Dielectric and Electro-Optical Properties of Antiferroelectric Liquid Crystalline Materials

Antiferroelectric liquid crystals (AFLCs) are a recent class of materials in the family of liquid crystals which have high prospect of application in displays with better results as compared to conventional nematic displays. Beside technological applications, AFLCs are very interesting from the point of view of basic studies in soft condensed matter systems as these materials are showing various new sub-phases, viz. SmC_α^*, SmC_β^*, SmC_γ^* and many others with distinct macroscopic properties in a narrow temperature region in addition to the most common wide-range low-temperature SmC_a^* phase. In the present article, we report the structure of various sub-phases of AFLCs, their dielectric behaviour and the electro-optical response of some of the materials studied by our group.     

Quantifying the impact of model-plant mismatch on controller performance

In model predictive control (MPC) of processes, the model fidelity plays an important role. The performance of MPC depends on the quality of the model and hence on the model-plant mismatch (MPM). A poor model may not necessarily lead to degradation in the performance. Moreover, performance degradation may also be a consequence of poor tuning and/or disturbances. Hence, it is highly desirable to be able to isolate the role of MPM in poor control and quantify its impact. This work seeks to address these issues and two rules that aid in the diagnosis of poor performance are proposed. The methodology described here is based on the analysis of closed-loop data from the process. In this work, it is also shown that the impact of MPM on control quality depends on the setpoint directions. This directionality aspect of MPM is discussed by drawing analogies with the concept of gain directionality in multivariable systems. The ability of the proposed methodology to diagnose poor controller performance is demonstrated via representative simulation examples and an industrial case study.     

Nanomechanics of Surface Modified Nanohydroxyapatite Particulates Used in Biomaterials

Hydroxyapatite is an important constituent of natural bone, and possesses excellent biocompatibility and bioactivity, but its brittle nature limits its use for bone tissue engineering. Nanohydroxyapatite (nanoHAP) has been used in synthesis of biomimetic composites for more than a decade, yet the mechanics of nanoHAP particles is not fully understood. The present work attempts to advance the current understanding of mechanics of hydroxyapatite at nanoscale, by carrying out systematic nanoindentation experiments on nanoHAP and surface modified nanoHAP [prepared by in situ mineralization in presence of polyacrylic acid (PAAc)]. Quantitative nanomodulus maps of both modified and unmodified HAP nanoparticles indicate that various surface features of HAP nanoparticles can be probed. Dips in values of elastic moduli across the nanoparticle surfaces in modified nanohydroxyapatite are indicative of composite responses from both polymer and mineral phases (PAAc-HAP) on the surface. Nanoindentation experiments were performed at 100, 1,000, 3,000, 5,000, and 8,000?μN loads, respectively, to obtain the indentation response from both shallow and deep penetration depths. Nanoindentation results at shallow penetration depths are influenced by nanoscale surface roughness of irregular-shaped HAP nanoparticles and nonuniform distribution of PAAc in the microstructure. Significant nonbonded interactions between HAP and PAAc, as well as the mechanical properties of individual constituents (HAP and PAAc) lead to superior nanomechanical properties of surface-modified nanoHAP as compared to unmodified HAP. The overall inelastic nanomechanical response (including damage leading to reduced overall elastic modulus) is strongly influenced by the nature of the interfaces between the nanoparticles, especially when indent size is much larger than the particle size.     

Constitutive,Basal, and β-Alanine-Mediated Activation of the Human Mas-Related G Protein-Coupled Receptor D Induces Release of the Inflammatory Cytokine IL-6 and Is Dependent on NF-κB Signaling

G protein-coupled receptors (GPCRs) have emerged as key players in regulating (patho)physiological processes, including inflammation. Members of the Mas-related G protein coupled receptors (MRGPRs), a subfamily of GPCRs, are largely expressed by sensory neurons and known to modulate itch and pain. Several members of MRGPRs are also expressed in mast cells, macrophages, and in cardiovascular tissue, linking them to pseudo-allergic drug reactions and suggesting a pivotal role in the cardiovascular system. However, involvement of the human Mas-related G-protein coupled receptor D (MRGPRD) in the regulation of the inflammatory mediator interleukin 6 (IL-6) has not been demonstrated to date. By stimulating human MRGPRD-expressing HeLa cells with the agonist β-alanine, we observed a release of IL-6. β-alanine-induced signaling through MRGPRD was investigated further by probing downstream signaling effectors along the Gαq/Phospholipase C (PLC) pathway, which results in an IkB kinases (IKK)-mediated canonical activation of nuclear factor kappa-B (NF-κB) and stimulation of IL-6 release. This IL-6 release could be blocked by a Gαq inhibitor (YM-254890), an IKK complex inhibitor (IKK-16), and partly by a PLC inhibitor (U-73122). Additionally, we investigated the constitutive (ligand-independent) and basal activity of MRGPRD and concluded that the observed basal activity of MRGPRD is dependent on the presence of fetal bovine serum (FBS) in the culture medium. Consequently, the dynamic range for IL-6 detection as an assay for β-alanine-mediated activation of MRGPRD is substantially increased by culturing the cells in FBS free medium before treatment. Overall, the observation that MRGPRD mediates the release of IL-6 in an in vitro system, hints at a role as an inflammatory mediator and supports the notion that IL-6 can be used as a marker for MRGPRD activation in an in vitro drug screening assay.     

CdSe quantum dots sensitized nanoporous hematite for photoelectrochemical generation of hydrogen

A novel system of CdSe quantum dots (QDs) sensitized porous hematite (α-Fe₂O₃) films has been investigated as a potential photoelectrode for hydrogen generation via photoelectrochemical (PEC) splitting of water. Before sensitization, nanoporous hematite thin films were prepared by spray pyrolysis. Characterizations for crystalline phase formation, crystallite size, absorption spectra, and flatband potential were carried out to analyze PEC data. Loading time of sensitizer to hematite thin films was found to be crucial in affecting its PEC properties. Film having sensitizer loading time as 42 h exhibited best photocurrent density of 550 μA cm⁻² at 1.0 V versus SCE. Current study, for the first time, explores the possibility of using low band gap QDs sensitization on a low band gap film, hematite in PEC splitting of water.     

Ni-doped TiO2 hollow spheres as electrocatalysts in water electrolysis for hydrogen and oxygen production

This work represented the electrocatalytic properties of Ni-doped titania hollow sphere materials in hydrogen and oxygen evolution during water electrolysis from acidic media. Titania hollow sphere particles were synthesized using poly(styrene-methacrylic acid) latex as template material, and various amount of nickel were doped over the sphere using nickel (II) sulfate as the precursor of nickel. The presence of rutile TiO₂ and NiO phases were revealed during XRD analysis, indicating the critical growth of nickel on the surface of the hollow sphere catalysts. BET surface area results also shown the 166.76 m² g^?1 value for 30 wt% Ni/TiO₂ hollow sphere sample. The SEM and TEM images were confirmed the hollow sphere structure of the catalysts with diameter of 0.8–0.9 μm. The cyclic voltammetric studies proved the presence of both hydrogen and oxygen evolution peaks for all the hollow sphere samples. The anodic peak current density value, which usually represents the oxygen evolution phenomenon, was revealed as 13 mA cm^?2 for 25 wt% Ni-loaded sample; whereas, the hydrogen evolution peak was most intense for 30 wt% Ni/TiO₂ material with cathodic peak current density of 32 mA cm^?2. The average value of ?1.42 were determined as the reaction order of the system irrespective of the nickel loading and heating duration in the synthesis of hollow sphere materials. During photocatalytic water splitting, 30 wt% Ni/TiO₂ hollow sphere sample yielded the highest amount of hydrogen in all irradiation time span.     

Green framework for future heterogeneous wireless networks

Energy-efficient communication has sparked tremendous interest in recent years as one of the main design goals of future wireless Heterogeneous Networks (HetNets). This has resulted in paradigm shift of current operation from data oriented to energy-efficient oriented networks. In this paper, we propose a framework for green communications in wireless HetNets. This framework is cognitive in holistic sense and aims at improving energy efficiency of the whole system, not just one isolated part of the network. In particular, we propose a cyclic approach, named as energy-cognitive cycle, which extends the classic cognitive cycle and enables dynamic selection of different available strategies for reducing the energy consumption in the network while satisfying the quality of service constraints.