CONQUEST: A Coarse-Grained Algorithm for Constructing Summaries of Distributed Discrete Datasets

In this paper we present a coarse-grained parallel algorithm, CONQUEST, for constructing bounded-error summaries of high-dimensional binary attributed data in a distributed environment. Such summaries enable more expensive analysis techniques to be applied efficiently under constraints on computation, communication, and privacy with little loss in accuracy. While the discrete and high-dimensional nature of the dataset makes the problem difficult in its serial formulation, the loose-coupling of distributed servers hosting the data and the heterogeneity in network bandwidth present additional challenges. CONQUEST is based on a novel linear algebraic tool, PROXIMUS, which is shown to be highly effective on a serial platform. In contrast to traditional fine-grained parallel techniques that distribute the kernel operations, CONQUEST adopts a coarse-grained parallel formulation that relies on the principle of sampling to reduce communication overhead while maintaining high accuracy. Specifically, each individual site computes its local patterns independently. Various sites cooperate in dynamically orchestrated work groups to construct consensus patterns from these local patterns. Individual sites may then decide to continue their participation in the consensus or leave the group. Such parallel formulation implicitly resolves load-balancing and privacy issues while reducing communication volume significantly. Experimental results on an Intel Xeon cluster demonstrate that this strategy is capable of excellent performance in terms of compression time, ratio, and accuracy with respect to post-processing tasks.     

In-situ generation of large microporous skeleton in mesoporous silica framework using different dicarboxylic acids

Mesoporous Santa Barbara Amorphous-15 is known to possess a small fraction of micropores, in the walls of mesopores. The ratio of micropore to mesopore area can have a profound influence on the application of this highly ordered material in various fields. The present work aims to investigate the influence of dicarboxylic acids as organic structure interrupting agents on the micropore to mesopore ratio. The physiochemical characterization of the synthesized samples including electron microscopy, nitrogen adsorption–desorption isotherms, MAS ²⁹Si-NMR, FT-IR demonstrate a distinct change in the morphology and micropore area due to the different dicarboxylic acids used during synthesis. Our results show that the decrease in chain length of the dicarboxylic acid has a direct relation to the increase in micropore area which has a significant role in the adsorption properties of mesoporous silica. Thus the dicarboxylic acid mediated tuning of the micropores area of mesoporous silica can be used for various applications.     

1,2,3-Triazolophanes—Cyclophanes with an Array of Molecular Structures and Supramolecular Architectures

1,2,3-Triazolophanes are a class of cyclophanes that has attracted enormous attention in recent times. With the advent of the intramolecular copper-mediated alkyne azide cycloaddition (CuAAC) reaction 1,2,3-triazolophanes of various molecular structure and supramolecular architecture have been synthesized. 1,2,3-Triazolophanes find a variety of applications as molecular hosts, ion sensors, peptidomimics, and supramolecular building blocks, among others.     

MRI mediated, non-invasive tracking of intratumoral distribution of nanocarriers in rat glioma

Nanocarrier mediated therapy of gliomas has shown promise. The success of systemic nanocarrier-based chemotherapy is critically dependent on the so-called leaky vasculature to permit drug extravasation across the blood-brain barrier. Yet, the extent of vascular permeability in individual tumors varies widely, resulting in a correspondingly wide range of responses to the therapy. However, there exist no tools currently for rationally determining whether tumor blood vessels are amenable to nanocarrier mediated therapy in an individualized, patient specific manner today. To address this need for brain tumor therapy, we have developed a multifunctional 100?nm scale liposomal agent encapsulating a gadolinium-based contrast agent for contrast-enhanced magnetic resonance imaging with prolonged blood circulation. Using a 9.4?T MRI system, we were able to track the intratumoral distribution of the gadolinium-loaded nanocarrier in a rat glioma model for a period of three days due to improved magnetic properties of the contrast agent being packaged in a nanocarrier. Such a nanocarrier provides a tool for non-invasively assessing the suitability of tumors for nanocarrier mediated therapy and then optimizing the treatment protocol for each individual tumor. Additionally, the ability to image the tumor in high resolution can potentially constitute a surgical planning tool for tumor resection.     

Optical and Electrical Properties of Colloidal Quantum Dots in Electrolytic Environments: Using Biomolecular Links in Chemically-Directed Assembly of Quantum Dot Networks

The threshold of the absorption spectra of colloidal cadmium sulfide (CdS) quantum dots in electrolytic solutions is shown to shift as the concentration of the electrolyte is varied. The shift in the absorption threshold as a function of the electrolytic concentration is given by electrolytic screening of the field caused by the intrinsic spontaneous polarization of these würtzite quantum dots. These electrolyte-dependent absorption properties are compared with Fermi-level tuning in carbon nanotubes in electrolytic environments.Moreover, concepts for integrating such colloidal quantum dots in high density networks with biomolecular links are discussed. Such biomolecular links are used to facilitate the chemically-directed assembly of quantum dots networks with densities approximating 10¹⁷ cm⁻³.     

Effects of in situ and ex situ formations of silica nanoparticles on polyethersulfone membranes

This study deals with the observed changes in the structure and performance of polyethersulfone (PES) membranes due to in situ formation and ex situ addition of silica particles (SiO₂). Hydrolysis and condensation of tetraethyl orthosilicate (TEOS) inside the PES polymer matrix and the reaction of TEOS with ammonium hydroxide were chosen to form in situ and ex situ SiO₂ formations, respectively. The resultant structure confirmed by X-ray diffraction for the composite PES membranes showed the retention of the amorphous nature even after the addition of SiO₂. The FTIR study revealed the functional groups corresponding to silica networks with enhanced OH signatures on the surface of the composite membranes. Field emission scanning electron microscopic images showed the variation in the surface and cross-sectional structures for the pure and composite membranes. Considerable reduction in the thickness of the skin, difference in the pore structure and ‘finger-like’ cross-sectional morphology with the presence of SiO₂ was observed in PES membranes. Both SiO₂/PES composite membranes were showed a minor change in their glass transition temperature (T _g). The ex situ methodically formed composite membrane displayed an increase in the pure water flux and decrease in bovine serum albumin rejection as compared to in situ and pure PES membranes. These kinds of composite membranes can be utilized for water treatment applications demanding higher water flux.     

Electrochemical investigations on cobalt-microencapsulated MmNi2.38Al0.82Co0.66Si0.77Fe0.13Mn0.24 hydrogen storage alloys for Ni–MH batteries

Cobalt coatings were applied over lanthanum process-rich MmNi_2.38Al_0.82Co_0.66Si_0.77Fe_0.13Mn_0.24 alloy particles by an autocatalytic electroless deposition process. Electrode characteristics such as electrochemical capacity and cycle life were studied for the uncoated and coated alloys. The structure and morphology of the surface modified samples were characterized with XRD and SEM/EDAX techniques. The cobalt coating forms a thin layer on the surface of the core material and the coated alloys exhibit a 15% improvement in performance over the bare alloy. A comparison of the electrochemical impedance behaviour of the bare and cobalt-coated metal hydride electrodes at different states-of-charge reveals that the relaxation period is distinct for different SOCs. The cobalt microencapsulations influence the apparent activation energy of the dehydriding process. The calculated equivalent rate constant (k_eq) values confirm the improvement in reversibility for the cobalt-coated alloy as compared to the bare alloy.