182 research outputs found
Space deployable domed solar concentrator with foldable panels and hinge therefor
A space deployable solar energy concentrator is formed of a dome-shaped arrangement of compactly stowable flat panel segments mounted on a collapsible, space-deployable support structure of interconnected linear components. The support structure is comprised of a plurality of tensioned, curvilinear edge strips which extend in a radial direction from a prescribed vertex of a surrounding umbrella-like framework of radially extending rib members. Between a respective pair of radially-extending, curvilinear edge strips an individual wedge-shaped panel section is formed of a plurality of multi-segment lens panel strips each of which is supported in tension between the pair of edge strips by a pair of circumferentially extending catenary cord members connected to a pair of ribs of the surrounding umbrella-like framework. A respective lens panel strip is comprised of a plurality of flat, generally rectangular-shaped, energy-directing panels arranged side-by-side in the circumferential direction of the dome. Adjacent panels are interconnected by flexible U-shaped hinges which overlap opposing edges of adjacent panels and engage respective cylindrically-shaped, load distribution bars that slide within the flexible hinges. Because each U-shaped hinge is flexible, it is permitted to shift in the circumferential direction of the panel section to facilitate stowage and deployment of the dome
A Logic Model for the Integration of Mental Health Into Chronic Disease Prevention and Health Promotion
Mental illnesses such as depression or anxiety affect an individual's ability to undertake health-promoting behaviors. Chronic diseases can have a profound impact on an individual's mental health; in turn, mental health status affects an individual's ability to participate in treatment and recovery. A group of mental health and public health professionals convened to develop a logic model for addressing mental health as it relates to chronic disease prevention and health promotion. The model provides details on inputs, activities, and desired outcomes, and the designers of the model welcome input from other mental health and public health practitioners
Modifying styrene-maleic acid co-polymer for studying lipid nanodiscs
International audienceRecently, styrene-maleic acid copolymer lipid nanodiscs have become an increasingly popular tool for the study of membrane proteins. In the work we report here, we have developed a novel method for the efficient preparation of labeled nanodiscs, under chemically mild conditions, by modification of the hydrolyzed styrene-maleic acid copolymer. This protocol is designed to be easily accessible to biochemistry laboratories. We use this procedure to prepare various fluorescent nanodiscs labeled with different fluorophores. By studying the development of Förster resonance energy transfer, we demonstrate the rapid exchange of co-polymer between nanodiscs. This demonstration, in conjunction of previous work, indicates that the lipid nanodiscs prepared using this polymer are very dynamic structures with rapid exchange of the different components
Out-of-equilibrium collective oscillation as phonon condensation in a model protein
In the first part of the present paper (theoretical), the activation of
out-of-equilibrium collective oscillations of a macromolecule is described as a
classical phonon condensation phenomenon. If a macromolecule is modeled as an
open system, that is, it is subjected to an external energy supply and is in
contact with a thermal bath to dissipate the excess energy, the internal
nonlinear couplings among the normal modes make the system undergo a
non-equilibrium phase transition when the energy input rate exceeds a threshold
value. This transition takes place between a state where the energy is
incoherently distributed among the normal modes, to a state where the input
energy is channeled into the lowest frequency mode entailing a coherent
oscillation of the entire molecule. The model put forward in the present work
is derived as the classical counterpart of a quantum model proposed long time
ago by H. Fr\"ohlich in the attempt to explain the huge speed of enzymatic
reactions. In the second part of the present paper (experimental), we show that
such a phenomenon is actually possible. Two different and complementary THz
near-field spectroscopic techniques, a plasmonic rectenna, and a micro-wire
near-field probe, have been used in two different labs to get rid of artefacts.
By considering a aqueous solution of a model protein, the BSA (Bovine Serum
Albumin), we found that this protein displays a remarkable absorption feature
around 0.314 THz, when driven in a stationary out-of-thermal equilibrium state
by means of optical pumping. The experimental outcomes are in very good
qualitative agreement with the theory developed in the first part, and in
excellent quantitative agreement with a theoretical result allowing to identify
the observed spectral feature with a collective oscillation of the entire
molecule.Comment: 49 pages, 10 figures; Physical Review X, (2018) in pres
Offset truss hex solar concentrator
A solar energy concentrator system comprises an offset reflector structure made up of a plurality of solar energy reflector panel sections interconnected with one another to form a piecewise approximation of a portion of a (parabolic) surface of revolution rotated about a prescribed focal axis. Each panel section is comprised of a plurality of reflector facets whose reflective surfaces effectively focus reflected light to preselected surface portions of the interior sidewall of a cylindrically shaped solar energy receiver. The longitudinal axis of the receiver is tilted at an acute angle with respect to the optical axis such that the distribution of focussed solar energy over the interior surface of the solar engine is optimized for dynamic solar energy conversion. Each reflector panel section comprises a flat, hexagonally shaped truss support framework and a plurality of beam members interconnecting diametrically opposed corners of the hexagonal framework recessed within which a plurality of (spherically) contoured reflector facets is disposed. The depth of the framework and the beam members is greater than the thickness of a reflector facet such that a reflector facet may be tilted (for controlling the effective focus of its reflected light through the receiver aperture) without protruding from the panel section
\u27Living cantilever arrays\u27 for characterization of mass of single live cells in fluids
The size of a cell is a fundamental physiological property and is closely regulated by various environmental and genetic factors. Optical or confocal microscopy can be used to measure the dimensions of adherent cells, and Coulter counter or flow cytometry ( forward scattering light intensity) can be used to estimate the volume of single cells in a flow. Although these methods could be used to obtain the mass of single live cells, no method suitable for directly measuring the mass of single adherent cells without detaching them from the surface is currently available. We report the design, fabrication, and testing of \u27living cantilever arrays\u27, an approach to measure the mass of single adherent live cells in fluid using silicon cantilever mass sensor. HeLa cells were injected into microfluidic channels with a linear array of functionalized silicon cantilevers and the cells were subsequently captured on the cantilevers with positive dielectrophoresis. The captured cells were then cultured on the cantilevers in a microfluidic environment and the resonant frequencies of the cantilevers were measured. The mass of a single HeLa cell was extracted from the resonance frequency shift of the cantilever and was found to be close to the mass value calculated from the cell density from the literature and the cell volume obtained from confocal microscopy. This approach can provide a new method for mass measurement of a single adherent cell in its physiological condition in a non-invasive manner, as well as optical observations of the same cell. We believe this technology would be very valuable for single cell time-course studies of adherent live cells
The architecture of Rhodobacter sphaeroides chromatophores
International audienceThe chromatophores of Rhodobacter (Rb.) sphaeroides represent a minimal bio-energetic system, which efficiently converts light energy into usable chemical energy. Despite extensive studies, several issues pertaining to the morphology and molecular architecture of this elemental energy conversion system remain controversial or unknown. To tackle these issues, we combined electron microscope tomography, immuno-electron microscopy and atomic force microscopy. We found that the intracellular Rb. sphaeroides chromatophores form a continuous reticulum rather than existing as discrete vesicles. We also found that the cytochrome bc 1 complex localizes to fragile chromatophore regions, which most likely constitute the tubular structures that interconnect the vesicles in the reticulum. In contrast, the peripheral light-harvesting complex 2 (LH2) is preferentially hexagonally packed within the convex vesicular regions of the membrane network. Based on these observations, we propose that the bc 1 complexes are in the inter-vesicular regions and surrounded by reaction center (RC) core complexes, which in turn are bounded by arrays of peripheral antenna complexes. This arrangement affords rapid cycling of electrons between the core and bc 1 complexes while maintaining efficient excitation energy transfer from LH2 domains to the RCs
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