1,460 research outputs found
Helen Coleman, Ruby Joscelyn Dunn and Geoffrey Dunn to James H. Meredith (5 October 1962)
https://egrove.olemiss.edu/mercorr_pro/1833/thumbnail.jp
Spin dependent masses and Sim(2) symmetry
Recently, Cohen and Glashow pointed out that all known experimental tests of
relativistic kinematics are consistent with invariance of physics under the
four-parameter subgroup Sim(2) of the Lorentz group. The massive one-particle
irreducible representations of ISim(2), that is Sim(2) times spacetime
translations, are all one-dimensional, labeled by spin along a preferred axis.
Consequently particle theories based on this symmetry can accomodate lepton
number conserving masses for left-handed neutrinos without the need to
introduce sterile states. The same property of massive particle
representations, however, also leads to the possibility that particle masses
may be split within the diffferent spins of a representation of the ordinary
Poincare group. In this article we investigate the low-energy structure of
theories with spin dependent masses and comment on the bounds on such effects.Comment: 6 page
Thermodynamics of non-local materials: extra fluxes and internal powers
The most usual formulation of the Laws of Thermodynamics turns out to be
suitable for local or simple materials, while for non-local systems there are
two different ways: either modify this usual formulation by introducing
suitable extra fluxes or express the Laws of Thermodynamics in terms of
internal powers directly, as we propose in this paper. The first choice is
subject to the criticism that the vector fluxes must be introduced a posteriori
in order to obtain the compatibility with the Laws of Thermodynamics. On the
contrary, the formulation in terms of internal powers is more general, because
it is a priori defined on the basis of the constitutive equations. Besides it
allows to highlight, without ambiguity, the contribution of the internal powers
in the variation of the thermodynamic potentials. Finally, in this paper, we
consider some examples of non-local materials and derive the proper expressions
of their internal powers from the power balance laws.Comment: 16 pages, in press on Continuum Mechanics and Thermodynamic
Efficacy of exercise counselling as an aid for smoking cessation: a randomized controlled trial.
To examine whether exercise counselling increases smoking abstinence and reduces tobacco withdrawal and gains in weight and body fat
Bone segmentation and 3D visualization of CT images for traumatic pelvic injuries
Pelvic bone segmentation is a vital step in analyzing pelvic CT images, which assists physicians with diagnostic decision making in cases of traumatic pelvic injuries. Due to the limited resolution of the original CT images and the complexity of pelvic structures and their possible fractures, automatic pelvic bone segmentation in multiple CT slices is very difficult. In this study, an automatic pelvic bone segmentation approach is proposed using the combination of anatomical knowledge and computational techniques. It is developed for solving the problem of accurate and efficient bone segmentation using multiple consecutive pelvic CT slices obtained from each patient. Our proposed segmentation method is able to handle variation of bone shapes between slices there by making it less susceptible to inter‐personal variability between different patients' data. Moreover, the designed training models are validated using a cross‐validation process to demonstrate the effectiveness. The algorithm's capability is tested on a set of 20 CT data sets. Successful segmentation results and quantitative evaluations are present to demonstrate the effectiveness and robustness of proposed algorithm, well suited for pelvic bone segmentation purposes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106095/1/ima22076.pd
Myo4p and She3p are required for cortical ER inheritance in Saccharomyces cerevisiae
Myo4p is a nonessential type V myosin required for the bud tip localization of ASH1 and IST2 mRNA. These mRNAs associate with Myo4p via the She2p and She3p proteins. She3p is an adaptor protein that links Myo4p to its cargo. She2p binds to ASH1 and IST2 mRNA, while She3p binds to both She2p and Myo4p. Here we show that Myo4p and She3p, but not She2p, are required for the inheritance of cortical ER in the budding yeast Saccharomyces cerevisiae. Consistent with this observation, we find that cortical ER inheritance is independent of mRNA transport. Cortical ER is a dynamic network that forms cytoplasmic tubular connections to the nuclear envelope. ER tubules failed to grow when actin polymerization was blocked with the drug latrunculin A (Lat-A). Additionally, a reduction in the number of cytoplasmic ER tubules was observed in Lat-A–treated and myo4Δ cells. Our results suggest that Myo4p and She3p facilitate the growth and orientation of ER tubules
Molecular architecture of Gαo and the structural basis for RGS16-mediated deactivation
Heterotrimeric G proteins relay extracellular cues from heptahelical transmembrane receptors to downstream effector molecules. Composed of an α subunit with intrinsic GTPase activity and a βγ heterodimer, the trimeric complex dissociates upon receptor-mediated nucleotide exchange on the α subunit, enabling each component to engage downstream effector targets for either activation or inhibition as dictated in a particular pathway. To mitigate excessive effector engagement and concomitant signal transmission, the Gα subunit's intrinsic activation timer (the rate of GTP hydrolysis) is regulated spatially and temporally by a class of GTPase accelerating proteins (GAPs) known as the regulator of G protein signaling (RGS) family. The array of G protein-coupled receptors, Gα subunits, RGS proteins and downstream effectors in mammalian systems is vast. Understanding the molecular determinants of specificity is critical for a comprehensive mapping of the G protein system. Here, we present the 2.9 Å crystal structure of the enigmatic, neuronal G protein Gαo in the GTP hydrolytic transition state, complexed with RGS16. Comparison with the 1.89 Å structure of apo-RGS16, also presented here, reveals plasticity upon Gαo binding, the determinants for GAP activity, and the structurally unique features of Gαo that likely distinguish it physiologically from other members of the larger Gαi family, affording insight to receptor, GAP and effector specificity
Stokes' first problem for some non-Newtonian fluids: Results and mistakes
The well-known problem of unidirectional plane flow of a fluid in a
half-space due to the impulsive motion of the plate it rests upon is discussed
in the context of the second-grade and the Oldroyd-B non-Newtonian fluids. The
governing equations are derived from the conservation laws of mass and momentum
and three correct known representations of their exact solutions given. Common
mistakes made in the literature are identified. Simple numerical schemes that
corroborate the analytical solutions are constructed.Comment: 10 pages, 2 figures; accepted for publication in Mechanics Research
Communications; v2 corrects a few typo
SIM(2)-invariant Modifications of Electrodynamic Theory
In the Cohen-Glashow Very Special Relativity we exhibit possible
modifications to the Maxwell theory and to the quantum electrodynamics
Lagrangian in some generality, and discuss characteristic features depending on
the modifications. Modified gauge transformations in SIM(2)-invariant theories
are introduced, and in these theories gauge fields with two polarization states
can have nonzero mass. Also considered are SIM(2)-covariant modifications to
the Proca-type field equations for a massive spin-1 particle
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