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Absorption Process (absorption + process)
Selected AbstractsAbsorption of H2S in NaOCl caustic aqueous solutionENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2001Luke Chen Pilot plant experimental data were collected to study the feasibility of H2S removal from air streams utilizing aqueous solutions. Solutions of NaOCl/NaOH were tested in a packed bed scrubber and found to be effective. An efficiency of 99.2% H2S removal was achieved at a gas flow rate of 790 lb/f2 -hr and liquid-gas ratio of 5.06. Sodium hydroxide was found to be the active ingredient in the absorption process. A minimum alkalinity of pH 11 in the scrubbing solution was required for the H2S to be efficiently absorbed in the packed bed scrubber. For gas flow rates up to 2,100 lb/f2 hr, the height of a transfer unit (HTU) varied from 1.8 ft to 2 ft with different proportions of NaOCl and NaOH in the solution. [source] Steam absorption process of water/LiBr system inside vertical small bore pipesHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 1 2005Masanori Kiyota Abstract In a previous paper, a numerical model for absorption within vertical pipes was proposed and compared with the experiments. Agreements were good for pipes with an OD 28,15 mm but at 10 mm pipe experiments fell below the predicted values. For smaller diameters, the difference between the surface area of the falling liquid film and that of the outer surface of the pipe is not negligible and the thickness of the liquid film is also not negligible. In this paper a new model is formulated in cylindrical coordinates and experiments using pipes with 9.52 mm and 7 mm OD are done. Smooth pipes and two kinds of internally finned pipes, originally developed and used to enhance the heat transfer characteristics of the evaporator and condenser of a refrigerator using HFC as refrigerant, are tested in the experiments. The absorption performance is enhanced by 30% when compared to the smooth pipes, but the difference between the finned pipes is small. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(1): 18,28, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20040 [source] Direct Laser Writing of Photoresponsive Colloids for Microscale Patterning of 3D Porous Structures,ADVANCED MATERIALS, Issue 1 2009Matthew C. George 3D patterning of colloidal structures is enabled by the phototriggered aggregation of photoresponsive colloids. We use direct laser writing to locally control aggregation behavior of photoresponsive colloids via a 2-photon absorption process. 3D structures composed of porous walls are harvested after rinsing away unexposed colloidal species. Aggregation is fully reversible with sufficient agitation. [source] Time-dependent density functional theory calculations of X-ray absorptionINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2003J. J. Rehr Abstract There has been dramatic progress in recent years both in calculations and in the interpretation of X-ray absorption spectra (XAS). Often an independent-electron approximation with final state potentials is adequate. However, for soft X-rays (i.e., energies less than about 1 keV) local field effects can be important. Such local fields arise from the dynamic screening of both the external X-ray field and the coupling to the core hole created in the absorption process. These effects require a theory that goes beyond the independent-electron approximation. We developed an efficient approach for treating such effects in molecules and solids based on a generalization of time-dependent density functional theory (TDDFT), with a local approximation for the screening response. The approach has been implemented in our self-consistent, real-space Green's function code FEFF8 in terms of screened dipole transition matrix elements. Typical results are discussed for the XAS of the N4,5 edges of solid Xe and for the L2,3 edges of 3d transition metals. Our approach accounts for the deviations of the L3/L2 intensity branching ratio from the 2:1 value of the independent electron approximation. For the N4,5 edges of Xe, the approach also accounts for the observed fine structure. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 [source] Comparative study of hydrogen, argon, and xenon uptake into a propane hydrateAICHE JOURNAL, Issue 10 2010Joanne A. Abbondondola Abstract The rate of absorption of hydrogen, argon, and xenon into a Type II propane clathrate hydrate has been studied. The propane hydrate is synthesized from 250-,m ice grains, is estimated to have a porosity of 65% and has roughly the consistency of chalk. Hydrogen is rapidly absorbed by the hydrate sample and approaches the equilibrium vapor pressure in an hour before a very slow residual absorption process ensues. For an initial hydrogen pressure of 1.5 MPa, about 4.5% of the available 512 cages are occupied by hydrogen after 1 h, and 4.9% after 18 h. In contrast, for both argon and xenon significantly more gas is absorbed by the hydrate but at a much slower rate: about 5% as fast for xenon and 1% as fast for argon. We conclude that hydrogen readily diffuses through the propane hydrate microcrystal structure, while argon and xenon are probably absorbed by growing new double hydrate while consuming the propane hydrate. Although considerably higher pressures would be required to store significant quantities of hydrogen in propane hydrate, it appears that the crystal can be loaded and emptied in relatively short times. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Profile of P-glycoprotein distribution in the rat and its possible influence on the salbutamol intestinal absorption processJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2004Belén Valenzuela Abstract The intrinsic absorption of salbutamol in different intestinal segments of the rat was measured and related with the corresponding intestinal P-glycoprotein (P-gp) expression levels. The apparent absorption rate constants (ka, h,1) observed in each fraction by means of the "in situ" rat gut absorption method after perfusion of a 0.29-mM isotonic solution of salbutamol were used as absorption indexes. In a separate series of studies, a semiquantitative analysis of the mRNA expression of P-gp by means of polymerase chain reaction and Western blot with an antibody raised against the P-gp were also performed. The "in situ" ka values determined in the different segments (h,1) showed that the absorption is not homogeneous along the intestinal tract, that is, 0.499,±,0.054 for colon, 0.474,±,0.052 for the proximal segment, 0.345,±,0.014 for the mean, and 0.330,±,0.023 for the distal fraction. Addition of verapamil to the perfusion fluid did provide a better absorption of salbutamol in the distal segment. The analysis of the mRNA expression and levels of P-gp showed that the enzyme content in each section of the intestine was inversely related to salbutamol absorption. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:1641,1648, 2004 [source] Localized biexcitons in AlxGa1,xN ternary alloy epitaxial layersPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003Y. Yamada Abstract Excitonic optical properties of AlxGa1,xN ternary alloy epitaxial layers have been studied by means of photoluminescence (PL), time-resolved PL, and PL excitation (PLE) spectroscopy. The luminescence line due to radiative recombination of biexcitons was clearly observed in an Al0.08Ga0.92N epitaxial layer. The PL decay time of excitons and biexcitons was estimated to be 350 and 210 ps, respectively. PLE spectroscopy of biexcitons enabled us to observe a two-photon absorption process of biexcitons. On the basis of the energy separation between exciton resonance and two-photon biexciton resonance, the binding energy of biexcitons in Al0.08Ga0.92N was estimated to be 15 ± 2 meV. This value was approximately 2.5 times as large as the binding energy of biexcitons in GaN. This value was also found to be comparable to the observed energy separation between the exciton luminescence and the biexciton luminescence, which indicated the strong localization of biexcitons. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Time evolution of absorption process in nonlinear metallic photonic crystalsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S1 2009Mahi R. Singh Abstract The time evolution of the absorption coefficient in metallic photonic crystals has been studied numerically. These crystals are made from metallic spheres which are arranged periodically in air. The refractive index of the metallic spheres depends on the plasma frequency. Probe and pump fields are applied to monitor the absorption process. Ensembles of three-level particles are embedded in the crystal. Nanoparticles are interactiing with the metallic crystals via the electron-photon interaction. It is found that when the resonance states lie away from the band edges system goes to transparent sate. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Modified suspension-PVC particles as absorbents of ortho -dichlorobenzene from waterPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2 2003M. Shach-Caplan Abstract Modified porous PVC particles are studied as absorbents of o-dichlorobenzene (DCB), from water. The modified particles were produced by an in-situ stabilizer-free polymerization/crosslinking of a monomer/crosslinker/peroxide solution absorbed within commercial porous suspension-type PVC particles. The modifying monomers used include styrene with divinyl benzene (DVB) as a crosslinking comonomer, methyl methacrylate (MMA), butyl acrylate (BA), or ethylhexyl acrylate (EHA) with ethylene glycol dimethacrylate (EGDMA) as a crosslinking comonomer. The effect of the nature of the monomers, morphology, porosity, surface area and composition of the modified PVC particles on DCB absorption was studied. Batch experiments (absorption rate and isotherms) were used to screen the PVC absorbents on the basis of absorption rate and absorption capacity. Continuous absorption column experiments were conducted to study the parameters characterizing the absorption process. Both the unmodified and modified PVC particles absorb DCB from water. The PBA and PEHA-modified PVC particles approach equilibrium capacity faster and have greater absorption capacity than neat PVC, PS-modified PVC and PMMA-modified PVC particles. The absorption characteristics are influenced by the modifying polymer's Tg. The rubbery nature of PBA and PEHA yields better absorption in spite of the significantly lower surface area and porosity obtained in the modified PVC particles. Thus, indicating that fast adsorption followed by bulk absorption of DCB is taking place. A clear influence of the crosslinking effect was not established. The continuous absorption experiments were found more efficient than the batch absorption experiments. Copyright © 2003 John Wiley & Sons, Ltd. [source] Pharmacokinetic,pharmacodynamic modelling of the analgesic effects of lumiracoxib, a selective inhibitor of cyclooxygenase-2, in ratsBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2010DA Vásquez-Bahena Background and purpose:, This study establishes a pharmacokinetic/pharmacodynamic (PK/PD) model to describe the time course and in vivo mechanisms of action of the antinociceptive effects of lumiracoxib, evaluated by the thermal hyperalgesia test in rats. Experimental approach:, Female Wistar fasted rats were injected s.c. with saline or carrageenan in the right hind paw, followed by either 0, 1, 3, 10 or 30 mg·kg,1 of oral lumiracoxib at the time of carrageenan injection (experiment I), or 0, 10 or 30 mg·kg,1 oral lumiracoxib at 4 h after carrageenan injection (experiment II). Antihyperalgesic responses were measured as latency time (LT) to a thermal stimulus. PK/PD modelling of the antinociceptive response was performed using the population approach with NONMEM VI. Results:, A two-compartment model described the plasma disposition. A first-order model, including lag time and decreased relative bioavailability as a function of the dose, described the absorption process. The response model was: LT=LT0/(1 +MED). LT0 is the baseline response, and MED represents the level of inflammatory mediators. The time course of MED was assumed to be equivalent to the predicted profile of COX-2 activity and was modelled according to an indirect response model with a time variant synthesis rate. Drug effects were described as a reversible inhibition of the COX-2 activity. The in vivo estimate of the dissociation equilibrium constant of the COX-2-lumiracoxib complex was 0.24 µg·mL,1. Conclusions:, The model developed appropriately described the time course of pharmacological responses to lumiracoxib, in terms of its mechanism of action and pharmacokinetics. [source] Recovery of CO2 with MEA and K2CO3 absorption in the IGCC systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2004Baoqun Wang Abstract Recovery of CO2 with monoethanolamine (MEA) and hot potassium carbonate (K2CO3) absorption processes in an integrated gasification combined cycle (IGCC) power plant was studied for the purpose of development of greenhouse gas control technology. Based on energy and exergy analysis of the two systems, improvement options were provided to further reduce energy penalty for the CO2 separation in the IGCC system. In the improvement options, the energy consumption for CO2 separation is reduced by about 32%. As a result, the thermal efficiency of IGCC system is increased by 2.15 percentage-point for the IGCC system with MEA absorption, and by 1.56 percentage-point for the IGCC system with K2CO3 absorption. Copyright © 2004 John Wiley & Sons, Ltd. [source] Saturated absorption and reverse saturated absorption of Cu:SiO2 at , = 532 nmPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2004R. A. Ganeev Abstract Nonlinear absorption in copper-doped silicate glasses was investigated by the Z-scan technique using second harmonic radiation of a Nd:YAG laser (, = 532 nm, , = 55 ps). The simultaneous influence of saturated and reverse saturated nonlinear absorption processes was analyzed. The nonlinear absorption coefficient and the saturation intensity of copper-doped glasses at laser intensity of 5.4 × 109 W cm,2 were measured to be 6 × 10,6 cm W,1 and 4.3 × 108 W cm,2, respectively. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Future investigations of GPS and CSS radio sources with LOFARASTRONOMISCHE NACHRICHTEN, Issue 2-3 2009I.A.G. Snellen Abstract In the next few years, the Low Frequency Array (LOFAR) will open up one of the last astronomically unexplored wavelength regimes. While the LOFAR core is currently being erected in the Netherlands, its outer stations will cover a large part of Europe, resulting in an unprecedented angular resolution at > meter wavelengths. Next to many other exciting scientific endeavours, LOFAR will be the first instrument to probe the low frequency spectra of Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources. It will give new insights into their absorption processes, and probe associated extended emission (possibly linked to earlier epochs of activity) in these enigmatic class of young active galactic nuclei. Furthermore, LOFAR will be sensitive to possibly the most distant GPS and CSS sources, of which their spectral turnovers have redshifted down to the lowest observable radio frequencies (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Pharmacokinetics of ribavirin in patients with hepatitis C virusBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 6 2006Janet R. Wade Aim A population pharmacokinetic analysis was performed using plasma concentration data (n = 7025) from 380 patients to examine the relationship between ribavirin dose and its pharmacokinetics. Methods Ribavirin pharmacokinetics were described by a three-compartment model with sequential zero-order and a first-order absorption processes. Interoccasion variability and food effects were included. Results Lean body weight (range 41,91 kg) was the only covariate with a clinically significant influence on ribavirin pharmacokinetics, affecting clearance (15.3,23.9 l h,1) and the volume of the larger peripheral compartment. Conclusion The model provided a good description of the available data, confirmed by accurate estimates of parameter values and low residual variability (17%). [source] | ||||||||||||||||||||||