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Sample records for absorption model

  1. Absorption in dielectric models

    Churchill, R J

    2015-01-01

    We develop a classical microscopic model of a dielectric. The model features nonlinear interaction terms between polarizable dipoles and lattice vibrations. The lattice vibrations are found to act as a pseudo-reservoir, giving broadband absorption of electromagnetic radiation without the addition of damping terms in the dynamics. The effective permittivity is calculated using a perturbative iteration method and is found to have the form associated with real dielectrics. Spatial dispersion is naturally included in the model and we also calculate the wavevector dependence of the permittivity.

  2. Absorption spectroscopy of EBT model GAFCHROMIC film.

    Devic, Slobodan; Tomic, Nada; Pang, Zhiyu; Seuntjens, Jan; Podgorsak, Ervin B; Soares, Christopher G

    2007-01-01

    The introduction of radiochromic films has solved some of the problems associated with conventional 2D radiation detectors. Their high spatial resolution, low energy dependence, and near-tissue equivalence make them ideal for measurement of dose distributions in radiation fields with high dose gradients. Precise knowledge of the absorption spectra of these detectors can help to develop more suitable optical densitometers and potentially extend the use of these films to other areas such as the measurement of the radiation beam spectral information. The goal of this study is to present results of absorption spectra measurements for the new GAFCHROMIC film, EBT type, exposed to 6 MV photon beam in the dose range from 0 to 6 Gy. Spectroscopic analysis reveals that in addition to the two main absorption peaks, centered at around 583 and 635 nm, the absorption spectrum in the spectral range from 350 to 800 nm contains six more absorption bands. Comparison of the absorption spectra reveals that previous HD-810, MD-55, as well as HS GAFCHROMIC film models, have nearly the same sensitive layer base material, whereas the new EBT model, GAFCHROMIC film has a different composition of its sensitive layer. We have found that the two most prominent absorption bands in EBT model radiochromic film do not change their central wavelength position with change in a dose deposited to the film samples.

  3. A new model for quasar absorption clouds

    Doroshkevich, A.G. (Academy of Sciences of USSR, Moscow (USSR). Inst. of Applied Mathematics); Muecket, J.P.; Mueller, V. (Academy of Sciences of GDR, Potsdam (German Democratic Republic). Central Inst. for Astrophysics)

    1990-09-15

    A local model for intervening absorption clouds in quasar spectra is discussed. At the boundary of cold clouds in the hot intergalactic gas a non-linear temperature profile results from electron heat conductivity and radiative energy losses both depending on ionization rates. This transition region causes the excitation of a wide range of ionization levels in the heavy elements of the gas. The predicted column densities along the line-of-sight are comparable with data from identified metal absorption systems at high redshifts. (author).

  4. Mathematical model of zinc absorption: effects of dietary calcium, protein and iron on zinc absorption.

    Miller, Leland V; Krebs, Nancy F; Hambidge, K Michael

    2013-02-28

    A previously described mathematical model of Zn absorption as a function of total daily dietary Zn and phytate was fitted to data from studies in which dietary Ca, Fe and protein were also measured. An analysis of regression residuals indicated statistically significant positive relationships between the residuals and Ca, Fe and protein, suggesting that the presence of any of these dietary components enhances Zn absorption. Based on the hypotheses that (1) Ca and Fe both promote Zn absorption by binding with phytate and thereby making it unavailable for binding Zn and (2) protein enhances the availability of Zn for transporter binding, the model was modified to incorporate these effects. The new model of Zn absorption as a function of dietary Zn, phytate, Ca, Fe and protein was then fitted to the data. The proportion of variation in absorbed Zn explained by the new model was 0·88, an increase from 0·82 with the original model. A reduced version of the model without Fe produced an equally good fit to the data and an improved value for the model selection criterion, demonstrating that when dietary Ca and protein are controlled for, there is no evidence that dietary Fe influences Zn absorption. Regression residuals and testing with additional data supported the validity of the new model. It was concluded that dietary Ca and protein modestly enhanced Zn absorption and Fe had no statistically discernable effect. Furthermore, the model provides a meaningful foundation for efforts to model nutrient interactions in mineral absorption.

  5. 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.

  6. Absorption of acoustic waves by sunspots. II - Resonance absorption in axisymmetric fibril models

    Rosenthal, C. S.

    1992-01-01

    Analytical calculations of acoustic waves scattered by sunspots which concentrate on the absorption at the magnetohydrodynamic Alfven resonance are extended to the case of a flux-tube embedded in a uniform atmosphere. The model is based on a flux-tubes of varying radius that are highly structured, translationally invariant, and axisymmetric. The absorbed fractional energy is determined for different flux-densities and subphotospheric locations with attention given to the effects of twist. When the flux is highly concentrated into annuli efficient absorption is possible even when the mean magnetic flux density is low. The model demonstrates low absorption at low azimuthal orders even in the presence of twist which generally increases the range of wave numbers over which efficient absorption can occur. Resonance absorption is concluded to be an efficient mechanism in monolithic sunspots, fibril sunspots, and plage fields.

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

    Schleimer, Stephanie; Pedersen, Torben

    2011-01-01

    and empirically test a process model of absorptive capacity. The setting of our empirical study is 213 subsidiaries of multinational enterprises and the focus is on the capacity of these subsidiaries to successfully absorb best practices in marketing strategy from their headquarters. This setting allows us...... to explore the process model in its entirety, including different drivers of subsidiary absorptive capacity (organizational mechanisms and contextual drivers), the three original dimensions of absorptive capacity (recognition, assimilation, application), and related outcomes (implementation...

  8. Model systems for understanding absorption tuning by opsin proteins

    Nielsen, Mogens Brøndsted

    2009-01-01

    This tutorial review reports on model systems that have been synthesised and investigated for elucidating how opsin proteins tune the absorption of the protonated retinal Schiff base chromophore. In particular, the importance of the counteranion is highlighted. In addition, the review advocates...... is avoided, and it becomes clear that opsin proteins induce blueshifts in the chromophore absorption rather than redshifts....

  9. Modelling absorption and photoluminescence of TPD

    Vragovic, Igor [Dpto. de Fisica Aplicada and Inst. Universitario de Materiales de Alicante, Universidad de Alicante, E-03080 Alicante (Spain)], E-mail: igor.vragovic@ua.es; Calzado, Eva M.; Diaz Garcia, Maria A.; Himcinschi, C. [Max-Planck-Institut fuer Mikrostrukturphysik, D-06120 Halle (Germany); Gisslen, L.; Scholz, R. [Walter Schottky Institut, Technische Universitaet Muenchen, D-85748 Garching (Germany)

    2008-05-15

    We analyse the optical spectra of N,N{sup '}-diphenyl-N,N{sup '}-bis(3-methyl-phenyl)-(1,1{sup '}-biphenyl)-4,4{sup '}-diamine (TPD) doped polystyrene films. The aim of the present paper is to give a microscopic interpretation of the significant Stokes shift between absorption and photoluminescence, which makes this material suitable for stimulated emission. The optimized geometric structures and energies of a neutral TPD monomer in ground and excited states are obtained by ab initio calculations using Hartree-Fock and density functional theory. The results indicate that the second distinct peak observed in absorption may arise either from a group of higher electronic transitions of the monomer or from the lowest optical transitions of a TPD dimer.

  10. Proposing a model for absorption capacity of technology

    Hossein Gholizadeh

    2015-01-01

    Full Text Available Absorption capacity of knowledge is the concept which is been introduced in this situation. This phenomenon describes why some countries are in a better condition with a view to technology. Many countries believe that the power to stay in the battle and excel other competitors directly depends on their abilities in taking knowledge. Many countries have used their technological gap with developed countries as an accelerator for improving their absorption capacity. In this study, authors tried to produce a complete definition for absorption capacity through analyzing different research. Then with using expert opinions, a categorization for dimensions of absorption capacity will be prepared by using the structural equation modeling analysis, and finally a model for measuring absorption capacity is suggested. The results show effective dimensions in 5 different section. Studies depict that the most important one is keeping which could be a fundamental for long-term policies of 1404.

  11. Estimation of the Human Absorption Cross Section Via Reverberation Models

    Steinböck, Gerhard; Pedersen, Troels; Fleury, Bernard Henri;

    2016-01-01

    Since the presence of persons affects the reverberation time observed for in-room channels, the absorption cross section of a person can be estimated from measurements via Sabine's and Eyring's models for the reverberation time. We propose an estimator relying on the more accurate model by Eyring...... and compare the obtained results to those of Sabine's model. We find that the absorption by persons is large enough to be measured with a wideband channel sounder and that estimates of the human absorption cross section differ for the two models. The obtained values are comparable to values reported...... in the literature. We also suggest the use of controlled environments with low average absorption coefficients to obtain more reliable estimates. The obtained values can be used to predict the change of reverberation time with persons in the propagation environment. This allows prediction of channel characteristics...

  12. 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.

  13. Models to predict intestinal absorption of therapeutic peptides and proteins.

    Antunes, Filipa; Andrade, Fernanda; Ferreira, Domingos; Nielsen, Hanne Morck; Sarmento, Bruno

    2013-01-01

    Prediction of human intestinal absorption is a major goal in the design, optimization, and selection of drugs intended for oral delivery, in particular proteins, which possess intrinsic poor transport across intestinal epithelium. There are various techniques currently employed to evaluate the extension of protein absorption in the different phases of drug discovery and development. Screening protocols to evaluate protein absorption include a range of preclinical methodologies like in silico, in vitro, in situ, ex vivo and in vivo. It is the careful and critical use of these techniques that can help to identify drug candidates, which most probably will be well absorbed from the human intestinal tract. It is well recognized that the human intestinal permeability cannot be accurately predicted based on a single preclinical method. However, the present social and scientific concerns about the animal well care as well as the pharmaceutical industries need for rapid, cheap and reliable models predicting bioavailability give reasons for using methods providing an appropriate correlation between results of in vivo and in vitro drug absorption. The aim of this review is to describe and compare in silico, in vitro, in situ, ex vivo and in vivo methods used to predict human intestinal absorption, giving a special attention to the intestinal absorption of therapeutic peptides and proteins.

  14. 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 part......, starch, sugars and dietary fibre. Besides a chemical description of the feed, the model further requires information about daily dry matter intake and feeding frequency....

  15. Model predicting impact of complexation with cyclodextrins on oral absorption.

    Gamsiz, Ece D; Thombre, Avinash G; Ahmed, Imran; Carrier, Rebecca L

    2013-09-01

    Significant effort and resource expenditure is dedicated to enabling low-solubility oral drug delivery using solubilization technologies. Cyclodextrins (CD) are cyclic oligosaccharides which form inclusion complexes with many drugs and are often used as solubilizing agents. It is not clear prior to developing a drug delivery device with CD what level of absorption enhancement might be achieved; modeling can provide useful guidance in formulation and minimize resource intensive iterative formulation development. A model was developed to enable quantitative, dynamic prediction of the influence of CD on oral absorption of low solubility drug administered as a pre-formed complex. The predominant effects of CD considered were enhancement of dissolution and slowing of precipitation kinetics, as well as binding of free drug in solution. Simulation results with different parameter values reflective of typical drug and CD properties indicate a potential positive (up to five times increase in drug absorption), negative (up to 50% decrease in absorption) or lack of effect of CD. Comparison of model predictions with in vitro and in vivo experimental results indicate that a systems-based dynamic model incorporating CD complexation and key process kinetics may enable quantitative prediction of impact of CD delivered as a pre-formed complex on drug bioavailability.

  16. Theoretical modeling of the absorption spectrum of aqueous riboflavin

    Zanetti-Polzi, Laura; Aschi, Massimiliano; Daidone, Isabella; Amadei, Andrea

    2017-02-01

    In this study we report the modeling of the absorption spectrum of riboflavin in water using a hybrid quantum/classical mechanical approach, the MD-PMM methodology. By means of MD-PMM calculations, with which the effect of riboflavin internal motions and of solvent interactions on the spectroscopic properties can be explicitly taken into account, we obtain an absorption spectrum in very good agreement with the experimental spectrum. In particular, the calculated peak maxima show a consistent improvement with respect to previous computational approaches. Moreover, the calculations show that the interaction with the environment may cause a relevant recombination of the gas-phase electronic states.

  17. Compression-absorption (resorption) refrigerating machinery. Modeling of reactors; Machine frigorifique a compression-absorption (resorption). Modelisation des reacteurs

    Lottin, O.; Feidt, M.; Benelmir, R. [LEMTA-UHP Nancy-1, 54 - Vandoeuvre-les-Nancy (France)

    1997-12-31

    This paper is a series of transparencies presenting a comparative study of the thermal performances of different types of refrigerating machineries: di-thermal with vapor compression, tri-thermal with moto-compressor, with ejector, with free piston, adsorption-type, resorption-type, absorption-type, compression-absorption-type. A prototype of ammonia-water compression-absorption heat pump is presented and modeled. (J.S.)

  18. Ray tracing and ECRH absorption modeling in the HSX stellarator

    Weir, G. M.; Likin, K. M.; Marushchenko, N. B.; Turkin, Y.

    2015-09-01

    To increase flexibility in ECRH experiments on the helically symmetric experiment (HSX), a second gyrotron and transmission line have been installed. The second antenna includes a steerable mirror for off-axis heating, and the launched power may be modulated for use in heat pulse propagation experiments. The extraordinary wave at the second harmonic of the electron gyrofrequency or the ordinary wave at the fundamental resonance are used for plasma start-up and heating on HSX. The tracing visualized ray tracing code (Marushchenko et al 2007 Plasma Fusion Res. 2 S1129) is used to estimate single-pass absorption and to model multi-pass wave damping in the three-dimensional HSX geometry. The single-pass absorption of the ordinary wave at the fundamental resonance is calculated to be as high as 30%, while measurements of the total absorption indicate that 45% of the launched power is absorbed. A multi-pass ray tracing model correctly predicts the experimental absorption and indicates that the launched power is absorbed within the plasma core (r/a≤slant 0.2 ).

  19. Computational Model of a Biomass Driven Absorption Refrigeration System

    Munyeowaji Mbikan

    2017-02-01

    Full Text Available The impact of vapour compression refrigeration is the main push for scientists to find an alternative sustainable technology. Vapour absorption is an ideal technology which makes use of waste heat or renewable heat, such as biomass, to drive absorption chillers from medium to large applications. In this paper, the aim was to investigate the feasibility of a biomass driven aqua-ammonia absorption system. An estimation of the solid biomass fuel quantity required to provide heat for the operation of a vapour absorption refrigeration cycle (VARC is presented; the quantity of biomass required depends on the fuel density and the efficiency of the combustion and heat transfer systems. A single-stage aqua-ammonia refrigeration system analysis routine was developed to evaluate the system performance and ascertain the rate of energy transfer required to operate the system, and hence, the biomass quantity needed. In conclusion, this study demonstrated the results of the performance of a computational model of an aqua-ammonia system under a range of parameters. The model showed good agreement with published experimental data.

  20. 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.

  1. Cascaded process model based control: packed absorption column application.

    Govindarajan, Anand; Jayaraman, Suresh Kumar; Sethuraman, Vijayalakshmi; Raul, Pramod R; Rhinehart, R Russell

    2014-03-01

    Nonlinear, adaptive, process-model based control is demonstrated in a cascaded single-input-single-output mode for pressure drop control in a pilot-scale packed absorption column. The process is shown to be nonlinear. Control is demonstrated in both servo and regulatory modes, for no wind-up in a constrained situation, and for bumpless transfer. Model adaptation is demonstrated and shown to provide process insight. The application procedure is revealed as a design guide to aid others in implementing process-model based control.

  2. Intergalactic Helium Absorption in Cold Dark Matter Models

    Croft, R A C; Katz, N; Hernquist, L E; Croft, Rupert A. C.; Weinberg, David H.; Katz, Neal; Hernquist, Lars

    1996-01-01

    Observations from the HST and the HUT have recently detected HeII absorption along the lines of sight to two high redshift quasars. We use cosmological simulations with gas dynamics to investigate HeII absorption in the cold dark matter (CDM) theory of structure formation. We consider two Omega=1 CDM models with different normalizations and one Omega_0=0.4 CDM model, all incorporating the photoionizing UV background spectrum computed by Haardt & Madau (1996). The simulated gas distribution, combined with the H&M spectral shape, accounts for the relative observed values of taubar_HI and taubar_HeII, the effective mean optical depths for HI and HeII absorption. If the background intensity is as high as H&M predict, then matching the absolute values of taubar_HI and taubar_HeII requires a baryon abundance larger (by factors between 1.5 and 3 for the various CDM models) than our assumed value of Omega_b h^2=0.0125. The simulations reproduce the evolution of taubar_heII over the observed redshift range...

  3. A Simple Disk Wind Model for Broad Absorption Line Quasars

    Higginbottom, N; Long, K S; Sim, S A; Matthews, J H

    2013-01-01

    Approximately 20% of quasi-stellar objects (QSOs) exhibit broad, blue-shifted absorption lines in their ultraviolet spectra. Such features provide clear evidence for significant outflows from these systems, most likely in the form of accretion disk winds. These winds may represent the "quasar" mode of feedback that is often invoked in galaxy formation/evolution models, and they are also key to unification scenarios for active galactic nuclei (AGN) and QSOs. To test these ideas, we construct a simple benchmark model of an equatorial, biconical accretion disk wind in a QSO and use a Monte Carlo ionization/radiative transfer code to calculate the ultraviolet spectra as a function of viewing angle. We find that for plausible outflow parameters, sightlines looking directly into the wind cone do produce broad, blue-shifted absorption features in the transitions typically seen in broad absorption line QSOs. However, our benchmark model is intrinsically X-ray weak in order to prevent overionization of the outflow, an...

  4. Mathematical Model of Natural Gas Desulfurization Based on Membrane Absorption

    Wang Shuli; Ma Jun; Wang Ganyu; Zhou Heng

    2014-01-01

    Models of mass transfer kinetics combined with mass transfer differential equation and mass transfer resistance equation were established on the basis of double-iflm theory. Mass transfer process of H2S absorption by means of polypro-pylene hydrophobic microporous hollow ifber membrane contactor was simulated using MDEA (N-methyldiethanolamine) as the absorption liquid and corresponding experiments of natural gas desulfurization were performed. The simulation re-sults indicated that the removal rate of hydrogen sulifde showed positive dependence on the absorption liquid concentration and gas pressure. However, the desulfurization rate showed negative dependence on gas lfow. The simulated values were in good agreement with the experimental results. The in-tube concentration of hydrogen sulifde at the same point increased with increase in the gas velocity. Axial concentration of hydrogen sulifde decreased rapidly at the beginning, and the de-crease saw a slowdown during the latter half period. Hydrogen sulifde concentration dropped quickly in the radial direction, and the reduction in the radial direction was weakened with the increase of axial length due to the gradual reduction of hy-drogen sulifde concentration along the tube. The desulfurization rate under given operating conditions can be predicted by this model, and the theoretical basis for membrane module design can also be provided.

  5. Absorption Cycle Heat Pump Model for Control Design

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

    2015-01-01

    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 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 operational data and different scenarios are simulated to investigate the operational stability of the heat pump. Finally, this paper provides suggestions and examples of derivation of lower order linear models for control design. © Copyright IEEE - All rights reserved....

  6. A two-dimensional mathematical model of percutaneous drug absorption

    Kubota K

    2004-06-01

    Full Text Available Abstract Background When a drug is applied on the skin surface, the concentration of the drug accumulated in the skin and the amount of the drug eliminated into the blood vessel depend on the value of a parameter, r. The values of r depend on the amount of diffusion and the normalized skin-capillary clearence. It is defined as the ratio of the steady-state drug concentration at the skin-capillary boundary to that at the skin-surface in one-dimensional models. The present paper studies the effect of the parameter values, when the region of contact of the skin with the drug, is a line segment on the skin surface. Methods Though a simple one-dimensional model is often useful to describe percutaneous drug absorption, it may be better represented by multi-dimensional models. A two-dimensional mathematical model is developed for percutaneous absorption of a drug, which may be used when the diffusion of the drug in the direction parallel to the skin surface must be examined, as well as in the direction into the skin, examined in one-dimensional models. This model consists of a linear second-order parabolic equation with appropriate initial conditions and boundary conditions. These boundary conditions are of Dirichlet type, Neumann type or Robin type. A finite-difference method which maintains second-order accuracy in space along the boundary, is developed to solve the parabolic equation. Extrapolation in time is applied to improve the accuracy in time. Solution of the parabolic equation gives the concentration of the drug in the skin at a given time. Results Simulation of the numerical methods described is carried out with various values of the parameter r. The illustrations are given in the form of figures. Conclusion Based on the values of r, conclusions are drawn about (1 the flow rate of the drug, (2 the flux and the cumulative amount of drug eliminated into the receptor cell, (3 the steady-state value of the flux, (4 the time to reach the steady

  7. Mathematical Modeling of Intestinal Iron Absorption Using Genetic Programming

    Colins, Andrea; Gerdtzen, Ziomara P.; Nuñez, Marco T.; Salgado, J. Cristian

    2017-01-01

    Iron is a trace metal, key for the development of living organisms. Its absorption process is complex and highly regulated at the transcriptional, translational and systemic levels. Recently, the internalization of the DMT1 transporter has been proposed as an additional regulatory mechanism at the intestinal level, associated to the mucosal block phenomenon. The short-term effect of iron exposure in apical uptake and initial absorption rates was studied in Caco-2 cells at different apical iron concentrations, using both an experimental approach and a mathematical modeling framework. This is the first report of short-term studies for this system. A non-linear behavior in the apical uptake dynamics was observed, which does not follow the classic saturation dynamics of traditional biochemical models. We propose a method for developing mathematical models for complex systems, based on a genetic programming algorithm. The algorithm is aimed at obtaining models with a high predictive capacity, and considers an additional parameter fitting stage and an additional Jackknife stage for estimating the generalization error. We developed a model for the iron uptake system with a higher predictive capacity than classic biochemical models. This was observed both with the apical uptake dataset used for generating the model and with an independent initial rates dataset used to test the predictive capacity of the model. The model obtained is a function of time and the initial apical iron concentration, with a linear component that captures the global tendency of the system, and a non-linear component that can be associated to the movement of DMT1 transporters. The model presented in this paper allows the detailed analysis, interpretation of experimental data, and identification of key relevant components for this complex biological process. This general method holds great potential for application to the elucidation of biological mechanisms and their key components in other complex

  8. A simple disc wind model for broad absorption line quasars

    Higginbottom, N.; Knigge, C.; Long, K. S.; Sim, S. A.; Matthews, J. H.

    2013-12-01

    Approximately 20 per cent of quasi-stellar objects (QSOs) exhibit broad, blue-shifted absorption lines in their ultraviolet spectra. Such features provide clear evidence for significant outflows from these systems, most likely in the form of accretion disc winds. These winds may represent the `quasar' mode of feedback that is often invoked in galaxy formation/evolution models, and they are also key to unification scenarios for active galactic nuclei (AGN) and QSOs. To test these ideas, we construct a simple benchmark model of an equatorial, biconical accretion disc wind in a QSO and use a Monte Carlo ionization/radiative transfer code to calculate the ultraviolet spectra as a function of viewing angle. We find that for plausible outflow parameters, sightlines looking directly into the wind cone do produce broad, blue-shifted absorption features in the transitions typically seen in broad absorption line (BAL) QSOs. However, our benchmark model is intrinsically X-ray weak in order to prevent overionization of the outflow, and the wind does not yet produce collisionally excited line emission at the level observed in non-BAL QSOs. As a first step towards addressing these shortcomings, we discuss the sensitivity of our results to changes in the assumed X-ray luminosity and mass-loss rate, Ṁwind. In the context of our adopted geometry, Ṁwind ˜ Ṁacc is required in order to produce significant BAL features. The kinetic luminosity and momentum carried by such outflows would be sufficient to provide significant feedback.

  9. 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.

  10. Modelling polarization dependent absorption: The vectorial Lambert-Beer law

    Franssens, G.

    2014-07-01

    The scalar Lambert-Beer law, describing the absorption of unpolarized light travelling through a linear non-scattering medium, is simple, well-known, and mathematically trivial. However, when we take the polarization of light into account and consider a medium with polarization dependent absorption, we now need a Vectorial Lambert-Beer Law (VLBL) to quantify this interaction. Such a generalization of the scalar Lambert-Beer law appears not to be readily available. A careful study of this topic reveals that it is not a trivial problem. We will see that the VLBL is not and cannot be a straightforward vectorized version of its scalar counterpart. The aim of the work is to present the general form of the VLBL and to explain how it arises. A reasonable starting point to derive the VLBL is the Vectorial Radiative Transfer Equation (VRTE), which models the absorption and scattering of (partially) polarized light travelling through a linear medium. When we turn off scattering, the VRTE becomes an infinitesimal model for the VLBL holding in the medium. By integrating this equation, we expect to find the VLBL. Surprisingly, this is not the end of the story. It turns out that light propagation through a medium with polarization-dependent absorption is mathematically not that trivial. The trickiness behind the VLBL can be understood in the following terms. The matrix in the VLBL, relating any input Stokes vector to the corresponding output Stokes vector, must necessarily be a Mueller matrix. The subset of invertible Mueller matrices forms a Lie group. It is known that this Lie group contains the ortho-chronous Lorentz group as a subgroup. The group manifold of this subgroup has a (well-known) non-trivial topology. Consequently, the manifold of the Lie group of Mueller matrices also has (at least the same, but likely a more general) non-trivial topology (the full extent of which is not yet known). The type of non-trivial topology, possessed by the manifold of (invertible

  11. 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

    system. The Extended UNIQUAC model is used to represent the system behavior. The model is created based on models for the constituent binary subsystems. The developed model provides accurate representation of VLE and heat of absorption for the studied system and subsystem in the temperature range of 0...

  12. Modeling of light absorption in tissue during infrared neural stimulation.

    Thompson, Alexander C; Wade, Scott A; Brown, William G A; Stoddart, Paul R

    2012-07-01

    A Monte Carlo model has been developed to simulate light transport and absorption in neural tissue during infrared neural stimulation (INS). A range of fiber core sizes and numerical apertures are compared illustrating the advantages of using simulations when designing a light delivery system. A range of wavelengths, commonly used for INS, are also compared for stimulation of nerves in the cochlea, in terms of both the energy absorbed and the change in temperature due to a laser pulse. Modeling suggests that a fiber with core diameter of 200 μm and NA=0.22 is optimal for optical stimulation in the geometry used and that temperature rises in the spiral ganglion neurons are as low as 0.1°C. The results show a need for more careful experimentation to allow different proposed mechanisms of INS to be distinguished.

  13. 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...

  14. Magnetospheres of hot Jupiters: hydrodynamic models & ultraviolet absorption

    Alexander, R D; Mohammed, H; Nichols, J D; Ercolano, B

    2015-01-01

    We present hydrodynamic simulations of stellar wind-magnetosphere interactions in hot Jupiters such as WASP-12b. For fiducial stellar wind rates we find that a planetary magnetic field of a few G produces a large magnetospheric cavity, which is typically 6-9 planetary radii in size. A bow shock invariably forms ahead of the magnetosphere, but the pre-shock gas is only mildly supersonic (with typical Mach numbers of $\\simeq$1.6-1.8) so the shock is weak. This results in a characteristic signature in the ultraviolet light curve: a broad absorption feature that leads the optical transit by 10-20% in orbital phase. The shapes of our synthetic light-curves are consistent with existing observations of WASP-12b, but the required near-UV optical depth ($\\tau \\sim 0.1$) can only be achieved if the shocked gas cools rapidly. We further show that radiative cooling is inefficient, so we deem it unlikely that a magnetospheric bow shock is responsible for the observed near-UV absorption. Finally, we apply our model to two ...

  15. New simulation model of absorption pump with internal storage

    San Juan, Cristina; Soutullo, Silvia; Enriquez, Ricardo; Ferrer, Jose Antonio; Heras, M Rosario [Energy Efficiency in Buildings R and D Unit. CIEMAT., Avenida Complutense 22, 28040 Madrid, (Spain)], email: cristina.sanjuan@ciemat.es

    2010-07-01

    In hot climates, such as in Spain, conditioning systems are used to provide a good level of thermal comfort during summer. Systems are usually composed of one liquid absorption pump and external storage in a water tank. The aim of this study is to present a new technology whereby energy is stored in crystallized salts through the use of 4 heat pumps. A case study was carried out in the Plataforma Solar de Almeria, Spain, where the performance of both conventional and new cooling systems were analyzed through the use of a dynamic model in TRNSYS. Results showed that for the new system, adaptability increases with the number of independent blocks and its performance is influenced by the control strategy. In addition it was found that 15m3 of external storage are required in conventional systems to achieve the same performance as the new system. This study showed that the new system requires less storage room than conventional systems.

  16. Jam-absorption driving with a car-following model

    Taniguchi, Yohei; Nishi, Ryosuke; Ezaki, Takahiro; Nishinari, Katsuhiro

    2015-09-01

    Jam-absorption driving (JAD) refers to the action performed by a single car to dynamically change its headway to remove a traffic jam. Because of its irregular motion, a car performing JAD perturbs other cars following it, and these perturbations may grow to become the so-called secondary traffic jams. A basic theory for JAD (Nishi et al. 2013) does not consider accelerations of cars or the stability of traffic flow. In this paper, by introducing car-following behaviors, we implement these elements in JAD. Numerous previous studies on the instability of traffic flow showed that even in a region whose density is below a critical density, perturbation may grow if its initial magnitude is large. According to these previous studies, we expect that the perturbations caused by JAD, if they are sufficiently small, do not grow to become secondary traffic jams. Using a microscopic car-following model, we numerically confirmed that the stability of a flow obeying the model depends on the magnitude of JAD perturbations. On the basis of this knowledge, numerical results indicate that parameter regions exist where JAD allows traffic jams to be removed without causing secondary traffic jams. Moreover, JAD is robust against a parameter of acceleration in the model, as well as the choice of car-following models.

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

    Cohen, M. B.; Lehtinen, N. G.; Inan, U. S.

    2012-12-01

    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 propagation known as the Helliwell absorption curves, but some recent studies have found that the model overestimates (by 20-100 dB) the VLF energy reaching the magnetosphere. It was subsequently suggested that conversion of wave energy into electrostatic modes may be responsible for the error. We utilize a newly available extensive record of VLF transmitter energy reaching the magnetosphere, taken from the DEMETER satellite, and perform a direct comparison with a sophisticated full wave model of trans-ionospheric propagation. Although the model does not include the effect of ionospheric irregularities, it correctly predicts the average total power injected into the magnetosphere within several dB. The results, particularly at nighttime, appear to be robust against the variability of the ionospheric electron density. We conclude that the global effect of irregularity scattering on whistler mode conversion to quasi-electrostatic may be no larger than 6 dB.

  18. Modelling Alkali Line Absorption and Molecular Bands in Cool DAZs

    Homeier, D; Allard, F; Hauschildt, P H; Schweitzer, A; Stancil, P C; Weck, P F; Homeier, Derek; Allard, Nicole F.; Allard, France; Hauschildt, Peter H.; Schweitzer, Andreas; Stancil, Phillip C.; Weck, Philippe F.

    2005-01-01

    Two peculiar stars showing an apparent extremely broadened and strong NaI D absorption have been discovered in surveys for cool white dwarfs by Oppenheimer et al. (2001) and Harris et al. (SDSS, 2003). We discuss the nature of these objects using PHOENIX atmosphere models for metal-poor brown dwarfs/very low mass stars, and new white dwarf LTE and NLTE models for hydrogen- and helium-dominated atmospheres with metals. These include complete molecular formation in chemical equilibrium and a model for the alkali resonance line broadening based on the damping profiles of Allard et al. (2003), as well as new molecular line opacities for metal hydrides. First results of our calculations indicate good agreement with a hydrogen-dominated WD atmosphere with a Na abundance roughly consistent with a state of high accretion. We analyse deviations of the abundances of Na, K, Mg and Ca from the cosmic pattern and comment on implications of these results for standard accretion scenarios.

  19. Optimization of absorption placement using geometrical acoustic models and least squares.

    Saksela, Kai; Botts, Jonathan; Savioja, Lauri

    2015-04-01

    Given a geometrical model of a space, the problem of optimally placing absorption in a space to match a desired impulse response is in general nonlinear. This has led some to use costly optimization procedures. This letter reformulates absorption assignment as a constrained linear least-squares problem. Regularized solutions result in direct distribution of absorption in the room and can accommodate multiple frequency bands, multiple sources and receivers, and constraints on geometrical placement of absorption. The method is demonstrated using a beam tracing model, resulting in the optimal absorption placement on the walls and ceiling of a classroom.

  20. Measurements of the Absorption by Auditorium SEATING—A Model Study

    BARRON, M.; COLEMAN, S.

    2001-01-01

    One of several problems with seat absorption is that only small numbers of seats can be tested in standard reverberation chambers. One method proposed for reverberation chamber measurements involves extrapolation when the absorption coefficient results are applied to actual auditoria. Model seat measurements in an effectively large model reverberation chamber have allowed the validity of this extrapolation to be checked. The alternative barrier method for reverberation chamber measurements was also tested and the two methods were compared. The effect on the absorption of row-row spacing as well as absorption by small numbers of seating rows was also investigated with model seats.

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

    Ahmed Mojahid Sid Ahmed Mohammed Salih; Gilani Syed Ihtsham Ul-Haq

    2014-01-01

    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 equa...

  2. A mechanism-based approach for absorption modeling: the Gastro-Intestinal Transit Time (GITT) model.

    Hénin, Emilie; Bergstrand, Martin; Standing, Joseph F; Karlsson, Mats O

    2012-06-01

    Absorption models used in the estimation of pharmacokinetic drug characteristics from plasma concentration data are generally empirical and simple, utilizing no prior information on gastro-intestinal (GI) transit patterns. Our aim was to develop and evaluate an estimation strategy based on a mechanism-based model for drug absorption, which takes into account the tablet movement through the GI transit. This work is an extension of a previous model utilizing tablet movement characteristics derived from magnetic marker monitoring (MMM) and pharmacokinetic data. The new approach, which replaces MMM data with a GI transit model, was evaluated in data sets where MMM data were available (felodipine) or not available (diclofenac). Pharmacokinetic profiles in both datasets were well described by the model according to goodness-of-fit plots. Visual predictive checks showed the model to give superior simulation properties compared with a standard empirical approach (first-order absorption rate + lag-time). This model represents a step towards an integrated mechanism-based NLME model, where the use of physiological knowledge and in vitro–in vivo correlation helps fully characterize PK and generate hypotheses for new formulations or specific populations.

  3. 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.

  4. Electromagnetically Induced Transparency and Absorption in Metamaterials: The Radiating Two-Oscillator Model and Experimental Confirmation

    Tassin, Philippe; Zhao, Rongkuo; Jain, Aditya; Koschny, Thomas; Soukoulis, Costas M

    2012-01-01

    Several classical analogues of electromagnetically induced transparency (EIT) in metamaterials have been demonstrated. A simple two-resonator model can describe their absorption spectrum qualitatively, but fails to provide information about the scattering properties-e.g., transmission and group delay. Here we develop an alternative model that rigourously includes the coupling of the radiative resonator to the external electromagnetic fields. This radiating two-oscillator model can describe both the absorption spectrum and the scattering parameters quantitatively. The model also predicts metamaterials with a narrow spectral feature in the absorption larger than the background absorption of the radiative element. This classical analogue of electromagnetically induced absorption (EIA) is shown to occur when both the dissipative loss of the radiative resonator and the coupling strength are small. These predictions are subsequently demonstrated in experiments.

  5. Conscious and anaesthetised Göttingen mini-pigs as an in-vivo model for buccal absorption - pH-dependent absorption of metoprolol from bioadhesive tablets

    Meng-Lund, Emil; Jacobsen, Jette; Andersen, Morten B;

    2014-01-01

    Abstract The potential of buccal mucosa as a site for systemic absorption has attracted increased attention in recent years creating a need for new predictive in-vivo models. The aim of this study was to evaluate anaesthetised and conscious Göttingen mini-pigs as a model for buccal drug absorption...

  6. Absorption of beta-carotene and other carotenoids in humans and animal models : a review

    Vliet, T. van

    1996-01-01

    Objective: To review available information on absorption and further metabolism of different carotenoids in man and to discuss animal models and approaches in the study of carotenoid absorption and metabolism in man. Conclusions: Humans appear to absorb various carotenoids in a relatively non-specif

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

    Faramarzi, Leila; Kontogeorgis, Georgios; Thomsen, Kaj

    2009-01-01

    The extended UNIQUAC model [K. Thomsen, R Rasmussen, Chem. Eng. Sci. 54 (1999) 1787-1802] was applied to the thermodynamic representation of carbon dioxide absorption in aqueous monoethanolamine (MEA), methyldiethanolamine (MDEA) and varied strength mixtures of the two alkanolamines (MEA-MDEA). F......The extended UNIQUAC model [K. Thomsen, R Rasmussen, Chem. Eng. Sci. 54 (1999) 1787-1802] was applied to the thermodynamic representation of carbon dioxide absorption in aqueous monoethanolamine (MEA), methyldiethanolamine (MDEA) and varied strength mixtures of the two alkanolamines (MEA......) 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 solutions containing CO2...

  8. Drug Absorption Modeling as a Tool to Define the Strategy in Clinical Formulation Development

    Kuentz, Martin

    2008-01-01

    The purpose of this mini review is to discuss the use of physiologically-based drug absorption modeling to guide the formulation development. Following an introduction to drug absorption modeling, this article focuses on the preclinical formulation development. Case studies are presented, where the emphasis is not only the prediction of absolute exposure values, but also their change with altered input values. Sensitivity analysis of technologically relevant parameters, like the drug’s partic...

  9. Modeling moisture absorption kinetics of barley grain using viscoelastic model and neural networks

    M Kamali

    2015-09-01

    Full Text Available Introduction: Barley is one of the most important grains with high digestible starch making it a main source of energy in human nutrition as well as in livestock rations formulation and feeding. Starch is the main part of barley grain and it has an inverse relation with its protein. It has a digestible foodstuff of 80 to 84 percent of its dry matter content. Barley as livestock foodstuff should be processed and it is done in several ways. A customary method for processing barley in dairy farms is its size reduction by milling (Hunt, 1996. An alternative method of barley processing is steam rolling. However, because of the high cost of steam generators a method of soaking with heating has been considered as an alternative method for steam rolling (Yang et al., 2000. The rate of moisture absorption by grains during the soaking process varies considerably and depends on the size of the grain, water temperature and the length of soaking. High temperature water soaking is an ordinary way to reduce the time duration for reaching a high rate of moisture absorption during the soaking process (Kashaninejad et al., 2009. Various studies have shown that these models have adequate accuracy in analyzing drying and moisture absorption processes for most agricultural products (Abu-Ghannam and McKenna, 1997. Some researchers have modeled beans moisture absorption behavior using 14 mathematical models and found that the Weibull model had the most conformity with variations in experimental data (Shafaei and Masoumi, 2014c. Observations made by researchers indicate that the moisture absorption process in various materials encompasses a primary phase with a fast rate and a second phase with a lower rate. The second phase in moisture absorption is called the relaxation phase. The main problem with all the mathematical and experimental models is the lack of the model’s ability to evaluate the rate of moisture absorption in the secondary phase. Artificial Neural

  10. 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.

  11. Asymmetric and common absorption of shocks in nonlinear autoregressive models

    Dijk, Dick van; Franses, Philip Hans; Boswijk, Peter

    2000-01-01

    textabstractA key feature of many nonlinear time series models is that they allow for the possibility that the model structure experiences changes, depending on for example the state of the economy or of the financial market. A common property of these models is that it generally is not possible to fully understand the structure of the model by considering the estimated values of the model parameters only. Put differently, it often is difficult to interpret a specific nonlinear model. To shed...

  12. 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.

  13. 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.

  14. A polar cap absorption model optimization based on the vertical ionograms analysis

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

    2016-11-01

    Space weather events significantly affect the high frequency (HF) radio wave propagation. The now-casting and forecasting of HF radio wave absorption is important for the HF communication industries. This paper assimilates vertical sounding data into an absorption model to improve its performance as a now-casting tool. The approach is a modification of the algorithm elaborated by Sauer and Wilkinson, which is based on the riometer data. The optimization is focused on accounting for short timescale variation of the absorption. It should be noted that the expression of the frequency dependence of absorption induced by the energetic particle precipitation employed in Sauer and Wilkinson model is based on the riometer data at frequencies of 20, 30, and 50 MHz. The approach suggested in this paper provides an opportunity for expanding the frequency dependence of the absorption for frequencies below 10 MHz. The simulation of the vertical ionograms in the polar cap region uses a computational model designed to overcome the high frequency wave propagation problem in high latitude of the Earth. HF radio wave absorption induced by solar UV illumination, X-ray flares and energetic particles precipitation is taken into consideration in our model. The absorption caused by the energetic particle precipitation is emphasized, because the study is focused on HF wave propagation in polar cap region. A comparison of observed and simulated vertical ionograms enables the coefficients, which relate absorption (day-time and night-time) to integral proton flux to be refined. The values of these coefficients determined from evaluation of the data recorded by any reliable ionosonde are valid for absorption calculation in high-latitude region.

  15. Asymmetric and common absorption of shocks in nonlinear autoregressive models

    D.J.C. van Dijk (Dick); Ph.H.B.F. Franses (Philip Hans); H.P. Boswijk (Peter)

    2000-01-01

    textabstractA key feature of many nonlinear time series models is that they allow for the possibility that the model structure experiences changes, depending on for example the state of the economy or of the financial market. A common property of these models is that it generally is not possible to

  16. Four-State Model for Three-Branch Molecule's Two-Photon Absorption Properties

    SU Yan; WANG Pei-Ji; ZHAO Peng; RONG Zhen-Yu

    2006-01-01

    @@ We present a four-state model for calculating the two-photon absorption of multi-branched molecules by using the time-depended function method. The numerical results indicate that the two-photon absorption cross section has a strong enhancement for three-branch molecules compared to two-branch structures. The maximal two-photon-absorption cross section is 2.358 × 10-47 cm 4 s/photon. At the same time, the charge-transfer process for the charge-transfer states is visualized in order to explain mechanism about the maximal TPA cross section.

  17. 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.

  18. [Establishment and evaluation of a dynamic in vitro intestinal absorption model of lipid formulations].

    Liu, Ying; Yi, Tao; Di, Huan; Xiao, Lu; He, Ji-Kui

    2011-08-01

    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 x L(-1), D-glucose for 15 mmol x L(-1) and K+ for 5.5 mmol x 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 lipid formulations.

  19. Atomistic modeling of H absorption in Pd nanoparticles

    Ruda, M., E-mail: ruda@cab.cnea.gov.a [Centro Atomico Bariloche, 8400 Bariloche (Argentina); Centro Regional Universitario Bariloche, U.N. Comahue (Argentina); Crespo, E.A., E-mail: crespo@uncoma.edu.a [Depto. de Fisica, Fac. de Ingenieria, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquen (Argentina); Debiaggi, S. Ramos de, E-mail: ramos@uncoma.edu.a [Depto. de Fisica, Fac. de Ingenieria, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquen (Argentina); CONICET (Argentina)

    2010-04-16

    Size affects the properties of absorption of H in Palladium nanoparticles. Because of their higher proportion of surface atoms compared to the bulk, the pressure-composition (P-C) isotherms of the nanoparticles are modified. We performed atomistic simulations for different-sized Pd nanoparticles and for the bulk at different H concentrations using the Monte Carlo technique in the TP{mu}N ensemble to calculate the P-C isotherms. The Pd-H interatomic potentials are of the Embedded Atom (EAM) type and have been recently developed by Zhou et al. . From the related van't Hoff equation we obtained |{Delta}H{sup o}| = (28 {+-} 7) kJ/0.5 mol of H{sub 2} and |{Delta}S{sup o}| = (71 {+-} 19) J/0.5 mol of H{sub 2}.K for the PdH formation in the bulk. For Pd nanoparticles previous simulations results based on a different set of EAM potentials showed that H was absorbed primarily in the surface before diffusing into the inside of small Pd clusters . Considering the better performance of Zhou's potentials for the bulk, in this work we analyzed the evolution of the equilibrium microstructure of Pd nanoparticles as a function of their size and H concentration. Our simulations predict enhanced hydrogen solubilities and vanishing plateaux when compared to the bulk and that H is absorbed in the subsurface of the nanoparticles.

  20. Absorption coefficient modeling of microcrystalline silicon thin film using Maxwell-Garnett effective medium theory.

    Chen, Sheng-Hui; Wang, Hsuan-Wen; Chang, Ting-Wei

    2012-03-12

    Considering the Mott-Davis density of state model and Rayleigh scattering effect, we present an approach to model the absorption profile of microcrystalline silicon thin films in this paper. Maxwell-Garnett effective medium theory was applied to analyze the absorption curves. To validate the model, several experimental profiles have been established and compared with those results from the model. With the assistance of the genetic algorithm, our results show that the absorption curves from the model are in good agreement with the experiments. Our findings also indicate that, as the crystal volume fraction increases, not only do the defects in amorphous silicon reduce, but the bulk scattering effect is gradually enhanced as well.

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

    Edson Bazzo; Janilson Arcangelo Rossa

    2009-01-01

    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...

  2. Feasibility of a 3D human airway epithelial model to study respiratory absorption.

    Reus, Astrid A; Maas, Wilfred J M; Jansen, Harm T; Constant, Samuel; Staal, Yvonne C M; van Triel, Jos J; Kuper, C Frieke

    2014-03-01

    The respiratory route is an important portal for human exposure to a large variety of substances. Consequently, there is an urgent need for realistic in vitro strategies for evaluation of the absorption of airborne substances with regard to safety and efficacy assessment. The present study investigated feasibility of a 3D human airway epithelial model to study respiratory absorption, in particular to differentiate between low and high absorption of substances. Bronchial epithelial models (MucilAir™), cultured at the air-liquid interface, were exposed to eight radiolabeled model substances via the apical epithelial surface. Absorption was evaluated by measuring radioactivity in the apical compartment, the epithelial cells and the basolateral culture medium. Antipyrine, caffeine, naproxen and propranolol were highly transported across the epithelial cell layer (>5%), whereas atenolol, mannitol, PEG-400 and insulin were limitedly transported (absorption. The intra-experimental reproducibility of the results was considered adequate based on an average coefficient of variation (CV) of 15%. The inter-experimental reproducibility of highly absorbed compounds was in a similar range (CV of 15%), but this value was considerably higher for those compounds that were limitedly absorbed. No statistical significant differences between different donors and experiments were observed. The present study provides a simple method transposable in any lab, which can be used to rank the absorption of chemicals and pharmaceuticals, and is ready for further validation with respect to reproducibility and capacity of the method to predict respiratory transport in humans.

  3. 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

  4. Examination of the relationship between riometer-derived absorption and the integral proton flux in the context of modeling polar cap absorption

    Fiori, R. A. D.; Danskin, D. W.

    2016-11-01

    Energetic protons can penetrate into the ionosphere increasing ionization in the D region causing polar cap absorption that may potentially block high-frequency radio communications for transpolar flights. The protons are guided by the geomagnetic field into the high-latitude polar cap region. Riometers monitor variations in ionospheric absorption by observing the level of background cosmic radio noise. Current polar cap absorption modeling techniques are based on the linear relationship between absorption and the square root of the integral proton flux, which has previously only been demonstrated using data from a single high-latitude polar station. The proportionality constant describing this relationship is evaluated for two different polar cap absorption events occurring 7-11 March 2012 and 23 January 2012 to 1 February 2012. Examination of the proportionality constant using data from riometers distributed between 60° and 90° magnetic latitude reveals a previously unreported latitudinal dependence for data at magnetic latitudes of ≤66.8° on the dayside and ≤70.8° on the nightside. Incorporating the latitudinal dependence into the current D Region Absorption Prediction absorption model improves the agreement between measurement-derived and modeled parameters by increasing the correlation coefficient between data sets, reducing the root-mean-square error, and reducing the bias.

  5. 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...

  6. 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...

  7. 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.

  8. Modelling of the Absorption and Desorption Process of Chemical Heat Pumps

    Gui-PingLin; Xiu-GanYuan

    1993-01-01

    A simple model for the desorption and absorption process of the chemical heat pump is presented in this paper .It is based on the assumption of a definite reaction front.The results from this model are compared with those obtained by finite difference method and it is observed that there is almost no difference between them.

  9. 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.

  10. 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

    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......The integrated glucose-insulin (IGI) model is a previously published semimechanistic model that describes plasma glucose and insulin concentrations after glucose challenges. The aim of this work was to use knowledge of physiology to improve the IGI model's description of glucose absorption...... 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...

  11. Parallel LC circuit model for multi-band absorption and preliminary design of radiative cooling.

    Feng, Rui; Qiu, Jun; Liu, Linhua; Ding, Weiqiang; Chen, Lixue

    2014-12-15

    We perform a comprehensive analysis of multi-band absorption by exciting magnetic polaritons in the infrared region. According to the independent properties of the magnetic polaritons, we propose a parallel inductance and capacitance(PLC) circuit model to explain and predict the multi-band resonant absorption peaks, which is fully validated by using the multi-sized structure with identical dielectric spacing layer and the multilayer structure with the same strip width. More importantly, we present the application of the PLC circuit model to preliminarily design a radiative cooling structure realized by merging several close peaks together. This omnidirectional and polarization insensitive structure is a good candidate for radiative cooling application.

  12. Studies on Absorption and Tansport of Limoninoids from Fructus Evodiae in Caco-2 Cell Monolayer Model

    2009-01-01

    Objective To study the intestinal absorption and transepithelial transport of three limoninoids: evodol (EVO), limonin (LIM), and shihulimonin A (SHIA), isolated from Fructus Evodiae [the unripe fruit of Evodia rutaecarpa and Evodia rutaecarpa var. bodinieri] in the human intestine. Methods The in vitro cultured human colon carcinoma cell line, Caco-2 cell monolayer model, was applied to studying the absorption and transepithelial transport of the three limoninoids from apical (AP) to basolateral (BL) side and from BL to AP side. The three limoninoids were measured by reversed-phase high performance liquid chromatography coupled with ultraviolet absorption detector. Transport parameters and apparent permeability coefficients (Papp) were then calculated and compared with those of Propranolol as a control substance of high permeability and Atenolol as a control substance of poor permeability. Results The Papp value of EVO and LIM from AP to BL side for absorption and transport were 1.78 × 10-5 cm/s and 1.16 × 10-5 cm/s, respectively, which was comparable to that of Propranolol with Papp 2.18 × 10-5 cm/s. Conclusion The absorption and transport of both EVO and LIM are main passive diffusion as the dominating process in Caco-2 cell monolayer model, and they were estimated to be high absorbed compounds. SHIA in Caco-2 cell monolayer model may be involved in metabolism in the transport processes.

  13. Cheminformatics Modeling of Amine Solutions for Assessing their CO2 Absorption Properties.

    Kuenemann, Melaine A; Fourches, Denis

    2017-03-07

    As stricter regulations on CO2 emissions are adopted worldwide, identifying efficient chemical processes to capture and recycle CO2 is of critical importance for industry. The most common process known as amine scrubbing suffers from the lack of available amine solutions capable of capturing CO2 efficiently. Tertiary amines characterized by low heats of reaction are considered good candidates but their absorption properties can significantly differ from one analogue to another despite high structural similarity. Herein, after collecting and curating experimental data from the literature, we have built a modeling set of 41 amine structures with their absorption properties. Then we analyzed their chemical composition using molecular descriptors and non-supervised clustering. Furthermore, we developed a series of quantitative structure-property relationships (QSPR) to assess amines' CO2 absorption properties from their structural characteristics. These models afforded reasonable prediction performances (e. g., Q(2)LOO =0.63 for CO2 absorption amount) even though they are solely based on 2D chemical descriptors and individual machine learning techniques (random forest and neural network). Overall, we believe the chemical analysis and the series of QSPR models presented in this proof-of-concept study represent new knowledge and innovative tools that could be very useful for screening and prioritizing hypothetical amines to be synthesized and tested experimentally for their CO2 absorption properties.

  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. Radial diffusion in Saturn's radiation belts - A modeling analysis assuming satellite and ring E absorption

    Hood, L. L.

    1983-01-01

    A modeling analysis is carried out of six experimental phase space density profiles for nearly equatorially mirroring protons using methods based on the approach of Thomsen et al. (1977). The form of the time-averaged radial diffusion coefficient D(L) that gives an optimal fit to the experimental profiles is determined under the assumption that simple satellite plus Ring E absorption of inwardly diffusing particles and steady-state radial diffusion are the dominant physical processes affecting the proton data in the L range that is modeled. An extension of the single-satellite model employed by Thomsen et al. to a model that includes multisatellite and ring absorption is described, and the procedures adopted for estimating characteristic satellite and ring absorption times are defined. The results obtained in applying three representative solid-body absorption models to evaluate D(L) in the range where L is between 4 and 16 are reported, and a study is made of the sensitivity of the preferred amplitude and L dependence for D(L) to the assumed model parameters. The inferred form of D(L) is then compared with that which would be predicted if various proposed physical mechanisms for driving magnetospheric radial diffusion are operative at Saturn.

  16. Hydrolysis-dependent absorption of disaccharides in the rat small intestine (chronic experiments and mathematical modeling).

    Gromova, L V; Gruzdkov, A A

    1999-06-01

    In order to throw light on the mechanisms responsible for the enzyme-dependent absorption of disaccharides membrane hydrolysis of maltose and trehalose and the absorption of glucose (free and that derived from disaccharides) were studied in isolated loops (20 cm) of the rat small intestine in chronic experiments. The rates of glucose absorption were 0.26-0.81 micromol x min(-1) x cm(-1) when the loop was perfused with a 12.5 to 75.0 mmol/l free glucose solution, which is only insignificantly higher than the rates observed during perfusion with equivalent maltose solutions. The coupling coefficient (the ratio of glucose absorption rate to the rate of disaccharide hydrolysis) decreased from 0.90 to 0.60 with the increasing maltose concentrations in the infusate from 6.25 to 37.5 mmol/l, but remained unchanged (approximately 0.95) within the same range of trehalose concentrations. The permeability of the pre-epithelial barrier was equivalent to that of unstirred water layer of less than 40 microm thickness. Fluid absorption was within the range of 0.73-2.55 microl x min(-1) x cm(-1), and it showed a correlation with the rates of glucose absorption. The results agree with a model developed on the assumption that free glucose and that released from disaccharides share the same membrane transporters. It could be concluded that a close coupling of disaccharide hydrolysis with derived glucose absorption in chronic experiments is achieved mainly due to a high activity of glucose transporters, which are presumably not associated with membrane disaccharidases. The transcellular active transport is a predominant mechanism of disaccharide-derived glucose absorption under conditions close to physiological.

  17. Models of Five Absorption Line Systems Along the Line of Sight Toward PG0117+213

    Masiero, J R; Ding, J; Churchill, C W; Kacprzak, G G

    2005-01-01

    We present our investigation into the physical conditions of the gas in five intervening quasar absorption line systems along the line of sight toward the quasar PG 0117+213, with redshifts of z=0.57, z=0.72, z=1.04, z=1.32 and z=1.34. Photoionization modeling of HST, Keck I, and Palomar data, using the code Cloudy, is employed to derive densities and metallicities of the multiple phases of gas required to fit the absorption profile for each system. We discuss the implications of these models for galaxy evolution, including the interpretation of ``CIV deficiency'' and damped Lyman alpha absorbers (DLAs), and the relationships between galaxy morphology, galaxy luminosity, and absorption signature.

  18. Strong absorption model and radial parameters of medium-weight nuclei

    Kuterbekov, K A

    2002-01-01

    The results of analysis of the angular distributions of differential cross sections for elastic scattering in the medium-weight nuclei in the framework strong absorption model are given. There are presented the A-relations of interaction radius, the data of radial parameters of even isotopes with mass number A=64-124 are obtained. (author)

  19. Particle-in-a-Box Model of Exciton Absorption and Electroabsorption in Conjugated Polymers

    Pedersen, Thomas Garm

    2001-01-01

    The recently proposed particle-in-a-box model of one-dimensional excitons in conjugated polymers is applied in calculations of optical absorption and electroabsorption spectra. It is demonstrated that for polymers of long conjugation length a superposition of single exciton resonances produces...

  20. 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 ...

  1. Experimental and modeling studies on the absorption of NO in aqueous ferrous EDTA solutions

    Gambardella, F; Alberts, MS; Winkelman, JGM; Heeres, EJ; Alberts, Michel S.; Heeres, H.J.

    2005-01-01

    This work describes an experimental and modeling study on an industrial relevant process (i.e., the absorption of NO in aqueous Fell(EDTA) solutions) to accurately determine the equilibrium constant of the reaction in the temperature range of 299-329 K. The experiments were carried out in a stirred

  2. Excited state absorption in glasses activated with rare earth ions: Experiment and modeling

    Piatkowski, Dawid; Mackowski, Sebastian

    2012-10-01

    We present semiempirical approach based on the Judd-Ofelt theory and apply it for modeling the spectral properties of fluoride glasses activated with the rare earth (RE) ions. This method provide a powerful tool for simulating both ground state absorption (GSA) and excited state absorption (ESA) spectra of RE ions, e.g. Nd3+, Ho3+, Er3+ and Tm3+ in the ZBLAN glass matrix. The results of theoretical calculations correspond to the experimentally measured data. We also demonstrate that the spectra obtained using the presented approach are applicable in the analysis of up-conversion excitation schemes in these optoelectronically relevant materials.

  3. Modeling of a Von Platen-Munters diffusion absorption refrigeration cycle

    Agostini, Bruno; Agostini, Francesco; Habert, Mathieu

    2016-09-01

    This article presents a thermodynamical model of a Von-Platen diffusion absorption refrigeration cycle for power electronics applications. It is first validated by comparison with data available in the literature for the classical water-ammonia-helium cycle for commercial absorption fridges. Then new operating conditions corresponding to specific ABB applications, namely high ambient temperature and new organic fluids combinations compatible with aluminium are simulated and discussed. The target application is to cool power electronics converters in harsh environments with high ambient temperature by providing refrigeration without compressor, for passive components losses of about 500 W, with a compact and low cost solution.

  4. 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.

  5. Interactions of hypericin with a model mutagen - Acridine orange analyzed by light absorption and fluorescence spectroscopy

    Pietrzak, Monika; Szabelski, Mariusz; Kasparek, Adam; Wieczorek, Zbigniew

    2017-02-01

    The present study was designed to estimate the ability of hypericin to interact with a model mutagen - acridine orange. The hetero-association of hypericin and acridine orange was investigated with absorption and fluorescence spectroscopy methods in aqueous solution of DMSO. The data indicate that hypericin forms complexes with acridine orange and that the association constants are relatively high and depend on DMSO concentration. The absorption spectra of the hypericin - acridine orange complexes were examined as well. Owing to its ability to interact with flat aromatic compounds, hypericin may potentially be used as an interceptor molecule.

  6. Application of Absorption Modeling in Rational Design of Drug Product Under Quality-by-Design Paradigm.

    Kesisoglou, Filippos; Mitra, Amitava

    2015-09-01

    Physiologically based absorption models can be an important tool in understanding product performance and hence implementation of Quality by Design (QbD) in drug product development. In this report, we show several case studies to demonstrate the potential application of absorption modeling in rational design of drug product under the QbD paradigm. The examples include application of absorption modeling—(1) prior to first-in-human studies to guide development of a formulation with minimal sensitivity to higher gastric pH and hence reduced interaction when co-administered with PPIs and/or H2RAs, (2) design of a controlled release formulation with optimal release rate to meet trough plasma concentrations and enable QD dosing, (3) understanding the impact of API particle size distribution on tablet bioavailability and guide formulation design in late-stage development, (4) assess impact of API phase change on product performance to guide specification setting, and (5) investigate the effect of dissolution rate changes on formulation bioperformance and enable appropriate specification setting. These case studies are meant to highlight the utility of physiologically based absorption modeling in gaining a thorough understanding of the product performance and the critical factors impacting performance to drive design of a robust drug product that would deliver the optimal benefit to the patients.

  7. Microwave Absorption and Response Modeling of Nanocomposites Embedded SiC Nanoparticles

    LU Ran; FANG Xiao-Yong; KANG Yu-Qing; YUAN Jie; CAO Mao-Sheng

    2009-01-01

    @@ We study the mechanism of microwave response properties of SiCp/paraffin nanocomposites and propose a mi-crowave absorption model of nanocomposites based on the conservation law of energy and the theory of electro-magnetic scattering. Using the model we calculate the reflectivity of SiCp/paraffin nanocomposites ranging from 2 CHz to 18 GHz. The calculated results are very consistent with the experimental data in the frequency range investigated.

  8. 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.

  9. Molecular modeling of C 60:cobaltocene and nickelocene complexes, comparison with IR absorption

    Byszewski, P.; Antonova, K.; Kowalska, E.; Radomska, J.; Baran, J.

    2000-06-01

    C 60 was reacted with cobaltocene and nickelocene. The samples of the composition C 60(Cocp 2) 3 and C 60Nicp 2 were obtained in the reaction. Their thermal stability was measured by Thermogravimetry and Differential Scanning Calorimetry and the vibrational spectrum was investigated by infrared absorption. Hydrocarbon groups may be evacuated from the reaction products by annealing, while metal atoms remain dispersed between fullerenes. The experiments are compared with the molecular modeling results obtained by applying the PM3 model.

  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. Multiscale modeling of light absorption in tissues: limitations of classical homogenization approach.

    Mottin, Stephane; Panasenko, Grigory; Ganesh, S Sivaji

    2010-12-31

    In biophotonics, the light absorption in a tissue is usually modeled by the Helmholtz equation with two constant parameters, the scattering coefficient and the absorption coefficient. This classic approximation of "haemoglobin diluted everywhere" (constant absorption coefficient) corresponds to the classical homogenization approach. The paper discusses the limitations of this approach. The scattering coefficient is supposed to be constant (equal to one) while the absorption coefficient is equal to zero everywhere except for a periodic set of thin parallel strips simulating the blood vessels, where it is a large parameter ω. The problem contains two other parameters which are small: ε, the ratio of the distance between the axes of vessels to the characteristic macroscopic size, and δ, the ratio of the thickness of thin vessels and the period. We construct asymptotic expansion in two cases: ε --> 0, ω --> ∞, δ --> 0, ωδ --> ∞, ε2ωδ --> 0 and ε --> 0, ω --> ∞, δ --> 0, ε2ωδ --> ∞, and and prove that in the first case the classical homogenization (averaging) of the differential equation is true while in the second case it is wrong. This result may be applied in the biomedical optics, for instance, in the modeling of the skin and cosmetics.

  12. An analytical solution for the model of drug distribution and absorption in small intestine

    Mingyu, Xu

    1990-11-01

    According to the physiological and anatomical characteristics of small intestine, neglecting the effect of its motility on the distribution and absorption of drug and nutrient, Y. Miyamoto et al.[1] proposed a model of two-dimensional laminar flow in a circular porous tube with permeable wall and calculated the concentration profile of drug by numerical analysis. In this paper, we give a steady state analytical solution of the above model including deactivation term. The obtained results are in agreement with the results of their numerical analysis. Moreover the analytical solution presented in this paper reveals the relation among the physiological parameters of the model and describes the basic absorption rule of drug and nutrient through the intestinal wall and hence provides a theoretical basis for determining the permeability and reflection coefficient through in situ experiments.

  13. Comparison between two models of absorption of matter waves by a thin time-dependent barrier

    Barbier, Maximilien; Beau, Mathieu; Goussev, Arseni

    2015-11-01

    We report a quantitative, analytical, and numerical comparison between two models of the interaction of a nonrelativistic quantum particle with a thin time-dependent absorbing barrier. The first model represents the barrier by a set of time-dependent discontinuous matching conditions, which are closely related to Kottler boundary conditions used in stationary-wave optics as a mathematical basis for Kirchhoff diffraction theory. The second model mimics the absorbing barrier with an off-diagonal δ potential with a time-dependent amplitude. We show that the two models of absorption agree in their predictions in a semiclassical regime, the regime readily accessible in modern experiments with ultracold atoms.

  14. 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....

  15. 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

  16. Modeling of ammonia absorption chillers integration in energy systems of process plants

    Bruno, J.C.; Castells, F. [Universitat Rovira i Virgili, Tarragona (Spain). Dept. d' Enginyeria Quimica; Miquel, J. [Universitat Politecnica de Catalunya (Spain). Dept. de Mecanica de Fluids

    1999-12-01

    A mathematical programming approach is proposed to study the integration of absorption chillers in combined heat and power plants. The aim of this work is to determine the economic viability of the introduction of ammonia absorption chillers in energy systems instead of using the more conventional compression cycles. This procedure selects the best refrigeration alternative taking into account both absorption and compression cycles. To select the most suitable refrigeration cycle for a given refrigeration load, it is not only necessary to model the performance of each cycle, but also to take into account the interactions between the energy system and the considered cycles, optimizing the performance of the global plant. This approach has been implemented in the computer program XV, and tested in an energy plant in the petrochemical complex of Tarragona (Catalunya, Spain). The refrigeration demands to be met are at 0 and -20{sup o}C. The results highlighted the benefit obtained with the simultaneous presence of ammonia absorption cycles and a cogeneration based energy plant. (author)

  17. 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...

  18. Dynamic Model and Performance of Absorption Heat Pump in Shut-down Process

    WANG Lei; LU Zhen

    2002-01-01

    The dynamic model of LiBr absorption heat pump in shut-down process is established. The simulation results show good agreement with the experiments. The dynamic performance of high-pressure generator, low-pressure generator and heat exchanger are analyzed in detail. The proper shut-down mode of the heat pump is presented,which, in consideration of solution parameters, has a great effect on the possibility of crystallization of some components.

  19. The Phenion (R) Full-Thickness Skin Model for Percutaneous Absorption Testing

    2010-01-01

    In recent years many efforts have been made to replace dermal toxicity testing of chemicals in the animal by in vitro assays. As a member of a German research consortium, we have previously contributed to the validation of an in vitro test protocol for percutaneous absorption studies on the basis of reconstructed human epidermis and both human and pig skin ex vivo. Aiming to assess the barrier properties of a newly developed reconstructed skin model, this protocol has now been transferred to ...

  20. Microscopic modeling of País grape seed extract absorption in the small intestine.

    Morales, Cristian; Roeckel, Marlene; Fernández, Katherina

    2014-02-01

    The concentration profiles and the absorbed fraction (F) of the País grape seed extract in the human small intestine were obtained using a microscopic model simulation that accounts for the extracts' dissolution and absorption. To apply this model, the physical and chemical parameters of the grape seed extract solubility (C s), density (ρ), global mass transfer coefficient between the intestinal and blood content (k) (effective permeability), and diffusion coefficient (D) were experimentally evaluated. The diffusion coefficient (D = 3.45 × 10(-6) ± 5 × 10(-8) cm(2)/s) was approximately on the same order of magnitude as the coefficients of the relevant constituents. These results were chemically validated to discover that only the compounds with low molecular weights diffused across the membrane (mainly the (+)-catechin and (-)-epicatechin compounds). The model demonstrated that for the País grape seed extract, the dissolution process would proceed at a faster rate than the convective process. In addition, the absorbed fraction was elevated (F = 85.3%). The global mass transfer coefficient (k = 1.53 × 10(-4) ± 5 × 10(-6) cm/s) was a critical parameter in the absorption process, and minor changes drastically modified the prediction of the extract absorption. The simulation and experimental results show that the grape seed extract possesses the qualities of a potential phytodrug.

  1. Modeling size-dependent photosynthesis: light absorption and the allometric rule.

    Finkel, Z V; Irwin, A J

    2000-06-07

    Microalgal photosynthesis can be predicted using empirical allometric or mechanistic bio-optic models. These two descriptions are usually considered independently. We compare the size scaling of photosynthesis predicted by these two models. Size scaling exponents for phytoplankton often deviate from the allometric 3/4 rule. This may be because the allometric model does not account for the size dependence of light absorption and its effect on the size scaling of photosynthesis. In contrast to the allometric model and experimental data, the bio-optic model predicts photosynthesis should be independent of cell size when intracellular pigment concentrations are low or inversely related to cell diameter. A composite of the allometric and bio-optic models is described and compared to laboratory data of light-limited nutrient-saturated diatom photosynthesis. The allo-bio-optic model provides a mechanistic explanation for the anomalous size scaling found in laboratory and field studies of microalgal photosynthesis and growth.

  2. Oral absorption of ginsenoside Rb1 using in vitro and in vivo models.

    Han, Min; Sha, Xianyi; Wu, Yunjuan; Fang, Xiaoling

    2006-04-01

    This research attempts to clarify the cause for poor oral absorption of ginsenoside Rb1 (Rb1), one main ingredient of the well known Panax notoginseng saponins (PNS) for curing hemorrhage. Caco-2 cell monolayers were used as an in vitro model to reveal the transport mechanism of Rb1 across the intestinal mucosa. Moreover, the serum concentration-time profiles of Rb1 after tail venous (IV), portal venous (PV), intraduodenal (ID) and peroral (PO) administration to rats were compared to evaluate the first-pass effects of stomach, intestine and liver. In vitro experiments showed that uptake by Caco-2 cell monolayers was temperature dependent, but was not influenced by cyclosporine A and ketoconazole. The change in the apical pH showed no obvious effects on the uptake of Rb1. The uptake and transport were non-saturable, and flux from the apical compartment to the basolateral compartment (A-B) increased linearly with increasing concentration, which indicated a passive transport. Meanwhile, an apparent permeability coefficient of (5.90 +/- 1.02) x 10(-8) cm/s (C0 = 1 mg/mL) predicted an incomplete absorption. The investigation on the pharmacokinetic behavior of Rb1 after different routes of administration to rats showed a significant difference between PO (F(PO) was 0.64%), ID (F(ID) was 2.46%) and PV (F(PV) was 59.49%) administration, and the first-pass effect of the intestine is more significant than that of the stomach and liver in the absorption process. In summary, elimination in the stomach, large intestine and liver contributed to the poor absorption of Rb1, but the low membrane permeability might be a more important factor dominating the extent of absorption.

  3. Modeling of Liquid Film along Absorber Cylinders in an Absorption Chiller

    Suzuki, Hiroshi; Yamanaka, Tomofumi; Nagamoto, Wataru; Sugiyama, Takahide

    A two-dimensional liquid film model of LiBr solution falling along absorber cylinders has been studied to obtain boundary conditions for computing vapor flow in the absorber-evaporator of an absorption chiller. The model was established based on the assumptions that LiBr concentration and temperature profiles in the liquid film obey the third order polynomial expressions. It was indicated that mass flux and absorbed heat on the liquid surface can be calculated with simple numerical computations on the present analytical model. The overall heat transfer coefficient and total absorbed mass per second calculated with the present liquid film model was compared with experimental data for validation. The results calculated with the present model showed good agreement with the experimental data. Then, it was concluded the present model was useful enough for determining surface conditions on the LiBr liquid film around absorber cylinders.

  4. 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...

  5. Modeling of the Interminiband Absorption Coefficient in InGaN Quantum Dot Superlattices

    Giovanni Giannoccaro

    2016-01-01

    Full Text Available In this paper, a model to estimate minibands and theinterminiband absorption coefficient for a wurtzite (WZ indium gallium nitride (InGaN self-assembled quantum dot superlattice (QDSL is developed. It considers a simplified cuboid shape for quantum dots (QDs. The semi-analytical investigation starts from evaluation through the three-dimensional (3D finite element method (FEM simulations of crystal mechanical deformation derived from heterostructure lattice mismatch under spontaneous and piezoelectric polarization effects. From these results, mean values in QDs and barrier regions of charge carriers’ electric potentials and effective masses for the conduction band (CB and three valence sub-bands for each direction are evaluated. For the minibands’ investigation, the single-particle time-independent Schrödinger equation in effective mass approximation is decoupled in three directions and resolved using the one-dimensional (1D Kronig–Penney model. The built-in electric field is also considered along the polar axis direction, obtaining Wannier–Stark ladders. Then, theinterminiband absorption coefficient in thermal equilibrium for transverse electric (TE and magnetic (TM incident light polarization is calculated using Fermi’s golden rule implementation based on a numerical integration into the first Brillouin zone. For more detailed results, an absorption coefficient component related to superlattice free excitons is also introduced. Finally, some simulation results, observations and comments are given.

  6. Modeling power law absorption and dispersion for acoustic propagation using the fractional Laplacian.

    Treeby, Bradley E; Cox, B T

    2010-05-01

    The efficient simulation of wave propagation through lossy media in which the absorption follows a frequency power law has many important applications in biomedical ultrasonics. Previous wave equations which use time-domain fractional operators require the storage of the complete pressure field at previous time steps (such operators are convolution based). This makes them unsuitable for many three-dimensional problems of interest. Here, a wave equation that utilizes two lossy derivative operators based on the fractional Laplacian is derived. These operators account separately for the required power law absorption and dispersion and can be efficiently incorporated into Fourier based pseudospectral and k-space methods without the increase in memory required by their time-domain fractional counterparts. A framework for encoding the developed wave equation using three coupled first-order constitutive equations is discussed, and the model is demonstrated through several one-, two-, and three-dimensional simulations.

  7. A simplified nonlinear model of the Marangoni instability in gas absorption

    Skurygin, E. F.; Poroyko, T. A.

    2016-04-01

    The process of gas absorption into initially motionless liquid layer is investigated. The convective instability caused by the temperature dependence of the surface tension. The critical time of transition of the process to unstable convective regime, as well as the intensity of mass transfer in a surface convection are estimated numerically. The mathematical model includes the equations of convective diffusion, thermal conduction and fluid motion. The problem was solved numerically in the two-dimensional formulation. In the coordinate along the interface the concentration of the absorbed substance is represented by three terms of the trigonometric Fourier series. A difference approximation of equations with an exponentially changing grid in the direction normal to the interface is used. The simulations results agree with the well-known experimental data on the absorption of carbon dioxide in water.

  8. Simulation model of a single-stage lithium bromide-water absorption cooling unit

    Miao, D.

    1978-01-01

    A computer model of a LiBr-H2O single-stage absorption machine was developed. The model, utilizing a given set of design data such as water-flow rates and inlet or outlet temperatures of these flow rates but without knowing the interior characteristics of the machine (heat transfer rates and surface areas), can be used to predict or simulate off-design performance. Results from 130 off-design cases for a given commercial machine agree with the published data within 2 percent.

  9. DDA Modeling for the Mid-IR Absorption of Irregularly Shaped Crystalline Forsterite Grains

    Lindsay, Sean; Wooden, D. H.; Kelley, M. S.; Harker, D. E.; Woodward, C. E.; Murphy, J.

    2010-10-01

    An analysis of the Spitzer IRS spectra of the Deep Impact ejecta of comet 9P/Tempel 1 (Wooden et al. 2010, 42nd DPS Meeting) in conjunction with the dynamics of the ejecta grains (Kelley et al. 2010, 42nd DPS Meeting) strongly suggests that ecliptic comets have comae dominated by large (> 10 - 20 micron in radii) porous grains with Mg-rich crystal inclusions. In fact, Kelley et al. (2010) conclude that many ecliptic comets may be dominated by such grains with a high crystalline fraction, approximately 40% by mass, despite their generally weak silicate emission feature. To date, no model for the optical properties in the mid-IR of multi-mineralic large porous grains with silicate crystal inclusions, has been performed. We have initiated a program to compute the absorption and scattering efficiencies for these grains. Presented here are the 3 - 40 micron absorption efficiencies for models of sub-micron sized crystalline forsterite grains of irregular shape. We use the Discrete Dipole Approximation (DDA) to create discrete targets of forsterite that can be included in large porous aggregates. Computations are performed on the NAS Pleiades supercomputer. Our calculated absorption efficiencies for individual grains of forsterite are in agreement with laboratory measurements (Tamanai et al. 2006; Koike et al. 2003) and the continuous distribution of ellipsoids (CDE) method by Harker et al. (2007). We find for discrete grains that grain shape has a strong effect on the peak location of a crystalline resonance and that mimicking the physical properties of forsterite is important. Also presented are the absorption efficiencies for simple multi-component aggregates and for collections of forsterite crystals of different size and shape to replicate laboratory samples. This research is supported by the NASA GSRP Program.

  10. 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...... of pure MDEA vapor pressure, vapor-liquid equilibrium (VLE) (total pressure and CO2 partial pressure), freezing point depression (SLE), excess enthalpy, heat capacity and heat of absorption were used to adjust model parameters. The model was then used to predict the NMR spectroscopic data. The developed...

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

    Chirkunov, Yu. A., E-mail: chr101@mail.ru [Novosibirsk State Technical University, Marks Avenue 20, Novosibirsk 630073 (Russian Federation)

    2015-10-15

    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

  12. Predicting dermal absorption of gas-phase chemicals: transient model development, evaluation, and application

    Gong, M.; Zhang, Y.; Weschler, Charles J.

    2014-01-01

    for scenarios in which (A) a previously unexposed occupant encounters gas-phase phthalates in three different environments over a single 24-h period; (B) the same as 'A', but the pattern is repeated for seven consecutive days. In the 24-h scenario, the transient model predicts more phthalate absorbed into skin......A transient model is developed to predict dermal absorption of gas-phase chemicals via direct air-to-skin-to-blood transport under non-steady-state conditions. It differs from published models in that it considers convective mass-transfer resistance in the boundary layer of air adjacent to the skin...... and less absorbed into blood than would a steady-state model. In the 7-day scenario, results calculated by the transient and steady-state models converge over a time period that varies between 3 and 4days for all but the largest phthalate (DEHP). Dermal intake is comparable to or larger than inhalation...

  13. Modeling of normal incidence absorption in p-type GaAs/AlGaAs quantum well infrared detectors

    Brown, Gail J.; Szmulowicz, Frank

    1995-04-01

    The absorption of infrared radiation at normal incidence in p-type GaAs/AlGaAs quantum wells, unlike in n-type, is fundamentally allowed. We have measured and theoretically modeled the bound-to-continuum absorption in these p-type materials. The infrared absorption coefficient was calculated are based on the electronic structure, wave functions and optical matrix elements obtained from an 8 X 8 envelope-function approximation (EFA) calculation. The 8 X 8 EFA Hamiltonian incorporates the coupling between the heavy, light, spin-orbit, and conduction bands. In calculating the continuum states for bound-to- continuum intersubband absorption, we do not enclose the well in an artificial box with infinite walls. A comparison of the theoretical absorption and measured photoresponse results verified the accuracy of our model and provided a basis for optimizing the design of p-type quantum wells for infrared detection.

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

    Santacruz, Luis Andres; Solarte, Efrain [Departamento de Fisica, Universidad del Valle, Cali (Colombia); Garcia, Hernando, E-mail: landress18@gmail.com [Department of Physics, Southern Illinois University, Edwardsville (United States)

    2011-01-01

    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, {epsilon}{sub eff} using this result we have analyzed the light absorption process in the case of Silicon with two types of metallic inclusions.

  15. 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.

  16. Electromagnetic absorption in a multilayered slab model of tissue under near-field exposure conditions

    Chatterjee, I.; Hagmann, M.J.; Gandhi, O.P.

    1980-01-01

    The electromagnetic energy deposited in a semi-infinite slab model consisting of skin, fat, and muscle layers is calculated for both plane-wave and near-field exposures. The plane-wave spectrum (PWS) approach is used to calculate the energy deposited in the model by fields present due to leakage from equipment using electromagnetic energy. This analysis applies to near-field exposures where coupling of the target to the leakage source can be neglected. Calculations were made for 2,450 MHz, at which frequency the layered slab adequately models flat regions of the human body. Resonant absorption due to layering is examined as a function of the skin and fat thicknesses for plane-wave exposure and as a function of the physical extent of the near-field distribution. Calculations show that for fields that are nearly constant over at least a free-space wavelength, the energy deposition (for skin, fat, and muscle combination that gives resonant absorption) is equal to or less than that resulting from plane-wave exposure, but is appreciably greater than that obtained for a homogeneous muscle slab model.

  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. 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

  19. 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....

  20. Multiple Absorption-Line Spectroscopy of the Intergalactic Medium. I. Model

    Yao, Yangsen; Danforth, Charles W; Keeney, Brian A; Stocke, John T

    2011-01-01

    We present a physically-based absorption-line model for the spectroscopic study of the intergalactic medium (IGM). This model adopts results from Cloudy simulations and theoretical calculations by Gnat and Sternberg (2007) to examine the resulting observational signatures of the absorbing gas with the following ionization scenarios: collisional ionization equilibrium (CIE), photoionization equilibrium, hybrid (photo- plus collisional ionization), and non-equilibrium cooling. As a demonstration, we apply this model to new observations made with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope of the IGM absorbers at z~0.1877 along the 1ES 1553+113 sight line. We identify Ly alpha, C III, O VI, and N V absorption lines with two distinct velocity components (blue at z_b=0.18757; red at z_r=0.18772) separated by Delta(cz)/(1+z)~38 km/s. Joint analyses of these lines indicate that none of the examined ionization scenarios can be applied with confidence to the blue velocity component, although phot...

  1. Mathematical Model of a Lithium-Bromide/Water Absorption Refrigeration System Equipped with an Adiabatic Absorber

    Salem M. Osta-Omar

    2016-11-01

    Full Text Available The objective of this paper is to develop a mathematical model for thermodynamic analysis of an absorption refrigeration system equipped with an adiabatic absorber using a lithium-bromide/water (LiBr/water pair as the working fluid. The working temperature of the generator, adiabatic absorber, condenser, evaporator, the cooling capacity of the system, and the ratio of the solution mass flow rate at the circulation pump to that at the solution pump are used as input data. The model evaluates the thermodynamic properties of all state points, the heat transfer in each component, the various mass flow rates, and the coefficient of performance (COP of the cycle. The results are used to investigate the effect of key parameters on the overall performance of the system. For instance, increasing the generator temperatures and decreasing the adiabatic absorber temperatures can increase the COP of the cycle. The results of this mathematical model can be used for designing and sizing new LiBr/water absorption refrigeration systems equipped with an adiabatic absorber or for optimizing existing aforementioned systems.

  2. 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.

  3. 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.

  4. X-Ray Modeling of the Intrinsic Absorption in NGC 4151

    Denes Couto, Jullianna; Kraemer, Steven; Turner, T. Jane; Crenshaw, D. Michael

    2017-01-01

    We have investigated the relationship between the long term X-ray spectral variability in the Seyfert 1.5 galaxy NGC 4151 and its intrinsic absorption, by comparing our 2014 simultaneous ultraviolet/X-Ray observations taken with Hubble STIS Echelle and Chandra HETGS with archival observations from Chandra, XMM-Newton and Suzaku. The observations were divided into "high" and "low" states, with the low states showing strong and unabsorbed extended emission at energies below 2 keV. Our X-ray model consists of a broken powerlaw, neutral reflection and the two dominant absorption components identified by Kraemer et al (2005), X-High and D+Ea, which are present in all epochs. The model fittings suggest that the absorbers are very stable, with the principal changes in the intrinsic absorption resulting from variations in the ionization state of the gas in response to the variable strength of the ionizing continuum. However, the low states show evidence of larger column densities in one or both of the absorbers. Among plausible explanations for the column increase, we discuss the possibility of an expanding/contracting X-ray corona. X-High is consistent with being part of a magnetohydrodynamic (MHD) wind, while D+Ea is possibly radiatively driven, which suggests that at a sufficiently large radial distance there could be a break point between MHD-dominated and radiatively driven outflows. Preliminary results on the analysis of the AGN mass outflow rates and kinematics of the ionized gas in the extended emission region of NGC 4151 will also be presented.

  5. Selenocompounds in juvenile white sturgeon: estimating absorption, disposition, and elimination of selenium using Bayesian hierarchical modeling.

    Huang, Susie Shih-Yin; Strathe, Anders Bjerring; Hung, Silas S O; Boston, Raymond C; Fadel, James G

    2012-03-01

    The biological function of selenium (Se) is determined by its form and concentration. Selenium is an essential micronutrient for all vertebrates, however, at environmental levels, it is a potent toxin. In the San Francisco Bay-Delta, Se pollution threatens top predatory fish, including white sturgeon. A multi-compartmental Bayesian hierarchical model was developed to estimate the fractional rates of absorption, disposition, and elimination of selenocompounds, in white sturgeon, from tissue measurements obtained in a previous study (Huang et al., 2012). This modeling methodology allows for a population based approach to estimate kinetic physiological parameters in white sturgeon. Briefly, thirty juvenile white sturgeon (five per treatment) were orally intubated with a control (no selenium) or a single dose of Se (500 μg Se/kg body weight) in the form of one inorganic (Selenite) or four organic selenocompounds: selenocystine (SeCys), l-selenomethionine (SeMet), Se-methylseleno-l-cysteine (MSeCys), or selenoyeast (SeYeast). Blood and urine Se were measured at intervals throughout the 48h post intubation period and eight tissues were sampled at 48 h. The model is composed of four state variables, conceptually the gut (Q1), blood (Q2), and tissue (Q3); and urine (Q0), all in units of μg Se. Six kinetics parameters were estimated: the fractional rates [1/h] of absorption, tissue disposition, tissue release, and urinary elimination (k12, k23, k32, and k20), the proportion of the absorbed dose eliminated through the urine (f20), and the distribution blood volume (V; percent body weight, BW). The parameter k12 was higher in sturgeon given the organic Se forms, in the descending order of MSeCys > SeMet > SeCys > Selenite > SeYeast. The parameters k23 and k32 followed similar patterns, and f20 was lowest in fish given MSeCys. Selenium form did not affect k20 or V. The parameter differences observed can be attributed to the different mechanisms of transmucosal transport

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

    Lv, Jitao; Luo, Lei; Zhang, Jing; Christie, Peter; Zhang, Shuzhen

    2012-03-01

    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 HgCl(2)(0) 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.

  7. 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.

  8. 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.

  9. 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.

  10. A simple physical model for steam absorption into a falling film of aqueous lithium bromide solution on a horizontal tube

    Auracher, Hein; Wohlfeil, Arnold; Ziegler, Felix

    2008-03-01

    For one horizontal tube in an absorber the Nusselt solution for film thickness and velocity distribution was applied, assuming steady state in heat transfer and a semi-infinite body’s concentration profile with unsteady state mass transfer. The model was applied to the absorption of steam into aqueous lithium bromide in absorption chillers. The results are compared to published experimental values and show fair agreement.

  11. Integrated numerical model of nitrogen transportation, absorption and transformation by two-dimension in soil-crop system

    WANG Hong-qi; SHU Yan; QI Yong-qiang; ZHANG Jun

    2005-01-01

    A series of simulation experiments of nitrogen transportation, absorption and transformation were conducted, and the different cropping patterns of winter wheat and wastewater irrigation plans were taken into consideration. Based on the experiments, an integrated model of crop growth, roots distribution, water and nitrogen absorption by roots, water and nitrogen movement and transformation in soilcrop system by two-dimension was developed. Parameters and boundary conditions were identified and an effective computing method for optimizing watering and wastewater irrigating plans was provided.

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

    Shafirstein, Gal [Department of Otolaryngology, College of Medicine, University of Arkansas for Medical Sciences, 4301 W. Markham, 543, Little Rock, AR 72205 (United States); Moros, Eduardo G, E-mail: shafirsteingal@uams.edu [Division of Radiation Physics and Informatics, Department of Radiation Oncology, College of Medicine, University of Arkansas for Medical Sciences, 4301 W. Markham, 771, Little Rock, AR 72205 (United States)

    2011-03-07

    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 {mu}m stratum corneum, 350 {mu}m epidermis and papillary dermis (EPD) and 1000 {mu}m dermis. Five SGD of 60 {mu}m radius and 300 {mu}m height were embedded linearly with 370 {mu}m separation. A WR-10 waveguide positioned 20 {mu}m 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.

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

    Shafirstein, Gal; Moros, Eduardo G.

    2011-03-01

    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™). 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.

  14. Radial diffusion in the Uranian radiatian belts - Inferences from satellite absorption loss models

    Hood, L. L.

    1989-01-01

    Low-energy charged particle (LECP) phase space density profiles available from the Voyager/1986 Uranus encounter are analyzed, using solutions of the time-averaged radial diffusion equation for charged particle transport in a dipolar planetary magnetic field. Profiles for lower-energy protons and electrons are first analyzed to infer radial diffusion rate as a function of L, assuming that satellite absorption is the dominant loss process and local sources for these particles are negligible. Satellite macrosignatures present in the experimentally derived profiles are approximately reproduced in several cases, lending credence to the loss model and indicating that magnetospheric distributed losses are not as rapid as satellite absorption near the minimum satellite L shells for the particles. Diffusion rates and L dependences are found to be similar to those previously inferred in the inner Jovian magnetosphere (Thomsen et al., 1977) and for the inner Saturnian magnetosphere (Hood, 1985). Profiles for higher energy electrons and protons are also analyzed using solutions that allow for the existence of significant particle sources as well as sinks. Possible implications for radial diffusion mechanisms in the Uranian radiation belts are discussed.

  15. 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 the few BALs detected in this quasar sample obey key predictions of models of radiatively driven disk-winds in which (1) the local disk luminosity launches the wind, (2) the central UV radiation drives it outwards, and (3) the wind acceleration (i.e., terminal velocity) depends on the strength of the X......-ray to UV emission ratio, i.e., aOX. The latter means that quasars with flat aOX (like radio-louds) should not have strong, high-velocity (BAL-like) outflows. These results are of interest not only to studies of disk wind scenarios and quasar structure, but also to studies of quasar feedback: NALs...

  16. Modeling the absorption spectra of Er3+ and Yb3+ in a phosphate glass

    Gruber, John B.; Sardar, Dhiraj K.; Zandi, Bahram; Hutchinson, J. Andrew; Trussell, C. Ward

    2003-10-01

    Absorption spectra of Er3+ and Yb3+ ions, codopants in a phosphate glass, are reported at 8 K and at wavelengths between 350 and 1600 nm. Detailed structure appearing in the spectra, associated with individual multiplet states, 2S+1LJ, of Er3+(4f11) and Yb3+(4f13) is interpreted using a ligand-field coordination sphere model to characterize the microscopic environment surrounding the rare earth ions in multiple sites. Inhomogeneous broadening of the spectra is likely due to different configurations of PO4 tetrahedra clustered about a caged rare earth ion in the amorphous host. Similarity between the Er3+ spectrum in the glass and in the spectrum of single-crystal LiErP4O12, where Er3+ occupies sites of C2 symmetry, suggests that an averaged site symmetry of C2 is a reasonable approximation for Er3+ and Yb3+ ions in the phosphate glass. Calculated splitting of multiplet states by the ligand-field cluster model are compared with energy levels derived from the observed absorption peaks and well-defined shoulders. Inhomogeneous broadening of the spectra limit the precision in establishing the energy of the multiplet splittings, but the analysis is useful for modeling studies of the Er:Yb:phosphate glass as an eye-safe laser (1.53 μm). The splitting of the Yb3+(4f13)2FJ states is determined using parameters obtained from the Er3+ set by means of the three-parameter theory. No adjustments were made to the Yb3+ parameters that predict multiplet splittings in reasonable agreement with experimental data.

  17. 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 ...

  18. A Biophysicochemical Model for NO Removal by the Chemical Absorption-Biological Reduction Integrated Process.

    Zhao, Jingkai; Xia, Yinfeng; Li, Meifang; Li, Sujing; Li, Wei; Zhang, Shihan

    2016-08-16

    The chemical absorption-biological reduction (CABR) integrated process is regarded as a promising technology for NOx removal from flue gas. To advance the scale-up of the CABR process, a mathematic model based on mass transfer with reaction in the gas, liquid, and biofilm was developed to simulate and predict the NOx removal by the CABR system in a biotrickling filter. The developed model was validated by the experimental results and subsequently was used to predict the system performance under different operating conditions, such as NO and O2 concentration and gas and liquid flow rate. NO distribution in the gas phase along the biotrickling filter was also modeled and predicted. On the basis of the modeling results, the liquid flow rate and total iron concentration were optimized to achieve >90% NO removal efficiency. Furthermore, sensitivity analysis of the model revealed that the performance of the CABR process was controlled by the bioreduction activity of Fe(III)EDTA. This work will provide the guideline for the design and operation of the CABR process in the industrial application.

  19. A diffusive virus infection dynamic model with nonlinear functional response, absorption effect and chemotaxis

    Wang, Wei; Ma, Wanbiao; Lai, Xiulan

    2017-01-01

    From a biological perspective, a diffusive virus infection dynamic model with nonlinear functional response, absorption effect and chemotaxis is proposed. In the model, the diffusion of virus consists of two parts, the random diffusion and the chemotactic movement. The chemotaxis flux of virus depends not only on their own density, but also on the density of infected cells, and the density gradient of infected cells. The well posedness of the proposed model is deeply investigated. For the proposed model, the linear stabilities of the infection-free steady state E0 and the infection steady state E* are extensively performed. We show that the threshold dynamics can be expressed by the basic reproduction number R0 of the model without chemotaxis. That is, the infection-free steady state E0 is globally asymptotically stable if R0 virus is uniformly persistent if R0 > 1. In addition, we use the cross iteration method and the Schauder's fixed point theorem to prove the existence of travelling wave solutions connecting the infection-free steady state E0 and the infection steady state E* by constructing a pair of upper-lower solutions. At last, numerical simulations are presented to confirm theoretical findings.

  20. 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%.

  1. Multi-objective optimisation of a vehicle energy absorption structure based on surrogate model

    谢素超; 周辉

    2014-01-01

    In order to optimize the crashworthy characteristic of energy-absorbing structures, the surrogate models of specific energy absorption (SEA) and ratio of SEA to initial peak force (REAF) with respect to the design parameters were respectively constructed based on surrogate model optimization methods (polynomial response surface method (PRSM) and Kriging method (KM)). Firstly, the sample data were prepared through the design of experiment (DOE). Then, the test data models were set up based on the theory of surrogate model, and the data samples were trained to obtain the response relationship between the SEA & REAF and design parameters. At last, the structure optimal parameters were obtained by visual analysis and genetic algorithm (GA). The results indicate that the KM, where the local interpolation method is used in Gauss correlation function, has the highest fitting accuracy and the structure optimal parameters are obtained as: the SEA of 29.8558 kJ/kg (corresponding toa=70 mm andt= 3.5 mm) and REAF of 0.2896 (corresponding toa=70 mm andt=1.9615 mm). The basis function of the quartic PRSM with higher order than that of the quadratic PRSM, and the mutual influence of the design variables are considered, so the fitting accuracy of the quartic PRSM is higher than that of the quadratic PRSM.

  2. Modelling the absorption refrigeration cycle using partially miscible working fluids by group contribution methods

    Larkeche, O.; Meniai, A.-H.; Cachot, T.

    2012-06-01

    The present study concerns the cycle performance modelling of a particular configuration of an absorption refrigeration machine based on phase separation as well as development of a strategy for computer aided design of absorbents. The model uses predictive methods based on the group contribution concept for the computation of the thermodynamic phase equilibria involved such as liquid-liquid and vapour-liquid as well as enthalpy-concentration diagrams. The proposed absorbents computer-aided design strategy is based on the exploration of a number of structural group combinations obtained from a selected set of functional groups, according to the chemistry laws. The model was tested on four different absorbent-refrigerant pairs reported in the literature, namely (benzyl ethyl amine-glycerol), (water-hexanoic acid), (water-2-hexanone) and (water-ethyl propionate) as well as on pairs where the absorbent compound is generated by the proposed absorbent design strategy and the refrigerant is water. The results show that quite good values of the coefficient of performance (COP) can be obtained, indicating that this cycle configuration is promising and energetically efficient, mainly due to hardware savings, i.e. absence of condenser. However, other working fluid combinations have to be tested using the proposed model.

  3. A population pharmacokinetic model for the complex systemic absorption of ropivacaine after femoral nerve block in patients undergoing knee surgery.

    Gaudreault, François; Drolet, Pierre; Fallaha, Michel; Varin, France

    2012-12-01

    Because of its slow systemic absorption and flip-flop kinetics, ropivacaine's pharmacokinetics after a peripheral nerve block has never been thoroughly characterized. The purpose of this study was to develop a population pharmacokinetic model for ropivacaine after loco-regional administration and to identify patient characteristics that may influence the drug's absorption and disposition. Frequent plasma samples were taken up to 93 h after a 100 mg dose given as femoral block for postoperative analgesia in 15 orthopedic patients. Ropivacaine plasma concentration-time data were analyzed using a nonlinear mixed effects modeling method. A one-compartment model with parallel inverse Gaussian and time-dependent inputs best described ropivacaine plasma concentration-time curves. Ropivacaine systemic absorption was characterized by a rapid phase (mean absorption time of 25 ± 4.8 min) followed by a much slower phase (half-life of 3.9 ± 0.65 h). Interindividual variability (IIV) for these parameters, 58 and 9 %, indicated that the initial absorption phase was more variable. The apparent volume of distribution (V/F = 77.2 ± 11.5 L, IIV = 26 %) was influenced by body weight (Δ 1.49 % per kg change) whereas the absorption rate constant (slower phase) of ropivacaine was affected by age (Δ 2.25 % per year change). No covariate effects were identified for the apparent clearance of the drug (CL/F =10.8 ± 1.0 L/h, 34  IIV = 34 %). These findings support our hypothesis that modeling a complex systemic absorption directly from plasma concentration-time curves exhibiting flip-flop kinetics is possible. Only the age-effect was considered as relevant for possible dosing adjustments.

  4. 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

    2013-11-04

    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

  5. Scientific Review on the Ionospheric Absorption and Research Prospects of a Complex Eikonal Model for One-Layer Ionosphere

    Alessandro Settimi

    2014-01-01

    Full Text Available The present paper conducts a scientific review on ionospheric absorption, extrapolating the research prospects of a complex eikonal model for one-layer ionosphere. As regards the scientific review, here a quasi-longitudinal (QL approximation for nondeviative absorption is deduced which is more refined than the corresponding equation reported by Davies (1990. As regards the research prospects, a complex eikonal model for one-layer ionosphere is analyzed in depth here, already discussed by Settimi et al. (2013. A simple formula is deduced for a simplified problem. A flat, layered ionospheric medium is considered, without any horizontal gradient. The authors prove that the QL nondeviative amplitude absorption according to the complex eikonal model is more accurate than Rawer’s theory (1976 in the range of middle critical frequencies.

  6. 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...... properties of carbon dioxide and ammonia to supercritical conditions....

  7. 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

  8. 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.

  9. Constraints on Hydrodynamical Subgrid Models from Quasar Absorption Line Studies of the Simulated Circumgalactic Medium

    Hummels, Cameron; Smith, Britton; Turk, Matthew

    2012-01-01

    Cosmological hydrodynamical simulations of galaxy evolution are increasingly able to produce realistic galaxies, but the largest hurdle remaining is in constructing subgrid models that accurately describe the behavior of stellar feedback. As an alternate way to test and calibrate such models, we propose to focus on the circumgalactic medium. To do so, we generate a suite of adaptive-mesh refinement (AMR) simulations for a Milky-Way-massed galaxy run to z=0, systematically varying the feedback implementation. We then post-process the simulation data to compute the absorbing column density for a wide range of common atomic absorbers throughout the galactic halo, including H I, Mg II, Si II, Si III, Si IV, C IV, N V, O VI, and O VII. The radial profiles of these atomic column densities are compared against several quasar absorption line studies, to determine if one feedback prescription is favored. We find that although our models match some of the observations (specifically those ions with lower ionization stre...

  10. Analytic model of energy-absorption response functions in compound X-ray detector materials.

    Yun, Seungman; Kim, Ho Kyung; Youn, Hanbean; Tanguay, Jesse; Cunningham, Ian A

    2013-10-01

    The absorbed energy distribution (AED) in X-ray imaging detectors is an important factor that affects both energy resolution and image quality through the Swank factor and detective quantum efficiency. In the diagnostic energy range (20-140 keV), escape of characteristic photons following photoelectric absorption and Compton scatter photons are primary sources of absorbed-energy dispersion in X-ray detectors. In this paper, we describe the development of an analytic model of the AED in compound X-ray detector materials, based on the cascaded-systems approach, that includes the effects of escape and reabsorption of characteristic and Compton-scatter photons. We derive analytic expressions for both semi-infinite slab and pixel geometries and validate our approach by Monte Carlo simulations. The analytic model provides the energy-dependent X-ray response function of arbitrary compound materials without time-consuming Monte Carlo simulations. We believe this model will be useful for correcting spectral distortion artifacts commonly observed in photon-counting applications and optimal design and development of novel X-ray detectors.

  11. Parameters for Modeling Aerosol Absorption: Measurements in Biomass Burning Smoke, Urban/Industrial Plumes, and NW Pacific Marine Airmasses

    Kline, J. T.; Huebert, B. J.; Howell, S. G.; Uematsu, M.; Tsuruta, H.

    2003-12-01

    Absorbing aerosols such as elemental carbon (EC) play a large role in the Earth's radiation budget. However, the impact of EC emissions is hard to model accurately because the light absorption per mass of elemental carbon (EC specific absorption, ESA) varies with the source type and the conditions of the combustion that created it. The wavelength dependence of this absorption also varies with the size and nature of the absorbing material. We measured the ESA of ambient aerosol by measuring both light absorption at 7 wavelengths (as the reduction in light transmission through a quartz Aethalometer filter) and EC (by a thermal/chemical method) at Amami Ohshima, Japan as a part of the APEX program in the Spring of 2002. We also measured light scattering at 3 wavelengths so we could compute wavelength-dependent single-scatter albedos. We found that in smoke from sugar-cane burning the absorption varied as the inverse square of the wavelength, while in plumes from Asian mainland population centers it varied as the inverse of wavelength to the first power. We argue that models should therefore use different, wavelength-dependent "constants" for different conditions. Modelers also need to understand the degree to which the parameters they use depend on measurements that can contain large uncertainties.

  12. 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

  13. Simulations and Modelling of Absorption Cooling Unit by Means of Peltier Module

    Vladimír KOCÚR

    2011-07-01

    Full Text Available Article refers to function of absorption cooling unit simulated by means of Peltier module. Although, this system works on entirely different physical principle, it is necessary to use it as equivalent of absorption cooling what is proved in more detail in article.

  14. Simulations and Modelling of Absorption Cooling Unit by Means of Peltier Module

    Vladimír KOCÚR; Jozef ŠURIANSKY

    2011-01-01

    Article refers to function of absorption cooling unit simulated by means of Peltier module. Although, this system works on entirely different physical principle, it is necessary to use it as equivalent of absorption cooling what is proved in more detail in article.

  15. 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.

  16. 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…

  17. Dynamics of the one-dimensional Heisenberg model and optical absorption of spinons in cuprate antiferromagnetic chains

    Lorenzana, J.; Eder, R

    1997-01-01

    We use numerical and analytical results to construct a simple ansatz for the energy dynamical correlation function of the one-dimensional antiferromagnetic Heisenberg model. This is applied to compute the phonon-assisted absorption spectra of magnetic excitations (spinons) in quasi-one-dimensional s

  18. Analysis of water absorption of bean and chickpea during soaking using Peleg model

    S.M. Shafaei

    2016-06-01

    Full Text Available Peleg model was used to determine the instance moisture content of three varieties of bean (Talash, Sadri and Mahali Khomein and three varieties of chickpea (Desi, small Kabuli and large Kabuli during soaking. The experiments were carried out at three different temperatures (5, 25 and 45 °C in triplicate using distilled water. The moisture content versus time curves were plotted at different experimental temperatures, for six varieties. The results indicated that water absorption increased as the temperature increased. The obtained Peleg model constants were investigated relative to temperature. Activation and free activation energy, as well as entropy and enthalpy changes for the three studied varieties of both chickpea and bean were calculated at three temperatures using Peleg model constants and regression analysis. In the case of bean, the results showed a linear decrease in the coefficients k1 and k2. Furthermore for chickpea, the coefficient of k1 decreased linearly and the effect of temperature on the coefficient k2 was partial and decreasing. Likewise, the results indicated that the seeds enthalpy enhanced significantly as soaking temperature increased from 5 to 45 °C, the raising trend in entropy and released energy was not significant, however (P < 0.05. Maximum and minimum free activation energy in soaking process were observed in chickpea variety of Chico (301.28 kJ mol−1 and bean variety of Mahali Khomein (86.77 kJ mol−1, respectively. In addition, negative values of enthalpy changes of varieties demonstrated that the changes in moisture content during soaking process were associated with exothermic and energetically favorable transformation.

  19. Time-dependent excitation and ionization modelling of absorption-line variability due to GRB 080310

    Vreeswijk, P M; Raassen, A J J; Smette, A; De Cia, A; Woźniak, P R; Fox, A J; Vestrand, W T; Jakobsson, P

    2012-01-01

    We model the time-variable absorption of FeII, FeIII, SiII, CII and CrII detected in UVES spectra of GRB 080310, with the afterglow radiation exciting and ionizing the interstellar medium in the host galaxy at a redshift of z=2.42743. To estimate the rest-frame afterglow brightness as a function of time, we use a combination of the optical VRI photometry obtained by the RAPTOR-T telescope array -- which are presented in this paper -- and Swift's X-Ray Telescope observations. Excitation alone, which has been successfully applied for a handful of other GRBs, fails to describe the observed column-density evolution in the case of GRB 080310. Inclusion of ionization is required to explain the column-density decrease of all observed FeII levels (including the ground state 6D9/2) and increase of the FeIII 7S3 level. The large population of ions in this latter level (up to 10% of all FeIII) can only be explained through ionization of FeII, whereby a large fraction of the ionized FeII ions -- we calculate 31% using th...

  20. Dermal absorption and skin damage following hydrofluoric acid exposure in an ex vivo human skin model.

    Dennerlein, Kathrin; Kiesewetter, Franklin; Kilo, Sonja; Jäger, Thomas; Göen, Thomas; Korinth, Gintautas; Drexler, Hans

    2016-04-25

    The wide industrial use of hydrofluoric acid (HF) poses a high risk for accidental dermal exposure. Despite local and systemic hazards associated with HF, information on percutaneous penetration and tissue damage is rare. In the present ex vivo study, the dermal absorption of HF (detected in terms of fluoride ions) was quantified and the skin damaging potential as a function of concentration and exposure duration was assessed. Percutaneous penetration of HF (c=5, 30, and 50%) at 3 exposure durations (3, 5, and 10 min) was investigated in a static diffusion cell model using freshly excised human skin. Alterations of skin were histologically evaluated. HF rapidly penetrated through skin under formation of a considerable intradermal reservoir (∼ 13-67% of total absorbed fluoride). Histologically, epidermal alterations were detected already after exposure to 5% HF for 3 min. The degree of skin damage increased with rising concentration and exposure duration leading to coagulation necrosis. For HF concentrations of ≥ 30%, skin damage progressed into deeper skin layers. Topically applied HF concentration was the principal parameter determining HF induced skin effects. The intradermal HF retention capacity associated with progression and prolongation of HF induced skin effects must be considered in the review of skin decontamination procedures.

  1. The mechanism of lowering cholesterol absorption by calcium studied by using an in vitro digestion model.

    Vinarova, Liliya; Vinarov, Zahari; Tcholakova, Slavka; Denkov, Nikolai D; Stoyanov, Simeon; Lips, Alex

    2016-01-01

    Studies in humans show that a calcium-enriched diet leads to lower cholesterol in blood serum. This phenomenon is usually explained in the literature with a reduced cholesterol absorption in the small intestine. Our study aims to clarify the effect of calcium on the solubilisation of cholesterol and fatty acid in the dietary mixed micelles (DMM), viz. on the bioaccessibility of these lipophilic substances in the gut. We use an in vitro digestion model which mimics very closely the intestinal pH-profile and the composition of the intestinal fluids. We quantified the effects of Ca(2+) concentration on the lipid solubilization for fats and oils with different saturated/unsaturated fatty acid (FA) contents. We found that the increase of calcium significantly decreases the solubilization of cholesterol, FA and MG. Most importantly, we observe a clear positive correlation between the amounts of solubilized cholesterol, on one side, and solubilized free fatty acids and monoglycerides, on the other side. The main conclusion is that Ca(2+) ions strongly affect the bioaccessibility of both cholesterol and saturated FA. Therefore, calcium may decrease the serum cholesterol via two complementary mechanisms: (1) fatty acid precipitation by calcium ions reduces the solubilisation capacity of the DMM, thus decreasing the levels of solubilised (bioaccessible) cholesterol; (2) the observed strong decrease of the bioaccessible saturated FA, in its own turn, may suppress the cholesterol synthesis in the liver.

  2. Source Attribution of Observed Absorption Profiles During the Two Column Aerosol Project (TCAP) Using a Regional Model

    Fast, J. D.; Berg, L. K.; Chand, D.; Ferrare, R. A.; Flynn, C. J.; Hostetler, C. A.; Redemann, J.; Sedlacek, A. J., III; Shilling, J.; Shinozuka, Y.; Tomlinson, J. M.; Zelenyuk, A.

    2015-12-01

    Relatively large uncertainties remain in climate model predictions of absorption resulting from black carbon (BC) and brown carbon (BrC). In this study, we focus on comparing simulated profiles of BC, biomass burning aerosols, absorption, and other aerosol optical properties obtained from the regional WRF-Chem model with in situ and remote sensing measurements made during the Department of Energy's Two-Column Aerosol Project (TCAP). TCAP was designed to investigate changes in aerosol mixing state, aerosol radiative forcing, CCN concentration, and cloud-aerosol interactions in two atmospheric columns: one over Cape Cod, Massachusetts and another located approximately 200 km to the east over the ocean. Measurements from the NASA second-generation airborne High Resolution Spectral Lidar reveal the presence distinct aerosol layers associated with the marine boundary layer, residual layer transported over the ocean and in the free troposphere. Analyses of SP2 and aerosol optical measurements indicate that particles in the free troposphere were more 'aged' and had a lower single scattering albebo than for aerosol layers at lower altitudes; however, BC concentrations aloft were lower in the free troposphere. Instead, particle classes derived from the miniSPLAT single particle measurements suggest that the increased absorption aloft may be due biomass burning aerosols. The model suggests that ambient winds likely transported smoke from large wildfires in central Canada as well as smoke from other fires into the sampling domain. The simulated percentage of biomass burning aerosols was consistent with the miniSPLAT data, but the model currently treats all organic matter as non-absorbing. Therefore, we perform sensitivity simulations to examine how the model's absorption and AOD responds to assumptions used for BrC associated with biomass burning and whether the predicted profiles agree with absorption data and wavelength dependent AOD data from 4STAR.

  3. 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.

  4. CFD MODELING OF SOLAR COLLECTOR WITH NANO-FLUID DIRECT ABSORPTION FOR CIVIL APPLICATION

    Simonetti, Marco; Chiavazzo, Eliodoro; Asinari, Pietro

    2013-01-01

    Direct solar absorption has been considered often in the past as a possible configuration of solar thermal collectors for residential and small commercial applications. Of course, a direct absorption could improve the performance of solar collectors by skipping one step of the heat transfer mechanism of standard devices and by modifying the temperature distribution inside the collector. In fact, classical solar thermal collectors have a metal sheet as absorber, designed such that water has th...

  5. Absorption of manganese and iron in a mouse model of hemochromatosis.

    Jonghan Kim

    Full Text Available Hereditary hemochromatosis, an iron overload disease associated with excessive intestinal iron absorption, is commonly caused by loss of HFE gene function. Both iron and manganese absorption are regulated by iron status, but the relationships between the transport pathways of these metals and how they are affected by HFE-associated hemochromatosis remain poorly understood. Loss of HFE function is known to alter the intestinal expression of DMT1 (divalent metal transporter-1 and Fpn (ferroportin, transporters that have been implicated in absorption of both iron and manganese. Although the influence of HFE deficiency on dietary iron absorption has been characterized, potential effects on manganese metabolism have yet to be explored. To investigate the role of HFE in manganese absorption, we characterized the uptake and distribution of the metal in Hfe (-/- knockout mice after intravenous, intragastric, and intranasal administration of (54Mn. These values were compared to intravenous and intragastric administration of (59Fe. Intestinal absorption of (59Fe was increased and clearance of injected (59Fe was also increased in Hfe(-/- mice compared to controls. Hfe (-/- mice displayed greater intestinal absorption of (54Mn compared to wild-type Hfe(+/+ control mice. After intravenous injection, the distribution of (59Fe to heart and liver was greater in Hfe (-/- mice but no remarkable differences were observed for (54Mn. Although olfactory absorption of (54Mn into blood was unchanged in Hfe (-/- mice, higher levels of intranasally-instilled (54Mn were associated with Hfe(-/- brain compared to controls. These results show that manganese transport and metabolism can be modified by HFE deficiency.

  6. 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

  7. Modeling the Oxygen K Absorption in the Interstellar Medium: An XMM-Newton View of Sco X-1

    Garcia, J.; Ramirez, J. M.; Kallman, T. R.; Witthoeft, M.; Bautista, M. A.; Mendoza, C.; Palmeri, P.; Quinet, P.

    2011-01-01

    We investigate the absorption structure of the oxygen in the interstellar medium by analyzing XMM-Newton observations of the low mass X-ray binary Sco X-1. We use simple models based on the O I atomic cross section from different sources to fit the data and evaluate the impact of the atomic data in the interpretation of astrophysical observations. We show that relatively small differences in the atomic calculations can yield spurious results. We also show that the most complete and accurate set of atomic cross sections successfully reproduce the observed data in the 21 - 24.5 Angstrom wavelength region of the spectrum. Our fits indicate that the absorption is mainly due to neutral gas with an ionization parameter of Epsilon = 10(exp -4) erg/sq cm, and an oxygen column density of N(sub O) approx. = 8-10 x 10(exp 17)/sq cm. Our models are able to reproduce both the K edge and the K(alpha) absorption line from O I, which are the two main features in this region. We find no conclusive evidence for absorption by other than atomic oxygen.

  8. 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...... means (RMSPE) of 5.86, 5.75, 11.3, and 4.12, respectively. The epithelial blood flow was predicted with 26.3% RMSPE. Sensitivity analyses indicated that when ruminal butyrate concentration increased from 4.0 to 37.4 mmol/L, blood flow of the epithelium increased 47% and the ruminal disappearance rate...... of propionate increased 11%. The concentration gradient of propionate between ruminal fluid and epithelium was no more than 3:1 and increased with increasing blood flow. In conclusion, a dynamic model based on rumen epithelial blood flow and bidirectional fluxes of VFA between ruminal fluid and epithelium gave...

  9. 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.

  10. 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

  11. Modeling and identification on nonlinear saturable and reverse-saturable absorptions of gold nanorods using femtosecond Z-scan technique

    Rui Wang; Yingshuai Wang; Dan'ao Han; Chuantao Zheng; Jiyan Leng; Han Yang

    2012-01-01

    An improved Z-scan analysis approach is proposed by establishing and solving the saturable absorption (SA) and reverse-SA (RSA) models,respectively.Near-infrared femtosecond Z-scans are carried out on the synthesized gold nanorods (NRs) possessing the average length of 46 nm using a femtosecond laser operated at the wavelength of 800 nm,which is close to the peak position of longitudinal surface plasmon resonance (SPR) (710 nm) of gold NRs.At lower input intensity of less than 400 GW/cm2,the normalized transmission exhibits only SA phenomenon; however,when it exceeds 400 GW/cm2,both SA and RSA are observed.By using the presented Z-scan modeling and theory,the three-photon absorption (3PA) is identified in the material,and the 3PA cross-section is determined to be 1.58× 10-71 cm6s2.

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

    El Amili, Abdelkrim; Kervella, Gaël; Alouini, Mehdi

    2013-04-01

    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.

  13. Solving local structure around dopants in metal nanoparticles with ab initio modeling of X-ray absorption near edge structure.

    Timoshenko, Janis; Shivhare, Atal; Scott, Robert W J; Lu, Deyu; Frenkel, Anatoly I

    2016-07-20

    We adopted ab initio X-ray absorption near edge structure (XANES) modeling for structural refinement of local environments around metal impurities in a large variety of materials. Our method enables both direct modeling, where the candidate structures are known, and the inverse modeling, where the unknown structural motifs are deciphered from the experimental spectra. We present also estimates of systematic errors, and their influence on the stability and accuracy of the obtained results. We illustrate our approach by revealing the evolution of local environment of palladium atoms in palladium-doped gold thiolate clusters upon chemical and thermal treatments.

  14. Light absorption by pollution, dust, and biomass burning aerosols. A global model study and evaluation with AERONET measurements

    Chin, Mian; Holben, B.N. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Lab. for Atmospheres; Diehl, T.; Eck, T.F. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Lab. for Atmospheres; Maryland Univ., Baltimore County, MD (United States); Dubovik, O. [Univ. de Lille 1/CNRS, Villeneuve d' Ascq (France). Lab. d' Optique Atmospherique; Sinyuk, A. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Lab. for Atmospheres; Science Systems and Applications, Inc., Lanham, MD (United States); Streets, D.G. [Argonne National Lab., Argonne, IL (United States)

    2009-07-01

    Atmospheric aerosol distributions from 2000 to 2007 are simulated with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model to attribute light absorption by aerosol to its composition and sources from pollution, dust, and biomass burning. The 8-year, global averaged total aerosol optical depth ({tau}), absorption optical depth ({tau}{sub a}), and single scattering albedo ({omega}) at 550 nm are estimated at 0.14, 0.0086, and 0.95, respectively, with sulfate making the largest fraction of {tau} (37%), followed by dust (30%), sea salt (16%), organic matter (OM) (13%), and black carbon (BC) (4%). BC and dust account for 43% and 53% of {tau}{sub a}, respectively. From a model experiment with ''tagged'' sources, natural aerosols are estimated to be 58% of {tau} and 53% of {tau}{sub a}, with pollution and biomass burning aerosols to share the rest. Comparing with data from the surface sunphotometer network AERONET, the model tends to reproduce much better the AERONET direct measured data of {tau} and the Aangstroem exponent ({alpha}) than its retrieved quantities of {omega} and {tau}{sub a}. Relatively small in its systematic bias of {tau} for pollution and dust regions, the model tends to underestimate {tau} for biomass burning aerosols by 30-40%. The modeled {alpha} is 0.2-0.3 too low (particle too large) for pollution and dust aerosols but 0.2-0.3 too high (particle too small) for the biomass burning aerosols, indicating errors in particle size distributions in the model. Still, the model estimated {omega} is lower in dust regions and shows a much stronger wavelength dependence for biomass burning aerosols but a weaker one for pollution aerosols than those quantities from AERONET. These comparisons necessitate model improvements on aerosol size distributions, the refractive indices of dust and black carbon aerosols, and biomass burning emissions in order to better quantify the aerosol absorption in the atmosphere. (orig.)

  15. 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...

  16. Point defect absorption by grain boundaries in α -iron by atomic density function modeling

    Kapikranian, O.; Zapolsky, H.; Patte, R.; Pareige, C.; Radiguet, B.; Pareige, P.

    2015-12-01

    Using the atomic density function theory (ADFT), we examine the point defect absorption at [110] symmetrical tilt grain boundaries in body-centered cubic iron. It is found that the sink strength strongly depends on misorientation angle. We also show that the ADFT is able to reproduce reasonably well the elastic properties and the point defect formation volume in α -iron.

  17. Feasibility of a 3D human airway epithelial model to study respiratory absorption

    Reus, A.A.; Maas, W.J.M.; Jansen, H.T.; Constant, S.; Staal, Y.C.M.; Triel, J.J. van; Kuper, C.F.

    2014-01-01

    The respiratory route is an important portal for human exposure to a large variety of substances. Consequently, there is an urgent need for realistic in vitro strategies for evaluation of the absorption of airborne substances with regard to safety and efficacy assessment. The present study investiga

  18. Infrared absorption line intensities for U (5) model of linear triatomic molecules

    于少英

    1999-01-01

    The symmetry of the rotation-vibration spectra for linear triatomic molecules is described by means of the group U(5). The rotation-vibration levels of linear triatomic molecules HCN and COS are calculated. The infrared absorption line intensities are calculated for the COS molecule. The results are in good agreement with the experimental values.

  19. 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

  20. 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

  1. Modelling the In Situ Infrared Reflection-Absorption Spectra of the Diffuse Layer

    1989-05-01

    Absorption Spectra of the Diffuse Layer by P.W. Faguy, S. McCullough and W.R. Fawcett Prepared for Presentation at The Electrochemical Society Meeting Los...Research 800 N. Quincy Arlington, VA 22217-5000 ,a. IL bgm. Nme Prepared for Presentation at: The- Electrochemical Society Meeting, Los Angeles, CA, May

  2. Inline monitoring of CO2 absorption processes using simple analytical techniques and multivariate modeling

    Ham, L.V. van der; Bakker, D.E.; Geers, L.F.G.; Goetheer, E.L.V.

    2014-01-01

    The solvent and the dissolved CO2 concentrations are two essential properties of CO2 absorption processes. Currently, they are typically monitored using time-consuming offline analytical techniques. Initial development efforts aiming at a cost-effective and reliable inline monitoring system are desc

  3. The Improvement of The Absorption Process Using A Computational Optimization in An Atmospheric General Circulation Model

    Sekiguchi, Miho; Nakajima, Teruyuki

    2009-03-01

    This study improves the gaseous absorption process scheme of the broadband radiative transfer code "mstrnX" that was developed by the Center for Climate System Research (CCSR) for efficient calculation of atmospheric radiative transfer in the general circulation models. This scheme is adopted the optimization method to decrease the number of quadrature points for wavenumber integration by using the correlated k-distribution method and to increase the computational efficiency in each spectral band. The objective function of the standard version is defined as the sum of errors in radiation fluxes and heating rate in six standard atmospheres, and we added six other atmospheric profiles in the doubling CO2 condition for the doubling CO2 version. The preferable errors of radiative flux is thought about 1-2 W/m2, however, it is desirable that the errors of radiative forcing of CO2 is less than 0.3 W/m2. So, we improve the doubling CO2 version to calculate the radiative forcings precisely. When integration points and weights are determined in each band, we select the results whose errors of the instantaneous radiative forcing at TOA, troposphere and surface are under 0.2 W/m2. Moreover, radiative forcings of other WMGHGs are considered as same as CO2. Then, we build a global warming version with 29 bands and 111 integration points. In this version, the maximum radiation flux error is less than 0.6 W/m2 in LW and 0.45 W/m2 in SW at all altitude, and the maximum heating rate error is less than 0.2 K/day in the troposphere and the stratosphere for any standard atmosphere. The radiative forcing can be evaluated with small errors not exceeding one standard deviation of samples of forcings from the AOGCMs except for the changes of N2O+CFCs case in the RTMIP experiment. It is found that the proposed optimization method is effective in maintaining a low computational cost with accuracy good enough for dynamical simulations with a GCM. MstrnX is now available from the Open

  4. Advances and challenges in PBPK modeling--Analysis of factors contributing to the oral absorption of atazanavir, a poorly soluble weak base.

    Berlin, Mark; Ruff, Aaron; Kesisoglou, Filippos; Xu, Wei; Wang, Michael Hong; Dressman, Jennifer B

    2015-06-01

    Many active pharmaceutical ingredients (APIs) exhibit a highly variable pharmacokinetic (PK) profile. This behavior may be attributable to pre-absorptive, absorptive and/or post-absorptive factors. Pre-absorptive factors are those related to dosage form disintegration, drug dissolution, supersaturation, precipitation and gastric emptying. Absorptive factors are involved with drug absorption and efflux mechanisms, while drug distribution and clearance are post-absorptive factors. This study aimed to investigate the relative influence of the aforementioned parameters on the pharmacokinetic profile of atazanavir, a poorly soluble weakly basic compound with highly variable pharmacokinetics. The pre-absorptive behavior of the drug was examined by applying biorelevant in vitro tests to reflect upper gastrointestinal behavior in the fasted and fed states. The in vitro results were implemented, along with permeability and post-absorptive data obtained from the literature, into physiologically based pharmacokinetic (PBPK) models. Sensitivity analysis of the resulting plasma profiles revealed that the pharmacokinetic profile of atazanavir is affected by an array of factors rather than one standout factor. According to the in silico model, pre-absorptive and absorptive factors had less impact on atazanavir bioavailability compared to post-absorptive parameters, although active drug efflux and extraction appear to account for the sub-proportional pharmacokinetic response to lower atazanavir doses in the fasted state. From the PBPK models it was concluded that further enhancement of the formulation would bring little improvement in the pharmacokinetic response to atazanavir. This approach may prove useful in assessing the potential benefits of formulation enhancement of other existing drug products on the market.

  5. Development of a Novel Oral Cavity Compartmental Absorption and Transit Model for Sublingual Administration: Illustration with Zolpidem.

    Xia, Binfeng; Yang, Zhen; Zhou, Haiying; Lukacova, Viera; Zhu, Wei; Milewski, Mikolaj; Kesisoglou, Filippos

    2015-05-01

    Intraoral (IO) delivery is an alternative administration route to deliver a drug substance via the mouth that provides several advantages over conventional oral dosage forms. The purpose of this work was to develop and evaluate a novel, physiologically based oral cavity model for projection and mechanistic analysis of the clinical pharmacokinetics of intraoral formulations. The GastroPlus™ Oral Cavity Compartmental Absorption and Transit (OCCAT™) model was used to simulate the plasma concentration versus time profiles and the fraction and rate of intraoral drug transit/absorption for Intermezzo® sublingual tablets (zolpidem tartrate). The model was evaluated by the goodness-of-fit between simulated and observed concentrations and the deviation of key PK parameters (e.g., C max, T max, and AUC). In addition, a sensitivity analysis was conducted to demonstrate the interplay and impact of key modeling parameters on the fraction absorbed via oral mucosa (F a_IO). The OCCAT™ model captured the observed pharmacokinetics for Intermezzo® sublingual tablets (R (2) > 0.9). The predicted deviations (%) for C max, AUC0-inf, AUC0-20 min, and T max were 5.7, 28.0, 11.8, and 28.6%, respectively, indicating good prediction accuracy. The model also estimated ~18% of total drug was absorbed via the IO route. Furthermore, the sensitivity analysis indicated that the F a_IO was not only associated with drug diffusivity and unbound fraction in epithelium tissue (f ut) but also depended on the physicochemical properties of compounds for IO delivery (e.g., solubility and logD pH = 7.4). The novel physiologically based IO absorption OCCAT™ model showed satisfactory performance and will be helpful to guide development of future intraoral formulations.

  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. A model for the vertical sound speed and absorption profiles in Titan's atmosphere based on Cassini-Huygens data.

    Petculescu, Andi; Achi, Peter

    2012-05-01

    Measurements of thermodynamic quantities in Titan's atmosphere during the descent of Huygens in 2005 are used to predict the vertical profiles for the speed and intrinsic attenuation (or absorption) of sound. The calculations are done using one author's previous model modified to accommodate non-ideal equations of state. The vertical temperature profile places the tropopause about 40 km above the surface. In the model, a binary nitrogen-methane composition is assumed for Titan's atmosphere, quantified by the methane fraction measured by the gas chromatograph/mass spectrometer (GCMS) onboard Huygens. To more accurately constrain the acoustic wave number, the variation of thermophysical properties (specific heats, viscosity, and thermal conductivity) with altitude is included via data extracted from the NIST Chemistry WebBook [URL webbook.nist.gov, National Institute of Standards and Technology Chemistry WebBook (Last accessed 10/20/2011)]. The predicted speed of sound profile fits well inside the spread of the data recorded by Huygens' active acoustic sensor. In the N(2)-dominated atmosphere, the sound waves have negligible relaxational dispersion and mostly classical (thermo-viscous) absorption. The cold and dense environment of Titan can sustain acoustic waves over large distances with relatively small transmission losses, as evidenced by the small absorption. A ray-tracing program is used to assess the bounds imposed by the zonal wind-measured by the Doppler Wind Experiment on Huygens-on long-range propagation.

  8. Computing the Absorption and Emission Spectra of 5-Methylcytidine in Different Solvents: A Test-Case for Different Solvation Models.

    Martínez-Fernández, L; Pepino, A J; Segarra-Martí, J; Banyasz, A; Garavelli, M; Improta, R

    2016-09-13

    The optical spectra of 5-methylcytidine in three different solvents (tetrahydrofuran, acetonitrile, and water) is measured, showing that both the absorption and the emission maximum in water are significantly blue-shifted (0.08 eV). The absorption spectra are simulated based on CAM-B3LYP/TD-DFT calculations but including solvent effects with three different approaches: (i) a hybrid implicit/explicit full quantum mechanical approach, (ii) a mixed QM/MM static approach, and (iii) a QM/MM method exploiting the structures issuing from molecular dynamics classical simulations. Ab-initio Molecular dynamics simulations based on CAM-B3LYP functionals have also been performed. The adopted approaches all reproduce the main features of the experimental spectra, giving insights on the chemical-physical effects responsible for the solvent shifts in the spectra of 5-methylcytidine and providing the basis for discussing advantages and limitations of the adopted solvation models.

  9. Identifying and Quantifying Adulterants in Extra Virgin Olive Oil of the Picual Varietal by Absorption Spectroscopy and Nonlinear Modeling.

    Aroca-Santos, Regina; Cancilla, John C; Matute, Gemma; Torrecilla, José S

    2015-06-17

    In this research, the detection and quantification of adulterants in one of the most common varieties of extra virgin olive oil (EVOO) have been successfully carried out. Visible absorption information was collected from binary mixtures of Picual EVOO with one of four adulterants: refined olive oil, orujo olive oil, sunflower oil, and corn oil. The data gathered from the absorption spectra were used as input to create an artificial neural network (ANN) model. The designed mathematical tool was able to detect the type of adulterant with an identification rate of 96% and to quantify the volume percentage of EVOO in the samples with a low mean prediction error of 1.2%. These significant results make ANNs coupled with visible spectroscopy a reliable, inexpensive, user-friendly, and real-time method for difficult tasks, given that the matrices of the different adulterated oils are practically alike.

  10. Modeling and simulation of a 100 kWe HT-PEMFC subsystem integrated with an absorption chiller subsystem

    Arsalis, Alexandros

    2012-01-01

    A 100 kWe liquid-cooled HT-PEMFC subsystem is integrated with an absorption chiller subsystem to provide electricity and cooling. The system is designed, modeled and simulated to investigate the potential of this technology for future novel energy system applications. Liquid-cooling can provide...... better temperature control and is preferable for middle-scale transport applications, such as commercial vessels, because stack cooling can be achieved within smaller volumes. A commercial ship requiring cooling and electricity is taken as the case study for the application of the proposed system. All...... electrical power output of 100 kWe. The heat exhausted to the absorption chiller subsystem is 107 kW and can satisfy a cooling duty of up to 128 or 64.5 kW for a LiBr-water double-effect system or a water-NH3 single-effect system, respectively. Finally, the projected total cost is comparable to conventional...

  11. Factors Affecting Energy Absorption of a Plate during Shock Wave Impact Using a Damage Material Model

    2010-08-07

    array according to the Taguchi method . An orthogonal array is generated to govern the arrangement of the five parameters in the 16 calculations... Taguchi method described in Chapter 3. Energy absorption of the plate was the response investigated and was calculated as strain energy at first... Taguchi method . Table 6.1 shows the energy absorbed by first element failure for each of the 16 simulations. Those results were placed in the

  12. Thermodynamic modelling of a double-effect LiBr-H2O absorption refrigeration cycle

    Iranmanesh, A.; Mehrabian, M. A.

    2012-12-01

    The goal of this paper is to estimate the conductance of components required to achieve the approach temperatures, and gain insights into a double-effect absorption chiller using LiBr-H2O solution as the working fluid. An in-house computer program is developed to simulate the cycle. Conductance of all components is evaluated based on the approach temperatures assumed as input parameters. The effect of input data on the cycle performance and the exergetic efficiency are investigated.

  13. Supersonic Mass Flux Measurements via Tunable Diode Laser Absorption and Non-Uniform Flow Modeling

    Chang, Leyen S.; Strand, Christopher L.; Jeffries, Jay B.; Hanson, Ronald K.; Diskin, Glenn S.; Gaffney, Richard L.; Capriotti, Diego P.

    2011-01-01

    Measurements of mass flux are obtained in a vitiated supersonic ground test facility using a sensor based on line-of-sight (LOS) diode laser absorption of water vapor. Mass flux is determined from the product of measured velocity and density. The relative Doppler shift of an absorption transition for beams directed upstream and downstream in the flow is used to measure velocity. Temperature is determined from the ratio of absorption signals of two transitions (lambda(sub 1)=1349 nm and lambda(sub 2)=1341.5 nm) and is coupled with a facility pressure measurement to obtain density. The sensor exploits wavelength-modulation spectroscopy with second-harmonic detection (WMS-2f) for large signal-to-noise ratios and normalization with the 1f signal for rejection of non-absorption related transmission fluctuations. The sensor line-of-sight is translated both vertically and horizontally across the test section for spatially-resolved measurements. Time-resolved measurements of mass flux are used to assess the stability of flow conditions produced by the facility. Measurements of mass flux are within 1.5% of the value obtained using a facility predictive code. The distortion of the WMS lineshape caused by boundary layers along the laser line-of-sight is examined and the subsequent effect on the measured velocity is discussed. A method for correcting measured velocities for flow non-uniformities is introduced and application of this correction brings measured velocities within 4 m/s of the predicted value in a 1630 m/s flow.

  14. 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

  15. A discrete interaction model/quantum mechanical method to describe the interaction of metal nanoparticles and molecular absorption.

    Morton, Seth Michael; Jensen, Lasse

    2011-10-07

    A frequency-dependent quantum mechanics/molecular mechanics method for the calculation of response properties of molecules adsorbed on metal nanoparticles is presented. This discrete interaction model/quantum mechanics (DIM/QM) method represents the nanoparticle atomistically, thus accounting for the local environment of the nanoparticle surface on the optical properties of the adsorbed molecule. Using the DIM/QM method, we investigate the coupling between the absorption of a silver nanoparticle and of a substituted naphthoquinone. This system is chosen since it shows strong coupling due to a molecular absorption peak that overlaps with the plasmon excitation in the metal nanoparticle. We show that there is a strong dependence not only on the distance of the molecule from the metal nanoparticle but also on its orientation relative to the nanoparticle. We find that when the transition dipole moment of an excitation is oriented towards the nanoparticle there is a significant increase in the molecular absorption as a result of coupling to the metal nanoparticle. In contrast, we find that the molecular absorption is decreased when the transition dipole moment is oriented parallel to the metal nanoparticle. The coupling between the molecule and the metal nanoparticle is found to be surprisingly long range and important on a length scale comparable to the size of the metal nanoparticle. A simple analytical model that describes the molecule and the metal nanoparticle as two interacting point objects is found to be in excellent agreement with the full DIM/QM calculations over the entire range studied. The results presented here are important for understanding plasmon-exciton hybridization, plasmon enhanced photochemistry, and single-molecule surface-enhanced Raman scattering.

  16. Modeling the structure and absorption spectra of stilbazolium merocyanine in polar and nonpolar solvents using hybrid QM/MM techniques.

    Murugan, N Arul; Kongsted, Jacob; Rinkevicius, Zilvinas; Aidas, Kestutis; Ågren, Hans

    2010-10-28

    We have performed Car-Parrinello mixed quantum mechanics/molecular mechanics (CP-QM/MM) calculations for stilbazolium merocyanine (SM) in polar and nonpolar solvents in order to explore the role of solute molecular geometry, solvation shell structure, and different interaction mechanisms on the absorption spectra and its dependence on solvent polarity. On the basis of the average bond length values and group charge distributions, we find that the SM molecule remains in a neutral quinonoid form in chloroform (a nonpolar solvent) while it transforms to a charge-separated benzenoid form in water (a polar solvent). Based on a quantum mechanical/molecular mechanical response technique, with different MM descriptions for the water environment, absorption spectra were obtained as averages over configurations derived from the CP-QM/MM simulations. We show that for SM in water the solute polarization plays a major role in predictions of the λ(max) and solvatochromic shift and that once this effect is included the contributions from solvent polarization and intermolecular charge transfer become less important. For SM in chloroform and water solvents, we have also performed absorption spectra calculations using a polarizable continuum model in order to address its relative performance compared to the QM/MM response technique. In the case of SM in water, our study supports the notion that, in order to predict accurate absorption spectra and solvatochromic shifts, it is important to use a discrete description of the solvent when it, as in water, is involved in site-specific interaction with the solute molecule. The technique is thus shown to outperform the more conventional polarizable continuum model in predicting the solvatochromic shift.

  17. 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.

  18. RF dosimetry: a comparison between power absorption of female and male numerical models from 0.1 to 4 GHz

    Sandrini, L; Vaccari, A; Malacarne, C; Cristoforetti, L; Pontalti, R [ITC-irst-Bioelectromagnetism Lab., FCS Department, 38050 Povo (Trento) (Italy)

    2004-11-21

    Realistic numerical models of human subjects and their surrounding environment represent the basic points of radiofrequency (RF) electromagnetic dosimetry. This also involves differentiating the human models in men and women, possibly with different body shapes and postures. In this context, the aims of this paper are, firstly, to propose a female dielectric anatomical model (fDAM) and, secondly, to compare the power absorption distributions of a male and a female model from 0.1 to 4 GHz. For realizing the fDAM, a magnetic resonance imaging tomographer to acquire images and a recent technique which avoids the discrete segmentation of body tissues into different types have been used. Simulations have been performed with the FDTD method by using a novel filtering-based subgridding algorithm. The latter is applied here for the first time to dosimetry, allowing an abrupt mesh refinement by a factor of up to 7. The results show that the whole-body-averaged specific absorption rate (WBA-SAR) of the female model is higher than that of the male counterpart, mainly because of a thicker subcutaneous fat layer. In contrast, the maximum averaged SAR over 1 g (1gA-SAR) and 10 g (10gA-SAR) does not depend on gender, because it occurs in regions where no subcutaneous fat layer is present.

  19. Massive Warm/Hot Galaxy Coronae as Probed by UV/X-Ray Oxygen Absorption and Emission. I. Basic Model

    Faerman, Yakov; Sternberg, Amiel; McKee, Christopher F.

    2017-01-01

    We construct an analytic phenomenological model for extended warm/hot gaseous coronae of L* galaxies. We consider UV O vi Cosmic Origins Spectrograph (COS)-Halos absorption line data in combination with Milky Way (MW) X-ray O vii and O viii absorption and emission. We fit these data with a single model representing the COS-Halos galaxies and a Galactic corona. Our model is multi-phased, with hot and warm gas components, each with a (turbulent) log-normal distribution of temperatures and densities. The hot gas, traced by the X-ray absorption and emission, is in hydrostatic equilibrium in an MW gravitational potential. The median temperature of the hot gas is 1.5× {10}6 K and the mean hydrogen density is ∼ 5× {10}-5 {{cm}}-3. The warm component as traced by the O vi, is gas that has cooled out of the high density tail of the hot component. The total warm/hot gas mass is high and is 1.2× {10}11 {M}ȯ . The gas metallicity we require to reproduce the oxygen ion column densities is 0.5 solar. The warm O vi component has a short cooling time (∼ 2× {10}8 years), as hinted by observations. The hot component, however, is ∼ 80 % of the total gas mass and is relatively long-lived, with {t}{cool}∼ 7× {10}9 years. Our model supports suggestions that hot galactic coronae can contain significant amounts of gas. These reservoirs may enable galaxies to continue forming stars steadily for long periods of time and account for “missing baryons” in galaxies in the local universe.

  20. Modeling IR Spectral Energy Distributions: A Pilot Study of Starburst Parameters and Silicate Absorption Curves for Some GOALS Galaxies

    Dopita, Michael A; Kewley, Lisa J; Rich, Jeff A; Sanders, Dave; Appleton, Phillip N; Chan, Ben H P; Charmandaris, Vassilis; Evans, Aaron S; Frayer, David T; Howell, Justin H; Inami, Hanae; Mazzarella, Joseph A; Petric, Andreea; Stierwalt, Sabrina; Surace, Jason

    2010-01-01

    This paper describes a pilot study into the spectral energy distribution (SED) fitting and the derivation of physical parameters for 19 galaxies observed as part of the Great Observatories All-sky LIRG Survey (GOALS) survey as observed with the \\emph{Spitzer Space Telescope}. For this we have used the pan-spectral fitting tools developed in a series of papers by Dopita and his co-workers. We show that the standard Lee and Draine `astronomical silicate' model cannot provide a good fit to the silicate absorption features as observed in the heavily dust-extinguished ($A_{\\rm V} \\sim 50$mag.) starbursts. We have derived an empirical fit to the `starburst silicate' absorption in these objects. This absorption curve is consistent with the silicate grains being systematically larger in starburst environments than in the local Galactic interstellar medium. We demonstrate the sensitivity of the SED fitting to each of the fitted parameters, and derive these parameters for those galaxies which do not have an embedded AG...

  1. 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

    2016-05-28

    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.

  2. Cerebrospinal fluid absorption disorder of arachnoid villi in a canine model of hydrocephalus

    Zhao Ke

    2010-01-01

    Full Text Available Background: Hydrocephalus results from inadequate passage of cerebrospinal fluid (CSF from its point of production within the cerebral ventricles to its point of absorption into systemic circulation. Aims: The objective of this study was to investigate the disorders of CSF absorption by arachnoid villi during the different phases of hydrocephalus. Materials and Methods: Silicone oil was injected into the fourth ventricle of 15 canines as an experimental group. Saline solution (0.9% NaCl was injected in another nine canines as a control group. In order to block CSF transport through the cribriform plate, an external ethmoidectomy was performed in five dogs from experimental group and three dogs from control group at three days (acute stage, two weeks (sub-acute stage, and 12 weeks (chronic stage respectively. Tritiated water was injected into the canines′ cortical subarachnoid space and blood levels were measured at intervals of 1h, 4h, 8h, 16h and 48h respectively. Time-concentration curve of tritiated water was drafted. The area under the curve (AUC was calculated for variance analysis and t-testing. Results: In the chronic group, the tritiated water concentration rose slowly to a peak at 16h. It was significantly lower than other groups at 1h, 4h, 8h and 16h, but was higher than other groups at 48h. Analysis of the AUC showed significant differences among all the groups (P<0.01. There were no significant differences in the AUC between control groups, the acute group, and the sub-acute group (P>0.05; however, the AUC of the chronic group was significantly lower than other groups (P<0.05. Conclusions: The CSF absorption ability of arachnoid villi is significantly damaged in a long-term state of hydrocephalus.

  3. Treatment of overlapping gaseous absorption with the correlated-k method in hot Jupiter and brown dwarf atmosphere models

    Amundsen, David S; Manners, James; Baraffe, Isabelle; Mayne, Nathan J

    2016-01-01

    The correlated-k method is frequently used to speed up radiation calculations in both one-dimensional and three-dimensional atmosphere models. An inherent difficulty with this method is how to treat overlapping absorption, i.e. absorption by more than one gas in a given spectral region. We have evaluated the applicability of three different methods in hot Jupiter and brown dwarf atmosphere models, all of which have been previously applied within models in the literature: (i) Random overlap, both with and without resorting and rebinning, (ii) equivalent extinction and (iii) pre-mixing of opacities, where (i) and (ii) combine k-coefficients for different gases to obtain k-coefficients for a mixture of gases, while (iii) calculates k-coefficients for a given mixture from the corresponding mixed line-by-line opacities. We find that the random overlap method is the most accurate and flexible of these treatments, and is fast enough to be used in one-dimensional models with resorting and rebinning. In three-dimensio...

  4. Numerical modelling of wave energy absorption by a floating point absorber system

    Backer, G. De; Banasiak, R.; Beels, C. [Ghent University Civil Engineering Department, Zwijnaarde (Belgium); J. De Rouck, J. De

    2007-07-01

    Point absorbers are wave energy converters (WECs) consisting of small (floating) bodies oscillating with either one or more degrees of freedom. They can either move with respect to a fixed reference, or with respect to a floating reference. Different buoy geometries are evaluated to obtain the ideal values of size, shape and draft with regard to power absorption for a given moderate wave climate. In this paper, the performance of a heaving point absorber in a floating platform is analysed in a linear way.

  5. Treatment of overlapping gaseous absorption with the correlated-k method in hot Jupiter and brown dwarf atmosphere models

    Amundsen, David S.; Tremblin, Pascal; Manners, James; Baraffe, Isabelle; Mayne, Nathan J.

    2017-02-01

    The correlated-k method is frequently used to speed up radiation calculations in both one-dimensional and three-dimensional atmosphere models. An inherent difficulty with this method is how to treat overlapping absorption, i.e. absorption by more than one gas in a given spectral region. We have evaluated the applicability of three different methods in hot Jupiter and brown dwarf atmosphere models, all of which have been previously applied within models in the literature: (i) random overlap, both with and without resorting and rebinning, (ii) equivalent extinction and (iii) pre-mixing of opacities, where (i) and (ii) combine k-coefficients for different gases to obtain k-coefficients for a mixture of gases, while (iii) calculates k-coefficients for a given mixture from the corresponding mixed line-by-line opacities. We find that the random overlap method is the most accurate and flexible of these treatments, and is fast enough to be used in one-dimensional models with resorting and rebinning. In three-dimensional models such as global circulation models (GCMs) it is too slow, however, and equivalent extinction can provide a speed-up of at least a factor of three with only a minor loss of accuracy while at the same time retaining the flexibility gained by combining k-coefficients computed for each gas individually. Pre-mixed opacities are significantly less flexible, and we also find that particular care must be taken when using this method in order to to adequately resolve steep variations in composition at important chemical equilibrium boundaries. We use the random overlap method with resorting and rebinning in our one-dimensional atmosphere model and equivalent extinction in our GCM, which allows us to e.g. consistently treat the feedback of non-equilibrium chemistry on the total opacity and therefore the calculated P-T profiles in our models.

  6. Modeling of simultaneous heat and mass transfer processes in ammonia-water absorption systems from general correlations

    Sieres, Jaime; Fernandez-Seara, Jose [University of Vigo, Area de Maquinas y Motores Termicos, E.T.S. de Ingenieros Industriales, Vigo (Spain)

    2007-11-15

    This paper presents a general differential mathematical model to analyze the simultaneous heat and mass transfer processes that occur in different components of an ammonia-water absorption system: absorber, desorber, rectifier, distillation column, condenser and evaporator. Heat and mass transfer equations are considered, taking into account the heat and mass transfer resistances in the liquid and vapour phases. The model considers the different regions: vapour phase, liquid phase and an external heating or cooling medium. A finite difference numerical method has been considered to solve the resulting set of nonlinear differential equations and an iterative algorithm is proposed for its solution. A map of possible solutions of the mass transferred composition z is presented when varying the interface temperature, which enables to establish a robust implementation code. The analysis is focused on the processes presented in ammonia-water absorption systems. The model is applied to analyze the ammonia purification process in an adiabatic packed rectification column and the numerical results show good agreement with experimental data. (orig.)

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

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

    Because the heat capacity of absorption refrigerating machines is large compared with vapor compression refrigerating machines, the dynamic characteristics at the change in cooling load conditions are problems to be improved. The control method of energy input and of weak solution flow rate following cooling load variations was investigated. As the changes in cooling load and cooling capacity are moderate, the optimal operation conditions corresponding to the cooling load can be estimated with steady state characteristics. If the relation between the cooling load and the optimal operation conditions is well known, a feed forward control can be employed. In this report a new control algorithm, which is called MOL (Multi-variable Open Loop) control, is proposed. Comparing the MOL control with the conventional chilled water outlet temperature proportional control, the MOL control enables the smooth changes in cooling capacity and the reduction in fuel consumption.

  8. A revised model for Jeffrey nanofluid subject to convective condition and heat generation/absorption.

    Hayat, Tasawar; Aziz, Arsalan; Muhammad, Taseer; Alsaedi, Ahmed

    2017-01-01

    Here magnetohydrodynamic (MHD) boundary layer flow of Jeffrey nanofluid by a nonlinear stretching surface is addressed. Heat generation/absorption and convective surface condition effects are considered. Novel features of Brownian motion and thermophoresis are present. A non-uniform applied magnetic field is employed. Boundary layer and small magnetic Reynolds number assumptions are employed in the formulation. A newly developed condition with zero nanoparticles mass flux is imposed. The resulting nonlinear systems are solved. Convergence domains are explicitly identified. Graphs are analyzed for the outcome of sundry variables. Further local Nusselt number is computed and discussed. It is observed that the effects of Hartman number on the temperature and concentration distributions are qualitatively similar. Both temperature and concentration distributions are enhanced for larger Hartman number.

  9. Development of a Novel Simplified PBPK Absorption Model to Explain the Higher Relative Bioavailability of the OROS® Formulation of Oxybutynin.

    Olivares-Morales, Andrés; Ghosh, Avijit; Aarons, Leon; Rostami-Hodjegan, Amin

    2016-11-01

    A new minimal Segmented Transit and Absorption model (mSAT) model has been recently proposed and combined with intrinsic intestinal effective permeability (P eff,int ) to predict the regional gastrointestinal (GI) absorption (f abs ) of several drugs. Herein, this model was extended and applied for the prediction of oral bioavailability and pharmacokinetics of oxybutynin and its enantiomers to provide a mechanistic explanation of the higher relative bioavailability observed for oxybutynin's modified-release OROS® formulation compared to its immediate-release (IR) counterpart. The expansion of the model involved the incorporation of mechanistic equations for the prediction of release, transit, dissolution, permeation and first-pass metabolism. The predicted pharmacokinetics of oxybutynin enantiomers after oral administration for both the IR and OROS® formulations were in close agreement with the observed data. The predicted absolute bioavailability for the IR formulation was within 5% of the observed value, and the model adequately predicted the higher relative bioavailability observed for the OROS® formulation vs. the IR counterpart. From the model predictions, it can be noticed that the higher bioavailability observed for the OROS® formulation was mainly attributable to differences in the intestinal availability (F G ) rather than due to a higher colonic f abs , thus confirming previous hypotheses. The predicted f abs was almost 70% lower for the OROS® formulation compared to the IR formulation, whereas the F G was almost eightfold higher than in the IR formulation. These results provide further support to the hypothesis of an increased F G as the main factor responsible for the higher bioavailability of oxybutynin's OROS® formulation vs. the IR.

  10. THE USE OF AN ARTIFICIAL NEURAL NETWORK FOR MODELING THE MOISTURE ABSORPTION AND THICKNESS SWELLING OF ORIENTED STRAND BOARD

    Şükrü Özşahin

    2012-01-01

    Full Text Available In this study, an artificial neural network (ANN approach was employed for modeling the moisture absorption (MA and thickness swelling (TS properties of oriented strand board (OSB in various applications. A series of ANN models were developed for the analysis and prediction of correlations between processing parameters and MA and TS of OSB. An ANN model was found for modeling the effects of OSB treatment variables on the MA and TS. The required data for training and testing of the model were obtained from the experimental results of Salay (2010. In designing this model, the MA and TS of the OSB were determined using OSB treatment variables, including board layup type, resin type, application rate of resin, and wax content. When experimental data and results obtained from the ANN were compared by regression analysis using Matlab, it was determined that both groups of data (test and train were consistent. It was demonstrated that the well-trained feed forward and back propagation multilayer ANN model is a powerful and sufficient tool for the prediction of MA and TS; therefore, by using ANN outputs, satisfactory results can be estimated, rather than measured and hence time and cost are reduced in all the required experimental activities.

  11. Abnormal absorption and scattering effect of human ear model for electromagnetic waves

    NIE Min; PEI Changxing; LI Jiandong; MA Chen; YANG Zhen

    2005-01-01

    @@ To explore the effect of human ear outline structure for electromagnetic waves, two human ear's models, a big one (model 1) and a small one (model 2), were made in proportion as real human ears (Fig. 1). The installation picture is shown in Fig. 2, and its geometry structure and size are shown in Figs. 3 and 4, respectively.

  12. Study on the Mechanism of Intestinal Absorption of Epimedins A, B and C in the Caco-2 Cell Model

    Yan Chen

    2014-01-01

    Full Text Available Epimedium spp. is commonly used in Traditional Chinese Medicine. Epimedins A, B, and C are three major bioactive flavonoids found in Epimedium spp. that share similar chemical structures. In this study, the intestinal absorption mechanism of these three compounds was investigated using the Caco-2 cell monolayer model in both the apical-to-basolateral (A-B and the basolateral-to-apical (B-A direction. The absorption permeability (PAB of epimedins A, B, and C were extremely low and increased as the concentration of the epimedins increased from 5 to 20 μM, but, at 40 μM, the PAB values were reduced. Meanwhile, the amount of transported compounds increased in a time-dependent manner. The PAB of epimedins A and C were significantly increased and efflux ratios decreased in the presence of verapamil (an inhibitor of P-glycoprotein and dipyridamole (an inhibitor of breast cancer resistance protein while, in the presence of MK571 (an inhibitor of multidrug resistance proteins, the absorption of epimedins A and C did not change significantly, indicating that P-gp and BCRP might be involved in the transport of epimedins A and C. The PAB of epimedin B significantly increased while its secretory permeability (PBA significantly decreased in the presence of dipyridamole, indicating that BCRP might be involved in the transport of epimedin B. No obvious changes in the transport of epimedin B were observed in the presence of verapamil and MK571. In summary, our results clearly demonstrate, for the first time, that poor bioavailability of these three prenylated flavonoids is the result of poor intrinsic permeability and efflux by apical efflux transporters.

  13. Modeling of optimum light absorption in random plasmonic solar cell using effective medium theory

    Piralaee, M.; Asgari, A.

    2016-12-01

    Random plasmonic nanostructures are very suitable candidates for light trapping in thin film solar cells because of their ability of efficient transportation and localization of light in a broad spectrum. In this work, besides the introducing of a novel structure of plasmonic thin-film solar cell, in which metal nanoparticles are randomly distributed through the photoactive layer of solar cell, we are presenting a new simple calculation method which can predict the behavior of plasmonic solar cells. To avoid the difficulty of analytical calculation and due to small size of constituents of the structure, we have used the effective medium theory to describe its optical properties. We have used a general description of effective dielectric function that can support each effective medium theory named spectral density theory, which takes into account the percolation of metal component and also interaction among inclusions. Using this method, the optimum values of nanoparticle's filling fraction for each wavelength within the active layer can be found where the solar cell can have the maximum absorption of light, thereupon the optimum external quantum efficiency.

  14. On the Use of Difference Bands for Modeling SF_6 Absorption in the 10μm Atmospheric Window

    Faye, Mbaye; Manceron, Laurent; Roy, P.; Boudon, Vincent; Loete, Michel

    2016-06-01

    To model correctly the SF_6 atmospheric absorption requires the knowledge of the spectroscopic parameters of all states involved in the numerous hot bands in the 10,5μm atmospheric transparency window. However, due to their overlapping, a direct analysis of the hot bands near the 10,5μm absorption of SF_6 in the atmospheric window is not possible. It is necessary to use another strategy, gathering information in the far and mid infrared regions on initial and final states to compute the relevant total absorption. In this talk, we present new results from the analysis of spectra recorded at the AILES beamline at the SOLEIL Synchrotron facility. For these measurements, we used a IFS125HR interferometer combined with the synchrotron radiation in the 100-3200 wn range, coupled to a cryogenic multiple pass cell. The optical path length was varied from 45 to 141m with measuring temperatures between 223 and 153+/-5 K. The new information obtained on νb{2}+νb{4}-νb{5}, 2νb{5}-νb{6} and νb{3}+νb{6}-νb{4} allowed to derive improved parameters for νb{5}, 2νb{5} and νb{3}+νb{6}. In turn, they are used to model the more important νb{3}+νb{5}-νb{5} and νb{3}+νb{6}-νb{6} hot band contributions. By including these new parameters in the XTDS model, we substantially improved the SF_6 parameters used to model the atmosphere. F. Kwabia Tchana, F. Willaert, X. Landsheere, J. M. Flaud, L. Lago, M. Chapuis, P. Roy, L. Manceron. A new, low temperature long-pass cell for mid-IR to THz Spectroscopy and Synchrotron Radiation Use. Rev. Sci. Inst. 84, 093101, (2013) C. Wenger, V. Boudon, M. Rotger, M. Sanzharov, and J.-P. Champion,"XTDS and SPVIEW: Graphical tools for Analysis and Simulation of High Resolution Molecular Spectra", J. Mol. Spectrosc. 251, 102 (2008)

  15. Predicting laser-induced bulk damage and conditioning for deuterated potassium di-hydrogen phosphate crystals using ADM (absorption distribution model)

    Liao, Z M; Spaeth, M L; Manes, K; Adams, J J; Carr, C W

    2010-02-26

    We present an empirical model that describes the experimentally observed laser-induced bulk damage and conditioning behavior in deuterated Potassium dihydrogen Phosphate (DKDP) crystals in a self-consistent way. The model expands on an existing nanoabsorber precursor model and the multi-step absorption mechanism to include two populations of absorbing defects, one with linear absorption and another with nonlinear absorption. We show that this model connects previously uncorrelated small-beam damage initiation probability data to large-beam damage density measurements over a range of ns pulse widths relevant to ICF lasers such as the National Ignition Facility (NIF). In addition, this work predicts the damage behavior of laser-conditioned DKDP and explains the upper limit to the laser conditioning effect. The ADM model has been successfully used during the commissioning and early operation of the NIF.

  16. 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.

  17. Random incidence absorption coefficients of porous absorbers based on local and extended reaction models

    Jeong, Cheol-Ho

    2011-01-01

    Room surfaces have been extensively modeled as locally reacting in room acoustic predictions although such modeling could yield significant errors under certain conditions. Therefore, this study aims to propose a guideline for adopting the local reaction assumption by comparing predicted random...... incidence acoustical characteristics of typical building elements made of porous materials assuming extended and local reaction. For each surface reaction, five well-established wave propagation models, the Delany-Bazley, Miki, Beranek, Allard-Champoux, and Biot model, are employed. Effects of the flow...

  18. 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.

  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.

  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. Reconstruction of spatial distributions of sound velocity and absorption in soft biological tissues using model ultrasonic tomographic data

    Burov, V. A.; Zotov, D. I.; Rumyantseva, O. D.

    2014-07-01

    A two-step algorithm is used to reconstruct the spatial distributions of the acoustic characteristics of soft biological tissues-the sound velocity and absorption coefficient. Knowing these distributions is urgent for early detection of benign and malignant neoplasms in biological tissues, primarily in the breast. At the first stage, large-scale distributions are estimated; at the second step, they are refined with a high resolution. Results of reconstruction on the base of model initial data are presented. The principal necessity of preliminary reconstruction of large-scale distributions followed by their being taken into account at the second step is illustrated. The use of CUDA technology for processing makes it possible to obtain final images of 1024 × 1024 samples in only a few minutes.

  2. Applications of Lagrangian Dispersion Modeling to the Analysis of Changes in the Specific Absorption of Elemental Carbon

    Doran, J. C.; Fast, Jerome D.; Barnard, James C.; Laskin, Alexander; Desyaterik, Yury; Gilles, Marry K.; Hopkins, Rebecca J.

    2008-03-07

    We use a Lagrangian dispersion model driven by a mesoscale model with four-dimensional data assimilation to simulate the dispersion of elemental carbon (EC) over a region encompassing Mexico City and its surroundings, the study domain for the 2006 MAX-MEX experiment, which was a component of the MILAGRO campaign. The results are used to identify periods when biomass burning was likely to have had a significant impact on the concentrations of elemental carbon at two sites, T1 and T2, downwind of the city, and when emissions from the Mexico City Metropolitan Area (MCMA) were likely to have been more important. They are also used to estimate the median ages of EC affecting the specific absorption of light, aABS, at 870 nm as well as to identify periods when the urban plume from the MCMA was likely to have been advected over T1 and T2. Values of aABS at T1, the nearer of the two sites to Mexico City, were smaller at night and increased rapidly after mid-morning, peaking in the mid-afternoon. The behavior is attributed to the coating of aerosols with substances such as sulfate or organic carbon during daylight hours, but such coating appears to be limited or absent at night. Evidence for this is provided by scanning electron microscope images of aerosols collected at three sampling sites. During daylight hours the values of aABS did not increase with aerosol age for median ages in the range of 1-4 hours. There is some evidence for absorption increasing as aerosols were advected from T1 to T2 but the statistical significance of that result is not strong.

  3. 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...

  4. 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.

  5. Dynamics of the 1D Heisenberg model and optical absorption of spinons in cuprate antiferromagnetic chains

    Lorenzana, J.; Eder, R.

    1996-01-01

    Published in: Phys. Rev. B 55 (1997) 3358-3361 Citing articles (CrossRef) citations recorded in [Science Citation Index] Abstract: We use numerical and analytical results to construct a simple ansatz for the energy dynamical correlation function of the 1D antiferromagnetic Heisenberg model. This is

  6. 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...

  7. Ultraviolet observations of Titan from OAO-2. [and formation of atmospheric model with energy absorption

    Caldwell, J. J.

    1974-01-01

    High altitude deposition of energy in Titan's atmosphere can have a significant effect on the spectral distribution of emitted thermal radiation from the satellite. This reasoning led to the prediction of emission peaks at wavelengths corresponding to allowed bands of CH4 and trace photolysis products such as C2H6. Intermediate resolution infrared spectrophotometry has encouraged this interpretation of the infrared properties of Titan, and provided the basis for initial, detailed model.

  8. Correlation of in vitro and in vivo models for the oral absorption of peptide drugs.

    Föger, F; Kopf, A; Loretz, B; Albrecht, K; Bernkop-Schnürch, A

    2008-06-01

    The aim of this study was to evaluate two in vitro models, Caco-2 monolayer and rat intestinal mucosa, regarding their linear correlation with in vivo bioavailability data of therapeutic peptide drugs after oral administration in rat and human. Furthermore the impact of molecular mass (Mm) of the according peptides on their permeability was evaluated. Transport experiments with commercially available water soluble peptide drugs were conducted using Caco-2 cell monolayer grown on transwell filter membranes and with freshly excised rat intestinal mucosa mounted in Using type chambers. Apparent permeability coefficients (P (app)) were calculated and compared with in vivo data derived from the literature. It was shown that, besides a few exceptions, the Mm of peptides linearly correlates with permeability across rat intestinal mucosa (R (2) = 0.86; y = -196.22x + 1354.24), with rat oral bioavailability (R (2) = 0.64; y = -401.90x + 1268.86) as well as with human oral bioavailability (R (2) = 0.91; y = -359.43x + 1103.83). Furthermore it was shown that P (app) values of investigated hydrophilic peptides across Caco-2 monolayer displayed lower permeability than across rat intestinal mucosa. A correlation between P (app) values across rat intestinal mucosa and in vivo oral bioavailability in human (R (2) = 0.98; y = 2.11x + 0.34) attests the rat in vitro model to be a very useful prediction model for human oral bioavailability of hydrophilic peptide drugs. Presented correlations encourage the use of the rat in vitro model for the prediction of human oral bioavailabilities of hydrophilic peptide drugs.

  9. 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.

  10. Pressure-Dependent Anharmonic Correlated Einstein Model Extended X-ray Absorption Fine Structure Debye-Waller Factors

    Van Hung, Nguyen

    2014-02-01

    A pressure-dependent anharmonic correlated Einstein model is derived for extended X-ray absorption fine structure (EXAFS) Debye-Waller factors (DWFs), which are presented in terms of cumulant expansion up to the third order. The model is based on quantum thermodynamic perturbation theory and includes anharmonic effects based on empirical potentials. Explicit analytical expressions of the pressure-dependent changes in the interatomic distance, anharmonic effective potential, thermodynamic parameters, first, second, and third EXAFS cumulants, and thermal expansion coefficient have been derived. This model avoids the use of extensive full lattice dynamical calculations, yet provides good and reasonable agreement of numerical results for Cu with experimental results of X-ray diffraction (XRD) analysis and pressure-dependent EXAFS. Significant pressure effects are shown by the decrease in the pressure-induced changes in the interatomic distance, EXAFS cumulants and thermal expansion coefficient, as well as by the increase in the pressure-induced changes in the interatomic effective potential, effective spring constant, correlated Einstein frequency, and temperature.

  11. 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.

  12. 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.

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

    Christensen, Morten

    Methods for mechanical generation of 2-dimensional (2-D) and 3-dimensional (3-D) linear water waves in physical models are presented. The results of a series of laboratory 3-D wave generation tests are presented and discussed. The tests preformed involve reproduction of wave fields characterised...... by 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...

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

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

    The conditions, chemical reactions and gas mixing in industrial progresses involving gasification or combustion can be monitored by in situ measurement of gas temperature and gas composition. This can be done spectroscopically, though the result is highly dependent on the quality of reference data...... [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...

  15. Zinc absorption from low phytic acid genotypes of maize (Zea mays L.), Barley (Hordeum vulgare L.), and Rice (Oryza sativa L.) assessed in a suckling rat pup model.

    Lönnerdal, Bo; Mendoza, Concepcion; Brown, Kenneth H; Rutger, J Neil; Raboy, Victor

    2011-05-11

    Dietary phytic acid is a major causative factor for low Zn bioavailability in many cereal- and legume-based diets. The bioavailability of Zn in seed of low phytic acid (lpa) variants of maize ( Zea mays L.), rice ( Oryza sativa L.), and barley ( Hordeum vulgare L.) was evaluated using a suckling rat pup model. Suckling rat pups (14 days old, n = 6-8/treatment) were fasted for 6 h and intubated with (65)Zn-radiolabeled suspensions prepared using seed produced by either wild-type (normal phytic acid) or lpa genotypes of each cereal. Test solutions were radiolabeled overnight (all genotypes) or immediately prior to intubation (barley genotypes). Pups were killed 6 h postintubation and tissues removed and counted in a gamma counter. Zn absorption was low from wild-type genotypes of maize (21, 33%) and rice (26%), and phytic acid reduction resulted in significantly higher Zn absorption, 47-52 and 35-52%, respectively. Zn absorption from wild-type barley incubated overnight was high (86-91%), and phytate reduction did not improve Zn absorption (84-90%), which is likely due to endogenous phytase activity. When the wild-type barley solutions were prepared immediately before intubation, Zn absorption was significantly lower (63, 78%) than from the lpa cultivars (92, 96%). Variation in seed or flour phenolic acid levels did not affect Zn absorption. Differences in seed Zn levels did not substantially affect Zn absorption. Thus, when phytic acid is abundant in a diet, it has a larger effect on Zn absorption than the level of Zn. Therefore, reducing the phytic acid content of staple cereal grains may contribute to enhancing Zn nutrition of populations consuming these staple foods.

  16. 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

  17. A theoretical model of accelerated irradiation creep at low temperatures by transient interstitial absorption

    Stoller, R.E.; Grossbeck, M.L.; Mansur, L.K.

    1990-01-01

    A theoretical model has been developed using the reaction rate theory of radiation effects to explain experimental results that showed higher than expected values of irradiation creep at low temperatures in the Oak Ridge Research Reactor. The customary assumption that the point defect concentrations are at steady state was not made; rather, the time dependence of the vacancy and interstitial concentrations and the creep rate were explicitly calculated. For temperatures below about 100 to 200{degree}C, the time required for the vacancy concentration to reach steady state exceeds the duration of the experiment. For example, if materials parameters typical of austenitic stainless steel are used, the calculated vacancy transient dose at 100{degree}C is about 100 dpa. At 550{degree}C this transient is over by 10{sup {minus}8} dpa. During the time that the vacancy population remains lower than its steady state value, dislocation climb is increased since defects of primarily one type are being absorbed. Using the time-dependent point defect concentrations, the dislocation climb velocity has been calculated as a function of time and a climb-enabled glide creep model had been invoked. The extended transient time for the vacancies leads to high creep rates at low temperatures. In agreement with the experimental observations, a minimum in the temperature dependence of creep is predicted at a temperature between 50 and 350{degree}C. The temperature at which the minimum occurs decreases as the irradiation dose increases. Predicted values of creep at 8 dpa are in good agreement with the results of the ORR-MFE-6J/7J experiment.

  18. Investigation of the effects of soluble fibers on the absorption of resveratrol and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PHIP) in the Caco-2 cellular model of intestinal absorption.

    Willenberg, Ina; Wonik, Jasmin; Schebb, Nils Helge

    2015-01-01

    Soluble fibers are known to modulate intestinal absorption of non-polar compounds in the small intestine. Little is known about the modulation of absorption of more polar compounds. In the present study, we applied the Caco-2-transwell-system in order to investigate the modulation of intestinal bioavailability by soluble fibers. The system was tested using pectin and carrageenan as model soluble fibers at a concentration of 0.1% (w/v), which did not compromise the integrity of the cell monolayer. Modulation of absorption was evaluated for the heterocyclic amine aromatic 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PHIP) and the polyphenol resveratrol. Neither pectin nor carrageenan reduced the high flux of PHIP, apparent permeability coefficient (Papp) of 16 × 10(-6) cm s(-1). The low Papp of resveratrol was reduced by both soluble fibers, particularly by pectin. These results suggest that the low bioavailability of polyphenols could be further reduced by soluble fibers. Because of their co-occurrence in several fruits, these findings warrant further research.

  19. Predicting absorption and pharmacokinetic profile of carbamazepine from controlled-release tablet formulation in humans using rabbit model

    Homšek Irena

    2011-01-01

    Full Text Available Controlled-release (CR pharmaceutical formulations offer several advantages over the conventional, immediate release dosage forms of the same drug, including reduced dosing frequency, decreased incidence and/or intensity of adverse effects, greater selectivity of pharmacological activity, reduced drug plasma fluctuation, and better compliance. After a drug product has been registered, and is already on market, minor changes in formulation might be needed. At the same time, the product has to remain effective and safe for patients that could be confirmed via plasma drug concentrations and pharmacokinetic characteristics. It is challenging to predict human absorption and pharmacokinetic characteristics of a drug based on the in vitro dissolution test and the animal pharmacokinetic data. Therefore, the objective of this study was to establish correlation of the pharmacokinetic parameters of carbamazepine (CBZ CR tablet formulation between the rabbit and the human model, and to establish in vitro in vivo correlation (IVIVC based on the predicted fractions of absorbed CBZ. Although differences in mean plasma concentration profiles were notified, the data concerning the predicted fraction of drug absorbed were almost superimposable. Accordingly, it can be concluded that rabbits may be representative as an in vivo model for predicting the pharmacokinetics of the CR formulation of CBZ in humans.

  20. Probing recent star formation with absorption-line strengths in hierarchical models and observations

    Trager, S C

    2009-01-01

    Stellar population parameters derived from spectral line-strengths provide a powerful probe of galaxy properties and formation histories. We implement the machinery for extracting single-stellar-population-equivalent stellar population parameters from synthetic spectra generated by a hierarchical galaxy formation model. We find that the SSP-equivalent age is related to the light-weighted age in a complicated fashion that reflects the influence of recently-formed stars and is poorly correlated with the mass-weighted age. The tendency for SSP-equivalent ages to be biased young means that archaeological downsizing overstates the mass-weighted downsizing in age with mass. We find that the SSP-equivalent metallicity closely tracks the mass- and light-weighted metallicities, so that observed mass--metallicity relations for old galaxies closely reflect the underlying trends. We construct mock catalogues of early-type galaxies in a Coma cluster-sized halo and compare them directly to observations of early-type galaxi...

  1. Nonlinear absorption coefficient and optically detected electrophonon resonance in cylindrical GaAs/AlAs quantum wires with different confined phonon models

    Khoa, Doan Quoc; Phuong, Le Thi Thu; Hoi, Bui Dinh

    2017-03-01

    A quantum kinetic equation for electrons interacting with confined phonons is used to investigate the nonlinear absorption of an intense electromagnetic wave by electrons in cylindrical GaAs/AlAs quantum wires. The analytic expression for absorption coefficient is calculated for three models of confined optical phonons: the dielectric continuum (DC), hydrodynamic continuum (HC), and Huang-Zhu (HZ) models. The absorption coefficient depends on the square of the electromagnetic wave amplitude. The electrophonon resonance and optically detected electrophonon resonance (ODEPR) are observed through the absorption spectrum. The full width at half maximum (the line-width) of the ODEPR peaks is obtained by a computational method. The line-width is found to increase with increasing temperature and decrease with increasing the quantum wire radius. In particular, numerical results show that the DC and HZ models lead to a similar behaviour of electron - confined phonon interaction whereas the HC model results in a quite different one, especially at small quantum wire radius. For large quantum wire radii, above mentioned phonon models have equivalent contributions to the ODEPR line-width.

  2. An absorption mechanism and polarity-induced viscosity model for CO2 capture using hydroxypyridine-based ionic liquids.

    An, Xiaowei; Du, Xiao; Duan, Donghong; Shi, Lijuan; Hao, Xiaogang; Lu, Houfang; Guan, Guoqing; Peng, Changjun

    2017-01-04

    A series of new hydroxypyridine-based ionic liquids (ILs) are synthesized and applied in CO2 capture through chemical absorption, in which one IL, i.e., tetrabutylphosphonium 2-hydroxypyridine ([P4444][2-Op]), shows a viscosity as low as 193 cP with an absorption capacity as high as 1.20 mol CO2 per mol IL. Because the traditional anion-CO2 absorption mechanism cannot provide an explanation for the influences of cations and temperature on CO2 absorption capacity, herein, a novel cation-participating absorption mechanism based on the proton transfer is proposed to explain the high absorption capacity and the existence of a turning point of absorption capacity with the increase of temperature for the capture of CO2 using [P4444][n-Op] (n = 2, 3, 4) ILs. Also, the relationship between the viscosity of ILs and the linear interaction energy is proposed for the first time, which can guide how to design and synthesize ILs with low viscosity. Quantum chemistry calculations, which are based on the comprehensive analysis of dipole moment, cation-anion interaction energy and surface electrostatic potential, indicate that the different viscosities of hydroxypyridine-based ILs and the changes after CO2 absorption mainly resulted from the different distribution of negative charges in the anion.

  3. Harmonic Models in Cartesian and Internal Coordinates to Simulate the Absorption Spectra of Carotenoids at Finite Temperatures.

    Cerezo, Javier; Zúñiga, José; Requena, Alberto; Ávila Ferrer, Francisco J; Santoro, Fabrizio

    2013-11-12

    When large structural displacements take place between the ground state (GS) and excited state (ES) minima of polyatomic molecules, the choice of a proper set of coordinates can be crucial for a reliable simulation of the vibrationally resolved absorption spectrum. In this work, we study two carotenoids that undergo structural displacements from GS to ES minima of different magnitude, from small displacements for violaxanthin to rather large ones for β-carotene isomers. Their finite-temperature (77 and 300 K) spectra are simulated at the harmonic level, including Duschinsky effect, by time-dependent (TD) and time-independent (TI) approaches, using (TD)DFT computed potential energy surfaces (PES). We adopted two approaches to construct the harmonic PES, the Adiabatic (AH) and Vertical Hessian (VH) models and, for AH, two reference coordinate frames: Cartesian and valence internal coordinates. Our results show that when large displacements take place, Cartesian coordinates dramatically fail to describe curvilinear displacements and to account for the Duschinsky matrix, preventing a realistic simulation of the spectra within the AH model, where the GS and ES PESs are quadratically expanded around their own equilibrium geometry. In contrast, internal coordinates largely amend such deficiencies and deliver reasonable spectral widths. As expected, both coordinate frames give similar results when small displacements occur. The good agreement between VH and experimental line shapes indicates that VH model, in which GS and ES normal modes are both evaluated at the GS equilibrium geometry, is a good alternative to deal with systems exhibiting large displacements. The use of this model can be, however, problematic when imaginary frequencies arise. The extent of the nonorthogonality of the Dushinsky matrix in internal coordinates and its correlation with the magnitude of the displacement of the GS and ES geometries is analyzed in detail.

  4. Non-Directional Radiation Spread Modeling and Non-Invasive Estimating the Radiation Scattering and Absorption Parameters in Biological Tissue

    S. Yu. Makarov

    2015-01-01

    Full Text Available The article dwells on a development of new non-invasive measurement methods of optical parameters of biological tissues, which are responsible for the scattering and absorption of monochromatic radiation. It is known from the theory of radiation transfer [1] that for strongly scattering media, to which many biological tissues pertain, such parameters are parameters of diffusion approximation, as well as a scattering coefficient and an anisotropy parameter.Based on statistical modeling the paper examines a spread of non-directional radiation from a Lambert light beam with the natural polarization that illuminates a surface of the biological tissue. Statistical modeling is based on the Monte Carlo method [2]. Thus, to have the correct energy coefficient values of Fresnel reflection and transmission in simulation of such radiation by Monte Carlo method the author uses his finding that is a function of the statistical representation for the incidence of model photons [3]. The paper describes in detail a principle of fixing the power transmitted by the non-directional radiation into biological tissue [3], and the equations of a power balance in this case.Further, the paper describes the diffusion approximation of a radiation transfer theory, often used in simulation of radiation propagation in strongly scattering media and shows its application in case of fixing the power transmitted into the tissue. Thus, to represent an uneven power distribution is used an approximating expression in conditions of fixing a total input power. The paper reveals behavior peculiarities of solution on the surface of the biological tissue inside and outside of the incident beam. It is shown that the solution in the region outside of the incident beam (especially far away from it, essentially, depends neither on the particular power distribution across the surface, being a part of the tissue, nor on the refractive index of the biological tissue. It is determined only by

  5. Renormalization Group Approach to the X-Ray Absorption Problem and Application to the Vigman-Finkelshtein Model for Magnetic Impurities in Metals.

    Nunes de Oliveira, Luiz

    The renormalization group techniques developed by Wilson for the Kondo problem are applied to three related problems: the absorption of x-rays by metals, the absorption of x-rays by impurities in metals, and the specific heat of dilute magnetic alloys. In the first problem considered, the x-ray absorption problem, the metal is represented by a half-filled conduction band and a deep level representing a core state. The absorption of an x-ray photon excites an electron from this core level to the conduction band creating a core hole whose positive charge interacts with the conduction electrons. The absorption spectrum is, for the first time, calculated in the energy range 10('-10)D ) (omega)(,T)) expression to seven decimal places; the prefactor (mu)(,o) is calculated for the first time. For (omega)-(omega)(,T) (TURNEQ) D, remarkably small deviations (e.g., deviations of 15% for (omega)-(omega)(,T) = .3D) from the Nozieres-De Dominicis power law are found. As a second application of the renormalization group techniques, the x-ray absorption spectrum for the resonant level model for impurities in metals is calculated. In this model, the metal is represented by a half-filled conduction band and the impurity by two levels: a core level from which an electron is excited to the conduction band by the absorption of an x-ray photon, and a resonant level, coupled to the conduction electrons, whose energy is lowered by the interaction with the core hole created by the absorption of the x-ray. In the x-ray absorption process, the resonant level is thus shifted to lower energy. The absorption spectrum approaches a power law in the energy range (omega)-(omega)(,T) >> (GAMMA), where (GAMMA) is the width of the resonant level, and a different power law in the range (omega)-(omega)(,T) body effect found in the spectrum of certain systems having a discrete level coupled to a continuum of energies) is elaborated. The problem of the specific heat of dilute magnetic alloys is attacked

  6. 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...

  7. Evaluation of metallothionein formation as a proxy for zinc absorption in an in vitro digestion/caco-2 cell culture model

    Caco-2 cell metallothionein (MT) formation was studied to determine if MT could be used as a proxy for zinc (Zn) absorption in a cell culture model. MT intracellular concentration was determined by using a cadmium/hemoglobin affinity assay. Cellular Zn uptake was determined in acid digests (5% HNO3)...

  8. 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

  9. How plant architecture affects light absorption and photosynthesis in tomato: towards an ideotype for plant architecture using a functional-structural plant model

    Sarlikioti, V.; Visser, de P.H.B.; Buck-Sorlin, G.H.; Marcelis, L.F.M.

    2011-01-01

    Background and Aims - Manipulation of plant structure can strongly affect light distribution in the canopy and photosynthesis. The aim of this paper is to find a plant ideotype for optimization of light absorption and canopy photosynthesis. Using a static functional structural plant model (FSPM), a

  10. A computer model simulating human glucose absorption and metabolism in health and metabolic disease states [version 1; referees: 2 approved, 1 approved with reservations

    Richard J. Naftalin

    2016-04-01

    Full Text Available A computer model designed to simulate integrated glucose-dependent changes in splanchnic blood flow with small intestinal glucose absorption, hormonal and incretin circulation and hepatic and systemic metabolism in health and metabolic diseases e.g. non-alcoholic fatty liver disease, (NAFLD, non-alcoholic steatohepatitis, (NASH and type 2 diabetes mellitus, (T2DM demonstrates how when glucagon-like peptide-1, (GLP-1 is synchronously released into the splanchnic blood during intestinal glucose absorption, it stimulates superior mesenteric arterial (SMA blood flow and by increasing passive intestinal glucose absorption, harmonizes absorption with its distribution and metabolism. GLP-1 also synergises insulin-dependent net hepatic glucose uptake (NHGU. When GLP-1 secretion is deficient post-prandial SMA blood flow is not increased and as NHGU is also reduced, hyperglycaemia follows. Portal venous glucose concentration is also raised, thereby retarding the passive component of intestinal glucose absorption.   Increased pre-hepatic sinusoidal resistance combined with portal hypertension leading to opening of intrahepatic portosystemic collateral vessels are NASH-related mechanical defects that alter the balance between splanchnic and systemic distributions of glucose, hormones and incretins.The model reveals the latent contribution of portosystemic shunting in development of metabolic disease. This diverts splanchnic blood content away from the hepatic sinuses to the systemic circulation, particularly during the glucose absorptive phase of digestion, resulting in inappropriate increases in insulin-dependent systemic glucose metabolism.  This hastens onset of hypoglycaemia and thence hyperglucagonaemia. The model reveals that low rates of GLP-1 secretion, frequently associated with T2DM and NASH, may be also be caused by splanchnic hypoglycaemia, rather than to intrinsic loss of incretin secretory capacity. These findings may have therapeutic

  11. In search of metal hydrides: an X-ray absorption and emission study of [NiFe] hydrogenase model complexes.

    Hugenbruch, Stefan; Shafaat, Hannah S; Krämer, Tobias; Delgado-Jaime, Mario Ulises; Weber, Katharina; Neese, Frank; Lubitz, Wolfgang; DeBeer, Serena

    2016-04-28

    Metal hydrides are invoked as important intermediates in both chemical and biological H2 production. In the [NiFe] hydrogenase enzymes, pulsed EPR and high-resolution crystallography have argued that the hydride interacts primarily at the Ni site. In contrast, in [NiFe] hydrogenase model complexes, it is observed that the bridging hydride interacts primarily with the Fe. Herein, we utilize a combination of Ni and Fe X-ray absorption (XAS) and emission (XES) spectroscopies to examine the contribution of the bridging hydride to the observed spectral features in [(dppe)Ni(μ-pdt)(μ-H)Fe(CO)3](+). The corresponding data on (dppe)Ni(μ-pdt)Fe(CO)3 are used as a reference for the changes that occur in the absence of a hydride bridge. For further interpretation of the observed spectral features, all experimental spectra were calculated using a density functional theory (DFT) approach, with excellent agreement between theory and experiment. It is found that the iron valence-to-core (VtC) XES spectra reveal clear signatures for the presence of a Fe-H interaction in the hydride bridged model complex. In contrast, the Ni VtC XES spectrum largely reflects changes in the local Ni geometry and shows little contribution from a Ni-H interaction. A stepwise theoretical analysis of the hydride contribution and the Ni site symmetry provides insights into the factors, which govern the different metal-hydride interactions in both the model complexes and the enzyme. Furthermore, these results establish the utility of two-color XES to reveal important insights into the electronic structure of various metal-hydride species.

  12. In Situ Perfusion Model in Rat Colon for Drug Absorption Studies: Comparison with Small Intestine and Caco-2 Cell Model.

    Lozoya-Agullo, Isabel; González-Álvarez, Isabel; González-Álvarez, Marta; Merino-Sanjuán, Matilde; Bermejo, Marival

    2015-09-01

    Our aim is to develop and to validate the in situ closed loop perfusion method in rat colon and to compare with small intestine and Caco-2 cell models. Correlations with human oral fraction absorbed (Fa) and human colon fraction absorbed (Fa_colon) were developed to check the applicability of the rat colon model for controlled release (CR) drug screening. Sixteen model drugs were selected and their permeabilities assessed in rat small intestine and colon, and in Caco-2 monolayers. Correlations between colon/intestine/Caco-2 permeabilities versus human Fa and human Fa_colon have been explored to check model predictability and to apply a BCS approach in order to propose a cut off value for CR screening. Rat intestine perfusion with Doluisio's method and single-pass technique provided a similar range of permeabilities demonstrating the possibility of combining data from different laboratories. Rat colon permeability was well correlated with Caco-2 cell-4 days model reflecting a higher paracellular permeability. Rat colon permeabilities were also higher than human colon ones. In spite of the magnitude differences, a good sigmoidal relationship has been shown between rat colon permeabilities and human colon fractions absorbed, indicating that rat colon perfusion can be used for compound classification and screening of CR candidates.

  13. Exploration of parameters influencing the self-absorption losses in luminescent solar concentrators with an experimentally validated combined ray-tracing/Monte-Carlo model

    Krumer, Zachar; van Sark, Wilfried G. J. H. M.; de Mello Donegá, Celso; Schropp, Ruud E. I.

    2013-09-01

    Luminescent solar concentrators (LSCs) are low cost photovoltaic devices, which reduce the amount of necessary semiconductor material per unit area of a photovoltaic solar energy converter by means of concentration. The device is comprised of a thin plastic plate in which luminescent species (fluorophores) have been incorporated.The fluorophores absorb the solar light and radiatively re-emit a part of the energy. Total internal reflection traps most of the emitted light inside the plate and wave-guides it to a narrow side facet with a solar cell attached, where conversion into electricity occurs. The eciency of such devices is as yet rather low, due to several loss mechanisms, of which self-absorption is of high importance. Combined ray-tracing and Monte-Carlosimulations is a widely used tool for efficiency estimations of LSC-devices prior to manufacturing. We have applied this method to a model experiment, in which we analysed the impact of self-absorption onto LSC-efficiency of fluorophores with different absorption/emission-spectral overlap (Stokes-shift): several organic dyes and semiconductor quantum dots (single compound and core/shell of type-II). These results are compared with the ones obtained experimentally demonstrating a good agreement. The validated model is used to investigate systematically the influence of spectral separation and luminescence quantum efficiency on the intensity loss inconsequence of increased self-absorption. The results are used to adopt a quantity called the self-absorption cross-section and establish it as reliable criterion for self-absorption properties of materials that can be obtained from fundamental data and has a more universal scope of application, than the currently used Stokes-shift.

  14. 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.

  15. 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

  16. 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

  17. 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.

  18. Analytical modeling of photon absorption coefficient in mono and bilayer circular graphene quantum dots for light absorber applications

    Tamandani, Shahryar; Darvish, Ghafar

    2017-02-01

    We present an analytical method to calculate photon absorption coefficient in mono and bilayer circular graphene quantum dots (CGQDs). We use kobo equation to extract new closed relation as the main goal. First, we calculate real and imaginary part of optical conductance separately. Then, joint density of states is obtained using a new relation that was extracted for the energy levels of mono and bilayer circular grapheme quantum dots. In this work we use closed equations to calculate energy levels in CGQDs. Next we obtain a new closed formula to calculate the photon absorption coefficient. The results show that the absorption coefficient is related to the size of CGQDs and number of layers. The photon absorption coefficient becomes lower with larger size of CGQDs. It is seen that the results of our method is compatible with the results of practical works. We also compare photon absorption in biased and unbiased bilayer CGQDs and investigate the effect of external magnetic field on photon absorption. rights reserved

  19. Comparison of line-by-line and band models of near-IR methane absorption applied to outer planet atmospheres

    Sromovsky, L. A.; Fry, P. M.; Boudon, V.; Campargue, A.; Nikitin, A.

    2012-03-01

    Recent improvements in high spectral resolution measurements of methane absorption at wavenumbers between 4800 cm-1 and 7919 cm-1 have greatly increased the number of lines with known lower state energies, the number of weak lines, and the number of lines observed at low temperatures (Campargue, A., Wang, L., Kassi, S., Mašát, M., Votava, O. [2010]. J. Quant. Spectrosc. Radiat. Trans. 111, 1141-1151; Campargue, A., Wang, L., Liu, A.W., Hu, S.M., Kassi, S. [2010]. Chem. Phys. 373, 203-210; Mondelain, D., Kassi, S., Wang, L.C. [2011]. Phys. Chem. Chem. Phys. 13, 7985-7996; Nikitin, A.V. et al. [2011a]. J. Mol. Spectrosc. 268, 93-106; Nikitin, A.V. et al. [2010]. J. Quant. Spectrosc. Radiat. Trans. 111, 2211-2224; Wang, L., Kassi, S., Campargue, A. [2010]. J. Quant. Spectrosc. Radiat. Trans. 111, 1130-1140; Wang, L., Kassi, S., Liu, A.W., Hu, S.M., Campargue, A. [2011]. J. Quant. Spectrosc. Radiat. Trans. 112, 937-951), making it possible to fit near-IR spectra of Titan using line-by-line calculations instead of band models (Bailey, J., Ahlsved, L., Meadows, V.S. [2011]. Icarus 213, 218-232; de Bergh, C. et al. [2011]. Planet. Space Sci. doi:10.1016/j.pss.2011.05.003). Using these new results, we compiled an improved line list relative that used by Bailey et al. by updating several spectral regions with either calculated or more recently measured line parameters, revising lower state energy estimates for lines lacking them, and adding room temperature lines to make the list applicable over a wider range of temperatures. We compared current band models with line-by-line calculations using this new line list, both to assess the behavior of band models, and to identify remaining issues with line-by-line calculations when applied to outer planet atmospheres and over a wider range of wavelengths. Comparisons were made for a selection of uniform paths representing outer planet conditions and for representative non-uniform paths within the atmospheres of Uranus, Saturn

  20. Water Vapor Radiometer-Global Positioning System Comparison Measurements and Calibration of the 20 to 32 Gigahertz Tropospheric Water Vapor Absorption Model

    Keihm, S. J.; Bar-Sever, Y.; Liljegren, J.

    2000-10-01

    Collocated measurements of opacity (from water vapor radiometer (WVR) brightness temperatures) and wet path delay (from ground-based tracking of Global Positions System (GPS) satellites) are used to constrain the model of atmospheric water vapor absorption in the 20 to 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 5 months of data were obtained from two experiment sites. At the Cloud and Radiation Testbed (CART) site near Lamont, Oklahoma, three independent WVRs provided near-continuous opacity measurements over the interval from July through September 1998. At NASA's Goldstone tracking station in the California desert, two WVRs obtained opacity data over the September through October 1997 interval. At both sites, a 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 three candidate absorption models referenced in the recent literature. With one exception, all three models provide agreement within approximately 5 percent 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 to 3 percent level. This accuracy is sufficient to meet the requirements of the tropospheric calibration system now being deployed at Goldstone to support the Cassini Gravitational Wave Experiment.

  1. A two-dimensional mathematical model of non-linear dual-sorption of percutaneous drug absorption

    George K

    2005-07-01

    Full Text Available Abstract Background Certain drugs, for example scopolamine and timolol, show non-linear kinetic behavior during permeation process. This non-linear kinetic behavior is due to two mechanisms; the first mechanism being a simple dissolution producing mobile and freely diffusible molecules and the second being an adsorption process producing non-mobile molecules that do not participate in the diffusion process. When such a drug is applied on the skin surface, the concentration of the drug accumulated in the skin and the amount of the drug eliminated into the blood vessel depend on the value of a parameter, C, the donor concentration. The present paper studies the effect of the parameter value, C, when the region of the contact of the skin with drug, is a line segment on the skin surface. To confirm that dual-sorption process gives an explanation to non-linear kinetic behavior, the characteristic features that are used in one-dimensional models are (1 prolongation of half-life if the plot of flux versus time are straight lines soon after the vehicle removal, (2 the decrease in half-life with increase in donor concentration. This paper introduces another feature as a characteristic to confirm that dual-sorption model gives an explanation to the non-linear kinetic behavior of the drug. This new feature is "the prolongation of half-life is not a necessary feature if the plots of drug flux versus time is a non-linear curve, soon after the vehicle removal". Methods From biological point of view, a drug absorption model is said to be nonlinear if the sorption isotherm is non-linear. When a model is non-linear the relationship between lag-time and donor concentration is non-linear and the lag time decreases with increase in donor concentration. A two-dimensional dual-sorption model is developed for percutaneous absorption of a drug, which shows non-linear kinetic behavior in the permeation process. This model may be used when the diffusion of the drug in

  2. Application of biopartitioning micellar chromatography and QSRR modeling for prediction of gastrointestinal absorption and design of novel β-hydroxy-β-arylalkanoic acids.

    Dobričić, Vladimir; Savić, Jelena; Nikolic, Katarina; Vladimirov, Sote; Vujić, Zorica; Brborić, Jasmina

    2017-03-30

    Gastrointestinal absorption of thirteen novel β-hydroxy-β-arylalkanoic acids (HAA) with anti-inflammatory activity was predicted by use of biopartitioning micellar chromatography and compared to ibuprofen. All tested HAA have lower retention factors (k) and lower expected gastrointestinal absorption than ibuprofen, whereas derivatives with the highest values of k are 1C, 2APTF and 2C. Quantitative structure-retention relationship (QSRR) analysis was performed in order to identify molecular descriptors with the highest influence on k and ANN(k) model was selected as optimal. Descriptors which form this model (nBM, P_VSA_LogP_8 and Eta_L) indicate that replacement of phenyl ring with a saturated or partially unsaturated one, as well as presence of halogens and nitro group should positively affect k values. On the basis of these conclusions, six novel HAA were designed and selected QSRR model was used for the prediction of their k values.

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

    Bonito, R.; Argiroffi, C.; Peres, G. [Dip. di Fisica e Chimica, Università di Palermo, P.zza del Parlamento 1, I-90134 Palermo (Italy); Orlando, S.; Miceli, M.; Ibgui, L. [INAF-Osservatorio Astronomico di Palermo, P.zza del Parlamento 1, I-90134 Palermo (Italy); Matsakos, T. [Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States); Stehle, C., E-mail: sbonito@astropa.unipa.it [LERMA, Observatoire de Paris, Université Pierre et Marie Curie, Ecole Normale Superieure, Universite Cergy-Pontoise, CNRS, F-75014 Paris (France)

    2014-11-10

    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.

  4. 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

  5. Water absorption in brick masonry

    Brocken, H.J.P.; Smolders, H.R.

    1996-01-01

    The water absorption in brick, mortar that was cured separately, and masonry samples was studied using NMR. Models of the moisture transport are usually formulated on the basis of a diffusion equation. In the case of water absorption in separate brick and mortar samples, the moisture diffusivity in

  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.

  7. Evolution of a detailed physiological model to simulate the gastrointestinal transit and absorption process in humans, part II: extension to describe performance of solid dosage forms.

    Thelen, Kirstin; Coboeken, Katrin; Willmann, Stefan; Dressman, Jennifer B; Lippert, Jörg

    2012-03-01

    The physiological absorption model presented in part I of this work is now extended to account for dosage-form-dependent gastrointestinal (GI) transit as well as disintegration and dissolution processes of various immediate-release and modified-release dosage forms. Empirical functions of the Weibull type were fitted to experimental in vitro dissolution profiles of solid dosage forms for eight test compounds (aciclovir, caffeine, cimetidine, diclofenac, furosemide, paracetamol, phenobarbital, and theophylline). The Weibull functions were then implemented into the model to predict mean plasma concentration-time profiles of the various dosage forms. On the basis of these dissolution functions, pharmacokinetics (PK) of six model drugs was predicted well. In the case of diclofenac, deviations between predicted and observed plasma concentrations were attributable to the large variability in gastric emptying time of the enteric-coated tablets. Likewise, oral PK of furosemide was found to be predominantly governed by the gastric emptying patterns. It is concluded that the revised model for GI transit and absorption was successfully integrated with dissolution functions of the Weibull type, enabling prediction of in vivo PK profiles from in vitro dissolution data. It facilitates a comparative analysis of the parameters contributing to oral drug absorption and is thus a powerful tool for formulation design.

  8. Characterization of the Aqueous Uranyl-Silicate Complex Using X-Ray Absorption Spectroscopy and Ab Initio Modeling

    Vu, M.; Massey, M.; Huang, P.

    2015-12-01

    The speciation of aqueous uranium ions is an important factor in predicting its mobility and fate in the environment. Two major controls on speciation are pH and the presence of complexing ligands. For the case of aqueous uranyl, UO22+(aq), some common complexes include uranyl-hydroxy, uranyl-carbonato, and uranyl-calcium-carbonato complexes, all of which differ in chemical reactivity and mobility. Uranyl-silicate complexes are also known but remain poorly characterized. In this work, we studied uranyl speciation in a series of aqueous solutions of 0.1 mM uranyl and 2 mM silicate with pH ranging from 4 to 7. Extended X-Ray Absorption Fine Structure (EXAFS) spectra of these samples were recorded at the Stanford Synchrotron Radiation Lightsource (SLAC National Accelerator Laboratory). Of particular note are the uranyl and silicate concentrations employed in our experiments, which are lower than conditions in previously reported EXAFS studies and approach conditions in natural groundwater systems. Preliminary analyses of EXAFS data indicate that uranyl speciation changes across the pH range, consistent with published thermodynamic data that suggest uranyl-silicate complexes may be important for pH ~ 5 and below, while uranyl-carbonato complexes become dominant at circumneutral pH. To guide the interpretation of the EXAFS data, molecular-scale simulations were carried out using density functional theory. We considered two classes of models: (i) hydrated clusters, and (ii) ab initio molecular dynamics simulations of 3D-periodic models involving uranyl and silicate in water. These calculations reveal that at pH ~ 5, the uranyl speciation is the [UO2(H2O)4H3SiO4]+ complex formed by the substitution of an equatorial uranyl water with a monodentate silicate ligand. The evidence from experiments and simulations provide a consistent picture for the uranyl-silicate complex, which may be important in the transport of uranyl in acidic, silicate-rich waters.

  9. 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.

  10. Population pharmacokinetic modelling of tramadol using inverse Gaussian function for the assessment of drug absorption from prolonged and immediate release formulations.

    Brvar, Nina; Mateović-Rojnik, Tatjana; Grabnar, Iztok

    2014-10-01

    This study aimed to develop a population pharmacokinetic model for tramadol that combines different input rates with disposition characteristics. Data used for the analysis were pooled from two phase I bioavailability studies with immediate (IR) and prolonged release (PR) formulations in healthy volunteers. Tramadol plasma concentration-time data were described by an inverse Gaussian function to model the complete input process linked to a two-compartment disposition model with first-order elimination. Although polymorphic CYP2D6 appears to be a major enzyme involved in the metabolism of tramadol, application of a mixture model to test the assumption of two and three subpopulations did not reveal any improvement of the model. The final model estimated parameters with reasonable precision and was able to estimate the interindividual variability of all parameters except for the relative bioavailability of PR vs. IR formulation. Validity of the model was further tested using the nonparametric bootstrap approach. Finally, the model was applied to assess absorption kinetics of tramadol and predict steady-state pharmacokinetics following administration of both types of formulations. For both formulations, the final model yielded a stable estimate of the absorption time profiles. Steady-state simulation supports switching of patients from IR to PR formulation.

  11. 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...

  12. X-ray Absorption by the Low-redshift Intergalactic Medium A Numerical Study of the Lambda CDM model

    Chen, X; Katz, N; Davé, R; Chen, Xuelei; Weinberg, David H.; Katz, Neal; Dave', Romeel

    2003-01-01

    Using a hydrodynamic simulation of a LCDM universe, we investigate the "X-ray forest" absorption imprinted on the spectra of background quasars by the intervening intergalactic medium (IGM). In agreement with previous studies, we find that OVII and OVIII produce the strongest absorption features. The strong oxygen absorbers that might be detectable with Chandra or XMM-Newton arise in gas with T ~ 10^6 K and overdensities delta >~ 100 that are characteristic of galaxy groups. Future X-ray missions could detect weaker oxygen absorption produced by gas with a wider range of temperatures and the lower densities of unvirialized structures; they could also detect X-ray forest absorption by C, N, Ne, Fe, and possibly Si. If the IGM metallicity is 0.1 solar, then the predicted number of systems strong enough for a ~5\\sigma detection with Chandra or XMM-Newton is extremely low, though scatter in metallicity would increase the number of strong absorbers even if the mean metallicity remained the same. Our simulation rep...

  13. Assessment and modulation of acamprosate intestinal absorption: comparative studies using in situ, in vitro (CACO-2 cell monolayers) and in vivo models.

    Zornoza, Teodoro; Cano-Cebrián, María José; Nalda-Molina, Ricardo; Guerri, Consuelo; Granero, Luis; Polache, Ana

    2004-08-01

    The purpose of this study was to explore the intestinal absorption mechanism of acamprosate and to attempt to improve the bioavailability (BA) of the drug through modulation of its intestinal absorption using two enhancers (polysorbate 80 and sodium caprate) based on in situ, in vitro and in vivo models and comparing the results obtained. Intestinal transport of the drug, in the absence and in presence of polysorbate 80 (0.06, 0.28 and 9.6 mM) or sodium caprate (13 and 16 mM) was measured by using an in situ rat gut technique and Caco-2 cell monolayers. Additionally, the effect of sodium caprate on drug oral bioavailability, measured as urinary recovery, was quantified by performing in vivo experiments with the rat as animal model. Only sodium caprate was able to increase the absorption rate constant (ka) of acamprosate in the mid-intestine of the rats from 0.29 +/- 0.07 h-1 in the absence of the promoter to 0.51 +/- 0.19 h-1 in the presence of C10 16 mM, along with the apparent permeability (Papp) obtained in Caco-2 cells (around two-fold). However, the drug bioavailability in rats (around 20%) did not improve in the presence of any of the concentrations tested (13, 16 and 50 mM). It is concluded that acamprosate absorption likely occurs via paracellular pathway and can be enhanced by sodium caprate in situ and in vitro but not in vivo-thus suggesting that although in situ and in vitro studies could be useful in early screening to select a potential promoter, in vivo studies in animal models are necessary to confirm the utility of the enhancer and to determine the influence of physiological variables.

  14. Multifunctional hybrids for electromagnetic absorption

    Huynen, I. [Research Center in Micro and Nanoscopic Materials and Electronic Devices, CeRMiN, Universite catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Information and Communications Technologies, Electronics and Applied Mathematics (ICTEAM), Microwave Laboratory, Universite catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Quievy, N. [Institute of Condensed Matter and Nanosciences (IMCN), Universite catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Bailly, C. [Research Center in Micro and Nanoscopic Materials and Electronic Devices, CeRMiN, Universite catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Institute of Condensed Matter and Nanosciences (IMCN), Universite catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Institute of Mechanics, Materials and Civil Engineering (iMMC), Universite catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Bollen, P. [Information and Communications Technologies, Electronics and Applied Mathematics (ICTEAM), Microwave Laboratory, Universite catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Institute of Condensed Matter and Nanosciences (IMCN), Universite catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Institute of Mechanics, Materials and Civil Engineering (iMMC), Universite catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Detrembleur, C. [Center for Education and Research on Macromolecules (CERM), University of Liege, Sart-Tilman B6a, 4000 Liege (Belgium); Eggermont, S.; Molenberg, I. [Information and Communications Technologies, Electronics and Applied Mathematics (ICTEAM), Microwave Laboratory, Universite catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Thomassin, J.M.; Urbanczyk, L. [Center for Education and Research on Macromolecules (CERM), University of Liege, Sart-Tilman B6a, 4000 Liege (Belgium)

    2011-05-15

    Highlights: > EM absorption requires low dielectric constant and {approx}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.

  15. [FREE CONSUMPTION OF GLUCOSE SOLUTION BY RATS AS A CRITERION FOR EVALUATION ITS ABSORPTION IN THE SMALL INTESTINE (Experimental study and mathematical modeling)].

    Gruzdkov, A A; Gromova, L V; Dmitrieva, Yu V; Alekseeva, A S

    2015-06-01

    The aim of the work is to analyze the relationship between consumption of glucose solution by rats and its absorption, and to use this fact for assessment of the absorptive capacity of the small intestine in non anesthetized animals in vivo. Consumption of glucose solution (200 g/l) by fasted rats was recorded in the control, and after administration of phloridzin--inhibitor of glucose active transport- or 3 hours after the restriction stress. On the mathematical model we studied the relative role of factors that can influence the temporal dynamics of glucose consumption by rats. The rate of glucose consumption was observed being decreased in the presence of phloridzin (1 mM), and be increased after the stress. The results of modeling are consistent with the experimental data and show that the rate of consumption of glucose solutions considerably more depends on the transport activity of the small intestine than on glucose concentration in the solution, or on the substrate regulation of the stomach emptying. Analysis of dynamics of consumption of glucose solution by intact rats may be considered as one of promising approaches to assessing the absorptive capacity of the small intestine under natural conditions.

  16. Stabilization effect ofWeibel modes due to inverse bremsstrahlung absorption in laser fusion plasma using Krook collisions model

    S BELGHIT; A SID

    2016-12-01

    In this work, the Weibel instability due to inverse bremsstrahlung absorption in laser fusion plasma has been investigated. The stabilization effect due to the coupling of the self-generated magnetic field by Weibel instability with the laser wave field is explicitly showed. The main result obtained in this work is that the inclusion of self-generated magnetic field due to Weibel instability to the inverse bremsstrahlung absorption causes a stabilizing effect of excited Weibel modes. We found a decrease in the spectral range of Weibel unstable modes.This decrease is accompanied by a reduction of two orders in the growth rate of instability or even stabilization of these modes. It has been shown that the previous analyses of the Weibel instability due to inverse bremsstrahlunghave overestimated the values of the generated magnetic fields. Therefore, the generation of magnetic fields by the Weibel instability due to inverse bremsstrahlung should not affect the experiences of an inertial confinement fusion.

  17. Improved Modeling of Midlatitude D-Region Ionospheric Absorption of High Frequency Radio Signals During Solar X-Ray Flares

    2009-06-01

    Nickisch raytracing codes are examined. Figure 6.4.8 shows the raypaths predicted by the HASEL raytracing code for the 5 MHz blo-wwv and 15 MHz...regions in which ω ν>> and non-deviative absorption can be represented by an f -2 dependence. The raytracing code developed by Mark Hausman and L.J...Nickisch of NWRA [Huang and Reinisch, 2006; Nickisch, 1988], which is based upon the Jones-Stephenson raytracing algorithm [Jones and Stephenson

  18. Mesoscale modeling of photoelectrochemical devices: light absorption and carrier collection in monolithic, tandem, Si|WO3 microwires.

    Fountaine, Katherine T; Atwater, Harry A

    2014-10-20

    We analyze mesoscale light absorption and carrier collection in a tandem junction photoelectrochemical device using electromagnetic simulations. The tandem device consists of silicon (E(g,Si) = 1.1 eV) and tungsten oxide (E(g,WO3) = 2.6 eV) as photocathode and photoanode materials, respectively. Specifically, we investigated Si microwires with lengths of 100 µm, and diameters of 2 µm, with a 7 µm pitch, covered vertically with 50 µm of WO3 with a thickness of 1 µm. Many geometrical variants of this prototypical tandem device were explored. For conditions of illumination with the AM 1.5G spectra, the nominal design resulted in a short circuit current density, J(SC), of 1 mA/cm(2), which is limited by the WO3 absorption. Geometrical optimization of photoanode and photocathode shape and contact material selection, enabled a three-fold increase in short circuit current density relative to the initial design via enhanced WO3 light absorption. These findings validate the usefulness of a mesoscale analysis for ascertaining optimum optoelectronic performance in photoelectrochemical devices.

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

    Gajjar, Rachna M; Kasting, Gerald B

    2014-11-15

    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 (14)C-radiolabed compound were tested - 5, 10, 20, and 40μLcm(-2), corresponding to specific doses ranging in mass from 5.0 to 63mgcm(-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.

  20. The Effect of Surface Heterogeneity on Cloud Absorption Estimates

    Chiu, Jui-Yuan C.; Marshak, Alexander; Wiscombe, Warren J.

    2004-01-01

    This study presents a systematic and quantitative analysis of the effect of inhomogeneous surface albedo on shortwave cloud absorption estimates. We use 3D radiative transfer modeling with gradually complex clouds over a simplified surface to calculate cloud absorption. We find that averaging surface albedo always underestimates cloud absorption, and thus accounting for surface heterogeneity always enhances cloud absorption. However, the impact on cloud absorption estimates is not enough to explain the discrepancy between measured and model calculated shortwave cloud absorptions.

  1. Temperature dependent O3 absorption cross sections for GOME, SCIAMACHY and GOME-2: I. Re-analysis of Flight Model Data and Retrieval Tests.

    Chehade, Wissam; Weber, Mark; Gorshelev, Victor; Serdyuchenko, Anna; Burrows, John P.

    For a long term coverage of global O3 measurements from SCIAMACHY (SCanning Imag-ing Absorption spectroMeter for Atmospheric CHartographY), GOME1, and GOME2 (Global Ozone Monitoring Experiment), high quality absorption cross section spectra is a pre-requisite. Laboratory measurements of cross section spectra of O3 (at 203K, 223K, 243K, 273K and 293K) were performed using CATGAS (Calibration Apparatus for Trace Gas Absorption Spec-troscopy) under representative in-flight conditions with SCIAMACHY and GOME-2 spectrom-eters to obviate the need of an instrumental slit function correction. For the data acquired from the CATGAS campaigns, a re-analysis is carried out to improve the overestimation in the total O3 retrieval by SCIAMACHY and GOME2 using the flight model (FM) reference data from SCIAMACHY and GOME2, respectively, with respect to GOME1. The reanalysis attempts to re-evaluate the concatenation of ozone optical density measurements obtained from CATGAS measurements and applying new ways to absolutely calibrate the cross-.sections using absolute reference cross-section data at reference wavelengths, Finally, a satellite retrieval error analy-sis will be performed to validate the updated satellite reference cross-sections. The updated reference data can be used for combining the data from the three instruments (plus the two upcoming GOME-2) generating a consisting long-term dataset of total ozone.

  2. Enhancement of the dissolution rate and gastrointestinal absorption of pranlukast as a model poorly water-soluble drug by grinding with gelatin.

    Chono, Sumio; Takeda, Eri; Seki, Toshinobu; Morimoto, Kazuhiro

    2008-01-22

    The effect of grinding with gelatin on the dissolution behavior and gastrointestinal absorption of a poorly water-soluble drug was evaluated using the antiasthmatic agent, pranlukast, as a model poorly water-soluble drug. A ground pranlukast-gelatin mixture was prepared by grinding equal quantities of pranlukast and gelatin. In the dissolution testing, the dissolution rate of pranlukast in the suspension of the ground pranlukast-gelatin mixture under conditions of pH 3.0, 5.0 and 7.0 was markedly faster than that in the suspension of pranlukast. According to powder X-ray diffractometry (PXRD) and differential scanning calorimetry (DSC) analysis, the enhanced dissolution rate of pranlukast produced by grinding with gelatin was caused by changing the crystalline state of pranlukast into an amorphous state. In an animal experiment, the bioavailability of pranlukast following oral administration of the ground pranlukast-gelatin mixture to rats was threefold greater than that following administration of pranlukast. In the in vitro permeation experiment, the amount of permeated pranlukast through Caco-2 cell monolayers after application of the ground pranlukast-gelatin mixture was greater than that after application of pranlukast. These results suggest that the enhancement of the gastrointestinal absorption of pranlukast by grinding with gelatin is due to enhancement of the dissolution rate. Grinding a poorly water-soluble drug with gelatin is a useful method of enhancing its gastrointestinal absorption.

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

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

    2015-05-20

    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 absorption processes are largely determined by the one-photon absorption strength, whereas all even-photon absorption strengths are largely dominated by the two-photon absorption strength, in both cases modulated by powers of the polarizability of the final excited state. We demonstrate how to selectively enhance a specific multiphoton absorption process.

  4. 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 dev......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...... a 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......% of the alkylresorcinol dose was recovered in the lymph. DHPPA was identified in both human ileostomal effluent and pig bile, indicating availability of DHPPA for absorption and enterohepatic circulation.Conclusion: Intact alkylresorcinols have advantages over DHBA and DHPPA as plasma biomarkers for whole-grain wheat...

  5. 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.)

  6. 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...

  7. Simulation model of absorption and scattering properties of laser light applied to urban aerosols over the city of Popayan, Colombia

    Bastidas, Alvaro E.; Rodriguez, Edith; Jaramillo, Mauricio; Solarte, Efrain

    2004-11-01

    Aerosols are among the most spatially variable components of the atmosphere, and thus their study requires their monitoring over a broad geographic range. The backscattering of light from suspended solid and liquid particles in the atmosphere obeys Mie scattering theory. Light attenuation in the spectral region from 300 to 4000 nm due to Mie scattering exceeds that due to molecular (Rayleigh) scattering and ozone absorption combined. This occurs despite the fact that aerosol particle concentrations in the atmosphere are many orders of magnitude smaller than molecular concentrations. Starting from the characteristics of urban aerosols measured over the city of Popayan, Colombia), 2° 27" N; 76° 37' W, with a PM10 particle selector, we present the results of a study of light attenuation properties generated using Matlab computer code, to simulate and predict measurements with a Lidar system operating at 514.5 nm.

  8. 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.

  9. 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.

  10. 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) (∼1690 cm-1) the Cdbnd O stretching modes at unhydrated groups, (ii) (1655-1673 cm-1) the Cdbnd O 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) (∼1640 cm-1) the Cdbnd O 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 < 50 μg ml-1) corresponds to solution spectra indicating that native collagen molecules interact with water adsorbed on the titania surface. In films prepared from solutions (c ⩾ 50 μg ml-1) collagen multilayers are formed. The amide I mode is blue-shifted by 18 cm-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.

  11. 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

    2015-03-05

    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.

  12. Light absorption engineering of hydrogenated nanocrystalline silicon by femtosecond laser.

    Zheng, D Q; Ma, Y J; Xu, L; Su, W A; Ye, Q H; Oh, J I; Shen, W Z

    2012-09-01

    The light absorption coefficient of hydrogenated nanocrystalline silicon has been engineered to have a Gaussian distribution by means of absorption modification using a femtosecond laser. The absorption-modified sample exhibits a significant absorption enhancement of up to ∼700%, and the strong absorption does not depend on the incident light. We propose a model responsible for this interesting behavior. In addition, we present an optical limiter constructed through this absorption engineering method.

  13. A complete multi-scale simulation of light absorption within a fluidized bed photoreactor using integrated particle, fluid and photon behaviour models.

    Braham, R J; Harris, A T

    2013-08-07

    Photocatalysis is a process that offers the ability to degrade a wide range of pollutants through a non-intensive process using renewable light sources. Despite this promise, in practice the take-up of photocatalysis has been slow, in part because little work has been done on the optimal design of photocatalytic reactors. The use of fluidized beds for photocatalytic applications has many advantages through their high illuminated surface area, reduced mass transfer constraints and retention of the photocatalyst. However this photoreactor design has received little attention compared to other possible designs, especially in regards to modelling and simulation. The models that have been developed simplify the behaviour of the fluidized bed, and in doing so lose much of the dynamic behaviour of the system that would be present in most realistic operations. This report details the development of a fully simulated fluidized bed photoreactor, where the movement of the particle and fluid phases was determined by discrete element modelling and computational fluid dynamics, respectively, and the behaviour of the photons was modelled using geometric optics. The accuracy of the model was assessed comparing it to the light transmitted through an experimental fluidized bed. Previously unreported photon absorption behaviour was found, particularly in regards to how the photons are absorbed throughout the space. At lower heights of the bed the photons are overwhelmingly absorbed at the walls of the reaction volume, while higher up the bed there is a broad zone of relatively even absorption throughout the entire space. This has implications for the design of this class of reactor. Two possible fluidized bed photoreactor designs are discussed based on this effect, one having a very small reaction volume and having a very dense particle phase, while the other has large reaction volume with a more distributed particle phase.

  14. Impact of transporters in oral absorption

    Gram, Luise K; Rist, Gerda Marie; Steffansen, Bente

    2009-01-01

    was to investigate whether transporters were involved in the intestinal absorption of an organic anion A275 and to compare the impact of interactions related to transporters in the Caco-2 cell model versus the in vivo rat model of intestinal absorption. In both models, it was investigated whether intestinal...... permeation of A275 was concentration dependent and affected by inhibitors or competitive organic anions. Interactions related to transporters in intestinal permeation was clearly demonstrated in the Caco-2 cell model but was not directly evident for in vivo rat absorption. However, an observed biphasic...... in vivo absorption and a large intervariability between rats might mask a dose-dependent absorption of A275. To avoid these suggested interactions, a dose of at least 10 mg/kg, which saturates the intestinal transporters involved in A275 absorption, should be administered, but at doses below that the risk...

  15. Effects of Gyroresonance Absorption and Self Absorption on the Gyrosynchrotron Radiation Spectrum

    ZHOU Ai-Hua; SU Ying-Na; HUANG Guang-Li

    2004-01-01

    Effects of gyroresonance absorption and self absorption on the gyrosynchrotron radiation spectrum are investi gated with a model in a magnetic dipole field. It is found that the gyroresonance absorption and self absorption suppress substantially the gyrosynchrotron radiation at lower frequencies where the radio source is optically thick.The suppression of the gyroresonance absorption on the spectrum increases with the increasing temperature and density of thermal electrons. The suppression of the self absorption on the spectrum increases as increasing number density of the nonthermal electrons. The influences of the gyroresonance absorption and the self one on the spectrum are compared quantitatively. It is shown that only when the number density of the nonthermal electron reaches a higher value of about 3 × 104 cm-3 above 10keV, can the effect of the self absorption on the spectrum compare with the effect of the gyroresonance absorption.

  16. Proportion-corrected scaled voxel models for Japanese children and their application to the numerical dosimetry of specific absorption rate for frequencies from 30 MHz to 3 GHz

    Nagaoka, Tomoaki; Kunieda, Etsuo; Watanabe, Soichi

    2008-12-01

    The development of high-resolution anatomical voxel models of children is difficult given, inter alia, the ethical limitations on subjecting children to medical imaging. We instead used an existing voxel model of a Japanese adult and three-dimensional deformation to develop three voxel models that match the average body proportions of Japanese children at 3, 5 and 7 years old. The adult model was deformed to match the proportions of a child by using the measured dimensions of various body parts of children at 3, 5 and 7 years old and a free-form deformation technique. The three developed models represent average-size Japanese children of the respective ages. They consist of cubic voxels (2 mm on each side) and are segmented into 51 tissues and organs. We calculated the whole-body-averaged specific absorption rates (WBA-SARs) and tissue-averaged SARs for the child models for exposures to plane waves from 30 MHz to 3 GHz; these results were then compared with those for scaled down adult models. We also determined the incident electric-field strength required to produce the exposure equivalent to the ICNIRP basic restriction for general public exposure, i.e., a WBA-SAR of 0.08 W kg-1.

  17. Modeling of absorption and scattering properties of core -shell nanoparticles for application as nanoantenna in optical domain

    Devi, Jutika; Saikia, Rashmi; Datta, Pranayee

    2016-10-01

    The present paper describes the study of core-shell nanoparticles for application as nanoantenna in the optical domain. To obtain the absorption and extinction efficiencies as well as the angular distribution of the far field radiation pattern and the resonance wavelengths for these metal-dielectric, dielectric-metal and metal-metal core-shell nanoparticles in optical domain, we have used Finite Element Method based COMSOL Multiphysics Software and Mie Theory. From the comparative study of the extinction efficiencies of core-shell nanoparticles of different materials, it is found that for silica - gold core - shell nanoparticles, the resonant wavelength is greater than that of the gold - silver, silver-gold and gold-silica core - shell nanoparticles and also the radiation pattern of the silica-gold core-shell nanoparticle is the most suitable one from the point of view of directivity. The dielectric functions of the core and shell material as well as of the embedded matrix are extremely important and plays a very major role to tune the directivity and resonance wavelength. Such highly controllable parameters of the dielectric - metal core - shell nanoparticles make them suitable for efficient coupling of optical radiation into nanoscale structures for a broad range of applications in the field of communications.

  18. Nonlinear system identification by Gustafson-Kessel fuzzy clustering and supervised local model network learning for the drug absorption spectra process.

    Teslic, Luka; Hartmann, Benjamin; Nelles, Oliver; Skrjanc, Igor

    2011-12-01

    This paper deals with the problem of fuzzy nonlinear model identification in the framework of a local model network (LMN). A new iterative identification approach is proposed, where supervised and unsupervised learning are combined to optimize the structure of the LMN. For the purpose of fitting the cluster-centers to the process nonlinearity, the Gustafsson-Kessel (GK) fuzzy clustering, i.e., unsupervised learning, is applied. In combination with the LMN learning procedure, a new incremental method to define the number and the initial locations of the cluster centers for the GK clustering algorithm is proposed. Each data cluster corresponds to a local region of the process and is modeled with a local linear model. Since the validity functions are calculated from the fuzzy covariance matrices of the clusters, they are highly adaptable and thus the process can be described with a very sparse amount of local models, i.e., with a parsimonious LMN model. The proposed method for constructing the LMN is finally tested on a drug absorption spectral process and compared to two other methods, namely, Lolimot and Hilomot. The comparison between the experimental results when using each method shows the usefulness of the proposed identification algorithm.

  19. 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.

  20. 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...

  1. Transport of sennosides and sennidines from Cassia angustifolia and Cassia senna across Caco-2 monolayers--an in vitro model for intestinal absorption.

    Waltenberger, B; Avula, B; Ganzera, M; Khan, I A; Stuppner, H; Khan, S I

    2008-05-01

    Laxative effects of Senna preparations are mainly mediated by rheinanthrone, a metabolite formed in the intestinal flora from dianthrones. Nevertheless, it was not clear whether dianthrones are bioavailable at all and contribute to the overall effects of this important medicinal plant. Using the Caco-2 human colonic cell line as an in vitro model of the human intestinal mucosal barrier, the bioavailability of dianthrones was studied in apical to basolateral (absorptive) and basolateral to apical (secretive) direction. Permeability coefficients (P(c)) and percent transport were calculated based on quantitations by HPLC. From the data obtained it was concluded that sennosides A and B, as well as their aglycones sennidine A and B are transported through the Caco-2 monolayers in a concentration-dependent manner and their transport was linear with time. The absorption in apical to basolateral direction was poor and P(c) values were comparable to mannitol. The transport was higher in the secretory direction, indicating a significant efflux (e.g. by efflux pumps) of the (poorly) absorbed compounds in the intestinal lumen again. Our findings support the general understanding that the laxative effects of Senna are explainable mainly by metabolites and not by the natively present dianthrones.

  2. Estimation of rhG-CSF absorption kinetics after subcutaneous administration using a modified Wagner-Nelson method with a nonlinear elimination model.

    Hayashi, N; Aso, H; Higashida, M; Kinoshita, H; Ohdo, S; Yukawa, E; Higuchi, S

    2001-05-01

    The clearance of recombinant human granulocyte-colony stimulating factor (rhG-CSF) is known to decrease with dose increase, and to be saturable. The average clearance after intravenous administration will be lower than that after subcutaneous administration. Therefore, the apparent absolute bioavailability with subcutaneous administration calculated from the AUC ratio is expected to be an underestimate. The absorption pharmacokinetics after subcutaneous administration was examined using the results of the bioequivalency study between two rhG-CSF formulations with a dose of 2 microg/kg. The analysis was performed using a modified Wagner-Nelson method with the nonlinear elimination model. The apparent absolute bioavailability for subcutaneous administration was 56.9 and 67.5% for each formulation, and the ratio between them was approximately 120%. The true absolute bioavailability was, however, estimated to be 89.8 and 96.9%, respectively, and the ratio was approximately 108%. The absorption pattern was applied to other doses, and the predicted clearance values for subcutaneous and intravenous administrations were then similar to the values for several doses reported in the literature. The underestimation of bioavailability was around 30%, and the amplification of difference was 2.5 times, from 8 to 20%, because of the nonlinear pharmacokinetics. The neutrophil increases for each formulation were identical, despite the different bioavailabilities. The reason for this is probably that the amount eliminated through the saturable process, which might indicate the amount consumed by the G-CSF receptor, was identical for each formulation.

  3. 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.

    2013-01-01

    V, 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...

  4. 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.

  5. 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;

    2014-01-01

    comparable to freshly isolated porcine intestinal mucus (PIM). Further, this multicomponent biosimilar mucus mixture was optimized with regards to the lipid content in order to obtain cellular biocompatibility with well-differentiated Caco-2 cell monolayers. In contrast, PIM was found to severely disrupt...... 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....

  6. Modeling optical properties of polymer-solvent complexes: the chloroform influence on the P3HT and N2200 absorption spectra.

    Dias Ledo, Rodrigo Maia; Leal, Luciano Almeida; de Brito Silva, Patrick Pascoal; da Cunha, Wiliam Ferreira; de Souza, Leonardo Evaristo; Almeida Fonseca, Antonio Luciano; Ceschin, Artemis Marti; da Silva Filho, Demétrio Antonio; Ribeiro Junior, Luiz Antonio

    2017-02-01

    The optical properties of polymer/solvent systems composed by the polymers P3HT and PolyeraActivInk N2200 under the present of chloroform as solvent are experimentally and theoretically investigated using UV-Vis spectroscopy, molecular dynamics (MD), and density functional theory (DFT) calculations. The study is focused on obtaining the theoretical methodologies that properly describes the experimentally obtained absorption spectra of polymer-solvent complexes. In order to investigate the solvent influence, two different approaches are taken into account: the solvation shell method (SSM) and the polarizable continuum model (PCM). Our findings shown that SSM simulations, which combine MD and DFT calculations, are in good agreement with the experimental data. Moreover, it is obtained that simulations in the framework of PCM do not provide a fair description of the real system. Importantly, these results may pave the way for better descriptions of some optoelectronic properties of interest in polymer/solvent systems. Graphical Abstract ᅟ.

  7. 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.

  8. 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 ...

  9. 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.

    Seim, Gretchen L; Ahn, Cedric I; Bodis, Mary S; Luwedde, Flavia; Miller, Dennis D; Hillier, Stephen; Tako, Elad; Glahn, Raymond P; Young, Sera L

    2013-08-01

    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 these hypotheses by measuring Fe concentration and relative bioavailable Fe content of 12 samples of geophagic earth and 4 samples of pure clay minerals. Further, we assessed the impact of these samples on the bioavailability of Fe from an Fe-rich test meal (cooked white beans, WB). Fe concentrations were measured with inductively coupled plasma atomic emission spectroscopy. Fe bioavailability was determined using an in vitro digestion/Caco-2 cell model in which ferritin formation was used as an index of Fe bioavailability. Geophagic earth and clay mineral samples were evaluated with this model, both alone and in combination with WB (1 : 16 ratio, sample : WB). Median Fe concentration of the geophagic earth was 3485 (IQR 2462, 14 ,571) μg g⁻¹ and mean Fe concentration in the clay minerals was 2791 (±1782) μg g⁻¹. All specimens had Fe concentrations significantly higher (p ≤ 0.005) than the Fe concentration of WB (77 μg g⁻¹). Ferritin formation (i.e. Fe uptake) in cells exposed to geophagic earths and clay minerals was significantly lower than in cells exposed to WB (p ≤ 0.05) and Fe uptake responses of 11 of the 16 samples were not significantly different from the blank, indicating no bioavailable Fe. When samples were combined with WB, 5 of 16 had mean ferritin levels that were significantly lower (p ≤ 0.05, one tail) than the WB alone, indicating that the samples inhibited Fe uptake from the WB. None of the ferritin responses of cells exposed to both WB and earth/clay were significantly higher than WB alone. Thus, although geophagic earths and mineral clays are high in total Fe, very little of this Fe is bioavailable. Further, some

  10. Lyman-alpha Absorption from Heliosheath Neutrals

    Wood, B E; Linsky, J L; Malama, Y G; Wood, Brian E.; Izmodenov, Vladislav V.; Linsky, Jeffrey L.; Malama, Yury G.

    2006-01-01

    We assess what information HST observations of stellar Ly-alpha lines can provide on the heliosheath, the region of the heliosphere between the termination shock and heliopause. To search for evidence of heliosheath absorption, we conduct a systematic inspection of stellar Ly-alpha lines reconstructed after correcting for ISM absorption (and heliospheric/astrospheric absorption, if present). Most of the stellar lines are well centered on the stellar radial velocity, as expected, but the three lines of sight with the most downwind orientations relative to the ISM flow (Chi1 Ori, HD 28205, and HD 28568) have significantly blueshifted Ly-alpha lines. Since it is in downwind directions where heliosheath absorption should be strongest, the blueshifts are almost certainly caused by previously undetected heliosheath absorption. We make an initial comparison between the heliosheath absorption and the predictions of a pair of heliospheric models. A model with a complex multi-component treatment of plasma within the he...

  11. Analysis of frequency dependent pump light absorption

    Wohlmuth, Matthias; Pflaum, Christoph

    2011-03-01

    Simulations have to accurately model thermal lensing in order to help improving resonator design of diode pumped solid state lasers. To this end, a precise description of the pump light absorption is an important prerequisite. In this paper, we discuss the frequency dependency of the pump light absorption in the laser crystal and its influence on the simulated laser performance. The results show that the pump light absorption has to include the spectral overlap of the emitting pump source and the absorbing laser material. This information can either be used for a fully frequency dependent absorption model or, at least in the shown examples, to compute an effective value for an exponential Beer-Lambert law of absorption. This is particularly significant at pump wavelengths coinciding with a peak of absorption. Consequences for laser stability and performance are analyzed for different pump wavelengths in a Nd:YAG laser.

  12. Assessing the absorption of new pharmaceuticals.

    Hidalgo, I J

    2001-11-01

    The advent of more efficient methods to synthesize and screen new chemical compounds is increasing the number of chemical leads identified in the drug discovery phase. Compounds with good biological activity may fail to become drugs due to insufficient oral absorption. Selection of drug development candidates with adequate absorption characteristics should increase the probability of success in the development phase. To assess the absorption potential of new chemical entities numerous in vitro and in vivo model systems have been used. Many laboratories rely on cell culture models of intestinal permeability such as, Caco-2, HT-29 and MDCK. To attempt to increase the throughput of permeability measurements, several physicochemical methods such as, immobilized artificial membrane (IAM) columns and parallel artificial membrane permeation assay (PAMPA) have been used. More recently, much attention has been given to the development of computational methods to predict drug absorption. However, it is clear that no single method will sufficient for studying drug absorption, but most likely a combination of systems will be needed. Higher throughput, less reliable methods could be used to discover 'loser' compounds, whereas lower throughput, more accurate methods could be used to optimize the absorption properties of lead compounds. Finally, accurate methods are needed to understand absorption mechanisms (efflux-limited absorption, carrier-mediated, intestinal metabolism) that may limit intestinal drug absorption. This information could be extremely valuable to medicinal chemists in the selection of favorable chemo-types. This review describes different techniques used for evaluating drug absorption and indicates their advantages and disadvantages.

  13. 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

  14. Canopy Light Absorption and Application of the Light-Use Efficiency Model of Photosynthesis in a Northern Great Plains Grassland

    Flanagan, L. B.; Sharp, E. J.; Gamon, J. A.

    2014-12-01

    The fraction of absorbed photosynthetically active radiation (fAPAR) is fundamentally important for model calculations of ecosystem productivity across large areas. The main objective of this study was to better understand factors influencing fAPAR, its relationship with seasonal variation in canopy greenness (Normalized Difference Vegetation Index (NDVI)), and the consequences of potential seasonal changes in the NDVI- fAPAR relationship for light-use efficiency model calculations of ecosystem photosynthesis in a semi-arid grassland. We used two approaches to determine fAPAR, (i) incoming and outgoing radiance measurements above and below the canopy, and (ii) an inversion approach based on incident photosynthetically active radiation and the light response curve of net ecosystem productivity (NEP) measured by eddy covariance at low light levels. The two approaches resulted in fAPAR values that were very strongly correlated during the initial development of the canopy until peak leaf area index (LAI) was reached. A strong linear relationship also occurred between fAPAR and NDVI, based on reflectance measurements made along a tram system above the grassland canopy during initial LAI development. After peak LAI, there was hysteresis in the NDVI- fAPAR relationship. Light-use efficiency model calculations of ecosystem photosynthesis made using fAPAR values were strongly correlated with chamber CO2 exchange measurements during the initial development of the canopy leaf area. After peak LAI, a relative stress function, based on either soil moisture or vapour pressure deficit (VPD) measurements, was necessary to reduce quantum yield and model calculations of ecosystem photosynthesis during periods of relatively low soil moisture and higher VPD later in the growing season. Both stress functions were similarly effective in improving the correlation between modeled and measured ecosystem photosynthesis values.

  15. 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)

  16. A Three-dimensional Heterogeneous Mass Transfer Model for the Absorption of Gas into Multiphase System%多项体系气体吸收的三维非均相传质模型

    蔡旺锋; 张丹; 许春建; 周明

    2005-01-01

    A three-dimensional heterogeneous mass transfer model was proposed to investigate the enhancement of dispersed particles on gas absorption. The strategy to calculate local and overall enhancement factors is proposed.Instead of a global grid, the composite overlapping grid is adopted, which simplifies the setup and solution of the three-dimensional model equations. It is found that dispersed particle hold-up, particle size, liquid-solid partition coefficient of transported component, characteristic contact time, and the shortest distance between particles and gas-liquid interface have major influence on absorption enhancement factor. The particle-particle interaction on gas absorption and the lateral diffusion of transported component in liquid film were studied with the multi-particle simulation. The proposed model predicted the experimental data from the literature reasonably well.

  17. Electromodulated absorption in smoky quartz

    Brom, W.E. van den; Volger, J.

    1974-01-01

    The optical absorption coefficient of “smoky” quartz (containing aluminium) can be modulated by applying an electric field. The effect saturates at high fields and low temperatures and reaches a maximum at 535 nm. The results are discussed in terms of a model consisting of a colour centre, dipolar i

  18. Solar spectral optical properties of pigments--Part I: model forderiving scattering and absorption coefficients from transmittance andreflectance measurements

    Levinson, Ronnen; Berdahl, Paul; Akbari, Hashem

    2004-06-01

    Pigment characterization is performed by dispersing thepigment into a transparent film of refractive index 1.5, andmeasuringspectral transmittance and reflectance. Measurements of the filmreflectance backed with black and white substrates are also used. A modelfor extracting the spectral backscattering coefficient S and absorptioncoefficient K from spectrometer measurements is presented. Interfacereflectances complicate the model. The film's diffuse reflectance andtransmittance measurements are used to determine S and K as functions ofa model parameter sigma that represents the ratio of forward to totalscattering. Sigma is used to estimate the rate at which incidentcollimated light becomes diffuse, and is determined by fitting themeasured film reflectance backed by black. A typical value is sigma=0.8.Then, the measured film reflectance backed by white is compared with acomputed value as a self-consistency check. Measurements on severalcommon pigments are used to illustrate the method.

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

    Mahmoud Fathy

    2016-07-01

    Full Text Available Abstract 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.

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

    Nielsen, Jesper Bo

    2010-01-01

    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 also......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...

  1. Justification of Drug Product Dissolution Rate and Drug Substance Particle Size Specifications Based on Absorption PBPK Modeling for Lesinurad Immediate Release Tablets.

    Pepin, Xavier J H; Flanagan, Talia R; Holt, David J; Eidelman, Anna; Treacy, Don; Rowlings, Colin E

    2016-09-01

    In silico absorption modeling has been performed, to assess the impact of in vitro dissolution on in vivo performance for ZURAMPIC (lesinurad) tablets. The dissolution profiles of lesinurad tablets generated using the quality control method were used as an input to a GastroPlus model to estimate in vivo dissolution in the various parts of the GI tract and predict human exposure. A model was set up, which accounts for differences of dosage form transit, dissolution, local pH in the GI tract, and fluid volumes available for dissolution. The predictive ability of the model was demonstrated by confirming that it can reproduce the Cmax observed for independent clinical trial. The model also indicated that drug product batches that pass the proposed dissolution specification of Q = 80% in 30 min are anticipated to be bioequivalent to the clinical reference batch. To further explore the dissolution space, additional simulations were performed using a theoretical dissolution profile below the proposed specification. The GastroPlus modeling indicates that such a batch will also be bioequivalent to standard clinical batches despite having a dissolution profile, which would fail the proposed dissolution specification of Q = 80% in 30 min. This demonstrates that the proposed dissolution specification sits comfortably within a region of dissolution performance where bioequivalence is anticipated and is not near an edge of failure for dissolution, providing additional confidence to the proposed specifications. Finally, simulations were performed using a virtual drug substance batch with a particle size distribution at the limit of the proposed specification for particle size. Based on these simulations, such a batch is also anticipated to be bioequivalent to clinical reference, demonstrating that the proposed specification limits for particle size distribution would give products bioequivalent to the pivotal clinical batches.

  2. 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...

  3. 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.

  4. Synchrotron radiation and long path cryogenic cells: New tools and results for modelling SF6 absorption in the 10μm atmospheric window

    Faye, Mbaye; Boudon, Vincent; Loete, Michel; Roy, Pascale; Manceron, Laurent

    2015-04-01

    Sulfur hexa?uoride (SF6) is a heavy and stable molecule used in many sectors, such as the electrical industry, but also as a gas tracer to model air masse motions in the Earth atmosphere. This anthropogenic species is also an atmospheric pollutant owing to its greenhouse effect capability. Although its six fundamental modes have been largely studied up to now, it is not the case for the numerous hot bands that represent the most important part of the SF6 spectrum at room temperature. So, to model correctly the SF6 atmospheric absorption requires the knowledge of the spectroscopic parameters of all states involved in these hot bands. Nevertheless, due to their overlapping, a direct analysis of the hot bands near the 10,5μm absorption of SF6 in the atmospheric window is not possible. It is necessary to use another strategy, gathering information in the far and mid infrared regions on initial and final states to recompute the relevant total absorption. Here, we present new results of an analysis of spectra recorded at the AILES beam line at the SOLEIL Synchrotron facility. For these measurements, we used a IFS125HR interferometer in the 100 - 3200 cm-1 range, coupled to a cryogenic multiple pass cell [1]. The optical path length was adjusted to 93m; the SF6 sample was cooled down to 153 K. We could record 17 rovibrational bands of SF6 in this region with a resolution of 0.0025 cm-1. These results allowed us to perform the detailed analysis of several bands. Adding to previous knowledge on ν3, ν2, 2ν3 and new results on 3ν3, 2ν1 + ν3, ν1 + ν3, ν2 + ν3, ν3 - ν2 , ν3 - ν1 , we developed a global fit of the ν1, ν2, ν3 parameters, thus permitting the modelling of the ν3 + ν1 - ν1, ν3 + ν2 - ν2 hot bands. New information has also been obtained on ν6 and ν3 + ν5 and another strategy will be detailed to model the more important ν3 + ν5 - ν5 and ν3 + ν6 - ν6 hot band contributions. Including these new parameters in the XTDS model [2], we

  5. Electron tomography: a short overview with an emphasis on the absorption potential model for the forward problem

    Fanelli, D.; Öktem, O.

    2008-02-01

    This review of the development and current status of electron tomography deals mainly with the mathematical and algorithmic aspects. After a very brief description of the role of electron tomography in structural biology, we turn our attention to the derivation of the forward operator. Starting from the Schrödinger equation, the electron-specimen interaction is modelled as a diffraction tomography problem and the picture is completed by adding a description of the optical system of the transmission electron microscope. The first-order Born approximation enables one to explicitly express the intensity for any finite wavenumber in terms of the propagation operator acting on the specimen convolved with a point spread function, derived from the optics in the transmission electron microscope. Next, we focus on the difficulties that cause the reconstruction problem to be quite challenging. Special emphasis is put on explaining the extremely low signal-to-noise ratio in the data combined with the incomplete data problems, which lead to severe ill-posedness. The next step is to derive the standard phase contrast model used in the electron tomography community. The above-mentioned expression for the intensity generalizes the standard phase contrast model which can be obtained by replacing the propagation operator by its high-energy limit, the x-ray transform, as the wavenumber tends to infinity. The importance of more carefully including the wave nature of the electron-specimen interaction is supported by performing an asymptotic analysis of the intensity as the wavenumber tends to infinity. Next we provide an overview of the various reconstruction methods that have been employed in electron tomography and we conclude by mentioning a number of open problems. Besides providing an introduction to electron tomography written in the 'language of inverse problems', the authors hope to raise interest among experts in integral geometry and regularization theory for the

  6. Toward Improving Atmospheric Models and Ozone Projections: Laboratory UV Absorption Cross Sections and Equilibrium Constant of ClOOCl

    Wilmouth, D. M.; Klobas, J. E.; Anderson, J. G.

    2015-12-01

    Thirty years have now passed since the discovery of the Antarctic ozone hole, and despite comprehensive international agreements being in place to phase out CFCs and halons, polar ozone losses generally remain severe. The relevant halogen compounds have very long atmospheric lifetimes, which ensures that seasonal polar ozone depletion will likely continue for decades to come. Changes in the climate system can further impact stratospheric ozone abundance through changes in the temperature and water vapor structure of the atmosphere and through the potential initiation of solar radiation management efforts. In many ways, the rate at which climate is changing must now be considered fast relative to the slow removal of halogens from the atmosphere. Photochemical models of Earth's atmosphere play a critical role in understanding and projecting ozone levels, but in order for these models to be accurate, they must be built on a foundation of accurate laboratory data. ClOOCl is the centerpiece of the catalytic cycle that accounts for more than 50% of the chlorine-catalyzed ozone loss in the Arctic and Antarctic stratosphere every spring, and so uncertainties in the ultraviolet cross sections of ClOOCl are particularly important. Additionally, the equilibrium constant of the dimerization reaction of ClO merits further study, as there are important discrepancies between in situ measurements and lab-based models, and the JPL-11 recommended equilibrium constant includes high error bars at atmospherically relevant temperatures (~75% at 200 K). Here we analyze available data for the ClOOCl ultraviolet cross sections and equilibrium constant and present new laboratory spectroscopic results.

  7. Predicting absorption and dispersion in acoustics by direct simulation Monte Carlo: Quantum and classical models for molecular relaxation.

    Hanford, Amanda D; O'Connor, Patrick D; Anderson, James B; Long, Lyle N

    2008-06-01

    In the current study, real gas effects in the propagation of sound waves are simulated using the direct simulation Monte Carlo method for a wide range of frequencies. This particle method allows for treatment of acoustic phenomena at high Knudsen numbers, corresponding to low densities and a high ratio of the molecular mean free path to wavelength. Different methods to model the internal degrees of freedom of diatomic molecules and the exchange of translational, rotational and vibrational energies in collisions are employed in the current simulations of a diatomic gas. One of these methods is the fully classical rigid-rotor/harmonic-oscillator model for rotation and vibration. A second method takes into account the discrete quantum energy levels for vibration with the closely spaced rotational levels classically treated. This method gives a more realistic representation of the internal structure of diatomic and polyatomic molecules. Applications of these methods are investigated in diatomic nitrogen gas in order to study the propagation of sound and its attenuation and dispersion along with their dependence on temperature. With the direct simulation method, significant deviations from continuum predictions are also observed for high Knudsen number flows.

  8. 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.

  9. Mechanism for enhanced absorption of a solid dispersion formulation of LY2300559 using the artificial stomach duodenum model.

    Polster, Christopher S; Wu, Sy-Juen; Gueorguieva, Ivelina; Sperry, David C

    2015-04-06

    An artificial stomach duodenum (ASD) model has been used to demonstrate the performance difference between two formulations of LY2300559, a low-solubility acidic developmental drug. The two formulations investigated were a conventional high-shear wet granulation (HSWG) formulation and a solid dispersion formulation. A pharmacokinetic study in humans demonstrated the enhanced performance of the solid dispersion formulation relative to the HSWG formulation. The Cmax and AUC of the solid dispersion was 2.6 and 1.9 times greater, respectively, compared to the HSWG formulation. In the ASD, the solid dispersion formulation performance was characterized by three main phases: (1) rapid release in the stomach, creating a supersaturated concentration of drug, (2) precipitation in the stomach, and (3) rapid redissolution of the precipitate in the duodenum to concentration levels that are supersaturated relative to crystalline drug. A series of complementary experiments were employed to describe this performance behavior mechanistically. Imaging experiments with a pH indicating dye showed that local pH gradients from meglumine in the solid dispersion formulation were responsible for creating a high initial supersaturation concentration in the stomach. Upon dissipation of meglumine, the drug precipitated in the stomach as an amorphous solid. Because the precipitated drug is in an amorphous form, it can then rapidly redissolve as it transits to the more neutral environment of the duodenum. This unexpected sequence of physical state changes gives a mechanistic explanation for the enhanced in vivo performance of the solid dispersion formulation relative to the HSWG formulation.

  10. INTEGRATION OF NPP SEMI MECHANISTIC - MODELLING, REMOTE SENSING AND CIS IN ESTIMATING CO 2 ABSORPTION OF FOREST VEGETATION IN LORE LINDU NATIONAL PARK

    GODE GRAVENHORsr

    2006-01-01

    Full Text Available Net Primary Production, NPP, is one of the most important variables characterizing the performance of an ecosystem. It is the difference between the total carbon uptake from the air through photosynthesis and the carbon loss due to respiration by living plants. However, field measurements of NPP are time-consuming and expensive. Current techniques are therefore not useful for obtaining NPP estimates over large areas. By combining the remote sensing and GIS technology and modelling, we can estimate NPP of a large ecosystem with a little ease. This paper discusses the use of a process based physiological sunshade canopy models in estimating NPP of Lore Lindu National Park (LLNP. The discussion includes on how to parameterize the models and how to scale up from leaf to the canopy. The version documented in this manuscript is called NetPro Model, which is a potential NPP model where water effect is not included yet. The model integrates CIS and the use of Remote Sensing, and written in Visual Basic 6.0 programming language and Map Objects 2.1. NetPro has the capability of estimating NPP of Cs vegetation under present environmental condition and under future scenarios (increasing [CO2], increasing temperature and increasing or decreasing leaf nitrogen level. Based on site-measured parameterisation of VaM* (Photosynthetic capacity, /Jj (Respiration and leaf nitrogen ONi, the model was run under increasing CO2 level and temperature and varied leaf nitrogen. The output of the semi-mechanistic modelling is radiation use efficiency (?. Analysis of remote sensing data give Normalized Difference Vegetation Index (NDVI and related Leaf Area Index (LAI and traction of absorbed Photosynthetically Active Radiation (/M > AK. Climate data are obtained from 12 meteorological stations around die parks, which includes global radiations, minimum and maximum temperature. CO2 absorbed by vegetation (Gross Primary Production, GPP is then calculated using the above

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. Bioacoustic Absorption Spectroscopy

    2016-06-07

    frequencies (Ching and Weston, 1971). RESULTS Measured resonance frequencies of absorption lines, which were attributed to adult (~ 1.3 khz) and juvenile ...of adult and juvenile sardines. These results suggest that bioacoustic absorption spectroscopy measurements permit isolation of juvenile from adult...from broadband tomographic transmission loss measurements over large areas . 2. Depths of sardines and contours of phytoplankton concentrations vs. time

  17. The HI absorption "Zoo"

    Geréb, K.; Maccagni, F. M.; Morganti, R.; Oosterloo, T. A.

    2015-01-01

    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 o

  18. Oxygen Absorption in Cooling Flows.

    Buote

    2000-04-01

    The inhomogeneous cooling flow scenario predicts the existence of large quantities of gas in massive elliptical galaxies, groups, and clusters that have cooled and dropped out of the flow. Using spatially resolved, deprojected X-ray spectra from the ROSAT PSPC, we have detected strong absorption over energies approximately 0.4-0.8 keV intrinsic to the central approximately 1&arcmin; of the galaxy NGC 1399, the group NGC 5044, and the cluster A1795. These systems have among the largest nearby cooling flows in their respective classes and low Galactic columns. Since no excess absorption is indicated for energies below approximately 0.4 keV, the most reasonable model for the absorber is warm, collisionally ionized gas with T=105-106 K in which ionized states of oxygen provide most of the absorption. Attributing the absorption only to ionized gas reconciles the large columns of cold H and He inferred from Einstein and ASCA with the lack of such columns inferred from ROSAT and also is consistent with the negligible atomic and molecular H inferred from H i and CO observations of cooling flows. The prediction of warm ionized gas as the product of mass dropout in these and other cooling flows can be verified by Chandra and X-Ray Multimirror Mission.

  19. Geometrical interpretation of optical absorption

    Monzon, J. J.; Barriuso, A. G.; Sanchez-Soto, L. L. [Departamento de Optica, Facultad de Fisica, Universidad Complutense, E-28040 Madrid (Spain); Montesinos-Amilibia, J. M. [Departamento de Geometria y Topologia, Facultad de Matematicas, Universidad Complutense, E-28040 Madrid (Spain)

    2011-08-15

    We reinterpret the transfer matrix for an absorbing system in very simple geometrical terms. In appropriate variables, the system appears as performing a Lorentz transformation in a (1 + 3)-dimensional space. Using homogeneous coordinates, we map that action on the unit sphere, which is at the realm of the Klein model of hyperbolic geometry. The effects of absorption appear then as a loxodromic transformation, that is, a rhumb line crossing all the meridians at the same angle.

  20. Non-linear absorption of 1.3-μm wavelength femtosecond laser pulses focused inside semiconductors: Finite difference time domain-two temperature model combined computational study

    Bogatyrev, I. B.; Grojo, D.; Delaporte, P.; Leyder, S.; Sentis, M.; Marine, W.; Itina, T. E.

    2011-11-01

    We present a theoretical model, which describes local energy deposition inside IR-transparent silicon and gallium arsenide with focused 1.3-μm wavelength femtosecond laser pulses. Our work relies on the ionization rate equation and two temperature model (TTM), as we simulate the non-linear propagation of focused femtosecond light pulses by using a 3D finite difference time domain method. We find a strong absorption dependence on the initial free electron density (doping concentration) that evidences the role of avalanche ionization. Despite an influence of Kerr-type self-focusing at intensity required for non-linear absorption, we show the laser energy deposition remains confined when the focus position is moved down to 1-mm below the surface. Our simulation results are in agreement with the degree of control observed in a simple model experiment.

  1. 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

  2. Aerosol absorption and radiative forcing

    P. Stier

    2007-05-01

    Full Text Available We present a comprehensive examination of aerosol absorption with a focus on evaluating the sensitivity of the global distribution of aerosol absorption to key uncertainties in the process representation. For this purpose we extended the comprehensive aerosol-climate model ECHAM5-HAM by effective medium approximations for the calculation of aerosol effective refractive indices, updated black carbon refractive indices, new cloud radiative properties considering the effect of aerosol inclusions, as well as by modules for the calculation of long-wave aerosol radiative properties and instantaneous aerosol forcing. The evaluation of the simulated aerosol absorption optical depth with the AERONET sun-photometer network shows a good agreement in the large scale global patterns. On a regional basis it becomes evident that the update of the BC refractive indices to Bond and Bergstrom (2006 significantly improves the previous underestimation of the aerosol absorption optical depth. In the global annual-mean, absorption acts to reduce the short-wave anthropogenic aerosol top-of-atmosphere (TOA radiative forcing clear-sky from –0.79 to –0.53 W m−2 (33% and all-sky from –0.47 to –0.13 W m−2 (72%. Our results confirm that basic assumptions about the BC refractive index play a key role for aerosol absorption and radiative forcing. The effect of the usage of more accurate effective medium approximations is comparably small. We demonstrate that the diversity in the AeroCom land-surface albedo fields contributes to the uncertainty in the simulated anthropogenic aerosol radiative forcings: the usage of an upper versus lower bound of the AeroCom land albedos introduces a global annual-mean TOA forcing range of 0.19 W m−2 (36% clear-sky and of 0.12 W m−2 (92% all-sky. The consideration of black carbon inclusions on cloud radiative properties results in a small global annual-mean all-sky absorption of 0.05 W

  3. Bioaccessibility of nitro- and oxy-PAHs in fuel soot assessed by an in vitro digestive model with absorptive sink.

    Zhang, Yanyan; Pignatello, Joseph J; Tao, Shu

    2016-11-01

    Ingestion of soot present in soil or other environmental particles is expected to be an important route of exposure to nitro and oxygenated derivatives of polycyclic aromatic hydrocarbons (PAHs). We measured the apparent bioaccessibility (Bapp) of native concentrations of 1-nitropyrene (1N-PYR), 9-fluorenone (9FLO), anthracene-9,10-dione (ATQ), benzo[a]anthracene-7,12-dione (BaAQ), and benzanthrone (BZO) in a composite fuel soot sample using a previously-developed in vitro human gastrointestinal model that includes silicone sheet as a third-phase absorptive sink. Along with Bapp, we determined the 24-h sheet-digestive fluid partition coefficient (Ks,24h), the soot residue-fluid distribution ratio of the labile sorbed fraction after digestion (Kr,lab), and the maximum possible (limiting) bioaccessibility, Blim. The Bapp of PAH derivatives was positively affected by the presence of the sheet due to mass-action removal of the sorbed compounds. In all cases Bapp increased with imposition of fed conditions. The enhancement of Bapp under fed conditions is due to increasingly favorable mass transfer of target compounds from soot to fluid (increasing bile acid concentration, or adding food lipids) or transfer from fluid to sheet (by raising small intestinal pH). Food lipids may also enhance Bapp by mobilizing contaminants from nonlabile to labile states of the soot. Compared to the parent PAH, the derivatives had larger Kr,lab, despite having lower partition coefficients to various hydrophobic reference phases including silicone sheet. The Blim of the derivatives under the default conditions of the model ranged from 65.5% to 34.4%, in the order, 1N-PYR > ATQ > 9FLO > BZO > BaAQ, with no significant correlation with hydrophobic parameters, nor consistent relationship with Blim of the parent PAH. Consistent with earlier experiments on a wider range of PAHs, the results suggest that a major determinant of bioaccessibility is the distribution of chemical between

  4. Modelling of the electron density profile in the lowest part of ionosphere D-region on the basis of radiowave absorption data. 1. Theoretical model.

    Mukhtarov, P.; Pancheva, D.

    1996-11-01

    A simplified full-wave method adapted to the propagation of very obliquely incident LF radio waves is developed. For a selected ionosphere model the wave-field structure is calculated inside a horizontally stratified ionosphere and the peculiarities of the reflected field are clearly described. The penetration of the investigated radio waves in the lower ionosphere at noon-time is found to be restricted to a layer several wavelengths thick. The reflected wave is created entirely by the mechanism of partial reflections and the region responsible for its formation is usually below 70 km. The influence of some typical parameters of the electron density profile, as well as the atmospheric pressure and temperature, on the attenuation of the investigated radio waves is demonstrated. It is also found that the reflection at very oblique incidence depends mainly on the height of the bottom of the ionosphere.

  5. Sound absorption mapping of highway noise barrier

    Grosso, Andrea

    2012-01-01

    International audience; Sound propagation from highway to the urban areas can be reduced using noise barriers. The general computational modeling takes typically into account sound ray lines, reflection and diffraction, although the absorption distribution over the surface in not considered. The sound absorption coefficient can be calculated using a PU probe, by the impedance measured “in situ” close by the surface. Well known methods are available on the market for estimating the sound absor...

  6. 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 ...

  7. Dietary amino acids fed in free form or as protein do differently affect amino acid absorption in a rat everted sac model

    Nolles, J.A.; Peeters, I.G.S.; Bremer, B.I.; Moorman, R.; Koopmanschap, R.E.; Verstegen, M.W.A.; Schreurs, V.V.A.M.

    2008-01-01

    In the present study, the effect of free amino acid (FAA) diets on the intestinal absorption rate of methionine and leucine was studied 'ex vivo' with rats adapted for different periods of time to the diets, using the everted sac method. The adaptation period to the 21% FAA diet with an amino acid c

  8. 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.

  9. 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...

  10. Effect of phytate reduction of sorghum, through genetic modification, on iron and zinc availability as assessed by an in vitro dialysability bioaccessibility assay, Caco-2 cell uptake assay, and suckling rat pup absorption model.

    Kruger, Johanita; Taylor, John R N; Du, Xiaogu; De Moura, Fabiana F; Lönnerdal, Bo; Oelofse, André

    2013-11-15

    Improved iron and zinc availability from sorghum, a commonly consumed staple, will benefit many malnourished communities in rural Africa burdened with high prevalence of iron and zinc deficiency. This research compared the effect of genetic phytate reduction in sorghum on iron and zinc bioaccessibility and uptake measured by in vitro dialysability and Caco-2 cell uptake assays to that of iron and zinc absorption measured by a suckling rat pup model. The phytate reduction (80-86%) in these sorghums significantly increased zinc availability. The Caco-2 cell method, but not the dialysability assay, proved useful in estimating zinc absorption. The measured increase in iron availability differed between the methods, possibly due to the effect of varying mineral (Ca, Fe, Zn, P) contents of the sorghums. This effect was most prominent in the iron uptake results. More research is needed to determine the effect of naturally occurring variations in mineral contents of sorghum on the iron uptake by Caco-2 cells.

  11. 大鼠在体肠灌流模型对豆腐果苷在体吸收的初步研究%Absorption behavior of helicid using rat in situ recirculating perfusion model

    贾元威; 谢海棠; 沈杰; 王幼林; 梁大虎; 罗强

    2011-01-01

    Aim To study helicid absorption behavior by using rat in situ recirculating perfusion model. Methods This study was built on HPLC quantitative method of helicid in Krebs-Ringer solution , and detection of phenolsulfonphthalein concentration in Krebs-Ringer solution through ultraviolet spectrophotometer model 752, using rat in situ recirculating perfusion model to do preliminary study on the absorption behavior of helicid. Results The absorption of helicid in rat ' s superior part of duodenum to inferior part of ileum in 2 hours was quick and the trend of absorption reached flat within 15 ~ 20 min. Conclusion The method successfully builds rat in situ recirculating perfusion model and makes a preliminary study on the absorption behavior of helicid, thus lays the foundation of the following research of helicid in vivo disposition situation.%目的 应用大鼠在体肠灌流模型对豆腐果苷吸收机制进行研究.方法 该实验在建立豆腐果苷在Krebs-Ringer缓冲液中的检测方法,及应用752紫外分光光度计测定Krebs-Ringer缓冲液中酚红溶液浓度的基础上,应用大鼠肠灌流模型研究豆腐果苷的吸收情况.结果 通过该模型对豆腐果苷在大鼠十二指肠上部至回肠下部肠段中2 h内吸收情况的研究发现,豆腐果苷吸收迅速,15~20 min吸收即可达到平台.结论 该实验建立了大鼠小肠灌流模型,并且将该模型用于豆腐果苷吸收情况的初步研究,为揭示豆腐果苷体内处置情况奠定了基础.

  12. 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...

  13. Study on Absorption of Theaflavin and EGCG in Caco-2 Cell Model%TF1与EGCG在Caco-2细胞中的吸收规律研究

    孟庆; 屠幼英

    2015-01-01

    为了探究茶黄素单体(TF1)与表没食子儿茶素没食子酸酯(EGCG)在生物体中的吸收规律,本实验建立了体外 Caco-2单层细胞模型,模拟小肠对 TF1与 EGCG的吸收,并研究了浓度和时间对吸收的影响。结果表明,在10~100µmol·L-1范围内,TF1与 EGCG 在 Caco-2单层细胞模型中的吸收呈现表观渗透系数 Papp随浓度增加而上升的规律。但两者的外排率也呈现同样的规律,并且外排率上升的幅度均大于二者吸收率上升的幅度。由于 TF1与 EGCG 在细胞单层模型中的 Papp 均小于1×10-6 cm·s -1,说明两者都属于难吸收的药物,但是TF1在Caco-2细胞模型中的吸收率高于EGCG。因其外排比均大于2,说明两者在细胞模型上的外排是被动转运。从吸收时间看,TF1的外排规律与EGCG一致。%In order to explore the absorption regularity of TF1 and EGCG in the organism. This research used the Caco-2 cell monolayer model in vitro to simulate the absorption of TF1 and EGCG in the small intestine. The influences of concentration and time on the absorption regularity of TF1 and EGCG in Caco-2 cell monolayer model were investigated. The results illustrated that the absorption of TF1 and EGCG in Caco-2 model showed that the apparent permeability coefficient raised with the increasing of concentrations of two compound in the range of 10~100 µ mol·L-1. The efflux rates of the TF1 and EGCG showed the same rules as absorption. However, the increasing range of efflux rate was higher than that of absorption rate. The values of Papp about TF 1 and EGCG in the cell model were lower than 1×10-6 cm·s -1, which indicated that both of them belonged to the kind of drugs which were difficult to absorb. However, with comparing the absorption rate, TF1 was higher than EGCG in this model. Both of efflux transport showed the passive process because the efflux rates of TF 1 and EGCG were larger than 2 and higher than in cell

  14. 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

    2009-12-03

    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.

  15. Continuous Light Absorption Photometer (CLAP) Final Campaign Report

    Jefferson, Anne [National Oceanic and Atmospheric Administration (NOAA), Washington, DC (United States)

    2014-05-01

    The Continuous Light Absorption Photometer (CLAP) measures the aerosol absorption of radiation at three visible wavelengths; 461, 522, and 653 nanometers (nm). Data from this measurement is used in radiative forcing calculations, atmospheric heating rates, and as a prediction of the amount of equivalent black carbon in atmospheric aerosol and in models of aerosol semi-direct forcing. Aerosol absorption measurements are essential to modeling the energy balance of the atmosphere.

  16. Aerosol scattering and absorption during the EUCAARI-LONGREX flights of the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146: can measurements and models agree?

    Highwood, E. J.; Northway, M. J.; McMeeking, G. R.; Morgan, W. T.; Liu, D.; Osborne, S.; Bower, K.; Coe, H.; Ryder, C.; Williams, P.

    2012-08-01

    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 mixed organics and

  17. 大鼠在体单向肠灌流模型研究肉桂酸肠道吸收特性%Study of intestinal absorption of cinnamic acid in one-way intestinal perfusion rat model

    杨本坤; 王素军; 曾洁; 钟运鸣; 臧林泉

    2013-01-01

    Objective To investigate the absorption characteristic of cinnamic acid in rat intestine and the influence of transporter protein on cinnamic acid absorption. Methods One-way intestinal perfusion rat model was established. HPLC was used to measure the content of cinnamon acid in intestine. The absorption rate constant (Ka) and the apparent absorption coefficient ( Peff) were obtained to analyze the absorption kinetics of cinnamon acid. Results The values of Ka and Peff of cinnamic acid in three different regions of rat intestine showed duodenum > jejunum > ileum. The values of Ka and Peff in the same region with different concentrations of cinnamic acid did not show a statistical difference. The values of Ka and Peff of cinnamic acid did not change when treated with MRP2 inhibitor (domethacin) in jejunum, but which significantly increased when treated with Pgp inhibitor ( verapamil hydrochloride) in duodenum. Conclusion Duodenum and jejunum may be the main sites of cinnamic acid absorption, by which mechanism is related to passive diffusion influenced by Pgp,but not MRP2.%目的 研究肉桂酸在大鼠肠道的吸收部位和吸收机制,以及转运蛋白对肉桂酸肠道吸收的影响.方法 建立在体单向肠灌流模型,采用HPLC法测定肉桂酸在肠道中的浓度变化,通过吸收速度常数(Ka)和表观吸收系数(Peff)来研究肉桂酸的吸收动力学特征.结果 肉桂酸在各个肠段的Ka和Peff结果为十二指肠>空肠>回肠,十二指肠和空肠的Ka和Peff值显著性高于回肠(P<0.05),不同浓度肉桂酸在同一肠段的Ka和Peff值差异无统计学意义,加入MRP2抑制剂(吲哚美辛)后Ka和Peff值差异亦无统计学意义,但加入Pgp抑制剂(盐酸维拉帕米)后其值则显著性增加.结论 十二指肠、空肠是肉桂酸吸收的主要部位,吸收机制为被动转运,肠道转运受Pgp转运蛋白的影响,但不受MRP2转运蛋白的影响.

  18. QED-driven laser absorption

    Levy, Matthew; Blackburn, T.; Ratan, N.; Sadler, J.; Ridgers, C.; Kasim, M.; Ceurvorst, L.; Holloway, J.; Baring, M.; Bell, A.; Glenzer, S.; Gregori, G.; Ilderton, A.; Marklund, M.; Tabak, M.; Wilks, S.; Norreys, P.

    2016-10-01

    Absorption covers the physical processes which convert intense photon flux into energetic particles when a high-power laser (I >1018 W cm-2 where I is intensity at 1 μm wavelength) illuminates optically-thick matter. It underpins important applications of petawatt laser systems today, e.g., in isochoric heating of materials. Next-generation lasers such as ELI are anticipated to produce quantum electrodynamical (QED) bursts of γ-rays and anti-matter via the multiphoton Breit-Wheeler process which could enable scaled laboratory probes, e.g., of black hole winds. Here, applying strong-field QED to advances in plasma kinematic theory, we present a model elucidating absorption limited only by an avalanche of self-created electron-positron pairs at ultra-high-field. The model, confirmed by multidimensional QED-PIC simulations, works over six orders of magnitude in optical intensity and reveals this cascade is initiated at 1.8 x 1025 W cm-2 using a realistic linearly-polarized laser pulse. Here the laser couples its energy into highly-collimated electrons, ions, γ-rays, and positrons at 12%, 6%, 58% and 13% efficiency, respectively. We remark on attributes of the QED plasma state and possible applications.

  19. Comparison of isorhamnetin absorption properties in total flavones of Hippophae rhamnoides L. with its pure form in a Caco-2 cell model mediated by multidrug resistance-associated protein.

    Xie, Yan; Duan, Jingze; Fu, Qingxue; Xia, Mengxin; Zhang, Lei; Li, Guowen; Wu, Tao; Ji, Guang

    2015-06-20

    Total flavones of Hippophae rhamnoides L. (TFH) are extracted from the widely distributed thorny bush Sea buckthorn (Hippophae rhamnoides L.). Isorhamnetin (IS) is one of the representative ingredients in TFH. In this study, the absorption properties of IS in TFH and its pure form were compared through transepithelial transport and cellular uptake experiments in a Caco-2 cell model. Our results show that the absorption properties of IS in TFH and its pure form were remarkably different: (1) Both PappAB and PappBA of IS in TFH were dramatically increased compared with those of IS pure form; consequently, its Pratio was 2.3-fold higher than that of IS; (2) Both the accumulation and efflux of IS in TFH were significantly enhanced compared with the single compound. One likely reason for these differences is that the multiple components in TFH significantly down regulated the mRNA expression level of MRP2, which lead to a decrease in the protein level of MRP2, based on western blotting and RT-PCR assays. This study highlights the significant differences in the absorption properties of flavonoid components in different forms and the potential multi-component interactions in TFH.

  20. Vitamin D and intestinal calcium absorption.

    Christakos, Sylvia; Dhawan, Puneet; Porta, Angela; Mady, Leila J; Seth, Tanya

    2011-12-05

    The principal function of vitamin D in calcium homeostasis is to increase calcium absorption from the intestine. Calcium is absorbed by both an active transcellular pathway, which is energy dependent, and by a passive paracellular pathway through tight junctions. 1,25Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) the hormonally active form of vitamin D, through its genomic actions, is the major stimulator of active intestinal calcium absorption which involves calcium influx, translocation of calcium through the interior of the enterocyte and basolateral extrusion of calcium by the intestinal plasma membrane pump. This article reviews recent studies that have challenged the traditional model of vitamin D mediated transcellular calcium absorption and the crucial role of specific calcium transport proteins in intestinal calcium absorption. There is also increasing evidence that 1,25(OH)(2)D(3) can enhance paracellular calcium diffusion. The influence of estrogen, prolactin, glucocorticoids and aging on intestinal calcium absorption and the role of the distal intestine in vitamin D mediated intestinal calcium absorption are also discussed.

  1. Acoustic absorption by sunspots

    Braun, D. C.; Labonte, B. J.; Duvall, T. L., Jr.

    1987-01-01

    The paper presents the initial results of a series of observations designed to probe the nature of sunspots by detecting their influence on high-degree p-mode oscillations in the surrounding photosphere. The analysis decomposes the observed oscillations into radially propagating waves described by Hankel functions in a cylindrical coordinate system centered on the sunspot. From measurements of the differences in power between waves traveling outward and inward, it is demonstrated that sunspots appear to absorb as much as 50 percent of the incoming acoustic waves. It is found that for all three sunspots observed, the amount of absorption increases linearly with horizontal wavenumber. The effect is present in p-mode oscillations with wavelengths both significantly larger and smaller than the diameter of the sunspot umbrae. Actual absorption of acoustic energy of the magnitude observed may produce measurable decreases in the power and lifetimes of high-degree p-mode oscillations during periods of high solar activity.

  2. Chaotic systems with absorption

    Altmann, Eduardo G; Tél, Tamás

    2013-01-01

    Motivated by applications in optics and acoustics we develop a dynamical-system approach to describe absorption in chaotic systems. We introduce an operator formalism from which we obtain (i) a general formula for the escape rate $\\kappa$ in terms of the natural conditionally-invariant measure of the system; (ii) an increased multifractality when compared to the spectrum of dimensions $D_q$ obtained without taking absorption and return times into account; and (iii) a generalization of the Kantz-Grassberger formula that expresses $D_1$ in terms of $\\kappa$, the positive Lyapunov exponent, the average return time, and a new quantity, the reflection rate. Simulations in the cardioid billiard confirm these results.

  3. Hydrogen Absorption by Niobium.

    1982-04-13

    incorporate an independent means for ascertaining surface cleanliness (e.g. AES). The form of the absorption curve in Fig. 7 appears to agree with that...very interesting study and is well within the capabilities of the systen designed, if the surface cleanliness can be assured. Wire specimens have a...assessing surface cleanliness would be an important supporting technique for understanding the results of these measurements. The simple kinetic

  4. Photoinduced absorption of polyalkylthienylenevinylenes

    Botta, C. (Ist. di Chimica delle Macromolecole (CNR), Milano (Italy)); Bradley, D.D.C. (Cambridge Univ. (United Kingdom). Cavendish Lab.); Friend, R.H. (Cambridge Univ. (United Kingdom). Cavendish Lab.); Musco, A. (Ist. di Scienze Chimiche, Univ. di Urbino (Italy))

    1993-03-15

    We present a photoinduced absorption study of alkyl substituted poly(2,5-thienylenevinylene)s. Three photoinduced states are detected in both the solid state and in solution. The two low-energy bands are assigned to bipolarons, while a third band peaked near the band edge has a different origin. In solution photoexcitated states are very long-lived and we propose that photoexcitation recombine via a solvent-assisted photo-doping mechanism. (orig.)

  5. 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.

  6. Corrosion Problems in Absorption Chillers

    Stetson, Bruce

    1978-01-01

    Absorption chillers use a lithium bromide solution as the medium of absorption and water as the refrigerant. Discussed are corrosion and related problems, tests and remedies, and cleaning procedures. (Author/MLF)

  7. 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.

  8. 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

  9. Acoustic Absorption Characteristics of People.

    Kingsbury, H. F.; Wallace, W. J.

    1968-01-01

    The acoustic absorption characteristics of informally dressed college students in typical classroom seating are shown to differ substantially from data for formally dressed audiences in upholstered seating. Absorption data, expressed as sabins per person or absorption coefficient per square foot, shows that there is considerable variation between…

  10. Excited-state nonlinear absorption and its description using density matrix theory

    李淳飞; 司金海; 杨淼; 王瑞波; 张雷

    1995-01-01

    A density matrix theory with a ten-energy-level model in the molecular system irradiated bya pulsed laser at non-resonant wavelength is proposed. The reverse saturable absorption under ns and pspulses and the transformation from reverse saturable absorption to saturable absorption under strong ps pulses are described by this model. The correctness of the theoretical model is proved by experiments.

  11. Calculation of the Infrared Absorption for MX Compounds

    2003-01-01

    In the theory calculation of lattice vibration, one acoustic and three optical branches were found to compose the phonon vibrating spectrum.Some isolated modes with frequencies lying outside the continuum branches will arise under the defect states.These local model results in the sharp peaks in the infrared absorption and Raman spectra.From calculation of the infrared absorption,the local mode with the infrared activity is obtained in the infrared absorption spectrum of MX compounds.

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

    O.A. Vasylieva

    2013-12-01

    Full Text Available 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.

  13. Nasal Absorption of Macromolecules from Powder Formulations and Effects of Sodium Carboxymethyl Cellulose on Their Absorption

    Tanaka, Akiko; Furubayashi, Tomoyuki; Matsushita, Akifumi; Inoue, Daisuke; Kimura, Shunsuke; Katsumi, Hidemasa; Sakane, Toshiyasu; Yamamoto, Akira

    2016-01-01

    The nasal absorption of macromolecules from powder formulations and the effect of sodium carboxymethyl cellulose (CMC-Na) as a pharmaceutical excipient on their absorption were studied. Model macromolecules were fluorescein isothiocyanate-labeled dextran (average molecular weight of 4.4kDa, FD4) and insulin. The plasma concentration of FD4 after application of the powder containing 50% starch (control) was higher than that after application of the solution, and the absorption from 50% starch powder was enhanced by the substitution of starch with CMC-Na. The fractional absorption of FD4 after administration of the CMC-Na powder formulation was 30% and 40% higher than that after administration from the solution and the starch powder, respectively. The nasal absorption of insulin from the powder and the effect of CMC-Na were similar with those of FD4. The effective absorption of FD4 and insulin after application of powder with CMC-Na could be due to the increase in the nasal residence of FD4 and insulin. No damage in the nasal mucosa or dysfunction of the mucociliary clearance was observed after application of the drug powder and CMC-Na. The present findings indicate that nasal delivery of powder formulations with the addition of CMC-Na as an excipient is a promising approach for improving the nasal absorption of macromolecules. PMID:27598527

  14. A Theoretical Modeling of Light Absorption and Scattering Properties about Microcystis Aeruginosa%铜绿微囊藻吸收和散射特性理论模拟

    戴红亮; 吕恒; 李云梅; 查桂红; 李晓俊; 王瑜

    2013-01-01

    According to ADA theory and Kramers-Kronig relationship,the real and imaginary parts of complex refractive index were estimated by the datasets of microcystis aeruginosa algal absorption and particle size distribution.Then,the optical properties of microcystis aeruginosa were calculated based on the Mie theory.The relative deviations between modeled and measured scattering efficiency factors are 10.08%,and 4.8% between absorption efficiency factors.The agreements between simulation result and actual measurement show that homogenous spherical model can be used to reproduce the absorption and scattering property of microcystis aeruginosa.%基于奇异衍射近似理论和Kramers-Kronig关系,通过实测铜绿微囊藻的吸收光谱数据和粒径分布估算出铜绿微囊藻折射率的实部和虚部,结合Mie散射理论,计算出铜绿微囊藻的吸收效率光谱、散射效率光谱.对比模拟结果与实验结果发现:该模型估算得到的散射光谱与实验的散射光谱之间误差为10.08%,吸收效率的误差为4.8%.从模拟结果与实测结果来看,均匀球形模型能够较好的重现铜绿微囊藻的吸收和散射特征.

  15. Watching adsorption and electron beam induced decomposition on the model system Mo(CO){sub 6}/Cu(1 1 1) by X-ray absorption and photoemission spectroscopies

    Paufert, Pierre, E-mail: pierre.paufert@u-bourgogne.fr [ICB, UMR 6303 CNRS-Université de Bourgogne, BP 47870, 21078 Dijon cedex (France); Fonda, Emiliano [Synchrotron SOLEIL, BP48, St Aubin, 91192 Gif sur Yvette cedex (France); Li, Zheshen [ISA, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C (Denmark); Domenichini, Bruno, E-mail: bruno.domenichini@u-bourgogne.fr [ICB, UMR 6303 CNRS-Université de Bourgogne, BP 47870, 21078 Dijon cedex (France); Bourgeois, Sylvie [ICB, UMR 6303 CNRS-Université de Bourgogne, BP 47870, 21078 Dijon cedex (France)

    2013-11-01

    An in-depth study of the first steps of electron beam assisted growth of Mo from molybdenum hexacarbonyl on Cu(1 1 1) has been carried out exploiting the complementarity of X-ray photoemission and X-ray absorption spectroscopies. Frank van der Merwe (2D) growth mode has been observed for the completion of the two first monolayers of adsorbed molecules through a simple physisorption process. Irradiation of the Mo(CO){sub 6} deposit by 1 keV electron beam induces a modification of molybdenum coordination, the average number of C-neighbors decreasing from 6 to 3. Decomposed molecules remain on the surface after annealing at 520 K and organize themselves, the molybdenum atoms moving in Cu(1 1 1) surface fcc hollow sites. After annealing at 670 K, metallic molybdenum growth begins, if the total amount of adsorbed Mo atoms exceeds 1.2 monolayers.

  16. Watching adsorption and electron beam induced decomposition on the model system Mo(CO)6/Cu(1 1 1) by X-ray absorption and photoemission spectroscopies

    Paufert, Pierre; Fonda, Emiliano; Li, Zheshen; Domenichini, Bruno; Bourgeois, Sylvie

    2013-11-01

    An in-depth study of the first steps of electron beam assisted growth of Mo from molybdenum hexacarbonyl on Cu(1 1 1) has been carried out exploiting the complementarity of X-ray photoemission and X-ray absorption spectroscopies. Frank van der Merwe (2D) growth mode has been observed for the completion of the two first monolayers of adsorbed molecules through a simple physisorption process. Irradiation of the Mo(CO)6 deposit by 1 keV electron beam induces a modification of molybdenum coordination, the average number of C-neighbors decreasing from 6 to 3. Decomposed molecules remain on the surface after annealing at 520 K and organize themselves, the molybdenum atoms moving in Cu(1 1 1) surface fcc hollow sites. After annealing at 670 K, metallic molybdenum growth begins, if the total amount of adsorbed Mo atoms exceeds 1.2 monolayers.

  17. Part-body and multibody effects on absorption of radio-frequency electromagnetic energy by animals and by models of man

    Gandhi, O. P.; Hagmann, M. J.; Dandrea, J. A.

    1979-01-01

    Fine structure in the whole-body resonant curve for radio-frequency energy deposition in man can be attributed to part-body resonances. As for head resonance, which occurs near 350 MHz in man, the absorptive cross section is nearly three times the physical cross section of the head. The arm has a prominent resonance at 150 MHz. Numerical solutions, antenna theory, and experimental results on animals have shown that whole-body energy deposition may be increased by 50 percent or more because of multiple bodies that are strategically located in the field. Empirical equations for SARs are also presented along with test data for several species of laboratory animals. Barbiturate anesthesia is sufficiently disruptive of thermoregulation that delta Ts of colonic temperature yield energy dose values in several mammals that compare quite favorably with those based on whole-body calorimetry.

  18. 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.

  19. 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.

  20. Study of Intestinal Absorption of Emodin in One-way Intestinal Perfusion Rat Model%在体单向肠灌流模型研究大黄素的大鼠肠吸收特性

    张艳; 王平; 王进荣; 于宜平; 孟宪丽

    2012-01-01

    目的 研究大黄素在大鼠不同肠段的吸收特性,以及P-糖蛋白(P-gp)和多药耐药相关蛋白(MRP2)对大黄素肠吸收的影响.方法 采用大鼠在体单向肠灌流模型,HPLC法测定肠灌流液中大黄素的浓度,计算不含抑制剂药物组及含抑制剂药物组大黄素的吸收速率常数(Ka)和表观吸收系数(Papp).结果 十二指肠段吸收能力显著强于其他肠段(P<0.05);大黄素在回肠、结肠、空肠段之间的吸收差异无统计学意义(P>0.05);加入P-gp 抑制剂后,大黄素肠吸收的Ka、Papp 值与不合抑制剂组比较差异也没有统计学意义(P>0.05);加入高、中浓度MRP2抑制剂后,大黄素肠吸收的Ka、Papp 值与不含抑制剂组比较,差异均有统计学意义(P<0.01),且有剂量依赖性.结论 大黄素在大鼠体内的主要吸收部位为十二指肠.大黄素的肠吸收过程不受P-gp的外排影响,但受到MRP2的肠道外排转运影响,大黄素可能为MRP2的底物.%Objective To investigate the absorption characteristic of emodin in rats intestine and to observe the impact of P-glycoprotein(P-gp) and multidrug resistance-associated protein( MRP2) on intestinal absorption of emodin. Methods The rat one-way intestinal perfusion model was used. The concentration of emodin was determined by RP-HPLC. The absorption rate constant(Kα) and the apparent absorption coefficient(Papp) in each intestinal section were calculated in rats with or without P-gp inhibilor(verapamil hydrochloride) or MRP2 inhibitor(indomethacin). Results The value of Ka and Papp in the duodenum was signifcantly higher than in other intestinal sections(P 0.05). Compared with the group without inhibitor, the value of Ka and Papp had signifcantly increased(P 0.05) affter adding the inhibitor of P-gp. Conclusion The main absorption position of emodin is in the duodenum of rats. P-gp has no effect on the intestinal absorption of emodin, but MRP2 can promote the intestinal absorption of

  1. 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...

  2. 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.

  3. Aerosol Absorption Measurements from LANDSAT and CIMEL

    Kaufman, Y. J.; Tanre, D.; Karnieli, A.; Remer, L.; Holben, B.

    1999-01-01

    Spectral remote observations of dust properties from space and from the ground create a powerful tool for determination of dust absorption of solar radiation with an unprecedented accuracy. Absorption is a key component in understanding dust impact on climate. We use Landsat space-borne measurements at 0.47 to 2.2 micrometer over Senegal with ground-based sunphotometers to find that Saharan dust absorption of solar radiation is two to four times smaller than in models. Though dust absorbs in the blue, almost no absorption was found for wavelengths greater than 0.6 micrometer. The new finding increases by 50% recent estimated solar radiative forcing by dust and decreases the estimated dust heating of the lower troposphere. Dust transported from Asia shows slightly higher absorption probably due to the presence of black carbon from populated regions. Large-scale application of this method to satellite data from the Earth Observing System can reduce significantly the uncertainty in the dust radiative effects.

  4. Is oral absorption of vigabatrin carrier-mediated?

    Nøhr, M. K.; Juul, R. V.; Thale, Z. I.;

    2015-01-01

    by significant increases in the apparent Michaelis constant. Based on the mechanistic model, a high capacity low affinity carrier is proposed to be involved in intestinal vigabatrin absorption. PAT1-ligands increased the Michaelis constant of vigabatrin after oral co-administration indicating that this carrier......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...

  5. Inflammation neither increases hepatic hepcidin nor affects intestinal (59)Fe-absorption in two murine models of bowel inflammation, hemizygous TNF(ΔARE/+) and homozygous IL-10(-/-) mice.

    Buffler, M; Becker, C; Windisch, W; Schümann, K

    2015-10-01

    Hepcidin-synthesis was reported to be stimulated by inflammation. In contrast, hepcidin synthesis was inhibited by TNFα and serum hepcidin was low. To elucidate these contradictions, we compare data on hepcidin expression, on iron absorption and homoeostasis and markers of inflammation between two murine models of intestinal inflammation and corresponding wild-types as determined by standard methods. In TNF(ΔARE/+) and IL-10(-/-)-mice hepatic hepcidin expression and protein content was significantly lower than in corresponding wild-types. However, (59)Fe whole-body retention showed no difference between knock-outs and corresponding wild-types 7d after gavage, in neither strain. Compared to wild-types, body weight, hepatic non-haem iron content, hemoglobin and hematocrit were significantly decreased in TNF(ΔARE/+) mice, while erythropoiesis increased. These differences were not seen in IL-10(-/-) mice. Duodenal IL-6 and TNFα content increased significantly in TNF(ΔARE/+) mice, while ferritin-H decreased along with hepatic hepcidin expression, ferritin L, and non-haem iron. In IL-10(-/-) mice, these changes were less marked or missing for non-haem iron. Duodenal ferritin-L and ferroportin increased significantly, while HFE decreased. Our results corroborate the conflicting combination of low hepcidin with inflammation and without increased intestinal iron absorption. Speculating on underlying mechanism, decreased hepcidin may result from stimulated erythropoiesis. Unaltered intestinal iron-absorption may compromise between the stimulation by increased erythropoiesis and inhibition by local and systemic inflammation. The findings suggest intense interaction between counterproductive mechanisms and ask for further research.

  6. The Zone of Inertia: Absorptive Capacity and Organizational Change

    Godkin, Lynn

    2010-01-01

    Purpose: The purpose of this paper is to describe how interruptions in organizational learning effect institutional absorptive capacity and contribute to organizational inertia. Design/methodology/approach: An exploratory model is presented as a heuristic to describe how interruptions in organizational learning affect absorptive capacity.…

  7. 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.

  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. 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

  10. 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.

  11. Diffuse interstellar absorption bands

    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 detections 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.

  12. The absorption of polymeric composites

    Řídký, R.; Popovič, M.; Rolc, S.; Drdlová, M.; Krátký, J.

    2016-06-01

    An absorption capacity of soft, viscoelastic materials at high strain rates is important for wide range of practical applications. Nowadays there are many variants of numerical models suitable for this kind of analysis. The main difficulty is in selection of the most realistic numerical model and a correct setup of many unknown material constants. Cooperation between theoretical simulations and real testing is next crucial point in the investigation process. Standard open source material database offer material properties valid for strain rates less than 250 s-1. There are experiments suitable for analysis of material properties with strain rates close to 2000 s-1. The high strain-rate characteristics of a specific porous blast energy absorbing material measured by modified Split Hopkinson Pressure Bar apparatus is presented in this study. Testing these low impedance materials using a metallic split Hopkinson pressure bar setup results in poor signal to noise ratios due to impedance mismatching. These difficulties are overcome by using polymeric Hopkinson bars. Conventional Hopkinson bar analysis cannot be used on the polymeric bars due to the viscoelastic nature of the bar material. One of the possible solution leads to complex and frequency depended Young modulus of testing bars material. This testing technique was applied to materials composed of porous glass/ceramic filler and polymeric binder, with density of 125 - 300 kg/m3 and particle size in range of 50 µm - 2 mm. The achieved material model was verified in practical application of sandwich structure includes polymeric composites under a blast test.

  13. New in vitro dermal absorption database and the prediction of dermal absorption under finite conditions for risk assessment purposes

    Buist, H.E.; Burgsteden, J.A. van; Freidig, A.P.; Maas, W.J.M.; Sandt, J.J.M. van de

    2010-01-01

    Most QSARs for dermal absorption predict the permeability coefficient, Kp, of a molecule, which is valid for infinite dose conditions. In practice, dermal exposure mostly occurs under finite dose conditions. Therefore, a simple model to predict finite dose dermal absorption from infinite

  14. Assessing the Atmospheric Impact of CF3CClH2 (HCFC-133a): Laboratory Measurements of OH Kinetics and UV and Infrared Absorption Spectra Combined with Model Calculations

    McGillen, M.; Bernard, F.; Fleming, E. L.; Jackman, C. H.; Burkholder, J. B.

    2014-12-01

    CF3CClH2 (HCFC-133a) was recently detected in the atmosphere and its atmospheric mixing ratio has quadrupled over the last 10 years. As expected for this class of compound, HCFC-133a is both an ozone-depleting substance and a greenhouse gas. Precise knowledge of its atmospheric degradation and radiative efficiency is critical to understanding its effect upon the atmosphere. The predominant atmospheric loss process for HCFC-133a is via reaction with the OH radical, where the rate coefficient for this reaction is poorly constrained, especially below room temperature. UV photolysis is a minor loss process, although large discrepancies exist among the reported spectrum measurements. The infrared spectrum of HCFC-133a is presently not available in the literature. The primary focus of this work was to reduce the uncertainties in the atmospheric loss processes of HCFC-133a and its radiative efficiency. Rate coefficient measurements for the OH + HCFC-133a reaction over the temperature range 233-397 K will be reported. In addition, UV absorption spectrum measurements over the wavelength (184.95-240 nm) and temperature (213-323 K) ranges and infrared absorption measurements from 500-4000 cm-1 will be reported. These results are used in 2-D atmospheric model calculations to quantify the atmospheric loss processes, atmospheric lifetime, ozone depletion potential, radiative efficiency, and global warming potential of HCFC-133a. These important metrics will enable informed policy decisions regarding HCFC-133a.

  15. 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...

  16. 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.

  17. 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.

  18. 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.

  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. [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 absorption and had promotion effect on myricetrin and hyperoside absorption (P absorption of Protocatechuic acid (P absorption of various compositions was that small intestine > 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.

  1. Evaluation of time-resolved multi-distance methods to retrieve absorption and reduced scattering coefficients of adult heads in vivo: Optical parameters dependences on geometrical structures of the models used to calculate reflectance

    Tanifuji, T.

    2016-03-01

    Time-resolved multi-distance measurements are studied to retrieve absorption and reduced scattering coefficients of adult heads, which have enough depth sensitivity to determine the optical parameters in superficial tissues and brain separately. Measurements were performed by putting the injection and collection fibers on the left semi-sphere of the forehead, with the injection fiber placed toward the temporal region, and by moving the collection fiber between 10 and 60 mm from the central sulcus. It became clear that optical parameters of the forehead at all collection fibers were reasonably determined by selecting the appropriate visibility length of the geometrical head models, which is related to head surface curvature at each position.

  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. A Predictive Model for Satellite-Derived Phytoplankton Absorption Over the Louisiana Shelf Hypoxic Zone: Effects of Nutrients and Physical Forcing

    2008-06-06

    model, the Modular Ocean Data Assimilation System size of summertime hypoxia [Mississippi River/Gulf of (MODAS) [ Carnes et aL, 1996]. Real-time...satellite- derived and model-predicted a,,, in the (a) Mississippi River I plume (Box A) and (b) Atchafalaya River plume (Box B). losi ph (m Both satellite...produc- column mixing. tivity of the Texas-Louisiana continental shelf, J Mar Syst., 11,237- 247.doi: 10.1016/SO924-7963(97)00019-5. Carnes , M. R., D. N

  5. 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.

  6. Acoustic Absorption of Natural Fiber Composites

    Hasina Mamtaz

    2016-01-01

    Full Text Available The current study is a bibliographic observation on prevailing tendencies in the development of acoustic absorption by natural fiber composites. Despite having less detrimental environmental effects and thorough availability, natural fibers are still unsuitable for wide implementation in industrial purposes. Some shortcomings such as the presence of moisture contents, thicker diameter, and lower antifungus quality hold up the progress of natural fiber composites in staying competitive with synthetic composites. The review indicates the importance of the pretreatment of fresh natural fiber to overcome these shortcomings. However, the pretreatment of natural fiber causes the removal of moisture contents which results in the decrease of its acoustic absorption performance. Incorporation of granular materials in treated fiber composite is expected to play a significant role as a replacement for moisture contents. This review aims to investigate the acoustic absorption behavior of natural fiber composites due to the incorporation of granular materials. It is intended that this review will provide an overview of the analytical approaches for the modeling of acoustic wave propagation through the natural fiber composites. The possible influential factors of fibers and grains were described in this study for the enhancement of low frequency acoustic absorption of the composites.

  7. Microwave peak absorption frequency of liquid

    HAN GuangZe; CHEN MingDong

    2008-01-01

    Microwave-assisted extraction is a new effective method which has practical ap-plications in many fields. Microwave heating is one of its physical mechanisms, and it also has the characteristic of selectivity. When the applied microwave fre-quency equals a certain absorption frequency of the material (or specific compo-nent), the material will intensively absorb microwave energy. This is also known as resonant absorption, and the frequency is called the peak absorption frequency which depends on the physical structure of the material. In this work, dynamic hy-drogen bond energy was included in molecular activation energy; with the liquid cell model, the expression of interaction energy between dipolar molecules was derived. The rotational relaxation time was gotten from the Eyring viscosity formula. Then based on the relationship between dielectric dissipation coefficient and re-laxation time, the expression of microwave peak absorption frequency as a func-tion of the material physical structure, rotational inertia and electrical dipole mo-ment of molecules was established. These theoretical formulas were applied to water and benzene, and the calculated results agree fairly well with the experi-mental data. This work can not only deepen the study of the interaction between microwave and material, but also provide a possible guide for the experiment of microwave-assisted extraction.

  8. Microwave peak absorption frequency of liquid

    2008-01-01

    Microwave-assisted extraction is a new effective method which has practical ap-plications in many fields. Microwave heating is one of its physical mechanisms,and it also has the characteristic of selectivity. When the applied microwave fre-quency equals a certain absorption frequency of the material (or specific compo-nent),the material will intensively absorb microwave energy. This is also known as resonant absorption,and the frequency is called the peak absorption frequency which depends on the physical structure of the material. In this work,dynamic hy-drogen bond energy was included in molecular activation energy; with the liquid cell model,the expression of interaction energy between dipolar molecules was derived. The rotational relaxation time was gotten from the Eyring viscosity formula. Then based on the relationship between dielectric dissipation coefficient and re-laxation time,the expression of microwave peak absorption frequency as a func-tion of the material physical structure,rotational inertia and electrical dipole mo-ment of molecules was established. These theoretical formulas were applied to water and benzene,and the calculated results agree fairly well with the experi-mental data. This work can not only deepen the study of the interaction between microwave and material,but also provide a possible guide for the experiment of microwave-assisted extraction.

  9. Intestinal absorption of specific structured triacylglycerols

    Mu, Huiling; Høy, Carl-Erik

    2001-01-01

    To clarify the intestinal absorption pathway of medium-chain fatty acids from MMM-type structured triaclyglycerols containing both medium- and long-chain fatty acids, we studied the lymphatic transport of 1,3-dioctanoyl-2-linoleoyl-sn- glycerol (8:0/18:2/8:0), 1,3-didecanoyl-2-linoleoyl...... and activated into CoA, and reacylated into triacylglycerols in the enterocyte, The hydrolysis of MLM-type STAG is predominantly partial hydrolysis, whereas part of the STAG can also be hydrolyzed to free glycerol and free fatty acids. - Mu, H., and CE. Hoy. Intestinal absorption of specific structured......-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...

  10. Ozone absorption in a mechanically stirred reactor

    LJILJANA TAKIC; VLADA VELJKOVIC; MIODRAG LAZIC; SRDJAN PEJANOVIC

    2007-01-01

    Ozone absorption in water was investigated in a mechanically stirred reactor, using both the semi-batch and continuous mode of operation. A model for the precise determination of the volumetric mass transfer coefficient in open tanks without the necessity of the measurement the ozone concentration in the outlet gas was developed. It was found that slow ozone reactions in the liquid phase, including the decomposition of ozone, can be regarded as one pseudo-first order reaction. Under the exami...

  11. 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.

  12. Development of a nanogel formulation for transdermal delivery of tenoxicam: a pharmacokinetic-pharmacodynamic modeling approach for quantitative prediction of skin absorption.

    Elkomy, Mohammed H; El Menshawe, Shahira F; Eid, Hussein M; Ali, Ahmed M A

    2017-04-01

    This study investigates potentials of solid lipid nanoparticles (SLN)-based gel for transdermal delivery of tenoxicam (TNX) and describes a pharmacokinetic-pharmacodynamic (PK-PD) modeling approach for predicting concentration-time profile in skin. A 2(3) factorial design was adopted to study the effect of formulation factors on SLN properties and determine the optimal formulation. SLN-gel tolerability was investigated using rabbit skin irritation test. Its anti-inflammatory activity was assessed by carrageenan-induced rat paw edema test. A published Hill model for in vitro inhibition of COX-2 enzyme was fitted to edema inhibition data. Concentration in skin was represented as a linear spline function and coefficients were estimated using non-linear regression. Uncertainty in predicted concentrations was assessed using Monte Carlo simulations. The optimized SLN was spherical vesicles (58.1 ± 3.1 nm) with adequate entrapment efficiency (69.6 ± 2.6%). The SLN-gel formulation was well-tolerated. It increased TNX activity and skin level by 40 ± 13.5, and 227 ± 116%, respectively. Average Cmax and AUC0-24 predicted by the model were 2- and 3.6-folds higher than the corresponding values computed using in vitro permeability data. SLN-gel is a safe and efficient carrier for TNX across skin in the treatment of inflammatory disorders. PK-PD modeling is a promising approach for indirect quantitation of skin deposition from PD activity data.

  13. 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.

  14. [Bone and Nutrition. Vitamin D independent calcium absorption].

    Masuyama, Ritsuko

    2015-07-01

    Vitamin D endocrine system is required for normal calcium and bone homeostasis. Trans-epithelial calcium absorption is initiated with calcium entry into the intestinal epithelial cells from luminal fluid through calcium permeable channels, and those expressions are strongly supported by vitamin D action. On the other hands, dietary treatment, mineral supplementation or restriction, successfully improves intestinal calcium absorption in global vitamin D receptor knock-out (VDR KO) mice, though vitamin D dependent active transport pathway is lacking. Dietary rescue of intestinal calcium absorption provided a positive calcium balance in this mouse model, and suggested that the major role of vitamin D function on calcium homeostasis was considered to be intestinal active absorption. To elucidate the entire process of intestinal calcium absorption, vitamin D independent calcium transport system was characterized into either trans-cellular or para-cellular process.

  15. Exercise, Insulin Absorption Rates, and Artificial Pancreas Control

    Frank, Spencer; Hinshaw, Ling; Basu, Rita; Basu, Ananda; Szeri, Andrew J.

    2016-11-01

    Type 1 Diabetes is characterized by an inability of a person to endogenously produce the hormone insulin. Because of this, insulin must be injected - usually subcutaneously. The size of the injected dose and the rate at which the dose reaches the circulatory system have a profound effect on the ability to control glucose excursions, and therefore control of diabetes. However, insulin absorption rates via subcutaneous injection are variable and depend on a number of factors including tissue perfusion, physical activity (vasodilation, increased capillary throughput), and other tissue geometric and physical properties. Exercise may also have a sizeable effect on the rate of insulin absorption, which can potentially lead to dangerous glucose levels. Insulin-dosing algorithms, as implemented in an artificial pancreas controller, should account accurately for absorption rate variability and exercise effects on insulin absorption. The aforementioned factors affecting insulin absorption will be discussed within the context of both fluid mechanics and data driven modeling approaches.

  16. Electro-absorption of silicene and bilayer graphene quantum dots

    Abdelsalam, Hazem; Talaat, Mohamed H.; Lukyanchuk, Igor; Portnoi, M. E.; Saroka, V. A.

    2016-07-01

    We study numerically the optical properties of low-buckled silicene and AB-stacked bilayer graphene quantum dots subjected to an external electric field, which is normal to their surface. Within the tight-binding model, the optical absorption is calculated for quantum dots, of triangular and hexagonal shapes, with zigzag and armchair edge terminations. We show that in triangular silicene clusters with zigzag edges a rich and widely tunable infrared absorption peak structure originates from transitions involving zero energy states. The edge of absorption in silicene quantum dots undergoes red shift in the external electric field for triangular clusters, whereas blue shift takes place for hexagonal ones. In small clusters of bilayer graphene with zigzag edges the edge of absorption undergoes blue/red shift for triangular/hexagonal geometry. In armchair clusters of silicene blue shift of the absorption edge takes place for both cluster shapes, while red shift is inherent for both shapes of the bilayer graphene quantum dots.

  17. 班豆在浸泡加工过程中吸水特性的模拟%Modeling of Water Absorption of Pinto Beans During Blanching and Soaking

    潘忠礼

    2002-01-01

    在生产速食干豆过程中,主要包括浸泡、蒸煮和干燥等工序.浸泡的温度和时间直接影响到在浸泡过程中固性物的损失和最终产品的质量.该研究测定了班豆在浸泡过程中在不同温度和时间下的吸水和固性物的损失特性,同时利用数学模型预测了在变温情况下班豆的吸水特性.该研究结果将对生产高质量的速食班豆有一定的指导作用.%Blanching and soaking are essential thermal processing steps in the process of precooked pinto beans. Appropriate blanching and soaking conditions could reduce antinutritional factors, such as trypsin inhibitors, improve the quality of finished products, and reduce processing time and solid losses. The characteristics of water absorption (hydration ratio and moisture content) and solid losses of pinto beans were measured at various temperatures (30 to 100℃) and time periods (5 min to 24 h). It was found that the hydration ratio, moisture content, and solid loss increased with the increased temperature and time. But the rate of water absorption decreased with the increase of time. To obtain high quality product with minimum processing time and solid loss, variable temperature for blanching and soaking is normally used. Models for predicting the hydration ratio and moisture content were developed and validated under variable blanching and soaking temperatures and time periods.

  18. Absorption of CH330331, a novel 4-anilinoquinazoline inhibitor of epidermal growth factor receptor tyrosine kinase: comparative studies using in vitro, in situ and in vivo models.

    Sun, Haiyan; Bi, Huichang; Huang, Min; Liu, Dong; Qin, Zhenyu

    2010-11-01

    CH330331 is a prototype of a new class of synthetic small molecule tyrosine kinase inhibitors (TKIs). In vitro Caco-2 cell monolayers, the in situ single-pass rat intestinal perfusion (SPIP) technique with mesenteric vein cannulated and an in vivo animal model were employed to investigate its permeability and transepithelial transport mechanisms. The Caco-2 model showed that the transport of CH330331 across the monolayers from the apical (AP) to basolateral (BL) side was 6- to 10-fold higher than that from the BL to AP side. The apparent permeability coefficient (P(app) ) values of CH330331 at 5-20 µg/ml from the AP to BL and from BL to AP side were 5.30-2.21 × 10(-6)  cm/s, with a decrease in P(app) values from the AP to BL side at increased CH330331 concentrations. In the perfused rat intestinal model, a concentration dependent change in permeability was detected where P(blood) at 5 µg/ml (1.66 ± 0.69 × 10(-6)  cm/s) and 10 µg/ml (1.80 ± 0.45 × 10(-6)  cm/s) was significantly different from P(blood) at 20 µg/ml (0.98 ± 0.31 × 10(-6)  cm/s, prat. All the results confirmed that the transepithelial transport of CH330331 was rapid and saturable, which might involve an active mechanism. The oral bioavailability of CH330331 was relatively high in vivo.

  19. Total light absorption in graphene

    Thongrattanasiri, Sukosin; de Abajo, F Javier Garcia

    2011-01-01

    We demonstrate that 100% light absorption can take place in a single patterned sheet of doped graphene. General analysis shows that a planar array of small lossy particles exhibits full absorption under critical-coupling conditions provided the cross section of each individual particle is comparable to the area of the lattice unit-cell. Specifically, arrays of doped graphene nanodisks display full absorption when supported on a substrate under total internal reflection, and also when lying on a dielectric layer coating a metal. Our results are relevant for infrared light detectors and sources, which can be made tunable via electrostatic doping of graphene.

  20. 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.

  1. 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.

  2. Dermal absorption of semivolatile organic compounds from the gas phase: Sensitivity of exposure assessment by steady state modeling to key parameters.

    Pelletier, Maud; Bonvallot, Nathalie; Ramalho, Olivier; Blanchard, Olivier; Mercier, Fabien; Mandin, Corinne; Le Bot, Barbara; Glorennec, Philippe

    2017-02-26

    Recent research has demonstrated the importance of dermal exposure for some semivolatile organic compounds (SVOCs) present in the gas phase of indoor air. Though models for estimating dermal intake from gaseous SVOCs exist, their predictions can be subject to variations in input parameters, which can lead to large variation in exposure estimations. In this sensitivity analysis for a steady state model, we aimed to assess these variations and their determinants using probabilistic Monte Carlo sampling for 8 SVOCs from different chemical families: phthalates, bisphenols, polycyclic aromatic hydrocarbons (PAHs), organophosphorus (OPs), organochlorines (OCs), synthetic musks, polychlorinated biphenyls (PCBs) and polybromodiphenylethers (PBDEs). Indoor SVOC concentrations were found to be the most influential parameters. Both Henry's law constant (H) and octanol/water partition coefficient (Kow) uncertainty also had significant influence. While exposure media properties such as volume fraction of organic matter in the particle phase (fom-part), particle density (ρpart), concentration ([TSP]) and transport coefficient (ɣd) had a slight influence for some compounds, human parameters such as body weight (W), body surface area (A) and daily exposure (t) make a marginal or null contribution to the variance of dermal intake for a given age group. Inclusion of a parameter sensitivity analysis appears essential to reporting uncertainties in dermal exposure assessment.

  3. 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

  4. Effect of antibiotic treatment on fat absorption in mice with cystic fibrosis

    Wouthuyzen-Bakker, Marjan; Bijvelds, Marcel J. C.; de Jonge, Hugo R.; De Lisle, Robert C.; Burgerhof, Johannes G. M.; Verkade, Henkjan J.

    2012-01-01

    INTRODUCTION: Improving fat absorption remains a challenge in cystic fibrosis (CF). Antibiotics (AB) treatment has been shown to improve body weight in CF mice. The mechanism may include improvement in fat absorption. We aimed to determine the effect of AB on fat absorption in two CF mouse models. R

  5. 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.

  6. NLP modeling for the optimization of LiBr-H2O absorption refrigeration systems with exergy loss rate, heat transfer area, and cost as single objective functions

    Mussati, Sergio F.; Gernaey, Krist; Morosuk, Tatiana

    2016-01-01

    exergy loss rate, the total heat transfer area, and the total annual cost of the system. It was found that the optimal solution obtained by minimization of the total exergy loss rate provides “theoretical” upper bounds not only for the total heat transfer area of the system but also for each process unit...... and all stream temperatures, while the optimal solution obtained by minimization of the total heat transfer area provides the lower bounds for these model variables, to solve a cost optimization problem. The minimization of the total exergy loss rate by varying parametrically the available total heat...... and quantitatively with increasing available total heat transfer area. These optimization results allowed to find a “practical” value of the total heat transfer area, i.e. no benefits can be obtained by increasing the available total heat transfer area above this value since the minimal total exergy loss value...

  7. 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...... 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...... substantially constant and small, whereby the guided light can be modulated only by bending losses. Alternatively, the invention may be applied to enhance the extinction ratio of existing absorption modulators such as Electro-Absorption Modulators (EAMs) in which case extinction by absorption and extinction...

  8. Circadian Regulation of Macronutrient Absorption.

    Hussain, M Mahmood; Pan, Xiaoyue

    2015-12-01

    Various intestinal functions exhibit circadian rhythmicity. Disruptions in these rhythms as in shift workers and transcontinental travelers are associated with intestinal discomfort. Circadian rhythms are controlled at the molecular level by core clock and clock-controlled genes. These clock genes are expressed in intestinal cells, suggesting that they might participate in the circadian regulation of intestinal functions. A major function of the intestine is nutrient absorption. Here, we will review absorption of proteins, carbohydrates, and lipids and circadian regulation of various transporters involved in their absorption. A better understanding of circadian regulation of intestinal absorption might help control several metabolic disorders and attenuate intestinal discomfort associated with disruptions in sleep-wake cycles.

  9. OZONE ABSORPTION IN RAW WATERS

    LJILJANA TAKIĆ

    2008-03-01

    Full Text Available The ozone absorption in raw water entering the main ozonization step at the Belgrade drinking water supply plant was investigated in a continuous stirred tank reactor (CSTR. A slow chemical reaction rate of dissolved ozone and pollutants present in raw water have been experimentally determined. The modified Hatta number was defined and calculated as a criterion which determines whether and to which extent the reactions of ozone and pollutants influence the rate of the pure physical ozone absorption.

  10. 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...

  11. The Stellar Initial Mass Function in Early-type Galaxies from Absorption Line Spectroscopy. IV. A Super-Salpeter IMF in the Center of NGC 1407 from Non-parametric Models

    Conroy, Charlie; van Dokkum, Pieter G.; Villaume, Alexa

    2017-03-01

    It is now well-established that the stellar initial mass function (IMF) can be determined from the absorption line spectra of old stellar systems, and this has been used to measure the IMF and its variation across the early-type galaxy population. Previous work focused on measuring the slope of the IMF over one or more stellar mass intervals, implicitly assuming that this is a good description of the IMF and that the IMF has a universal low-mass cutoff. In this work we consider more flexible IMFs, including two-component power laws with a variable low-mass cutoff and a general non-parametric model. We demonstrate with mock spectra that the detailed shape of the IMF can be accurately recovered as long as the data quality is high (S/N ≳ 300 Å‑1) and cover a wide wavelength range (0.4–1.0 μm). We apply these flexible IMF models to a high S/N spectrum of the center of the massive elliptical galaxy NGC 1407. Fitting the spectrum with non-parametric IMFs, we find that the IMF in the center shows a continuous rise extending toward the hydrogen-burning limit, with a behavior that is well-approximated by a power law with an index of ‑2.7. These results provide strong evidence for the existence of extreme (super-Salpeter) IMFs in the cores of massive galaxies.

  12. The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. IV. A Super-Salpeter IMF in the center of NGC 1407 from Non-Parametric Models

    Conroy, Charlie; Villaume, Alexa

    2016-01-01

    It is now well-established that the stellar initial mass function (IMF) can be determined from the absorption line spectra of old stellar systems, and this has been used to measure the IMF and its variation across the early-type galaxy population. Previous work focused on measuring the slope of the IMF over one or more stellar mass intervals, implicitly assuming that this is a good description of the IMF and that the IMF has a universal low-mass cutoff. In this work we consider more flexible IMFs, including two-component power-laws with a variable low-mass cutoff and a general non-parametric model. We demonstrate with mock spectra that the detailed shape of the IMF can be accurately recovered as long as the data quality are high (S/N$\\gtrsim300$) and cover a wide wavelength range (0.4um-1.0um). We apply these flexible IMF models to a high S/N spectrum of the center of the massive elliptical galaxy NGC 1407. Fitting the spectrum with non-parametric IMFs, we find that the IMF in the center shows a continuous ri...

  13. Subgap Absorption in Conjugated Polymers

    Sinclair, M.; Seager, C. H.; McBranch, D.; Heeger, A. J; Baker, G. L.

    1991-01-01

    Along with X{sup (3)}, the magnitude of the optical absorption in the transparent window below the principal absorption edge is an important parameter which will ultimately determine the utility of conjugated polymers in active integrated optical devices. With an absorptance sensitivity of conjugated polymers poly(1,4-phenylene-vinylene) (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm{sup {minus}1} to 10 cm{sup {minus}1}. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration of fluorination.

  14. Absorption and Photoluminescence in Organic Cavity QED

    Herrera, Felipe

    2016-01-01

    Organic microcavities can be engineered to reach exotic quantum regimes of strong and ultrastrong light-matter coupling. However, the microscopic interpretation of their spectroscopic signals can be challenging due to the competition between coherent and dissipative processes involving electrons, vibrations and cavity photons. We develop here a theoretical framework based on the Holstein-Tavis-Cummings model and a Markovian treatment of dissipation to account for previously unexplained spectroscopic features of organic microcavities consistently. We identify conditions for the formation of dark vibronic polaritons, a new class of light-matter excitations that are not visible in absorption but lead to strong photoluminescence lines. We show that photon leakage from dark vibronic polaritons can be responsible for enhancing photoluminescence at the lower polariton frequency, and also explain the apparent breakdown of reciprocity between absorption and emission in the vicinity of the bare molecular transition fre...

  15. Skin absorption through atopic dermatitis skin

    Halling-Overgaard, A-S; Kezic, S; Jakasa, I

    2017-01-01

    Patients with atopic dermatitis have skin barrier impairment in both lesional and non-lesional skin. They are typically exposed to emollients daily and topical anti-inflammatory medicaments intermittently, hereby increasing the risk of developing contact allergy and systemic exposed to chemicals...... ingredients found in these topical preparations. We systematically searched for studies that investigated skin absorption of various penetrants, including medicaments, in atopic dermatitis patients, but also animals with experimentally induced dermatitis. We identified 40 articles, i.e. 11 human studies...... examining model penetrants, 26 human studies examining atopic dermatitis drugs and 3 animal studies. We conclude that atopic dermatitis patients have nearly two-fold increased skin absorption when compared to healthy controls. There is a need for well-designed epidemiological and dermato...

  16. 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

  17. 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

  18. Multiplexed absorption tomography with calibration-free wavelength modulation spectroscopy

    Cai, Weiwei; Kaminski, Clemens F., E-mail: cfk23@cam.ac.uk [Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB2 3RA (United Kingdom)

    2014-04-14

    We propose a multiplexed absorption tomography technique, which uses calibration-free wavelength modulation spectroscopy with tunable semiconductor lasers for the simultaneous imaging of temperature and species concentration in harsh combustion environments. Compared with the commonly used direct absorption spectroscopy (DAS) counterpart, the present variant enjoys better signal-to-noise ratios and requires no baseline fitting, a particularly desirable feature for high-pressure applications, where adjacent absorption features overlap and interfere severely. We present proof-of-concept numerical demonstrations of the technique using realistic phantom models of harsh combustion environments and prove that the proposed techniques outperform currently available tomography techniques based on DAS.

  19. Fat-soluble vitamin intestinal absorption: absorption sites in the intestine and interactions for absorption.

    Goncalves, Aurélie; Roi, Stéphanie; Nowicki, Marion; Dhaussy, Amélie; Huertas, Alain; Amiot, Marie-Josèphe; Reboul, Emmanuelle

    2015-04-01

    The interactions occurring at the intestinal level between the fat-soluble vitamins A, D, E and K (FSVs) are poorly documented. We first determined each FSV absorption profile along the duodenal-colonic axis of mouse intestine to clarify their respective absorption sites. We then investigated the interactions between FSVs during their uptake by Caco-2 cells. Our data show that vitamin A was mostly absorbed in the mouse proximal intestine, while vitamin D was absorbed in the median intestine, and vitamin E and K in the distal intestine. Significant competitive interactions for uptake were then elucidated among vitamin D, E and K, supporting the hypothesis of common absorption pathways. Vitamin A also significantly decreased the uptake of the other FSVs but, conversely, its uptake was not impaired by vitamins D and K and even promoted by vitamin E. These results should be taken into account, especially for supplement formulation, to optimise FSV absorption.

  20. 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.

  1. Could the New Absorption Cross Section of J/psi Change the Aspect of Nuclear Absorption Mechanism

    2001-01-01

    The enlarged new absorption cross section of J/psi by pion and rho mesons were put into the hadron and string cascade model, JPCIAE, and the J/psi suppression factors in p-A, O-U, S-U and Pb-Pb minimum bias collisions at 200 AGeV/c were calculated with nuclear absorption mechanism only. The results seem to indicate that, with new enlarged cross section it is still hard to change the aspect that nuclear absorption itself could not easily account for the J/psi anomalous suppression in Pb-Pb collisions.

  2. Ultra-Thin Metal Films for Enhanced Solar Absorption

    Ahmad, N; Teng, M; Cryan, M J

    2012-01-01

    This paper presents modelled results for optical absorption in ultra-thin films of nickel, gold and silver over the solar spectrum. It is found in the case of nickel there is an optimum thickness for maximum solar absorption around 10-13nm. This effect is not observed for gold or silver. It is postulated that this is an interference effect occurring due the particular real and imaginary refractive profile of nickel across the solar spectrum.

  3. Multi-Phase Galaxy Formation and Quasar Absorption Systems

    Maller, Ariyeh H.

    2005-01-01

    The central problem of galaxy formation is understanding the cooling and condensation of gas in dark matter halos. It is now clear that to match observations this requires further physics than the simple assumptions of single phase gas cooling. A model of multi-phase cooling (Maller & Bullock 2004) can successfully account for the upper cutoff in the masses of galaxies and provides a natural explanation of many types of absorption systems (Mo & Miralda-Escude 1996). Absorption systems are our...

  4. Transport of trans-tiliroside (kaempferol-3-β-D-(6"-p-coumaroyl-glucopyranoside) and related flavonoids across Caco-2 cells, as a model of absorption and metabolism in the small intestine.

    Luo, Zijun; Morgan, Michael R A; Day, Andrea J

    2015-01-01

    1. Absorption and metabolism of tiliroside (kaempferol 3-β-D-(6"-p-coumaroyl)-glucopyranoside) and its related compounds kaempferol, kaempferol-3-glucoside and p-coumaric acid were investigated in the small intestinal Caco-2 cell model. Apparent permeation (Papp) was determined as 0.62 × 10(-6) cm/s, 3.1 × 10(-6) cm/s, 0 and 22.8 × 10(-6) cm/s, respectively. 2. Mechanistic study showed that the transportation of tiliroside, kaempferol-3-glucoside and p-coumaric acid in Caco-2 model were transporter(s) involved, while transportation of kaempferol was solely by passive diffusion mechanism. 3. Efflux transporters, multi-drug-resistance-associated protein-2 (MRP2), were shown to play a role in limiting the uptake of tiliroside. Inhibitors of MRP2, (MK571 and rifampicin) and co-incubation with kaempferol (10 μM), increased transfer from the apical to the basolateral side by three to five fold. 4. Metabolites of kaempferol-3-glucoside and p-coumaric acid were not detected in the current Caco-2 model, while tiliroside was metabolised to a limited extent, with two tiliroside mono-glucuronides identified; and kaempferol was metabolised to a higher extent, with three mono-glucuronides and two mono-sulfates identified. 5. In conclusion, tiliroside was metabolised and transported across Caco-2 cell membrane to a limited extent. Transportation could be increased by applying MRP2 inhibitors or co-incubation with kaempferol. It is proposed that tiliroside can be absorbed by human; future pharmacokinetics studies are warranted in order to determine the usefulness of tiliroside as a bioactive agent.

  5. 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 [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Akiyama, Masayuki [Astronomical Institute, Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai 980-8578 (Japan); Hasinger, Günther [Institute for Astronomy, 2680 Woodlawn Drive Honolulu, HI 96822-1839 (United States); Miyaji, Takamitsu [Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada, Baja California (Mexico); Watson, Michael G. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)

    2014-05-10

    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.

  6. Terahertz absorption of dilute aqueous solutions.

    Heyden, Matthias; Tobias, Douglas J; Matyushov, Dmitry V

    2012-12-21

    Absorption of terahertz (THz) radiation by aqueous solutions of large solutes reports on the polarization response of their hydration shells. This is because the dipolar relaxation of the solute is dynamically frozen at these frequencies, and most of the solute-induced absorption changes, apart from the expulsion of water, are caused by interfacial water. We propose a model expressing the dipolar response of solutions in terms of a single parameter, the interface dipole moment induced in the interfacial water by electromagnetic radiation. We apply this concept to experimental THz absorption of hydrated sugars, amino acids, and proteins. None of the solutes studied here follow the expectations of dielectric theories, which predict a negative projection of the interface dipole on the external electric field. We find that this prediction is not able to describe the available experimental data, which instead suggests a nearly zero interface dipole for sugars and a more diverse pattern for amino acids. Hydrophobic amino acids, similarly to sugars, give rise to near zero interface dipoles, while strongly hydrophilic ones are best described by a positive projection of the interface dipole on the external field. The sign of the interface dipole is connected to the slope of the absorption coefficient with the solute concentration. A positive slope, implying an increase in the solution polarity relative to water, mirrors results frequently reported for protein solutions. We therefore use molecular dynamics simulations of hydrated glucose and lambda repressor protein to calculate the interface dipole moments of these solutes and the concentration dependence of the THz absorption. The absorption at THz frequencies increases with increasing solute concentration in both cases, implying a higher polarity of the solution compared to bulk water. The structure of the hydration layer, extracted from simulations, is qualitatively similar in both cases, with spatial correlations

  7. Importance of the green color, absorption gradient, and spectral absorption of chloroplasts for the radiative energy balance of leaves.

    Kume, Atsushi

    2017-03-14

    Terrestrial green plants absorb photosynthetically active radiation (PAR; 400-700 nm) but do not absorb photons evenly across the PAR waveband. The spectral absorbance of photosystems and chloroplasts is lowest for green light, which occurs within the highest irradiance waveband of direct solar radiation. We demonstrate a close relationship between this phenomenon and the safe and efficient utilization of direct solar radiation in simple biophysiological models. The effects of spectral absorptance on the photon and irradiance absorption processes are evaluated using the spectra of direct and diffuse solar radiation. The radiation absorption of a leaf arises as a consequence of the absorption of chloroplasts. The photon absorption of chloroplasts is strongly dependent on the distribution of pigment concentrations and their absorbance spectra. While chloroplast movements in response to light are important mechanisms controlling PAR absorption, they are not effective for green light because chloroplasts have the lowest spectral absorptance in the waveband. With the development of palisade tissue, the incident photons per total palisade cell surface area and the absorbed photons per chloroplast decrease. The spectral absorbance of carotenoids is effective in eliminating shortwave PAR (<520 nm), which contains much of the surplus energy that is not used for photosynthesis and is dissipated as heat. The PAR absorptance of a whole leaf shows no substantial difference based on the spectra of direct or diffuse solar radiation. However, most of the near infrared radiation is unabsorbed and heat stress is greatly reduced. The incident solar radiation is too strong to be utilized for photosynthesis under the current CO2 concentration in the terrestrial environment. Therefore, the photon absorption of a whole leaf is efficiently regulated by photosynthetic pigments with low spectral absorptance in the highest irradiance waveband and through a combination of pigment density

  8. Absorption chillers integration in a combined heat and power plant

    Bruno, J. C.; Fernandez, F.; Castells, F. [Barcelona Univ., Tarragona (Spain). Dept. d`Enginyeria Quimica i Bioqumica

    1996-11-01

    Inclusion of an absorption cycle within a combined heat and power plant (CHP) was evaluated. To determine the most suitable configuration of the energy network generation system and absorption chiller, a simulation and optimization model was constructed. To validate the optimization model, a case study using actual data from existing operating plants has been used. In the case described the cooling facilities from the absorption cycle were used to lower the inlet temperature to the compressor of the gas turbine to improve the overall plant efficiency. Waste steam from the steam network was used in the generator of the absorption chiller. A reduction in steam wastes, and an improvement in overall plant efficiency was observed. A simulation model of a single effect absorption chiller, using water-lithium bromide as the working fluid pair, was used to validate the methodology. Results showed that the benefits of integrating the absorption refrigeration cycle (ARC) depends directly on the refrigeration demand, and on the benefit produced by the waste steam recovered. The increase in power generation, allowing a reduction in primary energy consumption, showed a slight economic advantage over the conventional compression cycle. 13 refs., 7. tabs., 6 figs.

  9. Near-infrared free carrier absorption in heavily doped silicon

    Baker-Finch, Simeon C., E-mail: simeon.bakerfinch@gmail.com [School of Engineering, Australian National University, Canberra, ACT 0200 (Australia); PV Lighthouse, Coledale, NSW 2515 (Australia); McIntosh, Keith R. [PV Lighthouse, Coledale, NSW 2515 (Australia); Yan, Di; Fong, Kean Chern; Kho, Teng C. [School of Engineering, Australian National University, Canberra, ACT 0200 (Australia)

    2014-08-14

    Free carrier absorption in heavily doped silicon can have a significant impact on devices operating in the infrared. In the near infrared, the free carrier absorption process can compete with band to band absorption processes, thereby reducing the number of available photons to optoelectronic devices such as solar cells. In this work, we fabricate 18 heavily doped regions by phosphorus and boron diffusion into planar polished silicon wafers; the simple sample structure facilitates accurate and precise measurement of the free carrier absorptance. We measure and model reflectance and transmittance dispersion to arrive at a parameterisation for the free carrier absorption coefficient that applies in the wavelength range between 1000 and 1500 nm, and the range of dopant densities between ∼10{sup 18} and 3 × 10{sup 20} cm{sup −3}. Our measurements indicate that previously published parameterisations underestimate the free carrier absorptance in phosphorus diffusions. On the other hand, published parameterisations are generally consistent with our measurements and model for boron diffusions. Our new model is the first to be assigned uncertainty and is well-suited to routine device analysis.

  10. Comparison of serum calcium measurements with respect to five models of atomic absorption spectrometers using NBS-AACC calcium reference method and isotope-dilution mass spectrometry as the definitive method.

    Copeland, B E; Grisley, D W; Casella, J; Bailey, H

    1976-10-01

    Utilizing the recently described reference method for calcium (NBS-AACC) and the recently developed definitive (referee) NBS method for serum calcium measurement by isotopedilution mass spectrometry (IDMS), an evaluation of five recent-model atomic absorption spectrometers was carried out. Under optimal conditions of instrument operation using aqueous standards, significant differences were found during the comparative analyses of three lyophilized pool samples and one liquid serum pool sample. Use of the NBS-AACC serum calcium protocol did not guarantee analytic results within +/- 2% of the IDMS value. In four of eight comparisons, differences from IDMS greater than 2% were observed. Several variables were studied to account for these differences. It was shown that a serum matrix, when present in standards used to bracket the unknown sample, reduced differences between instruments in four of four instances and improved the accuracy of the results from a range of -1.1 to +3.5% to +0.1 to +1.0%. It is concluded that a serum sample with a verified IDMS calcium value is a valuable tool that establishes an accurate and stable reference point for serum calcium measurement. The use of transfer-of-NBS-technology multipliers is suggested. Regional quality control serum pools and clinical chemistry survey sample materials that have been analyzed for calcium concentration by the NBS-IDMS definitive method are examples of these multipliers.

  11. 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.

  12. 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.

  13. 大鼠单向灌流模型研究田蓟苷的在体肠吸收%Study on intestinal absorption of tilianin in rats of single-pass perfusion model

    王婷婷; 李伟; 袁勇; 王丽萍; 王新春

    2013-01-01

    Objective:To study the intestinal absorption mechanism of tilianin in rats.Method:The single-pass perfusion model was established in rats.The concentrations of tilianin with in situ intestinal peffusion were determined by HPLC.The impact factors,such as verapamil,reserpine,phloridzin and rifampicin,on Ka and Papp of tilianin in rat jejunum were investigated.Result:Compared with the control group,Ka and Paapp in rat jejunum were significantly higher after being added with verapamil and reserpine (P <0.05).Papp of tilianin in rat jejunum was significantly lower after being added with phloridzin (P < 0.05).Compared with the control group,both Ka and Papp of tilianin in rat jejunum were not significantly higher after being added with rifampicin.Conclusion:Tilianin is the substrate of P-gp,BCRP and SGLT1.The effluent effect of P-gp and BCRP is the main mechanism of tilianin in intestinal absorption,indicating that tilianin can realize intestinal absorption and transport by relying on SGLT1.Tilianin is not the substrate of bile salt transporter protein.%目的:研究田蓟苷的大鼠小肠吸收机制.方法:采用大鼠单向灌流模型,高效液相色谱法测定在体肠灌流田蓟苷的浓度变化,考察加入维拉帕米、利血平、根皮苷及利福平对田蓟苷在大鼠空肠段的K2,papp的影响.结果:与对照组相比,加入维拉帕米、利血平后,田蓟苷在大鼠空肠段的Ka,Papp有显著性增加(P<0.05);加入根皮苷后,田蓟苷在大鼠空肠段的Papp显著性降低(P<0.05);加入利福平,田蓟苷在大鼠空肠段的Ka,Papp没有显著性增加.结论:田蓟苷是P-糖蛋白(P-gp)、乳腺癌多药耐药蛋白(BCRP)及Na+依赖葡萄糖转运载体1(SCLT1)的底物,P-gp与BCRP外排作用是田蓟苷小肠吸收的主要外排机制,田蓟苷能够依赖SGLT1实现在小肠的吸收转运;田蓟苷不是胆盐转运蛋白的底物.

  14. Diabetic lipohypertrophy delays insulin absorption.

    Young, R J; Hannan, W J; Frier, B M; Steel, J M; Duncan, L J

    1984-01-01

    The effect of lipohypertrophy at injection sites on insulin absorption has been studied in 12 insulin-dependent diabetic patients. The clearance of 125I-insulin from sites with lipohypertrophy was significantly slower than from complementary nonhypertrophied sites (% clearance in 3 h, 43.8 +/- 3.5 +/- SEM) control; 35.3 +/- 3.9 lipohypertrophy, P less than 0.05). The degree of the effect was variable but sufficient in several patients to be of clinical importance. Injection-site lipohypertrophy is another factor that modifies the absorption of subcutaneously injected insulin.

  15. Quasistellar Objects Intervening Absorption Lines

    Charlton, J C; Charlton, Jane C.; Churchill, Christopher W.

    2000-01-01

    We briefly review, at a level appropriate for graduate students and non-specialists, the field of quasar absorption lines (QALs). Emphasis is on the intervening absorbers. We present the anatomy of a quasar spectrum due to various classes of intervening absorption systems, and a brief historical review of each absorber class (Lyman-alpha forest and Lyman limit systems, and metal-line and damped Lyman-alpha absorbers). We also provide several heuristic examples on how the physical properties of both the intergalactic medium and the gaseous environments associated with earlier epoch galaxies can be inferred from QALs. The evolution of these environments from z=4 are discussed.

  16. 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

  17. 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.

  18. 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.

  19. Development of Exhaust Gas Driven Absorption Chiller-Heater

    Inoue, Naoyuki; Endou, Tetsuya; Saito, Kiyoshi; Kawai, Sunao

    Waste heat from co-generation systems are usually recovered by hot water or steam, those are used to drive absorption refrigerators at cooling time, and those are used for heating via heat exchangers at heating time. However waste heat from micro gas turbines are discharged in the form of exhaust gas, it is simple that exhaust gas is directly supplied to absorption chiller-heaters. In the first report we studied cooling cycle, and this second paper, we evaluated various absorption heating cycles for exhaust gas driven absorption chiller-heaters, and adopted one of these cycles for the prototype machine. Also, we experimented with the prototype for wide range condition and got the heating characteristics. Based on the experimental data, we developed a simulation model of the static characteristics, and then studied how to increase the output by limited exhaust gas.

  20. THEORETICAL STUDY OF THE ABSORPTION SPECTRA OF TRIAMTERENE

    M. Ramegowda

    2013-03-01

    Full Text Available ABSTRACT: Time dependent density functional theory (TDDFT calculations have been carried out to study the electronic structure and the UV absorption spectra of Triamterene. The UV spectra have been investigated with inclusion of solvent effect. The B3LYP functional with a 6-31G(d, p basis sets have been used to compute absorption energies. The solvent effects have been described within the polarizable continuum model (PCM. The geometries are optimized using density functional theory (DFT with B3LYP functional combined with 6-31G(d, p basis sets. The vertical absorption energies both in gas phase and in polar solvents such as ethanol, methanol and water were computed. Red-shift of the absorption maximum in the polar solvents is discussed in terms of electrostatic interaction energy, oscillator strength and dipole moment.

  1. [The absorption and metabolism of oxymatrine in rat intestine].

    Cai, Li-yun; Wu, Li-li; Yu, Xiao-ming; Liu, Jun-jin; Han, Wei-chao; Wei, Qiang; Tang, Lan

    2015-10-01

    The purpose of this study is to systematically investigate the characteristics of absorption and metabolism of oxymatrine (OMT) using rat intestinal perfusion model. Ultra performance liquid chromatography (UPLC) and high performance liquid chromatography-electrospray ionization-quadrupole-time of flight mass spectrometry (HPLC-ESI(+)-Q-TOF-MS) were used to test absorption of OMT in intestine at 100, 200 and 400 µmol · L(-1). The absorption rate and permeability of OMT is not dependent on concentration, but through passive absorption in intestine (P > 0.05). In the rat intestine, the absorbed amount of OMT was significantly different in four sections of the intestine in an order of duodenum > jejunum > ileum > colon (P < 0.05). OMT is metabolized into two metabolites in duodenum and jejunum, and matrine (MT) is the major one.

  2. Absorption heat pump for space applications

    Nguyen, Tuan; Simon, William E.; Warrier, Gopinath R.; Woramontri, Woranun

    1993-01-01

    In the first part, the performance of the Absorption Heat Pump (AHP) with water-sulfuric acid and water-magnesium chloride as two new refrigerant-absorbent fluid pairs was investigated. A model was proposed for the analysis of the new working pairs in a heat pump system, subject to different temperature lifts. Computer codes were developed to calculate the Coefficient of Performance (COP) of the system with the thermodynamic properties of the working fluids obtained from the literature. The study shows the potential of water-sulfuric acid as a satisfactory replacement for water-lithium bromide in the targeted temperature range. The performance of the AHP using water-magnesium chloride as refrigerant-absorbent pair does not compare well with those obtained using water-lithium bromide. The second part concentrated on the design and testing of a simple ElectroHydrodynamic (EHD) Pump. A theoretical design model based on continuum electromechanics was analyzed to predict the performance characteristics of the EHD pump to circulate the fluid in the absorption heat pump. A numerical method of solving the governing equations was established to predict the velocity profile, pressure - flow rate relationship and efficiency of the pump. The predicted operational characteristics of the EHD pump is comparable to that of turbomachinery hardware; however, the overall efficiency of the electromagnetic pump is much lower. An experimental investigation to verify the numerical results was conducted. The pressure - flow rate performance characteristics and overall efficiency of the pump obtained experimentally agree well with the theoretical model.

  3. 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.

  4. Migrant labor absorption in Malaysia.

    Nayagam, J

    1992-01-01

    The use of migrant workers to ease labor shortages caused by rapid industrialization in Malaysia during the twentieth century is examined. "This paper will focus on: (1) the extent, composition and distribution of migrant workers; (2) the labor shortage and absorption of migrant workers; and (3) the role of migrant workers in the government's economic restructuring process."

  5. Neutron Absorption in Geological Material

    Løvhøiden, G.; Andersen, E.

    1990-01-01

    Thermal neutron absorption cross section of geological samples is determined with the steady state neutron source method. Cross section measurements of North Sea sediments demonstrate that also materials with high contents of clay minerals may be investigated with the steady state method.

  6. 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...

  7. Clustering of absorption line systems

    Petitjean, P

    1996-01-01

    Absorption line systems are luminosity unbiased tracers of the spatial distribution of baryons over most of the history of the Universe. I review the importance of studying the clustering properties of the absorbers and the impact of VLT in this subject. The primary aim of the project is to track the evolution of the structures of the Universe back in time.

  8. Active Absorption Wave Maker System for Irregular Waves

    柳淑学; 王先涛; 李木国; 郭美谊

    2003-01-01

    The key problem in physical model tests with highly reflective structures is to prevent the multiple reflections between the reflective structures and the wave maker. An active absorption wave maker system is described and the representative frequency method for irregular waves is proposed in this paper. Physical model tests are conducted to verify the effectiveness of the proposed method.

  9. 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.

  10. 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.

  11. Sound absorption property of openpore aluminum foams

    WANG Fang

    2007-02-01

    Full Text Available This paper presents a study on sound absorption property of aluminum foam by evaluating its sound absorption coefficients using standing wave tube method. Experimental results showed that the average values of sound absorption coefficients (over the test frequency range are all above 0.4, which indicate very good sound absorption property of the aluminum foams. The sound absorption coefficient is affected by frequency and pore structure, and reaches its maximum value at around 1 000 Hz. With the increase of porosity and decrease of cell diameter, the sound absorption coefficient values increase.

  12. Chromophore design for large two-photon absorption

    Dudley, Christopher

    2014-11-01

    Conjugated oligothiophene chromophores are compared and studied for designing large linear and nonlinear absorption cross-sections. Optical properties of chromophores synthesized by the Naval Research Laboratory are modeled to construct a design factor of merit to predict and understand two-photon absorption (TPA) designs. Computer modeling to optimize parameters to produce photo active chromophores is conducted. Geometry, π-center (electron relay) and the electron donor or acceptor groups attached to the π-centers are considered for importance in TPA. This work could serve equally well as guide for quick back of the envelop research or industrial design verifications as well as an outline for introducing computation methods to students.

  13. The distribution of absorptive power dissipation in irradiated nanoparticulate system

    Li, Jiayu; Yang, Jian; Gu, Xiaobing

    2016-10-01

    The knowledge of local radiant absorption is important to the nanostructure optimization, it is beneficial to the applications in energy harvesting, optical heating, photocatalysis, etc. In this paper, FDTD model is constructed for the distribution of absorptive power dissipation in irradiated nanoparticulate system. The theoretical model extended from Mie theory is used to examine the FDTD model, the parameters and conditions set for FDTD simulation are confirmed based on the comparison. Then, the influence of Ag nanoparticle on the absorptive properties of nearby TiO2 nanoparticle is investigated by FDTD simulation at the wavelength of 0.25 μm. It is indicated that suitable distance between TiO2 and Ag particles is beneficial to the spectral radiant absorption of TiO2 particle. Considering the agglomeration of nanoparticles and the oxidation at the TiO2-Ag interface, the Ag core coated with Al2O3 shell is suggested, and the simulated results indicated that the shell thickness and the Ag core size need to be optimized for enhancing the radiant absorption of TiO2 particle.

  14. 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.

  15. Simultaneous absorption of H2S and CO2 in solutions of alkanolamines

    Bosch, H.; Kuipers, J.A.M.; Swaaij, W.P.M. van; Versteeg, G.F.

    1989-01-01

    An absorption model has been developed which is able to calculate the simultaneous absorption rates (and corresponding enhancement factors) of two gaseous components into a reactive liquid. In the liquid phase multiple complex parallel reversible reactions may take place. This model, for example, ca

  16. Mechanical Parameters Effects on Acoustic Absorption at Polymer Foam

    Lyes Dib

    2015-01-01

    Full Text Available Polymer foams have acoustic absorption properties that play an important role in reducing noise level. When the skeleton is set to motion, it is necessary to use generalized Biot-Allard model which takes into account the deformation of the skeleton and the fluid and the interactions between them. The aim of this work is to study the quality of acoustic absorption in polyurethane foam and to show the importance of the structural vibration of this foam on the absorption by varying mechanical parameters (Young’s modulus E, Poisson’s coefficient ν, structural damping factor η, and the density ρ1. We calculated the absorption coefficient analytically using classical Biot formulation (us, uf and numerically using Biot mixed formulation (us, p in 3D COMSOL Multiphysics. The obtained results are compared together and show an excellent agreement. Afterwards, we studied the effect of varying each mechanical parameter independently on the absorption in interval of ±20%. The simulations show that these parameters have an influence on the sound absorption around the resonance frequency fr.

  17. 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...

  18. Effect of Nitrogen Application Models on the Dynamic of Nutrient Absorption of Spring Maize%施氮模式对春玉米养分吸收动态的影响

    隽英华; 汪仁; 孙文涛; 邢月华; 宫亮; 蔡广兴

    2011-01-01

    By the test in spring maize field and laboratory analysis, the dynamic behavior of nutrient absorption of spring maize and the fertilizer N use efficiency were studied as affected by models of nitrogen application. The results showed that nitrogen application enhanced N, P and K contents of maize plant, and improved the maize yield character. With growth stages, the N and K contents of each organ of maize plant decreased, and P content changed with no rule. Compared with other models of nitrogen application, two topdressings and one deep application both showed greater preponderance, whose output-input ratio, N agronomic efficiency and fertilizer N use efficiency were 7.78, 29.05 kg/kg and 40.13% and 6.93, 24.38 kg/kg and 39.92%, respectively. Considered fertilizer requirement characteristics of maize and fertilizer properties, it was filtrated that, P and K fertilizers as basic fertilizer, and N fertilizer as basic fertilizer, jointing fertilizer and big trumpet fertilizer and as basic fertilizer with one deep application were the best techniques of fertilizer application.%通过春玉米田间试验和室内分析,研究施氮模式对春玉米养分吸收动态及氮肥利用率的影响.结果表明,施氮提高了玉米植株氮、磷、钾含量,改善了玉米产量性状.随着生育期推进,玉米植株各器官氮、钾含量逐渐降低,磷含量变化无规律性.与其他施氮模式相比,二次追肥和一次深施处理显示出较大的优势,其中,产投比分别为7.78和6.93,氮肥农学效率分别为29.05 kg/kg和24.38 kg/kg,氮肥利用率分别为40.13%和39.92%.结合玉米的生理需肥特性和肥料性质,磷、钾肥作基肥,氮肥作基肥+拔节肥追肥+大喇叭口肥追肥和氮肥一次深施为适宜的施肥技术.

  19. Photodetector with enhanced light absorption

    Kane, James

    1985-01-01

    A photodetector including a light transmissive electrically conducting layer having a textured surface with a semiconductor body thereon. This layer traps incident light thereby enhancing the absorption of light by the semiconductor body. A photodetector comprising a textured light transmissive electrically conducting layer of SnO.sub.2 and a body of hydrogenated amorphous silicon has a conversion efficiency about fifty percent greater than that of comparative cells. The invention also includes a method of fabricating the photodetector of the invention.

  20. Practical absorption limits of MPP absorber

    MAA Dah-You

    2006-01-01

    The construction and properties of microperforated panel (MPP) absorber are discussed. The absorption limit of the absorber had been shown that low values of the perforate constant k = d(f/10)1/2 and the orifice diameter d (in mm) are essential for MPP to have high absorption in wide frequency band. To find the exact limits, take 1 for k as a start, because both specific resistance and high absorption require k around one. And the orifice diameter d is chosen as 0.1 mm, so that the peak absorption coefficient (resonance absorption) is at 1000 Hz,and high sound frequency may be in the absorption region. Is it possible for a single layer of such an MPP to cover the whole absorption region required in practice? The half-absorption limit is not a good criterion, because low absorption comes in also in some cases. The 0.5 absorption coefficient limit is suggested for practical region, as a standard for comparison. Absorption curves were drawn for different load resistances, of absorption coefficients versus frequency.Ordinary MPP absorber absorbs in slightly over two octaves, and the new absorber with r = 1 (specific resistance equal to the characteristic impedance in air)is slightly better than these, 2.5 octaves. The new absorbers with r > 1, are much better than these, and some satisfies high absorption in broad frequency range. Realization of these will mean great progress of MPP absorbers.

  1. Temperature-dependent 780-nm laser absorption by engineering grade aluminum, titanium, and steel alloy surfaces

    Rubenchik, Alexander M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wu, Sheldon S. Q. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kanz, V. Keith [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); LeBlanc, Mary M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lowdermilk, W. Howard [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rotter, Mark D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Stanley, Joel R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-07-17

    When modeling laser interaction with metals for various applications it requires a knowledge of absorption coefficients for real, commercially available materials with engineering grade (unpolished, oxidized) surfaces. But, most currently available absorptivity data pertain to pure metals with polished surfaces or vacuum-deposited thin films in controlled atmospheres. A simple laboratory setup is developed for the direct calorimetric absorptivity measurements using a diode-array laser emitting at 780 nm. A scheme eliminating the effect of convective and radiative losses is implemented. Futhermore, the obtained absorptivity results differ considerably from existing data for polished pure metals and are essential for the development of predictive laser-material interaction models.

  2. 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

  3. Water and solute absorption from carbohydrate-electrolyte solutions in the human proximal small intestine: a review and statistical analysis.

    Shi, Xiaocai; Passe, Dennis H

    2010-10-01

    The purpose of this study is to summarize water, carbohydrate (CHO), and electrolyte absorption from carbohydrate-electrolyte (CHO-E) solutions based on all of the triple-lumen-perfusion studies in humans since the early 1960s. The current statistical analysis included 30 reports from which were obtained information on water absorption, CHO absorption, total solute absorption, CHO concentration, CHO type, osmolality, sodium concentration, and sodium absorption in the different gut segments during exercise and at rest. Mean differences were assessed using independent-samples t tests. Exploratory multiple-regression analyses were conducted to create prediction models for intestinal water absorption. The factors influencing water and solute absorption are carefully evaluated and extensively discussed. The authors suggest that in the human proximal small intestine, water absorption is related to both total solute and CHO absorption; osmolality exerts various impacts on water absorption in the different segments; the multiple types of CHO in the ingested CHO-E solutions play a critical role in stimulating CHO, sodium, total solute, and water absorption; CHO concentration is negatively related to water absorption; and exercise may result in greater water absorption than rest. A potential regression model for predicting water absorption is also proposed for future research and practical application. In conclusion, water absorption in the human small intestine is influenced by osmolality, solute absorption, and the anatomical structures of gut segments. Multiple types of CHO in a CHO-E solution facilitate water absorption by stimulating CHO and solute absorption and lowering osmolality in the intestinal lumen.

  4. Resonant Optical Absorption in Semiconductor Quantum Wells

    YU Li-Yuan; CAO Jun-Cheng

    2004-01-01

    @@ We have calculated the intraband photon absorption coefficients of hot two-dimensional electrons interacting with polar-optical phonon modes in quantum wells. The dependence of the photon absorption coefficients on the photon wavelength λ is obtained both by using the quantum mechanical theory and by the balance-equation theory. It is found that the photon absorption spectrum displays a local resonant maximum, corresponding to LO energy, and the absorption peak vanishes with increasing the electronic temperature.

  5. 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.)

  6. Drug gastrointestinal absorption in rat: Strain and gender differences.

    Oltra-Noguera, Davinia; Mangas-Sanjuan, Victor; González-Álvarez, Isabel; Colon-Useche, Sarin; González-Álvarez, Marta; Bermejo, Marival

    2015-10-12

    Predictive animal models of intestinal drug absorption are essential tools in drug development to identify compounds with promising biopharmaceutical properties. In situ perfusion absorption studies are routinely used in the preclinical setting to screen drug candidates. The objective of this work is to explore the differences in magnitude and variability on intestinal absorption associated with rat strain and gender. Metoprolol and Verapamil absorption rate coefficients were determined using the in situ closed loop perfusion model in four strains of rats and in both genders. Strains used were Sprague-Dawley, Wistar-Han, Wistar-Unilever, Long-Evans and CD∗IGS. In the case of Metoprolol only CD∗IGS and Wistar Unilever showed differences between males and females. For Verapamil, Wistar Han and Sprague-Dawley strains do not show differences between male and female rats. That means that in these strains permeability data from male and female could be combined. In male rats, which are commonly used for permeability estimation, there were differences for Metoprolol permeability between Sprague-Dawley (with lower permeability values) and the other strains, while for Verapamil Sprague-Dawley and Wistar-Han showed the lower permeability values. In conclusion, the selection of rat's strain and gender for intestinal absorption experiments is a relevant element during study design and data from different strains may not be always comparable.

  7. 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

  8. 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...

  9. The Regulation of Iron Absorption and Homeostasis

    Wallace, Daniel F

    2016-01-01

    Iron is an essential element in biology, required for numerous cellular processes. Either too much or too little iron can be detrimental, and organisms have developed mechanisms for balancing iron within safe limits. In mammals there are no controlled mechanisms for the excretion of excess iron, hence body iron homeostasis is regulated at the sites of absorption, utilisation and recycling. This review will discuss the discoveries that have been made in the past 20 years into advancing our understanding of iron homeostasis and its regulation. The study of iron-associated disorders, such as the iron overload condition hereditary haemochromatosis and various forms of anaemia have been instrumental in increasing our knowledge in this area, as have cellular and animal model studies. The liver has emerged as the major site of systemic iron regulation, being the location where the iron regulatory hormone hepcidin is produced. Hepcidin is a negative regulator of iron absorption and recycling, achieving this by binding to the only known cellular iron exporter ferroportin and causing its internalisation and degradation, thereby reducing iron efflux from target cells and reducing serum iron levels. Much of the research in the iron metabolism field has focussed on the regulation of hepcidin and its interaction with ferroportin. The advances in this area have greatly increased our knowledge of iron metabolism and its regulation and have led to the development of novel diagnostics and therapeutics for iron-associated disorders.

  10. Compression-absorption cascade refrigeration system

    Fernandez-Seara, Jose; Sieres, Jaime; Vazquez, Manuel [Area de Maquinas y Motores Termicos, Escuela Tecnica Superior de Ingenieros Industriales, Universidade de Vigo, Campus Lagoas-Marcosende, 9, 36200 Vigo (Spain)

    2006-04-01

    This paper describes the study carried out to analyse a refrigeration system in cascade with a compression system at the low temperature stage and an absorption system at the high temperature stage to generate cooling at low temperatures, as well as the possibility of powering it by means of a cogeneration system. CO{sub 2} and NH{sub 3} have been considered as refrigerants in the compression stage and the pair NH{sub 3}-H{sub 2}O in the absorption stage. The analysis has been realized by means of a mathematical model of the refrigeration system implemented in a computer program and taking into account the characteristic operating conditions of a cogeneration system with gas engines. The paper presents the results obtained regarding the performance of the refrigeration system and the adaptability between the power requirements of the refrigeration system and the power supplied by the cogeneration system taking into account the present Spanish Regulations about the use of cogeneration systems. [Author].

  11. Percutaneous absorption of methimazole: an in vitro study of the absorption pharmacokinetics for two different vehicles.

    Hill, K E; Mills, P C; Jones, B R; Bolwell, C F; Aberdein, D; Chambers, J P

    2015-12-01

    The use of transdermal medications in cats has become popular in veterinary medicine due to the ease of administration compared to oral medication. However, the research to support systemic absorption of drugs applied to the pinna after transdermal administration in cats is limited. The aim of this study was to characterize the percutaneous absorption pharmacokinetics of methimazole in a lipophilic vehicle compared to methimazole in Pluronic(®) lecithin organogel (PLO) using a finite dose applied to feline ear skin in an in vitro Franz cell model. The two formulations of methimazole (10 mg) were applied to the inner stratum corneum of six pairs of feline ears. The receptor medium was sampled up to 30 h post-administration, and methimazole concentrations were measured using high-performance liquid chromatography (HPLC). Histological examination of all ears was undertaken as small differences in the thickness of ear skin may have contributed to inter-individual differences in methimazole absorption between six cats. Methimazole was absorbed more completely across the pinnal skin when administered in the lipophilic vehicle compared to administration in the PLO gel (P < 0.001).

  12. Carbon Dioxide Absorption Heat Pump

    Jones, Jack A. (Inventor)

    2002-01-01

    A carbon dioxide absorption heat pump cycle is disclosed using a high pressure stage and a super-critical cooling stage to provide a non-toxic system. Using carbon dioxide gas as the working fluid in the system, the present invention desorbs the CO2 from an absorbent and cools the gas in the super-critical state to deliver heat thereby. The cooled CO2 gas is then expanded thereby providing cooling and is returned to an absorber for further cycling. Strategic use of heat exchangers can increase the efficiency and performance of the system.

  13. 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.Abso

  14. Parametric analysis of a double-effect steam absorption chiller

    Mohammed Salih Ahmed, Mojahid Sid Ahmed; Gilani, Syed Ihtsham Ul-Haq

    2012-06-01

    The development in the field of refrigeration and cooling systems based on absorption cycles has attained its own internal dynamic in the last decade. A major obstacle for developing model is the lack of available component specifications. These specifications are commonly proprietary of the chiller's manufacturers and normally the available information is not sufficient. This work presented a double-effect parallel-flow-type steam absorption chiller model based on thermodynamic and energy equations. The chiller studied is 1250 RT (Refrigeration Tons) using lithium bromide -water as working pair. The mathematical equations that govern the operation of the steam absorption chiller are developed, and from the available design data the values of the overall heat transfer coefficient multiplied by the heat exchanger surface area and the characteristics of each component of the absorption chiller at the design point are calculated. For thermo physical and thermodynamic properties for lithium bromide-water solution, set of computationally efficient formulations are used. The model gives the required information about temperature, concentration, and flow rate at each state point of the system. The model calculates the heat load at each component as well as the performance of the system.

  15. Coronal heating by resonant absorption: The effects of chromospheric coupling

    Belien, A. J. C.; Martens, P. C. H.; Keppens, R.

    1999-01-01

    We present the first 2.5 dimensional numerical model calculations of the nonlinear wave dynamics and heating by resonant absorption in coronal loops with thermal structuring of the transition region and higher chromosphere. The numerical calculations were done with the Versatile Advection Code. The

  16. Lifshitz Tails for the Interband Light Absorption Coefficient

    W Kirsch; M Krishna

    2010-09-01

    In this paper we consider the interband light absorption coefficient (ILAC) for various models. We show that at the lower and upper edges of the spectrum the Lifshitz tails behaviour of the density of states implies similar behaviour for the ILAC at appropriate energies. The Lifshitz tails property is also exhibited at some points corresponding to the internal band edges of the spectrum.

  17. Light-Induced Absorption in Nominally Pure Bismuth Silicon Oxide

    李飞飞; 许京军; 孔勇发; 黄辉; 张光寅; 杨春晖; 徐玉恒

    2001-01-01

    Light-induced absorption in the nominally pure bismuth silicon oxide is investigated experimentally and the result shows that it consists of transient and persistent parts. The experimental evidence is analysed based on the model of three groups of trap (donor) centres.

  18. The Mechanism of Interfacial Mass Transfer in Gas Absorption Process

    马友光; 冯惠生; 徐世昌; 余国琮

    2003-01-01

    Based on the method of molecular thermodynamics ,the mass transfer mechanism at gas-liquid interface is studied theoretically,and a nowe mathematical model is proposed,Using laser holographic interference technique,the hydrodynamics and mass transfer characteristics of CO2 absorption are measured,It is shown that the calculated results are in good agreement with the experimental data.

  19. Gas-phase SO2 in absorption towards massive protostars

    Keane, JV; Boonman, AMS; Tielens, AGGM; van Dishoeck, EF; Dishoeck, E. F.; Lahuis, F. van; Wright, C. M.; Doty, S. D.

    2001-01-01

    We present the first detection of the v(3) ro-vibrational band of gas-phase SO2 in absorption in the mid-infrared spectral region around 7.3 mum of a sample of deeply embedded massive protostars. Comparison with model spectra shows that the derived excitation temperatures correlate with previous C2H

  20. Absorption recovery in strongly saturated quantum-well electroabsorption modulators

    Højfeldt, Sune; Romstad, F.; Mørk, Jesper

    2003-01-01

    We observe experimentally that a quantum-well electroabsorption modulator, when strongly saturated by a highly energetic optical pulse, may exhibit an absorption recovery time much longer than for excitation with a low-energy pulse. Using a comprehensive drift-diffusion. type model, we are able...