544 research outputs found
Differentiating complex network models: An engineering perspective
AbstractNetwork models that can capture the underlying network’s topologies and functionalities are crucial for the development of complex network algorithms and protocols. In the engineering community, the performances of network algorithms and protocols are usually evaluated by running them on a network model. In most if not all reported work, the criteria used to determine such a network model rely on how close it matches the network data in terms of some basic topological characteristics. However, the intrinsic relations between a network topology and its functionalities are still unclear. A question arises naturally: For a network model which can reproduce some topological characteristics of the underlying network, is it reasonable and valid to use this model to be a test-bed for evaluating the network’s performances? To answer this question, we take a close look at several typical complex network models of the AS-level Internet as examples of study. We find that although a model can represent the Internet in terms of topological metrics, it cannot be used to evaluate the Internet performances. Our findings reveal that the approaches using topological metrics to discriminate network models, which have been widely used in the engineering community, may lead to confusing or even incorrect conclusions
Semi-Tensor Product of Hypermatrices with Application to Compound Hypermatrices
The semi-tensor product (STP) of matrices is extended to the STP of
hypermatrices. Some basic properties of the STP of matrices are extended to the
STP of hypermatrices. The hyperdeterminant of hypersquares is introduced. Some
algebraic and geometric structures of matrices are extended to hypermatrices.
Then the compound hypermatrix is proposed. The STP of hypermatrix is used to
compound hypermatrix. Basic properties are proved to be available for compound
hypermatrix.Comment: 8 page
Global Controllability Criteria and Motion Planning of Regular Affine Systems With Drifts
In this article, we give a condition for the global controllability of affine
nonlinear control systems with drifts on Euclidean spaces. Under regularity
assumptions, the condition is necessary and sufficient in the codimension-1 and
codimension-2 cases, and holds for systems of higher codimensions under mild
restrictions. We then investigate motion planning problems for codimension-1
affine systems, and give proof of the global existence of the lift to control
curves for certain drifted systems using the homotopy continuation method
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Hydrophobic, fluorinated silica xerogel for low-k applications.
A new hydrophobic hybrid silica film was synthesized by introducing one silicon precursor (as modifiers) into another precursor (network former). Hybrid films have improved properties. Hydrolysis and condensation of dimethyldiethoxysilane (DMDES) (solvent (EtOH) to DMDES molar ratio R = 4, water to DMDES molar ratio r = 4, 0.01 N HCl catalyst) was analyzed using high-resolution liquid 29Si NMR. It was found that after several hours, DMDES hydrolyzed and condensed into linear and cyclic species. Films from triethoxyfluorosilane (TEFS) have been shown to be promising interlayer dielectric materials for future integrated circuit applications due to their low dielectric constant and high mechanical properties (i.e., Young's modulus (E) and hardness (H)). Co-condensing with TEFS, linear structures from DMDES hydrolysis and condensation reactions rendered hybrid films hydrophobic, and cyclic structures induced the formation of pores. Hydrophobicity characterized by contact angle, thermal stability by thermogravimetric analysis (TGA), Fourier transform Infrared spectroscopy (FTIR), contact angle, and dynamic secondary ion mass spectroscopy (DSIMS), dielectric constant determined by impedance measurement, and mechanical properties (E and H) determined by nanoindentation of TEFS and TEFS + DMDES films were compared to study the effect of DMDES on the TEFS structure. Hybrid films were more hydrophobic and thermally stable. DMDES incorporation affected the dielectric constant, but showed little enhancement of mechanical properties
Insulin-stimulated phosphorylation of protein phosphatase 1 regulatory subunit 12B revealed by HPLC-ESI-MS/MS
BACKGROUND: Protein phosphatase 1 (PP1) is one of the major phosphatases responsible for protein dephosphorylation in eukaryotes. Protein phosphatase 1 regulatory subunit 12B (PPP1R12B), one of the regulatory subunits of PP1, can bind to PP1cδ, one of the catalytic subunits of PP1, and modulate the specificity and activity of PP1cδ against its substrates. Phosphorylation of PPP1R12B on threonine 646 by Rho kinase inhibits the activity of the PP1c-PPP1R12B complex. However, it is not currently known whether PPP1R12B phosphorylation at threonine 646 and other sites is regulated by insulin. We set out to identify phosphorylation sites in PPP1R12B and to quantify the effect of insulin on PPP1R12B phosphorylation by using high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. RESULTS: 14 PPP1R12B phosphorylation sites were identified, 7 of which were previously unreported. Potential kinases were predicted for these sites. Furthermore, relative quantification of PPP1R12B phosphorylation sites for basal and insulin-treated samples was obtained by using peak area-based label-free mass spectrometry of fragment ions. The results indicate that insulin stimulates the phosphorylation of PPP1R12B significantly at serine 29 (3.02 ± 0.94 fold), serine 504 (11.67 ± 3.33 fold), and serine 645/threonine 646 (2.34 ± 0.58 fold). CONCLUSION: PPP1R12B was identified as a phosphatase subunit that undergoes insulin-stimulated phosphorylation, suggesting that PPP1R12B might play a role in insulin signaling. This study also identified novel targets for future investigation of the regulation of PPP1R12B not only in insulin signaling in cell models, animal models, and in humans, but also in other signaling pathways
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