A Facile Molecular Approach to Amorphous Nickel Pnictides and Their Reconstruction to Crystalline Potassium-Intercalated γ-NiOOHx Enabling High-Performance Electrocatalytic Water Oxidation and Selective Oxidation of 5-Hydroxymethylfurfural

The low-temperature molecular precursor approach can be beneficial to conventional solid-state methods, which require high temperatures and lead to relatively large crystalline particles. Herein, a novel, single-step, room-temperature preparation of amorphous nickel pnictide (NiE; EP, As) nanomaterials is reported, starting from NaOCE(dioxane)_n and NiBr₂(thf)_1.5. During application for the oxygen evolution reaction (OER), the pnictide anions leach, and both materials fully reconstruct into nickel(III/IV) oxide phases (similar to γ-NiOOH) comprising edge-sharing (NiO₆) layers with intercalated potassium ions and a d-spacing of 7.27 Å. Remarkably, the intercalated γ-NiOOH_x phases are nanocrystalline, unlike the amorphous nickel pnictide precatalysts. This unconventional reconstruction is fast and complete, which is ascribed to the amorphous nature of the nanostructured NiE precatalysts. The obtained γ-NiOOH_x can effectively catalyse the OER for 100 h at a high current density (400 mA cm⁻²) and achieves outstandingly high current densities (>600 mA cm⁻²) for the selective, value-added oxidation of 5-hydroxymethylfurfural (HMF). The NiP-derived γ-NiOOH_x shows a higher activity for both processes due to more available active sites. It is anticipated that the herein developed, effective, room-temperature molecular synthesis of amorphous nickel pnictide nanomaterials can be applied to other functional transition-metal pnictides.     

Wet-electrochemical growth of CdTe layers for photovoltaic applications

Journal of Materials Science: Materials in Electronics - Cadmium telluride (CdTe) thin films have been prepared using a low-cost potentiostatic electrochemical technique from an aqueous...     

Robust design and optimization procedure for piled-raft foundation to support tall wind turbine in clay and sand

A geotechnical design and optimization procedure for piled-raft foundations to support tall wind turbines in clayey and sandy soil are presented in this paper. From the conventional geotechnical design, it was found that the differential settlement controlled the final design and was considered as the response of concern in the optimization procedure. A parametric study was subsequently conducted to examine the effect of the soil shear strength parameters and wind speed (random variables) on the design parameters (number and length of piles and radius of raft). Finally, a robust design optimization procedure was conducted using a Genetic Algorithm coupled with a Monte Carlo simulation considering the total cost of the foundation and the standard deviation of differential settlement as the objectives. This procedure resulted in a set of acceptable designs forming a Pareto front which can be readily used to select the best design for given performance requirements and cost limitations.     

Exogenous Sphingosine 1-Phosphate Protects Murine Splenocytes Against Hypoxia-Induced Injury

Sphingosine-1-phosphate (S1P), a biologically active pleiotropic lipid, is involved in several physiological processes especially in the area of vascular biology and immunology encompassing cell survival, angiogenesis, vascular tone, immune response etc. by interacting with specific cell surface receptors. Hypoxia, a condition common to innumerable pathologies, is known to lethally affect cell survival by throwing off balance global gene expression, redox homeostasis, bioenergetics etc. Several molecular events of cellular adaptations to hypoxia have been closely linked to stabilization of hypoxia inducible factor-1α (HIF-1α). Signalling functions of S1P in physiological events central to hypoxia-induced pathologies led us to investigate efficacy of exogenous S1P in preconditioning murine splenocytes to sustain during cellular stress associated with sub-optimal oxygen. The present study recapitulated the pro-survival benefits of exogenous S1P under normobaric hypoxia. Results indicate a direct effect of S1P supplementation on boosting cellular adaptive responses via HIF-1α stabilization and, activation of pro-survival mediators ERK and Akt. Overwhelming anti-oxidative and anti-inflammatory benefits of S1P preconditioning could also be captured in the present study, as indicated by improved redox homeostasis, reduced oxidative damage, balanced anti/pro-inflammatory cytokine profiles and temporal regulation of nitric oxide secretion and intra-cellular calcium release. Hypoxia induced cell death and the associated stress in cellular milieu in terms of oxidative damage and inflammation could be alleviated with exogenous S1P preconditioning.     

A comparison of charge transport behavior in functionalized and non-functionalized poly 3,4-(ethylenedioxythiophene) films

Poly 3,4-(ethylenedioxythiophene) (PEDOT) films electropolymerized from an aqueous micellar solution containing sodium dioctyl sulfosuccinate and the monomer were functionalized with 1-fluoro-2-nitro-4-azidobenzene (FNAB) molecules by a photochemical nitrene insertion reaction. The variation in redox activity and the changes in the charge transfer and diffusion (through bulk) behavior of the functionalized and the non-functionalized PEDOT films have been followed by electrochemical impedance spectroscopy and cyclic voltammetry. While the functionalized film allows a reversible insertion and extraction of guest cations and anions, the non-functionalized film is capable of exchanging only anions. The higher level of oxidation attained in the functionalized film is also reflected in the longer diffusion length (l_D) observed for the ions in this film. In both films the barrier to charge transfer is resistive rather than capacitive. Both charge transfer and diffusion resistance (R_CT and R_D) are lower for the functionalized film, a consequence of a higher surface roughness and a more nodular morphology and therefore higher optical contrast and faster color-bleach kinetics are achieved in this film. For the functionalized and the non-functionalized films, both R_CT and R_D are greatly enhanced during reduction than for oxidation. In particular, in the low frequency regime, the hindered diffusion-controlled extraction of anions from the bulk of the film is also evident from the larger R_D as compared to R_CT and the difference in their magnitudes is more pronounced for the functionalized film thus confirming that functionalization is a useful method for controlling the redox response of conducting polymer films.     

Comparative studies on physico-chemical characterization of yeast cells entrapped with alginate and hybrid beads

Natural polymers used as carrier materials in immobilization technology have the advantage of being non-toxic, biocompatible and biodegradable. In the present investigation, immobilization of yeast cells using different polymers has been carried out and the properties such as morphological, hardening, thermal stability and characterization of functional groups of alginate and hybrid beads (alginate–carrageenan and alginate–xanthan gum) have been studied by different techniques such as scanning electron microscope, texture analyzer, differential scanning calorimetry, and Fourier transfer infrared spectroscopy. The swelling behavior in terms of pH variation as well as flow properties of alginate and hybrid beads has also been examined. The hybrid beads prepared from alginate and carrageenan were found to be the best in terms of strength, cell holding capacity, pH and thermal stability. The reusability of beads was also studied in terms of enzyme activity of the entrapped yeast cells. The beads prepared by alginate–carrageenan were found to be more stable than alginate and alginate–xanthan beads. The yeast cells entrapped in alginate–carrageenan beads showed no significant decrease in enzyme activity up to seven batches. Thus, alginate–carrageenan beads can be used as a polymeric carrier/support to develop a stable and long-term immobilized cell system, which indicates its high potential for commercial applications in food and pharmaceutical sector.     

Differential Modulation of S1PR(1–5) and Specific Activities of SphK and nSMase in Pulmonary and Cerebral Tissues of Rats Exposed to Hypobaric Hypoxia

Recent preclinical and clinical studies have unfolded the potential of pharmacological modulation of activities of sphingosine‐1‐phosphate (S1P) receptors and S1P metabolizing enzymes for the development of therapeutic interventions against a variety of pathologies. An understanding of differential and temporal effects of hypoxia exposure on the key components of S1P signalling would certainly aid in designing improved drug development strategies in this direction. In view of this, the aim of the present study was to assess the effect of progressive hypobaric hypoxia exposure on expression of S1P receptors (S1PR_1–5) and specific activities of S1P synthesizing enzymes—neutral sphingomyelinase (nSMase) and sphingosine kinase (Sphk) in pulmonary and cerebral tissues of rats exposed to simulated altitude of 21,000 feet in an animal decompression chamber. Along with this, development of cerebral and pulmonary edema and markers of inflammation were studied at 12, 24, and 48 h to validate our study model of hypobaric hypoxia‐induced stress. The protein expression of S1PR_1–5 and activities of Sphk and nSMase enzymes were observed to be dramatically affected by simulated hypobaric hypoxia exposure, concurrent with deterioration of pathology, with 12 h of exposure appearing to be the most critical of the various time points studied.     

Controlling the assembly of hydrophobized gold nanoparticles at the air-water interface by varying the interfacial tension

Controlled assembly is the key to harness the nanoscale properties of nanoparticles in most technological applications and it has been an important challenge as it leads to the manipulation of interparticle properties. The present work depicts the control of the assembly of nanoparticles in the monolayers by evaporation kinetics and particle interactions at the air-liquid interface. In the presence of attractive particle-particle and particle-monolayers interactions, nanoparticles self assemble into a superlattice structure upon drying from a colloidal suspension on to the preformed lipid monolayers. This self-assembly mechanism produces monolayers with long-range ordering. However, rapid dewetting and high rate of evaporation can significantly undermine the extent of ordering. Using gold nanoparticles as vehicles for experimentation and by changing the monolayers and solvent, we here demonstrate that the extent of ordering of nanoparticles can be controlled.     

‘<Emphasis Type=Italic>Lead Free</Emphasis>’ thick film thermistors: a study of variation in glass frit concentration and organics composition

There is a need to develop environment friendly electronic materials due to worldwide constraint for the use of hazardous chemicals such as lead, cadmium which are the main constituents of the electronic components. Considering such need, the work on lead free thick film thermistors has been initiated. Thick film materials have been proved to possess economical processing and functional advantage over other technologies and quick turnaround production of hybrid microcircuits. Thick film thermistors are different from the conventional thermistors (bulk) not only by the preparation process but also in composition, transport properties etc. In this paper, we have specifically focused on the influence of glass frit content and organic composition on the properties of lead free spinel based NTC thermistors. We noted that the glass frit concentration is responsible for the change in physical as well as electrical properties of the thick film thermistor. However, the type of organic vehicle (i.e., composition) did not show any adverse effect on microstructure and electrical properties of the thermistor.     

Positron lifetime studies and coincidence Doppler broadening spectroscopy of Al–6Mg–<Emphasis Type="Italic">x</Emphasis>Sc (<Emphasis Type="Italic">x</Emphasis> = 0 to 0.6 wt.%) alloy

Positron annihilation spectroscopy (PAS), comprising of both positron lifetime and coincidence Doppler broadening measurements, has been employed for studying the phase decomposition behaviour of scandium doped Al–6Mg alloys. Micro structural and age hardening studies have also been conducted to substantiate the explanation of the results of PAS. Samples with scandium concentration ranging from 0 to 0.6 wt.% have been studied. The measured positron lifetimes of undoped alloy reveal that GP zones are absent in the as-prepared Al–6Mg alloy. The observed positron lifetimes and the results of coincidence Doppler broadening measurements largely stem from the entrap of positrons at the interface between aluminium rich primary dendrites and the magnesium enriched interdendritic eutectic mixture of Mg₅Al₈ (β) and the primary solid solution of aluminium (α). The study also provides evidence of the formation of scandium vacancy complexes in Al–6Mg alloys doped with scandium upto a concentration of 0.2 wt.%. However such complex formation ceases to continue beyond 0.2 wt.% Sc; instead, the formation of fine coherent precipitates of Al₃Sc is recorded in the as prepared alloy containing 0.6 wt.% scandium. The positron annihilation studies coupled with CDBS have also corroborated with the fact that the fine coherent precipitates of Al₃Sc are formed upon annealing the Al–6Mg alloys doped with scandium of concentration 0.2 wt.% and above. Transmission electron microscopic studies have provided good evidence of precipitate formation in annealed Al–6Mg–Sc alloys. Elevated temperature annealing leads to dissociation of the scandium-vacancy complexes, thereby leading to the enhancement of the mobility of magnesium atoms. This has facilitated fresh nucleation and growth of Mg₅Al₈ precipitates in the above alloys at 673 K.