Absorption Phenomena Research Articles

Probiotics: A Promising Tool for Calcium Absorption

As we know nutrients are necessary for the development and proper functioning of the human organism. Bioavailabilities of nutrients are the major concern rather than the supply of an adequate amount of nutrients in the diet. Many of the researches have been shown that the consumption of probiotics along with dairy foods buffers the acidity of the stomach and increases the bacterial survival rate into the intestine. A dairy product with probiotics also provides many of essential nutrients, including protein and calcium. From all the necessary nutrients the calcium having a major role in the human body including the development of bone and teeth are also regulating enzymes and many more. Calcium is the most essential nutrient, about 99% of calcium found in teeth and bone in the body and only 1% is found in serum. A numbers of researches have shown that adequate amount of calcium intake leads to reduce risk of fracture, Osteoporosis and Hypoglycaemia and diabetes in some population. Many of the researches suggested that the Probiotics having a significant role in improvement of calcium uptake and absorption, hence the present review gives information about the relationship of probiotics and calcium, ensuring higher bioavailability of calcium and promising a better bone health. Here, the review study showed a significant role of probiotics in calcium absorption and thus the bioavailabilities. Moreover, it is focused on glimpse of various studies and in-vitro models associated with the phenomena of calcium absorption and uptake.

Ag nanoparticles embedded in Nd:YAG crystals irradiated with tilted beam of 200 MeV Xe ions: optical dichroism correlated to particle reshaping

We report on the fabrication of reshaped Ag nanoparticles (NPs) embedded in a Nd:YAG crystal by combining Ag ion implantation and swift heavy Xe ion irradiation. The localized surface plasmon resonance (LSPR) effect is proved to be efficiently modulated according to the phenomenon of polarization-dependent absorption. The LSPR peak located at 448 nm shows red shift and blue shift at 0° and 90° polarization, respectively, which is in good agreement with calculation by discrete dipole approximation. Based on the near-field intensity distribution, the interaction between reshaped NPs shows a non-ignorable effect on the optical absorption. Furthermore, the polarization-dependence of the photoluminescence (PL) intensity is analyzed, which is positively related to the modulated LSPR absorption. It demonstrates the potential of the enhancement of PL intensity by embedded plasmonic Ag NPs. This work breaks the conventional view of the quenching effect of NPs by ion irradiation and opens a new way to realize the modulation of optical dichroism.

Spectral analysis of the hypoelliptic Robin problem

This paper is devoted to a functional analytic approach to the study of the hypoelliptic Robin problem for a second-order, uniformly elliptic differential operator with a complex parameter $$\lambda $$ , under the probabilistic condition that either the absorption phenomenon or the reflection phenomenon occurs at each point of the boundary. We solve the long-standing open problem of the asymptotic eigenvalue distribution for the homogeneous Robin problem when $$\vert \lambda \vert $$ tends to $$\infty $$ . More precisely, we prove the spectral properties of the closed realization of the uniformly elliptic differential operator, similar to the elliptic (non-degenerate) case. However, in the degenerate case we cannot use Green’s formula to characterize the adjoint operator of the closed realization. Hence, we shift our attention to its resolvent. In the proof, we make use of the Boutet de Monvel calculus in order to study the resolvent and its adjoint in the framework of $$L^{2}$$ Sobolev spaces.

Kinetic Equilibrium Study of CO2 poisoning Observed in Anion Exchange Membranes When Exposed to Ambient Air and Varying Levels of CO2 ppm

One of the hurdles in Anion exchange membrane fuel cell technology is weaker understanding of CO2 poisoning observed when they are exposed to air. Our previous work suggests that OH- ions depletes in approximately 15 min to form CO3 2- and HCO3 - ions when exposed to ambient air at 30 °C and 95%RH[1]. However, an actual fuel cell device is operated at a much higher temperature. In this study we have obtained the CO2 absorption data at different temperatures and different CO2 concentration environment. Our data suggest that the air equilibrated AEM concentration of CO3 2- increases at higher temperatures whereas HCO3 - concentration follows a decreasing trend. The OH- ion has a very insignificant change at higher temperatures but we observe that the equilibrium OH- concentration is higher at lower ppm level of CO2 environment. This indicates that the CO2 reaction is dependent on CO2 concentration in air. We have also studied the transient change in ionic conductivity of OH- AEM films in ambient air. Here, we observe the nature of drop in conductivity when exposed to air. We have attempted to fit the conductivity data to mathematical models that will give us more insights into absorption phenomenon of CO2. Acknowledgements: This research was funded by the Department of energy through NREL. The AEM samples were supplied by Dr. Bryan Pivovar’s group at NREL. Reference A.G. Divekar, A. M. Park, Z. R. Owczarczyk, S. Seifert, B. S. Pivovar and A. M. Herring, ECS Transactions, 80, 1005 (2017). Figure 1

A UPLC-ESI-MS/MS Method for Simultaneous Quantitation of Chlorogenic Acid, Scutellarin, and Scutellarein in Rat Plasma: Application to a Comparative Pharmacokinetic Study in Sham-Operated and MCAO Rats after Oral Administration of Erigeron breviscapus Extract.

Erigeron breviscapus, a traditional Chinese medicine, is clinically used for the treatment of occlusive cerebral vascular diseases. We developed a sensitive and reliable ultra-performance liquid chromatography-electrospray-tandem mass spectrometry (UPLC-ESI-MS/MS) method for simultaneous quantitation of chlorogenic acid, scutellarin, and scutellarein, the main active constituents in Erigeron breviscapus, and compared the pharmacokinetics of these active ingredients in sham-operated and middle cerebral artery occlusion (MCAO) rats orally administrated with Erigeron breviscapus extract. Plasma samples were collected at 15 time points after oral administration of the Erigeron breviscapus extract. The levels of chlorogenic acid, scutellarin, and scutellarein in rat plasma at various time points were determined by a UPLC-ESI-MS/MS method, and the drug concentration versus time plots were constructed to estimate pharmacokinetic parameters. The concentration of chlorogenic acid in the plasma reached the maximum plasma drug concentration in about 15 min and was below the limit of detection after 4 h. Scutellarin and scutellarein showed the phenomenon of multiple absorption peaks in sham-operated and MCAO rats, respectively. Compared with the sham-operated rats, the terminal elimination half-life of scutellarein in the MCAO rats was prolonged by more than two times and the area under the curve of each component in the MCAO rats was significantly increased. The results showed chlorogenic acid, scutellarin, and scutellarein in MCAO rats had higher drug exposure than that in sham-operated rats, which provided a reference for the development of innovative drugs, optimal dosing regimens, and clinical rational drug use.

Hybrid PCM—aluminium foams’ thermal storages: an experimental study

The latent heat absorption phenomenon associated with melting of a suitable phase change material can be an effective way to improve the thermal energy storage (TES) behaviour in many applications. However, the most suitable materials to be used in heating and refrigeration systems find intrinsic limitations due to their poor heat transfer capabilities. This work experimentally studies the use of aluminium foams as heat transfer medium to improve the overall heat transfer of paraffin waxes that can be possible phase change materials to be implemented in hybrid sensible latent water TESs. The experimental tests were run in a dedicated setup designed, developed and built at the Department of Management and Engineering of the University of Padova. The effects of the use of aluminium foams as enhancing heat transfer medium were studied by comparing the loading and unloading processes of a paraffin wax with melting temperature around 40°C, with and without metal foams, in a water thermal storage unit. The effects of three different foams with 5, 20, and 40 pores per inch (PPI) were investigated.

Simulation of laser induced absorption phenomena in transparent materials

The laser-induced damage in transparent optical materials represents an important active field of research as part of laser/material interactions studies. Most of research activities within this field are aiming to laser micro-processing of transparent optical materials, glasses and ceramics. An example of such laser micro-processing techniques is drilling micro channels through a glass plate and drilling transverse holes through single mode optical fibre cladding and core. The latter example of research activity has an important purpose consisting of designing and manufacturing micro-nanoscale optical fibre sensors with improved capabilities. Regarding these applicative research activities, there are two important correlated issues here to be underlined. The first one consists in the fact that high intensity laser field induced electron density variation into a transparent material is the main mechanism of breakdown and damage, that is, basis of micro-processing. The second one refers to the necessity of developing simulation procedures based on accurate theoretical models of these physical processes in order to use an accurate computer control of micro-processing technology. The main purpose of this work is to present the results of simulations in electron density variation induced by high intensity laser pulses in various transparent materials.

Armamentarium of nanoscaled lipid drug delivery systems customized for oral administration: In silico docking patronage, absorption phenomenon, preclinical status, clinical status and future prospects.

Poor drug solubility and bioavailability remain a significant and frequently encountered concern for pharmaceutical scientists. Nanoscaled lipid drug delivery systems (NSLDDS) have exhibited great potentials in oral delivery of poorly water-soluble drugs, primarily for lipophilic drugs, with several successful clinical products. In the past few years, we have find out that optimized composition of drug in lipid, surfactant, or mixture of lipid and surfactant omits the solubility, permeability and bioavailability issues, which are potential limitations for oral absorption of poorly water-soluble drugs. Lipids not only vary in structures and physiochemical properties, but also in their digestibility and absorption pathway; therefore selection of lipid excipients and dosage form has a pronounced effect on biopharmaceutical aspects of drug absorption and distribution both in vitro and in vivo. Therefore, in current critical review, a comprehensive overview of the different lipid based nanostructured drug delivery systems intended for oral administration has been presented. In addition, implication of in silico docking in designing of NSLDDS as well as mechanism of absorption of different lipid based nanoformulations through intestinal absorption window has also been offered. Moreover, attention has also been paid to NSLDDS that are currently undergoing preclinical or clinical analysis.

Thermal instability and kinetic analysis on m-chloroperbenzoic acid

m-Chloroperbenzoic acid (MCPBA) has been widely applied as an oxidant agent for various oxidations in organic chemistry. The understanding of thermal instability and kinetics is a prerequisite for safer storage and transportation. This study investigated the thermal decomposition characteristics of MCPBA under dynamic and adiabatic conditions by performing TG, DSC and ARC tests, respectively. Kinetic parameters were computed using Starink method and compensation effect. Thermal safety parameters, including critical temperature of thermal explosion (Tb) and time to maximum rate under adiabatic conditions (TMRad), were determined to assess the thermal hazard of MCPBA. The experimental results showed two major thermal decomposition processes and a coupling phenomenon of heat absorption and generation. The mean value of Ea was determined as 57.630 kJ mol−1, and the best model to describe the overall reaction mechanism was three-dimensional diffusion model with integral form \(G\left( \alpha \right) = \left[ {1 - \left( {1 - \alpha } \right)^{1/3} } \right]^{2}\) for 0.05 < α < 0.80. The TMRad was 24 h with an apparent onset temperature of 345.82 K. This study provided a guidance to determine the safety measures in MCPBA storage and transportation.

Electromagnetically-induced Transparency in Metamaterials for the Potential Applications

Metamaterial (MM) is artificial material in which an unit cell, having a size much smaller than the wavelength of external electromagnetic (EM) wave, is periodically arranged. This MM offers a new tool that can significantly improve the effectiveness of absorber and the sensitivity of sensor through its powerful localization and field enhancement. This review presents recent the potential applications of electromagnetically-induced transparency (EIT) and absorption (EIA) phenomena in MM-based absorber and MM-based sensors, and summarizes the sensitivity differences from the existing sensors. These phenomena provide a high-performance platform for a variety of sensors with easy adjustment of the EM response, and can produce effective narrow- or multi-band absorption.

Saturable Absorption Enchantment of Au Nanorods Based on Energy Transfer between Longitudinal and Transverse Energy Levels**Supported by the National Natural Science Foundation of China under Grant Nos 11404410 and 11504105, and the Hunan Provincial Natural Science Foundation under Grant No 2016JJ3140.

Four kinds of Au nanorods (NRs) with different aspect ratios are designed to adjust the relationship between resonance energy level of longitudinal (L) and transverse (T) modes. During the femto-second Z-scan experiments, huge saturable absorption phenomena are observed while the energy level T is located between one to two times of the energy level L. This means that the energy may transfer between longitudinal and transverse energy levels in the same and/or different Au NRs. It effectively depresses the production of revised saturated absorption and increases the saturable absorption efficiency. This method is significant for the preparation of high-efficiency saturable absorption devices.

Simulation approach to decomposition kinetics and thermal hazards of hexamethylenetetramine

The thermal stability of HMT under dynamic, isothermal and adiabatic conditions was investigated using differential scanning calorimeter (DSC) and accelerating rate calorimeter (ARC), respectively. It is found from the dynamic DSC results that the exothermic decomposition reaction appears immediately after endothermic peak, a coupling phenomenon of heat absorption and generation, and the endothermic peak and exothermic peak were indentified at about 277–289 and 279–296 °C (Tpeak) with the heating rates 1, 2, 4 and 8 °C min−1. The ARC results reveal that the initial decomposition temperature of HMT is about 236.55 °C, and the total gas production in decomposition process is 6.9 mol kg−1. Based on the isothermal DSC and ARC data, some kinetic parameters have been determined using thermal safety software. The simulation results show that the exothermic decomposition process of HMT can be expressed by an autocatalytic reaction mechanism. There is also a good agreement between the kinetic model and kinetic parameters simulated based on the isothermal DSC and ARC data. Thermal hazards of HMT can be evaluated by carrying out thermal explosion simulations, which were based on kinetic models (Isothermal DSC and ARC) to predict several thermal hazard indicators, such as TD24, TD8, TCL, SADT, ET and CT so that we can optimize the conditions of transportation and storage for chemical, also minimizing industrial disasters.

Multichannel unidirectional perfect absorbers on sandwich structures with truncated symmetric photonic crystals

We experimentally studied unidirectional perfect absorbers with asymmetric sandwich structures composed of two thick metallic films with different thicknesses and a truncated symmetric photonic crystal (PC). Single-channel and multichannel near-perfect absorbers were obtained by adjusting period number of the PC. According to electromagnetic field intensity distributions at absorption wavelengths, the physical mechanism of near-perfect absorption derived from the coupling effect between optical Tamm state and Fabry-Pérot resonance. The unidirectional absorption phenomena were attributed to weak electric field distributions at absorption wavelengths for opposing directions of light incidence. The experimental values showed good agreement with theoretical results.

Study of coherence effects in a four-level Ξ−Λ type system

We theoretically study the two- and three-photon coherence in a Ξ−Λ type four-level system for stationary as well moving atoms at the room temperature using density matrix formalism. We discuss the role of dressed states to elucidate the electromagnetically induced transparency and electromagnetically induced absorption phenomena. The presence of the third field induces absorption at the line centre. A negative dispersion slope owing to the enhanced absorption results in super-luminal light propagation and the group index variation with the coupling field is switched from sub- to super-luminal. Group index with probe detuning shows super-luminal light propagation behaviour at the dressed state positions. The three optical fields trigger four-wave mixing as a result of the third order nonlinearity. The transient evolution is also discussed for optimum strengths of the coupling and drive fields to realize the optical switching in the system.

Propagation Characteristics of High-Power Vortex Laguerre-Gaussian Laser Beams in Plasma

The propagation characteristics of high-power laser beams in plasma is an important research topic and has many potential applications in fields such as laser machining, laser-driven accelerators and laser-driven inertial confined fusion. The dynamic evolution of high-power Laguerre-Gaussian (LG) beams in plasma is numerically investigated by using the finite-difference time-domain (FDTD) method based on the nonlinear Drude model, with both plasma frequency and collision frequency modulated by the light intensity of laser beam. The numerical algorithms and implementation techniques of FDTD method are presented for numerically simulating the nonlinear permittivity model of plasma and generating the LG beams with predefined parameters. The simulation results show that the plasma has different field modulation effects on the two exemplified LG beams with different cross-sectional patterns. The self-focusing and stochastic absorption phenomena of high-power laser beam in plasma are also demonstrated. This research also provides a new means for the field modulation of laser beams by plasma.

Physicochemical and thermodynamic investigation of hydrogen absorption and desorption in LaNi3.8Al1.0Mn0.2 using the statistical physics modeling

Abstract In the present work, experimental absorption and desorption isotherms of hydrogen in LaNi3.8Al1.0Mn0.2 metal at two temperatures (T = 433 K, 453 K) have been fitted using a monolayer model with two energies treated by statistical physics formalism by means of the grand canonical ensemble. Six parameters of the model are adjusted, namely the numbers of hydrogen atoms per site nα and nβ, the receptor site densities Nmα and Nmβ, and the energetic parameters Pα and Pβ. The behaviors of these parameters are discussed in relationship with temperature of absorption/desorption process. Then, a dynamic investigation of the simultaneous evolution with pressure of the two α and β phases in the absorption and desorption phenomena using the adjustment parameters. Thanks to the energetic parameters, we calculated the sorption energies which are typically ranged between 276.107 and 310.711 kJ/mol for absorption process and between 277.01 and 310.9 kJ/mol for desorption process comparable to usual chemical bond energies. The calculated thermodynamic parameters such as entropy, Gibbs free energy and internal energy from experimental data showed that the absorption/desorption of hydrogen in LaNi3.8Al1.0Mn0.2 alloy was feasible, spontaneous and exothermic in nature.

Growth and crystallization of Cobalt-doped TiO2 alloys: Effect of substrate and annealing temperature

This work presents a study of the structural and optical properties of cobalt-doped titanium dioxide thin films prepared via the DC Magnetron Co-Sputtering technique using TiO2 and Co targets with 99.99% purity; these thin films were deposited on three different substrates: Soda-lime glass, titanium foil and silicon wafer. The resulting films deposited on glass were then submitted to annealing processes at temperatures ranging from 500 °C to 600 °C. X-ray diffraction measurements revealed limited crystallization of the as-deposited samples, whilst the annealed samples showed several crystalline phases, including cobalt oxide (Co3O4) and a ternary phase (CoTi2O5); SEM studies helped to corroborate that the inclusion of TiO2 into the thin film decreases its crystallinity, obtaining nanostructures smaller in size as compared with samples containing cobalt. UV-vis-NIR measurements revealed an increase in transparence of the thin films after annealing at 600 °C, evidencing extrinsic absorption phenomena, consistent with the formation of binary phases inside the semiconductor matrix. From XPS measurements, the oxidation states for Co and Ti were obtained.

Internal heat generation/or absorption phenomena in three-dimensional natural convection flow within enclosure filled with different working fluids

PurposeThe purpose of this study is to investigate the effects of heat generation or absorption on heat transfer and fluid flow within two- and three-dimensional enclosure for homogeneous medium filled with different metal liquid. Numerical results are presented and analyzed in terms of fluid flow, thermal field structures, as well as average Nusselt number profiles over a wide range of dimensionless quantities, Grashof number (Gr) (104 and 105), SQ (varied between −500 to 500) and Prandtl number (Pr = 0.015, 0.024 and 0.0321). The results indicate that when the conductive regime is established for a Grashof number Gr = 104, the 2D model is valid and predicts all three-dimensional results with negligible difference. This was not the case in the convective regime (Gr = 105) where the effect of the third direction becomes important, where a 2D-3D difference was seen with about 37 per cent. Also, in most cases, the authors find that the heat absorption phenomena have the opposite effect with respect to the heat generation.Design/methodology/approachNumerical results are presented and analyzed in terms of fluid flow, thermal field structures, as well as average Nusselt number profiles over a wide range of dimensionless quantities.FindingsGrashof number (Gr) (104 and 105), SQ (varied between −500 to 500) and Prandtl number (Pr = 0.015, 0.024 and 0.0321).Originality/valueThe results indicate that when the conductive regime is established for a Grashof number Gr = 104, the 2D model is valid and predicts all three-dimensional results with negligible difference.

Bandwidth-enhanced polarization-insensitive metamaterial absorber based on fractal structures

This paper presents a broadband polarization insensitive prefect metamaterial absorber based on fractal structures. Through the combination of fractal and circular structure, the bandwidth is extended without increasing the size of the unit cell. A simple equivalent circuit model has been proposed describing the absorption phenomenon to predict the frequency of absorption of the proposed absorber. The simulated result shows that the absorber's full width half maximum is 18.5%. With rotational symmetry structures, the absorber is insensitive to the polarization. The incident angles at which the metamaterial absorber can maintain 50% of the absorbance are up to 50°. With the geometrical scalability, the absorber can be extended to any frequencies. This absorber is fabricated and measured at X-band, and the experimental results coincide well with the simulation results.

A mesoscale approach for modeling capillary water absorption and transport phenomena in cementitious materials

This paper proposes a mesoscale approach for simulating moisture transport by capillary action in partly-saturated porous cementitious composites. The modeling approach explicitly accounts for moisture transport through a mesostructure composed of coarse aggregates, surrounding cementitious mortar and interfaces. These latter, namely interface transition zones (ITZs), allow to describe the interaction between aggregates and mortar, and may cause an alternative path for the internal moisture movements. Basic morphology effects of the ITZs are simulated using a ribbon approach. Random spatial distribution of cement particles are stacked in the meso-geometry. Aggregate particles are introduced as randomly perturbed polygons and the moisture transport is modeled as a diffusion problem and solved by means of the finite element method. The proposed constitutive models are based on a proper description of the permeability and pore size distribution which strongly affect the local moisture content. Numerical results at both macro- and mesoscale levels demonstrate the soundness and capability of the proposed approach. The integrated modeling results actually demonstrate the potential of the mesoscale approach and shows the role of the ITZs as an internal interconnected network.