28,084 research outputs found
Method and device for detecting voids in low density material Patent
Method and photodetector device for locating abnormal voids in low density material
A lightweight, high output soil sampler
Sampler is useful on or under earth's surface or on sea bottom. Larger sample amount is obtained relative to sampler size and weight and limited particle size sample material is continuously delivered. Silicone rubber linear in transport tube nearly eliminates grinding or particulate processing during sampling, and reduces required torque
Lunar analogs of fluvial landscapes - Possible implications, 1 March 1968 - 1 February 1970
Geomorphic approach to possibility of fluid erosion on moo
Mineral fabrication and golgi apparatus activity in the mouse calvarium
There is diverse opinion about the mechanism of bone mineralization with only intermittent reports of any direct organellar role played by the golgi apparatus (juxtanuclear body). Light and laser confocal microscopy was combined with electron microscopy and elemental EDX (energy dispersive X-ray microanalysis) in comparing “young” osteocytes in situ in fresh and “slam” frozen developing mouse calvarium, with similar cells (MC3T3-E1) maintained in vitro. The distribution of “nascent” electron dense mineral was examined histochemically (von Kossa, GBHA), including tetracycline (TC) staining as a fluorescent complex with bone salt, while golgi body activity was demonstrated by transfection with a specific green fluorescent construct (GFP/mannosidase II). In tissue culture golgi body activity and mineralization were both blocked by brefeldin A (an established golgi inhibitor) and restored by forskolin, enabling an association with mineral fabrication to be quantified as changing fluorescence intensity (AU) of GFP or TC markers. Results from osteocytes in situ supported previous descriptions of intracellular electron dense objects (microspheres and nanospheres) in a juxtanuclear pattern, containing Ca, P and transitory Si, in a spectrum recapitulated in the calcifying culture after 10 days, when GFP fluorophore surged from 71.7 ± 1.4SD to 133.7 ± 2.7SD AU by 14 days (p < 0.0001). At this stage TC fluorophore mean intensity was 23.8 ± 3.7SD AU (14 days) rising to 45.0 ± 5.1SD AU by 17 days, compared to its stationary 21.7 ± 3.6SD when treated 3 days previously with BFA golgi inhibitor (p < 0.0001), until forskolin reversal. It was concluded from the changing juxtanuclear morphology, Si mineralization mediation and the variably controlled activity versus stasis that the inorganic phase of bone is a complex golgi-directed fabrication with implications for bone matrix biology and evolution
Preliminary design study - Oxidizer tank helium pressure regulator, Flox-Atlas, airborne Final report
Oxidizer tank helium pressure regulator compatible with fluorine-liquid oxyge
Non-local fluctuation correlations in active gels
Many active materials and biological systems are driven far from equilibrium
by embedded agents that spontaneously generate forces and distort the
surrounding material. Probing and characterizing these athermal fluctuations is
essential for understanding the properties and behaviors of such systems. Here
we present a mathematical procedure to estimate the local action of
force-generating agents from the observed fluctuating displacement fields. The
active agents are modeled as oriented force dipoles or isotropic compression
foci, and the matrix on which they act is assumed to be either a compressible
elastic continuum or a coupled network-solvent system. Correlations at a single
point and between points separated by an arbitrary distance are obtained,
giving a total of three independent fluctuation modes that can be tested with
microrheology experiments. Since oriented dipoles and isotropic compression
foci give different contributions to these fluctuation modes, ratiometric
analysis allows us characterize the force generators. We also predict and
experimentally find a high-frequency ballistic regime, arising from individual
force generating events in the form of the slow build-up of stress followed by
rapid but finite decay. Finally, we provide a quantitative statistical model to
estimate the mean filament tension from these athermal fluctuations, which
leads to stiffening of active networks.Comment: 12 pages, 7 figures; some clarifications and ammended figure
notation
Simplification of the tug-of-war model for cellular transport in cells
The transport of organelles and vesicles in living cells can be well
described by a kinetic tug-of-war model advanced by M\"uller, Klumpp and
Lipowsky. In which, the cargo is attached by two motor species, kinesin and
dynein, and the direction of motion is determined by the number of motors which
bind to the track. In recent work [Phys. Rev. E 79, 061918 (2009)], this model
was studied by mean field theory, and it was found that, usually the tug-of-war
model has one, two, or three distinct stable stationary points. However, the
results there are mostly obtained by numerical calculations, since it is hard
to do detailed theoretical studies to a two-dimensional nonlinear system. In
this paper, we will carry out further detailed analysis about this model, and
try to find more properties theoretically. Firstly, the tug-of-war model is
simplified to a one-dimensional equation. Then we claim that the stationary
points of the tug-of-war model correspond to the roots of the simplified
equation, and the stable stationary points correspond to the roots with
positive derivative. Bifurcation occurs at the corresponding parameters, under
which the simplified one-dimensional equation exists root with zero derivative.
Using the simplified equation, not only more properties of the tug-of-war model
can be obtained analytically, the related numerical calculations will become
more accurate and more efficient. This simplification will be helpful to future
studies of the tug-of-war model
Sapping Features of the Colorado Plateau: a Comparative Planetary Geology Field Guide
This book is an attempt to determine geomorphic criteria to be used to distinguish between channels formed predominantly by sapping and seepage erosion and those formed principally by surface runoff processes. The geologic nature of the Colorado Plateau has resulted in geomorphic features that show similarities to some areas on Mars, especially certain valley networks within thick sandstone formations. Where spring sapping is an effective process, the valleys that develop are unique in terms of their morphology and network pattern
Comprehensive Observations of a Solar Minimum CME with STEREO
We perform the first kinematic analysis of a CME observed by both imaging and
in situ instruments on board STEREO, namely the SECCHI, PLASTIC, and IMPACT
experiments. Launched on 2008 February 4, the CME is tracked continuously from
initiation to 1 AU using the SECCHI imagers on both STEREO spacecraft, and is
then detected by the PLASTIC and IMPACT particle and field detectors on board
STEREO-B. The CME is also detected in situ by ACE and SOHO/CELIAS at Earth's L1
Lagrangian point. The CME hits STEREO-B, ACE, and SOHO on 2008 February 7, but
misses STEREO-A entirely. This event provides a good example of just how
different the same event can look when viewed from different perspectives. We
also demonstrate many ways in which the comprehensive and continuous coverage
of this CME by STEREO improves confidence in our assessment of its kinematic
behavior, with potential ramifications for space weather forecasting. The
observations provide several lines of evidence in favor of the observable part
of the CME being narrow in angular extent, a determination crucial for deciding
how best to convert observed CME elongation angles from Sun-center to actual
Sun-center distances.Comment: 27 pages, 10 figures, AASTEX v5.2, accepted by Ap
Separatrix Reconnections in Chaotic Regimes
In this paper we extend the concept of separatrix reconnection into chaotic
regimes. We show that even under chaotic conditions one can still understand
abrupt jumps of diffusive-like processes in the relevant phase-space in terms
of relatively smooth realignments of stable and unstable manifolds of unstable
fixed points.Comment: 4 pages, 5 figures, submitted do Phys. Rev. E (1998
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