Science.gov

Sample records for laser-induced retinal lesions

  1. Hedgehog Signaling Components Are Expressed in Choroidal Neovascularization in Laser-induced Retinal Lesion

    PubMed Central

    Nochioka, Katsunori; Okuda, Hiroaki; Tatsumi, Kouko; Morita, Shoko; Ogata, Nahoko; Wanaka, Akio

    2016-01-01

    Choroidal neovascularization is one of the major pathological changes in age-related macular degeneration, which causes devastating blindness in the elderly population. The molecular mechanism of choroidal neovascularization has been under extensive investigation, but is still an open question. We focused on sonic hedgehog signaling, which is implicated in angiogenesis in various organs. Laser-induced injuries to the mouse retina were made to cause choroidal neovascularization. We examined gene expression of sonic hedgehog, its receptors (patched1, smoothened, cell adhesion molecule down-regulated by oncogenes (Cdon) and biregional Cdon-binding protein (Boc)) and downstream transcription factors (Gli1-3) using real-time RT-PCR. At seven days after injury, mRNAs for Patched1 and Gli1 were upregulated in response to injury, but displayed no upregulation in control retinas. Immunohistochemistry revealed that Patched1 and Gli1 proteins were localized to CD31-positive endothelial cells that cluster between the wounded retina and the pigment epithelium layer. Treatment with the hedgehog signaling inhibitor cyclopamine did not significantly decrease the size of the neovascularization areas, but the hedgehog agonist purmorphamine made the areas significantly larger than those in untreated retina. These results suggest that the hedgehog-signaling cascade may be a therapeutic target for age-related macular degeneration. PMID:27239075

  2. Hedgehog Signaling Components Are Expressed in Choroidal Neovascularization in Laser-induced Retinal Lesion.

    PubMed

    Nochioka, Katsunori; Okuda, Hiroaki; Tatsumi, Kouko; Morita, Shoko; Ogata, Nahoko; Wanaka, Akio

    2016-04-28

    Choroidal neovascularization is one of the major pathological changes in age-related macular degeneration, which causes devastating blindness in the elderly population. The molecular mechanism of choroidal neovascularization has been under extensive investigation, but is still an open question. We focused on sonic hedgehog signaling, which is implicated in angiogenesis in various organs. Laser-induced injuries to the mouse retina were made to cause choroidal neovascularization. We examined gene expression of sonic hedgehog, its receptors (patched1, smoothened, cell adhesion molecule down-regulated by oncogenes (Cdon) and biregional Cdon-binding protein (Boc)) and downstream transcription factors (Gli1-3) using real-time RT-PCR. At seven days after injury, mRNAs for Patched1 and Gli1 were upregulated in response to injury, but displayed no upregulation in control retinas. Immunohistochemistry revealed that Patched1 and Gli1 proteins were localized to CD31-positive endothelial cells that cluster between the wounded retina and the pigment epithelium layer. Treatment with the hedgehog signaling inhibitor cyclopamine did not significantly decrease the size of the neovascularization areas, but the hedgehog agonist purmorphamine made the areas significantly larger than those in untreated retina. These results suggest that the hedgehog-signaling cascade may be a therapeutic target for age-related macular degeneration. PMID:27239075

  3. Neuroprotective therapy for argon-laser-induced retinal injury

    NASA Astrophysics Data System (ADS)

    Belkin, Michael; Rosner, Mordechai; Solberg, Yoram; Turetz, Yosef

    1999-06-01

    Laser photocoagulation treatment of the central retina is often complicated by an immediate side effect of visual impairment, caused by the unavoidable laser-induced destruction of the normal tissue lying adjacent to the lesion and not affected directly by the laser beam. Furthermore, accidental laser injuries are at present untreatable. A neuroprotective therapy for salvaging the normal tissue might enhance the benefit obtained from treatment and allow safe perifoveal photocoagulation. We have developed a rat model for studying the efficacy of putative neuroprotective compounds in ameliorating laser-induced retinal damage. Four compounds were evaluated: the corticosteroid methylprednisolone, the glutamate-receptor blocker MK-801, the anti-oxidant enzyme superoxide dismutase, and the calcim-overload antagonist flunarizine. The study was carried out in two steps: in the first, the histopathological development of retinal laser injuries was studied. Argon laser lesions were inflicted in the retinas of 18 pigmented rats. The animals were sacrificed after 3, 20 or 60 days and their retinal lesions were evaluated under the light microscope. The laser injury mainly involved the outer layers of the retina, where it destroyed significant numbers of photoreceptor cells. Over time, evidence of two major histopathological processes was observed: traction of adjacent nomral retinal cells into the central area of the lesion forming an internal retinal bulging, and a retinal pigmented epithelial proliferative reaction associated with subretinal neovascularization and invations of the retinal lesion site by phagocytes. The neuroprotective effects of each of the four compounds were verified in a second step of the study. For each drug tested, 12 rats were irradiated wtih argon laser inflictions: six of them received the tested agent while the other six were treated with the corresponding vehicle. Twenty days after laser expsoure, the rats were sacrificed and their lesions were

  4. Treatment of laser-induced retinal injuries by neuroprotection

    NASA Astrophysics Data System (ADS)

    Solberg, Yoram; Rosner, Mordechai; Belkin, Michael

    1997-05-01

    Retinal laser photocoagulation treatments are often complicated with immediate side-effect of visual impairment. To determine whether glutamate-receptor blockers can serve as adjuvant neuroprotective therapy, we examined the effect of MK-801, an NMDA-receptor antagonist, on laser-induced retinal injury in a rat model. Argon laser retinal lesions were created in the retina of 36 DA rats. Treatment with intraperitoneal injections of MK-801 or saline was started immediately after the laser photocoagulation. The animals were sacrificed after 3, 20 or 60 days and the retinal lesions were evaluated histologically and morphometrically. Photoreceptor-cell loss was significantly smaller in MK-801-treated rats than controls. The proliferative membrane composed of retinal pigment epithelial cells which was seen at the base of the lesion in control retinas, was smaller in the MK-801-treated retinas. MK-801 exhibited neuroprotective and anti-proliferative properties in the retina. Glutamate-receptor blockers should be further investigated for serving as adjuvant therapy to retinal photocoagulation treatments.

  5. Laser-induced retinal damage thresholds for annular retinal beam profiles

    NASA Astrophysics Data System (ADS)

    Kennedy, Paul K.; Zuclich, Joseph A.; Lund, David J.; Edsall, Peter R.; Till, Stephen; Stuck, Bruce E.; Hollins, Richard C.

    2004-07-01

    The dependence of retinal damage thresholds on laser spot size, for annular retinal beam profiles, was measured in vivo for 3 μs, 590 nm pulses from a flashlamp-pumped dye laser. Minimum Visible Lesion (MVL)ED50 thresholds in rhesus were measured for annular retinal beam profiles covering 5, 10, and 20 mrad of visual field; which correspond to outer beam diameters of roughly 70, 160, and 300 μm, respectively, on the primate retina. Annular beam profiles at the retinal plane were achieved using a telescopic imaging system, with the focal properties of the eye represented as an equivalent thin lens, and all annular beam profiles had a 37% central obscuration. As a check on experimental data, theoretical MVL-ED50 thresholds for annular beam exposures were calculated using the Thompson-Gerstman granular model of laser-induced thermal damage to the retina. Threshold calculations were performed for the three experimental beam diameters and for an intermediate case with an outer beam diameter of 230 μm. Results indicate that the threshold vs. spot size trends, for annular beams, are similar to the trends for top hat beams determined in a previous study; i.e., the threshold dose varies with the retinal image area for larger image sizes. The model correctly predicts the threshold vs. spot size trends seen in the biological data, for both annular and top hat retinal beam profiles.

  6. Retinal lesions in septicemia.

    PubMed

    Neudorfer, M; Barnea, Y; Geyer, O; Siegman-Igra, Y

    1993-12-15

    We explored the association between septicemia and specific retinal lesions in a prospective controlled study. Hemorrhages, cotton-wool spots, or Roth's spots were found in 24 of 101 septicemic patients (24%), compared to four of 99 age- and gender-matched control patients (4%) (P = .0002). There was no significant association between types of organisms or focus of infection and the presence of specific lesions. Histologic examination of affected eyes disclosed cytoid bodies in the nerve fiber layer without inflammation. A definite association between septicemia and retinal lesions was found and indicates the need for routine ophthalmoscopy in septicemic patients. PMID:8250076

  7. The neuroprotective effect of hyperbaric oxygen treatment on laser-induced retinal damage in rats

    NASA Astrophysics Data System (ADS)

    Vishnevskia-Dai, Victoria; Belokopytov, Mark; Dubinsky, Galina; Nachum, Gal; Avni, Isaac; Belkin, Michael; Rosner, Mordechai

    2005-04-01

    Retinal damage induced by mechanical trauma, ischemia or laser photocoagulation increases considerably by secondary degeneration processes. The spread of damage may be ameliorated by neuroprotection that is aimed at reducing the extent of the secondary degeneration and promote healing processes. Hyperbaric oxygen (HBO) treatment consists of inspiration of oxygen at higher than one absolute atmospheric pressure. Improved neural function was observed in patients with acute brain trauma or ischemia treated with HBO. This study was designed to evaluate the neuroprotective effect of hyperbaric oxygen (HBO) on laser induced retinal damage in a rat model. Standard argon laser lesions were created in 25 pigmented rats divided into three groups: Ten rats were treated immediately after the irradiation with HBO three times during the first 24 hr followed by 12 consecutive daily treatments. Five rats received a shorter treatment regimen of 10 consecutive HBO treatments. The control group (10 rats) underwent the laser damage with no additional treatment. The retinal lesions were evaluated 20 days after the injury. All outcome measures were improved by the longer HBO treatment (P<0.01). The shorter HBO treatment was less effective, showing an increase only in nuclei density at the central area of lesion (P< 0.01). Hyperbaric oxygen seems to exert a neuroprotective effect on laser-induced retinal damage in a rat model. In the range of HBO exposures studied, longer exposure provides more neuroprotection. These results encourage further evaluation of the potential therapeutic use of hyperbaric oxygen in diseases and injuries of the retina.

  8. [Multifocal Vitelliform Retinal Lesion].

    PubMed

    Streicher, T; Špirková, J; Ilavská, M

    2015-06-01

    The authors present retrospective follow up of patient with bilateral multifocal vitelliform retinal lesion during the 18 years period. At this time, spontaneous improvement of objective picture on retina and subjective visual troubles was observed. It is probable, that this case is a part of the same symptom complex as a variant of Best´s hereditary disease. This conclusion was based on initial stadium of phenotypical expressivity and additional evaluations. The course and outcomes of visual functions were different. The hereditary transmission was not confirmed. PMID:26201364

  9. Therapeutic effect of the NMDA antagonist MK-801 on low-level laser induced retinal injury

    NASA Astrophysics Data System (ADS)

    Yan, W.-H.; Wu, J.; Chen, P.; Dou, J.-T.; Pan, C.-Y.; Mu, Y.-M.; Lu, J.-M.

    2009-03-01

    The aim of this article was to explore the mechanism of injury in rat retina after constant low-level helium-neon (He-Ne) laser exposure and therapeutic effects of MK-801, an N-methyl-D-aspartate (NMDA) receptor antagonist, on laser-induced retinal injury. He-Ne laser lesions were created in the central retina of adult Wistar Kyoto rats and were followed immediately by intraperitoneal injection of MK-801 (2 mg/kg) or saline, macroscopical and microscopical lesion were observed by funduscope and light microscope. Ultrastructural changes of the degenerating cells were examined by electron microscopy. Photoreceptor apoptosis was evaluated by TdT-mediated dUTP nick end-labeling (TUNEL). mRNA levels were measured by in situ hybridization and NMDA receptor expression was determined by immunohistochemistry. Laser induced damage was histologically quantified by image-analysis morphometry. Electroretinograms (ERGs) were recorded at different time point after the cessation of exposure to constant irradiation. There was no visible bleeding, exudation or necrosis under funduscope. TUNEL and electron microscopy showed photoreceptor apoptosis after irradiation. MK-801-treated animals had significantly fewer TUNEL-positive cells in the photoreceptors than saline-treated animals after exposure to laser. In situ hybridization (ISH) showed that the NMDAR mRNA level of MK-801-treated rats decreased in the inner plexiform layer 6 h after the cessation of exposure to constant irradiation when compared with that of saline-treated rats. So did Immunohistochemistry (IHC). Electroretinogram showed that b-wave amplitudes of MK-801-treated group were higher than that of saline-treated group after laser exposure. These findings suggest that Low level laser may cause the retinal pathological changes under given conditions. High expression of NMDAR is one of the possible mechanisms causing experimental retinal laser injury of rats. MK-801 exhibits the therapeutic effect due to promote the

  10. High-dose methylprednisolone treatment of laser-induced retinal injury exacerbates acute inflammation and long-term scarring

    NASA Astrophysics Data System (ADS)

    Schuschereba, Steven T.; Cross, Michael E.; Scales, David K.; Pizarro, Jose M.; Edsall, Peter R.; Stuck, Bruce E.; Marshall, John

    1999-06-01

    Purpose. To evaluate therapeutics for attenuating retinal laser injury. Methods. New Zealand Red rabbits (n=76) were pretreated (IV) with either a single dose of hydroxyethyl starch conjugated deferoxamine (HES-DFO, n=29) (6.1 ml/kg, 16.4 mg/ml) or methylprednisolone sodium succinate (MP, n=22) (30 mg/kg, followed by taper of 30, 20, 20, and 10 mg/kg/day for a total of 5d). Controls were untreated (n=25). Fifteen min later, animals were irradiated with a multiline cw argon laser (285 mW, 10 msec pulse durations, 16 lesions/eye). Funduscopy, fluorescein angiography, histology, and morphometry were performed at 10 min, 1h, 3h, 24h, 1 mo, and 6 mo after irradiation. Leukocytes were counted at lesion centers for retinal and choroidal compartments at 1, 3, and 24h. Results. At 3h, percent area incrase for the lesions was highest for MP (44%) and lowest for HES-DFO (16%)(p<0.05). In hemorrhagic lesions, MP treatment resulted in the highest increase of retinal neotrophils by 24h (p<0.05), and by 1 and 6 mo extensive chorio-retinal scarring occurred in nonhemorrhagic and hemorrhagic lesions. Also, no benefit was demonstrated on sparing of photoreceptors with MP treatment. Conclusions. Treatment of laser-induced retinal injury with methylprednisolone (MP) exacerbates acute inflammation and long-term chorio-retinal scarring; however, hydroxyethyl starch conjugated deferoxamine therapy ameliorates these aspects of injury. Data suggest caution in the use of MP therapy for laser injuries.

  11. Retinal hemorrhagic lesions from femtosecond visible laser pulses

    NASA Astrophysics Data System (ADS)

    Stein, Cindy D.; Toth, Cynthia A.; Cain, Clarence P.; Noojin, Gary D.; Stolarski, David J.; Rockwell, Benjamin A.; Roach, William P.

    1994-08-01

    We present our clinical evaluation of hemorrhagic and non-hemorrhagic 90 fs single pulses in rabbits and primates. The rabbit and primate eye present unique in vivo models for evaluation of retinal and choroidal laser induced hemorrhages with distinct differences in their retinal anatomy. We found two different hemorrhagic events to occur in the posterior pole with delivery of 90 fs pulses. First, in the Dutch Belted rabbit, we found large amounts of energy per pulse (from 20 to 60 times ED50) were required for formation of subretinal hemorrhages. Second, in the Rhesus monkey, we found significant numbers of small intraretinal hemorrhages from relatively low energy 90 fs pulses. Both the Dutch Belted rabbit and the Rhesus monkey failed to consistently show subretinal hemorrhagic lesions form very high pulse energies. Our findings suggest more energy absorption at the level of the retinal circulation than the choroidal circulation with our pulse parameters. The effects of the laser on the retinal circulation may be due to the use of a wavelength of 580 nm. At this wavelength the oxyhemoglobin to melanin absorption ratio is nearly at its peak (approximately 0.40), perhaps allowing improved absorption in the retinal vasculature. One precaution with this finding, however, are the distinct differences between primate and non-primate ocular systems. Further studies are required to resolve the differences in damage at the level of the RPE and choroid between rabbits and primates.

  12. c-Met Modulates RPE Migratory Response to Laser-Induced Retinal Injury

    PubMed Central

    Lashkari, Kameran

    2012-01-01

    Retinal laser injuries are often associated with aberrant migration of the retinal pigment epithelium (RPE), which can cause expansion of the scar beyond the confines of the original laser burn. In this study, we devised a novel method of laser-induced injury to the RPE layer in mouse models and began to dissect the mechanisms associated with pathogenesis and progression of laser-induced RPE injury. We have hypothesized that the proto-oncogene receptor, c-Met, is intimately involved with migration of RPE cells, and may be an early responder to injury. Using transgenic mouse models, we show that constitutive activation of c-Met induces more robust RPE migration into the outer retina of laser-injured eyes, while abrogation of the receptor using a cre-lox method reduces these responses. We also demonstrate that retinal laser injury increases expression of both HGF and c-Met, and activation of c-Met after injury is correlated with RPE cell migration. RPE migration may be responsible for clinically significant anatomic changes observed after laser injury. Abrogation of c-Met activity may be a therapeutic target to minimize retinal damage from aberrant RPE cell migration. PMID:22808260

  13. Automated lesion detectors in retinal fundus images.

    PubMed

    Figueiredo, I N; Kumar, S; Oliveira, C M; Ramos, J D; Engquist, B

    2015-11-01

    Diabetic retinopathy (DR) is a sight-threatening condition occurring in persons with diabetes, which causes progressive damage to the retina. The early detection and diagnosis of DR is vital for saving the vision of diabetic persons. The early signs of DR which appear on the surface of the retina are the dark lesions such as microaneurysms (MAs) and hemorrhages (HEMs), and bright lesions (BLs) such as exudates. In this paper, we propose a novel automated system for the detection and diagnosis of these retinal lesions by processing retinal fundus images. We devise appropriate binary classifiers for these three different types of lesions. Some novel contextual/numerical features are derived, for each lesion type, depending on its inherent properties. This is performed by analysing several wavelet bands (resulting from the isotropic undecimated wavelet transform decomposition of the retinal image green channel) and by using an appropriate combination of Hessian multiscale analysis, variational segmentation and cartoon+texture decomposition. The proposed methodology has been validated on several medical datasets, with a total of 45,770 images, using standard performance measures such as sensitivity and specificity. The individual performance, per frame, of the MA detector is 93% sensitivity and 89% specificity, of the HEM detector is 86% sensitivity and 90% specificity, and of the BL detector is 90% sensitivity and 97% specificity. Regarding the collective performance of these binary detectors, as an automated screening system for DR (meaning that a patient is considered to have DR if it is a positive patient for at least one of the detectors) it achieves an average 95-100% of sensitivity and 70% of specificity at a per patient basis. Furthermore, evaluation conducted on publicly available datasets, for comparison with other existing techniques, shows the promising potential of the proposed detectors. PMID:26378502

  14. N-acetylcysteine and acute retinal laser lesions in the colubrid snake eye

    NASA Astrophysics Data System (ADS)

    Elliott, William R., III; Rentmeister-Bryant, Heike K.; Barsalou, Norman; Beer, Jeremy; Zwick, Harry

    2004-07-01

    This study examined the role of oxidative stress and the effect of a single dose treatment with N-Acetylcysteine (NAC) on the temporal development of acute laser-induced retinal injury. We used the snake eye/Scanning Laser Ophthalmoscope (SLO) model, an in vivo, non-invasive ocular imaging technique, which has the ability to image cellular retinal detail and allows for studying morphological changes of retinal injury over time. For this study 12 corn-snakes (Elaphe g. guttata) received 5 laser exposures per eye, followed by either a single dose of the antioxidant NAC (150mg/kg, IP in sterile saline) or placebo. Laser exposures were made with a Nd: VO4 DPSS, 532nm laser, coaxially aligned to the SLO. Shuttered pulses were 20msec x 50 mW; 1mJ each. Retinal images were taken using a Rodenstock cSLO and were digitally recorded at 1, 6, 24-hrs, and at 3-wks post-exposure. Lesions were assessed by two raters blind to the conditions of the study yielding measures of damaged area and counts of missing or damaged photoreceptors. Treated eyes showed a significant beneficial effect overall, and these results suggest that oxidative stress plays a role in laser-induced retinal injury. The use of NAC or a similar antioxidant shows promise as a therapeutic tool.

  15. Investigation of laser-induced retinal damage. Annual report, 1 Apr 91-31 Mar 92

    SciTech Connect

    Glickman, R.D.; Lam, K.W.

    1992-04-22

    Laser-induced, photooxidative damage in ocular tissue was studied with a quantitative assay using high performance liquid chromatography (HPLC) to separate oxidized and reduced ascorbic acid in exposed tissue components. We demonstrated that ascorbic acid, incubated with whole, bovine retinal pigment epithelial (RPE) cells, was oxidized when the reaction mixture was exposed to the output of an argon-ion continuous wave laser The amount of ascorbic acid oxidized was proportional to the irradiance of the sample, and the reaction was wavelength-dependent, with short-wavelength visible light more effective than long-wavelengths in driving the, reaction. The photosensitizing activity was associated with the RPE melanin pigment granules, and was not lost after disrupting or heating the RPE cells. Because melanin was known to form free radicals when illuminated, we hypothesized that ascorbic acid detoxified the light-activated melanin free radicals while being itself oxidized in process. If the supply of reduced ascorbic acid were exhausted, however, the activated melanin could have been the source of tissue-damaging radicals. This model was consistent with a photochemical damage mechanism involving light-activated melanin.

  16. Ex-plant retinal laser induced threshold studies in the millisecond time regime

    NASA Astrophysics Data System (ADS)

    Schulmeister, Karl; Husinsky, Johannes; Seiser, Bernhard; Edthofer, Florian; Tuschl, Helga; Lund, David J.

    2006-02-01

    Excised bovine retinas were used as model for threshold determination of laser induced thermal damage in the pulse regime of 1 ms to 655 ms for a range of laser spot size diameters. The thresholds as determined by fluorescence viability staining compare very well with the prediction of thermal damage models. Both models compare well with published and new Rhesus monkey threshold data. A distinctive dependence of the threshold on laser spot size diameter for different pulse duration was found which indicates that current (ICNIRP, ANSI and IEC) laser exposure limits for large spots can be increased in this pulse duration regime. A time dependent α max is proposed which only for the case of long exposure durations has the current value of 100 mrad, but decreases to smaller angles for short exposure durations, effectively increasing the permissible exposure level. An explanation based on intra-retinal scattering is offered for the unexpected spot size dependence for spot diameters less than about 80 µm. The time dependence and nature of damage is discussed for pulse durations shorter than 1 ms where bubble induced damage seems to lead to a threshold a factor of 10 lower than the thermally induced threshold, resulting in the need to lower the MPE values for this condition. Possible changes of the MPE values are offered and discussed.

  17. Laser-induced fluorescence spectroscopy of benign and malignant cutaneous lesions

    NASA Astrophysics Data System (ADS)

    Borisova, Ekaterina G.; Troyanova, P. P.; Stoyanova, V. P.; Avramov, Lachezar A.

    2005-04-01

    The goals of this work were investigation of pigmented skin lesions by the method of laser-induced fluorescence spectroscopy. Fluorescence spectra were obtained from malignant and benign skin lesions after excitation with nitrogen laser at 337 nm, namely: benign nevi, dysplastic nevi, malignant melanoma (MM), keratopapilloma, base-cell papilloma and base-cell carcinoma, as well as from healthy skin areas near to the lesion that were used posteriori to reveal changes between healthy and lesion skin spectra. Initially lesions were classified by ABCD-dermatscopic method. All suspicious lesions were excised and were investigated histologically. Spectrum of healthy skin consists of one main maximum at 470-500 nm spectral region and secondary maxima at in the regions round 400 and 440 nm. In the cases of nevi and melanoma significant decrease of fluorescence intensity, which correlated with the type of pigment lesion was observed. This reduction of the signal is related to the accumulation of melanin in the lesions that re-absorb strongly the fluorescence from native skin fluorophores in whole visible spectral region. In cases of papilloma and base-cell carcinoma an intensity decrease was also observed, related to accumulation of pigments in these cutaneous lesions. An relative increase of the fluorescence peak at 440 nm were registered in the case of base-cell carcinoma, and appearance of green fluorescence, related to increase of keratin content in benign papilloma lesions were detected. The results, obtained in this investigation of the different pigment lesions could be used for better comprehension of the skin optical properties. The fluorescence spectroscopy of the human skin are very prominent for early diagnosis and differentiation of cutaneous diseases and gives a wide range of possibilities related to real-time determination of existing pathological condition.

  18. Evaluation of retinal laser lesion healing by perimetric electroretinography

    NASA Astrophysics Data System (ADS)

    Schmeisser, Elmar T.

    1996-04-01

    Eight Cynomolgus fasciculata who had graded laser lesions placed in one eye 6 years previously were evaluated by a stimulation and electrophysiologic recording technique to produce maps of retinal function. All animal testing was performed under IACUC approved protocols. The single q-switched pulses from a neodymium-YAG laser produced lesions of 4 types: no visible change, minimal visible lesions, `white dot' lesions (localized circumscribed retinal blanching) and `red dot' lesions (contained retinal hemorrhage) in the eye at the time of placement. Single exposures had been made in four locations: 5 degrees superior, inferior and temporal to the fovea, and one foveally. The multifocal (perimetric) electroretinogram was recorded from specialized contact lenses through hospital grade amplifiers. Initial analyses gave field maps that demonstrated apparent relative loss of function in some lesion sites. However, these losses were variable and occasionally patchy (i.e. disconnected areas of low signal). Repeated examinations of the same retinal areas showed high variability, even with 15 minute acquisition times and no apparent gaze drift. Apparent losses did not appear to correlate with visible retinal changes at the lesion site. Further research is needed to determine the biological substrate for this variability in response topography.

  19. Elemental analysis of tissue pellets for the differentiation of epidermal lesion and normal skin by laser-induced breakdown spectroscopy.

    PubMed

    Moon, Youngmin; Han, Jung Hyun; Shin, Sungho; Kim, Yong-Chul; Jeong, Sungho

    2016-05-01

    By laser induced breakdown spectroscopy (LIBS) analysis of epidermal lesion and dermis tissue pellets of hairless mouse, it is shown that Ca intensity in the epidermal lesion is higher than that in dermis, whereas Na and K intensities have an opposite tendency. It is demonstrated that epidermal lesion and normal dermis can be differentiated with high selectivity either by univariate or multivariate analysis of LIBS spectra with an intensity ratio difference by factor of 8 or classification accuracy over 0.995, respectively. PMID:27231610

  20. Elemental analysis of tissue pellets for the differentiation of epidermal lesion and normal skin by laser-induced breakdown spectroscopy

    PubMed Central

    Moon, Youngmin; Han, Jung Hyun; Shin, Sungho; Kim, Yong-Chul; Jeong, Sungho

    2016-01-01

    By laser induced breakdown spectroscopy (LIBS) analysis of epidermal lesion and dermis tissue pellets of hairless mouse, it is shown that Ca intensity in the epidermal lesion is higher than that in dermis, whereas Na and K intensities have an opposite tendency. It is demonstrated that epidermal lesion and normal dermis can be differentiated with high selectivity either by univariate or multivariate analysis of LIBS spectra with an intensity ratio difference by factor of 8 or classification accuracy over 0.995, respectively. PMID:27231610

  1. Fundamental studies in the molecular basis of laser-induced retinal damage. Annual report, September 1981-August 1982

    SciTech Connect

    Lewis

    1982-09-01

    This research led to new insights in the fundamental mechanisms involved in laser induced retinal damage and some of the fundamental work on these mechanisms lead to new and exciting avenues in the development of rapidly adjustable molecular light filters with important new possibilities for pulsed-laser eye protection. This report summarizes the significant progress of the past year: (1) Development and Fundamental Mechanism of a Rapidly Adjustable Molecular Filter for Pulsed Laser Eye Protection - this research direction resulted from our investigations on cones of the red-eared swamp turtle, Pseudemys scripta elegans. (2) The Optical Density of Turtle Oil Droplet Solutions - it is important both from a practical and fundamental point of view to determine the optical density of turtle oil-droplet suspensions. In view of the high optical densities in this system, tunable-laser resonance Raman spectroscopy, which is the only technique that has been able to provide high-resolution data, is the only technique that is potentially able to obtain the information. (3) Laser-Induced Molecular Alterations in Turtle Retina. (4) Light Driven Enzymatic Reactions in Photoreceptors. (5) Molecular Cytology of Rod Outer Segments.

  2. Automated placement of retinal laser lesions in vivo

    NASA Astrophysics Data System (ADS)

    Barrett, Steven F.; Wright, Cameron H. G.; Jerath, Maya R.; Lewis, R. Stephen, II; Dillard, Bryan C.; Rylander, Henry G., III; Welch, Ashley J.

    1995-03-01

    Researchers at the University of Texas at Austin's Biomedical Engineering Laser Laboratory investigating the medical applications of lasers have worked toward the development of a retinal robotic laser system. The overall goal of the ongoing project is to precisely place and control the depth of laser lesions for the treatment of various retinal diseases such as diabetic retinopathy and retinal tears. Researchers at the USAF Academy's Department of Electrical Engineering and the Optical Radiation Division of Armstrong Laboratory have also become involved with this research due to similar related interests. Separate low speed prototype subsystems have been developed to control lesion depth using lesion reflectance feedback parameters and lesion placement using retinal vessels as tracking landmarks. Both subsystems have been successfully demonstrated in vivo on pigmented rabbits using an argon continuous wave laser. Work is ongoing to build a prototype system to simultaneously control lesion depth and placement. Following the dual-use concept, this system is being adapted for clinical use as a retinal treatment system as well as a research tool for military laser-tissue interaction studies. Specifically, the system is being adapted for use with an ultra-short pulse laser system at Armstrong Laboratory and Frank J. Seiler Research Laboratory to study the effects of ultra-short laser pulses on the human retina. The instrumentation aspects of the prototype subsystems were presented at SPIE Conference 1877 in January 1993. Since then our efforts have concentrated on combining the lesion depth control subsystem and the lesion placement subsystem into a single prototype capable of simultaneously controlling both parameters. We have designated this combined system CALOSOS for Computer Aided Laser Optics System for Ophthalmic Surgery. We have also investigated methods to improve system response time. Use of high speed nonstandard frame rate CCD cameras and high speed frame

  3. Laser-induced autofluorescence properties of base-cell lesions: analysis and algorithms for diagnosis and differentiation

    NASA Astrophysics Data System (ADS)

    Borisova, E.; Troyanova, P.; Avramov, L.

    2006-09-01

    The goals of this work were investigation of base-cell skin lesions by the method of laser-induced autofluorescence spectroscopy. Fluorescence spectra were obtained from benign base-cell papilloma and malignant base-cell carcinoma, as well as from healthy skin areas near to the lesions that were used posteriori to reveal changes between healthy and lesion skin spectra. Preliminarily lesions were classified by dermatoscopic method (MoleMax II, DERMA Instruments). All suspicious lesions were excised and were investigated histologically. The experimental set-up consists of a nitrogen laser (337 nm, 14 μJ, 10 Hz), lenses, filters, optical fibers, and a microspectrometer (PC2000, "Ocean Optics"). A computer controls this system. Spectrum of healthy skin consists of one main maximum at 470-500 nm spectral region and secondary maxima at in the regions around 400 and 440 nm. In cases of papilloma and base-cell carcinoma an intensity decrease was observed, related to accumulation of pigments in these cutaneous lesions. An relative increase of the fluorescence peak at 440 nm were registered in the case of base-cell carcinoma, related to metabolism activity increase, and appearance of green fluorescence, related to increase of keratin content in benign papilloma lesions were detected. The results, obtained were used to develop multispectral diagnostic algorithm of these base-cell lesions. An sensitivity of 89,4% and 91,0% and specificity of 99,6% and 97,4% for differentiation between normal skin and papilloma and carcinoma respectively were obtained. The capability of the human skin fluorescence spectroscopy for early diagnosis and differentiation of cutaneous lesions is shown.

  4. Evaluation of vernier acuity near healed retinal laser lesions

    NASA Astrophysics Data System (ADS)

    Schmeisser, Elmar T.

    1997-05-01

    Seven Cynomolgus fasciculata who had graded laser lesions placed in own eye 6 years previously were evaluated for their vernier acuity by electrophysiologic recording techniques. In these experiments, 95 percent contrast vernier acuity targets were presented at high luminance levels to anesthetized primates. Visual evoked potentials were recorded by conventional means form scalp electrodes through hospital grade amplifiers. All animal testing was performed under IACUC approved protocols. The single q-switched pulses form a neodymium-YAG laser had produced lesions of 4 types: no visible change, minimal visible lesions, 'white dot' lesions and 'red dot' lesions in the eye at the time of placement. Single exposures had been made in four locations: 5 degrees superior, inferior and temporal to the fovea, and one foveally. Vernier recording proved somewhat successful in smaller animals with less than contained retinal hemorrhage lesions in the fovea. Initial analyses demonstrated a significant decrease of the pattern response signal/noise in the experimental eye overall, and an apparent relative loss of vernier signal in some lesioned eyes. Animals with the more severe lesions have somewhat degraded small patten responses and no recordable vernier response. Apparent lesser losses produced less effect.

  5. Detection of colonic malignant lesions by digital imaging of UV laser-induced autofluorescence.

    PubMed

    Chwirot, B W; Michniewicz, Z; Kowalska, M; Nussbeutel, J

    1999-03-01

    The objective of our study was to investigate whether digital imaging of autofluorescence could be applied in the detection of colonic malignancies. Autofluorescence was excited with a 325 nm line from a He-Cd laser. Images were recorded in vitro in six spectral bands. The material for study was 50 resected specimens for which images of 64 areas were recorded. The main result is the observation that for a majority of malignant and premalignant lesions the intensity of autofluorescence was lower than for the corresponding normal mucosa in all of the spectral bands selected for imaging. The spectral bands centered around 440 nm and 475 nm seem to be most promising in terms of possible future clinical applications. PMID:10089825

  6. Discrimination of retinal images containing bright lesions using sparse coded features and SVM.

    PubMed

    Sidibé, Désiré; Sadek, Ibrahim; Mériaudeau, Fabrice

    2015-07-01

    Diabetic Retinopathy (DR) is a chronic progressive disease of the retinal microvasculature which is among the major causes of vision loss in the world. The diagnosis of DR is based on the detection of retinal lesions such as microaneurysms, exudates and drusen in retinal images acquired by a fundus camera. However, bright lesions such as exudates and drusen share similar appearances while being signs of different diseases. Therefore, discriminating between different types of lesions is of interest for improving screening performances. In this paper, we propose to use sparse coding techniques for retinal images classification. In particular, we are interested in discriminating between retinal images containing either exudates or drusen, and normal images free of lesions. Extensive experiments show that dictionary learning techniques can capture strong structures of retinal images and produce discriminant descriptors for classification. In particular, using a linear SVM with the obtained sparse coded features, the proposed method achieves superior performance as compared with the popular Bag-of-Visual-Word approach for image classification. Experiments with a dataset of 828 retinal images collected from various sources show that the proposed approach provides excellent discrimination results for normal, drusen and exudates images. It achieves a sensitivity and a specificity of 96.50% and 97.70% for the normal class; 99.10% and 100% for the drusen class; and 97.40% and 98.20% for the exudates class with a medium size dictionary of 100 atoms. PMID:25935125

  7. Fundamental studies in the molecular basis of laser-induced retinal damage. Annual report, February-September 1981

    SciTech Connect

    Lewis

    1981-09-01

    Laser-spectroscopy experiments have focused on cones in the red-eared swamp turtle, Pseudemys scripta elegans. Choice of this system was based on the desire to correlate molecular data with the extensive data being collected on this system by Dr. Zwick in his studies on laser hazards at LAIR. Thus, a detailed collaborative effort was initiated on this system during the past year. The experiments resulted in important information that opens new avenues to explore fundamental molecular mechanisms of retinal damage with laser irradiation. Results of these experiments are summarized in the following sections: I. Elucidation of the role of oil droplets in the absorption of light by the turtle retina; II. A Selective Probe of Membrane Potentials in Turtle Cone Cells; III. Angstrom Resolution Light Microscopy of Photoreceptor Cells; IV. Identification and Selective Staining of Other Important Molecular Components of Photoreceptor Cells.

  8. Non-invasive detection of laser-induced retinal injury through the vitreous using dynamic light scattering (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Ansari, Rafat R.; Naiman, Melissa; Bouhenni, Rachida; Dunmire, Jeffery; Liu, Ying; Rafiq, Qundeel; Edward, Deepak; Gothard, David

    2016-03-01

    Laser radiation entering the eye has the potential of damaging the retina. As an inflammatory response, the proteins can rush to the lesion site created by laser exposure. We explore the hypothesis if these proteins can be detected non-invasively. In this preliminary study, we developed a new brief-case size dynamic light scattering instrument to detect these proteins in-vivo in the rabbit vitreous. The results were validated with bio-chemical analysis.

  9. Significance of retinal laser lesion location and subretinal hemorrhage in bridging choroidal neovascular complexes

    NASA Astrophysics Data System (ADS)

    Schuschereba, Steven T.; Clarkson, Donna R.; Valo, Lynn M.; Brown, Jeremiah, Jr.; Stuck, Bruce E.

    2003-06-01

    Purpose: To determine funduscopic criteria that will help predict when bridging choroidal neovascular (CNV) complexes will develop after laser retinal trauma and to define early preventive treatment targets. Methods: Ten rhesus monkeys were used and retinal lesions were produced by Nd:YAG exposures (20ns, 1-2mJ, 1064nm, min. spot size) simulating human accidental laser trauma to the central fundus. Funduscopy and fluorescein/ICG angiography were conducted at day 1, 4, and 14, and at 2 and 4 months, and animals terminated for histologic evaluation. Predisposition for bridging fibrovascular complexes was evaluated for single lesions, two small lesions showing coalescing hemorrhages, and multiple lesions involved with large field subretinal and vitreous hemorrhages. Results: Elevated CNVs were present in all single lesions with confined subretinal hemorrhages. All lesion sets that showed initial and small coalescing subretinal hemorrhages formed bridging CNV scars. No bridging CNVs occurred in lesion sets involving a vitreous hemorrhage adjacent to a confined, but small subretinal hemorrhage. In large field subretinal hemorrhages involving multiple laser lesions, complex CNV formation occurred. Extensive secondary photoreceptor losses occurred in confined hemorrhage and CNV zones. Conclusion: Trauma presenting with evidence of coalescing and confined subretinal hemorrhages between two adjacent lesions has a high chance of forming choroidal neovascular bridge complexes between the involved lesions. CNV formation may be related to the long residence time, break down products, and clearance processes of extravasated blood. Removal of trapped blood and curtailing angiogenesis and cellular proliferation may be helpful treatment strategies.

  10. Optimization of an Image-Guided Laser-Induced Choroidal Neovascularization Model in Mice

    PubMed Central

    Sun, Ye; Fu, Zhongjie; Liu, Chi-Hsiu; Evans, Lucy; Tian, Katherine; Saba, Nicholas; Fredrick, Thomas; Morss, Peyton; Chen, Jing; Smith, Lois E. H.

    2015-01-01

    The mouse model of laser-induced choroidal neovascularization (CNV) has been used in studies of the exudative form of age-related macular degeneration using both the conventional slit lamp and a new image-guided laser system. A standardized protocol is needed for consistent results using this model, which has been lacking. We optimized details of laser-induced CNV using the image-guided laser photocoagulation system. Four lesions with similar size were consistently applied per eye at approximately double the disc diameter away from the optic nerve, using different laser power levels, and mice of various ages and genders. After 7 days, the mice were sacrificed and retinal pigment epithelium/choroid/sclera was flat-mounted, stained with Isolectin B4, and imaged. Quantification of the area of the laser-induced lesions was performed using an established and constant threshold. Exclusion criteria are described that were necessary for reliable data analysis of the laser-induced CNV lesions. The CNV lesion area was proportional to the laser power levels. Mice at 12-16 weeks of age developed more severe CNV than those at 6-8 weeks of age, and the gender difference was only significant in mice at 12-16 weeks of age, but not in those at 6-8 weeks of age. Dietary intake of omega-3 long-chain polyunsaturated fatty acid reduced laser-induced CNV in mice. Taken together, laser-induced CNV lesions can be easily and consistently applied using the image-guided laser platform. Mice at 6-8 weeks of age are ideal for the laser-induced CNV model. PMID:26161975

  11. Probing the immune and healing response of murine intestinal mucosa by time-lapse 2-photon microscopy of laser-induced lesions with real-time dosimetry

    PubMed Central

    Orzekowsky-Schroeder, Regina; Klinger, Antje; Freidank, Sebastian; Linz, Norbert; Eckert, Sebastian; Hüttmann, Gereon; Gebert, Andreas; Vogel, Alfred

    2014-01-01

    Gut mucosa is an important interface between body and environment. Immune response and healing processes of murine small intestinal mucosa were investigated by intravital time-lapse two-photon excited autofluorescence microscopy of the response to localized laser-induced damage. Epithelial lesions were created by 355-nm, 500-ps pulses from a microchip laser that produced minute cavitation bubbles. Size and dynamics of these bubbles were monitored using a novel interferometric backscattering technique with 80 nm resolution. Small bubbles (< 2.5 µm maximum radius) merely resulted in autofluorescence loss of the target cell. Larger bubbles (7-25 µm) affected several cells and provoked immigration of immune cells (polymorphonuclear leucocytes). Damaged cells were expelled into the lumen, and the epithelium healed within 2 hours by stretching and migration of adjacent epithelial cells. PMID:25360369

  12. Discrimination of human coronary artery atherosclerotic lipid-rich lesions by time-resolved laser-induced fluorescence spectroscopy.

    PubMed

    Marcu, L; Fishbein, M C; Maarek, J M; Grundfest, W S

    2001-07-01

    Lesion composition plays a significant role in atherosclerotic lesion instability and rupture. Current clinical techniques cannot fully characterize lesion composition or accurately identify unstable lesions. This study investigates the use of time-resolved fluorescence spectroscopy for unstable atherosclerotic lesion diagnosis. The fluorescence of human coronary artery samples was induced with nitrogen laser and detected in the 360- to 510-nm wavelength range. The samples were sorted into 7 groups according to the AHA classification: normal wall and types I, II(a) (fatty streaks), III (preatheroma), IV (atheroma), V(a) (fibrous), and V(b) (calcified) lesions. Spectral intensities and time-dependent parameters [average lifetime tau(f); decay constants: tau(1) (fast-term), tau(2) (slow-term), A(1) (fast-term amplitude contribution)] derived from the time-resolved spectra of coronary samples were used for tissue characterization. We determined that a few intensity values at longer wavelengths (>430 nm) and time-dependent parameters at peak emission region (390 nm) discriminate between all types of arterial samples except between normal wall and type I lesions. The lipid-rich lesions (more unstable) can be discriminated from fibrous lesions (more stable) on the basis of time-dependent parameters (lifetime and fast-term decay). We inferred that features of lipid fluorescence are reflected on lipid-rich lesion emission. Our results demonstrate that analysis of the time-resolved spectra may be used to enhance the discrimination between different grades of atherosclerotic lesions and provide a means of discrimination between lipid-rich and fibrous lesions. PMID:11451759

  13. Temperature-Controlled Retinal Photocoagulation Reliably Generates Uniform Subvisible, Mild, or Moderate Lesions

    PubMed Central

    Koinzer, Stefan; Baade, Alexander; Schlott, Kerstin; Hesse, Carola; Caliebe, Amke; Roider, Johann; Brinkmann, Ralf

    2015-01-01

    Purpose Conventional retinal photocoagulation produces irregular lesions and does not allow reliable control of ophthalmoscopically invisible lesions. We applied automatically controlled retinal photocoagulation, which allows to apply uniform lesions without titration, and aimed at five different predictable lesion intensities in a study on rabbit eyes. Methods A conventional 532-nm photocoagulation laser was used in combination with a pulsed probe laser. They facilitated real-time fundus temperature measurements and automatic exposure time control for different predefined time/temperature dependent characteristics (TTC). We applied 225 control lesions (exposure time 200 ms) and 794 TTC lesions (5 intensities, exposure times 7–800 ms) in six rabbit eyes with variable laser power (20–66.4 mW). Starting after 2 hours, we examined fundus color and optical coherence tomographic (OCT) images over 3 months and classified lesion morphologies according to a seven-stage OCT classifier. Results Visibility rates in funduscopy (OCT) after 2 hours were 17% (68%) for TTC intensity group 1, 38% (90%) for TTC group 2 and greater than 94% (>98%) for all consecutive groups. TTC groups 1 through 4 correlated to increasing morphological lesion intensities and increasing median funduscopic and OCT diameters. Group 5 lesions were as large as, but more intense than group 4 lesions. Conclusions Automatic, temperature controlled photocoagulation allows to apply predictable subvisible, mild, or moderate lesions without manual power titration. Translational Relevance The technique will facilitate standardized, automatically controlled low and early treatment of diabetic retinopathy study (ETDRS) intensity photocoagulation independently of the treating physician, the treated eye and lesion location. PMID:26473086

  14. Spatial and temporal vision of macaques after central retinal lesions

    SciTech Connect

    Merigan, W.H.; Pasternak, T.; Zehl, D.

    1981-07-01

    Spatial contrast and temporal modulation sensitivity of two macaque monkeys were measured at three luminance levels before and after binocular laser coagulation of the fovea. The radius of the lesions ranged from 1.6 to 2.2 degree from the center of the fovea. After placement of the lesions, the visibility of high spatial frequencies was greatly reduced, although sensitivity at middle and low spatial frequencies was unaffected. No loss of spatial resolution was found at the lowest luminance tested. When temporal modulation sensitivity was tested with 4 deg targets, foveal lesions had no effect at any temporal frequency or luminance. However, with a 0.57 degree target, sensitivity to lower temporal frequencies was impaired. Thus visual loss after destruction of the fovea is limited to high luminance, small targets, and the resolution of fine detail.

  15. Retinal spot size with wavelength

    NASA Astrophysics Data System (ADS)

    Rockwell, Benjamin A.; Hammer, Daniel X.; Kennedy, Paul K.; Amnotte, Rodney E.; Eilert, Brent; Druessel, Jeffrey J.; Payne, Dale J.; Phillips, Shana L.; Stolarski, David J.; Noojin, Gary D.; Thomas, Robert J.; Cain, Clarence P.

    1997-06-01

    We have made an indirect in-vivo determination of spot size focusing in the rhesus monkey model. Measurement of the laser induced breakdown threshold both in-vitro and in-vivo allow correlation and assignment of a spot size after focusing through the living eye. We discuss and analyze the results and show how trends in minimum visible lesion data should be assessed in light of chromatic aberration. National laser safety standards are based on minimal visual lesion (MVL) threshold studies in different animal models. The energy required for a retinal lesion depends upon may parameters including wavelength and retinal spot size. We attempt to explain trends in reported MVL threshold studies using a model of the eye which allows calculation of changes in retinal spot size due to chromatic aberration.

  16. Homonymous Ganglion Cell Layer Thinning After Isolated Occipital Lesion: Macular OCT Demonstrates Transsynaptic Retrograde Retinal Degeneration.

    PubMed

    Meier, Paolo G; Maeder, Philippe; Kardon, Randy H; Borruat, François-Xavier

    2015-06-01

    A 48-year-old man was examined 24 months after medial and surgical treatment of an isolated well-circumscribed right occipital lobe abscess. An asymptomatic residual left homonymous inferior scotoma was present. Fundus examination revealed temporal pallor of both optic discs, and optical coherence tomography (OCT) revealed mild temporal loss of retinal nerve fiber layer in both eyes. No relative afferent pupillary defect was present. Assessment of the retinal ganglion cell layer demonstrated homonymous thinning in a pattern corresponding to the homonymous visual field loss. There were no abnormalities of the lateral geniculate nuclei or optic tracts on review of the initial brain computed tomography and follow-up magnetic resonance imaging. We believe our patient showed evidence of transsynaptic retrograde degeneration after an isolated right occipital lobe lesion, and the homonymous neuronal loss was detected on OCT by assessing the retinal ganglion cell layer. PMID:25285723

  17. Measurement of Tension Release During Laser Induced Axon Lesion to Evaluate Axonal Adhesion to the Substrate at Piconewton and Millisecond Resolution

    PubMed Central

    Vassalli, Massimo; Basso, Michele; Difato, Francesco

    2013-01-01

    The formation of functional connections in a developing neuronal network is influenced by extrinsic cues. The neurite growth of developing neurons is subject to chemical and mechanical signals, and the mechanisms by which it senses and responds to mechanical signals are poorly understood. Elucidating the role of forces in cell maturation will enable the design of scaffolds that can promote cell adhesion and cytoskeletal coupling to the substrate, and therefore improve the capacity of different neuronal types to regenerate after injury. Here, we describe a method to apply simultaneous force spectroscopy measurements during laser induced cell lesion. We measure tension release in the partially lesioned axon by simultaneous interferometric tracking of an optically trapped probe adhered to the membrane of the axon. Our experimental protocol detects the tension release with piconewton sensitivity, and the dynamic of the tension release at millisecond time resolution. Therefore, it offers a high-resolution method to study how the mechanical coupling between cells and substrates can be modulated by pharmacological treatment and/or by distinct mechanical properties of the substrate. PMID:23748878

  18. Minimum visible retinal lesions from pico- and femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Roach, William P.; Toth, Cynthia A.; Stein, Cindy D.; Noojin, Gary D.; Stolarski, David J.; Cain, Clarence P.

    1994-08-01

    Threshold measurements for Minimum Visible Lesions (MVL) at the retina are reported for femtosecond (fs) and picosecond (ps) laser pulses in Rhesus monkey eyes using visible wavelengths. The 50% probability for damage (ED50) dosages are calculated for 1 hour and 24 hour post-exposures at the 95% confidence level. The ED50 values are found to decrease with pulsewidth down to 600 fs. At 90 fs the ED50 dosages were noted to increase slightly when compared with the 3 ps and 600 fs values. Fluorescein angiography (FA) was accomplished at both 1 hour and 24 hour post-exposure and did not demonstrate lower threshold for damage, which has been the case for MVL's created with longer pulse durations (>= nanoseconds). At the 90 fs pulse duration, MVLs were not observed below 0.1 (mu) J. At energies greater than 0.1 (mu) J, both MVL and the absence of MVL's were observed up to 1.4 (mu) J. Above 1.4 (mu) J all energies delivered showed MVL development. Out of 138 data points taken at 90 fs, 94 were between 0.1 and 14 (mu) J, and the observed lesions are distributed with approximately 50% probability throughout this energy rate.

  19. Homonymous Hemianopic Hyporeflective Retinal Abnormality on Infrared Confocal Scanning Laser Photography: A Novel Sign of Optic Tract Lesion.

    PubMed

    Monteiro, Mario L R; Araújo, Rafael B; Suzuki, Ana C F; Cunha, Leonardo P; Preti, Rony C

    2016-03-01

    Infrared confocal scanning laser photography of a patient with long-standing optic tract lesion revealed a homonymous hemianopic hyporeflective image contralateral to the visual field defect. Spectral domain optical coherence tomography showed thinning of the retinal nerve fiber and retinal ganglion cell layer and thickening of the inner nuclear layer (with microcystic degeneration) in the macular area, matching the infrared image. Hyporeflective image on infrared laser photography is associated with retinal degeneration secondary to anterior visual pathway disease and, when located in homonymous hemianopic retinas, may represent a new sign of an optic tract lesion. PMID:26172159

  20. Association of reduced Connexin 43 expression with retinal vascular lesions in human diabetic retinopathy.

    PubMed

    Tien, Thomas; Muto, Tetsuya; Zhang, Joyce; Sohn, Elliott H; Mullins, Robert F; Roy, Sayon

    2016-05-01

    Connexin 43 (Cx43) downregulation promotes apoptosis in retinal vascular cells of diabetic animal models; however, its relevance to human diabetic retinopathy has not been established. In this study, we investigated whether diabetes alters Cx43 expression and promotes retinal vascular lesions in human retinas. Diabetic human eyes (aged 64-94 years) and non-diabetic human eyes (aged 61-90 years) were analyzed in this study. Retinal protein samples and retinal capillary networks were assessed for Cx43 level by Western blot (WB) analysis and immunostaining. In parallel, retinal capillary networks were stained with hematoxylin and periodic acid Schiff to determine the extent of pericyte loss (PL) and acellular capillaries (AC) in these retinas. Cx43 protein expression was significantly reduced in the diabetic retinas compared to non-diabetic retinas as indicated by WB analysis (81 ± 11% of control). Additionally, a significant decrease in the number of Cx43 plaques per unit length of vessel was observed in the diabetic retinas compared to those of non-diabetic retinas (62 ± 10% of control; p < 0.005). Importantly, a strong inverse relationship was noted between Cx43 expression and the relative number of AC (r = -0.89; p < 0.0005), and between Cx43 expression and number of pericyte loss (r = -0.88; p < 0.0005). Overall, these results show that Cx43 expression is reduced in the human diabetic retinas and Cx43 reduction is associated with increased vascular cell death. These findings suggest that diabetes decreases retinal Cx43 expression and that the development of PL and AC is associated with reduced Cx43 expression in human diabetic retinopathy. PMID:26738943

  1. Segmentation and classification of bright lesions to diagnose diabetic retinopathy in retinal images.

    PubMed

    Santhi, D; Manimegalai, D; Parvathi, S; Karkuzhali, S

    2016-08-01

    In view of predicting bright lesions such as hard exudates, cotton wool spots, and drusen in retinal images, three different segmentation techniques have been proposed and their effectiveness is compared with existing segmentation techniques. The benchmark images with annotations present in the structured analysis of the retina (STARE) database is considered for testing the proposed techniques. The proposed segmentation techniques such as region growing (RG), region growing with background correction (RGWBC), and adaptive region growing with background correction (ARGWBC) have been used, and the effectiveness of the algorithms is compared with existing fuzzy-based techniques. Images of eight categories of various annotations and 10 images in each category have been used to test the consistency of the proposed algorithms. Among the proposed techniques, ARGWBC has been identified to be the best method for segmenting the bright lesions based on its sensitivity, specificity, and accuracy. Fifteen different features are extracted from retinal images for the purpose of identification and classification of bright lesions. Feedforward backpropagation neural network (FFBPNN) and pattern recognition neural network (PRNN) are used for the classification of normal/abnormal images. Probabilistic neural network (PNN), radial basis exact fit (RBE), radial basis fewer neurons (RB), and FFBPNN are used for further bright lesion classification and achieve 100% accuracy. PMID:27060730

  2. Detection and classification of retinal lesions for grading of diabetic retinopathy.

    PubMed

    Usman Akram, M; Khalid, Shehzad; Tariq, Anam; Khan, Shoab A; Azam, Farooque

    2014-02-01

    Diabetic Retinopathy (DR) is an eye abnormality in which the human retina is affected due to an increasing amount of insulin in blood. The early detection and diagnosis of DR is vital to save the vision of diabetes patients. The early signs of DR which appear on the surface of the retina are microaneurysms, haemorrhages, and exudates. In this paper, we propose a system consisting of a novel hybrid classifier for the detection of retinal lesions. The proposed system consists of preprocessing, extraction of candidate lesions, feature set formulation, and classification. In preprocessing, the system eliminates background pixels and extracts the blood vessels and optic disc from the digital retinal image. The candidate lesion detection phase extracts, using filter banks, all regions which may possibly have any type of lesion. A feature set based on different descriptors, such as shape, intensity, and statistics, is formulated for each possible candidate region: this further helps in classifying that region. This paper presents an extension of the m-Mediods based modeling approach, and combines it with a Gaussian Mixture Model in an ensemble to form a hybrid classifier to improve the accuracy of the classification. The proposed system is assessed using standard fundus image databases with the help of performance parameters, such as, sensitivity, specificity, accuracy, and the Receiver Operating Characteristics curves for statistical analysis. PMID:24480176

  3. Recovery from retinal lesions: molecular plasticity mechanisms in visual cortex far beyond the deprived zone.

    PubMed

    Hu, Tjing-Tjing; Van den Bergh, Gert; Thorrez, Lieven; Heylen, Kevin; Eysel, Ulf T; Arckens, Lutgarde

    2011-12-01

    In cats with central retinal lesions, deprivation of the lesion projection zone (LPZ) in primary visual cortex (area 17) induces remapping of the cortical topography. Recovery of visually driven cortical activity in the LPZ involves distinct changes in protein expression. Recent observations, about molecular activity changes throughout area 17, challenge the view that its remote nondeprived parts would not be involved in this recovery process. We here investigated the dynamics of the protein expression pattern of remote nondeprived area 17 triggered by central retinal lesions to explore to what extent far peripheral area 17 would contribute to the topographic map reorganization inside the visual cortex. Using functional proteomics, we identified 40 proteins specifically differentially expressed between far peripheral area 17 of control and experimental animals 14 days to 8 months postlesion. Our results demonstrate that far peripheral area 17 is implicated in the functional adaptation to the visual deprivation, involving a meshwork of interacting proteins, operating in diverse pathways. In particular, endocytosis/exocytosis processes appeared to be essential via their intimate correlation with long-term potentiation and neurite outgrowth mechanisms. PMID:21571696

  4. Bright Retinal Lesions Detection using Colour Fundus Images Containing Reflective Features

    SciTech Connect

    Giancardo, Luca; Karnowski, Thomas Paul; Chaum, Edward; Meriaudeau, Fabrice; Tobin Jr, Kenneth William; Li, Yaquin

    2009-01-01

    In the last years the research community has developed many techniques to detect and diagnose diabetic retinopathy with retinal fundus images. This is a necessary step for the implementation of a large scale screening effort in rural areas where ophthalmologists are not available. In the United States of America, the incidence of diabetes is worryingly increasing among the young population. Retina fundus images of patients younger than 20 years old present a high amount of reflection due to the Nerve Fibre Layer (NFL), the younger the patient the more these reflections are visible. To our knowledge we are not aware of algorithms able to explicitly deal with this type of reflection artefact. This paper presents a technique to detect bright lesions also in patients with a high degree of reflective NFL. First, the candidate bright lesions are detected using image equalization and relatively simple histogram analysis. Then, a classifier is trained using texture descriptor (Multi-scale Local Binary Patterns) and other features in order to remove the false positives in the lesion detection. Finally, the area of the lesions is used to diagnose diabetic retinopathy. Our database consists of 33 images from a telemedicine network currently developed. When determining moderate to high diabetic retinopathy using the bright lesions detected the algorithm achieves a sensitivity of 100% at a specificity of 100% using hold-one-out testing.

  5. Red lesion detection using background estimation and lesions characteristics in diabetic retinal image

    NASA Astrophysics Data System (ADS)

    Zhang, Dongbo; Peng, Yinghui; Yi, Yao; Shang, Xingyu

    2013-10-01

    Detection of red lesions [hemorrhages (HRs) and microaneurysms (MAs)] is crucial for the diagnosis of early diabetic retinopathy. A method based on background estimation and adapted to specific characteristics of HRs and MAs is proposed. Candidate red lesions are located by background estimation and Mahalanobis distance measure and then some adaptive postprocessing techniques, which include vessel detection, nonvessel exclusion based on shape analysis, and noise points exclusion by double-ring filter (only used for MAs detection), are conducted to remove nonlesion pixels. The method is evaluated on our collected image dataset, and experimental results show that it is better than or approximate to other previous approaches. It is effective to reduce the false-positive and false-negative results that arise from incomplete and inaccurate vessel structure.

  6. Deficiency in the metabolite receptor SUCNR1 (GPR91) leads to outer retinal lesions

    PubMed Central

    Lapalme, Eric; Leboeuf, Dominique; Carbadillo, Jose; Rubic, Tina; Picard, Emilie; Mawambo, Gaelle; Tetreault, Nicolas; Joyal, Jean-Sebastien; Chemtob, Sylvain; Sennlaub, Florian; SanGiovanni, John Paul; Guimond, Martin; Sapieha, Przemyslaw

    2013-01-01

    Age-related macular degeneration (AMD) is a prominent cause of blindness in the Western world. To date, its molecular pathogenesis as well as the sequence of events leading to retinal degeneration remain largely ill-defined. While the invasion of choroidal neovasculature in the retina is the primary mechanism that precipitates loss of sight, an earlier dry form may accompany it. Here we provide the first evidence for the protective role of the Retinal Pigment Epithelium (RPE)-resident metabolite receptor, succinate receptor 1 (SUCNR1; G-Protein coupled Receptor-91 (GPR91), in preventing dry AMD-like lesions of the outer retina. Genetic analysis of 925 patients with geographic atrophy and 1199 AMD-free peers revealed an increased risk of developing geographic atrophy associated with intronic variants in the SUCNR1 gene. In mice, outer retinal expression of SUCNR1 is observed in the RPE as well as microglial cells and decreases progressively with age. Accordingly, Sucnr1−/− mice show signs of premature sub-retinal dystrophy with accumulation of oxidized-LDL, abnormal thickening of Bruch's membrane and a buildup of subretinal microglia. The accumulation of microglia in Sucnr1-deficient mice is likely triggered by the inefficient clearance of oxidized lipids by the RPE as bone marrow transfer of wild-type microglia into Sucnr1−/− mice did not salvage the patho-phenotype and systemic lipolysis was equivalent between wild-type and control mice. Our findings suggest that deficiency in SUCNR1 is a possible contributing factor to the pathogenesis of dry AMD and thus broaden our understanding of this clinically unmet need. PMID:23833031

  7. Advancing bag-of-visual-words representations for lesion classification in retinal images.

    PubMed

    Pires, Ramon; Jelinek, Herbert F; Wainer, Jacques; Valle, Eduardo; Rocha, Anderson

    2014-01-01

    Diabetic Retinopathy (DR) is a complication of diabetes that can lead to blindness if not readily discovered. Automated screening algorithms have the potential to improve identification of patients who need further medical attention. However, the identification of lesions must be accurate to be useful for clinical application. The bag-of-visual-words (BoVW) algorithm employs a maximum-margin classifier in a flexible framework that is able to detect the most common DR-related lesions such as microaneurysms, cotton-wool spots and hard exudates. BoVW allows to bypass the need for pre- and post-processing of the retinographic images, as well as the need of specific ad hoc techniques for identification of each type of lesion. An extensive evaluation of the BoVW model, using three large retinograph datasets (DR1, DR2 and Messidor) with different resolution and collected by different healthcare personnel, was performed. The results demonstrate that the BoVW classification approach can identify different lesions within an image without having to utilize different algorithms for each lesion reducing processing time and providing a more flexible diagnostic system. Our BoVW scheme is based on sparse low-level feature detection with a Speeded-Up Robust Features (SURF) local descriptor, and mid-level features based on semi-soft coding with max pooling. The best BoVW representation for retinal image classification was an area under the receiver operating characteristic curve (AUC-ROC) of 97.8% (exudates) and 93.5% (red lesions), applying a cross-dataset validation protocol. To assess the accuracy for detecting cases that require referral within one year, the sparse extraction technique associated with semi-soft coding and max pooling obtained an AUC of 94.2 ± 2.0%, outperforming current methods. Those results indicate that, for retinal image classification tasks in clinical practice, BoVW is equal and, in some instances, surpasses results obtained using dense detection (widely

  8. Fundamental studies in the molecular basis of laser-induced retinal damage. Annual report, 1 May 1985-30 April 1986

    SciTech Connect

    Lewis, A.

    1986-12-31

    Progress on the fundamental effects of femtosecond laser pulses with retinal pigments, new insights into the detailed interactions of light with photoreceptor cells, and tremendous advances in new forms of super-resolution microscopy are discussed. The common Nd:YAG laser pumping a dye laser is used.

  9. Protective effect of basic fibroblast growth factor on retinal injury induced by argon laser photocoagulation

    NASA Astrophysics Data System (ADS)

    Chen, P.; Zhang, C. P.; San, Q.; Wang, C. Z.; Yang, Z. F.; Kang, H. X.; Qian, H. W.

    2010-12-01

    Laser photocoagulation treatment is often complicated by a side effect of visual impairment, which is caused by the unavoidable laser-induced retinal destruction. At present no specific is found to cure this retinopathy. The aim of this study was to observe the neuroprotective effect of bFGF on laser-induced retinal injury. Chinchilla rabbits were divided into three groups and argon laser lesions were created in the retinas. Then bFGF or dexamethasone, a widely used ophthalmic preparation, or saline was given severally by retrobulbar injection. The retinal lesions were evaluated histologically and morphometrically, and visual function was examined by ERG. The results showed that bFGF administration better preserved morphology of retinal photoreceptors and significantly diminished the area of the lesions. Furthermore, bFGF promoted the restoration of the ERG b-wave amplitude. In rabbits treated with dexamethasone, however, the lesions showed almost no ameliorative changes. This is the first study to investigate the potential role of bFGF as a remedial agent in laser photocoagulation treatment. These findings suggest that bFGF has significant neuroprotective properties in the retina and this type of neuroprotection may be of clinical significance in reducing iatrogenic laser-induced retinal injuries in humans.

  10. Visible-lesion threshold dependency on retinal spot size for ultrashort laser pulses in the near infrared

    NASA Astrophysics Data System (ADS)

    Cain, Clarence P.; Toth, Cynthia A.; Noojin, Gary D.; Stolarski, David J.; Payne, Dale J.; Rockwell, Benjamin A.

    1998-05-01

    Single pulses in the near-infrared (1060 nanometers) were used to measure retinal spot size dependence of minimum visible lesion (MVL) thresholds in rhesus monkey eyes at a pulsewidth of 150 femtoseconds. We report the MVL thresholds determined at 1 hour and 24 hours post exposure which were obtained with 2 different lenses placed in front of the eye to vary the retinal spot size. Also we report the fluorescein angiography thresholds (FAVL) for the above measurements. These new data points will be added to the databank for Retinal Maximum Permissible Exposure (MPE) as a function of spot size for this pulsewidth and a comparison will be made with previous spot size dependency studies. Our measurements show that the retinal ED50 threshold fluence decreases for increasing retinal spot sizes. The fluence at the MVL threshold decreased by a factor of 3 for an increase in retinal image diameter by a factor of 4.5 times from the smallest to largest spot size.

  11. Quantification of Early Stages of Cortical Reorganization of the Topographic Map of V1 Following Retinal Lesions in Monkeys

    PubMed Central

    Botelho, Eliã P.; Ceriatte, Cecília; Soares, Juliana G.M.; Gattass, Ricardo; Fiorani, Mario

    2014-01-01

    We quantified the capacity for reorganization of the topographic representation of area V1 in adult monkeys. Bias-free automated mapping methods were used to delineate receptive fields (RFs) of an array of neuronal clusters prior to, and up to 6 h following retinal lesions. Monocular lesions caused a significant reorganization of the topographic map in this area, both inside and outside the cortical lesion projection zone (LPZ). Small flashed stimuli revealed responses up to 0.85 mm inside the boundaries of the LPZ, with RFs representing regions of undamaged retina immediately surrounding the lesion. In contrast, long moving bars that spanned the scotoma resulting from the lesion revealed responsive units up to 1.87 mm inside the LPZ, with RFs representing interpolated responses in this region. This reorganization is present immediately after monocular retinal lesioning. Both stimuli showed a similar and significant (5-fold) increase of the RF scatter in the LPZ, 0.56 mm (median), compared with the undamaged retina, 0.12 mm. Our results reveal an array of preexisting subthreshold functional connections of up to 2 mm in V1, which can be rapidly mobilized independently from the differential qualitative reorganization elicited by each stimulus. PMID:23010747

  12. Choroidal abnormalities and masquerade syndromes confounding the diagnosis of laser-induced eye injuries

    NASA Astrophysics Data System (ADS)

    Hacker, Henry D.; Zwick, Harry; Brown, Jeremiah, Jr.; Dicks, Ronald; Cheramie, Rachel; Stuck, Bruce E.

    2005-04-01

    The diagnosis of a laser-induced eye injury occurring in occupational or military environments is often complicated by confounding symptoms, the possibility of pre-existing pathology, and/or a lack of visual deficits that can be clearly associated with a specific incident. Two recent cases are described that illustrate the importance of a thorough differential diagnosis when coexisting retinal pathologies are present with potentially different (e.g. laser or disease) etiologies. Indocyanine green angiography (ICG) and ocular coherence tomography (OCT) used in combination with standard ophthalmic imaging can provide helpful insights as to the etiology of these lesions. Vascular choroidal abnormalities such as hemangiomas or occult histoplasmosis infection can produce findings that can mimic the leakage that may be evident from neovascular membranes associated with laser injury. Further evaluation with OCT and conventional fluorescein angiography (FA) is helpful to look for the classic signature of retinal disruption and retinal pigment layer changes that are often present in association with laser injury. Furthermore, a careful situational assessment of a potential laser exposure is important to confirm the diagnosis of laser-induced eye injury.

  13. In vivo laser-induced breakdown in the rabbit eye

    NASA Astrophysics Data System (ADS)

    Cain, Clarence P.; DiCarlo, Cheryl D.; Kennedy, Paul K.; Noojin, Gary D.; Amnotte, Rodney E.; Roach, William P.

    1995-05-01

    Threshold measurements for femtosecond laser pulsewidths have been made for retinal minimum visible lesions (MVLs) in Dutch Belted rabbit and rhesus monkey eyes. Laser-induced breakdown (LIB) thresholds in biological materials including vitreous, normal saline, tap water, and ultrapure water have been measured and reported using an artificial eye. We have recorded on video the first LIB causing bubble formation in any eye in vivo using albino rabbit eyes (New Zealand white) with 120- femtosecond (fs) pulses and pulse energies as low as 5 microjoules ((mu) J). These bubbles were clearly formed anterior to the retina within the vitreous humor and, with 60 (mu) J of energy, they lasted for several seconds before disappearing and leaving no apparent damage to the retina. We believe this to be true LIB because of the lack of pigmentation or melanin granules within the albino rabbit eye (thus no absorptive elements) and because of the extremely high peak powers within the 5-(mu) J, 120-fs laser pulse. These high peak powers produce self-focusing of the pulse within the vitreous. The bubble formation at the breakdown site acts as a limiting mechanism for energy transmission and may explain why high-energy femotsecond pulses at energies up to 100 (mu) J sometimes do not cause severe damage in the pigmented rabbit eye. This fact may also explain why it is so difficult to produce hemorrhagic lesions in either the rabbit or primate eye with 100-fs laser pulses.

  14. Patients with diffuse uveitis and inactive toxoplasmic retinitis lesions test PCR positive for Toxoplasma gondii in their vitreous and blood

    PubMed Central

    Novais, Eduardo A; Commodaro, Alessandra G; Santos, Fábio; Muccioli, Cristina; Maia, André; Nascimento, Heloisa; Moeller, Cecilia T A; Rizzo, Luiz V; Grigg, Michael E; Belfort, Rubens

    2016-01-01

    Background/aims To determine if patients with inactive chorioretinitis lesions who experience chronic toxoplasmic uveitis test PCR positive for Toxoplasma in their ocular fluids. Methods Two patients undergoing long-term anti-toxoplasmic treatment developed chronic uveitis and vitritis. They underwent therapeutic and diagnostic pars plana vitrectomy. Patient specimens were tested for toxoplasmosis by real-time PCR and nested PCR. Patient specimens were also tested for the presence of Toxoplasma antibodies that recognise allelic peptide motifs to determine parasite serotype. Results Patients tested positive for Toxoplasma by real-time PCR at the B1 gene in the vitreous and aqueous humours of patient 1, but only the vitreous of patient 2. Patients were not parasitemic by real-time PCR in plasma and blood. During surgery, only old hyperpigmented toxoplasmic scars were observed; there was no sign of active retinitis. Multilocus PCR–DNA sequence genotyping at B1, NTS2 and SAG1 loci established that two different non-archetypal Toxoplasma strains had infected patients 1 and 2. A peptide-based serotyping ELISA confirmed the molecular findings. Conclusions No active lesions were observed, but both patients possessed sufficient parasite DNA in their vitreous to permit genotyping. Several hypotheses to explain the persistence of the vitritis and anterior uveitis in the absence of active retinitis are discussed. PMID:24518074

  15. Detection of retinal lesions in diabetic retinopathy: comparative evaluation of 7-field digital color photography versus red-free photography.

    PubMed

    Venkatesh, Pradeep; Sharma, Reetika; Vashist, Nagender; Vohra, Rajpal; Garg, Satpal

    2015-10-01

    Red-free light allows better detection of vascular lesions as this wavelength is absorbed by hemoglobin; however, the current gold standard for the detection and grading of diabetic retinopathy remains 7-field color fundus photography. The goal of this study was to compare the ability of 7-field fundus photography using red-free light to detect retinopathy lesions with corresponding images captured using standard 7-field color photography. Non-stereoscopic standard 7-field 30° digital color fundus photography and 7-field 30° digital red-free fundus photography were performed in 200 eyes of 103 patients with various grades of diabetic retinopathy ranging from mild to moderate non-proliferative diabetic retinopathy to proliferative diabetic retinopathy. The color images (n = 1,400) were studied with corresponding red-free images (n = 1,400) by one retina consultant (PV) and two senior residents training in retina. The various retinal lesions [microaneurysms, hemorrhages, hard exudates, soft exudates, intra-retinal microvascular anomalies (IRMA), neovascularization of the retina elsewhere (NVE), and neovascularization of the disc (NVD)] detected by all three observers in each of the photographs were noted followed by determination of agreement scores using κ values (range 0-1). Kappa coefficient was categorized as poor (≤0), slight (0.01-0.20), fair (0.2 -0.40), moderate (0.41-0.60), substantial (0.61-0.80), and almost perfect (0.81-1). The number of lesions detected by red-free images alone was higher for all observers and all abnormalities except hard exudates. Detection of IRMA was especially higher for all observers with red-free images. Between image pairs, there was substantial agreement for detection of hard exudates (average κ = 0.62, range 0.60-0.65) and moderate agreement for detection of hemorrhages (average κ = 0.52, range 0.45-0.58), soft exudates (average κ = 0.51, range 0.42-0.61), NVE (average κ = 0.47, range 0.39-0.53), and NVD

  16. Effect of change in macular birefringence imaging protocol on retinal nerve fiber layer thickness parameters using GDx VCC in eyes with macular lesions.

    PubMed

    Dada, Tanuj; Tinwala, Sana I; Dave, Vivek; Agarwal, Anand; Sharma, Reetika; Wadhwani, Meenakshi

    2014-08-01

    This study evaluates the effect of two macular birefringence protocols (bow-tie retardation and irregular macular scan) using GDx VCC on the retinal nerve fiber layer (RNFL) thickness parameters in normal eyes and eyes with macular lesions. In eyes with macular lesions, the standard protocol led to significant overestimation of RNFL thickness which was normalized using the irregular macular pattern protocol. In eyes with normal macula, absolute RNFL thickness values were higher in irregular macular pattern protocols with the difference being statistically significant for all parameters except for inferior average thickness. This has implications for monitoring glaucoma patients who develop macular lesions during the course of their follow-up. PMID:24469116

  17. Functional and behavioral metrics for evaluating laser retinal damage

    NASA Astrophysics Data System (ADS)

    DiCarlo, Cheryl D.; Martinsen, Gary L.; Garza, Thomas; Grado, Andres; Morin, Juan; Brown, Araceli; Stolarski, David; Cain, Clarence

    2006-02-01

    The use of lasers by both the military and civilian community is rapidly expanding. Thus, the potential for and severity of laser eye injury and retinal damage is increasing. Sensitive and accurate methods to evaluate and follow laser retinal damage are needed. The multifocal electroretinogram (mfERG) has the potential to meet these criteria. In this study, the mfERG was used to evaluate changes to retinal function following laser exposure. Landolt C contrast acuity was also measured in the six behaviorally trained Rhesus monkeys. The monkeys then received Nd:YAG laser lesions (1064 nm, 9 ns pulse width) in each eye. One eye received a single foveal lesion of approximately 0.13 mJ total intraocular exposure (TIE) and the other received six parafoveal lesions which varied in TIE from 0.13 to 4 mJ. mfERGs and behavioral data were collected both pre- and post-exposure. mfERGs were recorded using stimuli that contained 103, 241, and 509 hexagons. Landolt C contrast acuity was measured with five sizes of Landolt C (0.33 to 11.15 cycles/degree) of varying contrast. mfERG response densities were sensitive to the functional retinal changes caused by the laser insult. In general, larger lesions showed greater mfERG abnormalities than smaller laser lesions. Deficits in contrast acuity were found to be more severe in the eyes with foveal injuries. Although the mfERG and contrast acuity assess different areas of the visual system, both are sensitive to laser-induced retinal damage and may be complementary tests for laser eye injury triage.

  18. Laser induced ignition

    NASA Astrophysics Data System (ADS)

    Liedl, G.; Schuöcker, D.; Geringer, B.; Graf, J.; Klawatsch, D.; Lenz, H. P.; Piock, W. F.; Jetzinger, M.; Kapus, P.

    2007-05-01

    Nowadays, combustion engines and other combustion processes play an overwhelming and important role in everyday life. As a result, ignition of combustion processes is of great importance, too. Usually, ignition of a combustible material is defined in such a way that an ignition initiates a self-sustained reaction which propagates through the inflammable material even in the case that the ignition source has been removed. In most cases, a well defined ignition location and ignition time is of crucial importance. Spark plugs are well suited for such tasks but suffer from some disadvantages, like erosion of electrodes or restricted positioning possibilities. In some cases, ignition of combustible materials by means of high power laser pulses could be beneficial. High power lasers offer several different possibilities to ignite combustible materials, like thermal ignition, resonant ignition or optical breakdown ignition. Since thermal and resonant ignitions are not well suited on the requirements mentioned previously, only optical breakdown ignition will be discussed further. Optical breakdown of a gas within the focal spot of a high power laser allows a very distinct localization of the ignition spot in a combustible material. Since pulse duration is usually in the range of several nanoseconds, requirements on the ignition time are fulfilled easily, too. Laser peak intensities required for such an optical breakdown are in the range of 10 11 W/cm2. The hot plasma which forms during this breakdown initiates the following self-propagating combustion process. It has been shown previously that laser ignition of direct injection engines improves the fuel consumption as well as the exhaust emissions of such engines significantly. The work presented here gives a brief overview on the basics of laser induced ignition. Flame propagation which follows a successful ignition event can be distinguished into two diffrent regimes. Combustion processes within an engine are usually

  19. Real-Time In Vivo Imaging of Retinal Cell Apoptosis after Laser Exposure

    PubMed Central

    Schmitz-Valckenberg, Steffen; Guo, Li; Maass, Annelie; Cheung, William; Vugler, Anthony; Moss, Stephen E.; Munro, Peter M. G.; Fitzke, Frederick W.; Cordeiro, M. Francesca

    2008-01-01

    Purpose To investigate whether the detection of apoptosing retinal cells (DARC) could detect cells undergoing apoptosis in a laser model of retinal damage. Methods Laser lesions were placed, with the use of a frequency-doubled Nd:YAG laser, on the retina in 34 eyes of anesthetized Dark Agouti rats. Lesion size and laser-induced retinal elevation were analyzed using in vivo reflectance imaging. Development of retinal cell apoptosis was assessed using intravitreal fluorescence-labeled annexin 5 in vivo with DARC technology from baseline until 90 minutes after laser application. Histologic analysis of retinal flat mounts and cross-sections was performed. Results The lateral and anteroposterior depth extension of the zone of laser damage was significantly larger for higher exposure settings. A strong diffuse signal, concentrated at the outer retina, was seen with DARC for low exposures (<300 ms and <300 mW). In comparison, higher exposures (>300 ms and >300 mW) resulted in detectable hyperfluorescent spots, mainly at the level of the inner retinal layers. Dose-dependent effects on spot density and positive correlation of spot density between lesion size (P < 0.0001) and retinal elevation (P < 0.0001) were demonstrated. Histology confirmed the presence of apoptosing retinal cells in the inner nuclear and the ganglion cell layers. Conclusions This is the first time that DARC has been used to determine apoptotic effects in the inner nuclear layer. The ability to monitor changes spatially and temporally in vivo promises to be a major advance in the real-time assessment of retinal diseases and treatment effects. PMID:18281610

  20. IKK2 Inhibition Attenuates Laser-Induced Choroidal Neovascularization

    PubMed Central

    Lu, Huayi; Lu, Qingxian; Gaddipati, Subhash; Kasetti, Ramesh Babu; Wang, Wei; Pasparakis, Manolis; Kaplan, Henry J.; Li, Qiutang

    2014-01-01

    Choroidal neovascularization (CNV) is aberrant angiogenesis associated with exudative age-related macular degeneration (AMD), a leading cause of blindness in the elderly. Inflammation has been suggested as a risk factor for AMD. The IKK2/NF-κB pathway plays a key role in the inflammatory response through regulation of the transcription of cytokines, chemokines, growth factors and angiogenic factors. We investigated the functional role of IKK2 in development of the laser-induced CNV using either Ikk2 conditional knockout mice or an IKK2 inhibitor. The retinal neuronal tissue and RPE deletion of IKK2 was generated by breeding Ikk2−/flox mice with Nestin-Cre mice. Deletion of Ikk2 in the retina caused no obvious defect in retinal development or function, but resulted in a significant reduction in laser-induced CNV. In addition, intravitreal or retrobulbar injection of an IKK2 specific chemical inhibitor, TPCA-1, also showed similar inhibition of CNV. Furthermore, in vitro inhibition of IKK2 in ARPE-19 cells significantly reduced heat shock-induced expression of NFKBIA, IL1B, CCL2, VEGFA, PDGFA, HIF1A, and MMP-2, suggesting that IKK2 may regulate multiple molecular pathways involved in laser-induced CNV. The in vivo laser-induced expression of VEGFA, and HIF1A in RPE and choroidal tissue was also blocked by TPCA-1 treatment. Thus, IKK2/NF-κB signaling appears responsible for production of pro-inflammatory and pro-angiogenic factors in laser-induced CNV, suggesting that this intracellular pathway may serve as an important therapeutic target for aberrant angiogenesis in exudative AMD. PMID:24489934

  1. Segmentation and quantification of retinal lesions in age-related macular degeneration using polarization-sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Baumann, Bernhard; Götzinger, Erich; Pircher, Michael; Sattmann, Harald; Schütze, Christopher; Schlanitz, Ferdinand; Ahlers, Christian; Schmidt-Erfurth, Ursula; Hitzenberger, Christoph K.

    2010-11-01

    We present polarization-sensitive optical coherence tomography (PS-OCT) for quantitative assessment of retinal pathologies in age-related macular degeneration (AMD). On the basis of the polarization scrambling characteristics of the retinal pigment epithelium, novel segmentation algorithms were developed that allow one to segment pathologic features such as drusen and atrophic zones in dry AMD as well as to determine their dimensions. Results from measurements in the eyes of AMD patients prove the ability of PS-OCT for quantitative imaging based on the retinal features polarizing properties. Repeatability measurements were performed in retinas diagnosed with drusen and geographic atrophy in order to evaluate the performance of the described methods. PS-OCT appears as a promising imaging modality for three-dimensional retinal imaging and ranging with additional contrast based on the structures' tissue-inherent polarization properties.

  2. Segmentation and quantification of retinal lesions in age-related macular degeneration using polarization-sensitive optical coherence tomography

    PubMed Central

    Baumann, Bernhard; Götzinger, Erich; Pircher, Michael; Sattmann, Harald; Schütze, Christopher; Schlanitz, Ferdinand; Ahlers, Christian; Schmidt-Erfurth, Ursula; Hitzenberger, Christoph K.

    2011-01-01

    We present polarization-sensitive optical coherence tomography (PS-OCT) for quantitative assessment of retinal pathologies in age-related macular degeneration (AMD). On the basis of the polarization scrambling characteristics of the retinal pigment epithelium, novel segmentation algorithms were developed that allow one to segment pathologic features such as drusen and atrophic zones in dry AMD as well as to determine their dimensions. Results from measurements in the eyes of AMD patients prove the ability of PS-OCT for quantitative imaging based on the retinal features polarizing properties. Repeatability measurements were performed in retinas diagnosed with drusen and geographic atrophy in order to evaluate the performance of the described methods. PS-OCT appears as a promising imaging modality for three-dimensional retinal imaging and ranging with additional contrast based on the structures’ tissue-inherent polarization properties. PMID:21198152

  3. Laser-induced macular holes demonstrate impaired choroidal perfusion

    NASA Astrophysics Data System (ADS)

    Brown, Jeremiah, Jr.; Allen, Ronald D.; Zwick, Harry; Schuschereba, Steven T.; Lund, David J.; Stuck, Bruce E.

    2003-06-01

    Choroidal perfusion was evaluated following the creation of a laser induced macular hole in a nonhuman primate model. Two Rhesus monkeys underwent macular exposures delivered by a Q-switched Nd:YAG laser. The lesions were evaluated with fluorescein angiography and indocyanine green (ICG) angiography . Each lesion produced vitreous hemorrhage and progressed to a full thickness macular hole. ICG angiography revealed no perfusion of the choriocapillaris beneath the lesion centers. Histopathologic evaluation showed replacement of the choriocapillaris with fibroblasts and connective tissue. Nd:YAG, laser-induced macular holes result in long term impairment of choroidal perfusion at the base of the hole due to choroidal scarring and obliteration of the choriocapillaris.

  4. IKK2 inhibition using TPCA-1-loaded PLGA microparticles attenuates laser-induced choroidal neovascularization and macrophage recruitment.

    PubMed

    Gaddipati, Subhash; Lu, Qingxian; Kasetti, Ramesh Babu; Miller, M Clarke; Lu, Qingjun; Trent, John O; Kaplan, Henry J; Li, Qiutang

    2015-01-01

    The inhibition of NF-κB by genetic deletion or pharmacological inhibition of IKK2 significantly reduces laser-induced choroid neovascularization (CNV). To achieve a sustained and controlled intraocular release of a selective and potent IKK2 inhibitor, 2-[(aminocarbonyl)amino]-5-(4-fluorophenyl)-3-thiophenecarboxamide (TPCA-1) (MW: 279.29), we developed a biodegradable poly-lactide-co-glycolide (PLGA) polymer-delivery system to further investigate the anti-neovascularization effects of IKK2 inhibition and in vivo biosafety using laser-induced CNV mouse model. The solvent-evaporation method produced spherical TPCA-1-loaded PLGA microparticles characterized with a mean diameter of 2.4 ¼m and loading efficiency of 80%. Retrobulbar administration of the TPCA-1-loaded PLGA microparticles maintained a sustained drug level in the retina during the study period. No detectable TPCA-1 level was observed in the untreated contralateral eye. The anti-CNV effect of retrobulbarly administrated TPCA-1-loaded PLGA microparticles was assessed by retinal fluorescein leakage and isolectin staining methods, showing significantly reduced CNV development on day 7 after laser injury. Macrophage infiltration into the laser lesion was attenuated as assayed by choroid/RPE flat-mount staining with anti-F4/80 antibody. Consistently, laser induced expressions of Vegfa and Ccl2 were inhibited by the TPCA-1-loaded PLGA treatment. This TPCA-1 delivery system did not cause any noticeable cellular or functional toxicity to the treated eyes as evaluated by histology and optokinetic reflex (OKR) tests; and no systemic toxicity was observed. We conclude that retrobulbar injection of the small-molecule IKK2 inhibitor TPCA-1, delivered by biodegradable PLGA microparticles, can achieve a sustained and controllable drug release into choroid/retina and attenuate laser-induced CNV development without causing apparent systemic toxicity. Our results suggest a potential clinical application of TPCA-1 delivered

  5. Intravenous transferrin, RGD peptide and dual-targeted nanoparticles enhance anti-VEGF intraceptor gene delivery to laser-induced CNV

    PubMed Central

    Singh, SR; Grossniklaus, HE; Kang, SJ; Edelhauser, HF; Ambati, BK; Kompella, UB

    2010-01-01

    Choroidal neovascularization (CNV) leads to loss of vision in age-related macular degeneration (AMD), the leading cause of blindness in adult population over 50 years old. In this study, we developed intravenously administered, nanoparticulate, targeted nonviral retinal gene delivery systems for the management of CNV. CNV was induced in Brown Norway rats using a 532 nm laser. We engineered transferrin, arginine–glycine–aspartic acid (RGD) peptide or dual-functionalized poly-(lactide-co-glycolide) nanoparticles to target delivery of anti-vascular endothelial growth factor (VEGF) intraceptor plasmid to CNV lesions. Anti-VEGF intraceptor is the only intracellularly acting VEGF inhibitory modality. The results of the study show that nanoparticles allow targeted delivery to the neovascular eye but not the control eye on intravenous administration. Functionalizing the nanoparticle surface with transferrin, a linear RGD peptide or both increased the retinal delivery of nanoparticles and subsequently the intraceptor gene expression in retinal vascular endothelial cells, photoreceptor outer segments and retinal pigment epithelial cells when compared to nonfunctionalized nanoparticles. Most significantly, the CNV areas were significantly smaller in rats treated with functionalized nanoparticles as compared to the ones treated with vehicle or nonfunctionalized nanoparticles. Thus, surface-functionalized nanoparticles allow targeted gene delivery to the neovascular eye on intravenous administration and inhibit the progression of laser-induced CNV in a rodent model. PMID:19194480

  6. Retinitis Pigmentosa

    MedlinePlus

    ... Action You are here Home › Retinal Diseases Listen Retinitis Pigmentosa What is retinitis pigmentosa? What are the symptoms? ... available? Are there any related diseases? What is retinitis pigmentosa? Retinitis pigmentosa (RP) refers to a group of ...

  7. Retinal Inhibition of CCR3 Induces Retinal Cell Death in a Murine Model of Choroidal Neovascularization

    PubMed Central

    Wang, Haibo; Han, Xiaokun; Gambhir, Deeksha; Becker, Silke; Kunz, Eric; Liu, Angelina Jingtong; Hartnett, M. Elizabeth

    2016-01-01

    Inhibition of chemokine C-C motif receptor 3 (CCR3) signaling has been considered as treatment for neovascular age-related macular degeneration (AMD). However, CCR3 is expressed in neural retina from aged human donor eyes. Therefore, broad CCR3 inhibition may be harmful to the retina. We assessed the effects of CCR3 inhibition on retina and choroidal endothelial cells (CECs) that develop into choroidal neovascularization (CNV). In adult murine eyes, CCR3 colocalized with glutamine-synthetase labeled Műller cells. In a murine laser-induced CNV model, CCR3 immunolocalized not only to lectin-stained cells in CNV lesions but also to the retina. Compared to non-lasered controls, CCR3 mRNA was significantly increased in laser-treated retina. An intravitreal injection of a CCR3 inhibitor (CCR3i) significantly reduced CNV compared to DMSO or PBS controls. Both CCR3i and a neutralizing antibody to CCR3 increased TUNEL+ retinal cells overlying CNV, compared to controls. There was no difference in cleaved caspase-3 in laser-induced CNV lesions or in overlying retina between CCR3i- or control-treated eyes. Following CCR3i, apoptotic inducible factor (AIF) was significantly increased and anti-apoptotic factor BCL2 decreased in the retina; there were no differences in retinal vascular endothelial growth factor (VEGF). In cultured human Műller cells exposed to eotaxin (CCL11) and VEGF, CCR3i significantly increased TUNEL+ cells and AIF but decreased BCL2 and brain derived neurotrophic factor, without affecting caspase-3 activity or VEGF. CCR3i significantly decreased AIF in RPE/choroids and immunostaining of phosphorylated VEGF receptor 2 (p-VEGFR2) in CNV with a trend toward reduced VEGF. In cultured CECs treated with CCL11 and/or VEGF, CCR3i decreased p-VEGFR2 and increased BCL2 without increasing TUNEL+ cells and AIF. These findings suggest that inhibition of retinal CCR3 causes retinal cell death and that targeted inhibition of CCR3 in CECs may be a safer if CCR3 inhibition

  8. Retinal Inhibition of CCR3 Induces Retinal Cell Death in a Murine Model of Choroidal Neovascularization.

    PubMed

    Wang, Haibo; Han, Xiaokun; Gambhir, Deeksha; Becker, Silke; Kunz, Eric; Liu, Angelina Jingtong; Hartnett, M Elizabeth

    2016-01-01

    Inhibition of chemokine C-C motif receptor 3 (CCR3) signaling has been considered as treatment for neovascular age-related macular degeneration (AMD). However, CCR3 is expressed in neural retina from aged human donor eyes. Therefore, broad CCR3 inhibition may be harmful to the retina. We assessed the effects of CCR3 inhibition on retina and choroidal endothelial cells (CECs) that develop into choroidal neovascularization (CNV). In adult murine eyes, CCR3 colocalized with glutamine-synthetase labeled Műller cells. In a murine laser-induced CNV model, CCR3 immunolocalized not only to lectin-stained cells in CNV lesions but also to the retina. Compared to non-lasered controls, CCR3 mRNA was significantly increased in laser-treated retina. An intravitreal injection of a CCR3 inhibitor (CCR3i) significantly reduced CNV compared to DMSO or PBS controls. Both CCR3i and a neutralizing antibody to CCR3 increased TUNEL+ retinal cells overlying CNV, compared to controls. There was no difference in cleaved caspase-3 in laser-induced CNV lesions or in overlying retina between CCR3i- or control-treated eyes. Following CCR3i, apoptotic inducible factor (AIF) was significantly increased and anti-apoptotic factor BCL2 decreased in the retina; there were no differences in retinal vascular endothelial growth factor (VEGF). In cultured human Műller cells exposed to eotaxin (CCL11) and VEGF, CCR3i significantly increased TUNEL+ cells and AIF but decreased BCL2 and brain derived neurotrophic factor, without affecting caspase-3 activity or VEGF. CCR3i significantly decreased AIF in RPE/choroids and immunostaining of phosphorylated VEGF receptor 2 (p-VEGFR2) in CNV with a trend toward reduced VEGF. In cultured CECs treated with CCL11 and/or VEGF, CCR3i decreased p-VEGFR2 and increased BCL2 without increasing TUNEL+ cells and AIF. These findings suggest that inhibition of retinal CCR3 causes retinal cell death and that targeted inhibition of CCR3 in CECs may be a safer if CCR3 inhibition

  9. Retinal Ganglion Cell Atrophy in Homonymous Hemianopia due to Acquired Occipital Lesions Observed Using Cirrus High-Definition-OCT

    PubMed Central

    Yamashita, Tsutomu; Miki, Atsushi; Goto, Katsutoshi; Araki, Syunsuke; Takizawa, Go; Ieki, Yoshiaki; Kiryu, Junichi; Tabuchi, Akio; Iguchi, Yasuyuki; Kimura, Kazumi; Yagita, Yoshiki

    2016-01-01

    Purpose. To report a reduction in macular ganglion cell layer and inner plexiform layer (GCL+IPL) thickness and circumpapillary retinal nerve fiber layer (cpRNFL) thickness using spectral-domain optical coherence tomography in patients with homonymous hemianopia due to posterior cerebral artery (PCA) stroke. Methods. Seven patients with PCA stroke were examined using Cirrus high-definition-OCT. The GCL+IPL thicknesses were divided into the hemianopic and unaffected sides. The relationship between the time after stroke and the GCL+IPL thicknesses in the hemianopic side was evaluated. Results. The average thicknesses of the GCL+IPL were 64.6 and 82.0 μm on the hemianopic and unaffected sides, respectively, and the measurement was significantly thinner on the former side (p = 0.018). A regression analysis revealed a negative linear relationship (R2 = 0.574, p = 0.049) between the time after stoke and the GCL+IPL thicknesses on the hemianopic side. The supratemporal and inferotemporal cpRNFL thicknesses in the eyes ipsilateral to the stroke showed a significant reduction. Conclusion. Our findings confirmed our previous observations that the degeneration of retinal ganglion cells can occur after PCA stroke. GCL+IPL thinning was demonstrated in the hemiretinae corresponding to the affected hemifields. Also, it is suggested that the retinal changes observed are progressive. PMID:27274865

  10. Melissa officinalis Extract Inhibits Laser-Induced Choroidal Neovascularization in a Rat Model

    PubMed Central

    Lee, Eun Kyoung; Kim, Young Joo; Kim, Jin Young; Song, Hyun Beom; Yu, Hyeong Gon

    2014-01-01

    Purpose This study investigated the effect of Melissa officinalis extract on laser-induced choroidal neovascularization (CNV) in a rat model. The mechanism by which M. officinalis extract acted was also investigated. Methods Experimental CNV was induced by laser photocoagulation in Brown Norway rats. An active fraction of the Melissa leaf extract was orally administered (50 or 100 mg/kg/day) beginning 3 days before laser photocoagulation and ending 14 days after laser photocoagulation. Optical coherence tomography and fluorescein angiography were performed in vivo to evaluate the thickness and leakage of CNV. Choroidal flat mount and histological analysis were conducted to observe the CNV in vitro. Vascular endothelial growth factor (VEGF), matrix metalloproteinase (MMP)-2, and MMP-9 expression were measured in retinal and choroidal-scleral lysates 7 days after laser injury. Moreover, the effect of M. officinalis extract on tertiary-butylhydroperoxide (t-BH)-induced VEGF secretion and mRNA levels of VEGF, MMP-2, and MMP-9 were evaluated in human retinal epithelial cells (ARPE-19) as well as in human umbilical vein endothelial cells (HUVECs). Results The CNV thickness in M. officinalis-treated rats was significantly lower than in vehicle-treated rats by histological analysis. The CNV thickness was 33.93±7.64 µm in the high-dose group (P<0.001), 44.09±12.01 µm in the low-dose group (P = 0.016), and 51.00±12.37 µm in the control group. The proportion of CNV lesions with clinically significant fluorescein leakage was 9.2% in rats treated with high-dose M. officinalis, which was significantly lower than in control rats (53.4%, P<0.001). The levels of VEGF, MMP-2, and MMP-9 were significantly lower in the high-dose group than in the control group. Meanwhile, M. officinalis extract suppressed t-BH-induced transcription of VEGF and MMP-9 in ARPE-19 cells and HUVECs. Conclusions Systemic administration of M. officinalis extract suppressed laser-induced CNV

  11. Three dimensional distribution of the vitelliform lesion, photoreceptors, and retinal pigment epithelium in the macula of patients with Best vitelliform macular dystrophy

    PubMed Central

    Kay, Christine N.; Abramoff, Michael D.; Mullins, Robert F.; Kinnick, Tyson R.; Lee, Kyuongmoo; Eyestone, Mari E.; Chung, Mina M.; Sohn, Elliott H.; Stone, Edwin M.

    2015-01-01

    Objective To describe the anatomical phenotypes of Best vitelliform macular dystrophy (BVMD) with spectraldomain optical coherence tomography (SD-OCT) in a large series of patients with confirmed mutations in the BEST1 gene. Methods In our retrospective observational case series, we assessed 15 patients (30 eyes) with a clinical diagnosis of vitelliform macular dystrophy who were found to have mutations in the BEST1 gene. Color fundus photographs and SD-OCT images were evaluated and compared with those of 15 age-matched controls (30 eyes). Using a validated 3-dimensional SD-OCT segmentation algorithm, we calculated the equivalent thickness of photoreceptors and the equivalent thickness of the retinal pigment epithelium for each patient. The photoreceptor equivalent thickness and the retinal pigment epithelium (RPE) equivalent thickness were compared in all patients, in a region of the macula outside the central lesion for patients with BVMD and outside the fovea in control patients. Paired t tests were used for statistical analysis. Results The SD-OCT findings revealed that the vitelliform lesion consists of material above the RPE and below the outer segment tips. Additionally, drusen-like deposition of sub-RPE material was notable, and several patients exhibited a sub-RPE fibrotic nodule. Patients with BVMD had a mean photoreceptor equivalent thickness of 28.3 μm, and control patients had a mean photoreceptor equivalent thickness of 21.8 μm, a mean difference of 6.5 μm (P < .01), whereas the mean RPE equivalent thickness was not statistically different between patients with BVMD and control patients (P=.53). Conclusions The SD-OCT findings suggest that vitelliform material is located in the subretinal space and that BVMD is associated with diffuse photoreceptor outer segment abnormalities overlying a structurally normal RPE. Clinical Relevance: These findings provide new insight into the pathophysiology of BVMD and thus have implications for the development of

  12. Heat shock protein expression as guidance for the therapeutic window of retinal laser therapy

    NASA Astrophysics Data System (ADS)

    Wang, Jenny; Huie, Philip; Dalal, Roopa; Lee, Seungjun; Tan, Gavin; Lee, Daeyoung; Lavinksy, Daniel; Palanker, Daniel

    2016-03-01

    Unlike conventional photocoagulation, non-damaging retinal laser therapy (NRT) limits laser-induced heating to stay below the retinal damage threshold and therefore requires careful dosimetry. Without the adverse effects associated with photocoagulation, NRT can be applied to critical areas of the retina and repeatedly to manage chronic disorders. Although the clinical benefits of NRT have been demonstrated, the mechanism of therapeutic effect and width of the therapeutic window below damage threshold are not well understood. Here, we measure activation of heat shock response via laser-induced hyperthermia as one indication of cellular response. A 577 nm laser is used with the Endpoint Management (EpM) user interface, a titration algorithm, to set experimental pulse energies relative to a barely visible titration lesion. Live/dead staining and histology show that the retinal damage threshold in rabbits is at 40% of titration energy on EpM scale. Heat shock protein 70 (HSP70) expression in the retinal pigment epithelium (RPE) was detected by whole-mount immunohistochemistry after different levels of laser treatment. We show HSP70 expression in the RPE beginning at 25% of titration energy indicating that there is a window for NRT between 25% and 40% with activation of the heat shock protein expression in response to hyperthermia. HSP70 expression is also seen at the perimeter of damaging lesions, as expected based on a computational model of laser heating. Expression area for each pulse energy setting varied between laser spots due to pigmentation changes, indicating the relatively narrow window of non-damaging activation and highlighting the importance of proper titration.

  13. Blue light-induced retinal lesions, intraretinal vascular leakage and edema formation in the all-cone mouse retina

    PubMed Central

    Geiger, P; Barben, M; Grimm, C; Samardzija, M

    2015-01-01

    Little is known about the mechanisms underlying macular degenerations, mainly for the scarcity of adequate experimental models to investigate cone cell death. Recently, we generated R91W;Nrl−/− double-mutant mice, which display a well-ordered all-cone retina with normal retinal vasculature and a strong photopic function that generates useful vision. Here we exposed R91W;Nrl−/− and wild-type (wt) mice to toxic levels of blue light and analyzed their retinas at different time points post illumination (up to 10 days). While exposure of wt mice resulted in massive pyknosis in a focal region of the outer nuclear layer (ONL), the exposure of R91W;Nrl−/− mice led to additional cell death detected within the inner nuclear layer. Microglia/macrophage infiltration at the site of injury was more pronounced in the all-cone retina of R91W;Nrl−/− than in wt mice. Similarly, vascular leakage was abundant in the inner and outer retina in R91W;Nrl−/− mice, whereas it was mild and restricted to the subretinal space in wt mice. This was accompanied by retinal swelling and the appearance of cystoid spaces in both inner and ONLs of R91W;Nrl−/− mice indicating edema in affected areas. In addition, basal expression levels of tight junction protein-1 encoding ZO1 were lower in R91W;Nrl−/− than in wt retinas. Collectively, our data suggest that exposure of R91W;Nrl−/− mice to blue light not only induces cone cell death but also disrupts the inner blood–retinal barrier. Macular edema in humans is a result of diffuse capillary leakage and microaneurysms in the macular region. Blue light exposure of the R91W;Nrl−/− mouse could therefore be used to study molecular events preceding edema formation in a cone-rich environment, and thus potentially help to develop treatment strategies for edema-based complications in macular degenerations. PMID:26583326

  14. Laser-induced fluorescence in medical diagnostics

    NASA Astrophysics Data System (ADS)

    Andersson-Engels, Stefan; Johansson, Jonas; Svanberg, Katarina; Svanberg, Sune

    1990-07-01

    We have performed extensive investigations using laser-induced fluorescence in animal as well as human tissue in order to localize diseased tissue and thus discriminate such tissue from normal surrounding areas. In characterizing different tissue types the endogenous fluorescence (autofluorescence) as well as specific fluorescence from different photosensitising substances was utilized. We have investigated different experimental and human malignant tumors in vivo and in vitro as well as atherosclerotic lesions in vitro. A fiber-optic fluorosensor was constructed and used in the experiments and in the clinical examination of patients. Dimensionless spectroscopic functions were formed to ensure that the signals were independent of clinically uncontrollable variables such as distance variations, tissue topography, light source fluctuations and variations in detection efficiency. A multi-color two-dimensional imaging system was constructed for real-time imaging. The system was tested peroperatively and during standard examination patient procedures. Besides utilizing the time-integrated fluorescence signal we have also investigated the possibility of incorporating time-resolved fluorescence characterization.

  15. Progressive outer retinal necrosis-like retinitis in immunocompetent hosts.

    PubMed

    Chawla, Rohan; Tripathy, Koushik; Gogia, Varun; Venkatesh, Pradeep

    2016-01-01

    We describe two young immunocompetent women presenting with bilateral retinitis with outer retinal necrosis involving posterior pole with centrifugal spread and multifocal lesions simulating progressive outer retinal necrosis (PORN) like retinitis. Serology was negative for HIV and CD4 counts were normal; however, both women were on oral steroids at presentation for suspected autoimmune chorioretinitis. The retinitis in both eyes responded well to oral valaciclovir therapy. However, the eye with the more fulminant involvement developed retinal detachment with a loss of vision. Retinal atrophy was seen in the less involved eye with preservation of vision. Through these cases, we aim to describe a unique evolution of PORN-like retinitis in immunocompetent women, which was probably aggravated by a short-term immunosuppression secondary to oral steroids. PMID:27511757

  16. Cytomegalovirus retinitis

    MedlinePlus

    ... to prevent its return. Alternative Names Cytomegalovirus retinitis Images Eye CMV retinitis CMV (cytomegalovirus) References Crumpacker CS. ... 5. Read More Antibody HIV/AIDS Immune response Retinal detachment Systemic WBC count Update Date 12/10/ ...

  17. Laser-Induced Thermal Acoustics

    NASA Astrophysics Data System (ADS)

    Cummings, Eric Bryant

    1995-01-01

    Laser-induced thermal acoustics (LITA) is a new technique for remote nonintrusive measurement of thermophysical gas properties. LITA involves forming, via opto-acoustic effects, grating-shaped perturbations of gas properties by the use of intersecting beams from a short-pulse laser. A third beam scatters coherently into a signal beam off the perturbation grating via acousto-optical effects. The evolution of the gas perturbations modulates the scattered signal beam. Accurate values of the sound speed, transport properties, and composition of the gas can be extracted by analyzing the signal beam. An analytical expression for the spectrum, absolute magnitude, and time history of the LITA signal is derived. The optoacoustic effects of thermalization and electrostriction are treated. Finite beam-diameter, beam-duration, and thermalization-rate effects are included in the analysis. The expression accurately models experimental signals over a wide range of gas conditions. Experimental tests using LITA have been conducted on pure and NO_2-seeded air and helium at pressures ranging from {~ }0.1 kPa-14 MPa. Carbon dioxide has been explored near its liquid-vapor critical point. Accuracies of 0.1% in sound speed measurements have been achieved in these tests. Accuracies of {~}1% have been achieved in measurements of thermal diffusivity, although beam misalignment effects have typically degraded this accuracy by a factor of {~} 10-20. Using LITA, susceptibility spectra have been taken of approximately a femtogram of NO_2 . The effects of fluid motion and turbulence have been explored. LITA velocimetry has been demonstrated, in which the Doppler shift of light scattered from a flowing fluid is measured. LITA velocimetry requires no particle seeding, has a coherent signal beam, and can be applied to pulsed flows. LITA has also been applied to measure single-shot |chi^{(1) }|^2 or "Rayleigh scattering" spectra of a gas by the use of a technique of wavelength -division multiplexing

  18. Laser-induced thermal acoustics

    NASA Astrophysics Data System (ADS)

    Cummings, Eric B.

    Laser-induced thermal acoustics (LITA) is a new technique for remote nonintrusive measurement of thermophysical gas properties. LITA involves forming, via opto-acoustic effects, grating-shaped perturbations of gas properties using intersecting beams from a short-pulse laser. A third beam scatters coherently into a signal beam off the perturbation grating via acousto-optical effects. The evolution of the gas perturbations modulates the scattered signal beam. Accurate values of the sound speed, transport properties, and composition of the gas can be extracted by analyzing the signal beam.An analytical expression for the spectrum, absolute magnitude, and time history of the LITA signal is derived. The optoacoustic effects of thermalization and electrostriction are treated. Finite beam-diameter, beam-duration, and thermalization-rate effects are included in the analysis. The expression accurately models experimental signals over a wide range of gas conditions.Experimental tests using LITA have been conducted on pure and [...]-seeded air and helium at pressures ranging from ~0.1 kPa-14 MPa. Carbon dioxide has been explored near its liquid-vapor critical point. Accuracies of 0.1% in sound speed measurements have been achieved in these tests. Accuracies of ~1% have been achieved in measurements of thermal diffusivity, although beam misalignment effects have typically degraded this accuracy by a factor of ~10-20. Using LITA, susceptibility spectra have been taken of approximately a femtogram of [...]. The effects of fluid motion and turbulence have been explored. LITA velocimetry has been demonstrated, in which the Doppler shift of light scattered from a flowing fluid is measured. LITA velocimetry requires no particle seeding, has a coherent signal beam, and can be applied to pulsed flows. LITA has also been applied to measure single-shot [...] or "Rayleigh scattering" spectra of a gas using a technique of wavelength-division multiplexing, called multiplex LITA. The LITA

  19. Real-time control of lesion size based on reflectance images

    NASA Astrophysics Data System (ADS)

    Jerath, Maya R.; Kaisig, Danielle; Rylander, Henry G., III; Welch, Ashley J.

    1992-08-01

    Laser-induced lesion size is controlled in real time based on a two dimensional reflectance image recorded by a CCD array during lesion formation. A feedback system using components of the reflectance image achieves uniform lesions by compensating for light absorption variability in biological media. Lesions are formed in a phantom using an argon laser to simulate retinal photocoagulation. The tissue model consists of an absorptive high temperature black paint layer and an egg white protein layer. Reflectance images are acquired as the lesion forms at a standard frame rate using a 512 X 512 CCD camera attached to an ITI 151 series image processor and a Sun 3/260 computer. A shutter controlled by the computer is closed when certain preset conditions are met in the images. Results show a low variance in the sizes of the lesions (diameter or depth) produced under different irradiation conditions and the ability to produce lesions of a predefined size under varying illumination conditions. Real time control from reflectance images based on certain parameters is demonstrated as a feasible method of controlling lesion size.

  20. Laser-induced caesium-137 decay

    SciTech Connect

    Barmina, E V; Simakin, A V; Shafeev, G A

    2014-08-31

    Experimental data are presented on the laser-induced beta decay of caesium-137. We demonstrate that the exposure of a gold target to a copper vapour laser beam (wavelengths of 510.6 and 578.2 nm, pulse duration of 15 ns) for 2 h in an aqueous solution of a caesium-137 salt reduces the caesium-137 activity by 70%, as assessed from the gamma activity of the daughter nucleus {sup 137m}Ba, and discuss potential applications of laser-induced caesium-137 decay in radioactive waste disposal. (letters)

  1. Mestastable State Population in Laser Induced Plasmas

    NASA Technical Reports Server (NTRS)

    Kwong, V. H. S.; Kyriakides, C.; Ward, W. K.

    2006-01-01

    Laser induced plasma has been used as a source of neutrals and ions in the study of astrophysical plasmas. The purity of state of this source is essential in the determination of collision parameters such as the charge transfer rate coefficients between ions and neutrals. We will show that the temperature of the laser induced plasma is a rapidly decreasing function of time. The temperature is initially high but cools off rapidly through collisions with the expanding plasma electrons as the plasma recombines and streams into the vacuum. This rapid expansion of the plasma, similar to a supersonic jet, drastically lowers the internal energy of the neutrals and ions.

  2. Demarcation laser photocoagulation induced retinal necrosis and rupture resulting in large retinal tear formation.

    PubMed

    Quezada, Carlos; Pieramici, Dante J; Matsui, Rodrigo; Rabena, Melvin; Graue, Federico

    2015-06-01

    Retinal tears after laser photocoagulation are a rare complication that occurs after intense laser. It is talked about among retina specialist occurring particularly at the end of a surgical case while applying endophotocoagulation; to the best our knowledge, there are no reports in the literature of a large retinal tear induced after attempted in-office demarcation laser photocoagulation (DLP) that simulated a giant retinal tear. DLP has been employed in the management of selected cases of macula sparring rhegmatogenous retinal detachment (RRD). Even though extension of the retinal detachment through the "laser barrier" is considered a failure of treatment, few complications have been described with the use of this less invasive retinal detachment repair technique. We describe a case of a high myopic woman who initially was treated with demarcation laser photocoagulation for an asymptomatic retinal detachment associated with a single horseshoe tear and a full thickness large retinal tear was created where the laser was placed. Intense laser photocoagulation resulted in abrupt laser induced retinal necrosis and rupture creating this large retinal break. Proper laser technique should reduce the risks associated with this procedure. PMID:25770055

  3. Study Of Laser-Induced Copolymerization

    NASA Technical Reports Server (NTRS)

    Miner, Gilda A.; Meador, Willard E.; Chang, C. Ken

    1993-01-01

    Report describes experiments on photopolymerization of styrene/maleic anhydride copolymer published as part of Laser Polymerization Program at NASA Langley Research Center. Presents basic study of copolymerization of styrene and maleic anhydride under laser-induced initiation and polymerization. Helps to clarify different theories on such initiation and represents significant advances in understanding of basic processes.

  4. Retinitis Pigmentosa.

    ERIC Educational Resources Information Center

    Carr, Ronald E.

    1979-01-01

    The author describes the etiology of retinitis pigmentosa, a visual dysfunction which results from progressive loss of the retinal photoreceptors. Sections address signs and symptoms, ancillary findings, heredity, clinical diagnosis, therapy, and research. (SBH)

  5. Multifocal electroretinogram (MFERG) evaluation of laser-induced secondary damage in the non-human primate (NHP)

    NASA Astrophysics Data System (ADS)

    Zwick, Harry; Stuck, Bruce E.; Akers, A.; Edsall, Peter; DiCarlo, Cheryl D.; Lund, David J.

    2005-04-01

    Laser induced retinal damage may involve primary injury to the central retina and secondary damage, including intraretinal scar formation (IRSF) retinal traction (RT) and retinal nerve fiber layer injury (RNFL). We have evaluated these laser induced retinal pathologies with MFERG in non-human primates (NHPs) with a Veris (4.9) MFERG system 103 Hexagons, centered on the macula with non-scaled arrays and in one NHP with a 2-frame/M-step sequence to assess long term exposure effects within the RNFL. Chemical restraint was achieved using Ketamine stability HCL (10 mg/kg IM) and Propofol (0.5 mg-1.2/Kg/min via syringe pump). Peribulbar eye blocks were performed using 2% lidocain or a mixture of 2% Lidocain/Marcain (monitored ocular motility was less than 40 microns in retinal space). Primary and secondary damage effects were induced with either q-switched single pulse Neodymium (1064 nm, 1.0 mJ) or Argon CW (10 to 1000 msec, 10-150 mW). MFERG demonstrated capability to detect primary and secondary induced retinal damage in both 1st and 2nd order kernels. Primary and secondary damage in the central retina was often suppressed in amplitude and with longer latencies relative to the MFERG norm. Preliminary investigations in one NHP with Primary and secondary RNFL damage at 9 to 14 months showed recovery with non-scaled array one frame / M-step sequence but demonstrated significant abnormalities for a two frame/ M-step sequence. Utilization of advanced Veris recording parameters involving spatial and temporal manipulation of the stimulus parameters can improve detection of functional deficits induced by focal laser retinal injury.

  6. Improved assessment of laser-induced choroidal neovascularization

    PubMed Central

    Toma, Hassanain S.; Barnett, Joshua M.; Penn, John S.; Kim, Stephen J.

    2011-01-01

    The primary objective of this study was to develop and evaluate new methods of analyzing laser-induced choroidal neovascularization (CNV), in order to make recommendations for improving the reporting of experimental CNV in the literature. Six laser burns of sufficient power to rupture Bruch's membrane were concentrically placed in each eye of 18 adult Norway rats. Eyes received intravitreal injections of either triamcinolone acetonide, ketorolac, or balanced salt solution (BSS). Fluorescein angiography (FA) was performed 2 and 3 weeks after injection, followed by choroidal flat mount preparation. Vascular leakage on FAs and vascular budding on choroidal mounts were quantified by measuring either the cross-sectional area of each CNV lesion contained within the best-fitting polygon using Adobe Photoshop (Lasso Technique or Quick Selection Technique), or the area of bright pixels within a lesion using Image-Pro Plus. On choroidal mounts, the Lasso Technique and Image-Pro Plus detected a significant difference in lesion size between either ketorolac or triamcinolone when compared to BSS, while the Quick Selection Technique did not (Lasso Technique, 0.78 and 0.64; Image-Pro Plus, 0.77 and 0.65). On FA, the Lasso Technique and Quick Selection Technique detected a significant difference in lesion size between either ketorolac or triamcinolone when compared to BSS, while Image-Pro Plus did not (Lasso Tool, 0.81 and 0.54; Quick Selection Tool, 0.76 and 0.57). Choroidal mounts and FA are both valuable for imaging experimental CNV. Adobe Photoshop and Image-Pro Plus are both able to detect subtle differences in CNV lesion size, when images are not manipulated. The combination of choroidal mounts and FA provides a more comprehensive assessment of CNV anatomy and physiology. PMID:20553963

  7. Spectroscopy During Laser Induced Shock Wave Lithotripsy

    NASA Astrophysics Data System (ADS)

    Engelhardt, R.; Meyer, W.; Hering, P.

    1988-06-01

    In the course of laser induced shock wave lithotripsy (LISL) by means of a flashlamp pumped dye laser a plasma is formed on the stone's surface. Spectral analysis of the plasma flash leads to chemical stone analysis during the procedure. A time resolved integral analysis of scattered and laser induced fluorescence light makes stone detection possible and avoids tissue damage. We used a 200 μm fiber to transmit a 2 μs, 50 mJ pulse to the stone's surface and a second 200 μ fiber for analysis. This transmission system is small and flexible enough for controlled endoscopic use in the treatment of human ureter or common bile duct stones. Under these conditions the stone selective effect of lasertripsy leads only to minor tissue injury.

  8. Interaction of Laser Induced Micro-shockwaves

    NASA Astrophysics Data System (ADS)

    Leela, Ch.; Bagchi, Suman; Tewari, Surya P.; Kiran, P. Prem

    Laser induced Shock Waves (LISWs) characterized by several optical methods provide Equation of State (EOS) for a variety of materials used in high-energy density physics experiments at Mbar pressures [1, 2]. Other applications include laser spark ignition for fuel-air mixtures, internal combustion engines, pulse detonation engines, laser shock peening [3], surface cleaning [4] and biological applications (SW lithotripsy) [5] to name a few.

  9. Automated retinal robotic laser system.

    PubMed

    Barrett, S F; Wright, C H; Jerath, M R; Lewis, R S; Dillard, B C; Rylander, H G; Welch, A J

    1995-01-01

    Researchers at the University of Texas and the USAF Academy have worked toward the development of a retinal robotic laser system. The overall goal of this ongoing project is to precisely place and control the depth of laser lesions for the treatment of various retinal diseases such as diabetic retinopathy and retinal tears. Separate low speed prototype subsystems have been developed to control lesion depth using lesion reflectance feedback parameters and lesion placement using retinal vessels as tracking landmarks. Both subsystems have been successfully demonstrated in vivo on pigmented rabbits using an argon continuous wave laser. Recent efforts have concentrated on combining the two subsystems into a single prototype capable of simultaneously controlling both lesion depth and placement. We have designated this combined system CALOSOS for Computer Aided Laser Optics System for Ophthalmic Surgery. Following the dual-use concept, this system is being adapted for clinical use as a retinal treatment system as well as a research tool for military laser-tissue interaction studies. PMID:7654990

  10. Differentiation of cutaneous melanoma from surrounding skin using laser-induced breakdown spectroscopy

    PubMed Central

    Han, Jung Hyun; Moon, Youngmin; Lee, Jong Jin; Choi, Sujeong; Kim, Yong-Chul; Jeong, Sungho

    2015-01-01

    Laser-induced breakdown spectroscopy (LIBS) has the potential to be used as a surgical tool for simultaneous tissue ablation and elemental analysis of the ablated tissue. LIBS may be used to distinguish melanoma lesions from the surrounding dermis based on the quantitative difference of elements within melanoma lesions. Here, we measured the elements in homogenized pellets and real tissues from excised skin samples of melanoma-implanted mice. In addition, statistical analysis of LIBS spectra using principal component analysis and linear discriminant analysis was performed. Our results showed that this method had high detection sensitivity, highlighting the potential of this tool in clinical applications. PMID:26819817

  11. Hyperspectral laser-induced autofluorescence imaging of dental caries

    NASA Astrophysics Data System (ADS)

    Bürmen, Miran; Fidler, Aleš; Pernuš, Franjo; Likar, Boštjan

    2012-01-01

    Dental caries is a disease characterized by demineralization of enamel crystals leading to the penetration of bacteria into the dentine and pulp. Early detection of enamel demineralization resulting in increased enamel porosity, commonly known as white spots, is a difficult diagnostic task. Laser induced autofluorescence was shown to be a useful method for early detection of demineralization. The existing studies involved either a single point spectroscopic measurements or imaging at a single spectral band. In the case of spectroscopic measurements, very little or no spatial information is acquired and the measured autofluorescence signal strongly depends on the position and orientation of the probe. On the other hand, single-band spectral imaging can be substantially affected by local spectral artefacts. Such effects can significantly interfere with automated methods for detection of early caries lesions. In contrast, hyperspectral imaging effectively combines the spatial information of imaging methods with the spectral information of spectroscopic methods providing excellent basis for development of robust and reliable algorithms for automated classification and analysis of hard dental tissues. In this paper, we employ 405 nm laser excitation of natural caries lesions. The fluorescence signal is acquired by a state-of-the-art hyperspectral imaging system consisting of a high-resolution acousto-optic tunable filter (AOTF) and a highly sensitive Scientific CMOS camera in the spectral range from 550 nm to 800 nm. The results are compared to the contrast obtained by near-infrared hyperspectral imaging technique employed in the existing studies on early detection of dental caries.

  12. Retinal Imaging and Image Analysis

    PubMed Central

    Abràmoff, Michael D.; Garvin, Mona K.; Sonka, Milan

    2011-01-01

    Many important eye diseases as well as systemic diseases manifest themselves in the retina. While a number of other anatomical structures contribute to the process of vision, this review focuses on retinal imaging and image analysis. Following a brief overview of the most prevalent causes of blindness in the industrialized world that includes age-related macular degeneration, diabetic retinopathy, and glaucoma, the review is devoted to retinal imaging and image analysis methods and their clinical implications. Methods for 2-D fundus imaging and techniques for 3-D optical coherence tomography (OCT) imaging are reviewed. Special attention is given to quantitative techniques for analysis of fundus photographs with a focus on clinically relevant assessment of retinal vasculature, identification of retinal lesions, assessment of optic nerve head (ONH) shape, building retinal atlases, and to automated methods for population screening for retinal diseases. A separate section is devoted to 3-D analysis of OCT images, describing methods for segmentation and analysis of retinal layers, retinal vasculature, and 2-D/3-D detection of symptomatic exudate-associated derangements, as well as to OCT-based analysis of ONH morphology and shape. Throughout the paper, aspects of image acquisition, image analysis, and clinical relevance are treated together considering their mutually interlinked relationships. PMID:21743764

  13. Quantitative analysis of retinal OCT.

    PubMed

    Sonka, Milan; Abràmoff, Michael D

    2016-10-01

    Clinical acceptance of 3-D OCT retinal imaging brought rapid development of quantitative 3-D analysis of retinal layers, vasculature, retinal lesions as well as facilitated new research in retinal diseases. One of the cornerstones of many such analyses is segmentation and thickness quantification of retinal layers and the choroid, with an inherently 3-D simultaneous multi-layer LOGISMOS (Layered Optimal Graph Image Segmentation for Multiple Objects and Surfaces) segmentation approach being extremely well suited for the task. Once retinal layers are segmented, regional thickness, brightness, or texture-based indices of individual layers can be easily determined and thus contribute to our understanding of retinal or optic nerve head (ONH) disease processes and can be employed for determination of disease status, treatment responses, visual function, etc. Out of many applications, examples provided in this paper focus on image-guided therapy and outcome prediction in age-related macular degeneration and on assessing visual function from retinal layer structure in glaucoma. PMID:27503080

  14. Laser induced surface stress on water droplets.

    PubMed

    Wang, Neng; Lin, Zhifang; Ng, Jack

    2014-10-01

    Laser induced stress on spherical water droplets is studied. At mechanical equilibrium, the body stress vanishes therefore we consider only the surface stress. The surface stress on sub-wavelength droplets is slightly weaker along the light propagation direction. For larger droplets, due to their light focusing effect, the forward stress is significantly enhanced. For a particle roughly 3 micron in radius, when it is excited at whispering gallery mode with Q ∼ 10⁴ by a 1 Watt Gaussian beam, the stress can be enhanced by two orders of magnitude, and can be comparable with the Laplace pressure. PMID:25321955

  15. Kinetic Approach for Laser-Induced Plasmas

    SciTech Connect

    Omar, Banaz; Rethfeld, Baerbel

    2008-10-22

    Non-equilibrium distribution functions of electron gas and phonon gas excited with ultrashort intense laser pulses are calculated for laser-induced plasmas occurring in solids. The excitation during femtosecond irradiation and the subsequent thermalization of the free electrons, as well as the dynamics of phonons are described by kinetic equations. The microscopic collision processes, such as absorption by inverse bremsstrahlung, electron-electron collisions, and electron-phonon interactions are considered by complete Boltzmann collision integrals. We apply our kinetic approach for gold by taking s-band electron into account and compare it with the case of excitation of d-band electrons.

  16. Laser-induced electric breakdown in solids

    NASA Technical Reports Server (NTRS)

    Bloembergen, N.

    1974-01-01

    A review is given of recent experimental results on laser-induced electric breakdown in transparent optical solid materials. A fundamental breakdown threshold exists characteristic for each material. The threshold is determined by the same physical process as dc breakdown, namely, avalanche ionization. The dependence of the threshold on laser pulse duration and frequency is consistent with this process. The implication of this breakdown mechanism for laser bulk and surface damage to optical components is discussed. It also determines physical properties of self-focused filaments.

  17. Modeling of Laser-Induced Metal Combustion

    SciTech Connect

    Boley, C D; Rubenchik, A M

    2008-02-20

    Experiments involving the interaction of a high-power laser beam with metal targets demonstrate that combustion plays an important role. This process depends on reactions within an oxide layer, together with oxygenation and removal of this layer by the wind. We present an analytical model of laser-induced combustion. The model predicts the threshold for initiation of combustion, the growth of the combustion layer with time, and the threshold for self-supported combustion. Solutions are compared with detailed numerical modeling as benchmarked by laboratory experiments.

  18. Laser Induced Chemical Liquid Phase Deposition (LCLD)

    SciTech Connect

    Nanai, Laszlo; Balint, Agneta M.

    2012-08-17

    Laser induced chemical deposition (LCLD) of metals onto different substrates attracts growing attention during the last decade. Deposition of metals onto the surface of dielectrics and semiconductors with help of laser beam allows the creation of conducting metal of very complex architecture even in 3D. In the processes examined the deposition occurs from solutions containing metal ions and reducing agents. The deposition happens in the region of surface irradiated by laser beam (micro reactors). Physics -chemical reactions driven by laser beam will be discussed for different metal-substrate systems. The electrical, optical, mechanical properties of created interfaces will be demonstrated also including some practical-industrial applications.

  19. Automated retinal layer segmentation and characterization

    NASA Astrophysics Data System (ADS)

    Luisi, Jonathan; Briley, David; Boretsky, Adam; Motamedi, Massoud

    2014-05-01

    Spectral Domain Optical Coherence Tomography (SD-OCT) is a valuable diagnostic tool in both clinical and research settings. The depth-resolved intensity profiles generated by light backscattered from discrete layers of the retina provide a non-invasive method of investigating progressive diseases and injury within the eye. This study demonstrates the application of steerable convolution filters capable of automatically separating gradient orientations to identify edges and delineate tissue boundaries. The edge maps were recombined to measure thickness of individual retinal layers. This technique was successfully applied to longitudinally monitor changes in retinal morphology in a mouse model of laser-induced choroidal neovascularization (CNV) and human data from age-related macular degeneration patients. The steerable filters allow for direct segmentation of noisy images, while novel recombination of weaker segmentations allow for denoising post-segmentation. The segmentation before denoising strategy allows the rapid detection of thin retinal layers even under suboptimal imaging conditions.

  20. Computer-aided retinal photocoagulation system

    NASA Astrophysics Data System (ADS)

    Barrett, Steven F.; Wright, Cameron H.; Jerath, Maya R.; Lewis, R. Stephen; Dillard, Bryan C.; Rylander, Henry G.; Welch, Ashley J.

    1996-01-01

    Researchers at the University of Texas at Austin's Biomedical Engineering Laser Laboratory and the U.S. Air Force Academy's Department of Electrical Engineering are developing a computer-assisted prototype retinal photocoagulation system. The project goal is to rapidly and precisely automatically place laser lesions in the retina for the treatment of disorders such as diabetic retinopathy and retinal tears while dynamically controlling the extent of the lesion. Separate prototype subsystems have been developed to control lesion parameters (diameter or depth) using lesion reflectance feedback and lesion placement using retinal vessels as tracking landmarks. Successful subsystem testing results in vivo on pigmented rabbits using an argon continuous wave laser are presented. A prototype integrated system design to simultaneously control lesion parameters and placement at clinically significant speeds is provided.

  1. Confocal Laser Induced Fluorescence of Argon Plasmas

    NASA Astrophysics Data System (ADS)

    Scime, Earl; Soderholm, Mark

    2015-11-01

    Laser Induced Fluorescence (LIF) provides measurements of flow speed, temperature and when absolutely calibrated, density of ions or neutrals in a plasma. Traditionally, laser induced fluorescence requires two ports on a plasma device. One port is used for laser injection and the other is used for fluorescence emission collection. Traditional LIF is tedious and time consuming to align. These difficulties motivate the development of an optical configuration that requires a single port and remains fully aligned at all times; confocal LIF. Our confocal optical design employs a single two inch diameter lens to both inject the laser light and collect the stimulated emission from an argon plasma. A pair of axicon lenses create an annular beam path for the emission collection and the pump laser light is confined inside the annulus of the collection beam. The measurement location is scanned radially by manually adjusting the final focusing lens position. Here we present optical modeling of and initial results from the axicon based confocal optical system. The confocal measurements are compared to traditional, two-port, LIF measurements over the same radial range. This work is supported by US National Science Foundation grant number PHY-1360278.

  2. Cytomegalovirus retinitis mimicking intraocular lymphoma.

    PubMed

    Gooi, Patrick; Farmer, James; Hurley, Bernard; Brodbaker, Elliott

    2008-12-01

    We present a case of an unusual retinal infiltrate requiring retinal biopsy for definitive diagnosis. A 62-year-old man with treated lymphoma presented with decreased vision in the right eye associated with a white retinal lesion, which extended inferonasally from an edematous disc. Intraocular lymphoma was considered as a diagnosis; thus, the patient was managed with vitrectomy and retinal biopsy. Cytological analysis of the vitreous aspirate could not rule out a lymphoproliferative disorder. The microbial analysis was negative. Histology of the lesion showed extensive necrosis and large cells with prominent nucleoli. To rule out lymphoma, a battery of immunostains was performed and all were negative. However the limited amount of tissue was exhausted in the process. Subsequently, a hematoxylin and eosin (H/E) slide was destained, on which a CMV immunostain was performed. This revealed positivity in the nuclei and intranuclear inclusions within the large atypical cells. A diagnosis of CMV retinitis was made. Retinal biopsy may provide a definitive diagnosis and direct patient care toward intravenous gancyclovir in the case of CMV or toward radiation and chemotherapy for intraocular lymphoma. When faced with a limited amount of tissue, destaining regular H/E slides is a possible avenue to performing additional immunohistochemical studies. PMID:19668455

  3. Laser-induced autofluorescence study of caries model in vitro.

    PubMed

    Borisova, Ekaterina; Uzunov, Tzonko; Avramov, Latchezar

    2006-04-01

    Laser-induced autofluorescence spectra of teeth irradiated by a 337 nm nitrogen laser were measured during in vitro caries formation through initial enamel demineralization and introducing of carious bacterial flora in the lesions developed. Spectra obtained from sound teeth consist of an intensive maximum at 480-500 nm and secondary maximum at 430-450 nm. In the process of caries formation, we observed an increase in the intensity at 430-450 nm and the appearance of two maxima in the red spectral region-at 590-650 nm. The intensity increase at 430-450 nm was related to the tooth demineralization. Bacteria presence and their metabolism products induced an increase in the absorption in the UV-blue spectral region at 350-420 nm and the appearance of a fluorescence signal in the long-wave spectral region at 590-650 nm. From the point of view of tissue optics, these results allow caries to be considered as consisting of two different phenomena-tissue destruction and bacterial flora and its metabolism products increase. The results could be used to obtain a more complete picture of caries formation on the base of its fluorescent properties. PMID:16568211

  4. Diode laser contact transscleral retinal photocoagulation: a clinical study.

    PubMed Central

    McHugh, D A; Schwartz, S; Dowler, J G; Ulbig, M; Blach, R K; Hamilton, P A

    1995-01-01

    AIM--To examine the clinical efficacy of contact transscleral retinal photocoagulation with a diode laser. METHODS--Transscleral retinal photocoagulation was performed on 36 eyes. The conditions treated included peripheral retinal breaks associated with retinal detachments (30 eyes) and giant retinal tears (six eyes). Of the 30 eyes with retinal detachments, 28 underwent transscleral photocoagulation to the site of drainage of subretinal fluid in an attempt to reduce the risk of hemorrhage. RESULTS--Threshold lesions were obtained with irradiances of between 95.4 W/cm2 and 191 W/cm2. Satisfactory chorioretinal adhesion was achieved in all eyes with retinal breaks and giant retinal tears. The only significant complications of treatment encountered were punctate choroidal haemorrhages (three eyes). Drainage related choroidal haemorrhage following earlier photocoagulation occurred in two of 28 eyes. CONCLUSIONS--This study confirms the clinical potential of transscleral diode laser photocoagulation in the therapy of surgical retinal conditions. Images PMID:8562540

  5. Retinal Prosthesis

    PubMed Central

    Weiland, James D.; Humayun, Mark S.

    2015-01-01

    Retinal prosthesis have been translated from the laboratory to the clinical over the past two decades. Currently, two devices have regulatory approval for the treatment of retinitis pigmentosa. These devices provide partial sight restoration and patients use this improved vision in their everyday lives. Improved mobility and object detection are some of the more notable findings from the clinical trials. However, significant vision restoration will require both better technology and improved understanding of the interaction between electrical stimulation and the retina. This paper reviews the recent clinical trials, highlights technology breakthroughs that will contribute to next generation of retinal prostheses. PMID:24710817

  6. Foveomacular retinitis.

    PubMed Central

    Kuming, B S

    1986-01-01

    A group of patients is described who developed the clinical features of foveomacular retinitis. No causative factors were isolated, and all patients strongly denied any type of sun gazing. It is possible that there is a group of patients who have the features of foveomacular retinitis but have not had any direct exposure to the sun. These patients would then constitute a primary type of foveomacular retinitis, as opposed to a secondary type which has a known cause and is synonymous with solar retinopathy. Images PMID:3790482

  7. Laser-induced fluorescence imaging of bacteria

    NASA Astrophysics Data System (ADS)

    Hilton, Peter J.

    1998-12-01

    This paper outlines a method for optically detecting bacteria on various backgrounds, such as meat, by imaging their laser induced auto-fluorescence response. This method can potentially operate in real-time, which is many times faster than current bacterial detection methods, which require culturing of bacterial samples. This paper describes the imaging technique employed whereby a laser spot is scanned across an object while capturing, filtering, and digitizing the returned light. Preliminary results of the bacterial auto-fluorescence are reported and plans for future research are discussed. The results to date are encouraging with six of the eight bacterial strains investigated exhibiting auto-fluorescence when excited at 488 nm. Discrimination of these bacterial strains against red meat is shown and techniques for reducing background fluorescence discussed.

  8. CW CO2 Laser Induced Chemical Reactions

    NASA Astrophysics Data System (ADS)

    Pola, Joseph

    1989-05-01

    CW CO2 laser driven reactions between sulfur hexafluoride and carbon oxide, carbon suboxide, carbonyl sulfide and carbon disulfide proceed at subatmospheric pressures and yield fluorinated carbon compounds and sulfur tetrafluoride. CW CO2 laser driven reactions of organic compounds in the presence of energy-conveying sulfur hexafluoride show reaction course different from that normally observed due to elimination of reactor hot surface effects. The examples concern the decomposition of polychlorohydrocarbons, 2-nitropropane, tert.-butylamine, allyl chloride, spirohexane, isobornyl acetate and the oxidation of haloolefins. CW CO2 laser induced fragmentation of 1-methyl-l-silacyclobutanes and 4-silaspiro(3.4)octane in the presence of sulfur hexafluoride is an effective way for preparation and deposition of stable organosilicon polymers.

  9. Laser induced fluorescence of dental caries

    NASA Technical Reports Server (NTRS)

    Albin, S.; Byvik, C. E.; Buoncristiani, A. M.

    1988-01-01

    Significant differences between the optical spectra taken from sound regions of teeth and carious regions have been observed. These differences appear both in absorption and in laser induced fluorescence spectra. Excitation by the 488 nm line of an argon ion laser beam showed a peak in the emission intensity around 553 nm for the sound dental material while the emission peak from the carious region was red-shifted by approximately 40 nm. The relative absorption of carious region was significantly higher at 488 nm; however its fluorescence intensity peak was lower by an order of magnitude compared to the sound tooth. Implications of these results for a safe, reliable and early detection of dental caries are discussed.

  10. Laser-Induced Spallation of Microsphere Monolayers.

    PubMed

    Hiraiwa, Morgan; Stossel, Melicent; Khanolkar, Amey; Wang, Junlan; Boechler, Nicholas

    2016-08-01

    The detachment of a semiordered monolayer of polystyrene microspheres adhered to an aluminum-coated glass substrate is studied using a laser-induced spallation technique. The microsphere-substrate adhesion force is estimated from substrate surface displacement measurements obtained using optical interferometry, and a rigid-body model that accounts for the inertia of the microspheres. The estimated adhesion force is compared with estimates obtained using an adhesive contact model together with interferometric measurements of the out-of-plane microsphere contact resonance, and with estimated work of adhesion values for the polystyrene-aluminum interface. Scanning electron microscope images of detached monolayer regions reveal a unique morphology, namely, partially detached monolayer flakes composed of single hexagonal close packed crystalline domains. This work contributes to the fields of microsphere adhesion and contact dynamics, and demonstrates a unique monolayer delamination morphology. PMID:27409715

  11. Laser-Induced Incandescence: Detection Issues

    NASA Technical Reports Server (NTRS)

    VanderWal, Randall L.

    1996-01-01

    Experimental LII (laser-induced incandescence) measurements were performed in a laminar gasjet flame to test the sensitivity of different LII signal collection strategies to particle size. To prevent introducing a particle size dependent bias in the LII signal, signal integration beginning with the excitation laser pulse is necessary . Signal integration times extending to 25 or 100 nsec after the laser pulse do not produce significant differences in radial profiles of the LII signal due to particle size effects with longer signal integration times revealing a decreased sensitivity to smaller primary particles. Long wavelength detection reduces the sensitivity of the LII signal to primary particle size. Excitation of LII using 1064 nm light is recommended to avoid creating photochemical interferences thus allowing LII signal collection to occur during the excitation pulse without spectral interferences.

  12. Laser-induced breakdown spectroscopy in China

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Yuan, Ting-Bi; Hou, Zong-Yu; Zhou, Wei-Dong; Lu, Ji-Dong; Ding, Hong-Bin; Zeng, Xiao-Yan

    2014-08-01

    Laser-induced breakdown spectroscopy (LIBS) has been regarded as a future superstar for chemical analysis for years due to its unique features such as little or no sample preparation, remote sensing, and fast and multi-element analysis. Chinese LIBS community is one of the most dynamically developing communities in the World. The aim of the work is to inspect what have been done in China for LIBS development and, based on the understanding of the overall status, to identify the challenges and opportunities for the future development. In this paper, the scientific contributions from Chinese LIBS community are reviewed for the following four aspects: fundamentals, instrumentation, data processing and modeling, and applications; and the driving force of LIBS development in China is analyzed, the critical issues for successful LIBS application are discussed, and in our opinion, the potential direction to improve the technology and to realize large scale commercialization in China is proposed.

  13. Laser-induced autofluorescence of caries

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Hibst, Raimund; Flemming, Gabriela; Schneckenburger, Herbert

    1993-07-01

    The laser induced autofluorescence from carious regions of human teeth was studied using a krypton ion laser at 407 nm as an excitation source, a fiberoptical detection system combined with a polychromator and an optical multichannel analyzer. In addition, time-resolved and time-gated fluorescence measurements in the nanosecond range were carried out. It was found that carious regions contain different fluorophores which emit in the red spectral range. The emission spectra with maxima around 590 nm, 625 nm and 635 nm are typical for metalloporphyrins, copro- and protoporphyrin. During excitation the fluorescence was bleached. Non-carious regions showed a broad fluorescence band with a maximum in the short-wavelength spectral region with shorter fluorescence decay times than the carious regions. Therefore, caries can be detected by spectral analysis of the autofluorescence as well as by determination of the fluorescence decay times or by time-gated imaging.

  14. Laser-induced fluorescence-cued, laser-induced breakdown spectroscopy biological-agent detection

    SciTech Connect

    Hybl, John D.; Tysk, Shane M.; Berry, Shaun R.; Jordan, Michael P

    2006-12-01

    Methods for accurately characterizing aerosols are required for detecting biological warfare agents. Currently, fluorescence-based biological agent sensors provide adequate detection sensitivity but suffer from high false-alarm rates. Combining single-particle fluorescence analysis with laser-induced breakdown spectroscopy (LIBS) provides additional discrimination and potentially reduces false-alarm rates. A transportable UV laser-induced fluorescence-cued LIBS test bed has been developed and used to evaluate the utility of LIBS for biological-agent detection. Analysis of these data indicates that LIBS adds discrimination capability to fluorescence-based biological-agent detectors.However, the data also show that LIBS signatures of biological agent simulants are affected by washing. This may limit the specificity of LIBS and narrow the scope of its applicability in biological-agent detection.

  15. Retinal Disorders

    MedlinePlus

    ... be serious enough to cause blindness. Examples are Macular degeneration - a disease that destroys your sharp, central vision Diabetic eye disease Retinal detachment - a medical emergency, when the retina is ... children. Macular pucker - scar tissue on the macula Macular hole - ...

  16. Retinal Detachment

    MedlinePlus

    ... immediately. Treatment How is retinal detachment treated? Small holes and tears are treated with laser surgery or ... laser surgery tiny burns are made around the hole to “weld” the retina back into place. Cryopexy ...

  17. Clinical Features of Newly Diagnosed Cytomegalovirus Retinitis in Northern Thailand

    PubMed Central

    Ausayakhun, Somsanguan; Keenan, Jeremy D; Ausayakhun, Sakarin; Jirawison, Choeng; Khouri, Claire M; Skalet, Alison H; Heiden, David; Holland, Gary N; Margolis, Todd P

    2011-01-01

    Purpose To characterize the clinical manifestations of cytomegalovirus (CMV) retinitis in northern Thailand. Design Prospective, observational cross-sectional study. Methods We recorded characteristics of 52 consecutive patients newly diagnosed with CMV retinitis at a tertiary university-based medical center in northern Thailand. Indirect ophthalmoscopy by experienced ophthalmologists was supplemented with fundus photography to determine the proportion of eyes with various clinical features of CMV retinitis. Results Of the 52 patients with CMV retinitis, 55.8% were female. All were HIV-positive. The vast majority (90.4%) had started antiretroviral therapy. CMV retinitis was bilateral in 46.2% of patients. Bilateral visual acuity worse than 20/60 was observed in 23.1% of patients. Of 76 eyes with CMV retinitis, 61.8% had zone I disease and 21.6% had lesions involving the fovea. Lesions larger than 25% of the retinal area were observed in 57.5% of affected eyes. CMV retinitis lesions commonly had marked or severe border opacity (47.4% of eyes). Vitreous haze was often present (46.1% of eyes). Visual impairment was more common in eyes with larger retinitis lesions. Retinitis lesion size, used as a proxy for duration of disease, was associated with fulminant appearance (OR 1.24 [1.01 – 1.51]), and marked or severe border opacity (OR 1.36 [1.11 – 1.67]). Based on lesion size, retinitis preceded antiretroviral treatment in each patient. Conclusions Patients presenting to a tertiary medical center in northern Thailand have advanced CMV retinitis, possibly due to delayed diagnosis. Earlier screening and treatment of CMV retinitis may limit progression of disease and prevent visual impairment in this population. PMID:22265148

  18. Laser-Induced Damage of Calcium Fluoride

    SciTech Connect

    Espana, Aubrey L.; Joly, Alan G.; Hess, Wayne P.; Dickinson, J T.

    2004-12-01

    Radiation damage of materials has long been of fundamental interest, especially since the growth of laser technology. One such source of damage comes from UV laser light. Laser systems continue to move into shorter wavelength ranges, but unfortunately are limited by the damage threshold of their optical components. For example, semiconductor lithography is making its way into the 157nm range and requires a material that can not only transmit this light (air cannot), but also withstand the highly energetic photons present at this shorter wavelength. CaF2, an alkaline earth halide, is the chosen material for vacuum UV 157 nm excimer radiation. It can transmit light down to 120 nm and is relatively inexpensive. Although it is readily available through natural and synthetic sources, it is often times difficult to find in high purity. Impurities in the crystal can result in occupied states in the band gap that induce photon absorption [2] and ultimately lead to the degradation of the material. In order to predict how well CaF2 will perform under irradiation of short wavelength laser light, one must understand the mechanisms for laser-induced damage. Laser damage is often a two-step process: initial photons create new defects in the lattice and subsequent photons excite these defects. When laser light is incident on a solid surface there is an initial production of electron-hole (e-h) pairs, a heating of free electrons and a generation of local heating around optically absorbing centers [3]. Once this initial excitation converts to the driving energy for nuclear motion, the result is an ejection of atoms, ions and molecules from the surface, known as desorption or ablation [3]. Secondary processes further driving desorption are photoabsorption, successive excitations of self-trapped excitons (STE's) and defects, and ionization of neutrals by incident laser light [3]. The combination of laser-induced desorption and the alterations to the electronic and geometrical

  19. Railgun system using a laser-induced plasma armature

    SciTech Connect

    Onozuka, M.; Oda, Y.; Azuma, K.

    1996-05-01

    Development of an electromagnetic railgun system that utilizes a laser-induced plasma armature formation has been conducted to investigate the application of the railgun system for high-speed pellet injection into fusion plasmas. Using the laser-induced plasma formation technique, the required breakdown voltage was reduced by one-tenth compared with that for the spark-discharged plasma. The railgun system successfully accelerated the laser-induced plasma armature by an electromagnetic force that accelerated the pellet. The highest velocity of the solid hydrogen pellets, obtained so far, was 2.6 km/sec using a 2m-long railgun. {copyright} {ital 1996 American Institute of Physics.}

  20. Diagnostics of pigmented skin tumors based on laser-induced autofluorescence and diffuse reflectance spectroscopy

    SciTech Connect

    Borisova, E; Avramov, L; Troyanova, P; Pavlova, P

    2008-06-30

    Results of investigation of cutaneous benign and malignant pigmented lesions by laser-induced autofluorescence spectroscopy (LIAFS) and diffuse reflectance spectroscopy (DRS) are presented. The autofluorescence of human skin was excited by a 337-nm nitrogen laser. A broadband halogen lamp (400-900 nm) was used for diffuse reflectance measurements. A microspectrometer detected in vivo the fluorescence and reflectance signals from human skin. The main spectral features of benign (dermal nevi, compound nevi, dysplastic nevi) and malignant (melanoma) lesions are discussed. The combined usage of the fluorescence and reflectance spectral methods to determine the type of the lesion, which increases the total diagnostic accuracy, is compared with the usage of LIAFS or DRS only. We also applied colorimetric transformation of the reflectance spectra detected and received additional evaluation criteria for determination of type of the lesion under study. Spectra from healthy skin areas near the lesion were detected and changes between healthy and lesion skin spectra were revealed. The influence of the main skin pigments on the detected spectra is discussed and evaluation of possibilities for differentiation between malignant and benign lesions is performed based on their spectral properties. This research shows that the non-invasive and high-sensitive in vivo detection by means of appropriate light sources and detectors should be possible, related to the real-time determination of existing pathological conditions. (special issue devoted to application of laser technologies in biophotonics and biomedical studies)

  1. Laser-induced electron capture mass spectrometry

    PubMed

    Wang; Giese

    2000-02-15

    Two techniques are reported for detection of electrophorederivatized compounds by laser-induced electron capture time-of-flight mass spectrometry (LI-EC-TOF-MS). In both cases, a nitrogen laser is used to induce the electron capture. The analyte is deposited in a matrix consisting of a compound with a low ionization potential such as benzo[ghi]perylene in the first technique, where the electron for electron capture apparently comes from this matrix. In the second technique, the analyte is deposited on a silver surface in the absence of matrix. It seems that "monoenergetic" ions instantly desorb from the target surface in the latter case, since the peak width in the continuous extraction mode essentially matches the pulse width of the laser (4 ns). Ten picomoles of 3-O-(pentafluorobenzyl)-alpha-estradiol were detected at a S/N > or = 50, where the spot size of the laser was approximately 0.25% of the sample spot. It is attractive that simple conditions can enable sensitive detection of electrophores on routine TOF-MS equipment. The technique can be anticipated to broaden the range of analytes in both polarity and size that can be detected by EC-MS relative to the range for GC/EC-MS. PMID:10701262

  2. Laser-Induced Magnetic Dipole Spectroscopy.

    PubMed

    Hintze, Christian; Bücker, Dennis; Domingo Köhler, Silvia; Jeschke, Gunnar; Drescher, Malte

    2016-06-16

    Pulse electron paramagnetic resonance measurements of nanometer scale distance distributions have proven highly effective in structural studies. They exploit the magnetic dipole-dipole coupling between spin labels site-specifically attached to macromolecules. The most commonly applied technique is double electron-electron resonance (DEER, also called pulsed electron double resonance (PELDOR)). Here we present the new technique of laser-induced magnetic dipole (LaserIMD) spectroscopy based on optical switching of the dipole-dipole coupling. In a proof of concept experiment on a model peptide, we find, already at a low quantum yield of triplet excitation, the same sensitivity for measuring the distance between a porphyrin and a nitroxide label as in a DEER measurement between two nitroxide labels. On the heme protein cytochrome C, we demonstrate that LaserIMD allows for distance measurements between a heme prosthetic group and a nitroxide label, although the heme triplet state is not directly observable by an electron spin echo. PMID:27163749

  3. Laser Induced Birefringence in Pure Liquids

    NASA Astrophysics Data System (ADS)

    Harrison, Neil J.

    1991-01-01

    Available from UMI in association with The British Library. Laser induced birefringence or the Optical Kerr effect is a subject that has undergone much research over previous years and is an established technique for the study of many classes of materials. To date the measurements on various media have been characterized by the substantial time required to obtain results and the generally poor sensitivity of the apparatus used. This work describes the development of a new apparatus which is the first in the field to automate the signal capture and analysis utilizing a 1 Gigasample/second digitizing oscilloscope connected to a microcomputer to provide fast, accurate transient analysis. Careful design of the apparatus enabled operation at two inducing wavelengths of 532nm and 1064nm. The sensitivity and accuracy of the apparatus coupled with the rapid transient evaluation was tested on a number of well characterized samples including benzene, nitrobenzene, toluene and benzoyl chloride and was found to give excellent agreement with other workers. The apparatus was used to investigate the properties of the organic pure liquid series the n-alkanes before making the first measurements on the 1-alkenes, 1-alkynes, alcohols, carboxylic acids and three alkdienes. Results from these experiments were used to evaluate the contributions of sigma and pi bonds to the Optical Kerr effect in simple organic molecules. A review of all previously published Optical Kerr effect results for pure liquids was also carried out and the first comprehensive table of results complied.

  4. Anions in laser-induced plasmas

    NASA Astrophysics Data System (ADS)

    Shabanov, S. V.; Gornushkin, I. B.

    2016-07-01

    The equation of state for plasmas containing negative atomic and molecular ions (anions) is modeled. The model is based on the assumption that all ionization processes and chemical reactions are at local thermal equilibrium and the Coulomb interaction in the plasma is described by the Debye-Hückel theory. In particular, the equation of state is obtained for plasmas containing the elements Ca, Cl, C, Si, N, and Ar. The equilibrium reaction constants are calculated using the latest experimental and ab initio data of spectroscopic constants for the molecules CaCl_2, CaCl, Cl_2, N_2, C_2, Si_2, CN, SiN, SiC, and their positive and negative ions. The model is applied to laser-induced plasmas (LIPs) by including the equation of state into a fluid dynamic numerical model based on the Navier-Stokes equations describing an expansion of LIP plumes into an ambient gas as a reactive viscous flow with radiative losses. In particular, the formation of anions Cl-, C-, Si-, {{Cl}}2^{ - }, {{Si}}2^{ - }, {{C}}2^{ - }, CN-, SiC-, and SiN- in LIPs is investigated in detail.

  5. Medical Applications of Laser Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Pathak, A. K.; Rai, N. K.; Singh, Ankita; Rai, A. K.; Rai, Pradeep K.; Rai, Pramod K.

    2014-11-01

    Sedentary lifestyle of human beings has resulted in various diseases and in turn we require a potential tool that can be used to address various issues related to human health. Laser Induced Breakdown Spectroscopy (LIBS) is one such potential optical analytical tool that has become quite popular because of its distinctive features that include applicability to any type/phase of samples with almost no sample preparation. Several reports are available that discusses the capabilities of LIBS, suitable for various applications in different branches of science which cannot be addressed by traditional analytical methods but only few reports are available for the medical applications of LIBS. In the present work, LIBS has been implemented to understand the role of various elements in the formation of gallstones (formed under the empyema and mucocele state of gallbladder) samples along with patient history that were collected from Purvancal region of Uttar Pradesh, India. The occurrence statistics of gallstones under the present study reveal higher occurrence of gallstones in female patients. The gallstone occurrence was found more prevalent for those male patients who were having the habit of either tobacco chewing, smoking or drinking alcohols. This work further reports in-situ LIBS study of deciduous tooth and in-vivo LIBS study of human nail.

  6. Laser Induced Fluorescence of the Iodine Ion

    NASA Astrophysics Data System (ADS)

    Hargus, William

    2014-10-01

    Iodine (I2) has been considered as a potential electrostatic spacecraft thruster propellant for approximately 2 decades, but has only recently been demonstrated. Energy conversion efficiency appears to be on par with xenon without thruster modification. Intriguingly, performance appears to exceed xenon at high acceleration potentials. As part of a continuing program for the development of non-intrusive plasma diagnostics for advanced plasma spacecraft propulsion, we have identified the I II 5d5D4 o state as metastable, and therefore containing a reservoir of excited state ions suitable for laser probing. The 5d5D4 o - 6p5P3 transition at 695.878 nm is convenient for diode laser excitation with the 5s5S2 o - 6p5P3 transition at 516.12 nm as an ideal candidate for non-resonant fluorescence collection. We have constructed a Penning type iodine microwave discharge lamp optimized for I II production for table-top measurements. This work demonstrates I II laser-induced fluorescence in a representative iodine discharge and will validate our previous theoretical work based on the limited available historical I II spectral data.

  7. Volume of a laser-induced microjet

    NASA Astrophysics Data System (ADS)

    Kawamoto, Sennosuke; Hayasaka, Keisuke; Noguchi, Yuto; Tagawa, Yoshiyuki

    2015-11-01

    Needle-free injection systems are of great importance for medical treatments. In spite of their great potential, these systems are not commonly used. One of the common problems is strong pain caused by diffusion shape of the jet. To solve this problem, the usage of a high-speed highly-focused microjet as needle-free injection system is expected. It is thus crucial to control important indicators such as ejected volume of the jet for its safe application. We conduct experiments to reveal which parameter influences mostly the ejected volume. In the experiments, we use a glass tube of an inner diameter of 500 micro-meter, which is filled with the liquid. One end is connected to a syringe and the other end is opened. Radiating the pulse laser instantaneously vapors the liquid, followed by the generation of a shockwave. We find that the maximum volume of a laser-induced bubble is approximately proportional to the ejected volume. It is also found that the occurrence of cavitation does not affect the ejected volume while it changes the jet velocity.

  8. Laser-induced lipolysis on adipose cells

    NASA Astrophysics Data System (ADS)

    Solarte, Efrain; Gutierrez, O.; Neira, Rodrigo; Arroyave, J.; Isaza, Carolina; Ramirez, Hugo; Rebolledo, Aldo F.; Criollo, Willian; Ortiz, C.

    2004-10-01

    Recently, a new liposuction technique, using a low-level laser (LLL) device and Ultrawet solution prior to the procedure, demonstrated the movement of fat from the inside to the outside of the adipocyte (Neira et al., 2002). To determine the mechanisms involved, we have performed Scanning and Transmission Electron Microscopy studies; Light transmittance measurements on adipocyte dilutions; and a study of laser light propagation in adipose tissue. This studies show: 1. Cellular membrane alterations. 2. LLL is capable to reach the deep adipose tissue layer, and 3. The tumescence solution enhances the light propagation by clearing the tissue. MRI studies demonstrated the appearance of fat on laser treated abdominal tissue. Besides, adipocytes were cultivated and irradiated to observe the effects on isolated cells. These last studies show: 1. 635 nm-laser alone is capable of mobilizing cholesterol from the cell membrane; this action is enhanced by the presence of adrenaline and lidocaine. 2. Intracellular fat is released from adipocytes by co joint action of adrenaline, aminophyline and 635 nm-laser. Results are consistent with a laser induced cellular process, which causes fat release from the adipocytes into the intercellular space, besides the modification of the cellular membranes.

  9. Laser Induced Fluorescence on Molecular Discharges

    NASA Astrophysics Data System (ADS)

    Mulders, Hjalmar; Rijke, Arij; Girault, Vincent; Stoffels, Winfred

    2008-10-01

    In the last half century, mercury has been used widely as the radiating species in many low pressure fluorescent lamps. Mercury primarily radiates at 254 nm and 185 nm. These photons excite a phosphor that fluoresces back to the ground state producing visible photons. This process reduces the efficiency because much of the energy of the UV photons has to be discarded. Using a species that emits light closer to or even in the visible range reduces these losses. Ideally the species (or a mixture of several species) should build up the whole visible spectrum, much like in HID lamps. InBr seems to be a good candidate for such a lamp, because it is an efficient radiator that emits most of its light around 370 nm; much closer to the visible part of the spectrum. In order to get insight in the energy transfer processes going on in these molecules we have conducted a laser induced fluorescence (LIF) experiment on InBr vapour and on a plasma. We have measured the decay times of different rovibrational levels of the InBr-molecule as well as the spectral distribution of the fluorescence from these levels. From the former we calculated the rotational temperature of the plasma and from the latter we calculated the Franck-Condon factors for the A-state as well as the vibrational temperature.

  10. Laser-induced hydrocarbon contamination in vacuum

    NASA Astrophysics Data System (ADS)

    Riede, Wolfgang; Allenspacher, Paul; Schröder, Helmut; Wernham, Denny; Lien, Yngve

    2005-12-01

    We investigated laser-induced deposition processes on BK7 substrates under the influence of pulsed Q-switched Nd:YAG laser radiation, starting from small toluene partial pressures in a background vacuum environment. The composition and structure of the deposit was analyzed using microscopic methods like Nomarski DIC, dark-field and white-light interference microscopy, TEM, EDX and XPS. We found a distinct threshold for deposition built-up dependant on the partial pressure of toluene (0.2 J/cm2 at 0.1 mbar, 0.8 J/cm2 at 0.01 mbar toluene). The deposits strictly followed the spherical geometry of the laser spot. No deposit accumulated on MgF2 AR coated BK7 samples even at high toluene partial pressures. The onset of deposit was accompanied by periodic surface ripples formation. EDX and XPS analysis showed a carbon-like layer which strongly absorbed the 1 μm laser radiation. The typical number of shots applied was 50 000. In addition, long term lifetime tests of more than 5 Mio. shots per site were run.

  11. Classical cutoffs for laser-induced nonsequential double ionization

    SciTech Connect

    Milosevic, D.B.; Becker, W.

    2003-12-01

    Classical cutoffs for the momenta of electrons ejected in laser-induced nonsequential double ionization are derived for the recollision-impact-ionization scenario. Such simple cutoff laws can aid in the interpretation of the observed electron spectra.

  12. Vacuum ultraviolet laser induced fluorescence on a Si atomic beam

    NASA Technical Reports Server (NTRS)

    O'Brian, T. R.; Lawler, J. E.

    1991-01-01

    A broadly applicable vacuum ultraviolet experiment is described for measuring radiative lifetimes of neutral and singly-ionized atoms in a beam environment to 5-percent accuracy using laser induced fluorescence. First results for neutral Si are reported.

  13. Improved Imaging With Laser-Induced Eddy Currents

    NASA Technical Reports Server (NTRS)

    Chern, Engmin J.

    1993-01-01

    System tests specimen of material nondestructively by laser-induced eddy-current imaging improved by changing method of processing of eddy-current signal. Changes in impedance of eddy-current coil measured in absolute instead of relative units.

  14. Comparision of laser-induced and classical ultasound

    NASA Astrophysics Data System (ADS)

    Niederhauser, Joel J.; Jaeger, Michael; Frenz, Martin

    2003-06-01

    A classical medical ultrasound system was combined with a pulsed laser source to allow laser-induced ultrasound imaging (optoacoustics). Classical ultrasound is based on reflection and scattering of an incident acoustic pulse at internal tissue structures. Laser-induced ultrasound is generated in situ by heating optical absorbing structures, such as blood vessels, with a 5 ns laser pulse (few degrees or fraction of degree), which generates pressure transients. Laser-induced ultrasound probes optical properties and therefore provides much higher contrast and complementary information compared to classical ultrasound. An ultrasound array transducer in combination with a commercial medical imaging system was used to record acoustic transients of both methods. Veins and arteries in a human forearm were identified in vivo using classical color doppler and oxygenation dependent optical absorption at 660 nm and 1064 nm laser wavelength. Safety limits of both methods were explored. Laser-induced ultrasound seems well suited to improve classical ultrasound imaging of subcutaneous regions.

  15. Retinal Detachment Associated with AIDS-Related Cytomegalovirus Retinitis: Risk Factors in a Resource-Limited Setting

    PubMed Central

    Yen, Michael; Chen, Jenny; Ausayakhun, Somsanguan; Kunavisarut, Paradee; Vichitvejpaisal, Pornpattana; Ausayakhun, Sakarin; Jirawison, Choeng; Shantha, Jessica; Holland, Gary N; Heiden, David; Margolis, Todd P; Keenan, Jeremy D

    2014-01-01

    Purpose To determine risk factors predictive of retinal detachment in patients with cytomegalovirus (CMV) retinitis in a setting with limited access to ophthalmic care. Design Case-control study. Methods Sixty-four patients with CMV retinitis and retinal detachment were identified from the Ocular Infectious Diseases and Retina Clinics at Chiang Mai University. Three control patients with CMV retinitis but no retinal detachment were selected for each case, matched by calendar date. The medical records of each patient were reviewed, with patient-level and eye-level features recorded for the clinic visit used to match cases and controls, and also for the initial clinic visit at which CMV retinitis was diagnosed. Risk factors for retinal detachment were assessed separately for each of these time points using multivariate conditional logistic regression models that included 1 eye from each patient. Results Patients with a retinal detachment were more likely than controls to have low visual acuity (OR, 1.24 per line of worse vision on the logMAR scale; 95%CI, 1.16-1.33) and bilateral disease (OR, 2.12; 95%CI, 0.92-4.90). Features present at the time of the initial diagnosis of CMV retinitis that predicted subsequent retinal detachment included bilateral disease (OR, 2.68; 95%CI, 1.18-6.08) and lesion size (OR, 2.64 per 10% increase in lesion size; 95%CI, 1.41-4.94). Conclusion Bilateral CMV retinitis and larger lesion sizes, each of which is a marker of advanced disease, were associated with subsequent retinal detachment. Earlier detection and treatment may reduce the likelihood that patients with CMV retinitis develop a retinal detachment. PMID:25448999

  16. Temperature controlled retinal photocoagulation

    NASA Astrophysics Data System (ADS)

    Schlott, Kerstin; Koinzer, Stefan; Baade, Alexander; Birngruber, Reginald; Roider, Johann; Brinkmann, Ralf

    2013-06-01

    Retinal photocoagulation lacks objective dosage in clinical use, thus the commonly applied lesions are too deep and strong, associated with pain reception and the risk of visual field defects and induction of choroidal neovascularisations. Optoacoustics allows real-time non-invasive temperature measurement in the fundus during photocoagulation by applying short probe laser pulses additionally to the treatment radiation, which excite the emission of ultrasonic waves. Due to the temperature dependence of the Grüneisen parameter, the amplitudes of the ultrasonic waves can be used to derive the temperature of the absorbing tissue. By measuring the temperatures in real-time and automatically controlling the irradiation by feedback to the treatment laser, the strength of the lesions can be defined. Different characteristic functions for the time and temperature dependent lesion sizes were used as rating curves for the treatment laser, stopping the irradiation automatically after a desired lesion size is achieved. The automatically produced lesion sizes are widely independent of the adjusted treatment laser power and individual absorption. This study was performed on anaesthetized rabbits and is a step towards a clinical trial with automatically controlled photocoagulation.

  17. Metal surface nitriding by laser induced plasma

    NASA Astrophysics Data System (ADS)

    Thomann, A. L.; Boulmer-Leborgne, C.; Andreazza-Vignolle, C.; Andreazza, P.; Hermann, J.; Blondiaux, G.

    1996-10-01

    We study a nitriding technique of metals by means of laser induced plasma. The synthesized layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problem. The nitriding method is tested on the synthesis of titanium nitride which is a well-known compound, obtained at present by many deposition and diffusion techniques. In the method of interest, a laser beam is focused on a titanium target in a nitrogen atmosphere, leading to the creation of a plasma over the metal surface. In order to understand the layer formation, it is necessary to characterize the plasma as well as the surface that it has been in contact with. Progressive nitrogen incorporation in the titanium lattice and TiN synthesis are studied by characterizing samples prepared with increasing laser shot number (100-4000). The role of the laser wavelength is also inspected by comparing layers obtained with two kinds of pulsed lasers: a transversal-excited-atmospheric-pressure-CO2 laser (λ=10.6 μm) and a XeCl excimer laser (λ=308 nm). Simulations of the target temperature rise under laser irradiation are performed, which evidence differences in the initial laser/material interaction (material heated thickness, heating time duration, etc.) depending on the laser features (wavelength and pulse time duration). Results from plasma characterization also point out that the plasma composition and propagation mode depend on the laser wavelength. Correlation of these results with those obtained from layer analyses shows at first the important role played by the plasma in the nitrogen incorporation. Its presence is necessary and allows N2 dissociation and a better energy coupling with the target. Second, it appears that the nitrogen diffusion governs the nitriding process. The study of the metal nitriding efficiency, depending on the laser used, allows us to explain the differences observed in the layer features

  18. Laser-induced gas-surface interactions

    NASA Astrophysics Data System (ADS)

    Chuang, T. J.

    Chemical reactions in homogeneous systems activated by laser radiation have been extensively investigated for more than a decade. The applications of lasers to promote gas-surface interactions have just been realized in recent years. The purpose of this paper is to examine the fundamental processes involved in laser-induced gas-surface chemical interactions. Specifically, the photon-enhanced adsorption, adsorbate-adsorbate and adsorbate-solid reactions, product formation and desorption processes are discussed in detail. The dynamic processes involved in photoexcitation of the electronic and vibrational states, the energy transfer and relaxation in competition with chemical interactions are considered. These include both single and multiple photon adsorption, and fundamental and overtone transitions in the excitation process, and inter- and intra-molecular energy transfer, and coupling with phonons, electron-hole pairs and surface plasmons in the energy relaxation process. Many current experimental and theoretical studies on the subject are reviewed and discussed with the goal of clarifying the relative importance of the surface interaction steps and relating the resulting concepts to the experimentally observed phenomena. Among the many gas-solid systems that have been investigated, there has been more extensive use of CO adsorbed on metals, and SF 6 and XeF 2 interactions with silicon as examples to illustrate the many facets of the electronically and vibrationally activated surface processes. Results on IR laser stimulated desorption of C 5H 5N and C 5D 5N molecules from various solid surfaces are also presented. It is clearly shown that rapid intermolecular energy exchange and molecule to surface energy transfer can have important effects on photodesorption cross sections and isotope selectivities. It is concluded that utilization of lasers in gas-surface studies not only can provide fundamental insight into the mechanism and dynamics involved in heterogeneous

  19. Retinal detachment

    MedlinePlus

    ... of the first symptoms of new flashes of light and floaters. ... diabetes. See your eye care specialist once a year. You may need more frequent visits if you have risk factors for retinal detachment. Be alert to symptoms of new flashes of light and floaters.

  20. Laser-induced thermal acoustic velocimetry

    NASA Astrophysics Data System (ADS)

    Schlamp, Stefan

    2000-11-01

    Laser-Induced Thermal Acoustics (LITA) is a non- intrusive, remote, four-wave mixing laser diagnostic technique for measurements of the speed of sound and of the thermal diffusivity in gases. If the gas composition is known, then its temperature and density can be inferred. Beam misalignments and bulk fluid velocities can influence the time history and intensity of LITA signals. A closed-form analytic expression for LITA signals incorporating these effects is derived. The magnitude of beam misalignment and the flow velocity can be inferred from the signal shape using a least-squares fit of this model to the experimental data. High-speed velocimetry using homodyne detection is demonstrated with NO2-seeded air in a supersonic blow-down nozzle. The measured speed of sound deviates less than 2% from the theoretical value assuming isentropic quasi-1D flow. Boundary layer effects degrade the velocity measurements to errors of 20%. Heterodyne detection is used for low-speed velocimetry up to Mach number M = 0.1. The uncertainty of the velocity measurements was ~0.2 m/s. The sound speed measurements were repeatable to 0.5%. The agreement between theory and experiments is very good. A one-hidden-layer feed-forward neural network is trained using back-propagation learning and a steepest descent learning rule to extract the speed of sound and flow velocity from a heterodyne LITA signal. The effect of the network size on the performance is demonstrated. The accuracy is determined with a second set of LITA signals that were not used during the training phase. The accuracy is found to be better than that of a conventional frequency decomposition technique while being computationally as efficient. This data analysis method is robust with respect to noise, numerically stable, and fast enough for real-time data analysis. The accuracy and uncertainty of non-resonant LITA measurements is investigated. The error in measurements of the speed of sound and of the thermal diffusivity

  1. Laser-Induced-Fluorescence Photogrammetry and Videogrammetry

    NASA Technical Reports Server (NTRS)

    Danehy, Paul; Jones, Tom; Connell, John; Belvin, Keith; Watson, Kent

    2004-01-01

    surface of the target. The improved method is denoted laser-induced-fluorescence photogrammetry.

  2. Laser-Induced Damage of Calcium Fluoride

    SciTech Connect

    Espana, A.; Joly, A.G.; Hess, W.P.; Dickinson, J.T.

    2004-01-01

    As advances continue to be made in laser technology there is an increasing demand for materials that have high thresholds for laser-induced damage. Laser damage occurs when light is absorbed, creating defects in the crystal lattice. These defects can lead to the emission of atoms, ions and molecules from the sample. One specific field where laser damage is of serious concern is semiconductor lithography, which is beginning to use light at a wavelength of 157 nm. CaF2 is a candidate material for use in this new generation of lithography. In order to prevent unnecessary damage of optical components, it is necessary to understand the mechanisms for laser damage and the factors that serve to enhance it. In this research, we study various aspects of laser interactions with CaF2, including impurity absorbance and various forms of damage caused by incident laser light. Ultraviolet (UV) laser light at 266 nm with both femtosecond (fs) and nanosecond (ns) pulse widths is used to induce ion and neutral particle emission from cleaved samples of CaF2. The resulting mass spectra show significant differences suggesting that different mechanisms for desorption occur following excitation using the different pulse durations. Following irradiation by ns pulses at 266 nm, multiple single-photon absorption from defect states is likely responsible for ion emission whereas the fs case is driven by a multi-photon absorption process. This idea is further supported by the measurements made of the transmission and reflection of fs laser pulses at 266 nm, the results of which reveal a non-linear absorption process in effect at high incident intensities. In addition, the kinetic energy profiles of desorbed Ca and K contaminant atoms are different indicating that a different mechanism is responsible for their emission as well. Overall, these results show that purity plays a key role in the desorption of atoms from CaF2 when using ns pulses. On the other hand, once the irradiance reaches high

  3. Laser induced incandescence and laser induced breakdown spectroscopy based sensor development

    NASA Astrophysics Data System (ADS)

    Eseller, Kemal Efe

    In this doctoral dissertation, two laser-based sensors were evaluated for different applications. Laser Induced Incandescence (LII) is a technique which can provide non-intrusive quantitative measurement of soot and it provides a unique diagnostic tool to characterize engine performance. Since LII is linearly proportional to the soot volume fraction, it can provide in situ, real time measurement of soot volume fraction with high temporal and spatial resolution. LII has the capability to characterize soot formation during combustion. The soot volume fraction from both flames and a soot generator was investigated with LII. The effects of experimental parameters, such as laser fluence, gate delay, gate width and various laser beam focusing, on LII signal was studied. Laser Induced Breakdown Spectroscopy (LIBS), a diagnostic tool for in situ elemental analysis, has been evaluated for on-line, simultaneous, multi-species impurity monitoring in hydrogen. LIBS spectra with different impurity levels of nitrogen, argon, and oxygen were recorded and the intensity of the spectral lines of Ar, O, N, and H observed were used to form calibration plots for impurities in hydrogen measurements. An ungated detection method for LIBS has been developed and applied to equivalence ratio measurements of CH4/air and biofuel/air. LIBS has also been used to quantitatively analyze the composition of a slurry sample. The quenching effect of water in slurry samples causes low LIBS signal quality with poor sensitivity. Univariate and multivariate calibration was performed on LIBS spectra of dried slurry samples for elemental analysis of Mg, Si and Fe. Calibration results show that the dried slurry samples give good correlation between spectral intensity and elemental concentration.

  4. Integrated computer-aided retinal photocoagulation system

    NASA Astrophysics Data System (ADS)

    Barrett, Steven F.; Wright, Cameron H. G.; Oberg, Erik D.; Rockwell, Benjamin A.; Cain, Clarence P.; Jerath, Maya R.; Rylander, Henry G., III; Welch, Ashley J.

    1996-05-01

    Successful retinal tracking subsystem testing results in vivo on rhesus monkeys using an argon continuous wave laser and an ultra-short pulse laser are presented. Progress on developing an integrated robotic retinal laser surgery system is also presented. Several interesting areas of study have developed: (1) 'doughnut' shaped lesions that occur under certain combinations of laser power, spot size, and irradiation time complicating measurements of central lesion reflectance, (2) the optimal retinal field of view to achieve simultaneous tracking and lesion parameter control, and (3) a fully digital versus a hybrid analog/digital tracker using confocal reflectometry integrated system implementation. These areas are investigated in detail in this paper. The hybrid system warrants a separate presentation and appears in another paper at this conference.

  5. Retinal Detachment Vision Simulator

    MedlinePlus

    ... Retina Treatment Retinal Detachment Vision Simulator Retinal Detachment Vision Simulator Mar. 01, 2016 How does a detached or torn retina affect your vision? If a retinal tear is occurring, you may ...

  6. Interrelationships between the Retinal Neuroglia and Vasculature in Diabetes

    PubMed Central

    2014-01-01

    For years, diabetic retinopathy has been defined based on vascular lesions, and neural abnormalities were not regarded as important. This review summarizes evidence that the neural retina has important effects on the retinal vasculature under normal conditions, and the interaction between the retinal neuroglial cells and vascular function is altered in diabetes. Importantly, new evidence raises a possibility that abnormalities within retinal neuroglial cells (notably photoreceptors) might actually be causing or initiating the vascular disease in diabetic retinopathy. PMID:25003068

  7. Time-resolved aluminium laser-induced plasma temperature measurements

    NASA Astrophysics Data System (ADS)

    Surmick, D. M.; Parigger, C. G.

    2014-11-01

    We seek to characterize the temperature decay of laser-induced plasma near the surface of an aluminium target from laser-induced breakdown spectroscopy measurements of aluminium alloy sample. Laser-induced plasma are initiated by tightly focussing 1064 nm, nanosecond pulsed Nd:YAG laser radiation. Temperatures are inferred from aluminium monoxide spectra viewed at systematically varied time delays by comparing experimental spectra to theoretical calculations with a Nelder Mead algorithm. The temperatures are found to decay from 5173 ± 270 to 3862 ± 46 Kelvin from 10 to 100 μs time delays following optical breakdown. The temperature profile along the plasma height is also inferred from spatially resolved spectral measurements and the electron number density is inferred from Stark broadened Hβ spectra.

  8. Laser-induced fluorescence of space-exposed polyurethane

    NASA Technical Reports Server (NTRS)

    Hill, Ralph H., Jr.

    1993-01-01

    The object of this work was to utilize laser-induced fluorescence technique to characterize several samples of space-exposed polyurethane. These samples were flown on the Long Duration Exposure Facility (LDEF), which was in a shuttle-like orbit for nearly 6 years. Because of our present work to develop laser-induced-fluorescence inspection techniques for polymers, space-exposed samples and controls were lent to us for evaluation. These samples had been attached to the outer surface of LDEF; therefore, they were subjected to thermal cycling, solar ultraviolet radiation, vacuum, and atomic oxygen. It is well documented that atomic oxygen and ultraviolet exposure have detrimental effects on many polymers. This was a unique opportunity to make measurements on material that had been naturally degraded by an unusual environment. During our past work, data have come from artificially degraded samples and generally have demonstrated a correlation between laser-induced fluorescence and tensile strength or elasticity.

  9. Laser-induced differential normalized fluorescence method for cancer diagnosis

    DOEpatents

    Vo-Dinh, T.; Panjehpour, M.; Overholt, B.F.

    1996-12-03

    An apparatus and method for cancer diagnosis are disclosed. The diagnostic method includes the steps of irradiating a tissue sample with monochromatic excitation light, producing a laser-induced fluorescence spectrum from emission radiation generated by interaction of the excitation light with the tissue sample, and dividing the intensity at each wavelength of the laser-induced fluorescence spectrum by the integrated area under the laser-induced fluorescence spectrum to produce a normalized spectrum. A mathematical difference between the normalized spectrum and an average value of a reference set of normalized spectra which correspond to normal tissues is calculated, which provides for amplifying small changes in weak signals from malignant tissues for improved analysis. The calculated differential normalized spectrum is correlated to a specific condition of a tissue sample. 5 figs.

  10. Laser-induced differential normalized fluorescence method for cancer diagnosis

    DOEpatents

    Vo-Dinh, Tuan; Panjehpour, Masoud; Overholt, Bergein F.

    1996-01-01

    An apparatus and method for cancer diagnosis are disclosed. The diagnostic method includes the steps of irradiating a tissue sample with monochromatic excitation light, producing a laser-induced fluorescence spectrum from emission radiation generated by interaction of the excitation light with the tissue sample, and dividing the intensity at each wavelength of the laser-induced fluorescence spectrum by the integrated area under the laser-induced fluorescence spectrum to produce a normalized spectrum. A mathematical difference between the normalized spectrum and an average value of a reference set of normalized spectra which correspond to normal tissues is calculated, which provides for amplifying small changes in weak signals from malignant tissues for improved analysis. The calculated differential normalized spectrum is correlated to a specific condition of a tissue sample.

  11. Crystal structure of laser-induced subsurface modifications in Si

    DOE PAGESBeta

    Verburg, P. C.; Smillie, L. A.; Römer, G. R. B. E.; Haberl, B.; Bradby, J. E.; Williams, J. S.; Huis in ’t Veld, A. J.

    2015-06-04

    Laser-induced subsurface modification of dielectric materials is a well-known technology. Applications include the production of optical components and selective etching. In addition to dielectric materials, the subsurface modification technology can be applied to silicon, by employing near to mid-infrared radiation. An application of subsurface modifications in silicon is laser-induced subsurface separation, which is a method to separate wafers into individual dies. Other applications for which proofs of concept exist are the formation of waveguides and resistivity tuning. However, limited knowledge is available about the crystal structure of subsurface modifications in silicon. In this paper, we investigate the geometry and crystalmore » structure of laser-induced subsurface modifications in monocrystalline silicon wafers. Finally, in addition to the generation of lattice defects, we found that transformations to amorphous silicon and Si-iii/Si-xii occur as a result of the laser irradiation.« less

  12. Crystal structure of laser-induced subsurface modifications in Si

    SciTech Connect

    Verburg, P. C.; Smillie, L. A.; Römer, G. R. B. E.; Haberl, B.; Bradby, J. E.; Williams, J. S.; Huis in ’t Veld, A. J.

    2015-06-04

    Laser-induced subsurface modification of dielectric materials is a well-known technology. Applications include the production of optical components and selective etching. In addition to dielectric materials, the subsurface modification technology can be applied to silicon, by employing near to mid-infrared radiation. An application of subsurface modifications in silicon is laser-induced subsurface separation, which is a method to separate wafers into individual dies. Other applications for which proofs of concept exist are the formation of waveguides and resistivity tuning. However, limited knowledge is available about the crystal structure of subsurface modifications in silicon. In this paper, we investigate the geometry and crystal structure of laser-induced subsurface modifications in monocrystalline silicon wafers. Finally, in addition to the generation of lattice defects, we found that transformations to amorphous silicon and Si-iii/Si-xii occur as a result of the laser irradiation.

  13. Laser-induced fluorescence as a method of early caries diagnosis

    NASA Astrophysics Data System (ADS)

    Mielczarek, Agnieszka; Wiewior, Piotr

    2001-07-01

    Use of lasers in dentistry dates back 20 years but is still not fully exploited, especially when concerning the hard dental tissues. Over the past many efforts and actions have been involved in testing and developing new methods for caries diagnosis. The implementation of these methods in general dental practice is unfortunately still limited because too little scientific evidence exists to support them. One of the age-old concerns for dentists is that decay is often discovered too late. Dentists commonly use x-ray imaging for early caries detection, but this method cannot reveal decay at a sufficiently early stage to avoid restorative methods. Generally, if a caries lesion si detected by x-ray, the mineral loss within the tooth is normally very high and will need invasive treatment. Several laser based techniques, as also other optical methods of detecting caries lesions at an early stage seem to be very promising. Fluorescence of tooth structure is observed when hard tissues are illuminated using laser light. Decayed areas appear dark and provide a contrast against the healthy background surrounding them, so discriminating sound and carious tissues. The aim of this study was to present the possibilities of using laser induced fluorescence in the diagnosis of early caries lesions. The current state-of-the-art is presented, as well as results of our investigations. In our studies an argon ion laser was used to illuminate the teeth and the fluorescence pictures were captured with a CCD camera and then analyzed. Results confirmed that laser induced fluorescence can be used as a sensitive method of caries diagnosis.

  14. Laser induced breakdown spectroscopy inside liquids: Processes and analytical aspects

    NASA Astrophysics Data System (ADS)

    Lazic, V.; Jovićević, S.

    2014-11-01

    This paper provides an overview of the laser induced breakdown spectroscopy (LIBS) inside liquids, applied for detection of the elements present in the media itself or in the submerged samples. The processes inherent to the laser induced plasma formation and evolution inside liquids are discussed, including shockwave generation, vapor cavitation, and ablation of solids. Types of the laser excitation considered here are single pulse, dual pulse and multi-pulse. The literature relative to the LIBS measurements and applications inside liquids is reviewed and the most relevant results are summarized. Finally, we discuss the analytical aspects and release some suggestions for improving the LIBS sensitivity and accuracy in liquid environment.

  15. Evolution of laser-induced plasma in solvent aerosols

    NASA Astrophysics Data System (ADS)

    Hening, Alexandru; Wroblewski, Ronald; George, Robert; McGirr, Scott

    2014-10-01

    This paper describes a novel technique for the detection of contaminants in air using the process of laser-induced filamentation. This work is focused primarily on the visible and infrared spectrum. Characterization of the temporal and spatial evolution of laser-generated plasma in solvent aerosols is necessary for the development of potential applications. Atmospheric aerosols impact capabilities of applications such as range from laser-induced ionized micro channels and filaments able to transfer high electric pulses over a few hundreds of meters, to the generation of plasma artifacts in air, far away from the laser source.

  16. Ultrafast molecular imaging by laser-induced electron diffraction

    SciTech Connect

    Peters, M.; Nguyen-Dang, T. T.; Cornaggia, C.; Saugout, S.; Charron, E.; Keller, A.; Atabek, O.

    2011-05-15

    We address the feasibility of imaging geometric and orbital structures of a polyatomic molecule on an attosecond time scale using the laser-induced electron diffraction (LIED) technique. We present numerical results for the highest molecular orbitals of the CO{sub 2} molecule excited by a near-infrared few-cycle laser pulse. The molecular geometry (bond lengths) is determined within 3% of accuracy from a diffraction pattern which also reflects the nodal properties of the initial molecular orbital. Robustness of the structure determination is discussed with respect to vibrational and rotational motions with a complete interpretation of the laser-induced mechanisms.

  17. New therapeutic modalities of retinal laser injury. Final report, 1 Mar 89-1 Mar 92

    SciTech Connect

    Lam, T.T.; Tso, M.O.

    1992-03-31

    Efficacies of three different regimens of high dose of methylprednisolone (MP) treatment on laser-induced non-hemorrhage retinal injury and tissue plasminogen activator (t-PA) in sub-retinal hemorrhage laser injury were evaluated in a sub-human primate model and a rat model respectively. Clinical, histopathological, and morphometric criteria were employed for evaluating the efficacy of MP. High dose and prolonged treatment (4 days) was the most effective regimen while high dose for 8 hours showed limited effect in non-hemorrhagic retinal injury. Intravitreal t-PA showed no apparent beneficial effect in sub-retinal hemorrhage after laser injury. Hence, patients with laser retinal injury may benefit from high dose MP treatment for an appropriate period of time.

  18. Impairing autophagy in retinal pigment epithelium leads to inflammasome activation and enhanced macrophage-mediated angiogenesis

    PubMed Central

    Liu, Jian; Copland, David A.; Theodoropoulou, Sofia; Chiu, Hsi An Amy; Barba, Miriam Durazo; Mak, Ka Wang; Mack, Matthias; Nicholson, Lindsay B.; Dick, Andrew D.

    2016-01-01

    Age-related decreases in autophagy contribute to the progression of age-related macular degeneration (AMD). We have now studied the interaction between autophagy impaired in retinal pigment epithelium (RPE) and the responses of macrophages. We find that dying RPE cells can activate the macrophage inflammasome and promote angiogenesis. In vitro, inhibiting rotenone-induced autophagy in RPE cells elicits caspase-3 mediated cell death. Co-culture of damaged RPE with macrophages leads to the secretion of IL-1β, IL-6 and nitrite oxide. Exogenous IL-6 protects the dysfunctional RPE but IL-1β causes enhanced cell death. Furthermore, IL-1β toxicity is more pronounced in dysfunctional RPE cells showing reduced IRAK3 gene expression. Co-culture of macrophages with damaged RPE also elicits elevated levels of pro-angiogenic proteins that promote ex vivo choroidal vessel sprouting. In vivo, impaired autophagy in the eye promotes photoreceptor and RPE degeneration and recruitment of inflammasome-activated macrophages. The degenerative tissue environment drives an enhanced pro-angiogenic response, demonstrated by increased size of laser-induced choroidal neovascularization (CNV) lesions. The contribution of macrophages was confirmed by depletion of CCR2+ monocytes, which attenuates CNV in the presence of RPE degeneration. Our results suggest that the interplay between perturbed RPE homeostasis and activated macrophages influences key features of AMD development. PMID:26847702

  19. Laser-Induced Breakdown Spectroscopy of Trace Metals

    NASA Technical Reports Server (NTRS)

    Simons, Stephen (Technical Monitor); VanderWal, Randall L.; Ticich, Thomas M.; West, Joseph R., Jr.

    2004-01-01

    An alternative approach for laser-induced breakdown spectroscopy (LIBS) determination of trace metal determination in liquids is demonstrated. The limits of detection (LOD) for the technique ranged from 10 ppb to 10 ppm for 15 metals metals (Mg, Al, Si, Ca, Ti, Cr, Fe, Co, Ni, Cu, Zn, As, Cd, Hg, Pb) tested.

  20. Plasma erosion rate diagnostics using laser-induced fluorescence

    NASA Technical Reports Server (NTRS)

    Gaeta, C. J.; Turley, R. S.; Matossian, J. N.; Beattie, J. R.; Williamson, W. S.

    1992-01-01

    An optical technique for measuring the sputtering rate of a molybdenum surface immersed in a xenon plasma has been developed and demonstrated. This approach, which may be useful in real-time wear diagnostics for ion thrusters, relies on laser-induced fluorescence to determine the density of sputtered molybdenum atoms.

  1. Using Laser-Induced Incandescence To Measure Soot in Exhaust

    NASA Technical Reports Server (NTRS)

    Bachalo, William D.; Sankar, Subramanian V.

    2005-01-01

    An instrumentation system exploits laser-induced incandescence (LII) to measure the concentration of soot particles in an exhaust stream from an engine, furnace, or industrial process that burns hydrocarbon fuel. In comparison with LII soot-concentration-measuring systems, this system is more complex and more capable.

  2. Laser-induced copper deposition with weak reducing agents

    NASA Astrophysics Data System (ADS)

    Kochemirovsky, V. A.; Fateev, S. A.; Logunov, L. S.; Tumkin, I. I.; Safonov, S. V.; Khairullina, E. M.

    2013-11-01

    The study showed that organic alcohols with 1,2,3,5,6 hydroxyl groups can be used as reducing agents for laser-induced copper deposition from solutions (LCLD).Multiatomic alcohols, sorbitol, xylitol, and glycerol, are shown to be effective reducing agents for performing LCLD at glass-ceramic surfaces. High-conductivity copper tracks with good topology were synthesized.

  3. Noninvasive laser-induced photoacoustic tomography for structural and functional in vivo imaging of the brain.

    PubMed

    Wang, Xueding; Pang, Yongjiang; Ku, Geng; Xie, Xueyi; Stoica, George; Wang, Lihong V

    2003-07-01

    Imaging techniques based on optical contrast analysis can be used to visualize dynamic and functional properties of the nervous system via optical signals resulting from changes in blood volume, oxygen consumption and cellular swelling associated with brain physiology and pathology. Here we report in vivo noninvasive transdermal and transcranial imaging of the structure and function of rat brains by means of laser-induced photoacoustic tomography (PAT). The advantage of PAT over pure optical imaging is that it retains intrinsic optical contrast characteristics while taking advantage of the diffraction-limited high spatial resolution of ultrasound. We accurately mapped rat brain structures, with and without lesions, and functional cerebral hemodynamic changes in cortical blood vessels around the whisker-barrel cortex in response to whisker stimulation. We also imaged hyperoxia- and hypoxia-induced cerebral hemodynamic changes. This neuroimaging modality holds promise for applications in neurophysiology, neuropathology and neurotherapy. PMID:12808463

  4. A mechanical model of retinal detachment

    NASA Astrophysics Data System (ADS)

    Chou, Tom; Siegel, Michael

    2012-08-01

    We present a model of the mechanical and fluid forces associated with exudative retinal detachments where the retinal photoreceptor cells separate, typically from the underlying retinal pigment epithelium (RPE). By computing the total fluid volume flow arising from transretinal, vascular and RPE pump currents, we determine the conditions under which the subretinal fluid pressure exceeds the maximum yield stress holding the retina and RPE together, giving rise to an irreversible, extended retinal delamination. We also investigate localized, blister-like retinal detachments by balancing mechanical tension in the retina with both the retina-RPE adhesion energy and the hydraulic pressure jump across the retina. For detachments induced by traction forces, we find a critical radius beyond which the blister is unstable to growth. Growth of a detached blister can also be driven by inflamed lesions in which the tissue has a higher choroidal hydraulic conductivity, has insufficient RPE pump activity, or has defective adhesion bonds. We determine the parameter regimes in which the blister either becomes unstable to growth, remains stable and finite-sized, or shrinks, allowing possible healing. The corresponding stable blister radius and shape are calculated. Our analysis provides a quantitative description of the physical mechanisms involved in exudative retinal detachments and can help guide the development of retinal reattachment protocols or preventative procedures.

  5. Laser induced autofluorescence for diagnosis of non-melanoma skin cancer

    NASA Astrophysics Data System (ADS)

    Drakaki, E.; Makropoulou, M.; Serafetinides, A. A.; Merlemis, N.; Kalatzis, I.; Sianoudis, I. A.; Batsi, O.; Christofidou, E.; Stratigos, A. J.; Katsambas, A. D.; Antoniou, Ch.

    2015-01-01

    Non melanoma skin cancer is one of the most frequent malignant tumors among humans. A non-invasive technique, with high sensitivity and high specificity, would be the most suitable method for basal cell carcinoma (BCC) or other malignancies diagnostics, instead of the well established biopsy and histopathology examination. In the last decades, a non-invasive, spectroscopic diagnostic method was introduced, the laser induced fluorescence (LIF), which could generate an image contrast between different states of skin tissue. The noninvasiveness consists in that this biophotonic method do not require tissue sample excision, what is necessary in histopathology characterization and biochemical analysis of the skin tissue samples, which is worldwide used as an evaluation gold standard. The object of this study is to establish the possibilities of a relatively portable system for laser induced skin autofluorescence to differentiate malignant from nonmalignant skin lesions. Unstained human skin samples, excised from humans undergoing biopsy examination, were irradiated with a Nd:YAG-3ω laser (λ=355 nm, 6 ns), used as an excitation source for the autofluorescence measurements. A portable fiber-based spectrometer was used to record fluorescence spectra of the sites of interest. The ex vivo results, obtained with this spectroscopic technique, were correlated with the histopathology results. After the analysis of the fluorescence spectra of almost 60 skin tissue areas, we developed an algorithm to distinguish different types of malignant lesions, including inflammatory areas. Optimization of the data analysis and potential use of LIF spectroscopy with 355 nm Nd:YAG laser excitation of tissue autofluorescence for clinical applications are discussed.

  6. Laser-induced dental caries and plaque diagnosis on patients by sensitive autofluorescence spectroscopy and time-gated video imaging: preliminary studies

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Schneckenburger, Herbert

    1994-09-01

    The laser-induced in vivo autofluorescence of human teeth was investigated by means of time- resolved/time-gated fluorescence techniques. The aim of these studies was non-contact caries and plaque detection. Carious lesions and dental plaque fluoresce in the red spectral region. This autofluorescence seems to be based on porphyrin-producing bacteria. We report on preliminary studies on patients using a novel method of autofluorescence imaging. A special device was constructed for time-gated video imaging. Nanosecond laser pulses for fluorescence excitation were provided by a frequency-doubled, Q-switched Nd:YAG laser. Autofluorescence was detected in an appropriate nanosecond time window using a video camera with a time-gated image intensifier (minimal time gate: 5 ns). Laser-induced autofluorescence based on porphyrin-producing bacteria seems to be an appropriate tool for detecting dental lesions and for creating `caries-images' and `dental plaque' images.

  7. In vivo visualizing the dynamics of bone marrow stem cells in mouse retina and choroidal-retinal circulation

    NASA Astrophysics Data System (ADS)

    Wang, Heuy-Ching H.; Zwick, Harry; Edsall, Peter R.; Cheramie, Rachel D.; Lund, David J.; Stuck, Bruce

    2007-02-01

    It has recently been shown that bone marrow cells can differentiate into various lineage cells including neural cells in vitro and in vivo. Therefore it is an attractive therapeutic intervention to apply autologous bone marrow-derived stem cells that may offer neuroprotection to laser-induced retinal injuries. The purpose of this study is to develop a method with which to visualize bone marrow stem cells dynamics in mouse retinal circulation. We have used a physiological method, confocal scanning laser ophthalmoscope (SLO), to track the highly enriched stem/progenitor cells circulating in the retina. Stem cells were enriched by immunomagnetic depletion of cells committed to the T- and B lymphocytic, myeloid and erythorid lineages. CellTracker TM Green-labeled stem cells were injected into the tail veins of mice with laser-induced focal retinal injuries. Bone marrow stem cells labeled with CellTracker TM Green were visible in the retinal circulation for as long as 1 hour and 30 minutes. These studies suggest that stem cell-enriched bone marrow cells may have the ability to mobilize into laser-induced retinal injuries and possibly further proliferate, differentiate and functionally integrate into the retina.

  8. Combined branch retinal vein and artery occlusion in toxoplasmosis.

    PubMed

    Aggio, Fabio Bom; Novelli, Fernando José de; Rosa, Evandro Luis; Nobrega, Mário Junqueira

    2016-01-01

    A 22-year-old man complained of low visual acuity and pain in his left eye for five days. His ophthalmological examination revealed 2+ anterior chamber reaction and a white, poorly defined retinal lesion at the proximal portion of the inferotemporal vascular arcade. There were retinal hemorrhages in the inferotemporal region extending to the retinal periphery. In addition, venous dilation, increased tortuosity, and ischemic retinal whitening along the inferotemporal vascular arcade were also observed. A proper systemic work-up was performed, and the patient was diagnosed with ocular toxoplasmosis. He was treated with an anti-toxoplasma medication, and his condition slowly improved. Inferior macular inner and middle retinal atrophy could be observed on optical coherence tomography as a sequela of ischemic injury. To our knowledge, this is the first report of combined retinal branch vein and artery occlusion in toxoplasmosis resulting in a striking and unusual macular appearance. PMID:27463632

  9. Branch retinal vein occlusion.

    PubMed

    Hamid, Sadaf; Mirza, Sajid Ali; Shokh, Ishrat

    2008-01-01

    Retinal vein occlusions (RVO) are the second commonest sight threatening vascular disorder. Branch retinal vein occlusion (BRVO) and central retinal vein occlusion (CRVO) are the two basic types of vein occlusion. Branch retinal vein occlusion is three times more common than central retinal vein occlusion and- second only to diabetic retinopathy as the most common retinal vascular cause of visual loss. The origin of branch retinal vein occlusion undoubtedly includes both systemic factors such as hypertension and local anatomic factors such as arteriovenous crossings. Branch retinal vein occlusion causes a painless decrease in vision, resulting in misty or distorted vision. Current treatment options don't address the underlying aetiology of branch retinal vein occlusion. Instead they focus on treating sequelae of the occluded venous branch, such as macular oedema, vitreous haemorrhage and traction retinal detachment from neovascularization. Evidences suggest that the pathogenesis of various types of retinal vein occlusion, like many other ocular vascular occlusive disorders, is a multifactorial process and there is no single magic bullet that causes retinal vein occlusion. A comprehensive management of patients with retinal vascular occlusions is necessary to correct associated diseases or predisposing abnormalities that could lead to local recurrences or systemic event. Along with a review of the literature, a practical approach for the management of retinal vascular occlusions is required, which requires collaboration between the ophthalmologist and other physicians: general practitioner, cardiologist, internist etc. as appropriate according to each case. PMID:19385476

  10. Angiographic results of retinal-retinal anastomosis and retinal-choroidal anastomosis after treatments in eyes with retinal angiomatous proliferation

    PubMed Central

    Saito, Masaaki; Iida, Tomohiro; Kano, Mariko; Itagaki, Kanako

    2012-01-01

    Background The purpose of this study was to evaluate the angiographic results of retinal-retinal anastomosis (RRA) and retinal-choroidal anastomosis (RCA) for eyes with retinal angiomatous proliferation (RAP) after treatment with intravitreal bevacizumab injections as monotherapy or intravitreal bevacizumab combined with photodynamic therapy. Methods In this interventional, consecutive case series, we retrospectively reviewed five naïve eyes from four patients (mean age 80 years) treated with three consecutive monthly intravitreal bevacizumab (1.25 mg/0.05 mL) injections as initial treatment, and followed up for at least 3 months. In cases with over 3 months of follow-up and having recurrence of RAP or leakage by fluorescein angiography, retreatment was performed with a single intravitreal bevacizumab injection and photodynamic therapy. Results Indocyanine green angiography showed RRA in three eyes with subretinal neovascularization and RCA in two eyes with choroidal neovascularization at baseline. At 3 months after baseline (month 3), neither the RRA nor RCA was occluded in any eye on indocyanine green angiography. Retreatment with intravitreal bevacizumab plus photodynamic therapy was performed in three eyes at months 3 (persistent leakage on fluorescein angiography), 6, and 7 (recurrence of RAP lesion), which achieved obvious occlusion of the RRA and RCA. Mean best-corrected visual acuity improved from 0.13 to 0.21 at month 3 (P = 0.066). No complications or systemic adverse events were noted. Conclusion Although intravitreal bevacizumab for RAP was effective in improving visual acuity during short-term follow-up, intravitreal bevacizumab could not achieve complete occlusion of RRA and RCA, which could lead to recurrence of a RAP lesion and exudation. Retreatment with intravitreal bevacizumab plus photodynamic therapy ultimately achieved complete occlusion of the RRA and RCA. PMID:22969283

  11. Analysis of organic vapors with laser induced breakdown spectroscopy

    SciTech Connect

    Nozari, Hadi; Tavassoli, Seyed Hassan; Rezaei, Fatemeh

    2015-09-15

    In this paper, laser induced breakdown spectroscopy (LIBS) is utilized in the study of acetone, ethanol, methanol, cyclohexane, and nonane vapors. Carbon, hydrogen, oxygen, and nitrogen atomic emission spectra have been recorded following laser-induced breakdown of the organic vapors that are mixed with air inside a quartz chamber at atmospheric pressure. The plasma is generated with focused, Q-switched Nd:YAG radiation at the wavelength of 1064 nm. The effects of ignition and vapor pressure are discussed in view of the appearance of the emission spectra. The recorded spectra are proportional to the vapor pressure in air. The hydrogen and oxygen contributions diminish gradually with consecutive laser-plasma events without gas flow. The results show that LIBS can be used to characterize organic vapor.

  12. Supersonic laser-induced jetting of aluminum micro-droplets

    SciTech Connect

    Zenou, M.; Sa'ar, A.; Kotler, Z.

    2015-05-04

    The droplet velocity and the incubation time of pure aluminum micro-droplets, printed using the method of sub-nanosecond laser induced forward transfer, have been measured indicating the formation of supersonic laser-induced jetting. The incubation time and the droplet velocity were extracted by measuring a transient electrical signal associated with droplet landing on the surface of the acceptor substrate. This technique has been exploited for studying small volume droplets, in the range of 10–100 femto-litters for which supersonic velocities were measured. The results suggest elastic propagation of the droplets across the donor-to-acceptor gap, a nonlinear deposition dynamics on the surface of the acceptor and overall efficient energy transfer from the laser beam to the droplets.

  13. Laser induced melting and crystallization of boron doped amorphous silicon

    SciTech Connect

    Nebel, C.E.; Schoeniger, S.; Dahlheimer, B.; Stutzmann, M.

    1997-07-01

    Transient reflectivity experiments have been performed to measure the dynamics of laser-induced melting of amorphous silicon (a-Si) and the crystallization to {micro}c-Si of films with different thicknesses on Corning 7059 glass. The laser-induced melting takes place with a velocity of 13 to 24 m/s, while the solidification is about a factor 10 slower. The crystallization starts at the Si/glass interface and at the surface. In the center of the films Si remains liquid for an extended period of time. The crystallization dynamics point towards an heterogeneous morphology of laser-crystallized Si, where the surface and the interface layers are composed of small grains and the bulk of larger grains.

  14. Estimating explosive performance from laser-induced shock waves

    NASA Astrophysics Data System (ADS)

    Gottfried, Jennifer

    2015-06-01

    A laboratory-scale method for predicting explosive performance (e.g., detonation velocity and pressure) based on milligram quantities of material is currently being developed. This technique is based on schlieren imaging of the shock wave generated in air by the formation of a laser-induced plasma on the surface of an energetic material. A large suite of pure and composite conventional energetic materials has been tested. Based on the observed linear correlation between the laser-induced shock velocity and the measured performance from full-scale detonation testing, this method is a potential screening tool for the development of new energetic materials and formulations prior to detonation testing. Recent results on the extension of this method to metal-containing energetic materials will be presented.

  15. Applications of laser-induced gratings to spectroscopy and dynamics

    SciTech Connect

    Rohlfing, E.A.

    1993-12-01

    This program has traditionally emphasized two principal areas of research. The first is the spectroscopic characterization of large-amplitude motion on the ground-state potential surface of small, transient molecules. The second is the reactivity of carbonaceous clusters and its relevance to soot and fullerene formation in combustion. Motivated initially by the desire to find improved methods of obtaining stimulated emission pumping (SEP) spectra of transients, most of our recent work has centered on the use of laser-induced gratings or resonant four-wave mixing in free-jet expansions. These techniques show great promise for several chemical applications, including molecular spectroscopy and photodissociation dynamics. The author describes recent applications of two-color laser-induced grating spectroscopy (LIGS) to obtain background-free SEP spectra of transients and double resonance spectra of nonfluorescing species, and the use of photofragment transient gratings to probe photodissociation dynamics.

  16. Analysis of organic vapors with laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Nozari, Hadi; Rezaei, Fatemeh; Tavassoli, Seyed Hassan

    2015-09-01

    In this paper, laser induced breakdown spectroscopy (LIBS) is utilized in the study of acetone, ethanol, methanol, cyclohexane, and nonane vapors. Carbon, hydrogen, oxygen, and nitrogen atomic emission spectra have been recorded following laser-induced breakdown of the organic vapors that are mixed with air inside a quartz chamber at atmospheric pressure. The plasma is generated with focused, Q-switched Nd:YAG radiation at the wavelength of 1064 nm. The effects of ignition and vapor pressure are discussed in view of the appearance of the emission spectra. The recorded spectra are proportional to the vapor pressure in air. The hydrogen and oxygen contributions diminish gradually with consecutive laser-plasma events without gas flow. The results show that LIBS can be used to characterize organic vapor.

  17. Supersonic laser-induced jetting of aluminum micro-droplets

    NASA Astrophysics Data System (ADS)

    Zenou, M.; Sa'ar, A.; Kotler, Z.

    2015-05-01

    The droplet velocity and the incubation time of pure aluminum micro-droplets, printed using the method of sub-nanosecond laser induced forward transfer, have been measured indicating the formation of supersonic laser-induced jetting. The incubation time and the droplet velocity were extracted by measuring a transient electrical signal associated with droplet landing on the surface of the acceptor substrate. This technique has been exploited for studying small volume droplets, in the range of 10-100 femto-litters for which supersonic velocities were measured. The results suggest elastic propagation of the droplets across the donor-to-acceptor gap, a nonlinear deposition dynamics on the surface of the acceptor and overall efficient energy transfer from the laser beam to the droplets.

  18. Laser-induced periodic surface structuring of biopolymers

    NASA Astrophysics Data System (ADS)

    Pérez, Susana; Rebollar, Esther; Oujja, Mohamed; Martín, Margarita; Castillejo, Marta

    2013-03-01

    We report here on a systematic study about the formation of laser-induced periodic surface structures (LIPSS) on biopolymers. Self-standing films of the biopolymers chitosan, starch and the blend of chitosan with the synthetic polymer poly (vinyl pyrrolidone), PVP, were irradiated in air with linearly polarized laser beams at 193, 213 and 266 nm, with pulse durations in the range of 6-17 ns. The laser-induced periodic surface structures were topographically characterized by atomic force microscopy and the chemical modifications induced by laser irradiation were inspected via Raman spectroscopy. Formation of LIPSS parallel to the laser polarization direction, with periods similar to the laser wavelength, was observed at efficiently absorbed wavelengths in the case of the amorphous biopolymer chitosan and its blend with PVP, while formation of LIPSS is prevented in the crystalline starch biopolymer.

  19. Variation of retinal ED50 with exposure duration for near-IR sources

    NASA Astrophysics Data System (ADS)

    Lund, David J.; Fuller, Daniel R.; Hoxie, Stephen W.; Edsall, P. R.

    1997-05-01

    A body of data relates the ED50 for laser-induced retinal damage to exposure duration for visible-wavelength laser exposure and for 1064 nm laser exposure. The database, extending from sub-nanosecond exposures to kilosecond exposures, can for the most part, be fit to models based on thermal interactions, thermal-mechanical mechanisms, and photochemical processes. Exceptions to this fit occur between 1 and 100 microseconds where the damage mechanism transitions from exclusively thermal to thermal-mechanical. Disagreement exists as to whether this anomalous dip of ED50 is real or is an artifact of the data. We determined the laser-induced retinal ED50 in Rhesus monkey eyes for several exposure durations from 12 nanoseconds to 1000 milliseconds at 755 nm using a dye laser, an alexandrite laser, and a Ti:Sapphire laser. These data do not show a dip in ED50 in the microsecond time period.

  20. Laser-induced incandescence applied to droplet combustion

    NASA Astrophysics Data System (ADS)

    Wal, Randall L. Vander; Dietrich, Daniel L.

    1995-02-01

    Laser-induced incandescence (LII) is ideally suited for obtaining high temporally and spatially resolved measurements of soot volume fraction in transient combustion phenomena. We demonstrate qualitative two-dimensional nonintrusive optical measurements of the soot evolution versus time from single fiber-supported burning fuel droplets of heptane and decane. Quantitative measurement of the soot volume fraction is also demonstrated through calibration of the LII signal against a small coflow ethylene diffusion flame.

  1. Post-acceleration of laser-induced ion beams

    NASA Astrophysics Data System (ADS)

    Nassisi, V.; Delle Side, D.

    2015-04-01

    A complete review of the essential and recent developments in the field of post-acceleration of laser-induced ion beams is presented. After a brief introduction to the physics of low-intensity nanosecond laser-matter interaction, the details of ions extraction and acceleration are critically analyzed and the key parameters to obtain good-quality ion beams are illustrated. A description of the most common ion beam diagnosis system is given, together with the associated analytical techniques.

  2. Lowering evaluation uncertainties in laser-induced damage testing

    NASA Astrophysics Data System (ADS)

    Jensen, Lars O.; Mrohs, Marius; Gyamfi, Mark; Mädebach, Heinrich; Ristau, Detlev

    2015-11-01

    As a consequence of the statistical nature of laser-induced damage threshold measurements in the nanosecond regime, the evaluation method plays a vital role. Within the test procedure outlined in the corresponding ISO standard, several steps of data reduction are required, and the resulting damage probability distribution as a function of laser fluence needs to be fitted either based on an empirical regression function or described by models for the respective damage mechanism.

  3. Laser-induced breakdown spectroscopy for specimen analysis

    DOEpatents

    Kumar, Akshaya; Yu-Yueh, Fang; Burgess, Shane C.; Singh, Jagdish P.

    2006-08-15

    The present invention is directed to an apparatus, a system and a method for detecting the presence or absence of trace elements in a biological sample using Laser-Induced Breakdown Spectroscopy. The trace elements are used to develop a signature profile which is analyzed directly or compared with the known profile of a standard. In one aspect of the invention, the apparatus, system and method are used to detect malignant cancer cells in vivo.

  4. Ultratrace analysis of transuranic actinides by laser-induced fluorescence

    DOEpatents

    Miller, S.M.

    1983-10-31

    Ultratrace quantities of transuranic actinides are detected indirectly by their effect on the fluorescent emissions of a preselected fluorescent species. Transuranic actinides in a sample are coprecipitated with a host lattice material containing at least one preselected fluorescent species. The actinide either quenches or enhances the laser-induced fluorescence of the preselected fluorescent species. The degree of enhancement or quenching is quantitatively related to the concentration of actinide in the sample.

  5. Lasing effects in a laser-induced plasma plume

    NASA Astrophysics Data System (ADS)

    Nagli, Lev; Gaft, Michael

    2015-11-01

    We have studied coherent emission from optically pumped preliminarily created laser induced plasma and demonstrate the possibility to create laser sources based on laser plasma as an active medium. The effect was studied in detail with Al plasma, and preliminary but promising results were also obtained with other atoms from the 13th and 14th groups of the periodic table. These lasers may be used as coherent light sources in a variety of optical applications.

  6. Coherent microwave radiation from a laser induced plasma

    SciTech Connect

    Shneider, M. N.; Miles, R. B.

    2012-12-24

    We propose a method for generation of coherent monochromatic microwave/terahertz radiation from a laser-induced plasma. It is shown that small-scale plasma, located in the interaction region of two co-propagating plane-polarized laser beams, can be a source of the dipole radiation at a frequency equal to the difference between the frequencies of the lasers. This radiation is coherent and appears as a result of the so-called optical mixing in plasma.

  7. Photodiagnostics of turbulent flows using laser-induced fluorescence

    NASA Technical Reports Server (NTRS)

    Bershader, D.; Gross, K. P.

    1983-01-01

    An optical probe technique that will allow remote measurements of temperature (and density), along with their time dependent fluctuations, to be made in a supersonic turbulent wind tunnel flow was developed. Laser-induced fluorescence from nitric oxide which was seeded into the flowing gas medium (nitrogen) at low concentrations was used. The fluorescence emission intensity following laser excitation of the nitric oxide (NO) ground state rotational levels is then related to thermodynamic quantities of the bulk fluid.

  8. Ultratrace analysis of transuranic actinides by laser-induced fluorescence

    DOEpatents

    Miller, Steven M.

    1988-01-01

    Ultratrace quantities of transuranic actinides are detected indirectly by their effect on the fluorescent emissions of a preselected fluorescent species. Transuranic actinides in a sample are coprecipitated with a host lattice material containing at least one preselected fluorescent species. The actinide either quenches or enhances the laser-induced fluorescence of the preselected fluorescent species. The degree of enhancement or quenching is quantitatively related to the concentration of actinide in the sample.

  9. Laser-induced transient grating setup with continuously tunable period

    SciTech Connect

    Vega-Flick, A.; Eliason, J. K.; Maznev, A. A.; Nelson, K. A.; Khanolkar, A.; Abi Ghanem, M.; Boechler, N.; Alvarado-Gil, J. J.

    2015-12-15

    We present a modification of the laser-induced transient grating setup enabling continuous tuning of the transient grating period. The fine control of the period is accomplished by varying the angle of the diffraction grating used to split excitation and probe beams. The setup has been tested by measuring dispersion of bulk and surface acoustic waves in both transmission and reflection geometries. The presented modification is fully compatible with optical heterodyne detection and can be easily implemented in any transient grating setup.

  10. Laser-Induced Fluorescence Helps Diagnose Plasma Processes

    NASA Technical Reports Server (NTRS)

    Beattie, J. R.; Mattosian, J. N.; Gaeta, C. J.; Turley, R. S.; Williams, J. D.; Williamson, W. S.

    1994-01-01

    Technique developed to provide in situ monitoring of rates of ion sputter erosion of accelerator electrodes in ion thrusters also used for ground-based applications to monitor, calibrate, and otherwise diagnose plasma processes in fabrication of electronic and optical devices. Involves use of laser-induced-fluorescence measurements, which provide information on rates of ion etching, inferred rates of sputter deposition, and concentrations of contaminants.

  11. Laser Induced Breakdown Spectroscopy:. AN Application on Multilayered Archeological Ceramics

    NASA Astrophysics Data System (ADS)

    Ponterio, R.; Trusso, S.; Vasi, C.; Aragona, S.; Mavilia, L.

    2004-10-01

    In this work we show an example of application of Laser Induced Breakdown Spectroscopy (LIBS) in combination with another laser-based technique: Raman micro-spectroscopy for the identification of pigments and glaze on pottery found archaeological excavations in Amendolea castle site (south of Italy in Calabrian peninsula); the objects belong to medieval period. The spectral data indicates the qualitative elemental composition of the examined materials and, in addition, give us useful information on the stratigraphy of the paint layers.

  12. ACUTE RETINAL ARTERIAL OCCLUSIVE DISORDERS

    PubMed Central

    Hayreh, Sohan Singh

    2011-01-01

    acuity improvement during the first 7 days differs significantly (p<0.001) among the 4 types of CRAO; among them, in eyes with initial visual acuity of counting finger or worse, visual acuity improved, remained stable or deteriorated in nonarteritic CRAO in 22%, 66% and 12% respectively; in nonarteritic CRAO with cilioretinal artery sparing in 67%, 33% and none respectively; and in transient nonarteritic CRAO in 82%, 18% and none respectively. Arteritic CRAO shows no change. Recent studies have shown that administration of local intra-arterial thrombolytic agent not only has no beneficial effect but also can be harmful. Prevalent multiple misconceptions on CRAO are discussed. Branch retinal artery occlusion Pathogeneses, clinical features and management of various types of BRAO are discussed at length. The natural history of visual acuity outcome shows a final visual acuity of 20/40 or better in 89% of permanent BRAO cases, 100% of transient BRAO and 100% of nonarteritic CLRAO alone. Cotton wools spots These are common, non-specific acute focal retinal ischemic lesions, seen in many retinopathies. Their pathogenesis and clinical features are discussed in detail. Amaurosis fugax Its pathogenesis, clinical features and management are described. PMID:21620994

  13. Biomedical application of laser-induced tissue oxygenation

    NASA Astrophysics Data System (ADS)

    Asimov, M. M.

    2007-03-01

    Concentration of oxygen in tissue plays an important role in enhancing in vivo wide variety of biochemical reactions including cell metabolism. Aerobic cell metabolism is primary mechanism in energy production in tissue. Controlling this mechanism gives unique possibility of biological stimulation to reach therapeutic effect. This goal could be reached by laser-induced photodissociation of oxyhemoglobin in cutaneous blood vessels. This phenomenon is considered as a main mechanism of biostimulating and therapeutic effect of low energy laser radiation. Laser-induced photodissociation of oxyhemoglobin in vivo manifests itself through the changes of the value of arterial blood saturation before and during the laser irradiation. High sensitive pulse oxymeter could be used for the measurements of the level of arterial blood saturation. Unique possibility is reached in local increase the concentration of oxygen by additional releasing it into tissue. Laser-induced enrichment of tissue oxygenation stimulates of cell metabolism and allows develop new effective methods for laser therapy as well as phototherapy of pathologies where elimination of local tissue hypoxia is critical.

  14. Determination of cobalt in low-alloy steels using laser-induced breakdown spectroscopy combined with laser-induced fluorescence.

    PubMed

    Li, Jiaming; Guo, Lianbo; Zhao, Nan; Yang, Xinyan; Yi, Rongxing; Li, Kuohu; Zeng, Qingdong; Li, Xiangyou; Zeng, Xiaoyan; Lu, Yongfeng

    2016-05-01

    Cobalt element plays an important role for the properties of magnetism and thermology in steels. In this work, laser-induced breakdown spectroscopy combined with laser-induced fluorescence (LIBS-LIF) was studied to selectively enhance the intensities of Co lines. Two states of Co atoms were resonantly excited by a wavelength-tunable laser. LIBS-LIF with ground-state atom excitation (LIBS-LIFG) and LIBS-LIF with excited-state atom excitation (LIBS-LIFE) were compared. The results show that LIBS-LIFG has analytical performance with LoD of 0.82μg/g, R(2) of 0.982, RMSECV of 86μg/g, and RE of 9.27%, which are much better than conventional LIBS and LIBS-LIFE. This work provided LIBS-LIFG as a capable approach for determining trace Co element in the steel industry. PMID:26946032

  15. Interventions for asymptomatic retinal breaks and lattice degeneration for preventing retinal detachment

    PubMed Central

    Wilkinson, Charles P

    2015-01-01

    Background Asymptomatic retinal breaks and lattice degeneration are visible lesions that are risk factors for later retinal detachment. Retinal detachments occur when fluid in the vitreous cavity passes through tears or holes in the retina and separates the retina from the underlying retinal pigment epithelium. Creation of an adhesion surrounding retinal breaks and lattice degeneration, with laser photocoagulation or cryotherapy, has been recommended as an effective means of preventing retinal detachment. This therapy is of value in the management of retinal tears associated with the symptoms of flashes and floaters and persistent vitreous traction upon the retina in the region of the retinal break, because such symptomatic retinal tears are associated with a high rate of progression to retinal detachment. Retinal tears and holes unassociated with acute symptoms and lattice degeneration are significantly less likely to be the sites of retinal breaks that are responsible for later retinal detachment. Nevertheless, treatment of these lesions frequently is recommended, in spite of the fact that the effectiveness of this therapy is unproven. Objectives The objective of this review was to assess the effectiveness and safety of techniques used to treat asymptomatic retinal breaks and lattice degeneration for the prevention of retinal detachment. Search methods We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2014, Issue 2), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to February 2014), EMBASE (January 1980 to February 2014), PubMed (January 1948 to February 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in

  16. Transscleral contact retinal photocoagulation with an 810-nm semiconductor diode laser

    SciTech Connect

    Jennings, T.; Fuller, T.; Vukich, J.A.; Lam, T.T.; Joondeph, B.C.; Ticho, B.; Blair, N.P.; Edward, D.P. )

    1990-07-01

    Since the 810-nm wavelength has marked transmissibility through the sclera and absorption by melanin, it would be ideal for transscleral photocoagulation. We performed experiments to determine if consistent transscleral chorioretinal lesions could be produced in Dutch belted pigmented rabbits using the 810-nm laser, and if this modality caused less blood-retinal barrier disruption than retinal cryopexy of clinically equivalent treatment areas. The laser applications produced whitish to grayish-white retinal lesions when the surgeon, under direct visualization, used low powers and long durations (5 to 10 seconds), and controlled the treatment duration. Histopathologic evaluation of a lesion demonstrated an intact sclera overlying the chorioretinal lesion. Vitreous protein concentration, which was measured to assess blood-retinal barrier disruption, was significantly less in eyes treated with transscleral photocoagulation than in eyes treated with cryopexy of clinically equivalent treatment areas. We conclude that transscleral 810-nm laser treatment may be a viable clinical alternative to retinal cryopexy.

  17. A simple dental caries detection system using full spectrum of laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Rocha-Cabral, Renata Maciel; Mendes, Fausto Medeiros; Maldonado, Edison Puig; Zezell, Denise Maria

    2015-06-01

    Objectives: to develop an apparatus for the detection of early caries lesions in enamel using the full extent of the tooth fluorescence spectrum, through the integration of a laser diode, fiber optics, filters and one portable spectrometer connected to a computer, all commercially available; to evaluate the developed device in clinical and laboratory tests, and compare its performance with commercial equipment. Methods: clinical examinations were performed in patients with indication for exodontics of premolars. After examinations, the patients underwent surgery and the teeth were stored individually. The optical measurements were repeated approximately two months after extraction, on the same sites previously examined, then histological analysis was carried out. Results: the spectral detector has presented high specificity and moderate sensitivity when applied to differentiate between healthy and damaged tissues, with no significant differences from the performance of the commercial equipment. The developed device is able to detect initial damages in enamel, with depth of approximately 300 μm. Conclusions: we successfully demonstrated the development of a simple and portable system based in laser-induced fluorescence for caries detection, assembled from common commercial parts. As the spectral detector acquires a complete recording of the spectrum from each tissue, it is possible to use it for monitoring developments of caries lesions.

  18. In-vivo laser-induced bubbles in the primate eye with femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Cain, Clarence P.; DiCarlo, Cheryl D.; Noojin, Gary D.; Amnotte, Rodney E.; Rockwell, Benjamin A.; Roach, William P.

    1996-05-01

    Threshold measurements for laser-induced breakdown (LIB) and bubble generation for femtosecond laser pulsewidths have been made in vivo for rhesus monkey eyes. These LIB thresholds are compared with model-predicted thresholds for water and minimum visible lesion thresholds in Dutch Belted rabbit and rhesus monkey eyes. LIB thresholds in biological materials including vitreous, normal saline, tap water, and ultrapure water have been measured and reported using an artificial eye. We have recorded on video the first LIB causing bubble formation in any eye in vivo using albino rabbit eyes, pigmented rabbit eyes, and rhesus monkey eyes. External optics were used to focus the image within the vitreous and the bubbles generated were clearly formed anterior to the retina within the vitreous humor. The length of time that the bubbles are visible depends on the pulse energy delivered and may last for several seconds. However, for pulse energies near thresholds, the bubbles have a very short lifetime and may be seen on the video for only one frame. The plasma formation at the breakdown site acts as a limiting mechanism for energy transmission and may explain why high-energy femtosecond pulses at energies up to 100 microjoules sometimes do not cause severe damage to the retina. This fact may also explain why it is so difficult to product hemmorrhagic lesions in either the rabbit or primate eye with 100-femtosecond laser pulses.

  19. Genetic pediatric retinal diseases

    PubMed Central

    Say, Emil Anthony T.

    2014-01-01

    Hereditary pediatric retinal diseases are a diverse group of disorders with pathologies affecting different cellular structures or retinal development. Many can mimic typical pediatric retinal disease such as retinopathy of prematurity, vitreous hemorrhage, retinal detachment and cystoid macular edema. Multisystem involvement is frequently seen in hereditary pediatric retinal disease. A thorough history coupled with a good physical examination can oftentimes lead the ophthalmologist or pediatrician to the correct genetic test and correct diagnosis. In some instances, evaluation of parents or siblings may be required to determine familial involvement when the history is inconclusive or insufficient and clinical suspicion is high.

  20. Q-Switched Alexandrite Laser-induced Chrysiasis

    PubMed Central

    Victor Ross, E.

    2015-01-01

    Background: Chyriasis is an uncommon side effect that occurs in patients who are receiving prolonged treatment with either intravenous or intramuscular gold as a distinctive blue-gray pigmentation of light-exposed skin. Laser-induced chrysiasis is a rarely described phenomenon in individuals who have received systemic gold and are subsequently treated with a Q-switched laser. Purpose: To describe the characteristics of patients with laser-induced chrysiasis. Methods: The authors describe a 60-year-old woman who developed chrysiasis at Q-switched alexandrite laser treatment sites. They also reviewed the medical literature using PubMed, searching the terms chrysiasis, gold, and laser-induced. Patient reports and previous reviews of these subjects were critically assessed and the salient features are presented. Results: Including the authors’ patient, laser-induced chrysiasis has been described in five Caucasian arthritis patients (4 women and 1 man); most of the patients had received more than 8g of systemic gold therapy during a period of 3 to 13 years. Gold therapy was still occurring or had been discontinued as long as 26 years prior to laser treatment. All of the patients immediately developed blue macules at the Q-switched laser treatment site. Resolution of the dyschromia occurred in a 70-year-old woman after two treatment sessions with a long-pulsed ruby laser and the authors’ patient after a sequential series of laser sessions using a long-pulsed alexandrite laser, followed by a nonablative fractional laser and an ablative carbon dioxide laser. Conclusion: Laser-induced chrysiasis has been observed following treatment with Q-switched lasers in patients who are receiving or have previously been treated with systemic gold. It can occur decades after treatment with gold has been discontinued. Therefore, inquiry regarding a prior history of treatment with gold—particularly in older patients with arthritis—should be considered prior to treatment with a Q

  1. Laser-induced breakdown spectroscopy with high detection sensitivity

    NASA Astrophysics Data System (ADS)

    Shen, X. K.; Ling, H.; Lu, Y. F.

    2009-02-01

    Laser-induced breakdown spectroscopy (LIBS) with spatial confinement and LIBS combined with laser-induced fluorescence (LIF) have been investigated to improve the detection sensitivity and selectivity of LIBS. An obvious enhancement in the emission intensity of Al atomic lines was observed when a cylindrical wall was placed to spatially confine the plasma plumes. The maximum enhancement factor for the emission intensity of Al atomic lines was measured to be around 10. Assuming local thermodynamic equilibrium conditions, the plasma temperatures are estimated to be in the range from 4000 to 5800 K. It shows that the plasma temperature increased by around 1000 K when the cylindrical confinement was applied. Fast imaging of the laser-induced Al plasmas shows that the plasmas were compressed into a smaller volume with a pipe presented. LIBS-LIF has been investigated to overcome the matrix effects in LIBS for the detection of trace uranium in solids. A wavelength-tunable laser with an optical parametric oscillator was used to resonantly excite the uranium atoms and ions within the plasma plumes generated by a Q-switched Nd:YAG laser. Both atomic and ionic lines can be selected to detect their fluorescence lines. A uranium concentration of 462 ppm in a glass sample can be detected using this technique at an excitation wavelength of 385.96 nm for resonant excitation of U II and a fluorescence line wavelength of 409.01 nm from U II. The mechanism of spatial confinement effects and the influence of relevant operational parameters of LIBS-LIF are discussed.

  2. Characteristic Findings of Optical Coherence Tomography in Retinal Angiomatous Proliferation

    PubMed Central

    Lim, Eun-Hae; Kim, Chul Gu; Cho, Sung Won; Lee, Tae Gon

    2013-01-01

    Purpose To identify the unique pathologic findings of retinal angiomatous proliferation (RAP) in optical coherence tomography (OCT). Methods Retrospectively, 29 eyes of 25 patients with age-related macular degeneration and complicated RAP were analyzed. All 29 eyes had choroidal neovascularization (CNV) in the area of pigment epithelial detachment (PED) or adjacent to it, which was visible with fluorescein angiography or indocyanine green angiography. Cross-sectional images were obtained by OCT scanning through the CNV lesions. Results Six distinctive findings of OCT included drusen (100%), inner retinal cyst (80%), outer retinal cyst (68%), fibrovascular PED (84%), serous retinal detachment (40%), and PED (68%). Conclusions Through analysis of OCT findings, we revealed six different types of lesions distinctive of RAP which may provide helpful diagnostic information for subsequent treatment and predicting the prognosis of RAP. PMID:24082773

  3. Effect of cytokeratin 17 on retinal pigment epithelium degeneration and choroidal neovascularization

    PubMed Central

    Shen, Yi; Zhuang, Pei; Xiao, Tao; Chiou, George CY

    2016-01-01

    AIM To study the effects of cytokeratin 17 (CK17) on sodium iodate (NaIO3) induced rat retinal pigment epithelium (RPE) degeneration, laser induced rat choroidal neovascularization (CNV), and oxidative stress of human retinal pigment epithelium cells (ARPE-19) and human umbilical vein endothelial cell (HUVEC). METHODS Thirty 8-week-old male Brown Norway rats were randomly divided into 3 groups, 10 rats in control group treated with solvent alone; 10 rats in NaIO3 group treated with solvent and 35 mg/kg NaIO3 injection through hypoglossal vein and 10 rats in CK17+NaIO3 group treated with 1% CK17 eye drop 3 times a day for 1wk before and 4wk after NaIO3 injection. RPE function was measured with c-wave of electroretinogram (ERG). Another 20 rats were randomly divided into 2 groups. Of them 10 rats in CK17 group were anesthetized to receive Nd:YAG laser and given 1% CK17 eye drop before same as above; 10 rats in control were received Nd:YAG and treated with solvent. The development of choroidal neovascularization (CNV) was determined by fundus fluorescein angiography (FFA) performed on 4wk after laser. Methylthiazoly tetrazolium (MTT) assay was used to study effect of CK17 on various oxidants induced injury in ARPE-19 and HUVEC in vitro. RESULTS Four weeks after NaIO3 injection, the c-wave amplitude of ERG was 0.393±0.02 V in the control group, 0.184±0.018 V in NaIO3 group and 0.3±0.01 V in CK17+NaIO3 group. There was a significant reversal of the c-wave by CK17 as compared to NaIO3 group (P<0.01). Four weeks after laser, the size of the CNV lesion was 2.57±0.27 mm2 in control group and 1.64±0.08 mm2 in CK17 group. The lesion size significantly diminished in CK17 group (P<0.01). The in vitro results showed CK17 also reversed the various oxidants induced injuries in ARPE-19 at the dose of 100 µg/mL and enhanced the injury in HUVECs at different concentrations. CONCLUSION CK17 can significantly protect RPE from NaIO3 induced degeneration in vivo and in vitro and

  4. Treatment of a supratentorial primitive neuroectodermal tumor using magnetic resonance-guided laser-induced thermal therapy.

    PubMed

    Jethwa, Pinakin R; Lee, Jason H; Assina, Rachid; Keller, Irwin A; Danish, Shabbar F

    2011-11-01

    Supratentorial primitive neuroectodermal tumors (PNETs) are rare tumors that carry a poorer prognosis than those arising from the infratentorial compartment (such as medulloblastoma). The overall prognosis for these patients depends on several factors including the extent of resection, age at diagnosis, CSF dissemination, and site in the supratentorial space. The authors present the first case of a patient with a newly diagnosed supratentorial PNET in which cytoreduction was achieved with MR-guided laser-induced thermal therapy. A 10-year-old girl presented with left-sided facial weakness and a large right thalamic mass extending into the right midbrain. The diagnosis of supratentorial PNET was made after stereotactic biopsy. Therapeutic options for this lesion were limited because of the risks of postoperative neurological deficits with resection. The patient underwent MR-guided laser-induced thermal ablation of her tumor. Under real-time MR thermometry, thermal energy was delivered to the tumor at a core temperature of 90°C for a total of 960 seconds. The patient underwent follow-up MR imaging at regular intervals to evaluate the tumor response to the thermal ablation procedure. Initial postoperative scans showed an increase in the size of the lesion as well as the amount of the associated edema. Both the size of the lesion and the edema stabilized by 1 week and then decreased below preablation levels at the 3-month postsurgical follow-up. There was a slight increase in the size of the lesion and associated edema at the 6-month follow-up scan, presumably due to concomitant radiation she received as part of her postoperative care. The patient tolerated the procedure well and has had resolution of her symptoms since surgery. Further study is needed to assess the role of laser-induced thermal therapy for the treatment of intracranial tumors. As such, it is a promising tool in the neurosurgical armamentarium. Postoperative imaging has shown no evidence of definitive

  5. H sup minus beam characterization using laser-induced neutralization

    SciTech Connect

    Yuan, V.W.; Garcia, R.; Johnson, K.F.; Saadatmand, K.; Sander, O.R.; Sandoval, D.; Shinas, M.

    1991-01-01

    The Laser-induced neutralization techniques, LINDA, is important as a noninterceptive diagnostic for quantitatively measuring beam emittance values. It is also valuable for its capability to characterize, both quantitatively and qualitatively, the performance and match of linac components. In this paper we present LINDA experimental results that show how the output beam of a radio-frequency quadrupole (RFQ) and drift-tube linac (DTL) combination changes with the variation of RFQ-DTL relative phase and of DTL cavity power. We also present results showing the effect of a longitudinal buncher on beam emissions. 2 refs., 4 figs.

  6. Remote sensing of phytoplankton using laser-induced fluorescence

    SciTech Connect

    Babichenko, S.; Poryvkina, L.; Arikese, V. ); Kaitala, S. ); Kuosa, H. )

    1993-06-01

    The results of remote laser sensing of brackish-water phytoplankton on board a research vessel are presented. Field data of laser-induced fluorescence of phytoplankton obtained during the several cruises in the mouth of tile Gulf of Finland are compared with the results of standard chlorophyll a analysis of water samples and phytoplankton species determination by microscopy. The approach of fluorescence excitation by tunable laser radiation is applied to study the spatial distribution of a natural phytoplankton community. The remote analysis of the pigment composition of a phytoplankton community using the method of selective pigment excitation is described. The possibility of elaborating methods of quantitative laser remote biomonitoring is discussed.

  7. Laser-induced backward transfer of nanoimprinted polymer elements

    NASA Astrophysics Data System (ADS)

    Feinaeugle, Matthias; Heath, Daniel J.; Mills, Benjamin; Grant-Jacob, James A.; Mashanovich, Goran Z.; Eason, Robert W.

    2016-04-01

    Femtosecond laser-induced backward transfer of transparent photopolymers is demonstrated in the solid state, assisted by a digital micromirror spatial light modulator for producing shaped deposits. Through use of an absorbing silicon carrier substrate, we have been able to successfully transfer solid-phase material, with lateral dimensions as small as ~6 µm. In addition, a carrier of silicon incorporating a photonic waveguide relief structure enables the transfer of imprinted deposits that have been accomplished with surface features exactly complementing those present on the substrate, with an observed minimum feature size of 140 nm.

  8. Laser-Induced Breakdown Spectroscopy (LIBS): specific applications

    NASA Astrophysics Data System (ADS)

    Trtica, M. S.; Savovic, J.; Stoiljkovic, M.; Kuzmanovic, M.; Momcilovic, M.; Ciganovic, J.; Zivkovic, S.

    2015-12-01

    A short overview of Laser Induced Breakdown Spectroscopy (LIBS) with emphasis on the new trends is presented. Nowadays, due to unique features of this technique, LIBS has found applications in a great variety of fields. Achievements in the application of LIBS in nuclear area, for hazardous materials detection and in geology were considered. Also, some results recently obtained at VINCA Institute, with LIBS system based on transversely excited atmospheric (TEA) CO2 laser, are presented. Future investigations of LIBS will be oriented toward further improvement of the analytical performance of this technique, as well as on finding new application fields.

  9. Infrared laser-induced breakdown spectroscopy emissions from energetic materials

    NASA Astrophysics Data System (ADS)

    Yang, Clayton S.; Brown, E.; Hommerich, Uwe; Trivedi, Sudhir B.; Samuels, Alan C.; Snyder, A. Peter

    2011-05-01

    Laser-induced breakdown spectroscopy (LIBS) has shown great promise for applications in chemical, biological, and explosives (CBE) sensing and has significant potential for real time standoff detection and analysis. We have studied LIBS emissions in the mid-infrared (MIR) spectral region for potential applications in CBE sensing. Detailed MIR-LIBS studies were performed for several energetic materials for the first time. In this study, the IR signature spectral region between 4 - 12 um was mined for the appearance of MIR-LIBS emissions that are directly indicative of oxygenated breakdown products as well as partially dissociated and recombination molecular species.

  10. Femtosecond laser-induced electronic plasma at metal surface

    SciTech Connect

    Chen Zhaoyang; Mao, Samuel S.

    2008-08-04

    We develop a theoretical analysis to model plasma initiation at the early stage of femtosecond laser irradiation of metal surfaces. The calculation reveals that there is a threshold intensity for the formation of a microscale electronic plasma at the laser-irradidated metal surface. As the full width at half maximum of a laser pulse increases from 15 to 200 fs, the plasma formation threshold decreases by merely about 20%. The dependence of the threshold intensity on laser pulse width can be attributed to laser-induced surface electron emission, in particular due to the effect of photoelectric effect.

  11. Laser-induced thermal-acoustic velocimetry with heterodyne detection

    SciTech Connect

    Schlamp, Stefan; Cummings, Eric B.; Sobota, Thomas H.

    2000-02-15

    Laser-induced thermal acoustics (LITA) was used with heterodyne detection to measure simultaneously and in a single laser pulse the sound speed and flow velocity of NO{sub 2} -seeded air in a low-speed wind tunnel up to Mach number M=0.1 . The uncertainties of the velocity and the sound speed measurements were {approx}0.2 m/s and 0.5%, respectively. Measurements were obtained through a nonlinear least-squares fit to a general, analytic closed-form solution for heterodyne-detected LITA signals from thermal gratings. Agreement between theory and experiment is exceptionally good. (c) 2000 Optical Society of America.

  12. Nonresonant Referenced Laser-Induced Thermal Acoustics Thermometry in Air

    NASA Astrophysics Data System (ADS)

    Hart, Roger C.; Balla, R. Jeffrey; Herring, Gregory C.

    1999-01-01

    We report a detailed investigation of nonresonant laser-induced thermal acoustics (LITA) for the single-shot measurement of the speed of sound ( v S ) in an oven containing room air. A model for the speed of sound that includes important acoustic relaxation effects is used to convert the speed of sound into temperature. A reference LITA channel is used to reduce uncertainties in v S . Comparing thermocouple temperatures with temperatures deduced from our v S measurements and model, we find the mean temperature difference from 300 to 650 K to be 1% ( 2 ). The advantages of using a reference LITA channel are discussed.

  13. Laser-Induced Underwater Plasma And Its Spectroscopic Applications

    SciTech Connect

    Lazic, Violeta

    2008-09-23

    Applications of Laser Induced Breakdown Spectroscopy (LIBS) for analysis of immersed solid and soft materials, and for liquid impurities are described. A method for improving the LIBS signal underwater and for obtaining quantitative analyses in presence of strong shot-to-shot variations of the plasma properties is proposed. Dynamic of the gas bubble formed by the laser pulse is also discussed, together with its importance in Double-Pulse (DP) laser excitation. Results of the studies relative to an application of multi-pulse sequence and its effects on the plasma and gas bubble formation are also presented.

  14. Interaction between jets during laser-induced forward transfer

    SciTech Connect

    Patrascioiu, A.; Florian, C.; Fernández-Pradas, J. M.; Morenza, J. L.; Serra, P.; Hennig, G.; Delaporte, P.

    2014-07-07

    Simultaneous two-beam laser-induced forward transfer (LIFT) was carried out for various inter-beam separations, analyzing both the resulting printing outcomes and the corresponding liquid transfer dynamics. In a first experiment, droplets of an aqueous solution were printed onto a substrate at different inter-beam distances, which proved that a significant departure from the single-beam LIFT dynamics takes places at specific separations. In the second experiment, time-resolved imaging analysis revealed the existence of significant jet-jet interactions at those separations; such interactions proceed through a dynamics that results in remarkable jet deflection for which a possible onset mechanism is proposed.

  15. Laser-induced fluorescence measurement of combustion chemistry intermediates

    NASA Technical Reports Server (NTRS)

    Crosley, David R.

    1986-01-01

    Laser-induced fluorescence (LIF) can measure the trace (often free radical) species encountered as intermediates in combustion chemistry; OH, CS, NH, NS, and NCO are typical of the species detected in flames by LIF. Attention is given to illustrative experiments designed to accumulate a quantitative data base for LIF detection in low pressure flow systems and flames, as well as to flame measurements conducted with a view to the detection of new chemical intermediaries that may deepen insight into the chemistry of combustion.

  16. Trace metal mapping by laser-induced breakdown spectroscopy

    SciTech Connect

    Kaiser, Jozef; Novotny, Dr. Karel; Hrdlicka, A; Malina, R; Hartl, M; Kizek, R; Adam, V

    2012-01-01

    Abstract: Laser-Induced Breakdown Spectroscopy (LIBS) is a sensitive optical technique capable of fast multi-elemental analysis of solid, gaseous and liquid samples. The potential applications of lasers for spectrochemical analysis were developed shortly after its invention; however the massive development of LIBS is connected with the availability of powerful pulsed laser sources. Since the late 80s of 20th century LIBS dominated the analytical atomic spectroscopy scene and its application are developed continuously. Here we review the utilization of LIBS for trace elements mapping in different matrices. The main emphasis is on trace metal mapping in biological samples.

  17. Colloid formation and laser-induced bleaching in fluorite

    SciTech Connect

    LeBret, Joel B.; Cramer, Loren P.; Norton, M. Grant; Dickinson, J. T.

    2004-11-08

    Colloid formation and subsequent laser-induced bleaching in fluorite has been studied by transmission electron microscopy and electron diffraction. At high incident electron-beam (e-beam) energies, Ca colloids with diameter {approx}10 nm form a simple cubic superlattice with lattice parameter a{approx}18 nm. The colloids themselves are topotactic with the fluorite matrix forming low-energy interfaces close to a {sigma}=21 special grain boundary in cubic materials. Laser irradiation using {lambda}=532 nm has been shown to effectively bleach the e-beam-irradiated samples returning the fluorite to its monocrystalline state. The bleached samples appear more resistant to further colloid formation.

  18. Laser-induced fluorescence spectroscopy of the secondary cataract

    NASA Astrophysics Data System (ADS)

    Maslov, N. A.; Larionov, P. M.; Rozhin, I. A.; Druzhinin, I. B.; Chernykh, V. V.

    2016-06-01

    Excitation-emission matrices of laser-induced fluorescence of lens capsule epithelium, the lens nucleus, and the lens capsule are investigated. A solid-state laser in combination with an optical parametric generator tunable in the range from 210 to 350 nm was used for excitation of fluorescence. The spectra of fluorescence of all three types of tissues exhibit typical features that are specific to them and drastically differ from one another. This effect can be used for intrasurgical control of presence of residual lens capsule epithelium cells in the capsular bag after surgical treatment of a cataract.

  19. Laser-induced reaction alumina coating on ceramic composite

    NASA Astrophysics Data System (ADS)

    Xiao, Chenghe

    Silicon carbide ceramics are susceptible to corrosion by certain industrial furnace environments. It is also true for a new class of silicon carbide-particulate reinforced alumina-matrix composite (SiCsb(P)Alsb2Osb3) since it contains more than 55% of SiC particulate within the composite. This behavior would limit the use of SiCsb(P)Alsb2Osb3 composites in ceramic heat exchangers. Because oxide ceramics corrode substantially less in the same environments, a laser-induced reaction alumina coating technique has been developed for improving corrosion resistance of the SiCsb(P)Alsb2Osb3 composite. Specimens with and without the laser-induced reaction alumina coating were subjected to corrosion testing at 1200sp°C in an air atmosphere containing Nasb2COsb3 for 50 ˜ 200 hours. Corroded specimens were characterized via x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). The uncoated SiCsbP/Alsb2Osb3 composite samples experienced an initial increase in weight during the exposure to Nasb2COsb3 at 1200sp°C due to the oxidation of residual aluminum metal in the composite. There was no significant weight change difference experienced during exposure times between 50 and 200 hours. The oxidation layer formed on the as-received composite surface consisted of Si and Alsb2Osb3 (after washing with a HF solution). The oxidation layer grew outward and inward from the original surface of the composite. The growth rate in the outward direction was faster than in the inward direction. The formation of the Si/Alsb2Osb3 oxidation layer on the as-received composite was nonuniform, and localized corrosion was observed. The coated samples experienced very little mass increase. The laser-induced reaction alumina coating effectively provided protection for the SiCsbP/Alsb2Osb3 composite by keeping the corrodents from contacting the composite and by the formation of some refractory compounds such as Nasb2OAlsb2Osb3SiOsb2 and Nasb2Alsb{22}Osb

  20. Spatial confinement effects in laser-induced breakdown spectroscopy

    SciTech Connect

    Shen, X. K.; Sun, J.; Ling, H.; Lu, Y. F.

    2007-08-20

    The spatial confinement effects in laser-induced breakdown of aluminum (Al) targets in air have been investigated both by optical emission spectroscopy and fast photography. A KrF excimer laser was used to produce plasmas from Al targets in air. Al atomic emission lines show an obvious enhancement in the emission intensity when a pair of Al-plate walls were placed to spatially confine the plasma plumes. Images of the Al plasma plumes showed that the plasma plumes evolved into a torus shape and were compressed in the Al walls. The mechanism for the confinement effects was discussed using shock wave theory.

  1. Search for laser-induced formation of antihydrogen atoms.

    PubMed

    Amoretti, M; Amsler, C; Bonomi, G; Bowe, P D; Canali, C; Carraro, C; Cesar, C L; Charlton, M; Ejsing, A M; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Jørgensen, L V; Kellerbauer, A; Lagomarsino, V; Lodi Rizzini, E; Macrì, M; Madsen, N; Manuzio, G; Mitchard, D; Montagna, P; Posada, L G C; Pruys, H; Regenfus, C; Rotondi, A; Telle, H H; Testera, G; Van der Werf, D P; Variola, A; Venturelli, L; Yamazaki, Y; Zurlo, N

    2006-11-24

    Antihydrogen can be synthesized by mixing antiprotons and positrons in a Penning trap environment. Here an experiment to stimulate the formation of antihydrogen in the n = 11 quantum state by the introduction of light from a CO2 continuous wave laser is described. An overall upper limit of 0.8% with 90% C.L. on the laser-induced enhancement of the recombination has been found. This result strongly suggests that radiative recombination contributes negligibly to the antihydrogen formed in the experimental conditions used by the ATHENA Collaboration. PMID:17155742

  2. Progress in fieldable laser-induced breakdown spectroscopy (LIBS)

    NASA Astrophysics Data System (ADS)

    Miziolek, Andrzej W.

    2012-06-01

    In recent years there has been great progress in the Laser Induced Breakdown Spectroscopy (LIBS) technology field. Significant advances have been made both in fundamental and applied research as well as in data processing/chemometrics. Improvements in components, most notably lasers/optics and spectrometers are enabling the development of new devices that are suitable for field use. These new commercial devices recently released to the marketplace, as well as ones currently under development, are bringing the potential of LIBS for CBRNE threat analysis into real-world applications.

  3. Optical Coherence Tomography of Retinal and Choroidal Tumors

    PubMed Central

    Say, Emil Anthony T.; Shah, Sanket U.; Ferenczy, Sandor; Shields, Carol L.

    2011-01-01

    Optical coherence tomography (OCT) has revolutionized the field of ophthalmology since its introduction 20 years ago. Originally intended primarily for retina specialists to image the macula, it has found its role in other subspecialties that include glaucoma, cornea, and ocular oncology. In ocular oncology, OCT provides axial resolution to approximately 7 microns with cross-sectional images of the retina, delivering valuable information on the effects of intraocular tumors on the retinal architecture. Some effects include retinal edema, subretinal fluid, retinal atrophy, photoreceptor loss, outer retinal thinning, and retinal pigment epithelial detachment. With more advanced technology, OCT now provides imaging deeper into the choroid using a technique called enhanced depth imaging. This allows characterization of the thickness and reflective quality of small (<3 mm thick) choroidal lesions including choroidal nevus and melanoma. Future improvements in image resolution and depth will allow better understanding of the mechanisms of visual loss, tumor growth, and tumor management. PMID:21811667

  4. Optical Coherence Tomography of Retinal and Choroidal Tumors

    PubMed Central

    Say, Emil Anthony T.; Shah, Sanket U.; Ferenczy, Sandor; Shields, Carol L.

    2012-01-01

    Optical coherence tomography (OCT) has revolutionized the field of ophthalmology since its introduction 20 years ago. Originally intended primarily for retina specialists to image the macula, it has found its role in other subspecialties that include glaucoma, cornea, and ocular oncology. In ocular oncology, OCT provides axial resolution to approximately 7 microns with cross-sectional images of the retina, delivering valuable information on the effects of intraocular tumors on the retinal architecture. Some effects include retinal edema, subretinal fluid, retinal atrophy, photoreceptor loss, outer retinal thinning, and retinal pigment epithelial detachment. With more advanced technology, OCT now provides imaging deeper into the choroid using a technique called enhanced depth imaging. This allows characterization of the thickness and reflective quality of small (<3 mm thick) choroidal lesions including choroidal nevus and melanoma. Future improvements in image resolution and depth will allow better understanding of the mechanisms of visual loss, tumor growth, and tumor management. PMID:23008756

  5. Retinal metastasis from unknown primary: diagnosis, management, and clinicopathologic correlation

    PubMed Central

    Taubenslag, Kenneth J.; Kim, Stephen J.; Attia, Albert; Abel, Ty W.; Nickols, Hilary Highfield; Ancell, Kristin K.; Daniels, Anthony B.

    2015-01-01

    Summary A 75-year-old man was incidentally found to have a yellow-white retinal lesion with scattered hemorrhages. He was empirically treated elsewhere for viral retinitis without resolution and later transferred to the Vanderbilt Eye Institute, where retinal biopsy with silicone oil tamponade showed retinal metastasis. He had no prior history of cancer, and multiple systemic imaging evaluations failed to identify a primary site. Histopathology and immunohistochemistry of the biopsy were consistent with non-small-cell lung carcinoma. Due to the radiation-attenuating properties of silicone oil, the patient underwent silicone oil removal prior to receiving external beam radiotherapy (EBRT). The retinal metastasis responded completely to EBRT, and at final follow-up, 18 months after initial presentation, no primary tumor has been identified. PMID:27330472

  6. Neuroprotectin D1 Attenuates Laser-induced Choroidal Neovascularization in Mouse

    PubMed Central

    Sheets, Kristopher G.; Zhou, Yongdong; Ertel, Monica K.; Knott, Eric J.; Regan, Cornelius E.; Elison, Jasmine R.; Gordon, William C.; Gjorstrup, Per

    2010-01-01

    Purpose To examine the effects of neuroprotectin D1 (NPD1), a stereospecific derivative of docosahexaenoic acid, on choroidal neovascularization (CNV) in a laser-induced mouse model. Specifically, this was assessed by clinically grading laser-induced lesions, measuring leakage area, and volumetrically quantifying vascular endothelial cell proliferation. Methods C57Bl/6 mice were treated with vehicle control or NPD1, and choroidal neovascularization was induced by laser rupture of Bruch's membrane; treatment was administered throughout the first week of recovery. One and two weeks after CNV induction, fundus fluorescein angiography was performed. Angiograms were clinically graded to assess leakage severity, while leakage area was measured by image analysis of angiograms. Proliferation of vascular endothelial cells was evaluated volumetrically by three-dimensional laser confocal immunofluorescent microscopy of cytoskeletal, nuclear, and endothelial cell markers. Results At seven days after CNV induction, NPD1-treated mice had 60% fewer clinically relevant lesions than controls, dropping to 80% fewer by 14 days. NPD1 mice exhibited 25% smaller leakage area than controls at 7 days and 44% smaller area at 14 days. Volumetric immunofluorescence revealed 46% less vascular endothelial cell volume in 7-day NPD1-treated mice than in 7-day controls, and by 14 days NPD1 treatment was 68% lower than controls. Furthermore, comparison of 7- and 14-day volumes of NPD1-treated mice revealed a 50% reduction at 14 days. Conclusions NPD1 significantly inhibits choroidal neovascularization. There are at least two possible mechanisms that could explain the neuroprotective action of NPD1. Ultimately, nuclear factor-κB could be inhibited with a reduction in cyclooxygenase-2 (COX-2) to reduce vascular endothelial growth factor (VEGF) expression, and/or activation of the resolution phase of the inflammatory response/survival pathways could be upregulated. Moreover, NPD1 continues to be

  7. [Identification of invoice based on laser-induced photoluminescence spectrum].

    PubMed

    Yang, Qin; Yang, Yong; Tian, Yong-hong

    2011-12-01

    The rapid identification of invoice authenticity was studied based on laser-induced photoluminescence spectrum. First, the spectral curves of eighty invoice samples were obtained by laser-induced photoluminescence detection system, and genetic algorithm (GA) was applied to fit and separate overlapped spectral region between 566 and 669 nm by three Gaussian peaks. Spectral feature parameters extracted by GA were employed as the inputs of BP neural networks, and then an identification model was built. One hundred and four data were converted to 13 Gaussian parameters, and for authentic and false invoices the coefficients of determination (R2) were 0.99789 and 0.99683 and the relative standard deviations (RSD) were 0.017052 and 0.022362, respectively. It was showed that Gaussian fitting algorithm could not only simplify the parameters of models, but also improve the explanation of analysis models. Through comparison analysis of the results, it was found that the model, whose thirteen feature parameters and two evaluated parameters were all applied as BP inputs, was the best, and the corrected identification rates of sixty calibration samples and twenty validation samples were both 100%. So the identification method studied in the present research played a good role in the classification and identification, and offered a new approach to the rapid identification of invoice authenticity. PMID:22295788

  8. A model for traumatic brain injury using laser induced shockwaves

    NASA Astrophysics Data System (ADS)

    Selfridge, A.; Preece, D.; Gomez, V.; Shi, L. Z.; Berns, M. W.

    2015-08-01

    Traumatic brain injury (TBI) represents a major treatment challenge in both civilian and military medicine; on the cellular level, its mechanisms are poorly understood. As a method to study the dysfunctional repair mechanisms following injury, laser induced shock waves (LIS) are a useful way to create highly precise, well characterized mechanical forces. We present a simple model for TBI using laser induced shock waves as a model for damage. Our objective is to develop an understanding of the processes responsible for neuronal death, the ways in which we can manipulate these processes to improve cell survival and repair, and the importance of these processes at different levels of biological organization. The physics of shock wave creation has been modeled and can be used to calculate forces acting on individual neurons. By ensuring that the impulse is in the same regime as that occurring in practical TBI, the LIS model can ensure that in vitro conditions and damage are similar to those experienced in TBI. This model will allow for the study of the biochemical response of neurons to mechanical stresses, and can be combined with microfluidic systems for cell growth in order to better isolate areas of damage.

  9. Nanorod Surface Plasmon Enhancement of Laser-Induced Ultrafast Demagnetization

    PubMed Central

    Xu, Haitian; Hajisalem, Ghazal; Steeves, Geoffrey M.; Gordon, Reuven; Choi, Byoung C.

    2015-01-01

    Ultrafast laser-induced magnetization dynamics in ferromagnetic thin films were measured using a femtosecond Ti:sapphire laser in a pump-probe magneto-optic Kerr effect setup. The effect of plasmon resonance on the transient magnetization was investigated by drop-coating the ferromagnetic films with dimensionally-tuned gold nanorods supporting longitudinal surface plasmon resonance near the central wavelength of the pump laser. With ~4% nanorod areal coverage, we observe a >50% increase in demagnetization signal in nanorod-coated samples at pump fluences on the order of 0.1 mJ/cm2 due to surface plasmon-mediated localized electric-field enhancement, an effect which becomes more significant at higher laser fluences. We were able to qualitatively reproduce the experimental observations using finite-difference time-domain simulations and mean-field theory. This dramatic enhancement of ultrafast laser-induced demagnetization points to possible applications of nanorod-coated thin films in heat-assisted magnetic recording. PMID:26515296

  10. Kr II laser-induced fluorescence for measuring plasma acceleration.

    PubMed

    Hargus, W A; Azarnia, G M; Nakles, M R

    2012-10-01

    We present the application of laser-induced fluorescence of singly ionized krypton as a diagnostic technique for quantifying the electrostatic acceleration within the discharge of a laboratory cross-field plasma accelerator also known as a Hall effect thruster, which has heritage as spacecraft propulsion. The 728.98 nm Kr II transition from the metastable 5d(4)D(7/2) to the 5p(4)P(5/2)(∘) state was used for the measurement of laser-induced fluorescence within the plasma discharge. From these measurements, it is possible to measure velocity as krypton ions are accelerated from near rest to approximately 21 km/s (190 eV). Ion temperature and the ion velocity distributions may also be extracted from the fluorescence data since available hyperfine splitting data allow for the Kr II 5d(4)D(7/2)-5p(4)P(5/2)(∘) transition lineshape to be modeled. From the analysis, the fluorescence lineshape appears to be a reasonable estimate for the relatively broad ion velocity distributions. However, due to an apparent overlap of the ion creation and acceleration regions within the discharge, the distributed velocity distributions increase ion temperature determination uncertainty significantly. Using the most probable ion velocity as a representative, or characteristic, measure of the ion acceleration, overall propellant energy deposition, and effective electric fields may be calculated. With this diagnostic technique, it is possible to nonintrusively characterize the ion acceleration both within the discharge and in the plume. PMID:23126755

  11. Laser induced alignment of molecules dissolved in Helium nanodroplets

    NASA Astrophysics Data System (ADS)

    Stapelfeldt, Henrik

    2013-05-01

    Laser induced alignment, the method to confine the principal axes of molecules along axes fixed in the laboratory frame, is now used in a range of applications in physics and chemistry. With a few exceptions all studies have focused on isolated molecules in the gas phase. In this talk we present experimental studies of laser induced alignment of molecules embedded in the solvent of a superfluid helium nanodroplet. Alignment is conducted in both the adiabatic and the nonadiabtic regime where the alignment pulse is much longer or shorter, respectively, than the rotational period of the molecules. In the nonadiabatic limit, induced by a few-hundred femtosecond long laser pulse, we show that methyliodide molecules reach an alignment maximum 20 ps after the alignment pulse and gradually loose the alignment completely in another 60 ps. This dynamics is completely different from that of isolated methyliodide molecules where alignment occurs in regularly spaced (by 33.3 ps), narrow time windows, termed revivals. Adiabatic alignment, induced by 10 ns laser pulses, resembles the gas phase behavior although the observed degree of alignment falls below that of isolated molecules. Work done in collaboration with Dominik Pentkehner, Department of Chemistry, Aarhus University; Jens Hedegaard Nielsen, Department of Physics, Aarhus University; Alkwin Slenczka, Department of Chemistry, Regensburg University; and Klaus Mølmer, Department of Physics, Aarhus University.

  12. 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.

  13. Laser-induced breakdown spectroscopy of tantalum plasma

    NASA Astrophysics Data System (ADS)

    Khan, Sidra; Bashir, Shazia; Hayat, Asma; Khaleeq-ur-Rahman, M.; Faizan-ul-Haq

    2013-07-01

    Laser Induced Breakdown spectroscopy (LIBS) of Tantalum (Ta) plasma has been investigated. For this purpose Q-switched Nd: YAG laser pulses (λ ˜ 1064 nm, τ ˜ 10 ns) of maximum pulse energy of 100 mJ have been employed as an ablation source. Ta targets were exposed under the ambient environment of various gases of Ar, mixture (CO2: N2: He), O2, N2, and He under various filling pressure. The emission spectrum of Ta is observed by using LIBS spectrometer. The emission intensity, excitation temperature, and electron number density of Ta plasma have been evaluated as a function of pressure for various gases. Our experimental results reveal that the optical emission intensity, the electron temperature and density are strongly dependent upon the nature and pressure of ambient environment. The SEM analysis of the ablated Ta target has also been carried out to explore the effect of ambient environment on the laser induced grown structures. The growth of grain like structures in case of molecular gases and cone-formation in case of inert gases is observed. The evaluated plasma parameters by LIBS analysis such as electron temperature and the electron density are well correlated with the surface modification of laser irradiated Ta revealed by SEM analysis.

  14. Detection of explosives with laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Qian-Qian; Liu, Kai; Zhao, Hua; Ge, Cong-Hui; Huang, Zhi-Wen

    2012-12-01

    Our recent work on the detection of explosives by laser-induced breakdown spectroscopy (LIBS) is reviewed in this paper. We have studied the physical mechanism of laser-induced plasma of an organic explosive, TNT. The LIBS spectra of TNT under single-photon excitation are simulated using MATLAB. The variations of the atomic emission lines intensities of carbon, hydrogen, oxygen, and nitrogen versus the plasma temperature are simulated too. We also investigate the time-resolved LIBS spectra of a common inorganic explosive, black powder, in two kinds of surrounding atmospheres, air and argon, and find that the maximum value of the O atomic emission line SBR of black powder occurs at a gate delay of 596 ns. Another focus of our work is on using chemometic methods such as principle component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) to distinguish the organic explosives from organic materials such as plastics. A PLS-DA model for classification is built. TNT and seven types of plastics are chosen as samples to test the model. The experimental results demonstrate that LIBS coupled with the chemometric techniques has the capacity to discriminate organic explosive from plastics.

  15. Laser-induced grating spectroscopy of cadmium telluride

    NASA Astrophysics Data System (ADS)

    Petrovic, Mark S.; Suchocki, Andrzej; Powell, Richard C.; Cantwell, Gene; Aldridge, Jeff

    1989-08-01

    Laser-induced transient gratings produced by two-photon absorption of picosecond pulses at 1.064 μm were used to examine the room-temperature nonlinear optical responses of CdTe crystals with different types of conductivity. Pulse-probe degenerate four-wave mixing measurements of grating dynamics on subnanosecond time scales were used to measure the ambipolar diffusion coefficient (Da) of charge carriers in the crystals. The value of Da =3.0 cm2 s-1 which was obtained is in very good agreement with theoretical estimates. A long-lived contribution to the signal consistent with a trapped charge photorefractive effect was observed at large grating spacings for n-type conductivity, and is tentatively attributed to a larger trap density in this sample. Measurements of the relative scattering efficiencies of successive diffracted orders in the Raman-Nath regime allowed for calculation of the laser-induced change in the index of refraction, due to the creation of free carriers. The value of Δn=4×10-4 which was obtained is in good agreement with theoretical estimates.

  16. Analytical application of femtosecond laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Melikechi, Noureddine; Markushin, Yuri

    2015-05-01

    We report on significant advantages provided by femtosecond laser-induced breakdown spectroscopy (LIBS) for analytical applications in fields as diverse as protein characterization and material science. We compare the results of a femto- and nanosecond-laser-induced breakdown spectroscopy analysis of dual-elemental pellets in terms of the shot-to-shot variations of the neutral/ionic emission line intensities. This study is complemented by a numerical model based on two-dimensional random close packing of disks in an enclosed geometry. In addition, we show that LIBS can be used to obtain quantitative identification of the hydrogen composition of bio-macromolecules in a heavy water solution. Finally, we show that simultaneous multi-elemental particle assay analysis combined with LIBS can significantly improve macromolecule detectability up to near single molecule per particle efficiency. Research was supported by grants from the National Science Foundation Centers of Research Excellence in Science and Technology (0630388), National Aeronautics and Space Administration (NX09AU90A). Our gratitude to Dr. D. Connolly, Fox Chase Cancer Center.

  17. Nanorod Surface Plasmon Enhancement of Laser-Induced Ultrafast Demagnetization

    NASA Astrophysics Data System (ADS)

    Xu, Haitian; Hajisalem, Ghazal; Steeves, Geoffrey M.; Gordon, Reuven; Choi, Byoung C.

    2015-10-01

    Ultrafast laser-induced magnetization dynamics in ferromagnetic thin films were measured using a femtosecond Ti:sapphire laser in a pump-probe magneto-optic Kerr effect setup. The effect of plasmon resonance on the transient magnetization was investigated by drop-coating the ferromagnetic films with dimensionally-tuned gold nanorods supporting longitudinal surface plasmon resonance near the central wavelength of the pump laser. With ~4% nanorod areal coverage, we observe a >50% increase in demagnetization signal in nanorod-coated samples at pump fluences on the order of 0.1 mJ/cm2 due to surface plasmon-mediated localized electric-field enhancement, an effect which becomes more significant at higher laser fluences. We were able to qualitatively reproduce the experimental observations using finite-difference time-domain simulations and mean-field theory. This dramatic enhancement of ultrafast laser-induced demagnetization points to possible applications of nanorod-coated thin films in heat-assisted magnetic recording.

  18. Direct probing of chromatography columns by laser-induced fluorescence

    SciTech Connect

    McGuffin, V.L.

    1992-12-07

    This report summarizes the progress and accomplishments of this research project from September 1, 1989 to February 28, 1993. During this period, we have accomplished all of the primary scientific objectives of the research proposal: (1) constructed and evaluated a laser-induced fluorescence detection system that allows direct examination of the chromatographic column, (2) examined nonequilibrium processes that occur upon solute injection and elution, (3) examined solute retention in liquid chromatography as a function of temperature and pressure, (4) examined solute zone dispersion in liquid chromatography as a function of temperature and pressure, and (5) developed appropriate theoretical models to describe these phenomena. In each of these studies, substantial knowledge has been gained of the fundamental processes that are responsible for chromatographic separations. In addition to these primary research objectives, we have made significant progress in three related areas: (1) examined pyrene as a fluorescent polarity probe insupercritical fluids and liquids as a function of temperature and pressure, (2) developed methods for the class-selective identification of polynuclear aromatic hydrocarbons in coal-derived fluids by microcolumn liquid chromatography with fluorescence quenching detection, and (3) developed methods for the determination of saturated and unsaturated (including omega-3) fatty acids in fish oil extracts by microcolumn liquid chromatography with laser-induced fluorescence detection. In these studies, the advanced separation and detection techniques developed in our laboratory are applied to practical problems of environmental and biomedical significance.

  19. Laser-induced breakdown spectroscopy of tantalum plasma

    SciTech Connect

    Khan, Sidra; Bashir, Shazia; Hayat, Asma; Khaleeq-ur-Rahman, M.; Faizan–ul-Haq

    2013-07-15

    Laser Induced Breakdown spectroscopy (LIBS) of Tantalum (Ta) plasma has been investigated. For this purpose Q-switched Nd: YAG laser pulses (λ∼ 1064 nm, τ∼ 10 ns) of maximum pulse energy of 100 mJ have been employed as an ablation source. Ta targets were exposed under the ambient environment of various gases of Ar, mixture (CO{sub 2}: N{sub 2}: He), O{sub 2}, N{sub 2}, and He under various filling pressure. The emission spectrum of Ta is observed by using LIBS spectrometer. The emission intensity, excitation temperature, and electron number density of Ta plasma have been evaluated as a function of pressure for various gases. Our experimental results reveal that the optical emission intensity, the electron temperature and density are strongly dependent upon the nature and pressure of ambient environment. The SEM analysis of the ablated Ta target has also been carried out to explore the effect of ambient environment on the laser induced grown structures. The growth of grain like structures in case of molecular gases and cone-formation in case of inert gases is observed. The evaluated plasma parameters by LIBS analysis such as electron temperature and the electron density are well correlated with the surface modification of laser irradiated Ta revealed by SEM analysis.

  20. Direct probing of chromatography columns by laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    McGuffin, V. L.

    1992-12-01

    This report summarizes the progress and accomplishments of this research project from 1 Sep. 1989 to 28 Feb. 1993. During this period, we have accomplished all of the primary scientific objectives of the research proposal: (1) constructed and evaluated a laser-induced fluorescence detection system that allows direct examination of the chromatographic column, (2) examined nonequilibrium processes that occur upon solute injection and elution, (3) examined solute retention in liquid chromatography as a function of temperature and pressure, (4) examined solute zone dispersion in liquid chromatography as a function of temperature and pressure, and (5) developed appropriate theoretical models to describe these phenomena. In each of these studies, substantial knowledge has been gained of the fundamental processes that are responsible for chromatographic separations. In addition to these primary research objectives, we have made significant progress in three related areas: (1) examined pyrene as a fluorescent polarity probe in supercritical fluids and liquids as a function of temperature and pressure, (2) developed methods for the class-selective identification of polynuclear aromatic hydrocarbons in coal-derived fluids by microcolumn liquid chromatography with fluorescence quenching detection, and (3) developed methods for the determination of saturated and unsaturated (including omega-3) fatty acids in fish oil extracts by microcolumn liquid chromatography with laser-induced fluorescence detection. In these studies, the advanced separation and detection techniques developed in our laboratory are applied to practical problems of environmental and biomedical significance.

  1. Calibration analysis of zeolites by laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Horňáčková, M.; Grolmusová, Z.; Horňáček, M.; Rakovský, J.; Hudec, P.; Veis, P.

    2012-08-01

    Laser induced breakdown spectroscopy was used for calibration analysis of different types of microporous crystalline aluminosilicates with exactly ordered structure — zeolites. The LIBS plasma was generated using a Q-switched Nd:YAG laser operating at the wavelength of 532 nm and providing laser pulses of 4 ns duration. Plasma emission was analysed by echelle type emission spectrometer, providing wide spectral range 200-950 nm. The spectrometer was equipped with intensified CCD camera providing rapid spectral acquisition (gating time from 5 ns). The optimum experimental conditions (time delay, gate width and laser pulse energy) have been determined for reliable use of LIBS for quantitative analysis. Samples of different molar ratios of Si/Al were used to create the calibration curves. Calibration curves for different types of zeolites (mordenite, type Y and ZSM-5) were constructed. Molar ratios of Si/Al for samples used for calibration were determined by classical wet chemical analysis and were in the range 5.3-51.8 for mordenite, 2.3-12.8 for type Y and 14-600 for ZSM-5. Zeolites with these molar ratios of Si/Al are usually used as catalysts in alkylation reactions. Laser induced breakdown spectroscopy is a suitable method for analysis of molar ratio Si/Al in zeolites, because it is simple, fast, and does not require sample preparation compared with classical wet chemical analysis which are time consuming, require difficult sample preparation and manipulation with strong acids and bases.

  2. Editor's Highlight: Plasma miR-183/96/182 Cluster and miR-124 are Promising Biomarkers of Rat Retinal Toxicity.

    PubMed

    Peng, Qinghai; Collette, Walter; Giddabasappa, Anand; David, John; Twamley, Michelle; Kalabat, Dalia; Aguirre, Shirley A; Huang, Wenhu

    2016-08-01

    Retinal toxicity is one of the leading causes of attrition in drug development, and drug-induced retinal toxicity remains an issue in both drug discovery and postmarketed drugs. Derisking strategies to help with early identification of retinal injury utilizing a predictive retinal miRNA biomarker would greatly benefit decision-making in drug discovery programs, ultimately reducing attrition due to retinal toxicity. Our previous work demonstrated elevation of circulating retina-enriched miRNAs in a retinal toxicity model. To further validate our previous observation, 2 additional rat retinal injury models were utilized in this study: NaIO3-induced retinal injury and laser-induced choroidal neovascularization (CNV) injury model. Following induction of retina tissue injuries, circulating miR-183/96/182 cluster (miR-183 cluster), and miR-124 was investigated, as well as evaluations using an electroretinogram (ERG) and histopathology analysis. Data revealed that circulating miR-183/96/182 cluster was significantly increased (2- to 15-fold) compared with baseline/control in both laser-induced CNV and NaIO3-induced retinal injury models. Moreover, the severity of the retinal injury evaluated by ERG and histopathology correlated highly with elevation of these retina-enriched miRNAs in plasma. MiR-124 was also significantly increased in comparison with baseline/control by ∼25-fold postrepeat-doses of 30 mg/kg NaIO3 treatment. Increased level of these plasma miRNA biomarkers appeared to be dose- and time-dependent upon NaIO3 or laser treatment. The results suggest that the retina-enriched miRNAs (miR-183/96/182 cluster and miR-124) could serve as convenient and predictive biomarkers of retinal toxicity in drug development. PMID:27208084

  3. Genetics Home Reference: retinitis pigmentosa

    MedlinePlus

    ... Me Understand Genetics Home Health Conditions retinitis pigmentosa retinitis pigmentosa Enable Javascript to view the expand/collapse boxes. Download PDF Open All Close All Description Retinitis pigmentosa is a group of related eye disorders that ...

  4. Determination of phosphorus in steel by the combined technique of laser induced breakdown spectrometry with laser induced fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Kondo, Hiroyuki; Hamada, Naoya; Wagatsuma, Kazuaki

    2009-09-01

    Laser induced breakdown spectrometry (LIBS) combined with laser induced fluorescence spectrometry (LIFS) has been applied for detection of trace-level phosphorus in steel. The plasma induced by irradiation of Nd:YAG laser pulse for ablation was illuminated by the 3rd harmonic of Ti:Sapphire laser tuned to one of the resonant lines for phosphorus in the wavelength region of 253-256 nm. An excitation line for phosphorus was selected to give the highest signal-to-noise ratio. Fluorescence signals, P213.62 and P214.91 nm, were observed with high selectivity at the contents as low as several tens µg g - 1 . Fluorescence intensities were in a good linear correlation with the contents. Fluorescence intensity ratio of a collisionally assisted line (213.62 nm) to a direct transition line (214.91 nm) was discussed in terms of the analytical conditions and experimental results were compared with a calculation based on rate equations. Since the fluorescence signal light in the wavelength range longer than 200 nm can be transmitted relatively easily, even through fiber optics of moderate length, LIBS/LIFS would be a versatile technique in on-site applications for the monitoring of phosphorus contents in steel.

  5. Detection of trace phosphorus in steel using laser-induced breakdown spectroscopy combined with laser-induced fluorescence.

    PubMed

    Shen, X K; Wang, H; Xie, Z Q; Gao, Y; Ling, H; Lu, Y F

    2009-05-01

    Monitoring of light-element concentration in steel is very important for quality assurance in the steel industry. In this work, detection in open air of trace phosphorus (P) in steel using laser-induced breakdown spectroscopy (LIBS) combined with laser-induced fluorescence (LIF) has been investigated. An optical parametric oscillator wavelength-tunable laser was used to resonantly excite the P atoms within plasma plumes generated by a Q-switched Nd:YAG laser. A set of steel samples with P concentrations from 3.9 to 720 parts in 10(6) (ppm) were analyzed using LIBS-LIF at wavelengths of 253.40 and 253.56 nm for resonant excitation of P atoms and fluorescence lines at wavelengths of 213.55 and 213.62 nm. The calibration curves were measured to determine the limit of detection for P in steel, which is estimated to be around 0.7 ppm. The results demonstrate the potential of LIBS-LIF to meet the requirements for on-line analyses in open air in the steel industry. PMID:19412215

  6. [Morphologic aspects of therapy-resistant cytomegalovirus retinitis].

    PubMed

    Meyer, P; Bernauer, W; Daicker, B; Zimmerli, W; Rüttimann, S

    1992-05-01

    Intravenous ganciclovir treatment was performed in eight male AIDS patients with primary unilateral CMV-retinitis. Three patients developed slowly progressive CMV-retinitis in the fellow eye despite adequate dose of ganciclovir. These different CMV-manifestations are shown in a sequence of fundus pictures. Three types of CMV-lesions were observed in connection with this study. Untreated central lesions showed the aspect of crumbled cheese and ketchup. Untreated lesions in the peripherie were yellowish-white, granular, "dry" and showed in most cases no haemorrhages. Lesions appearing during treatment showed initially "dry" white opaque subretinal areas, turning later on to the typical aspect of untreated lesions. The progression could not be stopped by highdose ganciclovir i.v. and thus bilateral blindness resulted after 12 to 22 months. The level of CD4-lymphocytes in the blood was diminished in all patients, but much more in patients with progressive disease. PMID:1319528

  7. The retinal ciliopathies.

    PubMed

    Adams, N A; Awadein, Ahmed; Toma, Hassanain S

    2007-09-01

    While the functions of many of the proteins located in or associated with the photoreceptor cilia are poorly understood, disruption of the function of these proteins may result in a wide variety of phenotypes ranging from isolated retinal degeneration to more pleiotropic phenotypes. Systemic findings include neurosensory hearing loss, developmental delay, situs-inversus, infertility, disorders of limb and digit development, obesity, kidney disease, liver disease, and respiratory disease. The concept of "retinal ciliopathies" brings to attention the importance of further molecular analysis of this organelle as well as provides a potential common target for therapies for these disorders. The retinal ciliopathies include retinitis pigmentosa, macular degeneration, cone-dystrophy, cone-rod dystrophy, Leber congenital amaurosis, as well as retinal degenerations associated with Usher syndrome, primary ciliary dyskinesia, Senior-Loken syndrome, Joubert syndrome, Bardet-Biedl syndrome, Laurence-Moon syndrome, McKusick-Kaufman syndrome, and Biemond syndrome. Mutations for these disorders have been found in retinitis pigmentosa-1 (RP1), retinitis pigmentosa GTPase regulator (RPGR), retinitis pigmentosa GTPase regulator interacting protein (RPGR-IP), as well as the Usher, Bardet-Biedl, and nephronophthisis genes. Other systemic disorders associated with retinal degenerations that may also involve ciliary abnormalities include: Alstrom, Edwards-Sethi, Ellis-van Creveld, Jeune, Meckel-Gruber, Orofaciodigital Type 9, and Gurrieri syndromes. Understanding these conditions as ciliopathies may help the ophthalmologist to recognize associations between seemingly unrelated diseases and have a high degree of suspicion that a systemic finding may be present. PMID:17896309

  8. Laser-Induced Fluorescence in Gaseous [I[subscript]2] Excited with a Green Laser Pointer

    ERIC Educational Resources Information Center

    Tellinghuisen, Joel

    2007-01-01

    A green laser pointer could be used in a flashy demonstration of laser-induced fluorescence in the gas phase by directing the beam of the laser through a cell containing [I[subscript]2] at its room temperature vapor pressure. The experiment could be used to provide valuable insight into the requirements for laser-induced fluorescence (LIF) and the…

  9. Thermal distribution in biological tissue at laser induced fluorescence and photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Krasnikov, I. V.; Seteikin, A. Yu.; Drakaki, E.; Makropoulou, M.

    2012-03-01

    Laser induced fluorescence spectroscopy and photodynamic therapy (PDT) are techniques currently introduced in clinical applications for visualization and local destruction of malignant tumours as well as premalignant lesions. During the laser irradiation of tissues for the diagnostic and therapeutic purposes, the absorbed optical energy generates heat, although the power density of the treatment light for surface illumination is normally low enough not to cause any significantly increased tissue temperature. In this work we tried to evaluate the utility of Monte Carlo modeling for simulating the temperature fields and the dynamics of heat conduction into the skin tissue under several laser irradiation conditions with both a pulsed UV laser and a continuous wave visible laser beam. The analysis of the results showed that heat is not localized on the surface, but it is collected inside the tissue. By varying the boundary conditions on the surface and the type of the laser radiation (continuous or pulsed) we can reach higher than normal temperature inside the tissue without simultaneous formation of thermally damaged tissue (e.g. coagulation or necrosis zone).

  10. Thermal distribution in biological tissue at laser induced fluorescence and photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Krasnikov, I. V.; Seteikin, A. Yu.; Drakaki, E.; Makropoulou, M.

    2011-10-01

    Laser induced fluorescence spectroscopy and photodynamic therapy (PDT) are techniques currently introduced in clinical applications for visualization and local destruction of malignant tumours as well as premalignant lesions. During the laser irradiation of tissues for the diagnostic and therapeutic purposes, the absorbed optical energy generates heat, although the power density of the treatment light for surface illumination is normally low enough not to cause any significantly increased tissue temperature. In this work we tried to evaluate the utility of Monte Carlo modeling for simulating the temperature fields and the dynamics of heat conduction into the skin tissue under several laser irradiation conditions with both a pulsed UV laser and a continuous wave visible laser beam. The analysis of the results showed that heat is not localized on the surface, but it is collected inside the tissue. By varying the boundary conditions on the surface and the type of the laser radiation (continuous or pulsed) we can reach higher than normal temperature inside the tissue without simultaneous formation of thermally damaged tissue (e.g. coagulation or necrosis zone).

  11. Laser induced fluorescence as a diagnostic tool integrated into a scanning fiber endoscope for mouse imaging

    NASA Astrophysics Data System (ADS)

    Brown, Christopher M.; Maggio-Price, Lillian; Seibel, Eric J.

    2007-02-01

    Scanning fiber endoscope (SFE) technology has shown promise as a minimally invasive optical imaging tool. To date, it is capable of capturing full-color 500-line images, at 15 Hz frame rate in vivo, as a 1.6 mm diameter endoscope. The SFE uses a singlemode optical fiber actuated at mechanical resonance to scan a light spot over tissue while backscattered or fluorescent light at each pixel is detected in time series using several multimode optical fibers. We are extending the capability of the SFE from a RGB reflectance imaging device to a diagnostic tool by imaging laser induced fluorescence (LIF) in tissue, allowing for correlation of endogenous fluorescence to tissue state. Design of the SFE for diagnostic imaging is guided by a comparison of single point spectra acquired from an inflammatory bowel disease (IBD) model to tissue histology evaluated by a pathologist. LIF spectra were acquired by illuminating tissue with a 405 nm light source and detecting intrinsic fluorescence with a multimode optical fiber. The IBD model used in this study was mdr1a-/- mice, where IBD was modulated by infection with Helicobacter bilis. IBD lesions in the mouse model ranged from mild to marked hyperplasia and dysplasia, from the distal colon to the cecum. A principle components analysis (PCA) was conducted on single point spectra of control and IBD tissue. PCA allowed for differentiation between healthy and dysplastic tissue, indicating that emission wavelengths from 620 - 650 nm were best able to differentiate diseased tissue and inflammation from normal healthy tissue.

  12. Model-based planning and real-time predictive control for laser-induced thermal therapy

    PubMed Central

    Feng, Yusheng; Fuentes, David

    2014-01-01

    In this article, the major idea and mathematical aspects of model-based planning and real-time predictive control for laser-induced thermal therapy (LITT) are presented. In particular, a computational framework and its major components developed by authors in recent years are reviewed. The framework provides the backbone for not only treatment planning but also real-time surgical monitoring and control with a focus on MR thermometry enabled predictive control and applications to image-guided LITT, or MRgLITT. Although this computational framework is designed for LITT in treating prostate cancer, it is further applicable to other thermal therapies in focal lesions induced by radio-frequency (RF), microwave and high-intensity-focused ultrasound (HIFU). Moreover, the model-based dynamic closed-loop predictive control algorithms in the framework, facilitated by the coupling of mathematical modelling and computer simulation with real-time imaging feedback, has great potential to enable a novel methodology in thermal medicine. Such technology could dramatically increase treatment efficacy and reduce morbidity. PMID:22098360

  13. Tissue characterization in some clinical specialities utilizing laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Svanberg, Katarina; Andersson-Engels, Stefan; Baert, Luc; Bak-Jensen, Elisabeth; Berg, Roger; Brun, Arne; Colleen, Stig; Idvall, Ingrid; D'Hallewin, Marie-Ange; Ingvar, Christian; Johansson, Jonas; Karlsson, Sven-Erik; Lundgren, Rolf; Salford, Leif G.; Stenram, Unne; Stromblad, Lars-Goran; Svanberg, Sune; Wang-Nordman, Ingrid

    1994-05-01

    Laser-induced fluorescence (LIF) can be used for noninvasive spectroscopic identification of biological tissue and is of special interest in early tumor detection. The basis for this optical biopsy method is the interaction of the laser light with tissue chromophores, such as tryptophan, collagen, elastin, NADH, beta-carotene and hemoglobin. The UV-excited fluorescence that arises from the native chromophores, the autofluorescence, has a broad distribution, peaking at about 490 nm with a lower intensity in tumor compared to normal tissue. The tumor detection potential is enhanced with exogenously administrated tumor- marking agents, such as hematoporphyrin (HPD, commercial name Photofrin), with two fluorescence peaks at about 630 and 690 nm. We have developed clinical instrumentation both for tissue point monitoring and for full real-time image processing. Seventy-one patients were investigated in vivo and surgical samples from additional 20 patients. In 46 patients the autofluorescence only was monitored. In 45 patients low-dose Photofrin injection was used. The in vivo investigations included different kinds of lung tumors, urinary bladder tumors, and malignant gliomas. The in vitro measurements were performed in breast tumors and prostatic tumors. Invasive and early tumors and also precancerous lesions can be revealed utilizing LIF in low-dose Photofrin injected patients.

  14. Laser-induced plasma generation and evolution in a transient spray.

    PubMed

    Kawahara, Nobuyuki; Tsuboi, Kazuya; Tomita, Eiji

    2014-01-13

    The behaviors of laser-induced plasma and fuel spray were investigated by visualizing images with an ultra-high-speed camera. Time-series images of laser-induced plasma in a transient spray were visualized using a high-speed color camera. The effects of a shockwave generated from the laser-induced plasma on the evaporated spray behavior were investigated. The interaction between a single droplet and the laser-induced plasma was investigated using a single droplet levitated by an ultrasonic levitator. Two main conclusions were drawn from these experiments: (1) the fuel droplets in the spray were dispersed by the shockwave generated from the laser-induced plasma; and (2) the plasma position may have shifted due to breakdown of the droplet surface and the lens effect of droplets. PMID:24921999

  15. Laser-induced surface modification and metallization of polymers

    NASA Astrophysics Data System (ADS)

    Frerichs, H.; Stricker, J.; Wesner, D. A.; Kreutz, E. W.

    1995-02-01

    Laser-induced surface modification of different polymers is presented as a suitable pretreatment of surfaces in a two-step metallization process. Materials such as polyamide (PA), polypropylene (PP), polystyrene (PS), polycarbonate (PC), acrylbutadienestyrene (ABS), styreneacrylnitrile (SAN), polybutadieneterephthalate (PBT), and polyoxymethylene (POM) were treated by excimer-laser radiation at 248 nm in air. The aim of this study is to investigate different processing regimes of surface modification and ablation to increase surface roughness. Therefore, the laser-processing variables fluence F, repetition rate v and pulse number N are varied and the ablation depth, optical penetration depth, absorption coefficient and ablation threshold are determined. The metallization of pretreated (laser, wet chemical and plasma etching) polymers is investigated for different surface morphologies. The used metallization processes were electroplating and physical vapour deposition (PVD). The adhesion of the deposited films is measured with scratch and tape test methods in order to determine the regimes of suitable surface modification for metallization.

  16. Laser-induced damage measurements with 266-nm pulses

    NASA Astrophysics Data System (ADS)

    Deaton, T. F.; Smith, W. L.

    1980-07-01

    Results of a survey of laser-induced damage thresholds for optical components at 266-nm are reported. The thresholds were measured at two pulse durations; 0.150 ns and 1.0 ns. The 30 samples tested include four commercial dielectric reflectors, three metallic reflectors, two anti-reflection films, a series of eight half-wave oxide and fluoride films, and twelve bare surfaces (fluoride crystals, silica, sapphire, BK-7 glass, cesium dideuterium arsenate and potassium dihydrogen phosphate). The 266-nm pulses were obtained by frequency-quadrupling a Nd:YAG, glass laser. Equivalent plane imagery and calorimetry were used to measure the peak fluence of each of the UV pulses with an accuracy of + or - of 15%; the uncertainty in the threshold determinations is typically + or - 30%.

  17. Quantitative analysis of gallstones using laser-induced breakdown spectroscopy

    SciTech Connect

    Singh, Vivek K.; Singh, Vinita; Rai, Awadhesh K.; Thakur, Surya N.; Rai, Pradeep K.; Singh, Jagdish P

    2008-11-01

    The utility of laser-induced breakdown spectroscopy (LIBS) for categorizing different types of gallbladder stone has been demonstrated by analyzing their major and minor constituents. LIBS spectra of three types of gallstone have been recorded in the 200-900 nm spectral region. Calcium is found to be the major element in all types of gallbladder stone. The spectrophotometric method has been used to classify the stones. A calibration-free LIBS method has been used for the quantitative analysis of metal elements, and the results have been compared with those obtained from inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements. The single-shot LIBS spectra from different points on the cross section (in steps of 0.5 mm from one end to the other) of gallstones have also been recorded to study the variation of constituents from the center to the surface. The presence of different metal elements and their possible role in gallstone formation is discussed.

  18. Laser induced sonofusion: A new road toward thermonuclear reactions

    NASA Astrophysics Data System (ADS)

    Sadighi-Bonabi, Rasoul; Gheshlaghi, Maryam

    2016-03-01

    The Possibility of the laser assisted sonofusion is studied via single bubble sonoluminescence (SBSL) in Deuterated acetone (C3D6O) using quasi-adiabatic and hydro-chemical simulations at the ambient temperatures of 0 and -28.5 °C. The interior temperature of the produced bubbles in Deuterated acetone is 1.6 × 106 K in hydro-chemical model and it is reached up to 1.9 × 106 K in the laser induced SBSL bubbles. Under these circumstances, temperature up to 107 K can be produced in the center of the bubble in which the thermonuclear D-D fusion reactions are promising under the controlled conditions.

  19. Hydroxylapatite nanoparticles obtained by fiber laser-induced fracture

    NASA Astrophysics Data System (ADS)

    Boutinguiza, M.; Lusquiños, F.; Riveiro, A.; Comesaña, R.; Pou, J.

    2009-03-01

    This work presents the results of laser-induced fragmentation of hydroxylapatite microparticles in water dissolution. Calcined fish bones in form of powder, which were previously milled to achieve microsized particles, were used as precursor material. Two different laser sources were employed to reduce the size of the suspended particles: a pulsed Nd:YAG laser and a Ytterbium doped fiber laser working in continuous wave mode. The morphology as well as the composition of the obtained particles was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and conventional and high resolution transmission electron microscopy (TEM, HRTEM). The results show that nanometric particles of hydroxylapatite and β-tricalcium phosphate as small as 10 nm diameter can be obtained.

  20. Apparatus, system, and method for laser-induced breakdown spectroscopy

    SciTech Connect

    Effenberger, Jr., Andrew J; Scott, Jill R; McJunkin, Timothy R

    2014-11-18

    In laser-induced breakdown spectroscopy (LIBS), an apparatus includes a pulsed laser configured to generate a pulsed laser signal toward a sample, a constructive interference object and an optical element, each located in a path of light from the sample. The constructive interference object is configured to generate constructive interference patterns of the light. The optical element is configured to disperse the light. A LIBS system includes a first and a second optical element, and a data acquisition module. The data acquisition module is configured to determine an isotope measurement based, at least in part, on light received by an image sensor from the first and second optical elements. A method for performing LIBS includes generating a pulsed laser on a sample to generate light from a plasma, generating constructive interference patterns of the light, and dispersing the light into a plurality of wavelengths.

  1. Laser-induced fluorescence spectroscopy in tissue local necrosis detection

    NASA Astrophysics Data System (ADS)

    Cip, Ondrej; Buchta, Zdenek; Lesundak, Adam; Randula, Antonin; Mikel, Bretislav; Lazar, Josef; Veverkova, Lenka

    2014-03-01

    The recent effort leads to reliable imaging techniques which can help to a surgeon during operations. The fluorescence spectroscopy was selected as very useful online in vivo imaging method to organics and biological materials analysis. The presented work scopes to a laser induced fluorescence spectroscopy technique to detect tissue local necrosis in small intestine surgery. In first experiments, we tested tissue auto-fluorescence technique but a signal-to-noise ratio didn't express significant results. Then we applied a contrast dye - IndoCyanine Green (ICG) which absorbs and emits wavelengths in the near IR. We arranged the pilot experimental setup based on highly coherent extended cavity diode laser (ECDL) used for stimulating of some critical areas of the small intestine tissue with injected ICG dye. We demonstrated the distribution of the ICG exciter with the first file of shots of small intestine tissue of a rabbit that was captured by high sensitivity fluorescent cam.

  2. Laser-induced stress transients: applications for molecular delivery

    NASA Astrophysics Data System (ADS)

    Flotte, Thomas J.; Lee, Shun; Zhang, Hong; McAuliffe, Daniel J.; Douki, Tina; Doukas, Apostolos G.

    1995-05-01

    Lasers can be used to enhance the delivery of a number of molecules. Other investigators have demonstrated local release of molecules from liposomes following laser irradiation, microbeam disruption of the cell membrane to increase cell transport, microbeam ablation of the zona pellucida surrounding the ovum to increase the chances of fertilization, and increased transcutaneous transport following ablation of the stratum corneum. Our experiments have shown that laser-induced stress transients can be utilized as a vector for intracellular delivery of molecules that may or may not normally cross the cell membrane. These two conditions have been tested with Photofrin and DNA. This technology may have applications in cell and molecular biology, cancer therapy, gene therapy, and others.

  3. Laser-induced single point nanowelding of silver nanowires

    NASA Astrophysics Data System (ADS)

    Dai, Shuowei; Li, Qiang; Liu, Guoping; Yang, Hangbo; Yang, Yuanqing; Zhao, Ding; Wang, Wei; Qiu, Min

    2016-03-01

    Nanowelding of nanomaterials opens up an emerging set of applications in transparent conductors, thin-film solar cells, nanocatalysis, cancer therapy, and nanoscale patterning. Single point nanowelding (SPNW) is highly demanded for building complex nanostructures. In this letter, the precise control of SPNW of silver nanowires is explored in depth, where the nanowelding is laser-induced through the plasmonic resonance enhanced photothermal effect. It is shown that the illumination position is a critical factor for the nanowelding process. As an example of performance enhancement, output at wire end can be increased by 65% after welding for a plasmonic nanocoupler. Thus, single point nanowelding technique shows great potentials for high-performance electronic and photonic devices based on nanowires, such as nanoelectronic circuits and plasmonic nanodevices.

  4. Thermal characterization of nanofluids using laser induced thermal lens technique

    NASA Astrophysics Data System (ADS)

    Kurian, Achamma; Kumar, Rajesh B.; George, Sajan D.

    2009-08-01

    A laser induced thermal lens technique has been employed to evaluate the dynamic thermal parameter, the thermal diffusivity, of gold nanofluids. Gold nanoparticles were synthesized by citrate reduction of HAuCl4 in water. The UVVIS optical absorption spectra show an absorption peak around 540 nm owing to surface Plasmon resonance band of the gold particles. The thermal diffusivity of gold nanoparticles was evaluated by knowing the time constant of transient thermal lens obtained by fitting the experimental curve to the theoretical model of the mode-matched thermal lens. Analyses of the results show that the nanofluid exhibits lower thermal diffusivity value in comparison to the host medium, water. Further investigations also reveal that the concentration of nanoparticles in the fluid have influence on the measured thermal diffusivity value. Results are interpreted in terms of interfacial thermal resistance around the nanoparticles as well as on the clustering of nanoparticles.

  5. Elemental analysis of slurry samples with laser induced breakdown spectroscopy

    SciTech Connect

    Eseller, Kemal E.; Tripathi, Markandey M.; Yueh, Fang-Yu; Singh, Jagdish P.

    2010-05-01

    Direct analysis of wet slurry samples with laser induced breakdown spectroscopy (LIBS) is challenging due to problems of sedimentation, splashing, and surface turbulence. Also, water can quench the laser plasma and suppress the LIBS signal, resulting in poor sensitivity. The effect of water on LIBS spectra from slurries was investigated. As the water content decreased, the LIBS signal was enhanced and the standard deviation was reduced. To improve LIBS slurry analysis, dried slurry samples prepared by applying slurry on PVC coated slides were evaluated. Univariate and multivariate calibration was performed on the LIBS spectra of the dried slurry samples for elemental analysis of Mg, Si, and Fe. Calibration results show that the dried slurry samples give a good correlation between spectral intensity and elemental concentration.

  6. Laser-induced modification of transparent crystals and glasses

    SciTech Connect

    Bulgakova, N M; Stoian, Razvan; Rosenfeld, A

    2010-12-29

    We analyse the processes taking place in transparent crystals and glasses irradiated by ultrashort laser pulses in the regimes typical of various applications in optoelectronics and photonics. We consider some phenomena, which have been previously described by the authors within the different model representations: charging of the dielectric surface due to electron photoemission resulting in a Coulomb explosion; crater shaping by using an adaptive control of the laser pulse shape; optimisation of the waveguide writing in materials strongly resistant to laser-induced compaction under ordinary irradiation conditions. The developed models and analysis of the processes relying on these models include the elements of the solid-state physics, plasma physics, thermodynamics, theory of elasticity and plasticity. Some important experimental observations which require explanations and adequate description are summarised. (photonics and nanotechnology)

  7. Radioactive contamination screening with laser-induced fluorescence

    SciTech Connect

    Sheely, R.; Di Benedetto, J.

    1994-06-01

    The ability to induce, detect and discriminate fluorescence of uranium oxides makes available new capabilities for screening the surface of large complex facilities for uranium. This paper will present the results of field tests evaluate laser-induced fluorescence (LIF) as a contamination screening tool and report on the progress to produce a field portable instrument for uranium surveys on exposed surfaces. The principal effect is to illuminate the surface of an object or an area with a remotely-located light source, and to evaluate the re-radiated emission energy. A gated intensified CCD camera was used with ultraviolet (UV) laser excitation to discriminate the phosphorescent (persistent) green uranium emission from the prompt background fluorescence which results from excitation of plants, concrete, soils, and other background materials.

  8. Detection of early caries by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Sasazawa, Shuhei; Kakino, Satoko; Matsuura, Yuji

    2015-07-01

    To improve sensitivity of dental caries detection by laser-induced breakdown spectroscopy (LIBS) analysis, it is proposed to utilize emission peaks in the ultraviolet. We newly focused on zinc whose emission peaks exist in ultraviolet because zinc exists at high concentration in the outer layer of enamel. It was shown that by using ratios between heights of an emission peak of Zn and that of Ca, the detection sensitivity and stability are largely improved. It was also shown that early caries are differentiated from healthy part by properly setting a threshold in the detected ratios. The proposed caries detection system can be applied to dental laser systems such as ones based on Er:YAG-lasers. When ablating early caries part by laser light, the system notices the dentist that the ablation of caries part is finished. We also show the intensity of emission peaks of zinc decreased with ablation with Er:YAG laser light.

  9. Quantitative investigation of soot distribution by laser-induced incandescence.

    PubMed

    Bryce, D J; Ladommatos, N; Zhao, H

    2000-09-20

    Strategies employed for quantitative measurement by laser-induced incandescence are detailed. Data are obtained for several laminar diffusion flames formed from blended Diesel fuels of known composition. A tomographic procedure is developed to scale the two-dimensional data to soot volume fraction and to correct for the trapping of signal by the soot field. Scaling is achieved by use of laser extinction along the measurement plane. The findings are used in discussions of measurement issues within turbulent environments. Data are augmented with elastic scattering measurements, allowing particle-size and number-density distributions to be inferred. A degree of axial and radial similarity among various flames suggests that the processes of soot formation and oxidation occur over similar time scales for each fuel. PMID:18350100

  10. Laser-induced microbubble poration of localized single cells.

    PubMed

    Fan, Qihui; Hu, Wenqi; Ohta, Aaron T

    2014-05-01

    Laser-induced microbubbles were used to porate the cell membranes of localized single NIH/3T3 fibroblasts. Microsecond laser pulses were focused on an optically absorbent substrate, creating a vapour microbubble that oscillated in size at the laser focal point in a fluidic chamber. The shear stress accompanying the bubble size oscillation was able to porate nearby cells. Cell poration was demonstrated with the delivery of FITC-dextran dye with various molecular weights. Under optimal poration conditions, the cell poration efficiency was up to 95.2 ± 4.8%, while maintaining 97.6 ± 2.4% cell viability. The poration system is able to target a single cell without disturbing surrounding cells. PMID:24632785

  11. Uncertainty analysis of planar laser-induced fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Tavoularis, Stavros; Vanderwel, Christina

    2014-11-01

    We present a thorough analysis of the uncertainty of the planar laser-induced fluorescence (PLIF) method. We consider the measurement of concentration maps in cross-sections parallel to and normal to the axis of a slender plume containing Rhodamine 6G as a passive scalar tracer and transported by a turbulent shear flow. In particular, we identify two previously unexplored sources of error contributed by non-uniformity of the concentration across the laser sheet and by secondary fluorescence. We propose new methods to evaluate and correct for these sources of error and demonstrate that the corrected concentration measurements accurately determined the injected dye mass flow rate of the plume in the far field. Supported by NSERC.

  12. Laser-induced vibration of a thin soap film.

    PubMed

    Emile, Olivier; Emile, Janine

    2014-09-21

    We report on the vibration of a thin soap film based on the optical radiation pressure force. The modulated low power laser induces a counter gravity flow in a vertical free-standing draining film. The thickness of the soap film is then higher in the upper region than in the lower region of the film. Moreover, the lifetime of the film is dramatically increased by a factor of 2. Since the laser beam only acts mechanically on the film interfaces, such a film can be employed in an optofluidic diaphragm pump, the interfaces behaving like a vibrating membrane and the liquid in-between being the fluid to be pumped. Such a pump could then be used in delicate micro-equipment, in chips where temperature variations are detrimental and even in biological systems. PMID:25017934

  13. Laser induced breakdown spectroscopy for the discrimination of Candida strains.

    PubMed

    Manzoor, S; Ugena, L; Tornero-Lopéz, J; Martín, H; Molina, M; Camacho, J J; Cáceres, J O

    2016-08-01

    The present study reports the evaluation of Laser Induced Breakdown Spectroscopy (LIBS) and Neural Networks (NN) for the discrimination of different strains of various species of Candida. This genus of yeast was selected due to its medical relevance as it is commonly found in cases of fungal infection in humans. Twenty one strains belonging to seven species of Candida were included in the study. Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS) was employed as a complementary technique to provide information about elemental composition of Candida cells. The use of LIBS spectra in combination with optimized NN models provided reliable discrimination among the distinct Candida strains with a high spectral correlation index for the samples analyzed, without any false positive or false negative. Therefore, this study indicates that LIBS-NN based methodology has the potential to be used as fast fungal identification or even diagnostic method. PMID:27216662

  14. Microfabrication of Fresnel zone plates by laser induced solid ablation

    NASA Astrophysics Data System (ADS)

    Rodrigues, Vanessa R. M.; Thomas, John; Santhosh, Chidangil; Ramachandran, Hema; Mathur, Deepak

    2016-07-01

    A novel and simple single-step method of inscribing optical elements on metal-coated transparent substrates is demonstrated. Laser induced solid ablation (LISA) demands very low laser energies (nJ), as can be amply provided by a femtosecond laser oscillator. Here, LISA is used to write Fresnel zone plates on indium and tungsten coated glass. With up to 100 zones, remarkable agreement is obtained between measured and expected values of the focal length. LISA has enabled attainment of focal spot sizes that are 38% smaller than what would be obtained using conventional lenses of the same numerical aperture. The simplicity with which a high degree of automation can readily be achieved using LISA makes this cost-effective method amenable to a wide variety of applications related to microfabrication of optical elements.

  15. Application of the method of laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Fateeva, Natalia L.; Matvienko, Gennadii G.

    2004-02-01

    Great attention is now paid to ecology of the environment, in whic plants are of great importance. However the present methods of biophysical analysis of plant states are very labor-intensive and require a lot of time. The structure of protein-pigment complexes is known to break in different dissolvents that results in the shift of maxima of chlorophyll absorption and fluorescence bands. That is why development of methods for remote diagnostics of plants is of great scientific and practical interest. They would make it possible to determine species and state of plants rather quickly and accurately. We have developed a setup and methods for optical diagnostics of the physiological state of plants to investigate the dynamics of the fastest part of fluorescence of plants in vivo. The method of laser-induced fluorescence makes it possible to observe the level of vegetative development of living plants, as well as their state under the impact of some stress factors.

  16. Combined Endoscopic Optical Coherence Tomography and Laser Induced Fluorescence

    NASA Astrophysics Data System (ADS)

    Barton, Jennifer K.; Tumlinson, Alexandre R.; Utzinger, Urs

    Optical coherence tomography (OCT) and laser-induced fluorescence (LIF) are promising modalities for tissue characterization in human patients and animal models. OCT detects coherently backscattered light, whereas LIF detects fluorescence emission of endogenous biochemicals, such as reduced nicotinamide adenine dinucleotide (NADH), flavin adenine dinucleotide (FAD), collagen, and fluorescent proteins, or exogenous substances such as cyanine dyes. Given the complementary mechanisms of contrast for OCT and LIF, the combination of the two modalities could potentially provide more sensitive and specific detection of disease than either modality alone. Sample probes for both OCT and LIF can be implemented using small diameter optical fibers, suggesting a particular synergy for endoscopic applications. In this chapter, the mechanisms of contrast and diagnostic capability for both OCT and LIF are briefly examined. Evidence of complementary capability is described. Example published combined OCT-LIF systems are reviewed, one successful commercial instrument is discussed, and example applications are provided.

  17. Femtosecond laser-induced surface structures on carbon fibers.

    PubMed

    Sajzew, Roman; Schröder, Jan; Kunz, Clemens; Engel, Sebastian; Müller, Frank A; Gräf, Stephan

    2015-12-15

    The influence of different polarization states during the generation of periodic nanostructures on the surface of carbon fibers was investigated using a femtosecond laser with a pulse duration τ=300  fs, a wavelength λ=1025  nm, and a peak fluence F=4  J/cm². It was shown that linear polarization results in a well-aligned periodic pattern with different orders of magnitude concerning their period and an alignment parallel and perpendicular to fiber direction, respectively. For circular polarization, both types of uniform laser-induced periodic surface structures (LIPSS) patterns appear simultaneously with different dominance in dependence on the position at the fiber surface. Their orientation was explained by the polarization-dependent absorptivity and the geometrical anisotropy of the carbon fibers. PMID:26670499

  18. Laser-induced breakdown spectroscopy analysis of energetic materials

    NASA Astrophysics Data System (ADS)

    de Lucia, Frank C.; Harmon, Russell S.; McNesby, Kevin L.; Winkel, Raymond J.; Miziolek, Andrzej W.

    2003-10-01

    A number of energetic materials and explosives have been studied by laser-induced breakdown spectroscopy (LIBS). They include black powder, neat explosives such as TNT, PETN, HMX, and RDX (in various forms), propellants such as M43 and JA2, and military explosives such as C4 and LX-14. Each of these materials gives a unique spectrum, and generally the spectra are reproducible shot to shot. We observed that the laser-produced microplasma did not initiate any of the energetic materials studied. Extensive studies of black powder and its ingredients by use of a reference spectral library have demonstrated excellent accuracy for unknown identification. Finally, we observed that these nitrogen- and oxygen-rich materials yield LIBS spectra in air that have correspondingly different O:N peak ratios compared with air. This difference can help in the detection and identification of such energetic materials.

  19. Enhancing Laser Induced Plasma Emissions using Various Excitation Modalities

    NASA Astrophysics Data System (ADS)

    Johnson, Lewis; Akpovo, Charlemagne; Gebreegziabher, Samson; Martinez, Jorge, Jr.

    2008-11-01

    Detection of hazardous materials with Laser Induced Breakdown Spectroscopy (LIBS) requires a detailed understanding of the sample matrix as well as the surrounding environment. We report on our efforts to understand and manipulate the continuum and atmospheric levels while enhancing surface and substrate material identifications. Comparisons are made between: single pulse (SP) nanosecond (ns); SP femtosecond (fs); SP fs-self-channeled (fs-sc); Dual pulse (DP) ns; DP ns -- fs; and DP ns fs-sc; and multi--pulse Continuous Wave (CW) plasmas formed on the sample surface. Plasma emission spectra from atmospheric oxygen and nitrogen, as well as aluminum and Copper substrates, and hazardous oxygen and nitrogen rich materials residues are analyzed.

  20. Optically Probed Laser-Induced Field-Free Molecular Alignment

    NASA Astrophysics Data System (ADS)

    Faucher, O.; Lavorel, B.; Hertz, E.; Chaussard, F.

    Molecular alignment induced by laser fields has been investigated in research laboratories for over two decades. It led to a better understanding of the fundamental processes at play in the interaction of strong laser fields with molecules, and also provided significant contributions to the fields of high harmonic generation, laser spectroscopy, and laser filamentation. In this chapter, we discuss molecular alignment produced under field-free conditions, as resulting from the interaction of a laser pulse of duration shorter than the rotational period of the molecule. The experimental results presented will be confined to the optically probed alignment of linear as well as asymmetric top molecules. Special care will be taken to describe and compare various optical methods that can be employed to characterize laser-induced molecular alignment. Promising applications of optically probed molecular alignment will be also demonstrated.

  1. Development of Isotope Analysis Based on Laser Induced Fluorescence

    SciTech Connect

    Sakai, T.; Watanabe, K.; Uritani, A.; Tomita, H.; Iguchi, T.

    2009-03-17

    We have proposed Laser Induced Fluorescence analysis using Doppler Shift of laser ablated atoms for Isotope Analysis (LIF-DS-IA). This isotope analysis is expected to have a small mass discrimination effect because the detection target is fluorescence photons instead of ions, which distort the measured isotope ratio by the space charge effect. We demonstrate this technique to be feasible through the model calculations. We experimentally confirmed the fundamental behavior in LIF-DS-IA that the shift in the irradiating laser frequency corresponds to that of peak position in the time domain LIF spectra. The reason of poor mass resolution in the present system was considered to be inadequate definition in the field of view of the fluorescence detector.

  2. Laser-induced thermal acoustics (LITA) signals from finite beams

    NASA Astrophysics Data System (ADS)

    Cummings, E. B.; Leyva, I. A.; Hornung, H. G.

    1995-06-01

    Laser-induced thermal acoustics (LITA) is a four-wave mixing technique that may be employed to measure sound speeds, transport properties, velocities, and susceptibilities of fluids. It is particularly effective in high-pressure gases ( greater than 1 bar). An analytical expression for LITA signals is derived by the use of linearized equations of hydrodynamics and light scattering. This analysis, which includes full finite-beam-size effects and the optoacoustic effects of thermalization and electrostriction, predicts the amplitude and the time history of narrow-band time-resolved LITA and broadband spectrally resolved (mulitplex) LITA signals. The time behavior of the detected LITA signal depends significantly on the detection solid angle, with implications for the measurement of diffusivities by the use of LITA and the proper physical picture of LITA scattering. This and other elements of the physics of LITA that emerge from the analysis are discussed. Theoretical signals are compared with experimental LITA data.

  3. Neural network data analysis for laser-induced thermal acoustics

    NASA Astrophysics Data System (ADS)

    Schlamp, Stefan; Hornung, Hans G.; Cummings, Eric B.

    2000-06-01

    A general, analytical closed-form solution for laser-induced thermal acoustic (LITA) signals using homodyne or heterodyne detection and using electrostrictive and thermal gratings is derived. A one-hidden-layer feed-forward neural network is trained using back-propagation learning and a steepest descent learning rule to extract the speed of sound and flow velocity from a heterodyne LITA signal. The effect of the network size on the performance is demonstrated. The accuracy is determined with a second set of LITA signals that were not used during the training phase. The accuracy is found to be better than that of a conventional frequency decomposition technique while being computationally as efficient. This data analysis method is robust with respect to noise, numerically stable and fast enough for real-time data analysis.

  4. Terahertz generation in multiple laser-induced air plasmas

    SciTech Connect

    Chen, M.-K.; Kim, Jae Hun; Yang, C.-E.; Yin, Stuart Shizhuo; Hui Rongqing; Ruffin, Paul

    2008-12-08

    An investigation of the terahertz wave generation in multiple laser-induced air plasmas is presented. First, it is demonstrated that the intensity of the terahertz wave increases as the number of air plasmas increases. Second, the physical mechanism of this enhancement effect of the terahertz generation is studied by quantitatively measuring the intensity of the generated terahertz wave as a function of phase difference between adjacent air plasmas. It is found out that the superposition is the main mechanism to cause this enhancement. Thus, the results obtained in this paper not only provide a technique to generate stronger terahertz wave but also enable a better understanding of the mechanism of the terahertz generation in air plasma.

  5. Elemental Analysis of Soils by Laser Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Gondal, Mohammed Ashraf; Dastageer, Mohamed A.

    The chemical and elemental composition of soil is very complex as it contains many constituents like minerals, organic matters, living organisms, fossils, air and water. Considering the diversity of soil contents, quality and usability, a systematic scientific study on the elemental and chemical composition of soil is very important. In order to study the chemical composition of soil, Laser induced breakdown spectroscopy (LIBS) has been applied recently. The important features of LIBS system and its applications for the measurement of nutrients in green house soil, on-line monitoring of remediation process of chromium polluted soil, determination of trace elements in volcanic erupted soil samples collected from ancient cenozoic lava eruption sites and detection of toxic metals in Gulf war oil spill contaminated soil using LIBS are described in this chapter.

  6. Laser-induced breakdown spectroscopy expands into industrial applications

    NASA Astrophysics Data System (ADS)

    Noll, Reinhard; Fricke-Begemann, Cord; Brunk, Markus; Connemann, Sven; Meinhardt, Christoph; Scharun, Michael; Sturm, Volker; Makowe, Joachim; Gehlen, Christoph

    This paper presents R&D activities in the field of laser-induced breakdown spectroscopy for industrial applications and shows novel LIBS systems running in routine operation for inline process control tasks. Starting with a comparison of the typical characteristics of LIBS with XRF and spark-discharge optical emission spectrometry, the principal structure of LIBS machines embedded for inline process monitoring will be presented. A systematic requirement analysis for LIBS systems following Ishikawa's scheme was worked out. Stability issues are studied for laser sources and Paschen-Runge spectrometers as key components for industrial LIBS systems. Examples of industrial applications range from handheld LIBS systems using a fiber laser source, via a set of LIBS machines for inline process control tasks, such as scrap analysis, coal analysis, liquid slag analysis and finally monitoring of drill dust.

  7. Laser-induced breakdown spectroscopy analysis of energetic materials.

    PubMed

    De Lucia, Frank C; Harmon, Russell S; McNesby, Kevin L; Winkel, Raymond J; Miziolek, Andrzej W

    2003-10-20

    A number of energetic materials and explosives have been studied by laser-induced breakdown spectroscopy (LIBS). They include black powder, neat explosives such as TNT, PETN, HMX, and RDX (in various forms), propellants such as M43 and JA2, and military explosives such as C4 and LX-14. Each of these materials gives a unique spectrum, and generally the spectra are reproducible shot to shot. We observed that the laser-produced microplasma did not initiate any of the energetic materials studied. Extensive studies of black powder and its ingredients by use of a reference spectral library have demonstrated excellent accuracy for unknown identification. Finally, we observed that these nitrogen- and oxygen-rich materials yield LIBS spectra in air that have correspondingly different O:N peak ratios compared with air. This difference can help in the detection and identification of such energetic materials. PMID:14594077

  8. Laser induced fluorescence applied to turbulent reacting flows

    NASA Technical Reports Server (NTRS)

    Daily, J. W.

    1976-01-01

    The saturated fluorescence method makes use of the great simplifications which occur when under conditions of intense radiation the excitation process becomes saturated. A description is presented of the saturated fluorescence method, taking into account rate equations and saturation, radiative transfer, the two-level system, a multilevel system, and measurements under saturation conditions. The detectability limits of the method are investigated. Fluorescence trapping is found to place an upper limit on the number density of the fluorescing species that can be measured without signal loss. Turbulence places time and spatial constraints on the measurements, but otherwise poses no difficulties. Saturated laser induced fluorescence spectroscopy appears to be a most promising method for measuring species concentrations in flames.

  9. Laser-induced jet formation in liquid films

    NASA Astrophysics Data System (ADS)

    Brasz, Frederik; Arnold, Craig

    2014-11-01

    The absorption of a focused laser pulse in a liquid film generates a cavitation bubble on which a narrow jet can form. This is the basis of laser-induced forward transfer (LIFT), a versatile printing technique that offers an alternative to inkjet printing. We study the influence of the fluid properties and laser pulse energy on jet formation using numerical simulations and time-resolved imaging. At low energies, surface tension causes the jet to retract without transferring a drop, and at high energies, the bubble breaks up into a splashing spray. We explore the parameter space of Weber number, Ohnesorge number, and ratio of film thickness to maximum bubble radius, revealing regions where uniform drops are transferred.

  10. Flexible Boron-Doped Laser-Induced Graphene Microsupercapacitors.

    PubMed

    Peng, Zhiwei; Ye, Ruquan; Mann, Jason A; Zakhidov, Dante; Li, Yilun; Smalley, Preston R; Lin, Jian; Tour, James M

    2015-06-23

    Heteroatom-doped graphene materials have been intensely studied as active electrodes in energy storage devices. Here, we demonstrate that boron-doped porous graphene can be prepared in ambient air using a facile laser induction process from boric acid containing polyimide sheets. At the same time, active electrodes can be patterned for flexible microsupercapacitors. As a result of boron doping, the highest areal capacitance of as-prepared devices reaches 16.5 mF/cm(2), 3 times higher than nondoped devices, with concomitant energy density increases of 5-10 times at various power densities. The superb cyclability and mechanical flexibility of the device are well-maintained, showing great potential for future microelectronics made from this boron-doped laser-induced graphene material. PMID:25978090

  11. Dynamic response of shear thickening fluid under laser induced shock

    SciTech Connect

    Wu, Xianqian Yin, Qiuyun; Huang, Chenguang; Zhong, Fachun

    2015-02-16

    The dynamic response of the 57 vol./vol. % dense spherical silica particle-polyethylene glycol suspension at high pressure was investigated through short pulsed laser induced shock experiments. The measured back free surface velocities by a photonic Doppler velocimetry showed that the shock and the particle velocities decreased while the shock wave transmitted in the shear thickening fluid (STF), from which an equation of state for the STF was obtained. In addition, the peak stress decreased and the absorbed energy increased rapidly with increasing the thickness for a thin layer of the STF, which should be attributed to the impact-jammed behavior through compression of particle matrix, the deformation or crack of the hard-sphere particles, and the volume compression of the particles and the polyethylene glycol.

  12. Picosecond laser-induced water condensation in a cloud chamber.

    PubMed

    Sun, Haiyi; Liu, Yonghong; Ju, Jingjing; Tian, Ye; Bai, Yafeng; Liu, Yaoxiang; Du, Shengzhe; Wang, Cheng; Wang, Tiejun; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2016-09-01

    We investigated water condensation in a laboratory cloud chamber induced by picosecond (ps) laser pulses at ~350 ps (800 nm/1-1000 Hz) with a maximum peak power of ~25 MW. The peak power was much lower than the critical power for self-focusing in air (~3-10 GW depending on the pulse duration). Sparks, airflow and snow formation were observed under different laser energies or repetition rates. It was found that weaker ps laser pulses can also induce water condensation by exploding and breaking down ice crystals and/or water droplets into tiny particles although there was no formation of laser filament. These tiny particles would grow until precipitation in a super-saturation zone due to laser-induced airflow in a cold region with a large temperature gradient. PMID:27607654

  13. OH Planar Laser-Induced Fluorescence from Microgravity Droplet Combustion

    NASA Technical Reports Server (NTRS)

    Winter, Michael; Wegge, Jason; Kang, Kyung-Tae

    1997-01-01

    Droplet combustion under microgravity conditions has been extensively studied, but laser diagnostics have just begun to be employed in microgravity droplet experiments. This is due in part to the level of difficulty associated with laser system size, power and economic availability. Hydroxyl radical (OH) is an important product of combustion, and laser-induced fluorescence (LIF) has proved to be an adequate and sensitive tool to measure OH. In this study, a frequency doubled Nd:YAG laser and a doubled dye laser, compact and reliable enough to perform OH PLIF experiments aboard a parabolic flight-path aircraft, has been developed and successfully demonstrated in a methanol droplet flame experiment. Application to microgravity conditions is planned aboard parabolic flight-path aircraft.

  14. Analysis of fresco by laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Caneve, L.; Diamanti, A.; Grimaldi, F.; Palleschi, G.; Spizzichino, V.; Valentini, F.

    2010-08-01

    The laser-based techniques have been shown to be a very powerful tool for artworks characterization and are used in the field of cultural heritage for the offered advantages of minimum invasiveness, in situ applicability and high sensitivity. Laser induced breakdown spectroscopy, in particular, has been applied in this field to many different kinds of ancient materials with successful results. In this work, a fragment of a Roman wall painting from the archaeological area of Pompeii has been investigated by LIBS. The sample elemental composition resulting from LIBS measurements suggested the presence of certain pigments. The ratio of the intensities of different lines related to some characteristic elements is proposed as an indicator for pigment recognition. The depth profiling permitted to put in evidence the presence of successive paint layers with different compositions. A comparison with the results obtained by the microscopy inspection of the sample has been done.

  15. Hydrogen retention in tungsten materials studied by Laser Induced Desorption

    NASA Astrophysics Data System (ADS)

    Zlobinski, M.; Philipps, V.; Schweer, B.; Huber, A.; Reinhart, M.; Möller, S.; Sergienko, G.; Samm, U.; 't Hoen, M. H. J.; Manhard, A.; Schmid, K.; Textor Team

    2013-07-01

    Development of methods to characterise the first wall in ITER and future fusion devices without removal of wall tiles is important to support safety assessments for tritium retention and dust production and to understand plasma wall processes in general. Laser based techniques are presently under investigation to provide these requirements, among which Laser Induced Desorption Spectroscopy (LIDS) is proposed to measure the deuterium and tritium load of the plasma facing surfaces by thermal desorption and spectroscopic detection of the desorbed fuel in the edge of the fusion plasma. The method relies on its capability to desorb the hydrogen isotopes in a laser heated spot. The application of LID on bulk tungsten targets exposed to a wide range of deuterium fluxes, fluences and impact energies under different surface temperatures is investigated in this paper. The results are compared with Thermal Desorption Spectrometry (TDS), Nuclear Reaction Analysis (NRA) and a diffusion model.

  16. Infrared Signatures of Laser Induced Plasma in Air

    NASA Astrophysics Data System (ADS)

    Hening, Alexandru; Lu, Ryan; Ramirez, Ayax; Advanced Technology Team

    2014-03-01

    Characterization of the temporal and spatial evolution of laser generated plasma in air is necessary for the development of potential applications which range from laser induced ionized micro channels and filaments able to transfer high electric pulses over few hundreds of meters, to the generation of plasma artifacts in air, far away from the laser source. This work is focused mainly on the infrared spectrum. The influence of laser parameters (energy per pulse, pulse duration, repetition rate, wavelength and etc.) on the plasma formation and evolution has been investigated. Laser transmission losses through the air as well as through the breakdown plasma as well as their effect on infrared plasma signature are to be presented.

  17. Laser-induced photo-thermal magnetic imaging

    NASA Astrophysics Data System (ADS)

    Thayer, David A.; Lin, Yuting; Luk, Alex; Gulsen, Gultekin

    2012-08-01

    Due to the strong scattering nature of biological tissue, optical imaging beyond the diffusion limit suffers from low spatial resolution. In this letter, we present an imaging technique, laser-induced photo-thermal magnetic imaging (PMI), which uses laser illumination to induce temperature increase in a medium and magnetic resonance imaging to map the spatially varying temperature, which is proportional to absorbed energy. This technique can provide high-resolution images of optical absorption and can potentially be used for small animal as well as breast cancer and lymph node imaging. First, we describe the theory of PMI, including the modeling of light propagation and heat transfer in tissue. We also present experimental data with corresponding predictions from theoretical models, which show excellent agreement.

  18. Laser-Induced Acoustic Desorption of Natural and Functionalized Biochromophores

    PubMed Central

    2015-01-01

    Laser-induced acoustic desorption (LIAD) has recently been established as a tool for analytical chemistry. It is capable of launching intact, neutral, or low charged molecules into a high vacuum environment. This makes it ideally suited to mass spectrometry. LIAD can be used with fragile biomolecules and very massive compounds alike. Here, we apply LIAD time-of-flight mass spectrometry (TOF-MS) to the natural biochromophores chlorophyll, hemin, bilirubin, and biliverdin and to high mass fluoroalkyl-functionalized porphyrins. We characterize the variation in the molecular fragmentation patterns as a function of the desorption and the VUV postionization laser intensity. We find that LIAD can produce molecular beams an order of magnitude slower than matrix-assisted laser desorption (MALD), although this depends on the substrate material. Using titanium foils we observe a most probable velocity of 20 m/s for functionalized molecules with a mass m = 10 000 Da. PMID:25946522

  19. Optical properties of laser-induced heavily doped Si

    NASA Astrophysics Data System (ADS)

    Ravindra, N. M.; Mhoronge, J. F.; Jouanne, M.

    1985-09-01

    An analysis of experimental studies (Slaoui et al., 1983) of the optical properties of laser-induced heavily doped Si layers is presented. The analysis has been made on the basis of models like those of Penn (1962) and Breckenridge et al. (1974). The calculations show that, in general, the effective number of electrons contributing to optically induced electronic transitions, increases as does the imaginary part of the complex dielectric constant. This reflects an increased absorption coefficient for these As-doped samples. These studies have been carried out on samples of Si heavily doped by ion-implantation followed by a laser-annealing process. The conclusions based on these studies are seen to be in accord with those of Aspnes et al. (1984) and Vina and Cardona (1984).

  20. Titanium monoxide spectroscopy following laser-induced optical breakdown

    NASA Astrophysics Data System (ADS)

    Parigger, Christian G.; Woods, Alexander C.; Keszler, Anna; Nemes, László; Hornkohl, James O.

    2012-07-01

    This work investigates Titanium Monoxide (TiO) in ablation-plasma by employing laser-induced breakdown spectroscopy (LIBS) with 1 to 10 TW/cm2 irradiance, pulsed, 13 nanosecond, Q-switched Nd:YAG laser radiation at the fundamental wavelength of 1064 nm. The analysis of TiO is based on our first accurate determination of transition line strengths for selected TiO A-X, B-X, and E-X transitions, particularly TiO A-X γ and B-X γ' bands. Electric dipole line strengths for the A3Φ-X3δ and B3Π-X3δ bands of TiO are computed. The molecular TiO spectra are observed subsequent to laser-induced breakdown (LIB). We discuss analysis of diatomic molecular spectra that may occur simultaneously with spectra originating from atomic species. Gated detection is applied to investigate the development in time of the emission spectra following LIB. Collected emission spectra allow one to infer micro-plasma parameters such as temperature and electron density. Insight into the state of the micro-plasma is gained by comparing measurements with predictions of atomic and molecular spectra. Nonlinear fitting of recorded and computed diatomic spectra provides the basis for molecular diagnostics, while atomic species may overlap and are simultaneously identified. Molecular diagnostic approaches similar to TiO have been performed for diatomic molecules such as AlO, C2, CN, CH, N2, NH, NO and OH.

  1. Experimental Studies of Laser-Induced Breakdown in Transparent Dielectrics

    SciTech Connect

    Carr, C W

    2003-09-23

    The mechanisms by which transparent dielectrics damage when exposed to high power laser radiation has been of scientific and technological interest since the invention of the laser. In this work, a set of three experiments are presented which provide insight into the damage initiation mechanisms and the processes involved in laser-induced damage. Using an OPO (optical parametric oscillator) laser, we have measured the damage thresholds of deuterated potassium dihydrogen phosphate (DKDP) from the near ultraviolet into the visible. Distinct steps, whose width is of order K{sub b}T, are observed in the damage threshold at photon energies associated with the number of photons (3{yields}2 or 4{yields}3) needed to promote a ground state electron across the energy gap. The wavelength dependence of the damage threshold suggests that a primary mechanism for damage initiation in DKDP is a multi-photon process in which the order is reduced through excited defect state absorption. In-situ fluorescence microscopy, in conjunction with theoretical calculations by Liu et al., has been used to establish that hydrogen displacement defects are potentially responsible for the reduction in the multi-photon cross-section. During the damage process, the material absorbs energy from the laser pulse and produces an ionized region that gives rise to broadband emission. By performing a time-resolved investigation of this emission, we demonstrate both that it is blackbody in nature, and we provide the first direct measurement of the localized temperature during and following laser damage initiation for various optical materials. For excitation using nanosecond laser pulses, the plasma, when confined in the bulk, is in thermal equilibrium with the lattice. These results allow for a detailed characterization of temperature, pressure, and electron densities occurring during laser-induced damage.

  2. Kr II laser-induced fluorescence for measuring plasma acceleration

    SciTech Connect

    Hargus, W. A. Jr.

    2012-10-15

    We present the application of laser-induced fluorescence of singly ionized krypton as a diagnostic technique for quantifying the electrostatic acceleration within the discharge of a laboratory cross-field plasma accelerator also known as a Hall effect thruster, which has heritage as spacecraft propulsion. The 728.98 nm Kr II transition from the metastable 5d{sup 4}D{sub 7/2} to the 5p{sup 4}P{sub 5/2}{sup Ring-Operator} state was used for the measurement of laser-induced fluorescence within the plasma discharge. From these measurements, it is possible to measure velocity as krypton ions are accelerated from near rest to approximately 21 km/s (190 eV). Ion temperature and the ion velocity distributions may also be extracted from the fluorescence data since available hyperfine splitting data allow for the Kr II 5d{sup 4}D{sub 7/2}-5p{sup 4}P{sub 5/2}{sup Ring-Operator} transition lineshape to be modeled. From the analysis, the fluorescence lineshape appears to be a reasonable estimate for the relatively broad ion velocity distributions. However, due to an apparent overlap of the ion creation and acceleration regions within the discharge, the distributed velocity distributions increase ion temperature determination uncertainty significantly. Using the most probable ion velocity as a representative, or characteristic, measure of the ion acceleration, overall propellant energy deposition, and effective electric fields may be calculated. With this diagnostic technique, it is possible to nonintrusively characterize the ion acceleration both within the discharge and in the plume.

  3. Discriminating crude oil grades using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    El-Hussein, A.; Marzouk, A.; Harith, M. A.

    2015-11-01

    The analysis of crude oil using laser-based analytical techniques such as laser-induced breakdown spectroscopy (LIBS) has become of great interest to various specialists in different fields such as geology, petro-chemistry and environmental science. In this work, a detailed study is presented wherein the implementation of an efficient and simple LIBS technique to identify the elemental constituents of crude oil and to distinguish between different grades of petroleum crude oil is discussed. Laser-induced plasma (LIP) technique has been used in this work for direct measurements of atomic, ionic and molecular species in dry crude oil samples with API gravities ranging between 18 and 36. The technique was implemented using the first harmonic of a pulsed Nd-YAG laser source. Atomic and molecular emission bands were observed, consisting of characteristic spectral lines of atoms and diatomic molecular bands, namely from C, H, Si, Na, Ca, Mg, AL, Fe, Ti, Mo, C2 and CN. The intensities of high-resolution spectral lines for some atoms and molecules of elements such as Ca, Na, Fe, Mo, C2 and CN were evaluated at different wavelengths along the obtained spectra. The molecular bands and the elemental spectral lines were used to assess the possibility of adopting the LIBS technique in differentiating between crude oil samples with different American Petroleum Institute (API) gravity values. The results indicate the presence of a distinct correlation between the API gravity values of the various oil samples and the spectral line intensities of the elements and some molecular radical constituents. In addition, the possibility of identifying the API gravity values of unknown oil samples is also indicated.

  4. Biological effects of laser-induced stress waves

    SciTech Connect

    Doukas, A.; Lee, S.; McAuliffe, D.

    1995-12-31

    Laser-induced stress waves can be generated by one of the following mechanisms: Optical breakdown, ablation or rapid heating of an absorbing medium. These three modes of laser interaction with matter allow the investigation of cellular and tissue responses to stress waves with different characteristics and under different conditions. The most widely studied phenomena are those of the collateral damage seen in photodisruption in the eye and in 193 run ablation of cornea and skin. On the other hand, the therapeutic application of laser-induced stress waves has been limited to the disruption of noncellular material such as renal stones, atheromatous plaque and vitreous strands. The effects of stress waves to cells and tissues can be quite disparate. Stress waves can fracture tissue, damage cells, and increase the permeability of the plasma membrane. The viability of cell cultures exposed to stress waves increases with the peak stress and the number of pulses applied. The rise time of the stress wave also influences the degree of cell injury. In fact, cell viability, as measured by thymidine incorporation, correlates better with the stress gradient than peak stress. Recent studies have also established that stress waves induce a transient increase of the permeability of the plasma membrane in vitro. In addition, if the stress gradient is below the damage threshhold, the cells remain viable. Thus, stress waves can be useful as a means of drug delivery, increasing the intracellular drug concentration and allowing the use of drugs which are impermeable to the cell membrane. The present studies show that it is important to create controllable stress waves. The wavelength tunability and the micropulse structure of the free electron laser is ideal for generating stress waves with independently adjustable parameters, such as rise time, duration and peak stress.

  5. Laser-induced synergistic effects around absorbing nanoclusters in live cells

    NASA Astrophysics Data System (ADS)

    Zharov, Vladimir P.; Letfullin, Renat R.; Galitovskay, Elena

    2005-04-01

    Background and Objective: The application of nanotechnology for laser thermal-based killing of abnormal cells (e.g. cancer cells) targeted with absorbing nanoparticles (e.g. gold solid nanospheres, nanoshells, or rod) is becoming an extensive area of research. We develop an approach to enhance the efficiency of selective nanophotothermolysis of cancer cells through laser-induced synergistic effects around gold nanoparticles aggregated in nanoclusters on cell membrane. Study Design/Materials and Methods: A concept of selective target damages by laser-induced synergistic interaction of optical, thermal, and acoustic fields around clustered nanoparticles is presented with focus on overlapping bubbles from nanoparticles aggregated on cell's membrane. The experimental verification of this concept in vitro was performed by the use a tunable laser pulses (420-570 nm, 8-12 ns, 0.1-300 μJ, laser flux of 0.1-10 J/cm2) for irradiation of MDA-MB-231 breast cancer cells targeted with primary antibodies to which selecttively 40-nm gold nanoparticles were attached by the means of secondary antibodies. The photothermal, electron and atomic force microscopes in combination with viability test (annexin -V-Propidium iodide) were employed to study the nanoparticle's spatial organization, the dynamics of microbubble formations around the particle's clusters, and cells damage. Results: An aggregation of nanoparticles on cell membrane was observed with simultaneous increase bubble formation phenomena, and red-shifted absorption due to plasmon-plasmon resonances into nanoclusters. It led to a significant enhancement, at least two orders of magnitude, of the efficiency of selectively killing cancer cells with nanosecond laser pulses. Conclusion: Described approach allows using relatively small nanoparticles which would be easier delivery to target site with further creation of nanoclusters with larger sizes which provide more profound thermal and related phenomena leading to more

  6. VANISHING RETINAL DETACHMENT

    PubMed Central

    2015-01-01

    Purpose: The purpose of this report is to describe a case of rhegmatogenous retinal detachment in the setting of chronic kidney disease that exhibited complete retinal reattachment after serial hemodialysis. Methods: Retrospective case report. Results: A 58-year-old woman with acute vision loss was found to have a macula-involving rhegmatogenous retinal detachment. Due to chronic kidney disease, she continued with routinely scheduled hemodialysis for 1 week until surgical clearance was obtained. Preoperative examination revealed complete reattachment of the retina with a persistent retinal tear. Barrier laser was applied to the tear and the retina remained attached until the most recent follow-up 8 months later. The workup of alternate etiologies was unrevealing. Conclusion: This case describes a temporal association between hemodialysis and resolution of subretinal fluid due to rhegmatogenous retinal detachment. A potential causal linkage is suggested based on shifting fluid dynamics associated with hemodialysis. A shift in treatment paradigm is not advised. PMID:26352323

  7. Laser-induced damage in biological tissue: Role of complex and dynamic optical properties of the medium

    NASA Astrophysics Data System (ADS)

    Ahmed, Elharith M.

    Since its invention in the early 1960's, the laser has been used as a tool for surgical, therapeutic, and diagnostic purposes. To achieve maximum effectiveness with the greatest margin of safety it is important to understand the mechanisms of light propagation through tissue and how that light affects living cells. Lasers with novel output characteristics for medical and military applications are too often implemented prior to proper evaluation with respect to tissue optical properties and human safety. Therefore, advances in computational models that describe light propagation and the cellular responses to laser exposure, without the use of animal models, are of considerable interest. Here, a physics-based laser-tissue interaction model was developed to predict the spatial and temporal temperature and pressure rise during laser exposure to biological tissues. Our new model also takes into account the dynamic nature of tissue optical properties and their impact on the induced temperature and pressure profiles. The laser-induced retinal damage is attributed to the formation of microbubbles formed around melanosomes in the retinal pigment epithelium (RPE) and the damage mechanism is assumed to be photo-thermal. Selective absorption by melanin creates these bubbles that expand and collapse around melanosomes, destroying cell membranes and killing cells. The Finite Element (FE) approach taken provides suitable ground for modeling localized pigment absorption which leads to a non-uniform temperature distribution within pigmented cells following laser pulse exposure. These hot-spots are sources for localized thermo-elastic stresses which lead to rapid localized expansions that manifest themselves as microbubbles and lead to microcavitations. Model predictions for the interaction of lasers at wavelengths of 193, 694, 532, 590, 1314, 1540, 2000, and 2940 nm with biological tissues were generated and comparisons were made with available experimental data for the retina

  8. Restoration of Retinal Structure and Function after Selective Photocoagulation

    PubMed Central

    Jones, Bryan W.; Huie, Philip; Paulus, Yannis M.; Lavinsky, Daniel; Leung, Loh-Shan S.; Nomoto, Hiroyuki; Beier, Corinne; Marc, Robert E.; Palanker, Daniel

    2013-01-01

    CNS neurons change their connectivity to accommodate a changing environment, form memories, or respond to injury. Plasticity in the adult mammalian retina after injury or disease was thought to be limited to restructuring resulting in abnormal retinal anatomy and function. Here we report that neurons in the mammalian retina change their connectivity and restore normal retinal anatomy and function after injury. Patches of photoreceptors in the rabbit retina were destroyed by selective laser photocoagulation, leaving retinal inner neurons (bipolar, amacrine, horizontal, ganglion cells) intact. Photoreceptors located outside of the damaged zone migrated to make new functional connections with deafferented bipolar cells located inside the lesion. The new connections restored ON and OFF responses in deafferented ganglion cells. This finding extends the previously perceived limits of restorative plasticity in the adult retina and allows for new approaches to retinal laser therapy free of current detrimental side effects such as scotomata and scarring. PMID:23595739

  9. Differential Diagnosis of Retinal Vasculitis

    PubMed Central

    Abu El-Asrar, Ahmed M.; Herbort, Carl P.; Tabbara, Khalid F.

    2009-01-01

    Retinal vaculitis is a sight-threatening inflammatory eye condition that involves the retinal vessels. Detection of retinal vasculitis is made clinically, and confirmed with the help of fundus fluorescein angiography. Active vascular disease is characterized by exudates around retinal vessels resulting in white sheathing or cuffing of the affected vessels. In this review, a practical approach to the diagnosis of retinal vasculitis is discussed based on ophthalmoscopic and fundus fluorescein angiographic findings. PMID:20404987

  10. The peptidomimetic Vasotide targets two retinal VEGF receptors and reduces pathological angiogenesis in murine and nonhuman primate models of retinal disease

    PubMed Central

    Sidman, Richard L.; Li, Jianxue; Lawrence, Matthew; Hu, Wenzheng; Musso, Gary F.; Giordano, Ricardo J.; Cardó-Vila, Marina; Pasqualini, Renata; Arap, Wadih

    2016-01-01

    Blood vessel growth from preexisting vessels (angiogenesis) underlies many severe diseases including major blinding retinal diseases such as retinopathy of prematurity (ROP) and aged macular degeneration (AMD). This observation has driven development of antibody inhibitors that block a central factor in AMD, named vascular endothelial growth factor (VEGF), from binding to its receptors VEGFR-1 and VEGFR-2. However, some patients are insensitive to current anti-VEGF drugs or develop resistance, and the required repeated intravitreal injection of these large molecules is costly and clinically problematic. Here, we have evaluated a small cyclic retro-inverted peptidomimetic, D(Cys-Leu-Pro-Arg-Cys), abbreviated as D(CLPRC), and hereafter named Vasotide, that inhibits retinal angiogenesis by binding selectively to the VEGF receptors, VEGFR-1 and Neuropilin-1 (NRP-1). Delivery of Vasotide in eye drops or via intraperitoneal injection in a laser-induced monkey model of human wet AMD, a mouse genetic knockout model of the AMD subtype called retinal angiomatous proliferation (RAP), and a mouse oxygen-induced model of retinopathy of prematurity (ROP) markedly decreased retinal angiogenesis in all three animal models. This prototype drug candidate is a promising new dual receptor inhibitor of the VEGF ligand with potential for translation into safer, less invasive applications to combat pathological angiogenesis in retinal disorders. PMID:26468327

  11. Laser induced damage of fused silica polished optics due to a droplet forming organic contaminant.

    PubMed

    Bien-Aimé, Karell; Néauport, Jérome; Tovena-Pecault, Isabelle; Fargin, Evelyne; Labrugère, Christine; Belin, Colette; Couzi, Michel

    2009-04-20

    We report on the effect of organic molecular contamination on single shot laser induced damage density at the wavelength of 351 nm, with a 3 ns pulse length. Specific contamination experiments were made with dioctylphthalate (DOP) in liquid or gaseous phase, on the surface of fused silica polished samples, bare or solgel coated. Systematic laser induced damage was observed only in the case of liquid phase contamination. Different chemical and morphological characterization methods were used to identify and understand the damage process. We demonstrate that the contaminant morphology, rather than its physicochemical nature, can be responsible for the decrease of laser induced damage threshold of optics. PMID:19381171

  12. Theoretical analysis for temperature dependence of laser- induced damage threshold of optical thin films

    NASA Astrophysics Data System (ADS)

    Mikami, K.; Motokoshi, S.; Somekawa, T.; Jitsuno, T.; Fujita, M.; Tanaka, KA; Azechi, H.

    2016-03-01

    The temperature dependence of the laser-induced damage threshold on optical coatings was studied in detail for laser pulses from 123 K to 473 K at different temperatures. The laser-induced damage threshold increased with decreasing temperatures when we tested long pulses (200 ps and 4 ns). The temperature dependence, however, was reversed for pulses shorter than a few picoseconds (100 fs testing). We propose a scaling model with a flowchart that includes three separate processes: free-electron generation, electron multiplication, and electron heating. Furthermore, we calculated the temperature dependence of laser-induced damage thresholds at different temperatures. Our calculation results agreed well with the experimental results.

  13. Development of laser induced breakdown spectroscopy instrumentatin for safeguards applications

    SciTech Connect

    Barefield Il, James E; Clegg, Samuel M; Le, Loan A; Lopez, Leon N

    2010-01-01

    In September 2006, a Technical Meeting on Application of Laser Spectrometry Techniques in IAEA Safeguards was held at IAEA headquarters (HQ). One of the principal recommendations from this meeting was the need to 'pursue the development of novel complementary access instrumentation based on laser induced breakdown spectroscopy (LIBS) for the detection of gaseous and solid signatures and indicators of nuclear fuel cycle processes and associated materials.' Pursuant to this recommendation the Department of Safeguards (SG) under the Division of Technical Support (SGTS) convened the Experts and Users Advisory Meeting on Laser Induced Breakdown Spectroscopy (LIBS) for Safeguards Applications. This meeting was held at IAEA HQ from July 7-11,2008 and hosted by the Novel Technologies Unit (NTU). The meeting was attended by 12 LIBS experts from the Czech Republic, the European Commission, France, the Republic of Korea, the United States of America, Germany, the United Kingdom of Great Britain, Canada, and Northern Ireland. After a presentation of the needs of the IAEA inspectors, the LIBS experts were in agreement that needs as presented could be partially or fully fulfilled using LIBS instrumentation. The needs of the IAEA inspectors were grouped in the following broad categories: (1) Improvements to in-field measurements/environmental sampling; (2) Monitoring status of activity in a Hot Cell; (3) Verifying status of activity at a declared facility via process monitoring; and (4) Need for pre-screening of environmental samples before analysis. Under the Department of Energy/National Nuclear Security Administration (DOE/NNSA) Next Generation Safeguards Initiative (NGSI) Los Alamos National Laboratory is exploring three potential applications of LIBS for international safeguards. As part of this work, we are developing: (1) a user-friendly man-portable LIBS system to characterize samples across a wide range of elements in the periodic table from hydrogen up to heavy elements

  14. Retinal vascular regeneration.

    PubMed

    Otani, Atsushi; Friedlander, Martin

    2005-01-01

    We discuss the potential use of stem cells for therapeutic angiogenesis in the treatment of retinal diseases. We demonstrate that the clinical utility of these EPC may be not limited in the treatment of ischemic retinal diseases but may also have application for the treatment of retinal degenerative disorders and for a form of cell-based gene therapy. One of the greatest potential benefits of bone marrow derived EPC therapy is the possible use of autologous grafts. Nonetheless, potential toxicities and unregulated cell growth will need to be carefully evaluated before this approach is brought to the clinics. PMID:15804843

  15. Author's reply to 'Rickettsia retinitis cases in India: a few comments'.

    PubMed

    Kawali, Ankush A; Mahendradas, Padmamalini; Gupta, Kanav; Srinivasan, Priya; Avadhani, Kavitha; Yadav, Naresh Kumar; Shetty, Rohit

    2016-12-01

    Diagnosis of rickettsial retinitis remains presumptive when gold standard tests are not available or not done due to financial constrains. History of tick bite followed by fever with skin rash particularly in winter and spring season may point towards Rickettsiosis. The absence of scarring post resolution of rickettsial retinitis suggests inner retinal involvement in contrast to toxoplasmosis. Bilaterality of the disease, 2-4 weeks of latent period, and multifocal nature of retinitis lesions (cotton wool spot-like lesions) especially around the disc and posterior pole may suggest an immune response to recent systemic infection. The use of only antibiotics or only steroids or both together for treatment of rickettsial retinitis is controversial and warrants randomized controlled trials. PMID:27271975

  16. Selective retinal therapy with a continuous line scanning laser

    NASA Astrophysics Data System (ADS)

    Paulus, Yannis M.; Jain, ATul; Gariano, Ray F.; Nomoto, Hiroyuki; Schuele, Georg; Sramek, Christopher; Charalel, Resmi; Palanker, Daniel

    2010-02-01

    This study evaluates the effects of exposure duration, beam diameter, and power on the safety, selectivity, and healing of retinal lesions created using a continuous line scanning laser. A 532 nm laser (PASCALTM) with retinal beam diameters of 40 and 66 μm was applied to 60 eyes of 30 Dutch-Belted rabbits. Retinal exposure duration varied from 15 to 60 μs. Lesions were acutely assessed by ophthalmoscopy and fluorescein angiography (FA). RPE flatmounts were evaluated with live-dead fluorescent assay (LD). Histological analysis was performed at 1 hour, 1 and 3 days, 1 and 2 weeks, and 1 and 2 months following laser treatment. Ophthalmoscopic visibility (OV) of the lesions corresponded to photoreceptor damage on histological analysis at 1 hour. In subvisible lesions, FA and LD yielded similar thresholds of RPE damage. The ratios of the threshold of rupture and of OV to FA visibility (measures of safety and selectivity) increased with decreasing duration and beam diameter. Above the threshold of OV, histology showed focal RPE damage and photoreceptor loss at one day without inner retinal effects. By one week, continuity of photoreceptor and RPE layers was restored. By 1 month, photoreceptors appeared normal while hypertrophy and hyperpigmentation of the RPE persisted. Retinal therapy with a fast scanning continuous laser achieves selective targeting of the RPE and, at higher power, of the photoreceptors. The damage zone in the photoreceptor layer is quickly filled-in, likely due to photoreceptor migration from adjacent zones. Continuous scanning laser can treat large retinal areas within standard eye fixation time.

  17. Laser-induced incandescence measurements of particles in aeroengine exhausts

    NASA Astrophysics Data System (ADS)

    Black, John D.

    1999-09-01

    Laser Induced Incandescence (LII) has been demonstrated as a non-intrusive technique for measurement of particle concentration in the exhausts of aero-engines on sea level test beds as part of a European Union collaborative program (AEROJET) aimed at replacing gas sampling rakes behind development engines with non-intrusive instrumentation. Currently emissions of CO, NOx, unburned hydrocarbon, and smoke from aero-engines must be shown to be less than internationally specified limits. Measurements are made on development engines on sea level test beds by applying a number of standard analytical methods to extracted exhaust gas samples. The hardware required for exhaust gas sampling is heavy and complex and is expensive to build and install. As a result, only the minimum number of emissions tests are conducted during an engine development program, and emissions data is only available to combustion engineers late in the program. Hence, there is a need for more versatile and less costly non-intrusive measurement techniques. Molecular species can be measured using Fourier Transform Infrared (FTIR) spectroscopy, while LII is a promising smoke measuring technique. The development of an LII system specifically designed for exhaust applications is described.

  18. Laser-induced surface modification and metallization of polymers

    NASA Astrophysics Data System (ADS)

    Frerichs, Hartmut; Wesner, David A.; Kreutz, Ernst-Wolfgang

    1995-04-01

    Laser-induced surface modification of various polymers is presented as a suitable pretreatment of surfaces in a two-step metallization process. Materials such as polyamide (PA), polypropylene (PP), polystyrene (PS), polycarbonate (PC), acrylbutadienestyrene (ABS), styreneacrylnitril (SAN), polybutadieneterphtalate (PBT), and polyoxymethylen (POM) were treated by excimer laser radiation ((lambda) equals 248 nm) in air. The aim of this study is to investigate different processing regimes of surface modification. Therefore the laser processing variables fluence F, repetition rate v and pulse number N are varied and the absorption coefficient, optical penetration depth, ablation depth and ablation threshold are determined. The surface morphology and surface roughness are studied by optical surface profilometry and secondary electron microscopy (SEM). The influence of laser treatment on chemical composition of modified and ablated surfaces is analyzed by X-ray photoelectron spectroscopy (XPS). Depending on the processing parameters and materials properties different microstructures and values of surface roughness are generated on the micrometer length scale. Pretreatment for the subsequent metallization is performed with laser radiation, wet chemical and plasma etching. The metallization of polymers is investigated for different surface morphologies. The used metallization processes are electroplating and physical vapor deposition (PVD). Adhesion of the deposited films, measured with scratch and tape test methods, is used as a criterion for determining regimes of suitable surface modification for subsequent metallization.

  19. Electrodes for microfluidic devices produced by laser induced forward transfer

    NASA Astrophysics Data System (ADS)

    Germain, Chris; Charron, Luc; Lilge, Lothar; Tsui, Ying Y.

    2007-07-01

    The laser induced forward transfer (LIFT) process was used to create conductive lines and pads for rapid prototyping and repairing microdevices. Single 0.1-10 μJ pulses from a 120 fs 800 nm titanium:sapphire laser were used to transfer films consisting of 40-80 nm thick gold to create the lines. Experiments were conducted in air ambient. The laser was focused using 4× and 10× microscope objectives and produced 5-20 μm diameter metal spots which were overlapped to produce conductive lines. Electrodes with widths between 10 and 50 μm have been produced and their resistances have been measured. The resistivities of these LIFT produced Au electrodes were found to be approximately (1-4) × 10 -6 Ω m. It has also been shown that the conductivity of the lines can be further improved by electrical curing. The LIFT process was used to repair heaters for microfluidic applications and preliminarily create electrodes for control of electro-osmotic flow in microfluidic devices.

  20. Laser-induced breakdown plasma-based sensors

    NASA Astrophysics Data System (ADS)

    Griffin, Steven T.

    2010-04-01

    Laser Induced Breakdown Spectroscopy (LIBS) is dependent on the interaction between the initiating Laser sequence, the sampled material and the intermediate plasma states. Pulse shaping and timing have been empirically demonstrated to have significant impact on the signal available for active/passive detection and identification. The transient nature of empirical LIBS work makes data collection for optimization an expensive process. Guidance from effective computer simulation represents an alternative. This computational method for CBRNE sensing applications models the Laser, material and plasma interaction for the purpose of performance prediction and enhancement. This paper emphasizes the aspects of light, plasma, and material interaction relevant to portable sensor development for LIBS. The modeling structure emphasizes energy balances and empirical fit descriptions with limited detailed-balance and finite element approaches where required. Dusty plasma from partially decomposed material sample interaction with pulse dynamics is considered. This heuristic is used to reduce run times and computer loads. Computer simulations and some data for validation are presented. A new University of Memphis HPC/super-computer (~15 TFLOPS) is used to enhance simulation. Results coordinated with related effort at Arkansas State University. Implications for ongoing empirical work are presented with special attention paid to the application of compressive sensing for signal processing, feature extraction, and classification.

  1. Femtosecond laser-induced periodic surface structures on silica

    SciTech Connect

    Hoehm, S.; Rosenfeld, A.; Krueger, J.; Bonse, J.

    2012-07-01

    The formation of laser-induced periodic surface structures (LIPSS) on two different silica polymorphs (single-crystalline synthetic quartz and commercial fused silica glass) upon irradiation in air with multiple linearly polarized single- and double-fs-laser pulse sequences ({tau} = 150 fs pulse duration, {lambda} = 800 nm center wavelength, temporal pulse separation {Delta}t < 40 ps) is studied experimentally and theoretically. Two distinct types of fs-LIPSS [so-called low-spatial-frequency LIPSS (LSFL) and high-spatial-frequency LIPSS (HSFL)] with different spatial periods and orientations were identified. Their appearance was characterized with respect to the experimental parameters peak laser fluence and number of laser pulses per spot. Additionally, the 'dynamics' of the LIPSS formation was addressed in complementary double-fs-pulse experiments with varying delays, revealing a characteristic change of the LSFL periods. The experimental results are interpreted on the basis of a Sipe-Drude model considering the carrier dependence of the optical properties of fs-laser excited silica. This new approach provides an explanation of the LSFL orientation parallel to the laser beam polarisation in silica - as opposed to the behaviour of most other materials.

  2. Future Development for Laser-Induced Thermal Acoustics

    NASA Astrophysics Data System (ADS)

    Schlamp, Stefan

    2002-07-01

    The development of novel flow diagnostic techniques typically proceeds in certain stages from a proof of principle in a laboratory to a commercial product either for use in industry or as turn-key research tool. While the first usable versions are brought to market, further progress is made in the laboratory by improvements, refinements, and extensions of the technique. Consider Particle Image Velocimetry (PIV), which started by double-exposing a photographic film with the image of an illuminated particle-laden flow and where today turn-key, off-the-shelf CCD systems are available for purchase, which include the necessary data analysis software. At the same time, 3d PIV, dual-plane PIV, Doppler Global Velocimetry (DGV), etc. are being used in laboratories and will doubtless be available as integrated systems in the near future. In this paper, the origin, an overview over the current status and an outlook on the future potential of Laser-Induced Thermal Acoustics (LITA) will be given, where the focus will be on the possible technique extensions to other than the current applications. As such, it represents a collection of ideas and avenues for future research, which have not been applied as of yet, but are conceptually feasible.

  3. Drift mechanism of laser-induced electron acceleration in vacuum

    NASA Astrophysics Data System (ADS)

    Morgovsky, L.

    2015-12-01

    Laser-induced electron acceleration in vacuum is possible due to the ejection of electrons from the beam as a consequence of the transverse drift orthogonal to the propagation direction. The transverse drift is derived from the general solution of the equations of motion of the electrons in the field of a plane electromagnetic wave with arbitrary polarization. It is shown that the energy gain is proportional to the square of the field strength additionally modulated by the function of the injection and ejection phases. In particular, for a linearly polarized beam this function is reduced to the squared difference between the cosines of these phases. The finite laser pulse duration restricts the range of the field strength suitable for direct electron acceleration in vacuum within certain limits. It is demonstrated that the high efficiency of energy transfer from the laser wave into the kinetic energy of the accelerated electrons demands phase matching between the electron quiver phase at the exit point and the phase of the energy transfer.

  4. Construction of a Laser Induced Breakdown Spectroscopy Setup

    NASA Astrophysics Data System (ADS)

    Mays, Joseph; Palmer, Andria; Amos, James; Dynka, Tom; Ujj, Lazlo

    Laser Induced Breakdown Spectroscopy (LIBS) is a practical spectroscopy to determine the chemical and atomic composition of materials. The third harmonic output of a Nd:YAG Q-switched laser generating 5ns pulses with 10Hz repetition rate was used to ablate the sample and create a micro-plasma. The emission of the radiating plasma was focused into an optical fiber with 0.22 numerical aperture. The spectra was measured with an Ocean Optics micro spectrometer. A synchronized shutter was used to select single laser pulses. In order to reach the breakdown threshold of the sample using the available energy of the laser pulses (<5 mJ) a beam expander and a parabolic mirror was used for tight focusing. The optical and technical details including the characterization of the system will be presented. LIBS spectra taken from a variety of metal and organic samples show appropriate selectivity for quantitative and qualitative analysis for materials. UWF NIH MARC U-STAR 1T34GM110517-01, UWF Office of Undergraduate Research.

  5. Analysis of human nails by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Hosseinimakarem, Zahra; Tavassoli, Seyed Hassan

    2011-05-01

    Laser-induced breakdown spectroscopy (LIBS) is applied to analyze human fingernails using nanosecond laser pulses. Measurements on 45 nail samples are carried out and 14 key species are identified. The elements detected with the present system are: Al, C, Ca, Fe, H, K, Mg, N, Na, O, Si, Sr, Ti as well as CN molecule. Sixty three emission lines have been identified in the spectrum that are dominated by calcium lines. A discriminant function analysis is used to discriminate among different genders and age groups. This analysis demonstrates efficient discrimination among these groups. The mean concentration of each element is compared between different groups. Correlation between concentrations of elements in fingernails is calculated. A strong correlation is found between sodium and potassium while calcium and magnesium levels are inversely correlated. A case report on high levels of sodium and potassium in patients with hyperthyroidism is presented. It is shown that LIBS could be a promising technique for the analysis of nails and therefore identification of health problems.

  6. Laser-induced incandescence applied to dusty plasmas

    NASA Astrophysics Data System (ADS)

    van de Wetering, F. M. J. H.; Oosterbeek, W.; Beckers, J.; Nijdam, S.; Kovačević, E.; Berndt, J.

    2016-07-01

    This paper reports on the laser heating of nanoparticles (diameters ≤slant 1 μm) confined in a reactive plasma by short (150 ps) and intense (∼ 63 mJ) UV (355 nm) laser pulses (laser-induced incandescence, LII). Important parameters such as the particle temperature and radius follow from analysis of the emission spectrum of the heated nanoparticles. The nanoparticles are not ideal black bodies, which is taken into account by calculating their emissivity using a light-scattering theory relevant to our conditions (Mie theory). Three sets of refractive index data from the literature serve as model input. The obtained radii range between 100 and 165 nm, depending on the choice of refractive index data set. By fitting the temperature decay of the particles to a heat exchange model, the product of their mass density and specific heat is determined as (1.3+/- 0.5) J K‑1 cm‑3, which is considerably smaller than the value for bulk graphite at the temperature our particles attain (3000 K): 4.8 J K‑1 cm‑3. The particle sizes obtained in situ with LII are compared with ex situ scanning electron microscopy analysis of collected particles. Quantitative assessment of the LII measurements is hampered by transport of particles in the plasma volume and the fact that LII probes locally, whereas the samples with collected particles have a more global character.

  7. Laser-induced fluorescence for discrimination of crops and weeds

    NASA Astrophysics Data System (ADS)

    Hilton, Peter J.

    2000-11-01

    This paper reports the use of Laser Induced Fluorescence (LIF) of plants to discriminate between crops and weeds for potential use in an intelligent crop spraying system. Past and current work in intelligent crop spraying has concentrated on using multi-spectral reflectance data in particular using near infrared (NIR) and color. Texture and shape image processing has also been used with limited success and is usually computationally expensive. Also, most of these approaches are error prone since they rely on ambient solar illumination and so are susceptible to errors caused by cloud variations, shadows and other non-uniformities. There are several commercial spraying systems available that detect presence or absence of plants using the NIR 'red-edge' effect without discrimination between species. 'Weedseeker' and 'Detectspray' are two examples of such systems, the 'Weedseeker' system being one of the few active systems, incorporating its own light source. However, both systems suffer from poor spatial resolution. The use of plant or chlorophyll fluorescence for discrimination between species is a relatively under researched area. This paper shows that LIF of several crops and weeds can be used to discriminate between species. Spectra are presented for two crop and two weed species over a range of discrete laser excitation wavelengths. The technique can be directly implemented with a laser imaging system for real-time detection and discrimination of crops and weeds.

  8. Laser-induced Forward Transfer of Ag Nanopaste

    PubMed Central

    Breckenfeld, Eric; Kim, Heungsoo; Auyeung, Raymond C. Y.; Piqué, Alberto

    2016-01-01

    Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of these processes such as inkjet3 and laser-induced forward transfer (LIFT)4 have become increasingly popular as interest in printable electronics and maskless patterning has grown. These additive manufacturing processes are inexpensive, environmentally friendly, and well suited for rapid prototyping, when compared to more traditional semiconductor processing techniques. While most direct-write processes are confined to two-dimensional structures and cannot handle materials with high viscosity (particularly inkjet), LIFT can transcend both constraints if performed properly. Congruent transfer of three dimensional pixels (called voxels), also referred to as laser decal transfer (LDT)5-9, has recently been demonstrated with the LIFT technique using highly viscous Ag nanopastes to fabricate freestanding interconnects, complex voxel shapes, and high-aspect-ratio structures. In this paper, we demonstrate a simple yet versatile process for fabricating a variety of micro- and macroscale Ag structures. Structures include simple shapes for patterning electrical contacts, bridging and cantilever structures, high-aspect-ratio structures, and single-shot, large area transfers using a commercial digital micromirror device (DMD) chip. PMID:27077645

  9. Laser-induced thermoelastic effects can evoke tactile sensations.

    PubMed

    Jun, Jae-Hoon; Park, Jong-Rak; Kim, Sung-Phil; Min Bae, Young; Park, Jang-Yeon; Kim, Hyung-Sik; Choi, Seungmoon; Jung, Sung Jun; Hwa Park, Seung; Yeom, Dong-Il; Jung, Gu-In; Kim, Ji-Sun; Chung, Soon-Cheol

    2015-01-01

    Humans process a plethora of sensory information that is provided by various entities in the surrounding environment. Among the five major senses, technology for touch, haptics, is relatively young and has relatively limited applications largely due to its need for physical contact. In this article, we suggest a new way for non-contact haptic stimulation that uses laser, which has potential advantages such as mid-air stimulation, high spatial precision, and long working distance. We demonstrate such tactile stimulation can be enabled by laser-induced thermoelastic effects by means of physical and perceptual studies, as well as simulations. In the physical study, the mechanical effect of laser on a human skin sample is detected using low-power radiation in accordance with safety guidelines. Limited increases (< ~2.5 °C) in temperature at the surface of the skin, examined by both thermal camera and the Monte Carlo simulation, indicate that laser does not evoke heat-induced nociceptive sensation. In the human EEG study, brain responses to both mechanical and laser stimulation are consistent, along with subjective reports of the non-nociceptive sensation of laser stimuli. PMID:26047142

  10. Fast analysis of wood preservers using laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Uhl, A.; Loebe, K.; Kreuchwig, L.

    2001-06-01

    Laser-induced breakdown spectroscopy (LIBS) is used for the investigation of wood preservers in timber and in furniture. Both experiments in laboratory and practical applications in recycling facilities and on a building site prove the new possibilities for the fast detection of harmful agents in wood. A commercial system was developed for mobile laser-plasma-analysis as well as for industrial use in sorting plants. The universal measuring principle in combination with an Echelle optics permits real simultaneous multi-element-analysis in the range of 200-780 nm with a resolution of a few picometers. It enables the user to detect main and trace elements in wood within a few seconds, nearly independent of the matrix, knowing that different kinds of wood show an equal elemental composition. Sample preparation is not required. The quantitative analysis of inorganic wood preservers (containing, e.g. Cu, Cr, B, As, Pb, Hg) has been performed exactly using carbon as reference element. It can be shown that the detection limits for heavy metals in wood are in the ppm-range. Additional information is given concerning the quantitative analysis. Statistical data, e.g. the standard deviation (S.D.), were determined and calibration curves were used for each particular element. A comparison between ICP-AES and LIBS is given using depth profile correction factors regarding the different penetration depths with respect to the different volumes in wood analyzed by both analytical methods.

  11. Laser-induced breakdown spectroscopy combined with spatial heterodyne spectroscopy.

    PubMed

    Gornushkin, Igor B; Smith, Ben W; Panne, Ulrich; Omenetto, Nicoló

    2014-01-01

    A spatial heterodyne spectrometer (SHS) is tested for the first time in combination with laser-induced breakdown spectroscopy (LIBS). The spectrometer is a modified version of the Michelson interferometer in which mirrors are replaced by diffraction gratings. The SHS contains no moving parts and the gratings are fixed at equal distances from the beam splitter. The main advantage is high throughput, about 200 times higher than that of dispersive spectrometers used in LIBS. This makes LIBS-SHS a promising technique for low-light standoff applications. The output signal of the SHS is an interferogram that is Fourier-transformed to retrieve the original plasma spectrum. In this proof-of-principle study, we investigate the potential of LIBS-SHS for material classification and quantitative analysis. Brass standards with broadly varying concentrations of Cu and Zn were tested. Classification via principal component analysis (PCA) shows distinct groupings of materials according to their origin. The quantification via partial least squares regression (PLS) shows good precision (relative standard deviation < 10%) and accuracy (within ± 5% of nominal concentrations). It is possible that LIBS-SHS can be developed into a portable, inexpensive, rugged instrument for field applications. PMID:25226262

  12. Ultraviolet Laser-induced ignition of RDX single crystal

    NASA Astrophysics Data System (ADS)

    Yan, Zhonghua; Zhang, Chuanchao; Liu, Wei; Li, Jinshan; Huang, Ming; Wang, Xuming; Zhou, Guorui; Tan, Bisheng; Yang, Zongwei; Li, Zhijie; Li, Li; Yan, Hongwei; Yuan, Xiaodong; Zu, Xiaotao

    2016-02-01

    The RDX single crystals are ignited by ultraviolet laser (355 nm, 6.4 ns) pulses. The laser-induced damage morphology consisted of two distinct regions: a core region of layered fracture and a peripheral region of stripped material surrounding the core. As laser fluence increases, the area of the whole crack region increases all the way, while both the area and depth of the core region increase firstly, and then stay stable over the laser fluence of 12 J/cm2. The experimental details indicate the dynamics during laser ignition process. Plasma fireball of high temperature and pressure occurs firstly, followed by the micro-explosions on the (210) surface, and finally shock waves propagate through the materials to further strip materials outside and yield in-depth cracks in larger surrounding region. The plasma fireball evolves from isotropic to anisotropic under higher laser fluence resulting in the damage expansion only in lateral direction while maintaining the fixed depth. The primary insights into the interaction dynamics between laser and energetic materials can help developing the superior laser ignition technique.

  13. Dust Removal on Mars Using Laser-Induced Breakdown Spectroscopy

    NASA Technical Reports Server (NTRS)

    Graff, T. G.; Morris, R. V.; Clegg, S. M.; Wiens, R. C.; Anderson, R. B.

    2011-01-01

    Dust coatings on the surface of Mars complicate and, if sufficiently thick, mask the spectral characteristics and compositional determination of underlying material from in situ and remote sensing instrumentation. The Laser-Induced Breakdown Spectroscopy (LIBS) portion of the Chemistry & Camera (ChemCam) instrument, aboard the Mars Science Laboratory (MSL) rover, will be the first active remote sensing technique deployed on Mars able to remove dust. ChemCam utilizes a 5 ns pulsed 1067 nm high-powered laser focused to less than 400 m diameter on targets at distances up to 7 m [1,2]. With multiple laser pulses, dust and weathering coatings can be remotely analyzed and potentially removed using this technique [2,3]. A typical LIBS measurement during MSL surface operations is planned to consist of 50 laser pulses at 14 mJ, with the first 5 to 10 pulses used to analyze as well as remove any surface coating. Additionally, ChemCam's Remote Micro-Imager (RMI) is capable of resolving 200 m details at a distance of 2 m, or 1 mm at 10 m [1,4]. In this study, we report on initial laboratory experiments conducted to characterize the removal of dust coatings using similar LIBS parameters as ChemCam under Mars-like conditions. These experiments serve to better understand the removal of surface dust using LIBS and to facilitate the analysis of ChemCam LIBS spectral data and RMI images.

  14. Airborne laser induced fluorescence imaging. Innovative technology summary report

    SciTech Connect

    1999-06-01

    Laser-Induced Fluorescence (LIF) was demonstration as part of the Fernald Environmental Management Project (FEMP) Plant 1 Large Scale Demonstration and Deployment Project (LSDDP) sponsored by the US Department of Energy (DOE) Office of Science and Technology, Deactivation and Decommissioning Focus Area located at the Federal Energy Technology Center (FETC) in Morgantown, West Virginia. The demonstration took place on November 19, 1996. In order to allow the contaminated buildings undergoing deactivation and decommissioning (D and D) to be opened to the atmosphere, radiological surveys of floors, walls and ceilings must take place. After successful completion of the radiological clearance survey, demolition of the building can continue. Currently, this process is performed by collecting and analyzing swipe samples for radiological analysis. Two methods are used to analyze the swipe samples: hand-held frisker and laboratory analysis. For the purpose of this demonstration, the least expensive method, swipe samples analyzed by hand-held frisker, is the baseline technology. The objective of the technology demonstration was to determine if the baseline technology could be replaced using LIF.

  15. Modeling chemical reactions in laser-induced plasmas

    NASA Astrophysics Data System (ADS)

    Shabanov, S. V.; Gornushkin, I. B.

    2015-11-01

    Under the assumption of local thermal equilibrium, a numerical algorithm is proposed to find the equation of state for laser-induced plasmas (LIPs) in which chemical reactions are permitted in addition to ionization processes. The Coulomb interaction in plasma is accounted for by the Debye-Hückel method. The algorithm is used to calculate the equation of state for LIPs containing carbon, silicon, nitrogen, and argon. The equilibrium reaction constants are calculated using the latest experimental and ab initio data of spectroscopic constants for the molecules {N}_2, {C}_2, {Si}_2, {CN}, {SiN}, {SiC} and their ions. The algorithm is incorporated into a fluid dynamic numerical model based on the Navier-Stokes equations describing an expansion of LIP plumes into an ambient gas. The dynamics of LIP plumes obtained by the ablation of SiC, solid silicon, or solid carbon in an ambient gas containing {N}_2 and Ar is simulated to study formation of molecules and molecular ions.

  16. Laser-induced Forward Transfer of Ag Nanopaste.

    PubMed

    Breckenfeld, Eric; Kim, Heungsoo; Auyeung, Raymond C Y; Piqué, Alberto

    2016-01-01

    Over the past decade, there has been much development of non-lithographic methods(1-3) for printing metallic inks or other functional materials. Many of these processes such as inkjet(3) and laser-induced forward transfer (LIFT)(4) have become increasingly popular as interest in printable electronics and maskless patterning has grown. These additive manufacturing processes are inexpensive, environmentally friendly, and well suited for rapid prototyping, when compared to more traditional semiconductor processing techniques. While most direct-write processes are confined to two-dimensional structures and cannot handle materials with high viscosity (particularly inkjet), LIFT can transcend both constraints if performed properly. Congruent transfer of three dimensional pixels (called voxels), also referred to as laser decal transfer (LDT)(5-9), has recently been demonstrated with the LIFT technique using highly viscous Ag nanopastes to fabricate freestanding interconnects, complex voxel shapes, and high-aspect-ratio structures. In this paper, we demonstrate a simple yet versatile process for fabricating a variety of micro- and macroscale Ag structures. Structures include simple shapes for patterning electrical contacts, bridging and cantilever structures, high-aspect-ratio structures, and single-shot, large area transfers using a commercial digital micromirror device (DMD) chip. PMID:27077645

  17. Laser induced alignment of state-selected CH3I.

    PubMed

    He, Lanhai; Bulthuis, Jaap; Luo, Sizuo; Wang, Jia; Lu, Chunjing; Stolte, Steven; Ding, Dajun; Roeterdink, Wim G

    2015-10-01

    Hexapole state selection is used to prepare CH3I molecules in the |JKM〉 = |1±1∓1〉 state. The molecules are aligned in a strong 800 nm laser field, which is linearly polarised perpendicular to the weak static extraction field E of the time of flight setup. The molecules are subsequently ionised by a second time delayed probe laser pulse. It will be shown that in this geometry at high enough laser intensities the Newton sphere has sufficient symmetry to apply the inverse Abel transformation to reconstruct the three dimensional distribution from the projected ion image. The laser induced controllable alignment was found to have the upper and lower extreme values of 〈P2(cos θ)〉 = 0.7 for the aligned molecule and -0.1 for the anti-aligned molecule, coupled to 〈P4(cos θ)〉 between 0.3 and 0.0. The method to extract the alignment parameters 〈P2(cos θ)〉 and 〈P4(cos θ)〉 directly from the velocity map ion images will be discussed. PMID:26314900

  18. Laser induced fluorescence measurements of the cylindrical Hall thruster plume

    SciTech Connect

    Spektor, R.; Diamant, K. D.; Beiting, E. J.; Raitses, Y.; Fisch, N. J.

    2010-09-15

    An investigation of a fully cylindrical Hall thruster was performed using laser induced fluorescence (LIF) to measure ion velocity profiles in the plume. The measurements confirm a previously reported 9% increase in the exhaust energy when the cathode keeper draws an excess current (overrun mode). Furthermore, the velocity directions in the plume remain relatively unchanged for the cusped and direct magnetic field configuration in both overrun and nonoverrun modes. Previously reported plume narrowing in the overrun mode was confirmed and found to be due to the shift of the acceleration and ionization regions toward the anode. The electric field inferred from the LIF measurements allowed calculation of the electron ExB drift. Close to the centerline of the thruster, electrons drift azimuthally with velocity decreasing away from the centerline, thus creating shear. This shear can be a source of plasma instabilities and influence electron transport. Further away from the centerline, electrons drift in the opposite direction with their velocity increasing with increasing radius. In that region, electrons rotate without shear.

  19. Laser-induced porous graphene films from commercial polymers

    PubMed Central

    Lin, Jian; Peng, Zhiwei; Liu, Yuanyue; Ruiz-Zepeda, Francisco; Ye, Ruquan; Samuel, Errol L. G.; Yacaman, Miguel Jose; Yakobson, Boris I.; Tour, James M.

    2014-01-01

    Synthesis and patterning of carbon nanomaterials cost effectively is a challenge in electronic and energy storage devices. Here report a one-step, scalable approach for producing and patterning porous graphene films with 3-dimensional networks from commercial polymer films using a CO2 infrared laser. The sp3-carbon atoms are photothermally converted to sp2-carbon atoms by pulsed laser irradiation. The resulting laser-induced graphene (LIG) exhibits high electrical conductivity. The LIG can be readily patterned to interdigitated electrodes for in-plane microsupercapacitors with specific capacitances of >4 mF·cm−2 and power densities of ~9 mW·cm−2. Theoretical calculations partially suggest that enhanced capacitance may result from LIG’s unusual ultra-polycrystalline lattice of pentagon-heptagon structures. Combined with the advantage of one-step processing of LIG in air from commercial polymer sheets, which would allow the employment of a roll-to-roll manufacturing process, this technique provides a rapid route to polymer-written electronic and energy storage devices. PMID:25493446

  20. Cavity ringdown and laser-induced incandescence measurements of soot.

    PubMed

    Vander Wal, R L; Ticich, T M

    1999-03-20

    Currently laser-induced incandescence (LII) is widely used for the measurement of soot volume fraction. A particularly important aspect of the technique that has received less attention, however, is calibration. The applicability of cavity ringdown (CRD) for measurement of soot volume fraction f(v) is assessed, and the calibration of LII by means of CRD is demonstrated. The accuracy of CRD for f(v) determination is validated by comparison with traditional light extinction and path-integrated LII. By use of CRD, the quantification of LII for parts in 10(9) (ppb) f(v) levels is demonstrated. Results are presented that demonstrate the accuracy of CRD for a single laser pulse to be better than ?5% for measurement of ppb soot volume-fraction levels over a 1-cm path length. By use of CRD, spatially resolved LII signals from soot within methane-air diffusion flames are calibrated for ppb f(v) levels, thereby avoiding the extrapolation required of less sensitive methods in current use. PMID:18305765

  1. Laser-induced breakdown spectroscopy in industrial and security applications

    SciTech Connect

    Bol'shakov, Alexander A.; Yoo, Jong H.; Liu Chunyi; Plumer, John R.; Russo, Richard E.

    2010-05-01

    Laser-induced breakdown spectroscopy (LIBS) offers rapid, localized chemical analysis of solid or liquid materials with high spatial resolution in lateral and depth profiling, without the need for sample preparation. Principal component analysis and partial least squares algorithms were applied to identify a variety of complex organic and inorganic samples. This work illustrates how LIBS analyzers can answer a multitude of real-world needs for rapid analysis, such as determination of lead in paint and children's toys, analysis of electronic and solder materials, quality control of fiberglass panels, discrimination of coffee beans from different vendors, and identification of generic versus brand-name drugs. Lateral and depth profiling was performed on children's toys and paint layers. Traditional one-element calibration or multivariate chemometric procedures were applied for elemental quantification, from single laser shot determination of metal traces at {approx}10 {mu}g/g to determination of halogens at 90 {mu}g/g using 50-shot spectral accumulation. The effectiveness of LIBS for security applications was demonstrated in the field by testing the 50-m standoff LIBS rasterizing detector.

  2. Ultraviolet Laser-induced ignition of RDX single crystal.

    PubMed

    Yan, Zhonghua; Zhang, Chuanchao; Liu, Wei; Li, Jinshan; Huang, Ming; Wang, Xuming; Zhou, Guorui; Tan, Bisheng; Yang, Zongwei; Li, Zhijie; Li, Li; Yan, Hongwei; Yuan, Xiaodong; Zu, Xiaotao

    2016-01-01

    The RDX single crystals are ignited by ultraviolet laser (355 nm, 6.4 ns) pulses. The laser-induced damage morphology consisted of two distinct regions: a core region of layered fracture and a peripheral region of stripped material surrounding the core. As laser fluence increases, the area of the whole crack region increases all the way, while both the area and depth of the core region increase firstly, and then stay stable over the laser fluence of 12 J/cm(2). The experimental details indicate the dynamics during laser ignition process. Plasma fireball of high temperature and pressure occurs firstly, followed by the micro-explosions on the (210) surface, and finally shock waves propagate through the materials to further strip materials outside and yield in-depth cracks in larger surrounding region. The plasma fireball evolves from isotropic to anisotropic under higher laser fluence resulting in the damage expansion only in lateral direction while maintaining the fixed depth. The primary insights into the interaction dynamics between laser and energetic materials can help developing the superior laser ignition technique. PMID:26847854

  3. Laser-Induced Incandescence Measurements in Low Gravity

    NASA Technical Reports Server (NTRS)

    VanderWal, R. L.

    1997-01-01

    A low-gravity environment offers advantages to investigations concerned with soot growth or flame radiation by eliminating of buoyancy-induced convection. Basic to each type of study is knowledge of spatially resolved soot volume fraction, (f(sub v). Laser-induced incandescence (LII) has emerged as a diagnostic for soot volume fraction determination because it possesses high temporal and spatial resolution, geometric versatility and high sensitivity. Implementation and system characterization of LII in a drop tower that provides 2.2 sec of low-gravity (micro)g) at the NASA Lewis Research Center are described here. Validation of LII for soot volume fraction determination in (micro)g is performed by comparison between soot volume fraction measurements obtained by light extinction [20] and LII in low-gravity for a 50/50 mixture (by volume) of 0 acetylene/nitrogen issuing into quiescent air. Quantitative soot volume fraction measurements within other laminar flames of ethane and propane and a turbulent diffusion flame in (micro)g via LII are also demonstrated. An analysis of LII images of a turbulent acetylene diffusion flame in 1-g and (micro)g is presented.

  4. Elemental analysis of cotton by laser-induced breakdown spectroscopy

    SciTech Connect

    Schenk, Emily R.; Almirall, Jose R.

    2010-05-01

    Laser-induced breakdown spectroscopy (LIBS) has been applied to the elemental characterization of unprocessed cotton. This research is important in forensic and fraud detection applications to establish an elemental fingerprint of U.S. cotton by region, which can be used to determine the source of the cotton. To the best of our knowledge, this is the first report of a LIBS method for the elemental analysis of cotton. The experimental setup consists of a Nd:YAG laser that operates at the fundamental wavelength as the LIBS excitation source and an echelle spectrometer equipped with an intensified CCD camera. The relative concentrations of elements Al, Ba, Ca, Cr, Cu, Fe, Mg, and Sr from both nutrients and environmental contributions were determined by LIBS. Principal component analysis was used to visualize the differences between cotton samples based on the elemental composition by region in the U.S. Linear discriminant analysis of the LIBS data resulted in the correct classification of >97% of the cotton samples by U.S. region and >81% correct classification by state of origin.

  5. Laser-Induced Fluorescence in plasmas at UC Irvine

    NASA Astrophysics Data System (ADS)

    McWilliams, R.

    2003-10-01

    For about 25 years laser-induced fluorescence (LIF) has been performed at UC Irvine with many people contributing over that time period. A central contributor to the work has been Raul Stern, whether directly involved with the experiments at hand or via physics advice obtained wherever he could be found worldwide spreading the joys of LIF. At Irvine LIF has been developed (1,2) and used for ion tagging (3), spatial diffusion (4,5), velocity-space diffusion (6), optical tomography (7), and plasma processing (8) among many other fascinating experimental results. This talk will review the LIF work at Irvine with special note of Stern's contributions and influence. 1.) D. Hill, S. Fornaca, M. Wickham, Rev. Sci. Instrum. 54, 309 (1983) 2.) G.D. Severn, D.A. Edrich, and R. McWilliams, Rev. Sci. Instrum. 69, 10 (1998). 3.) R. Stern, D. Hill, N. Rynn, Phys. Lett. A93, 127 (1983) 4.) M. Okubo, R. McWilliams, Phys. Fluids 30, 2849 (1987). 5.) R. McWilliams, M. K. Okubo and N. S. Wolf, Phys. Fluids B 2(3), 523 (1990). 6.) J. Bowles, R. McWilliams, N. Rynn, Phys. Plasmas 1, 3814 (1994). 7.) R. McWilliams, R. Koslover), Phys. Rev. Lett. 58, 37 (1987). 8.) R. McWilliams, D. Edrich, Thin Solid Films 435, 1 (2003).

  6. Independent component analysis classification of laser induced breakdown spectroscopy spectra

    NASA Astrophysics Data System (ADS)

    Forni, Olivier; Maurice, Sylvestre; Gasnault, Olivier; Wiens, Roger C.; Cousin, Agnès; Clegg, Samuel M.; Sirven, Jean-Baptiste; Lasue, Jérémie

    2013-08-01

    The ChemCam instrument on board Mars Science Laboratory (MSL) rover uses the laser-induced breakdown spectroscopy (LIBS) technique to remotely analyze Martian rocks. It retrieves spectra up to a distance of seven meters to quantify and to quantitatively analyze the sampled rocks. Like any field application, on-site measurements by LIBS are altered by diverse matrix effects which induce signal variations that are specific to the nature of the sample. Qualitative aspects remain to be studied, particularly LIBS sample identification to determine which samples are of interest for further analysis by ChemCam and other rover instruments. This can be performed with the help of different chemometric methods that model the spectra variance in order to identify a the rock from its spectrum. In this paper we test independent components analysis (ICA) rock classification by remote LIBS. We show that using measures of distance in ICA space, namely the Manhattan and the Mahalanobis distance, we can efficiently classify spectra of an unknown rock. The Mahalanobis distance gives overall better performances and is easier to manage than the Manhattan distance for which the determination of the cut-off distance is not easy. However these two techniques are complementary and their analytical performances will improve with time during MSL operations as the quantity of available Martian spectra will grow. The analysis accuracy and performances will benefit from a combination of the two approaches.

  7. Ultraviolet Laser-induced ignition of RDX single crystal

    PubMed Central

    Yan, Zhonghua; Zhang, Chuanchao; Liu, Wei; Li, Jinshan; Huang, Ming; Wang, Xuming; Zhou, Guorui; Tan, Bisheng; Yang, Zongwei; Li, Zhijie; Li, Li; Yan, Hongwei; Yuan, Xiaodong; Zu, Xiaotao

    2016-01-01

    The RDX single crystals are ignited by ultraviolet laser (355 nm, 6.4 ns) pulses. The laser-induced damage morphology consisted of two distinct regions: a core region of layered fracture and a peripheral region of stripped material surrounding the core. As laser fluence increases, the area of the whole crack region increases all the way, while both the area and depth of the core region increase firstly, and then stay stable over the laser fluence of 12 J/cm2. The experimental details indicate the dynamics during laser ignition process. Plasma fireball of high temperature and pressure occurs firstly, followed by the micro-explosions on the (210) surface, and finally shock waves propagate through the materials to further strip materials outside and yield in-depth cracks in larger surrounding region. The plasma fireball evolves from isotropic to anisotropic under higher laser fluence resulting in the damage expansion only in lateral direction while maintaining the fixed depth. The primary insights into the interaction dynamics between laser and energetic materials can help developing the superior laser ignition technique. PMID:26847854

  8. Seedless Laser Velocimetry Using Heterodyne Laser-Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Hart, Roger C.; Balla, R. Jeffrey; Herring, G. C.; Jenkins, Luther N.; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    A need exists for a seedless equivalent of laser Doppler velocimetry (LDV) for use in low-turbulence or supersonic flows or elsewhere where seeding is undesirable or impractical. A compact laser velocimeter using heterodyne non-resonant laser-induced thermal acoustics (LITA) to measure a single component of velocity is described. Neither molecular (e.g. NO2) nor particulate seed is added to the flow. In non-resonant LITA two beams split from a short-pulse pump laser are crossed; interference produces two counterpropagating sound waves by electrostriction. A CW probe laser incident on the sound waves at the proper angle is directed towards a detector. Measurement of the beating between the Doppler-shifted light and a highly attenuated portion of the probe beam allows determination of one component of flow velocity, speed of sound, and temperature. The sound waves essentially take the place of the particulate seed used in LDV. The velocimeter was used to study the flow behind a rearward-facing step in NASA Langley Research Center's Basic Aerodynamics Research Tunnel. Comparison is made with pitot-static probe data in the freestream over the range 0 m/s - 55 m/s. Comparison with LDV is made in the recirculation region behind the step and in a well-developed boundary layer in front of the step. Good agreement is found in all cases.

  9. Laser-induced thermoelastic effects can evoke tactile sensations

    NASA Astrophysics Data System (ADS)

    Jun, Jae-Hoon; Park, Jong-Rak; Kim, Sung-Phil; Min Bae, Young; Park, Jang-Yeon; Kim, Hyung-Sik; Choi, Seungmoon; Jung, Sung Jun; Hwa Park, Seung; Yeom, Dong-Il; Jung, Gu-In; Kim, Ji-Sun; Chung, Soon-Cheol

    2015-06-01

    Humans process a plethora of sensory information that is provided by various entities in the surrounding environment. Among the five major senses, technology for touch, haptics, is relatively young and has relatively limited applications largely due to its need for physical contact. In this article, we suggest a new way for non-contact haptic stimulation that uses laser, which has potential advantages such as mid-air stimulation, high spatial precision, and long working distance. We demonstrate such tactile stimulation can be enabled by laser-induced thermoelastic effects by means of physical and perceptual studies, as well as simulations. In the physical study, the mechanical effect of laser on a human skin sample is detected using low-power radiation in accordance with safety guidelines. Limited increases (< ~2.5 °C) in temperature at the surface of the skin, examined by both thermal camera and the Monte Carlo simulation, indicate that laser does not evoke heat-induced nociceptive sensation. In the human EEG study, brain responses to both mechanical and laser stimulation are consistent, along with subjective reports of the non-nociceptive sensation of laser stimuli.

  10. The stochastic nature of growth of laser-induced damage

    NASA Astrophysics Data System (ADS)

    Carr, C. W.; Cross, David A.; Liao, Zhi M.; Norton, Mary A.; Negres, Raluca A.

    2015-07-01

    Laser fluence and operational tempo of ICF systems operating in the UV are typically limited by the growth of laser- induced damage on their final optics (primarily silica optics). In the early 2000 time frame, studies of laser damage growth with relevant large area beams revealed that for some laser conditions damage sites located on the exit surface of a fused silica optic grew following an exponential growth rule: D(n) = D0 exp (n α(φ)), where D is final site diameter, D0 is the initial diameter of the site, φ is the laser fluence, α(φ) is the growth coefficient, and n is the number of exposures. In general α is a linear function of φ, with a threshold of φTH. In recent years, it has been found that that growth behavior is actually considerably more complex. For example, it was found that α is not a constant for a given fluence but follows a probability distribution with a mean equal to α(φ). This is complicated by observations that these distributions are actually functions of the pulse shape, damage site size, and initial morphology of damage initiation. In addition, there is not a fixed fluence threshold for damage sites growth, which is better described by a probability of growth which depends on site size, morphology and laser fluence. Here will review these findings and discuss implications for the operation of large laser systems.

  11. Laser-induced forward transfer (LIFT) of congruent voxels

    NASA Astrophysics Data System (ADS)

    Piqué, Alberto; Kim, Heungsoo; Auyeung, Raymond C. Y.; Beniam, Iyoel; Breckenfeld, Eric

    2016-06-01

    Laser-induced forward transfer (LIFT) of functional materials offers unique advantages and capabilities for the rapid prototyping of electronic, optical and sensor elements. The use of LIFT for printing high viscosity metallic nano-inks and nano-pastes can be optimized for the transfer of voxels congruent with the shape of the laser pulse, forming thin film-like structures non-lithographically. These processes are capable of printing patterns with excellent lateral resolution and thickness uniformity typically found in 3-dimensional stacked assemblies, MEMS-like structures and free-standing interconnects. However, in order to achieve congruent voxel transfer with LIFT, the particle size and viscosity of the ink or paste suspensions must be adjusted to minimize variations due to wetting and drying effects. When LIFT is carried out with high-viscosity nano-suspensions, the printed voxel size and shape become controllable parameters, allowing the printing of thin-film like structures whose shape is determined by the spatial distribution of the laser pulse. The result is a new level of parallelization beyond current serial direct-write processes whereby the geometry of each printed voxel can be optimized according to the pattern design. This work shows how LIFT of congruent voxels can be applied to the fabrication of 2D and 3D microstructures by adjusting the viscosity of the nano-suspension and laser transfer parameters.

  12. Laser induced mechanisms controlling the size distribution of metallic nanoparticles.

    PubMed

    Liu, Zeming; Vitrant, Guy; Lefkir, Yaya; Bakhti, Said; Destouches, Nathalie

    2016-09-21

    This paper describes a model to simulate changes in the size distribution of metallic nanoparticles (NPs) in TiO2 films upon continuous wave light excitation. Interrelated laser induced physical and chemical processes initiated directly by photon absorption or by plasmon induced thermal heating are considered. Namely the model takes into account the NP coalescence, Ostwald ripening, the reduction of silver ions and the oxidation of metallic NPs, competitive mechanisms that can lead to counter-intuitive behaviors depending on the exposure conditions. Theoretical predictions are compared successfully to the experimental results deduced from a thorough analysis of scanning transmission electron microscopy (STEM) pictures of Ag:TiO2 films processed with a scanning visible laser beam at different speeds. Ag:TiO2 systems are considered for many applications in solar energy conversion, photocatalysis or secured data printing. Numerical investigations of such a system provide a better understanding of light induced growth and shrinking processes and open up prospects for designing more efficient photocatalytic devices based on metal NP doped TiO2 or for improving the size homogeneity in self-organized metallic NP patterns, for instance. PMID:27539293

  13. Mid-infrared emission from laser-induced breakdown spectroscopy.

    PubMed

    Yang, Clayton S-C; Brown, Ei E; Hommerich, Uwe H; Trivedi, Sudhir B; Samuels, Alan C; Snyder, A Peter

    2007-03-01

    Laser-induced breakdown spectroscopy (LIBS) is a powerful analytical technique for detecting and identifying trace elemental contaminants by monitoring the visible atomic emission from small plasmas. However, mid-infrared (MIR), generally referring to the wavelength range between 2.5 to 25 microm, molecular vibrational and rotational emissions generated by a sample during a LIBS event has not been reported. The LIBS investigations reported in the literature largely involve spectral analysis in the ultraviolet-visible-near-infrared (UV-VIS-NIR) region (less than 1 microm) to probe elemental composition and profiles. Measurements were made to probe the MIR emission from a LIBS event between 3 and 5.75 microm. Oxidation of the sputtered carbon atoms and/or carbon-containing fragments from the sample and atmospheric oxygen produced CO(2) and CO vibrational emission features from 4.2 to 4.8 microm. The LIBS MIR emission has the potential to augment the conventional UV-VIS electronic emission information with that in the MIR region. PMID:17389073

  14. Visualization of plasma turbulence with laser-induced fluorescence (invited)

    SciTech Connect

    Levinton, Fred M.; Trintchouk, Fedor

    2001-01-01

    Turbulence is a key factor limiting the performance of fusion devices. Plasma edge turbulence determines the boundary values of the plasma density and temperature, which in turn determine the internal gradients and controls global plasma transport. In recent years, significant progress has been made in modeling turbulence behavior in plasmas and its effect on transport. Progress has also been made in diagnostics for turbulence measurement; however, there is still a large gap in our understanding of it. An approach to improve this situation is to experimentally visualize the turbulence, that is, a high resolution 2-D image of the plasma density. Visualization of turbulence can improve the connection to theory and help validate theoretical models. One method that has been successfully developed to visualize turbulence in gases and fluids is planar laser-induced fluorescence. We have recently applied this technique to visualize turbulence and structures in a plasma. This was accomplished using an Alexandrite laser that is tunable between 700 and 800 nm, and from 350 to 400 nm with second harmonic generation. The fluorescence light from an argon ion transition has been imaged onto an intensified charged coupled device camera that is gated in synchronization with the laser. Images from the plasma show a rotating structure at 30 kHz in addition to small scale turbulence.

  15. Laser induced fluorescence of argon ion in plasma presheaths

    SciTech Connect

    Atta Khedr, M.; Hala, A.M.; Oksuz, L.; Hershkowitz, N.

    1999-07-01

    A turnable diode laser system has been used to measure ion velocity distribution functions of ArII in plasma presheaths using laser-induced fluorescence (LIF). The diode laser system can examine the velocity distribution function with marginally greater resolution than the dye laser owing to their smaller line width (0.001 nm). LIF of ArII requires excitation at 668.61 nm. the diode laser is centered at that wavelength with a tuning range of 0.15 nm and the optical amplifier (MOPA) is at 10 nm. LIF measurements of presheaths as a function of pressure (0.5--3 mTorr) were made in a DC hot-filament produced multidipole plasma discharge near a negatively biased plate. The ion velocity has range of 10{sup 3}cm/s--10{sup 5} cm/s for presheaths thickness 0.5 cm--5cm. These measurements are compared with results obtained by using a double sided Langmuir probe (Mach probe) and an emissive probe.

  16. Concentration measurements with Laser-Induced Thermal Acoustics

    NASA Astrophysics Data System (ADS)

    Schlamp, Stefan; Sobota, Thomas H.

    2001-03-01

    Laser-induced thermal acoustics (LITA) is used to measure the concentration of iodine vapor (40-150 ppm) in air instantaneously (1 μs), remotely, and non-intrusively. Two focused, pulsed intersecting laser beams inscribe a density grating in the fluid. A cw interrogation beam directed at the Bragg angle on the grating is scattered into a coherent signal beam whose intensity depends on the instantaneous density grating magnitude. The signal beam is detected by a photomultiplier tube and its history recorded by a digital storage oscilloscope. The species in question (e.g., I_2) and the dilution species are excited resonantly (by thermalization) and non-resonantly (by electrostriction), respectively. The signals show oscillations at (twice) the grating's Brillouin frequency for the case of thermalization (electrostriction). The ratio of the thermalization to the electrostriction grating magnitudes is proportional to the resonant species concentration. They are extracted by a least-squares fitting scheme. For good accuracy, the ratio must be of order unity. For this case, the standard error is 5%. The speed of sound (error <1%) and flow velocity (error <1%) can be measured simultaneously.

  17. Laser induced focusing for over-dense plasma beams

    SciTech Connect

    Schmidt, Peter; Boine-Frankenheim, Oliver; Mulser, Peter

    2015-09-15

    The capability of ion acceleration with high power, pulsed lasers has become an active field of research in the past years. In this context, the radiation pressure acceleration (RPA) mechanism has been the topic of numerous theoretical and experimental publications. Within that mechanism, a high power, pulsed laser beam hits a thin film target. In contrast to the target normal sheath acceleration, the entire film target is accelerated as a bulk by the radiation pressure of the laser. Simulations predict heavy ion beams with kinetic energy up to GeV, as well as solid body densities. However, there are several effects which limit the efficiency of the RPA: On the one hand, the Rayleigh-Taylor-instability limits the predicted density. On the other hand, conventional accelerator elements, such as magnetic focusing devices are too bulky to be installed right after the target. Therefore, we present a new beam transport method, suitable for RPA-like/over-dense plasma beams: laser induced focusing.

  18. Production of biomolecule microarrays through laser induced forward transfer

    NASA Astrophysics Data System (ADS)

    Fernandez-Pradas, Juan Marcos; Serra, Pere; Colina, Monica; Morenza, Jose-Luis

    2004-10-01

    Biomolecule microarrays are a kind of biosensors that consist in patterns of different biological molecules immobilized on a solid substrate and capable to bind specifically to their complementary targets. In particular, DNA and protein microarrays have been revealed to be very efficient devices for genen and protein identification, what has converted them in powerful tools for many applications, like clinical diagnose, drug discovery analysis, genomics and proteomics. The production of these devices requires the manipulation of tiny amounts of a liquid solution containing biomolecules without damaging them. In this work laser induced forward transfer (LIFT) has been used for spotting a biomolecule in order to check the viability of this technique for the production of microarrays. A pulsed Nd:YAG laser beam (355 nm wavelength) has been used to transfer droplets of a biomolecule containing solution onto a solid slide. Optical microscopy of the transferred material has been carried out to investigate the morphological characteristics of the droplets obtained under different irradiation conditions. Afterwards, a DNA microarray has been spotted. The viability of the transference has been tested by checking the biological activity of the biomolecule in front of its specific complementary target. This has revealed that, indeed, the LIFT technique is adequate for the production of DNA microarrays.

  19. Laser-induced breakdown spectroscopy enhanced by a micro torch.

    PubMed

    Liu, L; Huang, X; Li, S; Lu, Yao; Chen, K; Jiang, L; Silvain, J F; Lu, Y F

    2015-06-01

    A commercial butane micron troch was used to enhance plasma optical emissions in laser-induced breakdown spectroscopy (LIBS). Fast imaging and spectroscopic analyses were used to observe plasma evolution in the atmospheric pressure for LIBS without and with using a micro torch. Optical emission intensities and signal-to-noise ratios (SNRs) as functions of delay time were studied. Enhanced optical emission and SNRs were obtained by using a micro torch. The effects of laser pulse energy on the emission intensities and SNRs were studied. The same spectral intensity could be obtained using micro torch with much lower laser pulse energy. The investigation of SNR evolution with delay time at different laser pulse energies showed that the SNR enhancement factor is higher for plasmas generated by lower laser pulse energies than those generated by higher laser energies. The calibration curves of emission line intensities with elemental concentrations showed that detection sensitivities of Mn I 404.136 nm and V I 437.923 nm were improved by around 3 times. The limits of detection for both Mn I 404.136 nm and V I 437.923 nm are reduced from 425 and 42 ppm to 139 and 20 ppm, respectively, after using the micro torch. The LIBS system with micro torch was demonstrated to be cost-effective, compact, and capable of sensitivity improvement, especially for LIBS system operating with low laser pulse energy. PMID:26072861

  20. Laser-induced porous graphene films from commercial polymers.

    PubMed

    Lin, Jian; Peng, Zhiwei; Liu, Yuanyue; Ruiz-Zepeda, Francisco; Ye, Ruquan; Samuel, Errol L G; Yacaman, Miguel Jose; Yakobson, Boris I; Tour, James M

    2014-01-01

    The cost effective synthesis and patterning of carbon nanomaterials is a challenge in electronic and energy storage devices. Here we report a one-step, scalable approach for producing and patterning porous graphene films with three-dimensional networks from commercial polymer films using a CO2 infrared laser. The sp(3)-carbon atoms are photothermally converted to sp(2)-carbon atoms by pulsed laser irradiation. The resulting laser-induced graphene (LIG) exhibits high electrical conductivity. The LIG can be readily patterned to interdigitated electrodes for in-plane microsupercapacitors with specific capacitances of >4 mF cm(-2) and power densities of ~9 mW cm(-2). Theoretical calculations partially suggest that enhanced capacitance may result from LIG's unusual ultra-polycrystalline lattice of pentagon-heptagon structures. Combined with the advantage of one-step processing of LIG in air from commercial polymer sheets, which would allow the employment of a roll-to-roll manufacturing process, this technique provides a rapid route to polymer-written electronic and energy storage devices. PMID:25493446

  1. Laser-Induced Ignition Modeling and Comparison with Experiments

    NASA Astrophysics Data System (ADS)

    Dors, Ivan; Qin, W.; Chen, Y.-L.; Parigger, C.; Lewis, J. W. L.

    2000-11-01

    We have studied experimentally the ignition resulting from optical breakdowns in mixtures of oxygen and the fuel ammonia induced by a 10 nanosecond pulsewidth laser for a time of hundreds of milliseconds using laser spectroscopy. In these studies, we have for the first time characterized the laser-induced plasma, the formation of the combustion radicals, the detonation wave, the flame front and the combustion process itself. The objective of the modeling is to understand the fluid dynamic and chemical kinetic effects following the nominal 10 ns laser pulse until 1 millisecond after laser breakdown. The calculated images match the experimentally recorded data sets and show spatial details covering volumes of 1/10000 cc to 1000 cc. The code was provided by CFD Research Corporation of Huntsville, Alabama, and was appropriately augmented to compute the observed phenomena. The fully developed computational model now includes a kinetic mechanism that implements plasma equilibrium kinetics in ionized regions, and non-equilibrium, multistep, finite rate reactions in non-ionized regions. The predicted fluid phenomena agree with various flow patterns characteristic of laser spark ignition as measured in the CLA laboratories. Comparison of calculated and measured OH and NH concentration will be presented.

  2. Laser-induced breakdown spectroscopy analyses of tungsten surfaces

    NASA Astrophysics Data System (ADS)

    Nishijima, D.; Hollmann, E. M.; Doerner, R. P.; Rudakov, D. L.

    2016-02-01

    Tungsten (W) surfaces are analyzed with laser-induced breakdown spectroscopy (LIBS). Interactions of W with nanosecond (ns) and femtosecond (fs) laser pulses are found to be quite different in terms of the ambient Ar gas pressure dependence of the average ablation rate and W I line intensity. Collinear double-pulse LIBS (115 + 115 mJ) using two ns lasers (with interpulse separation Δt 12 = 5.32 μs) improves the signal-to-noise ratio over the whole Ar pressure range P Ar = 6.7 × 10-1 - 6.7 × 104 Pa in contrast with single-pulse LIBS (SP-LIBS) with 230 mJ, where a signal enhancement by a factor of ˜2-3 is obtained only at P Ar > 103 Pa. SP-LIBS with a ns laser has succeeded in obtaining a sharp transition between thin W layer with a thickness of ˜100 nm and the graphite substrate. A He I (587.5 nm) line has been successfully detected with SP-LIBS with a ns laser from W containing He bubbles (˜20-30 nm layers) in the near-surface region.

  3. Study of Bacterial Samples Using Laser Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    W, A. Farooq; M, Atif; W, Tawfik; M, S. Alsalhi; Z, A. Alahmed; M, Sarfraz; J, P. Singh

    2014-12-01

    Laser-induced breakdown spectroscopy (LIBS) technique has been applied to investigate two different types of bacteria, Escherichia coli (B1) and Micrococcus luteus (B2) deposited on glass slides using Spectrolaser 7000. LIBS spectra were analyzed using spectrolaser software. LIBS spectrum of glass substrate was compared with bacteria spectra. Ca, Mg, Na, K, P, S, Cl, Fe, Al, Mn, Cu, C, H and CN-band appeared in bacterial samples in air. Two carbon lines at 193.02 nm, 247.88 nm and one hydrogen line at 656.28 nm with intensity ratios of 1.9, 1.83 and 1.53 appeared in bacterial samples B1 and B2 respectively. Carbon and hydrogen are the important components of the bio-samples like bacteria and other cancer cells. Investigation on LIBS spectra of the samples in He and Ar atmospheres is also presented. Ni lines appeared only in B2 sample in Ar atmosphere. From the present experimental results we are able to show that LIBS technique has a potential in the identification and discrimination of different types of bacteria.

  4. Wavelet-based laser-induced ultrasonic inspection in pipes

    NASA Astrophysics Data System (ADS)

    Baltazar-López, Martín E.; Suh, Steve; Chona, Ravinder; Burger, Christian P.

    2006-02-01

    The feasibility of detecting localized defects in tubing using Wavelet based laser-induced ultrasonic-guided waves as an inspection method is examined. Ultrasonic guided waves initiated and propagating in hollow cylinders (pipes and/or tubes) are studied as an alternative, robust nondestructive in situ inspection method. Contrary to other traditional methods for pipe inspection, in which contact transducers (electromagnetic, piezoelectric) and/or coupling media (submersion liquids) are used, this method is characterized by its non-contact nature. This characteristic is particularly important in applications involving Nondestructive Evaluation (NDE) of materials because the signal being detected corresponds only to the induced wave. Cylindrical guided waves are generated using a Q-switched Nd:YAG laser and a Fiber Tip Interferometry (FTI) system is used to acquire the waves. Guided wave experimental techniques are developed for the measurement of phase velocities to determine elastic properties of the material and the location and geometry of flaws including inclusions, voids, and cracks in hollow cylinders. As compared to the traditional bulk wave methods, the use of guided waves offers several important potential advantages. Some of which includes better inspection efficiency, the applicability to in-situ tube inspection, and fewer evaluation fluctuations with increased reliability.

  5. [The Progress in Remote Laser-Induced Breakdown Spectroscopy].

    PubMed

    Zhang, Ting-ting; Wan, Xiong; Shu, Rong; Liu, Peng-xi

    2015-07-01

    As a kind of spectroscopic technique, the remote laser-induced breakdown spectroscopy (Remote LIBS) can measure elemental compositions of remote targets by using high-power lasers and focusing approaches. In this paper, three remote detection approaches (open path LIBS, fiber optic LIBS and compact probe fiber optic LIBS) and their system architectures are summarized and analyzed. Conventional open path LIBS, with high requirement of specifications of lasers, optical systems, spectrographs and detectors, has always been a research focus in remote testing field. Fiber optic LIBS has the advantages of simplification of optical focusing system and high collection efficiency of the plasma light. This paper reviews the progress in new techniques of LIBS, for instance Filament-LIBS techniques and LIBS combines with other spectral detection techniques, and emphatically analyzes their characteristics and advantages. These new techniques have greatly broadened the detection range of LIBS, enhanced material recognition ability of LIBS, and made a great contribution to expanding applications of remote LIBS. Latest development of applications of remote LIBS in fields of deep space exploration, hazardous material detection, pollution testing, metallurgical industries and heritage restoration is introduced in detail. With the development of laser techniques, spectral detection and calibration techniques, the detection range of remote LIBS has been expended, their application fields has been extended, and the detection precision and accuracy have been improved. PMID:26717768

  6. Measuring turbulent fluid dispersion using laser induced phosphorescence

    NASA Astrophysics Data System (ADS)

    van der Voort, Dennis; Dam, Nico; van de Water, Willem; Kunnen, Rudie; Clercx, Herman; van Heijst, Gertjan

    2015-11-01

    Fluid dispersion due to turbulence is an important subject in both natural and engineering processes, from cloud formation to turbulent mixing and liquid spray combustion. The combination of small scales and often high velocities results in few experimental techniques that can follow the course of events. We introduce a novel technique, which measures the dispersion of ``tagged'' fluid particles by means of laser-induced phosphorescence, using a solution containing a europium-based molecular complex with a relatively long phosphorescence half-life. This technique is used to measure transport processes in both the dispersion of droplets in homogeneous isotropic turbulence and the dispersion of fluid of near-nozzle spray breakup processes. By tagging a small amount of droplets/fluid via laser excitation, the tagged droplets can be tracked in a Lagrangian way. The absolute dispersion of the droplets can be measured in a variety of turbulent flows. Using this technique it is shows that droplets around St =τp /τη ~ 1 (Stokes number) disperse faster than true fluid tracers in homogeneous isotropic turbulence, as well as differences between longitudinal and radial dispersion in turbulent sprays. This work is part of the research programme of the Foundation for Fundamental Research on Matter (FOM), which is part of the Dutch Organisation for Scientific Research (NWO).

  7. Oxide nanoparticles synthesis via laser-induced plasma in liquid

    NASA Astrophysics Data System (ADS)

    Goto, Taku; Weihs, Hansel; Honda, Mitsuhiro; Kulinich, Sergei; Shimizu, Yoshiki; Ito, Tsuyohito

    2014-10-01

    Laser ablation in fluids has recently attracted a lot of attention as one of synthetic techniques to prepare new attractive nanomaterials, with the ability to control both product chemistry and morphology in many systems. In this study, we generated laser-induced plasma in H2O - ethanol mixtures, while ablating metal targets to produce oxide nanoparticles and to study the effect of the medium on their properties. The ablated targets used in this study were Zn or Sn plates. A nanosecond Nd:YAG laser with the wavelength of 532 nm (10 Hz, 20--30 mJ/pulse) was applied to irradiate the targets. The liquid media were maintained at 0.1 to 30 MPa to study the effect of pressure. We found that the H2O/ethanol ratio (at atmospheric pressure) can control the properties of the produced ZnO nanoparticles, such as defects and oxidation degree. The properties were examined by photoluminescence (PL) spectroscopy, X-ray diffraction, electron microscopies, and so on. More details will be presented at the symposium.

  8. Femtosecond laser induced nanostructuring for surface enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Messaoudi, H.; Das, S. K.; Lange, J.; Heinrich, F.; Schrader, S.; Frohme, M.; Grunwald, R.

    2014-03-01

    The formation of periodical nanostructures with femtosecond laser pulses was used to create highly efficient substrates for surface-enhanced Raman spectroscopy (SERS). We report about the structuring of silver and copper substrates and their application to the SERS of DNA (herring sperm) and protein molecules (egg albumen). The maximum enhancement factors were found on Ag substrates processed with the second harmonic generation (SHG) of a 1-kHz Ti:sapphire laser and structure periods near the SHG wavelength. In the case of copper, however, the highest enhancement was obtained with long-period ripples induced with at fundamental wavelength. This is explained by an additional significant influence of nanoparticles on the surface. Nanostructured areas in the range of 1.25 mm2 were obtained in 10 s. The surfaces were characterized by scanning electron microscopy, Fast Fourier Transform and Raman spectroscopy. Moreover, the role of the chemical modification of the metal structures is addressed. Thin oxide layers resulting from working in atmosphere which improve the biocompatibility were indicated by vibration spectra. It is expected that the detailed study of the mechanisms of laser-induced nanostructure formation will stimulate further applications of functionalized surfaces like photocatalysis, selective chemistry and nano-biology.

  9. Laser-induced breakdown spectroscopy of molten aluminum alloy

    NASA Astrophysics Data System (ADS)

    Rai, Awadhesh K.; Yueh, Fang-Yu; Singh, Jagdish P.

    2003-04-01

    We have demonstrated that a fiber-optic laser-induced breakdown spectroscopy (LIBS) probe is suitable for measuring the concentration of minor constituents of a molten Al alloy in a laboratory furnace. For the first time to our knowledge we are able to record the LIBS spectra in several spectral regions of seven different molten Al alloy samples by inserting the LIBS probe inside the molten alloys, allowing us to obtain a ratio calibration curve for minor constituents (Cr, Mg, Zn, Cu, Si, etc.), using Fe as a reference element. A ratio calibration curve for Fe with a major element (Al) can also be obtained with which the concentration of Fe in the alloy can be determined. The effects of the surrounding atmosphere on the LIBS spectra of the molten alloy were investigated. Effects of focal length of the lens on the LIBS signals were also studied. LIBS spectra of a solid Al alloy recorded with the same LIBS probe were compared with the LIBS spectra of the molten alloy. Our results suggest that the LIBS probe is useful for monitoring the elemental composition of an Al melt in an industrial furnace at different depths and different positions inside the melt.

  10. Laser induced formation of micro-rough structures

    NASA Astrophysics Data System (ADS)

    Singh, Rajiv K.; Fitz-Gerald, James M.

    1997-01-01

    Laser induced micro-rough structures (LIMS) are a by-product of laser ablation process and are created during multiple pulse irradiation on the surface of the material. Although LIMS have been found to be deleterious for the thin film deposition process, these surfaces have wide variety of applications in synthesis of adherent coatings in thermal expansion mismatched systems. Earlier models, based on interference effects of the laser beam, to explain the evolution of LIMS, are not consistent with the experimental results. Experiments were conducted on a wide variety of materials (e.g. SiC, alumina, YBaCuO superconductor, etc.) to understand the mechanisms for generation of the micro-rough structures. A novel model was developed to explain the characteristics of LIMS such as (i) feature orientation (ii) evolution of surface structures as a function of pulses, (iii) formation of LIMS within a energy window near ablation threshold and (iv) periodicity which is independent of the laser wavelength and incident angle.

  11. Development and applications of laser-induced incandescence

    NASA Technical Reports Server (NTRS)

    Vanderwal, Randy L.; Dietrich, Daniel L.; Zhou, Zhiquang; Choi, Mun Y.

    1995-01-01

    Several NASA-funded investigations focus on soot processes and radiative influences of soot in diffusion flames given their simplicity, practical significance, and potential for theoretical modeling. Among the physical parameters characterizing soot, soot volume fraction, f(sub v), a function of particle size and number density, is often of chief practical interest in these investigations, as this is the geometrical property that directly impacts radiative characteristics and the temperature field of the flame and is basic to understanding soot growth and oxidation processes. Diffusion flames, however, present a number of challenges to the determination of f(sub v) via traditional extinction measurements. Laser-induced incandescence (LII) possesses several advantages compared to line-of-sight extinction techniques for determination of f(sub v). Since LII is not a line-of-sight technique, similar to fluorescence, it possesses geometric versatility allowing spatially resolved measurements of f(sub v) in real time in nonaxisymmetric systems without using deconvolution techniques. The spatial resolution of LII is determined by the detector and imaging magnification used. Neither absorption by polycyclic aromatic hydrocarbons (PAH's) nor scattering contributes to the signal. Temporal capabilities are limited only by the laser pulse and camera gate duration, with measurements having been demonstrated with 10 ns resolution. Because of these advantages, LII should be applicable to a variety of combustion processes involving both homogeneous and heterogeneous phases. Our work has focussed on characterization of the technique as well as exploration of its capabilities and is briefly described.

  12. Slag analysis with laser-induced breakdown spectrometry.

    PubMed

    Kraushaar, M; Noll, R; Schmitz, H U

    2003-10-01

    Laser-induced breakdown spectrometry (LIBS) has been applied for multi-elemental analysis of slag samples from a steel plant. In order to avoid the time-consuming step of sample preparation, the liquid slag material can be filled in special probes. After cooling of the liquid slag and solidification, the samples can be analyzed with LIBS. Chemical analysis of slag is an essential input parameter used for numerical simulations to control liquid steel processing. The relative variation range of element concentrations in slag samples from steel production can amount to up to 30%. A multivariate calibration model is used to take into account matrix effects caused by these varying concentrations. By optimizing the measuring parameters as well as the calibration models, an agreement between the standard X-ray fluorescence (XRF) analysis and LIBS analysis in terms of the coefficient of determination r2 of 0.99 for the main analytes CaO, SiO2, and Fetot of converter slag samples was achieved. The average repeatability of the LIBS measurement for these elements in terms of the relative standard deviation of the determined concentration is improved to less than 1.0%. With these results, the basis is established for future on-line applications of LIBS in the steel-making industry for slag analysis. PMID:14639759

  13. Laser-induced thermoelastic effects can evoke tactile sensations

    PubMed Central

    Jun, Jae-Hoon; Park, Jong-Rak; Kim, Sung-Phil; Min Bae, Young; Park, Jang-Yeon; Kim, Hyung-Sik; Choi, Seungmoon; Jung, Sung Jun; Hwa Park, Seung; Yeom, Dong-Il; Jung, Gu-In; Kim, Ji-Sun; Chung, Soon-Cheol

    2015-01-01

    Humans process a plethora of sensory information that is provided by various entities in the surrounding environment. Among the five major senses, technology for touch, haptics, is relatively young and has relatively limited applications largely due to its need for physical contact. In this article, we suggest a new way for non-contact haptic stimulation that uses laser, which has potential advantages such as mid-air stimulation, high spatial precision, and long working distance. We demonstrate such tactile stimulation can be enabled by laser-induced thermoelastic effects by means of physical and perceptual studies, as well as simulations. In the physical study, the mechanical effect of laser on a human skin sample is detected using low-power radiation in accordance with safety guidelines. Limited increases (< ~2.5 °C) in temperature at the surface of the skin, examined by both thermal camera and the Monte Carlo simulation, indicate that laser does not evoke heat-induced nociceptive sensation. In the human EEG study, brain responses to both mechanical and laser stimulation are consistent, along with subjective reports of the non-nociceptive sensation of laser stimuli. PMID:26047142

  14. Laser-induced forward transfer of hybrid carbon nanostructures

    NASA Astrophysics Data System (ADS)

    Palla-Papavlu, A.; Filipescu, M.; Vizireanu, S.; Vogt, L.; Antohe, S.; Dinescu, M.; Wokaun, A.; Lippert, T.

    2016-06-01

    Chemically functionalized carbon nanowalls (CNWs) are promising materials for a wide range of applications, i.e. gas sensors, membranes for fuel cells, or as supports for catalysts. However, the difficulty of manipulation of these materials hinders their integration into devices. In this manuscript a procedure for rapid prototyping of CNWs and functionalized CNWs (i.e. decorated with SnO2 nanoparticles) is described. This procedure enables the use of laser-induced forward transfer (LIFT) as a powerful technique for printing CNWs and CNW:SnO2 pixels onto rigid and flexible substrates. A morphological study shows that for a large range of laser fluences i.e. 500-700 mJ/cm2 it is possible to transfer thick (4 μm) CNW and CNW:SnO2 pixels. Micro-Raman investigation of the transferred pixels reveals that the chemical composition of the CNWs and functionalized CNWs does not change as a result of the laser transfer. Following these results one can envision that CNWs and CNW:SnO2 pixels obtained by LIFT can be ultimately applied in technological applications.

  15. Enhancing the analytical performance of laser-induced breakdown spectroscopy

    SciTech Connect

    Cremers, D.A.; Chinni, R.C.; Pichahchy, A.E.; Thornquist, H.K.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The objective of this work is to enhance the analytical capabilities of laser-induced breakdown spectroscopy (LIBS). LIBS is a method of elemental analysis in which powerful laser pulses are focused on a sample to form a microplasma. LIBS is perhaps the most versatile elemental analysis method, applicable to a variety of different real-world analysis problems. Therefore, it is important to enhance the capabilities of the method as much as possible. Accomplishments include: (1) demonstration of signal enhancements of 5--30 times from soils and metals using a double pulse method; (2) development of a model of the observed enhancement obtained using double pulses; (3) demonstration that the analytical performance achievable using low laser-pulse energies (10 and 25 mJ) can match that achievable using an energy of 100 mJ; and (4) demonstration that time-gated detection is not necessary with LIBS.

  16. Retinal vein occlusion

    MedlinePlus

    ... Berrocal MH, Rodriguez FJ, et al. Pan-American Collaborative Retina Study Group (PACORES). Comparison of two doses ... retinal vein occlusion: results from the Pan-American Collaborative Retina Study Group at 6 months of follow- ...

  17. [Acute retinal necrosis].

    PubMed

    Lucke, K; Reinking, U; el-Hifnawi, E; Dennin, R H; Laqua, H

    1988-12-01

    The authors report on three patients with acute retinal necrosis who were treated with the virostatic agent Acyclovir and who underwent vitreoretinal surgery with silicone oil filling for total retinal detachment. In two eyes the retina was reattached, but useful vision was only preserved in one patient. Titers from blood and the vitreous, as well as microscopic findings in retinal biopsies, support the view that the necrosis is caused by a herpes simplex virus infection. After therapy with Acyclovir was instituted no further progression on the necrosis was observed. However, the development of retinal detachment could not be prevented. Early diagnosis and antiviral therapy are essential to improve the otherwise poor prognosis in this rare syndrome. PMID:3221657

  18. Red-shift law of intense laser-induced electro-absorption in solids

    NASA Astrophysics Data System (ADS)

    Deng, Hong-Xiang; Zu, Hao-Yue; Wu, Shao-Yi; Sun, Kai; Zu, Xiao-Tao

    2014-02-01

    A theoretical study on the red-shift of laser-induced electro-absorption is presented. It is found that laser-induced red-shift scales with the cube root of the pump laser intensity in the optical tunneling regime and has an obvious deviation from this scale in the multi-photon regime. Our results show that in the optical tunneling regime, the laser-induced red shift has the same law as that in the direct current (DC) approximation. Though the scales are the same in the optical tunneling regime, the physical pictures in the two cases are quite different. The electro-absorption in the DC case is a tunneling-assisted transition process, while the laser-induced electro-absorption is a mixed multi-photon process.

  19. APPLICATIONS OF CAPILLARY ELECTROPHORESIS/LASER-INDUCED FLUORESCENCE DETECTION TO GROUND WATER MIGRATION STUDIES

    EPA Science Inventory

    Capillary electrophoresis (CE) has been applied to the determination of groundwater migration based on laser-induced fluorescence (LIF) detection and traditional spectrofluorimetry. The detection limits of injected dye-fluorescent whitening agent (tinopal) in the low parts per tr...

  20. Mid-infrared Molecular Emission Studies from Energetic Materials using Laser-Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Brown, Ei; Hommerich, Uwe; Yang, Clayton; Trivedi, Sudhir; Samuels, Alan; Snyder, Peter

    2011-10-01

    Laser-induced breakdown spectroscopy (LIBS) is a powerful diagnostic tool for detection of trace elements by monitoring the atomic and ionic emission from laser-induced plasmas. The laser-induced plasma was produced by focusing a 30 mJ pulsed Nd:YAG laser (1064 nm) to dissociate, atomize, and ionize target molecules. In this work, LIBS emissions in the mid-infrared (MIR) region were studied for potential applications in chemical, biological, and explosives (CBE) sensing. We report on the observation of MIR emissions from energetic materials (e.g. ammonium compounds) due to laser-induced breakdown processes. All samples showed LIBS-triggered oxygenated breakdown products as well as partially dissociated and recombination molecular species. More detailed results of the performed MIR LIBS studies on the energetic materials will be discussed at the conference.

  1. Penta(cyclopentadienyl)-[eta]5-cyclopentadienylmanganesetricarbonyl: Structure and laser-induced conversion to fullerenes

    SciTech Connect

    Barrow, Mark P.; Cammack, J. Kevin; Goebel, Matthias; Wasser, Ian M.; Vollhardt, K.Peter C.; Drewello, Thomas

    1998-08-28

    The title compound [Cp5CpMn(CO)3], 1, has been characterized by X-ray crystallography and shown by laser-induced desorption/ionization (LDI) to undergo coalescence to fullerene C60 and other carbon clusters.

  2. Laser-induced fluorescence detection strategies for sodium atoms and compounds in high-pressure combustors

    NASA Technical Reports Server (NTRS)

    Weiland, Karen J. R.; Wise, Michael L.; Smith, Gregory P.

    1993-01-01

    A variety of laser-induced fluorescence schemes were examined experimentally in atmospheric pressure flames to determine their use for sodium atom and salt detection in high-pressure, optically thick environments. Collisional energy transfer plays a large role in fluorescence detection. Optimum sensitivity, at the parts in 10 exp 9 level for a single laser pulse, was obtained with the excitation of the 4p-3s transition at 330 nm and the detection of the 3d-3p fluorescence at 818 nm. Fluorescence loss processes, such as ionization and amplified spontaneous emission, were examined. A new laser-induced atomization/laser-induced fluorescence detection technique was demonstrated for NaOH and NaCl. A 248-nm excimer laser photodissociates the salt molecules present in the seeded flames prior to atom detection by laser-induced fluorescence.

  3. Retinal detachment in pseudophakia.

    PubMed

    Galin, M A; Poole, T A; Obstbaum, S A

    1979-07-01

    In a series of cataract patients excluding myopic individuals, under age 60 years, and cases in which vitreous loss occurred, retinal detachment was no less frequent after intracapsular cataract extraction and Sputnik iris supported lenses than in controls. Both groups were followed up for a minimum of two years. The detachments predominantly occurred from retinal breaks in areas of the retina that looked normal preoperatively. PMID:464014

  4. Giant retinal tears.

    PubMed

    Shunmugam, Manoharan; Ang, Ghee Soon; Lois, Noemi

    2014-01-01

    A giant retinal tear (GRT) is a full-thickness neurosensory retinal break that extends circumferentially around the retina for three or more clock hours in the presence of a posteriorly detached vitreous. Its incidence in large population-based studies has been estimated as 1.5% of rhegmatogenous retinal detachments, with a significant male preponderance, and bilaterality in 12.8%. Most GRTs are idiopathic, with trauma, hereditary vitreoretinopathies and high myopia each being causative in decreasing frequency. The vast majority of GRTs are currently managed with a pars plana vitrectomy; the use of adjunctive circumferential scleral buckling is debated, but no studies have shown a clear anatomical or visual advantage with its use. Similarly, silicone oil tamponade does not influence long-term outcomes when compared with gas. Primary and final retinal reattachment rates are achieved in 88% and 95% of patients, respectively. Even when the retina remains attached, however, visual recovery may be limited. Furthermore, fellow eyes of patients with a GRT are at higher risk of developing retinal tears and retinal detachment. Prophylactic treatment under these circumstances may be considered but there is no firm evidence of its efficacy at the present time. PMID:24138895

  5. Reflectance, scattering, and laser induced fluorescence for the detection of dental caries

    NASA Astrophysics Data System (ADS)

    Drakaki, Eleni; Makropoulou, Myrsini; Khabbaz, Maruan; Serafetinides, Alexandros A.

    2003-10-01

    Directional dependence of reflected laser light and of the laser induced fluorescence signals performed both on the intact hard dental tissues, such as enamel, dentine, cementum and on the tissues pathologically affected by caries (superficial, intermediate, and deep). The laser induced fluorescence spectra were collected at different angles of observation and were correlated with the different scattering and reflectance properties of the hard dental samples

  6. Laser-induced periodic annular surface structures on fused silica surface

    SciTech Connect

    Liu, Yi; Brelet, Yohann; Forestier, Benjamin; Houard, Aurelien; Yu, Linwei; Deng, Yongkai; Jiang, Hongbing

    2013-06-24

    We report on the formation of laser-induced periodic annular surface structures on fused silica irradiated with multiple femtosecond laser pulses. This surface morphology emerges after the disappearance of the conventional laser induced periodic surface structures, under successive laser pulse irradiation. It is independent of the laser polarization and universally observed for different focusing geometries. We interpret its formation in terms of the interference between the reflected laser field on the surface of the damage crater and the incident laser pulse.

  7. Spectroscopic analysis of fire suppressants and refrigerants by laser-induced breakdown spectroscopy.

    PubMed

    Lancaster, E D; McNesby, K L; Daniel, R G; Miziolek, A W

    1999-03-20

    Laser-induced breakdown spectroscopy is evaluated as a means of detecting the fire suppressants CF(3)Br, C(3)F(7)H, and CF(4) and the refrigerant C(2)F(4)H(2). The feasibility of employing laser-induced breakdown spectroscopy for time- and space-resolved measurement of these agents during use, storage, and recharge is discussed. Data are presented that demonstrate the conditions necessary for optimal detection of these chemicals. PMID:18305769

  8. Properties and Applications of Laser-Induced Gratings in Rare Earth Doped Glasses.

    NASA Astrophysics Data System (ADS)

    Behrens, Edward Grady

    Scope and method of study. Four-wave-mixing techniques were used in an attempt to create permanent laser-induced grating in Pr^{3+}-, Nd ^{3+}-, Eu^ {3+}-, and Er^{3+ }-doped glasses. The permanent laser-induced grating signal intensity and build-up and erase times were investigated as function of the write beam crossing angle, write beam power, and temperature. Thermal lensing measurements were conducted on Eu^{3+} - and Nd^{3+}-doped glasses and room temperature Raman and resonant Raman spectra were obtained for Eu^{3+}-doped glasses. The permanent laser-induced grating signal intensity was studied in Eu^{3+} -doped alkali-metal glasses as a function of the alkali -metal network modifier ion and a model was developed by treating the sample as a two-level system. Optical device applications of the permanent laser-induced gratings were studied by creating some simple devices. Findings and conclusions. Permanent laser-induced gratings were created in the Pr^{3+ }- and Eu^{3+} -doped glasses. The permanent laser-induced grating is associated with a structural phase change of the glass host. The structural change is produced by high energy phonons which are emitted by radiationless relaxation processes of the rare earth ion. Nd^{3+} and Er^{3+} relax nonradiatively by the emission of phonons of much lower energy which are unable to produce the structural phase change needed to form a permanent laser-induced grating. The difference in energy of the emitted phonons is responsible for the differing characteristics of the thermal lensing experiments. The model does a good job of predicting the experimental results for the asymmetry and other parameters of the two-level system. The application of these laser -induced gratings for optical devices demonstrates their importance to optical technology.

  9. Simultaneous measurement of Raman scattering and laser-induced OH fluorescence in nonpremixed turbulent jet flames.

    PubMed

    Barlow, R S; Dibble, R W; Lucht, R P

    1989-03-01

    Spontaneous Raman scattering and laser-induced fluorescence are combined to perform simultaneous point measurements of major species concentrations, temperature, and hydroxyl radical concentration in turbulent nonpremixed flames. The Raman-scattering data for major species concentrations and temperature characterize the instantaneous, local, collisional quenching environment of the OH molecule. Collisional quenching corrections are applied for each laser shot so that absolute hydroxyl concentrations are obtained in turbulent flames using linear laser-induced fluorescence. PMID:19749889

  10. Laser-induced pattern formation in liquid sulfur. An indication of laser-induced phase transition to ordered polymer

    NASA Astrophysics Data System (ADS)

    Sakaguchi, Y.; Tamura, K.

    2007-04-01

    Liquid sulfur is a well-known liquid which exhibits a polymerization transition at T_p=159 °C. Recently, it was found from our experiments that such a transition can be induced below Tp through laser illumination and that an iridescent pattern appears under strong illumination with a pulsed laser of more than 60 mJ/cm2 pulse. It is proposed that the visible change in iridescence is due to a macroscopic reconstruction of laser-generated polymers and that a laser-induced phase transition takes place from a freely expanded polymer phase to an ordered polymer phase when increasing the laser illumination. To further examine this possibility, the time variation of the iridescent pattern has been fully investigated using a macro lens, a polarized microscope and an optical microscope. In an analysis of the iridescent pattern, a rapid decrease in the area was observed after an initial slow decrease, suggesting a type of phase transition. Results from the observation of a quenched sulfur sample with a polarized microscope gave evidence that the iridescent region consists of polymers. Through observation of the liquid with a microscope, a striped pattern with micrometer sized spacing was noted in the iridescent pattern. A drastic color change was observed in the pattern from its generation to its disappearance. Sample thickness dependence of the pattern was also observed. These results were well explained by assuming the self-arrangement of laser-generated colloidal polymers.

  11. Laser-induced interstitial thermotherapy of benign prostatic hyperplasia and prostate cancer

    NASA Astrophysics Data System (ADS)

    Muschter, Rolf

    1994-12-01

    Urinary outflow obstruction by prostatic enlargement is usually treated by resection or, recently, less invasively by thermal `ablation' of tissue through the urethra. With the latter technique, the amount of tissue that can be removed is limited by the limited penetration depth of suitable radiation sources, e.g. lasers, or conduction of heat. Interstitial thermotherapy was expected to overcome this problem. Our initial in vitro and animal studies with different light guides for interstitial application of Nd:YAG laser radiation showed small carbonized lesions with bare fibers, but large homogeneous coagulation zones with special `ITT' (interstitial thermotherapy) fibers. Further studies using these applicators resulted in a technique to be apt for clinical routine in the treatment of symptomatic prostatic enlargement. The tip of the light guide was repeatedly inserted into the prostate either transurethrally through a cystoscope under direct vision or percutaneously from the perineum under transrectal ultrasound guidance. The number of fiber placements depended on the size and configuration of the gland. Irradiation was performed either for 10 min with 5 or 7 W or in the advanced `turbo'- mode for 5 or 3 min per fiber placement using automatically stepwise reduced power (20 W for 30 s, 15 W for 30 s, 10 W for 30 s, and 7 W for 210 or 90 s). By optical feedback control the laser was switched off automatically in the case of carbonization to avoid fiber damage. From July 15, 1991 to October 1, 1993 239 patients with BPH and 14 patients with advanced prostate cancer, suffering from severe urinary outflow obstruction, were treated by laser induced interstitial thermotherapy. The results and complications of treatment are reported.

  12. Magnetic Resonance-Guided Focal Laser-Induced Interstitial Thermal Therapy in a Canine Prostate Model

    PubMed Central

    Stafford, R. Jason; Shetty, Anil; Elliott, Andrew M.; Klumpp, Sherry A.; McNichols, Roger J.; Gowda, Ashok; Hazle, John D.; Ward, John F.

    2014-01-01

    Purpose To evaluate a newly FDA-cleared closed-loop, magnetic resonance (MR)-guided laser-induced interstitial thermal therapy (LITT) system for targeted ablation of prostate tissue in order to assess targeting ability, lesion generation and feasibility. Materials and Methods Mongrel dogs with (n = 2) and without (n = 5) canine transmissible venereal tumors in the prostate were imaged with a 1.5-T MR imaging scanner. Real-time 3D MR imaging was used to accurately position water-cooled 980-nm laser applicators to pre-determined targets within the canine prostates. Destruction of targeted tissue was guided with MR temperature imaging in real time for precise control of thermal ablation. MR predictions of thermal damage were correlated with findings from post-treatment images and compared to histopathology. Results Template-based targeting using MR guidance allowed the laser applicator to be placed within a mean of 1.1 mm (SD = 0.7 mm) of the target location. The mean width and length of the ablation zone by MR were 13.7 mm (SD = 1.3 mm) and 19.0 mm (SD = 4.2 mm) using single and compound exposures. The thermal damage predicted by MR correlated with the thermal damage determined by post-treatment imaging with a slope near unity and excellent correlation (R2 = 0.94). Conclusions This LITT system provided rapid and localized heating of tissue with minimal collateral thermal spread or injury. Combined with real-time monitoring and template-based planning, MR-guided LITT is an attractive modality for prostate cancer focal therapy. PMID:20727549

  13. Laser-induced transepidermal elimination of dermal content by fractional photothermolysis.

    PubMed

    Hantash, Basil M; Bedi, Vikramaditya P; Sudireddy, Vasanthi; Struck, Steven K; Herron, G Scott; Chan, Kin Foong

    2006-01-01

    The wound healing process in skin is studied in human subjects treated with fractional photothermolysis. In-vivo histological evaluation of vacuoles formed over microthermal zones (MTZs) and their content is undertaken. A 30-W, 1550-nm single-mode fiber laser system delivers an array of 60 microm or 140 microm 1e2 incidence microbeam spot size at variable pulse energy and density. Treatments span from 6 to 20 mJ with skin excisions performed 1-day post-treatment. Staining with hematoxylin and eosin demonstrates an intact stratum corneum with vacuolar formation within the epidermis. The re-epithelialization process with repopulation of melanocytes and keratinocytes at the basal layer is apparent by 1-day post-treatment. The dermal-epidermal (DE) junction is weakened and separated just above zones of dermal coagulation. Complete loss of dermal cell viability is noted within the confines of the MTZs 1-day post-treatment, as assessed by lactate dehydrogenase. All cells falling outside the irradiation field remain viable. Content within the epidermal vacuoles stain positively with Gomori trichrome, suggesting a dermal origin. However, the positive staining could be due to loss of specificity after thermal alteration. Nevertheless, this dermal extrusion hypothesis is supported by very specific positive staining with an antihuman elastin antibody. Fractional photothermolysis creates microthermal lesions that allow transport and extrusion of dermal content through a compromised DE junction. Some dermal material is incorporated into the microepidermal necrotic debris and shuttled up the epidermis to eventually be exfoliated through the stratum corneum. This is the first report of a nonablative laser-induced transport mechanism by which dermal content can be predictably extruded biologically through the epidermis. Thus, treatment with the 1550-nm fiber laser may provide the first therapeutic option for clinical indications, including pigmentary disorders such as medically

  14. Laser-induced transepidermal elimination of dermal content by fractional photothermolysis

    NASA Astrophysics Data System (ADS)

    Hantash, Basil M.; Bedi, Vikramaditya P.; Sudireddy, Vasanthi; Struck, Steven K.; Herron, G. Scott; Chan, Kin Foong

    2006-07-01

    The wound healing process in skin is studied in human subjects treated with fractional photothermolysis. In-vivo histological evaluation of vacuoles formed over microthermal zones (MTZs) and their content is undertaken. A 30-W, 1550-nm single-mode fiber laser system delivers an array of 60 µm or 140 µm 1/e2 incidence microbeam spot size at variable pulse energy and density. Treatments span from 6 to 20 mJ with skin excisions performed 1-day post-treatment. Staining with hematoxylin and eosin demonstrates an intact stratum corneum with vacuolar formation within the epidermis. The re-epithelialization process with repopulation of melanocytes and keratinocytes at the basal layer is apparent by 1-day post-treatment. The dermal-epidermal (DE) junction is weakened and separated just above zones of dermal coagulation. Complete loss of dermal cell viability is noted within the confines of the MTZs 1-day post-treatment, as assessed by lactate dehydrogenase. All cells falling outside the irradiation field remain viable. Content within the epidermal vacuoles stain positively with Gomori trichrome, suggesting a dermal origin. However, the positive staining could be due to loss of specificity after thermal alteration. Nevertheless, this dermal extrusion hypothesis is supported by very specific positive staining with an antihuman elastin antibody. Fractional photothermolysis creates microthermal lesions that allow transport and extrusion of dermal content through a compromised DE junction. Some dermal material is incorporated into the microepidermal necrotic debris and shuttled up the epidermis to eventually be exfoliated through the stratum corneum. This is the first report of a nonablative laser-induced transport mechanism by which dermal content can be predictably extruded biologically through the epidermis. Thus, treatment with the 1550-nm fiber laser may provide the first therapeutic option for clinical indications, including pigmentary disorders such as medically

  15. Pulsed laser-induced evaporation of liquids and its applications

    NASA Astrophysics Data System (ADS)

    Kim, Dongsik

    The interaction of laser irradiation with materials is very important in a variety of laser-based manufacturing processes and scientific studies. Particularly, the interaction of a short laser pulse with absorbing liquids or solid materials in contact with liquid is central to a number of applications, including laser cleaning of microcontaminants, pulsed laser deposition of thin film materials, laser tissue removal, and laser surface texturing. In this dissertation, experimental and theoretical works on the following topics are summarized: (1) physical mechanisms of pulsed laser induced ablation of absorbing liquids at laser fluence below the plasma ignition threshold, (2) analysis of rapid vaporization at the absorbing solid/transparent liquid interface, (3) laser cleaning of surface contaminates. Concerning the first topic, the near-threshold ablation process at low laser fluences and the high power explosive vaporization process accompanying subsequent ablation plume dynamics are elucidated. Acoustic-wave detection by a piezoelectric pressure transducer, visualization by laser flash photography, and optical reflection/transmission measurements are carried out for the in-situ diagnosis of the process. Quantification of the acoustic-field generation and detection of the bubble-nucleation dynamics in the rapid vaporization at the solid liquid interface are performed by photoacoustic beam deflection technique and optical interferometry, respectively. Finally, experiments are carried out for the development of a practical laser cleaning tool and the analysis of the contaminant-removal mechanism. The results show that the near-threshold ablation by a short laser pulse is initiated by the tensile component of the thermoelastic stress without significant increase of liquid temperature at low laser fluences. On the other hand, if the heating rate is rapid enough to achieve high degree of superheating of the liquid, explosive vaporization takes place due to the abrupt

  16. Laser induced x-ray `RADAR' particle physics model

    NASA Astrophysics Data System (ADS)

    Lockley, D.; Deas, R.; Moss, R.; Wilson, L. A.; Rusby, D.; Neely, D.

    2016-05-01

    The technique of high-power laser-induced plasma acceleration can be used to generate a variety of diverse effects including the emission of X-rays, electrons, neutrons, protons and radio-frequency radiation. A compact variable source of this nature could support a wide range of potential applications including single-sided through-barrier imaging, cargo and vehicle screening, infrastructure inspection, oncology and structural failure analysis. This paper presents a verified particle physics simulation which replicates recent results from experiments conducted at the Central Laser Facility at Rutherford Appleton Laboratory (RAL), Didcot, UK. The RAL experiment demonstrated the generation of backscattered X-rays from test objects via the bremsstrahlung of an incident electron beam, the electron beam itself being produced by Laser Wakefield Acceleration. A key initial objective of the computer simulation was to inform the experimental planning phase on the predicted magnitude of the backscattered X-rays likely from the test objects. This objective was achieved and the computer simulation was used to show the viability of the proposed concept (Laser-induced X-ray `RADAR'). At the more advanced stages of the experimental planning phase, the simulation was used to gain critical knowledge of where it would be technically feasible to locate key diagnostic equipment within the experiment. The experiment successfully demonstrated the concept of X-ray `RADAR' imaging, achieved by using the accurate timing information of the backscattered X-rays relative to the ultra-short laser pulse used to generate the electron beam. By using fast response X-ray detectors it was possible to derive range information for the test objects being scanned. An X-ray radar `image' (equivalent to a RADAR B-scan slice) was produced by combining individual X-ray temporal profiles collected at different points along a horizontal distance line scan. The same image formation process was used to generate

  17. Laser induced damage in optical materials: tenth ASTM symposium.

    PubMed

    Glass, A J; Guenther, A H

    1979-07-01

    The tenth annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, Colorado, 12-14 September 1978. The symposium was held under the auspices of ASTM Committee F-1, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Project Agency, the Department of Energy, and the Office of Naval Research. About 175 scientists attended, including representatives of the United Kingdom, France, Canada, Japan, West Germany, and the Soviet Union. The symposium was divided into sessions concerning the measurement of absorption characteristics, bulk material properties, mirrors and surfaces, thin film damage, coating materials and design, and breakdown phenomena. As in previous years, the emphasis of the papers presented was directed toward new frontiers and new developments. Particular emphasis was given to materials for use from 10.6 microm to the UV region. Highlights included surface characterization, thin film-substrate boundaries, and advances in fundamental laser-matter threshold interactions and mechanisms. The scaling of damage thresholds with pulse duration, focal area, and wavelength was also discussed. In commemoration of the tenth symposium in this series, a number of comprehensive review papers were presented to assess the state of the art in various facets of laser induced damage in optical materials. Alexander J. Glass of Lawrence Livermore Laboratory and Arthur H. Guenther of the Air Force Weapons Laboratory were co-chairpersons. The eleventh annual symposium is scheduled for 30-31 October 1979 at the National Bureau of Standards, Boulder, Colorado. PMID:20212622

  18. Lanthanide-based laser-induced phosphorescence for spray diagnostics

    NASA Astrophysics Data System (ADS)

    van der Voort, D. D.; Maes, N. C. J.; Lamberts, T.; Sweep, A. M.; van de Water, W.; Kunnen, R. P. J.; Clercx, H. J. H.; van Heijst, G. J. F.; Dam, N. J.

    2016-03-01

    Laser-induced phosphorescence (LIP) is a relatively recent and versatile development for studying flow dynamics. This work investigates certain lanthanide-based molecular complexes for their use in LIP for high-speed sprays. Lanthanide complexes in solutions have been shown to possess long phosphorescence lifetimes (˜1-2 ms) and to emit light in the visible wavelength range. In particular, europium and terbium complexes are investigated using fluorescence/phosphorescence spectrometry, showing that europium-thenoyltrifluoracetone-trioctylphosphineoxide (Eu-TTA-TOPO) can be easily and efficiently excited using a standard frequency-tripled Nd:YAG laser. The emitted spectrum, with maximum intensity at a wavelength of 614 nm, is shown not to vary strongly with temperature (293-383 K). The decay constant of the phosphorescence, while independent of ambient pressure, decreases by approximately 12 μs/K between 323 and 373 K, with the base level of the decay constant dependent on the used solvent. The complex does not luminesce in the gas or solid state, meaning only the liquid phase is visualized, even in an evaporating spray. By using an internally excited spray containing the phosphorescent complex, the effect of vaporization is shown through the decrease in measured intensity over the length of the spray, together with droplet size measurements using interferometric particle imaging. This study shows that LIP, using the Eu-TTA-TOPO complex, can be used with different solvents, including diesel surrogates. Furthermore, it can be easily handled and used in sprays to investigate spray breakup and evaporation.

  19. Liquid Jet Formation in Laser-Induced Forward Transfer

    NASA Astrophysics Data System (ADS)

    Brasz, C. Frederik

    Laser-induced forward transfer (LIFT) is a direct-write technique capable of printing precise patterns of a wide variety of materials. In this process, a laser pulse is focused through a transparent support and absorbed in a thin donor film, propelling material onto an adjacent acceptor substrate. For fluid materials, this transfer occurs through the formation of a narrow liquid jet, which eventually pinches off due to surface tension. This thesis examines in detail the fluid mechanics of the jet formation process occurring in LIFT. The main focus is on a variant of LIFT known as blister-actuated LIFT (BA-LIFT), in which the laser pulse is absorbed in an ink-coated polymer layer, rapidly deforming it locally into a blister to induce liquid jet formation. The early-time response of a fluid layer to a deforming boundary is analyzed with a domain perturbation method and potential-flow simulations, revealing scalings for energy and momentum transfer to the fluid and providing physical insight on how and why a jet forms in BA-LIFT. The remaining chapters explore more complex applications and modifications of LIFT. One is the possibility of high-repetition rate printing and limits on time delay and separation between pulses imposed by a tilting effect found for adjacent jets. Another examines a focusing effect achieved by perturbing the interface with ring-shaped disturbances. The third contains an experimental study of LIFT using a silver paste as the donor material instead of a Newtonian liquid. The transfer mechanism is significantly different, although with repeated pulses at one location, a focusing effect is again observed. All three of these chapters investigate how perturbations to the interface can strongly influence the jet formation process.

  20. Laser induced spark ignition of methane-oxygen mixtures

    NASA Technical Reports Server (NTRS)

    Santavicca, D. A.; Ho, C.; Reilly, B. J.; Lee, T.-W.

    1991-01-01

    Results from an experimental study of laser induced spark ignition of methane-oxygen mixtures are presented. The experiments were conducted at atmospheric pressure and 296 K under laminar pre-mixed and turbulent-incompletely mixed conditions. A pulsed, frequency doubled Nd:YAG laser was used as the ignition source. Laser sparks with energies of 10 mJ and 40 mJ were used, as well as a conventional electrode spark with an effective energy of 6 mJ. Measurements were made of the flame kernel radius as a function of time using pulsed laser shadowgraphy. The initial size of the spark ignited flame kernel was found to correlate reasonably well with breakdown energy as predicted by the Taylor spherical blast wave model. The subsequent growth rate of the flame kernel was found to increase with time from a value less than to a value greater than the adiabatic, unstretched laminar growth rate. This behavior was attributed to the combined effects of flame stretch and an apparent wrinkling of the flame surface due to the extremely rapid acceleration of the flame. The very large laminar flame speed of methane-oxygen mixtures appears to be the dominant factor affecting the growth rate of spark ignited flame kernels, with the mode of ignition having a small effect. The effect of incomplete fuel-oxidizer mixing was found to have a significant effect on the growth rate, one which was greater than could simply be accounted for by the effect of local variations in the equivalence ratio on the local flame speed.

  1. Infrared laser induced plasma diagnostics of silver target

    SciTech Connect

    Ahmat, L. Nadeem, Ali; Ahmed, I.

    2014-09-15

    In the present work, the optical emission spectra of silver (Ag) plasma have been recorded and analyzed using the laser induced breakdown spectroscopy technique. The emission line intensities and plasma parameters were investigated as a function of lens to sample distance, laser irradiance, and distance from the target surface. The electron number density (n{sub e}) and electron temperature (T{sub e}) were determined using the Stark broadened line profile and Boltzmann plot method, respectively. A gradual increase in the spectral line intensities and the plasma parameters, n{sub e} from 2.89 × 10{sup 17} to 3.92 × 10{sup 17 }cm{sup −3} and T{sub e} from 4662 to 8967 K, was observed as the laser irradiance was increased 2.29 × 10{sup 10}–1.06 × 10{sup 11} W cm{sup −2}. The spatial variations in n{sub e} and T{sub e} were investigated from 0 to 5.25 mm from the target surface, yielding the electron number density from 4.78 × 10{sup 17} to 1.72 × 10{sup 17 }cm{sup −3} and electron temperature as 9869–3789 K. In addition, the emission intensities and the plasma parameters of silver were investigated by varying the ambient pressure from 0.36 to 1000 mbars.

  2. Characterization Of High Explosives Detonations Via Laser-Induced Plasmas

    SciTech Connect

    Villa-Aleman, E.

    2015-10-08

    One objective of the Department of Energy’s National Security Administration is to develop technologies that can help the United States government to detect foreign nuclear weapons development activities. The realm of high explosive (HE) experiments is one of the key areas to assess the nuclear ambitions of a country. SRNL has participated in the collection of particulates from HE experiments and characterized the material with the purpose to correlate particulate matter with HE. Since these field campaigns are expensive, on-demand simulated laboratory-scale explosion experiments are needed to further our knowledge of the chemistry and particle formation in the process. Our goal is to develop an experimental test bed in the laboratory to test measurement concepts and correlate particle formation processes with the observables from the detonation fireball. The final objective is to use this knowledge to tailor our experimental setups in future field campaigns. The test bed uses pulsed laser-induced plasmas to simulate micro-explosions, with the intent to study the temporal behavior of the fireball observed in field tests. During FY15, a plan was prepared and executed which assembled two laser ablation systems, procured materials for study, and tested a Step-Scan Fourier Transform Infrared Spectrometer (SS-FTIR). Designs for a shadowgraph system for shock wave analysis, design for a micro-particulate collector from ablated pulse were accomplished. A novel spectroscopic system was conceived and a prototype system built for acquisition of spectral/temporal characterization of a high speed event such as from a high explosive detonation. Experiments and analyses will continue into FY16.

  3. Laser-induced fluorescence in diagnosis of dental caries

    NASA Astrophysics Data System (ADS)

    Drakaki, Eleni A.; Makropoulou, Mersini I.; Khabbaz, Maruan; Serafetinides, Alexandros A.

    2003-09-01

    laser induces better discrimination in deep caries diagnosis.

  4. [Laser Induced Fluorescence Spectrum Characteristics of Paddy under Nitrogen Stress].

    PubMed

    Yang, Jian; Shi, Shuo; Gong, Wei; Du, Lin; Zhu, Bo; Ma, Ying-ying; Sun, Jia

    2016-02-01

    Order to guide fertilizing andreduce waste of resources as well as enviro nmental pollution, especially eutrophication, which are caused by excessive fertilization, a system of laser-induced fluorescence(LIF) was built. The system aimed to investigate the correlation between nitrogen(N) content of paddy leaf and the fluorescence intensity. We measuredNcontent and SPAD of paddy leaf (the samples came from the second upper leaves of paddy in tillering stage and the study area was located in Jianghan plain of China) by utilizing the Plant Nutrient (Tester TYS-3N). The fluorescence spectrum was also obtained by using the systembuilt based on theLIFtechnology. Fluorescence spectra of leaf with different N-content were collected and then a fluorescence spectra database wasestablished. It is analyzed that the relationship between the parameters of fluorescence (F₇₄₀/F₆₈₅ is the ratio of fluorescence intensity of 740 nm. dividing that of 685 nm) and the N level of paddy. It is found that the effect of different N-content on the fluorescence spectrum characteristics is significant. The experiment demonstrated the positive correlation between fluorescence parameters and paddy leaf N-content. Results showed a positive linear correlation between the ratio of peak fluorescence (F₇₄₀/F₆₈₅) and N-content The correlation coefficient (r) reached 0.871 8 and the root mean square error (RMSE) was 0.076 82. The experiment demonstrated that LIF spectroscopy detection technology has the advantages of rapidand non-destructive measurement, and it also has the potential to measure plant content of nutrient elements. It will provide a more accurate remote sensing method to rapidly detect the crop nitrogen levels. PMID:27209764

  5. Laser Induced Fluorescence Diagnostic for the ASTRAL Plasma Source.

    NASA Astrophysics Data System (ADS)

    Boivin, Robert; Kamar, Ola; Munoz, Jorge

    2006-10-01

    A Laser Induced Fluorescence (LIF) diagnostic is presented in this poster. The ion temperature measurements are made in the ASTRAL (Auburn Steady sTate Research fAciLity) helicon plasma source using a diode laser based LIF diagnostic. ASTRAL produces Ar plasmas with the following parameters: ne = 10^10 to 10^13 cm-3, Te = 2 to 10 eV and Ti = 0.03 to 0.5 eV. A series of 7 large coils produce an axial magnetic field up to 1.3 kGauss. Operating pressure varies from 0.1 to 100 mTorr and any gas can be used for the discharge. A fractional helix antenna is used to introduce rf power up to 2 kWatt. A number of diagnostics are presently installed on the plasma device (Langmuir Probe, Spectrometer, LIF system). The LIF diagnostic makes use of a diode laser with the following characteristics: 1.5 MHz bandwidth, Littrow external cavity, mode-hop free tuning range up to 16 GHz, total power output of about 15 mW. The wavelength is measured by a precision wavemeter and frequent monitoring prevents wavelength drift. For Ar plasma, a new LIF scheme has been developed. The laser tuned at 686.354 nm, is used to pump the 3d^4F5/2 Ar II metastable level to the 4p^4D5/2 state. The fluorescence radiation between the 4p^4D5/2 and the 4s^4P3/2 terms (442.6 nm) is monitored by a PMT.

  6. Application of Laser Induced Breakdown Spectroscopy under Polar Conditions

    NASA Astrophysics Data System (ADS)

    Clausen, J. L.; Hark, R.; Bol'shakov, A.; Plumer, J.

    2015-12-01

    Over the past decade our research team has evaluated the use of commercial-off-the-shelf laser-induced breakdown spectroscopy (LIBS) for chemical analysis of snow and ice samples under polar conditions. One avenue of research explored LIBS suitability as a detector of paleo-climate proxy indicators (Ca, K, Mg, and Na) in ice as it relates to atmospheric circulation. LIBS results revealed detection of peaks for C and N, consistent with the presence of organic material, as well as major ions (Ca, K, Mg, and Na) and trace metals (Al, Cu, Fe, Mn, Ti). The detection of Ca, K, Mg, and Na confirmed that LIBS has sufficient sensitivity to be used as a tool for characterization of paleo-climate proxy indicators in ice-core samples. Techniques were developed for direct analysis of ice as well as indirect measurements of ice via melting and filtering. Pitfalls and issues of direct ice analysis using several cooling techniques to maintain ice integrity will be discussed. In addition, a new technique, laser ablation molecular isotopic spectroscopy (LAMIS) was applied to detection of hydrogen and oxygen isotopes in ice as isotopic analysis of ice is the main tool in paleoclimatology and glaciology studies. Our results demonstrated that spectra of hydroxyl isotopologues 16OH, 18OH, and 16OD can be recorded with a compact spectrograph to determine hydrogen and oxygen isotopes simultaneously. Quantitative isotopic calibration for ice analysis can be accomplished using multivariate chemometric regression as previously realized for water vapor. Analysis with LIBS and LAMIS required no special sample preparation and was about ten times faster than analysis using ICP-MS. Combination of the two techniques in one portable instrument for in-field analysis appears possible and would eliminate the logistical and cost issues associated with ice core management.

  7. Spectrally resolved laser-induced fluorescence for bioaerosols standoff detection

    NASA Astrophysics Data System (ADS)

    Buteau, Sylvie; Stadnyk, Laurie; Rowsell, Susan; Simard, Jean-Robert; Ho, Jim; Déry, Bernard; McFee, John

    2007-09-01

    An efficient standoff biological warfare detection capability could become an important asset for both defence and security communities based on the increasing biological threat and the limits of the presently existing protection systems. Defence R&D Canada (DRDC) has developed, by the end of the 90s, a standoff bioaerosol sensor prototype based on intensified range-gated spectrometric detection of Laser Induced Fluorescence (LIF). This LIDAR system named SINBAHD monitors the spectrally resolved LIF originating from inelastic interactions with bioaerosols present in atmospheric cells customizable in size and in range. SINBAHD has demonstrated the capability of near real-time detection and classification of bioaerosolized threats at multi-kilometre ranges. In spring 2005, DRDC has initiated the BioSense demonstration project, which combines the SINBAHD technology with a geo-referenced Near InfraRed (NIR) LIDAR cloud mapper. SINBAHD is now being used to acquire more signatures to add in the spectral library and also to optimize and test the new BioSense algorithm strategy. In September 2006, SINBAHD has participated in a two-week trial held at DRDC-Suffield where different open-air wet releases of live and killed bioagent simulants, growth media and obscurants were performed. An autoclave killing procedure was performed on two biological materials (Bacillus subtilis var globigii or BG, and Bacillus thuringiensis or Bt) before being aerosolized, disseminated and spectrally characterized with SINBAHD. The obtained results showed no significant impact of this killing process on their normalised spectral signature in comparison with their live counterparts. Correlation between the detection signals from SINBAHD, an array of slit samplers and a FLuorescent Aerosol Particle Sensor (C-FLAPS) was obtained and SINBAHD's sensitivity could then be estimated. At the 2006 trial, a detection limit of a few tens of Agent Containing Particles per Liter of Air (ACPLA) was obtained

  8. Single shot thermometry using laser induced thermal grating

    NASA Astrophysics Data System (ADS)

    Qu, Pubo; Guan, Xiaowei; Zhang, Zhenrong; Wang, Sheng; Li, Guohua; Ye, Jingfeng; Hu, Zhiyun

    2015-05-01

    With the concern of environmental protection and reducing the fossil fuel consumption, combustion processes need to be more efficient and less contaminable. Therefore, the ability to obtain important thermophysical parameters is crucial to combustion research and combustor design. Traditional surveying techniques were difficult to apply in a confined space, especially the physically intrusions of detectors can alter the combustion processes. Laser-based diagnostic techniques, like CARS, SVRS, PLIF and TDLAS, allow the in situ, non-intrusive, spatially and temporally resolved measurements of combustion parameters in hostile environments. We report here a new non-intrusive optical diagnostic technique, based on laser-induced thermal grating. Thermal gratings generated in NO2/N2 binary mixtures, arise from the nonlinear interaction between the medium and the light radiation from the interference of two pulsed, frequency-doubled Nd:YAG lasers (532 nm). This leads to the formation of a dynamic grating through the resonant absorption and the subsequent collisional relaxation. By the temporally resolved detection of a continuous wave, frequency-doubled Nd:YVO4 probe laser beam (671 nm) diffracted by LITG. The temporal behavior of the signal is a function of the local temperature and other properties of gas, various parameters of the target gas can be extracted by analyzing the signal. The accurate singleshot temperature measurements were carried out at different test conditions using a stainless steel pressurized cell, data averaged on 100 laser shots were compared with simultaneously recorded thermocouple data, and the results were consistent with each other. The LITG signal is shown to grow with increasing the gas pressure and is spatially coherent, which makes the LITG thermometry technique a promising candidate in high pressure environments.

  9. A handheld laser-induced fluorescence detector for multiple applications.

    PubMed

    Fang, Xiao-Xia; Li, Han-Yang; Fang, Pan; Pan, Jian-Zhang; Fang, Qun

    2016-04-01

    In this paper, we present a compact handheld laser-induced fluorescence (LIF) detector based on a 450 nm laser diode and quasi-confocal optical configuration with a total size of 9.1 × 6.2 × 4.1 cm(3). Since there are few reports on the use of 450 nm laser diode in LIF detection, especially in miniaturized LIF detector, we systematically investigated various optical arrangements suitable for the requirements of 450 nm laser diode and system miniaturization, including focusing lens, filter combination, and pinhole, as well as Raman effect of water at 450 nm excitation wavelength. As the result, the handheld LIF detector integrates the light source (450 nm laser diode), optical circuit module (including a 450 nm band-pass filter, a dichroic mirror, a collimating lens, a 525 nm band-pass filter, and a 1.0mm aperture), optical detector (miniaturized photomultiplier tube), as well as electronic module (including signal recording, processing and displaying units). This detector is capable of working independently with a cost of ca. $2000 for the whole instrument. The detection limit of the instrument for sodium fluorescein solution is 0.42 nM (S/N=3). The broad applicability of the present system was demonstrated in capillary electrophoresis separation of fluorescein isothiocyanate (FITC) labeled amino acids and in flow cytometry of tumor cells as an on-line LIF detector, as well as in droplet array chip analysis as a LIF scanner. We expect such a compact LIF detector could be applied in flow analysis systems as an on-line detector, and in field analysis and biosensor analysis as a portable universal LIF detector. PMID:26838391

  10. Laser-induced growth of nanocrystals embedded in porous materials

    NASA Astrophysics Data System (ADS)

    Capoen, Bruno; Chahadih, Abdallah; El Hamzaoui, Hicham; Cristini, Odile; Bouazaoui, Mohamed

    2013-06-01

    Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated porous xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in porous silica xerogels, which allows

  11. Characterisation of CFRP surface contamination by laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Malinowski, Pawel H.; Sawczak, Miroslaw; Wandowski, Tomasz; Ostachowicz, Wieslaw M.; Cenian, Adam

    2014-03-01

    The application of Carbon Fibre Reinforced Polymers (CFRP) in aeronautics has been increasing. The CFRP elements are joint using rivets and adhesive bonding. The reliability of the bonding limits the use of adhesive bonding for primary aircraft structures, therefore it is important to assess the bond quality. The performance of adhesive bonds depends on the physico-chemical properties of the adhered surfaces. This research is focused on characterization of surfaces before bonding. In-situ examination of large surface materials, determine the group of methods that are preferred. The analytical methods should be non-destructive, enabling large surface analysis in relatively short time. In this work a spectroscopic method was tested that can be potentially applied for surface analysis. Four cases of surface condition were investigated that can be encountered either in the manufacturing process or during aircraft service. The first case is related to contamination of CFRP surface with hydraulic fluid. This fluid reacts with water forming a phosphoric acid that can etch the CFRP. Second considered case was related to silicone-based release agent contamination. These agents are used during the moulding process of composite panels. Third case involved moisture content in CFRP. Moisture content lowers the adhesion quality and leads to reduced performance of CFRP resulting in reduced performance of the adhesive bond. The last case concentrated on heat damage of CFRP. It was shown that laser induced fluorescence method can be useful for non-destructive evaluation of CFRP surface and some of the investigated contaminants can be easily detected.

  12. Analysis of slags using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Sanghapi, Hervé K.; Ayyalasomayajula, Krishna K.; Yueh, Fang Y.; Singh, Jagdish P.; McIntyre, Dustin L.; Jain, Jinesh C.; Nakano, Jinichiro

    2016-01-01

    The feasibility of laser-induced breakdown spectroscopy (LIBS) for the analysis of gasification slags was investigated by comparing LIBS results to the results of an ICP-OES analyzer. A small amount of slag sample was placed on a piece of double sided adhesive tape attached to a glass microscope slide and analyzed for Al, Ca, Fe, Si, and V which are major elements found in slags. The partial least squares regression (PLS-R) and univariate simple linear regression (SLR) calibration methods indicated that apart from V (accuracy up to + 20%) the accuracy of analysis varies within 0.35-6.5% for SLR and 0.06-10% for PLS-R. A paired-sample t-test within the 95% confidence level yielded p-values greater than 0.05, meaning no appreciable statistical difference was observed between the univariate SLR with internal standardization and the multivariate PLS-R for most of the analytes. From the results obtained in this work, LIBS response varies depending on the element and the technique used for quantitative analysis. Simultaneous use of the univariate calibration curves with internal standard (intensity ratio) and PLS regression in multi-elemental analysis can help reduce the matrix effect of slags associated to their high variation in concentration. Overall, these results demonstrate the capability of LIBS as an alternative technique for analyzing gasification slags. Estimated limits of detection for Al, Ca, Fe, Si and V were 0.167, 0.78, 0.171, 0.243 and 0.01 wt.%, respectively.

  13. Laser-induced selective copper plating of polypropylene surface

    NASA Astrophysics Data System (ADS)

    Ratautas, K.; Gedvilas, M.; Stankevičiene, I.; JagminienÄ--, A.; Norkus, E.; Li Pira, N.; Sinopoli, S.; Emanuele, U.; Račiukaitis, G.

    2016-03-01

    Laser writing for selective plating of electro-conductive lines for electronics has several significant advantages, compared to conventional printed circuit board technology. Firstly, this method is faster and cheaper at the prototyping stage. Secondly, material consumption is reduced, because it works selectively. However, the biggest merit of this method is potentiality to produce moulded interconnect device, enabling to create electronics on complex 3D surfaces, thus saving space, materials and cost of production. There are two basic techniques of laser writing for selective plating on plastics: the laser-induced selective activation (LISA) and laser direct structuring (LDS). In the LISA method, pure plastics without any dopant (filler) can be used. In the LDS method, special fillers are mixed in the polymer matrix. These fillers are activated during laser writing process, and, in the next processing step, the laser modified area can be selectively plated with metals. In this work, both methods of the laser writing for the selective plating of polymers were investigated and compared. For LDS approach, new material: polypropylene with carbon-based additives was tested using picosecond and nanosecond laser pulses. Different laser processing parameters (laser pulse energy, scanning speed, the number of scans, pulse durations, wavelength and overlapping of scanned lines) were applied in order to find out the optimal regime of activation. Areal selectivity tests showed a high plating resolution. The narrowest width of a copper-plated line was less than 23 μm. Finally, our material was applied to the prototype of the electronic circuit board on a 2D surface.

  14. Lanthanide-based laser-induced phosphorescence for spray diagnostics.

    PubMed

    van der Voort, D D; Maes, N C J; Lamberts, T; Sweep, A M; van de Water, W; Kunnen, R P J; Clercx, H J H; van Heijst, G J F; Dam, N J

    2016-03-01

    Laser-induced phosphorescence (LIP) is a relatively recent and versatile development for studying flow dynamics. This work investigates certain lanthanide-based molecular complexes for their use in LIP for high-speed sprays. Lanthanide complexes in solutions have been shown to possess long phosphorescence lifetimes (∼1-2 ms) and to emit light in the visible wavelength range. In particular, europium and terbium complexes are investigated using fluorescence/phosphorescence spectrometry, showing that europium-thenoyltrifluoracetone-trioctylphosphineoxide (Eu-TTA-TOPO) can be easily and efficiently excited using a standard frequency-tripled Nd:YAG laser. The emitted spectrum, with maximum intensity at a wavelength of 614 nm, is shown not to vary strongly with temperature (293-383 K). The decay constant of the phosphorescence, while independent of ambient pressure, decreases by approximately 12 μs/K between 323 and 373 K, with the base level of the decay constant dependent on the used solvent. The complex does not luminesce in the gas or solid state, meaning only the liquid phase is visualized, even in an evaporating spray. By using an internally excited spray containing the phosphorescent complex, the effect of vaporization is shown through the decrease in measured intensity over the length of the spray, together with droplet size measurements using interferometric particle imaging. This study shows that LIP, using the Eu-TTA-TOPO complex, can be used with different solvents, including diesel surrogates. Furthermore, it can be easily handled and used in sprays to investigate spray breakup and evaporation. PMID:27036779

  15. Detection of uranium using laser-induced breakdown spectroscopy.

    PubMed

    Chinni, Rosemarie C; Cremers, David A; Radziemski, Leon J; Bostian, Melissa; Navarro-Northrup, Claudia

    2009-11-01

    The goal of this work is a detailed study of uranium detection by laser-induced breakdown spectroscopy (LIBS) for application to activities associated with environmental surveillance and detecting weapons of mass destruction (WMD). The study was used to assist development of LIBS instruments for standoff detection of bulk radiological and nuclear materials and these materials distributed as contaminants on surfaces. Uranium spectra were analyzed under a variety of different conditions at room pressure, reduced pressures, and in an argon atmosphere. All spectra displayed a high apparent background due to the high density of uranium lines. Time decay curves of selected uranium lines were monitored and compared to other elements in an attempt to maximize detection capabilities for each species in the complicated uranium spectrum. A survey of the LIBS uranium spectra was conducted and relative emission line strengths were determined over the range of 260 to 800 nm. These spectra provide a guide for selection of the strongest LIBS analytical lines for uranium detection in different spectral regions. A detection limit for uranium in soil of 0.26% w/w was obtained at close range and 0.5% w/w was achieved at a distance of 30 m. Surface detection limits were substrate dependent and ranged from 13 to 150 microg/cm2. Double-pulse experiments (both collinear and orthogonal arrangements) were shown to enhance the uranium signal in some cases. Based on the results of this work, a short critique is given of the applicability of LIBS for the detection of uranium residues on surfaces for environmental monitoring and WMD surveillance. PMID:19891832

  16. Laser induced vibrational energy transfer in iron pentacarbonyl

    NASA Astrophysics Data System (ADS)

    Langsam, Yedidyah; Ronn, A. M.

    1984-01-01

    The internal kinetics of Fe(CO)5 as well as the kinetics between Fe(CO)5 and other nonreactive species were studied using the technique of laser induced fluorescence. The energy transfer behavior of this large polyatomic is discussed in terms of existing V-V and V-T/R theories and collisional energy transfer. Iron pentacarbonyl's vibrational energy structure is treated by means of a simple three and four level energy transfer scheme. Subsequent to excitation of the 10 μ region by a CO2 laser, infrared fluorescence has been detected from the ˜16, ˜5, and ˜4 μ regions of Fe(CO)5. A single exponential decay rate of 13.6 ms-1 Torr-1 is observed from the ˜5 μ region, in good agreement with other decay rates established for smaller polyatomics possessing similar vibrational level structure. Under conditions of low fluence (˜30 mJ/cm2), this region is activated at a rate of 474 ms-1 Torr-1 suggesting a rapid near resonant collisional energy transfer. Under conditions of high fluence (˜5 J/cm2), the activation of the ˜5 μ region proceeds at a rate of 1250 ms-1 Torr-1 suggesting a different pathway for the determining step of the excitation process. The rare gas deactivation rates as well as those with Ni(CO)4, CO(CO)3No, and CO (as well as the reverse rate) and the crossover rate from excited Fe(CO)5 to CO in high rare gas dilution have also been determined.

  17. Laser-induced breakdown spectroscopy based deminers' probe

    NASA Astrophysics Data System (ADS)

    Hauck, James P.; Walker, Mark; Hamadani, Siavosh; Bloomhardt, Natalie; Eagan, Justin

    2009-05-01

    We report on a prototype Laser Induced Breakdown Spectroscopy (LIBS) Deminers' Probe used to identify underground objects. We have built a prototype, and are in the process of developing a more advanced LIBS based Deminer' s Probe used to prod objects underground, and then sense them by creating a micro-plasma plume of the surface material and analyzing the spectrum of the emitted light to identify the object. It is expected that the Deminer will be able to eliminate many false positives, which consume most of the Deminers' time. SARA Fiber-Optics coupled LIBS system consists in a probe that can be inserted into the ground to provide a path for both the laser beam to the target, and for the micro-plasma plume fluorescence from the target to a spectrometer or spectrometers for analysis. The probe is closely modeled after the conventional Deminers' probe, resembling a saber. We have demonstrated that this simple system is capable of producing remarkably different spectra from different materials. Our next steps are to add a number of features to the Deminers' Probe. These include: a new optical configuration to increase the irradiance and fluence created by the pulsed laser at the target, a multiple channel fluorescence reception system that can increase the amount of light delivered to the spectrometers, a fluidic system to clear the detritus away from the probe tip, and a complete operational/control and readout system for the Deminer to use. Mine-lane tests are planned to be performed in the later part of 2009, or shortly thereafter.

  18. Characterisation of estuarine intertidal macroalgae by laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Gameiro, Carla; Utkin, Andrei B.; Cartaxana, Paulo

    2015-12-01

    The article reports the application of laser-induced fluorescence (LIF) for the assessment of macroalgae communities of estuarine intertidal areas. The method was applied for the characterisation of fifteen intertidal macroalgae species of the Tagus estuary, Portugal, and adjacent coastal area. Three bands characterised the LIF spectra of red macroalgae with emission maxima in the ranges 577-583 nm, 621-642 nm and 705-731 nm. Green and brown macroalgae showed one emission maximum in the red region (687-690 nm) and/or one in the far-red region (726-732 nm). Characteristics of LIF emission spectra were determined by differences in the main fluorescing pigments: phycoerythrin, phycocyanin and chlorophyll a (Chl a). In the green and brown macroalgae groups, the relative significance of the two emission maxima seems to be related to the thickness of the photosynthetic layer. In thick macroalgae, like Codium tomentosum or Fucus vesiculosus, the contribution of the far-red emission fluorescence peak was more significant, most probably due to re-absorption of the emitted red Chl a fluorescence within the dense photosynthetic layer. Similarly, an increase in the number of layers of the thin-blade green macroalgae Ulva rigida caused a shift to longer wavelengths of the red emission maximum and the development of a fluorescence peak at the far-red region. Water loss from Ulva's algal tissue also led to a decrease in the red/far-red Chl fluorescence ratio (F685/F735), indicating an increase in the density of chloroplasts in the shrinking macroalgal tissue during low tide exposure.

  19. Laser-induced growth of nanocrystals embedded in porous materials

    PubMed Central

    2013-01-01

    Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated porous xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in porous silica xerogels, which allows

  20. Improvement of retinal blood vessel detection using morphological component analysis.

    PubMed

    Imani, Elaheh; Javidi, Malihe; Pourreza, Hamid-Reza

    2015-03-01

    Detection and quantitative measurement of variations in the retinal blood vessels can help diagnose several diseases including diabetic retinopathy. Intrinsic characteristics of abnormal retinal images make blood vessel detection difficult. The major problem with traditional vessel segmentation algorithms is producing false positive vessels in the presence of diabetic retinopathy lesions. To overcome this problem, a novel scheme for extracting retinal blood vessels based on morphological component analysis (MCA) algorithm is presented in this paper. MCA was developed based on sparse representation of signals. This algorithm assumes that each signal is a linear combination of several morphologically distinct components. In the proposed method, the MCA algorithm with appropriate transforms is adopted to separate vessels and lesions from each other. Afterwards, the Morlet Wavelet Transform is applied to enhance the retinal vessels. The final vessel map is obtained by adaptive thresholding. The performance of the proposed method is measured on the publicly available DRIVE and STARE datasets and compared with several state-of-the-art methods. An accuracy of 0.9523 and 0.9590 has been respectively achieved on the DRIVE and STARE datasets, which are not only greater than most methods, but are also superior to the second human observer's performance. The results show that the proposed method can achieve improved detection in abnormal retinal images and decrease false positive vessels in pathological regions compared to other methods. Also, the robustness of the method in the presence of noise is shown via experimental result. PMID:25697986

  1. Photovoltaic retinal prosthesis

    NASA Astrophysics Data System (ADS)

    Loudin, James; Mathieson, Keith; Kamins, Ted; Wang, Lele; Galambos, Ludwig; Huie, Philip; Sher, Alexander; Harris, James; Palanker, Daniel

    2011-03-01

    Electronic retinal prostheses seek to restore sight to patients suffering from retinal degenerative disorders. Implanted electrode arrays apply patterned electrical stimulation to surviving retinal neurons, producing visual sensations. All current designs employ inductively coupled coils to transmit power and/or data to the implant. We present here the design and initial testing of a photovoltaic retinal prosthesis fabricated with a pixel density of up to 177 pixels/mm2. Photodiodes within each pixel of the subretinal array directly convert light to stimulation current, avoiding the use of bulky coil implants, decoding electronics, and wiring, and thereby reducing surgical complexity. A goggles-mounted camera captures the visual scene and transmits the data stream to a pocket processor. The resulting images are projected into the eyes by video goggles using pulsed, near infrared (~900 nm) light. Prostheses with three pixel densities (15, 55, and 177 pix/mm2) are being fabricated, and tests indicate a charge injection limit of 1.62 mC/cm2 at 25Hz. In vitro tests of the photovoltaic retinal stimulation using a 512-element microelectrode array have recorded stimulated spikes from the ganglion cells, with latencies in the 1-100ms range, and with peak irradiance stimulation thresholds varying from 0.1 to 1 mW/mm2. With 1ms pulses at 25Hz the average irradiance is more than 100 times below the IR retinal safety limit. Elicited retinal response disappeared upon the addition of synaptic blockers, indicating that the inner retina is stimulated rather than the ganglion cells directly, and raising hopes that the prosthesis will preserve some of the retina's natural signal processing.

  2. Confocal scanning laser ophthalmoscopic imaging resolution of secondary retinal effects induced by laser radiation

    NASA Astrophysics Data System (ADS)

    Zwick, Harry; Lund, David J.; Stuck, Bruce E.; Zuclich, Joseph A.; Elliot, Rowe; Schuschereba, Steven T.; Gagliano, Donald A.; Belkin, M.; Glickman, Randolph D.

    1996-02-01

    We have evaluated secondary laser induced retinal effects in non-human primates with a Rodenstock confocal scanning laser ophthalmoscope. A small eye animal model, the Garter snake, was employed to evaluate confocal numerical aperture effects in imaging laser retinal damage in small eyes vs. large eyes. Results demonstrate that the confocal image resolution in the Rhesus monkey eye is sufficient to differentiate deep retinal scar formation from retinal nerve fiber layer (NFL) damage and to estimate the depth of the NFL damage. The best comparison with histological depth was obtained for the snake retina, yielding a ratio close to 1:1 compared to 2:1 for the Rhesus. Resolution in the Garter snake allows imaging the photoreceptor matrix and therefore, evaluation of the interrelationship between the primary damage site (posterior retina), the photoreceptor matrix, and secondary sites in the anterior retina such as the NFL and the epiretinal vascular system. Alterations in both the retinal NFL and epiretinal blood flow rate were observed within several minutes post Argon laser exposure. Unique aspects of the snake eye such as high tissue transparency and inherently high contrast cellular structures, contribute to the confocal image quality. Such factors may be nearly comparable in primate eyes suggesting that depth of resolution can be improved by smaller confocal apertures and more sensitive signal processing techniques.

  3. Characterization of a Spontaneous Retinal Neovascular Mouse Model

    PubMed Central

    Hasegawa, Eiichi; Sweigard, Harry; Husain, Deeba; Olivares, Ana M.; Chang, Bo; Smith, Kaylee E.; Birsner, Amy E.; D’Amato, Robert J.; Michaud, Norman A.; Han, Yinan; Vavvas, Demetrios G.; Miller, Joan W.; Haider, Neena B.; Connor, Kip M.

    2014-01-01

    Background Vision loss due to vascular disease of the retina is a leading cause of blindness in the world. Retinal angiomatous proliferation (RAP) is a subgroup of neovascular age-related macular degeneration (AMD), whereby abnormal blood vessels develop in the retina leading to debilitating vision loss and eventual blindness. The novel mouse strain, neoretinal vascularization 2 (NRV2), shows spontaneous fundus changes associated with abnormal neovascularization. The purpose of this study is to characterize the induction of pathologic angiogenesis in this mouse model. Methods The NRV2 mice were examined from postnatal day 12 (p12) to 3 months. The phenotypic changes within the retina were evaluated by fundus photography, fluorescein angiography, optical coherence tomography, and immunohistochemical and electron microscopic analysis. The pathological neovascularization was imaged by confocal microscopy and reconstructed using three-dimensional image analysis software. Results We found that NRV2 mice develop multifocal retinal depigmentation in the posterior fundus. Depigmented lesions developed vascular leakage observed by fluorescein angiography. The spontaneous angiogenesis arose from the retinal vascular plexus at postnatal day (p)15 and extended toward retinal pigment epithelium (RPE). By three months of age, histological analysis revealed encapsulation of the neovascular lesion by the RPE in the photoreceptor cell layer and subretinal space. Conclusions The NRV2 mouse strain develops early neovascular lesions within the retina, which grow downward towards the RPE beginning at p15. This retinal neovascularization model mimics early stages of human retinal angiomatous proliferation (RAP) and will likely be a useful in elucidating targeted therapeutics for patients with ocular neovascular disease. PMID:25188381

  4. Can retinal microtrauma by internal limiting membrane peeling cause retinal angiomatosis proliferans?

    PubMed Central

    Rishi, Pukhraj; Dhupper, Maneesh; Rishi, Ekta

    2011-01-01

    A 32-year-old male presented with decreased vision in right eye since 1 month following trauma with plastic ball. Best-corrected visual acuity (BCVA) was 20/160 in right eye and 20/20 in left. Right eye examination revealed angle recession, choroidal rupture, and macular hole. He underwent vitrectomy, internal limiting membrane (ILM) peeling, and 14% C3F8 gas injection. After 6 weeks, BCVA was 20/30; fundus showed macular hole closure. Six months after surgery, fundus revealed retinal vascular lesions suggestive of stage I RAP-like lesions; vision was maintained. Clinical findings were confirmed on Video ICGA, FFA, and OCT. The patient was periodically reviewed and lesions were nonprogressive until last follow-up, 13 months after surgery. It seems quite probable that ILM peeling may have caused retinal microtrauma leading to the formation of RAP-like lesions. What factors lead to such an event is as yet not clearly understood. Hence, larger studies with a longer follow-up are warranted to better understand these findings. PMID:22279405

  5. Degeneration of retinal ganglion cells in diabetic dogs and mice: Relationship to glycemic control and retinal capillary degeneration

    PubMed Central

    Howell, Scott J.; Mekhail, Mena N.; Azem, Rami; Ward, Nicole L.

    2013-01-01

    Purpose The purpose of this study was to investigate (i) the effect of diabetes on retinal ganglion cell death in diabetic dogs and mice, (ii) the effect of prolonged glycemic control on diabetes-induced death of retinal ganglion cells, (iii) whether retinal ganglion cell death in diabetes is associated with degeneration of retinal capillaries, and (iv) the effect of diet on diabetes-induced degeneration of retinal ganglion cells in mice. Methods Diabetes was induced in dogs using streptozotocin, and levels of glycemic control (good, moderate, and poor) were maintained for 5 years. Diabetes was studied in two mouse models (diabetes induced in C57Bl/6J mice using streptozotocin and spontaneously diabetic Ins2Akita mice). Retinal ganglion cell death was investigated by counting the number of axons from the ganglion cells in the optic nerve and with terminal transferase deoxyuridine triphosphate nick-end labeling and annexin V staining in mice. Results As reported previously, the development and severity of vascular lesions of diabetic retinopathy in diabetic dogs were strongly associated with glycemic control. Loss of retinal ganglion cells was extensive in dogs kept in poor glycemic control, and was essentially prevented in diabetic dogs kept in good glycemic control for the 5 years of study. In contrast, “moderate” glycemic control (intermediate between poor and good glycemic control) caused a significant increase in vascular pathology, but did not cause loss of retinal axons in the optic nerve. Using this validated optic nerve axon counting method, the two mouse models of diabetic retinopathy were studied to assess ganglion cell death. Despite 10 months of diabetes (a duration that has been shown to cause retinal capillary degeneration in both models), neither mouse model showed loss of optic nerve axons (thus suggesting no loss of retinal ganglion cells). Likewise, other parameters of cell death (terminal transferase deoxyuridine triphosphate nick

  6. Finite element model of thermal processes in retinal photocoagulation

    NASA Astrophysics Data System (ADS)

    Sramek, Christopher; Paulus, Yannis M.; Nomoto, Hiroyuki; Huie, Phil; Palanker, Daniel

    2009-02-01

    Short duration (< 20 ms) pulses are desirable in patterned scanning laser photocoagulation to confine thermal damage to the photoreceptor layer, decrease overall treatment time and reduce pain. However, short exposures have a smaller therapeutic window (defined as the ratio of rupture threshold power to that of light coagulation). We have constructed a finite-element computational model of retinal photocoagulation to predict spatial damage and improve the therapeutic window. Model parameters were inferred from experimentally measured absorption characteristics of ocular tissues, as well as the thresholds of vaporization, coagulation, and retinal pigment epithelial (RPE) damage. Calculated lesion diameters showed good agreement with histological measurements over a wide range of pulse durations and powers.

  7. Effect of charred Radix et Rhizoma Rhei in a laser-induced choroidal neovascularization murine model.

    PubMed

    Han, Dongmei; Yao, Yuan; Sun, Yong; Gong, Yuanyuan; Wu, Xingwei

    2015-04-01

    A pharmaceutical composition (patent no. WO2012079419) exhibited favorable outcomes in a clinical trial of wet age‑related macular degeneration. The aims of the present study were to explore the effects of one composition component, charred Radix et Rhizoma Rhei (CRRR), in a laser‑induced choroidal neovascularization (CNV) murine model. A total of 30 eight‑week‑old C57BL/6 mice were subjected to diode laser treatment, and CNV was induced by rupturing the Bruch's membrane. The mice were then randomly divided into two groups: the CRRR‑treated group that was administered CRRR water extract (concentration, 0.6 g/100 ml; dose, 1 ml/0.1 kg twice a day for 21 days); and the control group that was treated with saline (dose, 1 ml/0.1 kg twice a day for 21 days). The retinal tissue was subjected to quantitative polymerase chain reaction (qPCR) and western blot analysis to determine the expression levels of interleukin‑10 (IL‑10) and vascular epithelial growth factor (VEGF) at day seven following laser treatment. At weeks 2 and 3 after laser treatment, fundus fluorescein angiography was performed and graded to assess the severity of lesion leakage. Retinal flat mounts were prepared for three‑dimensional confocal microscopy at day 22 after laser treatment. At days 14 and 21 after laser treatment, no statistically significant differences were observed between the clinically relevant lesions of the CRRR‑treated and control mice. CNV volumes were not found to be significantly different between the CRRR‑treated and control mice. The expression levels of IL‑10 were significantly increased in the CRRR‑treated mice (P<0.05). However, no statistically significant differences were observed between the VEGF expression levels of the CRRR‑treated and control mice. In conclusion, CRRR did not appear to significantly inhibit CNV in this murine model. The function of CRRR in the pharmaceutical composition may be due to the effects of IL‑10 and a synergistic effect

  8. Probabilistic retinal vessel segmentation

    NASA Astrophysics Data System (ADS)

    Wu, Chang-Hua; Agam, Gady

    2007-03-01

    Optic fundus assessment is widely used for diagnosing vascular and non-vascular pathology. Inspection of the retinal vasculature may reveal hypertension, diabetes, arteriosclerosis, cardiovascular disease and stroke. Due to various imaging conditions retinal images may be degraded. Consequently, the enhancement of such images and vessels in them is an important task with direct clinical applications. We propose a novel technique for vessel enhancement in retinal images that is capable of enhancing vessel junctions in addition to linear vessel segments. This is an extension of vessel filters we have previously developed for vessel enhancement in thoracic CT scans. The proposed approach is based on probabilistic models which can discern vessels and junctions. Evaluation shows the proposed filter is better than several known techniques and is comparable to the state of the art when evaluated on a standard dataset. A ridge-based vessel tracking process is applied on the enhanced image to demonstrate the effectiveness of the enhancement filter.

  9. In vivo analysis of the time and spatial activation pattern of microglia in the retina following laser-induced choroidal neovascularization.

    PubMed

    Crespo-Garcia, Sergio; Reichhart, Nadine; Hernandez-Matas, Carlos; Zabulis, Xenophon; Kociok, Norbert; Brockmann, Claudia; Joussen, Antonia M; Strauss, Olaf

    2015-10-01

    Microglia play a major role in retinal neovascularization and degeneration and are thus potential targets for therapeutic intervention. In vivo assessment of microglia behavior in disease models can provide important information to understand patho-mechanisms and develop therapeutic strategies. Although scanning laser ophthalmoscope (SLO) permits the monitoring of microglia in transgenic mice with microglia-specific GFP expression, there are fundamental limitations in reliable identification and quantification of activated cells. Therefore, we aimed to improve the SLO-based analysis of microglia using enhanced image processing with subsequent testing in laser-induced neovascularization (CNV). CNV was induced by argon laser in MacGreen mice. Microglia was visualized in vivo by SLO in the fundus auto-fluorescence (FAF) mode and verified ex vivo using retinal preparations. Three image processing algorithms based on different analysis of sequences of images were tested. The amount of recorded frames was limiting the effectiveness of the different algorithms. Best results from short recordings were obtained with a pixel averaging algorithm, further used to quantify spatial and temporal distribution of activated microglia in CNV. Morphologically, different microglia populations were detected in the inner and outer retinal layers. In CNV, the peak of microglia activation occurred in the inner layer at day 4 after laser, lacking an acute reaction. Besides, the spatial distribution of the activation changed by the time over the inner retina. No significant time and spatial changes were observed in the outer layer. An increase in laser power did not increase number of activated microglia. The SLO, in conjunction with enhanced image processing, is suitable for in vivo quantification of microglia activation. This surprisingly revealed that laser damage at the outer retina led to more reactive microglia in the inner retina, shedding light upon a new perspective to approach

  10. Laser-induced breakdown emission in hydrocarbon fuel mixtures

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kazunobu; Bak, Moon Soo; Tanaka, Hiroki; Carter, Campbell; Do, Hyungrok

    2016-04-01

    Time-resolved emission measurements of laser-induced breakdown plasmas have been carried out to investigate the effect that gas species might have on the kinetics, particularly in excited states, and the resulting plasma properties. For this purpose, fuel-oxygen (O2)-carbon dioxide (CO2) mixtures with either helium (He) or nitrogen (N2) balance are prepared while maintaining their atomic compositions. The fuels tested in this study are methane (CH4), ethylene (C2H4), propane (C3H8), and butane (C4H10). The breakdown is produced in the mixtures (CH4/CO2/O2/He, C2H4/O2/He, C3H8/CO2/O2/He and C4H10/CO2/O2/He or CH4/CO2/O2/N2, C2H4/O2/N2, C3H8/CO2/O2/N2 and C4H10/CO2/O2/N2) at room conditions using the second harmonic of a Q-switched Nd:YAG laser (with pulse duration of 10 ns). The temporal evolution of plasma temperature is deduced from the ratio of two oxygen lines (777 nm and 823 nm) through Boltzmann analysis, while the evolution of electron number density is estimated based on Stark broadening of the Balmer-alpha (H α ) line at 656 nm and the measured plasma temperature. From the results, the temporal evolution of emission spectra and decay rates of atomic line-intensities are found to be almost identical between the breakdown plasma in the different mixtures given balancing gases. Furthermore, the temporal evolution of plasma temperature and electron number density are also found to be independent of the species compositions. Therefore, this behavior—of the breakdown emissions and plasma properties in the different mixtures with identical atomic composition—may be because the breakdown gases reach similar thermodynamic and physiochemical states immediately after the breakdown.

  11. Morphological studies of laser-induced photoacoustic damage

    NASA Astrophysics Data System (ADS)

    Flotte, Thomas J.; Yashima, Yutaka; Watanabe, Shinichi; McAuliffe, Daniel J., Sr.; Jacques, Steven L.

    1990-06-01

    Argon-fluoride excimer laser ablation of stratum comeum causes deeper tissue damage than expected for thermal or photochemical mechanisms, suggesting thatphotoacoustic waves have arole in tissue damage. Laserirradiation (193 nm, 14 ns pulses, 1-2 Hz) attworadiantexposures, 60 and 160 mJ/cm2perpulse was usedto ablate the stratumcomeumofskin. Light and electron microscopy ofimmediate biopsies demonstrated damage to fibroblasts as deep as 88 and 220 jun, respectively, below the ablation site. Ablation throughwaterwas usedtoinertially confine the ablation zone. Partial ablationofs.c. through airproducedno damage, whereas partial ablation through water damaged skin to amean depth of 1 14.5 8.8( Full thickness ablation of s.c. through air and water produced damage zones measuring 192.2 16.2 and 293.0 71.6 rim, respectively (p <0.05). The increased depth ofdamage in the presence ofinertial confinementprovided by the layer of water strongly supports a photoacoustic mechanism ofdamage. The depths ofdamage for thelarge spot, line, and small spots were 43 1 164 urn, 269 96xni, andno damage. The spot size dependence ofthedepthofdamage is consistentwiththe geometric attenuation one would expect to be present from a pressure wave related phenomena. Sequential biopsies were taken over a 7 day period for light and transmission electron microscopy. At 24 hours, there was necrosis of the epidermis and papillary dermis subjacent to the ablation site, with neutrophils surrounding and demarcating the affected area. The necrotic zone sloughedby48 hours. Thereepithelializationwas completeby7 days. The sequenceofrepairis similartoknife wound healing which we have previously studied, and is analogous to other wound healing processes. We have used an experimental model of ArF excimer laser ablation of stratum corneum to investigate laser-induced photoacoustic damage. The evidence for the injury being due to pressure transients is indirectbutcompelling. Whether these pressuretransients are

  12. Application of femtosecond-laser induced nanostructures in optical memory.

    PubMed

    Shimotsuma, Yasuhiko; Sakakura, Masaaki; Miura, Kiyotaka; Qiu, Jiarong; Kazansky, Peter G; Fujita, Koji; Hirao, Kazuyuki

    2007-01-01

    The femtosecond laser induced micro- and nanostructures for the application to the three-dimensional optical data storage are investigated. We have observed the increase of refractive index due to local densification and atomic defect generation, and demonstrated the real time observation of photothermal effect after the femtosecond laser irradiation inside a glass by the transient lens (TrL) method. The TrL signal showed a damped oscillation with about an 800 ps period. The essential feature of the oscillation can be reproduced by the pressure wave creation and propagation to the outward direction from the irradiated region. The simulation based on elastodynamics has shown that a large thermoelastic stress is relaxed by the generation of the pressure wave. In the case of soda-lime glass, the velocity of the pressure wave is almost same as the longitudinal sound velocity at room temperature (5.8 microm/ns). We have also observed the localized photo-reduction of Sm3+ to Sm2+ inside a transparent and colorless Sm(3+)-doped borate glass. Photoluminescence spectra showed that some the Sm3+ ions in the focal spot within the glass sample were reduced to Sm2+ ions after femtosecond laser irradiation. A photo-reduction bit of 200 nm in three-dimensions can be recorded with a femtosecond laser and readout clearly by detecting the fluorescence excited by Ar+ laser (lambda = 488 nm). A photo-reduction bit can be also erased by photo-oxidation with a cw Ar+ laser (lambda = 514.5 nm). Since photo-reduction bits can be spaced 150 nm apart in a layer within glass, a memory capacity of as high as 1 Tbit can be achieved in a glass piece with dimensions of 10 mm x 10 mm x 1 mm. We have also demonstrated the first observation of the polarization-dependent periodic nanostructure formation by the interference between femtosecond laser light and electron acoustic waves. The observed nanostructures are the smallest embedded structures ever created by light. The period of self

  13. Modeling of Laser Induced Damage in NIF UV Optics

    SciTech Connect

    Feit, M D; Rubenchik, A M

    2001-02-21

    Controlling damage to nominally transparent optical elements such as lenses, windows and frequency conversion crystals on high power lasers is a continuing technical problem. Scientific understanding of the underlying mechanisms of laser energy absorption, material heating and vaporization and resultant mechanical damage is especially important for UV lasers with large apertures such as NIF. This LDRD project was a single year effort, in coordination with associated experimental projects, to initiate theoretical descriptions of several of the relevant processes. In understanding laser damage, we distinguish between damage initiation and the growth of existent damage upon subsequent laser irradiation. In general, the effect of damage could be ameliorated by either preventing its initiation or by mitigating its growth. The distinction comes about because initiation is generally due to extrinsic factors such as contaminants, which provide a means of local laser energy absorption. Thus, initiation tends to be local and stochastic in nature. On the other hand, the initial damaging event appears to modify the surrounding material in such a way that multiple pulse damage grows more or less regularly. More exactly, three ingredients are necessary for visible laser induced damage. These are adequate laser energy, a mechanism of laser energy absorption and mechanical weakness. For damage growth, the material surrounding a damage site is already mechanically weakened by cracks and probably chemically modified as well. The mechanical damage can also lead to electric field intensification due to interference effects, thus increasing the available laser energy density. In this project, we successfully accounted for the pulselength dependence of damage threshold in bulk DKDP crystals with the hypothesis of small absorbers with a distribution of sizes. We theoretically investigated expected scaling of damage initiation craters both to baseline detailed numerical simulations

  14. Fundamental studies in the molecular basis of laser-induced retinal damage. Annual report, September 1983-September 1984

    SciTech Connect

    Lewis, A.

    1984-09-01

    Advances made in the work for the Ocular Hazards Program at the Letterman Army Institute of Research (LAIR) are described. The research has seen the first application of femtosecond lasers to the visual system; it is giving new insights into how these ultimate laser sources interact with biological tissue in general and with the visual system in particular. The authors have discovered that simple anions can activate visual photoreceptors in the dark; among these anionic activators is the dental agent fluoride. Research has continued into identifying selectively and spatially the image of various elements in photoreceptors and adjacent tissue. The authors were able to extend our preparation procedures to view the elemental composition of such components as melanin granules. The sensitive and selective spatial images should play important roles in extending understanding of the fundamental mechanisms of laser damage. The staining procedures developed can be applied to study laser-damaged retina. Data were obtained demonstrating rapid mechanical motions in vertebrate photoreceptors. Such rapid mechanical motions which parallel electrophysiological responses in the cell may lie at the very basis of photoreceptor function. Laser-damage mechanisms should now be reevaluated in terms of this new data. The effect of laser light on these newly discovered mechanical motions will surely lead to new and improved understanding of low-level laser ocular hazards.

  15. Fundamental studies in the molecular basis of laser-induced retinal damage. Annual report, September 1982-August 1983

    SciTech Connect

    Lewis

    1983-09-01

    This research led to major discoveries in two general areas. First, it was shown that there are a series of anionic activators of visual cells. These anionic activators turn on, in the dark, the enzymatic processes usually stimulated by light. Among these anionic activators is fluoride, the important additive in dental care. It is possible that the discovery of anionic activators will allow modulation of visual sensitivity and excitation. A second major advance was the development of a staining method that allows the direct observation with light microscopy of actin filaments in rod outer segments. This discovery will now allow viewing these important actin filaments in live cells under physiologically relevant experimental conditions. It will also allow for the development of new methods to probe pathological and damaged conditions in visual photoreceptor cells. The above discoveries are described in two separate sections, the first entitled Anionic Activators of Photoreceptor Cells in the Dark, and the second entitled Visualization of Actin in Photoreceptor Cells by Light Microscopy.

  16. Pathway to Retinal Oximetry

    PubMed Central

    Beach, James

    2014-01-01

    Events and discoveries in oxygen monitoring over the past two centuries are presented as the background from which oximetry of the human retina evolved. Achievements and the people behind them are discussed, showing parallels between the work in tissue measurements and later in the eye. Developments in the two-wavelength technique for oxygen saturation measurements in retinal vessels are shown to exploit the forms of imaging technology available over time. The last section provides a short summary of the recent research in retinal diseases using vessel oximetry. PMID:25237591

  17. Luminosity and contrast normalization in color retinal images based on standard reference image

    NASA Astrophysics Data System (ADS)

    S. Varnousfaderani, Ehsan; Yousefi, Siamak; Belghith, Akram; Goldbaum, Michael H.

    2016-03-01

    Color retinal images are used manually or automatically for diagnosis and monitoring progression of a retinal diseases. Color retinal images have large luminosity and contrast variability within and across images due to the large natural variations in retinal pigmentation and complex imaging setups. The quality of retinal images may affect the performance of automatic screening tools therefore different normalization methods are developed to uniform data before applying any further analysis or processing. In this paper we propose a new reliable method to remove non-uniform illumination in retinal images and improve their contrast based on contrast of the reference image. The non-uniform illumination is removed by normalizing luminance image using local mean and standard deviation. Then the contrast is enhanced by shifting histograms of uniform illuminated retinal image toward histograms of the reference image to have similar histogram peaks. This process improve the contrast without changing inter correlation of pixels in different color channels. In compliance with the way humans perceive color, the uniform color space of LUV is used for normalization. The proposed method is widely tested on large dataset of retinal images with present of different pathologies such as Exudate, Lesion, Hemorrhages and Cotton-Wool and in different illumination conditions and imaging setups. Results shows that proposed method successfully equalize illumination and enhances contrast of retinal images without adding any extra artifacts.

  18. The Role of Fundus Autofluorescence in Late-Onset Retinitis Pigmentosa (LORP) Diagnosis

    PubMed Central

    Lee, Tamara J.; Hwang, John C.; Chen, Royce W. S.; Lima, Luiz H.; Wang, Nan-Kai; Tosi, Joaquin; Freund, K. Bailey; Yannuzzi, Lawrence A.; Tsang, Stephen H.

    2015-01-01

    Purpose To demonstrate the utility and characteristics of fundus autofluorescence in late-onset retinitis pigmentosa. Methods Observational case series. Patients diagnosed with late-onset retinitis pigmentosa were identified retrospectively in an institutional setting. Twelve eyes of six patients were identified and medical records were reviewed. Results All patients presented with slowly progressive peripheral field loss and initial clinical examination revealed only subtle retinal changes. There was a notable lack of intraretinal pigment migration in all patients. Five out of six patients underwent magnetic resonance imaging of the brain to rule out intracranial processes and all were referred from another ophthalmologist for further evaluation. Fundus autofluorescence was ultimately employed in all patients and revealed more extensive retinal pathology than initially appreciated on clinical examination. Fundus autofluorescence directed the workup toward a retinal etiology in all cases and led to the eventual diagnosis of late-onset retinitis pigmentosa through electroretinogram testing. Conclusion Fundus autofluorescence may be a more sensitive marker for retinal pathology than stereo fundus biomicroscopy alone in late-onset retinitis pigmentosa. Early use of fundus autofluorescence imaging in the evaluation of patients with subtle retinal lesions and complaints of peripheral field loss may be an effective strategy for timely and cost-efficient diagnosis. PMID:23899229

  19. Time-Resolved Aluminum Monoxide Emission Measurements in Laser-Induced Plasma

    NASA Astrophysics Data System (ADS)

    Surmick, David; Parigger, Christian

    2014-03-01

    Laser-induced plasmas are useful for diagnostic applications in a wide variety of fields. One application is the creation of laser-induced plasmas on the surface of an aluminum sample to simulate an aluminized flame. In this study, aluminum monoxide emissions are measured to characterize the temperature along the laser-induced plasma as a function of time delay following laser-induced optical breakdown. The breakdown event is achieved by focusing 1064 nanometer laser radiation from an Nd:YAG laser onto the surface of an aluminum sample. Light from the plasma is dispersed with the use of a Czerny-Turner spectrograph, and time resolved emission spectra are recorded with an intensified, gated detector. Temperatures are inferred from the diatomic molecular emissions by fitting the experimentally collected to theoretically calculated spectra using a Nelder-Mead algorithm. For computation of synthetic spectra we utilize accurate line strengths for selected AlO molecular bands. Atomic emissions from aluminum are also investigated in our study of laser-induced plasma.

  20. Changes in cortical grey matter density associated with long-standing retinal visual field defects

    PubMed Central

    Boucard, Christine C.; Hernowo, Aditya T.; Maguire, R. Paul; Jansonius, Nomdo M.; Roerdink, Jos B. T. M.; Hooymans, Johanna M. M.

    2009-01-01

    Retinal lesions caused by eye diseases such as glaucoma and age-related macular degeneration can, over time, eliminate stimulation of parts of the visual cortex. This could lead to degeneration of inactive cortical neuronal tissue, but this has not been established in humans. Here, we used magnetic resonance imaging to assess the effects of prolonged sensory deprivation in human visual cortex. High-resolution anatomical magnetic resonance images were obtained in subjects with foveal (age-related macular degeneration) and peripheral (glaucoma) retinal lesions as well as age-matched controls. Comparison of grey matter between patient and control groups revealed density reductions in the approximate retinal lesion projection zones in visual cortex. This indicates that long-term cortical deprivation, due to retinal lesions acquired later in life, is associated with retinotopic-specific neuronal degeneration of visual cortex. Such degeneration could interfere with therapeutic strategies such as the future application of artificial retinal implants to overcome lesion-induced visual impairment. PMID:19467992

  1. Suppression of Laser-Induced Choroidal Neovascularization by the Oral Medicine Targeting Histamine Receptor H4 in Mice

    PubMed Central

    Ijima, Ryo; Kaneko, Hiroki; Ye, Fuxiang; Takayama, Kei; Nagasaka, Yosuke; Kataoka, Keiko; Funahashi, Yasuhito; Iwase, Takeshi; Kachi, Shu; Kato, Seiichi; Terasaki, Hiroko

    2015-01-01

    Purpose This study aimed to examine relationship of histamine receptor H4 (HRH4) and the pathogenesis of laser-induced choroidal neovascularization (laser-CNV) and to determine whether oral administration of HRH4 antagonists suppressed laser-CNV in mice. Methods Laser photocoagulation was performed in mice to induce the laser-CNV. Histamine was administered intravitreously, and CNV volume was measured. Laser photocoagulation and intravitreous injection of HRH4 antagonist JNJ7777120 were performed after intraperitoneal injection of clodronate liposome, which depletes circulating monocyte-derived macrophages; CNV volume was compared with that in mice injected with control (dimethyl sulfoxide [DMSO]/PBS). Three days after laser-CNV, the F4/80+CD11b+ macrophage population in retinal pigment epithelium (RPE)/choroid complex was quantified with flow cytometry in wild-type and Hrh4−/− mice. The long-acting HRH4 antagonist JNJ28307474 was then administrated periorally, and the laser-CNV volume was compared with controls. Results Intravitreous injection of histamine did not affect laser-CNV volume. The laser-CNV from the eye injected with JNJ7777120 was equivalent to that injected with the DMSO/PBS in mice that had intraperitoneally received clodronate liposome. Flow cytometry after laser-CNV induction revealed a smaller F4/80+CD11b+ macrophage population in the RPE/choroid complex of Hrh4−/− mice than in wild-type mice. Oral administration of JNJ28307474 significantly reduced laser-CNV volume in wild-type mice. Conclusions Our results suggested that HRH4-positive macrophages played an important role in the pathogenesis of laser-CNV and that they require a different ligand from that of histamine. The oral administration of an HRH4 antagonist successfully reduced laser-CNV. Translational Relevance Our results indicate that drugs targeting HRH4 are potentially a novel oral treatment for age-related macular degeneration. PMID:25774332

  2. A case of atypical progressive outer retinal necrosis after highly active antiretroviral therapy.

    PubMed

    Woo, Se Joon; Yu, Hyeong Gon; Chung, Hum

    2004-06-01

    This is a report of an atypical case of progressive outer retinal necrosis (PORN) and the effect of highly active antiretroviral therapy (HAART) on the clinical course of viral retinitis in an acquired immunodeficiency syndrome (AIDS) patient. A 22-year-old male patient infected with human immunodeficiency virus (HIV) presented with unilaterally reduced visual acuity and a dense cataract. After cataract extraction, retinal lesions involving the peripheral and macular areas were found with perivascular sparing and the mud-cracked, characteristic appearance of PORN. He was diagnosed as having PORN based on clinical features and was given combined antiviral treatment. With concurrent HAART, the retinal lesions regressed, with the regression being accelerated by further treatment with intravenous acyclovir and ganciclovir. This case suggests that HAART may change the clinical course of PORN in AIDS patients by improving host immunity. PORN should be included in the differential diagnosis of acute unilateral cataract in AIDS patients. PMID:15255240

  3. Self-emission and enhancement of laser-induced emission of electrons from ferroelectrics

    NASA Astrophysics Data System (ADS)

    Geissler, K. K.; Meineke, A.; Riege, H.; Handerek, J.

    1994-02-01

    We report on laser-induced electron emission (LIEE) from ferroelectrics (FE) at 266, 355 and 532 nm wavelength. The self-emission of charges up to 20 nC/cm 2 with kinetic energies up to several keV was observed with PLZT ceramics at laser-pulse energy densities of 13 mJ/cm 2 and a pulse width of 5 ns FWHM after high-voltage-induced polarization switching. The driving electric field is generated by the laser-induced change of the spontaneous polarization in a time scale of 1 ns. The dependence of the emission on the laser-pulse energy density is shown and the relation between the enhancement of LIEE and the laser-induced self-emission is discussed.

  4. Laser-induced fluorescence of fused silica irradiated by ArF excimer laser

    SciTech Connect

    Zhang Haibo; Yuan Zhijun; Zhou Jun; Dong Jingxing; Wei Yunrong; Lou Qihong

    2011-07-01

    Laser-induced fluorescence (LIF) of high-purity fused silica irradiated by ArF excimer laser is studied experimentally. LIF bands of the fused silica centered at 281 nm, 478 nm, and 650 nm are observed simultaneously. Furthermore, the angular distribution of the three fluorescence peaks is examined. Microscopic image of the laser modified fused silica indicates that scattering of the generated fluorescence by laser-induced damage sites is the main reason for the angular distribution of LIF signals. Finally, the dependence of LIF signals intensities of the fused silica on laser power densities is presented. LIF signals show a squared power density dependence, which indicates that laser-induced defects are formed mainly via two-photon absorption processes.

  5. Laser-induced fluorescence imaging of coronary arteries for open-heart surgery applications

    NASA Astrophysics Data System (ADS)

    Taylor, Roderick S.; Gladysz, D.; Brown, Derek W.; Higginson, Lyall A. J.

    1991-07-01

    A technique utilizing laser induced fluorescence has been developed to obtain direct real-time imaging of the coronary artery network for open heart surgery applications. Both excimer pumped dye and cw argon-ion laser radiation transmitted through a fused silica fiber were used as laser sources to irradiate swine, bovine, and human cadaver hearts whose coronary arteries had been injected with strongly fluorescent dyes. The laser induces fluorescence originating from within the coronary arteries and detected by the surgeon's eye, allows the entire coronary network to be directly viewed. A comparison between laser induced fluorescence and the use of direct visual inspection of arteries following injection of the dye Cardio-Green(R) as well as conventional thermal imaging is presented. The limitations imposed on each technique by layers of fat on top of the coronary arteries are also described. The possibility of using these techniques to detect mechanical or laser beam perforations during laser endarterectomy procedures is discussed.

  6. Quantitative measurement of electron number in nanosecond and picosecond laser-induced air breakdown

    NASA Astrophysics Data System (ADS)

    Wu, Yue; Sawyer, Jordan C.; Su, Liu; Zhang, Zhili

    2016-05-01

    Here we present quantitative measurements of total electron numbers in laser-induced air breakdown at pressures ranging from atmospheric to 40 barg by 10 ns and 100 ps laser pulses. A quantifiable definition for the laser-induced breakdown threshold is identified by a sharp increase in the measurable total electron numbers via dielectric-calibrated coherent microwave scattering. For the 10 ns laser pulse, the threshold of laser-induced breakdown in atmospheric air is defined as the total electron number of ˜106. This breakdown threshold decreases with an increase of pressure and laser photon energy (shorter wavelength), which is consistent with the theory of initial multiphoton ionization and subsequent avalanche processes. For the 100 ps laser pulse cases, a clear threshold is not present and only marginal pressure effects can be observed, which is due to the short pulse duration leading to stronger multiphoton ionization and minimal collisional avalanche ionization.

  7. Standoff Detection of Volatile Organic Compounds In Air Using Laser Induced Fluorescence

    NASA Astrophysics Data System (ADS)

    Clark, Jerry; Alexander, Alonzo; Wiggins, Delonia; Williams, Sydney; Akpovo, Charlemagne; Mezonlin, Ephrem; Johnson, Joseph, III; CenterPlasma Science; Technology (CePaST) Team

    2011-10-01

    The use of laser-induced fluorescence has proven to be an excellent method of detecting important intermediates in turbulent systems. However, Acetylene detection in air at ambient temperatures has proven more challenging. Molecular spectra were collected in laser induced acetylene plasmas using a 250 mJ Nd:YAG laser and an optical parametric oscillator (OPO) to achieve the 260 nm wavelength and greater than 3 mJ energy necessary to excite acetylene molecules. The acetylene laser-induced fluorescence excitation was observed at the 228 nm wavelength. Using various concentration ratios, acetylene was mixed with air to specifically determine the capabilities of standoff acetylene detection at atmospheric pressure. These results will lead to further research and development of turbulence based battlefield ready detection devices. Research supported in part by NSF grants to FAMU.

  8. Photophysics of Laser Dye-Doped Polymer Membranes for Laser-Induced Fluorescence Photogrammetry

    NASA Technical Reports Server (NTRS)

    Dorrington, Adrian A.; Jones, Thomas W.; Danehy, Paul M.

    2004-01-01

    Laser-induced fluorescence target generation in dye-doped polymer films has recently been introduced as a promising alternative to more traditional photogrammetric targeting techniques for surface profiling of highly transparent or reflective membrane structures. We investigate the photophysics of these dye-doped polymers to help determine their long-term durability and suitability for laser-induced fluorescence photogrammetric targeting. These investigations included experimental analysis of the fluorescence emission pattern, spectral content, temporal lifetime, linearity, and half-life. Results are presented that reveal an emission pattern wider than normal Lambertian diffuse surface scatter, a fluorescence time constant of 6.6 ns, a pump saturation level of approximately 20 micro J/mm(exp 2), and a useful lifetime of more than 300,000 measurements. Furthermore, two demonstrations of photogrammetric measurements by laser-induced fluorescence targeting are presented, showing agreement between photogrammetric and physically measured dimensions within the measurement scatter of 100 micron.

  9. Sensitive Measurement of Trace Mercury Using Low Pressure Laser-Induced Plasma

    NASA Astrophysics Data System (ADS)

    Wang, Zhenzhen; Deguchi, Yoshihiro; Kuwahara, Masakazu; Zhang, Xiaobo; Yan, Junjie; Liu, Jiping

    2013-11-01

    The emission of trace heavy metals, such as mercury (Hg), from power plants and other industries is a severe environmental problem concerning the public health. The laser-induced plasma technique was employed to measure Hg under various conditions, which reveals several merits of this method at low pressure. The main interferences of laser-induced breakdown spectroscopy (LIBS), which include the black-body-like emission from plasma itself and coexisting molecular and atomic emissions, decreased significantly using low pressure laser-induced plasma. Under low pressure conditions, Hg signal was rather clear without serious influence even if there is no delay time from the laser irradiation, which means the gated detection device is not necessary. This method featured the detection limit of 0.3 ppm at pressure 700 Pa. Additionally, the feasible of this method in real applications was demonstrated by measuring Hg in combustion gas which performed preferable results.

  10. Laser-induced breakdown spectroscopy detection of heavy metal in water based on graphite conch method

    NASA Astrophysics Data System (ADS)

    Wang, Chunlong; Liu, Jianguo; Zhao, Nanjing; Shi, Huan; Liu, Lituo; Ma, Mingjun; Zhang, Wei; Chen, Dong; Liu, Jing; Zhang, Yujun; Liu, Wenqing

    2012-10-01

    The laser-induced breakdown spectroscopy emission characteristics of trace heavy metal lead in water is studied based on graphite conch method, with a 1064nm wavelength Nd: YAG laser as excitation source, the echelle spectrometer and ICCD detector are used for spectral separation and high sensitive detection with high resolution and wide spectral range. The delay time 900ns and gate time 1600ns are determined in the experiment. The calibration curve of Pb is plotted based on the different concentration measurement results, and a limit of detection of 0.0138mg / L is obtained for Pb in water. Graphite conch method effectively overcomes the current problems on laser-induced breakdown spectroscopy detection of heavy metal in water. The detection limits and stability are improved. The reference data is provided for further study on the fast measurement of trace heavy metals in water by laser induced breakdown spectroscopy technique.

  11. Analysis of plutonium oxide surrogate residue using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Zheng, Hongbo; Yueh, Fang Yu; Miller, Tracy; Singh, Jagdish P.; Zeigler, Kristine E.; Marra, James C.

    2008-09-01

    Laser-induced breakdown spectroscopy was used to determine the elemental composition of a CeO 2 composite powder for process control verification during lanthanide borosilicate glass fabrication. Cerium oxide is used as a surrogate for plutonium oxide, which along with other canister contents will be combined with frit to make glass. Laser-induced breakdown spectroscopy data for the composition of the CeO 2 batch containing concentrations of Ce, Cr, Si, Fe, Ta, Ni, Zn, Al Mg, Gd, and W were quantitatively determined from laser-induced breakdown spectroscopy spectra of both pellet and powder samples. The results of both forms were compared and it was determined that the pellet data gave slightly better precision than the powder sample.

  12. Laser-induced thermotherapy for lung tissue--evaluation of two different internally cooled application systems for clinical use.

    PubMed

    Ritz, Joerg P; Lehmann, Kai S; Mols, Anke; Frericks, Bernd; Knappe, Verena; Buhr, Heinz J; Holmer, Christoph

    2008-04-01

    Thermal ablation techniques like radiofrequency or laser-induced thermotherapy (LITT) are increasingly used to treat tumors of parenchymatous organs. Minimal access, parenchymal preservation, and a low complication rate render them suitable for pulmonary tumors as well. Their successful clinical application depends on the induction of sufficiently large lesions and a knowledge of the energy parameters required for complete thermal ablation. The aim of this study was to establish a dose-response relationship for a percutaneous and an intraoperative system for LITT of lung tissue. Thermal lesions were induced in healthy porcine lungs using an Nd:YAG laser (1,064 nm). LITT was performed with a percutaneous application system in group I (n = 18) and an intraoperative application system in group II (n = 90). Laser energy was applied for 600-1,200 s in a power range of 20-32 W (12,000-38,400 J). The lesions were longitudinally and transversally measured, and the volume was calculated after the intervention. Furthermore, an open application system was used to perform LITT under in vivo conditions during lung perfusion and ventilation in domestic pigs. Lesion volumes in both groups showed a plateau-like curve when the laser power increased from an initial level of 25 W. With the percutaneous puncture system (group I), the application of 28 W (16,800 J) for 10 min generated the largest lesions with a volume of 12.54 +/- 1.33 cm(3), an axial diameter of 39.33 +/- 2.52 mm, and a diametrical diameter of 24.67 +/- 1.15 mm. A longer application time was not possible due to thermal instability of the applicator. Moreover, group I started developing extensive carbonizations at a laser power of 22 W (13,200 J). The intraoperative application system (group II) achieved the largest lesion volumes of 11.03 +/- 2.54 cm(3) with diameters of 34.6 +/- 4.22 mm (axial) and 25.6 +/- 2.51 mm (diametrical) by an exposure time of 20 min and a power of 32 W (38,400 J). Here extensive

  13. Comparisons of laser-saturated, laser-induced, and planar laser-induced fluorescence measurements of nitric oxide in a lean direct-injection spray flame.

    PubMed

    Cooper, C S; Ravikrishna, R V; Laurendeau, N M

    1998-07-20

    We report quantitative, spatially resolved laser-saturated fluorescence (LSF), linear laser-induced fluorescence (LIF), and planar laser-induced fluorescence (PLIF) measurements of nitric oxide (NO) concentration in a preheated, lean direct-injection spray flame at atmospheric pressure. The spray is produced by a hollow-cone, pressure-atomized nozzle supplied with liquid heptane, and the overall equivalence ratio is unity. NO is excited by means of the Q(2)(26.5) transition of the gamma(0, 0) band. LSF and LIF detection are performed in a 2-nm region centered on the gamma(0, 1) band. PLIF detection is performed in a broad ~70-nm region with a peak transmission at 270 nm. Quantitative radial NO profiles obtained by LSF are presented and analyzed so as to correct similar LIF and PLIF profiles. Excellent agreement is achieved among the three fluorescence methodologies. PMID:18285943

  14. Vascular Lesions.

    PubMed

    Jahnke, Marla N

    2016-08-01

    Vascular lesions in childhood are comprised of vascular tumors and vascular malformations. Vascular tumors encompass neoplasms of the vascular system, of which infantile hemangiomas (IHs) are the most common. Vascular malformations, on the other hand, consist of lesions due to anomalous development of the vascular system, including the capillary, venous, arterial, and lymphatic systems. Capillary malformations represent the most frequent type of vascular malformation. IHs and vascular malformations tend to follow relatively predictable growth patterns in that IHs grow then involute during early childhood, whereas vascular malformations tend to exhibit little change. Both vascular tumors and vascular malformations can demonstrate a wide range of severity and potential associated complications necessitating specialist intervention when appropriate. Evaluation and treatment of the most common types of vascular lesions are discussed in this article. [Pediatr Ann. 2016;45(8):e299-e305.]. PMID:27517358

  15. Investigation of possible fs-LASIK induced retinal damage

    NASA Astrophysics Data System (ADS)

    Schumacher, S.; Sander, M.; Stolte, A.; Doepke, C.; Baumgaertner, W.; Lubatschowski, H.

    2006-02-01

    Rapid development of new laser technologies enabled the application of ultra short lasers in refractive surgery. Focused ultra short laser pulses in near-infrared spectral range can generate a laser induced breakdown (LIB) in the cornea, which will disrupt the tissue. Cutting depth and position can be established by varying the laser focus. The fs-LASIK technique allows both flap and lenticule to be formed by using fs-pulses without the presence of any mechanical impact. During the cutting process not all of the pulse energy is deposited into the cornea; approximately half of the remaining energy propagates through the eye and reaches the retina. Though defocused, the transmitted energy can still induce damage to the retina due to absorption by the retinal pigment epithelium and the transfer of thermal energy to surrounding tissue. The fs-LASIK process was simulated with two laser systems; one continous-wave and one in the fs-regime. For the simulation the exposure time and focusing numerical aperature which defines the retinal spot size were varied. The Damage thresholds of the laser beam exposed eyes were determined in terms of ophthalmoscopic and histopathologic observations.

  16. Generating Recombinant Antibodies against Putative Biomarkers of Retinal Injury

    PubMed Central

    Kierny, Michael R.; Cunningham, Thomas D.; Bouhenni, Rachida A.; Edward, Deepak P.; Kay, Brian K.

    2015-01-01

    Candidate biomarkers, indicative of disease or injury, are beginning to overwhelm the process of validation through immunological means. Recombinant antibodies developed through phage-display offer an alternative means of generating monoclonal antibodies faster than traditional immunization of animals. Peptide segments of putative biomarkers of laser induced injury in the rabbit, discovered through mass spectrometry, were used as targets for a selection against a library of phage-displayed human single-chain variable fragment (scFv) antibodies. Highly specific antibodies were isolated to four of these unique peptide sequences. One antibody against the retinal protein, Guanine Nucleotide-Binding Protein Beta 5 (GBB5), had a dissociation constant ~300 nM and recognized the full-length endogenous protein in retinal homogenates of three different animal species by western blot. Alanine scanning of the peptide target identified three charged and one hydrophobic amino acid as the critical binding residues for two different scFvs. To enhance the utility of the reagent, one scFv was dimerized through a Fragment-crystallizable hinge region (i.e., Fc) and expressed in HEK-293 cells. This dimeric reagent yielded a 25-fold lower detection limit in western blots. PMID:25902199

  17. Laser-induced synthesis and decay of Tritium under exposure of solid targets in heavy water

    NASA Astrophysics Data System (ADS)

    Barmina, E. V.; Timashev, S. F.; Shafeev, G. A.

    2016-03-01

    The processes of laser-assisted synthesis of Tritium nuclei and their laser-induced decay in cold plasma in the vicinity of solid targets (Au, Ti, Se, etc.) immersed into heavy water are experimentally realized at peak laser intensity of 1010-1013 W/cm2. Initial stages of Tritium synthesis and their laser-induced beta-decay are interpreted on the basis of non-elastic interaction of plasma electrons having kinetic energy of 5-10 eV with nuclei of Deuterium and Tritium, respectively.

  18. Single-Walled Carbon Nanotubes, Carbon Nanofibers and Laser-Induced Incandescence

    NASA Technical Reports Server (NTRS)

    Schubert, Kathy (Technical Monitor); VanderWal, Randy L.; Ticich, Thomas M.; Berger, Gordon M.; Patel, Premal D.

    2004-01-01

    Laser induced incandescence applied to a heterogeneous, multi-element reacting flows is characterized by a) temporally resolved emission spectra, time-resolved emission at selected detection wavelengths and fluence dependence. Laser fluences above 0.6 Joules per square centimeter at 1064 nm initiate laser-induced vaporization, yielding a lower incandescence intensity, as found through fluence dependence measurements. Spectrally derived temperatures show that values of excitation laser fluence beyond this value lead to a super-heated plasma, well above the vaporization of temperature of carbon. The temporal evolution of the emission signal at these fluences is consistent with plasma dissipation processes, not incandescence from solid-like structures.

  19. (Study of flow properties of wet solids using laser induced photochemical anemometry)

    SciTech Connect

    Falco, B.

    1990-07-23

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves that use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  20. (Study of flow properties of wet solids using laser induced photochemical anemometry)

    SciTech Connect

    Falco, B.

    1990-04-03

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  1. (Study of flow properties of wet solids using laser induced photochemical anemometry)

    SciTech Connect

    Falco, B.; Nocera, D.

    1990-01-23

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  2. (Study of flow properties of wet solids using laser induced photo chemical anemometry)

    SciTech Connect

    Falco, B.

    1992-04-09

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  3. Detection of Broadband Terahertz Waves with a Laser-Induced Plasma in Gases

    SciTech Connect

    Dai Jianming; Xie Xu; Zhang, X.-C.

    2006-09-08

    We report the experimental results and theoretical analysis of broadband detection of terahertz (THz) waves via electric-field-induced second-harmonic generation in laser-induced air plasma with ultrashort laser pulses. By introducing the second-harmonic component of the white light in the laser-induced plasma as a local oscillator, coherent detection of broadband THz waves with ambient air is demonstrated for the first time. Our results show that, depending on the probe intensity, detection of THz waves in air can be categorized as incoherent, hybrid, and coherent detection. Coherent detection is achieved only when the tunnel ionization process dominates in gases.

  4. Non-gated laser-induced breakdown spectroscopy in bulk water by position-selective detection

    SciTech Connect

    Tian, Ye; Xue, Boyang; Song, Jiaojian; Lu, Yuan; Zheng, Ronger

    2015-09-14

    Temporal and spatial evolutions of the laser-induced plasma in bulk water are investigated using fast imaging and emission spectroscopic techniques. By tightly focusing a single-pulse nanosecond Nd: YAG laser beam into the bulk water, we generate a strongly expanded plasma with high reproducibility. Such a strong expanding plasma enables us to obtain well-resolved spectral lines by means of position-selective detection; hence, the time-gated detector becomes abdicable. The present results suggest not only a possible non-gated approach for underwater laser-induced breakdown spectroscopy but also give an insight into the plasma generation and expansion in bulk water.

  5. Influence of energy and wavelength on femtosecond laser-induced nucleation of protein

    NASA Astrophysics Data System (ADS)

    Murai, Ryota; Yoshikawa, Hiroshi Y.; Hasenaka, Hitoshi; Takahashi, Yoshinori; Maruyama, Mihoko; Sugiyama, Shigeru; Adachi, Hiroaki; Takano, Kazufumi; Matsumura, Hiroyoshi; Murakami, Satoshi; Inoue, Tsuyoshi; Mori, Yusuke

    2011-06-01

    The influence of energy and wavelength on femtosecond laser-induced nucleation of protein was systematically investigated with Hen Egg White Lysozyme and Glucose Isomerase at two different wavelengths, λ = 780 nm and 260 nm. We found that the enhancement of nucleation probability at a laser wavelength of λ = 780 nm was comparable with that at λ = 260 nm, which produces more protein dimers. The nucleation was dependent on laser pulse energy and could be induced beyond the threshold energy of cavitation bubbles. These results indicate that the photophysical processes like cavitation bubbles formation are main triggers for the femtosecond laser-induced nucleation.

  6. Laser-induced wavelength-controlled self-assembly of colloidal quasi-resonant quantum dots.

    PubMed

    Tsipotan, Aleksey S; Gerasimova, Marina A; Slabko, Vitaliy V; Aleksandrovsky, Aleksandr S

    2016-05-16

    Self-assembly of colloidal semiconductor quantum dots controlled solely by laser-induced interaction is demonstrated for the first time. Pairs of CdTe nanoparticles are formed under irradiation with nanosecond pulses at wavelengths 555 or 560 nm. Formation of pairs is justified by corresponding changes of absorption spectra. Conditions of the experiment are in excellent agreement with those predicted by the theory of laser-induced dipole-dipole interaction of QDs. The fraction of QDs assembled into pairs is up to 47%. PMID:27409936

  7. Escherichia coli identification and strain discrimination using nanosecond laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Diedrich, Jonathan; Rehse, Steven J.; Palchaudhuri, Sunil

    2007-04-01

    Three strains of Escherichia coli, one strain of environmental mold, and one strain of Candida albicans yeast have been analyzed by laser-induced breakdown spectroscopy using nanosecond laser pulses. All microorganisms were analyzed while still alive and with no sample preparation. Nineteen atomic and ionic emission lines have been identified in the spectrum, which is dominated by calcium, magnesium, and sodium. A discriminant function analysis has been used to discriminate between the biotypes and E. coli strains. This analysis showed efficient discrimination between laser-induced breakdown spectroscopy spectra from different strains of a single bacteria species.

  8. Comparison of calcium phosphate coatings formed on femtosecond laser-induced and sand-blasted titanium

    NASA Astrophysics Data System (ADS)

    Liang, C. Y.; Yang, X. J.; Wei, Q.; Cui, Z. D.

    2008-11-01

    High energy femtosecond laser process was employed to create regular surface patterning on titanium while sand blasting treatment made a coarse surface. Both laser-induced titanium and blasted titanium could promote the formation of calcium phosphate compounds after the acid and alkali treatment, but little crystallized hydroxyapatite was grown on the laser-induced titanium in 1.5SBF only for 6 h, whereas Ca 4P 6O 19 was formed on the sand-blasted titanium. The femtosecond laser process together with common acid and alkali treatment might provide potential choice to enhance the biocompatibility of titanium and its alloys.

  9. Optimally enhanced optical emission in laser-induced air plasma by femtosecond double-pulse

    NASA Astrophysics Data System (ADS)

    Chen, Anmin; Li, Suyu; Li, Shuchang; Jiang, Yuanfei; Shao, Junfeng; Wang, Tingfeng; Huang, Xuri; Jin, Mingxing; Ding, Dajun

    2013-10-01

    In laser-induced breakdown spectroscopy, a femtosecond double-pulse laser was used to induce air plasma. The plasma spectroscopy was observed to lead to significant increase of the intensity and reproducibility of the optical emission signal compared to femtosecond single-pulse laser. In particular, the optical emission intensity can be optimized by adjusting the delay time of femtosecond double-pulse. An appropriate pulse-to-pulse delay was selected, that was typically about 50 ps. This effect can be especially advantageous in the context of femtosecond laser-induced breakdown spectroscopy, plasma channel, and so on.

  10. Optimally enhanced optical emission in laser-induced air plasma by femtosecond double-pulse

    SciTech Connect

    Chen, Anmin; Li, Suyu; Li, Shuchang; Jiang, Yuanfei; Ding, Dajun; Shao, Junfeng; Wang, Tingfeng; Huang, Xuri; Jin, Mingxing

    2013-10-15

    In laser-induced breakdown spectroscopy, a femtosecond double-pulse laser was used to induce air plasma. The plasma spectroscopy was observed to lead to significant increase of the intensity and reproducibility of the optical emission signal compared to femtosecond single-pulse laser. In particular, the optical emission intensity can be optimized by adjusting the delay time of femtosecond double-pulse. An appropriate pulse-to-pulse delay was selected, that was typically about 50 ps. This effect can be especially advantageous in the context of femtosecond laser-induced breakdown spectroscopy, plasma channel, and so on.

  11. Benefits and applications of laser-induced sparks in real scale model measurements.

    PubMed

    Gómez-Bolaños, Javier; Delikaris-Manias, Symeon; Pulkki, Ville; Eskelinen, Joona; Hæggström, Edward; Jeong, Cheol-Ho

    2015-09-01

    The characteristics of using a laser-induced spark as a monopole source in scale model measurements were assessed by comparison with an electric spark and a miniature spherical loudspeaker. Room impulse responses of first order directivity sources were synthesized off-line using six spatially distributed sparks. The source steering direction was scanned across the horizontal and vertical plane to assess the origin of early reflections. The results confirm that the characteristics of the laser-induced spark outperform those of typical sources. Its monopole characteristics enable the authors to synthesize room responses of directional sources, e.g., to obtain directional information about reflections inside scale models. PMID:26428809

  12. Biological effect of shock waves on rat brain: pathological evaluation by compact Ho:YAG-laser-induced cavitational shock wave generator

    NASA Astrophysics Data System (ADS)

    Nakagawa, Atsuhiro; Hirano, T.; Kusaka, Y.; Sato, Motoyuki; Shirane, R.; Takayama, Kazuya; Yoshimoto, Takashi

    2003-07-01

    To introduce shock wave as a new treatment modality for the lesions in the vicinity of brain and skull, pressure-dependent brain damages after exposure of shock wave were investigated. A novel compact Ho:YAG laser-induced cavitational shock wave generator (diameter: 15 mm, weight: 20g) was used intstead of clinical lithotriptors due to their wide distribution of shock waves. In the first part, we have developed and investigated characteristics of present generator by means of high-speed photography, shadowgraphy, and pressure measurement. Generation of localized shock wave without harmful effect of laser was observed after irradiation of Ho:YAG laser in the brass tube with internal water supply. Mechanical effect of accompanying laser-induced liquid jet was mitigated after placement of latex diaphragm with acrylic water reservoir. Maximum overpressure of generated shock wave was 15 MPa before placement of diaphragm, and 5 MPa after placement of diaphragm. In the second part, shock wave-induced brain damages were investigated in 5 male Sprague-Dawley rats. While subarachnoid hemorrhage could be observed between 1 and 5 MPa, intracerebral hemorrhage, and laceration of tissue were also observed above 5 MPa. We therefore conclude that overpressure of exposing shock wave over brain surface should be managed under 1 MPa.

  13. [Ocular fundus lesions in systemic lupus erythematosus model mice].

    PubMed

    Nakamura, A; Yokoyama, T; Kodera, S; Zhang, D; Hirose, S

    1998-01-01

    To evaluate spontaneous development of the ocular fundus abnormalities associated with collagen disease, we investigated the ocular fundus lesions in systemic lupus erythematosus (SLE) models. (NZW x BXSB) F1 mice were employed as SLE models with antiphospholipid syndrome. The abnormal findings in the ocular fundus were recorded with a fundus camera for small animals (KOWA Co., Ltd.), and the chorioretinal lesions were studied histopathologically. As in the systemic symptoms of SLE, the incidence of ocular fundus abnormalities in these (NZW x BXSB) F1 mice was significantly higher in males than in females, suggesting the influence of the Yaa (Y chromosome-linked autoimmune acceleration) gene. Lesions in the fundus appeared in the form of white spots, which increased in number along with the course of the disease. The lesion developed into retinal detachment in some animals. Dilatation of veins and narrowing of arteries were marked. These lesions were very similar to multifocal posterior pigment epitheliopathy (MPPE) in humans in that white spots appear first and then develop into exudative retinal detachment caused by retinal pigment epithelial disorder. Histopathological findings included 1. structural destruction of the photoreceptor cell layer, 2. degeneration and loss of the retinal pigment epithelium, and 3. narrowing and occlusion of the choriocapillaris associated with thrombus formation, cellular infiltration into the surrounding tissues, and wall thickening of the choroidal arterioles. The study of these SLE mouse may contribute to the elucidation of abnormalities in the fundus associated with collagen diseases, including the relationship between thrombus formation and antiphospholipid syndrome. PMID:9489364

  14. Adjunctive use of systematic retinal thickness map analysis to monitor disease activity in punctate inner choroidopathy.

    PubMed

    Madhusudhan, Savitha; Keane, Pearse A; Denniston, Alastair K

    2016-12-01

    A challenge in the management of 'white dot syndromes' is the lack of sensitive objective measures of disease activity. Retinal thickness maps from spectral domain optical coherence tomography (SD-OCT) inform treatment decisions in other retinal conditions such as age-related macular degeneration and diabetic maculopathy. In this report, we demonstrate their value in providing quantitative monitoring of a patient with punctate inner choroidopathy (PIC). Retinal thickness maps referenced against a baseline scan reliably detected focal areas of increased macular volume in active PIC lesions during symptomatic episodes, highlighting these as 'hot spots' that could be quantified, providing an objective basis for treatment decisions. PMID:26965893

  15. MR-Guided Laser-Induced Thermotherapy of the Infratemporal Fossa and Orbit in Malignant Chondrosarcoma via a Modified Technique

    SciTech Connect

    Vogl, Thomas J.; Mack, Martin G.; Straub, Ralf; Eichler, Katrin; Zangos, Stephan

    2001-12-15

    A 76-year-old patient presented with a recurrent mass of a malignant chondrosarcoma in the right infratemporal fossa and in the left maxillary sinus with orbital invasion. The patient was treated with a palliative intention with MR-guided laser-induced thermotherapy using a modified applicator technique. Following treatment clinical symptoms improved and MRI revealed complete laser-induced tumor necrosis.

  16. Tissue temperature control using a water-cooled applicator: implications for transurethral laser-induced thermotherapy of benign prostatic hyperplasia.

    PubMed

    Sturesson, C; Andersson-Engels, S

    1997-03-01

    A prototype to a water-cooled applicator to be used in transurethral laser-induced thermotherapy of benign prostatic hyperplasia was developed. The flexible applicator was made of Teflon tubes except for the distal outer part which was made of glass, providing a transparent medium for laser radiation and enabling efficient cooling of the surrounding tissue. For heating, laser light from a Nd:YAG laser emitting at 1064 nm, which was coupled into an optical fiber with an institutionally made diffusing tip, was used. Cooling was performed by flushing water through the applicator. By using a mathematical model it was possible to connect the temperature rise of the water in the applicator to the maximum tissue temperature. Tissue light absorption was calculated using Monte Carlo simulations and the heat conduction equation was solved numerically using a finite-difference technique. Experiments on porcine liver in vitro showed that the maximum tissue temperature could be estimated with an average accuracy of 0.4 degree C by measuring the difference in outlet and inlet applicator water temperature and using the thermal model. The results presented suggest that the described method for temperature control can be used during laser prostatectomy to maximize the lesion size while preventing carbonization. PMID:9089598

  17. Vessel Segmentation in Retinal Images Using Multi-scale Line Operator and K-Means Clustering

    PubMed Central

    Saffarzadeh, Vahid Mohammadi; Osareh, Alireza; Shadgar, Bita

    2014-01-01

    Detecting blood vessels is a vital task in retinal image analysis. The task is more challenging with the presence of bright and dark lesions in retinal images. Here, a method is proposed to detect vessels in both normal and abnormal retinal fundus images based on their linear features. First, the negative impact of bright lesions is reduced by using K-means segmentation in a perceptive space. Then, a multi-scale line operator is utilized to detect vessels while ignoring some of the dark lesions, which have intensity structures different from the line-shaped vessels in the retina. The proposed algorithm is tested on two publicly available STARE and DRIVE databases. The performance of the method is measured by calculating the area under the receiver operating characteristic curve and the segmentation accuracy. The proposed method achieves 0.9483 and 0.9387 localization accuracy against STARE and DRIVE respectively. PMID:24761376

  18. Retinal Detachment: Torn or Detached Retina Diagnosis

    MedlinePlus

    ... Eye Health / Eye Health A-Z Detached or Torn Retina Sections Retinal Detachment: What Is a Torn ... Retina Treatment Retinal Detachment Vision Simulator Retinal Detachment: Torn or Detached Retina Diagnosis Written by: Kierstan Boyd ...

  19. Retinal Detachment: Torn or Detached Retina Symptoms

    MedlinePlus

    ... Eye Health / Eye Health A-Z Detached or Torn Retina Sections Retinal Detachment: What Is a Torn ... Retina Treatment Retinal Detachment Vision Simulator Retinal Detachment: Torn or Detached Retina Symptoms Written by: Kierstan Boyd ...

  20. Effect of surrounding gases and water vapor on the induced electric current associated with a laser-induced plasma

    NASA Astrophysics Data System (ADS)

    Matsuta, Hideyuki

    2016-04-01

    The effect of surrounding gases and water vapor on the laser-induced electric current was investigated. Laser-induced plasma was generated on an aluminum alloy target. The laser-induced plasma was optically examined to estimate the excitation temperature and electron density in room air. There was a linear relationship between the maximum amplitude of the laser-induced current and the electron density. As the electron mean free path of the surrounding gas increased, the observed amplitude of the current increased. The amplitude of the induced current signal in dry air became maximum upon mixing with the optimum amount of water vapor. This enhancement of the induced current signal might be due to the large relative permittivity of water vapor. The laser-induced plasma as a whole seems to be a low-temperature plasma consisting of electrons, a large amount of cold surrounding gas, injected hot atoms, hot ions, and hot particles.

  1. Small Animal Retinal Imaging

    NASA Astrophysics Data System (ADS)

    Choi, WooJhon; Drexler, Wolfgang; Fujimoto, James G.

    Developing and validating new techniques and methods for small animal imaging is an important research area because there are many small animal models of retinal diseases such as diabetic retinopathy, age-related macular degeneration, and glaucoma [1-6]. Because the retina is a multilayered structure with distinct abnormalities occurring in different intraretinal layers at different stages of disease progression, there is a need for imaging techniques that enable visualization of these layers individually at different time points. Although postmortem histology and ultrastructural analysis can be performed for investigating microscopic changes in the retina in small animal models, this requires sacrificing animals, which makes repeated assessment of the same animal at different time points impossible and increases the number of animals required. Furthermore, some retinal processes such as neurovascular coupling cannot be fully characterized postmortem.

  2. Inherited Retinal Degenerative Disease Registry

    ClinicalTrials.gov

    2016-03-21

    Eye Diseases Hereditary; Retinal Disease; Achromatopsia; Bardet-Biedl Syndrome; Bassen-Kornzweig Syndrome; Batten Disease; Best Disease; Choroidal Dystrophy; Choroideremia; Cone Dystrophy; Cone-Rod Dystrophy; Congenital Stationary Night Blindness; Enhanced S-Cone Syndrome; Fundus Albipunctatus; Goldmann-Favre Syndrome; Gyrate Atrophy; Juvenile Macular Degeneration; Kearns-Sayre Syndrome; Leber Congenital Amaurosis; Refsum Syndrome; Retinitis Pigmentosa; Retinitis Punctata Albescens; Retinoschisis; Rod-Cone Dystrophy; Rod Dystrophy; Rod Monochromacy; Stargardt Disease; Usher Syndrome

  3. [News in Retinal Imaging].

    PubMed

    Werkmeister, R; Schmidl, D; Garhöfer, G; Schmetterer, L

    2015-09-01

    New developments in retinal imaging have revolutionised ophthalmology in recent years. In particular, optical coherence tomography (OCT) provides highly resolved and well reproducible images and has rung in a new era in ophthalmological imaging. The technology was introduced in the early 1990 s, and has rapidly developed. There have been improvements in resolution, sensitivity and processing speed. There have also been developments in functional processing. OCT angiography is the first application in routine clinical work. PMID:26372783

  4. Laser-induced fluorescence of metal-atom impurities in a neutral beam

    SciTech Connect

    Burrell, C.F.; Pyle, R.V.; Sabetimani, Z.; Schlachter, A.S.

    1984-10-01

    The need to limit impurities in fusion devices to low levels is well known. We have investigated, by the technique of laser-induced fluorescence, the concentration of heavy-metal atoms in a neutral beam caused by their evaporation from the hot filaments in a conventional high-current multifilament hydrogen-ion source.

  5. Laser-Induced Damage Threshold and Certification Procedures for Optical Materials

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This document provides instructions for performing laser-induced-damage-threshold tests and pass-fail certification tests on optical materials used in pulsed-laser systems. The optical materials to which these procedures apply include coated and uncoated optical substrates, laser crystals, Q-switches, polarizers, and other optical components employed in pulsed-laser systems.

  6. Means and method for capillary zone electrophoresis with laser-induced indirect fluorescence detection

    DOEpatents

    Yeung, Edwards; Kuhr, Werner G.

    1991-04-09

    A means and method for capillary zone electrphoresis with laser-induced indirect fluorescence detection. A detector is positioned on the capillary tube of a capillary zone electrophoresis system. The detector includes a laser which generates a laser beam which is imposed upon a small portion of the capillary tube. Fluorescence of the elutant electromigrating through the capillary tube is indirectly detected and recorded.

  7. Recognition of edible oil by using BP neural network and laser induced fluorescence spectrum

    NASA Astrophysics Data System (ADS)

    Mu, Tao-tao; Chen, Si-ying; Zhang, Yin-chao; Guo, Pan; Chen, He; Zhang, Hong-yan; Liu, Xiao-hua; Wang, Yuan; Bu, Zhi-chao

    2013-09-01

    In order to accomplish recognition of the different edible oil we set up a laser induced fluorescence spectrum system in the laboratory based on Laser induced fluorescence spectrum technology, and then collect the fluorescence spectrum of different edible oil by using that system. Based on this, we set up a fluorescence spectrum database of different cooking oil. It is clear that there are three main peak position of different edible oil from fluorescence spectrum chart. Although the peak positions of all cooking oil were almost the same, the relative intensity of different edible oils was totally different. So it could easily accomplish that oil recognition could take advantage of the difference of relative intensity. Feature invariants were extracted from the spectrum data, which were chosen from the fluorescence spectrum database randomly, before distinguishing different cooking oil. Then back propagation (BP) neural network was established and trained by the chosen data from the spectrum database. On that basis real experiment data was identified by BP neural network. It was found that the overall recognition rate could reach as high as 83.2%. Experiments showed that the laser induced fluorescence spectrum of different cooking oil was very different from each other, which could be used to accomplish the oil recognition. Laser induced fluorescence spectrum technology, combined BP neural network,was fast, high sensitivity, non-contact, and high recognition rate. It could become a new technique to accomplish the edible oil recognition and quality detection.

  8. Study of mid IR fiber transmission and mode patterns under laser induced stimulated Brillouin scattering

    NASA Technical Reports Server (NTRS)

    Yu, C.; Chong, Yat C.; Zhou, Hongyi

    1990-01-01

    Mid IR fiber transmission and exit radiation mode patterns at various incident CO2 laser power levels appear to be effective diagnostic tools for monitoring laser induced stimulated Brillouin scattering in various mid IR fibers. Such processes are deemed to be essential mechanisms for fiber-optic amplifiers and switches as potential replacements of current repeaters and bistable devices.

  9. North American Symposium on Laser Induced Breakdown Spectroscopy (NASLIBS): introduction to feature issue.

    PubMed

    Singh, Jagdish P; Almirall, Jose; Sabsabi, Mohamad; Miziolek, Andrzej W

    2012-03-01

    This feature issue highlights the topics of the 2011 North American Symposium on Laser Induced Breakdown Spectroscopy (NASLIBS). These include LIBS application to Security and Forensic, Biomedical and Environmental, Liquid Analysis and Fundamentals of LIBS, Instrumentation/Commercialization, Fusion with LIBS, and New Frontiers. PMID:22410934

  10. Raman and Fluorescence Study of Erbium-Doped Laser-Induced Crystals-in-Glass

    NASA Astrophysics Data System (ADS)

    Knorr, Brian; Veenhuizen, Keith; Stone, Adam; Jain, Himanshu; Dierolf, Volkmar

    Laser induced crystallization of glasses is a spatially selective process which has the potential to produce photonic integrated circuits in a glass matrix. Low temperature Combined Excitation Emission Spectroscopy in Er:LaBGeO5 show that erbium incorporates at predominantly one majority site in both glass-ceramics and laser-induced crystals-in-glass, but that other minority sites also exist. The energy levels of the majority site were quantified. The fluorescence characteristics of the erbium ions in any site in the laser-induced crystals were found to be only weakly influenced by the irradiation conditions during growth. On the other hand, a hidden parameter, potentially boron deficiency-related defects, resulted in a significant change in the incorporation behavior of the erbium ions. Simultaneous scanning confocal Raman and fluorescence spectroscopy showed that the energies of the Raman modes are shifted, and the erbium fluorescence intensity varies, in a non-uniform manner, despite the host glass being homogeneously doped, across the cross-sections of laser-induced crystals in glass. These fluctuations within the Raman and fluorescence are spatially correlated, implying that different erbium sites form preferentially at different locations in the crystal cross-section.

  11. Use of laser induced breakdown spectroscopy for the analysis of poultry products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Laser Induced Breakdown Spectroscopy is evaluated as a potential method to characterize a wide range of poultry product quality and safety characteristics. In one part of this study, breast meat quality indices, including pH and water holding capacity, were treated as dependent variables for correla...

  12. Optimization study of the femtosecond laser-induced forward-transfer process with thin aluminum films

    NASA Astrophysics Data System (ADS)

    Bera, Sudipta; Sabbah, A. J.; Yarbrough, J. M.; Allen, C. G.; Winters, Beau; Durfee, Charles G.; Squier, Jeff A.

    2007-07-01

    The parameters for an effective laser-induced forward-transfer (LIFT) process of aluminum thin films using a femtosecond laser are studied. Deposited feature size as a function of laser fluence, donor film thickness, quality of focus, and the pulse duration are varied, providing a metric of the most desirable conditions for femtosecond LIFT with thin aluminum films.

  13. Laser-induced blood serum fluorescence and Raman spectroscopy for cancer diagnosis

    NASA Astrophysics Data System (ADS)

    Li, Xiaozhou; Wang, Qiuyu; Lin, Junxiu

    1999-09-01

    Laser induced auto-fluorescence and Raman spectra of serum from cancerous and normal people are measured and analyzed. The content of (beta) -carotene in the serum from normal man is higher than that from the cancerous one, this result agrees with other reports.

  14. Means and method for capillary zone electrophoresis with laser-induced indirect fluorescence detection

    DOEpatents

    Yeung, Edward S.; Kuhr, Werner G.

    1996-02-20

    A means and method for capillary zone electrphoresis with laser-induced indirect fluorescence detection. A detector is positioned on the capillary tube of a capillary zone electrophoresis system. The detector includes a laser which generates a laser beam which is imposed upon a small portion of the capillary tube. Fluorescence of the elutant electromigrating through the capillary tube is indirectly detected and recorded.

  15. Impulse characteristics of laser-induced blast wave in monoatomic gases

    NASA Astrophysics Data System (ADS)

    Yu, X. L.; Ohtani, T.; Sasoh, A.; Kim, S.; Urabe, N.; Jeung, I.-S.

    The paper focuses on physical gas-dynamic characteristics of impulse generation by laser Induced blast wave (LIBW) in a laser-driven in tube accelerator (LITA). Propagation, reflection of blast wave and wave structure were intensively studied by using an ICCD camera system through shadowgraph.

  16. Application of laser-induced fluorescence to neoplasm diagnosis using bis-1[alanylo-N]ethylodeuteroporphyrin

    NASA Astrophysics Data System (ADS)

    Kwasny, Miroslaw; Mierczyk, Zygmunt; Graczyk, Alfreda; Chwirot, S.; Chwirot, B. W.; Pirozynska, E.; Zuchewicz, K.

    1996-03-01

    This study presents possibilities of neoplasm localization applying the laser-induced fluorescence method using new porphyrin derivatives -- complexes of protoporphyrin and amino acids. These compounds show a strong retention in diseased tissues. Their spectral characteristics and photosensitizing properties are similar to hematoporphyrin derivatives, so they can be used both in the photodynamic therapy method and neoplasm diagnosis.

  17. [The Spectral Analysis of Laser-Induced Plasma in Laser Welding with Various Protecting Conditions].

    PubMed

    Du, Xiao; Yang, Li-jun; Liu, Tong; Jiao, Jiao; Wang, Hui-chao

    2016-01-01

    The shielding gas plays an important role in the laser welding process and the variation of the protecting conditions has an obvious effect on the welding quality. This paper studied the influence of the change of protecting conditions on the parameters of laser-induced plasma such as electron temperature and electron density during the laser welding process by designing some experiments of reducing the shielding gas flow rate step by step and simulating the adverse conditions possibly occurring in the actual Nd : YAG laser welding process. The laser-induced plasma was detected by a fiber spectrometer to get the spectral data. So the electron temperature of laser-induced plasma was calculated by using the method of relative spectral intensity and the electron density by the Stark Broadening. The results indicated that the variation of protecting conditions had an important effect on the electron temperature and the electron density in the laser welding. When the protecting conditions were changed, the average electron temperature and the average electron density of the laser-induced plasma would change, so did their fluctuation range. When the weld was in a good protecting condition, the electron temperature, the electron density and their fluctuation were all low. Otherwise, the values would be high. These characteristics would have contribution to monitoring the process of laser welding. PMID:27228732

  18. Long-distance remote laser-induced breakdown spectroscopy using filamentation in air

    NASA Astrophysics Data System (ADS)

    Stelmaszczyk, Kamil; Rohwetter, Philipp; Méjean, Guillaume; Yu, Jin; Salmon, Estelle; Kasparian, Jérôme; Ackermann, Roland; Wolf, Jean-Pierre; Wöste, Ludger

    2004-11-01

    We demonstrate remote elemental analysis at distances up to 90m, using a laser-induced breakdown spectroscopy scheme based on filamentation induced by the nonlinear propagation of unfocused ultrashort laser pulses. A detailed signal analysis suggests that this technique, remote filament-induced breakdown spectroscopy, can be extended up to the kilometer range.

  19. Prospects for single-molecule detection in liquids by laser-induced fluorescence

    SciTech Connect

    Trkula, M.; Keller, R.A.; Martin, J.C.; Jett, J.H.; Dovichi, N.J.

    1983-01-01

    A laser-induced fluoresence determination of aqueous solutions of rhodamine 6G resulted in a detection limit of 18 attograms, or 22,000 molecules, of rhodamine 6G. These results allow the projection to single-molecule detection with reasonable improvements in the experimental apparatus.

  20. Use of laser-induced ionization to detect soot inception in premixed flames

    SciTech Connect

    Manzello, Samuel L.; Lee, Eui Ju; Mulholland, George W

    2005-08-20

    Experimental measurements of laser-induced ionization were performed for ethene-air premixed flames operated near the soot inception point. Soot was ionized with a pulsed laser operated at 532 nm. The ionization signal was collected with a tungsten electrode located in the postflame region. Ionization signals were collected by use of both single-electrode and dual-electrode configurations. Earlier laser-induced- ionization studies focused on the use of a single biased electrode to generate the electric field, with the burner head serving as the path to ground. In many practical combustion systems, a path to ground is not readily available. To apply the laser-induced- ionization diagnostic to these geometries, a dual-electrode geometry must be employed. The influence of electrode configuration, flame equivalence ratio, and flame height on ionization signal detection was determined. The efficacy of the laser-induced-ionization diagnostic in detecting soot inception in the postflame region of a premixed flame by use of a dual-electrode configuration was investigated. Of the dual-electrode configurations tested, the dual-electrode geometry oriented parallel to the laser beam was observed to be most sensitive for detecting the soot inception point in a premixed flame.