5,164 research outputs found
The cytochemical localization of adenyl cyclase activity in rat sublingual gland
Adenyl cyclase activity in mucous acinar cells and serous demilune cells of the rat sublingual gland was localized cytochemically. After incubation with adenylyl-imidodiphosphate (AMP-PNP) as substrate, deposits of reaction product are found along the cell membranes bordering the secretory surfaces of serous demilune cells. These are the membranes which participate directly in secretion by fusing with the granule membranes. The granule membranes of the demilune cells do not reveal reaction product, but the membranes of the granules which are fused with and become part of the cell membrane do show deposits. Thus, it appears that the cell membranes which fuse with granule membranes during secretion are associated with a high level of adenyl cyclase activity. In support of this, the luminal membranes of the mucous acinar cells which do not fuse with granule membranes during secretion are not associated with detectable amounts of adenyl cyclase activity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49675/1/1001440407_ftp.pd
Double-Well Potential : The WKB Approximation with Phase Loss and Anharmonicity Effect
We derive a general WKB energy splitting formula in a double-well potential
by incorporating both phase loss and anharmonicity effect in the usual WKB
approximation. A bare application of the phase loss approach to the usual WKB
method gives better results only for large separation between two potential
minima. In the range of substantial tunneling, however, the phase loss approach
with anharmonicity effect considered leads to a great improvement on the
accuracy of the WKB approximation.Comment: 14 pages, revtex, 1 figure, will appear at Phys. Rev.
A finite element simulation for orthogonal cutting of UD-CFRP incorporating a novel fibre - matrix interface model
AbstractThe rapid increase in industrial utilisation of carbon fibre reinforced plastic (CFRP) composites in recent years has led to growing interest in numerical modelling of material behaviour and defect formation when machining CFRP. The inhomogeneous/anisotropic nature of CFRP however presents considerable challenges in accurately modelling workpiece defects such as debonding between the matrix and fibre phase following cutting operations. Much of the published literature has involved the use of zero thickness cohesive elements to represent the fibre-matrix interface, despite the inability of such elements to model compressive stresses. This paper details a new approach for characterising the interface region in a two-dimensional explicit finite element simulation when orthogonal machining unidirectional (UD) CFRP laminates. A cohesive zone model based on a traction-separation law is applied to small thickness (0.25ÎŒm) interface elements in order to accommodate compressive failure, which is implemented via a bespoke user subroutine. Fibre fracture is based on a maximum principal stress criterion while elastic-plastic behaviour to failure is used to represent matrix damage. The influence of varying fibre orientations (45°, 90°, 135°) on predicted cutting and thrust forces were validated against published experimental data. While the former was generally within 5% of experimental data for workpieces with 90° and 135° fibre directions, predicted thrust forces were typically underestimated by âŒ30-60%. The corresponding chip formation mechanisms and sub-surface damage due to the different material phases were also investigated. The proposed model was able to predict composite behaviour and defect formation that was comparable to experimental high speed camera images outlined in the literature
Instantonic approach to triple well potential
By using a usual instanton method we obtain the energy splitting due to
quantum tunneling through the triple well barrier. It is shown that the term
related to the midpoint of the energy splitting in propagator is quite
different from that of double well case, in that it is proportional to the
algebraic average of the frequencies of the left and central wells.Comment: Revtex, 11 pages, Included one eps figur
A Multi-dimensional Code for Isothermal Magnetohydrodynamic Flows in Astrophysics
We present a multi-dimensional numerical code to solve isothermal
magnetohydrodynamic (IMHD) equations for use in modeling astrophysical flows.
First, we have built a one-dimensional code which is based on an explicit
finite-difference method on an Eulerian grid, called the total variation
diminishing (TVD) scheme. Recipes for building the one-dimensional IMHD code,
including the normalized right and left eigenvectors of the IMHD Jacobian
matrix, are presented. Then, we have extended the one-dimensional code to a
multi-dimensional IMHD code through a Strang-type dimensional splitting. In the
multi-dimensional code, an explicit cleaning step has been included to
eliminate non-zero at every time step. To estimate the
proformance of the code, one- and two-dimensional IMHD shock tube tests, and
the decay test of a two-dimensional Alfv\'{e}n wave have been done. As an
example of astrophysical applications, we have simulated the nonlinear
evolution of the two-dimensional Parker instability under a uniform gravity.Comment: Accepted for publication in ApJ, using aaspp4.sty, 22 text pages with
10 figure
Studies on Hypoxia: XI. Long-Term Effects on the Epiphyseal PlateâA Histomeric and Radioautographic Study
Rats were exposed to hypoxia for one week. The mean thickness of epiphyseal plates from control rats was 430 micrometers (ÎŒm) which was reduced to 313 ÎŒm in hypoxic rats. Radioautographic incorporation of 3H-phenylalanine by connective tissue cells in hypoxic rats was reduced up to 38% in control rats.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66916/2/10.1177_00220345760550031301.pd
Massive torsion modes, chiral gravity, and the Adler-Bell-Jackiw anomaly
Regularization of quantum field theories introduces a mass scale which breaks
axial rotational and scaling invariances. We demonstrate from first principles
that axial torsion and torsion trace modes have non-transverse vacuum
polarization tensors, and become massive as a result. The underlying reasons
are similar to those responsible for the Adler-Bell-Jackiw (ABJ) and scaling
anomalies. Since these are the only torsion components that can couple
minimally to spin 1/2 particles, the anomalous generation of masses for these
modes, naturally of the order of the regulator scale, may help to explain why
torsion and its associated effects, including CPT violation in chiral gravity,
have so far escaped detection. As a simpler manifestation of the reasons
underpinning the ABJ anomaly than triangle diagrams, the vacuum polarization
demonstration is also pedagogically useful. In addition it is shown that the
teleparallel limit of a Weyl fermion theory coupled only to the left-handed
spin connection leads to a counter term which is the Samuel-Jacobson-Smolin
action of chiral gravity in four dimensions.Comment: 7 pages, RevTeX fil
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