Laser In Conjunction Research Articles

Successful treatment of congenital melanocytic nevus on tragus with CO2 laser

Background: Congenital melanocytic nevus (CMN) has an increasing risk of malignancy and may cause cosmetic and psychological problems. Surgery has been the main therapy for most cases. However, it is often not suitable for all lesions. Treatment of these lesions can be challenging to plastic surgeons. CO2 laser, with the special function, is another effective treatment for some CMN. Methods: Both lesions were treated with a short-pulsed CO2 laser in conjunction with a local anesthetic; the superfluous tissue was pruned and ablated to get a crude tragus and then carefully shaped to form an aesthetically tragus. Results: Showed good cosmetic results without pigment recurrence and scar formation 1 year after operation in both patients, the exception being a small area of cartilage that was covered with epithelial tissues on the surface in patient 1. Conclusions: CO2 laser treatment is a useful modality in treating some CMN that are located on sites deemed inoperable. It can help to shape the lesions into their original form with the advantage of hemostasis and tissue manipulation proving to be effective, thus avoiding suturing and skin grafting. Taking the thermal damage into account can help to minimize the side effects and attain a desirable cosmetic outcome.

Direct modulation of a tuneable slotted Fabry-Pérot laser with adaptive modulation OFDM

Next generation optical access networks will require low cost lasers in conjunction with network flexibility and higher data rates. This work presents the direct modulation of a low cost tuneable slotted Fabry-Pérot laser (tuneable over 14 nm) with AM-OFDM. Characteristics of this dual section laser are presented and transmission of 10 Gb/s over 50 km is achieved with this device.

Opto-VLSI-Based Beamformer for Radio-Frequency Phased-Array Antennas

An Opto-VLSI-based tunable beamformer for radio frequency (RF) smart antennas is reported and its concept is demonstrated. RF beam steering is achieved by uploading appropriate phase holograms onto the Opto-VLSI processor so that RF true-time delays (TTDs) are independently generated for each element of the antenna array by simply using several erbium-doped fiber amplifier (EDFA) loops to realize independent tunable fiber lasers in conjunction with a dispersive optical fiber. Experimental results demonstrate RF beam steering up to 30° with a 4-element linear patch antenna array operating at 1.85 GHz.

Bactericidal effect of the 908 nm diode laser on Enterococcus faecalis in infected root canals

Aim:The aim of this study is to evaluate the bactericidal effect of 908 nm diode laser in conjunction with various irrigation regimes in disinfection of apical third of root dentin.Materials and Methods:Sixty prepared teeth with single canals were contaminated with Enterococcus faecalis. The specimens were divided into 6 groups (n = 10): Group 1 and 3 and 5 were subjected to chemo-mechanical preparation using 5.25% sodium hypochlorite (NaOCl), 17% Ethylenediaminetetraacetic acid (EDTA); 1.3% NaOCl, MTAD (mixture of doxycycline, citric acid and a detergent (Tween 80); and, 8.5% saline, respectively followed by 908 nm diode laser irradiation; Group 2 and 4, followed the same procedure as Group1 and 3, however without laser irradiation; and, Group 6, rinsed with saline solution (control). Dentin shavings from apical third were analyzed for the presence of E. faecalis using culture method and Polymerase Chain reaction (PCR).Results:One-way Analysis of variance showed statistically significant differences between the laser irradiated groups, non irradiated groups and the control group.Conclusion:908 nm diode used in conjunction with conventional chemomechanical techniques demonstrated a significant elimination of E. faecalis in the apical third of root dentin.

Lasers or light sources for treating port-wine stains

Port-wine stains are birthmarks caused by malformations of blood vessels in the skin. Port-wine stains manifest themselves in infancy as a flat, red mark and do not regress spontaneously but may, if untreated, become darker and thicker in adult life. The profusion of various lasers and light sources makes it difficult to decide which equipment is the best for treating port-wine stains. To study participant satisfaction, clinical efficacy, and adverse effects of the treatment of port-wine stains by lasers and light sources. We searched the following databases up to April 2010: the Cochrane Skin Group Specialised Register, the Cochrane Central Register of Controlled Trials (Clinical Trials) in The Cochrane Library, MEDLINE (from 2005), EMBASE (from 2007), LILACS (Latin American and Caribbean Health Science Information database, from 1982), and reference lists of articles. We also searched online trials registries for ongoing trials and contacted trial authors where appropriate. Randomised clinical trials (RCTs) of lasers or light sources for the treatment of port-wine stains. Our outcomes of interest were participant satisfaction, reduction in redness of the port-wine stain as determined by clinical evaluation, and short- and long-term adverse effects of the treatments. Three authors independently extracted data and assessed trial quality. We included 5 RCTs involving a total of 103 participants; all of the trials used a within-participant design. The interventions and outcomes were too varied to be combined statistically. All trials used the pulsed dye laser for comparisons.None of the studies focused on participant satisfaction, which was one of our primary outcomes, but participant preference was evaluated in three of five studies. Participants preferred the pulsed dye laser to intense pulsed light based on the clinical effect. They marginally preferred the Neodymium:YAG (yttrium-aluminium-garnet) (Nd:YAG) laser to the pulsed dye laser due to shorter lasting purpura, and pulsed dye laser in conjunction with cooling was preferred to treatment with pulsed dye laser alone.All trials examined short-term efficacy of less than six months after treatments with the pulsed dye laser, intense pulsed light, and Nd:YAG laser. The pulsed dye laser was evaluated in all five trials. Depending upon the setting of the pulsed dye laser, this resulted in more than 25% reduction in redness. This was after 1 to 3 treatments for up to 4 to 6 months postoperatively in 50% to 100% of the participants. There was only one study each of intense pulsed light and Nd:YAG laser.Two trials had no occurrence of long-term adverse effects, i.e. six months after treatment. Three trials reported pigmentary alterations in 3% to 24% of the participants, with the highest percentage occurring in Chinese participants with darker skin types. In one study one participant experienced scarring of the skin caused by a too-high dose of the laser used. Short-term side-effects included pain, crusting, and blistering in the first two weeks after treatment. The pulsed dye laser leads to clinically relevant clearance of port-wine stains. A limited number of RCTs evaluated the efficacy from intense pulsed light and other laser types. High-quality RCTs are needed to assess individual efficacy from different lasers and light sources, as well as participant satisfaction.

Laserstapedotomie

In addition to hearing aids, stapesplasty represents the standard treatment of otosclerosis-induced hearing loss. In this procedure, the stapes superstructure is replaced by a prosthesis that is attached to the long process of the incus and communicates through a perforation in the footplate with the perilymphatic space of the inner ear. The removal of the stapes superstructure and perforation of the footplate are the critical steps of this surgical procedure. With the introduction of laser-assisted perforation techniques, the surgical safety of this method has been improved compared to conventional techniques. KTP, argon, as well as diode, Er:YAG and CO(2) lasers are used for stapedotomy. By using the CO(2) laser in conjunction with a scanner system, the number of laser applications required for the perforation of the footplate has been markedly reduced. In contrast to other systems, a more reproducible perforation diameter of the stapes footplate is achieved with a CO(2) laser equipped with a scanner. Complications such as uncontrolled leakage of perilymph, irradiation of inner ear structures or the occurrence of pressure waves with subsequent damage to the inner ear can be reduced by using a CO(2) laser. In this review, the surgical technique of CO(2) laser stapedotomy, including clinically established variants and paying particular attention to the one-shot technique, are described and discussed in comparison to other laser systems.

Detection of sulfur in the reinforced concrete structures using a dual pulsed LIBS system

In concrete structures, an excessive amount of sulfate ions can cause severe damage to the strength and the stability of the building structures and hence a sensitive and reliable technique for sulfate ion detection in concrete is highly desirable. Laser-induced breakdown spectroscopy (LIBS) is one of the most reliable and sensitive techniques to identify the presence of potentially dangerous sulfur in the concrete structure. The atomic emission lines of sulfur lying in the 200–900 nm region are mostly singly ionized states and hence inherently very weak. In order to enhance the sensitivity of the conventional LIBS system, we employed a dual pulsed LIBS system for detection of weak spectral line of sulfur in concrete using the S II peak at 545.38 nm as a marker for quantifying sulfur content in the concrete. The 1064 nm fundamental and 266 nm fourth harmonic of the Nd:YAG laser in conjunction with Spectrograph/gated ICCD camera are the core factors in improvement of sensitivity. Furthermore, the dual pulsed LIBS system and the fine maneuvering of the gate parameters and interpulse delay yielded improvement in the sensitivity, and resulted in a systematic correlation of the LIBS signal with the concentration of sulfur in the concrete sample. In order to quantify the sulfur content in concrete, a calibration curve was also drawn by recording the LIBS spectra of sample having sulfur in various concentrations. The limit of detection achieved with our dual pulsed LIBS system is approximately 38 μg/g.

Photoionization from the5p 2P3/2state of rubidium

We report two-step photoionization studies from the 5$p$ ${}^{2}$${P}_{3/2}$ excited state of rubidium using two dye lasers simultaneously pumped by a common Nd:YAG laser in conjunction with a thermionic diode ion detector. The photoionization cross section at the first ionization threshold is measured as 18.8 \ifmmode\pm\else\textpm\fi{} 3 Mb and at excess energies of 0.013, 0.106, 0.229, and 0.329 eV is measured as 15, 13.6, 12.6, and 12.5 Mb, respectively. The measured value of the photoionization cross section at the threshold is used to calibrate the oscillator strengths of the 5$p$ ${}^{2}$${P}_{3/2}$ \ensuremath{\rightarrow} $n$d ${}^{2}$${D}_{5/2}$ (22 \ensuremath{\leqslant} $n$ \ensuremath{\leqslant} 52) Rydberg transitions.

Management of ear lobule keloids using 980-nm diode laser

The objective of the study was to evaluate the 980-nm diode laser in conjunction with corticosteroids in the treatment of ear lobule keloids. Several methods have been described for the treatment of keloid scars, but none of them have been 100% successful. Advances in laser techniques have enabled surgeons to define the most appropriate lasers for use in the treatment of different scar types. The diode laser pulses are delivered interstitially in a single repeated mode in non-overlapping sites using a bare optical fiber, followed by intralesional triamcinolone acetonide injection. The number of sessions varies between two to five for the management of more than 75% of keloid size, with a total success rate of 75% and no recurrence in the follow-up of 12 months. The technique used proved to be effective in the treatment of ear lobule keloids.

Requirement for Lamin B Receptor and Its Regulation by Importin β and Phosphorylation in Nuclear Envelope Assembly during Mitotic Exit

Lamin B receptor (LBR), a chromatin and lamin B-binding protein in the inner nuclear membrane, has been proposed to target the membrane precursor vesicles to chromatin mediated by importin β during the nuclear envelope (NE) assembly. However, the mechanisms for the binding of LBR with importin β and the membrane targeting by LBR in NE assembly remain largely unknown. In this report, we show that the amino acids (aa) 69-90 of LBR sequences are required to bind with importin β at aa 45-462, and the binding is essential for the NE membrane precursor vesicle targeting to the chromatin during the NE assembly at the end of mitosis. We also show that this binding is cell cycle-regulated and dependent on the phosphorylation of LBR Ser-71 by p34(cdc2) kinase. RNAi knockdown of LBR causes the NE assembly failure and abnormal chromatin decondensation of the daughter cell nuclei, leading to the daughter cell death at early G(1) phase by apoptosis. Perturbation of the interaction of LBR with importin β by deleting the LBR N-terminal spanning region or aa 69-73 also induces the NE assembly failure, the abnormal chromatin decondensation, and the daughter cell death. The first transmembrane domain of LBR promotes the NE production and expansion, because overexpressing this domain is sufficient to induce membrane overproduction of the NE. Thus, these results demonstrate that LBR targets the membrane precursor vesicles to chromatin by interacting with importin β in a LBR phosphorylation-dependent manner during the NE assembly at the end of mitosis and that the first transmembrane domain of LBR promotes the LBR-bearing membrane production and the NE expansion in interphase.

Oscillator strength measurements of the 5s5p 3P 1 → 5s nd 3D 2 Rydberg transitions of cadmium

We report oscillator strengths distribution in the bound region of cadmium corresponding to the 5s5p 3P 1 → 5s nd 3D 2 (21 ≤ n ≤ 52) Rydberg transitions. The experiment was performed using two frequency doubled dye lasers simultaneously pumped by a common Nd:YAG laser in conjunction with an atomic beam set-up. The absolute photoionization cross section of the 5s5p 3P 1 intermediate state at the 5s 2S 1/2 ionization threshold has been measured as 20 (4) Mb using the saturation technique. The measured value of the photoionization cross section at threshold is used to extract the f-values of the above mentioned Rydberg transitions.

Laser-induced photoacoustic imaging for breast cancer detection using multivariate image analysis.

Abstract:Time-resolved photoacoustic imaging has been used to characterize breast tissue for the purpose of discriminating between normal and maligned areas of the tissue. Ultrasonic thermoelastic waves were generated in breast tissue by the absorption of nanosecond laser pulses at 193 nm produced by Q-switched Excimer laser in conjunction with a Michelson interferometer used to detect the thermoelastic waves and plot the 2-D and the 3-D image through IR- CCD. The concepts behind the use of photo-acoustic techniques for off-line detection of breast cancer tumor features were presented in earlier research papers [1][2]. This paper illustrates the application of multivariate image analysis (MIA) techniques to detect the presence of tumor features of breast cancer. MIA is used to rapidly detect the presence and quantity of common tumor features as they scanned by an RGB camera. Multiway principal component analysis is used to decompose the acquired three-channel tumor images into a two dimensional principal components (PC) space. Masking score point clusters in the score space and highlighting corresponding pixels in the image space of the two dominant PCs enables isolation of tumor defect pixels based on contrast and color information. The technique provides a qualitative result that can be used for early tumor detection. The proposed technique can potentially be used on-line to prescreen the existence of tumors through vision based systems.

Optical pulse coding in hybrid distributed sensing based on Raman and Brillouin scattering employing Fabry–Perot lasers

We demonstrate simultaneous strain and temperature sensing based on hybrid Raman and Brillouin scattering with enhanced performance thanks to the combined use of standard Fabry-Perot lasers in conjunction with optical pulse coding techniques. The combination of both techniques allows for an improvement of ~8.7 dB in temperature resolution and ~3 dB in strain resolution, with respect to standard distributed feedback lasers, as confirmed by experiments, resulting in a final temperature / strain resolution of ~0.27K / ~30microepsilon over 25-km sensing fiber range, avoiding the use of optical amplification and wavelength averaging techniques.

Laser-induced effects in different biological samples

Experiments were carried out on cancerous HeLa cells and blood serum using a double integrating sphere and a He-Ne laser to investigate the optical properties and cellular effects due to photodynamic therapy (PDT). In the first experiment, HeLa cells were exposed to Photofrin at concentrations of 0, 10, 20, 30, 50 and 112.4 microg/ml at an irradiance of 0.2 W/cm(2) using diode laser light. Using a confocal microscope, cell debris and morphological changes in HeLa cells were recorded at different Photofrin concentrations. The results showed cell debris in HeLa cells at the highest concentration of Photofrin. In a second experiment, photobleaching was observed in HeLa cells in the presence of various concentrations of 5-aminolaevulinic acid ranging from 0-50 microg/ml. There was progressive degradation of the 635 nm peak during continuous laser irradiation at an irradiance of 0.2 W/cm(2). We conclude that cells demonstrating high initial fluorescence undergo bleaching at a faster rate than those with lower fluorescence. Finally in a third experiment, cancerous and noncancerous blood serum was irradiated at an irradiance of 0.1 W/cm(2) using a He-Ne laser in conjunction with a double integrating sphere system. Forward and back scattering of normal and malignant serum showed an exponential decrease in fluorescence amplitude. The results indicate that there is notable amplitude difference between malignant and normal blood serum with malignant blood serum showing decreased scattering. These results have important implications for photodiagnosis and photodynamic therapy.

In vivo carotid artery closure by laser activation of hyaluronan-embedded gold nanorods

We prove the first application of near-infrared-absorbing gold nanorods (GNRs) for in vivo laser closure of a rabbit carotid artery. GNRs are first functionalized with a biopolymeric shell and then embedded in hyaluronan, which gives a stabilized and handy laser-activable formulation. Four rabbits undergo closure of a 3-mm longitudinal incision performed on the carotid artery by means of a 810-nm diode laser in conjunction with the topical application of the GNRs composite. An effective surgery is obtained by using a 40-W/cm(2) laser power density. The histological and electron microscopy evaluation after a 30-day follow-up demonstrates complete healing of the treated arteries with full re-endothelization at the site of GNRs application. The absence of microgranuloma formation and/or dystrophic calcification is evidence that no host reaction to nanoparticles interspersed through the vascular tissue occurred. The observation of a reshaping and associated blue shift of the NIR absorption band of GNRs after laser treatment supports the occurrence of a self-terminating process, and thus of additional safety of the minimally invasive laser procedure. This study underlines the feasibility of using GNRs for in vivo laser soldering applications, which represents a step forward toward the introduction of nanotechnology-based therapies in minimally invasive clinical practices.

Isotopic Selectivity in Two-Color Multiphoton Ionization Spectroscopy of Zirconium

A two-color multiphoton ionization spectroscopy of Zr has been performed using an atomic beam and pulsed dye lasers in conjunction with the use of a time-of-flight mass spectrometer. Zr atoms were excited from the ground state [4d25s2(3F2)] to the 17430 cm-1 state [4d25s5p(3D1°)] by one dye laser, and subsequently ionized by another dye laser. From the experiment, a total of 124 peaks originating from the 17430 cm-1 state were observed in the 565–593 and 610–652 nm regions. In addition 68 single-color multiphoton ionization peaks were observed. From the results of the ion mass analysis, isotopic selectivities between odd and even isotopes were observed at six ionization peaks. This suggests the existence of J = 0 states at 48288.4, 48866.9, 49384.5, 50092.2, 52022.3, and 52004.3 cm-1.

Photopatterning, Etching, and Derivatization of Self-Assembled Monolayers of Phosphonic Acids on the Native Oxide of Titanium

Electron-hole pair formation at titania surfaces leads to the formation of reactive species that degrade organic materials. Here, we describe the degradation of self-assembled monolayers of alkylphosphonic acids on the native oxide of titanium following exposure to UV light. The rate of degradation was found to decrease as the length of the adsorbate molecule increased. Increasing order in the monolayer, resulting from the enhanced dispersion forces between longer adsorbates, impedes the progress of oxygen-containing molecules to the oxide surface and slows the rate of oxidation. Rates of degradation on titanium oxide are substantially greater than rates of degradation on aluminum oxide because of the photocatalytic effect of the titanium oxide substrate. Micrometer-scale patterns may be fabricated readily using a UV laser in conjunction with a mask, and nanometer-scale patterns may be fabricated using a scanning near-field optical microscope coupled to a UV laser. Photodegraded adsorbates may be replaced by contrasting molecules to yield chemical contrast. Such patterned materials have been utilized to fabricate patterns from polymer nanoparticles. The resist character is switchable--at lower exposures, the monolayer behaves as a positive tone resist, but at higher exposures, it exhibits negative tone behavior. Patterned samples may also be utilized as resists for solution-phase etching of the underlying substrate.

Angular momentum dependence of photoionization cross section from the excited states of lithium isotopes

We present measurements of the photoionization cross sections from the $3s$, $3d$, $4s$, $4p$, and $4d$ excited states of lithium isotopes near the first ionization threshold using two dye lasers pumped by a common Nd:YAG (yttrium aluminum garnet) laser in conjunction with an atomic beam--time-of-flight mass spectrometer system. It is observed that the photoionization cross section from the $3d$ and $4d$ excited state is maximum near the ionization threshold and decreases smoothly for the excess energies above the threshold. However, for the $3s$ and $4s$ excited states, the photoionization cross section is lower at the threshold, increases to a maximum value, and then decreases monotonically for the excess energies. It is also observed that a drop off in the cross section of the $nd$ states is more hydrogenic than that of the $np$ and $ns$ excited states.

Enhancement in microwave modulation efficiency of vertical cavity surface-emitting laser by optical feedback

We investigate a versatile vertical cavity surface-emitting laser (VCSEL) with a slight optical feedback from a simple wedge positioned at a well determined distance from the VCSEL. We use such a laser in conjunction with a miniature Rb atomic cell to detect coherent population trapping (CPT) when the external cavity mode spacing frequency corresponds to half the hyperfine frequency of Rb. The feedback greatly enhances the rf modulation efficiency of the VCSEL and as a result we obtain high contrast CPT signals at an input of −16dBm of rf modulation power compared to +1.25dBm needed in the absence of the external cavity.

Infrared Multiphoton Dissociation Spectroscopy of Cationized Threonine: Effects of Alkali-Metal Cation Size on Gas-Phase Conformation

The gas-phase structures of alkali-metal cation complexes of threonine (Thr) are examined using infrared multiple photon dissociation (IRMPD) spectroscopy utilizing light generated by a free electron laser in conjunction with quantum chemical calculations. Spectra of Li+(Thr) and Na+(Thr) are similar and relatively simple, whereas K+(Thr), Rb+(Thr), and Cs+(Thr) include distinctive new IR bands. Measured IRMPD spectra are compared to spectra calculated at a B3LYP/6-311+G(d,p) level to identify the structures present in the experimental studies. For the smaller metal cations, the spectra match those predicted for charge-solvated structures in which the ligand exhibits tridentate coordination, M1[N,CO,OH], binding to the amide and carbonyl groups of the amino acid backbone and to the hydroxyl group of the side chain. K+(Thr), Rb+(Thr), and Cs+(Thr) exhibit evidence of the charge-solvated complex, M3[COOH], in which the metal cation binds to the carboxylic acid group. Evidence for a small population of the zwitterionic analogue of this structure, ZW[CO2-], is also present, particularly for the Cs+ complex. Calculations indicate that the relative stability of the M3[COOH] structure is very strongly dependent on the size of the metal cation, consistent with the range of conformations observed experimentally. The present results are similar to those obtained previously for the analogous M+(Ser) complexes, although there are subtle distinctions that are discussed.