828 research outputs found

    Tissue fusion over non-adhering surfaces

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    Tissue fusion eliminates physical voids in a tissue to form a continuous structure and is central to many processes in development and repair. Fusion events in vivo, particularly in embryonic development, often involve the purse-string contraction of a pluricellular actomyosin cable at the free edge. However in vitro, adhesion of the cells to their substrate favors a closure mechanism mediated by lamellipodial protrusions, which has prevented a systematic study of the purse-string mechanism. Here, we show that monolayers can cover well-controlled mesoscopic non-adherent areas much larger than a cell size by purse-string closure and that active epithelial fluctuations are required for this process. We have formulated a simple stochastic model that includes purse-string contractility, tissue fluctuations and effective friction to qualitatively and quantitatively account for the dynamics of closure. Our data suggest that, in vivo, tissue fusion adapts to the local environment by coordinating lamellipodial protrusions and purse-string contractions

    Are Shakespeare's plays always metatheatrical?

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    The ambiguity of the term "metatheatre" derives in part from its text of origin, Lionel Abel's 1963 book of the same name. By his own admission, Abel's use of the term was "loose and sometimes erratic" (v). If we use the term in its broadest sense—to describe any theater that in some way draws attention to its own artifice—it becomes evident that early modern drama is always "metatheatrical" to some extent: these plays are designed never entirely to lose sight of the material realities of their performance, or of the physical co-presence of their audiences. If this is the case, how useful is the term "metatheatre"? Indeed, are Shakespeare's plays always metatheatrical? This article unpicks some of the conflicting notions of metatheatre suggested in Abel's book, and suggests a modified conceptual model based on the work of Arthur Koestler. Arguing against the tendency to see early modern theatrical self-consciousness as a form of proto-Brechtian alienation, it uses Koestler's concept of bisociation to think about the delight produced by "universes of discourse colliding, frames getting entangled, or contexts getting confused" (40). It considers several examples from performance, especially moments from productions at the reconstructed Shakespeare's Globe, to argue that metatheatre functions as a kind of imaginative game. This game may be prompted by cues in the written text, but it is one that can be played only in performance. While Harry Newman's essay for this special issue argues that metatheatricality was available to early modern readers "on the paper stage of printed playbooks" (104), my essay posits a decidedly more theatrical definition of the term, contending that the agency of the actors plays a central role in determining the metatheatricality of particular moments on stage

    Hadamard transforms for parallel digital communications. Applications to OFDM - DMT modulations on selective channels

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    Multicarrier modulations are often used to combate frequency selective channel . It is the case for digital broadcast with OFDM (Orthogonal Frequency Division Multiplex), or for Digital Subscriber Line Services on the telephone twisted pair with DMT modulation (Discrete MultiTone) . This paper proposes to substitute Fast Fourier Transforms (ANSI and ETSI normalized), by digital real transforms such as the Hadamard Transforms . As they only compute zeros and ones, their implementation is simple. Performances of this technique that we call HDM (Hadamard Division Multiplex) are presented for data transmission over the radio mobile urban channel . The channel estimation is performed by interpolating techniques using digital Transforms (Fourier and Hadamard) . For identical performances (in terms of bit error rate and spectral efficiency), the main advantage of the HDM system is a simpler implementation, eventually ensuring cheap mass production.L'utilisation de modulations multiporteuses est souvent préconisée pour combattre la sélectivité en fréquence du canal de transmission, c'est ainsi le cas de l'OFDM (Orthogonal Frequency Division Multiplex) pour le canal de radiodiffusion numérique et de la modulation DMT (Discrete MultiTone) sur les paires de cuivres des lignes téléphoniques. Cet article propose la substitution des Transformées de Fourier, à des transformées numériques réelles et si possible binaires. Notre étude s'est tournée vers l'exploitation des transformées de Hadamard, offrant un attrait particulier lié à leur simplicité de mise en œuvre. Les performances de ce système, que nous appellerons HDM (Hadamard Division Multiplex), sont présentées pour une transmission de données sur le canal radiomobile urbain. L'estimation du canal est réalisé par une méthode d'interpolation utilisant des transformées numériques (Fourier et Hadamard). A performances (en terme de taux d'erreur binaire et d'efficacité spectrale) identiques, l'atout majeur du système HDM réside dans sa grande simplicité d'implémentation

    The Hydro-electro-thermal Performance of Air-cooled, Open-cathode Polymer Electrolyte Fuel Cells: Combined Localised Current Density, Temperature and Water Mapping

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    In situ diagnostic techniques provide a means of understanding the internal workings of fuel cells so that improved designs and operating regimes can be identified. Here, a novel metrology approach is reported that combines current and temperature mapping with water visualisation using neutron radiography. The approach enables a hydro-electro-thermal performance map to be generated that is applied to an air-cooled, open-cathode polymer electrolyte fuel cell. This type of fuel cell exhibits a particularly interesting coupled relationship between water, current and heat, as the air supply has the due role of cooling the stack as well as providing the cathode reactant feed via a single source. It is found that water predominantly accumulates under the cooling channels (thickness of 70-100 μm under the cooling channels and 5-25 μm in the active channels at 0.5 A cm−2), in a similar fashion to the lands in a closed-cathode design, but contrary to passive open-cathode systems. The relationship between current, temperature and water accumulation is complex and highly dependent on location within the cell. However, there is a general trend that higher currents and cooling limitations, especially above 0.7 A cm−2 and below 3.9 × 10−3 m3 s−1, leads to temperatures above 60 °C, which dehydrate the membrane (water thickness of 10-25 um) and the cell operates below 0.5 V

    Nitrogen Blanketing and Hydrogen Starvation in Dead-Ended-Anode Polymer Electrolyte Fuel Cells Revealed by Hydro-Electro-Thermal Analysis

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    Dead-ended anode operation has a number of practical advantages that simplify system complexity and lower cost for polymer electrolyte fuel cells. However, dead-ended mode leads to performance loss over time which can only be reversed by performing intermittent purge events. This work applies a combined hydro-electro-thermal analysis to an air-cooled open-cathode fuel cell, presenting experimental functional maps of water distribution, current density and temperature. This approach has allowed the identification of a 'nitrogen blanketing' effect due to nitrogen cross-over from the cathode and a 'bypass' effect where a peripheral gap between the gasket and the GDL offers a hydrogen flow 'short circuit' to the border of the electrode. A consequence of high local current density at the margin of the electrode, and resulting high temperatures, may impact the lifetime of the cell in dead-end mode

    Assessment of myocardial injuries in ischemic and non-ischemic cardiomyopathies using magnetic resonance T1-rho mapping.

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    To identify clinical correlates of myocardial T1ρ and to examine how myocardial T1ρ values change under various clinical scenarios. A total of 66 patients (26% female, median age 57 years [Q1-Q3, 44-65 years]) with known structural heart disease and 44 controls (50% female, median age 47 years [28-57 years]) underwent cardiac magnetic resonance imaging at 1.5-T, including T1ρ mapping, T2 mapping, native T1 mapping, late gadolinium enhancement, and ECV imaging.In controls, T1ρ positively related with T2 (P=0.038) and increased from basal to apical levels (P<0.001). As compared to controls and remote myocardium, T1ρ significantly increased in all patients' sub-groups and all types of myocardial injuries: acute and chronic injuries, focal and diffuse tissue abnormalities, as well as ischemic and non-ischemic aetiologies (P<0.05). T1ρ was independently associated with T2 in patients with acute injuries (P=0.004) and with native T1 and ECV in patients with chronic injuries (P<0.05). Myocardial T1ρ mapping demonstrated good intra- and interobserver reproducibility (ICC=0.86 and 0.83, respectively). Myocardial T1ρ mapping appears to be reproducible and equally sensitive to acute and chronic myocardial injuries, whether of ischemic or non-ischemic origins. It may thus be a contrast-agent-free biomarker for gaining new and quantitative insight into myocardial structural disorders. These findings highlight the need for further studies through prospective and randomized trials

    FSHD myoblasts fail to downregulate intermediate filament protein vimentin during myogenic differentiation.

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    Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant hereditary neuromuscular disorder. The clinical features of FSHD include weakness of the facial and shoulder girdle muscles followed by wasting of skeletal muscles of the pelvic girdle and lower extremities. Although FSHD myoblasts grown in vitro can be induced to differentiate into myotubes by serum starvation, the resulting FSHD myotubes have been shown previously to be morphologically abnormal. Aim. In order to find the cause of morphological anomalies of FSHD myotubes we compared in vitro myogenic differentiation of normal and FSHD myoblasts at the protein level. Methods. We induced myogenic differentiation of normal and FSHD myoblasts by serum starvation. We then compared protein extracts from proliferating myoblasts and differentiated myotubes using SDS-PAGE followed by mass spectrometry identification of differentially expressed proteins. Results. We demonstrated that the expression of vimentin was elevated at the protein and mRNA levels in FSHD myotubes as compared to normal myotubes. Conclusions. We demonstrate for the first time that in contrast to normal myoblasts, FSHD myoblasts fail to downregulate vimentin after induction of in vitro myogenic differentiation. We suggest that vimentin could be an easily detectable marker of FSHD myotube
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