Science.gov

Sample records for laser assisted hatching

  1. Thermal effects in laser-assisted embryo hatching

    NASA Astrophysics Data System (ADS)

    Douglas-Hamilton, Diarmaid H.; Conia, Jerome D.

    2000-08-01

    Diode lasers [(lambda) equals 1480 nm] are used with in-vitro fertilization [IVF] as a promoter of embryo hatching. A focused laser beam is applied in vitro to form a channel in the zona pellucida (shell) of the pre-embryo. After transfer into the uterus, the embryo hatches: it extrudes itself through the channel and implants into the uterine wall. Laser-assisted hatching can result in improving implantation and pregnancy success rates. We present examples of zone pellucida ablation using animal models. In using the laser it is vital not to damage pre-embryo cells, e.g. by overheating. In order to define safe regimes we have derived some thermal side-effects of zona pellucida removal. The temperature profile in the beam and vicinity is predicted as function of laser pulse duration and power. In a crossed-beam experiment a HeNe laser probe detects the temperature-induced change in refractive index. We find that the diode laser beam produces superheated water approaching 200 C on the beam axis. Thermal histories during and following the laser pulse are given for regions in the neighborhood of the beam. We conclude that an optimum regime exists with pulse duration laser power approximately 100 mW.

  2. The effects of laser assisted hatching on pregnancy rates

    PubMed Central

    Ghannadi, Alireza; Kazerooni, Marjaneh; Jamalzadeh, Fatemeh; Amiri, Sahar; Rostami, Parifar; Absalan, Forouzan

    2011-01-01

    Background: For infertile women aged over 35 years, failure of the ZP (zona pellucida) to rupture is believed to be associated with a decreased implantation rate in in vitro fertilization (IVF) or intra cytoplasmic sperm injection (ICSI). Objective: In this research, laser assisted hatching (LAH) was offered to patients with advanced maternal age to evaluate a possible benefit. Materials and Methods: Nine hundred thirty two cycles of IVF/ICSI in females were analyzed. Women included in this study were allocated in 4 groups. In group I and II, embryos were cultured and transferred with and without LAH in women aged ≤35, whereas embryos of group III and IV were examined with and without LAH in women aged ≥ 35. Laser manipulations were performed using a suturn-Tm3 system using 2-3 pulses of 0.8 millisecond with 400 voltage duration. The size of the hole made in the zona was measured to be 5-10 µm, depending on the zona thickness of each individual embryo. Results: The performance of LAH significantly increased clinical pregnancy rates in all patients. In group I and II, the chemical (50.99% and 31.61% respectively), clinical (50% and 30.69% respectively) and multiple pregnancies (22.27% and 5.94% respectively) significantly differ between these groups. In the patients with advanced female age ≥35 the performance of LAH significantly increased chemical (30.12%) and clinical pregnancy (27.71%) rates compared to whom without LAH (18.96% and 16.37% respectively). Conclusion: Our data demonstrate in the patients who were less than 35 years old, multiple pregnancy rates were significantly increased compared to other groups who aged over 35 years old. In addition benefit of LAH in improving pregnancy rates after IVF or ICSI in women of advanced age (≥35) was shown. PMID:25587254

  3. Outcomes of vitrified-warmed cleavage-stage embryo hatching after in vitro laser-assisted zona pellucida thinning in patients

    PubMed Central

    Wang, En-Hua; Wang, An-Cong; Wang, Bao-Song; Li, Bin

    2016-01-01

    The aim of the present study was to determine whether the size of the zona pellucida (ZP) thinning area by laser-assisted hatching affected the potential development of vitrified-warmed embryos. A total of 196 vitrified-warmed cleavage-stage embryos (from 49 patients, four sister embryos per patient) were used in the study, i.e., four sister embryos from each patient were randomly assigned to four groups: a control group of embryos that were not zona-manipulated (zona intact, group A); one experimental group of embryos in which a quarter of the zona pellucida was thinned using laser-assisted ZP thinning (group B); a second experimental group of embryos in which half of ZP was thinned (group C); and a third group in which two-thirds of the ZP was thinned (group D). Subsequent blastocyst development was assessed. Microscopy was performed to study the hatching process of the embryos after zona thinning. The blastocyst formation rates were 71.43% in group A, 67.35% in group B, 65.31% in group C, and 51.02% in group D (groups B-D vs. group A, P=0.661, P=0.515, P=0.038, respectively). The rates of complete hatching were 30.61% in group A, 38.78% in group B, 61.22% in group C, and 48.98% in group D (groups B-D vs. group A, P=0.396, P=0.002, P=0.063, respectively). For a subgroup of patients, there was a significant difference in the complete hatching in all the groups for women aged <35 years (P=0.011), and there was a significant difference in the complete hatching in all the groups for secondary infertility women (P=0.022). There was no significant difference in the blastocyst formation rates in the different groups of women aged ≥35 years (P=0.340). In addition, there was no significant difference in the complete hatching in the different groups among women aged ≥35 years (P=0.492). The results of the present study showed that in vitrified-warmed embryo transfers at the cleavage-stage, and the two-thirds zona pellucida thinning group demonstrated a significantly

  4. Pregnancy achieved by transfer of thawed day 3 embryos that had been frozen after assisted hatching: a case report.

    PubMed

    Haydardedeoğlu, Bülent; Kılıçdağ, Esra Bulgan; Bağış, Tayfun

    2010-01-01

    Assisted Hatching (AH) is performed to increase implantation rates in assisted reproductive techniques, especially recurrent implantation failure and older age group. AH can be performed to four different techniques as laser, mechanical, enzymatic, chemical methods. In the literature, there is limited data about embryo freezing after AH. Herein, a successful pregnancy, which was achieved by transfer of thawed 3rd day embryos that had been frozen after AH, is presented.

  5. Femtosecond scalpel-optical tweezers: efficient tool for assisted hatching and trophectoderm biopsy

    NASA Astrophysics Data System (ADS)

    Sitnikov, D. S.; Ilina, I. V.; Khramova, Yu V.; Filatov, M. A.; Semenova, M. L.

    2016-08-01

    Ultrashort laser pulses have enabled highly precise and delicate processing of biological specimens. We present the results of using femtosecond (fs) laser pulses for dissection of zona pellucida (ZP) in mouse embryos during assisted hatching procedure and for trophectoderm biopsy as well. We studied the effects of application of fs laser radiation in the infrared (1028 nm) and visible (514 nm) wavelength ranges. Laser irradiation parameters were optimized so as not to compromise the viability of the treated embryos. Embryo biopsy was carried out in late-stage mouse preimplantation embryos. Femtosecond laser pulses were applied to detach the desired amount of trophectoderm cells from the blastocyst, while the optical tweezers trapped the cells and moved them out of the embryo. The parameters of laser radiation were optimized so as to efficiently perform embryo biopsy and preserve the viability of the treated embryos. The thermal effects can be significantly lower when fs lasers are used as compared to CW or long-pulse lasers. It is crucial when dealing with living cells or organisms.

  6. Laser assisted deposition

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1983-01-01

    Applications of laser-based processing techniques to solar cell metallization are discussed. Laser-assisted thermal or photolytic maskless deposition from organometallic vapors or solutions may provide a viable alternative to photovoltaic metallization systems currently in use. High power, defocused excimer lasers may be used in conjunction with masks as an alternative to direct laser writing to provide higher throughput. Repeated pulsing with excimer lasers may eliminate the need for secondary plating techniques for metal film buildup. A comparison between the thermal and photochemical deposition processes is made.

  7. Laser assisted hair-removal.

    PubMed

    Choudhary, S; Elsaie, M L; Nouri, K

    2009-10-01

    A number of lasers and light devices are now available for the treatment of unwanted hair. The goal of laser hair removal is to damage stem cells in the bulge of the hair follicle by targeting melanin, the endogenous chromophore for laser and light devices utilized to remove hair. The competing chromophores in the skin and hair, oxyhemoglobin and water, have a decreased absorption between 690 nm and 1000 nm, thus making this an ideal range for laser and light sources. Laser hair removal is achieved through follicular unit destruction based on selective photothermolysis. The principle of selective photothermolysis predicts that the thermal injury will be restricted to a given target if there is sufficient selective absorption of light and the pulse duration is shorter than the thermal relaxation time of the target. This review will focus on the mechanisms of laser assisted hair removal and provide an update on the newer technologies emerging in the field of lasers assisted hair removal.

  8. Laser Assisted Microsurgical Anastomosis.

    DTIC Science & Technology

    1983-09-22

    Miami School of Medicine This Paper describes new experimental microsurgical procedures that * utilize laser infrared energy emitted at 10.6 um to...dioxide laser microsurgical technique takes advantage of the very high absorption of laser energy (at 10.6 um) by water in soft tissue to effect successful...describes a new surgical technique that utilizes laser heat energy to repair transected rat sciatic nerves, and nerve grafts. The energy emitted at

  9. The effect of the site of laser zona opening on the complete hatching of mouse blastocysts and their cell numbers

    PubMed Central

    Sanmee, Usanee; Piromlertamorn, Waraporn

    2016-01-01

    Objective We studied the effect of the site of laser zona opening on the complete hatching of mouse blastocysts and the cell numbers of the completely hatched blastocysts. Methods Mouse blastocysts were randomly allocated to the inner cell mass (ICM) group (zona opening performed at the site of the ICM, n=125), the trophectoderm (TE) group (zona opening performed opposite to the ICM, n=125) and the control group (no zona opening, n=125). Results The rate of complete hatching of the blastocysts was not significantly different in the ICM and the TE group (84.8% vs 80.8%, respectively; p=0.402), but was significantly lower in the control group (51.2%, p<0.001). The cell numbers in the completely hatched blastocysts were comparable in the control group, the ICM group, and the TE group (69±19.3, 74±15.7, and 71±16.8, respectively; p=0.680). Conclusion These findings indicate that the site of laser zona opening did not influence the rate of complete hatching of mouse blastocysts or their cell numbers. PMID:27689037

  10. Laser assisted graffiti paints removing

    NASA Astrophysics Data System (ADS)

    Novikov, B. Y.; Chikalev, Y. V.; Shakhno, E. A.

    2011-02-01

    It's hard to imagine a modern city view without some drawings and inscriptions, usually called "graffiti". Traditional cleaning methods do not suit modern requirements. Investigation of possibilities of laser assisted paints removing is described in this article. The conditions for removing different paints from different surfaces were defined.

  11. Laser assisted graffiti paints removing

    NASA Astrophysics Data System (ADS)

    Novikov, B. Y.; Chikalev, Y. V.; Shakhno, E. A.

    2010-07-01

    It's hard to imagine a modern city view without some drawings and inscriptions, usually called "graffiti". Traditional cleaning methods do not suit modern requirements. Investigation of possibilities of laser assisted paints removing is described in this article. The conditions for removing different paints from different surfaces were defined.

  12. Influence of an Angular Hatching Exposure Strategy on the Surface Roughness During Picosecond Laser Ablation of Hard Materials

    NASA Astrophysics Data System (ADS)

    Daniel, Christian; Manderla, Jannik; Hallmann, Sina; Emmelmann, Claus

    Innovative chip breakers for cutting tools made of very hard materials require laser ablation and demand a high quality regarding the manufactured surface. When processing materials such as polycrystalline cubic boron-nitride or tungsten carbide the surface roughness by laser ablation reaches Sa = 1,0-2,9 μm compared to Sa = 0,42 μm achieved by grinding. Therefore in the presented research the influence of the hatching exposure strategy on surface roughness during picosecond laser ablation of tungsten carbide is examined. The areal, layerwise ablation process is separated into its elements which are represented by intersection zones between single and multiple laser vectors. Thus two mechanisms of roughness formation are identified and described by model functions. Further the mechanisms are transferred to areal ablation in which surface roughness decreases due to improved hatching angles compared to a commonly used one of φ= 0°/90°. With this approach the roughness is reduced by approximately factor 2,0-3,5 to Sa = 0,82 μm. In conclusion guidelines are derived which present favorable settings for high quality laser ablation processes.

  13. Effect of assisted hatching on pregnancy outcomes: a systematic review and meta-analysis of randomized controlled trials

    PubMed Central

    Li, Da; Yang, Da-Lei; An, Jing; Jiao, Jiao; Zhou, Yi-Ming; Wu, Qi-Jun; Wang, Xiu-Xia

    2016-01-01

    Emerging evidence suggests that assisted hatching (AH) techniques may improve clinical pregnancy rates, particularly in poor prognosis patients; however, there still remains considerable uncertainty. We conducted a meta-analysis to verify the effect of AH on pregnancy outcomes. We searched for related studies published in PubMed, Web of Science, and Cochrane library databases from start dates to October 10, 2015. Totally, 36 randomized controlled trials with 6459 participants were included. Summary odds ratios (ORs) with 95% confidence intervals (CIs) for whether by AH or not were estimated. We found a significant increase in clinical pregnancy (OR = 1.16, 95% CI = 1.00–1.36, I2 = 48.3%) and multiple pregnancy rates (OR = 1.50, 95% CI = 1.11–2.01, I2 = 44.0%) with AH when compared to the control. Numerous subgroup analyses stratified by hatching method, conception mode, extent of AH, embryos transfer status, and previous failure history were also carried out. Interestingly, significant results of clinical pregnancy as well as multiple pregnancy rates were observed among women who received intracytoplasmic sperm injection, and who received AH which the zona were completely removed. In summary, this meta-analysis supports that AH was associated with an increased chance of achieving clinical pregnancy and multiple pregnancy. Whether AH significantly changes live birth and miscarriage rates needs further investigations. PMID:27503701

  14. Mechanism Guides Hatch Through Hatchway

    NASA Technical Reports Server (NTRS)

    Barron, Daniel R.; Kennedy, Steven E.

    1993-01-01

    Elliptical hatch designed to move through hatchway to make pressure-assisted seal with either side of bulkhead. Compact three-degree-of-freedom mechanism guides hatch through hatchway or holds hatch off to one side to facilitate passage of crew and/or equipment. Hatches and mechanisms used in submarines, pressure chambers (including hyperbaric treatment chambers), vacuum chambers, and vacuum-or-pressure test chambers.

  15. Laser-assisted solar cell metallization processing

    NASA Technical Reports Server (NTRS)

    Rohatgi, A.; Gupta, S.; Mcmullin, P. G.; Palaschak, P. A.

    1985-01-01

    Laser-assisted processing techniques for producing high-quality solar cell metallization patterns are being investigated, developed, and characterized. The tasks comprising these investigations are outlined.

  16. Laser-assisted solar cell metallization processing

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1984-01-01

    Laser assisted processing techniques utilized to produce the fine line, thin metal grid structures that are required to fabricate high efficiency solar cells are investigated. The tasks comprising these investigations are summarized. Metal deposition experiments are carried out utilizing laser assisted pyrolysis of a variety of metal bearing polymer films and metalloorganic inks spun onto silicon substrates. Laser decomposition of spun on silver neodecanoate ink yields very promising results. Solar cell comb metallization patterns are written using this technique.

  17. Laser-assisted methods for nanofabrication

    NASA Astrophysics Data System (ADS)

    Kabashin, Andrei V.; Meunier, Michel

    2004-07-01

    An overview of laser-assisted nanofabrication methods, which has been developed in the Laser Processing Laboratory, is presented. All methods imply the laser-related ablation of material from a solid target and the production of nanoparticles or nanostructures. We consider the nanofabrication process in both the gaseous and in the liquid ambience under different parameters of laser radiation. A particular attention is given on the absence or presence of the plasma-related absorption of the laser radiation, which make possible different nanofabrication regimes. The methods lead to a production of nanomaterials, which are of importance for photonics and biosensing applications.

  18. Laser-assisted photoemission from surfaces

    SciTech Connect

    Saathoff, G.; Miaja-Avila, L.; Murnane, M. M.; Kapteyn, H. C.; Aeschlimann, M.

    2008-02-15

    We investigate the laser-assisted photoelectric effect from a solid surface. By illuminating a Pt(111) sample simultaneously with ultrashort 1.6 and 42 eV pulses, we observe sidebands in the extreme ultraviolet photoemission spectrum, and accurately extract their amplitudes over a wide range of laser intensities. Our results agree with a simple model, in which soft x-ray photoemission is accompanied by the interaction of the photoemitted electron with the laser field. This strong effect can definitively be distinguished from other laser surface interaction phenomena, such as hot electron excitation, above-threshold photoemission, and space-charge acceleration. Thus, laser-assisted photoemission from surfaces promises to extend pulse duration measurements to higher photon energies, as well as opening up measurements of femtosecond-to-attosecond electron dynamics in solid and surface-adsorbate systems.

  19. Laser-assisted solar cell metallization processing

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1984-01-01

    Laser-assisted processing techniques utilized to produce the fine line, thin metal grid structures that are required to fabricate high efficiency solar cells are examined. Two basic techniques for metal deposition are investigated; (1) photochemical decomposition of liquid or gas phase organometallic compounds utilizing either a focused, CW ultraviolet laser (System 1) or a mask and ultraviolet flood illumination, such as that provided by a repetitively pulsed, defocused excimer laser (System 2), for pattern definition, and (2) thermal deposition of metals from organometallic solutions or vapors utilizing a focused, CW laser beam as a local heat source to draw the metallization pattern.

  20. Laser-assisted serial tonsillectomy.

    PubMed

    Krespi, Y P; Ling, E H

    1994-10-01

    Laser ablation of the palatine tonsils is a useful alternative to tonsillectomy in adults. Cryptic tonsillitis is a common problem causing recurrent infection, sore throat, and halitosis. Elimination and/or obliteration of surface pockets (crypts) of the palatine tonsils utilizing the CO2 laser was effective in 86 patients treated in the past 4 years. Ablation of the tonsil surface was performed in stages under local anesthesia in an office setting; CO2 laser energy delivered through the "SwiftLase" handpiece extension provided char-free, superficial layer ablation of tissue. "SwiftLase" is easily installed onto existing CO2 laser units and provides high-power densities by utilizing a focused laser beam in an extremely fast uniform scan over an extended area (up to 4 mm) within a fraction of a second. This method and results of its use are discussed.

  1. 21 CFR 884.6200 - Assisted reproduction laser system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Assisted reproduction laser system. 884.6200... (CONTINUED) MEDICAL DEVICES OBSTETRICAL AND GYNECOLOGICAL DEVICES Assisted Reproduction Devices § 884.6200 Assisted reproduction laser system. (a) Identification. The assisted reproduction laser system is a...

  2. 21 CFR 884.6200 - Assisted reproduction laser system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Assisted reproduction laser system. 884.6200... (CONTINUED) MEDICAL DEVICES OBSTETRICAL AND GYNECOLOGICAL DEVICES Assisted Reproduction Devices § 884.6200 Assisted reproduction laser system. (a) Identification. The assisted reproduction laser system is a...

  3. 21 CFR 884.6200 - Assisted reproduction laser system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Assisted reproduction laser system. 884.6200... (CONTINUED) MEDICAL DEVICES OBSTETRICAL AND GYNECOLOGICAL DEVICES Assisted Reproduction Devices § 884.6200 Assisted reproduction laser system. (a) Identification. The assisted reproduction laser system is a...

  4. 21 CFR 884.6200 - Assisted reproduction laser system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Assisted reproduction laser system. 884.6200... (CONTINUED) MEDICAL DEVICES OBSTETRICAL AND GYNECOLOGICAL DEVICES Assisted Reproduction Devices § 884.6200 Assisted reproduction laser system. (a) Identification. The assisted reproduction laser system is a...

  5. 21 CFR 884.6200 - Assisted reproduction laser system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Assisted reproduction laser system. 884.6200... (CONTINUED) MEDICAL DEVICES OBSTETRICAL AND GYNECOLOGICAL DEVICES Assisted Reproduction Devices § 884.6200 Assisted reproduction laser system. (a) Identification. The assisted reproduction laser system is a...

  6. Chemically-Assisted Pulsed Laser-Ramjet

    NASA Astrophysics Data System (ADS)

    Horisawa, Hideyuki; Kaneko, Tomoki; Tamada, Kazunobu

    2010-10-01

    A preliminary study of a chemically-assisted pulsed laser-ramjet was conducted, in which chemical propellant such as a gaseous hydrogen/air mixture was utilized and detonated with a focused laser beam in order to obtain a higher impulse compared to the case only using lasers. CFD analysis of internal conical-nozzle flows and experimental measurements including impulse measurement were conducted to evaluate effects of chemical reaction on thrust performance improvement. From the results, a significant improvement in the thrust performances was confirmed with addition of a small amount of hydrogen to propellant air, or in chemically-augmented operation.

  7. Chemically-Assisted Pulsed Laser-Ramjet

    SciTech Connect

    Horisawa, Hideyuki; Kaneko, Tomoki; Tamada, Kazunobu

    2010-10-13

    A preliminary study of a chemically-assisted pulsed laser-ramjet was conducted, in which chemical propellant such as a gaseous hydrogen/air mixture was utilized and detonated with a focused laser beam in order to obtain a higher impulse compared to the case only using lasers. CFD analysis of internal conical-nozzle flows and experimental measurements including impulse measurement were conducted to evaluate effects of chemical reaction on thrust performance improvement. From the results, a significant improvement in the thrust performances was confirmed with addition of a small amount of hydrogen to propellant air, or in chemically-augmented operation.

  8. Mechanically assisted laser forming of thin beams

    NASA Astrophysics Data System (ADS)

    Mucha, Zygmunt; Widłaszewski, Jacek; Kurp, Piotr; Mulczyk, Krystian

    2016-12-01

    Laser-assisted forming techniques have been developed in recent years to aid plastic working of materials, which are difficult in processing at normal temperatures due to a high brittleness, effects of high work-hardening or a high spring-back phenomenon. This paper reports initial experimental investigations and numerical simulations of a mechanically-assisted laser forming process. The research is aimed at facilitating plastic shaping of thin-walled parts made of high temperature resistant alloys. Stainless steel plate, 1 mm thick, 20 mm wide, was mounted in the cantilever arrangement and a gravitational load was applied to its free end. A CO2 laser beam with rectangular cross-section traversed along the plate, towards the fixed edge. Laser spot covered the whole width of the plate. Experiments and simulations using the finite element method were performed for different values of mechanical load and with constant laser processing parameters. Experimentally validated numerical model allowed analysis of plastic deformation mechanism under the hybrid thermo-mechanical processing. The revealed mechanism of deformation consists in intense material plastic flow near the laser heated surface. This behavior results mainly from the tension state close to the heated surface and the decrease of material yield stress at elevated temperature. Stress state near the side edges of the processed plate favored more intense plastic deformation and the involved residual stress in this region.

  9. Computer-assisted interstitial laser coagulation for BPH

    NASA Astrophysics Data System (ADS)

    Ho, Gideon; Barrett, Adrian R. W.; Ng, Wan S.; Lim, Liam G.; Cheng, Wai S.

    2001-06-01

    Interstitial laser thermotherapy is a minimally invasive surgical procedure that utilizes laser to coagulate and treat benign prostatic hyperplasia. This study explores the use of a computer-assisted interstitial laser coagulation system to aid surgeons in performing this procedure.

  10. Metallic foil-assisted laser cell printing.

    PubMed

    Lin, Yafu; Huang, Yong; Chrisey, Douglas B

    2011-02-01

    Laser direct-write technology such as modified laser-induced forward transfer (LIFT) is emerging as a revolutionary technology for biological construct fabrication. While many modified LIFT-based cell direct writing successes have been achieved, possible process-induced cell injury and death is still a big hurdle for modified LIFT-based cell direct writing to be a viable technology. The objective of this study is to propose metallic foil-assisted LIFT using a four-layer structure to achieve better droplet size control and increase cell viability in direct writing of human colon cancer cells (HT-29). The proposed four layers include a quartz disk, a sacrificial and adhesive layer, a metallic foil, and a cell suspension layer. The bubble formation-induced stress wave is responsible for droplet formation. It is found that the proposed metallic foil-assisted LIFT approach is an effective cell direct-write technology and provides better printing resolution and high post-transfer cell viability when compared with other conventional modified LIFT technologies such as matrix-assisted pulsed-laser evaporation direct-write; at the same time, the possible contamination from the laser energy absorbing material is minimized using a metallic foil.

  11. Laser assisted Drug Delivery: Grundlagen und Praxis.

    PubMed

    Braun, Stephan Alexander; Schrumpf, Holger; Buhren, Bettina Alexandra; Homey, Bernhard; Gerber, Peter Arne

    2016-05-01

    Die topische Applikation von Wirkstoffen ist eine zentrale Therapieoption der Dermatologie. Allerdings mindert die effektive Barrierefunktion der Haut die Bioverfügbarkeit der meisten Externa. Fraktionierte ablative Laser stellen ein innovatives Verfahren dar, um die epidermale Barriere standardisiert, kontaktfrei zu überwinden. Die Bioverfügbarkeit im Anschluss applizierter Externa wird im Sinne einer laser assisted drug delivery (LADD) signifikant gesteigert. Das Prinzip der LADD wird bereits in einigen Bereichen der Dermatologie erfolgreich eingesetzt. Die vorliegende Übersichtsarbeit soll einen Überblick über die aktuellen aber auch perspektivischen Einsatzmöglichkeiten der LADD bieten.

  12. Laser-assisted photoelectric effect from surfaces.

    PubMed

    Miaja-Avila, L; Lei, C; Aeschlimann, M; Gland, J L; Murnane, M M; Kapteyn, H C; Saathoff, G

    2006-09-15

    We report the first observation of the laser-assisted photoelectric effect from a solid surface. By illuminating a Pt(111) sample simultaneously with ultrashort 1.6 eV and 42 eV pulses, we observe sidebands in the extreme ultraviolet photoemission spectrum. The magnitude of these sidebands as a function of time delay between the laser and extreme ultraviolet pulses represents a cross-correlation measurement of the extreme ultraviolet pulse. This effect promises to be useful to extend extreme ultraviolet pulse duration measurements to higher photon energies, as well as opening up femtosecond-to-attosecond time-scale electron dynamics in solid and surface-adsorbate systems.

  13. Laser-assisted growth of molybdenum rods

    NASA Astrophysics Data System (ADS)

    Björklund, K. L.; Heszler, P.; Boman, M.

    2002-01-01

    In this paper, we report for the first time the laser-assisted growth of molybdenum rods via the H 2 reduction of MoF 6 with a focused Ar + laser beam as the heat source. By varying the gas composition, total pressure, and laser power rods with different morphologies were deposited on a tungsten wire. At low H 2/MoF 6 molar ratios crystal-like rods were obtained and at higher molar ratios the rods became dendrite-like. The activation energy for the process was determined to be 77±7 kJ mol -1 in the temperature range 705-840 K. The reaction order showed to be nearly 3 with respect to the hydrogen partial pressure and zero order with respect to the molybdenum hexafluoride partial pressure. Compositional and morphological characterisation were performed with scanning electron microscopy, energy dispersed X-ray spectroscopy and Auger electron spectroscopy.

  14. Laser-assisted solar cell metallization processing

    NASA Technical Reports Server (NTRS)

    Meier, D. L.

    1986-01-01

    The status of the laser-assisted solar cell metallization processing is described. Metallo-organic silver films were spun-on by argon ion laser beam pyrolysis. The metallo-organic decomposition (MOD) film was spun-on an evaporated Ti/Pd film to produce tood adhesion. In a maskless process, the argon ion laser writes the contact pattern. The film is then built up to obtain the required conductivity using conventional silverplating process. The Ti/Pd film in the field is chemically etched using the plated silver film as the mask. The width of the contact pattern is determined by the power of the laser. Widths as thin as 20 microns were obtained using 0.66 W of laser power. Cells fabricated with the 50 micron line widths of 4 ohm-cm floating zone (Fz) silicon-produced efficiencies of 16.6% (no passivation) which were equivalent to the best cells using conventional metallization/lithography and no passivation.

  15. Laser-assisted surgery of endonasal diseases

    NASA Astrophysics Data System (ADS)

    Sroka, Ronald; Leunig, Andreas; Janda, P.; Rosler, P.; Grevers, G.; Baumgartner, Reinhold

    2000-06-01

    Clinical studies were performed to assess the clinical outcome of laser assisted endonasal turbinate surgery in long-term. By means of a pulsed Ho:YAG laser emitting at (lambda) equals 2100nm 57 patients suffering form nasal obstruction due to allergic rhinitis and vasomotoric rhinitis were treated under local anesthesia. Furthermore 50 patients were treated by means of light of a diode laser. The light was fed into a fiber being introduced into a fiber guidance system which serves for suction of smoke and pyrolyse products. The distal part of this system could be bent in the range of -5 degrees up to 45 degrees due to the optical axes of the fiber. The study was conducted by a standardized questionnaire, photo documentation, allergy test, mucocilliar function test, rhinomanometry, radiology and histology. Within 2 weeks after laser treatment a significant improvement of nasal airflow correlating to the extent of the ablated turbinate tissue could be determined. This effect lasted up until 1 year post treatment resulting in an improved quality of life in more than 80 percent of the patients. Side effects like nasal dryness and pain were rare, no immediate complications were observed. The total treatment time took 3-8 minutes/turbinate and nasal packing was not necessary after the laser procedure. In conclusion laser treatment by means of the fiber guidance system can be performed as an outpatient procedure under local anesthesia with excellent ablation of soft tissue in a short treatment time with promising results. It will become a time and cost effective treatment modality in endonasal laser surgery.

  16. Laser-Assisted Photoelectric Effect from Liquids.

    PubMed

    Arrell, C A; Ojeda, J; Mewes, L; Grilj, J; Frassetto, F; Poletto, L; van Mourik, F; Chergui, M

    2016-09-30

    The laser-assisted photoelectric effect from liquid surfaces is reported for the first time. Photoelectrons generated by 35.6 eV radiation from a liquid microjet of water under vacuum are dressed with a ℏω=1.55  eV laser field. The subsequent redistribution of the photoelectron energies consists in the appearance of sidebands shifted by energies equivalent to ℏω, 2ℏω, and 3ℏω. The response has been modeled to the third order and combined with energy-resolved measurements. This result opens the possibility to investigate the dynamics at surfaces of liquid solutions and provide information about the electron emission process from a liquid.

  17. Laser-Assisted Photoelectric Effect from Liquids

    NASA Astrophysics Data System (ADS)

    Arrell, C. A.; Ojeda, J.; Mewes, L.; Grilj, J.; Frassetto, F.; Poletto, L.; van Mourik, F.; Chergui, M.

    2016-09-01

    The laser-assisted photoelectric effect from liquid surfaces is reported for the first time. Photoelectrons generated by 35.6 eV radiation from a liquid microjet of water under vacuum are dressed with a ℏω =1.55 eV laser field. The subsequent redistribution of the photoelectron energies consists in the appearance of sidebands shifted by energies equivalent to ℏω , 2 ℏω , and 3 ℏω . The response has been modeled to the third order and combined with energy-resolved measurements. This result opens the possibility to investigate the dynamics at surfaces of liquid solutions and provide information about the electron emission process from a liquid.

  18. Laser-assisted rapid prototyping in Japan

    NASA Astrophysics Data System (ADS)

    Kathuria, Yash P.

    2002-04-01

    In the recent past years, developments in the rapid prototyping of various parts have taken new dynamic turns in manufacturing technology. Besides the use of new materials, unrelenting demands for the downsizing of miniature components in the micro-domain have expanded the application area of the rapid prototype product. Their requirements with reduced time lag have forced the manufacturers to adopt and develop innovative techniques which meet these demands. In order to overcome this problem, several techniques, predominantly laser stereolithography, have successfully been used in Japan for the past several years to generate a complex micro-/macro part of polymer resin based in two- or three-dimensional domains. The main disadvantage of this process is that they consist of two or more steps for producing metallic/metal-matrix composite microstructures. But recently developed new technologies of selective laser sintering/generating and ballistic particles manufacturing processes offer the possibility of the direct generation of these microstructures in a single step process. The last two processes actually have limitations on the feature size produced, due to the minimum size of the molten droplet. But the selective laser sintering technique can bind the particles by melting together at the interfacial grain contact area only and thus producing smaller feature sizes. Based upon these techniques, the present paper aims to review the current status and the future prospective of laser assisted rapid prototyping in Japan.

  19. Laser-assisted isotope separation of tritium

    DOEpatents

    Herman, Irving P.; Marling, Jack B.

    1983-01-01

    Methods for laser-assisted isotope separation of tritium, using infrared multiple photon dissociation of tritium-bearing products in the gas phase. One such process involves the steps of (1) catalytic exchange of a deuterium-bearing molecule XYD with tritiated water DTO from sources such as a heavy water fission reactor, to produce the tritium-bearing working molecules XYT and (2) photoselective dissociation of XYT to form a tritium-rich product. By an analogous procedure, tritium is separated from tritium-bearing materials that contain predominately hydrogen such as a light water coolant from fission or fusion reactors.

  20. Laser-Assisted Single Molecule Refolding

    NASA Astrophysics Data System (ADS)

    Zhao, Rui; Marshall, Myles; Aleman, Elvin; Lamichhane, Rajan; Rueda, David

    2010-03-01

    In vivo, many RNA molecules can adopt multiple conformations depending on their biological context such as the HIV Dimerization Initiation Sequence (DIS) or the DsrA RNA in bacteria. It is quite common that the initial interaction between the two RNAs takes place via complementary unpaired regions, thus forming a so-called kissing complex. However, the exact kinetic mechanism by which the two RNA molecules reach the dimerized state is still not well understood. To investigate the refolding energy surface of RNA molecules, we have developed new technology based on the combination of single molecule spectroscopy with laser induced temperature jump kinetics, called Laser Assisted Single-molecule Refolding (LASR). LASR enables us to induce folding reactions of otherwise kinetically trapped RNAs at the single molecule level, and to characterize their folding landscape. LASR provides an exciting new approach to study molecular memory effects and kinetically trapped RNAs in general. LASR should be readily applicable to study DNA and protein folding as well.

  1. An augmented reality assistance platform for eye laser surgery.

    PubMed

    Ee Ping Ong; Lee, Jimmy Addison; Jun Cheng; Beng Hai Lee; Guozhen Xu; Laude, Augustinus; Teoh, Stephen; Tock Han Lim; Wong, Damon W K; Jiang Liu

    2015-08-01

    This paper presents a novel augmented reality assistance platform for eye laser surgery. The aims of the proposed system are for the application of assisting eye doctors in pre-planning as well as providing guidance and protection during laser surgery. We developed algorithms to automatically register multi-modal images, detect macula and optic disc regions, and demarcate these as protected areas from laser surgery. The doctor will then be able to plan the laser treatment pre-surgery using the registered images and segmented regions. Thereafter, during live surgery, the system will automatically register and track the slit lamp video frames on the registered retina images, send appropriate warning when the laser is near protected areas, and disable the laser function when it points into the protected areas. The proposed system prototype can help doctors to speed up laser surgery with confidence without fearing that they may unintentionally fire laser in the protected areas.

  2. Hatching behavior in turtles.

    PubMed

    Spencer, Ricky-John; Janzen, Fredric J

    2011-07-01

    Incubation temperature plays a prominent role in shaping the phenotypes and fitness of embryos, including affecting developmental rates. In many taxa, including turtles, eggs are deposited in layers such that thermal gradients alter developmental rates within a nest. Despite this thermal effect, a nascent body of experimental work on environmentally cued hatching in turtles has revealed unexpected synchronicity in hatching behavior. This review discusses environmental cues for hatching, physiological mechanisms behind synchronous hatching, proximate and ultimate causes for this behavior, and future directions for research. Four freshwater turtle species have been investigated experimentally, with hatching in each species elicited by different environmental cues and responding via various physiological mechanisms. Hatching of groups of eggs in turtles apparently involves some level of embryo-embryo communication and thus is not a purely passive activity. Although turtles are not icons of complex social behavior, life-history theory predicts that the group environment of the nest can drive the evolution of environmentally cued hatching.

  3. Laser-assisted solar-cell metallization processing

    SciTech Connect

    Dutta, S.; Mcmullin, P.G.

    1984-03-01

    Laser assisted solar cell metallization processing which is a one step process is examined. The potential advantages of laser disposition techniques for photovoltaic systems are: a high resolution, no photolithography, clean and contamination free, in-situ sintering, and low contact resistance.

  4. Laser cutting with chemical reaction assist

    DOEpatents

    Gettemy, Donald J.

    1992-01-01

    A method for cutting with a laser beam where an oxygen-hydrocarbon reaction is used to provide auxiliary energy to a metal workpiece to supplement the energy supplied by the laser. Oxygen is supplied to the laser focus point on the workpiece by a nozzle through which the laser beam also passes. A liquid hydrocarbon is supplied by coating the workpiece along the cutting path with the hydrocarbon prior to laser irradiation or by spraying a stream of hydrocarbon through a nozzle aimed at a point on the cutting path which is just ahead of the focus point during irradiation.

  5. Laser cutting with chemical reaction assist

    DOEpatents

    Gettemy, D.J.

    1992-11-17

    A method is described for cutting with a laser beam where an oxygen-hydrocarbon reaction is used to provide auxiliary energy to a metal workpiece to supplement the energy supplied by the laser. Oxygen is supplied to the laser focus point on the workpiece by a nozzle through which the laser beam also passes. A liquid hydrocarbon is supplied by coating the workpiece along the cutting path with the hydrocarbon prior to laser irradiation or by spraying a stream of hydrocarbon through a nozzle aimed at a point on the cutting path which is just ahead of the focus point during irradiation. 1 figure.

  6. Laser Assisted Free-Free Transition in Electron - Atom Collision

    NASA Technical Reports Server (NTRS)

    Sinha, C.; Bhatia, A. K.

    2011-01-01

    Free-free transition is studied for electron-Hydrogen atom system in ground state at very low incident energies in presence of an external homogeneous, monochromatic and linearly polarized laser field. The incident electron is considered to be dressed by the laser in a non perturbative manner by choosing the Volkov solutions in both the channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the effect of electron exchange, short range as well as of the long range interactions. Laser assisted differential as well as elastic total cross sections are calculated for single photon absorption/emission in the soft photon limit, the laser intensity being much less than the atomic field intensity. A strong suppression is noted in the laser assisted cross sections as compared to the field free situations. Significant difference is noted in the singlet and the triplet cross sections.

  7. Investigation on femtosecond laser-assisted microfabrication in silica glasses

    NASA Astrophysics Data System (ADS)

    Liu, Hewei; Chen, Feng; Yang, Qing; Si, Jinhai; Hou, Xun

    2010-11-01

    Fabrication of microstructures embedded in silica glasses using a femtosecond (fs)-laser-assisted chemical etching technique is systematically studied in this work. By scanning the laser pulses inside samples followed by the treatment of 5%-diluted hydrofluoric (HF) acid, groups of straight channels are fabricated and the relationship between the etching rate and processing parameters, including laser power, scanning speed, scanning time and laser polarization, is demonstrated. Based on the optimization of these parameters, complicated microstructures such as channels, cavities and their combinations are manufactured. The work has great potential applications in microelectromechanical systems, biomedical detection and chemical analysis.

  8. Cytokines and Blastocyst Hatching.

    PubMed

    Seshagiri, Polani B; Vani, Venkatappa; Madhulika, Pathak

    2016-03-01

    Blastocyst implantation into the uterine endometrium establishes early pregnancy. This event is regulated by blastocyst- and/or endometrium-derived molecular factors which include hormones, growth factors, cell adhesion molecules, cytokines and proteases. Their coordinated expression and function are critical for a viable pregnancy. A rate-limiting event that immediately precedes implantation is the hatching of blastocyst. Ironically, blastocyst hatching is tacitly linked to peri-implantation events, although it is a distinct developmental phenomenon. The exact molecular network regulating hatching is still unclear. A number of implantation-associated molecular factors are expressed in the pre-implanting blastocyst. Among others, cytokines, expressed by peri-implantation blastocysts, are thought to be important for hatching, making blastocysts implantation competent. Pro-inflammatory (IL-6, LIF, GM-CSF) and anti-inflammatory (IL-11, CSF-1) cytokines improve hatching rates; they modulate proteases (MMPs, tPAs, cathepsins and ISP1). However, functional involvement of cytokines and their specific mediation of hatching-associated proteases are unclear. There is a need to understand mechanistic roles of cytokines and proteases in blastocyst hatching. This review will assess the available knowledge on blastocyst-derived pro-inflammatory and anti-inflammatory cytokines and their role in potentially regulating blastocyst hatching. They have implications in our understanding of early embryonic loss and infertility in mammals, including humans.

  9. Prospective study on laser-assisted laparascopic partial nephrectomy

    NASA Astrophysics Data System (ADS)

    Sroka, Ronald; Hennig, Georg; Zilinberg, Katja; Khoder, Wael Y.

    2012-02-01

    Introduction: Developments in laparoscopic partial nephrectomy (LPN) opened a demand for surgical tools compatible with laparoscopic manipulations to make laser assisted technique safe, feasible and reproducible. Warm ischemia and bleeding during laparoscopic partial nephrectomy place technical constraints on surgeons. Therefore it was the aim to develop a safe and effective laser assisted partial nephrectomy technique without need for ischemia. Patients and methods: A diode laser emitting light at 1318nm in cw mode was coupled into a bare fibre (core diameter 600 μm) thus able to transfer up to 100W to the tissue. After dry lab experience, a total of 10 patients suffering from kidney malformations underwent laparoscopic/retroperitoneoscopic partial nephrectomy. Clinically, postoperative renal function and serum c-reactive protein (CRP) were monitored. Laser induced coagulation depth and effects on resection margins were evaluated. Demographic, clinical and follow-up data are presented. Using a commercial available fibre guidance instrument for lanringeal intervention, the demands on an innovative laser fibre guidance instrument for the laser assisted laparoscopic partial nephrectomy (LLPN) are summarized. Results: Overall, all laparascopic intervention were succesfull and could be performed without conversion to open surgery. Mean operative time and mean blood loss were comparable to conventional open and laparascopic approaches. Laser assisted resection of the kidney tissue took max 15min. After extirpation of the tumours all patients showed clinical favourable outcome during follow up period. Tumour sizes were measured to be up 5cm in diameter. The depth of the coagulation on the removed tissue ranged between <1 to 2mm without effect on histopathological evaluation of tumours or resection margin. As the surface of the remaining kidney surface was laser assisted coagulated after removal. The sealing of the surface was induced by a slightly larger coagulation

  10. Apparatus for laser assisted thin film deposition

    DOEpatents

    Warner, Bruce E.; McLean, II, William

    1996-01-01

    A pulsed laser deposition apparatus uses fiber optics to deliver visible output beams. One or more optical fibers are coupled to one or more laser sources, and delivers visible output beams to a single chamber, to multiple targets in the chamber or to multiple chambers. The laser can run uninterrupted if one of the deposition chambers ceases to operate because other chambers can continue their laser deposition processes. The laser source can be positioned at a remote location relative to the deposition chamber. The use of fiber optics permits multi-plexing. A pulsed visible laser beam is directed at a generally non-perpendicular angle upon the target in the chamber, generating a plume of ions and energetic neutral species. A portion of the plume is deposited on a substrate as a thin film. A pulsed visible output beam with a high pulse repetition frequency is used. The high pulse repetition frequency is greater than 500 Hz, and more preferably, greater than about 1000 Hz. Diamond-like-carbon (DLC) is one of the thin films produced using the apparatus.

  11. Antihydrogen formation in laser-assisted positron-antiproton scattering

    NASA Astrophysics Data System (ADS)

    Li, Shu-Min; Miao, Yan-Gang; Zhou, Zi-Fang; Chen, Ji; Liu, Yao-Yang

    1998-09-01

    Antihydrogen formation in the laser-assisted positron-antiproton (nonrelativistic) radiative recombination is investigated. The state of incident positron is given by the Coulomb-Volkov wave function. The perturbative dressed wave function of the atom is obtained in the soft-photon approximation. Our calculation shows that for a geometry of laser polarization parallel to the incident direction, the formation cross section of antihydrogen is greatly reduced. Especially at high impact energy, the reduction is remarkable.

  12. Oxide-assisted laser surfacing of aluminum

    NASA Astrophysics Data System (ADS)

    Hoepp, E. E.; Kerr, Hugh W.

    1996-04-01

    CO2 laser processing has been carried out on pure aluminum substrates for travel speeds from 0.3 to 6.1 mm/s, using laser powers of about 100 W or 300 W, with various preplaced single or mixed powders including CoO, NiO, SiO2, Fe2O3 or TiO2 usually combined with enough aluminum powder to permit complete reduction of the oxides. The 100 W laser experiments included low, normal and high gravity experiments. The resulting tracks were tested qualitatively for scratch resistance, and examined metallographically. Two types of surfacing were observed; continuous oxide layers produced by melting and an oxidation- reduction reaction of the original oxides with aluminum, and alloying of the substrate by elements reduced by the reaction. Low gravity experiments produced more uniform thicknesses and generally less cracking in the continuous oxides than normal or high gravity experiments. Alloying of the substrate ranged from almost 100% intermetallic layers at low laser powers and low travel speeds to complex mixtures and bands of different phases, depending on the temporal stability of the process, the powder composition and thickness, the laser power and travel speed. Optimization of the process could provide useful wear resistant coatings in a space environment.

  13. Laser and optical system for laser assisted hydrogen ion beam stripping at SNS

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Rakhman, A.; Menshov, A.; Webster, A.; Gorlov, T.; Aleksandrov, A.; Cousineau, S.

    2017-03-01

    Recently, a high-efficiency laser assisted hydrogen ion (H-) beam stripping was successfully carried out in the Spallation Neutron Source (SNS) accelerator. The experiment was not only an important step toward foil-less H- stripping for charge exchange injection, it also set up a first example of using megawatt ultraviolet (UV) laser source in an operational high power proton accelerator facility. This paper reports in detail the design, installation, and commissioning result of a macro-pulsed multi-megawatt UV laser system and laser beam transport line for the laser stripping experiment.

  14. Respiratory complications after diode-laser-assisted tonsillotomy.

    PubMed

    Fischer, Miloš; Horn, Iris-Susanne; Quante, Mirja; Merkenschlager, Andreas; Schnoor, Jörg; Kaisers, Udo X; Dietz, Andreas; Kluba, Karsten

    2014-08-01

    Children with certain risk factors, such as comorbidities or severe obstructive sleep apnea syndrome (OSAS) are known to require extended postoperative monitoring after adenotonsillectomy. However, there are no recommendations available for diode-laser-assisted tonsillotomy. A retrospective chart review of 96 children who underwent diode-laser-assisted tonsillotomy (07/2011-06/2013) was performed. Data for general and sleep apnea history, power of the applied diode-laser (λ = 940 nm), anesthesia parameters, the presence of postoperative respiratory complications and postoperative healing were evaluated. After initially uncomplicated diode-laser-assisted tonsillotomy, an adjustment of post-anesthesia care was necessary in 16 of 96 patients due to respiratory failure. Respiratory complications were more frequent in younger children (3.1 vs. 4.0 years, p = 0.049, 95 % CI -1.7952 to -0.0048) and in children who suffered from nocturnal apneas (OR = 5.00, p < 0.01, 95 % CI 1.4780-16.9152) or who suffered from relevant comorbidities (OR = 4.84, p < 0.01, 95 % CI 1.5202-15.4091). Moreover, a diode-laser power higher than 13 W could be identified as a risk factor for the occurrence of a postoperative oropharyngeal edema (OR = 3.45, p < 0.01, 95 % CI 1.3924-8.5602). Postoperative respiratory complications should not be underestimated in children with sleep-disordered breathing (SDB). Therefore, children with SDB, children with comorbidities or children younger than 3 years should be considered "at risk" and children with confirmed moderate to severe OSAS should be referred to a PICU following diode-laser-assisted tonsillotomy. We recommend a reduced diode-laser power (<13 W) to reduce oropharyngeal edema.

  15. Laser-assisted positron-impact ionization of atomic hydrogen.

    PubMed

    Pan, Juan; Li, Shu-Min; Berakdar, Jamal

    2007-03-15

    We study the ionization of atomic hydrogen by a fast positron in the presence of an external linearly polarized laser field. We concentrate on the limit of a small momentum transfer and describe the fast positron's continuum states by Volkov wave functions. The ejected electron is described by a Coulomb-Volkov wave function. We are limited to small laser intensities such that the dressed state of the target is treatable within the time-dependent perturbation theory, even though the laser intensity is still quite high by laboratory standards. Numerical results for the triply differential cross sections and their dependencies on laser-field parameters are discussed and compared with the results of laser-assisted ionization by electron impact.

  16. Laser-assisted patch clamping: a methodology

    NASA Technical Reports Server (NTRS)

    Henriksen, G. H.; Assmann, S. M.; Evans, M. L. (Principal Investigator)

    1997-01-01

    Laser microsurgery can be used to perform both cell biological manipulations, such as targeted cell ablation, and molecular genetic manipulations, such as genetic transformation and chromosome dissection. In this report, we describe a laser microsurgical method that can be used either to ablate single cells or to ablate a small area (1-3 microns diameter) of the extracellular matrix. In plants and microorganisms, the extracellular matrix consists of the cell wall. While conventional patch clamping of these cells, as well as of many animal cells, requires enzymatic digestion of the extracellular matrix, we illustrate that laser microsurgery of a portion of the wall enables patch clamp access to the plasma membrane of higher plant cells remaining situated in their tissue environment. What follows is a detailed description of the construction and use of an economical laser microsurgery system, including procedures for single cell and targeted cell wall ablation. This methodology will be of interest to scientists wishing to perform cellular or subcellular ablation with a high degree of accuracy, or wishing to study how the extracellular matrix affects ion channel function.

  17. Laser-assisted treatment of dentinal hypersensitivity: a literature review

    PubMed Central

    Biagi, Roberto; Cossellu, Gianguido; Sarcina, Michele; Pizzamiglio, Ilaria Tina; Farronato, Giampietro

    2015-01-01

    Summary The purpose of this literature review was to evaluate the effectiveness of the laser-assisted treatment of dentinal hypersensitivity. A review with inclusion and exclusion criteria was performed from January 2009 to December 2014 with electronic data-bases: MedLine via PubMed, Science Direct and Cochrane Library. Research of paper magazines by hand was not considered. Forty-three articles were selected between literature reviews, in vitro studies, clinical trials, pilot and preliminary studies. The items were divided into laser-used groups for an accurate description, and then the reading of results into various typologies. Laser-assisted treatment reduces dentinal hypersensitivity-related pain, but also a psychosomatic component must be considered, so further studies and more suitable follow-ups are necessary. PMID:26941892

  18. Laser-assisted fabrication of highly viscous alginate microsphere

    NASA Astrophysics Data System (ADS)

    Lin, Yafu; Huang, Yong

    2011-04-01

    Encapsulated microspheres have been widely used in various biomedical applications. However, fabrication of encapsulated microspheres from highly viscous materials has always been a manufacturing challenge. The objective of this study is to explore a novel metallic foil-assisted laser-induced forward transfer (LIFT), a laser-assisted fabrication technique, to make encapsulated microspheres using high sodium alginate concentration solutions. The proposed four-layer approach includes a quartz disk, a sacrificial and adhesive layer, a metallic foil, and a transferred suspension layer. It is found that the proposed four-layer modified LIFT approach provides a promising fabrication technology for making of bead-encapsulated microspheres from highly viscous solutions. During the process, the microsphere only can be formed if the direct-writing height is larger than the critical direct-writing height; otherwise, tail structured droplets are formed; and the encapsulated microsphere diameter linearly increases with the laser fluence and decreases with the sodium alginate concentration.

  19. Wheelchair assisted with laser range finder

    NASA Astrophysics Data System (ADS)

    Kang, Cheol U.; Wang, Hongbo; Ishimatsu, Takakazu; Ochiai, Tsumoru

    1995-12-01

    The paper presents a wheel chair system with the capability of self-localization and obstacle avoidance. Firstly, the approaches of landmark recognition and the self-localization of the wheel chair are described. Then, the principal of the obstacle avoidance using a laser range finder is described. Subsequently, the total system of the wheel chair is introduced. Finally, a navigation experiment is given. Experimental results indicate the effectiveness of our system.

  20. Measurement of electronegativity at different laser wavelengths: accuracy of Langmuir probe assisted laser photo-detachment

    NASA Astrophysics Data System (ADS)

    Sirse, N.; Oudini, N.; Bendib, A.; Ellingboe, A. R.

    2016-08-01

    Langmuir probe (LP) assisted pulsed laser photo-detachment (LPD) of negative ions is one of the frequently used diagnostic techniques in electronegative plasmas. The technique is based on measuring the rise in electron saturation current following photo-detachment. During the photo-detachment process it is assumed that the background electron parameters (temperature and density) remain unchanged in the laser channel and the photo-detached electrons thermalize instantaneously with the background electrons (same temperature). Therefore, the measured electronegativity should be independent of laser wavelengths. However, our recent simulation results (2015 Phys. Plasmas 22 073509) demonstrates a failure of these assumptions and suggests that the measured rise in electron saturation current has a dependence on the laser wavelength. This letter presents experimental evidence in support of these simulation results. In this work, photo-detachment is performed at two different laser wavelengths in an oxygen inductively coupled plasma discharge. Electronegativity measured by LP assisted LPD is compared with those obtained by the hairpin probe (HPP) assisted LPD which is based on quasi-neutrality assumption. The experimental results reveal that the electronegativities measured by LP assisted LPD are affected by the laser wavelength, whereas, electronegativities measured by HPP assisted LPD are almost independent. The discrepancy between the measurements is higher at high electronegativities. In conclusion, the experimental results validate the weakness of assumptions to estimate electronegativity from LPD combined with LP and therefore emphasizes the need of a more realistic model to analyze raw data or an alternate solution is to utilize HPP.

  1. Laser-assisted removal of particles on silicon wafers

    NASA Astrophysics Data System (ADS)

    Vereecke, G.; Röhr, E.; Heyns, M. M.

    1999-04-01

    Laser cleaning is one of the new promising dry cleaning techniques considered by semiconductor companies to replace wet cleans in the near future. A dry laser cleaning tool was tested that uses an inert gas jet to remove particles lifted off by the action of a DUV excimer laser. A model was developed to simulate the cleaning process and analyze the influence of experimental parameters on laser cleaning efficiency. The best cleaning efficiencies obtained with 1.0 μm SiO2, ˜0.3 μm Si3N4, and 0.3 μm SiO2 particles deposited on Si wafers were 84±8%, 33±4%, and 12±7%, respectively. This is in qualitative agreement with theoretical calculations showing the existence of a size threshold for the removal of nonabsorbing particles by dry laser cleaning. Among the process parameters tested to optimize the process efficiency, fluence showed the highest influence on removal efficiency, before the number of laser pulses and the laser repetition rate. The use of high fluences was limited by the damaging of the wafer surface, which was not homogeneous on a macroscopic scale. The optimum number of laser pulses per unit area depended on the type of particle. The laser repetition rate had no significant influence on cleaning efficiency and can be used to reduce process time. The influence of capillary condensation on the process was demonstrated by the higher removal efficiency of 0.3 μm SiO2 and Si3N4 particles, 88±6% and 78%, respectively, upon exposure of wafers to air saturated with moisture prior to laser processing. This was attributed to the explosive evaporation of capillary condensed water, similar to the mechanism proposed for liquid assisted laser cleaning.

  2. Pulsed laser-assisted machining of Inconel 718 superalloy

    NASA Astrophysics Data System (ADS)

    Azhdari Tadavani, Soheila; Shoja Razavi, Reza; Vafaei, Reza

    2017-01-01

    Nickel-based superalloys including Inconel 718(IN718) are widely used in aerospace industries due to their superior high temperature strength, toughness, and corrosion resistance. These alloys are difficult to machine mainly because of their low thermal conductivity and high work hardening rate, which cause steep temperature gradient and high cutting forces at the tool edge. The application of laser assisted machining is the subject of many new researches since shear forces; surface coarsening and tool wear are reduced. The aim of this investigation was to evaluate laser assisted machining behavior of a 718 Inconel superalloy from the view point of machining specific energy, surface roughness, tool wear and chip appearance. Experimental apparatuses used included optical and scanning electron microscopy, spark emission spectroscopy, and EDS analysis. The results indicated that increasing the temperature to about 540 °C just ahead of primary shear zone, can result in 35% reduction of machining specific energy, in comparison with conventional machining. Furthermore, surface coarsening and tool wear were reduced by 22% and 23% respectively. Flank wear was the main deteriorating factor on cutting tools during laser assisted machining. SEM micrographs indicated that increase in temperature has no noticeable effect on finished workpiece surface. Analysis of variance obtained from regression analysis indicated that frequency of laser beam has the most influential effect on temperature. The optimum conditions for laser assisted machining of 718 superalloy is suggested as follows: 80 Hz frequency, 400 W power, 24 m/min cutting speed, and 0.052 mm/rev feed rate along with 540 °C temperature, 2.51 J/mm2 machining specific energy and 130 N cutting force.

  3. Pulse laser assist optical tweezers (PLAT) with long-duration pulse laser

    NASA Astrophysics Data System (ADS)

    Maeda, Saki; Sugiura, Tadao; Minato, Kotaro

    2011-07-01

    Optical tweezers is a technique to trap and to manipulate micron sized objects under a microscope by radiation pressure force exerted by a laser beam. Optical tweezers has been utilized for single-molecular measurements of force exerted by molecular interactions and for cell palpation. To extend applications of optical tweezers we have developed a novel optical tweezers system combined with a pulse laser. We utilize a pulse laser (Q-switched Nd: YAG laser, wavelength of 1064 nm) to assist manipulations by conventional optical tweezers with a continuous wave (CW) laser. The pulse laser beam is introduced into the same optics for conventional optical tweezers. In principle, instantaneous radiation force is proportional to instantaneous power of laser beam. As a result, pulse laser beam generates strong instantaneous force on an object to be manipulated. If the radiation force becomes strong enough to get over an obstacle structure and/or to be released from adhesion, the object will be free from these difficulties. We investigate the effect of pulse laser assistance with changing pulse duration of the laser. We report optimum pulse duration of 100 ns to 200 ns deduced from motion analysis of a particle in a beam spot. Our goal is to realize in-vivo manipulation and operation of a cell. For this purpose we need to reduce light energy of pulse laser beam and to avoid laser induced breakdown caused by strong light field. So we have developed a pulse laser with 160-ns pulse duration and have confirmed that availability on manipulation of living cells.

  4. Laser plasma formation assisted by ultraviolet pre-ionization

    SciTech Connect

    Yalin, Azer P. Dumitrache, Ciprian; Wilvert, Nick; Joshi, Sachin; Shneider, Mikhail N.

    2014-10-15

    We present experimental and modeling studies of air pre-ionization using ultraviolet (UV) laser pulses and its effect on laser breakdown of an overlapped near-infrared (NIR) pulse. Experimental studies are conducted with a 266 nm beam (fourth harmonic of Nd:YAG) for UV pre-ionization and an overlapped 1064 nm NIR beam (fundamental of Nd:YAG), both having pulse duration of ∼10 ns. Results show that the UV beam produces a pre-ionized volume which assists in breakdown of the NIR beam, leading to reduction in NIR breakdown threshold by factor of >2. Numerical modeling is performed to examine the ionization and breakdown of both beams. The modeled breakdown threshold of the NIR, including assist by pre-ionization, is in reasonable agreement with the experimental results.

  5. Laser-assisted new attachment procedure in private practice.

    PubMed

    Harris, David M; Gregg, Robert H; McCarthy, Delwin K; Colby, Leigh E; Tilt, Lloyd V

    2004-01-01

    Three private dental practices conducted a retrospective analysis of patients receiving the laser-assisted new attachment procedure (LANAP). Retrospective results were compared to clinical trial data from the University of Texas Health Sciences Center in San Antonio (UTHSCSA) to determine if outcomes from a controlled clinical trial can be duplicated in private practice. Results also are compared with published results of other surgical and nonsurgical therapies for inflammatory periodontal disease.

  6. Laser-assisted vacuum arc extreme ultraviolet source: a comparison of picosecond and nanosecond laser triggering

    NASA Astrophysics Data System (ADS)

    Beyene, Girum A.; Tobin, Isaac; Juschkin, Larissa; Hayden, Patrick; O'Sullivan, Gerry; Sokell, Emma; Zakharov, Vassily S.; Zakharov, Sergey V.; O'Reilly, Fergal

    2016-06-01

    Extreme ultraviolet (EUV) light generation by hybrid laser-assisted vacuum arc discharge plasmas, utilizing Sn-coated rotating-disc-electrodes, was investigated. The discharge was initiated by localized ablation of the liquid tin coating of the cathode disc by a laser pulse. The laser pulse, at 1064 nm, was generated by Nd:YAG lasers with variable energy from 1 to 100 mJ per pulse. The impact of shortening the laser pulse from 7 ns to 170 ps on the EUV generation has been investigated in detail. The use of ps pulses resulted in an increase in emission of EUV radiation. With a fixed discharge energy of ~4 J, the EUV conversion efficiency tends to plateau at ~2.4  ±  0.25% for the ps laser pulses, while for the ns pulses, it saturates at ~1.7  ±  0.3%. Under similar discharge and laser energy conditions, operating the EUV source with the ps-triggering resulted also in narrower spectral profiles of the emission in comparison to ns-triggering. The results indicate an advantage in using ps-triggering in laser-assisted discharges to produce brighter plasmas required for applications such as metrology.

  7. Laser assisted direct write process with novel beam profiles

    NASA Astrophysics Data System (ADS)

    Shang, Shuo; Wellburn, Dan; Fearon, Eamonn; Yan, Shilian; Edwardson, Stuart; Dearden, G.; Watkins, K. G.

    2013-05-01

    The Laser Assisted Direct Write (LADW) method can be used to generate electrical circuitry on a substrate by depositing metallic ink and curing the ink thermally with a laser. Compared to conventional oven curing, laser curing can be used in-situ, over complicated 3D contours, and selectively cure over heat sensitive substrates. The intensity distribution of the laser beam used has significant influence on many surface heating processes. A conventional Gaussian beam would lead to uneven heating across the beam path. To overcome this issue, Wellburn has designed a novel beam shaping device, which allows one to convert a Gaussian beam profile into an annular ring with a variable level of central plateau fill [1]. Shang et al. have developed and verified a predictive Finite Element Method (FEM) model to simulate the laser curing process for a generic combination of processing parameters. Laser modes can be flexibly varied within this model. Hence it can be used to predict the performance of curing with differently intensity distributions. This study investigates the curing process under different intensity profiles obtained with the beam shaping device. Electrical resistivity and scratch resistance of cured samples are tested as measures of the curing quality achieved. Results obtained are then compared with the FEM model predictions, and indicate the best intensity distribution for this particular application.

  8. Laser-assisted treatment of patients with hemorrhagic diathesis

    NASA Astrophysics Data System (ADS)

    Neckel, Claus P.

    2000-03-01

    Today more and more patients with bleeding disorder come to our office for treatment. The number of patients with therapeutic anticoagulation is growing steadily. Discontinuation of this therapy can often be crucial. On the other hand are oralsurgical procedures extremely sensitive to bleeding due to the constant presents of saliva with its high fibrinolytic activity. The aim of this study was to evaluate the use of a surgical diode (wavelength 810 nm) laser as accessory tool in the treatment of patients with hemorrhagic diathesis. Enclosed in the study were 123 patients with: (1) Coumarintherapy, a Quick test ratio of 15 - 25%; (2) More than 300 mg of ASS/die; (3) Hemophilia, a factor activity under 35%; (4) Morbus Werlhof with less than 30000 thrombocytes. 179 Surgical procedures: (1) Tooth extraction 86%; (2) Apexectomy 3%; (3) Tumorexcision 9%; (4) Curettage and flapsurgery 1%; (5) Gingivectomy 1%. All procedures were laser-assisted with a diode laser emitting 810 nm. The glass fibers used were depending on the procedures either 200, 400, or 600 micron. No coagulating agents or tissue adhesives were used in addition. The postoperative outcome and complication rates were compared to substitution therapy and tissue adhesives. Laser-assisted treatment of these patients shows a high predictability and success rate leaving out side effects of drugs and human cryoprecipitates. Postoperative impairment is diminished.

  9. Microwave assisted laser-induced breakdown spectroscopy at ambient conditions

    NASA Astrophysics Data System (ADS)

    Viljanen, Jan; Sun, Zhiwei; Alwahabi, Zeyad T.

    2016-04-01

    Signal enhancements in laser-induced breakdown spectroscopy (LIBS) using external microwave power are demonstrated in ambient air. Pulsed microwave at 2.45 GHz and of 1 millisecond duration was delivered via a simple near field applicator (NFA), with which an external electric field is generated and coupled into laser induced plasma. The external microwave power can significantly increase the signal lifetime from a few microseconds to hundreds of microseconds, resulting in a great enhancement on LIBS signals with the use of a long integration time. The dependence of signal enhancement on laser energy and microwave power is experimentally assessed. With the assistance of microwave source, a significant enhancement of ~ 100 was achieved at relatively low laser energy that is only slightly above the ablation threshold. A limit of detection (LOD) of 8.1 ppm was estimated for copper detection in Cu/Al2O3 solid samples. This LOD corresponds to a 93-fold improvement compared with conventional single-pulse LIBS. Additionally, in the microwave assisted LIBS, the self-reversal effect was greatly reduced, which is beneficial in measuring elements of high concentration. Temporal measurements have been performed and the results revealed the evolution of the emission process in microwave-enhanced LIBS. The optimal position of the NFA related to the ablation point has also been investigated.

  10. CO2 laser polishing of microfluidic channels fabricated by femtosecond laser assisted carving

    NASA Astrophysics Data System (ADS)

    Serhatlioglu, Murat; Ortaç, Bülend; Elbuken, Caglar; Biyikli, Necmi; Solmaz, Mehmet E.

    2016-11-01

    In this study, we investigate the effects of CO2 laser polishing on microscopic structures fabricated by femtosecond laser assisted carving (FLAC). FLAC is the peripheral laser irradiation of 2.5D structures suitable for low repetition rate lasers and is first used to define the microwell structures in fused silica followed by chemical etching. Subsequently, the bottom surface of patterned microwells is irradiated with a pulsed CO2 laser. The surfaces were characterized using an atomic force microscope (AFM) and scanning electron microscope (SEM) in terms of roughness and high quality optical imaging before and after the CO2 laser treatment. The AFM measurements show that the surface roughness improves more than threefold after CO2 laser polishing, which promises good channel quality for applications that require optical imaging. In order to demonstrate the ability of this method to produce low surface roughness systems, we have fabricated a microfluidic channel. The channel is filled with polystyrene bead-laden fluid and imaged with transmission mode microscopy. The high quality optical images prove CO2 laser processing as a practical method to reduce the surface roughness of microfluidic channels fabricated by femtosecond laser irradiation. We further compared the traditional and laser-based glass micromachining approaches, which includes FLAC followed by the CO2 polishing technique.

  11. Worldwide Spacecraft Crew Hatch History

    NASA Technical Reports Server (NTRS)

    Johnson, Gary

    2009-01-01

    The JSC Flight Safety Office has developed this compilation of historical information on spacecraft crew hatches to assist the Safety Tech Authority in the evaluation and analysis of worldwide spacecraft crew hatch design and performance. The document is prepared by SAIC s Gary Johnson, former NASA JSC S&MA Associate Director for Technical. Mr. Johnson s previous experience brings expert knowledge to assess the relevancy of data presented. He has experience with six (6) of the NASA spacecraft programs that are covered in this document: Apollo; Skylab; Apollo Soyuz Test Project (ASTP), Space Shuttle, ISS and the Shuttle/Mir Program. Mr. Johnson is also intimately familiar with the JSC Design and Procedures Standard, JPR 8080.5, having been one of its original developers. The observations and findings are presented first by country and organized within each country section by program in chronological order of emergence. A host of reference sources used to augment the personal observations and comments of the author are named within the text and/or listed in the reference section of this document. Careful attention to the selection and inclusion of photos, drawings and diagrams is used to give visual association and clarity to the topic areas examined.

  12. Laser-assisted advanced assembly for MEMS fabrication

    NASA Astrophysics Data System (ADS)

    Atanasov, Yuriy Andreev

    Micro Electro-Mechanical Systems (MEMS) are currently fabricated using methods originally designed for manufacturing semiconductor devices, using minimum if any assembly at all. The inherited limitations of this approach narrow the materials that can be employed and reduce the design complexity, imposing limitations on MEMS functionality. The proposed Laser-Assisted Advanced Assembly (LA3) method solves these problems by first fabricating components followed by assembly of a MEMS device. Components are micro-machined using a laser or by photolithography followed by wet/dry etching out of any material available in a thin sheet form. A wide range of materials can be utilized, including biocompatible metals, ceramics, polymers, composites, semiconductors, and materials with special properties such as memory shape alloys, thermoelectric, ferromagnetic, piezoelectric, and more. The approach proposed allows enhancing the structural and mechanical properties of the starting materials through heat treatment, tribological coatings, surface modifications, bio-functionalization, and more, a limited, even unavailable possibility with existing methods. Components are transferred to the substrate for assembly using the thermo-mechanical Selective Laser Assisted Die Transfer (tmSLADT) mechanism for microchips assembly, already demonstrated by our team. Therefore, the mechanical and electronic part of the MEMS can be fabricated using the same equipment/method. The viability of the Laser-Assisted Advanced Assembly technique for MEMS is demonstrated by fabricating magnetic switches for embedding in a conductive carbon-fiber metamaterial for use in an Electromagnetic-Responsive Mobile Cyber-Physical System (E-RMCPS), which is expected to improve the wireless communication system efficiency within a battery-powered device.

  13. Laser assisted processing; Proceedings of the Meeting, Hamburg, Federal Republic of Germany, Sept. 19, 20, 1988

    NASA Astrophysics Data System (ADS)

    Laude, Lucien D.; Rauscher, Gerhard

    The use of lasers in industrial material processing is discussed in reviews and reports. Sections are devoted to high-precision laser machining, deposition methods, ablation and polymers, and synthesis and oxidation. Particular attention is given to laser cutting of steel sheets, laser micromachining of material surfaces, process control in laser soldering, laser-induced CVD of doped Si stripes on SOS and their characterization by piezoresistivity measurements, laser CVD of Pt spots on glass, laser deposition of GaAs, UV-laser photoablation of polymers, ArF excimer-laser ablation of HgCdTe semiconductor, pulsed laser synthesis of Ti silicides and nitrides, the kinetics of laser-assisted oxidation of metallic films, and excimer-laser-assisted etching of solids for microelectronics.

  14. Argon laser-assisted treatment of benign eyelid lesions.

    PubMed

    Korkmaz, Şafak; Ekici, Feyzahan; Sül, Sabahattin

    2015-02-01

    We investigated the treatment of benign eyelid lesions with argon laser as an alternative therapy to surgical excision. The charts of 73 patients with 95 lesions treated with argon laser photocoagulation were reviewed retrospectively. In all patients, the procedure was performed for cosmetic reasons. The laser spot size ranged from 50 to 200 μm, the power varied from 300 to 700 mW, and the exposure time ranged between 0.1 and 0.2 s. The lesions were mostly located on the upper eyelid (66%); the lid margin was involved in 30 cases. The mean follow-up time was 7.2 ± 3.5 months (range 3-15 months). A histopathological diagnosis was confirmed for 81 lesions (85.3%). All patients were satisfied with the cosmetic result. No intraoperative complications occurred, and none of the patients complained of pain during laser application. All wounds epithelialized in 3-4 weeks with skin that appeared normal. Hypopigmentation of the treated areas were observed in three cases. No recurrence occurred during the follow-up period. Argon laser-assisted benign eyelid tumor excision is a useful, cheap, accessible, and well-tolerated alternative to traditional surgery.

  15. Hatching Eggs in the Classroom.

    ERIC Educational Resources Information Center

    Smith, Robert W.

    1984-01-01

    This article provides detailed instructions on how to hatch chicken eggs. Sections include: (1) making the incubator; (2) making the brooder; (3) guidelines for hatching eggs; (4) from incubator to brooder; and (5) recommended readings. (JMK)

  16. Laser-assisted solder closure of bronchial stumps

    NASA Astrophysics Data System (ADS)

    Oz, Mehmet C.; Williams, Matthew R.; Moscarelli, Richard D.; Kaynar, Murat; Fras, Christian I.; Libutti, Steven K.; Smith, Hillary; Setton, Adrianne J.; Treat, Michael R.; Nowygrod, Roman

    1992-06-01

    Broncho-pleural fistula is a difficult clinical problem without a simple solution. Laser-assisted solder techniques potentially offer a means to precisely fix tissue glues into the fistulae through a bronchoscopic approach. Using a canine model, secondary bronchi were sealed with cryoprecipitate made from solvent/detergent treated plasma (treated to inactivate membrane enveloped virus) mixed with indocyanine green (absorption 805 nm). Diode laser energy (emission 808 nm, 7.3 W/cm2) was applied to the solder until desiccation was observed. Leakage pressures ranged between 18 - 86 mmHg with a mean of 46 +/- 24 mmHg. Laser-assisted solder techniques provide a reliably strong seal over leaking bronchial stumps and use of dye enhancement prevents undesired collateral thermal injury to surrounding bronchial tissue. Solvent/detergent plasma, prepared by methods shown to inactivate large quantities of HIV, HBV, and HCV, is an effective source of cyroprecipitate and should allow widespread use of pooled human material in a clinical setting.

  17. An investigation on co-axial water-jet assisted fiber laser cutting of metal sheets

    NASA Astrophysics Data System (ADS)

    Madhukar, Yuvraj K.; Mullick, Suvradip; Nath, Ashish K.

    2016-02-01

    Water assisted laser cutting has received significant attention in recent times with assurance of many advantages than conventional gas assisted laser cutting. A comparative study between co-axial water-jet and gas-jet assisted laser cutting of thin sheets of mild steel (MS) and titanium (Ti) by fiber laser is presented. Fiber laser (1.07 μm wavelength) was utilised because of its low absorption in water. The cut quality was evaluated in terms of average kerf, projected dross height, heat affected zone (HAZ) and cut surface roughness. It was observed that a broad range process parameter could produce consistent cut quality in MS. However, oxygen assisted cutting could produce better quality only with optimised parameters at high laser power and high cutting speed. In Ti cutting the water-jet assisted laser cutting performed better over the entire range of process parameters compared with gas assisted cutting. The specific energy, defined as the amount of laser energy required to remove unit volume of material was found more in case of water-jet assisted laser cutting process. It is mainly due to various losses associated with water assisted laser processing such as absorption of laser energy in water and scattering at the interaction zone.

  18. Decay-Assisted Laser Spectroscopy of Neutron-Deficient Francium

    NASA Astrophysics Data System (ADS)

    Lynch, K. M.; Billowes, J.; Bissell, M. L.; Budinčević, I.; Cocolios, T. E.; De Groote, R. P.; De Schepper, S.; Fedosseev, V. N.; Flanagan, K. T.; Franchoo, S.; Garcia Ruiz, R. F.; Heylen, H.; Marsh, B. A.; Neyens, G.; Procter, T. J.; Rossel, R. E.; Rothe, S.; Strashnov, I.; Stroke, H. H.; Wendt, K. D. A.

    2014-01-01

    This paper reports on the hyperfine-structure and radioactive-decay studies of the neutron-deficient francium isotopes Fr202-206 performed with the Collinear Resonance Ionization Spectroscopy (CRIS) experiment at the ISOLDE facility, CERN. The high resolution innate to collinear laser spectroscopy is combined with the high efficiency of ion detection to provide a highly sensitive technique to probe the hyperfine structure of exotic isotopes. The technique of decay-assisted laser spectroscopy is presented, whereby the isomeric ion beam is deflected to a decay-spectroscopy station for alpha-decay tagging of the hyperfine components. Here, we present the first hyperfine-structure measurements of the neutron-deficient francium isotopes Fr202-206, in addition to the identification of the low-lying states of Fr202,204 performed at the CRIS experiment.

  19. Bioceramic 3D Implants Produced by Laser Assisted Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Lusquiños, Fernando; del Val, Jesús; Arias-González, Felipe; Comesaña, Rafael; Quintero, Félix; Riveiro, Antonio; Boutinguiza, Mohamed; Jones, Julian R.; Hill, Robert G.; Pou, Juan

    Cranial defect restoration requires a suitable implant capable to fulfill protective and aesthetic functions, such as polymeric and metallic implants. Nevertheless, the former materials cannot provide osteointegration of the implant within the host bone nor implant resorption, which is also required in pediatricorthopedics for normal patient growth. Resorbable and osteoconductivebioceramics are employed, such as silicate bioactive glasses. Nevertheless, manufacturing based on conventional casting in graphite moulds is not effective for warped shape implants suitable for patient tailored treatments. In this work, we analyze the application of rapid prototyping based on laser cladding to manufacture bioactive glass implants for low load bearing bone restoration. This laser-assisted additive technique is capable to produce three-dimensional geometries tailored to patient, with reduced fabrication time and implant composition modification. The obtained samples were characterized; the relationships between the processing conditions and the measured features were studied, in addition to the biological behavior analysis.

  20. Laser assisted machining: a state of art review

    NASA Astrophysics Data System (ADS)

    Punugupati, Gurabvaiah; Kandi, Kishore Kumar; Bose, P. S. C.; Rao, C. S. P.

    2016-09-01

    Difficult-to-cut materials have increasing demand in aerospace and automobile industries due to their high yield stress, high strength to weight ratio, high toughness, high wear resistance, high creep, high corrosion resistivity, ability to retain high strength at high temperature, etc. The machinability of these advanced materials, using conventional methods of machining is typical due to the high temperature and pressure at the cutting zone and tool and properties such as low thermal conductivity, high cutting forces and cutting temperatures makes the materials difficult to machine. Laser assisted machining (LAM) is a new and innovative technique for machining the difficult-to-cut materials. This paper deals with a review on the advances in lasers, tools and the mechanism of machining using LAM and their effects.

  1. Ex vivo laser lipolysis assisted with radially diffusing optical applicator

    NASA Astrophysics Data System (ADS)

    Hwang, Jieun; Hau, Nguyen Trung; Park, Sung Yeon; Rhee, Yun-Hee; Ahn, Jin-Chul; Kang, Hyun Wook

    2016-05-01

    Laser-assisted lipolysis has been implemented to reduce body fat in light of thermal interactions with adipose tissue. However, using a flat fiber with high irradiance often needs rapid cannula movements and even undesirable thermal injury due to direct tissue contact. The aim of the current study was to explore the feasibility of a radially diffusing optical applicator to liquefy the adipose tissue for effective laser lipolysis. The proposed diffuser was evaluated with a flat fiber in terms of temperature elevation and tissue liquefaction after laser lipolysis with a 980-nm wavelength. Given the same power (20 W), the diffusing applicator generated a 30% slower temperature increase with a 25% lower maximum temperature (84±3.2°C in 1 min p<0.001) in the tissue, compared with the flat fiber. Under the equivalent temperature development, the diffuser induced up to fivefold larger area of the adipose liquefaction due to radial light emission than the flat fiber. Ex vivo tissue tests for 5-min irradiation demonstrated that the diffuser (1.24±0.15 g) liquefied 66% more adipose tissue than the flat fiber (0.75±0.05 g). The proposed diffusing applicator can be a feasible therapeutic device for laser lipolysis due to low temperature development and wide coverage of thermal treatment.

  2. Surface plasmon resonance assisted rapid laser joining of glass

    SciTech Connect

    Zolotovskaya, Svetlana A.; Tang, Guang; Abdolvand, Amin; Wang, Zengbo

    2014-08-25

    Rapid and strong joining of clear glass to glass containing randomly distributed embedded spherical silver nanoparticles upon nanosecond pulsed laser irradiation (∼40 ns and repetition rate of 100 kHz) at 532 nm is demonstrated. The embedded silver nanoparticles were ∼30–40 nm in diameter, contained in a thin surface layer of ∼10 μm. A joint strength of 12.5 MPa was achieved for a laser fluence of only ∼0.13 J/cm{sup 2} and scanning speed of 10 mm/s. The bonding mechanism is discussed in terms of absorption of the laser energy by nanoparticles and the transfer of the accumulated localised heat to the surrounding glass leading to the local melting and formation of a strong bond. The presented technique is scalable and overcomes a number of serious challenges for a widespread adoption of laser-assisted rapid joining of glass substrates, enabling applications in the manufacture of microelectronic devices, sensors, micro-fluidic, and medical devices.

  3. Infrared laser-assisted desorption electrospray ionization mass spectrometry.

    PubMed

    Rezenom, Yohannes H; Dong, Jianan; Murray, Kermit K

    2008-02-01

    We have used an infrared laser for desorption of material and ionization by interaction with electrosprayed solvent. Infrared laser-assisted desorption electrospray ionization (IR LADESI) mass spectrometry was used for the direct analysis of water-containing samples under ambient conditions. An ion trap mass spectrometer was modified to include a pulsed Er:YAG laser at 2.94 microm wavelength coupled into a germanium oxide optical fiber for desorption at atmospheric pressure and a nanoelectrospray source for ionization. Analytes in aqueous solution were placed on a stainless steel target and irradiated with the pulsed IR laser. Material desorbed and ablated from the target was ionized by a continuous stream of charged droplets from the electrosprayed solvent. Peptide and protein samples analyzed using this method yield mass spectra similar to those obtained by conventional electrospray. Blood and urine were analyzed without sample pretreatment to demonstrate the capability of IR LADESI for direct analysis of biological fluids. Pharmaceutical products were also directly analyzed. Finally, the role of water as a matrix in the IR LADESI process is discussed.

  4. Lipase biofilm deposited by Matrix Assisted Pulsed Laser Evaporation technique

    NASA Astrophysics Data System (ADS)

    Aronne, Antonio; Bloisi, Francesco; Calabria, Raffaela; Califano, Valeria; Depero, Laura E.; Fanelli, Esther; Federici, Stefania; Massoli, Patrizio; Vicari, Luciano R. M.

    2015-05-01

    Lipase is an enzyme that finds application in biodiesel production and for detection of esters and triglycerides in biosensors. Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique derived from Pulsed Laser Deposition (PLD) for deposition of undamaged biomolecules or polymers, is characterized by the use of a frozen target obtained from a solution/suspension of the guest material (to be deposited) in a volatile matrix (solvent). The presence of the solvent avoids or at least reduces the potential damage of guest molecules by laser radiation but only the guest material reaches the substrate in an essentially solvent-free deposition. MAPLE can be used for enzymes immobilization, essential for industrial application, allowing the development of continuous processes, an easier separation of products, the reuse of the catalyst and, in some cases, enhancing enzyme properties (pH, temperature stability, etc.) and catalytic activity in non-aqueous media. Here we show that MAPLE technique can be used to deposit undamaged lipase and that the complex structure (due to droplets generated during extraction from target) of the deposited material can be controlled by changing the laser beam fluence.

  5. Laser-assisted sheet metal working in series production

    NASA Astrophysics Data System (ADS)

    Brecher, Christian; Emonts, Michael; Eckert, Markus

    2013-02-01

    Based on the demand for a responsible use of natural resources and energy the need for lightweight materials is increasing. The most common materials for lightweight production are high and highest strength steel. These materials are difficult to machine using conventional sheet metal working processes because the high strength leads to a limited formability and high tool wear. The Fraunhofer IPT developed the laser-assisted sheet metal working. Selective laser based heating of the part directly before machining softens the material locally. Thus the quality of the following cut can be increased, for example for shearing 1.4310 the clear cut surface ratio can be increased from 20% up to 100% using a shearing gap of 10% of the sheet thickness. Because of the softening of the material and thus the increased formability, parts with a higher complexity can be produced. For example 1.4310 can be bent laser-assisted with a radius of 0.25 mm instead of 2-3 mm using the conventional process. For the first time spring steel can be embossed with conventional tools up to 50% of the sheet thickness. For the implementation in series production a modular system upgrade "hy-PRESS" has been developed to include laser and scanner technology into existing presses. For decoupling the sensitive optical elements of the machine vibrations an active-passive damping system has been developed. The combination of this new hybrid process and the system technology allows to produce parts of high strength steel with a high complexity and quality.

  6. Investigations into ultraviolet matrix-assisted laser desorption

    SciTech Connect

    Heise, T.W.

    1993-07-01

    Matrix-assisted laser desorption (MALD) is a technique for converting large biomolecules into gas phase ions. Some characteristics of the commonly used uv matrices are determined. Solubilities in methanol range from 0.1 to 0.5 M. Solid phase absorption spectra are found to be similar to solution, but slightly red-shifted. Acoustic and quartz crystal microbalance signals are investigated as possible means of uv-MALD quantitation. Evidence for the existence of desorption thresholds is presented. Threshold values are determined to be in the range of 2 to 3 MW/cm{sup 2}. A transient imaging technique based on laser-excited fluorescence for monitoring MALD plumes is described. Sensitivity is well within the levels required for studying matrix-assisted laser desorption, where analyte concentrations are significantly lower than those in conventional laser desorption. Results showing the effect of film morphology, particularly film thickness, on plume dynamics are presented. In particular, MALD plumes from thicker films tend to exhibit higher axial velocities. Fluorescent labeling of protein and of DNA is used to allow imaging of their uv-MALD generated plumes. Integrated concentrations are available with respect to time, making it possible to assess the rate of fragmentation. The spatial and temporal distributions are important for the design of secondary ionization schemes to enhance ion yields and for the optimization of ion collection in time-of-flight MS instruments to maximize resolution. Such information could also provide insight into whether ionization is closely associated with the desorption step or whether it is a result of subsequent collisions with the matrix gas (e.g., proton transfer). Although the present study involves plumes in a normal atmosphere, adaptation to measurements in vacuum (e.g., inside a mass spectrometer) should be straightforward.

  7. Environmentally cued hatching in reptiles.

    PubMed

    Doody, J S

    2011-07-01

    Evidence is accumulating for the widespread occurrence of environmentally cued hatching (ECH) in animals, but its diversity and distribution across taxa are unknown. Herein I review three types of ECH in reptiles: early hatching, delayed hatching, and synchronous hatching. ECH is currently known from 43 species, including turtles, crocodilians, lizards, snakes, tuatara, and possibly worm lizards. Early hatching caused by physical disturbance (e.g., vibrations) is the most commonly reported ECH across all groups; although it apparently serves an antipredator function in some species, its adaptive value is unknown in most. Delayed hatching, characterized by metabolic depression or embryonic aestivation, and sometimes followed by a hypoxic cue (flooding), occurs in some turtles and possibly in monitor lizards and crocodilians; in some of these species delayed hatching serves to defer hatching from the dry season until the more favorable conditions of the wet season. Synchronous hatching, whereby sibling eggs hatch synchronously despite vertical thermal gradients in the nest, occurs in some turtles and crocodilians. Although vibrations and vocalizations in hatching-competent embryos can stimulate synchronous hatching, cues promoting developmentally less advanced embryos to catch up with more advanced embryos have not been confirmed. Synchronous hatching may serve to dilute predation risk by promoting synchronous emergence or reduce the period in which smells associated with hatching can attract predators to unhatched eggs. Within species, advancing our understanding of ECH requires three types of studies: (1) experiments identifying hatching cues and the plastic hatching period, (2) experiments disentangling hypotheses about multiple hatching cues, and (3) investigations into the environmental context in which ECH might evolve in different species (major predators or abiotic influences on the egg, embryo, and hatchling). Among species and groups, surveys for ECH are

  8. Thermal Aspects of Ductile Mode Micro Laser Assisted Machining

    SciTech Connect

    Virkar, Saurabh R.; Patten, John A.

    2011-01-17

    This paper presents the simulation work performed to study an innovative process called micro-Laser Assisted Machining ({mu}-LAM). {mu}-LAM is being used for machining hard and brittle semiconductor and ceramic materials such as Silicon Carbide. Numerical simulations were carried out using the commercial software AdvantEdge Version 5.4. The cutting tool is modeled as a single point diamond tip. The workpiece material (4H-SiC) is heated locally during the actual machining process by a laser beam, which passes through the diamond tool tip. The workpiece is heated beyond the thermal softening point in order to study the effect of increased temperature on the machining process. The initial work started with an approximate thermal softening curve to ensure that thermal effects can be incorporated in the simulation model. A new thermal softening curve was developed based upon experimental data and implemented in the material model. A thermal boundary was provided on the workpiece top surface to simulate the effect of laser heating. In all three cases the chip formation was observed and the changes in cutting and thrust forces were evaluated. The simulation results indicate a significant decrease in machining forces if Silicon Carbide is heated and thermally softened thus demonstrating the benefits of the {mu}-LAM process.

  9. Perspectives in nanostructure assisted laser manipulation of mammalian cells

    NASA Astrophysics Data System (ADS)

    Heinemann, Dag; Schomaker, Markus; Kalies, Stefan; Hoerdt, Anton; Murua Escobar, Hugo; Ripken, Tammo; Meyer, Heiko

    2015-03-01

    The interaction of cell-adhered nanostructures with laser light has attracted much interest within the biomedical field. Molecular delivery using a variety of plasmonic nanostructures, such as structured surfaces, nanoparticles and particle clusters, is currently evolving from its proof-of-concept into a routine method. Here, gold represents the material of choice, as it provides unique optical properties, different surface modifications as well as biocompatibility. In addition, new materials (e.g. polypyrrole) provide interesting alternatives. Applying this approach, a variety of molecules, such as fluorescent dyes, proteins, antisense structures, and DNA, has been transfected in order to manipulate the cellular functions in different experimental settings. Antisense structures, for example, allow the efficient down regulation of the gene activity of a target, providing insights into the gene's function. The delivery of proteins, as executing molecules in the cell, can exhibit an immediate effect on the cell behavior, allowing a minute observation of the intracellular kinetics. Direct cell manipulation can be achieved with this approach as well. Increasing the nanoparticle concentration and/or the radiant exposure, effective cell destruction is induced. Using targeted nanoparticles (e.g. by antibody conjugation) in combination with spatially selective laser irradiation permits well-directed cell manipulation even in mixed cultures and potentially in tissues. Furthermore, excited gold nanoparticles can directly trigger cellular reactions, which can possibly be utilized for cell stimulation. The manifold possibilities of nanostructure assisted laser manipulation are still in development.

  10. Hatch securing mechanism

    NASA Astrophysics Data System (ADS)

    Culling, Robert K.

    1992-09-01

    The invention is a hatch securing mechanism having a base attached to a hatchway and a hasp attached to a hatch lid. The base has an apertured retainer and a pinway element, the hasp being held between the retainer and pinway element during closure of the lid. A latch pin translatable in the pinway element has an angled tip which slides against a bevelled surface of the hasp to force the hasp into tighter, locked engagement with the base. The latch pin has a helical groove segment about the pin's axis, and a stud fixed to the pinway element engages the groove segment. The interaction of the stud and groove segment effects translation of the latch pin when the pin is manually rotated. The action of the latch pin also compresses an elastically deformable seal between the door and door frame so that the seal is increasingly effective against explosive blast pressures. The invention includes a lock mechanism for keeping the latch pin in a hasp retaining position unless the pin is manually moved.

  11. Laser Assisted Emittance Exchange: Downsizing the X-ray Free Electron Laser

    SciTech Connect

    Xiang, Dao; /SLAC

    2009-12-11

    A technique is proposed to generate electron beam with ultralow transverse emittance through laser assisted transverse-to-longitudinal emittance exchange. In the scheme a laser operating in the TEM10 mode is used to interact with the electron beam in a dispersive region and to initiate the emittance exchange. It is shown that with the proposed technique one can significantly downsize an x-ray free electron laser (FEL), which may greatly extend the availability of these light sources. A hard x-ray FEL operating at 1.5 {angstrom} with a saturation length within 30 meters using a 3.8 GeV electron beam is shown to be practically feasible.

  12. Resident surgeon efficiency in femtosecond laser-assisted cataract surgery

    PubMed Central

    Pittner, Andrew C; Sullivan, Brian R

    2017-01-01

    Purpose Comparison of resident surgeon performance efficiencies in femtosecond laser-assisted cataract surgery (FLACS) versus conventional phacoemulsification. Patients and methods A retrospective cohort study was conducted on consecutive patients undergoing phacoemulsification cataract surgery performed by senior ophthalmology residents under the supervision of 1 attending physician during a 9-month period in a large Veterans Affairs medical center. Medical records were reviewed for demographic information, preoperative nucleus grade, femtosecond laser pretreatment, operative procedure times, total operating room times, and surgical complications. Review of digital video records provided quantitative interval measurements of core steps of the procedures, including completion of incisions, anterior capsulotomy, nucleus removal, cortical removal, and intraocular lens implantation. Results Total room time, operation time, and corneal incision completion time were found to be significantly longer in the femtosecond laser group versus the traditional phacoemulsification group (each P<0.05). Mean duration for manual completion of anterior capsulotomy was shorter in the laser group (P<0.001). There were no statistically significant differences in the individual steps of nucleus removal, cortical removal, or intraocular lens placement. Surgical complication rates were not significantly different between the groups. Conclusion In early cases, resident completion of femtosecond cataract surgery is generally less efficient when trainees have more experience with traditional phacoemulsification. FLACS was found to have a significant advantage in completion of capsulotomy, but subsequent surgical steps were not shorter or longer. Resident learning curve for the FLACS technology may partially explain the disparities of performance. Educators should be cognizant of a potential for lower procedural efficiency when introducing FLACS into resident training. PMID:28203055

  13. Parametric modeling and optimization of laser scanning parameters during laser assisted machining of Inconel 718

    NASA Astrophysics Data System (ADS)

    Venkatesan, K.; Ramanujam, R.; Kuppan, P.

    2016-04-01

    This paper presents a parametric effect, microstructure, micro-hardness and optimization of laser scanning parameters (LSP) on heating experiments during laser assisted machining of Inconel 718 alloy. The laser source used for experiments is a continuous wave Nd:YAG laser with maximum power of 2 kW. The experimental parameters in the present study are cutting speed in the range of 50-100 m/min, feed rate of 0.05-0.1 mm/rev, laser power of 1.25-1.75 kW and approach angle of 60-90°of laser beam axis to tool. The plan of experiments are based on central composite rotatable design L31 (43) orthogonal array. The surface temperature is measured via on-line measurement using infrared pyrometer. Parametric significance on surface temperature is analysed using response surface methodology (RSM), analysis of variance (ANOVA) and 3D surface graphs. The structural change of the material surface is observed using optical microscope and quantitative measurement of heat affected depth that are analysed by Vicker's hardness test. The results indicate that the laser power and approach angle are the most significant parameters to affect the surface temperature. The optimum ranges of laser power and approach angle was identified as 1.25-1.5 kW and 60-65° using overlaid contour plot. The developed second order regression model is found to be in good agreement with experimental values with R2 values of 0.96 and 0.94 respectively for surface temperature and heat affected depth.

  14. Laser assisted die bending: a new application of high power diode lasers

    NASA Astrophysics Data System (ADS)

    Schuöcker, D.; Schumi, T.; Spitzer, O.; Bammer, F.; Schuöcker, G.; Sperrer, G.

    2015-02-01

    Nowadays high power lasers are mainly used for cutting of sheet metals, for welding, hardening and rapid prototyping. In the forming of sheet metals as bending or deep drawing lasers are not used. Nevertheless a few years ago a new application of high power lasers has been invented, where bending of materials that break at room temperature becomes possible by heating them along the bending edge with high power lasers thus allowing their treatment without cracks and rupture. For this purpose a large number of diode lasers are arranged in the bottom tool of a bending machine (a V-shaped die) which heat up the initially flat sheet metal during the bending process what is performed by pressing it into the die with a knife shaped upper tool where due to the laser heating the material is softened and thus cracks are avoided. For the technical realization of the new process of laser assisted die bending, modules equipped with numerous laser diodes and a total beam power of 2,5 kW are used. The light emitted by these modules enters a tool with a length of 15cm and is deflected towards the workpiece. By using ten of these modules with adjacent dies and by integrating those in a bending press a bending edge of sheet metals with a length of 1500mm can be realized. Such a bending press with laser assistance also needs energization with a power of practically 50kW, a respective water flow, a heat exchanger system and also a control for all functions of this system. Special measures have also been developed to avoid radiating of those tools that are not covered by a workpiece in the case of bending edges shorter than the full length of the bending tools whereas individual short circuiting of diode modules can be performed. Specific measures to ensure a safe operation without any harm to the operational person have been realized. Exploitation of the bending process has been carried out for titanium, where material thicknesses up to 3mm have been bent successfully.

  15. Laser-assisted tympanostomy (LAT) in adult individuals

    NASA Astrophysics Data System (ADS)

    Prokopakis, E. P.; Lachanas, V. A.; Helidonis, Emmanuel S.; Velegrakis, G.

    2004-06-01

    Objectives: To assess outcome, in adult individuals undergone Laser Assisted Tympanostomy (LAT) without ventilation tube placement. Method: LAT was performed on a total of 95 ears (72 individuals). Indications included serous otitis media with effusion (44 ears/31 patients), eustachian tube dysfunction (32 ears/24 patients), acute otitis media (13 ears/11 patients), and endoscopic visualization of the middle ear (6 ears/6 patients). Results: Middle ear disease was resolved after the closure of tympanostomy in 48% of patients with serous otitis media with effusion. In 78% of patients with Eustachian tube dysfunction symptoms were diminished. All patients with acute otitis media had a satisfactory outcome. LAT was found quite effective in patients undergoing middle ear endoscopy. Conclusion: LAT without ventilation tubes provides a safe alternative surgical option in adult patients in certain cases. The selection criteria for this procedure are addressed in detail.

  16. Matrix assisted pulsed laser deposition of melanin thin films

    NASA Astrophysics Data System (ADS)

    Bloisi, F.; Pezzella, A.; Barra, M.; Chiarella, F.; Cassinese, A.; Vicari, L.

    2011-07-01

    Melanins constitute a very important class of organic pigments, recently emerging as a potential material for a new generation of bioinspired biocompatible electrically active devices. In this paper, we report about the deposition of synthetic melanin films starting from aqueous suspensions by matrix assisted pulsed laser evaporation (MAPLE). In particular, we demonstrate that it is possible to deposit melanin films by MAPLE even if melanin (a) is not soluble in water and (b) absorbs light from UV to IR. AFM images reveal that the film surface features are highly depending on the deposition parameters. UV-VIS and FTIR spectra show both the optical properties and the molecular structure typical of melanins are preserved.

  17. Surgical adhesives for laser-assisted wound closure

    NASA Astrophysics Data System (ADS)

    Hodges, Diane E.; McNally-Heintzelman, Karen M.; Welch, Ashley J.

    2001-10-01

    Solid protein solder-doped polymer membranes were developed for laser-assisted tissue repair. Biodegradable polymer membranes of controlled porosity were fabricated with poly(L-lactic-co-glycolic acid) (PLGA), poly(ethylene glycol) (PEG), and salt particles, using a solvent-casting and particulate-leaching technique. The membranes provided a porous scaffold that readily absorbed the traditional protein solder composed of serum albumin, indocyanine green dye, and de-ionized water. In vitro investigations were conducted to assess the influence of various processing parameters on the strength of tissue repairs formed using the new membranes. These parameters included PLGA copolymer and PLGA/PEG blend ratios, membrane pore size, initial albumin weight fraction, and laser irradiance used to denature the solder. Altering the PLGA copolymer ratio had little effect on repair strength, however such variations are known to influence the degradation rate of the membranes. The repair strength increased with increased membrane pore size and bovine serum albumin concentration. The addition of PEG during the membrane casting stage increased the flexibility of the membranes but not necessarily the repair strength. Typically, the repair strength increased with increasing irradiance from 12 to 18 W/cm2. The new solder-doped polymer membranes provided all of the benefits associated with solid protein solders including high repair strength and improved edge coaptation. In addition, the flexible, moldable nature of the new membranes offers the capability of tailoring the membranes to a wide range of clinically relevant geometries.

  18. Pulsed laser deposition vs. matrix assisted pulsed laser evaporation for growth of biodegradable polymer thin films

    NASA Astrophysics Data System (ADS)

    Mercado, A. L.; Allmond, C. E.; Hoekstra, J. G.; Fitz-Gerald, J. M.

    2005-08-01

    Thin films of poly (lactide-co-glycolide) (PLGA), a biodegradable polymer, were deposited on Si wafers by both conventional pulsed laser deposition (PLD) and matrix assisted pulsed laser evaporation (MAPLE) using chloroform (CHCl3) as a matrix solvent. This research represents an initial study to investigate the deposition characteristics of each technique at comparable conditions to gain insight into the transport and degradation mechanisms of each approach. The deposited materials were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC) with refractive index (RI) detection. While FTIR and NMR results do not show a measurable departure from the native, in sharp contrast GPC results show a significant change (up to 95%) in molecular weight for both deposition methods. This result makes it clear that it is possible to overlook substantial degradation when incomplete chemical analysis is conducted.

  19. Thermal effects in laser-assisted pre-embryo zona drilling

    NASA Astrophysics Data System (ADS)

    Douglas-Hamilton, Diarmaid H.; Conia, Jerome D.

    2001-04-01

    Diode lasers ((lambda) equals 1480 nm) are used with in vitro fertilization to dissect the zone pellucida (shell) of pre- embryos. A focused laser beam is applied in vitro to form a channel or trench in the zona pellucida. The procedure is used to facilitate biopsy or as a promoter of embryo hatching. We present examples and measurements of zona pellucida ablation using animal models. In using the laser it is vital not to damage pre-embryo cells, e.g., by overheating. In order to define safe regimes we have derived some thermal side effects of zona pellucida removal. The temperature profile in the beam and vicinity is predicted as function of laser pulse duration and power. In a crossed- beam experiment a HeNe laser probe is used to detect the temperature-induced change in the refractive index of an aqueous solution, and estimate local thermal gradient. We find that the diode laser beam produces superheated water approaching 200 degree(s)C on the beam axis. Thermal histories during and following the laser pulse are given for regions in the neighborhood of the beam. We conclude that an optimum regime exists with pulse duration laser power approximately 100 mW.

  20. Automation and Optimization of Multipulse Laser Zona Drilling of Mouse Embryos During Embryo Biopsy.

    PubMed

    Wong, Christopher Yee; Mills, James K

    2017-03-01

    Laser zona drilling (LZD) is a required step in many embryonic surgical procedures, for example, assisted hatching and preimplantation genetic diagnosis. LZD involves the ablation of the zona pellucida (ZP) using a laser while minimizing potentially harmful thermal effects on critical internal cell structures.

  1. Chemical ionization of neutral peptides produced by matrix-assisted laser desorption

    NASA Astrophysics Data System (ADS)

    Belov, Mikhail E.; Myatt, Christopher P.; Derrick, Peter J.

    1998-03-01

    The cationization in the gas phase of neutral peptides formed under the conditions of matrix-assisted laser desorption (MALD) has been demonstrated. The beam of neutral peptides formed by MALD using one laser was intercepted several hundred micrometers above the sample surface by a beam of cations produced using a second laser. The intensity of cationized neutral gramicidin S formed in this way was comparable to the ion signal produced by conventional matrix-assisted laser desorption/ionization (MALDI). The threshold fluences for MALD of neutral peptides have been shown to be lower than those for formation of ions from the same samples by MALDI.

  2. First Demonstration of Laser-Assisted Charge Exchange for Microsecond Duration H- Beams

    NASA Astrophysics Data System (ADS)

    Cousineau, Sarah; Rakhman, Abdurahim; Kay, Martin; Aleksandrov, Alexander; Danilov, Viatcheslav; Gorlov, Timofey; Liu, Yun; Plum, Michael; Shishlo, Andrei; Johnson, David

    2017-02-01

    This Letter reports on the first demonstration of laser-assisted H- charge exchange for microsecond duration H- beam pulses. Laser-assisted charge exchange injection is a breakthrough technology that overcomes long-standing limitations associated with the traditional method of producing high intensity, time structured beams of protons in accelerators via the use of carbon foils for charge exchange injection. The central theme of this experiment is the demonstration of novel techniques that reduce the laser power requirement to allow high efficiency stripping of microsecond duration beams with commercial laser technology.

  3. Computer-Assisted Experiments with a Laser Diode

    ERIC Educational Resources Information Center

    Kraftmakher, Yaakov

    2011-01-01

    A laser diode from an inexpensive laser pen (laser pointer) is used in simple experiments. The radiant output power and efficiency of the laser are measured, and polarization of the light beam is shown. The "h/e" ratio is available from the threshold of spontaneous emission. The lasing threshold is found using several methods. With a…

  4. Femtosecond laser printing of living cells using absorbing film-assisted laser-induced forward transfer

    NASA Astrophysics Data System (ADS)

    Hopp, Béla; Smausz, Tomi; Szabó, Gábor; Kolozsvári, Lajos; Kafetzopoulos, Dimitris; Fotakis, Costas; Nógrádi, Antal

    2012-01-01

    The applicability of a femtosecond KrF laser in absorbing film-assisted, laser-induced forward transfer of living cells was studied. The absorbing materials were 50-nm-thick metal films and biomaterials (gelatine, Matrigel, each 50 μm thick, and polyhydroxybutyrate, 2 μm). The used cell types were human neuroblastoma, chronic myeloid leukemia, and osteogenic sarcoma cell lines, and primary astroglial rat cells. Pulses of a 500-fs KrF excimer laser focused onto the absorbing layer in a 250-μm diameter spot with 225 mJ/cm2 fluence were used to transfer the cells to the acceptor plate placed at 0.6 mm distance, which was a glass slide either pure or covered with biomaterials. While the low-absorptivity biomaterial absorbing layers proved to be ineffective in transfer of cells, when applied on the surface of acceptor plate, the wet gelatine and Matrigel layers successfully ameliorated the impact of the cells, which otherwise did not survive the arrival onto a hard surface. The best short- and long-term survival rate was between 65% and 70% for neuroblastoma and astroglial cells. The long-term survival of the transferred osteosarcoma cells was low, while the myeloid leukemia cells did not tolerate the procedure under the applied experimental conditions.

  5. Station Crew Opens Dragon's Hatch

    NASA Video Gallery

    The hatch between the newly arrived SpaceX Dragon spacecraft and the Harmony module of the International Space Station was opened by NASA Astronaut Don Pettit at 5:53 am EDT as the station flew 253...

  6. Station Crew Opens Dragon Hatch

    NASA Video Gallery

    Expedition 33 Commander Suni Williams and Flight Engineer Aki Hoshide opened the hatch to the SpaceX Dragon cargo ship at 1:40 p.m. EDT Wednesday, Oct. 10, marking a milestone for the first commerc...

  7. A new concept in laser-assisted chemistry - The electronic-field representation

    NASA Technical Reports Server (NTRS)

    George, T. F.; Zimmerman, I. H.; Yuan, J.-M.; Laing, J. R.; Devries, P. L.

    1977-01-01

    Electronic-field representation is proposed as a technique for laser-assisted chemistry. Specifically, it is shown that several field-assisted chemical processes can be described in terms of mixed matter-field quantum states and their associated energies. The technique may be used to analyze the effects exerted by an intense laser on both bound and unbound molecular systems, and to investigate other field-induced effects including multiphoton processes, emission, and photodissociation.

  8. Pulse laser assisted MOVPE for InGaN with high indium content

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Norihito; Hida, Ken-Nosuke; Kangawa, Yoshihiro; Kumagai, Yoshinao; Koukitu, Akinori

    2004-09-01

    In0.53Ga0.47N film was grown at 600 °C by Nd:YAG pulse laser assisted MOVPE. The optical and structural properties of the film were compared with that grown without laser assistance at the same condition. The results of XRD measurements showed that the crystallinity of the film grown with laser was better than that of the one grown without laser. The surface morphology and cross-sectional SEM image of the film grown with laser revealed that there were no In droplets on the film. The band-edge emission of the film grown with laser at room temperature and 77 K was observed at 840 nm. The results of micro-Raman measurement showed that the film grown with laser had better crystalline structure than that of the film grown without laser and the radiative recombination which contributed to photoluminescence mainly occurred at In0.53Ga0.47N region. Those results imply that pulse laser enhances the surface migration and reaction of elements in spite of low-growth temperature. We suggest that pulse laser assisted technique is effective for low-temperature growth of InGaN with high indium content.

  9. Laser-assisted focused He+ ion beam induced etching with and without XeF2 gas assist

    DOE PAGES

    Stanford, Michael G.; Mahady, Kyle; Lewis, Brett B.; ...

    2016-10-04

    Focused helium ion (He+) milling has been demonstrated as a high-resolution nanopatterning technique; however, it can be limited by its low sputter yield as well as the introduction of undesired subsurface damage. Here, we introduce pulsed laser- and gas-assisted processes to enhance the material removal rate and patterning fidelity. A pulsed laser-assisted He+ milling process is shown to enable high-resolution milling of titanium while reducing subsurface damage in situ. Gas-assisted focused ion beam induced etching (FIBIE) of Ti is also demonstrated in which the XeF2 precursor provides a chemical assist for enhanced material removal rate. In conclusion, a pulsed laser-assistedmore » and gas-assisted FIBIE process is shown to increase the etch yield by ~9× relative to the pure He+ sputtering process. These He+ induced nanopatterning techniques improve material removal rate, in comparison to standard He+ sputtering, while simultaneously decreasing subsurface damage, thus extending the applicability of the He+ probe as a nanopattering tool.« less

  10. NSA AERI Hatch Correction Data Set

    DOE Data Explorer

    Turner, David

    2012-03-23

    From 2000-2008, the NSA AERI hatch was determined to be indicated as open too frequently. Analysis suggests that the hatch was actually opening and closing properly but that its status was not being correctly reported by the hatch controller to the datastream. An algorithm was written to determine the hatch status from the observed

  11. Effects of laser energy and wavelength on the analysis of LiFePO₄ using laser assisted atom probe tomography

    DOE PAGES

    Santhanagopalan, Dhamodaran; Schreiber, Daniel K.; Perea, Daniel E.; ...

    2014-09-21

    The effects of laser wavelength (355 nm and 532 nm) and laser pulse energy on the quantitative analysis of LiFePO₄ by atom probe tomography are considered. A systematic investigation of ultraviolet (UV, 355 nm) and green (532 nm) laser assisted field evaporation has revealed distinctly different behaviors. With the use of a UV laser, the major issue was identified as the preferential loss of oxygen (up to 10 at%) while other elements (Li, Fe and P) were observed to be close to nominal ratios. Lowering the laser energy per pulse to 1 pJ/pulse from 50 pJ/pulse increased the observed oxygenmore » concentration to nearer its correct stoichiometry, which was also well correlated with systematically higher concentrations of ¹⁶O₂⁺ ions. Green laser assisted field evaporation led to the selective loss of Li (33% deficiency) and a relatively minor O deficiency. The loss of Li is likely a result of selective dc evaporation of Li between or after laser pulses. Comparison of the UV and green laser data suggests that the green wavelength energy was absorbed less efficiently than the UV wavelength because of differences in absorption at 355 and 532 nm for LiFePO₄. Plotting of multihit events on Saxey plots also revealed a strong neutral O₂ loss from molecular dissociation, but quantification of this loss was insufficient to account for the observed oxygen deficiency.« less

  12. Mechanism of aneurysm formation after 830-nm diode-laser-assisted microarterial anastomosis

    NASA Astrophysics Data System (ADS)

    Tang, Jing; Godlewski, Guilhem; Rouy, Simone

    1998-01-01

    A series of 830 nm diode laser assisted longitudinal aortorrhophy with a condition of 400 to 500 J/mm2 for one cm length of anastomosis versus conventional manual anastomoses were performed in 90 Wistar rats. With comparing with normal media process, a histologic examination of aneurysm formation was conducted. The results show that there are two important factors to cause aneurysm formation after laser assisted anastomosis: (1) vessel wall is damaged by laser heating; (2) proliferation of collagen fiber at adventitia is absent when media reconstruction.

  13. Laser transfer of biomaterials: Matrix-assisted pulsed laser evaporation (MAPLE) and MAPLE Direct Write

    NASA Astrophysics Data System (ADS)

    Wu, P. K.; Ringeisen, B. R.; Krizman, D. B.; Frondoza, C. G.; Brooks, M.; Bubb, D. M.; Auyeung, R. C. Y.; Piqué, A.; Spargo, B.; McGill, R. A.; Chrisey, D. B.

    2003-04-01

    Two techniques for transferring biomaterial using a pulsed laser beam were developed: matrix-assisted pulsed laser evaporation (MAPLE) and MAPLE direct write (MDW). MAPLE is a large-area vacuum based technique suitable for coatings, i.e., antibiofouling, and MDW is a localized deposition technique capable of fast prototyping of devices, i.e., protein or tissue arrays. Both techniques have demonstrated the capability of transferring large (mol wt>100 kDa) molecules in different forms, e.g., liquid and gel, and preserving their functions. They can deposit patterned films with spatial accuracy and resolution of tens of μm and layering on a variety of substrate materials and geometries. MDW can dispense volumes less than 100 pl, transfer solid tissues, fabricate a complete device, and is computed aided design/computer aided manufacturing compatible. They are noncontact techniques and can be integrated with other sterile processes. These attributes are substantiated by films and arrays of biomaterials, e.g., polymers, enzymes, proteins, eucaryotic cells, and tissue, and a dopamine sensor. These examples, the instrumentation, basic mechanisms, a comparison with other techniques, and future developments are discussed.

  14. In vitro investigation on Ho:YAG laser-assisted bone ablation underwater.

    PubMed

    Zhang, Xianzeng; Chen, Chuanguo; Chen, Faner; Zhan, Zhenlin; Xie, Shusen; Ye, Qing

    2016-07-01

    Liquid-assisted hard tissue ablation by infrared lasers has extensive clinical application. However, detailed studies are still needed to explore the underlying mechanism. In the present study, the dynamic process of bubble evolution induced by Ho:YAG laser under water without and with bone tissue at different thickness layer were studied, as well as its effects on hard tissue ablation. The results showed that the Ho:YAG laser was capable of ablating hard bone tissue effectively in underwater conditions. The penetration of Ho:YAG laser can be significantly increased up to about 4 mm with the assistance of bubble. The hydrokinetic forces associated with the bubble not only contributed to reducing the thermal injury to peripheral tissue, but also enhanced the ablation efficiency and improve the ablation crater morphology. The data also presented some clues to optimal selection of irradiation parameters and provided additional knowledge of the bubble-assisted hard tissue ablation mechanism.

  15. Compliance of laser-assisted microvascular anastomosis: a comparative study with manual anastomosis (preliminary results)

    NASA Astrophysics Data System (ADS)

    Demaria, Roland G.; Lhote, Francois-Marie; Dauzat, Michel; Juan, Jean-Marie; Oliva-Lauraire, Marie-Claire; Durrleman, Nicolas; Delacretaz, Guy P.; Albat, Bernard; Frapier, Jean-Marc; Chaptal, Paul-Andre; Godlewski, Guilhem

    1999-01-01

    The compliance of microvascular anastomosis is an important predictive factor for long term patency of graft or vascular reconstruction. This experimental study compare the compliance of manual suture and laser assisted end to end microvascular anastomosis. In nine New-Zealand white rabbits we performed manual end-to-end suture anastomosis on the left femoral artery and laser assisted anastomosis on the right femoral artery, with a diode laser (wavelength 988 nm, power output 500 mW). Compliance was obtained by echotracking (CBI 8000 sonomicrometry system with 20 MHz implantable microprobe from Crystal-Biotech, USA) on the anastomosis site as well as upstream, and downstream from the anastomosis. Vessel compliance was lower on the manual suture side compared to the laser assisted anastomosis side, especially downstream from the anastomosis.

  16. Convergence of anatomy, technology, and therapeutics: a review of laser-assisted drug delivers.

    PubMed

    Brauer, Jeremy A; Krakowski, Andrew C; Bloom, Bradley S; Nguyen, Tuyet A; Geronemus, Roy G

    2014-12-01

    This is a very exciting time in cutaneous laser surgery with an ever-expanding therapeutic armamentarium and an increased sophistication of available technology. These recent trends have allowed for both a rapid development of interest and exploration of laser-assisted drug delivery and its potential applications. We review the current literature on anatomy, technology, and therapeutics as it relates to laser-assisted drug delivery. The focus of our review is on two areas of interest that have received much attention to date - photodynamic therapy in the treatment of actinic keratoses and nonmelanoma skin cancers as well as the treatment of scarring. We will also discuss potential complications of existing modalities used independently and in laser-assisted drug delivery and conclude with future indications for this burgeoning therapeutic methodology.

  17. System technology for laser-assisted milling with tool integrated optics

    NASA Astrophysics Data System (ADS)

    Hermani, Jan-Patrick; Emonts, Michael; Brecher, Christian

    2013-02-01

    High strength metal alloys and ceramics offer a huge potential for increased efficiency (e. g. in engine components for aerospace or components for gas turbines). However, mass application is still hampered by cost- and time-consuming end-machining due to long processing times and high tool wear. Laser-induced heating shortly before machining can reduce the material strength and improve machinability significantly. The Fraunhofer IPT has developed and successfully realized a new approach for laser-assisted milling with spindle and tool integrated, co-rotating optics. The novel optical system inside the tool consists of one deflection prism to position the laser spot in front of the cutting insert and one focusing lens. Using a fiber laser with high beam quality the laser spot diameter can be precisely adjusted to the chip size. A high dynamic adaption of the laser power signal according to the engagement condition of the cutting tool was realized in order not to irradiate already machined work piece material. During the tool engagement the laser power is controlled in proportion to the current material removal rate, which has to be calculated continuously. The needed geometric values are generated by a CAD/CAM program and converted into a laser power signal by a real-time controller. The developed milling tool with integrated optics and the algorithm for laser power control enable a multi-axis laser-assisted machining of complex parts.

  18. Selective destruction of protein function by chromophore-assisted laser inactivation

    SciTech Connect

    Jay, D.G.

    1988-08-01

    Chromophore-assisted laser inactivation of protein function has been achieved. After a protein binds a specific ligand or antibody conjugated with malachite green (C.I. 42,000), it is selectively inactivated by laser irradiation at a wavelength of light absorbed by the dye but not significantly absorbed by cellular components. Ligand-bound proteins in solution and on the surfaces of cells can be denatured without other proteins in the same samples being affected. Chromophore-assisted laser inactivation can be used to study cell surface phenomena by inactivating the functions of single proteins on living cells, a molecular extension of cellular laser ablation. It has an advantage over genetics and the use of specific inhibitors in that the protein function of a single cell within the organism can be inactivated by focusing the laser beam.

  19. Effect of laser-assisted bleaching with Nd:YAG and diode lasers on shear bond strength of orthodontic brackets.

    PubMed

    Mirhashemi, Amirhossein; Emadian Razavi, Elham Sadat; Behboodi, Sara; Chiniforush, Nasim

    2015-12-01

    The aim of the present study was to assess the effect of laser-assisted bleaching with neodymium:yttrium-aluminum-garnet (Nd:YAG) and diode lasers on shear bond strength (SBS) of orthodontic brackets. One hundred and four extracted human premolars were randomly divided into four groups: group 1: No bleaching applied (control group); group 2: Teeth bleached with 40 % hydrogen peroxide; group 3: Teeth treated with 30 % hydrogen peroxide activated with Nd:YAG laser (1064 nm, 2.5 W, 25 Hz, pulse duration of 100 μs, 6 mm distance); and group 4: Teeth treated with 30 % hydrogen peroxide activated with diode laser (810 nm, 1 W, CW, 6 mm distance). Equal numbers of teeth in groups 2, 3, and 4 were bonded at start, 1 h, 24 h, and 1 week after bleaching. A universal testing machine measured the SBS of the samples 24 h after bonding. After bracket debonding, the amount of residual adhesive on the enamel surface was observed under a stereomicroscope to determine the adhesive remnant index (ARI) scores. The SBS in the unbleached group was significantly higher than that in the bleached groups bonded immediately and 1 h after laser-assisted bleaching (P < 0.05). In groups 3 and 4 at start and group 2 at start and 1 h after laser-assisted bleaching, the SBS was found to be significantly lower than that in the control group. Significant differences in the ARI scores existed among groups as well. The SBS of brackets seems to increase quickly within an hour after laser-assisted bleaching and 24 h after conventional bleaching. Thus, this protocol can be recommended if it is necessary to bond the brackets on the same day of bleaching.

  20. CO2-laser-assisted processing of glass fiber-reinforced thermoplastic composites

    NASA Astrophysics Data System (ADS)

    Brecher, Christian; Emonts, Michael; Schares, Richard Ludwig; Stimpfl, Joffrey

    2013-02-01

    To fully exploit the potential of fiber-reinforced thermoplastic composites (FRTC) and to achieve a broad industrial application, automated manufacturing systems are crucial. Investigations at Fraunhofer IPT have proven that the use of laser system technology in processing FRTC allows to achieve high throughput, quality, flexibility, reproducibility and out-of-autoclave processing simultaneously. As 90% of the FRP in Europe1 are glass fiber-reinforced a high impact can be achieved by introducing laser-assisted processing with all its benefits to glass fiber-reinforced thermoplastics (GFRTC). Fraunhofer IPT has developed the diode laser-assisted tape placement (laying and winding) to process carbon fiber-reinforced thermoplastic composites (CFRTC) for years. However, this technology cannot be transferred unchanged to process milky transparent GFRTC prepregs (preimpregnated fibers). Due to the short wavelength (approx. 980 nm) and therefore high transmission less than 20% of the diode laser energy is absorbed as heat into non-colored GFRTC prepregs. Hence, the use of a different wave length, e.g. CO2-laser (10.6 μm) with more than 90% laser absorption, is required to allow the full potential of laser-assisted processing of GFRTC. Also the absorption of CO2-laser radiation at the surface compared to volume absorption of diode laser radiation is beneficial for the interlaminar joining of GFRTC. Fraunhofer IPT is currently developing and investigating the CO2-laser-assisted tape placement including new system, beam guiding, process and monitoring technology to enable a resource and energy efficient mass production of GFRP composites, e.g. pipes, tanks, masts. The successful processing of non-colored glass fiber-reinforced Polypropylene (PP) and Polyphenylene Sulfide (PPS) has already been proven.

  1. Laser-assisted direct ink writing of planar and 3D metal architectures

    NASA Astrophysics Data System (ADS)

    Skylar-Scott, Mark A.; Gunasekaran, Suman; Lewis, Jennifer A.

    2016-05-01

    The ability to pattern planar and freestanding 3D metallic architectures at the microscale would enable myriad applications, including flexible electronics, displays, sensors, and electrically small antennas. A 3D printing method is introduced that combines direct ink writing with a focused laser that locally anneals printed metallic features “on-the-fly.” To optimize the nozzle-to-laser separation distance, the heat transfer along the printed silver wire is modeled as a function of printing speed, laser intensity, and pulse duration. Laser-assisted direct ink writing is used to pattern highly conductive, ductile metallic interconnects, springs, and freestanding spiral architectures on flexible and rigid substrates.

  2. Laser-assisted direct ink writing of planar and 3D metal architectures.

    PubMed

    Skylar-Scott, Mark A; Gunasekaran, Suman; Lewis, Jennifer A

    2016-05-31

    The ability to pattern planar and freestanding 3D metallic architectures at the microscale would enable myriad applications, including flexible electronics, displays, sensors, and electrically small antennas. A 3D printing method is introduced that combines direct ink writing with a focused laser that locally anneals printed metallic features "on-the-fly." To optimize the nozzle-to-laser separation distance, the heat transfer along the printed silver wire is modeled as a function of printing speed, laser intensity, and pulse duration. Laser-assisted direct ink writing is used to pattern highly conductive, ductile metallic interconnects, springs, and freestanding spiral architectures on flexible and rigid substrates.

  3. Four-wave-mixing-assisted Brillouin fiber laser with double-Brillouin-frequency spacing

    NASA Astrophysics Data System (ADS)

    Gan, G. K. W.; Yeo, K. S.; Adikan, F. R. Mahamd; Shee, Y. G.

    2015-01-01

    The generation of multiwavelength Brillouin fiber laser assisted by four wave mixing has been demonstrated. A maximum of 18 channels of laser Stokes lines are generated at a Brillouin Pump (BP) of 190 mW (∼22.5 dBm). The multiple peaks have a wavelength spacing of 0.176 nm (∼20 GHz). A tunable optical bandpass filter is incorporated to the design to suppress up to 6 dB of the noise floor hump exhibited at the multiwavelength laser spectrum while limiting the laser peaks attenuation thereby providing a much cleaner and better OSNR.

  4. Laser-assisted direct ink writing of planar and 3D metal architectures

    PubMed Central

    Skylar-Scott, Mark A.; Gunasekaran, Suman; Lewis, Jennifer A.

    2016-01-01

    The ability to pattern planar and freestanding 3D metallic architectures at the microscale would enable myriad applications, including flexible electronics, displays, sensors, and electrically small antennas. A 3D printing method is introduced that combines direct ink writing with a focused laser that locally anneals printed metallic features “on-the-fly.” To optimize the nozzle-to-laser separation distance, the heat transfer along the printed silver wire is modeled as a function of printing speed, laser intensity, and pulse duration. Laser-assisted direct ink writing is used to pattern highly conductive, ductile metallic interconnects, springs, and freestanding spiral architectures on flexible and rigid substrates. PMID:27185932

  5. Developments of pulse laser assist optical tweezers (PLAT) for in vivo manipulation

    NASA Astrophysics Data System (ADS)

    Maeda, Saki; Sugiura, Tadao; Minato, Kotaro

    2011-02-01

    Optical tweezers is a technique to trap and to manipulate micron sized objects under a microscope by radiation pressure force exerted by a laser beam. Optical tweezers has been utilized for single-molecular measurements of force exerted by molecular interactions and for cell palpation. To extend applications of optical tweezers we have developed a novel optical tweezers system combined with a pulse laser. We utilize a pulsed laser (Q-switched Nd: YAG laser, wavelength of 1064 nm) to assist manipulations by conventional optical tweezers achieved by a continuous wave (CW) laser. The pulsed laser beam is introduced into the same optics for conventional optical tweezers. In principle, instantaneous radiation force is proportional to instantaneous power of laser beam. As a result, pulsed laser beam generates strong instantaneous force on an object to be manipulated. If the radiation force becomes strong enough to get over an obstacle structure and/or to be released from adhesion, the object will be free from these difficulties. We have named this technique as Pulse Laser beam Assisted optical Tweezers (PLAT). We have successfully demonstrated to manipulate objects surface on a living cell for "in vivo manipulation."

  6. Technology Assessment of Laser-Assisted Materials Processing in Space

    NASA Technical Reports Server (NTRS)

    Nagarathnam, Karthik; Taminger, Karen M. B.

    2001-01-01

    Lasers are useful for performing operations such as joining, machining, built-up freeform fabrication, shock processing, and surface treatments. These attributes are attractive for the supportability of longer-term missions in space due to the multi-functionality of a single tool and the variety of materials that can be processed. However, current laser technology also has drawbacks for space-based applications, specifically size, power efficiency, lack of robustness, and problems processing highly reflective materials. A review of recent laser developments will be used to show how these issues may be reduced and indicate where further improvement is necessary to realize a laser-based materials processing capability in space. The broad utility of laser beams in synthesizing various classes of engineering materials will be illustrated using state-of-the art processing maps for select lightweight alloys typically found on spacecraft. With the advent of recent breakthroughs in diode-pumped solid-state lasers and fiber optic technologies, the potential to perform multiple processing techniques is increasing significantly. Lasers with suitable wavelengths and beam properties have tremendous potential for supporting future space missions to the moon, Mars and beyond.

  7. Design challenges for matrix assisted pulsed laser evaporation and infrared resonant laser evaporation equipment

    NASA Astrophysics Data System (ADS)

    Greer, James A.

    2011-11-01

    Since the development of the Matrix Assisted Pulsed Laser Evaporation (MAPLE) process by the Naval Research Laboratory (NRL) in the late 1990s, MAPLE has become an active area of research for the deposition of a variety of polymer, biological, and organic thin films. As is often the case with advancements in thin-film deposition techniques new technology sometimes evolves by making minor or major adjustments to existing deposition process equipment and techniques. This is usually the quickest and least expensive way to try out new ideas and to "push the envelope" in order to obtain new and unique scientific results as quickly as possible. This process of "tweaking" current equipment usually works to some degree, but once the new process is further refined overall designs for a new deposition tool based on the critical attributes of the new process typically help capitalize more fully on the all the salient features of the new and improved process. This certainly has been true for the MAPLE process. In fact the first MAPLE experiments the polymer/solvent matrix was mixed and poured into a copper holder held at LN2 temperature on a laboratory counter top. The holder was then quickly placed onto a LN2 cooled reservoir in a vacuum deposition chamber and placed in a vertical position on a LN2 cooled stage and pumped down as quickly as possible. If the sample was not placed into the chamber quickly enough the frozen matrix would melt and drip into the bottom of the chamber onto the chambers main gate valve making a bit of a mess. However, skilled and motivated scientists usually worked quickly enough to make this process work most of the time. The initial results from these experiments were encouraging and led to several publications which sparked considerable interest in this newly developed technique Clearly this approach provided the vision that MAPLE was a viable deposition process, but the equipment was not optimal for conducting MAPLE experiments on a regular basis

  8. Visualization of liquid-assisted hard tissue ablation with a pulsed CO2 laser

    NASA Astrophysics Data System (ADS)

    Li, X. W.; Chen, C. G.; Zhang, X. Z.; Zhan, Z. L.; Xie, S. S.

    2015-01-01

    To investigate the characteristics of liquid-mediated hard tissue ablation induced by a pulsed CO2 laser with a wavelength of 10.6 μm, a high speed camera was used to monitor the interaction between water, tissue and laser irradiation. The results showed that laser irradiation can directly impact on tissue through a vapor channel formed by the leading part of the laser pulse. The ablation debris plays a key role in liquid-assisted laser ablation, having the ability to keep the vapor channel open to extend actuation time. The runoff effect induced by vortex convection liquid flow can remove the tissue that obstructs the effect of the next laser pulse.

  9. Laser assisted vascular anastomosis (LAVA): a promising nonsuture technique for surgery

    NASA Astrophysics Data System (ADS)

    Chen, Chen; Peng, Fei; Xu, Dahai; Cheng, Qinghua

    2009-08-01

    The first successful experiment of laser vascular welding was reported in 1979. Laser assisted vascular anastomosis (LAVA) is looked as a particularly promising non-suture method in future. We performed a Medline literature search on laser vessel welding combined with cross-referencing. According to the former experimental animal studies, CO2-, argon-, diode-, KTP-, Holmium:YAG-, and Nd:YAG-lasers have been used for LAVA. Almost all lasers have been used in combination with stay suture and/or solders in order to improve the strength on anastomosis site. Advantages of LAVA are minimal vessel damage, faster operation and the potential for minimally invasive application. However, the clinical application of LAVA is still seldom employed because of aneurysm formation. In conclusion of the literature study, the diode laser is the most popular, but long-term evaluation is required.

  10. Oxygen assisted interconnection of silver nanoparticles with femtosecond laser radiation

    SciTech Connect

    Huang, H.; Zhou, Y.; Duley, W. W.

    2015-12-14

    Ablation of silver (Ag) nanoparticles in the direction of laser polarization is achieved by utilizing femtosecond laser irradiation in air at laser fluence ranging from ∼2 mJ/cm{sup 2} to ∼14 mJ/cm{sup 2}. This directional ablation is attributed to localized surface plasmon induced localized electric field enhancement. Scanning electron microscopy observations of the irradiated particles in different gases and at different pressures indicate that the ablation is further enhanced by oxygen in the air. This may be due to the external heating via the reactions of its dissociation product, atomic oxygen, with the surface of Ag particles, while the ablated Ag is not oxidized. Further experimental observations show that the ablated material re-deposits near the irradiated particles and results in the extension of the particles in laser polarization direction, facilitating the interconnection of two well-separated nanoparticles.

  11. Plasma instabilities in magnetically assisted pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Haverkamp, J. D.; Bourham, M. A.; Du, S.; Narayan, J.

    2008-06-01

    The laser ablation of a carbon target in a transverse magnetic field is studied using a quadruple Langmuir probe. Ion saturation signals indicate the presence of wavelike behaviour not found in field-free laser ablation of carbon. Results are discussed in terms of the lower-hybrid drift instability and the electron-ion hybrid instability. The results are found to be most consistent with the electron-ion hybrid instability.

  12. The dawn of computer-assisted robotic osteotomy with ytterbium-doped fiber laser.

    PubMed

    Sotsuka, Yohei; Nishimoto, Soh; Tsumano, Tomoko; Kawai, Kenichiro; Ishise, Hisako; Kakibuchi, Masao; Shimokita, Ryo; Yamauchi, Taisuke; Okihara, Shin-ichiro

    2014-05-01

    Currently, laser radiation is used routinely in medical applications. For infrared lasers, bone ablation and the healing process have been reported, but no laser systems are established and applied in clinical bone surgery. Furthermore, industrial laser applications utilize computer and robot assistance; medical laser radiations are still mostly conducted manually nowadays. The purpose of this study was to compare the histological appearance of bone ablation and healing response in rabbit radial bone osteotomy created by surgical saw and ytterbium-doped fiber laser controlled by a computer with use of nitrogen surface cooling spray. An Ytterbium (Yb)-doped fiber laser at a wavelength of 1,070 nm was guided by a computer-aided robotic system, with a spot size of 100 μm at a distance of approximately 80 mm from the surface. The output power of the laser was 60 W at the scanning speed of 20 mm/s scan using continuous wave system with nitrogen spray level 0.5 MPa (energy density, 3.8 × 10(4) W/cm(2)). Rabbits radial bone osteotomy was performed by an Yb-doped fiber laser and a surgical saw. Additionally, histological analyses of the osteotomy site were performed on day 0 and day 21. Yb-doped fiber laser osteotomy revealed a remarkable cutting efficiency. There were little signs of tissue damage to the muscle. Lased specimens have shown no delayed healing compared with the saw osteotomies. Computer-assisted robotic osteotomy with Yb-doped fiber laser was able to perform. In rabbit model, laser-induced osteotomy defects, compared to those by surgical saw, exhibited no delayed healing response.

  13. Melt expulsion during ultrasonic vibration-assisted laser surface processing of austenitic stainless steel.

    PubMed

    Alavi, S Habib; Harimkar, Sandip P

    2015-05-01

    Simultaneous application of ultrasonic vibrations during conventional materials processing (casting, welding) and material removal processes (machining) has recently been gaining widespread attention due to improvement in metallurgical quality and efficient material removal, respectively. In this paper, ultrasonic vibration-assisted laser surface melting of austenitic stainless steel (AISI 316) is reported. While the application of ultrasonic vibrations during laser processing delays the laser interaction with material due to enhancement of surface convection, it resulted in expulsion of melt from the irradiated region (forming craters) and transition from columnar to equiaxed dendritic grain structure in the resolidified melt films. Systematic investigations on the effect of ultrasonic vibrations (with vibrations frequency of 20 kHz and power output in the range of 20-40%) on the development of microstructure during laser surface melting (with laser power of 900 W and irradiation time in the range of 0.30-0.45 s) are reported. The results indicate that the proposed ultrasonic vibration-assisted laser processing can be designed for efficient material removal (laser machining) and improved equiaxed microstructure (laser surface modifications) during materials processing.

  14. Laser-assisted drug delivery in dermatology: from animal models to clinical practice.

    PubMed

    Ali, Faisal R; Al-Niaimi, Firas

    2016-02-01

    Topical medicaments are the mainstay of the dermatologists' therapeutic arsenal. Laser-assisted drug delivery enhances the ability of topically applied medicaments to penetrate the skin. We discuss the mechanisms of laser-assisted drug delivery and animal models that have informed clinical practice. We review clinical studies that have employed laser-assisted drug delivery for a range of indications to date including non-melanoma skin cancer, vitiligo, scarring, vaccination, local anaesthesia, analgesia, viral warts, infantile haemangiomas and cosmetic uses. Studies thus far suggest that laser pre-treatment improves transepidermal absorption of topical agents and allows for a much deeper penetration of drugs than is possible with topical medicaments alone. This may allow more efficacious action of current treatments, such that conventional duration of treatment can be shortened or lower concentrations of active agents be used, potentially obviating side effects of treatment. The prospect of using laser technologies to facilitate transdermal vaccination and as an adjunct for inflammatory dermatoses and cosmetic indications remains in its infancy. As larger trials are published, involving greater numbers of patients and utilising various laser and topical medicament parameters, we will enhance our understanding of this nascent modality of treatment delivery.

  15. Design and implementation of a system for laser assisted milling of advanced materials

    NASA Astrophysics Data System (ADS)

    Wu, Xuefeng; Feng, Gaocheng; Liu, Xianli

    2016-09-01

    Laser assisted machining is an effective method to machine advanced materials with the added benefits of longer tool life and increased material removal rates. While extensive studies have investigated the machining properties for laser assisted milling(LAML), few attempts have been made to extend LAML to machining parts with complex geometric features. A methodology for continuous path machining for LAML is developed by integration of a rotary and movable table into an ordinary milling machine with a laser beam system. The machining strategy and processing path are investigated to determine alignment of the machining path with the laser spot. In order to keep the material removal temperatures above the softening temperature of silicon nitride, the transformation is coordinated and the temperature interpolated, establishing a transient thermal model. The temperatures of the laser center and cutting zone are also carefully controlled to achieve optimal machining results and avoid thermal damage. These experiments indicate that the system results in no surface damage as well as good surface roughness, validating the application of this machining strategy and thermal model in the development of a new LAML system for continuous path processing of silicon nitride. The proposed approach can be easily applied in LAML system to achieve continuous processing and improve efficiency in laser assisted machining.

  16. Nanosecond Laser-Assisted Nitrogen Doping of Graphene Oxide Dispersions.

    PubMed

    Kepić, Dejan; Sandoval, Stefania; Pino, Ángel Pérez Del; György, Enikö; Cabana, Laura; Ballesteros, Belén; Tobias, Gerard

    2017-02-09

    N-doped reduced graphene oxide (RGO) has been prepared in bulk form by laser irradiation of graphene oxide (GO) dispersed in an aqueous solution of ammonia. A pulsed Nd:YAG laser with emission wavelengths in the infrared (IR) 1064 nm, visible (Vis) 532 nm, and ultraviolet (UV) 266 nm spectral regions was employed for the preparation of the N-doped RGO samples. Regardless of the laser energy employed, the resulting material presents a higher fraction of pyrrolic nitrogen compared to nitrogen atoms in pyridinic and graphitic coordination. Noticeably, whereas increasing the laser fluence of UV and Vis wavelengths results in an increase in the total amount of nitrogen, up to 4.9 at. % (UV wavelength at 60 mJ cm(-2) fluence), the opposite trend is observed when the GO is irradiated in ammonia solution through IR processing. The proposed laser-based methodology allows the bulk synthesis of N-doped reduced graphene oxide in a simple, fast, and cost efficient manner.

  17. Laser-assisted skin closure at 1.32 microns: the use of a software-driven medical laser system

    NASA Astrophysics Data System (ADS)

    Dew, Douglas K.; Hsu, Tung M.; Hsu, Long S.; Halpern, Steven J.; Michaels, Charles E.

    1991-06-01

    This study investigated the use of a computerized 1 .3 micron Nd:YAG laser to seal approximated wound edges in pig skin. The medical laser system used was the DLS Type 1 , 1 .32 micron Nd:YAG laser (Laser Surgery Software, Inc.). The purpose of this study was to evaluate the effectiveness of laser assisted skin closure using the DLS YAG laser in a large animal model. Effectiveness was judged on the basis of wound dehiscence, infection, unusual healing result and consistency of results. Comparative cosmetic result was also evaluated. In this study, the DLS YAG laser was used to close scalpel-induced, full-thickness wounds. The pig model was chosen for its many integumentary similarities to man. Controls included scalpel-induced wounds closed using suture, staple and some with norepair. After adequate anesthesia was achieved, the dorsum of Yucutan pigs (approximately 75- 100 pounds) each was clipped with animal hair clippers from the shoulder area to the hind legs. The area was then shaved with a razor blade, avoiding any inadvertent cuts or abrasions of the skin. The dorsum was divided into four rows of four parallel incisions made by a #15 scalpel blade. Full-thickness incisions, 9 cm long, were placed over the dorsum of the pigs and then closed either with one loosely approximating Prolene" suture (the "no repair' group), multiple interrupted 6-0 nylon sutures, staples or laser. The experimental tissue sealing group consisted of 1 69 laser assisted closures on 1 3 pigs. Sutured control wounds were closed with 6-0 nylon, full thickness, simple, interrupted sutures. Eight sutures were placed 1 cm apart along the 9 cm incision. Stapled control wounds were approximated using two evenly spaced 3-0 VicryP' sub-dermal sutures and the dermis closed using Proximate' skin staples. Eight staples were placed 1 cm apart along the 9 cm incision. The no-repair incisions were grossly approximated using a single 2-0 Prolene full thickness, simple, interrupted suture located at the

  18. Photoepilation: a growing trend in laser-assisted cosmetic dermatology.

    PubMed

    Nouri, Keyvan; Vejjabhinanta, Voraphol; Patel, Shalu S; Singh, Anita

    2008-03-01

    Excess hair is an age-old condition plaguing both men and women alike, of all races. Conditions such as hirsutism or hypertrichosis, procedures that involve grafted donor sites, transsexual transformations from male to female, and genetics are all responsible for excess or unwanted hair. Previous options for people seeking to remove or lessen the presence of hair have either been painful or resulted in short-term hair removal. With the recent advent of laser technology, hair removal has been added to the many capabilities of the new generation nonablative lasers and light systems. Lasers are not yet a permanent solution for hair removal, but they are able to provide a safe, fast, and effective method of hair reduction.

  19. Laser assisted high entropy alloy coating on aluminum: Microstructural evolution

    SciTech Connect

    Katakam, Shravana; Joshi, Sameehan S.; Mridha, Sanghita; Mukherjee, Sundeep; Dahotre, Narendra B.

    2014-09-14

    High entropy alloy (Al-Fe-Co-Cr-Ni) coatings were synthesized using laser surface engineering on aluminum substrate. Electron diffraction analysis confirmed the formation of solid solution of body centered cubic high entropy alloy phase along with phases with long range periodic structures within the coating. Evolution of such type of microstructure was a result of kinetics associated with laser process, which generates higher temperatures and rapid cooling resulting in retention of high entropy alloy phase followed by reheating and/or annealing in subsequent passes of the laser track giving rise to partial decomposition. The partial decomposition resulted in formation of precipitates having layered morphology with a mixture of high entropy alloy rich phases, compounds, and long range ordered phases.

  20. Spectral caustics in laser assisted Breit-Wheeler process

    NASA Astrophysics Data System (ADS)

    Nousch, T.; Seipt, D.; Kämpfer, B.; Titov, A. I.

    2016-04-01

    Electron-positron pair production by the Breit-Wheeler process embedded in a strong laser pulse is analyzed. The transverse momentum spectrum displays prominent peaks which are interpreted as caustics, the positions of which are accessible by the stationary phases. Examples are given for the superposition of an XFEL beam with an optical high-intensity laser beam. Such a configuration is available, e.g., at LCLS at present and at European XFEL in near future. It requires a counter propagating probe photon beam with high energy which can be generated by synchronized inverse Compton backscattering.

  1. Frequency-comb-assisted broadband precision spectroscopy with cascaded diode lasers.

    PubMed

    Liu, Junqiu; Brasch, Victor; Pfeiffer, Martin H P; Kordts, Arne; Kamel, Ayman N; Guo, Hairun; Geiselmann, Michael; Kippenberg, Tobias J

    2016-07-01

    Frequency-comb-assisted diode laser spectroscopy, employing both the accuracy of an optical frequency comb and the broad wavelength tuning range of a tunable diode laser, has been widely used in many applications. In this Letter, we present a novel method using cascaded frequency agile diode lasers, which allows us to extend the measurement bandwidth to 37.4 THz (1355-1630 nm) at megahertz resolution with scanning speeds above 1 THz/s. It is demonstrated as a useful tool to characterize a broadband spectrum for molecular spectroscopy, and in particular it enables us to characterize the dispersion of integrated microresonators up to the 4th-order.

  2. Frequency-comb-assisted broadband precision spectroscopy with cascaded diode lasers

    NASA Astrophysics Data System (ADS)

    Liu, Junqiu; Brasch, Victor; Pfeiffer, Martin H. P.; Kordts, Arne; Kamel, Ayman N.; Guo, Hairun; Geiselmann, Michael; Kippenberg, Tobias J.

    2016-07-01

    Frequency comb assisted diode laser spectroscopy, employing both the accuracy of an optical frequency comb and the broad wavelength tuning range of a tunable diode laser, has been widely used in many applications. In this letter we present a novel method using cascaded frequency agile diode lasers, which allows extending the measurement bandwidth to 37.4 THz (1355 to 1630 nm) at MHz resolution with scanning speeds above 1 THz/s. It is demonstrated as a useful tool to characterize a broadband spectrum for molecular spectroscopy and in particular it enables to characterize the dispersion of integrated microresonators up to the fourth order.

  3. Laser-assisted field evaporation of metal oxides: A time-dependent density functional theory study

    NASA Astrophysics Data System (ADS)

    Xia, Yu; Li, Zhibing

    2016-11-01

    To understand laser-assisted field evaporation of semiconductors and insulators at the microscopic level, we study the time evolution of the electronic and atomic structure of a MgO cluster in high electrostatic fields subjected to strong laser pulses. We find that the critical laser intensity for evaporation decreases linearly as the electrostatic field strength increases. The optical absorption enhancement in high electrostatic field is confirmed by the redshift of the optical absorption spectra, the reduction of the energy gap, and the increase of the absorption cross section.

  4. Ballistic laser-assisted solid transfer (BLAST) from a thin film precursor.

    PubMed

    Banks, David P; Grivas, Christos; Zergioti, Ioanna; Eason, Robert W

    2008-03-03

    A novel technique for the laser-induced forward transfer (LIFT) of material in solid phase from a thin film precursor is presented. Multiple, sub-threshold energy femtosecond pulses are used to lessen the adhesion of a donor film to a support substrate to facilitate forward transfer of solid 'pellets' of donor material to a receiver. A relatively higher intensity outer ring is added to the transfer laser pulses, by means of the near-field diffraction pattern of a circular aperture, to define the area for transfer in the donor film and allow for more reproducible pellet shapes. This technique has been termed Ballistic Laser-Assisted Solid Transfer (BLAST).

  5. Relativistic electronic dressing in laser-assisted electron-hydrogen elastic collisions

    SciTech Connect

    Attaourti, Y.; Manaut, B.; Makhoute, A.

    2004-06-01

    We study the effects of the relativistic electronic dressing in laser-assisted electron-hydrogen atom elastic collisions. We begin by considering the case when no radiation is present. This is necessary in order to check the consistency of our calculations and we then carry out the calculations using the relativistic Dirac-Volkov states. It turns out that a simple formal analogy links the analytical expressions of the unpolarized differential cross section without laser and the unpolarized differential cross section in the presence of a laser field.

  6. Functional polyethylene glycol derivatives nanostructured thin films synthesized by matrix-assisted pulsed laser evaporation

    NASA Astrophysics Data System (ADS)

    Cristescu, R.; Popescu, C.; Popescu, A.; Grigorescu, S.; Mihailescu, I. N.; Mihaiescu, D.; Gittard, S. D.; Narayan, R. J.; Buruiana, T.; Stamatin, I.; Chrisey, D. B.

    2009-09-01

    We report the thin film deposition by matrix-assisted pulsed laser evaporation (MAPLE) of a polymer conjugate with an hydrophilic sequence between metronidazole molecules that was covalently attached to both oligomer ends of carboxylate poly(ethylene glycol) (PEG 1.5-metronidazole). A pulsed KrF* excimer laser was used to deposit the drug-polymer composite films. Fourier transform infrared spectroscopy was used to demonstrate that MAPLE-transferred materials exhibited chemical properties similar to the starting materials. The dependence of the surface morphology on incident laser fluence is given.

  7. Investigating Thermal Interactions in the Case of Laser Assisted Joining of PMMA Plastic and Steel

    NASA Astrophysics Data System (ADS)

    Bauernhuber, Andor; Markovits, Tamás

    Laser transmission joining of dissimilar materials is a novel and promising area of researches on joining technology. However, processes during laser assisted metal plastic (LAMP) joining are not completely explained yet. In the course of this study, the authors investigated the joining process of PMMA plastic and steel by means of laser, as a part of their research on dissimilar material joining. The characteristic process temperature was measured during the joining by different heating conditions, to describe thermal interactions between the polymer and the metal part, and to better understand the mechanism of joining.

  8. The Laser-assisted photoelectric effect of He, Ne, Ar and Xe in intense extreme ultraviolet and infrared laser fields

    NASA Astrophysics Data System (ADS)

    Hayden, P.; Dardis, J.; Hough, P.; Richardson, V.; Kennedy, E. T.; Costello, J. T.; Düsterer, S.; Redlin, H.; Feldhaus, J.; Li, W. B.; Cubaynes, D.; Meyer, M.

    2016-02-01

    In this paper, we report results on two-colour above-threshold ionisation, where extreme ultraviolet pulses of femtosecond duration were synchronised to intense infrared laser pulses of picosecond duration, in order to study the laser-assisted photoelectric effect of atomic helium, neon, krypton and xenon which leads to the appearance of characteristic sidebands in the photoelectron spectra. The observed trends are found to be well described by a simple model based on the soft-photon approximation, at least for the relatively low optical intensities of up to ? employed in these early experiments.

  9. Performance optimization of water-jet assisted underwater laser cutting of AISI 304 stainless steel sheet

    NASA Astrophysics Data System (ADS)

    Mullick, Suvradip; Madhukar, Yuvraj K.; Roy, Subhransu; Nath, Ashish K.

    2016-08-01

    Recent development of water-jet assisted underwater laser cutting has shown some advantages over the gas assisted underwater laser cutting, as it produces much less turbulence, gas bubble and aerosols, resulting in a more gentle process. However, this process has relatively low efficiency due to different losses in water. Scattering is reported to be a dominant loss mechanism, which depends on the growth of vapor layer at cut front and its removal by water-jet. Present study reports improvement in process efficiency by reducing the scattering loss using modulated laser power. Judicious control of laser pulse on- and off-time could improve process efficiency through restricting the vapor growth and its effective removal by water-jet within the laser on- and off-time, respectively. Effects of average laser power, duty cycle and modulation frequency on specific energy are studied to get an operating zone for maximum efficiency. Next, the variation in laser cut quality with different process parameters are studied within this operating zone using Design of experiment (DOE). Response surface methodology (RSM) is used by implementing three level Box-Behnken design to optimize the variation in cut quality, and to find out the optimal process parameters for desired quality. Various phenomena and material removal mechanism involved in this process are also discussed.

  10. Laser-assisted cavity preparation and adhesion to erbium-lased tooth structure: part 1. Laser-assisted cavity preparation.

    PubMed

    De Moor, Roeland Jozef Gentil; Delmé, Katleen Ilse Maria

    2009-12-01

    The use of the ruby laser (693.4 nm) was first described in 1960, and it was applied for hard tissue ablation in 1964. Different wavelengths [Nd:YAG (1.065 microm), CO2 (9.6 microm), Ho:YAG (2.12 microm)] were consequently explored. Due to massive thermal side effects, these wavelengths caused increased temperature in dental pulp, as well as microcracks and carbonization. The use of this laser for dental hard tissue preparation was eventually abandoned. At the end of the 1980s, excimer lasers (ultraviolet) and the erbium laser (infrared) were developed, with the advantages of improved temperature control and smaller penetration depths. With the development of smaller devices and improved knowledge of how to limit damage to the surrounding tissues, new ablation techniques were established in the 1990s. There is still contradiction in the current literature, however, in that different wavelengths are advocated for hard tissue removal, and heterogeneity in laser parameters and power densities remain. In this review, the effects of the wavelengths presently used for cavity preparation are evaluated. We conclude that erbium lasers (Er:YAG and Er,Cr:YSGG) are most efficient and, with the right parameters, the thermal side effects are small. There is a substantial need for "gold standards", although this is difficult to establish in practice owing to different laser parameters (including pulse repetition rate, amount of cooling, energy delivered per pulse, and types of pulses) and target specificity (tissue interaction with sound or decayed enamel or dentin, and the extent of (de)mineralization) which influence tissue interaction.

  11. Significance of the Resonance Condition for Controlling the Seam Position in Laser-assisted TIG Welding

    NASA Astrophysics Data System (ADS)

    Emde, B.; Huse, M.; Hermsdorf, J.; Kaierle, S.; Wesling, V.; Overmeyer, L.; Kozakov, R.; Uhrlandt, D.

    As an energy-preserving variant of laser hybrid welding, laser-assisted arc welding uses laser powers of less than 1 kW. Recent studies have shown that the electrical conductivity of a TIG welding arc changes within the arc in case of a resonant interaction between laser radiation and argon atoms. This paper presents investigations on how to control the position of the arc root on the workpiece by means of the resonant interaction. Furthermore, the influence on the welding result is demonstrated. The welding tests were carried out on a cooled copper plate and steel samples with resonant and non-resonant laser radiation. Moreover, an analysis of the weld seam is presented.

  12. Thermal laser-assisted angioplasty of renal artery stenosis for renovascular hypertension.

    PubMed

    Tani, M; Mizuno, K; Midorikawa, H; Igari, T; Egawa, M; Niimura, S; Fukuchi, S; Hoshino, S

    1993-01-01

    Percutaneous transluminal laser-assisted angioplasty of a renal artery stenosis was performed in a 16-year-old woman with renovascular hypertension. The stenotic portion of the renal artery was predilated by delivering Nd-YAG laser energy to the terminal tip of a laser catheter. Although the luminal diameter did not increase sufficiently with laser angioplasty alone, it allowed passage of the balloon catheter and subsequent successful balloon angioplasty. Immediately after dilatation, the patient's blood pressure fell to normal, and plasma renin activity decreased. There were no serious complications. Thermal laser angioplasty seems to be an effective adjunct technique for the treatment of severe renal artery stenosis which does not allow initial passage of a balloon catheter.

  13. Ion-beam assisted laser fabrication of sensing plasmonic nanostructures

    PubMed Central

    Kuchmizhak, Aleksandr; Gurbatov, Stanislav; Vitrik, Oleg; Kulchin, Yuri; Milichko, Valentin; Makarov, Sergey; Kudryashov, Sergey

    2016-01-01

    Simple high-performance, two-stage hybrid technique was developed for fabrication of different plasmonic nanostructures, including nanorods, nanorings, as well as more complex structures on glass substrates. In this technique, a thin noble-metal film on a dielectric substrate is irradiated by a single tightly focused nanosecond laser pulse and then the modified region is slowly polished by an accelerated argon ion (Ar+) beam. As a result, each nanosecond laser pulse locally modifies the initial metal film through initiation of fast melting and subsequent hydrodynamic processes, while the following Ar+-ion polishing removes the rest of the film, revealing the hidden topography features and fabricating separate plasmonic structures on the glass substrate. We demonstrate that the shape and lateral size of the resulting functional plasmonic nanostructures depend on the laser pulse energy and metal film thickness, while subsequent Ar+-ion polishing enables to vary height of the resulting nanostructures. Plasmonic properties of the fabricated nanostructures were characterized by dark-field micro-spectroscopy, Raman and photoluminescence measurements performed on single nanofeatures, as well as by supporting numerical calculations of the related electromagnetic near-fields and Purcell factors. The developed simple two-stage technique represents a new step towards direct large-scale laser-induced fabrication of highly ordered arrays of complex plasmonic nanostructures. PMID:26776569

  14. Ion-beam assisted laser fabrication of sensing plasmonic nanostructures

    NASA Astrophysics Data System (ADS)

    Kuchmizhak, Aleksandr; Gurbatov, Stanislav; Vitrik, Oleg; Kulchin, Yuri; Milichko, Valentin; Makarov, Sergey; Kudryashov, Sergey

    2016-01-01

    Simple high-performance, two-stage hybrid technique was developed for fabrication of different plasmonic nanostructures, including nanorods, nanorings, as well as more complex structures on glass substrates. In this technique, a thin noble-metal film on a dielectric substrate is irradiated by a single tightly focused nanosecond laser pulse and then the modified region is slowly polished by an accelerated argon ion (Ar+) beam. As a result, each nanosecond laser pulse locally modifies the initial metal film through initiation of fast melting and subsequent hydrodynamic processes, while the following Ar+-ion polishing removes the rest of the film, revealing the hidden topography features and fabricating separate plasmonic structures on the glass substrate. We demonstrate that the shape and lateral size of the resulting functional plasmonic nanostructures depend on the laser pulse energy and metal film thickness, while subsequent Ar+-ion polishing enables to vary height of the resulting nanostructures. Plasmonic properties of the fabricated nanostructures were characterized by dark-field micro-spectroscopy, Raman and photoluminescence measurements performed on single nanofeatures, as well as by supporting numerical calculations of the related electromagnetic near-fields and Purcell factors. The developed simple two-stage technique represents a new step towards direct large-scale laser-induced fabrication of highly ordered arrays of complex plasmonic nanostructures.

  15. Ion-beam assisted laser fabrication of sensing plasmonic nanostructures.

    PubMed

    Kuchmizhak, Aleksandr; Gurbatov, Stanislav; Vitrik, Oleg; Kulchin, Yuri; Milichko, Valentin; Makarov, Sergey; Kudryashov, Sergey

    2016-01-18

    Simple high-performance, two-stage hybrid technique was developed for fabrication of different plasmonic nanostructures, including nanorods, nanorings, as well as more complex structures on glass substrates. In this technique, a thin noble-metal film on a dielectric substrate is irradiated by a single tightly focused nanosecond laser pulse and then the modified region is slowly polished by an accelerated argon ion (Ar(+)) beam. As a result, each nanosecond laser pulse locally modifies the initial metal film through initiation of fast melting and subsequent hydrodynamic processes, while the following Ar(+)-ion polishing removes the rest of the film, revealing the hidden topography features and fabricating separate plasmonic structures on the glass substrate. We demonstrate that the shape and lateral size of the resulting functional plasmonic nanostructures depend on the laser pulse energy and metal film thickness, while subsequent Ar(+)-ion polishing enables to vary height of the resulting nanostructures. Plasmonic properties of the fabricated nanostructures were characterized by dark-field micro-spectroscopy, Raman and photoluminescence measurements performed on single nanofeatures, as well as by supporting numerical calculations of the related electromagnetic near-fields and Purcell factors. The developed simple two-stage technique represents a new step towards direct large-scale laser-induced fabrication of highly ordered arrays of complex plasmonic nanostructures.

  16. Laser-assisted oral surgery in general practice

    NASA Astrophysics Data System (ADS)

    McCauley, Mark C.

    1995-04-01

    This presentation will demonstrate and discuss any surgical applications of the Argon dental laser. This presentation will also increase the awareness and basic understanding of the physical principals of the Argon laser. The wavelength of the Argon laser is specifically absorbed by red pigments such a hemoglobin which is abundant in oral soft tissue. The result is a sharp clean incision with minimal thermal damage to adjacent healthy tissue. Preprosthetic procedures such as full arch vestibuloplasty, labial and lingual frenectomy, and epulis fissuratum removal will be demonstrated. Other soft tissue management procedures such as minor periodontal pocket elimination surgery (gingivectomy), removal of hyperplastic granulation tissue from around poorly maintained implants, and the removal of granulation and/or cystic tissue from the apex of teeth undergoing endodontic (apicoec-tomy) surgery will also be demonstrated and discussed. Provided basic oral surgery protocol is followed, surgical procedures utilizing the Argon laser can be accomplished with minimal bleeding, minimal trauma and with minimal post-operative discomfort.

  17. Laser ablation assisted adhesive bonding of automotive structural composites

    SciTech Connect

    Boeman, R.G.; Paulauskas, F.L.; Warren, C.D.

    1999-07-03

    Laser ablation has been evaluated as a surface pretreatment prior to adhesive bonding. In prior experimental work, it was observed that when adhesively bonded, composite, single lap shear samples fail, the fracture often occurs at either the adhesive/adherend interface or in the resin rich surface layer of the composite. These two areas represent the weakest portion of the joint. Laser ablation pretreatment generates areas where the resin on the composite surface is selectively removed leaving behind exposed reinforcing fibers which are the major load bearing members of the composite. In a subsequent adhesive bonding operation, this allows portions of the fibers to be encapsulated in the adhesive while other portions of the fiber remain in the composite resin. This type of pretreatment permits fibers to bridge and reinforce the interface between adhesive and adherend. A secondary benefit is the removal of surface contaminantes by pyrolysis. Microscopic observation of laser ablated surfaces indicates a prominent, fiber rich area. Results of the mechanical evaluation indicated that the lap shear strength for laser ablated samples was significantly higher than specimens with no pretreatment or with solvent cleaning only, but were slightly lower than specimens that were mechanically roughened and cleaned with solvents prior to bonding.

  18. Measuring positron-atom binding energies through laser-assisted photorecombination

    NASA Astrophysics Data System (ADS)

    Surko, C. M.; Danielson, J. R.; Gribakin, G. F.; Continetti, R. E.

    2012-06-01

    Described here is a proposed experiment to use laser-assisted photorecombination of positrons from a trap-based beam and metal atoms in the gas phase to measure positron-atom binding energies. Signal rates are estimated, based in part upon experience studying resonant annihilation spectra using a trap-based positron beam.

  19. MATRIX-ASSISTED LASER DESORPTION IONIZATION OF SIZE AND COMPOSITION SELECTED AEROSOL PARTICLES. (R823980)

    EPA Science Inventory

    Matrix-assisted laser desorption/ionization (MALDI) was performed on individual,
    size-selected aerosol particles in the 2-8 mu m diameter range, Monodisperse aerosol droplets
    containing matrix, analyte, and solvent were generated and entrained in a dry stream of air, The dr...

  20. Characterization of nanoparticles by matrix assisted laser desorption ionization time-of-flight mass spectrometry.

    PubMed

    Ramalinga, Uma; Clogston, Jeffrey D; Patri, Anil K; Simpson, John T

    2011-01-01

    Determining the molecular weight of nanoparticles can be challenging. The molecular weight characterization of dendrimers, for example, with varying covalent and noncovalent modifications is critical to their use as therapeutics. As such, we describe in this chapter a protocol for the analysis of these molecules by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS).

  1. Efficacious insect and disease control with laser-guided air-assisted sprayer

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Efficacy of a newly developed air-assisted variable-rate sprayer was investigated for the control of arthropod pests and plant diseases in six commercial fields. The sprayer was integrated with a high-speed laser scanning sensor, a custom-designed signal processing program, an automatic flow control...

  2. Identification of Bacteria Using Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry

    ERIC Educational Resources Information Center

    Kedney, Mollie G.; Strunk, Kevin B.; Giaquinto, Lisa M.; Wagner, Jennifer A.; Pollack, Sidney; Patton, Walter A.

    2007-01-01

    Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS or simply MALDI) has become ubiquitous in the identification and analysis of biomacromolecules. As a technique that allows for the molecular weight determination of otherwise nonvolatile molecules, MALDI has had a profound impact in the molecular…

  3. Preliminary Results of Femtosecond Laser-assisted Cataract Surgery in a Private Clinic in Iran

    PubMed Central

    Nejat, Farhad; Sarahati, Sara; Nobari, Sahar Mojaled; Jadidi, Khosrow; Naderi, Mostafa; Nejat, Mohammad Amin

    2017-01-01

    Purpose: To report the preliminary results of femtosecond laser-assisted cataract surgery in Iranian patients. Methods: This prospective case series included 21 eyes of 21 patients with cataract. Mean patient age was 66.7 ± 10 years. The patients underwent femtosecond-laser assisted cataract surgery (VICTUS Femtosecond Laser Platform: Bausch + Lomb) and intraocular lens (IOL) implementation in Bina Eye Hospital, Tehran, Iran between May and October, 2014. Visual outcomes, intraocular pressure (IOP), and complications were evaluated three months after surgery. Results: Mean preoperative best-spectacle corrected visual acuity (BSCVA) was 0.40 ± 0.21 logMAR which significantly improved to 0.02 ± 0.03 logMAR three months postoperatively (P < 0.001). Mean preoperative IOP was 17.88 ± 2.70 mmHg which significantly decreased to 12.5 ± 1.51 mmHg three months after operation (P < 0.001). Mean duration of operation for these patients was 29.30 ± 8 minutes and mean femtosecond laser process time was 4.20 ± 2 minutes. In terms of complications, 9 patients developed fine subconjunctival hemorrhage and eye redness and 2 patients had mild corneal edema which all subsided within less than 7 days. Serious complications such as anterior or posterior capsule tears were not encountered. Conclusion: Femtosecond laser-assisted cataract surgery is a relatively new method of cataract PMID:28299005

  4. Matrix-assisted laser desorption fourier transform mass spectrometry for biological compounds

    SciTech Connect

    Hettich, R.; Buchanan, M.

    1990-01-01

    The recent development of matrix-assisted UV laser desorption (LD) mass spectrometry has made possible the ionization and detection of extremely large molecules (with molecular weights exceeding 100,000 Daltons). This technique has generated enormous interest in the biological community for the direct examination of large peptides and oligonucleotides. Although this matrix-assisted ionization method has been developed and used almost exclusively with time-of-flight (TOF) mass spectrometers, research is currently in progress to demonstrate this technique with trapped ion mass spectrometers, such as Fourier transform ion cyclotron resonance mass spectrometry (FTMS). The potential capabilities of FTMS for wide mass range, high resolution measurement, and ion trapping experiments suggest that this instrumental technique should be useful for the detailed structural characterization of large ions generated by the matrix-assisted technique. We have recently demonstrated that matrix-assisted ultraviolet laser desorption can be successfully used with FTMS for the ionization of small peptides. The objective of this report is to summarize the application and current limitations of matrix-assisted laser desorption FTMS for the characterization of peptides and oligonucleotides at the isomeric level. 4 refs., 3 figs., 2 tabs.

  5. Laser-assisted hair transplantation: histologic comparison between holmium:YAG and CO2 lasers

    NASA Astrophysics Data System (ADS)

    Chu, Eugene A.; Rabinov, C. Rose; Wong, Brian J.; Krugman, Mark E.

    1999-06-01

    The histological effects of flash-scanned CO2 (λ=10.6μm) and pulsed Holmium:YAG (Ho:YAG, λ=2.12μm) lasers were evaluated in human scalp following the creation of hair transplant recipient channels. Ho:YAG laser irradiation created larger zones of thermal injury adjacent to the laser channels than irradiation with the CO2 laser device. When the two lasers created recipient sites of nearly equal depth, the Holmium:YAG laser caused a larger region of lateral thermal damage (589.30μm) than the CO2 laser (118.07μm). In addition, Holmium:YAG irradiated specimens exhibited fractures or discontinuities beyond the region of clear thermal injury. This shearing effect is consistent with the photoacoustic mechanism of ablation associated with pulsed mid-IR laser irradiation. In contrast, channels created with the CO2 exhibited minimal epithelial disruption and significantly less lateral thermal damage. While the Holmium:YAG laser is a useful tool for ablation soft tissue with minimal char in select applications (sinus surgery, arthroscopic surgery), this study suggests that the use of the CO2 laser for the creation of transplantation recipient channels result in significantly less lateral thermal injury for the laser parameters employed.

  6. Laser-assisted guiding of electric discharges around objects

    PubMed Central

    Clerici, Matteo; Hu, Yi; Lassonde, Philippe; Milián, Carles; Couairon, Arnaud; Christodoulides, Demetrios N.; Chen, Zhigang; Razzari, Luca; Vidal, François; Légaré, François; Faccio, Daniele; Morandotti, Roberto

    2015-01-01

    Electric breakdown in air occurs for electric fields exceeding 34 kV/cm and results in a large current surge that propagates along unpredictable trajectories. Guiding such currents across specific paths in a controllable manner could allow protection against lightning strikes and high-voltage capacitor discharges. Such capabilities can be used for delivering charge to specific targets, for electronic jamming, or for applications associated with electric welding and machining. We show that judiciously shaped laser radiation can be effectively used to manipulate the discharge along a complex path and to produce electric discharges that unfold along a predefined trajectory. Remarkably, such laser-induced arcing can even circumvent an object that completely occludes the line of sight. PMID:26601188

  7. Laser-ablation-assisted microparticle acceleration for drug delivery

    NASA Astrophysics Data System (ADS)

    Menezes, V.; Takayama, K.; Ohki, T.; Gopalan, J.

    2005-10-01

    Localized drug delivery with minimal tissue damage is desired in some of the clinical procedures such as gene therapy, treatment of cancer cells, treatment of thrombosis, etc. We present an effective method for delivering drug-coated microparticles using laser ablation on a thin metal foil containing particles. A thin metal foil, with a deposition of a layer of microparticles is subjected to laser ablation on its backface such that a shock wave propagates through the foil. Due to shock wave loading, the surface of the foil containing microparticles is accelerated to very high speeds, ejecting the deposited particles at hypersonic speeds. The ejected particles have sufficient momentum to penetrate soft body tissues, and the penetration depth observed is sufficient for most of the pharmacological treatments. We have tried delivering 1μm tungsten particles into gelatin models that represent soft tissues, and liver tissues of an experimental rat. Sufficient penetration depths have been observed in these experiments with minimum target damage.

  8. Matrix-assisted laser-desorption mass spectrometry of DNA using an infrared free-electron laser

    NASA Astrophysics Data System (ADS)

    Haglund, Richard F., Jr.; Tang, Kai; Hillenkamp, Franz; Chen, C. H. Winston

    1993-07-01

    Sequencing the human genome requires an interdisciplinary approach combining aspects of biology, chemistry, physics, and engineering applied at the molecular level. One potentially interesting approach involves the use of matrix-assisted laser desorption-ionization mass spectroscopy (MALDI-MS), because of its high sensitivity, high speed, great accuracy, and ease of automation. However, while MALDI-MS has been successful in mass analysis of proteins and many large biomolecules, attempts to apply the technique to DNA sequencing have proven notoriously difficult. Because the choice of matrix materials for MALDI-MS is severely constrained by the application of conventional UV and visible laser sources, we are investigating the application of a tunable infrared free-electron laser to test the potential of infrared MALDI-MS for DNA sequencing. We describe the advantages of using tunable IR laser sources to choose matrix materials with optimal desorption, ionization, and thermomechanical properties, while avoiding the photochemical effects induced by ultraviolet and visible lasers. We also show the results of preliminary MALDI-MS experiments on small organic molecules using the Vanderbilt free-electron laser.

  9. Influencing Factors and Workpiece's Microstructure in Laser-Assisted Milling of Titanium

    NASA Astrophysics Data System (ADS)

    Wiedenmann, R.; Liebl, S.; Zaeh, M. F.

    Today's lightweight components have to withstand increasing mechanical and thermal loads. Therefore, advanced materials substitute conventional materials like steel or aluminum alloys. Using these high-performance materials the associated costs become prohibitively high. This paper presents the newest fundamental investigations on the hybrid process 'laser-assisted milling' which is an innovative technique to process such materials. The focus is on the validation of a numerical database for a CAD/CAM process control unit which is calculated by using simulation. Prior to that, the influencing factors on a laser-assisted milling process are systematically investigated using Design of Experiments (DoE) to identify the main influencing parameters coming from the laser and the milling operation.

  10. 78 FR 6173 - Diana Del Grosso, Ray Smith, Joseph Hatch, Cheryl Hatch, Kathleen Kelley, Andrew Wilklund, and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-29

    ... From the Federal Register Online via the Government Publishing Office ] DEPARTMENT OF TRANSPORTATION Surface Transportation Board Diana Del Grosso, Ray Smith, Joseph Hatch, Cheryl Hatch, Kathleen... Smith, Joseph Hatch, Cheryl Hatch, Kathleen Kelley, Andrew Wilklund, and Richard Kosiba...

  11. Laser-based dynamic evaporation and surface shaping of fused silica with assist gases: a path to rimless laser machining

    NASA Astrophysics Data System (ADS)

    Elhadj, S.; Matthews, M. J.; Guss, G. M.; Bass, I. L.

    2013-12-01

    Evaporation and ablation are fundamental processes which drive laser-material processing performance. In applications where surface shape is important, control of the temperature field and the resulting spatially varying material response must be considered. For that purpose, assist gases are useful in, first, lowering treatment temperatures and, second, in changing interfacial and bulk chemistry to limit capillary-driven flow. Additionally, laser-matter coupling is influenced by pulse length as it determines the heat affected zone. Using infrared imaging of CO2 laser-heated fused silica and surface profile measurements, we derive temperature and time dependent pitting rates along with shapes for a range of gases that include hydrogen, nitrogen, air, and helium. In the range of 1,500-4,500 K, evaporation, flow, and densification are shown to contribute to the pit shape. Analysis reveals a strong and complex dependence of rim formation on heating time and gas chemistry, mostly by lowering treatment temperature. Under dynamic heating, chemicapillarity appears to help in lowering rim height, in spite of the reactants mass transport limitations. Results on this gas-assisted approach suggest the possibility for sub-nanometer "rimless" laser-based machining.

  12. A novel robotic platform for laser-assisted transurethral surgery of the prostate.

    PubMed

    Russo, S; Dario, P; Menciassi, A

    2015-02-01

    Benign prostatic hyperplasia (BPH) is the most common pathology afflicting ageing men. The gold standard for the surgical treatment of BPH is transurethral resection of the prostate. The laser-assisted transurethral surgical treatment of BPH is recently emerging as a valid clinical alternative. Despite this, there are still some issues that hinder the outcome of laser surgery, e.g., distal dexterity is strongly reduced by the current endoscopic instrumentation and contact between laser and prostatic tissue cannot be monitored and optimized. This paper presents a novel robotic platform for laser-assisted transurethral surgery of BPH. The system, designed to be compatible with the traditional endoscopic instrumentation, is composed of a catheter-like robot provided with a fiber optic-based sensing system and a cable-driven actuation mechanism. The sensing system allows contact monitoring between the laser and the hypertrophic tissue. The actuation mechanism allows steering of the laser fiber inside the prostatic urethra of the patient, when contact must be reached. The design of the proposed robotic platform along with its preliminary testing and evaluation is presented in this paper. The actuation mechanism is tested in in vitro experiments to prove laser steering performances according to the clinical requirements. The sensing system is calibrated in experiments aimed to evaluate the capability of discriminating the contact forces, between the laser tip and the prostatic tissue, from the pulling forces exerted on the cables, during laser steering. These results have been validated demonstrating the robot's capability of detecting sub-Newton contact forces even in combination with actuation.

  13. Cosmetic and aesthetic skin photosurgery using a computer-assisted CO2 laser-scanning system

    NASA Astrophysics Data System (ADS)

    Dutu, Doru C. A.; Dumitras, Dan C.; Nedelcu, Ioan; Ghetie, Sergiu D.

    1997-12-01

    Since the first application of CO2 laser in skin photosurgery, various techniques such as laser pulsing, beam scanning and computer-assisted laser pulse generator have been introduced for the purpose of reducing tissue carbonization and thermal necrosis. Using a quite simple XY optical scanner equipped with two galvanometric driven mirrors and an appropriate software to process the scanning data and control the interaction time and energy density in the scanned area, we have obtained a device which can improve CO2 laser application in cosmetic and aesthetic surgery. The opto-mechanical CO2 laser scanner based on two total reflecting flat mirrors placed at 90 degree(s) in respect to the XY scanning directions and independently driven through a magnetic field provides a linear movement of the incident laser beam in the operating field. A DA converter supplied with scanning data by the software enables a scanning with linearity better than 1% for a maximum angular deviation of 20 degree(s). Because the scanning quality of the laser beam in the operating field is given not only by the displacement function of the two mirrors, but also by the beam characteristics in the focal plane and the cross distribution in the laser beam, the surgeon can control through software either the scanning field dimensions or the distance between two consecutive points of the vertically and/or horizontally sweep line. The development of computer-assisted surgical scanning techniques will help control the surgical laser, to create either a reproducible incision with a controlled depth or a controlled incision pattern with minimal incision width, a long desired facility for plastic surgery, neurosurgery, ENT and dentistry.

  14. Laser-assisted direct manufacturing of functionally graded 3D objects

    NASA Astrophysics Data System (ADS)

    Iakovlev, A.; Trunova, E.; Grevey, Dominique; Smurov, Igor

    2003-09-01

    Coaxial powder injection into a laser beam was applied for the laser-assisted direct manufacturing of 3D functionally graded (FG) objects. The powders of Stainless Steel 316L and Stellite grade 12 were applied. The following laser sources were used: (1) quasi-cw CO2 Rofin Sinar laser with 120 μm focal spot diameter and (2) pulsed-periodic Nd:YAG (HAAS HL 304P) with 200 μm focal spot diameter. The objects were fabricated layer-by-layer in the form of "walls", having the thickness of about 200 μm for CO2 laser and 300 μm for Nd:YAG laser. SEM analysis was applied for the FG objects fabricated by CO2 laser, yielding wall elements distribution in vertical direction. It was found that microhardness distribution is fully correlated with the components distribution. The compositional gradient can be smooth or sharp. Periodic multi-layered structures can be obtained as well. Minimal thickness of a layer with the fixed composition (for cw CO2 laser) is about 50 μm. Minimal thickness of a graded material zone, i.e. zone with composition variation from pure stainless steel to pure stellite is about 30 μm.

  15. Laser-assisted fibrinogen bonding of vascular tissue.

    PubMed

    Ashton, R C; Oz, M C; Lontz, J F; Matsumae, M; Taylor, R; Lemole, G M; Shapira, N; Lemole, G M

    1991-10-01

    Characterization of the stress-strain profiles of welded tissue would provide an additional means of analyzing this new technology and comparing it with alternative anastomosing techniques. Rabbit longitudinal aortotomies were repaired with either 7-O polypropylene sutures or an 808-nm diode laser (power density, 4.8 watts/cm2) after topical application of fibrinogen mixed with indocyanine green dye (peak absorption, 805 nm). The rabbits were sacrificed between 0 and 28 days, and the fresh aortic specimens were strained axially in diluted plasma solution until ultimate breakage occurred in order to produce a stress-strain profile graph. No significant differences were noted between sutured and bonded aorta at any time interval. Nonincised aortic tissue (378 lb/in2) withstood significantly higher stress (P less than 0.05) than both sutured (257 lb/in2) and bonded (210 lb/in2) groups at the time of creation. By 7 days after operation, however, no significant differences were noted among any of the three groups. At 28 days after operation, the laser-bonded aorta was significantly stronger than the control aorta (P less than 0.05). The only significant difference in modulus (stretchability) identified the sutured aorta (373 lb/in2) to be more rigid than the control aorta (231 lb/in2) (P less than 0.05). Both sutured and laser-bonded anastomoses are weaker than control aorta initially; however, after an early critical period, both treatments achieve the strength of control aorta. By 1 month postoperatively, sutured anastomoses have the disadvantage of being less distensible.

  16. Laser-assisted fabrication of batteries on wax paper

    NASA Astrophysics Data System (ADS)

    Chitnis, G.; Tan, T.; Ziaie, B.

    2013-11-01

    The functionality of paper-based diagnostic devices can be significantly enhanced by their integration with an on-board energy source. Here, we demonstrate the fabrication of paper-based electrochemical cells on wax paper using CO2 laser surface treatment and micromachining. A four cell zinc-copper battery shows a steady open-circuit voltage of ˜3 V and can provide 0.25 mA for at least 30 min when connected to a 10 kΩ load. Higher voltages and current values can be obtained by adjusting the number and size of electrochemical cells in the battery without changing the fabrication process.

  17. Plasma plume dynamics in magnetically assisted pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Haverkamp, J. D.; Bourham, M. A.; Du, S.; Narayan, J.

    2009-01-01

    The expansion of a laser produced plasma perpendicular to a magnetic field is studied with a quadruple Langmuir probe and a B-dot probe. In regions where the kinetic beta is less than one, we find plume deceleration and weak displacement of the magnetic field. As the plume expands into regions of weak magnetic field, plume deceleration stops and the displacement of the magnetic field is large. The diffusion time of the magnetic field lines was consistent with anomalously large resistivity driven by the presence of an instability. Electron temperatures are larger than in the field-free case due to Ohmic heating mediated by the anomalously large resistivity.

  18. Glassfrog embryos hatch early after parental desertion

    PubMed Central

    Delia, Jesse R. J.; Ramírez-Bautista, Aurelio; Summers, Kyle

    2014-01-01

    Both parental care and hatching plasticity can improve embryo survival. Research has found that parents can alter hatching time owing to a direct effect of care on embryogenesis or via forms of care that cue the hatching process. Because parental care alters conditions critical for offspring development, hatching plasticity could allow embryos to exploit variation in parental behaviour. However, this interaction of parental care and hatching plasticity remains largely unexplored. We tested the hypothesis that embryos hatch early to cope with paternal abandonment in the glassfrog Hyalinobatrachium fleischmanni (Centrolenidae). We conducted male-removal experiments in a wild population, and examined embryos' response to conditions with and without fathers. Embryos hatched early when abandoned, but extended development in the egg stage when fathers continued care. Paternal care had no effect on developmental rate. Rather, hatching plasticity was due to embryos actively hatching at different developmental stages, probably in response to deteriorating conditions without fathers. Our experimental results are supported by a significant correlation between the natural timing of abandonment and hatching in an unmanipulated population. This study demonstrates that embryos can respond to conditions resulting from parental abandonment, and provides insights into how variation in care can affect selection on egg-stage adaptations. PMID:24789892

  19. Glassfrog embryos hatch early after parental desertion.

    PubMed

    Delia, Jesse R J; Ramírez-Bautista, Aurelio; Summers, Kyle

    2014-06-22

    Both parental care and hatching plasticity can improve embryo survival. Research has found that parents can alter hatching time owing to a direct effect of care on embryogenesis or via forms of care that cue the hatching process. Because parental care alters conditions critical for offspring development, hatching plasticity could allow embryos to exploit variation in parental behaviour. However, this interaction of parental care and hatching plasticity remains largely unexplored. We tested the hypothesis that embryos hatch early to cope with paternal abandonment in the glassfrog Hyalinobatrachium fleischmanni (Centrolenidae). We conducted male-removal experiments in a wild population, and examined embryos' response to conditions with and without fathers. Embryos hatched early when abandoned, but extended development in the egg stage when fathers continued care. Paternal care had no effect on developmental rate. Rather, hatching plasticity was due to embryos actively hatching at different developmental stages, probably in response to deteriorating conditions without fathers. Our experimental results are supported by a significant correlation between the natural timing of abandonment and hatching in an unmanipulated population. This study demonstrates that embryos can respond to conditions resulting from parental abandonment, and provides insights into how variation in care can affect selection on egg-stage adaptations.

  20. Single-shot Laser-assisted Nanofabrication of Plasmonic Nanorings

    NASA Astrophysics Data System (ADS)

    Nepomnyashchii, A. V.; Kuchmizhak, A. A.; Gurbatov, S. O.; Vitrik, O. B.; Kulchin, Yu. N.

    Simple high-performing two-step technique for fabrication different functional plasmonic nanostructures including nanorods, separated and crossed nanorings, as well as more complex hybrid structures on both glass and silicon substrates was proposed. In this technique the noble metal film covering bulk glass or silicon substrates is irradiated by single tightly focused nanosecond laser pulse followed by slow polishing of the fabricated nanostructures by accelerated argon ion (Ar+) beam. Nanosecond laser pulse locally modifies its initial thickness of metal film through the initiation of ultrafast melting and subsequent hydrodynamic processes, while the following Ar+ polishing reveals only the features of its topography - plasmonic structures on the glass/Si substrate. We demonstrate that both the type and lateral size of the resulting functional plasmonic nanostructure are determined by the pulse energy, metal film thickness as well as the optical spot size, while subsequent Ar+ polishing allows varying the height of the resulting nanostructures. The proposed simple two-step high-throughput technique represents the next step towards direct lased-induced fabrication of complex functional plasmonic nanostructures and is well-suited for both large-scale fabrication of ordered arrays comprising hundreds of nanoelements and single nanostructure at a given point on the sample surface.

  1. Laser-assisted biosynthesis for noble nanoparticles production

    NASA Astrophysics Data System (ADS)

    Kukhtarev, Tatiana; Edwards, Vernessa; Kukhtareva, Nickolai; Moses, Sherita

    2014-08-01

    Extracellular Biosynthesis technique (EBS) for nanoparticles production has attracted a lot of attention as an environmentally friendly and an inexpensive methodology. Our recent research was focused on the rapid approach of the green synthesis method and the reduction of the homogeneous size distribution of nanoparticles using pulse laser application. Noble nanoparticles (NNPs) were produced using various ethanol and water plant extracts. The plants were chosen based on their biomedical applications. The plants we used were Magnolia grandiflora, Geranium, Aloe `tingtinkie', Aloe barbadensis (Aloe Vera), Eucalyptus angophoroides, Sansevieria trifasciata, Impatiens scapiflora. Water and ethanol extract, were used as reducing agents to produce the nanoparticles. The reaction process was monitored using a UV-Visible spectroscopy. NNPs were characterized by Fourier Transfer Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and the Dynamic Light Scattering technique (DLS). During the pulse laser Nd-YAG illumination (λ=1064nm, 532nm, PE= 450mJ, 200mJ, 10 min) the blue shift of the surface plasmon resonance absorption peak was observed from ~424nm to 403nm for silver NP; and from ~530nm to 520 nm for gold NPs. In addition, NNPs solution after Nd-YAG illumination was characterized by the narrowing of the surface plasmon absorption resonance band, which corresponds to monodispersed NNPS distribution. FTIR, TEM, DLS, Zeta potential results demonstrated that NNPs were surrounded by biological molecules, which naturally stabilized nanosolutions for months. Cytotoxicity investigation of biosynthesized NNPs is in progress.

  2. Laser Assisted Joining of Hybrid Polyamide-aluminum Structures

    NASA Astrophysics Data System (ADS)

    Lamberti, Christian; Solchenbach, Tobias; Plapper, Peter; Possart, Wulff

    The demand for hybrid polymer-metal structures is continuously growing due to their great potential in automotive, aerospace and packaging applications. The expected capabilities are highly diverse and include functional, chemical and mechanical as well as economical and ecological aspects. A novel laser beam joining process for hybrid polyamide-aluminum structures is reported. The spatial and temporal heat input is optimized for optimal bonding quality. At the interface it was proven that the polyamide was not decomposed as a result of excessive thermal stress. It was shown that laser or electro-chemical surface pre-treatment of the aluminum substrate has a distinctive effect on the shear strength of the joint. However, the bond quality does not correspond to a change of surface roughness. Therefore, mechanical interlocking in direct relation to surface topology of the pre-treated substrate is not the principal cause for the bonding phenomenon. Chemical analysis in terms of IR-spectroscopy has shown a physicochemical interaction based on hydrogen bonds.

  3. Characterization of ethylcellulose and hydroxypropyl methylcellulose thin films deposited by matrix-assisted pulsed laser evaporation

    NASA Astrophysics Data System (ADS)

    Palla-Papavlu, A.; Rusen, L.; Dinca, V.; Filipescu, M.; Lippert, T.; Dinescu, M.

    2014-05-01

    In this study is reported the deposition of hydroxypropyl methylcellulose (HPMC) and ethylcellulose (EC) by matrix-assisted pulsed laser evaporation (MAPLE). Both HPMC and EC were deposited on silicon substrates using a Nd:YAG laser (266 nm, 5 ns laser pulse and 10 Hz repetition rate) and then characterized by atomic force microscopy and Fourier transform infrared spectroscopy. It was found that for laser fluences up to 450 mJ/cm2 the structure of the deposited HPMC and EC polymer in the thin film resembles to the bulk. Morphological investigations reveal island features on the surface of the EC thin films, and pores onto the HPMC polymer films. The obtained results indicate that MAPLE may be an alternative technique for the fabrication of new systems with desired drug release profile.

  4. Improvement of mechanical properties by additive assisted laser sintering of PEEK

    SciTech Connect

    Kroh, M. Bonten, C.; Eyerer, P.

    2014-05-15

    The additive assisted laser sintering was recently developed at IKT: A carbon black (CB) additive is used to adjust the polymer's laser absorption behavior with the aim to improve the interconnection of sintered powder layers. In this paper a parameter study, Polyetheretherketone (PEEK) samples were prepared with different contents of carbon black and were laser sintered with varying thermal treatment. The samples were mechanically tested and investigated by optical light and transmission electron microscopy. An influence on the morphology at the border areas of particles and intersections of laser sintered layers was found. Depending on the viscosity of the raw material and CB content, different shapes of lamellae were observed. These (trans-) crystalline or polymorph structures, respectively, influence the thermal and mechanical behavior of the virgin PEEK. Moreover, the thermal treatment during the sintering process caused an improvement of mechanical properties like tensile strength and elongation at break.

  5. Multi-phonon-assisted absorption and emission in semiconductors and its potential for laser refrigeration

    SciTech Connect

    Khurgin, Jacob B.

    2014-06-02

    Laser cooling of semiconductors has been an elusive goal for many years, and while attempts to cool the narrow gap semiconductors such as GaAs are yet to succeed, recently, net cooling has been attained in a wider gap CdS. This raises the question of whether wider gap semiconductors with higher phonon energies and stronger electron-phonon coupling are better suitable for laser cooling. In this work, we develop a straightforward theory of phonon-assisted absorption and photoluminescence of semiconductors that involves more than one phonon and use to examine wide gap materials, such as GaN and CdS and compare them with GaAs. The results indicate that while strong electron-phonon coupling in both GaN and CdS definitely improves the prospects of laser cooling, large phonon energy in GaN may be a limitation, which makes CdS a better prospect for laser cooling.

  6. Surface-assisted laser desorption ionization mass spectrometry techniques for application in forensics.

    PubMed

    Guinan, Taryn; Kirkbride, Paul; Pigou, Paul E; Ronci, Maurizio; Kobus, Hilton; Voelcker, Nicolas H

    2015-01-01

    Matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) is an excellent analytical technique for the rapid and sensitive analysis of macromolecules (>700 Da), such as peptides, proteins, nucleic acids, and synthetic polymers. However, the detection of smaller organic molecules with masses below 700 Da using MALDI-MS is challenging due to the appearance of matrix adducts and matrix fragment peaks in the same spectral range. Recently, nanostructured substrates have been developed that facilitate matrix-free laser desorption ionization (LDI), contributing to an emerging analytical paradigm referred to as surface-assisted laser desorption ionization (SALDI) MS. Since SALDI enables the detection of small organic molecules, it is rapidly growing in popularity, including in the field of forensics. At the same time, SALDI also holds significant potential as a high throughput analytical tool in roadside, work place and athlete drug testing. In this review, we discuss recent advances in SALDI techniques such as desorption ionization on porous silicon (DIOS), nano-initiator mass spectrometry (NIMS) and nano assisted laser desorption ionization (NALDI™) and compare their strengths and weaknesses with particular focus on forensic applications. These include the detection of illicit drug molecules and their metabolites in biological matrices and small molecule detection from forensic samples including banknotes and fingerprints. Finally, the review highlights recent advances in mass spectrometry imaging (MSI) using SALDI techniques.

  7. Laser processing of natural stones: Study of laser cutting assisted by water saturation of marble

    NASA Astrophysics Data System (ADS)

    Kamata, Hirofumi; Kaneoka, Masaru; Tanaka, Kazuya; Sugimoto, Kenji

    2000-01-01

    Some possibilities of laser processing of natural stones were evaluated and the laser irradiation parameters suited for the following materials removal and melting processes were examined. 1) Surface roughening of granite, 2) Cutting of marble after water immersion, 3) Drilling of holes in natural stones for locating metal fittings, and 4) Surface melting and glazing of soft stones.

  8. Technique of percutaneous laser-assisted valve dilatation for valvar atresia in congenital heart disease.

    PubMed Central

    Rosenthal, E; Qureshi, S A; Kakadekar, A P; Anjos, R; Baker, E J; Tynan, M

    1993-01-01

    OBJECTIVE--To investigate the efficacy and safety of transcatheter laser-assisted valve dilatation for atretic valves in children with congenital heart disease. DESIGN--Prospective clinical study. SETTING--Supraregional paediatric cardiology centre. SUBJECTS--Eleven children (aged 1 day-11 years; weight 2.1-35.7 kg) with atresia of pulmonary (10) or tricuspid (one) valve underwent attempted laser-assisted valve dilatation as part of the staged treatment of their cyanotic heart disease. INTERVENTION--After delineating the atretic valve by angiography and/or echocardiography a 0.018 inch "hot tip" laser wire was used to perforate the atretic valve. Subsequently the valve was dilated with conventional balloon dilatation catheters up to the valve annulus diameter. RESULTS--Laser-assisted valve dilatation was successfully accomplished in nine children. In two neonates with pulmonary valve atresia, intact ventricular septum, and coexistent infundibular atresia the procedure resulted in cardiac tamponade: one died immediately and one later at surgery. During a follow up of 1-17 months (mean 11) two infants with pulmonary valve atresia and intact ventricular septum died (one with congestive cardiac failure). The remainder are either well palliated and do not require further procedures (three), or are awaiting further transcatheter or surgical procedures because of associated defects (four). CONCLUSIONS--Laser-assisted valve dilatation is a promising adjunct to surgery in this high risk group of patients. It may avoid surgery in some patients, and may reduce the number of surgical procedures in those requiring staged operations. Images PMID:8343325

  9. Three-dimensional laser-assisted processing of bioceramics

    NASA Astrophysics Data System (ADS)

    Comesaña, R.; Lusquiños, F.; del Val, J.; Malot, T.; Riveiro, A.; Quintero, F.; Boutinguiza, M.; Aubry, P.; Pou, J.

    The study of calcium phosphate bioceramics processing by rapid prototyping based on laser cladding was tackled in this work. This technique shows a great potential to provide a three-dimensional tailored implant adapted to the specific problem of each patient. Working window to produce stable geometrical features and repeatable microstructures was established by real time process monitoring and characterization of the processed material. The relationships between the processing parameters and the obtained properties are discussed, in addition to the biological behaviour of the produced parts. The obtained calcium phosphate phases (oxyapatite, tricalcium phosphate, tetracalcium phosphate and amorphous calcium phosphate) are found to favorably influence the degradability of the precursor hydroxyapatite in Tris-HCl buffer which is a good sign of the favorable behavior of this type of materials when implanted 'in vivo'.

  10. UV-laser-assisted liquid phase fluorination of PMMA

    NASA Astrophysics Data System (ADS)

    Wochnowski, C.; Di Ferdinando, M.; Giolli, C.; Vollertsen, F.; Bardi, U.

    2007-10-01

    Polymethylmethacrylate (PMMA) substrate was covered with liquid 1,2,3,5-tetrafluorobenzene by spin coating. Then the sample was irradiated by a KrF-excimer laser ( λ = 248 nm). Thus, fluorine is released from the fluorine-containing precursor diffusing into the polymeric substrate material where it is expected to substitute the hydrogen atoms of the polymeric molecule and form a water-repellent (hydrophobic) fluorinated polymer. After drying out the polymeric substrate, the sample surface was investigated by SEM, EDX, XPS and contact angle measurement method in order to determine the fluorine content and the wettability of the treated polymeric surface as well as the substitution sites inside the polymeric molecule. The measurements indicate some chemically bonded fluorine at the top of the sample layer. A UV-photochemical fluorination mechanism is proposed based on the XPS spectra evaluation.

  11. Comparison of fiber delivered CO2 laser and electrocautery in transoral robot assisted tongue base surgery.

    PubMed

    Karaman, Murat; Gün, Taylan; Temelkuran, Burak; Aynacı, Engin; Kaya, Cem; Tekin, Ahmet Mahmut

    2017-02-11

    To compare intra-operative and post-operative effectiveness of fiber delivered CO2 laser to monopolar electrocautery in robot assisted tongue base surgery. Prospective non-randomized clinical study. Twenty moderate to severe obstructive sleep apnea (OSA) patients, non-compliant with Continuous Positive Airway Pressure (CPAP), underwent Transoral Robotic Surgery (TORS) using the Da Vinci surgical robot in our University Hospital. OSA was treated with monopolar electrocautery in 10 patients, and with flexible CO2 laser fiber in another 10 patients. The following parameters in the two sets are analyzed: Intraoperative bleeding that required cauterization, robot operating time, need for tracheotomy, postoperative self-limiting bleeding, length of hospitalization, duration until start of oral intake, pre-operative and post-operative minimum arterial oxygen saturation, pre-operative and post-operative Epworth Sleepiness Scale score, postoperative airway complication and postoperative pain. Mean follow-up was 12 months. None of the patients required tracheotomy and there were no intraoperative complications related to the use of the robot or the CO2 laser. The use of CO2 laser in TORS-assisted tongue base surgery resulted in less intraoperative bleeding that required cauterization, shorter robot operating time, shorter length of hospitalization, shorter duration until start of oral intake and less postoperative pain, when compared to electrocautery. Postoperative apnea-hypopnea index scores showed better efficacy of CO2 laser than electrocautery. Comparison of postoperative airway complication rates and Epworth sleepiness scale scores were found to be statistically insignificant between the two groups. The use of CO2 laser in robot assisted tongue base surgery has various intraoperative and post-operative advantages when compared to monopolar electrocautery.

  12. A noncontact laser-guided system for endoscopic computer-assisted sinus surgery.

    PubMed

    Khan, Martin; Kosmecki, Barotsz; Reutter, Andreas; Ozbek, Christopher; Keeve, Erwin; Olze, Heidi

    2012-09-01

    The limited size of the nose leads to frequent instrument changes in navigated endonasal sinus surgery. Tracked instruments provide limited accuracy, and the pointer gives no navigation information during tissue removal. To overcome information loss, laser triangulation was integrated into navigation information. Accuracy and reliability of the laser-assisted distance-measuring system were evaluated within the distance of 0 and 20 mm. System accuracy of the laser endoscope was compared with a standard pointer using registration via bone screws and surface matching. Accuracy of the laser was 0.12 mm ± 0.12 mm with a reliability of 0.2 mm. The system accuracy of the laser endoscope was 0.59 mm ± 0.16 mm using bone screw registration and 0.64 mm ± 0.22 mm using surface matching. Additionally, laser endoscope is more accurate compared with the pointer using bone screw registration. Overall, navigation information was successfully integrated into an endoscope by laser triangulation with encouraging results.

  13. Magnetic-Field-Assisted Terahertz Quantum Cascade Laser Operating up to 225 K

    NASA Technical Reports Server (NTRS)

    Wade, A.; Fedorov, G.; Smirnov, D.; Kumar, S.; Williams, B. S.; Hu, Q.; Reno, J. L.

    2008-01-01

    Advances in semiconductor bandgap engineering have resulted in the recent development of the terahertz quantum cascade laser1. These compact optoelectronic devices now operate in the frequency range 1.2-5 THz, although cryogenic cooling is still required2.3. Further progress towards the realization of devices operating at higher temperatures and emitting at longer wavelengths (sub-terahertz quantum cascade lasers) is difficult because it requires maintaining a population inversion between closely spaced electronic sub-bands (1 THz approx. equals 4 meV). Here, we demonstrate a magnetic-field-assisted quantum cascade laser based on the resonant-phonon design. By applying appropriate electrical bias and strong magnetic fields above 16 T, it is possible to achieve laser emission from a single device over a wide range of frequencies (0.68-3.33 THz). Owing to the suppression of inter-landau-level non-radiative scattering, the device shows magnetic field assisted laser action at 1 THz at temperatures up to 215 K, and 3 THz lasing up to 225 K.

  14. Five-year comparative study on conventional and laser-assisted therapy of periimplantitis and periodontitis

    NASA Astrophysics Data System (ADS)

    Bach, Georg; Neckel, Claus P.

    2000-03-01

    Numerous groups have recommended the use of the diode laser to decontaminate infected root and implant surfaces. The aim of this study was to show the outcome after laser assisted and conventional therapy of periimplantitis and periodontitis administering approved treatment protocols. Between 1994 and 1999 a total of 50 patients with periimplantitis (20) and periodontitis (30) were treated in two groups each. Clinical, microbiological and radiographic evaluation was performed before and 6, 12, 24, 36, 48 and 60 months after treatment. In addition to the conventional treatment protocol, flap surgery, the tooth or implant surface was decontaminated with a 810 nm diode laser using 1 Watt output for 20 sec (CW mode). All accessible surfaces were decontaminated at the follow up dates. In the periimplantitis group recurrence of the marker bacteria was higher and faster over time for the conventionally operated patients. Also the clinical and radiographic reevaluation showed significantly better results. The laser group of the periodontitis patients also showed significantly better outcome in terms of clinical evaluation, microbiological counts, radiographic evaluation and tooth loss. In comparison to other long term studies our results for the conventional therapy were adequate, the laser assisted therapy brought up significantly better and reproducible results.

  15. Liquid-assisted laser ablation of advanced ceramics and glass-ceramic materials

    NASA Astrophysics Data System (ADS)

    Garcia-Giron, A.; Sola, D.; Peña, J. I.

    2016-02-01

    In this work, results obtained by laser ablation of advanced ceramics and glass-ceramic materials assisted by liquids are reported. A Q-switched Nd:YAG laser at its fundamental wavelength of 1064 nm with pulse-width in the nanosecond range was used to machine the materials, which were immersed in water and ethylene glycol. Variation in geometrical parameters, morphology, and ablation yields were studied by using the same laser working conditions. It was observed that machined depth and removed volume depended on the thermal, optical, and mechanical features of the processed materials as well as on the properties of the surrounding medium in which the laser processing was carried out. Variation in ablation yields was studied in function of the liquid used to assist the laser process and related to refractive index and viscosity. Material features and working conditions were also related to the obtained results in order to correlate ablation parameters with respect to the hardness of the processed materials.

  16. Plasma corticosterone in American kestrel siblings: effects of age, hatching order, and hatching asynchrony.

    PubMed

    Love, Oliver P; Bird, David M; Shutt, Laird J

    2003-04-01

    Although it is well documented that hatching asynchrony in birds can lead to competitive and developmental hierarchies, potentially greatly affecting growth and survival of nestlings, hatching asynchrony may also precipitate modulations in neuroendocrine development or function. Here we examine sibling variation in adrenocortical function in postnatally developing, asynchronously hatching American kestrels (Falco sparverius) by measurements of baseline and stress-induced levels of corticosterone at ages 10, 16, 22, and 28 days posthatching. There was a significant effect of hatching order on both baseline and stress-induced corticosterone levels during development and these effects grew stronger through development. First-hatched chicks exhibited higher baseline levels than later-hatched chicks throughout development and higher stress-induced levels during the latter half of development. Furthermore, there was significant hatching span (difference in days between first- and last-hatched chicks) x hatching order interaction on both baseline and stress-induced corticosterone levels during development. Hatching span was also positively correlated with both measures of corticosterone and body mass in first-hatched chicks, but was negatively correlated with these factors through most of the development in last-hatched chicks. It is known that hatching asynchrony creates mass and size hierarchies within kestrel broods and we suggest that hierarchies in adrenocortical function among siblings may be one physiological mechanism by which these competitive hierarchies are maintained.

  17. Studies on surface pitting during laser assisted removal of translucent ellipsoidal particulates from metallic substrates

    NASA Astrophysics Data System (ADS)

    Sugathan, Bijoy; Nilaya, J. Padma; Pillai, V. P. Mahadevan; Biswas, D. J.

    2017-04-01

    We report on the manifestation of field enhanced surface absorption during laser assisted removal of translucent particulates of ellipsoidal geometry from a metallic substrate surface. The surface pitting caused due to this effect has been experimentally probed as a function of the ratio of minor to major axis of the ellipsoid and the behavioral trend has been theoretically interpreted by invoking the principle of geometrical optics. The study also includes the effect of fluence and wavelength of the incident coherent radiation on the surface pitting. Probing of the surface topography has helped gain insight into the formation of multiple pits by a single particulate following its removal post laser exposure.

  18. Experimental and theoretical evaluation of the laser-assisted machining of silicon nitride

    NASA Astrophysics Data System (ADS)

    Rozzi, Jay Christopher

    This study focused on the experimental and theoretical evaluation of the laser assisted machining (LAM) of silicon nitride ceramics. A laser assisted machining facility was constructed whose main components consist of a COsb2 laser and a CNC lathe. Surface temperature histories were first measured and compared to a transient, three-dimensional numerical simulation for a rotating silicon nitride workpiece heated by a translating laser for ranges of the workpiece rotational and laser-translation speeds, as well as the laser beam diameter and power. Excellent agreement was obtained between the experimental and predicted temperature histories. Laser assisted machining experiments on silicon nitride ceramic workpieces were completed for a wide range of operating conditions. Data for cutting forces and surface temperature histories illustrated that the lower bound for the avoidance of cutting tool and/or workpiece fracture for LAM is defined by the YSiAlON glass transition temperature (920-970sp°C). As temperatures near the cutting tool increase to values above the glass transition temperature range, the glassy phase softened, facilitating plastic deformation and, correspondingly, the production of semi-continuous or continuous chips. The silicon nitride machined workpiece surface roughness (Rsb{a}=0.39\\ mum) for LAM at the nominal operating condition was nearly equivalent to a value associated with the grinding of silicon nitride using a diamond wheel (Rsb{a}=0.2\\ mum). By examining the machined surfaces and chips, it was shown that LAM does not produce detectable sub-surface cracking or significant silicon nitride microstructure alteration, respectively. A transient, three-dimensional numerical heat transfer model of laser assisted machining was constructed, which includes a preheat phase and material removal, with the associated changes in the workplace geometry. Excellent agreement was obtained between the measured and predicted temperature histories. The strong

  19. The Need for Speed in Matrix-Assisted Laser Desorption/Ionization Imaging Mass Spectrometry

    PubMed Central

    Prentice, Boone M.; Caprioli, Richard M.

    2016-01-01

    Imaging mass spectrometry (IMS) has emerged as a powerful analytical tool enabling the direct molecular mapping of many types of tissue. Specifically, matrix-assisted laser desorption/ ionization (MALDI) represents one of the most broadly applicable IMS technologies. In recent years, advances in solid state laser technology, mass spectrometry instrumentation, computer technology, and experimental methodology have produced IMS systems capable of unprecedented data acquisition speeds (>50 pixels/second). In applications of this technology, throughput is an important consideration when designing an IMS experiment. As IMS becomes more widely adopted, continual improvements in experimental setups will be important to address biologically and clinically relevant time scales. PMID:27570788

  20. Laser-assisted modification of polymers for microfluidic, micro-optics, and cell culture applications

    NASA Astrophysics Data System (ADS)

    Pfleging, W.; Adamietz, R.; Brückner, H. J.; Bruns, M.; Welle, A.

    2007-02-01

    Laser-assisted patterning of polymers is investigated for the direct fabrication of polymeric lab-on-a-chip devices in microsystem technology for capillary electrophoresis chips in bio-analytical applications. In many cases the laser process induces a chemical, physical and topographical change in the laser treated surface. This material modification significantly influences the lab-on-a-chip-functionalities. We will present our current research results in laser-assisted modification of polystyrene (PS) and polymethylmethacrylate (PMMA) with respect to applications in micro-optics, micro-fluidics and cell culture applications. For this purpose the refractive index change, the wettability and the adsorption of proteins and the adhesion of animal cells were investigated as function of laser- and processing parameters. The possible change of surface chemistry was characterized by X-ray photoelectron spectroscopy. The local UV-laser-assisted formation of chemical structures suitable for improved cell adhesion was realized on two- and three-dimensional PS and polycarbonate (PC) surfaces. Above and below the laser ablation threshold two different mechanisms were detected. In one case the produced debris was responsible for improved cell adhesion, while in the other case a photolytical activation of the polymer surface including a subsequent oxidization in oxygen or ambient air leads to a highly localized alteration of protein adsorption from cell culture media and increased cell adhesion. The highly localized control of wettability on polymeric surfaces was investigated for PS and PMMA. In the case of PS the dynamic advancing contact angle could be adjusted between 2° and 150°. This was possible for a suitable exposure dose and an appropriate choice of processing gas (helium or oxygen). A similar but not so significant effect was observed for PMMA below the laser ablation threshold. For PMMA the dynamic advancing contact angle could be adjusted between nearly 50° and

  1. Quantitative analysis of biopolymers by matrix-assisted laser desorption

    SciTech Connect

    Tang, K.; Allman, S.L.; Jones, R.B.; Chen, C.H. )

    1993-08-01

    During the past few years, major efforts have been made to use mass spectrometry to measure biopolymers because of the great potential benefit to biological and medical research. Although the theoretical details of laser desorption and ionization mechanisms of MALDI are not yet fully understood, several models have been presented to explain the production of large biopolymer ions. In brief, it is very difficult to obtain reliable measurements of the absolute quantity of analytes by MALDI. If MALDI is going to become a routine analytical tool, it is obvious that quantitative measurement capability must be pursued. Oligonucleotides and protein samples used in this work were purchased from commercial sources. Nicotinic acid was used as matrix for both types of biopolymers. From this experiment, it is seen that it is difficult to obtain absolute quantitative measurements of biopolymers using MALDI. However, internal calibration with molecules having similar chemical properties can be used to resolve these difficulties. Chemical reactions between biopolymers must be avoided to prevent the destruction of the analyte materials. 10 refs., 8 figs.

  2. Plume expansion dynamics of matrix-assisted laser desorption ionization.

    PubMed

    Liang, Chi-Wei; Lee, Chih-Hao; Lee, Yuan-Tseh; Ni, Chi-Kung

    2011-11-04

    High-resolution angular and velocity distributions for neutral analytes (tryptophan and poly-tryptophan) and matrix (2,4,6-trihydroxyacetophenon, THAP) are measured by using 355 nm laser desorption. The information suggests that two separate mechanisms dominate the angular and velocity distributions at the beginning and before the end of desorption. A molecular jet-like isentropic expansion dominates the plume expansion at the beginning of desorption. This only occurs at high surface temperature, thus resulting in a large velocity normal to the surface and a very narrow angular distribution. Most of the analytes are produced under these conditions. Before the end of desorption, the surface temperature decreases and the mechanism of thermal desorption at low vapor pressure takes over. The velocities become small and the angular distribution is close to cosθ. Only a very small amount of analytes are generated under these conditions. Compared to tryptophan, poly-tryptophan has a much narrower angular distribution, thereby suggesting that it is only produced at the higher surface temperatures.

  3. Oxygen-assisted multipass cutting of carbon fiber reinforced plastics with ultra-short laser pulses

    SciTech Connect

    Kononenko, T. V.; Komlenok, M. S.; Konov, V. I.; Freitag, C.; Onuseit, V.; Weber, R.; Graf, T.

    2014-03-14

    Deep multipass cutting of bidirectional and unidirectional carbon fiber reinforced plastics (CFRP) with picosecond laser pulses was investigated in different static atmospheres as well as with the assistance of an oxygen or nitrogen gas flow. The ablation rate was determined as a function of the kerf depth and the resulting heat affected zone was measured. An assisting oxygen gas flow is found to significantly increase the cutting productivity, but only in deep kerfs where the diminished evaporative ablation due to the reduced laser fluence reaching the bottom of the kerf does not dominate the contribution of reactive etching anymore. Oxygen-supported cutting was shown to also solve the problem that occurs when cutting the CFRP parallel to the fiber orientation where a strong deformation and widening of the kerf, which temporarily slows down the process speed, is revealed to be typical for processing in standard air atmospheres.

  4. [The pros and cons of femtosecond laser-assisted cataract surgery].

    PubMed

    Li, Z H; Ye, Z

    2016-02-01

    Femtosecond laser-assisted cataract surgery (FLACS) is known as an innovative new technology. Compared with traditional surgical approach, FLACS is more accurate, more predictable and less energy used. However, in the current stage of development, there still may be intraoperative and postoperative complications, or even serious complications. FLACS has obvious advantages in certain surgical steps, but there are still clear disadvantages, so it still cannot completely replace the traditional phacoemulsification surgery.

  5. Microcapillary sign of flap alignment in femtosecond laser-assisted in situ keratomileusis

    PubMed Central

    Fawzy, Fathy; Wahba, Sherine S; Fawzy, Nader

    2016-01-01

    We present an observational sign that ensures perfect alignment during femtosecond laser-assisted in situ keratomileusis (FS LASIK). Alignment is assured when a microsponge is used to dry the flap and the area of dryness exceeds the area of direct touch of the microsponge. The area might even reach the whole circumference of the flap at the first touch. This sign of alignment can be explained by microcapillary action. This sign was not elicited in flaps created by a microkeratome. PMID:27799731

  6. Metal-Assisted Laser-Induced Gas Plasma for the Direct Analysis of Powder Using Pulse CO2 Laser

    NASA Astrophysics Data System (ADS)

    Khumaeni, A.; Lie, Z. S.; Kurniawan, K. H.; Kagawa, K.

    2017-01-01

    Analysis of powder samples available in small quantities has been carried out using metal-assisted gas plasma by utilizing a transversely excited atmospheric (TEA) CO2 laser. The powder was homogeneously mixed with Si grease, and the mixed powder was painted on a metal subtarget. When a TEA CO2 laser was directly focused on the metal subtarget at atmospheric pressure of He gas, a high-temperature He gas plasma was induced. It is assumed that the powder particles were vaporized to be effectively atomized and excited in the gas plasma region. This method has been employed in the rapid analyses of elements in organic and inorganic powder samples present in small quantities. Detection of trace elements of Cr and Pb has been successfully made by using the supplement powder and loam soil, respectively. The detection limits of Pb in loam soil were approximately 20 mg/kg.

  7. Tailored surface-enhanced Raman nanopillar arrays fabricated by laser-assisted replication for biomolecular detection using organic semiconductor lasers.

    PubMed

    Liu, Xin; Lebedkin, Sergei; Besser, Heino; Pfleging, Wilhelm; Prinz, Stephan; Wissmann, Markus; Schwab, Patrick M; Nazarenko, Irina; Guttmann, Markus; Kappes, Manfred M; Lemmer, Uli

    2015-01-27

    Organic semiconductor distributed feedback (DFB) lasers are of interest as external or chip-integrated excitation sources in the visible spectral range for miniaturized Raman-on-chip biomolecular detection systems. However, the inherently limited excitation power of such lasers as well as oftentimes low analyte concentrations requires efficient Raman detection schemes. We present an approach using surface-enhanced Raman scattering (SERS) substrates, which has the potential to significantly improve the sensitivity of on-chip Raman detection systems. Instead of lithographically fabricated Au/Ag-coated periodic nanostructures on Si/SiO2 wafers, which can provide large SERS enhancements but are expensive and time-consuming to fabricate, we use low-cost and large-area SERS substrates made via laser-assisted nanoreplication. These substrates comprise gold-coated cyclic olefin copolymer (COC) nanopillar arrays, which show an estimated SERS enhancement factor of up to ∼ 10(7). The effect of the nanopillar diameter (60-260 nm) and interpillar spacing (10-190 nm) on the local electromagnetic field enhancement is studied by finite-difference-time-domain (FDTD) modeling. The favorable SERS detection capability of this setup is verified by using rhodamine 6G and adenosine as analytes and an organic semiconductor DFB laser with an emission wavelength of 631.4 nm as the external fiber-coupled excitation source.

  8. Microhardness of demineralized enamel following home bleaching and laser-assisted in office bleaching

    PubMed Central

    Ghanbarzadeh, Majid; Akbari, Majid; Hamzei, Haniye

    2015-01-01

    Background There is little data regarding the effect of tooth whitening on microhardness of white spot lesions. This study was conducted to investigate the effect of home-bleaching and laser-assisted in-office bleaching on microhardness of demineralized enamel. Material and Methods Forty bovine incisors were selected and immersed in a demineralizing solution for 12 weeks to induce white spot lesions. Enamel blocks were prepared and randomly assigned to two groups of 20 each. The first group underwent home bleaching with 15% carbamide peroxide which was applied for 8 hours a day over a period of 15 days. In the second group, in-office bleaching was performed by 40% hydrogen peroxide and powered by irradiation from an 810 nm gallium-aluminum-arsenide (GaAlAs) diode laser (CW, 2W). This process was performed for 3 sessions every seven days, in 15 days. The specimens were stored in Fusayama Meyer artificial saliva during the experiment. Surface microhardness was assessed before and after the bleaching therapies in both groups. Results Microhardness decreased significantly following both home bleaching and laser-assisted in-office bleaching (p<0.05). There were no significant differences in hardness values among the two groups either before (p=0.131) or after (p=0.182) the bleaching procedures. Conclusions Tooth whitening through home bleaching or laser-assisted in-office bleaching can result in a significant reduction in microhardness of white spot lesions. Therefore, it is suggested to take protective measures on bleached demineralized enamel. Key words:White spot lesion, bleaching, laser, microhardness, demineralized enamel, home bleaching, in-office bleaching. PMID:26330939

  9. Absorbing film assisted laser induced forward transfer of fungi (Trichoderma conidia)

    NASA Astrophysics Data System (ADS)

    Hopp, B.; Smausz, T.; Antal, Zs.; Kresz, N.; Bor, Zs.; Chrisey, D.

    2004-09-01

    We present an investigation on absorbing film assisted laser induced forward transfer (AFA-LIFT) of fungus (Trichoderma) conidia. A KrF excimer laser beam [λ =248nm,FWHM=30ns (FWHM, full width at half maximum)] was directed through a quartz plate and focused onto its silver coated surface where conidia of the Trichoderma strain were uniformly spread. The laser fluence was varied in the range of 0-2600mJ/cm2 and each laser pulse transferred a pixel of target material. The average irradiated area was 8×10-2mm2. After the transfer procedure, the yeast extract medium covered glass slide and the transferred conidia patterns were incubated for 20 h and then observed using an optical microscope. The transferred conidia pixels were germinated and the areas of the culture medium surfaces covered by the pixels were evaluated as a function of laser fluence. As the laser fluence was increased from 0 to 355mJ/cm2 the transferred and germinated pixel area increased from 0 to 0.25mm2. Further increase in fluence resulted in a drastic decrease down to an approximately constant value of 0.06mm2. The yield of successful transfer by AFA-LIFT and germination was as much as 75% at 355mJ/cm2. The results prove that AFA-LIFT can successfully be applied for the controlled transfer of biological objects.

  10. Polygonal pits on silicon surfaces that are created by laser-assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Saito, Mitsunori; Kimura, Saori

    2017-02-01

    Laser-assisted chemical etching was conducted for creating periodic textures on silicon surfaces. Silicon plates with the (111) surface orientation were immersed in an aqueous solution of potassium hydroxide, and a pulsed laser beam (532 nm wavelength, 5 ns duration, 10 pulse/s) was irradiated on their surface to promote anisotropic etching. The laser beam was patterned by using a glass capillary plate that contained a hexagonal array of micropores (10 μ m diameter, 12 m period). The focused beam projected the hexagonal image on the silicon surface, creating bright spots of 4 μ m period. During the laser irradiation process of 3 min, both laser-induced ablation and chemical etching took place at these bright spots. After stop of laser irradiation, the chemical etching progressed further, and consequently, a periodic array of triangular or hexagonal pits emerged on the silicon surface. The direction of the triangular pits changed by rotation of the silicon plate. When a silicon plate with the (100) surface orientation was used, diamond or rectangular pits were created on its surface. The mechanism of this polygonal texturing was explained by using the normal and intersecting vectors of the (100), (110), and (111) planes that exhibited different etching rates.

  11. Matrix-assisted laser transfer of electronic materials for direct-write applications

    NASA Astrophysics Data System (ADS)

    Auyeung, Raymond C. Y.; Wu, H. D.; Modi, R.; Pique, Alberto; Fitz-Gerald, J. M.; Young, Henry D.; Lakeou, Samuel; Chung, Russell; Chrisey, Douglas B.

    2000-11-01

    A novel laser-based direct-write technique, called Matrix Assisted Pulsed Laser Evaporation Direct Write (MAPLE-DW), has been developed for the rapid prototyping of electronic devices. MAPLE-DW is a maskless deposition process operating under ambient conditions which allows for the rapid fabrication of complex patterns of electronic materials. The technique utilizes a laser transparent substrate with one side coated with a matrix of the materials of interest mixed with an organic vehicle. The laser is focused through the transparent substrate onto the matrix coating which aids in transferring the materials of interest to an acceptor substrate placed parallel to the matrix surface. With MAPLE-DW, diverse materials including metals, dielectrics, ferroelectrics, ferrites and polymers have been transferred onto various acceptor substrates. The capability for laser-modifying the surface of the acceptor substance and laser-post-processing the transferred material has been demonstrated as well. This simple yet powerful technique has been used to fabricate passive thin film electronic components such as resistors, capacitors and metal lines with good functional properties. An overview of these key results along with a discussion of their materials and properties characterization will be presented.

  12. Laser-assisted nanomaterial deposition, nanomanufacturing, in situ monitoring and associated apparatus

    DOEpatents

    Mao, Samuel S; Grigoropoulos, Costas P; Hwang, David J; Minor, Andrew M

    2013-11-12

    Laser-assisted apparatus and methods for performing nanoscale material processing, including nanodeposition of materials, can be controlled very precisely to yield both simple and complex structures with sizes less than 100 nm. Optical or thermal energy in the near field of a photon (laser) pulse is used to fabricate submicron and nanometer structures on a substrate. A wide variety of laser material processing techniques can be adapted for use including, subtractive (e.g., ablation, machining or chemical etching), additive (e.g., chemical vapor deposition, selective self-assembly), and modification (e.g., phase transformation, doping) processes. Additionally, the apparatus can be integrated into imaging instruments, such as SEM and TEM, to allow for real-time imaging of the material processing.

  13. Laser-assisted gingivectomy in pediatric patients: a novel alternative treatment.

    PubMed

    Gontiya, G; Bhatnagar, S; Mohandas, U; Galgali, S R

    2011-01-01

    Gingival enlargement is quite a common pathology in pediatric patients and may be inflammatory, noninflammatory, or a combination of both. Idiopathic gingival fibromatosis, although rare, is a slowly progressive benign enlargement that affects the marginal gingiva, attached gingival, and interdental papilla. The fibromatosis may potentially cover the exposed tooth surfaces, causing esthetic and functional problems. The treatment of gingival fibromatosis is essential because it causes difficulties with mastication, speech problems, mispositioning of teeth, esthetic effects, and psychological difficulties for the patient. Traditional gingivectomy procedures have been a challenge for dentists who confront issues of patient cooperation and discomfort. In the last decade, laser procedures in oral cavity had shown many optimum effects in both hard and soft tissue procedures. Laser soft-tissue surgery has been shown to be well accepted by children. The following case report describes a laser-assisted gingivectomy procedure performed on a 13-year-old female.

  14. films crystallized on glass and platinized substrates by laser-assisted annealing at room temperature

    NASA Astrophysics Data System (ADS)

    Silva, J. P. B.; Khodorov, A.; Almeida, A.; Agostinho Moreira, J.; Pereira, M.; Gomes, M. J. M.

    2014-09-01

    In this work, Ba0.8Sr0.2TiO3 (BST) films were grown by pulse laser ablation on bare glass and platinized substrates. The crystalline phase was obtained with the help of laser-assisted annealing (LAA) at room temperature, in air environment. By adjusting LAA conditions, like frequency of the laser and number of shots, we were able to grow crack-free BST thin films with pure perovskite phase on bare glass and platinized substrates. The crystalline layer was found to be the same irrespective of the substrate used, c.a. 250 nm thick. The electric characteristics of the amorphous and LAA crystalline BST films deposited on platinized substrate were further studied and analyzed. While in amorphous films it was found that the oxygen defects are responsible for conduction, in LAA films the amorphous/crystalline interface layer plays an important role in current leakage.

  15. Selective tuning of high-Q silicon photonic crystal nanocavities via laser-assisted local oxidation.

    PubMed

    Chen, Charlton J; Zheng, Jiangjun; Gu, Tingyi; McMillan, James F; Yu, Mingbin; Lo, Guo-Qiang; Kwong, Dim-Lee; Wong, Chee Wei

    2011-06-20

    We examine the cavity resonance tuning of high-Q silicon photonic crystal heterostructures by localized laser-assisted thermal oxidation using a 532 nm continuous wave laser focused to a 2.5 μm radius spot-size. The total shift is consistent with the parabolic rate law. A tuning range of up to 8.7 nm is achieved with ∼ 30 mW laser powers. Over this tuning range, the cavity Qs decreases from 3.2×10(5) to 1.2×10(5). Numerical simulations model the temperature distributions in the silicon photonic crystal membrane and the cavity resonance shift from oxidation.

  16. Graphene matrix for signal enhancement in ambient plasma assisted laser desorption ionization mass spectrometry.

    PubMed

    Chang, Cuilan; Li, Xianjiang; Bai, Yu; Xu, Gege; Feng, Baosheng; Liao, Yiping; Liu, Huwei

    2013-09-30

    In this work, the signal intensity of ambient plasma assisted laser desorption ionization mass spectrometry (PALDI-MS) was significantly increased with graphene as matrix. The graphene functions as a substrate to trap analytes, absorb energy from the visible laser irradiation and transfer energy to the analytes to facilitate the laser desorption process. The desorbed analytes are further ionized by helium plasma and analyzed by MS. Compared with a traditional organic matrix, α-cyano-4-hydroxycinnamic acid (CHCA), graphene exhibited much higher desorption efficiency for most of the compounds benefitting from the strong optical absorption at 532nm. The performance has been confirmed by the facile analysis of more than forty compounds with various structures. Additionally, this method was successfully applied to distinguish three kinds of Chinese tea leaves by detecting the endogenous caffeine and theanine, which proved the utility, facility and convenience of this method for rapid screening of main components in real samples.

  17. Spectrum of temperature pulsations of the melt in gas-assisted cutting with fiber laser

    NASA Astrophysics Data System (ADS)

    Dubrov, Alexander V.; Zavalov, Yury N.; Dubrov, Vladimir D.; Grezev, Anatoly N.; Grezev, Nikolay V.; Makarova, Elena S.; Dubrovin, Nickolay G.

    2012-09-01

    Measurements of the temperature behavior in the zone of action of the laser-radiation on the molten metal have been performed using multichannel pyrometer. Measurements were carried out for test cutting of a 3-mm mild-steel plate with several values of cutting speed and pressure of assist gas (oxygen), using an 1800-watt Ytterbium fiber laser. It is shown that fluctuations of temperature are related to local melt's surface deformations due to unequal radiation absorption; thus the noise spectrum of temperature fluctuations reflects turbulent surface deformation caused by gas jet and capillary waves. The maximum density of turbulent energy dissipation ε depends on cutting conditions: its value rises with increasing cutting velocity and oxygen pressure in a described range of parameters. The maximum of ε is localized near depth of (1.2…1.5) mm along the cutting front. We can distinguish the specific radiation pulsation spectrum of laser cutting from other processes of radiation affection to the sample, including unwanted degrading of the quality of technological operations. The spectrum of capillary waves on the melt's surface is formed under the effect of assisted gas jet and has a function of ω-3, ω is cycle frequency. The results of this investigation can be useful for the development of monitoring and quality-control systems for the laser-cutting process.

  18. Matrix assisted pulsed laser deposition of light emitting polymer thin films

    NASA Astrophysics Data System (ADS)

    Fitz-Gerald, J. M.; Jennings, G.; Johnson, R.; Fraser, C. L.

    2005-02-01

    Matrix assisted laser processing allows for the deposition of functional and fragile materials with a minimum of breakdown and decomposition. In this communication we report on light emitting thin films of ruthenium tris(bipyridine)-centered star-shaped poly(methyl methacrylate), Ru(bpyPMMA2)3(PF6)2, grown by matrix assisted pulsed laser deposition. A pulsed excimer laser (KrF) operating at 248 nm was used for all experiments. Due to the absorption at 248 nm and the solubility characteristics of [Ru(bpyPMMA2)3](PF6)2, dimethoxy-ethane (DME) was used as a solvent [1]. Dilute solutions (2 wt. %) of [Ru(bpyPMMA2)3](PF6)2 and DME were flash frozen in liquid nitrogen producing a solid target. Thin films ranging from 20 to 100 nm were grown on Si in an Ar atmosphere at 200 mTorr at a laser fluence of 0.04 J/cm2. The deposited materials were characterized by proton nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC) equipped with refractive index (RI), and ultraviolet/visible (UV/vis) detection.

  19. Effects of Laser Energy and Wavelength on the Analysis of LiFePO4 Using Laser Assisted Atom Probe Tomography

    SciTech Connect

    Santhanagopalan, Dhamodaran; Schreiber, Daniel K.; Perea, Daniel E.; Martens, Rich; Janssen, Yuri; Kalifah, Peter; Meng, Ying S.

    2015-01-21

    The effects of laser wavelength (355 nm and 532 nm) and laser pulse energy on the quantitative accuracy of atom probe tomography (APT) examinations of LiFePO4 (LFP) are considered. A systematic investigation of ultraviolet (UV, 355 nm) and green (532 nm) laser assisted APT of LFP has revealed distinctly different behaviors. With the use of UV laser the major issue was identified as the preferential loss of oxygen (up to 10 at. %) while other elements (Li, Fe and P) were observed to be close to nominal ratios. Lowering the laser energy per pulse to 1 pJ increased the observed oxygen concentration to near its correct stoichiometry and was well correlated with systematically higher concentrations of 16O2+ ions. This observation supports the premise that lower laser energies lead to a higher probability of oxygen molecule ionization. Conversely, at higher laser energies the resultant lower effective electric field reduces the probability of oxygen molecule ionization. Green laser assisted field evaporation led to the selective loss of Li (~50% deficiency) and correct ratios of the remaining elements, including the oxygen concentration. The loss of Li is explained by selective dc evaporation of lithium between laser pulses and relatively negligible oxygen loss as neutrals during green-laser pulsing. Lastly, plotting of multihit events on a Saxey plot for the straight-flight path data (green laser only) revealed a surprising dynamic recombination process for some molecular ions mid-flight.

  20. p-Type zinc oxide films grown by infrared-light-assisted pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Hiraide, Toshihiro; Kurumi, Satoshi; Suzuki, Kaoru

    2013-03-01

    In this paper, ZnO films were grown on sapphire (0001) substrates by infrared-light-assisted pulsed-laser deposition (IRA-PLD). In addition, a nitrogen-plasma-assisted (PA-N) system was utilized for effectively doping the acceptor by radio frequency induction coupled plasma (RF-ICP). The effect of IRA-PLD and PA-N systems was investigated by studying the difference in substrate temperature with and without plasma assistance. We found that ZnO films exhibit no exciton emission with PA-N at a high temperature and that an increase in the substrate temperature yields ZnO films with a (002) and c-axis preferred orientation in a nitrogen (N2) gas atmosphere. ZnO films are changed from n-type to p-type at a substrate temperature of 673 K by IRA-PLD with an N2 background atmosphere.

  1. En face optical coherence tomography investigation of apical microleakage after laser-assisted endodontic treatment.

    PubMed

    Todea, Carmen; Balabuc, Cosmin; Sinescu, Cosmin; Filip, Laura; Kerezsi, Cristina; Calniceanu, Mircea; Negrutiu, Meda; Bradu, Adrian; Hughes, Michael; Podoleanu, Adrian Gh

    2010-09-01

    The aim of our study was to evaluate the potential of en face optical coherence tomography (OCT) for the detection of apical microleakage after 980 nm and 1,064 nm laser-assisted endodontic treatment. Ninety, human, single-rooted teeth with one straight root canal and closed apices were used. All roots were prepared biomechanically to the working length at an apical size 30 and 0.06 taper. The teeth were divided into three equal groups of 30 samples each, according to the treatment to be applied to the root canal. Group I received 980 nm diode laser (3 W, 0.01 s on time, 0.01 s off time, 5 s per procedure, four procedures); group II received neodymium:yttrium-aluminum-garnet (Nd:YAG) laser (1.5 W, 15 Hz, 5 s per procedure, four procedures). In group III the root canals were approached conventionally only. In all groups the root canal filling was performed with AH Plus endodontic sealer and gutta-percha points. An en face OCT prototype was used for the investigation of apical microleakage. According to one-way analysis of variance (ANOVA) and en face OCT, the number of defects in the laser groups was significantly lower (P < 0.005) than in the control group. No statistical differences were noted between the laser groups (P = 0.049). En face OCT imaging proved that laser-assisted endodontic treatment improved the prognosis of root canal filling and led to a reduction in apical microleakage.

  2. 46 CFR 174.220 - Hatches and coamings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... PERTAINING TO SPECIFIC VESSEL TYPES Special Rules Pertaining to Offshore Supply Vessels § 174.220 Hatches and coamings. (a) Each hatch exposed to the weather must be watertight, except that the following hatches may... inches) above the weather deck. (2) Each hatch in a cabin top. (b) Each hatch cover must— (1)...

  3. Cell adhesion response on femtosecond laser initiated liquid assisted silicon surface.

    PubMed

    Ulmeanu, M; Sima, L E; Ursescu, D; Enculescu, M; Bazan, X; Quintana, I

    2014-03-01

    Silicon substrates were irradiated at normal incidence with a femtosecond Ti:sapphire laser (Quatronix, 90 fs pulse duration, 1 kHz repetition rate, M(2) ~ 1.2, maximum energy peak 350 mJ ) operating at a wavelength of 400 nm and focused via a microscope objective (Newport; UV Objective Model, 37x 0.11 N.A.). The laser scanning was assisted by liquids precursors media such as methanol and 1,1,2-trichlorotrifluoroethane. By altering the processing parameters, such as incident laser energy, scanning speed, and different irradiation media, various surface structures were produced on areas with 1 mm(2) dimensions. We analyzed the dependence of the surface morphology on laser pulse energy, scanning speed and irradiation media. Well ordered areas are developed without imposing any boundary conditions for the capillary waves that coarsens the ripple pattern. To assess biomaterial-driven cell adhesion response we investigated actin filaments organization and cell morphological changes following growth onto processed silicon substrates. Our study of bone cell progenitor interaction with laser nanoprocessed silicon lines has shown that cells anchor mainly to contact points along the nanostructured surface. Consequently, actin filaments are stretched towards the 15 µm wide parallel lines increasing lateral cell spreading and changing the bipolar shape of mesenchymal stem cells.

  4. Laser Assisted Cancer Immunotherapy: An Experimental Theraputic Approach in Balb/c Mice

    NASA Astrophysics Data System (ADS)

    Gray, John

    2005-03-01

    Among the different therapeutic approaches to treat superficial malignant tumors, Laser Assisted Cancer Immunotherapy (LACI) shows promise. Experiments are in progress in our laboratory based on the concept of LACI which utilizes a light absorbing dye (Indocyanine Green, ICG), an immunoadjuvant (Glycated Chitosan, GC), and an infrared diode laser (1-15w) operating at 804 nm. Superficial tumors (5 to 7 mm in diameter) of the T4 cell line are grown in an animal model (Balb/C mice). The tumors are injected with ICG and GC prior to interstitial/surface irradiation of the tumor. The tumors' internal temperatures are monitored during the irradiation by invasive (microthermocouples) as well as noninvasive (infrared detector) modes. Along with the various experimental parameters, only the laser delivery (interstitial/surface) and laser intensity are varied in this initial stage so that the tumor temperature is in the range of 55 degrees C to 65 degrees C to ensure hyperthermic cell killing. The goal of the project is to determine the precise temperature range through which primary tumor necrosis and a vigorous immune response will end in tumor elimination. Experimental results coupled with a theoretical framework of laser-tissue interactions will be presented in the context of this therapeutic approach.

  5. Infrared laser therapy after surgically assisted rapid palatal expansion to diminish pain and accelerate bone healing.

    PubMed

    Abreu, Marcelo Emir Requia; Viegas, Vinicius Nery; Pagnoncelli, Rogerio Miranda; de Lima, Eduardo Martinelli Santayama; Farret, Alessandro Marchiori; Kulczynski, Fernando Zugno; Farret, Marcel Marchiori

    2010-01-01

    The aim of this study was to illustrate how gallium arsenite aluminum diode laser (824 nm) irradiation can reduce postsurgical edema and discomfort and accelerate sutural osseous regeneration after surgically assisted rapid palatal expansion (SARPE). An adult patient with an 8-mm transverse maxillary discrepancy was treated with SARPE. Infrared laser therapy was started on the 7th postoperative day, with a total of eight sessions at intervals of 48 hours. The laser probe spot had a size of 0.2827 cm2 and was positioned in contact with the following (bilateral) points: infraorbital foramen, nasal alar, nasopalatine foramen, median palatal suture at the height of the molars, and transverse palatine suture distal to the second molars. The laser was run in continuous mode with a power of 100 mW and a fluency of 1.5 J/cm2 for 20 seconds at each point. Subsequently, an absence of edema and pain was observed. Further, fast bone regeneration in the median palatal suture could be demonstrated by occlusal radiographs. These findings suggest that laser therapy can accelerate bone regeneration of the median palatal suture in patients who have undergone SARPE.

  6. A predictive thermal dynamic model for parameter generation in the laser assisted direct write process

    NASA Astrophysics Data System (ADS)

    Shang, Shuo; Fearon, Eamonn; Wellburn, Dan; Sato, Taku; Edwardson, Stuart; Dearden, G.; Watkins, K. G.

    2011-11-01

    The laser assisted direct write (LADW) method can be used to generate electrical circuitry on a substrate by depositing metallic ink and curing the ink thermally by a laser. Laser curing has emerged over recent years as a novel yet efficient alternative to oven curing. This method can be used in situ, over complicated 3D contours of large parts (e.g. aircraft wings) and selectively cure over heat sensitive substrates, with little or no thermal damage. In previous studies, empirical methods have been used to generate processing windows for this technique, relating to the several interdependent processing parameters on which the curing quality and efficiency strongly depend. Incorrect parameters can result in a track that is cured in some areas and uncured in others, or in damaged substrates. This paper addresses the strong need for a quantitative model which can systematically output the processing conditions for a given combination of ink, substrate and laser source; transforming the LADW technique from a purely empirical approach, to a simple, repeatable, mathematically sound, efficient and predictable process. The method comprises a novel and generic finite element model (FEM) that for the first time predicts the evolution of the thermal profile of the ink track during laser curing and thus generates a parametric map which indicates the most suitable combination of parameters for process optimization. Experimental data are compared with simulation results to verify the accuracy of the model.

  7. A Study on the Development of a Robot-Assisted Automatic Laser Hair Removal System

    PubMed Central

    Lim, Hyoung-woo; Park, Sungwoo; Noh, Seungwoo; Lee, Dong-Hun; Yoon, Chiyul; Koh, Wooseok; Kim, Youdan; Chung, Jin Ho; Kim, Hee Chan

    2014-01-01

    Abstract Background and Objective: The robot-assisted automatic laser hair removal (LHR) system is developed to automatically detect any arbitrary shape of the desired LHR treatment area and to provide uniform laser irradiation to the designated skin area. Methods: For uniform delivery of laser energy, a unit of a commercial LHR device, a laser distance sensor, and a high-resolution webcam are attached at the six axis industrial robot's end-effector, which can be easily controlled using a graphical user interface (GUI). During the treatment, the system provides real-time treatment progress as well as the total number of “pick and place” automatically. Results: During the test, it was demonstrated that the arbitrary shapes were detected, and that the laser was delivered uniformly. The localization error test and the area-per-spot test produced satisfactory outcome averages of 1.04 mm error and 38.22 mm2/spot, respectively. Conclusions: Results showed that the system successfully demonstrated accuracy and effectiveness. The proposed system is expected to become a promising device in LHR treatment. PMID:25343281

  8. Controlled growth of ZnO nanowires by nanoparticle-assisted laser ablation deposition

    NASA Astrophysics Data System (ADS)

    Okada, T.; Guo, R.; Nishimura, J.; Matsumoto, M.; Higashihata, M.; Nakamura, D.

    2008-02-01

    Vertically aligned ZnO nanowires have been successfully synthesized on c-cut sapphire substrates by a catalyst-free nanoparticle-assisted pulsed-laser ablation deposition (NAPLD) in Ar and N II background gases. In NAPLD, the nanoparticles formed in a background gas by laser ablation are used as a starting material for the growth of the nanowires. The surface density of the nanowires can be controlled by varying the density of nanoparticles, which are accomplished by changing the energy of the ablation laser, the repetition rate of the laser and so on. When single ZnO nanowire synthesized in a N II background gas was excited by 355 nm laser-pulse with a pulse-width of 8 ns, stimulated emission was clearly observed, indicating high quality of the nanowire. These nanowires were used as building blocks for an ultraviolet light emitting diode with a structure of n-ZnO/ZnO nanowire/p-GaN.

  9. High-speed deposition of titanium carbide coatings by laser-assisted metal–organic CVD

    SciTech Connect

    Gong, Yansheng; Tu, Rong; Goto, Takashi

    2013-08-01

    Graphical abstract: - Highlights: • A semiconductor laser was first used to prepare wide-area LCVD-TiC{sub x} coatings. • The effect of laser power for the deposition of TiC{sub x} coatings was discussed. • TiC{sub x} coatings showed a columnar cross section and a dense surface texture. • TiC{sub x} coatings had a 1–4 order lower laser density than those of previous reports. • This study gives the possibility of LCVD applying on the preparation of TiC{sub x} coating. - Abstract: A semiconductor laser-assisted chemical vapor deposition (LCVD) of titanium carbide (TiC{sub x}) coatings on Al{sub 2}O{sub 3} substrate using tetrakis (diethylamido) titanium (TDEAT) and C{sub 2}H{sub 2} as source materials were investigated. The influences of laser power (P{sub L}) and pre-heating temperature (T{sub pre}) on the microstructure and deposition rate of TiC{sub x} coatings were examined. Single phase of TiC{sub x} coatings were obtained at P{sub L} = 100–200 W. TiC{sub x} coatings had a cauliflower-like surface and columnar cross section. TiC{sub x} coatings in the present study had the highest R{sub dep} (54 μm/h) at a relative low T{sub dep} than those of conventional CVD-TiC{sub x} coatings. The highest volume deposition rate (V{sub dep}) of TiC{sub x} coatings was about 4.7 × 10{sup −12} m{sup 3} s{sup −1}, which had 3–10{sup 5} times larger deposition area and 1–4 order lower laser density than those of previous LCVD using CO{sub 2}, Nd:YAG and argon ion laser.

  10. Laser-assisted focused He+ ion beam induced etching with and without XeF2 gas assist

    SciTech Connect

    Stanford, Michael G.; Mahady, Kyle; Lewis, Brett B.; Fowlkes, Jason D.; Tan, Shida; Livengood, Richard; Magel, Gregory A.; Moore, Thomas M.; Rack, Philip D.

    2016-10-04

    Focused helium ion (He+) milling has been demonstrated as a high-resolution nanopatterning technique; however, it can be limited by its low sputter yield as well as the introduction of undesired subsurface damage. Here, we introduce pulsed laser- and gas-assisted processes to enhance the material removal rate and patterning fidelity. A pulsed laser-assisted He+ milling process is shown to enable high-resolution milling of titanium while reducing subsurface damage in situ. Gas-assisted focused ion beam induced etching (FIBIE) of Ti is also demonstrated in which the XeF2 precursor provides a chemical assist for enhanced material removal rate. In conclusion, a pulsed laser-assisted and gas-assisted FIBIE process is shown to increase the etch yield by ~9× relative to the pure He+ sputtering process. These He+ induced nanopatterning techniques improve material removal rate, in comparison to standard He+ sputtering, while simultaneously decreasing subsurface damage, thus extending the applicability of the He+ probe as a nanopattering tool.

  11. Basic studies on laser-assisted phacoemulsification using diode-pumped Er:YAG laser

    NASA Astrophysics Data System (ADS)

    Hausladen, Florian; Wurm, Holger; Stock, Karl

    2016-03-01

    The aim of this study was to determine the potential of a novel diode-pumped Er:YAG laser for phacoemulsification in basic experimental investigations. An appropriate experimental setup was created, including a translation stage for sample movement, a sample holder, a water spray for sample humidification and a surgical microscope with a CCD camera for video documentation. The analysis of the laser cuts and histological sections was done by light microscopy. As samples porcine eye lenses hardened by formalin were used. In ablation experiments with different spot diameters and radiant powers and a constant repetition rate νr = 200 Hz the maximum ablation depths of (4.346 +/- 0.044) mm have reached at (Ø = 480 μm, Φ = 24.15 W) with a maximum extend of thermal damage of (0.165 +/- 0.030) mm. The average ablation efficiency is 0.241 mm3/J. With a spot diameter of 308 μm the maximum ablation depth is (4.238 +/- 0.040) mm at 24.65 W with a mean ablation efficiency of 0.293 mm3/J. The extend of the thermally damaged region is (0.171 +/- 0.024) mm at this laser power. Using a sapphire cylinder with a diameter of 412 μm (length 38.5 mm) in direct tissue contact with water spray for sample humidification the ablation depth reaches (1.017 +/- 0.074) mm at 4.93 W and (1.840 +/- 0.092) mm at 9.87 W with a mean efficiency of 0.261 mm3/J. A thermal damage zone of (0.064 +/-0.024) mm at 9.87 W was measured. Additionally, at this high power, a progressive contamination and destruction of the cylinder end facet was observed. In conclusion, the investigations show that the diode-pumped Er:YAG laser has considerable potential for cataract surgery.

  12. Unpredictable long-term tissue effects in laser-assisted vasovasostomy

    NASA Astrophysics Data System (ADS)

    Gilbert, Peter T. O.

    2000-05-01

    Macroscopic Nd:YAG laser-assisted vasovasostomy was introduced to clinical practice as an attractive alternative to conventional microsurgical suture techniques. In this simple procedure the approximated vasal ends are welded by 0.5 sec laser pulses of 10 W power. The anastomosis is secured by two superficial seromuscular 5 - 0 PDS sutures placed on diametrically opposed sites of the vasal circumference. To date, 17 patients have undergone macroscopic laser-assisted vasovasostomy. In each case the operation was carried out under general anesthesia. There were no serious intra- or postoperative complications. Twelve patients were available for long-term followup (4 years). Sperm counts were obtained two months following surgery and from then on every two years. Whereas patency rate reached 75% at the first control examination, it dropped to 33% after two years. After that period no further deterioration was observed. Probably the main reason for this phenomenon is sperm leaking through mucosal defects at the anastomosis with subsequent formation of intramural sperm granuloma and delayed stenosis of the vasal lumen. This tissue reaction may also occur in the different suture techniques thus accounting for the well- established discrepancy of patency and pregnancy rates in microsurgical vasovasostomy.

  13. Laser-assisted metal spinning for an efficient and flexible processing of challenging materials

    NASA Astrophysics Data System (ADS)

    Brummer, C.; Eck, S.; Marsoner, S.; Arntz, K.; Klocke, F.

    2016-03-01

    The demand for components made from high performance materials like titanium or nickel-based alloys as well as strain-hardening stainless steel is steadily increasing. However, conventional forming operations conducted on these materials are generally very laborious and time-consuming. This is where the limitations of metal spinning also become apparent. Using a laser to apply heat localized to the forming zone during metal spinning facilitates to enhance the formability of a material. In order to analyse the potential of the new manufacturing process, experimental investigations on laser-assisted shear forming and multi-pass metal spinning have been performed with austenitic stainless steel X5CrNi18-10, nickel-based alloy Inconel 718 and titanium grade 2. It could be demonstrated that the formability of these materials can be enhanced by laser-assistance. Besides the resulting enhancement of forming limits for metal spinning of challenging materials, the forming forces were reduced and the product quality was improved significantly.

  14. Nanoscale physical properties of polymer glasses formed by solvent-assisted laser deposition

    NASA Astrophysics Data System (ADS)

    Shepard, Kimberly; Arnold, Craig; Priestley, Rodney

    2015-03-01

    High-energy, low-density nanostructured polymer glasses are formed via the solvent-assisted laser deposition technique MAPLE (Matrix Assisted Pulsed Laser Evaporation). During film deposition, micro- to nano-size polymer/solvent clusters are ejected via laser ablation from a frozen dilute polymer solution. During flight to the substrate under vacuum, the clusters experience rapid cooling and solvent stripping, forming polymer nanoglobules. Bulk polymer films are formed via the gradual assembly of these spherical-like nanostructured building blocks (i.e. nanoglobules). The MAPLE process thus enables investigation of the exceptional properties of glasses formed under extreme processing conditions. In the bulk state, we probe the effect of process parameters and chemical identity of the thermal behavior of a series of methacrylate polymers. We also employ multiple techniques to directly measure the properties of the polymer nanoglobules and connect the results to the global film properties. This talk will address nanoscale dilatometry via AFM, in which the volume of an individual polymer nanoglobule is tracked as it is heated through its glass transition, as well as Flash DSC analysis of the thermal properties of nanogram size MAPLE-deposited polymer glasses. We then discuss these findings in the context of the material's unconventional route to the glassy state.

  15. Laser-assisted heating of a plasmonic nanofluid in a microchannel

    NASA Astrophysics Data System (ADS)

    Walsh, Timothy

    The work presented in this study analyses the theoretical modeling and experimentation of laser-assisted heating of plasmonic nanofluids (PNFs) in a microchannel for accurate, efficient, and ultra-fast heating of a microdroplet. Suspended plasmonic nanoparticles exhibit strong light absorption and scattering upon the excitation of localized surface plasmons (LSPs), resulting in intense and rapid photothermal heating. Several multi-stepped computational models were utilized to theoretically characterize and verify the laser-assisted heating behavior of gold nanoshells (GNS) and gold nanorod (GNR) plasmonic nanofluid droplets in a microchannel. From the experimental investigation, a full range of controllable steady-state temperatures, room temperature to 100°C, are confirmed to be achievable for the 780-nm-tuned plasmonic nanofluid. Droplet fluid heating is verified to occur as a result of LSP excitation, in time scales of milliseconds, and to be repeatable over many cycles. Additionally, the significance and effects of parameters in the process, such as nanoparticle structure, volumetric concentration, microchannel depth, and laser power density are established. The obtained results in this research may be integrated into other existing microfluidic technologies and biological techniques, such as the polymerase chain reaction, where accurate and ultra-fast heating of microdroplets in a microchannel can greatly improve efficiency.

  16. Pyroelectricity Assisted Infrared-Laser Desorption Ionization (PAI-LDI) for Atmospheric Pressure Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Li, Yanyan; Ma, Xiaoxiao; Wei, Zhenwei; Gong, Xiaoyun; Yang, Chengdui; Zhang, Sichun; Zhang, Xinrong

    2015-08-01

    A new atmospheric pressure ionization method termed pyroelectricity-assisted infrared laser desorption ionization (PAI-LDI) was developed in this study. The pyroelectric material served as both sample target plate and enhancing ionization substrate, and an IR laser with wavelength of 1064 nm was employed to realize direct desorption and ionization of the analytes. The mass spectra of various compounds obtained on pyroelectric material were compared with those of other substrates. For the five standard substances tested in this work, LiNbO3 substrate produced the highest ion yield and the signal intensity was about 10 times higher than that when copper was used as substrate. For 1-adamantylamine, as low as 20 pg (132.2 fmol) was successfully detected. The active ingredient in (Compound Paracetamol and 1-Adamantylamine Hydrochloride Capsules), 1-adamantylamine, can be sensitively detected at an amount as low as 150 pg, when the medicine stock solution was diluted with urine. Monosaccharide and oligosaccharides in Allium Cepa L. juice was also successfully identified with PAI-LDI. The method did not require matrix-assisted external high voltage or other extra facility-assisted set-ups for desorption/ionization. This study suggested exciting application prospect of pyroelectric materials in matrix- and electricity-free atmospheric pressure mass spectrometry research.

  17. Modeling cross-hatch surface morphology in growing mismatched layers

    NASA Astrophysics Data System (ADS)

    Andrews, A. M.; Speck, J. S.; Romanov, A. E.; Bobeth, M.; Pompe, W.

    2002-02-01

    We propose and investigate a model for the development of cross-hatch surface morphology in growing mismatched layers. The model incorporates two important elements: (i) strain relaxation due to dislocation glide in the layer (film) interior that is also associated with misfit dislocation formation at the film/substrate interface and (ii) lateral surface transport that eliminates surface steps that originated from dislocation glide. A combination of dislocation-assisted strain relaxation and surface step flow leads to the appearance of surface height undulations during layer growth. A Monte Carlo simulation technique was applied to model dislocation nucleation events in the course of strain relaxation. The simulation was used to model the influence of dislocations on film surface height profiles. The surface height displacement was calculated from the analytic elasticity solutions for edge dislocations near a free surface. The results of the modeling predict that the average amplitude of the surface undulations and their apparent wavelength both increase with increasing film relaxation and film thickness. The developed cross-hatch pattern is characterized by an atomically smooth but mesoscopically (lateral dimensions ˜0.1-10 μm) rough surface morphology. The conclusions of the model are in agreement with atomic force microscopy observations of cross-hatch surface relief in In0.25Ga0.75As/GaAs samples grown well beyond the critical thickness for misfit dislocation formation.

  18. Matrix-assisted laser-desorption-ionization mass spectrometry of proteins using a free-electron laser

    SciTech Connect

    Cramer, R.; Hillenkamp, F.; Haglund, R.

    1995-12-31

    Matrix-assisted laser desorption-ionization (MALDI) mass spectrometry (MS) is one of the most promising techniques for spectral fingerprinting large molecules, such as proteins, oligonucleotides and carbohydrates. In the usual implementation of this technique, the analyte molecule is dissolved in an aromatic liquid matrix material which resonantly absorbs ultraviolet laser light. Resonant absorption by {pi}-{pi}* transitions volatilizes the matrix and initiates subsequent charge transfer to the analyte molecules, which are detected by time-of-flight mass spectrometry. Recent MALDI-MS studies with Er:YAG (2.94 {mu}m) and CO{sub 2}{sup 4} (9.4-10.6 {mu}m) lasers suggest that them is significant unexplored potential for mass spectrometry of macromolecules, including oligonucleotide, in the mid-infrared. Preliminary experiments show that it is possible to capitalize on the rich rovibronic absorption spectrum of virtually all organics to initiate resonant desorption in matrix material over the entire range of pH values. However, the mechanism of charge transfer is particularly problematic for infrared MALDI because of the low photon energy. In this paper, we report the results of MALI-MS studies on small proteins using the Vanderbilt FEL and several matrix materials. Proteins with masses up to roughly 6,000 amu were detected with high resolution in a linear time-of-flight mass spectrometer. By varying the pulse duration using a broadband Pockels cell, we have been able to compare the results of relatively long (5 {mu}s) and short (0.1 {mu}s) irradiation on the desorption and ionization processes. Compared to uv-MALDI spectra of identical analytes obtained with a nitrogen laser (337 nm) in the same time-of-flight spectrometer, the infrared results appear to show that the desorption and ionization process goes on over a somewhat longer time scale.

  19. Influence of instrument conditions on the evaporation behavior of uranium dioxide with UV laser-assisted atom probe tomography

    SciTech Connect

    Valderrama, B.; Henderson, H.B.; Gan, J.; Manuel, M.V.

    2015-04-01

    Atom probe tomography (APT) provides the ability to detect subnanometer chemical variations spatially, with high accuracy. However, it is known that compositional accuracy can be affected by experimental conditions. A study of the effect of laser energy, specimen base temperature, and detection rate is performed on the evaporation behavior of uranium dioxide (UO2). In laser-assisted mode, tip geometry and standing voltage also contribute to the evaporation behavior. In this investigation, it was determined that modifying the detection rate and temperature did not affect the evaporation behavior as significantly as laser energy. It was also determined that three laser evaporation regimes are present in UO2. Very low laser energy produces a behavior similar to DC-field evaporation, moderate laser energy produces the desired laser-assisted field evaporation characteristic and high laser energy induces thermal effects, negatively altering the evaporation behavior. The need for UO2 to be analyzed under moderate laser energies to produce accurate stoichiometry distinguishes it from other oxides. The following experimental conditions providing the best combination of mass resolving power, accurate stoichiometry, and uniform evaporation behavior: 50 K, 10 pJ laser energy, a detection rate of 0.003 atoms per pulse, and a 100 kHz repetition rate.

  20. Laser desorption and matrix-assisted laser desorption/ionization mass spectrometry of 29-kDa Au:SR cluster compounds.

    PubMed

    Schaaff, T Gregory

    2004-11-01

    Positive and negative ions generated by laser-based ionization methods from three gold:thiolate cluster compounds are mass analyzed by time-of-flight mass spectrometry. The three compounds have similar inorganic core masses ( approximately 29 kDa, approximately 145 Au atoms) but different n-alkanethiolate ligands associated with each cluster compound (Au:SR, R = butane, hexane, dodecane). Irradiation of neat films (laser desorption/ionization) and films generated by dilution of the cluster compounds in an organic acid matrix (matrix-assisted laser desorption/ionization) with a nitrogen laser (337 nm) produced distinct ion abundances that are relevant to different structural aspects of the cluster compound. Laser desorption/ionization of neat Au:SR compound films produces ions consistent with the inorganic core mass (i.e., devoid of original hydrocarbon content). Matrix-assisted laser desorption/ionization produces either ions with m/z values consistent with the core mass of the cluster compounds or ions with m/z values consistent with the approximate molecular weight of the cluster compounds, depending on ionization conditions. The ion abundances, and ionization conditions under which they are detected, provide insight into desorption/ionization processes for these unique cluster compounds as well as other analytes typically studied by matrix-assisted laser desorption/ionization.

  1. Rapid and Localized Synthesis of Single-Walled Carbon Nanotubes on Flat Surface by Laser-Assisted Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Kasuya, Keigo; Nagato, Keisuke; Jin, Yusuke; Morii, Hiroshi; Ooi, Takeshi; Nakao, Masayuki

    2007-04-01

    The synthesis of single-walled carbon nanotubes (SWNTs) at a controlled position on a flat surface was demonstrated by laser-assisted chemical vapor deposition (CVD). The developed multilayer substrate including an energy-confining layer (ECL) enabled the efficient heating of catalysts on the surface, resulting in the rapid and localized syntheses of SWNTs. Using a Nd:YAG laser as a heat source, we achieved the rapid synthesis with laser irradiation for 1 s and the localized synthesis in an area of approximately 1 μm diameter. In addition, the scanning of the laser irradiation spot at a rate of 1 μm/s enabled the line-patterned synthesis of SWNTs at a linewidth of 2 μm. The resulting synthesis of SWNTs on a flat surface by laser-assisted CVD will lead to the easy and controllable fabrication of SWNT-based nanodevices.

  2. Clinical outcomes using standard phacoemulsification and femtosecond laser-assisted surgery with toric intraocular lenses

    PubMed Central

    Espaillat, Arnaldo; Pérez, Obniel; Potvin, Richard

    2016-01-01

    Purpose To compare the 1-month and 1-year results of toric intraocular lens (IOL) implantation with standard (manual) phacoemulsification vs femtosecond laser-assisted surgery. Patients and methods Refractive data, visual acuity data, and ocular aberration measured with a wavefront aberrometer were collected for two groups of patients from one site. The first group had standard phacoemulsification, while the second group had femtosecond laser-assisted surgery, and both groups were implanted with toric IOLs, either monofocal or multifocal. Differences in visual acuity, refractive outcomes, and higher order aberrations – total, corneal, and internal – were evaluated at 1 month and 1 year postoperatively. Results Toric IOLs were implanted in 62 eyes using standard phacoemulsification and 53 eyes using femtosecond laser-assisted surgery. Uncorrected visual acuity and best-spectacle-corrected visual acuity at 1 month and 1 year were not statistically significantly different between the groups (P>0.05) nor was the mean cylinder or mean spherical equivalent refraction (P>0.12). Total ocular higher order aberrations were significantly different between the groups (P<0.05), but absolute differences appeared to be the same. Internal vertical coma was significantly lower in the femto group at 1 year (P=0.03). Differences in aberrations did not correlate with corrected or uncorrected visual acuity. Conclusion Patients who underwent uncomplicated lens surgery with toric IOLs in both the groups had comparable refractive outcomes in terms of visual acuity and residual refraction at 1 year. The femto group had significantly lower internal vertical coma at 1 year. PMID:27099462

  3. Laser-assisted high-pressure-induced polymerization of 2-(hydroxyethyl)methacrylate.

    PubMed

    Evlyukhin, E; Museur, L; Traore, M; Nikitin, S M; Zerr, A; Kanaev, A

    2015-02-26

    We report on a successful room-temperature polymerization of 2-(hydroxyethyl)methacrylate (HEMA) under high pressure. The polymerization is observed in a limited range of pressures 0.1 to 1.6 GPa without the use of any initiator. When the compressed sample is irradiated at 488 or 355 nm by a laser, the polymerization reaction rate is increased by a factor of 10 or 30, respectively. Moreover, the shift of the laser wavelength to the UV improves the polymerization yield of the recovered sample to 84%. The catalysis of the polymerization process by light results from a one-photon-assisted electron transfer to π* antibonding states of the monomer molecule. The observed polymerization is irreversible and almost complete, which makes this synthesis process suitable for applications.

  4. Antimony sulfide thin films prepared by laser assisted chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Shaji, S.; Garcia, L. V.; Loredo, S. L.; Krishnan, B.; Aguilar Martinez, J. A.; Das Roy, T. K.; Avellaneda, D. A.

    2017-01-01

    Antimony sulfide (Sb2S3) thin films were prepared by laser assisted chemical bath deposition (LACBD) technique. These thin films were deposited on glass substrates from a chemical bath containing antimony chloride, acetone and sodium thiosulfate under various conditions of normal chemical bath deposition (CBD) as well as in-situ irradiation of the chemical bath using a continuous laser of 532 nm wavelength. Structure, composition, morphology, optical and electrical properties of the Sb2S3 thin films produced by normal CBD and LACBD were analyzed by X-Ray diffraction (XRD), Raman Spectroscopy, Atomic force microscopy (AFM), X-Ray photoelectron spectroscopy (XPS), UV-vis spectroscopy and Photoconductivity. The results showed that LACBD is an effective synthesis technique to obtain Sb2S3 thin films for optoelectronic applications.

  5. Laser-assisted binary rearrangement collision: e++H-->Ps+p

    NASA Astrophysics Data System (ADS)

    Shu-Min, Li; Zi-Fang, Zhou; Jian-Ge, Zhou; Yao-Yang, Liu

    1993-06-01

    In the first Born approximation, the laser-assisted rearrangement collision between a positron and a hydrogen atom is systematically studied. In solving the dressed wave functions, the A.p gauge is adopted. To overcome the difficulty in the reduction of the S matrix, we have developed the Feynman integration technique. The scattering amplitude is reduced to one-dimensional integrals and analytical expressions. The numerical calculation is greatly simplified, which makes it possible to compute the integral cross sections for Ps formation including multiphoton processes. Our results indicate that when the laser field is presented, the cross sections for Ps formation are remarkably enhanced. This is of great importance in improving this kind of reaction.

  6. Heat transfer and material flow during laser assisted multi-layer additive manufacturing

    SciTech Connect

    Manvatkar, V.; De, A.; DebRoy, T.

    2014-09-28

    A three-dimensional, transient, heat transfer, and fluid flow model is developed for the laser assisted multilayer additive manufacturing process with coaxially fed austenitic stainless steel powder. Heat transfer between the laser beam and the powder particles is considered both during their flight between the nozzle and the growth surface and after they deposit on the surface. The geometry of the build layer obtained from independent experiments is compared with that obtained from the model. The spatial variation of melt geometry, cooling rate, and peak temperatures is examined in various layers. The computed cooling rates and solidification parameters are used to estimate the cell spacings and hardness in various layers of the structure. Good agreement is achieved between the computed geometry, cell spacings, and hardness with the corresponding independent experimental results.

  7. Some Experiences in 3D Laser Scanning for Assisting Restoration and Evaluating Damage in Cultural Heritage

    NASA Astrophysics Data System (ADS)

    Fuentes, L. M.; Finat, Javier; Fernández-Martin, J. J.; Martínez, J.; SanJose, J. I.

    The recent incorporation of laser devices provides advanced tools for assisting the conservation and restoration of Cultural Heritage. It is necessary to have as complete as possible understanding of the object state before evaluating or defining the reach of the restoration process. Thus, a special effort is devoted to surveying, measuring and generating a high-resolution 3D model prior to restoration planning. This work presents results of several experiments performed on damaged pieces for evaluation purposes in Cultural Heritage. Some software tools are applied for carving-work analysis, conservation-state monitoring, and simulation of weathering processes for evaluating temporal changes. In all cases considered, a high resolution information capture has been performed with a laser scanner, the Minolta 910. Our approach is flexible enough to be adapted to other kinds of pieces or Cultural Heritage artefacts, in order to provide an assessment for intervention planning in conservation and restoration tasks.

  8. Relativistic electronic dressing in laser-assisted ionization of atomic hydrogen by electron impact

    SciTech Connect

    Attaourti, Y.; Taj, S.

    2004-06-01

    Within the framework of the coplanar binary geometry where it is justified to use plane wave solutions for the study of the (e,2e) reaction and in the presence of a circularly polarized laser field, we introduce as a first step the Dirac-Volkov plane wave Born approximation 1 where we take into account only the relativistic dressing of the incident and scattered electrons. Then, we introduce the Dirac-Volkov plane wave Born approximation 2 where we take totally into account the relativistic dressing of the incident, scattered, and ejected electrons. We then compare the corresponding triple differential cross sections for laser-assisted ionization of atomic hydrogen by electron impact both for the nonrelativistic and the relativistic regime.

  9. Low-level laser-assisted liposuction: the Neira 4 L technique.

    PubMed

    Neira, Rodrigo; Toledo, Luiz; Arroyave, Jose; Solarte, Efrain; Isaza, Carolina; Gutierrez, Oscar; Criollo, William; Ramirez, Hugo; Gutierrez, Maria I; Ortiz-Neira, Clara L

    2006-01-01

    Low-level laser-assisted liposuction (LLLL), known as the Neira 4 L technique, is an excellent adjuvant tool for the surgeon practicing liposculpture. A low-level laser is used to create a transitory pore in the cell membrane of the adipocyte to move fat from inside the cell to the interstitial space outside without killing the cell. LLLL has been performed successfully in in-vitro and human adipose tissue cultures. It protects the patient from the surgical trauma of liposuction by protecting and preparing tissues for the surgical trauma; modulating the inflammatory response to prevent short and long-term side effects of surgery; and improving the quality and quantity of the healing process by accelerating recovery time, modulating secondary cicatrization, and preventing postoperative neuralgias.

  10. Design and development of a computer-assisted retinal laser surgery system.

    PubMed

    Wright, Cameron H G; Barrett, Steven F; Welch, Ashley J

    2006-01-01

    Since the mid-1980s, the development of a therapeutic, computer-assisted laser photocoagulation system to treat retinal disorders has progressed under the guidance of Dr. Welch, the Marion E. Forsman Centennial Professor of Engineering, Department of Biomedical Engineering, the University of Texas at Austin. This paper reviews the development of the system, related research in eye movement and laser-tissue interaction, and system implementation and testing. While subsets of these topics have been reported in prior publications, this paper brings the entire evolutionary design of the system together. We also discuss other recent "spinoff" uses of the system technology that have not been reported elsewhere and describe the impact of the latest technical advances on the overall system design.

  11. Matrix-Assisted Laser Desorption Ionization Imaging Mass Spectrometry: In Situ Molecular Mapping

    PubMed Central

    Angel, Peggi M.; Caprioli, Richard M.

    2013-01-01

    Matrix-assisted laser desorption ionization imaging mass spectrometry (IMS) is a relatively new imaging modality that allows mapping of a wide range of biomolecules within a thin tissue section. The technology uses a laser beam to directly desorb and ionize molecules from discrete locations on the tissue that are subsequently recorded in a mass spectrometer. IMS is distinguished by the ability to directly measure molecules in situ ranging from small metabolites to proteins, reporting hundreds to thousands of expression patterns from a single imaging experiment. This article reviews recent advances in IMS technology, applications, and experimental strategies that allow it to significantly aid in the discovery and understanding of molecular processes in biological and clinical samples. PMID:23259809

  12. Oxygen assisted laser cutting mechanism—a laminar boundary layer approach including the combustion process

    NASA Astrophysics Data System (ADS)

    Yilbaş, B. S.; Sahin, A. Z.

    1995-06-01

    The present study examines the combined effects of chemical reactions taking place between a gas jet and molten metal, the cooling effect of the jet and the evaporation of metal, during a CO 2 laser cutting process. A laminar boundary layer approach was used to develop a theoretical model for the oxygen gas jet laser cutting mechanism. An experiment was carried out to monitor the keyhole formation using a video recorder and detect the light emitted from the entrance and exist surfaces of the workpiece using a fibre-optic probe during the cutting process. The experimental study was extended to employ two different workpiece materials (stainless steel and mild steel) at two thicknesses, and varying oxygen assisting gas pressures. It is found that the theoretical model developed in the present study is valid for a cutting speed of about 30 mm s -1 and all jet velocities up to sonic, since the effect of shock is excluded in the model.

  13. Modulation-assisted tunneling in laser-fabricated photonic Wannier-Stark ladders

    NASA Astrophysics Data System (ADS)

    Mukherjee, Sebabrata; Spracklen, Alexander; Choudhury, Debaditya; Goldman, Nathan; Öhberg, Patrik; Andersson, Erika; Thomson, Robert R.

    2015-11-01

    We observe Wannier-Stark (W-S) localization in curved photonic lattices, realized using arrays of evanescently coupled optical waveguides. By correctly tuning the strength of inter-site coupling in the lattice, we observe that W-S states become increasingly localized, and eventually fully localized to one site, as the curvature of the lattice is increased. We then demonstrate that tunneling can be successfully restored in the lattice by applying a resonant sinusoidal modulation to the lattice position, an effect that is a direct analogue of photon-assisted tunneling. This precise tuning of the tunneling matrix elements, through resonant modulation-assisted tunneling, opens a novel route for the creation of gauge fields in laser-fabricated photonic lattices.

  14. Quantum dots assisted laser desorption/ionization mass spectrometric detection of carbohydrates: qualitative and quantitative analysis.

    PubMed

    Bibi, Aisha; Ju, Huangxian

    2016-04-01

    A quantum dots (QDs) assisted laser desorption/ionization mass spectrometric (QDA-LDI-MS) strategy was proposed for qualitative and quantitative analysis of a series of carbohydrates. The adsorption of carbohydrates on the modified surface of different QDs as the matrices depended mainly on the formation of hydrogen bonding, which led to higher MS intensity than those with conventional organic matrix. The effects of QDs concentration and sample preparation method were explored for improving the selective ionization process and the detection sensitivity. The proposed approach offered a new dimension to the application of QDs as matrices for MALDI-MS research of carbohydrates. It could be used for quantitative measurement of glucose concentration in human serum with good performance. The QDs served as a matrix showed the advantages of low background, higher sensitivity, convenient sample preparation and excellent stability under vacuum. The QDs assisted LDI-MS approach has promising application to the analysis of carbohydrates in complex biological samples.

  15. Evaluation of Laser-Assisted Trans-Nail Drug Delivery with Optical Coherence Tomography

    PubMed Central

    Tsai, Meng-Tsan; Tsai, Ting-Yen; Shen, Su-Chin; Ng, Chau Yee; Lee, Ya-Ju; Lee, Jiann-Der; Yang, Chih-Hsun

    2016-01-01

    The nail provides a functional protection to the fingertips and surrounding tissue from external injuries. The nail plate consists of three layers including dorsal, intermediate, and ventral layers. The dorsal layer consists of compact, hard keratins, limiting topical drug delivery through the nail. In this study, we investigate the application of fractional CO2 laser that produces arrays of microthermal ablation zones (MAZs) to facilitate drug delivery in the nails. We utilized optical coherence tomography (OCT) for real-time monitoring of the laser–skin tissue interaction, sparing the patient from an invasive surgical sampling procedure. The time-dependent OCT intensity variance was used to observe drug diffusion through an induced MAZ array. Subsequently, nails were treated with cream and liquid topical drugs to investigate the feasibility and diffusion efficacy of laser-assisted drug delivery. Our results show that fractional CO2 laser improves the effectiveness of topical drug delivery in the nail plate and that OCT could potentially be used for in vivo monitoring of the depth of laser penetration as well as real-time observations of drug delivery. PMID:27973451

  16. Electrically stimulated osteogenesis on Ti-PPy/PLGA constructs prepared by laser-assisted processes.

    PubMed

    Paun, Irina Alexandra; Stokker-Cheregi, Flavian; Luculescu, Catalin Romeo; Acasandrei, Adriana Maria; Ion, Valentin; Zamfirescu, Marian; Mustaciosu, Cosmin Catalin; Mihailescu, Mona; Dinescu, Maria

    2015-10-01

    This work describes a versatile laser-based protocol for fabricating micro-patterned, electrically conductive titanium-polypyrrole/poly(lactic-co-glycolic)acid (Ti-PPy/PLGA) constructs for electrically stimulated (ES) osteogenesis. Ti supports were patterned using fs laser ablation in order to create high spatial resolution microstructures meant to provide mechanical resistance and physical cues for cell growth. Matrix Assisted Pulsed Laser Evaporation (MAPLE) was used to coat the patterned Ti supports with PPy/PLGA layers acting as biocompatible surfaces having chemical and electrical properties suitable for cell differentiation and mineralization. In vitro biological assays on osteoblast-like MG63 cells showed that the constructs maintained cell viability without cytotoxicity. At 24 h after cell seeding, electrical stimulation with currents of 200 μA was applied for 4 h. This treatment was shown to promote earlier onset of osteogenesis. More specifically, the alkaline phosphatase activity of the stimulated cultures reached the maximum before that of the non-stimulated ones, i.e. controls, indicating faster cell differentiation. Moreover, mineralization was found to occur at an earlier stage in the stimulated cultures, as compared to the controls, starting with Day 6 of cell culture. At later stages, calcium levels in the stimulated cultures were higher than those in control samples by about 70%, with Ca/P ratios similar to those of natural bone. In all, the laser-based protocol emerges as an efficient alternative to existing fabrication technologies.

  17. Optimal dye concentration and power density for laser-assisted vascular anatomosis (LAVA)

    NASA Astrophysics Data System (ADS)

    Ren, Zhen; Furnary, Anthony; Xie, Hua; Lagerquist, Kathryn A.; Burke, Allen; Prahl, Scott A.; Gregory, Kenton W.

    2003-06-01

    Laser tissue welding with albumin solder/indocyanine green (ICG) dye is an effective technique in surgical reconstruction. This study was carried out in vitro to find optimal ICG concentration and power density (PD) in laser assisted vascular anastomosis (LAVA). Fresh porcine carotid arteries incised into vascular strips (n = 120) were welded by diode laser in end-to-end with 50% albumin solder of 0.01, 0.1, and 1.0 mM ICG and at power density of 27.7, 56.7, and 76.9 W/cm2. Direct temperature was measured by inserting thermocouples outside and inside vessel. Tensile strength was tested immediately and histological study was performed. Temperature (both outside and inside vessel) significantly gradually decreasd (p < 0.01) with the increasing of ICG concentration at PD 56.7 W/cm2. Tensile strength significantly gradually decreased (p < 0.01) with increasing of ICG concentration at PD 56.7 W/cm2. Histological study showed minimal thermal injury limited to adventitia of vessels and no appreciable difference in all groups. We find that ICG concentration within solder is most important factor affecting both tissue temperature and tensile strength during laser vessel welding. The optimal balance between stronger strength and minimal thermal injury of vessel may be achieved primarily by using PD 56.7 W/cm2 at 0.01 mM ICG within solder during LAVA.

  18. New software tools for enhanced precision in robot-assisted laser phonomicrosurgery.

    PubMed

    Dagnino, Giulio; Mattos, Leonardo S; Caldwell, Darwin G

    2012-01-01

    This paper describes a new software package created to enhance precision during robot-assisted laser phonomicrosurgery procedures. The new software is composed of three tools for camera calibration, automatic tumor segmentation, and laser tracking. These were designed and developed to improve the outcome of this demanding microsurgical technique, and were tested herein to produce quantitative performance data. The experimental setup was based on the motorized laser micromanipulator created by Istituto Italiano di Tecnologia and the experimental protocols followed are fully described in this paper. The results show the new tools are robust and effective: The camera calibration tool reduced residual errors (RMSE) to 0.009 ± 0.002 mm under 40× microscope magnification; the automatic tumor segmentation tool resulted in deep lesion segmentations comparable to manual segmentations (RMSE= 0.160 ± 0.028 mm under 40× magnification); and the laser tracker tool proved to be reliable even during cutting procedures (RMSE= 0.073 ± 0.023 mm under 40× magnification). These results demonstrate the new software package can provide excellent improvements to the previous microsurgical system, leading to important enhancements in surgical outcome.

  19. Effects of polarization direction on laser-assisted free-free scattering

    NASA Astrophysics Data System (ADS)

    deHarak, B. A.; Kim, B. N.; Weaver, C. M.; Martin, N. L. S.; Siavashpouri, Mahsa; Nosarzewski, Benjamin

    2016-06-01

    This work will detail the effects of laser polarization direction (relative to the momentum transfer direction) on laser-assisted free-free scattering. Such processes play a role in the gas breakdown that occurs in electric discharges as well as providing a method for the laser heating of a plasma (Musa et al 2010 J. Phys. B: At. Mol. Opt. Phys. 43 175201, Mason 1993 Rep. Prog. Phys. 56 1275). Experimental results will be presented for electron-helium scattering in the presence of an Nd:YAG laser field (hν =1.17 eV) where the polarization direction was varied in a plane that is perpendicular to the scattering plane. To date, all of our experimental results are well described by the Kroll-Watson approximation (KWA) (Kroll and Watson 1973 Phys. Rev. A 8 804). The good agreement between our experiments and calculations using the KWA includes the case where the polarization is perpendicular to the momentum transfer direction, for which the KWA predicts vanishing cross section; other workers have found that the KWA tends to be inaccurate for cases where it predicts small cross sections (e.g. Musa et al 2010 J. Phys. B: At. Mol. Opt. Phys. 43 175201). We also present simulations of the effects that multiple scattering might have on experimental measurements. In particular, we examine conditions that are expected to be similar to those of the experiments reported by Wallbank and Holmes (Wallbank and Holmes 1993 Phys. Rev. A 48 R2515).

  20. Implementation of an intuitive writing interface and a laparoscopic robot for gynaecological laser assisted surgery.

    PubMed

    Tang, H W; Van Brussel, H; Sloten, J Vander; Reynaerts, D; Koninckx, P R

    2005-07-01

    The research reported in this paper aims at applying the human handwriting skill to improve and facilitate the control of laser-assisted laparoscopic surgery operations performed by gynaecological surgeons. For the purpose, a laparoscopic robot was interfaced with a digitizing tablet. This interface, further called the intuitive writing interface (IWI), directly converts the hand trajectory, handwritten on the tablet, into an input signal to the robot. It replaces the traditional complex manipulations performed by the surgeon during manual laparoscopic surgery by natural handwriting. It provides the surgeon with an intuitive 'what-you-draw-is-what-you-cut' control facility by employing his/her familiar handwriting skills to control the laser ablation process accurately. The system was successfully built and tested in vitro. Performance tests on the robot resulted in tracking errors in the order of 1 mm in the target plane at an ablation speed of 20 mm/s. The high accuracy of the system was successfully demonstrated by cutting characters 4 mm high on an apple. These results indicate that laser ablation performance is upgraded by the IWI to the accuracy levels of human handwriting, which is much higher than can be obtained with manual laser laparoscopy. Safety features include the use of pen contact with the tablet as a safety switch, and back drivability in the robot joints for easy manual positioning and evacuation in case of emergency.

  1. Transient energy relaxation in scattering-assisted terahertz quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Wang, F.; Guo, X. G.; Cao, J. C.

    2017-03-01

    We adopt a self-consistent Maxwell-Bloch method to investigate the energy relaxation process from unsaturated to saturated in the scattering-assisted terahertz quantum cascade laser. In the lasing-establishment process, more nonequilibrium LO phonons are accumulated and more electrons are thermalized. At the same time, more efficient energy relaxation of the saturated situation can be found compared with the unsaturated situation. These phenomena stem from the improved electron transport efficiency across the active region, due to the lasing-induced lifetime reduction of electrons in the upper lasing subband. The simulation results are qualitatively identical with previous experimental results.

  2. Water-assisted femtosecond laser machining of electrospray nozzles on glass microfluidic devices.

    PubMed

    An, Ran; Hoffman, Michelle D; Donoghue, Margaret A; Hunt, Alan J; Jacobson, Stephen C

    2008-09-15

    Using water-assisted femtosecond laser machining, we fabricated electrospray nozzles on glass coverslips and on assembled microfluidic devices. Machining the nozzles after device assembly facilitated alignment of the nozzles over the microchannels. The basic nozzle design is a through-hole in the coverslip to pass liquids and a trough machined around the through-hole to confine the electrospray and prevent liquid from wicking across the glass surface. Electrospray from the nozzles was stable with and without pressure-driven flow applied and was evaluated using mass spectra of the peptide bradykinin.

  3. Derivatization of small biomolecules for optimized matrix-assisted laser desorption/ionization mass spectrometry.

    PubMed

    Tholey, Andreas; Wittmann, Christoph; Kang, Min-Jung; Bungert, Ditte; Hollemeyer, Klaus; Heinzle, Elmar

    2002-09-01

    Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) is a powerful tool for the measurement of low molecular mass compounds of biological interest. The limitations for this method are the volatility of many analytes, possible interference with matrix signals or bad ionization or desorption behavior of the compounds. We investigated the application of well-known and straightforward one-pot derivatization procedures to circumvent these problems. The derivatizations tested allow the measurement and the labeling of alcohols, aldehydes and ketones, carboxylic acids, alpha-ketocarboxylic acids and amines.

  4. Management of Gingival Overgrowth in a Cardiac Transplant Patient Using Laser-Assisted Gingivectomy/Gingivoplasty.

    PubMed

    Maddi, Abhiram; Alluri, Leela Subhashini; Ciancio, Sebastian G

    2015-07-01

    Drug-induced gingival overgrowth (DIGO) is an oral clinical manifestation associated with certain medications such as immunosuppressants that are administered to organ transplant patients to prevent graft rejection. In patients with cardiac transplants, management of DIGO is critical. In such patients, plaque biofilm accumulation at the gingival interface might be detrimental as it may lead to transient bacteremia as well as systemic inflammation resulting in thromboembolic events. This case report describes the management of DIGO in a cardiac transplant recipient by change of immunosuppressant medication, non-surgical periodontal therapy and laser-assisted gingivectomy.

  5. Sub-100 nm silicon nanowires by laser interference lithography and metal-assisted etching

    NASA Astrophysics Data System (ADS)

    de Boor, Johannes; Geyer, Nadine; Wittemann, Jörg V.; Gösele, Ulrich; Schmidt, Volker

    2010-03-01

    By combining laser interference lithography and metal-assisted etching we were able to produce arrays of silicon nanowires with uniform diameters as small as 65 nm and densities exceeding 2 × 107 mm - 2. The wires are single crystalline, vertically aligned, arranged in a square pattern and obey strict periodicity over several cm2. The applied technique allows for a tailoring of nanowire size and density. Using a controlled and scalable process to fabricate sub-100 nm silicon nanowires is an important step towards the realization of cost-effective electronic and thermoelectric devices.

  6. 9 CFR 91.29 - Hatches.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ....25 (e) and (f) are met and sufficient space shall be left clear on such hatches for passageway across... stowed, sufficient space shall be left clear for the proper removal and handling of such hay and feed...

  7. Hatches Open, Expedition 32 Expands to Six

    NASA Video Gallery

    The hatches between the Soyuz and the Rassvet module opened Tuesday at 3:23 a.m. when Flight Engineers Suni Williams, Yuri Malenchenko and Aki Hoshide entered the International Space Station. Exped...

  8. Gold nanoshell/polysaccharide nanofilm for controlled laser-assisted tissue thermal ablation.

    PubMed

    Redolfi Riva, Eugenio; Desii, Andrea; Sinibaldi, Edoardo; Ciofani, Gianni; Piazza, Vincenzo; Mazzolai, Barbara; Mattoli, Virgilio

    2014-06-24

    We report on the fabrication and characterization of a freestanding ultrathin, mucoadhesive gold nanoshell/polysaccharide multilayer nanocomposite (thermonanofilm, TNF), that can be used for controlled photothermal ablation of tissues through irradiation with near-infrared radiation (NIR) laser. The aim of this work is to provide a new strategy to precisely control particle concentration during photothermalization of cancerous lesions, since unpredictable and aspecific biodistributions still remains the central issue of inorganic nanoparticle-assisted photothermal ablation. Gold nanoshell encapsulation in polysaccharide matrix is achieved by drop casting deposition method combined with spin-assisted layer-by-layer (LbL) assembly. Submicrometric thickness of films ensures tissue adhesion. Basic laser-induced heating functionality has been demonstrated by in vitro TNF-mediated thermal ablation of human neuroblastoma cancer cells, evidenced by irreversible damage to cell membranes and nuclei. Ex vivo localized vaporization and carbonization of animal muscular tissue is also demonstrated by applying TNF onto tissue surface. Thermal distribution in the tissue reaches a steady state in a few seconds, with significant increases in temperature (ΔT > 50) occurring across an 1 mm span, ensuring control of local photothermalization and providing more safety and predictability with respect to traditional laser surgery. A steady-state model of tissue thermalization mediated by TNFs is also introduced, predicting the temperature distribution being known the absorbance of TNFs, the laser power, and the tissue thermal conductivity, thus providing useful guidelines in the development of TNFs. Thermonanofilms can find applications for local photothermal treatment of cancerous lesions and wherever high precision and control of heat treatment is required.

  9. In vivo laser assisted end-to-end anastomosis with ICG-infused chitosan patches

    NASA Astrophysics Data System (ADS)

    Rossi, Francesca; Matteini, Paolo; Esposito, Giuseppe; Scerrati, Alba; Albanese, Alessio; Puca, Alfredo; Maira, Giulio; Rossi, Giacomo; Pini, Roberto

    2011-07-01

    Laser assisted vascular repair is a new optimized technique based on the use of ICG-infused chitosan patch to close a vessel wound, with or even without few supporting single stitches. We present an in vivo experimental study on an innovative end-to-end laser assisted vascular anastomotic (LAVA) technique, performed with the application of ICGinfused chitosan patches. The photostability and the mechanical properties of ICG-infused chitosan films were preliminary measured. The in vivo study was performed in 10 New Zealand rabbits. After anesthesia, a 3-cm segment of the right common carotid artery was exposed, thus clamped proximally and distally. The artery was then interrupted by means of a full thickness cut. Three single microsutures were used to approximate the two vessel edges. The ICG-infused chitosan patch was rolled all over the anastomotic site and welded by the use of a diode laser emitting at 810 nm and equipped with a 300 μm diameter optical fiber. Welding was obtained by delivering single laser spots to induce local patch/tissue adhesion. The result was an immediate closure of the anastomosis, with no bleeding at clamps release. Thus animals underwent different follow-up periods, in order to evaluate the welded vessels over time. At follow-up examinations, all the anastomoses were patent and no bleeding signs were documented. Samples of welded vessels underwent histological examinations. Results showed that this technique offer several advantages over conventional suturing methods: simplification of the surgical procedure, shortening of the operative time, better re-endothelization and optimal vascular healing process.

  10. Investigations of ion-irradiated uranium dioxide nuclear fuel with laser-assisted atom probe tomography

    NASA Astrophysics Data System (ADS)

    Valderrama, Billy

    Performance in commercial light water reactors is dictated by the ability of its fuel material, uranium dioxide (UO2), to transport heat generated during the fission process. It is widely known that the service lifetime is limited by irradiation-induced microstructural changes that degrade the thermal performance of UO2. Studying the role of complex, often interacting mechanisms that occur during the early stages of microstructural evolution presents a challenge. Phenomena of particular interest are the segregation of fission products to form bubbles and their resultant effect on grain boundary (GB) mobility, and the effect of irradiation on fuel stoichiometry. Each mechanism has a profound consequence on fuel thermal conductivity. Several advanced analytical techniques, such as transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, etc. have been used to study these mechanisms. However, they each have limitations and cannot individually provide the necessary information for deeper understanding. One technique that has been under utilized is atom probe tomography (APT), which has a unique ability to spatially resolve small-scale chemical variations. APT uses the principle of field ionization to evaporate surface ions for chemical analysis. For low electrical conductivity systems, a pulsed laser is used to thermally assist in the evaporation process. One factor complicating the analysis is that laser-material interactions are poorly understood for oxide materials and literature using this technique with UO2 is lacking. Therefore, an initial systematic study to identify the optimal conditions for the analysis of UO2 using laser-assisted APT was conducted. A comparative study on the evaporation behavior between CeO2 and UO2 was followed. CeO2 was chosen due to its technological relevancy and availability of comparative studies with laser-assisted APT. Dissimilar evaporation behavior between these materials was identified and attributed

  11. Spectral Interference Elimination in Soil Analysis Using Laser-Induced Breakdown Spectroscopy Assisted by Laser-Induced Fluorescence.

    PubMed

    Yi, Rongxing; Li, Jiaming; Yang, Xinyan; Zhou, Ran; Yu, Huiwu; Hao, Zhongqi; Guo, Lianbo; Li, Xiangyou; Zeng, Xiaoyan; Lu, Yongfeng

    2017-02-21

    The complex and serious spectral interference makes it difficult to detect trace elements in soil using laser-induced breakdown spectroscopy (LIBS). To address it, LIBS-assisted by laser-induced fluorescence (LIBS-LIF) was applied to selectively enhance the spectral intensities of the interfered lines. Utilizing this selective enhancement effect, all the interference lines could be eliminated. As an example, the Pb I 405.78 nm line was enhanced selectively. The results showed that the determination coefficient (R(2)) of calibration curve (Pb concentration range = 14-94 ppm), the relative standard deviation (RSD) of spectral intensities, and the limit of detection (LOD) for Pb element were improved from 0.6235 to 0.9802, 10.18% to 4.77%, and 24 ppm to 0.6 ppm using LIBS-LIF, respectively. These demonstrate that LIBS-LIF can eliminate spectral interference effectively and improve the ability of LIBS to detect trace heavy metals in soil.

  12. Laser assisted and hermetic room temperature bonding based on direct bonding technology

    NASA Astrophysics Data System (ADS)

    Haneveld, Jeroen; Tijssen, Peter; Oonk, Johannes; Olde Riekerink, Mark; Tigelaar, Hildebrand; van't Oever, Ronny; Blom, Marko

    2014-03-01

    A novel method for laser assisted room temperature bonding of two substrates is presented. The method enables the packaging of delicate (bio)structures and/or finished (MEMS) devices, as there is no need for a high temperature annealing process. This also allows the bonding of two substrates with non-matching thermal expansion coefficients. The basis of the presented technology is the ability to create a direct pre-bond between two substrates. These can be two glass substrates, of which one has a thin film metal coating (e.g. Cr. Ti, Ta, Au…), or a silicon-glass combination. After (aligned) pre-bonding of the two wafers, a laser (e.g. a Nd:YAG laser) is used to form a permanent bond line on the bond interface, using the metal layer as a light absorber (or the silicon, in the case of a glass-silicon combination). The permanent bond line width is in the order of 10-50μm. The use of a laser to form the permanent bond ensures a hermetic sealing of the total package; a distinctive advantage over other, more conventional methods of room temperature bonding (e.g. adhesive bonding). He-leak testing showed leak rates in the order of 10-9 mbar l/s. This meets the failure criteria of the MIL-STD-883H standard of 5x10-8 mbar l/s. An added functionality of the proposed method is the possibility to create electrical circuitry on the bond interface, using the laser to modify the metal interlayer, rendering it electrically non-conductive. Biocompatible packages are also possible, by choosing the appropriate interlayer material. This would allow for the fabrication of implantable packages.

  13. Femtosecond laser assisted design of sutureless intrastromal graft as an alternative to partial thickness keratoplasty

    NASA Astrophysics Data System (ADS)

    Rossi, Francesca; Durkee, Heather; Pini, Roberto; Canovetti, Annalisa; Malandrini, Alex; Lenzetti, Ivo; Rubino, Pierangela; Leaci, Rosachiara; Neri, Alberto; Scaroni, Patrizia; Menabuoni, Luca; Macaluso, Claudio

    2014-02-01

    Minimally invasive laser assisted surgery in ophthalmology is continuously developing in order to find new surgical approaches, preserve patient tissue and improve surgical results in terms of cut precision, restoration of visual acuity, and invasiveness. In order to achieve these goals, the current approach in corneal transplant is lamellar keratoplasty, where only the anterior or posterior part of the patient's cornea is substituted depending on the lesion or pathology. In this work, we present a novel alternative approach: a case study of intrastromal sutureless transplant, where a portion of the anterior stroma of a donor cornea was inserted into the stroma of the recipient cornea, aiming to restore the correct thickness of the patient's cornea. The patient cornea was paracentrally thin, as the result of a trophic ulcer due to ocular pemphigoid. A discoid corneal graft from the anterior stroma of a donor eye was prepared: a femtosecond laser cut with a trapezoidal profile (thickness was 300 μm, minor and major basis were 3.00 and 3.50 mm, respectively). In the recipient eye, an intrastromal cut was also performed with the femtosecond laser using a specifically designed mask; the cut position was 275 μm in depth. The graft was loaded into an injector and inserted as an intrastromal presbyopic implant. The postoperative analysis evidenced a clear and stable graft that selectively restored corneal thickness in the thinned area. Intrastromal corneal transplant surgery is a minimally invasive alternative to anterior or posterior lamellar keratoplasty in select cases. We believe that Sutureless Intrastromal Laser Keratoplasty (SILK) could open up new avenues in the field of corneal transplantation by fully utilizing the potential and precision of existing lasers.

  14. Comparison of femtosecond laser-assisted descemetic and predescemetic lamellar keratoplasty for keratoconus

    PubMed Central

    Lu, Yan; Grisolia, Ana Beatriz Diniz; Ge, Yi-Rui; Xue, Chun-Yan; Cao, Qian; Yang, Li-Ping; Huang, Zhen-Ping

    2017-01-01

    Purpose: The purpose of this study is to compare the outcomes following femtosecond laser-assisted deep anterior lamellar keratoplasty (DALK) with 75% of stromal dissection (predescemetic group) and femtosecond laser-assisted DALK using big-bubble technique with total stromal resection (descemetic group) for the treatment of keratoconus. Subjects and Methods: Twenty eyes of 17 patients with keratoconus were studied. There were 10 eyes of 9 patients in predescemetic group and 10 eyes of 8 patients in descemetic group. The postoperative best-corrected visual acuity (BCVA), manifest refraction, keratometry, endothelial cell density (ECD), and central corneal thickness (CCT) were analyzed. Results: All surgeries were performed uneventfully. At 1 year after surgery, the BCVA, corneal astigmatism, keratometry, CCT, and ECD between two groups were not statistically significant (all P > 0.05). However, the mean manifest refraction was −9.43 ± 7.44 diopter (D) and −1.03 ± 1.13D in predescemetic and descemetic groups, respectively, which was statistically significant between two groups (P < 0.05). Conclusions: The results of BCVA and corneal astigmatism, keratometry, ECD, and CCT were comparable between two groups. However, the mean postoperative manifest refraction was lower in descemetic group. PMID:28300735

  15. Laser assisted micro-welding of ultra-thin glass wafers

    NASA Astrophysics Data System (ADS)

    Hevonkorpi, V.; Lundén, H.; Määttänen, A.

    2016-03-01

    The use of glass in semiconductor industry has been growing during the past years and the grow is estimated to continue and accelerate considerably during the coming years. For efficient manufacturing, especially when using ultra-thin wafers, novel bonding technologies are needed. In this paper, a laser assisted additive free glass-glass welding technology is presented. Furthermore, the use of laser assisted welding to manufacture hermetic packages for optical components is investigated. The reliability and robustness of the weld and the process is verified by damp heat (85 °C at 85% RH) testing. A large quantity, one hundred samples, was tested to define the repeatability of the welding process. D263T, a glass type commonly used in manufacturing consumer products, was selected. Glass-glass welding proved to be a reliable bonding method offering a non-outgassing, room temperature bonding. In addition, it was verified that the weld is hermetic having a good resistance to high temperature and moisture conditions. No changes in the welding seams were observed during or after damp heat testing.

  16. Developmental competence of mouse embryos following zona drilling using a non-contact holmium:yttrium scandian gallium garnet (Ho:YSGG) laser system.

    PubMed

    Schiewe, M C; Neev, J; Hazeleger, N L; Balmaceda, J P; Berns, M W; Tadir, Y

    1995-07-01

    The purpose of this study was to assess the efficacy of the holmium:yttrium scandian gallium garnet (Ho:YSGG) laser, operating in a pipette-free, non-contact mode, to assist hatching and sustain normal embryonic development. Two-cell mouse embryos were recovered and assigned to laser-assisted hatching (LAH) treatment or control human tubal fluid (HTF) culture with or without serum (HTF-s, HTF-o) or with late serum supplementation (HTF-o/s). The basic experimental apparatus for LAH consisted of a stationary 2.1 microns Ho:YSGG laser beam directed through a mechanical shutter into an input port of a Zeiss Axiomat inverted microscope. Fewer (P < 0.05) embryos developed to the blastocyst stage in the HTF-s group (81%) than in the LAH (90%), HTF-o (94%) and HTF-o/s (92%) groups. The level of hatching was significantly increased (P < 0.01) after the LAH treatment (57%) compared to HTF-o/s (32%), HTF-s (18%) or HTF-o (5%). Implantation rates were not significantly impaired following the LAH treatment (21%). These data demonstrate that LAH using the Ho:YSGG laser is a simple, accurate and effective procedure for assisted hatching.

  17. Laser-assisted inkjet printing of highly viscous fluids with sub-nozzle resolution

    NASA Astrophysics Data System (ADS)

    Delrot, Paul; Modestino, Miguel A.; Psaltis, Demetri; Moser, Christophe

    2016-04-01

    Drop-on-demand inkjet printing is mostly based on thermal and piezo-actuation, allowing for densely packed nozzles in inkjet printers. However, the droplet diameter is typically defined by the nozzle diameter, thus limiting the range of viscosity that can be jetted to 10-100 mPa.s to prevent nozzle clogging. Here, we present a laser-assisted system for the delivery of micro-droplets of highly viscous fluids with sub-nozzle resolution. Highly focused supersonic jets have recently been demonstrated by focusing a nanosecond pulse of light into a micro-capillary filled with dyed water, hence generating a cavitation bubble. The consequent pressure wave impact on the concave free surface of the liquid generated flow-focused micro-jets. We implemented this technique for the production of low velocity micro-droplets with photopolymer inks of increasing viscosity (0.6-148 mPa.s) into a 300 μm-wide glass capillary using low laser energies (3-70 μJ). Time-resolved imaging provided details on the droplet generation. Single micro-droplets of diameter 70-80 μm were produced on demand with inks of viscosity 0.6-9 mPa.s with good controllability and reproducibility, thus enabling to print two-dimensional patterns with a precision of 13 μm. Furthermore, the primary droplet produced with the most viscous fluid was about 66% of the capillary diameter. Preliminary results also showed that the process is linearly scalable to narrower capillaries (100-200 μm), thus paving the way for a compact laser-assisted inkjet printer. A possible application of the device would be additive manufacturing as the printed patterns could be consequently cured.

  18. Laser-Assisted Surface Modification of Alumina and Its Tribological Behavior

    NASA Astrophysics Data System (ADS)

    Wallstabe, R.

    2013-01-01

    High performance friction systems, e.g., dry clutches and brakes, require a good wear resistance and a friction coefficient that is nearly independent from sliding velocity and environmental conditions. Organic-based friction materials have reached their limitations regarding higher power densities. Engineering ceramics such as alumina (Al2O3) or silicon carbide (SiC) offer a great potential since remarkably higher thermal and mechanical loading is possible. However, the tribological performance of these monolithic ceramics is still insufficient. The aim of the present study was to assess the potential of a laser-assisted surface modification process in order to improve the tribological performance with regard to the application in dry friction systems. Therefore, commercially available alumina was modified using a newly developed laser-assisted preheating process and subsequent melting of the ceramic's surface using a CO2-laser and modification by additives such as TiC, TiN, B4C, WC, ZrB2, Cr, Ni, Cu, and Ti. A systematic variation of additives and process parameters led to different multiphase microstructures. Subsequently, these were characterized using scanning electron microscopy and surface analysis methods (wavelength dispersive X-ray spectroscopy, energy dispersive X-ray spectroscopy). Finally, the tribological properties were investigated using a laboratory tribometer. The surface-modified ceramics were tested in unidirectional sliding motion against steel disks. The tribological results of the surface-modified ceramics were compared to those of monolithic Al2O3 and SiC ceramics and showed a reduced dependence of friction coefficient on sliding velocity. Moreover, the multi-phase ceramics possessed a higher wear resistance than the monolithic ones.

  19. Detection of trace ink compounds in erased handwritings using electrospray-assisted laser desorption ionization mass spectrometry.

    PubMed

    Kao, Yi-Ying; Cheng, Sy-Chyi; Cheng, Chu-Nian; Shiea, Jentaie; Ho, Hsiu-O

    2014-06-01

    Writings made with erasable pens on paper surfaces can either be rubbed off with an eraser or rendered invisible by changing the temperature of the ink. However, trace ink compounds still remain in the paper fibers even after rubbing or rendering. The detection of these ink compounds from erased handwritings will be helpful in knowing the written history of the paper. In this study, electrospray-assisted laser desorption ionization/mass spectrometry was used to characterize trace ink compounds remaining in visible and invisible ink lines. The ink compounds were desorbed from the paper surface by irradiating the handwritings with a pulsed laser beam; the desorbed analytes were subsequently ionized in an electrospray plume and detected by a quadrupole time-of-flight mass spectrometry mass analyzer. Because of the high spatial resolution of the laser beam, electrospray-assisted laser desorption ionization/mass spectrometry analysis resulted in minimal damage to the sample documents.

  20. Rapid ablation of dental hard tissue using promoter-assisted pulsed Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Frederickson, Christopher J.; Lu, Quiang; Hayes, Donald J.; Wallace, David B.; Grove, Michael E.; Bell, Brent A.; Motamedi, Massoud; Rastegar, Sohi; Wright, C. G.; Arcoria, Charles J.

    1997-05-01

    Nd:YAG lasers have been used previously for selective removal of various material from teeth. To permit ablation of healthy enamel with the Nd:YAG laser, we have adopted a strategy in which micro-drops of photoabsorptive 'promoters' are placed on the enamel to enhance absorption of individual laser pulses. Ink-jet technology dispenses the micro-drops with micron- and millisecond-scale precision. Various promoters using drug and cosmetic dyes, indocyanine green, or carbon-black pigments have been studied. Typical ablation parameters are 1.064 micrometers ; 20-180 mJ per pulse; 100 microsecond(s) ; 10-30 pulses/sec; 0.2-2.0 nl drops. Recent results from the program include: (1) For a variety of promoters, a monotonic relationship obtains between absorption coefficient at 1.064 micrometers and the efficiency of ablation of enamel. (2) With different promoter volumes, the efficiency of ablation rises, plateaus, then falls with increasing volume. (3) At drilling rates of 30 pulses/sec, ablation efficiency approaches rates of 0.1 mm3/sec. LM and SEM observations show a glassy 'pebbled' crater surface indicative of hydroxyapatite that has cooled, condensed, and solidified on the crater walls. Together these results favor the view that a micro-drop promoter-assisted Nd:YAG drill can five clinically useful ablations hard dental tissue.

  1. 3-D patterning of silicon by laser-initiated, liquid-assisted colloidal (LILAC) lithography.

    PubMed

    Ulmeanu, M; Grubb, M P; Jipa, F; Quignon, B; Ashfold, M N R

    2015-06-01

    We report a comprehensive study of laser-initiated, liquid-assisted colloidal (LILAC) lithography, and illustrate its utility in patterning silicon substrates. The method combines single shot laser irradiation (frequency doubled Ti-sapphire laser, 50fs pulse duration, 400nm wavelength) and medium-tuned optical near-field effects around arrays of silica colloidal particles to achieve 3-D surface patterning of silicon. A monolayer (or multilayers) of hexagonal close packed silica colloidal particles act as a mask and offer a route to liquid-tuned optical near field enhancement effects. The resulting patterns are shown to depend on the difference in refractive index of the colloidal particles (ncolloid) and the liquid (nliquid) in which they are immersed. Two different topographies are demonstrated experimentally: (a) arrays of bumps, centred beneath the original colloidal particles, when using liquids with nliquidncolloid - and explained with the aid of complementary Mie scattering simulations. The LILAC lithography technique has potential for rapid, large area, organized 3-D patterning of silicon (and related) substrates.

  2. Laser assisted internal mammary artery-coronary artery anastomosis - an experimental study

    NASA Astrophysics Data System (ADS)

    Zhu, Hong-Sheng; Zhang, Liang-ping; Feng, Lian

    2005-07-01

    Objective: To observe the time required for anastomosis and the reliability for pressure tolerance after internal mammay artery (IMA) -coronary artery anastomosis. Method: Eight sheep underwent thoracotomy and left IMA harvest. In group I (T) the IMA were anastomosed to left anterior descending artery (LAD) with 7-0 prolene suture (n=4) and in group II (LA) IMA were anastomosed to LAD with laser. Result: The time required for laser technique was shorter than that required in suturing technique [117.5+/-39.48min (total) and 38.25+/-6.23 min vs 62.5+/-37.83 min (total) and 20+/-6.53 min respectively ] (p<0.01). Prior to closing thoracotomy both two groups endured the impact of pharmacologic vasopressor. No leakage at the anastomosed site was observed in both groups. After the closure of thoracotomy, well tolerance for both adrenalin and thoracic negative pressure was observed in the two groups. The peak systolic pressure induced by pharmacologic agent was similar in both groups. Neither stenosis nor thrombus or embolism was observed and immediate patency rate in both groups was 100%. Conclusion: Laser assisted technique seems to be favorable for patency rate and could lead to better result after coronary artery bypass grafting(CABG).

  3. High-throughput continuous flow femtosecond laser-assisted cell optoporation and transfection.

    PubMed

    Breunig, Hans Georg; Uchugonova, Aisada; Batista, Ana; König, Karsten

    2014-12-01

    We present a femtosecond-laser based nanoprocessing system for transient optical cell membrane poration to allow the introduction of foreign molecules into the interior of a cell with very high throughput. In the setup, cells flow through a micro-flow tube for spatial confinement and are simultaneously targeted by fs laser radiation. Beam-shaping generates a focal geometry along a line which is scanned across the micro-flow cell to increase the number of reachable cells. Successful cell membrane poration was observed indirectly by cell transfection even with cell-light interaction times in the millisecond range. The system was characterized by experiments with Chinese hamster ovary cells regarding cell viability, the uptake of extrinsic molecules and cell transfection efficiency. The continuous flow of cells enables a tremendous increase of cell throughput compared to previous nonflow approaches by treating millions of cells, although with only limited efficiency. The setup opens the possibility to realize a completely automated high-throughput laser-assisted cell-poration system which could be integrated in lab-on-a-chip devices.

  4. The effect of the matrix on film properties in matrix-assisted pulsed laser evaporation

    NASA Astrophysics Data System (ADS)

    Bubb, D. M.; Wu, P. K.; Horwitz, J. S.; Callahan, J. H.; Galicia, M.; Vertes, A.; McGill, R. A.; Houser, E. J.; Ringeisen, B. R.; Chrisey, D. B.

    2002-02-01

    Thin films of polyethylene glycol of average molecular weight 1400 amu have been deposited by matrix-assisted pulsed laser evaporation (MAPLE). The deposition was carried out in vacuum (˜10-6 Torr) with an ArF (λ=193 nm) laser at a fluence of 220-230 mJ/cm2. Films were deposited on NaCl plates and glass microscope slides. Both deionized water (H2O) and chloroform (CHCl3) were used as matrices. The physiochemical properties of the films are compared via Fourier transform infrared spectroscopy, and electrospray ionization mass spectrometry. The results show that the matrix used during MAPLE can greatly affect the chemical structure and molecular weight distribution of the deposited film. The infrared absorption spectrum shows evidence for C-Cl bond formation when CHCl3 is used as a matrix, while there is little evidence in the IR data for photochemical modification when H2O is used as a matrix. Time-of-flight analysis was performed using a quadrupole mass spectrometer to monitor evaporation of a frozen CHCl3 target during laser exposure. Using this approach, we determined that the TOF spectra for m/z=35 (Cl) and m/z=85 (CHCl2) differed significantly in both width and peak arrival time, indicating that neutral chlorine atoms were produced at the target surface. We attribute the reduction in molecular weight and structural modification of the film deposited using CHCl3 to the presence of these highly reactive species.

  5. Inert Gas Enhanced Laser-Assisted Purification of Platinum Electron-Beam-Induced Deposits.

    PubMed

    Stanford, Michael G; Lewis, Brett B; Noh, Joo Hyon; Fowlkes, Jason D; Rack, Philip D

    2015-09-09

    Electron-beam-induced deposition patterns, with composition of PtC5, were purified using a pulsed laser-induced purification reaction to erode the amorphous carbon matrix and form pure platinum deposits. Enhanced mobility of residual H2O molecules via a localized injection of inert Ar-H2 (4%) is attributed to be the reactive gas species for purification of the deposits. Surface purification of deposits was realized at laser exposure times as low as 0.1 s. The ex situ purification reaction in the deposit interior was shown to be rate-limited by reactive gas diffusion into the deposit, and deposit contraction associated with the purification process caused some loss of shape retention. To circumvent the intrinsic flaws of the ex situ anneal process, in situ deposition and purification techniques were explored that resemble a direct write atomic layer deposition (ALD) process. First, we explored a laser-assisted electron-beam-induced deposition (LAEBID) process augmented with reactive gas that resulted in a 75% carbon reduction compared to standard EBID. A sequential deposition plus purification process was also developed and resulted in deposition of pure platinum deposits with high fidelity and shape retention.

  6. Inert gas enhanced laser-assisted purification of platinum electron-beam-induced deposits

    SciTech Connect

    Stanford, Michael G.; Lewis, Brett B.; Noh, Joo Hyon; Fowlkes, Jason Davidson; Rack, Philip D.

    2015-06-30

    Electron-beam-induced deposition patterns, with composition of PtC5, were purified using a pulsed laser-induced purification reaction to erode the amorphous carbon matrix and form pure platinum deposits. Enhanced mobility of residual H2O molecules via a localized injection of inert Ar–H2 (4%) is attributed to be the reactive gas species for purification of the deposits. Surface purification of deposits was realized at laser exposure times as low as 0.1 s. The ex situ purification reaction in the deposit interior was shown to be rate-limited by reactive gas diffusion into the deposit, and deposit contraction associated with the purification process caused some loss of shape retention. To circumvent the intrinsic flaws of the ex situ anneal process, in situ deposition and purification techniques were explored that resemble a direct write atomic layer deposition (ALD) process. First, we explored a laser-assisted electron-beam-induced deposition (LAEBID) process augmented with reactive gas that resulted in a 75% carbon reduction compared to standard EBID. Lastly, a sequential deposition plus purification process was also developed and resulted in deposition of pure platinum deposits with high fidelity and shape retention.

  7. Infrared-laser-assisted photoionization of helium by coherent extreme ultraviolet light

    SciTech Connect

    Tong Xiaomin; Toshima, Nobuyuki

    2010-04-15

    We investigate the infrared (IR)-laser-assisted photoionization of He by a coherent extreme ultraviolet (euv) light solving the time-dependent Schroedinger equation. A combined field of the 13th and 15th harmonics created from the same IR laser source is used to ionize He atoms coherently. We show that the ionization probabilities oscillate as a function of the time delay between the IR and the euv pulses. On the other hand, the oscillation amplitude increases as the IR intensity increases, reaches a maximum when the IR intensity is around 6x10{sup 12} W/cm{sup 2}, and then decreases as the IR intensity increases further. Decomposing the ionization probabilities by the 13th and 15th harmonics, we illustrate that the oscillation amplitude is small for a lower IR laser intensity due to the fact that the transition strength by the 13th harmonic is much smaller than the one by the 15th harmonic. When the IR intensity increases further above 6x10{sup 12} W/cm{sup 2}, the transition strength by the 13th harmonic becomes larger than the one by the 15th harmonic and the oscillation amplitude is reduced again. By tuning the relative field strengths of the 13th and 15th harmonics or the IR intensity, we can control the oscillation amplitude.

  8. Laser desorption ionization of small molecules assisted by tungsten oxide and rhenium oxide particles.

    PubMed

    Bernier, Matthew C; Wysocki, Vicki H; Dagan, Shai

    2015-07-01

    Inorganic metal oxides have shown potential as matrices for assisting in laser desorption ionization with advantages over the aromatic acids typically used. Rhenium and tungsten oxides are attractive options due to their high work functions and relative chemical inertness. In this work, it is shown that ReO3 and WO3 , in microparticle (μP) powder forms, can efficiently facilitate ionization of various types of small molecules and provide minimized background contamination at analyte concentrations below 1 ng/µL. This study shows that untreated inorganic WO3 and ReO3 particles are valid matrix options for detection of protonatable, radical, and precharged species under laser desorption ionization. Qualitatively, the WO3 μP showed improved detection of apigenin, sodiated glucose, and precharged analyte choline, while the ReO3 μP allowed better detection of protonated cocaine, quinuclidine, ametryn, and radical ions of polyaromatic hydrocarbons at detection levels as low as 50 pg/µL. For thermometer ion survival yield experiments, it was also shown that the ReO3 powder was significantly softer than α-cyano-4-hydroxycinnaminic acid. Furthermore, it provided higher intensities of cocaine and polyaromatic hydrocarbons, at laser flux values equal to those used with α-cyano-4-hydroxycinnaminic acid.

  9. Beam steering laser assisted deposition system for high- T sub c superconducting thin film devices

    SciTech Connect

    Pham, T.T.; Chen, K.W. )

    1991-03-01

    We present the design and construction of a beam steering laser-assisted deposition system (LAD) for high quality epitaxial YBaCuO superconducting thin film production suitable for commercial application. Deposition of single layer or multilayer YBaCuO superconducting thin film on large and complex surfaced substrate is now feasible. Expitaxial and polycrystaline films with onsets at 90 K having 6 K transition widths have been produced. Dome-shaped magnetic shield enclosures, microwave cavity resonant in the TM{sub 010} mode, and short dipole antennas have been fabricated. The advantages of the laser ablation deposition method (J. T. Cheung and D. T. Chueng, J. Vac. Sci. Technol. {bold 21}, 182 (1982)) are its simplicity and cleanliness. Laser ablation deposition is a viable method to produce high quality thin film of the Tl-based compound (S. H. Liou and K. D. Aylesworth, Appl. Phys. Lett. {bold 54}, 760 (1989)) by using a small target in a sealed environment which is important in handling toxic material of a Tl-based compounds.

  10. Laser-processing of VO2 thin films synthesized by polymer-assisted-deposition

    NASA Astrophysics Data System (ADS)

    Breckenfeld, Eric; Kim, Heungsoo; Gorzkowski, Edward P.; Sutto, Thomas E.; Piqué, Alberto

    2017-03-01

    We investigate a novel route for synthesis and laser-sintering of VO2 thin films via solution-based polymer-assisted-deposition (PAD). By replacing the traditional solvent for PAD (water) with propylene glycol, we are able to control the viscosity and improve the environmental stability of the precursor. The solution stability and ability to control the viscosity makes for an ideal solution to pattern simple or complex shapes via direct-write methods. We demonstrate the potential of our precursor for printing applications by combining PAD with laser induced forward transfer (LIFT). We also demonstrate large-area film synthesis on 4 in. diameter glass wafers. By varying the annealing temperature, we identify the optimal synthesis conditions, obtaining optical transmittance changes of 60% at a 2500 nm wavelength and a two-order-of-magnitude semiconductor-to-metal transition. We go on to demonstrate two routes for improved semiconductor-to-metal characteristics. The first method uses a multi-coating process to produce denser films with large particles. The second method uses a pulsed-UV-laser sintering step in films annealed at low temperatures (<450° C) to promote particle growth and improve the semiconductor-to-metal transition. By comparing the hysteresis width and semiconductor-to-metal transition magnitude in these samples, we demonstrate that both methods yield high quality VO2 with a three-order-of-magnitude transition.

  11. Chromophore-assisted laser inactivation (CALI) to elucidate cellular mechanisms of cancer.

    PubMed

    Jay, D G; Sakurai, T

    1999-10-29

    Chromophore-assisted laser inactivation (CALI) is a new technology for acute protein inactivation in living cells. It targets laser energy to specific proteins via non-function-blocking antibodies that are labeled with the dye malachite green. Excitation of the dye generates short-lived free radicals that damage the bound protein without affecting other cellular components. The wavelength of laser light used (620 nm) is not readily absorbed by cells such that non-specific light damage does not occur. CALI provides an alternative to other inactivation strategies and has the advantages of high spatial and temporal resolution. The ultimate value of this technology for cancer research will be assessed by how effective CALI is in ascribing in situ function during cancer-relevant processes and in identifying and validating protein targets for drug discovery. Recent work using CALI on ezrin and pp60-c-src, two proteins that may be involved in cancer, suggests its potential. Further application of CALI will likely be of utility for understanding cellular mechanisms of cancer and developing cancer therapeutics.

  12. Inert gas enhanced laser-assisted purification of platinum electron-beam-induced deposits

    DOE PAGES

    Stanford, Michael G.; Lewis, Brett B.; Noh, Joo Hyon; ...

    2015-06-30

    Electron-beam-induced deposition patterns, with composition of PtC5, were purified using a pulsed laser-induced purification reaction to erode the amorphous carbon matrix and form pure platinum deposits. Enhanced mobility of residual H2O molecules via a localized injection of inert Ar–H2 (4%) is attributed to be the reactive gas species for purification of the deposits. Surface purification of deposits was realized at laser exposure times as low as 0.1 s. The ex situ purification reaction in the deposit interior was shown to be rate-limited by reactive gas diffusion into the deposit, and deposit contraction associated with the purification process caused some lossmore » of shape retention. To circumvent the intrinsic flaws of the ex situ anneal process, in situ deposition and purification techniques were explored that resemble a direct write atomic layer deposition (ALD) process. First, we explored a laser-assisted electron-beam-induced deposition (LAEBID) process augmented with reactive gas that resulted in a 75% carbon reduction compared to standard EBID. Lastly, a sequential deposition plus purification process was also developed and resulted in deposition of pure platinum deposits with high fidelity and shape retention.« less

  13. Revisiting the quantitative features of surface-assisted laser desorption/ionization mass spectrometric analysis.

    PubMed

    Wu, Ching-Yi; Lee, Kai-Chieh; Kuo, Yen-Ling; Chen, Yu-Chie

    2016-10-28

    Surface-assisted laser desorption/ionization (SALDI) coupled with mass spectrometry (MS) is frequently used to analyse small organics owing to its clean background. Inorganic materials can be used as energy absorbers and the transfer medium to facilitate the desorption/ionization of analytes; thus, they are used as SALDI-assisting materials. Many studies have demonstrated the usefulness of SALDI-MS in quantitative analysis of small organics. However, some characteristics occurring in SALDI-MS require certain attention to ensure the reliability of the quantitative analysis results. The appearance of a coffee-ring effect in SALDI sample preparation is the primary factor that can affect quantitative SALDI-MS analysis results. However, to the best of our knowledge, there are no reports relating to quantitative SALDI-MS analysis that discuss or consider this effect. In this study, the coffee-ring effect is discussed using nanoparticles and nanostructured substrates as SALDI-assisting materials to show how this effect influences SALDI-MS analysis results. Potential solutions for overcoming the existing problems are also suggested.This article is part of the themed issue 'Quantitative mass spectrometry'.

  14. Study of Pulse Laser Assisted Metalorganic Vapor Phase Epitaxy of InGaN with Large Indium Mole Fraction

    NASA Astrophysics Data System (ADS)

    Kangawa, Yoshihiro; Kawaguchi, Norihito; Hida, Ken-nosuke; Kumagai, Yoshinao; Koukitu, Akinori

    2004-08-01

    The indium composition of the InGaN film increases with decreasing growth temperature; however, the crystalline quality of the film is poor when it is grown at low temperatures. To form a high-quality InGaN film with a large indium mole fraction, Nd: YAG pulse laser assisted metalorganic vapor phase epitaxy (MOVPE) was carried out at low temperatures. The results suggest that film quality can be improved by pulse laser irradiation on the surface of the film.

  15. Buffer gas-assisted four-wave mixing resonances in alkali vapor excited by a single cw laser

    NASA Astrophysics Data System (ADS)

    Shmavonyan, Svetlana; Khanbekyan, Aleksandr; Khanbekyan, Alen; Mariotti, Emilio; Papoyan, Aram V.

    2016-12-01

    We report the observation of a fluorescence peak appearing in dilute alkali (Rb, Cs) vapor in the presence of a buffer gas when the cw laser radiation frequency is tuned between the Doppler-broadened hyperfine transition groups of an atomic D2 line. Based on steep laser radiation intensity dependence above the threshold and spectral composition of the observed features corresponding to atomic resonance transitions, we have attributed these features to the buffer gas-assisted four-wave mixing process.

  16. Comparative analysis of the performance of two different platforms for femtosecond laser-assisted cataract surgery

    PubMed Central

    Rivera, Robert P; Hoopes, Phillip C; Linn, Steven H; Hoopes, Phillip C

    2016-01-01

    Purpose To analyze and compare the intraoperative and postoperative outcomes of cataract surgery performed with two different femtosecond laser platforms. Methods Randomized controlled prospective intraindividual comparative study including 90 eyes of 45 patients aged between 61 and 86 years. All eyes underwent bilateral cataract surgery assisted with femtosecond laser technology. Eyes were randomized to one of two different femtosecond laser platforms: Catalys Precision system (Abbott Medical Optics Inc., Santa Ana, CA, USA) (Catalys group), and LenSx system (Alcon-LenSx Inc., Aliso Viejo, CA, USA) (LenSx group). Several intraoperative parameters and changes in corrected distance visual acuity and corneal endothelial density were evaluated and compared. Results The LenSx group showed a significantly higher cumulative dissipated energy and phacoemulsification power needed compared to the Catalys group (P≤0.043). Likewise, a longer patient interface preparation time, more severe perception of pressure by patient, and more cases of subconjunctival hemorrhage were found in the LenSx group (P≤0.014). A complete capsulotomy was achieved in more cases in the Catalys group compared to the LenSx group (P=0.002). Regarding corneal incisions, no statistically significant differences were found between groups (P≥0.071). The same occurred for postoperative corrected distance visual acuity (P≥0.48), endothelial cell density changes (P≥0.14), and the incidence of corneal edema or flare (P≥0.399). Conclusion Cataract surgery with the two evaluated femtosecond laser platforms is a safe procedure, with reduced phaco time and energy, and preservation of corneal endothelium integrity. However, both systems differ in the performance of capsulotomy and the procedure of docking, with an advantage of the Catalys over the LenSx system. PMID:27799734

  17. Laser ablation plasma-assisted stabilization of premixed methane/air flame

    NASA Astrophysics Data System (ADS)

    Li, Xiaohui; Yu, Yang; Peng, Jiangbo; Yu, Xin; Fan, Rongwei; Sun, Rui; Chen, Deying

    2016-01-01

    Laser ablation plasma has been applied to assist stabilization of premixed methane/air flames with a flow speed up to 15.3 m/s. The ablation plasma was generated using the 50 Hz, 1064 nm output of a Nd:YAG laser onto a tantalum slab. With the ablation plasma, the stabilization equivalence ratio has been extended to the fuel-leaner end and the blow off limits have been enhanced by from 3.6- to 14.8-folds for flames which can stabilize without the plasma. The laser pulse energy required for flameholding was reduced to 10 mJ, a 64 % reduction compared with that of gas breakdown plasma, which will ease the demand for high-power lasers for high-frequency plasma generation. The temporal evolutions of the flame kernels following the ablation plasma were investigated using the OH* chemiluminescence imaging approach, and the flame propagation speed ( v f) was measured from the flame kernel evolutions. With the ablation plasma, the v f with flow speed of 4.7-9.0 m/s and equivalence ratio of 1.4 has been enhanced from 0.175 m/s of laminar premixed methane/air flame to 2.79-4.52 and 1.59-5.46 m/s, respectively, in the early and late time following the ablation plasma. The increase in the combustion radical concentrations by the ablation plasma was thought to be responsible for the v f enhancement and the resulted flame stabilization.

  18. Comparison of laser-assisted fibrinogen-bonded and sutured canine arteriovenous anastomoses.

    PubMed

    Oz, M C; Libutti, S K; Ashton, R C; Lontz, J F; Lemole, G M; Nowygrod, R

    1992-07-01

    The effect of laser-assisted fibrinogen bonding (LAFB) on the development of intimal hyperplasia was studied with stress-strain profiles and histologic evaluation of canine arteriovenous fistulas (AVFs). In 19 animals femoral AVFs were created with an 808 nm diode laser after topical application of fibrinogen mixed with indocyanine green dye; in the contralateral limb a sutured AVF was created. The animals were divided into three groups. Group 1 dogs (n = 6) were killed serially up to 4 weeks after surgery to examine the healing of the anastomoses created with LAFB. Group 2 dogs (n = 6) were killed 1 month after surgery, and the fresh specimens were strained axially to produce a stress-strain profile graph. Group 3 dogs (n = 7) were killed 7 months after surgery, and the AVFs were infused with formalin under pressure and histologically prepared to allow comparison of the ratio of maximum to minimum intimal hypertrophy. Fibrinogen used for LAFB was resorbed during the first month after operation without evidence of foreign body reaction or inflammation. Tensile break force was not significantly different in the laser-bonded group (4.6 +/- 2.4 pounds) and the sutured group (4.3 +/- 1.7 pounds). The modulus (tensile break force per square inch), a measure of elasticity, identified the laser-bonded AVF (149 +/- 44 pounds per square inch) to be less rigid than the sutured AVF (203 +/- 35 pounds per square inch) (p less than 0.05). No significant differences in the degree of intimal hyperplasia were noted in any area of the anastomoses. Use of LAFB neither accelerates nor prevents intimal hyperplasia in a canine AVF model.(ABSTRACT TRUNCATED AT 250 WORDS)

  19. Optical pulse generation in a transistor laser via intra-cavity photon-assisted tunneling and excess base carrier redistribution

    SciTech Connect

    Feng, M.; Iverson, E. W.; Wang, C. Y.; Holonyak, N.

    2015-11-02

    For a direct-gap semiconductor (e.g., a p-n junction), photon-assisted tunneling is known to exhibit a high nonlinear absorption. In a transistor laser, as discussed here, the coherent photons generated at the quantum well interact with the collector junction field and “assist” electron tunneling from base to collector, thus resulting in the nonlinear modulation of the laser and the realization of optical pulse generation. 1 and 2 GHz optical pulses are demonstrated in the transistor laser using collector voltage control.

  20. Fabrication of microchannels in single-crystal GaN by wet-chemical-assisted femtosecond-laser ablation

    NASA Astrophysics Data System (ADS)

    Nakashima, Seisuke; Sugioka, Koji; Midorikawa, Katsumi

    2009-09-01

    We investigated micro- and nano-fabrication of wide band-gap semiconductor gallium nitride (GaN) using a femtosecond (fs) laser. Nanoscale craters were successfully formed by wet-chemical-assisted fs-laser ablation, in which the laser beam is focused onto a single-crystal GaN substrate in a hydrochloric acid (HCl) solution. This allows efficient removal of ablation debris produced by chemical reactions during ablation, resulting in high-quality ablation. However, a two-step processing method involving irradiation by a fs-laser beam in air followed by wet etching, distorts the shape of the crater because of residual debris. The threshold fluence for wet-chemical-assisted fs-laser ablation is lower than that for fs-laser ablation in air, which is advantageous for improving fabrication resolution since it reduces thermal effects. We have fabricated craters as small as 510 nm by using a high numerical aperture (NA) objective lens with an NA of 0.73. Furthermore, we have formed three-dimensional hollow microchannels in GaN by fs-laser direct-writing in HCl solution.

  1. Fabrication of microlens arrays on soda-lime glass using a laser direct-write technique and a thermal treatment assisted by a CO2 laser

    NASA Astrophysics Data System (ADS)

    Delgado, Tamara; Nieto, Daniel; Flores-Arias, María Teresa

    2015-10-01

    A low-cost method for fabricating microlens arrays on commercial soda-lime glass is presented. The hybrid technique is composed by a laser direct writing technique and a laser assisted post-thermal treatment. In particular we use a nanosecond Q-Switch Nd:YVO4 laser for fabricating the initial structure of microposts on soda-lime glass substrates and a CO2 laser combined with a furnace for reshaping and improving its morphological and optical qualities. This new fabrication approach lets us obtain a high quality microlenses array with a diameter of 50 μm, sag 1.5 μm, focal length 1 mm and a spot size of 7.8 μm. Furthermore, the proposed technique preserves the advantages of the laser direct-write technique in terms of design flexibility, simplicity, fast prototyping, low cost and so on; while the alternative laser assisted thermal treatment lets us overcome the bounding problems presented in other conventional thermal treatments.

  2. Killifish Hatching and Orientation experiment MA-161

    NASA Technical Reports Server (NTRS)

    Scheld, H. W.; Boyd, J. F.; Bozarth, G. A.; Conner, J. A.; Eichler, V. B.; Fuller, P. M.; Hoffman, R. B.; Keefe, J. R.; Kuchnow, K. P.; Oppenheimer, J. M.

    1976-01-01

    The killifish Fundulus heteroclitus was used as a model system for study of embryonic development and vestibular adaptation in orbital flight. Juvenile fish in a zero gravity environment exhibited looping swimming activity similar to that observed during the Skylab 3 mission. Hatchings from a 336 hour egg stage were also observed to loop. At splashdown, both juveniles and hatchings exhibited a typical diving response suggesting relatively normal vestibular function. Juveniles exhibited swimming patterns suggestive of abnormal swim bladders. The embryos exhibited no abnormalities resulting from development in a zero gravity environment.

  3. Laser-assisted surgery with different wavelengths: a preliminary ex vivo study on thermal increase and histological evaluation.

    PubMed

    Merigo, Elisabetta; Clini, Fabio; Fornaini, Carlo; Oppici, Aldo; Paties, Carlo; Zangrandi, Adriano; Fontana, Matteo; Rocca, Jean-Paul; Meleti, Marco; Manfredi, Maddalena; Cella, Luigi; Vescovi, Paolo

    2013-02-01

    Since the introduction of laser in clinical practice, different wavelengths have been used for oral surgery on the basis of the different characteristics and affinities of each one. The aim of this study was a comparison of different laser wavelengths in relation to both thermal increase and "histological quality" in a model of soft tissue surgery procedures. Thermal evaluation was realized, during laser-assisted surgery excision performed on a bovine tongue, by a thermal camera device to evaluate thermal increase on the surface of the sample and with four thermocouples to evaluate thermal increase on the depth of the specimen; temperature was recorded before starting surgical procedure and at the peak of every excision. The quality of excision, in terms of tissue damage and regularity, was realized by two blind examiners on the basis of established criteria. The highest superficial thermal increase was recorded for Superpulse 5-W CO2 laser, the lowest one for Er:YAG laser. The highest in depth thermal increase was recorded for 5 W Diode laser, the lowest one for Er:YAG laser. The best quality of incision was obtained with a 3-W CO2 laser and 3-W diode laser; epithelial, stromal, and vascular damages were evaluated with different degrees for all the used wavelengths with the best result, in terms of "tissue respect," for Er:YAG laser. In all the surgical procedures performed, thermal increase was evaluated until the end of the procedure; at remaining tissue level, thermal decrease was evaluable in the few seconds after surgery. The Er:YAG laser was the device with a lower influence on thermal increase; CO2 and diode lasers revealed a good histological quality. Further studies may be necessary to test the reliability of laser devices for the excision of all the types of specimens needing histological evaluation and diagnosis.

  4. Removal of surface contaminants using a chemical-free laser-assisted process

    NASA Astrophysics Data System (ADS)

    Engelsberg, Audrey C.

    1994-10-01

    Contamination control is a critical issue to the manufacture and maintenance of optical components. Particulates and thin films (organic and inorganic) can degrade optical performance. Current cleaning methods are focusing on aqueous-based cleaning and super- critical fluids. Concurrently, environmentally-conscious manufacturing processes are becoming essential for industrial applications. These manufacturing processes emphasize the reduction of water and chemical consumption and hazardous waste production. In this paper, we will introduce a chemical-free laser assisted process that has demonstrated its capability of removing particulates and films from various surfaces including optical. Since this process works with energy flux and a flowing inert gas, it's readily adaptable and cost effective for many industrial applications.

  5. Effect of sample compositions on chemical analysis using matrix-assisted laser desorption ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Schriemer, David; Dai, Yuqin; Li, Liang

    1996-11-01

    Matrix-assisted laser desorption ionization (MALDI) is an effective ionization technique for mass spectrometry. It take advantages of some unique properties of certain organic chemicals to provide entrapment, isolation, vaporization, and ionization of the analyte of interest. While the main application of the MALDI technique is currently in the area of biological molecule analysis, it is possible to use this technique for monitoring polymer chemistry such as degradation processes. This is potentially important for studying and developing environmentally degradable polymers. Direct analysis of the analyte in real-world samples is possible with MALDI. However, there is a significant effect of the overall composition of a sample on the detectability and performance of MALDI. Two examples are given to illustrate the positive and negative effects of buffers, salts, and additives on the MALDI sample preparation.

  6. Fibronectin layers by matrix-assisted pulsed laser evaporation from saline buffer-based cryogenic targets.

    PubMed

    Sima, F; Davidson, P; Pauthe, E; Sima, L E; Gallet, O; Mihailescu, I N; Anselme, K

    2011-10-01

    The deposition of fibronectin (FN) from saline buffer-based cryogenic targets by matrix-assisted pulsed laser evaporation (MAPLE) onto silicon substrates is reported. A uniform distribution of FN was revealed by Ponceau staining after control experiments on nitrocellulose paper. Well-organized particulates with heights from hundreds of nanometers up to more than 1 μm packed in homogeneous layers were evidenced by optical microscopy and profilometry on Si substrates. Atomic force microscopy images showed regions composed of buffer and FN aggregates forming a compact film. Comparison of infrared spectra of drop-cast and MAPLE-deposited FN confirmed the preservation of composition and showed no degradation of the protein. The protein deposition on Si was confirmed by antibody staining. Small aggregates and fluorescent fibrils were visualized by fluorescence microscopy. Superior attachment of human osteoprogenitor cells cultivated for 3 h proved the presence of stable and intact FN molecules after transfer.

  7. A meta-analysis of aneurysm formation in laser assisted vascular anastomosis (LAVA)

    NASA Astrophysics Data System (ADS)

    Chen, Chen; Peng, Fei; Xu, Dahai; Cheng, Qinghua

    2009-08-01

    Laser assisted vascular anastomosis (LAVA) is looked as a particularly promising non-suture method in future. However, aneurysm formation is one of the main reasons delay the clinical application of LAVA. Some scientists investigated the incidence of aneurysms in animal model. To systematically analyze the literature on reported incidence of aneurysm formation in LAVA therapy, we performed a meta-analysis comparing LAVA with conventional suture anastomosis (CSA) in animal model. Data were systematically retrieved and selected from PUBMED. In total, 23 studies were retrieved. 18 studies were excluded, and 5 studies involving 647 animals were included. Analysis suggested no statistically significant difference between LAVA and CSA (OR 1.24, 95%CI 0.66-2.32, P=0.51). Result of meta analysis shows that the technology of LAVA is very close to clinical application.

  8. Detection of dimethylarginines in protein hydrolysates by matrix-assisted laser desorption/ionization mass spectrometry.

    PubMed

    Hsieh, Cheng-Hsilin; Tam, Ming F

    2006-03-01

    We report a method to detect the presence of dimethylarginines on proteins. Peptides with dimethylarginines were hydrolyzed in acid. The hydrolysates were subjected to matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometric analysis using a mixture of alpha-cyano-4-hydroxycinnamic acid and nitrocellulose as matrix. Both asymmetric omega-N(G),N(G)-dimethylarginine and symmetric omega-N(G),N(G')-dimethylarginine give a clear signal at m/z 203. Recombinant Sbp1p modified by Hmt1p in vivo were isolated by affinity chromatography followed by electrophoresis on a polyacrylamide gel and subjected to acid hydrolysis. MALDI-TOF analysis of the acid hydrolysates confirmed the presence of dimethylarginines. The detection limit of the method is estimated at approximately 1pmol of protein.

  9. Cyan laser diode grown by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Turski, H. Muziol, G.; Wolny, P.; Cywiński, G.

    2014-01-13

    We demonstrate AlGaN-cladding-free laser diodes (LDs), operating in continuous wave (CW) mode at 482 nm grown by plasma-assisted molecular beam epitaxy (PAMBE). The maximum CW output power was 230 mW. LDs were grown on c-plane GaN substrates obtained by hydride vapor phase epitaxy. The PAMBE process was carried out in metal-rich conditions, supplying high nitrogen flux (Φ{sub N}) during quantum wells (QWs) growth. We found that high Φ{sub N} improves quality of high In content InGaN QWs. The role of nitrogen in the growth of InGaN on (0001) GaN surface as well as the influence of LDs design on threshold current density are discussed.

  10. Chemical reactivity in matrix-assisted laser desorption/ionization mass spectrometry

    PubMed

    Enjalbal; Sauvagnat; Lamaty; Lazaro; Martinez; Mouchet; Roux; Aubagnac

    1999-01-01

    During the control of a multistep organic synthesis on a soluble polymer (PEG) by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, a chemical reactivity was encountered when the matrix was acidic, for the samples where the amino moiety of the anchored compounds was protected as a Schiff base. Such imine hydrolysis was proven to be solely mediated by the acidic matrix during analyses since the expected protected structures were detected when the experiments were duplicated with a non-acidic matrix. Even if MALDI mass spectrometry was found to be more convenient than electrospray ionization mass spectrometry for the monitoring of liquid phase organic syntheses, the chemical reactivity imparted by the use of a matrix must be taken into account to avoid erroneous spectra interpretations. Copyright 1999 John Wiley & Sons, Ltd.

  11. Processing of mussel adhesive protein analog thin films by matrix assisted pulsed laser evaporation

    NASA Astrophysics Data System (ADS)

    Cristescu, R.; Patz, T.; Narayan, R. J.; Menegazzo, N.; Mizaikoff, B.; Mihaiescu, D. E.; Messersmith, P. B.; Stamatin, I.; Mihailescu, I. N.; Chrisey, D. B.

    2005-07-01

    Mussel adhesive proteins are a new class of biologically-derived materials that possess unique biocompatibility, bioactivity, and adhesion properties. We have demonstrated successful thin film growth of 3,4-dihydroxyphenyl- L-alanine modified poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (DOPA modified- PEO-PPO-PEO) block copolymer, a mussel adhesive protein analog, using matrix assisted pulsed laser evaporation. We have demonstrated that the main functional groups of the mussel adhesive protein analog are present in the transferred film. The effect of increasing of chain length of the mussel adhesive protein analog on film structure was also examined. These novel polymer thin films could have numerous medical and technological applications if their thin film properties are similar to what is found in bulk. This is the first report of successful MAPLE deposition of this material as thin films.

  12. Direct Surface Analysis of Fungal Species by Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

    SciTech Connect

    Valentine, Nancy B. ); Wahl, Jon H. ); Kingsley, Mark T. ); Wahl, Karen L. )

    2001-12-01

    Intact spores and/or hyphae of Aspergillus niger, Rhizopus oryzae, Trichoderma reesei and Phanerochaete chrysosporium are analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). This study investigates various methods of sample preparation and matrices to determine optimum collection and analysis criteria for fungal analysis by MALDI-MS. Fungi are applied to the MALDI sample target as untreated, sonicated, acid/heat treated, or blotted directly from the fungal culture with double-stick tape. Ferulic acid or sinapinic acid matrix solution is layered over the dried samples and analyzed by MALDI-MS. Statistical analysis of the data show that simply using double stick tape to collect and transfer to a MALDI sample plate typically worked as well as the other preparation methods, but requires the least sample handling.

  13. Identification of Bacillus Spores by Matrix-Assisted Laser Desorption Ionization–Mass Spectrometry

    PubMed Central

    Hathout, Yetrib; Demirev, Plamen A.; Ho, Yen-Peng; Bundy, Jonathan L.; Ryzhov, Victor; Sapp, Lisa; Stutler, James; Jackman, Joany; Fenselau, Catherine

    1999-01-01

    Unique patterns of biomarkers were reproducibly characterized by matrix-assisted laser desorption ionization (MALDI)–mass spectrometry and were used to distinguish Bacillus species members from one another. Discrimination at the strain level was demonstrated for Bacillus cereus spores. Lipophilic biomarkers were invariant in Bacillus globigii spores produced in three different media and in B. globigii spores stored for more than 30 years. The sensitivity was less than 5,000 cells deposited for analysis. Protein biomarkers were also characterized by MALDI analysis by using spores treated briefly with corona plasma discharge. Protein biomarkers were readily desorbed following this treatment. The effect of corona plasma discharge on the spores was examined. PMID:10508053

  14. Femtosecond laser assisted cataract surgery, beginning of a new era in cataract surgery

    PubMed Central

    Ali, Muhammad Hassaan; Javaid, Mamoona; Jamal, Samreen; Butt, Nadeem Hafeez

    2015-01-01

    The purpose of this article is to analyze and understand the mechanism of action, effectiveness, cost and time benefits, advantages and disadvantages of the femtosecond laser (FSL) assisted cataract surgery. A PubMed search was done using the topic and the keywords. Research shows considerable improvements in corneal incisions, anterior capsulotomy, and phacofragmentation using FSL. We will also discuss and compare FSL with conventional cataract extraction techniques in terms of both short-term and long-term advantages and disadvantages. Limitations of the studies reviewed include small sample size and short-term follow-up. The major dilemma is still considered to be its heavy financial feasibility to date. PMID:26903717

  15. The Sagnac effect in optical lattices with laser-assisted tunneling

    NASA Astrophysics Data System (ADS)

    Jiang, Bo-Nan; Wei, Xiao-Gang; Zhang, Guo-Wan; Li, Jia-Hua; Cheng, Yong-Jie; Xu, Cheng

    2016-05-01

    We propose a scheme to realize rotation sensing through the use of optical lattices with laser-assisted tunneling. We theoretically demonstrate that competition between the rotation and the spin-orbit coupling governs the spin-dependent response of the cyclotron dynamics of the spin-orbit coupled bosons. The Sagnac-type cumulative phase can be read out from the envelope of a beat-frequency time evolution of the population imbalance in the spin-balanced system and enhanced by cyclotron motion. We also theoretically show that the sensitivity limit of the spin-orbit-coupled system to rotational motion can reach 4×10-7 \\text{rads}-1\\text{Hz}-1/2 .

  16. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Experimental optimisation of the gas-assisted laser cutting of thick steel sheets

    NASA Astrophysics Data System (ADS)

    Malikov, A. G.; Orishich, Anatolii M.; Shulyat'ev, Viktor B.

    2009-06-01

    We report on the experimental optimisation of the oxygen-assisted CO2 laser cutting of low-carbon sheet steel 5 to 25 mm in thickness. It is shown that the cut edge roughness is minimal when the energy input per unit volume of the material removed and the incident beam power per unit sheet thickness remain constant at ~20 J mm-3 and ~200 W mm-1, respectively, over the entire range of sheet thicknesses examined. The corresponding Péclet number is Pe = 0.5. These results can be used to determine the optimal beam power and cutting speed for a particular sheet thickness. At sufficiently large thicknesses, the conditions that ensure the minimum roughness can be written in the form of relations between nondimensional parameters.

  17. Development of matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) for plant metabolite analysis

    SciTech Connect

    Korte, Andrew R

    2014-12-01

    This thesis presents efforts to improve the methodology of matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) as a method for analysis of metabolites from plant tissue samples. The first chapter consists of a general introduction to the technique of MALDI-MSI, and the sixth and final chapter provides a brief summary and an outlook on future work.

  18. Thermoresponsive poly(N-isopropylacrylamide)/graphene/Au nanocomposite hydrogel for water treatment by a laser-assisted approach.

    PubMed

    Cong, Huai-Ping; Qiu, Jia-Hua; Yu, Shu-Hong

    2015-03-01

    The thermoresponsive poly(N-isopropylacrylamide)/graphene/Au multicomponent hydrogel is prepared by the simultaneous in-situ formation of Au nanoparticles and the reduction of graphene oxide, assisted by NIR laser irradiation of a prefabricated PNIPAM/GO hydrogel with auric acid precursor, showing great potential for water treatment owing to the excellent photothermal effect.

  19. Ambulatory treatment of snoring with CO2 laser: laser-assisted UPPP (LAUP), results on 856 patients

    NASA Astrophysics Data System (ADS)

    Kamami, Yves-Victor

    1995-05-01

    The usual treatment of snoring in the absence of sleep apneas has been UPPP. Patients are often reluctant to undergo this painful procedure under general anesthesia. The Laser Assisted Uvulopalatoplasty (LAUP) is a new procedure, introduced six years ago by the author, using local anesthesia for the treatment of snoring in an office setting. This technique is designed to correct breathing abnormalities during sleep, caused by pharyngeal airway obstruction in patients suffering of Snoring or Obstructive Sleep Apnea Syndrome. This is done by reducing the amount of tissue in the uvula, the velum, and the upper part of the posterior pillars. LAUP allows surgery for the relief of snoring to be performed in the office, under local anesthesia. LAUP has many advantages over the traditional UPPP. It is simple, reliable, hemostatic, and less painful. It is also less expensive as it can be performed as an outpatient. This makes the LAUP more accessible to patients. Our experience with LAUP in 856 patients from December 1988 to July 1994 (141 women and 715 men) is described. Good results were obtained in 94.8% of patients and there were no complications. This new technique can be easily performed by other otolaryngologists after serious suitable training. LAUP provides a simple alternative for many patients who do not wish to undergo a traditional UPPP.

  20. Ambulatory treatment of sleep apnea syndrome with CO2 laser: laser-assisted UPPP (LAUP), results on 70 patients

    NASA Astrophysics Data System (ADS)

    Kamami, Yves-Victor

    1995-05-01

    The pharyngeal airway obstruction during sleep in the Obstructive Sleep Apnea Syndrome (OSAS) can be improved after treatment by LAUP (Laser Assisted Uvulopalatoplasty). This new technique, performed under local anesthesia, permits the snoring treatment without any hospitalization, or general anesthetic; like an ordinary dental visit. This is done by reducing the amount of tissue in the uvula, the velum, and the upper part of the posterior pillars. Our experience with the LAUP in Sleep Apnea Syndrome is described, from December 1988 to May 1994, in 70 patients. Among 62 patients classified as successful `responders', the respiratory disturbance index was reduced more than 50%. Among all the 70 patients: in 51.4 % of cases (36 patients), there's a healing of snoring and Sleep Apnea Syndrome. In 37.2% of cases (26 patients), there's an improvement reduction of length and number of apneas and a significant improvement in nocturnal oxygen saturation. 11.4% (8 patients), are relative failures, with always decrease of snoring, but still Sleep Apnea Syndrome, (with a higher B.M.I.). There were no important complications reported. Patients withstand it well and there's had a better tolerance of the C.P.A.P. in the cases of OSAS LRPP failures. Popularization of LAUP will require serious training of surgeon and further long-term studies.

  1. Lateral band-gap control of InGaAsP multiple quantum wells by laser-assisted metalorganic molecular beam epitaxy for a multiwavelength laser array

    NASA Astrophysics Data System (ADS)

    Iga, Ryuzo; Yamada, Takeshi; Sugiura, Hideo

    1994-02-01

    Multiple asymmetric quantum wells made up of InGaAsP and InAsP layers were fabricated using laser irradiation. They were formed in different irradiated areas during InGaAsP quantum well growth by Ar-ion laser assisted metalorganic molecular beam epitaxy (MOMBE). It was observed that during MOMBE the band gap of InGaAsP MQW was modified. Photoluminescence wavelengths of the MAQWs were studied to observe the variations in the bandgap with a delay in the starting time of laser irradiation. The photoluminescence of the MAQWs ranged from 1.3 to 1.5 micrometer and the PL intensity of the MAQWs in four different areas were all similar. This phenomena enabled the fabrication of multiwavelength laser array on a substrate in a single step growth.

  2. One-pot laser-assisted synthesis of porous carbon with embedded magnetic cobalt nanoparticles

    NASA Astrophysics Data System (ADS)

    Ghimbeu, Camélia Matei; Sopronyi, Mihai; Sima, Felix; Delmotte, Luc; Vaulot, Cyril; Zlotea, Claudia; Paul-Boncour, Valérie; Le Meins, Jean-Marc

    2015-05-01

    A novel one-pot laser-assisted approach is reported herein for the synthesis of ordered carbons with embedded cobalt nanoparticles. The process is based on a UV pulsed laser exposure of an ethanolic solution consisting of green carbon precursors, a structure directing agent and a cobalt salt. Very short irradiation times (5 to 30 min) are only required to polymerize and cross-link carbon precursors (i.e. phloroglucinol and glyoxylic acid) independent of a catalyst presence. The influence of three metallic salts (acetate, nitrate and chloride) on the phenolic resin and carbon characteristics (structure, texture and particle size/distribution) was systematically studied. When exposed to UV laser, the metallic salt exhibited a strong influence on the particle size and distribution in the carbon matrix rather than on the textural carbon properties. Using cobalt acetate, very small (3.5 nm) and uniformly dispersed particles were obtained by this simple, fast and green one-pot synthesis approach. An original combined 13C CP-MAS and DP-DEC solid state NMR spectroscopy analysis allowed to determine the structure of phenolic resins as well as the location of the cobalt salt in the resin. Complementarily, the 1H solid-state and relaxation NMR provided unique insights into the rigidity (cross-linking) of the phenolic resin and dispersion of the cobalt salt. The magnetic properties of cobalt nanoparticles were found to be size-dependent: large Co nanoparticles (~50 nm) behave as bulk Co whereas small Co nanoparticles are superparamagnetic.A novel one-pot laser-assisted approach is reported herein for the synthesis of ordered carbons with embedded cobalt nanoparticles. The process is based on a UV pulsed laser exposure of an ethanolic solution consisting of green carbon precursors, a structure directing agent and a cobalt salt. Very short irradiation times (5 to 30 min) are only required to polymerize and cross-link carbon precursors (i.e. phloroglucinol and glyoxylic acid

  3. Matrix-assisted laser desorption mass spectrometry of gas-phase peptide-metal complexes

    NASA Astrophysics Data System (ADS)

    Hortal, Ana R.; Hurtado, Paola; Martínez-Haya, Bruno

    2008-12-01

    Cation attachment to a model peptide has been investigated in matrix-assisted laser desorption experiments. Angiotensin I (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu) is chosen as a system for study, and Cu2+ and K+ salts are used as cationizing agents. Three fundamentally different types of samples are investigated: (1) a crystalline sample of Ang I, metal salt and MALDI matrix, prepared with the conventional dried droplet method; (2) a solvent-free fine powder mixture of the same three compounds, and (3) a solution of the angiotensin and the metal salt in an ionic liquid matrix (a molten organic salt that acts as a MALDI active solvent). Effective protonation and cationization of the peptide are achieved with the three methods. The transition metal systematically provides more efficient cationization than the alkali metal. At sufficiently high concentration of the salt, the attachment of up to four copper cations to the angiotensin is observed in the MALDI spectrum. In contrast, only one K+ cation is efficiently bound to the peptide. For a given salt concentration, the highest degree of cationization is obtained in the laser desorption from the ionic liquid matrix. This is attributed to the efficient transfer of free metal cations to the desorption plume, where the complexation takes place.

  4. Robot Assisted Stereotactic Laser Ablation for a Radiosurgery Resistant Hypothalamic Hamartoma

    PubMed Central

    Acharya, Vinita; Sather, Michael

    2016-01-01

    Hypothalamic hamartomas (HH) are benign tumors that can cause significant morbidity in adults as a cause of epilepsy, particularly gelastic seizures. Open and endoscopic resections of HH offer good seizure control but have high rates of morbidity and are technically challenging. Stereotactic radiosurgery has been an alternative treatment; however, it results in comparably poor seizure control. Recently, in children, stereotactic laser ablation has shown promise as a surgical technique that can combine the best features of both of these approaches for the treatment of HH. Here we present the first reported use of a frameless robot-assisted stereotactic system to treat an HH. The patient had failed two previous Gamma Knife radiosurgery treatments. Post-procedure he had a stable, but unintentional weight loss of 20 kg and a transient episode of hemiparesis the night of the operation. At six months postoperatively the patient remained seizure free. Stereotactic laser ablation may represent a new standard in the treatment of HH in adults, especially in those who have failed radiosurgery. Further study is warranted in this population to determine efficacy and safety profiles. PMID:27217984

  5. Laser-assisted Stark deceleration of polar diatomic molecules in the Χ1Σ state

    NASA Astrophysics Data System (ADS)

    Huang, Yunxia; Xu, Shuwu; Yang, Xiaohua

    2016-07-01

    The traditional Stark deceleration method is difficult to apply in chemically stable polar diatomic molecules in their ground (Χ1Σ) state because the Χ1Σ state normally experiences little Stark shift and the rovibronic ground level is mostly high-field-seeking. To solve this problem, we propose a laser-assisted Stark deceleration scheme to decelerate such molecules in the present paper. Our results show that, owing to the transverse bunching effect of the applied red-detuning laser beam, the molecules of the high-field-seeking level |J = 0, M = 0> in the Χ1Σ state can be effectively decelerated. Furthermore, the present scheme is more effective because the interaction between the molecules and the combined fields can produce the pseudo-first-order Stark effect, and thus increase the depth of the effective potential. Compared to those molecules in the low-field-seeking state |J = 1, MΩ = -1> in the usual electrostatic Stark deceleration, a higher molecular density and lower velocity can be achieved under an equivalent initial phase angle.

  6. Laser-assisted photothermal heating of a plasmonic nanoparticle-suspended droplet in a microchannel.

    PubMed

    Walsh, Timothy; Lee, Jungchul; Park, Keunhan

    2015-03-07

    The present article reports the numerical and experimental investigations on the laser-assisted photothermal heating of a nanoliter-sized droplet in a microchannel when plasmonic particles are suspended in the droplet. Plasmonic nanoparticles exhibit strong light absorption and scattering upon the excitation of localized surface plasmons (LSPs), resulting in intense and rapid photothermal heating in a microchannel. Computational models are implemented to theoretically verify the photothermal behavior of gold nanoshell (GNS) and gold nanorod (GNR) particles suspended in a liquid microdroplet. Experiments were conducted to demonstrate rapid heating of a sub-100 nL droplet up to 100 °C with high controllability and repeatability. The heating and cooling time to the steady state is on the order of 1 second, while cooling requires less time than heating. The effects of core parameters, such as nanoparticle structure, volumetric concentration, microchannel depth, and laser power density on heating are studied. The obtained results can be integrated into existing microfluidic technologies that demand accurate and rapid heating of microdroplets in a microchannel.

  7. Histologic evaluation of an Nd:YAG laser-assisted new attachment procedure in humans.

    PubMed

    Yukna, Raymond A; Carr, Ronald L; Evans, Gerald H

    2007-12-01

    This report presents histologic results in humans following a laser-assisted new attachment procedure (LANAP) for the treatment of periodontal pockets. Six pairs of single-rooted teeth with moderate to advanced chronic periodontitis associated with subgingival calculus deposits were treated. A bur notch was placed within the pocket at the clinically and radiographically measured apical extent of calculus. All teeth were scaled and root planed with ultrasonic and hand scalers. One of each pair of teeth received treatment of the inner pocket wall with a free-running pulsed neodymium:yttrium-aluminum-garnet (Nd:YAG) laser to remove the pocket epithelium, and the test pockets were lased a second time to seal the pocket. After 3 months, all treated teeth were removed en bloc for histologic processing. LANAP-treated teeth exhibited greater probing depth reductions and clinical probing attachment level gains than the control teeth. All LANAP-treated specimens showed new cementum and new connective tissue attachment in and occasionally coronal to the notch, whereas five of the six control teeth had a long junctional epithelium with no evidence of new attachment or regeneration. There was no evidence of any adverse histologic changes around the LANAP specimens. These cases support the concept that LANAP can be associated with cementum-mediated new connective tissue attachment and apparent periodontal regeneration of diseased root surfaces in humans.

  8. Detection of Biosignatures by Geomatrix-Assisted Laser Desorption/Ionization (GALDI) Mass Spectrometry

    SciTech Connect

    Jill R. Scott; Beizhan Yan; Daphne L. Stoner; J. Michelle Kotler; Nancy W. Hinman

    2007-04-01

    Identification of mineral-associated biosignatures is of significance for retrieving biochemical information from geological records here on Earth and detecting signs of life on other planets, such as Mars. The importance of the geomatrix for identifying amino acids (e.g., histidine, threonine, and cysteine) and small proteins (e.g., gramicidin S) was investigated by laser desorption Fourier transform mass spectrometry. The investigated geomatrices include analogues of Fe-bearing minerals such as hematite and Na-bearing evaporites (e.g., halite). Samples were prepared by two methods: 1) application of analyte to the geomatrix surface and 2) production of homogenous analyte:geomatrix mixtures. Comparison of the two sample preparation methods revealed that the mixing method produces a better signal/noise ratio than surface application for the analyses of amino acids. The composition of the geomatrix has a profound influence on the detection of biomolecules. Peaks corresponding to the cation-attached biomolecular ions were observed for the Na-bearing evaporite analogue. No detectable peaks for the biomolecular ion species were observed when the biomolecules were associated with Fe-bearing minerals. Instead, only minor peaks were observed that may correspond to ions from fragments of the biomolecules. Depending on the underlying mineral composition, geomatrix-assisted laser desorption/ionization shows promise for directly identifying biosignatures associated with minerals.

  9. Efficient Methods to Generate Reproducible Mass Spectra in Matrix-Assisted Laser Desorption Ionization of Peptides

    NASA Astrophysics Data System (ADS)

    Ahn, Sung Hee; Park, Kyung Man; Bae, Yong Jin; Kim, Myung Soo

    2013-06-01

    In our previous matrix-assisted laser desorption ionization (MALDI) studies of peptides, we found that their mass spectra were virtually determined by the effective temperature in the early matrix plume, Tearly, when samples were rather homogeneous. This empirical rule allowed acquisition of quantitatively reproducible spectra. A difficulty in utilizing this rule was the complicated spectral treatment needed to get Tearly. In this work, we found another empirical rule that the total number of particles hitting the detector, or TIC, was a good measure of the spectral temperature and, hence, selection of spectra with the same TIC resulted in reproducible spectra. We also succeeded in obtaining reproducible spectra throughout a measurement by controlling TIC near a preset value through feedback adjustment of laser pulse energy. Both TIC selection and TIC control substantially reduced the shot-to-shot spectral variation in a spot, spot-to-spot variation in a sample, and even sample-to-sample variation in MALDI using α-cyano-4-hydroxycinnamic acid or 2,5-dihydroxybenzoic acid as matrix. Based on the utilization of acquired data, TIC control was more efficient than TIC selection by an order of magnitude. Both techniques produced calibration curves with excellent linearity, suggesting their utility in quantification of peptides.

  10. Mid-infrared matrix assisted laser desorption ionization with a water/glycerol matrix

    NASA Astrophysics Data System (ADS)

    Caldwell, Kathleen L.; Murray, Kermit K.

    1998-05-01

    Matrix-assisted laser desorption ionization (MALDI) mass spectra were obtained using a water and glycerol matrix with a tunable mid-infrared optical parametric oscillator. The matrix consists of a 1:1 mixture of water and glycerol deposited on a thin layer of nitrocellulose and cooled to -30°C. When exposed to vacuum, most of the water evaporates, leaving a matrix of glycerol with residual water. The peptide bradykinin and the protein bovine insulin were used to test this new matrix. Mass spectra were obtained for bradykinin between 2.76 and 3.1 μm with the maximum analyte signal at 2.8 μm. Mass resolution in excess of 2000 for bradykinin and 500 for insulin was obtained with delayed ion extraction and a linear time of flight mass spectrometer. The addition of nitrocellulose to the matrix resulted in exceptionally durable samples: more than 10,000 laser shots which produced analyte signal could be obtained from a single sample spot.

  11. Laser Desorption Ionization of small molecules assisted by Tungsten oxide and Rhenium oxide particles

    PubMed Central

    Bernier, Matthew; Wysocki, Vicki; Dagan, Shai

    2015-01-01

    Inorganic metal oxides have shown potential as matrices for assisting in laser desorption ionization (LDI) with advantages over the aromatic acids typically used. Rhenium and tungsten oxides are an attractive option due to their high work functions and relative chemical inertness. In this work, it is shown that ReO3 and WO3, in microparticle (μP) powder forms, can efficiently ionize various types of small molecules and provide minimized background contamination at analyte concentrations below 1 ng/μL. This study shows that untreated inorganic WO3 and ReO3 particles are valid matrix options for detection of protonatable, radical, and precharged species under LDI. Qualitatively, the WO3 μP showed an improved detection of apigenin, sodiated glucose, and the precharged analyte choline, while the ReO3 μP allowed detection of protonated cocaine, quinuclidine, ametryn, and radical ions of polyaromatic hydrocarbons at detection levels as low as 50 pg/μL. For thermometer ion survival yield experiments, it was also shown that the ReO3 powder was significantly softer than CCA. Furthermore, it provided higher intensities of cocaine and polyaromatic hydrocarbons, at laser flux values equal to that used with CCA. PMID:26349643

  12. Double Sided Irradiation for Laser-assisted Shearing of Ultra High Strength Steels with Process Integrated Hardening

    NASA Astrophysics Data System (ADS)

    Brecher, Christian; Emonts, Michael; Eckert, Markus; Weinbach, Matthias

    Most small or medium sized parts produced in mass production are made by shearing and forming of sheet metal. This technology is cost effective, but the achievable quality and geometrical complexity are limited when working high and highest strength steel. Based on the requirements for widening the process limits of conventional sheet metal working the Fraunhofer IPT has developed the laser-assisted sheet metal working technology. With this enhancement it is possible to produce parts made of high and highest strength steel with outstanding quality, high complexity and low tool wear. Additionally laser hardening has been implemented to adjust the mechanical properties of metal parts within the process. Currently the process is limited to lower sheet thicknesses (<2 mm) to maintain short cycle times. To enable this process for larger geometries and higher sheet thicknesses the Fraunhofer IPT developed a system for double sided laser-assisted sheet metal working within progressive dies.

  13. Guidable Thermophoretic Janus Micromotors Containing Gold Nanocolorifiers for Infrared Laser Assisted Tissue Welding

    PubMed Central

    He, Wenping; Hu, Narisu; Liu, Liping; Gai, Meiyu

    2016-01-01

    Current wound sealing systems such as nanoparticle‐based gluing of tissues allow almost immediate wound sealing. The assistance of a laser beam allows the wound sealing with higher controllability due to the collagen fiber melting which is defined by loss of tertiary protein structure and restoration upon cooling. Usually one employs dyes to paint onto the wound, if water absorption bands are absent. In case of strong bleeding or internal wounds such applications are not feasible due to low welding depth in case of water absorption bands, dyes washing off, or the dyes becoming diluted within the wound. One possible solution of these drawbacks is to use autonomously movable particles composing of biocompatible gold and magnetite nanoparticles and biocompatible polyelectrolyte complexes. In this paper a proof of principle study is presented on the utilization of thermophoretic Janus particles and capsules employed as dyes for infrared laser‐assisted tissue welding. This approach proves to be efficient in sealing the wound on the mouse in vivo. The temperature measurement of single particle level proves successful photothermal heating, while the mechanical characterizations of welded liver, skin, and meat confirm mechanical restoration of the welded biological samples. PMID:27981009

  14. Few-XUV-photon laser-assisted double ionization of helium

    NASA Astrophysics Data System (ADS)

    Lui, Aihua; Thumm, Uwe

    2015-05-01

    We studied the few-photon IR laser-assisted double ionization of helium in ultrashort XUV pulse(s) by numerically solving the time-dependent Schrödinger equation in full dimensionality within a finite-element discrete-variable-representation scheme. We calculated energy and joint angle distributions in coplanar geometry, where the emitted electron momenta and identical polarization axis of the linearly polarized XUV and IR pulses lie in a plane. By analyzing joint angle distributions and asymmetries for two-XUV-photon double ionization, we identify ``sequential'' and ``non-sequential'' contributions for ultrashort XUV pulses whose spectra overlap the sequential (ℏω > 54.4 eV) and non-sequential (39.5 eV < ℏω < 54.4 eV) double ionization regimes. In addition, we show that emission angles between the two photoelectrons can be controlled by adjusting parameters of the XUV and assisting IR pulse. Supported by U.S. NSF and the Division of Chemical Sciences, Office of Basic Energy Sciences, Office of Energy Research, U.S. DoE.

  15. Treatment of Hemorrhagic Vocal Polyps by Pulsed Dye Laser-Assisted Laryngomicrosurgery

    PubMed Central

    Byeon, Hyung Kwon; Han, Ji Hyuk; Choi, Byeong Il; Hwang, Hye Jin; Kim, Ji-Hoon; Choi, Hong-Shik

    2015-01-01

    Objective. Conventional surgical techniques of laryngomicrosurgery (LMS) on hemorrhagic vocal polyps are often difficult due to obscuration of the surgical field by inadvertent bleeding from the lesion, and there are often significant amounts of mucosal epithelium loss. Here, we introduce our surgical technique using pulsed dye laser (PDL), which can effectively resect the polyp with vocal fold mucosa preservation. Methods. Patients who were diagnosed with hemorrhagic vocal polyp and who were surgically managed using PDL from March 2013 to October 2014 were retrospectively reviewed. Preoperative and postoperative clinical outcomes and surgical findings were evaluated. Results. A total of 39 patients were treated with PDL-assisted enucleation LMS. The average age was 43.7 years (range 20–73), and there were 20 males and 19 females (17 professional voice users). In all cases, the hemorrhagic polyp was successfully enucleated after application of PDL, thereby preserving the overlying epithelium. Postoperative voice outcomes were favorable with clear preservation of the vocal fold mucosal wave. Conclusion. PDL-assisted enucleation LMS for the treatment of hemorrhagic vocal polyps can be a safe and effective surgical technique. It can be considered a promising treatment option for hemorrhagic vocal polyps. PMID:26557700

  16. Laser-Assisted Atom Probe Tomography of Deformed Minerals: A Zircon Case Study.

    PubMed

    La Fontaine, Alexandre; Piazolo, Sandra; Trimby, Patrick; Yang, Limei; Cairney, Julie M

    2017-01-30

    The application of atom probe tomography to the study of minerals is a rapidly growing area. Picosecond-pulsed, ultraviolet laser (UV-355 nm) assisted atom probe tomography has been used to analyze trace element mobility within dislocations and low-angle boundaries in plastically deformed specimens of the nonconductive mineral zircon (ZrSiO4), a key material to date the earth's geological events. Here we discuss important experimental aspects inherent in the atom probe tomography investigation of this important mineral, providing insights into the challenges in atom probe tomography characterization of minerals as a whole. We studied the influence of atom probe tomography analysis parameters on features of the mass spectra, such as the thermal tail, as well as the overall data quality. Three zircon samples with different uranium and lead content were analyzed, and particular attention was paid to ion identification in the mass spectra and detection limits of the key trace elements, lead and uranium. We also discuss the correlative use of electron backscattered diffraction in a scanning electron microscope to map the deformation in the zircon grains, and the combined use of transmission Kikuchi diffraction and focused ion beam sample preparation to assist preparation of the final atom probe tip.

  17. Effects of Selected Nematicides on Hatching of Heterodera schachtii.

    PubMed

    Steele, A E

    1983-07-01

    Aldicarb, carbofuran, fensulfothion, and phenamiphos were tested in concentrations of 1-100 mug/ml for their effects on hatching of Heterodera schachtii. Exposure of cysts to 1 mug aldicarb or carbofuran/ml stimulated hatch whereas phenamiphos and, to a lesser degree, fensulfothion inhibited hatch. Addition of aldicarb to sugarbeet root diffusate or 4 mM zinc chloride suppressed activities of these hatching agents. Transfer of cysts previously treated with aldicarb or carbofuran to zinc chloride or water rapidly initiated hatch which finally exceeded the hatch from cysts not treated with the nematicides.

  18. Laser-Assisted Cold-Sprayed Corrosion- and Wear-Resistant Coatings: A Review

    NASA Astrophysics Data System (ADS)

    Olakanmi, E. O.; Doyoyo, M.

    2014-06-01

    Laser-assisted cold spray (LACS) process will be increasingly employed for depositing coatings because of its unique advantages: solid-state deposition of dense, homogeneous, and pore-free coatings onto a range of substrates; and high build rate at reduced operating costs without the use of expensive heating and process inert gases. Depositing coatings with excellent performance indicators via LACS demands an accurate knowledge and control of processing and materials' variables. By varying the LACS process parameters and their interactions, the functional properties of coatings can be manipulated. Moreover, thermal effect due to laser irradiation and microstructural evolution complicate the interpretation of LACS mechanical deformation mechanism which is essential for elucidating its physical phenomena. In order to provide a basis for follow-on-research that leads to the development of high-productivity LACS processing of coatings, this review focuses on the latest developments in depositing corrosion- and wear-resistant coatings with the emphasis on the composition, structure, and mechanical and functional properties. Historical developments and fundamentals of LACS are addressed in an attempt to describe the physics behind the process. Typical technological applications of LACS coatings are also identified. The investigations of all process sequences, from laser irradiation of the powder-laden gas stream and the substrate, to the impingement of thermally softened particles on the deposition site, and subsequent further processes, are described. Existing gaps in the literature relating to LACS-dependent microstructural evolution, mechanical deformation mechanisms, correlation between functional properties and process parameters, processing challenges, and industrial applications have been identified in order to provide insights for further investigations and innovation in LACS deposition of wear- and corrosion-resistant coatings.

  19. Human clinical and histologic evaluation of laser-assisted new attachment procedure.

    PubMed

    Nevins, Marc L; Camelo, Marcelo; Schupbach, Peter; Kim, Soo-Woo; Kim, David M; Nevins, Myron

    2012-10-01

    This investigation was designed to evaluate the healing response to the laser-assisted new attachment procedure (LANAP). Eight patients presenting with 12 teeth predetermined to be surgically extracted were enrolled and consented to treatment with full-mouth LANAP therapy. LANAP surgical therapy consisted of a first pass with a 360-Μm fiber diameter, laser settings with verified output of 4.0 W and energy density of 1,965 mJ/mm2, 100-Μs pulse duration, and 20 Hz applied from the gingival margin to the base of the pocket parallel to the root surface and moved laterally and apically to remove the diseased pocket epithelium. The teeth were aggressively scaled and root planed with piezo ultrasonic instrumentation. A second pass was performed with a 360-Μm fiber diameter, laser settings with verified output of 4.0 W and energy density of 1,965 mJ/mm2, 650-Μs pulse duration, and 20 Hz applied from the apical extent of the bone defect to the gingival margin. After 9 months of healing, en bloc biopsy extractions were provided. Ten teeth were analyzed histologically to assess the periodontal wound healing. Five teeth evidenced a degree of periodontal regeneration with new cementum, periodontal ligament, and alveolar bone. One tooth had new attachment with new cementum and inserting collagen fibers, and four teeth healed via a long junctional epithelium. LANAP therapy should be further investigated with long-term clinical trials to compare the stability of clinical results to conventional therapy. This report provides evidence that LANAP therapy can induce periodontal regeneration.

  20. Laser-assisted lipolysis for cankle remodelling: a prospective study in 30 patients.

    PubMed

    Leclère, Franck Marie; Moreno-Moraga, Javier; Mordon, Serge; Servell, Pascal; Unglaub, Frank; Kolb, Frédéric; Rimareix, Françoise; Trelles, Mario A

    2014-01-01

    Cankles refer to the area where the calf and ankle meet. Unaesthetic fat cankles, where definition between the calf and ankle is impossible, are a frustrating aesthetic deformity, which are exacerbated by their genetic conditioning and special resistance to diet. This article reports our experience with laser-assisted lipolysis (LAL) in cankle remodelling. A total of 30 patients were treated for unaesthetic fat cankles with LAL. The 924/975-nm diode laser used in this study consisted of two lasers, one emitting at 924 nm, and the other at 975 nm. According to our mathematical models, we assumed that to destroy 1 ml of fat, 0.1 kJ was required in dual emission mode at 924/975 nm. Patients were asked to file a satisfaction questionnaire. Ultrasound was used to measure the fat thickness pre- and postoperatively. Oedema in both lateral sulcus of the Achilles tendon was seen in all patients. It subsided after 4 weeks in nine cases and 6 weeks in 21 cases. Only two patients developed mild hyperpigmentation that disappeared, respectively, after 4 and 10 weeks. Pain during the anaesthesia and discomfort after the procedure were low with this technique. Mean down time was 1.0 day. Of the 30 patients, 29 would recommend this treatment. Overall, high patient and investigator satisfaction was confirmed by the sonography used to measure decrease in fat thickness. LAL in cankle remodelling is a safe and reproducible technique that is particularly appreciated by the patient. The procedure allows homogenous reduction of fatty tissue together with skin tightening.

  1. Blood pressure change during phacoemulsification and femtosecond laser-assisted cataract surgery

    PubMed Central

    Lin, Hung-Yuan; Tung, Ching-Jen; Xu, Guo-Xing; Wang, Chun-Chi; Chen, Hsin-Yang; Chuang, Ya-Jung; Li, Wen-Fu; Lin, Pi-Jung

    2016-01-01

    AIM To evaluate blood pressure (BP) changes during phacoemulsification (PC) and femtosecond laser (FSL)-assisted cataract surgery. METHODS A retrospective chart review was performed for all patients who received traditional phacoemulsification surgery (PC group) and FSL-assisted cataract surgery (FS group) from July 2013 to December 2014. Totally 206 eyes from 133 patients receiving the two types of procedures were included. Patient characteristics (age, gender, and hypertension history), pre- and post-operative BPs were collected. RESULTS The pro-operative systolic and diastolic BPs (mm Hg) were 124.89±20.48 vs 126.98±16.85, and 71.88±9.81 vs 73.56±10.03, in PC and FS groups, respectively. While the post-operative systolic and diastolic BPs (mm Hg) were 130.13±22.59 vs 134.77±17.52, and 73.41±11.62 vs 78.89±12.2, in PC and FS groups, respectively. Paired-sample t-tests showed obvious systolic and diastolic BP elevations in FS group after surgery (P=0.001 and 0.007) and no reliability in PC group (P=0.094 and 0.359). A linear regression model revealed systolic and diastolic BP elevations, which were related to longer surgical times for FS group (P=0.008 and 0.021). Age, gender, and hypertension history were not correlated with blood pressure elevation in either group. CONCLUSION BP increases but at a limited level after FSL-assisted cataract surgery compared to traditional phacoemulsification PMID:27990364

  2. Mechanical Hatching Egg Sanitization: A Fresh Look

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Three to four decades ago, hatching egg sanitization was done by immersion of eggs in an egg-gathering basket (plastic-coated metal wire) into a small vat with a heating element and disinfectant solution. This procedure failed miserably for several reasons. First, the eggs were not subjected to the...

  3. Improvements in springback control by external force laser-assisted sheet bending of titanium and aluminum alloys

    NASA Astrophysics Data System (ADS)

    Gisario, A.; Barletta, M.; Venettacci, S.

    2016-12-01

    The present investigation deals with an external-force laser assisted bending process of Grade 2 CP titanium and AA 7075 T6 aluminum sheets. High bending angles, sharp fillet radii and control of springback were achieved by tuning the contact pressure of a hydraulically driven tool with the local and selective heating of the bending zone by irradiation with a high power diode laser. First, the role of laser operational parameters, namely power, scanning speed and number of passes, in metal bending was investigated, allowing to identify the most suitable processing window. Second, a custom-built equipment to measure the bending angle during the forming process, together with the metal temperature, was implemented. Real-time monitoring of the bending angle and temperature allowed to evaluate the continuous evolution of the geometry of the metal substrates during the external force laser-assisted bending process. Experimental results showed both metal sheets could be bent to high angles with very low fillet radii by the appropriate combination of the tooling contact pressure and selective laser heating of the bending zone. Laser heating also reduces the risk of rupture in both metals during bending at high angles, limits the springback extent up to 10 times on titanium and 30 times on aluminum in comparison with conventional bending process and does not affect significantly the visual appearance of the bending zone.

  4. Electron cyclotron resonance plasma assisted pulsed laser deposition for compound host film synthesis and in situ doping

    SciTech Connect

    Lu, Y.F.; Sun, J.; Yu, D.; Shi, L.Q.; Dong, Z.B.; Wu, J.D.

    2006-05-15

    We developed a method for compound host film synthesis and in situ doping based on plasma assisted pulsed laser deposition by coablation of two targets with two pulsed laser beams. The feasibility of this method was demonstrated by the preparation of Er-doped GaN films. In the reactive nitrogen environment and with the assistance of nitrogen plasma generated from electron cyclotron resonance microwave discharge, the ablation of a polycrystalline GaAs target resulted in the reactive deposition of a GaN host film, whereas the ablation of a metallic Er target provided the host with Er atoms for in situ doping in the growing GaN host film. Hexagonal GaN films were formed on a silicon substrate as the host and Er was incorporated into the host with controlled concentration. We found that the composition of the compound host could be adjusted by varying the laser fluence on the target for host deposition or the energy of the plasma stream bombarding the growing host film. The dopant concentration could also be independently controlled to vary in a wide range by changing the pulse repetition ratio of the two laser beams or the laser fluence on the target for dopant supply. It was also proved that doping of very low concentrations could be easily realized by simply adjusting the pulse repetition rate and the fluence of the second laser.

  5. The Characterization of Laser Ablation Patterns and a New Definition of Resolution in Matrix Assisted Laser Desorption Ionization Imaging Mass Spectrometry (MALDI-IMS)

    NASA Astrophysics Data System (ADS)

    O'Rourke, Matthew B.; Raymond, Benjamin B. A.; Padula, Matthew P.

    2017-03-01

    Matrix assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) is a technique that has seen a sharp rise in both use and development. Despite this rapid adoption, there have been few thorough investigations into the actual physical mechanisms that underlie the acquisition of IMS images. We therefore set out to characterize the effect of IMS laser ablation patterns on the surface of a sample. We also concluded that the governing factors that control spatial resolution have not been correctly defined and therefore propose a new definition of resolution.

  6. Laser Assisted Milling of Ti-6Al-4V ELI with the Analysis of Surface Integrity and its Economics

    NASA Astrophysics Data System (ADS)

    Hedberg, Gary K.; Shin, Yung C.

    2015-09-01

    This study presents the experimental evaluation of laser assisted milling (LAML) of Ti-6AL-4V ELI (Ti-64), which is used in the orthopedic industry, by using localized preheating of the workpiece via laser irradiation. Improvements to the machinability of this material with LAML are assessed while considering the surface integrity. Suitable laser heating conditions as well as machining conditions are determined based on temperature prediction modeling. Machinability improvements are shown in terms of tool wear, material removal rates and cutting force reduction. Systematic characterization of samples is shown to demonstrate that the machined sub-surfaces are not adversely affected during LAML by precisely controlling laser heating, via hardness measurements, scanning electron microscopy (SEM) for microstructure analysis, and X-ray diffraction (XRD) for residual stresses. An economic analysis shows that LAML provides the cost reduction over conventional machining.

  7. Fiber laser with combined feedback of core and cladding modes assisted by an intracavity long-period grating.

    PubMed

    Sáez-Rodriguez, D; Cruz, J L; Díez, A; Andrés, M V

    2011-05-15

    We present a fiber laser made in a single piece of conventional doped-core fiber that operates by combined feedback of the fundamental core mode LP((0,1)) and the high-order cladding mode LP((0,10)). The laser is an all-fiber structure that uses two fiber Bragg gratings and a long-period grating to select the modes circulating in the cavity; the laser emits at the coupling wavelength between the core mode LP((0,1)) and the counterpropagating cladding mode LP((0,10)) in the Bragg gratings. This work demonstrates the feasibility of high-order mode fiber lasers assisted by long-period gratings.

  8. Matrix-assisted laser desorption/ionization mass spectrometry of covalently cationized polyethylene as a function of sample temperature

    NASA Astrophysics Data System (ADS)

    Wallace, W. E.; Blair, W. R.

    2007-05-01

    A pre-charged, low molecular mass, low polydispersity linear polyethylene was analyzed with matrix-assisted laser desorption/ionization (MALDI) mass spectrometry as a function of sample temperature between 25 °C and 150 °C. This temperature range crosses the polyethylene melting temperature. Buckminsterfullerene (C60) was used as MALDI matrix due to the high volatility of typical MALDI matrices making them unsuitable for heating in vacuum. Starting at 90 °C there is an increase in polyethylene ion intensity at fixed laser energy. By 150 °C the integrated total ion intensity had grown by six-fold indicating that melting did indeed increase ion yield. At 150 °C the threshold laser intensity to produce intact polyethylene ions decreased by about 25%. Nevertheless, significant fragmentation accompanied the intact polyethylene ions even at the highest temperatures and the lowest laser energies.

  9. Beating oscillation and Fano resonance in the laser assisted electron transmission through graphene δ-function magnetic barriers

    NASA Astrophysics Data System (ADS)

    Biswas, R.; Maity, S.; Sinha, C.

    2016-10-01

    We investigate theoretically the transmission of electrons through a pair of δ-function magnetic barriers in graphene in presence of external monochromatic, linearly polarized and CW laser field. The transmission coefficients are calculated in the framework of non-perturbative Floquet theory using the transfer matrix method. It is noted that the usual Fabry-Perot oscillations in transmission through the graphene magnetic barriers with larger inter barrier separation takes the shape of beating oscillations in presence of the external laser field. The laser assisted transmission spectra are also found to exhibit the characteristic Fano resonances (FR) for smaller values of the inter barrier separation. The appearance of the perfect node in the beating oscillation and the asymmetric Fano line shape can be controlled by varying the intensity of the laser field. The above features could provide some useful and potential information about the light - matter interactions and may be utilized in the graphene based optoelectronic device applications.

  10. Resonant Infrared Matrix Assisted Pulsed Laser Deposition of Polymers: Improving the Morphology of As-Deposited Films

    NASA Astrophysics Data System (ADS)

    Bubb, Daniel; Papantonakis, Michael; Collins, Brian; Brookes, Elijah; Wood, Joshua; Gurudas, Ullas

    2008-03-01

    Resonant infrared matrix assisted pulsed laser deposition has been used to deposit thin films of PMMA, a widely used industrial polymer. This technique is similar to conventional pulsed laser deposition, except that the polymer to be deposited is dissolved in a solvent and the solution is frozen before ablation in a vacuum chamber. The laser wavelength is absorbed by a vibrational band in the frozen matrix. The polymer lands on the substrate to form a film, while the solvent is pumped away. Our preliminary results show that the surface roughness of the as-deposited films depends strongly on the differential solubility radius, as defined by Hansen solubility parameters of the solvent and the solubility radius of the polymer. Our results will be compared with computational and experimental studies of the same polymer using a KrF (248 nm) laser. The ejection mechanism will be discussed as well as the implications of these results for the deposition of smooth high quality films.

  11. Prebreeding survival of Roseate Terns Sterna dougallii varies with sex, hatching order and hatching date

    USGS Publications Warehouse

    Nisbet, Ian C.T.; Monticelli, David; Spendelow, Jeffrey A.; Szczys, Patricia

    2016-01-01

    Unequal sex ratios can reduce the productivity of animal populations and are especially prevalent among endangered species. A cohort of 333 Roseate Tern Sterna dougallii chicks at a site where the adult sex ratio was skewed towards females was sexed at hatching and followed through fledging and return to the breeding area, and subsequently during adulthood. The entire regional metapopulation was sampled for returning birds. Prebreeding survival (from fledging to age 3 years) was lower in males than in females, but only among B-chicks (second in hatching order). Prebreeding survival also declined with hatching date. The proportion of females in this cohort increased from 54.6% at hatching to 56.2% at fledging and to an estimated 58.0% among survivors at age 3 years. This was more than sufficient to explain the degree of skew in the sex ratio of the adult population, but changes in this degree of skew during the study period make it difficult to identify the influence of a single cohort of recruits. Many studies of prebreeding survival in other bird species have identified effects of sex, hatching order or hatching date, but no previous study has tested for effects of all three factors simultaneously.

  12. 1. VIEW OF THE ENTRANCE TO THE HATCH ADIT (FEATURE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. VIEW OF THE ENTRANCE TO THE HATCH ADIT (FEATURE B-28), FACING WEST. (OCTOBER, 1995) - Nevada Lucky Tiger Mill & Mine, Hatch Adit, East slope of Buckskin Mountain, Paradise Valley, Humboldt County, NV

  13. [Laser ignition assisted spark-induced breakdown spectroscopy for element analysis of aluminum alloy with enhanced sensitivity].

    PubMed

    Peng, Fei-fei; Zhou, Qi; Chen, Yu-qi; Li, Run-hua

    2013-09-01

    The analytical performance of laser ignition assisted spark-induced breakdown spectroscopy (LI-SIBS) for the analysis of trace metal in aluminum alloy was reported in the present article. In order to improve the analytical performance of spark-induced breakdown spectroscopy, a low energy laser pulse was focused on the surface of the sample to produce plasma between discharge electrodes to trigger high voltage spark discharge. Under current geometrical arrangement, optimized discharge voltage and capacitance were determined, and copper in aluminum alloy was analyzed under optimized experimental condition. The limit of detection of copper in aluminum alloy was determined to be 0.7 ppm. Both signal stability and measurement accuracy for spark-induced breakdown spectroscopy were improved with the assistance of laser ignition. The discharge voltage could be reduced and the spatial resolution could be improved with the assistance of laser ignition at the same time. It was demonstrated that LI-SIBS has the characteristics of high sensitivity, good stability and better spatial resolution and is suitable for trace elements analysis in different alloys.

  14. Femtosecond laser-assisted keratoplasty combined with cataract extraction in a patient with keratoconus and oculocutaneous albinism

    PubMed Central

    Pásztor, Dorottya; Kolozsvári, Bence Lajos; Losonczy, Gergely; Fodor, Mariann

    2016-01-01

    In this study, we present a case of a 58-year-old male patient with oculocutaneous albinism, keratoconus, total cataract, and glaucoma originating from father-daughter incest. He underwent femtosecond laser-assisted keratoplasty with “open-sky” cataract extraction and posterior chamber intraocular lens implantation. One week after surgery his uncorrected visual acuity improved from hand motion to 20/200. Six months later corneal K values were 49.1 D in the flat and 50.0 D in the steep meridian. The graft had a central corneal thickness of 488 µm and was well fitted. The patient's quality of life improved substantially due to the surgery. To the best of our knowledge, this is the first report on the association of albinism with advanced keratoconus, total cataract, and glaucoma. Moreover, no previous report on femtosecond laser-assisted keratoplasty using VisuMax femtosecond laser system with “open-sky” cataract extraction is available in the literature. The VisuMax femtosecond laser-assisted keratoplasty ensures fast patient rehabilitation in such challenging cases. PMID:27146942

  15. Section BB Hatch Coating; Framing Plan on Line C Lodging ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Section B-B Hatch Coating; Framing Plan on Line C Lodging Knees at Hatch; Elevation A-A Hull Framing; Section at Hatch Frame 36, Starboard Looking Aft; Midship Section Frame 37, Port Looking Aft - Steam Schooner WAPAMA, Kaiser Shipyard No. 3 (Shoal Point), Richmond, Contra Costa County, CA

  16. 9 CFR 147.22 - Hatching egg sanitation.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Hatching egg sanitation. 147.22... Procedures § 147.22 Hatching egg sanitation. Hatching eggs should be collected from the nests at frequent... practices should be observed: (a) Cleaned and disinfected containers, such as egg flats, should be used...

  17. 9 CFR 147.22 - Hatching egg sanitation.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 9 Animals and Animal Products 1 2013-01-01 2013-01-01 false Hatching egg sanitation. 147.22... Procedures § 147.22 Hatching egg sanitation. Hatching eggs should be collected from the nests at frequent... practices should be observed: (a) Cleaned and disinfected containers, such as egg flats, should be used...

  18. 9 CFR 147.22 - Hatching egg sanitation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 9 Animals and Animal Products 1 2011-01-01 2011-01-01 false Hatching egg sanitation. 147.22... Procedures § 147.22 Hatching egg sanitation. Hatching eggs should be collected from the nests at frequent... practices should be observed: (a) Cleaned and disinfected containers, such as egg flats, should be used...

  19. 9 CFR 147.22 - Hatching egg sanitation.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 1 2012-01-01 2012-01-01 false Hatching egg sanitation. 147.22... Procedures § 147.22 Hatching egg sanitation. Hatching eggs should be collected from the nests at frequent... practices should be observed: (a) Cleaned and disinfected containers, such as egg flats, should be used...

  20. 9 CFR 147.22 - Hatching egg sanitation.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 9 Animals and Animal Products 1 2014-01-01 2014-01-01 false Hatching egg sanitation. 147.22... Procedures § 147.22 Hatching egg sanitation. Hatching eggs should be collected from the nests at frequent... practices should be observed: (a) Cleaned and disinfected containers, such as egg flats, should be used...

  1. 46 CFR 185.610 - Watertight doors and watertight hatches.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Watertight doors and watertight hatches. 185.610 Section... (UNDER 100 GROSS TONS) OPERATIONS Markings Required § 185.610 Watertight doors and watertight hatches. Watertight doors and watertight hatches must be marked on both sides in clearly legible letters at least...

  2. 46 CFR 169.747 - Watertight doors and hatches.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Watertight doors and hatches. 169.747 Section 169.747... Vessel Control, Miscellaneous Systems, and Equipment Markings § 169.747 Watertight doors and hatches. Each watertight door and watertight hatch must be marked on both sides in at least 1-inch...

  3. 46 CFR 169.747 - Watertight doors and hatches.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Watertight doors and hatches. 169.747 Section 169.747... Vessel Control, Miscellaneous Systems, and Equipment Markings § 169.747 Watertight doors and hatches. Each watertight door and watertight hatch must be marked on both sides in at least 1-inch...

  4. 46 CFR 185.610 - Watertight doors and watertight hatches.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Watertight doors and watertight hatches. 185.610 Section... (UNDER 100 GROSS TONS) OPERATIONS Markings Required § 185.610 Watertight doors and watertight hatches. Watertight doors and watertight hatches must be marked on both sides in clearly legible letters at least...

  5. 29 CFR 1918.43 - Handling hatch beams and covers.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... apply in cases where hatch beams are of such design that: (1) The width of the flange is 50 percent or more of the height of the web; and (2) The flange rests flat on the deck when the hatch beam is stood... position, unless the design of the system otherwise prevents unintentional movement. (h) Hatches shall...

  6. Consequences of Hatch Phenology on Stages of Fish Recruitment

    PubMed Central

    Bogner, David M.; Wuellner, Melissa R.

    2016-01-01

    Little is known about how hatch phenology (e.g., the start, peak, and duration of hatching) could influence subsequent recruitment of freshwater fishes into a population. We used two commonly sympatric fish species that exhibit different hatching phenologies to examine recruitment across multiple life stages. Nine yellow perch (Perca flavescens) and bluegill (Lepomis macrochirus) annual cohorts were sampled from 2004 through 2013 across larval, age-0, age-1, and age-2 life stages in a Nebraska (U.S.A.) Sandhill lake. Yellow perch hatched earlier in the season and displayed a more truncated hatch duration compared to bluegill. The timing of hatch influenced recruitment dynamics for both species but important hatching metrics were not similar between species across life stages. A longer hatch duration resulted in greater larval yellow perch abundance but greater age-1 bluegill abundance. In contrast, bluegill larval and age-0 abundances were greater during years when hatching duration was shorter and commenced earlier, whereas age-0 yellow perch abundance was greater when hatching occurred earlier. As a result of hatch phenology, yellow perch recruitment variability was minimized sooner (age-0 life stage) than bluegill (age-1 life stage). Collectively, hatch phenology influenced recruitment dynamics across multiple life stages but was unique for each species. Understanding the complexities of when progeny enter an environment and how this influences eventual recruitment into a population will be critical in the face of ongoing climate change. PMID:27764216

  7. Formation of cylindrical micro-lens array on fused silica glass surface using CO2 laser assisted reshaping technique

    NASA Astrophysics Data System (ADS)

    Choi, Hun-Kook; Ahsan, Md. Shamim; Yoo, Dongyoon; Sohn, Ik-Bu; Noh, Young-Chul; Kim, Jin-Tae; Jung, Deok; Kim, Jin-Hyeok; Kang, Ho-Min

    2015-12-01

    This paper demonstrates the laser assisted formation of plano-convex cylindrical and flat-top curved micro-lens array on fused silica glass surface. Initially, femtosecond laser pulses are irradiated on the sample glass to fabricate periodic linear micro-gratings on the glass surface. Afterwards, we reshape the micro-gratings by several times irradiation of a CO2 laser beam by focusing the laser beam on top of the micro-gratings. As a consequence, plano-convex cylindrical micro-lens array with a period varying from 20 to 40 μm are formed on fused silica glass surface. However, flat-top curved gratings' array is observed on the glass surface for a gratings' period of 50 μm. The fabricated micro-lenses show great consistency in size and shape throughout the sample area. Furthermore, we analyze the formation mechanism of micro-lens array on glass surface using the CO2 laser assisted reshaping technique. The proposed reshaping technique exhibits great potential for forming a large variety of micro-lens arrays on the surface of various transparent materials.

  8. Effects of filling material and laser power on the formation of intermetallic compounds during laser-assisted friction stir butt welding of steel and aluminum alloys

    NASA Astrophysics Data System (ADS)

    Fei, Xinjiang; Jin, Xiangzhong; Peng, Nanxiang; Ye, Ying; Wu, Sigen; Dai, Houfu

    2016-11-01

    In this paper, two kinds of materials, Ni and Zn, are selected as filling material during laser-assisted friction stir butt welding of Q235 steel and 6061-T6 aluminum alloy, and their influences on the formation of intermetallic compounds on the steel/aluminum interface of the joints were first studied. SEM was used to analyze the profile of the intermetallic compound layer and the fractography of tensile fracture surfaces. In addition, EDS was applied to investigate the types of the intermetallic compounds. The results indicate that a thin iron-abundant intermetallic compound layer forms and ductile fracture mode occurs when Ni is added, but a thick aluminum-abundant intermetallic compound layer generates and brittle fracture mode occurs when Zn is added. So the tensile strength of the welds with Ni as filling material is greater than that with Zn as filling material. Besides, the effect of laser power on the formation of intermetallic compound layer when Ni is added was investigated. The preheated temperature field produced by laser beam in the cross section of workpiece was calculated, and the tensile strength of the joints at different laser powers was tested. Results show that only when suitable laser power is adopted, can suitable preheating temperature of the steel reach, then can thin intermetallic compound layer form and high tensile strength of the joints reach. Either excessive or insufficient laser power will reduce the tensile strength of the joints.

  9. A general strategy to fabricate simple polyoxometalate nanostructures: electrochemistry-assisted laser ablation in liquid.

    PubMed

    Liu, Pu; Liang, Ying; Lin, Xianzhong; Wang, Chengxin; Yang, Guowei

    2011-06-28

    Polyoxometalate nanostructures have attracted much attention because of significant technical demands in applications such as catalysts, sensors, and smart windows. Therefore, researchers have recently developed many methods for the synthesis of these nanomaterials. However, these techniques have many visible flaws such as high temperatures or high pressure environments, various templates or additives, demanding and complicated synthesis procedures as well as the presence of impurities in the final products. We therefore propose a general strategy for the fabrication of particular polyoxometalate nanostructures by electrochemically assisted laser ablation in liquid (ECLAL). These polyoxometalates are usually simple as they typically contain two metals and are not soluble in water. This approach is a green, simple, and catalyst-free approach under an ambient environment. Apart from these merits, this novel technique allows researchers to choose and design interesting solid targets and to use an electrochemical approach toward the fabrication of polyoxometalate nanostructures for the purpose of fundamental research and for potential applications. Using the synthesis of Cu(3)Mo(2)O(9) nanorods as an example, we substantiate the validity of the proposed strategy. For the fabrication of Cu(3)Mo(2)O(9) nanostructures, we chose molybdenum as a solid target for laser ablation in liquid copper electrodes for the electrochemical reaction and water as a solvent for the ECLAL synthesis. We successfully fabricated Cu(3)(OH)(2)(MoO(4))(2) nanorods with magnetic properties. Interestingly, we obtained well-defined Cu(3)Mo(2)O(9) nanorods by annealing the Cu(3)(OH)(2)(MoO(4))(2) nanostructures at 500 °C. Additionally, the basic physics and chemistry involved in the ECLAL fabrication of nanostructures are discussed.

  10. Laser-assisted removal of a feline eosinophilic granuloma from the back of the tongue.

    PubMed

    Kovács, Katalin; Jakab, Csaba; Szász, Attila Marcell

    2009-09-01

    Recently, an increase in the occurrence of oral diseases in cats has been observed. Symptoms vary from case to case, but loss of appetite or fastidiousness can almost always be noted. Proliferative inflammatory eosinophilic granulomatosis is a common disease in cats, which may be localised to the skin, the mucocutaneous junctions or the oral cavity. The disease has three different manifestations: indolent cellular ulcer, eosinophilic plaque, and eosinophilic granuloma. The last mentioned form predominantly affects the medial surface of the thigh, the cheek, the tongue and the palate. Pain is not common, the lesion is nonpruritic if localised to the skin, but the nodular form in the oral cavity may make deglutition difficult. In this case, a 10.5-year-old cat was presented in poor condition due to feeding problems. Examination revealed a mass of unknown origin with macroscopically tumorous appearance, localised to the pharyngeal part of the tongue, which made swallowing and voluntary feeding difficult. The granuloma was removed by laser-assisted surgery. After adequate preparation, a LASER diode with 6-10 W output power was used, set to continuous constant-amplitude output (CW) running in a 0.6 mm optic fibre to the site of interest. The removed tissue was examined for pathomorphological features: haematoxylin and eosin, Giemsa, Azan and PAS stainings were performed to aid diagnosis. After surgery the cat recovered fast on steroids, and its condition and quality of life improved greatly. The traditional surgical technique was inapplicable due to the heavy vasculature and corresponding bleeding of the tongue.

  11. Causes of hatching failure in endangered birds

    PubMed Central

    Hemmings, N.; West, M.; Birkhead, T. R.

    2012-01-01

    About 10 per cent of birds' eggs fail to hatch, but the incidence of failure can be much higher in endangered species. Most studies fail to distinguish between infertility (due to a lack of sperm) and embryo mortality as the cause of hatching failure, yet doing so is crucial in order to understand the underlying problem. Using newly validated techniques to visualize sperm and embryonic tissue, we assessed the fertility status of unhatched eggs of five endangered species, including both wild and captive birds. All eggs were classified as ‘infertile’ when collected, but most were actually fertile with numerous sperm on the ovum. Eggs of captive birds had fewer sperm and were more likely to be infertile than those of wild birds. Our findings raise important questions regarding the management of captive breeding programmes. PMID:22977070

  12. Hatching asynchrony in Burrowing Owls is influenced by clutch size and hatching success but not by food.

    PubMed

    Wellicome, Troy I

    2005-01-01

    In most animals, siblings from a given reproductive event emerge over a very short period of time. In contrast, many species of birds hatch their young asynchronously over a period of days or weeks, handicapping last-hatched chicks with an age and size disadvantage. Numerous studies have examined the adaptive significance of this atypical hatching pattern, but few have attempted to explain the considerable intrapopulation variation that exists in hatching asynchrony. I explored proximate determinants of hatching asynchrony by monitoring 112 Burrowing Owl (Athene cunicularia) nests in the grasslands of southern Saskatchewan, Canada, over 4 years. Age disparities between first- and last-hatched siblings (i.e., hatching spans) varied considerably, ranging between 1 and 7 days (mode = 4 days). These hatching spans increased with increased hatching success. Hatching spans also increased with larger clutches, but the increase was less than predicted given the increased time required to lay more eggs. Hatching span was unrelated to number of prey cached in the nest during egg laying (an index of food availability), and was unaltered by a year of super-abundant prey. Furthermore, pairs given extra food during laying had hatching spans equal to those of unsupplemented control pairs. These results were inconsistent with both the energy constraint and facultative manipulation hypotheses, which predict that hatching asynchrony should vary with the level of food during laying, when incubation onset is determined. Burrowing Owls were apparently free of food limitation early in breeding, yet may not have been able to optimize hatching spans because food conditions during laying were largely unrelated to food conditions during brooding. Thus, one of the premises for facultative manipulation of hatching asynchrony-that laying females are able to forecast post-hatch food conditions-may not have been met for this population of Burrowing Owls.

  13. STS-96 Astronauts Adjust Unity Hatch

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Aboard the International Space Station (ISS), astronauts Rick D. Husband and Tamara E. Jernigan adjust the hatch for the U.S. built Unity node. The task was part of an overall effort of seven crew members to prepare the existing portion of the International Space Station (ISS). Launched on May 27, 1999, aboard the Orbiter Discovery, the STS-96 mission was the second ISS assembly flight and the first shuttle mission to dock with the station.

  14. Long-pulsed Nd:YAG laser-assisted hair removal in Fitzpatrick skin types IV-VI.

    PubMed

    Rao, Krishna; Sankar, Thangasamy K

    2011-09-01

    Unwanted hair is a common problem for which a variety of laser treatments is available. Laser treatment in dark-skinned individuals carries a higher risk of complications like hyperpigmentation and burn. The objective of this study was to evaluate efficacy and safety profile of laser-assisted hair removal in individuals with Fitzpatrick type IV-VI skin using long-pulsed Nd:YAG laser. Retrospective data was collected from 150 individuals with Fitzpatrick type IV-VI skin who underwent laser-assisted hair removal. This included area treated, fluence, number of treatments, and outcome. Data was also gathered on patient satisfaction and complications. The most common phototype was type IV (94%). The most frequently treated area was the face (84.7%) followed by the underarms and legs. Among the facial areas, the chin was the most frequently treated area followed by the upper lip and jaw line. The mean number of treatments was 8.9 (range 4-22). The maximum fluence averaged 26.8 Joules/cm(2) and was significantly higher for facial hair. Of the patients, 78.7% felt that their treatment was good or satisfactory. Mean hair reduction was 54.3%. Satisfaction from the treatment was significantly higher in individuals undergoing treatment of non-facial areas. Subsequent hair growth was slower and finer in 79.3% of the patients. There were no complications in 86% of the patients. All the complications were transient, with hyperpigmentation being the most frequent complication. Our results show that laser hair removal using the long-pulsed Nd:YAG laser is safe and effective in dark-skinned individuals with satisfactory results in most patients.

  15. Fast nucleotide identification through fingerprinting using gold nanoparticle-based surface-assisted laser desorption/ionisation.

    PubMed

    Larguinho, Miguel; Capelo, José L; Baptista, Pedro V

    2013-02-15

    We report a method centred on gold nanoparticle-based surface-assisted laser desorption/ionisation for analysis of deoxynucleotides and alkylated nucleobases. Gold nanoparticles allow for enhanced analysis capability by eliminating undesired signature peaks; thus more elegant mass spectra can be attained that allow identification by nucleotide mass fingerprint. The resulting fingerprinting patterns on the spectra are compared and associated with the presence of different nucleotides in the sample. This method can be easily extended to modified nucleotides implicated in genome lesions due to exposure to environment chemicals, such as DNA adducts (e.g. guanine adducts). The use of gold nanoparticles for surface-assisted laser desorption/ionisation can be an useful tool to resolve common issues of background noise when analysing nucleic acids samples.

  16. Patterning of Endothelial Cells and Mesenchymal Stem Cells by Laser-Assisted Bioprinting to Study Cell Migration

    PubMed Central

    Medina, Manuela; Rémy, Murielle; Thébaud, Noélie Brunehilde; Bareille, Reine; Chassande, Olivier; Amédée, Joëlle; Catros, Sylvain

    2016-01-01

    Tissue engineering of large organs is currently limited by the lack of potent vascularization in vitro. Tissue-engineered bone grafts can be prevascularized in vitro using endothelial cells (ECs). The microvascular network architecture could be controlled by printing ECs following a specific pattern. Using laser-assisted bioprinting, we investigated the effect of distance between printed cell islets and the influence of coprinted mesenchymal cells on migration. When printed alone, ECs spread out evenly on the collagen hydrogel, regardless of the distance between cell islets. However, when printed in coculture with mesenchymal cells by laser-assisted bioprinting, they remained in the printed area. Therefore, the presence of mesenchymal cell is mandatory in order to create a pattern that will be conserved over time. This work describes an interesting approach to study cell migration that could be reproduced to study the effect of trophic factors. PMID:27833916

  17. Laser diagnostics and modeling of plasma assisted CVD. Final technical report

    SciTech Connect

    1996-02-01

    Plasma assisted chemical vapor deposition (PACVD) represents a novel approach for utilizing the nonequilibrium effects of reactive plasmas for depositing a wide range of protective hardface coatings that have both wear and erosion application. The nonequilibrium plasma is the heart of this complex system and has the function of generating the reactive molecular fragments (radicals) and atomic species at concentration levels unattainable by other competing processes. It is now widely accepted that such advanced protective hardface coatings materials will play a vital role in the energy technologies of the coming decades, with major applications in diverse areas ranging from aerospace and commercial propulsion systems (jet engines) to automotive components and internal combustion engines, (ceramic heat engines), cutting and machining tools, electronic packaging, thermal management, and possibly room-temperature superconductors. Wear and associated erosion aspects are responsible for an enormous expenditure of energy and fiscal resources in almost all DOE applications. Many of the results from this investigation arc also applicable to other materials processing reactors such as electron beam, PVD, CVD, laser ablation, microwave, high energy cathodic arc, thermal plasma (rf or dc) and combustion spray. These also include the various hybrid systems such as the rf/dc arc as used in Japan for diamond deposition and e-beam PVD deposition of advanced titanium alloy coatings as used at the Paton Institute in Kiev, Ukraine.

  18. Measuring positron-atom binding energies through laser-assisted photo-recombination

    NASA Astrophysics Data System (ADS)

    Surko, C. M.; Danielson, J. R.; Continetti, R. E.; Gribakin, G. F.

    2013-05-01

    Trap-based positron beams are important for a range of atomic physics experiments. They have, for example, enabled the measurement of positron binding energies for over 60 molecules to date. However, in spite of numerous, accurate theoretical predictions, there have been no experiments to study positron attachment to atoms, due primarily to the difficulty of forming these attached states in two-body collisions. Described here is the proposal for an experiment to use laser-assisted photo-recombination (LAPR) of positrons and metal atoms in the vapor phase to study positron binding to atoms. This experiment relies on the development of a new hot-cell apparatus to provide a collision chamber for metal vapors. Signal rates are estimated for zinc atoms using 0 . 35 eV photons. Important facets of the design of the experiment are based upon experience studying resonant annihilation spectra of molecules using a trapped based beam. Work supported by NSF grant PHY 10-68023.

  19. Validation of a laser-assisted wound measurement device in a wound healing model.

    PubMed

    Constantine, Ryan S; Bills, Jessica D; Lavery, Lawrence A; Davis, Kathryn E

    2016-10-01

    In the treatment and monitoring of a diabetic or chronic wound, accurate and repeatable measurement of the wound provides indispensable data for the patient's medical record. This study aims to measure the accuracy of the laser-assisted wound measurement (LAWM) device against traditional methods in the measurement of area, depth and volume. We measured four 'healing' wounds in a Play-Doh(®) -based model over five subsequent states of wound healing progression in which the model was irregularly filled in to replicate the healing process. We evaluated the LAWM device against traditional methods including digital photograph assessment with National Institutes of Health ImageJ software, measurements of depth with a ruler and weight-to-volume assessment with dental paste. Statistical analyses included analysis of variance (ANOVA) and paired t-tests. We demonstrate that there are significantly different and nearly statistically significant differences between traditional ruler depth measurement and LAWM device measurement, but there are no statistically significant differences in area measurement. Volume measurements were found to be significantly different in two of the wounds. Rate of percentage change was analysed for volume and depth in the wound healing model, and the LAWM device was not significantly different than the traditional measurement technique. While occasionally inaccurate in its absolute measurement, the LAWM device is a useful tool in the clinician's arsenal as it reliably measures rate of percentage change in depth and volume and offers a potentially aseptic alternative to traditional measurement techniques.

  20. Matrix assisted laser desorption time of flight mass spectrometry (MALDI-TOF MS) in clinical microbiology.

    PubMed

    Angeletti, Silvia

    2016-09-06

    The microbiological management of patients with suspected bacterial infection includes the identification of the pathogen and the determination of the antibiotic susceptibility. These traditional approaches, based on the pure culture of the microorganism, require at least 36-48h. A new method, Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS), has been recently developed to profile bacterial proteins from whole cell extracts and obtain a bacterial fingerprint able to discriminate microorganisms from different genera and species. By whole cell-mass spectrometry, microbial identification can be achieved within minutes from cultured isolate, rather than traditional phenotypic or genotypic characterizations. From the year 2009 an explosion of applications of this technology has been observed with promising results. Several studies have been performed and showed that MALDI-TOF represents a reliable alternative method for rapid bacteria and fungi identification in clinical setting. A future area of expansion is represented by the application of MALDI-TOF technology to the antibiotic susceptibility test. In conclusion, the revision of the literature available up to date demonstrated that MALDI-TOF MS represents an innovative technology for the rapid and accurate identification of bacterial and fungal isolates in clinical settings. By an earlier microbiological diagnosis, MALDI-TOF MS contributes to a reduced mortality and hospitalization time of the patients and consequently has a significant impact on cost savings and public health.

  1. Influence of Septal Deviation on the Prognosis of Transcanalicular Diode Laser-Assisted Dacryocystorhinostomy

    PubMed Central

    Raposo, Alberto; Piqueras, Francisco; García-Purriños, Francisco; Martínez-Martinez, María Ll.; Lajara, Jerónimo

    2016-01-01

    Purpose. The objective of the present study is to determine whether the success rate in transcanalicular diode laser-assisted dacryocystorhinostomy (TCL DCR) is influenced by the variant septal deviation (SD). Methods. Patients were divided into two groups: one including operated lacrimal pathways (LP) with no anatomical nasosinusal variants and the other group of LP with SD. This study began on January 1, 2008, and ended on December 31, 2010, at Morales Meseguer Hospital. Variables were compared by means of ANOVA and a logistic regression model (LOGIT). Results. Out of the 159 LP operated on, 102 had no nasosinusal anatomic variant, but 39 LP were associated with SD. The first group evidenced a success rate of 67.64%, while the second group evidenced a success rate of 66.7%. Conclusion. We found no significant statistical differences between the success rates in the two groups (with SD and no anatomical variants). So we could avoid previous or concomitant septoplasty in some cases (mild and moderate SD). PMID:27144017

  2. Mesoscale elucidation of laser-assisted chemical deposition of Sn nanostructured electrodes

    NASA Astrophysics Data System (ADS)

    Liu, Zhixiao; Deng, Biwei; Cheng, Gary J.; Deng, Huiqiu; Mukherjee, Partha P.

    2015-06-01

    Nanostructured tin (Sn) is a promising high-capacity electrode for improved performance in lithium-ion batteries for electric vehicles. In this work, Sn nanoisland growth for nanostructured electrodes assisted by the pulse laser irradiation has been investigated based on a mesoscale modeling formalism. The influence of pertinent processing conditions, such as pulse duration, heating/cooling rates, and atom flux, on the Sn nanostructure formation is specifically considered. The interaction between the adsorbed atom and the substrate, represented by the adatom diffusion barrier, is carefully studied. It is found that the diffusion barrier predominantly affects the distribution of Sn atoms. For both α-Sn and β-Sn, the averaged coordination number is larger than 3 when the diffusion barrier equals to 0.15 eV. The averaged coordination number decreases as the diffusion barrier increases. The substrate temperature, which is determined by heating/cooling rates and pulse duration, can also affect the formation of Sn nanoislands. For α-Sn, when applied low heating/cooling rates, nanoislands cannot form if the diffusion barrier is larger than 0.35 eV.

  3. Hard tissue ablation with a spray-assisted mid-IR laser.

    PubMed

    Kang, H W; Rizoiu, I; Welch, A J

    2007-12-21

    The objective of this study was to understand the dominant mechanism(s) for dental enamel ablation with the application of water spray. A free-running Er,Cr:YSGG (yttrium, scandium, gallium, garnet) laser was used to ablate human enamel tissue at various radiant exposures. During dental ablation, distilled water was sprayed on the sample surface, and these results were compared to ablation without a spray (dry ablation). In order to identify dominant ablation mechanisms, transient acoustic waves were compared to ablation thresholds and the volume of material removed. The ablation profile and depth were measured using optical coherence tomography (OCT). Irregular surface modification, charring and peripheral cracks were associated with dry ablation, whereas craters for spray samples were relatively clean without thermal damage. In spite of a 60% higher ablation threshold for spray associated irradiations owing to water absorption, acoustic peak pressures were six times higher and ablation volume was up to a factor of 2 larger compared to dry ablation. The enhanced pressure and ablation performance of the spray-assisted process was the result of rapid water vaporization, material ejection with recoil stress, interstitial water explosion and possibly liquid-jet formation. With water cooling and abrasive/disruptive mechanical effects, the spray ablation can be a safe and efficient modality for dental treatment.

  4. Preparation of nanowire specimens for laser-assisted atom probe tomography

    NASA Astrophysics Data System (ADS)

    Blumtritt, H.; Isheim, D.; Senz, S.; Seidman, D. N.; Moutanabbir, O.

    2014-10-01

    The availability of reliable and well-engineered commercial instruments and data analysis software has led to development in recent years of robust and ergonomic atom-probe tomographs. Indeed, atom-probe tomography (APT) is now being applied to a broader range of materials classes that involve highly important scientific and technological problems in materials science and engineering. Dual-beam focused-ion beam microscopy and its application to the fabrication of APT microtip specimens have dramatically improved the ability to probe a variety of systems. However, the sample preparation is still challenging especially for emerging nanomaterials such as epitaxial nanowires which typically grow vertically on a substrate through metal-catalyzed vapor phase epitaxy. The size, morphology, density, and sensitivity to radiation damage are the most influential parameters in the preparation of nanowire specimens for APT. In this paper, we describe a step-by-step process methodology to allow a precisely controlled, damage-free transfer of individual, short silicon nanowires onto atom probe microposts. Starting with a dense array of tiny nanowires and using focused ion beam, we employed a sequence of protective layers and markers to identify the nanowire to be transferred and probed while protecting it against Ga ions during lift-off processing and tip sharpening. Based on this approach, high-quality three-dimensional atom-by-atom maps of single aluminum-catalyzed silicon nanowires are obtained using a highly focused ultraviolet laser-assisted local electrode atom probe tomograph.

  5. Sequence-specific fragmentation of matrix-assisted laser-desorbed protein/peptide ions.

    PubMed

    Brown, R S; Lennon, J J

    1995-11-01

    By utilizing delayed pulsed ion extraction of ions generated via the matrix-assisted laser desorption/ionization (MALDI) technique, fast (< 320 ns) metastable ion fragmentation is observed for both peptide and protein analytes in the ion source of a linear time-of-flight mass spectrometer. Small peptides such as the oxidized B chain of bovine insulin exhibit fragmentation at the amide linking bond between peptide residues. Overlapping sequence information is provided by fragmentation from both the C- and N-terminal ends of the peptide (cn-, yn-, and z*n-type fragment ions). Larger proteins can also exhibit a wealth of sequence specific fragment ions in favorable cases. One example is cytochrome c, which undergoes substantial (approximately 80%) fast fragmentation at the amide bonds along the amino acid backbone of the protein. Only amide bond cleavages initiating from the C-terminal end (cn fragments) are observed. The observed fragmentation pattern provides a significant amount of potential sequence information for these molecules. External mass calibration of the intact protonated molecular ions is demonstrated with mass accuracies typically around 100 ppm. Mass accuracies for the observed fragment ions ranged from +/- 0.20 Da for the smaller peptides studied (i.e., oxidized B chain of bovine insulin) to +/- 0.38 Da for the largest protein studied (cytochrome c), based upon the known sequences.

  6. Development of low-absorption AR coatings for CO2 laser by ion assisted deposition

    NASA Astrophysics Data System (ADS)

    Iwamoto, Hiromi; Ebata, Keiji; Nanba, Hirokuni

    2003-02-01

    We have developed an anti-reflection (AR) coating technique designed for high power carbon dioxide (CO2) lasers that has low absorption and high resistance to humidity. This was achieved by performing ion-assisted deposition (IAD) using a Xe ion beam to apply BaF2 and ZnSe used as coating materials with extremely low bulk absorption coefficients. It was found that to achieve highly compact BaF2 thin films with low absorption on polycrystalline ZnSe substrates, both a surface flatness treatment using Xe ion bombardment and an optimized IAD condition of relatively low ion energy up to 200 eV are required. The absorption of the new (BaF2/ZnSe) AR coated ZnSe lens is 0.10 to 0.12%, approximately half that of conventional (ThF4/ZnSe) AR coated lenses. The new lens has both excellent anti-aging performance and a high resistance to humidity.

  7. Preparation of nanowire specimens for laser-assisted atom probe tomography.

    PubMed

    Blumtritt, H; Isheim, D; Senz, S; Seidman, D N; Moutanabbir, O

    2014-10-31

    The availability of reliable and well-engineered commercial instruments and data analysis software has led to development in recent years of robust and ergonomic atom-probe tomographs. Indeed, atom-probe tomography (APT) is now being applied to a broader range of materials classes that involve highly important scientific and technological problems in materials science and engineering. Dual-beam focused-ion beam microscopy and its application to the fabrication of APT microtip specimens have dramatically improved the ability to probe a variety of systems. However, the sample preparation is still challenging especially for emerging nanomaterials such as epitaxial nanowires which typically grow vertically on a substrate through metal-catalyzed vapor phase epitaxy. The size, morphology, density, and sensitivity to radiation damage are the most influential parameters in the preparation of nanowire specimens for APT. In this paper, we describe a step-by-step process methodology to allow a precisely controlled, damage-free transfer of individual, short silicon nanowires onto atom probe microposts. Starting with a dense array of tiny nanowires and using focused ion beam, we employed a sequence of protective layers and markers to identify the nanowire to be transferred and probed while protecting it against Ga ions during lift-off processing and tip sharpening. Based on this approach, high-quality three-dimensional atom-by-atom maps of single aluminum-catalyzed silicon nanowires are obtained using a highly focused ultraviolet laser-assisted local electrode atom probe tomograph.

  8. Indoor radiation mapping using the Laser Assisted Ranging and Data System (LARADS). Innovative technology summary report

    SciTech Connect

    1998-11-01

    The US Department of Energy`s (DOE`s) nuclear facilities require characterization and documentation of the results as part of planning and decision-making for decontamination and decommissioning (D and D) projects and to release areas that have been cleaned up. Conducting radiation surveys of indoor and outdoor surfaces and generating accurate survey reports is an important component of the D and D program. The Laser Assisted Ranging and Data System (LARADS) is a characterization technology that provides real-time data on the location and concentration levels of radiological contamination. The system can be utilized with a number of available detection instruments and can be integrated with existing data analysis and mapping software technologies to generate superior quality survey data reports. This innovative technology is competitive with baseline technologies in terms of cost and survey times, but is much more flexible and provides more useful reports. The system also has the capability of electronically logging survey data, making it easy to store and retrieve. Such data are scientifically derived and not subject to interpretation. The LARADS is an extremely attractive alternative to manually generated survey data reports.

  9. The mechanism underlying calcium phosphate precipitation on titanium via ultraviolet, visible, and near infrared laser-assisted biomimetic process

    NASA Astrophysics Data System (ADS)

    Mahanti, Moumita; Nakamura, Maki; Pyatenko, Alexander; Sakamaki, Ikuko; Koga, Kenji; Oyane, Ayako

    2016-08-01

    We recently developed a rapid single-step calcium phosphate (CaP) precipitation technique on several substrates using a laser-assisted biomimetic process (LAB process). In this process, ultraviolet (UV, λ  =  355 nm) pulsed laser irradiation has been applied to a substrate that is immersed in a supersaturated CaP solution. In the present study, the LAB process for CaP precipitation on a titanium substrate was successfully expanded to include not only UV but also visible (VIS, λ  =  532 nm) and near infrared (NIR, λ  =  1064 nm) lasers. Surface heating and plasma-mediated surface reactions (micro-deformation, oxidization, photoexcitation, and wetting) generated by UV, VIS, or NIR lasers are considered to be involved in the CaP precipitation on the titanium surface in the LAB process. The kinetics of these reactions and consequently of CaP precipitation were dependent on the laser wavelength and fluence. The higher laser fluence did not always accelerate CaP precipitation on the substrate; rather, it was found that an optimal range of fluence exists for each laser wavelength. These results suggest that for efficient CaP precipitation, a suitable laser wavelength should be selected according to the optical absorption properties of the substrate material and the laser fluence should also be adjusted to induce surface heating and plasma-mediated surface reactions that are favorable for CaP precipitation.

  10. Rapid Detection of OXA-48-Producing Enterobacteriaceae by Matrix-Assisted Laser Desorption Ionization−Time of Flight Mass Spectrometry

    PubMed Central

    Oviaño, Marina; Barba, Maria José; Fernández, Begoña; Ortega, Adriana; Aracil, Belén; Oteo, Jesús; Campos, José

    2015-01-01

    A rapid and sensitive (100%) matrix-assisted laser desorption ionization−time of flight mass spectrometry (MALDI-TOF MS) assay was developed to detect OXA-48-type producers, using 161 previously characterized clinical isolates. Ertapenem was monitored to detect carbapenem resistance, and temocillin was included in the assay as a marker for OXA-48-producers. Structural analysis of temocillin is described. Data are obtained within 60 min. PMID:26677247

  11. Black phosphorus-assisted laser desorption ionization mass spectrometry for the determination of low-molecular-weight compounds in biofluids.

    PubMed

    He, Xiao-Mei; Ding, Jun; Yu, Lei; Hussain, Dilshad; Feng, Yu-Qi

    2016-09-01

    Quantitative analysis of small molecules by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been a challenging task due to matrix-derived interferences in low m/z region and poor reproducibility of MS signal response. In this study, we developed an approach by applying black phosphorus (BP) as a matrix-assisted laser desorption ionization (MALDI) matrix for the quantitative analysis of small molecules for the first time. Black phosphorus-assisted laser desorption/ionization mass spectrometry (BP/ALDI-MS) showed clear background and exhibited superior detection sensitivity toward quaternary ammonium compounds compared to carbon-based materials. By combining stable isotope labeling (SIL) strategy with BP/ALDI-MS (SIL-BP/ALDI-MS), a variety of analytes labeled with quaternary ammonium group were sensitively detected. Moreover, the isotope-labeled forms of analytes also served as internal standards, which broadened the analyte coverage of BP/ALDI-MS and improved the reproducibility of MS signals. Based on these advantages, a reliable method for quantitative analysis of aldehydes from complex biological samples (saliva, urine, and serum) was successfully established. Good linearities were obtained for five aldehydes in the range of 0.1-20.0 μM with correlation coefficients (R (2)) larger than 0.9928. The LODs were found to be 20 to 100 nM. Reproducibility of the method was obtained with intra-day and inter-day relative standard deviations (RSDs) less than 10.4 %, and the recoveries in saliva samples ranged from 91.4 to 117.1 %. Taken together, the proposed SIL-BP/ALDI-MS strategy has proved to be a reliable tool for quantitative analysis of aldehydes from complex samples. Graphical Abstract An approach for the determination of small molecules was developed by using black phosphorus (BP) as a matrix-assisted laser desorption ionization (MALDI) matrix.

  12. Nanoparticle-assisted laser desorption/ionization mass spectrometry: Novel sample preparation methods and nanoparticle screening for plant metabolite imaging

    SciTech Connect

    Yagnik, Gargey B.

    2016-02-19

    The main goal of the presented research is development of nanoparticle based matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS). This dissertation includes the application of previously developed data acquisition methods, development of novel sample preparation methods, application and comparison of novel nanoparticle matrices, and comparison of two nanoparticle matrix application methods for MALDI-MS and MALDI-MS imaging.

  13. The efficacy of laser-assisted in-office bleaching and home bleaching on sound and demineralized enamel

    PubMed Central

    Akbari, Majid; Mohammadpour, Sakineh

    2015-01-01

    Aims: This study investigated the effectiveness of laser-assisted in-office bleaching and home-bleaching in sound and demineralized enamel. Materials and Methods: The sample consisted of 120 freshly-extracted bovine incisors. Half of the specimens were stored in a demineralizing solution to induce white spot lesions. Following exposure to a tea solution for 7.5 days, the specimens were randomly assigned to 4 groups of 30 according to the type of enamel and the bleaching procedure employed. Groups 1 and 2 consisted of demineralized teeth subjected to in-office bleaching and home bleaching, whereas in groups 3 and 4, sound teeth were subjected to in-office and home bleaching, respectively. A diode laser (810 nm, 2 W, continuous wave, four times for 15 seconds each) was employed for assisting the in-office process. The color of the specimens was measured before (T1) and after (T2) staining and during (T3) and after (T4) the bleaching procedures using a spectrophotometer. The color change (ΔE) between different treatments stages was compared among the groups. Results: There were significant differences in the color change between T2 and T3 (ΔE T2–T3) and T2 and T4 (ΔE T2–T4) stages among the study groups (p<0.05). Pairwise comparison by Duncan test revealed that both ΔET2–T3 and ΔET2–T4 were significantly greater in demineralized teeth submitted to laser-assisted in-office bleaching (group 1) as compared to the other groups (P< 0.05). Conclusion: Laser-assisted in-office bleaching could provide faster and greater whitening effect than home bleaching on stained demineralized enamel, but both procedures produced comparable results on sound teeth. PMID:26877590

  14. Laser-Assisted Stir Welding of 25-mm-Thick HSLA-65 Plate

    NASA Astrophysics Data System (ADS)

    Williamson, Keith M.

    2002-12-01

    Laser-assisted stir welding is a hybrid process that combines energy from a laser with functional heating and mechanical energy to join materials in the solid state. The technology is an adaptation of friction stir welding which is particularly suited for joining thick plates. Aluminum plates up to 75 mm thick have been successfully joined using friction stir welding. Since joining occurs in the solid state, stir technology offers the capability for fabricating full penetration joints in thick plates with better mechanical properties and less weld distortion than is possible by fusion processes. Currently friction stir welding is being used in several industries to improve productivity, reduce weight, and increase the strength of welded structures. Examples include: (a) the aircraft/aerospace industry where stir technology is currently being used to fabricate the space shuttle's external tank as well as components of the Delta family of rockets; (b) the shipping industry where container manufacturers are using stir technology to produce lighter containers with more payload capacity; and (c) the oil industry where offshore platform manufactures are using automated stir welding plants to fabricate large panels and structures up to 16 meters long with widths as required. In all these cases, stir technology has been restricted to aluminum alloys; however, stainless and HSLA 65 steels have been recently stir welded with friction as the primary heat source. One of the difficulties in adapting stir welding to steel is tool wear aggravated by the high tool rubbing velocities needed to provide frictional heat input into the material. Early work showed that the tool shoulder reached temperatures above 1000 C and the weld seam behind the tool stayed within this temperature range for up to 25 mm behind the tool. Cross sections of stir welded samples showed that the heat-affected zone is relatively wide and follows the profile of the tool shoulder. Besides minimizing the tool

  15. Induced hatching to avoid infectious egg disease in whitefish.

    PubMed

    Wedekind, Claus

    2002-01-08

    Reacting to a threat before physical contact, e.g., induced by air- or water-borne substances, appears to be an elegant way of defense. The reaction may be behavioral, developmental, morphological, or physiological, and it can involve a shift in niche or life history. Hatching from eggs is a shift in niche and in life history. From niche shift and life history models, one would predict that the timing of hatching is, to some degree, phenotypically plastic, i.e., early or delayed hatching is likely to be inducible. Temporary increased larval mortality (e.g., increased predation on larvae) would favor delayed hatching, while relatively high egg mortality would favor early hatching. Here, I show experimentally that eggs of the whitefish (Coregonus sp.) hatch earlier in the presence of a virulent egg parasite and that this early hatching is induced by water-borne cues emitted from infected eggs.

  16. Hatching Behavior of Potato Cyst Nematodes from the Canary Islands

    PubMed Central

    Gonzalez, J. A.; Phillips, M. S.

    1996-01-01

    The present work investigated early hatching differences in naturally occuring field populations and newly reared populations of potato cyst nematodes from the Canary Islands. Hatching behavior of the two species appears to be distinct, with more juveniles hatched from G. pallida that hatch earlier and over a shorter time than G. rostochiensis. The hatching rate of 3-year-old PCN populations was more than double (mean 44.5% ñ 1) that shown by newly reared populations (mean 19.1% ñ 12.5), and those that could be classified as pathotype Pa 1 (Pa 1 and P 13) were found to hatch particularly poorly. Significant differences were also observed in the juveniles released in tap water between newly reared populations of both species, with mean hatch significantly higher for G. rostochiensis. The results are discussed in relation to the implication that these findings may have for competition between the two species of PCN in the field. PMID:19277163

  17. Characterization of silver ions adsorbed on gold nanorods: surface analysis by using surface-assisted laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Niidome, Yasuro; Nakamura, Yuki; Honda, Kanako; Akiyama, Yasuyuki; Nishioka, Koji; Kawasaki, Hideya; Nakashima, Naotoshi

    2009-04-07

    Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-MS) indicated AgBr2-, which adsorbed on gold nanorod surfaces, was a key material to control the anisotropic growth of gold nanorods.

  18. Ground states of a Bose-Einstein Condensate in a one-dimensional laser-assisted optical lattice

    NASA Astrophysics Data System (ADS)

    Sun, Qing; Hu, Jie; Wen, Lin; Liu, W.-M.; Juzeliūnas, G.; Ji, An-Chun

    2016-11-01

    We study the ground-state behavior of a Bose-Einstein Condensate (BEC) in a Raman-laser-assisted one-dimensional (1D) optical lattice potential forming a multilayer system. We find that, such system can be described by an effective model with spin-orbit coupling (SOC) of pseudospin (N-1)/2, where N is the number of layers. Due to the intricate interplay between atomic interactions, SOC and laser-assisted tunnelings, the ground-state phase diagrams generally consist of three phases-a stripe, a plane wave and a normal phase with zero-momentum, touching at a quantum tricritical point. More important, even though the single-particle states only minimize at zero-momentum for odd N, the many-body ground states may still develop finite momenta. The underlying mechanisms are elucidated. Our results provide an alternative way to realize an effective spin-orbit coupling of Bose gas with the Raman-laser-assisted optical lattice, and would also be beneficial to the studies on SOC effects in spinor Bose systems with large spin.

  19. Water-assisted CO(2) laser ablated glass and modified thermal bonding for capillary-driven bio-fluidic application.

    PubMed

    Chung, C K; Chang, H C; Shih, T R; Lin, S L; Hsiao, E J; Chen, Y S; Chang, E C; Chen, C C; Lin, C C

    2010-02-01

    The glass-based microfluidic chip has widely been applied to the lab-on-a-chip for clotting tests. Here, we have demonstrated a capillary driven flow chip using the water-assisted CO(2) laser ablation for crackless fluidic channels and holes as well as the modified low-temperature glass bonding with assistance of adhesive polymer film at 300 degrees Celsius. Effect of water depth on the laser ablation of glass quality was investigated. The surface hydrophilic property of glass and polymer film was measured by static contact angle method for hydrophilicity examination in comparison with the conventional polydimethylsiloxane (PDMS) material. Both low-viscosity deionized water and high-viscosity whole blood were used for testing the capillary-driving flow behavior. The preliminary coagulation testing in the Y-channel chip was also performed using whole blood and CaCl(2) solution. The water-assisted CO(2) laser processing can cool down glass during ablation for less temperature gradient to eliminate the crack. The modified glass bonding can simplify the conventional complex fabrication procedure of glass chips, such as high-temperature bonding, long consuming time and high cost. Moreover, the developed fluidic glass chip has the merit of hydrophilic behavior conquering the problem of traditional hydrophobic recovery of polymer fluidic chips and shows the ability to drive high-viscosity bio-fluids.

  20. Ground states of a Bose-Einstein Condensate in a one-dimensional laser-assisted optical lattice

    PubMed Central

    Sun, Qing; Hu, Jie; Wen, Lin; Liu, W.-M.; Juzeliūnas, G.; Ji, An-Chun

    2016-01-01

    We study the ground-state behavior of a Bose-Einstein Condensate (BEC) in a Raman-laser-assisted one-dimensional (1D) optical lattice potential forming a multilayer system. We find that, such system can be described by an effective model with spin-orbit coupling (SOC) of pseudospin (N-1)/2, where N is the number of layers. Due to the intricate interplay between atomic interactions, SOC and laser-assisted tunnelings, the ground-state phase diagrams generally consist of three phases–a stripe, a plane wave and a normal phase with zero-momentum, touching at a quantum tricritical point. More important, even though the single-particle states only minimize at zero-momentum for odd N, the many-body ground states may still develop finite momenta. The underlying mechanisms are elucidated. Our results provide an alternative way to realize an effective spin-orbit coupling of Bose gas with the Raman-laser-assisted optical lattice, and would also be beneficial to the studies on SOC effects in spinor Bose systems with large spin. PMID:27883037

  1. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

  2. Measurement of laser activated electron tunneling from semiconductor zinc oxide to adsorbed organic molecules by a matrix assisted laser desorption ionization mass spectrometer.

    PubMed

    Zhong, Hongying; Fu, Jieying; Wang, Xiaoli; Zheng, Shi

    2012-06-04

    Measurement of light induced heterogeneous electron transfer is important for understanding of fundamental processes involved in chemistry, physics and biology, which is still challenging by current techniques. Laser activated electron tunneling (LAET) from semiconductor metal oxides was observed and characterized by a MALDI (matrix assisted laser desorption ionization) mass spectrometer in this work. Nanoparticles of ZnO were placed on a MALDI sample plate. Free fatty acids and derivatives were used as models of organic compounds and directly deposited on the surface of ZnO nanoparticles. Irradiation of UV laser (λ=355 nm) with energy more than the band gap of ZnO produces ions that can be detected in negative mode. When TiO(2) nanoparticles with similar band gap but much lower electron mobility were used, these ions were not observed unless the voltage on the sample plate was increased. The experimental results indicate that laser induced electron tunneling is dependent on the electron mobility and the strength of the electric field. Capture of low energy electrons by charge-deficient atoms of adsorbed organic molecules causes unpaired electron-directed cleavages of chemical bonds in a nonergodic pathway. In positive detection mode, electron tunneling cannot be observed due to the reverse moving direction of electrons. It should be able to expect that laser desorption ionization mass spectrometry is a new technique capable of probing the dynamics of electron tunneling. LAET offers advantages as a new ionization dissociation method for mass spectrometry.

  3. Carbon dioxide laser-assisted nerve repair: effect of solder and suture material on nerve regeneration in rat sciatic nerve.

    PubMed

    Menovsky, Tomas; Beek, Johan F

    2003-01-01

    In order to further improve and explore the role of lasers for nerve reconstruction, this study was designed to investigate regeneration of sharply transected peripheral nerves repaired with a CO(2) milliwatt laser in combination with three different suture materials and a bovine albumin protein solder as an adjunct to the welding process. Unilateral sciatic nerve repair was performed in 44 rats. In the laser group, nerves were gently apposed, and two stay sutures (10-0 nylon, 10-0 polyglycolic acid, or 25 microm stainless steel) were placed epi/perineurially. Thereafter, the repair site was fused at 100 mW with pulses of 1.0 s. In the subgroup of laser-assisted nerve repair (LANR), albumen was used as a soldering agent to further reinforce the repair site. The control group consisted of nerves repaired by conventional microsurgical suture repair (CMSR), using 4-6 10-0 nylon sutures. Evaluation was performed at 1 and 6 weeks after surgery, and included qualitative and semiquantitative light microscopy. LANR performed with a protein solder results in a good early peripheral nerve regeneration, with an optimal alignment of nerve fibers and minimal connective tissue proliferation at the repair site. All three suture materials produced a foreign body reaction; the least severe was with polyglycolic acid sutures. CMSR resulted in more pronounced foreign-body granulomas at the repair site, with more connective-tissue proliferation and axonal misalignment. Furthermore, axonal regeneration in the distal nerve segment was better in the laser groups. Based on these results, CO(2) laser-assisted nerve repair with soldering in combination with absorbable sutures has the potential of allowing healing to occur with the least foreign-body reaction at the repair site. Further experiments using this combination are in progress.

  4. Matrix-assisted and polymer-assisted laser desorption/ionization time-of-flight mass spectrometric analysis of low molecular weight polystyrenes and polyethylene glycols.

    PubMed

    Woldegiorgis, Andreas; Löwenhielm, Peter; Björk, Anders; Roeraade, Johan

    2004-01-01

    Recently, matrices based on oligomers of dioxin and thiophene (polymer-assisted laser desorption/ionization (PALDI)) have been described for mass spectrometric (MS) analysis of low molecular weight compounds (Woldegiorgis A, von Kieseritzky F, Dahlstedt E, Hellberg J, Brinck T, Roeraade J. Rapid Commun. Mass Spectrom. 2004; 18: 841-852). In this paper, we report the use of PALDI matrices for low molecular weight polymers. An evaluation with polystyrene and polyethylene glycol showed that no charge transfer ionization occurs. Ionization is mediated through metal ion adduction. Comparison of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) data for two very low molecular weight polymers with data obtained from size-exclusion chromatography (SEC) revealed a systematic difference regarding mean molecular weight and dispersity. Further, the mass spectra obtained with PALDI matrices had a higher signal-to-noise ratio than the spectra obtained with conventional matrices. For polymers with higher molecular weights (>1500 Da), the conventional matrices gave better performance. For evaluation of the MALDI spectra, three non-linear mathematical models were evaluated to model the cumulative distributions of the different oligomers and their maximal values of Mw, Mn and PDI. Models based on sigmoidal or Boltzmann equations proved to be most suitable. Objective modeling tools are necessary to compare different sample and instrumental conditions during method optimization of MALDI analysis of polymers, since the bias between MALDI and SEC data can be misleading.

  5. Selection of the most influential factors on the water-jet assisted underwater laser process by adaptive neuro-fuzzy technique

    NASA Astrophysics Data System (ADS)

    Nikolić, Vlastimir; Petković, Dalibor; Lazov, Lyubomir; Milovančević, Miloš

    2016-07-01

    Water-jet assisted underwater laser cutting has shown some advantages as it produces much less turbulence, gas bubble and aerosols, resulting in a more gentle process. However, this process has relatively low efficiency due to different losses in water. It is important to determine which parameters are the most important for the process. In this investigation was analyzed the water-jet assisted underwater laser cutting parameters forecasting based on the different parameters. The method of ANFIS (adaptive neuro fuzzy inference system) was applied to the data in order to select the most influential factors for water-jet assisted underwater laser cutting parameters forecasting. Three inputs are considered: laser power, cutting speed and water-jet speed. The ANFIS process for variable selection was also implemented in order to detect the predominant factors affecting the forecasting of the water-jet assisted underwater laser cutting parameters. According to the results the combination of laser power cutting speed forms the most influential combination foe the prediction of water-jet assisted underwater laser cutting parameters. The best prediction was observed for the bottom kerf-width (R2 = 0.9653). The worst prediction was observed for dross area per unit length (R2 = 0.6804). According to the results, a greater improvement in estimation accuracy can be achieved by removing the unnecessary parameter.

  6. Matrix-assisted resonant infrared pulsed laser ablation of electroluminescent dendrimers

    NASA Astrophysics Data System (ADS)

    Torres-Pagan, Ricardo Daniel

    The deposition techniques for polymer thin films in organic light emitting diodes are limited to wet methods since molecular pyrolysis prevents the use of dry vacuum thermal evaporation methods. Wet methods have critical limitations such as poor thickness control, drying patterns and re-dissolution of previous layers. In this work, a novel approach, Matrix-Assisted Resonant Infrared Pulsed Laser Ablation (RIM-PLA) has been studied as an alternative deposition method for electroluminescent polymer films. RIM-PLA was successfully used for the deposition of two model dendrimers: fluorescent and phosphorescent Ir-cored. A free-electron laser was tuned to resonance frequencies for the vibrational modes of two solid matrix solvents: chloroform (C-H stretch; C-H bending) and toluene (C-H stretch; C=C stretch). The temperature-dependent absorption coefficients for each resonance mode were measured. Targets made from flash-frozen, low-concentration solutions of the dendrimers were irradiated at each frequency while varying fluence and exposure times. The molecular structure integrity of the targets was characterized. The deposited films were characterized to assess structure fidelity, roughness and topography, and luminance. All RIM-PLA deposited films were compared with spin-coated films. The ablation characteristics for each mode were found to be dependent on the solvent and not the dendrimer. Calculations from a temperature-rise model show that FEL pulsed-irradiation results in heating rates on the order of 108--109 K/s, resulting in metastable condensed targets. Thermodynamic and kinetic relations were used to calculate the relevance of three ablation mechanisms: normal vaporization, normal boiling and phase explosion. The latter mechanism has a critical threshold (> 0.8 Tc) for each solvent, and proceeds through spinodal decay followed by rapid homogeneous nucleation of vapor bubbles within the focal volume. For both chloroform modes, the primary ablation mechanism was

  7. Ruby laser-assisted depilation: The mode of action and potential ways of improved outcome

    NASA Astrophysics Data System (ADS)

    Topping, Adam Partington

    Aim - To improve efficacy and lessen side effects resulting from normal mode ruby laser (NMRL)-assisted depilation via a greater understanding of its mode of action and the development of novel methods of reducing associated epidermal damage. Employing a thermal imaging camera and ex vivo hair-bearing skin, the targets for the NMRL (pulse duration 900 musec and spot size 7 mm) were defined, the temperatures reached and the heat dissipation rates determined. Production of heat was confined to the hair follicles, with the peak temperatures reached varying considerably between hairs within the same treatment area and also between individuals. Histological assessment for a known indicator of cellular damage (p53 expression) identified the sites and extent of damage, which correlated with the peak temperatures measured. An energy meter was used to detect the penetration of NMRL light through ex vivo skin, which was found to be deeper than previously theorised. The black-haired mouse (C57B1/10) was assessed both macroscopically and histologically and found to be an acceptable animal model of NMRL depilation and associated epidermal damage. Attempts to reduce the epidermal damage by simply stopping the light reaching the epidermis using a chromophore block were assessed. Chromophore did indeed reduce the amount of epidermal damage detected in laser-irradiated ex vivo human skin, whereas in contrast it increased the wounding seen in the much thinner skin of the mouse. Nevertheless the mouse model showed that this technique did not affect the depilation efficacy. An alternative method of reducing epidermal damage using induction of the cells' intrinsic protective mechanisms (heat shock proteins, HSP) was assessed using cultured keratinocytes and the mouse model. Primarily, the sub-lethal temperature optimum for HSP expression in human keratinocytes was determined, then an in vitro model of NMRL-associated epidermal damage was established and the heat pre-treatment assessed

  8. Effects of hatching time for larval ambystomatid salamanders

    USGS Publications Warehouse

    Boone, M.D.; Scott, D.E.; Niewiarowski, P.H.

    2002-01-01

    In aquatic communities, the phenology of breeding may influence species interactions. In the early-breeding marbled salamander, Ambystoma opacum, timing of pond filling may determine whether interactions among larvae are competitive or predatory. The objectives of our studies were to determine how time of egg hatching affected size, larval period, and survival to metamorphosis in A. opacum, and if early-hatching in A. opacum influenced the competitive and predator-prey relationships with smaller larvae of the mole salamander, Ambystoma talpoideum. Salamander larvae were reared from hatching through metamorphosis in large, outdoor enclosures located in a natural temporary pond in Aiken County, South Carolina, in two experiments. In study 1, we reared early- and late-hatching A. opacum larvae separately from hatching through metamorphosis. In study 2, we examined how early- versus late-hatching A. opacum affected a syntopic species, A. talpoideum. In general, early-hatching A. opacum were larger and older at metamorphosis, had greater survival, and left the pond earlier than late-hatching larvae. Ambystoma talpoideum reared in the presence of early-hatching A. opacum had lower survival than in controls, suggesting that A. opacum may predate upon A. talpoideum when they gain a growth advantage over later-hatching larvae. Our studies demonstrate that time of pond filling and phenology of breeding may influence population dynamics and alter the nature of relationships that develop among species.

  9. Corticosterone stimulates hatching of late-term tree lizard embryos.

    PubMed Central

    Weiss, Stacey L.; Johnston, Gwynne; Moore, Michael C.

    2007-01-01

    The regulation of hatching in oviparous animals is important for successful reproduction and survival, but is poorly understood. We unexpectedly found that RU-486, a progesterone and glucocorticoid antagonist, interferes with hatching of viable tree lizard (Urosaurus ornatus) embryos in a dose-dependent manner and hypothesized that embryonic glucocorticoids regulate hatching. To test this hypothesis, we treated eggs with corticosterone (CORT) or vehicle on Day 30 (85%) of incubation, left other eggs untreated, and observed relative hatch order and hatch time. In one study, the CORT egg hatched first in 9 of 11 clutches. In a second study, the CORT egg hatched first in 9 of 12 clutches, before vehicle-treated eggs in 10 of 12 clutches, and before untreated eggs in 7 of 9 clutches. On average, CORT eggs hatched 18.2h before vehicle-treated eggs and 11.6h before untreated eggs. Thus, CORT accelerates hatching of near-term embryos and RU-486 appears to block this effect. CORT may mobilize energy substrates that fuel hatching and/or accelerate lung development, and may provide a mechanism by which stressed embryos escape environmental stressors. PMID:17208477

  10. Laser-assisted atom probe tomography of Ti/TiN films deposited on Si.

    PubMed

    Sanford, N A; Blanchard, P T; White, R; Vissers, M R; Diercks, D R; Davydov, A V; Pappas, D P

    2017-03-01

    Laser-assisted atom probe tomography (L-APT) was used to examine superconducting TiN/Ti/TiN trilayer films with nominal respective thicknesses of 5/5/5 (nm). Such materials are of interest for applications that require large arrays of microwave kinetic inductance detectors. The trilayers were deposited on Si substrates by reactive sputtering. Electron energy loss microscopy performed in a scanning transmission electron microscope (STEM/EELS) was used to corroborate the L-APT results and establish the overall thicknesses of the trilayers. Three separate batches were studied where the first (bottom) TiN layer was deposited at 500°C (for all batches) and the subsequent TiN/Ti bilayer was deposited at ambient temperature, 250°C, and 500°C, respectively. L-APT rendered an approximately planar TiN/Si interface by making use of plausible mass-spectral assignments to N3(1+), SiN(1+), and SiO(1+). This was necessary since ambiguities associated with the likely simultaneous occurrence of Si(1+) and N2(1+) prevented their use in rendering the TiN/Si interface upon reconstruction. The non-superconducting Ti2N phase was also revealed by L-APT. Neither L-APT nor STEM/EELS rendered sharp Ti/TiN interfaces and the contrast between these layers diminished with increased film deposition temperature. L-APT also revealed that hydrogen was present in varying degrees in all samples including control samples that were composed of single layers of Ti or TiN.

  11. A prospective 9-month human clinical evaluation of Laser-Assisted New Attachment Procedure (LANAP) therapy.

    PubMed

    Nevins, Marc; Kim, Soo-Woo; Camelo, Marcelo; Martin, Ignacio Sanz; Kim, David; Nevins, Myron

    2014-01-01

    This investigation was designed and implemented as a single-center, prospective study to evaluate the clinical response to the Laser-Assisted New Attachment Procedure (LANAP). Eight patients with advanced periodontitis were enrolled and treated with full-mouth LANAP therapy and monitored for 9 months. Fullmouth clinical measurements, including clinical attachment level (CAL), probing depth (PD), and recession, were provided at baseline and after 9 months of healing by a single calibrated examiner, including a total of 930 sites and 444 sites with initial PD equal to or greater than 5 mm. Clinical results for the 930 sites measured pre- and postoperatively revealed that mean PD was reduced from 4.62 ± 2.29 mm to 3.14 ± 1.48 mm after 9 months (P < .05). CAL decreased from 5.58 ± 2.76 mm to 4.66 ± 2.10 mm (P < .05) and recession increased from 0.86 ± 1.31 mm to 1.52 ± 1.62 after 9 months (P < .05). For the subset of 444 sites with initial PD greater than or equal to 5 mm, the PD decreased from 6.50 ± 2.07 mm to 3.92 ± 1.54 mm (P < .05) and CAL decreased from 7.42 ± 2.70 mm to 5.78 ± 2.06 mm (P < .05). As demonstrated by the clinical evaluation, the majority of treated sites demonstrated clinical improvement. LANAP therapy should be further investigated with long-term clinical trials to compare the stability of clinical results with conventional therapy.

  12. Detection of somatic mosaicism in DMD using computer-assisted laser densitometry

    SciTech Connect

    Sutherland, J.E.; Allingham-Hawkins, D.J.; MacKenzie, J.

    1994-09-01

    Approximately two-thirds of Duchenne muscular dystrophy (DMD) patients have a deletion in the dystrophin gene located at Xp21.1. Two PCR-based multiplex systems have been developed which detect 98% of deletions in affected males. Diagnosis of carrier females requires densitometry of PCR products following gel electrophoresis to calculate dosage of specific exons. We have developed a system in which fluorescently labelled PCR products are analysed using a GENESCANNER automated fragment analyser (ABI). Dosage is determined using computer-assisted laser densitometry (CALD). Recently, we diagnosed somatic mosaicism in the mother of an affected boy using this method. PCR analysis showed that the patient had a deletion that included exons 47-51 of his dystrophin gene. CALD analysis on the patient`s 36-year-old mother revealed a 29-34% reduction in the intensity of the bands corresponding to the deleted region of the gene rather than the 50% reduction normally seen in carrier females. A skin biopsy was obtain and monoclonal fibroblast colonies were tested by CALD for the deletion. Four of the twenty colonies screened were found to be deleted while the remaining colonies had two intact copies of the gene. We conclude that this patient is a somatic mosaic for DMD and that the mutation was the result of a post-zygotic event. This is the only case of somatic mosaicism detected among 800 women from 400 DMD families tested using CALD in our laboratory. At least one other case of possible somatic mosaicism has been reported but not confirmed. Germinal mosaicism is thought to occur in approximately 10% of mothers of sporadic DMD patients. Our findings indicate that somatic mosaicism is a much rarer condition among DMD carriers, thus suggesting that mitotic mutations in the dystrophin gene are more likely to occur later in embryogenesis after differentiation of the germline.

  13. High-throughput proteomics using matrix-assisted laser desorption/ ionization mass spectrometry.

    PubMed

    Cramer, Rainer; Gobom, Johan; Nordhoff, Eckhard

    2005-06-01

    It has become evident that the mystery of life will not be deciphered just by decoding its blueprint, the genetic code. In the life and biomedical sciences, research efforts are now shifting from pure gene analysis to the analysis of all biomolecules involved in the machinery of life. One area of these postgenomic research fields is proteomics. Although proteomics, which basically encompasses the analysis of proteins, is not a new concept, it is far from being a research field that can rely on routine and large-scale analyses. At the time the term proteomics was coined, a gold-rush mentality was created, promising vast and quick riches (i.e., solutions to the immensely complex questions of life and disease). Predictably, the reality has been quite different. The complexity of proteomes and the wide variations in the abundances and chemical properties of their constituents has rendered the use of systematic analytical approaches only partially successful, and biologically meaningful results have been slow to arrive. However, to learn more about how cells and, hence, life works, it is essential to understand the proteins and their complex interactions in their native environment. This is why proteomics will be an important part of the biomedical sciences for the foreseeable future. Therefore, any advances in providing the tools that make protein analysis a more routine and large-scale business, ideally using automated and rapid analytical procedures, are highly sought after. This review will provide some basics, thoughts and ideas on the exploitation of matrix-assisted laser desorption/ ionization in biological mass spectrometry - one of the most commonly used analytical tools in proteomics - for high-throughput analyses.

  14. The effect of laser energy on V2O5 thin film growth prepared by laser assisted molecular beam deposition

    NASA Astrophysics Data System (ADS)

    Abdel Samad, B.; Ashrit, P. V.

    2014-09-01

    Vanadium pentoxide V2O5 thin films were grown on glass substrates by the LAMBD deposition system with different laser energies. The structure, composition and optical properties of the films have been investigated with atomic force microscopy, x-ray photoemission spectroscopy, ellipsometry and the transmittance analysis. Upon the increase of laser energy, the results showed that the changes in the optical constants are consistent with the thickness changes of the film. The refractive index increases and the absorption coefficient increases when the laser energy increases. The AFM analysis showed a change of the roughness and structure of the deposited films at different laser energies. The prepared films deposited by LAMBD showed interesting properties with correct V2O5 phase without need of annealing after deposition.

  15. Temporal evolution of liquid-assisted hard bio-tissue ablation with infrared pulsed lasers under a liquid environment

    NASA Astrophysics Data System (ADS)

    Chen, Faner; Li, Qiang; Hua, Mingxin; Zhan, Zhenlin; Xie, Shusen; Zhang, Xianzeng

    2016-10-01

    Liquid-assisted hard biotissue ablation with the pulsed lasers takes advantages in precision and compatibility than mechanical tools in traditional surgery. The objective of this study was to monitor the dynamic process of the cavitation bubble evolution induced by Ho:YAG laser under water and identify the opening time of channel formation between the fiber tip to the target tissue surface. A free-running Ho:YAG laser was used in the experiment. The wavelength was 2.1 μm with a pulse duration of 350 us and pulse energy varied from 500 mJ to 2000 mJ. The high-speed camera (PCO. dimax, Germany, PCO) applied to monitor the whole ablation process was setting at a frame rate of 52000 frames/s. The results showed that the cavitation bubble induced by laser energy experienced an oscillation process including occurrence, expansion, contraction and subsequent collapse. A channel connected the fiber tip and target tissue surface was formed during the dynamic process which allowed the following pulse energy transmitted through the channel with a relative low absorption and directly interacted with the target tissue. The beginning time of channel formation, as well as the duration of channel opening, as functions of incident laser energy were also presented. A micro-explosion was observed near the tissue surface during the bubble collapse, which may contribute to produce a clean cut, reduce the thermal injury and improve the morphology of ablation crater.

  16. Incidence and Outcomes of Anterior Chamber Gas Bubble during Femtosecond Flap Creation for Laser-Assisted In Situ Keratomileusis.

    PubMed

    Rush, Sloan W; Cofoid, Philip; Rush, Ryan B

    2015-01-01

    Purpose. To report the incidence and outcomes of anterior chamber gas bubble formation during femtosecond laser flap creation for laser-assisted in situ keratomileusis (LASIK). Methods. The charts of 2,886 consecutive eyes that underwent femtosecond LASIK from May 2011 through August 2014 were retrospectively reviewed. The incidence, preoperative characteristics, intraoperative details, and postoperative outcomes were analyzed in subjects developing anterior chamber gas bubble formation during the procedure. Results. A total of 4 cases (0.14%) developed anterior chamber gas bubble formation during femtosecond laser flap creation. In all four cases, the excimer laser was unable to successfully track the pupil immediately following the anterior chamber bubble formation, temporarily postponing the completion of the procedure. There was an ethnicity predilection of anterior chamber gas formation toward Asians (p = 0.0055). An uncorrected visual acuity of 20/20 was ultimately achieved in all four cases without further complications. Conclusions. Anterior chamber gas bubble formation during femtosecond laser flap creation for LASIK is an uncommon event that typically results in a delay in treatment completion; nevertheless, it does influence final positive visual outcome.

  17. Nonthermal Laser Assisted Ge Quantum Dot Formation on Si(100)-2x1 by Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Er, Ali; Elsayed-Ali, Hani

    2009-11-01

    The effect of laser-induced electronic excitations on the self-assembly of Ge quantum dots (QDs) on Si(100)-2x1 grown by pulsed laser deposition is studied. The samples were cleaned by using modified Shiraki method and then transferred into the deposition chamber. The vacuum system was then pumped down, baked for at least 24 hours, and the sample was then flashed to 1200 C in order for the 2x1 reconstruction to form. The experiment was conducted under a pressure ˜1x10-10 Torr. A Q-switched Nd:YAG laser was used to ablate a Ge target. In-situ RHEED and STM and ex-situ AFM were used to study the morphology of the grown QD. The dependence of the QD morphology on substrate temperature and ablation and excitation laser energy density was studied. Electronic excitation is shown to affect the surface morphology. Laser irradiation of the Si substrate is shown to decrease the roughness of films grown at a substrate temperature of ˜400 ^oC. Electronic excitation also affected the surface coverage, cluster density, uniformity and decreased the temperature required to form 3-dimensional QDs to ˜250 C at which no crystalline film formation is possible without excitation laser. Possible mechanisms such as two hole localization following the phonon kick will be discussed.

  18. Nonthermal Laser Assisted Ge Quantum Dot Formation on Si(100)-2x1 by Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Er, Ali; Elsayed-Ali, Hani

    2009-11-01

    The effect of laser-induced electronic excitations on the self-assembly of Ge quantum dots (QDs) on Si(100)-2x1 grown by pulsed laser deposition is studied. The samples were first cleaned by using modified Shiraki method and then transferred into the deposition chamber. The vacuum system was then pumped down, baked for at least 24 hours, and the sample was then flashed to 1200 C in order for the 2x1 reconstruction to form. The experiment was conducted under a pressure ˜1x10-10 Torr. A Q-switched Nd:YAG laser was used to ablate a Ge target. In-situ RHEED and STM and ex-situ AFM were used to study the morphology of the grown QD. The dependence of the QD morphology on substrate temperature and ablation and excitation laser energy density was studied. Electronic excitation is shown to affect the surface morphology. Laser irradiation of the Si substrate is shown to decrease the roughness of films grown at a substrate temperature of ˜400 ^oC. Electronic excitation also affected the surface coverage, cluster density, uniformity and decreased the temperature required to form 3-dimensional QDs to ˜250 C at which no crystalline film formation is possible without excitation laser. Possible mechanisms such as two hole localization following the phonon kick will be discussed.

  19. Spread of hatch and delayed feed access affect post hatch performance of female broiler chicks up to day 5.

    PubMed

    Wang, Y; Li, Y; Willems, E; Willemsen, H; Franssens, L; Koppenol, A; Guo, X; Tona, K; Decuypere, E; Buyse, J; Everaert, N

    2014-04-01

    It is not rare that newly hatched chicks remain without feed for about 24 to 48 h before they are placed on farms due to a series of logistic operations. Furthermore, the spread in hatching time can also mount up to 30 to 48 h for late v. early hatchers. In other words, the practice is a complex combination of spread of hatch and delayed feed access. The present study was aimed to investigate the combined effects of hatching time with a delay in feed access of 48 h, starting from their hatch-time (biological age). When chicks had access to feed immediately after hatch, late hatchers had a higher feed intake and relative growth rate up to day 5 compared with their early hatched counterparts. Feed deprivation during the first 48 h resulted in retarded early growth rate, which was further aggravated by an impaired feed intake after refeeding. In addition, the differential effects of hatching time on relative growth rate and feed intake observed in immediately fed chicks were eliminated by the 48 h feed delay. The yolk utilization after hatch was faster for the late hatchers up to biological day 2 regardless of the feeding treatments. Hatching muscle glycogen content was higher in the late hatchers compared with that of their early counterparts at hatch and at biological day 2 independent of feeding treatment. Moreover, the liver glycogen content of the late hatchers was also higher at hatch. For the immediately fed chicks, the proportional breast muscle weight of the late hatchers was higher at biological day 2 and 5. For the starved chicks, on the other hand, this effect was only observed after they had access to feed (biological day 5). The different plasma T3 levels at hatch may have contributed to the different post hatch performance. It is concluded that the spread of hatch influenced post hatch performance, especially appetite and growth at least until day 5. Moreover, the delay in feed access interacted with the hatching time and caused adverse effects on the

  20. Microsized structures assisted nanostructure formation on ZnSe wafer by femtosecond laser irradiation

    SciTech Connect

    Wang, Shutong; Feng, Guoying E-mail: zhoush@scu.edu.cn

    2014-12-22

    Micro/nano patterning of ZnSe wafer is demonstrated by femtosecond laser irradiation through a diffracting pinhole. The irradiation results obtained at fluences above the ablation threshold are characterized by scanning electron microscopy. The microsized structure with low spatial frequency has a good agreement with Fresnel diffraction theory. Laser induced periodic surface structures and laser-induced periodic curvelet surface structures with high spatial frequency have been found on the surfaces of microsized structures, such as spikes and valleys. We interpret its formation in terms of the interference between the reflected laser field on the surface of the valley and the incident laser pulse.

  1. High-order multiphoton laser-assisted elastic electron scattering by Xe in a femtosecond near-infrared intense laser field: Plateau in energy spectra of scattered electrons

    NASA Astrophysics Data System (ADS)

    Ishida, Kakuta; Morimoto, Yuya; Kanya, Reika; Yamanouchi, Kaoru

    2017-02-01

    Multiphoton free-free transitions were observed in laser-assisted elastic electron scattering (LAES) by Xe atoms in a femtosecond near-infrared intense laser field. The distinct peak structures at the energy shifts of n -photons (n =+1 ,+2 ,+3 ,+4 ,+5 , and +6 ) were identified in the observed energy spectrum, and the energy and angular distributions of the LAES signals were in good agreement with those obtained by numerical simulations based on the Kroll-Watson theory. The LAES signal intensities at the scattering angles at 9.1° and 11.8° exhibited a clear plateau structure as a function of the harmonic order n , and the mechanism of these nonperturbative LAES processes was interpreted by a classical mechanical description.

  2. Improved laser-assisted vascular tissue fusion using solder-doped polymer membranes on a canine model

    NASA Astrophysics Data System (ADS)

    McNally-Heintzelman, Karen M.; Sorg, Brian S.; Hammer, Daniel X.; Heintzelman, Douglas L.; Hodges, Diane E.; Welch, Ashley J.

    2000-05-01

    Newly developed light-activated surgical adhesives have been investigated as a substitute to traditional protein solders for vascular tissue fusion without the need for sutures. Canine femoral arteries (n equals 14), femoral veins (n equals 14) and carotid arteries (n equals 10) were exposed, and a 0.3 to 0.6 cm longitudinal incision was made in the vessel walls. The surgical adhesive, composed of a poly(L-lactic-co-glycolic acid) scaffold doped with the traditional protein solder mix of bovine serum albumin and indocyanine green dye, was used to close the incisions in conjunction with an 805 nm diode laser. Blood flow was restored to the vessels immediately after the procedure and the incision sites were checked for patency. The new adhesives were flexible enough to be wrapped around the vessels while their solid nature avoided the problems associated with 'runaway' of the less viscous liquid protein solders widely used by researchers. Assessment parameters included measurement of the ex vivo intraluminal bursting pressure one to two hours after surgery, as well as histology. The acute intraluminal bursting pressures were significantly higher in the laser-solder group (greater than 300 mmHg) compared to the suture control group (less than 150 mmHg) where four evenly spaced sutures were used to repair the vessel (n equals 4). Histological analysis showed negligible evidence of collateral thermal damage to the underlying tissue in the laser-solder repair group. These initial results indicated that laser-assisted vascular repair using the new adhesives is safe, easy to perform, and contrary to conventional suturing, provides an immediate leak-free closure. In addition, the flexible and moldable nature of the new adhesives should allow them to be tailored to a wide range of tissue geometries, thus greatly improving the clinical applicability of laser-assisted tissue repair.

  3. Laser-assisted cell fusion and cytoplast transfer in early mammalian embryos

    NASA Astrophysics Data System (ADS)

    Clement-Sengewald, Annette; Schutze, Karin; Heinze, A.; Palma, G. A.; Poesl, H.; Brem, G.

    1993-07-01

    A UV-laser microbeam was successfully used to induce fusion of early embryonic cells. The developmental capacity of the laser-fused cells was examined using in vitro culture methods. Blastomeres within mouse two-cell embryos were fused with 3 - 10 subsequent laser pulses in order to produce tetraploid embryos. Thirty-one percent of the laser treated embryos fused and 10% of those developed to the morula or blastocyst stage. With 1 - 10 successive laser pulses cattle oocytes were fused with cytoplasts. Thirty-six percent of the laser treated cells fused and 10% of those cleaved to the 6- and 8-cell stage. These preliminary results indicate that a UV- laser microbeam combined with an optical tweezers may facilitate the manipulation of embryonic cells and can be a helpful tool in polyploidy studies and in cytoplasmic transfer experiments.

  4. Flow and heat transfer characteristics of assisting gas impingining onto an alumina coated hole in relation to laser drilling

    NASA Astrophysics Data System (ADS)

    Shuja, S. Z.; Yilbas, B. S.

    2014-07-01

    Flow and heat transfer characteristics of the assisting gas impinging onto the coated holes are investigated in relation to the laser drilling process. The alumina coating with thickness of 250 μm is considered at the surface of the carbon steel substrate. Three cases are considered by incorporating different locations of the coating on the carbon steel. These cases include coating at the top of the workpiece, coating at the bottom of the workpiece, and coating both at the top and at the bottom of the workpiece. A no-coating situation of the hole is also presented for the comparison reason. To resemble the laser drilling process, the wall temperature of the coating and the carbon steel substrate is kept at the melting temperatures during the simulations. A numerical scheme incorporating the control volume approach is introduced and the Reynolds stress turbulence model is used to account for the turbulence effect of the impinging assisting gas. An experiment is carried out in line with the simulation conditions to examine the morphological changes at the coating-carbon steel interface. It is found that the assisting gas temperature exceeds the melting temperature of the steel substrate along the coating thickness and as the assisting gas progresses further into the hole, heat transfer from the assisting gas to the hole wall takes place. This, in turn, increases thermal erosion at the hole wall in the vicinity of the coating-steel substrate interface. The Nusselt number and the skin friction attain large values along the coating thickness in the hole.

  5. Ceria nanocubic-ultrasonication assisted dispersive liquid-liquid microextraction coupled with matrix assisted laser desorption/ionization mass spectrometry for pathogenic bacteria analysis.

    PubMed

    Abdelhamid, Hani Nasser; Bhaisare, Mukesh L; Wu, Hui-Fen

    2014-03-01

    A new ceria (CeO2) nanocubic modified surfactant is used as the basis of a novel nano-based microextraction technique for highly sensitive detection of pathogenic bacteria (Pseudomonas aeruginosa and Staphylococcus aureus). The technique uses ultrasound enhanced surfactant-assisted dispersive liquid-liquid microextraction (UESA-DLLME) with and without ceria (CeO2) followed by matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). In order to achieve high separation efficiency, we investigated the influential parameters, including extraction time of ultrasonication, type and volume of the extraction solvent and surfactant. Among various surfactants, the cationic surfactants can selectively offer better extraction efficiency on bacteria analysis than that of the anionic surfactants due to the negative charges of bacteria cell membranes. Extractions of the bacteria lysate from aqueous samples via UESA-DLLME-MALDI-MS were successfully achieved by using cetyltrimethyl ammonium bromide (CTAB, 10.0 µL, 1.0×10(-3) M) as surfactants in chlorobenzene (10.0 µL) and chloroform (10.0 µL) as the optimal extracting solvent for P. aeruginosa and S. aureus, respectively. Ceria nanocubic was synthesized, and functionalized with CTAB (CeO2@CTAB) and then characterized using transmission electron microscopy (TEM) and optical spectroscopy (UV and FTIR). CeO2@CTAB demonstrates high extraction efficiency, improve peaks ionization, and enhance resolution. The prime reasons for these improvements are due to the large surface area of nanoparticles, and its absorption that coincides with the wavelength of MALDI laser (337 nm, N2 laser). CeO2@CTAB-based microextraction offers lowest detectable concentrations tenfold lower than that of without nanoceria. The present approach has been successfully applied to detect pathogenic bacteria at low concentrations of 10(4)-10(5) cfu/mL (without ceria) and at 10(3)-10(4) cfu/mL (with ceria) from bacteria suspensions. Finally, the

  6. Laser assisted crystallization of ferromagnetic amorphous ribbons: A multimodal characterization and thermal model study

    NASA Astrophysics Data System (ADS)

    Katakam, Shravana; Devaraj, Arun; Bowden, Mark; Santhanakrishnan, S.; Smith, Casey; Ramanujan, R. V.; Thevuthasan, Suntharampillai; Banerjee, Rajarshi; Dahotre, Narendra B.

    2013-11-01

    This paper focuses on laser-based de-vitrification of amorphous soft magnetic Fe-Si-B ribbons and its consequent influence on the magnetic properties. Laser processing resulted in a finer scale of crystallites due to rapid heating and cooling during laser annealing compared to conventional furnace annealing process. A significant increase in saturation magnetization is observed for laser-annealed ribbons compared to both as-received and furnace annealed samples coupled with an increase in coercivity compared to the as received samples. The combined effect of thermal histories and stresses developed during laser annealing results in the formation of nano-crystalline phase along the laser track. The phase evolution is studied by micro-XRD and TEM analysis. Solute partitioning and compositional variation within the phases are obtained by Local Electrode Atom probe analysis. The evolution of microstructure is rationalized using a Finite Element based heat transfer multi-physics model.

  7. Laser Assisted Crystallization of Ferromagnetic Amorphous Ribbons: A Multimodal Characterization and Thermal Model Study

    SciTech Connect

    Katakam, Shravana K.; Devaraj, Arun; Bowden, Mark E.; Santhanakrishnan, S.; Smith, Casey; Ramanujan, Raju; Thevuthasan, Suntharampillai; Banerjee, Rajarshi; Dahotre, Narendra B.

    2013-11-14

    This paper focuses on laser-based de-vitrification of amorphous soft magnetic Fe-Si-B ribbons and its consequent influence on the magnetic properties. Laser processing resulted in a finer scale of crystallites due to rapid heating and cooling during laser annealing compared to conventional furnace annealing process. A significant increase in saturation magnetization is observed for laser-annealed ribbons compared to both as-received and furnace annealed samples coupled with an increase in coercivity compared to as received sample. The combined effect of thermal histories and stresses developed during laser annealing results in the formation of nano-crystalline phase along the laser track. The phase evolution is traced with the aid of micro-XRD and TEM analysis. The solute partitioning and compositional variation within the phases are obtained by Local Electrode Atom probe analysis. The evolution of microstructure is rationalized using a Finite Element based heat transfer multi-physics model.

  8. Ovulation Order Mediates a Trade-Off between Pre-Hatching and Post-Hatching Viability in an Altricial Bird

    PubMed Central

    Sockman, Keith W.

    2008-01-01

    Simultaneously dependent siblings often compete for parentally provided resources. This competition may lead to mortality, the probability of which may be a function, in part, of the individual offspring's production order. In birds, serial ovulation followed by hatching asynchrony of simultaneous dependents leads to differences in post-hatching survival that largely depend on ovulation (laying) order. This has led to the widespread assumption that early-laid eggs are of greater value and therefore should possess different maternally manipulated characteristics than later-laid eggs. However, this perspective ignores the potential effect of laying order on pre-hatching viability, an effect which some studies suggest should offset the effect of laying order on post-hatching viability. I examined the relationship between laying order and hatching and fledging probability in wild, free-living Lincoln's sparrows (Melospiza lincolnii). In broods with complete hatching success, first-laid and therefore first-hatched offspring had the highest probability of fledging, and fledging probability declined with increasing laying order. However, first-laid eggs were less likely than later-laid eggs to hatch. This effect of laying order on pre-hatching viability seemed to offset that on post-hatching viability, and, consistently, maternal investment in egg size varied little if at all with respect to laying order. These results suggest that ovulation order mediates a trade-off between pre-hatching and post-hatching viability and should encourage a re-evaluation of the solitary role post-embryonic survival often plays when researchers make assumptions about the value of propagules based on the order in which they are produced. PMID:18335056

  9. [Special application of matrix-assisted laser desorption ionization time-of-flight mass spectrometry in clinical microbiological diagnostics].

    PubMed

    Nagy, Erzsébet; Abrók, Marianna; Bartha, Noémi; Bereczki, László; Juhász, Emese; Kardos, Gábor; Kristóf, Katalin; Miszti, Cecilia; Urbán, Edit

    2014-09-21

    Matrix-assisted laser desorption ionization time-of-flight mass spectrometry as a new possibility for rapid identification of bacteria and fungi revolutionized the clinical microbiological diagnostics. It has an extreme importance in the routine microbiological laboratories, as identification of the pathogenic species rapidly will influence antibiotic selection before the final determination of antibiotic resistance of the isolate. The classical methods for identification of bacteria or fungi, based on biochemical tests, are influenced by many environmental factors. The matrix-assisted laser desorption ionization time-of-flight mass spectrometry is a rapid method which is able to identify a great variety of the isolated bacteria and fungi based on the composition of conserved ribosomal proteins. Recently several other applications of the method have also been investigated such as direct identification of pathogens from the positive blood cultures. There are possibilities to identify bacteria from the urine samples in urinary tract infection or from other sterile body fluids. Using selective enrichment broth Salmonella sp from the stool samples can be identified more rapidly, too. The extended spectrum beta-lactamase or carbapenemase production of the isolated bacteria can be also detected by this method helping the antibiotic selection in some cases. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry based methods are suitable to investigate changes in deoxyribonucleic acid or ribonucleic acid, to carry out rapid antibiotic resistance determination or other proteomic analysis. The aim of this paper is to give an overview about present possibilities of using this technique in the clinical microbiological routine procedures.

  10. Phonon-assisted population inversion of a single InGaAs/GaAs quantum dot by pulsed laser excitation.

    PubMed

    Quilter, J H; Brash, A J; Liu, F; Glässl, M; Barth, A M; Axt, V M; Ramsay, A J; Skolnick, M S; Fox, A M

    2015-04-03

    We demonstrate a new method to realize the population inversion of a single InGaAs/GaAs quantum dot excited by a laser pulse tuned within the neutral exciton phonon sideband. In contrast to the conventional method of inverting a two-level system by performing coherent Rabi oscillation, the inversion is achieved by rapid thermalization of the optically dressed states via incoherent phonon-assisted relaxation. A maximum exciton population of 0.67±0.06 is measured for a laser tuned 0.83 meV to higher energy. Furthermore, the phonon sideband is mapped using a two-color pump-probe technique, with its spectral form and magnitude in very good agreement with the result of path-integral calculations.

  11. Quantitative analysis of synthetic polymers using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Chen, Hui; He, Meiyu; Pei, Jian; He, Haifeng

    2003-12-01

    Quantitative analyses of synthetic polymers were accomplished using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS). Many factors have hindered the development of quantitative measurement of polymers via MALDI TOF MS, e.g., laser power, matrix, cation salt, and cocrystallization. By probing the optimal conditions, two sets of polymers were studied. Fair repeatability of the samples ensures acceptable results. In set 1, two poly(ethylene glycols) with different end groups showed equal desorption/ionization efficiencies. Two synthetic polymers in set 2 with different chemical properties resulted in different MALDI responses. Good linearity was achieved by plotting the relationship between the sample concentration ratio and the total signal intensity ratio in both sets.

  12. Laser micro-machinability of borosilicate glass surface-modified by electric field-assisted ion-exchange method

    NASA Astrophysics Data System (ADS)

    Matsusaka, S.; Kobayakawa, T.; Hidai, H.; Morita, N.

    2012-08-01

    In order to improve the laser micro-machinability of borosilicate glass, the glass surface was doped with metal (silver or copper) ions by an electric field-assisted ion-exchange method. Doped ions drifted and diffused into the glass substrate under a DC electric field. The concentration of metal ions within the doped area was approximately constant because the ion penetration was caused by substitution between dopant metal and inherent sodium ions. Nanosecond ultraviolet laser irradiation of metal-containing regions produced flat, smooth and defect-free holes. However, the shapes of holes were degraded when the processed hole bottoms reached ion penetration depths. A numerical analysis of ionic drift-diffusion behaviour in glass material under an electric field was also carried out. The calculated results for penetration depth and ionic flux showed good agreement with the measured values.

  13. Ion-to-Neutral Ratios and Thermal Proton Transfer in Matrix-Assisted Laser Desorption/Ionization

    NASA Astrophysics Data System (ADS)

    Lu, I.-Chung; Chu, Kuan Yu; Lin, Chih-Yuan; Wu, Shang-Yun; Dyakov, Yuri A.; Chen, Jien-Lian; Gray-Weale, Angus; Lee, Yuan-Tseh; Ni, Chi-Kung

    2015-07-01

    The ion-to-neutral ratios of four commonly used solid matrices, α-cyano-4-hydroxycinnamic acid (CHCA), 2,5-dihydroxybenzoic acid (2,5-DHB), sinapinic acid (SA), and ferulic acid (FA) in matrix-assisted laser desorption/ionization (MALDI) at 355 nm are reported. Ions are measured using a time-of-flight mass spectrometer combined with a time-sliced ion imaging detector. Neutrals are measured using a rotatable quadrupole mass spectrometer. The ion-to-neutral ratios of CHCA are three orders of magnitude larger than those of the other matrices at the same laser fluence. The ion-to-neutral ratios predicted using the thermal proton transfer model are similar to the experimental measurements, indicating that thermal proton transfer reactions play a major role in generating ions in ultraviolet-MALDI.

  14. Azo-derivatives thin films grown by matrix-assisted pulsed laser evaporation for non-linear optical applications

    NASA Astrophysics Data System (ADS)

    Constantinescu, C.; Matei, A.; Ionita, I.; Ion, V.; Marascu, V.; Dinescu, M.; Vasiliu, C.; Emandi, A.

    2014-05-01

    Azo-dye compounds, in bulk or as thin films, are extensively studied due to their particular optical properties. These properties include non-linear interaction, e.g. two-photon absorption, optical limiting and all-optical poling, with potential applications in optoelectronics and sensors development. Herein, we report on the deposition of pyrazolone derivatives, namely 1-phenyl-3-methyl-4-(1‧-azo-2‧-sodium carboxylate)-pyrazole-5-one thin films, for applications in second harmonic generation. Matrix-assisted pulsed laser evaporation was employed for layers growth, using a Nd:YAG device operating at 266 nm (4ω). The structure and surface morphology of the deposited films were examined by Fourier transform infrared spectroscopy, atomic force microscopy, and scanning electron microscopy. Spectroscopic-ellipsometry was employed to investigate thin film optical properties. Significant second harmonic generation capabilities of the compound were pointed out by using a femtosecond Ti:sapphire laser.

  15. Multimodal Vacuum-Assisted Plasma Ion (VaPI) Source with Transmission Mode and Laser Ablation Sampling Capabilities

    NASA Astrophysics Data System (ADS)

    Keelor, Joel D.; Farnsworth, Paul B.; Weber, Arthur L.; Abbott-Lyon, Heather; Fernández, Facundo M.

    2016-05-01

    We have developed a multimodal ion source design that can be configured on the fly for various analysis modes, designed for more efficient and reproducible sampling at the mass spectrometer atmospheric pressure (AP) interface in a number of different applications. This vacuum-assisted plasma ionization (VaPI) source features interchangeable transmission mode and laser ablation sampling geometries. Operating in both AC and DC power regimes with similar results, the ion source was optimized for parameters including helium flow rate and gas temperature using transmission mode to analyze volatile standards and drug tablets. Using laser ablation, matrix effects were studied, and the source was used to monitor the products of model prebiotic synthetic reactions.

  16. Recent advances in bacteria identification by matrix-assisted laser desorption/ionization mass spectrometry using nanomaterials as affinity probes.

    PubMed

    Chiu, Tai-Chia

    2014-04-28

    Identifying trace amounts of bacteria rapidly, accurately, selectively, and with high sensitivity is important to ensuring the safety of food and diagnosing infectious bacterial diseases. Microbial diseases constitute the major cause of death in many developing and developed countries of the world. The early detection of pathogenic bacteria is crucial in preventing, treating, and containing the spread of infections, and there is an urgent requirement for sensitive, specific, and accurate diagnostic tests. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is an extremely selective and sensitive analytical tool that can be used to characterize different species of pathogenic bacteria. Various functionalized or unmodified nanomaterials can be used as affinity probes to capture and concentrate microorganisms. Recent developments in bacterial detection using nanomaterials-assisted MALDI-MS approaches are highlighted in this article. A comprehensive table listing MALDI-MS approaches for identifying pathogenic bacteria, categorized by the nanomaterials used, is provided.

  17. Recent Advances in Bacteria Identification by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Using Nanomaterials as Affinity Probes

    PubMed Central

    Chiu, Tai-Chia

    2014-01-01

    Identifying trace amounts of bacteria rapidly, accurately, selectively, and with high sensitivity is important to ensuring the safety of food and diagnosing infectious bacterial diseases. Microbial diseases constitute the major cause of death in many developing and developed countries of the world. The early detection of pathogenic bacteria is crucial in preventing, treating, and containing the spread of infections, and there is an urgent requirement for sensitive, specific, and accurate diagnostic tests. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is an extremely selective and sensitive analytical tool that can be used to characterize different species of pathogenic bacteria. Various functionalized or unmodified nanomaterials can be used as affinity probes to capture and concentrate microorganisms. Recent developments in bacterial detection using nanomaterials-assisted MALDI-MS approaches are highlighted in this article. A comprehensive table listing MALDI-MS approaches for identifying pathogenic bacteria, categorized by the nanomaterials used, is provided. PMID:24786089

  18. Fabrication of silicon nanowire arrays by near-field laser ablation and metal-assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Brodoceanu, D.; Alhmoud, H. Z.; Elnathan, R.; Delalat, B.; Voelcker, N. H.; Kraus, T.

    2016-02-01

    We present an elegant route for the fabrication of ordered arrays of vertically-aligned silicon nanowires with tunable geometry at controlled locations on a silicon wafer. A monolayer of transparent microspheres convectively assembled onto a gold-coated silicon wafer acts as a microlens array. Irradiation with a single nanosecond laser pulse removes the gold beneath each focusing microsphere, leaving behind a hexagonal pattern of holes in the gold layer. Owing to the near-field effects, the diameter of the holes can be at least five times smaller than the laser wavelength. The patterned gold layer is used as catalyst in a metal-assisted chemical etching to produce an array of vertically-aligned silicon nanowires. This approach combines the advantages of direct laser writing with the benefits of parallel laser processing, yielding nanowire arrays with controlled geometry at predefined locations on the silicon surface. The fabricated VA-SiNW arrays can effectively transfect human cells with a plasmid encoding for green fluorescent protein.

  19. Excimer laser assisted re-oxidation of BaTiO{sub 3} thin films on Ni metal foils

    SciTech Connect

    Bharadwaja, S. S. N. Ko, S. W.; Qu, W.; Clark, T.; Rajashekhar, A.; Motyka, M.; Podraza, N.; Randall, C. A.; Trolier-McKinstry, S.

    2016-01-14

    Excimer laser assisted re-oxidation for reduced, crystallized BaTiO{sub 3} thin films on Ni-foils was investigated. It was found that the BaTiO{sub 3} can be re-oxidized at an oxygen partial pressure of ∼50 mTorr and substrate temperature of 350 °C without forming a NiO{sub x} interface layer between the film and base metal foil. The dielectric permittivity of re-oxidized films was >1000 with loss tangent values <2% at 100 Hz, 30 mV{sub rms} excitation signal. Electron Energy Loss Spectroscopy indicated that BaTiO{sub 3} thin films can be re-oxidized to an oxygen stoichiometry close to ∼3 (e.g., stoichiometric). High resolution cross sectional transmission electron microscopy showed no evidence of NiO{sub x} formation between the BaTiO{sub 3} and the Ni foil upon excimer laser re-oxidation. Spectroscopic ellipsometry studies on laser re-oxidized [001]{sub C} and [111]{sub C} BaTiO{sub 3} single crystals indicate that the re-oxidation of BaTiO{sub 3} single crystals is augmented by photo-excitation of the ozone, as well as laser pulse induced temperature and local stress gradients.

  20. Effect of process parameters on the mechanical properties of carbon nitride thin films synthesized by plasma assisted pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Tabbal, M.; Mérel, P.; Chaker, M.

    We present an investigation of the effect of the process parameters, namely deposition pressure and laser intensity, on the growth and mechanical properties of carbon nitride (CNx) thin films synthesized by plasma assisted pulsed laser deposition. Deposition at high remote plasma pressure (200 mTorr) enhances both growth rate and nitrogen incorporation (up to 40 at.%), but nano-indentation measurements indicate that these films are very soft and have poor mechanical properties. At low remote plasma pressure (0.5 mTorr), the nitrogen content varies from 24 to 16 at.% with increasing laser intensity as the films become much harder and more elastic, with hardness and Young's modulus values reaching 24 GPa and 230 GPa, respectively. These effects are explained in terms of a thermalization of the laser plasma at 200 mTorr and indicate that plasma activation of nitrogen does not provide any particular benefit to the film properties when deposition is performed at high pressure. However, at low pressure, the benefit of plasma activation is evidenced through enhanced nitrogen incorporation in the films while preserving the highly energetic species in the ablation plume. Such conditions lead to the synthesis, at room temperature, of hard and elastic films having properties close to those of fullerene-like CNx.

  1. Current status of matrix-assisted laser desorption ionisation-time of flight mass spectrometry in the clinical microbiology laboratory.

    PubMed

    Kok, Jen; Chen, Sharon C A; Dwyer, Dominic E; Iredell, Jonathan R

    2013-01-01

    The integration of matrix-assisted laser desorption ionisation-time of flight mass spectrometry (MALDI-TOF MS) into many clinical microbiology laboratories has revolutionised routine pathogen identification. MALDI-TOF MS complements and has good potential to replace existing phenotypic identification methods. Results are available in a more clinically relevant timeframe, particularly in bacteraemic septic shock. Novel applications include strain typing and the detection of antimicrobial resistance, but these are not widely used. This review discusses the technical aspects, current applications, and limitations of MALDI-TOF MS.

  2. Few layer graphene matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Cho, Donghyun; Hong, Sangsu; Shim, Sangdeok

    2013-08-01

    We present the employment of few layer graphene (FLG) as a matrix for the analysis of low molecular weight polymeric compounds using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The practicality of FLG as a matrix for MALDI experiments is demonstrated by analyzing low molecular weight polymers, polar polyethylene glycol (PEG) of 1000 Da and nonpolar polymethylmethacrylate (PMMA) of 650 Da. The high quality MS spectra without low-mass interference signals without any further sampling procedure were acquired.

  3. Processing of mussel-adhesive protein analog copolymer thin films by matrix-assisted pulsed laser evaporation

    NASA Astrophysics Data System (ADS)

    Patz, T.; Cristescu, R.; Narayan, R.; Menegazzo, N.; Mizaikoff, B.; Messersmith, P. B.; Stamatin, I.; Mihailescu, I. N.; Chrisey, D. B.

    2005-07-01

    We have demonstrated the successful thin film growth of a mussel-adhesive protein analog, DOPA-modified PEO-PPO-PEO block copolymer PF127, using matrix-assisted pulsed laser evaporation (MAPLE). The MAPLE-deposited thin films were examined using Fourier transform infrared spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and contact-angle measurements. We have found that the main functional groups of the mussel-adhesive protein analog are present in the transferred film. These adhesive materials have several potential electronic, medical, and marine applications.

  4. Laser-Assisted Sheet Metal Working by the Integration of Scanner System Technology into a Progressive Die

    NASA Astrophysics Data System (ADS)

    Brecher, Christian; Emonts, Michael; Eckert, Markus

    Within the sheet metal working industry the demand for thinner sheet materials with very high strength is growing due to the increasing importance for saving energy and responsible usage of natural resources. High strength and low ductility restrict application of state-of-the-art technology to shear, bend or deep draw parts with the needed complexity and quality. The Fraunhofer IPT has developed a "hy-PRESS" system to combine laser-assisted preheating and conventional punching to a hybrid technology in a progressive die, which allows to shear, bend and deep draw high strength materials with a high quality and complexity in progressive dies.

  5. Ion Yields in the Coupled Chemical and Physical Dynamics Model of Matrix-Assisted Laser Desorption/Ionization

    NASA Astrophysics Data System (ADS)

    Knochenmuss, Richard

    2015-08-01

    The Coupled Chemical and Physical Dynamics (CPCD) model of matrix assisted laser desorption ionization has been restricted to relative rather than absolute yield comparisons because the rate constant for one step in the model was not accurately known. Recent measurements are used to constrain this constant, leading to good agreement with experimental yield versus fluence data for 2,5-dihydroxybenzoic acid. Parameters for alpha-cyano-4-hydroxycinnamic acid are also estimated, including contributions from a possible triplet state. The results are compared with the polar fluid model, the CPCD is found to give better agreement with the data.

  6. Quantification of Carbohydrates and Related Materials Using Sodium Ion Adducts Produced by Matrix-Assisted Laser Desorption Ionization

    NASA Astrophysics Data System (ADS)

    Ahn, Sung Hee; Park, Kyung Man; Moon, Jeong Hee; Lee, Seong Hoon; Kim, Myung Soo

    2016-11-01

    The utility of sodium ion adducts produced by matrix-assisted laser desorption ionization for the quantification of analytes with multiple oxygen atoms was evaluated. Uses of homogeneous solid samples and temperature control allowed the acquisition of reproducible spectra. The method resulted in a direct proportionality between the ion abundance ratio I([A + Na]+)/I([M + Na]+) and the analyte concentration, which could be used as a calibration curve. This was demonstrated for carbohydrates, glycans, and polyether diols with dynamic range exceeding three orders of magnitude.

  7. Laser-assisted coplanar symmetric (e, 2e) triple differential cross sections

    NASA Astrophysics Data System (ADS)

    Khalil, D.; Tlidi, M.; Makhoute, A.; Ajana, I.

    2017-04-01

    The modification due to an external linearly polarized monochromatic laser field on the dynamics of the ionization process of an atomic hydrogen by electron-impact is studied theoretically for a coplanar symmetric geometry. The interaction of the laser field with the unbound electrons is treated in a non-perturbative way. The wave functions of the ingoing and outgoing electrons in the laser field are treated as non-relativistic Volkov waves, while the interaction of the bound electron with the laser field is treated by using first-order perturbation theory, assuming that the electric field strength associated with the external laser field is much less than the atomic unit e/{a}2=5× {10}9 {{V}} {{{cm}}}-1. The influence of the laser parameters on the angular distribution is analyzed and several illustrative examples are discussed. Significant changes are noted both in the shape and magnitude of the triple differential cross sections (TDCS) by the application of the laser field. Numerical results show that the TDCS are strongly dependent on the dressing of the projectile by the laser field at low frequency in (e, 2e) spectroscopy region.

  8. Laser-assisted solid-state synthesis of carbon nanotube/silicon core/shell structures.

    PubMed

    Mahjouri-Samani, M; Zhou, Y S; Fan, L; Gao, Y; Xiong, W; More, K L; Jiang, L; Lu, Y F

    2013-06-28

    A single-step solid-state synthetic approach was developed for the synthesis of silicon-coated carbon nanotube (CNT) core/shell structures. This was achieved through laser-induced melting and evaporation of CNT-deposited Si substrates using a continuous wavelength CO2 laser. The synthesis location of the CNT/Si structures was defined by the laser-irradiated spots. The thickness of the coating was controlled by tuning the laser power and synthesis time during the coating process. This laser-based synthetic technique provides a convenient approach for solid-state, controllable, gas-free, simple and cost-effective fabrication of CNT/Si core/shell structures.

  9. System and method for laser assisted sample transfer to solution for chemical analysis

    DOEpatents

    Van Berkel, Gary J; Kertesz, Vilmos

    2014-01-28

    A system and method for laser desorption of an analyte from a specimen and capturing of the analyte in a suspended solvent to form a testing solution are described. The method can include providing a specimen supported by a desorption region of a specimen stage and desorbing an analyte from a target site of the specimen with a laser beam centered at a radiation wavelength (.lamda.). The desorption region is transparent to the radiation wavelength (.lamda.) and the sampling probe and a laser source emitting the laser beam are on opposite sides of a primary surface of the specimen stage. The system can also be arranged where the laser source and the sampling probe are on the same side of a primary surface of the specimen stage. The testing solution can then be analyzed using an analytical instrument or undergo further processing.

  10. Evaluation of combined matrix-assisted laser desorption/ionization time-of-flight and matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry experiments for peptide mass fingerprinting analysis.

    PubMed

    da Silva, David; Wasselin, Thierry; Carré, Vincent; Chaimbault, Patrick; Bezdetnaya, Lina; Maunit, Benoît; Muller, Jean-François

    2011-07-15

    Peptide Mass Fingerprinting (PMF) is still of significant interest in proteomics because it allows a large number of complex samples to be rapidly screened and characterized. The main part of post-translational modifications is generally preserved. In some specific cases, PMF suffers from ambiguous or unsuccessful identification. In order to improve its reliability, a combined approach using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICRMS) was evaluated. The study was carried out on bovine serum albumin (BSA) digest. The influence of several important parameters (the matrix, the sample preparation method, the amount of the analyte) on the MOWSE score and the protein sequence coverage were evaluated to allow the identification of specific effects. A careful investigation of the sequence coverage obtained by each kind of experiment ensured the detection of specific peptides for each experimental condition. Results highlighted that DHB-FTICRMS and DHB- or CHCA-TOFMS are the most suited combinations of experimental conditions to achieve PMF analysis. The association (convolution) of the data obtained by each of these techniques ensured a significant increase in the MOWSE score and the protein sequence coverage.

  11. 45 CFR 1226.10 - Hatch Act restrictions.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 45 Public Welfare 4 2010-10-01 2010-10-01 false Hatch Act restrictions. 1226.10 Section 1226.10 Public Welfare Regulations Relating to Public Welfare (Continued) CORPORATION FOR NATIONAL AND COMMUNITY SERVICE PROHIBITIONS ON ELECTORAL AND LOBBYING ACTIVITIES Volunteer Activities § 1226.10 Hatch...

  12. 29 CFR 1918.43 - Handling hatch beams and covers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... stable piles not closer to the hatch coaming than three feet (.91 m). Exception: On the working side of... their sides, or stood on an edge close together and lashed. Exception: This paragraph (b) shall not apply in cases where hatch beams are of such design that: (1) The width of the flange is 50 percent...

  13. Effect of storage environment on hatching of Globodera ellingtonae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Globodera spp. eggs go through a diapause stage in which development remains dormant until favorable hatching conditions are reached. Because of the regulatory concerns with Globodera spp., it is often only possible to rear eggs for research in the greenhouse. However, hatch is often lower for green...

  14. 29 CFR 780.211 - Contract production of hatching eggs.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 3 2014-07-01 2014-07-01 false Contract production of hatching eggs. 780.211 Section 780... eggs. It is common practice for hatcherymen to enter into arrangements with farmer poultry raisers for the production of hatching eggs which the hatchery agrees to buy. Ordinarily, the farmer furnishes...

  15. 29 CFR 780.211 - Contract production of hatching eggs.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 3 2011-07-01 2011-07-01 false Contract production of hatching eggs. 780.211 Section 780... eggs. It is common practice for hatcherymen to enter into arrangements with farmer poultry raisers for the production of hatching eggs which the hatchery agrees to buy. Ordinarily, the farmer furnishes...

  16. 29 CFR 780.211 - Contract production of hatching eggs.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 3 2010-07-01 2010-07-01 false Contract production of hatching eggs. 780.211 Section 780... eggs. It is common practice for hatcherymen to enter into arrangements with farmer poultry raisers for the production of hatching eggs which the hatchery agrees to buy. Ordinarily, the farmer furnishes...

  17. 29 CFR 780.211 - Contract production of hatching eggs.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 3 2012-07-01 2012-07-01 false Contract production of hatching eggs. 780.211 Section 780... eggs. It is common practice for hatcherymen to enter into arrangements with farmer poultry raisers for the production of hatching eggs which the hatchery agrees to buy. Ordinarily, the farmer furnishes...

  18. 29 CFR 780.211 - Contract production of hatching eggs.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 3 2013-07-01 2013-07-01 false Contract production of hatching eggs. 780.211 Section 780... eggs. It is common practice for hatcherymen to enter into arrangements with farmer poultry raisers for the production of hatching eggs which the hatchery agrees to buy. Ordinarily, the farmer furnishes...

  19. 46 CFR 122.610 - Watertight doors and watertight hatches.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Watertight doors and watertight hatches. 122.610 Section... Markings Required § 122.610 Watertight doors and watertight hatches. Watertight doors and watertight...: “WATERTIGHT DOOR—KEEP CLOSED” or “WATERTIGHT HATCH—KEEP CLOSED”, unless such markings are deemed...

  20. 46 CFR 131.893 - Watertight doors and watertight hatches.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Watertight doors and watertight hatches. 131.893 Section... OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.893 Watertight doors and watertight hatches. Each watertight door in a bulkhead that must be watertight in compliance with the requirements...

  1. 46 CFR 131.893 - Watertight doors and watertight hatches.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Watertight doors and watertight hatches. 131.893 Section... OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.893 Watertight doors and watertight hatches. Each watertight door in a bulkhead that must be watertight in compliance with the requirements...

  2. 46 CFR 122.610 - Watertight doors and watertight hatches.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Watertight doors and watertight hatches. 122.610 Section... Markings Required § 122.610 Watertight doors and watertight hatches. Watertight doors and watertight...: “WATERTIGHT DOOR—KEEP CLOSED” or “WATERTIGHT HATCH—KEEP CLOSED”, unless such markings are deemed...

  3. 14. VIEW OF NORTHSOUTH ROAD WHICH PARALLELS ROAD TO HATCH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. VIEW OF NORTH-SOUTH ROAD WHICH PARALLELS ROAD TO HATCH ADIT (FEATURE B-28). NOTE MODERN 'LAY DOWN' FENCE ON ROAD. ROAD LIES TO THE WEST OF THE HATCH ADIT AND PHOTOGRAPH IS VIEW TO THE SOUTH. (OCTOBER, 1995) - Nevada Lucky Tiger Mill & Mine, East slope of Buckskin Mountain, Paradise Valley, Humboldt County, NV

  4. 46 CFR 108.145 - Hatches and tonnage openings.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Hatches and tonnage openings. 108.145 Section 108.145 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Construction and Arrangement Structural Fire Protection § 108.145 Hatches and...

  5. 46 CFR 108.145 - Hatches and tonnage openings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Hatches and tonnage openings. 108.145 Section 108.145 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Construction and Arrangement Structural Fire Protection § 108.145 Hatches and...

  6. Pulse duration effects on laser-assisted electron transfer cross section for He2+ ions colliding with atomic hydrogen

    NASA Astrophysics Data System (ADS)

    Domínguez-Gutiérrez, Francisco Javier; Cabrera-Trujillo, Remigio

    2014-08-01

    We study the effect of the pulse duration for an ultra-fast and intense laser on the fundamental process of electron capture by analyzing the excitation probability into the n = 2 and n = 3 states when He2+ collides with atomic hydrogen in the 0.05-10 keV/amu energy range, a region of interest for diagnostic processes on plasma and fusion power reactors. We solve the time-dependent Schrödinger equation to calculate the electron capture probability by means of a finite-differences, as well as by an electron-nuclear dynamics approach. In particular, we study the effects of 1, 3, 6, and 10 fs laser pulses at FWHM, wavelength of 780 nm and intensity of 3.5 × 1012 W/cm2. We report good agreement for the laser-free state and total electron transfer cross-sections when compared to available theoretical and experimental data. The effect of the laser pulse on the electron capture probability as a function of the impact parameter is such that the charge exchange probability increases considerably in the impact parameter radial region with an increase in the amplitude oscillations and a phase shift on the Stückelberg oscillations. We find an increase on the total electron exchange cross-section for low projectile collision energy when compared to the laser-free case with a minimal effect at high collision energies. We find that the 1 fs laser pulse has a minimal effect, except for very low collision energies. Although in general, the longer the laser pulse, the larger the electron capture probability, at very low collision energies all pulse widths have an effect. For processes in the atto-second region, our findings suggest that to enhance the laser-assisted charge exchange, the best region for short pulses is at very low collision energies. We also find that the s and p state charge exchange cross section are equally affected. We provide a qualitative discussion of these findings.

  7. Water-assisted pulsed Er:YAG laser interaction with silicon

    SciTech Connect

    Kim, Jaehun; Ki, Hyungson

    2015-07-07

    Silicon is virtually transparent to the Er:YAG laser with a wavelength of 2.94 μm. In this study, we report that moderately doped silicon (1–10 Ω cm) can be processed by a pulsed Er:YAG laser with a pulse duration of 350 μs and a peak laser intensity of 1.7 × 10{sup 5} W/cm{sup 2} by applying a thin water layer on top of silicon as a light absorbing medium. In this way, water is heated first by strongly absorbing the laser energy and then heats up the silicon wafer indirectly. As the silicon temperature rises, the free carrier concentration and therefore the absorption coefficient of silicon will increase significantly, which may enable the silicon to get directly processed by the Er:YAG laser when the water is vaporized completely. We also believe that the change in surface morphology after melting could contribute to the increase in the laser beam absorptance. It was observed that 525 nm-thick p-type wafer specimens were fully penetrated after 15 laser pulses were irradiated. Bright yellow flames were observed during the process, which indicates that the silicon surface reached the melting point.

  8. Thermo-optical response of cartilage during feedback-controlled laser-assisted reshaping

    NASA Astrophysics Data System (ADS)

    Wong, Brian J.; Milner, Thomas E.; Anvari, Bahman; Sviridov, Alexander P.; Omelchenko, Alexander I.; Vagratashvili, Victor; Sobol, Emil N.; Nelson, J. Stuart

    1997-05-01

    Cartilage undergoes characteristic deformation following laser irradiation below the ablation threshold. Measurements of surface temperature and integrated scattered light intensity were performed during laser irradiation. Porcine auricular cartilage (1 - 2 mm thickness) was irradiated with an Nd:YAG laser (lambda equals 1.32 micrometer) with varying dose (J/cm2). Surface temperature was monitored using a single element HgCdTe infrared detector, responsive between 10 - 14 micrometer. A HeNe laser beam (lambda equals 632.8 nm) was incident on the back surface of the cartilage specimen and fractional integrated back scattered light intensity was measured using an integrating sphere and a silicon photodiode. Laser irradiation (2 W, 5.83 W/cm2, 50 Hz PRR) was allowed to proceed until surface temperature reached 70 degrees Celsius. Cartilage deformation was observed in each instance. Integrated scattered light intensity reached a plateau before the peak temperature (70 degrees) was reached. At increased laser power (10 W, 39.45 W/cm2, 50 Hz PRR), a feedback controlled cryogen spray was used to maintain surface temperature below 50 degrees Celsius. A similar plateau response was also noted in integrated scattered light intensity. This signal may be used to optimize the process of stress relaxation in laser cartilage reshaping. Several clinical applications are discussed.

  9. Direct laser-assisted processing of polymers for microfluidic and micro-optical applications

    NASA Astrophysics Data System (ADS)

    Pfleging, Wilhelm; Boehm, Johannes; Finke, Steffi; Gaganidze, E.; Hanemann, Thomas; Heidinger, Roland; Litfin, Karsten

    2003-07-01

    In the microscopic world the need of functional prototypes increases, e.g. as a precondition for a mould insert fabrication for micro-injection moulding. In this work the direct fabrication of prototypes made from polymers with an accuracy down to the micrometer range will be presented. For this purpose the direct patterning or modification of polymers with UV-laser radiation is performed for applications in fluidic and micro-optics. Different UV laser sources such as excimer and frequency-multiplied Nd:YAG were used. In the case of complex designs for fluidic applications it is powerful to use Nd:YAG laser radiation as patterning tool because of their high laser repetition rates: CAD data from complex fluidic designs were transmitted directly via CAM module into the polymeric surface. Because of the very small laser pulse duration of about 400-500 ps the thermal-induced damage during ablation decreases significantly. Process parameters, ablation rates and attainable surface qualities for capillary-electrophoreses chips will be presented. With the aid of a motorised aperture or a rotating mask system, excimer laser radiation is used to enable a well defined patterning of grooves with sharp edges and smooth sidewalls. The direct ablation of polymethylmethacrylate (PMMA), as well as the laser induced modification of the polymeric chemistry is used for the preparation of passive integrated-optical waveguides. Two types of concepts of waveguides are discussed: 1. Laser patterned grooves are filled with index matched materials which leads either to an increase or a decrease of the refractive index relative to pure PMMA. 2. Localised laser-induced polymer modification leads immediately to an integrated waveguide with higher refractive index. Both types of waveguides-concepts are characterised by their optical properties, which will be discussed in detail.

  10. Resonant Infrared Matrix-Assisted Pulsed Laser Evaporation Of Inorganic Nanoparticles And Organic/Inorganic Hybrid Nanocomposites

    SciTech Connect

    Pate, Ryan; Lantz, Kevin R.; Stiff-Roberts, Adrienne D.; Dhawan, Anuj; Vo-Dinh, Tuan

    2010-10-08

    In this research, resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) has been used to deposit different classes of inorganic nanoparticles, including bare, un-encapsulated ZnO and Au nanoparticles, as well as ligand-encapsulated CdSe colloidal quantum dots (CQDs). RIR-MAPLE has been used for thin-film deposition of different organic/inorganic hybrid nanocomposites using some of these inorganic nanoparticles, including CdSe CQD-poly[2-methoxy-5-(2'-ethylhexyloxy )-1,4-(1-cyanovinylene)phenylene](MEH-CN-PPV) nanocomposites and Au nanoparticle-poly(methyl methacrylate)(PMMA) nanocomposites. The unique contribution of this research is that a technique is demonstrated for the deposition of organic-based thin-films requiring solvents with bond energies that do not have to be resonant with the laser energy. By creating an emulsion of solvent and ice in the target, RIR-MAPLE using a 2.94 {mu}m laser can deposit most material systems because the hydroxyl bonds in the ice component of the emulsion matrix are strongly resonant with the 2.94 {mu}m laser. In this way, the types of materials that can be deposited using RIR-MAPLE has been significantly expanded. Furthermore, materials with different solvent bond energies can be co-deposited without concern for material degradation and without the need to specifically tune the laser energy to each material solvent bond energy, thereby facilitating the realization of organic/inorganic hybrid nanocomposite thin-films. In addition to the structural characterization of the inorganic nanoparticle and hybrid nanocomposite thin-films deposited using this RIR-MAPLE technique, optical characterization is presented to demonstrate the potential of such films for optoelectronic device applications.

  11. Surface plasma wave assisted second harmonic generation of laser over a metal film

    SciTech Connect

    Chauhan, Santosh; Parashar, J.

    2015-01-15

    Second harmonic generation of laser mode converted surface plasma wave (SPW) over a corrugated metal film is studied. The laser, impinged on the metal film, under attenuated total reflection configuration, excites SPW over the metal–vacuum interface. The excited SPW extends over a much wider surface area than the laser spot cross-section. It exerts a second harmonic ponderomotive force on metal electrons, imparting them velocity that beats with the surface ripple to produce a nonlinear current, driving resonant second harmonic surface plasma wave.

  12. Laser fabrication of Au nanorod aggregates microstructures assisted by two-photon polymerization.

    PubMed

    Masui, Kyoko; Shoji, Satoru; Asaba, Kenji; Rodgers, Thomas C; Jin, Feng; Duan, Xuan-Ming; Kawata, Satoshi

    2011-11-07

    We demonstrate fabrication of Au nanorod aggregates microstructures by means of a femtosecond near-infrared laser. The laser light was tightly focused into colloidal Au nanorods dispersed in photopolymerizable metyl-methacrylate (MMA) compound to induce two-photon polymerization (TPP). TPP of MMA glued the nanorods together to form solid microstrucures of aggregates. The laser light excited a local surface plasmon, resulting in confinement of TPP in the vicinity of nanorods. Concurrenly occurring optical accumulation of nanorods created a unique mechanism for the formation of nanorod aggregates into desired microstructures. This technique would be a clue for a novel micro/nanofabrication method for plasmonic materials and devices.

  13. Comparative evaluation of visual outcomes and corneal asphericity after laser-assisted in situ keratomileusis with the six-dimension Amaris excimer laser system

    PubMed Central

    Piao, JunJie; Li, Ying-Jun; Whang, Woong-Joo; Choi, Mihyun; Kang, Min Ji; Lee, Jee Hye; Yoon, Geunyoung; Joo, Choun-Ki

    2017-01-01

    Purpose To compare the visual and refractive outcomes after laser-assisted in situ keratomileusis (LASIK) surgery for correction of myopia or myopic astigmatism using a six-dimensional Amaris excimer laser. Methods In this retrospective cohort study, we enrolled 47 eyes of 28 patients (age: 19–36 years) with myopia or myopic astigmatism. We used the Custom Ablation Manager protocol and performed ablations with the SCHWIND AMARIS system. LASIK flaps were cut with an iFS Advanced Femtosecond Laser. Mean static (SCC) and dynamic cyclotorsion (DCC) were evaluated. Visual and refractive outcomes were evaluated during 6 months’ follow-up. Corneal asphericity (Q-value) was analyzed at 4 months postoperatively. Results The spherical equivalent (SE) reduction was statistically significant reduce 1 day after refractive surgery (P < 0.001), with no additional significant changes during follow-up (P = 0.854). SCC registration rates were 81% in the Aberration-Free mode (AF) and 90% in the Corneal Wavefront mode (CW). SCC measurements were within ± 5 degrees in 57% (AF) and 68% (CW) of eyes. Mean DCC was within ± 1 degree in 96% (AF) or 95% (CW) of cases. At 6 months, the uncorrected distance visual acuity was 20/25 or better in all eyes. At last follow-up, both steep and flat keratometry values had significantly flattened in both groups (P < 0.001). Corneal asphericity also increased significantly during the postoperative period for an 8-mm corneal diameter (P < 0.001). Conclusions LASIK for myopia or myopic compound astigmatism correction using the six-dimensional AMARIS 750S excimer laser is safe, effective, and predictable. Postoperative corneal asphericity can be analyzed by linear regression to predict the changes in postoperative corneal asphericity with this approach. PMID:28187180

  14. Laser Assisted Non-surgical Periodontal Therapy: A Double Blind, Randomized Clinical Trial

    PubMed Central

    Everett, Joseph D.; Rossmann, Jeffrey A.; Kerns, David G.; Al-Hashimi, Ibtisam

    2017-01-01

    The objective of this study was to examine potential benefits of using laser therapy for secular decontamination in conjunction with scaling and root planing in the treatment of chronic periodontitis. The study was performed on 173 teeth in 14 patients in a split-mouth design, one side received scaling and root planing followed by laser therapy using a carbon dioxide (CO2) laser with an ablative handpiece (test group); the contralateral side received scaling and root planing without laser (control group). Clinical and laboratory parameters were evaluated prior to treatment and at 3 and 6 months following therapy; clinical measurements were performed by two blinded examiners. The clinical parameters included measurement of gingival recession (REC), bleeding on probing (BOP), clinical attachment level (CAL), pocket depth (PD), furcation involvement (FUR), and tooth mobility (MOB). Laboratory testing to determine the levels of periodontal pathogens was performed using PCR techniques. The results of the study revealed statistically significant differences in clinical and laboratory parameters at 3 and 6 months after therapy for both test and control groups, but no significant difference was observed between the two groups. However, sites receiving laser therapy tended to show a greater decrease in probing depths, gain in clinical attachment level, and reduced bacterial levels. In conclusion, the overall results of the study suggest a potential benefit of using laser therapy in conjunction with scaling and root planing for the treatment of chronic periodontitis. PMID:28357001

  15. The 808 nm Laser-Assisted Surgery as an Adjunct to Orthodontic Treatment of Delayed Tooth Eruption

    PubMed Central

    Seifi, Massoud; Vahid-Dastjerdi, Elahe; Ameli, Nazila; Badiee, Mohammad-Reza; Younessian, Farnaz; Amdjadi, Parisa

    2013-01-01

    Introduction: Failure of teeth to erupt from gingival tissues at usual developmental time is called delayed tooth eruption (DTE). Delayed tooth eruption lead to prolonged fixed orthodontic treatment and its eventual complications. The purpose of the present study was to evaluate the effect of laser-assisted (808 nm) surgical uncovering, on the tooth emergence and orthodontic treatment of DTE. Methods: A total of 16 orthodontic patients were included in this study and were equally assigned to an experimental and a control group. Subjects for experiment consisted of eight patients (6 girls and 2 boys) with a mean age of 14±0.9 years. All patients exhibited delayed second premolar eruption. The laser wavelength was 810 nm and it was set in a continuous wave mode at a power output of 1.6 watt with a 0.3-mm diameter fiber tip. When the target tissue was sufficiently anesthetized, the tip was directed at an angle of 10 to 20 degrees to the tissue (light contact mode); and was applied continuously for approximately 12 Seconds until an acceptable tooth exposure area was visible. The facial axis of the clinical crown (FACC) line represents the most prominent portion of the facial central lobe for premolars. All orthodontic brackets are aligned along this reference and are located on FA (Facial Axis) point. The standard for adequate tooth eruption was the accessibility of facial axis of the clinical crown (FACC) for bonding the brackets. Data gathered from the patients were statistically surveyed and compared by means of Tukey’s Test and Analysis of Variance (ANOVA). Results: All patients showed good gingival status, no significant bleeding during or immediately after the surgery, and acceptable level of healing after laser surgery. The biologic width of the teeth was preserved and no violation of this important periodontal parameter was observed. The average time for accessing the FA point in experimental group was 11±1.1 weeks and the mentioned period was increased to

  16. Laser-assisted direct joining of AISI304 stainless steel with polycarbonate sheets: Thermal analysis, mechanical characterization, and bonds morphology

    NASA Astrophysics Data System (ADS)

    Lambiase, F.; Genna, S.

    2017-02-01

    Laser-Assisted Metal and Plastic bonding (LAMP) of AISI304 sheets with polycarbonate sheets is investigated in this work. The process was performed by means of a high power diode laser with a maximum power of 200 W. The study introduces an integrated experimental approach aimed at understanding how the main process conditions (laser power and scanning speed) influence the direct-bonds quality, dimensions and presence of defects. To this end, the bonds dimension, shear strength, formation and dimension of bubbles in the bonded region were related to the temperature measurements and process parameters. According to the achieved results, the processing window that enables a good adhesion of the two materials is relatively small; this is due the activation of the adhesion phenomena that require overcoming an energy threshold. However, excessive energy levels reduce the bonds strength due to the increase in defects (bubbles) dimension that may combine (coalescence) leading to the formation of a central tunnel where the two substrates are completely detached.

  17. Optimization of Suture-Free Laser-Assisted Vessel Repair by Solder-Doped Electrospun Poly(ε-caprolactone) Scaffold

    PubMed Central

    Pabittei, Dara R.; Heger, Michal; Beek, Johan F.; van Tuijl, Sjoerd; Simonet, Marc; van der Wal, Allard C.; de Mol, Bas A.

    2010-01-01

    Poor welding strength constitutes an obstacle in the clinical employment of laser-assisted vascular repair (LAVR) and anastomosis. We therefore investigated the feasibility of using electrospun poly(ε-caprolactone) (PCL) scaffold as reinforcement material in LAVR of medium-sized vessels. In vitro solder-doped scaffold LAVR (ssLAVR) was performed on porcine carotid arteries or abdominal aortas using a 670-nm diode laser, a solder composed of 50% bovine serum albumin and 0.5% methylene blue, and electrospun PCL scaffolds. The correlation between leaking point pressures (LPPs) and arterial diameter, the extent of thermal damage, structural and mechanical alterations of the scaffold following ssLAVR, and the weak point were investigated. A strong negative correlation existed between LPP and vessel diameter, albeit LPP (484 ± 111 mmHg) remained well above pathophysiological pressures. Histological analysis revealed that thermal damage extended into the medial layer with a well-preserved internal elastic lamina and endothelial cells. Laser irradiation of PCL fibers and coagulation of solder material resulted in a strong and stiff scaffold. The weak point of the ssLAVR modality was predominantly characterized by cohesive failure. In conclusion, ssLAVR produced supraphysiological LPPs and limited tissue damage. Despite heat-induced structural/mechanical alterations of the scaffold, PCL is a suitable polymer for weld reinforcement in medium-sized vessel ssLAVR. PMID:20835847

  18. Vacuum compatible sample positioning device for matrix assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry imaging

    PubMed Central

    Aizikov, Konstantin; Smith, Donald F.; Chargin, David A.; Ivanov, Sergei; Lin, Tzu-Yung; Heeren, Ron M. A.; O’Connor, Peter B.

    2011-01-01

    The high mass accuracy and resolving power of Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR MS) make them ideal mass detectors for mass spectrometry imaging (MSI), promising to provide unmatched molecular resolution capabilities. The intrinsic low tolerance of FT-ICR MS to RF interference, however, along with typically vertical positioning of the sample, and MSI acquisition speed requirements present numerous engineering challenges in creating robotics capable of achieving the spatial resolution to match. This work discusses a two-dimensional positioning stage designed to address these issues. The stage is capable of operating in ∼1 × 10–8 mbar vacuum. The range of motion is set to 100 mm × 100 mm to accommodate large samples, while the positioning accuracy is demonstrated to be less than 0.4 micron in both directions under vertical load over the entire range. This device was integrated into three different matrix assisted laser desorption/ionization (MALDI) FT-ICR instruments and showed no detectable RF noise. The “oversampling” MALDI-MSI experiments, under which the sample is completely ablated at each position, followed by the target movement of the distance smaller than the laser beam, conducted on the custom-built 7T FT-ICR MS demonstrate the stability and positional accuracy of the stage robotics which delivers high spatial resolution mass spectral images at a fraction of the laser spot diameter. PMID:21639522

  19. Solvent Separating Secondary Metabolites Directly from Biosynthetic Tissue for Surface-Assisted Laser Desorption Ionisation Mass Spectrometry

    PubMed Central

    Rudd, David; Benkendorff, Kirsten; Voelcker, Nicolas H.

    2015-01-01

    Marine bioactive metabolites are often heterogeneously expressed in tissues both spatially and over time. Therefore, traditional solvent extraction methods benefit from an understanding of the in situ sites of biosynthesis and storage to deal with heterogeneity and maximize yield. Recently, surface-assisted mass spectrometry (MS) methods namely nanostructure-assisted laser desorption ionisation (NALDI) and desorption ionisation on porous silicon (DIOS) surfaces have been developed to enable the direct detection of low molecular weight metabolites. Since direct tissue NALDI-MS or DIOS-MS produce complex spectra due to the wide variety of other metabolites and fragments present in the low mass range, we report here the use of “on surface” solvent separation directly from mollusc tissue onto nanostructured surfaces for MS analysis, as a mechanism for simplifying data annotation and detecting possible artefacts from compound delocalization during the preparative steps. Water, ethanol, chloroform and hexane selectively extracted a range of choline esters, brominated indoles and lipids from Dicathais orbita hypobranchial tissue imprints. These compounds could be quantified on the nanostructured surfaces by comparison to standard curves generated from the pure compounds. Surface-assisted MS could have broad utility for detecting a broad range of secondary metabolites in complex marine tissue samples. PMID:25786067

  20. Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry Fails To Identify Nontuberculous Mycobacteria from Primary Cultures of Respiratory Samples

    PubMed Central

    van Eck, Kim; Faro, Dirk; Wattenberg, Melanie; de Jong, Arjan; Kuipers, Saskia

    2016-01-01

    We have assessed matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) identification (Bruker) of nontuberculous mycobacteria from newly positive liquid cultures of respiratory samples. Twelve (22%) of 54 isolates were identified directly from liquid medium. After subculture and with manual laser operation, this rose to 49/54 isolates (91%). MALDI-TOF MS is less promising than previously suggested. PMID:27147723

  1. Can-out hatch assembly with magnetic retention means

    DOEpatents

    Frank, Robert C.; Hoh, Joseph C.

    1986-01-01

    A can-out hatch assembly may be positioned in sealed engagement about an aperture within a chamber and is adapted to engage a cover on a container positioned over the aperture to allow the transfer of a contaminant from the chamber to the container while maintaining the contaminant as well as internal portions of the chamber and container isolated from the surrounding environment. With the container's cover engaged by the can-out hatch assembly, the hatch assembly as well as the cover may be pivotally displaced from the aperture with the cover maintaining the exterior portion of the hatch assembly isolated from the contaminant. After the contaminant is transferred from the chamber to the container, the hatch assembly and cover are again positioned in sealed engagement about the aperture. The hatch assembly then positions the cover upon the open end of the container in a sealed manner allowing the container to be removed while maintaining the chamber sealed relative to the surrounding environment. The can-out hatch assembly is particularly adapted for operation by remote control means within the sealed chamber.

  2. Can-out hatch assembly and positioning system

    DOEpatents

    Basnar, Paul J.; Frank, Robert C.; Hoh, Joseph C.

    1986-01-01

    A can-out hatch assembly is adapted to engage in a sealed manner the upper end of a covered sealed container around an aperture in a sealed chamber and to remove the cover from the container permitting a contaminant to be transferred between the container and the chamber while isolating internal portions of the container and chamber from the surrounding environment. A swing bracket is coupled at a first end thereof to the inner, lower wall of the sealed container adjacent to the aperture therein. To a second end of the swing bracket is mounted a hatch cover which may be positioned in sealed engagement about the chamber's aperture by rotating the hatch cover in a first direction when the swing bracket is in the full down position. Rotation of the hatch cover in a second direction releases it from sealed engagement with the chamber's aperture. A lid support rod also coupled to the second end of the swing bracket and inserted through an aperture in the center of the hatch cover may be rotated for threadably engaging the container's cover whereupon the cover may be removed from the container and the hatch cover displaced from the aperture by pivoting displacement of the swing bracket. The contaminant may then be either removed from the container and placed within the sealed chamber, or vice versa, followed by positioning of the cover upon the container and the hatch cover over the aperture in a sealed manner.

  3. Can-out hatch assembly and positioning system

    DOEpatents

    Basnar, Paul J.; Frank, Robert C.; Hoh, Joseph C.

    1986-01-07

    A can-out hatch assembly is adapted to engage in a sealed manner the upper end of a covered sealed container around an aperture in a sealed chamber and to remove the cover from the container permitting a contaminant to be transferred between the container and the chamber while isolating internal portions of the container and chamber from the surrounding environment. A swing bracket is coupled at a first end thereof to the inner, lower wall of the sealed container adjacent to the aperture therein. To a second end of the swing bracket is mounted a hatch cover which may be positioned in sealed engagement about the chamber's aperture by rotating the hatch cover in a first direction when the swing bracket is in the full down position. Rotation of the hatch cover in a second direction releases it from sealed engagement with the chamber's aperture. A lid support rod also coupled to the second end of the swing bracket and inserted through an aperture in the center of the hatch cover may be rotated for threadably engaging the container's cover whereupon the cover may be removed from the container and the hatch cover displaced from the aperture by pivoting displacement of the swing bracket. The contaminant may then be either removed from the container and placed within the sealed chamber, or vice versa, followed by positioning of the cover upon the container and the hatch cover over the aperture in a sealed manner.

  4. Can-out hatch assembly with magnetic retention means

    DOEpatents

    Frank, Robert C.; Hoh, Joseph C.

    1986-01-07

    A can-out hatch assembly may be positioned in sealed engagement about an aperture within a chamber and is adapted to engage a cover on a container positioned over the aperture to allow the transfer of a contaminant from the chamber to the container while maintaining the contaminant as well as internal portions of the chamber and container isolated from the surrounding environment. With the container's cover engaged by the can-out hatch assembly, the hatch assembly as well as the cover may be pivotally displaced from the aperture with the cover maintaining the exterior portion of the hatch assembly isolated from the contaminant. After the contaminant is transferred from the chamber to the container, the hatch assembly and cover are again positioned in sealed engagement about the aperture. The hatch assembly then positions the cover upon the open end of the container in a sealed manner allowing the container to be removed while maintaining the chamber sealed relative to the surrounding environment. The can-out hatch assembly is particularly adapted for operation by remote control means within the sealed chamber.

  5. Can-out hatch assembly and positioning system

    DOEpatents

    Basnar, P.J.; Frank, R.C.; Hoh, J.C.

    1985-07-03

    A can-out hatch assembly is adapted to engage in a sealed manner the upper end of a covered sealed container around an aperture in a sealed chamber and to remove the cover from the container permitting a contaminant to be transferred between the container and the chamber while isolating internal portions of the container and chamber from the surrounding environment. A swing bracket is coupled at a first end thereof to the inner, lower wall of the sealed container adjacent to the aperture therein. To a second end of the swing bracket is mounted a hatch cover which may be positioned in sealed engagement about the chamber's aperture by rotating the hatch cover in a first direction when the swing bracket is in the full down position. Rotation of the hatch cover in a second direction release it from sealed engagement with the chamber's aperture. A lid support rod also coupled to the second end of the swing bracket and inserted through an aperture in the center of the hatch cover may be rotated for theadably engaging the container's cover whereupon the cover may be removed from the container and the hatch cover displaced from the aperture by pivoting displacement of the swing bracket. The contaminant may then be either removed from the container and placed within the sealed chamber, or vice versa, followed by positioning of the cover upon the container and the hatch cover over the aperture in a sealed manner.

  6. Can-out hatch assembly with magnetic retention means

    DOEpatents

    Frank, R.C.; Hoh, J.C.

    1985-07-03

    A can-out hatch assembly may be positioned in sealed engagement about aperture within a chamber and is adapted to engage a cover on a container positioned over the aperture to allow the transfer of a contaminant from the chamber to the container while maintaining the contaminant as well as internal portions of the chamber and container isolated from the surrounding environment. With the container's cover engaged by the can-out hatch assembly, the hatch assembly as well as the cover may be pivotally displaced from the aperture with the cover maintaining the exterior portion of the hatch assembly isolated from the contaminant. After the contaminant is transferred from the chamber to the container, the hatch assembly and cover are again positioned in sealed engagement about the aperture. The hatch assembly then positions the cover upon the open end of the container in a sealed manner allowing the container to be removed while maintaining the chamber sealed relative to the surrounding environment. The can-out hatch assembly is particularly adapted for operation by remote control means within the sealed chamber.

  7. A novel report of hatching plasticity in the phylum Echinodermata.

    PubMed

    Armstrong, A Frances; Blackburn, Holly N; Allen, Jonathan D

    2013-02-01

    Hatching plasticity occurs in response to a wide range of stimuli across many animal taxa, including annelids, arthropods, mollusks, and chordates. Despite the prominence of echinoderms in developmental biology and more than 100 years of detailed examination of their development under a variety of conditions, environmentally cued hatching plasticity has never been reported in the phylum Echinodermata. Here we report plasticity in the timing and stage of hatching of embryos of the sand dollar Echinarachnius parma in response to reductions in salinity. Embryos of E. parma increased their time to hatching more than twofold in response to ecologically relevant salinity reductions, while maintaining an otherwise normal developmental schedule. Embryos that experienced the greatest delay in hatching time emerged from the fertilization envelope as four-arm pluteus larvae rather than hatching as blastulae or early gastrulae. Salinity manipulations across multiple male-female pairs indicated high variability in hatching time both within and among clutches, suggesting significant intraspecific variation in developmental responses to salinity.

  8. Computer-Assisted Laser Scanning and Video Microscopy for Analysis of Cryptosporidium parvum Oocysts in Soil, Sediment, and Feces

    PubMed Central

    Anguish, L. J.; Ghiorse, W. C.

    1997-01-01

    A computer-assisted laser scanning microscope equipped for confocal laser scanning and color video microscopy was used to examine Cryptosporidium parvum oocysts in two agricultural soils, a barnyard sediment, and calf fecal samples. An agar smear technique was developed for enumerating oocysts in soil and barnyard sediment samples. Enhanced counting efficiency and sensitivity (detection limit, 5.2 x 10(sup2) oocysts(middot)g [dry weight](sup-1)) were achieved by using a semiautomatic counting procedure and confocal laser scanning microscopy to enumerate immunostained oocysts and fragments of oocysts in the barnyard sediment. An agarose-acridine orange mounting procedure was developed for high-resolution confocal optical sectioning of oocysts in soil. Stereo images of serial optical sections revealed the three-dimensional spatial relationships between immunostained oocysts and the acridine orange-stained soil matrix material. In these hydrated, pyrophosphate-dispersed soil preparations, oocysts were not found to be attached to soil particles. A fluorogenic dye permeability assay for oocyst viability (A. T. Campbell, L. J. Robertson, and H. V. Smith, Appl. Environ. Microbiol. 58:3488-3493, 1992) was modified by adding an immunostaining step after application of the fluorogenic dyes propidium iodide and 4(prm1),6-diamidino-2-phenylindole. Comparison of conventional color epifluorescence and differential interference contrast images on one video monitor with comparable black-and-white laser-scanned confocal images on a second monitor allowed for efficient location and interpretation of fluorescently stained oocysts in the soil matrix. This multi-imaging procedure facilitated the interpretation of the viability assay results by overcoming the uncertainties caused by matrix interference and background fluorescence. PMID:16535523

  9. Furoic and mefenamic acids as new matrices for matrix assisted laser desorption/ionization-(MALDI)-mass spectrometry.

    PubMed

    Abdelhamid, Hani Nasser; Wu, Hui-Fen

    2013-10-15

    The present study introduces two novel organic matrices for matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the analysis of small molecules. The first matrix is "2-amino-4,5-diphenylfuran-3-carboxylic acid" (also called furoic acid, FA) which was synthesized and then characterized by ultraviolet (UV), infrared (FTIR), nuclear magnetic resonance NMR ((1)H and (13)C) and mass spectrometry. The compound has organic semiconductor properties and exhibits intense UV-absorption which is suitable for the UV-MALDI laser (N2 laser, 337 nm). The second matrix is mefenamic acid (MA). The two matrices can be successfully applied for various classes of compounds including adenosine-5'-triphosphate (ATP, 0.5 µL(10.0 nmol)), spectinomycin (spect, 0.5 µL(14.0 nmol)), glutathione (GSH, 0.5 µL(9.0 nmol)), sulfamethazole (SMT, 0.5 µL(2.0 nmol)) and mixture of peptides gramicidin D (GD, 0.5µL (9.0 nmol)). The two matrices can effectively absorb the laser energy, resulting in excellent desorption/ionization of small molecules. The new matrices offer a significant enhancement of ionization, less fragmentation, few interferences, nice reproducibility, and excellent stability under vacuum. Theoretical calculations of the physical parameters demonstrated increase in polarizability, molar volume and refractivity than the conventional organic matrices which can effectively enhance the proton transfer reactions between the matrices with the analyte molecules. While the reduction in density, surface tension and index of refraction can enhance homogeneity between the two new matrices with the analytes. Due to the sublimation energy of mefenamic acid is (1.2 times) higher than that of the DHB, it is more stable to be used in the vacuum.

  10. Laser-assisted lipolysis for arm contouring in Teimourian grades III and IV: A prospective study involving 22 patients

    PubMed Central

    Leclère, Franck Marie; Alcolea, Justo M; Vogt, Peter M; Moreno-Moraga, Javier; Casoli, Vincent; Mordon, Serge; Trelles, Mario A

    2016-01-01

    BACKGROUND: Upper arm deformities secondary to weight loss or senile elastosis have led to an increased demand for aesthetic contouring procedures. OBJECTIVE: To objectively assess whether, in Teimourian high-grade upper arm remodelling, laser-assisted lypolysis (LAL) alone could result in patient satisfaction. METHODS: Between 2012 and 2013, 22 patients were treated for excessive upper arm fat (Teimourian grade III and IV) solely with LAL. The laser used in the present study was a 1470 nm diode laser (Alma Lasers, Israel) with the following parameters: continuous mode, 15 W power and transmission through a 600 μm optical fibre. Previous mathematical modelling suggested that 0.1 kJ was required to destroy 1 mL of fat. Patients were asked to complete a satisfaction questionnaire. The arm circumference was measured pre- and postoperatively. Treatment parameters, adverse effects and outcomes were recorded. RESULTS: Pain during the anesthesia and discomfort after the procedure were minimal. Complications included ecchymoses and prolonged edema. The mean (± SD) arm circumference decreased 5.5±1.0 cm in the right arm (P<0.01) and 5.2±1.1 cm in the left arm (P<0.01) in grade III patients and 4.9±1.1 cm in the right arm (P<0.01) and 4.9±1.1 cm in the left arm (P<0.01) in grade IV patients. Although the circumference of both arms significantly decreased in grade III and grade IV patients, the skin tightening remained incomplete. Overall, the average opinion of treatment was poor for both patients and investigators. Of the 22 patients, only nine (41%) would recommend this treatment. CONCLUSION: LAL for upper arm remodelling is not sufficient to ensure full skin tightening for patients with Teimourian grades III and IV upper arm deformities. A complementary surgery is mandatory for grades III and IV. PMID:27054137

  11. Isotope dilution ICP-MS with laser-assisted sample introduction for direct determination of sulfur in petroleum products.

    PubMed

    Boulyga, Sergei F; Heilmann, Jens; Heumann, Klaus G

    2005-08-01

    Inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) with direct laser-assisted introduction of isotope-diluted samples into the plasma, using a laser ablation system with high ablation rates, was developed for accurate sulfur determinations in different petroleum products such as 'sulfur-free' premium gasoline, diesel fuel, and heating oil. Two certified gas oil reference materials were analyzed for method validation. Two different 34S-enriched spike compounds, namely, elementary sulfur dissolved in xylene and dibenzothiophene in hexane, were synthesized and tested for their usefulness in this isotope dilution technique. The isotope-diluted sample was adsorbed on a filter-paper-like material, which was fixed in a special holder for irradiation by the laser beam. Under these conditions no time-dependent spike/analyte fractionation was only observed for the dibenzothiophene spike during the laser ablation process, which means that the measured 34S/32S isotope ratio of the isotope-diluted sample remained constant-a necessary precondition for accurate results with the isotope dilution technique. A comparison of LA-ICP-IDMS results with the certified values of the gas oil reference materials and with results obtained from ICP-IDMS analyses with wet sample digestion demonstrated the accuracy of the new LA-ICP-IDMS method in the concentration range of 9.2 microg g(-1) ('sulfur-free' premium gasoline) to 10.4 mg g(-1) (gas oil reference material BCR 107). The detection limit for sulfur by LA-ICP-IDMS is 0.04 microg g(-1) and the analysis time is only about 10 min, which therefore also qualifies this method for accurate determinations of low sulfur contents in petroleum products on a routine level.

  12. Fabrication of organic light-emitting diode pixels by laser-assisted forward transfer

    NASA Astrophysics Data System (ADS)

    Fardel, Romain; Nagel, Matthias; Nüesch, Frank; Lippert, Thomas; Wokaun, Alexander

    2007-08-01

    Fabrication of a polymer light-emitting device was achieved by a laser forward transfer technique using the decomposition of a thin triazene polymer film by a XeCl excimer laser. The dry deposition process allows transfer of a bilayer consisting of the electroluminescent polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] covered with an aluminum electrode onto a receiver substrate. The soft transfer results in laterally well resolved pixels (≈500μm), whose fluorescence as well as electroluminescence spectra remain unaltered. The rectifying and smooth current-voltage characteristics add to the merits of this laser-based transfer method that opens up the possibility of direct-writing heat- and UV-sensitive materials.

  13. Gold-film coating assisted femtosecond laser fabrication of large-area, uniform periodic surface structures.

    PubMed

    Feng, Pin; Jiang, Lan; Li, Xin; Rong, Wenlong; Zhang, Kaihu; Cao, Qiang

    2015-02-20

    A simple, repeatable approach is proposed to fabricate large-area, uniform periodic surface structures by a femtosecond laser. 20 nm gold films are coated on semiconductor surfaces on which large-area, uniform structures are fabricated. In the case study of silicon, cross-links and broken structures of laser induced periodic surface structures (LIPSSs) are significantly reduced on Au-coated silicon. The good consistency between the scanning lines facilitates the formation of large-area, uniform LIPSSs. The diffusion of hot electrons in the Au films increases the interfacial carrier densities, which significantly enhances interfacial electron-phonon coupling. High and uniform electron density suppresses the influence of defects on the silicon and further makes the coupling field more uniform and thus reduces the impact of laser energy fluctuations, which homogenizes and stabilizes large-area LIPSSs.

  14. Scope for electric field assisted removal of ablated debris from laser machined features in silicon

    NASA Astrophysics Data System (ADS)

    Coyne, Edward; Mannion, Paul; O'Connor, Gerard M.; Favre, Sebastian; Glynn, Thomas J.

    2005-04-01

    The problem created by the re-deposition of ablated material when laser machining structures in silicon wafers is investigated. The study focuses on the specific case of machining wafer grade silicon with femtosecond pulses centered at a wavelength of 775 nm. Based on the evidence that a highly ionised plasma state exists immediately after laser ablation, this work explores the potential of using electric fields to channel the debris out of the laser machined feature before it becomes deposited. To this extent the work discusses the step-by-step development of different experimental arrangements, by first evaluating its effects, then identifying its limitations and finally by proposing and investigating potential solutions. It is found that a reduction in the amount of re-deposited debris is observed when a carrier-depleted region is generated in silicon materials.

  15. Circadian clock controlling egg hatching in the cricket (Gryllus bimaculatus).

    PubMed

    Itoh, M T; Sumi, Y

    2000-06-01

    Adult crickets (Gryllus bimaculatus) were maintained under a 12-h light:12-h dark cycle (LD 12:12). After oviposition, their eggs were incubated under different lighting regimens at 23 degrees C, and temporal profiles of egg hatching were examined. When the eggs were incubated in LD 12:12 or in DL 12:12 with a phase difference of 12h from LD 12:12, throughout embryogenesis, 88% to 97% of hatching occurred within 3 h of the dark-light transition on days 17 and 18 of embryogenesis; the phases of the egg-hatching rhythms in the LD 12:12 and DL 12:12 groups differed by about 12 h. In eggs incubated in constant darkness (DD) throughout embryogenesis, a circadian (about 24 h) rhythm of hatching was found, and the phase of the rhythm was similar to that seen in eggs incubated in LD 12:12, but not DL 12:12, throughout embryogenesis. When eggs that had been incubated in DD after oviposition were transferred to DL 12:12 in the middle or later stages of embryogenesis and were returned to DD after three cycles of DL 12:12, the rhythm of hatching synchronized (entrained) to DL 12:12. However, when eggs in the earlier stages of embryogenesis were transferred from DD to DL 12:12 and returned to DD after three cycles, 52% to 94% of hatching did not entrain to DL 12:12. To determine whether photoperiodic conditions to which the parents had been exposed influenced the timing of egg hatching, adult crickets were maintained in DL 12:12, and their eggs were incubated in LD 12:12, DL 12:12, or DD throughout embryogenesis. The egg-hatching rhythm was also found in the eggs incubated under these three lighting regimens. In DD, the phase of the rhythm was similar to that seen in eggs incubated in DL 12:12, not LD 12:12, throughout embryogenesis. The results indicate that in the cricket, the timing of egg hatching is under circadian control and that the circadian rhythm of hatching entrains to 24-h light:dark cycles, but only if the light:dark cycles are imposed midway through embryogenesis

  16. Systems and methods for laser assisted sample transfer to solution for chemical analysis

    DOEpatents

    Van Berkel, Gary J.; Kertesz, Vilmos; Ovchinnikova, Olga S.

    2014-06-03

    Systems and methods are described for laser ablation of an analyte from a specimen and capturing of the analyte in a dispensed solvent to form a testing solution. A solvent dispensing and extraction system can form a liquid microjunction with the specimen. The solvent dispensing and extraction system can include a surface sampling probe. The laser beam can be directed through the surface sampling probe. The surface sampling probe can also serve as an atomic force microscopy probe. The surface sampling probe can form a seal with the specimen. The testing solution including the analyte can then be analyzed using an analytical instrument or undergo further processing.

  17. Systems and methods for laser assisted sample transfer to solution for chemical analysis

    DOEpatents

    Van Berkel, Gary J; Kertesz, Vilmos; Ovchinnikova, Olga S

    2013-08-27

    Systems and methods are described for laser ablation of an analyte from a specimen and capturing of the analyte in a dispensed solvent to form a testing solution. A solvent dispensing and extraction system can form a liquid microjunction with the specimen. The solvent dispensing and extraction system can include a surface sampling probe. The laser beam can be directed through the surface sampling probe. The surface sampling probe can also serve as an atomic force microscopy probe. The surface sampling probe can form a seal with the specimen. The testing solution including the analyte can then be analyzed using an analytical instrument or undergo further processing.

  18. Systems and methods for laser assisted sample transfer to solution for chemical analysis

    DOEpatents

    Van Berkel, Gary J.; Kertesz, Vilmos; Ovchinnikova, Olga S.

    2015-09-29

    Systems and methods are described for laser ablation of an analyte from a specimen and capturing of the analyte in a dispensed solvent to form a testing solution. A solvent dispensing and extraction system can form a liquid microjunction with the specimen. The solvent dispensing and extraction system can include a surface sampling probe. The laser beam can be directed through the surface sampling probe. The surface sampling probe can also serve as an atomic force microscopy probe. The surface sampling probe can form a seal with the specimen. The testing solution including the analyte can then be analyzed using an analytical instrument or undergo further processing.

  19. Diode laser-assisted endoscopic dacryocystorhinostomy: a comparison of three different combinations of adjunctive procedures.

    PubMed

    Dogan, Remzi; Meric, Aysenur; Ozsütcü, Mustafa; Yenigun, Alper

    2013-08-01

    Chronic dacryocystitis is a frequently encountered condition which can be corrected by dacryocystorhinostomy. Today, the diode laser is increasingly put to use in such corrective operations. This study aims to answer the questions of which adjunctive procedures and which combinations of such procedures are necessary and effective in securing more successful outcomes in diode laser dacryocystorhinostomy. This prospective randomized study included eighty patients (13 male, 67 female) who underwent dacryocystorhinostomy in our hospital during the 2 year period of January 2009-January 2011. The patients were selected consecutively and were randomly allocated to three groups. Group 1 (30): diode laser + mitomycin C + silicone intubation; Group 2 (27): diode laser + silicone intubation; Group 3 (23): diode laser + mitomycin C. All patients were evaluated postoperatively on day 1, week 1, and on the 1st, 3rd, 6th, 12th, 18th, and 24th months. The postoperative evaluation consisted of preoperative and postoperative ostium measurements, recording postoperative complications, and calculating and comparing success rates and operative times. The mean ages of the patients were 63.4 for Group 1, 60.7 for Group 2, and 61.8 for Group 3. No statistically significant difference was found among the groups regarding pre- and postoperative ostium measurements. The success rates were 84.3, 80, and 76.9 % for Groups 1, 2, and 3, respectively. Complications noted in Group 1 were restenosis (3), premature silicone tube loss (1), development of granulation tissue (3), synechia (2), infection (2), and hemorrhage (3). Those for Group 2 were restenosis (5), premature tube loss (2), granulation (8), synechia (6), infection (3), and hemorrhage (4). Group 3 had 6 cases with stenosis, 5 with granulation, 3 with infection, 6 with synechia, and 5 with hemorrhage. The operative times of the groups were 25.5, 15.3, and 18.1 min, respectively, for Group 1, 2, and 3. All three groups had statistically

  20. Preliminary results on diode-laser assisted vaporization of prostate tissue

    NASA Astrophysics Data System (ADS)

    Sroka, Ronald; Seitz, Michael; Reich, Oliver; Bachmann, Alexander; Steinbrecher, Verena; Ackermann, Alexander; Stief, Christian

    2007-07-01

    Introduction and objectives: The aim was to identify the capability and the laser parameter of under water tissue vaporisation by means of a diode laser (1470 nm). Afterwards the feasibility and postoperative clinical outcome of vaporization of the prostate was investigated. Method: After acquiring suitable laser parameters in in-vitro experiments using a perfused tissue model patients (n=10) suffering from bladder outlet obstruction due to benign prostatic hyperplasia (BPH) were treated by diode laser. Their clinical outcome, in terms of acceptance and post-operatively voiding were evaluated. The diode laser emitted light of the wavelength of 1470 nm at 50 W (Biolitec GmbH) and delivered to the tissue by means of a side-fire fibre introduced through a 24F continuous-flow cystoscope. Normal saline was used for irrigation with an additive of 1% ethanol. The prostatic lobes (volume range 35-80ml) were vaporized within the prostatic capsular using sweeping and push and pull technique. The mean time of laser application was 2400 sec (1220-4000 sec) resulting in applied energies of 121 kJ in the mean (range: 61-200kJ). Results: During laser treatment none of the 10 patients showed any significant blood loss or any fluid absorption (no ethanol uptake). Foley catheters were removed between 18 and 168 hours postoperatively (mean: 49.8h+/-46h). After removal of the catheter the mean peak urine flow rate increased from 8.9ml/s +/- 2.9ml/s pre-operatively in comparison to 15.7ml/s +/- 5 ml/s (p=0.049) post-operatively. 8/10 patients were satisfied with their voiding outcome. None of the patients showed appearance of urgency, dysuria, hematuria, or incontinence but two patients required re-catheterization. After a follow-up of 1month, 8/10 patients showed evidence of good results and are satisfied with the outcome. Two patients required consecutive TUR-P. After a follow-up of 6-month the 8 patients are still satisfied. Conclusions: This very early and limited experience using