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Dorsal root ganglion neurons maintained in a 3D culture model exhibit similar electrophysiological properties to fresh explants
Tissue engineered culture models provide a powerful tool for neuroscience research1. They overcome limitations associated with monolayer cultures of neurons and glia by maintaining cells in a more realistic 3D spatial arrangement, and permit continuous monitoring and control of variables that cannot be achieved in animal models. Here we report the development of a system for recording electrophysiological behaviour in neurons in 3D culture
Aerosol particle molecular spectroscopy
The molecular spectroscopy of a solution particle by structure resonance modulation spectroscopy is discussed [S. Arnold and A. B. Pluchino, "Infrared Spectrum of a Single Aerosol Particle by Photothermal Modulation of Structure Resonances," Appl. Opt. 21, 4194 (1982); S. Arnold et al., "Molecular Spectroscopy of a Single Aerosol Particle," Opt. Lett. 9, 4 (1984)]. Analytical equations are derived for time dependence of the particle radius as it interacts with a low intensity IR source (<20 mW/cm^2). This formalism is found to be in good agreement with pulsed experiments. Working equations for the spectroscopy are derived for both constant and periodic IR excitation
Investigating the Effects of Finite Resolution on Observed Transverse Jet Profiles
Both the emission properties and evolution of Active Galactic Nuclei (AGN)
radio jets are dependent on the magnetic fields that thread them. Faraday
Rotation gradients are a very important way of investigating these magnetic
fields, and can provide information on the orientation and structure of the
magnetic field in the immediate vicinity of the jet; for example, a toroidal or
helical field component should give rise to a systematic gradient in the
observed Faraday rotation across the jet, as well as characteristic intensity
and polarization profiles. However, real observed radio images have finite
resolution, usually expressed via convolution with a Gaussian beam whose size
corresponds to the central lobe of the point source response function. This
will tend to blur transverse structure in the jet profile, raising the question
of how well resolved a jet must be in the transverse direction in order to
reliably detect transverse structure associated with a helical jet magnetic
field. We present results of simulated intensity, polarization and Faraday
rotation images designed to directly and empirically investigate the effect of
finite resolution on observed transverse jet structures
Development of a fiber optic high temperature strain sensor
From 1 Apr. 1991 to 31 Aug. 1992, the Georgia Tech Research Institute conducted a research program to develop a high temperature fiber optic strain sensor as part of a measurement program for the space shuttle booster rocket motor. The major objectives of this program were divided into four tasks. Under Task 1, the literature on high-temperature fiber optic strain sensors was reviewed. Task 2 addressed the design and fabrication of the strain sensor. Tests and calibration were conducted under Task 3, and Task 4 was to generate recommendations for a follow-on study of a distributed strain sensor. Task 4 was submitted to NASA as a separate proposal
Dynamics of coreless vortices and rotation-induced dissipation peak in superfluid films on rotating porous substrates
We analyze dynamics of 3D coreless vortices in superfluid films covering
porous substrates. The 3D vortex dynamics is derived from the 2D dynamics of
the film. The motion of a 3D vortex is a sequence of jumps between neighboring
substrate cells, which can be described, nevertheless, in terms of
quasi-continuous motion with average vortex velocity. The vortex velocity is
derived from the dissociation rate of vortex-antivortex pairs in a 2D film,
which was developed in the past on the basis of the Kosterlitz-Thouless theory.
The theory explains the rotation-induced dissipation peak in torsion-oscillator
experiments on He films on rotating porous substrates and can be used in
the analysis of other phenomena related to vortex motion in films on porous
substrates.Comment: 8 pages, 3 figures submitted to Phys. Rev.
A two-compartment mechanochemical model of the roles of\ud transforming growth factor Ī² and tissue tension in dermal wound healing
The repair of dermal tissue is a complex process of interconnected phenomena, where cellular, chemical and mechanical aspects all play a role, both in an autocrine and in a paracrine fashion. Recent experimental results have shown that transforming growth factorāĪ² (TGFĪ²) and tissue mechanics play roles in regulating cell proliferation, differentiation and the production of extracellular materials. We have developed a 1D mathematical model that considers the interaction between the cellular, chemical and mechanical phenomena, allowing the combination of TGFĪ² and tissue stress to inform the activation of fibroblasts to myofibroblasts. Additionally, our model incorporates the observed feature of residual stress by considering the changing zero-stress state in the formulation for effective strain. Using this model, we predict that the continued presence of TGFĪ² in dermal wounds will produce contractures due to the persistence of myofibroblasts; in contrast, early elimination of TGFĪ² significantly reduces the myofibroblast numbers resulting in an increase in wound size. Similar results were obtained by varying the rate at which fibroblasts differentiate to myofibroblasts and by changing the myofibroblast apoptotic rate. Taken together, the implication is that elevated levels of myofibroblasts is the key factor behind wounds healing with excessive contraction, suggesting that clinical strategies which aim to reduce the myofibroblast density may reduce the appearance of contractures
A fibrocontractive mechanochemical model of dermal wound\ud closure incorporating realistic growth factor kinetics
Fibroblasts and their activated phenotype, myofibroblasts, are the primary cell types involved in the contraction associated with dermal wound healing. Recent experimental evidence indicates that the transformation from fibroblasts to myofibroblasts involves two distinct processes: the cells are stimulated to change phenotype by the combined actions of transforming growth factor Ī² (TGFĪ²) and mechanical tension. This observation indicates a need for a detailed exploration of the effect of the strong interactions between the mechanical changes and growth factors in dermal wound healing. We review the experimental findings in detail and develop a model of dermal wound healing that incorporates these phenomena. Our model includes the interactions between TGFĪ² and collagenase, providing a more biologically realistic form for the growth factor kinetics than those included in previous mechanochemical descriptions. A comparison is made between the model predictions and experimental data on human dermal wound healing and all the essential features are well matched
On the magnetospheric ULF wave counterpart of substorm onset
One nearāubiquitous signature of substorms observed on the ground is the azimuthal structuring of the onset auroral arc in the minutes prior to onset. Termed auroral beads, these optical signatures correspond to concurrent exponential increases in ground ultralow frequency (ULF) wave power and are likely the result of a plasma instability in the magnetosphere. Here, we present a case study showing the development of auroral beads from a Time History of Events and Macroscale Interactions during Substorms (THEMIS) allāsky camera with near simultaneous exponential increases in auroral brightness, ionospheric and conjugate magnetotail ULF wave power, evidencing their intrinsic link. We further present a survey of magnetic field fluctuations in the magnetotail around substorm onset. We find remarkably similar superposed epoch analyses of ULF power around substorm onset from space and conjugate ionospheric observations. Examining periods of exponential wave growth, we find the groundā and spaceābased observations to be consistent, with average growth rates of ā¼0.01 sā1, lasting for ā¼4 min. Crossācorrelation suggests that the spaceābased observations lead those on the ground by approximately 1ā1.5 min. Meanwhile, spacecraft located premidnight and ā¼10 RE downtail are more likely to observe enhanced wave power. These combined observations lead us to conclude that there is a magnetospheric counterpart of auroral beads and exponentially increasing ground ULF wave power. This is likely the result of the linear phase of a magnetospheric instability, active in the magnetotail for several minutes prior to auroral breakup
Murphy et al. Reply to the Comment by Kopeikin on "Gravitomagnetic Influence on Gyroscopes and on the Lunar Orbit"
Lunar laser ranging analysis, as regularly performed in the solar system
barycentric frame, requires the presence of the gravitomagnetic term in the
equation of motion at the strength predicted by general relativity. The same
term is responsible for the Lense Thirring effect. Any attempt to modify the
strength of the gravitomagnetic interaction would have to do so in a way that
does not destroy the fit to lunar ranging data and other observations.Comment: 1 page; accepted for publication in Physcal Review Letters; refers to
gr-qc/070202
Human factors aspects of control room design: Guidelines and annotated bibliography
A human factors analysis of the workstation design for the Earth Radiation Budget Satellite mission operation room is discussed. The relevance of anthropometry, design rules, environmental design goals, and the social-psychological environment are discussed
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