Presence Of Absorption Research Articles

An Artificial Gut/Absorption Simulator: Understanding the Impact of Absorption on In Vitro Dissolution, Speciation, and Precipitation of Amorphous Solid Dispersions.

Upon dissolution, amorphous solid dispersions (ASDs) of poorly water-soluble compounds can generate supersaturated solutions consisting of bound and free drug species that are in dynamic equilibrium with each other. Only free drug is available for absorption. Drug species bound to bile micelles, polymer excipients, and amorphous and crystalline precipitate can reduce the drug solute's activity to permeate, but they can also serve as reservoirs to replenish free drug in solution lost to absorption. However, with multiple processes of dissolution, absorption, and speciation occurring simultaneously, it may become challenging to understand which processes lead to an increase or decrease in drug solution concentration. Closed, nonsink dissolution testing methods used routinely, in the absence of drug removal, allow only for static equilibrium to exist and obscure the impact of each drug species on absorption. An artificial gut simulator (AGS) introduced recently consists of a hollow fiber-based absorption module and allows mass transfer of the drug from the dissolution media at a physiological rate after tuning the operating parameters. In the present work, ASDs of varying drug loadings were prepared with a BCS-II model compound, ketoconazole (KTZ), and hypromellose acetate succinate (HPMCAS) polymer. Simultaneous dissolution and absorption testing of the ASDs was conducted with the AGS, and simple analytical techniques were utilized to elucidate the impact of bound drug species on absorption. In all cases, a lower amount of crystalline precipitate was formed in the presence of absorption relative to the nonsink dissolution "control". However, formation of HPMCAS-bound drug species and crystalline precipitate significantly reduced KTZ absorption. Moreover, at high drug loading, inclusion of an absorption module was shown to enhance ASD dissolution. The rank ordering of the ASDs with respect to dissolution was significantly different when nonsink dissolution versus AGS was used, and this discrepancy could be mechanistically elucidated by understanding drug dissolution and speciation in the presence of absorption.

Strong light absorption and absorption absence in photonic crystals with helical structure in an external static magnetic field

In this paper, we investigate the light absorption in helically structured photonic crystals (HSPCs) in an external static magnetic field in the case when the parameter of magneto-optical activity is a function of the light wavelength. We investigate and compare the spectra of absorption, the spectra of imaginary parts of wave vectors of forward propagating eigenwaves, the spectra of the azimuth φ and ellipticity e of the total wave excited in the HSPC layer at its input surface for diffracting eigenwaves for both the absence and presence of an external magnetic field and, finally, in the absence and presence of absorption. All features of absorption are considered in detail, and their mechanisms are revealed.

The impact of plasmonic electrodes on the photocarrier extraction of inverted organic bulk heterojunction solar cells

Nano-patterning the semiconducting photoactive layer/back electrode interface of organic photovoltaic devices is a widely accepted approach to enhance the power conversion efficiency through the exploitation of numerous photonic and plasmonic effects. Yet, nano-patterning the semiconductor/metal interface leads to intertwined effects that impact the optical as well as the electrical characteristic of solar cells. In this work we aim to disentangle the optical and electrical effects of a nano-structured semiconductor/metal interface on the device performance. For this, we use an inverted bulk heterojunction P3HT:PCBM solar cell structure, where the nano-patterned photoactive layer/back electrode interface is realized by patterning the active layer with sinusoidal grating profiles bearing a periodicity of 300 nm or 400 nm through imprint lithography while varying the photoactive layer thickness (LPAL) between 90 and 400 nm. The optical and electrical device characteristics of nano-patterned solar cells are compared to the characteristics of control devices, featuring a planar photoactive layer/back electrode interface. We find that patterned solar cells show for an enhanced photocurrent generation for a LPAL above 284 nm, which is not observed when using thinner active layer thicknesses. Simulating the optical characteristic of planar and patterned devices through a finite-difference time-domain approach proves for an increased light absorption in presence of a patterned electrode interface, originating from the excitation of propagating surface plasmon and dielectric waveguide modes. Evaluation of the external quantum efficiency characteristic and the voltage dependent charge extraction characteristics of fabricated planar and patterned solar cells reveals, however, that the increased photocurrents of patterned devices do not stem from an optical enhancement but from an improved charge carrier extraction efficiency in the space charge limited extraction regime. Presented findings clearly demonstrate that the improved charge extraction efficiency of patterned solar cells is linked to the periodic surface corrugation of the (back) electrode interface.

Distributions of the Wigner reaction matrix for microwave networks with symplectic symmetry in the presence of absorption.

We report on experimental studies of the distribution of the reflection coefficients, and the imaginary and real parts of Wigner's reaction (K) matrix employing open microwave networks with symplectic symmetry and varying size of absorption. The results are compared to analytical predictions derived for the single-channel scattering case within the framework of random-matrix theory (RMT). Furthermore, we performed Monte Carlo simulations based on the Heidelberg approach for the scattering (S) and K matrix of open quantum-chaotic systems and the two-point correlation function of the S-matrix elements. The analytical results and the Monte Carlo simulations depend on the size of absorption. To verify them, we performed experiments with microwave networks for various absorption strengths. We show that deviations from RMT predictions observed in the spectral properties of the corresponding closed quantum graph and attributed to the presence of nonuniversal short periodic orbits does not have any visible effects on the distributions of the reflection coefficients and the K and S matrices associated with the corresponding open quantum graph.

ASSESSMENT AND IDENTIFICATION OF POLYOL BASED ON PALM OIL AND NATURAL FILLING MATERIALS FOR RENEWABLE COATING PAINT APPLICATION

Chitosan/clay hybrid nanoparticles have been prepared as natural antibacterial and anticorrosion agents to enhance the protective function of polyurethane-based coating paints. Chitosan is a material with antibacterial properties because it contains acetamide group which is widely used for hygiene purposes in the medical field. Clay is a natural clay particle with a hollow structure that allows loading and release of active substances such as surfactant ions that can contribute to improving the properties of the material. The polyurethane in this study was obtained from palm oil oleic acid, which was processed into polyol, toluene diisocyanate was added to produce polyurethane. Coating paint is efficiently loaded with chitosan and clay active substances which are combined to form a hybrid composite. Based on the FTIR data of polyurethane showing the formation of a hydroxyl group on the palm oil epoxide compound, the reaction lasted for 2 hours at 60oC as evidenced by the absorption of the OH wave number which widened at 3305.99 cm-1. The value of the wavelength of the OH group in the bentonite sample before and after purification has decreased, proving that the intercalation of surfactants into the bentonite interlayer causes the hydrophilic nature of bentonite to change to hydrophobicity. The d-spacing layer of raw bentonite has a maximum reflection angle peak of 7.26o with a d-spacing value of 1.132 nm, and the d-spacing size increases to 1.631 nm at the peak of the maximum reflection angle of 4.49o after purification. The presence of absorption at 1064.71 cm-1 in shrimp shell chitosan indicates COC vibration.

Loschmidt echo and Poincaré recurrences of entanglement

We study numerically the properties of entanglement of two interacting, or noninteracting, particles evolving in a regime of quantum chaos in the quantum Chirikov standard map. Such pairs can be viewed as interacting, on noninteracting, Einstein–Podolsky–Rosen pairs in a regime of quantum chaos. The analysis is done with such tools as the Loschmidt echo of entanglement and the Poincaré recurrences of entanglement in presence of absorption. The obtained results show unusual features of the entropy of entanglement and the spectrum of Schmidt decomposition with their dependence on interactions at different quantum chaos regimes.

Optical biosensor based on a photonic crystal with a defective layer designed to determine the concentration of SARS-CoV-2 in water

We propose a new optical biosensor based on a SiO2/Si photonic crystal with a defect layer, which can determine the concentration of SARS-CoV-2 in water by the defect mode shift. Two models of the dependence of the refractive index of the defect layer on the concentration of the pathogen in water were considered. The optimal parameters of the photonic crystal in our device were determined such as the thickness of the SiO2 and Si layers of the ideal photonic crystal of 0.720 and 0.275 μm, respectively, and the optimal thickness of the defect layer of 1.87 μm was also determined. It was also demonstrated that in the presence of absorption in the structure under study, it is much more advantageous to operate in the reflection mode compared to the transmission mode. Finally, the wavelength dependence of the defect mode on the SARS-CoV-2 concentration was obtained and the sensitivity of the sensor was determined to be 1020 nm/RIU.

Electrocoagulation Method Using Al/Graphite Electrode for Removal Surfactant LAS (Linear Alkylbenzene Sulfonate)

An increasing number of laundries have caused water contamination by surfactants. One commonly used surfactant is LAS (Linear Alkylbenzene Sulfonate), a material difficult to decompose, polluting the environment. Electrocoagulation was carried out using Al/Graphite electrode, applied to LAS surfactant artistic waste. This study aims to determine the functional ability of the Al/Graphite electrode in reducing surfactant through electrocoagulation. Various variations were carried out, on the voltage parameters (3,6,9,12) Volt; NaCl concentration (0;0.4;0.8;1.2;1.6;2) g/L; pH (3,5,7,9,11) and time (10,20,30,40,50) minutes. To analyze the changes in the sample before and after electrocoagulation, characterization was carried out using a UV-VIS spectrophotometer and FTIR. A kinetic study was conducted to determine the reaction order of electrocoagulation surfactant. Based on a study, removal at condition voltage 9 Volt, initial pH of the solution 9, electrocoagulation time 50 minute, and the addition of NaCl electrolyte 2 g/L, obtained surfactant concentration was 0,785 mg/L with removal efficiency 97,45%. UV-VIS spectra show a decreased absorption at a wavelength of 653 nm. FTIR spectra showed the presence of absorption on the same functional groups, which indicated that most of the surfactant pollutants could be separated from the wastewater through the electrocoagulation process. The second-order reaction was obtained in the surfactant electrocoagulation process.

New boundary conditions for the approximate flux-limited diffusion radiative transfer in circumstellar environments

Context. In order to constrain the models describing circumstellar environments, it is necessary to solve the radiative transfer equation in the presence of absorption and scattering, coupled with the equation for radiative equilibrium. However, solving this problem requires much CPU time, which makes the use of automatic minimisation procedures to characterise these environments challenging. Aims. In this context, the use of approximate methods is of primary interest. One promising candidate method is the flux-limited diffusion (FLD), which recasts the radiative transfer problem into a non-linear diffusion equation. One important aspect for the accuracy of the method lies in the implementation of appropriate boundary conditions (BCs). We present new BCs for the FLD approximation in circumstellar environments that we apply here to spherically symmetric envelopes. Methods. At the inner boundary, the entering flux (coming from the star and from the envelope itself) may be written in the FLD formalism and provides us with an adequate BC. At the free outer boundary, we used the FLD formalism to constrain the ratio of the mean radiation intensity over the emerging flux. In both cases we derived non-linear mixed BCs relating the surface values of the mean specific intensity and its gradient. We implemented these conditions and compared the results with previous benchmarks and the results of a Monte Carlo radiative transfer code. A comparison with results derived from BCs that were previously proposed in other contexts is presented as well. Results. For all the tested cases, the average relative difference with the benchmark results is below 2% for the temperature profile and below 6% for the corresponding spectral energy distribution or the emerging flux. We point out that the FLD method together with the new outer BC also allows us to derive an approximation for the emerging flux. This feature avoids additional formal solutions for the radiative transfer equation in a set of rays (ray-tracing computations). Conclusions. The FLD approximation together with the proposed new BCs performs well and captures the main physical properties of the radiative equilibrium in spherical circumstellar envelopes.

Synthesis of Methyl Ester Nitrate from Mahogany Seed Oil (Swietenia mahagoni Linn)

Nitration of methyl ester from mahogany oil (Swietenia mahagoniLinn) can be produced by Methyl Ester Nitrate (MEN), an additive that is useful for increasing Cetane Numbers in diesel fuel. This study aims to determine the yield of MEN that can be produced from mahogany seed oil after esterification, trans-esterification, and nitration and to identify the MEN compounds produced. Mahogany oil is obtained by pressing mahogany seeds and then degumming to remove the gum. Mahogany oil-free gum is esterified using methanol with the mole ratio of oil: methanol (1: 6), then trans-esterified, also using methanol with mole ratio (1:15) and a methyl ester is obtained. Then the methyl ester was nitrated with HNO3, sulfuric acid, and acetic anhydride to obtain a translucent reddish colored MEN product with a yield of 24.99%. The success of the synthesis was shown by the FTIR spectrophotometer in the presence of absorption at 1550 cm-1 which indicated the presence of the C-ONO2 group, the absorption at 1365 cm-1 indicated the presence of the NO2 group, and at 1118 cm-1 indicated the presence of the C-N group. The reaction mechanism that occurs during the predicted nitration reaction is an electrophilic substitution reaction and nucleophilic addition.

Peculiarities of reflection and transmission matrices of a system with magneto-optical activity and asymmetric transmission

We consider and compare the peculiarities of nonreciprocal optical properties of the following three systems: a) a planar layer of cholesteric liquid crystal (CLC) in the external magnetic field directed along the CLC helix axis, b) an asymmetric Fabry-Perot resonator with a planar CLC layer inside and, finally, c) an asymmetric Fabry-Perot resonator with a planar CLC layer inside in an external magnetic field, again, directed along CLC’s axis. We investigate the specific properties of matrices of reflection and transmission of such systems in all their details. Then we study the influence of absorption on nonreciprocal optical properties of these systems. Nonreciprocity depends on the polarization of the incident light in the absence/presence of absorption in such systems; while nonreciprocity appears for naturally polarized incident light in these systems only in the presence of absorption in the system. Nonreciprocity appears for naturally polarized incident light also in photonic crystals with the helix period gradient.

NTMpy: An open source package for solving coupled parabolic differential equations in the framework of the three-temperature model

The NTMpy code package allows for simulating the one-dimensional thermal response of multilayer samples after optical excitation, as in a typical pump-probe experiment. Several Python routines are combined and optimized to solve coupled heat diffusion equations in one dimension, on arbitrary piecewise homogeneous material stacks, in the framework of the so-called three-temperature model. The energy source deposited in the material is modelled as a light pulse of arbitrary cross-section and temporal profile. A transfer matrix method enables the calculation of realistic light absorption in presence of scattering interfaces as in multilayer samples. The open source code is fully object-oriented to enable a user-friendly and intuitive interface for adjusting the physically relevant input parameters. Here, we describe the mathematical background of the code, we lay out the workflow, and we validate the functionality of our package by comparing it to commercial software, as well as to experimental transient reflectivity data recorded in a pump-probe experiment with femtosecond light pulses. Program summaryProgram title: NTMpy v.0.1.1CPC Library link to program files:https://doi.org/10.17632/5czr76gmwr.1Developer's repository link:https://github.com/udcm-su/NTMpyCode Ocean capsule:https://codeocean.com/capsule/5661399Licensing provisions: MIT licenseProgramming language: PythonExternal routines: Python 3.5 or higher, numpy, matplotlib, bsplines, tqdmNature of problem: 1-dimensional coupled non linear partial differential equations; diffusion and relaxation dynamics formultiple systems and multiple layers.Solution method: Simulate the diffusion and relaxation dynamics of up to 3 coupled systems via an object oriented user interface. In order to approximate the solution and its derivatives in space B-Spline interpolation is used. The solution is developed in time via the Explicit Euler method.Additional comments including restrictions and unusual features: A routine to automatically select the ideal time step for stability of the algorithm is implemented. Routines for output of raw data in order to post process and pre- made visualization routines are implemented.

The effect of deformation of absorbing scatterers on Mie-type signatures in infrared microspectroscopy

Mie-type scattering features such as ripples (i.e., sharp shape-resonance peaks) and wiggles (i.e., broad oscillations), are frequently-observed scattering phenomena in infrared microspectroscopy of cells and tissues. They appear in general when the wavelength of electromagnetic radiation is of the same order as the size of the scatterer. By use of approximations to the Mie solutions for spheres, iterative algorithms have been developed to retrieve pure absorbance spectra. However, the question remains to what extent the Mie solutions, and approximations thereof, describe the extinction efficiency in practical situations where the shapes of scatterers deviate considerably from spheres. The aim of the current study is to investigate how deviations from a spherical scatterer can change the extinction properties of the scatterer in the context of chaos in wave systems. For this purpose, we investigate a chaotic scatterer and compare it with an elliptically shaped scatterer, which exhibits only regular scattering. We find that chaotic scattering has an accelerating effect on the disappearance of Mie ripples. We further show that the presence of absorption and the high numerical aperture of infrared microscopes does not explain the absence of ripples in most measurements of biological samples.

Impact of angular pointing error on BER performance of underwater optical wireless links.

Even in clear ocean water, underwater optical wireless communication (UOWC) is impaired not only by absorption and scattering, but also by oceanic turbulence and dynamic pointing errors which result in a fading channel, degrading the bit error rate (BER) performance. In this paper, for the first time, we quantify analytically the trade-off between geometric loss and misalignment in underwater scattering channels. A novel geometric loss model is developed which is used to compute the average BER in the presence of absorption and scattering over salinity-induced oceanic turbulence channels. Our findings suggest that UOWC systems are less sensitive to angular pointing errors due to jitter since scattering is able to alleviate such a fading effect at the expense of a higher attenuation due to geometric spread. Monte Carlo simulation results are further included to verify the developed BER expression which is valid over a wide range of signal-to-noise-ratio (SNR). Finally, the impact of inter-symbol interference (ISI) is also quantified by measuring the optical power penalty.

Features of the Solution of Direct and Inverse Scattering Problems for Inhomogeneities with a Small Wave Size

An acoustic field scattered by a single inhomogeneity consists of components of different orders of multipolarity. For symmetric or weak-contrast inhomogeneities of a small wave size, these components are related to multipole components of an initial incident field by a set of scattering coefficients. It is established that the admissible range of each of these coefficients on the complex plane is a circle in the presence of absorption in the inhomogeneity and a circumference in the absence of absorption. The solution of the inverse problem for the purpose of reconstructing the mentioned inhomogeneity may encounter difficulties, since the spatial spectrum of the secondary sources is excessively expanded due to the multiple scattering, and an error is introduced into the reconstruction results. Sets of values of the monopole scattering coefficient are established on the complex plane for which this effect manifests itself to the greatest extent.

Far-Field Subwavelength Acoustic Imaging by Deep Learning

Seeing and recognizing an object whose size is much smaller than the illumination wavelength is a challenging task for an observer placed in the far field, due to the diffraction limit. Recent advances in near and far field microscopy have offered several ways to overcome this limitation; however, they often use invasive markers and require intricate equipment with complicated image post-processing. On the other hand, a simple marker-free solution for high-resolution imaging may be found by exploiting resonant metamaterial lenses that can convert the subwavelength image information contained in the near-field of the object to propagating field components that can reach the far field. Unfortunately, resonant metalenses are inevitably sensitive to absorption losses, which has so far largely hindered their practical applications. Here, we solve this vexing problem and show that this limitation can be turned into an advantage when metalenses are combined with deep learning techniques. We demonstrate that combining deep learning with lossy metalenses allows recognizing and imaging largely subwavelength features directly from the far field. Our acoustic learning experiment shows that, despite being thirty times smaller than the wavelength of sound, the fine details of images can be successfully reconstructed and recognized in the far field, which is crucially enabled by the presence of absorption. We envision applications in acoustic image analysis, feature detection, object classification, or as a novel noninvasive acoustic sensing tool in biomedical applications.

Stable calculation of optical properties of large non-periodic dissipative multilayered systems

The calculation of the transfer matrix for a large non-periodic multilayered system may become unstable in the presence of absorption. We discuss the origin of this instability and we explore two methods to overcome it: the use of a total matrix to solve for all the fields at all the interfaces simultaneously and an expansion in the Bloch-like modes of a periodic artificially repeated system. We apply both methods to obtain the reflectance spectra of multilayered chirped structures composed of nanostructured porous silicon (PS). Both methods yield reliable and numerically stable results. The former allows an analysis of the field within all layers while the latter is much more efficient computationally, allowing the design of novel structures and the optimization of their parameters. We compare numerical and experimental results across a wide spectral range from the infrared to the ultraviolet.

Analytical model for diffuse reflectance in single fiber reflectance spectroscopy.

Cancer progression leads to changing scattering properties of affected tissues. Single fiber reflectance (SFR) spectroscopy detects these changes at small spatial scales, making it a promising tool for early in situ detection. Despite its simplicity and versatility, SFR signal modeling is hugely complicated so that, presently, only approximate models exist. We use a classic approach from geometrical probability to derive accurate analytical expressions for diffuse reflectance in SFR that shows a strong improvement over existing models. We consider the case of limited collection efficiency and the presence of absorption. A Monte Carlo light transport study demonstrates that we adequately describe the contribution of diffuse reflectance to the SFR signal. Additional steps are required to include semi-ballistic, non-diffuse reflectance also present in the SFR measurement.

Distribution of the Wigner–Smith time-delay matrix for chaotic cavities with absorption and coupled Coulomb gases

Within the random matrix theory approach to quantum scattering, we derive the distribution of the Wigner–Smith time delay matrix for a chaotic cavity with uniform absorption, coupled via N perfect channels. In the unitary class we obtain a compact expression for the distribution of the full matrix in terms of a matrix integral. In the other symmetry classes we derive the joint distribution of the eigenvalues. We show how the large N properties of this distribution can be analysed in terms of two interacting Coulomb gases living on two different supports. As an application of our results, we study the statistical properties of the Wigner time delay in the presence of absorption.

Mechanical properties of mild steel by adding Theobroma Cacao Peels Extract (TCPE) inhibitor

The ability of corrosion inhibitor Theobroma cacao Peels Extract (TCPE) has been tested to improve the mechanical properties of mild steel after corrosion occurred. These properties were examined to measure its hardness, tensile and fatigue. Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM) was used to analyze the morphology of the surface. The corrosion rate was found reducing, on the contrary, the efficiency was increasing as the increasing concentration on the extract. This raising was followed by an increase in mechanical properties, namely hardness, strength and fatigue strength. Indeed, the presence of absorption on the surface of the data was reinforced by EDX, X-ray photon spectroscopy (XPS), and AFM for topography. The addition of polar extract of cacao peels in HCl 1.5M is very useful to reduce the corrosion rate on the mild steel surface, and it can retain its mechanical properties after the corrosion occurred.