The characteristic study and sonocatalytic performance of CdSe–graphene as catalyst in the degradation of azo dyes in aqueous solution under dark conditions

The sonocatalytic degradation of azo dyes; methyl orange (MO) and rhodamine B (RhB) were studied catalyzed by cadmium selenide (CdSe)-graphene in dark ambiance. The CdSe–graphene composites were prepared by simple hydrothermal method. The characterizations of composites were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), specific surface area (BET) and with energy dispersive X-ray (EDX). The UV-spectroscopic analysis of the dyes was done by measuring the change in absorbance. The degradation of the organic dyes was calculated based on the decrease in concentration of the dyes with respect to regular time intervals. The rate coefficients for the sonocatalytic process were successfully established and the reusability tests were done to test the stability of the used catalysts.     

A feasible high spatiotemporal resolution breast DCE-MRI protocol for clinical settings

Three dimensional bilateral imaging is the standard for most clinical breast dynamic contrast-enhanced (DCE) MRI protocols. Because of high spatial resolution (sRes) requirement, the typical 1–2 min temporal resolution (tRes) afforded by a conventional full-k-space-sampling gradient echo (GRE) sequence precludes meaningful and accurate pharmacokinetic analysis of DCE time-course data. The commercially available, GRE-based, k-space undersampling and data sharing TWIST (time-resolved angiography with stochastic trajectories) sequence was used in this study to perform DCE-MRI exams on thirty one patients (with 36 suspicious breast lesions) before their biopsies. The TWIST DCE-MRI was immediately followed by a single-frame conventional GRE acquisition. Blinded from each other, three radiologist readers assessed agreements in multiple lesion morphology categories between the last set of TWIST DCE images and the conventional GRE images. Fleiss’ κ test was used to evaluate inter-reader agreement. The TWIST DCE time-course data were subjected to quantitative pharmacokinetic analyses. With a four-channel phased-array breast coil, the TWIST sequence produced DCE images with 20 s or less tRes and ~ 1.0×1.0×1.4 mm³ sRes. There were no significant differences in signal-to-noise (P=.45) and contrast-to-noise (P=.51) ratios between the TWIST and conventional GRE images. The agreements in morphology evaluations between the two image sets were excellent with the intra-reader agreement ranging from 79% for mass margin to 100% for mammographic density and the inter-reader κ value ranging from 0.54 (P<.0001) for lesion size to 1.00 (P<.0001) for background parenchymal enhancement. Quantitative analyses of the DCE time-course data provided higher breast cancer diagnostic accuracy (91% specificity at 100% sensitivity) than the current clinical practice of morphology and qualitative kinetics assessments. The TWIST sequence may be used in clinical settings to acquire high spatiotemporal resolution breast DCE-MRI images for both precise lesion morphology characterization and accurate pharmacokinetic analysis.     

Quasi-tree mobility management for internet connectivity of mobile ad hoc networks

The location of mobile nodes must be managed to enable Internet connectivity of mobile ad hoc networks. Node mobility can be managed efficiently using a tree topology in which a mobile node registers with an Internet gateway along a tree path without using flooding. However, a node that loses connectivity to its parent has to find and connect to a new parent through a join-handshaking process. This tends to increase control overhead and impose some delay on on-going communication. Furthermore, the node may join its descendant because of the synchronization delay in updating topology change, creating a loop that significantly increases control overhead. We improve these problems by maintaining a quasi-tree topology in which a node maintains multiple parents. We also present a technique for detection and resolution of loops. The simulation results show that the quasi-tree mobility management approach far outperforms the traditional approaches and is highly robust against the significant increases in tree size and node mobility.     

Efficient Synthesis of Pt Nanoparticles Supported on Hydrophobic Graphitized Carbon Nanofibers for Electrocatalysts Using Noncovalent Functionalization

As an alternative to the oxidative acid treatment, a noncovalent π–π interaction method is employed to deposit Pt electrocatalysts on highly hydrophobic carbon nanofibers (CNFs) for the application of polymer electrolyte membrane (PEM) fuel cells. Three different functionalization agents, namely benzyl mercaptan (BM), 1‐aminopyrene (AP), and 1‐pyrenecarboxylic acid (PCA), are used to functionalize CNFs and the effect of these groups on the electrochemical properties is examined. While the BM and AP act as a poison to Pt catalyst, the functionalization of CNF with PCA improves the distribution and loading of Pt as well as reducing the sintering of Pt particles. From the carbon corrosion test, unlike the oxidative acid treatment, the PCA treatment sustains the corrosion resistance of CNFs because it preserves the intrinsic properties of CNFs without damaging their surface structure. Therefore, the PCA treatment is a very effective way to prepare catalysts for PEM fuel cells and also extended to the fabrication of graphitized‐carbon‐supported catalysts of other precious metal for various applications.     

Polymer dispersed liquid crystal device with integrated luminescent solar concentrator

Polymer dispersed Liquid crystal (PDLC) windows are regarded as a good choice for curtain-free windows. However, conventional PDLC needs external electricity to operate, which causes extra energy consumption. These devices cannot be combined with traditional solar cells for energy savings. In this study, a new design of luminescent solar concentrator (LSC)-based PDLC device is presented. In particular, we successfully demonstrate that the PDLC can be integrated with LSC as its back scatter and potentially contributes towards the enhancement of power output by minimising backside light losses. Multi-luminophore LSC is employed to increase the absorption of air mass 1.5 solar irradiance. The edge emission measurements show multiple-luminophore-based PDLC-LSC gives the maximum edge emission power which is 1.7 times more than that of single luminophore-based PDLC-LSC device. Photocurrent measurements are also performed as an additional evidence for the improved performance of PDLC-LSC device. Finally, the visual properties of PDLC-LSC devices are evaluated to realise the compatibility of using such devices in the built environment.     

Dramatic Structural Enhancement of Chirality in Photopatternable Nanocomposites of Chiral Poly(fluorene‐alt‐benzothiadiazole) (PFBT) in Achiral SU‐8 Photoresist

Materials with large optical activity at visible wavelengths are of great interest in photonics, particularly as one of the routes towards optical metamaterials. Here, dramatic structural enhancement of the optical activity of chiral poly(fluorene‐alt‐benzothiadiazole) (PFBT) when dispersed in SU‐8 to form a nanocomposite is reported. The supramolecular helical organization of PFBT chains in these optically clear nanocomposite films produces specific rotation at visible wavelengths that is 68 times that of a pure chiral PFBT film of the same optical absorbance. Photopatterning and development under standard conditions for SU‐8 leave behind a residual film of dispersed PFBT/SU‐8 aggregates in the nominally unexposed regions where the SU‐8 matrix is removed. After annealing, the patterned film exhibits specific rotation 58 times that of a pure chiral PFBT film of the same optical absorbance. Photopatterned and annealed films have a dissymmetry ratio as high as |g_abs| = 0.32. This dramatic enhancement is attributed to supramolecular helical organization of the aggregates within the nanocomposites and of the aggregates liberated from the SU‐8 matrix in the exposed regions.