179 research outputs found
Rac1-Dependent Phosphorylation and Focal Adhesion Recruitment of Myosin IIA Regulates Migration and Mechanosensing
SummaryBackgroundCell migration requires coordinated formation of focal adhesions (FAs) and assembly and contraction of the actin cytoskeleton. Nonmuscle myosin II (MII) is a critical mediator of contractility and FA dynamics in cell migration. Signaling downstream of the small GTPase Rac1 also regulates FA and actin dynamics, but its role in regulation of MII during migration is less clear.ResultsWe found that Rac1 promotes association of MIIA with FA. Live-cell imaging showed that, whereas most MIIA at the leading edge assembled into dorsal contractile arcs, a substantial subset assembled in or was captured within maturing FA, and this behavior was promoted by active Rac1. Protein kinase C (PKC) activation was necessary and sufficient for integrin- and Rac1-dependent phosphorylation of MIIA heavy chain (HC) on serine1916 (S1916) and recruitment to FA. S1916 phosphorylation of MIIA HC and localization in FA was enhanced during cell spreading and ECM stiffness mechanosensing, suggesting upregulation of this pathway during physiological Rac1 activation. Phosphomimic and nonphosphorylatable MIIA HC mutants demonstrated that S1916 phosphorylation was necessary and sufficient for the capture and assembly of MIIA minifilaments in FA. S1916 phosphorylation was also sufficient to promote the rapid assembly of FAs to enhance cell migration and for the modulation of traction force, spreading, and migration by ECM stiffness.ConclusionsOur study reveals for the first time that Rac1 and integrin activation regulates MIIA HC phosphorylation through a PKC-dependent mechanism that promotes MIIA association with FAs and acts as a critical modulator of cell migration and mechanosensing
Theory of Adsorption and Surfactant Effect of Sb on Ag (111)
We present first-principles studies of the adsorption of Sb and Ag on clean
and Sb-covered Ag (111). For Sb, the {\it substitutional} adsorption site is
found to be greatly favored with respect to on-surface fcc sites and to
subsurface sites, so that a segregating surface alloy layer is formed. Adsorbed
silver adatoms are more strongly bound on clean Ag(111) than on Sb-covered Ag.
We propose that the experimentally reported surfactant effect of Sb is due to
Sb adsorbates reducing the Ag adatom mobility. This gives rise to a high
density of Ag islands which coalesce into regular layers.Comment: RevTeX 3.0, 11 pages, 0 figures] 13 July 199
Impurity Scattering from -layers in Giant Magnetoresistance Systems
The properties of the archetypal Co/Cu giant magnetoresistance (GMR)
spin-valve structure have been modified by the insertion of very thin
(sub-monolayer) -layers of various elements at different points within
the Co layers, and at the Co/Cu interface. Different effects are observed
depending on the nature of the impurity, its position within the periodic
table, and its location within the spin-valve. The GMR can be strongly enhanced
or suppressed for various specific combinations of these parameters, giving
insight into the microscopic mechanisms giving rise to the GMR.Comment: 5 pages, 2 figure
Universal scaling of magnetoconductance in magnetic nanocontacts (Invited)
We present results of half-metallic ferromagnets formed by atomic nanocontact of CrO2â CrO2 and
CrO2âNi that show as much as 400% magnetoconductance. Analysis of the magnetoconductance
versus conductance data for all materials known to exhibit so-called ballistic magnetoresistance
strongly suggests that the magnetoconductance of nanocontacts follows universal scaling. If the
maximum magnetoconductance is normalized to unity and the conductance is scaled to the
resistivity of the material, then all data points fall into a universal curve that is independent of the
contact material and the transport mechanism. The analysis was applied to all available
magnetoconductance data of magnetic nanocontacts in the literature, and the results agree with
theory that takes into account the spin scattering within a magnetic domain wall
Surface Core Level Shifts of Clean and Oxygen Covered Ru(0001)
We have performed high resolution XPS experiments of the Ru(0001) surface,
both clean and covered with well-defined amounts of oxygen up to 1 ML coverage.
For the clean surface we detected two distinct components in the Ru 3d_{5/2}
core level spectra, for which a definite assignment was made using the high
resolution Angle-Scan Photoelectron Diffraction approach. For the p(2x2),
p(2x1), (2x2)-3O and (1x1)-O oxygen structures we found Ru 3d_{5/2} core level
peaks which are shifted up to 1 eV to higher binding energies. Very good
agreement with density functional theory calculations of these Surface Core
Level Shifts (SCLS) is reported. The overriding parameter for the resulting Ru
SCLSs turns out to be the number of directly coordinated O atoms. Since the
calculations permit the separation of initial and final state effects, our
results give valuable information for the understanding of bonding and
screening at the surface, otherwise not accessible in the measurement of the
core level energies alone.Comment: 16 pages including 10 figures. Submitted to Phys. Rev. B. Related
publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm
Co-ordination between Rashba spin-orbital interaction and space charge effect and enhanced spin injection into semiconductors
We consider the effect of the Rashba spin-orbital interaction and space
charge in a ferromagnet-insulator/semiconductor/insulator-ferromagnet junction
where the spin current is severely affected by the doping, band structure and
charge screening in the semiconductor. In diffusion region, if the the
resistance of the tunneling barriers is comparable to the semiconductor
resistance, the magnetoresistance of this junction can be greatly enhanced
under appropriate doping by the co-ordination between the Rashba effect and
screened Coulomb interaction in the nonequilibrium transport processes within
Hartree approximation.Comment: 4 pages, 3 figure
Thin Al, Au, Cu, Ni, Fe, and Ta films as oxidation barriers for Co in air
We have investigated the effectiveness of Al, Au, Cu, Ni, Fe, and Ta films with thicknesses up to 4
nm for protecting a Co surface from oxidation in air at room temperature. The distinct change in the
Co 2p3/2 core-level line shape observed by x-ray photoelectron spectroscopy upon the oxidation of
Co makes it a simple matter to identify the fractions of the Co that are in the metallic state and in
the oxidized state. We find that the best choices for protecting Co from oxidation are Al and Ta. We
found that Au, which is one of the most popular choices, is not particularly effective for protecting
Co
What we talk about when we talk about "global mindset": managerial cognition in multinational corporations
Recent developments in the global economy and in multinational corporations have placed significant emphasis on the cognitive orientations of managers, giving rise to a number of concepts such as âglobal mindsetâ that are presumed to be associated with the effective management of multinational corporations (MNCs). This paper reviews the literature on global mindset and clarifies some of the conceptual confusion surrounding the construct. We identify common themes across writers, suggesting that the majority of studies fall into one of three research perspectives: cultural, strategic, and multidimensional. We also identify two constructs from the social sciences that underlie the perspectives found in the literature: cosmopolitanism and cognitive complexity and use these two constructs to develop an integrative theoretical framework of global mindset. We then provide a critical assessment of the field of global mindset and suggest directions for future theoretical and empirical research
Spintronics: Fundamentals and applications
Spintronics, or spin electronics, involves the study of active control and
manipulation of spin degrees of freedom in solid-state systems. This article
reviews the current status of this subject, including both recent advances and
well-established results. The primary focus is on the basic physical principles
underlying the generation of carrier spin polarization, spin dynamics, and
spin-polarized transport in semiconductors and metals. Spin transport differs
from charge transport in that spin is a nonconserved quantity in solids due to
spin-orbit and hyperfine coupling. The authors discuss in detail spin
decoherence mechanisms in metals and semiconductors. Various theories of spin
injection and spin-polarized transport are applied to hybrid structures
relevant to spin-based devices and fundamental studies of materials properties.
Experimental work is reviewed with the emphasis on projected applications, in
which external electric and magnetic fields and illumination by light will be
used to control spin and charge dynamics to create new functionalities not
feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes
from the published versio
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