Science.gov

Sample records for laser-induced retinal lesions

  1. Neuroprotective Treatment of Laser-Induced Retinal Injuries

    DTIC Science & Technology

    2001-10-01

    to evaluate the neuroprotective effect of dextromethorphan , memantine and brimonidine in our rat model of laser- induced retinal-lesions Methods: Argon... dextromethorphan , memantine or brimonidine. The control groups (18 rats for each compound) received the solvent at the same volume and schedule as...size and the magnitude of photoreceptor nuclei loss within the lesions. Conclusions: Systemic treatments with dextromethorphan , memantine or brimonidine

  2. Effects of methylprednisolone on laser-induced retinal injuries

    NASA Astrophysics Data System (ADS)

    Rosner, Mordechai; Tchirkov, Marina; Dubinski, Galina; Solberg, Yoram; Belkin, Michael

    1997-05-01

    Methylprednisolone have been demonstrated to ameliorate retinal photic injury. In the current study we examined its effect on laser induced retinal injury. Retinal lesions were inflicted by argon laser in 36 pigmented DA rats. The treated groups received intra-peritoneally methylprednisolone in saline, injected 3 times a day for 2 days, starting immediately after exposure. The controls received the vehicle on the same schedule. The rats were sacrificed 3, 20 or 60 days after laser exposure and the lesions were evaluated by light microscopy and morphometric measurements. Laser injuries were associated with disruption of the outer retinal layers. Three and 20 days after exposure, the loss of the photoreceptor-cell nuclei was significantly milder in the treated groups as compared with controls. There was no difference 60 days after exposure. In conclusion, methylprednisolone reduced temporarily the photoreceptor cell loss in argon laser induced retinal injury, when treatment was started immediately after laser exposure. There was no long term effect.

  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. Laser Induced Retinal Damage Thresholds for Annular Retinal Beam Profiles

    DTIC Science & Technology

    2004-01-01

    Thompson-Gerstman granular model of laser-induced thermal damage to the retina ."°20 The study documented in this paper is a continuation of our earlier...Retinal Beam Profiles DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report: TITLE: Laser Interaction...mrad of visual field; which correspond to outer beam diameters of roughly 70, 160, and 300 tin, respectively, on the primate retina . Annular beam

  5. Copolymer-1 vaccination regimens for neuroprotection in laser-induced retinal injuries

    NASA Astrophysics Data System (ADS)

    Belokopytov, Mark; Dubinsky, Galina; Belkin, Michael; Epstein, Yoram; Rosner, Mordechai

    2005-04-01

    The neuroprotective effect of immunization by glatiramer acetate (Copolymer-1, Cop-1, Copaxone) in adjuvant against laser-induced retinal damage was previously reported. The present study quantitatively compares various regimens of this vaccination for reducing the spread of laser-induced retinal damage and investigates the cellular mechanism of Cop-1 activity. Standard argon laser lesions were created in 78 DA pigmented rats divided into five groups: three Cop-1 single treatment groups (treated 7 days before, immediately after, or 24 hours after the injury), one group treated twice (7 days before and 20 days after injury), and a control group treated with adjuvant 7 days before the injury. The retinal lesions were evaluated 3, 20, and 60 days after the injury. Immunostaining of the retinas of the pretreated and control group animals 3 days after the laser injury was performed for T-cell detection. Cop-1 pre-immunization reduced photoreceptor loss at all time points as measured over the central zone of the lesion and 3 and 20 days after lasing as measured over the whole damaged area. Lesion diameter was reduced only 60 days after laser injury in pre-treated animals. Cop-1 given immediately after injury reduced cell loss as measured 20 and 60 days later in the whole lesion and 20 days after the laser irradiation, when measured in the center of lesion. It had no effect on lesion diameter. Late treatment reduced only the lesion diameter at all time points. Repeated treatment enhanced the neuroprotective effect, decreasing the cell loss in the center of lesion and reducing the diameter of lesion. T-cells were detected in the retinal lesions of pre-immunized animals and not in non-treated group, demonstrating the cellular immune mechanism of Cop-1. Immunization with Cop-1 is neuroprotective against laser-induced retinal injuries, and repeating the treatment enhances this effect. Cellular immune action of Cop-1 of was detected.

  6. 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.

  7. 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

  8. Research towards development of a dynamic reflectometer for control of laser-induced retinal photocoagulation

    NASA Astrophysics Data System (ADS)

    Frish, Michael B.; Pierce, Vicky G.; Ferguson, R. D.; Birngruber, Reginald

    1992-08-01

    Laser-induced photocoagulation is used routinely to treat a variety of retinal disorders. In this procedure, absorption by the retina and choroid of focused laser light creates thermal lesions that provide the therapeutic effect. The treatment endpoint is determined by the ophthalmoscopical visibility of the coagulation resulting from the increased diffuse reflectivity of the fundus at the lesion site. To date, it is impossible, prior to treatment, to predict the effectiveness of a specific dosage of laser radiation -- the result can be assessed only after the exposure, and only subjectively. To avoid side effects like hemorrhage, macular pucker, and post-coagulative retinal detachments that can result from excessive local heating, a device for automatically controlling the laser exposure parameters is needed. Preliminary research aimed toward development of such a device has now been completed. The technique employs a simple electro-optical detector to monitor the changing reflectivity of the lesion during the laser exposure, and couples that information to a microcontroller which automatically adjusts the laser exposure parameters. The first results of a clinically realistic device are reported.

  9. Transplantation of quantum dot-labelled bone marrow-derived stem cells into the vitreous of mice with laser-induced retinal injury: survival, integration and differentiation.

    PubMed

    Wang, Heuy-Ching; Brown, Jeremiah; Alayon, Helena; Stuck, Bruce E

    2010-03-31

    Accidental laser exposure to the eyes may result in serious visual impairment due to retina degeneration. Currently limited treatment is available for laser eye injury. In the current study, we investigated the therapeutic potential of bone marrow-derived stem cells (BMSCs) for laser-induced retinal trauma. Lineage negative bone marrow cells (Lin(-) BMCs) were labelled with quantum dots (Qdots) to track the cells in vivo. Lin(-) BMCs survived well after intravitreal injection. In vivo bromodeoxyuridine (BrdU) labelling showed these cells continued to proliferate and integrate into injured retinas. Furthermore, they expressed markers that distinguished retinal pigment epithelium (RPE), endothelium, pericytes and photoreceptors. Our results suggest that BMSCs participate in the repair of retinal lesions by differentiating into retinal cells. Intravitreal transplantation of BMSCs is a potential treatment for laser-induced retinal trauma. Published by Elsevier Ltd.

  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. Fundamental Studies in the Molecular Basis of Laser Induced Retinal Damage.

    DTIC Science & Technology

    1986-12-31

    N-retinylidene Schiff bases (NRB) and N-retinylidene protonated Schiff bases (NRBH). The direct method was unable to detect any differences in the...RESOLUTIOM TESI CHAWI NATIONAL BUR[A4 OF STANOARDS 1%,3-A AD__ _ _ _ _ FUNDAMENTAL STUDIES IN THE MOLECULAR BASIS OF LASER INDUCED RETINAL DAMAGE ANNUAL... based on this guiding framework ....................... 8 III. Superresolution Near-field Scanning Optical Microscopy ............. 12 REFERENCES

  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. Therapeutic effect of bone marrow mesenchymal stem cells on laser-induced retinal injury in mice.

    PubMed

    Jiang, Yuanfeng; Zhang, Yan; Zhang, Lingjun; Wang, Meiyan; Zhang, Xiaomin; Li, Xiaorong

    2014-05-27

    Stem cell therapy has shown encouraging results for neurodegenerative diseases. The retina provides a convenient locus to investigate stem cell functions and distribution in the nervous system. In the current study, we investigated the therapeutic potential of bone marrow mesenchymal stem cells (MSCs) by systemic transplantation in a laser-induced retinal injury model. MSCs from C57BL/6 mice labeled with green fluorescent protein (GFP) were injected via the tail vein into mice after laser photocoagulation. We found that the average diameters of laser spots and retinal cell apoptosis were decreased in the MSC-treated group. Interestingly, GFP-MSCs did not migrate to the injured retina. Further examination revealed that the mRNA expression levels of glial fibrillary acidic protein and matrix metalloproteinase-2 were lower in the injured eyes after MSC transplantation. Our results suggest that intravenously injected MSCs have the ability to inhibit retinal cell apoptosis, reduce the inflammatory response and limit the spreading of damage in the laser-injured retina of mice. Systemic MSC therapy might play a role in neuroprotection, mainly by regulation of the intraocular microenvironment.

  14. 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.

  15. Magic angle magnetic resonance imaging of diode laser induced and naturally occurring lesions in equine tendons.

    PubMed

    Spriet, Mathieu; Murphy, Brian; Vallance, Stuart A; Vidal, Martin A; Whitcomb, Mary Beth; Wisner, Erik R

    2012-01-01

    Magic angle magnetic resonance (MR) imaging consists of imaging tendons at 55° to the magnetic field. In people, magic angle MR imaging is valuable for detection of chronic tendon lesions and allows calculation of tendon T1 values. Increased T1 values occur in people with chronic tendinopathy. The T1 values of normal equine tendons have been reported but there are no available data for abnormal equine tendons. Twelve limbs were studied. Two limbs had diode laser tendon lesions induced postmortem, four limbs had diode laser tendon lesions induced in vivo and six limbs had naturally occurring tendon lesions. The limbs were imaged at 1.5 T using both conventional MR imaging and magic angle MR imaging. The post-mortem laser induced lesions were identified only with magic angle MR imaging. The in vivo induced lesions and naturally occurring lesions were identified with both techniques but had a different appearance with the two imaging techniques. Magic angle imaging was helpful at identifying lesions that were hypointense on conventional imaging. Increased T1 values were observed in all abnormal tendons and in several tendons with a subjectively normal MR appearance. The increased T1 value may reflect diffuse changes in the biochemical composition of tendons. Magic angle imaging has potential as a useful noninvasive tool to assess the changes of the extracellular tendon matrix using T1 values.

  16. 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.

  17. 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.

  18. Investigating the recovery period of rat brain tissue after electrolytic and 980-nm laser induced lesions

    NASA Astrophysics Data System (ADS)

    Bozkulak, Ozguncem; Tabakoglu, H. Ozgur; Aksoy, Ayla; Canbeyli, Resit; Bilgin, Nes'e.; Kurtkaya, Ozlem; Sav, Aydin; Gulsoy, Murat

    2003-10-01

    The effects of 980-nm diode laser and electrolytic lesions in Wistar rat brain tissue were observed by immunohistochemical staining for CD68 marker and Hematoxylin-Eosin (H&E). Bilateral lesions; laser lesions (2W/2sec) in the right hemispheres, and electrolytic lesions (1.5mA/20sec) in the left hemispheres were done through in vivo stereotaxic neurosurgical procedure. Subjects were classified into three groups due to the recovery period. Subjects in Group I, II, and III were sacrificed after 0, 2 and 7 days of recovery period respectively. After saline perfusion their brains were dislocated, and paraffin embedded sections were taken. One section for H&E and one for CD68 were cut consecutively in 3μm thickness by examining the lesion in every 30-μm thickness. CD68 was found more efficient marker than H&E in observing the after-effects of both types of lesions. The total damage of laser was smaller than that of electrosurgical unit. The shape of the ablated area in laser induced lesions was more spherical than that of electrosurgical unit. The number of macrophages increased as the recovery period increased for all subjects. Group III showed the highest number of macrophages in three, and the number of macrophages around electrolytic lesion is nearly 1.5 times higher than that of laser lesion. The remarkable ablating ability, the damage zone created and the healing of nearby tissue clearly showed that the 980-nm diode laser is an effective and useful alternative to electrosurgical unit in neurosurgery.

  19. Lesion Optimization for Laser Ablation: Fluid Evacuation Prior to Laser-Induced Thermal Therapy.

    PubMed

    Wong, Timothy; Patel, Nitesh V; Feiteiro, Filipe; Danish, Shabbar F; Hanft, Simon

    2017-08-01

    Magnetic resonance-guided laser-induced thermal therapy (MRgLITT) is a minimally invasive surgical procedure for ablating intracranial lesions. The presence of a fluid body can sequester thermal energy generated by the laser catheter, which compromises the performance of MRgLITT, resulting in suboptimal ablation of cystic lesions. We report our use of stereotactic fluid evacuation followed by MRgLITT in 2 patients with cystic brain tumors. This is the first report on lesion optimization by fluid aspiration before MRgLITT. Two cystic tumors in 2 patients were treated. In 1 patient, an external ventricular drain was placed stereotactically to allow drainage of cystic fluid 1 day before laser ablation. In the second patient, a stereotactic biopsy needle was used to aspirate the cystic fluid immediately before laser ablation. The remaining solid portions of the both tumors were ablated using the Visualase system. Both patients were followed clinically and radiologically after the procedures. Stereotactic placement of an external ventricular drain and a biopsy needle both successfully resulted in fluid evacuation. MRgLITT was performed without any complications in both patients after fluid evacuation. Both patients demonstrated clinical and radiologic improvement after the procedure. Cystic fluid evacuation is a promising strategy for optimizing intracranial cystic lesions for MRgLITT. This novel approach may broaden the utility of MRgLITT in the management of various technically demanding lesions. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Laser-induced breakdown spectroscopy of dental lesions: diagnostic and therapeutic monitoring tool

    NASA Astrophysics Data System (ADS)

    Borisova, Ekaterina; Uzunov, Tzonko; Penev, Dimitar; Genova, Tsanislava; Avramov, Latchezar

    2016-01-01

    The carious decay develops a tiny area of demineralization on the enamel, which could be detected by element analytic techniques such as laser-induced breakdown spectroscopy (LIBS). That demineralization can quickly turn into a large lesion inside the tooth, it is often discovered too late to prevent the kind of decay that leads to cavities. The same optical LIBS detection approach could be used for monitoring of the caries removal using laser ablation or drilling techniques. For LIBS measurements we applied LIBS 2500Plus (Ocean Optics Inc., Dunedin, USA) system, which consists of seven spectrometric channels, covering spectral region from 200 to 980 nm, which optical resolution 0,05 nm, the spectrometers are connected with sample fiber bundle for 7-channels spectral system to the chamber for solid and liquid samples, Q-switched Nd:YAG laser, at 1 064 nm, with energy per pulse - 40 mJ, which is applied to induce plasma in the samples. LIBS spectra were obtained after single shot of the laser in the region of pathology. Samples investigated by LIBS are extracted teeth from patients, with periodontal problems on different stage of carious lesions, and their LIBS spectra are compared with the LIBS signals obtained from normal enamel and dentine tissues to receive complete picture of the carious lesion development. The major line of our investigations is related to the development of a methodology for real-time optical feedback control during selective ablation of tooth tissues using LIBS. Tooth structures, with and without pathological changes, are compared and their LIBS element analysis is used to differentiate major changes, which occur during tooth carious process and growth.

  1. Assessment of different excitation wavelengths for photodetecting neoplastic urothelial lesions by laser-induced autofluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Anidjar, Maurice; Cussenot, Oliver; Avrillier, Sigrid; Ettori, Dominique; Teillac, Pierre; Le Duc, Alain

    1996-04-01

    We have designed a program using laser induced autofluorescence spectroscopy as a possible way to characterize urothelial tumors of the bladder. The autofluorescence spectra were compared between normal, suspicious and tumor areas of human bladder. Three different pulsed laser wavelengths were used for excitation: 308 nm (excimer), 337 nm (nitrogen) and 480 nm (dye laser). Excitation light was delivered by a specially devised multifiber catheter introduced through the working channel of a regular cystoscope under saline irrigation. The fluorescence light was focused into an optical multichannel analyzer detection system. The data was evaluated in 25 patients immediately before resection of a bladder tumor. Spectroscopic results were compared with histopathology. Upon 337 nm and 480 nm excitations, the overall intensity of the fluorescence spectra from bladder tumors was clearly reduced in comparison with normal urothelium, regardless of the stage and the grade of the tumor. upon 308 nm excitation, the shape of tumor fluorescence spectra, including carcinoma in situ, differed drastically from that of normal tissue. In this case, no absolute intensity measurements are needed and clear diagnosis can be achieved from fluorescence intensity ratio (360/440 nm). This spectroscopic study could be particularly useful for the design of a simplified autofluorescence imaging device for real-time routine detection of occult urothelial neoplastic lesions.

  2. 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

  3. 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.

  4. Utilization of scanning laser ophthalmoscopy in laser-induced bilateral human retinal nerve fiber layer damage

    NASA Astrophysics Data System (ADS)

    Zwick, Harry; Gagliano, Donald A.; Ruiz, S.; Stuck, Bruce E.

    1995-05-01

    In this paper, we describe a military laser accident case where bilateral Q-switched laser exposure resulted in bilateral macular damage with immediate visual acuity loss in one eye (OS) and delayed visual acuity loss in the other exposed eye (OD), where retinal damage appeared more parafoveal. At 6 weeks post exposure, OS had recovered to 20/17 and OD had dropped to 20/100 Snellen activity. Retinal nerve fiber damage was observed in both eyes at this time. Contrast sensitivity measurements made in OS were suppressed across all spatial frequencies, even though Snellen acuity measured in the normal range. More severe high spatial frequency loss in contrast was measured in the right eye as well as low spatial frequency loss. Both OS and OD revealed a parafoveal preferred retinal locus with scanning laser ophthalmoscopy contrast sensitivity measurements, suggesting parafoveal retinal compensatory processes.

  5. Fundamental Studies in the Molecular Basis of Laser Induced Retinal Damage

    DTIC Science & Technology

    1989-12-30

    absorption of light in the chromophore. In all visual pigments, the chromophore is a derivative of retinal ( Vitamin A aldehyde). Thus, a detailed...average angle 8 to the subphase normal but have a random distribution of azimuthal angle, then ɘ> ZzZ- PcOs 3 0 <P>z - -L Psin 20cosO 5 The vanishing

  6. Laser-induced retinal damage threshold for repetitive-pulse exposure to 100-microsecs pulses

    DTIC Science & Technology

    2014-10-07

    summation (PS) model of Menendez et al.15–17 For this injury mechanism, the cumulative threshold is depen dent only on the number of pulses in the exposure...PS model of Menendez , et al.15 This is strong evidence that the threshold level damage mechanism for single pulse 100 μs duration retinal exposures... Menendez et al., “Probability summation model of multiple laser exposure effects,” Health Phys. 65(5), 523 528 (1993). 16. D. J. Lund and D. Sliney, “A

  7. Dynamics and detection of laser induced microbubbles in the retinal pigment epithelium (RPE)

    NASA Astrophysics Data System (ADS)

    Fritz, Andreas; Ptaszynski, Lars; Stoehr, Hardo; Brinkmann, Ralf

    2007-07-01

    Selective Retina Treatment (SRT) is a new method to treat eye diseases associated with disorders of the RPE. Selective RPE cell damage is achieved by applying a train of 1.7 μs laser pulses at 527 nm. The treatment of retinal diseases as e.g. diabetic maculopathy (DMP), is currently investigated within clinical studies, however 200 ns pulse durations are under investigation. Transient micro bubbles in the retinal pigment epithelium (RPE) are expected to be the origin of cell damage due to irradiation with laser pulses shorter than 50 μs. The bubbles emerge at the strongly absorbing RPE melanosomes. Cell membrane disruption caused by the transient associated volume increase is expected to be the origin of the angiographically observed RPE leakage. We investigate micro bubble formation and dynamics in porcine RPE using pulse durations of 150 ns. A laser interferometry system at 830 nm with the aim of an online dosimetry control for SRT was developed. Bubble formation was detected interferometrically and by fast flash photography. A correlation to cell damage observed with a vitality stain is found. A bubble detection algorithm is presented.

  8. 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.

  9. Novel Neuroprotective Strategies in Ischemic Retinal Lesions

    PubMed Central

    Szabadfi, Krisztina; Mester, Laszlo; Reglodi, Dora; Kiss, Peter; Babai, Norbert; Racz, Boglarka; Kovacs, Krisztina; Szabo, Aliz; Tamas, Andrea; Gabriel, Robert; Atlasz, Tamas

    2010-01-01

    Retinal ischemia can be effectively modeled by permanent bilateral common carotid artery occlusion, which leads to chronic hypoperfusion-induced degeneration in the entire rat retina. The complex pathways leading to retinal cell death offer a complex approach of neuroprotective strategies. In the present review we summarize recent findings with different neuroprotective candidate molecules. We describe the protective effects of intravitreal treatment with: (i) urocortin 2; (ii) a mitochondrial ATP-sensitive K+ channel opener, diazoxide; (iii) a neurotrophic factor, pituitary adenylate cyclase activating polypeptide; and (iv) a novel poly(ADP-ribose) polymerase inhibitor (HO3089). The retinoprotective effects are demonstrated with morphological description and effects on apoptotic pathways using molecular biological techniques. PMID:20386654

  10. Treatment of Laser-Induced Retinal Injury and Visual Loss Using Sustained Release of Intra-Vitreal Neurotrophic Growth Factors. Addendum

    DTIC Science & Technology

    2011-11-01

    superior retina parameters ( macular (area centralis, superior retina) region and peripapillary nerve fiber layer (NFL) thickness) showed significant...scar formation, golden halo of hyperreflectivity around lesions represents areas of retinal degeneration . OCT images were obtained in each

  11. Lesion strength control by automatic temperature guided retinal photocoagulation

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    Laser photocoagulation is an established treatment for a variety of retinal diseases. However, when using the same irradiation parameter, the size and strength of the lesions are unpredictable due to unknown inter- and intraindividual optical properties of the fundus layers. The aim of this work is to investigate a feedback system to generate desired lesions of preselectable strengths by automatically controlling the irradiation time. Optoacoustics were used for retinal temperature monitoring. A 532-nm continuous wave Nd:YAG laser was used for photocoagulation. A 75-ns/523-nm Q-switched Nd:YLF laser simultaneously excited temperature-dependent pressure transients, which were detected at the cornea by an ultrasonic transducer embedded in a contact lens. The temperature data were analyzed during the irradiation by a LabVIEW routine. The treatment laser was switched off automatically when the required lesion strength was achieved. Five different feedback control algorithms for different lesion sizes were developed and tested on rabbits in vivo. With a laser spot diameter of 133 μm, five different lesion types with ophthalmoscopically visible diameters ranging mostly between 100 and 200 μm, and different appearances were achieved by automatic exposure time control. The automatically controlled lesions were widely independent of the treatment laser power and the retinal pigmentation.

  12. [Retinal image analysis to detect lesions associated with diabetic retinopathy].

    PubMed

    Sánchez Gutiérrez, C I; López Gálvez, M I; Hornero Sánchez, R; Poza Crespo, J

    2004-12-01

    Diabetic retinopathy is a leading cause of vision loss in developed countries. Regular diabetic retinal eye screenings are needed to detect early signs of retinopathy, so that appropriate treatments can be rendered to prevent blindness. Digital imaging is becoming available as a means of screening for diabetic retinopathy. However, with the large number of patients undergoing screenings, medical professionals require a tremendous amount of time and effort in order to analyse and diagnose the fundus photographs. Our aim is to develop an automatic algorithm using digital image analysis for detecting these early lesions from retinal images. An automatic method to detect hard exudates, a lesion associated with diabetic retinopathy, is proposed. The algorithm is based on their colour, using a statistical classification, and their sharp edges, applying an edge detector, to localise them. A sensitivity of 79.62% with a mean number of 3 false positives per image is obtained in a database of 20 retinal images with variable colour, brightness and quality. It can also be seen that the number of the false negative cases increases when the hard exudates were very close to the vessel tree. The long term goal of the project is to automate the screening for diabetic retinopathy with retinal images. We have described the preliminary development of a tool to provide automatic analysis of digital fundus photographs to localise hard exudates. Future work will address the issue of improving the obtained results and also will focus on detecting other lesions.

  13. 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

  14. Properties and Types of Significant Photothermal Retinal Lesion Injuries

    DTIC Science & Technology

    2016-09-01

    formation 1flt does not display a currently valid OMB·control num ber PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION. 1. REPORT DATE (00...PROJECT NUMBER Risk of Significant Injury Teclmical Working Group: Wesley Burgei, Shannon Foley, Matt Pandullo, Melissa Nass-Flores, George L Fischer...photothennal retinal lesion injuries that is consistent with the language and intent of DoD Instruction 3200.19. 15. SUBJECT TERMS Non-lethal, risk of

  15. 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.

  16. Ophthalmic manifestations of laser-induced eye injuries

    NASA Astrophysics Data System (ADS)

    Belkin, Michael

    1996-04-01

    The basis for almost all laser-induced eye injuries is the concentration of the radiation in the visible and near infra red range on the retina. The effect of this concentration is that the energy required to produce a visible retinal lesion is minuscule, about 50 microjoule for a Q- switched 532 nm laser. Even at lower energies the radiation can cause dazzle and flash blindness. At higher energies it can produce lesions which are ophthalmoscopically invisible, and at even higher energies, lesions that are visible and permanent. Higher energies still produce vitreous hemorrhage. The functional results of visible lesions depend not only on the energy impinging on the retina but mostly on the location of the injury. Foveal lesions will cause permanent reduction in visual functions, extrafoveal injuries will cause temporary visual incapacitation, and lesions further away from the macula may cause unnoticeable damage. Temporary incapacitation by intraocular hemorrhage can be engendered by a lesion anywhere in the eye. The latter is usually absorbed spontaneously or can be surgically removed by vitrectomy. An over-threshold injury anywhere on the posterior pole of the eye will lead to severance of the retinal nerve fiber layer, and thus to blind spots in parts of the retina unaffected by the original lesion. A common late, visually devastating, effect of laser lesions is retinal scarring which may lead to retinal holes, retinal detachment and delayed blindness.

  17. In Vivo Imaging of Retinal Hypoxia Using HYPOX-4-Dependent Fluorescence in a Mouse Model of Laser-Induced Retinal Vein Occlusion (RVO)

    PubMed Central

    Uddin, Md. Imam; Jayagopal, Ashwath; McCollum, Gary W.; Yang, Rong; Penn, John S.

    2017-01-01

    Purpose To demonstrate the utility of a novel in vivo molecular imaging probe, HYPOX-4, to detect and image retinal hypoxia in real time, in a mouse model of retinal vein occlusion (RVO). Methods Retinal vein occlusion was achieved in adult mice by photodynamic retinal vein thrombosis (PRVT). One or two major retinal vein(s) was/were occluded in close proximity to the optic nerve head (ONH). In vivo imaging of retinal hypoxia was performed using, HYPOX-4, an imaging probe developed by our laboratory. Pimonidazole-adduct immunostaining was performed and used as a standard ex vivo method for the detection of retinal hypoxia in this mouse RVO model. The retinal vasculature was imaged using fluorescein angiography (FA) and isolectin B4 staining. Retinal thickness was assessed by spectral-domain optical coherence tomography (SD-OCT) analysis. Results By application of the standard ex vivo pimonidazole-adduct immunostaining technique, retinal hypoxia was observed within 2 hours post-PRVT. The observed hypoxic retinal areas depended on whether one or two retinal vein(s) was/were occluded. Similar areas of hypoxia were imaged in vivo using HYPOX-4. Using OCT, retinal edema was observed immediately post-PRVT induction, resolving 8 days later. Nominal preretinal neovascularization was observed at 10 to 14 days post-RVO. Conclusions HYPOX-4 is an efficient probe capable of imaging retinal hypoxia in vivo, in RVO mice. Future studies will focus on its use in correlating retinal hypoxia to the onset and progression of ischemic vasculopathies. PMID:28750413

  18. Transscleral Diode Photocoagulation of Large Retinal and Choroidal Vascular Lesions

    PubMed Central

    Feng, Yun; Ma, Zhizhong

    2012-01-01

    Background Transscleral retinal photocoagulation with a diode laser is used in glaucoma refractory to medical and surgical treatment. Our main research question was how the technique performed in large vascular lesions associated with hemangiomas of the retina and choroid. Methodology/Clinical Findings Patient charts were retrieved from the hospital files for patients who underwent the procedure and were followed for at least 24 months. Five patients (6 eyes) fit the criteria. Cases included Von Hippel’s disease (2 eyes), Coats’ disease (1 eye) and choroidal hemangioma (3 cases). Transscleral diode laser treatment was performed under retrobulbar and topical anesthesia with a retinopexy probe (IRIS DioPexy, IRIS Medical Instruments, Mountain View, CA) applied transsclerally under indirect ophthalmoscope visualization. We found an improvement in best-corrected visual acuity at 24 months postoperatively. Conclusions/Significance Transscleral photocoagulation may have a clinical application in these diseases as an alternate to the high cost of photodynamic therapy with photosensitizing agents. PMID:22792170

  19. Fluorocoxib A enables targeted detection of cyclooxygenase-2 in laser-induced choroidal neovascularization

    NASA Astrophysics Data System (ADS)

    Uddin, Md. Jashim; Moore, Chauca E.; Crews, Brenda C.; Daniel, Cristina K.; Ghebreselasie, Kebreab; McIntyre, J. Oliver; Marnett, Lawrence J.; Jayagopal, Ashwath

    2016-09-01

    Ocular angiogenesis is a blinding complication of age-related macular degeneration and other retinal vascular diseases. Clinical imaging approaches to detect inflammation prior to the onset of neovascularization in these diseases may enable early detection and timely therapeutic intervention. We demonstrate the feasibility of a previously developed cyclooxygenase-2 (COX-2) targeted molecular imaging probe, fluorocoxib A, for imaging retinal inflammation in a mouse model of laser-induced choroidal neovascularization. This imaging probe exhibited focal accumulation within laser-induced neovascular lesions, with minimal detection in proximal healthy tissue. The selectivity of the probe for COX-2 was validated in vitro and by in vivo retinal imaging with nontargeted 5-carboxy-X-rhodamine dye, and by blockade of the COX-2 active site with nonfluorescent celecoxib prior to injection of fluorocoxib A. Fluorocoxib A can be utilized for imaging COX-2 expression in vivo for further validation as an imaging biomarker in retinal diseases.

  20. 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.

  1. 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.

  2. N-Acetylcysteine and Acute Retinal Laser Lesion in the Colubrid Snake Eye

    DTIC Science & Technology

    2004-01-01

    immune response to acute laser injury. When we applied a thiol antioxidant, N- acetylcysteine ( NAC ) systemically, after the lesion but before the dyes... acetylcysteine on fluorescence, induced by the dye C-400, in acute retinal laser injury. Dye alone on the left. Dye plus NAC on the right. In the first two...UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP020041 TITLE: N- Acetylcysteine and Acute Retinal Laser Lesion in the

  3. Digital tracking and control of retinal images

    NASA Astrophysics Data System (ADS)

    Barrett, Steven F.; Jerath, Maya R.; Rylander, Henry G.; Welch, Ashley J.

    1994-01-01

    Laser-induced retinal lesions are used to treat a variety of eye disorders such as diabetic retinopathy and retinal tears. An instrumentation system has been developed to track a specific lesion coordinate on the retinal surface and provide corrective signals to maintain laser position on the coordinate. High-resolution retinal images are acquired via a CCD camera coupled to a fundus camera and video frame grabber. Optical filtering and histogram modification are used to enhance the retinal vessel network against the lighter retinal background. Six distinct retinal landmarks are tracked on the high contrast image obtained from the frame grabber using 2D blood vessel templates. An overview of the robotic laser system design is followed by implementation and testing of a development system for proof of concept and, finally, specifications for a real-time system are provided.

  4. 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

  5. Laser-Induced Photic Injury Phenocopies Macular Dystrophy.

    PubMed

    Zhang, Lijuan; Zheng, Andrew; Nie, Hongping; Bhavsar, Kavita V; Xu, Yu; Sliney, David H; Trokel, Stephen L; Tsang, Stephen H

    2016-01-01

    To describe the phenotypes associated with laser-induced retinal damage in children. Five patients with maculopathy and reduced visual acuity associated with laser pointer use were evaluated. Best-corrected visual acuity, retinal structure, and function were monitored with color fundus, infrared (IR), and red-free images, fundus autofluorescence (AF), spectral domain-optical coherence tomography (SD-OCT), and full-field electroretinography (ERG). All five laser pointer injury patients had retinal lesions resembling a macular dystrophy (one bilateral and four unilateral). These lesions were irregular in shape but all had a characteristic dendritic appearance with linear streaks radiating from the lesion. Photoreceptor damage was present in all patients, but serial OCT monitoring showed that subsequent photoreceptor recovery occurred over time in the eyes of at least four patients. One patient also had bilateral pigment epithelial detachments (PED). Both hyper- and hypoautofluorecence were observed in the laser damage area. In general, OCT and IR images are quite useful to diagnose laser damage, but AF is not as sensitive. Laser pointer damage in children can occasionally be misdiagnosed as a macular dystrophy disease, but the distinctive lesions and OCT features are helpful for differentiating laser damage from other conditions.

  6. Laser-Induced Photic Injury Phenocopies Macular Dystrophy

    PubMed Central

    Zhang, Lijuan; Zheng, Andrew; Nie, Hongping; Bhavsar, Kavita V.; Xu, Yu; Sliney, David H.; Trokel, Stephen L.; Tsang, Stephen H

    2016-01-01

    Objective To describe the phenotypes associated with laser-induced retinal damage in children. Methods Five patients with maculopathy and reduced visual acuity associated with laser pointer use were evaluated. Best-corrected visual acuity, retinal structure, and function were monitored with color fundus, infrared (IR), and red-free images, fundus autofluorescence (AF), spectral domain-optical coherence tomography (SD-OCT), and full-field electroretinography (ERG). Results All five laser pointer injury patients had retinal lesions resembling a macular dystrophy (1 bilateral and 4 unilateral). These lesions were irregular in shape but all had a characteristic dendritic appearance with linear streaks radiating from the lesion. Photoreceptor damage was present in all patients, but serial OCT monitoring showed that subsequent photoreceptor recovery occurred over time in the eyes of at least 4 patients. 1 patient also had bilateral pigment epithelial detachments (PED). Both hyper- and hypoautofluorecence were observed in the laser damage area. Conclusions In general, OCT and IR images are quite useful to diagnose laser damage, but AF is not as sensitive. Laser pointer damage in children can occasionally be misdiagnosed as a macular dystrophy disease, but the distinctive lesions and OCT features are helpful for differentiating laser damage from other conditions. PMID:26927809

  7. Long Term Effects Retinal Laser Lesions: Multifocal ERGs (Electroretinogram) and Vernier Visual Evoked Potentials (VEPs)

    DTIC Science & Technology

    1998-03-01

    and " red dot" lesions (contained retinal hemorrhage). Single exposures had been made both foveally and at 5 degrees eccentricity in the parafovea...superiorly, inferiorly and temporally. The multifocal ( perimetric ) electiroretinogram was recorded from specialized contact lenses through hospital grade amplifiers.

  8. Plasticity in adult cat visual cortex (area 17) following circumscribed monocular lesions of all retinal layers

    PubMed Central

    Calford, M B; Wang, C; Taglianetti, V; Waleszczyk, W J; Burke, W; Dreher, B

    2000-01-01

    In eight adult cats intense, sharply circumscribed, monocular laser lesions were used to remove all cellular layers of the retina. The extents of the retinal lesions were subsequently confirmed with counts of α-ganglion cells in retinal whole mounts; in some cases these revealed radial segmental degeneration of ganglion cells distal to the lesion.Two to 24 weeks later, area 17 (striate cortex; V1) was studied electrophysiologically in a standard anaesthetized, paralysed (artificially respired) preparation. Recording single- or multineurone activity revealed extensive topographical reorganization within the lesion projection zone (LPZ).Thus, with stimulation of the lesioned eye, about 75 % of single neurones in the LPZ had ‘ectopic’ visual discharge fields which were displaced to normal retina in the immediate vicinity of the lesion.The sizes of the ectopic discharge fields were not significantly different from the sizes of the normal discharge fields. Furthermore, binocular cells recorded from the LPZ, when stimulated via their ectopic receptive fields, exhibited orientation tuning and preferred stimulus velocities which were indistinguishable from those found when the cells were stimulated via the normal eye.However, the responses to stimuli presented via ectopic discharge fields were generally weaker (lower peak discharge rates) than those to presentations via normal discharge fields, and were characterized by a lower-than-normal upper velocity limit.Overall, the properties of the ectopic receptive fields indicate that cortical mechanisms rather than a retinal ‘periphery’ effect underlie the topographic reorganization of area 17 following monocular retinal lesions. PMID:10767137

  9. Plasticity Beyond V1: Reinforcement of Motion Perception upon Binocular Central Retinal Lesions in Adulthood.

    PubMed

    Burnat, Kalina; Hu, Tjing-Tjing; Kossut, Małgorzata; Eysel, Ulf T; Arckens, Lutgarde

    2017-09-13

    Induction of a central retinal lesion in both eyes of adult mammals is a model for macular degeneration and leads to retinotopic map reorganization in the primary visual cortex (V1). Here we characterized the spatiotemporal dynamics of molecular activity levels in the central and peripheral representation of five higher-order visual areas, V2/18, V3/19, V4/21a,V5/PMLS, area 7, and V1/17, in adult cats with central 10° retinal lesions (both sexes), by means of real-time PCR for the neuronal activity reporter gene zif268. The lesions elicited a similar, permanent reduction in activity in the center of the lesion projection zone of area V1/17, V2/18, V3/19, and V4/21a, but not in the motion-driven V5/PMLS, which instead displayed an increase in molecular activity at 3 months postlesion, independent of visual field coordinates. Also area 7 only displayed decreased activity in its LPZ in the first weeks postlesion and increased activities in its periphery from 1 month onward. Therefore we examined the impact of central vision loss on motion perception using random dot kinematograms to test the capacity for form from motion detection based on direction and velocity cues. We revealed that the central retinal lesions either do not impair motion detection or even result in better performance, specifically when motion discrimination was based on velocity discrimination. In conclusion, we propose that central retinal damage leads to enhanced peripheral vision by sensitizing the visual system for motion processing relying on feedback from V5/PMLS and area 7.SIGNIFICANCE STATEMENT Central retinal lesions, a model for macular degeneration, result in functional reorganization of the primary visual cortex. Examining the level of cortical reactivation with the molecular activity marker zif268 revealed reorganization in visual areas outside V1. Retinotopic lesion projection zones typically display an initial depression in zif268 expression, followed by partial recovery with

  10. 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.

  11. Cortical reorganization after long-term adaptation to retinal lesions in humans.

    PubMed

    Chung, Susana T L

    2013-11-13

    Single-unit recordings demonstrated that the adult mammalian visual cortex is capable of reorganizing after induced retinal lesions. In humans, whether the adult cortex is capable of reorganizing has only been studied using functional magnetic resonance imaging, with equivocal results. Here, we exploited the phenomenon of visual crowding, a major limitation on object recognition, to show that, in humans with long-standing retinal (macular) lesions that afflict the fovea and thus use their peripheral vision exclusively, the signature properties of crowding are distinctly different from those of the normal periphery. Crowding refers to the inability to recognize objects when the object spacing is smaller than the critical spacing. Critical spacing depends only on the retinal location of the object, scales linearly with its distance from the fovea, and is approximately two times larger in the radial than the tangential direction with respect to the fovea, thus demonstrating the signature radial-tangential anisotropy of the crowding zone. Using retinal imaging combined with behavioral measurements, we mapped out the crowding zone at the precise peripheral retinal locations adopted by individuals with macular lesions as the new visual reference loci. At these loci, the critical spacings are substantially smaller along the radial direction than expected based on the normal periphery, resulting in a lower scaling of critical spacing with the eccentricity of the peripheral locus and a loss in the signature radial-tangential anisotropy of the crowding zone. These results imply a fundamental difference in the substrate of cortical processing in object recognition following long-term adaptation to macular lesions.

  12. Significance of Retinal Lesions Potentially Caused by Dazzling Lasers

    DTIC Science & Technology

    2015-12-01

    due to reports that subthreshold lesions caused by lasers used in photocoagulation therapy to treat diabetic retinopathy often lead to minimal or...and the temperature incident on the retina: A study of photocoagulation therapy used to treat diabetic retinopathy showed that a peak temperature of...2011). More recently, the chart developed for use in the Early Treatment Diabetic Retinopathy Study, or “ETDRS chart,” has become the standard for

  13. Temperature Dependence of Laser Induced Breakdown

    DTIC Science & Technology

    1994-01-01

    consistent dependence on the temperature of the medium. The theory of the temperature dependence of LIB and experimental observations for all pulse...durations and their implications for retinal damage are discussed. Laser Induced Breakdown, Temperature dependence , Threshold valve, Nanosecond, Picosecond, Femtosecond, laser pulses.

  14. Loss of heterozygosity for the NF2 gene in retinal and optic nerve lesions of patients with neurofibromatosis 2

    PubMed Central

    Chan, Chi-Chao; Koch, Christian A; Kaiser-Kupfer, Muriel I; Parry, Dilys M; Gutmann, David H; Zhuang, Zhengping; Vortmeyer, Alexander O

    2008-01-01

    Individuals affected with the neurofibromatosis 2 (NF2) cancer predisposition syndrome develop specific ocular lesions. To determine whether these lesions result from altered NF2 gene expression, microdissection and PCR were used to investigate 40 ocular lesions from seven eyes of four NF2 patients for LOH, with markers that flank the NF2 gene on chromosome 22q. NF2 protein (merlin) expression was also evaluated in these lesions, using immunohistochemistry. Retinal hamartoma was observed in all seven eyes, including one with combined pigment epithelial and retinal hamartoma (CPERH). Retinal tufts were present in four eyes (three patients), retinal dysplasia in two eyes (two patients), optic nerve neurofibroma in one eye, iris naevoid hyperplasia in two eyes (two patients) and pseudophakia in all eyes. Markers were informative in three patients (six eyes from three unrelated families). One patient was non-informative due to prolonged decalcification. All retinal and optic nerve, but not iris lesions, demonstrated consistent LOH for the NF2 gene. Merlin was not expressed in the retina, optic nerve, or iris lesions. These results suggest that inactivation of the NF2 gene is associated with the formation of a variety of retinal and optic nerve lesions in NF2 patients. PMID:12210058

  15. An unknown combination of infantile spasms, retinal lesions, facial dysmorphism and limb abnormalities.

    PubMed

    Plomp, A S; Reardon, W; Benton, S; Taylor, D; Larcher, V F; Sundrum, R; Winter, R M

    2000-07-01

    A female patient is presented with infantile spasms, punched-out retinal lesions, facial dysmorphism, short upper arms, short thumbs, left lower limb hypoplasia with foot deformity, a hemivertebra, atrial septal defect, growth retardation and severe developmental delay. There is some similarity to patients with Aicardi syndrome (AS), but the retinal lesions in our patient are different and she does not have agenesis of the corpus callosum, one of the diagnostic features of AS. She might represent an atypical form of this syndrome with additional features, usually not present in AS. As there is no diagnostic test for AS yet, this diagnosis cannot be confirmed nor rejected with certainty. However, it might be more likely that our patient has another, possibly unique, condition.

  16. Axonal loss of retinal neurons in multiple sclerosis associated with optic radiation lesions.

    PubMed

    Klistorner, Alexander; Sriram, Prima; Vootakuru, Nikitha; Wang, Chenyu; Barnett, Michael H; Garrick, Raymond; Parratt, John; Levin, Netta; Raz, Noa; Van der Walt, Anneke; Masters, Lynette; Graham, Stuart L; Yiannikas, Con

    2014-06-17

    To investigate the potential links between thinning of retinal ganglion cell axons in eyes of patients with multiple sclerosis (MS) without past optic neuritis (ON) and MS-related inflammatory damage of the posterior visual pathway. Temporal retinal nerve fiber layer (tRNFL) thickness was analyzed in eyes with no history of ON (NON) from 53 patients with relapsing-remitting MS. Fifty normal age- and sex-matched controls were examined with optical coherence tomography. Low-contrast visual acuity charts were used for functional assessment of vision. The optic tract (OT) and optic radiation (OR) were identified using probabilistic tractography, and volume of T2 fluid-attenuated inversion recovery lesions and diffusion tensor imaging (DTI) indices were measured within both structures. Cross-sectional diameter of the OT was also calculated. tRNFL thickness was significantly reduced in NON eyes and was associated with reduced low-contrast visual acuity. Lesions within the OR were detected in the majority of patients. There was a significant correlation between thinning of the tRNFL and OR lesion volume (adjusted for non-OR lesion volume, age, sex, and disease duration). tRNFL thickness also correlated with OR DTI indices. No OT lesions were identified in any of the patients and no relationship between retinal nerve fiber layer loss and potential markers of OT lesions was found. The results demonstrate a strong tract-specific association between loss of tRNFL fibers and MS-related inflammation within OR. © 2014 American Academy of Neurology.

  17. Axonal loss of retinal neurons in multiple sclerosis associated with optic radiation lesions

    PubMed Central

    Sriram, Prima; Vootakuru, Nikitha; Wang, Chenyu; Barnett, Michael H.; Garrick, Raymond; Parratt, John; Levin, Netta; Raz, Noa; Van der Walt, Anneke; Masters, Lynette; Graham, Stuart L.; Yiannikas, Con

    2014-01-01

    Objective: To investigate the potential links between thinning of retinal ganglion cell axons in eyes of patients with multiple sclerosis (MS) without past optic neuritis (ON) and MS-related inflammatory damage of the posterior visual pathway. Methods: Temporal retinal nerve fiber layer (tRNFL) thickness was analyzed in eyes with no history of ON (NON) from 53 patients with relapsing-remitting MS. Fifty normal age- and sex-matched controls were examined with optical coherence tomography. Low-contrast visual acuity charts were used for functional assessment of vision. The optic tract (OT) and optic radiation (OR) were identified using probabilistic tractography, and volume of T2 fluid-attenuated inversion recovery lesions and diffusion tensor imaging (DTI) indices were measured within both structures. Cross-sectional diameter of the OT was also calculated. Results: tRNFL thickness was significantly reduced in NON eyes and was associated with reduced low-contrast visual acuity. Lesions within the OR were detected in the majority of patients. There was a significant correlation between thinning of the tRNFL and OR lesion volume (adjusted for non-OR lesion volume, age, sex, and disease duration). tRNFL thickness also correlated with OR DTI indices. No OT lesions were identified in any of the patients and no relationship between retinal nerve fiber layer loss and potential markers of OT lesions was found. Conclusion: The results demonstrate a strong tract-specific association between loss of tRNFL fibers and MS-related inflammation within OR. PMID:24838786

  18. Automatic detection and recognition of multiple macular lesions in retinal optical coherence tomography images with multi-instance multilabel learning

    NASA Astrophysics Data System (ADS)

    Fang, Leyuan; Yang, Liumao; Li, Shutao; Rabbani, Hossein; Liu, Zhimin; Peng, Qinghua; Chen, Xiangdong

    2017-06-01

    Detection and recognition of macular lesions in optical coherence tomography (OCT) are very important for retinal diseases diagnosis and treatment. As one kind of retinal disease (e.g., diabetic retinopathy) may contain multiple lesions (e.g., edema, exudates, and microaneurysms) and eye patients may suffer from multiple retinal diseases, multiple lesions often coexist within one retinal image. Therefore, one single-lesion-based detector may not support the diagnosis of clinical eye diseases. To address this issue, we propose a multi-instance multilabel-based lesions recognition (MIML-LR) method for the simultaneous detection and recognition of multiple lesions. The proposed MIML-LR method consists of the following steps: (1) segment the regions of interest (ROIs) for different lesions, (2) compute descriptive instances (features) for each lesion region, (3) construct multilabel detectors, and (4) recognize each ROI with the detectors. The proposed MIML-LR method was tested on 823 clinically labeled OCT images with normal macular and macular with three common lesions: epiretinal membrane, edema, and drusen. For each input OCT image, our MIML-LR method can automatically identify the number of lesions and assign the class labels, achieving the average accuracy of 88.72% for the cases with multiple lesions, which better assists macular disease diagnosis and treatment.

  19. Visual acuity loss in recessive retinitis pigmentosa and its correlation with macular lesions.

    PubMed

    Thobani, Azzrah; Fishman, Gerald A; Genead, Mohamed; Anastasakis, Anastasios

    2011-05-01

    To determine the visual acuity loss in patients with autosomal recessive retinitis pigmentosa and its relation to the presence of macular lesions. A total of 145 patients were included in the visual acuity analysis, and 139 patients were included in the analysis of their macular status. Patients with a history of parental consanguinity or an affected sister and parents unaffected with retinitis pigmentosa were considered as having an autosomal recessive mode of inheritance. Regardless of age, 68 patients (47%) had visual acuity of 20/40 or better, 109 (75%) had better than 20/200 in at least 1 eye, and 36 (25%) had an acuity of 20/200 or worse in both eyes. An evaluation of the macular status demonstrated that 55 patients (39.6%) had no macular lesion and 77 (55.4%) had an atrophic lesion (either bull's-eye or geographic). Seventy-five percent of patients with no macular lesion had a visual acuity of 20/40 or better and 34 patients (44%) with an atrophic lesion had a visual acuity better than 20/70. These data can be useful to counsel patients on the potential visual acuity impairment likely to be observed at different ages and identify the association of visual acuity loss with macular changes.

  20. Hierarchical detection of red lesions in retinal images by multiscale correlation filtering

    NASA Astrophysics Data System (ADS)

    Zhang, Bob; Wu, Xiangqian; You, Jane; Li, Qin; Karray, Fakhri

    2009-02-01

    This paper presents an approach to the computer aided diagnosis (CAD) of diabetic retinopathy (DR) -- a common and severe complication of long-term diabetes which damages the retina and cause blindness. Since red lesions are regarded as the first signs of DR, there has been extensive research on effective detection and localization of these abnormalities in retinal images. In contrast to existing algorithms, a new approach based on Multiscale Correlation Filtering (MSCF) and dynamic thresholding is developed. This consists of two levels, Red Lesion Candidate Detection (coarse level) and True Red Lesion Detection (fine level). The approach was evaluated using data from Retinopathy On-line Challenge (ROC) competition website and we conclude our method to be effective and efficient.

  1. Retinal image analysis to detect and quantify lesions associated with diabetic retinopathy.

    PubMed

    Sánchez, C I; Hornero, R; López, M I; Poza, J

    2004-01-01

    An automatic method to detect hard exudates, a lesion associated with diabetic retinopathy, is proposed. The algorithm found on their color, using a statistical classification, and their sharp edges, applying an edge detector, to localize them. A sensitivity of 79.62% with a mean number of 3 false positives per image is obtained in a database of 20 retinal image with variable color, brightness and quality. In that way, we evaluate the robustness of the method in order to make adequate to a clinical environment. Further efforts will be done to improve its performance.

  2. Natural History of Age-Related Retinal Lesions That Precede AMD in Mice Fed High or Low Glycemic Index Diets

    PubMed Central

    Weikel, Karen A.; FitzGerald, Paul; Shang, Fu; Caceres, M. Andrea; Bian, Qingning; Handa, James T.; Stitt, Alan W.

    2012-01-01

    Purpose. Epidemiologic data indicate that people who consume low glycemic index (GI) diets are at reduced risk for the onset and progression of age-related macular degeneration (AMD). The authors sought corroboration of this observation in an animal model. Methods. Five- and 16-month-old C57BL/6 mice were fed high or low GI diets until they were 17 and 23.5 months of age, respectively. Retinal lesions were evaluated by transmission electron microscopy, and advanced glycation end products (AGEs) were evaluated by immunohistochemistry. Results. Retinal lesions including basal laminar deposits, loss of basal infoldings, and vacuoles in the retinal pigment epithelium were more prevalent in the 23.5- than in the 17-month-old mice. Within each age group, consumption of a high GI diet increased the risk for lesions and the risk for photoreceptor abnormalities and accumulation of AGEs. Conclusions. Consuming high GI diets accelerates the appearance of age-related retinal lesions that precede AMD in mice, perhaps by increasing the deposition of toxic AGEs in the retina. The data support the hypothesis that consuming lower GI diets, or simulation of their effects with nutraceuticals or drugs, may protect against AMD. The high GI-fed C57BL/6 mouse is a new model of age-related retinal lesions that precede AMD and mimic the early stages of disease and may be useful for drug discovery. PMID:22205601

  3. Retinal pigment epithelial atrophy over polypoidal choroidal vasculopathy lesions during ranibizumab monotherapy.

    PubMed

    Hikichi, Taiichi; Kitamei, Hirokuni; Shioya, Shoko

    2016-05-16

    To evaluate the quantitative changes of retinal pigment epithelial (RPE) atrophy during 3-year follow-up period of ranibizumab monotherapy for polypoidal choroidal vasculopathy (PCV). We retrospectively reviewed consecutive 100 Japanese patients with unilateral symptomatic treatment-naïve PCV who received ranibizumab monotherapy for 3 years. Color fundus photography, spectral-domain optical coherence tomography, and fundus autofluorescence were evaluated for RPE atrophy. Multiple regression analysis was performed to investigate the predictive factors found during univariate analysis to identify an association with increased RPE atrophic areas. RPE atrophic areas overlapping PCV lesions were measured. The mean (standard deviation) number of injections was 11.4 (4.50). RPE atrophic area enlarged to 2.91 (5.41 mm(2)) 3 years after the first injection from 1.22 (1.72 mm(2)) at baseline, which differed significantly (P = 0.012). Multiple regression analysis showed that larger PCV lesions and larger RPE atrophic areas at baseline were associated with increased RPE atrophic areas. RPE atrophic area overlapping the baseline PCV lesions significantly increased during 3-year follow-up period, whereas RPE atrophic area not overlapping the baseline PCV lesions did not increase significantly. RPE atrophy progresses in eyes with PCV during ranibizumab monotherapy and the tendency for development of RPE atrophy within the PCV lesions.

  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. Gender-Dependent Effects of Enriched Environment and Social Isolation in Ischemic Retinal Lesion in Adult Rats

    PubMed Central

    Kiss, Peter; Szabadfi, Krisztina; Horvath, Gabor; Tamas, Andrea; Farkas, Jozsef; Gabriel, Robert; Reglodi, Dora

    2013-01-01

    Exposure to an enriched environment has been shown to have many positive effects on brain structure and function. Numerous studies have proven that enriched environment can reduce the lesion induced by toxic and traumatic injuries. Impoverished environment, on the other hand, can have deleterious effects on the outcome of neuronal injuries. We have previously shown that enriched conditions have protective effects in retinal injury in newborn rats. It is well-known that the efficacy of neuroprotective strategies can depend on age and gender. The aim of the present study, therefore, was to examine the effects of environmental enrichment and social isolation in retinal ischemia. We used bilateral common carotid artery occlusion to induce retinal hypoperfusion in adult Wistar rats of both genders. Groups were housed in standard, enriched or impoverished conditions. Impoverished environment was induced by social isolation. Retinas were processed for histological analysis after two weeks of survival. In the present study, we show that (1) enriched environment has protective effects in adult ischemic retinal lesion, while (2) impoverished environment further increases the degree of ischemic injury, and (3) that these environmental effects are gender-dependent: females are less responsive to the positive effects of environmental enrichment and more vulnerable to retinal ischemia in social isolation. In summary, our present study shows that the effects of both positive and negative environmental stimuli are gender-dependent in ischemic retinal lesions. PMID:23921682

  6. 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.

  7. Progression of retinal ganglion cell loss in multiple sclerosis is associated with new lesions in the optic radiations.

    PubMed

    Klistorner, A; Graham, E C; Yiannikas, C; Barnett, M; Parratt, J; Garrick, R; Wang, C; You, Y; Graham, S L

    2017-08-10

    The mechanism of retinal ganglion cell and retinal nerve fiber layer loss in multiple sclerosis (MS) remains unknown. This study aimed to investigate the association between temporal retinal nerve fiber layer (tRNFL) thinning and disease activity in the brain determined by T2 lesions on magnetic resonance imaging (MRI). Fifty-five consecutive patients with relapsing-remitting MS and 25 controls were enrolled. All patients underwent annual optical coherence tomography and high-resolution MRI scans for tRNFL thickness and brain lesion volume analysis, respectively. Significant tRNFL thickness reduction was observed over the 3-year follow-up period at a relatively constant rate (1.02 μm/year). Thinning of tRNFL fibers was more prominent in younger patients (P = 0.01). The tRNFL loss was associated with new MRI lesions in the optic radiations (ORs). There was significantly greater tRNFL thinning in patients with new lesional activity in the ORs compared with patients with new lesions outside the ORs (P = 0.009). This study supports the notion that retrograde transneuronal degeneration caused by OR lesions might play a role in progressive retinal nerve fiber layer loss. In addition, the results of the study also indicate that the disease-related neurodegenerative changes in the retina start much earlier than the clinical diagnosis of MS. © 2017 EAN.

  8. Automated detection of dark and bright lesions in retinal images for early detection of diabetic retinopathy.

    PubMed

    Akram, Usman M; Khan, Shoab A

    2012-10-01

    There is an ever-increasing interest in the development of automatic medical diagnosis systems due to the advancement in computing technology and also to improve the service by medical community. The knowledge about health and disease is required for reliable and accurate medical diagnosis. Diabetic Retinopathy (DR) is one of the most common causes of blindness and it can be prevented if detected and treated early. DR has different signs and the most distinctive are microaneurysm and haemorrhage which are dark lesions and hard exudates and cotton wool spots which are bright lesions. Location and structure of blood vessels and optic disk play important role in accurate detection and classification of dark and bright lesions for early detection of DR. In this article, we propose a computer aided system for the early detection of DR. The article presents algorithms for retinal image preprocessing, blood vessel enhancement and segmentation and optic disk localization and detection which eventually lead to detection of different DR lesions using proposed hybrid fuzzy classifier. The developed methods are tested on four different publicly available databases. The presented methods are compared with recently published methods and the results show that presented methods outperform all others.

  9. Digital tracking and control of retinal images

    NASA Astrophysics Data System (ADS)

    Barrett, Steven F.; Jerath, Maya R.; Rylander, Henry G., III; Welch, Ashley J.

    1993-06-01

    Laser induced retinal lesions are used to treat a variety of eye diseases such as diabetic retinopathy and retinal detachment. An instrumentation system has been developed to track a specific lesion coordinate on the retinal surface and provide corrective signals to maintain laser position on the coordinate. High resolution retinal images are acquired via a CCD camera coupled to a fundus camera and video frame grabber. Optical filtering and histogram modification are used to enhance the retinal vessel network against the lighter retinal background. Six distinct retinal landmarks are tracked on the high contrast image obtained from the frame grabber using two-dimensional blood vessel templates. The frame grabber is hosted on a 486 PC. The PC performs correction signal calculations using an exhaustive search on selected image portions. An X and Y laser correction signal is derived from the landmark tracking information and provided to a pair of galvanometer steered mirrors via a data acquisition and control subsystem. This subsystem also responds to patient inputs and the system monitoring lesion growth. This paper begins with an overview of the robotic laser system design followed by implementation and testing of a development system for proof of concept. The paper concludes with specifications for a real time system.

  10. 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.

  11. Microscopic mammalian retinal pigment epithelium lesions induce widespread proliferation with differences in magnitude between center and periphery

    PubMed Central

    Lundh von Leithner, Peter; Ciurtin, Coziana

    2010-01-01

    Purpose The vertebrate retina develops from the center to the periphery. In amphibians and fish the retinal margin continues to proliferate throughout life, resulting in retinal expansion. This does not happen in mammals. However, some mammalian peripheral retinal pigment epithelial (RPE) cells continue to divide, perhaps as a vestige of this mechanism. The RPE cells are adjacent to the ciliary margin, a known stem cell source. Here we test the hypothesis that peripheral RPE is fundamentally different from central RPE by challenging different regions with microscopic laser burns and charting differential responses in terms of levels of proliferation and the regions over which this proliferation occurs. Methods Microscopic RPE lesions were undertaken in rats at different eccentricities and the tissue stained for proliferative markers Ki67 and bromodeoxyuridine (BrdU) and the remodeling metalloproteinase marker 2 (MMP2). Results All lesions produced local RPE proliferation and tissue remodeling. Significantly more mitosis resulted from peripheral than central lesions. Unexpectedly, single lesions also resulted in RPE cells proliferating across the entire retina. Their number did not increase linearly with lesion number, indicating that they may be a specific population. All lesions repaired and formed apparently normal relations with the neural retina. Repaired RPE was albino. Conclusions These results highlight regional RPE differences, revealing an enhanced peripheral repair capacity. Further, all lesions have a marked impact on both local and distant RPE cells, demonstrating a pan retinal signaling mechanism triggering proliferation across the tissue plane. The RPE cells may represent a distinct population as their number did not increase with multiple lesions. The fact that repairing cells were hypopigmented is of interest because reduced pigment is associated with enhanced proliferative capacities in the developing neural retina. PMID:20360994

  12. Comparison of lesions predisposing to rhegmatogenous retinal detachment by race of subjects.

    PubMed

    Foos, R Y; Simons, K B; Wheeler, N C

    1983-11-01

    Because rhegmatogenous retinal detachments are thought to be much less common in blacks than in whites, we compared the incidence of various lesions known to cause or predispose to this condition (synchysis senilis, posterior vitreous detachment, breaks, tears, and holes of the peripheral fundus, and lattice degeneration of the retina) in a series of postmortem eyes on the basis of race. Our statistical analysis also included trauma, myopia, and chorioretinitis. The series included 322 black subjects and 2,012 white subjects. The subjects ranged in age from 20 to 93 years at the time of death. Although the initial data showed a racial difference in the incidence of synchysis senilis of grade 3 (50% destruction) or higher and posterior vitreous detachment (P = .033 and P = .021, respectively), we found no difference when the data were age-corrected.

  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. Investigation of Laser-Induced Retinal Damage

    DTIC Science & Technology

    1993-04-20

    glutathione (Fig. 1), tocopherol (vitamin E), and taurine (Lam & Glickman, 1992). 500 .SH GSH + Laser 400 6 300 200 GS" Standards, Unexposed 100J• 1 O0 ~GSSG...melanin granules were exposed to laser for 2 min at irradiance of 400 mW/cm 2. A 2-Wl aliquot was then injected into Delta HPLC column. No oxidized...oxidation was determined from the distribution of label in the AA and DHA fractions following separation on HPLC . [from Glickman et al., 1993] The

  15. Live or let die - retinal ganglion cell death and survival during development and in the lesioned adult CNS.

    PubMed

    Bähr, M

    2000-10-01

    Programmed cell death or apoptosis is a common and widespread phenomenon that is important for proper development of the nervous system. In the adult CNS, however, apoptosis contributes to secondary cell loss after various types of lesions. The retino-tectal system has been successfully used as a convenient model system to study the molecular mechanisms of neuronal apoptosis and survival during development and in the lesioned adult CNS. This review describes the current knowledge about the interactions of cell death and survival pathways in general and for retinal ganglion cells specifically.

  16. Argon laser-induced damage in the goldfish (C. auratus) retina following whole-body hyperthermia

    NASA Astrophysics Data System (ADS)

    Deaton, Michael A.; Lund, David J.; Schuschereba, Steven T.; Dahlberg, Ann M.; Cowan, Beth L.; Lester, Paul; Odom, Daniel G.

    1990-07-01

    The heat shock response is a phenomenon common to all cells and is characterized by an increase in the rate of synthesis of intracellular heat shock proteins (HSPs) . The response occurs following rapid transient increases in terrerature sufficient to cause stress but not cell death. HSPs appear to perform protective functions that raise the cell''s tolerance to diverse noxious stimuli. Thus we postulated that we could limit laser-induced retinal darriage through induction of the heat shock -response. Corrmon goldfish (C. auratus) made hyperthermic by immersion in 35C water for 15 minutes and radiolabeled with [355]methionine showed retinal liSPs with apparent molecular weights of 110 90 70 and 35 kilodaltons. To test the protective effects of HSPs against laser injury goldfish were made hyperthermic and 4 and 24 hr later their retinas were irradiated with argon laser light (51 4 . 5 nm spot size at the cornea 3. 0 mm irradiance 125 mW/cm2) . NonhyperLhermic animals served as controls. Following 24 hr of recovery fish were terminated and retinas fixed for histology. Fundus photographs were taken irrunediately after laser exposure . Lesion diameters were measured from fundus photographs and evaluated statistically. The mean retinal lesion diameters of fish not subjected to hyperthermJ. a laser exposed 4 hr post hyperLhermia and laser exposed 24 hr post hyperthermia were 10. 25 1. 4 SD 8. 82 2. 1 SD and 6. 78

  17. Murine Ccl2/Cx3cr1 Deficiency Results in Retinal Lesions Mimicking Human Age-Related Macular Degeneration

    PubMed Central

    Tuo, Jingsheng; Bojanowski, Christine M.; Zhou, Min; Shen, Defen; Ross, Robert J.; Rosenberg, Kevin I.; Cameron, D. Joshua; Yin, Chunyue; Kowalak, Jeffrey A.; Zhuang, Zhengping; Zhang, Kang; Chan, Chi-Chao

    2007-01-01

    Purpose Senescent Ccl2-/- mice are reported to develop cardinal features of human age-related macular degeneration (AMD). Loss-of-function single-nucleotide polymorphisms within CX3CR1 are also found to be associated with AMD. The authors generated Ccl2-/-/Cx3cr1-/- mice to establish a more characteristic and reproducible AMD model. Methods Single Ccl2- and Cx3cr1-deficient mice were crossbred to obtain Ccl2-/-/Cx3cr1-/- mice. Funduscopy, histopathology, retinal A2E quantification, proteomics, RT-PCR gene expression assay, immunochemistry, and Western blotting were used to examine the retina and to evaluate gene expression within the retinal tissue. Results By 6 weeks of age, all Ccl2-/-/Cx3cr1-/- mice developed AMD-like retinal lesions, including drusen, retinal pigment epithelium alteration, and photoreceptor degeneration. Furthermore, choroidal neovascularization occurred in 15% of the mice. These degenerative lesions progressed with age. A2E, a major lipofuscin fluorophore that accumulated during AMD progression, was significantly higher in the Ccl2-/-/Cx3cr1-/- retina than in the wild-type retina. Complement cofactor was higher in the Ccl2-/-/Cx3cr1-/- RPE. Proteomics data indicated that four proteins were differentially expressed in Ccl2-/-/Cx3cr1-/- retina compared with control. One of these proteins, ERp29, an endoplasmic reticulum protein, functions as an escort chaperone and in protein folding. Conclusions The authors concluded that Ccl2-/-/Cx3cr1-/- mice develop a broad spectrum of AMD abnormalities with early onset and high penetrance. These observations implicate certain chemokines and endoplasmic reticulum proteins in AMD pathogenesis. Similar to the mechanism of neurodegeneration caused by dysfunction of endoplasmic reticulum proteins, decreased chaperoning may cause misfolded protein accumulation, leading to drusen formation and retinal degeneration. PMID:17652758

  18. In vivo imaging of a new indocyanine green micelle formulation in an animal model of laser-induced choroidal neovascularization.

    PubMed

    Meyer, Johanna; Cunea, Alexander; Sonntag-Bensch, Dagmar; Welker, Pia; Licha, Kai; Holz, Frank G; Schmitz-Valckenberg, Steffen

    2014-09-04

    We investigated a novel formulation of indocyanine green (ICG/HS 15) in an animal model of laser-induced choroidal neovascularization (CNV). The ICG was formulated with the nonionic solubilizer and emulsifying agent Kolliphor HS 15 to create ICG/HS 15 to improve the chemical stability and fluorescence efficacy. In vivo imaging was performed in rats that had undergone laser photocoagulation. Retinal uptake and fluorescence intensity of ICG and ICG/HS 15 were compared following intravenous injection of 3 dosages (0.05, 0.1, and 0.15 mg/kg body weight) at 7, 14, and 21 days following laser treatment. Postmortem analysis included histology with frozen sections and flat mounts. Immediately following injection of ICG or ICG/HS 15, a strong fluorescence was visible in the retinal vasculature and at the site of laser lesions. Pixel intensity was higher for ICG/HS 15 compared to conventional ICG at 8 minutes after injection for all different injection days and dosages. Over time, a continuous decrease of the fluorescent signal was observed for up to 60 minutes to baseline level. Flow cytometry data showed an increased uptake of micellar dye of macrophages and endothelial cells. Histology revealed an accumulation of the micellar dye within the laser lesion. Micelle formulated ICG can be visualized in the retinal vasculature and laser-induced CNV in vivo and ex vivo. Micellar ICG/HS 15 showed in vivo stronger signal intensity when compared to ICG for all tested dosages. Following further investigations, ICG/HS 15 may be evaluated in patients with retinal and choroidal diseases for more refined diagnosis. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  19. Retinal detachment.

    PubMed

    Cavallerano, A A

    1992-01-01

    Retinal detachment is a separation of the neurosensory retina from the retinal pigment epithelium. Most retinal detachments are rhegmatogenous, and identification of risk factors and predisposing lesions are important aspects of patient management. Retinal detachment is relatively rare, but can pose a significant threat to vision if there is macular involvement. Prompt diagnosis combined with patient education and appropriate intervention often can avert irrevocable visual impairment. This paper presents an overview of the categories of retinal detachment, discusses the pathogenesis of the various types of detachment, and provides recommendations for primary care of patients with predisposing factors and high-risk characteristics.

  20. Polarisation-sensitive OCT is useful for evaluating retinal pigment epithelial lesions in patients with neovascular AMD

    PubMed Central

    Schütze, Christopher; Teleky, Katharina; Baumann, Bernhard; Pircher, Michael; Götzinger, Erich; Hitzenberger, Christoph K; Schmidt-Erfurth, Ursula

    2016-01-01

    Background/aims To examine the reproducibility of lesion dimensions of the retinal pigment epithelium (RPE) in neovascular age-related macular degeneration (AMD) with polarisation-sensitive optical coherence tomography (PS-OCT), specifically imaging the RPE. Methods Twenty-six patients (28 eyes) with neovascular AMD were included in this study, and examined by a PS-OCT prototype. Each patient was scanned five times at a 1-day visit. The PS-OCT B-scan located closest to the macular centre presenting with RPE atrophy was identified, and the longitudinal diameter of the lesion was quantified manually using AutoCAD 2008. This procedure was followed for the identical B-scan position in all five scans per eye and patient. Reproducibility of qualitative changes in PS-OCT was evaluated. Interobserver variability was assessed. Results were compared with intensity-based spectral-domain OCT (SD-OCT) imaging. Results Mean variability of all atrophy lesion dimensions was 0.10 mm (SD±=0.06 mm). Coefficient of variation (SD±/mean) was 0.06 on average (SD±=0.03). Interobserver variability assessment showed a mean difference of 0.02 mm across all patients regarding RPE lesion size evaluation (paired t test: p=0.38). Spearman correlation coefficient was r=0.98, p<0.001. Results revealed a good overall reproducibility of ∼90%. PS-OCT specifically detected the RPE in all eyes compared with conventional intensity-based SD-OCT that was not capable to clearly identify RPE atrophy in 25 eyes (89.3%, p<0.01). Conclusions PS-OCT offers good reproducibility of RPE atrophy assessment in neovascular AMD, and may be suitable for precise RPE evaluation in clinical practice. PS-OCT unambiguously identifies RPE changes in choroidal neovascularisation compared with intensity-based SD-OCT that does not identify the RPE status reliably. PMID:26183936

  1. 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

  2. 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.

  3. Laser Induced Breakdown Spectroscopy (LIBS)

    DTIC Science & Technology

    2010-03-31

    Gold Bond Powder Allopurinol (PIM 020F, French) Aluminum ophorite explosive. Methanol Aspirin Alphaprodine (PIM 878) Amatex. Aluminum Phosphide...can, directly or indirectly, change the electric charges of atoms or molecules . It is produced when radionuclides decay. LASER-INDUCED BREAKDOWN

  4. Retinal lesions induce fast intrinsic cortical plasticity in adult mouse visual system.

    PubMed

    Smolders, Katrien; Vreysen, Samme; Laramée, Marie-Eve; Cuyvers, Annemie; Hu, Tjing-Tjing; Van Brussel, Leen; Eysel, Ulf T; Nys, Julie; Arckens, Lutgarde

    2016-09-01

    Neuronal activity plays an important role in the development and structural-functional maintenance of the brain as well as in its life-long plastic response to changes in sensory stimulation. We characterized the impact of unilateral 15° laser lesions in the temporal lower visual field of the retina, on visually driven neuronal activity in the afferent visual pathway of adult mice using in situ hybridization for the activity reporter gene zif268. In the first days post-lesion, we detected a discrete zone of reduced zif268 expression in the contralateral hemisphere, spanning the border between the monocular segment of the primary visual cortex (V1) with extrastriate visual area V2M. We could not detect a clear lesion projection zone (LPZ) in areas lateral to V1 whereas medial to V2M, agranular and granular retrosplenial cortex showed decreased zif268 levels over their full extent. All affected areas displayed a return to normal zif268 levels, and this was faster in higher order visual areas than in V1. The lesion did, however, induce a permanent LPZ in the retinorecipient layers of the superior colliculus. We identified a retinotopy-based intrinsic capacity of adult mouse visual cortex to recover from restricted vision loss, with recovery speed reflecting the areal cortical magnification factor. Our observations predict incomplete visual field representations for areas lateral to V1 vs. lack of retinotopic organization for areas medial to V2M. The validation of this mouse model paves the way for future interrogations of cortical region- and cell-type-specific contributions to functional recovery, up to microcircuit level.

  5. Implementation Guidance Document: Properties and Types of Significant Photothermal Retinal Lesion Injuries

    DTIC Science & Technology

    2017-04-17

    damage to a person that permanently impairs physiological function and restricts the employment or other activities of that person for the rest of his...reference, Hirsch et al. states that each eye "can see 60° nasally (toward the nose), 100° temporally (away from the nose), 75° inferiorly (down), and 60...few threshold lesions on one or both eyes is not likely capable of causing a single scotoma with a 25% or more loss in the visual field. It is also

  6. The anti-angiogenic role of discoidin domain receptor 2 (DDR2) in laser-induced choroidal neovascularization.

    PubMed

    Zhu, Tong; Zhu, Jie; Bu, Xin; Zhao, Hu; Zhang, Shuya; Chang, Yuan; Li, Rong; Yao, Libo; Wang, Yusheng; Su, Jin

    2015-02-01

    Choroidal neovascularization (CNV), an aberrant growth of blood vessels in the choroid layer of the eye, is a major cause of vision loss. In view of our recent finding that discoidin domain receptor 2 (DDR2), a collagen-binding receptor tyrosine kinase, is involved in control of vascular endothelial activity and tumor angiogenesis, the present study aims to investigate whether and how DDR2 affects the pathogenesis of CNV. We initially found that a spontaneous DDR2 mutant mouse colony (slie) exhibited enhanced amplitude of laser-induced CNV. The inhibitory role of DDR2 in CNV development was further confirmed by experiments through intravitreous injection of DDR2 small interference RNA (siRNA) or DDR2-expressing adenovirus. Quantitative real-time polymerase chain reaction (qPCR) and immunoblot analysis showed that DDR2 regulates the expression of several major pro-angiogenic factors in the laser-injured choroid as well as in retinal pigment epithelium (RPE) cells. In addition, it was demonstrated that the CNV-induced increases in the phosphorylation levels of Akt and mTOR were affected by the upregulation or downregulation of DDR2. Thus, the data from this study for the first time revealed that DDR2 negatively regulates the development of experimental CNV in vivo, which may provide a novel target for preventing human pathological ocular neovascularization. Key messages: DDR2 does not affect retinal development. DDR2 inhibits laser-induced CNV. DDR2 regulates angiogenic factor expression in CNV lesion as well as in RPE cells. DDR2 is involved in modulation of CNV-induced activation of PI3K pathway.

  7. Cat retinal ganglion cell receptive-field alterations after 6-hydroxydopamine induced dopaminergic amacrine cell lesions

    SciTech Connect

    Maguire, G.W.; Smith, E.L. III

    1985-06-01

    Optic tract single-unit recordings were used to study ganglion cell response functions of the intact cat eye after 6-hydroxydopamine (6-OHDA) lesioning of the dopaminergic amacrine cell (AC) population of the inner retina. The impairment of the dopaminergic AC was verified by high pressure-liquid chromatography with electrochemical detection of endogenous dopamine content and by (/sup 3/H)dopamine high-affinity uptake; the dopaminergic ACs of the treated eyes demonstrated reduced endogenous dopamine content and reduced (/sup 3/H)dopamine uptake compared with that of their matched controls. Normal appearing (/sup 3/H)GABA and (/sup 3/H)-glycine uptake in the treated retinas suggests the absence of any nonspecific action of the 6-OHDA on the neural retina. The impairment of the dopaminergic AC population was found to alter a number of response properties in off-center ganglion cells, but this impairment had only a modest effect on the on-center cells. An abnormally high proportion of the off-center ganglion cells in the 6-OHDA treated eyes possessed nonlinear, Y-type receptive fields. These cells also possessed shift-responses of greater than normal amplitude, altered intensity-response functions, reduced maintained activities, and more transient center responses. Of the on-center type cells, only the Y-type on-center cells were affected by 6-OHDA, possessing higher than normal maintained activities and altered intensity-response functions. The on-center X-cells were unaffected by 6-OHDA treatment. The dopaminergic AC of the photopically adapted cat retina therefore modulates a number of ganglion cell response properties and within the limits of this study is most prominent in off-center ganglion cell circuitry.

  8. A Mouse Model for Laser-induced Choroidal Neovascularization.

    PubMed

    Shah, Ronil S; Soetikno, Brian T; Lajko, Michelle; Fawzi, Amani A

    2015-12-27

    The mouse laser-induced choroidal neovascularization (CNV) model has been a crucial mainstay model for neovascular age-related macular degeneration (AMD) research. By administering targeted laser injury to the RPE and Bruch's membrane, the procedure induces angiogenesis, modeling the hallmark pathology observed in neovascular AMD. First developed in non-human primates, the laser-induced CNV model has come to be implemented into many other species, the most recent of which being the mouse. Mouse experiments are advantageously more cost-effective, experiments can be executed on a much faster timeline, and they allow the use of various transgenic models. The miniature size of the mouse eye, however, poses a particular challenge when performing the procedure. Manipulation of the eye to visualize the retina requires practice of fine dexterity skills as well as simultaneous hand-eye-foot coordination to operate the laser. However, once mastered, the model can be applied to study many aspects of neovascular AMD such as molecular mechanisms, the effect of genetic manipulations, and drug treatment effects. The laser-induced CNV model, though useful, is not a perfect model of the disease. The wild-type mouse eye is otherwise healthy, and the chorio-retinal environment does not mimic the pathologic changes in human AMD. Furthermore, injury-induced angiogenesis does not reflect the same pathways as angiogenesis occurring in an age-related and chronic disease state as in AMD. Despite its shortcomings, the laser-induced CNV model is one of the best methods currently available to study the debilitating pathology of neovascular AMD. Its implementation has led to a deeper understanding of the pathogenesis of AMD, as well as contributing to the development of many of the AMD therapies currently available.

  9. Laser Induced Surface Chemical Epitaxy

    DTIC Science & Technology

    1990-03-01

    Laser-Induced Surface Chemical Epitaxy ( LSCE ). The essential features of LSCE as applied to CdTe epitaxy involve: coadsorption of DMCd and DMTe on a GaAs...DIAGRAM OF THE LSCE PROCESS UHV environment 1M substra1e 9 /X Adsorbed thin film produced CH 3 -Cd-GH 3 CH 3 -Te-CH, by molecular beam source hv ’ CH...with Anneal W/// substraIe %/"/,’ Figure 1.1. Schematic of the LSCE process. (1-2) t I 2. EXPERIMENTAL APPROACH 2.1 Experimental Apparatus The

  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. 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.

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

    PubMed

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

    2010-01-01

    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.

  13. Laser-induced magnetization curve

    NASA Astrophysics Data System (ADS)

    Takayoshi, Shintaro; Sato, Masahiro; Oka, Takashi

    2014-12-01

    We propose an all optical ultrafast method to highly magnetize general quantum magnets using a circularly polarized terahertz laser. The key idea is to utilize a circularly polarized laser and its chirping. Through this method, one can obtain magnetization curves of a broad class of quantum magnets as a function of time even without any static magnetic field. We numerically demonstrate the laser-induced magnetization process in realistic quantum spin models and find a condition for the realization. The onset of magnetization can be described by a many-body version of Landau-Zener mechanism. In a particular model, we show that a plateau state with topological properties can be realized dynamically.

  14. Treatment of retinal detachment due to macular holes without chorio-retinal lesions. A seven-year follow-up study.

    PubMed

    Theodossiadis, G P

    1982-04-01

    For the treatment of retinal detachment arising from macular holes we do not apply cryotherapy, light-coagulation, or diathermy in the area of the macula. Our method involves merely the fixation of a silastic sponge of 14-17 mm length and 7.5 mm diameter at the posterior part of the eyeball corresponding to macula and along the meridian of 12-6 o'clock axis. The sponge is stretched and then fixed at both ends to the sclera away from the posterior pole. The stretching and fixation of the sponge creates the proper indentation which closes the macular hole. By avoiding energy application we obtain better visual acuity. The present paper describes the results we have had in the last 7 years exclusively using this technique.

  15. Macular Ganglion Cell Layer and Peripapillary Retinal Nerve Fibre Layer Thickness in Patients with Unilateral Posterior Cerebral Artery Ischaemic Lesion: An Optical Coherence Tomography Study

    PubMed Central

    Anjos, Rita; Vieira, Luisa; Costa, Livio; Vicente, André; Santos, Arnaldo; Alves, Nuno; Amado, Duarte; Ferreira, Joana; Cunha, João Paulo

    2016-01-01

    ABSTRACT The purpose of this study is to evaluate the macular ganglion cell layer (GCL) and peripapillary retinal nerve fibre layer (RNFL) thickness in patients with unilateral posterior cerebral artery (PCA) ischaemic lesions using spectral-domain optical coherence tomography (SD-OCT). A prospective, case-control study of patients with unilateral PCA lesion was conducted in the neuro-ophthalmology clinic of Centro Hospitalar Lisboa Central. Macular and peripapillary SD-OCT scans were performed in both eyes of each patient. Twelve patients with PCA lesions (stroke group) and 12 healthy normal controls were included in this study. Peripapillary RNFL comparison between both eyes of the same subject in the stroke group found a thinning in the superior-temporal (p = 0.008) and inferior-temporal (p = 0.023) sectors of the ipsilateral eye and nasal sector (p = 0.003) of the contralateral eye. Macular GCL thickness comparison showed a reduction temporally in the ipsilateral eye (p = 0.004) and nasally in the contralateral eye (p = 0.002). Peripapillary RNFL thickness was significantly reduced in both eyes of patients with PCA compared with controls, affecting all sectors in the contralateral eye and predominantly temporal sectors in the ipsilateral eye. A statistically significant decrease in macular GCL thickness was found in both hemiretinas of both eyes of stroke patients when compared with controls (p < 0.05). This study shows that TRD may play a role in the physiopathology of lesions of the posterior visual pathway. PMID:27928376

  16. 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

  17. 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

  18. Solar retinitis.

    PubMed

    SHIRLEY, S Y

    1963-07-20

    Retinal burns can be produced by direct gazing at the sun. This lesion is caused by the thermal effects of the visible and near infrared rays focused on the pigment structure behind the retina. It is rarely seen, as the normal eye will tolerate only fleeting glances at the sun, but is fairly common during a solar eclipse. A case of solar retinitis is presented in which treatment with corticosteroids lessened the retinal edema but the patient suffered a bilateral central scotoma and vision reduced to the 20/40 level. In viewing a solar eclipse a No. 4 density filter is recommended; as a rough test this filter will abolish the readability of print on a 60-watt incandescent frosted electric light bulb.

  19. Solar Retinitis

    PubMed Central

    Shirley, S. Y.

    1963-01-01

    Retinal burns can be produced by direct gazing at the sun. This lesion is caused by the thermal effects of the visible and near infrared rays focused on the pigment structure behind the retina. It is rarely seen, as the normal eye will tolerate only fleeting glances at the sun, but is fairly common during a solar eclipse. A case of solar retinitis is presented in which treatment with corticosteroids lessened the retinal edema but the patient suffered a bilateral central scotoma and vision reduced to the 20/40 level. In viewing a solar eclipse a No. 4 density filter is recommended; as a rough test this filter will abolish the readability of print on a 60-watt incandescent frosted electric light bulb. ImagesFig. 1Fig. 2 PMID:13977409

  20. 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.

  1. Retinitis Pigmentosa

    MedlinePlus

    ... Action You are here Home › Retinal Diseases Listen Retinitis Pigmentosa What is retinitis pigmentosa? What are the symptoms? ... is available? What treatment is available? What is retinitis pigmentosa? Retinitis pigmentosa, also known as RP, refers to ...

  2. Down-regulation of pigment epithelium-derived factor in uveitic lesion associates with focal vascular endothelial growth factor expression and breakdown of the blood-retinal barrier.

    PubMed

    Deeg, Cornelia A; Altmann, Frank; Hauck, Stefanie M; Schoeffmann, Stephanie; Amann, Barbara; Stangassinger, Manfred; Ueffing, Marius

    2007-05-01

    Spontaneous equine recurrent uveitis (ERU) is an incurable autoimmune disease affecting the eye. Identifying biological markers or pathways associated with this disease may allow the understanding of its pathogenesis at a molecular level. The vitreous is the body fluid closest to the disease-affected tissue and possibly also an effector of pathological processes relevant for ERU. Surgical removal of vitreous leads to cessation of relapses in spontaneous uveitis of both man and horse, therefore vitreous composites are likely to contribute to disease progression. Uveitic vitreous is likely to contain potential biomarkers in relatively undiluted quantities. With the goal to identify these markers, we systematically compared vitreous from healthy and disease-affected eyes by proteomic profiling. Nine differentially expressed proteins were identified, that are functionally related to immune response, inflammation, and maintenance of the blood-retinal barrier. One of these, pigment epithelium-derived factor, a protein involved in maintaining a proper blood-retina barrier as well as protecting from neoangiogenesis was additionally found to be down-regulated within uveitic retinal lesions whereas, conversely, vascular endothelial growth factor was found to be up-regulated at these sites. Together, these changes point to as of yet undiscovered biological pathways involved in the pathogenesis of this autoimmune disease.

  3. Novel serum proteomic signatures in a non-human primate model of retinal injury

    PubMed Central

    Dunmire, Jeffrey J.; Bouhenni, Rachida; Hart, Michael L.; Wakim, Bassam T.; Chomyk, Anthony M.; Scott, Sarah E.; Nakamura, Hiroshi

    2011-01-01

    Purpose To identify candidate protein biomarkers in sera indicative of acute retinal injury. Methods We used laser photocoagulation as a model of acute retinal injury in Rhesus macaques. In a paired-control study design, we collected serum from each animal (n=6) at 4 h, 1 day, and 3 days following a mock procedure and then again following retinal laser treatment that produced mild lesions. Samples were fractionated by isoelectric focusing, digested with trypsin, and analyzed by liquid chromatography/tandem mass spectrometry (LC-MS/MS). Spectral counting was used to determine relative protein abundances and identify proteins with statistically significant differences between control and treated sera. Results Mild retinal injury was confirmed by fundus photography and histological examination. The average number of total proteins detected by LC-MS/MS was 908±82 among samples from all three time points. Following statistical analysis and employing stringent filtering criteria, a total of 19 proteins were identified as being significantly more abundant in sera following laser-induced retinal injury, relative to control sera. Many of the proteins detected were unique to one time point. However, four proteins (phosphoglycerate kinase 1, keratin 18, Lewis alpha-3-fucosyltransferase, and ephrin receptor A2) showed differences that were significant at both 4 h and 1 day after laser treatment, followed by a decrease to baseline levels by day 3. Conclusions A serum biomarker response to mild retinal laser injury was demonstrated in a primate model. Among the proteins detected with highest significant differences, most are upregulated within 24 h, and their appearance in the serum is transient. It is conceivable that a panel of these proteins could provide a means for detecting the acute-phase response to retinal injury. Further investigation of these candidate biomarkers and their correlation to retinal damage is warranted. PMID:21527995

  4. Foveal photoreceptor explanation of short-term visual acuity recovery associated with laser-induced foveal damage

    NASA Astrophysics Data System (ADS)

    Langus, Amir; Zwick, Harry; Stuck, Bruce E.; Belkin, Michael

    2003-06-01

    Both human laser accident cases and non-human primate behavioral studies demonstrate the possibility of full visual acuity recovery following foveal laser injury. Current explanations of such recovery require suppositions of complex retinal reorganization dynamics or neural reorganization at higher order visual brain systems. However, recent investigation based on data of retinal photoreceptor and ganglion cell topography and connectivity, suggest that the amount of static inherent plasticity, already exists at the retinal level, may also explain visual acuity recovery in the presence of laser-induced foveal damage. Modeling the off-axis visual acuity while utilizing this data, produces a more gradual fall-off in visual acuity, and supports the notion that visual acuity recovery may reside in the topographical organization of the cones. Moreover, considering the filling-in phenomena, which can conceal the presence of retinal damage from being recognized, together with eye movements, could nullify scotoma, as long as the retinal damage is not too extensive.

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

    PubMed

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

    2015-11-19

    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.

  6. Choroidal melanoma clinically simulating a retinal angioma.

    PubMed

    Shields, J A; Joffe, L; Guibor, P

    1978-01-01

    An amelanotic fundus lesion in a 35-year-old man was associated with a dilated retinal vessel, thus suggesting the diagnosis of retinal angioma. Fluorescein angiography and B-scan ultrasonography were not diagnostic, but a radioactive phosphorus uptake test suggested the lesion was malignant. The enucleated globe showed a malignant choroidal melanoma drained by a large retinal vein.

  7. 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)

  8. 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.

  9. Laser-induced fluorescence detection of stomach cancer using hypericin

    NASA Astrophysics Data System (ADS)

    Dets, Sergiy M.; Buryi, Alexander N.; Melnik, Ivan S.; Joffe, Alexander Y.; Rusina, Tatyana V.

    1996-12-01

    Natural photodynamic pigment hypericin having intrinsic antitumor properties was applied for fluorescence detection of cancer. Clinical investigation of hypericin was performed to ensure high tumor/normal fluorescence contrast in digestion organs. Laser-induced autofluorescence and exogenous fluorescence analysis of normal tissue and stomach adenocarcinoma was performed using helium-cadmium laser (8 mW, 442 nm). Twenty-one patients have undergone procedure of fluorescence detection of tumors before and after photosensitization. For sensitization of patients we used five or seven capsules containing hypericin in amount of 1 mg which have been administered orally. Strong yellow-red fluorescence of hypericin in tissue with maximum at 603 nm and autofluorescence peak at 535 nm gives an intensity ratio I(603 nm)/I(535 nm) of 2 - 2.5 from cancerous tissue and provides 85% specificity. Preliminary in vivo results of auto- and fluorescence analysis using hypericin photosensitization from one patient with esophageal cancer and eleven patients with stomach cancer proven histologically are encouraging and indicate the high reliability of laser-induced fluorescence technique with hypericin in detection of early stage malignant lesions.

  10. Laser induced white lighting of graphene foam

    PubMed Central

    Strek, Wieslaw; Tomala, Robert; Lukaszewicz, Mikolaj; Cichy, Bartlomiej; Gerasymchuk, Yuriy; Gluchowski, Pawel; Marciniak, Lukasz; Bednarkiewicz, Artur; Hreniak, Dariusz

    2017-01-01

    Laser induced white light emission was observed from porous graphene foam irradiated with a focused continuous wave beam of the infrared laser diode. It was found that the intensity of the emission increases exponentially with increasing laser power density, having a saturation level at ca. 1.5 W and being characterized by stable emission conditions. It was also observed that the white light emission is spatially confined to the focal point dimensions of the illuminating laser light. Several other features of the laser induced white light emission were also discussed. It was observed that the white light emission is highly dependent on the electric field intensity, allowing one to modulate the emission intensity. The electric field intensity ca. 0.5 V/μm was able to decrease the white light intensity by half. Origins of the laser-induced white light emission along with its characteristic features were discussed in terms of avalanche multiphoton ionization, inter-valence charge transfer and possible plasma build-up processes. It is shown that the laser-induced white light emission may be well utilized in new types of white light sources. PMID:28112254

  11. Laser induced white lighting of graphene foam

    NASA Astrophysics Data System (ADS)

    Strek, Wieslaw; Tomala, Robert; Lukaszewicz, Mikolaj; Cichy, Bartlomiej; Gerasymchuk, Yuriy; Gluchowski, Pawel; Marciniak, Lukasz; Bednarkiewicz, Artur; Hreniak, Dariusz

    2017-01-01

    Laser induced white light emission was observed from porous graphene foam irradiated with a focused continuous wave beam of the infrared laser diode. It was found that the intensity of the emission increases exponentially with increasing laser power density, having a saturation level at ca. 1.5 W and being characterized by stable emission conditions. It was also observed that the white light emission is spatially confined to the focal point dimensions of the illuminating laser light. Several other features of the laser induced white light emission were also discussed. It was observed that the white light emission is highly dependent on the electric field intensity, allowing one to modulate the emission intensity. The electric field intensity ca. 0.5 V/μm was able to decrease the white light intensity by half. Origins of the laser-induced white light emission along with its characteristic features were discussed in terms of avalanche multiphoton ionization, inter-valence charge transfer and possible plasma build-up processes. It is shown that the laser-induced white light emission may be well utilized in new types of white light sources.

  12. Laser-induced gas breakdown and ignition

    NASA Astrophysics Data System (ADS)

    Chen, Ying-Ling Ann

    Laser-induced gas breakdown and ignition are studied in atmospheric pressure gas flow. The nanosecond-pulsed, 1064-nm Nd:YAG laser was used to create the cascade-type optical breakdown in air, oxygen, ammonia, and the combustible ammonia/oxygen mixture. We investigate the formation of the initial plasma and the chemical and gasdynamic development of the breakdown kernel. The spatial and temporal features of the energy deposition process are presented for laser breakdowns in still air. The generation of air-breakdown events is very stable between laser pulses when the incident laser power is two times larger than the threshold value. The effects associated with the ammonia flow-speed in the range of 1- 7 cm/sec are shown to be significant for the plasma. formation and stability of both laser-induced breakdown and ignition kernel, even though the flow field is laminar. The post-breakdown development of laser breakdown and ignition is studied using high-speed photographic and spectroscopic techniques including shadowgraphs, planar laser-induced fluorescence (PLIF), spontaneous emission and Rayleigh scattering. These time- resolved two-dimensional images provide gasdynamic, radiative and NH radical concentration and temperature information to aid the understanding of the kernel dynamics. The asymmetric feature of the initial plasma and the gas dynamics that leads to the backstreaming effect in laser-induced breakdown is suggested and evaluated.

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

    PubMed

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

    2016-08-10

    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.

  14. Laser scleral buckling: a new method to treat retinal detachment

    NASA Astrophysics Data System (ADS)

    Ren, Qiushi; Simon, Gabriel; Parel, Jean-Marie A.; Takesue, Yoshiko; Shen, Jin-Hui; Smiddy, William E.

    1993-06-01

    Scleral indentation was induced in cadaver eyes by shrinkage of scleral collagen fibers using a pulsed solid state Ho:YAG (2.1 micrometers ) laser with fiber optic delivery. Applying Ho:YAG laser radiation permits control of the amount of laser induced buckling effect by selecting laser treatment parameters such as beam spot, radiant exposure, and number of pulses. With treatment using 11.3 +/- 1.2 J/cm2 laser radiant exposure and 5 pulses, laser induced scleral shrinkage affected only the external two-thirds of scleral tissue. No thermal damage or disruption was observed in subjacent retinal pigment epithelium, chorioid, or retina. Coupling of two appropriately selected lasers may allow laser induced scleral buckling and transscleral retinal photocoagulation using the same laser probe for retinal reattachment surgery.

  15. 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.

  16. Laser-induced regeneration of cartilage

    NASA Astrophysics Data System (ADS)

    Sobol, Emil; Shekhter, Anatoly; Guller, Anna; Baum, Olga; Baskov, Andrey

    2011-08-01

    Laser radiation provides a means to control the fields of temperature and thermo mechanical stress, mass transfer, and modification of fine structure of the cartilage matrix. The aim of this outlook paper is to review physical and biological aspects of laser-induced regeneration of cartilage and to discuss the possibilities and prospects of its clinical applications. The problems and the pathways of tissue regeneration, the types and features of cartilage will be introduced first. Then we will review various actual and prospective approaches for cartilage repair; consider possible mechanisms of laser-induced regeneration. Finally, we present the results in laser regeneration of joints and spine disks cartilages and discuss some future applications of lasers in regenerative medicine.

  17. On laser-induced harpooning reactions

    NASA Astrophysics Data System (ADS)

    Weiner, J.

    1980-05-01

    In the present paper, the switching of chemical reactivity by a nonresonant laser field in simple gas-phase collisions of the type A + BC to AB + C is discussed in terms of a second-order optical/collision perturbation. A simple expression relating laser-induced harpooning cross sections to the laser power density is derived and is applied to Hg/Cl2 collisions.

  18. Selective Nitrations: Laser-Induced Nitrations

    DTIC Science & Technology

    1989-01-01

    Produt Mol Thermalt Laser-Induced Propane Nitrornethane 22.0 (32.3) 32 Nitroethane 16.6 (24I.2) 17 1-nitropropane 13.2 (2 4. 2) 15 2-nitropropane 48.2...Alrich Library of FT-IR Spectra, Ed. 1, Charles J. Pouchert (1985, Alrich Chemical Company, Inc., Milwaukee, WI), p. 397. 11. Norton, R. H. and Beer , R

  19. 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.

  20. Retinitis pigmentosa

    PubMed Central

    Hamel, Christian

    2006-01-01

    Retinitis pigmentosa (RP) is an inherited retinal dystrophy caused by the loss of photoreceptors and characterized by retinal pigment deposits visible on fundus examination. Prevalence of non syndromic RP is approximately 1/4,000. The most common form of RP is a rod-cone dystrophy, in which the first symptom is night blindness, followed by the progressive loss in the peripheral visual field in daylight, and eventually leading to blindness after several decades. Some extreme cases may have a rapid evolution over two decades or a slow progression that never leads to blindness. In some cases, the clinical presentation is a cone-rod dystrophy, in which the decrease in visual acuity predominates over the visual field loss. RP is usually non syndromic but there are also many syndromic forms, the most frequent being Usher syndrome. To date, 45 causative genes/loci have been identified in non syndromic RP (for the autosomal dominant, autosomal recessive, X-linked, and digenic forms). Clinical diagnosis is based on the presence of night blindness and peripheral visual field defects, lesions in the fundus, hypovolted electroretinogram traces, and progressive worsening of these signs. Molecular diagnosis can be made for some genes, but is not usually performed due to the tremendous genetic heterogeneity of the disease. Genetic counseling is always advised. Currently, there is no therapy that stops the evolution of the disease or restores the vision, so the visual prognosis is poor. The therapeutic approach is restricted to slowing down the degenerative process by sunlight protection and vitaminotherapy, treating the complications (cataract and macular edema), and helping patients to cope with the social and psychological impact of blindness. However, new therapeutic strategies are emerging from intensive research (gene therapy, neuroprotection, retinal prosthesis). PMID:17032466

  1. Laser Induced Breakdown Spectroscopy of Metals

    NASA Astrophysics Data System (ADS)

    Palmer, Andria; Lawhead, Carlos; Ujj, Laszlo

    2015-03-01

    Laser Induced Breakdown Spectroscopy (LIBS) is a very practical spectroscopy to determine the chemical composition of materials. Recent technical developments resulted in equipment used on the MARS Rover by NASA. It is capable of measuring the emission spectra of laser induced plasma created by energetic laser pulses focused on the sample (rocks, metals, etc.). We have develop a Laser Induced Breakdown Spectroscopy setup and investigated the necessary experimental and methodological challenges needed to make such material identification measurements. 355 and 532 nm laser pulses with 5 ns temporal duration was used to generate micro-plasma from which compositions can be determined based on known elemental and molecular emission intensities and wavelengths. The performance of LIBS depends on several parameters including laser wavelength, pulse energy, pulse duration, time interval of observation, geometrical configuration of collecting optics, and the properties of ambient medium. Spectra recorded from alloys (e.g. US penny coin) and pure metals will be presented. Special thanks for the financial support of the Office of Undergraduate Research of UWF.

  2. Laser injury promotes migration and integration of retinal progenitor cells into host retina

    PubMed Central

    Jiang, Caihui; Klassen, Henry; Zhang, Xinmei

    2010-01-01

    Purpose The migration and integration of grafted cells into diseased host tissue remains a critical challenge, particularly in the field of retinal progenitor cell (RPC) transplantation. It seems that natural physical barriers at the outer retina can impede the migration of grafted RPCs into the host retina. The purpose of this study was to investigate the integration and differentiation of murine RPCs transplanted into the subretinal space of mice with laser-induced damage to the outer retina. Methods RPCs were harvested from the neural retinas of postnatal day 1 enhanced green fluorescent protein (GFP) mice. Retinal photocoagulation was performed using a diode laser. Two µl containing ~6×105 expanded RPCs in suspension were injected into the subretinal space of the recipient animals following laser treatment. Cell morphometry was performed to assess the integration of donor cells. Immunohistochemistry and western blot were performed on recipient retinas. Results Three weeks after transplantation, 1,158±320 cells per eye had migrated into the recipient outer nuclear layer (ONL). Most of these cells resided in the ONL around the retinal laser lesion. A subpopulation of these cells developed morphological features reminiscent of mature photoreceptors, expressed photoreceptor specific proteins including synaptic protein, and appeared to form synaptic connections with bipolar neurons. Retinal photocoagulation resulted in a significantly increased expression of matrix metalloproteinase-2 (MMP-2), MMP-9, and cluster differentiation 44 (CD44s), and a decreased expression of neurocan. Conclusions Transplanted RPCs migrate and integrate into the laser-injured ONL where they differentiate into photoreceptors with morphological features reminiscent of mature photoreceptors, express synaptic protein, and appear to form synaptic connections with retinal bipolar neurons. Following retinal photocoagulation, the enhanced level of integration of grafted RPCs is partially

  3. 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

  4. Improved assessment of laser-induced choroidal neovascularization.

    PubMed

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

    2010-12-01

    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.

  5. Detection of lead in water using laser-induced breakdown spectroscopy and laser-induced fluorescence.

    PubMed

    Lui, Siu L; Godwal, Yogesh; Taschuk, Michael T; Tsui, Ying Y; Fedosejevs, Robert

    2008-03-15

    Laser-induced breakdown spectroscopy (LIBS) is a well-known technique for fast, stand-off, and nondestructive analysis of the elemental composition of a sample. We have been investigating micro-LIBS for the past few years and demonstrating its application to microanalysis of surfaces. Recently, we have integrated micro-LIBS with laser-induced fluorescence (LIF), and this combination, laser ablation laser-induced fluorescence (LA-LIF), allows one to achieve much higher sensitivity than traditional LIBS. In this study, we use a 170 microJ laser pulse to ablate a liquid sample in order to measure the lead content. The plasma created was re-excited by a 10 microJ laser pulse tuned to one of the lead resonant lines. Upon optimization, the 3sigma limit of detection was found to be 35 +/- 7 ppb, which is close to the EPA standard for the level of lead allowed in drinking water.

  6. 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.

  7. 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.

  8. 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

  9. Laser-Induced Transfer of Metal Nanoparticles

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Arseniy I.; Koch, Jürgen; Chichkov, Boris N.

    2010-10-01

    A novel approach for the fabrication of metallic micro- and nanostructures based on femtosecond laser-induced transfer of metallic nanodroplets is developed. The size of the transferred droplets depends on the volume of laser-molten metal and can be varied by changing the laser beam focus on the sample surface and the metal film thickness. Controllable fabrication of high quality spherical gold micro- and nanoparticles with sizes between 170 nm and 1500 nm is realized. Fabrication of miscellaneous structures consisting of gold particles as elementary building blocks is demonstrated.

  10. Optical Probes for Laser Induced Shocks

    DTIC Science & Technology

    1992-03-01

    waves generated by a laser -induced plasma were investigated using a pump - and-probe technique. Both 7-ns and 40-ps laser pulses at 1.06 gIm were employed...what follows, a TEM00 the time it takes to ablate a layer of thickness 60, i.e., the laser beam is assumed. To describe this I apply the results...Frauchiger and W. Liithy, Opt. Quantum Electron. 19, 231 (1987). transverse the irradiated spot during the laser pulse, as is ’It should read i 10(dv

  11. Laser Induced Damage in Optical Materials: 1979.

    DTIC Science & Technology

    1980-07-01

    an oscillator in laser fusion systems [8, 9]. Tm:YLF, pumped by an XeF laser , and emitting at 453 nm [10], is an efficient storage laser and is being...Chicklis, [4] Wilson, R., Varian Associates (private E.P. and Jenssen, H.P., XeF pumped communication). Tm:YLF an excimer excited storage laser , Technical...caused by pulsed laser -induced thermal stress were not signifi- cantly influenced by transverse heat conduction. However, the fluence levels were above

  12. Laser induced fluorescence technique for environmental applications

    NASA Astrophysics Data System (ADS)

    Utkin, Andrei B.; Felizardo, Rui; Gameiro, Carla; Matos, Ana R.; Cartaxana, Paulo

    2014-08-01

    We discuss the development of laser induced fluorescence sensors and their application in the evaluation of water pollution and physiological status of higher plants and algae. The sensors were built on the basis of reliable and robust solid-state Nd:YAG lasers. They demonstrated good efficiency in: i) detecting and characterizing oil spills and dissolved organic matter; ii) evaluating the impact of stress on higher plants (cork oak, maritime pine, and genetically modified Arabidopsis); iii) tracking biomass changes in intertidal microphytobenthos; and iv) mapping macroalgal communities in the Tagus Estuary.

  13. Laser-induced breakdown spectroscopy in Asia

    NASA Astrophysics Data System (ADS)

    Wang, Zhen-Zhen; Deguchi, Yoshihiro; Zhang, Zhen-Zhen; Wang, Zhe; Zeng, Xiao-Yan; Yan, Jun-Jie

    2016-12-01

    Laser-induced breakdown spectroscopy (LIBS) is an analytical detection technique based on atomic emission spectroscopy to measure the elemental composition. LIBS has been extensively studied and developed due to the non-contact, fast response, high sensitivity, real-time and multi-elemental detection features. The development and applications of LIBS technique in Asia are summarized and discussed in this review paper. The researchers in Asia work on different aspects of the LIBS study in fundamentals, data processing and modeling, applications and instrumentations. According to the current research status, the challenges, opportunities and further development of LIBS technique in Asia are also evaluated to promote LIBS research and its applications.

  14. 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.

  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 fluorescence model of human goiter

    NASA Astrophysics Data System (ADS)

    Jaliashvili, Z. V.; Medoidze, T. D.; Mardaleishvili, K. M.; Ramsden, J. J.; Melikishvili, Z. G.

    2008-03-01

    Laser induced fluorescence (LIF) with wide area surveillance for resected thyroid tissue solid chunks is presented. The characteristic LIF spectra of goiter were established. The state of tissue at each point represents a superposition of normal and pathology states. To our knowledge two co-existing pathological effects were observed optically for the first time. It is demonstrated that the LIF spectral functions and their intensities well-labeled such areas and represent a good tool for medical diagnostics of goiter and for the definition of the degree of abnormality and geometrical sizes of these areas.

  19. Kinetic Approach for Laser-Induced Plasmas

    NASA Astrophysics Data System (ADS)

    Omar, Banaz; Rethfeld, Bärbel

    2008-10-01

    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.

  20. Local Production of the Alternative Pathway Component Factor B Is Sufficient to Promote Laser-Induced Choroidal Neovascularization

    PubMed Central

    Schnabolk, Gloriane; Coughlin, Beth; Joseph, Kusumam; Kunchithapautham, Kannan; Bandyopadhyay, Mausumi; O'Quinn, Elizabeth C.; Nowling, Tamara; Rohrer, Bärbel

    2015-01-01

    Purpose. Complement factor B (CFB) is a required component of the alternative pathway (AP) of complement, and CFB polymorphisms are associated with age-related macular degeneration (AMD) risk. Complement factor B is made in the liver, but expression has also been detected in retina and retinal pigment epithelium (RPE)-choroid. We investigated whether production of CFB by the RPE can promote AP activation in mouse choroidal neovascularization (CNV). Methods. Transgenic mice expressing CFB under the RPE65 promoter were generated and crossed onto factor B-deficient (CFB-KO) mice. Biological activity was determined in vitro using RPE monolayers and in vivo using laser-induced CNV. Contribution of systemic CFB was investigated using CFB-KO reconstituted with CFB-sufficient serum. Results. Transgenic mice (CFB-tg) expressed CFB in RPE-choroid; no CFB was detected in serum. Cultured CFB-tg RPE monolayers secreted CFB apically and basally upon exposure to oxidative stress that was biologically active. Choroidal neovascularization sizes were comparable between wild-type and CFB-tg mice, but significantly increased when compared to lesions in CFB-KO mice. Injections of CFB-sufficient serum into CFB-KO mice resulted in partial reconstitution of systemic AP activity and significantly increased CNV size. Conclusions. Mouse RPE cells express and secrete CFB sufficient to promote RPE damage and CNV. This further supports that local complement production may regulate disease processes; however, the reconstitution experiments suggest that additional components may be sequestered from the bloodstream. Understanding the process of ocular complement production and regulation will further our understanding of the AMD disease process and the requirements of a complement-based therapeutic. PMID:25593023

  1. Laser-induced torques in metallic ferromagnets

    NASA Astrophysics Data System (ADS)

    Freimuth, Frank; Blügel, Stefan; Mokrousov, Yuriy

    2016-10-01

    We study laser-induced torques in bcc Fe, hcp Co, and L 10 FePt based on first-principles electronic structure calculations and the Keldysh nonequilibrium formalism. We find that the torques have two contributions, one from the inverse Faraday effect (IFE) and one from the optical spin-transfer torque (OSTT). Depending on the ferromagnet at hand and on the quasiparticle broadening the two contributions may be of similar magnitude, or one contribution may dominate over the other. Additionally, we determine the nonequilibrium spin polarization in order to investigate its relation to the torque. We find the torques and the perpendicular component of the nonequilibrium spin polarization to be odd in the helicity of the laser light, while the spin polarization that is induced parallel to the magnetization is helicity independent. The parallel component of the nonequilibrium spin polarization is orders of magnitude larger than the perpendicular component. In the case of hcp Co we find good agreement between the calculated laser-induced torque and a recent experiment.

  2. Laser-induced fluorescence spectroscopy at endoscopy

    NASA Astrophysics Data System (ADS)

    Qu, Jianan Y.; MacAulay, Calum E.; Lam, Stephen; Palcic, Branko

    1994-07-01

    A spectrofluorometry system has been developed for the collection of laser induced fluorescense spectra of tissue during endoscopy. In this system, a catheter with seven optical fibers was used to deliver the excitation light and collect the emitted fluorescence. The system enables one to switch from regular endoscopy into fluorescence measurement in 50 ms using a computerized shutter system. The fluorescence spectra can be recorded in 100 ms. This spectrofluorometry system has been used to obtain spectra from bronchial, larynx and nasopharyngeal tissues when employed with the appropriate endoscopes. The results demonstrate that laser induced fluorescence can be used to differentiate abnormal tissue from normal tissue. The illumination and fluorescence collection patterns of this system have been modeled using a Monte Carlo simulation. The Monte Carlo simulation data shows that the spectra recorded by our collection pattern is very close to the intrinsic spectra of tissue. The experimental results and the Monte Carlo simulation suggest that changes in fluorescence intensity are more robust for the detection of early cancers than the differences in spectral characteristics.

  3. Laser-induced ionization of Na vapor

    SciTech Connect

    Wu, R.C.Y.; Judge, D.L.; Roussel, F.; Carre, B.; Breger, P.; Spiess, G.

    1982-01-01

    The production of Na/sub 2//sup +/ ions by off-resonant laser excitation in the 5800-6200A region mainly results from two-photon absorption by the Na/sub 2/ molecule to highly excited gerade states followed by (a) direct ionization by absorbing a third photon or (b) coupling to the molecular Na/sub 2/ D/sup 1/PI..mu.. Rydberg state which is subsequently ionized by absorbing a third photon. This mechanism, i.e., a two-photon resonance three photon ionization process, explains a recent experimental observation of Roussel et al. It is suggested that the very same mechanism is also responsible for a similar observation reported by Polak-Dingels et al in their work using two crossed Na beams. In the latter two studies the laser-induced associative ionization processes were reported to be responsible for producing the Na/sub 2//sup +/ ion. From the ratio of molecular to atomic concentration in the crossed beam experiment of Polak-Dingels et al we estimate that the cross section for producing Na/sub 2//sup +/ through laser-induced associative ionization is at least four orders of magnitude smaller than ionization through the two-photon resonance three photon ionization process in Na/sub 2/ molecules.

  4. Laser-induced ionization of Na vapor

    NASA Astrophysics Data System (ADS)

    Wu, C. Y. Robert; Judge, D. L.; Roussel, F.; Carré, B.; Breger, P.; Spiess, G.

    1982-09-01

    The production of Na2+ ions by off-resonant laser excitation in the 5800-6200Å region mainly results from two-photon absorption by the Na2 molecule to highly excited gerade states followed by (a) direct ionization by absorbing a third photon or (b) coupling to the molecular Na2 D1Πu Rydberg state which is subsequently ionized by absorbing a third photon. This mechanism, i.e., a two-photon resonance three photon ionization process, explains a recent experimental observation of Roussel et al. It is suggested that the very same mechanism is also responsible for a similar observation reported by Polak-Dingels et al in their work using two crossed Na beams. In the latter two studies the laser-induced associative ionization processes were reported to be responsible for producing the Na2+ ion. From the ratio of molecular to atomic concentration in the crossed beam experiment of Polak-Dingels et al. we estimate that the cross section for producing Na2+ through laser-induced associative ionization is at least four orders of magnitude smaller than ionization through the two-photon resonance three photon ionization process in Na2 molecules.

  5. Foveo-macular retinitis, solar retinopathy, and trauma.

    PubMed Central

    Grey, R. H.

    1978-01-01

    Three patients are described with foveal lesions resembling minute holes following trauma. The similarity of the lesions to foveomacular retinitis and solar retinopathy suggests that all these conditions produce a similar, localised neuroretinal lesion with sparing of the pigment epithelium. Loss of the photoreceptors at the fovea would be expected to produce a lesion resembling a small retinal hole. Images PMID:687552

  6. Visible-Light Optical Coherence Tomography Angiography for Monitoring Laser-Induced Choroidal Neovascularization in Mice

    PubMed Central

    Shah, Ronil S.; Soetikno, Brian T.; Yi, Ji; Liu, Wenzhong; Skondra, Dimitra; Zhang, Hao F.; Fawzi, Amani A.

    2016-01-01

    Purpose This study sought to determine the earliest time-point at which evidence of choroidal neovascularization (CNV) could be detected with visible-light optical coherence tomography angiography (vis-OCTA) in a mouse model of laser-induced CNV. Methods Visible light-OCTA was used to study laser-induced CNV at different time-points after laser injury to monitor CNV development and measure CNV lesion size. Measurements obtained from vis-OCTA angiograms were compared with histopathologic measurements from isolectin-stained choroidal flatmounts. Results Choroidal neovascularization area measurements between the vis-OCTA system and isolectin-stained choroidal flatmounts were significantly different in area for days 2 to 4 postlaser injury, and were not significantly different in area for days 5, 7, and 14. Choroidal neovascularization area measurements taken from the stained flatmounts were larger than their vis-OCTA counterparts for all time-points. Both modalities showed a similar trend of CNV size increasing from the day of laser injury until a peak of day 7 postlaser injury and subsequently decreasing by day 14. Conclusions The earliest vis-OCTA can detect the presence of aberrant vessels in a mouse laser-induced CNV model is 5 days after laser injury. Visible light-OCTA was able to visualize the maximum of the CNV network 7 days postlaser injury, in accordance with choroidal flatmount immunostaining. Visible light-OCTA is a reliable tool in both detecting the presence of CNV development, as well as accurately determining the size of the lesion in a mouse laser-induced CNV model. PMID:27409510

  7. Bilateral retinitis following typhoid fever.

    PubMed

    Prabhushanker, M; Topiwalla, Tasneem T; Ganesan, Geetha; Appandaraj, Sripal

    2017-01-01

    Post typhoid fever immune related reactions affecting the eye is a rare finding which can have various presentations in which typhoid retinopathy is not a well recognized sequelae. Here we present a case of 59 year old male who presented with right eye sudden painless loss of vision 4 weeks after typhoid fever which was diagnosed and treated successfully. His BCVA was 2/60 in right eye and 6/6 in left eye. Fundus examination showed retinitis along with macular serous detachment in right eye and retinitis in left eye. Significant improvement in BCVA in right eye was observed after treatment with oral steroid with resolving retinitis lesions. Diagnosis of post typhoid immune mediated retinitis was made with good resolution following treatment. Immune mediated retinitis is a rare sequelae to typhoid infection which can be successfully treated with systemic steroids with good resolution of the lesions.

  8. Laser-Induced Damage with Femtosecond Pulses

    NASA Astrophysics Data System (ADS)

    Kafka, Kyle R. P.

    The strong electric fields of focused femtosecond laser pulses lead to non-equilibrium dynamics in materials, which, beyond a threshold intensity, causes laser-induced damage (LID). Such a strongly non-linear and non-perturbative process renders important LID observables like fluence and intensity thresholds and damage morphology (crater) extremely difficult to predict quantitatively. However, femtosecond LID carries a high degree of precision, which has been exploited in various micro/nano-machining and surface engineering applications, such as human eye surgery and super-hydrophobic surfaces. This dissertation presents an array of experimental studies which have measured the damage behavior of various materials under femtosecond irradiation. Precision experiments were performed to produce extreme spatio-temporal confinement of the femtosecond laser-solid damage interaction on monocrystalline Cu, which made possible the first successful direct-benchmarking of LID simulation with realistic damage craters. A technique was developed to produce laser-induced periodic surface structures (LIPSS) in a single pulse (typically a multi-pulse phenomenon), and was used to perform a pump-probe study which revealed asynchronous LIPSS formation on copper. Combined with 1-D calculations, this new experimental result suggests more drastic electron heating than expected. Few-cycle pulses were used to study the LID performance and morphology of commercial ultra-broadband optics, which had not been systematically studied before. With extensive surface analysis, various morphologies were observed, including LIPSS, swelling (blisters), simple craters, and even ring-shaped structures, which varied depending on the coating design, number of pulses, and air/vacuum test environment. Mechanisms leading to these morphologies are discussed, many of which are ultrafast in nature. The applied damage behavior of multi-layer dielectric mirrors was measured and compared between long pulse (150 ps

  9. Retinal injury thresholds for blue wavelength lasers.

    PubMed

    Lund, David J; Stuck, Bruce E; Edsall, Peter

    2006-05-01

    The interaction mechanism leading to laser-induced retinal alteration can be thermal or non-thermal, depending upon the wavelength of the laser radiation and the duration of the exposure. To investigate the effect of exposure duration on the interaction mechanism, retinal injury thresholds in the rhesus monkey were experimentally measured for exposure to laser radiation at wavelengths of 441.6, 457.9, 476.5, and 496.5 nm. Exposure durations were 0.1, 1, 5, 16, and 100 s; and 1/e retinal irradiance diameters were 50, 125, and 327 microm. Tissue response was observed via ophthalmoscope 1 h and 48 h post exposure. Thermal and non-thermal damage thresholds were obtained depending upon the exposure duration. These threshold data are in agreement with data previously reported in the literature for 100-s duration exposures, but differences were noted for shorter exposures. The current study yielded an estimated injury threshold for 1-s duration, 327-microm retinal irradiance diameter exposures at 441.6 nm, which is an order of magnitude higher than that previously reported. This study provides evidence that laser-induced retinal damage is primarily induced via thermal mechanisms for exposures shorter than 5 s in duration. Arguments are presented that support an amendment of the thermal hazard function, R(lambda).

  10. 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.

  11. 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.

  12. Femtosecond Laser-Induced Damage of Dielectrics

    NASA Astrophysics Data System (ADS)

    Lenzner, M.

    Optical damage in non-metals (dielectrics) may severely affect the performance of high-power laser systems as well as the efficiency of optical systems based on nonlinear processes and has therefore been subject to extensive research for some 30 years. The current knowledge of laser-induced optical damage in these materials is reviewed. Emphasis is placed on the recent extension of available experimental data into the femtosecond range. Recent results are presented achieved with a sub-10 fs laser system which explores the limits of time resolution as well as the limit of intensities that a solid can sustain without irreversible damage. It is concluded that sub-10fs laser pulses open up the way to reversible nonperturbative nonlinear optics at intensities greater than 1014 W/cm2 (slightly below damage threshold) and to nanometer-precision laser ablation (slightly above threshold) in dielectric materials.

  13. 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.

  14. Laser Induced Fluorescence Spectroscopy of Boron Carbide

    NASA Astrophysics Data System (ADS)

    Cheung, A. S.-C.; Ng, Y. W.; Pang, H. F.

    2011-06-01

    Laser induced fluorescence spectrum of boron carbide (BC) between 490 and 560 nm has been recorded and analyzed. Gas-phase BC molecule was produced by the reaction of B2H6 and CH4 in the presence of magnesium atom from laser ablation process. The (0, 0), (1, 0), and (2, 0) bands of the B4 Σ- - X4 Σ- transition were recorded and rotationally analyzed. Spectra of both isotopes: 10BC and 11BC were observed. Equilibrium molecular constants for the B4 Σ- and the X4 Σ- states for both isotopes were determined. A comparison of the determined gas-phase molecular constants with those obtained using matrix isolation spectroscopy and the theoretical calculations will be presented. Financial support from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. HKU 701008P) is gratefully acknowledged.

  15. Laser Induced Fluorescence Spectrum of Iridium Monophosphide

    NASA Astrophysics Data System (ADS)

    Pang, H. F.; Liu, Anwen; Cheung, A. S.-C.

    2009-06-01

    Laser induced fluorescence spectrum of IrP in the spectral region between 380-600 nm has been studied. Reacting laser ablated iridium atoms with 1% PH_3 seeded in argon produced the IrP molecule. A few vibronic transitions have been recorded. Preliminary analysis of the rotational structure indicated that these vibronic bands are with Ω^' = 0 and Ω^'' = 0 and is likely to be ^{1}Σ - X ^{1}Σ transition. Vibrational separation of the excited state is estimated to be about 442 cm^{-1}. The ground state bond length is determined to be 1.766 Å. This work represents the first experimental investigation of the spectra of IrP.

  16. 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.

  17. Femtosecond laser induced breakdown for combustion diagnostics

    SciTech Connect

    Kotzagianni, M.; Couris, S.

    2012-06-25

    The focused beam of a 100 fs, 800 nm laser is used to induce a spark in some laminar premixed air-methane flames operating with variable fuel content (equivalence ratio). The analysis of the light escaping from the plasma revealed that the Balmer hydrogen lines, H{sub {alpha}} and H{sub {beta}}, and some molecular origin emissions were the most prominent spectral features, while the CN ({Beta}{sup 2}{Sigma}{sup +}-{Chi}{sup 2}{Sigma}{sup +}) band intensity was found to depend linearly with methane content, suggesting that femtosecond laser induced breakdown spectroscopy can be a useful tool for the in-situ determination and local mapping of fuel content in hydrocarbon-air combustible mixtures.

  18. 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.

  19. Laser-induced inactivation of Plasmodium falciparum

    PubMed Central

    2012-01-01

    Background Haemozoin crystals, produced by Plasmodium during its intra-erythrocytic asexual reproduction cycle, can generate UV light via the laser-induced, non-linear optical process of third harmonic generation (THG). In the current study the feasibility of using haemozoin, constitutively stored in the parasite’s food vacuole, to kill the parasite by irradiation with a near IR laser was evaluated. Methods Cultured Plasmodium parasites at different stages of development were irradiated with a pulsed NIR laser and the viability of parasites at each stage was evaluated from their corresponding growth curves using the continuous culture method. Additional testing for germicidal effects of haemozoin and NIR laser was performed by adding synthetic haemozoin crystals to Escherichia coli in suspension. Cell suspensions were then irradiated with the laser and small aliquots taken and spread on agar plates containing selective agents to determine cell viability (CFU). Results Parasites in the late-trophozoites form as well as trophozoites in early-stage of DNA synthesis were found to be the most sensitive to the treatment with ~4-log reduction in viability after six passes through the laser beam; followed by parasites in ring phase (~2-log reduction). A ~1-log reduction in E. coli viability was obtained following a 60 min irradiation regimen of the bacteria in the presence of 1 μM synthetic haemozoin and a ~2-log reduction in the presence of 10 μM haemozoin. Minimal (≤15%) cell kill was observed in the presence of 10 μM haemin. Conclusions Laser-induced third-harmonic generation by haemozoin can be used to inactivate Plasmodium. This result may have clinical implications for treating severe malaria symptoms by irradiating the patient’s blood through the skin or through dialysis tubing with a NIR laser. PMID:22873646

  20. Retinitis pigmentosa

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/001029.htm Retinitis pigmentosa To use the sharing features on this page, please enable JavaScript. Retinitis pigmentosa is an eye disease in which there is ...

  1. 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)

  2. 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)

  3. 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.}

  4. Rapid laser induced energy transfer in atomic systems

    NASA Technical Reports Server (NTRS)

    Harris, S. E.; Young, J. F.

    1978-01-01

    Analytical and experimental studies of the rapid transfer of stored populations from metastable states to selected target states of a different species are reported. Both laser-induced or laser-switched collision and laser-induced two-photon spontaneous emission are described. It is shown that the laser-induced collision method is particularly useful in the visible and UV spectral regions. It has applications in photochemistry, gas-phase kinetics, and in high-power, high-energy gas-phase lasers. The anti-Stokes source is useful in the VUV and soft X-ray spectral regions.

  5. 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.

  6. Laser induced single spot oxidation of titanium

    NASA Astrophysics Data System (ADS)

    Jwad, Tahseen; Deng, Sunan; Butt, Haider; Dimov, S.

    2016-11-01

    Titanium oxides have a wide range of applications in industry, and they can be formed on pure titanium using different methods. Laser-induced oxidation is one of the most reliable methods due to its controllability and selectivity. Colour marking is one of the main applications of the oxidation process. However, the colourizing process based on laser scanning strategies is limited by the relative large processing area in comparison to the beam size. Single spot oxidation of titanium substrates is proposed in this research in order to increase the resolution of the processed area and also to address the requirements of potential new applications. The method is applied to produce oxide films with different thicknesses and hence colours on titanium substrates. High resolution colour image is imprinted on a sheet of pure titanium by converting its pixels' colours into laser parameter settings. Optical and morphological periodic surface structures are also produced by an array of oxide spots and then analysed. Two colours have been coded into one field and the dependencies of the reflected colours on incident and azimuthal angles of the light are discussed. The findings are of interest to a range of application areas, as they can be used to imprint optical devices such as diffusers and Fresnel lenses on metallic surfaces as well as for colour marking.

  7. 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.

  8. Laser induced fluorescence of trapped molecular ions

    SciTech Connect

    Winn, J.S.

    1980-10-01

    Laser induced fluoresence (LIF) spectra (laser excitation spectra) are conceptually among the most simple spectra to obtain. One need only confine a gaseous sample in a suitable container, direct a laser along one axis of the container, and monitor the sample's fluorescence at a right angle to the laser beam. As the laser wavelength is changed, the changes in fluorescence intensity map the absorption spectrum of the sample. (More precisely, only absorption to states which have a significant radiative decay component are monitored.) For ion spectroscopy, one could benefit in many ways by such an experiment. Most optical ion spectra have been observed by emission techniques, and, aside from the problems of spectral analysis, discharge emission methods often produce the spectra of many species, some of which may be unknown or uncertain. Implicit in the description of LIF given above is certainty as to the chemical identity of the carrier of the spectrum. This article describes a method by which the simplifying aspects of LIF can be extended to molecular ions (albeit with a considerable increase in experimental complexity over that necessary for stable neutral molecules).

  9. Laser Induced Fluorescence Spectroscopy of Cobalt Monoboride

    NASA Astrophysics Data System (ADS)

    Pang, H. F.; Ng, Y. W.; Cheung, A. S.-C.

    2011-06-01

    Laser induced fluorescence spectrum of cobalt monoboride (CoB) in the visible region between 465 and 560 nm has been observed. CoB molecule was produced by the reaction of laser ablated cobalt atom and diborane (B_2H_6) seeded in argon. Over twenty five vibronic bands have been recorded, and both Co10B and Co11B isotopic species have been observed and analyzed. Preliminary analysis of the rotational lines showed that the observed vibronic bands belong to two categories namely: the Ω' = 2 - Ω'' = 2 and the Ω' = 3 - Ω'' = 3 transitions, which indicated the ground state of CoB is consistent with an assignment of a ^3Δ_i state predicted from ab initio calculations. Unresolved hyperfine structure arising from the Co nucleus (I = 7/2) causes a broadening of spectral lines. This work represents the first experimental investigation of the spectrum of the CoB molecule. Financial support from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. HKU 701008P) is gratefully acknowledged.

  10. Laser-induced crystallization and crystal growth.

    PubMed

    Sugiyama, Teruki; Masuhara, Hiroshi

    2011-11-04

    Recent streams of laser studies on crystallization and crystal growth are summarized and reviewed. Femtosecond multiphoton excitation of solutions leads to their ablation at the focal point, inducing local bubble formation, shockwave propagation, and convection flow. This phenomenon, called "laser micro tsunami" makes it possible to trigger crystallization of molecules and proteins from their supersaturated solutions. Femtosecond laser ablation of a urea crystal in solution triggers the additional growth of a single daughter crystal. Intense continuous wave (CW) near infrared laser irradiation at the air/solution interface of heavy-water amino acid solutions results in trapping of the clusters and evolves to crystallization. A single crystal is always prepared in a spatially and temporally controlled manner, and the crystal polymorph of glycine depends on laser power, polarization, and solution concentration. Upon irradiation at the glass/solution interface, a millimeter-sized droplet is formed, and a single crystal is formed by shifting the irradiation position to the surface. Directional and selective crystal growth is also possible with laser trapping. Finally, characteristics of laser-induced crystallization and crystal growth are summarized.

  11. 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.

  12. Laser-induced plasma spectroscopy: principles, methods and applications

    SciTech Connect

    Lazic, Violeta; Colao, Francesco; Fantoni, Roberta; Spizzichino, Valeria; Jovicevic, Sonja

    2006-12-01

    Principles of the Laser Induced Plasma Spectroscopy and its advances are reported. Methods for obtaining quantitative analyses are described, together with discussion of some applications and the specific problems.

  13. Laser-induced shockwave propagation from ablation in a cavity

    SciTech Connect

    Zeng Xianzhong; Mao Xianglei; Mao, Samuel S.; Wen, S.-B.; Greif, Ralph; Russo, Richard E.

    2006-02-06

    The propagation of laser-induced shockwaves from ablation inside of cavities was determined from time-resolved shadowgraph images. The temperature and electron number density of the laser-induced plasma was determined from spectroscopic measurements. These properties were compared to those for laser ablation on the flat surface under the same energy and background gas condition. A theoretical model was proposed to determine the amount of energy and vaporized mass stored in the vapor plume based on these measurements.

  14. Retinoids and Retinal Diseases

    PubMed Central

    Kiser, Philip D.; Palczewski, Krzysztof

    2016-01-01

    Recent progress in molecular understanding of the retinoid cycle in mammalian retina stems from painstaking biochemical reconstitution studies supported by natural or engineered animal models with known genetic lesions and studies of humans with specific genetic blinding diseases. Structural and membrane biology have been used to detect critical retinal enzymes and proteins and their substrates and ligands, placing them in a cellular context. These studies have been supplemented by analytical chemistry methods that have identified small molecules by their spectral characteristics, often in conjunction with the evaluation of models of animal retinal disease. It is from this background that rational therapeutic interventions to correct genetic defects or environmental insults are identified. Thus, most presently accepted modulators of the retinoid cycle already have demonstrated promising results in animal models of retinal degeneration. These encouraging signs indicate that some human blinding diseases can be alleviated by pharmacological interventions. PMID:27917399

  15. 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)

  16. Retinal Vasculitis

    PubMed Central

    Rosenbaum, James T.; Sibley, Cailin H.; Lin, Phoebe

    2016-01-01

    Purpose of review Ophthalmologists and rheumatologists frequently miscommunicate in consulting on patients with retinal vasculitis. This report seeks to establish a common understanding of the term, retinal vasculitis, and to review recent papers on this diagnosis. Recent findings 1) The genetic basis of some rare forms of retinal vascular disease have recently been described. Identified genes include CAPN5, TREX1, and TNFAIP3; 2) Behçet’s disease is a systemic illness that is very commonly associated with occlusive retinal vasculitis; 3) retinal imaging including fluorescein angiography and other newer imaging modalities has proven crucial to the identification and characterization of retinal vasculitis and its complications; 4) although monoclonal antibodies to IL-17A or IL-1 beta failed in trials for Behçet’s disease, antibodies to TNF alpha, either infliximab or adalimumab, have demonstrated consistent benefit in managing this disease. Interferon treatment and B cell depletion therapy via rituximab may be beneficial in certain types of retinal vasculitis. Summary Retinal vasculitis is an important entity for rheumatologists to understand. Retinal vasculitis associated with Behçet’s disease responds to monoclonal antibodies that neutralize TNF, but the many other forms of non-infectious retinal vasculitis may require alternate therapeutic management. PMID:26945335

  17. 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.

  18. Laser-Induced Incandescence: Excitation Intensity

    NASA Astrophysics Data System (ADS)

    Vander Wal, Randall L.; Jensen, Kirk A.

    1998-03-01

    Assumptions of theoretical laser-induced incandescence (LII) models along with possible effects of high-intensity laser light on soot aggregates and the constituent primary particles are discussed in relation to selection of excitation laser fluence. Ex situ visualization of laser-heated soot by use of transmission electron microscopy reveals significant morphological changes (graphitization) induced by pulsed laser heating. Pulsed laser transmission measurements within a premixed laminar sooting flame suggest that soot vaporization occurs for laser fluences greater than 0.5 J cm 2 at 1064 nm. Radial LII intensity profiles at different axial heights in a laminar ethylene gas jet diffusion flame reveal a wide range of signal levels depending on the laser fluence that is varied over an eight fold range. Results of double-pulse excitation experiments in which a second laser pulse heats in situ the same soot that was heated by a prior laser pulse are detailed. These two-pulse measurements suggest varying degrees of soot structural change for fluences below and above a vaporization threshold of 0.5 J cm 2 at 1064 nm. Normalization of the radial-resolved LII signals based on integrated intensities, however, yields self-similar profiles. The self-similarity suggests robustness of LII for accurate relative measurement of soot volume fraction despite the morphological changes induced in the soot, variations in soot aggregate and primary particle size, and local gas temperature. Comparison of LII intensity profiles with soot volume fractions ( f v ) derived by light extinction validates LII for quantitative determination of f v upon calibration for laser fluences ranging from 0.09 to 0.73 J cm 2 .

  19. Laser-induced incandescence: excitation intensity.

    PubMed

    Vander Wal, R L; Jensen, K A

    1998-03-20

    Assumptions of theoretical laser-induced incandescence (LII) models along with possible effects of high-intensity laser light on soot aggregates and the constituent primary particles are discussed in relation to selection of excitation laser fluence. Ex situ visualization of laser-heated soot by use of transmission electron microscopy reveals significant morphological changes (graphitization) induced by pulsed laser heating. Pulsed laser transmission measurements within a premixed laminar sooting flame suggest that soot vaporization occurs for laser fluences greater than 0.5 J/cm(2) at 1064 nm. Radial LII intensity profiles at different axial heights in a laminar ethylene gas jet diffusion flame reveal a wide range of signal levels depending on the laser fluence that is varied over an eight fold range. Results of double-pulse excitation experiments in which a second laser pulse heats in situ the same soot that was heated by a prior laser pulse are detailed. These two-pulse measurements suggest varying degrees of soot structural change for fluences below and above a vaporization threshold of 0.5 J/cm(2) at 1064 nm. Normalization of the radial-resolved LII signals based on integrated intensities, however, yields self-similar profiles. The self-similarity suggests robustness of LII for accurate relative measurement of soot volume fraction despite the morphological changes induced in the soot, variations in soot aggregate and primary particle size, and local gas temperature. Comparison of LII intensity profiles with soot volume fractions (f(v)) derived by light extinction validates LII for quantitative determination of f(v) upon calibration for laser fluences ranging from 0.09 to 0.73 J/cm(2).

  20. 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

  1. Automatic temperature controlled retinal photocoagulation.

    PubMed

    Schlott, Kerstin; Koinzer, Stefan; Ptaszynski, Lars; Bever, Marco; Baade, Alex; Roider, Johann; Birngruber, Reginald; Brinkmann, Ralf

    2012-06-01

    Laser coagulation is a treatment method for many retinal diseases. Due to variations in fundus pigmentation and light scattering inside the eye globe, different lesion strengths are often achieved. The aim of this work is to realize an automatic feedback algorithm to generate desired lesion strengths by controlling the retinal temperature increase with the irradiation time. Optoacoustics afford non-invasive retinal temperature monitoring during laser treatment. A 75 ns/523 nm Q-switched Nd:YLF laser was used to excite the temperature-dependent pressure amplitudes, which were detected at the cornea by an ultrasonic transducer embedded in a contact lens. A 532 nm continuous wave Nd:YAG laser served for photocoagulation. The ED50 temperatures, for which the probability of ophthalmoscopically visible lesions after one hour in vivo in rabbits was 50%, varied from 63°C for 20 ms to 49°C for 400 ms. Arrhenius parameters were extracted as ΔE=273 J mol(-1) and A=3 x 10(44) s(-1). Control algorithms for mild and strong lesions were developed, which led to average lesion diameters of 162 ± 34 μm and 189 ± 34 μm, respectively. It could be demonstrated that the sizes of the automatically controlled lesions were widely independent of the treatment laser power and the retinal pigmentation.

  2. Automatic temperature controlled retinal photocoagulation

    NASA Astrophysics Data System (ADS)

    Schlott, Kerstin; Koinzer, Stefan; Ptaszynski, Lars; Bever, Marco; Baade, Alex; Roider, Johann; Birngruber, Reginald; Brinkmann, Ralf

    2012-06-01

    Laser coagulation is a treatment method for many retinal diseases. Due to variations in fundus pigmentation and light scattering inside the eye globe, different lesion strengths are often achieved. The aim of this work is to realize an automatic feedback algorithm to generate desired lesion strengths by controlling the retinal temperature increase with the irradiation time. Optoacoustics afford non-invasive retinal temperature monitoring during laser treatment. A 75 ns/523 nm Q-switched Nd:YLF laser was used to excite the temperature-dependent pressure amplitudes, which were detected at the cornea by an ultrasonic transducer embedded in a contact lens. A 532 nm continuous wave Nd:YAG laser served for photocoagulation. The ED50 temperatures, for which the probability of ophthalmoscopically visible lesions after one hour in vivo in rabbits was 50%, varied from 63°C for 20 ms to 49°C for 400 ms. Arrhenius parameters were extracted as ΔE=273 J mol-1 and A=3.1044 s-1. Control algorithms for mild and strong lesions were developed, which led to average lesion diameters of 162+/-34 μm and 189+/-34 μm, respectively. It could be demonstrated that the sizes of the automatically controlled lesions were widely independent of the treatment laser power and the retinal pigmentation.

  3. Retinal detachment

    PubMed Central

    2010-01-01

    Introduction Rhegmatogenous retinal detachment (RRD) is the most common form of retinal detachment, where a retinal "break" allows the ingress of fluid from the vitreous cavity to the subretinal space, resulting in retinal separation. It occurs in about 1 in 10,000 people a year. Methods and outcomes We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of interventions to prevent progression from retinal breaks or lattice degeneration to retinal detachment? What are the effects of different surgical interventions in people with rhegmatogenous retinal detachment? What are the effects of interventions to treat proliferative vitreoretinopathy occurring as a complication of retinal detachment or previous treatment for retinal detachment? We searched: Medline, Embase, The Cochrane Library, and other important databases up to June 2010 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). Results We found 21 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. Conclusions In this systematic review, we present information relating to the effectiveness and safety of the following interventions: corticosteroids, cryotherapy, daunorubicin, fluorouracil plus low molecular weight heparin, laser photocoagulation, pneumatic retinopexy, scleral buckling, short-acting or long-acting gas tamponade, silicone oil tamponade, and vitrectomy. PMID:21406128

  4. Retinal detachment

    PubMed Central

    2009-01-01

    Introduction Rhegmatogenous retinal detachment (RRD) is the most common form of retinal detachment, where a retinal "break" allows the ingress of fluid from the vitreous cavity to the subretinal space, resulting in retinal separation. It occurs in about 1 in 10,000 people a year. Methods and outcomes We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of interventions to prevent progression from retinal breaks or lattice degeneration to retinal detachment? What are the effects of different surgical interventions in people with rhegmatogenous retinal detachment? What are the effects of interventions to treat proliferative vitreoretinopathy occurring as a complication of retinal detachment or previous treatment for retinal detachment? We searched: Medline, Embase, The Cochrane Library, and other important databases up to March 2009 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). Results We found 20 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. Conclusions In this systematic review, we present information relating to the effectiveness and safety of the following interventions: corticosteroids; cryotherapy; daunorubicin; fluorouracil plus low-molecular-weight heparin; laser photocoagulation; pneumatic retinopexy; scleral buckling; short-acting or long-acting gas tamponade; silicone oil tamponade; and vitrectomy. PMID:19450333

  5. 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

  6. Cytomegalovirus retinitis associated with acquired immunodeficiency syndrome.

    PubMed

    Geng, Shuang; Ye, Jun-jie; Zhao, Jia-liang; Li, Tai-sheng; Han, Yang

    2011-04-01

    Cytomegalovirus (CMV) retinitis is the most severe intraocular complication that results in total retinal destruction and loss of visual acuity in patients with acquired immunodeficiency syndrome (AIDS). This study aimed to investigate the fundus characteristics, systemic manifestations and therapeutic outcomes of CMV retinitis associated with AIDS. It was a retrospective case series. CMV retinitis was present in 39 eyes (25 patients). Best corrected visual acuities, anterior segment, fundus features, fundus fluorescence angiography (FFA) and CD4(+) T-lymphocyte counts of the patients with CMV retinitis associated with AIDS were analyzed. Intravitreal injections of ganciclovir (400 µg) were performed in 4 eyes (2 patients). Retinal vasculitis, dense, full-thickness, yellow-white lesions along vascular distribution with irregular granules at the border, and hemorrhage on the retinal surface were present in 28 eyes. The vitreous was clear or mildly opaque. Late stage of the retinopathy was demonstrated in 8 eyes characterized as atrophic retina, sclerotic and attenuated vessels, retinal pigment epithelium (RPE) atrophy, and optic nerve atrophy. Retinal detachment was found in 3 eyes. The average CD4(+) T-lymphocyte count in peripheral blood of the patients with CMV retinitis was (30.6 ± 25.3) × 10(6)/L (range, (0 - 85) × 10(6)/L). After intravitreal injections of ganciclovir, visual acuity was improved and fundus lesions regressed. CMV retinitis is the most severe and the most common intraocular complication in patients with AIDS. For the patients with yellow-white retinal lesions, hemorrhage and retinal vasculitis without clear cause, human immunodeficiency virus (HIV) serology should be performed. Routine eye examination is also indicated in HIV positive patients.

  7. 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

  8. 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

  9. 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.

  10. UV Laser-Induced DNA Photochemistry

    DTIC Science & Technology

    1991-05-13

    nicking of DNA) can be described by a Poisson distribution (Armitage, 1971; Kroeber and LaForge, 1980). Such a distribution can be used to determine...specificity of the alkali-sensitive lesions induced in DNA by high intensity ultraviolet laser radiation", Photochem. Photohiol. 52:509-517 Kroeber , D.W

  11. Comparative study of 1,064-nm laser-induced skin burn and thermal skin burn.

    PubMed

    Zhang, Yi-Ming; Ruan, Jing; Xiao, Rong; Zhang, Qiong; Huang, Yue-Sheng

    2013-01-01

    Infrared lasers are widely used in medicine, industry, and other fields. While science, medicine, and the society in general have benefited from the many practical uses of lasers, they also have inherent safety issues. Although several procedures have been put forward to protect the skin from non-specific laser-induced damage, individuals receiving laser therapy or researchers who use laser are still at risk for skin damage. This study aims to understand the interaction between laser and the skin, and to investigate the differences between the skin damage caused by 1,064-nm laser and common thermal burns. Skin lesions on Wistar rats were induced by a 1,064-nm CW laser at a maximum output of 40 W and by a copper brass bar attached to an HQ soldering iron. Histological sections of the lesions and the process of wound healing were evaluated. The widths of the epidermal necrosis and dermal denaturalization of each lesion were measured. To observe wound healing, the epithelial gap and wound gap were measured. Masson's trichrome and picrosirius red staining were also used to assess lesions and wound healing. The thermal damage induced by laser intensified significantly in both horizontal dimension and in vertical depth with increased duration of irradiation. Ten days after wounding, the dermal injuries induced by laser were more severe. Compared with the laser-induced skin damage, the skin burn induced by an HQ soldering iron did not show a similar development or increased in severity with the passage of time. The results of this study showed the pattern of skin damage induced by laser irradiation and a heated brass bar. This study also highlighted the difference between laser irradiation and thermal burn in terms of skin damage and wound healing, and offers insight for further treatment.

  12. Intrinsic laser-induced breakdown of silicate glasses

    NASA Astrophysics Data System (ADS)

    Glebov, Leonid B.

    2002-03-01

    This paper is a survey of experimental results in laser- induced damage observed mainly at State Optical Institute (St. Petersburg, Russia; at School of Optics/CREOL (Orlando, FL) which expounds conditions of observation of an intrinsic breakdown of high-purity silicate glasses and proposes the general idea of its mechanism. It is shown that the surface laser-induced breakdown of dielectrics is resulted from photo- and thermo-ionization of surface defects but not from interaction of laser radiation with dielectric material itself. Conditions of thermal ionization of the volume of dielectric materials are determined in dependence on features of absorption of material and temporal features of laser radiation. Statistical properties of laser-induced breakdown of high-purity glasses are caused by statistical properties of laser radiation while the breakdown itself is a deterministic process. Elimination of impact of self-focusing on the results of the breakdown threshold measurements is observed if the spot size of laser radiation in focal plane is less than the wavelength. No photoionization of glass matrix is detected before laser- induced breakdown, and there is no effect of photoionization of impurities and defects on intrinsic breakdown. A mechanism of intrinsic laser-induced breakdown is proposed which is a spasmodic transformation of the electronic level structure in a wide-bandgap dielectric caused by the electric field of laser radiation. This is a collective process converting a transparent material to the opaque state but not an individual process of any type of ionization.

  13. Retinal meteor.

    PubMed

    Venkatesh, Ramesh; Gurav, Prachi; Dave, Prachi Abhishek; Roy, Sankhadeep

    2017-09-01

    We describe a case of a 65-year old man diagnosed with retinal vasoproliferative tumour secondary to posterior uveitis. The fluorescein angiography shows an interesting meteor-like leak emanating from the tumour and rising towards the superior retina in the later frames of the angiogram. Pictorially, we call it the "Retinal Meteor" and also describe the possible mechanism for this pattern of leakage.

  14. Retinal remodeling.

    PubMed

    Jones, B W; Kondo, M; Terasaki, H; Lin, Y; McCall, M; Marc, R E

    2012-07-01

    Retinal photoreceptor degeneration takes many forms. Mutations in rhodopsin genes or disorders of the retinal pigment epithelium, defects in the adenosine triphosphate binding cassette transporter, ABCR gene defects, receptor tyrosine kinase defects, ciliopathies and transport defects, defects in both transducin and arrestin, defects in rod cyclic guanosine 3',5'-monophosphate phosphodiesterase, peripherin defects, defects in metabotropic glutamate receptors, synthetic enzymatic defects, defects in genes associated with signaling, and many more can all result in retinal degenerative disease like retinitis pigmentosa (RP) or RP-like disorders. Age-related macular degeneration (AMD) and AMD-like disorders are possibly due to a constellation of potential gene targets and gene/gene interactions, while other defects result in diabetic retinopathy or glaucoma. However, all of these insults as well as traumatic insults to the retina result in retinal remodeling. Retinal remodeling is a universal finding subsequent to retinal degenerative disease that results in deafferentation of the neural retina from photoreceptor input as downstream neuronal elements respond to loss of input with negative plasticity. This negative plasticity is not passive in the face of photoreceptor degeneration, with a phased revision of retinal structure and function found at the molecular, synaptic, cell, and tissue levels involving all cell classes in the retina, including neurons and glia. Retinal remodeling has direct implications for the rescue of vision loss through bionic or biological approaches, as circuit revision in the retina corrupts any potential surrogate photoreceptor input to a remnant neural retina. However, there are a number of potential opportunities for intervention that are revealed through the study of retinal remodeling, including therapies that are designed to slow down photoreceptor loss, interventions that are designed to limit or arrest remodeling events, and

  15. 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.

  16. 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.

  17. 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.

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

    DOE PAGES

    Verburg, P. C.; Smillie, L. A.; Römer, G. R. B. E.; ...

    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

  19. Research on laser induced acoustic source based underwater communication system

    NASA Astrophysics Data System (ADS)

    Lei, Lihua; Zhou, Ju; Zhang, Lei; Wan, Xiaoyun

    2016-10-01

    Acoustic transducers are traditionally used to generate underwater acoustical energy with the device physically immersed in water. Novel methods are required for communicating from an in-air platform or surface vessel to a submerged vessel. One possible noncontact downlink communication system involves the use of laser induced acoustic source. The most common mechanisms of opto-acoustic energy conversion are, by order of increasing laser energy density and efficiency, thermal expansion, surface evaporation and optical breakdown. The laser induced acoustic source inherently bears the obvious advantage of not requiring any physical transducer in the medium. At the same time, acoustic energy propagation is efficient in water, whereas optical energy propagate well in air, leading to a more efficiency opto-acoustic communication method. In this paper, an opto-acoustic underwater Communication system is described, aiming to study and analysis whether laser induced sound could achieve good performance for effective communication in practical application.

  20. 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.

  1. 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.

  2. Impact-Ionization Cooling in Laser-Induced Plasma Filaments

    SciTech Connect

    Filin, A.; Romanov, D. A.; Compton, R.; Levis, R. J.

    2009-04-17

    The ionization rates and subsequent electron dynamics for laser-induced plasma channels are measured for the noble gas series He, Ne, Ar, Kr, and Xe at 1.0 atm. The cw fluorescence emission increases superlinearly in the series from He to Xe in agreement with Ammosov-Delone-Krainov tunnel ionization calculations. The electron temperature after laser-induced plasma formation, measured by four-wave mixing, evolves from >20 eV to <1 eV kinetic energies with time constants ranging from 1 ns for He to 100 ps for Xe in agreement with an impact-ionization cooling model.

  3. 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.

  4. Laser induced breakdown spectroscopy stratigraphic characterization of multilayered painted surfaces

    NASA Astrophysics Data System (ADS)

    Staicu, A.; Apostol, I.; Pascu, A.; Iordache, I.; Damian, V.; Pascu, M. L.

    2012-08-01

    Laser spectroscopy techniques are modern and competitive methods for elemental analysis. Laser induced breakdown spectroscopy (LIBS), due to its advantages as minimally invasive method that provides real time monitoring and selectivity, is a suitable tool to analyze sample composition. Based on the known emission spectra of heavy metals such as Pb, Zn, Au, Ca, a stratigraphic study regarding the identification of the painting layers content of different mock-up samples was performed. LIBS was used to monitor the laser induced stepwise selective removal of the painting layers and to analyze their composition. The obtained LIBS spectra were correlated with profilometric measurements.

  5. Retinal detachment

    PubMed Central

    2014-01-01

    Introduction Rhegmatogenous retinal detachment (RRD) is the most common form of retinal detachment, where a retinal 'break' allows the ingress of fluid from the vitreous cavity to the subretinal space, resulting in retinal separation. It occurs in about 1 in 10,000 people a year. Methods and outcomes We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of different surgical interventions in people with rhegmatogenous retinal detachment? What are the effects of interventions to treat proliferative vitreoretinopathy occurring as a complication of retinal detachment or previous treatment for retinal detachment? We searched: Medline, Embase, The Cochrane Library, and other important databases up to September 2013 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). Results We found 14 studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. Conclusions In this systematic review, we present information relating to the effectiveness and safety of the following interventions: corticosteroids, daunorubicin, fluorouracil plus low molecular weight heparin, pneumatic retinopexy, scleral buckling, short-acting or long-acting gas tamponade, silicone oil tamponade, and vitrectomy. PMID:24807890

  6. Retinal Injuries From Single and Multiple Picosecond Laser Pulses

    DTIC Science & Technology

    1994-04-30

    cell diameter -10 pm) can experience a pressure transient of >22 Kbar when the melanin granules contained within the cells are exposed to these laser...0719 Bolling AFB DC 20332-0001 Dr Walter KozumboF 11. SUPPLEMENTARY NOTES 60iia oontais~u solar -, plates: All D210 Mproduot- ioins ull. be 12 blaokSn...Maximum 200 words) We investigate laser-induced shock waves from melanin particles as a possible cause of retinal injury from ultrashort pulse laser

  7. 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.

  8. 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

  9. Foveomacular retinitis.

    PubMed

    Kuming, B S

    1986-11-01

    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.

  10. 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

  11. Detection of uranium in solids by using laser-induced breakdown spectroscopy combined with laser-induced fluorescence

    SciTech Connect

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

    2008-04-10

    Detection of uranium in solids by using laser-induced breakdown spectroscopy has been investigated in combination with laser-induced fluorescence. An optical parametric oscillator wavelength-tunable laser 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 by using this technique at an excitation wavelength of 385.96 nm for resonant excitation of U II and a fluorescence line wavelength of 409.0 nm from U II.

  12. Hereditary Retinal Dystrophy.

    PubMed

    Hohman, Thomas C

    2016-12-30

    As our understanding of the genetic basis for inherited retinal disease has expanded, gene therapy has advanced into clinical development. When the gene mutations associated with inherited retinal dystrophies were identified, it became possible to create animal models in which individual gene were altered to match the human mutations. The retina of these animals were then characterized to assess whether the mutated genes produced retinal phenotypes characteristic of disease-affected patients. Following the identification of a subpopulation of patients with the affected gene and the development of techniques for the viral gene transduction of retinal cells, it has become possible to deliver a copy of the normal gene into the retinal sites of the mutated genes. When this was performed in animal models of monogenic diseases, at an early stage of retinal degeneration when the affected cells remained viable, successful gene augmentation corrected the structural and functional lesions characteristic of the specific diseases in the areas of the retina that were successfully transduced. These studies provided the essential proof-of-concept needed to advance monogenic gene therapies into clinic development; these therapies include treatments for: Leber's congenital amaurosis type 2, caused by mutations to RPE65, retinoid isomerohydrolase; choroideremia, caused by mutations to REP1, Rab escort protein 1; autosomal recessive Stargardt disease, caused by mutations to ABCA4, the photoreceptor-specific ATP-binding transporter; Usher 1B disease caused by mutations to MYO7A, myosin heavy chain 7; X-linked juvenile retinoschisis caused by mutations to RS1, retinoschisin; autosomal recessive retinitis pigmentosa caused by mutations to MERTK, the proto-oncogene tyrosine-protein kinase MER; Leber's hereditary optic neuropathy caused by mutations to ND4, mitochondrial nicotinamide adenine dinucleotide ubiquinone oxidoreductase (complex I) subunit 4 and achromatopsia, caused by

  13. Paravascular inner retinal abnormalities in healthy eyes.

    PubMed

    Osaka, Rie; Manabe, Saki; Miyoshi, Yukiko; Nakano, Yuki; Yamashita, Ayana; Shiragami, Chieko; Hirooka, Kazuyuki; Muraoka, Yuki; Tsujikawa, Akitaka

    2017-07-02

    To investigate the prevalence and characteristics of paravascular inner retinal abnormalities in healthy eyes. In this prospective observational case series, we included 178 healthy eyes (178 patients) with no ocular diseases. Eyes with co-existing ocular diseases, e.g., epiretinal membrane, glaucoma, or high myopia, were excluded from the current study. The posterior pole and paravascular areas of the temporal arcade vessels were comprehensively examined by dense radial scanning of optical coherence tomography (OCT) with the extended field imaging technique. On fundus photography, no inner retinal abnormalities were detected along the temporal arcade vessels. On OCT sections, paravascular inner retinal abnormalities were seen in 77 (43.3%) eyes. In 71 (39.9%) eyes, inner retinal cystoid or fissure-like spaces that had no connection to the vitreous cavity were seen adjacent to the temporal arcade vessels. Most of these lesions were detected only on several consecutive OCT sections. In four (2.2%) eyes, inner retinal cleavages with openings to the vitreous cavity were seen adjacent to the temporal arcade vessels. These lesions were more frequently detected in the inferior hemisphere and along the major retinal veins. No eyes showed typical broad defects of the inner retinal tissue. There were no significant differences in age, gender, visual acuity, refractive error, or axial length between eyes with or without paravascular inner retinal abnormalities. Paravascular cystoid or fissure-like spaces were frequently seen in the inner retina of healthy eyes. However, we detected no typical paravascular inner retinal defects in healthy eyes.

  14. 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.

  15. 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.

  16. Laser-induced fluorescence of oral mucosa cancer

    NASA Astrophysics Data System (ADS)

    Jaliashvili, Z. V.; Medoidze, T. D.; Melikishvili, Z. G.; Gogilashvili, K. T.

    2017-10-01

    The laser-induced fluorescence (LIF) spectra have been measured for cancer-infused and control mice mucosa tissues. It was established that there is quite a difference between their LIF spectral shapes. These spectral shapes are used to express the diagnostic of different states of tissues: from normal to cancer.

  17. Laser-induced collisional autoionization in europium and strontium atoms.

    PubMed

    Buffa, R

    1995-01-15

    An experiment that involves laser-induced collisional autoionization in europium and strontium atoms is proposed and the spectral line shape of the cross section is calculated on the basis of data available in the literature. The feasibility of the experiment both in oven cells and in a crossed-atomic-beam geometry is discussed.

  18. 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.

  19. 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.

  20. Laser-induced plasma emission: from atomic to molecular spectra

    NASA Astrophysics Data System (ADS)

    De Giacomo, Alessandro; Hermann, Jörg

    2017-05-01

    The aim of this paper is the description of the optical emission spectral features of the plasma produced by laser-matter interaction, from a fundamental point of view. The laser induced plasma emission spectra are discussed in connection with the basic mechanisms that take place in the plasma phase at different time delays from the laser pulse. The laser induced plasma being a dynamic system, the hierarchy of the elementary mechanisms changes continuously because the electron number density and the electron temperature decrease during the expansion. As a consequence of this, over the duration of the plasma’s persistence the prevailing emitting species changes from ions to atoms and from atoms to molecules. Both atomic and molecular emission spectroscopy are discussed, to convey a complete description of the temporal evolution of laser induced plasma. Current literature, as well as the traditional plasma theories, are presented and discussed in order to give to the reader a general idea of the potentialities and drawbacks of emission spectroscopy in the study of laser induced plasma and its various applications.

  1. Laser-induced ultrafast spin current pulses: a thermodynamic approach.

    PubMed

    Fognini, A; Michlmayr, T U; Vaterlaus, A; Acremann, Y

    2017-06-01

    The ultrafast demagnetization process allows for the generation of femtosecond spin current pulses. Here, we present a thermodynamic model of the spin current generation process, based on the chemical potential gradients as the driving force for the spin current. We demonstrate that the laser-induced spin current can be estimated by an easy to understand diffusion model.

  2. Laser-Induced Breakdown Spectroscopy: Capabilities and Applications

    DTIC Science & Technology

    2010-07-01

    Pyrotech. 2010. 43. Samuels, A. C.; DeLucia, F. C., Jr.; McNesby, K. L.; Miziolek, A. W. Laser-Induced Breakdown Spectroscopy of Bacterial Spores , Molds ...surfaces and complex print job definition through scripting. It is currently being used to determine limits of detection for explosive residues using LIBS

  3. 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 ...

  4. Retinal Detachment

    MedlinePlus

    The retina is a layer of tissue in the back of your eye that senses light and sends images ... for reading, driving, and seeing fine detail. A retinal detachment lifts or pulls the retina from its ...

  5. 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 - ...

  6. Idiopathic juxtafoveal retinal telangiectasis and retinal macroaneurysm treated with indocyanine green dye-enhanced photocoagulation.

    PubMed

    Steigerwalt, R D; Pascarella, A; Arrico, L; Librando, A; Plateroti, R; Plateroti, A M; Plateroti, P; Nebbioso, M

    2012-12-01

    This case report presents the use of indocyanine green dye-enhanced photocoagulation (ICG-DEP) for the treatment of idiopathic juxtafoveal retinal telangiectasis and a retinal macroaneurysm. A 35-year-old male with 20/20 vision had been followed for 5 years for a retinal macroaneurysm with retinal telangiectasis outside the macular area. He then presented with a recently decreased vision in his right. He had macular edema with a new area of idiopathic juxtafoveal retinal telangiectasis. After 4 focal argon laser treatments, angiographic closure of the lesions was not obtained and the retinal edema remained. After 3 sessions of ICG-DEP, the lesions were closed and the edema absorbed. The 810 nm infrared laser with ICG-DEP should be considered for the treatment of idiopathic juxtafoveal retinal telangiectasis and retinal macroaneurysms. In this case the procedure appears to be safe and well tolerated. It may allow for more direct energy absorption than that of the argon laser to these types of retinal lesions with better tissue closure.

  7. Minimally invasive non-thermal laser technology using laser-induced optical breakdown for skin rejuvenation.

    PubMed

    Habbema, Louis; Verhagen, Rieko; Van Hal, Robbert; Liu, Yan; Varghese, Babu

    2012-02-01

    We describe a novel, minimally invasive laser technology for skin rejuvenation by creating isolated microscopic lesions within tissue below the epidermis using laser induced optical breakdown. Using an in-house built prototype device, tightly focused near-infrared laser pulses are used to create optical breakdown in the dermis while leaving the epidermis intact, resulting in lesions due to cavitation and plasma explosion. This stimulates a healing response and consequently skin remodelling, resulting in skin rejuvenation effects. Analysis of ex-vivo and in-vivo treated human skin samples successfully demonstrated the safety and effectiveness of the microscopic lesion creation inside the dermis. Treatments led to mild side effects that can be controlled by small optimizations of the optical skin contact and treatment depth within the skin. The histological results from a limited panel test performed on five test volunteers show evidence of microscopic lesion creation and new collagen formation at the sites of the optical breakdown. This potentially introduces a safe, breakthrough treatment procedure for skin rejuvenation without damaging the epidermis with no or little social down-time and with efficacy comparable to conventional fractional ablative techniques. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Minimally invasive non-thermal laser technology using laser-induced optical breakdown for skin rejuvenation

    PubMed Central

    Habbema, Louis; Verhagen, Rieko; Van Hal, Robbert; Liu, Yan; Varghese, Babu

    2012-01-01

    We describe a novel, minimally invasive laser technology for skin rejuvenation by creating isolated microscopic lesions within tissue below the epidermis using laser induced optical breakdown. Using an in-house built prototype device, tightly focused near-infrared laser pulses are used to create optical breakdown in the dermis while leaving the epidermis intact, resulting in lesions due to cavitation and plasma explosion. This stimulates a healing response and consequently skin remodelling, resulting in skin rejuvenation effects. Analysis of ex-vivo and in-vivo treated human skin samples successfully demonstrated the safety and effectiveness of the microscopic lesion creation inside the dermis. Treatments led to mild side effects that can be controlled by small optimizations of the optical skin contact and treatment depth within the skin. The histological results from a limited panel test performed on five test volunteers show evidence of microscopic lesion creation and new collagen formation at the sites of the optical breakdown. This potentially introduces a safe, breakthrough treatment procedure for skin rejuvenation without damaging the epidermis with no or little social down-time and with efficacy comparable to conventional fractional ablative techniques. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) PMID:22045580

  9. 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

  10. The Study of Carious Teeth by Laser-Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hamzaoui, S.; Nouir, R.; Jaidene, N.

    2017-03-01

    The aim of this work is a multi-component analysis of the element composition of the enamel and carious parts of teeth and the quantification of enamel demineralization using laser-induced breakdown spectroscopy (LIBS). For each tooth the P/Ca ratios of the emission line intensities in the enamel part and those in the carious regions were compared. Since zinc is a trace element, the same procedure was performed for Zn/Ca ratios in the enamel and carious parts. These comparisons showed that the mineral loss from carious lesions occurs at different rates for the studied elements. Calcium has the highest casualty rate. On the other hand, the zinc level diminishes also in the carious region but at a lower rate. The lines were obtained from plume plasma emission generated on the enamel and carious regions.

  11. Syphilis presenting as retinal detachment and orchitis in a young man with HIV.

    PubMed

    Yogo, Norihiro; Nichol, Aran Cunningham; Campbell, Thomas B; Erlandson, Kristine M

    2014-02-01

    Retinal detachment and testicular lesions are 2 rare presentations of syphilis. We describe a man with bilateral retinal detachment from ocular syphilis and syphilitic orchitis as a manifestation of syphilis and HIV coinfection.

  12. 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.

  13. Retinal manifestations in fibromuscular dysplasia.

    PubMed

    Meire, F M; De Laey, J J; Van Thienen, M N; Schuddinck, L

    1991-01-01

    Fibromuscular dysplasia of the arteries (FMD) is a segmental angiopathy which may produce obstruction of the carotid, cerebral, renal, mesenteric, coronary or iliac arteries. Except for lesions related to arterial hypertension, retinal manifestations have not yet been reported. This paper describes the case of a 10-year-old boy with progressive deafness, a history of an unexplained stroke and progressive occlusions of the retinal arterioles in the fundus periphery. This resulted in retinal neovascularization and recurrent retinal and vitreous hemorrhages. Despite repeated photo- and cryocoagulation the eyes progressed to a tractional retinal detachment which was successfully treated by vitrectomy and scleral buckling. The diagnosis of FMD was made on the basis of a histopathological examination of a temporal artery biopsy. The child also presented an asymptomatic but severe aneurysmal dilatation of the aorta and CT scan and MRI showed dilated cerebral arteries. The father of our patient had died at the age of 27 years either from myocardial infarction or rupture of a dissecting aortic aneurysm. He was highly myopic and had lost one eye from retinal detachment. The younger brother of our patient also presents aneurysmal dilatation of the aorta and tortuous cerebral vessels. Ocular examination is still normal. The findings in this family are compatible with an autosomal dominant inheritance with variable expression.

  14. Magnetic Resonance-Guided Laser-Induced Thermal Therapy for Recurrent Brain Metastases in the Motor Strip After Stereotactic Radiosurgery

    PubMed Central

    Halpern, Casey H; Grant, Gerald A; Deb, Sayantan; Li, Gordon H

    2016-01-01

    The authors report a challenging case of a brain metastasis located in the motor cortex, which was not responsive to radiosurgery. Use of a novel technique, magnetic resonance-guided laser-induced thermotherapy (MRgLITT), resulted in the complete obliteration of the lesion without adverse effects or evidence of tumor recurrence at follow-up. This case illustrates that MRgLITT may provide a viable alternative for patients with brain metastases refractory to radiosurgery or in deep locations, where both stereotactic radiosurgery (SRS) and surgical resection may be ineffective.   PMID:28083463

  15. 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.

  16. Compositional Analysis of Drugs by Laser-Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Beldjilali, S. A.; Axente, E.; Belasri, A.; Baba-Hamed, T.; Hermann, J.

    2017-07-01

    The feasibility of the compositional analysis of drugs by calibration-free laser-induced breakdown spectroscopy (LIBS) was investigated using multivitamin tablets as a sample material. The plasma was produced by a frequencyquadrupled Nd:YAG laser delivering UV pulses with a duration of 5 ns and an energy of 12 mJ, operated at a repetition rate of 10 Hz. The relative fractions of the elements composing the multivitamin drug were determined by comparing the emission spectrum of the laser-produced plume with the spectral radiance computed for a plasma in a local thermodynamic equilibrium. Fair agreement of the measured fractions with those given by the manufacturer was observed for all elements mentioned in the leafl et of the drug. Additional elements such as Ca, Na, Sr, Al, Li, K, and Si were detected and quantifi ed. The present investigations demonstrate that laser-induced breakdown spectroscopy is a viable technique for the quality control of drugs.

  17. 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.

  18. 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.

  19. Laser-induced incandescence calibration via gravimetric sampling

    NASA Technical Reports Server (NTRS)

    Choi, M. Y.; Vander Wal, R. L.; Zhou, Z.

    1996-01-01

    Absolute calibration of laser-induced incandescence (LII) is demonstrated via comparison of LII signal intensities with gravimetrically determined soot volume fractions. This calibration technique does not rely upon calculated or measured optical characteristics of soot. The variation of the LII signal with gravimetrically measured soot volume fractions ranging from 0.078 to 1.1 ppm established the linearly of the calibration. With the high spatial and temporal resolution capabilities of laser-induced incandescence (LII), the spatial and temporal fluctuations of the soot field within a gravimetric chimney were characterized. Radial uniformity of the soot volume fraction, f(sub v) was demonstrated with sufficient averaging of the single laser-shot LII images of the soot field thus confirming the validity of the calibration method for imaging applications. As illustration, instantaneous soot volume fractions within a Re = 5000 ethylene/air diffusion flame measured via planar LII were established quantitatively with this calibration.

  20. 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.

  1. 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.

  2. 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.

  3. Flame-enhanced laser-induced breakdown spectroscopy.

    PubMed

    Liu, L; Li, S; He, X N; Huang, X; Zhang, C F; Fan, L S; Wang, M X; Zhou, Y S; Chen, K; Jiang, L; Silvain, J F; Lu, Y F

    2014-04-07

    Flame-enhanced laser-induced breakdown spectroscopy (LIBS) was investigated to improve the sensitivity of LIBS. It was realized by generating laser-induced plasmas in the blue outer envelope of a neutral oxy-acetylene flame. Fast imaging and temporally resolved spectroscopy of the plasmas were carried out. Enhanced intensity of up to 4 times and narrowed full width at half maximum (FWHM) down to 60% for emission lines were observed. Electron temperatures and densities were calculated to investigate the flame effects on plasma evolution. These calculated electron temperatures and densities showed that high-temperature and low-density plasmas were achieved before 4 µs in the flame environment, which has the potential to improve LIBS sensitivity and spectral resolution.

  4. Nanosecond-gated laser induced breakdown spectroscopy in hydrocarbon mixtures

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kazunobu; Bak, Moon Soo; Tanaka, Hiroki; Do, Hyungrok

    2015-09-01

    Nanosecond-gated laser induced breakdown spectroscopy have been carried out in four different hydrocarbon gas mixtures (CH4/CO2/O2/N2, C2H4/O2/N2, C3H8/CO2/O2/N2 and C4H10/CO2/O2/N2) to investigate the effect of gas species on the laser induced breakdown kinetics and resulting the plasma emission. For this purpose, each mixture that consists of different species has the same atom composition. It is found that the temporal emission spectra and the decay rates of atomic line-intensities are almost identical for the breakdowns in the four different mixtures. This finding may indicate that the breakdown plasmas of these mixtures reach a similar thermodynamic and physiochemical state after its formation, resulting in a similar trend of quenching of excited species.

  5. Thrombospondin-2 Expression During Retinal Vascular Development and Neovascularization

    PubMed Central

    Fei, Ping; Palenski, Tammy L.; Wang, Shoujian; Gurel, Zafer; Hankenson, Kurt D.; Sorenson, Christine M.

    2015-01-01

    Abstract Purpose: To determine thrombospondin-2 (TSP2) expression and its impact on postnatal retinal vascular development and retinal neovascularization. Methods: The TSP2-deficient (TSP2−/−) mice and a line of TSP2 reporter mice were used to assess the expression of TSP2 during postnatal retinal vascular development and neovascularization. The postnatal retinal vascularization was evaluated using immunostaining of wholemount retinas prepared at different postnatal days by collagen IV staining and/or TSP2 promoter driven green fluorescent protein (GFP) expression. The organization of astrocytes was evaluated by glial fibrillary acidic protein (GFAP) staining. Retinal vascular densities were determined using trypsin digestion preparation of wholemount retinas at 3- and 6-weeks of age. Retinal neovascularization was assessed during the oxygen-induced ischemic retinopathy (OIR). Choroidal neovascularization (CNV) was assessed using laser-induced CNV. Results: Using the TSP2-GFP reporter mice, we observed significant expression of TSP2 mRNA in retinas of postnatal day 5 (P5) mice, which increased by P7 and remained high up to P42. Similar results were observed in retinal wholemount preparations, and western blotting for GFP with the highest level of GFP was observed at P21. In contrast to high level of mRNA at P42, the GFP fluorescence or protein level was dramatically downregulated. The primary retinal vasculature developed at a faster rate in TSP2−/− mice compared with TSP2+/+ mice up to P5. However, the developing retinal vasculature in TSP2+/+ mice caught up with that of TSP2−/− mice after P7. No significant differences in retinal vascular density were observed at 3- or 6-weeks of age. TSP2−/− mice also exhibited a similar sensitivity to the hyperoxia-mediated vessel obliteration and similar level of neovascularization during OIR as TSP2+/+ mice. Lack of TSP2 expression minimally affected laser-induced CNV compared with TSP2+/+ mice. Conclusions

  6. Retine revisited.

    PubMed

    Douglas, D E

    2002-10-01

    Retine, so named by Albert Szent-Györgyi, an inhibitor of the growth of transplanted malignant tumours in animals, is present in all mammalian tissues and in urine. Its inhibitory activity was extensively investigated by Szent-Györgyi, but its exact chemical identity was not determined. Details of the reported physical and chemical properties of retine and its ubiquitous occurrence identify it as being identical to a complex mixture of lipid 2,4-diketones of similar ubiquitous occurrence. This lipid mixture has been extensively studied, and individual members have been synthesized.

  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. Thermometry in pressurized sooting flames using laser-induced gratings

    NASA Astrophysics Data System (ADS)

    Brown, Michael S.; Roberts, William L.

    1997-11-01

    We have performed non-intrusive thermometry in rich ethylene/air flames using a frequency measurement based on laser-induced gratings. Light from a cw probe beam is coherently scattered from a thermal or electrostrictive grating induced by the pulsed pump beams. The Doppler modulation of the signal beam is determined by the local speed of sound from which a temperature can be extracted. Soot particles, acting as blackbody absorbers do contribute to the signal.

  9. 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.

  10. Misalignment Effects in Laser-Induced Grating Experiments.

    PubMed

    Kiefer, Johannes; Sahlberg, Anna-Lena; Hot, Dina; Aldén, Marcus; Li, Zhongshan

    2016-12-01

    Laser-induced grating spectroscopy (LIGS) is an experimental method in which two pulsed laser beams and a continuous-wave laser beam have to be superimposed under well-defined angles to generate a coherent signal beam. In this Note, the possible effects of different forms of misalignment are examined. This includes the overlap of the pump lasers as well as the influence of the probe laser alignment on the temporal profile of the signal.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Laser induced unzipping: A thermal route to polymer ablation

    NASA Astrophysics Data System (ADS)

    Blanchet, Graciela B.; Fincher, C. R., Jr.

    1994-09-01

    The data presented here show that polytetrafluoroethylene (PTFE) and polymethylmethacrylate (PMMA) can be ablated by the evaporation of solid polymer targets with a pulsed ultraviolet laser. In situ measurements of the plume composition show that the products emitted under laser irradiation are primarily monomer and other species resulting from energetic collisions within the plasma. The similarities between the ablative and pyrolisis mass spectra suggest that ablation of PTFE and PMMA occur through a laser induced pyrolitic decomposition.

  17. Laser-induced gas breakdown - Spectroscopic and chemical studies.

    NASA Technical Reports Server (NTRS)

    De Montgolfier, PH.; Dumont, P.; Mille, Y.; Villermaux, J.

    1972-01-01

    Discussion of the results of several experimental investigations on laser-induced gas breakdown. The experiments included time-resolved spectroscopy, direct detection of H atoms with a TiO2 probe, and chemical reactions; each of them provided insight into the behavior of the medium at different times. Chemical reactions and explosions have been initiated by the laser beam when a plasma was created. No primary multiphotonic absorption and no macroscopic chemical reactions were observed below the breakdown threshold.

  18. Laser induced tuning of cholesteric liquid crystal without alignment layers

    NASA Astrophysics Data System (ADS)

    Cheng, M.-C.; Huang, T.-C.; Lee, C.-Y.; Hsiao, Vincent K. S.

    2014-12-01

    We demonstrate a laser induced tuning effect on non-chiral azobenzene-doped CLC (Azo-CLCs) without using orientated substrate. The reversible tuning range is 90 nm under alternative violet (405 nm) and green (532 nm) laser exposure corresponded to the response time of 3 and 15 s, respectively. The current demonstrations may find applications in photoactive micro- or nano-photonic devices where orientated substrate is difficult to be incorporated.

  19. Laser-induced gas breakdown - Spectroscopic and chemical studies.

    NASA Technical Reports Server (NTRS)

    De Montgolfier, PH.; Dumont, P.; Mille, Y.; Villermaux, J.

    1972-01-01

    Discussion of the results of several experimental investigations on laser-induced gas breakdown. The experiments included time-resolved spectroscopy, direct detection of H atoms with a TiO2 probe, and chemical reactions; each of them provided insight into the behavior of the medium at different times. Chemical reactions and explosions have been initiated by the laser beam when a plasma was created. No primary multiphotonic absorption and no macroscopic chemical reactions were observed below the breakdown threshold.

  20. 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.

  1. All-SPEEK flexible supercapacitor exploiting laser-induced graphenization

    NASA Astrophysics Data System (ADS)

    Lamberti, A.; Serrapede, M.; Ferraro, G.; Fontana, M.; Perrucci, F.; Bianco, S.; Chiolerio, A.; Bocchini, S.

    2017-09-01

    Flexible supercapacitors have emerged as one of the more promising and efficient space-saving energy storage system for portable and wearable electronics. Laser-induced graphenization has been recently proposed as a powerful and scalable method to directly convert a polymeric substrate into a 3D network of few layer graphene as high-performance supercapacitor electrode. Unfortunately this outstanding process has been reported to be feasible only for few thermoplastic polymers, strongly limiting its future developments. Here we show that laser induced graphenization of sulfonated poly(ether ether ketone) (SPEEK) can be obtained and the mechanism of this novel process is proposed. The resulting material can act at the same time as binder-free electrode and current collector. Moreover SPEEK is also used both as separator and polymeric electrolyte allowing the assembling of an all-SPEEK flexible supercapacitor. Chemico-physical characterization provides deep understanding of the laser-induced graphenization process, reported on this polymer for the first time, while the device performance studied by cyclic voltammetry, charging-discharging, and impedance spectroscopy prove the enormous potential of the proposed approach.

  2. Laser induced plasma expansion and existence of local thermodynamic equilibrium

    NASA Astrophysics Data System (ADS)

    Skočić, Miloš; Bukvić, Srdjan

    2016-11-01

    In this paper we present a simple model of the laser induced plasma (LIP) expansion in a low pressure surrounding atmosphere. The model is based on assumption that expansion process is dominantly governed by kinematics of the heavy particles. The model is accompanied with a simple, yet effective, Monte-Carlo simulation. Results of the simulation are compared with spectroscopic measurements of the laser induced copper plasma expanding in low pressure (200 Pa) hydrogen atmosphere. We found that characteristic expansion time of the LIP is proportional to the linear dimension of the initial volume heated up by the laser. For sufficiently large initial volume copper plasma remains in local thermodynamic equilibrium on the submicrosecond-microsecond scale. It is shown that diagnostics based on the spectral lines of the hydrogen atmosphere is not suitable for characterization of the core of the copper plasma. We have demonstrated importance of radially resolved spectroscopic measurements as a key step for correct diagnostics and understanding of laser induced plasma.

  3. Study of fast laser induced cutting of silicon materials

    NASA Astrophysics Data System (ADS)

    Weinhold, S.; Gruner, A.; Ebert, R.; Schille, J.; Exner, H.

    2014-03-01

    We report on a fast machining process for cutting silicon wafers using laser radiation without melting or ablating and without additional pretreatment. For the laser induced cutting of silicon materials a defocused Gaussian laser beam has been guided over the wafer surface. In the course of this, the laser radiation caused a thermal induced area of tension without affecting the material in any other way. With the beginning of the tension cracking process in the laser induced area of tension emerged a crack, which could be guided by the laser radiation along any direction over the wafer surface. The achieved cutting speed was greater than 1 m/s. We present results for different material modifications and wafer thicknesses. The qualitative assessment is based on SEM images of the cutting edges. With this method it is possible to cut mono- and polycrystalline silicon wafers in a very fast and clean way, without having any waste products. Because the generated cracking edge is also very planar and has only a small roughness, with laser induced tension cracking high quality processing results are easily accessible.

  4. Hydrogen leak detection using laser-induced breakdown spectroscopy.

    PubMed

    Ball, A J; Hohreiter, V; Hahn, D W

    2005-03-01

    Laser-induced breakdown spectroscopy (LIBS) is investigated as a technique for real-time monitoring of hydrogen gas. Two methodologies were examined: The use of a 100 mJ laser pulse to create a laser-induced breakdown directly in a sample gas stream, and the use of a 55 mJ laser pulse to create a laser-induced plasma on a solid substrate surface, with the expanding plasma sampling the gas stream. Various metals were analyzed as candidate substrate surfaces, including aluminum, copper, molybdenum, stainless steel, titanium, and tungsten. Stainless steel was selected, and a detailed analysis of hydrogen detection in binary mixtures of nitrogen and hydrogen at atmospheric pressure was performed. Both the gaseous plasma and the plasma initiated on the stainless steel surface generated comparable hydrogen emission signals, using the 656.28 Halpha emission line, and exhibited excellent signal linearity. The limit of detection is about 20 ppm (mass) as determined for both methodologies, with the solid-initiated plasma yielding a slightly better value. Overall, LIBS is concluded to be a viable candidate for hydrogen sensing, offering a combination of high sensitivity with a technique that is well suited to implementation in field environments.

  5. Temperature mapping of laser-induced hyperthermia in an ocular phantom using magnetic resonance thermography.

    PubMed

    Maswadi, Saher M; Dodd, Stephen J; Gao, Jia-Hong; Glickman, Randolph D

    2004-01-01

    Laser-induced heating in an ocular phantom is measured with magnetic resonance thermography (MRT) using temperature-dependent phase changes in proton resonance frequency. The ocular phantom contains a layer of melanosomes isolated from bovine retinal pigment epithelium. The phantom is heated by the 806-nm output of a continuous wave diode laser with an irradiance of 2.4 to 21.6 W/cm2 in a beam radius of 0.8 or 2.4 mm, depending on the experiment. MRT is performed with a 2 T magnet, and a two-turn, 6-cm-diam, circular radio frequency coil. Two-dimensional temperature gradients are measured within the plane of the melanin layer, as well as normal to it, with a temperature resolution of 1 degrees C or better. The temperature gradients extending within the melanin layer are broader than those orthogonal to the layer, consistent with the higher optical absorption and consequent heating in the melanin. The temperature gradients in the phantom measured by MRT closely approximate the predictions of a classical heat diffusion model. Three-dimensional temperature maps with a spatial resolution of 0.25 mm in all directions are also made. Although the temporal resolution is limited in the prototype system (22.9 s for a single image "slice"), improvements in future implementations are likely. These results indicate that MRT has sufficient spatial and temperature resolution to monitor target tissue temperature during transpupillary thermotherapy in the human eye.

  6. Lymphocytic Microparticles Modulate Angiogenic Properties of Macrophages in Laser-induced Choroidal Neovascularization

    PubMed Central

    Tahiri, Houda; Omri, Samy; Yang, Chun; Duhamel, François; Samarani, Suzanne; Ahmad, Ali; Vezina, Mark; Bussières, Martin; Vaucher, Elvire; Sapieha, Przemyslaw; Hickson, Gilles; Hammamji, Karim; Lapointe, Réjean; Rodier, Francis; Tremblay, Sophie; Royal, Isabelle; Cailhier, Jean-François; Chemtob, Sylvain; Hardy, Pierre

    2016-01-01

    Pathological choroidal neovascularization (CNV) is the common cause of vision loss in patients with age-related macular degeneration (AMD). Macrophages possess potential angiogenic function in CNV. We have demonstrated that human T lymphocyte-derived microparticles (LMPs) exert a potent antiangiogenic effect in several pathological neovascularization models. In this study, we investigated the alteration of proangiogenic properties of macrophages by LMPs treatment in vitro and in vivo models. LMPs regulated the expression of several angiogenesis-related factors in macrophages and consequently stimulated their antiangiogenic effects evidenced by the suppression of the proliferation of human retinal endothelial cells in co-culture experiments. The involvement of CD36 receptor in LMPs uptake by macrophages was demonstrated by in vitro assays and by immunostaining of choroidal flat mounts. In addition, ex vivo experiments showed that CD36 mediates the antiangiogenic effect of LMPs in murine and human choroidal explants. Furthermore, intravitreal injection of LMPs in the mouse model of laser-induced CNV significantly suppressed CNV in CD36 dependent manner. The results of this study suggested an ability of LMPs to alter the gene expression pattern of angiogenesis-related factors in macrophages, which provide important information for a new therapeutic approach for efficiently interfering with both vascular and extravascular components of CNV. PMID:27874077

  7. Lymphocytic Microparticles Modulate Angiogenic Properties of Macrophages in Laser-induced Choroidal Neovascularization.

    PubMed

    Tahiri, Houda; Omri, Samy; Yang, Chun; Duhamel, François; Samarani, Suzanne; Ahmad, Ali; Vezina, Mark; Bussières, Martin; Vaucher, Elvire; Sapieha, Przemyslaw; Hickson, Gilles; Hammamji, Karim; Lapointe, Réjean; Rodier, Francis; Tremblay, Sophie; Royal, Isabelle; Cailhier, Jean-François; Chemtob, Sylvain; Hardy, Pierre

    2016-11-22

    Pathological choroidal neovascularization (CNV) is the common cause of vision loss in patients with age-related macular degeneration (AMD). Macrophages possess potential angiogenic function in CNV. We have demonstrated that human T lymphocyte-derived microparticles (LMPs) exert a potent antiangiogenic effect in several pathological neovascularization models. In this study, we investigated the alteration of proangiogenic properties of macrophages by LMPs treatment in vitro and in vivo models. LMPs regulated the expression of several angiogenesis-related factors in macrophages and consequently stimulated their antiangiogenic effects evidenced by the suppression of the proliferation of human retinal endothelial cells in co-culture experiments. The involvement of CD36 receptor in LMPs uptake by macrophages was demonstrated by in vitro assays and by immunostaining of choroidal flat mounts. In addition, ex vivo experiments showed that CD36 mediates the antiangiogenic effect of LMPs in murine and human choroidal explants. Furthermore, intravitreal injection of LMPs in the mouse model of laser-induced CNV significantly suppressed CNV in CD36 dependent manner. The results of this study suggested an ability of LMPs to alter the gene expression pattern of angiogenesis-related factors in macrophages, which provide important information for a new therapeutic approach for efficiently interfering with both vascular and extravascular components of CNV.

  8. Fundamental Studies in the Molecular Basis of Laser Induced Retinal Damage.

    DTIC Science & Technology

    1981-09-01

    vertebrates is not achromatic. There is a difference between the focus point for red and blue light , which is approximately 1 diopter for the human eye (8...detected kinetically at certain time intervals after rhodopsin light excitation. The data we obtained is seen in Figure 4. Only vibrational modes of...carotene are observed (11,12). Vibrational modes of rhodopsin (13) are absent. Retinas exposed to a stimulating light 11 ps and 14 jis before the

  9. Fundamental Studies in the Molecular Basis of Laser Induced Retinal Damage.

    DTIC Science & Technology

    1983-09-01

    major discoveries in two general areas. First, we have been able to show that there are a series of anionic activators of visual cells. These anionic... activators turn on, in the dark, the enzymatic processes which are usually stimulated by light. Among these anionic activators is fluoride, the...important additive in dental care. It is possible that our discovery of anionic activators will allow us to modulate visual sensitivity and excitation. A

  10. Investigation of Laser-Induced Retinal Damage: Wavelength and Pulsewidth Dependent Mechanisms

    DTIC Science & Technology

    1994-08-31

    OMENTAMlN PAGE AD- A285 186 *Q IV N a f 1 31 Aug 94Final’ Technical Report 1L4 pr 91 to 30-’*W* ?.PROM IN RAIATO AES AND ADDRES(ES R REPORIN NUMBERS ...Dneptiartment of Optalmologyce reia- aaer . Universigty ofd TexasHealth Sience ent erhatimA Sa AnonoOTSCR--91-020 7703 Floyds CurlDriv SandAtnop TX...78284-6230 Ph.D.T~94 O6A .SPERFORMING /MOAN(AITORNGAE NAME(SAM AND ORESS(E7 10. HSPO MN 5BN/MNIZTIORN AGENCY REPORT NUMBER AFOSR/NL 110 Duncan Ave

  11. Fundamental Studies in the Molecular Basis of Laser Induced Retinal Damage.

    DTIC Science & Technology

    1991-04-15

    Among these new emerging lensless techniques is the method of molecular exciton microscopy (MEM) in which energy transfer is used between a crystal of...finally to lensless light microscopy with the potential to place in the hands of cell biologists a microscope with a variety of magnifications from a few...resolution lensless light microscopy . In summary, although these exciting developments in our laboratory have not yet yielded fruit for the ocular

  12. Investigation of Laser-Induced Retinal Damage: Wavelength and Pulsewidth Dependent Mechanisms

    DTIC Science & Technology

    1994-06-30

    photosensitized oxidation reaction. 5 Melanin granules from bovine RPE cells were washed free of other cellular debris by successive centrifugation and...melanin oxidizes the ascorbic acid by a free radical mechanism, and is consistent with the hypothesis that melanin may serve as a photosensitizer . The...loss in the ability to mobilize ascorbic acid. Therefore a decline in the redox state of the aging eye may result in melanin acting as a photosensitizer

  13. Fundamental Studies in the Molecular Basis of Laser Induced Retinal Damage.

    DTIC Science & Technology

    1985-04-01

    motion is stimulated by rhodopsin light-absorption. The results we got dramatically support 4. out earlier suggestion (5). In D20 (see Figure 4) both...large amplified response to a single photon. In essence one photon stimulates these enzymes to hydrolyze 400,000 cyclic GMP molecules to produce on a...vanadate, fluoride, molybdate and tungstate activate rod outer segment PDE in the absence of light. Since tung- state stimulates ROS PDE at low

  14. Fundamental Studies in the Molecular Basis of Laser Induced Retinal Damage.

    DTIC Science & Technology

    1984-09-01

    opportunity to investi- gate our earlier suggestion (5) that proton motion is stimulated by rhodopsin light-absorption. The results we got...proton. This enzymatic machinery results in a large amplified response to a single photon. In essence one photon stimulates these enzymes to hydrolyze...demonstrate that vanadate, fluoride, molybdate and tungstate activate rod outer segment PDE in the absence of light. Since tung- state stimulates ROS

  15. Screening Diabetic Retinopathy Through Color Retinal Images

    NASA Astrophysics Data System (ADS)

    Li, Qin; Jin, Xue-Min; Gao, Quan-Xue; You, Jane; Bhattacharya, Prabir

    Diabetic Retinopathy (DR) is a common complication of diabetes that damages the eye's retina. Recognition DR as early as possible is very important to protect patients' vision. We propose a method for screening DR and distin-guishing Prolifetive Diabetic Retinopathy (PDR) from Non-Prolifetive Retino-pathy (NPDR) automatatically through color retinal images. This method evaluates the severity of DR by analyzing the appearnce of bright lesions and retinal vessel patterns. The bright lesions are extracted through morphlogical re-consturction. After that, the retinal vessels are automatically extracted using multiscale matched filters. Then the vessel patterns are analyzed by extracting the vessel net density. The experimental results domonstrate that it is a effective solution to screen DR and distinguish PDR from NPDR by only using color retinal images.

  16. The use of MRI-guided laser-induced thermal ablation for epilepsy.

    PubMed

    Tovar-Spinoza, Zulma; Carter, David; Ferrone, David; Eksioglu, Yaman; Huckins, Sean

    2013-11-01

    Epilepsy surgery is constantly researching for new options for patients with refractory epilepsy. MRI-guided laser-induced thermal ablation for epilepsy is an exciting new minimally invasive technology with an emerging use for lesionectomy of a variety of epileptogenic focuses (hypothalamic hamartomas, cortical dysplasias, cortical malformations, tubers) or as a disconnection tool allowing a new option of treatment without the hassles of an open surgery. MRI-guided laser interstitial thermal therapy (MRgLITT) is a procedure for destroying tissue-using heat. To deliver this energy in a minimally invasive fashion, a small diameter fiber optic applicator is inserted into the lesion through a keyhole stereotactic procedure. The thermal energy induces damage to intracellular DNA and DNA-binding structures, ultimately leading to cell death. The ablation procedure is supervised by real-time MRI thermal mapping and confirmed by immediate post-ablation T1 or FLAIR MRI images. The present report includes an overview of the development and practice of an MR-guided laser ablation therapy known as MRI-guided laser interstitial thermal therapy (MRgLITT). The role of modern image-guided trajectory planning in MRgLITT will also be discussed, with particular emphasis on the treatment of refractory epilepsy using this novel, minimally invasive technique. MRI-guided laser-induced thermal ablation for epilepsy is an exciting new minimally invasive technology that finds potential new applications every day in the neurosurgical field. It certainly brings a new perspective on the way we practice epilepsy surgery even though long-term results should be properly collected and analyzed.

  17. Retinitis pigmentosa associated with peripheral sea fan neovascularization.

    PubMed

    Kadayifçilar, S; Eldem, B; Kiratli, H

    2000-10-01

    To describe a case with retinitis pigmentosa associated with sea fan type retinal neovascularization. Complete ocular examination including fluorescein angiography was performed in a 9-year-old girl. Ophthalmoscopically, in addition to arteriolar narrowing and bone corpuscular pigmentation of both retinae, a vascular lesion with surrounding intraretinal exudation was noted in the upper equatorial region of the right eye. On fluorescein angiography, the lesion stained in the form of a sea fan neovascularization. Sea fan type of neovascularization can be seen in association with retinitis pigmentosa. Fluorescein angiography is important in identifying the exact nature of such a lesion.

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. Q-Switched Alexandrite Laser-induced Chrysiasis.

    PubMed

    Cohen, Philip R; Ross, E Victor

    2015-09-01

    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. To describe the characteristics of patients with laser-induced chrysiasis. 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. 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. 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-switched laser. Also, treatment with a long-pulsed laser

  3. 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.

  4. 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.

  5. Annual review of retinal research.

    PubMed

    Cohen, J

    1976-09-01

    This paper reviews recent ophthalmological manuscripts pertaining to wasting retinal nerve fibers, retinopathy related to systemic lymphomas, hypertensive retinopathy, diabetic retinopathy, retinal oxalosis, macular and foveal anomalies, retinal pigment epithelium, retinitis pigmentosa, retinoblastoma, histoplasmosis, toxoplasmosis, and retinal tears and detachments.

  6. 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.

  7. 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.

  8. Laser-Induced-Emission Spectroscopy In Hg/Ar Discharge

    NASA Technical Reports Server (NTRS)

    Maleki, Lutfollah; Blasenheim, Barry J.; Janik, Gary R.

    1992-01-01

    Laser-induced-emission (LIE) spectroscopy used to probe low-pressure mercury/argon discharge to determine influence of mercury atoms in metastable 6(Sup3)P(Sub2) state on emission of light from discharge. LIE used to study all excitation processes affected by metastable population, including possible effects on excitation of atoms, ions, and buffer gas. Technique applied to emissions of other plasmas. Provides data used to make more-accurate models of such emissions, exploited by lighting and laser industries and by laboratories studying discharges. Also useful in making quantitative measurements of relative rates and cross sections of direct and two-step collisional processes involving metastable level.

  9. 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.

  10. Communication: Bubbles, crystals, and laser-induced nucleation.

    PubMed

    Knott, Brandon C; LaRue, Jerry L; Wodtke, Alec M; Doherty, Michael F; Peters, Baron

    2011-05-07

    Short intense laser pulses of visible and infrared light can dramatically accelerate crystal nucleation from transparent solutions; previous studies invoke mechanisms that are only applicable for nucleation of ordered phases or high dielectric phases. However, we show that similar laser pulses induce CO(2) bubble nucleation in carbonated water. Additionally, in water that is cosupersaturated with argon and glycine, argon bubbles escaping from the water can induce crystal nucleation without a laser. Our findings suggest a possible link between laser-induced nucleation of bubbles and crystals.

  11. Evidence of laser induced degradation and graphitization of aromatic pollutants

    NASA Astrophysics Data System (ADS)

    Mele, A.; Letardi, T.; di Lazarro, P.

    The laser-induced photodecomposition and graphitization of polynuclear aromatic hydrocarbons is investigated by irradiating solid pollutant samples with an Nd-YAG laser, leaving a carbon-rich, black powder. The irradiation of anthracene and benzopyrene forms the ions Cn(+)-, CnH(+)-, and CnH2(+)- in a wide plume produced by a pulsed-CO2 laser. The tendency of aromatic compounds to fragment is noted, and the notion that ion formation is governed by the mechanism that produces ablation in the laser cloud is suggested. Optical multichannel analyzer emission spectra indicate the production of the Cn species, suggesting applications to the treatment of aromatic product wastes.

  12. Laser induced fluorescence of biochemical for UV LIDAR application.

    PubMed

    Gupta, L; Sharma, R C; Razdan, A K; Maini, A K

    2014-05-01

    Laser induced fluorescence spectroscopy in the ultraviolet regime has been used for the detection of biochemical through a fiber coupled CCD detector from a distance of 2 m. The effect of concentration and laser excitation energy on the fluorescence spectra of nicotinamide adenine dinucleotide (NADH) has been investigated. The signature fluorescence peak of NADH was centred about 460 nm. At lower concentration Raman peak centred at 405 nm was also observed. The origin of this peak has been discussed. Detection limit with the proposed set up is found to be 1 ppm.

  13. Laser induced nanoparticles and crystals and their characterization

    NASA Astrophysics Data System (ADS)

    Rezaee, Mohammadreza; Compton, Robert

    2014-03-01

    Intense nanosecond lasers are used to fabricate nanoparticles by direct laser solid interactions as well as laser produced shock wave induced crystallization in saturated solutions. In particular, laser graphite interactions under liquid nitrogen results in variety of interesting new carbon nanoclusters. In particular, exfoliation of graphite to produce graphene is considered. Laser produced shock wave in unsaturated salt (e.g. NaCl, NaClO3) solution immediately produces thousands of tiny crystals. These nonmaterials are examined using Raman spectroscopy under liquid nitrogen, RUN), laser induced fluorescence, plasma spectroscopy, UV-Vis spectroscopy as well as conventional characterization methods such as SEM and HRTEM imaging.

  14. Laser-induced incandescence from laser-heated silicon nanoparticles

    NASA Astrophysics Data System (ADS)

    Menser, Jan; Daun, Kyle; Dreier, Thomas; Schulz, Christof

    2016-11-01

    This work describes the application of temporally and spectrally resolved laser-induced incandescence to silicon nanoparticles synthesized in a microwave plasma reactor. Optical properties for bulk silicon presented in the literature were extended for nanostructured particles analyzed in this paper. Uncertainties of parameters in the evaporation submodel, as well as measurement noise, are incorporated into the inference process by Bayesian statistics. The inferred nanoparticle sizes agree with results from transmission electron microscopy, and the determined accommodation coefficient matches the values of the preceding study.

  15. Communication: Bubbles, crystals, and laser-induced nucleation

    NASA Astrophysics Data System (ADS)

    Knott, Brandon C.; LaRue, Jerry L.; Wodtke, Alec M.; Doherty, Michael F.; Peters, Baron

    2011-05-01

    Short intense laser pulses of visible and infrared light can dramatically accelerate crystal nucleation from transparent solutions; previous studies invoke mechanisms that are only applicable for nucleation of ordered phases or high dielectric phases. However, we show that similar laser pulses induce CO2 bubble nucleation in carbonated water. Additionally, in water that is cosupersaturated with argon and glycine, argon bubbles escaping from the water can induce crystal nucleation without a laser. Our findings suggest a possible link between laser-induced nucleation of bubbles and crystals.

  16. Computer simulations of laser-induced melting of aluminum

    NASA Astrophysics Data System (ADS)

    Tang, Hong; Bai, Mingze; Dou, Yusheng; Ran, Qi; Lo, Glenn V.

    2013-04-01

    Laser-induced solid-to-liquid phase transitions in 100 nm aluminum film were simulated using a hybrid model that combines molecular dynamics (MD) with a continuum description of the laser excitation and a two-temperature method (TTM) to model the relaxation of conduction band electrons. When the laser fluence provides more energy than needed for a complete melting of the film, the phase transition is characterized by an ultrafast collapse of the crystal structure within 2-3 ps. Otherwise, the transition involves a homogeneous nucleation and growth of liquid zones inside the crystal and a heterogeneous propagation of transition fronts from the external surfaces or nucleated liquid zones.

  17. Laser Induced Bunch Lengthening on the ACO Storage Ring FEL,

    DTIC Science & Technology

    1982-09-01

    AA1455 LASE AINDUCED BUNCH LENGTHENING ON THE AC 0 TORAGE RING 1/ FELU )SANFORD UNI CA HIGH ENERGY PHSC LAB K AD RBNSON ET AL 5 P A2 H E PL910 F49620...Deacon,t Michel F. Velghe and John M. Madey High Energy Physics Laboratory Stanford University Stanford, California 94305-2184 c " ’j CD. L * Work...electron bunch length and energy preod t .... high current can lead to a number of anomalous effects at Wic us high current, including laser-induced

  18. Visualization of jet development in laser-induced plasmas.

    PubMed

    Brieschenk, Stefan; O'Byrne, Sean; Kleine, Harald

    2013-03-01

    Laser-induced plasmas in gases are known to generate gaseous jets in the postplasma gas plume. The gaseous jet typically develops toward the laser source, and the experiments presented here show, for the first time to our knowledge, that, under certain conditions, these jets can develop in the opposite direction or may not form at all. The data suggest that this is related to the ratio between the energy absorbed in the plasma and the threshold breakdown energy, effectively leading to multiple plasma initiation sites in the focal waist.

  19. Expansion of radiative cooling of the laser induced plasma

    SciTech Connect

    Wen, Sy-Bor; Mao, Xianglei; Liu, Chunyi; Greif, Ralph; Russo,Richard

    2006-05-05

    To study the expansion and cooling process of the laser induced plasma generated by nanosecond pulsed laser ablation, experiments have been conducted which measure the position of the external shockwaves and the temperature of the vapor plumes. The positions of external shockwaves were determined by a femtosecond laser time-resolved imaging system. Vapor plume temperature was determined from spectroscopic measurements of the plasma emission lines. A model which considers the mass, momentum, and energy conservation of the region affected by the laser energy was developed. It shows good agreement to the experimental data.

  20. Enhancement of terahertz wave generation from laser induced plasma

    SciTech Connect

    Xie Xu; Xu Jingzhou; Dai Jianming; Zhang, X.-C.

    2007-04-02

    It is well known that air plasma induced by ultrashort laser pulses emits broadband terahertz waves. The authors report the study of terahertz wave generation from the laser induced plasma where there is a preexisting plasma background. When a laser beam from a Ti:sapphire amplifier is used to generate a terahertz wave, enhancement of the generation is observed if there is another laser beam creating a plasma background. The enhancement of the terahertz wave amplitude lasts hundreds of picoseconds after the preionized background is created, with a maximum enhancement up to 250% observed.

  1. Laser-induced removal of organic contaminants from metal substrates

    NASA Astrophysics Data System (ADS)

    Song, Wen D.; Lu, Yongfeng; Chen, Q.; Low, Tohsiew

    1998-08-01

    Laser-induced removal of organic contaminants, such as grease and wax, on Cr substrate surfaces was studied. The laser cleaning efficiency was analyzed by an optical microscope and an Auger Electron Spectroscopy (AES). It was found that the contaminants in the irradiated area can be effectively removed by pulsed laser irradiation and cleaning efficiency can be reached to 80% above under a certain cleaning condition without damage. The damage threshold of Cr substrates was obtained by numerical simulation, which is in good consistency with the experimental threshold.

  2. 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.

  3. Interaction of laser-induced stress waves with metals

    NASA Technical Reports Server (NTRS)

    Clauer, A. H.; Fairand, B. P.

    1979-01-01

    An investigation of the effect of high intensity laser induced stress waves on the hardness and tensile strength of 2024 and 7075 aluminum and on the fatigue properties of 7075 aluminum were investigated. Laser shocking increases the hardness of the underaged 2024-T351 but has little or no effect on the peak aged 2024-T351 and 7075-T651 or the overaged 7075-T73. The fretting fatigue life of fastener joints of 7075-T6 was increased by orders of magnitude by laser shocking the region around the fastener hole; the fatigue crack propagation rates were decreased by laser shocking.

  4. 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.

  5. 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.

  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 breakdown system for colloid characterization in dilute aqueous suspensions

    SciTech Connect

    Brachman, A; Mihardja, S; Palmer, C A; Wruck, D

    1999-08-11

    Detection and sizing of colloids by acoustic detection of laser-induced breakdown and elemental analysis of colloids by laser-induced breakdown spectroscopy are investigated in dilute aqueous suspensions. Development and testing of the methods are performed with standard polystyrene suspensions and prepared suspensions of defined composition and particle size. Application of the methods to analysis of field and laboratory samples is discussed. Am atomic emission lines are observed by laser-induced breakdown spectroscopy of an Am hydroxycarbonate suspension.

  8. Optimal management of cytomegalovirus retinitis in patients with AIDS

    PubMed Central

    Stewart, Michael W

    2010-01-01

    Cytomegalovirus (CMV) retinitis is the most common cause of vision loss in patients with acquired immunodeficiency syndrome (AIDS). CMV retinitis afflicted 25% to 42% of AIDS patients in the pre-highly active antiretroviral therapy (HAART) era, with most vision loss due to macula-involving retinitis or retinal detachment. The introduction of HAART significantly decreased the incidence and severity of CMV retinitis. Optimal treatment of CMV retinitis requires a thorough evaluation of the patient’s immune status and an accurate classification of the retinal lesions. When retinitis is diagnosed, HAART therapy should be started or improved, and anti-CMV therapy with oral valganciclovir, intravenous ganciclovir, foscarnet, or cidofovir should be administered. Selected patients, especially those with zone 1 retinitis, may receive intravitreal drug injections or surgical implantation of a sustained-release ganciclovir reservoir. Effective anti-CMV therapy coupled with HAART significantly decreases the incidence of vision loss and improves patient survival. Immune recovery uveitis and retinal detachments are important causes of moderate to severe loss of vision. Compared with the early years of the AIDS epidemic, the treatment emphasis in the post- HAART era has changed from short-term control of retinitis to long-term preservation of vision. Developing countries face shortages of health care professionals and inadequate supplies of anti-CMV and anti-HIV medications. Intravitreal ganciclovir injections may be the most cost effective strategy to treat CMV retinitis in these areas. PMID:20463796

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

    PubMed Central

    Wilkinson, Charles P

    2016-01-01

    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 problems is frequently recommended, in spite of the fact that the effectiveness of this therapy is unproven. Objectives The purpose of this review was to evaluate the effectiveness of interventions for asymptomatic retinal breaks and lattice degeneration. Search methods We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 1), MEDLINE (January 1950 to January 2012), EMBASE (January 1980 to January 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 28 January 2012. Textbooks regarding retinal detachment and the reference lists of relevant reports were reviewed for additional

  10. 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.

  11. Spectrally optimal illuminations for diabetic retinopathy detection in retinal imaging

    NASA Astrophysics Data System (ADS)

    Bartczak, Piotr; Fält, Pauli; Penttinen, Niko; Ylitepsa, Pasi; Laaksonen, Lauri; Lensu, Lasse; Hauta-Kasari, Markku; Uusitalo, Hannu

    2017-01-01

    Retinal photography is a standard method for recording retinal diseases for subsequent analysis and diagnosis. However, the currently used white light or red-free retinal imaging does not necessarily provide the best possible visibility of different types of retinal lesions, important when developing diagnostic tools for handheld devices, such as smartphones. Using specifically designed illumination, the visibility and contrast of retinal lesions could be improved. In this study, spectrally optimal illuminations for diabetic retinopathy lesion visualization are implemented using a spectrally tunable light source based on digital micromirror device. The applicability of this method was tested in vivo by taking retinal monochrome images from the eyes of five diabetic volunteers and two non-diabetic control subjects. For comparison to existing methods, we evaluated the contrast of retinal images taken with our method and red-free illumination. The preliminary results show that the use of optimal illuminations improved the contrast of diabetic lesions in retinal images by 30-70%, compared to the traditional red-free illumination imaging.

  12. Spectrally optimal illuminations for diabetic retinopathy detection in retinal imaging

    NASA Astrophysics Data System (ADS)

    Bartczak, Piotr; Fält, Pauli; Penttinen, Niko; Ylitepsa, Pasi; Laaksonen, Lauri; Lensu, Lasse; Hauta-Kasari, Markku; Uusitalo, Hannu

    2017-04-01

    Retinal photography is a standard method for recording retinal diseases for subsequent analysis and diagnosis. However, the currently used white light or red-free retinal imaging does not necessarily provide the best possible visibility of different types of retinal lesions, important when developing diagnostic tools for handheld devices, such as smartphones. Using specifically designed illumination, the visibility and contrast of retinal lesions could be improved. In this study, spectrally optimal illuminations for diabetic retinopathy lesion visualization are implemented using a spectrally tunable light source based on digital micromirror device. The applicability of this method was tested in vivo by taking retinal monochrome images from the eyes of five diabetic volunteers and two non-diabetic control subjects. For comparison to existing methods, we evaluated the contrast of retinal images taken with our method and red-free illumination. The preliminary results show that the use of optimal illuminations improved the contrast of diabetic lesions in retinal images by 30-70%, compared to the traditional red-free illumination imaging.

  13. Laser-induced thermal desorption of aniline from silica surfaces

    NASA Astrophysics Data System (ADS)

    Voumard, Pierre; Zenobi, Renato

    1995-10-01

    A complete study on the energy partitioning upon laser-induced thermal desorption of aniline from silica surfaces was undertaken. The measurements include characterization of the aniline-quartz adsorption system using temperature-programmed desorption, the extrapolation of quasiequilibrium desorption temperatures to the regime of laser heating rates on the order of 109-1010 K/s by computational means, measurement of the kinetic energy distributions of desorbing aniline using a pump-probe method, and the determination of internal energies with resonance-enhanced multiphoton ionization spectroscopy. The measurements are compared to calculations of the surface temperature rise and the resulting desorption rates, based on a finite-difference mathematical description of pulsed laser heating. While the surface temperature of laser-heated silica reaches about 600-700 K at the time of desorption, the translational temperature of laser-desorbed aniline was measured to be Tkin=420±60 K, Tvib was 360±60 K, and Trot was 350±100 K. These results are discussed using different models for laser-induced thermal desorption from surfaces.

  14. 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.

  15. Laser-induced nucleation of carbon dioxide bubbles

    NASA Astrophysics Data System (ADS)

    Ward, Martin R.; Jamieson, William J.; Leckey, Claire A.; Alexander, Andrew J.

    2015-04-01

    A detailed experimental study of laser-induced nucleation (LIN) of carbon dioxide (CO2) gas bubbles is presented. Water and aqueous sucrose solutions supersaturated with CO2 were exposed to single nanosecond pulses (5 ns, 532 nm, 2.4-14.5 MW cm-2) and femtosecond pulses (110 fs, 800 nm, 0.028-11 GW cm-2) of laser light. No bubbles were observed with the femtosecond pulses, even at high peak power densities (11 GW cm-2). For the nanosecond pulses, the number of bubbles produced per pulse showed a quadratic dependence on laser power, with a distinct power threshold below which no bubbles were observed. The number of bubbles observed increases linearly with sucrose concentration. It was found that filtering of solutions reduces the number of bubbles significantly. Although the femtosecond pulses have higher peak power densities than the nanosecond pulses, they have lower energy densities per pulse. A simple model for LIN of CO2 is presented, based on heating of nanoparticles to produce vapor bubbles that must expand to reach a critical bubble radius to continue growth. The results suggest that non-photochemical laser-induced nucleation of crystals could also be caused by heating of nanoparticles.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    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 5d4D7/2 to the 5p ^4P^circ _{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 5d4D7/2-5p ^4P^circ _{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.

  18. 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.

  19. 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.

  20. 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.

  1. Laser-induced filaments in the mid-infrared

    NASA Astrophysics Data System (ADS)

    Zheltikov, A. M.

    2017-05-01

    Laser-induced filamentation in the mid-infrared gives rise to unique regimes of nonlinear wave dynamics and reveals in many ways unusual nonlinear-optical properties of materials in this frequency range. The λ 2 scaling of the self-focusing threshold P cr, with radiation wavelength λ, allows the laser powers transmitted by single mid-IR filaments to be drastically increased without the loss of beam continuity and spatial coherence. When extended to the mid-infrared, laser filamentation enables new methods of pulse compression. Often working around the universal physical limitations, it helps generate few-cycle and subcycle field waveforms within an extraordinarily broad range of peak powers, from just a few up to hundreds of P cr. As a part of a bigger picture, laser-induced filamentation in the mid-infrared offers important physical insights into the general properties of the nonlinear-optical response of matter as a function of the wavelength. Unlike their near-infrared counterparts, which can be accurately described within the framework of perturbative nonlinear optics, mid-infrared filaments often entangle perturbative and nonperturbative nonlinear-optical effects, showing clear signatures of strong-field optical physics. With the role of nonperturbative nonlinear-optical phenomena growing, as a general tendency, with the field intensity and the driver wavelength, extension of laser filamentation to even longer driver wavelengths, toward the long-wavelength infrared, promises a hic sunt dracones land.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. Bim is Responsible for the Inherent Sensitivity of the Developing Retinal Vasculature to Hyperoxia

    PubMed Central

    Wang, Shoujian; Park, SunYoung; Fei, Ping; Sorenson, Christine M.

    2010-01-01

    Apoptosis plays an important role in development and remodeling of vasculature during organogenesis. Coordinated branching and remodeling of the retinal vascular tree is essential for normal retinal function. Bcl-2 family members, such as bim can not only influence apoptosis, but also cell adhesive and migratory properties essential during vascular development. Here we examined the impact of bim deficiency on postnatal retinal vascularization, as well as retinal neovascularization during oxygen-induced ischemic retinopathy (OIR) and laser-induced choroidal neovascularization. Loss of bim expression was associated with increased retinal vascular density in mature animals. This was mainly attributed to increased numbers of pericytes and endothelial cells. However, the initial spread of the superficial layer of retinal vasculature and, the appearance and density of the tip cells were similar in bim +/+ and bim -/- mice. In addition, hyaloid vessel regression was attenuated in the absence of bim. Furthermore, in the absence of bim retinal vessel obliteration and neovascularization did not occur during OIR. Instead, normal inner retinal vascularization proceeded independent of changes in oxygen levels. In contrast, choroidal neovascularization occurred equally well in bim +/+ and bim -/- mice. Together our data suggest bim expression may be responsible for the inherent sensitivity of the developing retinal vasculature to changes in oxygen levels, and promotes vessel obliteration in response to hyperoxia. PMID:21047504

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

    PubMed

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

    2017-02-21

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

  8. Evaluation of laser-induced thin-layer removal by using shadowgraphy and laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Rabasović, M. S.; Šević, D.; Lukač, N.; Jezeršek, M.; Možina, J.; Gregorčič, P.

    2016-03-01

    Shadow photography and laser-induced breakdown spectroscopy (LIBS) are studied as methods for monitoring the selective removal of thin (i.e., under 100 μm) layers by laser ablation. We used a laser pulse of 5 ns and 16 mJ at 1064 nm to ablate an 18-μm-thin copper layer from the fiberglass substrate. On the basis of shadowgraphs of the laser-induced shock waves, we measured the optodynamic energy-conversion efficiency, defined as the ratio between the mechanical energy of the shock wave and the excitation-pulse energy. Our results show that this efficiency is significantly higher for the laser pulse-copper interaction than for the interaction between the excitation pulse and the substrate. LIBS was simultaneously employed in our experimental setup. The optical emission from the plasma plume was collected by using a spectrograph and recorded with a streak camera. We show that advancing of laser ablation through the copper layer and reaching of the substrate can be estimated by tracking the spectral region between 370 and 500 nm. Therefore, the presented results confirm that LIBS method enables an on-line monitoring needed for selective removal of thin layers by laser.

  9. 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. Copyright © 2016 Elsevier B.V. All rights reserved.

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

    SciTech Connect

    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{sup 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.

  11. Distinguishing torpedo maculopathy from similar lesions of the posterior segment.

    PubMed

    Villegas, Victor M; Schwartz, Stephen G; Flynn, Harry W; Capó, Hilda; Berrocal, Audina M; Murray, Timothy G; Harbour, J William

    2014-01-01

    Torpedo maculopathy is a congenital solitary, oval-shaped lesion typically located temporal to the center of the macula. Congenital hypertrophy of the retinal pigment epithelium (RPE), RPE lesions of Gardner syndrome, and other lesions can present with similar characteristics. Because of its unique clinical and imaging features, torpedo maculopathy generally can be differentiated from other posterior segment lesions.

  12. Two Photon Absorption Laser Induced Fluorescence for Fusion Class Plasmas

    NASA Astrophysics Data System (ADS)

    Elliott, Drew B.

    Neutral hydrogen particles play an important role in many fusion systems. The edge region of fusion plasmas is strongly influenced by these neutral particles and is of growing importance because of the challenges of plasma material interaction. A two photon absorption laser induced fluorescence diagnostic at West Virginia University has been constructed to measure the local density and velocity distribution of these neutral particles. The diagnostic measures the ground state of hydrogen isotopes by way of two photon absorption from the 1s to 3d state and subsequent single photon emission to the 2 p state. These measurements are absolutely calibrated by comparing the integrated emission spectra to that of a measurement performed on a known density of calibration gas and knowing the relative absorption cross sections for the two species. Measurements were performed on deuterium atoms in the Helicity Injected Torus with Steady Induction 3 and calibrated using the standard krypton calibration scheme. Measured neutral densities were well below predicted values and the measurement process identified a flaw in the krypton calibration scheme. A new calibration scheme using xenon gas was developed to eliminate any possibility of chromatic aberration through refractive optics. This new xenon calibration scheme required measurement of the relative absorption cross section between the 5p6 to 4p 57f to 5p55 d Xe scheme and the 4p6 to 4 p55p to 4p 55s Kr scheme, then comparison of the Xe to Kr relative cross section to the Kr to H relative cross section to determine the overall Xe to H relative absorption cross section. Doppler free two photon absorption laser induced fluorescence measurements were also performed on the compact helicon for waves and instabilities experiment (CHEWIE), for hydrogen, deuterium, and krypton neutrals. The Doppler free technique increased signal intensity and narrowed the measured spectral width of the absorption line. The Doppler free technique

  13. 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…

  14. Laser induced irreversible absorption changes in alkali halides at 10.6 µm

    NASA Astrophysics Data System (ADS)

    Wu, S.-T.; Bass, M.

    1981-12-01

    Laser induced irreversible changes in the absorption of alkali halides has been observed by using repetitively pulsed laser calorimetry. These changes occur at intensities below that required for laser induced breakdown and necessitate a change in the definition of laser damage threshold. A simple model is proposed to explain these observations based on the accumulation of microscopic failures as a result of each pulse.

  15. 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…

  16. Foveomacular retinitis and associated optical coherence tomography findings.

    PubMed

    Topouzis, Fotis; Koskosas, Archimidis; Pappas, Theofanis; Anastasopoulos, Eleftherios; Raptou, Anastasia; Psilas, Konstantinos

    2007-01-01

    A 45-year-old man presented with clinical manifestations of foveomacular retinitis, including visual symptoms and foveal lesions characteristic of solar retinopathy, but repeated questions failed to elicit a history of sun gazing. Cross-sectional retinal images produced by optical coherence tomography revealed localized loss of retinal pigment epithelium cells in both eyes. A different pattern of reflectivity at the level of the photoreceptor layer was observed between the right and left eye, reflecting asymmetry in tissue damage. This case is described to provide additional evidence that solar retinopathy and foveomacular retinitis are the same entity and may also have common optical coherence tomography findings.

  17. 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.

  18. Influence of absorption induced thermal initiation pathway on irradiance threshold for laser induced breakdown

    PubMed Central

    Varghese, Babu; Bonito, Valentina; Jurna, Martin; Palero, Jonathan; Verhagen, Margaret Hortonand Rieko

    2015-01-01

    We investigated the influence of thermal initiation pathway on the irradiance threshold for laser induced breakdown in transparent, absorbing and scattering phantoms. We observed a transition from laser-induced optical breakdown to laser-induced thermal breakdown as the absorption coefficient of the medium is increased. We found that the irradiance threshold after correction for the path length dependent absorption and scattering losses in the medium is lower due to the thermal pathway for the generation of seed electrons compared to the laser-induced optical breakdown. Furthermore, irradiance threshold gradually decreases with the increase in the absorption properties of the medium. Creating breakdown with lower irradiance threshold that is specific at the target chromophore can provide intrinsic target selectivity and improve safety and efficacy of skin treatment methods that use laser induced breakdown. PMID:25909007

  19. 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.

  20. Laser-induced silver nanojoining of gold nanoparticles.

    PubMed

    Son, Myounghee; Kim, Seol Ji; Kim, Jong-Yeob; Jang, Du-Jeon

    2013-08-01

    Gold nanoparticles have been silver-joined to fabricate nanowires by irradiating gold nanospheres of 25 nm in diameter and silver nanospheres of 8 nm in diameter held together on a carbon-coated copper grid with a 30 ps laser pulse of 532 nm for 20 min at a fluence of 3.0 mJ/cm2. Laser-induced nanojoining of silver nanoparticles as well as that of gold nanoparticles has also been carried out by varying the wavelength and fluence of irradiation laser pulses. Irradiation at an optimum condition of laser fluence is essential for the proper silver nanojoining of gold nanospheres to produce gold@silver core-shell composite nanowires. The excitation of the surface plasmon resonances of the base-metallic gold nanospheres rather than the filler-metallic silver nanospheres paves the way for the silver nanojoining of gold nanoparticles.

  1. Microfabrication of polystyrene microbead arrays by laser induced forward transfer

    NASA Astrophysics Data System (ADS)

    Palla-Papavlu, Alexandra; Dinca, Valentina; Paraico, Iurie; Moldovan, Antoniu; Shaw-Stewart, James; Schneider, Christof W.; Kovacs, Eugenia; Lippert, Thomas; Dinescu, Maria

    2010-08-01

    In this study we describe a simple method to fabricate microarrays of polystyrene microbeads (PS-μbeads) on Thermanox coverslip surfaces using laser induced forward transfer (LIFT). A triazene polymer layer which acts as a dynamic release layer and propels the closely packed microspheres on the receiving substrate was used for this approach. The deposited features were characterized by optical microscopy, scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. Ultrasonication was used to test the adherence of the transferred beads. In addition, the laser ejection of the PS-μbead pixels was investigated by time resolved shadowgraphy. It was found that stable PS-μbeads micropatterns without any specific immobilization process could be realized by LIFT. These results highlight the increasing role of LIFT in the development of biomaterials, drug delivery, and tissue engineering.

  2. 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.

  3. Laser-induced phase separation of silicon carbide.

    PubMed

    Choi, Insung; Jeong, Hu Young; Shin, Hyeyoung; Kang, Gyeongwon; Byun, Myunghwan; Kim, Hyungjun; Chitu, Adrian M; Im, James S; Ruoff, Rodney S; Choi, Sung-Yool; Lee, Keon Jae

    2016-11-30

    Understanding the phase separation mechanism of solid-state binary compounds induced by laser-material interaction is a challenge because of the complexity of the compound materials and short processing times. Here we present xenon chloride excimer laser-induced melt-mediated phase separation and surface reconstruction of single-crystal silicon carbide and study this process by high-resolution transmission electron microscopy and a time-resolved reflectance method. A single-pulse laser irradiation triggers melting of the silicon carbide surface, resulting in a phase separation into a disordered carbon layer with partially graphitic domains (∼2.5 nm) and polycrystalline silicon (∼5 nm). Additional pulse irradiations cause sublimation of only the separated silicon element and subsequent transformation of the disordered carbon layer into multilayer graphene. The results demonstrate viability of synthesizing ultra-thin nanomaterials by the decomposition of a binary system.

  4. 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

  5. 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    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.

  8. 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.

  9. Analytical study of seashell using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Ying, LI; Yanhong, GU; Ying, Zhang; Yuandong, LI; Yuan, LU

    2017-02-01

    Seashell has been applied as an indicator for ocean research and element analysis of the seashell is used to track biological or environmental evolution. In this work, laser-induced breakdown spectroscopy (LIBS) was applied for elementary analysis of an ezo scallop-shell, and a graphite enrichment method was used as the assistance. It was found that LIBS signal intensity of Ca fluctuated less than 5%, in spite of the sampling positions, and Sr/Ca was related to the shell growth. A similar variation was also found when using a direct LIBS analysis on the shell surface, and it might be more practicable to track shell growth by investigating Sr/Ca ratio with Sr ionic line at 421.6 nm. The obtained results prove that calcium (Ca) is qualified as an internal reference for shell analysis, and LIBS is a potential analytical method for seashell study.

  10. 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.

  11. Optofluidic lens actuated by laser-induced solutocapillary forces

    NASA Astrophysics Data System (ADS)

    Malyuk, A. Yu.; Ivanova, N. A.

    2017-06-01

    We demonstrate an adaptive liquid lens controlled by laser-induced solutocapillary forces. The liquid droplet serving as a lens is formed in a thin layer of binary liquid mixture by surface tension driven flows caused by the thermal action of laser irradiation. The shape of droplet, its aperture and the focal length are reversibly changed without hysteresis by varying the intensity of the laser beam. The focal length variation range of the droplet-lens lies in between infinity (a flat layer) to 15 mm (a curved interface). The droplet-lens is capable to adjust the in-plane lateral position in response to a displacement of the laser beam. The proposed laser controlled droplet-lens will enable to develop smart liquid optical devices, which can imitate the accommodation reflex and pupillary light reflex of the eye.

  12. Femtosecond laser-induced modification at aluminum/diamond interface

    NASA Astrophysics Data System (ADS)

    Okada, Tatsuya; Tomita, Takuro; Ueki, Tomoyuki; Masai, Yuki; Bando, Yota; Tanaka, Yasuhiro

    2017-02-01

    We investigated femtosecond-laser-induced modification at an Al/diamond interface. The interface was irradiated from the backside through the diamond substrate, which is transparent to the laser beam. Extremely high pulse energies, i.e., 200 and 100 µJ/pulse, were used to irradiate the interface. The cross-section of the laser-irradiated line was observed with conventional and high-voltage transmission electron microscopy. The modification of the laser-irradiated interface was characterized by the formation of an amorphous phase sandwiched between the deformed Al film and the diamond substrate. The major chemical component of the amorphous phase was identified as carbon, blown from the diamond substrate. The newly formed interface between the amorphous phase and the diamond substrate was concave. In addition, a fine ripple structure with an average spacing one-quarter the wavelength of the laser light was formed only in the sample irradiated by the higher-energy pulses.

  13. 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.

  14. Particulate measurement issues in diesel exhausts using laser induced incandescence

    SciTech Connect

    Gupta, S. B.; Poola, R. B.; Sekar, R.

    2000-07-03

    A number of studies in the recent past have identified Laser Induced Incandescence (LII) as a versatile technique for in-flame measurement of soot concentrations. Recently, a number of researchers have focused their attention in adapting this technique to measure particulate in diesel exhausts. However the agreement with established physical sampling techniques, such as the EPA recommended filter paper collection method, was found to be less than ideal. This paper reports the efforts to adapt this technique for diesel exhaust characterization. Many of the factors affecting LII signal were identified through computer modeling. Parameters that could not be determined through such a model were determined experimentally following a parametric study. Subsequently, LII measurements were performed in the exhaust of a modified lab burner, with conditions close to that of diesel engine exhausts. Such measurements show excellent agreement with those performed using the standard filter paper collection technique.

  15. Laser-induced phase separation of silicon carbide

    NASA Astrophysics Data System (ADS)

    Choi, Insung; Jeong, Hu Young; Shin, Hyeyoung; Kang, Gyeongwon; Byun, Myunghwan; Kim, Hyungjun; Chitu, Adrian M.; Im, James S.; Ruoff, Rodney S.; Choi, Sung-Yool; Lee, Keon Jae

    2016-11-01

    Understanding the phase separation mechanism of solid-state binary compounds induced by laser-material interaction is a challenge because of the complexity of the compound materials and short processing times. Here we present xenon chloride excimer laser-induced melt-mediated phase separation and surface reconstruction of single-crystal silicon carbide and study this process by high-resolution transmission electron microscopy and a time-resolved reflectance method. A single-pulse laser irradiation triggers melting of the silicon carbide surface, resulting in a phase separation into a disordered carbon layer with partially graphitic domains (~2.5 nm) and polycrystalline silicon (~5 nm). Additional pulse irradiations cause sublimation of only the separated silicon element and subsequent transformation of the disordered carbon layer into multilayer graphene. The results demonstrate viability of synthesizing ultra-thin nanomaterials by the decomposition of a binary system.

  16. 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.

  17. 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.

  18. 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.

  19. Prediction of absorption coefficients by pulsed laser induced photoacoustic measurements.

    PubMed

    Priya, Mallika; Satish Rao, B S; Ray, Satadru; Mahato, K K

    2014-06-05

    In the current study, a pulsed laser induced photoacoustic spectroscopy setup was designed and developed, aiming its application in clinical diagnostics. The setup was optimized with carbon black samples in water and with various tryptophan concentrations at 281nm excitations. The sensitivity of the setup was estimated by determining minimum detectable concentration of tryptophan in water at the same excitation, and was found to be 0.035mM. The photoacoustic experiments were also performed with various tryptophan concentrations at 281nm excitation for predicting optical absorption coefficients in them and for comparing the outcomes with the spectrophotometrically-determined absorption coefficients for the same samples. Absorption coefficients for a few serum samples, obtained from some healthy female volunteers, were also determined through photoacoustic and spectrophotometric measurements at the same excitations, which showed good agreement between them, indicating its clinical implications.

  20. 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.

  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. Printing biological solutions through laser-induced forward transfer

    NASA Astrophysics Data System (ADS)

    Duocastella, M.; Fernández-Pradas, J. M.; Domínguez, J.; Serra, P.; Morenza, J. L.

    2008-12-01

    Laser-induced forward transfer (LIFT) is a direct-writing technique adequate for the high-resolution printing of a wide range of materials, including biological molecules. In this article, the preparation through LIFT of microarrays of droplets from a solution containing rabbit antibody immunoglobulin G (IgG) is presented. The microarrays were prepared at different laser pulse energy conditions, obtaining microdroplets with a circular and well-defined contour. The transfer process has a double threshold: a minimum energy density required to generate an impulsion on the liquid film, and a minimum pulse energy, which corresponds to the onset for material ejection. In addition, it was demonstrated that the transfer process can be correctly described through a simple model which relates the energy density threshold with the amount of released material. Finally, a fluorescence assay was carried out in which the preservation of the activity of the transferred biomolecules was demonstrated.

  3. 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.

  4. 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

    2016-09-05

    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.

  5. Laser-induced periodic surface structures: Fingerprints of light localization

    NASA Astrophysics Data System (ADS)

    Skolski, J. Z. P.; Römer, G. R. B. E.; Obona, J. V.; Ocelik, V.; Huis in't Veld, A. J.; de Hosson, J. Th. M.

    2012-02-01

    The finite-difference time-domain (FDTD) method is used to study the inhomogeneous absorption of linearly polarized laser radiation below a rough surface. The results are first analyzed in the frequency domain and compared to the efficacy factor theory of Sipe and coworkers. Both approaches show that the absorbed energy shows a periodic nature, not only in the direction orthogonal to the laser polarization, but also in the direction parallel to it. It is shown that the periodicity is not always close to the laser wavelength for the perpendicular direction. In the parallel direction, the periodicity is about λ/Re(ñ), with ñ being the complex refractive index of the medium. The space-domain FDTD results show a periodicity in the inhomogeneous energy absorption similar to the periodicity of the low- and high-spatial-frequency laser-induced periodic surface structures depending on the material's excitation.

  6. 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.

  7. Laser-induced phase separation of silicon carbide

    PubMed Central

    Choi, Insung; Jeong, Hu Young; Shin, Hyeyoung; Kang, Gyeongwon; Byun, Myunghwan; Kim, Hyungjun; Chitu, Adrian M.; Im, James S.; Ruoff, Rodney S.; Choi, Sung-Yool; Lee, Keon Jae

    2016-01-01

    Understanding the phase separation mechanism of solid-state binary compounds induced by laser–material interaction is a challenge because of the complexity of the compound materials and short processing times. Here we present xenon chloride excimer laser-induced melt-mediated phase separation and surface reconstruction of single-crystal silicon carbide and study this process by high-resolution transmission electron microscopy and a time-resolved reflectance method. A single-pulse laser irradiation triggers melting of the silicon carbide surface, resulting in a phase separation into a disordered carbon layer with partially graphitic domains (∼2.5 nm) and polycrystalline silicon (∼5 nm). Additional pulse irradiations cause sublimation of only the separated silicon element and subsequent transformation of the disordered carbon layer into multilayer graphene. The results demonstrate viability of synthesizing ultra-thin nanomaterials by the decomposition of a binary system. PMID:27901015

  8. 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.

  9. Investigation of the laser-induced damage of dispersive coatings

    NASA Astrophysics Data System (ADS)

    Angelov, Ivan B.; von Conta, Aaron; Trushin, Sergei A.; Major, Zsuzsanna; Karsch, Stefan; Krausz, Ferenc; Pervak, Vladimir

    2011-12-01

    Different dispersive coatings were tested in terms of laser-induced damage threshold by using a Ti:Sapphire laser yielding 1 mJ, 30 fs pulses at 500 Hz repetition rate at 790 nm central wavelength. The beam was focused down to 140 μm. Single layer coatings of Au, Ag, Nb2O5, SiO2, Ta2O5 and mixtures of Ta2O5 and silica were examined as well as different dispersive coatings. We observed a direct dependence of the damage threshold on the band gap of the materials used to produce the different samples. The damage threshold values for the dispersive coatings employing the same high index material lay within a range of 30% of each other.

  10. Ultrafast laser induced breakdown spectroscopy of electrode/electrolyte interfaces

    NASA Astrophysics Data System (ADS)

    Zorba, Vassilia; Syzdek, Jaroslaw; Mao, Xianglei; Russo, Richard E.; Kostecki, Robert

    2012-06-01

    Direct chemical analysis of electrode/electrolyte interfaces can provide critical information on surface phenomena that define and control the performance of Li-based battery systems. In this work, we introduce the use of ex situ femtosecond laser induced breakdown spectroscopy to probe compositional variations within the solid electrolyte interphase (SEI) layer. Nanometer-scale depth resolution was achieved for elemental and molecular depth profiling of SEI layers formed on highly oriented pyrolytic graphite electrodes in an organic carbonate-based electrolyte. This work demonstrates the unique ability of ultrafast laser spectroscopy as a highly versatile, light element-sensitive technique for direct chemical analysis of interfacial layers in electrochemical energy storage systems.

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

    SciTech Connect

    Sadighi-Bonabi, Rasoul; Gheshlaghi, Maryam

    2016-03-15

    The Possibility of the laser assisted sonofusion is studied via single bubble sonoluminescence (SBSL) in Deuterated acetone (C{sub 3}D{sub 6}O) 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 × 10{sup 6} K in hydro-chemical model and it is reached up to 1.9 × 10{sup 6} K in the laser induced SBSL bubbles. Under these circumstances, temperature up to 10{sup 7} K can be produced in the center of the bubble in which the thermonuclear D-D fusion reactions are promising under the controlled conditions.

  12. The motional Stark effect with laser-induced fluorescence diagnostic

    NASA Astrophysics Data System (ADS)

    Foley, Elizabeth; Levinton, Fred

    2007-11-01

    Traditional motional Stark effect (MSE) diagnostics exploit the polarization properties of light generated from a neutral hydrogenic beam via collisionally-induced fluorescence (CIF). MSE uses this information to determine a spatially resolved profile of the magnetic field pitch angle in a magnetized plasma. The use of laser-induced fluorescence with MSE on a dedicated diagnostic neutral beam enables an MSE pitch angle measurement at fields as low as 0.001 T, which cannot be achieved by CIF systems. The LIF system also affords the option of very precisely measuring the magnetic field magnitude as well as direction. The MSE-LIF diagnostic is under development in our laboratory, where we have a diagnostic neutral beam system, a dye laser, and a helicon plasma source. This poster will present the latest results relating to MSE-LIF measurements in plasma, as well as an analysis of the relative utility of magnetic field magnitude vs pitch angle measurements for equilibrium reconstruction.

  13. 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.

  14. Containerless study of metal evaporation by laser induced fluorescence

    NASA Technical Reports Server (NTRS)

    Schiffman, Robert A.; Nordine, Paul C.

    1987-01-01

    Laser induced fluorescence (LIF) detection of atomic vapors was used to study evaporation from electromagnetically levitated and CW CO2 laser-heated molybdenum spheres and resistively-heated tungsten filaments. Electromagnetic (EM) levitation in combination with laser heating of tungsten, zirconium, and aluminum specimens was also investigated. LIF intensity vs temperature data were obtained for molybdenum atoms and six electronic states of atomic tungsten, at temperatures up to the melting point of each metal. The detected fraction of the emitted radiation was reduced by self-absorption effects at the higher experimental temperatures. Vaporization enthalpies derived from data for which less than half the LIF intensity was self-absorbed were -636 + or - 24 kJ/g-mol for Mo and 831 + or - 32 kJ/g-mol for W. Space-based applications of EM levitation in combination with radiative heating are discussed.

  15. Digital barcodes of suspension array using laser induced breakdown spectroscopy

    PubMed Central

    He, Qinghua; Liu, Yixi; He, Yonghong; Zhu, Liang; Zhang, Yilong; Shen, Zhiyuan

    2016-01-01

    We show a coding method of suspension array based on the laser induced breakdown spectroscopy (LIBS), which promotes the barcodes from analog to digital. As the foundation of digital optical barcodes, nanocrystals encoded microspheres are prepared with self-assembly encapsulation method. We confirm that digital multiplexing of LIBS-based coding method becomes feasible since the microsphere can be coded with direct read-out data of wavelengths, and the method can avoid fluorescence signal crosstalk between barcodes and analyte tags, which lead to overall advantages in accuracy and stability to current fluorescent multicolor coding method. This demonstration increases the capability of multiplexed detection and accurate filtrating, expanding more extensive applications of suspension array in life science. PMID:27808270

  16. Laser-induced single point nanowelding of silver nanowires

    SciTech Connect

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

    2016-03-21

    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.

  17. Collisional Effects On Laser-Induced Fluorescence Flame Measurements

    NASA Astrophysics Data System (ADS)

    Crosley, David R.

    1981-08-01

    Abstract. Laser-induced fluorescence (LIF) is a method of considerable utility for the measurement of the transient free radicals which are the keys to the chemistry of flames. Collisions experienced by the electronically excited state can alter the magnitude and the spectral form of the fluorescence signals. Recent studies on both quenching and energy transfer collisions, and their influence on LIF measurements, are treated in this review; special emphasis is given to the important and popular OH molecule. Different solutions to the problem of accounting for quenching are considered, and both effects and exploitation of energy transfer within the excited state are discussed. Although further research is needed to better quantify these collisional effects, LIF can currently provide data significant for the understanding of combustion chemistry.

  18. 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.

  19. Laser-induced acoustic desorption of natural and functionalized biochromophores.

    PubMed

    Sezer, Uğur; Wörner, Lisa; Horak, Johannes; Felix, Lukas; Tüxen, Jens; Götz, Christoph; Vaziri, Alipasha; Mayor, Marcel; Arndt, Markus

    2015-06-02

    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.

  20. 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.

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

    PubMed

    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.

  2. 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.

  3. 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.

  4. 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.

  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. 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.

  7. 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.

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

    SciTech Connect

    Carr, Christopher Wren

    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 KbT, are observed in the damage threshold at photon energies associated with the number of photons (3→2 or 4→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.

  9. 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.

  10. 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.

  11. Noninvasive thermography of laser-induced hyperthermia using magnetic resonance

    NASA Astrophysics Data System (ADS)

    Maswadi, Saher M.; Glickman, Randolph D.; Dodd, Stephen J.; Gao, Jia Hong

    2004-07-01

    The possibility to induce selective hyperthermia in a target tissue or organ is of great interest for the treatment of cancer and other diseases. An emerging application of thermotherapy is for choroidal neovascularization, a complication of age-related macular degeneration. The therapy is currently limited because the temperature required for optimal tissue response is unknown. We report here an investigation of near infrared laser-induced heating in an ocular phantom. Magnetic resonance thermography (MRT) was used as a non-invasive method to determine the temperature distribution inside the phantom during exposure to a continuous wave diode laser at 806 nm wavelength with 1 watt maximum output. The laser beam had a quasi-gaussian profile, with a radius of 0.8-2.4 mm at target. High quality temperature images were obtained from temperature-dependent phase shifts in the proton resonance frequency with a resolution of 1deg C or better, using a 2T magnet. A phantom with a layer of bovine RPE melanin of 1.5 mm thickness was used to determine the spatial resolution of the MRT measurements. Three dimensional temperature maps were also constructed showing a spatial resolution of 0.25 mm in all direction. The heat distribution depended on the laser parameters, as well as the orientation of the melanin layer with respect to the incident laser beam. The temperature profiles determined by MRT closely followed predictions of a heat diffusion model, based on the optical properties of infrared light in melanin. These results support the use of MRT to optimize laser-induced hyperthermia in a small organ such as the eye.

  12. Titanium monoxide spectroscopy following laser-induced optical breakdown

    SciTech Connect

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

    2012-07-30

    This work investigates Titanium Monoxide (TiO) in ablation-plasma by employing laser-induced breakdown spectroscopy (LIBS) with 1 to 10 TW/cm{sup 2} 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 {gamma} and B-X {gamma} Prime bands. Electric dipole line strengths for the A{sup 3}{Phi}-X{sup 3}{delta} and B{sup 3}{Pi}-X{sup 3}{delta} 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, C{sub 2}, CN, CH, N{sub 2}, NH, NO and OH.

  13. 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.

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

    PubMed

    Feng, Yusheng; Fuentes, David

    2011-01-01

    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.

  15. 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

  16. Missed retinal breaks in rhegmatogenous retinal detachment.

    PubMed

    Takkar, Brijesh; Azad, Shorya; Shashni, Adarsh; Pujari, Amar; Bhatia, Indrish; Azad, Rajvardhan

    2016-01-01

    To evaluate the causes and associations of missed retinal breaks (MRBs) and posterior vitreous detachment (PVD) in patients with rhegmatogenous retinal detachment (RRD). Case sheets of patients undergoing vitreo retinal surgery for RRD at a tertiary eye care centre were evaluated retrospectively. Out of the 378 records screened, 253 were included for analysis of MRBs and 191 patients were included for analysis of PVD, depending on the inclusion criteria. Features of RRD and retinal breaks noted on examination were compared to the status of MRBs and PVD detected during surgery for possible associations. Overall, 27% patients had MRBs. Retinal holes were commonly missed in patients with lattice degeneration while missed retinal tears were associated with presence of complete PVD. Patients operated for cataract surgery were significantly associated with MRBs (P=0.033) with the odds of missing a retinal break being 1.91 as compared to patients with natural lens. Advanced proliferative vitreo retinopathy (PVR) and retinal bullae were the most common reasons for missing a retinal break during examination. PVD was present in 52% of the cases and was wrongly assessed in 16%. Retinal bullae, pseudophakia/aphakia, myopia, and horse shoe retinal tears were strongly associated with presence of PVD. Traumatic RRDs were rarely associated with PVD. Pseudophakic patients, and patients with retinal bullae or advanced PVR should be carefully screened for MRBs. Though Weiss ring is a good indicator of PVD, it may still be over diagnosed in some cases. PVD is associated with retinal bullae and pseudophakia, and inversely with traumatic RRD.

  17. Missed retinal breaks in rhegmatogenous retinal detachment

    PubMed Central

    Takkar, Brijesh; Azad, Shorya; Shashni, Adarsh; Pujari, Amar; Bhatia, Indrish; Azad, Rajvardhan

    2016-01-01

    AIM To evaluate the causes and associations of missed retinal breaks (MRBs) and posterior vitreous detachment (PVD) in patients with rhegmatogenous retinal detachment (RRD). METHODS Case sheets of patients undergoing vitreo retinal surgery for RRD at a tertiary eye care centre were evaluated retrospectively. Out of the 378 records screened, 253 were included for analysis of MRBs and 191 patients were included for analysis of PVD, depending on the inclusion criteria. Features of RRD and retinal breaks noted on examination were compared to the status of MRBs and PVD detected during surgery for possible associations. RESULTS Overall, 27% patients had MRBs. Retinal holes were commonly missed in patients with lattice degeneration while missed retinal tears were associated with presence of complete PVD. Patients operated for cataract surgery were significantly associated with MRBs (P=0.033) with the odds of missing a retinal break being 1.91 as compared to patients with natural lens. Advanced proliferative vitreo retinopathy (PVR) and retinal bullae were the most common reasons for missing a retinal break during examination. PVD was present in 52% of the cases and was wrongly assessed in 16%. Retinal bullae, pseudophakia/aphakia, myopia, and horse shoe retinal tears were strongly associated with presence of PVD. Traumatic RRDs were rarely associated with PVD. CONCLUSION Pseudophakic patients, and patients with retinal bullae or advanced PVR should be carefully screened for MRBs. Though Weiss ring is a good indicator of PVD, it may still be over diagnosed in some cases. PVD is associated with retinal bullae and pseudophakia, and inversely with traumatic RRD. PMID:27990367

  18. Multimodal imaging in a case of bilateral outer retinitis associated with mumps infection.

    PubMed

    Kahloun, Rim; Ben Amor, Hager; Ksiaa, Imen; Zina, Sourour; Jelliti, Bechir; Ben Yahia, Salim; Khairallah, Moncef

    2016-12-27

    To report the results of multimodal imaging of acute outer retinitis associated to mumps infection. A patient with mumps-associated outer retinitis evaluated by color fundus photography, spectral domain optical coherence tomography (SD-OCT), optical coherence tomography angiography, fundus autofluorescence (FAF), fluorescein angiography (FA), and indocyanine green angiography (ICGA). We report a case of a 12-year-old boy who developed bilateral outer retinitis related to mumps. Ophthalmoscopy showed confluent areas of outer retinitis involving the posterior pole and the periphery with a centrifugal gyrate pattern. SD-OCT revealed a marked disorganization of the outer retinal layers with multiple highly reflective spicules. FA shows diffuse late hyperfluorescence with optic disk staining. ICGA shows macular and peripheral hyperfluorescent lesions with a geographical pattern in the late phases. The patient was treated with acyclovir and oral prednisone. Four weeks after presentation visual acuity remained unchanged, and retinal changes seen at the acute phase had resolved leading to extensive retinal atrophy and optic disk pallor. SD-OCT showed atrophy of the retinal pigment epithelial and outer retinal layers. FAF revealed scattered hyperautofluorescent lesions. Electrophysiology showed generalized retinal dysfunction. Mumps infection should be considered in the differential diagnosis of bilateral necrotizing outer retinitis in children and young adults. A multimodal imaging approach may help distinguish mumps-associated retinitis from other causes of viral retinitis and facilitate appropriate management.

  19. Formation of carbon nanotubes: In situ optical analysis using laser-induced incandescence and laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Cau, M.; Dorval, N.; Attal-Trétout, B.; Cochon, J.-L.; Foutel-Richard, A.; Loiseau, A.; Krüger, V.; Tsurikov, M.; Scott, C. D.

    2010-04-01

    Gas-phase production of carbon nanotubes in presence of a metal catalyst with a continuous wave CO2 laser is investigated by combining coherent anti-Stokes Raman scattering (CARS), laser-induced fluorescence (LIF), and laser-induced incandescence (LII). These in situ techniques provide a unique investigation of the different transformation processes of the primarily carbon and metal vapors issued from the vaporization of the target by the laser and the temperature at which these processes occur. Continuous-wave laser provides with stable continuous vaporization conditions very well suited for such in situ investigations. Temperature profiles inside the reactor are known from CARS measurements and flow calculations. Carbon soot, density, and size of carbon aggregates are determined by LII measurements. LIF measurements are used to study the gas phases, namely, C2 and C3 radicals which are the very first steps of carbon recombination, and metal catalysts gas phase. Spectral investigations allow us to discriminate the signal from each species by selecting the correct pair of excitation/detection wavelengths. Spatial distributions of the different species are measured as a function of target composition and temperature. The comparison of LIF and LII signals allow us to correlate the spatial evolution of gas and soot in the scope of the different steps of the nanotube growth already proposed in the literature and to identify the impact of the chemical nature of the catalyst on carbon condensation and nanotube nucleation. Our study presents the first direct evidence of the nanotube onset and that the nucleation proceeds from a dissolution-segregation process from metal particles as assumed in the well-known vapor-liquid-solid model. Comparison of different catalysts reveals that this process is strongly favored when Ni is present.

  20. Retinal complications after bungee jumping.

    PubMed

    Filipe, J A; Pinto, A M; Rosas, V; Castro-Correia, J

    Bungee jumping is becoming a popular sport in the Western world with some cases of ophthalmic complications being reported in recent literature. The authors reported a case of a 23-year-old healthy female who presented retinal complications following a bungee jumping. Her fundi showed superficial retinal hemorrhages in the right eye and a sub-internal limiting membrane hemorrhage affecting the left eye. A general examination, including a full neurological examination, was normal and laboratorial investigations were all within normal values. More studies are necessary to identify risk factors and the true incidence of related ocular lesions, but until then, we think this sport activity should be desencouraged, especially to those that are not psychological and physically fit.

  1. 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

  2. [Posterior vitreous detachment with collapse, and peripheral retinal degeneration in the aetiology of idiopathic retinal detachment. A synapsis of clinical observations and anatomical studies (author's transl)].

    PubMed

    Hruby, K

    1981-10-01

    The crucial aetiological factors of idiopathic retinal detachment are posterior vitreous detachment with collapse, and degenerative lesions in the fundus periphery. Posterior vitreous detachment does not imply diagnostic problems to the expert in this field. On the other hand, the peripheral retinal degenerations include wide range of lesions the clinical and pathoanatomical study of which has so far not resulted in a complete picture. The author of the present paper attempts to get closer to a clearly arranged classification and terminology of those peripheral retinal degenerations, which are of importance to the aetiology, prophylaxis and treatment of idiopathic retinal detachment.

  3. 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

  4. Automated retinal robotic laser system instrumentation

    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.

    1995-05-01

    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 ultimate 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. Researchers at the USAF Academy's Department of Electrical Engineering have also become involved with this research due to similar 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. 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 designed this combined system CALOSOS for Computer Aided Laser Optics System for Ophthalmic Surgery. An initial CALOSOS prototype design is provided. We have also investigated methods to improve system response time. The use of high speed non-standard frame rate CCD cameras and high speed local bus frame grabbers hosted on personal computers are being investigated. A review of system testing in vivo to date is provided in SPIE Conference proceedings 2374-49 (Novel Applications of Lasers and Pulsed Power, Dual-Use Applications of Lasers: Medical session).

  5. A freely available semi-automated method for quantifying retinal ganglion cells in entire retinal flatmounts.

    PubMed

    Geeraerts, E; Dekeyster, E; Gaublomme, D; Salinas-Navarro, M; De Groef, L; Moons, L

    2016-06-01

    Glaucomatous optic neuropathies are characterized by progressive loss of retinal ganglion cells (RGCs), the neurons that connect the eye to the brain. Quantification of these RGCs is a cornerstone in experimental optic neuropathy research and commonly performed via manually quantifying parts of the retina. However, this is a time-consuming process subject to inter- and intra-observer variability. Here we present a freely available ImageJ script to semi-automatically quantify RGCs in entire retinal flatmounts after immunostaining for the RGC-specific transcription factor Brn3a. The blob-like signal of Brn3a-immunopositive RGCs is enhanced via eigenvalues of the Hessian matrix and the resulting local maxima are counted as RGCs. After the user has outlined the retinal flatmount area, the total RGC number and retinal area are reported and an isodensity map, showing the RGC density distribution across the retina, is created. The semi-automated quantification shows a very strong correlation (Pearson's r ≥ 0.99) with manual counts for both widefield and confocal images, thereby validating the data generated via the developed script. Moreover, application of this method in established glaucomatous optic neuropathy models such as N-methyl-D-aspartate-induced excitotoxicity, optic nerve crush and laser-induced ocular hypertension revealed RGC loss conform with literature. Compared to manual counting, the described automated quantification method is faster and shows user-independent consistency. Furthermore, as the script detects the RGC number in entire retinal flatmounts, the method allows detection of regional differences in RGC density. As such, it can help advance research investigating the degenerative mechanisms of glaucomatous optic neuropathies and the effectiveness of new neuroprotective treatments. Because the script is flexible and easy to optimize due to a low number of critical parameters, it can potentially be applied in combination with other tissues or

  6. Bone marrow transplantation transfers age-related susceptibility to neovascular remodeling in murine laser-induced choroidal neovascularization.

    PubMed

    Espinosa-Heidmann, Diego G; Malek, Goldis; Mettu, Priyatham S; Caicedo, Alejandro; Saloupis, Peter; Gach, Sarah; Dunnon, Askia K; Hu, Peng; Spiga, Maria-Grazia; Cousins, Scott W

    2013-11-13

    Neovascular remodeling (NVR), the progression of small capillaries into large-caliber arterioles with perivascular fibrosis, represents a major therapeutic challenge in neovascular age-related macular degeneration (AMD). Neovascular remodeling occurs after laser-induced choroidal neovascularization (CNV) in aged but not young mice. Additionally, bone marrow-derived cells, including macrophages, endothelial precursor cells, and mesenchymal precursor cells, contribute to CNV severity. In this study, we investigated the impact of aged bone marrow transplantation (BMT) on the degree of fibrosis, size, and vascular morphology of CNV lesions in a mouse model of laser-induced CNV. Young (2 months) and old (16 months) mice were transplanted with green fluorescent protein (GFP)-labeled bone marrow isolated from either young or old donors. Laser CNV was induced 1 month following transplant, and eyes were analyzed via choroidal flat mounts and immunohistochemistry 1 month postlaser. The identity of cells infiltrating CNV lesions was determined using specific markers for the labeled transplanted cells (GFP+), macrophages (F4/80+), perivascular mesenchymal-derived cells (smooth muscle actin, SMA+), and endothelial cells (CD31+). Bone marrow transplantation from aged mice transferred susceptibility to NVR into young recipients. Inversely, transplantation of young marrow into old mice prevented NVR, preserving small size and minimal fibrosis. Mice with NVR demonstrated a greater relative contribution of marrow-derived SMA+ perivascular mesenchymal cells as compared to other cells. Our findings indicate that the status of bone marrow is an important determining factor of neovascular severity. Furthermore, we find that perivascular mesenchymal cells, rather than endothelial cells, derived from aged bone marrow may contribute to increased CNV severity in this murine model of experimental neovascularization.

  7. Bone Marrow Transplantation Transfers Age-Related Susceptibility to Neovascular Remodeling in Murine Laser-Induced Choroidal Neovascularization

    PubMed Central

    Espinosa-Heidmann, Diego G.; Malek, Goldis; Mettu, Priyatham S.; Caicedo, Alejandro; Saloupis, Peter; Gach, Sarah; Dunnon, Askia K.; Hu, Peng; Spiga, Maria-Grazia; Cousins, Scott W.

    2013-01-01

    Purpose. Neovascular remodeling (NVR), the progression of small capillaries into large-caliber arterioles with perivascular fibrosis, represents a major therapeutic challenge in neovascular age-related macular degeneration (AMD). Neovascular remodeling occurs after laser-induced choroidal neovascularization (CNV) in aged but not young mice. Additionally, bone marrow–derived cells, including macrophages, endothelial precursor cells, and mesenchymal precursor cells, contribute to CNV severity. In this study, we investigated the impact of aged bone marrow transplantation (BMT) on the degree of fibrosis, size, and vascular morphology of CNV lesions in a mouse model of laser-induced CNV. Methods. Young (2 months) and old (16 months) mice were transplanted with green fluorescent protein (GFP)-labeled bone marrow isolated from either young or old donors. Laser CNV was induced 1 month following transplant, and eyes were analyzed via choroidal flat mounts and immunohistochemistry 1 month postlaser. The identity of cells infiltrating CNV lesions was determined using specific markers for the labeled transplanted cells (GFP+), macrophages (F4/80+), perivascular mesenchymal-derived cells (smooth muscle actin, SMA+), and endothelial cells (CD31+). Results. Bone marrow transplantation from aged mice transferred susceptibility to NVR into young recipients. Inversely, transplantation of young marrow into old mice prevented NVR, preserving small size and minimal fibrosis. Mice with NVR demonstrated a greater relative contribution of marrow-derived SMA+ perivascular mesenchymal cells as compared to other cells. Conclusions. Our findings indicate that the status of bone marrow is an important determining factor of neovascular severity. Furthermore, we find that perivascular mesenchymal cells, rather than endothelial cells, derived from aged bone marrow may contribute to increased CNV severity in this murine model of experimental neovascularization. PMID:24135751

  8. 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

  9. In Vitro Effect of Laser-Induced Hydrodynamics on Cancer Cells.

    PubMed

    Elagin, V V; Pavlikov, A I; Yusupov, V I; Shirmanova, M V; Zagaynova, E V; Bagratashvili, V N

    2015-11-01

    We studied the effect of laser-induced hydrodynamic on viability of Colo-26 murine colon carcinoma cells in vitro. Laser-induced hydrodynamics was generated by a laser (λ=1.56 μ, power 3 W, 5 min exposure); to this end, the fiber end was submersed into a buffer above the cell monolayer. It was found that laser-induced hydrodynamics destructed the monolayer at standoff distances of between the working end of the laser fiber to cell monolayer of 1 and 5 mm and triggers apoptotic and necrotic death in remaining cells at a distance of 4 mm from the emitter.

  10. Theoretical modeling on the laser induced effect of liquid crystal optical phased beam steering

    NASA Astrophysics Data System (ADS)

    He, Xiaoxian; Wang, Xiangru; Wu, Liang; Tan, Qinggui; Li, Man; Shang, Jiyang; Wu, Shuanghong; Huang, Ziqiang

    2017-01-01

    Non-mechanical laser beam steering has been reported previously in liquid crystal array devices. To be one of the most promising candidates to be practical non-mechanical laser deflector, its laser induced effect still has few theoretical model. In this paper, we propose a theoretical model to analyze this laser induced effect of LC-OPA to evaluate the deterioration on phased beam steering. The model has three parts: laser induced thermal distribution; temperature dependence of material parameters and beam steering deterioration. After these three steps, the far field of laser beam is obtained to demonstrate the steering performance with the respect to the incident laser beam power and beam waist.

  11. 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

  12. Ketorolac inhibits choroidal neovascularization by suppression of retinal VEGF

    PubMed Central

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

    2011-01-01

    We assessed the effect of topical ketorolac on laser-induced choroidal neovascularization (CNV), measured retinal PGE2 and VEGF levels after laser treatment, and determined the effect of ketorolac on PGE2 and VEGF production. Six laser burns were placed in eyes of rats which then received topical ketorolac 0.4% or artificial tears four times daily until sacrifice. Fluorescein angiography (FA) was performed at 2 and 3 weeks and retinal pigment epithelium-choroid-sclera flat mounts were prepared. The retina and vitreous were isolated at 1, 3, 5, 7, and 14 days after laser treatment and tested for VEGF and PGE2. Additional animals were lasered and treated with topical ketorolac or artificial tears and tested at 3 and 7 days for retinal and vitreous VEGF and PGE2. Ketorolac reduced CNV on FA by 27% at 2 weeks (P < 0.001) and 25% at 3 weeks (P < 0.001). Baseline retina and vitreous PGE2 levels were 29.4 μg/g and 16.5 μg/g respectively, and reached 51.2 μg/g and 26.9 μg/g respectively, 24 h after laser treatment (P < 0.05). Retinal VEGF level was 781 pg/g 24 h after laser treatment and reached 931 pg/g by 7 days (P < 0.01). Ketorolac reduced retinal PGE2 by 35% at 3 days (P < 0.05) and 29% at 7 days (P < 0.001) and retinal VEGF by 31% at 3 days (P = 0.10) and 19% at 7 days (P < 0.001). Topical ketorolac inhibited CNV and suppressed retinal PGE2 and VEGF production. PMID:20659449

  13. Neuropilin 1 Involvement in Choroidal and Retinal Neovascularisation

    PubMed Central

    Fernández-Robredo, Patricia; Sim, Dawn A.; Fruttiger, Marcus

    2017-01-01

    Purpose Inhibiting VEGF is the gold standard treatment for neovascular age-related macular degeneration (AMD). It is also effective in preventing retinal oedema and neovascularisation (NV) in diabetic retinopathy (DR) and retinal vein occlusions (RVO). Neuropilin 1 (Nrp1) is a co-receptor for VEGF and many other growth factors, and therefore a possible alternative drug target in intra ocular neovascular disease. Here we assessed choroidal and retinal NV in an inducible, endothelial specific knock out model for Nrp1. Methods Crossing Nrp1 floxed mice with Pdgfb-CreERT2 mice produced tamoxifen-inducible, endothelial specific Nrp1 knock out mice (Nrp1ΔEC) and Cre-negative, control littermates. Cre-recombinase activity was confirmed in the Ai3(RCL-EYFP) reporter strain. Animals were subjected to laser-induced CNV (532 nm) and spectral domain-optical coherence tomography (SD-OCT) was performed immediately after laser and at day 7. Fluorescein angiography (FA) evaluated leakage and postmortem lectin staining in flat mounted RPE/choroid complexes was also used to measure CNV. Furthermore, retinal neovascularisation in the oxygen induced retinopathy (OIR) model was assessed by immunohistochemistry in retinal flatmounts. Results In vivo FA, OCT and post-mortem lectin staining showed a statistically significant reduction in leakage (p<0.05), CNV volume (p<0.05) and CNV area (p<0.05) in the Nrp1ΔEC mice compared to their Cre-negative littermates. Also the OIR model showed reduced retinal NV in the mutant animals compared to wild types (p<0.001). Conclusion We have demonstrated reduced choroidal and retinal NV in animals that lack endothelial Nrp1, confirming a role of Nrp1 in those processes. Therefore, Nrp1 may be a promising drug target for neovascular diseases in the eye. PMID:28107458

  14. The association between retinal vasculature changes and stroke: a literature review and Meta-analysis

    PubMed Central

    Wu, Hui-Qun; Wu, Huan; Shi, Li-Li; Yu, Li-Yuan; Wang, Li-Yuan; Chen, Ya-Lan; Geng, Jin-Song; Shi, Jian; Jiang, Kui; Dong, Jian-Cheng

    2017-01-01

    AIM To determine the association between retinal vasculature changes and stroke. METHODS MEDLINE and EMBASE were searched for relevant human studies to September 2015 that investigated the association between retinal vasculature changes and the prevalence or incidence of stroke; the studies were independently examined for their qualities. Data on clinical characteristics and calculated summary odds ratios (ORs) were extracted for associations between retinal microvascular abnormalities and stroke, including stroke subtypes where possible, and adjusted for key variables. RESULTS Nine cases were included in the study comprising 20 659 patients, 1178 of whom were stroke patients. The retinal microvascular morphological markers used were hemorrhage, microaneurysm, vessel caliber, arteriovenous nicking, and fractal dimension. OR of retinal arteriole narrowing and retinal arteriovenous nicking and stroke was 1.42 and 1.91, respectively, indicating that a small-caliber retinal arteriole and retinal arteriovenous nicking were associated with stroke. OR of retinal hemorrhage and retinal microaneurysm and stroke was 3.21 and 3.83, respectively, indicating that retinal microvascular lesions were highly associated with stroke. Results also showed that retinal fractal dimension reduction was associated with stroke (OR: 2.28 for arteriole network, OR: 1.80 for venular network). CONCLUSION Retinal vasculature changes have a specific relationship to stroke, which is promising evidence for the prediction of stroke using computerized retinal vessel analysis. PMID:28149786

  15. Retinal Changes Induced by Heavy Particles: A New Therapy Modality

    DTIC Science & Technology

    1975-11-01

    time. The changes in this x-ray series were erythema and edema of the lids, conjunctivitis, and an iritis . A chronic purulent lacrimatlon was...radiation produced edema, iritis , and cloud- ing of the vitreous within 24 hours without a retinal lesion. The nature of the lesions produced by the

  16. 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

  17. 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

  18. Ocular Lesions in Red-Tailed Hawks ( Buteo jamaicensis) With Naturally Acquired West Nile Disease.

    PubMed

    Wünschmann, A; Armién, A G; Khatri, M; Martinez, L C; Willette, M; Glaser, A; Alvarez, J; Redig, P

    2017-03-01

    Ocular lesions are common in red-tailed hawks with West Nile (WN) disease. These lesions consist of pectenitis, choroidal or retinal inflammation, or retinal necrosis, but detailed investigation of the ocular lesions is lacking. Postmortem examination of the eyes of 16 red-tailed hawks with naturally acquired WN disease and 3 red-tailed hawks without WN disease was performed using histopathology, immunohistochemistry for West Nile virus (WNV) antigen, glial fibrillary acid protein, cleaved caspase-3, and the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling method. Retinal lesions were classified as type I or type II lesions. Type I lesions were characterized by lymphoplasmacytic infiltrates in the subjacent choroid with degeneration limited to the outer retina (type Ia lesion) or with degeneration and necrosis of the outer retina or outer and inner retina (type Ib lesion) while retinal collapse, atrophy, and scarring were hallmarks of type II lesions. Type II retinal lesions were associated with a more pronounced choroiditis. Although not statistically significant, WNV antigen tended to be present in larger quantity in type Ib lesions. Type I lesions are considered acute while type II lesions are chronic. The development of retinal lesions was associated with the presence of an inflammatory infiltrate in the choroid. A breakdown of the blood-retina barrier is suspected to be the main route of infection of the retina. Within the retina, virus appeared to spread via both neuronal and Müller cell processes.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. Measurement of Irradiated Pyroprocessing Samples via Laser Induced Breakdown Spectroscopy

    SciTech Connect

    Phongikaroon, Supathorn

    2016-10-31

    The primary objective of this research is to develop an applied technology and provide an assessment to remotely measure and analyze the real time or near real time concentrations of used nuclear fuel (UNF) dissolute in electrorefiners. Here, Laser-Induced Breakdown Spectroscopy (LIBS), in UNF pyroprocessing facilities will be investigated. LIBS is an elemental analysis method, which is based on the emission from plasma generated by focusing a laser beam into the medium. This technology has been reported to be applicable in the media of solids, liquids (includes molten metals), and gases for detecting elements of special nuclear materials. The advantages of applying the technology for pyroprocessing facilities are: (i) Rapid real-time elemental analysis|one measurement/laser pulse, or average spectra from multiple laser pulses for greater accuracy in < 2 minutes; (ii) Direct detection of elements and impurities in the system with low detection limits|element specific, ranging from 2-1000 ppm for most elements; and (iii) Near non-destructive elemental analysis method (about 1 g material). One important challenge to overcome is achieving high-resolution spectral analysis to quantitatively analyze all important fission products and actinides. Another important challenge is related to accessibility of molten salt, which is heated in a heavily insulated, remotely operated furnace in a high radiation environment with an argon atmosphere.

  4. Laser-induced forward transfer of low viscosity inks

    NASA Astrophysics Data System (ADS)

    Sopeña, P.; Fernández-Pradas, J. M.; Serra, P.

    2017-10-01

    Laser-induced forward transfer (LIFT) is a laser-based printing technique which has been revealed as an interesting alternative to inkjet printing for the deposition of inks in direct writing applications. The principle of operation of the technique relies on the focusing of a laser beam on a thin film of the ink and the release of a tiny fraction of material through the action of a laser pulse, being usually assumed that such pulse should be very short, of the order of ns and below. However, with the aim of reducing production costs it would be desirable to operate with longer pulses (hundreds of ns and above), so that less expensive lasers could be employed. In this work we prove that it is feasible to carry out the LIFT of liquids with relatively long laser pulses (a few hundreds of ns). To that aim we have investigated the influence of laser fluence on the printed droplets and identified an evolution of their morphology with that parameter somewhat different from the one characteristic of the LIFT of liquids with much shorter pulses. A further time-resolved imaging study has revealed the onset of up to three different transfer mechanisms which correlate well with the deposition outcomes.

  5. 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.

  6. 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

  7. 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.

  8. Laser-induced solid-phase doped graphene.

    PubMed

    Choi, Insung; Jeong, Hu Young; Jung, Dae Yool; Byun, Myunghwan; Choi, Choon-Gi; Hong, Byung Hee; Choi, Sung-Yool; Lee, Keon Jae

    2014-08-26

    There have been numerous efforts to improve the performance of graphene-based electronic devices by chemical doping. Most studies have focused on gas-phase doping with chemical vapor deposition. However, that requires a complicated transfer process that causes undesired doping and defects by residual polymers. Here, we report a solid-phase synthesis of doped graphene by means of silicon carbide (SiC) substrate including a dopant source driven by pulsed laser irradiation. This method provides in situ direct growth of doped graphene on an insulating SiC substrate without a transfer step. A numerical simulation on the temperature history of the SiC surface during laser irradiation reveals that the surface temperature of SiC can be accurately controlled to grow nitrogen-doped graphene from the thermal decomposition of nitrogen-doped SiC. Laser-induced solid-phase doped graphene is highly promising for the realization of graphene-based nanoelectronics with desired functionalities.

  9. Ultrafast laser induced local magnetization dynamics in Heusler compounds

    NASA Astrophysics Data System (ADS)

    Elliott, P.; Müller, T.; Dewhurst, J. K.; Sharma, S.; Gross, E. K. U.

    2016-12-01

    The overarching goal of the field of femtomagnetism is to control, via laser light, the magnetic structure of matter on a femtosecond time scale. The temporal limits to the light-magnetism interaction are governed by the fact that the electron spin interacts indirectly with light, with current studies showing a laser induced global loss in the magnetic moment on a time scale of the order of a few 100 s of femtoseconds. In this work, by means of ab-initio calculations, we show that more complex magnetic materials - we use the example of the Heusler and half-Heusler alloys - allow for purely optical excitations to cause a significant change in the local moments on the order of 5 fs. This, being purely optical in nature, represents the ultimate mechanism for the short time scale manipulation of spins. Furthermore, we demonstrate that qualitative behaviour of this rich magnetic response to laser light can be deduced from the ground-state spectrum, thus providing a route to tailoring the response of some complex magnetic materials, like the Heuslers, to laser light by the well established methods for material design from ground-state calculations.

  10. Ultrafast laser induced local magnetization dynamics in Heusler compounds

    PubMed Central

    Elliott, P.; Müller, T.; Dewhurst, J. K.; Sharma, S.; Gross, E. K. U.

    2016-01-01

    The overarching goal of the field of femtomagnetism is to control, via laser light, the magnetic structure of matter on a femtosecond time scale. The temporal limits to the light-magnetism interaction are governed by the fact that the electron spin interacts indirectly with light, with current studies showing a laser induced global loss in the magnetic moment on a time scale of the order of a few 100 s of femtoseconds. In this work, by means of ab-initio calculations, we show that more complex magnetic materials - we use the example of the Heusler and half-Heusler alloys - allow for purely optical excitations to cause a significant change in the local moments on the order of 5 fs. This, being purely optical in nature, represents the ultimate mechanism for the short time scale manipulation of spins. Furthermore, we demonstrate that qualitative behaviour of this rich magnetic response to laser light can be deduced from the ground-state spectrum, thus providing a route to tailoring the response of some complex magnetic materials, like the Heuslers, to laser light by the well established methods for material design from ground-state calculations. PMID:27966585

  11. 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.

  12. Evaluation of immunoglobulins in bovine colostrum using laser induced fluorescence.

    PubMed

    Abdel-Salam, Z; Abdel Ghany, Sh; Harith, M A

    2014-11-01

    The objective of the present study was to exploit laser induced fluorescence (LIF) as a spectrochemical analytical technique for evaluation of immunoglobulin (IgG) in bovine colostrum. Colostrum samples were collected from different American Holstein cows at different times after calving. Four samples were gathered from each cow; the first three samples were obtained from the first three milkings (colostrum) and the fourth sample (milk) was obtained a week after calving. It has been demonstrated that LIF can be used as a simple, fast, sensitive and less costly spectrochemical analytical technique for qualitative estimation of IgG in colostrum. LIF results have been confirmed via the quantitative evaluation of IgG in the same samples adopting the single radial immunodiffusion conventional technique and a very good agreement has been obtained. Through LIF it was possible to evaluate bovine colostrum after different milking times and to differentiate qualitatively between colostrum from different animals which may reflect their general health status. A fluorescence linear calibration curve for IgG concentrations from 0 up to 120 g L(-1) has been obtained. In addition, it is feasible to adopt this technique for in situ measurements, i.e. in dairy cattle farms as a simple and fast method for evaluation of IgG in bovine colostrum instead of using lengthy and complicated conventional techniques in laboratories.

  13. 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.

  14. Laser-Induced Incandescence Calibration via Gravimetric Sampling

    NASA Technical Reports Server (NTRS)

    VanderWal, R. L.; Zhou, Z.; Choi, M. Y.

    1995-01-01

    Various beam imaging and/or sheet forming optics delivered light at 1064 nm from a pulsed Nd:YAG laser for use either as a beam of 3 mm radius or as a laser sheet. Imaging measurements were performed with a grated intensified array camera equipped with an ultraviolet f4.5 lens and a 40 mm extension tube. Point measurements were performed using an ultraviolet 250 mm focal length lens to collect and focus the laser induced incandescence (LII) signal into a 1 meter long quartz optical fiber which directed the LII signal to a 1/4 meter monochromator. An aperture preceding the lens restricted the signal collection region to 1 cm along the laser beam at the center of the gravimetric chimney. Signals from the PMT were processed by a boxcar integrator whereas the images were captured digitally using a frame-grabber with 16 MByte of on-board memory. Both 'point' and planar measurements were made with detector gates of 250 ns to minimize possible morphology bias in collection of the LII signal. Additionally, the imaging measurements were performed with broadband spectral collection of the LII signal to maximize the signal and again minimize any potential effects of morphology dependent heating and/or cooling rates. Digital delay generators controlled the firing of he laser, detector gates and data acquisition. Neutral density filters were used for both sets of measurements to maintain signal levels within linear dynamic ranges of the detectors, the range being determined prior to experiments.

  15. Laser-induced differential fluorescence for cancer diagnosis without biopsy

    SciTech Connect

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

    1997-01-01

    An optical diagnostic procedure based on laser-induced fluorescence was developed for direct {ital in vivo} cancer diagnosis without requiring biopsy. The methodology was applied in a clinical study involving over 100 patients in order to differentiate normal tissue from malignant tumors of the esophagus. Endogenous fluorescence of normal and malignant tissues was measured directly with the use of a fiber-optic probe inserted through an endoscope. The measurements were performed {ital in vivo} during routine endoscopy. Detection of the fluorescence signal from the tissue was performed with the use of laser excitation. This report describes the differential normalized fluorescence (DNF) procedure using the amplified spectral differences between the normalized fluorescence of malignant tissue and normal mucosa. The results of this DNF approach were compared with histopathology results of the biopsy samples and indicated excellent agreement in the classification of normal tissue and malignant tumors for the samples investigated. Data related to various grades of Barrett{close_quote}s esophagus are discussed. The DNF procedure could lead to the development of a rapid and cost-effective technique for cancer diagnosis. {copyright} {ital 1997} {ital Society for Applied Spectroscopy}

  16. The LILIA (laser induced light ions acceleration) experiment at LNF

    NASA Astrophysics Data System (ADS)

    Agosteo, S.; Anania, M. P.; Caresana, M.; Cirrone, G. A. P.; De Martinis, C.; Delle Side, D.; Fazzi, A.; Gatti, G.; Giove, D.; Giulietti, D.; Gizzi, L. A.; Labate, L.; Londrillo, P.; Maggiore, M.; Nassisi, V.; Sinigardi, S.; Tramontana, A.; Schillaci, F.; Scuderi, V.; Turchetti, G.; Varoli, V.; Velardi, L.

    2014-07-01

    Laser-matter interaction at relativistic intensities opens up new research fields in the particle acceleration and related secondary sources, with immediate applications in medical diagnostics, biophysics, material science, inertial confinement fusion, up to laboratory astrophysics. In particular laser-driven ion acceleration is very promising for hadron therapy once the ion energy will attain a few hundred MeV. The limited value of the energy up to now obtained for the accelerated ions is the drawback of such innovative technique to the real applications. LILIA (laser induced light ions acceleration) is an experiment now running at LNF (Frascati) with the goal of producing a real proton beam able to be driven for significant distances (50-75 cm) away from the interaction point and which will act as a source for further accelerating structure. In this paper the description of the experimental setup, the preliminary results of solid target irradiation and start to end simulation for a post-accelerated beam up to 60 MeV are given.

  17. 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.

  18. Continuous-wave laser-induced glass fiber generation

    NASA Astrophysics Data System (ADS)

    Nishioka, Nobuyasu; Hidai, Hirofumi; Matsusaka, Souta; Chiba, Akira; Morita, Noboru

    2017-09-01

    Pulsed-laser-induced glass fiber generation has been reported. We demonstrate a novel glass fiber generation technique by continuous-wave laser illumination and reveal the generation mechanism. In this technique, borosilicate glass, metal foil, and a heat insulator are stacked and clamped by a jig as the sample. Glass fibers are ejected from the side surface of the borosilicate glass by laser illumination of the sample from the borosilicate glass side. SEM observation shows that nanoparticles are attached on the glass fibers. High-speed imaging reveals that small bubbles are formed at the side surface of the borosilicate glass and the bursting of the bubble ejects the fibers. The temperature at the fiber ejection point is estimated to be 1220 K. The mechanism of the fiber ejection includes the following steps: the metal thin foil heated by the laser increases the temperature of the surrounding glass by heat conduction. Since the absorption coefficient of the glass is increased by increasing the temperature, the glass starts to absorb the laser irradiation. The heated glass softens and bubbles form. When the bubble bursts, molten glass and gas inside the bubble scatter into the air to generate the glass fibers.

  19. 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.

  20. Laser-induced temperature-rise measurement by infrared imaging

    NASA Astrophysics Data System (ADS)

    Gu, Jianhui; Tam, Siu Chung; Lam, Yee Loy; Zheng, Qiguang; Wei, Xueqin

    2000-06-01

    The characteristics of laser-induced temperature-rise are important information in laser material processing. In our experiment, several kinds of metals such as mild carbon steel, stainless steel, aluminum alloy and copper, and non-metals namely epoxy and polymethyl methacrylate were irradiated by using a high-power CW CO2 laser beam, while the temperature distribution and variation on their surfaces were measured by using a fast scanning infrared camera to image the laser irradiated area. The CO2 laser beam power was varied from several tens of Watts to several hundreds of Watts for the irradiating of different materials. 2-D and 3-D temperature distributions and the temperature variations against the time of laser irradiation on certain points within the laser-irradiated area were recorded and measured. It is found that the temperature distribution on the surfaces of the irradiated materials was tightly related to the laser beam mode, and the temperature fluctuations corresponded to the laser beam power fluctuations. The results of this research could be applied to laser material processing.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Flame imaging using planar laser induced fluorescence of sulfur dioxide

    NASA Astrophysics Data System (ADS)

    Honza, Rene; Ding, Carl-Philipp; Dreizler, Andreas; Böhm, Benjamin

    2017-09-01

    Laser induced fluorescence of sulfur dioxide (SO2-PLIF) has been demonstrated as a useful tool for flame imaging. Advantage was taken from the strong temperature dependence of the SO2 fluorescence signal. SO2 fluorescence intensity increases by more than one order of magnitude if the temperature changes from ambient conditions to adiabatic flame temperatures of stoichiometric methane-air flames. This results in a steep gradient of SO2-PLIF intensities at the reaction zone and therefore can be used as a reliable flame marker. SO2 can be excited electronically using the fourth-harmonic of an Nd:YAG laser at 266 nm. This is an attractive alternative to OH-LIF, a well-recognized flame front marker, because no frequency-doubled dye lasers are needed. This simplifies the experimental setup and is advantageous for measurements at high repetition rates where dye bleaching can become an issue. To prove the performance of this approach, SO2-PLIF measurements were performed simultaneously with OH-PLIF on laminar premixed methane-air Bunsen flames for equivalence ratios between 0.9 and 1.25. These measurements were compared to 1D laminar flamelet simulations. The SO2 fluorescence signal was found to follow the temperature rise of the flame and is located closer to the steep temperature gradient than OH. Finally, the combined SO2- and OH-PLIF setup was applied to a spark ignition IC-engine to visualize the development of the early flame kernel.

  6. Intraoperative metastases detection by laser-induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Vari, Sandor G.; Papazoglou, Theodore G.; van der Veen, Maurits J.; Fishbein, Michael C.; Young, J. D.; Chandra, Mudjianto; Papaioannou, Thanassis; Beeder, Clain; Shi, Wei-Qiang; Grundfest, Warren S.

    1991-06-01

    The authors studied the ability of Laser Induced Fluorescence Spectroscopy (LIFS) for the intraoperative identification of metastases using a photosensitizing agent Photofrin IIr to enhance spectroscopic detection. A He-Cd laser source (442 nm) was used to produce low-power illumination of tissue via a hand-held 400 micrometers fiberoptic probe. Through the same fiber, reflected and emitted light was returned to an optical multi-channel analyzer (OMA III) for analysis. Spectroscopic signals were displayed on a screen for immediate examination. Lobund Wistar rats, inoculated with Pollard rat adenocarcinoma cells, were used as an animal model. Photofrin IIr was administered intraperitoneal 24 or 48 hours prior to surgical exploration in doses varying from 0.75-7.5 mg/kg. Metastases detection was performed during abdominal exploration directed to ipsilateral and contralateral inguinal, iliac, para-aortic and renal lymph nodes. Nineteen tissue samples, identified as abnormal by LIFS, were removed for histologic analysis; 11 of these samples were larger than 5mm and histologic examination revealed malignancy in all cases. While LIFS signals showed malignancy in 8 tissue samples with dimensions less than 5mm, histology confirmed this in only 3. However, serial histologic sections were not performed. From the initial results, it was concluded that LIFS detection of malignant tissue is feasible and enhanced by the addition of Photofrin IIr. LIFS may be a promising technique for the intraoperative detection of primary malignant and metastatic tissue.

  7. 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.

  8. 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.

  9. Production of miniaturized biosensors through laser-induced forward transfer

    NASA Astrophysics Data System (ADS)

    Fernández-Pradas, J. M.; Duocastella, M.; Colina, M.; Serra, P.; Morenza, J. L.

    2007-05-01

    Lasers are adequate tools for the production of patterns with high spatial resolution owing to the high focusing power of their radiation. Laser induced forward transfer (LIFT) is a direct-writing technique allowing the deposition of tiny amounts of material from a donor thin film through the action of a pulsed laser beam. A laser pulse is focused onto the donor thin film through a transparent support, what results in the transference of a small area of the film onto a receptor substrate that is placed parallel to the film-support system. Although LIFT was originally developed to operate with solid films, it has been demonstrated that deposition is also viable from liquid films. In this case, a small amount of liquid is directly ejected from the film onto the receptor substrate, where it rests deposited in the form of a microdroplet. This makes LIFT adequate for biosensors preparation, since biological solutions can be transferred onto solid substrates to produce micrometric patterns of biomolecules. In this case, the liquid solvent acts as transport vector of the biomolecules. The viability of the technique has been demonstrated through the preparation of functional miniaturized biosensors showing similar performances and higher scales of integration than those prepared through more conventional techniques.

  10. Liquids microprinting through laser-induced forward transfer

    NASA Astrophysics Data System (ADS)

    Serra, P.; Duocastella, M.; Fernández-Pradas, J. M.; Morenza, J. L.

    2009-03-01

    Laser-induced forward transfer (LIFT) is a direct-writing technique which allows the deposition of tiny amounts of material from a donor thin film onto a receptor substrate. When LIFT is applied to liquid donor films, the laser radiation affects only a localized fraction of the liquid, thereby impelling the unaffected portion towards the receptor substrate. Thus, transfer takes place with no melting or vaporization of the deposited fraction and, in this way, LIFT can be used to successfully print complex materials like inorganic inks and pastes, biomolecules in solution, and even living cells and microorganisms. In addition, and for a wide range of liquid rheologies, the material can be deposited in the form of circular microdroplets; this provides LIFT with a high degree of spatial resolution leading to feature sizes below 10 μm, and making it competitive in front of conventional printing techniques. In this work, a revision of the main achievements of the LIFT of liquids is carried out, correlating the morphological characteristics of the generated features with the results of the study of the transfer process. Special emphasis is put on the characterization of the dynamics of liquid ejection, which has provided valuable information for the understanding of microdroplets deposition. Thus, new time-resolved imaging analyses have shown a material release behavior which contrasts with most of the previously made assumptions, and that allows clarifying some of the questions open during the study of the LIFT technique.

  11. Laser induced crystallization of hydrogenated amorphous silicon-carbon alloys

    NASA Astrophysics Data System (ADS)

    Summonte, C.; Rizzoli, R.; Servidori, M.; Milita, S.; Nicoletti, S.; Bianconi, M.; Desalvo, A.; Iencinella, D.

    2004-10-01

    Laser induced crystallization of hydrogenated amorphous silicon carbon alloy (a-Si1-xCx:H) films has been investigated by means of synchrotron x-ray diffraction. The a-Si1-xCx:H films were deposited on (100) silicon wafers by very high frequency plasma enhanced chemical vapor deposition at 100MHz in hydrogen diluted silane-methane gas mixtures. The substrate was kept at 250°C or 350°C and the stoichiometry was changed from x =0.20 to 0.63. The structural characterization of the as-grown films has been carried out by Rutherford backscattering (hydrogen concentration) and infrared spectroscopy (film ordering). The films were irradiated by a KrF excimer laser (248nm ) with varying energy density and number of pulses. After irradiation, the formation of SiC crystallites has been revealed by synchrotron x-ray diffraction. Besides SiC nanocrystals, the formation of crystalline Si and graphite is observed for under- (x <0.50) and over-stoichiometric (x>0.50) samples, respectively. The essential role played by hydrogen concentration and hydrogen bonding configuration in determining the melting threshold and the consequent SiC grain formation is highlighted.

  12. Laser-induced periodic surface structures, modeling, experiments, and applications

    NASA Astrophysics Data System (ADS)

    Römer, G. R. B. E.; Skolski, J. Z. P.; Oboňa, J. Vincenc; Ocelík, V.; de Hosson, J. T. M.; Huis in't Veld, A. J.

    2014-03-01

    Laser-induced periodic surface structures (LIPSSs) consist of regular wavy surface structures, or ripples, with amplitudes and periodicity in the sub-micrometer range. A summary of experimentally observed LIPSSs is presented, as well as our model explaining their possible origin. Linearly polarized continuous wave (cw) or pulsed laser light, at normal incidence, can produce LIPSSs with a periodicity close to the laser wavelength, and direction orthogonal to the polarization on the surface of the material. Ripples with a periodicity (much) smaller than the laser wavelength develop when applying laser pulses with ultra-short durations in the femtosecond and picosecond regime. The direction of these ripples is either parallel or orthogonal to the polarization direction. Finally, when applying numerous pulses, structures with periodicity larger than the laser wavelength can form, which are referred to as "grooves". The physical origin of LIPSSs is still under debate. The strong correlation of the ripple periodicity to the laser wavelength, suggests that their formation can be explained by an electromagnetic approach. Recent results from a numerical electromagnetic model, predicting the spatially modulated absorbed laser energy, are discussed. This model can explain the origin of several characteristics of LIPSSs. Finally, applications of LIPSSs will be discussed.

  13. Ultrafast laser induced local magnetization dynamics in Heusler compounds.

    PubMed

    Elliott, P; Müller, T; Dewhurst, J K; Sharma, S; Gross, E K U

    2016-12-14

    The overarching goal of the field of femtomagnetism is to control, via laser light, the magnetic structure of matter on a femtosecond time scale. The temporal limits to the light-magnetism interaction are governed by the fact that the electron spin interacts indirectly with light, with current studies showing a laser induced global loss in the magnetic moment on a time scale of the order of a few 100 s of femtoseconds. In this work, by means of ab-initio calculations, we show that more complex magnetic materials - we use the example of the Heusler and half-Heusler alloys - allow for purely optical excitations to cause a significant change in the local moments on the order of 5 fs. This, being purely optical in nature, represents the ultimate mechanism for the short time scale manipulation of spins. Furthermore, we demonstrate that qualitative behaviour of this rich magnetic response to laser light can be deduced from the ground-state spectrum, thus providing a route to tailoring the response of some complex magnetic materials, like the Heuslers, to laser light by the well established methods for material design from ground-state calculations.

  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. 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.

  16. Unsupervised verification of laser-induced breakdown spectroscopy dataset clustering

    NASA Astrophysics Data System (ADS)

    Wójcik, Michał R.; Zdunek, Rafał; Antończak, Arkadiusz J.

    2016-12-01

    Laser-induced breakdown spectroscopy is a versatile, optical technique used in a wide range of qualitative and quantitative analyses conducted with the use of various chemometric techniques. The aim of this research is to demonstrate the possibility of unsupervised clustering of an unknown dataset using K-means clustering algorithm, and verifying its input parameters through investigating generalized eigenvalues derived with linear discriminant analysis. In all the cases, principal component analyses have been applied to reduce data dimensionality and shorten computation time of the whole operation. The experiment was conducted on a dataset collected from twenty four different materials divided into six groups: metals, semiconductors, ceramics, rocks, metal alloys and others with the use of a three-channel spectrometer (298.02-628.73nm overall spectral range) and a UV (248nm) excimer laser. Additionally, two more complex groups containing all specimens and all specimens excluding rocks were created. The resulting spaces of eigenvalues were calculated for every group and three different distances in the multidimensional space (cosine, square Euclidean and L1). As expected, the correct numbers of specimens within groups with small deviations were obtained, and the validity of the unsupervised method has thus been proven.

  17. Laser-induced forward transfer: Propelling liquids with light

    NASA Astrophysics Data System (ADS)

    Fernández-Pradas, J. M.; Florian, C.; Caballero-Lucas, F.; Sopeña, P.; Morenza, J. L.; Serra, P.

    2017-10-01

    Laser-induced forward transfer (LIFT) constitutes an interesting alternative to conventional printing techniques in microfabrication applications. Originally developed to print inorganic materials from solid films, it was later proved that LIFT was feasible for printing liquids as well, which substantially broadened the range of printable materials. Any material which can be suspended or dissolved in an ink can be in principle printed through LIFT. The principle of operation of LIFT relies on the localized absorption of a focused laser pulse in a thin film of the ink containing the material to print (donor). This results in the generation of a cavitation bubble which expansion displaces a fraction of the liquid around it, leading to the formation of a jet which propagates away the donor and towards the receiving substrate, placed at a short distance from the liquid free surface. The contact of the jet with this receiving substrate results in the deposition of a sessile droplet. Thus, each droplet results from a single laser pulse, and the generation of micropatterns is achieved through the printing of successive droplets. A similar ejection and deposition process is produced by generating a cavitation bubble below the surface of a liquid contained in a reservoir in the film-free laser printing configuration. In this work we review our main achievements on the laser printing of inks, paying special attention to the analysis of the liquid transfer dynamics and its correlation with the printing outcomes.

  18. Laser-induced photoacoustic tomography for small animals

    NASA Astrophysics Data System (ADS)

    Wang, Xueding; Pang, Yongjiang; Stoica, George; Wang, Lihong V.

    2003-06-01

    Photoacoustic tomography, also called opto-acoustic tomography when laser excitation is used, is a novel medical imaging modality that combines the merits of both light and ultrasound. Here, we present our study of laser-induced photoacoustic tomography of organs of small animals. Pulses of 6.5 ns in width from an Nd:YAG laser at 532 nm or 1064 nm are employed to generate the distribution of thermoelastic expansion in the sample. A wide-band ultrasonic transducer that is non-focused in the imaging plane scans around the sample to realize a full-view detection of the imaged cross-section. A modified back-projection algorithm is applied to reconstruct the distribution of optical absorption inside the biological sample. Using optical energy depositions that fall below safe levels, tissue structures in ex-vivo rat kidneys and in-situ mouse brains covered by the skin and skull are imaged successfully with the high intrinsic optical contrast and the high spatial resolution of ultrasound.

  19. 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.

  20. 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.

  1. Discrimination of forensic trace evidence using laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Bridge, Candice Mae

    Elemental analysis in forensic laboratories can be tedious and many trace evidence items are not analyzed to determine their elemental composition. Presently, scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDS) is the primary analytical tool for determining the elemental composition of trace evidence items. However, due to the time it takes to obtain the required vacuum and the limited number of samples that can be analyzed at any one time, SEM-EDS can be impractical for a high volume of evidence items. An alternative instrument that can be used for this type of analysis is laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). While LA-ICP-MS is a very precise and quantitative analytical method that determines elemental composition based on isotopic mass measurements; however, the instrumentation is relatively expensive and therefore is budgetarily prohibitive for many forensic laboratories. It is the purpose of this research to evaluate an inexpensive instrument that can potentially provide rapid elemental analysis for many forensic laboratories. Laser induced breakdown spectroscopy (LIBS) is an analytical method that meets these requirements and offers information about the elemental composition based on ionic, atomic and diatomic molecular emissions.

  2. Laser-induced endothelial cell activation supports fibrin formation

    PubMed Central

    Atkinson, Ben T.; Jasuja, Reema; Chen, Vivien M.; Nandivada, Prathima; Furie, Bruce

    2010-01-01

    Laser-induced vessel wall injury leads to rapid thrombus formation in an animal thrombosis model. The target of laser injury is the endothelium. We monitored calcium mobilization to assess activation of the laser-targeted cells. Infusion of Fluo-4 AM, a calcium-sensitive fluorochrome, into the mouse circulation resulted in dye uptake in the endothelium and circulating hematopoietic cells. Laser injury in mice treated with eptifibatide to inhibit platelet accumulation resulted in rapid calcium mobilization within the endothelium. Calcium mobilization correlated with the secretion of lysosomal-associated membrane protein 1, a marker of endothelium activation. In the absence of eptifibatide, endothelium activation preceded platelet accumu-lation. Laser activation of human umbilical vein endothelial cells loaded with Fluo-4 resulted in a rapid increase in calcium mobilization associated cell fluorescence similar to that induced by adenosine diphosphate (10μM) or thrombin (1 U/mL). Laser activation of human umbilical vein endothelial cells in the presence of corn trypsin inhibitor treated human plasma devoid of platelets and cell microparticles led to fibrin for-mation that was inhibited by an inhibitory monoclonal anti–tissue factor antibody. Thus laser injury leads to rapid endothelial cell activation. The laser activated endothelial cells can support formation of tenase and prothrombinase and may be a source of activated tissue factor as well. PMID:20675401

  3. 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.

  4. 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

  5. Sample treatment and preparation for laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Jantzi, Sarah C.; Motto-Ros, Vincent; Trichard, Florian; Markushin, Yuri; Melikechi, Noureddine; De Giacomo, Alessandro

    2016-01-01

    One of the most widely cited advantages of laser-induced breakdown spectroscopy (LIBS) is that it does not require sample preparation, but this may also be the biggest factor holding it back from becoming a mature analytical technique like LA-ICP-MS, ICP-OES, or XRF. While there are certain specimen types that have enjoyed excellent LIBS results without any sample treatment (mostly homogeneous solids such as metals, glass, and polymers), the possible applications of LIBS have been greatly expanded through the use of sample preparation techniques that have resulted in analytical performance (i.e., limits of detection, accuracy, and repeatability) on par with XRF, ICP-OES, and often ICP-MS. This review highlights the work of many LIBS researchers who have developed, adapted, and improved upon sample preparation techniques for various specimen types in order to improve the quality of the analytical data that LIBS can produce in a large number of research domains. Strategies, not only for solids, but also liquids, gases, and aerosols are discussed, including newly developed nanoparticle enhancement and biological imaging and tagging techniques.

  6. 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.

  7. Theory of terahertz emission from femtosecond-laser-induced microplasmas.

    PubMed

    Thiele, I; Nuter, R; Bousquet, B; Tikhonchuk, V; Skupin, S; Davoine, X; Gremillet, L; Bergé, L

    2016-12-01

    We present a theoretical investigation of terahertz (THz) generation in laser-induced gas plasmas. The work is strongly motivated by recent experimental results on microplasmas, but our general findings are not limited to such a configuration. The electrons and ions are created by tunnel ionization of neutral atoms, and the resulting plasma is heated by collisions. Electrons are driven by electromagnetic, convective, and diffusive sources and produce a macroscopic current which is responsible for THz emission. The model naturally includes both ionization current and transition-Cherenkov mechanisms for THz emission, which are usually investigated separately in the literature. The latter mechanism is shown to dominate for single-color multicycle laser pulses, where the observed THz radiation originates from longitudinal electron currents. However, we find that the often discussed oscillations at the plasma frequency do not contribute to the THz emission spectrum. In order to predict the scaling of the conversion efficiency with pulse energy and focusing conditions, we propose a simplified description that is in excellent agreement with rigorous particle-in-cell simulations.

  8. 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.

  9. Laser induced damage and fracture in fused silica vacuum windows

    SciTech Connect

    Campbell, J.H.; Hurst, P.A.; Heggins, D.D.; Steele, W.A.; Bumpas, S.E.

    1996-11-01

    Laser-induced damage, that initiates catastrophic fracture, has been observed in large ({le}61 cm dia) fused silica lenses that also serve as vacuum barriers in Nova and Beamlet lasers. If the elastic stored energy in the lens is high enough, the lens will fracture into many pieces (implosion). Three parameters control the degree of fracture in the vacuum barrier window: elastic stored energy (tensile stress), ratio of window thickness to flaw depth, and secondary crack propagation. Fracture experiments were conducted on 15-cm dia fused silica windows that contain surface flaws caused by laser damage. Results, combined with window failure data on Beamlet and Nova, were used to develop design criteria for a ``fail-safe`` lens (that may catastrophically fracture but not implode). Specifically, the window must be made thick enough so that the peak tensile stress is less than 500 psi (3.4 MPa) and the thickness/critical flaw size is less than 6. The air leak through the window fracture and into the vacuum must be rapid enough to reduce the load on the window before secondary crack growth occurs. Finite element stress calculations of a window before and immediately following fracture into two pieces show that the elastic stored energy is redistributed if the fragments ``lock`` in place and thereby bridge the opening. In such cases, the peak stresses at the flaw site can increase, leading to further (i.e. secondary) crack growth.

  10. 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

  11. Laser-induced Forward Transfer of Ag Nanopaste.

    PubMed

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

    2016-03-31

    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.

  12. 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.

  13. Femtosecond laser induced damage of pulse compression gratings

    NASA Astrophysics Data System (ADS)

    Kong, Fanyu; Huang, Haopeng; Wang, Leilei; Shao, Jianda; Jin, Yunxia; Xia, Zhilin; Chen, Junming; Li, Linxin

    2017-12-01

    Laser induced damage of Au-coated gratings (ACG) and metal multilayer dielectric gratings (MMDG) for pulse compression were measured using 800 ± 35 nm femto-laser with pulse width of 30.2 fs. The -1st order diffraction efficiency of the ACG is over 90% in wavelength range from 700 to 1000 nm. The MMDG has a 148 nm bandwidth (750-897 nm) with -1st order diffraction efficiency greater than 90%. The laser damage experiment on grating samples was performed in air for single-shot damage. The single-shot damage threshold of the ACG and MMDG was determined to be 0.32 ± 0.02 J/cm2 and 0.31 ± 0.02 J/cm2, respectively. The damage morphologies of the ACG revealed that the damage was attributed to the pinholes at the base of the grating pillars and the weak adhesion between metal layer and photoresist gratings layer. The damage feature combined with near field distribution of MMDG indicated that the damage was due to the nonlinear ionization process of the valence electrons in HfO2 film. According to analysis results, the laser damage resistance of the ACG can be enhanced through avoiding the appearance of pinholes and increasing adhesion between metal layer and photoresist layer. And for the MMDG, good performance of HfO2 film, low near field enhancement and single HfO2 grating structures may increase its laser damage resistance.

  14. Laser-Induced Breakdown Spectroscopy of Cinematographic Film

    NASA Astrophysics Data System (ADS)

    Oujja, M.; Abrusci, C.; Gaspard, S.; Rebollar, E.; Amo, A. del; Catalina, F.; Castillejo, M.

    Laser-induced breakdown spectroscopy (LIBS) was used to characterize the composition of black-and-white, silver-gelatine photographic films. LIB spectra of samples and reference gelatine (of various gel strengths, Bloom values 225 and 75 and crosslinking degrees) were acquired in vacuum by excitation at 266 nm. The elemental composition of the gelatine used in the upper protective layer and in the underlying emulsion is revealed by the stratigraphic analysis carried out by delivering successive pulses on the same spot of the sample. Silver (Ag) lines from the light-sensitive silver halide salts are accompanied by iron, lead and chrome lines. Fe and Pb are constituents of film developers and Cr is included in the hardening agent. The results demonstrate the analytical capacity of LIBS for study and classification of different gelatine types and the sensitivity of the technique to minor changes in gelatine composition. In addition LIBS analysis allows extracting important information on the chemicals used as developers and hardeners of archival cinematographic films.

  15. 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.

  16. Laser-induced fluorescence in the detection of esophageal carcinoma

    NASA Astrophysics Data System (ADS)

    Wang, Kenneth K.; Gutta, Kumar; Laukka, Mark A.; Densmore, John

    1995-01-01

    Laser induced fluorescence (LIF) is a technique which can perform an 'optical biopsy' of gastrointestinal mucosa. LIF was performed in resected specimens using a pulsed N2-laser coupled fiberoptically to a probe. Fluorescence was measured using a 0.2 meter spectroscope with an intensified photodiode array. Measurements were made on fresh (<30 minutes after resection) esophageal specimens containing normal mucosa, Barrett's esophagus, and adenocarcinoma. Each tissue section was examined using an optical probe consisting of a central fiber for delivering the excitation energy and a 6 fiber bundle surrounding the central fiber for detection of the fluorescence. An excitation wavelength of 337 nm was used which generated 3-ns pulses while fluorescence intensities were acquired from 300-800 nm. Spectra were obtained from each section in a standardized fashion and background spectra subtracted. Fluorescence readings were taken from 54 normal esophageal sections and 32 sections of adenocarcinoma. A fluorescence index obtained from the tumor sections was 0.68+/- 0.01 compared with 0.51+/- 0.01 for the normal sections (p<0.001). Using a discriminant value of 0.65, this technique had a sensitivity of 81% and a specificity of 100% for detection of malignant tissue. The positive predictive value was 100% and the negative predictive value was 90% for an overall accuracy of 93%. LIF is a promising technique which has the capability of distinguishing normal versus malignant tissue in the esophagus with good accuracy.

  17. 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.

  18. 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.

  19. Analysis of bakery products by laser-induced breakdown spectroscopy.

    PubMed

    Bilge, Gonca; Boyacı, İsmail Hakkı; Eseller, Kemal Efe; Tamer, Uğur; Çakır, Serhat

    2015-08-15

    In this study, we focused on the detection of Na in bakery products by using laser-induced breakdown spectroscopy (LIBS) as a quick and simple method. LIBS experiments were performed to examine the Na at 589 nm to quantify NaCl. A series of standard bread sample pellets containing various concentrations of NaCl (0.025-3.5%) were used to construct the calibration curves and to determine the detection limits of the measurements. Calibration graphs were drawn to indicate functions of NaCl and Na concentrations, which showed good linearity in the range of 0.025-3.5% NaCl and 0.01-1.4% Na concentrations with correlation coefficients (R(2)) values greater than 0.98 and 0.96. The obtained detection limits for NaCl and Na were 175 and 69 ppm, respectively. Performed experimental studies showed that LIBS is a convenient method for commercial bakery products to quantify NaCl concentrations as a rapid and in situ technique. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

    PubMed

    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.

  1. Laser induced breakdown spectroscopy with picosecond pulse train

    NASA Astrophysics Data System (ADS)

    Lednev, Vasily N.; Pershin, Sergey M.; Sdvizhenskii, Pavel A.; Grishin, Mikhail Ya; Davydov, Mikhail A.; Stavertiy, Anton Ya; Tretyakov, Roman S.

    2017-02-01

    Picosecond pulse train and nanosecond pulse were compared for laser ablation and laser induced breakdown spectroscopy (LIBS) measurements. A detailed study revealed that the picosecond pulse train ablation improved the quality of laser craters (symmetric crater walls and the absence of large redeposited droplets), which was explained by a smaller heat affected zone and suppression of melt splash. Greater plasma dimensions and brighter plasma emission were observed by gated imaging for picosecond pulse train compared to nanosecond pulse ablation. Increased intensity of atomic and ionic lines in gated and time integrated spectra provided better signal-to-noise ratio for picosecond pulse train sampling. Higher temperature and electron density were detected during first microsecond for the plasma induced by the picosecond pulse train. Improved shot-to-shot reproducibility for atomic/ionic line intensity in the case of picosecond pulse train LIBS was explained by more effective atomization of target material in plasma and better quality of laser craters. Improved precision and limits of detections were determined for picosecond pulse train LIBS due to better reproducibility of laser sampling and increased signal-to-noise ratio.

  2. Laser induced breakdown spectroscopy application in joint European torus

    NASA Astrophysics Data System (ADS)

    Semerok, A.; L'Hermite, D.; Weulersse, J.-M.; Lacour, J.-L.; Cheymol, G.; Kempenaars, M.; Bekris, N.; Grisolia, C.

    2016-09-01

    The results on the first successful application of Laser Induced Breakdown Spectroscopy (LIBS) for remote in situ diagnostics of plasma facing components (a deposited layer on a divertor tile) in Joint European Torus (JET) are presented. The studies were performed with an available JET EDGE LIDAR laser system. For in-depth analysis of deposited layers on JET divertor tiles, a number of laser shots were applied onto the same divertor place without laser beam displacement. The spectral lines of D, CII and impurity elements (CrI, BeII, …) were identified in a wide spectral range (400-670 nm). With the increase in a number of laser shots applied onto the same divertor place, we observed consecutive changes in spectral line intensities of deuterium, carbon, and impurities with the appearance of spectral lines of tungsten substrate (WI). In-depth analysis of deposited layers on JET divertor tiles was made on the basis of the spectral line behaviour in reference to the applied laser shots. The possibility of surface cartography with laser beam displacement on the tile surface was demonstrated as well. Based on the results obtained, we may conclude that LIBS method is applicable for in situ remote analysis of deposited layers of JET plasma facing components.

  3. Theory of terahertz emission from femtosecond-laser-induced microplasmas

    NASA Astrophysics Data System (ADS)

    Thiele, I.; Nuter, R.; Bousquet, B.; Tikhonchuk, V.; Skupin, S.; Davoine, X.; Gremillet, L.; Bergé, L.

    2016-12-01

    We present a theoretical investigation of terahertz (THz) generation in laser-induced gas plasmas. The work is strongly motivated by recent experimental results on microplasmas, but our general findings are not limited to such a configuration. The electrons and ions are created by tunnel ionization of neutral atoms, and the resulting plasma is heated by collisions. Electrons are driven by electromagnetic, convective, and diffusive sources and produce a macroscopic current which is responsible for THz emission. The model naturally includes both ionization current and transition-Cherenkov mechanisms for THz emission, which are usually investigated separately in the literature. The latter mechanism is shown to dominate for single-color multicycle laser pulses, where the observed THz radiation originates from longitudinal electron currents. However, we find that the often discussed oscillations at the plasma frequency do not contribute to the THz emission spectrum. In order to predict the scaling of the conversion efficiency with pulse energy and focusing conditions, we propose a simplified description that is in excellent agreement with rigorous particle-in-cell simulations.

  4. Stereotactic-guided laser-induced interstitial thermotherapy (SLITT) in gliomas with intraoperative morphologic monitoring in open MR

    NASA Astrophysics Data System (ADS)

    Lumenta, Christianto B.; Leonardi, Massimo A.; von Einsiedel, Helga

    2001-01-01

    Stereotactic guided laser-induced interstitial thermotherapy (SLITT) is a minimal invasive method to produce thermo necrosis in cerebral tumor tissue. Clinical data about dose/response relationship and patients outcome is poor. Twenty-four patients with brain tumors were treated with SLITT, totally 30 laser procedures were performed. Under local anesthesia 600 micrometers laser-fiber were inserted by the stererotactic-guided technique. IN open MR the denaturation of the tumor by a Neodym-YAG-laser was monitored using T1-weighted 3D tumor FLASH sequences. Laser energy was applied in steps of 400 to 1200 Joules. Development of necrosis at a mean total energy-dose of 2979 Joules could be monitored in all procedures. Initial signal changes were seen after a mean of 1250 Joules. Mean max total lesion size was 21.2 mm. The higher the total energy, the larger the thermo lesion, but no linear relationship could be seen. Tumor tissue response showed no dependency form tumor grading. Although lesion-size basically is energy dependent, it should be applied individually, since thermo response in brain tumors varies due to different optical properties. Energy application in steps of 500 Joules monitored in near on-line modus in an open MR-system is safe and feasible. Conclusions about the clinical value of SLITT are not definite.

  5. Spontaneous closure of a blue laser induced full thickness macular hole.

    PubMed

    Porrúa, L; Oblanca, N; González-López, J J

    2017-01-01

    A 14 year-old boy attended our clinic complaining of a scotoma after an accidental exposure to a 10W, 450nm laser beam from a blue-light handheld laser device. Optical coherence tomography confirmed a full thickness macular hole. As visual acuity (VA) remained 20/20 Snellen, observation was decided. Spontaneous closure was confirmed after one month. Reckless use of high-power handheld laser devices may induce severe retinal lesions, including full thickness macular holes. Observation is a sensible treatment option in this type of macular hole, especially when VA is preserved. The pathophysiology of these cases differs from senile full thickness macular holes. Copyright © 2016 Sociedad Española de Oftalmología. Publicado por Elsevier España, S.L.U. All rights reserved.

  6. 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.

  7. 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.

  8. CAPILLARY ELECTROPHORESIS/LASER-INDUCED FLUORESCENCE DETECTION OF FLUORESCEIN AS A GROUNDWATER MIGRATION TRACER

    EPA Science Inventory

    Capillary electrophoresis (CE) has been applied to the determination of the groundwater migration tracer dye fluorescein based on laser-induced fluorescence (LIF) detection and compared to determinations obtained with traditional spectrofluorimetry. Detection limits of injected d...

  9. 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...

  10. Nanoparticle Enhanced Laser Induced Breakdown Spectroscopy for Improving the Detection of Molecular Bands

    NASA Astrophysics Data System (ADS)

    Koral, Can; De Giacomo, Alessandro; Mao, Xianglei; Zorba, Vassilia; Russo, Richard E.

    2016-11-01

    Enhancement of molecular band emission in laser-induced plasmas is important for improving sensitivity and limits of detection in molecular sensing and molecular isotope analysis. In this work we introduce the use of Nanoparticle Enhanced Laser Induced Breakdown (NELIBS) for the enhancement of molecular band emission in laser-induced plasmas, and study the underlying mechanisms responsible for the observed enhancement. The use of Ag nanoparticles leads to an order of magnitude enhancement for AlO (B2Σ+ → Χ+ Σ+) system emission from an Al-based alloy. We demonstrate that the mechanism responsible for the enhancement of molecular bands differs from that of atomic emission, and can be traced down to the increased number of atomic species in NELIBS which lead to AlO molecular formation. These findings showcase the potential of NELIBS as a simple and viable technology for enhancing molecular band emission in laser-induced plasmas.

  11. 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.

  12. Laser-Induced Breakdown Spectroscopy on Solution Samples Using Surface Excitation

    DTIC Science & Technology

    1996-12-01

    and R. Kellner, "New IR Fiber-Optic Chemical Sensor for in Situ Measurements of Chlorinated Hydrocarbons in Water," Applied Spectroscopy 47 (9), 1484...34Quantitative Elemental Analysis of Iron Ore by Laser-Induced Breakdown Spectroscopy," Applied Spectroscopy 45 (4), 701-705 (1991). 7. D.A. Cremers...to 950 nm," Applied Spectroscopy 49 (10), 1490-1499 (1995). 17. J. Belliveau, L. Cadwell, K. Coleman, L. Huwel, and H. Griffin, "Laser- Induced

  13. Density jumps in the plasma of a nanosecond laser-induced spark and their dynamics

    SciTech Connect

    Malyutin, A A; Podvyaznikov, V A; Chevokin, V K

    2011-01-31

    Experimental investigation of the structure of a laser-induced spark emerging in the focusing of 50-ns radiation pulses is described. Two density jumps were discovered in the plasma of the laser-induced spark. One of them is localised in the vicinity of the focal plane of the lens, the other propagates from this plane in the laser propagation direction at a constant velocity of {approx}7.5 km s{sup -1}. (laser plasma)

  14. 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.

  15. 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.

  16. Doppler splitting generated by shock waves in laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Bukvić, Srdjan; Skočić, Miloš

    2017-06-01

    We present a classical spectroscopic approach for investigation of the fast plasma expansion present in Laser Induced Plasma. We show that characteristic form of the spectral lines, caused by significant Doppler effect, contains valuable information regarding the expansion velocity, plasma deceleration, emitters temperature, electron density and so on. The proposed numerical procedure is simple since the inverse Abel transform is not a necessary step. We illustrate this technique analyzing expansion of laser induced copper plasma in ambient gas at low (20Pa) pressure.

  17. Subsurface defects of fused silica optics and laser induced damage at 351 nm.

    PubMed

    Hongjie, Liu; Jin, Huang; Fengrui, Wang; Xinda, Zhou; Xin, Ye; Xiaoyan, Zhou; Laixi, Sun; Xiaodong, Jiang; Zhan, Sui; Wanguo, Zheng

    2013-05-20

    Many kinds of subsurface defects are always present together in the subsurface of fused silica optics. It is imperfect that only one kind of defects is isolated to investigate its impact on laser damage. Therefore it is necessary to investigate the impact of subsurface defects on laser induced damage of fused silica optics with a comprehensive vision. In this work, we choose the fused silica samples manufactured by different vendors to characterize subsurface defects and measure laser induced damage. Contamination defects, subsurface damage (SSD), optical-thermal absorption and hardness of fused silica surface are characterized with time-of-flight secondary ion mass spectrometry (TOF-SIMS), fluorescence microscopy, photo-thermal common-path interferometer and fully automatic micro-hardness tester respectively. Laser induced damage threshold and damage density are measured by 351 nm nanosecond pulse laser. The correlations existing between defects and laser induced damage are analyzed. The results show that Cerium element and SSD both have a good correlation with laser-induced damage thresholds and damage density. Research results evaluate process technology of fused silica optics in China at present. Furthermore, the results can provide technique support for improving laser induced damage performance of fused silica.

  18. Clinical and Echographic Long-Term Follow-Up of a Retinal Macrocyst: A Case Report

    PubMed Central

    Serna-Ojeda, Juan Carlos; Pinkus-Herrera, Christian Denisse; Moreno-Londono, Maria Victoria; Rodriguez-Loaiza, Jose Luis; Gonzalez-Gonzalez, Maria Cristina

    2014-01-01

    The purpose of this paper is to report the case of a 62-year-old male diagnosed with a retinal macrocyst secondary to a long-standing retinal detachment in his right eye. At fundoscopy examination, an oval, elevated retinal lesion in the superior nasal quadrant was noted. Ultrasonography was performed, with a B-mode echography showing an oval, anechoic image and a standardized A-mode echography with a reflectivity spike higher than 98%, which was compatible with a retinal macrocyst. The patient refused surgical treatment for the retinal detachment and was followed for 14 months with stable visual acuity and no clinical or echographic changes. PMID:25028580

  19. Exosomes derived from MSCs ameliorate retinal laser injury partially by inhibition of MCP-1

    PubMed Central

    Yu, Bo; Shao, Hui; Su, Chang; Jiang, Yuanfeng; Chen, Xiteng; Bai, Lingling; Zhang, Yan; Li, Qiutang; Zhang, Xiaomin; Li, Xiaorong

    2016-01-01

    Although accumulated evidence supports the notion that mesenchymal stem cells (MSCs) act in a paracrine manner, the mechanisms are still not fully understood. Recently, MSC-derived exosomes (MSC-Exos), a type of microvesicle released from MSCs, were thought to carry functional proteins and RNAs to recipient cells and play therapeutic roles. In the present study, we intravitreally injected MSCs derived from either mouse adipose tissue or human umbilical cord, and their exosomes to observe and compare their functions in a mouse model of laser-induced retinal injury. We found that both MSCs and their exosomes reduced damage, inhibited apoptosis, and suppressed inflammatory responses to obtain better visual function to nearly the same extent in vivo. Obvious down-regulation of monocyte chemotactic protein (MCP)-1 in the retina was found after MSC-Exos injection. In vitro, MSC-Exos also down-regulated MCP-1 mRNA expression in primarily cultured retinal cells after thermal injury. It was further demonstrated that intravitreal injection of an MCP-1-neutralizing antibody promoted the recovery of retinal laser injury, whereas the therapeutic effect of exosomes was abolished when MSC-Exos and MCP-1 were administrated simultaneously. Collectively, these results suggest that MSC-Exos ameliorate laser-induced retinal injury partially through down-regulation of MCP-1. PMID:27686625

  20. Dramatic Inhibition of Retinal and Choroidal Neovascularization by Oral Administration of a Kinase Inhibitor

    PubMed Central

    Seo, Man Seong; Kwak, Nohoon; Ozaki, Hiroaki; Yamada, Haruhiko; Okamoto, Naoyuki; Yamada, Eri; Fabbro, Doriano; Hofmann, Francesco; Wood, Jeanette M.; Campochiaro, Peter A.

    1999-01-01

    The most common cause of new blindness in young patients is retinal neovascularization, and in the elderly is choroidal neovascularization. Therefore, there has been a great deal of attention focused on the development of new treatments for these disease processes. Previous studies have demonstrated partial inhibition of retinal neovascularization in animal models using antagonists of vascular endothelial growth factor or other signaling molecules implicated in the angiogenesis cascade. These studies have indicated potential for drug treatment, but have left many questions unanswered. Is it possible to completely inhibit retinal neovascularization using drug treatment with a mode of administration that is feasible to use in patients? Do agents that inhibit retinal neovascularization have any effect on choroidal neovascularization? In this study, we demonstrate complete inhibition of retinal neovascularization in mice with oxygen-induced ischemic retinopathy by oral administration of a partially selective kinase inhibitor that blocks several members of the protein kinase C family, along with vascular endothelial growth factor and platelet-derived growth factor receptor tyrosine kinases. The drug also blocks normal vascularization of the retina during development but has no identifiable adverse effects on mature retinal vessels. In addition, the kinase inhibitor causes dramatic inhibition of choroidal neovascularization in a laser-induced murine model. These data provide proof of concept that pharmacological treatment is a viable approach for therapy of both retinal and choroidal neovascularization. PMID:10362799