Absolute Absorption Research Articles

Internal temperature determination for laser noise cancellers

Noise cancellers of the type described by Hobbs [Appl. Opt. 36, 903 (1997)], used in dual-beam laser spectroscopy, provide an analog logarithmic output that is monotonic in, but not linearly related to, the sample absorbance. If the goal of a spectroscopic experiment is to determine an absolute absorbance or a spectral lineshape, rather than simply a line location, the conversion function between detector output and absorbance needs to be known. That function depends on the internal temperature of the transistors used in the device’s current splitter, and an incorrect assumption about the temperature leads to errors in absorbance or distortions in the extracted lineshape. Neither the original design nor a commercial implementation (Newport Nirvana) gives a direct indication of the temperature. A simple laboratory procedure for determining the transistor temperature is described.

ANALOGY BETWEEN THE PRINCIPLE OF EQUIVALENCE AND THE RELATIONAL PRINCIPLE OF COMPLETE SUPPLY

The paper analyzes the analogy between the principle of total absorption in the relational theory and the principle of equivalence in the general theory of relativity. Using the formulation of these principles in metaphysical terms allows us to conclude that the supercategory of relational particles manifests itself in dynamics as a self-consistent absolute absorber. Questions of interpretation of leading actions in the theory of direct interparticle interaction are considered. It is shown that the strict symmetry of the Fokker action with respect to retarded and advanced actions can be violated when the processes of particle creation and annihilation are taken into account.

An Ultra-Thin, Triple-Band, Incident Angle-Insensitive Perfect Metamaterial Absorber.

We created an ultra-thin, triple-band incident angle-insensitive perfect metamaterial absorber (MMA) with a metallic patch and a continuous metal ground isolated by a central dielectric substrate. The top metallic patch, placed across the edges of the 0.58 mm thickness Rogers RO4003C (lossy) substrate, forms the bulk of the projected absorber's ultra-thin layer. Nonetheless, absorption is exceedingly strong, covering C-band, X-band and K-band and reaching levels of 97.8%, 99.9%, and 99.9%, respectively, under normal and even oblique (0° to 45°) incident conditions. In chosen ranges of frequency of 6.24, 10.608, and 18.624 GHz for both TM and TE mode, the displayed Q-factors were 62.4, 17.68, and 26.61, respectively. We correspondingly calculated the RAB (relative absorption bandwidth) to evaluate absorption performance. An equivalent circuit proved its performance capabilities, indicating that it would produce a high-quality MMA from ADS software. Furthermore, the absorber's performance has been verified in free space on a sample being tested using a different array of unit cells. Moreover, the proposed structures with HFSS simulators to display the MMA's absolute absorption at each absorption peak are somewhat inconsistent with the results of the CST simulator. Because of its superior performance, the ultra-thin absorber is suited for a wide range of applications, including satellite applications such as radar systems, stealth technology, imaging, and electromagnetic interference reduction.

Formation and consumption of HO2 radicals in ns pulse O2–He plasmas over a liquid water surface

Hydroperoxyl (HO2) radicals are an important precursor in the formation of hydrogen peroxide (H2O2), a key species in plasma-liquid interactions, such that their formation and consumption pathways need to be understood. In this work, the generation and decay of HO2 have been studied in a controlled environment, in ns pulse discharge O2–He plasmas in contact with a liquid water surface. For this, time-resolved, absolute number densities of HO2 in O2–He mixtures excited by a repetitive ns pulse discharge are measured in situ by cavity ring down spectroscopy (CRDS). The discharge cell with external electrodes to generate the plasma and a water reservoir are integrated into the CRDS cavity. The high-reflectivity cavity mirrors are purged with helium to protect them from water vapor condensation. The experimental results are obtained at near room temperature, both during the discharge pulse burst and in the afterglow. The HO2 number density is inferred from the CRDS data using a spectral model exhibiting good agreement with previous measurements of absolute HO2 absorption cross sections. HO2 is generated during the discharge burst and decays in the afterglow between the bursts. The HO2 number density is also measured vs. the O2 fraction in the mixture. Comparison with the kinetic modeling predictions demonstrates good agreement with the data and identifies the dominant HO2 generation and decay processes. HO2 in the plasma is formed predominantly by the recombination of H atoms, generated by the electron impact dissociation of water vapor, with O2 molecules. Reactions with O atoms and hydroxyl (OH) radicals are among the main HO2 decay processes in the afterglow. HO2 is also detected when O2 is not present in the mixture. In this case, it is generated primarily by the recombination of OH radicals, via the formation of H2O2. The results demonstrate that CRDS can also be used for HO2 and other plasma chemical reaction product measurements in atmospheric pressure plasma jets impinging on a liquid water surface in ambient air.

Pharmacokinetics of danofloxacin after single oral and intravenous administration in non-laying hens.

The current study aimed to explore the pharmacokinetics of danofloxacin in non-laying hens after a single oral (PO) and intravenous (IV) dose, both at 5mg/kg body weight (BW). Eighteen 13-week-old healthy hens were equally and randomly divided into two groups. After both doses, blood samples (approximately 1ml) were collected at different time points. Danofloxacin concentrations were quantified by a validated high-performance liquid chromatography (HPLC) method followed by a non-compartmental analysis using the software of WinNonLin. The elimination half-lives (t1/2λz s) after PO and IV routes were determined as 8.15 ± 3.37 and 7.69 ± 3.40 h, respectively. After IV administration, danofloxacin had an initial concentration (C0 ) of 3.62 μg/ml, a volume of distribution at steady state (VSS ) of 3579.72 ± 454.29 ml/kg, and a total body clearance (Cl) of 0.49ml/h/g. After PO administration, the absolute bioavailability and absorption half-life (t1/2ka ) were calculated as 100.99% ± 23.10% and 0.82 ± 0.58 h, respectively. Based on the calculated ratio values of AUC/MIC and Cmax /MIC, an oral dose of 5 mg/kg danofloxacin would be expected to successfully treat hens infected with strains with MIC values ≤0.1 μg/ml.

Thermal Performance of a Dimpled Tube Parabolic Trough Solar Collector (PTSC) with SiO2 Nanofluid

In this research work, dimple texture tubes and silicon dioxide (SiO2) nanofluid were used to analyze the performance parameters of a solar water heater. For this purpose, SiO2 was mixed with deionized (DI) water using an ultrasonic dispersion device to prepare the nanofluids (SiO2/DI-H2O). The size of the nanoparticle was in the range of 10-15 nm. Different volume concentrations of the nanoparticles in the range of 0.1% to 0.5%, in steps of 0.1%, were chosen to prepare the nanofluids to carry out the experiments. Apart from this, computational fluid dynamics (CFD) tool was used to numerically analyze the parameters affecting the performance of the solar water heater, as well as the fluid flow pattern in the dimple texture tube. During the experiment, the mass flow rate of the base fluid (water) varied in the range of 0.5 kg/min to 3.0 kg/min in steps of 0.5 kg/min. The added advantage of the dimple texture tube design led to an increase in turbulence in the flow pattern, resulting 34.2% increase in the convective heat transfer efficiency compared with the plain tube. Among all experimental modules, SiO2/DI-H2O with a mass flow rate of 2.5 kg/min and 0.3% volume concentration gives overall optimized results in absolute energy absorption, gradient temperature, and efficiency of the solar water heater. The efficiency metrics of the experimental results were compared with the simulation results, and it was in the acceptable range with an overall deviation of ±7.42%.

Application of photogrammetry reconstruction for hyperthermia quality control measurements

PurposeHyperthermia is a cancer treatment in which the target region is heated to temperatures of 40–44 °C usually applying external electromagnetic field sources. The behavior of the hyperthermia applicators (antennas) in clinical practice should be periodically checked with phantom experiments to verify the applicator’s performance over time. The purpose of this study was to investigate the application of photogrammetry reconstructions of 3D applicator position in these quality control procedure measurements. MethodsPhotogrammetry reconstruction was applied at superficial hyperthermia scenario using the Lucite cone applicator (LCA) and phased-array heating in the head and neck region using the HYPERcollar3D. Wire-frame models of the entire measurement setups were created from multiple-view images and used for recreation of the setup inside 3D electromagnetic field simulation software. We evaluated applicator relation (Ra) between measured and simulated absolute specific absorption rate (SAR) for manually created and photogrammetry reconstructed simulation setups. ResultsWe found a displacement of 7.9 mm for the LCA and 8.2 mm for the HYPERcollar3D setups when comparing manually created and photogrammetry reconstructed applicator models placements. Ra improved from 1.24 to 1.18 for the LCA and from 1.17 to 1.07 for the HYPERcollar3D when using photogrammetry reconstructed simulation setups. ConclusionPhotogrammetry reconstruction technique holds promise to improve measurement setup reconstruction and agreement between measured and simulated absolute SAR.

Analytical model for extracting optical properties from absorptance of femtosecond-laser structured hyperdoped silicon

We set up an analytical optical model to emulate the absorptance spectra of light scattering, sulfur-hyperdoped silicon that we fabricate by using femtosecond laser pulses. The model allows us to distinguish between contributions to the absolute sub-bandgap absorptance from the path length enhancement of photons due to laser-induced surface roughness, on the one hand, and from the actual hyperdoped layer, on the other hand. Both effects are quantified via the two free parameters of the model. By varying the laser fluence and the areal pulse density, we create a range from almost planar to heavily structured hyperdoped Si samples that we show to behave almost like a Lambertian scatterer. The optical depth a1, i.e., the product of the absorption coefficient close to the Si bandgap energy and the effective thickness of the hyperdoped layer, scales with the surface area enhancement, which we identify as the main driving force for large sub-bandgap absorptances of this material type. It reaches maximum values of nearly a1 = 0.4, which refers to an absolute absorptance of 82% at a wavelength of 1450 nm. We furthermore discuss, quantify, and reduce possible error sources when determining the absorptance of such optically rough, hyperdoped samples with a spectrophotometer.

A new conceptional model for deriving average dermal absorption estimates from studies with multiple tested concentrations for non-dietary risk assessment of pesticides

Dermal absorption values are used to translate external dermal exposure into potential systemic exposure for non-dietary risk assessment of pesticides. While the Environmental Protection Agency of the United States of America (US EPA) derives a common dermal absorption factor for active substances covering all related products, the European Food Safety Authority (EFSA) requests specific product-based estimates for individual concentrations covering the intended use rates. The latter poses challenges, because it disconnects exposure dose from applied dose in absorption studies, which may not be suitable in scenarios where concentration is not relevant. We analyzed the EFSA dermal absorption database, collected 33 human in vitro studies from CropLife Europe (CLE) companies, where ≥3 in-use dilution concentrations were tested, and 15 dermal absorption triple pack datasets. This shows that absolute dermal absorption correlates with absolute applied dose on a decadic logarithm-scale, which is concordant with the toxicological axiom that risk is driven by exposure dose. This method is radically different from the current European approach focused on concentrations and offers new insights into the relationship of internal and external exposure doses when utilizing data from in vitro studies. A single average dermal absorption value can be simply derived from studies with multiple tested concentrations, by calculating the y-intercept of a linear model on a decadic logarithm scale while assuming a slope of 1. This simplifies risk assessment and frees resources to explore exposure refinements. It also serves as a basis to harmonize dermal absorption estimation globally for use in exposure-driven risk assessments.

Infrared multiple‐angle incidence resolution spectrometry for vapor‐deposited amorphous water

AbstractInfrared multiple‐angle incidence resolution spectrometry (IR‐MAIRS) is a recently developed spectroscopic technique that combines oblique incidence transmission measurements and chemometrics (multivariate analysis) to obtain both pure in‐plane (IP) and out‐of‐plane (OP) vibration spectra for a thin sample. IR‐MAIRS is established for analyzing the molecular orientation of organic thin films at atmospheric pressure, but it should also be powerful for the structural characterization of vapor‐deposited thin samples prepared in a vacuum. The application of IR‐MAIRS to vapor‐deposited amorphous water is particularly interesting in the fields of physical and interstellar chemistry, because it is a representative model material for interstellar icy dust grains. We recently developed an experimental setup for in situ IR‐MAIRS under low‐temperature, ultrahigh‐vacuum conditions, which thus facilitates measurements of interstellar ice analogs such as vapor‐deposited amorphous water. This review considers the theoretical framework of IR‐MAIRS and our recent experimental results for vapor‐deposited amorphous water. We present spectroscopic signatures for the perpendicular orientation of dangling‐OH bonds for three‐coordinated water molecules at the surface of amorphous water at 90 K. The absolute absorption cross section of the three‐coordinated dangling‐OH bonds is quantitatively measured as 1.0 ± 0.2 × 10−18 cm2 at 3696 cm−1. As IR‐MAIRS can essentially be conducted using only a Fourier‐transform IR spectrometer and an angle‐controllable linear polarizer, it is a useful, low‐cost, and simple spectroscopic technique for studying laboratory analogs of interstellar ices including vapor‐deposited amorphous water.

Monte Carlo calculations of the extraction of scintillation light from cryogenic N-type GaAs

The high scintillation luminosity of n-type GaAs at 10 °K is surprising because (1) with a refractive index of 3.5, escape is inhibited by total internal reflection and (2) narrow-beam experiments at 90 °K report infrared absorption coefficients of several per cm. This paper presents Monte Carlo calculations showing that the high luminosity at 10 °K can be explained if (1) the narrow-beam absorption is almost all optical scattering and (2) the absolute absorption coefficient is below 0.1 per cm. Sixteen surface reflector configurations are simulated for a range of internal scattering and absolute absorption coefficients, and these can guide the design of cryogenic scintillating GaAs targets for the direct detection of dark matter. The discussion section presents a possible infrared scattering mechanism based on the metallic nature of n-type GaAs. A supplement file describes (1) the Monte Carlo program steps in detail and (2) how narrow-beam and integrating sphere experiments can measure the cryogenic optical scattering and absolute absorption coefficients.

A Model-Based Iterative Learning Approach for Diffuse Optical Tomography.

Diffuse optical tomography (DOT) utilises near-infrared light for imaging spatially distributed optical parameters, typically the absorption and scattering coefficients. The image reconstruction problem of DOT is an ill-posed inverse problem, due to the non-linear light propagation in tissues and limited boundary measurements. The ill-posedness means that the image reconstruction is sensitive to measurement and modelling errors. The Bayesian approach for the inverse problem of DOT offers the possibility of incorporating prior information about the unknowns, rendering the problem less ill-posed. It also allows marginalisation of modelling errors utilising the so-called Bayesian approximation error method. A more recent trend in image reconstruction techniques is the use of deep learning, which has shown promising results in various applications from image processing to tomographic reconstructions. In this work, we study the non-linear DOT inverse problem of estimating the (absolute) absorption and scattering coefficients utilising a 'model-based' learning approach, essentially intertwining learned components with the model equations of DOT. The proposed approach was validated with 2D simulations and 3D experimental data. We demonstrated improved absorption and scattering estimates for targets with a mix of smooth and sharp image features, implying that the proposed approach could learn image features that are difficult to model using standard Gaussian priors. Furthermore, it was shown that the approach can be utilised in compensating for modelling errors due to coarse discretisation enabling computationally efficient solutions. Overall, the approach provided improved computation times compared to a standard Gauss-Newton iteration.

Time-resolved measurements of HO2 radical in a heated plasma flow reactor

Time-resolved, absolute HO2 number density in diluted H2O2-Ar, CH4O2-Ar, and C2H4O2-Ar mixtures excited by a repetitive ns pulse discharge in a heated plasma flow reactor is measured by Cavity Ringdown Spectroscopy (CRDS). The experimental results are obtained at T = 300–600 K and P = 130 Torr, both during the discharge pulse burst and in the afterglow. The HO2 number density is inferred from the CRDS data using a spectral model exhibiting good agreement with previous measurements of absolute HO2 absorption cross sections. In the room-temperature H2O2 mixture, as well as in CH4O2 and C2H4O2 mixtures over the entire temperature range studied, HO2 is generated only during the discharge burst and decays in the afterglow. However, in the H2O2 mixture at elevated temperatures, T = 400–600 K, HO2 persists in the afterglow up to 10 ms after the discharge burst, comparable with the flow residence time in the reactor. Comparison with kinetic modeling shows that the sustained reactivity after the source of radicals is turned off is due to a chain propagation/ hydrogen oxidation process, which dominates the radical recombination reactions. The kinetic modeling predictions are in good agreement with the relative HO2 number density measured in all three mixtures, although the model underpredicts the absolute number densities in H2O2 at T = 400–600 K by up to a factor of two. Detection of the sustained low-temperature reactivity in H2O2, initiated by the radical generation in the plasma, suggests that the plasma excitation may also affect kinetics of oxidation and reforming of fuels exhibiting low-temperature chemistry below hot ignition point.

Brown carbon from biomass burning imposes strong circum-Arctic warming

Brown carbon from biomass burning imposes strong circum-Arctic warming

Near-infrared absorption thermometry exploiting an anomalously large spectral line-shift for the Yb3+ cubic centre in CaF2:Yb3+/Er3+ nanoparticles

Near-infrared absorption spectra of Yb3+ in Er3+ co-doped CaF2 upconverting nanoparticles have been measured. The Yb3+ ion 2F7/2→2F5/2 inter-multiplet optical absorption spectra show negatively charged preferential clusters and non-locally charge compensated cubic centers as the dominant centres. The temperature dependent absorption spectra measured between 10 K and 413 K for Yb3+ cubic centres exhibit an anomalously large blue-shift of 16.90 ± 0.02 cm−1. The CaF2:Yb3+/Er3+ nanoparticles show an absolute thermal sensitivity Sa of 0.044 ± 0.001 cm−1⋅K−1 and the maximum relative thermal sensitivity Sr of 2.290 ± 0.010%·K−1 at 413 K region based on the large cubic centre absorption line-shift and a value of Sr of 0.0723 ± 0.001%·K−1 at 10 K (0.0562 ± 0.010%·K−1 at 413 K) from the line-width. The observed absolute absorption thermal sensitivity is 10 times higher (and the relative absorption thermal sensitivity is 2 times higher) than that obtained using the fluorescence intensity ratio of the thermally coupled 2H11/2,4S3/2 energy levels of Er3+ in co-doped nanoparticles.

Absolute absorption cross section of 2-EHN in IR region

This paper presents the first determination of the absolute absorption cross section of 2-EHN from 850 to 3000 cm−1. The domain of application of our measurement and its accuracy are discussed. DFT calculations were used for band attributions and the identification of the different isomers existing at room temperature.The cross section measurements were used to study the adsorption/desorption processes of the gas that can occur on stainless steel cell walls and the evolution of this equilibrium when introducing 1 atm. of dry air. We also discuss the error made by neglecting those effects in terms of quantitative chemistry and air-broadening measurement.

L’assorbimento del glucosio in dialisi peritoneale: strumenti utili per il team multidisciplinare

Dialysis patients are often affected by protein energy wasting and the maintenance of an optimal nutritional state is a difficult goal to achieve. Moreover protein energy wasting is one of the strongest risk factors for mortality in chronic dialysis patients. To estimate glucose absorption in peritoneal dialysis is essential to determine patient’s dietary energy requirements and to prevent possible metabolic complications. The currently accepted methods of estimating glucose absorption are two. The first one is based on the average glucose absorption of continuous ambulatory peritoneal dialysis (CAPD) and is calculated with the Grodstein et al. formula. The second one is based on the Peritoneal equilibration test curves (D/D0 formula, Bodnar et al.) and takes into account transport characteristics. None of the two formulas perfectly calculated the absolute glucose absorption, even if the D/D0 is much closer to the true value, compared to Grodstein et al. formula. In this paper we described the multidisciplinary management experience of peritoneal dialysis patients, with a focus on the estimation of the patient’s energy requirements. Analyzing glucose absorption in a systematic way and monitoring the changes in glucose absorption during the time could significantly contribute to adjusting nutritional treatment. However it is always necessary to critically evaluate the results obtained by both formulas.

Effects of Chemical Treatment on the Physical Properties of Typha

Plant-based concretes are produced from plant aggregates and a binder. Plant fibers are mainly composed of saccharides (sugars) and these sugars can decrease the concentration of Ca2+ ions in the cement pore solution and delay the formation of hydration products. To improve the interfacial bond between fibers and matrix a chemical treatment is widely used. This study investigates the effect of sodium hydroxide treatment on physical and hygroscopic properties of Typha aggregates. In particular, a 5% sodium hydroxide solution is used to treat these aggregates and their bulk and absolute densities, porosity, water content and water absorption are evaluated accordingly. Results indicate that bulk and absolute densities increase after treatment from 56.44 kg/m3 to 122.57 kg/m3 and 541.93 kg/m3 to 555.17 kg/m3, respectively. NaOH treatment reduces porosity of Typha from 89.58 % to 77.92% and decreases water content from 1.4 % to 1%. The treatment with sodium hydroxide reduces substantially the water absorption of the aggregates.

Simultaneous high-speed keyhole depth and absorptance measurements in laser spot welding of dissimilar metals

The integration of aluminum parts for purposes of lightweighting requires joining aluminum to steel. This process is infamously difficult, due to the poor laser weldability of aluminum and the brittle intermetallic phases that form when the two metals mix. Precise control of the process is enabled by deep understanding of the underlying physics. To aid in this effort, we collect simultaneous time-resolved keyhole depth measured by inline coherent imaging and absolute absorptance measured by integrating sphere radiometry, during spot welds on 6061 aluminum, 316 stainless steel, and on both materials in lap weld configuration. We find that laser welding through steel into aluminum carried the benefits of steel keyhole welding (laser absorptance near or above 0.9, predictable keyhole formation), while also leading to more stable keyholes (standard deviation of keyhole depth was reduced by 50% compared to steel welding alone). In comparison, laser welding through aluminum into steel faced similar problems as aluminum welding alone, such as unpredictable keyhole formation and large fluctuations in depth and absorptance (more than twice as large compared to steel alone).

New line positions and effective line intensities of the ν2 band cis-HONO near 1661 cm−1 from quantum cascade laser absorption spectroscopy

High-resolution quantum cascade laser absorption spectrum of cis-HONO of the v2 band has been recorded and analyzed, for the first time, in the mid-infrared region of 1659.2–1662.2 cm−1 (R-branch of the v2 band, N=O stretch). Positions and effective line intensities were determined for about 60 new lines. The absolute absorption frequencies were directly measured during spectral scan using a wavelength meter with an accuracy of ∼0.0017 cm−1. The corresponding simulation spectrum was calculated using the PGOPHER code. The calculated line positions are in a good agreement with the experimentally measured frequencies within the wavelength meter uncertainty. Effective line intensities were determined, with uncertainties of about 17%, by scaling the measured HONO absorption intensities to the previously reported line intensity of a cis-HONO line located in the same spectral region near 1659.85 cm−1.