Photoacoustic Analysis Research Articles

Hydrodynamic cavitation of brewery spent grain diluted by wastewater

This study examined the influence of hydrodynamic cavitation on the biodegradability and composition of brewery spent grain diluted by mechanically pre-treated municipal wastewater. An orifice plate with a conical concentric hole (3/10mm as an inlet/outlet diameter) was used as the constriction in the cavitation device; the corresponding cavitation number was 0.036. Hydrodynamic cavitation was applied at an inlet pressure of 7bar, maintaining 30 recirculation passes through the cavitation zone. As a result, the concentration of soluble organic compounds (expressed as soluble chemical oxygen demand), BOD5 value, and BOD5/COD ratio increased. The BOD5/COD ratio was enhanced from 0.074 to 0.091, indicating improved biodegradability of the brewery spent grain. Moreover, solubilization of carbohydrates occurred, as confirmed by the hemicellulose removal with a related monosaccharides release of 87%. On the other hand, the COD value and the concentrations of both total solids and volatile solids decreased significantly, revealing the effective destruction of complex organic compounds via cavitation.Additionally, Fourier transform infrared photoacoustic spectroscopy analysis was conducted to check the findings. It confirmed that hydrodynamic cavitation did not lead to the formation of new compounds that would interfere with the biological treatment of the brewery spent grain diluted by mechanically pre-treated wastewater.

Repeated application of organic waste affects soil organic matter composition: Evidence from thermal analysis, FTIR-PAS, amino sugars and lignin biomarkers

Land application of organic waste is an important alternative to landfilling and incineration because it helps restore soil fertility and has environmental and agronomic benefits. These benefits may be related to the biochemical composition of the waste, which can result in the accumulation of different types of carbon compounds in soil. The objective of this study was to identify and characterise changes in soil organic matter (SOM) composition after repeated applications of organic waste. Soil from the CRUCIAL field experiment in Denmark was sampled after 12 years of annual application of household waste compost, cattle manure and sewage sludge, and was compared to a control treatment that had received NPK fertilisation. Soils were characterised using CO2-evolved gas analysis (CO2-EGA) during ramped thermal analysis, mid-infrared photoacoustic spectroscopy (FTIR-PAS) and analysis of amino-sugar and lignin phenols. SOM from the compost and cattle manure treatments had greater thermal stability than the sludge and NPK treatments, which was consistent with the thermal stability of the applied wastes. Compost-amended soils and manure-amended soils also had a greater lignin content with a lower degree of oxidation and a greater contribution of bacterial amino sugars relative to fungal amino sugars compared to soils from the NPK treatment. The high soil C accumulation rate combined with low amino sugar C in SOM from the compost treatment suggested less stimulation of microbial activity, while the cattle manure seemed to result in both microbial stimulation and accumulation of thermally stable forms of C. FTIR-PAS revealed greater C=O vibration of carboxylic groups and amides in sludge and NPK treatments, indicating more oxidised SOM and the presence of proteins. Taken together, these results show that there was accumulation in soil of different C compounds for the different types of applied organic waste, which appeared to be related to the degree to which microbial activity was stimulated and the type of microbial communities applied with the wastes or associated with the decomposition of applied wastes. This in turn may have important effects on ecosystem functioning and long-term soil C storage.

Greenhouse Gas Emissions and Denitrification within Depressional Wetlands of the Southeastern US Coastal Plain in an Agricultural Landscape

Carolina Bays are depressional wetlands on the Coastal Plain of the southeastern United States. These wetlands are often the recipient of nutrient runoff from adjacent agricultural lands and there is potential for production of greenhouse gases during nitrification and denitrification processes occurring in the wetland sediments. Because of their saturated conditions, Carolina Bays may improve regional water quality through denitrification of soil nitrate. Three small bays in South Carolina were selected for denitrification and greenhouse gas analysis. A transect of four points was sampled within each Carolina Bay in May, July, September, and November over a two year period. Gas emissions were measured in-situ using a photoacoustic gas analyzer and soil samples were brought back to the lab for denitrification enzyme activity and microbial analysis. Emissions of nitrous oxide (N2O) averaged 1.8 mg m−2 d−1, with a median of 0.47 (with a range of below detectable limits to 9.414 mg m−2 d−1). Many measurement events of N2O were below detection and did not vary within the bays. The carbon dioxide emissions from Carolina Bays averaged 15.8 g m−2 d−1 and were largely controlled by temperature. Denitrification enzyme activity had a larger response to nitrate additions further into the bays. Gram + bacteria were also greater deeper into the bays, while Gram- and fungal populations were greater at the field/wetland interface. Manure application had some minor effects on DEA within the bays, but did not appear to increase gas emissions over the period measured.

Plasmonic Nanoparticles with Quantitatively Controlled Bioconjugation for Photoacoustic Imaging of Live Cancer Cells.

Detection and imaging of single cancer cells is critical for cancer diagnosis and understanding of cellular dynamics. Photoacoustic imaging (PAI) provides a potential tool for the study of cancer cell dynamics, but faces the challenge that most cancer cells lack sufficient endogenous contrast. Here, a type of colloidal gold nanoparticles (AuNPs) are physically fabricated and are precisely functionalized with quantitative amounts of functional ligands (i.e., polyethyleneglycol (PEG) and (Arginine(R)–Glycine(G)–Aspartic(D))4 (RGD) peptides) to serve as an exogenous contrast agent for PAI of single cells. The functionalized AuNPs, with a fixed number of PEG but different RGD densities, are delivered into human prostate cancer cells. Radioactivity and photoacoustic analyses show that, although cellular uptake efficiency of the AuNPs linearly increases along with RGD density, photoacoustic signal generation efficiency does not and only maximize at a moderate RGD density. The functionalization of the AuNPs is in turn optimized based on the experimental finding, and single cancer cells are imaged using a custom photoacoustic microscopy with high‐resolution. The quantitatively functionalized AuNPs together with the high‐resolution PAI system provide a unique platform for the detection and imaging of single cancer cells, and may impact not only basic science but also clinical diagnostics on a range of cancers.

Characterizing cellular morphology by photoacoustic spectrum analysis with an ultra-broadband optical ultrasonic detector.

Photoacoustic spectrum analysis (PASA) has been demonstrated as a new method for quantitative tissue imaging and characterization. The ability of PASA in evaluating micro-size tissue features was limited by the bandwidth of detectors for photoacoustic (PA) signal acquisition. We improve upon such a limit, and report on developments of PASA facilitated by an optical ultrasonic detector based on micro-ring resonator. The detector's broad and flat frequency response significantly improves the performance of PASA and extents its characterization capability from the tissue level to cellular level. The performance of the system in characterizing cellular level (a few microns) stochastic objects was first shown via a study on size-controlled optically absorbing phantoms. As a further demonstration of PASA's potential clinical application, it was employed to characterize the morphological changes of red blood cells (RBCs) from a biconcave shape to a spherical shape as a result of aging. This work demonstrates that PASA equipped with the micro-ring ultrasonic detectors is an effective technique in characterizing cellular-level micro-features of biological samples.

Feasibility of lung clearance index in a clinical setting in pre-school children.

Lung function testing in pre-school children in the clinical setting is challenging. Most cannot perform spirometry and many infant lung function tests require sedation. Lung clearance index (LCI) derived from the multiple-breath washout (MBW) test has been shown to be sensitive to early disease changes but may be time consuming and so a shortened test (LCI0.5) may be more feasible in young children. We sought to establish feasibility of MBW in unsedated pre-school children in a clinic setting and hypothesised use of LCI0.5 would increase success rates.116 pre-school children (28 healthy controls and 88 with respiratory disease), median age 4.0 years (range 2-6 years), underwent MBW tests unsedated in a clinic setting, using sulfur hexafluoride as a tracer gas and an adapted photoacoustic gas analyser.81 (70%) out of 116 children completed LCI and 72% completed LCI0.5 measurement. Test success increased significantly in patients over 3 years (0% at <2.5 years, 33% at 2.5-3 years and 70% at >3 years, p<0.0001). LCI was elevated in those with respiratory disease compared with healthy controls.MBW is feasible in a clinic setting in unsedated pre-schoolers, particularly in those >3 years old, and LCI is raised in those with respiratory disease. Use of LCI0.5 did not increase success rate in pre-schoolers.

Evaluation of thermal stability and time resolved acoustic fingerprint spectra of 1-(2-methoxy,-3,5-dinitrophenyl)-1H-1,2,3-triazole

The paper reports the study of thermal stability and decomposition mechanisms of the newly synthesized phenyl series energetic molecule named 1-(2-methoxy,-3,5-dinitrophenyl)-1H-1,2,3-triazole (S5) using time resolved pulsed photoacoustic (PA) pyro analysis technique. The thermal PA spectra of the compound was recorded using a Q-Switched Nd-YAG laser (532nm, 7ns, 10Hz). TG-DTA technique was carried out for ascertaining the melting and decomposition temperature of the compound. The results of these two methods confirm that S5 is thermally stable in the range of 30–350°C. We have earlier reported that phenyl series 1,2,3-triazoles require high incident laser energy than that of benzyl series 1,2,3-triazoles [1]. However, our further investigation shows that the change in the position of principal functional groups affects the process of thermal decomposition. Also, the thermal stability of the compound is evaluated on the basis of quality factor (Q) of the PA cavity. Further, we have used GC–MS and FTIR techniques to identify some of the gaseous components released from the compounds.

Comparison of models for predicting pore space indices and their relationships with CO2 and N2O fluxes in a corn–soybean field

Several models predict soil pore space indices (the relative gas diffusion coefficient, Ds/Do and the pore tortuosity, τ), but information is lacking on which models predicted indices better relate to soil processes. We compared pore space indices’ predictive models based on air-filled porosity (fa) alone vs. models using air-filled porosity and total pore space (Φ) (fa + Φ). We also assessed the relationships between these indices and CO2 and N2O. The study was conducted from 2011 to 2014 on a silt loam soil at Lincoln University. Soil samples were collected at 0–10 and 10–20 cm depth and oven dried at 105 °C for 72 h. After drying, fa and Φ were calculated and later used in models for predicting Ds/Do and τ. CO2 and N2O were measured with a Shimadzu gas chromatograph (GC) and a photoacoustic gas analyzer (PSA). Results showed that Ds/Do predicted using fa alone (Marshall and Buckingham) was higher as compared with values predicted with models based on fa + Φ (Sallam et al., Millington, and Jin and Jury) (P &lt; 0.001). However, values of τ predicted with models based on fa alone were lowest (P &lt; 0.001). CO2 and N2O measured with GC better related with Ds/Do and τ.

Preparation and Photoacoustic Analysis of Cellular Vehicles Containing Gold Nanorods.

Gold nanorods are attractive for a range of biomedical applications, such as the photothermal ablation and the photoacoustic imaging of cancer, thanks to their intense optical absorbance in the near-infrared window, low cytotoxicity and potential to home into tumors. However, their delivery to tumors still remains an issue. An innovative approach consists of the exploitation of the tropism of tumor-associated macrophages that may be loaded with gold nanorods in vitro. Here, we describe the preparation and the photoacoustic inspection of cellular vehicles containing gold nanorods. PEGylated gold nanorods are modified with quaternary ammonium compounds, in order to achieve a cationic profile. On contact with murine macrophages in ordinary Petri dishes, these particles are found to undergo massive uptake into endocytic vesicles. Then these cells are embedded in biopolymeric hydrogels, which are used to verify that the stability of photoacoustic conversion of the particles is retained in their inclusion into cellular vehicles. We are confident that these results may provide new inspiration for the development of novel strategies to deliver plasmonic particles to tumors.

Preparation and Photoacoustic Analysis of Cellular Vehicles Containing Gold Nanorods

Gold nanorods are attractive for a range of biomedical applications, such as the photothermal ablation and the photoacoustic imaging of cancer, thanks to their intense optical absorbance in the near-infrared window, low cytotoxicity and potential to home into tumors. However, their delivery to tumors still remains an issue. An innovative approach consists of the exploitation of the tropism of tumor-associated macrophages that may be loaded with gold nanorods in vitro. Here, we describe the preparation and the photoacoustic inspection of cellular vehicles containing gold nanorods. PEGylated gold nanorods are modified with quaternary ammonium compounds, in order to achieve a cationic profile. On contact with murine macrophages in ordinary Petri dishes, these particles are found to undergo massive uptake into endocytic vesicles. Then these cells are embedded in biopolymeric hydrogels, which are used to verify that the stability of photoacoustic conversion of the particles is retained in their inclusion into cellular vehicles. We are confident that these results may provide new inspiration for the development of novel strategies to deliver plasmonic particles to tumors.

Nanosecond pulsed laser ablation of Ge investigated by employing photoacoustic deflection technique and SEM analysis

Nanosecond pulsed laser ablation phenomena of single crystal Ge (100) has been investigated by employing photoacoustic deflection as well as SEM analysis techniques. Nd: YAG laser (1064nm, 10ns, 1–10Hz) at various laser fluences ranging from 0.2 to 11Jcm−2 is employed as pump beam to ablate Ge targets. In order to evaluate in-situe ablation threshold fluence of Ge by photoacoustic deflection technique, Continuous Wave (CW) He–Ne laser (632nm, power 10mW) is employed as a probe beam. It travels parallel to the target surface at a distance of 3mm and after passing through Ge plasma it causes deflection due to density gradient of acoustic waves. The deflected signal is detected by photodiode and is recorded by oscilloscope. The threshold fluence of Ge, the velocity of ablated species and the amplitude of the deflected signal are evaluated. The threshold fluence of Ge comes out to be 0.5Jcm−2 and is comparable with the analytical value. In order to compare the estimated value of threshold with ex-situe measurements, the quantitative analysis of laser irradiated Ge is performed by using SEM analysis. For this purpose Ge is exposed to single and multiple shots of 5, 10, 50 and 100 at various laser fluences ranging from 0.2 to 11Jcm−2. The threshold fluence for single and multiple shots as well as incubation coefficients are evaluated. It is observed that the value of incubation co-efficient decreases with increasing number of pulses and is therefore responsible for lowering the threshold fluence of Ge. SEM analysis also reveals the growth of various features such as porous structures, non-uniform ripples and blisters on the laser irradiated Ge. It is observed that both the fluence as well as number of laser shots plays a significant role for the growth of these structures.

Growth of organic nonlinear optical (NLO) ammonium D,L-tartrate (AMT) single crystal by conventional and unidirectional method and its characterization

High-quality, transparent uniaxial ammonium D,L-tartrate (AMT) single crystal having dimension of 15 mm diameter and 60 mm length was grown by Sankaranarayanan–Ramasamy (SR) method with a growth rate of 1 mm per day. Single-crystal X-ray diffraction was carried out to confirm the AMT crystals. The presence of functional groups of crystallized AMT molecules were identified by FTIR spectral analysis. The dislocation density of the AMT crystals grown by slow evaporation solution technique (SEST) and SR method were characterized using chemical etching analysis. A comparative laser damage threshold analysis was made on the AMT crystals grown by conventional and SR method which shows that the crystal grown by SR method has higher damage threshold. The SR method grown AMT crystal has higher microhardness and also higher optical transmittance compared to conventional method grown crystal. The thermal properties of the SEST and SR method grown AMT crystals were measured by photoacoustic spectrum analysis. The second harmonic generation efficiency of AMT was determined using the powder Kurtz–Perry technique.

Nanoparticle-based photoacoustic analysis for highly sensitive lateral flow assays.

This paper demonstrates a photoacoustics-based lateral flow test that takes advantage of the strong interaction of light and gold nanoparticles to quantitatively detect a disease biomarker. For a commercially available lateral flow test strip, the photoacoustic analysis improved the detection limit by two orders of magnitude compared to colorimetric measurements.

Quantifying Gleason scores with photoacoustic spectral analysis: feasibility study with human tissues.

Gleason score is a highly prognostic factor for prostate cancer describing the microscopic architecture of the tumor tissue. The standard procedure for evaluating Gleason scores, namely biopsy, is to remove prostate tissue for observation under microscope. Currently, biopsies are guided by transrectal ultrasound (TRUS). Due to the low sensitivity of TRUS to prostate cancer (PCa), non-guided and saturated biopsies are frequently employed, unavoidably causing pain, damage to the normal prostate tissues and other complications. More importantly, due to the limited number of biopsy cores, current procedure could either miss early stage small tumors or undersample aggressive cancers. Photoacoustic (PA) measurement has the unique capability of evaluating tissue microscopic architecture information at ultrasonic resolution. By frequency domain analysis of the broadband PA signal, namely PA spectral analysis (PASA), the microscopic architecture within the assessed tissue can be quantified. This study investigates the feasibility of evaluating Gleason scores by PASA. Simulations with the classic Gleason patterns and experiment measurements from human PCa tissues have demonstrated strong correlation between the PASA parameters and the Gleason scores.

Allan Deviation Plot as a Tool for Quartz-Enhanced Photoacoustic Sensors Noise Analysis.

We report here on the use of the Allan deviation plot to analyze the long-term stability of a quartz-enhanced photoacoustic (QEPAS) gas sensor. The Allan plot provides information about the optimum averaging time for the QEPAS signal and allows the prediction of its ultimate detection limit. The Allan deviation can also be used to determine the main sources of noise coming from the individual components of the sensor. Quartz tuning fork thermal noise dominates for integration times up to 275 s, whereas at longer averaging times, the main contribution to the sensor noise originates from laser power instabilities.

Characterization of bone microstructure using photoacoustic spectrum analysis.

Osteoporosis is a progressive bone disease that is characterized by a decrease in bone mass and the deterioration in bone microarchitecture. This study investigates the feasibility of characterizing bone microstructure by analyzing the frequency spectrum of the photoacoustic (PA) signal from the bone. Modeling and numerical simulation of PA signal were performed on trabecular bone simulations and CT scans with different trabecular thicknesses. The resulting quasi-linear photoacoustic spectra were fittted by linear regression, from which the spectral parameter slope was quantified. The simulation based on two different models both demonstrate that bone specimens with thinner trabecular thicknesses have higher slope. Experiment on osteoporotic rat femoral heads with different mineral content was conducted. The finding from the experiment was in good agreement with the simulation, demonstrating that the frequency-domain analysis of PA signals can provide an objective assessment of bone microstructure and deterioration. Considering that PA measurement is non-ionizing, non-invasive, and has sufficient penetration in both calcified and non-calcified tissues, this new bone evaluation method based on photoacoustic spectral analysis holds potential for clinical management of osteoporosis and other bone diseases.

Studies on Characteristics and Formation of Soot Nanoparticles in an Ethylene/Air Inverse Diffusion Flame

AbstractAn ethylene/air inverse diffusion flame burner was assumed to generate a stable flame, and soot samples were captured at different locations around the outer edge along the height of the flame. The soot samples were then analyzed with transmission electron microscopy (TEM), gas chromatography-mass spectrometry (GC-MS), and other detection means, and a photoacoustic analyzer was introduced to detect the mass concentration of soot nanoparticles after inception based on their optical features. The results showed that the plot of soot concentration had the same tendency as the gas temperature’s, which increased first and then declined with the increase in flame height, but these two curves had two different turning points. As to the measurements of TEM, the morphology of soot particles exhibited diverse shapes and structures at different flame heights. Alkanes, cycloalkanes, olefins, benzene, anthracene, pyrene, and aromatic compounds were determined as the main components of soot by the detection of ...

Design and modeling of a photoacoustic gas analyzer with a thermal source for carbon isotope ratio analysis

A diagram is suggested and numerical simulation is carried out of a photoacoustic gas analyzer with a thermal source and first order interference filter for carbon isotope ratio analysis. An optimal spectral range for gas analyzer operation is selected. In the wavelength range selected, the spectral parameters of the atmosphere are analyzed, as well as of some gases, which, being present in samples under study, could affect the measurement results. The gas analyzer suggested allows us to measure the carbon isotope ratio 13C/12C in CO2 samples with a minimal error of about 0.5‰, and could be useful for detection of such gases as SO2, CO, and NH3, absorption lines of which fall in the selected spectral range.

Лазерный оптико-акустический анализ сложных газовых смесей

Лазерный оптико-акустический анализ сложных газовых смесей

Study of thermal stability and acoustic fingerprint spectra of phenyl and benzyl triazole derivatives using time resolved pulsed photoacoustic pyro analysis technique

The paper reports the use of pulsed laser based photoacoustic (PA) pyro analysis technique to study the thermal decomposition, stability and acoustic fingerprints of nitro rich phenyl and benzyl triazole derivatives. Two compounds named as 1-(3-methoxy-2,6-dinitrophenyl) -1H-1,2,3-triazole (S10) and 1-(4-methoxy-3,5-dinitrobenzyl)-1H-1,2,3-triazole (S4) are studied using visible 532nm and UV 266nm wavelengths, respectively, obtained from Q-switched Nd:YAG laser of 7ns pulse duration and repetition rate 10Hz. These compounds are also subjected to the thermo gravimetric–differential thermal analysis (TG–DTA) technique. The obtained results of pulsed PA and TG-DTA techniques are used to understand the thermal stability and decomposition mechanism of HEMs. We have also evaluated the thermal quality factor ‘Q’ which plays very important role to test the thermal stability of the S4 and S10 irrespective of incident laser wavelengths.