The electromagnetic shielding performance of carbon foams is measured using the nested reverberation chamber method in the frequency band 1–4GHz, which is the frequency range of most cellular phones ...and microwave ovens. Good values of shielding effectiveness are obtained even with a small thickness of carbon foam. The results are used to assess the correct electrical conductivity values for the investigated materials using a multiple reflection model to compute the material transmission coefficient. The potential applications of such materials are in the lightweight microwave shielding structures that are partially transparent to optical frequencies.
Osteophytes are highly prevalent in osteoarthritis (OA) and are associated with pain and functional disability. These pathological outgrowths of cartilage and bone typically form at the junction of ...articular cartilage, periosteum and synovium. The aim of this study was to identify the cells forming osteophytes in OA.
Fluorescent genetic cell-labelling and tracing mouse models were induced with tamoxifen to switch on reporter expression, as appropriate, followed by surgery to induce destabilisation of the medial meniscus. Contributions of fluorescently labelled cells to osteophytes after 2 or 8 weeks, and their molecular identity, were analysed by histology, immunofluorescence staining and RNA in situ hybridisation.
mice and
mice crossed with multicolour
reporter mice were used for identification and clonal tracing of mesenchymal progenitors. Mice carrying
,
,
,
,
or
were crossed with tdTomato reporter mice to lineage-trace chondrocytes and stem/progenitor cell subpopulations.
Articular chondrocytes, or skeletal stem cells identified by
,
or
expression, did not give rise to osteophytes. Instead, osteophytes derived from
-expressing stem/progenitor cells in periosteum and synovium that are descendants from the
-expressing embryonic joint interzone. Further, we show that
-expressing progenitors in periosteum supplied hybrid skeletal cells to the early osteophyte, while
-expressing progenitors from synovial lining contributed to cartilage capping the osteophyte, but not to bone.
Our findings reveal distinct periosteal and synovial skeletal progenitors that cooperate to form osteophytes in OA. These cell populations could be targeted in disease modification for treatment of OA.
We investigated how the electrical contact of carbon foam with metallic surface can reduce its shielding properties. The bubble structure of the foam does not ensure a good electrical contact with ...the metal, and it leads to a significant reduction of the shielding effectiveness. A finite element numerical simulation was carried out by adopting a bubble/pore model of the internal microstructure of the foam, recovered by means of scanning electron microscope images. Experimental tests were carried out by inserting carbon foam samples into a coaxial transmission line. Numerical results agree well with experimental result showing significant performance reduction with respect to an ideal electrical contact.
The healing of bone often involves a cartilage intermediate, yet how such cartilage is induced and utilized during repair is not fully understood. By studying a model of large-scale bone regeneration ...in the lower jaw of adult zebrafish, we show that chondrocytes are crucial for generating thick bone during repair. During jawbone regeneration, we find that chondrocytes co-express genes associated with osteoblast differentiation and produce extensive mineralization, which is in marked contrast to the behavior of chondrocytes during facial skeletal development. We also identify the likely source of repair chondrocytes as a population of Runx2(+)/Sp7(-) cells that emanate from the periosteum, a tissue that normally contributes only osteoblasts during homeostasis. Analysis of Indian hedgehog homolog a (ihha) mutants shows that the ability of periosteal cells to generate cartilage in response to injury depends on a repair-specific role of Ihha in the induction as opposed to the proliferation of chondrocytes. The large-scale regeneration of the zebrafish jawbone thus employs a cartilage differentiation program distinct from that seen during development, with the bone-forming potential of repair chondrocytes potentially due to their derivation from osteogenic cells in the periosteum.
According to an evolutionist approach, laughter is a multifaceted behaviour affecting social, emotional, motor and speech functions. Albeit previous studies have suggested that high-frequency ...electrical stimulation (HF-ES) of the pregenual anterior cingulate cortex (pACC) may induce bursts of laughter—suggesting a crucial contribution of this region to the cortical control of this behaviour—the complex nature of laughter implies that outward connections from the pACC may reach and affect a complex network of frontal and limbic regions. Here, we studied the effective connectivity of the pACC by analysing the cortico-cortical evoked potentials elicited by single-pulse electrical stimulation of pACC sites whose HF-ES elicited laughter in 12 patients. Once these regions were identified, we studied their clinical response to HF-ES, to reveal the specific functional target of pACC representation of laughter. Results reveal that the neural representation of laughter in the pACC interacts with several frontal and limbic regions, including cingulate, orbitofrontal, medial prefrontal and anterior insular regions—involved in interoception, emotion, social reward and motor behaviour. These results offer neuroscientific support to the evolutionist approach to laughter, providing a possible mechanistic explanation of the interplay between this behaviour and emotion regulation, speech production and social interactions.
This article is part of the theme issue ‘Cracking the laugh code: laughter through the lens of biology, psychology and neuroscience’.
Most bones in mammals display a limited capacity for natural large-scale repair. The ribs are a notable exception, yet the source of their remarkable regenerative ability remains unknown. Here, we ...identify a
-expressing periosteal subpopulation that orchestrates large-scale regeneration of murine rib bones. Deletion of the obligate Hedgehog co-receptor,
, in
-expressing cells prior to injury results in a near-complete loss of callus formation and rib bone regeneration. In contrast to its role in development, Hedgehog signaling is dispensable for the proliferative expansion of callus cells in response to injury. Instead, Sox9-positive lineage cells require Hh signaling to stimulate neighboring cells to differentiate via an unknown signal into a skeletal cell type with dual chondrocyte/osteoblast properties. This type of callus cell may be critical for bridging large bone injuries. Thus despite contributing to only a subset of callus cells,
-positive progenitors play a major role in orchestrating large-scale bone regeneration.
This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
Evolutionary algorithms are heuristic methods that have yielded promising results for solving nonlinear, nondifferentiable, and multi-modal optimization problems in the power systems area. The ...differential evolution (DE) algorithm is an evolutionary algorithm that uses a rather greedy and less stochastic approach to problem solving than do classical evolutionary algorithms, such as genetic algorithms, evolutionary programming, and evolution strategies. DE also incorporates an efficient way of self-adapting mutation using small populations. The potentialities of DE are its simple structure, easy use, convergence property, quality of solution, and robustness. This paper proposes a new approach for solving economic load dispatch problems with valve-point effect. The proposed method combines the DE algorithm with the generator of chaos sequences and sequential quadratic programming (SQP) technique to optimize the performance of economic dispatch problems. The DE with chaos sequences is the global optimizer, and the SQP is used to fine-tune the DE run in a sequential manner. The combined methodology and its variants are validated for two test systems consisting of 13 and 40 thermal units whose incremental fuel cost function takes into account the valve-point loading effects. The proposed combined method outperforms other state-of-the-art algorithms in solving load dispatch problems with the valve-point effect.
We present an accurate measurement of the electrical conductivity of carbon/carbon (C/C) composites in higher range of microwave frequencies. The composite is an 8mm thick C/C laminate 2D woven ...fabric, machined to create a rectangular waveguide. Transmission and reflection parameters are acquired within a broad frequency band, ranging from 23 to 30GHz, and used for the evaluation of the power loss in the waveguide and to extract the C/C electrical conductivity. The obtained conductivity values at microwave frequencies are about 10 times lower than those measured at very low frequencies. The effects of temperature are also investigated, and the variation of the conductivity with the temperature is reported.
The numerical simulation and the measurement of electromagnetic shielding at microwave frequencies of thermal protection system for hypersonic vehicles is presented using nested reverberation ...chamber. An example of a possible thermal protection system for a re-entry vehicle is presented. This system based on carbon material is electromagnetically characterized. The characterization takes into account not only the materials but also the final assembly configuration of the thermal protection system. The frequency range is 2–8GHz. The results of measurements and simulations show that the microwave shielding effectiveness of carbon materials is above 60dB for a single tile and that the tile inter-distance is able to downgrade the shielding effectiveness on the average to about 40dB.
► The tile-to-tile gap in a thermal protection system has been analyzed. ► Electromagnetic shielding capability was measured and numerically computed. ► Material losses enhance the gap field attenuation compared to good conductors. ► A typical gap of 1mm ensures at least 40dB within the 2–8GHz frequency range.
To determine the role of fibroblast growth factor (FGF) signalling from the apical ectodermal ridge (AER), we inactivated Fgf4 and Fgf8 in AER cells or their precursors at different stages of mouse ...limb development. We show that FGF4 and FGF8 regulate cell number in the nascent limb bud and are required for survival of cells located far from the AER. On the basis of the skeletal phenotypes observed, we conclude that these functions are essential to ensure that sufficient progenitor cells are available to form the normal complement of skeletal elements, and perhaps other limb tissues. In the complete absence of both FGF4 and FGF8 activities, limb development fails. We present a model to explain how the mutant phenotypes arise from FGF-mediated effects on limb bud size and cell survival.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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