9,110 research outputs found
Clonal variation in cell surface display of an H-2 protein lacking a cytoplasmic tail
Truncated variants of the gene encoding H-2Ld, an integral membrane protein encoded by the major histocompatibility complex, were constructed by in vitro mutagenesis to elucidate the function of charged amino acids found on the cytoplasmic side of the transmembrane (TM) region. Analysis of cloned L cells transfected with these genes shows that the seven amino acids following the TM segment, four of which are basic, enhance the cell surface expression of H-2Ld protein but are not required for it. However, some clones do not express a tailless H-2Ld protein on the cell surface but express it intracellularly where it has a long half-life. Turnover measurements on cell surface H-2Ld proteins suggest that the basic residues following the TM segment are not a "stop transfer" sequence (Blobel, G., 1980, Proc. Natl. Acad. Sci. USA., 77:1496-1500) which anchors the H-2Ld protein in the membrane. Pulse-chase and endoglycosidase H sensitivity studies show that H-2Ld proteins lacking some or all of the basic residues and H-2Ld proteins which have a full-length cytoplasmic tail are processed with different kinetics. These results suggest an involvement of the membrane-proximal region of the cytoplasmic tail in the intracellular transport of H-2Ld. We further suggest that the L cell clones which do and do not express a tailless H-2Ld protein on the cell surface differ in the ability to transport a tailless integral membrane protein to the cell surface
Sunspot rotation. I. A consequence of flux emergence
Context. Solar eruptions and high flare activity often accompany the rapid
rotation of sunspots. The study of sunspot rotation and the mechanisms driving
this motion are therefore key to our understanding of how the solar atmosphere
attains the conditions necessary for large energy release.
Aims. We aim to demonstrate and investigate the rotation of sunspots in a 3D
numerical experiment of the emergence of a magnetic flux tube as it rises
through the solar interior and emerges into the atmosphere. Furthermore, we
seek to show that the sub-photospheric twist stored in the interior is injected
into the solar atmosphere by means of a definitive rotation of the sunspots.
Methods. A numerical experiment is performed to solve the 3D resistive
magnetohydrodynamic (MHD) equations using a Lagrangian-Remap code. We track the
emergence of a toroidal flux tube as it rises through the solar interior and
emerges into the atmosphere investigating various quantities related to both
the magnetic field and plasma.
Results. Through detailed analysis of the numerical experiment, we find clear
evidence that the photospheric footprints or sunspots of the flux tube undergo
a rotation. Significant vertical vortical motions are found to develop within
the two polarity sources after the field emerges. These rotational motions are
found to leave the interior portion of the field untwisted and twist up the
atmospheric portion of the field. This is shown by our analysis of the relative
magnetic helicity as a significant portion of the interior helicity is
transported to the atmosphere. In addition, there is a substantial transport of
magnetic energy to the atmosphere. Rotation angles are also calculated by
tracing selected fieldlines; the fieldlines threading through the sunspot are
found to rotate through angles of up to 353 degrees over the course of the
experiment
Tuija Rankama (ed.): Mesolithic Interfaces: Variability in Lithic Technologies in Eastern Fennoscandia. Monographs of the Archaeological Society of Finland 1.
Defence Policy and the Unification of the Canadian Armed Forces: An Analysis
This thesis paper is an analysis of the relationship between defence policy and the unification of the Canadian Armed Forces. While much of the literature and commentary in recent years has centered upon the ‘management’ aspects of unification, this thesis argues that unification was devised in order to re-assert civilian control and direction over the services. Unification then, affects not only the administration of the services, but also, the ‘structuring of influence’ between the civilian authority and the defence establishment, which in turn contributes to the method through which defence priorities are determined.
The thesis also examines the congruence between ‘structuring of influence’ as it pertains to defence policy and the transition in the policy-making process, which was to become evident as the avenues of political input expanded, differentiated and centralized. To this end, the thesis shall discuss the transition in the policy-making process during the tenure of Prime Ministers Diefenbaker, Pearson and Trudeau in relation to the corresponding re-definition of defence priorities
Are Good Deeds Being Punished?: Independent Charity Patient Assistance Programs and the Anti-Kickback Statute
Real-Time Cavity QED with Single Atoms
The combination of cold atoms and large coherent coupling enables investigations in a new regime in cavity QED with single-atom trajectories monitored in real time with high signal-to-noise ratio. The underlying “vacuum-Rabi” splitting is clearly reflected in the frequency dependence of atomic transit signals recorded atom by atom, with evidence for mechanical light forces for intracavity photon number <1. The nonlinear optical response of one atom in a cavity is observed to be in accord with the one-atom quantum theory but at variance with semiclassical predictions
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