Physical ageing of the contact line on colloidal particles at liquid interfaces

Young's law predicts that a colloidal sphere in equilibrium with a liquid interface will straddle the two fluids, its height above the interface defined by an equilibrium contact angle. This has been used to explain why colloids often bind to liquid interfaces, and has been exploited in emulsification, water purification, mineral recovery, encapsulation and the making of nanostructured materials. However, little is known about the dynamics of binding. Here we show that the adsorption of polystyrene microspheres to a water/oil interface is characterized by a sudden breach and an unexpectedly slow relaxation. The relaxation appears logarithmic in time, indicating that complete equilibration may take months. Surprisingly, viscous dissipation appears to play little role. Instead, the observed dynamics, which bear strong resemblance to ageing in glassy systems, agree well with a model describing activated hopping of the contact line over nanoscale surface heterogeneities. These results may provide clues to longstanding questions on colloidal interactions at an interface.     

Numerical study of hydrogen explosions in a refuelling environment and in a model storage room

Numerical simulations have been carried out for large scale hydrogen explosions in a refuelling environment and in a model storage room. For the first scenario, a high pressure hydrogen jet released in a congested refuelling environment was ignited and the subsequent explosion analysed. The computational domain mimics the experimental set up for a vertical downwards release in a vehicle refuelling environment experimentally tested by Shirvill et al. [6]. For completeness of the analysis, an analytical model has also been developed to provide the transient pressure conditions at nozzle exit. The numerical study is based on the traditional computational fluid dynamics (CFD) techniques solving Reynolds averaged Navier-Stokes equations. The Pseudo diameter approach is used to bypass the shock-laden flow structure in the immediate vicinity of the nozzle. For combustion, the Turbulent Flame Closure (TFC) model is used while the shear stress transport (SST) model is used for turbulence. In the second scenario, premixed hydrogen-air clouds with different hydrogen concentrations from 15% to 60% in volume were ignited in a model storage room. Analysis was carried out to derive the dependence of overpressure on hydrogen concentrations for safety considerations.     

Thermal annealing effect on zinc nitride thin films deposited by reactive rf-magnetron sputtering process

Zinc nitride films were deposited by reactive radio-frequency magnetron sputtering using a zinc target in a nitrogen and argon plasma. The deposited films were annealed in either air or O₂ at 300 °C to investigate the annealing effect on the microstructure, optical properties, and electronic characteristics of zinc nitride films. It was found that the annealing process decreased the crystallinity of zinc nitride films. It was also found that the optical band gap decreased from 1.33 eV to 1.14 eV after annealing. The analysis of film composition suggested that the concentration of oxygen increased slightly after annealing. Although the conduction type of both as-deposited and annealed films were n-type, the annealed films exhibited a higher resistivity, lower carrier concentration and lower mobility than the as-deposited films. Also, it was found that the as-deposited films did not exhibit any photoconducting behavior whereas the annealed films exhibited a pronounced photoconducting behavior.     

Highly selective homogeneous ethylene epoxidation in gas (ethylene)‐expanded liquid: Transport and kinetic studies

Recently a homogeneous liquid‐phase ethylene oxide (EO) process with nearly total EO selectivity, catalyzed by methyltrioxorhenium with H₂O₂ as an oxidant, was reported. Fundamental mass transfer and kinetic studies of this reaction are reported in the present work. Volumetric expansion studies revealed that the liquid reaction phase (methanol + H₂O₂/H₂O) is expanded by up to 12% by compressed ethylene in the 20–40^°C range and up to 50 bars. This represents an increase in ethylene solubility by approximately one‐order of magnitude, attributed to the unique exploitation of near‐critical ethylene (P_c = 50.76 bar; T_c = 9.5^°C). Interphase mass‐transfer coefficients for ethylene dissolution into the liquid phase were obtained experimentally. Operating at conditions that enhanced the ethylene solubility and eliminated interphase mass‐transfer limitations maximized the EO productivity (1.61–4.97 g EO/h/g cat), rendering it comparable to the conventional process. Intrinsic kinetic parameters, estimated from fixed‐time semibatch reactor studies, disclosed the moderate activation energy (57 ± 2 kJ/mol). © 2012 American Institute of Chemical Engineers AIChE J, 59: 180–187, 2013     

A low-power 72.8-GHz static frequency divider in AlInAs/InGaAs HBTtechnology

We report a 72.8-GHz fully static frequency divider in AlInAs/InGaAs HBT IC technology. The CML divider operates with a 350-mV logic swing at less than 0-dBm input power up to a maximum clock rate of 63 GHz and requires 8.6 dBm of input power at the maximum clock rate of 72.8 GHz. Power dissipation per flip-flop is 55 mW with a 3.1-V power supply. To our knowledge, this is the highest frequency of operation for a static divider in any technology. The power-delay product of 94 fJ/gate is the lowest power-delay product for a circuit operating above 50 GHz in any technology. A low-power divider on the same substrate operates at 36 GHz with 6.9 mW of dissipated power per flip-flop with a 3.1-V supply. The power delay of 24 fJ/gate is, to our knowledge, the lowest power-delay product for a static divider operating above 30 GHz in any technology. We briefly review the requirements for benchmarking a logic family and examine the historical trend of maximum clock rate in high-speed circuit technology     

Partial removal of protein associated with arabinoxylans: Impact on the viscoelasticity,crosslinking content,and microstructure of the gels formed

Arabinoxylans (AX) treated with protease and dialyzed (AXP) or only dialyzed (AXD) formed gels showing an increase in the elastic modulus G′ (1291 and 1419 Pa, respectively) and the ferulic acid dimers (3.34 and 3.10 μg/mg polysaccharide, respectively) and trimers (0.51 and 0.53 μg/mg polysaccharide, respectively) in comparison to AX gels (767 Pa, 0.56 and 0.12 μg/mg polysaccharide, respectively). Nevertheless, the G′ values and crosslinking contents were not different among the AXP and AXD gels, suggesting that the amount of protein removed (54%) does not affect these parameters. Confocal laser scanning microscopy analysis showed that AXP treatment promotes the homogeneity of the gels. In addition, scanning electron microscopy observations indicated that AXD and particularly AXP gels had a more compact microstructure. Thus, the partial removal of protein associated with AX does not impact the viscoelasticity and crosslinking content of the gels formed but could improve their microstructural characteristics. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47300.     

Major metals in human cancer: calcium, magnesium, sodium and potassium

Major elements calcium, magnesium, sodium and potassium in normal and neoplastic tissues were determined by atomic absorption spectrophotometry. Samples of neoplastic tissues were taken from surgically resected materials from different regions; oral, respiratory, gastro-intestinal, breast, reproductive regions and bone marrow and diverse types of neoplasms. Samples from areas which, on gross examination, looked normal were designated as uninvolved and were also analysed together with controls from normal Indian subjects. In neoplastic tissues concentrations of magnesium, sodium and potassium were found to be enhanced, while variability was noted for the distribution of calcium in the normal and malignant state.     

Adsorption of 1-Butanethiol from kerosene oil on red mud

Adsorption studies indicate that low concentration and high temperature favour the removal of 1-butanethiol from kerosene oil by adsorption on red mud. A first order mechanism has been proposed to describe the adsorption in the present system. Equilibrium data at different temperatures fit well in the Langmuir isotherm equation. Thermodynamic parameters for the present system indicate the feasibility of removal of 1-butanethiol from kerosene oil by adsorption on red mud.     

High-energy radiation-resistant vulcanizates. II. EPDM

In this article, Part II of the series, we report a detail study on stabilization of EPDM vulcanizates in γ-radiation environment. The special additives (antirads), namely pyrene (Py), brominated acenaphthene (BrAc), poly(acenaphthene sulfide) (PAcSu) and poly(pyrene sulfide) (PPySu) were used for the stabilization studies. The efficiency of these antirads for EPDM had been monitored by the means of electrical resistivity, wide-angle X-ray diffraction, and mechanical properties. The stabilization of EPDM to withstand 200 Mrads of γ radiation in air environment is achieved. © 1994 John Wiley & Sons, Inc.     

High-energy radiation-resistant elastomeric vulcanizates. I. Chlorosulfonated polyethylene

In this article, a detailed study on the stabilization of chlorosulfonated polyethylene (CSP) vulcanizates in γ radiation is reported. The special additives (antirads) for the stabilization are synthesized from polynuclear aromatics and formulated in the laboratory. The effect of these antirad formulations on the physicochemical structure and performance properties of these materials is studied by monitoring the degradation in γ radiation using resistivity, wide-angle X-ray diffraction, and mechanical properties. Antirad formulations to stabilize CSP against a total dosage of 200 Mrads of γ radiation have been achieved. © 1994 John Wiley & Sons, Inc.