Change In Extinction Coefficient Research Articles

Hemoglobin and cytochrome c. reinterpreting the origins of oxygenation and oxidation in erythrocytes and in vivo cancer lung cells

Maintaining life (respiration), cell death (apoptosis), oxygen transport and immunity are main biological functions of heme containing proteins. These functions are controlled by the axial ligands and the redox status of the iron ion (oscillations between Fe2+ and Fe3+) in the heme group. This paper aims to evaluate the current state of knowledge on oxidation and oxygenation effects in heme proteins. We determined the redox status of the iron ion in whole blood (without and with anticoagulant), hemoglobin in erythrocytes, in isolated cytochrome c and cytochrome c in mitochondria of the human lung cancer cells using UV–VIS electronic absorption spectroscopy, Raman spectroscopy and Raman imaging. Here we discussed the mechanism responsible for the Q electronic absorption band spectral behavior, i.e., its splitting, and its change in extinction coefficient, as well as vibrational modifications upon oxygenation and oxidation. We compared the redox status of heme in hemoglobin of human erythrocytes and cytochrome c in mitochondria of human lung cancer cells. Presented results allow simultaneous identification of oxy- and deoxy-Hb, where 1547 and 1604 cm−1 vibrations correspond to deoxygenated hemoglobin, while 1585 and 1638 cm−1 correspond to oxyhemoglobin, respectively. Our results extend knowledge of oxidation and oxygenation effects in heme proteins. We demonstrated experimentally the mechanism of electronic-vibrational coupling for the Q band splitting. Presented results extend knowledge on oxidation and oxygenation effects in heme proteins and provide evidence that both processes are strongly coupled. We showed that retinoic acid affects the redox state of heme in cytochrome c in mitochondria. The change of the redox status of cytochrome c in mitochondria from the oxidized form to the reduced form has very serious consequences in dysfunction of mitochondria resulting in inhibition of respiration, apoptosis and cytokine induction.

Combining Multi-Dimensional SAR Parameters to Improve RVoG Model for Coniferous Forest Height Inversion Using ALOS-2 Data

This paper considers extinction coefficient changes with height caused by the inhomogeneous distribution of scatterers in heterogeneous forests and uses the InSAR phase center height histogram and Gaussian function to fit the normalized extinction coefficient curve so as to reflect the vertical structure of the heterogeneous forest. Combining polarization decomposition based on the physical model and the PolInSAR parameter inversion method, the ground and volume coherence matrices can be separated based on the polarization characteristics and interference coherence diversity. By combining the new abovementioned parameters, the semi-empirical improved RVoG inversion model can be used to both quantify the effects of temporal decorrelation on coherence and phase errors and avoid the effects of small vertical wavenumbers on the large temporal baseline of spaceborne data. The model provided robust inversion for the height of the coniferous forest and enhanced the parameter estimation of the forest structure. This study addressed the influence of vertical structure differences on the extinction coefficient, though the coherence of the ground and volume in sparse vegetation areas could not be accurately estimated, and the oversensitivity of temporal decorrelation caused by inappropriate vertical wavenumbers. According to this method we used spaceborne L-band ALOS-2 PALSAR data on the Saihanba forest in Hebei Province acquired in 2020 for the purpose of height inversion, with a temporal baseline range of 14–70 days and the vertical wavenumber range of 0.01–0.03 rad/m. The results are further validated using sample data, with R2 reaching 0.67.

Effect of Sr doping on structural, morphological, optical and electrical properties of spray pyrolized CdO thin films

Cadmium oxide (CdO) and strontium (Sr) doped cadmium oxide (SCO) thin films have been fabricated onto glass substrate by spray pyrolysis technique. The CdO and SCO films have been deposited at 350 °C substrate temperature and their structure, morphology, optical, electrical properties have been investigated & analyzed as a function of Sr-concentration (0–4 mol%). X-ray diffraction analysis confirms that the films are polycrystalline and they have cubic structure and shows preferential growth in (200) plane. The average grain size of the films has been found 22.23 nm. SEM image reveals that the undoped film has rock like morphology and the morphology significantly changes with Sr-doping concentration. Results of optical properties show that optical transmittance, refractive index and extinction coefficient changes markedly with Sr doping. As the doping concentration of Sr increases from 0 to 4%, the band gap value decrease from 2.67 to 2.49 eV and the Urbach energy increases. Temperature dependent electrical resistivity indicates that all the films possess poor metal like behavior. The Hall measurement confirms that both doped and undoped CdO films are n-type semiconductor.

Effect of host medium absorption on the radiative properties of dispersed media consisting of optically soft particles

Light scattering by particles immersed in an absorbing host medium has been an important issue in many fields, such as ocean optics, atmospheric radiation, remote sensing and so on. The traditional theory ignores the effect of host medium absorption on particle scattering, which may result in inaccurate results. In this paper, the scattering coefficient, extinction coefficient and phase function of the dispersed medium consisting of optically soft particles are investigated with considering the effect of host medium absorption on particle scattering. The results are based on the recently developed Mie theory for the absorbing host medium. It is found that neglecting the host medium absorption on particle scattering will result in a small change in extinction coefficients but a great change in scattering coefficients. Meanwhile, the relative error of scattering coefficients caused by using the conventional Mie theory increases obviously with the increase of particle size and the absorption index of the host medium, while the relative error of extinction coefficients fluctuates with the particle size. Moreover, the relative error of scattering coefficients of polydisperse particles is more significant than that of monodisperse particles.

Heat transfer control by dispersed metallic particles in glassy mold flux film for continuous steel casting

AbstractTo assess the effect of metallic particles (MPs) on heat transfer in glassy mold flux, a structurally stable glassy mold flux system composed of CaO–Al2O3–CaF2 was examined with 0, 2, or 5 wt% of FeO or Fe MPs. The change of extinction coefficient by Mie Scattering of the Fe particles and absorption by FeO was quantified using Fourier transformation infrared ray spectroscopy and an Ultraviolet/Visible spectrometry. Thermal conductivity of mold flux film with dispersed MPs was quantified using laser flash technique. One‐dimensional Debye temperature was calculated, and particle morphology and size distribution were observed using image analysis to explain variations in thermal conductivity among the glass samples. Finally, to simulate the heat transfer ratio by both the conduction and radiation, the actual heat flux through mold flux film was measured using an Infrared Emitter Technique. The overall heat transfer rate across liquid flux film could be reduced significantly by a dispersion of MPs.

A New Temporal Dimension for Multisignal Sedimentation Velocity as a Tool to Analyze Multicomponent Interactions

Multisignal sedimentation velocity (MSSV) analysis is a powerful method for determining the stoichiometry of reversibly formed multi-protein complexes. For example, it has been used to unravel the number and stoichiometry of co-existing complexes, for example, in receptor-ligand interactions and in systems of adaptor proteins. By globally analyzing absorbance data acquired simultaneously at different wavelengths, differences in the component spectra can be exploited to obtain information on the composition of all hydrodynamically resolved species. For fluorescence data that are acquired only at a single excitation wavelength, it was recently shown that the characteristic quantum yield of photoswitching of reversibly photoswitchable fluorescent proteins leads to a temporal fluorescence signal change on the time-scale of sedimentation, which can substitute for spectral discrimination of components in an analysis analogous to MSSV. In the present work, we have embarked on combining the two concepts by considering the temporal extinction coefficient changes associated with reversible photoswitching in the context of spectral decomposition of components. To this end, we report pilot experiments, for the first time acquiring and analyzing multi-wavelength absorbance data with temporal modulation of extinction amplitudes. Theoretically, the combination of spectral and temporal signal domain is expected to greatly enhance the discrimination of sedimenting components, thereby facilitating the study of multi-protein complexes with a higher number of components in solution.

Extinction Coefficient of Optical Fibers Irradiated by Thermal Neutrons and Compressed

Results of experimental studies of the extinction coefficient of optical fibers preliminary irradiated by thermal neutrons and compressed are presented. In this case, mechanical stresses arising in the multimode optical fiber (MOF) irradiated by thermal neutrons lead to further increase in the extinction coefficients. It is established that with increasing loading on the irradiated multimode optical fiber, the extinction coefficient changes in a wide range of wavelengths. Microfractures of the multimode optical fiber subjected to compression take place with a certain delay relative to the instant of maximum force application. This can be caused by the inertia of the process of mechanical failure of the MOF.

Polarization dependence of optical pump-induced change of graphene extinction coefficient

We used pump-probe spectroscopy to study the dependence of optical pump-induced change of graphene extinction coefficient on polarization. We find that the optical pump-induced change of graphene extinction coefficient is polarization-dependent for light with energy identical to that of the excitation light; this dependence decreases rapidly after optical excitation. However, the change of extinction coefficient is isotropic for light with energy much smaller than that of the excitation light. The spatial distribution of momenta of non-equilibrium carriers accounts for this polarization dependence. These results provide a potential way for manipulating graphene’s transient optical response characteristics for applications in ultrafast photonics.

Specific absorption spectra of hemoglobin at different PO2 levels: potential noninvasive method to detect PO2 in tissues

Hemoglobin (Hb), as one of main components of blood, has a unique quaternary structure. Its release of oxygen is controlled by oxygen partial pressure (PO2). We investigate the specific spectroscopic changes in Hb under different PO2 levels to optimize clinical methods of measuring tissue PO2. The transmissivity of Hb under different PO2 levels is measured with a UV/Vis fiber optic spectrometer. Its plotted absorption spectral curve shows two high absorption peaks at 540 and 576 nm and an absorption valley at 560 nm when PO2 is higher than 100 mm Hg. The two high absorption peaks decrease gradually with a decrease in PO2, whereas the absorption valley at 560 nm increases. When PO2 decreases to approximately 0 mm Hg, the two high absorption peaks disappear completely, while the absorption valley has a hypochromic shift (8 to 10 nm) and forms a specific high absorption peak at approximately 550 nm. The same phenomena can be observed in visible reflectance spectra of finger-tip microcirculation. Specific changes in extinction coefficient and absorption spectra of Hb occur along with variations in PO2, which could be used to explain pathological changes caused by tissue hypoxia and for early detection of oxygen deficiency diseases in clinical monitoring.

Electrical, optical, and thermal properties of Sn-doped phase change material Ge2Sb2Te5

In this article, effect of Sn on the electrical, optical, and thermal properties of Ge2Sb2Te5 is studied. Ge2Sb2Te5, Ge1.55Sb2Te5Sn0.45, and Ge1.1Sb2Te5Sn0.9 alloys are prepared by melt quenching technique and their thin films are prepared by thermal evaporation on glass substrates. These materials are then characterized by differential scanning calorimetry, X-ray diffraction, optical method, and impedance measurements. Doping with Sn maintains the NaCl-type crystalline structure of Ge2Sb2Te5. Activation energy (Ea) for crystallization is calculated by Kissinger’s method. Ea decreases slightly from 2.56 eV for Ge2Sb2Te5 to 2.24 eV for Ge1.1Sb2Te5Sn0.9. The distinct change in extinction coefficient (k) of Ge2Sb2Te5 and Sn-doped amorphous films is found in the visible region. A large increase in optical contrast (C) is observed in the Sn-doped phase change materials. The phase change transition is studied using impedance measurements as a function of temperature. Impedance measurements show the appearance of nucleation centers in samples heated at temperatures below crystallization temperature (Tc) and above glass transition temperature (Tg).

Theoretical Estimation of Extinction Coefficient Due to Time Evolution of Particle Size Distribution

The extinction coefficient of atmospheric aerosol particles influences the earth's radiation balance directly or indirectly and it can be determined by the scattering and absorption characteristics of aerosol particles. The problem of estimating the change of extinction coefficient due to time evolution of particle size distribution is studied and an improved method for calculating the single particle extinction efficiency is proposed. Through this improved method, the single particle extinction efficiency can be expressed simply in powers of particle diameter based on the anomalous diffraction approximate for the particle size range from 0.1 to 10 µm in diameter first, and then the change of the overall extinction coefficient undergoing (individually and simultaneous) Brownian and gravitational coagulation as well as condensation can be estimated comprehensively with the moment method based on the general dynamic equation. The feasibility and reliability of this method are investigated and the effect of time evolution of particle size distribution on the extinction coefficient is also estimated systemically. Simulation experiments indicate that the extinction coefficient obtained with the improved method coincides fairly well with that using the Mie theory, which provides a simple, dependable, and efficient method to estimate the change of extinction coefficient during the particle dynamic processes.

Research on bimodal particle extinction coefficient during Brownian coagulation and condensation for the entire particle size regime

The extinction coefficient of atmospheric aerosol particles influences the earth’s radiation balance directly or indirectly, and it can be determined by the scattering and absorption characteristics of aerosol particles. The problem of estimating the change of extinction coefficient due to time evolution of bimodal particle size distribution is studied, and two improved methods for calculating the Brownian coagulation coefficient and the condensation growth rate are proposed, respectively. Through the improved method based on Otto kernel, the Brownian coagulation coefficient can be expressed simply in powers of particle volume for the entire particle size regime based on the fitted polynomials of the mean enhancement function. Meanwhile, the improved method based on Fuchs–Sutugin kernel is developed to obtain the condensation growth rate for the entire particle size regime. And then, the change of the overall extinction coefficient of bimodal distributions undergoing Brownian coagulation and condensation can be estimated comprehensively for the entire particle size regime. Simulation experiments indicate that the extinction coefficients obtained with the improved methods coincide fairly well with the true values, which provide a simple, reliable, and general method to estimate the change of extinction coefficient for the entire particle size regime during the bimodal particle dynamic processes.

Wide-spectral-range, Expanded-beam Spectroscopic Ellipsometer and its Application for Imaging/Mapping of Graded Nanocrystalline Si:H Films

ABSTRACTA prototype expanded-beam spectroscopic ellipsometer has been developed that uses uncollimated (non-parallel, diffuse) illumination with a detection system consisting of an angle-of-incidence-sensitive pinhole camera for high-speed, large-area imaging/mapping applications. The performance of this novel instrument is being tested for imaging/mapping of mixed-phase hydrogenated silicon films having graded amorphous (a-Si:H) and nanocrystalline (nc-Si:H) components throughout the film depth. The speed of the measurement system makes the instrument suitable for use on production lines. The precision enables detection of subnanometer thicknesses, and refractive index and extinction coefficient changes of 0.01. Angle-of-incidence and mirror calibrations are made via well-known sample structures. Alternative commercial instrumentation for mapping by spectroscopic ellipsometry must translate the sample or ellipsometer in two dimensions. For this instrumentation, even a 15 × 15 cm2 sample with cm2 resolution requires > 200 measurements and at least 15 min. By imaging along one dimension in parallel, the expanded-beam system can measure with similar resolution in < 2 min. The focus of recent instrumentation efforts is on improving the overall system spectral range and its performance.

Estimating conformation content of a protein using citrate-stabilized Au nanoparticles

Herein we report the use of the optical properties of citrate-stabilized gold nanoparticles (Au NPs) for estimation of native or denatured conformation content in a mixture of a protein in solution. The UV-vis extinction spectrum of citrate-stabilized Au NPs is known to broaden differently in the presence of native and denatured states of alpha-amylase, bovine serum albumin (BSA) or amyloglucosidase (AMG). On the other hand, herein we show that when a mixture of native and denatured protein was present in the medium, the broadening of the spectrum differed for different fractional content of the conformations. Also, the total area under the extinction spectrum varied linearly with the change in the mole fraction content of a state and for a constant total protein concentration. Transmission electron microscopy (TEM) measurements revealed different levels of agglomeration for different fractional contents of the native or denatured state of a protein. In addition, time-dependent denaturation of a protein could be followed using the present method. The rate constants calculated for denaturation indicated a possible fast change in conformation of a protein before complete thermal denaturation. The observations have been explained based on the changes in extinction coefficient (thereby oscillator strength) upon interaction of citrate-stabilized NPs with proteins being in different states and levels of agglomeration.

Vertical distribution of aerosols over the east coast of India inferred from airborne LIDAR measurements

Abstract. The information on altitude distribution of aerosols in the atmosphere is essential in assessing the impact of aerosol warming on thermal structure and stability of the atmosphere. In addition, aerosol altitude distribution is needed to address complex problems such as the radiative interaction of aerosols in the presence of clouds. With this objective, an extensive, multi-institutional and multi-platform field experiment (ICARB-Integrated Campaign for Aerosols, gases and Radiation Budget) was carried out under the Geosphere Biosphere Programme of the Indian Space Research Organization (ISRO-GBP) over continental India and adjoining oceans during March to May 2006. Here, we present airborne LIDAR measurements carried out over the east Coast of the India during the ICARB field campaign. An increase in aerosol extinction (scattering + absorption) was observed from the surface upwards with a maximum around 2 to 4 km. Aerosol extinction at higher atmospheric layers (>2 km) was two to three times larger compared to that of the surface. A large fraction (75–85%) of aerosol column optical depth was contributed by aerosols located above 1 km. The aerosol layer heights (defined in this paper as the height at which the gradient in extinction coefficient changes sign) showed a gradual decrease with an increase in the offshore distance. A large fraction (60–75%) of aerosol was found located above clouds indicating enhanced aerosol absorption above clouds. Our study implies that a detailed statistical evaluation of the temporal frequency and spatial extent of elevated aerosol layers is necessary to assess their significance to the climate. This is feasible using data from space-borne lidars such as CALIPSO, which fly in formation with other satellites like MODIS AQUA and MISR, as part of the A-Train constellation.

Tuning of oxidation states in the LaNiO3−δ perovskite around the insulator-metal transition

The LaNiO3−δ perovskite has been studied during its reoxygenation process at the reversible insulator-metal transition by spectroscopic ellipsometry for different pressures and temperatures conditions. First, it was demonstrated that the reoxygenation dynamics increases with both increasing pressure and temperature. Considering the temperature dependent experiments, two regimes of kinetics have been identified: a slow reoxygenation dynamics at low temperature (below 523 K) and fast dynamics above 623 K. Second, contrary to our expectations, the reoxygenation process of a preliminary reduced sample is completed after a sufficient time delay even for the smallest investigated temperature of 473 K or oxygen pressure of 0.03 μbar, respectively. Modeling the change in extinction coefficient as a function of time during the reoxygenation, it was found that the oxygen diffusion coefficient varies from 4.2×10−14 to 1.1×10−13 cm2/s depending on the temperature (473 to 523 K). This oxygen diffusion constant is similar in magnitude order to those observed in the YBCO superconductor. At the light of these investigations, a pulsed oxygen injection was used, allowing a control of the injected oxygen quantity and by consequence, it was possible to precisely tune the oxidation state for a LaNiO3−δ film between the reversible reduced sample and the stoichiometric compound. In situ ellipsometry measurements are simultaneously performed to follow changes in optical constants.

The effect of water colour on lake hydrodynamics: a modelling study

Summary1. The one‐dimensional equation solver, PROgram for Boundary layers in the Environment, was used to simulate the temperature structure of Lake Erken, a medium‐sized Swedish lake, assuming differing extinction coefficients for a series of modelled years driven by observed meteorological data and by a set of idealized meteorological data.2. Results suggested that, as expected, larger extinction coefficients initially led to surface waters becoming warmer. The reverse was true late in the summer, however, as the warming induced by greater absorption of solar radiation was outweighed by the cooling effects of entrained colder hypolimnetic water.3. There was between a two‐ and fourfold inter‐annual variation in the effects on key physical lake parameters, induced by changing extinction coefficient, such as maximum heat flux, heat content and Schmidt stability.4. The change in surface heat flux induced by a change in extinction coefficient was up to almost 50 W m−2.5. In the summer, changes in extinction coefficient from 0.5 to 0.2 m−1 led to a dramatic shift in the duration of the stratified period as well as to enormous changes in Schmidt stability and hypolimnetic temperature.6. Future changes to extinction coefficients of small and medium‐sized lakes are likely to have wide‐ranging effects on lake thermal structure and ecology.

Measurements of Internal Distance Changes of the 30 S Ribosome Using FRET with Multiple Donor–Acceptor Pairs: Quantitative Spectroscopic Methods

We present analytical and experimental procedures for determining distance changes within the 30 S subunit of the Escherichia coli ribosome using Förster resonance energy transfer (FRET). We discuss ways to contend with complexities when using FRET to measure distance changes within large multi-subunit macromolecular complexes, such as the ribosome. Complications can arise due to non-stoichiometric labeling of donor and acceptor probes, as well as environmental effects that are specific to each conjugation site. We show how to account for changes in extinction coefficients, quenching, labeling stoichiometry and other variations in the spectroscopic properties of the dye to enable more accurate calculation of distances from FRET data. We also discuss approximations that concern the orientation of the transition moments of the two dye molecules, as well as the impact of other errors in the measurement of absolute distances. Thirteen dye-pair locations with different distances using 18 independent FRET pairs conjugated to specific 30 S protein residues have been used to determine distance changes within the 30 S subunit upon association with the 50 S subunit, forming the 70 S ribosome. Here, we explain the spectroscopic methods we have used, which should be of general interest in studies that aim at obtaining quantitative distance information from FRET.

Sulphide centres on (111) AgBr surfaces: the effect of thiocyanate on electronic properties

Sensitometric and spectroscopic techniques are used to study the effect of sodium thiocyanate addition to sulphur-sensitized AgBr octahedra. Thiocyanate increased the speed of an oversensitized emulsion, causing it to have a speed comparable to the optimally suphur-sensitized emulsion at high irradiance and greater speed at low irradiance. Thiocyanate decreased the absorption by sulphide centres at shorter wavelengths (500–650 nm), but increased the absorption at longer wavelengths. The long-wavelength sensitivity (> 500 nm) was also increased by thiocyanate, whereas the activation energy for this response was reduced. These results are interpreted with a model that assumes that thiocyanate interacts with multiple-sulphide centres to lower their ground state energy level. This interaction reduces the degree of free-hole/trapped-electron recombination which occurs at these centres and which is responsible for the over-sensitization effect. A computer simulation based on this model gave simulated reciprocity failure data which were qualitatively consistent with the experimental trends. The effects of thiocyanate on absorption are interpreted as a change in extinction coefficient.

Predictions of the change in extinction coefficient for prolate particles under shear

The following study investigates the microstructural changes induced by shear in dilute suspensions of colloidal Fe2O3 rods (aspect ratio=8.4) using rheo-optic techniques. The large extinction coefficient for the hematite system at the wavelength used (λmax=392 nm) enables rheo-optic experiments on truly dilute suspensions to be undertaken. Optical absorbance spectra have been measured over a range of shear rates for unpolarized light and for light polarized relative to the shear direction. The measured absorbance changes may be attributed to the shear-induced anisotropy in the suspension. Numerical methods are used to obtain solutions of the convective-diffusion equation, which are used to predict the measured change in extinction coefficient with shear for colloidal hematite rods measured using optical rheometry.