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Activatable type I photosensitizers are an effective way to overcome the insufficiency and imprecision of photodynamic therapy in the treatment of hypoxic tumors, however, the incompletely inhibited photoactivity of pro‐photosensitizer and the limited oxidative phototoxicity of post‐photosensitizer are major limitations. It is still a great challenge to address these issues using a single and facile design. Herein, a series of totally caged type I pro‐photosensitizers (Pro‐I‐PSs) are rationally developed that are only activated in tumor hypoxic environment and combine two oxygen‐independent therapeutic mechanisms under single‐pulse laser irradiation to enhance the phototherapeutic efficacy. Specifically, five benzophenothiazine‐based dyes modified with different nitroaromatic groups, BPN 1−5, are designed and explored as latent hypoxia‐activatable Pro‐I‐PSs. By comparing their optical responses to nitroreductase (NTR), it is identified that the 2‐methoxy‐4‐nitrophenyl decorated dye (BPN 2) is the optimal Pro‐I‐PSs, which can achieve NTR‐activated background‐free fluorescence/photoacoustic dual‐modality tumor imaging. Furthermore, upon activation, BPN 2 can simultaneously produce an oxygen‐independent photoacoustic cavitation effect and a photodynamic type I process at single‐pulse laser irradiation. Detailed studies in vitro and in vivo indicated that BPN 2 can effectively induce cancer cell apoptosis through synergistic effects. This study provides promising potential for overcoming the pitfalls of hypoxic‐tumor photodynamic therapy. [ABSTRACT FROM AUTHOR]

Over the past few decades, the number of patients with neurological diseases has increased significantly, posing huge challenges and opportunities for the development of brain imaging technology. As a hybrid imaging method combining optical excitation and acoustic detection techniques, photoacoustic tomography (PAT), has experienced rapid development, due to high optical contrast and spatial resolution at depth inside tissues. With the development of lasers, ultrasonic detectors, and data computations, PAT has been widely applied for the diagnosis of oncology, dermatosis, etc. However, the energy of light and ultrasound would be greatly attenuated while penetrating the skull, due to the reflection, absorption, and scattering effects, resulting in limited application of PAT in brain imaging. In this review, we summarized the achievements of PAT and its application in the detection of brain diseases including glioma, stroke, traumatic brain injury, Alzheimer's disease, epilepsy, and Parkinson's disease. Moreover, various PAT systems and multi‐modality photoacoustic imaging are introduced for potential clinical applications. Finally, the challenges and current limitations of PAT for further brain imaging are also discussed. [ABSTRACT FROM AUTHOR]

Integrated multimodal imaging in theranostics nanomaterials offers extensive prospects for precise and noninvasive cancer treatment. Precisely controlling the structural evolution of plasmonic nanoparticles is crucial in the development of photothermal agents. However, previous successes have been limited to static assemblies and single‐component structures. Here, an activatable plasmonic theranostics system utilizing self‐assembled 1D silver‐coated gold nanochains (1D nanochains) is presented for precise tumor diagnosis and effective treatment. The absorbance of the adaptable core–shell chain structure can shift from visible to near‐infrared (NIR) regions due to the fusion between nearby Au@Ag nanoparticles induced by elevated H2O2 levels in the tumor microenvironment (TME), resulting in the creation of a novel 3D aggregates with strong NIR absorption. With a high photothermal conversion efficiency of 60.2% at 808 nm, nanochains utilizing the TME‐activated characteristics show remarkable qualities for photoacoustic imaging and significantly limit tumor growth in vivo. This study may pave the way for precise tumor diagnosis and treatment through customizable, optically tunable adaptive plasmonic nanostructures. [ABSTRACT FROM AUTHOR]

Liver fibrosis, a major global health issue, is marked by excessive collagen deposition that impairs liver function. Noninvasive methods for the direct visualization of collagen content are crucial for the early detection and monitoring of fibrosis progression. This study investigates the potential of spectral photoacoustic imaging (sPAI) to monitor collagen development in liver fibrosis. Utilizing a novel data-driven superpixel photoacoustic unmixing (SPAX) framework, we aimed to distinguish collagen presence and evaluate its correlation with fibrosis progression. We employed an established diethylnitrosamine (DEN) model in rats to study liver fibrosis over various time points. Our results revealed a significant correlation between increased collagen photoacoustic signal intensity and advanced fibrosis stages. Collagen abundance maps displayed dynamic changes throughout fibrosis progression. These findings underscore the potential of sPAI for the noninvasive monitoring of collagen dynamics and fibrosis severity assessment. This research advances the development of noninvasive diagnostic tools and personalized management strategies for liver fibrosis. [ABSTRACT FROM AUTHOR]

Endoscopy, enabling high-resolution imaging of deep tissues and internal organs, plays an important role in basic research and clinical practice. Recent advances in photoacoustic microscopy (PAM), demonstrating excellent capabilities in high-resolution functional imaging, have sparked significant interest in its integration into the field of endoscopy. However, there are challenges in achieving functional PAM in the endoscopic setting. This Perspective article discusses current progress in the development of endoscopic PAM and the challenges related to functional measurements. Then, it points out potential directions to advance endoscopic PAM for functional imaging by leveraging fiber optics, microfabrication, optical engineering, and computational approaches. Finally, it highlights emerging opportunities for functional endoscopic PAM in basic and translational biomedicine. [ABSTRACT FROM AUTHOR]

A compact photoacoustic spectroscopy system integrated with a non-coaxial multi-pass cell was developed for improving the instrument performance in the measurement of methane. The multi-pass cell with compact light spot mode was proposed for concentrating the light radiation within a limited space, which effectively reduces the instrument dimension. A distributed feedback (DFB) laser with a central wavelength of 1653 nm was employed to excite the photoacoustic signal of methane. A total of 21 round trips of reflection were achieved in an acoustic resonant cavity with a radius of 4 mm and a length of 36 mm. Four microphones were installed around the cavity to collect the signal. An 11-fold enhancement of the photoacoustic signal was achieved through the multi-pass cell, compared to a single-pass cell with dimension of 10 cm. The system was used to measure different concentrations of methane, which showed good linearity. The continuous detection of 10 ppm methane gas was carried out for 6000 s. The Allan standard deviation analysis indicates that the limit of detection of the system was 5.7 ppb with an optimum integration time of 300 s. [ABSTRACT FROM AUTHOR]

The water vapor in the ambient air affects the accuracy of the photoacoustic (PA) dissolved gas analysis system for transformer health monitoring. A laser PA system was evaluated by dry and humidified standard gases to study the influence of water vapor concentration on PA gas detection. Theoretical analysis was conducted on the effect of gas molecule relaxation on PA signal detection. A high‐frequency resonant PA cell and a low‐frequency nonresonant PA cell were used to detect acetylene (C2H2) and carbon monoxide (CO), respectively. The experimental results show that the PA signal of humidified CO is about 12 times higher than PA signal of dry gas for the resonant PA detection system, respectively. In addition, as the frequency is increased from 30 to 980 Hz, the PA signals of humidified and dry CO attenuate by 1.5 and 6.9 times, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a photoacoustic trace gas sensor based on a multi-pass enhanced open spherical photoacoustic cell (M-OPAC) was developed. A high-performance spherical photoacoustic (PA) cell was specially designed with high resonant frequency for suppressing various environmental noises, and integrated with a Herriot-type multi-pass optical system for enhancing PA signal. For evaluating the developed PA sensor system, details of theoretical simulation and experimental test were investigated for ambient water vapor (H2O) detection by utilizing a DFB diode laser with a central wavelength of 1391 nm, and wavelength modulation spectroscopy with second harmonic (WMS-2f) detection technique was employed. Compared to the conventional single-pass PA detection strategy, the developed multi-pass PA sensor shows a sensitivity enhancement of 4.3 times and demonstrates a good immunity to ambient noises. Moreover, the developed spherical open photoacoustic cell can be used for open monitoring of atmospheric adsorbent gases, which indicates a great potential for in-site and real-time gas monitoring without complex gas sampling procedures. [ABSTRACT FROM AUTHOR]

Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS) is a technique in which the sound wave is detected by a quartz tuning fork (QTF). It enables particularly high specificity with respect to the excitation frequency and is well known for an extraordinarily sensitive analysis of gaseous samples. We have developed the first photoacoustic (PA) cell for QEPAS on solid samples. Periodic heating of the sample is excited by modulated light from an interband cascade laser (ICL) in the infrared region. The cell represents a half-open cylinder that exhibits an acoustical resonance frequency equal to that of the QTF and, therefore, additionally amplifies the PA signal. The antinode of the sound pressure of the first longitudinal overtone can be accessed by the sound detector. A 3D finite element (FE) simulation confirms the optimal dimensions of the new cylindrical cell with the given QTF resonance frequency. An experimental verification is performed with an ultrasound micro-electromechanical system (MEMS) microphone. The presented frequency-dependent QEPAS measurement exhibits a low noise signal with a high-quality factor. The QEPAS-based investigation of three different solid synthetics resulted in a linearly dependent signal with respect to the absorption. [ABSTRACT FROM AUTHOR]

Purpose: Fluorescence-guided surgery (FGS) can play a key role in improving radical resection rates by assisting surgeons to gain adequate visualization of malignant tissue intraoperatively. Designed ankyrin repeat proteins (DARPins) possess optimal pharmacokinetic and other properties for in vivo imaging. This study aims to evaluate the preclinical potential of epithelial cell adhesion molecule (EpCAM)-binding DARPins as targeting moieties for near-infrared fluorescence (NIRF) and photoacoustic (PA) imaging of cancer. Methods: EpCAM-binding DARPins Ac2, Ec4.1, and non-binding control DARPin Off7 were conjugated to IRDye 800CW and their binding efficacy was evaluated on EpCAM-positive HT-29 and EpCAM-negative COLO-320 human colon cancer cell lines. Thereafter, NIRF and PA imaging of all three conjugates were performed in HT-29_luc2 tumor-bearing mice. At 24 h post-injection, tumors and organs were resected and tracer biodistributions were analyzed. Results: Ac2-800CW and Ec4.1-800CW specifically bound to HT-29 cells, but not to COLO-320 cells. Next, 6 nmol and 24 h were established as the optimal in vivo dose and imaging time point for both DARPin tracers. At 24 h post-injection, mean tumor-to-background ratios of 2.60 ± 0.3 and 3.1 ± 0.3 were observed for Ac2-800CW and Ec4.1-800CW, respectively, allowing clear tumor delineation using the clinical Artemis NIRF imager. Biodistribution analyses in non-neoplastic tissue solely showed high fluorescence signal in the liver and kidney, which reflects the clearance of the DARPin tracers. Conclusion: Our encouraging results show that EpCAM-binding DARPins are a promising class of targeting moieties for pan-carcinoma targeting, providing clear tumor delineation at 24 h post-injection. The work described provides the preclinical foundation for DARPin-based bimodal NIRF/PA imaging of cancer. [ABSTRACT FROM AUTHOR]

A high-precision low-cost mid-infrared photoacoustic sensor for greenhouse composite gases based on aspherical beam shaping is proposed and demonstrated. The assembled optical source module and luminous characteristics of infrared source are innovatively investigated and analyzed with aspherical beam shaping. The proposed aspherical-beam-shaping-technique could effectively reduce optical loss and enhance system sensitivity, achieving an effective power utilization ratio of a radiation source of 91% and sidewall noise ratio of 8.9%. Experiments verify the 1.7 times improvement in responsivity and 50% enhancement in minimum detection limit (MDL) on average. In terms of comprehensive greenhouse gas composites and with short integration time of 1 s, MDLs of CO2, CH4, N2O, NF3, SF6, PFC-14, and HFC-134a are 73 ppb, 267 ppb, 72 ppb, 81 ppb, 14 ppb, 9 ppb and 115 ppb, respectively. Furthermore, a 48 h continuous monitoring of H2O, CO2 and CH4 in the atmosphere is conducted and verifies the performance of the gas sensor. The developed sensor allows for the rapid route of low-cost and high-precision detection of multiple greenhouse gases. [ABSTRACT FROM AUTHOR]

The present manuscript deals with the identification of the spectral lines of the rare earth elements (REEs) in the LIBS spectra of the black sands collected from the Thiruvananthapuram (Kerala) beach using laser-induced breakdown spectroscopy (LIBS). LIBS spectra of the sand sample show the presence of spectral lines of Na, Mg, Mn, Al, and Cr. Along with these elements, the spectral lines of REEs such as Ce, Nd, Sm, Dy, Ho, Tm, etc., and the radioactive element Thorium (Th) are also present in the LIBS spectra of the black sand sample. The presence of REEs and radioactive elements makes the sand suitable for profitable extraction using various methods for different applications. The results of LIBS (presence of all REEs in sand) are also verified by photoacoustic spectroscopy (PAS). The Plasma temperature has been calculated using the Boltzmann plot to explain the distribution of the atoms in various higher energy states/levels. An attempt is made to explain the various transitions involved in the spectral lines of the rare earth ions in the LIBS spectra of the black sand sample using a possible energy level diagram. The concentration of some REEs (Dy, Sm, and Nd) and LOD has been calculated by using the calibration curve method. To the best of our knowledge, the investigation of rare earth and radioactive elements in the black sand of the Kerala beach using LIBS is reported for the first time. [ABSTRACT FROM AUTHOR]

Metastasis causes greater than 90% of cancer-associated deaths, presenting huge challenges for detection and efficient treatment of cancer due to its high heterogeneity and widespread dissemination to various organs. Therefore, it is imperative to combat cancer metastasis, which is the key to achieving complete cancer eradication. Immunotherapy as a systemic approach has shown promising potential to combat metastasis. However, current clinical immunotherapies are not effective for all patients or all types of cancer metastases owing to insufficient immune responses. In recent years, immunological nanomaterials with intrinsic immunogenicity or immunomodulatory agents with efficient loading have been shown to enhance immune responses to eliminate metastasis. In this review, we would like to summarize various types of immunological nanomaterials against metastasis. Moreover, this review will summarize a series of immunological nanomaterial-mediated immunotherapy strategies to combat metastasis, including immunogenic cell death, regulation of chemokines and cytokines, improving the immunosuppressive tumour microenvironment, activation of the STING pathway, enhancing cytotoxic natural killer cell activity, enhancing antigen presentation of dendritic cells, and enhancing chimeric antigen receptor T cell therapy. Furthermore, the synergistic anti-metastasis strategies based on the combinational use of immunotherapy and other therapeutic modalities will also be introduced. In addition, the nanomaterial-mediated imaging techniques (e.g., optical imaging, magnetic resonance imaging, computed tomography, photoacoustic imaging, surface-enhanced Raman scattering, radionuclide imaging, etc.) for detecting metastasis and monitoring anti-metastasis efficacy are also summarized. Finally, the current challenges and future prospects of immunological nanomaterial-based anti-metastasis are also elucidated with the intention to accelerate its clinical translation. [ABSTRACT FROM AUTHOR]

This comprehensive review highlights the versatile applications of photothermal techniques, particularly thermal lens spectrometry (TLS) and photoacoustic spectrometry (PAS), in the field of nanomaterials characterization. TLS is an effective technique in the trace detection of different compounds in liquid samples, photodegradation studies, and analysis of photocatalytic reaction rate, as well as the study of molecular dynamics, impacting both environmental and catalytical research. It enables the optimization of thermal diffusivity in soot nanofluids and offers insights into seed germination and plant yield enhancement in nanobiophotonics. The review also explores the thermal and elastic characterization of Fe2O3 polymorphs by photoacoustic spectroscopy (PAS). Investigating the metal mirror demonstrates PAS's efficacy in determining its reflection coefficient and thermal diffusivity. ZnO nanoparticles' strong absorption on diatomite surfaces is revealed through PAS, emphasizing their effectiveness in light absorption enhancement. Furthermore, PA techniques address working frequency limitations in studying silicon-based nanomaterials. Thus, thermal lens and photoacoustic spectroscopy assume pivotal roles in unveiling the nuanced attributes of various nanostructured materials, thereby propelling advancements in the realms of science and technology. [ABSTRACT FROM AUTHOR]

Background: Ultrasound and photoacoustic (US/PA) imaging is a promising tool for in vivo visualization and assessment of drug delivery. However, the acoustic properties of the skull limit the practical application of US/PA imaging in the brain. To address the challenges in targeted drug delivery to the brain and transcranial US/PA imaging, we introduce and evaluate an intracerebral delivery and imaging strategy based on the use of laser-activated perfluorocarbon nanodroplets (PFCnDs). Methods: Two specialized PFCnDs were developed to facilitate blood‒brain barrier (BBB) opening and contrast-enhanced US/PA imaging. In mice, PFCnDs were delivered to brain tissue via PFCnD-induced BBB opening to the right side of the brain. In vivo, transcranial US/PA imaging was performed to evaluate the utility of PFCnDs for contrast-enhanced imaging through the skull. Ex vivo, volumetric US/PA imaging was used to characterize the spatial distribution of PFCnDs that entered brain tissue. Immunohistochemical analysis was performed to confirm the spatial extent of BBB opening and the accuracy of the imaging results. Results: In vivo, transcranial US/PA imaging revealed localized photoacoustic (PA) contrast associated with delivered PFCnDs. In addition, contrast-enhanced ultrasound (CEUS) imaging confirmed the presence of nanodroplets within the same area. Ex vivo, volumetric US/PA imaging revealed PA contrast localized to the area of the brain where PFCnD-induced BBB opening had been performed. Immunohistochemical analysis revealed that the spatial distribution of immunoglobulin (IgG) extravasation into the brain closely matched the imaging results. Conclusions: Using our intracerebral delivery and imaging strategy, PFCnDs were successfully delivered to a targeted area of the brain, and they enabled contrast-enhanced US/PA imaging through the skull. Ex vivo imaging, and immunohistochemistry confirmed the accuracy and precision of the approach. [ABSTRACT FROM AUTHOR]

A new imaging technique called photoacoustic imaging (PAI) combines the advantages of ultrasound imaging and optical absorption to provide structural and functional details of tissues. It has broad application prospects in the accurate diagnosis and treatment monitoring of brain tumours. However, the existing photoacoustic image classification algorithms cannot effectively distinguish benign tumours from malignant tumours. To address this problem, the YoLov8-MedSAM model is proposed in this research to provide precise and adaptable brain tumour identification and detection segmentation. Additionally, it employs convolutional neural networks (CNNs) to classify and identify tumours in order to distinguish between benign and malignant variations in PAI. The experimental results show that the method proposed in this study not only effectively detects and segments brain tumours of various shapes and sizes but also increases the accuracy of brain tumour classification to 97.02%. The method provides richer and more valuable diagnostic information to the clinic and effectively optimizes the diagnosis and treatment strategy of brain tumours. [ABSTRACT FROM AUTHOR]

Noninvasive monitoring of cardiac development can potentially prevent cardiac anomalies in adulthood. Mouse models provide unique opportunities to study cardiac development and disease in mammals. However, high‐resolution noninvasive functional analyses of murine embryonic cardiac models are challenging because of the small size and fast volumetric motion of the embryonic heart, which is deeply embedded inside the uterus. In this study, a real time volumetric optoacoustic spectroscopy (VOS) platform for whole‐heart visualization with high spatial (100 µm) and temporal (10 ms) resolutions is developed. Embryonic heart development on gestational days (GDs) 14.5–17.5 and quantify cardiac dynamics using time‐lapse‐4D image data of the heart is followed. Additionally, spectroscopic recordings enable the quantification of the blood oxygenation status in heart chambers in a label‐free and noninvasive manner. This technology introduces new possibilities for high‐resolution quantification of embryonic heart function at different gestational stages in mammalian models, offering an invaluable noninvasive method for developmental biology. [ABSTRACT FROM AUTHOR]

The precise detection of volatile organic compounds plays a pivotal role in addressing environmental concerns, industrial safety, and medical diagnostics. The accurate identification and quantification of these compounds because of their ubiquity and potential health hazards has fueled the development of advanced sensing technologies. This work presents a sensing system in the realm of long-wavelength infrared spectroscopy for achieving enhanced selectivity and sensitivity of benzene, toluene, and propane detection through quartz-enhanced photoacoustic spectroscopy. High-resolution gas spectroscopy is made possible by the use of specially designed InAs/AlSb-based quantum cascade lasers, emitting in the wavelength range 13–15 μm, and quartz tuning forks. The sensor system, characterized by its robustness and precision, demonstrates exceptional capabilities in benzene, toluene, and propane detection. The system's capacity for practical applications in environmental monitoring and medical diagnostics is demonstrated by its ability to distinguish these volatile organic compounds with a minimum detection limit of 113 ppb, 3 ppb, and 3 ppm for toluene, benzene, and propane at an integration time of 10 s, even in complex gas matrices. This work advances gas sensing technology while also offering insightful information on spectral interferences, a persistent problem in the field. The results usher in a new era of sophisticated and reliable gas sensing techniques meeting the growing demand for precise volatile organic compounds detectors for environmental monitoring purposes. [ABSTRACT FROM AUTHOR]

SF6 leaked from gas insulation equipment will interfere with the detection of dissolved characteristic gases in transformer oil. In order to determine the impact of SF6 on the detection of dissolved C2H4 gas in oil, a photoacoustic (PA) C2H4 detection system based on the combination of mid‐infrared thermal radiation source and near‐infrared laser was constructed. The excitation light from two bands was incident on a non‐resonant PA cell. The thermal radiation light source and the laser light source were switched to evaluate the interference level of SF6 on the detection of C2H4. The experimental results show that SF6 has significant interference to C2H4 when using a mid‐infrared thermal radiation light source. The interference coefficient is 2014%. The near‐infrared laser based on PA detection method can effectively suppress the interference of SF6 on C2H4. The minimum detection limit of C2H4 reaches 0.6 ppm when the average time is 60 s. [ABSTRACT FROM AUTHOR]

In the context of the Internet of Things, there is a growing demand for real-time monitoring of water distribution systems (WDS). Among the various leak detection methods, acoustic leak detection is considered to be a suitable method. However, existing methods are not very effective in environments with high daytime ambient noise. To address this issue, this paper conducted on-site data collection experiments and designed a monitoring system that combines traditional nighttime monitoring with daytime monitoring, combining water company pipeline inspections and repair work. A large number of daytime audio samples were collected. In this paper, the logarithmic spectrogram (log spectrogram) was used to represent the features of the leak signal. By comparing the features of the signal during day and night, noisy and quiet environments, and leak and normal signals, we identified the interfering frames that required noise reduction, and applied frame-level noise reduction processing to the signal. Based on this, a log PS-ResNet18 model was developed to identify leaks, and its performance was compared with other classification models [including traditional nighttime detection methods, random forests, XGBoost, and convolutional neural network (CNN)]. The results showed that the log PS-ResNet18 model had the best performance, with an all-day accuracy rate of 99.4% and a daytime accuracy rate of 99.3%. In addition, by conducting ablation experiments to explore the role and contribution of the log PS-ResNet18 and noise reduction methods in the model, the results showed that the log spectrogram and noise reduction methods increased the all-day accuracy rate by 18.8% and 23.2%, respectively, and by 24.7% when used together. In another practical application, the log PS-ResNet18 model achieved an all-day detection accuracy rate of 99.6%. This study demonstrated the applicability of the log spectrogram and CNN combination in daytime leak detection, overcoming research limitations in the field. This research presents the log PS-ResNet18 framework, which combines deep learning models and denoised logarithmic spectrograms to improve leak detection in water supply pipelines under daytime environmental noise. The research focuses on field data collection and analysis of cast iron pipes with different diameters in Hangzhou (HZ). The model was tested on cast iron pipes in Lishui (LS) and proved to be effective. The proposed method is highly versatile and can be applied to different regions and pipe materials after sufficient sample collection and model training validation. The research recommends a comprehensive leak monitoring solution that involves initial intelligent detection using front-end noise meters and secondary identification of suspicious audio signals using the log PS-ResNet18 model in the cloud. This enables water utility operators to respond quickly to pipeline leaks, leading to more efficient water resource conservation and improved water supply service quality. [ABSTRACT FROM AUTHOR]

This article reports the nonlinear refractive index (n2) and nonlinear absorption coefficient (β) of acid blue 129 (AB 129) dye-doped polyvinyl alcohol (PVA) thin film with different dye concentrations using Z-scan technique. The experimental technique consists of a continuous wave laser with 5 mW power working at 635 nm wavelength. The normalized transmittance curve suggests that the dye-doped polymer film exhibits a self-defocusing nonlinear index of refraction and a large nonlinear absorption coefficient ascribed to the behaviour of reverse saturable absorption. The order of third-order NLO susceptibility of the sample is estimated to be 10‒5 esu. The dye-doped polymer films show a low-limiting threshold of 0.15 kW cm–2 at 0.04 mM dye concentration and believed that the prepared thin film is a suitable candidate for application in optical limiting. The self-diffraction pattern is observed at far-field and estimated the nonlinear refractive index of the thin film using this technique. The results of the nonlinear refractive index of the sample obtained from the self-diffraction method are comparable with Z-scan results. [ABSTRACT FROM AUTHOR]

This article provides an overview of the progress made in skin imaging using two emerging imaging modalities, optical coherence tomography (OCT) and photoacoustic imaging (PAI). Over recent years, these technologies have significantly advanced our understanding of skin structure and function, offering non-invasive and high-resolution insights previously unattainable. The review begins by briefly describing the fundamental principles of how OCT and PAI capture images. It then explores the evolving applications of OCT in dermatology, ranging from diagnosing skin disorders to monitoring treatment responses. This article continues by briefly describing the capabilities of PAI imaging, and how PAI has been used for melanoma and non-melanoma skin cancer detection and characterization, vascular imaging, and more. The third section describes the development of multimodal skin imaging systems that include OCT, PAI, or both modes. A comparative analysis between OCT and PAI is presented, elucidating their respective strengths, limitations, and synergies in the context of skin imaging. [ABSTRACT FROM AUTHOR]

The significance of intelligent sensor systems has grown across diverse sectors, including healthcare, environmental surveillance, industrial automation, and security. Photoacoustic gas sensors are a promising type of optical gas sensor due to their high sensitivity, enhanced frequency selectivity, and fast response time. However, they have limitations such as dependence on a high-power light source, a requirement for a high-quality acoustic signal detector, and sensitivity to environmental factors, affecting their accuracy and reliability. Machine learning has great potential in the analysis and interpretation of sensor data as it can identify complex patterns and make accurate predictions based on the available data. We propose a novel approach that utilizes wavelet analysis and neural networks with enhanced architectures to improve the accuracy and sensitivity of photoacoustic gas sensors. Our proposed approach was experimentally tested for methane concentration measurements, showcasing its potential to significantly advance the field of gas detection and analysis, providing more accurate and reliable results. [ABSTRACT FROM AUTHOR]

A miniaturized, broadband (800–5000 Hz) absorber with >95% absorption is proposed and realized. The absorber is designed using quarter-wavelength resonator tubes coiled as a rectangular "meta-atom." The study describes the basic theoretical aspects of the absorber and compares it with the numerical simulations, fabrication, and experimental validation. The meta-atom, simple in design and made with fabrication-friendly materials, can provide greater spatial coverage through tiling over large surfaces. [ABSTRACT FROM AUTHOR]

Lanthanum doped MgTiO 3 (La–MgTiO 3 ; n (La): n (Mg) = 0.05:0.95) was synthesized using a sol–gel method, and a layer of this material was supported on quartz microspheres to produce La–MgTiO 3 (x%)/SiO 2 microspheres (LMTO(x%)/SiO 2 ; where x% represents the weight fraction of La–MgTiO 3 in the microspheres). The crystal size of MgTiO 3 decreased from 43.4 nm in La–MgTiO 3 to 29.2 nm in LMTO(20 %)/SiO 2 , and the bandgap energies increased from 3.34 eV (La–MgTiO 3) to 3.91 eV (LMTO(20 %)/SiO 2). The supported La–MgTiO 3 contributed the most to the total surface area of the LMTO(x%)/SiO 2 microspheres; further, the specific surface area of the microspheres decreased with decreasing La–MgTiO 3 content. The photoluminescence intensity of the microspheres was significantly lower than that of La–MgTiO 3. The activity of La–MgTiO 3 was enhanced after loading onto the quartz microspheres. The maximum photocatalytic activity was obtained using LMTO(40 %)/SiO 2 , while the azophloxine degradation efficiency slightly decreased after five reaction cycles. [ABSTRACT FROM AUTHOR]

David Mauzerall was born on July 22, 1929 to a working-class family in the small, inland textile town of Sanford, Maine. Those humble origins instilled a lifelong frugality and an innovative spirit. After earning his PhD degree in 1954 in physical organic chemistry with Frank Westheimer at the University of Chicago, he joined The Rockefeller Institute for Medical Research (now University) as a postdoctoral fellow that summer, rose to the rank of professor, and remained there for the rest of his career. His work over more than 60 years encompassed porphyrin biosynthesis, photoinduced electron-transfer reactions in diverse architectures (solutions, bilayer lipid membranes, reaction centers, chromatophores, and intact leaves), the light-saturation curve of photosynthesis, statistical treatments of photoreactions, and "all-things porphyrins." His research culminated in studies he poetically referred to as "listening to leaves" through the use of pulsed photoacoustic spectroscopy to probe the course and thermodynamics of photosynthesis in its native state. His research group was always small; indeed, of 185 total publications, 39 were singly authored. In brief, David Mauzerall has blended a deep knowledge of distinct disciplines of physical organic chemistry, photochemistry, spectroscopy and biophysics with ingenious experimental methods, incisive mathematical analysis, pristine personal integrity, and unyielding love of science to deepen our understanding of photosynthesis in its broadest context. He thought creatively – and always independently. His work helped systematize the fields of photosynthesis and the origin of life and made them more quantitative. The present article highlights a number of salient scientific discoveries and includes comments from members of his family, friends, and collaborators (Gary Brudvig, Greg Edens, Paul Falkowski, Alzatta Fogg, G. Govindjee, Nancy Greenbaum, Marilyn Gunner, Harvey Hou, Denise and Michele Mauzerall, Thomas Moore, and William Parson) as part of a celebration of his 95th birthday. [ABSTRACT FROM AUTHOR]

Freeze- and spray-dried inclusion complexes (ICs) of chlorhexidine (CHX) in β-cyclodextrin were characterized by Fourier transform (FT)-Raman, 1H nuclear magnetic resonance (NMR), and photoacoustic spectroscopy. The active Raman modes of CHX were simulated using the density functional theory. By considering semiempirical calculations, it was observed that the guest penetrates on the wider rim of the host in a proportion of 1:2. We observe from the FT-Raman analysis that the drying method influences the CHX:β-cyclodextrin conformational adjustment by the rearrangement of hydrophilic biguanides of the guest. The photoacoustic spectroscopy results inferred that the freeze-drying method provided a better inclusion due to a lower interaction between phenyl groups and hexamethylene of CHX. The freeze-dried IC achieved a faster dissolution pattern. These ICs provided immediate drug dissolution profiles in an aqueous medium better than a pure drug. The release profiles of freeze- and spray-dried ICs were explained by Fickian diffusion. These data support further planning and development projects of novel immediate release systems based on CHX. [ABSTRACT FROM AUTHOR]

The significance of intelligent sensor systems has grown across diverse sectors, including healthcare, environmental surveillance, industrial automation, and security. Photoacoustic gas sensors are a promising type of optical gas sensor due to their high sensitivity, enhanced frequency selectivity, and fast response time. However, they have limitations such as dependence on a high-power light source, a requirement for a high-quality acoustic signal detector, and sensitivity to environmental factors, affecting their accuracy and reliability. Machine learning has great potential in the analysis and interpretation of sensor data as it can identify complex patterns and make accurate predictions based on the available data. We propose a novel approach that utilizes wavelet analysis and neural networks with enhanced architectures to improve the accuracy and sensitivity of photoacoustic gas sensors. Our proposed approach was experimentally tested for methane concentration measurements, showcasing its potential to significantly advance the field of gas detection and analysis, providing more accurate and reliable results.

The quartz tuning fork used as an acoustic sensor in quartz-enhanced photo-acoustic spectroscopy gas detection systems is usually read out by means of a transimpedance preamplifier based on a low-noise operational amplifier closed in a feedback loop. The gain–bandwidth product of the operational amplifier used in the circuit is a key parameter which must be properly chosen to guarantee that the circuit works as expected. Here, we demonstrate that if the value of this parameter is not sufficiently large, the response of the preamplifier exhibits a peak at a frequency which does not coincide with the series resonant frequency of the quartz tuning fork. If this peak frequency is selected for modulating the laser bias current and is also used as the reference frequency of the lock-in amplifier, a penalty results in terms of signal-to-noise ratio at the output of the QEPAS sensor. This worsens the performance of the gas sensing system in terms of ultimate detection limits. We show that this happens when the front-end preamplifier of the quartz tuning fork is based on some amplifier models that are typically used for such application, both when the integration time of the lock-in amplifier filter is long, to boost noise rejection, and when it is short, in order to comply with a relevant measurement rate.

Photoacoustic imaging (PAI)‐guided photothermal therapy (PTT) in the second near‐infrared (NIR‐II, 1000–1700 nm) window has been attracting attention as a promising cancer theranostic platform. Here, it is reported that the π‐extended porphyrins fused with one or two nanographene units (NGP‐1 and NGP‐2) can serve as a new class of NIR‐responsive organic agents, displaying absorption extending to ≈1000 and ≈1400 nm in the NIR‐I and NIR‐II windows, respectively. NGP‐1 and NGP‐2 are dispersed in water through encapsulation into self‐assembled nanoparticles (NPs), achieving high photothermal conversion efficiency of 60% and 69%, respectively, under 808 and 1064 nm laser irradiation. Moreover, the NIR‐II‐active NGP‐2‐NPs demonstrated promising photoacoustic responses, along with high photostability and biocompatibility, enabling PAI and efficient NIR‐II PTT of cancer in vivo. [ABSTRACT FROM AUTHOR]

A comprehensive investigation into the interaction between a continuous wave (CW) laser and lightweight quartz fiber reinforced phenolic (LQFRP) composite would provide valuable insights into the characteristics and performance of ablation. To simulate the CW laser ablation of LQFRP composite, a 2D symmetrical element model was developed, incorporating the heat conduction equation, resin pyrolysis mechanism, and deformed geometry module. This model was the first to examine the internal pyrolysis degree and gas flow field of LQFRP composite under CW laser irradiation, and its predictions were in reasonable agreement with experimental measurements. Additionally, the model was used to simulate CW laser ablation with varying spot sizes and power densities. The results revealed that during the laser ablation process, an internal high‐pressure zone formed on the side of the ablation hole. The volatilization of SiO2 was identified as the dominant dissipation mechanism for material removal. The width of the ablation hole was positively correlated with the laser spot size, while the depth of the ablation hole was positively correlated with the laser power density. Highlights: The model first studied the internal pyrolysis degree and flow field of LQFRP composite under laser irradiation.The volatilization of SiO2 was identified as the dominant dissipation mechanism for material removal.An internal high‐pressure zone formed on the side of the ablation hole during the laser ablation process.The width of the ablation hole was positively correlated with the laser spot size, while the depth of the ablation hole was positively correlated with the laser power density. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) exhibits both pro‐ and anti‐tumor effects. Therefore, real‐time in vivo imaging and quantification of tumor NO dynamics are essential for understanding the conflicting roles of NO played in pathophysiology. The current molecular probes, however, cannot provide high‐resolution imaging in deep tissues, making them unsuitable for these purposes. Herein, we designed a photoacoustic probe with an absorption maximum beyond 1000 nm for high spatial quantitative imaging of in vivo tumor NO dynamics. The probe exhibits remarkable sensitivity, selective ratiometric response behavior, and good tumor‐targeting abilities, facilitating ratiometric imaging of tumor NO throughout tumor progression in a micron‐resolution level. Using the probe as the imaging agent, we successfully quantified NO dynamics in tumor, liver and kidney. We have pinpointed an essential concentration threshold of around 80 nmol/cm3 for NO, which plays a crucial role in the "double‐edged‐sword" function of NO in tumors. Furthermore, we revealed a reciprocal relationship between the NO concentration in tumors and that in the liver, providing initial insights into the possible NO‐mediated communication between tumor and the liver. We believe that the probe will help resolve conflicting aspects of NO biology and guide the design of imaging agents for tumor diagnosis and anti‐cancer drug screening. [ABSTRACT FROM AUTHOR]

Elastography can be used as a diagnostic method for quantitative characterization of tissue hardness information and thus, differential changes in pathophysiological states of tissues. In this study, we propose a new method for shear wave elastography (SWE) based on laser-excited shear wave, called photoacoustic shear wave elastography (PASWE), which combines photoacoustic (PA) technology with ultrafast ultrasound imaging. By using a focused laser to excite shear waves and ultrafast ultrasonic imaging for detection, high-frequency excitation of shear waves and noncontact elastic imaging can be realized. The laser can stimulate the tissue with the light absorption characteristic to produce the thermal expansion, thus producing the shear wave. The frequency of shear wave induced by laser is higher and the frequency band is wider. By tracking the propagation of shear wave, Young's modulus of tissue is reconstructed in the whole shear wave propagation region to further evaluate the elastic information of tissue. The feasibility of the method is verified by experiments. Compared with the experimental results of supersonic shear imaging (SSI), it is proved that the method can be used for quantitative elastic imaging of the phantoms. In addition, compared with the SSI method, this method can realize the noncontact excitation of the shear wave, and the frequency of the shear wave excited by the laser is higher than that of the acoustic radiation force (ARF), so the spatial resolution is higher. Compared to the traditional PA elastic imaging method, this method can obtain a larger imaging depth under the premise of ensuring the imaging resolution, and it has potential application value in the clinical diagnosis of diseases requiring noncontact quantitative elasticity. [ABSTRACT FROM AUTHOR]

Photoacoustic imaging (PAI) is a noninvasive emerging imaging method based on the photoacoustic effect, which provides necessary assistance for medical diagnosis. It has the characteristics of large imaging depth and high contrast. However, limited by the equipment cost and reconstruction time requirements, the existing PAI systems distributed with annular array transducers are difficult to take into account both the image quality and the imaging speed. In this paper, a triple-path feature transform network (TFT-Net) for ring-array photoacoustic tomography is proposed to enhance the imaging quality from limited-view and sparse measurement data. Specifically, the network combines the raw photoacoustic pressure signals and conventional linear reconstruction images as input data, and takes the photoacoustic physical model as a prior information to guide the reconstruction process. In addition, to enhance the ability of extracting signal features, the residual block and squeeze and excitation block are introduced into the TFT-Net. For further efficient reconstruction, the final output of photoacoustic signals uses 'filter-then-upsample' operation with a pixel-shuffle multiplexer and a max out module. Experiment results on simulated and in-vivo data demonstrate that the constructed TFT-Net can restore the target boundary clearly, reduce background noise, and realize fast and high-quality photoacoustic image reconstruction of limited view with sparse sampling. [ABSTRACT FROM AUTHOR]

We propose a novel high‐performance dual‐resonance enhanced photoacoustic spectroscopy (DRE‐PAS) gas sensor based on a highly sensitive fiber optic cantilever beam microphone and a high‐Q spherical photoacoustic cell (PAC). The first‐order resonant frequency (FORF) of the spherical PAC is analyzed by finite element analysis to match the FORF of the cantilever microphone for the double resonance enhancement of the photoacoustic signal. The photoacoustic spectroscopy (PAS) system, including the DRE‐PAS sensor, a 1532.8 nm distributed feedback laser, and a high‐speed spectrometer, has been successfully exploited for trace acetylene (C2H2) detection. The experimental results show that the limit of detection (LOD) is 106.8 parts‐per‐billion (ppb) with an integral time of 1 s, and the LOD can be further reduced to 11.03 ppb by Allan‐Werle deviation for 100 s integral time. The normalized noise equivalent absorption coefficient can be obtained as 2.44 × 10−8 cm−1 WHz−1/2. The reported DRE‐PAS gas sensor has the superior characteristics of photoacoustic signal enhancement, high sensitivity, and strong antielectromagnetic interference capability, which can provide a new solution for PAS development. [ABSTRACT FROM AUTHOR]

The photoinduced dipole force (PiDF) is an attractive force arising from the Coulombic interaction between the light-induced dipoles on the illuminated tip and the sample. It shows extreme sample-tip distance and refractive index dependence, which is promising for nanoscale infrared (IR) imaging of ultrathin samples. However, the existence of PiDF in the mid-IR region has not been experimentally demonstrated due to the coexistence of photoinduced thermal force (PiTF), typically one to two orders of magnitude higher than PiDF. In this study, we demonstrate that, with the assistance of surface phonon polaritons, the PiDF of c-quartz can be enhanced to surpass its PiTF, enabling a clear observation of PiDF spectra reflecting the properties of the real part of permittivity. Leveraging the detection of the PiDF of phonon polaritonic substrate, we propose a strategy to enhance the sensitivity and contrast of photoinduced force responses in transmission images, facilitating the precise differentiation of the heterogeneous distribution of ultrathin samples. [ABSTRACT FROM AUTHOR]

Internal discharge and overheating faults in sulfur hexafluoride (SF6) gas-insulated electrical equipment will generate a series of characteristic gas products. Hydrogen fluoride (HF) is one of the main decomposition gases under discharge failure. Because of its extremely corrosive nature, it can react with other materials in gas-insulated switchgear (GIS), resulting in a short existence time, so it needs to be detected online. Resonant gas photoacoustic spectroscopy has the advantage of high sensitivity, fast response, and no sample gas consumption, and can be used for the online detection of flowing gas. In this paper, a simulated GIS corona discharge experimental platform was built, and the HF generated in the discharge was detected online by gas photoacoustic spectroscopy. The absorption peak of HF molecule near 1312.59 nm was selected as the absorption spectral line, and a resonant photoacoustic cell was designed. To improve the detection sensitivity of HF, wavelength modulation and second-harmonic detection technology were used. The online monitoring of HF in the simulated GIS corona discharge fault was successfully realized. The experimental results show that the sensitivity of the designed photoacoustic spectroscopy detection system for HF is 0.445 μV/(μL/L), and the limit of detection (LOD) is 0.611 μL/L. [ABSTRACT FROM AUTHOR]

Photoacoustic imaging (PAI) is a rapidly developing emerging non-invasive biomedical imaging technique that combines the strong contrast from optical absorption imaging and the high resolution from acoustic imaging. Abnormal biological tissues (such as tumors and inflammation) generate different levels of thermal expansion after absorbing optical energy, producing distinct acoustic signals from normal tissues. This technique can detect small tissue lesions in biological tissues and has demonstrated significant potential for applications in tumor research, melanoma detection, and cardiovascular disease diagnosis. During the process of collecting photoacoustic signals in a PAI system, various factors can influence the signals, such as absorption, scattering, and attenuation in biological tissues. A single ultrasound transducer cannot provide sufficient information to reconstruct high-precision photoacoustic images. To obtain more accurate and clear image reconstruction results, PAI systems typically use a large number of ultrasound transducers to collect multi-channel signals from different angles and positions, thereby acquiring more information about the photoacoustic signals. Therefore, to reconstruct high-quality photoacoustic images, PAI systems require a significant number of measurement signals, which can result in substantial hardware and time costs. Compressed sensing is an algorithm that breaks through the Nyquist sampling theorem and can reconstruct the original signal with a small number of measurement signals. PAI based on compressed sensing has made breakthroughs over the past decade, enabling the reconstruction of low artifacts and high-quality images with a small number of photoacoustic measurement signals, improving time efficiency, and reducing hardware costs. This article provides a detailed introduction to PAI based on compressed sensing, such as the physical transmission model-based compressed sensing method, two-stage reconstruction-based compressed sensing method, and single-pixel camera-based compressed sensing method. Challenges and future perspectives of compressed sensing-based PAI are also discussed. [ABSTRACT FROM AUTHOR]

Background: It is challenging to visually identify tiny and concealed foreign objects within the body due to their small size and subcutaneous location while they can cause infections. Methods: A non‐contact photoacoustic system based on Rosencwaig‐Gersho photoacoustic theory and dual modulator method is developed for detecting foreign objects in meat. Result: The experiments conducted validate the successful development of this measurement technique with 10 μm spatial resolution and its corresponding mathematical model, demonstrating an 11% Mean Absolute Percentage Error (MAPE) in comparison to the experimental results. Dual modulator successfully regulates laser energy at MPE limit. Conclusion: The utilization of non‐contact photoacoustic signal intensity measurements enables the identification of foreign objects within the body. Further, the application of mathematical modelling can validate the measurement outcomes. These findings serve as a foundation for creating an affordable and straightforward foreign body detector. [ABSTRACT FROM AUTHOR]

Chirality, an intrinsic property of certain entities in the universe, is characterized by the absence of mirror symmetry. Understanding chirality is crucial as it influences molecular interactions and properties. Circular dichroism (CD), measured using circularly polarized light, is a standard technique for probing chirality, but its sensitivity is often limited. Here, we explore extrinsic chirality (i.e. a property arising from asymmetric achiral materials when observed from out of normal incidence directions), using photo-acoustic spectroscopy (PAS). PAS allows direct measurement of local absorption, by monitoring the heat produced and transferred to the surrounding air, regardless the transmitted, reflected, and scattered light that flows away from the sample. In conventional techniques, the CD is usually measured by taking into account only the extinction as transmitted (or reflected) light. In this study, we introduce a new PAS setup that employs an oblique-incidence laser to study extrinsic chirality in silver-coated self-assembled metasurfaces. Our experimental results reveal intriguing CD trends dependent on the angle of incidence and wavelength, indicative of extrinsic chirality. This study expands the application of PAS, enabling simultaneous analysis of multiple wavelengths and providing valuable insights into chiral metasurfaces. [ABSTRACT FROM AUTHOR]

Photoacoustic spectroscopy (PAS) is an important technique for the characterization of materials by measuring the heat produced due to the non-radiative transitions. Here, the authors have fabricated a photoacoustic cell and made parametric studies to get maximum signal sensitivity. For the optimum signal, the cavity volume of the sample chamber is found to be 1.763 × 10–6 m3. After optimization of the cell, the thermal diffusivity of hummers method synthesized graphene oxide (GO) powder was measured using laser excitation at 980 nm and it is found to ∼(1.84 ± 0.10) × 10–4 m2/s. Also, the thermal diffusivity of the same sample was measured using 560 and 680 nm excitation wavelengths. No measurable change in thermal diffusivity with excitation wavelength is seen and it confirms that thermal diffusivity is independent of the excitation wavelength. Lastly, photoacoustic spectrum of the GO sample was measured in the 400–1200 nm range and compared with the spectrum of lamp black. [ABSTRACT FROM AUTHOR]

This study focused on quantifying the gas concentrations of ethylene, benzene, toluene, and ozone within an urban area in the southern region of Romania. The gas sampling campaign, conducted between March and August 2021, took place in three different locations from the point of view of the architectural structure, and the sampling height was 1.5 m. Sampling occurred on weekdays (Monday through Friday) during daylight hours, with subsequent concentration analysis employing descriptive statistics, diurnal cycles, and seasonal assessments. A highly sensitive and selective detector, employing laser photoacoustic spectroscopy, was utilized to monitor pollutants. The average concentrations (±Standard Deviation) were determined as follows: ethylene at 116.82 ± 82.37 parts per billion (ppb), benzene at 1.13 ± 0.32 ppb, toluene at 5.48 ± 3.27 ppb, and ozone at 154.75 ± 68.02 ppb, with peak levels observed during the summer months. Diurnal patterns were observable for ethylene, benzene, and toluene, exhibiting higher concentrations during the early hours of the day followed by a decrease towards the evening. In contrast, ozone concentrations peaked in the evening compared to the early part of the day. Thus, perceptible effects were demonstrated on gas concentrations as a result of the influence of meteorological variables. Moreover, the high toluene/benzene ratio indicated traffic and industrial emissions as primary sources of these pollutants. Of the four gases monitored, benzene and ozone exceeded regulatory limits, particularly during the summer season, highlighting concerns regarding air quality in the studied urban environment. [ABSTRACT FROM AUTHOR]

Developing Type‐I photosensitizers provides an attractive approach to solve the dilemma of inadequate efficacy of photodynamic therapy (PDT) caused by the inherent oxygen consumption of traditional Type‐II PDT and anoxic tumor microenvironment. The challenge for the exploration of Type‐I PSs is to facilitate the electron transfer ability of photosensitization molecules for transforming oxygen or H2O to reactive oxygen species (ROS). Herein, we propose an electronic acceptor‐triggered photoinduced electron transfer (a‐PET) strategy promoting the separation of electron‐hole pairs by marriage of two organic semiconducting molecules of a non‐fullerene scaffold‐based photosensitizer and a perylene diimide that significantly boost the Type‐I PDT pathway to produce plentiful ROS, especially, inducing 3.5‐fold and 2.5‐fold amplification of hydroxyl (OH⋅) and superoxide (O2−⋅) generation. Systematic mechanism exploration reveals that intermolecular electron transfer and intramolecular charge separation after photoirradiation generate a competent production of radical ion pairs that promote the Type‐I PDT process by theoretical calculation and ultrafast femtosecond transient absorption (fs‐TA) spectroscopy. By complementary tumor diagnosis with photoacoustic imaging and second near‐infrared fluorescence imaging, this as‐prepared nanoplatform exhibits fabulous photocytotoxicity in harsh hypoxic conditions and terrific cancer revoked abilities in living mice. We envision that this work will broaden the insight into high‐efficiency Type‐I PDT for cancer phototheranostics. [ABSTRACT FROM AUTHOR]

Photoacoustic Spectroscopy (PAS) is a potential method for the noninvasive detection of blood glucose. However random blood glucose testing can help to diagnose diabetes at an early stage and is crucial for managing and preventing complications with diabetes. In order to improve the diagnosis, control, and treatment of Diabetes Mellitus, an appropriate approach of noninvasive random blood glucose is required for glucose monitoring. A polynomial kernel-based ridge regression is proposed in this paper to detect random blood glucose accurately using PAS. Additionally, we explored the impact of the biological parameter BMI on the regulation of blood glucose, as it serves as the primary source of energy for the body's cells. The kernel function plays a pivotal role in kernel ridge regression as it enables the algorithm to capture intricate non-linear associations between input and output variables. Using a Pulsed Laser source with a wavelength of 905 nm, a noninvasive portable device has been developed to collect the Photoacoustic (PA) signal from a finger. A collection of 105 individual random blood glucose samples was obtained and their accuracy was assessed using three metrics: Root Mean Square Error (RMSE), Mean Absolute Difference (MAD), and Mean Absolute Relative Difference (MARD). The respective values for these metrics were found to be 10.94 (mg/dl), 10.15 (mg/dl), and 8.86%. The performance of the readings was evaluated through Clarke Error Grid Analysis and Bland Altman Plot, demonstrating that the obtained readings outperformed the previously reported state-of-the-art approaches. To conclude the proposed IoT-based PAS random blood glucose monitoring system using kernel-based ridge regression is reported for the first time with more accuracy. [ABSTRACT FROM AUTHOR]

Herein, this study describes a sample preconcentration apparatus based on a metal–organic framework (MOF) of NH2‐UIO‐66@PDMS adsorbent, which is first coupled to photoacoustic spectroscopy (PAS) technology for detection of acetone. The MOF selectively traps acetone out of complex samples and releases it into the photoacoustic (PA) cell, where PA signal intensity is recorded by PAS sensing system based on a cheap amplitude modulated UV LED as light source. The signal intensity is enhanced by 11 times after preconcentration of NH2‐UIO‐66@PDMS (100 mg). The preconcentration apparatus not only enhances sensitivity of sensor, but also promotes the anti‐interference ability for common interferents (carbon dioxide, oxygen and water vapor, ethanol, propanol, etc.) of the sensor. As expected, the established PA sensor possesses a detection limit of 0.23 ppm for measuring acetone, which can feasibly be applied for the analysis of acetone in patients breath samples. This work provides a good example of the preconcentration effect of MOF for promoting PA sensor analytical performance, and the prospect of medical diagnosis. [ABSTRACT FROM AUTHOR]

Tumor-associated macrophages (TAMs) are a key component of the immunosuppressive cell and cytokine network. They play a critical role in allowing tumors to evade the immune system. To successfully combat cancer through immunotherapy, it is essential to re-educate TAMs. This study introduces a TAM-targeting nanoreporter that can reshape the tumor immune microenvironment, enhancing cancer immunotherapy. Additionally, the nanoreporter allows for the monitoring of TAM immune activation through protease-responsive photoacoustic/fluorescent imaging. [Display omitted] • This paper described a non-invasive optical imaging technique for tracing the immune activation of tumor-associated macrophages. • This nanoreporter could target TAMs and achieve precise controlled release of TLR agonists. • This "all-in-one" nanoplatform shows promise in cancer diagnosis, treatment and prognosis assessment. Tumor-associated macrophages (TAMs) are vital in the tumor microenvironment, contributing to immunosuppression and therapy tolerance. Despite their importance, the precise re-education of TAMs in vivo continues to present a formidable challenge. Moreover, the lack of real-time and efficient methods to comprehend the spatiotemporal kinetics of TAMs repolarization remains a significant hurdle, severely hampering the accurate assessment of treatment efficacy and prognosis. Herein, we designed a metal–organic frameworks (MOFs) based Caspase-1 nanoreporter (MCNR) that can deliver a TLR7/8 agonist to the TAMs and track time-sensitive Caspase-1 activity as a direct method to monitor the initiation of immune reprogramming. This nanosystem exhibits excellent TAMs targeting ability, enhanced tumor accumulation, and stimuli-responsive behavior. By inducing the reprogramming of TAMs, they were able to enhance T -cell infiltration in tumor tissue, resulting in inhibited tumor growth and improved survival in mice model. Moreover, MCNR also serves as an activatable photoacoustic and fluorescent dual-mode imaging agent through Caspase-1-mediated specific enzyme digestion. This feature enables non-invasive and real-time antitumor immune activation monitoring. Overall, our findings indicate that MCNR has the potential to be a valuable tool for tumor immune microenvironment remodeling and noninvasive quantitative detection and real-time monitoring of TAMs repolarization to immunotherapy in the early stage. [ABSTRACT FROM AUTHOR]

Differential photoacoustic spectroscopy (DPAS) cells are usually excited on the first longitudinal ring mode, with a microphone situated in the middle of each of the two resonator tubes. However, it is known from other photoacoustic spectroscopy cell designs that connecting the microphones via a capillary can lead to signal enhancement. By means of finite element method (FEM) simulations, we compared such a photoacoustic spectroscopy (PAS) cell with a capillary to a DPAS cell with a capillary attached to each of the two resonators and showed that the behavior of both systems is qualitatively the same: In both the PAS and the DPAS cell, in-phase and anti-phase oscillations of the coupled system (resonator–capillary) can be excited. In the DPAS cell, capillaries of suitable length also increase the pressure signal at the microphones according to the FEM simulations. For different capillary diameters (1.2 mm/1.7 mm/2.2 mm), the respective optimal capillary length (36–37.5 mm) and signal amplification was determined (94%, 70%, 53%). According to the results of these FEM simulations, a significant increase in sensitivity can, therefore, also be achieved in DPAS cells by expanding them with thin tubes leading to the microphones. [ABSTRACT FROM AUTHOR]

The ongoing biodiversity crisis, driven by factors such as land-use change and global warming, emphasizes the need for effective ecological monitoring methods. Acoustic monitoring of biodiversity has emerged as an important monitoring tool. Detecting human voices in soundscape monitoring projects is useful both for analyzing human disturbance and for privacy filtering. Despite significant strides in deep learning in recent years, the deployment of large neural networks on compact devices poses challenges due to memory and latency constraints. Our approach focuses on leveraging knowledge distillation techniques to design efficient, lightweight student models for speech detection in bioacoustics. In particular, we employed the MobileNetV3-Small-Pi model to create compact yet effective student architectures to compare against the larger EcoVAD teacher model, a well-regarded voice detection architecture in eco-acoustic monitoring. The comparative analysis included examining various configurations of the MobileNetV3-Small-Pi-derived student models to identify optimal performance. Additionally, a thorough evaluation of different distillation techniques was conducted to ascertain the most effective method for model selection. Our findings revealed that the distilled models exhibited comparable performance to the EcoVAD teacher model, indicating a promising approach to overcoming computational barriers for real-time ecological monitoring. [ABSTRACT FROM AUTHOR]

We report the development of a combined optical parametric oscillator based on a fan-out MgO:PPLN crystal and a HgGa2S4 crystal, providing smooth wavelength tuning in the spectral range from 2.5 to 10.8 μm. A transversely pumped Nd:YAG laser with a pulse energy of ∼4 mJ and a spatial beam distribution described by a second-order Gaussian function along the x axis and a fourth-order Gaussian function along the y axis is used as a pump source. A maximum achievable radiation energy of the optical parametric oscillator is at a level of 360 μJ for a wavelength of 3.3 μm, 130 μJ for a wavelength of 4.73 μm, and 110 μJ for a wavelength of 7.40 μm. The developed radiation source is used to record absorption spectra of gas mixtures of methane, propane and nitrogen dioxide. [ABSTRACT FROM AUTHOR]

Photoacoustic imaging (PAI) is a rapidly developing biomedical imaging technology. Linear array-based photoacoustic tomography (LA-PAT) is one of the most popular configurations of cross-sectional PAI due to its simplicity and clinical translatability. However, when using an optical fiber for LA-PAT, the optical beam shape is deformed due to rapid divergence and, therefore, a larger area on the tissue is illuminated (and the illumination across the linear array is non-uniform), leading to the acquisition of PA signals outside the desired cross-section, which generates artifacts and degrades image resolution. A Powell lens is an optical element that converts a circular beam profile to a nearly linear flat-top profile. In this paper, a Powell lens is used to generate a uniform line illumination scheme that is evaluated with Zemax OpticStudio 2023 R1.02. The system is then characterized experimentally, and the performance is compared with a conventional illumination scheme in LA-PAT. [ABSTRACT FROM AUTHOR]