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Highlights: Based on Fe-Hpdca-PDMS and carbon nanotube composite, an optoacoustic patch is developed, which can recover from the damage induced by cutting or laser irradiation at room temperature. The patch has high laser damage threshold (183.44 mJ cm−2) and optoacoustic energy conversion efficiency (10.66×10−3). The patch has been successfully examined in acoustic flow, thrombolysis, and wireless energy harvesting, which may provide new insights into the field of the design and fabrication of novel ultrasound devices for biomedical applications. Compared with traditional piezoelectric ultrasonic devices, optoacoustic devices have unique advantages such as a simple preparation process, anti-electromagnetic interference, and wireless long-distance power supply. However, current optoacoustic devices remain limited due to a low damage threshold and energy conversion efficiency, which seriously hinder their widespread applications. In this study, using a self-healing polydimethylsiloxane (PDMS, Fe-Hpdca-PDMS) and carbon nanotube composite, a flexible optoacoustic patch is developed, which possesses the self-healing capability at room temperature, and can even recover from damage induced by cutting or laser irradiation. Moreover, this patch can generate high-intensity ultrasound (> 25 MPa) without the focusing structure. The laser damage threshold is greater than 183.44 mJ cm−2, and the optoacoustic energy conversion efficiency reaches a major achievement at 10.66 × 10−3, compared with other carbon-based nanomaterials and PDMS composites. This patch is also been successfully examined in the application of acoustic flow, thrombolysis, and wireless energy harvesting. All findings in this study provides new insight into designing and fabricating of novel ultrasound devices for biomedical applications. [ABSTRACT FROM AUTHOR]

The photoacoustic effect is governed by a wave equation with a source term proportional to the time derivative of the optical heat deposition per unit volume and time. Although the typical configuration for generation of the photoacoustic effect makes use of pulsed or amplitude modulated optical beams, the form of the source term in the wave equation indicates that a continuous optical source moving in an absorbing medium is capable of sound generation as well. Here, the properties of simple sources moving in one, two, and three space dimensions are reviewed. The salient feature of sources moving in one-dimension at sound speed is that the amplitude of the acoustic wave increases with time without bound according to linear acoustics. Two schemes, one in the time-domain and the other in the frequency-domain, that take advantage of this principle for increasing the sensitivity of trace gas detection are reviewed. [ABSTRACT FROM AUTHOR]

Miniaturized sound generators are attractive to realize intriguing functions. Thermoacoustic device's application is seriously limited due to the frequency‐doubling phenomenon. To address this issue, photoacoustic sound generator is considered as a promising alternative. Here, based on vertical single‐wall carbon nanotubes (CNTs) array, we introduce a photoacoustic sound generator with internal nano‐Helmholtz cavity. Different from traditional device that generates sound by periodically heating up the open space air around material, this sound generator produces an audio signal by forming a forced vibration of the air inside the CNTs. Interestingly, anomalous photoacoustic behavior is observed that the sound pressure level (SPL) curve has a resonance peak, the corresponding frequency of which is inversely proportional to the CNTs array's height. Furthermore, the energy conversion efficiency of this photoacoustic device is 1.64 times as large as that of a graphene sponge‐based photoacoustic device. Most importantly, this device can be employed for music playing, bringing a new clew for the development of musical instruments in the future. [ABSTRACT FROM AUTHOR]

Nonlinear oscillations in micro- and nanoelectromechanical systems have emerged as an exciting research area in recent years due to their promise in realizing low-power, scalable, and reconfigurable mechanical memory and logic devices. Here, we report ultralow-power mechanical memory operations utilizing the nonlinear oscillation regime of GaN microcantilevers with embedded piezotransistive AlGaN/GaN heterostructure field effect transistors as highly sensitive deflection transducers. Switching between the high and low oscillatory states of the nonlinear oscillation regime was demonstrated using a novel phase-controlled opto-mechanical excitation setup, utilizing a piezo actuator and a pulsed laser as the primary and secondary excitation sources, respectively. Laser-based photoacoustic excitation was amplified through plasmonic absorption in Au nanoparticles deposited on a transistor. Thus, the minimum switching energy required for reliable memory operations was reduced to less than a picojoule (pJ), which translates to one of the lowest ever reported, when normalized for mass. [ABSTRACT FROM AUTHOR]

A thermodynamic analysis of the Cr-Ge system suggested that it was possible to produce a nanostructured Cr3Ge phase by mechanical alloying. The same analysis showed that, due to low activation energies, Cr-poor crystalline and/or amorphous alloy could also be formed. In fact, when the experiment was performed, Cr11Ge19 and amorphous phases were present for small milling times. For milling times larger than 15?h these additional phases decomposed and only the nanostructured Cr3Ge phase remained up to the highest milling time used (32?h). From the differential scanning calorimetry measurements, the Avrami exponent n was obtained, indicating that the nucleation and growth of the nanostructured Cr3Ge phase may be restricted to one or two dimensions, where the Cr and Ge atoms diffuse along the surface and grain boundaries. In addition, contributions from three-dimensional diffusion with a constant nucleation rate may be present. The thermal diffusivity of the nanostructured Cr3Ge phase was determined by photoacoustic absorption spectroscopy measurements. [ABSTRACT FROM AUTHOR]

Fiber laser technology has experienced a rapid growth over the past decade owing to increased applications in precision measurement and optical testing, medical care, and industrial applications, including laser welding, cleaning, and manufacturing. A fiber laser can output laser pulses with high energy, a high repetition rate, a controllable wavelength, low noise, and good beam quality, making it applicable in photoacoustic imaging. Herein, recent developments in fiber-laser-based photoacoustic microscopy (PAM) are reviewed. Multispectral PAM can be used to image oxygen saturation or lipid-rich biological tissues by applying a Q-switched fiber laser, a stimulated Raman scattering-based laser source, or a fiber-based supercontinuum source for photoacoustic excitation. PAM can also incorporate a single-mode fiber laser cavity as a high-sensitivity ultrasound sensor by measuring the acoustically induced lasing-frequency shift. Because of their small size and high flexibility, compact head-mounted, wearable, or hand-held imaging modalities and better photoacoustic endoscopes can be enabled using fiber-laser-based PAM. [ABSTRACT FROM AUTHOR]

Optoacoustic imaging is a new biomedical imaging technology with clear benefits over traditional optical imaging and ultrasound. While the imaging technology has improved since its initial development, the creation of dedicated contrast agents for optoacoustic imaging has been stagnant. Current exploration of contrast agents has been limited to standard commercial dyes that have already been established in optical imaging applications. While some of these compounds have demonstrated utility in optoacoustic imaging, they are far from optimal and there is a need for contrast agents with tailored optoacoustic properties. The synthesis, encapsulation within tumor targeting silica nanoparticles and applications in in vivo tumor imaging of optoacoustic contrast agents are reported. [ABSTRACT FROM AUTHOR]

Image performance in optoacoustic endoscopy depends markedly on the design of the transducer employed. Ideally, high-resolution performance is required over an expanded depth of focus. Current optoacoustic focused transducers achieve lateral resolutions in the range of tens of microns in the mesoscopic regime, but their depth of focus is limited to hundreds of microns by the nature of their spherical geometry. We designed an ultra-broadband axicon detector with a 2 mm central aperture and investigated whether the imaging characteristics exceeded those of a spherical detector of similar size. We show a previously undocumented ability to achieve a broadband elongated pencil-beam optoacoustic sensitivity with an axicon detection geometry, providing approximately 40 μm-lateral resolution maintained over a depth of focus of 950 μm—3.8 times that of the reference spherical detector. This performance could potentially lead to optoacoustic endoscopes that can visualize optical absorption deeper and with higher resolution than any other optical endoscope today. [ABSTRACT FROM AUTHOR]

X-ray Photoelectron Spectroscopy (XPS) and Photoacoustic (PA) techniques are useful to identify the structure and optical properties of chemical compounds used in archaeology, among others. In the present study XPS and PA techniques were used to analyze seven samples obtained from the Talavera House, during the conservation and restoration works carried out in the 2012-2013 period. Talavera House is located between the República del Salvador, Talavera and Roldán streets, in the historic center of Mexico City. The objective of this study was to identify the chemical compounds added to the lime when burned in the furnace and its use in the tanneries during the 18th century, both elements located in the second yard, as well as in the construction of the corridor in the 20th century located in the first courtyard. The samples were collected at these points and analyzed by XPS and Photoacoustic (PA) techniques, comparing these results with other excavated sites. [ABSTRACT FROM AUTHOR]

Self-assembled Fe3O4 nanoparticles are attracting more and more interests in biomedical field, such as dual photoacoustic devices and magnetic resonance imaging. At present, however, the preparation of self-assembled Fe3O4 nanoparticles mainly relies on the modifications of some toxic polymers, such as 4-vinylpyridine, polyacrylonitrile, and phenol formaldehyde resin. Additionally, the synthetic methods used were too complicated. The biological toxicity and complex methods significantly limit the biomedical applications of self-assembled Fe3O4 nanoparticles. In this work, natural polysaccharide chitosan was used to modify Fe3O4 nanoparticles. The self-assembled Fe3O4 nanochains were obtained easily by controlling the ratio of chitosan and Fe3O4 nanoparticles. The formation mechanism of Fe3O4 nanochains was proposed and demonstrated by experiments and numerical simulation. It is found that the thickness of chitosan is a key factor that affects the magnetic field distributions and magnetic attraction of Fe3O4 nanoparticles. The prepared chitosan-modified Fe3O4 nanochains would be a promising candidate with good biocompatibility for biomedical applications. [ABSTRACT FROM AUTHOR]

Photoacoustics is a promising technique for in-depth imaging of biological tissues. However, the lateral resolution of photoacoustic imaging is limited by size of the optical excitation spot, and therefore by light diffraction and scattering. Several super-resolution approaches, among which methods based on localization of labels and particles, have been suggested, presenting promising but limited solutions. This work demonstrates a novel concept for extended-resolution imaging based on separation and localization of multiple sub-pixel absorbers, each characterized by a distinct acoustic response. Sparse autoencoder algorithm is used to blindly decompose the acoustic signal into its various sources and resolve sub-pixel features. This method can be used independently or as a combination with other super-resolution techniques to gain further resolution enhancement and may also be extended to other imaging schemes. In this paper, the general idea is presented in details and experimentally demonstrated. [ABSTRACT FROM AUTHOR]

The rapid spatial guidance of terahertz (THz) radiation is a key problem in modern THz spectroscopy and imaging. Single-crystal α-TeO2 has advanced optical and elastic characteristics. This crystal widely used in acousto-optical devices in the visible and near-infrared (IR) ranges. Its application in the THz frequency range at temperatures of approximately 300 K is limited by high radiation absorption. We studied the electrodynamic characteristics of a paratellurite crystal in a wide frequency region at temperatures ranging from 77 to 300 K using pulsed broadband THz spectroscopy and IR Fourier spectroscopy. The temperature evolution of the complex refractive index, as well as the impact of phonon contributions and second-order processes on the absorption of radiation for polarisation along the crystallographic directions of [001] and [110], was evaluated. It was determined that at temperatures below 100 K, intrinsic absorption processes are significantly suppressed, which is mainly caused by a decrease in first- and second-order phonon contributions. The temperature dependencies of the refraction index and absorption coefficient of paratellurite in the THz range were obtained. We demonstrate that crystal cooling leads to a shift in the high-frequency boundary of the deflected THz radiation from 15 to 40 cm−1 along the [001] crystallographic axis. [ABSTRACT FROM AUTHOR]

Optoelectronic oscillators have dominated the scene of microwave oscillators in the last few years thanks to their great performances regarding frequency stability and phase noise. However, miniaturization of such devices is an up-to-date challenge. Recently, devices based on a phonon–photon interaction have gathered a lot of interest thanks to their extreme compactness and working frequency directly in the GHz. In this frame, a still-missing element to obtain long-term frequency stability performances is an on-chip delay within the feedback loop. Here, we experimentally show filtering and slow propagation of 2 GHz acoustic waves on a Gallium Arsenide membrane heterogeneously integrated on a silicon wafer. By engineering the dispersion of an acoustical waveguide, we evidence a group velocity below 1000 m/s for the mode able to propagate. Thus, an integrated delay implementation is at reach for potential improvement of opto-acoustic devices such as optomechanical oscillators or wireless applications. [ABSTRACT FROM AUTHOR]

Thermal diffusion and thermoelastic bending are two consequences of heating generated on the sample surface. Both are employed in Open Photoacoustic Cell (OPC) technique to measure the thermal diffusivity of the sample. In this work, we explore the potential use of the OPC technique to study the effectiveness of thermoelastic bending process and thermal diffusion process on photoacoustic signal (S) generation in solids. More specifically, it is observed that if the thermoelastic bending process becomes more effective while the sample thickness is decreased, this information can be used to obtain a method to self-check the value of the thermal diffusivity parameter measured. The method is based on the measurement of the thermoelastic bending parameter as a function of the sample thickness (ls). The expected dependence of the thermoelastic bending parameter (C2) with the sample thickness, according to the theoretical model, is C2 ∝ ls-3. Our results for aluminum metallic samples give a C2 ∝ ls-2.8 dependence. Also, a thermal diffusivity value of αexp = (8.4 ± 0.3) × 10-5 m2/s was measured for metallic aluminum. This value is in good agreement when compared with the theoretical value αAl = 8.6 × 10-5 m2/s. [ABSTRACT FROM AUTHOR]

A simple and reliable methodology for determining the Young's modulus of magnetorheological elastomers is proposed based on the resonance frequencies of the amplitude of the photoacoustic signal. An explicit expression for the pressure changes within a photoacoustic cell, due to the thermal expansion of the air and the elastic bending of a clamped circular elastic membrane, is derived and analyzed. It is found that the resonance behavior of the amplitude of the photoacoustic signal is due to the contribution of the axial bending of its thickness. It is also shown that the Young's modulus of the membrane is proportional to its density, the square of its resonance frequencies and the fourth power of its radius, and inversely proportional to the square of its thickness. The application of the proposed approach to membranes made up of spherical microparticles of carbonyl iron powder embedded in a matrix of silicone rubber with weight concentrations of 0%, 5.2%, and 13.7% yields accurate and reproducible results, which are in good agreement with reported data in the literature. The highest accuracy on the measurement of the resonance frequencies and therefore on the Young's modulus is found for the first resonance peak. When a magnetic field is applied to the samples to modify their stiffness, it is observed that the Young's modulus increases with the magnetic field. This novel application of the photoacoustic technique opens the possibility of performing mechanical characterization of a broad diversity of magnetorheological membranes. [ABSTRACT FROM AUTHOR]

Recently, the coherent generation of GHz acoustic waves using ultrashort laser pulses has demonstrated the ability to probe the sound velocity in vegetal cells and in cell-mimicking soft micro-objects with micrometer resolution, opening tremendous potentialities for single-cell biology. However, manipulating biological media in physiological conditions is often a technical challenge when using a laser-based setup. In this article, we present a new opto-acoustic bio-transducer composed of a thin metal film sputtered on a transparent heat sink that allows reducing importantly the laser-induced cellular stresses, and offers a wide variety of optical configurations. In particular, by exploiting the acoustic reflection coefficient at the sample-transducer interface and the photoacoustic interaction inside the transparent sample, the density and compressibility of the sample can be probed simultaneously. Using an ad hoc signal analysis based on Hilbert and wavelet transforms, these quantities are measured accurately for a reference fluid. Similar analysis performed in a single vegetal cell also suggests high sensitivity to the state of the transducer-cell interface, and notably to the presence of the plasma membrane that encloses the cell vacuole. [ABSTRACT FROM AUTHOR]

This investigation have studied photoacoustic (PA) technique to percutaneous permeation of topical hydroxy-(29H,31H-phthalocyaninate) aluminum (PcAlOH) on pig ear skin. The PcAlOH was incorporated in an emulsion (O/W) (1 mg/dl) with assessed stability parameters of: pH, short and long term stability tests (in the several conditions). The skin was prepared through a heat separation technique, and with a scalpel, the outer skin of the cartilage was removed. The skins were then cut into 4 cm2 pieces and treated with sodium bromide 2 mol/L for 6 h at 37 °C. The epidermis layer was washed with purified water, dried, and stored under reduced pressure until use. The skin permeation kinetics was determined by photoacoustic technique in an open photoacoustic cell. Short (after preparation) and long-term stability tests showed no phase separation. The emulsion developed pH 7.6 and after incorporating the pH was unchanged. The typical times for percutaneous permeation of the emulsion base and emulsion + PcAlOH were 182 (±6) and 438 (±3) s, respectively. This study indicated that the formulations containing PcAlOH have stabile characteristics and show promising results in absorption into the skin. The presence of the photosensitive agent in the formulation contributed significantly to the greater absorption time than observed in the base formulation. The used photoacoustic technical to examine the penetration kinetics of PcAlOH in pig ear skin was adequate and may be employed in the determination of the percutaneous permeation of phthalocyanines. [ABSTRACT FROM AUTHOR]

Multidimensional visible spectroscopy using pulse shaping to produce pulses with stable controllable phases and delays has emerged as an elegant tool to acquire electronic spectra faster and with greatly reduced instrumental and data processing errors. Recent migration of this approach using acousto-optic modulator (AOM) pulse shaping to the mid-infrared region has proved useful for acquiring two dimensional infrared (2D IR) vibrational echo spectra. The measurement of spectral diffusion in 2D IR experiments hinges on obtaining accurate 2D line shapes. To date, pulse shaping 2D IR has not been used to study the time-dependent spectral diffusion of a vibrational chromophore. Here we compare the spectral diffusion data obtained from a standard non-collinear 2D IR spectrometer using delay lines to the data obtained from an AOM pulse shaper based 2D IR spectrometer. The pulse shaping experiments are performed in stationary, partially rotating, and fully rotating reference frames and are the first in the infrared to produce 2D spectra collected in a fully rotating frame using a phase controlled pulse sequence. Rotating frame experiments provide a dramatic reduction in the number of time points that must be measured to obtain a 2D IR spectrum, with the fully rotating frame giving the greatest reduction. Experiments were conducted on the transition metal carbonyl complex tricarbonylchloro(1,10-phenanthroline)rhenium(I) in chloroform. The time dependent data obtained from the different techniques and with different reference frames are shown to be in agreement. [ABSTRACT FROM AUTHOR]

Elasticity is one basic property of hybrid organic-inorganic perovskites. It highly relates to many fundamental processes in solid physics. The investigation of elasticity is of interest not only to explore the intrinsic properties of a material, but also to improve their potential application performance. In this study, we predict photoacoustic eigen-spectrum (PAES) of single crystal. Then by solving the inverse problem of the generation of PAES, we propose a noncontact method to determine a complete set of elastic constants of single crystal in one test. Experiments confirm the proposed method accurately determines all elastic constants of MAPbBr3. Since this method is totally noncontact and does not require multiple specimens cutting along different crystal axes, it could be more competent for rare, tiny and brittle specimen, or when the specimen is immersed in turbid or opaque medium. Benefitting from these superiorities, the proposed method might be found prominent values in materials science and applications. [ABSTRACT FROM AUTHOR]

Photoacoustic endoscopy (PAE) is a method of in-vivo imaging that uses tissue absorption properties. In PAE, the main tools used to detect the acoustic signal are mechanical ultrasound transducers, which require direct contact and which are difficult to miniaturize. All-optic photoacoustic sensors can challenge this issue as they can provide contact-free sensing. Here, we demonstrate sensing of photo-acoustic signals through a multimode fiber (MMF) which can provide an ultra-thin endoscopic photoacoustic sensor. Furthermore, we show the advantage of using the optical-flow method for speckle sensing and extract the photoacoustic signal despite the mode-mixing along the MMF. Moreover, it is demonstrated for the first time that the speckle reconstruction method can be used without the need for imaging of the speckles as this enables the use of multimode fibers for the speckle method. [ABSTRACT FROM AUTHOR]

It is still a high challenge to develop a simple, sensitive and portable approach for bioassay in strong scattering medium. Herein, a photoacoustic (PA) device is developed for the detection of alkaline phosphatase (ALP) in serum with silver nanoparticles (AgNPs) as signal probe, without any requirements for expensive equipment, professional operation and pre-processing of real samples. ALP as an important disease marker could catalyze the breakdown of sodium L-ascorbyl-2-phosphate (AAP) into ascorbic acid (AA), thereby reducing Ag+ to AgNPs. AgNPs could generate strong PA signal under the irradiation of modulated 638-nm laser due to their localized plasmon resonance, and detected by the self-made portable PA device. Under the optimized experimental conditions, the present PA device exhibits excellent photostability and reproducibility with the relative standard deviation (RSD) of 2.2% at the concentration of 25 U L−1 ALP. Linear calibration graph is obtained within 5–70 U L−1 for ALP, along with a detection limit of 1.1 U L−1. This portable PA device is applied to detect ALP in serum samples, providing satisfactory spiking recoveries and competitive analytical performances with the current techniques. The PA-based analytical strategy obviously opens up a new avenue to the detection of disease-correlated biomarker in practice. A portable photoacoustic device is developed for the detection of alkaline phosphatase in serum with silver nanoparticles as signal probe. Image 1 • A portable photoacoustic device is developed for the determination of alkaline phosphatase in serum. • Silver nanoparticles as photoacoustic probe exhibit excellent photostability and reproducibility. • This portable device is free from expensive equipment, professional operation and pre-processing of real samples. [ABSTRACT FROM AUTHOR]

Most imaging studies of immunotherapy have focused on tracking labeled T cell biodistribution in vivo for understanding trafficking and homing parameters and predicting therapeutic efficacy by the presence of transferred T cells at or in the tumour mass. Conversely, we investigate here a novel concept for longitudinally elucidating anatomical and pathophysiological changes of solid tumours after adoptive T cell transfer in a preclinical set up, using previously unexplored in-tandem macroscopic and mesoscopic optoacoustic (photoacoustic) imaging. We show non-invasive in vivo observations of vessel collapse during tumour rejection across entire tumours and observe for the first time longitudinal tumour rejection in a label-free manner based on optical absorption changes in the tumour mass due to cellular decline. We complement these observations with high resolution episcopic fluorescence imaging of T cell biodistribution using optimized T cell labeling based on two near-infrared dyes targeting the cell membrane and the cytoplasm. We discuss how optoacoustic macroscopy and mesoscopy offer unique contrast and immunotherapy insights, allowing label-free and longitudinal observations of tumour therapy. The results demonstrate optoacoustic imaging as an invaluable tool in understanding and optimizing T cell therapy. [ABSTRACT FROM AUTHOR]

Recent experiments [N. F. Declercq and E. Lamkanfi, Appl. Phys. Lett. 93, 2 (2008)] showed evidence of the relationship between the generation of leaky Rayleigh waves and the formation of the two reflected lobes and a null strip for bounded beam incidence at the Rayleigh angle. The evidence was based on an experimental setup using a sound barrier on a liquid solid interface. The current paper presents a finite element investigation of the experiments and confirms the earlier conclusions. In addition, unexplained experimental observations are clarified. Furthermore, a detailed investigation of the influence of the bonding properties between the barrier and the solid on the observed radiation patterns is achieved, which is of broader importance to the nondestructive characterization of bonding in general. [ABSTRACT FROM AUTHOR]

We present a new concept for waveguide acousto-optical devices based on coupled Mach–Zehnder interferometers driven by acoustic waves. These acousto-optical multiple interference devices use the periodic refractive index modulation induced by the acoustic wave to realize functionalities such as ON/OFF switching for an arbitrary time interval, as well as for efficient light modulation at high harmonics of the acoustic frequency and pulse shaping for, e.g., integrated Q-switches. We also discuss application of the concepts to light modulation by very high acoustic frequencies, where the acoustic wavelengths become much shorter than the optical ones. [ABSTRACT FROM AUTHOR]

High-resolution ultrasound imaging systems for inspection of defects and flaws in materials are of great demand in many industries. Among these systems, Vibro-acoustography (VA) has shown excellent capabilities as a noncontact method for nondestructive high-resolution imaging applications. This method consists of mixing two confocal ultrasound beams, slightly shifted in frequency, to produce a dynamic (oscillatory) radiation force in the region of their intersection. This force vibrates the object placed at the focus of the confocal transducer. As a result of the applied force, an acoustic emission field at the difference frequency of the primary incident ultrasound beams is produced. In addition to the difference frequency acoustic emission signal, there exists another signal at the sum frequency, formed in the intersection region of the two primary beams. The goal of this study is to investigate the formation of high-resolution images using the sum frequency of ultrasound waves in VA while concurrently forming the conventional difference-frequency VA image, thereby increasing the amount of information acquired during a single scan. A theoretical model describing the sum-frequency wave propagation, including beam forming and image formation in the confocal configuration, is developed and verified experimentally. Moreover, sample experiments are performed on a flawed fiber-reinforced ceramic composite plate. Images at both the difference and sum frequencies are compared and discussed. Results show that the sum-frequency image produces a high-resolution C scan of the plate by which the flaws and structural details of the plate can be detected. [ABSTRACT FROM AUTHOR]

Polyfluorene-based polymer blends have been utilized in the development of optoelectronic devices. The constituent copolymers are chemically designed to facilitate more efficient electron/hole mobility, thereby enhancing control over exciton formation and dissociation. When appropriate pairs of these are blended together, intermolecular charged-particle localizations are induced, leading to significant intermolecular charge-transfer character and luminescence that exhibit some sensitivity to their interfacial orientation. The authors report on a time-dependent density functional theory quantum chemical investigation of the relevant excited states of the polymer blend poly[9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine]/poly(9,9-dioctylfluorene-co-benzothiadiazole. They show that the calculated excited states generally agree with experimental observations although there is a consistent underestimation of the charge-transfer states. Further, they show sensitivity to lateral shifts in interfacial stacking. Finally, solvation with a low dielectric solvent greatly stabilizes the charge-transfer states. [ABSTRACT FROM AUTHOR]

The theory of photoacoustic tomography imaging using an acoustic lens imaging system has been investigated, and the photoacoustic (PA) Fourier imaging property of an acoustic lens is presented. The theoretical results show that an acoustic lens is able to realize two-dimensional PA Fourier imaging and the focal depth of the acoustic lens is 20 mm. The PA signals with the advantage of time resolution can be resolved in time domain by time-resolved technique. Therefore, this long focal depth characteristic of the acoustic lens can be combined with time-resolved technique to realize PA tomography imaging. It is demonstrated by experiments that this method is able to provide PA tomography images of biological tissue. The images are clear and contrast sharply with their backgrounds. The depth resolution is 1.54 mm. [ABSTRACT FROM AUTHOR]

A purely optical method to generate and to steer an ultrasonic beam is presented. The generation of the ultrasonic beam in the kilohertz to megahertz regime is achieved by using the optoacoustic effect in a layer attached to the surface of a water tank, which absorbs time-modulated laser pulses. In order to tailor the emitted acoustic wave, diffractive optics concepts are applied to acoustics. To this end, the laser light intensity distribution at the absorbing surface is controlled by sending a computer-calculated pattern to a transmissive high-resolution liquid-crystal display in the beam path. This results in an acoustic analog to the “diffractive optical elements” in laser optics, with the emitted ultrasonic wave emerging in a predetermined way. The proof of principle is demonstrated for examples such as phase gratings and binary Fresnel lenses. The optoacoustic ultrasound generation with holographic diffractive steering is a flexible method with the potential of new applications in ultrasound diagnostics. [ABSTRACT FROM AUTHOR]

X-ray powder diffraction by p-type CuSnSe, prepared by the vertical Bridgman--Stockbarger technique, shows that this material crystallizes in a monoclinic structure, space group Cc, with unit cell parameters =6.5936(1) , b= 12.1593(4) , c=6.6084(3) , and = 108.56(2)degrees. The temperature variation of the hole concentration p obtained from the Hall effect and electrical resistivity measurements from about 160 to 300 K, is explained as due to the thermal activation of an acceptor level with an ionization energy of 0.067 eV, whereas below 100 K, the conduction in the impurity band dominates the electrical transport process. From the analysis of the p vs T data, the density-of-states effective mass of the holes is estimated to be nearly of the same magnitude as the free electron mass. In the valence band, the temperature variation of the hole mobility is analyzed by taking into account the scattering of charge carriers by ionized and neutral impurities, and acoustic phonons. In the impurity band, the mobility is explained as due to the thermally activated hopping transport. From the analysis of the optical absorption spectra at room temperature, the fundamental energy gap was determined to be 0.843 eV. The photoconductivity spectra show the presence of a narrow band gap whose main peak is observed at 0.771 eV. This band is attributed to a free-to-bound transition from the defect acceptor level to the conduction band. The origin of this acceptor state, consistent with the chemical composition of the samples and screening effects, is tentatively attributed to selenium interstitial. c 2001 American Institute of Physics. [DOI: 10.1063/1.1383984]. X-ray powder diffraction by p-type CuSnSe, prepared by the vertical Bridgman--Stockbarger technique, shows that this material crystallizes in a monoclinic structure, space group Cc, with unit cell parameters =6.5936(1) , b= 12.1593(4) , c=6.6084(3) , a... [ABSTRACT FROM AUTHOR]

Probing the prostate: Molecular imaging can help improve detection of cancer, but some modalities require ionizing radiation, making them nonideal for repeated imaging. Kothapalli et al. developed a probe that could perform ultrasound and photoacoustic imaging simultaneously, two modalities that do not require ionizing radiation. Testing the transrectal ultrasound and photoacoustic device in vitro, in mouse models, and using excised human prostates demonstrated the ability to view anatomical features within tissue and vascular contrast within tumors. Administering a dye improved photoacoustic contrast when imaging the prostates of human subjects with cancer. This device allows for real-time anatomical, functional, and molecular imaging of the human prostate and could be easily adopted into clinical workflows. Imaging technologies that simultaneously provide anatomical, functional, and molecular information are emerging as an attractive choice for disease screening and management. Since the 1980s, transrectal ultrasound (TRUS) has been routinely used to visualize prostatic anatomy and guide needle biopsy, despite limited specificity. Photoacoustic imaging (PAI) provides functional and molecular information at ultrasonic resolution based on optical absorption. Combining the strengths of TRUS and PAI approaches, we report the development and bench-to-bedside translation of an integrated TRUS and photoacoustic (TRUSPA) device. TRUSPA uses a miniaturized capacitive micromachined ultrasonic transducer array for simultaneous imaging of anatomical and molecular optical contrasts [intrinsic: hemoglobin; extrinsic: intravenous indocyanine green (ICG)] of the human prostate. Hemoglobin absorption mapped vascularity of the prostate and surroundings, whereas ICG absorption enhanced the intraprostatic photoacoustic contrast. Future work using the TRUSPA device for biomarker-specific molecular imaging may enable a fundamentally new approach to prostate cancer diagnosis, prognostication, and therapeutic monitoring. [ABSTRACT FROM AUTHOR]

A benchmark experiment is reported that demonstrates the shortening of hard X‐ray pulses in a synchrotron‐based optical pump–X‐ray probe measurement. The pulse‐shortening device is a photoacoustic Bragg switch that reduces the temporal resolution of an incident X‐ray pulse to approximately 7.5 ps. The Bragg switch is employed to monitor propagating sound waves in nanometer thin epitaxial films. From the experimental data, the pulse duration, diffraction efficiency and switching contrast of the device can be inferred. A detailed efficiency analysis shows that the switch can deliver up to 109 photons s−1 in high‐repetition‐rate synchrotron experiments. [ABSTRACT FROM AUTHOR]

Abstract Near-infrared (NIR) absorbing dyes have been attached much importance recently, since the promising prospect in photoacoustic (PA) imaging and photothermal (PT) therapy in cancer treatment. In this work, PA signal and PT effect of pyrene derivatives (C12 and C13) prepared via click reaction were evaluated, systematically. It was studied about the further application of loading the representative trisubstituted pyrene derivative (C13) into biocompatible liposomes and subsequent PA measurement. C13 showed the excellent PA effect, whether it's embedded or not. Since temperature increment of the dyes were remarkable in PT test, the same representative derivative C13 was picked and loaded into PNIPAM-b-PNBM polymer micelles as photothermal conversion agent. Preliminary studies suggested that the trisubstituted pyrene derivatives had great potential to replace the function of temperature stimulus. Graphical abstract Image 1 Highlights • A series of near-infrared dyes based on pyrene derivatives show the excellent PA and PT effect. • Representative pyrene derivative was loaded into biocompatible liposomes and micelles with multiple responses. • Representative pyrene derivative effectively may controllably promote the diffusion rate of Nile Red under NIR irradiation. [ABSTRACT FROM AUTHOR]

Highlights • A photoacoustic and fluorescence dual-mode probe for LTA 4 H sensing was developed. • Cy-ASP has high selectivity and high sensitivity toward LTA 4 H. • Combined with PA technology, Cy-ASP could image the activity of LTA 4 H in mice without dissection. • The probe Cy-ASP could fast locate the inflammation site in mice. Abstract Inflammation widely occurs in various tissues and organs in the human body. Rapid and accurate diagnosis of inflammation is essential to avoid severe complications. This study aims to obtain a non-destructive, fast, and comprehensive tool for the detection of pathogenic sites of inflammation in vivo. A fluorescence and photoacoustic dual-mode imaging probe, Cy-ASP, was first developed to detect inflammatory biomarker LTA 4 H with good sensitivity and selectivity in living small animal. Furthermore, the relationship between LTA 4 H and NF-κB in an LPS-induced cell was investigated. This work provides a new idea for the clinical diagnosis of pneumonia and hepatitis and revealing the upstream regulatory mechanism of LTA 4 H in the pneumonia model. [ABSTRACT FROM AUTHOR]

Background: Current multispectral photoacoustic instruments must use large and separate combinational structures to obtain various biological tissue information for multispectral ranges.Objective: The optical aberration generated from the multispectral photoacoustic systems may reduce the image quality of biological tissue because the improper structures for combining light of different wavelength cannot produce good optical ray convergence points. To prevent this, complex combined structures need to be considered at the design level for multispectral photoacoustic systems.Methods: In place of an optical refracted lens system, reflective mirrors could be designed for optical systems. To verify our proposed idea, we assessed optical distortion performance using red, green, and blue light, and combined optical light sources to compare their chromatic aberration characteristics.Results: The high optical performance is realized regardless of the wavelength for a light source combined with multiple wavelengths, because our optical system was designed with only a reflective surface.Conclusions: The designed optical system using a reflective mirror can provide multispectral optical sources (such as infrared, visible, and ultraviolet optical lights) with only one light ray path, without any chromatic aberrations. [ABSTRACT FROM AUTHOR]

Bragg diffraction which provides effective acoustooptic interaction of three-color radiation with a single acoustic wave at a high frequency of sound is proposed and tested in a single crystal of paratellurite at the wavelengths of λ= 0.488, 0.514, and 0.633 μm. Maximal diffraction efficiency of radiation with λ=0.633 μm at acoustic frequency of 150 MHz is 88% and that with λ= 0.488 μm and λ=0.514 μm is 60%. In diffraction efficiency range from 0 to 40% the dependence of all beams on acoustic power is the same. [ABSTRACT FROM AUTHOR]

The possibility of efficiently using metamaterials in acousto-optics has been demonstrated. Diffraction reflection and transmission curves of metamedia with a nonuniform spatial distribution of nanoparticles have been studied taking into account absorption of light. The influence of size (geometric) effects of nanoparticles on diffraction reflection and transmission curves has been shown. In particular, it has been shown that the variation of the concentration of dielectric nanoparticles in a medium allows completely removing extraneous oscillations and suppressing the "tails" of the diffraction reflection curve. It has been demonstrated that the response function of acousto-optical devices can be controlled by varying the material, concentration, size, shape, and spatial orientation of inclusions, as well as the polarization of incident radiation. [ABSTRACT FROM AUTHOR]

Background: MIRUS™ is a device for target-controlled inhalational sedation in the ICU in combination with use of isoflurane, or sevoflurane, or desflurane. The feasibility of this device has recently been proven; however, ICU staff exposure may restrict its application. We investigated ICU ambient room pollution during daily work to estimate ICU personnel exposure while using MIRUS™.Methods: This observational study assessed pollution levels around 15 adult surgical patients who received volatile anaesthetics-based sedation for a median of 11 hours. Measurements were performed by photoacoustic gas monitoring in real-time at different positions near the patient and in the personnel's breathing zone. Additionally, the impact of the Clean Air™ open reservoir scavenging system on volatile agent pollution was evaluated.Results: Baseline concentrations [ppm] during intervention and rest periods were isoflurane c¯mean = 0.58 ± 0.49, c¯max = 5.72; sevoflurane c¯mean = 0.22 ± 0.20, c¯max = 7.93; and desflurane c¯mean = 0.65 ± 0.57, c¯max = 6.65. Refilling MIRUS™ with liquid anaesthetic yielded gas concentrations of c¯mean = 2.18 ± 1.48 ppm and c¯max = 13.03 ± 9.37 ppm in the personnel's breathing zone. Air pollution in the patient's room was approximately five times higher without a scavenging system.Conclusion: Ambient room pollution was minimal in most cases, and the measured values were within or below the recommended exposure limits. Caution should be taken during refilling of the MIRUS™ system, as this was accompanied by higher pollution levels. The combined use of air-conditioning and gas scavenging systems is strongly recommended. [ABSTRACT FROM AUTHOR]

Photoacoustic imaging using a focused, scanning detector in combination with a pulsed light source is a common technique to visualize light-absorbing structures in biological tissue. In the acoustic resolution mode, where the imaging resolution is given by the properties of the transducer, there are various challenges related to the choice of sensors and the optimization of the illumination. These are addressed by linking a Monte Carlo simulation of energy deposition to a time-domain model of acoustic propagation and detection. In this model, the spatial and electrical impulse responses of the focused transducer are combined with a model of acoustic attenuation in a single response matrix, which is used to calculate detector signals from a volumetric distribution of absorbed energy density. Using the radial symmetry of the detector, the calculation yields a single signal in less than a second on a standard personal computer. Various simulation results are shown, comparing different illumination geometries and demonstrating spectral imaging. Finally, simulation results and experimental images of an optically characterized phantom are compared, validating the accuracy of the model. The proposed method will facilitate the design of photoacoustic imaging devices and will be used as an accurate forward model for iterative reconstruction techniques. [ABSTRACT FROM AUTHOR]

We provide the first demonstration of an acousto-optically modulated quantum cascade laser (AOM QCL) system as a diagnostic for combustion by measuring nitric oxide (NO), a highly regulated emission produced in gas turbines. The system provides time-resolved broadband spectral measurements of the present gas species via a single line of sight measurement, offering advantages over widely used narrowband absorption spectroscopy (e.g., the potential for simultaneous multispecies measurements using a single laser) and considerably faster (>15 kHz rates and potentially up to MHz) than sampling techniques, which employ fourier transform infrared (FTIR) or GC/MS. The developed AOM QCL system yields fast tunable output covering a spectral range of 1725-1930 cm-1 with a linewidth of 10-15 cm-1. For the demonstration experiment, the AOM QCL system has been used to obtain time-resolved spectral measurements of NO formation during the shock heating of mixture of a 10% nitrous oxide (N2O) in a balance of argon over a temperature range of 1245-2517 K and a pressure range of 3.6-5.8 atm. Results were in good agreement with chemical kinetic simulations. The system shows revolutionary promise for making simultaneous time-resolved measurements of multiple species concentrations and temperature with a single line of sight measurement. [ABSTRACT FROM AUTHOR]

Abstract: A broadband digital frequency synthesizer for acoustooptical filters has been designed and studied. The range of synthesized frequencies has been expanded as compared to synthesizers based on phase locking. The interface for control of the proposed design has been developed. Using the user can enter frequency values by himself. A prototype of a dual-channel frequency synthesizer with possibility of independent operation of channels has been produced. [ABSTRACT FROM AUTHOR]

Rate coefficients, kVT, for the deactivation of vibrationally excited C6F14 and C8F18 with average excitation energies ranging from 5000 to 30 000 cm-1 were measured via time resolved optoacoustics for a series of 13 deactivators. Relative collision efficiencies (β=kVT/kHS=〈〈ΔE〉〉/), an intrinsic measure of the deactivator, were calculated. The average energy removed per collision, 〈〈ΔE〉〉, was linear with since β was found to be independent of energy for all deactivator-substrate combinations. The trends for the deactivators with the 6 and 8 carbon atom substrates were similar except that β was ∼15% smaller for the larger substrate. The efficiency for the rare gases increases from helium to neon to argon and then decreases to krypton followed by a slight leveling off for xenon. This trend with deactivator mass was also observed for the polyatomic deactivators studied. The rapid rise and slow fall in β vs mass can be simulated by an encounter between the deactivator and a diatomic substrate containing a pseudo atom with a mass of ∼30 amu. [ABSTRACT FROM AUTHOR]

Presents an original combination of two cascaded multifrequency acousto-optic modulators, based on the tangential phase matching anisotropic interaction. Result of the diffraction os a light beam by multiple acoutic waves; Information on the multifrequency tangential phase matching interaction in paratellurite.

Reports on the use of an acousto-optic modulator in stabilizing a free-running continuous wave (CW) laser diode in the presence of strong reflections from a high finesse Fabry-Perot resonator. Demonstration of CW cavity ring-down spectroscopy of water vapor at both 1 atmosphere and 5 torr; Ring-down repetition rates of 10-50 kHz.

Abstract—: A new approach to solution of the problem of remote determination of spectrally complex optical signals and identification on this base of two objects out of a set of possible spatially inseparable objects located in one small ground pixel is considered. Computer simulation is performed; it is shown that the results of measurements of the mean powers of filtered signals at the outputs of two (or more) selected reference multiband acoustooptical filters (MAOFs) can ensure subsequent programmed (digital) separation of spectrally complex optical signals and identification of the objects corresponding to these signals. By the example of an arbitrarily chosen group of ten types of objects and three types of the background, computer verification of the new method is carried out with the use of realizable parameters of modern MAOFs. It has been found that, in conditions of the actual accuracy of setting and/or measuring of the energy of the main components of the problem (~1%), this method can provide unambiguous correct decision about the type of the object located on part of a pixel with a probability of ~99.9%. [ABSTRACT FROM AUTHOR]

Modelling nutrient release profiles from a population of controlled release fertiliser (CRF) is essential for synchronising their release with plant nutrient requirements. A mechanistic model succeeds in describing the release profiles from a single granule. Yet, a large deviation will appear when it is used for a population of CRF due to the large variation in a CRF population. Least Squares Support Vector Machines (LS-SVM) that incorporated the variation were used to predict nutrient release from a CRF population using the photoacoustic spectra of the coating, coating percentage, and frequency distribution of granule radii as inputs. The predicted release profiles were in good agreement with observations both for ‘S’ and inverse ‘L’ release patterns. LS-SVM model was effective and accurate in modelling nutrient release from a CRF population. [ABSTRACT FROM AUTHOR]

We have studied the features of noncollinear acousto-optic filtering of quasi-nondiffracting Bessel light beams in uniaxial crystals. We have obtained coupled wave equations for the vector amplitudes of an incident ordinary (o-type) Bessel beam and an extraordinary (e-type) diffracted beam for different modes. We have found an expression for the diffraction efficiency as a function of the parameters of interacting ordinary and extraordinary Bessel beams, and also as a function of the values of the overlap integrals. Using the overlap integral method, we have shown that regardless of the mode order for the Bessel light beam, under transverse phase matching conditions for ordinary and extraordinary diffracted Bessel beams in the optical spectral range 0.4-1.1 μm we can achieve a filter transmission bandwidth of ~0.6 nm in paratellurite crystals. [ABSTRACT FROM AUTHOR]