bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of voltage treatment applied on photoacoustic and photoelectrochemical current spectra in final preparation processes of porous TiO2 electrodes
Authors: Toyoda Taro , Hayashi Masashi
Published: January 2003

We report the effect of different voltages in a concentrated KCl electrolyte applied to highly porous, polycrystalline TiO2 films during their final preparation processes on photoacoustic (PA) and photoelectrochemical (PEC) current spectra. Below the band-gap energy region, the PA signal intensities of the TiO2 films with different voltage treatment applied are higher than those without treatment and they increase with an increase of applied voltage. These experimental results suggest an innerband transition from an increase in carrier concentration due to the formation of donor levels by partially reduced Ti ions (Ti4+→Ti3+) by the voltage treatment. The PEC current spectra for applied voltage treatment over −1.5 V show two peaks above the band-gap energy region whose intensities increase rapidly above applied voltage of −1.5 V (eight times larger for voltage of −3.5 V than those without treatment), which is similar to that of the PA intensity at a photon energy of 2.0 eV. The modulation frequency dependence of the PEC current intensity at the peak position shows different characteristics depending on the voltage treatment applied, indicating the difference in PEC current response due to the formation of donor levels by the treatment.
Photoacoustic spectroscopy applied to the study of clay soils
Authors: dos Santos D. R. , Toledo R. , Massunaga M. S. O. , Carrió J. G. , Auler L. T. , da Silva E. C. , Garcia-Quiroz A. , Vargas H.
Published: January 2003

The optical absorption spectra and mineralogical composition of soil samples were characterized using photoacoustic spectroscopy and x-ray diffraction. The photoacoustic spectra observed showed transition bands associated with Fe3+ ions in octahedral or tetrahedral symmetry. From the phase behavior, both the nonradiative relaxation time τ and the characteristic thermal diffusion time τβ were determined. The x-ray diffraction analysis showed that kaolinite is a major crystalline phase (86 wt %) followed by minor quantities of anatase, gibbsite, and quartz. Rietveld refinements showed that the Fe3+ cations partially substitute for Al3+ cations in octahedral sites of the kaolinite structure.
Choi’s proof as a recipe for quantum process tomography
Authors: Leung Debbie W.
Published: January 2003

Quantum process tomography is a procedure by which an unknown quantum operation can be fully experimentally characterized. We reinterpret Choi’s proof [Linear Algebr. Appl. 10, 285 (1975)] of the fact that any completely positive linear map has a Kraus representation as a method for quantum process tomography. The analysis for obtaining the Kraus operators is extremely simple. We discuss the systems in which this tomography method is particularly suitable.
Robust procedures for converting among Lindblad, Kraus and matrix representations of quantum dynamical semigroups
Authors: Havel Timothy F.
Published: January 2003

Given a quantum dynamical semigroup expressed as an exponential superoperator acting on a space of N-dimensional density operators, eigenvalue methods are presented by which canonical Kraus and Lindblad operator sum representations can be computed. These methods provide a mathematical basis on which to develop novel algorithms for quantum process tomography—the statistical estimation of superoperators and their generators—from a wide variety of experimental data. Theoretical arguments and numerical simulations are presented which imply that these algorithms will be quite robust in the presence of random errors in the data.
Photoacoustic determination of phase transition in BaTiO3 induced by high pressure at room temperature
Authors: Villagrán-Muniz M. , Navarrete M. , Mejı́a-Uriarte E. V.
Published: January 2003

The high-pressure behavior of BaTiO3 was investigated by the photoacoustic technique in a diamond anvil cell at room temperature up to 3 GPa. Only one phase transition was observed with an increase in pressure: BaTiO3 tetragonal→cubic. The phase transition induced by high pressure was detected by sequential measurements of photoacoustic signals generated by short laser pulses applied to the diamond front face for each pressure applied. A correlation analysis of the photoacoustic data signal sequence values clearly shows a phase transition within an uncertainty of ±5%.
Photoacoustics as a tool for the diagnosis of radicular stress: Measurements in eucalyptus seedlings
Authors: Barja P. R. , Mansanares A. M. , da Silva E. C. , Alves P. L. C. A.
Published: January 2003

In reforesting companies (cellulose industry), eucalyptus is usually cultivated in small plastic containers (50 mL). As seedlings remain for about 120 days in these containers—until transplantation—their roots become space restricted, with consequent limitations in water and nutrient absorption. These restrictions may lead to plant stress, decreasing productivity. In this work, we used the photoacoustic technique to evaluate the photosynthetic activity of Eucalyptus grandis, E. urophylla and E. urograndis seedlings subjected to this limited space availability, seeking a correlation with morphological parameters and fluorescence measurements in these seedlings. Photoacoustic, fluorescence, and morphological analysis were conducted every 15 days, from 45 to 120 days after sowing. Fluorescence and photosynthetic rate were evaluated in vivo and in situ, the latter one using the open photoacoustic technique. Data show that root dry matter diminished markedly at 90 and 120 days after sowing; this behavior showed a high correlation with the gas exchange component of the photoacoustic signal, as well as with the fluorescence ratio Fv/Fm. These results indicate that the soil volume of the container becomes insufficient for the roots after 90 days, probably leading to a nutritional deficiency in plants, which explains the decrease observed in the photosynthetic rate of seedlings.
Protocols and data analysis in quantitative optothermal in vivo transdermal diffusion measurements
Authors: Xiao Perry , Cowen Judith A. , Imhof Robert E
Published: January 2003

We report the development of measurement protocols and data analysis techniques that allow the optothermal diffusion measurements of externally applied substances through human skin to be interpreted quantitatively. We present the theoretical background relating measured optothermal decay times to surface concentration, from which mass diffusion and partition coefficients can be calculated. The methods are illustrated using propylene glycol and a number of other diols as examples.
Generation and detection of H electrodiffusion waves
Authors: Remhof A. , van Mechelen J. L. M. , Koeman N. J. , Rector J. H. , Wijngaarden R. J. , Griessen R.
Published: January 2003

Hydrogen electrodiffusion waves are forced oscillations of the H concentration within a host metal, driven by an electric field. Simulations show that they suffer less from the drawbacks of ordinary diffusion waves such as heavy damping. H in Y/V bilayers fulfills all the requirements to generate and to detect H electrodiffusion waves. We demonstrate the possibility to spatially modulate the H concentration in a thin V film and to drive H “pulses” via an applied electric field. The electric field is also used to control the hydrogen uptake of the sample. We visualize the temporal and spatial evolution of the H distribution in the V film using the switchable mirror material YHx as an optical hydrogen indicator.
Resonant photoacoustic detection of NO2 traces with a Q-switched green laser
Authors: Slezak Verónica , Codnia Jorge , Peuriot Alejandro L. , Santiago Guillermo
Published: January 2003

Resonant photoacoustic detection of NO2 traces by means of a high repetition pulsed green laser is presented. The resonator is a cylindrical Pyrex glass cell with a measured Q factor 380 for the first radial mode in air at atmospheric pressure. The system is calibrated with known mixtures in dry air and a minimum detectable volume concentration of 50 parts in 109 is obtained (S/N=1). Its sensitivity allows one to detect and quantify NO2 traces in the exhaust gases of cars. Previously, the analysis of gas adsorption and desorption on the walls and of changes in the sample composition is carried out in order to minimize errors in the determination of NO2 content upon application of the extractive method. The efficiency of catalytic converters of several models of automobiles is studied and the NO2 concentration in samples from exhausts of different types of engine (gasoline, diesel, and methane gas) at idling operation are measured.
Application of thermoacoustic effect to refrigeration
Authors: Jin T. , Chen G. B. , Wang B. R. , Zhang S. Y.
Published: January 2003

Thermoacoustic effect, as a subprocess of the photoacoustic effect, can also convert heat to acoustic wave by a thermoacoustic prime mover, and can also pump heat by acoustic wave in a thermoacoustic refrigerator. The present study focuses on a thermoacoustically driven pulse tube refrigerator, utilizing sound from a thermoacoustic prime mover to drive a pulse tube refrigerator. Experiments emphasize on the characteristics of both the thermoacoustic prime mover and the combined refrigeration system, including resonant frequency, onset temperature, pressure amplitude, and refrigeration temperature, etc. A cryogenic temperature lower than 120 K has been achieved from the present system. Much effort is also devoted to the influence of some working gases, such as helium–argon mixture, on the performance of the system.
Compact photothermal-refractometric detector for high performance liquid chromatography based on a polarization interferometer
Authors: Luk’yanov A. Yu. , Bendrysheva S. N. , Proskurnin M. A. , Bendryshev A. A. , Elefterov A. I. , Shpigun O. A.
Published: January 2003

A combined photothermal-refractometric detector for high-performance liquid chromatography is proposed. Five metal complexes as 4-pyridylazo-2-naphthol chelates and three sugars were investigated as model substances. For these compounds, detection limits, repeatability, and reproducibility of determination were calculated. Obtained results were compared with results for traditional detectors, which show that photothermal detection has higher sensitivity than photometric and other absorption detectors.
Analysis of energy flow in regenerator of thermoacoustic engines
Authors: Jin Tao , Wang Ben-ren , Zhang Shu-yi
Published: January 2003

The energy flow inside a thermoacoustic regenerator of fluid-filled porous media is analyzed. Based on Biot’s acoustic propagation theory of porous materials, a theoretical model is proposed to consider dynamic solid–fluid interaction, which was generally neglected in traditional models of regenerators. Theoretical expressions for the energy flux and critical temperature gradient are given.
Combination of thermal lensing and electron-probe microanalysis for characterizing flat glass surfaces
Authors: Proskurnin M. A. , Kononets M. Yu. , Min’kovskii E. M. , Proskurnina E. V. , Bendrysheva S. N. , Tarasov A. R. , Lisichkin G. V.
Published: January 2003

Thermal lensing and electron-probe microanalysis were used for studying surfaces of quartz glass samples with chemically bonded Reactivrot B5A organic dye. The possibility of using both methods and a combination of them to characterize glass surfaces and bonded dye properties is discussed. Thermal lensing was used for determining the thermal stability of dye covers. The limit of detection of bonded Reactivrot B5A on a glass surface by thermal lensing is 1.6×10−10 mol cm−2.
Calibration of optothermal stratum corneum hydration measurements
Authors: Xiao Peng , Guo Xinxin , Cui Yingxin , Imhof Robert E.
Published: January 2003

We report the development of a method for measuring the absolute water content within the top 100 μm of condensed samples using the optothermal technique. It relies on the measurements of a calibration curve for a particular class of materials to calculate the water content from measurement of the optothermal decay time. Examples of measurements of the water content in the solvent dimethyl sulfoxide and in human stratum corneum are presented.
Nonradiative recombination processes of carriers in InGaN/GaN probed by the microscopic transient lens spectroscopy
Authors: Okamoto Koichi , Inoue Kenichi , Kawakami Yoichi , Fujita Shigeo , Terazima Masahide , Tsujimura Ayumu , Kidoguchi Isao
Published: January 2003

Temporally and spatially resolved observations of the nonradiative recombination (NR) processes of carriers in low dislocated GaN and InGaN/GaN were successfully obtained by using microscopic transient lens spectroscopy. The heat generations and conductivities of NR processes were detected by the signal intensities and the time profiles. We found that the thermal conductivities were not so different at the seed region (threading dislocation density (TDD)=1–2×109 cm−2) and the wing region (TDD=1–2×106 cm−2) of air-bridged lateral epitaxially grown GaN and InGaN/GaN, but the amount of heat generated at the wing regions was much smaller than that at the seed regions.
Continuous wave photothermal deflection spectrometry based on Fresnel diffraction theory: Experimental applications
Authors: Hu Cheng , Zhao Jianhua , Shen Jun
Published: January 2003

Recently we developed a one-dimensional continuous wave photothermal deflection model based on Fresnel diffraction theory with a set of closed-form analytical signal expressions for both fundamental and second harmonic responses. This article reports its experimental applications in thermal property measurements, demonstrating the simplicity, validity, and usefulness of these analytical signal expressions. The thermal diffusivity of air was found to be (2.2±0.1)×10−5 m2/s that is consistent with literature value; the thermal effusivities of a rubber and a graphite plate sample were determined to be (1.2±0.2)×103 W s1/2 m−2 K−1 and (5.6±0.2)×103 W s1/2 m−2 K−1, respectively, which are in good agreement with the measured values of the same samples by a photoacoustic method.
Deep level photothermal spectroscopy for characterizing Ni impurities in Si by a temperature dependent piezoelectric photothermal signal
Authors: Sato S. , Memon A. , Fukuyama A. , Tanaka S. , Ikari T.
Published: January 2003

The temperature variation of the piezoelectric photothermal (PPT) signal intensity of n-type Ni-doped Si was measured from 100 to 300 K. We observed one distinctive peak at 150 K in Ni-doped sample. Since no intense peak could be observed for the controlled sample, we consider this 150 K peak is due to Ni impurity. The activation energy, electron capture cross section, photoionization cross section and concentrations for Ni-deep level are obtained by fitting the observed curve to that from the theoretical analysis based on a rate equation for electrons. The best-fitted parameters are well agreed with that obtained by usual deep level transient spectroscopy measurements and isothermal capacitance transient spectroscopy. Additionally, photoionization cross section of Ni-deep level in Si can be obtained by this method. Since no electrodes are necessary in this experimental technique, the PPT measurement for studying the deep level in semiconductor is very useful.
Investigation of Belousov–Zhabotinsky reaction kinetics using thermal lens spectrometry
Authors: Proskurnin M. A. , Nedosekin D. A. , Kuznetsova V. V.
Published: January 2003

Thermal lensing is proposed for monitoring unstirred Belousov–Zhabotinsky reaction with a mixture of free Fe(II) and its chelate with 1,10-phenanthroline as a catalyst and a photometric indicator of the reaction process. The optimum initial concentrations of components for stable oscillations in system are found. The sensitivity and reproducibility of thermal lensing was compared to spectrophotometry and potentiometry by the model determination of bromide ions by its inhibition effect on the reaction kinetics.
Near-surface depth-resolved midinfrared emission spectroscopy
Authors: Notingher I. , Imhof R. E. , Xiao P. , Pascut F. C.
Published: January 2003

We report the development of a practical instrument that enables depth-resolved midinfrared spectra to be measured in a noncontacting, nondestructive way on samples of arbitrary shape and size and without any prior preparation of the surface. The technique used, thermal emission decay Fourier transform infrared (TED-FTIR) spectroscopy combines time-domain optothermal radiometry with step-scanning FTIR spectroscopy. The instrument uses purpose-designed optics and software to measure optothermal transients at a predetermined number of interferometer path differences, from which depth-resolved spectra in the range 700–1800 cm−1 with a resolution of 12 cm−1 can be calculated. The depth range is limited by the optical and thermal properties of the sample, being ∼10 μm for common organic materials.
Thermal characterization of starch–water system by photopyroelectric technique and adiabatic scanning calorimetry
Authors: Cruz-Orea A. , Bentefour E. H. , Jamée P. , Chirtoc M. , Glorieux C. , Pitsi G. , Thoen J.
Published: January 2003

Starch is one of the most important carbohydrate sources in human nutrition. For the thermal analysis of starch, techniques such as differential scanning calorimetry have been extensively used. As an alternative, we have applied a photopyroelectric (PPE) configuration and adiabatic scanning calorimetry (ASC) to study the thermal properties of starch–water systems. For this study we used nixtamalized corn flour and potato starch with different quantities of distilled water, in order to obtain samples with different moisture content. By using PPE and ASC methods we have measured, for each technique separately, the heat capacity by unit volume (ρcp) at room temperature for a corn flour sample at 90% moisture. The obtained values agree within experimental uncertainty. By using these techniques we also studied the thermal behavior of potato starch, at 80% moisture, in the temperature range where phase transitions occur. In this case the PPE signal phase could be used as a sensitive and versatile monitor for phase transitions.
Thermal diffusivity anisotropy in calamitic-nematic lyotropic liquid crystal
Authors: Pereira J. R. D. , Palangana A. J. , Bento A. C. , Baesso M. L. , Mansanares A. M. , da Silva E. C.
Published: January 2003

The temperature dependence of the thermal diffusivity, α, of a lyotropic liquid crystal is investigated using the thermal lens technique in the range of 12–52 °C. The sample under study presents a calamitic-nematic phase between 15.0 and 47.2 °C. Below and above these transition temperatures it is in the isotropic phase (the phase below 15.0 °C is named reentrant-isotropic, IRE). The sample is aligned in a magnetic field before measurements, with the micelles parallel or perpendicular to the cuvette sidewalls, thus allowing the determination of the thermal diffusivity in both directions. The observed anisotropy in the thermal transport parameter is analyzed based on a model, which considers the geometry of the micelles and the order parameter S as a function of temperature.
Ultrafast dynamics of aqueous solutions in size-controlled reverse micelles
Authors: Hirose Yasushi , Yui Hiroharu , Fujinami Masanori , Sawada Tsuguo
Published: January 2003

The ultrafast refractive index change in the aerosol OT/water/n-heptane reverse micelle system induced by a relaxation process of photoexcited auramine O (AuO) molecules in the micelles was measured by the ultrafast transient lens (UTL) method. A decrease of the refractive index of the solutions was observed following the photoexcitation of AuO molecules, and it was composed of two decay components. The time constants of these two decay components agreed well with the lifetimes of the intermediate states of the relaxation process of AuO, that is, the locally excited state and the twisted intramolecular charge transfer (TICT) state. The UTL signal of the relaxation process of AuO in bulk water was also measured, from which it was found that the decay component corresponding to the decay of the TICT state was not due to the refractive index change of the AuO molecules themselves. This component seemed to originate from the structural change of the reverse micelles induced by the TICT state.
Laser picosecond acoustics with oblique probe light incidence
Authors: Matsuda O. , Wright O. B.
Published: January 2003

Laser picosecond acoustics involves the excitation and detection of picosecond acoustic strain pulses in thin films with ultrashort light pulses. The use of oblique probe light incidence permits a greater degree of freedom in choosing the optical probing conditions and thereby should allow the extraction of more information about the profile of the propagating acoustic strain pulses. Here, we present a theory for the modulation of light reflected at oblique incidence from a solid containing an acoustic strain distribution. The theory can account for the real and imaginary parts of the reflectance variation, and involves both the effect of the transient surface motion and of the photoelastically modulated dielectric constants in the solid. We show, in particular, how the theory can be applied to extract the contribution to the reflectance change arising from the surface motion in an opaque isotropic solid, thereby allowing direct access to the shape of the acoustic strain pulse propagating therein.
Optical coherence and Doppler tomography for monitoring tissue changes induced by laser thermal therapy—An in vivo feasibility study
Authors: Yang Victor X. D. , Pekar Julius , Lo Stewart S. W. , Gordon Maggie L. , Wilson Brian C. , Vitkin I. Alex
Published: January 2003

A high-speed optical coherence and Doppler tomography system suitable for real-time monitoring of the microstructural and microvascular tissue changes induced by laser thermal therapy is described. The performance of the system is demonstrated experimentally in vivo by noting the morphological change, manifest as an increase in the optical extinction coefficient, and the reduction in the blood flow during and after laser thermal therapy in an animal model.
Optical method using fluence or radiance measurements to monitor thermal therapy
Authors: Chin Lee , Pop Mihaela , Whelan William , Sherar Michael , Vitkin Alex
Published: January 2003

We present data from a two-region (coagulated and native tissue) Monte Carlo simulation in spherical geometry to assess the feasibility of using optical fluence and radiance information for determining the boundary of tissue coagulation during thermal therapy. Our results demonstrate that radiance offers directional sensitivity that might be useful in monitoring asymmetric coagulation growth. Preliminary experimental data from fluence monitoring of radio-frequency kidney thermal therapy further indicates that fluence information might be insufficient for determining the coagulation boundary. Therefore, in addition to optical fluence, we are also exploring the potential of radiance monitoring as a method for establishing the position of the coagulation boundary during radio-frequency thermal therapy.
Photothermal techniques applied to thermophysical properties measurements (plenary)
Authors: Vargas H. , Miranda L. C. M.
Published: January 2003

In this article, we present a bird’s eye view of applications of photothermal techniques for evaluation of the thermal properties of different materials. This is followed by the presentation of specific techniques for direct measurements of thermal diffusivity and thermal effusivity and indirect measurements of heat capacity. The presentation finishes by discussing the use of alternative photothermal techniques for the investigation of thermal and transport properties of gases and liquids.
Photothermal characterization of materials biomineralized by mollusks (invited)
Authors: Gómez O. , Quintana P. , Aguilar D. H. , Alvarado-Gil J. J. , Yánez-Limón M. , Diaz L. , Aldana D.
Published: January 2003

In this article the potential of photoacoustic techniques in the optical and thermal characterization of mollusk-made biominerals is explored. The case of two bivalve species with strong structural and architectural differences, oysters (Crassostrea virginica) and mussels (Ischadium recurvum) is considered. The difference between them is closely related to the dominance of different polymorphs of calcium carbonate in crystalline phases known as aragonite and calcite. The thermal diffusivity, visible and infrared absorption spectra, and x-ray analysis show differences between aragonite and calcite made biominerals. Photoacoustic spectra show absorption bands related to Fe, Mn, and organic pigments.
Determination of thermal diffusivity using the critical angle in thermal wave reflection at an interface
Authors: Shendeleva M. L.
Published: January 2003

Reflection and refraction of a plane thermal wave of oblique incidence at an interface is considered theoretically. The thermal wave is generated by an instantaneous plane heat source inclined at a certain angle to the interface. The Green functions for the reflected and transmitted waves are obtained by satisfying boundary conditions. It is shown that the reflection coefficient exhibits a sharp maximum when the angle of incidence coincides with a critical angle. This property can be used for measurements of thermal parameters of two media in thermal contact.
Investigation of metal–glaze structures with photoacoustic and infrared methods
Authors: Suszyński Z. , Majchrzak P. , Arsoba R. , Napieralski A. , Tylman W.
Published: January 2003

This article presents methods of investigation of thermal properties of metal–insulator joints. The thermal parameters of joined materials and interlayer were determined based on photoacoustic contrast images and neural network computations. Possibilities of visualization of the quality of adhesion between glaze and metal using infrared detection with induction heating also is presented.
Counting particles by means of optoacoustics: Potential limits in real solutions
Authors: Autrey Tom , Egerev Sergey , Foster Nancy S. , Fokin Andrey , Ovchinnikov Oleg
Published: January 2003

The irradiation of an inhomogeneous liquid sample with a long train of short laser pulses and subsequent recording of a histogram of the magnitudes of the acoustic responses can serve as a diagnostic tool for various applications. The absorption of an incident light by a suspended particle may cause a cavitation event. Exploitation of the random cavitation events which, in turn act as effective acoustic radiators, may provide a useful measurement tool rather than an inconvenience.
Influence of surface roughness on photothermal depth profiling (invited)
Authors: Walther H. G.
Published: January 2003

Surface roughness must be taken into account for accurate interpretation of photothermal measurements. An expression for photothermal signals from rough samples was derived by combining the effect of roughness induced thermal wave dispersion with equivalent layer model. The performance of the proposed model was successfully demonstrated by comparing calculations with radiometric measurements from rough steel samples.
In-vivo hydration profile mapping of human stratum corneum using fiber-optic optothermal radiometry
Authors: Pascut Flavius C. , Xiao Peng , Imhof Robert E.
Published: January 2003

We report the development of an instrument, a fiber-optic optothermal transient emission radiometer (OTTER), which overcomes an important limitation in our current bench-top optothermal instrument in being able to perform in-vivo measurements at arbitrary human skin sites. Its main component is a hand-held probe with laser delivery fiber, MCT detector and compact infrared emission focusing optics. This probe can be used to scan the surface of the sample, a process in which optothermal transient signal maps can be measured. The optics design has been optimized using the Zemax ray-tracing software and was found to be 3.4 times more efficient than our current OTTER optics. Preliminary results showing the effect of moisturizing cream as a three-dimensional stratum corneum hydration map is presented.
Mathematical modeling and inverse algorithm for optothermal data analysis
Authors: Cui Yingxin , Xiao Peng , Imhof Robert E. , Glorieux Christ
Published: January 2003

A multilayered mathematical model has been developed for optothermal data analysis of thermally homogeneous but optically inhomogeneous samples. Based on this model, an inverse algorithm using neural networks was designed for calculating the depth profile of an optical excitation absorption coefficient from optothermal measurement data. The performance of the algorithm was tested on simulated data and measured data.
Wide-field time-resolved fluorescence anisotropy imaging (TR-FAIM): Imaging the rotational mobility of a fluorophore
Authors: Siegel J. , Suhling K. , Lévêque-Fort S. , Webb S. E. D. , Davis D. M. , Phillips D. , Sabharwal Y. , French P. M. W.
Published: January 2003

We report a picosecond time-gated fluorescence lifetime imaging (FLIM) system extended to perform time-resolved fluorescence anisotropy imaging (TR-FAIM). Upon excitation with linearly polarized laser pulses, the parallel and perpendicular components of the fluorescence emission from a sample are imaged simultaneously using a polarization-resolved imager. The imaging technique presented here quantitatively reports the rotational mobility of a fluorophore as it varies according to the local environment. In a single acquisition run it yields maps of both rotational correlation time and fluorescence lifetime as they vary across a sample. TR-FAIM has been applied to imaging standard multiwell plate samples of rhodamine 6G dissolved in methanol, ethylene glycol, trimethylene glycol, and glycerol. The observed rotational correlation times and fluorescence lifetimes, which report the local viscosity and refractive index of the local rhodamine 6G environment, respectively, are in good agreement with previously published single point measurements. By considering the linear dependence of the rotational correlation time on viscosity up to 20 cP, we are able to obtain a two-dimensional viscosity map. Wide-field maps of rotational correlation time, and therefore viscosity, have been obtained. This illustrates the potential to image the local viscosity and fluorescence lifetime distributions of fluorophore tagged proteins in cells.
Thermal diffusivity of composites determined by photoacoustic piezoelectric technique
Authors: Sun Li , Zhang Shu-yi , Zhao Yan-zhu , Li Zi-quan , Cheng Li-ping
Published: January 2003

The thermal diffusivity of fiber-reinforced composites (Al2O3x/SAE321) has been studied by a photoacoustic piezoelectric technique based on a simplified thermoelastic theory. It is shown that this method is easy to perform and especially effective in determining the average thermal characters of materials with microinhomogeneous structures.
On the use of photothermal techniques for monitoring constructed wetlands
Authors: Gatts C. E. N. , Faria R. T. , Vargas H. , Lannes L. S. , Aragon G. T. , Ovalle A. R. C.
Published: January 2003

Wetlands are a valued part of landscapes throughout the world. The steady increase of industrial facilities and disorganized urbanization processes, especially in developing countries, became a serious menace to these systems. The capability of wetlands to serve as a sink for nonpoint pollutants, particularly nutrients, is remarkable, but not limitless. For this reason, efforts to preserve them are considered a strategic issue for several countries. In addition, due to the exploding costs for sewage treatment, constructed wetlands for wastewater treatment (reed-bed systems) have been widely used under a variety of different conditions. Wetlands present unique characteristics related to biogeochemical cycles, the transport and transformation of chemicals due to interrelated physical, and chemical, and biological processes. Particularly, vegetated wetlands can act as a source for greenhouse gases through the emission of sediment-produced methane (CH4) to atmosphere. From studies concerning the behavior of Salvinia auriculata Aublet., we intend to demonstrate the potential use of photothermal techniques for monitoring gaseous emissions in wetlands.
Use of thermal lensing for the determination of pyrogens
Authors: Orlova N. V. , Proskurnin M. A. , Samburova V. A. , Dryagleva I. D. , Brusnichkin A. V.
Published: January 2003

The conditions of spectrophotometric determination of lipopolysaccharides (LPS) by methylene blue dye were proposed. The limit of detection of LPS is 100 ng/ml. The conditions of spectrophotometric determination of LPS with Stains-all were proposed, the limit of detection of LPS is 500 ng/ml. The optimization of spectrophotometric determination of LPS by the reaction of 2-keto-3-deoxyoctonic acid with thiobarbituric acid in the presence of periodate and metaarsenite was made, the limit of detection is 800 ng/ml. The limit of detection by thermal lensing is 70 ng/ml. The thermal-lens method was successfully used for LPS determination in the endotoxin standard from E. coli.
Diesel engines gas emissions monitored by photoacoustic spectroscopy
Authors: Schramm D. U. , Sthel M. S. , da Silva M. G. , Carneiro L. O. , Souza A. P. , Vargas H.
Published: January 2003

In Brazil, there has been an increasing demand for power generators, driven by diesel oil and other fossil fuels, because of the lack of rain and consequent decreased availability of hydroelectric energy, leading to the rationing of energy. It is known that the combustion of diesel oil in power generators is the main source of many contaminant gases such as nitrogen oxides, SO2, CO, and hydrocarbons. In this work, we carried out a thorough analysis, using the photoacoustic technique of gas samples collected in a closed room where a power generator was turned on for 60 min to saturate the ambient. Some substances such as SO2 and NO2 were detected in the parts per million range.
Current mode versus voltage mode measurement of signals from pyroelectric sensors
Authors: Chirtoc M. , Bentefour E. H. , Antoniow J. S. , Glorieux C. , Thoen J. , Delenclos S. , Sahraoui A. H. , Longuemart S. , Kolinsky C. , Buisine J. M.
Published: January 2003

Usually, in photothermal experiments using pyroelectric sensors, the instrumental transfer function is cancelled by normalization to reference measurements, regardless of current (C) or voltage (V) mode processing of signals. Nevertheless, there are several advantages when using a current preamplifier, instead of a high-impedance voltage preamplifier. Due to the low input impedance of the former, the capacitance of the sensor (and its temperature dependence), the capacitance of the connection cable, and the loss resistance of the pyroelectric crystal do not influence the signal. Moreover, the whole input circuitry is less prone to electromagnetic pick up through stray capacitances. In (C) mode, the frequency characteristic is linear (with −180° constant phase) up to a rather high frequency, instead of having (in V mode) a 1/f dependence above a certain frequency and a variable phase shift from 0° to −90°.
Thermal resistance of adhesive tapes measured by the photopyroelectric method
Authors: Chirtoc M. , Chirtoc I. , Pittois S. , Glorieux C. , Thoen J.
Published: January 2003

Using the photopyroelectric method, we have determined the thermal resistance r and the thermal conductivity k of adhesive tapes, which are consistent with those previously reported for similar samples. Moreover, the method is capable of separating the different components of r that add up in the total resistance introduced by an adhesive tape placed between two surfaces: A component due to the sample material itself, a component in the presence of material inhomogeneities, and a contact resistance due to surface roughness. The first two components are characteristic of the sample material while the latter depends on the adhesive properties of the sample and on the surface state of the support material. In our case, it was equivalent to an air gap in the submicron range.
Imaging setup for temperature, topography, and surface displacement measurements of microelectronic devices
Authors: Grauby S. , Dilhaire S. , Jorez S. , Claeys W.
Published: January 2003

We present an imaging system that enables the extraction of three different types of information: First, the topography measurement of an electronic device at rest; then, two other informations are obtained when the same device is submitted to a transient current: on one hand, the induced surface displacement and on the other hand, the qualitative surface temperature variations field. The same bench includes two imaging techniques, one based upon interferometry, the other upon thermoreflectance, both of them using a light-emitting diode as a source of light. Results on a microheater are presented.
Photopyropiezoelectric elastic bending method
Authors: Todorović D. M. , Nikolić P. M. , Bojičić A. , Smiljanić M. , Vasiljević-Radović D. G. , Radulović K. T.
Published: January 2003

A method of investigation of semiconductors and metal–semiconductor structures based on two techniques: The elastic bending technique and pyropiezoelectric (PPE) technique was presented. The method was demonstrated on a metal–semiconductor–metal (MSM) structure, which is attached to a PPE detector. Two different ac voltages can be measured: One on the electrodes of MSM structure—the ac-photovoltage, and another on the electrodes of the PPE detector—the PPE voltage. The ac photovoltage is a consequence of the photogenerated plasma processes in the sample (MSM structure). Photogenerated plasma waves in a semiconductor are followed by the thermal and elastic waves (the elastic bending). Then, the pyroelectric voltage is a consequence of the thermal processes and the piezoelectric voltage is a consequence of elastic bending in the sample-PPE detector system. A theoretical model for a metal–semiconductor–metal-pyro(piezo)electric system is given including the space-charge regions and electronic states on the semiconductor surfaces, thermodiffusion, thermoelastic, and electronic deformation effects in a semiconductor. The photoelectric and pyropiezoelectric effects are investigated by analyzing the ac voltages as a function of the modulation frequency of excitation beam.
Application of an optical birefringence interferometer to photothermal detection for characterizing thermal diffusivities
Authors: Xu X. D. , Zhang S. Y. , Kuo P. K.
Published: January 2003

In the pulsed photothermal displacement detection, the signals are strongly dependent upon the thermal properties of materials. The thermoelastic displacement excited by a pulsed laser is detected by a birefringence interferometer. Meanwhile, thermal diffusivities of plate samples are evaluated by a three-dimensional thermoelastic displacement model. Based on the experimental data of several copper plate samples, the thermal diffusivities of the plates are theoretically simulated. The experimental measurements and the theoretical simulated results demonstrate that the technique is an effective method for evaluating thermal diffusivities of plate materials.
Nonstationary temperature distribution caused by bulk absorption of laser pulse
Authors: Gurevich Yuri , Logvinov Georgi , de Rivera Luis Niño , Titov Oleg
Published: January 2003

Nonequilibrium temperature is calculated and analyzed in a one-dimensional sample irradiated by a laser rectangular pulse. The general solution is obtained for arbitrary pulse duration compared with the relaxation time of nonstationary thermal diffusion (characteristic time of the problem).
Signal processing in pulsed photoacoustic detection of traces by means of a fast Fourier transform-based method
Authors: Slezak Verónica
Published: January 2003

This work describes a simple numerical procedure which, applied to a digitally recorded signal, allows the recovery of a spectrum of higher-frequency resolution than the direct use of the fast Fourier transform alone. The advantages of the method and its limitations are analyzed in applications to theoretical functions. The particular use in pulsed photoacoustic spectroscopy is shown when a low concentration (5 ppmV) NO2–air mixture is monitored upon irradiation with visible laser pulses (∼8 ns full width at half maximum). This way, the shape of the resonance peak is determined with high precision.
On the influence of the coupling fluid in photopyroelectric measurements
Authors: Salazar A.
Published: January 2003

In this work, the influence of the coupling fluid in the measurement of the thermal properties of solid samples using a photopyroelectric (PPE) setup in the standard back configuration is analyzed. It is demonstrated theoretically and experimentally that due to the coupling fluid, the thermal diffusivity of the sample is underestimated. However, its influence disappears when performing relative measurements as a function of the temperature. That is the reason why the PPE technique is very appropriate for the thermal characterization of phase transitions.
Photothermal sensing of nanoscale targets
Authors: Zharov Vladimir , Lapotko Dmitri
Published: January 2003

The further development of a photothermal (PT) method for the sensing of nanoscale absorbing targets is presented. This method is based on the irradiation of nanotargets with a short laser pulse and time-resolved PT visualization of laser-induced thermal effects around targets. It is accomplished with second probe beam that senses the target with adjustable time delay after the pump laser pulse. It is shown that an analysis of diffraction limited PT images at a different time delay after a laser pulse can yield information on target size. The practical capability of this approach is demonstrated for visualization of nanoscale gold particles with a tunable parametric pulse laser-OPO (420–570 nm, 0.1–100 μJ, 8 ns width), as a pump laser and Raman-shifter (639 nm, 13 ns width), as a probe laser with a tunable delay of the probe pulse relative to the pump pulse in the range of 0–5000 ns.
Real-time imaging of surface acoustic waves in thin films and microstructures on opaque substrates (invited)
Authors: Sugawara Y. , Wright O. B. , Matsuda O.
Published: January 2003

We present a real-time imaging technique for surface acoustic waves on samples with opaque substrates. We image the surface acoustic wave propagation on a silicon substrate coated with a gold film, and derive the dispersion relation for propagation in symmetry directions. In addition, we image surface acoustic waves at frequencies up to 2 GHz on a diamond substrate coated with a gold film, and on a microstructure deposited on a silicon substrate.
Photothermal and electronic elastic effects in microelectromechanical structures
Authors: Todorović D. M.
Published: January 2003

The dynamic thermoelastic and electronic deformation bending in various micromechanical systems were investigated. The elastic bending effect was investigated as a function of modulation frequency including the generation and propagation processes of the plasma, thermal, and elastic waves. The theoretical model for two microstructures (circular plate and cantilever beam) was given and the relations for dynamic elastic bending were derived. The elastic bending was calculated and analyzed for both type of microplates. This investigation is important for the analysis of the possibility to use these semiconducting optically driven microstructures as sensors and actuators.
Thermal contact resistance evaluation in polymer-based carbon fiber composites
Authors: Macedo F. , Ferreira J. A.
Published: January 2003

The thermal contact resistance of polymer-based carbon fiber composites was calculated from experimental thermal conductivity values. Thermal conductivity of the composites increases as the fiber content increases. In order to explain the variation with size and volume fraction of the conductive inclusions in the composite, an effective medium model, which includes the effect of interfacial thermal resistance, was applied. Two different geometries for the fiber distribution in the matrix were considered. The calculated thermal contact resistance obtained from the effective medium models is in good agreement with the theoretical predictions. Once tested and validated, these models can also contribute to evaluate the best choice of materials for composite production, as maximum values for the thermal conductivity can be estimated.
Determination of the diffusion coefficient of CO2, O2, and water vapor for poly-3-hydroxy octanoate membranes
Authors: da Silva M. G. , Gonçalves S. S. , Sthel M. S. , Schramm D. U. , Sanchez R. R. , Rieumont J. B. , Vargas H.
Published: January 2003

The constant use of norecyclable material throughout the last century has become a huge pollution problem. Consequently, the development of biocompatible and biodegradable material plays an important role nowadays in this context. In order to contribute to this aim, this article is concerned with the use of photoacoustic methodologies to investigate the diffusion coefficient of CO2 and water vapors for poly-3-hydroxy octanoate which is a biodegradable and biocompatible material. In addition, a second methodology based on the paramagnetic properties of O2 molecules was also applied to investigate the diffusion coefficient of O2.
Loss factor determination of composite laminates by the photoacoustic technique
Authors: Navarrete M. , Villagrán-Muniz M.
Published: January 2003

This article presents a method for identifying elastic and damping properties of unidirectional composite laminates by using photoacoustic (PA) signal data. In this method, the laser pulse is used as a standard source of ultrasound. The analysis was developed considering that the acoustic wave propagation onto the material is the impulse response from a second-order system. The loss fact η(θ) and the engineering constant E(θ) were determined for a five-fiber orientation angle in three samples with different thicknesses. Samples based on glass fibers and epoxy matrix were prepared with low fiber volume fraction, for this purpose. The constants for each direction were measured from the PA signal data obtained in successive positions between the laser source and the transducer. For E(θ) we used the first arrival time delay, and for η(θ) the first peak amplitude. The values obtained by this method show good agreement with those in literature and demonstrate the efficiency of the proposed method. In principle, with this method, all elastic constants and damping factors can be determined simultaneously.
On the use of the optothermal window technique for the determination of iron (II) content in fortified commercial milk
Authors: Cardoso S. L. , Dias C. M. F. , Lima J. A. P. , Massunaga M. S. O. , da Silva M. G. , Vargas H.
Published: January 2003

This work reports on the use of the optothermal window and a well-proven phenanthroline colorimetry method for determination of iron (II) content in a commercial fortified milk. Initially, iron (II) in distilled water was determined using a series of calibration samples with ferrous sulfate acting as the source of iron (II). In the following phase, this calibration methodology was applied to commercial milk as the sample matrix. The phenanthroline colorimetry [American Public Health Association, Washington, DC (1998)] was chosen in an attempt to achieve proper selectivity (i.e., to obtain the absorption band, the wavelength of which is centered near the radiation wavelength available for our experiments: Excitation wavelength at a 514-nm line of a 20-mW tunable Ar ion laser). Finally, samples of commercially available fortified milk were analyzed in an attempt to access Fe (II) content.