Grado de aclaramiento de tatuajes y eventos adversos, posterior a una sesión con láser q-switch

Introducción: Los resultados de la remoción de tatuajes con láser de sesión a sesión según los parámetros utilizados son limitados en la literatura. Objetivo: Evaluar los cambios en el aclaramiento de tatuajes y factores asociados posterior a una sesión con láser y los efectos adversos. Materiales y Métodos: Estudio longitudinal retrospectivo de antes y después de 1 sesión de con láser para remoción de tatuajes, donde se determinaron parámetros del tratamiento, aclaramiento y efectos adversos. Resultados: Se evaluaron 35 pacientes para un total de 98 sesiones, fototipo de piel II y IV. Equipos utilizados laser Q-Switch Nd Yag 1064 (83.3%), láser Q-Switch Nd YAG 532(11.3%) y laser Q-Switch Rubí (4.1%). El aclaramiento posterior a la sesión de láser fue evaluado por dos evaluadores independientes, mostrando concordancia significativa (Kappa de 0.615, p<0.001), con aclaración en un 96% de los tatuajes después de la sesión de láser. (p< 0.001). Se encontraron cambios significativos entre la densidad de energía aplicada y las categorías de aclaramiento de la escala de 0 a 3, siendo a mayor densidad mayor el nivel de aclaramiento (p= 0.05). No se encontró asociación significativa entre el número de pases y el aclaramiento del tatuaje. Los efectos adversos fueron del 5.4%. Cicatriz 2%, hiperpigmentación 2% y hipopigmentación 1%. Conclusión: Posterior a una sesión de remoción de tatuajes con láser Q-Switch hay un aclaramiento significativo en un 96% asociado con la densidad de energía, a mayor densidad de energía mayor el nivel de aclaramiento y no al número de pases realizados.

Synthesis and characterization of thermally stable second-order nonlinear optical side-chain polyimides containing thiazole and benzothiazole push-pull chromophores

Push-pull nonlinear optical (NLO) chromophores containing thiazole and benzothiazole acceptors were synthesized and characterized. Using these chromophores a series of second-order NLO polyimides were Successfully prepared from 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), pyromellitic dianhydride (PMDA) and 3,3'4,4'-benzophenone tetracarboxylic dianhydride (BTDA) by a standard condensation polymerization technique. These polyimides exhibit high glass transition temperatures ranging from 160 to 188 degrees C. UV-vis spectrum of polyimide exhibited a slight blue shift and decreases in absorption due to birefringence. From the order parameters, it was found that chromophores were aligned effectively. Using in situ poling and temperature ramping technique, the optical temperatures for corona poling were obtained. It was found that the optimal temperatures of polyimides approach their glass transition temperatures. These polyimides demonstrate relatively large d(33) values range between 35.15 and 45.20 pm/V at 532 nm. (C) 2008 Elsevier B.V. All rights reserved.

Retrievals of thick cloud optical depth from the Geoscience Laser Altimeter System (GLAS) by calibration of solar background signal

Laser beams emitted from the Geoscience Laser Altimeter System (GLAS), as well as other spaceborne laser instruments, can only penetrate clouds to a limit of a few optical depths. As a result, only optical depths of thinner clouds (< about 3 for GLAS) are retrieved from the reflected lidar signal. This paper presents a comprehensive study of possible retrievals of optical depth of thick clouds using solar background light and treating GLAS as a solar radiometer. To do so one must first calibrate the reflected solar radiation received by the photon-counting detectors of the GLAS 532-nm channel, the primary channel for atmospheric products. Solar background radiation is regarded as a noise to be subtracted in the retrieval process of the lidar products. However, once calibrated, it becomes a signal that can be used in studying the properties of optically thick clouds. In this paper, three calibration methods are presented: (i) calibration with coincident airborne and GLAS observations, (ii) calibration with coincident Geostationary Opera- tional Environmental Satellite (GOES) and GLAS observations of deep convective clouds, and (iii) cali- bration from first principles using optical depth of thin water clouds over ocean retrieved by GLAS active remote sensing. Results from the three methods agree well with each other. Cloud optical depth (COD) is retrieved from the calibrated solar background signal using a one-channel retrieval. Comparison with COD retrieved from GOES during GLAS overpasses shows that the average difference between the two retriev- als is 24%. As an example, the COD values retrieved from GLAS solar background are illustrated for a marine stratocumulus cloud field that is too thick to be penetrated by the GLAS laser. Based on this study, optical depths for thick clouds will be provided as a supplementary product to the existing operational GLAS cloud products in future GLAS data releases.

Nanostructured europium oxide thin films deposited by pulsed laser ablation of a metallic target in a He buffer atmosphere

Nanostrucured europium oxide and hydroxide films were obtained by pulsed Nd:YAG (532 nm) laser ablation of a europium metallic target, in the presence of a 1 mbar helium buffer atmosphere. Both the produced film and the ambient plasma were characterized. The plasma was monitored by an electrostatic probe, for plume expansion in vacuum or in the presence of the buffer atmosphere. The time evolution of the ion saturation current was obtained for several probe to substrate distances. The results show the splitting of the plume into two velocity groups, being the lower velocity profile associated with metal cluster formation within the plume. The films were obtained in the presence of helium atmosphere, for several target-to-substrate distances. They were analyzed by Rutherford backscattering spectrometry, x-ray diffraction, and atomic force microscopy, for as-deposited and 600 degrees C treated-in-air samples. The results show that the as-deposited samples are amorphous and have chemical composition compatible with europium hydroxide. The thermally treated samples show x-ray diffraction peaks of Eu(2)O(3), with chemical composition showing excess oxygen. Film nanostructuring was shown to be strongly correlated with cluster formation, as shown by velocity splitting in probe current versus time plots. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3457784]

Histopathology and laser autofluorescence of ischemic kidneys of rats

The purpose of this research was to evaluate the severity of renal ischemia/reperfusion injury as determined by histology and by laser-induced fluorescence (LIF) with excitation wavelengths of 442 nm and 532 nm. Wistar rats (four groups of six animals) were subjected to left renal warm ischemia for 20, 40, 60 and 80 min followed by 10 min of reperfusion. Autofluorescence was determined before ischemia (control) and then every 5-10 min thereafter. Tissue samples for histology were harvested from the right kidney (control) and from the left kidney after reperfusion. LIF and ischemia time showed a significant correlation (p < 0.0001 and r (2)=0.47, and p=0.006 and r (2)=0.25, respectively, for the excitation wavelengths of 442 nm and 532 nm). Histological scores showed a good correlation with ischemia time (p < 0.0001). The correlations between optical spectroscopy values and histological damage were: LIF at 442 nm p < 0.0001, LIF at 532 nm p=0.001; IFF (peak of back scattered light/LIF) at 442 nm p > 0.05, and IFF at 532 nm p > 0.05. After reperfusion LIF tended to return to preischemic basal levels which occurred in the presence of histological damage. This suggests that factors other than morphological alterations may have a more relevant effect on changes observed in LIF. In conclusion, renal ischemia/reperfusion changed tissue fluorescence induced by laser. The excitation light of 442 nm showed a better correlation with the ischemia time and with the severity of tissue injury.

Controlling the absorption and emission properties of polyparaphenylenevinylene films

In this work we used the conversion process of a precursor polymer into polyparaphenylenevinylene (PPV) at low temperatures in order to control the effective conjugation degree of spin-casted PPV films. The absorption and emission spectra of the films were studied by following a partial substitution of chloride counterions from poly(xylylidene tetrahydrothiophenium chloride) (PTHT), used as a precursor, by sodium acid dodecyl benzenesulfonate (DBS), added as a surfactant salt. Upon controlling the DBS amount and conversion temperature (T-c) of PTHT/DBS to PPV films, the band gap of PPV changed from 409 to 506 nm, and 505 to 532 nm, values obtained from absorbance and emission measurements, respectively. Based on these experimental data, we proposed a physical model which represents the chemical structure of PPV as a distribution of conjugated chain segments (like oligomers) alternated by non-conjugated segments (structural defects and/or from the precursor polymer). (C) 2008 Elsevier B.V. All rights reserved.

Renal ischemia in rats: Mitochondria function and laser autofluorescence

Ischemia-reperfusion injury is the major cause of organ dysfunction or even nonfunction following transplantation. It can attenuate the long-term survival of transplanted organs. To evaluate the severity of renal ischemia injury determined by histology, we applied laser(442 nm and 532 nm) induced fluorescence (LIF), mitochondria respiration, and membrane swelling to evaluate 28 Wistar rats that underwent left kidney warm ischemia for 20, 40, 60, or 80 minutes. LIF performed before ischemia (control) was repeated at 20, 40, 60, and 80 minutes thereafter. We harvested left kidney tissue samples immediately after LIF determination for histology and mitochondrial analyses: state 3 and 4 respiration, respiration control rate (RCR), and membrane swelling. The association of optic spectroscopy with histological damage showed: LIF, 442 nm (r(2) = 0.39, P < .001) and 532 nm, (r(2) = 0.18, P = .003); reflecting laser/fluorescence-induced, 442 nm (r(2) = 0.20, P = .002) and 532 nm (r(2) = 0.004, P = .67). The associations between mitochondria function and tissue damage were: state 3 respiration (r(2) = 0.43, P = .0004), state 4 respiration (r(2) = 0.03, P = 0.38), RCR (r(2) = 0.28, P = .007), and membrane swelling (r(2) = 0.02, P = .43). The intensity of fluorescence emitted by tissue excited by laser, especially at a wave length of 442 nm, was determined in real time. Mitochondrial state 3 respiration and respiratory control ratio also exhibited good correlations with the grade of ischemic tissue damage.

Laser microstructuring for fabricating superhydrophobic polymeric surfaces

In this paper we show the fabrication of hydrophobic polymeric surfaces through laser microstructuring. By using 70-ps pulses from a Q-switched and mode-locked Nd:YAG laser at 532 nm, we were able to produce grooves with different width and separation, resulting in square-shaped pillar patterns. We investigate the dependence of the morphology on the surface static contact angle for water, showing that it is in agreement with the Cassie-Baxter model. We demonstrate the fabrication of a superhydrophobic polymeric surface, presenting a water contact angle of 157 degrees. The surface structuring method presented here seems to be an interesting option to control the wetting properties of polymeric surfaces. (C) 2010 Elsevier B.V. All rights reserved.

Protoporphyrin IX Nanoparticle Carrier: Preparation, Optical Properties, and Singlet Oxygen Generation

The present study is focused on developing a nanoparticle carrier for the photosensitizer protoporphyrin IX for use in photodynamic therapy. The entrapment of protoporphyrin IX (Pp IX) in silica spheres was achieved by modification of Pp IX molecules with an organosilane reagent. The immobilized drug preserved its optical properties and the capacity to generate singlet oxygen, which was detected by a direct method from its characteristic phosphorescence decay curve at near-infrared and by a chemical method using 1,3-diphenylisobenzofuran to trap singlet oxygen. The lifetime of singlet oxygen when a suspension of Pp IX-loaded particles in acetonitrile was excited at 532 nm was determined as 52 mu s, which is in good agreement with the value determined for methylene blue in acetonitrile solution under the same conditions. The Pp IX-loaded silica particles have an efficiency of singlet oxygen generation (eta Delta) higher than the quantum yield of free porphyrins. This high efficiency of singlet oxygen generation was attributed to changes on the monomer-dimer equilibrium after photosentisizer immobilization.

Generation and suppression of singlet oxygen in hair by photosensitization of melanin

We have studied the spectroscopic properties of hair (white, blond, red, brown, and black) under illumination with visible light, giving special emphasis to the photoinduced generation of singlet oxygen ((1)O(2)). Irradiation of hair shafts (lambda(ex)>400 nm) changed their properties by degrading the melanin. Formation of C3 hydroperoxides in the melanin indol groups was proven by (1)H NMR. After 532-nm excitation, all hair shafts presented the characteristic (1)O(2) emission (lambda(em) = 1270 nm), whose intensity varied inversely with the melanin content. (1)O(2) lifetime was also shown to vary with hair type, being five times shorter in black hair than in blond hair, indicating the role of melanin as a (1)O(2) suppressor. Lifetime ranged from tenths of a nanosecond to a few microseconds, which is much shorter than the lifetime expected for (1)O(2) in the solvents in which the hair shafts were suspended, indicating that (1)O(2) is generated and suppressed inside the hair structure. Both eumelanin and pheomelanin were shown to produce and to suppress (1)O(2), with similar efficiencies. The higher amount of (1)O(2) generated in blond hair and its longer lifetime is compatible with the stronger damage that light exposure causes in blond hair. We propose a model to explain the formation and suppression of (1)O(2) in hair by photosensitization of melanin with visible light and the deleterious effects that an excess of visible light may cause in hair and skin. 2011 Published by Elsevier Inc.

N3-Dye-Induced Visible Laser Anatase-to-Rutile Phase Transition on Mesoporous TiO(2) Films

Titanium dioxide has been extensively used in photocatalysis and dye-sensitized solar cells, where control of the anatase-to-rutile phase transformation may allow the realization of more efficient devices exploiting the synergic effects at anatase/rutile interfaces. Thus, a systematic study showing the proof of concept of a dye-induced morphological transition and an anatase-to-rutile transition based on visible laser (532 nm) and nano/micro patterning of mesoporous anatase (Degussa P25 TiO(2)) films is described for the first time using a confocal Raman microscope. At low laser intensities, only the bleaching of the adsorbed N3 dye was observed. However, high enough temperatures to promote melting/densification processes and create a deep hole at the focus and an extensive phase transformation in the surrounding material were achieved using Is laser pulses of 25-41 mW/cm(2), in resonance with the MLCT band. The dye was shown to play a key role, being responsible for the absorption and efficient conversion of the laser light into heat. As a matter of fact, the dye is photothermally decomposed to amorphous carbon or to gaseous species (CO(x), NO(x), and H(2)O) under a N(2) or O(2) atmosphere, respectively.

Fluorescence spectroscopy for the detection of tongue carcinoma - validation in an animal model

The efficacy of fluorescence spectroscopy to detect squamous cell carcinoma is evaluated in an animal model following laser excitation at 442 and 532 nm. Lesions are chemically induced with a topical DMBA application at the left lateral tongue of Golden Syrian hamsters. The animals are investigated every 2 weeks after the 4th week of induction until a total of 26 weeks. The right lateral tongue of each animal is considered as a control site (normal contralateral tissue) and the induced lesions are analyzed as a set of points covering the entire clinically detectable area. Based on fluorescence spectral differences, four indices are determined to discriminate normal and carcinoma tissues, based on intraspectral analysis. The spectral data are also analyzed using a multivariate data analysis and the results are compared with histology as the diagnostic gold standard. The best result achieved is for blue excitation using the KNN (K-nearest neighbor, a interspectral analysis) algorithm with a sensitivity of 95.7% and a specificity of 91.6%. These high indices indicate that fluorescence spectroscopy may constitute a fast noninvasive auxiliary tool for diagnostic of cancer within the oral cavity. (C) 2008 Society of Photo-Optical Instrumentation Engineers.

Refractive index changes in photochromic SbPO4-WO3 glass by exposure to band-gap radiation

We report photoinduced photo-darkening in SbPO4-WO3 glass by exposure to 532 nm light with a power density of 143 mW/cm(2). The time of exposure was varied between 0 and 256 min following which visible photo-darkening, peaking at 850 nm was observed. Spectrophotometer measurement of absorption was performed for both treated and untreated regions of the sample. Time exposure to below band-gap light results in a single exponent Gaussian absorption function over an exceptionally wide range of wavelengths (500 nm-1600 nm), with a 1/e width of 647.5 nm. Kramers-Kronig transform of the change in the absorption indicates a negative local change in the refractive index. The dispersed refractive index change at 1550 nm, Delta n, is calculated to be similar to -5 x 10(-8). The peak absorption increases with time of exposure and the photo-darkening remains irreversible at room temperature. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.

Nonlinear optical properties of tungstate fluorophosphate glasses

The optical nonlinearity of tungstate fluorophosphate glasses, synthesized in the NaPO3-BaF2-WO3 system, was investigated through experiments based on the third-order susceptibility, chi((3)). Nonlinear (NL) refraction and NL absorption measurements in the picosecond regime were performed using the Z-scan technique at 532 nm. NL refractive index, n(2)proportional toRe chi((3)), ranging from 0.4x10(-14) cm(2)/W to 0.6x10(-14) cm(2)/W were determined. The two-photon absorption coefficient, alpha(2)proportional toIm chi((3)), for excitation at 532 nm, vary from 0.3 to 0.5 cm/GW. Light induced birefringence experiments performed in the femtosecond regime indicate that the response time of the nonlinearity at 800 nm is faster than 100 fs. The experiments show that chi((3)) is enhanced when the WO3 concentration increases and this behavior is attributed to the hyperpolarizabilities associated to W-O bonds. (C) 2004 American Institute of Physics.

Excited state dynamics of the Ho3+ ions in holmium singly doped and holmium, praseodymium-codoped fluoride glasses

The deactivation of the two lowest excited states of Ho3+ was investigated in Ho3+ singly doped and Ho3+, Pr3+-codoped fluoride (ZBLAN) glasses. We establish that 0.1-0.3 mol % Pr3+ can efficiently deactivate the first excited (I-5(7)) state of Ho3+ while causing a small reduction of similar to 40% of the initial population of the second excited (I-5(6)) state. The net effect introduced by the Pr3+ ion deactivation of the Ho3+ ion is the fast recovery of the ground state of Ho3+. The Burshstein model parameters relevant to the Ho3+-> Pr3+ energy transfer processes were determined using a least squares fit to the measured luminescence decay. The energy transfer upconversion and cross relaxation parameters for 1948, 1151, and 532 nm excitations of singly Ho3+-doped ZBLAN were determined. Using the energy transfer rate parameters we determine from the measured luminescence, a rate equation model for 650 nm excitation of Ho3+-doped and Ho3+, Pr3+-doped ZBLAN glasses was developed. The rate equations were solved numerically and the population inversion between the I-5(6) and the I-5(7) excited states of Ho3+ was calculated to examine the beneficial effects on the gain associated with Pr3+ codoping. (c) 2007 American Institute of Physics.