Photoacoustic Analysis Research Articles

Performance of an Infrared Photoacoustic Single Gas Analyzer in Measuring Ammonia from Poultry Houses

A single-gas photoacoustic analyzer, Chillgard RT, was evaluated for its performance of measuring ammonia (NH3) concentrations in poultry production under laboratory and field conditions, using a multi-gas photoacoustic analyzer, INNOVA 1412, as a reference method. Calibration gases were used to evaluate the cross-interferences of carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and water vapor on NH3 measurements by Chillgard RT. The response times of Chillgard RT and INNOVA were measured in the laboratory using four vessels containing broiler litter. Side-by-side field comparisons between the Chillgard RT and INNOVA were conducted on a laying-hen farm and a broiler farm over two five-month periods. A strong linear relationship existed between the Chillgard RT and INNOVA NH3 readings. The NH3 measurement by the Chillgard RT showed no effect by CO2, N2O, CH4, or water vapor under typical operational conditions in poultry operations. The Chillgard RT demonstrated a faster response to NH3 than the INNOVA. Following 120-s measurements, the Chillgard RT and INNOVA achieved 99.6% and 96.7% of the expected values, respectively, when the INNOVA was configured at a 30-s sampling interval. The INNOVA response time was positively affected by water vapor level in the air samples. The Chillgard RT overestimated NH3 concentrations by 3.24%, 10%, and 22.9% for laying-hen houses, stored boiler litter, and broiler houses, respectively, as compared to the INNOVA. Thus, performance of the Chillgard RT should be carefully validated before used in field NH3 measurements.

EPS04.2 Infant lung function: First report of a novel infant multiple breath washout apparatus

Objectives The value of lung clearance index (LCI) is well recognised in children and adults and has also been shown to be elevated in infants with CF. At present, there are considerable technical challenges in measuring LCI in infants. There is no simple method of assessing lung function in this population. The Innocor photoacoustic gas analyser measures very low concentrations of the inert tracer gas SF6. This has been developed into a novel mixed open–closed circuit system: expired gas is collected during washout to measure Functional Residual Capacity (FRC) and cumulative expired volume. This permits a low deadspace and ability to perform at rapid ventilation rates. Methods A prototype system was assessed using a lung model based on a mechanically driven 100 ml syringe and ventilation tank. The model delivered FRC's of 100–250 ml, with corresponding tidal volumes of 30–90 ml and respiratory rates of 20–40 min −1 . Improvements to hardware and washin protocol were made following initial testing. Results Following modification, overall mean error of FRC measurement was 0.04%. Actual mean FRC (ml) are shown in Table 1. Of 21 repeats, only 1 measurement was outside ±5% error range for FRC. Table 1Model FRC a (ml)Measured FRC (95% CI) (ml)Mean (SD) % error10299.2 (97.0–101.5)−1.76 (1.8)202203.3 (199.4–207.3)1.17 (2.34)252250.6 (247.4–253.8)−0.18 (1.63)aIncludes deadspace. Conclusion This system is capable of highly accurate measurement of FRC at volumes down to 100 ml in a realistic infant lung simulation. Accuracy is superior to previously described systems at higher FRC, and within the targets set by guidelines. In vivo testing is due to commence in 2015.

Diagnostics of bronchopulmonary diseases through Mahalanobis distance-based absorption spectral analysis of exhaled air

Accurate diagnosis of different bronchopulmonary diseases is important in clinical practice. This study involved 20 healthy volunteers and 77 patients with bronchopulmonary diseases, including chronic obstructive pulmonary disease (COPD), bronchial asthma, pulmonary tuberculosis, and community-acquired pneumonia. The absorption spectrum of exhaled air samples was recorded on an intra-cavity photo-acoustic gas analyzer (ILPA-1, Special Technologies, Ltd., Russia) with photo-acoustic detectors and CO2 laser with a tuning range from 9.2 to 10.8 μm. In conclusion, analysis of the Mahalanobis distance-based absorption spectral profiles of breath air from bronchopulmonary patients and healthy volunteers allows the formulation of a preliminary diagnosis.

Photoacoustic signal and noise analysis for Si thin plate: signal correction in frequency domain.

Methods for photoacoustic signal measurement, rectification, and analysis for 85 μm thin Si samples in the 20-20 000 Hz modulation frequency range are presented. Methods for frequency-dependent amplitude and phase signal rectification in the presence of coherent and incoherent noise as well as distortion due to microphone characteristics are presented. Signal correction is accomplished using inverse system response functions deduced by comparing real to ideal signals for a sample with well-known bulk parameters and dimensions. The system response is a piece-wise construction, each component being due to a particular effect of the measurement system. Heat transfer and elastic effects are modeled using standard Rosencweig-Gersho and elastic-bending theories. Thermal diffusion, thermoelastic, and plasmaelastic signal components are calculated and compared to measurements. The differences between theory and experiment are used to detect and correct signal distortion and to determine detector and sound-card characteristics. Corrected signal analysis is found to faithfully reflect known sample parameters.

Effects of forage-to-concentrate ratio and dietary fiber manipulation on gas emissions and olfactometry from manure of Holstein heifers

The objective of this experiment was to determine the effects of differing ratios of forage to concentrate (F:C) and fiber levels on odor and gas emissions from manure. Eight Holstein dairy heifers (362.45±4.53 d of age and 335.6±7.41 kg of body weight) were randomly assigned to a split-plot, 4×4 Latin square design (21-d periods) with F:C as the whole plot (20 or 80% forage) and fiber level as sub-plot (0, 20, 40, or 60% inclusion of corn stover). Gas concentration was determined using an infrared photoacoustic analyzer over a 24-h period using a steady-state flux chamber setup. Odorous air samples were collected from chamber headspace and evaluated by 6h uman assessors using a forced-choice dynamic olfactometry technique. Emissions of CO2 were greater for the low than high concentrate diets, and no differences were observed for NH3 and CH4 emissions between F:C. Although F:C had no effect on NH3 emissions, as dietary fiber increased, a linear interaction with opposite effects was found for high and low concentrate diets. Nitrous oxide emissions were below minimum detectable levels. Neither F:C nor neutral detergent fiber level affected odor intensity. Odor emissions were successfully assessed, and manipulation of dietary fiber has the potential to influence CH4 and NH3 emissions.

Application of PTR-MS for measuring odorant emissions from soil application of manure slurry.

Odorous volatile organic compounds (VOC) and hydrogen sulfide (H2S) are emitted together with ammonia (NH3) from manure slurry applied as a fertilizer, but little is known about the composition and temporal variation of the emissions. In this work, a laboratory method based on dynamic flux chambers packed with soil has been used to measure emissions from untreated pig slurry and slurry treated by solid-liquid separation and ozonation. Proton-transfer-reaction mass spectrometry (PTR-MS) was used to provide time resolved data for a range of VOC, NH3 and H2S. VOC included organic sulfur compounds, carboxylic acids, phenols, indoles, alcohols, ketones and aldehydes. H2S emission was remarkably observed to take place only in the initial minutes after slurry application, which is explained by its high partitioning into the air phase. Long-term odor effects are therefore assessed to be mainly due to other volatile compounds with low odor threshold values, such as 4-methylphenol. PTR-MS signal assignment was verified by comparison to a photo-acoustic analyzer (NH3) and to thermal desorption GC/MS (VOC). Due to initial rapid changes in odorant emissions and low concentrations of odorants, PTR-MS is assessed to be a very useful method for assessing odor following field application of slurry. The effects of treatments on odorant emissions are discussed.

Diagnosis of chronic obstructive pulmonary disease using opticoacoustic analysis

The aim of this study was to investigate a role of the exhaled air analysis as a simple and non-invasive diagnostic method for chronic obstructive pulmonary disease (COPD). Methods. EBC samples were analyzed in 26 patients with acute exacerbation of COPD and in 19 healthy volunteers using a photoacoustic gas analyzer ILPA-1 based on CO 2 laser spectral analysis. The data obtained were used for integral estimation (IE) within two spectral ranges. Results. IEs of COPD patients and healthy subjects differed significantly and were not related to gender. IE values in both spectral ranges were related to forced vital capacity of COPD patients and were inversely related to the heart beat rate of COPD patients in 10P spectral range. Conclusion. This method is useful in diagnosis of COPD including early stage of the disease.

A laser photoacoustic analysis of residual CO₂ and H₂O in larch stems.

Every so often, the results obtained from investigations into the effects of varying environmental conditions on the tree growth rate at the same sites and on the change in the carbon balance in plants, using traditional methods, are found to differ widely. We believe that the reason for the ambiguity of the data has to do with failure to account for the role of the residual CO2 (and H2O) in the tree wood exhibiting a climate response. In our earlier work, the results of a laser photoacoustic gas analysis of CO2 and H2O vacuum-desorbed from disc tree rings of evergreen conifer trees were presented. In this paper, laser photoacoustic measurements of tree ring gases in deciduous conifer trees and CO2 carbon isotope composition determined by means of a mass spectrometer are given. Conclusions are made regarding the response of annual larch CO2 disc tree ring distributions to climatic parameters (temperatures and precipitation). The data about the CO2 disc content for different sites are compared.

Dye-doped organosilicate nanoparticles as cell-preserving labels for photoacoustic signal generation.

Nanoparticle-assisted ultrasound generation by pulsed laser or photoacoustic (PA) techniques has been employed in the study of several tissues both in vivo and in vitro. Among the many applications of this technology, the detection of few cells in vitro is of particular interest. However, the toxicity induced by laser irradiation used for PA signal generation, whether in the absence or the presence of PA enhancers, within single isolated cells has not yet been investigated in detail. Herein, we report our studies of the cellular health of two different nanoparticle-labeled cell lines one hour after being subjected to a single laser pulse in vitro. We selected for this study an Hs936 skin epithelial melanoma cell line, which can be naturally detected photoacoustically, as well as a T47D human mammary breast gland epithelial cell line which has proven difficult to detect photoacoustically due to the absence of natural melanin. We have evaluated the amplitude of the PA signal derived from these two cell types, unlabeled and labeled with nanoparticles of two types (gold nanoparticles, AuNPs, or rhodamine 6G-doped organosilicate nanoparticles, R6G-NPOs), and assessed their health one hour subsequent to laser treatment. The current work corroborates previous findings that, for unlabeled cells, Hs936 produces a detectable PA signal whereas the T47D line does not. Cells labeled with AuNPs or R6G-NPOs produced a detectable PA signal of similar amplitude for the two cell lines. A significant number of Hs936 cells (both unlabeled cells and those labeled with AuNPs) exhibited cell nuclei alterations, as revealed by DAPI staining conducted an hour after photo treatment. Remarkably, the T47D cells suffered damage only when labeled with AuNPs. A significant finding, the R6G-NPOs proved capable of non-destructive PA signal generation in both cell types. Our findings advocate a transformational path forward for the use of dye-doped silicate nanoparticles in cell-compatible PA studies permitting the handling and culturing of cells subsequent to their photoacoustic analysis.

Methane and nitrous oxide analyzer comparison and emissions from dairy freestall barns with manure flushing and scraping

Continuous methane (CH4) and nitrous oxide (N2O) emission measurements were conducted at two crossflow-ventilated dairy freestall barns located in the state of Wisconsin, USA during a 19-month period from 2008 to 2010. The two cross-flow mechanically ventilated buildings (275 and 375 cow capacities) were evaluated in the National Air Emissions Monitoring Study. In September of 2008, the barns' manure collection systems were changed from flushing open gutter using manure basin effluent to a tractor scrape. A photoacoustic multi-gas analyzer (PAMGA) and a direct methane/non-methane hydrocarbon analyzer (GC-FID) provided side-by-side measurements of methane (CH4) for 13 months. The PAMGA also measured nitrous oxide (N2O), and a side-by-side comparison was performed with a gas-filter correlation analyzer (GFC) for six months. Barn ventilation rates were measured by recording run times of the 127-cm diameter exhaust fans. All 125 belt-driven exhaust fans were identical, and in situ airflow measurements using the Fan Assessment Numeration System (FANS) were conducted once at the beginning and twice during the test. Daily CH4 and N2O emission rates were calculated over approximately 19 and 6 month periods respectively, on per barn, head, animal unit, floor area space and barn capacity bases. The differences between the analyzers' concentration measurements were compared in conjunction with water vapor and other gases. The analyzer type had a significant impact on the average CH4 emission rate (p < 0.001) and the average N2O emission rate (p < 0.05). Based on the CH4 measurements with the GC-FID, average daily mean CH4 emissions were approximately 290 g AU−1 d−1 (390 g cow−1 d−1) with very limited seasonal effects. Little variation was observed in CH4 emission rates before and after the change in manure collection method, suggesting that most of the CH4 emissions were enteric losses directly from the cows. The average daily mean N2O emission rates based on the GFC were very low, with an approximate rate of only 690 mg AU−1 d−1 (970 mg cow−1 d−1). The change in manure collection had no apparent effect on N2O emission.

Biomonitoring occupational sevoflurane exposure at low levels by urinary sevoflurane and hexafluoroisopropanol

This study aimed to correlate environmental sevoflurane levels with urinary concentrations of sevoflurane (Sev-U) or its metabolite hexafluoroisopropanol (HFIP) in order to assess and discuss the main issues relating to which biomarker of sevoflurane exposure is best, and possibly suggest the corresponding biological equivalent exposure limit values. Individual sevoflurane exposure was measured in 100 healthcare operators at five hospitals in north-east Italy using the passive air sampling device Radiello®, and assaying Sev-U and HFIP concentrations in their urine collected at the end of the operating room session. All analyses were performed by gas chromatography-mass spectrometry. Environmental sevoflurane levels in the operating rooms were also monitored continuously using an infrared photoacoustic analyzer. Our results showed very low individual sevoflurane exposure levels, generally below 0.5ppm (mean 0.116ppm; range 0.007–0.940ppm). Sev-U and HFIP concentrations were in the range of 0.1–17.28μg/L and 5–550μg/L, respectively. Both biomarkers showed a statistically significant correlation with the environmental exposure levels (Sev-U, r=0.49; HFIP, r=0.52), albeit showing fairly scattered values. Sev-U values seem to be influenced by peaks of exposure, especially at the end of the operating-room session, whereas HFIP levels by exposure on the previous day, the data being consistent with the biomarkers’ very different half-lives (2.8 and 19h, respectively). According to our results, both Sev-U and HFIP are appropriate biomarkers for assessing sevoflurane exposure at low levels, although with some differences in times/patterns of exposure. More work is needed to identify the best biomarker of sevoflurane exposure and the corresponding biological equivalent exposure limit values.

Carbon Dioxide and Nitrous Oxide Emissions Impacted by Bioenergy Sorghum Management

Modern bioenergy feedstocks, such as bioenergy sorghum [Sorghum bicolor (L.) Moench], are being developed to supply future cellulosic biofuel demands. How these cropping systems impact greenhouse gas (GHG) emission of CO2 and N2O from the soil is unknown and field research is necessary to elucidate the effects of agronomic management practices on soil trace gas emissions. We studied the effects of N fertilization (0 vs. 280 kg urea‐N ha−1), residue management (0 vs. 50% of sorghum biomass returned), crop sequence (corn [Zea mays L.]–sorghum vs. sorghum–sorghum), and their interactions on CO2 and N2O emissions from bioenergy production scenarios on a Weswood (fine‐silty, mixed, superactive, thermic Udifluventic Haplustept) silty clay loam soil in central Texas. Gas fluxes were measured approximately weekly throughout the 2010 and 2011 growing season and at a reduced rate during the fallow season with a photoacoustic gas analyzer integrated with a static chamber. Overall, CO2 and N2O fluxes were relatively higher than those observed by others in the United States despite drought conditions throughout much of 2010 and 2011. Highest emissions of both gases were observed during the growing season, often following a precipitation–irrigation event and shortly after N fertilization. Residue return increased cumulative CO2 emissions each year, probably due to increased heterotrophic microbial activity. Nitrogen addition significantly increased cumulative emissions of N2O both years but only impacted cumulative CO2 emissions in 2011. While crop rotation impacted biomass yield, it had no significant effect on cumulative CO2 or N2O emissions. Additional research is needed to identify the optimal N and residue application rates that provide high yields with minimal soil GHG emissions and aid in sustaining long‐term soil quality.

Certain features of gas emission from the wood of annual rings of conifers

Results of our studies of gas content in rings of tree discs have shown that a significant part of the CO2 generated by cell respiration remains in tree stems. The content of this CO2 exceeds the atmospheric CO2 in most cases and forms the distribution over tree rings. In our investigations, we first used photoacoustic gas analysis. In this work, we discuss certain features of the chronologies (year-to-year distribution) of gas samples.

Enhancement in threshold voltage with thickness in memory switch fabricated using GeSe1.5S0.5 thin films

Investigations on the electrical switching, structural, optical and photoacoustic analysis have been undertaken on chalcogenide GeSe1.5S0.5 thin films of various thicknesses prepared by vacuum evaporation technique. The decrease of band gap energy with increase in film thickness has been explained using the ‘density of states model’. The structural units of the films are characterized using Raman spectroscopy and the deconvoluted Raman peaks obtained from Gaussian fit around 188cm−1, 204cm−1 and 214cm−1 favors Ge–chalcogen tetrahedral units forming corner and edge sharing tetrahedra. All the thin films samples have been exhibited memory-type electrical switching behavior. An enhancement in the threshold voltages of GeSe1.5S0.5 thin films have been observed with increase in film thickness. The thickness dependence of switching voltages provide an insight into the switching mechanism and it is explained by the Joule heating effect.

Ammonia and nitrous oxide emissions from a commercial broiler house.

Complex variation in gas emissions from animal facilities has been shown in recent research reports. Uncertainties in these emission estimates are driving research activities concerning different animal species across the globe. Greenhouse gas (NO and CO) and NH concentrations were measured in a modern, tunnel-ventilated, commercial broiler house in Mississippi during five flocks (spanning approximately 1 yr). These were flocks 9 through 13 on reused pine shavings litter, representing litter reuse beyond 2 yr. Gas concentrations obtained from a photoacoustic multigas analyzer were coupled with ventilation measurements of air flow through the house to develop NH and NO emission rates. Ammonia emission during a flock (43 d) averaged approximately 14.8 ± 9.8 kg d in the commercial house (equivalent to 23.5 g bird marketed or 0.54 g bird d). Nitrous oxide emission averaged 2.3 ± 1.7 kg d in the house (equivalent to 3.64 g bird marketed or 0.085 g bird d). Emission rates increased with time from Day 1 to Day 43 and reached average values on Day 23 and 24 for NH and NO. Even with extended litter reuse, estimates of NH emissions from the broiler house agree well with recently published research that reused litter in eight or fewer flocks. This is important information for farmers who may not be able to afford to replace the litter with fresh bedding material annually.

Enhanced photoacoustic gas analyser response time and impact on accuracy at fast ventilation rates during multiple breath washout.

BackgroundThe Innocor device contains a highly sensitive photoacoustic gas analyser that has been used to perform multiple breath washout (MBW) measurements using very low concentrations of the tracer gas SF6. Use in smaller subjects has been restricted by the requirement for a gas analyser response time of <100 ms, in order to ensure accurate estimation of lung volumes at rapid ventilation rates.MethodsA series of previously reported and novel enhancements were made to the gas analyser to produce a clinically practical system with a reduced response time. An enhanced lung model system, capable of delivering highly accurate ventilation rates and volumes, was used to assess in vitro accuracy of functional residual capacity (FRC) volume calculation and the effects of flow and gas signal alignment on this.Results10–90% rise time was reduced from 154 to 88 ms. In an adult/child lung model, accuracy of volume calculation was −0.9 to 2.9% for all measurements, including those with ventilation rate of 30/min and FRC of 0.5 L; for the un-enhanced system, accuracy deteriorated at higher ventilation rates and smaller FRC. In a separate smaller lung model (ventilation rate 60/min, FRC 250 ml, tidal volume 100 ml), mean accuracy of FRC measurement for the enhanced system was minus 0.95% (range −3.8 to 2.0%). Error sensitivity to flow and gas signal alignment was increased by ventilation rate, smaller FRC and slower analyser response time.ConclusionThe Innocor analyser can be enhanced to reliably generate highly accurate FRC measurements down at volumes as low as those simulating infant lung settings. Signal alignment is a critical factor. With these enhancements, the Innocor analyser exceeds key technical component recommendations for MBW apparatus.

130 Enhanced photoacoustic gas analyser (Innocor) for multiple breath washout. Improvements to analyser response time maintains accuracy at fast ventilation rates, and produces a system that meets all washout technology performance targets

130 Enhanced photoacoustic gas analyser (Innocor) for multiple breath washout. Improvements to analyser response time maintains accuracy at fast ventilation rates, and produces a system that meets all washout technology performance targets

Ammonia and Greenhouse Gas Emissions from Co-Composting of Dead Hens with Manure as Affected by Forced Aeration Rate

<abstract> <bold><sc>Abstract.</sc></bold> The effect of ventilation rate (VR) on ammonia and greenhouse gas emissions from co-composting dead hens mixed with hen manure was quantified. Three VR levels of 0.9, 0.7, and 0.5 m³ h^-1 were evaluated. Gaseous concentrations were measured using a multi-gas infrared photoacoustic analyzer, VR was measured with flowmeters, and the gas emission rate was computed from the VR and gas concentration. Decomposition of the carcasses over the 11-week composting period was greater than 88%. VR was found to significantly affect NH₃, CO₂, and CH₄ emissions (p < 0.05). Specifically, cumulative emissions per kg of initial matter for VR of 0.9, 0.7, and 0.5 m³ h^-1 were, respectively, 2.4, 2.0, and 1.2 g NH₃; 78, 66, and 42 g CO₂; 120, 90, and 52 mg CH₄; and 6.4, 6.1, and 5.1 mg N₂O. Hence, the study results suggest that the ventilation rate can be adjusted to reduce NH₃ and GHG emissions from animal mortality compositing.

Validation of a Photoacoustic Gas Analyser for the Measurement of Functional Residual Capacity Using Multiple-Breath Inert Gas Washout

Background: The respiratory mass spectrometer is the current gold-standard technique for performing multiple-breath inert gas washout (MBW), but is expensive and lacks portability. A number of alternative techniques have recently been described. Objectives: We aimed to validate, using an in vitro lung model, an open-circuit MBW system that utilises a portable photoacoustic gas analyser, with sulphur hexafluoride (SF₆) as the inert tracer gas. Methods: An acrylic glass lung model was utilised to assess the accuracy of functional residual capacity (FRC) measurements derived from MBW. Measurements were performed in triplicate at 20 combinations of simulated FRC, tidal volume and respiratory rate. FRC measured using MBW (FRC_mbw) was compared to FRC calculated from the known dimensions of the model (FRC_calc). MBW was also performed in 10 healthy subjects and 14 patients with asthma. Results: The MBW system measured FRC with high precision. The mean bias of FRC_mbw with respect to FRC_calc was -0.4% (95% limits of agreement of -4.6 and 3.9%). The mean coefficient of variation of triplicate FRC measurements was 4.0% in vivo and 1.0% in vitro. MBW slightly underestimated low lung volumes and overestimated high lung volumes, but this did not cause a significant error in lung clearance index except at lung volumes below 1,500 ml. Conclusions: The open-circuit MBW system utilising SF₆ as the inert tracer gas and a photoacoustic gas analyser is both accurate and repeatable within the adult range of lung volumes. Further modifications would be required before its use in young children or infants.

The Functional Pitch of an Organ: Quantification of Tissue Texture with Photoacoustic Spectrum Analysis

To investigate the use of photoacoustic (PA) spectrum analysis (PASA) to identify microstructural changes corresponding to fat accumulation in mouse livers ex vivo and in situ. The laboratory animal protocol for this work was approved by the university committee on use and care of animals. Six mice with normal livers and six mice with fatty livers were examined ex vivo with a PA system at 1200 nm, and nine similar pairs of mice were examined at 532 nm. To explore the feasibility of this technique for future study in an in vivo mouse model, an additional pair of normal and fatty mouse livers was scanned in situ with an ultrasonographic (US) and PA dual-modality imaging system. The PA signals acquired were analyzed by using the proposed PASA method. Results of the groups were compared by using the Student t test. Prominent differences between the PASA parameters from the fatty and normal mouse livers were observed. The analysis of the PASA parameters from six normal and six fatty mouse livers indicates that there are differences of up to 5 standard deviations between the PASA parameters of the normal livers and those of the fatty livers at 1200 nm; for parameters from nine normal and nine fatty mouse livers at 532 nm, the differences were approximately 2 standard deviations (P < .05) for each PASA parameter. The results supported our hypothesis that the PASA allows quantitative identification of the microstructural changes that differentiate normal from fatty livers. Compared with that at 532 nm, PASA at 1200 nm is more reliable for fatty liver diagnosis. Online supplemental material is available for this article.