-correlates with the spectral index before the second HXR peak's maximum,
suggesting that particle acceleration sensitively depends on the magnetic field
strength and/or reconnection rate. Asymmetries are observed between the FPs: on
average, the eastern FP is 2.2 times brighter in HXR flux and 1.8 times weaker
in magnetic field strength, and moves 2.8 times faster away from the neutral
line than the western FP; the estimated coronal column density to the eastern
FP from the LT source is 1.7 times smaller. The two FPs have marginally
different spectral indexes. The eastern-to-western FP HXR flux ratio and
magnetic field strength ratio are anti-correlated only before the second HXR
peak's maximum. Neither magnetic mirroring nor column density alone can explain
the totality of these observations, but their combination, together with other
transport effects, might provide a full explanation. We have also developed
novel techniques to remove particle contamination from HXR counts and to
estimate effects of pulse pileup in imaging spectroscopy, which can be applied
to other RHESSI flares in similar circumstances.Comment: 22 pages, 14 figures, 4 tables; ApJ 2009, in pres
Episodic X-ray Emission Accompanying the Activation of an Eruptive Prominence: Evidence of Episodic Magnetic Reconnection
We present an X-ray imaging and spectroscopic study of a partially occulted
C7.7 flare on 2003 April 24 observed by RHESSI that accompanied a prominence
eruption observed by TRACE. (1) The activation and rise of the prominence
occurs during the preheating phase of the flare. The initial X-ray emission
appears as a single coronal source at one leg of the prominence and it then
splits into a double source. Such a source splitting happens three times, each
coinciding with an increased X-ray flux and plasma temperature, suggestive of
fast reconnection in a localized current sheet and an enhanced energy release
rate. In the late stage of this phase, the prominence displays a helical
structure. These observations are consistent with the tether-cutting and/or
kink instability model for triggering solar eruptions. (2) The eruption of the
prominence takes place during the flare impulsive phase. Since then, there
appear signatures predicted by the classical CSHKP model of two-ribbon flares
occurring in a vertical current sheet trailing an eruption. These signatures
include an EUV cusp and current-sheet-like feature (or ridge) above it. There
is also X-ray emission along the EUV ridge both below and above the cusp, which
in both regions appears closer to the cusp at higher energies in the thermal
regime. This trend is reversed in the nonthermal regime. (3) Spectral analysis
indicates thermal X-rays from all sources throughout the flare, while during
the impulsive phase there is additional nonthermal emission which primarily
comes from the coronal source below the cusp. This source also has a lower
temperature, a higher emission measure, and a much harder nonthermal spectrum
than the upper sources.Comment: 8 pages, 5 figures, submitted to Ap
Topology of Knotted Optical Vortices
Optical vortices as topological objects exist ubiquitously in nature. In this
paper, by making use of the -mapping topological current theory, we
investigate the topology in the closed and knotted optical vortices. The
topological inner structure of the optical vortices are obtained, and the
linking of the knotted optical vortices is also given.Comment: 11 pages, no figures, accepted by Commun. Theor. Phys. (Beijing, P.
R. China
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