343,330 research outputs found
Assessment of mapping exposed ferrous and ferric iron compounds using Skylab-EREP data
The author has identified the following significant results. The S190B color photography is as useful as LANDSAT data for the mapping of color differences in the rocks and soils of the terrain. An S192 ratio of 0.79 - 0.89 and 0.93 - 1.05 micron bands produced an apparently successful delineation of ferrous, ferric, and other materials, in agreement with theory and ratio code studies. From an analysis of S191 data, basalt and dacite were separated on the basis of differences in spectral emissivity in the 8.3 - 12 micron region
Microstructured blood vessel surrogates reveal structural tropism of motile malaria parasites
Plasmodium sporozoites, the highly motile forms of the malaria parasite, are transmitted naturally by mosquitoes and traverse the skin to find, associate with, and enter blood capillaries. Research aimed at understanding how sporozoites select blood vessels is hampered by the lack of a suitable experimental system. Arrays of uniform cylindrical pillars can be used to study small cells moving in controlled environments. Here, an array system displaying a variety of pillars with different diameters and shapes is developed in order to investigate how Plasmodium sporozoites associate to the pillars as blood vessel surrogates. Investigating the association of sporozoites to pillars in arrays displaying pillars of different diameters reveals that the crescent-shaped parasites prefer to associate with and migrate around pillars with a similar curvature. This suggests that after transmission by a mosquito, malaria parasites may use a structural tropism to recognize blood capillaries in the dermis in order to gain access to the blood stream
Deformation-Driven Diffusion and Plastic Flow in Two-Dimensional Amorphous Granular Pillars
We report a combined experimental and simulation study of deformation-induced
diffusion in compacted two-dimensional amorphous granular pillars, in which
thermal fluctuations play negligible role. The pillars, consisting of
bidisperse cylindrical acetal plastic particles standing upright on a
substrate, are deformed uniaxially and quasistatically by a rigid bar moving at
a constant speed. The plastic flow and particle rearrangements in the pillars
are characterized by computing the best-fit affine transformation strain and
non-affine displacement associated with each particle between two stages of
deformation. The non-affine displacement exhibits exponential crossover from
ballistic to diffusive behavior with respect to the cumulative deviatoric
strain, indicating that in athermal granular packings, the cumulative
deviatoric strain plays the role of time in thermal systems and drives
effective particle diffusion. We further study the size-dependent deformation
of the granular pillars by simulation, and find that different-sized pillars
follow self-similar shape evolution during deformation. In addition, the yield
stress of the pillars increases linearly with pillar size. Formation of
transient shear lines in the pillars during deformation becomes more evident as
pillar size increases. The width of these elementary shear bands is about twice
the diameter of a particle, and does not vary with pillar size.Comment: 14 pages, 11 figure
Within the Pillars of Hercules
The Kiona’s hull sliced neatly through the batting waves, her sails pulling forward with the ceaseless breath of the northwestern winds. The boards of the ship hummed beneath Carrice Leon’s feet, interlaced with the rhythmic beating of 170 oars against serene waters. In the distance, white spires were beginning to peak just above the starboard horizon, a shimmering beacon in the endless blue. They were making good time, despite the previous day’s storm. Carrice looked up to find the sun high in the sky. “Starboard side, in-oars!” Her voice boomed across the length of the deck, ringing clear over the wind and waves below. The crew manning the right side of the deck clattered their oars into oarlocks as the port side continued to row in perfect synchrony. Carrice nodded to herself as the soft wood of the helm’s wheel glided smoothly against her hands, nudging the Kiona further starboard. “Oars in,” she commanded; more clattering of oars onto the deck ensued. The ship was running with the wind. Why not show off a little and sail in. [excerpt
Strain superlattices and macroscale suspension of Graphene induced by corrugated substrates
We investigate the organized formation of strain, ripples and suspended
features in macroscopic CVD-prepared graphene sheets transferred onto a
corrugated substrate made of an ordered arrays of silica pillars of variable
geometries. Depending on the aspect ratio and sharpness of the corrugated
array, graphene can conformally coat the surface, partially collapse, or lay,
fakir-like, fully suspended between pillars over tens of micrometers. Upon
increase of pillar density, ripples in collapsed films display a transition
from random oriented pleats emerging from pillars to ripples linking nearest
neighboring pillars organized in domains of given orientation.
Spatially-resolved Raman spectroscopy, atomic force microscopy and electronic
microscopy reveal uniaxial strain domains in the transferred graphene, which
are induced and controlled by the geometry. We propose a simple theoretical
model to explain the transition between suspended and collapsed graphene. For
the arrays with high aspect ratio pillars, graphene membranes stays suspended
over macroscopic distances with minimal interaction with pillars tip apex. It
offers a platform to tailor stress in graphene layers and open perspectives for
electron transport and nanomechanical applications
Surface compositional mapping by spectral ratioing of ERTS-1 MSS data in the Wind River Basin and Range, Wyoming
The author has identified the following significant results. ERTS data collected in August and October 1972 were processed on digital and special purpose analog recognition computers using ratio enhancement and pattern recognition. Ratios of band-averaged laboratory reflectances of some minerals and rock types known to be in the scene compared favorably with ratios derived from the data by ratio normalization procedures. A single ratio display and density slice of the visible channels of ERTS MSS data, Channel 5/Channel 4 (R5,4), separated the Triassic Chugwater formation (redbeds) from other formations present and may have enhanced iron oxide minerals present at the surface in abundance. Comparison of data sets collected over the same area at two different times of the year by digital processing indicated that spectral variation due to environmental factors was reduced by ratio processing
Spitzer Space Telescope observations of the Carina Nebula: The steady march of feedback-driven star formation
We report the first results of imaging the Carina Nebula with Spitzer/IRAC,
providing a catalog of point sources and YSOs based on SED fits. We discuss
several aspects of the extended emission, including dust pillars that result
when a clumpy molecular cloud is shredded by massive star feedback. There are
few "extended green objects" (EGOs) normally taken as signposts of outflow
activity, and none of the HH jets detected optically are seen as EGOs. A
population of "extended red objects" tends to be found around OB stars, some
with clear bow-shocks. These are dusty shocks where stellar winds collide with
flows off nearby clouds. Finally, the relative distributions of O stars and
subclusters of YSOs as compared to dust pillars shows that while some YSOs are
located within pillars, many more stars and YSOs reside just outside pillar
heads. We suggest that pillars are transient phenomena, part of a continuous
outwardly propagating wave of star formation driven by massive star feedback.
As pillars are destroyed, they leave newly formed stars in their wake, which
are then subsumed into the young OB association. Altogether, the current
generation of YSOs shows no strong deviation from a normal IMF. The number of
YSOs suggests a roughly constant star-formation rate over the past 3Myr,
implying that star formation in pillars constitutes an important mechanism to
construct unbound OB associations. Accelerated pillars may give birth to O-type
stars that, after several Myr, could appear to have formed in isolation.Comment: 25 pages, 15 figures, MNRAS accepte
Nano-engineered non-uniform strain in graphene
Recent experiments showed that non-uniform strain can be produced by
depositing graphene over pillars. We employed atomistic calculations to study
the non-uniform strain and the induced pseudo-magnetic field up to 5000 Tesla
in graphene on top of nano-pillars. By decreasing the distance between the
nano-pillars a complex distribution for the pseudo-magnetic field can be
generated. Furthermore, we performed tight-binding calculations of the local
density of states (LDOS) by using the relaxed graphene configuration obtained
from the atomistic calculations. We find that the quasiparticle LDOS are
strongly modified near the pillars, both at low energies showing sub-lattice
polarization, and at high energies showing shifts of the van Hove singularity.
Our study shows that changing the specific pattern of the nano-pillars allows
us to create a desired shape of the pseudo-magnetic field profile while the
LDOS maps provide an input for experimental verifications by scanning tunneling
microscopy.Comment: 5 pages, 2 figure
Seven Pillars of Wisdom
The persistence of financial instability calls into question the adequacy of the current regulatory regime. A critical review of the three pillars at the core of current financial regulation exposes some structural flaws. Four new pillars are proposed and compared with measures proposed to shore up the current financial architecture.
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