Non-equilibrium mechanics and dynamics of motor activated gels

The mechanics of cells is strongly affected by molecular motors that generate forces in the cellular cytoskeleton. We develop a model for cytoskeletal networks driven out of equilibrium by molecular motors exerting transient contractile stresses. Using this model we show how motor activity can dramatically increase the network's bulk elastic moduli. We also show how motor binding kinetics naturally leads to enhanced low-frequency stress fluctuations that result in non-equilibrium diffusive motion within an elastic network, as seen in recent \emph{in vitro} and \emph{in vivo} experiments.Comment: 21 pages, 8 figure

Basic deposited integrated magnetic circuit element for fast computer circuitry

A deposited configuration, consisting of a magnetic thin film and coupling loop, was studied with a view to the future development of integrated magnetic circuitry. A line charge model, predicting flux linkages of coupling loops to an accuracy of about one percent was established. The almost complete linkage of the film flux with a deposited loop, due to the very close coupling, was verified. A decrease of about 20 percent in film flux at both ends of the easy axis was noted for the experimental assemblies used. Circulating loop currents were shown to be the chief parasitic factor which modified the switching of the magnetic film. The change in switching time due to eddy currents was small when the loop conductor size was of the same order as the magnetic film. For resistive loop loading, the average field during switching is a good measure of the slowing due to the loading. The film-loop assembly has good potentialities as a circuit element, with good transmission of both read-out and control signals occurring in the loop. The field calibration for these control signals was shown to be the same for both bias and drive field applications

Magnetic flux reversal in laminated Ni-Fe films

Anomalously fast flux reversal has been observed in films made of Ni-Fe layers separated by SiO. The speed of reversal increases as the number of identical layers of Ni-Fe increases. For a 5-layer film, the anomalous speed is observed in films with the SiO thickness as great as 1600 Å. Reversal time curves presented as a family of curves of 1/τ = fh_┴ with h_s as a parameter have two regions. The high-drive region has a lower slope in the laminated films when compared to the single-layer films. For this family of curves, a switching coefficient S_(w') can be defined, as the inverse slope, in a manner similar to the definition of S_w for 1/τ = f(h_(s)) with h_┴ as a parameter. For films with from two to five layers, Sw' is constant at 1 x 10^(-3) μs and is smaller by an order of magnitude for the single-layer films. A dual loop experiment is used to confirm that coherent rotation is not a dominant mechanism. It is concluded that a model must satisfy the following criteria to successfully describe flux reversal in the laminated films: It must provide rapid flux reversal for fields less than H_k, an insensitivity to transverse fields either constant or pulsed, and an interaction that can survive over a wide range of SiO thicknesses

A Chandra View of the Normal SO Galaxy NGC 1332: II: Solar Abundances in the Hot Gas and Implications for SN Enrichment

We present spectral analysis of the diffuse emission in the normal, isolated, moderate-Lx S0 NGC 1332, constraining both the temperature profile and the metal abundances in the ISM. The characteristics of the point source population and the gravitating matter are discussed in two companion papers. The diffuse emission comprises hot gas, with an ~isothermal temperature profile (~0.5 keV), and emission from unresolved point-sources. In contrast with the cool cores of many groups and clusters, we find a small central temperature peak. We obtain emission-weighted abundance contraints within 20 kpc for several key elements: Fe, O, Ne, Mg and Si. The measured iron abundance (Z_Fe=1.1 in solar units; >0.53 at 99% confidence) strongly excludes the very sub-solar values often historically reported for early-type galaxies but agrees with recent observations of brighter galaxies and groups. The abundance ratios, with respect to Fe, of the other elements were also found to be ~solar, although Z_o/Z_Fe was significantly lower (<0.4). Such a low O abundance is not predicted by simple models of ISM enrichment by Type Ia and Type II supernovae, and may indicate a significant contribution from primordial hypernovae. Revisiting Chandra observations of the moderate-Lx, isolated elliptical NGC 720, we obtain similar abundance constraints. Adopting standard SNIa and SNII metal yields, our abundance ratio constraints imply 73+/-5% and 85+/-6% of the Fe enrichment in NGC 1332 and NGC 720, respectively, arises from SNIa. Although these results are sensitive to the considerable systematic uncertainty in the SNe yields, they are in good agreement with observations of more massive systems. These two moderate-Lx early-type galaxies reveal a consistent pattern of metal enrichment from cluster scales to moderate Lx/Lb galaxies. (abridged)Comment: 12 pages, 4 figures, accepted for publication in ApJ. Minor changes to match published versio

Transient shapes of the magnetic bubble domains during gradient propagation and overshoot

Characteristic transient shapes were observed for free magnetic bubble domains during gradient translation and overshoot using high speed photography with 10 nsec laser pulse illumination. The two flanks of the bubble start to expand transversely to the driven motion direction at about.5\musec after the onset of a 7.4 Oe/rad, 2 μsec gradient field pulse. They expand transversely at 2.6 m/sec and continue for 3 μsec after the termination of the gradient pulse. During this expansion, the tip of the flanks move longitudinally at 2.6 m/sec lagging behind the bubble center moving at 5.3 m/sec. Considerable scatter exists in the transverse motion after the driven phase especially in the recovery where some bubbles require as long as 15μsec to regain their round shape. The transverse expansion was found to be independent of the bias compensation applied; however, the transient distortion during the driven phase and the recovery time from the transverse expansion were sensitive to the compensation. This transverse motion as well as the transient shape of the bubble can be explained qualitatively on the basis of a model involving opposite winding vertical Bloch lines

Are we seeing accretion flows in a 250kpc-sized Ly-alpha halo at z=3?

Using MUSE on the ESO-VLT, we obtained a 4 hour exposure of the z=3.12 radio galaxy MRC0316-257. We detect features down to ~10^-19 erg/s/cm^2/arcsec^2 with the highest surface brightness regions reaching more than a factor of 100 higher. We find Ly-alpha emission out to ~250 kpc in projection from the active galactic nucleus (AGN). The emission shows arc-like morphologies arising at 150-250 kpc from the nucleus in projection with the connected filamentary structures reaching down into the circum-nuclear region. The most distant arc is offset by 700 km/s relative to circum-nuclear HeII 1640 emission, which we assume to be at the systemic velocity. As we probe emission closer to the nucleus, the filamentary emission narrows in projection on the sky, the relative velocity decreases to ~250 km/s, and line full-width at half maximum range from 300-700 km/s. From UV line ratios, the emission on scales of 10s of kpc from the nucleus along a wide angle in the direction of the radio jets is clearly excited by the radio jets and ionizing radiation of the AGN. Assuming ionization equilibrium, the more extended emission outside of the axis of the jet direction would require 100% or more illumination to explain the observed surface brightness. High speed (>300 km/s) shocks into rare gas would provide sufficiently high surface brightness. We discuss the possibility that the arcs of Ly-alpha emission represent accretion shocks and the filamentary emission represent gas flows into the halo, and compare our results with gas accretion simulations.Comment: 4 pages, 2 figures, 1 table, A&A letters accepte

Globalising assessment: an ethnography of literacy assessment, camels and fast food in the Mongolian Gobi

What happens when standardised literacy assessments travel globally? The paper presents an ethnographic account of adult literacy assessment events in rural Mongolia. It examines the dynamics of literacy assessment in terms of the movement and re-contextualisation of test items as they travel globally and are received locally by Mongolian respondents. The analysis of literacy assessment events is informed by Goodwin’s ‘participation framework’ on language as embodied and situated interactive phenomena and by Actor Network Theory. Actor Network Theory (ANT) is applied to examine literacy assessment events as processes of translation shaped by an ‘assemblage’ of human and non-human actors (including the assessment texts)

Study of an advanced General Aviation Turbine Engine (GATE)

The best technology program for a small, economically viable gas turbine engine applicable to the general aviation helicopter and aircraft market for 1985-1990 was studied. Turboshaft and turboprop engines in the 112 to 746 kW (150 to 1000 hp) range and turbofan engines up to 6672 N (1500 lbf) thrust were considered. A good market for new turbine engines was predicted for 1988 providing aircraft are designed to capitalize on the advantages of the turbine engine. Parametric engine families were defined in terms of design and off-design performance, mass, and cost. These were evaluated in aircraft design missions selected to represent important market segments for fixed and rotary-wing applications. Payoff parameters influenced by engine cycle and configuration changes were aircraft gross mass, acquisition cost, total cost of ownership, and cash flow. Significant advantage over a current technology, small gas turbine engines was found especially in cost of ownership and fuel economy for airframes incorporating an air-cooled high-pressure ratio engine. A power class of 373 kW (500 hp) was recommended as the next frontier for technology advance where large improvements in fuel economy and engine mass appear possible through component research and development

Efficiency in nanostructured thermionic and thermoelectric devices

Advances in solid-state device design now allow the spectrum of transmitted electrons in thermionic and thermoelectric devices to be engineered in ways that were not previously possible. Here we show that the shape of the electron energy spectrum in these devices has a significant impact on their performance. We distinguish between traditional thermionic devices where electron momentum is filtered in the direction of transport only and a second type, in which the electron filtering occurs according to total electron momentum. Such 'total momentum filtered' kr thermionic devices could potentially be implemented in, for example, quantum dot superlattices. It is shown that whilst total momentum filtered thermionic devices may achieve efficiency equal to the Carnot value, traditional thermionic devices are limited to efficiency below this. Our second main result is that the electronic efficiency of a device is not only improved by reducing the width of the transmission filter as has previously been shown, but also strongly depends on whether the transmission probability rises sharply from zero to full transmission. The benefit of increasing efficiency through a sharply rising transmission probability is that it can be achieved without sacrificing device power, in contrast to the use of a narrow transmission filter which can greatly reduce power. We show that devices which have a sharply-rising transmission probability significantly outperform those which do not and it is shown such transmission probabilities may be achieved with practical single and multibarrier devices. Finally, we comment on the implications of the effect the shape of the electron energy spectrum on the efficiency of thermoelectric devices.Comment: 11 pages, 15 figure