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Laser Radiation (laser + radiation)
Kinds of Laser Radiation Selected AbstractsEffects of Different Doses of Low Power Continuous Wave He,Ne Laser Radiation on Some Seed Thermodynamic and Germination Parameters, and Potential Enzymes Involved in Seed Germination of Sunflower (Helianthus annuus L.)PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2010Rashida Perveen In this study, water-soaked seeds of sunflower were exposed to He,Ne laser irradiation of different energies to determine whether or not He,Ne laser irradiation caused changes to seed thermodynamic and germination parameters as well as effects on the activities of germination enzymes. The experiment comprised four energy levels: 0 (control), 100, 300 and 500 mJ of laser energy and each treatment replicated four times arranged in a completely randomized design. The experimentation was performed under the greenhouse conditions in the net-house of the Department of Botany, University of Agriculture, Faisalabad. The seed thermodynamic parameters were calculated according to seed germination thermograms determined with a calorimeter at 25.8°C for 72 h. Various thermodynamic parameters of seed (,H, (,S)e, (,S)c, (,S)e/,t and (,S)c/,t) were affected significantly due to presowing laser treatment. Significant changes in seed germination parameters and enzyme activities were observed in seeds treated with He,Ne laser. The He,Ne laser seed treatment resulted in increased activities of amylase and protease. These results indicate that the low power continuous wave He,Ne laser light seed treatment has considerable biological effects on seed metabolism. This seed treatment technique can be potentially employed to enhance agricultural productivity. [source] Degradation behavior of nanoreinforced epoxy systems under pulse laserJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2009M. Calhoun Abstract Nanocomposites using EPON 824 as their matrix were exposed to pulse laser at 532 nm for various time intervals. The developed nanomaterials used for this study were manufactured using EPON 824 with multiwalled carbon nanotubes (MWCNTs) at a loading rate of 0.15% by weight and nanoclays at a loading rate of 2% by weight as reinforcements. The effect of laser irradiation on polymer composites has been investigated. The degradation mechanism for the epoxy was of a laser induced burning nature. Of all specimens tested, the ultimate strength of the MWCNT-reinforced specimens decreased the most as a function of radiation time; the nanoclay-reinforced epoxy retained the most strength after 2 min of laser radiation. In addition, the threshold fluence for decomposition indicated that less energy was required to initiate decomposition in the MWCNT-reinforced epoxy than in the nanoclay-reinforced epoxy. This can be attributed to the high thermal conductivity of the carbon nanotubes. Measurement of surface damage in the material was observed via electron microscopy. Fourier transform infrared spectroscopy was used to investigate changes to the molecular structure as a function of exposure time. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Automatic annular laser trapping: a system for high-throughput sperm analysis and sortingJOURNAL OF BIOPHOTONICS, Issue 3 2009Linda Shi Abstract An automatic microscope system is designed to study the response of sperm motility to an annular laser trap. A continuous annular laser trap provides a parallel way to analyze and sort sperm based on their motility and to study the effects of laser radiation, optical force and external obstacles. In the described automatic microscope system, the phase contrast images of swimming sperm are digitized to the computer at video rates. The microscope stage is controlled in real-time to relocate the sperm of interest to the annular trap with a normal or tangential entering angle. The sperm is continuously tracked and the swimming behavior is identified. Using this system, parallel sorting on human and gorilla sperm are achieved and threshold power levels separating the "fast" group and the "slow" group are compared for those two species. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Root surface roughness following Er:YAG laser irradiation at different radiation energies and working tip angulationsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 7 2002Matthias Folwaczny Abstract Objectives: The determination of roughness of root surfaces following treatment with 2.94 µm Er:YAG laser radiation at different radiation energies and working tip angulations. Materials and methods: The study sample comprised 85 extracted human molars, premolars, canines and incisors (n = 85). The source of laser radiation was an Er:YAG laser device (KAVO-Key II, System Aesculap Meditec) emitting pulsed infrared radiation at a wavelength of 2.94 µm, with a pulse duration of 250 µs, and a pulse repetition rate of 10 pps. The samples were randomly divided into three experimental units, for treatment with a constant amount of 380 laser pulses at a radiation energy of 60 mJ, 100 mJ, and 180 mJ. Each experimental unit was divided into five subgroups of five samples, which were irradiated at a working tip angulations of 15°, 30°, 45°, 60°, and 90°. Five samples were treated mechanically using curettes. Five samples were left untreated as control. The mean (Ra) and maximum (Rmax) surface roughness of each sample was measured using a profilometer. The statistical analysis was undertaken using anova and Scheffé-test at a level of significance of 5% (p < 0.05). Results: Er:YAG laser radiation led to an Ra which ranged from 0.52 µm (± 0.10) to 0.81 µm (± 0.26) and to an Rmax between 3.4 µm (± 0.48) and 9.26 µm (± 3.08). The Ra and Rmax for samples treated with curettes was 0.51 µm (± 0.11) and 5.08 µm (± 4.98), respectively. That for the untreated control samples were 0.53 µm (± 0.15) and 7.07 µm (± 5.48), respectively. Conclusions: The mean and maximum surface roughness of root surfaces following irradiation with Er:YAG laser was not significantly different to that obtained on samples treated with conventional hand instruments or left untreated. Furthermore, the surface roughness does not depend on the radiation energy and the angulation of the working tip. [source] Characterization by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry of the major photoproducts of temoporfin (m -THPC) and bacteriochlorin (m -THPBC)JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2001Marc Angotti Abstract The photobleaching of 5,10,15,20-tetrakis(m -hydroxyphenyl)chlorin (temoporfin, m -THPC) and 5,10,15,20-tetrakis(m -hydroxyphenyl)bacteriochlorin (bacteriochlorin, m -THPBC) was studied in ethanol,water (1 : 99, v/v) and in physiological medium (phosphate-buffered saline, PBS) with or without fetal calf serum (FCS). m -THPC solution was irradiated with the laser radiation of 650 nm, whereas m -THPBC solution underwent two consecutive irradiations at 532 and 650 nm. The photoproducts were characterized by UV,visible absorption spectrophotometry and by matrix-assisted laser desorption/ionization (MALDI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). Independent of the solvent used, the phototransformation of either photosensitizer yielded the formation of 5,10,15,20-tetrakis (m -hydroxyphenyl)porphyrin (m -THPP) through a major dehydrogenation process. Copyright © 2001 John Wiley & Sons, Ltd. [source] Scanning electron microscopy and transmission electron microscopy microstructural investigation of high-speed tool steel after Nd:YAG pulsed laser meltingJOURNAL OF MICROSCOPY, Issue 1 2006S. KAC Summary This article presents the microstructure of a pulsed Nd:YAG laser-melted high-speed steel, namely HS6-5-2. The high chemical homogeneity and fine structure of the melted zone was attributed to high cooling rates due to the short duration of interaction with the Nd:YAG pulsed laser radiation and the relatively small volume of the melted material. The structure obtained in the surface layer after laser melting has a high level of hardness and shows improved wear resistance. [source] Multiphoton microscopy in life sciencesJOURNAL OF MICROSCOPY, Issue 2 2000K. König Near infrared (NIR) multiphoton microscopy is becoming a novel optical tool of choice for fluorescence imaging with high spatial and temporal resolution, diagnostics, photochemistry and nanoprocessing within living cells and tissues. Three-dimensional fluorescence imaging based on non-resonant two-photon or three-photon fluorophor excitation requires light intensities in the range of MW cm,2 to GW cm,2, which can be derived by diffraction limited focusing of continuous wave and pulsed NIR laser radiation. NIR lasers can be employed as the excitation source for multifluorophor multiphoton excitation and hence multicolour imaging. In combination with fluorescence in situ hybridization (FISH), this novel approach can be used for multi-gene detection (multiphoton multicolour FISH). Owing to the high NIR penetration depth, non-invasive optical biopsies can be obtained from patients and ex vivo tissue by morphological and functional fluorescence imaging of endogenous fluorophores such as NAD(P)H, flavin, lipofuscin, porphyrins, collagen and elastin. Recent botanical applications of multiphoton microscopy include depth-resolved imaging of pigments (chlorophyll) and green fluorescent proteins as well as non-invasive fluorophore loading into single living plant cells. Non-destructive fluorescence imaging with multiphoton microscopes is limited to an optical window. Above certain intensities, multiphoton laser microscopy leads to impaired cellular reproduction, formation of giant cells, oxidative stress and apoptosis-like cell death. Major intracellular targets of photodamage in animal cells are mitochondria as well as the Golgi apparatus. The damage is most likely based on a two-photon excitation process rather than a one-photon or three-photon event. Picosecond and femtosecond laser microscopes therefore provide approximately the same safe relative optical window for two-photon vital cell studies. In labelled cells, additional phototoxic effects may occur via photodynamic action. This has been demonstrated for aminolevulinic acid-induced protoporphyrin IX and other porphyrin sensitizers in cells. When the light intensity in NIR microscopes is increased to TW cm,2 levels, highly localized optical breakdown and plasma formation do occur. These femtosecond NIR laser microscopes can also be used as novel ultraprecise nanosurgical tools with cut sizes between 100 nm and 300 nm. Using the versatile nanoscalpel, intracellular dissection of chromosomes within living cells can be performed without perturbing the outer cell membrane. Moreover, cells remain alive. Non-invasive NIR laser surgery within a living cell or within an organelle is therefore possible. [source] Effect of Er:YAG and Diode lasers on the adhesion of blood components and on the morphology of irradiated root surfacesJOURNAL OF PERIODONTAL RESEARCH, Issue 5 2006Letícia Helena Theodoro Objective:, The aim of this study was to evaluate in vitro, by scanning electron microscopy (SEM), the adhesion of blood components on root surfaces irradiated with Er:YAG (2.94 µm) and GaAlAs Diode (808 nm) lasers and the effects on the morphology of irradiated root surfaces. Methods:, One hundred samples of human teeth were obtained. They were previously planed and scaled with manual instruments and divided into five groups of 20 samples each: G1 (control group) , absence of treatment; G2 , Er:YAG laser (7.6 J/cm2); G3 , Er:YAG laser (12.9 J/cm2); G4 , Diode laser (90 J/cm2) and G5 , Diode laser (108 J/cm2). After these treatments, 10 samples of each group received a blood tissue but the remaining 10 did not. After laboratory treatments, the samples were obtained by SEM, the photomicrographs were analysed by the score of adhesion of blood components and the results were statistically analysed (Kruskall,Wallis and Mann,Whitney test). Results:, In relation to the adhesion of blood components, the study showed no significant differences between the control group and the groups treated with Er:YAG laser (p = 0.9633 and 0.6229). Diode laser radiation was less effective than control group and Er:YAG laser radiation (p < 0.01). Conclusions:, None of the proposed treatments increased the adhesion of blood components in a significant way when compared to the control group. Although the Er:YAG laser did not interfere in the adhesion of blood components, it caused more changes on the root surface, whereas the Diode laser inhibited the adhesion. [source] Yellow pigments in painting: characterisation and UV laser-induced modificationsJOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2009S. Acquaviva Abstract Artistic yellow pigments, commonly employed from antiquity, were investigated by morphological, spectrophotometric and compositional analyses. Namely, scanning electron microscopy,energy dispersive X-ray (SEM/EDX) characterisations and reflectance, attenuated total reflection,Fourier transform infrared spectroscopy (ATR-FTIR) and Raman spectroscopy were carried out on egg yolk tempera models to discriminate the pigments. The models were irradiated with excimer KrF (248 nm) laser at different working conditions, and the effects induced on colour were related to chemical and physical modifications through the same analyses, as a function of laser parameters. It came out that the effects on the pictorial layers are always related to the modifications of the binding medium and, in addition, the laser radiation induces dehydration and transformation of iron oxides in natural earths. Copyright © 2009 John Wiley & Sons, Ltd. [source] Anomalous behavior of the second and third harmonics generated by femtosecond Cr:forsterite laser pulses in SiC,polymer nanocomposite materials as functions of the SiC nanopowder contentJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2003S. O. Konorov Abstract Femtosecond pulses of 1.25 µm Cr:forsterite laser radiation were used to study second- and third-harmonic generation in silicon carbide nanopowders embedded in a poly(methyl methacrylate) (PMMA) film. Harmonic generation processes extend the analytical and sensing abilities of light-scattering techniques, including Raman spectroscopy, offering a convenient and efficient approach to the analysis of nanocomposite materials where nanoparticles tend to agglomerate, masking informative features in Raman spectra. The second- and third-harmonic yields are shown to display an anomalous, counterintuitive behavior as functions of the SiC nanopowder content in a polymer film. Whereas harmonic generation in polymer films with a high content of SiC nanocrystals is quenched by the absorption of agglomerating nanoparticles, the influence of absorption is less detrimental in nanocomposite films with a lower SiC content, leading to the growth of the second- and third-harmonic yields. Nanocomposite films with a lower SiC content are also characterized by a higher breakdown threshold, allowing pump pulses with higher fluences to be applied for more efficient harmonic generation. Copyright © 2003 John Wiley & Sons, Ltd. [source] Photoreduction of iron protoporphyrin IX chloride in non-ionic triton X-100 micelle studied by electronic absorption and resonance Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2001P. K. Shantha Resonance Raman and electronic absorption studies of iron protoporphyrin IX chloride (hemin) in non-ionic Triton X-100 micelle in the absence and presence of hindered imidazole (2-methylimidazole and 1,2-dimethylimidazole) and unhindered imidazole under various experimental conditions are reported. Hemin undergoes photoreduction at the metal center, both in the absence and presence of hindered imidazole, in anaerobic, alkaline and neutral pH conditions on photoexcitation by laser radiation at 441.6 and 457.9 nm. It is inferred from this study that only the monomer hemin encapsulated within the micelle under the alkaline pH conditions is photoreducible. The photoreduction of hemin in this micelle occurs from an electron transfer as a result of dissociation of coordinated hydroxyl ion to the iron atom in the photoexcited state, which may also involve the OH,Fe charge transfer transition around 360 nm. Copyright © 2001 John Wiley & Sons, Ltd. [source] Detection of radiation of powerful fiber lasers reflected back from metals in course of laser processingLASER PHYSICS LETTERS, Issue 5 2010V.N. Petrovskiy Abstract The method allowing to detect in real time the laser radiation reflected from metal in course of its processing by powerful fiber ytterbium lasers is proposed. It is shown that there is a correspondence between the behavior of a reflected back signal and the oscillatory processes in a liquid bath of the fused met al. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] X-Ray laser: past, present, and futureLASER PHYSICS LETTERS, Issue 6 2009S. Suckewer Abstract In this review we concentrate our attention on X-ray laser research and development covering the so called soft X-ray region (down to , 10 nm) and the "water window" region (down to 2.3 , 4.4 nm). We present the development of soft X-ray lasers (SXLs) and their applications using primarily collisional and recombination schemes. We present the paths towards compact systems and major achievements to date. We discuss conditions for using both schemes to reach the "water window" region. In this discussion we also present another possible schemes based on photo-pumping, inner shell transitions in atoms and ions and "Doppler Compression" of IR laser radiation down to the X-ray region with its intrinsic tunability possibility. A significant part of the review is dedicated to the wide range of applications of SXLs with wavelengths at and above 10 nm. Also discussed is the potential of extending the range of biological applications for the "water window" region. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Stimulated Raman scattering in Nd:SrWO4LASER PHYSICS LETTERS, Issue 1 2005H. Jelínková Abstract Stimulated Raman scattering process in Nd:SrWO4 crystal was employed to frequency down-shift the fundamental frequency of a Nd:YAG mode-locked laser system. A single-pass configuration of Raman crystal was investigated for this purpose. After that Nd:SrWO4 laser was built and coherent pumping by alexandrite laser radiation was used. The simultaneous generation of stimulated Raman scattering was proofed for the case of Q-switching and mode-locking of Nd:SrWO4 Raman cavity. For Nd:YAG 50 ps long (1064 nm) pulsed pumping a single-pass first Stokes maximum energy and conversion efficiency were 1.6 mJ and 25% , respectively. With the free-running Nd:SrWO4 laser the maximum energy of 90 mJ at wavelength 1057 nm was obtained. Q-switching with the LiF:F,2 saturable absorber gave up to 1.3 mJ energy at the first Stokes frequency (1170 nm) in the pulse length of 3 ns. In mode-locking regime (with saturable absorber ML51 in dichlorethan or 3955 in ethanol), the total generated energy was 1.8 mJ and 2.4 mJ for ML51 and 3955 dyes, respectively. The SRS output at 1170 nm was approximately 20% of those values. (© 2005 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Low and high order light scattering in particulate mediaLASER PHYSICS LETTERS, Issue 8 2004I. V. Meglinski Abstract We present the results of a theoretical study providing details of propagation of laser radiation within disperse randomly inhomogeneous intermediately single-to-multiple scattering media. A quantitative analysis of scattering orders in the transition from single to multiple scattering is presented. Crossed source-detector fiber optics geometry used to separate the intensity of single scattering from higher scattering orders. The results demonstrate good agreement between analytical and Monte Carlo techniques. This validates the use of the Monte Carlo approach in the intermediate single-to-multiple scattering regime. The method used can be applied to verify analytical results against experiment via the Monte Carlo calculations that include imperfections of the experiment. (© 2004 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Laser even harmonics generation by a plasma embedded in a static electric fieldLASER PHYSICS LETTERS, Issue 4 2004G. Ferrante Abstract Even order harmonics generation of the laser radiation due to electron-ion collisions in a plasma embedded in a constant electric field is investigated theoretically. Even harmonics are generated because the presence of a static electric field removes the invariance of the electron distribution function under the symmetry operation of velocity direction inversion. Efficiency generation dependencies are investigated vs different significant parameters as: harmonics number; the ratio of the electron quiver velocity to the thermal velocity; the orientation of the constant electric field with respect to the laser radiation electric field and its wavevector. It is shown that in the general case the polarization planes of different even harmonics are different and do not coincide with that of the generating laser radiation. (© 2004 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Nd:YAG laser interaction with mine wrapping materialsLASER PHYSICS LETTERS, Issue 2 2004T. Rothacher Abstract According to UN publications landmines are a daily threat in approximately 70 countries of the world. There exist different ways to destroy detected antipersonnel mines. Neutralisation of mines with laser is a possibility that offers several advantages like working from safe distance and possibly mine destruction by deflagration and without explosion. Previous work has shown the importance of an absorbing mine wrapping material to achieve the desired burning process. In this paper, interaction of Nd:YAG laser radiation with different realistic synthetic mine wrapping materials is investigated. Penetration duration of laser radiation at , = 1.064 ,m through samples with different thickness is measured. Penetration through all tested materials is achieved at an incident power of 28.8 W. With an investigated material thickness up to 3 mm, penetration duration is in the range of seconds. Also penetration through a real mine case consisting of bakelite is achieved. (© 2004 by HMS Consultants. Inc. Published exclusively by WILEY-VCH Verlag GmbH & Co.KGaA) [source] Welding and Marking of Plastics with LasersLASER TECHNIK JOURNAL, Issue 5 2010New absorbers increase possibilities for application Today laser radiation as a tool for The Authors welding, cutting and marking in manufacturing of plastic components and products has achieved a good market acceptance. It offers an alternative to conventional processes such as ultrasonic, vibration or friction welding, mechanical cutting, milling or water jet cutting, tampon printing or ink jet printing. Main advantages for laser marking are flexibility and a contact free process [1]. Laser welding of plastics offers advantages in case of cleanness of processed components, low thermal and mechanical stress to components and inner sensitive parts as well as flexibility [2]. Although laser beam welding seems to be a relatively expensive processing method, savings can be achieved by entirely consideration of production process and logistics. [source] Comparison of germanium oxide fibers with silica and sapphire fiber tips for transmission of erbium: YAG laser radiationLASERS IN SURGERY AND MEDICINE, Issue 8 2006Travis J. Polletto BS Abstract Background and Objectives Endoscopic applications of the Erbium:YAG laser have been limited due to the lack of a suitable optical fiber delivery system. The purpose of this study was to compare the transmission of Er:YAG laser radiation through germanium oxide trunk fibers with silica and sapphire fiber tips for potential use in contact tissue ablation during endoscopy. Study Design/Materials and Methods Er:YAG laser radiation with a wavelength of 2.94 µm, pulse length of 300 microseconds, pulse energies from 5 to 1,360 mJ, coupled into pulse repetition rates of 3,10 Hz, was through 1-m-long germanium oxide fibers with either 1-cm-long, 550-µm-diameter silica or sapphire tips. Results Transmission through the germanium oxide/sapphire fibers measured 65±5% compared with 55±4% for the germanium oxide/silica fibers (P<0.05). The damage threshold for the hybrid fibers averaged 309± 44 mJ and 126±43 mJ, respectively (n,=,7 fibers each) (P<0.05). The highest pulse energies transmitted through the fibers were 700 mJ and 220 mJ, respectively. Conclusions Improved index-matching of the trunk fiber and fiber tip at 2.94 µm resulted in higher transmission and damage thresholds for the germanium oxide/sapphire fibers. The germanium oxide/sapphire fiber may represent a promising mid-infrared optical fiber delivery system for use in endoscopic applications of the Er:YAG laser requiring a flexible, biocompatible, and robust fiber delivery system for contact tissue ablation. Lasers Surg. Med. 38:787,791, 2006. © 2006 Wiley-Liss, Inc. [source] Hybrid germanium/silica optical fibers for endoscopic delivery of erbium:YAG laser radiationLASERS IN SURGERY AND MEDICINE, Issue 1 2004Charles A. Chaney MS Abstract Background and Objectives Endoscopic applications of the erbium (Er):YAG laser have been limited due to the lack of an optical fiber delivery system that is robust, flexible, and biocompatible. This study reports the testing of a hybrid germanium/silica fiber capable of delivering Er:YAG laser radiation through a flexible endoscope. Study Design/Materials and Methods Hybrid optical fibers were assembled from 1-cm length, 550-,m core, silica fiber tips attached to either 350- or 425-,m germanium oxide "trunk" fibers. Er:YAG laser radiation (,,=,2.94 ,m) with laser pulse lengths of 70 and 220 microseconds, pulse repetition rates of 3,10 Hz, and laser output energies of up to 300 mJ was delivered through the fibers for testing. Results Maximum fiber output energies measured 180±30 and 82±20 mJ (n,=,10) under straight and tight bending configurations, respectively, before fiber interface damage occurred. By comparison, the damage threshold for the germanium fibers without silica tips during contact soft tissue ablation was only 9 mJ (n,=,3). Studies using the hybrid fibers for lithotripsy also resulted in fiber damage thresholds (55,114 mJ) above the stone ablation threshold (15,23 mJ). Conclusions Hybrid germanium/silica fibers represent a robust, flexible, and biocompatible method of delivering Er:YAG laser radiation during contact soft tissue ablation. However, significant improvement in the hybrid fibers will be necessary before they can be used for efficient Er:YAG laser lithotripsy. Lasers Surg. Med. 34:5,11, 2004. © 2004 Wiley-Liss, Inc. [source] Diode-pumped fiber lasers: A new clinical tool?LASERS IN SURGERY AND MEDICINE, Issue 3 2002Stuart D. Jackson PhD Abstract Background and Objective Diode-pumped fiber lasers are a compact and an efficient source of high power laser radiation. These laser systems have found wide recognition in the area of lasers as a result of these very practical characteristics and are now becoming important tools for a large number of applications. In this review, we outline the basic physics of fiber lasers and illustrate how a number of clinical procedures would benefit from their employment. Study Design/Materials and Methods The pump mechanisms, the relevant pump and laser transitions between the energy levels, and the main properties of the output from fiber lasers will be briefly reviewed. The main types of high power fiber lasers that have been demonstrated will be examined along with some recent medical applications that have used these lasers. We will also provide a general review of some important medical specialties, highlighting why these fields would gain from the introduction of the fiber laser. Results/Conclusion It is established that while the fiber laser is still a new form of laser device and hence not commercially available in a wide sense, a number of important medical procedures will benefit from its general introduction into medicine. With the number of medical and surgical applications requiring high power laser radiation steadily increasing, the demand for more efficient and compact laser systems providing this capacity will grow commensurately. The high power fiber laser is one system that looks like a promising modality to meet this need. Lasers Surg. Med. 30:184-190, 2002. © 2002 Wiley-Liss, Inc. [source] Induction of Persistent Double Strand Breaks Following Multiphoton Irradiation of Cycling and G1 -arrested Mammalian Cells,Replication-induced Double Strand BreaksPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2008Jane V. Harper DNA double strand breaks (DSBs) are amongst the most deleterious lesions induced within the cell following exposure to ionizing radiation. Mammalian cells repair these breaks predominantly via the nonhomologous end joining pathway which is active throughout the cell cycle and is error prone. The alternative pathway for repair of DSBs is homologous recombination (HR) which is error free and active during S- and G2/M-phases of the cell cycle. We have utilized near-infrared laser radiation to induce DNA damage in individual mammalian cells through multiphoton excitation processes to investigate the dynamics of single cell DNA damage processing. We have used immunofluorescent imaging of ,-H2AX (a marker for DSBs) in mammalian cells and investigated the colocalization of this protein with ATM, p53 binding protein 1 and RAD51, an integral protein of the HR DNA repair pathway. We have observed persistent DSBs at later times postlaser irradiation which are indicative of DSBs arising at replication, presumably from UV photoproducts or clustered damage containing single strand breaks. Cell cycle studies have shown that in G1 cells, a significant fraction of multiphoton laser-induced prompt DSBs persists for >4 h in addition to those induced at replication. [source] Dynamics of nanostructure formation using point defects on semiconductors by laser radiationPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2009A. Medvid Abstract Dynamics of nanostructures (nanocones and nanocavties) formation on surface of semiconductors by laser radiation based on Thermogradient effect (TGE) is studied. Nanostructures formation of both nanohills and nanocavities are explained by point defects redistribution in gradient of temperature at the irradiated surface. Study of photoluminescence (PL), atomic force microscopy (AFM) and Raman back-scattering spectra speak in favour of presence of quantum confinement effect (QCE) on the top of nanocones on the irradiated surface of semiconductor single crystals. Aggregation of vacancies under the irradiated surface forms nanocavities. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Quantum confinement effect in nanohills formed on a surface of Ge by laser radiationPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2007Artur Medvid Abstract Photoluminescence in visible range of spectra from nanohills formed on a surface of Ge single crystal by JAG:Nd laser radiation was found. This photoluminescence is explained by quantum confinement effect in quantum dots on a top of nanohills. Red shift of 300 cm,1 line micro-Raman back scattering spectrum is an evidence of this suggestion. The calculation of QDs diameter using band gap shift photoluminescence spectra and peak frequency in micro-Raman spectra as a function of diameter for spherical Ge particles gives diameters of nano-balls on the top of nanohills is 4 nm and 6 nm. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of excitation density on luminescence decay in Y3Al5O12:Ce and BaF2 crystals excited by free electron laser radiation in VUVPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005M. Kirm Abstract The influence of excitation density on luminescence decay in Y3Al5O12:Ce and BaF2 crystals at room temperature was investigated for the first time using pulsed free electron laser radiation in vacuum ultraviolet. Increased excitation density led to the remarkable shortening of luminescence decays with non-exponential behaviour in both crystals. The possible reasons for dramatic changes in the dynamics of electronic excitations in insulators excited by free electron laser radiation will be discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Microleakage of composite resin restorations in cervical cavities prepared by Er,Cr:YSGG laser radiationAUSTRALIAN DENTAL JOURNAL, Issue 2 2008S Shahabi Abstract Background:, Evaluation of microleakage is important for assessing the success of new methods for surface preparation and new adhesive restorative materials. The aim of this laboratory study was to assess microleakage at the margins of composite restorations in Er,Cr:YSGG laser prepared cavities on the cervical aspects of teeth by means of dye penetration, and compare this with conventionally prepared and conditioned cavities. Methods:, Class V cavities were produced on sound extracted human teeth, which had been assigned randomly to one of three groups (N = 10 each), as follows: Group 1 , prepared using a diamond cylindrical bur and then treated with 37% phosphoric acid; Group 2 , irradiated with an Er,Cr:YSGG laser (Biolase Waterlase) and then treated with 37% phosphoric acid; Group 3 , irradiated only with the laser. After application of bonding agent (Excite, Ivoclar Vivadent), all cavities were restored with composite resin (Heliomolar). After polishing the restorations, the teeth were thermocycled from 5,50°C for 500 cycles. Dye leakage was assessed after immersion in methylene blue, by examining longitudinal sections in a stereomicroscope at ×30 magnification. Results:, The extent of dye penetration was lowest in the laser only group (Group 3). Penetration of dye to dentine and axial walls occurred in 80 per cent of conventionally prepared (bur + acid) specimens, but in the laser group, dye penetration to the axial wall occurred in only 30 per cent of cases. There was a strong statistical association between treatment group and the distribution of microleakage scores (Chi-square, P = 0.0023). Conclusions:, For Class V cavities, with the adhesive materials employed, higher microleakage occurs with phosphoric acid etching of bur- or laser-cut surfaces, than with the surface created by use of the laser alone without additional conditioning. [source] Effect of laser cleaning on granite colorCOLOR RESEARCH & APPLICATION, Issue 2 2007Carlota M. Grossi Abstract This article presents the effect of laser radiation on the color of ornamental granites used for external cladding. The laboratory experimentation was undertaken on a widely used coarse-grain granite commercially known as Rosa Porriño. The irradiation was carried out with a Q-switched Nd:YAG laser at 1064 nm and several energy densities (fluences) on polished surfaces, dry and wet, uncoated, and artificially coated-simulating a black crust. Laser effects on the granite surface were determined by color measurements with a colorimeter. These measurements made possible to determine probable damage due to laser radiation and the diverse response of different minerals. The analysis of the data also suggests potential causes for the color change and applicability limits of the technique. The a*-parameter, or red,green component, is the most affected, leading to a change in hab (hue) and was interpreted as a result in variations in the Fe compounds, which strongly condition stone color. No significant changes in L* (luminosity or lightness) or Cab* (chroma) may indicate no relevant alterations in the surface polish. When using laser irradiation to remove black layers on granite surfaces, variations of L* can be indicative of the cleaning effectiveness. This research results may be useful to select laser parameters when managing ornamental granite cleaning operations. However, they also suggest the need of further experimentation in specific techniques of analysis as well as different laser wavelengths. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 152 , 159, 2007 [source] Anterior eye tissue transmission for the radiation with the wavelength from eye safe regionLASER PHYSICS LETTERS, Issue 12 2005H. Jelínková Abstract Comparison of the eye tissue transmission for six laser radiations from visible up to mid-infrared region was done. The attenuation of the alexandrite (visible 0.75 µm), and Nd:YAP (near infrared 1.08 µm) laser radiations was found to be minimal , a retina reachs ,46% energy of these lasers entering the eye. On the other side the radiations of 1.54 µm (Er:glass), 1.66 µm (Er:YAP), and 2.01 µm (Tm:YAG) lasers are absorbed by the anterior segments of the eye and no impact is appeared on the retina. The absorption values measured for 1.34 µm (Nd:YAP) was recorded to be between the curves obtained for two groups of radiation wavelengths mentioned above. On retina, only 0.5% of the cornea radiation level was found. In this case the anterior parts of the eye are affected partially but not so deeply as in the case of eye safe radiation application. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] | |||||||||||||||||||