293 research outputs found
V-Proportion: a method based on the Voronoi diagram to study spatial relations in neuronal mosaics of the retina
The visual system plays a predominant role in the human perception. Although all components of the eye are important to perceive visual information, the retina is a fundamental part of the visual system. In this work we study the spatial relations between neuronal mosaics in the retina. These relations have shown its importance to investigate possible constraints or connectivities between different spatially colocalized populations of neurons, and to explain how visual information spreads along the layers before being sent to the brain. We introduce the V-Proportion, a method based on the Voronoi diagram to study possible spatial interactions between two neuronal mosaics. Results in simulations as well as in real data demonstrate the effectiveness of this method to detect spatial relations between neurons in different layers
Transient differential reflectivity of ferromagnetic and paramagnetic phases in the bilayered manganite La1.24Sr1.76Mn2O7
Photoinduced effects in a single crystal of bilayered manganites,
La2-2xSr1+2xMn2O7 (x=0.38), were investigated in a wide range of temperatures
by pump-probe measurement at a photon energy of 1.6eV. In a ferromagnetic
metallic state, significant enhancement of positive rise in differential
reflectivity with a slow relaxing time of hundred picoseconds was observed just
below Tc=127K, indicating that the reflectivity change with the slow relaxation
time constant is induced by laser heating. We have also observed an
unconventional fast relaxing component that has a time constant of the order of
ten picoseconds. This fast relaxing component, whose absolute value has an
asymmetric peak at Tc, is presumably due to short-range correlation of
Jahn-Teller distortion.Comment: 13 pages, 4 figures, accepted to Solid State Communication
Active Membrane Fluctuations Studied by Micropipet Aspiration
We present a detailed analysis of the micropipet experiments recently
reported in J-B. Manneville et al., Phys. Rev. Lett. 82, 4356--4359 (1999),
including a derivation of the expected behaviour of the membrane tension as a
function of the areal strain in the case of an active membrane, i.e.,
containing a nonequilibrium noise source. We give a general expression, which
takes into account the effect of active centers both directly on the membrane,
and on the embedding fluid dynamics, keeping track of the coupling between the
density of active centers and the membrane curvature. The data of the
micropipet experiments are well reproduced by the new expressions. In
particular, we show that a natural choice of the parameters quantifying the
strength of the active noise explains both the large amplitude of the observed
effects and its remarkable insensitivity to the active-center density in the
investigated range. [Submitted to Phys Rev E, 22 March 2001]Comment: 14 pages, 5 encapsulated Postscript figure
Cross calibration between Hayabusa2/ONC-T and OSIRIS-REx/MapCam for comparative analyses between asteroids Ryugu and Bennu
Proximity observations of (162173) Ryugu by the telescopic Optical Navigation
Camera onboard Hayabusa2 and (101955) Bennu by MapCam onboard Origins, Spectral
Interpretation, Resource Identification, and Security-Regolith Explorer found
opposite spectral trends of space weathering on these carbonaceous asteroids.
Whether the space weathering trends on these asteroids evolved from the same
starting spectra would place an important constraint for understanding their
relation. However, systematic error between data obtained by the two imagers
needed to be reduced for accurate comparison. To resolve this problem, we cross
calibrated albedo and color data using the Moon as the common standard. We show
that the cross-calibrated reflectance can be obtained by upscaling the
pre-cross-calibrated reflectance of Bennu by 12 +/- 2% at v-band, reducing the
systematic errors down to 2%. The cross-calibrated data show that Bennu is
brighter by 16 +/- 2% at v-band and bluer in spectral slope by 0.19 +/- 0.05
(/um) than Ryugu. The spectra of fresh craters on Ryugu and Bennu before cross
calibration appeared to follow two parallel trend lines with offset, but they
converged to a single trend after cross calibration. Such a
post-cross-calibration perspective raise the possibility that Ryugu and Bennu
evolved from materials with similar visible spectra but evolved in diverging
directions by space weathering. The divergent evolution can be caused by the
difference in space weathering dose/process and/or composition of the starting
material. Thus, comparing the composition of samples returned from Ryugu and
Bennu may change the way we interpret the spectral variation of C-complex
asteroids
AKATSUKI-IR2 reveals unexpected opacity disruption affecting Venus's lower clouds every 9 days
The images of AKATSUKI acquired with the camera
IR2 at 1.74-2.3 µm report the discovery of an
equatorial disruption or “front” in the opacity of the
lower clouds of Venus at 50 km between 30ºN¿30ºS.
This feature appears on the night every 9 terrestrial
days during more than 8 months, and introduces a
dramatic and abrupt increase of the cloud opacity and
reducing the thermal radiance in a factor of about 1:2
from its brightest to the darkest side.Peer ReviewedPostprint (published version
Dietary t10,c12-CLA but not c9,t11 CLA Reduces Adipocyte Size in the Absence of Changes in the Adipose Renin–Angiotensin System in fa/fa Zucker Rats
In obesity, increased activity of the local renin–angiotensin system (RAS) and enlarged adipocytes with altered adipokine production are linked to the development of obesity-related health problems and cardiovascular disease. Mixtures of conjugated linoleic acid (CLA) isomers have been shown to reduce adipocyte size and alter the production of adipokines. The objective of this study was to investigate the effects of feeding individual CLA isomers on adipocyte size and adipokines associated with the local adipose RAS. Male fa/fa Zucker rats received either (a) control, (b) cis(c)9,trans(t)11-CLA, or (c) t10,c12-CLA diet for 8 weeks. The t10,c12-CLA isomer reduced adipocyte size and increased cell number in epididymal adipose tissue. RT-PCR and Western blot analysis revealed that neither CLA isomer altered mRNA or protein levels of angiotensinogen or AngII receptors in adipose tissue. Likewise, levels of the pro-inflammatory cytokines TNF-α and IL-6 or the anti-inflammatory cytokine IL-10 were unchanged in adipose tissue. Similarly, neither CLA isomer had any effect on phosphorylation nor DNA binding of NF-κB. Our results suggest that although the t10,c12-CLA isomer had beneficial effects on reducing adipocyte size in obese rats, this did not translate into changes in the local adipose RAS or associated adipokines
An artificial impact on the asteroid (162173) Ryugu formed a crater in the gravity-dominated regime
The Hayabusa2 spacecraft investigated the small asteroid Ryugu, which has a rubble-pile structure.
We describe an impact experiment on Ryugu using Hayabusa2’s Small Carry-on Impactor. The impact produced an artificial crater with a diameter >10 meters, which has a semicircular shape, an elevated rim, and a central pit. Images of the impact and resulting ejecta were recorded by the Deployable CAMera 3 for >8 minutes, showing the growth of an ejecta curtain (the outer edge of the ejecta) and deposition
of ejecta onto the surface. The ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface. The crater formed in the gravity-dominated regime; in other words, crater growth was limited by gravity not surface strength. We discuss implications for Ryugu’s surface age
Protein Conformational Changes in the Bacteriorhodopsin Photocycle: Comparison of Findings from Electron and X-Ray Crystallographic Analyses
Light-driven conformational changes in the membrane protein bacteriorhodopsin have been studied extensively using X-ray and electron crystallography, resulting in the deposition of >30 sets of coordinates describing structural changes at various stages of proton transport. Using projection difference Fourier maps, we show that coordinates reported by different groups for the same photocycle intermediates vary considerably in the extent and nature of conformational changes. The different structures reported for the same intermediate cannot be reconciled in terms of differing extents of change on a single conformational trajectory. New measurements of image phases obtained by cryo-electron microscopy of the D96G/F171C/F219L triple mutant provide independent validation for the description of the large protein conformational change derived at 3.2 Å resolution by electron crystallography of 2D crystals, but do not support atomic models for light-driven conformational changes derived using X-ray crystallography of 3D crystals. Our findings suggest that independent determination of phase information from 2D crystals can be an important tool for testing the accuracy of atomic models for membrane protein conformational changes
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