Gas-liquid mass transfer in three-phase fluidized beds with viscous pseudoplastic liquids

Liquid phase volumetric mass transfer coefficients for oxygen were determined in three-phase fluidized beds of 8 mm glass spheres fluidized by a cocurrent flow of air and pseudoplastic polysaccharide solutions (carboxymethyl cellulose, xanthan). A semi-theoretical relation for the effective shear rate was suggested. The mass transfer coefficients could be correlated, together with literature data for particle diameters of 3 mm and 5 mm in other liquids, using the terminal velocity as the particle-specific property.     

Microwave-Assisted Batch Extraction of Polyphenols from Sea Buckthorn Leaves

Extraction of polyphenols from sea buckthorn leaves using microwave-assisted extraction (MAE) is described. The influence of different parameters on the extraction process (reactor type, stirring rate, extraction time, temperature, ethanol/water ratio) was studied. The polyphenolic extracts were analyzed in order to determine the total phenolic content (TPC) either by the Folin–Ciocalteu method or by differential pulse voltammetry (DPV), and the concentration of the main polyphenolic compounds by high-performance liquid chromatography (HPLC). The specific microwave energy was also determined. MAE resulted in a shorter extraction time (7.5 versus 30 min for the conventional method). The best results for MAE were obtained at a temperature of 90°C, using a solvent/plant ratio of 20/1 and 50% ethanol in the extraction solvent. The highest values of antioxidant capacity were obtained for polyphenolic extracts resulted from microwave extraction.     

Development of Saturable Absorbers for Laser Passive Q‐Switching near 1.5 μm Based on Transparent Ceramic Co2+:MgAl2O4

We describe the development of a reasonable cost Co²⁺:MgAl₂O₄ transparent ceramic plates fabrication technology that allows the producing of parts functioning as passive laser Q‐switches in the 1.3–1.7 μm domain. The main relevant material characteristics were measured. The absorption band, positioned between 1.2 and 1.7 μm, is typical of the ⁴A₂ (⁴F) → ⁴T₁ (⁴F) transition of Co²⁺ substituting Mg²⁺ ions in their T_d symmetry sites. The measured ground‐state absorption cross section σ_gs = 2.9 × 10^?19 cm², saturation contrast γ = 0.12, and depleted ground‐state recovery time τ₂ = 110–430 ns render such parts suitable for the intended application. The radiative lifetime was estimated as . The spin‐orbit splitting constant was estimated as ξ_SL??150 cm^?1 for the ⁴F parent ground state, and ξ_SL ? –575 cm^?1 for the ⁴P parent excited state. Obtained specimens had a transmission of ~80% (t = 2 mm, λ = 600 nm) and included some opaque, white spots. Further improvement of host optical transmission and resistance to laser damage are necessary.     

Application of Selective 29Si Isotopic Enrichment to Studies of the Structure of Calcium Silicate Hydrate (C-S-H) Gels

Selective isotopic enrichment of SiO₂ with ²⁹Si in a mixture with tricalcium silicate (C₃S) has allowed the Si from this phase to be effectively labeled during the course of the hydration reaction, thus isolating its contribution to the reaction. A double Q₂ signal has been observed in ²⁹SI solid-state MAS NMR spectroscopy of C-S-H gels of relatively low Ca/Si ratio, prepared by hydration or by carbonation of a C₃S paste. The origin of the weaker, downfield peak is discussed and tentatively attributed to bridging tetrahedra of a dreierkette silicate chain structure.     

Improved LC-MS method for the determination of fatty acids in red blood cells by LC-orbitrap MS

We report a new method for fast and sensitive analyses of biologically relevant fatty acids (FAs) in red blood cells (RBC) by liquid chromatography mass spectrometry (LC-MS). A new chemical derivatization approach was developed forming picolylamides from FAs in a quantitative reaction. Fourteen derivatized FA standards, including saturated and unsaturated FAs from C14 to C22, were efficiently separated within 15 min. In addition, the use of a recently introduced benchtop orbitrap mass spectrometer under positive electrospray ionization (ESI) full scan mode showed a 2-10-fold improvement in sensitivity compared with a conventional tandem MS method, with a limit of detection in the low femtomole range for saturated and unsaturated FAs. The developed method was applied to determine FA concentrations in RBC with intra- and interday coefficients of variation below 10%.     

Taylor dispersion of contaminants by random waves

The longitudinal dispersion of contaminants due to mass transport induced by random surface waves is examined. The wave kinematics under random waves are first derived, including the second-order drift profile. The relationship between the dispersive coefficient and wave drift is then established following the approach in J. Hydraul. Res. (2000) 38:41–48. Subsequently, the magnitude of the longitudinal dispersive coefficient is examined under both developed and developing sea states, represented by the P–M spectrum and the Wen spectrum, respectively. The results show that the longitudinal dispersion by random waves is significantly stronger than an equivalent regular sea state with a similar wave energy density. Furthermore, the dispersive effect in the developing sea state is found to be stronger than the developed sea state with comparable wave-energy density, which can be attributed to the differences in the spectral shape between the two states.