Structure and nonlinear optical properties of novel transparent glass-ceramics based on Co2+:ZnO nanocrystals

Transparent glass-ceramics (GCs) based on Co2+:ZnO nanocrystals (mean diameter, 11 nm) are synthesized on the basis of cobalt-doped glasses of the K2O–ZnO–Al2O3–SiO2 system. For these GCs, the absorption band related to the 4A2(4F) → 4T1(4F) transition of Co2+ ions in tetrahedral sites spans until ~1.73 μm. Saturation of the absorption is demonstrated at 1.54 μm, with a saturation fluence Fs = 0.8 ± 0.1 Jcm−2 (σGSA = 1.7 ± 0.2 × 10−19 cm2) and a recovery time of 890 ± 10 ns. Passive Q-switching of an Er,Yb:glass laser is realized with the synthesized GCs. This laser generated 0.37 mJ/100 ns pulses at 1.54 μm. The developed GCs are promising as saturable absorbers for 1.6–1.7 μm crystalline erbium lasers

Meneco, a Topology-Based Gap-Filling Tool Applicable to Degraded Genome-Wide Metabolic Networks

International audienceIncreasing amounts of sequence data are becoming available for a wide range of non-model organisms. Investigating and modelling the metabolic behaviour of those organisms is highly relevant to understand their biology and ecology. As sequences are often incomplete and poorly annotated, draft networks of their metabolism largely suffer from incompleteness. Appropriate gap-filling methods to identify and add missing reactions are therefore required to address this issue. However, current tools rely on phenotypic or taxonomic information, or are very sensitive to the stoichiometric balance of metabolic reactions, especially concerning the co-factors. This type of information is often not available or at least prone to errors for newly-explored organisms. Here we introduce Meneco, a tool dedicated to the topological gap-filling of genome-scale draft metabolic networks. Meneco reformulates gap-filling as a qualitative combinatorial optimization problem, omitting constraints raised by the stoichiometry of a metabolic network considered in other methods, and solves this problem using Answer Set Programming. Run on several artificial test sets gathering 10,800 degraded Escherichia coli networks Meneco was able to efficiently identify essential reactions missing in networks at high degradation rates, outperforming the stoichiometry-based tools in scalability. To demonstrate the utility of Meneco we applied it to two case studies. Its application to recent metabolic networks reconstructed for the brown algal model Ectocarpus siliculosus and an associated bacterium Candidatus Phaeomarinobacter ectocarpi revealed several candidate metabolic pathways for algal-bacterial interactions. Then Meneco was used to reconstruct, from transcriptomic and metabolomic data, the first metabolic network for the microalga Euglena mutabilis. These two case studies show that Meneco is a versatile tool to complete draft genome-scale metabolic networks produced from heterogeneous data, and to suggest relevant reactions that explain the metabolic capacity of a biological system

A calibration technique for frequency domain photothermoacoustics

Photoacoustic (or more precisely, photothermoacoustic) signals are generated by the absorption of photons, expressed as acoustic waves, and can be related to the incident laser fluence rate. Here a calibration procedure for frequency domain (FD) photoacoustics is presented which utilizes the relationship between photoacoustic (PA) signal amplitude and laser fluence rate. The sample is irradiated with a continuous wave laser which is amplitude modulated at varying frequencies. Applying the calibration procedure to the PA detected signals, a linear relationship is obtained between the fluence rate and the signal amplitude

Models and measurements of light intensity changes during laser interstitial thermal therapy: implications for optical monitoring of the coagulation boundary location

abstract: We have developed a multi-region spherical Monte Carlo (MC) model to simulate the dynamic changes in light intensity measured during laser interstitial thermal therapy (LITT). Model predictions were validated experimentally in tissue-simulating albumen phantoms with well-characterized optical properties that vary dynamically with LITT in a way similar to tissue. For long treatments (2.5 W, similar to1800 s), the transient light intensity changes demonstrated better qualitative agreement with a three-region MC model (with an inner layer of fully coagulated optical properties, a middle layer of partially coagulated properties and an outer region of native properties); for short treatments (4 W, similar to240 s), better qualitative agreement was seen with a two-region MC model (with an inner layer of fully coagulated properties and outer region of native properties). These differences were attributed to differences in coagulation formation during low- and high-powered heating regimes, respectively. At the end of heating, a three-region coagulation zone was observed for both heating schemes. Quantitatively, final light intensity changes at the end of heating were compared with changes predicted by both two- and three-region MC for the same experimentally measured coagulation size and found to agree within similar to30% for both models. The developed MC model helps lend insight into the nature of thermal coagulation events occurring for low and high power LITT irradiation schemes. Cited Reference: CR: ALEXANDRAKIS G, 1998, APPL OPTICS, V37, P7401 BENNEDBAEK FN, 2001, BRIT J RADIOL, V74, P905 BEVAN PD, 2001, ULTRASOUND MED BIOL, V27, P809 BREMER C, 2002, EUR RADIOL, V12, P5 CHEONG WF, 1990, IEEE J QUANTUM ELECT, V26, P2166 CHIN LCL, 2001, PHYS MED BIOL, V46, P2407 DEJODE ML, 1999, PHYS MED BIOL, V44, P3027 EYRICH GKH, 2000, LASER SURG MED, V26, P467 GLASSNER AS, 1989, INTO RAY TRACING HENYEY LG, 1941, ASTROPHYS J, V93, P70 IIZUKA MN, 1999, LASER SURG MED, V25, P159 IIZUKA MN, 2000, PHYS MED BIOL, V45, P1335 KIENLE A, 1998, APPL OPTICS, V37, P779 MARTELLI F, 2000, PHYS MED BIOL, V45, P1359 PATTERSON MS, 1991, LASER MED SCI, V6, P155 PEARCE J, 1995, OPTICAL THERMAL RESP PHAM TH, 2000, APPL OPTICS, V39, P4733 PURDIE TG, 2000, PHYS MED BIOL, V45, P115 RITZ JP, 2001, LASER SURG MED, V29, P205 ROGGAN A, 1995, LASER INDUCED INTERS SHERAR MD, 2000, PHYS MED BIOL, V45, P3563 SHERAR MD, 2001, J UROLOGY, V166, P1707 SKINNER MG, 2000, PHYS MED BIOL, V45, P1375 SVAASAND LO, 1999, PHYS MED BIOL, V44, P801 VANSTAVEREN HJ, 1995, LASER MED SCI, V10, P137 VITKIN IA, 1997, MED PHYS, V24, P269 WANG LH, 1995, COMPUT METH PROG BIO, V47, P131 WHELAN WM, 1996, THESIS MCMASTER U HA WHELAN WM, 2001, PHYS MED BIOL, V46, N91 WILSON BC, 1983, MED PHYS, V10, P824 WOHLGEMUTH WA, 2001, LASER SURG MED, V29, P37

Physics in Medicine and Biology 50 14 N141 N153 IOP PUBLISHING LTD BRISTOL; DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND

A novel optoacoustic phantom made of polyvinyl chloride-plastisol (PVCP) for optoacoustic studies is described. The optical and acoustic properties of PVCP were measured. Titanium dioxide (TiO2) powder and black plastic colour (BPC) were used to introduce scattering and absorption, respectively, in the phantoms. The optical absorption coefficient (mu(a)) at 1064 nm was determined using an optoacoustic method, while diffuse reflectance measurements were used to obtain the optical reduced scattering coefficient These optical properties were calculated to be mu(a) = (12.818 +/- 0.001)A(BPC) cm(-1) and mu'(s) = (2.6 +/- 0.2) S-TiO2 + (1.4 +/- 0.1) cm(-1), where A(BPC) is the BPC per cent volume concentration, and S-TiO2 is the TiO2 volume concentration (mg mL(-1)). The speed of sound in PVCP was measured to be (1.40 +/- 0.02) x 10(3) m s(-1) using the pulse echo transmit receive method, with an acoustic attenuation of (0.56 +/- 1.01) f(Mhz)((1.51 +/- 0.06))(dB cm(-1)) in the frequency range of 0.61-1.25 MHz, and a density, calculated by measuring the displacement of water, of 1.00 +/- 0.04 g cm(-3). The speed of sound and density of PVCP are similar to tissue, and together with the user-adjustable optical properties, make this material well suited for developing tissue-equivalent phantoms for biomedical optoacoustics.CR: BINI MG, 1984, IEEE T BIO-MED ENG, V31, P317 CHEONG WF, 1990, IEEE J QUANTUM ELECT, V26, P2166 DEKORTE CL, 1997, ULTRASONIC IMAGING, V19, P112 DIAMOND KR, 2003, PHYS MED BIOL, V48, P4135 FARRELL TJ, 1992, MED PHYS, V19, P879 FARRELL TJ, 1992, PHYS MED BIOL, V37, P2281 HENRICHS PM, 2004, P SOC PHOTO-OPT INS, V5320, P8, DOI 10.1117/12.536869 HYDE DE, 2001, PHYS MED BIOL, V46, P369 IIZUKA MN, 1999, LASER SURG MED, V25, P159 KHARINE A, 2003, PHYS MED BIOL, V48, P357 KIENLE A, 1996, PHYS MED BIOL, V41, P221 MADSEN EL, 1999, J ULTRAS MED, V18, P615 MADSEN SJ, 1992, APPL OPTICS, V31, P3509 ORAEVSKY AA, 1993, P SOC PHOTO-OPT INS, V1882, P8 ORAEVSKY AA, 1997, APPL OPTICS, V36, P402 ROYSTON DD, 1996, J BIOMED OPT, V1, P110 SPIROU GM, 2004, P SOC PHOTO-OPT INS, V5320, P44, DOI 10.1117/12.535360 SUROWIEC A, 1992, INT J HYPERTHER, V8, P795 TANAKA T, 1981, SCI AM, V244, P124 TAYLOR JR, 1982, INTRO ERROR ANAL VANSTAVEREN HJ, 1991, APPL OPTICS, V30, P4507 WELCH AJ, 1995, OPTICAL THERMAL RESP XU T, 1995, APPL OPTICS, V42, P577

Physical Review E 72 5 051908 051908 AMERICAN PHYSICAL SOC COLLEGE PK; ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA

Frequency-domain correlation and spectral analysis photothermoacoustic (FD-PTA) imaging is a promising new technique, which is being developed to detect tumor masses in turbid biological tissue. Unlike conventional biomedical photoacoustics which uses time-of-flight acoustic information induced by a pulsed laser to indicate the tumor size and location, in this research, a new FD-PTA instrument featuring frequency sweep (chirp) and heterodyne modulation and lock-in detection of a continuous-wave laser source at 1064 nm wavelength is constructed and tested for its depth profilometric capabilities with regard to turbid media imaging. Owing to the linear relationship between the depth of acoustic signal generation and the delay time of signal arrival to the transducer, information specific to a particular depth can be associated with a particular frequency in the chirp signal. Scanning laser-fluence modulation frequencies with a linear frequency sweep method preserves the depth-to-delay time linearity and recovers FD-PTA signals from a range of depths. Combining with the depth information carried by the back-propagated acoustic chirp signal at each scanning position, one could rapidly generate subsurface three-dimensional images of the scanning area at optimal signal-to-noise ratios and low laser fluences, a combination of tasks that is difficult or impossible by use of pulsed photoacoustic detection. In this paper, results of PTA scans performed on tissue mimicking control phantoms with various optical, acoustical, and geometrical properties are presented. A mathematical model is developed to study the laser-induced photothermoacoustic waves in turbid media. The model includes both the scattering and absorption properties of the turbid medium. A good agreement is obtained between the experimental and numerical results. It is concluded that frequency domain photothermoacoustics using a linear frequency sweep method and heterodyne lock-in detection has the potential to be a reliable tool for biomedical depth-profilometric imaging.CR: ANDREEV VG, 2000, P SOC PHOTO-OPT INS, V3916, P36 BEARD PC, 2000, P SOC PHOTO-OPT INS, V3916, P100 FARRELL TJ, 1992, MED PHYS, V19, P879 FOURNIER D, 1993, 2666, US HOELEN CGA, 1999, P SOC PHOTO-OPT INS, V3597, P336 KARABUTOV A, 1993, LASER OPTOACOUSTICS KARABUTOV AA, 1995, APPL OPTICS, V34, P1484 KRAUTKRAMER J, 1983, ULTRASONIC TESTING M, P620 LIDE DR, 1999, CRC HDB CHEM PHYSICS, P14 MANDELIS A, 2001, DIFFUSION WAVE FIELD, P663 MANDELIS A, 2005, J OPT SOC AM B, V22, P1024 ORAEVSKY AA, 2000, P SPIE, V3916 ORAEVSKY AA, 2001, P SPIE, V4256 PILATOU MC, 2000, P SOC PHOTO-OPT INS, V3916, P48 ROYSTON DD, 1996, J BIOMED OPT, V1, P110 SELB J, P SPIE, V4256, P200 STAR WM, 1987, J PHOTOCH PHOTOBIO B, V1, P149 WANG LH, 1995, OPT LETT, V20, P629 WELCH AJ, 1995, TISSUE OPTICAL PROP

Media 7: Optimum selection of input polarization states in determining the sample Mueller matrix: a dual photoelastic polarimeter approach

Originally published in Optics Express on 27 August 2012 (oe-20-18-20466

Media 8: Optimum selection of input polarization states in determining the sample Mueller matrix: a dual photoelastic polarimeter approach

Originally published in Optics Express on 27 August 2012 (oe-20-18-20466