Nanostructures in Ti processed by severe plastic deformation

Metals and alloys processed by severe plastic deformation (SPD) can demonstrate superior mechanical properties, which are rendered by their unique defect structures. In this investigation, transmission electron microscopy and x-ray analysis were used to systematically study the defect structures, including grain and subgrain structures, dislocation cells, dislocation distributions, grain boundaries, and the hierarchy of these structural features, in nanostructured Ti produced by a two-step SPD procedure-warm equal channel angular pressing followed by cold rolling. The effects of these defect structures on the mechanical behaviors of nanostructured Ti are discussed

Integrin engagement suppresses RhoA activity via a c-Src-dependent mechanism

The Rho family GTPases Cdc42, Rac1 and RhoA control many of the changes in the actin cytoskeleton that are triggered when growth factor receptors and integrins bind their ligands. Rac1 and Cdc42 stimulate the formation of protrusive structures such as membrane ruffles, lamellipodia and filopodia. RhoA regulates contractility and assembly of actin stress fibers and focal adhesions. Although prolonged integrin engagement can stimulate RhoA, regulation of this GTPase by early integrin-mediated signals is poorly understood. Here we show that integrin engagement initially inactivates RhoA, in a c-Src-dependent manner, but has no effect on Cdc42 or Rac1 activity. Additionally, early integrin signaling induces activation and tyrosine phosphorylation of p190RhoGAP via a mechanism that requires c-Src. Dynamic modulation of RhoA activity appears to have a role in motility, as both inhibition and activation of RhoA hinder migration. Transient suppression of RhoA by integrins may alleviate contractile forces that would otherwise impede protrusion at the leading edge of migrating cells

Agonist-induced alteration in the membrane form of muscarinic cholinergic receptors

Incubation of 1321N1 human astrocytoma cells with carbachol resulted in a rapid loss of binding of [3H]N-methylscopolamine ([3H]NMS) to muscarinic cholinergic receptors measured at 4 degrees C on intact cells; loss of muscarinic receptors in lysates from the same cells measured with [3H]quinuclidinyl benzilate [( 3H]QNB) at 37 degrees C occurred at a slower rate. Upon removal of agonist from the medium, the lost [3H]NMS binding sites measured on intact cells recovered with a t1/2 of approximately 20 min, but only to the level to which [3H]QNB binding sites had been lost; no recovery of "lost" [3H]QNB binding sites occurred over the same period. Based on these data and the arguments of Galper et al. (Galper, J. B., Dziekan, L. C., O'Hara, D. S., and Smith, T. W. (1982) J. Biol. Chem. 257, 10344-10356) regarding the relative hydrophilicity of [3H]NMS versus [3H]QNB, it is proposed that carbachol induces a rapid sequestration of muscarinic receptors that is followed by a loss of these receptors from the cell. These carbachol-induced changes are accompanied by a change in the membrane form of the muscarinic receptor. Although essentially all of the muscarinic receptors from control cells co-purified with the plasma membrane fraction on sucrose density gradients, 20-35% of the muscarinic receptors from cells treated for 30 min with 100 microM carbachol migrated to a much lower sucrose density. This conversion of muscarinic receptors to a "light vesicle" form occurred with a t1/2 approximately 10 min, and reversed with a t1/2 approximately 20 min. In contrast to previous results in this cell line regarding beta-adrenergic receptors (Harden, T. K., Cotton, C. U., Waldo, G. L., Lutton, J. K., and Perkins, J. P. (1980) Science 210, 441-443), agonist binding to muscarinic receptors in the light vesicle fraction obtained from carbachol-treated cells was still regulated by GTP. One interpretation of these data is that agonists induce an internalization of muscarinic receptors with the retention of their functional interaction with a guanine nucleotide regulatory protein

Water and energy budgets over hydrological basins on short and long timescales

Quantifying regional water and energy fluxes much more accurately from observations is essential for assessing the capability of climate and Earth system models and their ability to simulate future change. This study uses satellite observations to produce monthly flux estimates for each component of the terrestrial water and energy budget over selected large river basins from 2002 to 2013. Prior to optimisation, the water budget residuals vary between 1.5 % and 35 % precipitation by basin, and the magnitude of the imbalance between the net radiation and the corresponding turbulent heat fluxes ranges between 1 and 12 W m−2 in the long-term average. In order to further assess these imbalances, a flux-inferred surface storage (Sfi) is used for both water and energy, based on integrating the flux observations. This exposes mismatches in seasonal water storage in addition to important inter-annual variability between GRACE (Gravity Recovery and Climate Experiment) and the storage suggested by the other flux observations. Our optimisation ensures that the flux estimates are consistent with the total water storage changes from GRACE on short (monthly) and longer timescales, while also balancing a coupled long-term energy budget by using a sequential approach. All the flux adjustments made during the optimisation are small and within uncertainty estimates, using a χ2 test, and inter-annual variability from observations is retained. The optimisation also reduces formal uncertainties for individual flux components. When compared with results from the previous literature in basins such as the Mississippi, Congo, and Huang He rivers, our results show better agreement with GRACE variability and trends in each case.</p

Atomic-scale modeling of the deformation of nanocrystalline metals

Nanocrystalline metals, i.e. metals with grain sizes from 5 to 50 nm, display technologically interesting properties, such as dramatically increased hardness, increasing with decreasing grain size. Due to the small grain size, direct atomic-scale simulations of plastic deformation of these materials are possible, as such a polycrystalline system can be modeled with the computational resources available today. We present molecular dynamics simulations of nanocrystalline copper with grain sizes up to 13 nm. Two different deformation mechanisms are active, one is deformation through the motion of dislocations, the other is sliding in the grain boundaries. At the grain sizes studied here the latter dominates, leading to a softening as the grain size is reduced. This implies that there is an ``optimal'' grain size, where the hardness is maximal. Since the grain boundaries participate actively in the deformation, it is interesting to study the effects of introducing impurity atoms in the grain boundaries. We study how silver atoms in the grain boundaries influence the mechanical properties of nanocrystalline copper.Comment: 10 pages, LaTeX2e, PS figures and sty files included. To appear in Mater. Res. Soc. Symp. Proc. vol 538 (invited paper). For related papers, see http://www.fysik.dtu.dk/~schiotz/publist.htm

Forces Sauces and Eggs for Soldiers: food, nostalgia, and the rehabilitation of the British military

This article identifies, and considers the political implications of, the association of the contemporary British military and British soldiers with nostalgia. This aspect of the discursive project of rehabilitating the British military post-Iraq has not hitherto been theorized. The article analyses a set of exemplifying texts, four military charity food brands (Eggs for Soldiers, Forces Sauces, Red Lion Foods, and Rare Tea Company Battle of Britain Tea) to ask how nostalgic rehabilitation of the British military unfolds at the intersections of militarization, commemoration, and post-2008 “conscience capitalism”. I outline how military charity food brands are a form of “conscience capitalism” through which the perpetuation of militarized logics are produced as a notionally apolitical social “cause”, rendered intelligible within the terms of existing commoditized discourses of post-2008 vintage nostalgia. I then ask what understandings of British soldiers and the British military are constituted within the discourse of nostalgic rehabilitation, and secondly what forms of commemoration are entailed. I argue that a nostalgic generalization of soldiers and the military nullifies the potential unruliness of individual soldiers and obscures the specifics of recent, controversial, wars. Secondly nostalgic civil–military engagement entails a commemorative logic in which forms of quasi-military service are brought into the most banal spaces of everyday civilian life

Small molecule inhibitors of RAS-effector protein interactions derived using an intracellular antibody fragment

Intracellular antibodies can inhibit disease-relevant protein interactions, but inefficient cellular uptake limits their utility. Using a RAS-targeting intracellular antibody as a screening tool, the authors here identify small molecules that inhibit RAS-effector interactions and readily penetrate cells

Optimization of the Strength-Fracture Toughness Relation in Particulate-Reinforced Aluminum Composites via Control of the Matrix Microstructure

The article of record as published may be found at http://dx.doi.org/10.1007/s11661-998-0119-9The evolution of the microstructure and mechanical properties of a 17.5 vol. pct SiC particulatereinforced aluminum alloy 6092-matrix composite has been studied as a function of postfabrication processing and heat treatment. It is demonstrated that, by the control of particulate distribution, matrix grain, and substructure and of the matrix precipitate state, the strength-toughness combination in the composite can be optimized over a wide range of properties, without resorting to unstable, underaged (UA) matrix microstructures, which are usually deemed necessary to produce a higher fracture toughness than that displayed in the peak-aged condition. Further, it is demonstrated that, following an appropriate combination of thermomechanical processing and unconventional heat treatment, the composite may possess better stiffness, strength, and fracture toughness than a similar unreinforced alloy. In the high- and low-strength matrix microstructural conditions, the matrix grain and substructure were found to play a substantial role in determining fracture properties. However, in the intermediate- strength regime, properties appeared to be optimizable by the utilization of heat treatments only. These observations are rationalized on the basis of current understanding of the grain size dependence of fracture toughness and the detailed microstructural features resulting from thermomechanical treatments.United States Army Research OfficeArmy Research LabratoryUnited States Air Force Office of Scientific ResearchWright Materials LabratoryDWA Composite