Chamber Measurements Research Articles

Spatial Acoustic Loudspeaker Measurements With a Moving Microphone

Acoustic loudspeaker measurements are an essential aspect in loudspeaker development and design. Established setups usually require acoustic measurement rooms or chambers where the speaker under test has to be installed for conducting the tests. Furthermore, typical spatial measurements require that the speaker has to be rotated on one or two axes. In addition to the traditional approach, there are different methods that use near-field measurements where the microphone is usually moved and the loudspeaker remains at a fixed position. Both techniques commonly make measurements at discrete points or angles in the spatial domain. In this article, the idea of making impulse response measurements in the near-field while the microphone is in movement is proposed and described. This approach leads to much faster results that can be comparable to the results of fixed-point measurements. The focus here is on the properties and the resulting processing of appropriate test signals and on the experimental verification of the method. This method will be applied to the measurement of line arrays, where directivity is of high interest, but it can also be used for other loudspeaker configurations.

Mobile Sleep Lab: Comparison of polysomnographic parameters with a conventional sleep laboratory.

In remote areas, visiting a laboratory for sleep testing is inconvenient. We, therefore, developed a Mobile Sleep Lab in a bus powered by fuel cells with two sleep measurement chambers. As the environment in the bus could affect sleep, we examined whether sleep testing in the Mobile Sleep Lab was as feasible as in a conventional sleep laboratory (Human Sleep Lab). We tested 15 healthy adults for four nights using polysomnography (the first two nights at the Human Sleep Lab or Mobile Sleep Lab with a switch to the other facility for the next two nights). Sleep variables of the four measurements were used to assess the discrepancy of different places or different nights. No significant differences were found between the laboratories other than the percentage of total sleep time in stage N3. Next, we analyzed the intraclass correlation coefficient to evaluate the test-retest reliability. The intraclass correlation coefficient between these two measurements: the Human Sleep Lab and Mobile Sleep Lab showed similar reliability for the same sleep variables. The intraclass correlation coefficient revealed that several sleep indexes, such as total sleep time, sleep efficiency, wake after sleep onset, percentage of stage N1, and stage R latency, showed poor reliabilities (<0.5) based on Koo and Li's criteria. In contrast, the percentage of stage N3 showed moderate (0.5-0.75) or good (0.75-0.9) reliabilities. As almost all sleep variables showed no difference and same level of test-retest reliability between the Mobile Sleep Lab and Human Sleep Lab, the Mobile Sleep Lab might be suitable for conducting polysomnography as a conventional sleep laboratory. The reduction in N3 in the Mobile Sleep Lab should be scrutinized in the larger sample, including sleep disorders. Practical application of the Mobile Sleep Lab can transform sleep medicine in remote areas.

Multi-Band Scattering Characteristics of Miniature Masson Pine Canopy Based on Microwave Anechoic Chamber Measurement

Using microwave remote sensing to invert forest parameters requires clear canopy scattering characteristics, which can be intuitively investigated through scattering measurements. However, there are very few ground-based measurements on forest branches, needles, and canopies. In this study, a quantitative analysis of the canopy branches, needles, and ground contribution of Masson pine scenes in C-, X-, and Ku-bands was conducted based on a microwave anechoic chamber measurement platform. Four canopy scenes with different densities by defoliation in the vertical direction were constructed, and the backscattering data for each scene were collected in the C-, X-, and Ku-bands across eight incidence angles and eight azimuth angles, respectively. The results show that in the vertical observation direction, the backscattering energy of the C- and X-bands was predominantly contributed by the ground, whereas the Ku-band signal exhibited higher sensitivity to the canopy structure. The backscattering energy of the scene was influenced by the incident angle, particularly in the cross-polarization, where backscattering energy increased with larger incident angles. The scene’s backscattering energy was influenced by the scattering and extinction of canopy branches and needles, as well as by ground scattering, resulting in a complex relationship with canopy density. In addition, applying orientation correction to the polarization scattering matrix can mitigate the impact of the incident angle and reduce the decomposition energy errors in the Freeman–Durden model. In order to ensure the reliability of forest parameter inversion based on SAR data, a greater emphasis should be placed on physical models that account for signal scattering and the extinction process, rather than relying on empirical models.

An investigation of high-Z material for bolus in electron beam therapy

Highlight. Electron beam treatment often requires bolus to augment surface dose to nearly 100%. There are no optimum bolus materials and hence a high-Z based clothlike material is investigated to reduce air column in treatment that provides optimum surface dose. This material is well suited as it can be used multiple times and can be sanitized. Characteristics of W-Si material is provided.Purpose /Objective(s). Electron beams are frequently used for superficial tumors. However, due to electron beam characteristics the surface dose is 75-95% of the prescribed dose depending on beam energy thus requiring placement of bolus to augment surface dose. Various types of boluses are commonly used in clinics, each having it's own unique limitation. Most bolus devices do not conform to the skin contour and create airgaps that are known to produce dose perturbations creating hot and cold spots. A cloth-like high-Z materials; Tungsten, (Z = 74) and Bismuth, (Z = 83) impregnated in silicone gel is investigated for electron bolus.Materials/Methods. Super soft silicone-gel based submillimeter thin tungsten and bismuth sheets were investigated for bolus for 6-12 MeV. Parallel plate ion chamber measurements were performed in a solid water phantom on a Varian machine. Depth dose characteristics were measured to optimize the thickness for surface dose to be 100% for selected electron therapy and validated with Monte Carlo simulations.Results. Silicone-gel tungsten and bismuth sheets produce significant electrons thus increasing surface dose. Based on measured depth dose, our data showed that tungsten sheets of 0.14 mm, 0.18 mm and 0.2 mm and Bismuth sheets of 0.42 mm, 0.18 mm and 0.2 mm provide 100% surface dose for 6, 9 and 12 MeV beams, respectively without any significant changes in depth dose except increasing surface dose.Conclusions. The new high-Z clothlike sheets are extremely soft but high tensile metallic bolus materials that can fit flawlessly on any skin contour. Only 0.2 mm thick sheets are needed for 100% surface dose without degradation of the depth dose characteristics. These materials are reusable and ideal for bolus in electron beam treatment. This investigation opens a new frontier in designing new bolus materials optimum for patient treatment.

The specifics of chamber measurements of greenhouse gas emissions in coastal and marine ecosystems

The article presents the results of measuring CO2 fluxes on the beach in areas with and without marine macrophytes and at the water-atmosphere boundary in Kievka Bay. Such studies were conducted for Kievka Bay for the first time. A chamber dynamic method and a laser gas analyzer were used to measure CO2 fluxes at all plots. Higher values of CO2 fluxes were noted on the beach in areas with dry beach macrophytes compared to wet beach macrophytes. Areas with macrophytes had 23 times higher values of CO2 fluxes compared to areas without beach macrophytes. To identify patterns and intensity of CO2 gas exchange between the sea and the atmosphere, long-term monitoring measurements are necessary, since there are many variable factors. When measuring gas exchange between the sea and the atmosphere, sharp short-term increases or decreases in CO2 concentration were noted on the graphs of concentration versus measurement time. This was not associated with technical failures of the gas analyzer or features of the floating chamber. This introduces difficulties in interpreting the data, since the linearity of the graph is lost and the error in the flow value increases.

Birch (Betula pubescens Ehrh.) Encroachment Alters Contribution of Plant Functional Groups to Ecosystem Carbon Cycling in a Rewetted Bog.

Rewetted bogs with high water levels (WL) and mire-specific vegetation are crucial carbon (C) sinks, but their function might be threatened by tree encroachment, a phenomenon widespread in the northern hemisphere that often coincides with low WL. This might impact C cycling both at the ecosystem and microform scale in multiple ways, but so far, data are lacking. We established two sites in the same former peat extraction area, one showing permanently high WL and mire-specific vegetation (open site, OS), while the other one has more fluctuating WL and a dense birch (Betula pubescens Ehrh.) population (tree site, TS). We measured the carbon dioxide (CO2) exchange at ecosystem (eddy covariance) and plot scale (chamber measurements) for 1 year to clarify the differences between the sites and the impact of birch encroachment on the contribution of the different bog-specific microforms and the trees to the ecosystem's CO2 balance. Overall, the OS had a CO2 balance of -262.4 ± 7.8 g CO2-C m-2 year-1 indicating CO2 uptake, while the TS was close to neutral (-28 ± 5.1 g CO2-C m-2 year-1). The smaller uptake at the TS was caused by higher (151%) ecosystem respiration, while gross primary production was 14% higher. However, the microform contributions to C uptake strongly differed: At the OS, both hummocks and hollows showed net uptake, while at the TS, most C (52%) was assimilated by the birches and the understory was a net CO2 source. This indicates a loss of peat C from the TS, while the successfully rewetted site was accumulating new peat. Accounting for plot-scale CH4 fluxes, both sites were a weak source of greenhouse gases, but a distinctly stronger C sink occurred at the OS. Our data show the possibility of increasing C removal from the atmosphere by full rewetting and the establishment of mire-specific vegetation.

Measurement of absorbed dose in water in brachytherapy

Abstract Introduction: The most commonly used method for measuring the activity of sources in brachytherapy involves well chambers, which are utilized to measure air kerma. Brachytherapy centers are required to employ the TG-43 algorithm, which calculates the dose distribution in water. Transitioning from air to water introduces uncertainties. The objective of this study is to develop a new method for measuring the absorbed dose in water for 192Ir radiation. Material and Methods: A prototype ionization chamber was used in this study. To determine the absorbed dose in water measured by this chamber, the definition of absorbed dose in water was applied directly. Perturbation factors were calculated using Monte Carlo simulations, while correction factors were derived from measurements taken with the ionization chamber. A water phantom was created, along with a positioning system for the ionization chamber and a holder for the source. Corrections were calculated for polarization, recombination, saturation, and the effects of pressure and temperature on the chamber signal were taken into account. Measurements were performed at the position of the maximum chamber signal, determined before each measurement, and repeated for various air kerma values and different sources. Results: The measurement results in water were compared to those obtained from the TG-43 algorithm. Results indicate a combined measurement uncertainty of 1.26%, representing a significant improvement over the well chamber measurements. Conclusion: Preliminary results indicate the potential for improving dosimetric accuracy in brachytherapy. By using values for absorbed dose in water, uncertainties associated with converting air kerma to dose distribution in water can be eliminated.

Radon dosimetry - comparison of selected measurement methods

Abstract Introduction: Recently, the measurement of radon concentration has become one of the necessary procedures for implementation and execution in dosimetry. The aim of this study was to compare effectiveness, accuracy and ease of use of three selected radon measurement methods: one active and two passive. Material and Methods: Lucas chambers (scintillation method), thermoluminescent detectors (TLD) and track detectors (CR-39) were used. Air measurements were performed for two different locations: Czeladz (C) and Krakow (K). The measuring devices were placed in the basements for a specified time (30 days) and, in case of active detectors, additional measurements were performed in the exposure-reading mode. Results: For the Lucas chamber, single-day and seasonal measurements were done. For all detectors, results from the winter session (C: 657 ± 16 Bq/m3, K: 825 ± 17 Bq/m3), CR-39 (C: 138 ± 47 Bq/m3, K: 72 ± 35 Bq/m3) and TLD (C: 0.82 ± 0.04 mGy, K: 0.82 ± 0.08 mGy), autumn (C: Lucas chamber 1458 ± 19 Bg/m3, CR-39 430 ± 92 Bq/m3, TLD 0.21 ± 0.01 mGy) and spring (most readings at background level) were compared. Additionally, an attempt was made to convert the obtained radon concentrations into doses. Conclusion: Lucas chambers, designed for measurements in the exposure-reading mode, can also be used in long-term measurements. Both track and thermoluminescent detectors can be used for long-term measurements. More than one method may be required to obtain accurate measurement information. The results of measurements conducted in the seasonal mode indicate that the implementation of protective procedures, such as systematic ventilation, can contribute to a significant reduction in high radon concentrations.

Clinical use of Gafchromic EBT4 film for in vivo dosimetry for total body irradiation.

In vivo dosimetry is a common requirement to validate dose accuracy/uniformity in total body irradiation (TBI). Several detectors can be used for in vivo dosimetry, including thermoluminescent dosimeters (TLDs), diodes, ion chambers, optically stimulated luminescent dosimeters (OSLDs), and film. TLDs are well established for use in vivo but required expertise and clinical system availability may make them impractical for multifractionated TBI. OSLDs offer quick readout, but recalls have restricted their use. The purpose of this work was to validate the newly available Gafchromic EBT4 film for TBI in vivo dosimetry. Film calibration curves were created under standard conditions (6MV/15MV, 1.5/3.0cm depth, 100cm source-to-surface distance (SSD), 10 × 10 cm2 field), and films were scanned at several time points (0.5-24h) to determine the shortest development time that yielded accurate dose measurements. 4 × 4 cm2 films were placed under 1.5cm thick bolus on the anterior and posterior sides of a solid water phantom to measure entrance and exit dose under TBI conditions (∼600cm SSD, 39.5 × 39.5 cm2 field, 6 MV/15 MV). These measurements were compared to ion chamber and diode readings for validation. Film measurements were also compared to OSLD measurements for three TBI patients. The shortest development time that resulted in accurate dosimetry and allowed for adequate physician review time was 4h (±4% dose accuracy). Film entrance and exit dose measurements were within±3.8% of ion chamber and diode readings for 6MV and 15MV beams. Patient film measurements were within ∼±5% for the majority of anatomical measurement locations; however, film and OSLD readings for some anatomic locations deviated by>10%. These results indicate that EBT4 film can be utilized for accurate in vivo dosimetry for TBI patients and shows good agreement with diode and ion chamber measurements. Further investigation into film and OSLD differences was not possible due to OSLD recalls.

Modulation of the Respiratory Epithelium Physiology by Flavonoids-Insights from 16HBEσcell Model.

Extensive evidence indicates that the compromise of airway epithelial barrier function is closely linked to the development of various diseases, posing a significant concern for global mortality and morbidity. Flavonoids, natural bioactive compounds, renowned for their antioxidant and anti-inflammatory properties, have been used for centuries to prevent and treat numerous ailments. Lately, a growing body of evidence suggests that flavonoids can enhance the integrity of the airway epithelial barrier. The objective of this study was to investigate the impact of selected flavonoids representing different subclasses, such as kaempferol (flavonol), luteolin (flavone), and naringenin (flavanone), on transepithelial electrical resistance (TEER), ionic currents, cells migration, and proliferation of a human bronchial epithelial cell line (16HBE14σ). To investigate the effect of selected flavonoids, MTT assay, trypan blue staining, and wound healing were assessed. Additionally, transepithelial resistance and Ussing chamber measurements were applied to investigate the impact of the flavonoids on the electrical properties of the epithelial barrier. This study showed that kaempferol, luteolin, and naringenin at micromolar concentrations were not cytotoxic to 16HBE14σ cells. Indeed, in MTT tests, a statistically significant change in cell metabolic activity for luteolin and naringenin was observed. However, our experiments showed that naringenin did not affect the proliferation of 16HBE14σ cells, while the effect of kaempferol and luteolin was inhibitory. Moreover, transepithelial electrical resistance measurements have shown that all of the flavonoids used in this study improved the epithelial integrity with the slightest effect of kaempferol and the significant impact of naringenin and luteolin. Finally, our observations suggest that luteolin increases the Cl- transport through cystic fibrosis transmembrane conductance regulator (CFTR) channel. Our findings reveal that flavonoids representing different subclasses exert distinct effects in the employed cellular model despite their similar chemical structures. In summary, our study sheds new light on the diverse effects of selected flavonoids on airway epithelial barrier function, underscoring the importance of further exploration into their potential therapeutic applications in respiratory health.

Establishment of an absolute measurement of the reference air kerma rate for HDR 192Ir brachytherapy sources

Before this study, no institution in China had undertaken the calculation and official establishment of reference values for the reference air kerma rate associated with high-dose rate 192Ir sources used in brachytherapy. This research, carried out at the National Institute of Metrology (NIM) in China, has successfully established an 192Ir reference radiation facility. Consequently, it has achieved the absolute measurement of the reference air kerma rate for high-dose rate brachytherapy using 192Ir sources. For this study, a medical afterloader machine was acquired. The radiation source employed was a high-dose rate 192Ir source for brachytherapy, produced by HTA Co., Ltd. A reference graphite cavity ionization chamber with a volume of 100 cm3 was designed to serve as the ionization chamber for absolute measurements. The determination of various correction factors and physical constants was achieved through a method that combines Monte Carlo simulations with experimental techniques. The study successfully accomplished the absolute measurement of the reference air kerma rate for the high-dose rate brachytherapy 192Ir radiation source. The expanded uncertainty of the measurement results was 0.72% (k = 2). The relative standard deviation for the RAKR of the same 192Ir radiation source was 0.073%. This study marks a significant advancement in the field of radiation therapy in China, particularly in the accurate dosimetry for brachytherapy using high-dose rate 192Ir sources. The study will contribute to the BIPM.RI(I)-K8 international comparison, organized by the Bureau International des Poids et Mesures (BIPM), thus facilitating the international recognition of the measurement values.

Quantifying Global Wetland Methane Emissions With In Situ Methane Flux Data and Machine Learning Approaches.

Wetland methane (CH4) emissions have a significant impact on the global climate system. However, the current estimation of wetland CH4 emissions at the global scale still has large uncertainties. Here we developed six distinct bottom-up machine learning (ML) models using in situ CH4 fluxes from both chamber measurements and the Fluxnet-CH4 network. To reduce uncertainties, we adopted a multi-model ensemble (MME) approach to estimate CH4 emissions. Precipitation, air temperature, soil properties, wetland types, and climate types are considered in developing the models. The MME is then extrapolated to the global scale to estimate CH4 emissions from 1979 to 2099. We found that the annual wetland CH4 emissions are 146.6±12.2TgCH4yr-1 (1Tg=1012g) from 1979 to 2022. Future emissions will reach 165.8±11.6, 185.6±15.0, and 193.6±17.2TgCH4yr-1 in the last two decades of the 21st century under SSP126, SSP370, and SSP585 scenarios, respectively. Northern Europe and near-equatorial areas are the current emission hotspots. To further constrain the quantification uncertainty, research priorities should be directed to comprehensive CH4 measurements and better characterization of spatial dynamics of wetland areas. Our data-driven ML-based global wetland CH4 emission products for both the contemporary and the 21st century shall facilitate future global CH4 cycle studies.

A Rapid and Simplified Approach to Correct Atmospheric Absorptions in Infrared Spectra.

Infrared (IR) spectroscopy is a powerful analytical technique used to identify and quantify different components within a sample. However, spectral interference from fluctuating concentrations of water vapor and CO2 in the measurement chamber can significantly impede the extraction of quantitative information. These temporal fluctuations cause absorption variations that interfere with the sample's spectrum, making accurate analysis challenging. While several techniques to overcome this problem exist in the literature, many are time-consuming or ineffective. We present a simple method utilizing just two sample spectra taken sequentially. The difference of these spectra, multiplied by a scaling factor, determined by minimization of the point-to-point spectral length, provides a correction spectrum. Subtracting this from the spectrum to be corrected results in a fully corrected spectrum. We demonstrate the effectiveness of this method via the improved ability to determine analyte concentration from corrected spectra over uncorrected spectra using a partial least square regression (PLSR) model. This technique therefore offers rapid, effective, and automated spectral correction, which is ideal for a nonexpert user in a clinical or industrial setting.

High spatial variability in wetland methane fluxes is tied to vegetation patch types

Wetlands are the largest natural source of methane (CH4), but spatial variability in fluxes complicates prediction, budgeting, and mitigation efforts. Despite the many environmental factors identified as CH4 drivers, the overall influence of wetland spatial heterogeneity on CH4 fluxes remains unclear. We identified five dominant patch types—submersed aquatic vegetation (SAV), emergent forbs, sedges/rushes, grasses, and open water—within a freshwater wetland in Maryland, USA, and measured CH4 fluxes using a combined chamber and eddy covariance approach from June to September 2021. Because patch types integrate co-occurring environmental factors, we hypothesized that CH4 flux is best characterized at the patch scale. Chamber measurements from representative patches showed distinct CH4 signals; fluxes from grasses and sedges/rushes were highest, while fluxes from SAV and forbs were lower but skewed, suggesting episodic emission pulses. Open water had the lowest fluxes. Differences between patches were consistent over time, and spatial variability was greater between patches than within them, highlighting patches as key drivers of flux variability. By combining chamber fluxes with eddy covariance data in a Bayesian framework, we provide evidence that patch-type fluxes scale over space and time. Understanding spatial heterogeneity is essential for quantifying wetland contributions to global biogeochemical cycles and predicting the impacts of environmental change on wetland ecosystem processes. Our study demonstrates the importance of vegetation patch types in structuring spatial variability and supports a patch-explicit representation to reduce uncertainty in wetland CH4 fluxes.

Causes for overestimation of the moisture recycling in an alpine meadow ecosystem of the Shule River Basin, Tibetan Plateau, China

Terrestrial moisture recycling is an essential hydrological component and a significant source of the atmosphere’s humidity budget in arid and semi-arid inland regions. Investigations on moisture recycling using the stable hydrogen and oxygen isotopes is currently a focal point in hydrologic research. However, the direct quantification of recycling ratio based on isotopic composition of evapotranspiration vapor is lacking. So, this causes challenges to compare studies, based in the same region and time period but with different methodologies. In this study, we measured the isotopic compositions of evapotranspiration vapor (δ18OET/δDET) from June to September 2018 in an alpine meadow ecosystem at the Shule River Basin by combining the Keeling plot model and in-situ chamber measurement. Using this data, the moisture recycled rate (mrr) was assessed based on the two-component (Model A) and three-component isotopic mixing models (Model B), respectively. Based on Model A and δ18OET, the analysis revealed that the mean recycled rate for the entire observation period was 35 %, while it was 26 % during the westerly period (the months dominated by the north branch of prevailing westerlies) and 44 % during the monsoon period (when subtropical moisture from the Indian monsoon penetrated the region). The recycled rate based on Model A and δDET was slightly larger with a mean value of 41 % during the entire observation period. The recycled rate based on Model B was also significantly higher in comparison with Model A, while the causes for this difference could be the assumption of substituting xylem water for transpiration vapor and the plant water source δD offset. The contribution of recycled moisture was notable lower for heavy rainfall comparing with light rainfall. Our findings provided a new perspective for the investigations of alpine meadow ecosystem hydrological processes.

Underestimation of global soil CO2 flux measurements caused by near-surface winds

Soil respiration (Rs) is the largest source of atmospheric CO2, and an accurate understanding of the relationship between near-surface winds, CO2 release from the soil surface, and measurement methods is critical for predicting future atmospheric CO2 concentrations. In this study, the relationship between wind speed and soil CO2 fluxes is elucidated on a global scale through meta-analysis, and the flux measurement methodology is further explored in conjunction with the results of a controlled trial to clarify the uncertainty of the measurement results. The results indicate that near-surface wind speed is positively correlated with soil CO2 release and that near-surface winds result in increased soil CO2 gas release. Wind disturbance affects both the concentration gradient and gas chamber measurements, and the lower calculated soil CO2 release conflicts with the notion that the wind pump effect and Bernoulli effect of negative pressure cause a greater surface gas exchange. The results of the log-response ratios indicate that near-surface winds lead to an underestimation of 12.19–19.75% in widely-used gas chamber method measurements. The results of this study imply that some of the current Rs measurements are biased and that the influence of near-surface winds on Rs measurements needs to be urgently addressed to assess the terrestrial carbon cycle more accurately and develop climate change response strategies.

Prediction of vibro-acoustic sound emissions based on mapped structural dynamics

In the product design of shell-like housing structures for vibrating bodies, acoustic emission plays a significant role in usability and customer comfort. Consequently, the prediction of the emitted sound, e.g., in the form of the radiated sound power, is desired in the earliest possible stage of the development cycle. In industry, performing extensive acoustic testing using microphone arrays or laser scanning vibrometry is often time-consuming or infeasible, as it requires an acoustically treated measurement chamber and specific measurement equipment. On the other hand, accelerometer data is more straightforward to obtain due to the lower cost of the sensors and relaxed constraints on the measurement chamber compared to acoustic measurements. Hence, this contribution utilizes available surface velocity data in an acoustic simulation of the free-field Helmholtz problem. In doing so, it compares a conventional element-based and a mesh-less data-driven mapping technique to investigate the reduction of the number of provided sensor positions for the radiation problem. The open-source boundary element framework NiHu is used to give accurate predictions of acoustic emissions over a wide frequency range. The approach is applied to an industrial problem and validated against microphone measurements.

Reconciling Top‐Down and Bottom‐Up Estimates of Ecosystem Respiration in a Mature Eucalypt Forest

AbstractEcosystem respiration (Reco) arises from interacting autotrophic and heterotrophic processes constrained by distinct drivers. Here, we evaluated up‐scaling of observed components of Reco in a mature eucalypt forest in southeast Australia and assessed whether a land surface model adequately represented all the fluxes and their seasonal temperature responses. We measured respiration from soil (Rsoil), heterotrophic soil microbes (Rh), roots (Rroot), and stems (Rstem) in 2018–2019. Reco and its components were simulated using the CABLE–POP (Community Atmosphere‐Biosphere Land Exchange–Population Orders Physiology) land surface model, constrained by eddy covariance and chamber measurements and enabled with a newly implemented Dual Arrhenius and Michaelis‐Menten (DAMM) module for soil organic matter decomposition. Eddy‐covariance based Reco (Reco.eddy, 1,439 g C m−2 y−1) was slightly higher than the sum of the respiration components (Reco.sum, 1,295 g C m−2 y−1) and simulated Reco (1,297 g C m−2 y−1). The largest mean contribution to Reco was from Rsoil (64%) across seasons. The measured contributions of Rh (49%), Rroot (15%), and Rstem (22%) to Reco.sum were very close to model outputs of 46%, 11%, and 22%, respectively. The modeled Rh was highly correlated with measured Rh (R2 = 0.66, RMSE = 0.61), empirically validating the DAMM module. The apparent temperature sensitivities (Q10) of Reco were 2.22 for Reco.sum, 2.15 for Reco.eddy, and 1.57 for CABLE‐POP. This research demonstrated that bottom‐up respiration component measurements can be successfully scaled to eddy covariance‐based Reco and help to better constrain the magnitude of individual respiration components as well as their temperature sensitivities in land surface models.

Geometrical acoustic modelling of occupied acoustic conditions in mosques: Application to a case study

Old religious buildings represent an essential cultural heritage whatever the country or the religion they belong to. Thanks to many researches carried out in the last years, their acoustics is now considered part of this heritage. However, for practical reasons, their acoustic characterization is often made under unoccupied conditions, while, given the frequent use of hard reflecting surfaces, the occupied conditions may differ significantly. Geometrical acoustics may represent, if properly used, a valid tool to simulate how sound propagates in an occupied space, allowing to investigate the effect on the full set of acoustic parameters. Occupancy in mosques may be more challenging to simulate than in other spaces because of the different postures of the worshippers and the usually high absorption that they introduce because of high density of occupants. To correctly simulate such effects, a specific modelling approach has been proposed starting from reverberant chamber measurements and validating them against on-site measurements. Using the proposed method, the effect of occupancy in the Jedid Mosque in Algiers, which was built in 1660, in a typical Ottoman style, and later restored in 1855, was studied. The mosque was chosen because it is large and reverberant to allow a better appreciation of the variations due to occupancy. The geometrical acoustic model was first carefully calibrated against measurements in unoccupied conditions, which also pointed out a clearly non-diffuse behaviour in the space, and, finally the occupancy was added. Results showed that due to the strong concentration of absorbing elements on the floor, where carpets already contributed to absorb sound, the occupancy mostly affected reverberation parameters, while clarity for speech remained poor.

Validation of MLC leaf open time calculation methods for PSQA in adaptive radiotherapy with tomotherapy units.

Treatment delivery safety and accuracy are essential to control the disease and protect healthy tissues in radiation therapy. For usual treatment, a phantom-based patient specific quality assurance (PSQA) is performed to verify the delivery prior to the treatment. The emergence of adaptive radiation therapy (ART) adds new complexities to PSQA. In fact, organ at risks and target volume re-contouring as well as plan re-optimization and treatment delivery are performed with the patient immobilized on the treatment couch, making phantom-based pretreatment PSQA impractical. In this case, phantomless PSQA tools based on multileaf collimator (MLC) leaf open times (LOTs) verifications provide alternative approaches for the Radixact® treatment units. However, their validity is compromised by the lack of independent and reliable methods for calculating the LOT performed by the MLC during deliveries. To provide independent and reliable methods of LOT calculation for the Radixact® treatment units. Two methods for calculating the LOTs performed by the MLC during deliveries have been implemented. The first method uses the signal recorded by the build-in detector and the second method uses the signal recorded by optical sensors mounted on the MLC. To calibrate the methods to the ground truth, in-phantom ionization chamber LOT measurements have been conducted on a Radixact® treatment unit. The methods were validated by comparing LOT calculations with in-phantom ionization chamber LOT measurements performed on two Radixact® treatment units. The study shows a good agreement between the two LOT calculation methods and the in-phantom ionization chamber measurements. There are no notable differences between the two methods and the same results were observed on the different treatment units. The two implemented methods have the potential to be part of a PSQA solution for ART in tomotherapy.