1,961 research outputs found
Social Balance on Networks: The Dynamics of Friendship and Enmity
How do social networks evolve when both friendly and unfriendly relations
exist? Here we propose a simple dynamics for social networks in which the sense
of a relationship can change so as to eliminate imbalanced triads--relationship
triangles that contains 1 or 3 unfriendly links. In this dynamics, a friendly
link changes to unfriendly or vice versa in an imbalanced triad to make the
triad balanced. Such networks undergo a dynamic phase transition from a steady
state to "utopia"--all friendly links--as the amount of network friendliness is
changed. Basic features of the long-time dynamics and the phase transition are
discussed.Comment: 16 pages, 11 figures, paper based on an invited talk at Dyonet06,
Dynamics on Complex Networks and Applications, Dresden, Germany, Feburary
200
Heavy Superheated Droplet Detectors as a Probe of Spin-independent WIMP Dark Matter Existence
At present, application of Superheated Droplet Detectors (SDDs) in WIMP dark
matter searches has been limited to the spin-dependent sector, owing to the
general use of fluorinated refrigerants which have high spin sensitivity. Given
their recent demonstration of a significant constraint capability with
relatively small exposures and the relative economy of the technique, we
consider the potential impact of heavy versions of such devices on the
spin-independent sector. Limits obtainable from a -loaded SDD
are estimated on the basis of the radiopurity levels and backgrounds already
achieved by the SIMPLE and PICASSO experiments. With 34 kgd exposure,
equivalent to the current CDMS, such a device may already probe to below
10 pb in the spin-independent cross section.Comment: 9 pages, 4 figures, accepted Phys. Rev.
Dynamics of Social Balance on Networks
We study the evolution of social networks that contain both friendly and
unfriendly pairwise links between individual nodes. The network is endowed with
dynamics in which the sense of a link in an imbalanced triad--a triangular loop
with 1 or 3 unfriendly links--is reversed to make the triad balanced. With this
dynamics, an infinite network undergoes a dynamic phase transition from a
steady state to "paradise"--all links are friendly--as the propensity p for
friendly links in an update event passes through 1/2. A finite network always
falls into a socially-balanced absorbing state where no imbalanced triads
remain. If the additional constraint that the number of imbalanced triads in
the network does not increase in an update is imposed, then the network quickly
reaches a balanced final state.Comment: 10 pages, 7 figures, 2-column revtex4 forma
Interpol: An R package for preprocessing of protein sequences
<p>Abstract</p> <p>Background</p> <p>Most machine learning techniques currently applied in the literature need a fixed dimensionality of input data. However, this requirement is frequently violated by real input data, such as DNA and protein sequences, that often differ in length due to insertions and deletions. It is also notable that performance in classification and regression is often improved by numerical encoding of amino acids, compared to the commonly used sparse encoding.</p> <p>Results</p> <p>The software "Interpol" encodes amino acid sequences as numerical descriptor vectors using a database of currently 532 descriptors (mainly from AAindex), and normalizes sequences to uniform length with one of five linear or non-linear interpolation algorithms. Interpol is distributed with open source as platform independent R-package. It is typically used for preprocessing of amino acid sequences for classification or regression.</p> <p>Conclusions</p> <p>The functionality of Interpol widens the spectrum of machine learning methods that can be applied to biological sequences, and it will in many cases improve their performance in classification and regression.</p
Wisconsin Farmers Take the 2-Pass Challenge Against Weeds
Single pass herbicide programs have become the standard for most Wisconsin corn producers. The apparent time and cost savings in controlling weeds with a single pre or post-emergence herbicide application is the driving force behind this trend. While there are situations where a single pass program will work, it has weaknesses that can result in inconsistent performance
Ski Promotes Tumor Growth Through Abrogation of Transforming Growth Factor-?? Signaling in Pancreatic Cancer
Objective: We hypothesized that human pancreatic cancer resists TGF-β signaling and cell death through increased Ski expression. Summary Background Data: Ski is an oncogenic protein that acts as a TGF-β repressor and prevents related gene transcription. Previous work suggests that Ski acts as an oncoprotein in melanoma and esophageal cancer. Ski expression and function have not been determined in human pancreatic cancer. Methods: Immunohistochemistry and immunoblots assessed Ski expression in human pancreatic cancer. Panc-1 cells were treated with or without Ski siRNA, and Ski and Smad protein expression, transcriptional reporter activation, and growth assays were determined. Panc-1 cells were inoculated in the flank of nude mice and tumor volume and histology assessed after administration of Ski siRNA or control vector. Results: Ski was abundantly expressed in human pancreatic cancer specimens assessed by immunohistochemistry (91%) and immunoblot analysis (67%). Panc-1 cells exhibited nascent Ski expression that was maximally inhibited 48 hours after transfection with Ski siRNA. TGF-β transcriptional activity was increased 2.5-fold in Ski siRNA-treated cells compared with control (P < 0.05). Ski siRNA increased TGF-β-induced Smad2 phosphorylation and p21 expression. Panc-1 growth in culture was decreased 2-fold at 72 hours. A Ski siRNA expression vector injected into nude mice resulted in a 5-fold decrease in growth. Conclusion: Inhibition of Ski through RNA interference restored TGF-β signaling and growth inhibition in vitro, and decreased tumor growth in vivo
Kink far below the Fermi level reveals new electron-magnon scattering channel in Fe
Many properties of real materials can be modeled using ab initio methods
within a single-particle picture. However, for an accurate theoretical
treatment of excited states, it is necessary to describe electron-electron
correlations including interactions with bosons: phonons, plasmons, or magnons.
In this work, by comparing spin- and momentum-resolved photoemission
spectroscopy measurements to many-body calculations carried out with a newly
developed first-principles method, we show that a kink in the electronic band
dispersion of a ferromagnetic material can occur at much deeper binding
energies than expected (E_b=1.5 eV). We demonstrate that the observed spectral
signature reflects the formation of a many-body state that includes a photohole
bound to a coherent superposition of renormalized spin-flip excitations. The
existence of such a many-body state sheds new light on the physics of the
electron-magnon interaction which is essential in fields such as spintronics
and Fe-based superconductivity.Comment: 6 pages, 2 figure
Exploiting HIV-1 protease and reverse transcriptase cross-resistance information for improved drug resistance prediction by means of multi-label classification
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