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Sample records for absorption model

  1. Time-dependent oral absorption models

    Higaki, K.; Yamashita, S.; Amidon, G. L.

    2001-01-01

    The plasma concentration-time profiles following oral administration of drugs are often irregular and cannot be interpreted easily with conventional models based on first- or zero-order absorption kinetics and lag time. Six new models were developed using a time-dependent absorption rate coefficient, ka(t), wherein the time dependency was varied to account for the dynamic processes such as changes in fluid absorption or secretion, in absorption surface area, and in motility with time, in the gastrointestinal tract. In the present study, the plasma concentration profiles of propranolol obtained in human subjects following oral dosing were analyzed using the newly derived models based on mass balance and compared with the conventional models. Nonlinear regression analysis indicated that the conventional compartment model including lag time (CLAG model) could not predict the rapid initial increase in plasma concentration after dosing and the predicted Cmax values were much lower than that observed. On the other hand, all models with the time-dependent absorption rate coefficient, ka(t), were superior to the CLAG model in predicting plasma concentration profiles. Based on Akaike's Information Criterion (AIC), the fluid absorption model without lag time (FA model) exhibited the best overall fit to the data. The two-phase model including lag time, TPLAG model was also found to be a good model judging from the values of sum of squares. This model also described the irregular profiles of plasma concentration with time and frequently predicted Cmax values satisfactorily. A comparison of the absorption rate profiles also suggested that the TPLAG model is better at prediction of irregular absorption kinetics than the FA model. In conclusion, the incorporation of a time-dependent absorption rate coefficient ka(t) allows the prediction of nonlinear absorption characteristics in a more reliable manner.

  2. Infrared absorption modeling of VOx microbolometer

    Aggoun, Mehdi; Jiang, Jianliang; Khan, M. K.

    2015-08-01

    The absorption model plays an important role in the design of the microbolometer structure regarding the determination of the optimum thickness of the structure layers. Moreover, the infrared absorption depends on the wavelength of the radiation and the material properties. In this paper, we presented an Infrared absorption model with absorption coefficient of 96% at maximum absorption wavelength of 9.89μm which is very close to the expected value 10μm. This model was established by using MATLAB so that the simulation of the infrared absorption of the VOx microbolometer could be accomplished. In order to confirm the role of this modeling in the design of the device structure, comparison with other structures is also studied in this paper.

  3. In Silico Modeling of Gastrointestinal Drug Absorption: Predictive Performance of Three Physiologically Based Absorption Models.

    Sjögren, Erik; Thörn, Helena; Tannergren, Christer

    2016-06-01

    Gastrointestinal (GI) drug absorption is a complex process determined by formulation, physicochemical and biopharmaceutical factors, and GI physiology. Physiologically based in silico absorption models have emerged as a widely used and promising supplement to traditional in vitro assays and preclinical in vivo studies. However, there remains a lack of comparative studies between different models. The aim of this study was to explore the strengths and limitations of the in silico absorption models Simcyp 13.1, GastroPlus 8.0, and GI-Sim 4.1, with respect to their performance in predicting human intestinal drug absorption. This was achieved by adopting an a priori modeling approach and using well-defined input data for 12 drugs associated with incomplete GI absorption and related challenges in predicting the extent of absorption. This approach better mimics the real situation during formulation development where predictive in silico models would be beneficial. Plasma concentration-time profiles for 44 oral drug administrations were calculated by convolution of model-predicted absorption-time profiles and reported pharmacokinetic parameters. Model performance was evaluated by comparing the predicted plasma concentration-time profiles, Cmax, tmax, and exposure (AUC) with observations from clinical studies. The overall prediction accuracies for AUC, given as the absolute average fold error (AAFE) values, were 2.2, 1.6, and 1.3 for Simcyp, GastroPlus, and GI-Sim, respectively. The corresponding AAFE values for Cmax were 2.2, 1.6, and 1.3, respectively, and those for tmax were 1.7, 1.5, and 1.4, respectively. Simcyp was associated with underprediction of AUC and Cmax; the accuracy decreased with decreasing predicted fabs. A tendency for underprediction was also observed for GastroPlus, but there was no correlation with predicted fabs. There were no obvious trends for over- or underprediction for GI-Sim. The models performed similarly in capturing dependencies on dose and

  4. Strong absorption model and its associated potential

    Using the example of 12C-208Pb elastic scattering at Elab=1449 MeV it is shown that, at sufficiently high energies, a full quantum mechanical inversion of heavy-ion scattering data can be performed. Furthermore it is pointed out that the strong absorption model as parametrized by McIntyre, Wang, and Becker is associated with a potential having strong repulsion at the origin. That repulsion is a remnant of the built-in point Coulomb S matrix. Finally, a systematic study is presented to define the necessary accuracy of experiment required to extend the knowledge of the nucleus-nucleus interaction to smaller radii

  5. Strong absorption model analysis of alpha scattering

    Angular distribution of alpha-particles at several energies, Eα = 21 ∼ 85.6 MeV from a number of nuclei between 20Ni and 119Sn, extending to wide angular range up to ∼ 160 deg. C in some cases, have been analyzed in terms of three-parameter strong absorption model of Frahn and Venter. Interaction radius and surface diffuseness are obtained from the parameter values rendering the best fit to the elastic scattering data. The inelastic scattering of alpha-particles from a number of nuclei, leading to quadrupole and octupole excitations has also been studied giving the deformation parameters βL. (author). 14 refs, 7 figs, 3 tabs

  6. Absorptive Capacity of Information Technology and Its Conceptual Model

    BI Xinhua; YU Cuiling

    2008-01-01

    In order to examine the problem of how to improve the use of information technology (IT) in enterprises, this paper makes an exploration from the perspective of organizational absorptive capacity. We propose the concept of IT absorptive capacity from an organizational level. A dynamic process model is developed to further analyze IT absorption. IT absorptive capacity of this process is embodied as six forms: identification, adoption, adaptation, acceptance, infusion, and knowledge management. By means of questionnaire surveys of 76 Chinese enterprises, the main factors that favor or disable the capacity of each stage are discovered. Using the method of system dynamics, a conceptual model of IT absorptive capacity is developed to analyze the action mechanism of the factors in detail. The model indicates that the critical factors are embodied in the aspect of management. Furthermore, it demonstrates that IT absorption is a spiral process, during which IT absorptive capacity evolves dynamically and, consequently, promotes IT use.

  7. Modeling water/lithium bromide absorption chillers in ASPEN Plus

    Highlights: → Single- and double-effect water/lithium bromide absorption chiller designs are numerically modeled using ASPEN. → The modeling procedure is described and the results are compared to published modeling data to access prediction accuracy. → Predictions for the single- and double-effect designs are within 3% and 5%, respectively of published data for all cycle parameters of interest. → The absorption cycle models presented allow investigation of using absorption chillers for waste heat utilization in the oil and gas industry. -- Abstract: Absorption chillers are a viable option for providing waste heat-powered cooling or refrigeration in oil and gas processing plants, thereby improving energy efficiency. In this paper, single- and double-effect water/lithium bromide absorption chiller designs are numerically modeled using ASPEN. The modeling procedure is described and the results are compared to published modeling data to access prediction accuracy. Predictions for the single- and double-effect designs are within 3% and 5%, respectively of published data for all cycle parameters of interest. The absorption cycle models presented not only allow investigation into the benefits of using absorption chillers for waste heat utilization in the oil and gas industry, but are also generically applicable to a wide range of other applications.

  8. Atmospheric Absorption Models for the Millimeter Wave Range

    Kuhn, Thomas

    2003-01-01

    This thesis deals with absorption models of water vapor, oxygen and nitrogen which are part of the Atmospheric Radiative Transfer System, ARTS, which is a joint development of the Department of Radio and Space Science, Chalmers University of Technology, Göteborg and the Institute of Environmental Physics, University of Bremen. ARTS is designed to be used in remotely sensed data analysis. Since the absorption models are embedded in the broader frame of the radiative transfer equation, the main...

  9. Water Transport Models of Moisture Absorption and Sweat Discharge Yarns

    WANG Fa-ming; ZHOU Xiao-hong; WANG Shan-yuan

    2008-01-01

    An important property of moisture absorption and sweat discharge yams is their water transport property. In the paper, two water transport models of moisture absorption and sweat discharge yams were developed to investigate the influence factors on their wicking rate. In parallel Column Pores Model, wicking rate is determined by the equivalent capillary radius R and length of the capillary tube L. In Pellets Accumulation Model, wicking rate is decided by the capillary radius r and length of the fiber unit assemble L0.

  10. Integro-differential models for percutaneous drug absorption

    Barbeiro, S.; Ferreira, J. A.

    2007-01-01

    In this paper we propose new mathematical models for percutaneous absorption of a drug. The new models are established by introducing, in the classical Fick's law, a memory term being the advection–diffusion equations of the classical models replaced by integro-differential equations. The well-posedness of the models is studied with Dirichlet, Neumann and natural boundary conditions. Methods for the computation of numerical solutions are proposed. Stability and convergence of the introduced m...

  11. Incorporating tissue absorption and scattering in rapid ultrasound beam modeling

    Christensen, Douglas; Almquist, Scott

    2013-02-01

    We have developed a new approach for modeling the propagation of an ultrasound beam in inhomogeneous tissues such as encountered with high-intensity focused ultrasound (HIFU) for treatment of various diseases. This method, called the hybrid angular spectrum (HAS) approach, alternates propagation steps between the space and the spatial frequency domains throughout the inhomogeneous regions of the body; the use of spatial Fourier transforms makes this technique considerably faster than other modeling approaches (about 10 sec for a 141 x 141 x 121 model). In HIFU thermal treatments, the acoustic absorption property of the tissues is of prime importance since it leads to temperature rise and the achievement of desired thermal dose at the treatment site. We have recently added to the HAS method the capability of independently modeling tissue absorption and scattering, the two components of acoustic attenuation. These additions improve the predictive value of the beam modeling and more accurately describes the thermal conditions expected during a therapeutic ultrasound exposure. Two approaches to explicitly model scattering were developed: one for scattering sizes smaller than a voxel, and one when the scattering scale is several voxels wide. Some anatomically realistic examples that demonstrate the importance of independently modeling absorption and scattering are given, including propagation through the human skull for noninvasive brain therapy and in the human breast for treatment of breast lesions.

  12. Model galactic coronae: Ionization structure and absorption-line spectra

    We describe a general model for a gaseous galactic corona, and demonstrate that it is in harmony with a variety of observational and theoretical constraints. We then compute the ionization equilibria of H, He, C, N, O, Si, and S atoms in the corona and determine the strengths of resonance absorption lines arising therein. To this end, we obtain approximate cross sections for ionization of the heavy-element ions by photons of energy E/sub γ/< or =100 eV.We use our results first to discuss the expected absorption spectrum of our Galaxy's corona. Subsequently, we discuss in detail the relevance of our computed equilibria to the suggestion that galactic coronae produce some redshift systems in quasar absorption spectra. Because our model coronae are not isothermal, the ionization structure existing along various lines of sight through them is not in accord with the concept of ''reasonable ionization equilibrium'': a concept assumed to be valid in most analyses of quasar spectra. However, our calculations indicate that typically one well-established redshift system in each quasar absorption spectrum could arise in the corona of an intervening galaxy. This is the number expected from statistical arguments if quasar redshifts are fully cosmological in origin

  13. Absorption Cycle Heat Pump Model for Control Design

    Vinther, Kasper; Just Nielsen, Rene; Nielsen, Kirsten Mølgaard;

    2015-01-01

    actual heat pump located at a larger district heating plant. The model is implemented in Modelica and is based on energy and mass balances, together with thermodynamic property functions for LiBr and water and staggered grid representations for heat exchangers. Model parameters have been fitted to......Heat pumps have recently received increasing interest due to green energy initiatives and increasing energy prices. In this paper, a nonlinear dynamic model of a single-effect LiBr-water absorption cycle heat pump is derived for simulation and control design purposes. The model is based on an...

  14. Remark on: the neutron spherical optical-model absorption.

    Smith, A. B.; Nuclear Engineering Division

    2007-06-30

    The energy-dependent behavior of the absorption term of the spherical neutron optical potential for doubly magic {sup 208}Pb and the neighboring {sup 209}Bi is examined. These considerations suggest a phenomenological model that results in an intuitively attractive energy dependence of the imaginary potential that provides a good description of the observed neutron cross sections and that is qualitatively consistent with theoretical concepts. At the same time it provides an alternative to some of the arbitrary assumptions involved in many conventional optical-model interpretations reported in the literature and reduces the number of the parameters of the model.

  15. Absorption lookup tables in the radiative transfer model ARTS

    We describe the lookup table approach that is used to store pre-calculated absorption data in the radiative transfer model ARTS. The table stores absorption cross sections as a function of frequency, pressure, temperature, and the water vapor volume mixing ratio, where the last dimension is only included for those gas species that require it. The table is used together with an extraction strategy, which uses polynomial interpolation, with recommended interpolation orders between five and seven. We also derived recommended default settings for grid spacings and interpolation orders, and verified that the approach gives very accurate results with these default settings. The tested instrument setups were for AMSU-B, HIRS, and Odin, three well-known satellite remote sensing instruments covering a wide range of frequencies and viewing geometries. Errors introduced by the lookup table were found to be always below a few millikelvin, in terms of the simulated brightness temperature.

  16. Models of ionospheric VLF absorption of powerful ground based transmitters

    İnan, Umran Savaş; Cohen, M. B; Lehtinen, N. G

    2012-01-01

    Models of ionospheric VLF absorption of powerful ground based transmitters M. B. Cohen,1 N. G. Lehtinen,1 and U. S. Inan1,2 Received 5 November 2012; accepted 16 November 2012; published 29 December 2012. [1] Ground based Very Low Frequency (VLF, 3–30 kHz) radio transmitters play a role in precipitation of energetic Van Allen electrons. Initial analyses of the contribution of VLF transmitters to radiation belt losses were based on early models of trans-ionospheric prop...

  17. A dynamic model of digestion and absorption in pigs

    Strathe, Anders Bjerring; Danfær, Allan Christian; Chwalibog, Andrzej

    2008-01-01

    The paper describes and evaluates the construction of a mathematical model to study the kinetics of digestion and absorption in growing pigs. The core of the model is based on a compartmental structure, which divides the gastro-intestinal tract into four anatomical segments: the stomach, two parts...... of the small intestine and the large intestine. Within the large intestine, a microbial sub compartment is also considered. In each of these segments, the major organic nutrients are considered: dietary protein, endogenous protein, amino acids, non-amino acid and non-protein nitrogen, lipids, fatty acids...

  18. A Comprehensive X-Ray Absorption Model for Atomic Oxygen

    Gorczyca, T. W.; Bautista, M. A.; Hasoglu, M. F.; Garcia, J.; Gatuzz, E.; Kaastra, J. S.; Kallman, T. R.; Manson, S. T.; Mendoza, C.; Raassen, A. J. J.; de Vries, C. P.; Zatsarinny, O.

    2013-01-01

    An analytical formula is developed to accurately represent the photoabsorption cross section of atomic Oxygen for all energies of interest in X-ray spectral modeling. In the vicinity of the K edge, a Rydberg series expression is used to fit R-matrix results, including important orbital relaxation effects, that accurately predict the absorption oscillator strengths below threshold and merge consistently and continuously to the above-threshold cross section. Further, minor adjustments are made to the threshold energies in order to reliably align the atomic Rydberg resonances after consideration of both experimental and observed line positions. At energies far below or above the K-edge region, the formulation is based on both outer- and inner-shell direct photoionization, including significant shake-up and shake-off processes that result in photoionization-excitation and double-photoionization contributions to the total cross section. The ultimate purpose for developing a definitive model for oxygen absorption is to resolve standing discrepancies between the astronomically observed and laboratory-measured line positions, and between the inferred atomic and molecular oxygen abundances in the interstellar medium from XSTAR and SPEX spectral models.

  19. Photosensitizer absorption coefficient modeling and necrosis prediction during Photodynamic Therapy.

    Salas-García, Irene; Fanjul-Vélez, Félix; Arce-Diego, José Luis

    2012-09-01

    The development of accurate predictive models for Photodynamic Therapy (PDT) has emerged as a valuable tool to adjust the current therapy dosimetry to get an optimal treatment response, and definitely to establish new personal protocols. Several attempts have been made in this way, although the influence of the photosensitizer depletion on the optical parameters has not been taken into account so far. We present a first approach to predict the spatio-temporal variation of the photosensitizer absorption coefficient during PDT applied to dermatological diseases, taking into account the photobleaching of a topical photosensitizer. This permits us to obtain the photons density absorbed by the photosensitizer molecules as the treatment progresses and to determine necrosis maps to estimate the short term therapeutic effects in the target tissue. The model presented also takes into account an inhomogeneous initial photosensitizer distribution, light propagation in biological media and the evolution of the molecular concentrations of different components involved in the photochemical reactions. The obtained results allow to investigate how the photosensitizer depletion during the photochemical reactions affects light absorption by the photosensitizer molecules as the optical radiation propagates through the target tissue, and estimate the necrotic tumor area progression under different treatment conditions. PMID:22704663

  20. Managing Creativity for Absorptive Capacity: The NIH Syndrome and the Implementation of Open Innovation Business Model

    Cokpekin, Özge

    The benefits of the open innovation business model and the absorptive capacity necessary to acquire and utilize external knowledge have been discussed extensively. An emerging literature stream has identified certain intra-organizational antecedents of absorptive capacity. However how firms...

  1. A model for partitioning particulate absorption into phytoplanktonic and detrital components

    Cleveland, J. S.; Perry, M. J.

    1994-01-01

    A model for partitioning total particulate absorption, measured on glass fiber filters, into phytoplanktonic and detrital components is developed. The model reconstructs absorption spectra for living phytoplankton using total particulate absorption at the red absorption maxima for chlorophylls a and b, concentrations of chlorophyll a and pheopigment, and mean normalized absorption spectra for laboratory-grown algal cultures. The model was developed in stages for two types of phytoplankton assemblages. Section A of the model applies to waters dominated by eukaryotic algae and is based on absorption spectra for chromophytic (phytoplankton containing chlorophyll c) and chlorophytic (containing chlorophyll b) species. Section B of the model, allowing more variability in spectral shape, was developed for algal communities with more diverse pigmentation. All spectra are processed through Section A, with an internal evaluation determining whether processing continues through Section B. Detrital spectra, generated as the difference between total particulate and modelled phytoplanktonic spectra, included pheopigment absorption and had high blue absorption. Blind tests on samples of known composition predicted absorption within 8-10% at 436 nm and 1-13% when averaged from 400 to 700 nm, which is within the expected accuracy of the glass fiber filter method. No true measure of phytoplankton absorption in field samples is available for testing the model, but results from methanol-extractions were used for comparison despite inclusion of pheopigment absorption as "phytoplankton". For samples collected from coastal waters of Washington State, the Sargasso Sea and coastal waters of Norway, modelled absorption (averaged over 400-700 nm) ranged from 25% lower to 0.5% higher than the methanol-extraction results; pheopigment absorption inappropriately included in the phytoplankton component accounts for the higher phytoplanktonic absorption estimated by the methanol technique

  2. The quasi deuteron model for low energy pion absorption

    In this thesis pion absorption in complex nuclei is studied in the quasi-deuteron model in which the pion is absorbed on a nucleon pair in the nucleus. The mechanism is studied in the low-energy domain since then the in-medium (pi→NN) operator turns out to be of simple character. In Ch. 2 and 3 this operator is constructed and analytical expressions are derived for (pi,NN) distributions in a plane wave impulse approximation for nuclei. The results turn out to be very useful for developing insight in the possibilities inherent in the QDM and the interpretation of the results in later chapters. Ch. 4 to 6 are devoted to the more realistic distorted wave calculations. In Ch. 4 the formal framework is presented and the calculational details are discussed. Ch.5 and 6 contain the comparison to stopped pion and in-flight data respectively. In Ch. 7 the main results are summarized. (Auth.)

  3. Modelling the Absorption Measurement Distribution (AMD) for Mrk 509

    Adhikari, T.; Rozanska, A.; Sobolewska, M.; Czerny, B.

    2015-07-01

    Absorption Measurement Distribution (AMD) measures the distribution of absorbing column over a range of ionization parameters of the X-ray absorbers in Seyfert galaxies. In this work, we modeled the AMD in Mrk 509 using its recently published broad band Spectral Energy Distribution (SED). This SED is used as an input for radiative transfer computations with full photoionization treatment using the photoionization codes Titan and Cloudy. Assuming a photoionized medium with a uniform total pressure (gas+radiation), we reproduced the discontunity in the observed AMD distribution which is usually described as the region of thermal instability of the absorber. We also studied the structure and properties of the warm absorber in Mrk 509.

  4. Evaluation and Modeling of the Digestion and Absorption of Novel Manufacturing Technology in Food Enterprises

    Kerong Zhang; Wuyi Liu

    2015-01-01

    The food industry is more and more in need of importing and absorption new technologies. Focusing on all the possible issues of contradiction and difficulty to improve the digestion and absorption of novel manufacturing technology, a set of customized dynamic quantitative evaluation models were put forward that made it easy to model and supervise the usages, digestion and absorption of novel manufacturing technology in food enterprises. According to the proposed set of evaluation models, anyo...

  5. A model for the spectral dependence of optically induced absorption in amorphous silicon

    Lawandy, N. M.

    1990-01-01

    A model based on transitions from localized band tail states to states above the mobility edge is used to explain the broad band induced absorptions observed in recent pump-probe experiments. The model gives the observed decrease of absorption with frequency at subband gap photo energies and high carrier densities (of about 10 to the 20th/cu cm). At lower carrier densities, the absorption has a maximun which is sensitive to the spatial extent of the band tail states.

  6. Constant optimization of oral drug absorption kinetics in the compartment absorption and transit models using particle swarm optimization algorithm

    Prabowo, K.; Sumaryada, T.; Kartono, A.

    2016-01-01

    Simulation of predictive modeling oral drug namely Compartment Absorption and Transit (CAT) using Particle Swarm Optimization (PSO) algorithm has been performed. This research will be carried out optimization of kinetic constant value oral drug use PSO algorithm to obtain the best global transport constant values for CAT equation that can predict drug concentration in plasma. The value of drug absorption rate constant for drug atenolol 25 mg is k10, k12, k21, k13 and k31 with each value is 0.8562, 0.3736, 0.2191, 0.4334 and 1.000 have been obtained thus raising the value of the coefficient of determination of a model CAT. From the experimental data plasma drug concentrations used are Atenolol, the coefficient of determination (R2) obtained from simulations atenolol 25 mg (PSO) was 81.72% and 99.46%. Better correlation between the dependent variable as the drug concentration and explanatory variables such as mass medication, plasma volume, and rate of absorption of the drug has increased in CAT models using PSO algorithm. Based on the results of CAT models fit charts can predict drug concentration in plasma.

  7. Wave scattering through classically chaotic cavities in the presence of absorption: A maximum-entropy model

    Pier A Mello; Eugene Kogan

    2002-02-01

    We present a maximum-entropy model for the transport of waves through a classically chaotic cavity in the presence of absorption. The entropy of the -matrix statistical distribution is maximized, with the constraint $\\langle {\\rm Tr}SS^{\\dagger}\\rangle = n: n$ is the dimensionality of , and 0 ≤ ≤ 1. For = 1 the -matrix distribution concentrates on the unitarity sphere and we have no absorption; for = 0 the distribution becomes a delta function at the origin and we have complete absorption. For strong absorption our result agrees with a number of analytical calculations already given in the literature. In that limit, the distribution of the individual (angular) transmission and reflection coefficients becomes exponential – Rayleigh statistics – even for = 1. For ≫ 1 Rayleigh statistics is attained even with no absorption; here we extend the study to < 1. The model is compared with random-matrix-theory numerical simulations: it describes the problem very well for strong absorption, but fails for moderate and weak absorptions. The success of the model for strong absorption is understood in the light of a central-limit theorem. For weak absorption, some important physical constraint is missing in the construction of the model.

  8. An Empirical Investigation into a Subsidiary Absorptive Capacity Process Model

    Schleimer, Stephanie; Pedersen, Torben

    2011-01-01

    literature. However, it remains to be surrounded by considerable ambiguity in terms of its actual meaning, the drivers influencing its evolution, and its impact on related outcomes. In this study, we take on some of the major criticisms and recent suggestions from the absorptive capacity literatu...

  9. Pharmacokinetic model for the absorption of subcutaneously injected soluble insulin and monomeric insulin analogues.

    Trajanoski, Z; Wach, P; Kotanko, P; Ott, A; Skraba, F

    1993-09-01

    A subcutaneous insulin absorption model is presented for parameter estimation from the time course of plasma insulin. Modifications of a published model were made for the absorption of soluble insulin and monomeric insulin analogues in the range of therapeutic concentrations and volumes. The modified diffusion-dissociation model with distributed parameters was approximated by a multiple-compartment model. Subcutaneous absorption of soluble insulin and monomeric insulin analogues with various volumes, concentrations, and injection depths was simulated. The model for soluble insulin exhibits volume, concentration, and injection depth dependent absorption, as experimentally observed. It was found that binding of soluble insulin in the subcutaneous tissue is negligible for U-40 and U-100 strengths. The absorption of identical doses (10 U) of soluble U-40 insulin was markedly faster (T-50% = 159.4 min) than the absorption of U-100 (T-50% = 196.2 min). According to the simulation results, the absorption rate of monomeric analogues is not dependent on concentration. No significant chances of the absorption rate could also be observed by varying volume and injection depth of the monomeric analogues. PMID:8218870

  10. Optical Absorptivity versus Molecular Composition of Model Organic Aerosol Matter

    Rincón, Angela G.; Guzmán, Marcelo I.; Hoffmann, Michael R.; Colussi, A. J.

    2009-01-01

    Aerosol particles affect the Earth’s energy balance by absorbing and scattering radiation according to their chemical composition, size, and shape. It is generally believed that their optical properties could be deduced from the molecular composition of the complex organic matter contained in these particles, a goal pursued by many groups via high-resolution mass spectrometry, although: (1) absorptivity is associated with structural chromophores rather than with molecular formulas, (2) compos...

  11. A diffusion-diffusion model for percutaneous drug absorption.

    Kubota, K; Ishizaki, T

    1986-08-01

    Several theories describing percutaneous drug absorption have been proposed, incorporating the mathematical solutions of differential equations describing percutaneous drug absorption processes where the vehicle and skin are regarded as simple diffusion membranes. By a solution derived from Laplace transforms, the mean residence time MRT and the variance of the residence time VRT in the vehicle are expressed as simple elementary functions of the following five pharmacokinetic parameters characterizing the percutaneous drug absorption: kd, which is defined as the normalized diffusion coefficient of the skin, kc, which is defined as the normalized skin-capillary boundary clearance, the apparent length of diffusion of the skin 1d, the effective length of the vehicle lv, and the diffusion coefficient of the vehicle Dv. All five parameters can be obtained by the methods proposed here. Results of numerical computation indicate that: concentration-distance curves in the vehicle and skin approximate two curves which are simply expressed using trigonometric functions when sufficient time elapses after an ointment application; the most suitable condition for the assumption that the concentration of a drug in the uppermost epidermis can be considered unchanged is the case where the partition coefficient between vehicle and skin is small, and the constancy of drug concentration is even more valid when the effective length of the vehicle is large; and the amount of a drug in the vehicle or skin and the flow rate of the drug from vehicle into skin or from skin into blood becomes linear on a semilogarithmic scale, and the slopes of those lines are small when Dv is small, when the partition coefficient between vehicle and skin is small, when lv is large, or when kc is small. A simple simulation method is also proposed using a biexponential for the concentration-time curve for the skin near the skin-capillary boundary, that is, the flow rate-time curve for drug passing from skin

  12. Electron and proton absorption calculations for a graphite/epoxy composite model. [large space structures

    Long, E. R., Jr.

    1979-01-01

    The Bethe-Bloch stopping power relations for inelastic collisions were used to determine the absorption of electron and proton energy in cured neat epoxy resin and the absorption of electron energy in a graphite/epoxy composite. Absorption of electron energy due to bremsstrahlung was determined. Electron energies from 0.2 to 4.0 MeV and proton energies from 0.3 to 1.75 MeV were used. Monoenergetic electron energy absorption profiles for models of pure graphite, cured neat epoxy resin, and graphite/epoxy composites are reported. A relation is determined for depth of uniform energy absorption in a composite as a function of fiber volume fraction and initial electron energy. Monoenergetic proton energy absorption profiles are reported for the neat resin model. A relation for total proton penetration in the epoxy resin as a function of initial proton energy is determined. Electron energy absorption in the composite due to bremsstrahlung is reported. Electron and proton energy absorption profiles in cured neat epoxy resin are reported for environments approximating geosynchronous earth orbit.

  13. Penetration of laser light through biological materials - discrete models of reflection, absorption and scattering

    In this paper discrete models of absorption (DiMoScaLL) of laser light by biological materials are described. Individual models are integrated into a complex model - DiMoRAS. All the models are realized by finite automates (homogeneous structures) (Authors)

  14. DOUBLE SHELL TANK (DST) HYDROXIDE DEPLETION MODEL FOR CARBON DIOXIDE ABSORPTION

    OGDEN DM; KIRCH NW

    2007-10-31

    This document generates a supernatant hydroxide ion depletion model based on mechanistic principles. The carbon dioxide absorption mechanistic model is developed in this report. The report also benchmarks the model against historical tank supernatant hydroxide data and vapor space carbon dioxide data. A comparison of the newly generated mechanistic model with previously applied empirical hydroxide depletion equations is also performed.

  15. DOUBLE-SHELL TANK (DST) HYDROXIDE DEPLETION MODEL FOR CARBON DIOXIDE ABSORPTION

    This document generates a supernatant hydroxide ion depletion model based on mechanistic principles. The carbon dioxide absorption mechanistic model is developed in this report. The report also benchmarks the model against historical tank supernatant hydroxide data and vapor space carbon dioxide data. A comparison of the newly generated mechanistic model with previously applied empirical hydroxide depletion equations is also performed

  16. Modelling of the X-ray broad absorption features in Narrow-Line Seyfert 1s

    Porquet, D; Dumont, A M

    2000-01-01

    We investigate the origin of the broad absorption features detected near 1-1.4 keV in several Narrow Line Seyfert 1 galaxies, by modelling the absorbing medium with various physical parameters, using the ionization code PEGAS. The observed properties of the X-ray absorption features can be reproduced by taking into account the peculiar soft X-ray excess which is well fitted by a blackbody plus an underlying power law. We equally stress that the emission coming from the absorbing medium (related to the covering factor) has a strong influence on the resulting X-ray spectrum, in particular on the apparent position and depth of the absorption features. A non-solar iron abundance may be required to explain the observed deep absorption. We also investigate the influence of an additional collisional ionization process (hybrid case) on the predicted absorption features.

  17. Modelling of the X-ray broad absorption features in Narrow-Line Seyfert 1s

    Porquet, Delphine; Mouchet, Martine; Dumont Anne-Marie

    2000-09-01

    We investigate the origin of the broad absorption features detected near 1-1.4 keV in several Narrow-Line Seyfert 1 galaxies, by modelling the absorbing medium with various physical parameters, using the ionization code PEGAS. The observed properties of the X-ray absorption features can be reproduced by taking into account the peculiar soft X-ray excess which is well fitted by a blackbody plus an underlying power law. We equally stress that the emission coming from the absorbing medium (related to the covering factor) has a strong influence on the resulting X-ray spectrum, in particular on the apparent position and depth of the absorption features. A non-solar iron abundance may be required to explain the observed deep absorption. We also investigate the influence of an additional collisional ionization process ("hybrid case") on the predicted absorption features.

  18. An Inverse Modeling Approach to Estimating Phytoplankton Pigment Concentrations from Phytoplankton Absorption Spectra

    Moisan, John R.; Moisan, Tiffany A. H.; Linkswiler, Matthew A.

    2011-01-01

    Phytoplankton absorption spectra and High-Performance Liquid Chromatography (HPLC) pigment observations from the Eastern U.S. and global observations from NASA's SeaBASS archive are used in a linear inverse calculation to extract pigment-specific absorption spectra. Using these pigment-specific absorption spectra to reconstruct the phytoplankton absorption spectra results in high correlations at all visible wavelengths (r(sup 2) from 0.83 to 0.98), and linear regressions (slopes ranging from 0.8 to 1.1). Higher correlations (r(sup 2) from 0.75 to 1.00) are obtained in the visible portion of the spectra when the total phytoplankton absorption spectra are unpackaged by multiplying the entire spectra by a factor that sets the total absorption at 675 nm to that expected from absorption spectra reconstruction using measured pigment concentrations and laboratory-derived pigment-specific absorption spectra. The derived pigment-specific absorption spectra were further used with the total phytoplankton absorption spectra in a second linear inverse calculation to estimate the various phytoplankton HPLC pigments. A comparison between the estimated and measured pigment concentrations for the 18 pigment fields showed good correlations (r(sup 2) greater than 0.5) for 7 pigments and very good correlations (r(sup 2) greater than 0.7) for chlorophyll a and fucoxanthin. Higher correlations result when the analysis is carried out at more local geographic scales. The ability to estimate phytoplankton pigments using pigment-specific absorption spectra is critical for using hyperspectral inverse models to retrieve phytoplankton pigment concentrations and other Inherent Optical Properties (IOPs) from passive remote sensing observations.

  19. Simulation Model for Dynamic Operation of Double-Effect Absorption Chillers

    Ahmed Mojahid Sid Ahmed Mohammed Salih

    2014-07-01

    Full Text Available The development in the field of refrigeration and air conditioning systems driven by absorption cycles acquired a considerable importance recently. For commercial absorption chillers, an essential challenge for creating chiller model certainly is the shortage of components technical specifications. These kinds of specifications are usually proprietary for chillers producers. In this paper, a double-effect parallel-flow-type steam absorption chiller model based on thermodynamic and energy equations is presented. The chiller studied is Lithium bromide-water with capacity of 1250 RT (Refrigeration Tons. The governing equations of the dynamic operation of the chiller are developed. From available design information, the values of the overall heat transfer coefficients multiplied by the surface area are computed. The dynamic operation of the absorption chiller is simulated to study the performance of the system. The model is able to provide essential details of the temperature, concentration, and flow rate at each state point in the chiller.

  20. Theoretical analysis of electronic absorption spectra of vitamin B12 models

    Andruniow, Tadeusz; Kozlowski, Pawel M.; Zgierski, Marek Z.

    2001-10-01

    Time-dependent density-functional theory (TD-DFT) is applied to analyze the electronic absorption spectra of vitamin B12. To accomplish this two model systems were considered: CN-[CoIII-corrin]-CN (dicyanocobinamide, DCC) and imidazole-[CoIII-corrin]-CN (cyanocobalamin, ImCC). For both models 30 lowest excited states were calculated together with transition dipole moments. When the results of TD-DFT calculations were directly compared with experiment it was found that the theoretical values systematically overestimate experimental data by approximately 0.5 eV. The uniform adjustment of the calculated transition energies allowed detailed analysis of electronic absorption spectra of vitamin B12 models. All absorption bands in spectral range 2.0-5.0 eV were readily assigned. In particular, TD-DFT calculations were able to explain the origin of the shift of the lowest absorption band caused by replacement of the-CN axial ligand by imidazole.

  1. On the SO2 Problem in Thermal Power Plants. 1. Absorption processes modeling

    Chr. Boyadjiev,

    2015-10-01

    Full Text Available A theoretical analysis, of the processes for gas purification from low SO2 concentration in the thermal power plants, is presented. A new approach, for qualitative analysis (convection-diffusion type of model and quantitative description (average concentration model of the absorption processes in column apparatuses, is proposed. The theoretical analysis of the physical absorption, chemical absorption and absorption with two-phase absorbent, is shown. The presented theoretical analysis of the methods and apparatuses for waste gases purification from SО2, using two-phase absorbent (CaCO3 suspension, shows, that the process is physical absorption practically and the mass transfer resistances in the gas and liquid phases are 44% and 56% respectively. In these conditions a new patent is proposed, where the process optimization is realized in two-zone column, where the upper zone is physical absorption in gas-liquid drops system and the lower zone is physical absorption in liquid-gas bubbles system. The chemical reaction takes place in the column tank.

  2. Consensus hologram QSAR modeling for the prediction of human intestinal absorption.

    Moda, Tiago L; Andricopulo, Adriano D

    2012-04-15

    Consistent in silico models for ADME properties are useful tools in early drug discovery. Here, we report the hologram QSAR modeling of human intestinal absorption using a dataset of 638 compounds with experimental data associated. The final validated models are consistent and robust for the consensus prediction of this important pharmacokinetic property and are suitable for virtual screening applications. PMID:22425566

  3. In silico modelling of mass transfer & absorption in the human gut

    Moxon, T.E.; Gouseti, O; Bakalis, S.

    2016-01-01

    An in silico model has been developed to investigate the digestion and absorption of starch and glucose in the small intestine. The main question we are aiming to address is the relative effect of gastric empting time and luminal viscosity on the rate of glucose absorption. The results indicate that all factors have a significant effect on the amount of glucose absorbed. For low luminal viscosities (e.g. lower than 0.1 Pas) the rate of absorption is controlled by the gastric emptying time. Fo...

  4. Modelling and data validation for the energy analysis of absorption refrigeration systems

    Martínez Maradiaga, David Estéfano

    2013-01-01

    Data validation and reconciliation techniques have been extensively used in the process industry to improve the data accuracy. These techniques exploit the redundancy in the measurements in order to obtain a set of adjusted measurements that satisfy the plant model. Nevertheless, not many applications deal with closed cycles with complex connectivity and recycle loops, as in absorption refrigeration cycles. This thesis proposes a methodology for the steady-state data validation of absorption ...

  5. Evaluating model parameterizations of submicron aerosol scattering and absorption with in situ data from ARCTAS 2008

    Alvarado, Matthew J.; Lonsdale, Chantelle R.; Macintyre, Helen L.; Bian, Huisheng; Chin, Mian; Ridley, David A.; Heald, Colette L.; Thornhill, Kenneth L.; Anderson, Bruce E.; Cubison, Michael J.; Jimenez, Jose L.; Kondo, Yutaka; Sahu, Lokesh K.; Dibb, Jack E.; Wang, Chien

    2016-07-01

    Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10-23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction

  6. A model for absorption of solar radiation by mineral dust within liquid cloud drops

    Zhang, Qing; Thompson, Jonathan E.

    2015-10-01

    Models of light scattering and absorption that consider the effect of insoluble inclusions present within liquid cloud droplets may assume the inclusion occupies random locations within the droplet. In certain cases, external forces can lead to certain orientations or alignments that are strongly preferred. Within this modeling study, we consider one such case in which an insoluble mineral dust inclusion (ρ=2.6 g/cm3) is placed within a liquid water drop (ρ=1.0 g/cm3). Such an instance mimics mineral dust aerosols being incorporated within cloud drops in Earth's atmosphere. Model results suggest super-micron mineral dust settles to the bottom of cloud droplets. However, Brownian motion largely randomizes the position of sub-micron mineral dust within the droplet. The inherent organization of the particles that result has important consequences for light absorption by mineral dust when present within a cloud drop. Modeled results suggest light absorption efficiency may be enhanced by as much as 4-6 fold for an isolated droplet experiencing direct solar illumination at solar zenith angles of diffuse rather than direct solar irradiation. In such cases, light absorption efficiency is decreased through including super-micron dust within water droplets. The study has important implications for modeling the absorption of sunlight by mineral dust aerosol within liquid water clouds. The angle of incidence dependence also reveals that experimental measurement of light absorption for cases in which particle alignment occurs may not always accurately reflect atmospheric absorption of sunlight. Therefore, care must be taken to extrapolate measurement data to climate models.

  7. A mathematical model of peritoneal fluid absorption in tissue.

    Stachowska-Pietka, Joanna; Waniewski, Jacek; Flessner, Michael F; Lindholm, Bengt

    2005-01-01

    To investigate how water flow and interstitial pressure change in tissue during a peritoneal dwell with isotonic fluid, we developed a mathematical model of water transport in the tissue. Transport through muscle alone (M) and through muscle with intact skin (MS) were considered for the rat abdominal wall, using various parameters for muscle and skin. Based on the concept of distributed capillary and lymphatic systems, two main transport barriers were taken into account. capillary membrane and interstitium. We calculated the tissue hydrostatic pressure profiles and compared them with experimental data. The theoretic steady-state pressure distribution for model M is in good agreement with the experimental data. In model MS, the theoretic distribution diverges from the data in the subcutaneous layer. The transient times for fluid flow in the tissue for both model simulations are rather long (40 minutes in model M and 95 minutes in model MS) and depend on intraperitoneal pressure. The fraction of fluid absorbed from the tissue by the lymphatics increases with time from 10% to 97% of fluid flow from the peritoneal cavity. PMID:16686276

  8. Effects of changing the amount of absorption in a computer model of Queen's Hall, Copenhagen, Denmark

    Vigeant, Michelle C.; Wang, Lily M.; Rindel, Jens Holger

    2006-01-01

    recording, and a final auralization is created by mixing all individual channel auralizations together. This study evaluates the objective and subjective effects of using four and thirteen channel IRs in an ODEON model of Queen’s Hall, a hall located in Copenhagen with variable absorption. Analyses of the...... results reveal great differences in the objective parameters of reverberation time (T30), clarity index (C50), sound pressure level (SPL) and lateral energy fraction (LF80) for each channel’s impulse response across the room absorption variations. Subjective studies were conducted to see the effect on...... auralizations of changing source orientation in various configurations of the room with different amounts of absorption. The results show that subjects could more easily identify source orientation with an increasing number of recording channels in the auralizations, but a significant effect with absorption was...

  9. Experimental measurement and modeling of the rate of absorption of carbon dioxide by aqueous ammonia

    Darde, Victor Camille Alfred; van Well, Willy J.M.; Fosbøl, Philip Loldrup;

    2011-01-01

    In this work, the rate of absorption of carbon dioxide by aqueous ammonia solvent has been studied by applying a newly built wetted wall column. The absorption rate in aqueous ammonia was measured at temperatures from 279 to 304K for 1 to 10wt% aqueous ammonia with loadings varying from 0 to 0.8mol......CO2/molNH3. The absorption rate in 30wt% aqueous mono-ethanolamine (MEA) was measured at 294 and 314K with loadings varying from 0 to 0.4 as comparison.It was found that at 304K, the rate of absorption of carbon dioxide by 10wt% NH3 solvent was comparable to the rates for 30wt% MEA at 294 and 314K (a.......The rate of absorption decreases strongly with decreasing ammonia concentrations and increasing CO2 loadings.The rate of absorption of carbon dioxide by aqueous ammonia solvent was modeled using the measurements of the unloaded solutions and the zwitter-ion mechanism. The model could successfully predict...

  10. Enhancement Factors in Ozone Absorption Based on the Surface Renewal Model and its Application

    2000-01-01

    Based on the Danckwerts surface renewal model, a simple explicit expression of theenhancement factor in ozone absorption with a first order ozone self-decomposition and parallel secondorder ozonation reactions has been derived. The results are compared with our previous work based onthe film theory. The 2,4-dichlorophenol destruction rate by ozonation is predicted using the enhancementfactor model in this paper.

  11. Comparison of a Reaction Front Model and a Finite Difference Model for the Simulation of Solid Absorption Process

    ZikangWu; ArneJakobsen; 等

    1994-01-01

    The pupose of this paper is to investigate the validity of a lumped model,i.e.a reaction front model,for the simulation of solid absorption process.A distributed model is developed for solid absorption process,and a dimensionless RF number is suggested to predict the qualitative shape of reaction degree profile.The simulation results from the reaction front model are compared with those from the distributed model solved by a finite difference scheme,and it is shown that they are in good agreement in almost all cased.no matter whether there is reaction front or not.

  12. In silico modelling of mass transfer & absorption in the human gut

    Moxon, T.E.; Gouseti, O.; Bakalis, S.

    2016-01-01

    An in silico model has been developed to investigate the digestion and absorption of starch and glucose in the small intestine. The main question we are aiming to address is the relative effect of gastric empting time and luminal viscosity on the rate of glucose absorption. The results indicate that all factors have a significant effect on the amount of glucose absorbed. For low luminal viscosities (e.g. lower than 0.1 Pas) the rate of absorption is controlled by the gastric emptying time. For viscosities higher than 0.1 Pas a 10 fold increase in viscosity can result in a 4 fold decrease of glucose absorbed. Our model, with the simplifications used to develop it, indicate that for high viscosity luminal phases, gastric emptying rate is not the controlling mechanism for nutrient availability. Developing a mechanistic model could help elucidate the rate limiting steps that control the digestion process. PMID:27143811

  13. Sulfur K-edge X-ray absorption spectroscopy of petroleum asphaltenes and model compounds

    The utility of sulfur K-edge X-ray absorption spectroscopy for the determination and quantification of sulfur forms in petroleum asphaltenes has been investigated. Both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra were obtained for a selected group of model compounds and for several petroleum asphaltene samples. For the model compounds the sulfur XANES was found to vary widely from compound to compound and to provide a fingerprint for the form of sulfur involved. The use of third derivatives of the spectra enabled discrimination of mixtures of sulfidic and thiophenic model compounds and allowed approximate quantification of the amount of each component in the mixtures and in the asphaltene samples. These results represent the first demonstration that nonvolatile sulfur forms can be distinguished and approximately quantified by direct measurement

  14. Photon absorption models in nanostructured semiconductor solar cells and devices

    Luque, Antonio

    2015-01-01

    This book is intended to be used by materials and device physicists and also solar cells researchers. It models the performance characteristics of nanostructured solar cells and resolves the dynamics of transitions between several levels of these devices. An outstanding insight into the physical behaviour of these devices is provided, which complements experimental work. This therefore allows a better understanding of the results, enabling the development of new experiments and optimization of new devices. It is intended to be accessible to researchers, but also to provide engineering tools w

  15. Thermodynamic modelling and kinetics of hydrogen absorption associated with phase transformations

    The intermetallic are used for hydrogen pressure containers in order to avoid leaks in the case of an hybrid container. The hydrogen atoms are absorbed by the intermetallic which act as a hydrogen sponge. This hydrogen absorption must be modelled for the container design. The Pressure-composition isotherms describe the equilibrium. Out of this equilibrium the kinetics are controlled by different processes, without taking into account the phase transformations. The author presents a new model of the p-c isotherms with the hydrogen absorption kinetics. (A.L.B.)

  16. Finite element analysis and modeling of water absorption by date pits during a soaking process

    Waezi-Zadeh, Motahareh; Ghazanfari, Ahmad; Noorbakhsh, Shahin

    2010-01-01

    Date pits for feed preparation or oil extraction are soaked in water to soften before milling or extrusion. Knowledge of water absorption by the date pits helps in better managing the soaking duration. In this research, the process of water absorption by date pits was modeled and analyzed using Fick’s second law of diffusion, finite element approach, and Peleg model. The moisture content of the pits reached to its saturation level of 41.5% (wet basis) after 10 d. The estimated coefficient of ...

  17. Modeling the thermal absorption factor of photovoltaic/thermal combi-panels

    In a photovoltaic/thermal combi-panel solar cells generate electricity while residual heat is extracted to be used for tap water heating or room heating. In such a panel the entire solar spectrum can be used in principle. Unfortunately long wavelength solar irradiance is poorly absorbed by the semiconductor material in standard solar cells. A computer model was developed to determine the thermal absorption factor of crystalline silicon solar cells. It was found that for a standard untextured solar cell with a silver back contact a relatively large amount of long wavelength irradiance is lost by reflection resulting in an absorption factor of only 74%. The model was then used to investigate ways to increase this absorption factor. One way is absorbing long wavelength irradiance in a second absorber behind a semi-transparent solar cell. According to the model this will increase the total absorption factor to 87%. The second way is to absorb irradiance in the back contact of the solar cell by using rough interfaces in combination with a non-standard metal as back contact. Theoretically the absorption factor can then be increased to 85%

  18. Measurements of the effective thermal neutron absorption cross-section in multi-grain models

    The effective macroscopic absorption cross-section Σaeff of thermal neutrons in a grained medium differs from the corresponding cross-section Σahom in the homogeneous medium consisting of the same components, contributing in the same amounts. The ratio of these cross-sections defines the grain parameter, G, which is a measure of heterogeneity of the system for neutron absorption. Heterogeneous models have been built as two- or three-component systems (Ag, Cu and Co3O4 grains distributed in a regular grid in Plexiglas, in various proportions between them). The effective absorption cross-section has been measured and the experimental grain parameter has been found for each model. The obtained values are in the interval 0.34 < G < 0.58, while G = 1 means the homogeneous material. (author)

  19. Thermodynamic Modeling of an Ammonia-Water Absorption System Associated with a Microturbine

    Edson Bazzo

    2009-03-01

    Full Text Available Thermodynamic modeling and Second Law analysis of a small-scale cogeneration system consisting of a 5 refrigerant ton absorption chiller connected by a thermosyphon heat exchanger to a 28 kWe natural gas microturbine are presented. The proposed configuration changes the heat source of the absorption chiller, replacing the original natural gas burning system. A computational algorithm was programmed to analyze the global efficiency of the combined cooling and power plant and the coefficient of performance of the absorption chiller. The results show the consistency of the proposed model and a good performance of the cogeneration system. The thermal efficiency of the combined cooling and power plant is approximately 41%, which represents a 67% increase relative to a single natural-gas microturbine.

  20. Finite element analysis and modeling of water absorption by date pits during a soaking process.

    Waezi-Zadeh, Motahareh; Ghazanfari, Ahmad; Noorbakhsh, Shahin

    2010-07-01

    Date pits for feed preparation or oil extraction are soaked in water to soften before milling or extrusion. Knowledge of water absorption by the date pits helps in better managing the soaking duration. In this research, the process of water absorption by date pits was modeled and analyzed using Fick's second law of diffusion, finite element approach, and Peleg model. The moisture content of the pits reached to its saturation level of 41.5% (wet basis) after 10 d. The estimated coefficient of diffusion was 9.89x10(-12) m(2)/s. The finite element model with a proposed ellipsoid geometry for a single date pit and the analytical model fitted better to the experimental data with R(2) of 0.98. The former model slightly overestimated the moisture content of the pits during the initial stages of the soaking and the latter model generally underestimated this variable through the entire stages of soaking process. PMID:20593512

  1. Antecedents of Absorptive Capacity: A New Model for Developing Learning Processes

    Rezaei-Zadeh, Mohammad; Darwish, Tamer K.

    2016-01-01

    Purpose: The purpose of this paper is to provide an integrated framework to indicate which antecedents of absorptive capacity (AC) influence its learning processes, and to propose testing of this model in future work. Design/methodology/approach Relevant literature into the antecedents of AC was critically reviewed and analysed with the objective…

  2. Time-dependent excitation and ionization modelling of absorption-line variability due to GRB080310

    Vreeswijk, P.M.; De Cia, A.; Jakobsson, P.;

    2013-01-01

    We model the time-variable absorption of Feii, Feiii, Siii, Cii and Crii detected in Ultraviolet and Visual Echelle Spectrograph (UVES) spectra of gamma-ray burst (GRB) 080310, with the afterglow radiation exciting and ionizing the interstellar medium in the host galaxy at a redshift of z = 2.427...

  3. Phenolic Acids from Wheat Show Different Absorption Profiles in Plasma: A Model Experiment with Catheterized Pigs

    Nørskov, Natalja; Hedemann, Mette Skou; Theil, Peter Kappel;

    2013-01-01

    The concentration and absorption of the nine phenolic acids of wheat were measured in a model experiment with catheterized pigs fed whole grain wheat and wheat aleurone diets. Six pigs in a repeated crossover design were fitted with catheters in the portal vein and mesenteric artery to study the ...

  4. Compound Hertzian Chain Model for Copper-Carbon Nanocomposites' Absorption Spectrum

    Kokabi, Alireza; Saeedi, Saman; Moftakharzadeh, Ali; Vesaghi, Mohammad Ali; Fardmanesh, Mehdi

    2011-01-01

    The infrared range optical absorption mechanism of Carbon-Copper composite thin layer coated on the Diamond-Like Carbon (DLC) buffer layer has been investigated. By consideration of weak interactions between copper nanoparticles in their network, optical absorption is modeled using their coherent dipole behavior induced by the electromagnetic radiation. The copper nanoparticles in the bulk of carbon are assumed as a chain of plasmonic dipoles, which have coupling resonance. Considering nearest neighbor interactions for this metallic nanoparticles, surface plasmon resonance frequency ({\\omega}\

  5. Two- and three-dimensional models for analysis of optical absorption in tungsten disulphide single crystals

    Dhairya A Dholakia; G K Solanki; S G Patel; M K Agarwal

    2001-06-01

    The optical energy gaps of WS2 single crystal were determined from the analysis of the absorption spectrum near the fundamental absorption edge at room temperature using light parallel to -axis incident normally on the basal plane. On the basis of two- and three-dimensional models it was found that both direct and indirect band transitions took place in WS2 and the indirect transition was of the allowed type. The optical energy gaps corresponding to both transitions were determined and the phonon energies associated with the indirect transitions estimated. The implications of the results have been discussed.

  6. A new analysis of fine-structure constant measurements and modelling errors from quasar absorption lines

    Wilczynska, Michael R.; Webb, John K.; King, Julian A.; Murphy, Michael T.; Bainbridge, Matthew B.; Flambaum, Victor V.

    2015-12-01

    We present an analysis of 23 absorption systems along the lines of sight towards 18 quasars in the redshift range of 0.4 ≤ zabs ≤ 2.3 observed on the Very Large Telescope (VLT) using the Ultraviolet and Visual Echelle Spectrograph (UVES). Considering both statistical and systematic error contributions we find a robust estimate of the weighted mean deviation of the fine-structure constant from its current, laboratory value of Δα/α = (0.22 ± 0.23) × 10-5, consistent with the dipole variation reported in Webb et al. and King et al. This paper also examines modelling methodologies and systematic effects. In particular, we focus on the consequences of fitting quasar absorption systems with too few absorbing components and of selectively fitting only the stronger components in an absorption complex. We show that using insufficient continuum regions around an absorption complex causes a significant increase in the scatter of a sample of Δα/α measurements, thus unnecessarily reducing the overall precision. We further show that fitting absorption systems with too few velocity components also results in a significant increase in the scatter of Δα/α measurements, and in addition causes Δα/α error estimates to be systematically underestimated. These results thus identify some of the potential pitfalls in analysis techniques and provide a guide for future analyses.

  7. Semimechanistic model describing gastric emptying and glucose absorption in healthy subjects and patients with type 2 diabetes

    Alskär, Oskar; Bagger, Jonatan I; Røge, Rikke M;

    2015-01-01

    and gastric emptying after tests with varying glucose doses. The developed model's performance was compared to empirical models. To develop our model, data from oral and intravenous glucose challenges in patients with type 2 diabetes and healthy control subjects were used together with present knowledge...... of small intestinal transit time, glucose inhibition of gastric emptying, and saturable absorption of glucose over the epithelium to improve the description of gastric emptying and glucose absorption in the IGI model. Duodenal glucose was found to inhibit gastric emptying. The performance of the saturable...... glucose absorption was superior to linear absorption regardless of the gastric emptying model applied. The semiphysiological model developed performed better than previously published empirical models and allows better understanding of the mechanisms underlying glucose absorption. In conclusion, our new...

  8. Modeling of the Temperature Effect on Oxygen Absorption by Iron-Based Oxygen Scavengers.

    Polyakov, Vladimir A; Miltz, Joseph

    2016-01-01

    A new engineering-oriented model for prediction of the effect of temperature on the kinetics of oxygen absorption by iron-based oxygen scavengers (IOSs) was developed. The model is based on the physicochemical mechanism of the O2 scavenging process by the active component of the IOS (iron powder). The conclusions of this study are: (1) the iron deposits formed on the iron particles are composed of 2 different layers: an inner layer of Fe3 O4 and an outer layer of FeOOH that vanishes with the depletion of oxygen. (2) The model considers the chemical processes in the heterogeneous closed system "Fe-H2 O-NaCl-O2 " and describes the kinetics of oxygen absorption by the powder, depending on the characteristics of the system. (3) The nonlinear ordinary differential equation (ODE) of the O2 absorption kinetics was derived and a simple approximate solution to this ODE was obtained theoretically that is similar to the empirical exponential formula published in the relevant literature. (4) The temperature dependence of the oxygen absorption rate is more complicated than that described by the Arrhenius equation. PMID:26650762

  9. Percutaneous absorption of an insect repellent p-menthane-3,8-DIOL: a model for human dermal absorption.

    Reifenrath, William G; Olson, James J; Vedula, Usha; Osimitz, Thomas G

    2009-01-01

    p-Menthane-3,8-diol(38DIOL) was recently introduced as a natural topical insect repellent in the commercial product "OFF! Botanicals" lotion. The objective of this study was to provide an estimate of the potential for 38DIOL systemic absorption in humans. Carbon-14-labeled 38DIOL formulated in the lotion and in an ethanol solution was applied to excised pig skin in an in vitro flow-through test system predictive of skin absorption in humans. Twenty-four hours after application, radiolabel recovered from the dermis and receptor fluid was summed to determine percent absorption. At a dose of approximately 80 microg/cm(2) of 38DIOL in the lotion, a value of 3.5 +/- 0.8% of applied dose was obtained with pig skin. The corresponding value for 38DIOL in ethanol (90 microg/cm(2)) was not significantly different (3.0 +/- 1.2%). Most of the applied dose of 38DIOL was found to evaporate from pig skin (77 +/- 8% for the lotion and 87 +/- 1% for ethanol solution), thus limiting percutaneous absorption values. For reference purposes, the pig skin absorptions of piperonyl butoxide (PBO) at 100 microg/cm(2) in isopropanol, N,N-diethyl-m-toluamide (DEET) at 500 microg/cm(2) in ethanol, and neat isododecane at 650 microg/cm(2) (in order of increasing volatility) were 15 +/- 6%, 23 +/- 3%, and 0.09 +/- 0.05% of applied dose respectively. Isododecane was lost almost exclusively from the skin surface by evaporation. For additional reference, absorptions of PBO, DEET, and 38DIOL were found to be higher with excised rat skin. PMID:19557607

  10. Mathematical Model of Fiber Optic Temperature Sensor Based on Optic Absorption and Experiment Testing

    2001-01-01

    On the basis of analysis on the temperature monitoring methods for high voltage devices, a new type of fiber optic sensor structure with reference channel is given. And the operation principle of fiber optic sensor is analysed at large based on the absorption of semiconductor chip. The mathematical model of both devices and the whole system are also given. It is proved by the experiment that this mathematical model is reliable.

  11. A Model For The Absorption Of Thermal Radiation By Gold-Black

    Quinlan, Brendan Robert

    2015-01-01

    The work presented here addresses an important topic in thermal radiation detection when gold-black is used as an absorber. Sought is a model to simulate the absorption of thermal radiation by gold-black. Fractal geometry is created to simulate the topology of gold-black. Then electrical circuits based on the topology are identified that capture the physics of the interaction between the gold-black material and incident electro-magnetic radiation. Parameters of the model are then adj...

  12. Enhancement Factors in Ozone Absorption Based on the Surface Renewal Model and its Application

    程江; 杨卓如; 陈焕钦; C.H.Kuo; M.E.Zappi

    2000-01-01

    Based on the Danckwerts surface renewal model, a simple explicit expression of the enhancement factor in ozone absorption with a first order ozone self-decomposition and parallel second order ozonation reactions has been derived. The results are compared with our previous work based on the film theory. The 2,4-dichlorophenol destruction rate by ozonation is predicted using the enhancement factor model in this paper.

  13. A model of ruminal volatile fatty acid absorption kinetics and rumen epithelial blood flow in lactating Holstein cows

    Storm, Adam Christian; Kristensen, Niels Bastian; Hanigan, Mark D

    2012-01-01

    Ruminal absorption of volatile fatty acids (VFA) is quantitatively the most important nutrient flux in cattle. Historically, VFA absorption models have been derived primarily from ruminal variables such as chemical composition of the fluid, volume, and pH. Recently, a mechanistic model incorporated...... the control of VFA absorption from epithelial surface area of the reticulorumen. In the present study, we hypothesized that ruminal absorption of VFA was controlled through epithelial permeability to VFA and rumen epithelial capillary blood flow. The objective of the study was to construct a model of...... VFA flux. Parameter estimates were derived by fitting the model to observed data. The model provided reliable unbiased estimates of ruminal VFA absorption and rumen epithelial blood flow. Blood flow was modeled using an equation that considered the effect of butyrate and dietary crude protein intake...

  14. A model for absorption determination of radioactive materials: application in the radio dosimetry and nutrition study

    A three-parameter model of the sigmoidal relationship is proposed to explain the food passage by intestinal tube. These parameters are: U = intestinal non-absorbed radioactivity; d parameter related to intestinal food dispersion; and t50 = time to maximal appearance of material from the intestinal lumen. In order to illustrate the applications of this model and its validity, the absorption of 65Zn from casein semi-purified diet was evaluated in rats. There was a good agreement between the predicted values and the experimental data when the sigmoidal component was added to the conventional multicompartimental equations. With this kind of model the time to maximal appearance (hours), the true absorption level, the fecal concentration and the intestinal dispersion of the ingested radioactivity material may be determined. (author)

  15. The potential of chitosan in enhancing peptide and protein absorption across the TR146 cell culture model-an in vitro model of the buccal epithelium

    Portero, Ana; Remuñán-López, Carmen; Nielsen, Hanne Mørck

    2002-01-01

    To investigate the potential of chitosan (CS) to enhance buccal peptide and protein absorption, the TR146 cell culture model, a model of the buccal epithelium, was used.......To investigate the potential of chitosan (CS) to enhance buccal peptide and protein absorption, the TR146 cell culture model, a model of the buccal epithelium, was used....

  16. A numerical model for the dynamic simulation of a recirculation single-effect absorption chiller

    Highlights: ► Dynamic simulation of a new recirculation single-effect H2O/LiBr absorption chiller is developed. ► The chiller is driven by two heat sources and exclusively cooled by the ambient air. ► Heat and mass transfer in the absorber and the desorber are described according to a detailed physical model. ► Analyse of the dynamic behaviour of the chiller after sudden changes in operation. - Abstract: A dynamic model for the simulation of a new single-effect water/lithium bromide absorption chiller is developed. The chiller is driven by two distinct heat sources, includes a custom integrated falling film evaporator–absorber, uses mixed recirculation and is exclusively cooled by the ambient air. Heat and mass transfer in the evaporator–absorber and in the desorber are described according to a physical model for vapour absorption based on Nusselt’s film theory. The other heat exchangers are handled using a simplified approach based on the NTU-effectiveness method. The model is then used to analyze the chiller response to a step drop of the heat recovery circuit flow rate, and to a sudden reduction of the cooling need in the conditioned space. In the latter case, a basic temperature regulation system is simulated. In both simulations, the performance of the chiller is well represented and consistent with expectations.

  17. Experimental validation of a model for diffusion-controlled absorption of organic compounds in the trachea

    Gerde, P. [National Inst. for Working Life, Solna (Sweden); Muggenburg, B.A.; Thornton-Manning, J.R. [and others

    1995-12-01

    Most chemically induced lung cancer originates in the epithelial cells in the airways. Common conceptions are that chemicals deposited on the airway surface are rapidly absorbed through mucous membranes, limited primarily by the rate of blood perfusion in the mucosa. It is also commonly thought that for chemicals to induce toxicity at the site of entry, they must be either rapidly reactive, readily metabolizable, or especially toxic to the tissues at the site of entry. For highly lipophilic toxicants, there is a third option. Our mathematical model predicts that as lipophilicity increases, chemicals partition more readily into the cellular lipid membranes and diffuse more slowly through the tissues. Therefore, absorption of very lipophilic compounds will be almost entirely limited by the rate of diffusion through the epithelium rather than by perfusion of the capillary bed in the subepithelium. We have reported on a preliminary model for absorption through mucous membranes of any substance with a lipid/aqueous partition coefficient larger than one. The purpose of this work was to experimentally validate the model in Beagle dogs. This validated model on toxicant absorption in the airway mucosa will improve risk assessment of inhaled

  18. Performance modelling and simulation of an absorption solar cooling system for Malaysia

    Solar radiation contains huge amounts of energy and is required for almost all the natural processes on earth. Solar-powered air-conditioning has many advantages when compared to normal electricity system. This paper presents a solar cooling system that has been designed for Malaysia and other tropical regions using evacuated tube solar collector and LiBr absorption system. A modelling and simulation of absorption solar cooling system is modeled in Transient System Simulation (TRNSYS) environment. The typical meteorological year file containing the weather parameters is used to simulate the system. Then a system optimization is carried out in order to select the appropriate type of collector, the optimum size of storage tank, the optimum collector slope and area and the optimum thermostat setting of the auxiliary boiler

  19. A Simple Model for the Absorption of Starlight by Dust in Galaxies

    Charlot, S

    2000-01-01

    We present a new model to compute the effects of dust on the integratedspectral properties of galaxies, based on an idealized prescription of the mainfeatures of the interstellar medium (ISM). The model includes the ionization ofHII regions in the interiors of the dense clouds in which stars form and theinfluence of the finite lifetime of these clouds on the absorption ofradiation. We compute the production of emission lines and the absorption ofcontinuum radiation in the HII regions and the subsequent transfer of line andcontinuum radiation in the surrounding HI regions and the ambient ISM. Thisenables us to interpret simultaneously all the observations of a homogeneoussample of nearby UV-selected starburst galaxies, including the ratio of far-IRto UV luminosities, the ratio of Halpha to Hbeta luminosities, the Halphaequivalent width, and the UV spectral slope. We show that the finite lifetimeof stellar birth clouds is a key ingredient to resolve an apparent discrepancybetween the attenuation of line and con...

  20. A new analysis of fine-structure constant measurements and modelling errors from quasar absorption lines

    Wilczynska, Michael R; King, Julian A; Murphy, Michael T; Bainbridge, Matthew B; Flambaum, Victor V

    2015-01-01

    We present an analysis of 23 absorption systems along the lines of sight towards 18 quasars in the redshift range of $0.4 \\leq z_{abs} \\leq 2.3$ observed on the Very Large Telescope (VLT) using the Ultraviolet and Visual Echelle Spectrograph (UVES). Considering both statistical and systematic error contributions we find a robust estimate of the weighted mean deviation of the fine-structure constant from its current, laboratory value of $\\Delta\\alpha/\\alpha=\\left(0.22\\pm0.23\\right)\\times10^{-5}$, consistent with the dipole variation reported in Webb et al. and King et al. This paper also examines modelling methodologies and systematic effects. In particular we focus on the consequences of fitting quasar absorption systems with too few absorbing components and of selectively fitting only the stronger components in an absorption complex. We show that using insufficient continuum regions around an absorption complex causes a significant increase in the scatter of a sample of $\\Delta\\alpha/\\alpha$ measurements, th...

  1. The influence of surface effects on the hydrogen absorption investigated on the V H model system

    Müller, K.-H.; Paulus, H.; Kiss, G.

    2001-07-01

    The system V-O-H has been chosen as a model system to investigate surface effects on hydrogen absorption in metals. By means of XPS, SIMS, and thermal desorption mass spectrometry (TDMS) methods, the influence of oxygen segregated from the bulk as well as adsorbed from the gas phase has been pointed out. Segregated oxygen obstructs the hydrogen absorption, whereas non-stoichiometric and stoichiometric oxides have a preventing effect already with coverages in the range of monolayers. Ion bombardment in connection with sputter-cleaning or SNMS and SIMS analyses produces additional absorption sites in the surface near region for hydrogen. These can be populated by hydrogen from the gas phase during H 2 exposure or diffusing from the bulk, if the sample was H 2 loaded before. Beside elements like vanadium, there exist alloys (e.g. TiFe, LaNi 5, TiMn 2), which are particularly suitable for practical storage purposes. It is important for the further development of such alloys but also for a better understanding of absorption kinetics to investigate the influence of surface effects also on these alloys.

  2. Application of Absorption Modeling to Predict Bioequivalence Outcome of Two Batches of Etoricoxib Tablets

    Mitra, Amitava; Kesisoglou, Filippos; Dogterom, Peter

    2014-01-01

    As part of the overall product development and manufacturing strategy, pharmaceutical companies routinely change formulation and manufacturing site. Depending on the type and level of change and the BCS class of the molecule, dissolution data and/or bioequivalence (BE) may be needed to support the change for immediate release dosage forms. In this report, we demonstrate that for certain weakly basic low-solubility molecules which rapidly dissolve in the stomach, absorption modeling could be u...

  3. Validity of the linear viscoelastic model for a polymer cylinder with ultrasonic hysteresis-type absorption in a nonviscous fluid

    Mitri, F G

    2016-01-01

    A necessary condition for the validity of the linear viscoelastic model for a (passive) polymeric cylinder with an ultrasonic hysteresis-type absorption submerged in a non-viscous fluid requires that the absorption efficiency is positive (Qabs > 0) satisfying the law of the conservation of energy. This condition imposes restrictions on the values attributed to the normalized absorption coefficients for the compressional and shear-wave wavenumbers for each partial-wave mode n. The forbidden values produce negative axial radiation force, absorption and extinction efficiencies, as well as an enhancement of the scattering efficiency, not in agreement with the conservation of energy law. Numerical results for the radiation force, extinction, absorption and scattering efficiencies are performed for three viscoelastic (VE) polymer cylinders immersed in a non-viscous host liquid (i.e. water) with particular emphasis on the shear-wave absorption coefficient of the cylinder, the dimensionless size parameter and the par...

  4. A mathematical model concerned in self-absorption correction to calibrate detection efficiency of the Ge gamma-ray spectrometer

    A self-absorption correction function used for cylindrical samples with different density in the Gamma-ray spectrum analysis is reported. The effects of the Gamma-ray energy and sample density on the self-absorption are unitized in the function model, and so a shortcut for detection efficiency calibration in the Gamma-ray spectrum analysis is found

  5. Semi-mechanistic modelling of ammonia absorption in an acid spray wet scrubber based on mass balance

    A model to describe reactive absorption of ammonia (NH3) in an acid spray scrubber was developed as a function of the combined overall mass transfer coefficient K. An experimental study of NH3 absorption using 1% dilute sulphuric acid was carried out under different operating conditions. An empiric...

  6. Modeling And Experimental Analysis Of Generator In Vapour Absorption Refrigeration System

    Christy V Vazhappilly

    2013-09-01

    Full Text Available A breadboard prototype of an absorption system for refrigeration using heat from the exhaust-gases is to be designed, built and tested. In the commercial vapour absorption refrigeration system a heating coil generator system has been employed to vaporize the ammonia efrigerant. In the present work, the heating coil generator system has been replaced by the frame plate type heat exchanger. The exhaust gases from the IC engine have been utilized to vaporize the ammonia refrigerant. The available heat in the exhaust gases has to be estimated based on actual I.C-Engine driving cycles. The frame plate type heat exchanger has to be modeled and flow analysis inside the heat exchanger has to be analyzed. In addition, the recoverable energy of the exhaust gases is to be analyzed for representative Internal Combustion Engine.

  7. Modeling swelling and absorption dynamics for holographic sensing in analytes sensitive photopolymer

    Liu, Hongpeng; Yu, Dan; Mao, Dongyao; Geng, Yaohui; Wang, Weibo

    2016-06-01

    A theoretical model is developed to describe holographic sensing and swelling of grating fringe in photopolymer. In experiments, diffraction spectrum responses of grating are characterized to exhibit holographic sensing processes. Analytic expressions between swelling of grating fringe and environmental factors, such as relative humidity and organic vapor concentrations, are extracted based on experimental results. The primary factors are introduced into the model to simulate the sensing process, including swelling ratio, nanozeolites dispersion, and organic vapor absorption. Finally, numerical results are presented for improving the sensitivity of holographic sensor. This work can accelerate the development of holographic sensor and provide a theoretical base for exploring sensing mechanism of polymer.

  8. Submodels of model of nonlinear diffusion in the inhomogeneous medium involving absorption

    We study the five-parameter model, describing the process of nonlinear diffusion in an inhomogeneous medium in the presence of absorption, for which the differential equation of the model admits a continuous Lie group of transformations, acting on the set of its solutions. We found six submodels of the original model of nonlinear diffusion, with different symmetry properties. Of these six submodels, the five submodels with transient absorption, for which the absorption coefficient depends on time according to a power law, represent the greatest interest with a mathematical point of view and with the point of view of physical applications. For each of these nonlinear submodels, we obtained formulas for producing new solutions that contain arbitrary constants, and we found all invariant submodels. All essentially distinct invariant solutions describing these invariant submodels are found in an explicit form or are reduced to finding the solution of nonlinear integral equations. The presence of the arbitrary constants in the integral equations that determine these solutions provide new opportunities for analytical and numerical study of boundary value problems for the received submodels and, thus, for the original model of nonlinear diffusion. For the received invariant submodels, we studied diffusion processes for which at the initial moment of the time at a fixed point is specified as a concentration and its gradient or as a concentration and its velocity. Solving of boundary value problems describing these processes is reduced to the solving of nonlinear integral equations. We established the existence and uniqueness of solutions of these boundary value problems under some additional conditions. The obtained results can be used to study the diffusion of substances, diffusion of conduction electrons and other particles, diffusion of physical fields and propagation of heat in inhomogeneous medium, and also to study a turbulence (Leith model, differential

  9. Modeling of water absorption induced cracks in resin-based composite supported ceramic layer structures.

    Huang, Min; Thompson, V P; Rekow, E D; Soboyejo, W O

    2008-01-01

    Cracking patterns in the top ceramic layers of the modeled dental multilayers with polymer foundation are observed when they are immersed in water. This article developed a model to understand this cracking mechanism. When water diffuses into the polymer foundation of dental restorations, the foundation will expand; as a result, the stress will build up in the top ceramic layer because of the bending and stretching. A finite element model based on this mechanism is built to predict the stress build-up and the slow crack growth in the top ceramic layers during the water absorption. Our simulations show that the stress build-up by this mechanism is high enough to cause the cracking in the top ceramic layers and the cracking patterns predicted by our model are well consistent with those observed in experiments on glass/epoxy/polymer multilayers. The model is then used to discuss the life prediction of different dental ceramics. PMID:17497681

  10. Proposing a Caco-2/HepG2 cell model for in vitro iron absorption studies.

    Scheers, Nathalie M; Almgren, Annette B; Sandberg, Ann-Sofie

    2014-07-01

    The Caco-2 cell line is well established as an in vitro model for iron absorption. However, the model does not reflect the regulation of iron absorption by hepcidin produced in the liver. We aimed to develop the Caco-2 model by introducing human liver cells (HepG2) to Caco-2 cells. The Caco-2 and HepG2 epithelia were separated by a liquid compartment, which allowed for epithelial interaction. Ferritin levels in cocultured Caco-2 controls were 21.7±10.3 ng/mg protein compared to 7.7±5.8 ng/mg protein in monocultured Caco-2 cells. The iron transport across Caco-2 layers was increased when liver cells were present (8.1%±1.5% compared to 3.5%±2.5% at 120 μM Fe). Caco-2 cells were exposed to 0, 80 and 120 μM Fe and responded with increased hepcidin production at 120 μM Fe (3.6±0.3 ng/ml compared to 2.7±0.3 ng/ml). The expression of iron exporter ferroportin in Caco-2 cells was decreased at the hepcidin concentration of 3.6 ng/ml and undetectable at external addition of hepcidin (10 ng/ml). The apical transporter DMT1 was also undetectable at 10 ng/ml but was unchanged at the lower concentrations. In addition, we observed that sourdough bread, in comparison to heat-treated bread, increased the bioavailability of iron despite similar iron content (53% increase in ferritin formation, 97% increase in hepcidin release). This effect was not observed in monocultured Caco-2 cells. The Caco-2/HepG2 model provides an alternative approach to in vitro iron absorption studies in which the hepatic regulation of iron transport must be considered. PMID:24746839

  11. The isolated perfused bovine udder as an in vitro model of percutaneous drug absorption. Skin viability and percutaneous absorption of dexamethasone, benzoyl peroxide, and etofenamate.

    Kietzmann, M; Löscher, W; Arens, D; Maass, P; Lubach, D

    1993-10-01

    Using udders from slaughtered cows as a new in vitro model of percutaneous drug absorption, the tissue viability and the percutaneous absorption of dexamethasone, benzoyl peroxide, and etofenamate were studied. The organ was perfused with gassed tyrode solution for up to 6 hr. As shown by measurement of glucose consumption, lactate production, lactate dehydrogenase activity, and pH in the perfusate, the tissue was viable over a 6-hr period. This was confirmed by a histological examination. Determination of the udder skin-fold thickness demonstrated that no edema developed within the perfusion period. A maximum skin penetration of dexamethasone was found after administration of dexamethasone dissolved in acetone with dimethyl sulfoxide, followed by ointment with salicylic acid, ointment without salicylic acid, and acetone solution. Experiments with benzoyl peroxide and etofenamate demonstrated that the perfused udder skin was capable of metabolizing drugs in vitro. In conclusion, the isolated perfused bovine udder is a new in vitro model, which maintains bovine udder skin with an isolated vasculature in a viable state. Using this in vitro model, we note it is possible to compare the dermal penetration, metabolism, and absorption of substances after topical administration of different drug formulations. PMID:8298184

  12. Modeling absorption spectra for detection of the combustion products of jet engines by laser remote sensing.

    Voitsekhovskaya, Olga K; Kashirskii, Danila E; Egorov, Oleg V; Shefer, Olga V

    2016-05-10

    The absorption spectra of exhaust gases (H2O, CO, CO2, NO, NO2, and SO2) and aerosol (soot and Al2O3) particles were modeled at different temperatures for the first time and suitable spectral ranges were determined for conducting laser remote sensing of the combustion products of jet engines. The calculations were conducted on the basis of experimental concentrations of the substances and the sizes of the aerosol particles. The temperature and geometric parameters of jet engine exhausts were also taken from the literature. The absorption spectra were obtained via the line-by-line method, making use of the spectral line parameters from the authors' own high-temperature databases (for NO2 and SO2 gases) and the HITEMP 2010 database, and taking into account atmospheric transmission. Finally, the theoretical absorption spectra of the exhaust gases were plotted at temperatures of 400, 700, and 1000 K, and the impact of aerosol particles on the total exhaust spectra was estimated in spectral ranges suitable for remote sensing applications. PMID:27168298

  13. Modeling and calculation of light absorption in silicon/metal nanocomposites

    Silicon thin films over a glass substrate has been considerate an economical and viable alternative for the photovoltaic industry. Implementation of this technology will contribute to preserve a clean environment helping to reach a sustainable future. Nevertheless, by their own nature, Silicon thin films present small light absorption, and its electrical energy conversion mechanisms, besides their non ideal character, are not completely understood. The inclusions of metal nanoparticles in semiconductors can modify and improve the light absorption properties of these materials by surface plasmon interaction. It is well known that metal nanoparticles, deposited on the surface of Si-Solar cells, improve considerable the efficiency of the cell and it has been shown that there is a strong correlation between the surface plasmon excitation frequency and that of the exciting light. To study the light interactions on such material, we have developed a theoretical model that takes into account the incorporation of metallic nano-particles over Silicon thin films. We have obtained an analytical expression for the effective permittivity of the Semiconductor/Nano-particle system, εeff using this result we have analyzed the light absorption process in the case of Silicon with two types of metallic inclusions.

  14. On the SO2 Problem in Thermal Power Plants. 2.Two-steps chemical absorption modeling

    Chr. Boyadjiev

    2015-10-01

    Full Text Available The modeling of the gas absorption in a new column apparatus for waste gases purification from SО2, using twophase absorbent (CaCO3 / H2O suspension is presented. The process is realized in a three-zone column. In the upper zone a physical absorption in gas-liquid drops system is realized and the big convective transfer in the gas phase leads to a decrease of the mass transfer resistances in this phase. In the middle zone a chemical absorption in liquid-gas bubbles system takes place and the big convective transfer in the liquid phase leads to a decrease of the mass transfer resistances in this phase. The large volume of the liquid in the middle zone causes an increase of the chemical reaction time and as a result a further decrease of the mass transfer resistances in the liquid phases is realized. The third zone is the column tank, where the chemical reaction takes place only.

  15. Modeling of multi-exciton transient absorption spectra of protochlorophyllide aggregates in aqueous solution.

    Sytina, Olga A; Novoderezhkin, Vladimir I; van Grondelle, Rienk; Groot, Marie Louise

    2011-11-01

    Protochlorophyllide (Pchlide) is a natural porphyrin, a precursor of chlorophyll, synthesized by plants for its photosynthetic apparatus. The pigment spontaneously forms aggregates when dissolved in neat water solution. We present here calculations of the transient absorption spectra and its comprising components (ground-state bleach, stimulated emission, and excited-state absorption) for a strongly excitonically coupled linear chain of four Pchlide chromophores, using exciton theory with phenomenological Gaussian line shapes and without energetic disorder. A refined multiexciton model that includes static disorder is applied to fit the experimental power-dependent transient absorption spectra of aqueous protochlorophyllide and the kinetics for delay times up to 20 ps after photoexcitation. We show that population up to the 4-exciton manifold is sufficient to explain the pronounced saturation of the bleaching and the shape changes in the instantaneous, t = 0.2 ps transient spectra when the pulse energy is increased from 10 to 430 nJ per pulse. The decay of the multiexciton manifold is relatively slow and is preceded by a spectroscopically distinct process. We suggest that the exciton states in the Pchlide aggregates are mixed with charge-transfer states (CTS) and that the population and repopulation of the CTS coupled to the exciton states explains the relatively slow decay of the multiexciton manifold. The relevance of our results to the optical properties and dynamics of natural photosynthetic complexes and the possible physical origin of CTS formation are discussed. PMID:21936513

  16. Tight binding model of conformational disorder effects on the optical absorption spectrum of polythiophenes.

    Bombile, Joel H; Janik, Michael J; Milner, Scott T

    2016-05-14

    Semiconducting polymers are soft materials with many conformational degrees of freedom. The limited understanding of how conformational disorder affects their optoelectronic properties is a key source of difficulties that limits their widespread usage in electronic devices. We develop a coarse-grained approach based on the tight binding approximation to model the electronic degrees of freedom of polythiophene chains, taking into account conformational degrees of freedom. Particularly important is dihedral disorder, which disrupts extended electronic states. Our tight binding model is parameterized using density functional theory (DFT) calculations of the one-dimensional band structures for chains with imposed periodic variations in dihedral angles. The model predicts valence and conduction bands for these chain conformations that compare well to DFT results. As an initial application of our model, we compute the optical absorption spectrum of poly(3-hexylthiophene) chains in solution. We observe a broadening of the absorption edge resulting from dihedral disorder, just shy of the experimental broadening. We conclude that the effects of molecular disorder on the optoelectronic properties of conjugated polymer single chains can be mostly accounted for by torsional disorder alone. PMID:27087455

  17. Difference in oral absorption of ginsenoside Rg1 between in vitro and in vivo models

    Min HAN; Xiao-ling FANG

    2006-01-01

    Aim:To clarify the cause of poor oral absorption of ginsenoside Rg1 (Rg1) ,the active ingredient in Panax notoginseng saponins (PNS) used for treating hemorrhage.Methods:Caco-2 cell monolayers were used as an in vitro model to study the transport mechanism of Rg1 across the intestinal mucosa.Moreover,the serum concentration-time profiles after peroral (po) ,intraduodenal (id) ,portal venous (pv) and tail venous (iv) administration of Rg1 in rats were compared to evaluate the first-pass effects in the stomach.intestine,and liver.Results:Uptake of Rg1 by Caco-2 cell monolayers was temperature-dependent,but was not influenced by cyclosporin A.The change in the apical pH produced no obvious effect on the uptake of Rg1.The uptake and transport of Rg1 was non-saturable;whereas the flux from the apical compartment to the basolateral compartment (A-B) increased in a linear manner with the increase in concentration,indicating passive transport.An apparent permeability coefficient of (2.59±0.17)×10-7 cm/s (C0=1mg/mL) predicted incomplete absorption.A significant difference was observed between the po (Fpo was 3.29% at a dose of 1500 mg/kg) ,id (Fid was 6.60% at a dose of 1200 mg/kg) and pv (Fpv was 50.56%) administration methods,and the barrier function of the intestine was more significant than those of the stomach and liver in the absorption process.Conclusion:Elimination in the stomach.large intestine and liver contributed to the low oral bioavailability of Rg,but low membrane permeability might be a more important factor in determining the extent of absorption.

  18. Experimental and Simulational Studies on the Theoretical Model of the Plasma Absorption Probe

    Plasma absorption probe (PAP) was developed for measuring the electron density in plasmas processing based on the surface-wave characteristics. In order to diagnose the plasma with lower density and higher pressure, a sensitive PAP was also developed. Both types of PAP were analyzed theoretically under the quasi-static approximation, which is highly problematic when a conductor exists in the resonance region of the probe. For this reason, a theoretical model for the PAP is presented in this paper. The model is derived from the electromagnetic wave equation. Its principle is then verified via experiments and numerical simulations. Both experimental and numerical results show that the electromagnetic theoretical model is valid as compared with the quasi-static model. Consequently, a new type of PAP, named as the electromagnetic PAP, is thus proposed for the measurement of electron density.

  19. EVALUATION OF THE STRUCTURAL FUNDS ABSORPTION RATE BY MEANS OF THE HERMIN MODEL

    Opritescu Elena Madalina

    2012-07-01

    Full Text Available The main objective of this article is to highlight the main method that could quantify the impact of the structural funds on the Gross Domestic Product. I also presented the regional disparities situation and the European funds absorption rate. The HERMIN model has been designed considering the evolution of macro-variables throughout transition and pre-accession process, as well as out of the need to analyze the gradual alignment of Romania’s economic policies to those of EU. The fact that, initially, the HERMIN model was designed for the European Union’s less developed economies represented the cornerstone in choosing it, as it was the case for Romania, too. However, the quantitative evaluation must always be accompanied by a qualitative evaluation, in order to comprise factors which cannot be measured by the econometrical modeling. For this purpose, when the results of econometrical model based evaluation are used, it is important to be aware of the fact that models simplify reality, no matter the impressive mathematical calculations they employ. Also, we must not omit the fact that Romania’s major development needs and the current economic context imperatively demand a high as possible level of structural funds absorption, as well as their efficient use, meant to generate a significant impact at a national, regional and local level. One of the main instruments employed to sustain economic growth, while also reducing disparities between regions is represented by the structural funds. These funds, consisting in financial contributions of the member states, according to their level of development, are redistributed in compliance with an extremely complex regulating and procedural frame, to those EU states of regions which are fallen behind from a social and economical development perspective Nevertheless, when absorption capacity of a member state is evaluated, the used percentage from the allocated funds is not the only

  20. Application of absorption modeling to predict bioequivalence outcome of two batches of etoricoxib tablets.

    Mitra, Amitava; Kesisoglou, Filippos; Dogterom, Peter

    2015-02-01

    As part of the overall product development and manufacturing strategy, pharmaceutical companies routinely change formulation and manufacturing site. Depending on the type and level of change and the BCS class of the molecule, dissolution data and/or bioequivalence (BE) may be needed to support the change for immediate release dosage forms. In this report, we demonstrate that for certain weakly basic low-solubility molecules which rapidly dissolve in the stomach, absorption modeling could be used to justify a BE study waiver even when there is failure to show dissolution similarity under some conditions. The development of an absorption model for etoricoxib is described here, which was then used to a priori predict the BE outcome of tablet batches manufactured at two sites. Dissolution studies in 0.01 N HCl media (pH 2.0) had demonstrated similarity of etoricoxib tablets manufactured at two different sites. However, dissolution testing at pH 4.5 and pH 6.8 media failed to show comparability of the tablets manufactured at the two sites. Single simulations and virtual trials conducted using the 0.01 N HCl dissolution showed similarity in AUC and C max for all tablet strengths for batches manufactured at the two manufacturing sites. These predicted results were verified in a definitive bioequivalence study, which showed that both tablet batches were bioequivalent. Since the development of traditional in vitro-in vivo correlations (IVIVC) for immediate release (IR) products is challenging, in cases such as etoricoxib, absorption modeling could be used as an alternative to support waiver of a BE study. PMID:25182387

  1. Excited-state characterization and effective three-photon absorption model of two-photon-induced excited-state absorption in organic push-pull charge-transfer chromophores

    We report experimental investigations of two-photon and excited-state absorption in D-π-A chromophores and propose a model to explain nonlinear absorption in the nanosecond regime. The key parameter is an effective three-photon absorption coefficient that depends on the two-photon absorption cross section and excited-state photophysical properties. We obtain all these parameters from independent measurements and then compare the model with nanosecond nonlinear transmission measurements. We find good agreement with the data, using no free parameters, for specific values of some published two-photon absorption cross sections. We conclude that excited singlet-singlet and triplet-triplet absorption are the dominant sources of nonlinear transmittance loss and that the chief role of two-photon absorption is to populate these states

  2. Quasilinear electron cyclotron absorption in a slab model for TBR-2

    The electron cyclotron radiation generated by a gyrotron of operating frequency f = 35 GHz and power of 60 kW is used for heating and current drive experiments in the tokamak TBR-2 a project currently under study. A quasilinear code, that contains a self-consistent diffusion coefficient for electron cyclotron waves, averaged over tokamak magnetic surfaces, and includes collisions by means of a linearized Fokker-Planck collison term was developed. This code is applied to a slab model for TBR-2, supposed with an initial current presenting features of lower hybrid generated currents. A numerical analysis of two situations with good absorption is done. (author)

  3. Absorption tuning of the green fluorescent protein chromophore: synthesis and studies of model compounds

    Brøndsted Nielsen, Mogens; Andersen, Lars Henrik; Rinza, Tomás Rocha

    2011-01-01

    The green fluorescent protein (GFP) chromophore is a heterocyclic compound containing a p-hydroxybenzylidine attached to an imidazol-5(4H)-one ring. This review covers the synthesis of a variety of model systems for elucidating the intrinsic optical properties of the chromophore in the gas phase...... and its response in particular to hydrogen bond interactions. The overall goal is to understand how the protein binding pocket influences the absorption behavior, and the current status of our ongoing efforts is presented....

  4. The energy spectrum and the optical absorption spectrum of C{sub 60} fullerene within the Hubbard model

    Silant’ev, A. V., E-mail: kvvant@rambler.ru [Mari State University (Russian Federation)

    2015-10-15

    Anticommutator Green’s functions and the energy spectrum of C{sub 60} fullerene are calculated in the approximation of static fluctuations within the Hubbard model. On the basis of this spectrum, an interpretation is proposed for the experimentally observed optical absorption bands of C{sub 60} fullerene. The parameters of C{sub 60} fullerene that characterize it within the Hubbard model are calculated by the optical absorption spectrum.

  5. Thermodynamic and kinetics models of hydrogen absorption bound to phase transformations; Modelisation thermodynamique et cinetiques d'absorption d'hydrogene associees aux transformations de phase

    Gondor, G.; Lexcellent, Ch. [Institut FEMTO-ST, Lab. de Mecanique Appliquee R. Chaleat (LMARC), 25 - Besancon (France)

    2007-07-01

    In order to design hydrogen gaseous pressure tanks, the absorption (desorption) of hydrogen has to be described and modelled. The equilibrium state can be described by the 'H{sub 2} gas pressure - H{sub 2} composition in the intermetallic compounds - isotherms' (PCI) curves. Several models of PCI curves already exist. At the beginning of the absorption, the hydrogen atoms and the intermetallic compounds form a solid solution ({alpha} phase). When the hydrogen concentration increases, a phase transformation appears changing the {alpha} solid solution into an hydride ({beta} phase) (solid solution + H{sub 2} {r_reversible} hydride). When all the solid solution has been transformed into hydride, the absorbed hydrogen atoms are in {beta} phase. A new thermodynamic model has been developed in order to take into account this transition phase. The equilibrium state is then given by a relation between the H{sub 2} gas pressure and the H{sub 2} concentration in the intermetallic compound for a fixed external temperature. Two kinetics models have been developed too; at first has been considered that the kinetics depend only of the entire concentration in the intermetallic compound and of the difference between the applied pressure and the equilibrium pressure. Then, has been considered that the hydrogen concentration changes in the metallic matrix. In this last case, for each hydrogenation process, the absorption velocity is calculated to determine the slowest local process which regulates the local evolution of the hydrogen concentration. These two models are based on the preceding thermodynamic model of the PCI curves. (O.M.)

  6. ISMabs: A COMPREHENSIVE X-RAY ABSORPTION MODEL FOR THE INTERSTELLAR MEDIUM

    Gatuzz, E.; Mendoza, C. [Centro de Física, Instituto Venezolano de Investigaciones Científicas (IVIC), P.O. Box 20632, Caracas 1020A (Venezuela, Bolivarian Republic of); García, J. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, 02138 (United States); Kallman, T. R. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gorczyca, T. W., E-mail: egatuzz@ivic.gob.ve, E-mail: claudio@ivic.gob.ve, E-mail: javier@head.cfa.harvard.edu, E-mail: timothy.r.kallman@nasa.gov, E-mail: thomas.gorczyca@wmich.edu [Department of Physics, Western Michigan University, Kalamazoo, MI 49008 (United States)

    2015-02-10

    We present an X-ray absorption model for the interstellar medium, to be referred to as ISMabs, that takes into account both neutral and ionized species of cosmically abundant elements, and includes the most accurate atomic data available. Using high-resolution spectra from eight X-ray binaries obtained with the Chandra High Energy Transmission Grating Spectrometer, we proceed to benchmark the atomic data in the model particularly in the neon K-edge region. Compared with previous photoabsorption models, which solely rely on neutral species, the inclusion of ions leads to improved spectral fits. Fit parameters comprise the column densities of abundant contributors that allow direct estimates of the ionization states. ISMabs is provided in the appropriate format to be implemented in widely used X-ray spectral fitting packages such as XSPEC, ISIS, and SHERPA.

  7. Specific absorption rate calculations of magnetite, using a modified linear response model for applications in magnetic hyperthermia

    Hernández S, A., E-mail: h.s.alfonso@gmail.com, E-mail: meduardo2001@hotmail.com; Cano, M. E., E-mail: h.s.alfonso@gmail.com, E-mail: meduardo2001@hotmail.com [Centro Universitario de la Ciénega, Universidad de Guadalajara, Ocotlán, Jalisco (Mexico); Torres-Arenas, J., E-mail: torresare@gmail.com [Division de Ciencias e Ingenierías, Universidad de Guanajuato, León, Guanajuato (Mexico)

    2014-11-07

    Currently the absorption of electromagnetic radiation by magnetic nanoparticles is studied for biomedical applications of cancer thermotherapy. Several experiments are conduced following the framework of the Rosensweig model, in order to estimate their specific absorption rate. Nevertheless, this linear approximation involves strong simplifications which constrain their accuracy and validity range. The main aim of this work is to incorporate the deviation of the sphericity assumption in particles shapes, to improve the determination of their specific absorption rate. The correction to the effective particles volume is computed as a measure of the apparent amount of magnetic material, interacting with the external AC magnetic field. Preliminary results using the physical properties of Fe3O4 nanoparticles, exhibit an important correction in their estimated specific absorption rate, as a function of the apparent mean particles radius. Indeed, we have observed using a small deviation (6% of the apparent radius), up to 40% of the predicted specific absorption rate by the Rosensweig linear approximation.

  8. Calculations of the mass absorption cross sections for carbonaceous nanoparticles modeling soot

    In this paper we use an atomistic model to calculate the mass specific absorption cross section coefficient (MAC) of carbonaceous particles of nanometer size. The carbonaceous particles are built numerically to reproduce most of the structural characteristics of typical primary nanoparticles that are agglomerated in soot emitted in the Troposphere from combustion sources. Our model is based on the knowledge of the atomic positions and polarizabilities inside the primary nanoparticles and is used to study the influence of these atomistic characteristics on the optical properties of these nanoparticles. The results indicate that the atomistic composition of the soot primary nanoparticles may have a sufficiently strong impact on the mass specific absorption cross section coefficient curves to allow detection of differences between nanoparticles by using UV–visible spectroscopic measurements, in a well-suited wavelength range, i.e., typically between 200 and 350 nm. In a more general way, our calculations show that MAC values as well as differences between MAC curves corresponding to different primary nanoparticles may strongly vary with wavelength. As a consequence, measurements at a given wavelength only are certainly not representative of the absorption properties of these nanoparticles and thus should be considered with caution. Moreover, our approach clearly shows significant differences with classical macroscopic electromagnetic theory when calculating the optical properties of realistic primary soot nanoparticles that, in fact, cannot be considered as homogeneous spherical particles due to the presence of defects in their atomistic structure. - Highlights: • We calculate the MAC curves of carbonaceous particles. • Relation between atomistic characteristics and MAC curves is characterized. • We show that MAC curves depend on the atomistic composition of the nanoparticles • Difference between nanoparticles may be characterized by spectroscopic

  9. Modeling the diffusion/absorption response of a nanopore coated microporous silicon interface

    Baker, C.; Laminack, W.; Gole, J. L.

    2016-03-01

    We outline a modeling study of an extrinsic semiconductor interface formed from the interaction of nanostructured metal oxide decorated porous silicon and used for sensing gas phase analytes. We consider simple conductometric sensors that operate at room temperature and atmospheric pressure. Nanostructured metal oxide deposition provides a matrix of responses to various analytes, facilitating the extraction of ambient gas concentrations from sensor responses. The sensors are simulated in four stages with an emphasis to the continual improvement of the modeling effort. Stage 1 focuses solely on the diffusion mechanics of an analyte gas into and out of a micro/nanoporous interface and the observed linear response at low concentrations. Stage 2 focuses on the non-linearity resulting primarily from the quenching of sensor response at higher concentrations and introduces an absorption response mechanism. Here, stage 3 demonstrates how the consideration of charge carrier density leads to the development of a new Fermi-distribution based response mechanism. Stage 4 establishes a combined absorption-Fermi-distribution response mechanism.

  10. Modeling of gamma-ray energy absorption buildup factors using response surface method

    Buildup factors are always useful for practical computations in gamma-ray shield design. Generally point kernel method being easier to handle is adopted for shielding calculations. This method models a gamma ray directly at the evaluation point without scattering which is multiplied by buildup factors to obtain the gamma dose rate. The American Nuclear Society Standard Committee working group (ANSI/ANS-6.4.3-1991) has compiled the energy absorption and exposure buildup factors from 1 mean free path to 40 mean free paths as a standard reference data base for a large number of elements including water, air and concrete. Literature study reveals that there is a substantially significant disagreement in the buildup factor data by different approximating formulae. In view of this, it is required to compute or predict the buildup factor for those materials. The buildup factor data have been computed by various codes. Some of the codes are ASFIT (Gopinath and Sakamoto et al, 1971), PALLAS (Takeuchi and Tanaka, 1984) and EGS4 (Nelson et al, 1985). Taylor (1954), Berger (1956), Capo (1958) have fitted Goldstein and Wilkins (1954) data to construct parametric buildup factor formulae. Harimaet et al. (1986) has developed geometric progress fitting formula for the ANSI/ANS-6.4.3 (ANSI, 1991). The energy absorption buildup factor is defined as the photon buildup factor in which the quantity of interest is the absorbed or deposited energy in the shield medium and the detector response function is that of absorption in the material. Geometric progression buildup factor formula was simplified using the new modeling (fitting algorithm) of gamma ray energy absorption buildup factor. Advantage of having the simplification of buildup factor formula provides the easiness of usage of point kernel method based gamma shielding in the sense that analytic expression of collided flux can be easily constructed. Furthermore, that analytical expression of collided flux can be optimized to

  11. CO2 Absorption in a Lab-Scale Fixed Solid Bed Reactor: Modelling and Experimental Tests

    Roberto Gabbrielli

    2004-09-01

    Full Text Available The CO2 absorption in a lab-scale fixed solid bed reactor filled with different solid sorbents has been studied under different operative conditions regarding temperature (20-200°C and input gas composition (N2, O2, CO2, H2O at 1bar pressure. The gas leaving the reactor has been analysed to measure the CO2 and O2 concentrations and, consequently, to evaluate the overall CO2 removal efficiency. In order to study the influence of solid sorbent type (i.e. CaO, coal bottom ash, limestone and blast furnace slag and of mass and heat transfer processes on CO2 removal efficiency, a one-dimensional time dependent mathematical model of the reactor, which may be considered a Plug Flow Reactor, has been developed. The quality of the model has been confirmed using the experimental results.

  12. Thermodynamic modeling and performance analysis of the variable-temperature heat reservoir absorption heat pump cycle

    Qin, Xiaoyong; Chen, Lingen; Ge, Yanlin; Sun, Fengrui

    2015-10-01

    For practical absorption heat pump (AHP) plants, not all external heat reservoir heat capacities are infinite. External heat reservoir heat capacity should be an effect factor in modeling and performance analysis of AHP cycles. A variable-temperature heat reservoir AHP cycle is modeled, in which internal working substance is working in four temperature levels and all irreversibility factors are considered. The irreversibility includes heat transfer irreversibility, internal dissipation irreversibility and heat leakage irreversibility. The general equations among coefficient of performance (COP), heating load and some key characteristic parameters are obtained. The general and optimal characteristics are obtained by using numerical calculations. Besides, the influences of heat capacities of heat reservoirs, internal dissipation irreversibility, and heat leakage irreversibility on cycle performance are analyzed. The conclusions can offer some guidelines for design and operation of AHP plants.

  13. NLP model based thermoeconomic optimization of vapor compression–absorption cascaded refrigeration system

    Highlights: • It addresses the size and cost estimation of cascaded refrigeration system. • Cascaded system is a promising decarburizing and energy efficient technology. • Second law analysis is carried out with modified Gouy-Stodola equation. • The total annual cost of plant operation is optimized in present work. - Abstract: This paper addresses the size and cost estimation of vapor compression–absorption cascaded refrigeration system (VCACRS) for water chilling application taking R410a and water–LiBr as refrigerants in compression and absorption section respectively which can help the design engineers in manufacturing and experimenting on such kind of systems. The main limitation in the practical implementation of VCACRS is its size and cost which are optimized in the present work by implementing Direct Search Method in non-linear programming (NLP) mathematical model of VCACRS. The main objective of optimization is to minimize the total annual cost of system which comprises of costs of exergy input and capital costs in monetary units. The appropriate set of decision variables (temperature of evaporator, condenser, generator, absorber, cascade condenser, degree of overlap and effectiveness of solution heat exchanger) minimizes the total annual cost of VCACRS by 11.9% with 22.4% reduction in investment cost at the base case whereas the same is reduced by 7.5% with 11.7% reduction in investment cost with reduced rate of interest and increased life span and period of operation. Optimization results show that the more investment cost in later case is well compensated through the performance and operational cost of the system. In the present analysis, optimum cascade condensing temperature is a strong function of period of operation and capital recovery factor. The cascading of compression and absorption systems becomes attractive for lower rate of interest and increase life span and operational period

  14. Electromagnetically induced absorption in detuned stub waveguides: a simple analytical and experimental model.

    Mouadili, A; Boudouti, E H El; Soltani, A; Talbi, A; Djafari-Rouhani, B; Akjouj, A; Haddadi, K

    2014-12-17

    We give an analytical and experimental demonstration of a classical analogue of the electromagnetic induced absorption (EIA) in a simple photonic device consisting of two stubs of lengths d1 and d2 grafted at the same site along a waveguide. By detuning the lengths of the two stubs (i.e. δ = d(2) - d(1)) we show that: (i) the amplitudes of the electromagnetic waves in the two stubs can be written following the two resonators model where each stub plays the role of a radiative resonator with low Q factor. The destructive interference between the waves in the two stubs may give rise to a sharp resonance peak with high Q factor in the transmission as well as in the absorption. (ii) The transmission coefficient around the resonance induced by the stubs can be written following a Fano-like form. In particular, we give an explicit expression of the position, width and Fano parameter of the resonances as a function of δ. (iii) By taking into account the loss in the waveguides, we show that at the transmission resonance, the transmission (reflection) increases (decreases) as a function of δ. Whereas the absorption goes through a maximum around 0.5 for a threshold value δth which depends on the attenuation in the system and then falls to zero. (iv) We give a comparison between the phase of the determinant of the scattering matrix, the so-called Friedel phase and the phase of the transmission amplitude. (v) The effect of the boundary conditions at the end of the resonators on the EIA resonance is also discussed. The analytical results are obtained by means of the Green's function method, whereas the experiments are carried out using coaxial cables in the radio-frequency regime. These results should have important consequences for designing integrated devices such as narrow-frequency optical or microwave filters and high-speed switches. PMID:25406973

  15. Shape dependency of the extinction and absorption cross sections of dust aerosols modeled as randomly oriented spheroids

    R. Wagner

    2011-09-01

    Full Text Available We present computational results on the shape dependency of the extinction and absorption cross sections of dustlike aerosol particles that were modeled as randomly oriented spheroids. Shape dependent variations in the extinction cross sections are largest in the size regime that is governed by the interference structure. Elongated spheroids best fitted measured extinction spectra of re-dispersed Saharan dust samples. For dust particles smaller than 1.5 μm in diameter and low absorption potential, shape effects on the absorption cross sections are very small.

  16. Modeling of high frequency radio wave absorption on oblique soundings during a solar X-ray flare

    Rogov, D. D.; Moskaleva, E. V.; Zaalov, N. Y.

    2015-01-01

    High frequency radio wave absorption induced by Solar Ultra-Violet (UV) and X-ray flux is investigated. The influence of the solar flare observed on 11 April 2013 on the structure of oblique sounding ionograms in the Arctic region of Russia is considered. An adjustable model of the ionosphere developed for high frequency (HF) propagation problems was employed for this purpose. The simulation algorithm has been designed to accept a large variety of ionospheric conditions. On the basis of the SWPC D-region Absorption model the absorption effects in the ionosphere at sub-auroral latitudes of the Earth were calculated. This approach does not require knowledge of the electron density and electron collision frequency profiles of the D-region ionosphere. The oblique ionograms simulated with the absorption effect and ionograms provided by Russian network of ionospheric observations deployed in Arctic region exhibit quite a good resemblance.

  17. Modeling and optimization of CO2 capture processes by chemical absorption

    CO2 capture processes by chemical absorption lead to a large energy penalty on efficiency of coal-fired power plants, establishing one of the main bottleneck to its industrial deployment. The objective of this thesis is the development and validation of a global methodology, allowing the precise evaluation of the potential of a given amine capture process. Characteristic phenomena of chemical absorption have been thoroughly studied and represented with state-of-the-art models. The e-UNIQUAC model has been used to describe vapor-liquid and chemical equilibria of electrolyte solutions and the model parameters have been identified for four solvents. A rate-based formulation has been adopted for the representation of chemically enhanced heat and mass transfer in columns. The absorption and stripping models have been successfully validated against experimental data from an industrial and a laboratory pilot plants. The influence of the numerous phenomena has been investigated in order to highlight the most limiting ones. A methodology has been proposed to evaluate the total energy penalty resulting from the implementation of a capture process on an advanced supercritical coal-fired power plant, including thermal and electric consumptions. Then, the simulation and process evaluation environments have been coupled with a non-linear optimization algorithm in order to find optimal operating and design parameters with respect to energetic and economic performances. This methodology has been applied to optimize five process flow schemes operating with an monoethanolamine aqueous solution at 30% by weight: the conventional flow scheme and four process modifications. The performance comparison showed that process modifications using a heat pump effect give the best gains. The use of technical-economic analysis as an evaluation criterion of a process performance, coupled with a optimization algorithm, has proved its capability to find values for the numerous operating and design

  18. Speciation model selection by Monte Carlo analysis of optical absorption spectra: Plutonium(IV) nitrate complexes

    Standard modeling approaches can produce the most likely values of the formation constants of metal-ligand complexes if a particular set of species containing the metal ion is known or assumed to exist in solution equilibrium with complexing ligands. Identifying the most likely set of species when more than one set is plausible is a more difficult problem to address quantitatively. A Monte Carlo method of data analysis is described that measures the relative abilities of different speciation models to fit optical spectra of open-shell actinide ions. The best model(s) can be identified from among a larger group of models initially judged to be plausible. The method is demonstrated by analyzing the absorption spectra of aqueous Pu(IV) titrated with nitrate ion at constant 2 molal ionic strength in aqueous perchloric acid. The best speciation model supported by the data is shown to include three Pu(IV) species with nitrate coordination numbers 0, 1, and 2. Formation constants are β1=3.2±0.5 and β2=11.2±1.2, where the uncertainties are 95% confidence limits estimated by propagating raw data uncertainties using Monte Carlo methods. Principal component analysis independently indicates three Pu(IV) complexes in equilibrium. (c) 2000 Society for Applied Spectroscopy

  19. Modelling millimetre wave propagation and absorption in a high resolution skin model: the effect of sweat glands

    The aim of this work was to investigate the potential effect of sweat gland ducts (SGD) on specific absorption rate (SAR) and temperature distributions during mm-wave irradiation. High resolution electromagnetic and bio-heat transfer models of human skin with SGD were developed using a commercially available simulation software package (SEMCAD X(TM)). The skin model consisted of a 30 μm stratum corneum, 350 μm epidermis and papillary dermis (EPD) and 1000 μm dermis. Five SGD of 60 μm radius and 300 μm height were embedded linearly with 370 μm separation. A WR-10 waveguide positioned 20 μm from the skin surface and delivering 94 GHz electromagnetic radiation was included in the model. Saline conductivity was assigned inside SGD. SAR and temperatures were computed with and without SGD. Despite their small scale, SAR was significantly higher within SGD than in the EPD without SGD. Without SGD, SAR and temperature maxima were in the dermis near EPD. With SGD, SAR maximum was inside SGD while temperature maximum moved to the EPD/stratum-corneum junction. Since the EPD participates actively in perception, the effect of SGD should be taken into account in nociceptive studies involving mm-waves. This research represents a significant step towards higher spatial resolution numerical modelling of the skin and shows that microstructures can play a significant role in mm-wave absorption and induced temperature distributions.

  20. Elucidation of the Intestinal Absorption Mechanism of Celastrol Using the Caco-2 Cell Transwell Model.

    Li, Hong; Li, Jie; Liu, Lu; Zhang, Yichuan; Luo, Yili; Zhang, Xiaoli; Yang, Peng; Zhang, Manna; Yu, Weifeng; Qu, Shen

    2016-08-01

    Celastrol, a triterpenoid isolated from stem (caulis) of Celastrus orbiculatus Thunb. (Celastraceae), has been known to have various pharmacological effects, including anti-inflammatory, anticancer, and antioxidant activities. However, the mechanism of the intestinal absorption of celastrol is unknown. The aim of this study was to investigate the intestinal absorption of celastrol using the Caco-2 cell transwell model. First, the bidirectional transport of celastrol in Caco-2 cell monolayers was observed. Then, the effects of time, concentration, temperature, paracellular pathway, and efflux transport inhibition on the transport of celastrol across the Caco-2 cell monolayers were investigated. The P-glycoprotein inhibitor verapamil and cyclosporin A, the multidrug resistance protein 2 inhibitor MK571, and the breast cancer resistance protein inhibitor reserpine were used. Additionally, the effects of celastrol on the activity of P-glycoprotein were evaluated using the rhodamine 123 uptake assay. In this study, we found that the intestinal transport of celastrol was a time- and concentration-dependent active transport. The paracellular pathway was not involved in the transport of celastrol, and the efflux of celastrol was energy dependent. The results indicated that celastrol is a substrate of P-glycoprotein but not multidrug resistance protein 2 or the breast cancer resistance protein. In addition, celastrol could not affect the uptake of rhodamine 123 in Caco-2 cells, which indicated that celastrol could not inhibit or induce the activity of P-glycoprotein. PMID:27159672

  1. Made-to-measure galaxy modelling utilising absorption line strength data

    Long, Richard

    2016-01-01

    We enhance the Syer & Tremaine made-to-measure (M2M) particle method of stellar dynamical modelling to model simultaneously both kinematic data and absorption line strength data thus creating a `chemo-M2M' modelling scheme. We apply the enhanced method to four galaxies (NGC 1248, NGC 3838, NGC 4452, NGC 4551) observed using the SAURON integral-field spectrograph as part of the ATLAS3D programme. We are able to reproduce successfully the 2D line strength data achieving mean chi^2 per bin values of ~1 with >95\\% of particles having converged weights. Because M2M uses a 3D particle system, we are also able to examine the underlying 3D line strength distributions. The extent to which these distributions are plausible representations of real galaxies requires further consideration. Overall we consider the modelling exercise to be a promising first step in developing a `chemo-M2M' modelling system and in understanding some of the issues to be addressed. Whilst the made-to-measure techniques developed have been ...

  2. Atmospheric absorption model for dry air and water vapor at microwave frequencies below 100 GHz derived from spaceborne radiometer observations

    Wentz, Frank J.; Meissner, Thomas

    2016-05-01

    The Liebe and Rosenkranz atmospheric absorption models for dry air and water vapor below 100 GHz are refined based on an analysis of antenna temperature (TA) measurements taken by the Global Precipitation Measurement Microwave Imager (GMI) in the frequency range 10.7 to 89.0 GHz. The GMI TA measurements are compared to the TA predicted by a radiative transfer model (RTM), which incorporates both the atmospheric absorption model and a model for the emission and reflection from a rough-ocean surface. The inputs for the RTM are the geophysical retrievals of wind speed, columnar water vapor, and columnar cloud liquid water obtained from the satellite radiometer WindSat. The Liebe and Rosenkranz absorption models are adjusted to achieve consistency with the RTM. The vapor continuum is decreased by 3% to 10%, depending on vapor. To accomplish this, the foreign-broadening part is increased by 10%, and the self-broadening part is decreased by about 40% at the higher frequencies. In addition, the strength of the water vapor line is increased by 1%, and the shape of the line at low frequencies is modified. The dry air absorption is increased, with the increase being a maximum of 20% at the 89 GHz, the highest frequency considered here. The nonresonant oxygen absorption is increased by about 6%. In addition to the RTM comparisons, our results are supported by a comparison between columnar water vapor retrievals from 12 satellite microwave radiometers and GPS-retrieved water vapor values.

  3. Absorptive and dispersive optical profiles in fluctuating environments: A stochastic model

    In this study, we determined the absorptive and dispersive optical profiles of a molecular system coupled with a thermal bath. Solvent effects were explicitly considered by modelling the non-radiative interaction with the solute as a random variable. The optical stochastical Bloch equations (OSBE) were solved using a time-ordered cumulant expansion with white noise as a correlation function. We found a solution for the Fourier component of coherence at the third order of perturbation for the nonlinear Four-wave mixing signal and produced analytical expressions for the optical responses of the system. Finally, we examined the behaviour of these properties with respect to the noise parameter, frequency detuning of the dynamic perturbation, and relaxation times.

  4. Development of an in vitro model to simulate the gastrointestinal digestion and absorption of stabilizing agents

    Uberti Francesca

    2014-01-01

    Full Text Available Each step in the winemaking process must be carefully planned and controlled to optimize the quality of wine. Among others, tartaric stabilization is a critical step in enology, and although effective, the usual practices to solve it show some qualitative limitations, and important economical and environmental impacts. For the reasons reported above, the wine producers are searching for alternative practices, with particular interest in the area of organic products. Biopolymers are possible alternatives in this field. The selection, the characterization and the safety aspects of new biopolymers are the objectives of the European project STABIWINE (Use of biopolymers for sustainable stabilization of quality wines. The first group of biopolymers analyzed includes polyaminoacids and, in particular, polymers of L-aspartic acid (PAA, which can be used as enological additives for tartaric stabilization. In order to contribute in drafting the toxicological dossier, the metabolic fate of PAAs has been assessed by in vitro models, mimicking gastrointestinal digestion and absorption.

  5. Adsorption of mercury on lignin: Combined surface complexation modeling and X-ray absorption spectroscopy studies

    Adsorption of mercury (Hg) on lignin was studied at a range of pH values using a combination of batch adsorption experiments, a surface complexation model (SCM) and synchrotron X-ray absorption spectroscopy (XAS). Surface complexation modeling indicates that three types of acid sites on lignin surfaces, namely aliphatic carboxylic-, aromatic carboxylic- and phenolic-type surface groups, contributed to Hg(II) adsorption. The bond distance and coordination number of Hg(II) adsorption samples at pH 3.0, 4.0 and 5.5 were obtained from extended X-ray absorption fine structure (EXAFS) spectroscopy analysis. The results of SCM and XAS combined reveal that the predominant adsorption species of Hg(II) on lignin changes from HgCl20 to monodentate complex –C–O–HgCl and then bidentate complex –C–O–Hg–O–C– with increasing pH value from 2.0 to 6.0. The good agreement between SCM and XAS results provides new insight into understanding the mechanisms of Hg(II) adsorption on lignin. - Highlights: ► Lignin exhibits a high Hg(II) adsorption capability. ► Adsorption of Hg(II) on lignin is strongly pH-dependent. ► HgCl20, –C–O–HgCl and –C–O–Hg–O–C– are the main adsorption species of Hg(II). - Adsorption of Hg(II) on lignin is strongly pH-dependent, and the main adsorption Hg(II) species change from HgCl20 to –C–O–HgCl and –C–O–Hg–O–C– as pH increases from 2.0 to 6.0.

  6. Appraisal of Surface Hopping as a Tool for Modeling Condensed Phase Linear Absorption Spectra.

    Petit, Andrew S; Subotnik, Joseph E

    2015-09-01

    Whereas surface hopping is usually used to study populations and mean-field dynamics to study coherences, in two recent papers, we described a procedure for calculating dipole-dipole correlation functions (and therefore absorption spectra) directly from ensembles of surface hopping trajectories. We previously applied this method to a handful of one-dimensional model problems intended to mimic the gas phase. In this article, we now benchmark this new procedure on a set of multidimensional model problems intended to mimic the condensed phase and compare our results against other standard semiclassical methods. By comparison, we demonstrate that methods that include only dynamical information from one PES (the standard Kubo approaches) exhibit large discrepancies with the results of exact quantum dynamics. Furthermore, for model problems with nonadiabatic excited state dynamics but no quantized vibrational structure in the spectra, our surface hopping approach performs comparably to using Ehrenfest dynamics to calculate the electronic coherences. That being said, however, when quantized vibrational structures are present in the spectra but the electronic states are uncoupled, performing the dynamics on the mean PES still outperforms our present method. These benchmark results should influence future studies that use ensembles of independent semiclassical trajectories to model linear as well as multidimensional spectra in the condensed phase. PMID:26575927

  7. Modelling and simulation of an absorption cycle with a blow pump; Modellierung und Simulation eines Absorptionskreislaufes mit einer Blasenpumpe

    Buecherl, Markus

    2011-07-01

    Diffusion-absorption refrigerators are commonly operated with ammonia and water. If a ionic liquid with negligible vapour pressure is substituted for water, the rectifier will be unnecessary. In the context of a diploma thesis, a diffusion-absorption refrigerator with a blower pump and ammonia and a ionic liquid as working fluid was modelled and simulated. For this, three models were selected from the relevant literature and compared. Changes in COP as a result of varied operating parameters were investigated as well. It was shown that it is possible, in principle, to operate a diffusion-absorption refrigerator with a ionic liquid. [German] Diffusions-Absorptions-Kaeltemaschinen werden in der Regel mit dem Arbeitsstoffpaar Ammoniak-Wasser betrieben. Ersetzt man das Absorptionsmittel Wasser gegen eine ionische Fluessigkeit, die nur einen vernachlaessigbaren Dampfdruck besitzt, kann man den Rektifikator einsparen. Im Rahmen einer Diplomarbeit wurde eine Diffusions-Absorptions-Kaeltemaschine mit einer Blasenpumpe und dem Arbeitsstoffpaar Ammoniak-Ionische Fluessigkeit modelliert und simuliert. Hierfuer wurden drei Modelle aus der Literatur ausgewaehlt. Diese Modelle wurden untereinander verglichen. Ausserdem wurde die Veraenderung des COP bei der Variation der Betriebsparameter fuer diese Berechnungsmodelle untersucht. Es konnte gezeigt werden, dass es prinzipiell moeglich ist, eine Diffusions-Absorptions-Kaeltemaschine mit ionischer Fluessigkeit zu betreiben.

  8. Testing and optical modeling of novel concentrating solar receiver geometries to increase light trapping and effective solar absorptance

    Yellowhair, Julius; Ho, Clifford K.; Ortega, Jesus D.; Christian, Joshua M.; Andraka, Charles E.

    2015-09-01

    Concentrating solar power receivers are comprised of panels of tubes arranged in a cylindrical or cubical shape on top of a tower. The tubes contain heat-transfer fluid that absorbs energy from the concentrated sunlight incident on the tubes. To increase the solar absorptance, black paint or a solar selective coating is applied to the surface of the tubes. However, these coatings degrade over time and must be reapplied, which reduces the system performance and increases costs. This paper presents an evaluation of novel receiver shapes and geometries that create a light-trapping effect, thereby increasing the effective solar absorptance and efficiency of the solar receiver. Several prototype shapes were fabricated from Inconel 718 and tested in Sandia's solar furnace at an irradiance of ~30 W/cm2. Photographic methods were used to capture the irradiance distribution on the receiver surfaces. The irradiance profiles were compared to results from raytracing models. The effective solar absorptance was also evaluated using the ray-tracing models. Results showed that relative to a flat plate, the new geometries could increase the effective solar absorptance from 86% to 92% for an intrinsic material absorptance of 86%, and from 60% to 73% for an intrinsic material absorptance of 60%.

  9. Thermodynamic modeling of hydrogen sulfide absorption by aqueous N-methyldiethanolamine using the Extended UNIQUAC model

    Sadegh, Negar; Stenby, Erling Halfdan; Thomsen, Kaj

    2015-01-01

    Aqueous MDEA is the most commonly used solvent for H2S removal from natural gas. A reliable thermodynamic model is required for the proper design of natural gas sweetening processes. In this study, a rigorous thermodynamic model is developed to represent properties of the H2S-MDEA-H2O ternary...

  10. Model of Yield Response of Corn to Plant Population and Absorption of Solar Energy

    Overman, Allen R.; Scholtz, Richard V.

    2011-01-01

    Biomass yield of agronomic crops is influenced by a number of factors, including crop species, soil type, applied nutrients, water availability, and plant population. This article is focused on dependence of biomass yield (Mg ha−1 and g plant−1) on plant population (plants m−2). Analysis includes data from the literature for three independent studies with the warm-season annual corn (Zea mays L.) grown in the United States. Data are analyzed with a simple exponential mathematical model which contains two parameters, viz. Ym (Mg ha−1) for maximum yield at high plant population and c (m2 plant−1) for the population response coefficient. This analysis leads to a new parameter called characteristic plant population, xc = 1/c (plants m−2). The model is shown to describe the data rather well for the three field studies. In one study measurements were made of solar radiation at different positions in the plant canopy. The coefficient of absorption of solar energy was assumed to be the same as c and provided a physical basis for the exponential model. The three studies showed no definitive peak in yield with plant population, but generally exhibited asymptotic approach to maximum yield with increased plant population. Values of xc were very similar for the three field studies with the same crop species. PMID:21297960

  11. Model of yield response of corn to plant population and absorption of solar energy.

    Allen R Overman

    Full Text Available Biomass yield of agronomic crops is influenced by a number of factors, including crop species, soil type, applied nutrients, water availability, and plant population. This article is focused on dependence of biomass yield (Mg ha(-1 and g plant(-1 on plant population (plants m(-2. Analysis includes data from the literature for three independent studies with the warm-season annual corn (Zea mays L. grown in the United States. Data are analyzed with a simple exponential mathematical model which contains two parameters, viz. Y(m (Mg ha(-1 for maximum yield at high plant population and c (m(2 plant(-1 for the population response coefficient. This analysis leads to a new parameter called characteristic plant population, x(c = 1/c (plants m(-2. The model is shown to describe the data rather well for the three field studies. In one study measurements were made of solar radiation at different positions in the plant canopy. The coefficient of absorption of solar energy was assumed to be the same as c and provided a physical basis for the exponential model. The three studies showed no definitive peak in yield with plant population, but generally exhibited asymptotic approach to maximum yield with increased plant population. Values of x(c were very similar for the three field studies with the same crop species.

  12. Modeling of carbon dioxide absorption by aqueous ammonia solutions using the Extended UNIQUAC model

    Darde, Victor Camille Alfred; van Well, Willy J. M.; Stenby, Erling Halfdan;

    2010-01-01

    An upgraded version of the Extended UNIQUAC thermodynamic model for the carbon dioxide-ammonia-water system has been developed, based on the original version proposed by Thomsen and Rasmussen. The original model was valid in the temperature range 0-110°C, the pressure range 0-10 MPa and the...... ranges, enthalpy change from partial evaporation measurements, speciation data, heat capacity, enthalpy of solution and enthalpy of dilution data have been used to refit 43 model parameters and standard state properties. Henry’s law constant correlations have been used for extrapolating standard state...

  13. A model of multi-pass absorption of external EC radiation at initial stage of discharge in ITER

    Minashin P.V.

    2015-01-01

    Full Text Available A model is developed for multi-pass absorption of external electron cyclotron radiation (ECR in tokamaks, which is used at initial stage of discharge to overcome the impurity radiation barrier (burn-through. Model is based on a semi-analytical solution of the ECR transport problem in the case of multiple reflection of radiation from the wall of the vacuum chamber. We estimate the efficiency of absorption of injected radiation for typical values of the electron temperature and density at the initial stage of discharge in ITER.

  14. WVR-GPS comparison measurements and calibration of the 20-32 GHz tropospheric water vapor absorption model

    Collocated measurements of opacity (from water vapor radiometer brightness temperatures) and wet path delay (from ground-based tracking of global positioning satellites) are used to constrain the model of atmospheric water vapor absorption in the 20-32 GHz band. A differential approach is presented in which the slope of opacity-versus-wet delay data is used as the absorption model constraint. This technique minimizes the effects of radiometric calibration errors and oxygen model uncertainties in the derivation of a best-fit vapor absorption model. A total of approximately five months of data was obtained from two experiment sites. At the Cloud and Radiation Testbed (CART) site near Lamont, Oklahoma, three independent water vapor radiometers (WVRs) provided near-continuous opacity measurements over the interval July-September 1998. At the NASA/Goldstone tracking station in the California desert two WVRs; obtained opacity data over the September-October 1997 interval. At both sites a Global Positioning Satellite (GPS) receiver and surface barometer obtained the data required for deriving the zenith wet delays over the same time frames. Measured values of the opacity-versus-wet delay slope parameter were obtained at four WVR frequencies (20.7, 22.2, 23.8, and 31.4 GHz) and compared with predictions of four candidate absorption models referenced in the literature. With one exception, all three models provide agreement within 5% of the opacity-versus-wet delay slope measurements at all WVR frequencies at both sites. One model provides agreement for all channels at both sites to the 2-3% level. This absorption model accuracy level represents a significant improvement over that attainable using radiosondes.

  15. A mathematical model for the absorption and metabolism of formaldehyde vapour by humans

    Epidemiological studies of occupational exposure to formaldehyde gas (HCHO) have suggested possible links between concentration and duration of exposure, and elevated risks of leukaemia and other cancers at sites distant from the site of contact. Formaldehyde is a highly water soluble gas which, when inhaled, reacts rapidly at the site of contact and is quickly metabolised by enzymes in the respiratory tissue. Inhaled formaldehyde is almost entirely absorbed in the respiratory tract and, for formaldehyde induced toxicity to occur at distant sites, HCHO must enter the blood and be transported to systemic tissues via the circulatory system. A mathematical model describing the absorption and removal of inhaled formaldehyde in the nasal tissue is therefore formulated to predict the proportion of formaldehyde entering into the blood. Accounting for the spatial distribution of the formaldehyde concentration and the metabolic activity within the mucosa, the concentration of formaldehyde in the mucus, the epithelium and the blood has been determined and was found to attain a steady-state profile within a few seconds of exposure. The increase of the formaldehyde concentration in the blood was predicted to be insignificant compared with the existing pre-exposure levels in the body, indicating that formaldehyde is rapidly removed in the nasal tissue. The results of the model thus suggest that it is highly unlikely that following inhalation by the nose, formaldehyde itself will cause toxicity at sites other than the initial site of contact in the respiratory tract

  16. Modelling the effect of oil/fat content in food systems on flavour absorption by LLDPE.

    Dekker, M.; Willige, van R.W.G.; Linssen, J.P.H.; Voragen, A.G.J.

    2003-01-01

    One of the phenomena in food packaging interactions is flavour absorption. Absorption of flavour compounds from food products into food-packaging materials can result in loss of flavour compounds or an unbalance in the flavour profile changing a product's quality. The food matrix influences the amou

  17. Testing Disk-Wind Models with Quasar CIV 1549Å Associated Absorption Lines

    Vestergaard, Marianne

    2012-01-01

    Narrow associated C IV 1549Å absorption lines (NALs) with a rest equivalent width EW =3 Å detected in z ˜ 2 radio-loud and radio-quiet quasars, (a) exhibit evidence of an origin in radiatively accelerated gas, and (b) may be closely related to broad absorption line (BAL) outflows. These NALs and...

  18. Extended UNIQUAC model for thermodynamic modeling of CO2 absorption in aqueous alkanolamine solutions

    Faramarzi, Leila; Kontogeorgis, Georgios; Thomsen, Kaj;

    2009-01-01

    modeling and they cover a very wide range of conditions. Vapor-liquid equilibrium (VLE) data for the aqueous alkanolamine systems containing CO2 in the pressure range of 3-13,000 kPa and temperatures of 25-200 C are used. The model is also regressed with the VLE and freezing point depression data of the...... binary aqueous alkanolamine systems (MEA-water and MDEA-water). The two just mentioned types of data cover the full concentration range of alkanolamines from extremely dilute to almost pure. The experimental freezing point depression data down to the temperature of -20 degrees C are used. Experimental...... almost 230 degrees C) are included in the parameter estimation process. The previously unavailable standard state properties of the alkanolamine ions appearing in this work, i.e. MEA protonate, MEA carbamate and MDEA protonate are determined. The concentration of the species in both MEA and MDEA...

  19. Identifying student and teacher difficulties in interpreting atomic spectra using a quantum model of emission and absorption of radiation

    Savall-Alemany, Francisco; Domènech-Blanco, Josep Lluís; Guisasola, Jenaro; Martínez-Torregrosa, Joaquín

    2016-06-01

    Our study sets out to identify the difficulties that high school students, teachers, and university students encounter when trying to explain atomic spectra. To do so, we identify the key concepts that any quantum model for the emission and absorption of electromagnetic radiation must include to account for the gas spectra and we then design two questionnaires, one for teachers and the other for students. By analyzing the responses, we conclude that (i) teachers lack a quantum model for the emission and absorption of electromagnetic radiation capable of explaining the spectra, (ii) teachers and students share the same difficulties, and (iii) these difficulties concern the model of the atom, the model of radiation, and the model of the interaction between them.

  20. Semiclassical calculations on one-, two-, three-, and four- photon absorption in truncated models of the hydrogen atom

    The results of semiclassical calculations on one-, two-, three-, and four-photon absorption in truncated models of the hydrogen atom are presented. The temporal behavior near ''resonance'' is confirmed to be Rabi-like, with a transition probability given by P (t) = ]γ2/[(ω0/N + delta - ω)2 + γ2

  1. Identifying Student and Teacher Difficulties in Interpreting Atomic Spectra Using a Quantum Model of Emission and Absorption of Radiation

    Savall-Alemany, Francisco; Domènech-Blanco, Josep Lluís; Guisasola, Jenaro; Martínez-Torregrosa, Joaquín

    2016-01-01

    Our study sets out to identify the difficulties that high school students, teachers, and university students encounter when trying to explain atomic spectra. To do so, we identify the key concepts that any quantum model for the emission and absorption of electromagnetic radiation must include to account for the gas spectra and we then design two…

  2. Mechanistic understanding of the effect of PPIs and acidic carbonated beverages on the oral absorption of itraconazole based on absorption modeling with appropriate in vitro data.

    Fotaki, Nikoletta; Klein, Sandra

    2013-11-01

    Proton pump inhibitors (PPIs) are potent gastric acid suppressing agents and are among the most widely sold drugs in the world. However, even though these antisecretory agents are regarded as safe, they can alter the pharmacokinetics of coadministered drugs. Due to the suppression of gastric acid secretion, they can significantly alter the intragastric pH conditions and are thus likely to affect the bioavailability of coadministered drugs requiring an acidic gastric environment for dissolution and subsequent absorption. Among these drugs can be found itraconazole, a poorly soluble triazole-type antifungal compound. Based on observations reported in the literature, gastric pH alterations due to the coadministration of PPIs or acidic beverages can significantly decrease (PPI) or increase (e.g., Coca-Cola) the bioavailability of this compound. In the present work we estimated the fraction of itraconazole that can be absorbed (fabs) from Sporanox capsules or an itraconazole-HBenBCD complex formulation after oral administration with and without coadministration of a PPI or an acidic (carbonated) beverage. For this purpose, the sensitivity of the two formulations toward the impact of various gastric variations (pH, volume, and emptying rate) as they can result from such administration conditions was studied using solubility and dissolution experiments and a physiologically based absorption model. Simulating coadministration of the two formulations with a PPI resulted in a significant (∼ 10-fold) decrease in itraconazole fabs, indicating the pH to be essential for in vivo dissolution and subsequent absorption. The fabs of itraconazole after coadministration of an acidic beverage (Coca-Cola) was far lower than the fabs obtained for itraconazole alone and did not support the observations reported in the literature. These results clearly indicate that in contrast to PPIs, which seem to affect itraconazole bioavailability mainly via intragastric pH changes, coadministered

  3. Modeling and Control of a Double-effect Absorption Refrigerating Machine

    Hihara, Eiji; Yamamoto, Yuuji; Saito, Takamoto; Nagaoka, Yoshikazu; Nishiyama, Noriyuki

    For the purpose of impoving the response to cooling load variations and the part load characteristics, the optimal operation of a double-effect absorption refrigerating machine was investigated. The test machine was designed to be able to control energy input and weak solution flow rate continuously. It is composed of a gas-fired high-temperature generator, a separator, a low-temperature generator, an absorber, a condenser, an evaporator, and high- and low-temperature heat exchangers. The working fluid is Lithium Bromide and water solution. The standard output is 80 kW. Based on the experimental data, a simulation model of the static characteristics was developed. The experiments and simulation analysis indicate that there is an optimal weak solution flow rate which maximizes the coefficient of performance under any given cooling load condition. The optimal condition is closely related to the refrigerant steam flow rate flowing from the separator to the high temperature heat exchanger with the medium solution. The heat transfer performance of heat exchangers in the components influences the COP. The change in the overall heat transfer coefficient of absorber has much effect on the COP compared to other components.

  4. Excitation dynamics in Phycoerythrin 545: modeling of steady-state spectra and transient absorption with modified Redfield theory.

    Novoderezhkin, Vladimir I; Doust, Alexander B; Curutchet, Carles; Scholes, Gregory D; van Grondelle, Rienk

    2010-07-21

    We model the spectra and excitation dynamics in the phycobiliprotein antenna complex PE545 isolated from the unicellular photosynthetic cryptophyte algae Rhodomonas CS24. The excitonic couplings between the eight bilins are calculated using the CIS/6-31G method. The site energies are extracted from a simultaneous fit of the absorption, circular dichroism, fluorescence, and excitation anisotropy spectra together with the transient absorption kinetics using the modified Redfield approach. Quantitative fit of the data enables us to assign the eight exciton components of the spectra and build up the energy transfer picture including pathways and timescales of energy relaxation, thus allowing a visualization of excitation dynamics within the complex. PMID:20643051

  5. The steady-state solutions of radiatively driven stellar winds for a nonSobolev, pure-absorption model

    The reasons for the principle conclusion of a paper by Poe et al. (1989) are summarized. To the extent that a pure-absorption model is applicable, radiatively driven stellar winds have no well defined steady state. The non-Sobolev pure-absorption radiation force from Owocki et al., leads to the conclusion that the solution topology at the sonic point is a node, not a saddle or x as in the solar case. The number of transonic solutions increases from one unique solution for the x type to a range of solutions for the node-type topology. Thus, in the pure-absorption approximation, line driven winds can have a range of possible mass-loss rates and terminal velocities. 5 refs

  6. Absorber Models for absorption of Carbon dioxide from sour natural gas byMethyl-diethanol Amine (MDEA

    Akpa

    2014-12-01

    Full Text Available Mathematical models of the absorber for the absorption of carbon dioxide (CO2from sour natural gas in Methyl-diethanol Amine (MDEAsolution were developed. The resulting ordinary differential model equations were solved numerically using theode45 solver of MATLAB 7.5. The accuracy of the models was ascertained using industrial plant data from the carbon dioxide absorber of the Obiafu/Obrikom Gas Treatment plant in Rivers State, Nigeria. The models predicted the CO2 concentration in the sweet gas, gas and solvent (MDEA temperature progressions along the packed absorber. The results obtained from solutions to the models compared favorably with the plant outputs with a maximum deviation between models predictions and industrial plant outputs of 0.44%. The models were used to simulate the influence of sour gas flow rates and solvent (MDEA concentration in solution on the performance (absorption rates of CO2 of the absorber.The results show that the absorption rate of CO2 increases with increasing gas flow rate and solvent concentration.

  7. Saturable absorption of sorafenib in patients with solid tumors: a population model.

    Hornecker, Marilyne; Blanchet, Benoit; Billemont, Bertrand; Sassi, Hind; Ropert, Stanislas; Taieb, Fabrice; Mir, Olivier; Abbas, Halim; Harcouet, Laura; Coriat, Romain; Dauphin, Alain; Goldwasser, François; Tod, Michel

    2012-10-01

    Sorafenib is an oral tyrosine kinase inhibitor approved for the treatment of advanced renal cell carcinoma and hepatocellular carcinoma. By using a population approach, this study aimed to characterise its pharmacokinetics. Plasma concentration-time data (n = 372) from 71 patients under sorafenib were analysed using nonlinear mixed-effect modelling to estimate population pharmacokinetic parameters, as well as relationships between these parameters and different covariates (demographic, biological). Simulations were done to compare different daily dosing regimens in a context of dose-escalation. A 1-compartment model with saturated absorption, first-order intestinal loss and elimination best described the pharmacokinetics of sorafenib. Absolute bioavailability significantly dropped with increasing daily doses of sorafenib. AUC increased less than proportionally with increasing doses [47.3 (41.3-63.3), 60.3 (56.3-64.4), 71.4 (51.3-99.1), 75.9 (45.5-100.9) mg/L.h for 400, 800, 1,200 and 1,600 mg/day, respectively]. According to the simulations, dividing the daily dose in three or four doses for daily dose >800 mg would significantly increase AUC compared with a twice daily dosing regimen (101.7 vs 81.6 mg/L.h for 400 mg q8h and 600 mg q12h respectively; 131.6 vs 91.5 mg/L.h for 400 mg q6h and 800 mg q12h, respectively). Thrice daily regimen may be most suitable in a context of dose-escalation (>800 mg/day) in non-responders to standard-dosing regimen. PMID:22006162

  8. Calculation and study on model of crushing load of HTR absorption sphere

    The absorption sphere shutdown system is the second shutdown system of 10 MW HTR. The absorption sphere contains 25% B4C, dispersing in graphite matrix. The crushing load, which is an important performance parameter of the absorption sphere, closely relates to the diameter. The effect of graphite sphere diameter and density on the crushing load was studied using the graphite sphere to simulate HTR absorption spheres. Three kinds of graphites with different densities were chosen and processed into five types of spheres with different diameters, and then the crushing experiment was conducted. The results show that the crushing load of the sphere is proportional to the square of the diameter, and increases with the density. For a certain diameter of graphite sphere, increasing the density of the sphere is an effective way to enhance the crushing load. (authors)

  9. Probability model for definition of service life of neutron absorption rods of WWER-1000 reactors

    Paper presents calculation ratios to the determine kinetics of inelastic deformation of shell and plastic sealing of WWER-1000 neutron absorption rod powder centre, considers peculiarities of neutron absorption rod loading with regard to variation of mechanical characteristics of structural materials of shell and swelling of powder absorber under effect of neutron flows, high temperature and cyclic loading. Progressing deformation of two variants of a neutron absorption rod made using O6Kh18N10T steel and EhP-630U alloy with regard to statistical spreading of parameters is studied. Estimations of a neutron absorption rod service life and of probability of destruction at reaching maximal permissible deformation of shell and maximal burn out of absorber are obtained. 8 refs., 2 figs., 3 tabs

  10. Using a stand-level model to predict light absorption in stands with vertically and horizontally heterogeneous canopies

    David I. Forrester; Rubén Guisasola; Xiaolu Tang; Axel T Albrecht; Tran Lam Dong; Guerric le Maire

    2014-01-01

    Background Forest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation (APAR), and therefore, accurate predictions of APAR are critical for many process-based forest growth models. The Lambert-Beer law can be applied to estimate APAR for simple homogeneous canopies composed of one layer, one species, and no canopy gaps. However, the vertical and horizontal structure of forest canopies is rarely homogeneous. Detailed tree-level models can ac...

  11. Incorporating a Generic Model of Subcutaneous Insulin Absorption into the AIDA v4 Diabetes Simulator 3. Early Plasma Insulin Determinations

    Lehmann, Eldon D.; Tarín, Cristina; Bondia, Jorge; Teufel, Edgar; Deutsch, Tibor

    2009-01-01

    Introduction AIDA is an interactive educational diabetes simulator that has been available without charge via the Internet for over 12 years. Recent articles have described the incorporation of a novel generic model of insulin absorption into AIDA as a way of enhancing its capabilities. The basic model components to be integrated have been overviewed, with the aim being to provide simulations of regimens utilizing insulin analogues, as well as insulin doses greater than 40 IU (the current upper limit within the latest release of AIDA [v4.3a]). Some preliminary calculated insulin absorption results have also recently been described. Methods This article presents the first simulated plasma insulin profiles from the integration of the generic subcutaneous insulin absorption model, and the currently implemented model in AIDA for insulin disposition. Insulin absorption has been described by the physiologically based model of Tarín and colleagues. A single compartment modeling approach has been used to specify how absorbed insulin is distributed in, and eliminated from, the human body. To enable a numerical solution of the absorption model, a spherical subcutaneous depot for the injected insulin dose has been assumed and spatially discretized into shell compartments with homogeneous concentrations, having as its center the injection site. The number of these compartments will depend on the dose and type of insulin. Insulin inflow arises as the sum of contributions to the different shells. For this report the first bench testing of plasma insulin determinations has been done. Results Simulated plasma insulin profiles are provided for currently available insulin preparations, including a rapidly acting insulin analogue (e.g., lispro/Humalog or aspart/Novolog), a short-acting (regular) insulin preparation (e.g., Actrapid), intermediate-acting insulins (both Semilente and neutral protamine Hagedorn types), and a very long-acting insulin analogue (e.g., glargine/Lantus), as

  12. Non-Fickian three-dimensional moisture absorption in polymeric composites: Development and validation of hindered diffusion model

    Grace, Landon

    The importance of environmental damage consideration in the design of polymeric composite structures is discussed, with emphasis on the relationship between absorbed moisture content and material property degradation. A brief overview of existing predictive models of moisture diffusion and their limitations is presented. The three-dimensional anisotropic Fickian diffusion model is expanded to include the effects of the interaction of diffusing molecules with the chemical and physical structure of polymeric composites. The numerical solution of this novel hindered diffusion model is obtained for a three-dimensional, anisotropic domain by using a forward-time centered-space finite difference technique. The numerical solution method is verified by comparing the results to known analytical solutions of a one-dimensional, "Langmuir-type" diffusion model and for the limiting case of the three-dimensional Fickian model. The proposed three-dimensional anisotropic hindered diffusion model (3D HDM) and its one-dimensional isotropic version are successfully applied to three experimental moisture absorption data sets reconstructed from existing literature. An analytical solution based on a judicious approximation to the 3D HDM is developed in an effort to increase the utility of the model in the recovery of polymeric composite diffusion properties from experimental data. The effectiveness of the recovery of absorption properties is assessed using artificially generated "synthetic" experimental data. The anisotropic diffusivities, equilibrium moisture content (Minfinity), and molecular binding (gamma) and unbinding (beta) probabilities that govern three-dimensional hindered diffusion are recovered using least-squares regression. Using both Fickian and non-Fickian synthetic moisture absorption data, diffusivities and equilibrium moisture content are recovered with less than 1% error. Values of gamma and beta are recovered with less than 3% error in the non-Fickian diffusion case

  13. A reflectance spectra model of heavy metal stressed leaves: advances in the PROSPECT model adding specific absorption coefficients of heavy metal ion

    This article aims to investigate the reflectance model of heavy metal copper stressed crop. Forty-six groups of copper-treated leaves were measured during a laboratory experiment in order to obtain the leaf biochemical component information and its corresponding scanning electron microscopy image. Then a new reflectance spectral model was developed on the basis of the classical broadleaf radiative transfer model-PROSPECT. Comparing with the PROSPECT model, new models mainly consider adding specific absorption coefficient of copper ion. The scattering process is described by a refractive index (n) and a leaf structure parameter (N). Absorption is modeled using pigment concentration, water content, dry matter content, copper ion contamination and the corresponding specific spectral absorption coefficients (Kab, Kw, Kd, KCu). Thus, reflectance spectral modeling is an inversion procedure to calculate the above 6 parameters accurately. To validate the model 16 leaves were tested in laboratory experiment. This experiment showed that the inversion values of KCu had very strong agreement with the published absorption spectra of Cupric Chloride. The linear regression analysis between simulated and measured reflectance provides a correlation coefficient of 0.93 and a root mean squares of 0.067

  14. FDTD chiral brain tissue model for specific absorption rate determination under radiation from mobile phones at 900 and 1800 MHz.

    Zamorano, M; Torres-Silva, H

    2006-04-01

    A new electrodynamics model formed by chiral bioplasma, which represents the human head inner structure and makes it possible to analyse its behaviour when it is irradiated by a microwave electromagnetic field from cellular phones, is presented. The finite-difference time-domain (FDTD) numeric technique is used, which allows simulation of the electromagnetic fields, deduced with Maxwell's equations, and allows us to simulate the specific absorption rate (SAR). The results show the SAR behaviour as a function of the input power and the chirality factor. In considering the chiral brain tissue in the proposed human head model, the two more important conclusions of our work are the following: (a) the absorption of the electromagnetic fields from cellular phones is stronger, so the SAR coefficient is higher than that using the classical model, when values of the chiral factor are of order of 1; (b) "inverse skin effect" shows up at 1800 MHz, with respect to a 900 MHz source. PMID:16552096

  15. FDTD chiral brain tissue model for specific absorption rate determination under radiation from mobile phones at 900 and 1800 MHz

    A new electrodynamics model formed by chiral bioplasma, which represents the human head inner structure and makes it possible to analyse its behaviour when it is irradiated by a microwave electromagnetic field from cellular phones, is presented. The finite-difference time-domain (FDTD) numeric technique is used, which allows simulation of the electromagnetic fields, deduced with Maxwell's equations, and allows us to simulate the specific absorption rate (SAR). The results show the SAR behaviour as a function of the input power and the chirality factor. In considering the chiral brain tissue in the proposed human head model, the two more important conclusions of our work are the following: (a) the absorption of the electromagnetic fields from cellular phones is stronger, so the SAR coefficient is higher than that using the classical model, when values of the chiral factor are of order of 1; (b) 'inverse skin effect' shows up at 1800 MHz, with respect to a 900 MHz source

  16. Interplay of metabolism and transport in determining oral drug absorption and gut wall metabolism: a simulation assessment using the "Advanced Dissolution, Absorption, Metabolism (ADAM)" model.

    Darwich, A S; Neuhoff, S; Jamei, M; Rostami-Hodjegan, A

    2010-11-01

    Bioavailability of orally administered drugs can be influenced by a number of factors including release from the formulation, dissolution, stability in the gastrointestinal (GI) environment, permeability through the gut wall and first-pass gut wall and hepatic metabolism. Although there are various enzymes in the gut wall which may contribute to gut first pass metabolism, Cytochrome P450 (CYP) 3A has been shown to play a major role. The efflux transporter P-glycoprotein (P-gp; MDR1/ABCB1) is the most extensively studied drug efflux transporter in the gut and might have a significant role in the regulation of GI absorption. Although not every CYP3A substrate will have a high extent of gut wall first-pass extraction, being a substrate for the enzyme increases the likelihood of a higher first-pass extraction. Similarly, being a P-gp substrate does not necessarily pose a problem with the gut wall absorption however it may reduce bioavailability in some cases (e.g. when drug has low passive permeability). An on-going debate has focused on the issue of the interplay between CYP3A and P-gp such that high affinity to P-gp increases the exposure of drug to CYP3A through repeated cycling via passive diffusion and active efflux, decreasing the fraction of drug that escapes first pass gut metabolism (F(G)). The presence of P-gp in the gut wall and the high affinity of some CYP3A substrates to this transporter are postulated to reduce the potential for saturating the enzymes, thus increasing gut wall first-pass metabolism for compounds which otherwise would have saturated CYP3A. Such inferences are based on assumptions in the modelling of oral drug absorption. These models should be as mechanistic as possible and tractable using available in vitro and in vivo information. We review, through simulation, this subject and examine the interplay between gut wall metabolism and efflux transporters by studying the fraction of dose absorbed into enterocytes (F(a)) and F(G) via

  17. Elevated CSF outflow resistance associated with impaired lymphatic CSF absorption in a rat model of kaolin-induced communicating hydrocephalus

    Li Jie

    2010-02-01

    Full Text Available Abstract Background We recently reported a lymphatic cerebrospinal fluid (CSF absorption deficit in a kaolin model of communicating hydrocephalus in rats with ventricular expansion correlating negatively with the magnitude of the impediment to lymphatic function. However, it is possible that CSF drainage was not significantly altered if absorption at other sites compensated for the lymphatic defect. The purpose of this study was to investigate the impact of the lymphatic absorption deficit on global CSF absorption (CSF outflow resistance. Methods Kaolin was injected into the basal cisterns of Sprague Dawley rats. The development of hydrocephalus was assessed using magnetic resonance imaging (MRI. In one group of animals at about 3 weeks after injection, the movement of intraventricularly injected iodinated human serum albumin (125I-HSA into the olfactory turbinates provided an estimate of CSF transport through the cribriform plate into nasal lymphatics (n = 18. Control animals received saline in place of kaolin (n = 10. In a second group at about 3.5 weeks after kaolin injection, intraventricular pressure was measured continuously during infusion of saline into the spinal subarachnoid space at various flow rates (n = 9. CSF outflow resistance was calculated as the slope of the steady-state pressure versus flow rate. Control animals for this group either received no injections (intact: n = 11 or received saline in place of kaolin (n = 8. Results Compared to saline injected controls, lateral ventricular volume in the kaolin group was significantly greater (0.087 ± 0.013 ml, n = 27 versus 0.015 ± 0.001 ml, n = 17 and lymphatic function was significantly less (2.14 ± 0.72% injected/g, n = 18 versus 6.38 ± 0.60% injected/g, n = 10. Additionally, the CSF outflow resistance was significantly greater in the kaolin group (0.46 ± 0.04 cm H2O.μL-1.min, n = 9 than in saline injected (0.28 ± 0.03 cm H2O.μL-1.min, n = 8 or intact animals (0.18 ± 0

  18. Experimental evidence and theoretical modeling of two-photon absorption dynamics in the reduction of intensity noise of solid-state Er:Yb lasers

    Amili, Abdelkrim El; Alouini, Mehdi

    2013-01-01

    A theoretical and experimental investigation of the intensity noise reduction induced by two-photon absorption in a Er,Yb:Glass laser is reported. The time response of the two-photon absorption mechanism is shown to play an important role on the behavior of the intensity noise spectrum of the laser. A model including an additional rate equation for the two-photon-absorption losses is developed and allows the experimental observations to be predicted.

  19. Assessment of In Vivo Clinical Product Performance of a Weak Basic Drug by Integration of In Vitro Dissolution Tests and Physiologically Based Absorption Modeling.

    Ding, Xuan; Gueorguieva, Ivelina; Wesley, James A; Burns, Lee J; Coutant, Carrie A

    2015-11-01

    Effective integration of in vitro tests and absorption modeling can greatly improve our capability in understanding, comparing, and predicting in vivo performances of clinical drug products. In this case, we used a proprietary drug candidate galunisertib to describe the procedures of designing key in vitro tests, analyzing relevant experimental and trial data, and integrating them into physiologically based absorption models to evaluate the performances of its clinical products. By simulating the preclinical study result, we estimated high in vivo permeability for the drug. Given the high sensitivity of its solubility to pH, supersaturation may play an important role in the absorption of galunisertib. Using the dynamic dissolution test, i.e., artificial stomach-duodenum (ASD) model and simulation, we concluded galunisertib in solution or tablet products could maintain supersaturation during the transit in the gastrointestinal tract (GIT). A physiologically based absorption model was established by incorporating these key inputs in the simulation of Trial 1 results of galunisertib solution. To predict the performance of three tablet products, we developed z-factor dissolution models from the multi-pH USP dissolution results and integrate them into the absorption model. The resultant biopharmaceutical models provided good prediction of the extent of absorption of all three products, but underestimated the rate of absorption of one tablet product. Leveraging the ASD result and optimization with the dissolution model, we identified the limitation of the model due to complexity of estimating the dissolution parameter z and its in vitro-in vivo correlation. PMID:26126932

  20. Absorption Capacity, Structural Similarity and Embodied Technology Spillovers in A ‘Macro’ Model: An Implementation within a CGE Framework

    Das, Gouranga; Powell, Alan A. L.

    2000-01-01

    In this paper, all technology transfers are embodied in trade flows within a three-region, one-traded-commodity version of the GTAP model. Exogenous Hicks-Neutral technical progress in one region can have uneven impacts on productivity elsewhere. Why? Destination regions’ ability to harness new technology depends on their absorptive capacity and the structural congruence of the source and destination. Together with trade volume, these two factors determine the recipient’s spillover coeffic...

  1. Modelling LiBr-H2O solution concentration/crystallization of low thermal-powered absorption air conditioning system

    A computer model is developed to predict the concentration of lithium bromide - water (LiBr-H2O) solution for used in low thermal energy-driven absorption air conditioning plants design. The computer program is capable to alert the users from undesirable solidification or crystallization zones. Good agreements between simulated concentration and experimental data from standard chart/table have been obtained. (Author)

  2. The average ion model. Computation of the absorption and emission coefficients in hot plasmas

    Gauthier, Jean-Claude; Geindre, Jean-Paul

    1988-06-01

    A program was developed to evaluate the emission and absorption plasma coefficient variations as a function of the density, temperature and the atomic number of the specimen. The treatment is simplified because of the reduced number of characteristic frequencies which are necessary for the hydrodynamic code. The approach is less efficient when applied to high Z atoms.

  3. An improved model for studies on transdermal drug absorption in-vivo in rats

    Vollmer, U.; Muller, B.W.; Wilffert, B.; Peters, Thies

    1993-01-01

    In rats, transdermal drug absorption can be studied under physiological conditions cannulating the peripheral skin vein, draining the area of the skin which is used for drug application, and collecting the blood. This method leads to decreased blood volume, which causes a reduction in skin blood flo

  4. An improved model for studies on transdermal drug absorption invivo in rats

    VOLLMER, U; MULLER, BW; WILFFERT, B; Peters, Thies

    1993-01-01

    In rats, transdermal drug absorption can be studied under physiological conditions by cannulating the peripheral skin vein, draining the area of the skin which is used for drug application, and collecting the blood. This method leads to decreased blood volume, which causes a reduction in skin blood

  5. Dietary inulin supplementation does not promote colonic iron absorption in a porcine model

    Prebiotics may enhance iron bioavailability by increasing iron absorption in the colon. Anemic pigs fitted with cecal cannulas were fed a low-iron diet with or without 4% inulin. Over 7 days, pigs were administered 1 mg 54 Fe in the morning feed followed by cannula infusion of 0.5 mg 58 Fe to measu...

  6. Study of Electromagnetic Radiation and Specific Absorption Rate of Mobile Phones with Fractional Human Head Models via Green's Functions

    Nookala S. Rao

    2011-01-01

    Full Text Available Problem statement: Electromagnetic Radiation from mobile hand set is identified as one of the side effects for increasing rate of brain tumor. Due to this reason, Mobile phone industries are attentive towards safety issues of human health. Specific Absorption Rate is one of the important parameter while modeling the radiation effect on human head. Brain material with homogeneity is treated as an equivalent model of human head. The radiation caused by antennas mounted on mobile set is assumed to be monopolar. Approach: Apart from the Specific Absorption Rate, period of exposure to radiation is an extremely important parameter while assessing the effects on brain tissue. Correlation between the amount of radiation versus spherical model of brain is a complex phenomena, addressed in various simulation models. In the present work the field distribution inside the head are modeled using Dyadic Greens Functions while describing the effect of radiation pattern. Multilayered homogeneous lossy spherical model is proposed as an equivalent to head. Results: In this paper we present the depth of penetration of radiation and its effect on brain tissue. In essence the amount of electromagnetic power absorbed by biological tissues for various exposure conditions and types of emitting sources, utilizing a detailed model of the human head. Conclusion: Bio-heat equation is used to predict heat distribution inside the brain when exposed to radiation. The medium is assumed to be homogeneous, isotropic, linear, non dispersive and stationary. A critical evaluation of the method is discussed.

  7. Optical absorption parameters of amorphous carbon films from Forouhi-Bloomer and Tauc-Lorentz models: a comparative study

    Laidani, N [Fondazione Bruno Kessler-Ricerca Scientifica e Tecnologica, Via Sommarive, 18, 38050 Povo, Trento (Italy); Bartali, R [Fondazione Bruno Kessler-Ricerca Scientifica e Tecnologica, Via Sommarive, 18, 38050 Povo, Trento (Italy); Gottardi, G [Fondazione Bruno Kessler-Ricerca Scientifica e Tecnologica, Via Sommarive, 18, 38050 Povo, Trento (Italy); Anderle, M [Fondazione Bruno Kessler-Ricerca Scientifica e Tecnologica, Via Sommarive, 18, 38050 Povo, Trento (Italy); Cheyssac, P [Laboratoire de Physique de la Matiere Condensee (UMR CNRS 6622), Universite de Nice Sophia-Antipolis, Parc Valrose, 06108 Nice cedex 2 (France)

    2008-01-09

    Parametrization models of optical constants, namely Tauc-Lorentz (TL), Forouhi-Bloomer (FB) and modified FB models, were applied to the interband absorption of amorphous carbon films. The optical constants were determined by means of transmittance and reflectance measurements in the visible range. The studied films were prepared by rf sputtering and characterized for their chemical properties. The analytical models were also applied to other optical data published in the literature pertaining to films produced by various deposition techniques. The different approaches used to determine important physical parameters of the interband transition yielded different results. A figure-of-merit was introduced to check the applicability of the models and the results showed that FB modified for an energy dependence of the dipole matrix element adequately represents the interband transition in the amorphous carbons. Further, the modified FB model shows a relative superiority over the TL ones for concerning the determination of the band gap energy, as it is the only one to be validated by an independent, though indirect, gap measurement by x-ray photoelectron spectroscopy. Finally, the application of the modified FB model allowed us to establish some important correlations between film structure and optical absorption properties.

  8. Optical absorption parameters of amorphous carbon films from Forouhi-Bloomer and Tauc-Lorentz models: a comparative study

    Parametrization models of optical constants, namely Tauc-Lorentz (TL), Forouhi-Bloomer (FB) and modified FB models, were applied to the interband absorption of amorphous carbon films. The optical constants were determined by means of transmittance and reflectance measurements in the visible range. The studied films were prepared by rf sputtering and characterized for their chemical properties. The analytical models were also applied to other optical data published in the literature pertaining to films produced by various deposition techniques. The different approaches used to determine important physical parameters of the interband transition yielded different results. A figure-of-merit was introduced to check the applicability of the models and the results showed that FB modified for an energy dependence of the dipole matrix element adequately represents the interband transition in the amorphous carbons. Further, the modified FB model shows a relative superiority over the TL ones for concerning the determination of the band gap energy, as it is the only one to be validated by an independent, though indirect, gap measurement by x-ray photoelectron spectroscopy. Finally, the application of the modified FB model allowed us to establish some important correlations between film structure and optical absorption properties

  9. Thermodynamic modelling and kinetics of hydrogen absorption associated with phase transformations; Modelisation thermodynamique et cinetiques d'absorption de l'hydrogene associees aux transformations de phase

    Gondor, G.; Lexcellent, Ch. [LMARC FEMTO-ST, 25 - Besancon (France)

    2007-07-01

    The intermetallic are used for hydrogen pressure containers in order to avoid leaks in the case of an hybrid container. The hydrogen atoms are absorbed by the intermetallic which act as a hydrogen sponge. This hydrogen absorption must be modelled for the container design. The Pressure-composition isotherms describe the equilibrium. Out of this equilibrium the kinetics are controlled by different processes, without taking into account the phase transformations. The author presents a new model of the p-c isotherms with the hydrogen absorption kinetics. (A.L.B.)

  10. Modeling of pressure-induced far-infrared absorption spectra Molecular hydrogen pairs. [in outer planets atmospheres

    Borysow, J.; Trafton, L.; Frommhold, L.; Birnbaum, G.

    1985-01-01

    Meyer et al. (1985) have calculated the accurate induced dipole moment function of H2-H2 from first principles, using highly correlated wave functions for the first time in such work. The present paper is concerned with the collision-induced translational-rotational absorption coefficient for molecular hydrogen pairs, taking into account computations on the basis of the fundamental theory considered by Meyer et al. Data have been obtained for temperatures in the range from 40 to 300 K. Criteria are developed for choosing among various model line shapes. It is found that certain models are capable of approximating the quantum profiles closely, with rms errors of only a few percent.

  11. Intestinal absorption of forsythoside A in in situ single-pass intestinal perfusion and in vitro Caco-2 cell models

    Wei ZHOU; Liu-qing DI; Juan WANG; Jin-jun SHAN; Shi-jia LIU; Wen-zheng JU; Bao-chang CAI

    2012-01-01

    Aim:To investigate the mechanisms underlying the intestinal absorption of the major bioactive component forsythoside A (FTA) extracted from Forsythiae fructus.Methods:An in vitro Caco-2 cell model and a single-pass intestinal perfusion in situ model in SD rats were used.Results:In the in vitro Caco-2 cell model,the mean apparent permeability value (Papp-value) was 4.15x 107 cm/s in the apical-tobasolateral (AP-BL) direction.At the concentrations of 2.6-10.4 μg/mL,the efflux ratio of FTA in the bi-directional transport experiments was approximately 1.00.After the transport,>96% of the apically loaded FTA was retained on the apical side,while >97% of the basolaterally loaded FTA was retained on the basolateral side.The Papp-values of FTA were inversely correlated with the transepithelial electrical resistance.The paracellular permeability enhancers sodium caprate and EDTA,the P-gp inhibitor verapamil and the multidrug resistance related protein (MRP) inhibitors cyclosporine and MK571 could concentration-dependently increase the Papp-values,while the uptake (OATP) transporter inhibitors diclofenac sodium and indomethacin could concentration-dependently decrease the Papp-values.The intake transporter SGLT1 inhibitor mannitol did not cause significant change in the Papp-values.In the in situ intestinal perfusion model,both the absorption rate constant (Ka) and the effective permeability (Peff-values) following perfusion of FTA 2.6,5.2,and 10.4 μg/mL via the duodenum,jejunum and ileum had no significant difference,although the values were slightly higher for the duodenum as compared to those in the jejunum and ileum.The low,medium and high concentrations of verapamil caused the largest increase in the Peff-values for duodenum,jejunum and ileum,respectively.Sodium caprate,EDTA and cyclosporine resulted in concentration-dependent increase in the Peff-values.Diclofenac sodium and indomethacin caused concentration-dependent decrease in the Peff-values.Mannitol did

  12. Using a stand-level model to predict light absorption in stands with vertically and horizontally heterogeneous canopies

    David I Forrester

    2014-09-01

    Full Text Available Background Forest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation (APAR, and therefore, accurate predictions of APAR are critical for many process-based forest growth models. The Lambert-Beer law can be applied to estimate APAR for simple homogeneous canopies composed of one layer, one species, and no canopy gaps. However, the vertical and horizontal structure of forest canopies is rarely homogeneous. Detailed tree-level models can account for this heterogeneity but these often have high input and computational demands and work on finer temporal and spatial resolutions than required by stand-level growth models. The aim of this study was to test a stand-level light absorption model that can estimate APAR by individual species in mixed-species and multi-layered stands with any degree of canopy openness including open-grown trees to closed canopies. Methods The stand-level model was compared with a detailed tree-level model that has already been tested in mixed-species stands using empirical data. Both models were parameterised for five different forests, including a wide range of species compositions, species proportions, stand densities, crown architectures and canopy structures. Results The stand-level model performed well in all stands except in the stand where extinction coefficients were unusually variable and it appears unlikely that APAR could be predicted in such stands using (tree- or stand-level models that do not allow individuals of a given species to have different extinction coefficients, leaf-area density or analogous parameters. Conclusion This model is parameterised with species-specific information about extinction coefficients and mean crown length, diameter, height and leaf area. It could be used to examine light dynamics in complex canopies and in stand-level growth models.

  13. Study of unsteady natural convection induced by absorption of radiation based on a three-waveband attenuation model

    The present study considers unsteady natural convection induced by the absorption of radiation for possible applications in the water quality management for the shallow regions of lakes and reservoirs. The direct absorption of the incoming radiation by the water body forms a stable thermal stratification, whilst residual radiation reaching the bottom bathymetry is re-emitted as a boundary flux, forming an unstable thermal stratification, which is a potential source for a Rayleigh-Benard type instability. The bottom boundary layer instability drives intermittent vertical convection in the form of rising plumes. The plume rise is, however, limited by the stable thermal stratification due to the direct absorption, which is controlled by the attenuation coefficient of water. The attenuation coefficient is therefore an important parameter in determining the plume rise and the associated vertical mixing. The wavelength dependency of the attenuation coefficient of water is accounted for by using a three-waveband model. A theoretical prediction is made for the plume rise distance, which represents the region of vigorous mixing. Two-dimensional numerical simulation provides verification for the accuracy of the theoretical prediction.

  14. Absorption of plant lignans from cereals in an experimental pig model.

    Bolvig, Anne Katrine; Adlercreutz, Herman; Theil, Peter Kappel; Jørgensen, Henry; Bach Knudsen, Knud Erik

    2016-05-01

    Plant lignans are diphenolic compounds ingested with whole grains and seeds and converted to enterolignans by the colonic microbiota. In the present study, we investigated absorption and metabolism of plant lignans and enterolignans in vivo after consumption of cereal-based diets. Six pigs fitted with catheters in the mesenteric artery and portal vein and with a flow probe attached to the portal vein along with twenty pigs for quantitative collection of urine were used for this study. The animals were fed bread based on wheat flour low in plant lignans and three lignan-rich breads based on whole-wheat grain, wheat aleurone flour or rye aleurone flour. Plant lignans and enterolignans in plasma were monitored daily at fast after 0-3 d of lignan-rich intake, and on the 4th day of lignan-rich intake a 10-h profile was completed. Urine samples were collected after 11 d of lignan-rich diet consumption. The concentrations of plant lignans were low at fast, and was 1·2-2·6 nmol/l after switching from the low-lignan diet to the lignan-rich diets. However, on the profile day, the concentration and quantitative absorption of plant lignans increased significantly from 33 nmol/h at fast to 310 nmol/h 0-2·5 h after ingestion with a gradual increase in the following periods. Quantitatively, the absorption of plant lignans across diets amounted to 7 % of ingested plant lignans, whereas the urinary excretion of plant lignans was 3 % across diets. In conclusion, there is a substantial postprandial uptake of plant lignans from cereals, suggesting that plant lignans are absorbed from the small intestine. PMID:27001342

  15. A new analysis of fine-structure constant measurements and modelling errors from quasar absorption lines

    Wilczynska, Michael R.; Webb, John K.; King, Julian A.; Murphy, Michael T.; Bainbridge, Matthew B.; Flambaum, Victor V.

    2015-01-01

    We present an analysis of 23 absorption systems along the lines of sight towards 18 quasars in the redshift range of $0.4 \\leq z_{abs} \\leq 2.3$ observed on the Very Large Telescope (VLT) using the Ultraviolet and Visual Echelle Spectrograph (UVES). Considering both statistical and systematic error contributions we find a robust estimate of the weighted mean deviation of the fine-structure constant from its current, laboratory value of $\\Delta\\alpha/\\alpha=\\left(0.22\\pm0.23\\right)\\times10^{-5...

  16. Modeling and Simulation of CO2 Absorption into Promoted Aqueous Potassium Carbonate Solution in Industrial Scale Packed Column

    Ali Altway

    2015-07-01

    Full Text Available Carbon dioxide gas is a harmful impurity which is corrosive and it can damage the utilities and the piping system in industries. Chemical absorption is the most economical separation method which is widely applied in chemical industries for CO2 removal process. Hot potassium carbonate (K2CO3 is the most effective solvent that has been used extensively, especially for the CO2 separation process from gas synthesis and natural gas. This paper aims to develop mathematical model for investigating the CO2 absorption into promoted hot K2CO3 solution in industrial scale packed column in an ammonia plant. The CO2 was removed from the gas stream by counter-current absorption in two stages column. To represent the gas-liquid system, a rigorous mathematical model based on the two-film theory was considered. The model consists of differential mass and heat balance and considers the interactions between mass-transfer and chemical kinetics using enhancement factor concept. Gas solubility, mass and heat transfer coefficients, reaction kinetics and equilibrium were estimated using correlations from literatures. The model was validated using plant data and was used to compute temperature and concentration profiles in the absorber. The variation of CO2 recovery with respect to changes in some operating variables was evaluated. The effect of various kinds of promoters added into K2CO3 solution on the CO2 recovery was also investigated. The simulation results agree well with the plant data. The results of the simulation prediction, for the absorber pressure of 33 atm with a lean flow rate of 32,0867 kg/h, temperature of 343 K, and semi lean flow rate of 2,514,122 kg/h, temperature of 385 K, showed %CO2 removal of 95.55%, while that of plant data is 96.8%. © 2015 BCREC UNDIP. All rights reservedReceived: 3rd July 2014; Revised: 5th January 2015; Accepted: 19th Januari 2015How to Cite: Altway, A., Susianto, S., Suprapto, S., Nurkhamidah, S., Nisa, N.I.F., Hardiyanto

  17. Oleic acid and docosahexaenoic acid cause an increase in the paracellular absorption of hydrophilic compounds in an experimental model of human absorptive enterocytes

    Surface active compounds present in food possibly have the ability to enhance the absorption of water soluble toxic agents. Therefore, we investigated whether fatty acids such as oleic acid and docosahexaenoic acid (DHA), both commonly present in food, negatively affect the integrity of tight junctions (TJ) in the intestinal epithelium and thereby increase the absorption of poorly absorbed hydrophilic substances. Caco-2 cells, which are derived from human absorptive enterocytes, were grown on permeable filters for 20-25 days. Differentiated cell monolayers were apically exposed for 90 min to mannitol in emulsions of oleic acid (5, 15 or 30 mM) or DHA (5, 15 or 30 mM) in an experimental medium with or without Ca2+ and Mg2+. Absorption of 14C-mannitol increased and trans-epithelial electrical resistance (TEER) decreased in cell monolayers exposed to oleic acid and DHA, compared to controls. Cytotoxicity, measured as leakage of LDH, was higher in groups exposed to 30 mM oleic acid and all concentrations of DHA. Morphology of the cell monolayers was studied by using fluorescence microscopy. Exposure of cell monolayers to 5 mM DHA for 90 min resulted in a profound alteration of the cell-cell contacts as detected by staining the cells for β-catenin. Oleic acid (30 mM) treatment also induced dissolution of the cell-cell contacts but the effect was not as pronounced as with DHA. Cell monolayers were also exposed for 180 min to 250 nM cadmium (Cd) in emulsions of oleic acid (5 or 30 mM) or DHA (1 or 5 mM), in an experimental medium with Ca2+ and Mg2+. Retention of Cd in Caco-2 cells was higher after exposure to 5 mM oleic acid but lower after exposure to 30 mM oleic acid and DHA. Absorption of Cd through the monolayers increased after DHA exposure but not after exposure to oleic acid. Our results indicate that fatty acids may compromise the integrity of the intestinal epithelium and that certain lipids in food may enhance the paracellular absorption of poorly absorbed

  18. Strong absorption model analysis of elastic K sup + scatterings on nuclei and a potential calculation by inversion

    Kim, Y J

    1999-01-01

    We analyze the elastic scattering of 800 MeV/c positive kaons from sup 1 sup 2 C and sup 4 sup 0 Ca nuclei within the framework of the McIntyre strong absorption model. The calculated differential cross-sections are found to be in excellent agreement with the observed data. Near- and far-side decompositions of the elastic cross-section have also been performed by following Fuller's formalism. The corresponding complex potentials are predicted by using the inversion procedure of the McIntyre S-matrix.

  19. Kinetics of intestinal iron absorption and its implications for the dosimetric model of the gastro-intestinal tract

    In the present ICRP model for the gastro-intestinal tract the uptake of substances into the systematic circulation is represented by a direct transfer from the small intestine compartment without consideration of any details of the absorptive process. This study was aimed at the investigation of transfer kinetics of substances across the gut wall. The kinetic behaviour of the essential trace element iron was chosen as example. A total of 23 healthy volunteers were given orally test doses of radioiron in aqueous solution. Whole body retention was measured for a period of at least three weeks after injestion. (author). 8 refs., 3 figs., 2 tabs

  20. Crashworthiness and composite materials: development of an experimental test method for the energy absorption determination and implementation of the relative numerical model

    Garattoni, Francesca

    2011-01-01

    In this PhD thesis the crashworthiness topic is studied with the perspective of the development of a small-scale experimental test able to characterize a material in terms of energy absorption. The material properties obtained are then used to validate a nu- merical model of the experimental test itself. Consequently, the numerical model, calibrated on the specific ma- terial, can be extended to more complex structures and used to simulate their energy absorption behavior. The experimental...

  1. FDTD chiral brain tissue model for specific absorption rate determination under radiation from mobile phones at 900 and 1800 MHz

    Zamorano, M; Torres-Silva, H [Departamento de Electronica, Universidad de Tarapaca, 18 de Septiembre 2222, Arica (Chile)

    2006-04-07

    A new electrodynamics model formed by chiral bioplasma, which represents the human head inner structure and makes it possible to analyse its behaviour when it is irradiated by a microwave electromagnetic field from cellular phones, is presented. The finite-difference time-domain (FDTD) numeric technique is used, which allows simulation of the electromagnetic fields, deduced with Maxwell's equations, and allows us to simulate the specific absorption rate (SAR). The results show the SAR behaviour as a function of the input power and the chirality factor. In considering the chiral brain tissue in the proposed human head model, the two more important conclusions of our work are the following: (a) the absorption of the electromagnetic fields from cellular phones is stronger, so the SAR coefficient is higher than that using the classical model, when values of the chiral factor are of order of 1; (b) 'inverse skin effect' shows up at 1800 MHz, with respect to a 900 MHz source.

  2. PHOTOIONIZATION MODELING OF OXYGEN K ABSORPTION IN THE INTERSTELLAR MEDIUM: THE CHANDRA GRATING SPECTRA OF XTE J1817-330

    Gatuzz, E.; Mendoza, C. [Centro de Fisica, Instituto Venezolano de Investigaciones Cientificas (IVIC), P.O. Box 20632, Caracas 1020A (Venezuela, Bolivarian Republic of); Garcia, J.; Lohfink, A. [Department of Astronomy and Maryland Astronomy Center for Theory and Computation, University of Maryland, College Park, MD 20742 (United States); Kallman, T. R.; Witthoeft, M. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bautista, M. A. [Department of Physics, Western Michigan University, Kalamazoo, MI 49008 (United States); Palmeri, P.; Quinet, P., E-mail: egatuzz@ivic.gob.ve, E-mail: claudio@ivic.gob.ve, E-mail: javier@astro.umd.edu, E-mail: alohfink@astro.umd.edu, E-mail: timothy.r.kallman@nasa.gov, E-mail: michael.c.witthoeft@nasa.gov, E-mail: manuel.bautista@wmich.edu, E-mail: palmeri@umons.ac.be, E-mail: quinet@umons.ac.be [Astrophysique et Spectroscopie, Universite de Mons-UMONS, B-7000 Mons (Belgium)

    2013-05-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 A broadband is described with a simple absorption model that takes into account the pile-up effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 A) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the XSTAR code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain a column density of N{sub H} = 1.38 {+-} 0.01 Multiplication-Sign 10{sup 21} cm{sup -2}; an ionization parameter of log {xi} = -2.70 {+-} 0.023; an oxygen abundance of A{sub O}= 0.689{sup +0.015}{sub -0.010}; and ionization fractions of O I/O = 0.911, O II/O = 0.077, and O III/O = 0.012 that are in good agreement with results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse and Sauval, a rescaling with the revision by Asplund et al. yields A{sub O}=0.952{sup +0.020}{sub -0.013}, a value close to solar that reinforces the new standard. We identify several atomic absorption lines-K{alpha}, K{beta}, and K{gamma} in O I and O II and K{alpha} in O III, O VI, and O VII-the last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n > 2 associated with ISM cold absorption.

  3. An Assessment of Microwave Absorption Models and Retrievals of Cloud Liquid Water Using Clear-Sky Data

    Passive microwave radiometers have a long history in the remote sensing of atmospheric liquid and water vapor. Retrieval of these quantities are sensitive to variations in pressure and temperature of the liquid and water vapor. Rather than use a statistical or climatological approach to account for the natural variability in atmospheric pressure and temperature, additional information on the atmospheric profile at the time of the radiometer measurements can be directly incorporated into the retrieval process. Such an approach has been referred to in the literature as a ''physical-iterative'' solution. This paper presents an assessment of the accuracy of the column liquid water path that can be expected using such an iterative technique as a result of uncertainties in the microwave emissions from oxygen and water vapor. It is shown that the retrieval accuracy is influenced by the accuracy of the instrument measurements and the quality of the atmospheric profiles of temperature and pressure, as one would expect. But also critical is the uncertainty in the absorption coefficients used in the underlying microwave radiative transfer model. The uncertainty in the absorption coefficients is particularly problematic in that it may well bias the liquid water retrieval. The differences between 3 absorption models examined in this paper are equivalent to a bias of 15 to 30 g/m2, depending on the total column water vapor. An examination of typical liquid water paths from the Southern Great Plains region of the United States shows that errors of this magnitude have significant implications for shortwave radiation and retrieval of cloud effective particle size

  4. Modification of a PAMPA model to predict passive gastrointestinal absorption and plasma protein binding.

    Bujard, Alban; Voirol, Hervé; Carrupt, Pierre-Alain; Schappler, Julie

    2015-09-18

    The Parallel Artificial Membrane Permeability Assay (PAMPA) is a well-known high throughput screening (HTS) technique for predicting in vivo passive absorption. In this technique, two compartments are separated by an artificial membrane that mimics passive permeability through biological membranes such as the dermal layer, the gastrointestinal tract (GIT), and the blood brain barrier (BBB). In the present study, a hexadecane artificial membrane (HDM)-PAMPA was used to predict the binding of compounds towards the human plasma using a mixture of human serum albumin (HSA) and alpha-1-acid glycoprotein (AGP). The ratio of HSA and AGP was equivalent to that found in the human plasma for both proteins (∼20:1). A pH gradient (5.0-7.4) was performed to increase the screening capacity and overcome the issue of passive permeability for acidic and amphoteric compounds. With this assay, the prediction of passive GIT absorption was maintained and the compounds were discriminated according to their permeability (on a no-to-high scale). The plasma protein binding (PPB) was estimated via the correlation of the differences between the amount of compound crossing the artificial membrane in assays conducted with and without protein using only a two end-point measurement. The use of a mixture of HSA and AGP to modulate drug permeation was compared to the use of the same concentrations of HSA and AGP used separately. The addition of HSA alone in the acceptor compartment was sufficient for estimating PPB, while it was demonstrated that AGP alone could enable the estimation of AGP binding. PMID:26118348

  5. Human intestinal absorption of imidacloprid with Caco-2 cells as enterocyte model

    In order to assess the risk to mammals of a chronic exposure to imidacloprid (IMI), we investigated its absorption with the human intestinal Caco-2 cell line. Measurements of transepithelial transport revealed an apparent permeability coefficient of 21.6 x 10-6 ± 3.2 x 10-6 cm/s reflecting a 100% absorption. The comparison of apical to basal (A-B) and basal to apical (B-A) transports showed that the monolayer presents a basal to apical polarized transport. Studies of apical uptake demonstrated that the transport was concentration-dependent and not saturable from 5 to 200 μM. Arrhenius plot analysis revealed two apparent activation energies, Ea(4-12deg.C) = 63.8 kJ/mol and Ea(12-37deg.C) 18.2 kJ/mol, suggesting two temperature-dependent processes. IMI uptake was equivalent when it was performed at pH 6.0 or 7.4. Depletion of Na+ from the transport buffer did not affect the uptake, indicating that a sodium-dependent transporter was not involved. Decrease of uptake with sodium-azide or after cell surface trypsin (Ti) treatment suggested the involvement of a trypsin-sensitive ATP-dependent transporter. Investigations on apical efflux demonstrated that initial velocities paralleled the increase of loading concentrations. A cell surface trypsin treatment did not affect the apical efflux. The lack of effect when the efflux was performed against an IMI concentration gradient suggested that an energy-dependent transporter was involved. However, the inhibition of P-glycoproteins (P-gp) and multidrug resistance-associated proteins (MRP) by taxol, vincristine, and daunorubicine had no effect on IMI intracellular accumulation suggesting the involvement of transporters distinct from classical ATP binding cassette transport (ABC-transport) systems. All results suggest that IMI is strongly absorbed in vivo by inward and outward active transporters

  6. The Influence of Water Vapor Absorption in the 290-350 nm Region on Solar Irradiance: Laboratory Studies and Model Simulation

    Zhu, L.; Du, J.; Huang, L.; Min, Q.

    2015-12-01

    Water vapor is the most abundant greenhouse gas in the earth's atmosphere. Absorption of the solar radiation by water vapor in the near UV region may partially account for the up to 30% discrepancy between the modeled and the observed solar energy absorbed by the atmosphere. But the magnitude of water vapor absorption in the near UV region at wavelengths shorter than 384 nm was not known prior to this study. We have determined absorption cross sections of water vapor at 5 nm intervals in the 290-350 nm region, by using cavity ring-down spectroscopy. Water vapor cross section values range from 2.94×10-24 to 2.13×10-25 cm2/molecule in the wavelength region studied. The effect of the water vapor absorption in the 290-350 nm region on the modeled radiation flux at the ground level has been evaluated using radiative transfer model.

  7. Rate-equation model for quantitative concentration measurements in flames with picosecond pump-probe absorption spectroscopy.

    Fiechtner, G J; King, G B; Laurendeau, N M

    1995-02-20

    Measurement of radical concentrations is important in understanding the chemical kinetics involved in combustion. Application of optical techniques allows for the nonintrusive determination of specific radical concentrations. One of the most challenging problems for investigators is to obtain flame data that are independent of the collisional environment. We seek to obviate this difficulty by the use of picosecond pump-probe absorption spectroscopy. A picosecond pump-probe absorption model is developed by rate-equation analysis. Implications are discussed for a laser-pulse width that is much smaller than the excited-state lifetime of the absorbing atom or molecule. The possibility of quantitative, quenching-independent concentration measurements is discussed, and detection limits for atomic sodium and the hydroxyl radical are estimated. For a three-level absorber-emitter, the model leads to a novel pump-probe strategy, called dual-beam asynchronous optical sampling, that can be used to obtain both the electronic quenching-rate coefficient and the doublet mixing-rate coefficient during a single measurement. We discuss the successful demonstration of the technique in a companion paper [Appl. Opt. 34, XXX (1995)]. PMID:21037640

  8. Two-phase flow modelling of a solar concentrator applied as ammonia vapor generator in an absorption refrigerator

    Ortega, N. [Posgrado en Ingenieria (Energia), Universidad Nacional Autonoma de Mexico, Privada Xochicalco s/n, Temixco, Morelos 62580 (Mexico); Garcia-Valladares, O.; Best, R.; Gomez, V.H. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Privada Xochicalco s/n, Temixco, Morelos 62580 (Mexico)

    2008-09-15

    A detailed one-dimensional numerical model describing the heat and fluid-dynamic behavior inside a compound parabolic concentrator (CPC) used as an ammonia vapor generator has been developed. The governing equations (continuity, momentum, and energy) inside the CPC absorber tube, together with the energy equation in the tube wall and the thermal analysis in the solar concentrator were solved. The computational method developed is useful for the solar vapor generator design applied to absorption cooling systems. The effect on the outlet temperature and vapor quality of a range of CPC design parameters was analyzed. These parameters were the acceptance half-angle and CPC length, the diameter and coating of the absorber tube, and the manufacture materials of the cover, the reflector, and the absorber tube. It was found that the most important design parameters in order to obtain a higher ammonia-water vapor production are, in order of priority: the reflector material, the absorber tube diameter, the selective surface, and the acceptance half-angle. The direct ammonia-water vapor generation resulting from a 35 m long CPC was coupled to an absorption refrigeration system model in order to determine the solar fraction, cooling capacity, coefficient of performance, and overall efficiency during a typical day of operation. The results show that approximately 3.8 kW of cooling at -10{sup o}C could be produced with solar and overall efficiencies up to 46.3% and 21.2%, respectively. (author)

  9. Absorption studies

    Absorption studies were once quite popular but hardly anyone does them these days. It is easier to estimate the blood level of the nutrient directly by radioimmunoassay (RIA). However, the information obtained by estimating the blood levels of the nutrients is not the same that can be obtained from the absorption studies. Absorption studies are primarily done to find out whether some of the essential nutrients are absorbed from the gut or not and if they are absorbed, to determine how much is being absorbed. In the advanced countries, these tests were mostly done to detect pernicious anaemia where vitamin B12 is not absorbed because of the lack of the intrinsic factor in the stomach. In the tropical countries, ''malabsorption syndrome'' is quire common. In this condition, several nutrients like fat, folic acid and vitamin B12 are not absorbed. It is possible to study absorption of these nutrients by radioisotopic absorption studies

  10. An in situ and operando X-ray absorption spectroscopy setup for measuring sub-monolayer model and powder catalysts.

    Weiher, Norbert; Bus, Eveline; Gorzolnik, Blazej; Möller, Martin; Prins, Roel; van Bokhoven, Jeroen Anton

    2005-09-01

    A new spectroscopic cell has been designed for studying model catalysts using in situ or operando X-ray absorption spectroscopy. The setup allows gas treatment and can be used between 100 and 870 K. Pressures from 10(-3) Pa up to 300 kPa can be applied. Measurements on model systems in this particular pressure range are a valuable extension of the commonly used UHV characterization techniques. Using this setup, we were able to analyze the Au L3 EXAFS of a silica wafer covered with sub-monolayer concentrations of gold (0.05 ML). By modifying the sample holder, powder catalysts can also be analyzed under plug-flow conditions. As an example, the reduction of a Au/SiO2 powder catalyst prepared from HAuCl4 was followed. PMID:16120994

  11. Nanostructuring for enhanced absorption and carrier collection in CZTS-based solar cells: Coupled optical and electrical modeling

    Abdelraouf, Omar A. M.; Allam, Nageh K.

    2016-04-01

    Earth-abundant Cu2ZnSnS4 (CZTS) is being considered as a potential photon-absorbing layer for low cost thin film solar cells. Nanostructured light trapping is recently investigated as a technique for enhancing the efficiency of CZTS solar cells. Herein, we used coupled electrical and optical modeling for different combinations of nanostructured CZTS solar cells to guide optimization of such nanostructures. The model is validated by a comparison of simulated I-V curves with previously reported experimental data. A very good agreement is achieved. Simulations are used to demonstrate that nanostructures can be tailored to maximize the absorption, carrier generation, carrier collection, and efficiency in CZTS solar cells. All proposed nanostructured solar cells showed enhancement in the overall conversion efficiency.

  12. Study of the strong-absorption-parameterization model for the elastic scattering of polarized 3H and 3He

    The strong absorption model has been used to analyze the spin -1/2 polarization data using three different parameterizations for the elastic scattering S-function namely; Ericson, Mclntyre and Berezhnoi-Shlyakhov. The cross-section ratio and the vector polarization angular distributions are calculated for the elastic scattering of polarized 3H from I2C, I6O, 26Mg and 30Si, targets at 36 MeV and 40Ca at 17 MeV. The same analysis has been applied for 3He elastically scattered from 26 Mg , 27A1,58Ni and 40Ca at different energies. The comparison between the model calculations and the data shows good agreement

  13. High-resolution numerical model of the middle and inner ear for a detailed analysis of radio frequency absorption

    In order to enable a detailed analysis of radio frequency (RF) absorption in the human middle and inner ear organs, a numerical model of these organs was developed at a spatial resolution of 0.1 mm, based on a real human tissue sample. The dielectric properties of the liquids (perilymph and endolymph) inside the bony labyrinth were measured on samples of ten freshly deceased humans. After inserting this model into a commercially available numerical head model, FDTD-based computations for exposure scenarios with generic models of handheld devices operated close to the head in the frequency range 400-3700 MHz were carried out. For typical output power values of real handheld mobile communication devices the obtained results showed only very small amounts of absorbed RF power in the middle and inner ear organs. Highest absorption in the middle and inner ear was found for the 400 MHz irradiation. In this case, the RF power absorbed inside the labyrinth and the vestibulocochlear nerve was as low as 166 μW and 12 μW, respectively, when considering a device of 500 mW output power operated close to the ear. For typical mobile phone frequencies (900 MHz and 1850 MHz) and output power values (250 mW and 125 mW) the corresponding values of absorbed RF power were found to be more than one order of magnitude lower than the values given above. These results indicate that temperature-related biologically relevant effects on the middle and inner ear, induced by the RF emissions of typical handheld mobile communication devices, are unlikely

  14. Comparison of models of fast saturable absorption in passively modelocked lasers.

    Wang, Shaokang; Marks, Brian S; Menyuk, Curtis R

    2016-09-01

    Fast saturable absorbers (FSAs) play a critical role in stabilizing many passively modelocked lasers. The most commonly used averaged model to study these lasers is the Haus modelocking equation (HME) that includes a third-order nonlinear FSA. However, it predicts a narrow region of stability that is inconsistent with experiments. To better replicate the laser physics, averaged laser models that include FSAs with higher-than-third-order nonlinearities have been introduced. Here, we compare three common FSA models to each other and to the HME using the recently-developed boundary tracking algorithms. The three FSA models are the cubic-quintic model, the sinusoidal model, and the algebraic model. We find that all three models predict the existence of a stable high-energy solution that is not present in the HME and have a much larger stable operating region. We also find that all three models predict qualitatively similar stability diagrams. We conclude that averaged laser models that include FSAs with higher-than-third-order nonlinearity should be used when studying the stability of passively modelocked lasers. PMID:27607630

  15. Comparison of Models of Fast Saturable Absorption in Passively Modelocked Lasers

    Wang, Shaokang; Menyuk, Curtis R

    2016-01-01

    Fast saturable absorbers (FSAs) play a critical role in stabilizing many passively modelocked lasers. The most commonly used averaged model to study these lasers is the Haus modelocking equation (HME) that includes a third-order nonlinear FSA. However, it predicts a narrow region of stability that is inconsistent with experiments. To better replicate the laser physics, averaged laser models that include FSAs with higher-than-third-order nonlinearities have been introduced. Here, we compare three common FSA models to each other and to the HME using the recently-developed boundary tracking algorithms. The three FSA models are the cubic-quintic model, the sinusoidal model, and the algebraic model. We find that all three models predict the existence of a stable high-energy solution that is not present in the HME and have a much larger stable operating region. We also find that all three models predict qualitatively similar stability diagrams. We conclude that averaged laser models that include FSAs with higher-th...

  16. PHANTOM MODEL OF HUMAN BRAIN TISSUE FOR CELLULAR PHONE FREQUENCIES IN ELECTROMAGNETIC FIELD RADIATION ABSORPTION STUDIES

    Özen, Şükrü; Köylü, Halis

    2010-01-01

    ABSTRACTThere is a necessity of tissue equivalent (phantom) models in research of electromagnetic (EM) effects in biologic tissues. Recently, many kinds of tissue models depend on the different aim were proposed. So many studies were carried on the interaction of human-head and cellular phone. The most of them are related to numerical models. Owing to difficulty of study on human body, simulation of human tissues is required. In this study two different, for 900MHz and for 1800MHz, brain equi...

  17. The New Cloud Absorption Radiometer (CAR) Software: One Model for NASA Remote Sensing Virtual Instruments

    Roth, Don J.; Rapchun, David A.; Jones, Hollis H.

    2001-01-01

    The Cloud Absorption Radiometer (CAR) instrument has been the most frequently used airborne instrument built in-house at NASA Goddard Space Flight Center, having flown scientific research missions on-board various aircraft to many locations in the United States, Azores, Brazil, and Kuwait since 1983. The CAR instrument is capable of measuring scattered light by clouds in fourteen spectral bands in UV, visible and near-infrared region. This document describes the control, data acquisition, display, and file storage software for the new version of CAR. This software completely replaces the prior CAR Data System and Control Panel with a compact and robust virtual instrument computer interface. Additionally, the instrument is now usable for the first time for taking data in an off-aircraft mode. The new instrument is controlled via a LabVIEW v5. 1.1-developed software interface that utilizes, (1) serial port writes to write commands to the controller module of the instrument, and (2) serial port reads to acquire data from the controller module of the instrument. Step-by-step operational procedures are provided in this document. A suite of other software programs has been developed to complement the actual CAR virtual instrument. These programs include: (1) a simulator mode that allows pretesting of new features that might be added in the future, as well as demonstrations to CAR customers, and development at times when the instrument/hardware is off-location, and (2) a post-experiment data viewer that can be used to view all segments of individual data cycles and to locate positions where 'start' and stop' byte sequences were incorrectly formulated by the instrument controller. The CAR software described here is expected to be the basis for CAR operation for many missions and many years to come.

  18. Modeling and experimental validation of the solar loop for absorption solar cooling system using double-glazed collectors

    Solar cooling applied to buildings is without a doubt an interesting alternative for reducing energy consumption in traditional mechanical steam compression air conditioning systems. The study of these systems should have a closely purely fundamental approach including the development of numerical models in order to predict the overall installation performance. The final objective is to estimate cooling capacity, power consumption, and overall installation performance with relation to outside factors (solar irradiation, outside temperature...). The first stage in this work consists of estimating the primary energy produced by the solar collector field. The estimation of this primary energy is crucial to ensure the evaluation of the cooling capacity and therefore the cooling distribution and thermal comfort in the building. Indeed, the absorption chiller performance is directly related to its heat source. This study presents dynamic models for double glazing solar collectors and compares the results of the simulation with experimental results taken from our test bench (two collectors). In the second part, we present an extensive collector field model (36 collectors) from our solar cooling installation at The University Institute of Technology in St Pierre, Reunion Island as well as our stratified tank storage model. A comparison of the simulation results with real scale solar experimental data taken from our installation enables validation of the double glazing solar collector and stratified tank dynamic models.

  19. Physiologically Based Absorption Modeling to Impact Biopharmaceutics and Formulation Strategies in Drug Development-Industry Case Studies.

    Kesisoglou, Filippos; Chung, John; van Asperen, Judith; Heimbach, Tycho

    2016-09-01

    In recent years, there has been a significant increase in use of physiologically based pharmacokinetic models in drug development and regulatory applications. Although most of the published examples have focused on aspects such as first-in-human (FIH) dose predictions or drug-drug interactions, several publications have highlighted the application of these models in the biopharmaceutics field and their use to inform formulation development. In this report, we present 5 case studies of use of such models in this biopharmaceutics/formulation space across different pharmaceutical companies. The case studies cover different aspects of biopharmaceutics or formulation questions including (1) prediction of absorption prior to FIH studies; (2) optimization of formulation and dissolution method post-FIH data; (3) early exploration of a modified-release formulation; (4) addressing bridging questions for late-stage formulation changes; and (5) prediction of pharmacokinetics in the fed state for a Biopharmaceutics Classification System class I drug with fasted state data. The discussion of the case studies focuses on how such models can facilitate decisions and biopharmaceutic understanding of drug candidates and the opportunities for increased use and acceptance of such models in drug development and regulatory interactions. PMID:26886317

  20. Understanding H isotope adsorption and absorption of Al-alloys using modeling and experiments (LDRD: #165724)

    Ward, Donald K. [Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Zhou, Xiaowang [Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Karnesky, Richard A. [Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Kolasinski, Robert [Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Foster, Michael E. [Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Thurmer, Konrad [Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Chao, Paul [Carnegie Mellon University, Pittsburgh, PA (United States); Epperly, Ethan Nicholas [Livermore Valley Charter Preparatory High School, Livermore, CA (United States); Zimmerman, Jonathan A. [Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Wong, Bryan M. [Univ. of California, Riverside, CA (United States); Sills, Ryan B. [Sandia National Laboratories (SNL-CA), Livermore, CA (United States)

    2015-09-01

    Current austenitic stainless steel storage reservoirs for hydrogen isotopes (e.g. deuterium and tritium) have performance and operational life-limiting interactions (e.g. embrittlement) with H-isotopes. Aluminum alloys (e.g.AA2219), alternatively, have very low H-isotope solubilities, suggesting high resistance towards aging vulnerabilities. This report summarizes the work performed during the life of the Lab Directed Research and Development in the Nuclear Weapons investment area (165724), and provides invaluable modeling and experimental insights into the interactions of H isotopes with surfaces and bulk AlCu-alloys. The modeling work establishes and builds a multi-scale framework which includes: a density functional theory informed bond-order potential for classical molecular dynamics (MD), and subsequent use of MD simulations to inform defect level dislocation dynamics models. Furthermore, low energy ion scattering and thermal desorption spectroscopy experiments are performed to validate these models and add greater physical understanding to them.

  1. Modeling of intensity-modulated continuous-wave laser absorption spectrometer systems for atmospheric CO(2) column measurements.

    Lin, Bing; Ismail, Syed; Wallace Harrison, F; Browell, Edward V; Nehrir, Amin R; Dobler, Jeremy; Moore, Berrien; Refaat, Tamer; Kooi, Susan A

    2013-10-10

    The focus of this study is to model and validate the performance of intensity-modulated continuous-wave (IM-CW) CO(2) laser absorption spectrometer (LAS) systems and their CO(2) column measurements from airborne and satellite platforms. The model accounts for all fundamental physics of the instruments and their related CO(2) measurement environments, and the modeling results are presented statistically from simulation ensembles that include noise sources and uncertainties related to the LAS instruments and the measurement environments. The characteristics of simulated LAS systems are based on existing technologies and their implementation in existing systems. The modeled instruments are specifically assumed to be IM-CW LAS systems such as the Exelis' airborne multifunctional fiber laser lidar (MFLL) operating in the 1.57 μm CO(2) absorption band. Atmospheric effects due to variations in CO(2), solar radiation, and thin clouds, are also included in the model. Model results are shown to agree well with LAS atmospheric CO(2) measurement performance. For example, the relative bias errors of both MFLL simulated and measured CO(2) differential optical depths were found to agree to within a few tenths of a percent when compared to the in situ observations from the flight of 3 August 2011 over Railroad Valley (RRV), Nevada, during the summer 2011 flight campaign. In addition, the horizontal variations in the model CO(2) differential optical depths were also found to be consistent with those from MFLL measurements. In general, the modeled and measured signal-to-noise ratios (SNRs) of the CO(2) column differential optical depths (τd) agreed to within about 30%. Model simulations of a spaceborne IM-CW LAS system in a 390 km dawn/dusk orbit for CO(2) column measurements showed that with a total of 42 W of transmitted power for one offline and two different sideline channels (placed at different locations on the side of the CO(2) absorption line), the accuracy of the

  2. Modeling unburned hydrocarbon formation due to absorption/desorption processes into the wall oil film

    This paper reports that as a result of continuing air pollution problems, very stringent regulations are being enforced to control emissions of unburned hydrocarbons (HC) from premixed-charge, spark-ignition engines. A number of attempts have been reported on modeling sources of HC emissions using various analytical tools. Over the past decade, the development of multi-dimensional reacting flow codes has advanced considerably. Perhaps the most widely used multi-dimensional engine simulation code is KIVA-II, which was developed at Lost Alamos National Laboratory. The ability to deal with moving boundary conditions caused by the piston movement is built in this code. This code also includes models for turbulent fluid flow, turbulent interaction between spray drops and gas, heat transfer, chemical reaction, and fuel spray. A standard k-ε turbulence model is used for gas flow. The fuel spray model is based on the stochastic particle technique, and includes sub-models for droplet injection, breakup, collision and coalescence, and evaporation

  3. Electronic absorption spectra and solvatochromic shifts by the vertical excitation model: solvated clusters and molecular dynamics sampling.

    Marenich, Aleksandr V; Cramer, Christopher J; Truhlar, Donald G

    2015-01-22

    A physically realistic treatment of solvatochromic shifts in liquid-phase electronic absorption spectra requires a proper account for various short- and long-range equilibrium and nonequilibrium solute-solvent interactions. The present article demonstrates that such a treatment can be accomplished using a mixed discrete-continuum approach based on the two-time-scale self-consistent state-specific vertical excitation model (called VEM) for electronic excitation in solution. We apply this mixed approach in combination with time-dependent density functional theory to compute UV/vis absorption spectra in solution for the n → π* ((1)A2) transition for acetone in methanol and in water, the π → π* ((1)A1) transition for para-nitroaniline (PNA) in methanol and in water, the n → π* ((1)B1) transition for pyridine in water, and the n → π* ((1)B1) transition for pyrimidine in water. Hydrogen bonding and first-solvation-shell-specific complexation are included by means of explicit solvent molecules, and solute-solvent dispersion is included by using the solvation model with state-specific polarizability (SMSSP). Geometries of microsolvated clusters were treated in two different ways, (i) using single liquid-phase global-minimum solute-solvent clusters containing up to two explicit solvent molecules and (ii) using solute-solvent cluster snapshots derived from molecular dynamics (MD) trajectories. The calculations in water involve using VEM/TDDFT excitation energies and oscillator strengths computed over 200 MD-derived solute-solvent clusters and convoluted with Gaussian functions. We also calculate ground- and excited-state dipole moments for interpretation. We find that inclusion of explicit solvent molecules generally improves the agreement with experiment and can be recommended as a way to include the effect of hydrogen bonding in solvatochromic shifts. PMID:25159827

  4. Properties of damped Ly α absorption systems and star-forming galaxies in semi-analytic models at z = 2

    Berry, Michael; Somerville, Rachel S.; Gawiser, Eric; Maller, Ariyeh H.; Popping, Gergö; Trager, Scott C.

    2016-05-01

    We investigate predictions from semi-analytic cosmological models of galaxy formation for the properties of star-forming galaxies (SFGs) and damped Ly α absorption systems (DLAS), and the relationship between these two populations. Our models reproduce fairly well the observed distributions of redshift, stellar mass, star formation rate (SFR), and dust extinction for z ˜ 2 SFGs. We predict that DLA hosts span a broad range of properties, with broad and relatively flat distributions of stellar and halo mass, SFR, and luminosity. The photometric colours of DLA host galaxies trace the colours of galaxies with similar luminosities, but the majority are much fainter than the limits of most existing surveys of SFGs. Generally, DLA host galaxies and SFGs at z = 2 follow similar trends between stellar mass, DLA cross-section, cold gas fraction, SFR, metallicity, and dust extinction as the global population of galaxies with the same stellar mass. Since DLAS select galaxies with larger cold gas masses, they tend to have larger cold gas fractions, lower metallicities, higher SFRs, and less dust extinction than galaxies at the same stellar mass. Our models reproduce the observed relations between impact parameter, column density, and metallicity, suggesting that the sizes of the gas discs giving rise to DLAS in our models are roughly correct. We find that molecular fractions and SFRs are in general significantly lower at the location of the DLA line of sight than the galaxy-averaged value.

  5. Modelling High Resolution Absorption Spectra with ExoMolLine Lists: NH3and CH4

    Barton, E. J.; Yurchenko, S. N.; Tennyson, J.;

    [1]. For this reason, a smart collaboration has been established between Optical Diagnostics Group at DTU and ExoMol, to combine high resolution spectra measured at elevated temperatures and empirically tuned ab initio methods to produce suitable molecular line lists for modelling molecules in...

  6. Maximum Recommended Dosage of Lithium for Pregnant Women Based on a PBPK Model for Lithium Absorption

    Scott Horton

    2012-01-01

    Full Text Available Treatment of bipolar disorder with lithium therapy during pregnancy is a medical challenge. Bipolar disorder is more prevalent in women and its onset is often concurrent with peak reproductive age. Treatment typically involves administration of the element lithium, which has been classified as a class D drug (legal to use during pregnancy, but may cause birth defects and is one of only thirty known teratogenic drugs. There is no clear recommendation in the literature on the maximum acceptable dosage regimen for pregnant, bipolar women. We recommend a maximum dosage regimen based on a physiologically based pharmacokinetic (PBPK model. The model simulates the concentration of lithium in the organs and tissues of a pregnant woman and her fetus. First, we modeled time-dependent lithium concentration profiles resulting from lithium therapy known to have caused birth defects. Next, we identified maximum and average fetal lithium concentrations during treatment. Then, we developed a lithium therapy regimen to maximize the concentration of lithium in the mother’s brain, while maintaining the fetal concentration low enough to reduce the risk of birth defects. This maximum dosage regimen suggested by the model was 400 mg lithium three times per day.

  7. The spectral variability of the GHZ-Peaked spectrum radio source PKS 1718-649 and a comparison of absorption models

    Tingay, S. J.; Macquart, J.-P.; Wayth, R. B.; Trott, C. M.; Emrich, D. [International Centre for Radio Astronomy Research, Curtin University, Bentley, WA 6102 (Australia); Collier, J. D.; Wong, G. F. [University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751 (Australia); Rees, G.; Stevens, J.; Carretti, E. [CSIRO Astronomy and Space Science (CASS), PO Box 76, Epping, NSW 1710 (Australia); Callingham, J. R.; Gaensler, B. M. [Sydney Institute for Astronomy, School of Physics (SiFA), The University of Sydney, NSW 2006 (Australia); McKinley, B.; Briggs, F. [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia); Bernardi, G. [Square Kilometre Array South Africa (SKA SA), Cape Town 7405 (South Africa); Bowman, J. D. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Cappallo, R. J.; Corey, B. E. [MIT Haystack Observatory, Westford, MA 01886 (United States); Deshpande, A. A. [Raman Research Institute, Bangalore 560080 (India); Goeke, R., E-mail: s.tingay@curtin.edu.au [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); and others

    2015-02-01

    Using the new wideband capabilities of the ATCA, we obtain spectra for PKS 1718-649, a well-known gigahertz-peaked spectrum radio source. The observations, between approximately 1 and 10 GHz over 3 epochs spanning approximately 21 months, reveal variability both above the spectral peak at ∼3 GHz and below the peak. The combination of the low- and high-frequency variability cannot be easily explained using a single absorption mechanism, such as free–free absorption or synchrotron self-absorption. We find that the PKS 1718-649 spectrum and its variability are best explained by variations in the free–free optical depth on our line of sight to the radio source at low frequencies (below the spectral peak) and the adiabatic expansion of the radio source itself at high frequencies (above the spectral peak). The optical depth variations are found to be plausible when X-ray continuum absorption variability seen in samples of active galactic nuclei is considered. We find that the cause of the peaked spectrum in PKS 1718-649 is most likely due to free–free absorption. In agreement with previous studies, we find that the spectrum at each epoch of observation is best fit by a free–free absorption model characterized by a power-law distribution of free–free absorbing clouds. This agreement is extended to frequencies below the 1 GHz lower limit of the ATCA by considering new observations with Parkes at 725 MHz and 199 MHz observations with the newly operational Murchison Widefield Array. These lower frequency observations argue against families of absorption models (both free–free and synchrotron self-absorption) that are based on simple homogenous structures.

  8. Radiation absorption and use by humid savanna grassland: assessment using remote sensing and modelling

    The components of the canopy radiation balance in photosynthetically active radiation (PAR), phytomass and leaf area index (LAI) were measured during a complete annual cycle in an annually burned African humid savanna. Directional reflectances measured by a hand-held radiometer were used to compute the canopy normalized difference vegetation index (NDVI). The fraction fAPAR of PAR absorbed by the canopy (APAR) and canopy reflectances were simulated by the scattering from arbitrarily inclined leaves (SAIL) and the radiation interception in row intercropping (RIRI) models. The daily PAR to solar radiation ratio was linearly related to the daily fraction of diffuse solar radiation with an annual value around 0.47. The observed fAPAR was non-linearly related to NDVI. The SAIL model simulated reasonably well directional reflectances but noticeably overestimated fAPAR during most of the growing season. Comparison of simulations performed with the 1D and 3D versions of the RIRI model highlighted the weak influence of the heterogeneous structure of the canopy after fire and of the vertical distribution of dead and green leaves on total fAPAR. Daily fAPAR values simulated by the 3D-RIRI model were linearly related to and 9.8% higher than observed values. For sufficient soil water availability, the net production efficiency ϵn of the savanna grass canopy was 1.92 and 1.28 g DM MJ−1 APAR (where DM stands for dry matter) during early regrowth and mature stage, respectively. In conclusion, the linear relationship between NDVI and fAPAR used in most primary production models operating at large scales may slightly overestimate fAPAR by green leaves for the humid savanna biome. Moreover, the net production efficiency of humid savannas is close to or higher than values reported for the other major natural biomes. (author)

  9. A Robust Monte Carlo Model for the Extraction of Biological Absorption and Scattering In Vivo

    Bender, Janelle E.; Vishwanath, Karthik; Moore, Laura K.; Brown, J. Quincy; Chang, Vivide; Palmer, Gregory M.; Ramanujam, Nirmala

    2009-01-01

    We have a toolbox to quantify tissue optical properties that is composed of specialized fiberoptic probes for UV-visible diffuse reflectance spectroscopy and a fast, scalable inverse Monte Carlo (MC) model. In this paper, we assess the robustness of the toolbox for quantifying physiologically relevant parameters from turbid tissue-like media. In particular, we consider the effects of using different instruments, fiberoptic probes, and instrument-specific settings for a wide range of optical p...

  10. ITM-Based FSI-Models for Rooms with Absorptive Boundaries

    Buchschmid, Martin

    2012-01-01

    A method for room acoustical simulations has been developed in order to compute the sound field in acoustic cavities with compound absorbers, mounted at the walls. To reduce the number of degrees of freedom and therefore the numerical effort, a model reduction method, based on a Component Mode Synthesis (CMS), is applied. Macrostructures are assembled out of single substructures applying shape functions at the interfaces. These substructures contain acoustic components like porous absorbers o...

  11. Shift of absorption energy during thin dye film growth: interpretation by geometric models of the growth morphology

    We measure absorption spectra of two different perylene molecules in thin films with thicknesses varied between 1 and 30 nm physical vapor deposited on glass substrates. Atomic force microscopy (reveals the formation of crystallized needles for N, N'-dimethyl perylene tetracarboxylic acid diimide and amorphous round-shaped islands for 1,6,7,12-tetrachloro-N,N'-dimethyl perylene tetracarboxylic. For both molecules, a spectral shift of the lowest energy transition to lower energies was observed with increasing film thickness. Common models taking electric fields, electronic coupling or exciton confinement into account cannot completely describe the observed spectral shift. Here we show that the experimental values can be fitted with an advanced layering model based on the energetic difference between bulk and interface/surface materials. In contrast to the known simple d−1 model, which describes the energetic shift for the special case of a layer-by-layer growth, we extend this idea to other film morphologies. - Highlights: • Description of energetic shift of transition energy of organic thin films. • Relation of differences in shift with film morphologies. • Theoretical explanation based on geometric considerations

  12. Shift of absorption energy during thin dye film growth: interpretation by geometric models of the growth morphology

    Trenkmann, Ines; Borczyskowski, Christian von; Graaf, Harald, E-mail: graaf@uni-bremen.de

    2014-12-31

    We measure absorption spectra of two different perylene molecules in thin films with thicknesses varied between 1 and 30 nm physical vapor deposited on glass substrates. Atomic force microscopy (reveals the formation of crystallized needles for N, N'-dimethyl perylene tetracarboxylic acid diimide and amorphous round-shaped islands for 1,6,7,12-tetrachloro-N,N'-dimethyl perylene tetracarboxylic. For both molecules, a spectral shift of the lowest energy transition to lower energies was observed with increasing film thickness. Common models taking electric fields, electronic coupling or exciton confinement into account cannot completely describe the observed spectral shift. Here we show that the experimental values can be fitted with an advanced layering model based on the energetic difference between bulk and interface/surface materials. In contrast to the known simple d{sup −1} model, which describes the energetic shift for the special case of a layer-by-layer growth, we extend this idea to other film morphologies. - Highlights: • Description of energetic shift of transition energy of organic thin films. • Relation of differences in shift with film morphologies. • Theoretical explanation based on geometric considerations.

  13. Mantle formation, coagulation, and the origin of cloud/core shine. I. Modelling dust scattering and absorption in the infrared

    Jones, A. P.; Köhler, M.; Ysard, N.; Dartois, E.; Godard, M.; Gavilan, L.

    2016-04-01

    Context. The observed cloudshine and coreshine (C-shine) have been explained in terms of grain growth leading to enhanced scattering from clouds in the J, H, and K photometric bands and the Spitzer IRAC 3.6 and 4.5 μm bands. Aims: Using our global dust-modelling approach THEMIS (The Heterogeneous dust Evolution Model at the IaS), we explore the effects of dust evolution in dense clouds, through aliphatic-rich carbonaceous mantle formation and grain-grain coagulation. Methods: We model the effects of wide band gap a-C:H mantle formation and the low-level aggregation of diffuse interstellar medium dust in the moderately-extinguished outer regions of molecular clouds. Results: The formation of wide band gap a-C:H mantles on amorphous silicate and amorphous carbon (a-C) grains leads to a decrease in their absorption cross-sections but no change in their scattering cross-sections at near-infrared wavelengths, resulting in higher albedos. Conclusions: The evolution of dust, with increasing density and extinction in the diffuse-to-dense molecular cloud transition, through mantle formation and grain aggregation, appears to be a likely explanation for the observed C-shine.

  14. Combining Networks, Ambidexterity and Absorptive Capacity to Explain Commercialization of Innovations: A Theoretical Model from Review and Extension

    2011-01-01

    From a thorough review of literature we investigate the key antecedents and mediators to commercialization of innovations. We posit that a firm¡¯s network, absorptive capacity and ambidexterity (ability to explore and exploit) each affect commercialization of Innovations. Further, we showed that networks are antecedents to absorptive capacity and ambidexterity, and absorptive capacity is an antecedent to ambidexterity. We integrate these concepts together and present an integrated theoretical...

  15. Converting Sabine absorption coefficients to random incidence absorption coefficients

    Jeong, Cheol-Ho

    2013-01-01

    Absorption coefficients measured by the chamber method are referred to as Sabine absorption coefficients, which sometimes exceed unity due to the finite size of a sample and non-uniform intensity in the reverberation chambers under test. In this study, conversion methods from Sabine absorption...... coefficients to random incidence absorption coefficients are proposed. The overestimations of the Sabine absorption coefficient are investigated theoretically based on Miki's model for porous absorbers backed by a rigid wall or an air cavity, resulting in conversion factors. Additionally, three optimizations...

  16. Modelling (using artificial neural-networks) the performance parameters of a solar-driven ejector-absorption cycle

    Theoretical thermodynamic analysis of the absorption thermal systems is at present too complex because of analytic functions calculating the thermodynamic properties of fluid couples involving the solution of complex differential equations and simulation programs. This paper proposes a new approach to performance analysis of a solar-driven ejector-absorption refrigeration system (EARS) with an aqua/ammonia working fluid. Use of artificial neural-networks (ANNs) has been proposed to determine the performance parameters as functions of only the working temperature, under various working conditions. Thus, this study is considered to be helpful in predicting the performance of an EARS prior to it being set up in an environment where the temperatures are known. The statistical coefficient of multiple determinations (R2 - value) equals to 0.976, 0.9825, 0.9855 for the coefficient of performance (COP), exergetic coefficient of performance (ECOP) and circulation ratio (F), respectively. These accuracies are acceptable for the design of an EARS. The present method greatly reduces the time required by design engineers to find the optimum solution and in many cases reaches a solution that could not be easily obtained from simple modelling programs. The importance of the ANN approach, apart from reducing the time required, is that it is possible to find solutions that make solar-energy applications more viable and thus more attractive to potential users, such as solar engineers. Also, this approach has the advantages of computational speed, low cost for feasibility, rapid turnaround (which is especially important during iterative design-phases), and ease of design by operators with little technical experience

  17. Modeling the effects of wind tunnel wall absorption on the acoustic radiation characteristics of propellers

    Baumeister, K. J.; Eversman, W.

    1986-01-01

    Finite element theory is used to calculate the acoustic field of a propeller in a soft walled circular wind tunnel and to compare the radiation patterns to the same propeller in free space. Parametric solutions are present for a 'Gutin' propeller for a variety of flow Mach numbers, admittance values at the wall, microphone position locations, and propeller to duct radius ratios. Wind tunnel boundary layer is not included in this analysis. For wall admittance nearly equal to the characteristic value of free space, the free field and ducted propeller models agree in pressure level and directionality. In addition, the need for experimentally mapping the acoustic field is discussed.

  18. Generation and Active Absorption of 2- and 3-Dimensional Linear Water Waves in Physical Models

    Christensen, Morten

    different directional wave spectra. The wave generator displacement signals applied in the tests are generated by means of linear digital filtering of Gaussian white noise in the time domain. An absorbing wave generator for 2-D wave facilities (wave channels) is developed. The absorbing wave generator is......-D wave facilities (wave basins) based on a similar principle is developed. A conventional directional wave generator is converted into an absorbing directional wave generator based on this principle and applied to a series of physical model tests. The test results show that the absorbing directional...

  19. Regional Climate Zone Modeling of a Commercial Absorption Heat Pump Hot Water Heater Part 1: Southern and South Central Climate Zones

    Geoghegan, Patrick J [ORNL; Shen, Bo [ORNL; Keinath, Christopher M. [Stone Mountain Technologies, Inc., Johnson City; Garrabrant, Michael A. [Stone Mountain Technologies, Inc., Johnson City

    2016-01-01

    Commercial hot water heating accounts for approximately 0.78 Quads of primary energy use with 0.44 Quads of this amount from natural gas fired heaters. An ammonia-water based commercial absorption system, if fully deployed, could achieve a high level of savings, much higher than would be possible by conversion to the high efficiency nonheat-pump gas fired alternatives. In comparison with air source electric heat pumps, the absorption system is able to maintain higher coefficients of performance in colder climates. The ammonia-water system also has the advantage of zero Ozone Depletion Potential and low Global Warming Potential. A thermodynamic model of a single effect ammonia-water absorption system for commercial space and water heating was developed, and its performance was investigated for a range of ambient and return water temperatures. This allowed for the development of a performance map which was then used in a building energy modeling software. Modeling of two commercial water heating systems was performed; one using an absorption heat pump and another using a condensing gas storage system. The energy and financial savings were investigated for a range of locations and climate zones in the southern and south central United States. A follow up paper will analyze northern and north/central regions. Results showed that the system using an absorption heat pump offers significant savings.

  20. Hand effect on head specific absorption rate (SAR) exposed by two realistic phone models

    There have been some reports about possible effect of the hand presence on the head SAR if hand phantom is included in the measurements of the head SAR compliance assessment procedure. The objective of this computational study was to examine the reported effect by using realistic head models and realistic CAD based phone models. A commercially available FDTD based EM solver was used to carry out the computational work. Based on the results of this study considering the SAR values without hand phantom as reference, following conclusions can be made: 1. In general presence of the hand lead to significantly less conservative SAR values in the head for large majority of cases 2. For lower band GSM frequencies the presence of the hand decreases the head SAR up to ∼70%. 3. For the upper band GSM frequencies the presence of the hand decreases the head SAR up to ∼55%. Based on the results of this study the present SAR compliance protocol where hand phantom is not included leads to more conservative head SAR results compared to the cases where hand is included.

  1. Optical reflection, transmission and absorption properties of single-layer black phosphorus from a model calculation

    Margulis, Vl A.; Muryumin, E. E.; Gaiduk, E. A.

    2016-05-01

    An effective anisotropic tight-binding model is developed to analytically describe the low-energy electronic structure and optical response of phosphorene (a black phosphorus (BP) monolayer). Within the framework of the model, we derive explicit closed-form expressions, in terms of elementary functions, for the elements of the optical conductivity tensor of phosphorene. These relations provide a convenient parametrization of the highly anisotropic optical response of phosphorene, which allows the reflectance, transmittance, and absorbance of this material to be easily calculated as a function of the frequency of the incident radiation at arbitrary angles of incidence. The results of such a calculation are presented for both a free-standing phosphorene layer and the phosphorene layer deposited on a {{SiO}}2 substrate, and for the two principal cases of polarization of the incident radiation either parallel to or normal to the plane of incidence. Our findings (e.g., a ‘quasi-Brewster’ effect in the reflectance of the phosphorene/{{SiO}}2 overlayer system) pave the way for developing a new, purely optical method of distinguishing BP monolayers.

  2. Copper absorption from human milk, cow's milk, and infant formulas using a suckling rat model

    Since copper deficiency is known to occur during infancy, it becomes important to assess copper uptake from various infant diets. The authors have investigated the uptake of copper from human milk, cow's milk, cow's milk formulas, cereal/milk formula and soy formula, compensating for the decay of 64Cu and using the suckling rat as a model. Radiocopper was added to the diet in trace amounts. Ultracentrifugation, ultrafiltration, and gel filtration were used to show that the added 64Cu bound to milk fractions and individual binding compounds in a manner analogous to the distribution of native copper, thus validating the use of extrinsically labeled diets. Labeled diets were intubated into 14-day-old suckling rats. Animals were killed after 6 h and tissues removed and counted. Liver copper uptake was 25% from human milk, 23% from cow's milk formula, 18% from cow's milk, 17% from premature (cow's milk based) infant formula, 17% from cereal/milk formula and 10% from soy formula. These results show that the rat pup model may provide a rapid, inexpensive, and sensitive method to assay bioavailability of copper from infant foods

  3. A heuristic model to quantify the impact of excess cyclodextrin on oral drug absorption from aqueous solution.

    Olesen, Niels Erik; Westh, Peter; Holm, René

    2016-05-01

    The intestinal drug solubilising capacity (Dtot(SC)) of a drug formulated as an aqueous cyclodextrin solution is a recently proposed quantity to predict the cyclodextrin concentration needed to fully solubilise the drug in the intestinal lumen. According to this concept, the cyclodextrin concentration in the drug product must be higher than the amount needed to solubilise the compound, due to the displacement of the drug from the cyclodextrin cavity by bile salts in the intestinal lumen. On the other hand, dosing cyclodextrin at >Dtot(SC) is expected to result in decreased free intestinal drug concentrations and thus potentially a lower fraction absorbed. In this study, data from three previous in vivo studies in rats with fixed concentrations of three compounds (danazol, cinnarizine and benzo[A]pyrene) and various cyclodextrin concentrations >Dtot(SC) were analysed. The model was developed for danazol and applied to the two other compounds. Absorption, as quantified from the area under the plasma concentration-time profile, was predicted by the model to decrease at elevated concentrations of co-administered cyclodextrin in accordance with the in vivo data. In addition, at high cyclodextrin concentrations a delay in Tmax and a decrease in Cmax were predicted, again in accordance with the experimental observations. These observations were rationalised in terms of the free intestinal drug concentration by a chemical equilibrium model for Dtot(SC). This model depends on the quantity termed the dimensionless dose concentration, Dtot(∗)=Do/Pn, given as the fraction of the permeation number (Pn) and dose number (Do). The model provides the formulation scientist with a critical quality attribute for assessing the implication of having excess cyclodextrin in an oral solution. PMID:26969263

  4. Interannual variability of CFC-11 absorption by the ocean: an offline model study

    Valsala, Vinu; Maksyutov, Shamil [CGER, National Institute for Environmental Studies, Tsukuba (Japan); Alsibai, Hayyan M. [Tsukuba University, Graduate School of System and Information Engineering, Tsukuba (Japan); Ikeda, Motoyoshi [Hokkaido University, Graduate School of Earth System Sciences, Sapporo (Japan)

    2011-04-15

    The global ocean Chlorofluorocarbon (CFC-11) was simulated in an offline model driven by re-analysis ocean currents in order to identify the mechanisms of interannual to interdecadal variability of air-sea CFC fluxes. The model was forced with the observed anthropogenic perturbations of atmospheric CFC-11 from the post industrial period (1938) following the OCMIP-II flux protocols along with the observed winds from 1960 to 1999 in the formulation of surface gas exchanges. The model ocean CFC-11 inventories, at the end of 1990s, accounted approximately 1% of the total atmospheric CFC-11, which is consistent with the corresponding observations. The mid-to-high latitude oceans were venue for strong (weak) oceanic sinks (sources) of CFC-11 during the winter (summer) months. The Southern Ocean (south of 40 S) and the North Atlantic (north of 35 N) provided two largest sinks of CFC-11, through which 31.4 and 14.6% of the global ocean CFC-11 entered, respectively. The eastern tropical Pacific Ocean exhibited large interannual variability of CFC-11 flux with a strong (weak) sink during La Nina (El Nino) years and represented 36% of the global CFC-11 flux variability. The North Atlantic and Southern Ocean were found as regions of large sink efficiency: a capacity to sink more CFC than outsource, although it reduced by 80 and 70%, respectively, in the last 40 years compared to 1960. The sink to source ratio of global ocean CFC-11 fluxes were reduced from 90 to 50% in the last 40 years. This indicates a saturation of CFC in the above-thermocline subsurface that makes the upper ocean less efficient in absorbing CFC in recent decades. A positive trend in CFC sink is now limited to the Southern Ocean, central tropical Pacific and western boundary current regions which possess active upwelling of old water with long time since last atmospheric contact. However, a globally averaged trend was a reduced CFC-11 sink, by emitting 30% of the total ocean CFC-11 that was absorbed during

  5. Use of Modeling and Simulation Tools for Understanding the Impact of Formulation on the Absorption of a Low Solubility Compound: Ciprofloxacin.

    Martinez, Marilyn; Mistry, Bipin; Lukacova, Viera; Polli, Jim; Hoag, Stephen; Dowling, Thomas; Kona, Ravikanth; Fahmy, Raafat

    2016-07-01

    This study explored the utility of mechanistic absorption models to describe the in vivo performance of a low solubility/low permeability compound in normal healthy subjects. Sixteen healthy human volunteers received three oral formulations and an intravenous infusion in a randomized crossover design. Plasma ciprofloxacin concentrations were estimated by HPLC. In vitro ciprofloxacin release from the oral tablets was tested under a variety of conditions. A mechanistic model was used to explore in vivo dissolution and intestinal absorption. Although dissolution rate influenced the location of drug release, absorption challenges appeared to be associated with permeability limitations in the lower small intestine and colon. The apparent relationship between drug solubilization within the upper small intestinal and formulation overall bioavailability suggested the presence of an intestinal absorption window in many individuals. Failure to absorb drug within this window appeared to be linked with the likelihood of in vivo drug precipitation. Challenges encountered during this modeling exercise included large intersubject variability in product in vivo dissolution and the apparent limitations in ciprofloxacin absorption. Although transporter activity was not included as a model parameter, this evaluation demonstrated how identifying the location of drug absorption across several formulations provided an opportunity to identify factors to consider when formulating similar low solubility/low permeability compounds. The use of mechanistic models was invaluable for our understanding of in vivo product performance and for the assessment of individual profiles rather than means. The latter was essential for understanding the potential challenges that may be encountered when introducing a formulation into a patient population. PMID:27116024

  6. Monitoring the initial pulmonary absorption of two different beclomethasone dipropionate aerosols employing a human lung reperfusion model

    Fritz Peter

    2005-02-01

    Full Text Available Abstract Background The pulmonary residence time of inhaled glucocorticoids as well as their rate and extend of absorption into systemic circulation are important facets of their efficacy-safety profile. We evaluated a novel approach to elucidate the pulmonary absorption of an inhaled glucocorticoid. Our objective was to monitor and compare the combined process of drug particle dissolution, pro-drug activation and time course of initial distribution from human lung tissue into plasma for two different glucocorticoid formulations. Methods We chose beclomethasone dipropionate (BDP delivered by two different commercially available HFA-propelled metered dose inhalers (Sanasthmax®/Becloforte™ and Ventolair®/Qvar™. Initially we developed a simple dialysis model to assess the transfer of BDP and its active metabolite from human lung homogenate into human plasma. In a novel experimental setting we then administered the aerosols into the bronchus of an extracorporally ventilated and reperfused human lung lobe and monitored the concentrations of BDP and its metabolites in the reperfusion fluid. Results Unexpectedly, we observed differences between the two aerosol formulations Sanasthmax®/Becloforte™ and Ventolair®/Qvar™ in both the dialysis as well as in the human reperfusion model. The HFA-BDP formulated as Ventolair®/Qvar™ displayed a more rapid release from lung tissue compared to Sanasthmax®/Becloforte™. We succeeded to explain and illustrate the observed differences between the two aerosols with their unique particle topology and divergent dissolution behaviour in human bronchial fluid. Conclusion We conclude that though the ultrafine particles of Ventolair®/Qvar™ are beneficial for high lung deposition, they also yield a less desired more rapid systemic drug delivery. While the differences between Sanasthmax®/Becloforte™ and Ventolair®/Qvar™ were obvious in both the dialysis and lung perfusion experiments, the latter

  7. Effects of posture on FDTD calculations of specific absorption rate in a voxel model of the human body

    A change in the posture of the human body can significantly affect the way in which it absorbs radiofrequency electromagnetic radiation. To study this, an anatomically realistic model of the body has been modified to develop new voxel models in postures other than the standard standing position with arms to the side. These postures were sitting, arms stretched out horizontally to the side and vertically above the head. Finite-difference time-domain (FDTD) calculations of the whole-body averaged specific energy absorption rate (SAR) have been performed from 10 MHz to 300 MHz at a resolution of 4 mm. Calculations show that the effect of a raised arm above the head posture was to increase the value of the whole-body averaged SAR at resonance by up to 35% when compared to the standard, arms by the side position. SAR values, both whole-body averaged and localized in the ankle, were used to derive the external electric field values required to produce the SAR basic restrictions of the ICNIRP guidelines. It was found that, in certain postures, external electric field reference levels alone would not provide a conservative estimate of localized SAR exposure and it would be necessary to invoke secondary reference levels on limb currents to provide compliance with restrictions

  8. Thermodynamic modeling of CO2 absorption in aqueous N-Methyldiethanolamine using Extended UNIQUAC model

    Sadegh, Negar; Stenby, Erling Halfdan; Thomsen, Kaj

    2015-01-01

    A Thermodynamic model that can predict the behavior of the gas sweetening process over the applicable conditions is of vital importance in industry. In this work, Extended UNIQUAC model parameters optimized for the CO2-MDEA-H2O system are presented. Different types of experimental data consisting...

  9. Light transport in turbid media with non-scattering, low-scattering and high absorption heterogeneities based on hybrid simplified spherical harmonics with radiosity model

    Yang, Defu; Chen, Xueli; Peng, Zhen; Wang, Xiaorui; Ripoll, Jorge; Wang, Jing; Liang, Jimin

    2013-01-01

    Modeling light propagation in the whole body is essential and necessary for optical imaging. However, non-scattering, low-scattering and high absorption regions commonly exist in biological tissues, which lead to inaccuracy of the existing light transport models. In this paper, a novel hybrid light transport model that couples the simplified spherical harmonics approximation (SPN) with the radiosity theory (HSRM) was presented, to accurately describe light transport in turbid media with non-s...

  10. Model calculation of the characteristic mass for convective and diffusive vapor transport in graphite furnace atomic absorption spectrometry

    Bencs, László; Laczai, Nikoletta; Ajtony, Zsolt

    2015-07-01

    A combination of former convective-diffusive vapor-transport models is described to extend the calculation scheme for sensitivity (characteristic mass - m0) in graphite furnace atomic absorption spectrometry (GFAAS). This approach encompasses the influence of forced convection of the internal furnace gas (mini-flow) combined with concentration diffusion of the analyte atoms on the residence time in a spatially isothermal furnace, i.e., the standard design of the transversely heated graphite atomizer (THGA). A couple of relationships for the diffusional and convectional residence times were studied and compared, including in factors accounting for the effects of the sample/platform dimension and the dosing hole. These model approaches were subsequently applied for the particular cases of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, V and Zn analytes. For the verification of the accuracy of the calculations, the experimental m0 values were determined with the application of a standard THGA furnace, operating either under stopped, or mini-flow (50 cm3 min- 1) of the internal sheath gas during atomization. The theoretical and experimental ratios of m0(mini-flow)-to-m0(stop-flow) were closely similar for each study analyte. Likewise, the calculated m0 data gave a fairly good agreement with the corresponding experimental m0 values for stopped and mini-flow conditions, i.e., it ranged between 0.62 and 1.8 with an average of 1.05 ± 0.27. This indicates the usability of the current model calculations for checking the operation of a given GFAAS instrument and the applied methodology.

  11. Influence of flavour absorption by food-packaging materials (low-density polyethylene, polycarbonate and polyethylene terephthalate) on taste perception of a model solution and orange juice

    Willige, van R.W.G.; Linssen, J.P.H.; Legger, A.; Voragen, A.G.J.

    2003-01-01

    The influence of flavour absorption by low-density polyethylene (LDPE), polycarbonate (PC) and polyethylene terephthalate (PET) on taste perception of a model solution containing seven flavour compounds and orange juice in glass bottles was studied with and without pieces of the respective plastic f

  12. Absorption Spectra of Astaxanthin Aggregates

    Olsina, Jan; Minofar, Babak; Polivka, Tomas; Mancal, Tomas

    2012-01-01

    Carotenoids in hydrated polar solvents form aggregates characterized by dramatic changes in their absorption spectra with respect to monomers. Here we analyze absorption spectra of aggregates of the carotenoid astaxanthin in hydrated dimethylsulfoxide. Depending on water content, two types of aggregates were produced: H-aggregates with absorption maximum around 390 nm, and J-aggregates with red-shifted absorption band peaking at wavelengths >550 nm. The large shifts with respect to absorption maximum of monomeric astaxanthin (470-495 nm depending on solvent) are caused by excitonic interaction between aggregated molecules. We applied molecular dynamics simulations to elucidate structure of astaxanthin dimer in water, and the resulting structure was used as a basis for calculations of absorption spectra. Absorption spectra of astaxanthin aggregates in hydrated dimethylsulfoxide were calculated using molecular exciton model with the resonance interaction energy between astaxanthin monomers constrained by semi-e...

  13. Submodels of the generalization of the Leith model of the phenomenological theory of turbulence and of the model of nonlinear diffusion in the inhomogeneous media without absorption

    We study a nonlinear equation which is equivalent to an equation of generalization of the Leith model of turbulence and to the equation of the model of nonlinear diffusion in an inhomogeneous media without absorption. Using this equation, all submodels admitting continuous Lie transformation groups, acting on the set of solutions of the equations of these submodels are obtained. For obtained submodels, all invariant submodels are found. All essentially distinct invariant solutions describing these invariant submodels are found explicitly, or their finding is reduced to solving nonlinear integral equations. The integral equations defining these solutions reveal new possibilities for analytical and numerical studies. The presence of arbitrary constants in these equations allows one to apply them to the study of different boundary value problems. We have proved the existence and uniqueness of the solution for some boundary value problems. We have investigated the following boundary value problems: (1) a distribution of front-density turbulent kinetic energy in a framework of the generalizion of the Leith model of wave turbulence for which either the spectrum and its wavenumber derivative or the spectrum and its time derivative are given at the initial moment of time at a fixed wavenumber; (2) a nonlinear diffusion process in an inhomogeneous media without absorption, for which either the concentration and its gradient or the concentration and its rate of change are given at the initial moment of time at a fixed point. Under certain additional conditions we have established the existence and uniqueness of the solutions to boundary value problems describing these processes. (paper)

  14. Scanning imaging absorption spectrometer for atmospheric chartography carbon monoxide total columns: statistical evaluation and comparison with chemistry transport model results

    de Laat, A.T.J.; Gloudemans, A.M.S.; Aben, I.; Krol, M.C.; Meirink, J.F.; van der Werf, G.R.; Schrijver, H.

    2007-01-01

    This paper presents a detailed statistical analysis of one year (September 2003 to August 2004) of global Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) carbon monoxide (CO) total column retrievals from the Iterative Maximum Likelihood Method (IMLM) algorithm, vers

  15. Scanning Imaging Absorption Spectrometer for Atmospheric Chartography carbon monoxide total columns: Statistical evaluation and comparison with chemistry transport model results

    Laat, de A.T.J.; Gloudemans, A.M.S.; Aben, I.; Krol, M.C.; Meirink, J.F.; Werf, van der G.R.; Schrijver, H.

    2007-01-01

    This paper presents a detailed statistical analysis of one year (September 2003 to August 2004) of global Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) carbon monoxide (CO) total column retrievals from the Iterative Maximum Likelihood Method (IMLM) algorithm, vers

  16. Modeling the absorption behavior of solar thermal collector coatings utilizing graded alpha-C:H/TiC layers.

    Gruber, D P; Engel, G; Sormann, H; Schüler, A; Papousek, W

    2009-03-10

    Wavelength selective coatings are of common use in order to enhance the efficiency of devices heated by radiation such as solar thermal collectors. The use of suitable materials and the optimization of coating layer thicknesses are advisable ways to maximize the absorption. Further improvement is achievable by embedding particles in certain layers in order to modify material properties. We focus on optimizing the absorption behavior of a solar collector setup using copper as substrate, a layer of amorphous hydrogenated carbon with embedded titanium carbide particles (a-C:H/TiC), and an antireflection coating of amorphous silicon dioxide (aSiO(2)). For the setup utilizing homogeneous particle distribution, a relative absorption of 90.98% was found, while inhomogeneous particle embedding yielded 98.29%. These results are particularly interesting since until now, absorption of more than 95% was found only by using embedded Cr but not by using the more biocompatible Ti. PMID:19277084

  17. Theoretical modeling of the spectroscopic absorption properties of luciferin and oxyluciferin: A critical comparison with recent experimental studies

    Highlights: ► The calculated absorption spectra were compared with experimental data. ► Shapes and absorption maxima were reproduced for luciferin and oxyluciferin spectra. ► The effect of the solvent largely changes the electronic transition probabilities. ► Higher excitations provide an important contribution to the main absorption peak. - Abstract: Firefly luciferin and its oxidated form, oxyluciferin, are two heterocyclic compounds involved in the enzymatic reaction, catalyzed by redox proteins called luciferases, which provides the bioluminescence in a wide group of arthropods. Whereas the electronic absorption spectra of D-luciferin in water at different pHs are known since 1960s, only recently reliable experimental electronic spectra of oxyluciferin have become available. In addition oxyluciferin is involved in a triple chemical equilibria (deprotonation of the two hydroxyl groups and keto-enol tautomerism of the 4-hydroxythiazole ring), that obligates to select during an experiment a predominant species, tuning pH or solvent polarity besides introducing chemical modifications. In this study we report the absorption spectra of luciferin and oxyluciferin in each principal chemical form, calculated by means of perturbed matrix method (PMM), which allowed us to successfully introduce the effect of the solvent on the spectroscopic absorption properties, and compare the result with available experimental data.

  18. Theoretical modeling of the spectroscopic absorption properties of luciferin and oxyluciferin: A critical comparison with recent experimental studies

    Anselmi, Massimiliano, E-mail: m.anselmi@caspur.it [Department of Chemistry, University of Rome ' La Sapienza' , P.le Aldo Moro 5, 00185 Rome (Italy); Marocchi, Simone [Department of Chemistry, University of Rome ' La Sapienza' , P.le Aldo Moro 5, 00185 Rome (Italy); Aschi, Massimiliano [Department of Chemistry, Chemical Engineering and Materials, University of L' Aquila, Via Vetoio (Coppito 1), 67100 Coppito, L' Aquila (Italy); Amadei, Andrea [Department of Chemistry, University of Rome ' Tor Vergata' , Via della Ricerca Scientifica 1, 00133 Rome (Italy)

    2012-01-02

    Highlights: Black-Right-Pointing-Pointer The calculated absorption spectra were compared with experimental data. Black-Right-Pointing-Pointer Shapes and absorption maxima were reproduced for luciferin and oxyluciferin spectra. Black-Right-Pointing-Pointer The effect of the solvent largely changes the electronic transition probabilities. Black-Right-Pointing-Pointer Higher excitations provide an important contribution to the main absorption peak. - Abstract: Firefly luciferin and its oxidated form, oxyluciferin, are two heterocyclic compounds involved in the enzymatic reaction, catalyzed by redox proteins called luciferases, which provides the bioluminescence in a wide group of arthropods. Whereas the electronic absorption spectra of D-luciferin in water at different pHs are known since 1960s, only recently reliable experimental electronic spectra of oxyluciferin have become available. In addition oxyluciferin is involved in a triple chemical equilibria (deprotonation of the two hydroxyl groups and keto-enol tautomerism of the 4-hydroxythiazole ring), that obligates to select during an experiment a predominant species, tuning pH or solvent polarity besides introducing chemical modifications. In this study we report the absorption spectra of luciferin and oxyluciferin in each principal chemical form, calculated by means of perturbed matrix method (PMM), which allowed us to successfully introduce the effect of the solvent on the spectroscopic absorption properties, and compare the result with available experimental data.

  19. Frequency Comb Spectroscopy of CO(2), CH(4), H(2)O, and Isotopes Over a 2 km Outdoor Path: Concentration Retrievals Using Different Absorption Models

    Rieker, G. B.; Giorgetta, F. R.; Coddington, I.; Swann, W. C.; Zolot, A. M.; Sinclair, L. C.; Baumann, E.; Cromer, C.; Newbury, N.

    2014-06-01

    A dual frequency comb spectrometer is used to make high signal-to-noise measurements of atmospheric absorption from 5990 to 6260 cm-1 with 0.0033 cm-1 point spacing and ˜4·10-8 cm-1 resolution over a 2 km outdoor air path. The spectra, which encompass over 700 absorption features of CO2, CH4, and H2O, are fit with several absorption models to assess the quality of the models and to retrieve the various species concentrations and air temperature. The models tested include the HITRAN 2008 and 2012 spectral databases with Voigt line-shape profiles as well as a recent model for CO2 that includes the effects of line mixing and speed dependence. Residuals are typically less than 2% of the peak absorbance, except for the HITRAN 2012 CH4 model, which exhibits larger residuals. Species concentration retrievals using the models are compared with a calibrated point sensor mounted on a tower near the open air path.

  20. Chemical Absorption Materials

    Thomsen, Kaj

    2011-01-01

    Chemical absorption materials that potentially can be used for post combustion carbon dioxide capture are discussed. They fall into five groups, alkanolamines, alkali carbonates, ammonia, amino acid salts, and ionic liquids. The chemistry of the materials is discussed and advantages and drawbacks...... are mentioned. References to review papers, papers with experimental data, and papers describing the thermodynamic modelling of the systems are given....

  1. Revisiting Absorptive Capacity

    de Araújo, Ana Luiza Lara; Ulhøi, John Parm; Lettl, Christopher

    Absorptive capacity has mostly been perceived as a 'passive' outcome of R&D investments. Recently, however, a growing interest into its 'proactive' potentials has emerged. This paper taps into this development and proposes a dynamic model for conceptualizing the determinants of the complementary...... learning processes of absorptive capacity, which comprise combinative and adaptive capabilities. Drawing on survey data (n=169), the study concludes that combinative capabilities primarily enhance transformative and exploratory learning processes, while adaptive capabilities strengthen all three learning...... processes, with emphasis on exploitative learning. Before concluding, the paper addresses implications for theory and practice and limitations of this study....

  2. Model calculation of the characteristic mass for convective and diffusive vapor transport in graphite furnace atomic absorption spectrometry

    A combination of former convective–diffusive vapor-transport models is described to extend the calculation scheme for sensitivity (characteristic mass — m0) in graphite furnace atomic absorption spectrometry (GFAAS). This approach encompasses the influence of forced convection of the internal furnace gas (mini-flow) combined with concentration diffusion of the analyte atoms on the residence time in a spatially isothermal furnace, i.e., the standard design of the transversely heated graphite atomizer (THGA). A couple of relationships for the diffusional and convectional residence times were studied and compared, including in factors accounting for the effects of the sample/platform dimension and the dosing hole. These model approaches were subsequently applied for the particular cases of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, V and Zn analytes. For the verification of the accuracy of the calculations, the experimental m0 values were determined with the application of a standard THGA furnace, operating either under stopped, or mini-flow (50 cm3 min−1) of the internal sheath gas during atomization. The theoretical and experimental ratios of m0(mini-flow)-to-m0(stop-flow) were closely similar for each study analyte. Likewise, the calculated m0 data gave a fairly good agreement with the corresponding experimental m0 values for stopped and mini-flow conditions, i.e., it ranged between 0.62 and 1.8 with an average of 1.05 ± 0.27. This indicates the usability of the current model calculations for checking the operation of a given GFAAS instrument and the applied methodology. - Highlights: • A calculation scheme for convective–diffusive vapor loss in GFAAS is described. • Residence time (τ) formulas were compared for sensitivity (m0) in a THGA furnace. • Effects of the sample/platform dimension and dosing hole on τ were assessed. • Theoretical m0 of 18 analytes were calculated for stopped & mini furnace gas flows. • Experimental

  3. Model calculation of the characteristic mass for convective and diffusive vapor transport in graphite furnace atomic absorption spectrometry

    Bencs, László, E-mail: bencs.laszlo@wigner.mta.hu [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Laczai, Nikoletta [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Ajtony, Zsolt [Institute of Food Science, University of West Hungary, H-9200 Mosonmagyaróvár, Lucsony utca 15–17 (Hungary)

    2015-07-01

    A combination of former convective–diffusive vapor-transport models is described to extend the calculation scheme for sensitivity (characteristic mass — m{sub 0}) in graphite furnace atomic absorption spectrometry (GFAAS). This approach encompasses the influence of forced convection of the internal furnace gas (mini-flow) combined with concentration diffusion of the analyte atoms on the residence time in a spatially isothermal furnace, i.e., the standard design of the transversely heated graphite atomizer (THGA). A couple of relationships for the diffusional and convectional residence times were studied and compared, including in factors accounting for the effects of the sample/platform dimension and the dosing hole. These model approaches were subsequently applied for the particular cases of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, V and Zn analytes. For the verification of the accuracy of the calculations, the experimental m{sub 0} values were determined with the application of a standard THGA furnace, operating either under stopped, or mini-flow (50 cm{sup 3} min{sup −1}) of the internal sheath gas during atomization. The theoretical and experimental ratios of m{sub 0}(mini-flow)-to-m{sub 0}(stop-flow) were closely similar for each study analyte. Likewise, the calculated m{sub 0} data gave a fairly good agreement with the corresponding experimental m{sub 0} values for stopped and mini-flow conditions, i.e., it ranged between 0.62 and 1.8 with an average of 1.05 ± 0.27. This indicates the usability of the current model calculations for checking the operation of a given GFAAS instrument and the applied methodology. - Highlights: • A calculation scheme for convective–diffusive vapor loss in GFAAS is described. • Residence time (τ) formulas were compared for sensitivity (m{sub 0}) in a THGA furnace. • Effects of the sample/platform dimension and dosing hole on τ were assessed. • Theoretical m{sub 0} of 18 analytes were

  4. A Preliminary Study on Dynamics and Models of N, P, K Absorption for High-Yield Cotton

    WANG Ke-ru; LI Shao-kun; CAO Lian-pu; SONG Guang-jie; CHEN Gang; CAO Suan-zhu

    2003-01-01

    The field experiments were carried out to investigate the dynamics and models of N, P and K ab-sorption for the cotton plants with a lint of 3 000 kg ha-1 in Xinjiang. The main results were as follows: Thecontents of N, P2O5, K2O in cotton leaves, stems, squares and bolls decreased obviously with the time over thewhole growth duration and the falling extent was greater in high-yield cotton than in CK. Contents of N inleaves, squares and bolls, in particular in the leaves of fruit-bearing shoot was higher in high-yield cotton thanin CK. Contents of P2O5 in squares and bolls and that of K2O in stems were higher in high-yield cotton than inCK during the whole growing period. The accumulations of N, P2O5 and K2O in the cotton plants could be de-scribed with a logistic curve equation. There was the fastest nutrient uptake at about 90 d for N, 92 d for P2O5and 85 d for K2O after emergence, respectively. Total nutrient accumulation of N, P2 O5 and K2O was 385.8,244.7 and 340.3 kg ha-1 , respectively. Approximately 12.5 kg N, 8.0 kg P2O5 and 11.1 kg K2O were neededfor producing 100 kg lint with the leaves and stems under the super high yield condition of 3 000 kg ha-1 inXinjiang.

  5. MAGNETOHYDRODYNAMIC MODELING OF THE ACCRETION SHOCKS IN CLASSICAL T TAURI STARS: THE ROLE OF LOCAL ABSORPTION IN THE X-RAY EMISSION

    We investigate the properties of X-ray emission from accretion shocks in classical T Tauri stars (CTTSs), generated where the infalling material impacts the stellar surface. Both observations and models of the accretion process reveal several aspects that are still unclear: the observed X-ray luminosity in accretion shocks is below the predicted value, and the density versus temperature structure of the shocked plasma, with increasing densities at higher temperature, deduced from the observations, is at odds with that proposed in the current picture of accretion shocks. To address these open issues, we investigate whether a correct treatment of the local absorption by the surrounding medium is crucial to explain the observations. To this end, we describe the impact of an accretion stream on a CTTS by considering a magnetohydrodynamic model. From the model results, we synthesize the X-ray emission from the accretion shock by producing maps and spectra. We perform density and temperature diagnostics on the synthetic spectra, and we directly compare the results with observations. Our model shows that the X-ray fluxes inferred from the emerging spectra are lower than expected because of the complex local absorption by the optically thick material of the chromosphere and of the unperturbed stream. Moreover, our model, including the effects of local absorption, explains in a natural way the apparently puzzling pattern of density versus temperature observed in the X-ray emission from accretion shocks

  6. A Quantitative Review and Meta-models of the Variability and Factors Affecting Oral Drug Absorption-Part II: Gastrointestinal Transit Time.

    Abuhelwa, Ahmad Y; Foster, David J R; Upton, Richard N

    2016-09-01

    This study aimed to conduct a quantitative meta-analysis for the values of, and variability in, gastrointestinal (GI) transit times of non-disintegrating single-unit ("tablet") and multiple-unit ("pellets/multi-unit tablet") solid dosage forms, characterize the effect of food on the values and variability in these parameters and present quantitative meta-models of the distributions of GI transit times in the respective GI regions to help inform models of oral drug absorption. The literature was systemically reviewed for the values of, and the variability in, gastric, small intestinal and colonic transit times under fed and fasted conditions. Meta-analysis used the "metafor" package of the R language. Meta-models of GI transit were assumed to be log-normally distributed between the studied populations. Twenty-nine studies including 125 reported means and standard deviations were used in the meta-analysis. Caloric content of administered food increased variability and delayed the gastric transit of both pellets and tablets. Conversely, food caloric content reduced the variability but had no significant influence on the mean small intestinal transit time (SITT). Food had no significant effect on the transit time through the colon. The transit of pellets through the colon was significantly slower than that of single-unit tablets which is most likely related to their smaller size. GI transit times may influence the dissolution and absorption of oral drugs. The meta-models of GI transit times may be used as part of semi-physiological absorption models to characterize the influence of transit time on the dissolution, absorption and in vivo pharmacokinetic profiles of oral drugs. PMID:27439620

  7. Characterization of intestinal absorption of C-glycoside flavonoid vicenin-2 from Lychnophora ericoides leafs in rats by nonlinear mixed effects modeling

    Gabriela A. Buqui

    2015-06-01

    Full Text Available AbstractVicenin-2 (apigenin-6,8-di-C-β-d-glucopyranoside is present in hydroalcoholic extracts of the Brazilian species Lychnophora ericoides Mart., Asteraceae, leaves, and the biological effects of this compound have been demonstrated including anti-inflammatory, antioxidant and anti-tumor effects in rat models. Given the potential of this compound as a pharmacological agent, the aims of this investigation were to evaluate the extent of intestinal absorption of vicenin-2, and to determine the intestinal permeation profile using an in situ single-pass intestinal perfusion technique. A validated HPLC–UV method was applied to measure the amount of unabsorbed vicenin-2 in the gut after an oral administration of 180 mg kg-1 in five rats. A nonlinear mixed effects model was used to determine the absorption pharmacokinetic parameters assuming a first order absorption and active secretion processes for this compound, wherein the active secretion was characterized by a zero-order process. The population pharmacokinetic parameters obtained were 0.274 min-1 for the first-order absorption rate constant, 16.3% min-1 for the zero-order rate constant; the final percentage of the original dose that was absorbed in vivo was 40.2 ± 2.5%. These parameters indicated that vicenin-2 was rapidly absorbed in the small intestine. In contrast to literature information indicating no absorption of vicenin-2 in Caco-2 cells, our results suggested that vicenin-2 can be absorbed in the small intestine of rats. The finding supports further investigation of vicenin-2 as a viable oral phytopharmaceutical agent for digestive diseases.

  8. A novel strategy for site-directed chemical reactions in single stranded DNA--absorption and NMR spectroscopic studies of model compounds.

    Asseline, U; Rozelle, T; Lancelot, G; Thuong, N T

    1992-01-01

    A new and simple model enabling a chemical species to be brought to a preselected site in single strand DNA is reported. Two oligonucleotides containing a propanediol linkage were hybridized to their complementary sequences with an extra-base opposite the propanediol derivative. Absorption studies results shown that the addition of a bisacridine derivative strongly increased the stabilities of both duplexes when added in a 1:1 ratio. NMR studies on one of these duplexes brought evidence of th...

  9. A general enhancement factor model for absorption and desorption systems: A CO2 capture case-study

    Gaspar, Jozsef; Fosbøl, Philip Loldrup

    2015-01-01

    This study derives a general method (GM) for reactive absorption and desorption calculation. It connects the Onda's approximation for reversible reactions with the van Krevelen's approach for instantaneous irreversible reactions. It is set-up for a reversible (m+n)-th order, forward reaction...

  10. The role of scattering and absorption on the optical properties of birefringent polycrystalline ceramics: Modeling and experiments on ruby (Cr:Al2O3)

    Penilla, E. H.; Hardin, C. L.; Kodera, Y.; Basun, S. A.; Evans, D. R.; Garay, J. E.

    2016-01-01

    Light scattering due to birefringence has prevented the use of polycrystalline ceramics with anisotropic optical properties in applications such as laser gain media. However, continued development of processing technology has allowed for very low porosity and fine grains, significantly improving transparency and is paving the way for polycrystalline ceramics to be used in demanding optical applications. We present a method for producing highly transparent Cr3+ doped Al2O3 (ruby) using current activated pressure assisted densification. The one-step doping/densification process produces fine grained ceramics with well integrated (doped) Cr, resulting in good absorption and emission. In order to explain the light transmission properties, we extend the analytical model based on the Rayleigh-Gans-Debye approximation that has been previously used for undoped alumina to include absorption. The model presented captures reflection, scattering, and absorption phenomena in the ceramics. Comparison with measured transmission confirms that the model adequately describes the properties of polycrystalline ruby. In addition the measured emission spectra and emission lifetime are found to be similar to single crystals, confirming the high optical quality of the ceramics.

  11. Multifunctional hybrids for electromagnetic absorption

    Highlights: → EM absorption requires low dielectric constant and ∼1 S/m electrical conductivity. → New hybrids were processed with CNT-filled polymer foam inserted in Al honeycomb. → The EM absorption in the GHz range is superior to any known material. → A closed form model is used to guide the design of the hybrid. → The architectured material is light with potential for thermal management. - Abstract: Electromagnetic (EM) interferences are ubiquitous in modern technologies and impact on the reliability of electronic devices and on living cells. Shielding by EM absorption, which is preferable over reflection in certain instances, requires combining a low dielectric constant with high electrical conductivity, which are antagonist properties in the world of materials. A novel class of hybrid materials for EM absorption in the gigahertz range has been developed based on a hierarchical architecture involving a metallic honeycomb filled with a carbon nanotube-reinforced polymer foam. The waveguide characteristics of the honeycomb combined with the performance of the foam lead to unexpectedly large EM power absorption over a wide frequency range, superior to any known material. The peak absorption frequency can be tuned by varying the shape of the honeycomb unit cell. A closed form model of the EM reflection and absorption provides a tool for the optimization of the hybrid. This designed material sets the stage for a new class of sandwich panels combining high EM absorption with mass efficiency, stiffness and thermal management.

  12. Quantum absorption refrigerator.

    Levy, Amikam; Kosloff, Ronnie

    2012-02-17

    A quantum absorption refrigerator driven by noise is studied with the purpose of determining the limitations of cooling to absolute zero. The model consists of a working medium coupled simultaneously to hot, cold, and noise baths. Explicit expressions for the cooling power are obtained for Gaussian and Poisson white noise. The quantum model is consistent with the first and second laws of thermodynamics. The third law is quantified; the cooling power J(c) vanishes as J(c) ∝ T(c)(α), when T(c)→0, where α=d+1 for dissipation by emission and absorption of quanta described by a linear coupling to a thermal bosonic field, where d is the dimension of the bath. PMID:22401189

  13. Mechanism of increased iron absorption in murine model of hereditary hemochromatosis: Increased duodenal expression of the iron transporter DMT1

    Fleming, Robert E.; Migas, Mary C.; Zhou, Xiaoyan; Jiang, Jinxing; Britton, Robert S.; Brunt, Elizabeth M.; Tomatsu, Shunji; Waheed, Abdul; Bacon, Bruce R; Sly, William S.

    1999-01-01

    Hereditary hemochromatosis (HH) is a common autosomal recessive disorder characterized by tissue iron deposition secondary to excessive dietary iron absorption. We recently reported that HFE, the protein defective in HH, was physically associated with the transferrin receptor (TfR) in duodenal crypt cells and proposed that mutations in HFE attenuate the uptake of transferrin-bound iron from plasma by duodenal crypt cells, leading to up-regulation of transporters for dietary iron. Here, we tes...

  14. Retrieval of trace gases vertical profile in the lower atmosphere combining. Differential Optical Absorption Spectroscopy with radiative transfer models

    Palazzi, Elisa

    2008-01-01

    The motivation for the work presented in this thesis is to retrieve profile information for the atmospheric trace constituents nitrogen dioxide (NO2) and ozone (O3) in the lower troposphere from remote sensing measurements. The remote sensing technique used, referred to as Multiple AXis Differential Optical Absorption Spectroscopy (MAX-DOAS), is a recent technique that represents a significant advance on the well-established DOAS, especially for what it concerns the study of...

  15. Modeling of gamma ray energy-absorption buildup factors for thermoluminescent dosimetric materials using multilayer perceptron neural network

    Kucuk, Nil; Manohara, S.R.; Hanagodimath, S.M.; Gerward, L.

    2013-01-01

    In this work, multilayered perceptron neural networks (MLPNNs) were presented for the computation of the gamma-ray energy absorption buildup factors (BA) of seven thermoluminescent dosimetric (TLD) materials [LiF, BeO, Na2B4O7, CaSO4, Li2B4O7, KMgF3, Ca3(PO4)2] in the energy region 0.015–15MeV, and...

  16. Five-Photon Absorption and Selective Enhancement of Multiphoton Absorption Processes

    Friese, Daniel Henrik; Bast, Radovan; Ruud, Kenneth

    2015-01-01

    We study one-, two-, three-, four-, and five-photon absorption of three centrosymmetric molecules using density functional theory. These calculations are the first ab initio calculations of five-photon absorption. Even- and odd-order absorption processes show different trends in the absorption cross sections. The behavior of all even- and odd-photon absorption properties shows a semiquantitative similarity, which can be explained using few-state models. This analysis shows that odd-photon abs...

  17. Absorption of ethanol, acetone, benzene and 1,2-dichloroethane through human skin in vitro: a test of diffusion model predictions

    The overall goal of this research was to further develop and improve an existing skin diffusion model by experimentally confirming the predicted absorption rates of topically-applied volatile organic compounds (VOCs) based on their physicochemical properties, the skin surface temperature, and the wind velocity. In vitro human skin permeation of two hydrophilic solvents (acetone and ethanol) and two lipophilic solvents (benzene and 1,2-dichloroethane) was studied in Franz cells placed in a fume hood. Four doses of each 14C-radiolabed compound were tested — 5, 10, 20, and 40 μL cm−2, corresponding to specific doses ranging in mass from 5.0 to 63 mg cm−2. The maximum percentage of radiolabel absorbed into the receptor solutions for all test conditions was 0.3%. Although the absolute absorption of each solvent increased with dose, percentage absorption decreased. This decrease was consistent with the concept of a stratum corneum deposition region, which traps small amounts of solvent in the upper skin layers, decreasing the evaporation rate. The diffusion model satisfactorily described the cumulative absorption of ethanol; however, values for the other VOCs were underpredicted in a manner related to their ability to disrupt or solubilize skin lipids. In order to more closely describe the permeation data, significant increases in the stratum corneum/water partition coefficients, Ksc, and modest changes to the diffusion coefficients, Dsc, were required. The analysis provided strong evidence for both skin swelling and barrier disruption by VOCs, even by the minute amounts absorbed under these in vitro test conditions. - Highlights: • Human skin absorption of small doses of VOCs was measured in vitro in a fume hood. • The VOCs tested were ethanol, acetone, benzene and 1,2-dichloroethane. • Fraction of dose absorbed for all compounds at all doses tested was less than 0.3%. • The more aggressive VOCs absorbed at higher levels than diffusion model predictions

  18. Mechanistic spray dryer mathematical model based on film theory to predict sulfur dioxide absorption and reaction by a calcium hydroxide slurry in the constant rate period

    Partridge, G.P. Jr.

    1987-01-01

    In the spray dryer, flue gas from a coal-fired boiler is contacted with an atomized lime slurry; during this contact SO/sub 2/ absorbs and reacts with dissolved Ca(OH)/sub 2/. The mathematical model developed in this activity superimposes SO/sub 2/ absorption and reaction phenomena on existing mathematical descriptions of spray dryer operation. The SO/sub 2/ removal appears to occur primarily in the constant rate period where a continuous liquid phase exists in the atomized slurry droplet. The constant rate period proceeds until evaporation has reduced the liquid phase volume to the point where the Ca(OH)/sub 2/ sorbent particles touch and the diffusion paths for reactants are restricted. The SO/sub 2/ absorption flux involves liquid phase as well as gas phase resistances. The liquid phase resistance includes mass transfer and chemical reaction phenomena associated with the absorption and reaction of SO/sub 2/ and Ca(OH)/sub 2/ and the dissolution of Ca(OH)/sub 2/. Instantaneous reaction occurs between SO/sub 2/ and Ca(OH)/sub 2/ in the liquid phase. Solid dissolution in the liquid film is unimportant and solid dissolution and reaction occur in series. A comprehensive model was developed for the constant rate period. The model is based on film theory and treats the atomized slurry droplet as a sphere of discrete sorbent particles with the fluid phase uniformly distributed around the individual sorbent particles. This concept allows prediction of the mass transfer coefficients and the enhancement due to increasing solids concentration as evaporation proceeds. Efficiency predicts using the model were compared with pilot plant data taken at different inlet flue gas temperatures, stoichiometric ratios and slurry flow rates.

  19. Calculation of two-photon absorption strengths with the approximate coupled cluster singles and doubles model CC2 using the resolution-of-identity approximation.

    Friese, Daniel H; Hättig, Christof; Ruud, Kenneth

    2012-01-21

    An implementation of two-photon absorption matrix elements using the approximate second-order coupled-cluster singles and doubles model CC2 is presented. In this implementation we use the resolution-of-the-identity approximation for the two-electron repulsion integrals to reduce the computational cost. To avoid storage of large arrays we introduce in addition a numerical Laplace transformation of orbital energy denominators for the response of the doubles amplitudes. The error due to the numerical Laplace transformation is found to be negligible. Using this new implementation, we performed a series of benchmark calculations on substituted benzene and azobenzene derivatives to get reference values for TD-DFT results. We show that results obtained with the Coulomb-attenuated B3LYP functional are in reasonable agreement with the coupled-cluster results, whereas other density functionals which do not have a long-range correction give considerably less accurate results. Applications to the AF240 dye molecule and a weakly bound molecular tweezer complex demonstrate that this new RI-CC2 implementation allows for the first time to compute two-photon absorption cross sections with a correlated wave function method for molecules with more than 70 atoms and to apply this method for benchmarking TD-DFT calculations on molecules which are of particular relevance for experimental studies of two-photon absorption. PMID:22130199

  20. Evaluation of the bioavailability of major withanolides of Withania somnifera using an in vitro absorption model system

    Santosh T Devkar

    2015-01-01

    Full Text Available Withania somnifera (L. Dunal, shows several pharmacological properties which are attributed mainly to the withanolides present in the root. The efficacy of medicinally active withanolides constituents depends on the absorption and transportation through the intestinal epithelium. We examined these characteristics by employing the Sino-Veda Madin-Darby canine kidney cells culture system, which under in vitro condition shows the absorption characteristics similar to the human intestinal epithelium. Thus, the aim of the present investigation was to assess the bioavailability of individual withanolides. Withanolides were diluted in Hank′s buffered saline at a concentration of 2 μg/ml were tested for permeability studies carried out for 1 h duration. Permeability was measured in terms of efflux pump (Peff in cm/s. Peff values of withanolide A (WN A, withanone (WNN, 1,2-deoxywithastramonolide (1,2 DWM, withanolide B (WN B, withanoside IV-V (WS IV-V, and withaferin A were 4.05 × 10−5 , 2.06 × 10−5 , 1.97 × 10−5 , 1.80 × 10−5 , 3.19 × 10−6 , 3.03 × 10−6 and 3.30 × 10−7 respectively. In conclusion, the nonpolar and low molecular weight compounds (WN A, WNN, 1,2 DWM, and WN B were highly permeable. As against this, the glycosylated and polar WS IV and WS V showed low permeability. Surprisingly and paradoxically, the highly biologically active withaferin A was completely impermeable, suggesting that further studies possibly using human epithelial colorectal adenocarcinoma (Caco-2 cells may be needed to delineate the absorption characteristics of withanolides, especially withaferin A.

  1. In vitro--in silico--in vivo drug absorption model development based on mechanistic gastrointestinal simulation and artificial neural networks: nifedipine osmotic release tablets case study.

    Ilić, Marija; Ðuriš, Jelena; Kovačević, Ivan; Ibrić, Svetlana; Parojčić, Jelena

    2014-10-01

    In vitro--in vivo correlations (IVIVC) are generally accepted as a valuable tool in modified release formulation development aimed at (i) quantifying the in vivo drug delivery profile and formulation related effects on absorption; (ii) establishing clinically relevant dissolution specifications and (iii) supporting the biowaiver claims. The aim of the present study was to develop relevant IVIVC models based on mechanistic gastrointestinal simulation (GIS) and artificial neural network (ANN) analysis and to evaluate their applicability and usefulness in biopharmaceutical drug characterisation. Nifedipine osmotic release tablets were selected as model drug product on the basis of their robustness, dissolution limited drug absorption and the availability of relevant literature data. Although the osmotic release tablets have been designed to be robust against the influence of physiological conditions in the gastrointestinal tract, notable differences in nifedipine dissolution kinetics were observed depending on the in vitro experimental conditions employed. The results obtained indicate that both GIS and ANN model developed were sensitive to input kinetics represented by the in vitro profiles obtained under various experimental conditions. Different in silico approaches may be successfully employed in the in vitro--in silico--in vivo model development. However, the results obtained may differ and relevant outcomes are sensitive to the methodology employed. PMID:24911992

  2. Simultaneous Pharmacokinetic Modeling of Alkylresorcinols and Their Main Metabolites Indicates Dual Absorption Mechanisms and Enterohepatic Elimination in Humans

    Marklund, Matti; Strömberg, Eric A,; Lærke, Helle Nygaard;

    2014-01-01

    Alkylresorcinols have proven to be useful biomarkers of whole-grain wheat and rye intake in many nutritional studies. To improve their utility, more knowledge regarding the fate of alkylresorcinols and their metabolites after consumption is needed.Objective: The objective of this study was to...... single dose (120 g) of rye bran and validated against fasting plasma concentrations from 8 women and 7 men with controlled rye bran intake (23, 45, or 90 g/d). Alkylresorcinols in the lymph and plasma of a pig fed a single alkylresorcinol dose (1.3 mmol) were quantified to assess absorption. Human...

  3. Assessment of the effect of type of dairy product and of chocolate matrix on the oral absorption of monomeric chocolate flavanols in a small animal model.

    Gossai, D; Lau-Cam, C A

    2009-03-01

    This study has examined the effects of type of dairy product (whole milk, skim milk, heavy cream) and chocolate matrix (baking, dark, dairy milk, white) on the oral absorption of the chocolate flavanols (+)-catechin and (-)-epicatechin in a small animal model. In the study, each flavanol compound, as a solution in water or a dairy product or as a chocolate dispersion in water, was administered intragastrically to male Sprague-Dawley rats in an amount equal to or equivalent to 350 mg/kg. In each instance, blood samples were collected over a 5 h period, and used to measure plasma total catechin concentrations by HPLC after enzymatic hydrolysis of flavanol conjugates. Pharmacokinetic data were evaluated using a one compartment approach. Whole milk and heavy cream, and to a much lesser extent skim milk, lowered the oral absorption of both (+)-catechin and (-)-epicatechin and altered the AUC, C(max), k(a), k(e) and t1/2 values in direct proportion to their fat, but not to their protein, content. In addition, the t(max) for solutions of (-)-epicatechin in water and skim milk occurred 2 h earlier than from solutions in whole milk and heavy cream. Similarly, dispersions of baking chocolate in water and in whole milk yielded plasma levels of monomeric catechins that were, respectively, about equal to and much lower than those from aqueous solutions of authentic flavanols. A determining role for a chocolate matrix (dark, dairy milk or white chocolate) on the oral absorption of its constitutive monomeric flavanols was suggested by the apparent variability in plasma total catechins levels that existed among them both before and after their spiking with equal amounts of exogenous (+)-catechin and (-)-epicatechin. Such a variability could reflect differences among different chocolates in terms of their physical properties, matrix components, and matrix characteristics imposed by the manufacturing process used for each type of chocolate. In all the experiments, (+)-catechin

  4. The Quantum Absorption Refrigerator

    Levy, Amikam

    2011-01-01

    A quantum absorption refrigerator driven by noise is studied with the purpose of determining the limitations of cooling to absolute zero. The model consists of a working medium coupled simultaneously to hot, cold and noise baths. Explicit expressions for the cooling power are obtained for Gaussian and Poisson white noise. The quantum model is consistent with the first and second laws of thermodynamics. The third law is quantified, the cooling power Jc vanishes as Jc proportional to Tc^{alpha}, when Tc approaches the absolute zero, where alpha = 2 for a bath with flat spectral density and alpha = 3 for an Ohmic spectral density.

  5. Technical note: An improved surgical model for the long-term studies of kinetics and quantification of nutrient absorption in swine.

    Hooda, S; Matte, J J; Wilkinson, C W; Zijlstra, R T

    2009-06-01

    An improved technique to study kinetics and quantitative absorption of nutrients in pigs is described. Three female pigs (35 kg of BW) were surgically modified with catheters in the hepatic portal vein and carotid artery and an ultrasonic flow probe around the portal vein. Catheter placement and patency was secured using distal modifications (rings and holes) and nonabsorbable suture. Catheters and flow probe cable were tunneled subcutaneously after exteriorization for further protection. Fibrosis and adhesions in the body cavity were minimized by avoiding excessive manipulation and drying of viscera. Pigs were supported during recovery by intravenous fluid therapy of AA and electrolytes until regular feeding resumed. Catheters were flushed daily with heparinized saline (200 IU/L). After 10 d, pigs were fed a diet based on wheat and soybean meal for 6 consecutive 7-d periods. On d 7, blood was collected postprandially every 15 min from -15 to 60 min, 30 to 240 min, 60 to 480 min, and 120 to 720 min. Blood flow was measured simultaneously. Plasma was analyzed for glucose, and net glucose absorption was calculated from plasma portal-arterial differences x plasma flow [blood flow x (1 - hematocrit)]. The specific improvements for long-term use of this model are distal modifications of the catheters, postoperative treatment using parental nutrition and gut motility drug, prevention of infection of body cavity by further tunneling of catheters and blood flow probe cable, and use of ultrasonic blood flow probes and meter. Blood flow measurements using an ultrasonic blood flow probe was not changed after 52 d compared with 10 d post-surgery, indicating the reliability of this model. This catheterized pig model, thus, will allow the long-term study of the kinetics of nutrient absorption. PMID:19251919

  6. Modelling of the generation phase of an absorption cooling cycle operating intermittently; Modelisation de la phase generation d'un cycle de refrigeration par absorption solaire a fonctionnement intermittent

    Boukhchana, Yasmina; Fellah, Ali; Ben Brahim, Ammar [Unite de Recherche, Thermodynamique Appliquee (99/UR/11-21), Universite de Gabes, Ecole Nationale d' ingenieurs, 6072 Gabes (Tunisia)

    2011-01-15

    No abstract prepared. [French] La modelisation en regime dynamique de la phase generation d'une installation frigorifique a absorption solaire a fonctionnement intermittent utilisant le couple ammoniac/eau a ete elaboree. L'etude basee sur l'intermittence du fonctionnement a permis d'elaborer, a travers les bilans matieres et thermiques, un modele thermodynamique reliant les temperatures, les debits et les fractions massiques dans les differents compartiments. Des journees ensoleillees representatives des quatre saisons de l'annee ont ete considerees. Les variations du taux d'ensoleillement, des temperatures et des concentrations ont ete explorees. Les resultats ont montre, moyennant les hypotheses adoptees en particulier a pression de fonctionnement constante, que la demarche proposee a permis d'avoir une temperature de generation autour de 135 C et une temperature de condensation de 60 C. Ces temperatures sont atteinte par l'adaptation de la convection naturelle a l'air pour le fonctionnement du condenseur. (orig.)

  7. Photoionization modeling of oxygen K absorption in the interstellar medium:the Chandra grating spectra of XTE J1817-330

    Gatuzz, E; Mendoza, C; Kallman, T R; Witthoeft, M; Lohfink, A; Bautista, M A; Palmeri, P; Quinet, P

    2013-01-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra towards the X-ray low-mass binary XTE J1817-330. The 11-25 A broadband is described with a simple absorption model that takes into account the pileup effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 A) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the xstar code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain: a column density of N(H)=1.38+/-0.01\\times 10^21 cm^-2; ionization parameter of log(xi)=-2.70+/-0.023; oxygen abundance of A(O)= 0.689^{+0.015}_{-0.010}; and ionization fractions of OI/O = 0.911, OII/O = 0.077, and OIII/O = 0.012 that are in good agreement with previous ...

  8. Modeling of gamma ray energy-absorption buildup factors for thermoluminescent dosimetric materials using multilayer perceptron neural network: A comparative study

    In this work, multilayered perceptron neural networks (MLPNNs) were presented for the computation of the gamma-ray energy absorption buildup factors (BA) of seven thermoluminescent dosimetric (TLD) materials [LiF, BeO, Na2B4O7, CaSO4, Li2B4O7, KMgF3, Ca3(PO4)2] in the energy region 0.015–15 MeV, and for penetration depths up to 10 mfp (mean-free-path). The MLPNNs have been trained by a Levenberg–Marquardt learning algorithm. The developed model is in 99% agreement with the ANSI/ANS-6.4.3 standard data set. Furthermore, the model is fast and does not require tremendous computational efforts. The estimated BA data for TLD materials have been given with penetration depth and incident photon energy as comparative to the results of the interpolation method using the Geometrical Progression (G-P) fitting formula. - Highlights: ► Gamma-ray energy absorption buildup factors estimation in TLD materials. ► The ANN approach can be alternative to G-P fitting method for BA calculations. ► The applied model is not time-consuming and easily predicted

  9. Magnetohydrodynamic modeling of the accretion shocks in classical T Tauri stars: the role of local absorption on the X-ray emission

    Bonito, R; Argiroffi, C; Miceli, M; Peres, G; Matsakos, T; Stehle, C; Ibgui, L

    2014-01-01

    We investigate the properties of X-ray emission from accretion shocks in classical T Tauri stars (CTTSs), generated where the infalling material impacts the stellar surface. Both observations and models of the accretion process reveal several aspects that are still unclear: the observed X-ray luminosity in accretion shocks is below the predicted value, and the density versus temperature structure of the shocked plasma, with increasing densities at higher temperature, deduced from the observations, is at odds with that proposed in the current picture of accretion shocks. To address these open issues we investigate whether a correct treatment of the local absorption by the surrounding medium is crucial to explain the observations. To this end, we describe the impact of an accretion stream on a CTTS by considering a magnetohydrodynamic model. From the model results we synthesize the X-ray emission from the accretion shock by producing maps and spectra. We perform density and temperature diagnostics on the synthe...

  10. Energy Absorption in a Load-Unload Cycle of Knee Implant Using Fractal Model of Rough Surfaces

    Hodaei, Mohammad; Farhang, Kambiz

    2016-05-01

    Roughness measurement of knee implant surfaces is investigated. The study of roughness measurement show that the topography of knee implant surface is multi-scale and surface spectra follows a power law behavior. A magnification of rough surface topography implies that there is no difference between original and magnified profile of implant surface. For implant surface, statistical parameters such as variance of height, curvature, and slope are found to be scale-dependent. Fractal representation of implant surface shows that the size-distribution of the multi-scale contacts spots follows a power law and is characterized by the fractal dimension of implant surface. Fractal surface description of the rough surfaces of knee implant is used to obtain force-displacement relationship of the contact force. Using an approximate function through the fusion of two piecewise functions, energy absorption of a knee implant in a single cycle of load-unload is obtained.

  11. A Quantitative Review and Meta-Models of the Variability and Factors Affecting Oral Drug Absorption-Part I: Gastrointestinal pH.

    Abuhelwa, Ahmad Y; Foster, David J R; Upton, Richard N

    2016-09-01

    This study aimed to conduct a quantitative meta-analysis for the values of, and variability in, gastrointestinal (GI) pH in the different GI segments; characterize the effect of food on the values and variability in these parameters; and present quantitative meta-models of distributions of GI pH to help inform models of oral drug absorption. The literature was systemically reviewed for the values of, and the variability in, GI pH under fed and fasted conditions. The GI tract was categorized into the following 10 distinct regions: stomach (proximal, mid-distal), duodenum (proximal, mid-distal), jejunum and ileum (proximal, mid, and distal small intestine), and colon (ascending, transverse, and descending colon). Meta-analysis used the "metafor" package of the R language. The time course of postprandial stomach pH was modeled using NONMEM. Food significantly influenced the estimated meta-mean stomach and duodenal pH but had no significant influence on small intestinal and colonic pH. The time course of postprandial pH was described using an exponential model. Increased meal caloric content increased the extent and duration of postprandial gastric pH buffering. The different parts of the small intestine had significantly different pH. Colonic pH was significantly different for descending but not for ascending and transverse colon. Knowledge of GI pH is important for the formulation design of the pH-dependent dosage forms and in understanding the dissolution and absorption of orally administered drugs. The meta-models of GI pH may also be used as part of semi-physiological pharmacokinetic models to characterize the effect of GI pH on the in vivo drug release and pharmacokinetics. PMID:27495120

  12. Structure of collagen adsorbed on a model implant surface resolved by polarization modulation infrared reflection-absorption spectroscopy.

    Brand, Izabella; Habecker, Florian; Ahlers, Michael; Klüner, Thorsten

    2015-03-01

    The polarization modulation infrared reflection-absorption spectra of collagen adsorbed on a titania surface and quantum chemical calculations are used to describe components of the amide I mode to the protein structure at a sub-molecular level. In this study, imino acid rich and poor fragments, representing the entire collagen molecule, are taken into account. The amide I mode of the collagen triple helix is composed of three absorption bands which involve: (i) (∼1690cm(-1)) the CO stretching modes at unhydrated groups, (ii) (1655-1673cm(-1)) the CO stretching at carbonyl groups at imino acids and glycine forming intramolecular hydrogen bonds with H atoms at both NH2 and, unusual for proteins, CH2 groups at glycine at a neighbouring chain and (iii) (∼1640cm(-1)) the CO stretching at carbonyl groups forming hydrogen bonds between two, often charged, amino acids as well as hydrogen bonds to water along the entire helix. The IR spectrum of films prepared from diluted solutions (c<50μgml(-1)) corresponds to solution spectra indicating that native collagen molecules interact with water adsorbed on the titania surface. In films prepared from solutions (c⩾50μgml(-1)) collagen multilayers are formed. The amide I mode is blue-shifted by 18cm(-1), indicating that intramolecular hydrogen bonds at imino acid rich fragments are weakened. Simultaneous red-shift of the amide A mode implies that the strength of hydrogen bonds at the imino acid poor fragments increases. Theoretically predicted distortion of the collagen structure upon adsorption on the titania surface is experimentally confirmed. PMID:25498816

  13. Optical diagnostics of a surface-wave-sustained neon plasma by collisional–radiative modelling and a self-absorption method

    A surface-wave-sustained microwave discharge in a coaxial tube configuration in neon at low pressure (300–700 Pa) was studied by optical emission spectroscopy. Spectra of the discharge were analysed by a self-absorption method and a collisional–radiative model. The self-absorption method was used to determine the densities of neon metastable states. The collisional–radiative model, using these densities, was applied to determine the axially resolved electron temperature and the reduced electric field strength in the discharge from the optical spectra. Two types of electron distribution functions were used in the calculations—a Maxwellian distribution function and a solution of electron Boltzmann kinetic equation. The spatially averaged neon metastable densities were in the range (0.12–0.53) × 1016 m−3 and (3.4–4.1) × 1016 m−3 for 1s3 and 1s5 states, respectively. The axial profile of the electron temperature was found to be approximately constant around 1.3–1.6 eV depending on the pressure. The reduced electric field strength decreased along the plasma column in the range 16.5–6.0 Td depending on the pressure. A large influence of gas cooling along the plasma column on the determined reduced electric field strengths was observed. (paper)

  14. Ray-tracing and Fokker-Planck modelling of the effect of plasma current on the propagation and absorption of lower hybrid waves

    Waves at a frequency close to the lower hybrid (LH) resonance are widely used in tokamaks for non-inductive current drive. Modelling of LH waves is usually carried out by combining a Ray-tracing (RT) code for computing the LH waves propagation to a solver of the Fokker-Planck (FP) equation which calculates an electron distribution function self-consistently with the waves absorption. The DELPHINE code has been developed along this approach with accurate treatment of the magnetic equilibrium and the fast electrons dynamics in momentum space. Using this code, the influence of the plasma current on the LH waves propagation and absorption is investigated in detail. High plasma current is found to broaden the absorbed LH spectrum towards high phase velocities, thus increasing the current drive efficiency of the waves. The shape of the current density profile also has an impact on the propagation of the waves and the resulting power deposition. In discharges where the current profile is dominated by LH current drive (LHCD), this dependence leads to the auto-regulation of the LHCD via the current density profile. The RT/FP technique reproduces at least qualitatively some of the experimental trends, though inconsistencies still remain. Perspectives for improving the relevance of the modelling are discussed

  15. NLP model of a LiBr–H2O absorption refrigeration system for the minimization of the annual operating cost

    In this paper the optimization of a LiBr–H2O absorption refrigeration system with the annual operating cost as the objective function to be minimized is presented. The optimization problem is established as a Non-Linear Programming (NLP) model allowing a formulation of the problem in a simple and structured way, and reducing the typical complexity of the thermal systems. The model is composed of three main parts: the thermodynamic model based on the exergy concept including also the proper formulation for the thermodynamic properties of the LiBr–H2O mixture, the second is the economic model and the third part composed by inequality constraints. The solution of the model is obtained using the CONOPT solver suitable for NLP problems (code is available on request). The results show the values of the decision variables that minimize the annual cost under the set of assumptions considered in the model and agree well with those reported in other works using different optimization approaches. - Highlights: ► The optimization of an ARS is presented using the annual operating cost as the objective function. ► The problem is established as an NLP model allowing a formulation in a simple and structured way. ► Several formulations for the thermodynamic properties were tested to implement the simpler ones. ► The results obtained agree well with those reported in the work being in comparison.

  16. Absorption of selected radionuclides

    In October 1978, the Institut fuer Energie- und Umweltforschung Heidelberg e.V. published a contribution to part 26 of the model study of radio-ecology at Biblis under the title 'Estimation of the absorption of radionuclides from the gastrointestinal tract in the blood'. Using the example of this contribution, a critical analysis is made to show how a selection of the information contained in various scientific publications and other items of literature can give uncritical readers the impression that all statements made are scientifically well founded. (orig./HP)

  17. Line-Parameter Measurements and Stringent Tests of Line-Shape Models Based on Cavity-Enhanced Absorption Spectroscopy

    Bielska, Katarzyna; Fleisher, Adam J.; Hodges, Joseph T.; Lin, Hong; Long, David A.; Reed, Zachary D.; Sironneau, Vincent; Truong, Gar-Wing; Wójtewicz, Szymon

    2014-06-01

    Laser methods that are based on cavity-enhanced absorption spectroscopy (CEAS) are well-suited for measuring molecular line parameters under conditions of low optical density, and as such they are complementary to broadband Fourier-transform spectroscopy (FTS) techniques. Attributes of CEAS include relatively low detection limits, accurate and precise detuning axes and high fidelity measurements of line shape. In many cases these performance criteria are superior to those obtained using direct laser absorption spectroscopy and FTS-based systems. In this presentation we will survey several examples of frequency-stabilized cavity ring-down spectroscopy (FS-CRDS)1 measurements obtained with laser spectrometers developed at the National Institute of Standards and Technology (NIST) in Gaithersburg Maryland. These experiments, which are motivated by atmospheric monitoring and remote-sensing applications that require high-precision and accuracy, involve nearinfrared transitions of carbon dioxide, water, oxygen and methane. We discuss spectra with signal-to-noise ratios exceeding 106, frequency axes with absolute uncertainties in the 10 kHz to 100 kHz range and linked to a Cs clock, line parameters with relative uncertainties at the 0.2 % level and isotopic ratios measured with a precision of 0.03 %. We also present FS-CRDS measurements of CO2 line intensities which are measured at atmospheric concentration levels and linked to gravimetric standards for CO2 in air, and we quantify pressure-dependent deviations between various theoretical line profiles and measured line shapes. Finally we also present recent efforts to increase data throughput and spectral coverage in CEAS experiments. We describe three new high-bandwidth CEAS techniques including frequency-agile, rapid scanning spectroscopy (FARS)2, which enables continuous-wave measurements of cavity mode linewidth and acquisition of ringdown decays with no dead time during laser frequency tuning, heterodyne

  18. Evidence for ultra-fast outflows in radio-quiet AGNs: II - detailed photo-ionization modeling of Fe K-shell absorption lines

    Tombesi, F; Reeves, J N; Palumbo, G G C; Braito, V; Dadina, M

    2011-01-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blueshifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and directly model the FeK absorbers with the Xstar photo-ionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35%. The outflow velocity distribution spans from \\sim10,000km/s (\\sim0.03c) up to \\sim100,000km/s (\\sim0.3c), with a peak and mean value of \\sim42,000km/s (\\sim0.14c). The ionization parameter is very high and in the range log\\xi 3-6erg s^{-1} cm, with a mean value of log\\xi 4.2 erg s^{-1} cm. The associated column densities are also large, in the range N_H\\sim10^{22}-10^{24...

  19. Assignment and modeling of the absorption spectrum of 13CH4 at 80 K in the region of the 2ν3 band (5853-6201 cm-1)

    Starikova, E.; Nikitin, A. V.; Rey, M.; Tashkun, S. A.; Mondelain, D.; Kassi, S.; Campargue, A.; Tyuterev, Vl. G.

    2016-07-01

    The absorption spectrum of the 13CH4 methane isotopologue has been recently recorded by Differential Absorption Spectroscopy (DAS) at 80 K in the 5853-6201 cm-1 spectral range. An empirical list of 3717 lines was constructed for this spectral range corresponding to the upper part of the Tetradecad dominated by the 2ν3 band near 5987 cm-1. In this work, we present rovibrational analyses of these spectra obtained via two theoretical approaches. Assignments of strong and medium lines were achieved with variational calculations using ab initio potential energy (PES) and dipole moment surfaces. For further analysis a non-empirical effective Hamiltonian (EH) of the methane polyads constructed by high-order Contact Transformations (CT) from an ab initio PES was employed. Initially predicted values of EH parameters were empirically optimized using 2898 assigned line positions fitted with an rms deviation of 5×10-3 cm-1. More than 1860 measured line intensities were modeled using the effective dipole transition moments approach with the rms deviation of about 10%. These new data were used for the simultaneous fit of the 13CH4 Hamiltonian parameters of the {Ground state/Dyad/Pentad/Octad/Tetradecad} system and the dipole moment parameters of the {Ground state-Tetradecad} system. Overall, 10 vibrational states and 28 vibration sublevels of the 13CH4 Tetradecad are determined. The comparison of their energy values with corresponding theoretical calculations is discussed.

  20. Characterization of the intestinal absorption of seven flavonoids from the flowers of Trollius chinensis using the Caco-2 cell monolayer model.

    Lijia Liu

    Full Text Available The human Caco-2 cell monolayer model was used to investigate the absorption property, mechanism, and structure-property relationship of seven representative flavonoids, namely, orientin, vitexin, 2"-O-β-L-galactopyranosylorientin, 2"-O-β-L-galactopyranosylvitexin, isoswertisin, isoswertiajaponin, and 2"-O-(2"'-methylbutanoylisoswertisin from the flowers of Trollius chinensis. The results showed that these flavonoids were hardly transported through the Caco-2 cell monolayer. The compounds with 7-OCH3 including isoswertisin, isoswertiajaponin and 2"-O-(2"'-methylbutanoylisoswertisin were absorbed in a passive diffusion manner, and their absorbability was increased in the same order as their polarity. The absorption of the remaining compounds with 7-OH including orientin, vitexin, 2"-O-β-L-galactopyranosylorientin, and 2"-O-β-L-galactopyranosylvitexin involved transporter mediated efflux in addition to passive diffusion. Among the four compounds with 7-OH, those with a free hydroxyl group at C-2" such as orientin and vitexin were the substrates of P-glycoprotein (P-gp and that with a free hydroxyl group at C-2' such as 2"-O-β-L-galactopyranosylorientin was the substrate of multidrug resistance protein 2 (MRP2. The results of this study also implied that the absorbability of the flavonoids should be taken into account when estimating the effective components of T. chinensis.

  1. FDTD calculations of specific energy absorption rate in a seated voxel model of the human body from 10 MHz to 3 GHz

    Finite-difference time-domain (FDTD) calculations have been performed to investigate the frequency dependence of the specific energy absorption rate (SAR) in a seated voxel model of the human body. The seated model was derived from NORMAN (NORmalized MAN), an anatomically realistic voxel phantom in the standing posture with arms to the side. Exposure conditions included both vertically and horizontally polarized plane wave electric fields between 10 MHz and 3 GHz. The resolution of the voxel model was 4 mm for frequencies up to 360 MHz and 2 mm for calculations in the higher frequency range. The reduction in voxel size permitted the calculation of SAR at these higher frequencies using the FDTD method. SAR values have been calculated for the seated adult phantom and scaled versions representing 10-, 5- and 1-year-old children under isolated and grounded conditions. These scaled models do not exactly reproduce the dimensions and anatomy of children, but represent good geometric information for a seated child. Results show that, when the field is vertically polarized, the sitting position causes a second, smaller resonance condition not seen in resonance curves for the phantom in the standing posture. This occurs at ∼130 MHz for the adult model when grounded. Partial-body SAR calculations indicate that the upper and lower regions of the body have their own resonant frequency at ∼120 MHz and ∼160 MHz, respectively, when the grounded adult model is orientated in the sitting position. These combine to produce this second resonance peak in the whole-body averaged SAR values calculated. Two resonance peaks also occur for the sitting posture when the incident electric field is horizontally polarized. For the adult model, the peaks in the whole-body averaged SAR occur at ∼180 and ∼600 MHz. These peaks are due to resonance in the arms and feet, respectively. Layer absorption plots and colour images of SAR in individual voxels show the specific regions in which the

  2. On the computation of a retina resistivity profile for applications in multi-scale modeling of electrical stimulation and absorption.

    Loizos, Kyle; RamRakhyani, Anil Kumar; Anderson, James; Marc, Robert; Lazzi, Gianluca

    2016-06-21

    This study proposes a methodology for computationally estimating resistive properties of tissue in multi-scale computational models, used for studying the interaction of electromagnetic fields with neural tissue, with applications to both dosimetry and neuroprosthetics. Traditionally, models at bulk tissue- and cellular-level scales are solved independently, linking resulting voltage from existing resistive tissue-scale models as extracellular sources to cellular models. This allows for solving the effects that external electric fields have on cellular activity. There are two major limitations to this approach: first, the resistive properties of the tissue need to be chosen, of which there are contradicting measurements in literature; second, the measurements of resistivity themselves may be inaccurate, leading to the mentioned contradicting results found across different studies. Our proposed methodology allows for constructing computed resistivity profiles using knowledge of only the neural morphology within the multi-scale model, resulting in a practical implementation of the effective medium theory; this bypasses concerns regarding the choice of resistive properties and accuracy of measurement setups. A multi-scale model of retina is constructed with an external electrode to serve as a test bench for analyzing existing and resulting resistivity profiles, and validation is presented through the reconstruction of a published resistivity profile of retina tissue. Results include a computed resistivity profile of retina tissue for use with a retina multi-scale model used to analyze effects of external electric fields on neural activity. PMID:27223656

  3. On the computation of a retina resistivity profile for applications in multi-scale modeling of electrical stimulation and absorption

    Loizos, Kyle; RamRakhyani, Anil Kumar; Anderson, James; Marc, Robert; Lazzi, Gianluca

    2016-06-01

    This study proposes a methodology for computationally estimating resistive properties of tissue in multi-scale computational models, used for studying the interaction of electromagnetic fields with neural tissue, with applications to both dosimetry and neuroprosthetics. Traditionally, models at bulk tissue- and cellular-level scales are solved independently, linking resulting voltage from existing resistive tissue-scale models as extracellular sources to cellular models. This allows for solving the effects that external electric fields have on cellular activity. There are two major limitations to this approach: first, the resistive properties of the tissue need to be chosen, of which there are contradicting measurements in literature; second, the measurements of resistivity themselves may be inaccurate, leading to the mentioned contradicting results found across different studies. Our proposed methodology allows for constructing computed resistivity profiles using knowledge of only the neural morphology within the multi-scale model, resulting in a practical implementation of the effective medium theory; this bypasses concerns regarding the choice of resistive properties and accuracy of measurement setups. A multi-scale model of retina is constructed with an external electrode to serve as a test bench for analyzing existing and resulting resistivity profiles, and validation is presented through the reconstruction of a published resistivity profile of retina tissue. Results include a computed resistivity profile of retina tissue for use with a retina multi-scale model used to analyze effects of external electric fields on neural activity.

  4. VAPID: Voigt Absorption-Profile [Interstellar] Dabbler

    Howarth, Ian D.

    2015-06-01

    VAPID (Voigt Absorption Profile [Interstellar] Dabbler) models interstellar absorption lines. It predicts profiles and optimizes model parameters by least-squares fitting to observed spectra. VAPID allows cloud parameters to be optimized with respect to several different data set simultaneously; those data sets may include observations of different transitions of a given species, and may have different S/N ratios and resolutions.

  5. Kinetics of gastro-intestinal absorption

    Knowledge of the kinetics of gastrointestinal absorption is required for reliable dose estimates for ingested radionuclides. A method is described by which absorption rates as a function of time as well as the total fraction absorbed (f1 value) can be determined by analysis of tracer concentrations in blood after oral and intravenous administration. The method was applied to study the absorption dynamics of Ca, Fe, and Mo in humans and is adapted to Ru, Zr, Sr and lanthanides. Radioactive or stable isotopes of the respective elements were used as tracers. The absorption kinetics and the total fractional absorption differ considerably for different elements. For a particular element, the absorption rates as well as the f1 values vary considerably with respect to the chemical form and the amount administered. Absorption patterns are characteristically different for uptake from solutions or from whole meals. This information may be used to improve the dosimetric model for the gastrointestinal tract. (author)

  6. The ℓ-distribution method for modeling non-gray absorption in uniform and non-uniform gaseous media

    André, Frédéric

    2016-08-01

    The ℓ-distribution modeling is proposed for radiative heat transfer in uniform and non-uniform non-gray gaseous media. The method is partly based on the application of results from the k-moment method. It combines this technique with several concepts from probability theory: the notion of rank transmutation maps allows extending the k-moment method to an infinite number of k-moments; copula models appear naturally to extend the method from uniform to non-uniform gas paths. The ℓ-distribution approach is shown to provide results: (1) more accurate - up to three orders of magnitude - than usual k-distribution approaches in uniform media, (2) as precise as correlated-k models in non-uniform situations. All these results are obtained at a computational cost lower than k-distribution models. Differences and similarities between k- and ℓ-distribution methods are discussed.

  7. Self-consistent particle-in-cell modelling of short pulse absorption and transport for high energy density physics experiments

    Ramsay, M. G.; Arber, T. D.; Sircombe, N. J.

    2016-03-01

    In order for detailed, solid density particle-in-cell (PIC) simulations to run within a reasonable time frame, novel approaches to modelling high density material must be employed. For the purposes of modelling high intensity, short pulse laser-plasma interactions, however, these approaches must be consistent with retaining a full PIC model in the low-density laser interaction region. By replacing the standard Maxwell field solver with an electric field update based on a simplified Ohm's law in regions of high electron density, it is possible to access densities at and above solid without being subject to the standard grid and time step constraints. Such a model has recently been implemented in the PIC code EPOCH. We present the initial results of a detailed two-dimensional simulation performed to compare the adapted version of the code with recent experimental results from the Orion laser facility.

  8. Property profiling of biosimilar mucus in a novel mucus-containing in vitro model for assessment of intestinal drug absorption

    Bøgh, Marie; Baldursdóttir, Stefania G; Müllertz, Anette; Nielsen, Hanne M

    2014-01-01

    Oral delivery of drugs, including peptide and protein therapeutics, can be impeded by the presence of the mucus surface-lining the intestinal epithelium. The aim of the present project was to design and characterize biosimilar mucus compatible with Caco-2 cell monolayers cultured in vitro to esta...... of the biorelevance of the Caco-2 cell culture model by application of mucus, resulting in an in vitro model of oral mucosa suitable for future assessment of innovative drug delivery approaches....

  9. Modeling of Artificial Neural Network for Predicting Specific Heat capacity of working fluid LiBr-H2O used in Vapor Absorption Refrigeration System

    Dheerendra Vikram Singh

    2011-05-01

    Full Text Available The objective of this work is to model an artificial neural network (ANN to predict the value of specific heat capacity of working fluid LiBr-H2O used in vapour absorption refrigeration systems. A feed forward back propagation algorithm is used for the network, which is most popular for ANN. The consistence between experimental and ANN’s approach result was achieved by a mean relative error -0.00573, sum of the squares due to error0.00321, coefficient of multiple determination R-square 0.99961and root mean square error 0.01573 for test data. These results had been achieved in Matlab environment and the use of derived equations in any programmable language for deriving the specific heat capacity of LiBr-H2O solution.

  10. The sensitivity of a coupled atmospheric-oceanic model to variations in the albedo and absorptivity of a stratospheric aerosol layer

    Considerable uncertainty exists regarding the precise physical parameters of a smoke or aerosol cloud that would be injected into the lower stratosphere by a catastrophic event such as a nuclear war, a major volcanic eruption, or an asteroid impact. In this paper, the sensitivity of the sea surface temperature of a one-dimensional coupled atmospheric-oceanic model to variations in the albedo and absorptivity of an aerosol cloud introduced into the lower stratosphere is examined. Zonally averaged results are produced for two latitudes in the southern hemisphere. The temperature response of the oceans to forcings by a cloud with realistic aerosol properties is examined, with particular emphasis on the impact on the surface climate on time scales of 6 months to 2 years

  11. The CAESAR project: Experimental and modeling investigations of methane reforming in a CAtalytically Enhanced Solar Absorption Receiver on a parabolic dish

    Muir, J.F.; Hogan, R.E. Jr.; Skocypec, R.D. [Sandia National Labs., Albuquerque, NM (US); Buck, R. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt, Stuttgart (DE). Inst. of Technical Thermodynamics

    1993-07-01

    A joint US/Federal Republic of Germany (FRG) project has successfully tested a unique solar-driven chemical reactor in the CAtalytically Enhanced Solar Absorption Receiver (CAESAR) experiment. The CAESAR test was a {open_quotes}proof-of-concept{close_quotes} demonstration of carbon-dioxide reforming of methane in a commercial-scale, solar, volumetric receiver/reactor on a parabolic dish concentrator. The CAESAR design; test facility and instrumentation; thermal and chemical tests; and analysis of test results are presented in detail. Numerical models for the absorber and the receiver are developed and predicted performance is compared with test data. Post test analyses to assess the structural condition of the absorber and the effectiveness of the rhodium catalyst are presented. Unresolved technical issues are identified and future development efforts are recommended.

  12. The CAESAR project: Experimental and modeling investigations of methane reforming in a catalytically enhanced solar absorption receiver on a parabolic dish

    Muir, J. F.; Hogan, R. E., Jr.; Skocypec, R. D.; Buck, R.

    1993-07-01

    A joint US/Federal Republic of Germany (FRG) project has successfully tested a unique solar-driven chemical reactor in the Catalytically Enhanced Solar Absorption Receiver (CAESAR) experiment. The CAESAR test was a proof-of-concept demonstration of carbon-dioxide reforming of methane in a commercial-scale, solar, volumetric receiver/reactor on a parabolic dish concentrator. The CAESAR design, test facility and instrumentation, thermal and chemical tests, and analysis of test results are presented in detail. Numerical models for the absorber and the receiver are developed and predicted performance is compared with test data. Post test analyses to assess the structural condition of the absorber and the effectiveness of the rhodium catalyst are presented. Unresolved technical issues are identified and future development efforts are recommended.

  13. In-situ determination of macroscopic thermal neutron absorption cross-section of borehole model materials using the integrated flux method

    The integrated thermal neutron flux method of determining the macroscopic thermal neutron absorption cross-section of samples consisting of approx. 400 kg of unconsolidated geologic material, saturated with fresh water, to be used in borehole models, is reported. One advantage of this method is that bulk cross-section determinations are made relative to a single standard, with fresh (distilled) water being used as the standard in this work. The values of matrix Σ determined for unconsolidated sand, limestone, and dolomite for the particular samples measured fall within the range of previously reported measurements of similar type samples. The method was checked using 50,000 ppm NaCl for which a value of 39.1 ± 0.5 c.u. was determined. (author)

  14. Pion absorption processes

    Proton and deuteron production from low-energy pion absorption in light nuclei leading to discrete and continuum states were measured. The LEP beam line at LAMPF was used with a stack of 8 intrinsic germanium crystals. The proton energy spectra are in general characterized by a broad bump at an energy approximately corresponding to π+d → pp reaction kinematics, suggestive of pion absorption on 2 nucleons. The energy-integrated cross-section for production of deuterons has an angular distribution similar to that for production of protons. The dependence of the total pion absorption cross-section on A is explained using a semi-classical model for pion transport in nuclei. The (π+,p) as well as (π+,d) reactions generally favor transitions involving larger angular momentum transfer to the residual nucleus when states of similar nuclear structure are considered. The low-energy excitation spectra from the (π+,p) reaction are similar to the spectra from (p,d) reaction on 12C and 13C. However, a calculation of the (π+,p) cross-section using the measured (p,d) reaction with the formulation of Wilkin to relate the two reactions is in moderate disagreement with the measured (π+,p) cross-sections. The excitation spectra from the (π+,p) reaction indicte the importance of two-step processes for the reaction. The (π+,d) reaction leading to the ground state of -- residual nucleus has been seen for 7Li, 12C, and 13C targets. The measured cross section for the 12C(π+,d)10C reaction to the 2+ state is much higher than that for the ground state. For the case of 18O, no counts were seen for excitation energy of +,d) reaction

  15. Progress of mathematical modeling for trandermal drug absorption%药物经皮吸收数学模型研究进展

    何星篧; 王晖

    2015-01-01

    Transdermal drug delivery is an administration route which can avoid the first-pass effect,maintain steady plasma concentrations and enhance bioavailability. Drug transporting through the skin by passage through the stratum corneum leads to the viable epidermis and the dermis.With the development of the computer technology,many mathematical models for predic-ting the absorption of drugs have been built according to physical and chemical properties of drugs and physiological characteristics of each skin layer.This article presented provides a summary of the progress of mathematical models for predicting percutaneous absorption of drugs.%经皮给药是一种能避免肝脏的首过效应及肠胃灭活、维持血药浓度、提高生物利用度的给药途径。而药物经皮吸收需透过角质层、活性表皮层、真皮层的屏障。近年来,随着计算机技术的发展,根据药物的不同理化特性及皮肤各层的生理特征,建立了许多预测药物经皮吸收方面的数学模型。该文就预测药物经皮吸收数学模型的研究进展进行了综述。

  16. D-xylose absorption

    D-xylose absorption is a laboratory test to determine how well the intestines absorb a simple sugar (D-xylose). The test ... test is primarily used to determine if nutrient absorption problems are due to a disease of the ...

  17. D-xylose absorption

    ... this page: //medlineplus.gov/ency/article/003606.htm D-xylose absorption To use the sharing features on this page, please enable JavaScript. D-xylose absorption is a laboratory test to determine ...

  18. Nutrition and magnesium absorption.

    Brink, E.J.

    1992-01-01

    The influence of various nutrients present in dairy products and soybean-based products on absorption of magnesium has been investigated. The studies demonstrate that soybean protein versus casein lowers apparent magnesium absorption in rats through its phytate component. However, true magnesium absorption was neither affected by soybean protein in the diet nor by supplemental phytate. The inhibitory influence of soybean protein and phytate on apparent magnesium absorption was found to be cau...

  19. MATHEMATICAL MODEL OF AN OPTICAL ENERGY ABSORPTION MODULE OF INTEGRATED SYSTEM OFF-LANE POWER HEATING SUPPLY OF AGRICULTURAL PRODUCTION

    Gazalov V. S.

    2014-10-01

    Full Text Available We have made energy estimation of absorbed solar fluxes with a glance of diffuse insolation which passes through double- glazing unit to the right-angled planar radiator. While designing the model it was conceded to assume that direct solar radiation is the radiation of a point source

  20. Aspects on modeled and the design of a system of refrigeration by absorption attended with solar energy; Aspectos sobre el modelado y diseno de un sistema de refrigeracion por absorcion asistido con energia solar

    Garcia Cascales, J. R.; Vera Garcia, F.; Cano Izquierdo, J. M.; Delgado Marin, J. P.; Martinez Sanchez, R.

    2008-07-01

    In this paper, we study the global modelling of an absorption system working with Br Li-H{sub 2}O. It satisfies the air-conditioning necessities of a classroom in an educational centre in Puerto Lumbreras. Murcia. This system utilises a set of solar collector to satisfy the thermal necessities of the vapour generator in the absorption system. For the dynamical simulation of the system we have used the TRNSYS software. The air-conditioned place has been modelled by using a TRNSYS module called PREBID. In this work, special attention is paid to the absorption equipment model developed by using neural networks which has been implemented in TRNSYS. The paper is closed drawing some conclusions. (Author)

  1. Efficacy of skin wash on dermal absorption: an in vitro study on four model compounds of varying solubility

    Nielsen, Jesper Bo

    2010-01-01

    PURPOSE: Following dermal exposure to chemicals causing systemic toxicity, the general advice to avoid further systemic exposure is to wash the skin. The present study uses four model compounds (benzoic acid, glyphosat, caffeine, malathion) with varying size and solubility to substantiate this...... advice and quantify the effect of skin wash following 6 h dermal exposure on subsequent extent of skin penetration and deposition within the skin compartment. METHOD: Percutaneous penetration through human skin is studied in an in vitro model with static diffusion cells. RESULTS: The study demonstrates...... that percutaneous penetration continues after end of exposure due to the reservoir present in the skin. However, penetration rate will decrease significantly, and it is evident that simple hand-wash after end of exposure not only reduces the amount of residue present in the upper skin compartment but...

  2. Absorption of calcium ions on oxidized graphene sheets and study its dynamic behavior by kinetic and isothermal models

    Fathy, Mahmoud; Abdel Moghny, Th.; Mousa, Mahmoud Ahmed; El-Bellihi, Abdel-Hameed A.-A.; Awadallah, Ahmed E.

    2016-07-01

    Sorption of calcium ion from the hard underground water using novel oxidized graphene (GO) sheets was studied in this paper. Physicochemical properties and microstructure of graphene sheets were investigated using Raman spectrometer, thermogravimetry analyzer, transmission electron microscope, scanning electron microscope. The kinetics adsorption of calcium on graphene oxide sheets was examined using Lagergren first and second orders. The results show that the Lagergren second-order was the best-fit model that suggests the conception process of calcium ion adsorption on the Go sheets. For isothermal studies, the Langmuir and Freundlich isotherm models were used at temperatures ranging between 283 and 313 K. Thermodynamic parameters resolved at 283, 298 and 313 K indicating that the GO adsorption was exothermic spontaneous process. Finally, the graphene sheets show high partiality toward calcium particles and it will be useful in softening and treatment of hard water.

  3. Binding of 5-fluorotryptamine to polynucleotides as a model for protein-nucleic acid interactions: fluorine-19 nuclear magnetic resonance, absorption, and fluorescence studies

    Fluorine-19 nuclear magnetic resonance (19F NMR), optical absorption, and fluorescence spectroscopy have been used to study the interaction of 5-fluorotryptamine (5FTA) with polynucleotides as a model for protein-nucleic acid interactions. In the presence of DNA, denatured DNA, poly(A), and poly(A)-poly(U), the 19F resonance of 5FTA shifted 0.3-0.6 ppm upfield while the presence of poly(I)-poly(C) had little effect on the chemical shift. Differences in the 19F chemical shift induced upon changing from H2O to 2H2O indicate difference in the solvent accesibility of 5FTA bound to the various polynucleotides. 19F NMR relaxation experiments were carried out for free 5FTA and in its nucleic acid complexes, and the results were interpreted by using a two correlation time model that included contributions to relaxation from dipolar coupling and chemical shift anisotropy. Values for the internal motion correlation time and the overall motion correlation time are reported. The effect of 5FTA on the melting transition of the double-stranded polynucleotides and on the quenching of 5FTA fluorescence was also studied. The 19F NMR results support the model of partial intercalation of the 5FTA chromophore into the polynucleotides, and the implications for protein-nucleic acid interactions are discussed

  4. Mantle formation, coagulation and the origin of cloud/core shine: I. Modelling dust scattering and absorption in the infra-red

    Jones, A P; Ysard, N; Dartois, E; Godard, M; Gavilan, L

    2016-01-01

    Context. The observed cloudshine and coreshine (C-shine) have been explained in terms of grain growth leading to enhanced scatter- ing from clouds in the J, H and K photometric bands and the Spitzer IRAC 3.6 and 4.5 {\\mu}m bands. Aims. Using our global dust modelling approach THEMIS (The Heterogeneous dust Evolution Model at the IaS) we explore the effects of dust evolution in dense clouds, through aliphatic-rich carbonaceous mantle formation and grain-grain coagulation. Methods. We model the effects of wide band gap a-C:H mantle formation and the low-level aggregation of diffuse interstellar medium dust in the moderately-extinguished outer regions of molecular clouds. Results. The formation of wide band gap a-C:H mantles on amorphous silicate and amorphous carbon (a-C) grains leads to a decrease in their absorption cross-sections but no change in their scattering cross-sections at near-IR wavelengths, resulting in higher albedos. Conclusions. The evolution of dust, with increasing density and extinction in t...

  5. Thermal modeling of a secondary concentrator integrated with an open direct-absorption molten-salt volumetric receiver in a beam-down tower system

    Lahlou, Radia; Armstrong, Peter; Grange, Benjamin; Almheiri, Saif; Calvet, Nicolas; Slocum, Alexander; Shamim, Tariq

    2016-05-01

    An upward-facing three-dimensional secondary concentrator, herein termed Final Optical Element (FOE), is designed to be used in a beam-down tower in combination with an open volumetric direct-absorption molten-salt receiver tank acting simultaneously as a thermal energy storage system. It allows reducing thermal losses from the open receiver by decreasing its aperture area while keeping minimal spillage losses. The FOE is exposed to high solar fluxes, a part of which is absorbed by its reflector material, leading to material degradation by overheating. Consequently, the FOE may require active cooling. A thermal model of the FOE under passive cooling mechanism is proposed as a first step to evaluate its sensitivity to some design parameters. Then, it will be used to evaluate the requirements for the active cooling system. The model provides insights on the FOE thermal behavior and highlights the effectiveness of a design modification on passive cooling enhancement. First prototype tests under reduced flux and with no active cooling will be used for model adjustment.

  6. Calcium absorption and achlorhydria

    Defective absorption of calcium has been thought to exist in patients with achlorhydria. The author compared absorption of calcium in its carbonate form with that in a pH-adjusted citrate form in a group of 11 fasting patients with achlorhydria and in 9 fasting normal subjects. Fractional calcium absorption was measured by a modified double-isotope procedure with 0.25 g of calcium used as the carrier. Mean calcium absorption (+/- S.D.) in the patients with achlorhydria was 0.452 +/- 0.125 for citrate and 0.042 +/- 0.021 for carbonate (P less than 0.0001). Fractional calcium absorption in the normal subjects was 0.243 +/- 0.049 for citrate and 0.225 +/- 0.108 for carbonate (not significant). Absorption of calcium from carbonate in patients with achlorhydria was significantly lower than in the normal subjects and was lower than absorption from citrate in either group; absorption from citrate in those with achlorhydria was significantly higher than in the normal subjects, as well as higher than absorption from carbonate in either group. Administration of calcium carbonate as part of a normal breakfast resulted in completely normal absorption in the achlorhydric subjects. These results indicate that calcium absorption from carbonate is impaired in achlorhydria under fasting conditions. Since achlorhydria is common in older persons, calcium carbonate may not be the ideal dietary supplement

  7. Modelling the Emission And/or Absorption Features in the High Resolution Spectra of the Southern Binary System: HH Car

    Koseoglu, Dogan; Bakış, Hicran

    2016-07-01

    High-resolution spectra (R=48000) of the southern close binary system, HH Car, has been analyzed with modern analysis techniques. Precise absolute parameters were derived from the simultaneous solution of the radial velocity, produced in this study and the light curves, published. According to the results of these analyses, the primary component is an O9 type main sequence star while the secondary component is a giant/subgiant star with a spectral type of B0. Hα emissions can be seen explicitly in the spectra of HH Car. These features were modelled using the absolute parameters of the components. Since components of HH Car are massive early-type stars, mass loss through stellar winds can be expected. This study revealed that the components of HH Car have stellar winds and the secondary component loses mass to the primary. Stellar winds and the gas stream between the components were modelled as a hot shell around the system. It is determined that the interaction between the winds and the gas stream leads to formation of a high temperature impact region.

  8. Solar powered absorption air conditioning

    Vardon, J. M.

    1980-04-01

    Artificial means of providing or removing heat from the building are discussed along with the problem of the appropriate building design and construction for a suitable heat climate inside the building. The use of a lithium bromide-water absorption chiller, powered by a hot water store heated by an array of stationary flat collectors, is analyzed. An iterative method of predicting the cooling output from a LiBr-water absorption refrigeration plant having variable heat input is described and a model allowing investigation of the performance of a solar collector and thermal storage system is developed.

  9. 1-d model for propagation and absorption of h.f. waves near ion cyclotron resonances in large tokamak plasmas

    The behaviour of h.f. waves near ion cyclotron and ion ion hybrid resonances in a tokamak is investigated by means of an one-dimensional finite element code. Our model takes into account: - strength and orientation of the poloidal component of the static magnetic field, - finite larmor radius corrections to the dielectric tensor, - ion cyclotron damping at the fundamental and first harmonic resonance, - electron Landau damping to lowest order msub(e)/msub(i). We assume that an incoming fast wave approaches the singular layer from the low or high field side making an arbitrary angle relative to the local magnetic flux surface and to the resonance layer. These initial conditions might be provided by ray tracing from the antenna. Then we calculate the electromagnetic wavefield and the power fluxes of the transmitted or reflected fast and slow waves as well as the power absorbed by ions and electrons. (orig.)

  10. Transdermic absorption of Melagenina II

    The transdermic absorption of Melagenina II (MII) was evaluated. MII was a labelled with 125I by the yodogen method and purified by column chromatography with Sephadex LH-20 in ethanol: water (7:3). In vitro absorption of (125I) - MII thought human skin was carried out in Keshary-Chien modified diffusion cells. Tape stripping method was applied after 24 hours to evaluate the accumulated activity in dermis and epidermis. In vivo assays were performed in Sprague Dawley rats to analyze absorption of MII until 24 hours after a single application and for five days a low penetrability of the drug while in vivo there were not found blood levels significantly greater than zero , nevertheless and important amount of radioactivity was found in feces and urine. The activity was concentrated mainly in the application site in both models

  11. He bubbles nucleation in lead-lithium and implications on tritium transport for HCLL breeding blanket design: mass transfer coefficient absorption model sensitivity analysis

    High helium (He) production rates support the conditions for He nucleation in liquid metal (LM) breeding blankets. The formation of bubbles in the LM might have an important impact on the hydrodynamics and on the tritium transport. The issue of He bubbles formation is, hence, highly relevant to tritium inventory control and recovery. Models for tritium and helium transport phenomena involving He nucleation, bubble growth, T absorption into He bubbles, T adsorption onto structural material and desorption to cooling system channels (CSC) are implemented into OpenFOAM CFD code (BelFoam solver). The code is capable of solving the mass transfer between different materials with a conjugated scalar transfer algorithm, so it takes into account LM-structural material interface T transport. In the present work, BelFoam solver results for a geometrically simplified horizontalU-bent channel of a helium cooled lithiumlead (HCLL) breeding unit (BU) are shown. In addition, for the T absortion model, a sensitivity analysis to the mass transfer coefficient is presented together with an analysis of the results.

  12. Reactive species output of a plasma jet with a shielding gas device—combination of FTIR absorption spectroscopy and gas phase modelling

    In this work, a simple modelling approach combined with absorption spectroscopy of long living species generated by a cold atmospheric plasma jet yields insight into relevant gas phase chemistry. The reactive species output of the plasma jet is controlled using a shielding gas device. The shielding gas is varied using mixtures of oxygen and nitrogen at various humidity levels. Through the combination of Fourier transform infrared (FTIR) spectroscopy, computational fluid dynamics (CFD) simulations and zero dimensional kinetic modelling of the gas phase chemistry, insight into the underlying reaction mechanisms is gained. While the FTIR measurements yield absolute densities of ozone and nitrogen dioxide in the far field of the jet, the kinetic simulations give additional information on reaction pathways. The simulation is fitted to the experimentally obtained data, using the CFD simulations of the experimental setup to estimate the correct evaluation time for the kinetic simulation. It is shown that the ozone production of the plasma jet continuously rises with the oxygen content in the shielding gas, while it significantly drops as humidity is increased. The production of nitrogen dioxide reaches its maximum at about 30% oxygen content in the shielding gas. The underlying mechanisms are discussed based on the simulation results. (paper)

  13. Variability of calcium absorption

    Variability in calcium absorption was estimated in three groups of normal subjects in whom Ca absorption was measured by standard isotopic-tracer methods at interstudy intervals ranging from 1 to 4 mo. Fifty absorption tests were performed in 22 subjects. Each was done in the morning after an overnight fast with an identical standard breakfast containing a Ca load of approximately 250 mg. Individual fractional absorption values were normalized to permit pooling of the data. The coefficient of variation (CVs) for absorption for the three groups ranged from 10.57 to 12.79% with the size of the CV increasing with interstudy duration. One other published study presenting replicate absorption values was analyzed in a similar fashion and was found to have a CV of absorption of 9.78%. From these data we estimate that when the standard double-isotope method is used to measure Ca absorption there is approximately 10% variability around any given absorption value within an individual human subject and that roughly two-thirds of this represents real biological variability in absorption

  14. Analysis of in situ electric field and specific absorption rate in human models for wireless power transfer system with induction coupling

    This study investigates the specific absorption rate (SAR) and the in situ electric field in anatomically based human models for the magnetic field from an inductive wireless power transfer system developed on the basis of the specifications of the wireless power consortium. The transfer system consists of two induction coils covered by magnetic sheets. Both the waiting and charging conditions are considered. The transfer frequency considered in this study is 140 kHz, which is within the range where the magneto-quasi-static approximation is valid. The SAR and in situ electric field in the chest and arm of the models are calculated by numerically solving the scalar potential finite difference equation. The electromagnetic modelling of the coils in the wireless power transfer system is verified by comparing the computed and measured magnetic field distributions. The results indicate that the peak value of the SAR averaged over a 10 g of tissue and that of the in situ electric field are 72 nW kg−1 and 91 mV m−1 for a transmitted power of 1 W, Consequently, the maximum allowable transmitted powers satisfying the exposure limits of the SAR (2 W kg−1) and the in situ electric field (18.9 V m−1) are found to be 28 MW and 43 kW. The computational results show that the in situ electric field in the chest is the most restrictive factor when compliance with the wireless power transfer system is evaluated according to international guidelines. (paper)

  15. Analysis of in situ electric field and specific absorption rate in human models for wireless power transfer system with induction coupling.

    Sunohara, Tetsu; Hirata, Akimasa; Laakso, Ilkka; Onishi, Teruo

    2014-07-21

    This study investigates the specific absorption rate (SAR) and the in situ electric field in anatomically based human models for the magnetic field from an inductive wireless power transfer system developed on the basis of the specifications of the wireless power consortium. The transfer system consists of two induction coils covered by magnetic sheets. Both the waiting and charging conditions are considered. The transfer frequency considered in this study is 140 kHz, which is within the range where the magneto-quasi-static approximation is valid. The SAR and in situ electric field in the chest and arm of the models are calculated by numerically solving the scalar potential finite difference equation. The electromagnetic modelling of the coils in the wireless power transfer system is verified by comparing the computed and measured magnetic field distributions. The results indicate that the peak value of the SAR averaged over a 10 g of tissue and that of the in situ electric field are 72 nW kg(-1) and 91 mV m(-1) for a transmitted power of 1 W, Consequently, the maximum allowable transmitted powers satisfying the exposure limits of the SAR (2 W kg(-1)) and the in situ electric field (18.9 V m(-1)) are found to be 28 MW and 43 kW. The computational results show that the in situ electric field in the chest is the most restrictive factor when compliance with the wireless power transfer system is evaluated according to international guidelines. PMID:24936747

  16. Modeling and numerical simulation of a novel solar-powered absorption air conditioning system driven by a bubble pump with energy storage

    QIU Jia; LIANG Jian; CHEN GuangMing; DU RuXu

    2009-01-01

    This paper presents a novel solar-powered absorption air conditioning system driven by a bubble pump with energy storage. It solves the problem of unreliable solar energy supply by storing the working fluids and hence, functions 24 h per day. First, the working principles are described and the dynamic models for the primary energy storage components are developed. Then, the system is evaluated based on a numerical simulation. Based on the meteorological data of a typical day in a subtropical area, with the area of a solar collector being set at 19.15 m2, whilst the initial charging mass, mass fraction and temperature of the solution are respectively set at 379.5 kg, 54.16% and 34.5 ℃, it is found that the respective coefficients of performance (COP) of the air conditioning system and the en-tire system (including the solar panel) are 0.7771 and 0.4372. In particular, the energy storage density of the system is 206.69 MJ/m3 which is much greater than those of chilled water or hot water storage systems under comparable conditions. This makes the new system much more compact and efficient. Finally, an automatic control strategy is given to achieve the highest COP when solar energy fluctuates.

  17. Stochastic Absorption of the Light of Background Sources due to Intergalactic Neutral Hydrogen I. Testing different line-number evolution models via the cosmic flux decrement

    Tepper-Garc{\\'\\i}a, Thorsten

    2007-01-01

    We test the accuracy of different models of the attenuation of light due to intergalactic neutral hydrogen by comparing their predictions of the evolution of the mean cosmic flux decrement D_A to its measurements based on observations. To this end, we use data available in the literature and our own measurements of D_A for 25 QSOs in the redshift range 2.64 < z < 5.41 taken from the SDSS Data Release 5. In order to perform the measurements of D_A, we fit a power-law to the continuum redward of the Lyman Alpha emission line, and extrapolate this fit to region blueward of it, where the flux is severely affected by absorption due to intervening HI absorbers. We compute, using numerical simulations, the redshift evolution of the mean flux depression due to the presence of Lyman Alpha Forest absorbers and Lyman limit systems randomly distributed along the line-of-sight, and compute its intrinsic scatter at the 1-, 2-, and 3$\\sigma$ level due to fluctuations in the absorber properties (column density, Doppler...

  18. Superposition model analysis from polarized electronic absorption spectra of Co2+ in trigonally distorted octahedra in brucite-type Co(OH)2

    Polarized electronic absorption spectra of Co2+ in trigonally compressed octahedra in brucite-type Co(OH)2 have been measured at 290 and 90 K by microscope-spectrometric techniques and analysed in terms of the superposition model (SM) of crystal fields. The resulting SM and interelectronic repulsion parameters are B-bar4=5260, B-bar2=4920, Racah B = 825, Racah C = 3550 cm-1 at 290 K and B-bar4=5320, B-bar2=3900, Racah B = 830, Racah C = 3500 cm-1 at 90 K (R0 = 2.1115 A; fixed exponential and spin-orbit parameters t4=5, t2=3, ζ = 500 cm-1). Together with a recent SM analysis of Li2Co3(SeO3)4, the B-bark refined for Co(OH)2 further confine the magnitude of the hitherto unknown 'correct' SM parameters of Co2+ for future application to structurally and/or chemically less well defined systems. (author)

  19. EVIDENCE FOR ULTRA-FAST OUTFLOWS IN RADIO-QUIET ACTIVE GALACTIC NUCLEI. II. DETAILED PHOTOIONIZATION MODELING OF Fe K-SHELL ABSORPTION LINES

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet active galactic nuclei (AGNs). These have been detected essentially through blueshifted Fe XXV/XXVI K-shell transitions. In the previous paper of this series we defined UFOs as those highly ionized absorbers with an outflow velocity higher than 10,000 km s–1 and assessed the statistical significance of the associated blueshifted absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. The present paper is an extension of that work. First, we report a detailed curve of growth analysis of the main Fe XXV/XXVI transitions in photoionized plasmas. Then, we estimate an average spectral energy distribution for the sample sources and directly model the Fe K absorbers in the XMM-Newton spectra with the detailed Xstar photoionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35% and that the majority of the Fe K absorbers are indeed associated with UFOs. The outflow velocity distribution spans from ∼10,000 km s–1 (∼0.03c) up to ∼100,000 km s–1 (∼0.3c), with a peak and mean value of ∼42,000 km s–1 (∼0.14c). The ionization parameter is very high and in the range log ξ ∼ 3-6 erg s–1 cm, with a mean value of log ξ ∼ 4.2 erg s–1 cm. The associated column densities are also large, in the range NH ∼ 1022-1024 cm–2, with a mean value of NH ∼ 1023 cm–2. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7 keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton-thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback

  20. Evidence for Ultra-fast Outflows in Radio-quiet Active Galactic Nuclei. II. Detailed Photoionization Modeling of Fe K-shell Absorption Lines

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Palumbo, G. G. C.; Braito, V.; Dadina, M.

    2011-11-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet active galactic nuclei (AGNs). These have been detected essentially through blueshifted Fe XXV/XXVI K-shell transitions. In the previous paper of this series we defined UFOs as those highly ionized absorbers with an outflow velocity higher than 10,000 km s-1 and assessed the statistical significance of the associated blueshifted absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. The present paper is an extension of that work. First, we report a detailed curve of growth analysis of the main Fe XXV/XXVI transitions in photoionized plasmas. Then, we estimate an average spectral energy distribution for the sample sources and directly model the Fe K absorbers in the XMM-Newton spectra with the detailed Xstar photoionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35% and that the majority of the Fe K absorbers are indeed associated with UFOs. The outflow velocity distribution spans from ~10,000 km s-1 (~0.03c) up to ~100,000 km s-1 (~0.3c), with a peak and mean value of ~42,000 km s-1 (~0.14c). The ionization parameter is very high and in the range log ξ ~ 3-6 erg s-1 cm, with a mean value of log ξ ~ 4.2 erg s-1 cm. The associated column densities are also large, in the range N H ~ 1022-1024 cm-2, with a mean value of N H ~ 1023 cm-2. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7 keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton-thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can

  1. Evidence for Ultra-Fast Outflows in Radio-Quiet AGNs. 2; Detailed Photoionization Modeling of Fe K-Shell Absorption Lines

    Tombesi, Francesco; Clapp, M.; Reeves, J. N.; Palumbo, G. G. C.; Braito, V.; Dadina, M.

    2011-01-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blue shifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and directly model the FeK absorbers with the Xstar photo-ionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35%. The outflow velocity distribution spans from \\sim10,000km/s (\\sim0.03c) up to \\siml00,000kmis (\\sim0.3c), with a peak and mean value of\\sim42,000km/s (\\sim0.14c). The ionization parameter is very high and in the range log\\xi 3-6 erg s/cm, with a mean value of log\\xi 4.2 erg s/cm. The associated column densities are also large, in the range N_H\\siml0(exp 22)-10(exp 24)/sq cm, with a mean value of N_H\\siml0(exp23)/sq cm. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can provide important clues on the connection between accretion disks, winds and jets.

  2. Absorption of volatile ruthenium

    Phase equilibrium and mass transfer measurements for the absorption of ruthenium tetroxide (RuO4) in aqueous and nitric acid solutions have been completed. Low concentration phase equilibrium measurements confirm that the system obeys Henry's law across 4 orders of magnitude in concentration. Mass transfer measurements from turbulent gas flow indicate that the diffusivity of RuO4 in air may increase slightly as its concentration is reduced by 5-6 orders of magnitude. The reaction of RuO4 with nitrous acid and nitrites in solution results in precipitated or colloidal RuO2. Initial, immediate decomposition of ∼ 50% of the RuO4 occurs at RuO4: HNO2 mole ratios between 10:1 and 1:2, and does not vary systematically with mole ratio in this range. A mathematical model of the RuO4 decontamination performance of a packed bed scrubber has been developed, and validated experimentally with a laboratory QVF system. A survey of modelling approaches for predicting the ruthenium decontamination performance of off-gas condensers has been carried out. (author)

  3. Zeeman atomic absorption spectroscopy

    A new method of background correction in atomic absorption spectroscopy has recently been introduced, based on the Zeeman splitting of spectral lines in a magnetic field. A theoretical analysis of the background correction capability observed in such instruments is presented. A Zeeman atomic absorption spectrometer utilizing a 50 Hz sine wave modulated magnetic field is described. (Auth.)

  4. Nutrition and magnesium absorption.

    Brink, E.J.

    1992-01-01

    The influence of various nutrients present in dairy products and soybean-based products on absorption of magnesium has been investigated. The studies demonstrate that soybean protein versus casein lowers apparent magnesium absorption in rats through its phytate component. However, true magnesium abs

  5. Petawatt laser absorption bounded

    Levy, Matthew C; Tabak, Max; Libby, Stephen B; Baring, Matthew G

    2014-01-01

    The interaction of petawatt ($10^{15}\\ \\mathrm{W}$) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light $f$, and even the range of $f$ is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that $f$ exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials.

  6. Comparison of box-air-mass-factors and radiances for Multiple-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) geometries calculated from different UV/visible radiative transfer models

    Wagner, T.; J. P. Burrows; Deutschmann, T.; Dix, B.; Von Friedeburg, C.; Frieß, U.; F. Hendrick; K.-P. Heue; Irie, H.; H. Iwabuchi; Y. Kanaya; Keller, J.; Mclinden, C. A.; Oetjen, H.; Palazzi, E.

    2007-01-01

    International audience The results of a comparison exercise of radiative transfer models (RTM) of various international research groups for Multiple AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) viewing geometry are presented. Besides the assessment of the agreement between the different models, a second focus of the comparison was the systematic investigation of the sensitivity of the MAX-DOAS technique under various viewing geometries and aerosol conditions. In contrast to...

  7. Optical absorption in irradiated natural beryl

    Three species of beryl irradiated with γ-rays of 60Co were studied by optical absorption. One became yellow and the other two Maxixe's blue. The effects of heat treatments were determined by the thermal isochronal decays of the optical absorption bands. Activation energies and frequency factor were obtained through the first order process kinetic model. Discussions lend us to assign for the UV band-edge the model of absorption by a hole center stabilized by a Fe2+ (substituting Al3+) ion in a neighbour oxygen. (Author)

  8. Gills as a glutathione-dependent metabolic barrier in Pacific oysters Crassostrea gigas: Absorption, metabolism and excretion of a model electrophile.

    Trevisan, Rafael; Mello, Danielle F; Delapedra, Gabriel; Silva, Danilo G H; Arl, Miriam; Danielli, Naissa M; Metian, Marc; Almeida, Eduardo A; Dafre, Alcir L

    2016-04-01

    The mercapturic acid pathway (MAP) is a major phase II detoxification route, comprising the conjugation of electrophilic substances to glutathione (GSH) in a reaction catalyzed by glutathione S-transferase (GST) enzymes. In mammals, GSH-conjugates are exported from cells, and the GSH-constituent amino acids (Glu/Gly) are subsequently removed by ectopeptidases. The resulting Cys-conjugates are reabsorbed and, finally, a mercapturic acid is generated through N-acetylation. This pathway, though very well characterized in mammals, is poorly studied in non-mammalian biological models, such as bivalve mollusks, which are key organisms in aquatic ecosystems, aquaculture activities and environmental studies. In the present work, the compound 1-chloro-2,4-dinitrobenzene (CDNB) was used as a model electrophile to study the MAP in Pacific oysters Crassostrea gigas. Animals were exposed to 10μM CDNB and MAP metabolites were followed over 24h in the seawater and in oyster tissues (gills, digestive gland and hemolymph). A rapid decay was detected for CDNB in the seawater (half-life 1.7h), and MAP metabolites peaked in oyster tissues as soon as 15min for the GSH-conjugate, 1h for the Cys-conjugate, and 4h for the final metabolite (mercapturic acid). Biokinetic modeling of the MAP supports the fast CDNB uptake and metabolism, and indicated that while gills are a key organ for absorption, initial biotransformation, and likely metabolite excretion, hemolymph is a possible milieu for metabolite transport along different tissues. CDNB-induced GSH depletion (4h) was followed by increased GST activity (24h) in the gills, but not in the digestive gland. Furthermore, the transcript levels of glutamate-cysteine ligase, coding for the rate limiting enzyme in GSH synthesis, and two phase II biotransformation genes (GSTpi and GSTo), presented a fast (4h) and robust (∼6-70 fold) increase in the gills. Waterborne exposure to electrophilic compounds affected gills, but not digestive gland

  9. Percutaneous absorption of nicotinic acid, phenol, benzoic acid and triclopyr butoxyethyl ester through rat and human skin in vitro: further validation of an in vitro model by comparison with in vivo data.

    Hotchkiss, S A; Hewitt, P; Caldwell, J; Chen, W L; Rowe, R R

    1992-10-01

    The in vitro percutaneous absorption of three model compounds, nicotinic acid, phenol and benzoic acid, and the herbicide triclopyr butoxyethyl ester (triclopyr BEE) has been investigated in flow-through diffusion cells using skin from male Fischer 344 rats and humans. After the application of the four chemicals to the epidermal surface of unoccluded full-thickness rat skin, the absorption of each compound across the skin and into the receptor fluid at 72 hr reached 3.7 +/- 0.3, 5.7 +/- 0.6, 26.7 +/- 3.7 and 48.3 +/- 1.2% (mean +/- SD, n = 2-7) of the applied dose for triclopyr BEE, nicotinic acid, phenol and benzoic acid, respectively. After the application of the four chemicals to the epidermal surface of unoccluded full-thickness human skin, the absorption of each compound across the skin and into the receptor fluid at 72 hr was significantly (P triclopyr BEE, nicotinic acid, phenol and benzoic acid, respectively. Occlusion of the skin surface with teflon caps often significantly (P < 0.05) enhanced the percutaneous absorption of the model compounds, although this effect was not uniform, varying with the compound under study and the skin (rat or human) used. When rat skin was occluded with teflon caps, the extent of absorption at 72 hr reached 8.6 +/- 0.8, 36.2 +/- 1.7 and 51.8 +/- 3.3% (mean +/- SD, n = 3-4) for nicotinic acid, phenol and benzoic acid, respectively. Corresponding values for human skin occluded with teflon caps were 3.3 +/- 1.6, 47.1 +/- 0.5 and 65.5 +/- 7.1% (mean +/- SD, n = 3-4). The experiments on the absorption of each model compound through rat and human skin were repeated and there was generally good agreement between the results from the two sets of experiments. The in vitro data reported compare favourably with data obtained by other workers using both in vitro and in vivo methodologies. The in vitro: in vivo correlation supports the use of the flow-through diffusion cell system as a model for the prediction of percutaneous absorption

  10. Quasar Absorption Studies

    Mushotzky, Richard (Technical Monitor); Elvis, Martin

    2004-01-01

    The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.

  11. Dust Sensitivity of Absorption-Line Indices

    MacArthur, L A

    2004-01-01

    We investigate the effects of dust extinction on integrated absorption-line indices that are widely used to derive constraints on the ages and metallicities of composite stellar systems. Typically, absorption-line studies have been performed on globular clusters or elliptical galaxies, which are mostly dust-free systems. However, many recent studies of integrated stellar populations have focused on spiral galaxies which may contain significant amounts of dust. It is almost universally assumed that the effects of dust extinction on absorption-line measurements are entirely negligible given the narrow baseline of the spectral features, but no rigorous study has yet been performed to verify this conjecture. In this analysis, we explore the sensitivity of the standard set of Lick absorption-line indices, the higher-order Balmer line indices, the 4000 A break, the near-IR calcium triplet indices, and the Rose indices to dust absorption according to population synthesis models that incorporate a multi-component mod...

  12. Optical absorption in LiF: Mg, Ti and its application to the Unified Interaction Model predictions of thermoluminescence dose response

    Issa, N.; Oster, L.; Horowitz, Y.S. [Physics Department, Ben Gurion University of the Negev, Beersheva, 84105 (Israel)

    2000-07-01

    The optical absorption (OA) spectrum of LiF: Mg, Ti has been investigated by I{sub m} - T{sub stop} pulsed annealing in steps of 3-4 C over the temperature range from 100 C to 300 C. In agreement with previous investigations, the 5.45 eV OA band is identified as a likely candidate for the recombination stage competitor responsible for composite peak 5 supra linearity. An additional OA band at 5.7 eV is also identified as a possible recombination stage competitor. First order kinetic analysis yields an activation energy of 0.80 {+-} 0.13 eV for the 4.0 eV band usually associated with peak 5, an energy which is similar in value to the binding energy of the Mg-Li{sub vac} trimer believed to form the peak 5 trapping structure. Dose response measurements result in dose filling constants of {beta} {sub TC} = 0.9 {+-} 0.1 x 10{sup -3} Gy{sup -1} and {beta} {sub cc} = 3.8 {+-} 0.8 x 10 {sup -4} Gy{sup -1} for the 4.0 eV and 5.45 eV OA bands respectively. It is demonstrated quantitatively in the framework of the Unified Interaction Model (UNIM) that the experimentally measured peak 5 supra linearity can be theoretically predicted for all possible dose response characteristics of the competitor, i.e., early, late or no entry into saturation up to dose levels of 5000 Gy. Previous objections in the literature to the identification of the 5.45 eV OA band as the recombination stage competitor are therefore judged invalid. (Author)

  13. Optical absorption in LiF: Mg, Ti and its application to the Unified Interaction Model predictions of thermoluminescence dose response

    The optical absorption (OA) spectrum of LiF: Mg, Ti has been investigated by Im - Tstop pulsed annealing in steps of 3-4 C over the temperature range from 100 C to 300 C. In agreement with previous investigations, the 5.45 eV OA band is identified as a likely candidate for the recombination stage competitor responsible for composite peak 5 supra linearity. An additional OA band at 5.7 eV is also identified as a possible recombination stage competitor. First order kinetic analysis yields an activation energy of 0.80 ± 0.13 eV for the 4.0 eV band usually associated with peak 5, an energy which is similar in value to the binding energy of the Mg-Livac trimer believed to form the peak 5 trapping structure. Dose response measurements result in dose filling constants of β TC = 0.9 ± 0.1 x 10-3 Gy-1 and β cc = 3.8 ± 0.8 x 10 -4 Gy-1 for the 4.0 eV and 5.45 eV OA bands respectively. It is demonstrated quantitatively in the framework of the Unified Interaction Model (UNIM) that the experimentally measured peak 5 supra linearity can be theoretically predicted for all possible dose response characteristics of the competitor, i.e., early, late or no entry into saturation up to dose levels of 5000 Gy. Previous objections in the literature to the identification of the 5.45 eV OA band as the recombination stage competitor are therefore judged invalid. (Author)

  14. Strategies for absorption screening in drug discovery and development

    Bohets, H; Annaert, Pieter; Mannens, G.; van Beijsterveldt, L; Anciaux, K.; Verboven, P.; Meuldermans, W; Lavrijsen, K.

    2001-01-01

    This review gives an overview of the current approaches to evaluate drug absorption potential in the different phases of drug discovery and development. Methods discussed include in silico models, artificial membranes as absorption models, in vitro models such as the Ussing chamber and Caco-2 monolayers, in situ rat intestinal perfusion and in vivo absorption studies. In silico models such as iDEATM can help optimizing chemical synthesis since the fraction absorbed (Fa) can be predicted based...

  15. Absorptive capacity and smart companies

    Patricia Moro González

    2014-12-01

    Full Text Available Purpose: The current competitive environment is substantially modifying the organizations’ learning processes due to a global increase of available information allowing this to be transformed into knowledge. This opportunity has been exploited since the nineties by the tools of “Business Analytics” and “Business Intelligence” but, nevertheless, being integrated in the study of new organizational capacities engaged in the process of creating intelligence inside organizations is still an outstanding task. The review of the concept of absorptive capacity and a detailed study from the perspective of this new reality will be the main objective of study of this paper.Design/methodology/approach: By comparing classical absorptive capacity and absorptive capacity from the point of view of information management tools in each one of the three stages of the organizational learning cycle, some gaps of the former are overcome/fulfilled. The academic/bibliographical references provided in this paper have been obtained from ISI web of knowledge, Scopus and Dialnet data bases, supporting the state of affairs on absorptive capacity and thereafter filtering by "Business Intelligence" and "Business Analytics". Specialized websites and Business Schools` Publications there have also been included, crowning the content on information management tools used that are currently used in the strategic consulting.Findings: Our contribution to the literature is the development of "smart absorptive capacity". This is a new capacity emerging from the reformulation of the classical concept of absorptive capacity wherein some aspects of its definition that might have been omitted are emphasized. The result of this new approach is the creation of a new Theoretical Model of Organizational Intelligence, which aims to explain, within the framework of the Resources and Capabilities Theory, the competitive advantage achieved by the so-called smart companies

  16. Absorptive capacity in organizational theories: learning, innovation, managerial cognition

    O.A. Vasylieva

    2013-01-01

    The paper studies an important issue of absorptive capacity that enables the companies to strengthen their position in the competitive global market. The concept of absorptive capacity in open innovation paradigm is defined within the following organizational theories: learning, innovation and managerial cognition. The model which links together and clarifies in a detailed way the relationships between absorptive capacity and the components is proposed.

  17. Zeeman atomic absorption spectrometry

    The design and development of a Zeeman atomic absorption spectrometer for trace element analysis are described. An instruction manual is included which details the operation, adjustment, and maintenance. Specifications and circuit diagrams are given

  18. Evidence for ultra-fast outflows in radio-quiet AGNs: II - detailed photo-ionization modeling of Fe K-shell absorption lines

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Palumbo, G.G.C.; Braito, V.; Dadina, M.

    2011-01-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blueshifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and direct...

  19. Temperature dependence of the HNO3 UV absorption cross sections

    Burkholder, James B.; Talukdar, Ranajit K.; Ravishankara, A. R.; Solomon, Susan

    1993-01-01

    The temperature dependence of the HNO3 absorption cross sections between 240 and 360 K over the wavelength range 195 to 350 nm has been measured using a diode array spectrometer. Absorption cross sections were determined using both (1) absolute pressure measurements at 298 K and (2) a dual absorption cell arrangement in which the absorption spectrum at various temperatures is measured relative to the room temperature absorption spectrum. The HNO3 absorption spectrum showed a temperature dependence which is weak at short wavelengths but stronger at longer wavelengths which are important for photolysis in the lower stratosphere. The 298 K absorption cross sections were found to be larger than the values currently recommended for atmospheric modeling (DeMore et al., 1992). Our absorption cross section data are critically compared with the previous measurements of both room temperature and temperature-dependent absorption cross sections. Temperature-dependent absorption cross sections of HNO3 are recommended for use in atmospheric modeling. These temperature dependent HNO3 absorption cross sections were used in a two-dimensional dynamical-photochemical model to demonstrate the effects of the revised absorption cross sections on loss rate of HNO3 and the abundance of NO2 in the stratosphere.

  20. Effect of oils on drug absorption

    Palin, K.J.

    1981-01-01

    Oil and emulsion vehicles have been shown to alter the oral absorption of many drugs. This may be due to enhanced lymph flow and/or altered gastro-intestinal motility in the presence of the oils. The oral absorption of a model compound (DOT) in the presence of three chemically different oils, arachis oil, Miglyol 812 and liquid paraffin was investigated in rats, the influence of lymphatic absorption and gastro-intestinal motility being determined. The findings were applied to the for.mulat...

  1. Seven-effect absorption refrigeration

    DeVault, Robert C.; Biermann, Wendell J.

    1989-01-01

    A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit.

  2. Bioavailability of iron in geophagic earths and clay minerals, and their effect on dietary iron absorption using an in vitro digestion/Caco-2 cell model

    Geophagy, the deliberate consumption of earth, is strongly associated with iron (Fe) deficiency. It has been proposed that geophagy may be practiced as a means to improve Fe status by increasing Fe intakes and, conversely, that geophagy may cause Fe deficiency by inhibiting Fe absorption. We tested ...

  3. The Spectral Variability of the GHz-Peaked Spectrum Radio Source PKS 1718-649 and a Comparison of Absorption Models

    Tingay, S J; Collier, J D; Rees, G; Callingham, J R; Stevens, J; Carretti, E; Wayth, R B; Wong, G F; Trott, C M; McKinley, B; Bernardi, G; Bowman, J D; Briggs, F; Cappallo, R J; Corey, B E; Deshpande, A A; Emrich, D; Gaensler, B M; Goeke, R; Greenhill, L J; Hazelton, B J; Johnston-Hollitt, M; Kaplan, D L; Kasper, J C; Kratzenberg, E; Lonsdale, C J; Lynch, M J; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Oberoi, D; Ord, S M; Prabu, T; Rogers, A E E; Roshi, A; Shankar, N Udaya; Srivani, K S; Subrahmanyan, R; Waterson, M; Webster, R L; Whitney, A R; Williams, A; Williams, C L

    2014-01-01

    Using the new wideband capabilities of the Australia Telescope Compact Array (ATCA), we obtain spectra for PKS 1718-649, a well-known gigahertz-peaked spectrum radio source. The observations, between approximately 1 and 10 GHz over three epochs spanning approximately 21 months, reveal variability both above the spectral peak at ~3 GHz and below the peak. The combination of the low and high frequency variability cannot be easily explained using a single absorption mechanism, such as free-free absorption or synchrotron self-absorption. We find that the PKS 1718-649 spectrum and its variability are best explained by variations in the free-free optical depth on our line-of-sight to the radio source at low frequencies (below the spectral peak) and the adiabatic expansion of the radio source itself at high frequencies (above the spectral peak). The optical depth variations are found to be plausible when X-ray continuum absorption variability seen in samples of Active Galactic Nuclei is considered. We find that the ...

  4. Seasonal Solar Thermal Absorption Energy Storage Development.

    Daguenet-Frick, Xavier; Gantenbein, Paul; Rommel, Mathias; Fumey, Benjamin; Weber, Robert; Gooneseker, Kanishka; Williamson, Tommy

    2015-01-01

    This article describes a thermochemical seasonal storage with emphasis on the development of a reaction zone for an absorption/desorption unit. The heat and mass exchanges are modelled and the design of a suitable reaction zone is explained. A tube bundle concept is retained for the heat and mass exchangers and the units are manufactured and commissioned. Furthermore, experimental results of both absorption and desorption processes are presented and the exchanged power is compared to the results of the simulations. PMID:26842331

  5. Atmospheric absorption of terahertz radiation and water vapor continuum effects

    The water vapor continuum absorption spectrum was investigated using Fourier Transform Spectroscopy. The transmission of broadband terahertz radiation from 0.300 to 1.500 THz was recorded for multiple path lengths and relative humidity levels. The absorption coefficient as a function of frequency was determined and compared with theoretical predictions and available water vapor absorption data. The prediction code is able to separately model the different parts of atmospheric absorption for a range of experimental conditions. A variety of conditions were accurately modeled using this code including both self and foreign gas broadening for low and high water vapor pressures for many different measurement techniques. The intensity and location of the observed absorption lines were also in good agreement with spectral databases. However, there was a discrepancy between the resonant line spectrum simulation and the observed absorption spectrum in the atmospheric transmission windows caused by the continuum absorption. A small discrepancy remained even after using the best available data from the literature to account for the continuum absorption. From the experimental and resonant line simulation spectra the air-broadening continuum parameter was calculated and compared with values available in the literature. -- Highlights: •Broadband absorption measurements of water vapor were performed at 300–1500 GHz. •The absorption coefficient of water vapor was modeled and compared with data. •The air-broadened continuum coefficient for water vapor was determined. •The modeled absorption coefficient is presented for 10–90% humidity at 0–3 THz

  6. Vitamin A absorption

    Investigation of the absorption of vitamin A and related substances is complicated by the multiplicity of forms in which they occur in the diet and by the possibility that they may be subject to different mechanisms of absorption. Present knowledge of these mechanisms is inadequate, especially in the case of carotenoids. Numerous tests of absorption have been developed. The most common has been the biochemical measurement of the rise in plasma vitamin A after an oral dose of retinol or retinyl ester, but standardization is inadequate. Radioisotope tests based upon assay of serum or faecal activity following oral administration of tritiated vitamin A derivaties hold considerable promise, but again standardization is inadequate. From investigations hitherto performed it is known that absorption of vitamin A is influenced by several diseases, although as yet the consistency of results and the correlation with other tests of intestinal function have often been poor. However, the test of vitamin A absorption is nevertheless of clinical importance as a specialized measure of intestinal function. (author)

  7. Central cooling: absorptive chillers

    Christian, J.E.

    1977-08-01

    This technology evaluation covers commercially available single-effect, lithium-bromide absorption chillers ranging in nominal cooling capacities of 3 to 1,660 tons and double-effect lithium-bromide chillers from 385 to 1,060 tons. The nominal COP measured at operating conditions of 12 psig input steam for the single-effect machine, 85/sup 0/ entering condenser water, and 44/sup 0/F exiting chilled-water, ranges from 0.6 to 0.65. The nominal COP for the double-effect machine varies from 1.0 to 1.15 with 144 psig entering steam. Data are provided to estimate absorption-chiller performance at off-nominal operating conditions. The part-load performance curves along with cost estimating functions help the system design engineer select absorption equipment for a particular application based on life-cycle costs. Several suggestions are offered which may be useful for interfacing an absorption chiller with the remaining Integrated Community Energy System. The ammonia-water absorption chillers are not considered to be readily available technology for ICES application; therefore, performance and cost data on them are not included in this evaluation.

  8. QED-driven laser absorption

    Levy, M C; Ratan, N; Sadler, J; Ridgers, C P; Kasim, M; Ceurvorst, L; Holloway, J; Baring, M G; Bell, A R; Glenzer, S H; Gregori, G; Ilderton, A; Marklund, M; Tabak, M; Wilks, S C; Norreys, P A

    2016-01-01

    Absorption covers the physical processes which convert intense photon flux into energetic particles when a high-power laser illuminates optically-thick matter. It underpins important petawatt-scale applications today, e.g., medical-quality proton beam production. However, development of ultra-high-field applications has been hindered since no study so far has described absorption throughout the entire transition from the classical to the quantum electrodynamical (QED) regime of plasma physics. Here we present a model of absorption that holds over an unprecedented six orders-of-magnitude in optical intensity and lays the groundwork for QED applications of laser-driven particle beams. We demonstrate 58% efficient \\gamma-ray production at $1.8\\times 10^{25}~\\mathrm{W~ cm^{-2}}$ and the creation of an anti-matter source achieving $4\\times 10^{24}\\ \\mathrm{positrons}\\ \\mathrm{cm^{-3}}$, $10^{6}~\\times$ denser than of any known photonic scheme. These results will find applications in scaled laboratory probes of bla...

  9. Percutaneous absorption from soil.

    Andersen, Rosa Marie; Coman, Garrett; Blickenstaff, Nicholas R; Maibach, Howard I

    2014-01-01

    Abstract Some natural sites, as a result of contaminants emitted into the air and subsequently deposited in soil or accidental industrial release, have high levels of organic and non-organic chemicals in soil. In occupational and recreation settings, these could be potential sources of percutaneous exposure to humans. When investigating percutaneous absorption from soil - in vitro or vivo - soil load, particle size, layering, soil "age" time, along with the methods of performing the experiment and analyzing the results must be taken into consideration. Skin absorption from soil is generally reduced compared with uptake from water/acetone. However, the absorption of some compounds, e.g., pentachlorophenol, chlorodane and PCB 1254, are similar. Lipophilic compounds like dichlorodiphenyltrichloroethane, benzo[A]pyrene, and metals have the tendency to form reservoirs in skin. Thus, one should take caution in interpreting results directly from in vitro studies for risk assessment; in vivo validations are often required for the most relevant risk assessment. PMID:25205703

  10. Observation of different phytoplankton groups and biomass using Differential Optical Absorption Spectroscopy on SCIAMACHY data and comparisons to in-situ, NASA biogeochemical Model and MERIS

    Bracher, Astrid; Taylor, Bettina; M. Vountas; Dinter, Tilman; J. P. Burrows; R. Röttgers; Peeken, Ilka

    2008-01-01

    In order to understand the marine phytoplanktons role in the global marine ecosystem and biogeochemical cycles it is necessary to derive global information on the distribution of major functional phytoplankton types (PFT) in the world oceans. In our study we use instead of the common ocean color sensors such as CZCS, SeaWiFS, MODIS, MERIS, with rather low spectral resolution, the Differential Optical Absorption Spectroscopy (DOAS) to study the retrieval of phytoplankton distribution and absor...

  11. Study of O, N, and F absorption in calcium-thermal alloy Zr 1% Nb (KTTs - 110) during fuel element model preparation

    The nuclear-physical methods of analysis (NPMA) are used to research an absorption of impurities (oxygen, nitrogen) from the technological environments during operations of welding of hardware products from zirconium alloys doped 1%Nb, and fluorine after a technological etching in solutions containing of fluorine. The techniques and engineering of carrying out of NPMA are described, the impurity concentrations of oxygen, nitrogen, fluorine and their allocation in surface layers of welded seams are defined before and after chemical treatments

  12. Absorption Spectra of Astaxanthin Aggregates

    Olsina, Jan; Durchan, Milan; Minofar, Babak; Polivka, Tomas; Mancal, Tomas

    2012-01-01

    Carotenoids in hydrated polar solvents form aggregates characterized by dramatic changes in their absorption spectra with respect to monomers. Here we analyze absorption spectra of aggregates of the carotenoid astaxanthin in hydrated dimethylsulfoxide. Depending on water content, two types of aggregates were produced: H-aggregates with absorption maximum around 390 nm, and J-aggregates with red-shifted absorption band peaking at wavelengths >550 nm. The large shifts with respect to absorption...

  13. Is oral absorption of vigabatrin carrier-mediated?

    Nøhr, M. K.; Juul, R. V.; Thale, Z. I.; Holm, R.; Kreilgaard, M.; Nielsen, Carsten Uhd

    2015-01-01

    The aim of the study was to investigate the intestinal transport mechanisms responsible for vigabatrin absorption in rats by developing a population pharmacokinetic (PK) model of vigabatrin oral absorption. The PK model was used to investigate whether vigabatrin absorption was carrier-mediated and...... if the proton-coupled amino acid transporter 1 (PAT1) was involved in the absorption processes. Vigabatrin (0.3-300 mg/kg) was administered orally or intravenously to Sprague Dawley rats in the absence or presence of PAT1-ligands l-proline, l-tryptophan or sarcosine. The PK profiles of vigabatrin...... were described by mechanistic non-linear mixed effects modelling, evaluating PAT1-ligands as covariates on the PK parameters with a full covariate modelling approach. The oral absorption of vigabatrin was adequately described by a Michaelis-Menten type saturable absorption. Using a Michaelis constant...

  14. High temperature measurement of water vapor absorption

    Keefer, Dennis; Lewis, J. W. L.; Eskridge, Richard

    1985-01-01

    An investigation was undertaken to measure the absorption coefficient, at a wavelength of 10.6 microns, for mixtures of water vapor and a diluent gas at high temperature and pressure. The experimental concept was to create the desired conditions of temperature and pressure in a laser absorption wave, similar to that which would be created in a laser propulsion system. A simplified numerical model was developed to predict the characteristics of the absorption wave and to estimate the laser intensity threshold for initiation. A non-intrusive method for temperature measurement utilizing optical laser-beam deflection (OLD) and optical spark breakdown produced by an excimer laser, was thoroughly investigated and found suitable for the non-equilibrium conditions expected in the wave. Experiments were performed to verify the temperature measurement technique, to screen possible materials for surface initiation of the laser absorption wave and to attempt to initiate an absorption wave using the 1.5 kW carbon dioxide laser. The OLD technique was proven for air and for argon, but spark breakdown could not be produced in helium. It was not possible to initiate a laser absorption wave in mixtures of water and helium or water and argon using the 1.5 kW laser, a result which was consistent with the model prediction.

  15. Two-Phonon Absorption

    Hamilton, M. W.

    2007-01-01

    A nonlinear aspect of the acousto-optic interaction that is analogous to multi-photon absorption is discussed. An experiment is described in which the second-order acousto-optically scattered intensity is measured and found to scale with the square of the acoustic intensity. This experiment using a commercially available acousto-optic modulator is…

  16. Chemical Absorption Materials

    Thomsen, Kaj

    2011-01-01

    Chemical absorption materials that potentially can be used for post combustion carbon dioxide capture are discussed. They fall into five groups, alkanolamines, alkali carbonates, ammonia, amino acid salts, and ionic liquids. The chemistry of the materials is discussed and advantages and drawbacks...

  17. ZINC ABSORPTION BY INFANTS

    Zinc is a vital mineral in human nutrition, and rare cases of overt zinc deficiency are well described in term and preterm infants. A variety of methods have been developed to assess zinc absorption, retention, and balance in humans, either using mass (metabolic) balance or stable isotope-based METH...

  18. Absorption driven focus shift

    Harrop, N.; Wolf, S.; Maerten, O.; Dudek, K.; Ballach, S.; Kramer, R.

    2016-03-01

    Modern high brilliance near infrared lasers have seen a tremendous growth in applications throughout the world. Increased productivity has been achieved by higher laser power and increased brilliance of lasers. Positive impacts on the performance and costs of parts are opposed to threats on process stability and quality, namely shift of focus position over time. A high initial process quality will be reduced by contamination of optics, eventually leading to a focus shift or even destruction of the optics. Focus analysis at full power of multi-kilowatt high brilliance lasers is a very demanding task because of high power densities in the spot and the high power load on optical elements. With the newly developed high power projection optics, the High-Power Micro-Spot Monitor High Brilliance (HP-MSM-HB) is able to measure focus diameter as low as 20 μm at power levels up to 10 kW at very low internal focus shift. A main driving factor behind thermally induced focus shift is the absorption level of the optical element. A newly developed measuring system is designed to determine the relative absorption level in reference to a gold standard. Test results presented show a direct correlation between absorption levels and focus shift. The ability to determine the absorption level of optical elements as well as their performance at full processing power before they are put to use, enables a high level of quality assurance for optics manufacturers and processing head manufacturers alike.

  19. Radiation Absorption Mechanism in Nonvolatile MNOS Structure

    2002-01-01

    The γ-ray radiation will speed up the discharge of the stored charge in nonvolatile MNOS structure. The radiation absorption mechanism to enhance the discharge is discussed. A direct radiation emission model from the interface traps distributing both in energy level and in space is given. The theoretical results based on this model are in good agreement with experimental measurement.

  20. Aerosol scattering and absorption during the EUCAARI-LONGREX flights of the Facility for Airborne Atmospheric Measurements (FAAM BAe-146: can measurements and models agree?

    E. J. Highwood

    2012-08-01

    Full Text Available Scattering and absorption by aerosol in anthropogenically perturbed air masses over Europe has been measured using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA operated by the Facility for Airborne Atmospheric Measurements (FAAM on 14 flights during the EUCAARI-LONGREX campaign in May 2008. The geographical and temporal variations of the derived shortwave optical properties of aerosol are presented. Values of single scattering albedo of dry aerosol at 550 nm varied considerably from 0.86 to near unity, with a campaign average of 0.93 ± 0.03. Dry aerosol optical depths ranged from 0.030 ± 0.009 to 0.24 ± 0.07. An optical properties closure study comparing calculations from composition data and Mie scattering code with the measured properties is presented. Agreement to within measurement uncertainties of 30% can be achieved for both scattering and absorption, but the latter is shown to be sensitive to the refractive indices chosen for organic aerosols, and to a lesser extent black carbon, as well as being highly dependent on the accuracy of the absorption measurements. Agreement with the measured absorption can be achieved either if organic carbon is assumed to be weakly absorbing, or if the organic aerosol is purely scattering and the absorption measurement is an overestimate due to the presence of large amounts of organic carbon. Refractive indices could not be inferred conclusively due to this uncertainty, despite the enhancement in methodology compared to previous studies that derived from the use of the black carbon measurements. Hygroscopic growth curves derived from the wet nephelometer indicate moderate water uptake by the aerosol with a campaign mean f(RH value (ratio in scattering of 1.5 (range from 1.23 to 1.63 at 80% relative humidity. This value is qualitatively consistent with the major chemical components of the aerosol measured by the aerosol mass spectrometer, which are primarily

  1. Investigation of two-photon absorption induced excited state absorption in a fluorenyl-based chromophore.

    Li, Changwei; Yang, Kun; Feng, Yan; Su, Xinyan; Yang, Junyi; Jin, Xiao; Shui, Min; Wang, Yuxiao; Zhang, Xueru; Song, Yinglin; Xu, Hongyao

    2009-12-01

    Two-photon absorption induced excited state absorption in the solution of a new fluorenyl-based chromophore is investigated by a time-resolved pump-probe technique using femtosecond pulses. With the help of an additional femtosecond open-aperture Z-scan technique, numerical simulations based on a three-energy level model are used to interpret the experimental results, and we determine the nonlinear optical parameters of this new chromophore uniquely. Large two-photon absorption cross section and excited state absorption cross section for singlet excited state are obtained, indicating a good candidate for optical limiting devices. Moreover, the influence of two-beam coupling induced energy transfer in neat N,N'-dimethylformamide solvent is also considered, although this effect is strongly restrained by the instantaneous two-photon absorption. PMID:19894682

  2. Percutaneous absorption in diseased skin: an overview.

    Chiang, Audris; Tudela, Emilie; Maibach, Howard I

    2012-08-01

    The stratum corneum's (SC) functions include protection from external hazardous environments, prevention of water loss and regulation of body temperature. While intact skin absorption studies are abundant, studies on compromised skin permeability are less common, although products are often used to treat affected skin. We reviewed literature on percutaneous absorption through abnormal skin models. Tape stripping is used to disrupt water barrier function. Studies demonstrated that physicochemical properties influence the stripping effect: water-soluble drugs are more affected. Abrasion did not affect absorption as much. Freezing is commonly used to preserve skin. It does not seem to modify water absorption, but still increases the penetration of compounds. Comparatively, heating the skin consistently increased percutaneous absorption. Removing SC lipids may increase percutaneous absorption of drugs. Many organic solvents are employed to delipidize. Delipidization with chloroform-methanol increased hydrophilic compound permeability, but not lipophilic. Acetone pre-treatment enhanced hydrophilic compound penetration. More data is needed to determine influence on highly lipophilic compound penetration. Sodium lauryl sulfate (SLS) induces irritant dermatitis and is frequently used as a model. Studies revealed that SLS increases hydrophilic compound absorption, but not lipophilic. However, skin irritation with other chemicals increases lipophilic penetration as much as hydrophilic. Animal studies show that UV exposure increases percutaneous absorption whereas human studies do not. Human studies show increased penetration in psoriatic and atopic dermatitis skin. The data summarized here begin to characterize flux alteration associated with damaged skin. Understanding the degree of alteration requires interpretation of involved conditions and the enlarging of our database to a more complete physicochemical spectrum. PMID:22912973

  3. On resonance absorption and continuum damping

    The absorption of power is studied with fluid and gyrokinetic plasma models, when two Alfven or ion-ion hybrid resonances provide for a weak damping in a partially standing wave-field. Examples chosen in slab and toroidal geometry show that the fluid predictions based on resonance absorption are generally very different from the Landau damping of mode-converted slow down. They in particular suggest that the continuum damping of toroidal Alfven eigenmodes (TAE) and the power deposition profiles obtained in the ion-cyclotron range of frequencies (ICRF) using fluid plasma models are very misleading. (author) 2 figs., 1 tab., 18 refs

  4. Analysis of the impact of controlled release formulations on oral drug absorption, gut wall metabolism and relative bioavailability of CYP3A substrates using a physiologically-based pharmacokinetic model.

    Olivares-Morales, Andrés; Kamiyama, Yoshiteru; Darwich, Adam S; Aarons, Leon; Rostami-Hodjegan, Amin

    2015-01-25

    Controlled release (CR) formulations are usually designed to achieve similar exposure (AUC) levels as the marketed immediate release (IR) formulation. However, the AUC is often lower following CR compared to IR formulations. There are a few exceptions when the CR formulations have shown higher AUC. This study investigated the impact of CR formulations on oral drug absorption and CYP3A4-mediated gut wall metabolism. A review of the current literature on relative bioavailability (Frel) between CR and IR formulations of CYP3A substrates was conducted. This was followed by a systematic analysis to assess the impact of the release characteristics and the drug-specific factors (including metabolism and permeability) on oral bioavailability employing a physiologically-based pharmacokinetic (PBPK) modelling and simulation approach. From the literature review, only three CYP3A4 substrates showed higher Frel when formulated as CR. Several scenarios were investigated using the PBPK approach; in most of them, the oral absorption of CR formulations was lower as compared to the IR formulations. However, for highly permeable compounds that were CYP3A4 substrates the reduction in absorption was compensated by an increase in the fraction that escapes from first pass metabolism in the gut wall (FG), where the magnitude was dependent on CYP3A4 affinity. The systematic simulations of various interplays between different parameters demonstrated that BCS class 1 highly-cleared CYP3A4 substrates can display up to 220% higher relative bioavailability when formulated as CR compared to IR, in agreement with the observed data collected from the literature. The results and methodology of this study can be employed during the formulation development process in order to optimize drug absorption, especially for CYP3A4 substrates. PMID:25444842

  5. Analysis of Decentralized Control for Absorption Cycle Heat Pumps

    Vinther, Kasper; Just Nielsen, Rene; Nielsen, Kirsten Mølgaard; Andersen, Palle; Pedersen, Tom Søndergård; Bendtsen, Jan Dimon

    Email Print Request Permissions This paper investigates decentralized control structures for absorption cycle heat pumps and a dynamic nonlinear model of a single-effect LiBr-water absorption system is used as case study. The model has four controllable inputs, which can be used to stabilize the...

  6. Absorptive Capacity and Diversity

    Kristinsson, Kári

    One of the most influential contributions to neo-Schumpeterian economics is Cohen and Levinthal‘s papers on absorptive capacity. Since their publication in the late 1980s and early 1990s the concept absorptive capacity has had substantial impact on research in economics and management, including...... international business, organizational economics, strategic management, technology management and last but not least neo-Schumpeterian economics. The goal of this dissertation is to examine what many consider as neglected arguments from the work by Cohen and Levinthal and thereby illuminate an otherwise...... overlooked area of research. Although research based on Cohen and Levinthal‘s work has made considerable impact, there is scarcity of research on certain fundamental points argued by Cohen and Levinthal. Among these is the importance of employee diversity as well as the type and nature of interaction between...

  7. Spectral Absorption Properties of Atmospheric Aerosols

    Bergstrom, R. W.; Pilewskie, P.; Russell, P. B.; Redemann, J.; Bond, T. C.; Quinn, P. K.; Sierau, B.

    2007-01-01

    We have determined the solar spectral absorption optical depth of atmospheric aerosols for specific case studies during several field programs (three cases have been reported previously; two are new results). We combined airborne measurements of the solar net radiant flux density and the aerosol optical depth with a detailed radiative transfer model for all but one of the cases. The field programs (SAFARI 2000, ACE Asia, PRIDE, TARFOX, INTEX-A) contained aerosols representing the major absorbing aerosol types: pollution, biomass burning, desert dust and mixtures. In all cases the spectral absorption optical depth decreases with wavelength and can be approximated with a power-law wavelength dependence (Absorption Angstrom Exponent or AAE). We compare our results with other recent spectral absorption measurements and attempt to briefly summarize the state of knowledge of aerosol absorption spectra in the atmosphere. We discuss the limitations in using the AAE for calculating the solar absorption. We also discuss the resulting spectral single scattering albedo for these cases.

  8. Salmon Protamine Decreases Serum and Liver Lipid Contents by Inhibiting Lipid Absorption in an In Vitro Gastrointestinal Digestion Model and in Rats.

    Hosomi, Ryota; Miyauchi, Kazumasa; Yamamoto, Daiki; Arai, Hirofumi; Nishiyama, Toshimasa; Yoshida, Munehiro; Fukunaga, Kenji

    2015-10-01

    Protamine has been used as an antiheparin drug and a natural preservative in various food products. However, limited studies have evaluated the physicochemical and functional properties of protamine. Hence, we assessed the mechanisms underlying the inhibition of lipid absorption following salmon protamine intake in in vitro and in vivo studies. In initial experiments, a salmon protamine hydrolyzate (PH) was prepared using in vitro simulated gastrointestinal digestion suppressed pancreatic lipase activity and micellar cholesterol solubility. This PH had higher bile acid-binding capacity and emulsion breakdown activity than casein hydrolyzate and l-arginine. However, the hypolipidemic functions of protamine were dramatically reduced by pancreatin digestion. In further experiments, groups of male Wistar rats were fed an AIN-93G diet containing 5% (wt/wt) salmon protamine or a protamine amino acid mixture. After 4 wk of feeding with experimental diets, reductions in serum and liver triacylglycerol (TAG) and cholesterol contents were observed in the presence of protamine, reflecting inhibition of TAG, cholesterol, and bile acid absorption. These data suggest that the formation of insoluble PH-bile acid complexes is critical before the bile acid-binding capacity is reduced. Therefore, dietary salmon protamine may ameliorate lifestyle-related diseases such as hyperlipidemia and obesity. PMID:26352573

  9. Analytical modeling and experimental investigation on optical properties of new class of nanofluids (Al2O3-CuO binary nanofluids) for direct absorption solar thermal energy

    Menbari, Amir; Alemrajabi, Ali Akbar

    2016-02-01

    Nanofluids play a major role in many modern engineering processes. Binary nanofluids are a new class of nanofluids that are prepared by dispersing simultaneously two dissimilar nanoparticles in a base fluid. They offer a good potential for use in direct absorption solar systems. The present study investigates both experimentally and analytically the optical properties of binary nanofluids for direct absorption in solar applications. For this purpose, two dissimilar nanoparticles, i.e. CuO and γ-Al2O3, are dispersed in water, ethylene glycol, and the ethylene glycol-water mixture to form binary nanofluids. In addition, a new method is developed for calculating the extinction coefficient of the binary nanofluids based on the classical electromagnetic theory. It will be shown that the extinction coefficients obtained from both analytical and experimental studies are in good agreement. Moreover, the extinction coefficient of the binary nanofluids is found to be approximately equal to the sum of the extinction coefficients of the constituent components, determined both analytically and experimentally. By increasing the nanoparticle volume fraction, improvements are observed in the extinction coefficient of the binary nanofluids prepared. Also, the analytical and experimental results of the study show that the extinction coefficient of the binary nanoparticles dispersed in water as the "base fluid" is greater than those of the binary nanoparticles dispersed in ethylene glycol or the mixture of ethylene glycol-water.

  10. 细胞共培养模型在口服药物吸收研究中的应用%Application of cell co-culture models in absorption of oral drug

    黎迎; 朱春燕

    2015-01-01

    细胞共培养体系能很好地模拟人体小肠生理环境,准确预测药物在肠道内的转运和代谢情况,增强体外细胞模型与整体动物实验研究之间的相关性,近年来在评价口服药物吸收方面发挥着越发重要的作用,已成为新药研发过程中评价药物口服吸收的热点。综述体外模拟肠道环境的细胞共培养模型,并对其应用于口服药物研发的体外评价吸收做出展望。%Cell co-culture system can better simulate the inner environment of human body ,predict drug transport and metabolism in intestinal environment and increase the relation between in vitro cell model and integral animal test .In recent years ,co-culture cell model plays an increasingly important role in evaluating the absorption of oral drugs ,which becomes the highlight in the evaluation of drug oral absorption during new drug discovery .This essay summarized co-culture cell model which simulates intestinal environment and their application ,and looked into the future of their application in evaluating oral drug intestinal absorption during oral drug discovery .

  11. Enhanced Water Vapor Absorption within Tropospheric Clouds: A Partial Explanation for Anomalous Absorption

    Crisp, David; Zuffada, Cinzia

    1996-01-01

    Comparisons between solar flux measurements and predictions obtained from theoretical radiative transfer models indicate that most of these models underestimate the globally averaged solar energy absorbed by cloudy atmospheres by up to 25Wm&sup-2;.The origin of this anomalous absorption has not yet been established, but it has been attributed to a variety of sources including oversimplified or missing physical processes in the existing models, uncertainties in the input data, and even measurement errors. We used a sophisticated atmospheric radiative transfer model to provide improved constraints on the physical processes that contribute to the absorption of solar radiation by Earth's atmosphere. The results are described herein.

  12. 脂质制剂体外动态肠吸收模型的建立及评价%Establishment and evaluation of a dynamic in vitro intestinal absorption model of lipid formulations

    刘颖; 易涛; 宦娣; 肖璐; 何吉奎

    2011-01-01

    A new dynamic in vitro intestinal absorption model for screening and evaluating lipid formulations was established by means of the characteristics of the intestinal digestion and absorption of the lipid formulations. This model was composed of two systems, including intestinal digestion and the intestinal tissue culture, which drew the evaluation method of intestinal absorption into the in vitro lipolysis model. The influence of several important model parameters such as Ca2+, D-glucose, K+ on the two systems of this model has been investigated. The results showed that increasing of Ca2+ concentration could be significantly conductive to intestinal digestion. The increasing of .D-glucose concentration could stepped significantly down the decay of the intestinal activity. K+ was able to maintain intestinal activity, but the influence of different concentration levels on the decay of the intestinal activity was of no significant difference. Thus the model parameters were set up as follows: Ca2+ for 10 mmol-L-1, D-glucose for 15 mmol-L-1 and K+ for 5.5 mmol-L-1. Type I lipid formulation was evaluated with this model, and there was a significant correlation between the absorption curve in vitro and absorption curve in vivo of rats (r = 0.995 6, P < 0.01). These results demonstrated that this model can be an attractive and great potential method for the screening, evaluating and predicting of the lipid formulations.%根据脂质制剂肠消化吸收的特性,本文在体外脂解模型基础上,引入肠吸收评价方法,建立了一种用于筛选评价脂质制剂的新型体外动态肠吸收模型,包括肠消化和肠组织培养两大体系.探究模型重要参数(Ca2+、葡萄糖、K+)的影响,发现Ca2+浓度的增加能显著增强脂质制剂的肠消化;葡萄糖浓度的递增能显著减慢肠组织活性衰减;K+虽能维持肠组织的活性,但其浓度变化对肠组织活性衰减并无显著性影响;最终选择Ca2+l0 mmol·L-1、葡萄糖15 mmol

  13. Sensitivity of the CCM climate to enhanced cloud absorption

    Kiehl, J. [National Center for Atmospheric Research (NCAR), Boulder, CO (United States)

    1995-09-01

    Recent indications suggest that clouds may be absorbing more solar radiation than was previously thought. This research investigates some of the evidence for this hypothesis; potential physical mechanisms are briefly discussed as well. The climatic implications of the enhanced absorption are investigated using the NCAR Community Climate Model (CCM). It is found that the model`s heat budget in the tropical warm pool agrees more closely with observations when enhanced absorption is included. On the whole, the addition of enhanced absorption improves the model`s performance in the tropics and degrades it in the extra-tropics. 3 figs.

  14. Absorption heat pumps

    Huhtinen, M.; Heikkilae, M.; Andersson, R.

    1987-03-01

    The aim of the study was to analyze the technical and economic feasibility of absorption heat pumps in Finland. The work was done as a case study: the technical and economic analyses have been carried out for six different cases, where in each the suitable size and type of the heat pump plant and the auxiliary components and connections were specified. The study also detailed the costs concerning the procurement, installation and test runs of the machinery, as well as the savings in energy costs incurred by the introduction of the plant. Conclusions were drawn of the economic viability of the applications studied. The following cases were analyzed: heat recovery from flue gases and productin of district heat in plants using peat, natural gas, and municipal wastes as a fuel. Heat recovery in the pulp and paper industry for the upgrading of pressure of secondary steam and for the heating of white liquor and combustion and drying the air. Heat recovery in a peat-fulled heat and power plant from flue gases that have been used for the drying of peat. According to the study, the absorption heat pump suits best to the production of district heat, when the heat source is the primary energy is steam produced by the boiler. Included in the flue as condensing is the purification of flue gases. Accordingly, benefit is gained on two levels in thick applications. In heat and power plants the use of absorption heat pumps is less economical, due to the fact that the steam used by the pump reduces the production of electricity, which is rated clearly higher than heat.

  15. Shell structure of pancakes and the absorption spectra of quasars

    The formation of the absorption lines of atomic hydrogen in the spectra of distant quasars is considered. A model is constructed of the formation of shells of a pancake formed in the adiabatic picture of the generation of the large-scale structure of the universe. It is shown that the absorption lines can form doublets and the equivalent widths of the corresponding lines are calculated. The physical conditions corresponding to the observed heavy-element absorption spectra are discussed

  16. Scattering with absorptive interaction

    Cassing, W.; Stingl, M.; Weiguny, A.

    1982-07-01

    The S matrix for a wide class of complex and nonlocal potentials is studied, with special attention given to the motion of singularities in the complex k plane as a function of the imaginary coupling strength. Modifications of Levinson's theorem are obtained and discussed. Analytic approximations to the S matrix in the vicinity of narrow resonances are exhibited and compared to numerical results of resonating-group calculations. The problem of defining resonances in the case of complex interactions is discussed, making contact with the usual analysis of scattering in terms of Argand diagrams. NUCLEAR REACTIONS Scattering theory, S matrix for absorptive potentials.

  17. Geospatial Absorption and Regional Effects

    IOAN MAC

    2009-01-01

    Full Text Available The geospatial absorptions are characterized by a specific complexity both in content and in their phenomenological and spatial manifestation fields. Such processes are differentiated according to their specificity to pre-absorption, absorption or post-absorption. The mechanisms that contribute to absorption are extremely numerous: aggregation, extension, diffusion, substitution, resistivity (resilience, stratification, borrowings, etc. Between these mechanisms frequent relations are established determining an amplification of the process and of its regional effects. The installation of the geographic osmosis phenomenon in a given territory (a place for example leads to a homogenization of the geospatial state and to the installation of the regional homogeneity.

  18. Temperature Dependence of Light Absorption by Water

    Cumming, J. B.

    2013-01-01

    A model is described that relates the temperature coefficient of the optical absorption spectrum of pure water to the frequency derivative of that spectrum and two parameters that quantify the dependence of a peak's amplitude and its position on temperature. When applied to experimental temperature coefficients, it provides a better understanding of the process than the analysis currently in use.

  19. Modelos in vitro para determinação da absorção de fármacos e previsão da relação dissolução/absorção In vitro models for the determination of drug absorption and a prediction of dissolution/absorption relationships

    Jacqueline de Souza

    2007-12-01

    and absorption of drugs using in vitro models. There are several methods for determining in vitro intestinal permeability. These include diffusion studies with intestinal segments from various species or with cultured cell monolayer. Some of the most commonly used cell models are Caco-2, TC-7, 2/4/A1 and MDCK. Caco-2 cells have been the most extensively characterized and useful cell models. The Caco-2 cell, a human colon adenocarcinoma, undergoes spontaneous enterocytic differentiation in culture. A dissolution Caco-2 system has been developed to predict dissolution/absorption relationships of oral solid dosage forms of drugs prior to human studies. The in vitro permeability models represent an important tool for drug discovery within the pharmaceutical industry. However, similar models are likely to generate false negative results with actively transported drugs, and the use of a sophisticated mathematical model could be required.

  20. The HI absorption 'Zoo'

    Gereb, K; Morganti, R; Oosterloo, T A

    2014-01-01

    We present an analysis of the HI absorption in a sample of 101 flux-selected radio AGN (S_1.4 GHz > 50 mJy) observed with the Westerbork Synthesis Radio Telescope (WSRT). HI absorption is detected in 32 galaxies, showing a broad variety of widths, shapes and kinematical properties. We characterize the HI spectra of the individual detections using the busy function (Westmeier et al. 2014). With the goal of identifying different morphological structures of HI, we study the kinematical and radio source properties of the detections as function of their width. Narrow lines (FWHM = 500 km/s). These detections are good candidates for being HI outflows. The detection rate of HI outflows is 5 percent in the total radio AGN sample. This fraction represents a lower limit, however it could suggests that, if outflows are a characteristic phenomenon of all radio sources, they would have a short depletion timescale compared to the lifetime of the AGN. Blueshifted and broad/asymmetric lines are more often present among young...

  1. Ultrasonic absorption in polymethylmethacrylate at low temperatures

    This chapter reports on a study of the absorption of longitudinal sound waves at frequencies between 15 and 195 MHz and temperatures between 0.4K and 300K using commercial PMMA. It demonstrates that the acoustic absorption of PMMA does not steadily decrease on cooling. Below 1K the absorption varies linearly with temperature and can be explained after a small modification of the so-called ''tunnelling model'' which is well-known in the description of inorganic glasses. This is an unexpected maximum at 12K which has a frequency independent position. This behavior is explained by assuming a high density of tunnelling states with well-defined asymmetries and tunnel splittings. It is pointed out that these states couple weakly to the amorphous network and are most probably due to rotational tunnelling of the ester methyl group

  2. EMPLOYMENT ABSORPTION IN MANUFACTURING INDUSTRY: YOGYAKARTA CASE

    Aurora Indra Putri

    2011-09-01

    Full Text Available Unemployment has been a main problem in economic development, especially in developing countries. Unemployment stems from the inability of the economy to absorb the growing labor force. This paper investigates factors influencing absorbtion of labor in Yogyakarta manufacturing industries. Variables hypothesized to affect the absorbtion are wage, labor productivity, non-wage spending, and output of production. It collects data from Indonesia Centre Bureau of Statistics, and uses panel data regression, namely common effect approach, to estimate the model. Employing Eviews software package, it finds that wage, labor productivity, and output production significantly influence labor absorption. However, non-wage spending does not significantly influence the absorption.Keywords: Labor absorption, wage, labor productivity, non-wage spendingJEL classification numbers: J01, J23, J24

  3. Proposal and analysis of a high-efficiency combined desalination and refrigeration system based on the LiBr-H2O absorption cycle-Part 1: System configuration and mathematical model

    Simultaneous production of fresh water and refrigeration are often required, e.g. in warm-climate water-deficient regions, and this study is a proposal and analysis of an efficient way of producing both of them by consuming mainly low-grade heat. After introducing the configuration choice methodology, a combined refrigeration and water system, ARHP-MEE (absorption refrigeration heat pump and multi-effect evaporation desalter), which is the integration of a LiBr-H2O refrigeration unit, a LiBr-H2O heat pump, and a low-temperature multi-effect evaporation desalination unit, is proposed, and the mathematical model is presented and validated. The model serves for conducting a performance analysis of the combined system, reported in Part 2 of this two-part paper.

  4. X-ray Absorption Spectroscopy and Coherent X-ray Diffraction Imaging for Time-Resolved Investigation of the Biological Complexes: Computer Modelling towards the XFEL Experiment

    Bugaev, A. L.; Guda, A. A.; Yefanov, O. M.; Lorenz, U.; Soldatov, A. V.; Vartanyants, I. A.

    2016-05-01

    The development of the next generation synchrotron radiation sources - free electron lasers - is approaching to become an effective tool for the time-resolved experiments aimed to solve actual problems in various fields such as chemistry’ biology’ medicine’ etc. In order to demonstrate’ how these experiments may be performed for the real systems to obtain information at the atomic and macromolecular levels’ we have performed a molecular dynamics computer simulation combined with quantum chemistry calculations for the human phosphoglycerate kinase enzyme with Mg containing substrate. The simulated structures were used to calculate coherent X-ray diffraction patterns’ reflecting the conformational state of the enzyme, and Mg K-edge X-ray absorption spectra, which depend on the local structure of the substrate. These two techniques give complementary information making such an approach highly effective for time-resolved investigation of various biological complexes, such as metalloproteins or enzymes with metal-containing substrate, to obtain information about both metal-containing active site or substrate and the atomic structure of each conformation.

  5. Effects of moisture absorption on degradation of E-glass fiber reinforced Vinyl Ester composite pipes and modelling of transient moisture diffusion using finite element analysis

    Highlights: • With increase in temperature, diffusion coefficient and absorbed moisture increased. • The diffusion coefficient and weight gain are higher in water than sea water. • Mechanical degradation caused decrease in failure force and maximum displacement. • The fiber–matrix interface at higher temperature is weaker than lower temperature. • ABAQUS can properly predict the saturation time of aged specimens. - Abstract: The main purpose of this study is to investigate the effects of humidity and temperature on the properties of GFRP specimens. Tubular specimens fabricated by a filament winding machine are submerged in the studied environment and the accuracy of Fick’s law on moisture diffusion behaviour is studied. The results prove that decreasing the exposure temperature reduces the diffusion coefficient and absorbed moisture. To analyse the effects of moisture uptake on mechanical and physical properties, buckling tests and scanning electron microscope were used. ABAQUS is employed to simulate the moisture absorption. The outcome shows good agreements between experimental and FEA results

  6. Molecular absorption in Cen A on VLBI scales

    Van Langevelde, H J; Beasley, A

    2004-01-01

    Centaurus A, the nearest AGN shows molecular absorption in the millimeter and radio regime. By observing the absorption with VLBI, we try to constrain the distribution of the gas, in particular whether it resides in the circumnuclear region. Analysis of VLBA observations in four OH and two H2CO transitions is presented here, as well as molecular excitation models parameterized with distance from the AGN. We conclude that the gas is most likely associated with the tilted molecular ring structure observed before in molecular emission and IR continuum. The formaldehyde absorption shows small scale absorption which requires a different distribution than the hydroxyl.

  7. Statistical method for predicting protein absorption peaks in terahertz region

    Terahertz vibrational spectroscopy has recently been demonstrated as a novel noninvasive technique for the characterization of biological molecules. But the interpretation of the experimentally measured terahertz absorption bands requires robust computational method. In this paper, we present a statistical method for predicting the absorption peak positions of a macromolecule in the terahertz region. The essence of this method is to calculate the absorption spectra of a biological molecule based on multiple short scale molecular dynamics trajectories instead of using a long time scale trajectory. The method was employed to calculate the absorption peak positions of the protein, thioredoxin from Escherichia coli (E.coli), in the range of 10-25 cm-1 to verify the reliability of this statistical method. The predicted absorption peak positions of thioredoxin show good correlation with measured results demonstrating that the proposed method is effective in terahertz absorption spectra modeling. Such approach can be applied to predict characteristic spectral features of biomolecules in the terahertz region. (authors)

  8. Sabine absorption coefficients to random incidence absorption coefficients

    Jeong, Cheol-Ho

    2014-01-01

    Absorption coefficients measured by the chamber method are referred to as Sabine absorption coefficients, which sometimes exceed unity due to the finite size of a specimen and non-uniform intensity in the test chamber. In this study, several methods that convert Sabine absorption coefficients into...... random incidence absorption coefficients for porous absorbers are investigated. Two optimization-based conversion methods are suggested: the surface impedance estimation for locally reacting absorbers and the flow resistivity estimation for extendedly reacting absorbers. The suggested conversion methods...

  9. Diffuse interstellar absorption bands

    XIANG FuYuan; LIANG ShunLin; LI AiGen

    2009-01-01

    The diffuse interstellar bands (DIBs) are a large number of absorption bands that are superposed on the interstellar extinction curve and are of interstellar origin. Since the discovery of the first two DIBs in the 1920s, the exact nature of DIBs still remains unclear. This article reviews the history of the detec-tions of DIBs in the Milky Way and external galaxies, the major observational characteristics of DIBs, the correlations or anti-correlations among DIBs or between DIBs and other interstellar features (e.g. the prominent 2175 Angstrom extinction bump and the far-ultraviolet extinction rise), and the proposed candidate carriers. Whether they are also present in circumstellar environments is also discussed.

  10. The HI absorption "Zoo"

    Geréb, K.; Maccagni, F. M.; Morganti, R.; Oosterloo, T. A.

    2015-03-01

    We present an analysis of the H I 21 cm absorption in a sample of 101 flux-selected radio AGN (S1.4 GHz> 50 mJy) observed with the Westerbork Synthesis Radio Telescope (WSRT). We detect H I absorption in 32 objects (30% of the sample). In a previous paper, we performed a spectral stacking analysis on the radio sources, while here we characterize the absorption spectra of the individual detections using the recently presented busy function. The H I absorption spectra show a broad variety of widths, shapes, and kinematical properties. The full width half maximum (FWHM) of the busy function fits of the detected H I lines lies in the range 32 km s-1 200 km s-1). We study the kinematical and radio source properties of each group, with the goal of identifying different morphological structures of H I. Narrow lines mostly lie at the systemic velocity and are likely produced by regularly rotating H I disks or gas clouds. More H I disks can be present among galaxies with lines of intermediate widths; however, the H I in these sources is more unsettled. We study the asymmetry parameter and blueshift/redshift distribution of the lines as a function of their width. We find a trend for which narrow profiles are also symmetric, while broad lines are the most asymmetric. Among the broadest lines, more lines appear blueshifted than redshifted, similarly to what was found by previous studies. Interestingly, symmetric broad lines are absent from the sample. We argue that if a profile is broad, it is also asymmetric and shifted relative to the systemic velocity because it is tracing unsettled H I gas. In particular, besides three of the broadest (up to FW20 = 825 km s-1) detections, which are associated with gas-rich mergers, we find three new cases of profiles with blueshifted broad wings (with FW20 ≳ 500 km s-1) in high radio power AGN. These detections are good candidates for being HI outflows. Together with the known cases of outflows already included in the sample (3C 293 and

  11. Two-Step Photon Absorption Driving the Chemical Reaction in the Model Ruthenium Nitrosyl System [Ru(py)4Cl(NO)](PF6)2·(1)/2H2O.

    Khadeeva, Liya; Kaszub, Wawrzyniec; Lorenc, Maciej; Malfant, Isabelle; Buron-Le Cointe, Marylise

    2016-05-01

    Various systems containing the [ML5NO] molecule, where M = Fe, Ru, ... and L = F, Cl, ..., exhibit switching under continuous light (CW) irradiation between the ground-state nitrosyl (GS), isonitrosyl (MSI), and side-on (MSII) configurations. The metastable populations, however, are often limited to a few percent. The [Ru(py)4Cl(NO)](PF6)2·(1)/2H2O system is thus a remarkable model compound as the GS to MSI transformation is nearly complete in a single crystal. A predominant two-step photon absorption process during GS to MSI switching under blue light is revealed by visible absorption spectroscopy, although a low concentration of the transient species hinders the determination of this process by the structural signature. During the depopulation of MSI, both two-step and direct processes are evidenced under red CW irradiation. Different intermediate visible spectra revealing transient species during GS to MSI and the reverse photochemical processes are discussed in relation to MSII properties. PMID:27054377

  12. Simulating Ru L3-Edge X-ray Absorption Spectroscopy with Time-Dependent Density Functional Theory: Model Complexes and Electron Localization in Mixed-Valence Metal Dimers

    Kuiken, Benjamin E. Van; Valiev, Marat; Daifuku, Stephanie L.; Bannan, Caitlin; Strader, Matthew L.; Cho, Hana; Huse, Nils; Schoenlein, Robert W.; Govind, Niranjan; Khalil, Munira

    2013-04-26

    Ruthenium L3-edge X-ray absorption (XA) spectroscopy probes unoccupied 4d orbitals of the metal atom and is increasingly being used to investigate the local electronic structure in ground and excited electronic states of Ru complexes. The simultaneous development of computational tools for simulating Ru L3-edge spectra is crucial for interpreting the spectral features at a molecular level. This study demonstrates that time-dependent density functional theory (TDDFT) is a viable and predictive tool for simulating ruthenium L3-edge XA spectroscopy. We systematically investigate the effects of exchange correlation functional and implicit and explicit solvent interactions on a series of RuII and RuIII complexes in their ground and electronic excited states. The TDDFT simulations reproduce all of the experimentally observed features in Ru L3-edge XA spectra within the experimental resolution (0.4 eV). Our simulations identify ligand-specific charge transfer features in complicated Ru L3-edge spectra of [Ru(CN)6]4- and RuII polypyridyl complexes illustrating the advantage of using TDDFT in complex systems. We conclude that the B3LYP functional most accurately predicts the transition energies of charge transfer features in these systems. We use our TDDFT approach to simulate experimental Ru L3-edge XA spectra of transition metal mixed-valence dimers of the form [(NC)5MII-CN-RuIII(NH3)5] (where M = Fe or Ru) dissolved in water. Our study determines the spectral signatures of electron delocalization in Ru L3-edge XA spectra. We find that the inclusion of explicit solvent molecules is necessary for reproducing the spectral features and the experimentally determined valencies in these mixed-valence complexes. This study validates the use of TDDFT for simulating Ru 2p excitations using popular quantum chemistry codes and providing a powerful interpretive tool for equilibrium and ultrafast Ru L3-edge XA spectroscopy.

  13. A new detection of LYα absorption from the heliotail

    We present new Hubble Space Telescope observations of H I Lyα absorption toward the F8 V star HD 35296. This line of sight is only a few degrees from the downwind direction of the local interstellar medium flow vector. As a consequence, Lyα absorption from the heliotail is detected in the spectrum, consistent with three previous downwind detections of heliotail absorption. The clustering of the heliotail absorption detections around the downwind direction demonstrates that the heliotail is pointed close to that direction, limiting the extent to which the interstellar magnetic field might be distorting and deflecting the heliotail. We explore this issue further using three-dimensional MHD models of the global heliosphere. The three computed models represent the first three-dimensional MHD models with both a kinetic treatment of neutrals and an extended grid in the tail direction, both of which are necessary to model Lyα absorption downwind. The models indicate only modest heliotail asymmetries and deflections, which are not large enough to be inconsistent with the clustering of heliotail absorption detections around the downwind direction. The models are reasonably successful at reproducing the observed absorption, but they do overpredict the Lyα opacity by a factor of 2-3. We discuss implications of these results in light of observations of the heliotail region from the Interstellar Boundary Explorer mission.

  14. Interpretation of NO2 absorption in twilight sky spectra

    McMahon, B. B.

    1984-07-01

    A multiple scattering model has been developed to calculate nitrogen dioxide (NO2) absorption in the light from the zenith sky during twilight. Model studies show that this absorption is not very sensitive to the atmospheric temperature profile or to tropospheric NO2. The model was used to interpret some ground-based measurements of NO2 sky absorption. Values for the total stratospheric column amount vary from 2 to 12 x 10 to the 15th molec/sq cm, and the mean altitude of the stratospheric concentration profile is around 35 km. These observations are in broad agreement with those of other workers.

  15. Absorption intestinale des vitamines liposolubles

    Reboul Emmanuelle

    2011-03-01

    Full Text Available The molecular mechanisms of fat-soluble vitamin intestinal absorption remain partly unknown, despite the fact that a better understanding of this process would certainly allow to improve their bioavailability. If their digestion-absorption process follows the fate of lipids globally, the recent discovery of membranes proteins involved in their absorption questioned the established dogmas. These new data should be taken into account to avoid dietary or drug interactions that may limit some fatsoluble vitamin bioavailability.

  16. Absorption intestinale des vitamines liposolubles

    Reboul Emmanuelle

    2011-01-01

    The molecular mechanisms of fat-soluble vitamin intestinal absorption remain partly unknown, despite the fact that a better understanding of this process would certainly allow to improve their bioavailability. If their digestion-absorption process follows the fate of lipids globally, the recent discovery of membranes proteins involved in their absorption questioned the established dogmas. These new data should be taken into account to avoid dietary or drug interactions that may limit some fat...

  17. X-ray Absorption Spectroscopy

    Yano, Junko; Yachandra, Vittal K.

    2009-07-09

    This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn4Ca cluster in Photosystem II is presented.

  18. Study on Kinetics of Hydrogen Absorption by Metal Hydride Slurries Ⅰ. Absorption of Hydrogen by Hydrogen Storage Alloy MlNi5 Suspended in Benzene

    安越; 陈长聘; 徐国华; 蔡官明; 王启东

    2002-01-01

    The absorption of hydrogen was studied in metal hydride slurry, which is formed by benzene and hydrogen storage alloy powder. The influence of temperature on the rate of absorption was discussed using three-phase mass transfer model. It is also concluded that the suitable absorption temperature is 313 K.

  19. Potassium emission absorption system. Topical report 12

    Bauman, L.E.

    1995-04-01

    The Potassium Emission Absorption System is one of the advanced optical diagnostics developed at Mississippi State University to provide support for the demonstration of prototype-scale coal-fired combustion magnetohydrodynamic (MHD) electrical power generation. Intended for application in the upstream of an MHD flow, the system directly measures gas temperature and neutral potassium atom number density through spectroscopic emission absorption techniques. From these measurements the electron density can be inferred from a statistical equilibrium calculation and the electron conductivity in the MHD channel found by use of an electron mobility model. The instrument has been utilized for field test measurements on MHD facilities for almost a decade and has been proven to provide useful measurements as designed for MHD nozzle, channel, and diffuser test sections. The theory of the measurements, a system description, its capabilities, and field test measurement results are reported here. During the development and application of the instrument several technical issues arose which when addressed advanced the state of the art in emission absorption measurement. Studies of these issues are also reported here and include: two-wavelength measurements for particle-laden flows, potassium D-line far wing absorption coefficient, bias in emission absorption measurements arising from dirty windows and misalignments, non-coincident multiwavelength emission absorption sampling errors, and lineshape fitting for boundary layer flow profile information. Although developed for NLHD application, the instrument could be applied to any high temperature flow with a resonance line in the 300 to 800 nm range, for instance other types of flames, rocket plumes or low temperature plasmas.

  20. Coherent single-photon absorption by single emitters coupled to 1D nanophotonic waveguides

    Chen, Yuntian; Wubs, Martijn; Mørk, Jesper;

    2012-01-01

    We have derived an efficient model that allows calculating the dynamical single-photon absorption of an emitter coupled to a waveguide. We suggest a novel and simple structure that leads to strong single-photon absorption.......We have derived an efficient model that allows calculating the dynamical single-photon absorption of an emitter coupled to a waveguide. We suggest a novel and simple structure that leads to strong single-photon absorption....

  1. Hot tube atomic absorption spectrochemistry.

    Woodriff, R; Stone, R W

    1968-07-01

    A small, commercially available atomic absorption instrument is used with a heated graphite tube for the atomic absorption analysis of liquid and solid silver samples. Operating conditions of the furnace are described and a sensitivity of about 5 ng of silver is reported. PMID:20068797

  2. Phytases for improved iron absorption

    Nielsen, Anne Veller Friis; Meyer, Anne S.

    2016-01-01

    Phytase enzymes present an alternative to iron supplements, because they have been shown to improve iron absorption by means of catalysing the degradation of a potent iron absorption inhibitor: phytic acid. Phytic acid is a hexaphosphate of inositol and is particularly prevalent in cereal grains...

  3. Light absorption by organic carbon from wood combustion

    Y. Chen

    2010-02-01

    Full Text Available Carbonaceous aerosols affect the radiative balance of the Earth by absorbing and scattering light. While black carbon (BC is highly absorbing, some organic carbon (OC also has significant absorption, especially at near-ultraviolet and blue wavelengths. To the extent that OC absorbs visible light, it may be a non-negligible contributor to positive direct aerosol radiative forcing. Quantification of that absorption is necessary so that radiative-transfer models can evaluate the net radiative effect of OC.

    In this work, we examine absorption by primary OC emitted from solid fuel pyrolysis. We provide absorption spectra of this material, which can be related to the imaginary refractive index. This material has polar character but is not fully water-soluble: more than 92% was extractable by methanol or acetone, compared with 73% for water and 52% for hexane. Water-soluble OC contributes to light absorption at both ultraviolet and visible wavelengths. However, a larger portion of the absorption comes from OC that is extractable only by methanol. Absorption spectra of water-soluble OC are similar to literature reports. We compare spectra for material generated with different wood type, wood size and pyrolysis temperature. Higher wood temperature is the main factor creating OC with higher absorption; changing wood temperature from a devolatilizing state of 210 °C to a near-flaming state of 360 °C causes about a factor of four increase in mass-normalized absorption at visible wavelengths. A clear-sky radiative transfer model suggests that, despite the absorption, both high-temperature and low-temperature OC result in negative top-of-atmosphere radiative forcing over a surface with an albedo of 0.19 and positive radiative forcing over bright surfaces. Unless absorption by real ambient aerosol is higher than that measured here, it probably affects global average clear-sky forcing very little, but could be important in energy balances over bright

  4. Efficient simultaneous reverse Monte Carlo modeling of pair-distribution functions and extended x-ray-absorption fine structure spectra of crystalline disordered materials

    Németh, Károly; Chapman, Karena W.; Balasubramanian, Mahalingam; Shyam, Badri; Chupas, Peter J.; Heald, Steve M.; Newville, Matt; Klingler, Robert J.; Winans, Randall E.; Almer, Jonathan D.; Sandi, Giselle; Srajer, George

    2012-02-01

    An efficient implementation of simultaneous reverse Monte Carlo (RMC) modeling of pair distribution function (PDF) and EXAFS spectra is reported. This implementation is an extension of the technique established by Krayzman et al. [J. Appl. Cryst. 42, 867 (2009)] in the sense that it enables simultaneous real-space fitting of x-ray PDF with accurate treatment of Q-dependence of the scattering cross-sections and EXAFS with multiple photoelectron scattering included. The extension also allows for atom swaps during EXAFS fits thereby enabling modeling the effects of chemical disorder, such as migrating atoms and vacancies. Significant acceleration of EXAFS computation is achieved via discretization of effective path lengths and subsequent reduction of operation counts. The validity and accuracy of the approach is illustrated on small atomic clusters and on 5500-9000 atom models of bcc-Fe and α-Fe2O3. The accuracy gains of combined simultaneous EXAFS and PDF fits are pointed out against PDF-only and EXAFS-only RMC fits. Our modeling approach may be widely used in PDF and EXAFS based investigations of disordered materials.

  5. On the nature of absorption features toward nearby stars

    Kohl, S.; Czesla, S.; Schmitt, J. H. M. M.

    2016-06-01

    Context. Diffuse interstellar absorption bands (DIBs) of largely unknown chemical origin are regularly observed primarily in distant early-type stars. More recently, detections in nearby late-type stars have also been claimed. These stars' spectra are dominated by stellar absorption lines. Specifically, strong interstellar atomic and DIB absorption has been reported in τ Boo. Aims: We test these claims by studying the strength of interstellar absorption in high-resolution TIGRE spectra of the nearby stars τ Boo, HD 33608, and α CrB. Methods: We focus our analysis on a strong DIB located at 5780.61 Å and on the absorption of interstellar Na. First, we carry out a differential analysis by comparing the spectra of the highly similar F-stars, τ Boo and HD 33608, whose light, however, samples different lines of sight. To obtain absolute values for the DIB absorption, we compare the observed spectra of τ Boo, HD 33608, and α CrB to PHOENIX models and carry out basic spectral modeling based on Voigt line profiles. Results: The intercomparison between τ Boo and HD 33608 reveals that the difference in the line depth is 6.85 ± 1.48 mÅ at the DIB location which is, however, unlikely to be caused by DIB absorption. The comparison between PHOENIX models and observed spectra yields an upper limit of 34.0 ± 0.3 mÅ for any additional interstellar absorption in τ Boo; similar results are obtained for HD 33608 and α CrB. For all objects we derive unrealistically large values for the radial velocity of any presumed interstellar clouds. In τ Boo we find Na D absorption with an equivalent width of 0.65 ± 0.07 mÅ and 2.3 ± 0.1 mÅ in the D2 and D1 lines. For the other Na, absorption of the same magnitude could only be detected in the D2 line. Our comparisons between model and data show that the interstellar absorption toward τ Boo is not abnormally high. Conclusions: We find no significant DIB absorption in any of our target stars. Any differences between modeled and

  6. Experimental methodology for obtaining sound absorption coefficients

    Carlos A. Macía M

    2011-07-01

    Full Text Available Objective: the authors propose a new methodology for estimating sound absorption coefficients using genetic algorithms. Methodology: sound waves are generated and conducted along a rectangular silencer. The waves are then attenuated by the absorbing material covering the silencer’s walls. The attenuated sound pressure level is used in a genetic algorithm-based search to find the parameters of the proposed attenuation expressions that include geometric factors, the wavelength and the absorption coefficient. Results: a variety of adjusted mathematical models were found that make it possible to estimate the absorption coefficients based on the characteristics of a rectangular silencer used for measuring the attenuation of the noise that passes through it. Conclusions: this methodology makes it possible to obtain the absorption coefficients of new materials in a cheap and simple manner. Although these coefficients might be slightly different from those obtained through other methodologies, they provide solutions within the engineering accuracy ranges that are used for designing noise control systems.

  7. Theoretical modeling of UV-Vis absorption and emission spectra in liquid state systems including vibrational and conformational effects: explicit treatment of the vibronic transitions.

    D'Abramo, Marco; Aschi, Massimiliano; Amadei, Andrea

    2014-04-28

    Here, we extend a recently introduced theoretical-computational procedure [M. D'Alessandro, M. Aschi, C. Mazzuca, A. Palleschi, and A. Amadei, J. Chem. Phys. 139, 114102 (2013)] to include quantum vibrational transitions in modelling electronic spectra of atomic molecular systems in condensed phase. The method is based on the combination of Molecular Dynamics simulations and quantum chemical calculations within the Perturbed Matrix Method approach. The main aim of the presented approach is to reproduce as much as possible the spectral line shape which results from a subtle combination of environmental and intrinsic (chromophore) mechanical-dynamical features. As a case study, we were able to model the low energy UV-vis transitions of pyrene in liquid acetonitrile in good agreement with the experimental data. PMID:24784250

  8. Effects of flavour absorption on foods and their packaging materials

    Willige, van, R.W.G.

    2002-01-01

    Keywords: flavour absorption, scalping, packaging, food matrix, lldpe, ldpe, pp, pc, pet, pen,b-lactoglobulin, casein, pectin, cmc, lactose, saccharose, oil, modelling, storage, oxygen permeability, taste perception, sensory quality.Absorption of flavour compounds by linear low-density polyethylene (LLDPE) was studied in model systems representing differences in composition of the food matrix. Proteins,b-lactoglobuline and casein, were able to bind flavours, resulting in suppression of absorp...

  9. Modelling the light absorption properties of particulate matter forming organic particles suspended in seawater.Part 1. Model description, classification of organic particles, and example spectra of the light absorption coefficient and the imaginary part of the refractive index of particulate matter for phytoplankton cells and phytoplankton-like particles

    Bogdan Woźniak

    2005-06-01

    Full Text Available Data on organic substances in the sea are applied to distinguish hypothetical chemical classes and physical types of suspended particulate organic matter (POM in seawater. Spectra of the light absorption coefficients of particulate matter apm(λ and the imaginary refractive index n'p(λ, are assessed for some of these classes and types of POM in seawater, that is, for live phytoplankton cells and phytoplankton-like particles. The spectral characteristics of these coefficients are established and the probable ranges of variability of their absolute magnitudes defined on the basis of the mass-specific coefficients of light absorption by the various organic substances forming the particles. Also presented are mathematical relationships linking the coefficients apm(λ and n'p(λ for the various chemical classes of POM with their physical parameters, such as the relative contents of organic matter, water, air or some other gas. This article is part of a bio-optical study undertaken by the authors, the objective of which is to implement remote sensing techniques in the investigation of Baltic ecosystems (Woźniak et al. 2004.

  10. Solar heating and cooling with absorption refrigeration

    Montlló Casabayó, Gerard

    2010-01-01

    This project is focused on solar heating and cooling installations that use solar thermal energy to produce heat for domestic hot water or space heating, and cooling for air conditioning through absorption refrigeration cycle. The first part of the project is a literature review of said technology. The main components of such installations are described and results and conclusions from existing installations are reviewed. The second part is focused on designing, modelling and simula...

  11. Cluster model calculation for X-ray magnetic circular dichroism at rare-earth (R) L sub 2 sub , sub 3 absorption edges in R sub 2 Fe sub 1 sub 4 B

    Asakura, K; Harada, I; Ogasawara, H; Fukui, K; Kotani, A

    2002-01-01

    X-ray magnetic circular dichroism (MCD) at the L sub 2 sub , sub 3 absorption edges for the entire series of rare-earth (RE) elements in R sub 2 Fe sub 1 sub 4 B (R=RE) is studied based on a cluster model including 10 RE and 16 Fe atoms. The cluster model takes into account band effects of RE 5d states, to which the electric dipole transition occurs from the core 2p states, as well as spin polarization of the 5d states due to the interatomic hybridization with the spin polarized Fe 3d states. We also take into account spin and orbital polarization of the 5d states due to the 5d-4f intra-atomic exchange interaction, and the 2p to 4f quadrupole transition. The calculated results are in satisfactory agreement with experimental ones, suggesting that the cluster model calculation provides a new method to calculate quantitatively MCD spectra of RE systems with complicated atomic arrangements. (author)

  12. Gastrointestinal citrate absorption in nephrolithiasis

    Fegan, J.; Khan, R.; Poindexter, J.; Pak, C. Y.

    1992-01-01

    Gastrointestinal absorption of citrate was measured in stone patients with idiopathic hypocitraturia to determine if citrate malabsorption could account for low urinary citrate. Citrate absorption was measured directly from recovery of orally administered potassium citrate (40 mEq.) in the intestinal lavage fluid, using an intestinal washout technique. In 7 stone patients citrate absorption, serum citrate levels, peak citrate concentration in serum and area under the curve were not significantly different from those of 7 normal subjects. Citrate absorption was rapid and efficient in both groups, with 96 to 98% absorbed within 3 hours. The absorption of citrate was less efficient from a tablet preparation of potassium citrate than from a liquid preparation, probably due to a delayed release of citrate from wax matrix. However, citrate absorption from solid potassium citrate was still high at 91%, compared to 98% for a liquid preparation. Thus, hypocitraturia is unlikely to be due to an impaired gastrointestinal absorption of citrate in stone patients without overt bowel disease.

  13. Gut Wall Metabolism. Application of Pre-Clinical Models for the Prediction of Human Drug Absorption and First-Pass Elimination.

    Jones, Christopher R; Hatley, Oliver J D; Ungell, Anna-Lena; Hilgendorf, Constanze; Peters, Sheila Annie; Rostami-Hodjegan, Amin

    2016-05-01

    Quantifying the multiple processes which control and modulate the extent of oral bioavailability for drug candidates is critical to accurate projection of human pharmacokinetics (PK). Understanding how gut wall metabolism and hepatic elimination factor into first-pass clearance of drugs has improved enormously. Typically, the cytochrome P450s, uridine 5'-diphosphate-glucuronosyltransferases and sulfotransferases, are the main enzyme classes responsible for drug metabolism. Knowledge of the isoforms functionally expressed within organs of first-pass clearance, their anatomical topology (e.g. zonal distribution), protein homology and relative abundances and how these differ across species is important for building models of human metabolic extraction. The focus of this manuscript is to explore the parameters influencing bioavailability and to consider how well these are predicted in human from animal models or from in vitro to in vivo extrapolation. A unique retrospective analysis of three AstraZeneca molecules progressed to first in human PK studies is used to highlight the impact that species differences in gut wall metabolism can have on predicted human PK. Compared to the liver, pharmaceutical research has further to go in terms of adopting a common approach for characterisation and quantitative prediction of intestinal metabolism. A broad strategy is needed to integrate assessment of intestinal metabolism in the context of typical DMPK activities ongoing within drug discovery programmes up until candidate drug nomination. PMID:26964996

  14. Quantum model of a solid-state spin qubit: Ni cluster on a silicon surface by the generalized spin Hamiltonian and X-ray absorption spectroscopy investigations

    Farberovich, Oleg V. [School of Physics and Astronomy, Beverly and Raymond Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978 (Israel); Research Center for Nanoscale Structure of Matter, Southern Federal University, Zorge 5, 344090 Rostov-on-Don (Russian Federation); Voronezh State University, Voronezh 394000 (Russian Federation); Mazalova, Victoria L., E-mail: mazalova@sfedu.ru [Research Center for Nanoscale Structure of Matter, Southern Federal University, Zorge 5, 344090 Rostov-on-Don (Russian Federation); Soldatov, Alexander V. [Research Center for Nanoscale Structure of Matter, Southern Federal University, Zorge 5, 344090 Rostov-on-Don (Russian Federation)

    2015-11-15

    We present here the quantum model of a Ni solid-state electron spin qubit on a silicon surface with the use of a density-functional scheme for the calculation of the exchange integrals in the non-collinear spin configurations in the generalized spin Hamiltonian (GSH) with the anisotropic exchange coupling parameters linking the nickel ions with a silicon substrate. In this model the interaction of a spin qubit with substrate is considered in GSH at the calculation of exchange integrals J{sub ij} of the nanosystem Ni{sub 7}–Si in the one-electron approach taking into account chemical bonds of all Si-atoms of a substrate (environment) with atoms of the Ni{sub 7}-cluster. The energy pattern was found from the effective GSH Hamiltonian acting in the restricted spin space of the Ni ions by the application of the irreducible tensor operators (ITO) technique. In this paper we offer the model of the quantum solid-state N-spin qubit based on the studying of the spin structure and the spin-dynamics simulations of the 3d-metal Ni clusters on the silicon surface. The solution of the problem of the entanglement between spin states in the N-spin systems is becoming more interesting when considering clusters or molecules with a spectral gap in their density of states. For quantifying the distribution of the entanglement between the individual spin eigenvalues (modes) in the spin structure of the N-spin system we use the density of entanglement (DOE). In this study we have developed and used the advanced high-precision numerical techniques to accurately assess the details of the decoherence process governing the dynamics of the N-spin qubits interacting with a silicon surface. We have studied the Rabi oscillations to evaluate the N-spin qubits system as a function of the time and the magnetic field. We have observed the stabilized Rabi oscillations and have stabilized the quantum dynamical qubit state and Rabi driving after a fixed time (0.327 μs). The comparison of the energy

  15. Quantum model of a solid-state spin qubit: Ni cluster on a silicon surface by the generalized spin Hamiltonian and X-ray absorption spectroscopy investigations

    We present here the quantum model of a Ni solid-state electron spin qubit on a silicon surface with the use of a density-functional scheme for the calculation of the exchange integrals in the non-collinear spin configurations in the generalized spin Hamiltonian (GSH) with the anisotropic exchange coupling parameters linking the nickel ions with a silicon substrate. In this model the interaction of a spin qubit with substrate is considered in GSH at the calculation of exchange integrals Jij of the nanosystem Ni7–Si in the one-electron approach taking into account chemical bonds of all Si-atoms of a substrate (environment) with atoms of the Ni7-cluster. The energy pattern was found from the effective GSH Hamiltonian acting in the restricted spin space of the Ni ions by the application of the irreducible tensor operators (ITO) technique. In this paper we offer the model of the quantum solid-state N-spin qubit based on the studying of the spin structure and the spin-dynamics simulations of the 3d-metal Ni clusters on the silicon surface. The solution of the problem of the entanglement between spin states in the N-spin systems is becoming more interesting when considering clusters or molecules with a spectral gap in their density of states. For quantifying the distribution of the entanglement between the individual spin eigenvalues (modes) in the spin structure of the N-spin system we use the density of entanglement (DOE). In this study we have developed and used the advanced high-precision numerical techniques to accurately assess the details of the decoherence process governing the dynamics of the N-spin qubits interacting with a silicon surface. We have studied the Rabi oscillations to evaluate the N-spin qubits system as a function of the time and the magnetic field. We have observed the stabilized Rabi oscillations and have stabilized the quantum dynamical qubit state and Rabi driving after a fixed time (0.327 μs). The comparison of the energy pattern with the

  16. Quantum Entanglement Molecular Absorption Spectrum Simulator

    Nguyen, Quang-Viet; Kojima, Jun

    2006-01-01

    Quantum Entanglement Molecular Absorption Spectrum Simulator (QE-MASS) is a computer program for simulating two photon molecular-absorption spectroscopy using quantum-entangled photons. More specifically, QE-MASS simulates the molecular absorption of two quantum-entangled photons generated by the spontaneous parametric down-conversion (SPDC) of a fixed-frequency photon from a laser. The two-photon absorption process is modeled via a combination of rovibrational and electronic single-photon transitions, using a wave-function formalism. A two-photon absorption cross section as a function of the entanglement delay time between the two photons is computed, then subjected to a fast Fourier transform to produce an energy spectrum. The program then detects peaks in the Fourier spectrum and displays the energy levels of very short-lived intermediate quantum states (or virtual states) of the molecule. Such virtual states were only previously accessible using ultra-fast (femtosecond) laser systems. However, with the use of a single-frequency continuous wave laser to produce SPDC photons, and QEMASS program, these short-lived molecular states can now be studied using much simpler laser systems. QE-MASS can also show the dependence of the Fourier spectrum on the tuning range of the entanglement time of any externally introduced optical-path delay time. QE-MASS can be extended to any molecule for which an appropriate spectroscopic database is available. It is a means of performing an a priori parametric analysis of entangled photon spectroscopy for development and implementation of emerging quantum-spectroscopic sensing techniques. QE-MASS is currently implemented using the Mathcad software package.

  17. Absorption of impinging water droplet in porous stones.

    Lee, J B; Radu, A I; Vontobel, P; Derome, D; Carmeliet, J

    2016-06-01

    This paper presents an experimental investigation and numerical analysis of the absorption of water droplets impacting porous stones. The absorption process of an impinging droplet is here fully characterized from spreading to evaporation in terms of absorbed mass during droplet depletion and moisture content distribution in a time-resolved manner for three different natural stones. High-speed imaging and neutron radiography are used to quantify moisture absorption in porous stones of varying moisture properties from deposition until depletion. During impact and spreading, the droplet exhibits a dynamic non-wetting behavior. At maximum spreading, the droplet undergoes pinning, resulting into the contact radius remaining constant until droplet depletion. Absorption undergoes two phases: initially, absorption is hindered due a contact resistance attributed to entrapped air; afterwards, a more perfect capillary contact occurs and absorption goes on until depletion, concurrently with evaporation and further redistribution. A finite-element numerical model for isothermal unsaturated moisture transport in porous media captures the phases of mass absorption in good agreement with the experimental data. Droplet spreading and absorption are highly determined by the impact velocity of the droplet, while moisture content redistribution after depletion is much less dependent on impact conditions. PMID:26975034

  18. Reproducibility of The Random Incidence Absorption Coefficient Converted From the Sabine Absorption Coefficient

    Jeong, Cheol-Ho; Chang, Ji-ho

    2015-01-01

    Absorption coefficients measured in reverberation chambers, Sabine absorption coefficients, suffer from two major problems. Firstly, they sometimes exceed unity. Secondly, the reproducibility of the Sabine absorption coefficients is quite poor, meaning that the Sabine absorption coefficients vary...

  19. Incomplete intestinal absorption of fructose.

    Kneepkens, C M; Vonk, R J; Fernandes, J.

    1984-01-01

    Intestinal D-fructose absorption in 31 children was investigated using measurements of breath hydrogen. Twenty five children had no abdominal symptoms and six had functional bowel disorders. After ingestion of fructose (2 g/kg bodyweight), 22 children (71%) showed a breath hydrogen increase of more than 10 ppm over basal values, indicating incomplete absorption: the increase averaged 53 ppm, range 12 to 250 ppm. Four of these children experienced abdominal symptoms. Three of the six children ...

  20. Absorption Of Dietary Lipid Components

    Abdulkadir Hurşit

    2015-01-01

    Although the digestion and absorption of lipids that are necessary for the survival of living organisms are well known in general terms, nevertheless how different lipids to be digested, how it is distributed into the bloodstream, and how to be used by the cells, are unknown issues by most non specialist people. In recent years, knowledge of lipid digestion and absorption has expanded considerably. More insight has been gained in the mechanism of action of H + pump as a transport system in fa...

  1. EXERCISE ENHANCING CALCIUM ABSORPTION MECHANISM

    Muliani

    2013-01-01

    Calcium has important role in many biological processes therefore calcium homeostasis should be maintained. Imbalance in calcium homeostasis would affects the bone metabolism, neuromuscular function, blood coagulation, cell proliferation and signal transduction. Homeostasis of calcium is maintained by three major organs: gastrointestinal tract, bone and kidney. Intestinal calcium absorption is the sole mechanism to supply calcium to the body. Calcium absorption controlled by calcitropic hormo...

  2. Detection of water vapour absorption around 363nm in measured atmospheric absorption spectra and its effect on DOAS evaluations

    Lampel, Johannes; Polyansky, Oleg. L.; Kyuberis, Alexandra A.; Zobov, Nikolai F.; Tennyson, Jonathan; Lodi, Lorenzo; Pöhler, Denis; Frieß, Udo; Platt, Ulrich; Beirle, Steffen; Wagner, Thomas

    2016-04-01

    Water vapour is known to absorb light from the microwave region to the blue part of the visible spectrum at a decreasing magnitude. Ab-initio approaches to model individual absorption lines of the gaseous water molecule predict absorption lines until its dissociation limit at 243 nm. We present first evidence of water vapour absorption at 363 nm from field measurements based on the POKAZATEL absorption line list by Polyansky et al. (2016) using data from Multi-Axis differential optical absorption spectroscopy (MAX-DOAS) and Longpath (LP)-DOAS measurements. The predicted absorptions contribute significantly to the observed optical depths with up to 2 × 10‑3. Their magnitude correlates well (R2 = 0.89) to simultaneously measured well-established water vapour absorptions in the blue spectral range from 452-499 nm, but is underestimated by a factor of 2.6 ± 0.6 in the ab-initio model. At a spectral resolution of 0.5nm this leads to a maximum absorption cross-section value of 5.4 × 10‑27 cm2/molec at 362.3nm. The results are independent of the employed cross-section data to compensate for the overlayed absorption of the oxygen dimer O4. The newly found absorption can have a significant impact on the spectral retrieval of absorbing trace-gas species in the spectral range around 363 nm. Its effect on the spectral analysis of O4, HONO and OClO are discussed.

  3. Drug absorption in vitro model: filter-immobilized artificial membranes. 2. Studies of the permeability properties of lactones in Piper methysticum Forst.

    Avdeef, A; Strafford, M; Block, E; Balogh, M P; Chambliss, W; Khan, I

    2001-12-01

    The assessment of transport properties of 23 drug and natural product molecules was made using the in vitro model based on filter-immobilized artificial membranes (filter-IAM), assembled from phosphatidylcholine in dodecane, in buffer solutions at pH 7.4. Five of the compounds were lactones extracted from the roots of the kava-kava plant. Experiments were designed to test the effects of stirring (0-600 rpm) during assays and the effects of varying the assay times (2-15 h). The highly mobile kava lactones permeated in the order dihydromethisticin (40)>yangonin (37)>kavain (34)>methisticin (32)>desmethoxyyangonin (26), the numbers in parentheses being the measured effective permeabilities in units of 10(-6) cm/s. By comparison, commercial drugs ranked: phenazopyridine (35)>testosterone (19)>propranolol (13)>ketoconazole (6.3)>piroxicam (2.2)>caffeine (1.7)>metoprolol (0.8)>terbutaline (0.01). In addition to permeability measurements, membrane retention of compounds was determined. Yangonin, desmethoxyyangonin, ketoconazole, and phenazopyridine were more than 60% retained by the artificial membranes containing phospholipids. Stirring during assay significantly increased the observed permeabilities for highly mobile molecules, but had minimal impact on the poorly permeable molecules. The influence of hydrogen bonding was explored by determining permeabilities using filters coated with dodecane free of phospholipids. In the filter-IAM method, concentrations were determined by microtitre plate UV spectrophotometry and by LC-MS. Higher-throughput was achieved with direct UV by the use of 96-well microtitre plate formats and with LC-MS by the use of cassette dosing (five-in-one). PMID:11684401

  4. Comparison of box-air-mass-factors and radiances for Multiple-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS geometries calculated from different UV/visible radiative transfer models

    T. Wagner

    2007-01-01

    Full Text Available The results of a comparison exercise of radiative transfer models (RTM of various international research groups for Multiple AXis Differential Optical Absorption Spectroscopy (MAX-DOAS viewing geometry are presented. Besides the assessment of the agreement between the different models, a second focus of the comparison was the systematic investigation of the sensitivity of the MAX-DOAS technique under various viewing geometries and aerosol conditions. In contrast to previous comparison exercises, box-air-mass-factors (box-AMFs for different atmospheric height layers were modelled, which describe the sensitivity of the measurements as a function of altitude. In addition, radiances were calculated allowing the identification of potential errors, which might be overlooked if only AMFs are compared. Accurate modelling of radiances is also a prerequisite for the correct interpretation of satellite observations, for which the received radiance can strongly vary across the large ground pixels, and might be also important for the retrieval of aerosol properties as a future application of MAX-DOAS. The comparison exercises included different wavelengths and atmospheric scenarios (with and without aerosols. The strong and systematic influence of aerosol scattering indicates that from MAX-DOAS observations also information on atmospheric aerosols can be retrieved. During the various iterations of the exercises, the results from all models showed a substantial convergence, and the final data sets agreed for most cases within about 5%. Larger deviations were found for cases with low atmospheric optical depth, for which the photon path lengths along the line of sight of the instrument can become very large. The differences occurred between models including full spherical geometry and those using only plane parallel approximation indicating that the correct treatment of the Earth's sphericity becomes indispensable. The modelled box-AMFs constitute an

  5. Intestinal absorption of specific structured triacylglycerols

    Mu, Huiling; Høy, Carl-Erik

    2001-01-01

    -sn-glycerol (10:0/18:2/10:0), and 1,3-didodecanoyl-2-linoleoyl-sn-glycerol (12:0/18:2/12:0) in a rat model. Safflower oil was used in the absorption study in order to compare the absorption of medium- chain fatty acids and long-chain fatty acids, The triacylglycerol species of lymph Lipids were separated on a...... lymph lipids after administration of the specific structured triacylglycerols (STAG), The recoveries of 8:0/18:2/8:0, 10:0/18:2/10:0, and 12:0/18:2/12:0 were 0.6%, 12%, and 5%, respectively, Several new triacylglycerol species were detected in the lymph Lipids, including MLL-, LLL-, and MMM...

  6. Microscopic Theory and Simulation of Quantum-Well Intersubband Absorption

    Li, Jianzhong; Ning, C. Z.

    2004-01-01

    We study the linear intersubband absorption spectra of a 15 nm InAs quantum well using the intersubband semiconductor Bloch equations with a three-subband model and a constant dephasing rate. We demonstrate the evolution of intersubband absorption spectral line shape as a function of temperature and electron density. Through a detailed examination of various contributions, such as the phase space filling effects, the Coulomb many-body effects and the non-parabolicity effect, we illuminate the underlying physics that shapes the spectra. Keywords: Intersubband transition, linear absorption, semiconductor heterostructure, InAs quantum well

  7. Relativistic Effects Around Black Holes: Smearing Absorption Edges

    Zhang, X. L.; Feng, Y. X.; Zhang, S. N.; Yao, Y.

    2002-01-01

    Broad iron absorption structures have been observed in the X-ray spectra of both AGNs and black hole X-ray binaries (BHXBs). A correctly modeled absorption structure can reveal the physical condition of the source, help to determine the continuum spectra and thus help to estimate other spectral lifes more accurately. The absorption structures are usually thought to be caused by the reflection of X-rays by the accretion disks around the central black holes, and the broadening can be a ttributed to the ionization states of the disk and relativistic effects.

  8. Laser absorption via QED cascades in counter propagating laser pulses

    Grismayer, Thomas; Martins, Joana L; Fonseca, Ricardo A; Silva, Luis O

    2015-01-01

    A model for laser light absorption in electron-positron plasmas self-consistently created via QED cascades is described. The laser energy is mainly absorbed due to hard photon emission via nonlinear Compton scattering. The degree of absorption depends on the laser intensity and the pulse duration. The QED cascades are studied with multi-dimensional particle-in-cell simulations complemented by a QED module and a macro-particle merging algorithm that allows to handle the exponential growth of the number of particles. Results range from moderate-intensity regimes ($\\sim$ 10 PW) where the laser absorption is negligible, to extreme intensities (> 100 PW) where the degree of absorption reaches 80%. Our study demonstrates good agreement between the analytical model and simulations. The expected properties of the hard photon emission and the generated pair-plasma are investigated, and the experimental signatures for near-future laser facilities are discussed.

  9. Toward the Standard Population Synthesis Model of the X-Ray Background: Evolution of X-Ray Luminosity and Absorption Functions of Active Galactic Nuclei Including Compton-thick Populations

    Ueda, Yoshihiro; Akiyama, Masayuki; Hasinger, Günther; Miyaji, Takamitsu; Watson, Michael G.

    2014-05-01

    We present the most up to date X-ray luminosity function (XLF) and absorption function of active galactic nuclei (AGNs) over the redshift range from 0 to 5, utilizing the largest, highly complete sample ever available obtained from surveys performed with Swift/BAT, MAXI, ASCA, XMM-Newton, Chandra, and ROSAT. The combined sample, including that of the Subaru/XMM-Newton Deep Survey, consists of 4039 detections in the soft (0.5-2 keV) and/or hard (>2 keV) band. We utilize a maximum likelihood method to reproduce the count rate versus redshift distribution for each survey, by taking into account the evolution of the absorbed fraction, the contribution from Compton-thick (CTK) AGNs, and broadband spectra of AGNs, including reflection components from tori based on the luminosity- and redshift-dependent unified scheme. We find that the shape of the XLF at z ~ 1-3 is significantly different from that in the local universe, for which the luminosity-dependent density evolution model gives much better description than the luminosity and density evolution model. These results establish the standard population synthesis model of the X-ray background (XRB), which well reproduces the source counts, the observed fractions of CTK AGNs, and the spectrum of the hard XRB. The number ratio of CTK AGNs to the absorbed Compton-thin (CTN) AGNs is constrained to be ≈0.5-1.6 to produce the 20-50 keV XRB intensity within present uncertainties, by assuming that they follow the same evolution as CTN AGNs. The growth history of supermassive black holes is discussed based on the new AGN bolometric luminosity function.

  10. Toward the standard population synthesis model of the X-ray background: Evolution of X-ray luminosity and absorption functions of active galactic nuclei including Compton-thick populations

    We present the most up to date X-ray luminosity function (XLF) and absorption function of active galactic nuclei (AGNs) over the redshift range from 0 to 5, utilizing the largest, highly complete sample ever available obtained from surveys performed with Swift/BAT, MAXI, ASCA, XMM-Newton, Chandra, and ROSAT. The combined sample, including that of the Subaru/XMM-Newton Deep Survey, consists of 4039 detections in the soft (0.5-2 keV) and/or hard (>2 keV) band. We utilize a maximum likelihood method to reproduce the count rate versus redshift distribution for each survey, by taking into account the evolution of the absorbed fraction, the contribution from Compton-thick (CTK) AGNs, and broadband spectra of AGNs, including reflection components from tori based on the luminosity- and redshift-dependent unified scheme. We find that the shape of the XLF at z ∼ 1-3 is significantly different from that in the local universe, for which the luminosity-dependent density evolution model gives much better description than the luminosity and density evolution model. These results establish the standard population synthesis model of the X-ray background (XRB), which well reproduces the source counts, the observed fractions of CTK AGNs, and the spectrum of the hard XRB. The number ratio of CTK AGNs to the absorbed Compton-thin (CTN) AGNs is constrained to be ≈0.5-1.6 to produce the 20-50 keV XRB intensity within present uncertainties, by assuming that they follow the same evolution as CTN AGNs. The growth history of supermassive black holes is discussed based on the new AGN bolometric luminosity function.

  11. Second order contributions to the absorption of massive particles

    Sancho, Pedro

    2008-01-01

    Recently, in analogy with multiphoton ionization, it has been suggested that multiparticle ionization can also be induced by massive systems. We explore in this paper the possibility that multiparticle absorption processes can also take place for massive particles. To study it we consider, in a perturbative way, a model of absorption which illustrates the analogies with Glauber's scheme for photons and previous analysis on matter-waves coherence. A major advantage of this approach is that the...

  12. Estimation of microwave absorption in the Jupiter atmosphere

    Coombs, W. C.

    1971-01-01

    A procedure for estimating the microwave absorption loss of the Jupiter atmosphere is presented. Estimation of microwave absorption by planetary atmospheres involves two different investigative disciplines (1) the determination of an acceptable model of the atmosphere itself and (2) the determination of the microwave attenuation rate applicable to each different volume sample of the atmosphere, and the integration of this loss over the varying radio propagation path for any given entry trajectory to obtain the total loss.

  13. Toward the Standard Population Synthesis Model of the X-Ray Background: Evolution of X-Ray Luminosity and Absorption Functions of Active Galactic Nuclei Including Compton-Thick Populations

    Ueda, Yoshihiro; Hasinger, Guenther; Miyaji, Takamitsu; Watson, Michael G

    2014-01-01

    We present the most up-to-date X-ray luminosity function (XLF) and absorption function of Active Galactic Nuclei (AGNs) over the redshift range from 0 to 5, utilizing the largest, highly complete sample ever available obtained from surveys performed with Swift/BAT, MAXI, ASCA, XMM-Newton, Chandra, and ROSAT. The combined sample, including that of the Subaru/XMM-Newton Deep Survey, consists of 4039 detections in the soft (0.5--2 keV) and/or hard ($>2$ keV) band. We utilize a maximum likelihood method to reproduce the count-rate versus redshift distribution for each survey, by taking into account the evolution of the absorbed fraction, the contribution from Compton-thick (CTK) AGNs, and broad band spectra of AGNs including reflection components from tori based on the luminosity and redshift dependent unified scheme. We find that the shape of the XLF at $z \\sim 1-3$ is significantly different from that in the local universe, for which the luminosity dependent density evolution model gives much better description...

  14. Absorption and Metabolism of Xanthophylls

    Eiichi Kotake-Nara

    2011-06-01

    Full Text Available Dietary carotenoids, especially xanthophylls, have attracted significant attention because of their characteristic biological activities, including anti-allergic, anti-cancer, and anti-obese actions. Although no less than forty carotenoids are ingested under usual dietary habits, only six carotenoids and their metabolites have been found in human tissues, suggesting selectivity in the intestinal absorption of carotenoids. Recently, facilitated diffusion in addition to simple diffusion has been reported to mediate the intestinal absorption of carotenoids in mammals. The selective absorption of carotenoids may be caused by uptake to the intestinal epithelia by the facilitated diffusion and an unknown excretion to intestinal lumen. It is well known that β-carotene can be metabolized to vitamin A after intestinal absorption of carotenoids, but little is known about the metabolic transformation of non provitamin A xanthophylls. The enzymatic oxidation of the secondary hydroxyl group leading to keto-carotenoids would occur as a common pathway of xanthophyll metabolism in mammals. This paper reviews the absorption and metabolism of xanthophylls by introducing recent advances in this field.

  15. In vitro solubility, dissolution and permeability studies combined with semi-mechanistic modeling to investigate the intestinal absorption of desvenlafaxine from an immediate- and extended release formulation

    Franek, F; Jarlfors, A; Larsen, F.;

    2015-01-01

    pH down the small intestine. Consequently, desvenlafaxine absorption from an IRF appears rate-limited by low Peff in the upper small intestine, which “delays” the predicted time to the maximal plasma concentration (tmax), consistent with clinical data. Conversely, desvenlafaxine absorption from the...... ERF appears rate-limited by dissolution due to the formulation, which tends to negate the influence of pH-dependent permeability on absorption. We suggest that desvenlafaxine Peff is mainly driven by transcellular diffusion of the unionized form. In the case of desvenlafaxine, poor metabolism does not...

  16. Nonlinear Terahertz Absorption of Graphene Plasmons.

    Jadidi, Mohammad M; König-Otto, Jacob C; Winnerl, Stephan; Sushkov, Andrei B; Drew, H Dennis; Murphy, Thomas E; Mittendorff, Martin

    2016-04-13

    Subwavelength graphene structures support localized plasmonic resonances in the terahertz and mid-infrared spectral regimes. The strong field confinement at the resonant frequency is predicted to significantly enhance the light-graphene interaction, which could enable nonlinear optics at low intensity in atomically thin, subwavelength devices. To date, the nonlinear response of graphene plasmons and their energy loss dynamics have not been experimentally studied. We measure and theoretically model the terahertz nonlinear response and energy relaxation dynamics of plasmons in graphene nanoribbons. We employ a terahertz pump-terahertz probe technique at the plasmon frequency and observe a strong saturation of plasmon absorption followed by a 10 ps relaxation time. The observed nonlinearity is enhanced by 2 orders of magnitude compared to unpatterned graphene with no plasmon resonance. We further present a thermal model for the nonlinear plasmonic absorption that supports the experimental results. The model shows that the observed strong linearity is caused by an unexpected red shift of plasmon resonance together with a broadening and weakening of the resonance caused by the transient increase in electron temperature. The model further predicts that even greater resonant enhancement of the nonlinear response can be expected in high-mobility graphene, suggesting that nonlinear graphene plasmonic devices could be promising candidates for nonlinear optical processing. PMID:26978242

  17. Absorption properties of identical atoms

    Sancho, Pedro, E-mail: psanchos@aemet.es

    2013-09-15

    Emission rates and other optical properties of multi-particle systems in collective and entangled states differ from those in product ones. We show the existence of similar effects in the absorption probabilities for (anti)symmetrized states of two identical atoms. The effects strongly depend on the overlapping between the atoms and differ for bosons and fermions. We propose a viable experimental verification of these ideas. -- Highlights: •The absorption rates of a pair of identical atoms in product and (anti)symmetrized states are different. •The modifications of the optical properties are essentially determined by the overlapping between the atoms. •The absorption properties differ, in some cases, for bosons and fermions.

  18. Absorption characteristics of bacteriorhodopsin molecules

    H K T Kumar; K Appaji Gowda

    2000-03-01

    The bacteriorhodopsin molecule absorbs light and undergoes a series of structural transformation following a well-defined photocycle. The complex photocycle is transformed to an equivalent level diagram by considering the lifetime of the intermediate states. Assuming that only and states are appreciably populated at any instant of time, the level diagram is further simplified to two-level system. Based on the rate equations for two-level system, an analytic expression for the absorption coefficient of bacteriorhodopsin molecule is derived. It is applied to study the behaviour of absorption coefficient of bacteriorhodopsin film in the visible wavelength region of 514 nm. The dependence of absorption coefficient of bacteriorhodopsin film on the thickness of the film, total number density of active molecules and initial number density of molecules in -state is presented in the graphical form.

  19. [Intestinal absorption kinetics of Polygonum capitatum extract in rats].

    Yang, Wu; Hou, Jia; Lu, Yuan; Chen, Peng-cheng; Liao, Shang-gao; Huang, Yong

    2015-11-01

    A UPLC-ESI-MS/MS method was used to determinate the main active fractions gallic acid, protocatechuic acid, myricetrin, hyperoside and quercitrin in Polygonum capitatum extracts by in situ intestinal perfusion models; the absorption rate constants and cumulative penetration rate of absorption were calculated. The effect of different drug concentrations, different intestine segments, bile and P-gp inhibitors on the absorption mechanism of Gallic acid and other compositions in P. capitatum extracts. The experimental results showed that gallic acid, protocatechuic acid, myricetrin and quercitrin were observed saturated at high concentration (P inhibition effect on protocatechuic acid absorption and had promotion effect on myricetrin and hyperoside absorption (P colon. This indicated that the absorption mechanism of P. capitatum extracts in rat intestine was in line with fist-order kinetics characteristics. The composition could be absorbed in all of the different intestinal segments, and the absorption was mainly concentrated in small intestine. The protocatechuic acid may be the substrate of P-gp. PMID:27071271

  20. Light absorption by organic carbon from wood combustion

    Y. Chen

    2009-09-01

    Full Text Available Carbonaceous aerosols affect the radiative balance of the Earth by absorbing and scattering light. While BC is highly absorbing, some organic compounds also have significant absorption, which is greater at near-ultraviolet and blue wavelengths. To the extent that OC absorbs visible light, it may be a non-negligible contributor to direct aerosol radiative forcing.

    In this work, we examine absorption by primary OC emitted from solid fuel pyrolysis. We provide absorption spectra of this material, which can be related to the imaginary refractive index. This material has polar character but is not fully water-soluble: more than 92% was extractable by methanol or acetone, compared with 73% for water and 52% for hexane. Water-soluble organic carbon contributed to light absorption at both ultraviolet and visible wavelengths. However, a larger portion came from organic carbon that is extractable only by methanol. The spectra of water-soluble organic carbon are similar to others in the literature. We compared spectra for material generated with different wood type, wood size and pyrolysis temperature. Higher wood temperature is the main factor creating organic aerosol with higher absorption, causing about a factor of four increase in mass-normalized absorption at visible wavelengths. A simple model suggests that, despite the absorption, both high-temperature and low-temperature carbon have negative climate forcing over a surface with average albedo.

  1. Absorption of focused light by spherical plasmas

    For light focused on spherical plasmas, we obtain new results giving the power absorbed by inverse bremsstrahlung and resonance absorption as a function of the focusing scheme. For a given beam profile and lens, there is an optimum focus to maximize total absorption. Linearly polarized beams lead to asymmetric absorption. Good agreement with experimental absorption and scattered light data is obtained

  2. Absorption Efficiency of Receiving Antennas

    Andersen, Jørgen Bach; Frandsen, Aksel

    2005-01-01

    A receiving antenna with a matched load will always scatter some power. This paper sets an upper and a lower bound on the absorption efficiency (absorbed power over sum of absorbed and scattered powers), which lies between 0 and 100% depending on the directivities of the antenna and scatter...... patterns. It can approach 100% as closely as desired, although in practice this may not be an attractive solution. An example with a small endfire array of dipoles shows an efficiency of 93%. Several examples of small conical horn antennas are also given, and they all have absorption efficiencies less than...

  3. Aerosol Absorption Measurements in MILAGRO.

    Gaffney, J. S.; Marley, N. A.; Arnott, W. P.; Paredes-Miranda, L.; Barnard, J. C.

    2007-12-01

    During the month of March 2006, a number of instruments were used to determine the absorption characteristics of aerosols found in the Mexico City Megacity and nearby Valley of Mexico. These measurements were taken as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX-Mex) that was carried out in collaboration with the Megacity Interactions: Local and Global Research Observations (MILAGRO) campaign. MILAGRO was a joint effort between the DOE, NSF, NASA, and Mexican agencies aimed at understanding the impacts of a megacity on the urban and regional scale. A super-site was operated at the Instituto Mexicano de Petroleo in Mexico City (designated T-0) and at the Universidad Technologica de Tecamac (designated T-1) that was located about 35 km to the north east of the T-0 site in the State of Mexico. A third site was located at a private rancho in the State of Hidalgo approximately another 35 km to the northeast (designated T-2). Aerosol absorption measurements were taken in real time using a number of instruments at the T-0 and T-1 sites. These included a seven wavelength aethalometer, a multi-angle absorption photometer (MAAP), and a photo-acoustic spectrometer. Aerosol absorption was also derived from spectral radiometers including a multi-filter rotating band spectral radiometer (MFRSR). The results clearly indicate that there is significant aerosol absorption by the aerosols in the Mexico City megacity region. The absorption can lead to single scattering albedo reduction leading to values below 0.5 under some circumstances. The absorption is also found to deviate from that expected for a "well-behaved" soot anticipated from diesel engine emissions, i.e. from a simple 1/lambda wavelength dependence for absorption. Indeed, enhanced absorption is seen in the region of 300-450 nm in many cases, particularly in the afternoon periods indicating that secondary organic aerosols are contributing to the aerosol absorption. This is likely due

  4. Energy absorption in sandwich laminate structures

    White, Robert

    2010-01-01

    The significant result of this thesis is that the energy absorption of a sandwich laminate can be estimated using a simple spring force model. This means for a maritime vessel that the maximum survivable impact speed of the vessel can be estimated using nothing more than the speed of the craft and the mass ratio of the craft and the impactor. The calculation requires one to know the sandwich equivalent spring constant which is shown to be closely related to foam core shear and compressive mod...

  5. Absorption heat cycles. An experimental and theoretical study

    A flow sheeting programme, SHPUMP, was developed for simulating different absorption heat cycles. The programme consists of ten different modules which allow the user to construct his own absorption cycle. The ten modules configurate evaporators, absorbers, generators, rectifiers, condensers, solution heat exchangers, pumps, valves, mixers and splitters. Seven basic and well established absorption cycles are available in the configuration data base of the programme. A new Carnot model is proposed heat cycles. Together with exergy analysis, general equations for the Carnot coefficient of performance and equations for thermodynamic efficiency, exergetic efficiency and exergy index, are derived, discussed and compared for both absorption heat pumps and absorption heat transformers. Utilizing SHPUMP, simulation results are presented for different configurations where absorption heat cycles are suggested to be incorporated in three different unit operations within both pulp and paper and oleochemical industries. One of the application studies reveled that an absorption heat transformer incorporated with an evaporation plant in a major pulp and paper industry, would save 18% of the total prime energy consumption in one of the evaporation plants. It was also concluded that installing an absorption heat pump in a paper drying plant would result in steam savings equivalent to 12 MW. An experimental absorption heat transformer unit operating with self-circulation has been modified and thoroughly tested. A reference heat transformer plant has been designed and installed in a major pulp and paper mill where it is directly incorporated with one of the evaporation plants. Preliminary plant operation data are presented. 72 refs, 63 figs, 33 tabs

  6. Transient light absorption induced in glassby femtosecond laser pulses

    The dynamics of the transient light absorption induced in K8 optical glass by filamented femtosecond laser pulses have been studied using time-resolved transmitted-light microscopy at wavelengths from 450 to 700 nm. The transient absorption measured as a function of probe beam wavelength is compared to that predicted by the Drude plasma model. We conclude that, just 450 fs after a pump pulse, the transient absorption is dominated by transient electronic states, presumably, self-trapped excitons, with an excitation energy of 2.6 - 2.7 eV. These states are filled with free-carriers from a long-lived plasma, which acts as a 'carrier reservoir'. The relaxation of transient absorption has two components. The slow component, with τ1 ∼ 17-17.5 ps, is governed by the plasma thermalisation time, whereas the second, with τ1 >> 300 ps, is determined by the plasma lifetime. (nonlinear optical phenomena)

  7. Absorption Voltages and Insulation Resistance in Ceramic Capacitors with Cracks

    Teverovsky, Alexander

    2016-01-01

    Time dependence of absorption voltages (Vabs) in different types of low-voltage X5R and X7R ceramic capacitors was monitored for a maximum duration of hundred hours after polarization. To evaluate the effect of mechanical defects on Vabs, cracks in the dielectric were introduced either mechanically or by thermal shock. The maximum absorption voltage, time to roll-off, and the rate of voltage decrease are shown to depend on the crack-related leakage currents and insulation resistance in the parts. A simple model that is based on the Dow equivalent circuit for capacitors with absorption has been developed to assess the insulation resistance of capacitors. Standard measurements of the insulation resistance, contrary to the measurements based on Vabs, are not sensitive to the presence of mechanical defects and fail to reveal capacitors with cracks. Index Terms: Ceramic capacitor, insulation resistance, dielectric absorption, cracking.

  8. Multiple scattering of polarized light: influence of absorption

    This work continues previous research about multiple scattering of polarized light propagation in turbid media, putting emphasis on the imaginary part of the scatterers’ complex refractive index. The whole angle-dependent Müller matrix is evaluated by comparing results of a polarization sensitive radiative transfer solution to Maxwell theory. Turbid media of defined scatterer concentrations are modelled in three dimensions by sphere ensembles kept inside a cubic or spherical simulation volume. This study addresses the impact of absorption on polarization characteristics for selected media from low to high absorption. Besides that, effects caused by multiple and dependent scattering are shown for increasing volume concentration. In this context some unique properties associated with multiple scattering and absorption are pointed out. Further, scattering results in two dimensions are compared for examples of infinite parallel cylinders of high absorption and perpendicularly incident plane waves. (paper)

  9. INVESTIGATION ON SOUND ABSORPTION PROPERTIES OF KAPOK FIBERS

    Hai-fan Xiang; Dong Wang; Hui-chao Liu; Ning Zhao; Jian Xu

    2013-01-01

    Sound absorption properties of natural kapok fibers have been investigated.Kapok fibrous assemblies with different bulk density,thickness,fiber length and orientation were manufactured,and their acoustical performances were evaluated by using an impedance tube instrument.Results show that the kapok fiber has excellent acoustical damping performance due to its natural hollow structure,and the sound absorption coefficients of kapok fibrous assemblies are significantly affected by the bulk density,thickness and arrangement of kapok fibers but less dependent on the fiber length.Compared with assemblies of commercial glass wool and degreasing cotton fibers,the kapok fiber assemblies with the same thickness but much smaller bulk density may have the similar sound absorption coefficients.Theoretical modelling of the acoustical damping performance of kapok fibers shows a good agreement with the experimental data.All the results demonstrate that kapok fiber is a promising light and environment-friendly sound absorption material.

  10. Sound absorption performance of natural fibers and their composites

    YANG WeiDong; LI Yan

    2012-01-01

    This research aimed to study the sound absorption properties of natural fibers and their reinforced composites.Sound absorption coefficients of three types of natural fibers,i.e.,ramie,flax and jute fibers and their composites were measured by the two-microphone transfer function technique in the impedance tube.The results were compared with synthetic fibers and their composites.It was found that both natural fibers and their composites had superior capability of noise reduction.The multi-scale and hollow lumen structures of natural fibers contributed to the high sound absorption performance.Moreover,the sound absorption properties of these natural fibers were also calculated by the Delany-Bazley and Garai-Pompoli models.They showed good agreement with the experimental data.It was concluded that multi-functional composite materials can be made by natural fibers so that both the mechanical and acoustical functions can be achieved.

  11. Communication: XUV transient absorption spectroscopy of iodomethane and iodobenzene photodissociation

    Drescher, L.; Galbraith, M. C. E.; Reitsma, G.; Dura, J.; Zhavoronkov, N.; Patchkovskii, S.; Vrakking, M. J. J.; Mikosch, J.

    2016-07-01

    Time-resolved extreme ultraviolet (XUV) transient absorption spectroscopy of iodomethane and iodobenzene photodissociation at the iodine pre-N4,5 edge is presented, using femtosecond UV pump pulses and XUV probe pulses from high harmonic generation. For both molecules the molecular core-to-valence absorption lines fade immediately, within the pump-probe time-resolution. Absorption lines converging to the atomic iodine product emerge promptly in CH3I but are time-delayed in C6H5I. We attribute this delay to the initial π → σ* excitation in iodobenzene, which is distant from the iodine reporter atom. We measure a continuous shift in energy of the emerging atomic absorption lines in CH3I, attributed to relaxation of the excited valence shell. An independent particle model is used to rationalize the observed experimental findings.

  12. Resonant upscattering effects on 238U absorption rates

    The new requirements of accuracy in reactor physics calculations justify a review of the current models, like that one adopted in the cross-section processing, for a better evaluation of the keff and the resonant absorption rates. In this context, the aim of this paper is to investigate the effects of the free gas kernel developed by Sanchez on the 238U absorption rates. Homogeneous medium tests point out the increase of the absorption rates in the left wing of the resonances due to the upscattering produced by the new kernel. Heterogeneous tests show that the absorption in the left wing of the resonances is mostly affected by the scattering anisotropy in the laboratory system. (author)

  13. S matrix for absorptive Hamiltonians

    The existence of a matrix S such that SS = 1 in the presence of absorption is demonstrated. In the limit a of hermitian Hamiltonian the unitarity conditions SS = 1 is recovered. A dispersion relation for forward scattering is derived and the properties of the reactance matrices K and K are obtained. It is shown that K = K

  14. Exercise, Intestinal Absorption, and Rehydration

    2001-01-01

    @@ KEYPOINTS 1. The proximal small intestine (duodenum & jejunum) is the primary site of fluid absorption. It absorbs about 50% to 60% of any given fluid load. The colon or large intestine absorbs approximately 80 to 90% of the fluid it receives, but accounts for only about 15% of the total fluid load.

  15. QSO Absorption Lines from QSOs

    Bowen, D V; Ménard, B; Chelouche, D; Inada, N; Oguri, M; Richards, G T; Strauss, M A; Vanden Berk, Daniel E; York, D G; Bowen, David V.; Hennawi, Joseph F.; Menard, Brice; Chelouche, Doron; Inada, Naohisa; Oguri, Masamune; Richards, Gordon T.; Strauss, Michael A.; Berk, Daniel E. Vanden; York, Donald G.

    2006-01-01

    We present the results of a search for metal absorption lines in the spectra of background QSOs whose sightlines pass close to foreground QSOs. We detect MgII(2796,2803) absorption in Sloan Digital Sky Survey (SDSS) spectra of four z>1.5 QSOs whose lines of sight pass within 26-98 kpc of lower redshift (z~0.5-1.5) QSOs. The 100% [4/4 pairs] detection of MgII in the background QSOs is clearly at odds with the incidence of associated (z_abs ~ z_em) systems -- absorbers which exist towards only a few percent of QSOs. Although the quality of our foreground QSO spectra is not as high as the SDSS data, absorption seen towards one of the background QSOs clearly does not show up at the same strength in the spectrum of the corresponding foreground QSO. This implies that the absorbing gas is distributed inhomogeneously around the QSO, presumably as a direct consequence of the anisotropic emission from the central AGN. We discuss possible origins for the MgII lines, including: absorption by gas from the foreground QSO h...

  16. Radionuclide investigation of nutritive absorption

    The authors present the theoretical rationale, algorithm and results of verification of a new radionuclide method for the determination of nutritive absorption. The proposed method allows the determination of the amount of a labeled unabsorbed food ingredient without the collection and radiometry of feces, with a high degree of significance

  17. Powerful laser pulse absorption in partly homogenized foam plasma

    Cipriani, M.; Gus'kov, S. Yu.; De Angelis, R.; Andreoli, P.; Consoli, F.; Cristofari, G.; Di Giorgio, G.; Ingenito, F.; Rupasov, A. A.

    2016-03-01

    The internal volume structure of a porous medium of light elements determines unique features of the absorption mechanism of laser radiation; the characteristics of relaxation and transport processes in the produced plasma are affected as well. Porous materials with an average density larger than the critical density have a central role in enhancing the pressure produced during the ablation by the laser pulse; this pressure can exceed the one produced by target direct irradiation. The problem of the absorption of powerful laser radiation in a porous material is examined both analytically and numerically. The behavior of the medium during the process of pore filling in the heated region is described by a model of viscous homogenization. An expression describing the time and space dependence of the absorption coefficient of laser radiation is therefore obtained from the model. A numerical investigation of the absorption of a nanosecond laser pulse is performed within the present model. In the context of numerical calculations, porous media with an average density larger than the critical density of the laser-produced plasma are considered. Preliminary results about the inclusion of the developed absorption model into an hydrodynamic code are presented.

  18. Powerful laser pulse absorption in partly homogenized foam plasma

    The internal volume structure of a porous medium of light elements determines unique features of the absorption mechanism of laser radiation; the characteristics of relaxation and transport processes in the produced plasma are affected as well. Porous materials with an average density larger than the critical density have a central role in enhancing the pressure produced during the ablation by the laser pulse; this pressure can exceed the one produced by target direct irradiation. The problem of the absorption of powerful laser radiation in a porous material is examined both analytically and numerically. The behavior of the medium during the process of pore filling in the heated region is described by a model of viscous homogenization. An expression describing the time and space dependence of the absorption coefficient of laser radiation is therefore obtained from the model. A numerical investigation of the absorption of a nanosecond laser pulse is performed within the present model. In the context of numerical calculations, porous media with an average density larger than the critical density of the laser-produced plasma are considered. Preliminary results about the inclusion of the developed absorption model into an hydrodynamic code are presented

  19. An Unsteady Heterogeneous Mass Transfer Model for Gas Absorption Enhanced by Dispersed Third Phase Droplets%第三分散相液滴增强气体吸收的一维非稳态非均相传质模型

    沈树华; 马友光; 卢素敏; 朱春英

    2009-01-01

    A model for one-dimensional unsteady heterogeneous mass transfer was developed based on Danck-werts' surface renewal theory in order to describe the mass transfer enhancement of absorption process for a slightly soluble gas in a gas-liquid-liquid system. The model accounts for the mass transfer resistance within the dispersed phase and the effect of emulsion viscosity on mass transfer. An analytical solution for enhancement factor was ob-tained by Laplace domain transformation. The absorption rates of carbon dioxide in the dodecane-in-water and cas-tor oil-in-water systems were measured in a thermostatic reactor, and the enhancement factors were calculated at different volume fractions of dispersed phase and stirrer speeds. The model predictions agree well with the experi-mental data.

  20. Kinetic modeling of Fluorine vacancy/F center creation in LiF:Mg,Ti including vacancy-interstitial recombination: Evaluating the factors leading to the lack of supralinearity in the optical absorption F center concentration dose response

    Kinetic model simulations of charge carrier transport following irradiation of LiF:Mg,Ti (TLD-100) including Fluorine vacancy/F center creation by the radiation and dose-dependent vacancy-interstitial recombination are presented which describe the experimentally measured linear/exponentially saturating optical absorption dose response of the electron trapping centers at 4.0 eV, 4.77 eV, 5.08 eV (F band) and 5.45 eV. Linear/exponentially saturating dose response is commonly observed for centers which are not created by the radiation. The creation of Fluorine vacancies by the radiation could therefore be expected to lead to a supralinear dose response of the F center before the onset of saturation. Nonetheless, the dose response is linear from 10 Gy to 500 Gy and can be fitted with a dose-filling constant β = 6.1 · 10−5 Gy−1 corresponding to a 5% and 25% decrease from linearity at 103 Gy and 5 · 103 Gy respectively. The model attempts to resolve a central question concerning the mechanisms leading to the linear/exponentially saturating dose response of the F band even though Fluorine vacancies are being continuously created during the irradiation. The electron-trapping characteristics of the created vacancies are assumed to differ somewhat from the vacancies originally present in un-irradiated samples due to differences in their immediate environment. Vacancy-interstitial recombination for separation distances less than a critical distance, dc is demonstrated to be significant for D > 500 Gy (dc = 36 Å) and is an important mechanism contributing to the F center saturation at high dose-levels. The kinetic model accurately simulates the experimentally observed F center dose response over the entire investigated dose range of 10–105 Gy under the following conditions: (i) The concentration of vacancies initially present is unexpectedly high at ∼1023 m−3, possibly due to the highly doped, non-crystalline and hot-pressed nature of the LiF:Mg,Ti samples. (ii

  1. X-ray Absorption and Emission Spectroscopic Studies of [L2Fe2S2](n) Model Complexes: Implications for the Experimental Evaluation of Redox States in Iron-Sulfur Clusters.

    Kowalska, Joanna K; Hahn, Anselm W; Albers, Antonia; Schiewer, Christine E; Bjornsson, Ragnar; Lima, Frederico A; Meyer, Franc; DeBeer, Serena

    2016-05-01

    Herein, a systematic study of [L2Fe2S2](n) model complexes (where L = bis(benzimidazolato) and n = 2-, 3-, 4-) has been carried out using iron and sulfur K-edge X-ray absorption (XAS) and iron Kβ and valence-to-core X-ray emission spectroscopies (XES). These data are used as a test set to evaluate the relative strengths and weaknesses of X-ray core level spectroscopies in assessing redox changes in iron-sulfur clusters. The results are correlated to density functional theory (DFT) calculations of the spectra in order to further support the quantitative information that can be extracted from the experimental data. It is demonstrated that due to canceling effects of covalency and spin state, the information that can be extracted from Fe Kβ XES mainlines is limited. However, a careful analysis of the Fe K-edge XAS data shows that localized valence vs delocalized valence species may be differentiated on the basis of the pre-edge and K-edge energies. These findings are then applied to existing literature Fe K-edge XAS data on the iron protein, P-cluster, and FeMoco sites of nitrogenase. The ability to assess the extent of delocalization in the iron protein vs the P-cluster is highlighted. In addition, possible charge states for FeMoco on the basis of Fe K-edge XAS data are discussed. This study provides an important reference for future X-ray spectroscopic studies of iron-sulfur clusters. PMID:27097289

  2. Inferring surface solar absorption from broadband satellite measurements

    Cess, Robert D.; Vulis, Inna L.

    1989-01-01

    An atmospheric solar radiation model and surface albedo models that include wavelength dependence and surface anisotropy are combined to study the possibility of inferring the surface solar absorption from satellite measurements. The model includes ocean, desert, pasture land, savannah, and bog surface categories. Problems associated with converting narrowband measurements to broadband quantities are discussed, suggesting that it would be easier to infer surface solar absorption from broadband measurements directly. The practice of adopting a linear relationship between planetary and surface albedo to estimate surface albedos from satellite measurements is examined, showing that the linear conversion between broadband planetary and surface albedos is strongly dependent on vegetation type. It is suggested that there is a linear slope-offset relationship between surface and surface-atmosphere solar absorption.

  3. Mechanisms for oral absorption of poorly water-soluble compounds

    Lind, Marianne Ladegaard

    development of lipid-based formulations. However, in order for optimum formulations to be developed, knowledge of the mechanisms of absorption of poorly water-soluble drug substances is desired. Accordingly, the purpose of this PhD study was to study the effects of endogenous surfactants (bile salts......, phospholipids) and exogenous surfactants used in pharmaceutical formulations on the oral absorption of poorly water-soluble drug substances. Three different models were used for this purpose. The first model was the in vitro Caco-2 cell model. Simulated intestinal fluids which did not decrease cellular...... viability and monolayer integrity were developed. The effect of simulated intestinal fluids on the absorption of the poorly water-soluble drug substances, estradiol and diazepam, was studied. The flux of both drug substances across the Caco-2 cells was decreased when simulated intestinal fluids containing...

  4. Absorption of Sunlight by Water Vapor in Cloudy Conditions: A Partial Explaination for the Cloud Absorption Anomaly

    Crisp, D.

    1996-01-01

    The atmospheric radiative transfer algorithms used in most global general circulation models underestimate the globally-averaged solar energy absorbed by cloudy atmospheres by up to 25 Wm(sup -2)...Here, a sophisticated atmospheric radiative transfer model was used to provide a more comprehensive description of the physical processes that contribute to the absorption of solar radiation by the Earth's atmosphere.

  5. Absorption of solar radiation in broken clouds

    Zuev, V.E.; Titov, G.A.; Zhuravleva, T.B. [Institute of Atmospheric Optics, Tomsk (Russian Federation)

    1996-04-01

    It is recognized now that the plane-parallel model unsatisfactorily describes the transfer of radiation through broken clouds and that, consequently, the radiation codes of general circulation models (GCMs) must be refined. However, before any refinement in a GCM code is made, it is necessary to investigate the dependence of radiative characteristics on the effects caused by the random geometry of cloud fields. Such studies for mean fluxes of downwelling and upwelling solar radiation in the visible and near-infrared (IR) spectral range were performed by Zuev et al. In this work, we investigate the mean spectral and integrated absorption of solar radiation by broken clouds (in what follows, the term {open_quotes}mean{close_quotes} will be implied but not used, for convenience). To evaluate the potential effect of stochastic geometry, we will compare the absorption by cumulus (0.5 {le} {gamma} {le} 2) to that by equivalent stratus ({gamma} <<1) clouds; here {gamma} = H/D, H is the cloud layer thickness and D the characteristic horizontal cloud size. The equivalent stratus clouds differ from cumulus only in the aspect ratio {gamma}, all the other parameters coinciding.

  6. Estimation of lunar titanium content: Based on absorption features of Chang’E-1 interference imaging spectrometer (ⅡM)

    2010-01-01

    Two linear regression models based on absorption features extracted from CE-1 IIM image data are presented to discuss the relationship between absorption features and titanium content. We computed five absorption parameters (Full Wave at Half Maximum (FWHM), absorption position, absorption area, absorption depth and absorption asymmetry) of the spectra collected at Apollo 17 landing sites to build two regression models, one with FWHM and the other without FWHM due to the low relation coefficient between FWHM and Ti content. Finally Ti content measured from Apollo 17 samples and Apollo 16 samples was used to test the accuracy. The results show that the predicted values of the model with FWHM have many singular values and the result of model without FWHM is more stable. The two models are relatively accurate for high-Ti districts, while seem inexact and disable for low-Ti districts.

  7. The intestinal absorption of folates.

    Visentin, Michele; Diop-Bove, Ndeye; Zhao, Rongbao; Goldman, I David

    2014-01-01

    The properties of intestinal folate absorption were documented decades ago. However, it was only recently that the proton-coupled folate transporter (PCFT) was identified and its critical role in folate transport across the apical brush-border membrane of the proximal small intestine established by the loss-of-function mutations identified in the PCFT gene in subjects with hereditary folate malabsorption and, more recently, by the Pcft-null mouse. This article reviews the current understanding of the properties of PCFT-mediated transport and how they differ from those of the reduced folate carrier. Other processes that contribute to the transport of folates across the enterocyte, along with the contribution of the enterohepatic circulation, are considered. Important unresolved issues are addressed, including the mechanism of intestinal folate absorption in the absence of PCFT and regulation of PCFT gene expression. The impact of a variety of ions, organic molecules, and drugs on PCFT-mediated folate transport is described. PMID:24512081

  8. Theory of graphene saturable absorption

    Marini, A; de Abajo, F J Garcia

    2016-01-01

    Saturable absorption is a non-perturbative nonlinear optical phenomenon that plays a pivotal role in the generation of ultrafast light pulses. Here we show that this effect emerges in graphene at unprecedentedly low light intensities, thus opening avenues to new nonlinear physics and applications in optical technology. Specifically, we theoretically investigate saturable absorption in extended graphene by developing a non-perturbative single-particle approach, describing conduction-electron dynamics in the atomically-thin material using the two-dimensional Dirac equation for massless Dirac fermions, which is recast in the form of generalized Bloch equations. By solving the electron dynamics non-perturbatively, we account for both interband and intraband contributions to the intensity-dependent saturated conductivity and conclude that the former dominates regardless of the intrinsic doping state of the material. The results are in excellent agreement with atomistic quantum-mechanical simulations including high...

  9. Bent Electro-Absorption Modulator

    2002-01-01

    The present invention relates to a method and a device for modulating optical signals based on modulating bending losses in bend, quantum well semiconductor waveguide sections. The complex refractive index of the optical active semiconducting components of the waveguide section is modulated by...... applying a variable electric or electronmagnetic field. The modulation of the complex refractive index results in a modulation of the refractive index contrast and the absorption coefficient for the waveguide at the frequency of the light. By carefully adjusting the composition of the semiconducting...... components and the applied electric field in relation to the frequency of the modulated radiation, the bending losses (and possibly coupling losses) will provide extinction of light guided by the bent waveguide section. The refractive index contract may be modulated while keeping the absorption coefficient...

  10. Quasi-static energy absorption of hollow microlattice structures

    Liu, YL; Schaedler, TA; Jacobsen, AJ; Chen, X

    2014-12-01

    We present a comprehensive modeling and numerical study focusing on the energy quasi-static crushing behavior and energy absorption characteristics of hollow tube microlattice structures. The peak stress and effective plateau stress of the hollow microlattice structures are deduced for different geometrical parameters which gives volume and mass densities of energy absorption, D-v and D-m, scale with the relative density, (rho) over bar, as D-v similar to (rho) over bar (1) (5) and D-m similar to (rho) over bar (0 5), respectively, fitting very well to the experimental results of both 60 degrees inclined and 90 degrees predominately microlattices. Then the strategies for energy absorption enhancement are proposed for the engineering design of microlattice structures. By introducing a gradient in the thickness or radius of the lattice members, the buckle propagation can be modulated resulting in an increase in energy absorption density that can exceed 40%. Liquid filler is another approach to improve energy absorption by strengthening the microtruss via circumference expansion, and the gain may be over 100% in terms of volume density. Insight into the correlations between microlattice architecture and energy absorption performance combined with the high degree of architecture control paves the way for designing high performance microlattice structures for a range of impact and impulse mitigation applications for vehicles and structures. (C) 2014 Elsevier Ltd. All rights reserved.

  11. Analysis of crystallization risk in double effect absorption refrigeration systems

    Absorption refrigeration systems are an alternative to vapor compression ones in cooling and refrigeration applications. In comparison with single effect absorption units, double effect systems have improved performance. Also, they are more available commercially than the other multi effect absorption cycles. An important challenge in the operation of such systems is the possibility of crystallization within them. This is especially true in developing air-cooled absorption systems, which are attractive because cooling tower and associated installation and maintenance issues can be avoided. Therefore, distinguishing the working conditions that may cause crystallization can be useful in the design and control of these systems. In this paper a computational model has been developed to study and compare the effects of operating parameters on crystallization phenomena in three classes of double effect lithium bromide-water absorption refrigeration systems (series, parallel and reverse parallel) with identical refrigeration capacities. It is shown that the range of operating conditions without crystallization risks in the parallel and the reverse parallel configurations is wider than those of the series flow system. - Highlights: → We study crystallization of double effect absorption refrigeration systems. → We consider series, parallel and reverse parallel cycles. → We study the effect of operating conditions on crystallization. → We choose optimum distribution ratio for parallel and reverse parallel systems. → Crystallization possibility is low in parallel and reverse parallel cycles.

  12. Examination of oral absorption and lymphatic transport of halofantrine in a triple-cannulated canine model after administration in self-microemulsifying drug delivery systems (SMEDDS) containing structured triglycerides

    Holm, René; Porter, Christopher J H; Edwards, Glenn A;

    2003-01-01

    pathways. The MLM formulation produced a total bioavailability of 74.9%, which is higher than the total absorption previously observed after post-prandial administration. This could indicate the utility of disperse lipid-base formulations based on structured triglycerides for the oral delivery of...... availability was affected by the triglyceride incorporated into the multi-component delivery system and availabilities of 56.9% (MLM) and 37.2% (LML) were found. These data indicate that the pharmaceutical scientist can use the structure of the lipid to affect the relative contribution of the two absorption...

  13. Slowing down with resonance absorption

    The presence of heavy nuclei in nuclear reactors, in significant concentrations, facilitates the appearance of absorption resonances. For the moderation in the presence of absorbers an exact solution of the integral equations is possible by numerical methods. Approximated solutions for separated resonances in function of the practical width, (NR and NRIM approximations) are discussed in this paper. The method is generalized, presenting the solution by an intermediate approximation, in the definition of the resonance integral. (Author)

  14. Absorption properties of identical atoms

    Sancho, Pedro

    2013-01-01

    Emission rates and other optical properties of multiparticle systems in collective and entangled states differ from those in product ones. We show the existence of similar effects in the absorption probabilities for (anti)symmetrized states of two identical atoms. The effects strongly depend on the overlapping between the atoms and differ for bosons and fermions. We propose a viable experimental verification of these ideas.

  15. Absorption properties of identical atoms

    Sancho, Pedro

    2013-09-01

    Emission rates and other optical properties of multi-particle systems in collective and entangled states differ from those in product ones. We show the existence of similar effects in the absorption probabilities for (anti)symmetrized states of two identical atoms. The effects strongly depend on the overlapping between the atoms and differ for bosons and fermions. We propose a viable experimental verification of these ideas.

  16. Maximum-likelihood absorption tomography

    Maximum-likelihood methods are applied to the problem of absorption tomography. The reconstruction is done with the help of an iterative algorithm. We show how the statistics of the illuminating beam can be incorporated into the reconstruction. The proposed reconstruction method can be considered as a useful alternative in the extreme cases where the standard ill-posed direct-inversion methods fail. (authors)

  17. Chaos and multiple photon absorption

    An anharmonic vibrational mode of a molecule, driven by an intense infrared laser and coupled to a quasi-continuum of background modes, is found to undergo chaotic oscillations. This chaos leads to predominantly fluence-dependent rather than intensity-dependent multiple-photon absorption, as is found experimentally. The loss of coherence is associated with the decay of temporal correlation of background-mode oscillations

  18. Small quantum absorption refrigerator with reversed couplings.

    Silva, Ralph; Skrzypczyk, Paul; Brunner, Nicolas

    2015-07-01

    Small quantum absorption refrigerators have recently attracted renewed attention. Here we present a missing design of a two-qubit fridge, the main feature of which is that one of the two machine qubits is itself maintained at a temperature colder than the cold bath. This is achieved by "reversing" the couplings to the baths compared to previous designs, where only a transition is maintained cold. We characterize the working regime and the efficiency of the fridge. We demonstrate the soundness of the model by deriving and solving a master equation. Finally, we discuss the performance of the fridge, in particular the heat current extracted from the cold bath. We show that our model performs comparably to the standard three-level quantum fridge and thus appears appealing for possible implementations of nanoscale thermal machines. PMID:26274153

  19. Fluorescence and optical absorption in spodumene

    This work studied the mechanism of the isothermal decay's kinetic of the 15.600 cm-1 optical absorption band (A.O.) of irradiated spodumene, and the phosphorescence of irradiated spodumene in low temperatures. The kinetic mechanisms applying the bimolecular model to liberation, capture and recombination reactions are analysed. The coupled differential equations, resultants of this model, numerically using the Runge-Kutta method is solved, and a computer programs that allowed determine the kinetics parameters by try and error methods is developped. This work showed that the electrons are untrapped according to Arrhernios kinetic and that the parameters of the trap and recombination are proportional to a factor (√T - √To ), where To is the cutting temperature, bfore which the reactions do not occur. (author)

  20. Theory of strong-field attosecond transient absorption

    Wu, Mengxi; Chen, Shaohao; Camp, Seth; Schafer, Kenneth J.; Gaarde, Mette B.

    2016-03-01

    Attosecond transient absorption is one of the promising new techniques being developed to exploit the availability of sub-femtosecond extreme ultraviolet (XUV) pulses to study the dynamics of the electron on its natural time scale. The temporal resolution in a transient absorption setup comes from the control of the relative delay and coherence between pump and probe pulses, while the spectral resolution comes from the characteristic width of the features that are being probed. In this review we focus on transient absorption scenarios where an attosecond pulse of XUV radiation creates a broadband excitation that is subsequently probed by a few cycle infrared (IR) laser. Because the attosecond XUV pulses are locked to the IR field cycle, the exchange of energy in the laser-matter interaction can be studied with unprecedented precision. We focus on the transient absorption by helium atoms of XUV radiation around the first ionization threshold, where we can simultaneoulsy solve the time-dependent Schrödinger equation for the single atom response and the Maxwell wave equation for the collective response of the nonlinear medium. We use a time-domain method that allows us to treat on an equal footing all the different linear and nonlinear processes by which the medium can exchange energy with the fields. We present several simple models, based on a few-level system interacting with a strong IR field, to explain many of the novel features found in attosecond transient absorption spectrograms. These include the presence of light-induced states, which demonstrate the ability to probe the dressed states of the atom. We also present a time-domain interpretation of the resonant pulse propagation features that appear in absorption spectra in dense, macroscopic media. We close by reviewing several recent experimental results that can be explained in terms of the models we discuss. Our aim is to present a road map for understanding future attosecond transient absorption

  1. Evolution of absorption machines; Evolution des machines a absorption

    Soide, I.; Klemsdal, E. [Gaz de France (GDF), 75 - Paris (France); Le Goff, P.; Hornut, J.M. [LSGC-ENSIC, 54 - Nancy (France)

    1997-12-31

    Most of todays absorption air-conditioning machineries use the lithium bromide-water pair. The most performing can operate at a 150-160 deg. C, the temperature being limited by the corrosion resistance of metals with respect to LiBr solutions. Also, there is a revival of interest for water-ammonia systems. These systems require the use of a rectification column which reduces the coefficient of performance. Higher thermal performances are reached with hydrocarbon pairs and ternary mixtures (water-methanol-LiBr etc..). This paper presents different schemes of refrigerating heat pumps based on these different systems. (J.S.)

  2. Drug recovery following buccal absorption of propranolol.

    Henry, J A; Ohashi, K.; Wadsworth, J.; Turner, P.,

    1980-01-01

    1 Buccal absorption of propranolol in two volunteers was followed by repeated rinsing of the mouth with buffer solutions for twelve 2 min periods. Values for absorption, recovery and asymptotic recovery were calculated. 2 Large amounts of propranolol were recoverable from the buccal mucosa; recovery was biexponential and the amount recovered depended on the time allowed for absorption and on the pH of buffers used for recovery. 3 In the case of the drug studied, the buccal absorption test was...

  3. Plasmonically enhanced light absorption in graphene nanoribbons

    Woessner, Achim

    2012-01-01

    [ANGLÈS] Light absorption plays a crucial role in both optical detectors and photovoltaics. In order to improve the light absorption properties of materials different measures can be taken. This thesis considers light absorption of graphene in the mid infrared region of the electromagnetic spectrum. A numerical study of light absorption and of localized plasmons in nanostructured graphene is presented and discussed. We show that for nanostructured graphene in the mid infrared region of the sp...

  4. Free carrier absorption in quantum cascade structures

    Carosella, F.; Ndebeka-Bandou, C.; Ferreira, R.; Dupont, E; K. Unterrainer; Strasser, G.; Wacker, Andreas; Bastard, G.

    2011-01-01

    We show that the free carrier absorption in Quantum Cascade Lasers is very small and radically different from the classical Drude result on account of the orthogonality between the direction of the carrier free motion and the electric field of the laser emission. A quantum mechanical calculation of the free carrier absorption and inter-subband oblique absorption induced by interface defects, coulombic impurities and optical phonon absorption/emission is presented for QCL's with a double quant...

  5. Absorption and Transport of Sea Cucumber Saponins from Apostichopus japonicus

    Shuai Li

    2016-06-01

    Full Text Available The present study is focused on the intestinal absorption of sea cucumber saponins. We determined the pharmacokinetic characteristics and bioavailability of Echinoside A and Holotoxin A1; the findings indicated that the bioavailability of Holotoxin A1 was lower than Echinoside A. We inferred that the differences in chemical structure between compounds was a factor that explained their different characteristics of transport across the intestine. In order to confirm the absorption characteristics of Echinoside A and Holotoxin A1, we examined their transport across Caco-2 cell monolayer and effective permeability by single-pass intestinal perfusion. The results of Caco-2 cell model indicate that Echinoside A is transported by passive diffusion, and not influenced by the exocytosis of P-glycoprotein (P-gp, expressed in the apical side of Caco-2 monolayers as the classic inhibitor. The intestinal perfusion also demonstrated well the absorption of Echinoside A and poor absorption of Holotoxin A1, which matched up with the result of the Caco-2 cell model. The results demonstrated our conjecture and provides fundamental information on the relationship between the chemical structure of these sea cucumber saponins and their absorption characteristics, and we believe that our findings build a foundation for the further metabolism study of sea cucumber saponins and contribute to the further clinical research of saponins.

  6. Absorption and Transport of Sea Cucumber Saponins from Apostichopus japonicus.

    Li, Shuai; Wang, Yuanhong; Jiang, Tingfu; Wang, Han; Yang, Shuang; Lv, Zhihua

    2016-01-01

    The present study is focused on the intestinal absorption of sea cucumber saponins. We determined the pharmacokinetic characteristics and bioavailability of Echinoside A and Holotoxin A₁; the findings indicated that the bioavailability of Holotoxin A₁ was lower than Echinoside A. We inferred that the differences in chemical structure between compounds was a factor that explained their different characteristics of transport across the intestine. In order to confirm the absorption characteristics of Echinoside A and Holotoxin A₁, we examined their transport across Caco-2 cell monolayer and effective permeability by single-pass intestinal perfusion. The results of Caco-2 cell model indicate that Echinoside A is transported by passive diffusion, and not influenced by the exocytosis of P-glycoprotein (P-gp, expressed in the apical side of Caco-2 monolayers as the classic inhibitor). The intestinal perfusion also demonstrated well the absorption of Echinoside A and poor absorption of Holotoxin A₁, which matched up with the result of the Caco-2 cell model. The results demonstrated our conjecture and provides fundamental information on the relationship between the chemical structure of these sea cucumber saponins and their absorption characteristics, and we believe that our findings build a foundation for the further metabolism study of sea cucumber saponins and contribute to the further clinical research of saponins. PMID:27322290

  7. Absorption-edge calculations of inorganic nonlinear optical crystals

    Wu, Kechen; Chen, Chuangtian

    1992-03-01

    A theoretical model suitable for calculating absorption edges of inorganic nonlinear optical (NLO) crystals is introduced. This model is proved to be useful to elucidate the relationship between electronic structures of NLO-active groups and macroscopic properties of absorption edges on the UV side of most of the inorganic nonlinear optical crystals. A systematic calculation of absorption edges on the UV side for several important inorganic NLO crystals is carried out by means of DV-SCM-Xα method and all calculated results are in good agreement with experimental data. These inorganic NLO crystals include LiB3O5(LBO), β-BaB2O4(BBO), KB5, KDP, Na2SbF5, Ba2TiSi2O8, iodate and NaNO2. The calculated energy level structures of LiB3O5 and β-BaB2O4 crystals are compared with the measured XPS spectra. The unusual transparent spectra of KB5 and KDP crystals are partly explained from the microstructure point of view. The effect of lone electron pair in iodate and NaNO2 crystals on their absorption edges are discussed. All these results show that Anionic Group Theory of Nonlinear Optical Crystals is useful to evaluate the absorption edges of the inorganic nonlinear optical crystal and is a powerful tool in a Molecular Engineering approach to search for new nonlinear optical materials.

  8. Structural sound absorption in liquid metals

    Present article is devoted to structural sound absorption in liquid metals. The study of sound absorption in liquid metals shown that in all studied objects the structural absorption of sound was observed. The mechanism of structural relaxation in molten metal was revealed.

  9. Lactulose stimulates calcium absorption in postmenopausal women

    Heuvel, E.G.H.M. van den; Muijs, T.; Dokkum, W. van; Schaafsma, G.

    1999-01-01

    Animal studies have indicated that calcium absorption is increased by lactulose, a synthetic disaccharide. Therefore, the influence of lactulose on calcium absorption was measured in postmenopausal women who may benefit from the possible enhancing effect of lactulose on calcium absorption. Twelve po

  10. The risk of hydroquinone and sunscreen over-absorption via photodamaged skin is not greater in senescent skin as compared to young skin: nude mouse as an animal model.

    Hung, Chi-Feng; Chen, Wei-Yu; Aljuffali, Ibrahim A; Shih, Hui-Chi; Fang, Jia-You

    2014-08-25

    Intrinsic aging and photoaging modify skin structure and components, which subsequently change percutaneous absorption of topically applied permeants. The purpose of this study was to systematically evaluate drug/sunscreen permeation via young and senescent skin irradiated by ultraviolet (UV) light. Both young and senescent nude mice were subjected to UVA (10 J/cm(2)) and/or UVB radiation (175 mJ/cm(2)). Physiological parameters, immunohistology, and immunoblotting were employed to examine the aged skin. Hydroquinone and sunscreen permeation was determined by in vitro Franz cell. In vivo skin absorption was documented using a hydrophilic dye, rhodamine 123 (log P=-0.4), as a permeant. UVA exposure induced cyclooxygenase (COX)-2 and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) upregulation. Epidermal tight junction (TJ) were degraded by UVA. UVB increased transepidermal water loss (TEWL) from 13 to 24 g/m(2)/h. Hyperplasia and inflammation, but not loss of TJ, were also observed in UVB-treated skin. UVA+UVB- and UVA-irradiated skin demonstrated similar changes in histology and biomarkers. UVA+UVB or UVA exposure increased hydroquinone flux five-fold. A negligible alteration of hydroquinone permeation was shown with UVB exposure. Hydroquinone exhibited a lower penetration through senescent skin than young skin. Both UVA and UVB produced enhancement of oxybenzone flux and skin uptake. However, the amount of increase was less than that of hydroquinone delivery. Photoaging did not augment skin absorption of sunscreens with higher lipophilicity, including avobenzone and ZnO. Exposure to UVA generally increased follicular entrance of these permeants, which showed two- to three-fold greater follicular uptake compared to the untreated group. Photoaging had less impact on drug/sunscreen absorption with more lipophilic permeants. Percutaneous absorption did not increase in skin subjected to both intrinsic and extrinsic aging. PMID:24858384

  11. 44th Annual Anomalous Absorption Conference

    Beg, Farhat

    2014-03-03

    Conference Grant Report July 14, 2015 Submitted to the U. S. Department of Energy Attn: Dr. Sean Finnegan By the University of California, San Diego 9500 Gilman Drive La Jolla, California 92093 On behalf of the 44th Annual Anomalous Absorption Conference 8-13 June 2014, in Estes Park, Colorado Support Requested: $10,100 Amount expended: $3,216.14 Performance Period: 1 March 20 14 to 28 February 20 15 Principal Investigator Dr. Farhat Beg Center for Energy Research University of California, San Diego 9500 Gilman Drive La Jolla, California 92093-0417 858-822-1266 (telephone) 858-534-4543 (fax) fbeg@ucsd.edu Administrative Point of Contact: Brandi Pate, 858-534-0851, blpate®ucsd.edu I. Background The forty-fourth Anomalous Absorption Conference was held in Estes Park, Colorado from June 5-8, 2014 (aac2014.ucsd.edu). The first Anomalous Absorption Conference was held in 1971 to assemble experts in the poorly understood area of laser-plasma absorption. The goal of that conference was to address the anomalously large laser absorption seen in plasma experiments with respect to the laser absorption predicted by linear plasma theory. Great progress in this research area has been made in the decades since that first meeting, due in part to the scientific interactions that have occurred annually at this conference. Specifically, this includes the development of nonlinear laser-plasma theory and the simulation of laser interactions with plasmas. Each summer since that first meeting, this week-long conference has been held at unique locations in North America as a scientific forum for intense scientific exchanges relevant to the interaction of laser radiation with plasmas. Responsibility for organizing the conference has traditional rotated each year between the major Inertial Confinement Fusion (ICF) laboratories and universities including LANL, LLNL, LLE, UCLA UC Davis and NRL. As the conference has matured over the past four decades, its technical footprint has expanded

  12. Determination of phytoplankton composition using absorption spectra.

    Martínez-Guijarro, R; Romero, I; Pachés, M; Del Río, J G; Martí, C M; Gil, G; Ferrer-Riquelme, A; Ferrer, J

    2009-05-15

    Characterisation of phytoplankton communities in aquatic ecosystems is a costly task in terms of time, material and human resources. The general objective of this paper is not to replace microscopic counts but to complement them, by fine-tuning a technique using absorption spectra measurements that reduces the above-mentioned costs. Therefore, the objective proposed in this paper is to assess the possibility of achieving a qualitative determination of phytoplankton communities by classes, and also a quantitative estimation of the number of phytoplankton cells within each of these classes, using spectrophotometric determination. Samples were taken in three areas of the Spanish Mediterranean coast. These areas correspond to estuary systems that are influenced by both continental waters and Mediterranean Sea waters. 139 Samples were taken in 7-8 stations per area, at different depths in each station. In each sample, the absorption spectrum and the phytoplankton classes (Bacyllariophyceae (diatoms), Cryptophyceae, Clorophyceae, Chrysophyceae, Prasynophyceae, Prymnesophyceae, Euglenophyceae, Cyanophyceae, Dynophyceae and the Synechococcus sp.) were determined. Data were analysed by means of the Partial Least Squares (PLS) multivariate statistical technique. The absorbances obtained between 400 and 750 nm were used as the independent variable and the cell/l of each phytoplankton class was used as the dependent variable, thereby obtaining models which relate the absorbance of the sample extract to the phytoplankton present in it. Good results were obtained for diatoms (Bacillarophyceae), Chlorophyceae and Cryptophyceae. PMID:19269434

  13. AGN Absorption Linked to Host Galaxies

    Juneau, Stéphanie

    2013-01-01

    Multiwavelength identification of AGN is crucial not only to obtain a more complete census, but also to learn about the physical state of the nuclear activity (obscuration, efficiency, etc.). A panchromatic strategy plays an especially important role when the host galaxies are star-forming. Selecting far-Infrared galaxies at 0.3absorption and the specific star formation rate (sSFR) of the host galaxies, indicating a physical link between X-ray absorption and either the gas fraction or the gas geometry in the hosts. These findings have implications for our current understanding of both the AGN unification model and the nature of the black hole-galaxy connection. These proceedi...

  14. Absorption Measure Distribution in Mrk 509

    Adhikari, T. P.; Różańska, A.; Sobolewska, M.; Czerny, B.

    2015-12-01

    In this paper we model the observed absorption measure distribution (AMD) in Mrk 509, which spans three orders of magnitude in ionization level with a single-zone absorber in pressure equilibrium. AMD is usually constructed from observations of narrow absorption lines in radio-quiet active galaxies with warm absorbers. We study the properties of the warm absorber in Mrk 509 using recently published broadband spectral energy distribution observed with different instruments. This spectrum is an input in radiative transfer computations with full photoionization treatment using the titan code. We show that the simplest way to fully reproduce the shape of AMD is to assume that the warm absorber is a single zone under constant total pressure. With this assumption, we found theoretical AMD that matches the observed AMD determined on the basis of the 600 ks reflection grating spectrometer XMM-Newton spectrum of Mrk 509. The softness of the source spectrum and the important role of the free-free emission breaks the usual degeneracy in the ionization state calculations, and the explicit dependence of the depths of AMD dips on density open a new path to the density diagnostic for the warm absorber. In Mrk 509, the implied density is of the order of 108 cm-3.

  15. On the Absorption of X-ray Bright Broad Absorption Line Quasars

    Giustini, Margherita; Vignali, Cristian

    2008-01-01

    Most X-ray studies of BALQSOs found significant (N_H~10^{22-24} cm^{-2}) intrinsic column densities of gas absorbing an underlying typical power-law continuum emission, in agreement with expectations from radiatively driven accretion disk wind models. However, direct spectral analysis was performed only on a limited number of bright sources. We investigate the X-ray emission of a large BALQSO sample at medium to high redshift (0.8 ~ 5 x 10^{22} cm^{-2}) even including the faintest sources analyzed through hardness ratio analysis. The mean photon index is Gamma~1.9, with no significant evolution with redshift. The alpha_ox are typical of radio-quiet broad line AGN, in contrast with the known (from previous X-ray studies) ``soft X-ray weakness'' of BALQSOs and in agreement with the lack of X-ray absorption. We found the low-Absorption Index (AI) subsample to host the lowest X-ray absorbing column densities of the entire sample. X-ray selected BALQSOs show lower X-ray absorption than purely optically selec ted o...

  16. Theory and practice of nitrogen oxide absorption

    Nitrogen oxide (NO/sub x/) absorbers vary in purpose from bulk nitric acid production to abatement of trace NO/sub x/ concentrations from gas streams. Absorbers are typically of plate or packed tower design although some plate/packed combination towers potentially offer some useful advantages. Mathematical models for the design of NO/sub x/ absorbers vary from mechanistically based models for absorption into water and dilute HNO3 to empirically based models for absorption into concentrated HNO3 solutions. The NO/sub x/ content in effluent gas from modern high pressure nitric acid production towers can be reduced to well under 200 ppm. The basis for the design of low pressure NO/sub x/ absorbers for NO/sub x/ recovery or abatement has been established to a sufficient extent to be a reasonably predictive tool although published operating experience is minimal and experimental verification may be necessary for many cases. The availability of high efficiency packing potentially offers significant NO/sub x/ removal in minimal sized packed absorbers. An important issue in the design of NO/sub x/ abatement systems is the disposition of the effluent scrubber liquid. A partial recycle of this liquid to the absorber normally requires additional processes for regeneration of the scrub solution; if there is an in plant use for this effluent stream, then a substantial simplification of the system may be realized. Low pressure NO/sub x/ absorbers for the primary purpose of gaseous NO/sub x/ recovery and abatement are discussed

  17. Absorption effects in intermediate-energy electron scattering by difluoroethylene

    Full text: Although several solid-based ab-initio theoretical methods have been developed in the past few decades for the investigation on electron-molecule collisions, most of them can only be successfully applied in the low incident electron energy range. The extension of their application to the intermediate-energy range (roughly from the first ionization potential to around 1 keV) is not straightforward. It is known that at these energies the numerous open inelastic scattering channels are responsible for absorption effects that play an important role on the collision dynamics. In the last two decades, several model absorption potentials have been proposed to include absorption effects into the scattering dynamics and so, the resolution of the scattering equations is kept in the single-channel framework. Although these model-potential methods have shown to provide, in general, quite accurate differential (DCS), integral (ICS) and momentum-transfer (MTCS) cross sections for elastic electron-molecule collisions, most of the calculations have systematically underestimated the values of the grand-total (TCS) and total absorption (TACS) cross sections. In recent papers, our group has reported a modified version of the widely used Stazewska's version 3 of the quasi-free scattering model (QFSM3) absorption potential. In order to obtain a better description of screening effects due to the target electronic cloud, we have proposed a multiplicative screening factor that should be applied on the original QFSM3 absorption potential. In our works, we have shown that such a simple modification in the absorption model potential is capable of providing significant improvement in the calculated TCS and TAGS for a variety of targets for intermediate-energy electron-molecule collisions. In the present work we apply our modified model absorption potential to study electron scattering by a strongly polar molecule, cis-difluoroethylene in a wide incident energy range (1-500 e

  18. Constrained two-stream algorithm for calculating aerosol light absorption coefficient from the Particle Soot Absorption Photometer

    Müller, T. (Tessa); Virkkula, A.; Ogren, J.A.

    2014-01-01

    We present a new correction scheme for filter-based absorption photometers based on a constrained two-stream (CTS) radiative transfer model and experimental calibrations. The two-stream model was initialized using experimentally accessible optical parameters of the filter. Experimental calibrations were taken from the literature and from dedicated experiments for the present manuscript. Uncertainties in the model and calibration experiments are discussed and uncertainties fo...

  19. Effect of fractal parameters on absorption properties of soot in the infrared region

    Absorption coefficient of soot aggregates in the infrared region is investigated using multi-sphere T matrix algorithm. As the refractive index of soot is relatively high, the interaction between neighboring particles is important and Rayleigh approximation is invalid. The absorption cross section of soot is much higher than the Rayleigh approximation prediction. The effect of fractal parameters, dimension Df and prefactor kf, on absorption can be substantial and varies strongly with optical size parameter x and refractive index m. Families of fractal structures having similar absorption cross sections have been identified. It is noted that the fractal structures from the same family have similar particle distance correlation functions. Following this, an empirical model for absorption of soot as a function of m, x and fractal parameters has been developed. The model successfully predicts the absorption within ±5% for various fractal structures. Compared to Rayleigh approximation, the absorption enhancement can be as high as 200% at low temperatures and 120% at high temperatures. Effects of fractal parameters on absorption enhancement are important for low temperature applications but are not significant at high temperatures. This is mainly due to high refractive indices of soot at long wavelengths and shift of emitted radiation towards short wavelengths with increase in temperature. - Highlights: • Absorption of soot in the IR is investigated using MSTM method. • Absorption properties are discussed in terms of morphology of soot aggregates. • An empirical model for absorption of soot in the IR has been developed. • The model predicts absorption within ±5% for various fractal parameters

  20. Research program in nuclear and solid state physics. [including pion absorption spectra and muon spin precession

    1974-01-01

    The survey of negative pion absorption reactions on light and medium nuclei was continued. Muon spin precession was studied using an iron target. An impulse approximation model of the pion absorption process implied that the ion will absorb almost exclusively on nucleon pairs, single nucleon absorption being suppressed by energy and momentum conservation requirements. For measurements on both paramagnetic and ferromagnetic iron, the external magnetic field was supplied by a large C-type electromagnet carrying a current of about 100 amperes.