Impacts of conductive inner L-shaped obstacle and elastic bottom wall on MHD forced convection of a nanofluid in vented cavity

Journal of Thermal Analysis and Calorimetry - Forced convection of nanofluid in a vented cavity with elastic bottom wall is studied by using an inner conductive L-shaped object and magnetic field....     

Emodin,A Naturally Occuring Anthraquinone: Its Isolation and Spectrophotometric Determination in Rumex Cyprius Plant

A new method for isolation and specrophotometric determination of emodin is presented. Emodin was isolated by thin layer chromatography (tlc) and column chromatography (cc) techniques, as an orange long crystalline substance. Emodin exhibits two absorption maxima, at 420 and 520 nm. Stability of the color and the effect of pH were studied. Beer's law is obeyed in the range 2–30 ppm.

The method is applied to the determination of emodin in roots, stems, and leaves of Rumex cyprius plant.     

Atomic force microscope studies of membranes: Surface pore structures of Cyclopore and Anopore membranes

Non-contact atomic force microscopy has been used to investigate the surface pore structure of Cyclopore and Anopore microfiltration membranes in air. Three Cyclopore membranes and three Anopore membranes of different pore sizes were studied. Excellent high resolution images were obtained. Analysis of the images gave quantitative information on the surface pore structure, in particular the pore size distribution. Non-contact AFM is an excellent means of obtaining such information for microfiltration membranes.     

Spectrofluorimetric determination of terbium as its ternary complex with edta and tiron Compositional studies,optimization of fluorescence output and conversion to a flow system

The spectrofluorimetric determination of terbium(III) as its ternary complex with EDTA and Tiron was studied further with regard to composition of the complex and the procedure was optimized by a simplex method. The results suggest a 1:1 molar ratio of terbium to Tiron for the ternary complex. The optimization study indicated that the three chosen variables (pH, and EDTA and Tiron concentration) are not interactive. The method was converted for use in a segmented-flow system with basic Technicon units and a spectrophotofluorimeter as detector. This procedure is satisfactory for the determination of terbium(III) in the range 0.03–0.24 μg ml^?1 at a sampling rate of 30 h^?1. Results were satisfactory for the determination of terbium in lanthanide oxides, mixed oxides, the mineral bastnasite and a green phosphor (Gd_0.96 Ce_0.02 Tb_0.02 F₃).     

Automatic spectrophotometric method for the determination of europium in mixtures with yttrium and other lanthanides

Summary An automatic spectrophotometric method for the determination of europium in the presence of yttrium and other lanthanides is described. The method is based on a modification of a recently devised manual procedure consisting of the reduction, on a Jones reductor, of europium(III) to europium(II) which is used to reduce molybdophosphate to a molybdenum blue. The method is capable of analysing solutions containing 10–400 g of europium per ml at a rate of 20 samples per hour. There is no interference from yttrium or other lanthanides and the method is suitable for application to europium determination after a group separation. When applied to mineral samples coefficients of variation between 2.5 and 3.8% were obtained.

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Automatisches spektralphotometrisches Verfahren zur Bestimmung von Europium im Gemisch mit Yttrium und anderen Lanthaniden

Zusammenfassung Das Verfahren stellt eine Modifikation eines kürzlich ausgearbeiteten manuellen Verfahrens dar, das auf Reduktion (Jones Reduktor) zu Eu(II) und Reaktion mit Molybdophosphat zu Molybdänblau beruht. 20 Proben mit 10–400 g Eu/ml können je Stunde analysiert werden. Yttrium und andere Lanthanide stören nicht. Die Molybdänblaureaktion störende Substanzen können zuvor durch eine Gruppentrennung beseitigt werden. Bei der Analyse von mineralischen Proben wurden Variationskoeffizienten zwischen 2,5 und 3,8% erhalten.

     

Acid/Base‐Triggered Switching of Circularly Polarized Luminescence and Electronic Circular Dichroism in Organic and Organometallic Helicenes

Electronic circular dichroism and circularly polarized luminescence acid/base switching activity has been demonstrated in helicene‐bipyridine proligand 1 a and in its “rollover” cycloplatinated derivative 2 a . Whereas proligand 1 a displays a strong bathochromic shift (>160 nm) of the nonpolarized and circularly polarized luminescence upon protonation, complex 2 a displays slightly stronger emission. This strikingly different behavior between singlet emission in the organic helicene and triplet emission in the organometallic derivative has been rationalized by using quantum‐chemical calculations. The very large bathochromic shift of the emission observed upon protonation of azahelicene‐bipyridine 1 a has been attributed to the decrease in aromaticity (promoting a charge‐transfer‐type transition rather than a π–π* transition) as well as an increase in the HOMO–LUMO character of the transition and stabilization of the LUMO level upon protonation.     

Colloidal dynamics: influence of diffusion, inertia and colloidal forces on cluster formation

Computer simulations of colloidal suspensions are discussed. The simulations are based on the Langevin equations, pairwise interaction between colloidal particles and take into account Brownian, hydrodynamic and colloidal forces. Comparison of two models, one taking into account inertial term in Langevin equation and another based on diffusional approximation proposed in [D.L. Ermak, J.A. McCammon, J. Chem. Phys. 69 (1978) 1352], has shown that both models enable the prediction of the correct values of the diffusion coefficient and residence time of particle in a doublet and are therefore suitable to study the dynamics of formation and breakage of clusters in colloidal suspensions. It is shown that the appropriate selection of the time step and taking into account inertia of particles provides also the correct value of the average kinetic energy of each particle during the simulations, what allows to use the model based on full Langevin equations as a reference model to verify the validity of the numerical scheme for simulation using diffusion approximation.     

Recent Advances on the Development of Protein-Based Adhesives for Wood Composite Materials—A Review

The industrial market depends intensely on wood-based composites for buildings, furniture, and construction, involving significant developments in wood glues since 80% of wood-based products use adhesives. Although biobased glues have been used for many years, notably proteins, they were replaced by synthetic ones at the beginning of the 20th century, mainly due to their better moisture resistance. Currently, most wood adhesives are based on petroleum-derived products, especially formaldehyde resins commonly used in the particleboard industry due to their high adhesive performance. However, formaldehyde has been subjected to strong regulation, and projections aim for further restrictions within wood-based panels from the European market, due to its harmful emissions. From this perspective, concerns about environmental footprint and the toxicity of these formulations have prompted researchers to re-investigate the utilization of biobased materials to formulate safer alternatives. In this regard, proteins have sparked a new and growing interest in the potential development of industrial adhesives for wood due to their advantages, such as lower toxicity, renewable sourcing, and reduced environmental footprint. This work presents the recent developments in the use of proteins to formulate new wood adhesives. Herein, it includes the historical development of wood adhesives, adhesion mechanism, and the current hotspots and recent progress of potential proteinaceous feedstock resources for adhesive preparation.     

Evaluation of spectral dispersion of optical constants of a-Se films from their normal-incidence transmittance spectra using Swanepoel algebraic envelope approach

Spectral dispersions of index of refraction \({n(\lambda )}\) and extinction coefficient \({\kappa (\lambda )}\) of undoped amorphous selenium (a-Se) films of three thicknesses (d?≈?0.5, 0.75, and 1.0 µm) were evaluated by analyzing experimental room-temperature normal-incidence transmittance-wavelength (\({{T_{{\text{exp}}}}(\lambda )} - \lambda\)) data (λ =?400–1100 µm) of their air-supported {a-Se film/thick glass slide}-stacks using Swanepoel’s transmission envelope theory of uniform films. Above a wavelength \({{\lambda _c}\,\, \approx \,\,640\;{\text{nm}}}\), as-measured \({{T_{{\text{exp}}}}(\lambda )}\,\, - \,\lambda\) spectra display well-resolved maxima and minima, with minor shrinkage in transparent and weak absorption regions (750–1100 nm). Below \({\lambda _{\text{c}}}\), a smeared sharp decline of \({{T_{{\text{exp}}}}(\lambda )}\) with decreasing λ, signifying strong absorption in a-Se films and existence of band-tail localized states. For λ > λ _c, the \({n\,(\lambda )}\, - \,\lambda\) data retrieved from algebraic envelope procedures followed a Sellmeier-like dispersion relation, with the best-fit values of high-frequency dielectric constant \({{\varepsilon _\infty }\, \approx \,\,{\text{4.9}}}\), static index of refraction \({{n_{\text{0}}} = n\left( {E\, \to \,{\text{0}}} \right)\,\, \approx \,\,{\text{2.43}}}\), and resonance wavelength \({{\lambda _0}\, \approx \,490\,\,{\text{nm}}}\), which may be assigned to onset of photogeneration in a-Se. Urbach-like dependency of absorption coefficient \({\alpha (h{{\nu }})}\) of a-Se films on photon energy \({h{{\nu }}}\) was realized with an Urbach-tail breadth of 85 meV. All achieved optical parameters were found to be slightly dependent on film thickness. Findings of present algebraic analysis are consistent with reported literature results obtained on the basis of other optical analytical approaches.     

Quantification of particle-bubble interactions using atomic force microscopy: A review

The attachment of particles to bubbles in solution is of fundamental importance to several industrial processes, most notably in the process of froth flotation. During this process hydrophobic particles attach to air bubbles in solution, which allows them to be separated as froth at the surface. The addition of chemicals can help to modulate these interactions to increase the yield of the minerals of interest. Over the past decade the atomic force microscope (AFM) has been adapted for use in studying the forces involved in the attachment of single particles to bubbles in the laboratory. This allows the measurement of actual DLVO (Derjaguin, Landau, Vervey and Overbeek) forces and adhesive contacts to be measured under different conditions. In addition contact angles may be calculated from features of force versus distance curves. It is the purpose of this article to illustrate how the colloid probe technique can be used to make single particle-bubble interactions and to summarise the current literature describing such experiments.