1,283 research outputs found
Origin of Discrepancies in Inelastic Electron Tunneling Spectra of Molecular Junctions
We report inelastic electron tunneling spectroscopy (IETS) of multilayer
molecular junctions with and without incorporated metal nano-particles. The
incorporation of metal nanoparticles into our devices leads to enhanced IET
intensity and a modified line-shape for some vibrational modes. The enhancement
and line-shape modification are both the result of a low lying hybrid metal
nanoparticle-molecule electronic level. These observations explain the apparent
discrepancy between earlier IETS measurements of alkane thiolate junctions by
Kushmerick \emph{et al.} [Nano Lett. \textbf{4}, 639 (2004)] and Wang \emph{et
al.} [Nano Lett. \textbf{4}, 643 (2004)].Comment: 4 pages, 4 figures accepted for publication in Physical Review
Letter
Self-supervised automated wrapper generation for weblog data extraction
Data extraction from the web is notoriously hard. Of the types of resources available on the web, weblogs are becoming increasingly important due to the continued growth of the blogosphere, but remain poorly explored. Past approaches to data extraction from weblogs have often involved manual intervention and suffer from low scalability. This paper proposes a fully automated information extraction methodology based on the use of web feeds and processing of HTML. The approach includes a model for generating a wrapper that exploits web feeds for deriving a set of extraction rules automatically. Instead of performing a pairwise comparison between posts, the model matches the values of the web feeds against their corresponding HTML elements retrieved from multiple weblog posts. It adopts a probabilistic approach for deriving a set of rules and automating the process of wrapper generation. An evaluation of the model is conducted on a dataset of 2,393 posts and the results (92% accuracy) show that the proposed technique enables robust extraction of weblog properties and can be applied across the blogosphere for applications such as improved information retrieval and more robust web preservation initiatives
Information Extraction in Illicit Domains
Extracting useful entities and attribute values from illicit domains such as
human trafficking is a challenging problem with the potential for widespread
social impact. Such domains employ atypical language models, have `long tails'
and suffer from the problem of concept drift. In this paper, we propose a
lightweight, feature-agnostic Information Extraction (IE) paradigm specifically
designed for such domains. Our approach uses raw, unlabeled text from an
initial corpus, and a few (12-120) seed annotations per domain-specific
attribute, to learn robust IE models for unobserved pages and websites.
Empirically, we demonstrate that our approach can outperform feature-centric
Conditional Random Field baselines by over 18\% F-Measure on five annotated
sets of real-world human trafficking datasets in both low-supervision and
high-supervision settings. We also show that our approach is demonstrably
robust to concept drift, and can be efficiently bootstrapped even in a serial
computing environment.Comment: 10 pages, ACM WWW 201
Effect of Viscosity on Mechanics of Single, Skinned Fibers from Rabbit Psoas Muscle
AbstractMuscle contraction is highly dynamic and thus may be influenced by viscosity of the medium surrounding the myofilaments. Single, skinned fibers from rabbit psoas muscle were used to test this hypothesis. Viscosity within the myofilament lattice was increased by adding to solutions low molecular weight sugars (disaccharides sucrose or maltose or monosaccharides glucose or fructose). At maximal Ca2+ activation, isometric force (Fi) was inhibited at the highest solute concentrations studied, but this inhibition was not directly related to viscosity. Solutes readily permeated the filament lattice, as fiber diameter was unaffected by added solutes (except for an increased diameter with Fi<30% of control). In contrast, there was a linear dependence upon 1/viscosity for both unloaded shortening velocity and also the kinetics of isometric tension redevelopment; these effects were unrelated to either variation in solution osmolarity or inhibition of force. All effects of added solute were reversible. Inhibition of both isometric as well as isotonic kinetics demonstrates that viscous resistance to filament sliding was not the predominant factor affected by viscosity. This was corroborated by measurements in relaxed fibers, which showed no significant change in the strain-rate dependence of elastic modulus when viscosity was increased more than twofold. Our results implicate cross-bridge diffusion as a significant limiting factor in cross-bridge kinetics and, more generally, demonstrate that viscosity is a useful probe of actomyosin dynamics
Thermodynamic and Kinetic Analysis of Sensitivity Amplification in Biological Signal Transduction
Based on a thermodynamic analysis of the kinetic model for the protein
phosphorylation-dephosphorylation cycle, we study the ATP (or GTP) energy
utilization of this ubiquitous biological signal transduction process. It is
shown that the free energy from hydrolysis inside cells,
(phosphorylation potential), controls the amplification and sensitivity of the
switch-like cellular module; the response coefficient of the sensitivity
amplification approaches the optimal 1 and the Hill coefficient increases with
increasing . We discover that zero-order ultrasensitivity is
mathematically equivalent to allosteric cooperativity. Furthermore, we show
that the high amplification in ultrasensitivity is mechanistically related to
the proofreading kinetics for protein biosynthesis. Both utilize multiple
kinetic cycles in time to gain temporal cooperativity, in contrast to
allosteric cooperativity that utilizes multiple subunits in a protein.Comment: 19 pages, 7 figure
Intelligent Self-Repairable Web Wrappers
The amount of information available on the Web grows at an incredible high rate. Systems and procedures devised to extract these data from Web sources already exist, and different approaches and techniques have been investigated during the last years. On the one hand, reliable solutions should provide robust algorithms of Web data mining which could automatically face possible malfunctioning or failures. On the other, in literature there is a lack of solutions about the maintenance of these systems. Procedures that extract Web data may be strictly interconnected with the structure of the data source itself; thus, malfunctioning or acquisition of corrupted data could be caused, for example, by structural modifications of data sources brought by their owners. Nowadays, verification of data integrity and maintenance are mostly manually managed, in order to ensure that these systems work correctly and reliably. In this paper we propose a novel approach to create procedures able to extract data from Web sources -- the so called Web wrappers -- which can face possible malfunctioning caused by modifications of the structure of the data source, and can automatically repair themselves.\u
Electronic and optical properties of electromigrated molecular junctions
Electromigrated nanoscale junctions have proven very useful for studying
electronic transport at the single-molecule scale. However, confirming that
conduction is through precisely the molecule of interest and not some
contaminant or metal nanoparticle has remained a persistent challenge,
typically requiring a statistical analysis of many devices. We review how
transport mechanisms in both purely electronic and optical measurements can be
used to infer information about the nanoscale junction configuration. The
electronic response to optical excitation is particularly revealing. We briefly
discuss surface-enhanced Raman spectroscopy on such junctions, and present new
results showing that currents due to optical rectification can provide a means
of estimating the local electric field at the junction due to illumination.Comment: 19 pages, 8 figures, invited paper for forthcoming special issue of
Journal of Physics: Condensed Matter. For other related papers, see
http://www.ruf.rice.edu/~natelson/publications.htm
Quantum transport in a resonant tunnel junction coupled to a nanomechanical oscillator
We discuss the quantum transport of electrons through a resonant tunnel
junction coupled to a nanomechanical oscillator at zero temperature. By using
the Green's function technique we calculate the transport properties of
electrons through a single dot strongly coupled to a single oscillator. We
consider a finite chemical potential difference between the right and left
leads. In addition to the main resonant peak of electrons on the dot, we find
satellite peaks due to the creation of phonons. These satellite peaks become
sharper and more significant with increasing coupling strength between the
electrons and the oscillator. We also consider the energy transferred from the
electrons to the oscillator.Comment: Updated in response to referees' comments. Section IV amended
including figure
Instabilities in the transient response of muscle
We investigate the isometric transient response of muscle using a
quantitative stochastic model of the actomyosin cycle based on the swinging
lever-arm hypothesis. We first consider a single pair of filaments, and show
that when values of parameters such as the lever-arm displacement and the
crossbridge elasticity are chosen to provide effective energy transduction, the
T2 curve (the tension recovered immediately after a step displacement) displays
a region of negative slope. If filament compliance and the discrete nature of
the binding sites are taken into account, the negative slope is diminished, but
not eliminated. This implies that there is an instability in the dynamics of
individual half-sarcomeres. However, when the symmetric nature of whole
sarcomeres is taken into account, filament rearrangement becomes important
during the transient: as tension is recovered, some half-sarcomeres lengthen
while others shorten. This leads to a flat T2 curve, as observed
experimentally. In addition, we investigate the isotonic transient response and
show that for a range of parameter values the model displays damped
oscillations, as recently observed in experiments on single muscle fibers. We
conclude that it is essential to consider the collective dynamics of many
sarcomeres, rather than the dynamics of a single pair of filaments, when
interpreting the transient response of muscle.Comment: 11 pages, 11 figures, Submitted to Biophysical Journa
Using the words/leafs ratio in the DOM tree for content extraction
The main content in a webpage is usually centered and visible without the need to scroll. It
is often rounded by the navigation menus of the website and it can include advertisements,
panels, banners, and other not necessarily related information. The process to automatically
extract the main content of a webpage is called content extraction. Content extraction is
an area of research of widely interest due to its many applications. Concretely, it is useful
not only for the final human user, but it is also frequently used as a preprocessing stage of
different systems (i.e., robots, indexers, crawlers, etc.) that need to extract the main content
of a web document to avoid the treatment and processing of other useless information. In
thisworkwe present a newtechnique for content extraction that is based on the information
contained in theDOMtree. The technique analyzes the hierarchical relations of the elements
in the webpage and the distribution of textual information in order to identify the main
block of content. Thanks to the hierarchy imposed by the DOM tree the technique achieves a
considerable recall and precision. Using theDOMstructure for content extraction gives us the
benefits of other approaches based on the syntax of the webpage (such as characters, words
and tags), but it also gives us a very precise information regarding the related components
in a block (not necessarily textual such as images or videos), thus, producing very cohesive
blocks.
© 2013 Elsevier Inc. All rights reserved.This work has been partially supported by the Spanish Ministerio de Economia y Competitividad (Secretaria de Estado de Investigacion, Desarrollo e Innovacion) under Grant TIN2008-06622-C03-02 and by the Generalitat Valenciana under Grant PROMETEO/2011/052. Salvador Tamarit was partially supported by the Spanish MICINN under FPI Grant BES-2009-015019. David Insa was partially supported by the Spanish Ministerio de Eduacion under FPU Grant AP2010-4415.Insa Cabrera, D.; Silva Galiana, JF.; Tamarit, S. (2013). Using the words/leafs ratio in the DOM tree for content extraction. Journal of Logic and Algebraic Programming. 82(8):311-325. https://doi.org/10.1016/j.jlap.2013.01.002S31132582
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