13,708 research outputs found
Bethe-Peierls Approximation for Linear Monodisperse Polymers Re-examined
Bethe-Peierls approximation, as it applies to the thermodynamics of polymer
melts, is reviewed. We compare the computed configurational entropy of
monodisperse linear polymer melt with Monte Carlo data available in literature.
An estimation of the configurational contribution to the total liquid's Cp is
presented. We also discuss the relation between Kauzmann paradox and polymer
semiflexibility.Comment: 9 pages, 3 figure
Tools for NLO automation: extension of the golem95C integral library
We present an extension of the program golem95C for the numerical evaluation
of scalar integrals and tensor form factors entering the calculation of
one-loop amplitudes, which supports tensor ranks exceeding the number of
propagators. This extension allows various applications in Beyond the Standard
Model physics and effective theories, for example higher ranks due to
propagators of spin two particles, or due to effective vertices. Complex masses
are also supported. The program is not restricted to the Feynman diagrammatic
approach, as it also contains routines to interface to unitarity-inspired
numerical reconstruction of the integrand at the tensorial level. Therefore it
can serve as a general integral library in automated programs to calculate
one-loop amplitudes.Comment: 17 pages, 1 figure, the program can be downloaded from
http://golem.hepforge.org/95/. arXiv admin note: substantial text overlap
with arXiv:1101.559
Import pathways of precursor proteins into mitochondria
The precursor of porin, a mitochondrial outer membrane protein, competes for the import of precursors destined for the three other mitochondrial compartments, including the Fe/S protein of the bc1- complex (intermembrane space), the ADP/ATP carrier (inner membrane), subunit 9 of the F0-ATPase (inner membrane), and subunit beta of the F1- ATPase (matrix). Competition occurs at the level of a common site at which precursors are inserted into the outer membrane. Protease- sensitive binding sites, which act before the common insertion site, appear to be responsible for the specificity and selectivity of mitochondrial protein uptake. We suggest that distinct receptor proteins on the mitochondrial surface specifically recognize precursor proteins and transfer them to a general insertion protein component (GIP) in the outer membrane. Beyond GIP, the import pathways diverge, either to the outer membrane or to translocation contact-sites, and then subsequently to the other mitochondrial compartments
Trinification, the Hierarchy Problem and Inverse Seesaw Neutrino Masses
In minimal trinification models light neutrino masses can be generated via a
radiative see-saw mechanism, where the masses of the right-handed neutrinos
originate from loops involving Higgs and fermion fields at the unification
scale. This mechanism is absent in models aiming at solving or ameliorating the
hierarchy problem, such as low-energy supersymmetry, since the large
seesaw-scale disappears. In this case, neutrino masses need to be generated via
a TeV-scale mechanism. In this paper, we investigate an inverse seesaw
mechanism and discuss some phenomenological consequences.Comment: 10 pages, 11 figure
The role of gravity on macrosegregation in alloys
During dendritic solidification liquid flow is induced both by buoyancy forces and solidification shrinkage. There is strong evidence that the major reason for the liquid flow is the former, i.e., thermosolutal convection. In the microgravity environment, it is thought that the thermosolutal convection will be greatly diminished so that convection will be confined mainly to the flow of interdendritic liquid required to satisfy the solidification shrinkage. An attempt is made to provide improved models of dendritic solidification with emphasis on convection and macrosegregation. Macrosegregation is an extremely important subject to the commercial casting community. The simulation of thermosolutal convection in directionally solidified (DS) alloys is described. A linear stability analysis was used to predict marginal stability curves for a system that comprises a mushy zone underlying an all-liquid zone. The supercritical thermosolutal convection in directionally solidified dendritic alloys was also modeled. The model assumes a nonconvective initial state with planar and horizontal isotherms and isoconcentration that move upward at a constant solidification velocity. Results are presented for systems involving lead-tin alloys and show significant differences with results of plane-front solidification
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