Ratio Of Absorption Coefficients Research Articles

Dependency of crossover point on absorption changes in bilayer diffusion reflection measurements.

A better understanding of diffusion reflection (DR) behavior may allow it to be used for more noninvasive applications, including the development of in vivo non-damaging techniques, especially for medical topical diagnosis and treatments. For a bilayer opaque substance where the attenuation of the upper layer is larger than the attenuation of the lower layer, the DR crossover point ( ) is location where the photons coming from the bottom layer start affecting the DR. We aim to study the dependency of the on absorption changes in different layers for constant scattering and top layer thickness. Monolayer and bilayer optical tissue-like phantoms were prepared and measured using a DR system. The results were compared with Monte Carlo simulations. There is an agreement between the experiments and the simulations. correlates with the square root of the absorption coefficient ratio of the lower layer to the top layer. The experimental findings support and validate the theoretical prediction describing the dependency of the on the square root of the ratio of the layers' absorption coefficients. In addition, a secondary breaking point is suggested to be observed experimentally at the entrance to the noise area.

Controlling factors of latitudinal distribution of dissolved organic matter in the upper layers of the Indian Ocean

We studied chromophoric (CDOM) and fluorescent (FDOM) dissolved organic matter (DOM) and dissolved organic carbon in surface waters to determine the factors controlling the geographical distribution of DOM along two meridional transects in the Indian Ocean. For CDOM, we calculated the absorption coefficients, spectral slope, and absorption coefficient ratio from the observed absorption spectra. For FDOM, we calculated the biological (BIX) and humification (HIX) indices from the excitation emission matrices (EEMs); parallel factor analysis of the EEMs identified three fluorescent components, i.e., two humic-like and one protein-like. Using these DOM parameters, a factor analysis extracted fewer latent variables than the observed variables to account for the geographical distributions. We obtained three factors (F1, F2, and F3), which explained ~ 84% of the variance in the observed data. From the factor loadings, F1, F2, and F3 were interpreted as the effects of net primary production-derived DOM and its horizontal transport, photodegradation, and vertical transport by physical processes. We characterized seven marine biogeochemical provinces by factor scores. F1 scores gradually decreased from the northernmost to the Antarctic province, with a small maximum around the subtropical front. F2 scores were highest in the subtropical province and decreased in both the northward and southward directions. F3 scores were high in the Antarctic and northernmost provinces, and lowest in the subtropical province. Only BIX was insufficiently explained by these factors. BIX was highest in the northern part of the subtropical province, where photodegradation of DOM was the most intense. This suggests that the possible interaction between photodegradation, autochthonous production, and reworking by heterotrophic bacteria of DOM occurs in the subtropical province.

Enhancing quality evaluation in traditional Chinese medicine: Utilizing dual wavelength fusion fingerprint, electrochemical fingerprint, and DSC fingerprint

Developing a reliable and effective quality evaluation system for traditional Chinese medicine (TCM) is both challenging and crucial for its advancement. This study employs fingerprinting techniques to establish precise and comprehensive quality control for TCM, taking Xuezhikang capsules as an example and aiming to facilitate the internationalization of TCM. The “double wavelength absorption coefficient ratio fingerprint” and “Reliability theory” are developed to determine the fingerprint peak purity and fingerprint reliability respectively. Subsequently, the dual-wavelength fusion fingerprint was obtained to avoid the limitations of a single wavelength. In addition, an electrochemical fingerprint (ECFP) was obtained to assess the similarity of electroactive components in the sample, and the Differential Scanning Calorimetry quantized fingerprint (DSC QFP) was introduced for thermal analysis. Fingerprint-efficacy correlations between PL-EC* and dual-wavelength fusion fingerprint (DWFFP) provided valuable insights that there are 76.6 % of the fingerprint compounds exhibited electroactivity. Finally, samples were classified into grades 1∼3 by combining DWFFP, ECFP and DSC QFP through the mean method, meeting the evaluation standard (SL−M > 0.9, PL−M between 80 % and 120 %). This study provides valuable information for ensuring the quality of TCM products, which represents a significant step forward in enhancing the reliability and authenticity of TCM products.

Thermoluminescence and optically stimulated luminescence of α-Al2O3 with different carbon concentrations

Carbon-doped α-Al2O3 (α-Al2O3:C) single crystals (nominal carbon concentrations with 500, 1000, 1500 and 2000 ppm) were grown by the vertical gradient freezing (VGF) method. Thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of as-grown α-Al2O3:C crystals were studied. F and F+ center absorption (except for the sample with 500-ppm carbon) at 205 and 256 nm was enhanced with increasing carbon concentration. The results show that TL and OSL intensities from α-Al2O3:C are strongly correlated with the ratio of absorption coefficients from the F-center to the F + -center. Both TL and OSL intensities of the sample doped with 1000 ppm reach maximum when the ratio of absorption coefficients from the F-center to F + -center is at its highest. The OSL response of the sample doped with 1000 ppm carbon is 3.43 times that of the sample doped with 500 ppm carbon and is 2.47 times higher than that of the TLD-500 K. The activation energies for samples with 500, 1000, 1500 and 2000 ppm carbon were calculated as 1.33 ± 0.11, 1.58 ± 0.02, 1.52 ± 0.02 and 1.52 ± 0.04 eV, respectively. The OSL intensities from α-Al2O3:C appear strongly correlated with the ratio of absorption coefficients F-center to F + -center. These attractive features may pave the way for the VGF method to improve the luminescence and dosimetry properties.

Design and construction of the Texas Christian University impedance tube

The two-microphone impedance tube test method is a well-established and widely used technique for determining the acoustic absorption coefficient and impedance ratio of materials. This method uses two closely spaced microphones to simultaneously measure the incident and reflected sound waves. A two-microphone impedance tube measurement system made of 6061-T6 Aluminum with a diameter of 3 inches, a 0.5 inch wall thickness, and microphones spaced 2.7 inches apart has been constructed for undergraduate research at Texas Christian University (TCU). These geometrical values suggest a usable frequency range of 50 Hz to 2637.77 Hz as referenced in ASTM Standard E1050-19. Validation of the system was achieved by taking measurements on Owen Corning Type 705 pressed fiberglass board with a 1-inch thickness and comparing them to absorption data provided by the manufacturer. Additional validation measurements were taken without a test sample in place. All validation tests suggest that the TCU impedance tube is an accurate measurement system.

Heat and mass transfer under MHD mixed convection in a four‐sided lid‐driven square cavity

AbstractThis paper investigates the heat and mass transfer under magnetohydrodynamic mixed convection flow of a binary gas mixture in a four‐sided lid‐driven square cavity. The enclosure's left wall is sinusoidally heated and acts as a source term, while the right wall functions as a sink. The cavity's horizontal walls are adiabatic and impermeable to mass transfer. The governing equations under Boussinesq approximation and stream function‐vorticity formulation are solved using the alternating‐direction‐implicit scheme, a finite‐difference method. The numerical scheme's consistency and stability are demonstrated using the matrix method. The MATLAB code is written, validated against some existing studies, and used to perform numerical simulations. The numerical solutions are graphically examined by visualizing the streamline, isotherm, and concentration contours for nondimensional parameters, such as Hartmann number , heat absorption or generation coefficient , Richardson number , and buoyancy ratio . The magnetic field modifies the temperature and concentration distribution in the cavity, depending on the convection mode. The magnetic field forces the fluid to stagnate in different regions of the cavity, depending on the mode of convection. It was found that the difference between the maximum and minimum temperature and concentration at the cavity's midpoint increases up to 13 and 10 times, respectively, in the natural convection compared with the forced convection. The average Nusselt number on the vertical walls of the cavity is maximum in natural convection in the absence of a magnetic field but reaches a minimum value at in forced and mixed convection. The average Sherwood number on the cavity's vertical walls decreases with the magnetic field in mixed and natural convection.

Optoelectronic Digital Dust Meter in Cotton Gining Manufactory

The paper discusses the problems of environmental pollution and requirements for instruments and systems for measuring dust levels. It is demonstrated that among the problems of environmental protection, the most crucial one is the protection of the air basin. Dust is one of the most common types of industrial waste. Human health is affected not only by the type of dust, particle size and mineralogical composition, but also by the duration of exposure. Therefore, high sensitivity of instruments and systems for monitoring atmospheric pollution is required. The problem of environmental pollution can only be solved with the help of automatic, continuously operating analysers. It is advisable to develop and implement portable threshold alarms that have a significantly lower cost than the cost of automatic control and measurement equipment. The operating principle of an optoelectronic device for monitoring the degree of dust in cotton ginning rooms has been developed and presented, which allows simultaneous measurement of the attenuation (extinction) and light scattering of the same passing mass of aerosol. The calculation of specific absorption and dispersion coefficients in the ginning shops of cotton gin plants has been carried out. Experimental curves of the ratio of absorption and attenuation coefficients depending on the presence of the aerosol in the optoelectronic device are presented. Methods to reduce measurement error are revealed.

Dual carbon isotope-based brown carbon aerosol characteristics at a high-altitude site in the northeastern Himalayas: Role of biomass burning

PM2.5 samples (n = 34) were collected from January to April 2017 over Shillong (25.7°N, 91.9°E; 1064 m amsl), a high-altitude site situated in the northeastern Himalaya. The main aim was to understand the sources, characteristics, and optical properties of local vs long-range transported carbonaceous aerosols (CA) using chemical species and dual carbon isotopes (13C and 14C). Percentage biomass burning (BB)/biogenic fraction (fbio, calculated from 14C) varied from 67 to 92 % (78 ± 7) and correlated well with primary BB tracers like f60, and K+, suggesting BB as a considerable source. Rain events are shown to reduce the fbio fraction, indicating majority of BB-derived CA are transported. Further, δ13C (−26.6 ± 0.4) variability was very low over Shillong, suggesting it's limitations in source apportionment over the study region, if used alone. Average ratio of absorption coefficient of methanol-soluble BrC (BrCMS) to water-soluble BrC (BrCWS) at 365 nm was 1.8, indicating a significant part of BrC was water–insoluble. A good positive correlation between fbio and mass absorption efficiency of BrCWS and BrCMS at 365 nm with the higher slope for BrCMS suggests BB derived water-insoluble BrC was more absorbing. Relative radiative forcing (RRF, 300 to 2500 nm) of BrCWS and BrCMS with respect to EC were 11 ± 5 % and 23 ± 16 %, respectively. Further, the RRF of BrCMS was up to 60 %, and that of BrCWS was up to 22 % with respect to EC for the samples with fbio ≥ 0.85 (i.e., dominated by BB), reflecting the importance of BB in BrC RRF estimation.

Improving Colored Dissolved Organic Matter (CDOM) Retrievals by Sentinel2-MSI Data through a Total Suspended Matter (TSM)-Driven Classification: The Case of Pertusillo Lake (Southern Italy)

Colored dissolved organic matter (CDOM) is a significant constituent of aquatic systems and biogeochemical cycles. Satellite CDOM retrievals are challenging in inland waters, due to overlapped absorption properties of bio-optical parameters, like Total Suspended Matter (TSM). In this framework, we defined an accurate CDOM model using Sentinel2-MSI (S2-MSI) data in Pertusillo Lake (Southern Italy) adopting a classification scheme based on satellite TSM data. Empirical relationships were established between the CDOM absorption coefficient, aCDOM (440), and reflectance band ratios using ground-based measurements. The Green-to-Red (B3/B4 and B3/B5) and Red-to-Blue (B4/B2 and B5/B2) band ratios showed good relationships (R2 ≥ 0.75), which were further improved according to sub-region division (R2 up to 0.93). The best accuracy of B3/B4 in the match-ups between S2-MSI-derived and in situ band ratios proved the exportability on S2-MSI data of two B3/B4-based aCDOM (440) models, namely the fixed (for the whole PL) and the switching one (according to sub-region division). Although they both exhibited good agreements in aCDOM (440) retrievals (R2 ≥ 0.69), the switching model showed the highest accuracy (RMSE of 0.0155 m−1). Finally, the identification of areas exposed to different TSM patterns can assist with refining the calibration/validation procedures to achieve more accurate aCDOM (440) retrievals.

Establishing an integrated, four-dimensional quality assessment system for traditional Chinese medicine: A case study of Shuanghuanglian oral liquid

The quality of traditional Chinese medicine (TCM) is the premise to ensure its safety and effectiveness in clinical application. In this study, a complete quality control system for four-dimensional fingerprinting of TCM was innovatively constructed based on multiple detection techniques, and the quality of Shuanghuanglian oral liquid (SHL) was evaluated. Electrochemical fingerprinting (ECFP) as an emerging method without pretreatment provides rich and quantifiable information for SHL samples. The first quantitative ECFP of SHL was developed by the B-Z oscillation system. Eight characteristic parameters were analyzed and a good linear relationship was found between the oscillation lifetime and sample volume, by which the calculated values of the added sample volume (VL) showed different fluctuations between samples. What is more, high-performance liquid chromatography five-wavelength fusion fingerprint (HPLC-FWFP), GC fingerprint (GC-FP), and UV quantum fingerprint (UV-QFP) was established. Meanwhile, the purity of the peaks of the HPLC-FWFP was verified by the dual-wavelength absorption coefficient ratio spectrum (DWAR). Equal weighted ratio quantitative fingerprinting method (EWRQFM) was successfully proposed to extract all potential features for the overall quality assessment of the samples. Finally, a comprehensive evaluation strategy was proposed, namely the variation coefficient weighting algorithm (VCWA). The results of qualitative and quantitative evaluation of HPLC-FWFP, GC-FP, electrochemical quantum fingerprints (EC-QFP), and UV-QFP were integrated by this method. The established evaluation system is also a suitable strategy to control the quality of other TCM preparations.

Comparison of the dosimetric response of two Sr salts irradiated with 60Co γ-rays and synchrotron X-rays at ultra-high dose rate

As part of the development of innovative radiotherapy techniques using X-ray synchrotron sources, namely FLASH-radiotherapy and microbeam radiation therapy (MRT), two rod dosimeters based on strontium sulfate (SrSO4) and strontium carbonate (SrCO3) were developed and irradiated at the ESRF-ID17 Biomedical beamline to investigate new solid-state dosimeters.The radiation-induced defect in Sr-based dosimeters was detected by means of an electron paramagnetic resonance (EPR) spectrometer. For the study, the EPR response of the dosimeters irradiated with synchrotron X-rays in the 30–600 keV range and dose rate of 11.6 kGy/s was compared with the response after irradiation with a 60Co γ-ray source with a dose rate of 0.288 Gy/s.Both Sr dosimeters show an increased intensity of the EPR signal in the case of irradiation at the synchrotron with respect to the case of 60Co γ-ray irradiation. The measured enhancement of the delivered dose is explained by the fact that Sr shows an increased photoelectric interaction at orthovoltage X-ray energies, producing an increased number of free radicals.The experimental relative response rESRF of the EPR signals between samples irradiated at the ID17 beamline and the 60Co beam quality was found to be 9.66 for SrSO4 and 11.19 for SrCO3. Meanwhile, the theoritical relative responses rμen/ρESRF calculated as the ratio of mass energy absorption coefficients (μen/ρ) of the dosimeters to that for water at the ID17 with respect to the 60Co beam was found to be 11.85 for SrSO4 and 13.31 for SrCO3.The increased EPR response of Sr salt dosimeters irradiated with photons in the keV range proved that these detectors type could be a good candidate for the development of very sensible detectors for radiotherapy applications.

MANAGING, ASSESSING AND MONITORING URBAN SPRAWL USING REMOTE SENSING; CHANGE DETECTION, URBAN EXPANSION INTENSITY INDEX (UEII), AND SHANNON ENTROPY: A CASE STUDY OF AMMAN CITY, JORDAN (1990–2022)

Mapping and monitoring of land use land cover (LULC) changes in Amman city are important for sustainable regional development, urban planning, and environmental and land use management. To comprehend the temporal and the spatial variability of LULC change, six time-period satellite images of the study area have been examined based on remote sensing (RS) and geographic information system (GIS) techniques. The changes in LULC patterns of Amman city were monitored for the periods 1990-1995, 1995-1999, 1999-2004, 2004-2013, 2013-2017 and 2017-2022. Employing Spatio-temporal Landsat TM and ETM imagery acquired from 1990 to 2022 to comprehend, detect, and quantify the spatial pattern of urban sprawl. Supervised classification was used to extract built-up areas and measure changes in urban land-use class across the metropolis. The result of the urban expansion intensity index shows that urban expansion hits its peak between 2013 and 2017, with a 1.75 index resulting in high-speed development between the time frames. Shannon’s entropy approach was quantified to detect the urban sprawl phenomenon. The results showed that the Relative Shannon entropy values are above 0.5, indicating dispersedly spread-urban sprawl. Land Absorption Coefficient (LAC) and Land Consumption Ratio (LCR) were also used. A strong positive correlation between road networks and urban sprawl (0.7) indicates that urbanization plays a major role in the occurrence of urban sprawl. The findings obtained from this work would provide urban planners and decision-makers in Amman the tools and data they need, to implement planning interventions for sustainable future development and to mitigate the impacts of urban sprawl on different aspects on the environment.

Clinical treatment planning for kilovoltage radiotherapy using EGSnrc and Python.

Kilovoltage radiotherapy dose calculations are generally performed with manual point dose calculations based on water dosimetry. Tissue heterogeneities, irregular surfaces, and introduction of lead cutouts for treatment are either not taken into account or crudely approximated in manual calculations. Full Monte Carlo (MC) simulations can account for these limitations but require a validated treatment unit model, accurately segmented patient tissues and a treatment planning interface (TPI) to facilitate the simulation setup and result analysis. EGSnrc was used in this work to create a model of Xstrahl kilovoltage unit extending the range of energies, applicators, and validation parameters previously published. The novel functionality of the Python-based framework developed in this work allowed beam modification using custom lead cutouts and shields, commonly present in kilovoltage treatments, as well as absolute dose normalization using the output of the unit. 3D user-friendly planning interface of the developed framework facilitated non-co-planar beam setups for CT phantom MC simulations in DOSXYZnrc. The MC models of 49 clinical beams showed good agreement with measured and reference data, to within 2% for percentage depth dose curves, 4% for beam profiles at various depths, 2% for backscatter factors, 0.5 mm of absorber material for half-value layers, and 3% for outputfactors. End-to-end testing of the framework using custom lead cutouts resulted in good agreement to within 3% of absolute dose distribution between simulations and EBT3 GafChromic film measurements. Gamma analysis demonstrated poor agreement at the field edges which was attributed to the limitations of simulating smooth cutout shapes. Dose simulated in a heterogeneous phantom agreed to within 7% with measured values converted using the ratio of mass energy absorption coefficients of appropriate tissues andair.

PHANTOM EXPERIMENTAL STUDY ON PATIENT DOSES OBTAINED FROM 320-MULTIDETECTOR-ROW COMPUTED TOMOGRAPHY IN WHOLE-BRAIN PERFUSION SCAN.

This study aimed to precisely evaluate organ dose and effective dose (E) obtained from a 320-multidetector-row computed tomography (CT) scanner in brain perfusion scans and to estimate the conversion factor (k) between E and dose length product (DLP). A total of 270 thermoluminescent dosemeters were implanted in a male anthropomorphic phantom to measure air kerma. The ratios of mass-energy absorption coefficients were used to convert air kerma into organ doses. The organ doses ranged from 0.01 to 150mGy. Doses in brain, salivary glands and red bone marrow were relatively high, and dose in eye lens reached about 110mGy. The resulting effective dose was 5.30mSv. The resulting conversion factor k=(0.0022±0.0002) mSv·(mGy·cm)-1 was not significantly different from that of 0.0021mSv·(mGy·cm)-1 reported for head CT scan in ICRP Publication 102.

Aquatic particulate absorption coefficient combining extraction and bleaching optimized for inland waters

AbstractThe particulate absorption coefficient is one of the fundamental inherent optical properties describing interactions of light with material in water. Its spectral properties contain important information about chemical and biological constituents. It is often partitioned into algal and non‐algal fractions which provide useful information describing phytoplankton. Particulate absorption coefficient has been routinely measured in the ocean particularly to calibrate remote sensing algorithms. However, the methods to measure marine algal and non‐algal absorbing fractions might fail in freshwaters due to difficulties extracting green‐algae pigments and cyanobacterial phycocyanin and the high organic content of the non‐algal particles, making direct bleaching biased. In this work, we describe a method with sequential extraction, bleaching, and post‐processing to obtain unbiased pigments and non‐algal absorption fractions in freshwater environments, and we compare it against the resulting fractions obtained by only extraction or bleaching, using samples collected from 649 lakes across Canada. The resulting non‐algal particles spectra from our method appear free of interfering pigments while maintaining spectral shapes, as verified by the higher correlation coefficient between the 400 and 700 nm exponential coefficient (S, often referred to as slope) of the non‐algal particles spectra and the organic fraction of total suspended solids, and by having a better correlation between the ratio of absorption coefficient of phytoplankton at 620 and 676 nm and cyanobacterial biomass percentage. Overall, this method solves the two problems in freshwater particulate absorption partitioning associated with (1) unextracted pigments with methanol extraction methods and (2) bias introduced to non‐algal absorption spectra from NaOH bleaching.

A semianalytical algorithm for estimating particulate composition in inland waters based on Sentinel-3 OLCI images

The composition of suspended particles is a key factor in determining the underwater light field, which is of great significance for understanding the variability in the optical properties of water bodies. In this study, the ratio of the phytoplankton absorption coefficient to the backscattering coefficient at wavelength of 681 nm (aph(681)/bb(681)) was found to be an optimal optical indicator of the ratio of chlorophyll-a to the total suspended matter concentration (Chla/TSM), a parameter indicating the particulate composition. Therefore, a semianalytical algorithm was proposed to estimate Chla/TSM from remote sensing reflectance (Rrs(λ)) at 681 nm and 754 nm on Sentinel-3 Ocean and Land Color Instrument (OLCI) images. The validation dataset collected from 11 inland lakes and 3 reservoirs in China and 2 inland lakes in America was used to evaluate the algorithm’s performance. The evaluation results demonstrated that the proposed algorithm could have favorable performance in inland waters. Furthermore, comparison with two other state-of-the-art algorithms (Sun_13 and NTD675) showed that this proposed algorithm had higher estimation accuracy, with an overall winning rate (OWR) of 60%, an unbiased mean absolute percentage error (UMAPE) reduction from 72.95% to 46.44%, a root mean square error (RMSE) decline from 1.42 µg/mg to 0.83 µg/mg and a normalized root mean square error (NRMSE) decline from 11.36% to 6.62%. This algorithm was successfully applied to acquire the Chla/TSM tempo-spatial variation using the OLCI images of Lake Taihu from 2016 to 2019. It was found that the algorithm developed based on OLCI images can be applied to satellite sensors with similar bands, such as Medium-Resolution Imaging Spectrometer (MERIS), and Sentinel-2 multispectral instrument (MSI), etc. As a simple and effective algorithm, the proposed algorithm has the potential to monitor changes in Chla/TSM in inland waters on a global scale.

Estimation of vertical size-fractionated phytoplankton primary production in the northern South China Sea

Modelling vertical changes of size-fractionated phytoplankton primary production (PP) offers a holistic route to describe marine ecosystems and constitutes an important part of remote sensing to accurately estimate the depth-integrated PP in the global oceans. However, there is no size-fractionated PP model established in the Northern South China Sea (NSCS) yet. In situ measured hyperspectral absorption and irradiance data were used to estimate vertical size-fractionated PP. Results demonstrated that the estimated size-fractionated PP showed good agreement with in-situ measurement. r2s are 0.41, 0.69, and 0.83, and median absolute percentage difference are 23.33%, 25.86%, and 31.05% for pico-, nano-, and micro-PP, respectively. The intercept from the linear relationship between ratio of phytoplankton absorption coefficient (aph(4 3 5)/aph(6 7 6)) and quantum yield of photosynthesis have the biggest impact on estimation of PP based on Monte Carlo approach. The model derived PP profiles showed an exponential attenuation shape curve from the surface to the bottom in coastal water of NSCS. In contrast, a decreasing pattern with increasing depth with a maximum in the subsurface layer or at the chlorophyll maximum depth was observed in the open ocean of NSCS. Such an approach can be utilized to depict the vertical variations of size-fractionated PP, which can serve as supplementary of remote sense to reveal their three-dimensional structure.

Increasing the Efficiency of the Light-Absorbing Coating of Solar Collectors

A method for intensifying light absorption by the coating material of solar collectors based on the use of carbon nanotubes is considered. The increase in the optical absorption coefficient of the coating material was 11.7 %, the thermal conductivity of the coating material - 24.9 %, the ratio of the optical absorption coefficient to the thermal radiation coefficient (α/ε) - 9.2 %. The value of the mass concentration of carbon nanotubes in the coating layer, at which the stated results are achieved, has been established.

Light absorption enhancement due to mixing in black carbon and organic carbon generated during biomass burning

We report the direct observation of the light absorption enhancement effect due to the mixing of black carbon (BC) and organic carbon (OC) aerosols generated during biomass combustion. The biomass fuels viz. mango tree wood (Mangifera indica) and dung cake were burned and the dry absorption of the aerosol stream was measured using the 7-wavelength aethalometer. The absorption coefficients were measured for thermally denuded and undenuded aerosols. The measurements provided an enhancement ratio for black carbon in presence of organic carbon at seven different wavelengths. The near-source enhancement ratio for wood and dung cake at 880 nm was found to be 1.35 ± 0.06 and 1.59 ± 0.08, respectively. The enhancement effect was found to increase with the decrease in wavelength for both the fuels, indicating absorption by the brown carbon. The organic coating on the black carbon was estimated using the mie theory modelling. The organic coating factor on the black carbon was found to be 1.37 and 1.69 for wood and dung cake, respectively. The enhancement ratio at 370 nm increased with the increase in the absorption angstrom exponent (AAE). The enhancement ratio depicted negative linear dependence (r = −0.91) on the logarithmic ratio of black carbon and absorption coefficients of brown carbon at 370 nm across both fuels and burn conditions.

Control of spectral characteristics of the medical accelerator on the basis of comparison of mass weaking coefficients of different materials

Background. Radiation protection of patients undergoing radiation therapy using linear electron accelerators is based on ensuring the constancy of the equipment parameters set during commissioning. Therefore, studying the possibility of operational assessment of the spectrum characteristics consistency of the generated bremsstrahlung is a priority along with standard dosimetric parameter control procedures. Primarily, this refers to specifying the average measured energy of bremsstrahlung which provides an impartial assessment of the constancy of the whole wave path of the accelerator. However, there is no special diagnostic equipment to determine this parameter. At the same time, the literature data represent a growing interest in the use of CdTe sensors for the analysis of high-energy radiation, including the ones in medical accelerators. Purpose – developing and testing special diagnostic equipment based on semiconductor CdTe sensors, which would implement the assessment of the average measured energy of bremsstrahlung of the medical accelerator 6 MeV via comparing the mass attenuation coefficients in lead and aluminum. Materials and Methods. The paper deals with experimental evaluation of the Varian Clinac 600C linear accelerator (USA) spectrum characteristics carried out at Radiation Oncology Department of State Organization «Grigoriev Institute for Medical Radiology and Oncology of the National Academy of Medical Sciences of Ukraine» via determining the average measured energy of bremsstrahlung. The assessment of the average measured energy of the bremsstrahlung of the accelerator was performed based on comparing two mass attenuation coefficients of radiation with materials having significantly different atomic numbers, i.e. Al and Pb. The assessment of the mass attenuation coefficients was performed on the basis of measuring the average amplitudes of CdTe signals of the sensor, operating in the pulse mode in conjunction with a 16-bit ADC. Pulses of bremsstrahlung from the linear accelerator were recorded by a peak detector for 10 seconds of measurement by the hardware-software complex at 400 monitor units by CdTe sensor with aluminum and lead absorber. The study was performed at a distance of «source-surface» 100 cm with an area of the irradiation field of 20x20 cm. The spectral energy profile of the generated field of bremsstrahlung was studied. Results. The developed equipment was tested by CdTe sensor, which was created taking into account the energy sensitivity of the sensor itself as well as the spectraltemporal characteristics of the pulsed radiation of the accelerator. The approach dealing with assessing the average measured energy of bremsstrahlung of the linear electron accelerator, based on the dependence of the attenuation of radiation by the absorber layer on the radiation energy, has been experimentally confirmed. The theoretical dependence of the average measured energy of bremsstrahlung of the linear accelerator on the ratio of the mass attenuation coefficients of lead and aluminum has been obtained. The energy range from 0.1 to 6 MeV corresponds to the ratio of mass absorption coefficients of lead to aluminum, varying nonlinearly from 33.8 to 1.639. The average measured energy of the linear accelerator of 0.8 MeV corresponds to a mass coefficient ratio of about 1.23 for these materials. The assessed absolute error (from the set value during commissioning the linear accelerator) of the specified measured average energy of bremsstrahlung is up to 12.5% (0.72 MeV), corresponding to the ratio of mass attenuation coefficients – 1.340. Conclusions. The special diagnostic equipment for recording the spectrum characteristics of the Varian Clinac 600C linear accelerator (USA) based on semiconductor CdTe sensors, which along with 16-bit ADC make it possible to estimate the average measured energy of bremsstrahlung via comparing mass attenuation coefficients in Al and Pb has been substantiated and reduced to practice. The assessment of mass attenuation coefficients is carried out based on measuring the average amplitudes of pulses of СdTe sensors operating in a pulse mode.