11,137 research outputs found
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Self-routing lowest common ancestor networks
Multistage interconnection networks (MIN's) allow communication between terminals on opposing sides of a network. Lowest Common Ancestor Networks (LCAN's) [1] have switches capable of connecting bi-directional links in a permutation pattern that additionally permits communication between terminals on the same side. Self-routing LCAN's have interesting permutation routing capabilities and are highly partionable. This paper characterizes self-routing LCAN's and analyzes their permutation routing capabilities. It is shown that the routing network of the CM-5 is a particular instance of an LCAN
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Lowest common ancestor interconnection networks
Lowest Common Ancestor (LCA) networks are built using switches capable of connecting u + d inputs/outputs in a permutation pattern. For n source nodes and I stages of switches, n/d switches are used in stage l - n/d - u/d in stage l - 2, and in general , n-u^l-i-l/d^l-i switches in stage i. The resulting hierarchical structure possesses interesting connectivity and permutational properties. A full characterization of LCA networks is presented together with a permutation routing algorithm for a family of LCA networks. The algorithm uses the network itself to collect and disseminate information about the permutation. A schedule of O(dp log_d/u n) passes is obtained with a switch set-up cost factor of O(log_d/u n) (p is the minimum number of passes that an algorithm with global knowledge schedules)
Zero bias conductance peak in Majorana wires made of semiconductor-superconductor hybrid structures
Motivated by a recent experimental report[1] claiming the likely observation
of the Majorana mode in a semiconductor-superconductor hybrid
structure[2,3,4,5], we study theoretically the dependence of the zero bias
conductance peak associated with the zero-energy Majorana mode in the
topological superconducting phase as a function of temperature, tunnel barrier
potential, and a magnetic field tilted from the direction of the wire for
realistic wires of finite lengths. We find that higher temperatures and tunnel
barriers as well as a large magnetic field in the direction transverse to the
wire length could very strongly suppress the zero-bias conductance peak as
observed in Ref.[1]. We also show that a strong magnetic field along the wire
could eventually lead to the splitting of the zero bias peak into a doublet
with the doublet energy splitting oscillating as a function of increasing
magnetic field. Our results based on the standard theory of topological
superconductivity in a semiconductor hybrid structure in the presence of
proximity-induced superconductivity, spin-orbit coupling, and Zeeman splitting
show that the recently reported experimental data are generally consistent with
the existing theory that led to the predictions for the existence of the
Majorana modes in the semiconductor hybrid structures in spite of some apparent
anomalies in the experimental observations at first sight. We also make several
concrete new predictions for future observations regarding Majorana splitting
in finite wires used in the experiments.Comment: 5 pages, 6 figures: revised submitted versio
Microscopic Approach to Shear Viscosities in Superfluid Gases: From BCS to BEC
We compute the shear viscosity, , at general temperatures , in a
BCS-BEC crossover scheme which is demonstrably consistent with conservation
laws. The study of is important because it constrains microscopic
theories by revealing the excitation spectra. The onset of a normal state
pairing gap and the contribution from pair degrees of freedom imply that
at low becomes small, rather than exhibiting the upturn predicted by most
others. Using the local density approximation, we find quite reasonable
agreement with just-published experiments.Comment: 4 pages, 2 figure
Comment on "Density and Spin response of a strongly-interacting Fermi gas in the attractive and quasi-repulsive regime"
This is a comment on Phys. Rev. Lett. 108, 080401 (2012) by Palestini et al.
We pointed out that the diagrammatic method in that article violates gauge
invariance. As a consequence, there will a Meissner effect in the normal phase
and the contribution from collective modes are not mentioned in the
symmetry-broken phase.Comment: 1 page, no figur
A New Experiment to Study Hyperon CP Violation and the Charmonium System
Fermilab operates the world's most intense antiproton source, now exclusively
dedicated to serving the needs of the Tevatron Collider. The anticipated 2009
shutdown of the Tevatron presents the opportunity for a world-leading low- and
medium-energy antiproton program. We summarize the status of the Fermilab
antiproton facility and review physics topics for which a future experiment
could make the world's best measurements.Comment: 16 pages, 3 figures, to appear in Proceedings of CTP symposium on
Supersymmetry at LHC: Theoretical and Experimental Perspectives, The British
University in Egypt, Cairo, Egypt, 11-14 March 200
Enzymatic Cross-Linking of Dynamic Thiol-Norbornene Click Hydrogels
Enzyme-mediated in situ forming hydrogels are attractive for many biomedical applications because gelation afforded by enzymatic reactions can be readily controlled not only by tuning macromer compositions, but also by adjusting enzyme kinetics. For example, horseradish peroxidase (HRP) has been used extensively for in situ cross-linking of macromers containing hydroxyl-phenol groups. The use of HRP to initiate thiol-allylether polymerization has also been reported, yet no prior study has demonstrated enzymatic initiation of thiol-norbornene gelation. In this study, we discovered that HRP can generate the thiyl radicals needed for initiating thiol-norbornene hydrogelation, which has only been demonstrated previously using photopolymerization. Enzymatic thiol-norbornene gelation not only overcomes light attenuation issue commonly observed in photopolymerized hydrogels, but also preserves modularity of the cross-linking. In particular, we prepared modular hydrogels from two sets of norbornene-modified macromers, 8-arm poly(ethylene glycol)-norbornene (PEG8NB) and gelatin-norbornene (GelNB). Bis-cysteine-containing peptides or PEG-tetra-thiol (PEG4SH) was used as a cross-linker for forming enzymatically and orthogonally polymerized hydrogel. For HRP-initiated PEG-peptide hydrogel cross-linking, gelation efficiency was significantly improved via adding tyrosine residues on the peptide cross-linkers. Interestingly, these additional tyrosine residues did not form permanent dityrosine cross-links following HRP-induced gelation. As a result, they remained available for tyrosinase-mediated secondary cross-linking, which dynamically increased hydrogel stiffness. In addition to material characterizations, we also found that both PEG- and gelatin-based hydrogels exhibited excellent cytocompatibility for dynamic 3D cell culture. The enzymatic thiol-norbornene gelation scheme presented here offers a new cross-linking mechanism for preparing modularly and dynamically cross-linked hydrogels
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