Optimizing channel capacity in a MIMO–PSK wireless rayleigh fading channel

Due to the continual advancement of future generation communication systems, channel capacity is considered to be an important parameter for achieving greater signal strength by means of faster data transmission speed. Usually in multiple input multiple output (MIMO) systems, the diversity technique lessens the propagation speed significantly than the channel capacity. Using MIMO in combination with phase shift keying (PSK) modulation jointly known as MIMO–PSK systems, the present paper focuses on a novel distribution method in order to optimize the channel capacity over a Rayleigh fading channel. First, ergodic channel capacity and distribution capacity in terms of outage capacity is simulated for different MIMO–PSK configurations as well as channel conditions. Later, the channel performance of MIMO–PSK for the novel distribution conditions with antenna correlation effect is evaluated and finally the optimal channel capacity is determined.

     

Effect of temporal pH variation of the reaction mixture on Mg(OH)2 morphology precipitated from an aqueous Mg(NO3)2-NaOH system

To understand the impact of temporal pH variation on the crystallisation process, Mg(OH)₂ was synthesized via wet precipitation route from an aqueous Mg(NO₃)₂-NaOH system. A detailed analysis of morphological evolution and the nano-structural transformation was carried out to model the crystallisation process. Interestingly, low supersaturation at low pH level lying between 9.2 and 9.4 of the reaction mixture, was found to promote the growth of nanorod like 1-D structures. On the contrary, enhanced supersaturation created a chemical driving force favouring an edgewise growth of the nucleated primary nanocrystals along (101) and (110) crystallographic planes, which resulted in lamellar hexagonal nanostructures. The lamellar growth demonstrated an increment in the particle size and reduction in anisotropic strain and dislocation density due to proper nucleation in the samples. Such controlled growth and nucleation of the Mg(OH)₂ morphology presents a great scope of potential applications of this material.     

A Crystalline, 2D Polyarylimide Cathode for Ultrastable and Ultrafast Li Storage

Organic electrode materials are of long‐standing interest for next‐generation sustainable lithium‐ion batteries (LIBs). As a promising cathode candidate, imide compounds have attracted extensive attention due to their low cost, high theoretical capacity, high working voltage, and fast redox reaction. However, the redox active site utilization of imide electrodes remains challenging for them to fulfill their potential applications. Herein, the synthesis of a highly stable, crystalline 2D polyarylimide (2D‐PAI) integrated with carbon nanotube (CNT) is demonstrated for the use as cathode material in LIBs. The synthesized polyarylimide hybrid (2D‐PAI@CNT) is featured with abundant π‐conjugated redox‐active naphthalene diimide units, a robust cyclic imide linkage, high surface area, and well‐defined accessible pores, which render the efficient utilization of redox active sites (82.9%), excellent structural stability, and fast ion diffusion. As a consequence, high rate capability and ultrastable cycle stability (100% capacity retention after 8000 cycles) are achieved in the 2D‐PAI@CNT cathode, which far exceeds the state‐of‐the‐art polyimide electrodes. This work may inspire the development of novel organic electrodes for sustainable and durable rechargeable batteries.     

Investigation on the Synthesis of Zeolite NaX from Kerala Kaolin

The synthesis of zeolite NaX from a locally available kaolin has been studied. Two steps are involved in the reaction (1) thermal activation of the kaolin to get a dehydroxylated product called metakaolin (metakaolinisation) and (2) hydrothermal reaction (zeolitisation) of metakaolin in alkaline medium in presence of additional silica to crystallise the zeolite. The metakaolinisation temperature (400–1000°C) is found to have an important role in determining the type of zeolite formed during the hydrothermal reaction. Under specified conditions, the uncalcined kaolin is partially converted to hydroxy sodalite (HS), whereas the metakaolins prepared at 400, 500 and 600°C also change to HS but at a faster rate. Increasing the metakaolinisation temperature to 700°C, zeolite NaX is found to be the product (higher the temperature, faster the reaction). The quantity of additional silica which in turn determines the SiO₂/Al₂O₃ ratio of the reaction mixture and the time given for zeolitisation were also found to influence the formation of zeolite NaX. When metakaolin alone was used in the reaction (SiO₂/Al₂O₃ = 2), the product was X-ray amorphous. Higher ratios were obtained by the addition of sodium silicate. The ratios 3 and 5 gave phase pure NaX whereas 7 resulted in a mixture of NaA, NaP and HS zeolites. The optimum conditions to get phase pure zeolite NaX with good crystallinity from kaolin were found to be metakaolinisation of the clay at 900°C for 1 h, maintaining the mole ratios of SiO₂/Al₂O₃ = 3; Na₂O/SiO₂ = 1.1 and H₂O/Na₂O = 40 in the reaction mixture, an ageing of the reactants at room temperature for 24 h and heating at 87 ± 2°C for 15 h under autogenous pressure. Seeding was not essential for the zeolite crystallisation. X-ray diffraction, electron microscopy, IR and solid state NMR spectral analysis, water adsorption and calcium/magnesium exchange or binding capacity measurements and chemical analysis of the selected products substantiated these findings.     

Water-soluble polymeric chemosensor for detection of Cu2+ ions with high selectivity and sensitivity

Development of water-soluble chemosensors that are selective and sensitive to Cu²⁺ ions is of tremendous importance owing to their potential applications in biological systems. In the present work, we report the synthesis of a new water-soluble polymer containing pendant rhodamine units that are capable of highly selective and sensitive detection of Cu²⁺ ions in aqueous medium. Poly(2-pyrrolidinemethyl acrylate) was prepared using RAFT polymerization technique. The pyrrolidine nitrogen group in the polymer was subjected to Aza-Michael type addition with ethyl acrylate that was followed by covalent linking of rhodamine units to the polymer. This polymer was completely water-soluble and found to be capable of sensing Cu²⁺ ions in aqueous medium. Cu²⁺-induced opening of the spirolactam ring of the rhodamine units resulted in rapid and easily noticeable colour change, thus enabling a highly selective detection of Cu²⁺ in μmol range. The ability of these polymeric systems to detect Cu²⁺ ions in complete aqueous media has more importance than use of organic solvents to solubilize the polymer as reported previously, and thus opened a new window for application of these systems in the detection of copper ions in biological systems.     

Quinoline–Glycomimetic Conjugates Reducing Lipogenesis and Lipid Accumulation in Hepatocytes

Nonalcoholic fatty liver disease (NAFLD), which is characterized by excess accumulation of triglyceride in hepatocytes, is the major cause of chronic liver disease worldwide and no approved drug is available. The mechanistic target of rapamycin (mTOR) complexes has been implicated in promoting lipogenesis and fat accumulation in the liver, and thus, serve as attractive drug targets. The generation of non‐ or low cytotoxic mTOR inhibitors is required because existing cytotoxic mTOR inhibitors are not useful for NAFLD therapy. New compounds based on the privileged adenosine triphosphate (ATP) site binder quinoline scaffold conjugated to glucose and galactosamine derivatives, which have significantly low cytotoxicity, but strong mTORC1 inhibitory activity at low micromolar concentrations, have been synthesized. These compounds also effectively inhibit the rate of lipogenesis and lipid accumulation in cultured hepatocytes. This is the first report of glycomimetic–quinoline derivatives that reduce lipid load in hepatocytes.     

Hydrated metal salt and Y3Fe5O12–Na0.5K0.5NbO3-incorporated P(VDF-HFP) films: a promising combination of materials with multiferroic and energy harvesting properties

Journal of Materials Science - The composite approach is very effective in developing multiferroic systems with remarkable magnetoelectric coupling coefficients. In this work, P(VDF-HFP)-based...