Fundamentos del láser y su aplicación en la urología / The basics of laser and its application in urology

El láser, dispositivo de amplificación de luz por emisión estimulada de radiación, se trata de un dispositivo capaz de transformar otras energías en radiación electromagnética emitiendo haces de luz de distintas longitudes de onda. Se trata de aparatos que amplifican la luz y producen haces de luz coherentes cuya frecuencia va desde el infrarrojo hasta los rayos X. La emisión estimulada, proceso en que se basa el Láser, fue descrita por A. Einstein en 1917, pero no es hasta la década de los 60, cuando se observó el primer proceso láser en un cristal de rubí. Según el medio que emplean, los láseres suelen denominarse de estado sólido, de gas, semiconductores o líquidos. Los posibles usos del láser son casi ilimitados, convirtiéndose en una herramienta muy valiosa dentro de las Ciencias biomedicas, gracias a los diversos efectos (fotovaporización, fotodisrupción, fotocoagulación o fotoestimulación) que provoca al interactuar con los tejidos. Por este motivo, hoy día, el uso de láseres en el campo de la Urología nos ofrece un amplio abanico de posibilidades, que van desde la cirugía desobstructiva como la fragmentación de un cálculo o la resección y ablación del tejido prostático hasta la cirugía reconstructiva como es la soldadura de tejidos en la vasovasostomía o la reparación de una estenosis uretral (AU)

A laser, light amplification by stimulated emission of radiation, is a device able to transform other energies into electromagnetic radiation with emission of light beams of different wavelengths. They amplify the light and produce coherent light beams, the frequency of which varies from infrared to X ray. Stimulated emission, the process laser is based on, was described by A. Einstein in 1917, but it was not until the decade of the '60s when the first laser process was observed in a ruby crystal. Depending on the environment they use, lasers may be named as solid-state, gas, semiconductors or liquid. The possibility of uses for laser is almost unlimited, becoming a very valuable tool in biomedical sciences thanks to the various effects they produce when interacting with tissues (photovaporization, photodisruption, photocoagulation or photostimulation). For this reason, today, the use of lasers in the field of urology offers a wide range of possibilities, going from surgery for the treatment of obstruction, such as the fragmentation of a urinary stone or resection/ablation of prostatic tissue, to reconstructive surgery, such as tissue welding in vasovasostomy or urethral stenosis repair (AU)

Absolute sensitivity calibration of extreme ultraviolet photoresists.

One of the major challenges facing the commercialization of extreme ultraviolet (EUV) lithography remains simultaneously achieving resist sensitivity, line-edge roughness, and resolution requirement. Sensitivity is of particular concern owing to its direct impact on source power requirements. Most current EUV exposure tools have been calibrated against a resist standard with the actual calibration of the standard resist dating back to EUV exposures at Sandia National Laboratories in the mid 1990s. Here we report on an independent sensitivity calibration of two baseline resists from the SEMATECH Berkeley MET tool performed at the Advanced Light Source Calibrations and Standards beamline. The results show the baseline resists to be approximately 1.9 times faster than previously thought based on calibration against the long standing resist standard.

Radiometric quantities and units used in photobiology and photochemistry: recommendations of the Commission Internationale de L'Eclairage (International Commission on Illumination).

To characterize photobiological and photochemical phenomena, standardized terms and units are required. Without a uniform set of descriptors, much of the scientific value of publications can be lost. Attempting to achieve an international consensus for a common language has always been difficult, but now with truly international scientific publications, it is all the more important. As photobiology and photochemistry both represent the fusion of several scientific disciplines, it is not surprising that the physical terms used to describe exposures and dosimetric concepts can vary from author to author. There are, however, international organizations that were established to minimize the confusion produced by poor or inconsistent technical terminology. This note is to review the standardized terms and provide a background on how such terms are developed, with the hope that all readers will attempt to follow the standardized terminology.

[Nonlinear optical absorption characteristics of a novel organic material ZnTBP/CA/PhR].

The measurement of optical absorption spectrum in visible light range of a novel organic material Zn-tetrabenzoporphincrotonic acid/phenoxy resin (ZnTBP/CA/PhR) is reported in this paper. The nonlinear absorption property of the sample illuminated by lasers with different wavelengths was studied. And the absorption alteration and kinetic process of the major spectrum bands were observed. The saturation absorption (SA) and reverse saturation absorption (RSA) appeared as the input fluence increased, and re-reverse saturation absorption process of the material was demonstrated in the experiment. These properties occurred in a broad range of visible spectrum. The paper qualitatively analyses the physical mechanism during the whole course. Based on the nonlinear absorption characteristics, we showed some applications in photonics field of ZnTBP/CA/PhR.

[Studies on photoluminescence characteristics of curcumin in acrylamide polymer].

A photoluminescence polymer was prepared using acrylamide as a monomer, a large excess of ethyleneglycol dimethacrylate as the cross-linking agent, and curcumin as a fluorescence additive. The polymer was ground into powder and screened in order to get even powder, whose diameter was from 40 to 75 microm. The emission spectra of curcumin in solid powder polymer show a strong blue shift compared with that of curcumin in C2H5OH solution. Meanwhile, rhodamine 6G, tetraiodofluorescein and phloxin have the same phenomenon of blue shift. Based on these facts, we speculate that the mechanism is probably singlemolecular luminescence because of the limit effect in three dimension space of the polymer. The molecule fluorescence peak was also depending on its environment because the surrounding electron field affected the molecule luminescence in polymer.

ICH guideline for photostability testing: aspects and directions for use.

The ICH guideline Q1B for photostability testing gives guidance on the basic testing protocol required to evaluate the light sensitivity and stability of new drugs and products. The choice of the irradiation method, although complying with the guideline demands, may effect test results. High irradiances may shorten testing times, but can lead to enforcement of photodegradation, which was demonstrated for molsidomine tablets. The exposure to an artificial light source (xenon lamp) was compared and correlated to natural daylight. Suitable testing methods for nifedipine and molsidomine tablets were developed. Deviating from the guideline recommendations, the presentation of powder samples should be done in tiny aluminium pans, facilitating the test procedure, minimising the risk of falsified test results due to improper sampling and improving reproducibility. When using glass dishes for the presentation of tablets to photostability testing, they should be lined by e. g. aluminium foil to avoid influences of light reflected from the sample tray.

Photoelectrochemical oxygen sensor using copper-plated screen-printed carbon electrodes.

We report here an efficient photocatalytic amperometric sensor for the determination of dissolved oxygen (DO) in phosphate buffer solution using a disposable copper-plated screen-printed carbon electrode (CuSPE). The photoelectrochemical activity toward DO of the CuSPE was related to the formation of a p-type semiconductor Cu(I)2O. The solution pH and biased potential (E(bias)) were systematically optimized as pH 8 PBS and -0.7 V vs Ag/AgCl, respectively. Under optimized conditions, the calibration plot was linear in the range of 1-8 ppm with sensitivity and regression coefficient of 23.51 (microA cm2)(-1) ppm(-1) and 0.9982, respectively. The reproducibility of the system was good with seven successive measurements of DO yielding a RSD value of 1.87%. Real sample assays for groundwater and tap water were also consistent with those measured by a commercial DO meter. The principle used in DO measurement has an opportunity to extend into various research fields.