Fast Binary Embeddings and Quantized Compressed Sensing with Structured Matrices

This paper deals with two related problems, namely distance-preserving binary embeddings and quantization for compressed sensing. First, we propose fast methods to replace points from a subset Χ ⊂ ℝⁿ , associated with the euclidean metric, with points in the cube {±1}^m , and we associate the cube with a pseudometric that approximates euclidean distance among points in Χ. Our methods rely on quantizing fast Johnson-Lindenstrauss embeddings based on bounded orthonormal systems and partial circulant ensembles, both of which admit fast transforms. Our quantization methods utilize noise shaping, and include sigma-delta schemes and distributed noise-shaping schemes. The resulting approximation errors decay polynomially and exponentially fast in m, depending on the embedding method. This dramatically outperforms the current decay rates associated with binary embeddings and Hamming distances. Additionally, it is the first such binary embedding result that applies to fast Johnson-Lindenstrauss maps while preserving ℓ₂ norms. Second, we again consider noise-shaping schemes, albeit this time to quantize compressed sensing measurements arising from bounded orthonormal ensembles and partial circulant matrices. We show that these methods yield a reconstruction error that again decays with the number of measurements (and bits), when using convex optimization for reconstruction. Specifically, for sigma-delta schemes, the error decays polynomially in the number of measurements, and it decays exponentially for distributed noise-shaping schemes based on beta encoding. These results are near optimal and the first of their kind dealing with bounded orthonormal systems. © 2019 Wiley Periodicals, Inc.     

Iminosugar‐Cyclopeptoid Conjugates Raise Multivalent Effect in Glycosidase Inhibition at Unprecedented High Levels

A series of cyclopeptoid‐based iminosugar clusters has been evaluated to finely probe the ligand content‐dependent increase in α‐mannosidase inhibition. This study led to the largest binding enhancement ever reported for an enzyme inhibitor (up to 4700‐fold on a valency‐corrected basis), which represents a substantial advance over the multivalent glycosidase inhibitors previously reported. Electron microscopy imaging and analytical data support, for the best multivalent effects, the formation of a strong chelate complex in which two mannosidase molecules are cross‐linked by one inhibitor.     

Directional Metric Pseudo Subregularity of Set-valued Mappings: a General Model

Set-Valued and Variational Analysis - This paper investigates a new general pseudo subregularity model which unifies some important nonlinear (sub)regularity models studied recently in the...     

A hydrogen-bonded dichloromethane-perchlorate-water channel in the crystal structure ofcis-[Ru(bpy)2{PPh-(o-tolyl)2}Cl+][ClO4 −]·CH2Cl2·H2O

The complexcis-[Ru(bpy)₂{PPh(o-tolyl)₂}Cl⁺][ClO₄ ^–] crystallized from a solution in dichloromethane as the dichloromethane-water solvate. The structure was refined toR=4.5% for those 2433 reflections with |F _o|>6(|F _o|). The octahedral Ru(II) cation is associated with metal-ligand distances as follows: Ru–Cl=2.434(3)Å, Ru-PPh(o-tol)₂=2.382(2)Å, and Ru–N=2.037(7)–2.088(7)Å. The structure is stabilized by a hydrogen-bonded CH₂Cl₂...ClO₄ ^–...H₂O channel which incorporates adventitious water of crystallization.     

Special issue on “The Eighth International Symposium on Information and Communication Technology—SoICT 2017”

Journal of Heuristics -     

Tuning crystal structure of iridium-incorporated titanium dioxide nanosupport and its influence on platinum catalytic performance in direct ethanol fuel cells

Titanium dioxide (TiO₂) has recently been used as a promising support for platinum (Pt)-based catalysts; however, its very low electrical conductivity and understanding the effect of the TiO₂ structure on Pt electrocatalytic performance for ethanol electro-oxidation reaction (EOR) are major challenges in direct ethanol fuel cells. This study reports an easy and green approach to control the crystal structures of a robust iridium-incorporated TiO₂ nanomaterial and its effect on the Pt electrocatalytic performance for EOR. A green hydrothermal route is used to fabricate iridium-modified TiO₂ nanosupports with different structures by controlling the reaction temperature and time as well as solution pH without using further calcination, followed by the anchoring of Pt nanoparticles (NPs) via a surfactant-free modified reduction route. The experimental results indicate that the pure structure of the iridium-modified TiO₂ nanosupport can easily be obtained by controlling the solution pH. In terms of EOR, all prepared catalysts show more effective performance than the commercial Pt/C catalyst. Among the prepared catalysts, the Pt anchored on the rutile iridium-incorporated TiO₂ exhibits higher EOR performance than on the anatase iridium-incorporated TiO₂ nanosupport, with negative onset potential, high current density, and electrochemical stability. The enhancement is assigned to the great adsorption and desorption ability as well as the high natural resistance to metal NPs ripening on (110) facets of the rutile structure compared with the (101) facets of the anatase structure. This exploration can offer an efficient route for tuning the structure of metal oxides and understanding the effect of the structure of the TiO₂-based support on the Pt catalytic performance.