Self-Assembly of an Octanuclear Platinum(II) Tetragonal Prism from a New Pt-4(II) Organometallic Star-Shaped Acceptor and Its Nitroaromatic Sensing Study

2 + 4] self-assembly of a pyrene-functionalized Pt-8(II) tetragonal prism (2) is achieved using a newly designed star-shaped organometallic acceptor (1) in combination with an amide-based ``clip'' donor (L). The propensity of this prism (2) as a selective sensor for nitroaromatics (2,4-dinitrotoluene, 1,3,5-trinitrotoluene, and picric acid), which are the chemical constituents of many commercial explosives, has been examined.

From Molecular to Supramolecular: An Exploration into the Modes of Self-assembly in Conformationally Locked Polycyclitols

This brief account highlights the notable findings of our investigation into the supramolecular chemistry of conformationally locked polycyclitols in the solid state. The study was aimed at analyzing the crystal packing and unraveling the modalities of non-covalent interactions (particularly, intramolecular vis-a-vis intermolecular OH center dot center dot center dot O hydrogen bonds) in polyols. The know-how obtained thereof, was successfully utilized to engineer self-assemblies of designer polycyclitols, having hydrogen bond donors and acceptors fettered onto a trans-decalin scaffold. The results seek to draw particular attention to the intrinsic attribute of this rigid carbocyclic framework to lock functional groups into spatially invariant positions and bring potential intramolecular hydrogen bonding partners into favorable interaction geometry to engender predictability in the self-assembly patterns.

Spectral moment sum rules for the retarded Green's function and self-energy of the inhomogeneous Bose-Hubbard model in equilibrium and nonequilibrium

We derive exact expressions for the zeroth and the first three spectral moment sum rules for the retarded Green's function and for the zeroth and the first spectral moment sum rules for the retarded self-energy of the inhomogeneous Bose-Hubbard model in nonequilibrium, when the local on-site repulsion and the chemical potential are time-dependent, and in the presence of an external time-dependent electromagnetic field. We also evaluate these expressions for the homogeneous case in equilibrium, where all time dependence and external fields vanish. Unlike similar sum rules for the Fermi-Hubbard model, in the Bose-Hubbard model case, the sum rules often depend on expectation values that cannot be determined simply from parameters in the Hamiltonian like the interaction strength and chemical potential but require knowledge of equal-time many-body expectation values from some other source. We show how one can approximately evaluate these expectation values for the Mott-insulating phase in a systematic strong-coupling expansion in powers of the hopping divided by the interaction. We compare the exact moment relations to the calculated moments of spectral functions determined from a variety of different numerical approximations and use them to benchmark their accuracy. DOI: 10.1103/PhysRevA.87.013628

Coordination self-assembly of tetranuclear Pt(II) macrocycles with an organometallic backbone for sensing of acyclic dicarboxylic acids

Coordination self-assembly of a series of tetranuclear Pt(II) macrocycles containing an organometallic backbone incorporating ethynyl functionality is presented. The 1 : 1 combination of a linear acceptor 1,4-bistrans-Pt(PEt3)(2)(NO3)(ethynyl)]benzene (1) with three different dipyridyl donor `clips' (L-a-L-c) afforded three 2 + 2] self-assembled Pt-4(II) macrocycles (2a-2c) in quantitative yields, respectively L-a = 1,3-bis-(3-pyridyl)isothalamide; L-b = 1,3-bis(3-pyridyl)ethynylbenzene; L-c = 1,8-bis(4-pyridyl)ethynylanthracene]. These macrocycles were characterized by multinuclear NMR (H-1 and P-31); ESI-MS spectroscopy and the molecular structures of 2a and 2b were established by single crystal X-ray diffraction analysis. These macrocycles (2a-2c) are fluorescent in nature. The amide functionalized macrocycle 2a is used as a receptor to check the binding affinity of aliphatic acyclic dicarboxylic acids. Such binding affinity is examined using fluorescence and UV-Vis spectroscopic methods. A solution state fluorescence study showed that macrocycle 2a selectively binds (K-SV = 1.4 x 10(4) M-1) maleic acid by subsequent enhancement in emission intensity. Other aliphatic dicarboxylic acids such as fumaric, succinic, adipic, mesaconic and itaconic acids caused no change in the emission spectra; thereby demonstrating its potential use as a macrocyclic receptor in distinction of maleic acid from other aliphatic dicarboxylic acids.

Relative roles of instruction count and cycles per instruction in WCET estimation

Most of the existing WCET estimation methods directly estimate execution time, ET, in cycles. We propose to study ET as a product of two factors, ET = IC * CPI, where IC is instruction count and CPI is cycles per instruction. Considering directly the estimation of ET may lead to a highly pessimistic estimate since implicitly these methods may be using worst case IC and worst case CPI. We hypothesize that there exists a functional relationship between CPI and IC such that CPI=f(IC). This is ascertained by computing the covariance matrix and studying the scatter plots of CPI versus IC. IC and CPI values are obtained by running benchmarks with a large number of inputs using the cycle accurate architectural simulator, Simplescalar on two different architectures. It is shown that the benchmarks can be grouped into different classes based on the CPI versus IC relationship. For some benchmarks like FFT, FIR etc., both IC and CPI are almost a constant irrespective of the input. There are other benchmarks that exhibit a direct or an inverse relationship between CPI and IC. In such a case, one can predict CPI for a given IC as CPI=f(IC). We derive the theoretical worst case IC for a program, denoted as SWIC, using integer linear programming(ILP) and estimate WCET as SWIC*f(SWIC). However, if CPI decreases sharply with IC then measured maximum cycles is observed to be a better estimate. For certain other benchmarks, it is observed that the CPI versus IC relationship is either random or CPI remains constant with varying IC. In such cases, WCET is estimated as the product of SWIC and measured maximum CPI. It is observed that use of the proposed method results in tighter WCET estimates than Chronos, a static WCET analyzer, for most benchmarks for the two architectures considered in this paper.

Self-Adapting Peripherally Heterofunctionalized Hyperbranched Polymers: Formation of Janus and Tripodal Structures

A peripherally clickable hyperbranched polyester carrying numerous propargyl terminal groups was prepared by a simple melt transesterification polycondensation of a suitably designed AB(2) monomer; this clickable hyperscaffold was then transformed into a variety of different derivatives by using the Cu-catalyzed azide-yne click reaction. Functionalization of the periphery with equimolar quantities of mutually immiscible segments, such as hydrocarbon, fluorocarbon, and PEG, yielded frustrated molecular systems that readapt and form structures wherein the immiscible segments appear to self-segregate to generate either Janus structures (when two immiscible segments are present) or tripodal structures (when three immiscible segments are present). Evidence for such self-segregation was obtained from a variety of studies, such as differential scanning calorimetry, Langmuir isotherms, AFM imaging, and small-angle X-ray scattering measurements. Crystallization of one or more of the peripheral segments reinforced this self-segregation; the weight-fraction-normalized enthalpies of melting associated with the different domains revealed a competition between the segments to optimize their crystalline organization. When one or more of the segments are amorphous, the remaining segments crystallize more effectively and consequently exhibit a higher melting enthalpy. AFM images of monolayers, transferred from the Langmuir trough, revealed that the thickness matches the expected values; furthermore, contact angle measurements clearly demonstrated that the monolayer films are fairly hydrophobic, and in the case of the tripodal hybramers, the presence of domains of hydrocarbon and fluorocarbon appears to impart nanoscale chemical heterogeneity that is reflected in the strong hysteresis in the advancing and receding contact angles.

Self catalytic growth of SnO2 branched nanowires by thermal evaporation

For the first time, Tin oxide (SnO2) multiple branched nanowires (NWs) have been synthesized by thermal evaporation of tin (Sn) in presence of oxygen without use of metal catalysts at low substrate temperature of 500 degrees C. Synthesized product consists of multiple branched nanowires and were single crystalline in nature. Each of the nanowire capped with catalyst particle at their ends. Energy dispersive X-ray analysis on the nanowires and capped nanoparticle confirms that Sn act as catalyst for SnO2 nanowires growth. A self catalytic vapor-liquid-solid (VLS) growth mechanism was proposed to describe the SnO2 nanowires growth. (C) 2012 Elsevier B.V. All rights reserved.

Multi-component, Self-assembled, Functional Soft Materials

Supramolecular chemistry is an emerging tool for devising materials that can perform specified functions. The self-assembly of facially amphiphilic bile acid molecules has been extensively utilized for the development of functional soft materials. Supramolecular hydrogels derived from the bile acid backbone act as useful templates for the intercalation of multiple components. Based on this, synthesis of gel-nanoparticle hybrid materials, photoluminescent coating materials, development of a new enzyme assay technique, etc. were achieved in the author's laboratory. The present account highlights some of these achievements.

Fracture processes of self compacting Concrete using image analysis

The mode I fracture toughness of concrete can be experimentally determined using three point bend beam in conjunction with digital image correlation (DIC). Three different geometrically similar sizes of beams are cast for this study. To study the influence of fly ash and silica fume on fracture toughness of SCC, three SCC mixes are prepared with and without mineral additions. The scanning electron microscope (SEM) images are taken on the fractured surface to add information on fracture process in SCC. From this study, it is concluded that the fracture toughness of SCC with mineral addition is higher when compared to those without mineral addition.

Physics-Based Solution for Electrical Resistance of Graphene Under Self-Heating Effect

In this brief, we present a physics-based solution for the temperature-dependent electrical resistance of a suspended metallic single-layer graphene (SLG) sheet under Joule self-heating. The effect of in-plane and flexural phonons on the electron scattering rates for a doped SLG layer has been considered, which particularly demonstrates the variation of the electrical resistance with increasing temperature at different current levels using the solution of the self-heating equation. The present solution agrees well with the available experimental data done with back-gate electrostatic method over a wide range of temperatures.

Multicomponent self-sorting of a Pd-7 molecular boat and its use in catalytic Knoevenagel condensation

Unique three-component self-assembly of a cis-blocked 90 degrees Pd(II) acceptor with amixture of tri- and tetra-imidazole donors led to the self-sorting of a Pd-7 molecular boat with an internal nanocavity, which catalyses the Knoevenagel condensation of a series of aromatic aldehydes with 1,3-dimethylbarbituric acid and Meldrum's acid in aqueous media.

Pt-Ru decorated self-assembled TiO2-carbon hybrid nanostructure for enhanced methanol electrooxidation

Porous titanium oxide-carbon hybrid nanostructure (TiO2-C) with a specific surface area of 350 m(2)/g and an average pore-radius of 21 center dot 8 is synthesized via supramolecular self-assembly with an in situ crystallization process. Subsequently, TiO2-C supported Pt-Ru electro-catalyst (Pt-Ru/TiO2-C) is obtained and investigated as an anode catalyst for direct methanol fuel cells (DMFCs). X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM) have been employed to evaluate the crystalline nature and the structural properties of TiO2-C. TEM images reveal uniform distribution of Pt-Ru nanoparticles (d (Pt -aEuro parts per thousand Ru) = 1 center dot 5-3 center dot 5 nm) on TiO2-C. Methanol oxidation and accelerated durability studies on Pt-Ru/TiO2-C exhibit enhanced catalytic activity and durability compared to carbon-supported Pt-Ru. DMFC employing Pt-Ru/TiO2-C as an anode catalyst delivers a peak-power density of 91 mW/cm(2) at 65 A degrees C as compared to the peak-power density of 60 mW/cm(2) obtained for the DMFC with carbon-supported Pt-Ru anode catalyst operating under similar conditions.

Micro-Raman and photoluminescence studies of self-assembled quantum well microtubes on GaAs substrate

The Semiconductor Quantum Well (QW) microtubes have been fabricated by strain-induced self assembling technique. Three types of multilayer structures have consisted of GaAs/InxGa1-xAs strained layers containing with various thickness of Monolayers of (GaAs/AlGaAs) QW were grown by Varian Gen II Molecular Beam Epitaxy (MBE) on the GaAs (100) substrate. The shape of the rolled up microtubes provide a clear idea about the formation of three dimensional micro- and nanostructures. Micro-Raman and photoluminescence (PL) studies were performed to the QW microtubes and as compared with their grown area on the GaAs substrate. The results of Raman spectra show the frequency shift of phonon modes measured in tube and compared with the grown area due to residual strain. The PL peaks of the microtube were red-shifted due to the strain effect and transition of bandgap from Type-II to Type-I. (C) 2013 Elsevier B.V. All rights reserved.

Fretting studies on self-mated stainless steel and chromium carbide coated surfaces under controlled environment conditions

Adhesive wear has been widely accepted as the type of wear which is most frequently encountered under fretting conditions. Present study has been carried out to study the mode of failure and mechanisms associated under conditions where strong adhesion prevails at the contact interface. Mechanical variables such as normal load, displacement amplitude, and environment conditions were controlled so as to simulate adhesion as the governing mechanism at the contact interface. Self-mated Stainless Steel (SS) and chromium carbide with 25% nickel chrome binder coatings using plasma spray and high-velocity oxy-fuel (HVOF) processes on SS were considered as the material for contacting bodies. Damage in the form of plastic deformation, fracture, and material transfer has been observed. Further, chromium carbide with 25% nickel chrome binder coatings using HVOF process on SS shows less fretting damage, and can be considered as an effective palliative against fretting damage, even under high vacuum conditions. (C) 2013 Elsevier B.V. All rights reserved.

Joint Self-Iterating Equalization and Detection for Two-Dimensional Intersymbol-Interference Channels

We develop several novel signal detection algorithms for two-dimensional intersymbol-interference channels. The contribution of the paper is two-fold: (1) We extend the one-dimensional maximum a-posteriori (MAP) detection algorithm to operate over multiple rows and columns in an iterative manner. We study the performance vs. complexity trade-offs for various algorithmic options ranging from single row/column non-iterative detection to a multi-row/column iterative scheme and analyze the performance of the algorithm. (2) We develop a self-iterating 2-D linear minimum mean-squared based equalizer by extending the 1-D linear equalizer framework, and present an analysis of the algorithm. The iterative multi-row/column detector and the self-iterating equalizer are further connected together within a turbo framework. We analyze the combined 2-D iterative equalization and detection engine through analysis and simulations. The performance of the overall equalizer and detector is near MAP estimate with tractable complexity, and beats the Marrow Wolf detector by about at least 0.8 dB over certain 2-D ISI channels. The coded performance indicates about 8 dB of significant SNR gain over the uncoded 2-D equalizer-detector system.