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Sample records for argon laser photocoagulation

  1. Binocular indirect argon laser photocoagulator.

    OpenAIRE

    Mizuno, K

    1981-01-01

    The binocular indirect argon laser photocoagulator was newly designed to enable visualisation of the entire fundus during panretinal laser photocoagulation and to treat retinal tears immediately after buckling procedures of the sclera. The lamp housing of the binocular ophthalmoscope was remodelled and adjusted so that the laser beam and illuminating light are coaxial after leaving the ophthalmoscope. The blocking filter was permanently fixed in the eye-pieces to lighten the weight of the oph...

  2. Argon laser photocoagulation of cyclodialysis clefts after cataract surgery

    International Nuclear Information System (INIS)

    Three patients with cyclodialysis clefts, hypotony and hypotonic retinopathy subsequent to cataract surgery were treated with argon laser photocoagulation. The hypotony was reversed in each patient and their visual acuity was normalized. Laser photocoagulation is a noninvasive treatment that can be repeated easily and safely. The complications of the treatment are minor. A hypertensive episode commonly occurs in the early postoperative period. (au) 8 refs

  3. Grid pattern Argon Laser photocoagulation for diabetic diffuse macular edema

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    Karkhane R

    1998-05-01

    Full Text Available Purpose: to determine the effect of Grid pattern laser photocoagulation on diabetic diffuse macular edema with assessment of visual outcome. Patients & Methods: The author reviewed the medical records of 84 eyes of 62 patients with diabetic diffuse macular edema treated with Grid pattern green Argon laser photocoagulation in Farabi Eye Hospital between the years 1992-1995, the follow-up period was 16-48 months (average 24.55±6.42, median 28 mounths. Results: Visual acuity was improved in 11.9%; unchanged in 65.4% and worsened in 22.7% of eyes. Conclusion: In assessing long-term visual outcome, Grid laser photocoagulation is an effective modality in maintaining or improving visual acuity.

  4. Effect of Ginkgo biloba on the lesions induced by retinal argon laser photocoagulation in rabbits

    International Nuclear Information System (INIS)

    In rabbits, retinal argon laser photocoagulation disrupts the arrangement of cell layers and produces interstitial edema. Photochemical and thermal energy is released with production of free oxygenated radicals that are responsible for destruction of cell membranes. Retinal argon laser photocoagulation in rabbits was used as a pharmacologic model to evaluate the protective effect of EGB 761 against membrane lesions and edema. As a strong free radicals scavengers, EGB 761 confirms its protective action on cells membranes and its anti-edema effect

  5. Effect of Ginkgo biloba on the lesions induced by retinal argon laser photocoagulation in rabbits

    Energy Technology Data Exchange (ETDEWEB)

    Clairambault, P.; Pairault, C.; Droy-Lefaix, M.T.; Magnier, B.; Magnier, M.

    1986-01-09

    In rabbits, retinal argon laser photocoagulation disrupts the arrangement of cell layers and produces interstitial edema. Photochemical and thermal energy is released with production of free oxygenated radicals that are responsible for destruction of cell membranes. Retinal argon laser photocoagulation in rabbits was used as a pharmacologic model to evaluate the protective effect of EGB 761 against membrane lesions and edema. As a strong free radicals scavengers, EGB 761 confirms its protective action on cells membranes and its anti-edema effect.

  6. Comparative effects of argon green and krypton red laser photocoagulation for patients with diabetic exudative maculopathy.

    OpenAIRE

    Khairallah, M; Brahim, R; Allagui, M.; Chachia, N

    1996-01-01

    AIMS/BACKGROUND: Focal treatment of diabetic macular oedema is usually done using a haemoglobin absorbing wave-length, such as argon green laser. This study aimed to compare photocoagulation with argon green (514 nm) and krypton red (647 nm), which is poorly absorbed by haemoglobin, in the focal treatment of patients with diabetic exudative maculopathy. METHODS: A total of 151 eyes of 78 outpatients were assigned randomly to receive either argon green (n = 79) or krypton red (n = 72) laser tr...

  7. Pilot study about dose-effect relationship of ocular injury in argon laser photocoagulation

    Science.gov (United States)

    Chen, P.; Zhang, C. P.; Fu, X. B.; Zhang, T. M.; Wang, C. Z.; Qian, H. W.; San, Q.

    2011-03-01

    The aim of this article was to study the injury effect of either convergent or parallel argon laser beam on rabbit retina, get the dose-effect relationship for the two types of laser beams, and calculate the damage threshold of argon laser for human retinas. An argon laser therapeutic instrument for ophthalmology was used in this study. A total of 80 rabbit eyes were irradiated for 600 lesions, half of which were treated by convergent laser and the other half were done with parallel laser beam. After irradiation, slit lamp microscope and fundus photography were used to observe the lesions, change and the incidence of injury was processed statistically to get the damage threshold of rabbit retina. Based on results from the experiments on animals and the data from clinical cases of laser treatment, the photocoagulation damage thresholds of human retinas for convergent and parallel argon laser were calculated to be 0.464 and 0.285 mJ respectively. These data provided biological reference for safely operation when employing laser photocoagulation in clinical practice and other fields.

  8. A case of metastatic carcinoma of the iris successfully treated by argon laser photocoagulation and 60Co therapy

    International Nuclear Information System (INIS)

    A 69-year-old female developed visual impairment and congestion in the right eye. She had been treated for small cell carcinoma in the left lung for the past 8 months with cytostatics and radiation. Three whitish gray nodules were located on the iris at 10-11 o'clock in the right eye. Three smaller nodules were present in the chamber angle in the same sector. The corrected visual activity of the affected eye was 0.3. The left eye was intact. We performed total iridectomy and sclerotomy to remove the tumors. The resected tissue showed the same cell type as in the lung. Two days after surgery, multiple nodules appeared on the entire iris surface and the chamber angle apparently due to dissemination of tumor cells by the surgical procedure. Repeated argon laser photocoagulation aimed on the cancer nodules was very effective in supressing the tumor and maintaining the visual acuity without severe side effects for the next 5 months, until intravitreal metastasis and death ensued. 60Co therapy was noticeably effective to extinguish the tumor mass in the anterior chamber and in the vitreous cavity. We recommend argon laser photocoagulation for metastatic iris tumor in the initial stage and 60Co therapy in the terminal stage. (author)

  9. Comparative evaluation of diode laser versus argon laser photocoagulation in patients with central serous retinopathy: A pilot, randomized controlled trial [ISRCTN84128484

    Directory of Open Access Journals (Sweden)

    Venkatesh Pradeep

    2004-10-01

    Full Text Available Abstract Background To evaluate the efficacy of diode laser photocoagulation in patients with central serous retinopathy (CSR and to compare it with the effects of argon green laser. Methods Thirty patients with type 1 unilateral CSR were enrolled and evaluated on parameters like best corrected visual acuity (BCVA, direct and indirect ophthalmoscopy, amsler grid for recording scotoma and metamorphopsia, contrast sensitivity using Cambridge low contrast gratings and fluorescein angiography to determine the site of leakage. Patients were randomly assigned into 2 groups according to the statistical random table using sequence generation. In Group 1 (n = 15, diode laser (810 nm photocoagulation was performed at the site of leakage while in Group 2 (n = 15, eyes were treated with argon green laser (514 nm using the same laser parameters. Patients were followed up at 4, 8 and 12 weeks after laser. Results The mean BCVA in group 1 improved from a pre-laser decimal value of 0.29 ± 0.14 to 0.84 ± 0.23 at 4 weeks and 1.06 ± 0.09 at 12 weeks following laser. In group 2, the same improved from 0.32 ± 0.16 to 0.67 ± 0.18 at 4 weeks and 0.98 ± 0.14 at 12 weeks following laser. The improvement in BCVA was significantly better in group 1 (p Conclusion Diode laser may be a better alternative to argon green laser whenever laser treatment becomes indicated in patients with central serous retinopathy in terms of faster visual rehabilitation and better contrast sensitivity. In addition, diode laser also has the well-recognized ergonomic and economic advantages.

  10. 倒睫激光疗效106例观察%Treatment of trichiasis with argon laser photocoagulation

    Institute of Scientific and Technical Information of China (English)

    徐冬冬; 于伟鸿; 董方田

    2010-01-01

    Objective To observe the clinical effect with the use of Argon laser photocoagulation for the treatment of recurrent trichiasis patients. Methods A total of 106 lids (73 patients) with aberrant lashes were treated in our study. Each lash was treated with a beam of 50-200μm (spot size), 0.2s (time), and 500-1000mW .power). Topical or infiltration anesthesia was used. The beam was focused at the root of the aberrant cilium and a 2-3mm crater was produced at its base. This was then deepened to destroy the whole lash follicle. At the conclusion of the laser treatment, the patient was discharged on topical antibiotic eye drops three times a day for one week. Results Successful treatment with no evidence of recurrence was achieved in 64.2% of lids after one laser session. Of 101 lids (95.3%) achieved no recurrence with three sessions laser treatment. With one laser session, the success rate was 78.9% when aberrant lashes per lid were below 5 and 33.3%when aberrant lashes were from 5-10. If the aberrant lashes per lid were above 10, several sessions of laser was needed. With one laser session, the success rate of trachoma was 41.7%, 72.4% for blepharitis and 81.8% for idiopathic trichiasis. Conclusions Argon laser treatment appears to be a safe and effective method to the treatment of trichiasis. The success rate is lower when the aberrant lashes per lid are more. Among the different causes of trichiasis, trachoma carries a significant low success rate.%目的 对氩激光光凝后的倒睫患者进行随诊,观察这种方法的临床效果.方法 应用氩激光治疗倒睫毛,将能量设为500~1000m W,时间为200m s,光斑50~200μm,使激光束对准倒睫毛的根部,产生2~3m m直径的小凹陷,继续激光破坏毛囊.激光后应用抗生素滴眼液一周.结果 73位患者106只眼接受了氩激光治疗.每根倒睫所需激光点数(53.7±19.1)点,68只眼经1次激光治愈,成功率64.2%,经3次激光,101只眼(95.3%)达到治愈效果.眼睑≤5

  11. Laser photocoagulation for retinal vein occlusion

    Directory of Open Access Journals (Sweden)

    K. A. Mirzabekova

    2015-03-01

    Full Text Available Retinal vein occlusion (RVO is one of the leading causes of permanent vision loss. In adults, central retinal vein occlusion (CRVO occurs in 1.8% while branch retinal vein occlusion (BRVO occurs in 0.2%. Treatment strategy and disease prognosis are determined by RVO type (ischemic/non-ischemic. Despite numerous studies and many current CRVO and BRVO treatment approaches, the management of these patients is still being debated. Intravitreal injections of steroids (triamcinolone acetate, dexamethasone and vascular endothelial growth factor (VEGF inhibitors (bevacizumab, ranibizumab were shown to be fairly effective. However, it is unclear whether anti-VEGF agents are reasonable in ischemic RVOs. Laser photocoagulation remains the only effective treatment of optic nerve head and/or retinal neovascularization. Laser photocoagulation is also indicated for the treatment of macular edema. Both threshold and sub-threshold photocoagulation may be performed. Photocoagulation performed with argon (514 nm, krypton (647 nm, or diode (810 nm laser for macular edema provides similar results (no significant differences. The treatment may be complex and include medication therapy and/or surgery. Medication therapy includes anti-aggregant agents and antioxidants, i.e., emoxypine which may be used in acute RVO as well as in post-thrombotic retinopathy. 

  12. Laser photocoagulation - eye

    Science.gov (United States)

    ... special contact lens will be placed on your eye. The lens contains mirrors that help the doctor aim the laser. You will be instructed to look straight ahead or at a target light with your other eye. A laser will be focused on the bleeding ...

  13. Trans-spectral organic dye laser photocoagulation.

    OpenAIRE

    L'Esperance, F A

    1985-01-01

    Clinical research utilizing the yellow, orange, and red wavelengths of the dye laser (Rhodamine 6G and MD-631) appears to have considerable promise and may demonstrate that the liquid organic dye laser is the laser of choice for photocoagulation of many types of ocular defects. The effectiveness of the dye laser as a photocoagulation source is due to the trans-spectral availability of relatively high output power wavelengths. Therefore, a target tissue can be selectively coagulated with minim...

  14. Argon laser photocoagulation for 24 eyes of recurrent trichiasis%Argon激光治疗复发性倒睫24眼

    Institute of Scientific and Technical Information of China (English)

    朱承华; 卞春及

    2004-01-01

    AIM: To evaluate the efficacy and safety of Argon laser microsurgery for the treatment of recurrent trichiasis.METHODS: A total of 24 eyes (18 patients) with aberrant lashes were treated. Each lash was treated with a beam of 50-200 μ m (spot size), 0.25-0.5s (time), and 400-800mW(power). Some ingrowing lashes were dyed in methylene blue before the treatment. No anaesthetic was used for the procedure. The mean follow-up time was 6.12 months.RESULTS: Successful treatment with no evidence ofrecurrence was achieved in 83.3% eyes after one to four laser sessions. Irritating symptoms of all patients disappeared or were obviously relieved after treatment.There was a significant correlation between the number of aberrant lashes per eye and the number of required laser sessions. Complete healing of the treated area occurred within six weeks after the procedure, with no vascularization or distortion of the lid margin.CONCLUSION: Argon laser treatment appears to be a quick, simple and convenient, safe and effective alternarive to the other recognized methods in selected cases.%目的:评价氩激光治疗复发性倒睫的疗效和安全性.方法:Argon激光治疗18例(24眼)复发性倒睫,光斑50~200 u m,时间0.25~0.5s,能量400~800mW.部分倒睫用美蓝染色后治疗.治疗全过程无需麻醉,平均随访时间6.12mo.结果:经过1~4次氩激光治疗,其中83.33%痊愈.刺激症状消失或明显减轻.激光治疗次数与倒睫数量间明显相关.治疗6wk后所有患者无睑缘畸形和新生血管形成.结论:氩激光治疗复发性倒睫较其他治疗方法安全、有效、简便、副作用小.

  15. Long-term outcome following interstitial laser photocoagulation of benign cold thyroid nodules

    DEFF Research Database (Denmark)

    Døssing, Helle; Bennedbæk, Finn Noe; Hegedüs, Laszlo

    2011-01-01

    To evaluate the long-term efficacy of interstitial laser photocoagulation (ILP) in solitary benign thyroid nodules.......To evaluate the long-term efficacy of interstitial laser photocoagulation (ILP) in solitary benign thyroid nodules....

  16. Efficacy of Pattern Scan Laser photocoagulation for superficial conjunctival nevi ablation.

    Science.gov (United States)

    Park, Young Min; Lee, Ji-Eun; Lee, Jong Soo

    2016-07-01

    This study reports the efficacy and safety of Pattern Scan Laser (PASCAL) photocoagulation in the removal of superficial conjunctival nevi. Superficial conjunctival nevi were removed from 10 eyes of 10 patients using PASCAL. The laser spots were 200 μm in size, and the power delivered ranged from 250 to 300 mW. The duration of the laser pulse was kept at the minimum needed for adequate lesion removal. The duration of the laser pulse administered to the patients varied from 100 to 200 ms. Complete removal of the conjunctival nevus was observed in all the patients after PASCAL photocoagulation. Six months after treatment, complete re-epithelialization of the overlying conjunctiva was noted. No signs of recurrence or scarring were found in any of the patients during the follow-up period. Pure thermal denaturation is the main mechanism of PASCAL photocoagulation for removal of superficial conjunctival nevi. PASCAL can be considered as an alternative to conventional argon laser treatment or surgery. PMID:26914686

  17. Interstitial laser photocoagulation with diode laser unit in bovine liver

    International Nuclear Information System (INIS)

    To evaluate the extent of tissue coagulation during interstitial laser photocoagulation (ILP) in normal bovine liver, using a diode laser unit and various parameters, and to determine whether the procedure is applicable to clinical practice. Using an 18-gauge needle, experimental interstitial laser photocoagulation (ILP) was carried out in normal bovine liver. On the basis of differing parameters, three groups were established. For group 1, a single photofiber with laser power of 1, 3 and 5 watts and an exposure time of 60, 180, 300, 420 or 600 seconds was used. For groups 2 and 3, four needles were fixed at a distance of 1cm and 1.5cm ; in each case a needle fixation device was used, as well as a laser distributor for simultaneous laser exposure of photofibers. As a control, four photofibers were placed as for group 3, but to compare groups 2 and 3, each photofiber was exposed to a laser of 3 watts 300 seconds, without using a laser distributor. To evaluate the range of tissue coagulation, specimens were analyzed both with regard to cross-sectional gross findings and histopathologically. The largest diameter of thermal coagulation necrosis in Group 1 was 15 X 15mm, and this was ball-shaped. Coalescence of coagulation between each photofiber was observed in Group 2, and this was up to 25mm in diameter. In Group 3 and controls, coalescence was not found, though the extent of tissue coagulation increased with increasing wattage and exposure time. The extent of charring at the center of coagulation also increased with increasing wattage. Smoke bubbles emanating from the coagulation area were observed, and during ILP involving a single photofiber, increased from 3 watts, applied for 300 seconds. Using an 8-gauge needle and a diode laser ILP, we have shown that a range of tissue coagulation acutely ablates normal bovine liver. In selective cases, the procedure could be applied to clinical trials

  18. LASER PHOTOCOAGULATION IN DIABETIC MACULAR EDEMA: EFFECTS ON VISUAL ACUITY AND MACULAR EDEMA

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    M.H. Dehghan

    1999-06-01

    Full Text Available Due to the importance of clinically significant macular edema in diabetic patients, this study is aimed to determine if laser photocoagulation is effective in the treatment of clinically significant diabetic macular edema. In addition, the effects of risk factors arc surveyed* This is an existing data study considering patients with clinically significant diabetic macular edema, treated with argon-green laser photocoagulation in Labbafinejad hospital, department of lasertherapy, from 1995 to 1997. in 60 (42.6% eyes the treatment method was focal, in 22 (15.6% eyes grid, and in 59 (41.84 modified grid laser photocoagulation was performed. The results are based upon deterioration of visual acuity, occurance of moderate visual loss and improvement or persistence of CSME. We studied 114 eyes from 87 patients. Two years after initial treatment, visual acuity improved in 19.1% of eyes, unchanged in 9.5% and worsened in 71.4% of eyes. After this period the rate of moderate visual loss was 28.6% and CSME was improved in 23.8% of eyes. According to our study, baseline visual acuity and retinopathy severity were two important intervening factors in response to lasertherapy. Comparing our results with natural course of diabetic macular edema, indicates that in assessing visual outcome laser photocoagulation is an effective modality in treatment of CSME, but it is not effective in maintaining or improving visual acuity, which is due to patients delay in visiting ophthalmologists and paying not enough attention to follow-up visits.

  19. Optoacoustic online temperature determination during retinal laser photocoagulation

    Science.gov (United States)

    Schlott, Kerstin; Stalljohann, Jens; Weber, Benjamin; Kandulla, Jochen; Herrmann, Katharina; Birngruber, Reginald; Brinkmann, Ralf

    2007-07-01

    Retinal photocoagulation is an established treatment of different retinal diseases. The treatment relies on a short, local heating of the tissue which induces a denaturation. The resulting scar formation may for example prevent the further detachment of the retina. The extent of the coagulation is besides other parameters mostly dependent on the induced temperature increase. However, until today a temperature based dosimetry for photocoagulation does not exist. The dosage is rather based on the experience of the treating physicians to achieve visible whitish lesions on the retina. In this work a technique is presented, which allows an online temperature monitoring during photocoagulation. If an absorbing material is irradiated with short laser pulses, a thermoelastic expansion of the absorber induces an acoustic wave. Its amplitude is dependent on the temperature of the absorber. For analyzing the applicability of the optoacoustic temperature determination for dosimetry, measurements were performed on enucleated porcine eye globes. The pressure transients are detected by an ultrasonic transducer, which is embedded in an ophthalmologic contact lens. As long as no strong lesions occur, the determined temperatures are almost proportional to the power of the treatment laser. Using a spot diameter of 200 μm and different laser powers, the temperature rise at the end of the 400 ms irradiation was found to be approximately 0.16 °C/mW. The onset of the denaturation was observed around 50°C. The far aim of this project is an automatic regulation of the treatment laser onto a desired temperature course.

  20. Changes in colour contrast sensitivity associated with operating argon lasers.

    OpenAIRE

    Gündüz, K; Arden, G B

    1989-01-01

    A new test of colour vision using computer graphics has been used to obtain quantitative estimates of colour contrast sensitivity in ophthalmologists before and after they have treated patients by argon laser retinal photocoagulation. The colour vision of all subjects is normal when tested with the 100-hue test and HRR (Hardy, Rittler, Rand) plates, but colour contrast sensitivity measured along a tritan colour confusion line is selectively impaired after a treatment session. No such change o...

  1. Reversal of TTTS after fetoscopic laser photocoagulation for communicating vessels

    OpenAIRE

    Miyazaki, Masahide; Honda, Naotoshi; Yokoyama, Motofumi; Nakata, Masahiko

    2014-01-01

    We report a case of reversal of twin-to-twin transfusion syndrome (Stage IV TTTS) at 24  weeks of gestation after fetoscopic laser photocoagulation (FLP) for communicating vessels. The pathology of reversal of TTTS found that the ‘initial’ donor developed polyhydramnios whereas the ‘initial’ recipient developed oligohydramnios. With careful follow-up, the hydrops fetalis of the ‘initial’ recipient improved at 31 weeks of gestation. Because of the onset of labour pain at 34  weeks of gestation...

  2. Serous retinal detachment following panretinal photocoagulation (PRP) using Pattern Scan Laser (PASCAL) photocoagulator

    Science.gov (United States)

    Azar, Georges; Wolff, Benjamin; Cornut, Pierre-Loïc; Mauget-Faÿsse, Martine

    2012-01-01

    Objective: To report a case of serous retinal detachment after Pattern Scan Laser (PASCAL) treatment in a diabetic woman. Methods: A 34-year-old diabetic woman presented with florid diabetic retinopathy after a miscarriage during the 20th week of pregnancy. Her Best Corrected Visual Acuity (BCVA) was 20/40 right eye (OD) and 20/30 left eye (OS). Fundus exam showed multiple microaneurysms, large blot hemorrhages and venous dilation both eyes (OU). Fundus fluorescein angiography (FFA) revealed large areas of capillary nonperfusion and panretinal neovascularisation in all quadrants OU. Macular Spectral-Domain Optical Coherence Tomography scan (SD-OCT) did not show any foveal thickening. Panretinal photocoagulation (PRP) was immediately performed OU during the same day. Results: Two days after PASCAL treatment, her BCVA decreased to 20/80 OU and worsened to Count Fingers (CF) during the following days. Fundus exam revealed an extensive serous retinal detachment confirmed on SD-OCT. 2 sub-conjunctival injections of 0.1 ml Betamethasone were done OU. One month later, BCVA improved to 20/30 and SD-OCT confirmed regression of retinal detachment. Conclusions: PASCAL is considered to be a safe treatment, but one has to be aware of its potential side effects. It has to be used with caution in pregnant women.

  3. Experience with the Pascal® photocoagulator: An analysis of over 1200 laser procedures with regard to parameter refinement

    OpenAIRE

    Sheth, Saumil; Lanzetta, Paolo; Veritti, Daniele; Zucchiatti, Ilaria; Savorgnani, Carola; Bandello, Francesco

    2011-01-01

    Aim: To systematically refine and recommend parameter settings of spot size, power, and treatment duration using the Pascal® photocoagulator, a multi-spot, semi-automated, short-duration laser system. Materials and Methods: A retrospective consecutive series with 752 Caucasian eyes and 1242 laser procedures over two years were grouped into, (1) 374 macular focal / grid photocoagulation (FP), (2), 666 panretinal photocoagulation (PRP), and (3) 202 barrage photocoagulation (BP). Parameters for ...

  4. Posterior Pole Sparing Laser Photocoagulation Combined with Intravitreal Bevacizumab Injection in Posterior Retinopathy of Prematurity

    OpenAIRE

    2014-01-01

    Purpose. To report the results of the posterior pole sparing laser photocoagulation combined with intravitreal bevacizumab injection (IVB) in retinopathy of prematurity (ROP). Methods. A retrospective chart review of premature babies with ROP, all of whom received laser photocoagulation with IVB. Eleven eyes of 6 infants with advanced zone I ROP underwent laser ablation sparing posterior pole with concurrent IVB. The results were compared with those of full-laser treatment combined with IVB t...

  5. Congenital retinoschisis : successful collapse with photocoagulation.

    OpenAIRE

    Gopal L; Shanmugam M; Battu R; Shetty N

    2001-01-01

    We report a case of progressive congenital retinoschis is where the schisis cavity collapsed following argon laser photocoagulation. Despite reports to the contrary, we feel that in the absence of significant vitreous or inner layer traction, photocoagulation applied as light burns in the schisis cavity may be beneficial in collapsing the cavity. Whether or not this collapse of the schisis cavity reduces the risk of rhegmatogenous retinal detachment is unclear.

  6. Congenital retinoschisis : successful collapse with photocoagulation.

    Directory of Open Access Journals (Sweden)

    Gopal L

    2001-01-01

    Full Text Available We report a case of progressive congenital retinoschis is where the schisis cavity collapsed following argon laser photocoagulation. Despite reports to the contrary, we feel that in the absence of significant vitreous or inner layer traction, photocoagulation applied as light burns in the schisis cavity may be beneficial in collapsing the cavity. Whether or not this collapse of the schisis cavity reduces the risk of rhegmatogenous retinal detachment is unclear.

  7. Interstitial laser photocoagulation (ILP) of benign cystic thyroid nodules--a prospective randomized trial

    DEFF Research Database (Denmark)

    Døssing, Helle; Bennedbæk, Finn Noe; Hegedüs, Laszlo

    2013-01-01

    Recurrence rate, after aspiration, in cystic thyroid nodules is very high. Interstitial laser photocoagulation (ILP) is a minimally invasive procedure that reduces the need for surgery in patients with a benign solid thyroid nodule.......Recurrence rate, after aspiration, in cystic thyroid nodules is very high. Interstitial laser photocoagulation (ILP) is a minimally invasive procedure that reduces the need for surgery in patients with a benign solid thyroid nodule....

  8. Low-power interstitial laser photocoagulation for breast cancer

    Science.gov (United States)

    Harries, Simon A.; Amin, Zahir; Lees, William R.; Cooke, J.; Smith, Mark; Cook, Martin; Scurr, John H.; Kissin, Mark W.; Bown, Stephen G.

    1994-02-01

    Interstitial laser photocoagulation (ILP) is a new minimally invasive technique which can produce localized necrosis in the center of solid organs. Breast cancer can now be treated safely in selected patients by lumpectomy followed by radiotherapy. Taking the concept of conservative treatment a step further would it be possible to destroy breast cancers in situ leaving the area to heal by resorption and fibrosis? Thirty seven patients with early breast cancer scheduled for surgery underwent ILP in the interval between diagnosis and surgery. The technique was performed under local anaesthesia, and ultrasound (US) used to place an optical fiber into the tumor. Treatment was curtailed in 4 patients because of pain. Thermal necrosis varied from 2 - 25 mm as measured microscopically but in 4 patients no necrosis was evident. No complications arose as a result of treatment. When charring was present in the excised tumor a larger diameter of necrosis was evident than when charring was absent (mean 15 mm vs 5 mm) and a study in 10 patients using a pre-charred fiber produced a more predictable and larger diameter of necrosis (mean 17 mm). Ultrasound did not accurately predict the extent of laser induced necrosis (although it was better at predicting tumor size).

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

    Science.gov (United States)

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

    2015-06-01

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

  10. Macular grid photocoagulation. An experimental study on the primate retina

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, D.J.; Finkelstein, D.; Quigley, H.A.; Green, W.R.

    1988-01-01

    We studied the effect of macular grid photocoagulation on the retinal vessels, retina, retinal pigment epithelium, and choroid of normal cynomolgus monkeys. Argon blue-green laser photocoagulation, similar to that employed for treating macular edema due to branch retinal vein occlusion, resulted in a decreased retinal capillary area at both one and five months after treatment. The photoreceptors and retinal pigment epithelium between laser lesions were altered at three days after treatment, but their appearance returned to normal by five months. The significance of these findings is discussed with regard to resolution of macular edema and improvement in vision following grid photocoagulation.

  11. Percutaneous laser photocoagulation of osteoid osteoma: Assessment of treatment in nine cases

    International Nuclear Information System (INIS)

    Background: Osteoid osteoma is a benign bony neoplasm and its classic treatment is surgery. In the recent decades percutaneous laser therapy was suggested to be replaced by surgery. In this study we have reviewed the results of the first applications of interstitial laser photocoagulation for treatment of osteoid osteoma in Iranian patients. Materials and methods: In this case series study, we evaluated 9 known cases of osteoid osteoma that were referred for interstitial laser photocoagulation from orthopedic section of Imam Khomeini Hospital during 2001 and 2002. Diagnosis was confirmed by plain x-ray, cat scanning, isotope and MR scan. Interstitial laser photocoagulation was done by interventional radiologists of Medical Imaging Center. Percutaneous interstitial laser photocoagulation was performed by Nd-Yag laser, using 400-1000 joules energy (according to nidus size) and adjusting on 2 watts power. Results: The procedure was successful in all patients. We had pain relief in 24 hours. Follow up from 5 months to one year showed no recurrence. Conclusion: The procedure is a safe and effective method for patients and could be applied for proper cases

  12. Argon laser trabeculoplasty

    International Nuclear Information System (INIS)

    It was demonstrated in a pilot study in 1979 that intraocular pressure could be lowered by applying multiple small laser burns to the trabecular meshwork with a minimum of side effects. Concern was expressed in this study over the intraocular pressure elevation that may occur immediately after the procedure. Glaucoma patients were treated with a modification of the original technique, attempting to retain a pressure lowering effect, whereas at the same time reducing the deleterious effects of raised intraocular pressure and possible destruction of functioning meshwork. (Auth.)

  13. Retro-Mode Scanning Laser Ophthalmoscopy Planning for Navigated Macular Laser Photocoagulation in Macular Edema.

    Science.gov (United States)

    Boiko, Ernest V; Maltsev, Dmitrii S

    2016-01-01

    Purpose. To compare treatment areas and navigated macular laser photocoagulation (MLP) plans suggested by retro-mode scanning laser ophthalmoscopy (RM-SLO) image versus optical coherence tomography (OCT) central retinal thickness map and treatment planning among retina specialists. Methods. Thirty-nine eyes with diabetic or branch retinal vein occlusion-related ME undergoing navigated MLP with navigated photocoagulator had OCT and RM-SLO taken. OCT map and RM-SLO image were imported to the photocoagulator and aligned onto the retina. Two retina specialists placed laser spot marks separately based on OCT and RM-SLO images in a random fashion. The spots placed by each physician were compared between OCT and RM-SLO and among physicians. The areas of retinal edema on OCT and RM-SLO of the same eye were also compared. Results. The average number of laser spots using RM-SLO and OCT template was 189.6 ± 77.4 and 136.6 ± 46.8, respectively, P = 0.003. The average area of edema on RM-SLO image was larger than that on OCT map (14.5 ± 3.9 mm(2) versus 10.3 ± 2.8 mm(2), P = 0.005) because of a larger scanning area. There was narrow variability in treatment planning among retina specialists for both RM-SLO (P = 0.13) and OCT (P = 0.19). Conclusion. The RM-SLO image superimposed onto the fundus of the same eye can be used to guide MLP with narrow variability in treatment planning among retina specialists. The treatment areas suggested by RM-SLO-guided MLP plans for ME were shown to be larger than those suggested by OCT-guided plans. PMID:26989498

  14. Outcomes of diode laser photocoagulation for aggressive posterior retinopathy of prematurity

    OpenAIRE

    Arvas, Sema; Akar, Solmaz; Sarıcı, Ahmet; Uçar, Didar

    2012-01-01

    Aim: Agressive posterior retinopathy of prematurity is a special subtype of retinopathy of prematurity Accurate and timely diagnosis and treatment could prevent further ocular and visual morbidity In this study we aimed to evalute the outcomes of agressive posterior retinopathy of prematurity treated with diode laser photocoagulation Material and Method: Records of preterm infants who were diagnosed as agressive posterior retinopathy of prematurity and treated with diode laser photocoagulatio...

  15. Clinical periodontics with the argon laser

    Science.gov (United States)

    Finkbeiner, R. L.

    1995-04-01

    The argon laser has proven to be a valuable tool for the thermodynamic debridement of the periodontal lesion, incisions and tissue fusion. Illustrations of clinical applications and discussion of laser parameters will be provided.

  16. Posterior Pole Sparing Laser Photocoagulation Combined with Intravitreal Bevacizumab Injection in Posterior Retinopathy of Prematurity

    Directory of Open Access Journals (Sweden)

    Rebecca Kim

    2014-01-01

    Full Text Available Purpose. To report the results of the posterior pole sparing laser photocoagulation combined with intravitreal bevacizumab injection (IVB in retinopathy of prematurity (ROP. Methods. A retrospective chart review of premature babies with ROP, all of whom received laser photocoagulation with IVB. Eleven eyes of 6 infants with advanced zone I ROP underwent laser ablation sparing posterior pole with concurrent IVB. The results were compared with those of full-laser treatment combined with IVB to 8 eyes of 5 infants with advanced ROP without involvement of the posterior pole. Results. The posterior pole sparing laser with IVB was performed with zone I, stage 3+ ROP at the mean postmenstrual age of 36 weeks and 5 days. The plus sign decreased significantly at postoperative day 1, the neovascular proliferation regressed by postoperative week 1, and the normal vascularization started at postoperative day 32 on the average. Two months after treatment, vascularization of the spared avascular area was completed. There was no macular dragging, tractional retinal detachment, foveal destruction by laser scars, or any other adverse event. No significant anatomical differences were identified from those of full-laser ablation combined with IVB. Conclusions. Posterior pole sparing laser with IVB can give favorable results without destruction of posterior pole retina.

  17. Comparison of pain scores between patients undergoing panretinal photocoagulation using navigated or pattern scan laser systems

    Directory of Open Access Journals (Sweden)

    Umit Ubeyt Inan

    2016-02-01

    Full Text Available ABSTRACT Purpose: To compare the pain responses of patients with proliferative diabetic retinopathy (PDR undergoing panretinal photocoagulation (PRP using either pattern scan laser (PASCAL or navigated laser photocoagulation (NAVILAS. Methods: Patients diagnosed with PDR were randomly assigned to undergo either PASCAL or NAVILAS photocoagulation treatment. PRP was performed using the multi-shot mode with a spot size of 200-400 µm and a pulse duration of 30 ms to obtain a white-grayish spot on the retina. Parameters were identical in both procedures. After 30 min of PRP application, patients were asked to verbally describe their pain perception as either "none," "mild," "moderate," "severe," or "very severe" using a verbal rating scale (VRS and visual analog scale (VAS by indicating a score from "0" to "10," representing the severity of pain from "no pain" to "severe pain." Results: A total of 60 eyes of 60 patients (20 females and 40 males diagnosed with PDR were treated. The mean age of patients was 62.22 ± 9.19 years, and the mean diabetes duration was 195.47 ± 94.54 months. The mean number of laser spots delivered during PRP was 389.47 ± 71.52 in the NAVILAS group and 392.70 ± 54.33 in the PASCAL group (p=0.57. The difference in pain responses between patients in the NAVILAS and PASCAL groups was significant with regard to the mean VRS (1.10 ± 0.67 and 1.47 ± 0.69, respectively; p=0.042 and mean VAS (2.13 ± 1.17 and 2.97 ± 1.35, respectively; p=0.034 scores. Conclusions: Pain responses in patients undergoing PRP with a 30-ms pulse duration were significantly milder in the NAVILAS group than in the PASCAL group.

  18. Factors affecting reading speed in patients with diabetic macular edema treated with laser photocoagulation.

    Directory of Open Access Journals (Sweden)

    Elizabeth Pearce

    Full Text Available PURPOSE: To study the factors that may affect reading speed in patients with diabetic macular edema previously treated with laser photocoagulation. METHODS: Consecutive patients with type II diabetes treated with laser photocoagulation for diabetic macular edema (DME at least twelve months previously, with best corrected visual acuity of better than 65 letters (approximately 20/40 measured with Early Treatment Diabetic Retinopathy Study (ETDRS charts were included in this study. Patients previously treated with pan-retinal photocoagulation, vitrectomy, intravitreal steroid or anti-VEGF therapy were excluded. Any other ocular co-morbidities that may influence reading ability such as cataract, glaucoma or macular degeneration were also excluded. All patients were refracted by a certified examiner, the following measurements were collected: best corrected visual acuity (BCVA, contrast sensitivity with Pelli-Robson chart, reading speed with MNREAD chart, microperimetry with Nidek MP1, and central subfield thickness with Zeiss spectral domain optical coherent topography. RESULTS: The slow reading group had poorer contrast sensitivity (p = 0.001, reduced retinal sensitivity (p = 0.027 and less stable fixation (p = 0.013. Most interestingly the reduced retinal sensitivity findings were driven by the microperimetry value on the right subfield (p = 0.033, (nasal to the fovea in the right eye and temporal to the fovea in the left eye. Multiple linear regression analysis showed that contrast sensitivity is probably the most important factor that affects reading speed (p = 0.001. CONCLUSION: Reduced retinal sensitivity after laser treatment is associated with reduced reading speed in patients with diabetic macular edema.

  19. Anatomical and Refractive Results of Diode Laser Photocoagulation in Retinopathy of Prematurity

    Directory of Open Access Journals (Sweden)

    K. Sadeghi

    2012-04-01

    Full Text Available Introduction & Objective: Retinopathy of prematurity (ROP is a major cause of blindness in premature newborns. It accounts for 4% of childhood blindness in developed countries and up to 40% in developing countries. The aim of this study is to report the refractive and anatomical outcome of patients who had undergone laser photocoagulate on for retinopathy of prematurity (ROP.Materials & Methods: In this cross sectional study, a total of forty eyes of twenty patients who had undergone transscleral diode laser photocoagulation for ROP between 2004-2008 were studied for the following measures: grade of ROP pre- and postoperatively, birth weight, gestational age, perioperative and postoperative complications, and current refraction.Results: Mean birth weight of patients was 923±271 gr and mean gestational age was 27.3±2.6 wk. All eyes had threshold ROP and responded to laser treatment with regression of ROP. Perioperative complications included hemorrhages in 15% that resorbed spontaneously. The mean age of patients at the time of examination for this study was 4.13±1.30 yr and their anatomical status of retina was normal. Strabismus (more than 20 prism diopter was found in 10% of patients. The spherical equivalent of refraction at the time of examination was -2.31±3.38 diopter.Conclusion: Photocoagulation for ROP in our patients resulted in regression of threshold ROP. In addition, the analyses of refractive outcome demonstrated a predominance of myopia and astigmatism.(Sci J Hamadan Univ Med Sci 2012;19(1:22-26

  20. Krypton laser photocoagulation for neovascular lesions of age-related macular degeneration. Results of a randomized clinical trial. Macular Photocoagulation Study Group.

    Science.gov (United States)

    1990-06-01

    The Age-Related Macular Degeneration Study-Krypton Laser (AMDS-K) is a multicenter controlled clinical trial designed to determine whether krypton red laser photocoagulation is of value in preventing visual acuity loss in eyes with macular degeneration that have either choroidal neovascularization 1 to 199 microns from the center of the foveal avascular zone or choroidal neovascularization 200 microns or farther from the foveal avascular zone center with blood and/or blocked fluorescence extending within 200 microns of the foveal avascular zone center. Recruitment ended in December 1987 after 247 patients had been assigned to photocoagulation and 249 patients had been assigned to no treatment. At 3 years after randomization, 49% (86/174) of treated eyes, in contrast to 58% (98/169) of untreated eyes, had lost six or more lines of visual acuity. The average visual acuity of treated and untreated eyes at that time was 20/200 and 20/250, respectively. The benefit of laser treatment was largest among patients without evidence of hypertension and diminished to no apparent benefit among patients who had highly elevated blood pressure and/or used antihypertensive medication. Treatment of lesions meeting the AMDS-K eligibility criteria in eyes of patients with no hypertension is recommended. However, treatment cannot be recommended uniformly for patients with definite hypertension having lesions similar to those of patients enrolled in the AMDS-K. PMID:1693496

  1. Recurrent twin-twin transfusion syndrome after selective fetoscopic laser photocoagulation: a systematic review of the literature.

    LENUS (Irish Health Repository)

    Walsh, C A

    2012-11-01

    Selective fetoscopic laser photocoagulation (SFLP) is now the treatment of choice for twin-twin transfusion syndrome (TTTS). The incidence of recurrent TTTS following SFLP has been inconsistently reported across different studies. We performed a systematic review of TTTS recurrence following SFLP.

  2. Devices for the control of laser transmission across the sclera during transscleral photocoagulation.

    Science.gov (United States)

    Rol, P; Barth, W; Schwager, M; Zuber, N; Fankhauser, F; Fankhauser, S; Niederer, P

    1992-07-01

    Improving the reproducibility of transscleral photocoagulation necessitates controlling the transmission of the laser beam through the sclera. Two factors make such control problematic: the locally increased transparency of the sclera resulting from the contact procedure and the occurrence of time-related relaxation phenomena. Two instruments have been devised to help control these factors. The first is a mechanical compensation unit comprised of magnets and a spring that allows the force exerted on the sclera to be adjusted to between 0.1 and 0.4 N, the pressure being determined by the outer diameter of the contact tip. The second instrument monitors the portion of the aiming beam reflected by the sclera as a means of determining the exact level of power actually transmitted through it. This information theoretically could be fed back to the treatment laser, allowing the level of power being delivered to be adjusted accordingly. PMID:1407942

  3. Argon Laser Treatment of Strawberry Hemangioma in Infancy

    OpenAIRE

    Achauer, Bruce M.; Vander Kam, Victoria M.

    1985-01-01

    Argon laser therapy is effective for removing port-wine stains and for reducing cutaneous vascular and pigmented lesions. Strawberry hemangiomas, being much thicker lesions than port-wine stains, were considered not appropriate for argon laser treatment. Using argon laser therapy in 13 cases of strawberry hemangioma, we achieved poor to dramatic results.

  4. Experience with the Pascal® photocoagulator: An analysis of over 1200 laser procedures with regard to parameter refinement

    Directory of Open Access Journals (Sweden)

    Sheth Saumil

    2011-01-01

    Full Text Available Aim: To systematically refine and recommend parameter settings of spot size, power, and treatment duration using the Pascal® photocoagulator, a multi-spot, semi-automated, short-duration laser system. Materials and Methods: A retrospective consecutive series with 752 Caucasian eyes and 1242 laser procedures over two years were grouped into, (1 374 macular focal / grid photocoagulation (FP, (2, 666 panretinal photocoagulation (PRP, and (3 202 barrage photocoagulation (BP. Parameters for power, duration, spot number, and spot size were recorded for every group. Results: Power parameters for all groups showed a non-gaussian distribution; FP group, median 190 mW, range 100 - 950 mW, and PRP group, median 800 mW, range 100 - 2000 mW. On subgroup comparison, for similar spot size, as treatment duration decreased, the power required increased, albeit in a much lesser proportion than that given by energy = power x time. Most frequently used patterns were single spot (89% of cases in FP, 5 Χ 5 box (72% in PRP, and 2 Χ 2 box (78% in BP. Spot diameters as high as ≈ 700 μm on retina were given in the PRP group. Single session PRP was attempted in six eyes with a median spot count of 3500. Conclusion: Overall, due to the small duration of its pulse, the Pascal® photocoagulator tends to use higher powers, although much lower cumulative energies, than those used in a conventional laser. The consequent lesser heat dissipation, especially lateral, can allow one to use relatively larger spot sizes and give more closely spaced burns, without incurring significant side effects.

  5. Experience with the Pascal® photocoagulator: An analysis of over 1200 laser procedures with regard to parameter refinement

    Science.gov (United States)

    Sheth, Saumil; Lanzetta, Paolo; Veritti, Daniele; Zucchiatti, Ilaria; Savorgnani, Carola; Bandello, Francesco

    2011-01-01

    Aim: To systematically refine and recommend parameter settings of spot size, power, and treatment duration using the Pascal® photocoagulator, a multi-spot, semi-automated, short-duration laser system. Materials and Methods: A retrospective consecutive series with 752 Caucasian eyes and 1242 laser procedures over two years were grouped into, (1) 374 macular focal / grid photocoagulation (FP), (2), 666 panretinal photocoagulation (PRP), and (3) 202 barrage photocoagulation (BP). Parameters for power, duration, spot number, and spot size were recorded for every group. Results: Power parameters for all groups showed a non-gaussian distribution; FP group, median 190 mW, range 100 – 950 mW, and PRP group, median 800 mW, range 100 – 2000 mW. On subgroup comparison, for similar spot size, as treatment duration decreased, the power required increased, albeit in a much lesser proportion than that given by energy = power × time. Most frequently used patterns were single spot (89% of cases) in FP, 5 × 5 box (72%) in PRP, and 2 × 2 box (78%) in BP. Spot diameters as high as ≈ 700 μm on retina were given in the PRP group. Single session PRP was attempted in six eyes with a median spot count of 3500. Conclusion: Overall, due to the small duration of its pulse, the Pascal® photocoagulator tends to use higher powers, although much lower cumulative energies, than those used in a conventional laser. The consequent lesser heat dissipation, especially lateral, can allow one to use relatively larger spot sizes and give more closely spaced burns, without incurring significant side effects. PMID:21350276

  6. Cooperative phenomena in two-pulse, two-color laser photocoagulation of cutaneous blood vessels.

    Science.gov (United States)

    Barton, J K; Frangineas, G; Pummer, H; Black, J F

    2001-06-01

    A novel laser system has been developed to study the effects of multiple laser pulses of differing wavelengths on cutaneous blood vessels in vivo, using the hamster dorsal skin flap preparation and in vitro, using cuvettes of whole or diluted blood. The system permits sequenced irradiation with well-defined intrapulse spacing at 532 nm, using a long-pulse frequency-doubled Nd:YAG laser, and at 1064 nm, using a long-pulse Nd:YAG laser. Using this system, we have identified a parameter space where two pulses of different wavelengths act in a synergistic manner to effect permanent vessel damage at radiant exposures where the two pulses individually have little or no effect. Using a two-color pump-probe technique in vitro, we have identified a phenomenon we call greenlight-induced infrared absorption, where a pulse of green light causes photochemical and photothermal modifications to the chemical constituents of blood and results in enhanced infrared absorption. We identify a new chemical species, met-hemoglobin, not normally present in healthy human blood but formed during laser photocoagulation which we believe is implicated in the enhanced near-infrared absorption. PMID:11421070

  7. Argon laser application to endodontics

    Science.gov (United States)

    Blankenau, Richard J.; Ludlow, Marvin; Anderson, David

    1993-07-01

    The application of laser technology to endodontics has been studied for some time. At the present time several major problems are being investigated: (1) removal of infected tissues, (2) sterilization of canals, (3) obturation of canals, and (4) preservation of the vitality of supporting tissues. This list is not intended to imply other problems do not exist or have been solved, but it is a starting point. This paper reviews some of the literature that relates to laser applications to endodontics and concludes with some of the findings from our investigation.

  8. Argon laser irradiation of the otolithic organ

    Energy Technology Data Exchange (ETDEWEB)

    Okuno, T.; Nomura, Y.; Young, Y.H.; Hara, M. (Univ. of Tokyo (Japan))

    1990-12-01

    An argon laser was used to irradiate the otolithic organs of guinea pigs and cynomolgus monkeys. After stapedectomy, the argon laser (1.5 W x 0.5 sec/shot) irradiated the utricle or saccule without touching the sensory organs. The stapes was replaced over the oval window after irradiation. The animals used for acute observation were killed immediately for morphologic studies; those used for long-term observation were kept alive for 2, 4, or 10 weeks. Acute observation revealed that sensory and supporting cells were elevated from the basement membrane only in the irradiated area. No rupture of the membranous labyrinth was observed. Long-term observation revealed that the otolith of the macula utriculi had disappeared in 2-week specimens. The entire macula utricili had disappeared in 10-week specimens. No morphologic changes were observed in cochlea, semicircular canals, or membranous labyrinth. The saccule showed similar changes.

  9. Cyclo-photocoagulation in the management of aphakic glaucoma

    International Nuclear Information System (INIS)

    Transpupillary argon laser photocoagulation of the ciliary processes (TALC) through a widely dilated pupil, with or without cerebral depression, has been used in the management of glaucoma in aphakic eyes for a number of years. 58% of glaucoma in aphakics treated with TALC showed sustained and meaningful intraocular pressure reduction 2 months to 5 years after the procedure. Clinically, the TALC procedure is a relatively safe, effective, and an useful alternative approach in the management of selected cases of glaucoma in aphakics. (Auth.)

  10. Management of peripheral polypoidal choroidal vasculopathy with intravitreal bevacizumab and indocyanine green angiography-guided laser photocoagulation

    Directory of Open Access Journals (Sweden)

    Pukhraj Rishi

    2012-01-01

    Full Text Available A 69-year-old lady presented with complaints of decreased vision in left eye since one month. Best Corrected Visual Acuity (BCVA was 6/18 in that eye. Fundus examination revealed non-central geographic atrophy and soft drusens at macula in both eyes. Temporal periphery of left eye revealed subretinal exudates with altered sub-RPE hemorrhage mimicking peripheral exudative hemorrhagic chorioretinopathy (PEHCR. Fundus Fluorescein Angiogram showed window defects at macula and blocked fluorescence at temporal periphery in left eye. However, Indocyanine green angiography (ICGA revealed active peripheral choroidal polyps. The patient was successfully treated with intravitreal bevacizumab and ICGA-guided laser photocoagulation. 27 months after laser treatment, BCVA improved to 6/9. Rationale of consecutive anti-vascular endothelial growth factor (VEGF treatment followed by more definitive laser photocoagulation is that anti-VEGF aids in resolution of subretinal fluid, thus making the polyp more amenable to focal laser photocoagulation which stabilizes the choroidal vasculature and prevents further leakage.

  11. Argon laser-welded arteriovenous anastomoses.

    Science.gov (United States)

    White, R A; Kopchok, G; Donayre, C; White, G; Lyons, R; Fujitani, R; Klein, S R; Uitto, J

    1987-11-01

    This study compared the healing of laser-welded and sutured canine femoral arteriovenous anastomoses. Arteriovenous fistulas 2 cm in length were created bilaterally in the femoral vessels of 10 dogs and were studied at 1 (n = 2), 2 (n = 2), 4 (n = 3), and 8 (n = 3) weeks. In each animal, one anastomosis (control) was closed with running 6-0 polypropylene sutures, and the contralateral anastomosis (experimental) was sealed with an argon laser (0.5 watt, 4 minutes of exposure, 1830 J/cm2/1 cm length of anastomosis). At removal all experimental anastomoses were patent without hematomas, aneurysms, or luminal narrowing. Histologic examination at 4 weeks revealed that laser-welded anastomoses had less inflammatory response and almost normal collagen and elastin reorientation. At 8 weeks sutured anastomoses had significant intimal hyperplasia whereas laser repairs had normal luminal architecture. Tensile strength and collagen production, measured by the synthesis of hydroxyproline and the steady-state levels of type I and type III procollagen messenger ribonucleic acids, at the anastomoses and in adjacent vein and artery specimens were similar in sutured and laser-welded repairs at 2, 4, and 8 weeks. We conclude that argon laser welding of anastomoses is an acceptable alternative to suture techniques, with the advantage of improved healing without foreign body response and possible diminished intimal hyperplasia at the anastomotic line. PMID:3312648

  12. The evaluation of efficacy of subtenon triamcinolone injection combined with focal laser photocoagulation in diabetic macular edema

    Directory of Open Access Journals (Sweden)

    Hüseyin Öksüz

    2012-06-01

    Full Text Available Objectives: The aim of this study was to investigate efficacyand safety of subtenon triamcinolone (ST in combinationwith focal laser photocoagulation in diabetic macularedema (DME.Materials and methods: Medical records of patients withDME, treated with 40 mg subtenon injection of triamcinoloneacetonid prior to focal laser photocoagulation wereretrospectively analyzed. Seventeen eyes of 17 patientswith DME were enrolled in the study. All patients underwenta comprehensive ophthalmological examinationbefore the treatment. Efficacy of the treatment after STinjection was evaluated by visual acuity and flouresceinangiography (FA. Follow-up visits were performed at 1st,3rd, 6th and 12th months. Repeated measures ANOVA wasused for statistical analysis.Results: The mean age was 61.5 ± 8.7 years and themean visual acuity in the study eyes was 0.22 ± 0.13 beforethe treatment, 0.39 ± 0.15 at 1st month, 0.36 ± 0.18at 3rd month, 0.33 ± 0.15 at 6th month and 0.34 ± 0.16 at12th month. The differences in the visual acuity before thetreatment and follow-up visits were significant (p ˂0.05.Visual acuity was increased in 13 (%76,4 patients, decreasedin 1 (%5,8 and unchanged in 3 (%17,6.Conclusion: Injection of 40 mg of triamsinolon via subtenonroute combined with focal laser photocoagulation isa safe and beneficial treatment in cases of DME

  13. Short Pulse Duration High-Power Laser Photocoagulation during Vitrectomy for Diabetic Retinopathy Reduces Postoperative Inflammation.

    Directory of Open Access Journals (Sweden)

    Masahiko Sugimoto

    Full Text Available The aim of this preliminary study was to determine the effectiveness of short pulse duration, high-power laser photocoagulation (PC during vitrectomy for diabetic retinopathy (DR.The effects of short pulse duration PC with power of 340-360 mW and duration of 0.02 second were compared to conventional PC with power of 120-150 mW and duration of 0.2 second. The degree of inflammation was quantified by laser flare cell photometry before and at 1 day, 1 week, 4 week, and 12 weeks postoperatively. Twenty-two eyes of 22 consecutive patients were studied. Ten eyes were treated with short pulse duration PC and 12 eyes with conventional PC. The total energy was significantly lower in the short pulse duration PC group than in the conventional PC group (P = 0.007. The flare cell values were not significantly different between the two groups after 1 day, but at 1 week, the flare cell value was significantly lower in the short pulse duration PC group than in the conventional PC group (P = 0.04. This difference was also present at 4 and 12 weeks (P<0.05. The significant lower inflammation after short pulse duration PC than conventional PC indicates that the short pulse duration PC protocol should be considered to treat DR.

  14. Large vessel sealing with the argon laser.

    Science.gov (United States)

    White, R A; Kopchok, G; Donayre, C; Lyons, R; White, G; Klein, S R; Pizzurro, D; Abergel, R P; Dwyer, R M; Uitto, J

    1987-01-01

    This study compared the histology, biochemistry, and tensile strength of laser-welded and sutured canine venotomies, arteriotomies, and arteriovenous fistulas. Twelve animals had bilateral femoral vessels studied, with one repair (control) closed with interrupted 6-0 polypropylene sutures, and the contralateral repair (experimental) welded with the argon laser. Specimens were examined at weekly intervals from 1 to 4 weeks (four animals for each type of repair), and were evaluated histologically by hematoxylin and eosin, elastin, and trichrome stains; biochemically by the formation of [3H]hydroxyproline as an index of collagen synthesis; and mechanically by tensile strength determinations. At removal, all experimental closures were patent without hematomas, aneurysms, or luminal dilatation. Histologic and biochemical examination and tensile strength determinations suggest that laser welding may be an alternative to sutures for repair of large-diameter venotomies, arteriotomies, and arteriovenous fistulas, as healing is comparable to that seen with suture repairs up to 4 weeks postoperatively. PMID:3306233

  15. Vascular Welding Using The Argon Laser

    Science.gov (United States)

    White, Rodney A.; Donayre, Carlos; Kopchok, George; White, Geoffrey; Abergel, R. Patrick; Lyons, Richard; Klein, Stanley; Dwyer, Richard; Uitto, Jouni

    1987-03-01

    This study compared the histology, biochemistry, and tensile strength of laser welded and sutured canine venotomies, arteriotomies and arteriovenous fistulas. Bilateral femoral, carotid or jugular vessels were studied with one repair (control) closed with interrupted 6-0 polypropylene sutures, and the contralatral repair (experimental) welded with the argon laser. Specimens were examined at weekly intervals from 1 to 4 weeks for each type of repair and evaluated histologically by hematoxylineosin, elastin and trichrome stains, biochemically by the formation of [3H] hyaroxyproline as an index of collagen synthesis, ana mechanically by tensile strength determinations. At removal, all experimental closures were patent without hematomas, aneurysms or luminal dilatation. Histologic and biochemical examination and tensile strength determinations suggest that laser welaing may be an alternative to sutures for repair of large diameter venotomies, arteriotomies and arteriovenous fistulas, as they heal comparable to suture repairs up to 4 weeks postoperatively.

  16. Subthreshold diode-laser micropulse photocoagulation as a primary and secondary line of treatment in management of diabetic macular edema

    Directory of Open Access Journals (Sweden)

    Othman IS

    2014-03-01

    Full Text Available Ihab Saad Othman,1 Sherif Ahmed Eissa,1 Mohamed S Kotb,1 Sherin Hassan Sadek21Cairo University, Cairo, 2Fayoum University, Al Fayoum, EgyptBackground: The purpose of this study was to evaluate subthreshold diode-laser micropulse (SDM photocoagulation as a primary and secondary line of treatment for clinically significant diabetic macular edema (CSDME.Methods: In this prospective nonrandomized case series, 220 cases of nonischemic CSDME were managed primarily and secondarily by SDM photocoagulation on a 15% duty cycle with a mean power of 828 mW and a spot size of 75–125 µm. SDM treatment was repeated at 3–4-month intervals if residual leakage was observed. Additional intravitreal pharmacologic therapy was used according to the response. Follow-up varied from 12 to 19 (mean 14±2.8 months. Novel software designed by the authors was used to record the subvisible threshold laser applications and their parameters on the fundus image of the eye. Evaluation of the results of treatment was done using fluorescein angiography and optical coherence tomography (OCT. Primary outcome measures included changes in visual acuity and foveal thickness at OCT. Secondary outcome measures included visual loss of one or more Snellen lines and laser scars detectable on fundus biomicroscopy or fluorescein angiography.Results: In the primary treatment group, there was significant improvement or stabilization of visual acuity after the first 3–4 months, which was stable thereafter. Visual acuity was stable in the secondary treatment group. A corresponding reduction of macular thickness on OCT was noted during the follow-up period in both groups. Additional therapy included repeat SDM photocoagulation, intravitreal injection of triamcinolone, and pars plana vitrectomy. Laser marks seen as changes in retinal pigment epithelium on fundus biomicroscopy and fluorescein angiography were noted in 3.3% and 5.7% of cases. Our novel software could accurately record the

  17. Computer-aided retinal photocoagulation system

    Science.gov (United States)

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

    1996-01-01

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

  18. Efficacy and safety of green laser photocoagulation for threshold retinopathy of prematurity Eficácia e segurança da fotocoagulação com laser verde na retinopatia da prematuridade limiar

    OpenAIRE

    Rodrigo Pessoa Cavalcanti Lira; Antônio Bezerra de Melo Calheiros; Manuela Maria Valença Cordeiro Barbosa; Cristiano Viana de Oliveira; Sabrina Lima Siqueira Viana; Danielle Cabral Lima

    2008-01-01

    PURPOSE: To report the efficacy and safety of green laser photocoagulation for threshold retinopathy of prematurity (ROP). METHODS: We reviewed the clinical records of the neonates who had undergone green laser photocoagulation for threshold ROP at the Federal University of Pernambuco in Brazil between January 2004 and January 2006. All procedures were conducted with local anesthetic drops. The neonates were monitored throughout the procedure by a neonatologist. A frequency-doubled solid stat...

  19. Argon laser induced changes to the carbonate content of enamel

    Energy Technology Data Exchange (ETDEWEB)

    Ziglo, M.J. [Orthodontic Graduate Program, Faculty of Medicine and Dentistry, University of Alberta, Private Practice, Regina, Saskatchewan (Canada); Nelson, A.E., E-mail: aenelson@dow.com [Department of Chemical and Materials Engineering, Faculty of Engineering, University of Alberta (Canada); Heo, G.; Major, P.W. [Orthodontic Graduate Program, Faculty of Medicine and Dentistry, University of Alberta (Canada)

    2009-05-15

    Argon laser irradiation can be used to cure orthodontic brackets onto teeth in significantly less time than conventional curing lights. In addition, it has been shown that the argon laser seems to impart a demineralization resistance to the enamel. The purpose of this study was to use surface science techniques to ascertain if this demineralization resistance is possibly a result of a decrease in the carbonate content of enamel. Eleven mandibular third molars previously scheduled for extraction were collected and used in the present study. The teeth were sectioned in two and randomly assigned to either the argon laser (457-502 nm; 250 mW cm{sup -2}) or the control (no treatment) group. The sections assigned to the argon laser group were cured for 10 s and analyzed. To exaggerate any potential changes the experimental sections were then exposed to a further 110 s of argon laser irradiation. Surface analysis was performed using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results showed no statistically significant change in the carbonate content of enamel after argon laser irradiation (p > 0.05). Thus, it is suggested that any demineralization resistance imparted to the enamel surface by argon laser irradiation is not due to alterations in carbonate content.

  20. Argon laser induced changes to the carbonate content of enamel

    International Nuclear Information System (INIS)

    Argon laser irradiation can be used to cure orthodontic brackets onto teeth in significantly less time than conventional curing lights. In addition, it has been shown that the argon laser seems to impart a demineralization resistance to the enamel. The purpose of this study was to use surface science techniques to ascertain if this demineralization resistance is possibly a result of a decrease in the carbonate content of enamel. Eleven mandibular third molars previously scheduled for extraction were collected and used in the present study. The teeth were sectioned in two and randomly assigned to either the argon laser (457-502 nm; 250 mW cm-2) or the control (no treatment) group. The sections assigned to the argon laser group were cured for 10 s and analyzed. To exaggerate any potential changes the experimental sections were then exposed to a further 110 s of argon laser irradiation. Surface analysis was performed using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results showed no statistically significant change in the carbonate content of enamel after argon laser irradiation (p > 0.05). Thus, it is suggested that any demineralization resistance imparted to the enamel surface by argon laser irradiation is not due to alterations in carbonate content.

  1. Temperature controlled retinal photocoagulation

    Science.gov (United States)

    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.

  2. Green laser photocoagulator for the treatment of diabetic retinopathy developed at Raja Ramanna Centre for Advanced Technology

    Indian Academy of Sciences (India)

    S M Oak

    2010-12-01

    An all-solid-state green laser photocoagulator at 532 nm with output power varying from 100 mW to 1 W in a step of 10 mW and exposure time varying from 50 ms to 1000 ms in a step of 10 ms is developed for the treatment of diabetic retinopathy. The output power stability is better than ± 1.5% with a nearly diffraction-limited beam quality. The system includes various safety and operational features like internal power monitoring system, safety interlock, emergency switch-off, graphical LCD display with table-top touch mode portable control panel, smart delivery device selection, aiming laser beam with controllable intensity, foot switch, patient records, service mode etc. The system has successfully passed the clinical trials and is being used on patients.

  3. Clinical analysis of laser photocoagulation for diabetic retinopathy%糖尿病视网膜病变激光光凝治疗疗效分析

    Institute of Scientific and Technical Information of China (English)

    张志红; 王媛媛; 曹江欣

    2013-01-01

    目的探讨激光光凝治疗糖尿病视网膜病变(DR)的疗效。方法 以DR患者54例108眼为研究对象,对增殖期(PDR)96眼行标准全视网膜光凝,非增殖期(NPDR)22眼行弥漫视网膜光凝。结果 视力提高或不变90眼,有效率83.3%。FFA检查示有效率86.1%。结论 激光光凝术是治疗DR 的一个有效方法,要把握光凝时机,争取早期发现并及时治疗DR,提高激光光凝的疗效。%Objective :To evaluate the efficacy of laser coagulation for diabetic retinopathy. Method :Total 54 patients (108 eyes) of diabetic retinopathy were as the object of this study. 96 eyes with proliferative diabetic retinopathy (PDR) were given panretinal photocoagulation. 22 eyes with non-proliferative diabetic retinopathy(NPDR)were given scatter photocoagulation.Results : the eyes of vision improve or no change are 90,totle effective rate is 83.3. totle effective rate of FFA examination is 86.1%. Conclusion: Laser photocoagulation is an effective method for diabetic retinopathy. It has different efficacy for the different stages of diabetic retinopathy. It can improve the efficacy of laser photocoagulation that we seize the opportunity of laser photocoagulation for diabetic retinopathy,early detecting and timely treating diabetic retinopathy.

  4. Argon laser treatment of urethral stricture and vesical neck contracture.

    Science.gov (United States)

    Adkins, W C

    1988-01-01

    The physical characteristics of the argon laser wavelength allow a precise incision with excellent hemostasis and negligible heating of adjacent tissues resulting in less scarring. These qualities are used to advantage in the treatment of strictures. The argon laser was used to perform 13 internal urethrotomies and ten vesical neck incisions. The operative method used is similar to optical internal urethrotomy. The argon probe incises hemostatically, reducing the need for extensive fulguration of tissues at the operative site and thereby reducing the tendency for more scar tissue to form and compromise the operation. The same hemostasis reduces the need for postoperative indwelling urethral catheterization. Utility of the argon device in most instances allows treatment to be conducted on an outpatient basis without general anesthesia and without use of postoperative urethral catheters, yielding an effective, cost-saving therapy. PMID:3210887

  5. Laser propagation and energy absorption by an argon spark

    OpenAIRE

    Bindhu, C V; Harilal, S S; Tillack, M. S.; Najmabadi, F; Gaeris, A C

    2003-01-01

    The laser propagation and energy absorption of an argon spark induced by a laser at different pressures is investigated. 8 ns pulses from a frequency-doubled Q-switched Nd:YAG laser are used to create the spark. The pressure of the argon is varied from 1 atm to 10 Torr. Significant energy absorption by the plasma is observed at high pressures (>100 Torr) while there is negligible absorption when the pressure is lower than 50 Torr. The plasma kernel showed distinct behavior with respect to las...

  6. Digital imaging-based retinal photocoagulation system

    Science.gov (United States)

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

    1997-05-01

    Researchers at the USAF Academy and the University of Texas are developing a computer-assisted retinal photocoagulation system for the treatment of retinal disorders (i.e. diabetic retinopathy, retinal tears). Currently, ophthalmologists manually place therapeutic retinal lesions, an acquired technique that is tiring for both the patient and physician. The computer-assisted system under development can rapidly and safely place multiple therapeutic lesions at desired locations on the retina in a matter of seconds. Separate prototype subsystems have been developed to control lesion depth during irradiation and lesion placement to compensate for retinal movement. Both subsystems have been successfully demonstrated in vivo on pigmented rabbits using an argon continuous wave laser. Two different design approaches are being pursued to combine the capabilities of both subsystems: a digital imaging-based system and a hybrid analog-digital system. This paper will focus on progress with the digital imaging-based prototype system. A separate paper on the hybrid analog-digital system, `Hybrid Retinal Photocoagulation System', is also presented in this session.

  7. Comparison of Pain Response of Patients Undergoing Panretinal Photocoagulation for Proliferative Diabetic Retinopathy: 532 nm Standard Laser vs. Multispot Pattern Scan Laser

    Directory of Open Access Journals (Sweden)

    Göktuğ Seymenoğlu

    2013-08-01

    Full Text Available Purpose: To compare pain response of patients undergoing panretinal photocoagulation (PRP for proliferative diabetic retinopathy (PDR using 532 nm standard laser versus multispot pattern scan laser and to evaluate the relationship between pain response and patient characteristics. Material and Method: Thirty-five patients had PRP with the Pascal system in a single session, while other 35 patients had PRP with conventional laser in 2 sessions. Parameters used in conventional laser were as follows: spot size 200 µm, exposure time 0.2 s, and power sufficient to produce visible grey-white burns. We used same spot size, 20-30 ms exposure time, and higher levels of laser power in order to get a similar endpoint in the Pascal system. The patients were required to evaluate the severity of pain on a visual analog scale (VAS and verbally 5 minutes after PRP with Pascal and 5 minutes after the first session of PRP with conventional laser. The relationship between pain experienced and patient characteristics was evaluated. Results: At baseline, both groups did not differ significantly (p >0.05, for all with respect to sex, age, duration of diabetes, most recent HbA1c, treatment regimen, or patient experience. The patients in the Pascal group had a mean pain score of 0.55±0.70 on verbal scale and 1.54±1.22 on VAS compared to 2.17±1.18 and 5.54±3.28, respectively in the conventional laser group which was, statistically, significantly different in both scales (p<0.05. Discussion: Our study confirms that new generation pattern scanning photocoagulators satisfactorily decrease the pain by shortening the exposure time while increasing the laser power. (Turk J Ophthalmol 2013; 43: 221-4

  8. Reflectance feedback control of photocoagulation in vivo

    Science.gov (United States)

    Jerath, Maya R.; Chundru, Ravi K.; Barrett, Steven F.; 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. In this treatment, an argon laser beam is directed into the eye through the pupil onto the fundus where the heat resulting from the absorbed laser light coagulates the retinal tissue. This thermally damaged region is highly scattering and appears as a white disk. The size of the retinal lesions is critical for effective treatment and minimal complications. A real time feedback control system is implemented that monitors lesion growth using two-dimensional reflectance images acquired by a CCD camera. The camera views the lesion formation on axis with the coagulating laser beam. The reflectance images are acquired and processed as the lesion forms. When parameters of the reflectance images that are correlated to lesion dimensions meet certain preset thresholds, the laser is shuttered. Results of feedback controlled lesions formed in vivo in pigmented rabbits are presented. An ability to produce uniform lesions despite variation in the tissue absorption or changes in laser power is demonstrated. This lesion control system forms part of a larger automated system for retinal photocoagulation.

  9. [Experience with argon laser in urological diseases (author's transl)].

    Science.gov (United States)

    Rothauge, C F; Nöske, H D; Kraushaar, J

    1981-09-01

    The application of the Argon laser in urology has proved to be effective in resecting recurrent, exophytic urothelial tumors of the bladder up to the size of a raspberry. In cases of wide spread bladder tumors we only perform a radiation of the resected area as local recurrence prophylaxis following transurethral resection. The urethroscopic Argon laser irradiation makes laser urethrotomy and evaporisation of urethral strictures possible. Furthermore, a curative and conservative treatment of urethral tumors is possible in combination with chemotherapy. The same applies for the penis carcinoma. Urethral ruptures are also successfully treated by urethroscopic laser recanalization. A determination of the ureteral submucosal course, which may allow a prognosis about the probable maturation, is possible in cases of cystoureteral reflux with the help of laser diaphanoscopy. PMID:7197839

  10. Comparison of anesthesia with sevoflurane-N2O and midazolam-remifentanil in low-birth-weight premature infants undergoing diode laser photocoagulation

    OpenAIRE

    BUT, Abdulkadir; Arikan, Müge; ASLAN, Bilge; Öztürk, Levent; TABUK, Meltem; HORASANLI, Eyüp

    2012-01-01

    Aim: The present study aimed to compare anesthesia with sevoflurane-N2O and midazolam-remifentanil in terms of hemodynamic parameters and safety in low-birth-weight (LBW) premature infants undergoing diode laser photocoagulation (DLP) for retinopathy of prematurity (ROP). Materials and methods: A total of 91 infants undergoing DLP for ROP were enrolled in this study. All of the infants were established with LBW (

  11. Intravitreal Bevacizumab Alone or Combined with Macular Laser Photocoagulation for Recurrent or Persistent Macular Edema Secondary to Branch Retinal Vein Occlusion

    OpenAIRE

    Takafumi Hirashima; Tomoyuki Chihara; Toshitaka Bun; Takao Utsumi; Miou Hirose; Hideyasu Oh

    2014-01-01

    Background. To evaluate the efficacy of intravitreal bevacizumab (IVB) injection with or without macular laser photocoagulation (MLP) for recurrent or persistent macular edema (ME) secondary to branch retinal vein occlusion (BRVO). Methods. Thirty-four eyes underwent IVB injection for ME secondary to BRVO as a primary treatment. Twenty of the 34 eyes experienced recurrent or persistent ME after the first IVB. Nine of the 20 eyes (Group 1) were retreated with IVB combined with MLP. The remaini...

  12. Photocoagulation as treatment of diabetic retinopathy

    Science.gov (United States)

    Sanchez, J.; Fernandez, L.; de Pedraza, Maria L.; Gamella, C.; Santervas, R.

    1992-03-01

    Diabetes Mellitus is a chronic disease that is revealed with a lot of alterations due to factors such as an absolute or relative reduction of the insulin. It is usually accompanied by generalized arteriosclerosis and prepares for certain microvasculares pathologies such as retinopathy, nefropathy, and neuropathy. The first effects of diabetes in the retina seem to act on the capillaries. The functional modifications of the retinal circulation appear before the structural ones. These consist of the blood flux damage and the obligation of the hematorretinal barrier with extravasacy as can be proved in the fluorophotometry of the vitreous humor. Nowadays, medical treatments are more effective and only vitrectomy and photocoagulation are used in diabetic retinopathy. For that, the argon laser and the xenon arch are used. The treatment is usually spread panretine, with coagulation in a grid pattern around the eye, avoiding the macula and other vital structures, and treating the neoformed blood vessels. The rate of grave visual loss in the studies carried out with there techniques was 12 in relation to 28 in the non-treated cases. The most important factors of risk found, were the discal neoformed blood vessels and the hemorrhage of the vitreous humor. Adverse effects were found such as the reduction of visual sharpness and the contrition of the visual field, these are greater in patients treated with the xenon arch than in those treated with the argon laser.

  13. 21 CFR 874.4490 - Argon laser for otology, rhinology, and laryngology.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Argon laser for otology, rhinology, and laryngology. 874.4490 Section 874.4490 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND... Argon laser for otology, rhinology, and laryngology. (a) Identification. The argon laser device for...

  14. Laser-induced vibrational dynamics of ozone in solid argon

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Amstrup, B.; Henriksen, Niels Engholm

    We consider the vibrational dynamics, induced by an intense infrared laser pulse, in an ozone molecule with isotopic substitution, that is, (OOO)-O-16-O-16-O-18 and compare the dynamics in the gas phase and in solid ar on. not perturbed by argon on a time-scale of a few picoseconds and selective...

  15. Narrow spectral width laser diode for metastable argon atoms pumping

    Science.gov (United States)

    Gao, Jun; Li, Bin; Wang, Xinbing; Zuo, Duluo

    2016-03-01

    Diode laser pump source with narrow emitting spectrum for optically pumped metastable rare gas laser (OPRGL) of argon was achieved by employing a complex external cavity coupled with volume Bragg grating (VBG). A commercially available c-mount laser diode with rated power of 6 W was used and studied in both the free running mode and VBG external cavity. The maximum output power of 3.9 W with FWHM less than 25 pm and peak wavelength locked around 811.53 nm was obtained from the VBG external cavity laser diode. Precise control of VBG temperature enabled fine tuning of the emission wavelength over a range of 450 pm. Future researches on OPRGL of argon will benefit from it.

  16. Primary study of micropulse diode laser photocoagulation for central serous chorioretinopathy%微脉冲半导体激光治疗CSC的初步观察

    Institute of Scientific and Technical Information of China (English)

    徐建锋; 叶瑞珍; 李贵洲

    2013-01-01

    AIM: To investigate the effect of micropulse diode laser photocoagulation on central serous choroidretinopathy (CSC). METHODS: Twelve patients diagnosed with CSC by fluorescein angiography ( FFA) and optic coherence tomography ( OCT) examination were treated with micropulse diode laser photocoagulation. The data of visual acuity testing, ophthalmic examination, color photographs, FFA and OCT before photocoagulation and 1 week, 2 weeks, 1 month, 3 months after it were used to evaluate the effects of micropulse diode laser photocoagulation. RESULTS: All patients' self-conscious symptom and visual acuity improved differently. Nine and eleven eyes leakage point disappeared after micropulse diode laser photocoagulation in 2 weeks and one month in FFA. Nine and eleven eyes of subretinal effusion in OCT were absorbed after laser photocoagulation in 2 weeks and one month. All cases' leakage point and subretinal effusion disappeared after 3 months. The window defect in FFA did not occur in all laser treated eyes. CONCLUSION: The micropulse diode laser photocoagulation could shorten the course of CSC, improve the patient's visual acuity and reduce the complications.%目的:探讨微脉冲半导体激光治疗中心性浆液性脉络膜视网膜病变(central serous chorioretinopathy,CSC)的疗效.方法:自身对照病例研究.将经荧光素眼底血管造影(fundus fluorescein angiography,FFA)和光学相干断层扫描(optic coherence tomography,OCT)检查确诊的典型性CSC患者12例12眼行微脉冲半导体激光治疗前及治疗后随访观察1,2wk;1,3mo的临床资料进行分析,主要以治疗前后的视力、自觉症状、眼底情况、FFA及OCT检查的改变为观察指标,以评价微脉冲半导体激光对CSC的治疗效果.结果:所有患者自觉症状减轻或消退,视力及视觉质量均有不同程度改善.激光光凝2wk和1mo后,分别有9眼(75.0%)和11眼(91.7%)的黄斑区水肿完全消退,3mo后全部患者黄斑区水肿消退.光凝2

  17. Improved external valvuloplasty, intravenous laser photocoagulation and local sclerotheraphy treatment of primary deep venous valvular insufficiency: long term result

    Science.gov (United States)

    Wang, Chun-xi; Han, Li-na; Gu, Ying; Liang, Fa-qi; Zhang, Li; Liu, Hong-yi; Zhao, Wen-guang; Wang, Qi; Wang, Xiao-ling

    2007-11-01

    The purpose of this article is to report long-term follow-up of improved external vulvuloplasty, intravenous laser photocoagulation and local sclerotherapy treatment of primary deep venous valvular insufficiency in eight hundred and seventy-two patients from Nov. 2000 to May 2006. Patients were evaluated clinically and with duplex ultrasound at 1, 3, and 12 months, and yearly thereafter until the fifth year to assess treatment efficacy and adverse reactions. Successful occlusion of the great saphenous vein and absence of deep vein reflux on color Doppler imaging, were noted in 956 limbs of 852 cases( 1 month follow-up), 946 limbs of 842 cases (6 month to 1 year follow-up), 717 of 626 (1~2 year follow-up), 501 of 417 (2~3 year follow-up), 352 of 296 (3~5year follow-up), 142 of 106 (5 year follow-up) after initial treatment. The cumulative total number of recurrence of reflux was fifteen cases. The respective competence rate was 95.18%, 96.23%, 94.23%, 95.25%, 94.23% and 94.12%. Of note, all recurrence occurred before 9 months, with the majority noted before 3 months. Bruising was noted in 0.7% of patients, tightness along the course of treated vein in 1.0% of limbs. There have been no paresthesia of cases, skin burns and deep vein thrombosis.

  18. Ultrasound-guided interstitial laser photocoagulation of an autonomous thyroid nodule: the introduction of a novel alternative.

    Science.gov (United States)

    Døssing, Helle; Bennedbaek, Finn Noe; Hegedüs, Laszlo

    2003-09-01

    Radioiodine ((131)I) and surgery are the standard therapeutic options for the solitary autonomous thyroid nodule (AFTN). Percutaneous ethanol injection (PEI) has proven to be an effective technique and possible alternative to the conventional treatment options. However, PEI is not devoid of side effects and often necessitates multiple treatment sessions. We present a case of a 17-year-old female successfully treated with ultrasound (US)-guided percutaneous interstitial laser photocoagulation (ILP) for an AFTN. Initially, she had a serum thyrotropin (TSH) of 0.01 mU/L and normal peripheral thyroid hormone levels. Scintigraphically it was a hot nodule with suppression of extranodular uptake, and ultrasonographically it was a solitary solid 8.2-mL nodule. One treatment session (3 W for 650 seconds [1950 J]) normalized serum thyrotropin (TSH) level within 2 months and decreased the nodule volume to 4.9 mL (40% reduction) without further alterations during an additional 9 months of follow-up. Side effects were transient thyrotoxicosis and local pain as seen with PEI. To our knowledge, this is the first reported case of ILP used in a patient with a pretoxic thyroid nodule. US-guided thermic tissue coagulation with ILP could become a useful alternative for the AFTN in patients who cannot or will not undergo surgery or treatment with (131)I. PMID:14588105

  19. Beam characteristics of CAPEX XUV argon laser

    Czech Academy of Sciences Publication Activity Database

    Schmidt, Jiří; Koláček, Karel; Frolov, Oleksandr; Prukner, Václav; Štraus, Jaroslav; Kaufman, J.

    Vol. 8849. San Diego : The Society of Photo-Optical Instrumentation Engineers (SPIE), 2013 - (Klisnick, A.; Menoni, C.), s. 884917-884917 ISBN 978-0-8194-9699-7. ISSN 0277-786X. - (SPIE. 8849). [X-Ray Lasers and Coherent X-Ray Sources: Development and Applications X Conference. San Diego (US), 27.08.2013-29.08.2013] R&D Projects: GA MŠk(CZ) LG13029 Institutional support: RVO:61389021 Keywords : Capillary discharge * XUV laser * laser energy and divergence Subject RIV: BL - Plasma and Gas Discharge Physics

  20. Intracavity frequency doubling in a wide-aperture argon laser

    International Nuclear Information System (INIS)

    The four-mirror cavity with a BBO crystal for frequency doubling in a wide-aperture argon laser is optimised. The dependences of the second-harmonic power on the displacement of a focusing mirror, the displacement of the crystal, and the discharge current are measured. These dependences are in good agreement with calculations. After optimisation, ∼1 W of UV laser radiation at 244 nm was obtained with the conversion efficiency twice as large as that for the known similar lasers. It is shown that the increase in the efficiency was achieved mainly due to the increase in the discharge-tube aperture. (nonlinear optical phenomena)

  1. High intensity, argon ion laser-jet photochemistry

    Science.gov (United States)

    Wilson, R. Marshall; Schnapp, Karlyn A.; Hannemann, Klaus; Ho, Douglas M.; Memarian, Hamid R.; Azadnia, Ardeshir; Pinhas, Allan R.; Figley, Timothy M.

    A new technique for the study of high intensity solution photochemistry has been developed. With this laser-jet technique, a high velocity microjet is irradiated with the focussed output of an argon ion laser. Under these extremely high intensity conditions, photochemically generated transient species with suitable absorption properties are excited further and produce relatively large amounts of photoproducts which are not observed under low intensity conditions. The application of this laser-jet technique in the study of the photochemistry of radicals, biradicals, photoenols and the higher excited states of carbonyl and polycyclic aromatic compounds is described.

  2. Continuous wave Nd:YAG laser photocoagulation in proliferative diabetic retinopathy.

    OpenAIRE

    Menchini, U; Lanzetta, P; Soldano, F; Ferrari, E; Virgili, G

    1995-01-01

    AIMS--The therapeutic efficacy of the continuous wave (CW) Nd:YAG laser (working in the free running mode) was investigated in proliferative diabetic retinopathy (PDR) comparing it with a conventional laser source such as the krypton laser. METHODS--Twenty four eyes of 12 patients affected with bilateral PDR were included and divided in two groups. The right eyes were treated with a red krypton laser and the left eyes with a CW Nd:YAG laser. RESULTS--Three months after krypton photocoagulatio...

  3. Argon Laser Photoablation for Treating Benign Pigmented Conjunctival Nevi

    Science.gov (United States)

    Alsharif, Abdulrahman M.; Al-Gehedan, Saeed M.; Alasbali, Tariq; Alkuraya, Hisham S.; Lotfy, Nancy M.; Khandekar, Rajiv

    2016-01-01

    Purpose: To evaluate the outcomes of argon laser photoablation of benign conjunctival pigmented nevi with different clinical presentations. Patients and Methods: This interventional case series was conducted between July 2014 and January 2015. Patients presenting with benign conjunctival nevi were included. Data were collected on the clinical features at presentation, argon laser photoablation, and follow-up at 8 and 24 weeks. Postoperative photography allowed recording of the success of each case and the overall success rate. Complete removal of conjunctival pigments was considered an absolute success. Partial pigmentation requiring repeat laser treatment was considered a qualified success. Results: There were 14 eyes (four right eyes and ten left eyes) with benign pigmented conjunctival nevi. There were three males and eight females in the study sample. The median age was 36 (25% percentile: 26 years). Three patients had bilateral lesions. The nevi were located temporally in nine eyes, nasally in three eyes, and on the inferior bulbar conjunctiva in two eyes. The mean horizontal and vertical diameters of nevi were 5 ± 2 mm and 4 ± 2.7 mm, respectively. The mean follow-up period was 5 months. Following laser treatment, no eyes had subconjunctival hemorrhage, infection, scarring, neovascularization, recurrence, or corneal damage. The absolute success rate of laser ablation was 79%. Three eyes with elevated nevi had one to three sessions of laser ablation resulting in a qualified success rate of 100%. Conclusions: Argon laser ablation was a safe and effective treatment for the treatment of selective benign pigmented conjunctival nevi in Arab patients. PMID:27555708

  4. Argon laser in the treatment of diabetic retinopathy (Preliminary communication)

    International Nuclear Information System (INIS)

    The complications observed in the photocoagulation treatment of diabetic angiopathy and retinopathy include the following conditions: tractional retinal detachment, accelerated development of proliferating retinitis and massive hemmorrhaging into the vitreous body. (V.A.P.)

  5. Laser-induced vibrational dynamics of ozone in solid argon

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Amstrup, B.; Henriksen, Niels Engholm

    1997-01-01

    We consider the vibrational dynamics, induced by an intense infrared laser pulse, in an ozone molecule with isotopic substitution, that is, (OOO)-O-16-O-16-O-18 and compare the dynamics in the gas phase and in solid ar on. not perturbed by argon on a time-scale of a few picoseconds and selective...... bond-breaking in the molecule should be possible following the same laser control scheme as suggested in the gas phase. (C) 1997 Elsevier Science B.V....

  6. Argon laser trabeculoplasty as primary therapy in open angle glaucoma

    International Nuclear Information System (INIS)

    To determine the effect of Argon Laser Trabeculoplasty (ALT) as a primary mode of therapy in reducing the intraocular Pressure (IOP) of patients diagnosed with Primary Open Angle Glaucoma (POAG). A total of 35 eyes of 35 patients with the gender distribution of 27 men and 8 women who were newly diagnosed with POAG, were included in this study. Mean age of the patients was 55.2 years with the range of 32 to 76 years. All of them were treated with argon laser trabeculoplasty as a primary mode of therapy. Intra ocular pressure was measured objectively using Goldman applanation tonometer, pre-and-post laser therapy. The pre-laser mean IOP was 27.63 mmHg (range 21-40 mmHg). The post-laser mean IOP measured at 6 months follow up was 15.5 mmHg (range 11 - 33 mmHg) with mean decrease of 12.1 mmHg. The decrease in IOP was seen in 32 eyes (95%) with no change observed in 3 (5%) eyes. The result shows a marked decline in IOP in patients with POAG who underwent ALT as a primary mode of treatment. Further studies with large sample size and longer follow-up will help in making future recommendations. (author)

  7. Primary argon laser trabeculoplasty in the treatment of glaucoma

    International Nuclear Information System (INIS)

    During the last ten years, argon laser trabeculoplasty has been shown to be a very useful tool in the treatment of glaucoma when medical therapy has failed. In the present study laser was used as primary therapy in 27 patients with newly detected glaucoma. Pretreatment with topical timolol gave an immediate pressure drop in all eyes, and the dreaded actue pressure rise after laser treatment was avoided. Upon follow-up examination after two years, more than half the patients had an intraocular pressure below 21 mm Hg without additional therapy. Primary laser trabeculoplasty was found to be a safe and time-saving procedure. Expenses and complications associated with medical therapy are reduced. Many patients may avoid lifelong daily instillation of eye drops. 11 refs., 2 tabs

  8. Development of a Laser Probe for Argon Isotope Studies.

    Science.gov (United States)

    McConville, Paul

    Available from UMI in association with The British Library. The first objective of this study was to develop a laser outgassing facility for argon isotope studies. Apart from the laser and construction of the laser sample port, existing vacuum and mass spectrometer systems were used. Laser performance and optimum operating conditions were investigated. The second objective was test and evaluate the laser extraction technique by studies of simple geological samples. Previous laser ^{40} Ar-^{39}Ar dating studies by other workers had not systematically established the basis or characteristics of the method. Results from laser and complementary stepped heating studies of the ^{40}Ar-^ {39}Ar dating standard hornblende, hb3gr; a phlogopite sample from the Palabora (Phalaborwa) Complex; and biotites in a thin section of the Hamlet Bjerg granite from East Greenland, verified that: (1) Laser extraction reproduced within experimental error the stepped heating ^{40}Ar-^ {39}Ar and K-Ar ages of simple samples. (2) The precision of the technique i.e. the amount of sample required to give reliable ages, was limited in the present experiments largely by the level of the blanks and backgrounds to 10-100 ug samples. (3) Sample outgassing appeared to be limited to the order of 10 um outside the physical size of the laser pit, consistent with other estimates of the spatial definition in the literature. This could be understood by thermal diffusion and the length of the laser pulse. (4) The efficiency of the laser pulse in melting and outgassing mineral samples was shown to be dependent on silicate latent heats and mineral absorption at the laser wavelength. In addition, the ^{40} Ar-^{39}Ar age of the geologically significant Palabora Complex was determined as (2053 +/- 5) Ma. Excess argon led to a discrepancy between the laser and stepped heating ages of biotite and muscovite, (405 +/- 5) Ma, and laser ages of feldspars (510 +/- 20) Ma in the Hamlet Bjerg granite. This illustrated

  9. The predictive value of optical coherence tomography after grid laser photocoagulation for diffuse diabetic macular oedema

    DEFF Research Database (Denmark)

    Soliman, W.; Sander, B.; Soliman, K.A.E.N.;

    2008-01-01

    's correlation coefficient (r = - 0.37, p = 0.05 and r = 0.5, p = 0.01, respectively). Conclusions: it seems that the 1-month time-point after macular laser treatment is a critical point for establishing the outcome of this modality of management of DMO. Baseline OCT mapping of intraretinal fluid accumulation...... patterns and foveal thickness can help to predict the final visual outcome and final foveal thickness; but not the absolute change in either of these parameters after macular laser therapy Udgivelsesdato: 2008/5...

  10. Long-term outcome following interstitial laser photocoagulation of benign cold thyroid nodules

    DEFF Research Database (Denmark)

    Døssing, Helle; Bennedbæk, Finn Noe; Hegedüs, Laszlo

    2011-01-01

    discomfort were assigned to ILP. ILP (using one laser fiber) was performed under continuous ultrasound (US) guidance and with an output power of 1.5-3.5 W. Thyroid nodule volume was assessed by US and thyroid function determined by routine assays, before and during follow-up. Pressure symptoms and cosmetic...... complaints were evaluated on a visual analogue scale (0-10 cm). Of the total patients, six had thyroid surgery 6 months after ILP and three were lost to follow-up. The median follow-up for the remaining 69 patients was 67 months (range 12-114). Results The overall median nodule volume decreased from 8.2 ml...

  11. Effect of laser photocoagulation and bevacizumab intravitreal in proliferative diabetic retinopathy: review on biomarkers of oxidative stress

    Directory of Open Access Journals (Sweden)

    Andi A. Victor

    2014-06-01

    Full Text Available Background: This study was aimed to compare the effect of laser photocoagulation (LF, intravitreal bevacizumab (IVB and combined treatments on biomarkers of oxidative stress such as aldehhyde dehidrogenase (ALDH, malondialdehyde (MDA level, superoxide dismutase (SOD activities, and vitreal vascular endothelial growth factor (VEGF on proliferative diabetic retinopathy (DR patients.Methods: In this single blind randomized clinical trial, 72 eyes from 69 cases of proliferative DR in Cipto Mangunkusumo Hospital between February 2011 - June 2013 were randomized into 4 groups : 1 control (n = 18; 2 LF pre-vitrectomy (n = 18; 3 IVB pre-vitrectomy (n = 18; and 4 combined IVB and LF pre-vitrectomy (n = 18. One-way ANOVA was used to compare oxidative stress parameters in the four groups.Results: There were no statistically significant differences in the average plasma ALDH activity (0.034 ± 0.02; 0.027 ± 0.02; 0.025 ± 0.02; 0.031 ± 0.11 IU/mg protein; p = 0.66, vitreal MDA level (1.661 ± 1.21; 1.557 ± 1.32; 1.717 ± 1.54; 1.501 ± 1.09 nmol/mL; p = 0.96 and SOD activity (0.403 ± 0.50; 0.210 ± 0.18; 0.399 ± 0.49; 0.273 ± 0.32 U/mL; p = 0.38 among these four groups, respectively. However, the VEGF vitreal level (pg/mL showed a statistically significant difference (0.356 ± 0.60; 0.393 ± 0.45; 0.150 ± 0.24; 0.069 ± 0.13; p = 0.05. The VEGF level in combination group was five times lower than the control group (p = 0.05.Conclusion: Combined treatments of DR by IVB and LF were correlated with lower vitreal MDA and plasma VEGF level, but did not have any effect on plasma ALDH and vitreal SOD in proliferative DR. Combined treatments with IVB and LF are recommended for the management of proliferative DR patients.  

  12. Clinical features of neovascular glaucoma treated with multi-wavelength laser photocoagulation%多波长激光视网膜光凝治疗新生血管性青光眼的临床特点

    Institute of Scientific and Technical Information of China (English)

    吕刚; 唐连志; 张伟; 王涛; 黄红深

    2013-01-01

    目的:观察新生血管性青光眼(neovascular glaucoma,NVG)应用多波长激光进行全视网膜光凝(pan retinal photocoagulation,PRP)的临床特点.方法:NVG患者21例25眼积极抗青光眼治疗同时,应用多波长激光进行PRP,观察光凝特点及并发症.结果:所有患者PRP顺利完成,应用红光光凝较多,光凝时明显疼痛3例5眼,虹膜炎症反应2例3眼,前房和玻璃体少量出血4例4眼,未发生脉络膜视网膜脱离.眼压不同程度下降,眼痛、头痛症状缓解.结论:多波长激光有利于NVG患者PRP的顺利完成,且安全有效.%AIM: To observe clinical features of neovascular glaucoma ( NVG) treated with multi - wavelength laser photocoagulation (PRP).METHODS: Totally 21 patients (25 eyes) with NVG were performed actively anti-glaucoma treatment, at the same time, they were also performed multi-wavelength laser photocoagulation. Photocoagulation characteristics and complications were observed.RESULTS: The PRP was completed successfully on alleyes. Red photocoagulation was used more offen. Three cases (5 eyes) had obvious pain, 2 cases (3 eyes) had iris inflammation reaction, 4 cases (4 eyes) had anterior chamber and vitreous hemorrhage. Choroidal retinal detachment was not found. IOP was decreased at different degree, eye pain and headache symptoms were relieved.CONCLUSION; Multi-wavelength laser is conducive to the successful completion of pan retinal photocoagulation in neovascular glaucoma. It is safe and effective.

  13. Laser photocoagulation - eye

    Science.gov (United States)

    ... your chin in a chin rest. A special contact lens will be placed on your eye. The lens ... If your blood sugar has been very high, your doctor will give you medicines to lower your blood sugar level. Arrange to have ...

  14. O uso do laser de argônio no tratamento da triquíase Argon laser in the treatment of trichiasis

    Directory of Open Access Journals (Sweden)

    Nilson Lopes da Fonseca Junior

    2004-04-01

    Full Text Available OBJETIVO: Avaliar a eficácia da técnica de termoablação dos folículos pilosos dos cílios em triquíase com laser de argônio e observar a preferência dos pacientes submetidos a este tratamento, pela anestesia tópica com colírio anestésico ou pela anestesia local injetável. MÉTODOS: Estudo prospectivo de 55 pálpebras de 39 pacientes com triquíase, tratados com fotocoagulação dos folículos pilosos com "Argon green laser" (Alcon® - EUA. Neste estudo avaliou-se a idade e o sexo dos pacientes, o número de sessões realizadas, a evolução após as aplicações e a preferência pelo tipo de anestesia. Os parâmetros utilizados foram: (1 Mira - 150 µm; (2 Potência- 750 mW; (3 Tempo de exposição- 0,2 s. Cada cílio recebeu, no máximo, 9 disparos por sessão. RESULTADOS: Dentre os 39 participantes do estudo, 58,9% eram do sexo feminino e 41% do sexo masculino. A idade média foi de 71 anos. Houve cura em 69% (38 pálpebras, sendo 29% (16 pálpebras com apenas uma sessão de laser. Houve preferência estatisticamente significativa pelo procedimento realizado sob anestesia local injetável. CONCLUSÃO: Os resultados sugerem que a anestesia local no tratamento da triquíase com laser de argônio é a preferência da maioria dos pacientes e que a termoablação dos folículos pilosos com laser de argônio é tratamento efetivo para a triquíase.PURPOSE: To evaluate the effectiveness of thermoablation of eyelashes in trichiasis with Argon laser and to observe the patients' choice of topic or local anesthesia. METHODS: Prospective study of 55 eyelids of 39 patients with trichiasis treated with photocoagulation of the eyelash follicle with Argon green laser (Alcon® - USA. Age, sex, number of applications in each session, evolution after the application and preference for the anesthesic method were evaluated. The laser settings were: 150 µm aim 750 mW potency; 0.2 seconds exhibition. Each eyelash received no more than 9 applications per

  15. Intravitreal Bevacizumab Alone or Combined with Macular Laser Photocoagulation for Recurrent or Persistent Macular Edema Secondary to Branch Retinal Vein Occlusion

    Directory of Open Access Journals (Sweden)

    Takafumi Hirashima

    2014-01-01

    Full Text Available Background. To evaluate the efficacy of intravitreal bevacizumab (IVB injection with or without macular laser photocoagulation (MLP for recurrent or persistent macular edema (ME secondary to branch retinal vein occlusion (BRVO. Methods. Thirty-four eyes underwent IVB injection for ME secondary to BRVO as a primary treatment. Twenty of the 34 eyes experienced recurrent or persistent ME after the first IVB. Nine of the 20 eyes (Group 1 were retreated with IVB combined with MLP. The remaining 11 eyes (Group 2 were retreated with IVB alone. Results. In Group 1, the postoperative best corrected visual acuity (BCVA improved compared with the preoperative value at all follow-up visits, although no statistically significant improvement was observed at 6 months. In contrast, BCVA significantly improved from 0.53 to 0.40 at 6 months (P<0.05 in Group 2. Conclusion. Combined therapy tended to have a smaller effect on visual acuity compared with IVB monotherapy.

  16. Physiological responses of Vigna radiata L. to nitrogen and argon+ laser irradiation - Short Communication

    International Nuclear Information System (INIS)

    The effect of nitrogen laser (337.1 nm) and argon+ laser (514.5 nm) irradiation on physiological responses in the green gram seedlings was studied. The shoot and root lengths and fresh and dry weights of the seedlings increased with 30 min exposure to nitrogen laser and 5 min exposure to Argon+ laser. Protein content was maximum with 20 min exposure to N laser and 5 min exposure to Ar+ laser, while DNA and RNA contents were maximum at 5 min exposure with both the laser treatments

  17. Retinopexia pneumática e fotocooagulação a laser para tratamento de descolamento secundário à fosseta de disco óptico: relato de caso Pneumatic retinopexy and laser photocoagulation for treatment of optic disc pit detachment: case report

    Directory of Open Access Journals (Sweden)

    Alexandre Antonio Marques Rosa

    2006-02-01

    Full Text Available Os autores relatam o caso de um paciente com fosseta congênita de disco óptico associado a descolamento seroso macular, tratado com sucesso por meio de fotocoagulação com laser de argônio na borda temporal da fosseta, seguido de injeção intravítrea de 0,3 ml de C3F8 (100%. O paciente foi seguido por 12 meses. A resolução do descolamento foi acompanhada de melhora da acuidade visual, bem como o retorno da fóvea a sua configuração normal, comprovada através da tomografia de coerência óptica.The authors report a case of congenital optic disc pit with serous macular detachment successfully treated, with argon laser photocoagulation in the temporal border of the pit, followed by intravitreous injection of C3F8 (100% 0.3 ml. Patient was followed up for 12 months. Retinal reattachment was associated with improvement in visual acuity, as well as return of the fovea to its normal configuration shown by optical coherence tomography.

  18. Picosecond-laser-driven gas puff neonlike argon x-ray laser

    International Nuclear Information System (INIS)

    We have performed short-pulse laser-irradiated gas puff target experiments to generate a neonlike argon soft-x-ray laser by using a small laser system. A high-pressure solenoid valve forms a gas column through a narrow slit that is irradiated by two laser pulses containing 10 J of energy. Strong lasing is observed on two transitions, the 3p 1S0→3s 1P1 line at 46.9 nm and the 3d 1P1→3p 1P1 line at 45.1 nm. We present results from a systematic study in which the gas puff and laser conditions were varied to optimize the x-ray-laser output from a 0.9-cm-long gas column

  19. Effect of Argon Laser on Enamel Demineralization around Orthodontic Brackets: An In Vitro Study

    Science.gov (United States)

    Miresmaeili, Amirfarhang; Etrati Khosroshahi, Mohammad; Motahary, Pouya; Rezaei-Soufi, Loghman; Mahjub, Hossein; Dadashi, Maryam; Farhadian, Nasrin

    2014-01-01

    Objective This study was designed to evaluate the effect of argon laser irradiation on development and progress of enamel demineralization around orthodontic brackets. Materials and Methods: Fifty caries-free, intact human premolars were randomly assigned to one of the following five equal groups: Groups 1 (control) and 2: The brackets were bonded using conventional halogen light for 40s and argon laser for 10s, respectively. Teeth in group 3 were lased with argon laser for 10s before bracket bonding with halogen light. Group 4 was the same as group 3 except that brackets were also bonded with argon laser. In group 5 samples were bonded conventionally, immersed in an artificial caries solution for two days and then irradiated for 10s with argon laser. All samples were subjected to demineralization by artificial caries solution for 10 days. After bracket removal, samples were buccolingually sectioned and evaluated by polarized light microscopy. Decalcified lesion depth in each section was measured by a trained examiner in a blind fashion. Data were analyzed in SPSS 14 using one-way ANOVA and Tukey’s HSD post hoc test. Results: The control group showed the greatest mean lesion depth while group 5 revealed the lowest. The laser-treated groups had significantly lower mean lesion depth compared with the control group (P<0.05) except for group 4 (P=0.192). Conclusion: Argon laser irradiation for 10s before or during bracket bonding can increase caries resistance of intact and demineralized enamel. PMID:25584052

  20. Curative Effect Observation of Anti VEGF Drugs Combined Laser Photocoagulation in Treatment of Diabetic Macular Edema%抗VEGF药物联合激光光凝治疗糖尿病黄斑水肿的疗效观察

    Institute of Scientific and Technical Information of China (English)

    张凤; 王琇; 公慧敏

    2015-01-01

    目的:分析和研究抗 VEGF 药物联合激光光凝治疗糖尿病黄斑水肿的疗效。方法选取2012年8月~2014年9月糖尿病黄斑水肿患者44例,分为抗 VEGF +光凝组与光凝组,光凝组患者给予激光光凝;抗 VEGF +光凝组患者给予抗 VEGF 药物联合激光光凝治疗,对比治疗前和治疗6个月两组最佳矫正视力(BCVA)、黄斑中心凹厚度(CMT)、安全性和注射次数。结果治疗前,两组患者两组 BCVA 水平、CMT 水平经 t 检验显示差异无统计学意义(P >0.05)。治疗6个月两组 BCVA 水平均提高、CMT 水平均降低,经 t 检验显示差异有统计学意义(P <0.05),但抗 VEGF +光凝组 BCVA 水平、CMT 水平改善幅度优于光凝组,经t 检验显示差异有统计学意义(P <0.05)。经随访,光凝组和抗 VEGF +光凝组均未出现视网膜脱落、眼内炎、晶状体损伤、眼压升高、玻璃体积血、色素上皮撕裂、地图状萎缩等眼部不良反应或中风、心脏病等全身不良反应,组间经χ2检验显示差异无统计学意义(P >0.05)。结论抗 VEGF 药物联合激光光凝治疗糖尿病黄斑水肿的疗效确切,可改善患者视力和视网膜厚度。%Objective To analyze and research of VEGF drugs combined laser photocoagulation for treatment of diabetic macular edema. Methods Selected 44 patients with diabetic macular edema in August 2012 to September 2014,divided into anti VEGF+photocoagulation and photocoagulation group. Photocoagulation group patients given laser photocoagulation. Anti VEGF + photocoagulation group patients given fight VEGF drugs combined laser photocoagulation for treatment,compared before and 6 months after treatment in the two groups best corrected visual acuity(BCVA)and macular center concave thickness(CMT),security,and injection time. Results Before the treatment,two groups of patients,the CMT the BCVA level two groups of t test showed that

  1. Efficacy and safety of green laser photocoagulation for threshold retinopathy of prematurity Eficácia e segurança da fotocoagulação com laser verde na retinopatia da prematuridade limiar

    Directory of Open Access Journals (Sweden)

    Rodrigo Pessoa Cavalcanti Lira

    2008-02-01

    Full Text Available PURPOSE: To report the efficacy and safety of green laser photocoagulation for threshold retinopathy of prematurity (ROP. METHODS: We reviewed the clinical records of the neonates who had undergone green laser photocoagulation for threshold ROP at the Federal University of Pernambuco in Brazil between January 2004 and January 2006. All procedures were conducted with local anesthetic drops. The neonates were monitored throughout the procedure by a neonatologist. A frequency-doubled solid state laser, diode-pumped, with 532 nm wavelength was used. The presence of tunica vasculosa lentis or cataract were excluded before laser treatment. The following preoperative data were obtained for each patient: age, birth weight and the grade of ROP. Postoperative data included complications associated with the laser treatment, grade of ROP and evaluation whether further surgery was necessary due to failure of laser photocoagulation. RESULTS: Twenty-two neonates underwent photocoagulation with green laser for threshold ROP. A total of 31 eyes were included in the study. The mean gestational age was 30 ± 3 weeks and the mean birth weight was 1120 ± 490 g. Regression of the disease after laser therapy was observed in 30 eyes (96.7%. Despite treatment one eye presented stage 4A. Only 7 eyes required repetitive laser therapy. No adverse effects such as burning anterior segment tissues or bleeding in the anterior chamber occurred. No posterior segment side-effects were observed. Cataract formation was not observed at the last follow-up examination. CONCLUSIONS: Green laser photocoagulation remains an effective and safe alternative to red laser photocoagulation and to cryotherapy in the treatment of threshold ROP.OBJETIVOS: Avaliar a eficácia e segurança da fotocoagulação com laser verde na retinopatia da prematuridade (ROP limiar. MÉTODOS: Foram revisados prontuários dos neonatos submetidos à fotocoagulação com laser verde para ROP limiar, na

  2. Compatibility of the argon and KTP lasers with middle ear implants.

    Science.gov (United States)

    Wanamaker, H H; Silverstein, H

    1993-06-01

    Visible-spectrum lasers (argon, KTP) are becoming common tools in otology. Concern over transmission of disease by homograft tissue has focused attention on synthetic materials such as Silastic, Polycel, hydroxylapatite, and Teflon. This study sought to determine the effects of argon and KTP lasers on materials used in stapes and chronic ear surgery. Silastic sheeting, hydroxylapatite and polycel total ossicular replacement prostheses (TORPs) and partial ossicular replacement prostheses (PORPs), and platinum wire/Teflon stapes prostheses were exposed to argon and KTP laser energy at clinical power settings. Effects of the two lasers were similar. The presence of pigment (char or blood) was necessary to produce any effect. Silastic transmitted energy to underlying material. Hydroxylapatite cracked and shattered. Polycel vaporized and melted, as did Teflon. Clinical implications of these interactions on primary and revision otologic surgeries will be discussed. PMID:8388975

  3. Photocoagulation treatment of radiation retinopathy

    Energy Technology Data Exchange (ETDEWEB)

    Kinyoun, J.L.; Chittum, M.E.; Wells, C.G.

    1988-05-15

    We studied the visual and anatomic effects of focal photocoagulation for clinically significant radiation macular edema in five eyes of four patients and panretinal photocoagulation for proliferative radiation retinopathy in six eyes of three patients. Focal and limited scatter photocoagulation was successful in preventing further vision loss in all five eyes treated for macular edema. Three eyes treated with panretinal photocoagulation had regression of neovascularization. The other three eyes treated for proliferative retinopathy subsequently had dense vitreous hemorrhages that required vitrectomy for restoration of useful vision.

  4. Photocoagulation treatment of radiation retinopathy

    International Nuclear Information System (INIS)

    We studied the visual and anatomic effects of focal photocoagulation for clinically significant radiation macular edema in five eyes of four patients and panretinal photocoagulation for proliferative radiation retinopathy in six eyes of three patients. Focal and limited scatter photocoagulation was successful in preventing further vision loss in all five eyes treated for macular edema. Three eyes treated with panretinal photocoagulation had regression of neovascularization. The other three eyes treated for proliferative retinopathy subsequently had dense vitreous hemorrhages that required vitrectomy for restoration of useful vision

  5. Efficacy of anti-VEGF and laser photocoagulation in the treatment of visual impairment due to diabetic macular edema: a systematic review and network meta-analysis.

    Directory of Open Access Journals (Sweden)

    Stephane Régnier

    Full Text Available Compare the efficacy of ranibizumab, aflibercept, laser, and sham in the first-line treatment of diabetic macular edema (DME to inform technology assessments such as those conducted by the UK National Institute for Health and Care Excellence (NICE.MEDLINE, Embase, Cochrane Library, congress abstracts, ClinicalTrials.gov registry and Novartis data on file.Studies reporting 6- or 12-month results of randomized controlled trials (RCTs evaluating at least two of ranibizumab 0.5 mg pro re nata, aflibercept 2.0 mg bi-monthly, laser photocoagulation or sham. Study quality was assessed based on likelihood of bias in selection, attrition, detection and performance.Improvement in best-corrected visual acuity (BCVA measured as the proportion of patients gaining ≥10 letters on the Early Treatment Diabetic Retinopathy Study scale. The outcome was chosen following acceptance by NICE of a Markov model with 10-letter health states in the assessment of ranibizumab for DME.Bayesian network meta-analyses with fixed and random effects adjusted for differences in baseline BCVA or central retinal thickness.The analysis included 1,978 patients from eight RCTs. The random effects model adjusting for baseline BCVA was the best model based on total residual. The efficacy of ranibizumab was numerically, but not statistically, superior to aflibercept (odds ratio [OR] 1.59; 95% credible interval [CrI], 0.61-5.37. Ranibizumab and aflibercept were statistically superior to laser monotherapy with ORs of 5.50 (2.73-13.16 and 3.45 (1.62-6.84 respectively. The probability that ranibizumab is the most efficacious treatment was 73% compared with 14% for aflibercept, 12% for ranibizumab plus laser, and 0% for laser.Three of the eight RCTs included are not yet published. The models did not adjust for all potential effect modifiers.Ranibizumab was non-significantly superior to aflibercept and both anti-VEGF therapies had statistically superior efficacy to laser.

  6. Effect of argon on the performance of a fast-axial flow CO2 laser

    Science.gov (United States)

    Jelvani, S.; Amiri, Kh; Pazokian, H.; Montazerolghaem, M.; Mollabashi, M.; Naeimi, S. A.; Esmaeilpour, D.

    2011-01-01

    The performance characteristics of a fast-axial flow (FAF) cw CO2 laser are described. The dependences of the output power, efficiency, and discharge voltage on the discharge current of a FAF cw CO2 laser with optimised composition of the CO2:N2:He=1:4.4:7.6 gas mixture with a small amount of argon are studied experimentally at two pressures of 50 and 60 mbar in open and closed cycle regimes of the laser system.

  7. Argon laser phototherapy of human malignancies using rhodamine-123 as a new laser dye: The intracellular role of oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Castro, D.J.; Saxton, R.E.; Markley, J.; Foote, C.S.; Fetterman, H.R.; Castro, D.J.; Ward, P.H. (Univ. of California, Los Angeles (USA))

    1990-08-01

    Recent studies demonstrated that the cationic, mitochondrial-specific dye Rhodamine-123 (Rh-123), is an efficient tumor photosensitizer for Argon laser treatment of human cancer cells both in vitro and in tumors grown as xenografts in athymic mice. To demonstrate the photodynamic mechanism of action of this reaction, the intracellular role of oxygen and temperature changes in treated cells have to be defined. In the current study, a large panel of human tumor cell lines of diverse histologic origin were tested for in vitro sensitivity to Rh-123 and the Argon laser (514.5 nm) in oxygen, deuterium oxide (D2O), and nitrogen (N2) environment. Tumor cells in suspension were first sensitized to Rh-123 (1 or 20 micrograms/ml for 1 hour), cooled on ice to 4 degrees C, and then exposed to the Argon laser (delta T = 14 +/- 1 degree C). Cell proliferation measured by (3H)-thymidine uptake 24 hours after sensitization with Rh-123 and laser treatment was significantly decreased in tumor cells kept in oxygen and D2O atmospheres. No decrease in DNA synthesis was seen in Rh-123 and laser treated cells kept in an N2 environment. Control tumor cells treated with Rh-123 or the Argon laser separately did not show any decreased (3H)-thymidine uptake in oxygen, D2O or N2 environment. These results provide evidence of a photodynamic process since Rh-123 sensitization and Argon laser activation occur at nonthermal levels of energy and are oxygen dependent. The high effectiveness of this technique of photodynamic therapy with the Argon laser, and low toxicity of Rh-123 could make its clinical use very attractive for the treatment of superficial malignancies.

  8. Argon laser phototherapy of human malignancies using rhodamine-123 as a new laser dye: The intracellular role of oxygen

    International Nuclear Information System (INIS)

    Recent studies demonstrated that the cationic, mitochondrial-specific dye Rhodamine-123 (Rh-123), is an efficient tumor photosensitizer for Argon laser treatment of human cancer cells both in vitro and in tumors grown as xenografts in athymic mice. To demonstrate the photodynamic mechanism of action of this reaction, the intracellular role of oxygen and temperature changes in treated cells have to be defined. In the current study, a large panel of human tumor cell lines of diverse histologic origin were tested for in vitro sensitivity to Rh-123 and the Argon laser (514.5 nm) in oxygen, deuterium oxide (D2O), and nitrogen (N2) environment. Tumor cells in suspension were first sensitized to Rh-123 (1 or 20 micrograms/ml for 1 hour), cooled on ice to 4 degrees C, and then exposed to the Argon laser (delta T = 14 +/- 1 degree C). Cell proliferation measured by [3H]-thymidine uptake 24 hours after sensitization with Rh-123 and laser treatment was significantly decreased in tumor cells kept in oxygen and D2O atmospheres. No decrease in DNA synthesis was seen in Rh-123 and laser treated cells kept in an N2 environment. Control tumor cells treated with Rh-123 or the Argon laser separately did not show any decreased [3H]-thymidine uptake in oxygen, D2O or N2 environment. These results provide evidence of a photodynamic process since Rh-123 sensitization and Argon laser activation occur at nonthermal levels of energy and are oxygen dependent. The high effectiveness of this technique of photodynamic therapy with the Argon laser, and low toxicity of Rh-123 could make its clinical use very attractive for the treatment of superficial malignancies

  9. Application of argon laser LAK-1 for therapy in selected blood vessel diseases

    Science.gov (United States)

    Szymanczyk, Jacek; Golebiowska, Aleksandra; Michalska, I.; Nowakowski, Wlodzimierz

    1995-03-01

    Argon laser was applied in 172 patients with various vascular disorders and epidermal nevi. The best therapeutical results were obtained in facial telangiectasia and in cavernous hemangiomas, in which there was a complete or almost complete regression. In capillary facial hemangiomas in 49 patients (79%) clearing of 50% to 75% was obtained, and in epidermal nevi the full regression was in 4 (44%) of the cases, and 50% regression in 4 (44%). In telangiectasia of the lower limbs the results were not satisfactory. We stress that cavernous, and capillary hemangiomas, as well as facial telangiectasia are an indication for the argon laser therapy.

  10. Laser in ophthalmology. Laser i oftalmologien

    Energy Technology Data Exchange (ETDEWEB)

    Syrdalen, P. (Rikshospitalet, Oslo (Norway))

    1991-09-01

    The article presents a brief history of the use of laser in ophthalmology in Norway, from the introduction of the first argon-photocoalulator in 1972 to the excimer laser in 1990. The argon-photocoagulator is in daily us in all Eye Departments in Norway and the main group of patients treated are those with diabetic retionopathy. Glaucoma has been treated with argon-laser with good results for the last ten years. YAG-laser, introduced in Norway in 1985, is used to treat secondary cataracts which occur after extracapsular cataract extractions and implantation of artificial lenses. In 1990, the excimer laser was introduced for refractive surgery (myopia, astigmatism). 4 refs., 6 figs., 1 tab.

  11. 577nm阈下微脉冲激光治疗黄斑水肿时光凝斑的影像学观察%Image observation of laser spots from subthreshold micropulse laser (577nm) photocoagulation for macular edema

    Institute of Scientific and Technical Information of China (English)

    侯军军; 闰爱珍; 袁红; 贾亚丁

    2012-01-01

    目的 用多波长照相技术(F-10)观察577 nm阈下微脉冲激光光凝治疗黄斑水肿时光凝斑的形态学改变.方法 前瞻性系列病例研究.黄斑水肿患者17例(19眼)纳入研究.所有患者均经眼底荧光素血管造影(FFA)及光学相干断层扫描(OCT)检查确诊,其中,糖尿病黄斑水肿患者8例(10眼),视网膜中央静脉阻塞引起的黄斑水肿患者5例(5眼),视网膜分支静脉阻塞引起的黄斑水肿患者4例(4眼).首先在传统连续波激光下对患眼进行阈能量P测定,然后在F-10的retro mode模式检测下对这19眼进行阈下微脉冲光凝测试及治疗,微脉冲激光所用能量的调整参照阈能量P.留取患眼光凝前后眼底彩照及自发荧光成像,并随访观察术后1个月患眼中心凹厚度(CMT)及最佳矫正视力(BCVA)变化.分别采用配对t检验、配对秩和检验对数据进行分析.结果 术后即刻retro mode成像中,6眼在122.4%P能量下出现光凝斑;8眼在153.1%P能量下出现光凝斑;5眼在183.7%P能量下出现光凝斑.术后即刻在眼底彩照及自发荧光成像下光凝区未发生改变.术后1个月患眼CMT较术前明显降低,差异有统计学意义(t=4.238,P<0.01),BCVA与术前相比无明显变化.结论 Retro mode 成像可检测到阈下微脉冲激光光凝产生的不可见光凝斑,在治疗时可用于指导光凝能量大小的选择.%Objective To observe the laser spots created by subthreshold micropulse laser (577 nm) photocoagulation for macular edema with a multi-wavelength photographic technique (F-10).Methods It was a prospective case-series study.Seventeen patients (19 eyes) with macular edema diagnosed by fundus fluorescein angiography (FFA) and optical coherence tomography (OCT) were included.Eight patients (10 eyes) were diagnosed with diabetic macular edema (DME),5 patients (5 eyes) with macular edema attributable to central retinal vein occlusion (CRVO) and 4 patients (4 eyes) with macular edema

  12. Nitrogen/argon diluted acetylene and ethylene blue flames under infrared CO2 laser irradiation

    Directory of Open Access Journals (Sweden)

    Peter V. Pikhitsa

    2011-09-01

    Full Text Available We investigated changes in emission spectra from nitrogen/argon diluted laminar diffusion acetylene and ethylene blue flames irradiated by a powerful cw infrared CO2 laser. The changes in the radical emission bands can be interpreted as an indication of laser-induced decomposition of ethylene (for laser absorbing C2H4 fuel and of laser-absorbing intermediates (for non-absorbing C2H2 fuel. The results indicate that released active hydrogen plays an important role in addition/abstraction reactions without any participation of oxygen.

  13. Nitrogen/argon diluted acetylene and ethylene blue flames under infrared CO2 laser irradiation

    OpenAIRE

    Pikhitsa, Peter V.; Daegyu Kim; Mansoo Choi

    2011-01-01

    We investigated changes in emission spectra from nitrogen/argon diluted laminar diffusion acetylene and ethylene blue flames irradiated by a powerful cw infrared CO2 laser. The changes in the radical emission bands can be interpreted as an indication of laser-induced decomposition of ethylene (for laser absorbing C2H4 fuel) and of laser-absorbing intermediates (for non-absorbing C2H2 fuel). The results indicate that released active hydrogen plays an important role in addition/abstraction reac...

  14. Laser in ophthalmology

    International Nuclear Information System (INIS)

    The article presents a brief history of the use of laser in ophthalmology in Norway, from the introduction of the first argon-photocoalulator in 1972 to the excimer laser in 1990. The argon-photocoagulator is in daily us in all Eye Departments in Norway and the main group of patients treated are those with diabetic retionopathy. Glaucoma has been treated with argon-laser with good results for the last ten years. YAG-laser, introduced in Norway in 1985, is used to treat secondary cataracts which occur after extracapsular cataract extractions and implantation of artificial lenses. In 1990, the excimer laser was introduced for refractive surgery (myopia, astigmatism). 4 refs., 6 figs., 1 tab

  15. Vacuum ultraviolet argon excimer laser excited by optical-field-induced ionized electrons produced in an argon-filled hollow fiber

    Science.gov (United States)

    Kubodera, Shoichi; Kaku, Masanori; Katto, Masahito

    2011-10-01

    Short-wavelength lasers in the vacuum ultraviolet (VUV) spectral region between 100 and 200 nm have not yet been developed to the same degree as visible and infrared lasers. We have demonstrated the production of argon excimers via an optical-field-induced ionization (OFI) process by using a high-intensity infrared laser. We here report optical amplification of argon excimers at the wavelength of 126 nm by producing an extended OFI plasma inside an argon-filled hollow fiber with an inner diameter of 250 microns with a length of 5.0 cm. A gain-length product of 4.3 through the use of single-pass amplification with VUV optics was observed, indicating a small signal gain coefficient of 0.86 cm-1 with an uncertainty of 0.03. It was found that the hollow fiber served to extend the OFI plasma length and to guide the excitation of the infrared laser and the produced VUV emissions at 126 nm, but did not affect the OFI plasma conditions to produce argon excimer molecules. Short-wavelength lasers in the vacuum ultraviolet (VUV) spectral region between 100 and 200 nm have not yet been developed to the same degree as visible and infrared lasers. We have demonstrated the production of argon excimers via an optical-field-induced ionization (OFI) process by using a high-intensity infrared laser. We here report optical amplification of argon excimers at the wavelength of 126 nm by producing an extended OFI plasma inside an argon-filled hollow fiber with an inner diameter of 250 microns with a length of 5.0 cm. A gain-length product of 4.3 through the use of single-pass amplification with VUV optics was observed, indicating a small signal gain coefficient of 0.86 cm-1 with an uncertainty of 0.03. It was found that the hollow fiber served to extend the OFI plasma length and to guide the excitation of the infrared laser and the produced VUV emissions at 126 nm, but did not affect the OFI plasma conditions to produce argon excimer molecules. Part of this work has been supported by

  16. Laser light scattering in a laser-induced argon plasma: Investigations of the shock wave

    Energy Technology Data Exchange (ETDEWEB)

    Pokrzywka, B. [Obserwatorium Astronomiczne na Suhorze, Uniwersytet Pedagogiczny, ulica Podchorazych 2, 30-084 Krakow (Poland); Mendys, A., E-mail: agata.mendys@uj.edu.pl [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Dzierzega, K.; Grabiec, M. [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Pellerin, S. [GREMI, site de Bourges, Universite d' Orleans, CNRS, rue Gaston Berger BP 4043, 18028 Bourges (France)

    2012-08-15

    Shock wave produced by a laser induced spark in argon at atmospheric pressure was examined using Rayleigh and Thomson scattering. The spark was generated by focusing a laser pulse from the second harmonic ({lambda} = 532 nm) of a nanosecond Nd:YAG laser using an 80 mm focal length lens, with a fluence of 2 kJ{center_dot}cm{sup -2}. Images of the spark emission were recorded for times between 30 ns and 100 {mu}s after the laser pulse in order to characterize its spatial evolution. The position of the shock wave at several instants of its evolution and for several plasma regions was determined from the Rayleigh-scattered light of another nanosecond Nd:YAG laser (532 nm, 40 J{center_dot}cm{sup -2} fluence). Simultaneously, Thomson scattering technique was applied to determine the electron density and temperature in the hot plasma core. Attempts were made to describe the temporal evolution of the shock wave within a self-similar model, both by the simple Sedov-Taylor formula as well as its extension deduced by de Izarra. The temporal radial evolution of the shock position is similar to that obtained within theory taking into account the counter pressure of the ambient gas. Density profiles just behind the shock front are in qualitative agreement with those obtained by numerically solving the Euler equations for instantaneous explosion at a point with counter pressure. - Highlights: Black-Right-Pointing-Pointer We investigated shock wave evolution by Rayleigh scattering method. Black-Right-Pointing-Pointer 2D map of shockwave position for several times after plasma generation is presented. Black-Right-Pointing-Pointer Shock wave evolution is not satisfactorily described within self-similar models. Black-Right-Pointing-Pointer Evolution of shock position similar to theory taking into account counter pressure. Black-Right-Pointing-Pointer Density profile behind the shock similar to numerical solution of Euler equations.

  17. Laser light scattering in a laser-induced argon plasma: Investigations of the shock wave

    International Nuclear Information System (INIS)

    Shock wave produced by a laser induced spark in argon at atmospheric pressure was examined using Rayleigh and Thomson scattering. The spark was generated by focusing a laser pulse from the second harmonic (λ = 532 nm) of a nanosecond Nd:YAG laser using an 80 mm focal length lens, with a fluence of 2 kJ·cm−2. Images of the spark emission were recorded for times between 30 ns and 100 μs after the laser pulse in order to characterize its spatial evolution. The position of the shock wave at several instants of its evolution and for several plasma regions was determined from the Rayleigh-scattered light of another nanosecond Nd:YAG laser (532 nm, 40 J·cm−2 fluence). Simultaneously, Thomson scattering technique was applied to determine the electron density and temperature in the hot plasma core. Attempts were made to describe the temporal evolution of the shock wave within a self-similar model, both by the simple Sedov–Taylor formula as well as its extension deduced by de Izarra. The temporal radial evolution of the shock position is similar to that obtained within theory taking into account the counter pressure of the ambient gas. Density profiles just behind the shock front are in qualitative agreement with those obtained by numerically solving the Euler equations for instantaneous explosion at a point with counter pressure. - Highlights: ► We investigated shock wave evolution by Rayleigh scattering method. ► 2D map of shockwave position for several times after plasma generation is presented. ► Shock wave evolution is not satisfactorily described within self-similar models. ► Evolution of shock position similar to theory taking into account counter pressure. ► Density profile behind the shock similar to numerical solution of Euler equations.

  18. Transpupillary Argon Laser Cyclophotocoagulation in a Refractory Traumatic Glaucoma Patient with Aphakia and Aniridia

    Directory of Open Access Journals (Sweden)

    Umut Duygu Uzunel

    2016-01-01

    Full Text Available We present a case of transpupillary argon laser cyclophotocoagulation (TALC in a patient with traumatic aniridia and aphakia secondary to blunt trauma who had previous bilateral trabeculectomy. Four months after the trauma the patient’s intraocular pressure (IOP rose to 35 mmHg despite topical antiglaucomatous medication. Inferior 180 degrees cyclophotocoagulation was performed with transpupillary argon laser in the first session and his IOP fell to values of 12-17 mmHg. Twelve weeks after TALC, his IOP rose to 22 mmHg and we had to apply TALC to the residual ciliary processes. Seven months later his IOP was 13 mmHg with topical dorzolamide/timolol and latanoprost administration. TALC may be an effective treatment alternative for lowering IOP in patients with visible ciliary processes who do not respond to conventional medical or laser treatment.

  19. Second pain event related potentials to argon laser stimuli: recording and quantification.

    OpenAIRE

    Arendt-Nielsen, L.

    1990-01-01

    A non-invasive technique for quantification of argon laser induced burning second pain (C-fibre) is suggested. Using frequency analysis event related responses to burning pain can be detected in the EEG interval 1-2 seconds after laser stimulation. When the laser stimulus induced a burning pain perception, the power from 0.5-2.5 Hz of the EEG interval 1-2 seconds after stimulation differed significantly from the power calculated from the same time interval when no burning pain was perceived.

  20. The effect of chirped intense femtosecond laser pulses on the Argon cluster

    CERN Document Server

    Ghaforyan, H; Irani, E

    2016-01-01

    The interaction of intense femtosecond laser pulses with atomic Argon clusters has been investigated by using nano-plasma model. Based on the dynamic simulations, ionization process, heating and expansion of a cluster after irradiation by femtosecond laser pulses at intensities up to 2*1017 Wcm-2 are studied. The analytical calculation provides ionization ratefor different mechanisms and time evolution of the density of electrons for different pulse shapes. In this approach the strong dependence of laser intensity, pulse duration and laser shape on the electron energy, the electron density and the cluster size are presented using the intense chirped laser pulses. Based on the presented theoretical modifications, the effect of chirped laser pulse on the complex dynamical process of the interaction is studied. It is found that the energy of electrons and the radius of cluster for the negatively chirped pulsesare improved up to 20% in comparison to the unchirped and positively chirped pulses.

  1. 相干光断层扫描对532 nm激光治疗糖尿病黄斑水肿的疗效观察%Observation of optical coherence tomography on 532nm laser photocoagulation in the treatment of diabetic macular edema

    Institute of Scientific and Technical Information of China (English)

    潘颖喆; 高丰; 王慧; 殷晖

    2011-01-01

    Objective To observe the clinical effect of 532nm laser photocoagulation therapy on diabetic macular edema with optical coherence tomography. Methods 46 continuous patients ( 61 eyes ) with clinically significant diabetic macula edema were treated by 532nm laser photocoagulation. The retinal thickness and the volume of central fovea of macula were detected by optical coherence tomography in pre-photocoagulation and post-photocoagulation after 3 months. These data and the visual acuity were analyzed statistically. Results The visual acuity in 41 eyes improved and 17 eyes unchanged after 532 nm photocoagulation. The retinal thickness and the volume of central fovea of macula in pre-photocoagulation and post-photocoagulation after 3 months were 354.7 ± 93.2 μm/8.32 ± 0.53 mm3 and 203.5 ± 49.6 μm/7.24 ±0.41 mm3 respectively. Statistically, the difference in pre-photocoagulation and post-photocoagulation was significant. Conclusion 532nm laser photocoagulation is an effective treatment for diabetic macular edema. The change of retinal thickness and the volume can be measured exactly with optical coherence tomography pre- and post-photocoagulation, and thus the accurate effect of 532nm laser photocoagulation can be evaluated exactly.%目的 评价使用相干光断层扫描(OCT)对532 nm激光治疗糖尿病黄斑水肿的疗效进行观察的有效性.方法 对糖尿病性有临床意义的黄斑部水肿病例46例(61只眼),给予532 nm激光黄斑格栅样光凝、局灶光凝以及全视网膜光凝,在治疗前、治疗后3个月分别进行裸眼视力、眼底照相、荧光素眼底血管造影及OCT黄斑区视网膜厚度及视网膜容积等检查.比较光凝前后黄斑区视网膜厚度和视网膜容积的变化.结果 在46例(61只眼)中,41只眼视力提高,17只眼不变,所有患者荧光素眼底血管造影显示黄斑区荧光渗漏不同程度减轻或消失,OCT显示光凝治疗前黄斑中心凹视网膜神经上皮厚度为(354.7±93

  2. XUV radiation from gaseous nitrogen and argon target laser plasmas

    Czech Academy of Sciences Publication Activity Database

    Vrba, Pavel; Vrbová, M.; Brůža, P.; Pánek, D.; Krejčí, F.; Kroupa, M.; Jakůbek, J.

    2012-01-01

    Roč. 370, č. 1 (2012), s. 012049. ISSN 1742-6588. [Latin American Workshop on Plasma Physics (LAWPP 2011)/14/. Mar del Plata, 20.11.2011-25.11.2011] R&D Projects: GA MŠk LA08024; GA MŠk(CZ) LC528 Institutional research plan: CEZ:AV0Z20430508 Keywords : Laser plasma source of XUV radiation in water window range * RHMD Z* engine code Subject RIV: BH - Optics, Masers, Lasers http://iopscience.iop.org/1742-6596/370/1/012049/pdf/1742-6596_370_1_012049.pdf

  3. Reparative processes of the iris after irradiation with the argon-ion laser

    International Nuclear Information System (INIS)

    The reparative processes of the pigmented iris of the rabbit were analysed with ultrastructural methods. Clearing of the damaged area by macrophages is the first step in the reparative processes. Clump cells are macrophages which are observed from the first day of the injury until the ninth week. Repair of the anterior surface of the iris is largely finished after 32 days. The repair of collagenous fibres reaches its maximum activity 32 days after irradiation. The pigment epithelium has only an insignificant regeneration potential. Irradiation of the iris by the argon-ion laser results in an atropic, hyperpigmented scar. The rapid regeneration of a lesion induced by the argon-ion laser in the rabbit iris casts doubt as to whether this method could be applied to the human eye with equal success. (orig.) 891 AJ/orig. 892 MB

  4. Polycystic ovarian disease treated by laparoscopic argon laser capsule drilling: comparison of vaporization versus perforation technique.

    Science.gov (United States)

    Heylen, S M; Puttemans, P J; Brosens, I A

    1994-06-01

    Forty-four anovulatory women with polycystic ovarian disease (PCOD) were laparoscopically treated with the argon laser. Eighty percent of them were previously resistant to clomiphene citrate therapy. After surgery spontaneous ovulation occurred in 80% of the women. Spontaneous conception occurred in 55% of patients, and another 18% of the women who were previously resistant to clomiphene citrate conceived post-operatively after clomiphene citrate therapy. This gives an overall conception rate of 73% after 18 months (using life table analysis). Two different drilling techniques were used: classical vaporization of the ovarian capsule (22 women), and simple perforation of the ovarian capsule with subcapsular destruction of the ovarian stroma (22 women). No different ovulation or pregnancy rates were observed post-operatively between the two techniques. These results suggest that patients with PCOD can be induced to ovulate, and subsequently conceive, by laparoscopic argon laser treatment. The technique with minimal trauma to the ovarian capsule seems preferable. PMID:7962372

  5. Effects of argon laser radiation on aortic endothelial cells: Early membrane changes and proliferative response

    International Nuclear Information System (INIS)

    Membrane fluidity, transmembrane signaling responses, and proliferative characteristics of endothelial cells were studied to characterize biochemical and molecular changes after treatment with argon laser energy. Bovine aortic endothelial cells grown in monolayers were irradiated at 50, 100, and 200 J with an argon laser (wavelength, 488 and 514 nm). Proliferation, assayed by [3H]thymidine incorporation, was measured daily for 6 days. An initial lag phase was observed for irradiated cells when compared to nonirradiated controls (P less than 0.03), with eventual recovery by the third day. Membrane fluidity, determined by fluorescence anisotropy, was measured 1 hr after irradiation. A decrease in static rotational motion of 1,6-diphenyl-1,3,5-hexatriene (DPH) was noted in irradiated versus nonirradiated cells indicating a decrease in membrane fluidity (P less than 0.02). Dynamic studies of intracellular calcium and pH flux utilizing fluorescent probes demonstrated a preserved response to mitogenic stimulation. An increase in intracellular Ca2+ with a concomitant alkalinization of the intracellular milieu was observed in irradiated and non-irradiated cells in response to stimulation with endothelial cell growth factor (ECGF). These responses resemble those characterized for other mitogens. Argon laser energy applied to aortic endothelial cells decreases membrane fluidity early after irradiation. These alterations probably cause the initial lag observed in their proliferative response; however, the capacity to respond to exogenous mitogenic stimulation is maintained

  6. Spatial characterization of laser induced Yb plasma in argon using optical emission spectroscopy: Pressure effect

    International Nuclear Information System (INIS)

    Highlights: • Laser induced Yb plasma at different pressure of Argon is spatially investigated. • O-TOF profiles and excitation temperature are used to characterize the plasma. • At 100 Pa of argon background gas, shock wave begins to be formed. • Drag force expansion describes the plasma propagation at pressures bigger than 1 Pa. • Two components of velocity distribution of the Yb atoms are estimated. - Abstract: Spatial and temporal behavior of laser induced Ytterbium plasma plume is studied using optical emission spectroscopy technique. A third harmonic Nd:YAG nanosecond laser was used to generate Yb plasma plume at different Argon background pressures (1, 10, 102, 103 and 104 Pa). The plasma dynamics was investigated based on the spatial behavior of the excitation temperature coupled with optical time of flight (O-TOF) profiles of neutral Yb emission line (555.65 nm) along the propagation axe of the plasma plume. Drag force model was appropriate to describe the propagation dynamics at all pressures except of the lowest one (1 Pa) where free expansion model is dominant. The velocity distribution of Yb I atoms were extracted using two terms of Shifted Maxwell–Boltzmann (SMB) distribution. The correlation between the spatial comportment of both excitation temperature and O-TOF profiles is discussed

  7. Effects of argon laser on atheromatous plaques. A preliminary study on post-mortem arterial specimens

    International Nuclear Information System (INIS)

    The effects of argon laser radiation of human atheroma were studied in vitro. Lesions produced were craters from total tissue volatilization surrounded by a thin zone of coagulation. The degree of tissue destruction was related to the energy used and the direction of the laser beam in relation to the atheromatous stenotic lesion. These findings confirm that it is possible to destroy the atheroma under controlled conditions, but a the non-negligeable risk of perforation. By allowing visual control, the angioscope should ensure increased safety in use and provide hope for future applications of this method by the percutaneous route in the treatment of established atheromatous disease

  8. 21 CFR 886.4690 - Ophthalmic photocoagulator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ophthalmic photocoagulator. 886.4690 Section 886...) MEDICAL DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4690 Ophthalmic photocoagulator. (a) Identification. An ophthalmic photocoagulator is an AC-powered device intended to use the energy from an...

  9. Effects of laser photocoagulation on serum angiopoietin-1, angiopoietin-2, angiopoietin-1/angiopoietin-2 ratio, and soluble angiopoietin receptor Tie-2 levels in type 2 diabetic patients with proliferative diabetic retinopathy

    Institute of Scientific and Technical Information of China (English)

    Qiao-Ying; You; Fu-Yuan; Zhuge; Qi-Qian; Zhu; Xu-Wei; Si

    2014-01-01

    ·AIM: To determine the effects of laser photocoagulation on serum levels of angiopoietin-1(Ang-1),angiopoietin-2(Ang-2), soluble angiopoietin receptor Tie-2(Tie-2), Ang-1/Ang-2 ratio and vascular endothelial growth factor(VEGF) in patients with type 2diabetes mellitus(T2DM) and proliferative diabetic retinopathy(PDR). We also explored the role of the Ang/Tie system in PDR.·METHODS:Totally 160patientswithT2 DM, including50 patients with non-diabetic retinopathy(NDR), 58 patients with non-proliferative diabetic retinopathy(NPDR), and52 patients with PDR were enrolled in this study. Serum Ang-1, Ang-2, Tie-2 receptor and VEGF levels were measured using enzyme-linked immunosorbent assays for all patients and were repeated in 26 patients who underwent laser photocoagulation two months after the procedure.·RESULTS:ThemedianlevelsofAng-2andVEGFinserum were significantly higher in the NPDR group(4.23 ng/mL and 303.2 pg/mL, respectively) compared to the NDR group(2.67 ng/mL and 159.8 pg/mL, respectively, P <0.01), with the highest level in the PDR group(6.26 ng/mL and531.2 pg/mL, respectively, P <0.01). The median level of Ang-1 was significantly higher in the NPDR group(10.77ng/mL) compared to the NDR group(9.31 ng/mL) and the PDR groups(9.54 ng/mL)(P <0.05), while no difference was observed between the PDR and NDR groups. Ang-1/Ang-2 ratio of PDR group was lowest in three groups(1.49 vs 2.69 and 2.90, both P <0.01). The median level of Tie-2was not significantly different among three groups(P >0.05).Ang-2 was positively correlated with VEGF and Tie-2 in the PDR and NPDR groups(both P <0.05). Among the 26 patients who underwent laser photocoagulation, serum Ang-2 and VEGF levels significantly decreased(both P <0.05), whereas serum Ang-1 level and Ang-1/Ang-2ratio were weakly increased(P >0.05). The median levels of Ang-2 and VEGF in serum were highest in PDR group,however, Ang-1/Ang-2 ratio of PDR group was lowest in three groups.·CONCLUSION: Laser photocoagulation can

  10. The effect of argon laser irradiation on demineralization resistance of human enamel adjacent to orthodontic brackets: an in vitro study.

    Science.gov (United States)

    Noel, Lloyd; Rebellato, Joe; Sheats, Rose D

    2003-06-01

    Argon lasers, because of their significant timesavings over conventional curing lights, have been investigated for use in bonding orthodontic brackets. They are also being investigated for their ability to confer demineralization resistance on enamel, which is of great interest in orthodontics. A two-part in vitro study on 86 human posterior teeth was conducted to determine the effects of a five-second argon laser exposure on shear bond strength and to evaluate the effects of a five- and 10-second argon laser exposure (250 mW) on demineralization of enamel surrounding orthodontic brackets after exposure to an artificial caries bath. Brackets cured with the argon laser for five seconds yielded mean bond strengths similar to those attained with a 40-second conventional light-cured control (n = 13 per group, 20.4 vs 17.8 MPa). Brackets cured with the argon laser for 10 seconds resulted in significantly lower mean lesion depth when compared with a visible light control (n = 20 per group, 107.8 vs 137.2 microm, P = .038). There were no statistically significant differences in lesion depth between the five-second argon laser and the visible light control groups. Overall, there was a 15% and 22% reduction in lesion depths for the five- and 10-second group, respectively. Poor correlations were found between the clinical appearance of decalcifications and their lesion depth. Argon lasers used for bonding orthodontic brackets would save a significant amount of chair time while possibly conferring demineralization resistance upon the enamel. PMID:12828433

  11. Investigations of laser-induced plasma in argon by Thomson scattering

    International Nuclear Information System (INIS)

    The Thomson scattering method was applied to quantify the electron number density and temperature of a laser spark formed in argon. The laser spark was generated by focusing a 15 mJ beam from the second harmonic (λL = 532 nm) of a nanosecond Nd:YAG laser with an 80 mm focal length lens. Images of the spark emission were obtained for times between 1 ns and 20 μs after the laser pulse in order to characterize its spatial evolution. The electron density and temperature for the core of the plasma plume at different instants of its evolution were determined from the Thomson scattered spectra of another nanosecond Nd:YAG laser (532 nm, 10 to 60 mJ/pulse). In the time interval between 400 ns and 10 μs between the laser induced plasma and Thomson scattering probe pulses, we found ne and Te to decrease from 4.3 × 1023 m−3 to 2.4 × 1022 m−3 and from 50 700 K to 11 100 K, respectively. Special care was paid to the plasma disturbance by the probe laser pulse in Thomson scattering experiments due to absorption of laser photons by electrons through the inverse bremsstrahlung process.

  12. Investigations of laser-induced plasma in argon by Thomson scattering

    Energy Technology Data Exchange (ETDEWEB)

    Mendys, A., E-mail: agata.mendys@uj.edu.pl [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Dzierzega, K.; Grabiec, M. [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Pellerin, S. [GREMI - site de Bourges, Universite d' Orleans, CNRS, rue Gaston Berger BP 4043, 18028 Bourges (France); Pokrzywka, B. [Obserwatorium Astronomiczne na Suhorze, Uniwersytet Pedagogiczny, ulica Podchorazych 2, 30-084 Krakow (Poland); Travaille, G.; Bousquet, B. [Centre de Physique Moleculaire Optique et Hertzienne, Universite Bordeaux 1, 351 Cours de la Liberation, 33405 Talence CEDEX (France)

    2011-09-15

    The Thomson scattering method was applied to quantify the electron number density and temperature of a laser spark formed in argon. The laser spark was generated by focusing a 15 mJ beam from the second harmonic ({lambda}{sub L} = 532 nm) of a nanosecond Nd:YAG laser with an 80 mm focal length lens. Images of the spark emission were obtained for times between 1 ns and 20 {mu}s after the laser pulse in order to characterize its spatial evolution. The electron density and temperature for the core of the plasma plume at different instants of its evolution were determined from the Thomson scattered spectra of another nanosecond Nd:YAG laser (532 nm, 10 to 60 mJ/pulse). In the time interval between 400 ns and 10 {mu}s between the laser induced plasma and Thomson scattering probe pulses, we found n{sub e} and T{sub e} to decrease from 4.3 Multiplication-Sign 10{sup 23} m{sup -3} to 2.4 Multiplication-Sign 10{sup 22} m{sup -3} and from 50 700 K to 11 100 K, respectively. Special care was paid to the plasma disturbance by the probe laser pulse in Thomson scattering experiments due to absorption of laser photons by electrons through the inverse bremsstrahlung process.

  13. Morphology and characteristics of laser-induced aluminum plasma in argon and in air: A comparative study

    Science.gov (United States)

    Bai, Xueshi; Cao, Fan; Motto-Ros, Vincent; Ma, Qianli; Chen, Yanping; Yu, Jin

    2015-11-01

    In laser-induced breakdown spectroscopy (LIBS), ablation takes place in general in an ambient gas of the atmospheric pressure, often in air but also in noble gas such as argon or helium. The use of noble gas is known to significantly improve the performance of the technique. We investigate in this work the morphology and the characteristics of induced plasma in argon and in air. The purpose is to understand the mechanism of the analytical performance improvement by the use of argon ambient with respective to air ambient and the dependence on the other experimental parameters such as the laser fluence. The observation of plasma morphology in different ambient gases provides also information for better design of the detection system which optimizes the signal collection according to the used ambient gases. More specifically, the expansion of the plasma induced on an aluminum target with nanosecond infrared (1064 nm) laser pulse in two ambient gases, argon and the atmospheric air, has been studied with spectroscopic imaging at short delays and with emission spectroscopy at longer delays. With relatively low ablation laser fluence (65 J/cm2), similar morphologies have been observed in argon and in air over the early stage of plasma expansion, while diagnostics at longer delay shows stronger emission, higher electron density and temperature for plasma induced in argon. With higher ablation laser fluence (160 J/cm2) however, different expansion behaviors have been observed, with a stagnating aluminum vapor near the target surface in air while a propagating plume away from the target in argon. The craters left on the target surface show as well corresponding difference: in air, the crater is very shallow with a target surface chaotically affected by the laser pulse, indicating an effective re-deposition of the ablated material back to the crater; while in Ar a deeper crater is observed, indicating an efficient mass removal by laser ablation. At longer delays, a brighter

  14. Argon laser iridoplasty : A primary mode of therapy in primary angle closure glaucoma

    Directory of Open Access Journals (Sweden)

    Agarwal H

    1991-01-01

    Full Text Available Argon laser iridoplasty was performed in 40 eyes of 33 patients of primary angle closure glaucoma. There were 12 male and 21 female patients. The mean ages of the male and female patients were 51 years and 48.4 years respectively. Forty eyes were divided into two groups. Group I consisted of ten eyes of subacute angle closure glaucoma and group II included thirty eyes of chronic angle closure glaucoma. Argon laser iridoplasty was performed with Coherent 9000 model using laser settings of spot size 200 micron, duration 0.2 second and power 0.7 watt. A total of 80 spots were applied over 360 degree circumference. The intraocular pressure control (below 22 mm Hg was achieved after iridoplasty in all the eyes (100% in group I, where as in group II the intraocular pressure was controlled in 70% eyes. The follow up period varied from 3 months to one year with a mean of eight months. The success rate with iridoplasty was directly related to the extent of peripheral anterior synechiae, optic disc cupping and presence of visual field changes.

  15. Production of highly charged ions of argon by optical field ionization in a relativistic laser field

    International Nuclear Information System (INIS)

    We observed the highly charged ions of argon by optical field ionization in a relativistic intensity regime. Charge states up to Ar15+ were produced at the highest intensity of 800 nm, linearly polarized 20 fs Ti: sapphire laser pulses. The peak intensity of the pulse is determined by comparing the measured ion production curve for Ar9+ with ADK theory. The results of these measurements of the ionization indicate that the maximum peak intensity is achieved to ∼2x1019 W/cm2. (author)

  16. Temperature rise and tissue damage in the primate retina from argon laser irradiation

    International Nuclear Information System (INIS)

    Temperatures from argon laser irradiation were measured in vivo in Macaca mulatta retinae for exposure durations .002s to 100s with a microthermocouple probe specially designed for measuring transient tissue temperatures. Measured temperatures were compared to predicted temperatures from a mathematical model of temperature for the retina and choroid. Radiant energy levels required to produce retinal lesions were determined by both ophthalmoscopic and microscopic examination of the ocular fundus. Temperatures associated with retinal lesion formation were measured, for macular and paramacular exposures. Measured temperatures were used to improve a rate process model for predicting thermal damage to the retina

  17. Transurethral laser urethrotomy with argon laser: experience with 900 urethrotomies in 450 patients from 1978 to 1993.

    Science.gov (United States)

    Becker, H C; Miller, J; Nöske, H D; Klask, J P; Weidner, W

    1995-01-01

    From April 1978 to September 1993, the Department of Urology of Giessen Medical School used laser urethrotomy as standard endoscopic treatment in benign urethral strictures. In this period, 900 urethrotomies were performed in 450 patients. The majority of strictures treated were iatrogenic (65%), located in the posterior urethra (62.8%) and classified as short (laser urethrotomy was carried out in the 12 degrees position according to the technique of internal optical urethrotomy. An indwelling transurethral catheter was left for 48 h after urethrotomy. Uroflowmetry after argon laser urethrotomy revealed the efficacy of the method. A retrospective analysis of the operations was performed. Analysis showed that recurrence appeared on average after 15.2 months (range 1-39) in up to 70.1%. Nearly 50% of recurrence was evident within 1 year following surgery. Recurrence was independent of location, length and etiology of the stricture. We conclude according to our data that argon laser urethrotomy is technically feasible. Due to the high recurrence rate the method offers no advantage over conventional internal optical urethrotomy. PMID:8540160

  18. Demonstration of a neonlike argon soft-x-ray laser with a picosecond-laser-irradiated gas puff target.

    Science.gov (United States)

    Fiedorowicz, H; Bartnik, A; Dunn, J; Smith, R F; Hunter, J; Nilsen, J; Osterheld, A L; Shlyaptsev, V N

    2001-09-15

    We demonstrate a neonlike argon-ion x-ray laser, using a short-pulse laser-irradiated gas puff target. The gas puff target was formed by pulsed injection of gas from a high-pressure solenoid valve through a nozzle in the form of a narrow slit and irradiated with a combination of long, 600-ps and short, 6-ps high-power laser pulses with a total of 10 J of energy in a traveling-wave excitation scheme. Lasing was observed on the 3p (1)S(0)?3s (1)P(1) transition at 46.9 nm and the 3d (1)P(1)?3p (1)P(1) transition at 45.1 nm. A gain of 11 cm(-1) was measured on these transitions for targets up to 0.9 cm long. PMID:18049619

  19. Volume Measurements of Laser-generated Pits for In Situ Geochronology using KArLE (Potassium-Argon Laser Experiment)

    Science.gov (United States)

    French, R. A.; Cohen, B. A.; Miller, J. S.

    2014-01-01

    The Potassium-Argon Laser Experiment( KArLE), is composed of two main instruments: a spectrometer as part of the Laser-Induced Breakdown Spectroscopy (LIBS) method and a Mass Spectrometer (MS). The LIBS laser ablates a sample and creates a plasma cloud, generating a pit in the sample. The LIBS plasma is measured for K abundance in weight percent and the released gas is measured using the MS, which calculates Ar abundance in mols. To relate the K and Ar measurements, total mass of the ablated sample is needed but can be difficult to directly measure. Instead, density and volume are used to calculate mass, where density is calculated based on the elemental composition of the rock (from the emission spectrum) and volume is determined by pit morphology. This study aims to reduce the uncertainty for KArLE by analyzing pit volume relationships in several analog materials and comparing methods of pit volume measurements and their associated uncertainties.

  20. THz wave emission from argon in two-color laser field

    Institute of Scientific and Technical Information of China (English)

    杜玲玲; 赵松峰; 周效信; 赵增秀

    2015-01-01

    Terahertz (THz) wave emission from argon atom in a two-color laser pulses is studied numerically by solving the one-dimensional (1D) time-dependent Schr ¨odinger equation. The THz spectra we obtained include both discontinuous and continuum ones. By using the special basis functions that we previously proposed, our analysis points out that the discontinuous and continuum parts are contributed by bound–bound and continuum–continuum transition of atomic energy levels. Although the atomic wave function is strongly dressed during the interaction with laser fields, our identification for the discontinuous part of the THz wave shows that the transition between highly excited bound states can still be well described by the field-free basis function in the tunneling ionization regime.

  1. The Potassium-Argon Laser Experiment (KArLE): In Situ Geochronology for Planetary Robotic Missions

    Science.gov (United States)

    Cohen, Barbara

    2016-01-01

    The Potassium (K) - Argon (Ar) Laser Experiment (KArLE) will make in situ noble-gas geochronology measurements aboard planetary robotic landers and roverss. Laser-Induced Breakdown Spectroscopy (LIBS) is used to measure the K abun-dance in a sample and to release its noble gases; the evolved Ar is measured by mass spectrometry (MS); and rela-tive K content is related to absolute Ar abundance by sample mass, determined by optical measurement of the ablated volume. KArLE measures a whole-rock K-Ar age to 10% or better for rocks 2 Ga or older, sufficient to resolve the absolute age of many planetary samples. The LIBS-MS approach is attractive because the analytical components have been flight proven, do not require further technical development, and provide complementary measurements as well as in situ geochronology.

  2. Biostimulation of human carcinoma cells with the argon laser: a previously unreported potential iatrogenic effect of lasers

    Energy Technology Data Exchange (ETDEWEB)

    Castro, D.J.; Saxton, R.E.; Fetterman, H.R.; Castro, D.J.; Ward, P.H.

    1988-01-01

    The human squamous carcinoma cell line P3 was subjected to treatment with a single mode argon laser at 514.5 nm. The temperature and energy levels delivered to the target cells were determined by a reproducible method of dosimetry. At energy levels between 860 to 990 J/cm2 and a corresponding temperature of 39 +/- 1 degrees C, a significant delayed stimulation in DNA synthesis was noted after 24 hours, but the cells remained viable. However, at energy levels and temperatures higher or equal to 1100 J/cm2 (41 degrees C), an immediate suppression of DNA synthesis was accompanied by nonviability of the P3 carcinoma cells. These results indicate that the argon laser has potential for selective biostimulation on carcinoma cell duplication at the specific non-thermal range of 39 +/- 1 degrees C. Similar effects were not observed when the P3 carcinoma cells were heated to this same temperature using a standard heat bath. This phenomenon appears to represent a previously undescribed potential iatrogenic effect of the monochromatic laser beam in the treatment of cancer.

  3. Effect of pulse duration on resonant heating of laser-irradiated argon and deuterium clusters.

    Science.gov (United States)

    Gupta, Ayush; Antonsen, T M; Taguchi, T; Palastro, J

    2006-10-01

    We study the effect of pulse duration on the heating of single van der Waals bound argon and deuterium clusters by a strong laser field using a two-dimensional (2D) electrostatic particle-in-cell (PIC) code in the range of laser-cluster parameters such that kinetic as well as hydrodynamic effects are active. Heating is dominated by a collisionless resonant absorption process that involves energetic electrons transiting through the cluster. A size-dependent intensity threshold defines the onset of this resonance [T. Taguchi, Physical Review Letters, 92, 20 (2004)]. It is seen that increasing the laser pulse duration lowers this intensity threshold and the energetic electrons take multiple laser periods to transit the cluster instead of one laser period. Our simulations also show that strong electron heating is accompanied by the generation of a high-energy peak in the ion energy distribution function. We also calculate the yield of thermonuclear fusion neutrons from exploding deuterium clusters using the PIC model with periodic boundary conditions that allows for the interaction of ions from neighboring clusters. PMID:17155183

  4. 中药联合视网膜激光光凝术治疗外伤性黄斑出血临床研究%Clinical Study of Traumatic Macula Lutea Hemorrhage by TCM Combine with Retinal Laser Photocoagulation

    Institute of Scientific and Technical Information of China (English)

    姚学云

    2015-01-01

    目的:观察中药联合视网膜激光光凝术治疗外伤性黄斑出血的临床疗效。方法:64例确诊为外伤性黄斑出血患者随机分为对照组和治疗组各32例,对照组行视网膜激光光凝术治疗,治疗组在对照组基础上加用中药治疗。两组均以7 d为1个疗程,1个疗程后比较两组视力疗效、黄斑出血疗效和黄斑区荧光素渗漏疗效。结果:治疗组视力有效率为93.75%,对照组有效率为78.13%,两组有效率比较,差异有统计学意义( P<0.05);治疗组黄斑出血有效率为78.13%,对照组黄斑出血有效率为62.50%,两组有效率比较,差异有统计学意义(P<0.05);治疗组黄斑区荧光素渗漏有效率为87.5%,对照组黄斑区荧光素渗漏有效率为71.88%,两组有效率比较,差异有统计学意义( P<0.05)。结论:中药联合视网膜激光光凝术治疗外伤性黄斑出血疗效显著。%Objective:To observe the clinical effects of traumatic macula lutea hemorrhage by TCM combine with retinal laser photocoag-ulation. Methods:64 patients divided into control group and treatment group,each group is 32 cases. The control group was given retinal laser photocoagulation. The treatment group was based on the the control group with TCM. 1course is 7days,after the course,compare the curative effect of eyesight,macula lutea hemorrhage and fluorescein leakage in macular region. Results:The eyesight effective rate in the treatment group is 93. 75%,while in the control group is 78. 13%,compare with the effective rate between the two groups were sta-tistically significant(P<0. 05);In the treatment group,the effective rate of macula lutea hemorrhage is 78. 13%,while the control group is 62.50%,compare with the effective rate between the two groups were statistically significant(P<0. 05);In the treatment group,the effective rate of macular region fluorescein leakage is 87. 5%,while in the control group is 71. 88%,compare with

  5. Argon green-Nd: YAG dual laser posterior hyaloidotomy: An innovative approach toward treatment of premacular hemorrhage

    Directory of Open Access Journals (Sweden)

    Ashish Sharma

    2013-01-01

    Full Text Available Background: Neodymium: YAG (Nd: YAG laser and argon laser has been used to treat premacular hemorrhage either alone or rarely in combination. Materials and Methods: We describe a new technique of treating premacular hemorrhage by performing hyaloidotomy using a combination of argon green-Nd: YAG laser. We utilized subthreshold energy levels of Nd: YAG laser of 2.0 mJ as compared to the normal recommendation of 3.6-50 mJ. Results and Conclusions: This technique is easy, effective, and safe to manage premacular hemorrhage. The principle behind this combined laser treatment was to make the internal limiting membrane (ILM taut by initial exposure to argon green laser, which allowed us to employ the subthreshold energy levels of Nd: YAG laser. We would like to assess the role of this combined treatment modality in comparison to other modalities, including solitary laser therapy in the management of premacular hemorrhage by performing a prospective, randomized long-term study.

  6. Studies in Above- and Below-Threshold Harmonics in Argon with an Infrared Femtosecond Laser

    Science.gov (United States)

    Chew, Andrew; Yin, Yanchun; Li, Jie; Ren, Xiaoming; Cunningham, Eric; Wu, Yi; Chang, Zenghu

    2016-05-01

    We investigate and compare the above- and below-threshold harmonics in Argon gas using our recently-developed 1 kHz, two-cycle (11.4 fs), 3mJ, and carrier-envelope-phase(CEP)-stable laser at 1.6 μm. Such ultraviolet pulses can serve as pump or probe for studying dynamics in atoms and molecules. Unlike high harmonics with photon energy well above the ionization potential, the mechanism for generating harmonics near the ionization threshold is still under intense investigation. Previous work by Chini et al. on below-threshold harmonics was done using a 0.8 μm few-cycle Ti:Sapphire spectrally-broadened source with energy up to 300 μJ. It has been predicted by theory that free-free transitions dominate the below threshold harmonic generation as the laser wavelength increase from near infrared to mid-infrared. We are therefore interested in investigating how using a longer wavelength laser might lead to changes to the behavior of below-threshold harmonics when we vary various parameters. We report the π-periodity CEP dependence and ellipticity dependence of the above- and below-threshold harmonics. This material was based on work supported by National Science Foundation (1068604), Army Research Office (W911NF-14-1-0383), Air Force Office of Scientific Research (FA9550-15-1-0037) and the DARPA PULSE program by a Grant from AMRDEC (W31P4Q1310017).

  7. Comparison of the argon tunable dye laser with the flashlamp pulsed dye laser in treatment of facial telangiectasia

    Science.gov (United States)

    Broska, Pamela; Martinho, Elena; Goodman, Matthew M.

    1992-06-01

    A prospective, side-by-side comparison study of two different lasers for the treatment of solar- induced telangiectasia was carried out in 14 patients at the Beckman Laser Institute and Medical Clinic. The argon tunable dye laser (Coherent, Palo Alto, Calif.) was used in the method modified from Orenstein and Nelson to completely treat discrete telangiectasias on one cheek. Specifically, the argon tunable dye laser (ATDL) was set at 0.7 - 0.8 watts, 585 nm wavelength, shutter-pulsed at 0.1 second duration with a spot size of 0.1 mm, and individual vessels were 'traced out' with 4X loupe magnification. Each patient's opposite cheek was then treated in the standard fashion with the flashlamp pulsed dye laser (Candela, Natick, Mass.) using a technique similar to Polla's et al. Specifically, the flashlamp pulsed dye laser (FPDL) was set at 585 nm wavelength, pulsed mode of 450 microseconds pulse duration, spot size of 5 mm, overlapping 10 - 20%, with power densities of 5.5 to 6.5 joules/cm2. All patients had symmetrical cheek telangiectasias of several years' duration. Patients were treated on day 0, and examined on weeks 2, 4, and 6. Photos were taken at each visit, and evaluation was done by questionnaire and direct observation, as well as by photographic slides later projected to an impartial panel. Final evaluation by the panel at week 6 showed 11/14 patients with excellent results (75 - 100% clearing) at sites treated with the FPDL, compared with 4/14 with the ATDL. In contrast, 4/14 FPDL sites were graded as fair to minimal improvement, and 9/14 as fair for the ATDL. The patients' self-evaluations graded the final results very similar to that of the panel. Most patients were bothered by the ecchymosis and hyperpigmentation associated with the FPDL, resulting in less than 50% of the patients preferring the FPDL despite its more impressive results. We conclude that the final results favor the FPDL over the ATDL for treatments of facial telangiectasia. However, non

  8. Successful Surgical Management of Retinopathy of Prematurity Showing Rapid Progression despite Extensive Retinal Photocoagulation.

    Science.gov (United States)

    Gadkari, Salil S; Kulkarni, Sucheta R; Kamdar, Rushita R; Deshpande, Madan

    2015-01-01

    The management of retinopathy of prematurity (ROP) can be challenging in preterm babies with a gestational age oxygen therapy for respiratory distress, sepsis, neonatal jaundice). A premature infant presented with "hybrid" zone 1 disease in the right eye and aggressive posterior ROP in the left eye. Both eyes were adequately treated with laser photocoagulation; however, the eyes deteriorated and progressed to stage 4 ROP. Both eyes eventually underwent intravitreal bevacizumab followed by lens sparing vitrectomy with good anatomical and visual outcome. Anticipation of progression despite laser photocoagulation in certain clinical scenarios, frequent follow-up and timely surgical intervention is paramount. PMID:26180484

  9. Panretinal photocoagulation versus intravitreal injection retreatment pain in high-risk proliferative diabetic retinopathy

    Directory of Open Access Journals (Sweden)

    Célia Regina Farias de Araújo Lucena

    2013-02-01

    Full Text Available PURPOSE: To compare pain related to intravitreal injection and panretinal photocoagulation in the management of patients with high-risk proliferative diabetic retinopathy. METHODS: Prospective study including patients with high-risk proliferative diabetic retinopathy and no prior laser treatment randomly assigned to receive panretinal photocoagulation (PRP group or panretinal photocoagulation plus intravitreal ranibizumab (PRPplus group. In all patients, panretinal photocoagulation was administered in two sessions (weeks 0 and 2, and intravitreal ranibizumab was administered at the end of the first laser session in the PRPplus group. Retreatment was performed at weeks 16 and 32 if active new vessels were detected at fluorescein angiography. Patients in the PRPplus group received intravitreal ranibizumab and patients in the PRP group received 500-µm additional spots per quadrant of active new vessels. After the end of retreatment, a 100-degree Visual Analog Scale was used for pain score estimation. The patient was asked about the intensity of pain during the whole procedure (retinal photocoagulation session or intravitreal ranibizumab injection. Statistics for pain score comparison were performed using a non-parametric test (Wilcoxon rank sums. RESULTS: Seventeen patients from PRPplus and 14 from PRP group were evaluated for pain scores. There were no significant differences between both groups regarding gender, glycosylated hemoglobin and disease duration. Mean intravitreal injection pain (±SEM was 4.7 ± 2.1 and was significantly lower (p<0.0001 than mean panretinal photocoagulation pain (60.8 ± 7.8. Twelve out of 17 patients from the PRPplus group referred intensity pain score of zero, while the minimal score found in PRP group was found in one patient with 10.5. CONCLUSION: In patients with high-risk proliferative diabetic retinopathy who needed retreatment for persistent new vessels, there was more comfort for the patient when retreatment

  10. Laser light scattering from silicon particles generated in an argon diluted silane plasma

    Science.gov (United States)

    Qin, Y.; Kortshagen, U. R.; Aydil, E. S.

    2016-03-01

    We conducted laser light scattering (LLS) measurements in a 13.56 MHz capacitively coupled dusty plasma maintained in silane and argon to study the spatial distribution of silicon nanoparticles and nanoparticle agglomerates. Specifically, we focused on the temporal evolution of their spatial distribution in the plasma as a function of pressure and power. We observed three distinct types of temporal evolution behavior of the nanoparticle dust cloud in the plasma and classified these into three regimes based on pressure and power. Each regime features a distinct pattern in laser light scattering measurements. At low pressures (˜80-100 mTorr) and high powers (˜40-60 W) we observed periodically repeating expansions and contractions of a continuous dust cloud for the first time. Dust voids, which have been reported before, were also observed at high pressures (˜100-150 mTorr) and low powers (˜20-40 W) in the center of the plasma. A mechanism is proposed to explain the observed dynamics of the nanoparticles. The balance between the ion drag force and electrostatic forces and their dependence on particle size are hypothesized to be the dominant factors that determine the nanoparticle cloud dynamics.

  11. Developement of the Potassium-Argon Laser Experiment (KArLE) for In Situ Geochronology

    Science.gov (United States)

    Cohen, Barbara A.

    2012-01-01

    Absolute dating of planetary samples is an essential tool to establish the chronology of geological events, including crystallization history, magmatic evolution, and alteration. Thus far, radiometric geochronology of planetary samples has only been accomplishable in terrestrial laboratories on samples from dedicated sample return missions and meteorites. In situ instruments to measure rock ages have been proposed, but none have yet reached TRL 6, because isotopic measurements with sufficient resolution are challenging. We have begun work under the NASA Planetary Instrument Definition and Development Program (PIDDP) to develop the Potassium (K) - Argon Laser Experiment (KArLE), a novel combination of several flight-proven components that will enable accurate KAr isochron dating of planetary rocks. KArLE will ablate a rock sample, measure the K in the plasma state using laser-induced breakdown spectroscopy (LIBS), measure the liberated Ar using quadrupole mass spectrometry (QMS), and relate the two by measuring the volume of the abated pit using a optical methods such as a vertical scanning interferometer (VSI). Our preliminary work indicates that the KArLE instrument will be capable of determining the age of several kinds of planetary samples to 100 Myr, sufficient to address a wide range of geochronology problems in planetary science. Additional benefits derive from the fact that each KArLE component achieves analyses common to most planetary surface missions.

  12. Use of laser-excited atomic fluorescence spectroscopy for characterization of an argon inductively coupled plasma

    International Nuclear Information System (INIS)

    Laser-excited atomic fluorescence spectroscopy (LEAFS) is investigated and employed as a diagnostic technique for study of the argon inductively coupled plasma (ICP). Computer simulations are used to describe the behavior of nonsteady-state laser excited fluorescence (LEF) for multi-level atomic systems under conditions expected to be encountered in the ICP and an atmospheric pressure flame. These simulations are then compared to experimental data collected under similar conditions in the ICP and a flame. These studies show that LEAFS should be a useful tool for characterization of an ICP, with certain limitations. Relatively small changes in saturated LEF signals under changing quenching and mixing conditions are both predicted theoretically and observed experimentally for several atomic systems. This independence from quenching and mixing effects allows one to relate saturated LEF signals directly to relative number densities of species when spatially scanning over an inhomogeneous medium, such as an ICP discharge, where significant changes in quenching can be encountered in a single scan. SSI values are also found to be useful as indicators of relative collisional quenching rates and relative degree of LTE establishment in the ICP, as well as ease of saturation for a given transition

  13. Effect of Fast Curing Lights, Argon Laser, and Plasma Arc on Bond Strengths of Orthodontic Brackets: An In Vitro Study

    Directory of Open Access Journals (Sweden)

    M. Hashem-Hoseini

    2008-12-01

    Full Text Available Objective: Nowadays light-cured composites are used widely by orthodontists to bond brackets. As these composites require 20-40 seconds time per tooth to be light cured, more chair-time in needed compared to self-cured composites. In recent years, the argon laser and plasma arc lights have been introduced in dentistry to reduce this curing time. The purpose of this study was to compare bond strength of brackets bonded with the argon la-ser and plasma arc light with those bonded with the conventional halogen light.Materials and Methods: Fifty-one intact human premolars were randomly divided into three groups of 17 teeth each. Stainless steel twin premolar brackets (018- in Dyna lock, 3M Unitek were bonded to the teeth using one of these curing devices in each group: the halogen unit (Coltolux 75, Switzerland, the argon laser unit (Bo-5, Iran , and the plasma arc unit (Remecure 15, Belgium. The orthodontic adhesive was the same in the three groups (Transbond XT, 3M Unitek. After thermal cycling, the diametral tensilebond strength of specimens was measured using a debonding plier in a Zwick Universal Testing machine (Z/100, Germany.Results: The mean bond strengths was 17.344 MPa (SD=4.567 for halogen 19.172 MPa(SD=6.328 for laser and 19.322 MPa (SD=4.036 for plasma arc groups. No statistically significant difference existed in the mean bond strengths among three groups.Conclusion: Argon laser lights, significantly reducing the curing time of orthodonticbrackets without affecting bond strength, have the potential to be considered as advanta-geous alternatives to conventional halogen light.

  14. Assessment of Sesame Oil as a Radioprotector against Some Biochemical Alterations Induced by Argon Laser on Albino Rat Head

    International Nuclear Information System (INIS)

    The plant (Sesamum indicum) is a lovely annual shrub with white bell-shaped flowers tinged with a hint of blue, red or yellow. The rich, almost odourless oil expressed from the tiny seeds is very stable and contains an antioxidant system comprising sesamol and sesamolinol formed from sesamolin, which substantially reduces its oxidation rate. The objective of this study was designed to evaluate the efficacy of sesame oil to reduce the altered biochemical indices in brain of irradiated rats exposed to argon laser at wavelength 488 nm. Methods: Animals were divided into 4 groups. Group 1: Control group where 6 rats are dissected as control for other irradiated rats. Group 2: Irradiated with argon laser at wavelength 488 nm receiving energy (1.0 J x 3 times) on head of rats day by day. Group 3: Animals administered with sesame oil 500 mg/kg body wt/day for 20 successive days. Group 4: Irradiated with argon laser at wavelength 488 nm receiving an energy (1.0 J x 3 times) animals administered with sesame oil 500 mg/kg body wt/day through the radiation. Each group was dissected after 1, 9 and 14 days after exposure to laser radiation (presented in NCRRT). Results: The use of naturally occurring agents as antioxidant agents as sesame oil can slow the degenerative process in several neuro degenerative diseases. These data are addition to the antioxidant properties of the sesame oil against argon laser at wavelength 488 nm to indicate a possible role for the use in treatment of diseases involving free radicals and oxidative damage

  15. Multispectral angular domain optical tomography in scattering media with argon and diode laser sources

    Science.gov (United States)

    Chan, Paulman K. Y.; Vasefi, Fartash; Chapman, Glenn H.; Kaminska, Bozena; Pfeiffer, Nick

    2007-02-01

    Angular Domain Imaging (ADI) within highly scattering media employs micromachined angular filter tunnels to detect nonscattered photons which pass through the tunnels unattenuated while scattered photons collide with the tunnel walls. Each tunnel is micromachined approximately 51 μm wide by 10 mm long in silicon, giving a maximum acceptance angle of 0.29 degrees. The ADI technique is inherently independent of wavelength, and thus multispectral laser sources can be incorporated. Previous ADI experiments employed a 488-514 nm Argon ion laser source. This paper describes the construction of a new imaging system utilizing a high-power (up to 0.5 W) laser diode at the 670 nm wavelength, along with an aspheric and cylindrical lens system for shaping the beam into a collimated line of light. ADI results of biological samples (i.e. chicken breast tissue) are also presented. Image resolution is 204 μm or better in compressed chicken breast tissue approximately 3.8 mm in thickness. Digital image processing techniques are employed to improve image contrast, definition, and detectability of test structures. Because silicon is 40% reflective, scattered light at up to three times the acceptance angle is not sufficiently absorbed by the angular filter tunnels and contributes significant background noise, thus decreasing image contrast and detectability. Roughening of the tunnel surface using a NH4OH etchant solution scatters light hitting the walls, thus allowing it to be absorbed. Images after roughening show dramatic reductions in background scattered light levels between tunnels, suggesting that further experiments will make progress towards improved contrast and detectability of structures.

  16. Recurrent pterygia--laser therapy : A preliminary report

    OpenAIRE

    Saifuddin Shabbir; Baum Klaus

    1993-01-01

    We report our experience with the use of Argon laser photocoagulation for the treatment of recurrent pterygia. In this study, 36 patients and 42 eyes with recurrent pterygia having undergone previous surgery one or more times, were subjected to laser therapy. The patients were followed up for a period of 9-12 months. The success rate was 92.8% when laser therapy was employed in recurrent pterygia which were excised once, while it was 64.2% in cases where excisions were done two ...

  17. Color center laser optogalvanic spectroscopy of lithium, barium, neon and argon Rydberg states in hollow cathode discharges

    International Nuclear Information System (INIS)

    Numerous infrared transitions between Rydberg states of neon and argon have been measured by optogalvanic spectroscopy in commercial hollow cathode lamps using a color center laser operating in the range 3600-4100 cm-1. Transitions in lithium and barium atoms sputtered from the cathodes were also detected. The generality and high sensitivity of this technique indicates potential applications for frequency calibration in the infrared, atomic and molecular spectroscopy, and plasma diagnostics. (orig.)

  18. Time- and space-resolved spectroscopic characterization of a laser carbon plasma plume in an argon background

    International Nuclear Information System (INIS)

    We present time- and space-resolved spectroscopic observations of a laser-produced carbon plasma, in an argon background. An Nd : YAG laser pulse, 370 mJ, 3.5 ns, at 1.06 µm, with a fluence of 6.9 J cm−2, is used to produce a plasma from a solid graphite target in a 0.5 to 415 mTorr argon background. The spectral emission in the visible is recorded with 15 ns time resolution. We use 20 ns time resolution plasma imaging, filtered at characteristic carbon species emission wavelengths, to study the dynamics of the expanding plasma. The carbon plasma emission is found to evolve from the characteristic of single ionized carbon, to a more complex one, where C2 and C3 molecular bands dominate. Several plasma fronts, with either ionic or molecular composition, are seen to detach from the laser target plasma. The temporal and spatial features of the molecular carbon species evolution are found to be dependent on the actual argon background pressure. (paper)

  19. Comparison of indium 111 oxine-labeled platelet aggregation between sutured and argon laser-assisted vascular anastomoses

    International Nuclear Information System (INIS)

    The thrombogenicity of argon laser-assisted vascular anastomoses (LAVAs) was compared with that of sutured vascular anastomoses (SVAs) by measurement of platelet aggregation at the site of repair in a canine model. Sequential 1 cm longitudinal carotid and femoral arteriotomies (n = 80) or jugular and femoral phlebotomies (n = 80) were performed, with each vessel having two tandem, randomly positioned arteriotomies or phlebotomies separated by a 4 cm length of intact vessel. One incision was repaired by SVA with continuous 6-0 polypropylene sutures and the other by argon LAVA. For the laser fusions, argon laser energy was applied to the adventitial surface of the vessel with a 300 micron fiberoptic probe with 0.5 W power, 1100 joules per square centimeter energy fluence, and 150 second exposure per 1 cm length. The arterial and venous segments of SVAs and LAVAs and an equivalent length of normal vessel were harvested at 48 hours (n = 16, 16, 16), 2 weeks (n = 12, 12, 12), and 4 weeks (n = 12, 12, 12). Autologous indium 111 oxine-labeled platelets were injected intravenously 48 hours before removal of the vascular repairs and the radioactivity of the specimens was determined on removal with a NaI (T1) well-type scintillation counter. Anastomotic platelet adherence index (APAI) was calculated as the ratio of emissions of SVA or LAVA to normal reference vessel

  20. Laser scattering diagnostics of an argon atmospheric-pressure plasma jet in contact with vaporized water

    Science.gov (United States)

    Seo, B. H.; Kim, J. H.; You, S. J.; Seong, D. J.

    2015-12-01

    The radial profiles of the electron density, electron temperature, and molecular rotational temperature are investigated in an argon atmospheric-pressure plasma jet in contact with vaporized water, which is driven by a 13.56 MHz radio frequency by means of the Thomson and Raman laser scattering methods. There is a distinct difference in the radial profiles of the plasma parameters between plasmas in contact with water and those without water contact. In the case of plasmas without vaporized water contact, all the parameters have a single-peak distribution with maximum values at the center of the discharge. In the case of plasmas in contact with vaporized water, all parameters have double-peak distributions; a neighboring peak appears beside the main peak. The new peak may have originated from the ripple of the water surface, which works as a cathode, and the peak of the ripple offers a sharp curvature point, playing the role of a pin. Our experimental results and the underlying physics are described in detail.

  1. Towards real time speckle controlled retinal photocoagulation

    Science.gov (United States)

    Bliedtner, Katharina; Seifert, Eric; Stockmann, Leoni; Effe, Lisa; Brinkmann, Ralf

    2016-03-01

    Photocoagulation is a laser treatment widely used for the therapy of several retinal diseases. Intra- and inter-individual variations of the ocular transmission, light scattering and the retinal absorption makes it impossible to achieve a uniform effective exposure and hence a uniform damage throughout the therapy. A real-time monitoring and control of the induced damage is highly requested. Here, an approach to realize a real time optical feedback using dynamic speckle analysis is presented. A 532 nm continuous wave Nd:YAG laser is used for coagulation. During coagulation, speckle dynamics are monitored by a coherent object illumination using a 633nm HeNe laser and analyzed by a CMOS camera with a frame rate up to 1 kHz. It is obvious that a control system needs to determine whether the desired damage is achieved to shut down the system in a fraction of the exposure time. Here we use a fast and simple adaption of the generalized difference algorithm to analyze the speckle movements. This algorithm runs on a FPGA and is able to calculate a feedback value which is correlated to the thermal and coagulation induced tissue motion and thus the achieved damage. For different spot sizes (50-200 μm) and different exposure times (50-500 ms) the algorithm shows the ability to discriminate between different categories of retinal pigment epithelial damage ex-vivo in enucleated porcine eyes. Furthermore in-vivo experiments in rabbits show the ability of the system to determine tissue changes in living tissue during coagulation.

  2. Development of the Potassium-Argon Laser Experiment (KArLE) Instrument for In Situ Geochronology

    Science.gov (United States)

    Cohen, Barbara A.; Li, Z.-H.; Miller, J. S.; Brinckerhoff, W. B.; Clegg, S. M.; Mahaffy, P. R.; Swindle, T. D.; Wiens, R. C.

    2012-01-01

    Absolute dating of planetary samples is an essential tool to establish the chronology of geological events, including crystallization history, magmatic evolution, and alteration. Traditionally, geochronology has only been accomplishable on samples from dedicated sample return missions or meteorites. The capability for in situ geochronology is highly desired, because it will allow one-way planetary missions to perform dating of large numbers of samples. The success of an in situ geochronology package will not only yield data on absolute ages, but can also complement sample return missions by identifying the most interesting rocks to cache and/or return to Earth. In situ dating instruments have been proposed, but none have yet reached TRL 6 because the required high-resolution isotopic measurements are very challenging. Our team is now addressing this challenge by developing the Potassium (K) - Argon Laser Experiment (KArLE) under the NASA Planetary Instrument Definition and Development Program (PIDDP), building on previous work to develop a K-Ar in situ instrument [1]. KArLE uses a combination of several flight-proven components that enable accurate K-Ar isochron dating of planetary rocks. KArLE will ablate a rock sample, determine the K in the plasma state using laser-induced breakdown spectroscopy (LIBS), measure the liberated Ar using quadrupole mass spectrometry (QMS), and relate the two by the volume of the ablated pit using an optical method such as a vertical scanning interferometer (VSI). Our preliminary work indicates that the KArLE instrument will be capable of determining the age of several kinds of planetary samples to +/-100 Myr, sufficient to address a wide range of geochronology problems in planetary science.

  3. Integrated computer-aided retinal photocoagulation system

    Science.gov (United States)

    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.

  4. The second Born approximation of electron–argon elastic scattering in a bichromatic laser field

    Indian Academy of Sciences (India)

    Bin Zhou; Ming-Yang Zheng; Da-Yong Wen

    2012-03-01

    We study the elastic scattering of atomic argon by electron in the presence of a bichromatic laser field in the second Born approximation. The target atom is approximated by a simple screening potential and the continuum states of the impinging and emitting electrons are described as Volkov states. We evaluate the S-matrix elements numerically. The dependence of differential cross-section on the relative phase between the two laser components is presented. The results obtained in the first and second Born approximations are compared and analysed.

  5. Experimental investigation of the structure and the dynamics of nanosecond laser-induced plasma in 1-atm argon ambient gas

    Science.gov (United States)

    Ma, Qianli; Motto-Ros, Vincent; Bai, Xueshi; Yu, Jin

    2013-11-01

    We have investigated the structure and the dynamics of the plasma induced on a metallic target in 1-atm argon ambient by a nanosecond laser pulse with irradiance in the range of 10 GW/cm2. The structure is revealed to be sensitively dependent on the laser wavelength. A layered structure of different species characterizes the plasma induced by ultraviolet 355 nm pulse, while an effective mixing between the ablation vapor and the shocked ambient gas is observed with infrared 1064 nm pulse. The absorption property of the shocked gas is found to be crucial for determining the structure of the plasma.

  6. Generation of High-Order Harmonic Continuum Supporting Single Attosecond Pulse in Argon Driven by Intense 7 fs Laser Pulse

    Science.gov (United States)

    Zheng, Y. H.; Xiong, H.; Peng, Y.; Xu, H.; Yang, X.; Zeng, Z. N.; Chen, X. W.; Li, R. X.; Zeng, H. P.; Xu, Z. Z.

    High-order harmonic continuum in the cutoff is demonstrated with an argon gas cell driven by 0.4 mJ/7 fs (FWHM) ultrashort intense laser pulse. We find that the spectral structure, the modulation depth and the continuum bandwidth of the high-order harmonic spectra vary when the carrier-envelope phase (CEP) of driving laser pulse is stabilized at different values. At some CEP values, a continuous spectrum of <17% modulation depth and 10 eV continuum bandwidth is achieved, supporting a transform-limited 300 attosecond single pulse in time domain.

  7. Primary argon laser trabeculoplasty in the treatment of glaucoma; A resource saving treatment. Primaer lasertrabekuloplastikk ved glaukom; En resurssparende behandling

    Energy Technology Data Exchange (ETDEWEB)

    Odberg, T. (Hamar Regional Hospital (Norway))

    1990-11-01

    During the last ten years, argon laser trabeculoplasty has been shown to be a very useful tool in the treatment of glaucoma when medical therapy has failed. In the present study laser was used as primary therapy in 27 patients with newly detected glaucoma. Pretreatment with topical timolol gave an immediate pressure drop in all eyes, and the dreaded actue pressure rise after laser treatment was avoided. Upon follow-up examination after two years, more than half the patients had an intraocular pressure below 21 mm Hg without additional therapy. Primary laser trabeculoplasty was found to be a safe and time-saving procedure. Expenses and complications associated with medical therapy are reduced. Many patients may avoid lifelong daily instillation of eye drops. 11 refs., 2 tabs.

  8. Quantitative analysis of oxide materials by laser-induced breakdown spectroscopy with argon as an internal standard

    International Nuclear Information System (INIS)

    Laser-induced breakdown spectroscopy (LIBS) is demonstrated as a quantitative technique for geochemical analysis. This study demonstrates the applicability of LIBS to multielemental analysis of minerals using argon as an internal standard. Laser-induced breakdown spectroscopy has been applied to measure elements in oxide form. In the present study, the contents of several oxides, such as Fe2O3, CaO and MgO, in geological samples from the Tierga Mine (Zaragoza, Spain) were analyzed by LIBS. An argon environment was used to eliminate interference from air at atmospheric pressure. Furthermore, argon was used as an internal standard. The result was enhanced signal and enhanced linearity of the calibration curves. The Fe2O3, CaO and MgO concentrations determined by LIBS were compared with the results obtained using another analytical technique, inductively coupled plasma optical emission spectrometry (ICP-OES). The concentrations found using LIBS were in good agreement with the values obtained by ICP-OES. - Highlights: ► Multi-elemental quantitative analysis of oxide material using LIBS was developed. ► A buffer gas was used to minimize the matrix effect and as an internal standard. ► The LIBS results were compared with ICP, successfully

  9. The effects of proinflammatory cytokines on the apoptosis of corneal endothelial cells following argon laser iridotomy.

    Science.gov (United States)

    Eom, Youngsub; Kwon, Junki; Heo, Jeong-Hwa; Yun, Cheolmin; Kang, Su-Yeon; Kim, Hyo Myung; Song, Jong Suk

    2016-04-01

    The aim of this study was to evaluate the relationship between the expression of proinflammatory cytokines and the apoptosis of corneal endothelial cells after argon laser iridotomy (ALI). ALI was performed on each quadrant of the iris in the right eye of mice (ALI1 group). Left eyes were used as control group. The levels of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β, and interferon (IFN)-γ in mice eyes were measured, and TUNEL staining was performed 12 h after ALI. Mice in the ALI-Dexa group were pretreated daily with an intraperitoneal injection of dexamethasone for 4 days before undergoing ALI and compared with mice without dexamethasone pretreatment (ALI2 group). Twelve corneas from six rabbits were incubated ex vivo with (n = 6) or without (n = 6) IL-1β. TUNEL staining was performed 24 h after ex vivo incubation. In the mice experiment, the levels of IL-1β, TNF-α, TGF-β, and IFN-γ were increased in the ALI1 group compared to the control group. Although many TUNEL-positive cells were observed in the ALI1 group, those were not detected in the control group. Dexamethasone pretreatment inhibited the increase in the levels of all four proinflammatory cytokines and reduced TUNEL-positive cells. In the rabbit experiment, TUNEL-positive cells were increased in the incubated corneas with IL-1β compared to those without IL-1β. Expression of proinflammatory cytokines following ALI seems to play a role in the apoptosis of corneal endothelial cells after ALI. Dexamethasone pretreatment inhibited increases in proinflammatory cytokines and reduced the apoptosis of corneal endothelial cells. PMID:26657139

  10. Decay of femtosecond laser-induced plasma filaments in air, nitrogen, and argon for atmospheric and subatmospheric pressures.

    Science.gov (United States)

    Aleksandrov, N L; Bodrov, S B; Tsarev, M V; Murzanev, A A; Sergeev, Yu A; Malkov, Yu A; Stepanov, A N

    2016-07-01

    The temporal evolution of a plasma channel at the trail of a self-guided femtosecond laser pulse was studied experimentally and theoretically in air, nitrogen (with an admixture of ∼3% O_{2}), and argon in a wide range of gas pressures (from 2 to 760 Torr). Measurements by means of transverse optical interferometry and pulsed terahertz scattering techniques showed that plasma density in air and nitrogen at atmospheric pressure reduces by an order of magnitude within 3-4 ns and that the decay rate decreases with decreasing pressure. The argon plasma did not decay within several nanoseconds for pressures of 50-760 Torr. We extended our theoretical model previously applied for atmospheric pressure air plasma to explain the plasma decay in the gases under study and to show that allowance for plasma channel expansion affects plasma decay at low pressures. PMID:27575227

  11. On-line experimental results of an argon gas cell-based laser ion source (KEK Isotope Separation System)

    Science.gov (United States)

    Hirayama, Y.; Watanabe, Y. X.; Imai, N.; Ishiyama, H.; Jeong, S. C.; Jung, H. S.; Miyatake, H.; Oyaizu, M.; Kimura, S.; Mukai, M.; Kim, Y. H.; Sonoda, T.; Wada, M.; Huyse, M.; Kudryavtsev, Yu.; Van Duppen, P.

    2016-06-01

    KEK Isotope Separation System (KISS) has been developed at RIKEN to produce neutron rich isotopes with N = 126 to study the β -decay properties for application to astrophysics. The KISS is an element-selective mass-separation system which consists of an argon gas cell-based on laser ion source for atomic number selection and an ISOL mass-separation system. The argon gas cell of KISS is a key component to stop and collect the unstable nuclei produced in a multi-nucleon transfer reaction, where the isotopes of interest will be selectively ionized using laser resonance ionization. We have performed off- and on-line experiments to study the basic properties of the gas cell as well as of the KISS. We successfully extracted the laser-ionized stable 56Fe (direct implantation of a 56Fe beam into the gas cell) atoms and 198Pt (emitted from the 198Pt target by elastic scattering with a 136Xe beam) atoms from the KISS during the commissioning on-line experiments. We furthermore extracted laser-ionized unstable 199Pt atoms and confirmed that the measured half-life was in good agreement with the reported value.

  12. Realtime temperature determination during retinal photocoagulation on patients

    Science.gov (United States)

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

    2011-03-01

    Retinal photocoagulation is a long time established treatment for a variety of retinal diseases, most commonly applied for diabetic macular edema and diabetic retinopathy. The damage extent of the induced thermal coagulations depend on the temperature increase and the time of irradiation. So far, the induced temperature rise is unknown due to intraocular variations in light transmission and scattering and RPE/choroidal pigmentation, which can vary inter- and intraindividually by more than a factor of four. Thus in clinical practice, often stronger and deeper coagulations are applied than therapeutically needed, which lead to extended retinal damage and strong pain perception. The final goal of this project focuses on a dosimetry control, which automatically generates a desired temperature profile and thus coagulation strength for every individual coagulation spot, ideally unburden the ophthalmologist from any laser settings. In this paper we present the first realtime temperature measurements achieved on patients during retinal photocoagulation by means of an optoacoustic method, making use of the temperature dependence of the thermal expansion coefficient of retinal tissue. Therefore, nanosecond probe laser pulses are repetitively and simultaneously applied with the treatment radiation in order to excite acoustic waves, which are detected at the cornea with an ultrasonic transducer embedded in the contact lens and then are processed by PC.

  13. Argon Ion Laser Polymerized Acrylic Resin: A Comparative Analysis of Mechanical Properties of Laser Cured, Light Cured and Heat Cured Denture Base Resins

    OpenAIRE

    Murthy, S. Srinivasa; Murthy, Gargi S

    2015-01-01

    Background: Dentistry in general and prosthodontics in particular is evolving at greater pace, but the denture base resins poly methyl methacrylate. There has been vast development in modifying chemically and the polymerization techniques for better manipulation and enhancement of mechanical properties. One such invention was introduction of visible light cure (VLC) denture base resin. Argon ion lasers have been used extensively in dentistry, studies has shown that it can polymerize restorati...

  14. Update on Development of the Potassium-Argon Laser Experiment (KArLE) Instrument for In Situ Geochronology

    Science.gov (United States)

    Cohen, Barbara A.; Li, Z.-H.; Miller, J. S.; Brinckerhoff, W. B.; Clegg, S. M.; Mahaffy, P. R.; Swindle, T. D.; Wiens, R. C.

    2013-01-01

    Absolute dating of planetary samples is an essential tool to establish the chronology of geological events, including crystallization history, magmatic evolution, and alteration. We are addressing this challenge by developing the Potassium (K) -- Argon Laser Experiment (KArLE), building on previous work to develop a K-Ar in situ instrument. KArLE ablates a rock sample, determines the K in the plasma state using laser-induced breakdown spectroscopy (LIBS), measures the liberated Ar using quadrupole mass spectrometry (QMS), and relates the two by the volume of the ablated pit using laser confocal microscopy (LCM). Our goal is for the KArLE instrument to be capable of determining the age of several kinds of planetary samples to address a wide range of geochronolgy problems in planetary science.

  15. Non-perturbative generation of above-threshold harmonics from pre-excited argon atoms in intense mid-infrared laser fields

    CERN Document Server

    Li, Guihua; Li, Ziting; Yao, Jingpin; Zeng, Bin; Chu, Wei; Cheng, Ya

    2015-01-01

    We experimentally investigate the generation of above-threshold harmonics completely from argon atoms on an excited state using mid-infrared femtosecond laser pulses. The highly nonlinear dependences of the observed signal on the pulse energy and polarization of the driver laser pulses indicate its non-perturbative characteristic.

  16. Evaluation of the hydrogen peroxide and special colorant effects under irradiation by argon and diode laser on tooth-whitening in vitro

    International Nuclear Information System (INIS)

    The aim of this study is to determine if there is any interaction between special colorant found on bleaching agents that have 35 % of hydrogen peroxide on its composition, and argon or diode laser. The first part of the study was to characterize the extrinsic stain obtained through a staining solution containing products present on the day by day diet of the general population. Thirty-two inferior human extracted incisors, free of caries and without filling material were selected for the study. The laser devices employed were Argon laser (AccuCure 3000 TM - Lasermed), wave length 488 nm, with a 200 mW/cm2 for 30 seconds in continuos mode; and diode laser (L 808 Medical Laser - Lasering do Brasil), wave length 808 ± 10 nm, with 1,6 W/cm2 for 30 seconds in continuos mode. The application mode done by a scanning movement over the buccal surface. The bleaching agents used were: Opalescence Extra (OE) - Ultradent Products USA, hydrogen peroxide 35%, gel with Carotene to convert light into heat; Pola Office (PO) - SDI - USA single doses of hydrogen peroxide; Whiteness HP (WHP) - FGM - Brasil, hydrogen peroxide 35%; Opus White (OW) - Sharplan - Israel, hydrogen peroxide 35%. The temperature rise measurement was performed with a thermocouple model 120-202-AJ, Fenwal, inserted into the pulpar chamber. The bleaching material was applied on the tooth surface with 2 mm thickness and then the irradiation was perform. The thirty two teeth were randomized in four groups, two for each laser device. The obtain data demonstrated a superior performance of the Argon laser on tooth whitening and also better results concerning the temperature rise. The alteration on tooth coloration was verified through digital spectrophotometer (Shade-Eye EX - Shofu) and quantitative analyses showed statistical differences among the groups. The bleaching results for Argon laser combined with OE and WHP were superior for the other groups. The mean variation of the temperature rise obtained Argon laser

  17. Current uses of ophthalmic lasers.

    OpenAIRE

    O'Neill, D; GREGSON, R; McHugh, D

    1992-01-01

    Current laser treatments are quick, relatively painless, and well tolerated. Some ophthalmic techniques can be performed only by laser while others have a lower morbidity than alternative treatments. Peripheral retinal photocoagulation and focal photocoagulation now offer greatly improved visual prognosis for diabetic patients with proliferative diabetic retinopathy or diabetic macular disease. Selected cases of macular degeneration may be treated by focal laser photocoagulation. The role of ...

  18. Comparative investigation of laser ablation plumes in air and argon by analysis of spectral line shapes: Insights on calibration-free laser-induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    We investigate the characteristic features of plume expansion in air and argon resulting from ultraviolet laser ablation of solid matter in conditions typically applied in material analysis via laser-induced breakdown spectroscopy (LIBS). Barite crown glass is chosen as a target material for the characteristic emission spectrum suitable for plasma diagnostics. The space-integrated plasma emission spectrum recorded with an echelle spectrometer coupled to a gated detector is compared to the computed spectral radiance of a nonuniform plasma in local thermodynamic equilibrium. In particular, resonance lines of neutral sodium atoms and barium ions are observed to probe gradients of temperature and density within the plume. It is shown that laser ablation in argon leads to an almost uniform plasma whereas gradients of temperature and density are evidenced in ambient air. The discrepancy is attributed to the different physical properties of both gases leading to a stronger vapor–gas energy exchange in the case of air. However, strong gradients occur only in a thin peripheral zone, close to the vapor–gas contact front. The larger plasma core appears almost uniform. The peripheral zone of low temperature mostly contributes to the plasma emission spectrum by absorption and material analysis via calibration-free LIBS in air may ignore the nonuniform character of the plasma if only transitions of small optical thickness are considered. - Highlights: • Investigation of laser ablation plumes by analysis of spectral line shapes • Simulation of emission spectra from nonuniform laser-produced plasma • Plasma is more uniform for ablation in argon. • Plasma nonuniformity mostly affects optically thick lines. • Calibration-free LIBS may ignore gradients if optically thin lines are chosen

  19. Morphology of the primary damage caused by the argon-ion laser to the iris of the pigmented rabbit

    International Nuclear Information System (INIS)

    The effect of the argon-ion laser upon the iris of the pigmented rabbit were analysed by ultrastructural methods. Apart from the physical parameters of the energy source, the damage strongly depends on the concentration, location, and distribution of the iris pigment. The irradiation of the iris results in the formation of a crater. Depending on the distance of the epicentre of the impact, various degrees of ultrastructural damage are observed. The region immediately adjacent to the crater lumen at a revealing distance of 25 μm consists of homogenous masses, revealing a vacuolar structure. As the only residuals of destroyed cells, melanin granules are observed within the homogenous masses. Destruction of the collagen fibrils and their disintegration into subfibrils with elimination of all cell compartments is found in an area ranging from 25 μm to 300 μm from the wall of the crater. Damage to the chromatin structure is visible up to a distance of 300 μm to 375 μm from the wall of the crater. Characterised by an invasion of macrophages into the damaged area, the cleaning phase starts 24 h after irradiation. The results of this experiment indicate that because of the great energy dose required for man with the inherent widespread tissue damage and low probability of a lasting iridectomy, the cw argon-ion laser appears to be an unsuitable energy source for clinical iridectomy. (orig./AJ) 891 AJ/orig.- 892 MKO

  20. Detection of trace concentrations of helium and argon in gas mixtures by laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    McNaghten, E.D., E-mail: Edward.McNaghten@awe.co.u [AWE Aldermaston, Reading, Berkshire, RG7 4PR (United Kingdom); Parkes, A.M.; Griffiths, B.C. [AWE Aldermaston, Reading, Berkshire, RG7 4PR (United Kingdom); Whitehouse, A.I.; Palanco, S. [Applied Photonics Ltd., Skipton, North Yorkshire, BD23 2DE (United Kingdom)

    2009-10-15

    We report what we believe to be the first demonstration of the detection of trace quantities of helium and argon in binary and ternary gas mixtures with nitrogen by laser-induced breakdown spectroscopy (LIBS). Although significant quenching of helium transitions due to collisional deactivation of excited species was observed, it was found that losses in analytical sensitivity could be minimized by increasing the laser irradiance and decreasing the pressure at which the analyses were performed. In consequence, limits of detection of parts-per-million and tens of parts-per-million and linear dynamic ranges of several orders of magnitude in analyte concentration were obtained. The results of this study suggest that LIBS may have potential applications in the detection of other noble gases at trace concentrations.

  1. On the formation of narrow bubble tracks by laser beam in argon, nitrogen and hydrogen bubble chambers

    International Nuclear Information System (INIS)

    Long bubble tracks, < 1 mm in diameter, have been produced in liquid argon and nitrogen with a nitrogen laser beam (lambda = 337 mm), offering subnanosecond pulses with small beam divergence. Bubble formation was observed over a wide range of operating conditions, including those for ordinary bubble chamber operation, with a laser pulse of 10 μJ. Typical bubble densities obtained were 4-8 bubbles/cm, with maximum densities of 20 bubbles/cm. In liquid hydrogen, tracks of 3 m visible length were observed with track diameters from 1.5 to 6 mm and bubble densities from 2 to 25 bubbles/cm. Results and applications will be discussed. (orig.)

  2. Sequential multiphoton multiple ionization of atomic argon and xenon irradiated by x-ray free-electron laser pulses from SACLA

    International Nuclear Information System (INIS)

    We have investigated multiphoton multiple ionization of argon and xenon atoms at 5 keV using a new x-ray free electron laser (XFEL) facility, the SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan. The experimental results are compared with the new theoretical results presented here. The absolute fluence of the XFEL pulse has been determined with the help of the calculations utilizing two-photon processes in the argon atom. The high charge states up to +22 observed for Xe in comparison with the calculations point to the occurrence of sequential L-shell multiphoton absorption and of resonance-enabled x-ray multiple ionization. (paper)

  3. Grid photocoagulation combined with intravitreal bevacizumab for recurrent macular edema associated with retinal vein occlusion

    Directory of Open Access Journals (Sweden)

    Ogino K

    2011-07-01

    Full Text Available Ken Ogino, Akitaka Tsujikawa, Tomoaki Murakami, Yuki Muraoka, Yumiko Kurashige, Nagahisa YoshimuraDepartment of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, JapanPurpose: To report the efficacy of grid photocoagulation combined with intravitreal bevacizumab (IVB for macular edema recurring after previous IVBs associated with retinal vein occlusion (RVO.Methods: This retrospective study consisted of 19 eyes with branch retinal vein occlusion (BRVO and nine eyes with central retinal vein occlusion (CRVO, which were treated with grid photocoagulation combined with IVB for recurrent macular edema after previous IVBs. The mean duration of total follow-up was 29.3 ± 5.8 months.Results: After this combination therapy, foveal thickness was reduced, significant with slight improvement in visual acuity (VA. At 1 month after treatment, although 25 of the 28 eyes showed complete resolution of the cystoid space, the macular edema recurred to some extent in 19 eyes. Compared with initial values, final foveal thickness was reduced significantly in both BRVO and CRVO groups (P < 0.001, but improvement in VA was significant only for eyes with BRVO (P = 0.012. The total number of IVB was 2.8 ± 0.7 for eyes with either BRVO or CRVO.Conclusion: Grid photocoagulation combined with IVB has a substantial effect on reducing recurrent macular edema associated with RVO, but the effect on visual acuity is limited.Keywords: bevacizumab, grid laser photocoagulation, macular edema, optical coherence tomography, retinal vein occlusion

  4. Resonant holographic measurements of laser ablation plume expansion in vacuum and argon gas backgrounds

    Energy Technology Data Exchange (ETDEWEB)

    Lindley, R.A. [Michigan Univ., Ann Arbor, MI (United States)

    1993-10-01

    This thesis discusses the following on resonant holographic measurements of laser ablation plume expansion: Introduction to laser ablation; applications of laser ablation; The study of plume expansion; holographic interferometry; resonant holographic interferometry; accounting for finite laser bandwidth; The solution for doppler broadening and finite bandwidth; the main optical table; the lumonics laser spot shape; developing and reconstructing the holograms; plume expansion in RF/Plasma Environments; Determining {lambda}{sub o}; resonant refraction effects; fringe shift interpretation; shot-to-shot consistency; laser ablation in vacuum and low pressure, inert, background gas; theoretically modeling plume expansion in vacuum and low pressure, inert, background gas; and laser ablation in higher pressure, inert, background gas.

  5. Simulation and optimization of argon laser iridectomy: influence of irradiation duration on a corneal and lens thermal injury

    Science.gov (United States)

    Apiou-Sbirlea, Gabriela; L'Huillier, Jean P.

    1999-02-01

    A 3-D finite element model of the human eye is developed to study the heat transfers induced by an argon laser absorbed on the iris tissue. The main objective is to explain the appearance of complications inherent to the iridectomy such as corneal burns and lens opacities. Contraction burn preceding the iris opening by photovaporization is studied. The iris temperature threshold fixed as onset for the tissue removal is 300 degrees Celsius. For closed angle glaucoma, the thermal history on the corneal endothelium and lens due to recurrent laser shots with pulse durations of 0.5 sec, 0.05 sec and 0.04 sec are presented and discussed. Typically, an overheating of the lens and cornea endothelium by the side of the iridectomy site is observed. This phenomena is important on the cornea endothelium where the temperature increases to 70 degrees Celsius in case of two recurrent laser pulses of 0.5 sec in duration, 0.43 W in power and 0.5 sec in relaxation time. For irradiation time of 0.05 sec this overheating is much less important and the temperature on the cornea endothelium doesn't exceed 47 degrees Celsius. These computations confirm that short laser pulses decrease the amount of adverse effects and agree well with experiments reported by ophthalmologists.

  6. Successful surgical management of retinopathy of prematurity showing rapid progression despite extensive retinal photocoagulation

    Directory of Open Access Journals (Sweden)

    Salil S Gadkari

    2015-01-01

    Full Text Available The management of retinopathy of prematurity (ROP can be challenging in preterm babies with a gestational age <30 weeks, those with very low birth weight and multiple risk factors (eg., oxygen therapy for respiratory distress, sepsis, neonatal jaundice. A premature infant presented with "hybrid" zone 1 disease in the right eye and aggressive posterior ROP in the left eye. Both eyes were adequately treated with laser photocoagulation; however, the eyes deteriorated and progressed to stage 4 ROP. Both eyes eventually underwent intravitreal bevacizumab followed by lens sparing vitrectomy with good anatomical and visual outcome. Anticipation of progression despite laser photocoagulation in certain clinical scenarios, frequent follow-up and timely surgical intervention is paramount.

  7. Effectiveness of panretinal photocoagulation in severe diabetic retinopathy

    Science.gov (United States)

    Astakhov, Yuri S.; Shadrichev, Fedor Y.; Lisochkina, Alla B.

    1999-02-01

    Diabetic Retinopathy (DR) is one of the most severe complications of diabetes mellitus. In 1994, in St. Petersburg, a new system of ophthalmologic care for diabetic patients was set up. For Russia, this system represents an example of adequate care for subjects with DM, including screening strategies, documentation and education of patients and general ophthalmologists. According to our data, about one half of examined patients had DR, and about 20% of patients were in need of laser treatment. The aim of present study was to evaluate the effectiveness of panretinal photocoagulation (PRP) in cases of severe DR, including advanced nonproliferative DR (preproliferative DR) and proliferative DR. Data concerning 1073 diabetics are included in this study. PRP was performed in 736 cases (1163 eyes). DR stabilization was estimated after one year follow-up PRP enabled preventing severe visual loss in patients with preproliferative DR and proliferative DR. Our system of specialized ophthalmic care for diabetic patients proved to be effective.

  8. Modeling of the initiation and evolution of a laser-ionized column in the lower atmosphere - 314.5 nm wavelength resonant multiphoton ionization of naturally occurring argon

    Science.gov (United States)

    Fetzer, G. J.; Stockley, J. E.

    1992-01-01

    A 3+1 resonant multiphoton ionization process in naturally occurring argon is studied at 314.5 nm as a candidate for providing a long ionized channel through the atmosphere. Results are presented which indicate peak electron densities up to 10 exp 8/cu cm can be created using laser intensities on the order of 10 exp 8 W/sq cm.

  9. In vitro comparative study of share bond of light cured composite resins with halogen light and argon laser, using stainless steel brackets on human premolars

    International Nuclear Information System (INIS)

    The aim of this study in vitro was to compare the share bond strength of the light-cured composite resins Transbond XT (Unitek), with halogen light and argon laser. The Adhesive Remmant Index (ARI) was also investigated. The brackets Dyna lock (3M-UNITEK) were bonded to 75 human premolars, divided into 5 groups (15 each) according to time and the polymerization: Group H20, 15 brackets bonded with halogen light for 20s (10s both sides); Group H40, 15 brackets bonded with halogen light for 40s (20s both sides); Group A40, 15 brackets bonded with argon laser for 40s (20s both sides); Group A20, 15 brackets bonded with argon laser for 20s (10s both sides); Group A10, 15 brackets bonded with argon laser for 10s (5s both sides). The pulpal temperature changes were determined during a polymerization, not exceeding 3,5 deg C. After bonding, the teeth were submitted to a thermo cycled of 700 cycles between 5 deg C and 55 deg C, to simulate the consuming that the light cured composite resin would have in a short space of time. The specimens were then placed in PVC ring and embedded in acrylic resin (Aero-Jet). The tensile bond strength test was performed on an Universal Machine set at a crosshead speed of 1,5 mm/min, and for each rupture we registered a graphic and the best load required in Newtons, was converted to MPa and kgf. The share bond strength showed bigger values for the exposure time of 20 seconds, for the Group bonded for halogen light (H20), 7,45 kgf (7,64 MPa) and for argon laser 7,50 kgf (7,69 MPa); lesser values for the exposure time of 40s for the Group with halogen light (H40), 6,15 kgf (6,30 MPa) and argon laser Group (A40), 6,20 kgf (6,35 MPa) 0; and A10, 4,85 kgf (4,97 MPa). In the ARI Index, only A40 Group showed the 1 Index, with statistical results. In this Group, less than half of the remainder adhesive stayed on the surface of the enamel, conferring specimens failed at the enamel-adhesive interface. The results of the in vitro study demonstrate that

  10. Ionization of Argon n=2 (Ar+9 to Ar+16) by a 'relativistic' laser field

    International Nuclear Information System (INIS)

    The high field photoionization cross sections for the (n=2) shell of argon were measured with pulsed 800 nm radiation (27±5 fs duration) at an intensity of 1.5x1019 W/cm2±1x1019 W/cm2. The pondermotive energy for an electron at these field intensities is approximately 1 MeV. The best agreement with a calculated AC tunneling model was at an intensity of 0.6x1019 W/cm2. The difference between experimental and calculated relative charge state yields is less than an order of magnitude for Ar+9 to Ar+14 and Ar+16

  11. Effect of high power CO2 and Yb:YAG laser radiation on the characteristics of TIG arc in atmospherical pressure argon and helium

    Science.gov (United States)

    Wu, Shikai; Xiao, Rongshi

    2015-04-01

    The effects of laser radiation on the characteristics of the DC tungsten inert gas (TIG) arc were investigated by applying a high power slab CO2 laser and a Yb:YAG disc laser. Experiment results reveal that the arc voltage-current curve shifts downwards, the arc column expands, and the arc temperature rises while the high power CO2 laser beam vertically interacts with the TIG arc in argon. With the increase of the laser power, the voltage-current curve of the arc shifts downwards more significantly, and the closer the laser beam impingement on the arc to the cathode, the more the decrease in arc voltage. Moreover, the arc column expansion and the arc temperature rise occur mainly in the region between the laser beam incident position and the anode. However, the arc characteristics hardly change in the cases of the CO2 laser-helium arc and YAG laser-arc interactions. The reason is that the inverse Bremsstrahlung absorption coefficients are greatly different due to the different electron densities of the argon and helium arcs and the different wave lengths of CO2 and YAG lasers.

  12. Guiding of positive streamers in nitrogen, argon and N$_{2}$-O$_{2}$ mixtures by very low $n_{e}$ laser-induced pre-ionization trails

    CERN Document Server

    Nijdam, S

    2016-01-01

    In previous work we have shown that positive streamers in pure nitrogen can be guided by a laser-induced trail of low electron density. Here we show more detailed results from such measurements. We show the sensitivity of this laser-guiding on pressure p and found that the maximum delay between the laser pulse and voltage pulse for guiding scales with something between $1/p$ and $1/p^{2}$. We also show that when we use a narrower laser beam the laser guiding occurs less frequent and that when we move the laser beam away from the symmetry axis, guiding hardly is observed. Finally we show that laser guiding can also occur in pure argon.

  13. The Argon Geochronology Experiment (AGE)

    Science.gov (United States)

    Swindle, T. D.; Bode, R.; Fennema, A.; Chutjian, A.; MacAskill, J. A.; Darrach, M. R.; Clegg, S. M.; Wiens, R. C.; Cremers, D.

    2006-01-01

    This viewgraph presentation reviews the Argon Geochronology Experiment (AGE). Potassium-Argon dating is shown along with cosmic ray dating exposure. The contents include a flow diagram of the Argon Geochronology Experiment, and schematic diagrams of the mass spectrometer vacuum system, sample manipulation mechanism, mineral heater oven, and the quadrupole ion trap mass spectrometer. The Laser-Induced Breakdown Spectroscopy (LIBS) Operation with elemental abundances is also described.

  14. Dynamics of plasma expansion and shockwave formation in femtosecond laser-ablated aluminum plumes in argon gas at atmospheric pressures

    International Nuclear Information System (INIS)

    Plasma expansion with shockwave formation during laser ablation of materials in a background gasses is a complex process. The spatial and temporal evolution of pressure, temperature, density, and velocity fields is needed for its complete understanding. We have studied the expansion of femtosecond (fs) laser-ablated aluminum (Al) plumes in Argon (Ar) gas at 0.5 and 1 atmosphere (atm). The expansion of the plume is investigated experimentally using shadowgraphy and fast-gated imaging. The computational fluid dynamics (CFD) modeling is also carried out. The position of the shock front measured by shadowgraphy and fast-gated imaging is then compared to that obtained from the CFD modeling. The results from the three methods are found to be in good agreement, especially during the initial stage of plasma expansion. The computed time- and space-resolved fields of gas-dynamic parameters have provided valuable insights into the dynamics of plasma expansion and shockwave formation in fs-pulse ablated Al plumes in Ar gas at 0.5 and 1 atm. These results are compared to our previous data on nanosecond (ns) laser ablation of Al [S. S. Harilal et al., Phys. Plasmas 19, 083504 (2012)]. It is observed that both fs and ns plumes acquire a nearly spherical shape at the end of expansion in Ar gas at 1 atm. However, due to significantly lower pulse energy of the fs laser (5 mJ) compared to pulse energy of the ns laser (100 mJ) used in our studies, the values of pressure, temperature, mass density, and velocity are found to be smaller in the fs laser plume, and their time evolution occurs much faster on the same time scale. The oscillatory shock waves clearly visible in the ns plume are not observed in the internal region of the fs plume. These experimental and computational results provide a quantitative understanding of plasma expansion and shockwave formation in fs-pulse and ns-pulse laser ablated Al plumes in an ambient gas at atmospheric pressures

  15. Dynamics of plasma expansion and shockwave formation in femtosecond laser-ablated aluminum plumes in argon gas at atmospheric pressures

    Science.gov (United States)

    Miloshevsky, Alexander; Harilal, Sivanandan S.; Miloshevsky, Gennady; Hassanein, Ahmed

    2014-04-01

    Plasma expansion with shockwave formation during laser ablation of materials in a background gasses is a complex process. The spatial and temporal evolution of pressure, temperature, density, and velocity fields is needed for its complete understanding. We have studied the expansion of femtosecond (fs) laser-ablated aluminum (Al) plumes in Argon (Ar) gas at 0.5 and 1 atmosphere (atm). The expansion of the plume is investigated experimentally using shadowgraphy and fast-gated imaging. The computational fluid dynamics (CFD) modeling is also carried out. The position of the shock front measured by shadowgraphy and fast-gated imaging is then compared to that obtained from the CFD modeling. The results from the three methods are found to be in good agreement, especially during the initial stage of plasma expansion. The computed time- and space-resolved fields of gas-dynamic parameters have provided valuable insights into the dynamics of plasma expansion and shockwave formation in fs-pulse ablated Al plumes in Ar gas at 0.5 and 1 atm. These results are compared to our previous data on nanosecond (ns) laser ablation of Al [S. S. Harilal et al., Phys. Plasmas 19, 083504 (2012)]. It is observed that both fs and ns plumes acquire a nearly spherical shape at the end of expansion in Ar gas at 1 atm. However, due to significantly lower pulse energy of the fs laser (5 mJ) compared to pulse energy of the ns laser (100 mJ) used in our studies, the values of pressure, temperature, mass density, and velocity are found to be smaller in the fs laser plume, and their time evolution occurs much faster on the same time scale. The oscillatory shock waves clearly visible in the ns plume are not observed in the internal region of the fs plume. These experimental and computational results provide a quantitative understanding of plasma expansion and shockwave formation in fs-pulse and ns-pulse laser ablated Al plumes in an ambient gas at atmospheric pressures.

  16. Continued Development of in Situ Geochronology for Planetary Using KArLE (Potassium-Argon Laser Experiment)

    Science.gov (United States)

    Devismes, D.; Cohen, B. A.

    2016-01-01

    Geochronology is a fundamental measurement for planetary samples, providing the ability to establish an absolute chronology for geological events, including crystallization history, magmatic evolution, and alteration events, and providing global and solar system context for such events. The capability for in situ geochronology will open up the ability for geochronology to be accomplished as part of lander or rover complement, on multiple samples rather than just those returned. An in situ geochronology package can also complement sample return missions by identifying the most interesting rocks to cache or return to Earth. The K-Ar radiometric dating approach to in situ dating has been validated by the Curiosity rover on Mars as well as several laboratories on Earth. Several independent projects developing in situ rock dating for planetary samples, based on the K-Ar method, are giving promising results. Among them, the Potassium (K)-Argon Laser Experiment (KArLE) at MSFC is based on techniques already in use for in planetary exploration, specifically, Laser-induced Breakdown Spectroscopy (LIBS, used on the Curiosity Chemcam), mass spectroscopy (used on multiple planetary missions, including Curiosity, ExoMars, and Rosetta), and optical imaging (used on most missions).

  17. Technical aspects of laser treatment for acute retinopathy of prematurity under topical anesthesia

    OpenAIRE

    Jalali Subhadra; Azad Rajvardhan; Trehan Hemant; Dogra Mangat; Gopal Lingam; Narendran Venkatapathy

    2010-01-01

    Retinopathy of prematurity (ROP) is a significant cause of childhood blindness. The criteria for laser therapy have been revised from threshold ROP to include the earlier stage of high-risk prethreshold ROP. Laser photocoagulation is an established technique for the treatment of ROP. However, the detailed procedure and techniques for laser photocoagulation have not yet been published. Adequate and appropriate laser photocoagulation for ROP is different from the application of lasers in adult ...

  18. Experimental and computational study of complex shockwave dynamics in laser ablation plumes in argon atmosphere

    International Nuclear Information System (INIS)

    We investigated spatio-temporal evolution of ns laser ablation plumes at atmospheric pressure, a favored condition for laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass-spectrometry. The 1064 nm, 6 ns pulses from a Nd:YAG laser were focused on to an Al target and the generated plasma was allowed to expand in 1 atm Ar. The hydrodynamic expansion features were studied using focused shadowgraphy and gated 2 ns self-emission visible imaging. Shadowgram images showed material ejection and generation of shock fronts. A secondary shock is observed behind the primary shock during the time window of 100−500 ns with instabilities near the laser cone angle. By comparing the self-emission images obtained using fast photography, it is concluded that the secondary shocks observed in the shadowgraphy were generated by fast moving target material. The plume front estimates using fast photography exhibited reasonable agreement with data obtained from shadowgraphy at early times ≤400 ns. However, at later times, fast photography images showed plume confinement while the shadowgraphic images showed propagation of the plume front even at greater times. The structure and dynamics of the plume obtained from optical diagnostic tools were compared to numerical simulations. We have shown that the main features of plume expansion in ambient Ar observed in the experiments can be reproduced using a continuum hydrodynamics model which provided valuable insight into the expansion dynamics and shock structure of the plasma plume.

  19. Quantitative analyses of glass via laser-induced breakdown spectroscopy in argon

    Science.gov (United States)

    Gerhard, C.; Hermann, J.; Mercadier, L.; Loewenthal, L.; Axente, E.; Luculescu, C. R.; Sarnet, T.; Sentis, M.; Viöl, W.

    2014-11-01

    We demonstrate that elemental analysis of glass with a measurement precision of about 10% can be performed via calibration-free laser-induced breakdown spectroscopy. Therefore, plasma emission spectra recorded during ultraviolet laser ablation of different glasses are compared to the spectral radiance computed for a plasma in local thermodynamic equilibrium. Using an iterative calculation algorithm, we deduce the relative elemental fractions and the plasma properties from the best agreement between measured and computed spectra. The measurement method is validated in two ways. First, the LIBS measurements are performed on fused silica composed of more than 99.9% of SiO2. Second, the oxygen fractions measured for heavy flint and barite crown glasses are compared to the values expected from the glass composing oxides. The measured compositions are furthermore compared with those obtained by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. It is shown that accurate LIBS analyses require spectra recording with short enough delays between laser pulse and detector gate, when the electron density is larger than 1017 cm- 3. The results show that laser-induced breakdown spectroscopy based on accurate plasma modeling is suitable for elemental analysis of complex materials such as glasses, with an analytical performance comparable or even better than that obtained with standard techniques.

  20. Quantitative analyses of glass via laser-induced breakdown spectroscopy in argon

    International Nuclear Information System (INIS)

    We demonstrate that elemental analysis of glass with a measurement precision of about 10% can be performed via calibration-free laser-induced breakdown spectroscopy. Therefore, plasma emission spectra recorded during ultraviolet laser ablation of different glasses are compared to the spectral radiance computed for a plasma in local thermodynamic equilibrium. Using an iterative calculation algorithm, we deduce the relative elemental fractions and the plasma properties from the best agreement between measured and computed spectra. The measurement method is validated in two ways. First, the LIBS measurements are performed on fused silica composed of more than 99.9% of SiO2. Second, the oxygen fractions measured for heavy flint and barite crown glasses are compared to the values expected from the glass composing oxides. The measured compositions are furthermore compared with those obtained by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. It is shown that accurate LIBS analyses require spectra recording with short enough delays between laser pulse and detector gate, when the electron density is larger than 1017 cm−3. The results show that laser-induced breakdown spectroscopy based on accurate plasma modeling is suitable for elemental analysis of complex materials such as glasses, with an analytical performance comparable or even better than that obtained with standard techniques. - Highlights: • Plasma modeling including the calculation of the plasma pressure • Calibration-free LIBS based on accurate modeling of the plasma emission spectrum • Quantitative LIBS analysis of multicomponent optical glasses including oxygen • Good measurement accuracy obtained only for small delays between laser pulse and detector gate

  1. Quantitative analyses of glass via laser-induced breakdown spectroscopy in argon

    Energy Technology Data Exchange (ETDEWEB)

    Gerhard, C. [Laboratory of Laser and Plasma Technologies, University of Applied Sciences and Arts, Von-Ossietzky-Straße 99, 37085 Göttingen (Germany); Hermann, J., E-mail: Hermann@lp3.univ-mrs.fr [LP3, CNRS – Aix–Marseille University, 163 Av. de Luminy, 13288 Marseille (France); Mercadier, L. [LP3, CNRS – Aix–Marseille University, 163 Av. de Luminy, 13288 Marseille (France); Loewenthal, L. [Laboratory of Laser and Plasma Technologies, University of Applied Sciences and Arts, Von-Ossietzky-Straße 99, 37085 Göttingen (Germany); Axente, E.; Luculescu, C.R. [Laser–Surface–Plasma Interactions Laboratory, Lasers Department, National Institute for Lasers, Plasma and Radiation Physics, Măgurele (Romania); Sarnet, T.; Sentis, M. [LP3, CNRS – Aix–Marseille University, 163 Av. de Luminy, 13288 Marseille (France); Viöl, W. [Laboratory of Laser and Plasma Technologies, University of Applied Sciences and Arts, Von-Ossietzky-Straße 99, 37085 Göttingen (Germany)

    2014-11-01

    We demonstrate that elemental analysis of glass with a measurement precision of about 10% can be performed via calibration-free laser-induced breakdown spectroscopy. Therefore, plasma emission spectra recorded during ultraviolet laser ablation of different glasses are compared to the spectral radiance computed for a plasma in local thermodynamic equilibrium. Using an iterative calculation algorithm, we deduce the relative elemental fractions and the plasma properties from the best agreement between measured and computed spectra. The measurement method is validated in two ways. First, the LIBS measurements are performed on fused silica composed of more than 99.9% of SiO{sub 2}. Second, the oxygen fractions measured for heavy flint and barite crown glasses are compared to the values expected from the glass composing oxides. The measured compositions are furthermore compared with those obtained by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. It is shown that accurate LIBS analyses require spectra recording with short enough delays between laser pulse and detector gate, when the electron density is larger than 10{sup 17} cm{sup −3}. The results show that laser-induced breakdown spectroscopy based on accurate plasma modeling is suitable for elemental analysis of complex materials such as glasses, with an analytical performance comparable or even better than that obtained with standard techniques. - Highlights: • Plasma modeling including the calculation of the plasma pressure • Calibration-free LIBS based on accurate modeling of the plasma emission spectrum • Quantitative LIBS analysis of multicomponent optical glasses including oxygen • Good measurement accuracy obtained only for small delays between laser pulse and detector gate.

  2. Propagation dynamics of femtosecond laser pulses in a hollow fiber filled with argon: constant gas pressure versus differential gas pressure

    Science.gov (United States)

    Nurhuda, Muhammad; Suda, Akira; Midorikawa, Katsumi; Hatayama, Masatoshi; Nagasaka, Keigo

    2003-09-01

    We investigate the dynamics of femtosecond laser pulses propagating in a hollow fiber filled with argon, through a full numerical solution of the nonlinear Schrödinger equation. The simulation results show that, if the intensity is low and no ionization takes place, the spatial profile of the beam does not change very much so that its propagation model may be simplified to a one-dimensional model. If the intensity is high and ionization takes place, the spatial dynamics as well as temporal dynamics become very complicated because of self-focusing and defocusing. It is found that, for the same value of the B integral, self-focusing inside a hollow fiber can be substantially suspended by a differential gas pressure technique, where the gas pressure is set to be a minimum at the entrance and then increased with the propagation distance. Numerical simulations show that using such a technique, the energy transmitted during propagation inside hollow fiber is significantly enhanced, and the spatial phase is also improved.

  3. Panretinal photocoagulation for radiation-induced ocular ischemia

    International Nuclear Information System (INIS)

    We present preliminary findings on the effectiveness of panretinal photocoagulation in preventing neovascular glaucoma in eyes with radiation-induced ocular ischemia. Our study group consisted of 20 patients who developed radiation-induced ocular ischemia following cobalt-60 plaque radiotherapy for a choroidal or ciliary body melanoma. Eleven of the 20 patients were treated by panretinal photocoagulation shortly after the diagnosis of ocular ischemia, but nine patients were left untreated. In this non-randomized study, the rate of development of neovascular glaucoma was significantly lower (p = 0.024) for the 11 photocoagulated patients than for the nine who were left untreated

  4. Time-resolved tunable diode laser absorption spectroscopy of excited argon and ground-state titanium atoms in pulsed magnetron discharges

    Czech Academy of Sciences Publication Activity Database

    Sushkov, V.; Do, H.T.; Čada, Martin; Hubička, Zdeněk; Hippler, R.

    2013-01-01

    Roč. 22, č. 1 (2013), 1-10. ISSN 0963-0252 R&D Projects: GA ČR(CZ) GAP205/11/0386; GA ČR GAP108/12/2104 Institutional research plan: CEZ:AV0Z10100522 Keywords : absorption spectroscopy * diode laser * magnetron * argon metastable * HiPIMS * titanium * time-resolved Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.056, year: 2013 http://iopscience.iop.org/0963-0252/22/1/015002/

  5. Modern retinal laser therapy

    OpenAIRE

    Kozak, Igor; Luttrull, Jeffrey K.

    2014-01-01

    Medicinal lasers are a standard source of light to produce retinal tissue photocoagulation to treat retinovascular disease. The Diabetic Retinopathy Study and the Early Treatment Diabetic Retinopathy Study were large randomized clinical trials that have shown beneficial effect of retinal laser photocoagulation in diabetic retinopathy and have dictated the standard of care for decades. However, current treatment protocols undergo modifications. Types of lasers used in treatment of retinal dise...

  6. Lunar exospheric argon modeling

    Science.gov (United States)

    Grava, Cesare; Chaufray, J.-Y.; Retherford, K. D.; Gladstone, G. R.; Greathouse, T. K.; Hurley, D. M.; Hodges, R. R.; Bayless, A. J.; Cook, J. C.; Stern, S. A.

    2015-07-01

    Argon is one of the few known constituents of the lunar exosphere. The surface-based mass spectrometer Lunar Atmosphere Composition Experiment (LACE) deployed during the Apollo 17 mission first detected argon, and its study is among the subjects of the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) and Lunar Atmospheric and Dust Environment Explorer (LADEE) mission investigations. We performed a detailed Monte Carlo simulation of neutral atomic argon that we use to better understand its transport and storage across the lunar surface. We took into account several loss processes: ionization by solar photons, charge-exchange with solar protons, and cold trapping as computed by recent LRO/Lunar Orbiter Laser Altimeter (LOLA) mapping of Permanently Shaded Regions (PSRs). Recycling of photo-ions and solar radiation acceleration are also considered. We report that (i) contrary to previous assumptions, charge exchange is a loss process as efficient as photo-ionization, (ii) the PSR cold-trapping flux is comparable to the ionization flux (photo-ionization and charge-exchange), and (iii) solar radiation pressure has negligible effect on the argon density, as expected. We determine that the release of 2.6 × 1028 atoms on top of a pre-existing argon exosphere is required to explain the maximum amount of argon measured by LACE. The total number of atoms (1.0 × 1029) corresponds to ∼6700 kg of argon, 30% of which (∼1900 kg) may be stored in the cold traps after 120 days in the absence of space weathering processes. The required population is consistent with the amount of argon that can be released during a High Frequency Teleseismic (HFT) Event, i.e. a big, rare and localized moonquake, although we show that LACE could not distinguish between a localized and a global event. The density of argon measured at the time of LACE appears to have originated from no less than four such episodic events. Finally, we show that the extent of the PSRs that trap

  7. The Potassium-Argon Laser Experiment (KarLE): In Situ Geochronology for Mars and Beyond

    Science.gov (United States)

    Cohen, Barbara A.

    2014-01-01

    The search for life in the solar system depends upon discovering the right moments in planetary evolution: when habitable environments existed, when they declined, and when geologic processes operated to preserve traces of life after death. However, an incomplete knowledge of absolute Martian geochronology limits our ability to understand the timing of Martian evolutionary milestones, major climate changes, and stratigraphic epochs [1, 2]. Absolute dating relates these habitability markers to planetarywide geologic, atmospheric, and climate history places, and ties their occurrence to the history of the solar system, especially the Earth-Moon system and the timescale of evolution of life on Earth. KArLE is being developed to anchor the relative timeline of geological events to an absolute chronology that puts Mars into a wider solar system context. KArLE makes its measurements on rock samples that can be obtained by landers or rovers and inserted into a small, mechanically simple chamber. KArLE interrogates the samples using laser-induced breakdown spectrocopy (LIBS), mass spectrometry, and optical imaging. The KArLE experiment is flexible enough to accommodate any partner providing these instrument components, a creative approach that extends the ability of mission payloads to accomplish an additional highly-desirable science measurement for low cost and risk and minimal extra hardware.

  8. Management of cyclosporine-induced gingival hyperplasia by use of an argon laser

    Science.gov (United States)

    Blankenau, Richard J.; Triolo, P.; Powell, G. L.

    1994-09-01

    This is a report of a case study with interesting laser applications. A 7 year old female was referred to us for treatment of hyperplastic tissue. At age two the patient had successfully undergone a liver transplant. She had undergone two periodontal surgeries under general anesthetic for the same soft tissue problem. Other possible complications were chronic sinusitis and frequent headaches. She has allergies to penicillin and sulfa. Her daily medications are Predisone and Cyclosporin. We consulted with her transplant team and they had no contraindication for the proposed dental surgery. The doctor placed her on prophylactic erythromycin for the procedure, as a preventive measure. The patient desired not to have any more general anesthetics administered. Clinical examination revealed electric pulp tests were normal for all teeth tested. No visible carious lesions were observed and there was no need for radiographs at this time. Soft tissue revealed red inflamed fibrous tissue consistent with gingival hyperplasia. Probing demonstrated 4 - 6 mm pockets around the anterior teeth.

  9. Dynamics of the spectral behaviour of an ultrashort laser pulse in an argon-gas-filled capillary discharge-preformed plasma channel

    Directory of Open Access Journals (Sweden)

    Sakai S.

    2013-11-01

    Full Text Available We have reported the argon plasma waveguide produced in an alumina (Al2O3 capillary discharge and used to guide ultrashort laser pulses at intensities of the order of 1016  W/cm2. A one-dimensional magnetohydrodynamic (MHD code was used to evaluate the average degree of ionization of Ar in the preformed plasma channel. The spectrum of the propagated laser pulse in the Ar plasma waveguide was not modified and was well reproduced by a particle-in-cell (PIC simulation under initial ion charge state of Ar3+ in the preformed plasma waveguide. The optimum timing for the laser pulse injection was around 150 ns after initiation of a discharge with a peak current of 200 A.

  10. Dynamics of the spectral behaviour of an ultrashort laser pulse in an argon-gas-filled capillary discharge-preformed plasma channel

    Science.gov (United States)

    Sakai, S.; Higashiguchi, T.; Yugami, N.; Bobrova, N.; Sentoku, Y.; Kodama, R.

    2013-11-01

    We have reported the argon plasma waveguide produced in an alumina (Al2O3) capillary discharge and used to guide ultrashort laser pulses at intensities of the order of 1016 W/cm2. A one-dimensional magnetohydrodynamic (MHD) code was used to evaluate the average degree of ionization of Ar in the preformed plasma channel. The spectrum of the propagated laser pulse in the Ar plasma waveguide was not modified and was well reproduced by a particle-in-cell (PIC) simulation under initial ion charge state of Ar3+ in the preformed plasma waveguide. The optimum timing for the laser pulse injection was around 150 ns after initiation of a discharge with a peak current of 200 A.

  11. ToF-SIMS and laser-SNMS analysis of Madin-Darby canine kidney II cells with silver nanoparticles using an argon cluster ion beam.

    Science.gov (United States)

    Nees, Ricarda; Pelster, Andreas; Körsgen, Martin; Jungnickel, Harald; Luch, Andreas; Galla, Hans-Joachim; Arlinghaus, Heinrich F

    2016-06-01

    The use of nanoparticles is one of the fastest expanding fields in industrial as well as in medical applications, owing to their remarkable characteristics. Silver nanoparticles (AgNPs) are among the most-commercialized nanoparticles because of their antibacterial effects. Laser postionization secondary neutral mass spectrometry (laser-SNMS) and time-of-flight secondary ion mass spectrometry in combination with argon cluster ion sputtering was used for the first time to investigate the effects of AgNPs on Madin-Darby canine kidney (MDCK) II cells. Depth profiles and high-resolution three dimensional (3D) images of nanoparticles and organic compounds from cells were obtained using an Ar cluster ion beam for sputtering and Bi3 (+) primary ions for the analysis. The 3D distribution of AgNPs and other organic compounds in MDCK II cells could be readily detected with very high efficiency, sensitivity, and submicron lateral resolution. The argon cluster ion beam is well suited for the sputtering of biological samples. It enables a high sample removal rate along with low molecular degradation. The outer membrane, the cytoplasm, and the nuclei of the cells could be clearly visualized using the signals PO(+) and C3H8N(+) or CN(+) and C3H8N(+). The laser-SNMS images showed unambiguously that AgNPs are incorporated by MDCK II cells and often form silver aggregates with a diameter of a few micrometers, mainly close to the outside of the cell nuclei. PMID:26671480

  12. Investigation of local thermodynamic equilibrium of laser induced Al2O3–TiC plasma in argon by spatially resolved optical emission spectroscopy

    Directory of Open Access Journals (Sweden)

    K. Alnama

    2016-06-01

    Full Text Available Plasma plume of Al2O3–TiC is generated by third harmonic Q-switched Nd:YAG nanosecond laser. It is characterized using Optical Emission Spectroscopy (OES at different argon background gas pressures 10, 102, 103, 104 and 105 Pa. Spatial evolution of excitation and ionic temperatures is deduced from spectral data analysis. Temporal evolution of Ti I emission originated from different energy states is probed. The correlation between the temporal behavior and the spatial temperature evolution are investigated under LTE condition for the possibility to use the temporal profile of Ti I emission as an indicator for LTE validity in the plasma.

  13. Experimental study of K-shell X-ray emission from argon clusters irradiated by an ultra-intense laser pulse

    International Nuclear Information System (INIS)

    The K-shell X-ray emission of argon clusters irradiated by 1017 W cm-2 laser pulses was spectrally resolved and investigated as a function of different laser and cluster parameters. A special effort was first realized in order to control the laser focusing into the cluster jet and the temporal laser pulse contrast which both were observed to have a drastic influence on the X-ray emission. Cluster mean radius was then varied from 200 to 350 A as well as the laser pulse duration from 30 fs to 3.5 ps (FWHM). The X-ray emission was observed to reach a maximal value for a given laser pulse duration (typically a few times 100 fs), increasing with the cluster mean radius. These observations can be understood in terms of density resonance effect. The X-ray emission duration was also investigated above 3 keV with a streak camera (resolution about 1 ps (FWHM) at 1 kHz). This duration was observed to be close to 3.5 ps (FWHM) at the optimal X-ray emission

  14. Evaluation of the hydrogen peroxide and special colorant effects under irradiation by argon and diode laser on tooth-whitening in vitro; Avaliacao do efeito de corantes especiais e peroxido de hidrogenio irradiados por laser de argonio e laser de diodo no clareamento dental 'in vitro'

    Energy Technology Data Exchange (ETDEWEB)

    Gaspar, Jose Antonio

    2003-07-01

    The aim of this study is to determine if there is any interaction between special colorant found on bleaching agents that have 35 % of hydrogen peroxide on its composition, and argon or diode laser. The first part of the study was to characterize the extrinsic stain obtained through a staining solution containing products present on the day by day diet of the general population. Thirty-two inferior human extracted incisors, free of caries and without filling material were selected for the study. The laser devices employed were Argon laser (AccuCure 3000 TM - Lasermed), wave length 488 nm, with a 200 mW/cm{sup 2} for 30 seconds in continuos mode; and diode laser (L 808 Medical Laser - Lasering do Brasil), wave length 808 {+-} 10 nm, with 1,6 W/cm{sup 2} for 30 seconds in continuos mode. The application mode done by a scanning movement over the buccal surface. The bleaching agents used were: Opalescence Extra (OE) - Ultradent Products USA, hydrogen peroxide 35%, gel with Carotene to convert light into heat; Pola Office (PO) - SDI - USA single doses of hydrogen peroxide; Whiteness HP (WHP) - FGM - Brasil, hydrogen peroxide 35%; Opus White (OW) - Sharplan - Israel, hydrogen peroxide 35%. The temperature rise measurement was performed with a thermocouple model 120-202-AJ, Fenwal, inserted into the pulpar chamber. The bleaching material was applied on the tooth surface with 2 mm thickness and then the irradiation was perform. The thirty two teeth were randomized in four groups, two for each laser device. The obtain data demonstrated a superior performance of the Argon laser on tooth whitening and also better results concerning the temperature rise. The alteration on tooth coloration was verified through digital spectrophotometer (Shade-Eye EX - Shofu) and quantitative analyses showed statistical differences among the groups. The bleaching results for Argon laser combined with OE and WHP were superior for the other groups. The mean variation of the temperature rise

  15. Argon-40/Argon-39 Age Spectra of Apollo 17 Highlands Breccia Samples by Laser Step Heating and the Age of the Serenitatis Basin

    Science.gov (United States)

    Dalrymple, G. Brent; Ryder, Graham

    1996-01-01

    We have obtained high-resolution (21-63 steps) Ar-40/Ar-39 age spectra using a continuous laser system on 19 submilligram samples of melt rocks and clasts from Apollo 17 samples collected from the pre-Imbrian highlands in the easternmost part of the Serenitatis basin. The samples include poikilitic melt rocks inferred to have been formed in the Serenitatis basin-forming impact, aphanitic melt rock whose compositions vary and whose provenance is uncertain, and granulite, gabbro, and melt clasts. Three of the poikilitic melts have similar age spectrum plateau ages (72395,96, 3893 +/- 16 Ma (2sigma); 72535,7, 3887 +/- 16 Ma; 76315,150, 3900 +/- 16 Ma) with a weighted mean age of 3893 +/- 9 Ma, which we interpret as the best age for the Serenitatis basin- forming impact. Published Ar-40/Ar-39 age spectrum ages of Apollo 17 poikilitic melts are consistent with our new age but are much less precise. Two poikilitic melts did not give plateaus and the maxima in their age spectra indicate ages of greater than or equal to 3869 Ma (72558,7) and greater than or equal to 3743 Ma (77135,178). Plateau ages of two poikilitic melts and two gabbro clasts from 73155 range from 3854 +/- 16 Ma to 3937 +/- 16 Ma and have probably been affected by the ubiquitous (older?) clasts and by post- formation heating (impact) events. Plateau ages from two of the aphanitic melt 'blobs' and two granulites in sample 72255 fall in the narrow range of 3850 q 16 Ma to 3869 q 16 Ma with a weighted mean of 3862 +/- 8 Ma. Two of the aphanitic melt blobs from 72255 have ages of 3883 +/- 16 Ma and greater than or equal to 3894 Ma, whereas a poikilitic melt clast (of different composition from the 'Serenitatis' melts) has an age of 3835 +/- 16 Ma, which is the upper limit for the accretion of 72255. These data suggest that either the aphanitic melts vary in age, as is also suggested by their varying chemical compositions, or they formed in the 72255 accretionary event about 3.84-3.85 Ga and older relict

  16. Investigations of the cathode region of an argon arc plasma by degenerate four-wave mixing laser spectroscopy and optical emission spectroscopy

    International Nuclear Information System (INIS)

    Degenerate four-wave mixing (DFWM) laser spectroscopy was used in local studies of atmospheric pressure argon plasma generated in a free-burning arc. The results of plasma diagnostics using the DFWM method were compared to the results obtained with optical emission measurements. In the cathode region of the arc the maxima of both the DFWM signal and the emission coefficient for the 696.5 nm Ar I line depend on the distance from the cathode tip. This effect proves the departure of the plasma state from local thermal equilibrium (LTE) as it has been reported by many authors. On the other hand the Stark shifts of the 696.5 nm Ar I line determined by the DFWM method in relation to plasma diagnostic results show no deviations from LTE on the arc axis down to 1.0 mm from the cathode tip

  17. The effect of different photoactivation sources on a nanocomposite resin: LED, halogen and argon laser application - doi: 10.4025/actascitechnol.v35i3.16238

    Directory of Open Access Journals (Sweden)

    Aline Bassi Denis

    2013-06-01

    Full Text Available This paper evaluates the effects of different light sources on the monomer conversion (DC% and Vickers microhardness number (VHN of a nanocomposite resin. Three different depths were measured in this study (1, 2 and 3 mm, and photoactivation methods including a halogen lamp, a LED and an argon ion laser were used. In contrast to other studies, the conditions for each photoactivation source such as the exposure time and the same power density were considered and kept the same. It was also shown that increasing the depth lowered the VHN. At each of the depths, it was observed that the three light sources behaved similarly. The correlation between the VHN and DC% is shown. However, only a weak correlation was observed, which implies that a higher DC% value does not necessarily indicate a higher VHN.  

  18. Diode laser based light sources for biomedical applications

    DEFF Research Database (Denmark)

    Müller, André; Marschall, Sebastian; Jensen, Ole Bjarlin;

    2013-01-01

    lasers simultaneously offer tunability, high-power emission and compact size at fairly low cost. Therefore, diode lasers are increasingly preferred in important applications, such as photocoagulation, optical coherence tomography, diffuse optical imaging, fluorescence lifetime imaging, and terahertz...

  19. The application of laser plasma in ophthalmology

    International Nuclear Information System (INIS)

    The production and development of laser plasma are introduced, and the contribution of laser biomedicine and laser plasma technology to ophthalmology is analyzed. The latest three progresses (laser photocoagulation, photo-refractive keratotomy and laser iridectomy) of laser plasma applications in ophthalmology are presented

  20. Argon metastables in HiPIMS: validation of the ionization region model by direct comparison to time resolved tunable diode-laser diagnostics

    Science.gov (United States)

    Stancu, G. D.; Brenning, N.; Vitelaru, C.; Lundin, D.; Minea, T.

    2015-08-01

    The volume plasma interactions of high power impulse magnetron sputtering (HiPIMS) discharges operated with a Ti target is analyzed in detail by combining time-resolved diagnostics with modeling of plasma kinetics. The model employed is the ionization region model (IRM) with an improved and detailed treatment of the kinetics of the argon metastable (Arm) state, called m-IRM. The diagnostics used is tunable diode-laser absorption spectroscopy (TD-LAS) of the Arm state, which gives the line-of-sight density integrated along the laser path parallel to the target surface. The TD-LAS recordings exhibit quite complex temporal evolutions Arm(t), with distinct features that are shown to reflect the time evolution of the plasma (the electron density and temperature), and of the argon gas (gas rarefaction and refill). The Arm(t) function is thus a tracer for the most important aspects of internal discharge physics, and therefore suitable for model testing and validation. The IRM model is constructed to be locked to obey specific experimental macroscopic discharge parameters, specifically the discharge current ID(t) and the voltage UD(t). It has to this purpose been run with the appropriate process gas pressures (from 0.67 to 2.67 Pa), with the experimentally applied voltage pulse profiles UD(t), and with the resulting current pulse profiles ID(t) (with maxima from 0.5 to 70 A). It is shown that the model reproduces the features in the TD-LAS measurements: both the Arm(t) evolution in single pulses, and how the pulse shapes change with gas pressure and with pulse amplitude. The good agreement between the measurements and model output is in this work taken to validate the basic assumptions of the m-IRM. In addition, the m-IRM results have been used to unravel the connections between volume plasma kinetics and various features recorded in the TD-LAS measurement, and to generalize the foremost characteristics of the studied discharges.

  1. Behaviour of tunnelling transition rate of argon atom exposed to strong low-frequency elliptical laser field

    Indian Academy of Sciences (India)

    Miladinovic Tatjana B; Petrovic Violeta M

    2016-03-01

    We considered the tunnelling ionization of an electron under the influence of amonochromatic laser beam with the elliptical polarization. Arbitrary values of ellipticity were observed. The influence of ponderomotive potential and Stark shift on the ionization rate was discussed. A brief description of the dependence of the ponderomotive potential and the Keldysh parameter on the field intensity and ellipticity is given.

  2. Studies on an argon laser-induced photopolymerization employing both mono- and bischromophoric hemicyanine dye-borate complex as a photoinitiator: Part II

    International Nuclear Information System (INIS)

    Several photoredox pairs containing dichromophoric hemicyanine dyes have been evaluated as novel photoinitiators for free radical polymerization induced with an argon-ion laser irradiation. The tested photoredox couples are the pairs composed of the hemicyanine dye cations acting as electron acceptors and n-butyltriphenyl borate anions being the electron donors. The photoinitiating abilities of the series of dimmeric dichromophoric stilbazolium borates; 1,2-; 1,3-; and 1,4-bis-[4-(p-N,N-dialkylaminostyryl)pyridinyl]xylene di-n-butyltriphenylborates, were compared to the photochemistry of structurally related, monochromophoric styrylpyridinium borates. The obtained results clearly documented that the dicationic photoinitiators exhibit a marked increase in the photoinitiation ability compared to the initiators consisting of a single charged hemicyanine dye. Our studies revealed also that the rate of photopolymerization depends on ΔGel of electron transfer between borate anion and styrylpyridinium cation. The latter value was estimated for all series of styrylpyridinium borate salts. The relationship between the rate of polymerization and the free energy of activation shows the dependence predicted by the classical theory of electron transfer

  3. Studies on an argon laser-induced photopolymerization employing both mono- and bischromophoric hemicyanine dye-borate complex as a photoinitiator: Part II

    Energy Technology Data Exchange (ETDEWEB)

    Jedrzejewska, Beata [University of Technology and Life Sciences, Faculty of Chemical Technology and Engineering, Seminaryjna 3, 85-326 Bydgoszcz (Poland)], E-mail: beata@utp.edu.pl; Marciniak, Angelika; Paczkowski, Jerzy [University of Technology and Life Sciences, Faculty of Chemical Technology and Engineering, Seminaryjna 3, 85-326 Bydgoszcz (Poland)

    2008-10-15

    Several photoredox pairs containing dichromophoric hemicyanine dyes have been evaluated as novel photoinitiators for free radical polymerization induced with an argon-ion laser irradiation. The tested photoredox couples are the pairs composed of the hemicyanine dye cations acting as electron acceptors and n-butyltriphenyl borate anions being the electron donors. The photoinitiating abilities of the series of dimmeric dichromophoric stilbazolium borates; 1,2-; 1,3-; and 1,4-bis-[4-(p-N,N-dialkylaminostyryl)pyridinyl]xylene di-n-butyltriphenylborates, were compared to the photochemistry of structurally related, monochromophoric styrylpyridinium borates. The obtained results clearly documented that the dicationic photoinitiators exhibit a marked increase in the photoinitiation ability compared to the initiators consisting of a single charged hemicyanine dye. Our studies revealed also that the rate of photopolymerization depends on {delta}G{sub el} of electron transfer between borate anion and styrylpyridinium cation. The latter value was estimated for all series of styrylpyridinium borate salts. The relationship between the rate of polymerization and the free energy of activation shows the dependence predicted by the classical theory of electron transfer.

  4. Density of atoms in Ar*(3p{sup 5}4s) states and gas temperatures in an argon surfatron plasma measured by tunable laser spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Huebner, S.; Carbone, E. A. D.; Mullen, J. J. A. M. van der [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands); Sadeghi, N. [LIPhy, Universite Joseph Fourier and CNRS, UMR 5588, Grenoble F-38041 (France)

    2013-04-14

    This study presents the absolute argon 1 s (in Paschens's notation) densities and the gas temperature, T{sub g}, obtained in a surfatron plasma in the pressure range 0.65lasers. T{sub g} is deduced from the absorption line shapes when scanning the laser wavelengths. The line profile, which is a Doppler broadening dominated Gaussian at gas pressures of p<10 mbar, changes to a Voigt shape at p>10 mbar, for which the pressure broadening can no more be neglected. T{sub g} is in the range of 480-750 K, increasing with pressure and decreasing with the distance from the microwave launcher. Taking into account the line of sight effects of the absorption measurements, a good agreement is found with our previous measurements by Rayleigh scattering of T{sub g} at the tube center. In the studied pressure range, the Ar(4 s) atom densities are in the order of 10{sup 16}-10{sup 18} m{sup -3}, increasing towards the end of the plasma column, decreasing with the pressure. In the low pressure side, a broad minimum is found around 10

  5. Photocoagulation treatment for clinically significant radiation macular oedema

    Energy Technology Data Exchange (ETDEWEB)

    Kinyoun, J.L.; Zamber, R.W.; Lawrence, B.S.; Barlow, W.E.; Arnold, A.M. [Washington Univ., Seattle, WA (United States)

    1995-02-01

    Macular oedema is a leading cause of vision loss in patients with radiation retinopathy. In an effort to find an effective treatment for this vision threatening complication, 12 eyes (eight patients) were treated with photocoagulation for clinically significant radiation macular oedema (CSRMO) defined as central macular thickening, exudates threatening the macular centre, or one disc area of thickening in the macula. Median visual acuity improved from 20/100 pre-operatively to 20/90 at the initial post-operative examination (mean follow up 5 months) and to 20/75 at the final post-operative examination (mean follow up 39 months). At the final post-operative examination, visual acuity had improved in eight (67%) eyes and six (50%) eyes had complete resolution of the CSRMO; two (17%) other eyes had improved anatomically in that fewer CSRMO criteria were present. These results suggest that macular photocoagulation is effective in decreasing macular oedema and improving vision in eyes with CSRMO. (author).

  6. Photocoagulation treatment for clinically significant radiation macular oedema

    International Nuclear Information System (INIS)

    Macular oedema is a leading cause of vision loss in patients with radiation retinopathy. In an effort to find an effective treatment for this vision threatening complication, 12 eyes (eight patients) were treated with photocoagulation for clinically significant radiation macular oedema (CSRMO) defined as central macular thickening, exudates threatening the macular centre, or one disc area of thickening in the macula. Median visual acuity improved from 20/100 pre-operatively to 20/90 at the initial post-operative examination (mean follow up 5 months) and to 20/75 at the final post-operative examination (mean follow up 39 months). At the final post-operative examination, visual acuity had improved in eight (67%) eyes and six (50%) eyes had complete resolution of the CSRMO; two (17%) other eyes had improved anatomically in that fewer CSRMO criteria were present. These results suggest that macular photocoagulation is effective in decreasing macular oedema and improving vision in eyes with CSRMO. (author)

  7. In Situ Geochronology on the Mars 2020 Rover with KArLE (Potassium-Argon Laser Experiment)

    Science.gov (United States)

    Cohen, B. A.; Swindle, T. D.; Roark, S. E.

    2014-01-01

    If extinct and/or extant life is discovered on Mars, knowledge of the chronology of the biosphere will be of paramount importance. KArLE will provide absolute ages of Mars 2020 rocks, which will allow us to understand them in the context of Mars' geologic history, connect them to other landing sites, and compare Martian epochs of habitability with the Earth's history and evolution of life. KArLE significantly enhances the ability of Mars 2020 to meet its science objectives by performing in situ age dating on key lithologies, enabling targeted searches for ancient biosignatures and increasing the chances of identifying evidence for Martian microbial life. The KArLE investigation makes its measurements on a core sample obtained with the rover drill, inserted into a small, mechanically simple chamber, followed by interrogation by laser-induced breakdown spectroscopy (LIBS), mass spectrometry, and optical imaging. The KArLE experiment is flexible enough to accommodate any partner providing these instrument components, a creative approach that extends the ability of the Mars 2020 payload to accomplish an additional highly-desirable science measurement for low cost and risk and minimal extra hardware.

  8. In vitro comparative study of share bond of light cured composite resins with halogen light and argon laser, using stainless steel brackets on human premolars; Estudo comparativo in vitro da capacidade adesiva da resina fotoativada pela luz halogena e por laser de argonio, utilizando-se brackets metalicos em pre-molares humanos

    Energy Technology Data Exchange (ETDEWEB)

    Carillo, Vitoria Eugenia Bismarck

    2004-07-01

    The aim of this study in vitro was to compare the share bond strength of the light-cured composite resins Transbond XT (Unitek), with halogen light and argon laser. The Adhesive Remmant Index (ARI) was also investigated. The brackets Dyna lock (3M-UNITEK) were bonded to 75 human premolars, divided into 5 groups (15 each) according to time and the polymerization: Group H20, 15 brackets bonded with halogen light for 20s (10s both sides); Group H40, 15 brackets bonded with halogen light for 40s (20s both sides); Group A40, 15 brackets bonded with argon laser for 40s (20s both sides); Group A20, 15 brackets bonded with argon laser for 20s (10s both sides); Group A10, 15 brackets bonded with argon laser for 10s (5s both sides). The pulpal temperature changes were determined during a polymerization, not exceeding 3,5 deg C. After bonding, the teeth were submitted to a thermo cycled of 700 cycles between 5 deg C and 55 deg C, to simulate the consuming that the light cured composite resin would have in a short space of time. The specimens were then placed in PVC ring and embedded in acrylic resin (Aero-Jet). The tensile bond strength test was performed on an Universal Machine set at a crosshead speed of 1,5 mm/min, and for each rupture we registered a graphic and the best load required in Newtons, was converted to MPa and kgf. The share bond strength showed bigger values for the exposure time of 20 seconds, for the Group bonded for halogen light (H20), 7,45 kgf (7,64 MPa) and for argon laser 7,50 kgf (7,69 MPa); lesser values for the exposure time of 40s for the Group with halogen light (H40), 6,15 kgf (6,30 MPa) and argon laser Group (A40), 6,20 kgf (6,35 MPa) 0; and A10, 4,85 kgf (4,97 MPa). In the ARI Index, only A40 Group showed the 1 Index, with statistical results. In this Group, less than half of the remainder adhesive stayed on the surface of the enamel, conferring specimens failed at the enamel-adhesive interface. The results of the in vitro study demonstrate that

  9. Argon plasma coagulation

    Directory of Open Access Journals (Sweden)

    Zenker, Matthias

    2008-03-01

    Full Text Available Argon Plasma Coagulation (APC is an application of gas discharges in argon in electrosurgery, which is increasingly used especially in endoscopy. The major application fields are haemostasis, tissue devitalization and tissue reduction.This review describes the physics and technology of electrosurgery and APC. Some characteristics of the argon discharge are shown and discussed, and thermal effects in biological tissue are described. Subsequently, examples of medical applications are given.

  10. Combination of Intravitreal Bevacizumab and Peripheral Photocoagulation: An Alternative Treatment in Eales Disease

    OpenAIRE

    CP, Juarez; AL, Gramajo; JD, Luna

    2013-01-01

    To report the efficacy of combination therapy (bevacizumab and photocoagulation) in a case of Eales Disease this study has been performed. Bevacizumab (Avastin, 1.25 mg/0.05 ml) was injected intravitreously for the treatment of iris and retinal neovascularization in a 56-year old Hispanic female with photocoagulation treatment to control the recurrence of vitreous haemorrhage. Our results revealed that stabilization of the disease and improvement in visual acuity were achieved without any sig...

  11. Effect of macular photocoagulation on visual acuity of Omani patients with clinically significant macular edema

    Directory of Open Access Journals (Sweden)

    Zafar A Zaidi

    2009-01-01

    Full Text Available Background: The aim of this study was to determine the effect of macular laser treatment on the visual acuity (VA of Omani diabetic patients with clinically significant macular edema (CSME. Visual outcome was also correlated with duration and control of diabetes and presence or absence of hypertension and hyperlipidemia. Materials and Methods: This is a retrospective noncomparative cohort study involving 101 eyes of 72 Omani diabetic patients. Change in VA was determined using Snellen′s VA chart. The mean duration of follow-up was approximately 21 months (range, 16-24 months. Results: 29.7% of the patients maintained their vision, 35.6% showed improvement, whereas 34.7% showed a decrease in their vision. Positive visual outcome showed a statistically significant direct relationship with tight control of diabetes and absence of hypertension and an inverse relationship with the duration of diabetes. Presence of hyperlipedemia did not show a statistically significant relationship with positive visual outcome. However, it showed a trend to better visual outcome in the absence of hyperlipedemia. Peak incidence of macular edema was seen at the age of 52.3 years. Conclusion: Macular photocoagulation was found to be an effective method of treatment for CSME among Omani diabetic patients, which has resulted in a positive visual outcome in 65.3% of the patients (stable and improved vision. Effective control of diabetes, duration of diabetes, and hypertension are the factors which influence the postlaser visual outcome.

  12. The spectra of the multicharged argon hollow ions: Observation, modeling and using for diagnostics of the early stage of the heating of clusters by a super high contrast femtosecond laser pulses

    International Nuclear Information System (INIS)

    A study is made of the ultra-short laser pulse irradiation of Ar cluster targets. Experiments have been performed with large cluster sizes and using very high laser contrasts, which have allowed clear and unambiguous observation of exotic inner-shell transitions in near-neutral Ar ions. The interaction of the main laser pulse with the unperturbed target is a necessary requirement for observing these lines. Our measurements are supported by kinetics calculations in which a very detailed atomic model is used. The calculations predict all of the spectral features found experimentally, and support the notion that the X-ray emission arises from many ion stages of the Ar plasma, from near-neutral through He-like ions, and from a range of plasma temperatures and densities. Differences between X-ray argon clusters excited at the laser-cluster and laser-droplet interactions have been analyzed. X-ray spectral methods have been proposed to determine the parameters of the plasma formed at the early stages of its evolution. It has been shown that the spectra of hollow ions are the most informative in the first moments of the heating of a cluster, whereas the diagnostics of the late stages can be performed using the conventional lines of multicharged ions.

  13. Evaluation of efficacy of combined intravitreal bevacizumab and grid laser treatment in diabetic macular edema

    OpenAIRE

    Çetin Akpolat; Ferhat Evliyaoğlu; Muhammed Mustafa Kurt

    2015-01-01

    Objective: To evaluate the efficacy of combined treatment of intravitreal bevacizumab injection followed by grid laser photocoagulation in patients with diabetic macular edemaMethods: Patients with diabetic macular edema received single dose intravitreal bevacizumab injection and followed by grid laser photocoagulation treatment four weeks later in the retrospectively conducted study. All eyes had underwent a complete ophthalmic examination including optical coherence tomography at baseline a...

  14. Attosecond Time-Resolved Autoionization of Argon

    International Nuclear Information System (INIS)

    Autoionization of argon atoms was studied experimentally by transient absorption spectroscopy with isolated attosecond pulses. The peak position, intensity, linewidth, and shape of the 3s3p6np 1P Fano resonance series (26.6-29.2 eV) were modified by intense few-cycle near infrared laser pulses, while the delay between the attosecond pulse and the laser pulse was changed by a few femtoseconds. Numerical simulations revealed that the experimentally observed splitting of the 3s3p64p 1P line is caused by the coupling between two short-lived highly excited states in the strong laser field.

  15. A Comparative Study of Retinal Function in Rabbits after Panretinal Selective Retina Therapy versus Conventional Panretinal Photocoagulation

    Directory of Open Access Journals (Sweden)

    Young Gun Park

    2015-01-01

    Full Text Available Purpose. This study evaluates functional changes in electroretinographic findings after selective retina therapy (SRT compared to panretinal photocoagulation (PRP in rabbits. Methods. The right eyes of 12 Chinchilla rabbits received 200 laser treatment spots. The right eyes of six rabbits received SRT (SRT group, whereas the other six animals were treated using PRP on the right eye (PRP group. The eyes were investigated using full-field ERG 1 hour and 3 weeks after treatment. Histologic exam to assess the tissue response of lasers was performed on 3 weeks. Results. No significant changes in the mean ROD or CR b-wave amplitudes of the SRT lesions were evident, compared to baseline, 1 h after laser treatment (p=0.372 and 0.278, resp.. In addition, the OPs and 30 Hz flickers of the SRT lesions were not significantly altered (p=0.17 and 0.243, resp.. At 3 weeks, similar results were found. Comparing the two groups, the ROD b-wave amplitude was reduced in the PRP and SRT groups to 60.04±4.2% and 92.32±6.43% of baseline (p<0.001. Histologically, there was no visible photoreceptor alterations on week 3. Conclusions. SRT in rabbit eyes induced less functional loss than PRP in both rod-mediated retinal function and cone-mediated retinal function. In addition, SRT irradiated eyes had no functional loss compared to its control.

  16. Utilização do laser de argônio na remoção de sutura corneana Use of argon laser in corneal suture removal

    Directory of Open Access Journals (Sweden)

    Edélcio Vieira

    2004-12-01

    Full Text Available OBJETIVO: Descrever a técnica da retirada de sutura em córnea clara, evitando-se o contato da parte externa do fio com o meio intra-ocular e avaliar se esse procedimento evitaria infecções. MÉTODOS: Foi realizado estudo retrospectivo de 1.233 casos de retirada de sutura de mononylon 10.0 em córnea clara, utilizando-se laser de argônio para cortar o fio, no qual se avaliou a incidência de infecções. RESULTADOS: Em 1.071 olhos, um tiro foi suficiente para cortar o ponto. Em 162 olhos, o tiro do laser atingiu a parte epitelial da sutura, sendo necessários disparos extras para cortar a parte intra-estromal e, assim, retirá-la sem que a parte externa do fio passasse pelo interior da córnea. Não ocorreram complicações após a retirada da sutura. CONCLUSÕES: A técnica utilizada mostrou-se eficaz na remoção das suturas e possivelmente apresenta risco menor de infecção, uma vez que a parte do fio sobrejacente ao epitélio não entra em contato com as camadas mais internas da córnea, nem com a câmara anterior, não tendo sido observado nenhum caso de infecção nesta pesquisa.PURPOSE: To describe the technique of clear-cornea suture removal, that avoids the contact of the external part of the thread with the intraocular medium, and to evaluate whether this procedure would prevent infections. METHODS: A retrospective study of 1.233 cases of clear-cornea mononylon 10.0 suture removal, by the use of an argon laser to cut the thread, was performed. Incidence of infection was then assessed. RESULTS: In 1.071 eyes, one shot was enough to cut the stitch. In 162 eyes, the laser shot hit the epithelial part of the suture, making new shots necessary to cut the intrastromal part, and thus to remove it assuring that the outer part of the stitch would not come in to contact with the interior of the cornea. There were no complications after suture removal. CONCLUSIONS: The technique has shown to be effective in suture removal. And, possibly

  17. Depleted Argon from Underground Sources

    International Nuclear Information System (INIS)

    Argon is a strong scintillator and an ideal target for Dark Matter detection; however 39Ar contamination in atmospheric argon from cosmic ray interactions limits the size of liquid argon dark matter detectors due to pile-up. Argon from deep underground is depleted in 39Ar due to the cosmic ray shielding of the earth. In Cortez, Colorado, a CO2 well has been discovered to contain approximately 600 ppm of argon as a contamination in the CO2. We first concentrate the argon locally to 3% in an Ar, N2, and He mixture, from the CO2 through chromatographic gas separation, and then the N2 and He will be removed by continuous distillation to purify the argon. We have collected 26 kg of argon from the CO2 facility and a cryogenic distillation column is under construction at Fermilab to further purify the argon.

  18. Guiding of positive streamers in nitrogen, argon and N$_{2}$-O$_{2}$ mixtures by very low $n_{e}$ laser-induced pre-ionization trails

    OpenAIRE

    Nijdam, S.; Takahashi, E.

    2016-01-01

    In previous work we have shown that positive streamers in pure nitrogen can be guided by a laser-induced trail of low electron density. Here we show more detailed results from such measurements. We show the sensitivity of this laser-guiding on pressure p and found that the maximum delay between the laser pulse and voltage pulse for guiding scales with something between $1/p$ and $1/p^{2}$. We also show that when we use a narrower laser beam the laser guiding occurs less frequent and that when...

  19. Recent Developments in Laser Treatment of Diabetic Retinopathy

    OpenAIRE

    Yun, Samuel H.; Ron A. Adelman

    2015-01-01

    Laser photocoagulation has been the mainstay of diabetic retinopathy treatment since its development in mid-20 th century. With the advent of antivascular endothelial growth factor therapy, the role of laser therapy appeared to be diminished, however many advances in laser technology have been developed since. This review will describe recent advances in laser treatment of diabetic retinopathy including pattern scan laser, short-pulse duration and a reduced fluence laser, and navigated laser ...

  20. Argon in action

    CERN Multimedia

    Corinne Pralavorio

    2015-01-01

    Over the past few days, the SPS has been accelerating argon ions, which have started to be sent to the NA61/SHINE experiment. This operating mode, using a new type of ion, required a number of modifications to the accelerator.   Picture 1: a “super-cycle” of the SPS, featuring a proton cycle for the LHC, followed by an argon ion cycle for the North Area. Today, the accelerators are once again juggling particles and even performing completely new tricks. The SPS is supplying beams of argon ions for the first time, at energies never before achieved for this type of beam. They are destined for the NA61/SHINE experiment (see box) located in the North Area, which began receiving the beams on 11 February. Argon ions have a relatively large mass, as they consist of 40 nucleons, so they can be used in a similar way to lead ions. The main difficulty in accelerating them lies in the SPS, where the variation in acceleration frequency is limited. “The SPS was designed for a...

  1. Thermophysical properties of argon

    Energy Technology Data Exchange (ETDEWEB)

    Jaques, A.

    1988-02-01

    The entire report consists of tables of thermodynamic properties (including sound velocity, thermal conductivity and diffusivity, Prandtl number, density) of argon at 86 to 400/degree/K, in the form of isobars over 0.9 to 100 bars. (DLC)

  2. Análise química e morfológica do esmalte dentário humano tratado com laser argônio durante a colagem ortodôntica Chemical and morphological analysis of the human dental enamel treated with argon laser during orthodontic bonding

    Directory of Open Access Journals (Sweden)

    Glaucio Serra Guimarães

    2011-04-01

    Full Text Available INTRODUÇÃO: as principais utilizações do laser argônio na Ortodontia são a redução do tempo de polimerização durante a colagem ortodôntica e o aumento da resistência à cárie do esmalte dentário. OBJETIVO: o objetivo deste trabalho foi avaliar as alterações químicas e morfológicas do esmalte dentário humano tratado com laser argônio nos parâmetros da colagem ortodôntica. MÉTODOS: quinze primeiros pré-molares hígidos, extraídos por indicação ortodôntica, foram selecionados e seccionados no sentido do longo eixo em dois segmentos iguais. Uma metade de cada elemento dentário foi tratada e a outra permaneceu sem tratamento. Um total de 30 amostras foi analisado, criando o grupo laser (n = 15 e o grupo controle (n = 15. O tratamento foi feito com laser argônio com 250mW de potência por 5 segundos, com densidade de energia de 8J/cm². RESULTADOS: a análise de difração de raios X demonstrou duas fases em ambos os grupos, as fases apatita e monetita. A redução da fase monetita foi significativa após o tratamento com laser, sugerindo maior cristalinidade. A análise de Espectroscopia de Energia Dispersiva (EDS indicou aumento na razão cálcio-fósforo no grupo laser, compatível com a diminuição da fase monetita. A morfologia superficial do esmalte dentário apresentou-se mais lisa após o tratamento com laser argônio. CONCLUSÕES: o aumento de cristalinidade e a lisura superficial do esmalte no grupo laser são fatores sugestivos de aumento de resistência à cárie no esmalte dentário.INTRODUCTION: The main utilities of the argon laser in orthodontics are the high speed curing process in orthodontic bonding and the caries resistance promotion of the tooth enamel. OBJECTIVE: The objective of this study was to evaluate the chemical and morphological changes in the tooth enamel treated with the argon laser in the orthodontic bonding parameters. METHODS: Fifteen sound human first premolars, removed for orthodontic

  3. Regression Rates Following the Treatment of Aggressive Posterior Retinopathy of Prematurity with Bevacizumab Versus Laser: 8-Year Retrospective Analysis.

    Science.gov (United States)

    Nicoară, Simona D; Ștefănuţ, Anne C; Nascutzy, Constanta; Zaharie, Gabriela C; Toader, Laura E; Drugan, Tudor C

    2016-01-01

    BACKGROUND Retinopathy is a serious complication related to prematurity and a leading cause of childhood blindness. The aggressive posterior form of retinopathy of prematurity (APROP) has a worse anatomical and functional outcome following laser therapy, as compared with the classic form of the disease. The main outcome measures are the APROP regression rate, structural outcomes, and complications associated with intravitreal bevacizumab (IVB) versus laser photocoagulation in APROP. MATERIAL AND METHODS This is a retrospective case series that includes infants with APROP who received either IVB or laser photocoagulation and had a follow-up of at least 60 weeks (for the laser photocoagulation group) and 80 weeks (for the IVB group). In the first group, laser photocoagulation of the retina was carried out and in the second group, 1 bevacizumab injection was administered intravitreally. The following parameters were analyzed in each group: sex, gestational age, birth weight, postnatal age and postmenstrual age at treatment, APROP regression, sequelae, and complications. Statistical analysis was performed using Microsoft Excel and IBM SPSS (version 23.0). RESULTS The laser photocoagulation group consisted of 6 premature infants (12 eyes) and the IVB group consisted of 17 premature infants (34 eyes). Within the laser photocoagulation group, the evolution was favorable in 9 eyes (75%) and unfavorable in 3 eyes (25%). Within the IVB group, APROP regressed in 29 eyes (85.29%) and failed to regress in 5 eyes (14.71%). These differences are statistically significant, as proved by the McNemar test (P<0.001). CONCLUSIONS The IVB group had a statistically significant better outcome compared with the laser photocoagulation group, in APROP in our series. PMID:27062023

  4. Liquid argon neutrino detectors

    CERN Document Server

    Battistoni, G

    2001-01-01

    The liquid argon imaging technique, as proposed for the ICARUS detector, offers the possibility to perform complementary and simultaneous measurements of neutrinos, as those of CERN to Gran Sasso beam (CNGS) and those from cosmic ray events. For the currently allowed values of the Super-Kamiokande results, the combination of both CNGS and atmospheric data will provide a precise determination of the oscillation parameters. Since one can observe and unambiguously identify nu /sub e/, nu /sub mu / and nu /sub tau / components, this technology allows to explore the full (3*3) mixing matrix. The same class of detector can be proposed for high precision measurements at a neutrino factory. (3 refs).

  5. Intravitreal Bevacizumab Alone versus Combined with Macular Photocoagulation in Diabetic Macular Edema

    OpenAIRE

    Lee, Soo Jeong; Kim, Ei Tae; Moon, Yeon Sung

    2011-01-01

    Purpose To compare the efficacy between intravitreal bevacizumab and combination treatment (bevacizumab and macular photocoagulation) for the treatment of diabetic macular edema (DME). In addtion, changes of DME type were researched using optical coherence tomography. Methods The present study included 90 eyes with bevacizumab injection and 38 eyes with combination treatment. Using chart records, patients were reviewed until 6 months after treatment. The present study compared changes of visu...

  6. Grid photocoagulation combined with intravitreal bevacizumab for recurrent macular edema associated with retinal vein occlusion

    OpenAIRE

    Tsujikawa, Akitaka

    2011-01-01

    Ken Ogino, Akitaka Tsujikawa, Tomoaki Murakami, Yuki Muraoka, Yumiko Kurashige, Nagahisa YoshimuraDepartment of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, JapanPurpose: To report the efficacy of grid photocoagulation combined with intravitreal bevacizumab (IVB) for macular edema recurring after previous IVBs associated with retinal vein occlusion (RVO).Methods: This retrospective study consisted of 19 eyes with branch retinal vein occlusion (BRVO) ...

  7. Combined Phacoemulsification, Vitrectomy and Endolaser Photocoagulation in Patients with Diabetic Retinopathy and Cataract

    International Nuclear Information System (INIS)

    Objective: To determine the outcomes of early vitrectomy and endolaser photocoagulation effects during phacoemulsification in cataractous eyes with diabetic retinopathy. Study Design: Descriptive study. Place and Duration of Study: Ophthalmology Department Unit-II, DUHS, Civil Hospital, Karachi, and Al-Noor Eye Clinic, Karachi, from February 2009 to December 2010. Methodology: Consecutive 54 patients with 7 - 15 years duration of type II diabetes with severe non-proliferative diabetic retinopathy (NPDR) and early proliferative diabetic retinopathy (PDR) who had cataract grade I and II underwent vitrectomy, endolaser photocoagulation and phacoemulsification with IOL implantation. Best corrected visual acuity was main outcomes measure assessed till 6 months follow-up. Results: Out of 54 eyes, 32 patients were females and 22 were males. Majority 47 (87%) eyes gained significant (p < 0.001) improvement of best corrected visual acuity of four lines or better while 5 (9.3%) eyes retained stable visual acuity. In only 2 eyes, vision declined to 3/60 or less. Conclusion: Early vitrectomy with phacoemulsification in severe NPDR and early PDR patients, if assisted or augmented with endolaser photocoagulation, maximizes, early visual rehabilitation with less morbidity and may retard progression of retinopathy. (author)

  8. Intravitreal bevacizumab injection alone or combined with macular photocoagulation compared to macular photocoagulation as primary treatment of diabetic macular edema

    Directory of Open Access Journals (Sweden)

    Jovanović Sandra

    2015-01-01

    Full Text Available Background/Aim. Within diabetic retinopathy (DR, diabetic macular edema (DME is one of the leading causes of the loss of visual acuity. The aim of this study was to determine the efficacy of the intravitreal vascular endothelial growth factor (VEGF inhibitor application alone or combined with macular focal/grid lasephotocoagulation compared with laser treatment alone. Methods. This prospective randomized clinical trial included 72 patients (120 treated eyes with varying degrees of DR and DME. The DME treatment included intravitreal VEGF inhibitor bevacizumab (Avastin® application, with and without laser treatment. Bevacizumab (1.25 mg/0.05 mL was administered intravitreally in 4-6-week intervals. Laser is applied 4-6 weeks after last dose of the drug as a part of combined treatment, or as the primary treatment. Results. The mean reduction in central macular thickness (CMT for the eyes (n = 31 treated with bevacizumab alone was 162.23 μm, for the eyes (n = 53 treated with combined treatment the mean reduction in CMT was 124.24 μm, both statistically significant at p < 0.001. Laser macular photocolagulation as a part of combined treatment (in 53 eyes significantly contributed to the CMT reduction, based on the paired t-test results (366.28 vs 323.0 μm at p < 0.05. In our study, the mean visual acuity improvement of 0.161 logMAR was achieved in the group of eyes treated with bevacizumab alone, and 0.093 logMAR in the group with combined treatment, both statistically significant at p < 0.05. The effect of laser photocolagulation alone on visual acuity and CMT was not statistically significant. Conclusion. Treatment with bevacizumab alone or within combined treatment is more effective in treating DME than conventional macular laser treatment alone, both anatomically and functionally.

  9. Argon Welding Inside A Workpiece

    Science.gov (United States)

    Morgan, Gene E.

    1988-01-01

    Canopies convert large hollow workpiece into inert-gas welding chamber. Large manifold serves welding chamber for attachment of liner parts in argon atmosphere. Every crevice, opening and passageway provided with argon-rich environment. Weld defects and oxidation dramatically reduced; also welding time reduced.

  10. Multidimensional intermolecular dynamics from tunable far-infrared laser spectroscopy: Angular-radial coupling in the intermolecular potential of argon--H2O

    International Nuclear Information System (INIS)

    Five new vibration--rotation tunneling states of Ar--H2O [the Σ and Π(111) and the Σ and Π(212) internal rotor states and the n=1, Π(101) stretching-internal rotor combination level] have been accessed by tunable far-infrared laser spectroscopy. The measured vibrational band origins of transitions to these states are within 2% of predictions made from an anisotropic three-dimensional intermolecular potential surface (denoted AW1) derived from a nonlinear least-squares fit to previous far-infrared spectral data [J. Phys. Chem. 94, 7991(1990)]. This provides strong evidence that the AW1 intermolecular potential surface incorporates much of the essential physics of the intermolecular forces which bind the cluster. However, larger deviations from the predictions are found in the observed rotational term values. A detailed analysis of these deviations clearly demonstrates the need for even stronger angular-radial coupling in the Ar--H2O intermolecular potential than the already substantial coupling present in the AW1 surface. Specifically, the presently observed Σ(111) state and the n=1, Σ(000) state are found to be approximately 65:35 mixtures of the basis states which represent pure stretching and internal rotation. The Σ(212) level is found to be mixed just as strongly with n=2, Σ(101). The formalism for accurately deperturbing vibration--rotation--tunneling states coupled by Coriolis interactions used in the above analysis is presented

  11. Intravitreal bevacizumab injection alone or combined with macular photocoagulation compared to macular photocoagulation as primary treatment of diabetic macular edema

    OpenAIRE

    Jovanović Sandra; Čanadanović Vladimir; Sabo Ana; Grgić Zorka; Mitrović Milena; Rakić Dušan

    2015-01-01

    Background/Aim. Within diabetic retinopathy (DR), diabetic macular edema (DME) is one of the leading causes of the loss of visual acuity. The aim of this study was to determine the efficacy of the intravitreal vascular endothelial growth factor (VEGF) inhibitor application alone or combined with macular focal/grid lasephotocoagulation compared with laser treatment alone. Methods. This prospective randomized clinical trial included 72 patients (120 treated e...

  12. Pain and accuracy of focal laser treatment for diabetic macular edema using a retinal navigated laser (Navilas®

    Directory of Open Access Journals (Sweden)

    Kampik A

    2012-02-01

    Full Text Available Marcus Kernt*, Raoul E Cheuteu*, Sarah Cserhati, Florian Seidensticker, Raffael G Liegl, Julian Lang, Christos Haritoglou, Anselm Kampik, Michael W Ulbig, Aljoscha S Neubauer Department of Ophthalmology, Ludwig Maximilian University of Munich, Germany*These authors contributed equally to this studyAim: To investigate treatment-related pain and the accuracy of navigated laser photocoagulation in the treatment of clinically significant macular edema.Methods: Focal laser treatment of diabetic macular edema in 54 consecutive patients was digitally planned on fundus images and performed using the navigated laser photocoagulation system Navilas® (OD-OS GmbH, Teltow, Germany. Treatment-related pain was quantified on a visual analog scale directly after treatment and compared with a matched control group who received conventional laser treatment (n = 46. In addition, for Navilas-treated patients, the accuracy of spot placement on color images was analyzed 1 month after treatment.Results: In total, 5423 laser spots (mean 100 per eye were analyzed. With navigated treatment, 90% of laser spots were visible on color images, of which 96% were within 100 µm from the target. Eighty percent of the laser spots were placed and visible within the 100 µm target on an intention-to-treat basis for color imaging. Optical coherence topography confirmed that laser effects were limited to the outer retina. Treatment-related pain following navigated laser photocoagulation was significantly lower than that of conventional laser treatment (1.6 vs 4.4 on a visual analog scale, P < 0.001.Conclusion: Navigated laser effects could be visualized to a high percentage on post-treatment color images, and their location showed a high concordance to targeted areas. Patients reported that treatment-related pain following Navilas laser photocoagulation was significantly lower than pain following conventional laser treatment.Keywords: diabetic retinopathy, navigated laser therapy

  13. Low vision aid in exudative macular degeneration treated by photodynamic therapy and thermal laser photocoagulation%光动力治疗和热激光光凝治疗渗出性黄斑变性所致低视力

    Institute of Scientific and Technical Information of China (English)

    Montero JA; Ruiz-Moreno JM; Sanchez-de Castro MJ; Fabiani C

    2006-01-01

    · AIM: To determine the efficacy of low vision rehabilitation (LVR) in patients with age related macular degeneration (AMD) treated by photodynamic therapy (PDT) compared to those treated by thermal laser (TLP).examining the files of 42 patients (42 eyes) with AMD who had been treated either by TLP (Group 1) and PDT (Group 2). Once AMD was considered to be inactive they underwent visual rehabilitation in the LVR Unit in order to increase their ability for distant and near vision.received TLP. Average corrected visual acuity after laser therapy was 0.14 in Group 1, and 0.16 in Group 2. No statistically significant differences were found between both groups before and after laser therapy. Both groups showed improvement after LVR; however, statistically significant differences between both groups were found only for near vision.both PDT and TLP are associated to a decreased visual acuity after treatment, LVR may be more successful for near vision among patients treated by PDT%目的:比较观察光动力治疗(PDT)和热激光光凝(TLP)治疗对年龄相关性黄斑变性(AmD)患者低视力(LVR)的临床疗效.方法:对42例(42眼)AMD患者资料进行回顾性研究,其分别行TLP治疗(组1)或PDT治疗(组2).一旦确定AMD处于非活动期,患者在LVR部进行视力康复,以提高其远、近视功能.结果:18眼接受了PDT治疗,24眼进行TLP治疗.激光治疗后,组1患者的平均最佳矫正视力为0.14,组2平均为0.16.两组比较,视力于激光治疗前后都没有统计学差异;两组的LVR都有提高,但两组中只有近视力比较有统计学差异.结论:本研究结果表明,PDT和TLP治疗后患者的视力均有所下降,PDT治疗时,LVR患者近视力改善更为有效.

  14. Microwave Argon Plasma Torch

    Science.gov (United States)

    Felizardo, Edgar; Pencheva, Mariana; Benova, Evgenia; Dias, Fransisco; Tatarova, Elena

    2009-10-01

    A theoretical and experimental investigation of a microwave (2.45 GHz) Argon plasma torch driven by a surface wave is presented. The theoretical model couples in a self-consistent way the wave electrodynamics and the electron and heavy particle kinetics. The set of coupled equations includes: Maxwell's equations, the electron Boltzmann equation, including electron-electron collisions, and the particle balance equations for electrons, excited atoms (4s, 4p, 3d, 5s, 5p, 4d, 6s), and atomic (Ar^+) and molecular ions (Ar2^+). The input parameters of the model are: gas pressure (760 Torr), plasma radius (R = 0.75 cm), dielectric permittivity (ɛd = 4.0) and tube thickness (d = 0.15 cm) as well as the measured axial profile of the gas temperature (3500 K - 1500 K). The latter was determined from measurements of the rotational temperature of the OH molecular band in the range 306 - 315 nm. Phase and amplitude sensitive recording provides the data for the axial wavenumber and wave attenuation coefficient. The wavenumber decreases along the generated plasma torch. The electron density (Ne) axial profile as determined from measurements of Hβ Stark broadening is in agreement with the theoretical one.

  15. The Liquid Argon Purity Demonstrator

    Energy Technology Data Exchange (ETDEWEB)

    Adamowski, M.; Carls, B.; Dvorak, E.; Hahn, A.; Jaskierny, W.; Johnson, C.; Jostlein, H.; Kendziora, C.; Lockwitz, S.; Pahlka, B.; Plunkett, R.; Pordes, S.; Rebel, B.; Schmitt, R.; Stancari, M.; Tope, T.; Voirin, E.; Yang, T.

    2014-07-01

    The Liquid Argon Purity Demonstrator was an R&D test stand designed to determine if electron drift lifetimes adequate for large neutrino detectors could be achieved without first evacuating the cryostat. We describe here the cryogenic system, its operations, and the apparatus used to determine the contaminant levels in the argon and to measure the electron drift lifetime. The liquid purity obtained by this system was facilitated by a gaseous argon purge. Additionally, gaseous impurities from the ullage were prevented from entering the liquid at the gas-liquid interface by condensing the gas and filtering the resulting liquid before returning to the cryostat. The measured electron drift lifetime in this test was greater than 6 ms, sustained over several periods of many weeks. Measurements of the temperature profile in the argon, to assess convective flow and boiling, were also made and are compared to simulation.

  16. Electrical conductivity of compressed argon

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, R. [Univ. Regensburg (Germany); Windl, W.; Collins, L.; Kress, J.; Kwon, I. [Los Alamos National Lab., NM (United States)

    1997-10-01

    The authors report calculations of the electrical conductivity of solid argon as a function of compression within the density functional local density approximation formulation for a norm-conserving pseudopotential using both electron-phonon coupling and molecular dynamics techniques.

  17. Testing a liquid Argon calorimeter

    CERN Multimedia

    1976-01-01

    Physicists from Karlsruhe test a liquid argon calorimeter in the neutral beam b16 at the PS. The calorimeter was meant to supply some neutral particles identification at the Split-Field Magnet Facility for R416.

  18. The Liquid Argon Purity Demonstrator

    CERN Document Server

    Adamowski, M; Dvorak, E; Hahn, A; Jaskierny, W; Johnson, C; Jostlein, H; Kendziora, C; Lockwitz, S; Pahlka, B; Plunkett, R; Pordes, S; Rebel, B; Schmitt, R; Stancari, M; Tope, T; Voirin, E; Yang, T

    2014-01-01

    The Liquid Argon Purity Demonstrator was an R&D test stand designed to determine if electron drift lifetimes adequate for large neutrino detectors could be achieved without first evacuating the cryostat. We describe here the cryogenic system, its operations, and the apparatus used to determine the contaminant levels in the argon and to measure the electron drift lifetime. The liquid purity obtained by this system was facilitated by a gaseous argon purge. Additionally, gaseous impurities from the ullage were prevented from entering the liquid at the gas-liquid interface by condensing the gas and filtering the resulting liquid before returning to the cryostat. The measured electron drift lifetime in this test was greater than 6 ms, sustained over several periods of many weeks. Measurements of the temperature profile in the argon, to assess convective flow and boiling, were also made and are compared to simulation.

  19. Efficacy of patterned scan laser in treatment of macular edema and retinal neovascularization

    Directory of Open Access Journals (Sweden)

    Dimple Modi

    2009-08-01

    Full Text Available Dimple Modi, Paulpoj Chiranand, Levent AkdumanSaint Louis University School of Medicine, Department of Ophthalmology, Saint Louis University Eye Institute, St. Louis, Missouri, USAPurpose: To analyze the benefits, efficacy, and complications of the PASCAL® photocoagulation laser system (OptiMedica, Santa Clara, CA, USA in patients treated at our institution.Methods: We conducted a retrospective chart review of 19 patients (28 eyes who underwent laser treatment using the PASCAL® photocoagulation system from November 2006 to November 2007. These 28 eyes were divided into two groups; group 1 eyes underwent macular grid laser and group 2 eyes underwent panretinal photocoagulation. Treatment was performed for macular edema or for iris or retinal neovascularization. Outcomes measured included best-corrected visual acuity (BCVA, efficacy of laser treatment, complications, duration of the procedure, and pain perception, which were noted in the charts for panretinal treatments.Results: Follow-up was 5.9 ± 2.6 months for group 1 and 5.9 ± 4.0 months for group 2. In group 1, 9/28 eyes required a second treatment for remaining edema. BCVA was stable or better in 66% (14/21 and average central foveal thickness on ocular coherence tomography improved in 71% (15/21. Time to completion for a number of laser patterns for grid photocoagulation was felt to be too long for completing the total pattern safely, although we have not noted any related complications. In group 2, the neovascularization regressed at least partially in 3/7 patients. Patient-reported pain perception was 3.6 on a scale of 1 to 10 for group 2. Occasional hemorrhages occurred secondary to irregular laser uptake at different spots in the patterns. We observed no visual outcome consequences because of these hemorrhages during follow-up.Conclusions: Retinal photocoagulation by the PASCAL® laser has comparable efficacy to historical results with conventional retinal photocoagulation in short

  20. Electron densities and energies of a guided argon streamer in argon and air environments

    International Nuclear Information System (INIS)

    In this study we report the temporally and spatially resolved electron densities and mean energies of a guided argon streamer in ambient argon and air obtained by Thomson laser scattering. The plasma is driven by a positive monopolar 3.5 kV pulse, with a pulse width of 500 ns and a frequency of 5 kHz which is synchronized with the high repetition rate laser system. This configuration enables us to use the spatial and temporal stability of the guided streamer to accumulate a multitude of laser/plasma shots by a triple grating spectrometer equipped with an ICCD camera and to determine the electron parameters. We found a strong initial ne-overshoot with a maximum of 7 × 1019 m−3 and a mean electron energy of 4.5 eV. This maximum is followed by a fast decay toward the streamer channel. Moreover, a 2D distribution of the electron density is obtained which exhibits a peculiar mushroom-like shape of the streamer head with a diameter significantly larger than that of the emission profile. A correlation of the width of the streamer head with the expected pre-ionization channel is found. (paper)

  1. Laser treatment in diabetic retinopathy

    OpenAIRE

    Neubauer, Aljoscha Steffen; Ulbig, Michael W

    2007-01-01

    Diabetic retinopathy is a leading cause of visual impairment and blindness in developed countries due to macular edema and proliferative diabetic retinopathy (PDR). For both complications laser treatment may offer proven therapy: the Diabetic Retinopathy Study demonstrated that panretinal scatter photocoagulation reduces the risk of severe visual loss by >= 50% in eyes with high-risk characteristics. Pan-retinal scatter coagulation may also be beneficial in other PDR and severe nonproliferati...

  2. Healing process study in murine skin superficial wounds treated with the blue LED photocoagulator EMOLED

    Science.gov (United States)

    Rossi, Francesca; Cicchi, Riccardo; Tatini, Francesca; Bacci, Stefano; Alfieri, Domenico; De Siena, Gaetano; Pavone, Francesco S.; Pini, Roberto

    2015-07-01

    A faster healing process was observed in superficial skin wounds after irradiation with the EMOLED photocoagulator. The instrument consists of a compact handheld photocoagulation device, useful for inducing coagulation in superficial abrasions. In this work we present the results of an in vivo study, in a murine model. Two superficial wounds were produced on the back of 12 mice: one area was left untreated, the other one was treated with EMOLED. Healthy skin was used as a control. The animals were sacrificed 3 hours, 12 hours, 1 day, 6 day after treatment. The treatment effects on back skin was monitored by visual observations, histopathological analysis, immuno-histochemical analysis, and nonlinear microscopic imaging performed at each follow up time, finding no adverse reactions and no thermal damage in both treated areas and surrounding tissues. In addition, a faster healing process, a reduced inflammatory response, a higher collagen content, and a better-recovered skin morphology was evidenced in the treated tissue with respect to the untreated tissue. These morphological features were characterized by means of immuno-histochemical analysis, aimed at imaging fibroblasts and myofibroblasts, and by SHG microscopy, aimed at characterizing collagen organization, demonstrating a fully recovered aspect of dermis as well as a faster neocollagenesis in the treated regions. This study demonstrates that the selective photothermal effect we used for inducing immediate coagulation in superficial wounds is associated to a minimal inflammatory response, which provides reduced recovery times and improved healing process.

  3. Cicatrização da membrana timpânica na timpanocentese com laser de argônio comparado à técnica com microlanceta: estudo experimental em ratos Tympanic membrane healing in myringotomies performed with argon laser or microknife: an experimental study in rats

    Directory of Open Access Journals (Sweden)

    Lucio Almeida Castagno

    2006-12-01

    times were equivalent. All myringotomies healed within 10 days. CONCLUSION: Argon laser assisted myringotomy healed just as early on as incisional myringotomy on Wistar rats without middle ear diseases.

  4. Molecular formation dynamics of 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one, 1,3,5-trinitroperhydro-1,3,5-triazine, and 2,4,6-trinitrotoluene in air, nitrogen, and argon atmospheres studied using femtosecond laser induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    Femtosecond laser induced breakdown spectroscopic (LIBS) studies were performed on three high energy materials namely 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), and 2,4,6-trinitrotoluene (TNT). LIBS spectral features were obtained for these samples in three different atmospheres i.e. air, nitrogen, and argon. Different molecular to elemental ratios in these three atmospheres were investigated in detail. CN/C and CN/N ratios were observed to be prominent in nitrogen and air atmospheres. We attempt to elucidate the role of several reactions involving CN molecular formation in connection with discrepancies obtained in the measured ratios. The complete temporal dynamics of atomic C (247.82 nm) and CN (388.20 nm) molecular species in three different atmospheres are elaborated. The decay rates of C peak were found to be longest (96 ns–121 ns) in argon atmosphere for all the samples. The decay rates of CN peak (388.2 nm) were longer (161 ns–364 ns) in nitrogen compared to air and argon atmospheres. We also attempt to explicate the decay mechanisms with respect to the molecular species formation dynamics in different atmospheres. - Highlights: • LIBS studies of NTO, RDX, and TNT in nitrogen, air, and argon were performed using fs pulses. • Decay constants of C, CN in three atmospheres were recorded systematically. • Different molecular to elemental ratios were investigated in detail. • CN/C and CN/N ratios were observed to be prominent in nitrogen and air atmospheres

  5. Laser application in tracheobronchial tumors

    Science.gov (United States)

    Rau, B. Krishna; Krishna, Sharon

    2004-09-01

    Ninety three patients with obstructing tracheobronchial tumors were treated with Neodymium: Yttrium - Aluminum - Garnet (Nd:YAG) laser photocoagulation over a period of six years. There were sixty seven Males and 26 Females with a mean age of 44.3 years (range 6- 79 years). 21 benign and 72 malignant lesions were treated with a total 212 sessions of laser photocoagulation (mean 2.4 sessions). The anatomical distribution of lesions were as follows; larynx 9 (three benign and 6 malignant) trachea 39 (27 benign and 12 malignant) left main bronchus 27 (14 malignant) right main bronchus 24 (14 malignant) and vocal cords - 9 (three malignant). There were 21 patients with squamous cell carcinoma, two adenocarcinomas, one adenoid cystic carcinoma, 7 cases of locally infiltrating tumors from thyroid and esophagus, 6 cases of carcinoid tumor and 16 benign lesions. Twenty one patients had a tracheostomy tube in place when treatment was started. Eighteen of the 21 patients with tracheostomy were weaned off the tube in a mean of 5.5 days from the start of treatment. Lumen was restored in 31 (79.4%) patients. In the other eight (20.6%), lumen was achieved, but not sustained. Complications included bleeding in three cases which were managed conservatively, two cases of pneumothorax, and four cases of bronchospasm. There were six deaths during the follow up but none attributable to the procedure. Laser photocoagulation offered effective treatment in the majority of patients with obstructing tracheobronchial tumors, with acceptable morbidity.

  6. First measurements with ARGONTUBE, a 5 m long drift Liquid Argon TPC

    International Nuclear Information System (INIS)

    The Liquid Argon Time Projection Chamber (LAr TPC) technique is a promising technology for future neutrino detectors. At LHEP of the University of Bern (Switzerland), an R and D program towards large detectors are on-going. The main goal is to show the feasibility of long drift paths over many meters. Therefore, a liquid Argon TPC with 5 m of drift distance was constructed. Many other aspects of the liquid Argon TPC technology are also investigated, such as a new device to generate high voltage in liquid Argon (Greinacher circuit), a recirculation filtering system and the multi-photon ionization of liquid Argon with a UV laser. Two detectors are built: a medium size prototype for specific detector technology studies, and ARGONTUBE, a 5 m long device

  7. Dentine bond strength of a composite resin polymerized with conventional light and argon laser Resistência de união à dentina de resina composta polimerizada com luz halógena e laser de argônio

    Directory of Open Access Journals (Sweden)

    Patricia Ramos Lloret

    2004-09-01

    Full Text Available The use of argon laser (488 nm has been suggested as a new alternative for polymerizing adhesive materials. This study aimed to evaluate the tensile bond strength of a microfilled composite (A110, 3M inserted by incremental technique (3 increments of 1 mm and by single increment (3 mm polymerized by argon laser for 10, 20 and 30 seconds and halogen light for 40 seconds. Eighty (8 groups of 10 teeth freshly extracted bovine teeth were stored in a freezer in distilled water for one week. The crowns were cross-sectioned from the roots. Pulpectomy was performed and the pulp chambers were sealed with wax. The buccal surfaces of the teeth were ground with wet sandpaper (grains: 120, 400, and 600 to expose the surface dentin, and the teeth were then included in acrylic resin. A metal device was used to fix each sample and a black propylene matrix25 (3 mm high with an internal millimetric delimitation was used to insert the material according to the groups studied. The polymerization intervals were of 10, 20 and 30 seconds for the laser polymerization and 40 seconds for the conventional polymerization. Tensile tests were performed by a Universal Testing Machine 4442 (Instron at a speed of 0.5 mm/min and 500 N load. According to the methodology used, the incremental technique increased bond strength values. There was no difference between the studied polymerization techniques when resin was filled in 3 increments.O uso do laser de argônio (488 nm tem sido sugerido como uma nova alternativa para polimerização de materiais adesivos. Este estudo tem o objetivo de avaliar a resistência adesiva de uma resina composta microparticulada (A110, 3M inserida pela técnica incremental (3 incrementos de 1 mm e de incremento único (3 mm polimerizada com laser de argônio por 10, 20 e 30 segundos e com luz halógena por 40 segundos. Oitenta (8 grupos com 10 dentes dentes bovinos recém-extraídos foram armazenados em geladeira, em água destilada, por uma semana

  8. Fano factor in pure argon

    International Nuclear Information System (INIS)

    The Fano factor for 5.3 MeV alpha particles in pure argon has been measured with a gridded ionization chamber and estimated to be 0.20 (+0.01-0.02). The obtained value is consistent with the theoretical value if the contribution of elastic nuclear collisions to the Fano factor is taken into the consideration. There is no appreciable difference between the values for pure argon and for a gas mixture of Ar (10%)CH4 obtained in the previous measurement. (orig.)

  9. Miniaturized high-resolution wide-field contact lens for panretinal photocoagulation

    Directory of Open Access Journals (Sweden)

    Koushan K

    2014-04-01

    Full Text Available Keyvan Koushan, KV Chalam Department of Ophthalmology, University of Florida College of Medicine, Jacksonville, FL, USA Background and objective: We describe a miniaturized lightweight high-refractive-index panretinal contact lens for diagnostic and therapeutic visualization of the peripheral retina. Instrument design: The miniaturized high-resolution wide-field contact lens includes three optical elements in a light (15 g and miniaturized (16 mm footplate, 24 mm external aperture, and 21 mm vertical height casing contributing to a total dioptric power of +171 diopters. This lens provides up to 165° visualization of the retina for diagnostic and therapeutic applications while allowing easier placement due to its miniaturization. Conclusion: This new lens (50% lighter and 89% smaller improves upon earlier contact lenses for visualization of the peripheral retina. Keywords: contact lens, panretinal photocoagulation, retinal examination, peripheral retina, high resolution view, wide-angle lens, lens

  10. Successful treatment of radiation retinopathy with panretinal photocoagulation (PRP) in a patient of orbital MALT lymphoma

    International Nuclear Information System (INIS)

    Report a case of satisfactory progress radiation retinopathy after radiation for mucosa-associated lymphoid tissue (MALT) lymphoma. A 26-year-old male patient, referred to our department for lacrimal sac tumor. Biopsy was done by otolaryngology and radiation therapy was performed (total irradiation of 41.4 Gy) as pathological examination revealed MALT lymphoma. Soft exudates and macula edema appeared in posterior pole of the right fundus after radiotherapy. Right vision became 0.5 because of macula edema, and panretinal photocoagulation (PRP) was performed. After PRP, macula edema withdrew and right vision improved to 1.2. It is suggested that the fundus must be monitored after radiation therapy, and early treatment, such as PRP is effective in radiation retinopathy. (author)

  11. Effect of ultrasound-guided interstitial laser photocoagulation on benign solitary solid cold thyroid nodules

    DEFF Research Database (Denmark)

    Døssing, Helle; Bennedbaek, Finn Noe; Hegedüs, Laszlo

    2006-01-01

    ILP-3 group from 10.8 +/- 5.5 mL to 4.6 +/- 3.0 mL (p = 0.0005) during follow-up. The overall mean difference between the two groups was 13%, corresponding to an improved mean thyroid nodule volume reduction of 30% (p = 0.03). In both groups subjective symptoms were significantly reduced, and without...

  12. Treatment of twin-twin transfusion syndrome by fetoscopic laser photocoagulation

    Institute of Scientific and Technical Information of China (English)

    劉子建; 梁德楊; 馮德源; 梁子昂

    2004-01-01

    @@ Twin-twin transfusion syndrome (TTTS) is a serious obstetric complication, occurring in about 15% of monochorionic (MC) twin pregnancies. If untreated, the prognosis is poor, with an overall perinatal mortality of 80%.1 It is now clear that TTTS is the result of an unbalanced unidirectional blood flow through placental arteriovenous anastomoses (also termed deep anastomoses) between the two fetal circulations.2 The donor twin progressively becomes anemic, and develops growth restriction, oliguria, and oligohydramnios/anhydramnios; whereas the recipient becomes plethoric and polyuric, and develops congestive heart failure, cardiomegaly, polyhydramnios and fetal hydrops. Preterm labor is common because of gross polyhydramnios, and further deteriorations will lead to intrauterine death of both twins.

  13. Ultrasound-guided interstitial laser photocoagulation of an autonomous thyroid nodule

    DEFF Research Database (Denmark)

    Døssing, Helle; Bennedbaek, Finn Noe; Hegedüs, Laszlo

    2003-01-01

    Radioiodine ((131)I) and surgery are the standard therapeutic options for the solitary autonomous thyroid nodule (AFTN). Percutaneous ethanol injection (PEI) has proven to be an effective technique and possible alternative to the conventional treatment options. However, PEI is not devoid of side.......9 mL (40% reduction) without further alterations during an additional 9 months of follow-up. Side effects were transient thyrotoxicosis and local pain as seen with PEI. To our knowledge, this is the first reported case of ILP used in a patient with a pretoxic thyroid nodule. US-guided thermic tissue...

  14. Serial bevacizumab injections and laser photocoagulation for macular edema associated with a retinal artery macroaneurysm

    OpenAIRE

    Leung EH; Reddy AK; Vedula AS; Flynn Jr HW

    2015-01-01

    Ella H Leung,1 Ashvini K Reddy,2 Anil S Vedula,1 Harry W Flynn Jr1 1Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami, Miami, FL, 2Department of Ophthalmology, University of Virginia, Charlottesville, VA, USA Abstract: An 84-year-old female with a history of hypertension and dyslipidemia was referred for a retinal artery macroaneurysm with exudation that had extended into the macula. She underwent a total of six injections of bevacizumab, with some improvement in...

  15. Investigation of non-equilibrium argon and hydrogen plasmas

    International Nuclear Information System (INIS)

    Theoretical and experimental investigations are made into non-equilibrium argon and hydrogen partially-ionized plasmas characteristic of glow-discharge devices such as thyratrons and discharge tubes. For an argon plasma, the development and use of a collisional-radiative, steady-state, three-energy-level model is presented, and experimental measurements on pulsed argon plasmas are briefly mentioned. Two different theoretical argon plasma models are discussed; the first is numerically solved using a non-Maxwellian electron distribution function, while the second is solved analytically, including atom-atom inelastic collisions, assuming Maxwellian electron and atom distribution functions. For a hydrogen plasma, experimental measurements using fluorescence and laser-induced fluorescence have been made in a modified hydrogen thyratron over a wide current density range (from 100 to 8000 A/cm2) for the atomic hydrogen population densities n = 2,3,4. A pronounced rise in the atomic hydrogen excited state populations is observed after the end of the current pulse. A new method to measure the time-resolved electron density was developed and results are presented

  16. Recent developments in retinal lasers and delivery systems

    Directory of Open Access Journals (Sweden)

    Naresh Kumar Yadav

    2014-01-01

    Full Text Available Photocoagulation is the standard of care for several ocular disorders and in particular retinal conditions. Technology has offered us newer lasing mediums, wavelengths and delivery systems. Pattern scan laser in proliferative diabetic retinopathy and diabetic macular edema allows laser treatment that is less time consuming and less painful. Now, it is possible to deliver a subthreshold micropulse laser that is above the threshold of biochemical effect but below the threshold of a visible, destructive lesion thereby preventing collateral damage. The advent of solid-state diode yellow laser allows us to treat closer to the fovea, is more effective for vascular structures and offers a more uniform effect in patients with light or irregular fundus pigmentation. Newer retinal photocoagulation options along with their advantages is discussed in this review.

  17. Laser-Based Strategies to Treat Diabetic Macular Edema: History and New Promising Therapies

    Directory of Open Access Journals (Sweden)

    Young Gun Park

    2014-01-01

    Full Text Available Diabetic macular edema (DME is the main cause of visual impairment in diabetic patients. The management of DME is complex and often various treatment approaches are needed. At the present time, despite the enthusiasm for evaluating several new treatments for DME, including the intravitreal pharmacologic therapies (e.g., corticosteroids and anti-VEGF drugs, laser photocoagulation still remains the current standard in DME. The purpose of this review is to update our knowledge on laser photocoagulation for DME and describe the developments in laser systems. And we will also discuss the new laser techniques and review the latest results including benefits of combined therapy. In this paper, we briefly summarize the major laser therapeutics for the treatment of diabetic macular edema and allude to some future promising laser therapies.

  18. Laser-based strategies to treat diabetic macular edema: history and new promising therapies.

    Science.gov (United States)

    Park, Young Gun; Kim, Eun Yeong; Roh, Young Jung

    2014-01-01

    Diabetic macular edema (DME) is the main cause of visual impairment in diabetic patients. The management of DME is complex and often various treatment approaches are needed. At the present time, despite the enthusiasm for evaluating several new treatments for DME, including the intravitreal pharmacologic therapies (e.g., corticosteroids and anti-VEGF drugs), laser photocoagulation still remains the current standard in DME. The purpose of this review is to update our knowledge on laser photocoagulation for DME and describe the developments in laser systems. And we will also discuss the new laser techniques and review the latest results including benefits of combined therapy. In this paper, we briefly summarize the major laser therapeutics for the treatment of diabetic macular edema and allude to some future promising laser therapies. PMID:25332833

  19. Avaliação da camada de fibras nervosas na retinopatia diabética tratada por panfotocoagulação com laser de argônio Examination of the retinal nerve fiber layer in diabetic retinopathy treated by argon laser panphotocoagulation

    Directory of Open Access Journals (Sweden)

    Otacílio de Oliveira Maia Júnior

    2008-04-01

    Full Text Available OBJETIVO: Avaliar alterações na camada de fibras nervosas da retina na retinopatia diabética tratada por panfotocoagulação com laser de argônio. MÉTODOS: Estudo prospectivo de portadores de retinopatia diabética submetidos a panfotocoagulação retiniana. Inicialmente, foram realizados exame oftalmológico completo e tomografia de coerência óptica. Todos pacientes foram submetidos a panfotocoagulação em um dos olhos. A camada de fibras nervosas foi avaliada por meio da tomografia de coerência óptica na 1ª semana, no primeiro, terceiro e sexto meses do tratamento. RESULTADOS: A amostra foi composta por 27 pacientes (27 olhos portadores de diabetes mellitus tipo 2. A idade variou entre 41 e 64 anos (média de 53,7 ± 6,2 anos, sendo 10 (37% pacientes do sexo masculino e 17 (63% do feminino. Quanto ao tipo de retinopatia, 22,2% apresentavam RD proliferativa e 77,8%, RD não proliferativa muito grave. Houve aumento significante nas medidas da espessura da camada de fibras nervosas, permanecendo nos setores temporal, 3 e 4 horas após seis meses de seguimento. Não foi observada qualquer redução na espessura em todos parâmetros analisados. CONCLUSÃO: Não foi evidenciada, a curto e médio prazo, redução na espessura da camada de fibras nervosas em portadores de retinopatia diabética tratada por panfotocoagulação que possa ser identificável por meio da tomografia de coerência óptica. Por outro lado, alguns setores mostraram aumento na espessura durante o seguimento.PURPOSE: To evaluate the alterations in the retinal nerve fiber layer in diabetic retinopathy treated by argon laser panphotocoagulation. METHODS: Prospective study of patients with diabetic retinopathy submitted to retinal panphotocoagulation. Initially, complete ophthalmologic examination and optical coherence tomography were performed. All patients were submitted to panphotocoagulation with argon laser in one of the eyes. The retinal fiber layer was evaluated

  20. Liquid Argon Barrel Cryostat Arrived

    CERN Multimedia

    Pailler, P

    Last week the first of three cryostats for the ATLAS liquid argon calorimeter arrived at CERN. It had travelled for 46 days over several thousand kilometers from Japan to CERN. During three years it has been fabricated by Kawasaki Heavy Industries Ltd. at Harima, close to Kobe, under contract from Brookhaven National Laboratory (BNL) of the U.S.. This cryostat consists of two concentric cylinders made of aluminium: the outer vacuum vessel with a diameter of 5.5 m and a length of 7 m, and the inner cold vessel which will contain the electromagnetic barrel calorimeter immersed in liquid argon. The total weight will be 270 tons including the detectors and the liquid argon. The cryostat is now located in building 180 where it will be equipped with 64 feed-throughs which serve for the passage of 122,880 electrical lines which will carry the signals of the calorimeter. After integration of the calorimeter, the solenoidal magnet of ATLAS will be integrated in the vacuum vessel. A final cold test of the cryostat inc...

  1. Pain and accuracy of focal laser treatment for diabetic macular edema using a retinal navigated laser (Navilas®)

    OpenAIRE

    Kampik A; Haritoglou C; Lang J; Liegl RG; Seidensticker F; Cserhati S; Cheuteu RE; Kernt M; Ulbig MW; Neubauer AS

    2012-01-01

    Marcus Kernt*, Raoul E Cheuteu*, Sarah Cserhati, Florian Seidensticker, Raffael G Liegl, Julian Lang, Christos Haritoglou, Anselm Kampik, Michael W Ulbig, Aljoscha S Neubauer Department of Ophthalmology, Ludwig Maximilian University of Munich, Germany*These authors contributed equally to this studyAim: To investigate treatment-related pain and the accuracy of navigated laser photocoagulation in the treatment of clinically significant macular edema.Methods: Focal laser treatment of diabetic ma...

  2. Beneficial effect of combined aspiration and interstitial laser therapy in patients with benign cystic thyroid nodules

    DEFF Research Database (Denmark)

    Døssing, H; Bennedbaek, F N; Hegedüs, L

    2006-01-01

    The aim of this study was to evaluate the effect of combined cyst aspiration and ultrasound-guided interstitial laser photocoagulation (ILP) on recurrence rate and the volume of benign cystic thyroid nodules. 10 euthyroid outpatients with a solitary and cytologically benign partially cystic thyroid...

  3. Argon metastable dynamics and lifetimes in a direct current microdischarge

    Science.gov (United States)

    Stefanović, Ilija; Kuschel, Thomas; Schröter, Sandra; Böke, Marc

    2014-09-01

    In this paper we study the properties of a pulsed dc microdischarge with the continuous flow of argon. Argon metastable lifetimes are measured by tunable diode laser absorption spectroscopy (TDLAS) and are compared with calculated values which yield information about excitation and de-excitation processes. By increasing the gas flow-rate about 5 times from 10 to 50 sccm, the Arm lifetime increases from 1 to 5 μs due to the reduction of metastable quenching with gas impurities. Optical emission spectroscopy reveals nitrogen and water molecules as the main gas impurities. The estimated N2 density [N2] = 0.1% is too low to explain the measured metastable lifetimes. Water impurity was found to be the main de-excitation source of argon metastable atoms due to high quenching coefficients. The water impurity level of [H2O] = 0.15% to 1% is sufficient to bring calculated metastable lifetimes in line with experiments. The maximum value of water content in the discharge compared to the argon atoms is estimated to approximately 6%, due to the large surface to volume ratio of the microdischarge. The current pulse releases the water molecules from the electrode surface and they are either re-adsorbed in the time between 0.4 ms for [H2O] = 1% and 2.6 ms for [H2O] = 0.15% or pumped out of the discharge with the speed equal to the gas flow-rate. Depending on its partial pressure, the water impurity re-adsorption time is of the order of magnitude or less then the argon gas residence time.

  4. Pulse Compression by Filamentation in Argon with an Acoustic Optical Programmable Dispersive Filter for Predispersion Compensation

    Institute of Scientific and Technical Information of China (English)

    CHEN Xiao-Wei; JIANG Yong-Liang; LENG Yu-Xin; LIU Jun; GE Xiao-Chun; LI Ru-Xin; XU Zhi-Zhan

    2006-01-01

    @@ We have experimentally demonstrated pulses 0.4 mJ in duration smaller than 12 fs with an excellent spatial beam profile by self-guided propagation in argon. The original 52fs pulses from the chirped pulsed amplification laser system are first precompressed to 32 fs by inserting an acoustic optical programmable dispersive filter instrument into the laser system for spectrum reshaping and dispersion compensation, and the pulse spectrum is subsequently broadened by filamentation in an argon cell. By using chirped mirrors for post-dispersion compensation, the pulses are successfully compressed to smaller than 12fs.

  5. The thermal calculation of bone tissue slash modes by laser radiation

    OpenAIRE

    Letphullin, R.; Igoshin, V.

    1994-01-01

    Power laser application in medicine is based on the different interaction forms between coherent light flow and living biological tissue. Laser beam causes photothermal, photomechanical, photoablative and photo chemical effects on living tissues. Thermal effects : photocoagulation and vaporization, that tend to the thermal necrosis of living biotissues, are the results of the intensive IR laser radiation influence. Thermal necrosis area is determined by the sizes of the primary and secondary ...

  6. VISUAL OUTCOME AFTER LASER PHOTO COAGULATION IN DIA BETIC RETINOPATHY

    Directory of Open Access Journals (Sweden)

    Tariq

    2013-03-01

    Full Text Available ABSTRACT: PURPOSE: To evaluate the visual outcome after laser photocoag ulation in diabetic retinopathy. METHODS: One eye each of 100 patients were enrolled in our pro spective, randomized, clinical trial study with proliferative diabetic retinopathy/ maculopathy were assessed for visual outcome after treating them wit h laser photocoagulation. RESULTS: We observed that 62 (62% patients showed improvement by 1 or more lines on Snell’s chart, 26 (26% deteriorated from baseline visual acuity. The overall mean improved was 0.56 lines on Snell’s chart that is clinically significant. CONCLUSION: The results of present collection of hundred patients show a favourable influence of photo coagulation on the improvement and preservation of baseline visual acuity. Timely focal and grid laser photocoagulation helps in improving and stabilizing the visual acuity in patien ts with diabetic macular edema.

  7. MeV Argon ion beam generation with narrow energy spread

    CERN Document Server

    Xu, Jiancai; Shen, Baifei; Zhang, Hui; Li, Shun; Yu, Yong; Li, Jinfeng; Lu, Xiaoming; Wang, Cheng; Wang, Xinliang; Liang, Xiaoyan; Leng, Yuxin; Li, Ruxin; Xu, Zhizhan

    2016-01-01

    Laser driven particle acceleration has shown remarkable progresses in generating multi-GeV electron bunches and 10s of MeV ion beams based on high-power laser facilities. Intense laser pulse offers the acceleration field of 1012 Volt per meter, several orders of magnitude larger than that in conventional accelerators, enabling compact devices. Here we report that a highly-collimated argon ion beam with narrow energy spread is produced by irradiating a 45-fs fully-relativistic laser pulse onto an argon cluster target. The highly-charged (Argon ion with charge state of 16+) heavy ion beam has a minimum absolute energy spread of 0.19 MeV per nucleon at the energy peak of 0.39 MeV per nucleon. we identify a novel scheme from particle-in-cell simulations that greatly reduces the beam energy spread. The laser-driven intense plasma wakefield has a strong modulation on the ion beam in a way that the low energy part is cut off. The pre-accelerated argon ion beam from Coulomb explosion thus becomes more mono-energetic ...

  8. The scintillation of liquid argon

    CERN Document Server

    Heindl, T; Hofmann, M; Krücken, R; Oberauer, L; Potzel, W; Wieser, J; Ulrich, A

    2015-01-01

    A spectroscopic study of liquid argon from the vacuum ultraviolet at 110 nm to 1000 nm is presented. Excitation was performed using continuous and pulsed 12 keV electron beams. The emission is dominated by the analogue of the so called 2nd excimer continuum. Various additional emission features were found. The time structure of the light emission has been measured for a set of well defined wavelength positions. The results help to interpret literature data in the context of liquid rare gas detectors in which the wavelength information is lost due to the use of wavelength shifters.

  9. Dermatological laser treatment

    International Nuclear Information System (INIS)

    The article reviews the different lasers used in dermatology. Special emphasis is placed on the treatment of naevus flammeus (''portwine stain'') where lasers are the treatment of choice. Argon laser and pulsed dye laser are the main lasers used in vascular skin diseases, and the article focuses on these two types. Copper-vapour laser, neodymium-YAG laser and CO2 laser are also presented. Information is provided about the availability of laser technology in the different health regions in Norway. 5 refs., 2 figs

  10. Oral vascular malformations: laser treatment and management

    Science.gov (United States)

    Romeo, U.; Rocchetti, F.; Gaimari, G.; Tenore, G.; Palaia, G.; Lo Giudice, G.

    2016-03-01

    Vascular malformations are a very heterogeneous group of circulatory system's diseases that can involve different kind of vessels: arterial, venous or lymphatic ones. Many treatments, such as conventional surgery, embolization, steroid therapy and laser therapy, are available for vascular lesions. The laser approach relies more therapeutic techniques: the transmucosal thermophotocoagulation, intralesional photocoagulation, the excisional biopsy. Today laser is demonstrated to be the gold standard technique to treat vascular lesions that allows a safe and efficient treatment and a lower post-operative healing time. The only disadvantage is the risk of carbonization that could be avoided by using the multiple-spot single pulsed wave technique.

  11. The laser in urology

    Science.gov (United States)

    Hofstetter, Alfons G.

    2002-10-01

    Laser is an acronym for a physical principle and means: Light Amplification by stimulated Emission of Radiation. This principle offers a lot of tissue/light effects caused by the parameters: power density/time and the special qualities of the laser light. Nowadays for diagnosis and therapy following lasers are used in urology: Krypton- and Dye-lasers as well as the Neodymium-YAG- (nd:YAG-), Holmium-YAG (Ho:YAG-), Diode-, Argon- and the CO2-lasers.

  12. Spectroscopic Characterization of Post-Cluster Argon Plasmas During the Blast Wave Expansion

    International Nuclear Information System (INIS)

    In this work we present temperature diagnostics of an expanding laser-produced argon plasma. A short-pulse (35fs) laser with an intensity of I = 1017W/cm2 deposits ∼ 100 mJ of energy into argon clusters. This generates a hot plasma filament that develops into a cylindrically expanding shock. We develop spectral diagnostics for the temperatures of the argon plasma in the shock region and the preionized region ahead of the shock. A collisional-radiative model is applied to explore line intensity ratios derived from Ar II - Ar IV spectra that are sensitive to temperatures in a few eV range. The results of hydrodynamic simulations are employed to derive a time dependent radiative transport calculation that generates the theoretical emission spectra from the expanding plasma

  13. Studies with a liquid argon time projection chamber. Addressing technological challenges of large-scale detectors

    International Nuclear Information System (INIS)

    Michael Schenk evaluates new technologies and methods, such as cryogenic read-out electronics and a UV laser system, developed to optimise the performance of large liquid argon time projection chambers (LArTPC). Amongst others, the author studies the uniformity of the electric field produced by a Greinacher high-voltage generator operating at cryogenic temperatures, measures the linear energy transfer (LET) of muons and the longitudinal diffusion coefficient of electrons in liquid argon. The results are obtained by analysing events induced by cosmic-ray muons and UV laser beams. The studies are carried out with ARGONTUBE, a prototype LArTPC in operation at the University of Bern, Switzerland, designed to investigate the feasibility of drift distances of up to five metres for electrons in liquid argon.

  14. Above threshold ionization of Argon atoms by multicolor XUV radiation

    International Nuclear Information System (INIS)

    We analyse theoretically the Argon photoelectron spectra produced by strong and extreme ultraviolet radiation of six colors: from the 11th to the 16th harmonics of ω0 (800nm). In particular we concentrate in the range of the spectra where absorption of two photons occurs. The combination of photons of different frequencies results in eleven peaks that are separated by ω0. We point out that their relative intensities are very sensitive to the laser pulse parameters and target description. We also compare the theoretical description with experimental results finding good qualitative agreement

  15. The influence of C2H2 and dust formation on the time dependence of metastable argon density in pulsed plasmas

    OpenAIRE

    Stefanovic, Ilija; Sadeghi, Nader; Winter, Jörg

    2010-01-01

    Abstract Diode laser absorption at 772.38 nm is used to measure the time resolved density of Ar*(3 P 2) metastable atoms in a capacitively coupled radio-frequency (RF) discharge running in argon/acetylene mixture at 0.1 mbar. The RF power is pulsed at 100 Hz and the density of Ar*(3 P 2) atoms in the 5 ms ON time and in the afterglow are recorded. Different plasma conditions, namely: 1) pure argon, 2) argon + 7% acetylene before powder formation, 3) argon + 7% acetylene after dust particle...

  16. Lasers in Cardiovascular Surgery—Current Status

    OpenAIRE

    Hunter, John G.; Dixon, John A.

    1985-01-01

    The argon, carbon dioxide and neodymium-YAG lasers have been proposed as effective instruments for surgical procedures of the intact cardiovascular system. While argon and CO2 lasers cause superficial (0 to 1 mm) thermal injury, the Nd:YAG laser is better suited for effecting deep thermal necrosis (3 to 4 mm). Microsurgical vessel anastomoses can be done by “tissue welding” with any of the three clinical lasers. Myocardial revascularization may be accomplished by drilling “neocapillaries” in ...

  17. Transition probabilities for argon I

    International Nuclear Information System (INIS)

    Transition probabilities for ArI lines have been calculated on the basis of the (j,k)-coupling scheme for more than 16000 spectral lines belonging to the transition arrays 4s-np (n=4 to n=9), 5s-np (n=5 to n=9), 6s-np (n=6 to n=9), 7s-np (n=8 to n=9), 4p-ns (n=5 to n=10), 5p-ns (n=6 to n=9), 6p-ns (n=7 to n=8), 4p-nd (n=3 to n=9), 5p-nd (n=4 to n=9), 3d-np (n=5 to n=9), 4d-np (n=6 to n=9), 5d-np (n=7 to n=9), 3d-nf (n=4 to n=9), 4d-nf (n=4 to n=9), 5d-nf (n=5 to n=9), 4f-nd (n=5 to n=9) 5f-nd (n=6 to n=9), 4f-ng (n=5 to n=9), 5f-ng (n=6 to n=9). Inso far as values by other authors exist, comparison is made with these values. It turns out that the results obtained in (j,k)-coupling are close to those obtained in intermediate coupling except for intercombination lines. For high principal and/or orbital quantum numbers the transition probabilities for a multiplet approach those of the corresponding transitions in atomic hydrogen. The calculated values are applied to construct a simplified argon-atom model, which reflects the real transition properties and which allows simplified but realistic non-equilibrium calculations for argon plasmas which deviate from local thermodynamic equilibrium (LTE)

  18. Photoionized argon plasmas induced with intense soft x-ray and extreme ultraviolet pulses

    Czech Academy of Sciences Publication Activity Database

    Bartnik, A.; Wachulak, P.; Fok, T.; Węgrzyński, L.; Fiedorowicz, H.; Skrzeczanowski, W.; Pisarczyk, T.; Chodukowski, T.; Kalinowska, Z.; Dudžák, Roman; Dostál, Jan; Krouský, Eduard; Skála, Jiří; Ullschmied, Jiří; Hřebíček, Jan; Medřík, Tomáš

    2016-01-01

    Roč. 58, č. 1 (2016), s. 014009. ISSN 0741-3335 R&D Projects: GA MŠk LM2010014 EU Projects: European Commission(XE) 284464 - LASERLAB-EUROPE Institutional support: RVO:61389021 ; RVO:68378271 Keywords : laser-plasma * plasma radiation * photoionization * Argon plasma * Nd:YAG laser * PALS iodine laser Subject RIV: BL - Plasma and Gas Discharge Physics; BH - Optics, Masers, Lasers (FZU-D) Impact factor: 2.186, year: 2014 http://iopscience.iop.org/article/10.1088/0741-3335/58/1/014009

  19. Patterned retinal coagulation with a scanning laser

    Science.gov (United States)

    Palanker, Daniel; Jain, ATul; Paulus, Yannis; Andersen, Dan; Blumenkranz, Mark S.

    2007-02-01

    Pan-retinal photocoagulation in patients with diabetic retinopathy typically involves application of more than 1000 laser spots; often resulting in physician fatigue and patient discomfort. We present a semi-automated patterned scanning laser photocoagulator that rapidly applies predetermined patterns of lesions; thus, greatly improving the comfort, efficiency and precision of the treatment. Patterns selected from a graphical user interface are displayed on the retina with an aiming beam, and treatment can be initiated and interrupted by depressing a foot pedal. To deliver a significant number of burns during the eye's fixation time, each pulse should be considerably shorter than conventional 100ms pulse duration. We measured coagulation thresholds and studied clinical and histological outcomes of the application of laser pulses in the range of 1-200ms in pigmented rabbits. Laser power required for producing ophthalmoscopically visible lesions with a laser spot of 132μm decreased from 360 to 37mW with pulse durations increasing from 1 to 100ms. In the range of 10-100ms clinically and histologically equivalent light burns could be produced. The safe therapeutic range of coagulation (ratio of the laser power required to produce a rupture to that for a light burn) decreased with decreasing pulse duration: from 3.8 at 100ms, to 3.0 at 20ms, to 2.5 at 10ms, and to 1.1 at 1ms. Histology demonstrated increased confinement of the thermal damage with shorter pulses, with coagulation zone limited to the photoreceptor layer at pulses shorter than 10ms. Durations of 10-20ms appear to be a good compromise between the speed and safety of retinal coagulation. Rapid application of multiple lesions greatly improves the speed, precision, and reduces pain in retinal photocoagulation.

  20. MACULAR LASER GRID ALONE VERSUS COMBINED WITH INTRAVITREAL TRIAMCINOLONE PLUS BEVACIZUMAB FOR DIABETIC MACULAR EDEMA

    OpenAIRE

    Mehmet Demir; Efe Can; Dilek Guven; Sonmez Cinar; Atilla Demir

    2013-01-01

    Diabetic retinopathy is the leading cause of blindness among individuals of working age in advanced societies, most of the vision loss resulting from diabetic macular edema (DME). Macular laser photocoagulation or intravitreal tiamcinolone or anti-vascular endothelial growth factor injection are modalities of therapy for diabetic macular edema. This study aim was to present the clinical outcomes of 60 eyes of 41 patients with diffuse DME who treated with macular laser grid (MLG) alone or comb...

  1. Argon-39 Background in DUNE Photon Detectors

    Science.gov (United States)

    Sinev, Gleb; DUNE Collaboration

    2016-03-01

    The Deep Underground Neutrino Experiment (DUNE) is a 40-kt liquid argon detector that will be constructed 5000 ft underground in the Sanford Underground Research Facility in order to study neutrino and proton decay physics. Instrumenting liquid argon with photon detectors to record scintillation in addition to the ionization signal can significantly improve time and energy resolution of the experiment. Argon produces light with wavelength of 128 nm. The reference design for the photon detectors includes acrylic bars covered in wavelength shifter, where the scintillation light can be captured and reemitted with longer wavelengths, then detected using silicon photomultipliers. Radiological backgrounds may noticeably deteriorate the photon detection system performance, especially for low-energy interactions. A particularly important background comes from argon-39 decays, because argon-39 is present in natural argon that will be used in DUNE and the background rate increases with the size of the experiment. The effect of the argon-39 background has been studied and is presented in this talk.

  2. Emissive spectra of shock-heated argon

    International Nuclear Information System (INIS)

    To study the radiant properties of argon under weak shock compression, an aluminum target filled with gaseous argon at ambient states was impacted by a tungsten alloy projectile which was launched from a two-stage light gun to 2.00 km/s. The radiant signals of single shock-compressed argon were recorded by a six-channel pyrometer and oscilloscopes, which varied with time linearly for the five channels from 405 nm to 700 nm and exponentially for the channel 800 nm, and the corresponding velocity of shock wave was determined to be 4.10 ± 0.09 km/s. By the present experiment, it has been shown that the absorbability of the shock-heated argon is low for visual light and the optical depths of argon gas turn from thin to thick as wavelengths gradually increase. The time-resolved spectra in the rising-front of the radiant signal in the re-shocked argon were recorded by means of an OMA, and strong emissive spectrum bands near 450 nm light-wave length but no linear spectrum were found. The emissive spectrum properties of shock-compression argon were qualitatively explained by the state parameters and ionization degree

  3. A 20-Liter Test Stand with Gas Purification for Liquid Argon Research

    CERN Document Server

    Li, Yichen; Tang, Wei; Joshi, Jyoti; Qian, Xin; Diwan, Milind; Kettell, Steve; Morse, William; Rao, Triveni; Stewart, James; Tsang, Thomas; Zhang, Lige

    2016-01-01

    We describe the design of a 20-liter test stand constructed to study fundamental properties of liquid argon (LAr). This system utilizes a simple, cost-effective gas argon (GAr) purification to achieve ultra-high purity, which is necessary to study electron transport properties in LAr. An electron drift stack with up to 25 cm length is constructed to study electron drift, diffusion, and attachment at various electric fields. A gold photocathode and a pulsed laser are used as a bright electron source. The operational performance of this system is reported.

  4. Technical aspects of laser treatment for acute retinopathy of prematurity under topical anesthesia

    Directory of Open Access Journals (Sweden)

    Jalali Subhadra

    2010-01-01

    Full Text Available Retinopathy of prematurity (ROP is a significant cause of childhood blindness. The criteria for laser therapy have been revised from threshold ROP to include the earlier stage of high-risk prethreshold ROP. Laser photocoagulation is an established technique for the treatment of ROP. However, the detailed procedure and techniques for laser photocoagulation have not yet been published. Adequate and appropriate laser photocoagulation for ROP is different from the application of lasers in adult retinal vascular diseases, and many ophthalmologists need to be trained in this technique if the outreach of ROP treatment programs is to improve. Laser under topical anesthesia has been practiced in India as a preferred modality especially due to logistics and risks of general anesthesia in these pre-term babies. We discuss the details of the technique as practiced at tertiary care ophthalmic hospitals in India, so that the nuances in treatment parameters and clinical decision-making can be usefully applied to ophthalmic practice. This will ultimately lead to safe and effective treatment delivery in ROP.

  5. Effects of sub-Tenon's capsule triamcinolone acetonide injection combined with microa- neurysm photocoagulation on diabetic macular edema

    Directory of Open Access Journals (Sweden)

    Oshitari T

    2015-12-01

    Full Text Available Toshiyuki Oshitari, Sakiko Nonomura, Miyuki Arai, Yoko Takatsuna, Eiju Sato, Takayuki Baba, Shuichi Yamamoto Department of Ophthalmology and Visual Science, Graduate School of Medicine, Chiba University, Chuo-ku, Chiba, Japan Purpose: To compare the effects of sub-Tenon's capsule triamcinolone acetonide (STTA injection to that of STTA injection combined with microaneurysm photocoagulation (MAPC; STTA + MAPC on eyes with diabetic macular edema (DME. Patients and methods: The medical records of 138 eyes of 138 patients with DME treated by either STTA or STTA + MAPC were reviewed. The degree of DME was determined by the optical coherence tomographic features: patients with serous retinal detachment (SRD+; 38 eyes and patients without SRD (non-SRD; 100 eyes. The central macular thickness (CMT and the best-corrected visual acuity (BCVA were measured periodically for 6 months after the treatments. Results: The BCVA was significantly improved in the non-SRD group after STTA + MAPC. The CMT was significantly improved in all groups and improved considerably more in the non-SRD group than in the SRD+ group after STTA + MAPC. Conclusion: Our findings indicate that MAPC has an additive effect in the non-SRD type. Keywords: diabetic macular edema, sub-Tenon's triamcinolone acetonide injection, microaneurysm photocoagulation, best-corrected visual acuity, central macular thickness

  6. Argon plasma irradiation of polypropylene

    International Nuclear Information System (INIS)

    Polypropylene samples were exposed to argon plasma discharge and the changes of the PP surface properties were studied by different methods. Surface wettability was derived from contact angle measured by standard goniometry and chemical structure of the plasma modified PP was studied using X-ray photoelectron spectroscopy (XPS) and by Rutherford backscattering spectroscopy (RBS), surface morphology and roughness of samples using AFM. Zeta potential of pristine and modified PP was determined with the SurPASS. The presence of incorporated oxygen in the PP surface layer, about 60 nm thick, was observed in RBS spectra. Oxygen concentration is a decreasing function of the depth. With progressing aging time the oxygen concentration on the PP surface decreases. Plasma treatment results in a rapid decrease of the contact angle, which increases again with increasing aging time. In XPS measurement the oxygen containing structures, created by the plasma treatment, were found on the very surface of the modified PP and the zeta potential being changed too. The significant difference in zeta potential between pristine and plasma treated PP clearly indicates that the plasma treatment leads to a more hydrophilic PP surface.

  7. Status and perspecitves of liquid argon calorimeters

    International Nuclear Information System (INIS)

    The status of liquid argon calorimeters is reviewed, and experience obtained with these devices is described. Future perspectives of the liquid ionization chamber technique in calorimetry are also discussed. (orig.)

  8. Liquid argon neutrals detector (LAND) for PEP

    International Nuclear Information System (INIS)

    The physical effects limiting the gamma energy resolution of a liquid argon calorimeter without passive converter plates is discussed. An example of such a detector based on the General User's Magnet designed at this Summer Study is given

  9. Opacity of Shock-Generated Argon Plasmas

    Institute of Scientific and Technical Information of China (English)

    王藩侯; 陈敬平; 周显明; 李西军; 经福谦; 孟续军; 孙永盛

    2001-01-01

    Argon plasmas with uniform density and temperature are generated by a planar shock wave through argon gas. The opacities of argon plasma, covering the thermodynamic states at temperatures of 1.4-2.2eV and in densities of 0.0083- 0.015 g/cm3, are investigated by measuring the emitted radiance versus time at several visible wavelengths. Comparison of the measured opacities with those calculated demonstrates that the average atom model can be used well to describe the essential transport behaviour of photons in argon plasma under the abovementioned thermodynamic condition. A simplified and self-consistent method to deduce the reflectivity R(λ) at the baseplate surface is applied. It demonstrates that the values of R(λ) are all around 0.4 in the experiments, which are basically in agreement with those given by Erskine previously (1994 J. Quant. Spectrosc. Radiat.Transfer 51 97).

  10. 21 CFR 868.1075 - Argon gas analyzer.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Argon gas analyzer. 868.1075 Section 868.1075 Food... DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1075 Argon gas analyzer. (a) Identification. An argon gas analyzer is a device intended to measure the concentration of argon in a gas mixture to aid...

  11. Negative corona current pulses in argon and in mixture argon with SF6

    International Nuclear Information System (INIS)

    Waveforms of the first negative current pulses in a short negative point-to plane gap in pure argon and argon with SF6 admixture have been investigated with a nanosecond time resolution at a gas pressure 50 kPa as a function of applied gap voltage and content of SF6 in the mixture. We have made an attempt to explain the differences in the discharge development in pure argon and in argon with admixture of SF6 based on the observed changes of the pulse shape. The experimental results obtained will be discussed in context with existing computer simulation models (Authors)

  12. Measurements on scintillation light from liquid argon

    International Nuclear Information System (INIS)

    It is shown that an argon calorimeter can operate as a scintillation detector, provided that xenon is added. With the addition of 170 ppm xenon a light yield of 70% has been obtained. In addition the light yield is determined under influence of an electric field, from differently ionising particles and by the use of aluminium mirrors acting as light guides. Finally first measurements with a photomultiplier working at liquid argon temperatures are reported. (orig.)

  13. Potassium-argon/argon-40-argon-39 geochronology of Cenozoic alkali basalts from the South China Sea

    Institute of Scientific and Technical Information of China (English)

    YAN Quanshu; SHI Xuefa; YANG Yaomin; WANG Kunshan

    2008-01-01

    Based on the isotopic chronologic results of Cenozoic alkali basalts from the South China Sea,the characteristics of volcanic activi-ty of the South China Sea after spreading were studied.The potassium - argon ages of eight alkali basalt samples from the South China Sea,and the argon - argon ages of two samples among them are reported.Apparent ages of the whole rock are 3.80 to 7.91 Ma with an average value of 5.43 Ma (potassium- argon,whole rock),and there is little difference among samples at the same location,e.g.,4.76~5.78 Ma for location S04-12.The argon - argon ages for the two samples are 6.06 and 4.71 Ma,which lie within the age scope of potassium - argon method.The dating results indicate that rock-forming age is from late Miocene to Pli-ocene,which is consistent with erupting event for alkali basalts from adjacent regions of the South China Sea.Volcanic activities occur after the cessation of spreading of the South China Sea,which are controlled by lithospheric fault and the spreading center formed during the spreading period of the South China Sea.These dating results,combined with geochemical characteristics of these basalts,the published chronological data for the South China Sea and its adjacent regions,and the updated geophysical data near Hainan Island,suggest that after the cessation of spreading of the South China Sea,there occur widely distributing magmatic activities which primarily is alkali basalt,and the volcanic activity continues to Quaternary.The activity may be relative to Hainan mantle plume originated from core/mantle boundary.

  14. Long term refractive and structural outcome following laser treatment for zone 1 aggressive posterior retinopathy of prematurity

    OpenAIRE

    Parag K Shah; Ramakrishnan, Minu; Sadat, Bani; Bachu, Sandeep; V Narendran; Kalpana, N.

    2014-01-01

    Aim: To report the long term refractive, visual and structural outcome post-laser for zone 1 aggressive posterior retinopathy of prematurity (AP-ROP). Materials and Methods: A retrospective analysis was performed of refractive status of premature infants with zone 1 AP-ROP who underwent laser photocoagulation from 2002 to 2007 and followed up till 2013. Once the disease regressed, children were followed up six monthly with detailed examination regarding fixation pattern, ocular motility, nyst...

  15. Long term refractive and structural outcome following laser treatment for zone 1 aggressive posterior retinopathy of prematurity

    OpenAIRE

    Parag K Shah; Minu Ramakrishnan; Bani Sadat; Sandeep Bachu; V Narendran; Kalpana, N.

    2014-01-01

    Aim: To report the long term refractive, visual and structural outcome post-laser for zone 1 aggressive posterior retinopathy of prematurity (AP-ROP). Materials and Methods: A retrospective analysis was performed of refractive status of premature infants with zone 1 AP-ROP who underwent laser photocoagulation from 2002 to 2007 and followed up till 2013. Once the disease regressed, children were followed up six monthly with detailed examination regarding fixation pattern, ocular motility, ...

  16. Argon Collection And Purification For Proliferation Detection

    Energy Technology Data Exchange (ETDEWEB)

    Achey, R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hunter, D. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-10-09

    In order to determine whether a seismic event was a declared/undeclared underground nuclear weapon test, environmental samples must be taken and analyzed for signatures that are unique to a nuclear explosion. These signatures are either particles or gases. Particle samples are routinely taken and analyzed under the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) verification regime as well as by individual countries. Gas samples are analyzed for signature gases, especially radioactive xenon. Underground nuclear tests also produce radioactive argon, but that signature is not well monitored. A radioactive argon signature, along with other signatures, can more conclusively determine whether an event was a nuclear test. This project has developed capabilities for collecting and purifying argon samples for ultra-low-background proportional counting. SRNL has developed a continuous gas enrichment system that produces an output stream containing 97% argon from whole air using adsorbent separation technology (the flow diagram for the system is shown in the figure). The vacuum swing adsorption (VSA) enrichment system is easily scalable to produce ten liters or more of 97% argon within twelve hours. A gas chromatographic separation using a column of modified hydrogen mordenite molecular sieve has been developed that can further purify the sample to better than 99% purity after separation from the helium carrier gas. The combination of these concentration and purification systems has the capability of being used for a field-deployable system for collecting argon samples suitable for ultra-low-background proportional counting for detecting nuclear detonations under the On-Site Inspection program of the CTBTO verification regime. The technology also has applications for the bulk argon separation from air for industrial purposes such as the semi-conductor industry.

  17. Kinetic and experimental study of argon and argon--nitrogen mixtures excited by fission fragments

    International Nuclear Information System (INIS)

    Optical emission from argon and argon-nitrogen mixtures excited by fission fragments are studied in an effort to better understand the fission fragment energy deposition into the gas. A model of the energy flow in the gas is developed and compared with the experimental results

  18. Argon activation analysis, application to dating by the potassium-argon method

    International Nuclear Information System (INIS)

    Activation analysis using radiogenic argon-40 has been applied to rock-dating by the K-Ar method. The argon is extracted from the sample, purified, activated to saturation in a flux of 2 X 1013 neutrons/cm2 sec-1 and measured by gamma spectroscopy. The sensitivity obtained is such that it is possible to measure amounts of argon corresponding to age of a few thousand years only. However since it has not been possible to measure the amount of pollution of radiogenic argon by atmospheric argon with any accuracy, the measurable age limit is in fact of the order of MY. The method has been applied to basalts from the Mont-Dore region. The results obtained are in fairly good agreement with geological, stratigraphic and paleomagnetic data. (author)

  19. Lasers

    OpenAIRE

    Passeron, Thierry

    2012-01-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be succesfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-aulait macules should not be treated as the relapse...

  20. Attenuation of vacuum ultraviolet light in liquid argon

    CERN Document Server

    Neumeier, A; Oberauer, L; Potzel, W; Schönert, S; Dandl, T; Heindl, T; Ulrich, A; Wieser, J

    2015-01-01

    The transmission of liquid argon has been measured, wavelength resolved, for a wavelength interval from 118 to 250 nm. The wavelength dependent attenuation length is presented for pure argon. It is shown that no universal wavelength independent attenuation length can be assigned to liquid argon for its own fluorescence light due to the interplay between the wavelength dependent emission and absorption. A decreasing transmission is observed below 130 nm in both chemically cleaned and distilled liquid argon and assigned to absorption by the analogue of the first argon excimer continuum. For not perfectly cleaned argon a strong influence of impurities on the transmission is observed. Two strong absorption bands at 126.5 and 141.0 nm with approximately 2 and 4 nm width, respectively, are assigned to traces of xenon in argon. A broad absorption region below 180 nm is found for unpurified argon and tentatively attributed to the presence of water in the argon sample.

  1. Investigation of a Mercury-Argon Hot Cathode Discharge

    Science.gov (United States)

    Wamsley, Robert Charles

    Classical absorption and laser induced fluorescence (LIF) experiments are used to investigate processes in the cathode region of a Hg-Ar hot cathode discharge. The absorption and LIF measurements are used to test the qualitative understanding and develop a quantitative model of a hot cathode discharge. The main contribution of this thesis is a model of the negative glow region that demonstrates the importance of Penning ionization to the ionization balance in the negative glow. We modeled the excited argon balance equation using a Monte Carlo simulation. In this simulation we used the trapped radiative decay rate of the resonance levels and the Penning ionization rate as the dominant loss terms in the balance equation. The simulated data is compared to and found to agree with absolute excited argon densities measured in a classical absorption experiment. We found the primary production rate per unit volume of excited Ar atoms in the simulation is sharply peaked near the cathode hot spot. We used the ion production rate from this simulation and a Green's function solution to the ambipolar diffusion equation to calculate the contribution of Penning ionization to the total ion density. We compared the results of this calculation to our experimental values of the Hg ^+ densities in the negative glow. We found that Penning ionization is an important and possibly the dominant ionization process in the negative glow.

  2. Malignant melanoma of the choroid: treatment with episcleral /sup 198/Au plaque and xenon-arc photocoagulation

    Energy Technology Data Exchange (ETDEWEB)

    Moura, R.A.; McPherson, A.R.; Easley, J.

    1985-02-01

    A method of treatment for posteriorly located malignant melanomas of the choroid is reviewed. Twenty-six patients have been treated either by radioactive gold (/sup 198/Au) seed radiation plaque, alone or in combination with postradiation xenon-arc photocoagulation. Success, defined as the preservation of the globe with tumor ablated or regressed, was achieved in 92.3% of the treated eyes. These patients have been followed from 1 to 8.5 years, with an average follow-up of 44.84 months. Fifteen out of 26 patients (57.69%) had a final visual acuity of 20/50 or better. The main complications were radiation retinopathy (19.2%) and cystoid macular edema (19.2%). There were two enucleations, one after 29 months and one after 24 months following treatment.

  3. Lasers in Ophthalmology

    Institute of Scientific and Technical Information of China (English)

    1992-01-01

    In recent years,lasers have entered every fieldof medicine and especially so in ophthalmol-ogy.The scientific basis of lasers in ophthal-mology is based on three mechanisms:1.Photothermal effectLasers:argon,krypton,dye and diodeA thermal effect is generated when laserenergy is absorbed by pigment leading to in-creased vibration and therefore heat content.A

  4. Peripheral retinal ablation in the treatment of proliferative diabetic retinopathy during pregnancy.

    OpenAIRE

    Hercules, B L; Wozencroft, M; Gayed, I I; Jeacock, J

    1980-01-01

    The course of proliferative diabetic retinopathy involving the optic disc was followed, and the response to peripheral retinal photocoagulation monitored by argon laser in 11 patients during and after 13 pregnancies. Traditional obstetric practice assumes that pregnancy is a stimulus to irreversible progression of proliferative diabetic retinopathy, and that timely abortion and sterilisation are essential in order to achieve control of the neovascular process. Extensive photocoagulation will ...

  5. Characterization of SF6/Argon Plasmas for Microelectronics Applications; TOPICAL

    International Nuclear Information System (INIS)

    This report documents measurements in inductively driven plasmas containing SF(sub 6)/Argon gas mixtures. The data in this report is presented in a series of appendices with a minimum of interpretation. During the course of this work we investigated: the electron and negative ion density using microwave interferometry and laser photodetachment; the optical emission; plasma species using mass spectrometry, and the ion energy distributions at the surface of the rf biased electrode in several configurations. The goal of this work was to assemble a consistent set of data to understand the important chemical mechanisms in SF(sub 6) based processing of materials and to validate models of the gas and surface processes

  6. Attosecond Coherent Control of Single and Double Photoionization in Argon.

    Science.gov (United States)

    Hogle, C W; Tong, X M; Martin, L; Murnane, M M; Kapteyn, H C; Ranitovic, P

    2015-10-23

    Ultrafast high harmonic beams provide new opportunities for coherently controlling excitation and ionization processes in atoms, molecules, and materials on attosecond time scales by employing multiphoton two-pathway electron-wave-packet quantum interferences. Here we use spectrally tailored and frequency tuned vacuum and extreme ultraviolet harmonic combs, together with two phase-locked infrared laser fields, to show how the total single and double photoionization yields of argon can be coherently modulated by controlling the relative phases of both optical and electronic-wave-packet quantum interferences. This Letter is the first to apply quantum control techniques to double photoionization, which is a fundamental process where a single, high-energy photon ionizes two electrons simultaneously from an atom. PMID:26551112

  7. Electron-ion recombination study in argon at atmospheric pressure

    International Nuclear Information System (INIS)

    This study deals with a wall-stabilized arc burning in argon at atmospheric pressure. A transient mode is obtained using a fast thyristor connected to the electrodes, which short-circuits the discharge. By means of two wavelengths laser interferometry and spectroscopy measurements we have determined the temporal changes of the electron density, ground state atom density and excited atom density. We have shown that, when the electric field is suppressed, the electron temperature rapidly decreases to the gas temperature before changing electron and atom densities. This phenomenon is applied to determine the gas temperature and to evaluate the role played by ionization in electron density balance. The coefficients of ambipolar diffusion, ionization and recombination and an apparent recombination coefficient are determined versus electron temperature and compared with theoretical values

  8. Scintillation efficiency of liquid argon in low energy neutron-argon scattering

    International Nuclear Information System (INIS)

    Experiments searching for weak interacting massive particles with noble gases such as liquid argon require very low detection thresholds for nuclear recoils. A determination of the scintillation efficiency is crucial to quantify the response of the detector at low energy. We report the results obtained with a small liquid argon cell using a monoenergetic neutron beam produced by a deuterium-deuterium fusion source. The light yield relative to electrons was measured for six argon recoil energies between 11 and 120 keV at zero electric drift field

  9. Therapeutic application of lasers in ophthalmology

    International Nuclear Information System (INIS)

    Lasers have found application in diverse branches of medicine. In ophthalmology, laser technology has various therapeutic and diagnostic applications. The purpose of this article is to review the major therapeutic applications of lasers in different eye disorders. The effects of lasers on biological tissues and different laser techniques as well as the indications for laser therapy in various parts of the eye are discussed. Lasers are used to treat glaucoma and many vascular disorders of the retina. Laser treatment may be useful in preventing the development of neovascularization in diabetic retinopathy, BRVO, or CRVO. Laser techniques are also available for the treatment of the exudative form of age-related macular degeneration (AMD) and some malignant and benign intraocular tumors and in retina abnormalities which predispose to rhegmatogenous retinal detachment. Corneal laser surgery is the most frequently applied laser procedure in ophthalmology. PRK, LASIK, and LASEK are used to correct errors in vision such as myopia, hyperopia, and astigmatism. Laser photocoagulation is also helpful in cataract surgery. Nowadays, lasers have become so universal that it is difficult to imagine ophthalmology without them. We are still witnessing rapid advances in the development of laser techniques, especially in plastic surgery, cataract extraction, and ocular imaging. (authors)

  10. Contraction ionization waves in the argon contracted discharge

    International Nuclear Information System (INIS)

    An investigation of ionization waves in the argon contracted discharge and a definition of their arising propagation mechanism accounting for the specificity of elementary pocesses characteristic of argon are presented. (author)

  11. Thermal decomposition of barium valerate in argon

    DEFF Research Database (Denmark)

    Torres, P.; Norby, Poul; Grivel, Jean-Claude

    2015-01-01

    The thermal decomposition of barium valerate (Ba(C4H9CO2)(2)/Ba-pentanoate) was studied in argon by means of thermogravimetry, differential thermal analysis, IR-spectroscopy, X-ray diffraction and hot-stage optical microscopy. Melting takes place in two different steps, at 200 degrees C and 280...

  12. Antiapoptotic activity of argon and xenon.

    Science.gov (United States)

    Spaggiari, Sabrina; Kepp, Oliver; Rello-Varona, Santiago; Chaba, Kariman; Adjemian, Sandy; Pype, Jan; Galluzzi, Lorenzo; Lemaire, Marc; Kroemer, Guido

    2013-08-15

    Although chemically non-reactive, inert noble gases may influence multiple physiological and pathological processes via hitherto uncharacterized physical effects. Here we report a cell-based detection system for assessing the effects of pre-defined gas mixtures on the induction of apoptotic cell death. In this setting, the conventional atmosphere for cell culture was substituted with gas combinations, including the same amount of oxygen (20%) and carbon dioxide (5%) but 75% helium, neon, argon, krypton, or xenon instead of nitrogen. The replacement of nitrogen with noble gases per se had no effects on the viability of cultured human osteosarcoma cells in vitro. Conversely, argon and xenon (but not helium, neon, and krypton) significantly limited cell loss induced by the broad-spectrum tyrosine kinase inhibitor staurosporine, the DNA-damaging agent mitoxantrone and several mitochondrial toxins. Such cytoprotective effects were coupled to the maintenance of mitochondrial integrity, as demonstrated by means of a mitochondrial transmembrane potential-sensitive dye and by assessing the release of cytochrome c into the cytosol. In line with this notion, argon and xenon inhibited the apoptotic activation of caspase-3, as determined by immunofluorescence microscopy coupled to automated image analysis. The antiapoptotic activity of argon and xenon may explain their clinically relevant cytoprotective effects. PMID:23907115

  13. Argon-ion contamination of the plasmasphere

    International Nuclear Information System (INIS)

    This paper applies present observational and analytic knowledge on effects of plasma beam interaction wth the magnetosphere to the plasmasphere contamination problem of the argon ion engine exhaust expected to be deposited in the magnetosphere during the construction phase of the Satellite Power System. Effects of plasmasphere, ionosphere, and radiation belt modifications are discussed

  14. Near-infrared scintillation of liquid argon

    Science.gov (United States)

    Alexander, T.; Escobar, C. O.; Lippincott, W. H.; Rubinov, P.

    2016-03-01

    Since the 1970s it has been known that noble gases scintillate in the near infrared (NIR) region of the spectrum (0.7 μm motivation for using the NIR scintillation in liquid argon detectors, then briefly review early as well as more recent efforts and finally show encouraging preliminary results of a test performed at Fermilab.

  15. Silicon compounds of neon and argon

    Czech Academy of Sciences Publication Activity Database

    Roithová, J.; Schröder, Detlef

    -, č. 46 (2009), s. 8788-8790. ISSN 1433-7851 R&D Projects: GA ČR GA203/09/1223 Grant ostatní: ERC(XE) Adg HORIZOMS Institutional research plan: CEZ:AV0Z40550506 Keywords : argon * bond formation * dications * neon Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 11.829, year: 2009

  16. Effect of Cervical Length Recovery after Laser Surgery for Twin-Twin Transfusion Syndrome

    OpenAIRE

    Finneran, Matthew; Temming, Lorene; Templin, Megan; Stephenson, Courtney

    2016-01-01

    Objective To evaluate the impact of polyhydramnios on preoperative cervical length and whether cervical length recovery after amnioreduction during selective fetoscopic laser photocoagulation (SFLP) is associated with a greater gestational age at delivery in pregnancies complicated by twin-twin transfusion syndrome (TTTS). Methods Retrospective study of 50 pregnancies complicated by TTTS treated with SFLP between March 2010 and July 2014 at a single center. Preoperative maximum vertical pocke...

  17. Comparison of photosensitivity in germanium doped silica fibers using 244 nm and 266 nm continuous wave lasers

    DEFF Research Database (Denmark)

    Jensen, Jesper Bo; Varming, Poul; Liu, B.;

    2001-01-01

    Diode pumped continuous-wave UV lasers offer an interesting alternative to frequency doubled argon-ion lasers. We report the first photosensitivity comparison using these lasers on deuterium loaded standard telecommunication fibers and unloaded experimental fibers.......Diode pumped continuous-wave UV lasers offer an interesting alternative to frequency doubled argon-ion lasers. We report the first photosensitivity comparison using these lasers on deuterium loaded standard telecommunication fibers and unloaded experimental fibers....

  18. Visual Outcomes of Pan-retinal Photocoagulation in Diabetic Retinopathy at One-year Follow-up and Associated Risk Factors

    OpenAIRE

    Rema Mohan; Sujatha Purushothaman; Pradeepa Rajendra

    2005-01-01

    Purpose: To assess the visual outcomes at one-year follow-up after pan-retinal photocoagulation (PRP) in type 2 diabetes mellitus subjects with proliferative diabetic retinopathy (PDR) and associated risk factors. Materials and Methods: A retrospective study, using data from medical records of 5000 Type 2 diabetic patients who underwent a retinal examination between 1995 and 1999 at a diabetic centre. Ocular, clinical and biochemical parameters were assessed at baseline and at one-year fol...

  19. Changes of serum IL-1 and sIL-2R levels after intravenous photo-coagulation in patients with varicose greater saphenous vein

    International Nuclear Information System (INIS)

    Objective: To determine the changes of serum interleukin 2 (IL-2) and soluble interleukin 2 receptor (sIL-2R) levels in patients with varicose greater saphenous vein after intravenous photocoagulation. Methods: Fifty patients with varicose greater saphenous vein were divided into two groups (mild and severe) according to their clinical symptoms. Serum IL-2 and sIL-2R levels were determined with RIA and ELISA respectively in these patients and 30 controls. Results: Serum levels of IL-2 and sIL-2R in patients of the mild group were about the same as those in the controls. In patients of the severe group, levels of IL-2 decreased and levels of sIL-2R increased significantly. After photocoagulation, the IL-2 levels dropped at first but gradually rose; the reverse was true for the sIL-2R levels. The final levels of IL-2 and sIL-2R approached those before treatment in the mild group. In the severe group, the final IL-2 levels were higher and sIL-2R levels lower than those before photocoagulation. Conclusion: Determination of serum IL-2 and sIL-2R levels revealed information about the immune status of the patients and could be applied for judgement of the treatment effect

  20. Detrapping of tungsten nanoparticles in a direct-current argon glow discharge

    International Nuclear Information System (INIS)

    Nanoparticles are grown from the sputtering of a tungsten cathode in a direct current argon glow discharge. Laser light scattering of a vertical laser sheet going through the plasma reveals that the dust particle cloud is compressed and pushed towards the anode during the discharge. Scanning electron microscopy images of substrates exposed to the plasma for given durations show that dust particles are continuously falling down on the anode during the discharge. These observations are explained by the fact that the electrostatic force at the negative glow-anode sheath boundary cannot balance the ion drag, gravity, and thermophoresis forces for particles of more than a few tens of nanometres in diameter

  1. Effect of ultrasound-guided interstitial laser photocoagulation on benign solitary solid cold thyroid nodules - a randomised study

    DEFF Research Database (Denmark)

    Døssing, Helle; Bennedbaek, Finn Noe; Hegedüs, Laszlo

    2005-01-01

    thyroid function was determined by routine assays before and during follow-up. Pressure and cosmetic complaints before and at 6 months were evaluated on a visual analogue scale. ILP was performed under US guidance and with an output power of 2.5-3.5 W. RESULTS: In the ILP group, the nodule volume...... decreased from 8.2 ml (6.1; 11.9) (median; quartiles) to 4.8 ml (3.0; 6.6) after 6 months (P = 0.001). The overall median reduction was 44% (37; 52), which correlated with a significant decrease in pressure symptoms as well as cosmetic complaints. In the control group, a non-significant increase in median...... satisfactory clinical response in the majority of patients with a benign solitary solid cold thyroid nodule, and may become a clinically relevant alternative to surgery in selected patients....

  2. Laser therapy and macular degeneration

    Science.gov (United States)

    Menchini, Ugo; Virgili, Gianni; Giansanti, Fabrizio; Giacomelli, Giovanni; Cappelli, Stefania

    2001-10-01

    Among macular diseases, choroidal neovascularization (CNV) is one of the most common causes of visual loss, especially in the form associated with age-related macular degeneration and pathologic myopia. Research on these diseases has recently evaluated new treatment modalities that use laser light differently; among these, photodynamic therapy (PDT) has been introduced in the clinical practice, allowing us to expand the possibility of reducing visual loss in patients affected by CNV. With PDT, a photosensitizer (verteporfin, VisudyneTM) is injected intravenously, and it selectively binds to new vessels; low-power laser light exposure then activates the drug, leading to oxidative damage of the endothelium and new vessels thrombosis. Yet, other therapies, such as transpupillary termotherapy, or the use of photocoagulation to cause feeder-vessel occlusion, could proof effective, but they need further investigation.

  3. Laser filament-induced aerosol formation

    OpenAIRE

    Saathoff, H.; Henin, S.; Stelmaszczyk, K.; Petrarca, M.; Delagrange, R.; Hao, Z.; Lüder, J.; Möhler, O.; Y. Petit; Rohwetter, P.; Schnaiter, M.; Kasparian, J.; Leisner, T.; J.-P. Wolf; Wöste, L.

    2012-01-01

    Using the aerosol and cloud simulation chamber AIDA we investigated the laser filament induced particle formation in ambient air, humid synthetic air, humid nitrogen, argon-oxygen mixture, and pure argon in order to simulate the particle formation under realistic atmospheric conditions as well as to investigate the influence of typical gas-phase atmospheric constituents on the particle formation. Terawatt laser plasma filaments generated new particles in the size range 3 to 130 nm with partic...

  4. Explanation of the memory effect in argon

    Directory of Open Access Journals (Sweden)

    Marković Vidosav

    2005-01-01

    Full Text Available Memory effect - the long time variation of the electrical breakdown time delay on the relaxation time td (τ was observed in argon 24 hours after relaxation times and explained by the long-lived metastable states remaining from the preceding glow. However, the quenching processes reducing the effective lifetime of metastable states several orders of magnitude below that relevant for the time scale of observation were neglected. By applying approximate gas phase models it was found that the early afterglow kinetics up to hundreds of milliseconds is dominated by the decay of molecular argon ions Ar2+ and the approximate value of their ambipolar diffusion coefficient is determined. After that, nitrogen atoms present as impurities and recombined on the cathode surface and/or field emission determine the breakdown time delay down to the cosmic rays and natural radioactivity level.

  5. Flow Parameters of Argon plasma Discharge

    International Nuclear Information System (INIS)

    Owing to the viscosity, the plasma will be adhering to the inner surface of the outer electrode and outer surface of the inner one. As result that the discharge will be eroding the walls of coaxial system. The thickness of the boundary layer near the walls has been estimated at different positions from the breech of coaxial plasma gun. It is found that the thickness of layer 0.008 cm at the end of inner electrode (17 cm). A coaxial plasma gun device is operated in argon gas at ambient pressure 0.6 Torr and discharge voltage about 10 KV. The electron temperature of argon discharge has been determined by using spectroscopic technique. It is found that kTe=3.4 eV. By knowing the thickness of the boundary layer, the density can be determined. The Reynolds number R=105 and Mach number M=5 i.e. the flow is compressible and hypersonic

  6. ATLAS liquid argon calorimeter back end electronics

    CERN Document Server

    Bán, J; Bellachia, F; Blondel, A; Böttcher, S; Clark, A; Colas, Jacques; Díaz-Gómez, M; Dinkespiler, B; Efthymiopoulos, I; Escalier, M; Fayard, Lo; Gara, A; He, Y; Henry-Coüannier, F; Hubaut, F; Ionescu, G; Karev, A; Kurchaninov, L; Lafaye, R; Laforge, B; La Marra, D; Laplace, S; Le Dortz, O; Léger, A; Liu, T; Martin, D; Matricon, P; Moneta, L; Monnier, E; Oberlack, H; Parsons, J A; Pernecker, S; Perrot, G; Poggioli, L; Prast, J; Przysiezniak, H; Repetti, B; Rosselet, L; Riu, I; Schwemling, P; Simion, S; Sippach, W; Strässner, A; Stroynowski, R; Tisserant, S; Unal, G; Wilkens, H; Wingerter-Seez, I; Xiang, A; Yang, J; Ye, J

    2007-01-01

    The Liquid Argon calorimeters play a central role in the ATLAS (A Toroidal LHC Apparatus) experiment. The environment at the Large Hadron Collider (LHC) imposes strong constraints on the detectors readout systems. In order to achieve very high precision measurements, the detector signals are processed at various stages before reaching the Data Acquisition system (DAQ). Signals from the calorimeter cells are received by on-detector Front End Boards (FEB), which sample the incoming pulse every 25ns and digitize it at a trigger rate of up to 75~kHz. Off-detector Read Out Driver (ROD) boards further process the data and send reconstructed quantities to the DAQ while also monitoring the data quality. In this paper, the ATLAS Liquid Argon electronics chain is described first, followed by a detailed description of the off-detector readout system. Finally, the tests performed on the system are summarized.

  7. Horse shoe retinal tear, vitreous hemorrage, macular pucker 15 months after laser in Situ keratomileusis: case report

    Directory of Open Access Journals (Sweden)

    Gholamhossein Yaghoobi

    2013-02-01

    Full Text Available A 44 year old woman presented with decreased vision and floaters, started since 4 days before, in her right eye referred to our ophthalmology clinic. On examination, it was found that the best corrected visual acuity was limited to R-E: 20/80 and that of the left eye: 20/20. Fundus examination of the right eye revealed a rhegmatogenous subclinical retinal detachment and vitreous hemorrhage 15 months after surgery for myopia, but the left fundus was normal. Barrier diod laser photocoagulation around the tear was done. Subclinical retinal detachment and vitreous hemorrhage resolved one month after barrier laser photocoagulation, but visual acuity of patient reduced to 3/200 due to development of macular pucker.

  8. Current and future liquid argon neutrino experiments

    International Nuclear Information System (INIS)

    The liquid argon time projection chamber (LArTPC) detector technology provides an opportunity for precision neutrino oscillation measurements, neutrino cross section measurements, and searches for rare processes, such as SuperNova neutrino detection. These proceedings review current and future LArTPC neutrino experiments. Particular focus is paid to the ICARUS, MicroBooNE, LAr1, 2-LArTPC at CERN-SPS, LBNE, and 100 kton at Okinoshima experiments

  9. Influence of an external circuit on the pinch time in argon-filled capillary Z-pinch

    International Nuclear Information System (INIS)

    In this paper, we present a theoretical and experimental study on a capillary discharge for soft X-ray lasers. The theoretical analysis is based on the so called '' snow-plow '' model. By this model, it is possible to calculate pinch time as a function of current, gas pressure, tube diameter, discharge capacitance and inductance. In laboratory we have used table-top argon filled soft X-ray laser. By use of this machine, one can change the current from 10 kA to 35 kA, argon gas pressure from 100 mTorr to 800 mTorr. The laser output pulse was detected by an XRD. The calculated and measured results of pinch time are compared. (author)

  10. Liquid argon imaging a novel detection technology

    CERN Document Server

    Rubbia, Carlo

    2002-01-01

    Ionisation electrons may drift over large distances (meters) in a volume of highly purified liquid argon (O2 equivalent less than 0.1 ppb!) under the action of an electric field. With an appropriate readout system (i.e. a set of fine pitch wire grids) we have realised a massive, continuously sensitive 'bubble chamber' with multiple readouts of the same, small charge (a minimum ionising track segment, 2 mm long, yields • 10000 electrons). We have developed this technology since 1987, initially with small laboratory devices and later with progressively larger and more sophisticated detectors, the latest being the T600 module (740 ton of liquid Argon), which has been operated in Pavia, as a step toward the ICARUS programme in the Gran Sasso Laboratory (LNGS). With cloning of T600 we aim at a 3000 ton detector by 2005. Argon is a medium with density 1.4 g/cm3, similar in characteristics to the heavy freon used in the famous Gargamelle. With wire pitches of 2-3 mm, it provides an extremely high spatial re...

  11. Distribution and Abundance of Mars' Atmospheric Argon

    Science.gov (United States)

    Sprague, A. L.; Boynton, W. V.; Kerry, K. E.; Nelli, Steven; Murphy, Jim; Reedy, R. C.; Metzger, A. E.; Hunten, D. M.; Janes, K. D.; Crombie, M. K.

    2005-01-01

    One and one half Mars years (MY 26 and 27) of atmospheric Argon measurements are described and studied in the context of understanding how Argon, a minor constituent of Mars atmosphere that does not condense at Mars temperatures, can be used to study martian circulation and dynamics. Argon data are from the 2001 Mars Odyssey Gamma Subsystem (GS) of the suite of three instruments comprising the Gamma Ray Spectrometer (GRS). A comprehensive data analysis including gamma-ray production and attenuation by the atmosphere is included. Of particular interest is the enhanced abundance of Ar over the observed Ar abundance at lower latitudes at south (up to a factor of 10) and north (up to a factor of 4) polar regions during winter. Calibration of the measurements to actual Ar abundance is possible because GS measurements cover the same latitude and season as measurements made by the gas chromatograph mass spectrometer (GCMS) on Viking Landers 1 and 2 (VL1 and VL2). [2].

  12. Simultaneous operation of a test apparatus filled with liquid argon as bubble chamber, calorimeter and scintillation detector

    International Nuclear Information System (INIS)

    Physics motivations for the use of argon as a new bubble chamber liquid are discussed. Results, obtained from a 2.7 1 argon detector in SPS and SC beams at CERN, comprise its track sensitivity to ionizing particles and to a laser beam in the bubble chamber mode, its use as a calorimeter through the collection of free charges in an electric field and the recording of the scintillation light produced by ionizing particles. Various interference phenomena during the simultaneous use of the hybrid properties, as well as purity requirements on the liquid are discussed. Furthermore, nitrogen and argon/nitrogen mixtures were investigated. Applications of our technique for neutrino experiments at TeV accelerators and as vertex detectors are briefly outlined. In-line holography, successfully tested in BEBC, could simplify the optical track recording and improve the resolution in very large detectors. (orig.)

  13. Combined vitrectomy and intravitreal injection versus combined laser and injection for treatment of intractable diffuse diabetic macular edema

    OpenAIRE

    Saeed, Ahmed Mohammed

    2013-01-01

    Ahmed M SaeedDepartment of Ophthalmology, Benha University, Benha, EgyptBackground: The purpose of this study was to compare the safety and efficacy of combined vitrectomy, intravitreal triamcinolone acetonide (IVTA), and bevacizumab injection with that of IVTA and bevacizumab injection and subsequent macular grid laser photocoagulation for the treatment of intractable diffuse diabetic macular edema.Methods: This randomized controlled clinical trial was performed at Benha University Hospital,...

  14. Parametric scaling of neutral and ion excited state densities in an argon helicon source

    Science.gov (United States)

    McCarren, D.; Scime, E.

    2016-04-01

    We report measurements of the absolute density and temperature of ion and neutral excited states in an argon helicon source. The excited ion state density, which depends on ion density, electron density, and electron temperature, increases sharply with increasing magnetic field in the source. The neutral argon metastable density measurements are consistent with an increasing ionization fraction with increasing magnetic field strength. The ion temperature shows no evidence of increased heating with increasing magnetic field strength (which has only been observed in helicon sources operating at driving frequencies close to the lower hybrid frequency). The measurements were obtained through cavity ring down spectroscopy, a measurement technique that does not require the target excited state to be metastable or part of a fluorescence scheme; and is therefore applicable to any laser accessible atomic or ionic transition in a plasma.

  15. Effects of argon gas pressure on its metastable-state density in high-density plasmas

    International Nuclear Information System (INIS)

    The effect of argon gas pressure on its metastable density in inductively coupled plasmas (ICPs) is investigated by using the laser-induced fluorescence method. Our results show that the metastable-state density of argon varies with the gas pressure depending on the measurement position; the density decreases with the pressure at a position far from the ICP antenna, whereas it increases with the pressure at a position near the antenna. This contrast in the metastable-state density trend with the pressure is explained by considering the electron temperature variations at the two measurement positions. The theoretical interpretation and calculation using a global model are also addressed in detail in this paper

  16. Electron energy distributions and excitation rates in high-frequency argon discharges

    International Nuclear Information System (INIS)

    The electron energy distribution functions and rate coefficients for excitation and ionisation in argon under the action of an uniform high-frequency electric field were calculated by numerically solving the homogeneous Boltzmann equation. Analytic calculations in the limiting cases ω>>νsub(c) and ω<<νsub(c), where ω is the wave angular frequency and νsub(c) is the electron-neutral collision frequency for momentum transfer, are also presented and shown to be in very good agreement with the numerical computations. The results reported here are relevant for the modelling of high-frequency discharges in argon and, in particular, for improving recent theoretical descriptions of a plasma column sustained by surface microwaves. The properties of surface wave produced plasmas make them interesting as possible substitutes for other more conventional plasma sources for such important applications as plasma chemistry laser excitation, plasma etching spectroscopic sources etc...

  17. Laser in operative dentistry

    Directory of Open Access Journals (Sweden)

    E. Yasini

    1994-06-01

    Full Text Available Today laser has a lot of usage in medicine and dentistry. In the field of dentistry, laser is used in soft tissue surgery, sterilization of canals (in root canal therapy and in restorative dentistry laser is used for cavity preparation, caries removal, sealing the grooves (in preventive dentistry, etching enamel and dentin, composite polymerization and removal of tooth sensitivity. The use of Co2 lasers and Nd: YAG for cavity preparation, due to creating high heat causes darkness and cracks around the region of laser radiation. Also due to high temperature of these lasers, pulp damage is inevitable. So today, by using the Excimer laser especially the argon floride type with a wavelength of 193 nm, the problem of heat stress have been solved, but the use of lasers in dentistry, especially for cavity preparation needs more researches and evaluations.

  18. Effects of metastable species in helium and argon atmospheric pressure plasma jets (APPJs) on inactivation of periodontopathogenic bacteria

    Science.gov (United States)

    Yoon, Sung-Young; Kim, Kyoung-Hwa; Seol, Yang-Jo; Kim, Su-Jeong; Bae, Byeongjun; Huh, Sung-Ryul; Kim, Gon-Ho

    2016-05-01

    The helium and argon have been widely used as discharge gases in atmospheric pressure plasma jets (APPJs) for bacteria inactivation. The APPJs show apparent different in bullet propagation speed and bacteria inactivation rate apparently vary with discharge gas species. This work shows that these two distinctive features of APPJs can be linked through one factor, the metastable energy level. The effects of helium and argon metastable species on APPJ discharge mechanism for reactive oxygen nitrogen species (RONS) generation in APPJs are investigated by experiments and numerical estimation. The discharge mechanism is investigated by using the bullet velocity from the electric field which is obtained with laser induced fluorescence (LIF) measurement. The measured electric field also applied on the estimation of RONS generation, as electron energy source term in numerical particle reaction. The estimated RONS number is verified by comparing NO and OH densities to the inactivation rate of periodontitis bacteria. The characteristic time for bacteria inactivation of the helium-APPJ was found to be 1.63 min., which is significantly less than that of the argon-APPJ, 12.1 min. In argon-APPJ, the argon metastable preserve the energy due to the lack of the Penning ionization. Thus the surface temperature increase is significantly higher than helium-APPJ case. It implies that the metastable energy plays important role in both of APPJ bullet propagation and bacteria inactivation mechanism.

  19. Development of a low-cost inductively coupled argon plasma

    International Nuclear Information System (INIS)

    The aim of this investigation is to drastically reduce running costs of an inductively coupled plasma. This is done by reducing the argon consumption from 20 l/min to about 1 l/min. First, a sample introduction system operating on 0.1 l/min of carrier argon is described. This system ensures a high ratio of plasma argon and carrier argon even at the low total argon consumptions intended. Next, the developed low consumption plasma is presented. In the proposed design, air is blown perpendicularly against the outside of the torch. A different coil has been developed to make air-cooling efficient. Preliminary data on coupling efficiency for the air-cooled plasma are presented. A similarly low argon consumption has been achieved with water as an external coolant medium. It is concluded that a cheaper alternative to the current ICP has become available. (Auth.)

  20. Direct WIMP Detection Using Scintillation Time Discrimination in Liquid Argon

    OpenAIRE

    Boulay, M. G.; Hime, A.

    2004-01-01

    Discrimination between electron and nuclear recoil events in a liquid argon scintillation detector has been demonstrated with simulations by using the differences in the scintillation photon time distribution between these classes of events. A discrimination power greater than 10^{8} is predicted for a liquid argon experiment with a 10 keV threshold, which would mitigate electron and gamma-ray backgrounds, including beta decays of 39-Ar and 42-Ar in atmospheric argon. A dark matter search usi...

  1. 喉罩下经支气管镜钬激光联合氩气刀和二氧化碳冷冻治疗儿童获得性重度声门下狭窄%Study on tracheal intubation related severe subglottic stenosis under laryngeal mask by using holmium laser combined with argon plasma coagulation and cryotherapy through bronchoscopy

    Institute of Scientific and Technical Information of China (English)

    许煊; 祝彬; 石苗茜; 任海丽; 封志纯

    2015-01-01

    目的:探讨2例气管插管相关性重度声门下狭窄喉罩下支气管镜诊断及介入治疗的操作方法、有效性及安全性。方法2例男性患儿,年龄分别为4和11个月,因气管插管后出现脱机困难及呼吸困难,经CT及支气管镜检查,诊断为气管插管相关的重度声门下狭窄,在对家长进行详细告知支气管镜下介入手术不可预知情况并由家长签字同意后,遂对2例患儿进行经喉罩支气管镜下钬激光联合氩气刀和二氧化碳( CO2)冷冻治疗,分析患儿的临床资料、并发症及术后转归、随访情况。结果2例手术过程顺利,例1术后紧贴声门下的肉芽组织被完全清除,2例患儿声门下环形狭窄完全解除,治疗前呼吸道狭窄处周长约2.5 mm,治疗后,周长达5.2 mm,4.0 mm支气管镜进出无障碍,术后气管导管均成功拔除,呼吸困难均明显改善。2例患儿治疗后即刻、7 d、30 d和90 d镜下检查结果示狭窄处开放良好。术中有血氧饱和度下降及心率增快或减慢,暂停操作及恢复给氧后立即恢复,术中及术后未见异常血流动力学改变,2例目前仍在随访中。结论经喉罩钬激光、氩气刀及CO2冷冻治疗可用于后天性肉芽组织增生引起的声门下狭窄,方法安全、有效,近期效果显著,远期仍在进一步随访评估。%Objective To explore the operating methods,the effectiveness and safety for 2 cases of tracheal in-tubation related severe subglottic stenosis under laryngeal mask by using bronchoscopy in the diagnosis and interven-tional treatment. Methods Two male patients ( age at 4 and 11 months) both had difficulty breathing and weaning failure after endotracheal intubation,who were diagnosed with severe subglottic stenosis through CT and bronchoscopy examination. All parents signed their consent after being fully informed of treatment risks. Two cases were treated under bronchoscopic holmium laser combined with argon plasma coagulation and

  2. Effects of Nitrogen contamination in liquid Argon

    Science.gov (United States)

    Acciarri, R.; Antonello, M.; Baibussinov, B.; Baldo-Ceolin, M.; Benetti, P.; Calaprice, F.; Calligarich, E.; Cambiaghi, M.; Canci, N.; Carbonara, F.; Cavanna, F.; Centro, S.; Cocco, A. G.; Di Pompeo, F.; Fiorillo, G.; Galbiati, C.; Gallo, V.; Grandi, L.; Meng, G.; Modena, I.; Montanari, C.; Palamara, O.; Pandola, L.; Piano Mortari, G. B.; Pietropaolo, F.; Raselli, G. L.; Roncadelli, M.; Rossella, M.; Rubbia, C.; Segreto, E.; Szelc, A. M.; Ventura, S.; Vignoli, C.

    2010-06-01

    A dedicated test of the effects of Nitrogen contamination in liquid Argon has been performed at the INFN-Gran Sasso Laboratory (LNGS, Italy) within the WArP R&D program. A detector has been designed and assembled for this specific task and connected to a system for the injection of controlled amounts of gaseous Nitrogen into the liquid Argon. The purpose of the test is to detect the reduction of the Ar scintillation light emission as a function of the amount of the Nitrogen contaminant injected in the Argon volume. A wide concentration range, spanning from ~ 10-1 ppm up to ~ 103 ppm, has been explored. Measurements have been done with electrons in the energy range of minimum ionizing particles (γ-conversion from radioactive sources). Source spectra at different Nitrogen contaminations are analyzed, showing sensitive reduction of the scintillation yield at increasing concentrations. Direct PMT signal acquisition exploiting high time resolution by fast waveform recording allowed high precision extraction of the main characteristics of the scintillation light emission in contaminated LAr. In particular, the decreasing behavior in lifetime and relative amplitude of the slow component is found to be appreciable starting from Script O(1 ppm) of Nitrogen concentrations. The rate constant of the quenching process induced by Nitrogen in liquid Ar has been found to be kQ(N2) = 0.11 ± 0.01 μs-1ppm-1, consistent with a previous measurement of this quantity but with significant improvement in precision. On the other hand, no evidence for absorption by N2 impurities has been found up to the higher concentrations here explored.

  3. HARP: high pressure argon readout for calorimeters

    International Nuclear Information System (INIS)

    Steel tubes of approximately 8 mm O.D., filled with Argon gas to approx.200 bar, are considered as the active element for a charge collecting sampling calorimeter readout system. The tubes are permanently sealed and operated in the ion chamber mode, with the charge collection on a one-millimeter concentric anode. We present the motivation for such a device, including Monte Carlo predictions of performance. The method of construction and signal collection are discussed, with initial results on leakage and ageing of the filling gas. A prototype electromagnetic calorimeter is described

  4. Argon isotope fractionation induced by stepwise heating

    Science.gov (United States)

    Trieloff, Mario; Falter, Martina; Buikin, Alexei I.; Korochantseva, Ekaterina V.; Jessberger, Elmar K.; Altherr, Rainer

    2005-03-01

    Noble gas isotopes are widely used to elucidate the history of the rocks in which they have been trapped, either from distinct reservoirs or by accumulation following radioactive decay. To extract noble gases from their host rocks, stepwise heating is the most commonly used technique to deconvolve isotopically different components, e.g., atmospheric, in situ radiogenic, or excess radiogenic from mantle or crustal reservoirs. The accurate determination of the isotopic composition of these different components is of crucial importance, e.g., for ages obtained by 40Ar- 39Ar stepheating plateaus. However, diffusion theory-based model calculations predict that the stepwise thermal extraction process from mineral phases induces isotope fractionation and, hence, adulterates the original composition. Such effects are largely unconsidered, as they are small and a compelling experimental observation is lacking. We report the first unequivocal evidence for significant mass fractionation of argon isotopes during thermal extraction, observed on shungite, a carbon-rich Precambrian sedimentary rock. The degree of fractionation, as monitored by 38Ar/ 36Ar and 40Ar/ 36Ar ratios, very well agrees with theoretical predictions assuming an inverse square root dependence of diffusion coefficient and atomic mass, resulting in easier extraction of lighter isotopes. Hence, subatmospheric 40Ar/ 36Ar ratios obtained for argon extracted at low temperatures may not represent paleoatmospheric argon. Shungite argon resembles modern atmospheric composition, but constraints on the timing of trapping appear difficult to obtain, as shungites are multicomponent systems. In 40Ar- 39Ar stepwise heating, the isotope fractionation effect could cause systematic underestimations of plateau ages, between 0.15 and 0.4% depending on age, or considerably higher if samples contain appreciable atmospheric Ar. The magnitude of this effect is similar to the presently achieved uncertainties of this increasingly

  5. Near-infrared scintillation of liquid argon

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, T. [Fermilab; Escobar, C. O. [Campinas State U.; Lippincott, W. H. [Fermilab; Rubinov, P. [Fermilab

    2016-03-03

    Since the 1970s it has been known that noble gases scintillate in the near infrared (NIR) region of the spectrum (0.7 $\\mu$m < $\\lambda$; < 1.5$\\mu$m). More controversial has been the question of the NIR light yield for condensed noble gases. We first present the motivation for using the NIR scintillation in liquid argon detectors, then briefly review early as well as more recent efforts and finally show encouraging preliminary results of a test performed at Fermilab.

  6. Near-infrared scintillation of liquid argon

    CERN Document Server

    Alexander, T; Lippincott, W H; Rubinov, P

    2016-01-01

    Since the 1970s it has been known that noble gases scintillate in the near infrared (NIR) region of the spectrum (0.7 $\\mu$m < $\\lambda$; < 1.5$\\mu$m). More controversial has been the question of the NIR light yield for condensed noble gases. We first present the motivation for using the NIR scintillation in liquid argon detectors, then briefly review early as well as more recent efforts and finally show encouraging preliminary results of a test performed at Fermilab.

  7. Argon Purification Studies and a Novel Liquid Argon Re-circulation System

    CERN Document Server

    Mavrokoridis, K; Coleman, J; Lightfoot, P K; McCauley, N; McCormick, K J; Touramanis, C

    2011-01-01

    Future giant liquid argon (LAr) time projection chambers (TPCs) require a purity of better than 0.1 parts per billion (ppb) to allow the ionised electrons to drift without significant capture by any electronegative impurities. We present a comprehensive study of the effects of electronegative impurity on gaseous and liquid argon scintillation light, an analysis of the efficacy of various purification chemicals, as well as the Liverpool LAr setup, which utilises a novel re-circulation purification system. Of the impurities tested - Air, O_2, H_2O, N_2 and CO_2 in the range of between 0.01 ppm to 1000 ppm - H_2O was found to have the most profound effect on gaseous argon scintillation light, and N_2 was found to have the least. Additionally, a correlation between the slow component decay time and the total energy deposited with 0.01 ppm - 100 ppm O_2 contamination levels in liquid argon has been established. The superiority of molecular sieves over anhydrous complexes at absorbing Ar gas, N_2 gas and H_2O vapou...

  8. 联合方法治疗新生血管性青光眼疗效观察%Compound T rabeculectomy and Retinal Photocoagulation and Vitreous Injection Ranibizumab in the M anagement of New Vascular Glaucoma

    Institute of Scientific and Technical Information of China (English)

    林芳; 齐美华; 赵静

    2015-01-01

    Objective To comparatively evaluate the efficacy and safety profiles of compound trabeculecto-my and Retinal photocoagulation and Vitreous injection Ranibizumab in the management of New vascular glauco-ma .Method Clinical records of 8 patients (8 eyes) with New vascular glaucoma secondary to RVO whose fun-dus oculi can be watched to be treated with Retinal laser photocoagulation first the pathants were threated with Retinal laser photocoagulation ,the second were Vitreous injection Ranibizumab seven days with compound tra-beculectomy after surgery ,according to patients iop and Anterior chamber to teach patients to learning Eye mas-sage?Record visions ,central macular thickness(CM T ) ,intraocular pressure(IOP) ,the degrade of Retinal neo-vascularization of fundus oculi and new vessels changes of iris and angles in Preoperative and postoperative 3 months ,6 months ,1 2 months .Result The Vision:3 months:(0 .0 4 ± 0 .0 4 ) ,6 months:(0 .0 6 ± 0 .0 5 ) ,1 2 months:(0 .0 5 ± 0 .0 4 ) ,4 eye’s Vision were improved 3 eye’s Vision werenot improved .The one eye is No light perception .IOP:3 months:(1 3 .2 4 ± 2 .2 3 )mmhg ,6 months:(1 5 .4 ± 2 3 .4 2 )mmhg ,1 2 months:(1 8 .2 5 ± 3 .1 5 ) mmhg ,6 patients can controled IOP under 2 1 mmhg ,postoperative one patient iop can be controled in normal in first 3 months ,give Alphagan eye water in rising to 2 1 mmhg of iop ,iop can be control in 1 8 mmhg ,6 months lat-er the iop rise to 1 9 mmhg ,in 9 months the iop rised to 2 1 mmhg ,Brinzolamide eye water was used ,iop can be control in 2 0 mmhg ,in 1 2 months ,iop is 2 2 mmhg ,2 2 mmhg ,in Process ,the patient Supplement Retinal photo-coagulation twice new vessels changes of iris and angles:5 cases degrade ,3 cases Reduce ,FFA :Capillary zone de-grade of 5 cases;Capillary zone degrade of 3 cases in Supplement Retinal laser photocoagulation ,CM T :Before treatment and1 week ,2 weeks ,4 weeks ,8 weeks ,1 2 weeks after Vitreous cavity injection was:(4 4 0 .3 6 ± 5 0

  9. ARGON RECOIL ION ELECTRON CAPTURE FROM NEUTRAL ARGON AND HELIUM STUDIED BY TIME RESOLVED V.U.V. SPECTROSCOPY

    OpenAIRE

    Lesteven-Vaisse, I.; Chantepie, M.; Folkmann, F.; Lecler, D.; Ben Sitel, A.

    1989-01-01

    Electron capture phenomena in recoil ion V.U.V. spectroscopy are tested through the evolution of the observed argon spectrum by introduction of helium in addition to argon in the collision chamber. Taking into account these mixed gas data by the time-differential method and using decay time analysis, an improved analysis of argon recoil ion V.U.V. radiation is presented.

  10. Electron scattering and transport in liquid argon

    International Nuclear Information System (INIS)

    The transport of excess electrons in liquid argon driven out of equilibrium by an applied electric field is revisited using a multi-term solution of Boltzmann’s equation together with ab initio liquid phase cross-sections calculated using the Dirac-Fock scattering equations. The calculation of liquid phase cross-sections extends previous treatments to consider multipole polarisabilities and a non-local treatment of exchange, while the accuracy of the electron-argon potential is validated through comparison of the calculated gas phase cross-sections with experiment. The results presented highlight the inadequacy of local treatments of exchange that are commonly used in liquid and cluster phase cross-section calculations. The multi-term Boltzmann equation framework accounting for coherent scattering enables the inclusion of the full anisotropy in the differential cross-section arising from the interaction and the structure factor, without an a priori assumption of quasi-isotropy in the velocity distribution function. The model, which contains no free parameters and accounts for both coherent scattering and liquid phase screening effects, was found to reproduce well the experimental drift velocities and characteristic energies

  11. Pollution of liquid argon after neutron irradiation

    CERN Document Server

    Andrieux, M L; Collot, J; de Saintignon, P; Ferrari, A; Hostachy, J Y; Hoummada, A; Martin, P; Merkel, B; Puzo, P; Sauvage, D; Wielers, M

    2001-01-01

    The purpose of the neutron facility installed at SARA is to investigate the behavior of various materials to be used in the ATLAS liquid argon calorimeter, when submitted to fast neutron radiation. The samples are placed in a liquid argon cryostat a few cm away from the neutron source. Various pieces of the electromagnetic calorimeter have been tested in order to evaluate the rate of pollution of the liquid and consequently the possible signal loss in energy measurements. The average fluence was equivalent to the maximum expected in the calorimeter in about 10 years. The most striking feature of the results is that the pollution is not due to oxygen, at least for most of it. Using a particular value of the absorption length derived from these data, a simulation was carried out and the energy signal loss in the calorimeter could be predicted. Within the limits of our present knowledge, the conclusion is that damages due to this pollution will not be a problem. (17 refs).

  12. Pollution of liquid argon after neutron irradiation

    International Nuclear Information System (INIS)

    The purpose of the neutron facility installed at SARA is to investigate the behavior of various materials to be used in the ATLAS liquid argon calorimeter, when submitted to fast neutron radiation. The samples are placed in a liquid argon cryostat a few cm away from the neutron source. Various pieces of the electromagnetic calorimeter have been tested in order to evaluate the rate of pollution of the liquid and consequently the possible signal loss in energy measurements. The average fluence was equivalent to the maximum expected in the calorimeter in about 10 years. The most striking feature of the results is that the pollution is not due to oxygen, at least for most of it. Using a particular value of the absorption length derived from these data, a simulation was carried out and the energy signal loss in the calorimeter could be predicted. Within the limits of our present knowledge, the conclusion is that damages due to this pollution will not be a problem

  13. Ion-beam excitation of liquid argon

    CERN Document Server

    Hofmann, M; Heindl, T; Neumeier, A; Oberauer, L; Potzel, W; Roth, S; Schönert, S; Wieser, J; Ulrich, A

    2015-01-01

    The scintillation light of liquid argon has been recorded wavelength and time resolved with very good statistics in a wavelength interval ranging from 118 nm through 970 nm. Three different ion beams, protons, sulfur ions and gold ions, were used to excite liquid argon. Only minor differences were observed in the wavelength-spectra obtained with the different incident particles. Light emission in the wavelength range of the third excimer continuum was found to be strongly suppressed in the liquid phase. In time-resolved measurements, the time structure of the scintillation light can be directly attributed to wavelength in our studies, as no wavelength shifter has been used. These measurements confirm that the singlet-to-triplet intensity ratio in the second excimer continuum range is a useful parameter for particle discrimination, which can also be employed in wavelength-integrated measurements as long as the sensitivity of the detector system does not rise steeply for wavelengths longer than 190 nm. Using ou...

  14. Laser ablation of human atherosclerotic plaque without adjacent tissue injury

    Science.gov (United States)

    Grundfest, W. S.; Litvack, F.; Forrester, J. S.; Goldenberg, T.; Swan, H. J. C.

    1985-01-01

    Seventy samples of human cadaver atherosclerotic aorta were irradiated in vitro using a 308 nm xenon chloride excimer laser. Energy per pulse, pulse duration and frequency were varied. For comparison, 60 segments were also irradiated with an argon ion and an Nd:YAG laser operated in the continuous mode. Tissue was fixed in formalin, sectioned and examined microscopically. The Nd:YAG and argon ion-irradiated tissue exhibited a central crater with irregular edges and concentric zones of thermal and blast injury. In contrast, the excimer laser-irradiated tissue had narrow deep incisions with minimal or no thermal injury. These preliminary experiments indicate that the excimer laser vaporizes tissue in a manner different from that of the continuous wave Nd:YAG or argon ion laser. The sharp incision margins and minimal damage to adjacent normal tissue suggest that the excimer laser is more desirable for general surgical and intravascular uses than are the conventionally used medical lasers.

  15. Bilateral Simultaneous Rhegmatogenous Retinal Detachment following Laser in situ Keratomileusis

    Directory of Open Access Journals (Sweden)

    Erhan Yumusak

    2016-06-01

    Full Text Available A 21-year-old woman developed simultaneous rhegmatogenous retinal detachment after laser in situ keratomileusis (LASIK in both eyes. She underwent pars plana vitrectomy surgery combined with endolaser photocoagulation and silicone oil tamponade in the right eye. A week later, pneumatic retinopexy was done in the left eye. As the retinal tear did not seal, 360° scleral buckling surgery was performed and retina was attached. Bilateral simultaneous rhegmatogenous retinal detachment after LASIK for correction of myopia can be a serious complication. Patients should be informed about the possibility of this complication.

  16. The Effect of the Argon Carrier Gas in the Multiphoton Dissociation-Ionization of Tetracene

    OpenAIRE

    Carmen Cisneros; Ignacio ÃÂlvarez; Alfonso Guerrero; Alejandro San Román; Juan Carlos Poveda

    2008-01-01

    The multiphoton dissociation-ionization of tetracene at 355 nm using 6.5 nanosecond laser pulses, with and without argon as a carrier gas (CG), has been studied and compared. Ion fragments were analyzed in a time-of-flight mass spectrometer and separated according to their mass-to-charge ratio (m/z). The results show that the dynamic of photodissociation at ~1010 W⋅cm-2 intensities is strongly influenced by the CG. The suppression of fragmentation channels primarily those relating to the...

  17. Two-photon excitation/ionization of the 1s-shell of the argon atom

    CERN Document Server

    Novikov, S A

    2002-01-01

    The absolute values and the shape of the two-photon excitation/ionization cross section of the 1s-shell of the argon atom are calculated with inclusion of the many-particle effects, i.e., the relaxation of the atomic residue in the field of the vacancies created, and the decay of the vacancies into the channels of Auger and (or) radiative types. The wavefunctions of the one-particle states are calculated in non-relativistic approximation. The calculations are performed for both linear and circular polarization of the laser beam.

  18. Two-photon excitation/ionization of the 1s-shell of the argon atom

    International Nuclear Information System (INIS)

    The absolute values and the shape of the two-photon excitation/ionization cross section of the 1s-shell of the argon atom are calculated with inclusion of the many-particle effects, i.e., the relaxation of the atomic residue in the field of the vacancies created, and the decay of the vacancies into the channels of Auger and (or) radiative types. The wavefunctions of the one-particle states are calculated in non-relativistic approximation. The calculations are performed for both linear and circular polarization of the laser beam.

  19. Low-energy structure in the ionization of argon:Comparison of experiment with theory

    Institute of Scientific and Technical Information of China (English)

    Feng Li-Qiang; Chu Tian-Shu; Wang Li

    2013-01-01

    The above-threshold ionization of argon in an intense 70-fs,400-nm linearly polarized laser pulse has been investigated by the velocity map imaging techniques,combined with an attosecond-resolution quantum wave packet dynamics method.There is a quantitative agreement in all dominant features between the experiment and the theory.Moreover,a peak-splitting phenomenon in the first energy peak has been observed at high pulse intensity.Further,through the theoretical analysis,an ac Stark splitting with evident resonant and nonresonant ionization pathways has been found to be the physical reason for the experimental observations.

  20. Argon metastable state densities in inductively coupled plasma in mixtures of Ar and O2

    International Nuclear Information System (INIS)

    We have measured the densities of 1s5 and 1s3 argon metastables as a function of the abundance of molecular oxygen in an inductively coupled plasma (ICP) in mixtures of Ar and O2. Laser absorption spectroscopy was used to determine the densities of the metastables. It was found that even small abundances of oxygen lead to large increases in metastable density, mostly due to the reduction in the electron number density, since electron-induced quenching determines the metastable density. At abundances higher than 7% to 15% for powers between 50 and 150 W, quenching by oxygen molecules begins to dominate and the metastable density drops again.

  1. Refractive outcome following diode laser versus cryotherapy for eyes with retinopathy of prematurity.

    OpenAIRE

    Algawi, K; Goggin, M; O'Keefe, M.

    1994-01-01

    The refractive error in 15 eyes with threshold retinopathy of prematurity treated with diode laser photocoagulation was compared with 25 eyes with the same disease severity treated by cryotherapy. Myopia was present in 40% (six eyes) of the first group ranging from -1.50 to -3.50 dioptres; while 92% (23 eyes) showed myopia which ranged from -0.50 to -8.00 dioptres in the cryotherapy group. Sixty per cent (nine eyes) were hypermetropic at less than +3.0 dioptres in the laser group, while only ...

  2. Prophylactic laser treatment in early age related maculopathy reduced the incidence of exudative complications

    OpenAIRE

    Frennesson, C; Nilsson, S.

    1998-01-01

    AIM—To investigate the effect of prophylactic laser treatment on drusen area and incidence of exudative lesions in patients with soft drusen maculopathy.
METHODS—In a prospective study, patients with early age related maculopathy (ARM) and good visual acuity were randomised to laser treatment or to a control group. Each group consisted of two subgroups: a fellow eye group and a bilateral drusen group. At 3 years, 36 of 38 enrolled patients remained in the study. Photocoagulation was performed...

  3. Extremely Nonlinear Optics Using Shaped Pulses Spectrally Broadened in an Argon- or Sulfur Hexafluoride-Filled Hollow-Core Fiber

    OpenAIRE

    Andreas Hoffmann; Michael Zürch; Christian Spielmann

    2015-01-01

    In this contribution we present a comparison of the performance of spectrally broadened ultrashort pulses using a hollow-core fiber either filled with argon or sulfur hexafluoride (SF6) for demanding pulse-shaping experiments. The benefits of both gases for pulse-shaping are studied in the highly nonlinear process of high-harmonic generation. In this setup, temporally shaping the driving laser pulse leads to spectrally shaping of the output extreme ultraviolet (XUV) spectrum, where total yie...

  4. Nitrogen Removal from Molten Steel under Argon DC Glow Plasma

    Institute of Scientific and Technical Information of China (English)

    SUN Ming-shan; DING Wei-zhong; LU Xiong-gang

    2005-01-01

    Under argon DC glow plasma, the nitrogen removal from molten steel was studied. The experimental result showed that nitrogen mass percent could be reduced to 0.000 8%. The change of polarity had no impact on nitrogen removal when the nitrogen mass percent was low. The mechanism of denitrogenation of molten steel under argon DC glow plasma was discussed.

  5. WARP: a double phase argon programme for dark matter detection

    International Nuclear Information System (INIS)

    WARP (Wimp ARgon Programme) is a double phase Argon detector for Dark Matter search under construction at Laboratori Nazionali del Gran Sasso. We present recent results obtained operating a prototype with a sensitive mass of 2.3 litres deep underground

  6. Stopping Power of Solid Argon for Helium Ions

    DEFF Research Database (Denmark)

    Besenbacher, F.; Bøttiger, Jørgen; Grauersen, O.;

    1981-01-01

    By means of the Rutherford-backscattering method, the stopping cross section of solid argon has been measured for 0.5–3 MeV helium ions to an accuracy of not, vert, similar3%. The results agree within the experimental accuracies with our earlier measurements for gaseous argon over the energy region...

  7. Análise química e morfológica do esmalte dentário humano tratado com laser argônio durante a colagem ortodôntica Chemical and morphological analysis of the human dental enamel treated with argon laser during orthodontic bonding

    OpenAIRE

    Glaucio Serra Guimarães; Liliane Siqueira de Morais; Carlos Nelson Elias; Carlos André de Castro Pérez; Ana Maria Bolognese

    2011-01-01

    INTRODUÇÃO: as principais utilizações do laser argônio na Ortodontia são a redução do tempo de polimerização durante a colagem ortodôntica e o aumento da resistência à cárie do esmalte dentário. OBJETIVO: o objetivo deste trabalho foi avaliar as alterações químicas e morfológicas do esmalte dentário humano tratado com laser argônio nos parâmetros da colagem ortodôntica. MÉTODOS: quinze primeiros pré-molares hígidos, extraídos por indicação ortodôntica, foram selecionados e seccionados no sent...

  8. Commissioning of the ATLAS liquid argon calorimeters

    CERN Document Server

    Rezaie, Erfan

    ATLAS, a multi-purpose detector built at the LHC at CERN, requires an extensive commissioning campaign to be ready for proton-proton collisions. In this work, we focus on the commissioning of the liquid Argon (LAr) calorimeters, with emphasis on commissioning with cosmic rays. First we outline one phase of the commissioning work, which involves testing of the front-end electronics of the two endcap calorimeters. We then describe two cosmic ray generators as input to a Monte-Carlo simulation of cosmic rays in ATLAS, and compare their results. Finally, we explain a technique developed for this work which uses information from the Tile calorimeters to predict the timing of cosmic rays within the LAr calorimeters, because cosmic rays occur randomly in time whereas the electronics are clocked at [Special characters omitted.] . The results from this analysis tool are compared to default tools, using both simulated and real cosmic ray data in the calorimeters.

  9. Neutron Inelastic Scattering Study of Liquid Argon

    International Nuclear Information System (INIS)

    The inelastic scattering functions for liquid argon have been measured at 85.2 K. The coherent scattering function was obtained from a measurement on pure A-36 and the incoherent function was derived from the result obtained from the A-36 sample and the result obtained from a mixture of A-36 and A-40 for which the scattering is predominantly incoherent. The data, which are presented as smooth scattering functions at constant values of the wave vector transfer in the range 10 - 44/nm, are corrected for multiple scattering contributions and for resolution effects. Such corrections are shown to be essential in the derivation of reliable scattering functions from neutron scattering data. The incoherent data are compared to recent molecular dynamics results and the mean square displacement as a function of time is derived. The coherent data are compared to molecular dynamics results and also, briefly, to some recent theoretical models

  10. Ideas for future liquid Argon detectors

    International Nuclear Information System (INIS)

    We outline a strategy for future experiments on neutrino and astroparticle physics based on the use, at different detector mass scales (100 ton and 100 kton), of the liquid Argon Time Projection Chamber (LAr TPC) technique. The LAr TPC technology has great potentials for both cases with large degree of interplay between the two applications and a strong synergy. The ICARUS R and D programme has demonstrated that the technology is mature and that one can built a large (∼ 1 kton) LAr TPC. We believe that one can conceive and design a very large mass LAr TPC with a mass of 100 kton by employing a monolithic technology based on the use of industrial, large volume cryogenic tankers developed by the petro-chemical industry. We show a potential implementation of a large LAr TPC detector. Such a detector would be an ideal match for a Superbeam[New J. Phys. 4 (2002) 88 [arXiv:hep-ph/0208047

  11. Liquid-argon cylindrical pulsed ionization chamber

    International Nuclear Information System (INIS)

    A liquid-argon cylindrical ionization chamber with a working volume of 200 cm2 is described. The chamber anode is made of stainless steel in the form of a hollow cylinder 30 mm in diameter and 140 mm in length. A beryllium bronze wire in diameter of 0.1 mm and at a spacing of 1 mm is used for winding the chamber screen grid. The chamber cathode is a brass thin-walled cylinder having an internal diameter of 56 mm and a height of 156 mm. The cathode-grid gap is 10 mm, the cathode-case gap is 2 mm. A 0.5 l cooling bath filled with liquid nitrogen is used to refrigirate the chamber. The chamber is evacuated to about 10-5 mm Hg. The total concentration of electronegative impurities in argon does not exceed 6x10-9. Dependences of the chamber counting and amplitude responses, on the cathode voltage under irradiation with γ-quanta at energies of 0.898 MeV and 1.836 MeV are given. The value of the energy resolution was evaluated by differentiating the high-energy edge of the Compton spectrum. The total width at a peak half-height constitutes 5% for an electron energy of 1.612 MeV. To achieve better resolution of the chamber it is necessary to reduce preamplifier noises by three times, to increase the working gap of the chamber and decrease the grid-anode gap

  12. Formation of argon-boron bonds in the reactions of BFn+/2+ cations with neutral argon

    Czech Academy of Sciences Publication Activity Database

    Levee, L.; Calogero, C.; Barbieri, E.; Byrne, S.; Donahue, C.; Eisenberg, M.; Hattenbach, S.; Le, J.; Capitani, J. F.; Roithová, J.; Schröder, Detlef

    2012-01-01

    Roč. 323, 1 Jun (2012), s. 2-7. ISSN 1387-3806 R&D Projects: GA ČR GA203/09/1223 Grant ostatní: European Research Council(XE) AdG HORIZOMS Institutional support: RVO:61388963 Keywords : argon compound * boron fluoride * dication * gas phase reactivity * mass spectrometry * neon compound Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.142, year: 2012

  13. Photoionized argon plasmas induced with intense soft x-ray and extreme ultraviolet pulses

    Science.gov (United States)

    Bartnik, A.; Wachulak, P.; Fok, T.; Węgrzyński, Ł.; Fiedorowicz, H.; Skrzeczanowski, W.; Pisarczyk, T.; Chodukowski, T.; Kalinowska, Z.; Dudzak, R.; Dostal, J.; Krousky, E.; Skala, J.; Ullschmied, J.; Hrebicek, J.; Medrik, T.

    2016-01-01

    In this work, photoionized plasmas were created by irradiation of gaseous argon with soft x-ray (SXR) and extreme ultraviolet (EUV) intense radiation pulses. Two different laser-produced plasma sources, employing a low energy Nd:YAG laser and a high energy iodine laser system (PALS), were used for creation of photoionized plasmas. In both cases the EUV or SXR beam irradiated the Ar stream, injected into a vacuum chamber synchronously with the radiation pulse. Emission spectra, measured for the Ar photoionized plasmas indicated strong differences in ionization degree for plasmas produced using low and high energy systems. In case of the the EUV driving pulses, emission lines corresponding to neutral atoms and singly charged ions were observed. In case of the SXR pulses utilized for the photoionized plasma creation, only Ar V-VIII emission lines were recorded. Additionally, electron density measurements were performed by laser interferometry employing a femtosecond laser system synchronized with the irradiating system. Maximum electron density for the Ar photoionized plasma, induced using the high energy system, reached 1.9 · 1018 cm-3. Interferometric measurements performed for the moment of maximum intensity of the main laser pulse (t  =  0) revealed no fringe shift. Detection limit for the interferometric measurements was estimated. It allowed to estimate the upper limit for electron density at t  =  0 as 5 · 1016 cm-3.

  14. Measurement of the two-photon absorption cross-section of liquid argon with a time projection chamber

    CERN Document Server

    Badhrees, I; Kreslo, I; Messina, M; Moser, U; Rossi, B; Weber, M S; Zeller, M; Altucci, C; Amoruso, S; Bruzzese, R; Velotta, R

    2010-01-01

    This paper reports on laser-induced multiphoton ionization at 266 nm of liquid argon in a time projection chamber (LAr TPC) detector. The electron signal produced by the laser beam is a formidable tool for the calibration and monitoring of next-generation large-mass LAr TPCs. The detector that we designed and tested allowed us to measure the two-photon absorption cross-section of LAr with unprecedented accuracy and precision: $\\sigma_ex$=(1.24$\\pm$0.10stat $\\pm$0.30syst)$\\times$10^{-56} cm$^4$s{-1}.

  15. Current and Future of Laser Therapy in the Management of Glaucoma

    OpenAIRE

    Ekici, Feyzahan; Waisbourd, Michael; Katz, L. Jay

    2016-01-01

    There has been tremendous progress in the past decades in the utilization of lasers for treating patients with glaucoma. This article reviews the use of lasers in different areas of glaucoma, including the shift from argon laser trabeculoplasty (ALT) to selective laser trabeculoplasty (SLT), laser trabeculoplasty as an initial treatment for glaucoma, new laser trabeculoplasty procedures under investigation, and other recent laser treatment modalities such as endoscopic cyclophotocoagulation a...

  16. LArGe - A liquid argon scintillation veto for GERDA

    OpenAIRE

    Heisel, M.(Max-Planck-Institut für Kernphysik, Heidelberg, Germany)

    2011-01-01

    LArGe is a Gerda low-background test facility to study novel background suppression methods in a low-background environment, for possible applications in the Gerda experiment. Gerda searches for the neutrinoless double-beta decay in 76Ge, by operating naked germanium detectors submersed into 65 m3 of liquid argon. Similarly, LArGe runs Ge-detectors in 1 m3 (1.4 tons) of liquid argon, which in addition is instrumented with photomultipliers to detect argon scintillation light. The light is used...

  17. Practical reactor production of {sup 41}Ar from argon clathrate

    Energy Technology Data Exchange (ETDEWEB)

    Mercer, J.R. E-mail: jmercer@pharmacy.ualberta.ca; Duke, M.J.M.; McQuarrie, S.A

    2000-06-01

    The radionuclide {sup 41}Ar has many ideal properties as a gas flow tracer. However, the modest cross-section of {sup 40}Ar for thermal neutron activation makes preparation of suitable activities of {sup 41}Ar technically difficult particularly for low flux reactors. Argon can however be trapped in a molecular complex called a clathrate that can then be irradiated. We prepared argon clathrate and explored its irradiation and stability characteristics. Argon clathrate can be used to provide gigabecquerel quantities of {sup 41}Ar even with low power reactors.

  18. Membrane separation processes for argon plasma gas recovery

    OpenAIRE

    Harlacher, Thomas

    2014-01-01

    A mixture of argon and hydrogen is used as plasma gas in a thermal plasma synthesis for the production of silicon carbide. Next to argon and hydrogen, the exhaust gas of the ceramic synthesis contains carbon monoxide. Since argon is an expensive gas, the plasma gas needs to be recycled. For this purpose, the carbon monoxide has to be removed from the exhaust gas. The applicability of a membrane based gas separation process for this separation task was investigated in this study. A process rou...

  19. Stopping Power of Solid Argon for Helium Ions

    DEFF Research Database (Denmark)

    Besenbacher, F.; Bøttiger, Jørgen; Grauersen, O.; Hansen, Jens Leonhart; Sørensen, H.

    1981-01-01

    By means of the Rutherford-backscattering method, the stopping cross section of solid argon has been measured for 0.5–3 MeV helium ions to an accuracy of not, vert, similar3%. The results agree within the experimental accuracies with our earlier measurements for gaseous argon over the energy region...... studied. This proves that the gas/solid difference for argon predicted in recent stopping-power tabulations is significantly overestimated. With high-order Z1 correction terms included in the theoretical description, calculated shell corrections based on the Lindhard-Scharff model are in good agreement...

  20. Evidence of electric breakdown induced by bubbles in liquid argon

    CERN Document Server

    Bay, F; Murphy, S; Resnati, F; Rubbia, A; Sergiampietri, F; Wu, S

    2014-01-01

    We report on the results of a high voltage test in liquid argon in order to measure its dielectric rigidity. Under stable conditions and below the boiling point, liquid argon was found to sustain a uniform electric field of 100 kV/cm, applied in a region of 20 cm$^2$ area across 1 cm thick gap. When the liquid is boiling, breakdowns may occur at electric fields as low as 40 kV/cm. This test is one of the R&D efforts towards the Giant Liquid Argon Charge Imaging ExpeRiment (GLACIER) as proposed Liquid Argon Time Projection Chamber (LAr TPC) for the LBNO observatory for neutrino physics, astrophysics and nucleon decay searches.

  1. Excitation temperatures of atmospheric argon in dielectric barrier discharges

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yu; Wen Xiaohui; Yang Weihong [CAS Key Laboratory of Basic Plasma Physics and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2007-08-15

    A method for the determination of excitation temperatures based on optical emission spectroscopy and Fermi-Dirac distribution was set up and experiments were performed on atmospheric argon dielectric barrier discharges. Local thermodynamic equilibrium was proved to exist in the discharge and the validity of Boltzmann distribution is discussed. The main aim of this paper is to obtain the temperatures of atmospheric Ar II as a function of the discharge voltage, discharge frequency, argon flow rate and the argon fraction. It was found that the excitation temperatures are in the range 3800-4950 K. Besides, an increase in the argon flow rate resulting in a slight growth of the temperature and the add-in of air leading to the decrease in temperature was observed.

  2. The Effects of Dissolved Methane upon Liquid Argon Scintillation Light

    CERN Document Server

    Jones, B J P; Back, H O; Collin, G; Conrad, J M; Greene, A; Katori, T; Pordes, S; Toups, M

    2013-01-01

    In this paper we report on measurements of the effects of dissolved methane upon argon scintillation light. We monitor the light yield from an alpha source held 20 cm from a cryogenic photomultiplier tube (PMT) assembly as methane is injected into a high-purity liquid argon volume. We observe significant suppression of the scintillation light yield by dissolved methane at the 10 part per billion (ppb) level. By examining the late scintillation light time constant, we determine that this loss is caused by an absorption process and also see some evidence of methane-induced scintillation quenching at higher concentrations (50-100 ppb). Using a second PMT assembly we look for visible re-emission features from the dissolved methane which have been reported in gas-phase argon methane mixtures, and we find no evidence of visible re-emission from liquid-phase argon methane mixtures at concentrations between 10 ppb and 0.1%.

  3. The ATLAS Liquid Argon Calorimeter Construction, Integration, Commissioning

    CERN Document Server

    Aleksa, Martin

    2006-01-01

    The ATLAS liquid argon (LAr) calorimeter system consists of an electromagnetic barrel calorimeter and two end caps with electromagnetic, hadronic and forward calorimeters. The liquid argon sampling technique, with an accordion geometry was chosen for the barrel electromagnetic calorimeter (EMB) and adapted to the end cap (EMEC). The hadronic end cap calorimeter (HEC) uses a copper-liquid argon sampling technique with flat plate geometry and is subdivided in depth in two wheels per end-cap. Finally, the forward calorimeter (FCAL) is composed of three modules employing cylindrical electrodes with thin liquid argon gaps. The construction of the full calorimeter system is complete since mid-2004. Production modules constructed in the home institutes were integrated into wheels at CERN in 2003-2004, and inserted into the three cryostats. They passed their first complete cold test before the lowering into the ATLAS cavern. Results of quality checks (e.g. electrical, mechanical, ...) performed on all the 190304 read...

  4. Impact of changes in metabolic control on progression to photocoagulation for clinically significant macular oedema:a 20 year study of type 1 diabetes

    DEFF Research Database (Denmark)

    Sander, B.; Larsen, M.; Andersen, Elisabeth Wreford; Lund-Andersen, H.

    2013-01-01

    Aims/hypothesis Although increasing hyperglycaemia, arterial hypertension and longer duration of diabetes raise the risk of progression of diabetic retinopathy, short-term benefits in terms of improved metabolic control and lowered blood pressure have not been demonstrated. We therefore examined...... the effect of changes in glycaemia and arterial blood pressure on the incidence of clinically significant macular oedema in a population of diabetic patients. Methods We performed a retrospective review of all patients with type 1 diabetes who attended the retinopathy screening clinic at the Steno...... Diabetes Center from 1988 to 2008, using the endpoint referral to first photocoagulation treatment for clinically significant diabetic macular oedema. The analysis included 1,878 patients (median observation, 8 years). Changes were defined as the inter-visit change; in the case of an event the last event...

  5. Size Determination of Argon Clusters from a Rayleigh Scattering Experiment

    Institute of Scientific and Technical Information of China (English)

    LEI An-Le; ZHAI Hua-Jin; LIU Bing-Chen; LI Zhong; NI Guo-Yuan; XU Zhi-Zhan

    2000-01-01

    Argon clusters are produced in the process of adiabatic expansion of a high backing pressure gas into vacuum through a nozzle. The cluster size is determined by a Rayleigh scattering measurement. The scattered signal measured is proportional to the 2.78th power of gas stagnation pressure. The average cluster sizes vary from 100 to more than 12000 atoms/cluster with the argon gas backing pressures ranging between 3 to 45 atm.

  6. A purity monitoring system for liquid argon calorimeters

    International Nuclear Information System (INIS)

    For liquid argon calorimeters electronegative impurities dissolved in the medium degrade the detector response and deteriorate the energy resolution, especially at high energies. A concept for a purity monitoring system for liquid argon calorimeters has been developed and is presented here. Special combined monitors of 241Am- and 207Bi-cells are used to monitor the concentration of impurities. The working principle as well as results from test measurements are discussed

  7. Studies of Electron Avalanche Behavior in Liquid Argon

    OpenAIRE

    Kim, J.G.; Dardin, S. M.; Jackson, K.H.; Kadel, R. W.(Lawrence Berkeley National Laboratory and University of California, 94720, Berkeley, California, USA); Kadyk, J. A.; Peskov, V.; Wenzel, W. A.

    2002-01-01

    Electron avalanching in liquid argon is being studied as a function of voltage, pressure, radiation intensity, and the concentrations of certain additives, especially xenon. The avalanches produced in an intense electric field at the tip of a tungsten needle are initiated by ionization from a moveable americium (241Am) gamma ray source. Photons from xenon excimers are detected as photomultiplier signals in coincidence with the current pulse from the needle. In pure liquid argon the avalanche ...

  8. Pulse shape discrimination studies in a liquid Argon scintillation detector

    OpenAIRE

    Pollmann, T.

    2007-01-01

    Liquid rare gases have been gaining popularity as detector media in rare event searches, especially dark matter experiments, and one factor driving their adoption is the possibility to recognise different types of ionizing radiation by the pulse shapes they evoke. This work on pulse shape discrimination in a liquid argon scintillation detector was done in the framework of the GERDA experiment, where liquid argon scintillation signals may be used for background suppression purposes. Liquid arg...

  9. RF-ARGON PLASMA INDUCED SURFACE MODIFICATION OF PAPER

    OpenAIRE

    HALIL TURGUT SAHIN

    2008-01-01

    The radio frequency (RF) argon plasma induced surface modification of paper revealed novel surface characteristics and substantially changed surface topography. It was found that RF-argon glow discharge affects surface properties resulting in photo-degradation and chain-scission mechanism on paper network structure. High-power and extended treatment time caused increasing elemental carbon, while decreasing the oxygen concentration on paper surface. However, increased hydroxyls and the creatio...

  10. Electronic relaxation dynamics of a metal atom deposited on argon cluster

    International Nuclear Information System (INIS)

    This thesis is a study on the interaction between electronically excited atomic states and a non-reactive environment. We have theoretically and experimentally studied situations where a metal atom (Ba or K) is placed in a finite size environment (argon cluster). The presence of the medium affects the electronic levels of the atom. On the other side, the excitation of the atom induces a relaxation dynamics of the electronic energy through the deformation of the cluster. The experimental part of this work focuses on two aspects: the spectroscopy and the dynamics. In both cases a first laser electronically excites the metal atom and the second ionizes the excited system. The observable is the photoelectron spectrum recorded after photoionization and possibly information on the photoion which are also produced. This pump/probe technique, with also two lasers, provide the ultrafast dynamic when the lasers pulses used are of ultrashort (60 fs). The use of nanosecond lasers leads to resonance spectroscopic measurement, unresolved temporally, which give information on the position of the energy levels of the studied system. From a theoretical point-of-view, the excited states of M-Arn were calculated at the ab initio level, using large core pseudo-potential to limit the active electrons of the metal to valence electrons. The study of alkali metals (potassium) is especially well adapted to this method since only one electron is active. The ab-initio calculation and a Monte-Carlo simulation where coupled to optimize the geometry of the KArn (n = 1-10) cluster when K is in the ground state of the neutral and the ion, or excited in the 4p or 5s state. Calculations were also conducted in collaboration with B. Gervais (CIMAP, Caen) on KArn clusters having several tens of argon atoms. Absorption spectra were also calculated. From an experimental point-of-view, we were able to characterize the excited states of potassium and barium perturbed by the clusters. In both cases a

  11. Energy resolution for α-particles in doped liquid argon

    International Nuclear Information System (INIS)

    The report describes experiments on the effect of allene doped in liquid argon. In the case of doped argon, a large amount of charge is obtained even at low electric fields and the measured charge increases with the field gradually. This can be explained as follows; part of deposited energy which does not form charge in pure argon contributes to charge signal in doped argon through scintillation photons which ionize allene molecules. The main factors determining the energy resolution for α-particles are considered to be (1) fluctuation in the number of produced ion-electron pairs as expressed by the Fano factor, (2) fluctuation in recombination process, (3) fluctuation in photoionization, (4) fluctuation due to the condition of radioactive source and surface of electrodes, (5) fluctuation in geometrical efficiency due to the range and emission angle of α-particles in liquid argon, and (6) electronic noise of amplifier. The factors (1) and (3) can be neglected because of a large number of associated electrons or photons. In pure liquid argon, the factor (2) may be a cause of bad resolution since the fraction of the produced ion-electron paris which do not recombine is small and the photoionization process never occurs for photons emitted through recombination. (N.K.)

  12. Power Consideration for Pulsed Discharges in Potassium Seeded Argon

    Institute of Scientific and Technical Information of China (English)

    XIA Sheng-Guo; HE Jun-Jia; LIU Ke-Fu

    2007-01-01

    Minimization of energy consumed in plasma generation is critical for applications, in which a large volume of plasmas is needed. We suggest that a high electron density atmospheric pressure plasmas can be generated by pulsed discharges in potassium seeded argon at an elevated temperature with a very small power input. The ionization efficiency and power budget of pulsed discharges in such plasmas are analytically studied. The results show that ionization efficiency of argon, especially at small reduced electric field E/N (the ratio of the electric field to the gas number density), is improved effectively in the presence of small amount of potassium additives. Power input of pulsed discharge to sustain a prescribed average level of ionization in potassium seeded argon is three orders of magnitude lower than that in pure argon. Further, unlike in pure argon, it is found that very short high-voltage pulses with very high repetition rates are unnecessary in potassium seeded argon. A pulse with 100ns of pulse duration, 5kHz of repetition rate, and 2Td (1 Td = 1 ×10-21 Vm2) of E/N is enough to sustain an electron density of 10l9m-3 in 1 atm 1500 K Ar+0.1% K mixture, with a very small power input of about 0.08 × 104 W/m3.

  13. Effects of Laser Irradiation on Caries Prevention

    OpenAIRE

    Maryam Esmaeilzadeh; Hossein Bagheri; Yashar Rezaei

    2012-01-01

    INTRODUCTION: Although dental caries is a preventable disease, it is still common and remains a public health problem. One of the potentially effective preventive measures is the use of lasers. The purpose of this study was to review the studies about use of laser irradiation on the inhibition of carious lesions and the effectiveness of different commercial laser type (Nd:YAG, CO2, and Argon).METHODS: A literature search included journal databases, existing systematic reviews, and studies ide...

  14. Extremely Nonlinear Optics Using Shaped Pulses Spectrally Broadened in an Argon- or Sulfur Hexafluoride-Filled Hollow-Core Fiber

    Directory of Open Access Journals (Sweden)

    Andreas Hoffmann

    2015-11-01

    Full Text Available In this contribution we present a comparison of the performance of spectrally broadened ultrashort pulses using a hollow-core fiber either filled with argon or sulfur hexafluoride (SF6 for demanding pulse-shaping experiments. The benefits of both gases for pulse-shaping are studied in the highly nonlinear process of high-harmonic generation. In this setup, temporally shaping the driving laser pulse leads to spectrally shaping of the output extreme ultraviolet (XUV spectrum, where total yield and spectral selectivity in the XUV are the targets of the optimization approach. The effect of using sulfur hexafluoride for pulse-shaping the XUV yield can be doubled compared to pulse compression and pulse-shaping using argon and the spectral range for selective optimization of a single harmonic can be extended. The obtained results are of interest for extending the range of ultrafast science applications drawing on tailored XUV fields.

  15. Plasma and laser kinetics and field emission from carbon nanotube fibers for an Advanced Noble Gas Laser (ANGL)

    Science.gov (United States)

    Moran, Paul J.; Lockwood, Nathaniel P.; Lange, Matthew A.; Hostutler, David A.; Guild, Eric M.; Guy, Matthew R.; McCord, John E.; Pitz, Greg A.

    2016-03-01

    A metastable argon laser operating at 912 nm has been demonstrated by optically pumping with a pulsed titanium sapphire laser to investigate the temporal dynamics of an Advanced Noble Gas Laser (ANGL). Metastable argon concentrations on the order of 1011 cm-3 were maintained with the use of a radio frequency (RF) capacitively coupled discharge. The end-pumped laser produced output powers under 2 mW of average power with pulse lengths on the order of 100 ns. A comparison between empirical results and a four level laser model using longitudinally average pump and inter-cavity intensities is made. An alternative, highly-efficient method of argon metastable production for ANGL was explored using carbon nanotube (CNT) fibers.

  16. Retinal laser optical aids

    Directory of Open Access Journals (Sweden)

    Das Traprasad

    1991-01-01

    Full Text Available Knowledge of optics, comparative magnification and working field of view is essential for rational use of ophthalmoscopic contact lenses for retinal photocoagulation. The three commonly used contact lenses are described and compared.

  17. 氩激光治疗糖尿病视网膜病变264例观察%Observation on Photocoagulation with Arqon for Treatment of 264 Cases of Diabetic Retinopathy

    Institute of Scientific and Technical Information of China (English)

    包欣; 林菁; 谢田华; 朱靖; 史惠琴; 袁松涛

    2012-01-01

    目的:观察氩激光光凝治疗不同分期糖尿病视网膜病变(diabetic retinopathy,DR)的疗效.方法:对264例513眼DR患者按病变不同分期分别行黄斑格栅样光凝、次全视网膜光凝(sPRP)和全视网膜光凝(PRP).随访3月-5年,观察患者视力、眼底及荧光血管造影情况.结果:总计有24.0%(123/513)的患眼视力得以上升,49.7 %(255/513)视力保持不变,26.3 %(135/513)视力下降.非增殖性DR激光治疗有效率为87.5%,增殖性DR有效率58.4 %(P<0.05).1型DM有效率43.5%,2型DM有效率81.4%(P<0.05).结论:氩激光能有效控制DR,减缓DR患者视力的丧失,非增殖性DR疗效明显优于增殖性DR,2型DM疗效优于1型DM.%Objective: To observe curative effect of photocoagulation with arqon on background diabetic retinopathy and proliferative diabetic retinopathy. Methods: We classified 513 eyes with 264 patients as background diabetic retinopathy and proliferative diabetic retinopathy with or not with cystoid macular edema. They were treated with grid patten photocoagulation, secondary panretinal photocoagulation (sPRP) and panretinal photocoagulation respectively. Followed up with visual acuity, ophthalmic fundus characteristics and fundus fluorescein angiography (FFA) for 3 months to 5 years. Results: Mean preoperative visual acuities and ophthalmic fundus characteristics were compared across groups. In all patients, visual acuity improved in 123 eyes (24 %); was unchanged in 255 eyes (49.7 %); and decreased in 135 eyes (26.3 %). The effective rate of photocoagulation on nonproliferative diabetic retinopathy is 87.5 % compared with 58.4 % on proliferative diabetic retinopathy(P<0.05), 43.5 % on type 1 diabetes mellitus compared with 81.4 % on type 2 diabetes mellitus. Conclutions: Photocoagulation with arqon can effectively restrain the decrease of visual acuity especially in proliferative diabetic retinopathy patients with type 2 diabetes mellitus.

  18. INTRAVITREAL BEVACIZUMAB AS AN ADJUNCT TO LASER FOR DIFFUSE DIABETIC MACULAR EDEMA

    Directory of Open Access Journals (Sweden)

    Shah

    2015-10-01

    Full Text Available Background: Diabeteic retinopathy with its manifestation in the form of diabetic macular edema has become a leading cause of blindness all over the world. AIM: In the present study we evaluated, the anatomical and visual acuity outcomes after intravitreal bevacizumab and laser in Diffuse DME. MATERIALS AND METHODS: An OCT guided pilot study, evaluating the effect of intravitreal bevacizumab as an adjunct to laser , of 40 eyes of 40 diabetic patients having diffuse diabetic macular edema with maximum retinal thickness (MRT more than or equal to 350 μm was conducted at Government Medical College & Hospital, Chandigarh, India. The patients had minimum follow up of 6 months. RESULTS: There was a significant decrease in maximum retinal thickness with significant gain in visual acuity at 6 month. CONCLUSIONS: I ntravitreal bevacizumab combined with laser photocoagulation has better outcomes in the management of patients w ith diffuse diabetic macular edema. Since ours is a pilot study, further studies with larger number of patients and longer follow ups are essential to conclusively establish the superiority of IVB combined with laser photocoagulation in the management of D ME.

  19. New argon-argon (40Ar/39Ar) radiometric age dates from selected subsurface basalt flows at the Idaho National Laboratory, Idaho

    Science.gov (United States)

    Hodges, Mary K.; Turrin, Brent D.; Champion, Duane E.; Swisher, Carl C., III

    2015-01-01

    In 2011, the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, collected samples for 12 new argon-argon radiometric ages from eastern Snake River Plain olivine tholeiite basalt flows in the subsurface at the Idaho National Laboratory. The core samples were collected from flows that had previously published paleomagnetic data. Samples were sent to Rutgers University for argon-argon radiometric dating analyses.

  20. Evolution of Martian atmospheric argon: Implications for sources of volatiles

    Science.gov (United States)

    Hutchins, Kevin S.; Jakosky, Bruce M.

    We have examined processes affecting isotopes of argon (36Ar, 38Ar, 40Ar) in order to determine important atmospheric sources and sinks. Our simple model for argon evolution incorporates production of radiogenic argon in the mantle, outgassing of all argon species by extrusive and intrusive volcanism, and loss to space by knock-on sputtering above the exobase. Sputtering has been shown previously to be an important loss process for atmospheric species, especially isotopes of noble gases, which have few other mechanisms of escape. The integrated evolution of argon (36Ar, 38Ar, and 40Ar, respectively) is modeled in terms of these variables: (1) the planetary concentration of potassium, (2) the fraction of juvenile argon released catastrophically during the first 600 Myr., (3) potential variation in the time-history of sputtering loss from that suggested by Luhmann et al. [1992], and (4) the volume of total outgassing to the surface as compared to outgassing contributed by volcanic release. Our results indicate that Mars has lost between 85-95% of 36Ar and 70-88% of outgassed 40Ar. Due to this substantial loss, the planet must have outgassed the equivalent of between 10 and 100 times the total volume of gases released by extrusive and intrusive volcanics. This indicates that volcanic outgassing, alone, is insufficient to explain the present-day abundances of 36Ar and 40Ar in the Martian atmosphere. Similar calculations for 20Ne suggest outgassed volumes of between 100 and 1800 times in excess of that due to volcanism. This results in a distinct Ne/Ar elemental fractionation, with a preference for outgassing argon, of the order of 10 to 17. Although the results must be evaluated within the model uncertainties, the results are compelling in that they unequivocally show the existence of additional sources of atmospheric volatiles and helps define a means to identify them.

  1. Characterisation of GERDA Phase-I detectors in liquid argon

    International Nuclear Information System (INIS)

    GERDA will search for neutrinoless double beta decay in 76Ge by submerging bare enriched HPGe detectors in liquid argon. In GERDA Phase-I, reprocessed enriched-Ge detectors, which were previously operated by the Heidelberg-Moscow and IGEX collaborations, and reprocessed natural-Ge detectors from Genius-TF, will be redeployed. We have tested the operation and performance of bare HPGe detectors in liquid nitrogen and in liquid argon over more than three years with three non-enriched p-type prototype detectors. The detector handling and mounting procedures have been defined and the Phase-I detector technology, the low-mass assembly and the long-term stability in liquid argon have been tested successfully. The Phase-I detectors were reprocessed by Canberra Semiconductor NV, Olen, according to their standard technology but without the evaporation of a passivation layer. After their reprocessing, the detectors have been mounted in their low-mass holders and their characterisation in liquid argon performed. The leakage current, the counting characteristics and the efficiency of the detectors have been measured. The testing of the detectors was carried out in the liquid argon test stand of the GERDA underground Detector Laboratory (GDL) at LNGS. The detectors are now stored underground under vacuum until their operation in GERDA.

  2. Comparative evaluation between ranibizumab combined with laser and bevacizumab combined with laser versus laser alone for macular oedema secondary to branch retinal vein occlusion

    Directory of Open Access Journals (Sweden)

    Shorya Vardhan Azad

    2014-01-01

    Full Text Available Purpose: To evaluate the anatomical and functional efficacy of combination therapy of intravitreal ranibizumab with laser or intravitreal bevacizumab with laser treatment compared to only laser treatment for macular edema due to branch retinal vein occlusion (BRVO. Materials and Methods: Thirty eyes of 30 patients with BRVO of at least 6 weeks duration were randomized into three groups: Group 1 received a single dose of intravitreal Ranibizumab followed by grid laser treatment, Group 2 received a single dose of intravitreal Bevacizumab followed by grid laser treatment, and Group 3 received grid laser alone. Outcomes at 6 months follow-up were reported. Data were collected on best corrected visual acuity (BCVA, central foveal thickness (CFT, and gain in lines of Snellen acuity. Results: At 6 month follow-up, the difference in the mean BCVA and CFT between the three treatment groups was not statistically significant (P > 0.05, all comparisons. Six eyes (60% in Group 1, four eyes (40% in Group 2 and two eyes (20% in Group 3 had a statistically significant gain of ≥3 lines of Snellen acuity (P < 0.05. Conclusion: Both ranibizumab and bevacizumab combined with laser photocoagulation, resulted in better outcomes than grid laser treatment.

  3. A liquid argon time projection chamber for the solar neutrino problem

    International Nuclear Information System (INIS)

    The construction and successful test of a large liquid argon time projection chamber prototype detector is presented. This effort is a part of the ICARUS project which is aimed at the development of new detector techniques to uncover the very rare events like proton decay and solar neutrinos. The construction and test of this detector has been carried out at CERN from 1989 until the present time. The charge lifetime measured is 3.19 ± 0.13 ms. The authors also report on a precision measurement of lifetime by a laser monitoring chamber and the operation of the recirculation system essential to keeping liquid for a long time. They show that a liquid argon detector is very well suited to study mass-enhanced neutrino oscillation (MSW effect) from the Sun by detecting simultaneous two modes of reaction. Ratio of two modes provides a model independent probe of neutrino oscillation, free of deviations from different solar models. Contours plots are presented at various threshold energies

  4. a Liquid Argon Time Projection Chamber for the Solar Neutrino Problem

    Science.gov (United States)

    Cheng, Mao-Tung

    The construction and successful test of a large liquid argon time projection chamber prototype detector is presented. This effort is a part of the ICARUS project which is aimed at the development of new detector techniques to uncover the very rare events like proton decay and solar neutrinos. The construction and test of this detector has been carried out at CERN from 1989 until the present time. The charge lifetime measured is 3.19 +/- 0.13 ms. We also report on a precision measurement of lifetime by a laser monitoring chamber and the operation of the recirculation system essential to keeping liquid for a long time. We show that a liquid argon detector is very well suited to study mass-enhanced neutrino oscillation (MSW effect) from the Sun by detecting simultaneous two modes of reaction. Ratio of two modes provides a model independent probe of neutrino oscillation, free of deviations from different solar models. Contour plots are presented at various threshold energies.

  5. Transscleral diode laser retinopexy in retinal reattachment surgery Retinopexia com laser de diodo transescleral na cirurgia de descolamento de retina

    Directory of Open Access Journals (Sweden)

    João Carlos de Miranda Gonçalves

    2004-02-01

    Full Text Available PURPOSE: Transscleral diode retinal photocoagulation (diopexy is becoming an accepted technique in the treatment of selected retinal diseases. The objective of this study is to evaluate diopexy technique in the production of adhesive chorioretinal lesions during the surgical treatment of the rhegmatogenous retinal detachment. METHODS: 25 patients with rhegmatogenous retinal detachment were enrolled in a prospective clinical-surgical study to evaluate the technique of transscleral diode laser photocoagulation to obtain adhesive chorioretinal lesions during retinal reattachment surgery. The surgery consisted of the placement of an exoplant silicon to produce a buckle effect combined with a drainage of subretinal fluid in most cases. RESULTS: By a mean follow-up of 10 months, 21 of 25 eyes had their retinas reattached after only one surgery with diopexy used in all cases. CONCLUSION: Transscleral diode laser photocoagulation was a technically easy, controlled, effective, reproducible and safe means of obtaining chorioretinal adhesion in retinal reattachment surgery.OBJETIVO: Fotocoagulação transescleral com laser de diodo (diopexia está se tornando técnica utilizada no tratamento de algumas doenças retinianas. O objetivo deste estudo é avaliar a técnica de diopexia na produção de lesões coriorretinianas aderentes durante o tratamento cirúrgico do descolamento de retina regmatogênico. MÉTODOS: Vinte e cinco pacientes com descolamento de retina regmatogênico participaram deste estudo clínico-cirúrgico prospectivo para avaliar a técnica de fotocoagulação com laser de diodo transescleral para obter lesões coriorretinianas aderentes durante a cirurgia de descolamento de retina. A cirurgia consistiu de colocação de explante de silicone para produzir efeito de introflexão escleral combinado com drenagem do líquido subretiniano na maioria dos casos. RESULTADOS: Após um período médio de seguimento de 10 meses, em 21 dos 25 olhos

  6. Intravitreal Bevacizumab Injection Alone or Combined with Triamcinolone Versus Macular Photocoagulation In Bilateral Diabetic Macular Edema; Application of Bivariate Generalized Linear Mixed Model with Asymmetric Random Effects in a Subgroup of a Clinical Trial

    OpenAIRE

    Mehdi Yaseri; Hojjat Zeraati; Kazem Mohammad; Masoud Soheilian; Alireza Ramezani; Medi Eslani; Peyman, Gholam A

    2014-01-01

    Purpose: To compare the efficacy of intravitreal bevacizumab (IVB) injection alone or with intravitreal triamcinolone acetonide (IVB/IVT) versus macular photocoagulation (MPC) in bilateral diabetic macular edema (DME). Methods: In this study we revisited data from a subset of subjects previously enrolled in a randomized clinical trial. The original study included 150 eyes randomized to three treatment arms: 1.25 mg IVB alone, combined injection of 1.25 mg IVB and 2 mg IVT, and focal or mo...

  7. Lasers in endodontics: an overview

    Science.gov (United States)

    Frentzen, Matthias; Braun, Andreas; Koort, Hans J.

    2002-06-01

    The interest in endodontic use of dental laser systems is increasing. Developing laser technology and a better understanding of laser effects widened the spectrum of possible endodontic indications. Various laser systems including excimer-, argon+-, diode-, Nd:YAG-, Er:YAG- and CO2-lasers are used in pulp diagnosis, treatment of hypersensitivity, pulp capping, sterilization of root canals, root canal shaping and obturation or apicoectomy. With the development of new delivery systems - thin and flexible fibers - for many different wavelengths laser applications in endodontics may increase. Since laser devices are still relatively costly, access to them is limited. Most of the clinical applications are laser assisted procedures such as the removing of pulp remnants and debris or disinfection of infected root canals. The essential question is whether a laser can provide improved treatment over conventional care. To perform laser therapy in endodontics today different laser types with adopted wavelengths and pulse widths are needed, each specific to a particular application. Looking into the future we will need endodontic laser equipment providing optimal laser parameters for different treatment modalities. Nevertheless, the quantity of research reports from the last decade promises a genuine future for lasers in endodontics.

  8. Argon-40: Excess in submarine pillow basalts from Kilauea Volcano, Hawaii

    Science.gov (United States)

    Brent, Dalrymple G.; Moore, J.G.

    1968-01-01

    Submarine pillow basalts from Kilauea Volcano contain excess radiogenic argon-40 and give anomalously high potassium-argon ages. Glassy rims of pillows show a systematic increase in radiogenic argon-40 with depth, and a pillow from a depth of 2590 meters shows a decrease in radiogenic argon-40 inward from the pillow rim. The data indicate that the amount of excess radiogenic argon-40 is a direct function of both hydrostatic pressure and rate of cooling, and that many submarine basalts are not suitable for potassium-argon dating.

  9. Metastable argon beam source using a surface wave sustained plasma

    International Nuclear Information System (INIS)

    A new source of metastable argon atoms in the thermal energy range is reported. The source is based on expanding a plasma sustained by electromagnetic surface waves in a quartz tube through a converging nozzle and extracting a beam from the supersonic free-expansion jet. The beam was characterized by time-of-flight measurements which yielded the absolute intensity and velocity distribution of the argon metastables. The source produced a maximum intensity of 6.2x1014 metastables per second per steradian, the highest time-averaged intensity of thermal argon metastables of any source reported to date. A simple picture of an expanding plasma in a recombination regime is used to explain the dependence of the metastable intensity on absorbed power

  10. On the electric breakdown in liquid argon at centimeter scale

    Science.gov (United States)

    Auger, M.; Blatter, A.; Ereditato, A.; Goeldi, D.; Janos, S.; Kreslo, I.; Luethi, M.; von Rohr, C. Rudolf; Strauss, T.; Weber, M. S.

    2016-03-01

    We present a study on the dependence of electric breakdown discharge properties on electrode geometry and the breakdown field in liquid argon near its boiling point. The measurements were performed with a spherical cathode and a planar anode at distances ranging from 0.1 mm to 10.0 mm. A detailed study of the time evolution of the breakdown volt-ampere characteristics was performed for the first time. It revealed a slow streamer development phase in the discharge. The results of a spectroscopic study of the visible light emission of the breakdowns complement the measurements. The light emission from the initial phase of the discharge is attributed to electro-luminescence of liquid argon following a current of drifting electrons. These results contribute to set benchmarks for breakdown-safe design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

  11. Pressure regulation in the dry-boxes. Argon purification

    International Nuclear Information System (INIS)

    Each dry-box is equipped with an autonomous installation for circulation and purification of argon and for pressure regulation. This installation consists essentially of a ballast tank, a compressor and two valves electromagnetically controlled by a contact manometer. The compressor and the valves are enclosed in the tank to form a system as compact as possible. The argon is purified by passing it over a furnace filled with titanium-zirconium turnings brought to about 800 deg. C, branching off the main system. With this set-up as well as the automatic maintenance of a constant depression in the box, a quality of argon is obtained whose oxygen contact is undetectable by the manganous hydroxide method. (author)

  12. Bacteria Inactivation Using DBD Plasma Jet in Atmospheric Pressure Argon

    International Nuclear Information System (INIS)

    A coaxial dielectric barrier discharge plasma jet was designed, which can be operated in atmospheric pressure argon under an intermediate frequency sinusoidal resonant power supply, and an atmospheric pressure glow-like discharge was achieved. Two kinds of typical bacteria, i.e., the Staphylococcus aureus (S. aureus) and Escherichia coil (E. coil), were employed to study the bacterial inactivation mechanism by means of the non-thermal plasma. The killing log value (KLV) of S. aureus reached up to 5.38 with a treatment time of 90 s and that of E. coil up to 5.36 with 60 s, respectively. According to the argon emission spectra of the plasma jet and the scanning electron microscope (SEM) images of the two bacteria before and after the plasma treatment, it is concluded that the reactive species in the argon plasma played a major role in the bacterial inactivation, while the heat, electric field and UV photons had little effect. (plasma technology)

  13. Energy resolution studies of liquid argon ionization detectors

    International Nuclear Information System (INIS)

    A gridded ionization chamber was used to study the energy resolution in liquid argon with electrons from a 207Bi radioactive source. Argon was purified in the gas phase with a simple and reliable system, capable of reducing the impurity level below 1 ppb O2 equivalent, as inferred by a pulse shape analysis of the ionization signals. The electron spectrum was measured at different drift fields, up to 10.9 KV/cm. At this maximum field, a total energy resolution of 32 keV (fwhm), corresponding to a noise-subtracted energy resolution of 26 keV (fwhm), was obtained for the 976 keV conversion electron line. This value is the best reported so far in liquid argon but is still a factor of seven worse than the theoretical limit set by the Fano factor. The reasons for this discrepancy are discussed. (orig.)

  14. Attenuation measurements of vacuum ultraviolet light in liquid argon revisited

    CERN Document Server

    Neumeier, A; Himpsl, A; Hofmann, M; Oberauer, L; Potzel, W; Schönert, S; Ulrich, A

    2015-01-01

    The attenuation of vacuum ultraviolet light in liquid argon in the context of its application in large liquid noble gas detectors has been studied. Compared to a previous publication several technical issues concerning transmission measurements in general are addressed and several systematic effects were quantitatively measured. Wavelength-resolved transmission measurements have been performed from the vacuum ultraviolet to the near-infrared region. On the current level of sensitivity with a length of the optical path of 11.6 cm, no xenon-related absorption effects could be observed, and pure liquid argon is fully transparent down to the short wavelength cut-off of the experimental setup at 118 nm. A lower limit for the attenuation length of pure liquid argon for its own scintillation light has been estimated to be 1.10 m based on a very conservative approach.

  15. On the Electric Breakdown in Liquid Argon at Centimeter Scale

    CERN Document Server

    Auger, M; Ereditato, A; Goeldi, D; Janos, S; Kreslo, I; Luethi, M; von Rohr, C Rudolf; Strauss, T; Weber, M S

    2015-01-01

    We present a study on the dependence of electric breakdown discharge parameters on electrode geometry and the breakdown field in liquid argon near its boiling point. The measurements were performed with a spherical cathode and a planar anode at distances ranging from 0.1 mm to 10.0 mm. A detailed study of the time evolution of the breakdown volt-ampere characteristics was performed for the first time. It revealed a slow streamer development phase in the discharge. The results of a spectroscopic study of the visible light emission of the breakdowns complement the measurements. The light emission from the initial phase of the discharge is attributed to electro-luminescence of liquid argon following a current of drifting electrons. These results contribute to set benchmarks for breakdown-safe design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

  16. Liquid Argon Calorimetry with LHC-Performance Specifications

    CERN Multimedia

    2002-01-01

    % RD-3 Liquid Argon Calorimetry with LHC-Performance Specifications \\\\ \\\\Good electromagnetic and hadronic calorimetry will play a central role in an LHC detector. Among the techniques used so far, or under development, the liquid argon sampling calorimetry offers high radiation resistence, good energy resolution (electromagnetic and hadronic), excellent calibration stability and response uniformity. Its rate capabilities, however, do not yet match the requirements for LHC. \\\\ \\\\The aim of this proposal is to improve the technique in such a way that high granularity, good hermiticity and adequate rate capabilities are obtained, without compromising the above mentioned properties. To reach this goal, we propose to use a novel structure, the $^{\\prime\\prime}$accordion$^{\\prime\\prime}$, coupled to fast preamplifiers working at liquid argon temperature. Converter and readout electrodes are no longer planar and perpendicular to particles, as usual, but instead they are wiggled around a plane containing particles. ...

  17. Laser spectroscopy of thermal plasma

    International Nuclear Information System (INIS)

    Thermal plasma, due to its applications, is a research field of great importance, but reliable diagnostics of such plasma remains a challenging task. Spatially resolved methods, which provide local values of plasma parameters, are crucial for understanding the underlying physics. This can be achieved using pump–probe techniques. Two methods applicable and useful for thermal plasma diagnostics—four-wave mixing and scattering of laser beams—are discussed in this paper. Experimental examples of their application, namely four-wave mixing in argon arc plasma and scattering of laser light by laser-induced plasma, are presented. (paper)

  18. Optical properties of human sclera, and their consequences for transscleral laser applications.

    Science.gov (United States)

    Vogel, A; Dlugos, C; Nuffer, R; Birngruber, R

    1991-01-01

    The spectral dependence of the optical properties of human sclera adjacent to the limbus was investigated and related to the potentials of transscleral photocoagulation. The total transmission, absorption, and reflection, as well as the angular distribution of the transmitted and reflected light were measured at five laser wavelengths (442 nm, 514 nm, 633 nm, 804 nm, and 1,064 nm), both for noncontact and contact applications. Absorption and scattering coefficients were determined using the Kubelka-Munk model for light propagation through a scattering tissue. The scleral transmission is only 6% at 442 nm but increases to 35% at 804 nm and to 53% at 1,064 nm. The absorption is high at short wavelengths with 40% at 442 nm but it is only 6% at 804 nm and 1,064 nm. The reflection is generally higher than 40% and shows little wavelength dependence. The transmitted light is scattered diffusely at short wavelengths, but at 804 nm and 1,064 nm it exhibits a fairly narrow angular distribution in forward direction. Fiber contact leads to an increase of transmission, with a factor of 3.5 at 442 nm, of 2.0 at 804 nm, and 1.5 at 1,064 nm. Our results indicate that the diode laser (804 nm) and the Nd:YAG laser (1,064 nm) with contact delivery are best suited for transscleral photocoagulation. PMID:1895865

  19. Optical properties of human sclera, and their consequences for transscleral laser applications

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, A.; Dlugos, C.; Nuffer, R.; Birngruber, R. (H. Wacker Laboratory of Medical Laser Applications, University Eye Hospital Munich (West Germany))

    1991-01-01

    The spectral dependence of the optical properties of human sclera adjacent to the limbus was investigated and related to the potentials of transscleral photocoagulation. The total transmission, absorption, and reflection, as well as the angular distribution of the transmitted and reflected light were measured at five laser wavelengths (442 nm, 514 nm, 633 nm, 804 nm, and 1,064 nm), both for noncontact and contact applications. Absorption and scattering coefficients were determined using the Kubelka-Munk model for light propagation through a scattering tissue. The scleral transmission is only 6% at 442 nm but increases to 35% at 804 nm and to 53% at 1,064 nm. The absorption is high at short wavelengths with 40% at 442 nm but it is only 6% at 804 nm and 1,064 nm. The reflection is generally higher than 40% and shows little wavelength dependence. The transmitted light is scattered diffusely at short wavelengths, but at 804 nm and 1,064 nm it exhibits a fairly narrow angular distribution in forward direction. Fiber contact leads to an increase of transmission, with a factor of 3.5 at 442 nm, of 2.0 at 804 nm, and 1.5 at 1,064 nm. Our results indicate that the diode laser (804 nm) and the Nd:YAG laser (1,064 nm) with contact delivery are best suited for transscleral photocoagulation.

  20. [Optical properties of human sclera and their significance for trans-scleral laser use].

    Science.gov (United States)

    Vogel, A; Dlugos, C; Nuffer, R; Birngruber, R

    1991-01-01

    The spectral dependence of the optical properties of human sclera adjacent to the limbus was investigated and related to the potentials of transscleral photocoagulation. The total transmission, absorption and reflection and the angular distribution of the transmitted and reflected light were measured at five laser wavelengths (442 nm, 514 nm, 633 nm, 804 nm, and 1064 nm) for both noncontact and contact applications. The scleral transmission is only 6% at 442 nm, but increases to 35% at 804 nm and 53% at 1064 nm. The absorption is high at short wavelengths, with 40% at 442 nm, but it is only 6% at 804 nm and 1064 nm. The reflection is generally higher than 40% and shows little wavelength dependence. The transmitted light is scattered diffusely at short wavelengths, but at 804 nm and 1064 nm it exhibits a fairly narrow angular distribution in the forward direction. Fiber contact leads to an increase in transmission, with a factor of 3.5 at 442 nm, of 2.0 at 804 nm, and of 1.5 at 1064 nm. Our results indicate that the diode laser (804 nm) and the Nd:YAG laser (1064 nm) are best suited for transscleral photocoagulation and that contact delivery leads to a reduction of the energy required for cyclophotocoagulation. PMID:1794798

  1. Laser Peripheral Iridotomy with Iridoplasty in Primary Angle Closure Suspect: Anterior Chamber Analysis by Pentacam

    OpenAIRE

    Lee, Jong Rak; Choi, Jin Young; Kim, Yeon-Deok; Choi, Jaewan

    2011-01-01

    Purpose To compare conventional laser peripheral iridotomy (LPI) and LPI combined with laser peripheral iridoplasty in eyes with primary angle closure suspect (PACS) by assessment of anterior chamber dimensional changes using a Pentacam. Methods Forty-eight eyes of 24 subjects with bilateral PACS were recruited consecutively. Each eye was randomly allocated to treatment with conventional LPI, argon LPI only, or LPI plus iridoplasty, which consisted of simultaneous argon LPI and peripheral iri...

  2. Holographic schlieren investigation of laser-induced plasmas

    International Nuclear Information System (INIS)

    Quantitative holographic schlieren studies of a CO2 laser induced breakdown in argon have been made using a pulsed ruby laser. Complete mappings of the density gradient profiles at different temporal stages of the plasma are obtained. The density gradients are integrated to obtain density profiles which compare well with those obtained directly by holographic interferometry. (Auth.)

  3. Two-dimensional ion velocity distribution functions in inductively coupled argon plasma

    Energy Technology Data Exchange (ETDEWEB)

    Zimmerman, David C [Optical Sciences Company, Anaheim, CA 92806 (United States); McWilliams, Roger [Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697 (United States); Edrich, David A [Scientific Applications and Research Associates Inc., Cypress, CA 90630 (United States)

    2005-08-01

    Two-dimensional ion velocity distribution functions (IVDFs) of argon plasmas have been measured with optical tomography via laser-induced fluorescence (LIF). An inductive radio-frequency (RF) coil created the plasmas, and IVDFs were measured versus RF frequency, gas pressure and location (bulk plasma or presheath of a plate). Typical gas pressure was 0.3-0.4 mTorr, RF power 25 W and magnetic field 130 G. Effective perpendicular ion temperature decreased with increasing RF frequency, and changed little with pressure. Optical tomography reveals features of the presheath IVDF that cannot be deduced from LIF scans parallel and perpendicular to the plate alone. Progress also has been made toward performing optical tomography on a commercial ion beam source (Veeco/Ion Tech 3 cm RF Ion Source, Model no. 201). In particular, it has been discovered that the beam energy fluctuates in a range of about 20 eV over the timescale of a few minutes.

  4. The Effect of the Argon Carrier Gas in the Multiphoton Dissociation-Ionization of Tetracene

    Directory of Open Access Journals (Sweden)

    Carmen Cisneros

    2008-10-01

    Full Text Available The multiphoton dissociation-ionization of tetracene at 355 nm using 6.5 nanosecond laser pulses, with and without argon as a carrier gas (CG, has been studied and compared. Ion fragments were analyzed in a time-of-flight mass spectrometer and separated according to their mass-to-charge ratio (m/z. The results show that the dynamic of photodissociation at ~1010 W⋅cm-2 intensities is strongly influenced by the CG. The suppression of fragmentation channels primarily those relating to the formation of the CHm+ (m = 2, 4, C2H4+ and C5H4+2 ions. CH5+ and CH6+ were observed which have not been reported before in photodissociation tetracene experiments.

  5. Study of collisional and radiatif processes for atmospheric pressure argon plasma in stationary state and quenching

    International Nuclear Information System (INIS)

    The positive column of a wall-stabilized arc burning in argon at atmospheric pressure is studied. In the first part, experimental values of electron and atom number densities are presented. They have been obtained in stationary state and during the arc decay by means of spectroscopy and two wavelengths laser interferometry measurements. The theoretical study has been developed with a collisional-radiative model coupled with the electron energy balance. Electron-ion recombination and ionization coefficients have been calculated solving rate equations. Then the model has been adapted for studying a stationary plasma and the calculated results are in good agreement with the experimental values. The theoretical study of the plasma decay has allowed us to determine the influence of recombination, ionization, diffusion and convection in the evolution of densities and temperatures. Temporal variations of the difference between electron temperature and gas temperature have been explained by analysing the electron energy balance

  6. Modelling of a supersonic ICP argon-hydrogen expansion

    International Nuclear Information System (INIS)

    An expanding argon-hydrogen plasma is investigated by means of simulations. The model is a hydrodynamical model specific for plasma expansions, taking into account the conservation laws of mass, momentum and energy. The code includes the Rankine-Hugoniot relations to calculate shock jump conditions. Results are shown for the expansion from an inductively coupled plasma (ICP) with a separated Laval nozzle. The expansion discussed here is a 'weakly' under-expanding argon-hydrogen plasma. The results from the ICP expansion are verified with probe measurements

  7. Oxygen removal from tantalum and niobium in an argon atmosphere

    International Nuclear Information System (INIS)

    The rate of oxygen removal from tantalum and niobium has been determined as a function of argon pressure (0-760 Torr) at temperatures from 1900 to 24000C. The reduction of the reaction rate v depends only on the argon pressure and can be given by a factor α = v/v0. The following formulae are obtained for α: Ta: α = (1 + 0.15psub(Ar)sup(0.9))-1, Nb: α = (1 + 0.5psub(Ar)sup(0.9))-1.

  8. Photoionization in liquid argon doped with trimethylamine or triethylamine

    International Nuclear Information System (INIS)

    Ionization yields for alpha particles and 1 MeV electrons in liquid argon doped with trimethylamine and with triethylamine have been measured. In both liquids, a collected charge larger than Anderson's results is observed for alpha particles although that for electrons is similar to Anderson's value. By using a new equation for the collected charge, the photoionization quantum efficiencies for scintillation light in liquid argon are estimated to be 0.35+-0.05 for trimethylamine and greater than 0.23+-0.03 for triethylamine. (orig.)

  9. Superconductivity of compressed solid argon from first principles

    Science.gov (United States)

    Ishikawa, Takahiro; Asano, Masamichi; Suzuki, Naoshi; Shimizu, Katsuya

    2015-02-01

    We present first-principles calculations on the superconductivity of solid argon under high pressure. Solid argon is found to take the double hexagonal close-packed structure in pressure range from 420 to 690 GPa, where an insulator-to-metal transition occurs at around 590 GPa. The crystal structure transforms into the hexagonal close-packed structure at 690 GPa and into the face-centered cubic structure at 2300 GPa. The superconducting critical temperature is gradually increased with the successive phase transitions and reaches the maximum value of 12 K at 2600 GPa due to the enhancement of the Fermi surface nesting.

  10. Attosecond-correlated dynamics of two electrons in argon

    Indian Academy of Sciences (India)

    V Sharma; N Camus; B Fischer; M Kremer; A Rudenko; B Bergues; M Kuebel; N G Johnson; M F Kling; T Pfeifer; J Ullrich; R Moshammer

    2014-01-01

    In this work we explored strong field-induced decay of doubly excited transient Coulomb complex Ar** → Ar2++2. We measured the correlated two-electron emission as a function of carrier envelop phase (CEP) of 6 fs pulses in the non-sequential double ionization (NSDI) of argon. Classical model calculations suggest that the intermediate doubly excited Coulomb complex loses memory of its formation dynamics. We estimated the ionization time difference between the two electrons from NSDI of argon and it is 200 ± 100 as (N Camus et al, Phys. Rev. Lett. 108, 073003 (2012)).

  11. The ATLAS liquid argon electromagnetic calorimeter construction status

    CERN Document Server

    Jérémie, A

    2004-01-01

    The construction and assembly of the ATLAS liquid argon electromagnetic calorimeter was described. The calorimeter was built with accordion geometry composed of lead absorbers, liquid argon as ionizing medium and highly granular readout electrodes. The calorimeter was composed of the Barrel and the End-cap, both preceded by presampler sectors to ensure complete recovery of the energy resolution. The detection of cabling errors and testing of the whole calibration chain was done by sending a pulse through the calibration circuit with single readout. (Edited abstract) 3 Refs.

  12. The Erosion of Frozen Argon by Swift Helium Ions

    DEFF Research Database (Denmark)

    Besenbacher, F.; Bøttiger, Jørgen; Graversen, O.; Hansen, Jens Leonhart; Sørensen, H.

    The temperature, energy, and thickness dependence of the erosion rates of frozen argon films when irradiated with 0.1–3 MeV helium ions have been measured. The erosion yields Y are much too high to be explained by the concentional collisional cascade-sputtering theory and are furthermore unequivo......The temperature, energy, and thickness dependence of the erosion rates of frozen argon films when irradiated with 0.1–3 MeV helium ions have been measured. The erosion yields Y are much too high to be explained by the concentional collisional cascade-sputtering theory and are furthermore...

  13. Measurement of Longitudinal Electron Diffusion in Liquid Argon

    CERN Document Server

    Li, Yichen; Thorn, Craig; Qian, Xin; Diwan, Milind; Joshi, Jyoti; Kettell, Steve; Morse, William; Rao, Triveni; Stewart, Jim; Tang, Wei; Viren, Brett

    2015-01-01

    We report the measurement of longitudinal electron diffusion coefficients in liquid argon for electric fields between 100 and 2000 V/cm with a gold photocathode as a bright electron source. The measurement principle, apparatus, and data analysis are described. Our results, which are consistent with previous measurements in the region between 100 to 350 V/cm [1] , are systematically higher than the prediction of Atrazhev-Timoshkin[2], and represent the world's best measurement in the region between 350 to 2000 V/cm. The quantum efficiency of the gold photocathode, the drift velocity and longitudinal diffusion coefficients in gas argon are also presented.

  14. Time-resolved characterization of a filamentary argon discharge at atmospheric pressure in a capillary using emission and absorption spectroscopy

    Science.gov (United States)

    Schröter, Sandra; Pothiraja, Ramasamy; Awakowicz, Peter; Bibinov, Nikita; Böke, Marc; Niermann, Benedikt; Winter, Jörg

    2013-11-01

    An argon/nitrogen (0.999/0.001) filamentary pulsed discharge operated at atmospheric pressure in a quartz tube is characterized using voltage-current measurements, microphotography, optical emission spectroscopy (OES) and absorption spectroscopy. Nitrogen is applied as a sensor gas for the purpose of OES diagnostic. The density of argon metastable atoms Ar(3P2) is determined using tunable diode laser absorption spectroscopy (TDLAS). Using a plasma chemical model the measured OES data are applied for the characterization of the plasma conditions. Between intense positive pulses the discharge current oscillates with a damped amplitude. It is established that an electric current flows in this discharge not only through a thin plasma filament that is observed in the discharge image but also through the whole cross section of the quartz tube. A diffuse plasma fills the quartz tube during a time between intense current pulses. Ionization waves are propagating in this plasma between the spike and the grounded area of the tube producing thin plasma channels. The diameter of these channels increases during the pause between the propagation of ionization waves probably because of thermal expansion and diffusion. Inside the channels electron densities of ˜2 × 1013 cm-3, argon metastable densities ˜1014 cm-3 and a reduced electric field about 10 Td are determined.

  15. Measurement of the Cotton-Mouton effect in nitrogen, oxygen, carbon dioxide, argon, and krypton with the Q & A apparatus

    CERN Document Server

    Mei, Hsien-Hao; Chen, Sheng-Jui; Pan, Sheau-shi

    2008-01-01

    Experiments for vacuum birefringence and vacuum dichroism have set up high-finesse high magnetic experimental apparatuses which are ideal for gaseous Cotton-Mouton effect measurements. PVLAS Collaboration has recently measured Cotton-Mouton effects in krypton, xenon and neon at the wavelength of 1064 nm. In this Letter, we report on our measurement of Cotton-Mouton effects in nitrogen, oxygen, carbon dioxide, argon, and krypton at pressure P = 0.5-300 Torr, temperature T = 295-298 K, and laser wavelength of 1064 nm in a magnetic field B = 2.3 T, using our Q & A experimental setup, which are in agreement with the PVLAS results.

  16. Improvement in retinal venous oxygen saturation after panretinal photocoagulation is predictive of progression of proliferative diabetic retinopathy

    DEFF Research Database (Denmark)

    Torp, Thomas Lee; Kawasaki, Ryo; Wong, Tien Yin;

    blood pressure was 152/84mmHg. Retinal arterial and venous saturation was 96.7% and 67.4%, respectively. Patients in Group 1 and 2 did not differ in baseline retinal arterial and venous oxygen saturation, number of laser spots delivered, total laser energy delivered, or change in retinal arterial oxygen...... PRP was independently associated with PDR-activity. This might reflect absence in reduction in vascular endothelial growth factor (VEGF) and could be a potential non-invasive marker of disease activity.......®; OD-OS GmbH, Berlin, Germany). At follow-up, WFA was used to evaluate PDR activity and patients were categorized into two groups: progression (Group 1, n=10) or stability/regression of PDR (Group 2, n=29). Retinal oximetry measurements were performed on optic disc centered images using the in...

  17. Uranium-liquid argon calorimetry: preliminary results from the DO tests

    International Nuclear Information System (INIS)

    The motivations for using uranium and liquid argon in sampling calorimetry are reviewed and the pros and cons of the technique are discussed. Preliminary results of the DO uranium-liquid argon test program are presented. 9 refs., 7 figs

  18. Handheld Automated Microsurgical Instrumentation for Intraocular Laser Surgery

    Science.gov (United States)

    Yang, Sungwook; Lobes, Louis A.; Martel, Joseph N.; Riviere, Cameron N.

    2016-01-01

    Background and Objective Laser photocoagulation is a mainstay or adjuvant treatment for a variety of common retinal diseases. Automated laser photocoagulation during intraocular surgery has not yet been established. The authors introduce an automated laser photocoagulation system for intraocular surgery, based on a novel handheld instrument. The goals of the system are to enhance accuracy and efficiency and improve safety. Materials and Methods Triple-ring patterns are introduced as a typical arrangement for the treatment of proliferative retinopathy and registered to a preoperative fundus image. In total, 32 target locations are specified along the circumferences of three rings having diameters of 1, 2, and 3 mm, with a burn spacing of 600 μm. Given the initial system calibration, the retinal surface is reconstructed using stereo vision, and the targets specified on the preoperative image are registered with the control system. During automated operation, the laser probe attached to the manipulator of the active handheld instrument is deflected as needed via visual servoing in order to correct the error between the aiming beam and a specified target, regardless of any erroneous handle motion by the surgeon. A constant distance of the laser probe from the retinal surface is maintained in order to yield consistent size of burns and ensure safety during operation. Real-time tracking of anatomical features enables compensation for any movement of the eye. A graphical overlay system within operating microscope provides the surgeon with guidance cues for automated operation. Two retinal surgeons performed automated and manual trials in an artificial model of the eye, with each trial repeated three times. For the automated trials, various targeting thresholds (50–200 μm) were used to automatically trigger laser firing. In manual operation, fixed repetition rates were used, with frequencies of 1.0–2.5 Hz. The power of the 532 nm laser was set at 3.0 W with a

  19. Evaluation of the TA combined with Panretinal photocoagulation in treating the diabetic macular edema%TA联合全视网膜光凝治疗糖尿病性黄斑水肿的效果评价

    Institute of Scientific and Technical Information of China (English)

    孟晶; 张旭; 张日佳; 李诗娜; 李水莲

    2012-01-01

    statistical analysis methods by the SPSS data applications,including the t-test,the direct probability calculation,and repeated design analysis of variance. Results The average best corrected visual acuity in the combined treatment group were higher than the PRP treatment group 3 months and 6 months after treatment (P<0.05).The RNV leakage area was significantly lower in the combined treatment group after treatment of 1 month and 3 months (P <0.05),but was not significant after 6 months (P>0.05).The macular retinal thickness values lowered in the joint group after 1 month,3 months,6 months (P<0.05).The combined treatment group required lower laser energy than the PRP treatment group (P<0.01).The IOP in both groups were no different (P>0.05). Conclusions Intravitreal injection of TA combined with all retinal photocoagulation is a good way in treat the diabetic macular edema,which can reduce the energy needed for PRP,reduce the delay edema,and improve vision,which is a worthy recommendation in treating the diabetic macular edema.

  20. Optical emission spectroscopy of argon and hydrogen-containing plasmas

    Science.gov (United States)

    Siepa, Sarah; Danko, Stephan; Tsankov, Tsanko V.; Mussenbrock, Thomas; Czarnetzki, Uwe

    2015-09-01

    Optical emission spectroscopy (OES) on neutral argon is applied to investigate argon, hydrogen and hydrogen-silane plasmas. The spectra are analyzed using an extensive collisional-radiative model (CRM), from which the electron density and the electron temperature (or mean energy) can be calculated. The CRM also yields insight into the importance of different excited species and kinetic processes. The OES measurements are performed on pure argon plasmas at intermediate pressure. Besides, hydrogen and hydrogen-silane plasmas are investigated using argon as a trace gas. Especially for the gas mixture discharges, CRMs for low and high pressure differ substantially. The commonly used line-ratio technique is found to lose its sensitivity for gas mixture discharges at higher pressure. A solution using absolutely calibrated line intensities is proposed. The effect of radiation trapping and the shape of the electron energy distribution function on the results are discussed in detail, as they have been found to significantly influence the results. This work was supported by the Ruhr University Research School PLUS, funded by Germany's Excellence Initiative [DFG GSC 98/3].

  1. High-frequency electrodeless lamps in argon-mercury mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Denisova, N [Institute of Theoretical and Applied Mechanics, Novosibirsk (Russian Federation); Revalde, G [Institute of Atomic Physics and Spectroscopy, University of Latvia, Raina blvd. 19, Riga (Latvia); Skudra, A [Institute of Atomic Physics and Spectroscopy, University of Latvia, Raina blvd. 19, Riga (Latvia); Zissis, G [CPAT, University Toulouse 3, 118 rte de Narbonne, 31062 Toulouse (France); Zorina, N [Institute of Atomic Physics and Spectroscopy, University of Latvia, Raina blvd. 19, Riga (Latvia)

    2005-09-07

    In this paper, numerical and experimental investigations of high-frequency (HF) electrodeless lamps in argon-mercury mixtures are performed. The intensities of the mercury spectral lines having wavelengths {lambda} = 404.66, 435.83, 546.07 nm (7{sup 3}S{sub 1}-6{sup 3}P{sub 0,1,2}) and the resonance line {lambda} = 253.7 nm (6{sup 3} P{sub 1}-6{sup 1}S{sub 0}) are measured at a wide range of mercury pressures, varying the HF generator current and argon filling pressure. A stationary self-consistent model of HF electrodeless discharge lamp is developed including kinetics of the excited mercury and argon atomic states. Based on the developed model, the radiation characteristics of the discharge plasma are calculated. Numerical simulation of the line intensities behaviour in dependence on the mercury pressure, HF generator current and argon filling pressure is performed. The model results are in qualitative agreement with the experimental data. The calculations of the relative intensities of the visible triplet lines 7{sup 3}S{sub 1}-6{sup 3}P{sub 0,1,2} are presented for the first time in this paper.

  2. Measurement of the argon plasma temperature by use of pyrometer

    International Nuclear Information System (INIS)

    The author describes in detail how to use pyrometer to measure the plasma temperature. The temperatures of shock-generated argon plasmas are given in the present work. Measured results of temperature-pressure curve are compared with calculated results using Saha-Debye-Huckel model, which are in good agreement

  3. LArGe. A liquid argon scintillation veto for GERDA

    International Nuclear Information System (INIS)

    LArGe is a GERDA low-background test facility to study novel background suppression methods in a low-background environment, for possible applications in the GERDA experiment. GERDA searches for the neutrinoless double-beta decay in 76Ge, by operating naked germanium detectors submersed into 65 m3 of liquid argon. Similarly, LArGe runs Ge-detectors in 1 m3 (1.4 tons) of liquid argon, which in addition is instrumented with photomultipliers to detect argon scintillation light. The light is used in anti-coincidence with the germanium detectors, to effectively suppress background events that deposit energy in the liquid argon. This work adresses the design, construction, and commissioning of LArGe. The background suppression efficiency has been studied in combination with a pulse shape discrimination (PSD) technique for various sources, which represent characteristic backgrounds to GERDA. Suppression factors of a few times 103 have been achieved. First background data of LArGe (without PSD) yield a background index of (0.12-4.6).10-2 cts/(keV.kg.y) (90% c.l.), which is at the level of the Gerda phase I design goal. Furthermore, for the first time we measure the natural 42Ar abundance (in parallel to Gerda), and have indication for the 2νββ-decay in natural germanium. (orig.)

  4. Study of Liquid Argon Dopants for LHC Hadron Calorimetry

    CERN Multimedia

    2002-01-01

    Hadron calorimetry based on the Liquid Argon Ionisation Chamber technique is one of the choice techniques for LHC-experimentation. A systematic study of the effect of selected dopants on Liquid Argon (LAr) will be carried out with the aim to achieve an improvement on: \\item (i)~``Fast Liquid Argon'' search and study of dopants to increase the drift velocity. It has been already shown that CH&sub4. added at a fraction of one percent increases the drift velocity by a factor of two or more. \\item (ii)~``Compensated Liquid Argon'' search and study of dopants to increase the response to densely ionising particles, resulting in improved compensation, such as photosensitive dopants. \\end{enumerate}\\\\ \\\\ Monitoring of the parameters involved in understanding the response of a calorimeter is essential. In case of doped LAr, the charge yield, the non-saturated drift velocity and the electron lifetime in the liquid should be precisely and simultaneously monitored as they all vary with the level of dopant concentrati...

  5. Aging tests of ethylene contaminated argon/ethane

    International Nuclear Information System (INIS)

    We report on aging tests of argon/ethane gas with a minor (1800 ppM) component of ethylene. The measurements were first conducted with the addition of alcohol to test the suppression of aging by this additive, with exposure up to ∼1.5 C/cm. Tests have included: a proportional tube with ethanol, another with isopropyl alcohol, and for comparison a tube has also been run with ethanol and argon/ethane from CDF's old (ethylene-free) ethane supply. The aging test with ethanol showed no difference between the ethylene-free and the ethylene tube. Furthermore, raw aging rates of argon/ethane and argon/ethane/ethylene were measured by exposing tubes without the addition of alcohol to about 0.1 C/cm. Again, no significant difference was observed. In conclusion, we see no evidence that ethylene contamination up to 1800 ppM has any adverse effect on wire aging. However, this level of ethylene does seem to significantly suppress the gas gain

  6. The ATLAS Liquid Argon Calorimeter: Construction, Integration, Commissioning

    International Nuclear Information System (INIS)

    The ATLAS liquid argon (LAr) calorimeter system consists of an electromagnetic barrel calorimeter and two end caps with electromagnetic, hadronic and forward calorimeters. The liquid argon sampling technique, with an accordion geometry was chosen for the barrel electromagnetic calorimeter (EMB) and adapted to the end cap (EMEC). The hadronic end cap calorimeter (HEC) uses a copper-liquid argon sampling technique with flat plate geometry and is subdivided in depth in two wheels per end-cap. Finally, the forward calorimeter (FCAL) is composed of three modules employing cylindrical electrodes with thin liquid argon gaps.The construction of the full calorimeter system is complete since mid-2004. Production modules constructed in the home institutes were integrated into wheels at CERN in 2003-2004, and inserted into the three cryostats. They passed their first complete cold test before the lowering into the ATLAS cavern. Results of quality checks (e.g. electrical, mechanical, ...) performed on all the 190304 read-out channels after cool down will be reported. End 2004 the ATLAS barrel electromagnetic (EM) calorimeter was installed in the ATLAS cavern and since summer 2005 the front-end electronics are being connected and tested. Results of this first commissioning phase will be shown to demonstrate the high standards of quality control for our detectors

  7. X ray diagnostics of the argon filled dense plasma focus

    International Nuclear Information System (INIS)

    An experimental investigation has been conducted to use a Dense Plasma Focus Machine as a prospected high intensity pulsed x ray source. The argon was chosen for the plasma discharge. An effort to reach the highest x ray intensity emission has been made. Although it has not yet been possible to operate with as high energy in argon as in hydrogen, the argon focus provides an intensified ''point source'' of x ray. Based on the diagnostic data and the characteristic difference between argon and hydrogen, a theoretical model of the shock wave was proposed. The x ray energy spectrum of the focus was determined by a crystal spectrometer. Analyzing this spectrum, one can obtain a combined radiation from a 3 keV thermal plasma and a 48 keV electron beam bombarding the center electrode. The polarization of the x ray was measured at a direction perpendicular to the DPF axis. The change of the polarization with time indicated that the plasma impinged radially and then followed by an axial flow. The correlation of the x ray signal with the voltage signal showed that the plasma resistance was rising after the density reached its maximum, and associated the increase of the resistivity as a result of ion-acoustic instability

  8. Scattering of Slow Metastable Argon Atoms by Dielectric Nanospheres

    Science.gov (United States)

    Baudon, J.; Hamamda, M.; Grucker, J.; Perales, F.; Dutier, G.; Ducloy, M.; Bocvarski, V.

    2009-11-01

    The elastic scattering at low energy of metastable argon atoms with internal angular momentum J = 0 and 2 by dielectric nanospheres is investigated. The differential cross sections are calculated for both isotropic and anisotropic interactions. A polarization effect is clearly evidenced. The possible use of a metastable atom beam as a probe of an ensemble of nanospheres deposited on a passive substrate is examined.

  9. LArGe. A liquid argon scintillation veto for GERDA

    Energy Technology Data Exchange (ETDEWEB)

    Heisel, Mark

    2011-04-13

    LArGe is a GERDA low-background test facility to study novel background suppression methods in a low-background environment, for possible applications in the GERDA experiment. GERDA searches for the neutrinoless double-beta decay in {sup 76}Ge, by operating naked germanium detectors submersed into 65 m{sup 3} of liquid argon. Similarly, LArGe runs Ge-detectors in 1 m{sup 3} (1.4 tons) of liquid argon, which in addition is instrumented with photomultipliers to detect argon scintillation light. The light is used in anti-coincidence with the germanium detectors, to effectively suppress background events that deposit energy in the liquid argon. This work adresses the design, construction, and commissioning of LArGe. The background suppression efficiency has been studied in combination with a pulse shape discrimination (PSD) technique for various sources, which represent characteristic backgrounds to GERDA. Suppression factors of a few times 10{sup 3} have been achieved. First background data of LArGe (without PSD) yield a background index of (0.12-4.6).10{sup -2} cts/(keV.kg.y) (90% c.l.), which is at the level of the Gerda phase I design goal. Furthermore, for the first time we measure the natural {sup 42}Ar abundance (in parallel to Gerda), and have indication for the 2{nu}{beta}{beta}-decay in natural germanium. (orig.)

  10. Design of capsules capable of argon-filling

    International Nuclear Information System (INIS)

    The possibility of the use of polycarbosilane capsules as fuel container in inertial confinement fusion experiments was analyzed in the paper. Primary study indicates that the polycarbosilane capsules can be filled with argon by means of diffusion and possess reasonable retention time for deuterium. (author)

  11. Experimental and numerical study of high intensity argon cluster beams

    International Nuclear Information System (INIS)

    Experimental and numerical investigations of expansion of argon with homogeneous condensation in supersonic conical nozzle and in free jet behind it were carried out. Optimal parameters (stagnation pressure, nozzle-skimmer distance) for the formation of cluster beam with maximum intensity were determined. Two available models for nonequilibrium nucleation were tested. The numerical results are in satisfactory agreement with the measured data

  12. Thermal decomposition of yttrium(III) valerate in argon

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Yue, Zhao; Tang, Xiao; Pallewatta, Pallewatta G A P; Watenphul, A.; Zimmermann, M. v.

    2014-01-01

    The thermal decomposition of yttrium(III) valerate (Y(C4H9CO2)3) was studied in argon by means of thermogravimetry, differential thermal analysis, IR-spectroscopy, X-ray diffraction, in-situ synchrotron diffraction and hot-stage microscopy as well as room temperature optical microscopy. Melting...

  13. Turbulence and transport in a magnetized argon plasma

    International Nuclear Information System (INIS)

    An experimental study on turbulence and transport in the highly ionized argon plasma of a hollow cathode discharge is described. In order to determine the plasma parameters three standard diagnostics have been used, whilst two diagnostics have been developed to study the plasma turbulence. (Auth.)

  14. Study of a microwave discharge in argon/helium mixtures

    International Nuclear Information System (INIS)

    A discharge created by a surface wave in Argon-Helium mixture is studied. First, the helium influence on plasma parameters has been studied (electron density, electric field, effective collision frequency, etc...), then, on excitation processes in the discharge. Relations between plasma lines, electron density and electric field have been established

  15. Thermophysical properties of multi-shock compressed dense argon.

    Science.gov (United States)

    Chen, Q F; Zheng, J; Gu, Y J; Chen, Y L; Cai, L C; Shen, Z J

    2014-02-21

    In contrast to the single shock compression state that can be obtained directly via experimental measurements, the multi-shock compression states, however, have to be calculated with the aid of theoretical models. In order to determine experimentally the multiple shock states, a diagnostic approach with the Doppler pins system (DPS) and the pyrometer was used to probe multiple shocks in dense argon plasmas. Plasma was generated by a shock reverberation technique. The shock was produced using the flyer plate impact accelerated up to ∼6.1 km/s by a two-stage light gas gun and introduced into the plenum argon gas sample, which was pre-compressed from the environmental pressure to about 20 MPa. The time-resolved optical radiation histories were determined using a multi-wavelength channel optical transience radiance pyrometer. Simultaneously, the particle velocity profiles of the LiF window was measured with multi-DPS. The states of multi-shock compression argon plasma were determined from the measured shock velocities combining the particle velocity profiles. We performed the experiments on dense argon plasmas to determine the principal Hugonoit up to 21 GPa, the re-shock pressure up to 73 GPa, and the maximum measure pressure of the fourth shock up to 158 GPa. The results are used to validate the existing self-consistent variational theory model in the partial ionization region and create new theoretical models. PMID:24559345

  16. Thermal decomposition of yttrium(III) hexanoate in argon

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Suarez Guevara, Maria Josefina; Attique, Fahmida;

    2015-01-01

    The thermal decomposition of yttrium(III) hexanoate (Y(C5H11CO2)3)·xH2O in argon was studied by means of thermogravimetry, differential thermal analysis, IR-spectroscopy, X-ray diffraction at a laboratory Cu-tube source and in-situ experiments at a synchrotron radiation source as well as hot...

  17. The role of metastable atoms in argon-diluted silane radiofrequency plasmas

    OpenAIRE

    Sansonnens, L.; Howling, A.A.; Hollenstein, C.; Dorier, J. L.; Kroll, U.

    2008-01-01

    The evolution of the argon metastable states density has been studied by absorption spectroscopy in power-modulated plasmas of argon and a mixture of 4% silane in argon. A small concentration of silane suppresses the argon metastable states density by molecular quenching. This molecular quenching adds to the electronic collisional dissociation to increase the silane dissociation rate as compared with pure silane plasmas. Using time-resolved emission spectroscopy, the role of metastable states...

  18. Potassium-Argon ages on mesozoic tholeutic dike Swarm in Rio Grande do Norte, Brazil

    International Nuclear Information System (INIS)

    Potassium-argon ages are reported for samples from four localities which represent three laterally separated Mesozoic tholeitic dikes in Precambrian oF Rio Grande do Norte, Brazil. The ages for the dikes are between 167 Ma and 130 Ma. It is shown that most of the ages determined are minimum ages due to argon losses. The methodological approach to identify argon losses is described. Ecess argon cannot be of significant influence on the ages found. (author)

  19. Conversion of an atomic to a molecular argon ion and low pressure argon relaxation

    Science.gov (United States)

    M, N. Stankov; A, P. Jovanović; V, Lj Marković; S, N. Stamenković

    2016-01-01

    The dominant process in relaxation of DC glow discharge between two plane parallel electrodes in argon at pressure 200 Pa is analyzed by measuring the breakdown time delay and by analytical and numerical models. By using the approximate analytical model it is found that the relaxation in a range from 20 to 60 ms in afterglow is dominated by ions, produced by atomic-to-molecular conversion of Ar+ ions in the first several milliseconds after the cessation of the discharge. This conversion is confirmed by the presence of double-Gaussian distribution for the formative time delay, as well as conversion maxima in a set of memory curves measured in different conditions. Finally, the numerical one-dimensional (1D) model for determining the number densities of dominant particles in stationary DC glow discharge and two-dimensional (2D) model for the relaxation are used to confirm the previous assumptions and to determine the corresponding collision and transport coefficients of dominant species and processes. Project supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Grant No. ON171025).

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

    Science.gov (United States)

    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. Horse shoe retinal tear, vitreous hemorrage, macular pucker 15 months after laser in Situ keratomileusis: case report

    OpenAIRE

    Gholamhossein Yaghoobi; Behrouz Heydari

    2013-01-01

    A 44 year old woman presented with decreased vision and floaters, started since 4 days before, in her right eye referred to our ophthalmology clinic. On examination, it was found that the best corrected visual acuity was limited to R-E: 20/80 and that of the left eye: 20/20. Fundus examination of the right eye revealed a rhegmatogenous subclinical retinal detachment and vitreous hemorrhage 15 months after surgery for myopia, but the left fundus was normal. Barrier diod laser photocoagulation ...

  2. Observations of acoustic-wave-induced superluminescence in an argon plasma

    International Nuclear Information System (INIS)

    It is shown that in an argon discharge plasma it is possible to obtain overpopulation of certain electronic levels of atomic argon under the influence of acoustic waves. When the specified threshold is exceeded, then a superluminescence (in the form of light flashes) from the overpopulated electronic levels of atomic argon is observed

  3. INFRARED DIODE LASER RETINAL TREATMENT FOR CHRONIC HEADACHE

    Directory of Open Access Journals (Sweden)

    Subba Rao

    2013-12-01

    Full Text Available ABSTRACT: Nearly 60 to 70 crores of people all over the world are suffering from various types of chronic headache. This is one of the commonest medical problems. To get relief from headache various medical treatments are used with little success. The aim of our study is to give permanent treatment to chronic headache patients by using infrared diode laser selective retinal photocoagulati on. NIDEK infrared diode laser with NIDEK SL40 slit - lamp and NIDEK digital fundus camera for retinal evaluation, MAINSTER 135D lens for laser beam focusing and retinal examination and TOPCON non - contact tonometer for intra ocular pressure measurements are used. Diode laser is chosen because of its deep penetration into all the layers of retina and choroid. 500 cases of chronic headache were studied. Laser photocoagulation was given in selective areas of retina in 2 to 3 sessions with 15 days interval. 10 to 60 years age group were studied. 90% of patients who got laser treatment are relieved from their headache in severity and in frequency. 80% of patients needed 2 sittings and 20% of patients needed 3 sittings. 70% of patients got relief from headache by fi rst sitting itself. 50% of patients are not only relieved from their headaches but also noticed visual clarity improvement. Retinal ischaemia is one of the main cause for ocular pain and headache. Laser treatment will improve circulation by reducing ischae mia thereby relieves ocular pain and headache

  4. Laser filament-induced aerosol formation

    OpenAIRE

    Saathoff, H.; Henin, S.; Stelmaszczyk, K.; Petrarca, M.; Delagrange, R.; Hao, Z.; Lüder, J.; Möhler, O.; Y. Petit; Rohwetter, P.; Schnaiter, M.; Kasparian, J.; Leisner, T.; J.-P. Wolf; Wöste, L.

    2013-01-01

    Using the aerosol and cloud simulation chamber AIDA, we investigated the laser filament induced particle formation in ambient air, humid synthetic air, humid nitrogen, argon–oxygen mixture, and pure argon in order to simulate the particle formation under realistic atmospheric conditions as well as to investigate the influence of typical gas-phase atmospheric constituents on the particle formation. Terawatt laser plasma filaments generated new particles in the size range 3 to 130 nm with parti...

  5. Laser filament-induced aerosol formation

    OpenAIRE

    Saathoff, H.; Henin, S.; Stelmaszczyk, K.; Petrarca, M.; Delagrange, R.; Hao, Z.; Lüder, J.; Möhler, O.; Y. Petit; Rohwetter, P.; Schnaiter, M.; Kasparian, J.; Leisner, T.; Wolf, J.-P.; Wöste, L.

    2013-01-01

    Using the aerosol and cloud simulation chamber AIDA, we investigated the laser filament induced particle formation in ambient air, humid synthetic air, humid nitrogen, argon–oxygen mixture, and pure argon in order to simulate the particle formation under realistic atmospheric conditions as well as to investigate the influence of typical gas-phase atmospheric constituents on the particle formation. Terawatt laser plasma filaments generated new particles in the size range 3 to...

  6. Molecular dynamic simulation for laser-cluster interaction

    International Nuclear Information System (INIS)

    A three dimensional relativistic molecular dynamic model for studying the laser interaction with atomic clusters is presented. The model is used to simulate the interaction dynamics of deuterium, argon, and xenon clusters when irradiated by the short and high intensity laser pulses. The interaction of 82 A argon cluster by 100 fs, 806 nm laser pulse with the peak intensity of 8 x 1015 W/cm2 is studied and compared with the experimental results. The maximum ion energy in this case is found to be about 200 keV. Ion energies along and perpendicular to laser polarization direction is calculated and asymmetry along laser polarization direction is detected which is further explained on the basis of charge flipping model. The effect of cluster density on the energetics of the laser-cluster interaction is also being studied, which provides a qualitative understanding of the presence of optimum cluster size for maximum ion energies.

  7. Method to determine argon metastable number density and plasma electron temperature from spectral emission originating from four 4p argon levels

    CERN Document Server

    Mariotti, Davide; Sasaki, Takeshi; Koshizaki, Naoto; 10.1063/1.2390631

    2010-01-01

    A simple model and method is proposed here to determine argon metastable number densities and electron temperature with the assumption of a Maxwell-Boltzmann electron energy distribution. This method is based on the availability of experimental relative emission intensities of only four argon lines that originate from any of the 4p argon levels. The proposed model has a relatively wide range of validity for laboratory plasmas that contain argon gas and can be a valuable tool for the emerging field of atmospheric microplasmas, for which diagnostics is still limited.

  8. Observing the effect of laser photocoagulation for diabetic retinopathy%糖尿病视网膜病变激光光凝术的疗效观察

    Institute of Scientific and Technical Information of China (English)

    奈蒙

    2013-01-01

    目的 观察糖尿病性视网膜病变(diabetic retinopathy,DR)激光光凝疗效,探讨DR激光光凝术的治疗时机和治疗方式.方法 对79例(114眼)DR患者,根据分期、病情,选择不同方式的光凝治疗,记录患者激光前及激光后1~6个月的最佳视力及眼底血管荧光造影(FFA)情况,评定疗效.结果 79例(114眼)DR患者接受光凝治疗前后视力及FFA结果表明,非增生性DR (nonproliferative diabetic retinopathy,NPDR)患者激光光凝疗效优于增生期DR ( proliferative diabetic retinopathy,PDR)患者.结论 眼底激光是治疗DR有效、安全的方法.严格规范的治疗方式,合理的治疗时机,可保存中心视力,提高疗效,有效治疗糖尿病视网膜病变.

  9. EFFECTS OF ARGON ON THE PROPERTIES OF RF SPUTTERED AMORPHOUS SILICON

    OpenAIRE

    Shao-Qi, Peng; Qai, Yu; Xian, Zhang; Jing, Ye

    1981-01-01

    The Effects of argon on the properties of rf sputtered amorphous silicon film have been investigated. As the sputtering argon pressure is increased from 2 to 20 mTorr, the content of argon in the amorphous silicon film increases apparently (Argon/Silicon : from 10-2 to 5 x 10-2). The other properties measured as a function of argon pressure PAr show that as the PAr is increased, the photoconductivity, resistivity (300K), conductivity activation energy and optical gap increase also, while the ...

  10. First Commissioning of a Cryogenic Distillation Column for Low Radioactivity Underground Argon

    CERN Document Server

    Back, Henning O; Alton, Andrew; Condon, Christopher; de Haas, Ernst; Galbiati, Cristiano; Goretti, Augusto; Hohmann, Tristan; Ianni, Andrea; Kendziora, Cary; Loer, Ben; Montanari, David; Mosteiro, Pablo; Pordes, Stephen

    2012-01-01

    We report on the performance and commissioning of a cryogenic distillation column for low radioactivity underground argon at Fermi National Accelerator Laboratory. The distillation column is designed to accept a mixture of argon, helium, and nitrogen and return pure argon with a nitrogen contamination less than 10 ppm. In the first commissioning, we were able to run the distillation column in a continuous mode and produce argon that is 99.9% pure. After running in a batch mode, the argon purity was increased to 99.95%, with 500 ppm of nitrogen remaining. The efficiency of collecting the argon from the gas mixture was between 70% and 81%, at an argon production rate of 0.84-0.98 kg/day.

  11. DOE Center of Excellence in Medical Laser Applications. Final report, December 1, 1994--November 30, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Jacques, S.L.

    1998-01-01

    An engineering network of collaborating medical laser laboratories are developing laser and optical technologies for medical diagnosis and therapy and are translating the engineering into medical centers in Portland OR, Houston TX, and Galveston TX. The Center includes the University of Texas M.D. Anderson Cancer Center, the University of Texas-Austin, Texas A and M University, Rice University, the University Texas Medical Branch-Galveston, Oregon Medical Laser Center (Providence St. Vincent Medical Center, Oregon Health Sciences University, and Oregon Graduate Institute, Portland, OR), and the University of Oregon. Diagnostics include reflectance, fluorescence, Raman IR, laser photoacoustics, optical coherence tomography, and several new video techniques for spectroscopy and imaging. Therapies include photocoagulation therapy, laser welding, pulsed laser ablation, and light-activated chemotherapy of cancer (photodynamic therapy, or PDT). Medical applications reaching the clinic include optical monitoring of hyperbilirubinemia in newborns, fluorescence detection of cervical dysplasia, laser thrombolysis of blood clots in heart attack and brain stroke, photothermal coagulant of benign prostate hyperplasia, and PDT for both veterinary and human cancer. New technologies include laser optoacoustic imaging of breast tumors and hemorrhage in head trauma and brain stroke, quality control monitoring of dosimetry during PDT for esophageal and lung cancer, polarization video reflectometry of skin cancer, laser welding of artificial tissue replacements, and feedback control of laser welding.

  12. LASER-ASSISTED e-Ar SCATTERING INCO2 LASER FIELD

    Institute of Scientific and Technical Information of China (English)

    Zhu Zun-lue; Jiang Yu-hai; Sun Jin-feng

    2000-01-01

    Electron scattering from argon in a laser field is investigatedempolying the second-order perturbation theory. The absolutedifferential cross sections of e-Ar scattering with multiphoton exchangein special scattering geometries G1 (for small-angle scattering) and G2are calculated. Our results are found to be better than othertheoretical results as compared with the experimental data.

  13. 21 CFR 878.4810 - Laser surgical instrument for use in general and plastic surgery and in dermatology.

    Science.gov (United States)

    2010-04-01

    ... plastic surgery and in dermatology. 878.4810 Section 878.4810 Food and Drugs FOOD AND DRUG ADMINISTRATION... dermatology. (a) Identification. (1) A carbon dioxide laser for use in general surgery and in dermatology is a...) An argon laser for use in dermatology is a laser device intended to destroy or coagulate tissue...

  14. Melissa officinalis extract inhibits laser-induced choroidal neovascularization in a rat model.

    Directory of Open Access Journals (Sweden)

    Eun Kyoung Lee

    Full Text Available 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

  15. Spectra of heliumlike carbon, aluminium and argon under strongly coupled plasma

    International Nuclear Information System (INIS)

    Spectral line positions for the highly stripped helium like carbon, aluminium and argon embedded in intense plasma environments have been calculated theoretically to compare with the existing data available from laser plasma experiments. The changes in the ionization potentials for such ions have been determined and the excitation energies, oscillator strengths and transition probabilities for the transitions 1s2 1S → 1snp 1P (n 2-5) have been evaluated for the diagnostic determination of such plasmas. The ion sphere (IS) model was used for estimating the effect of strongly coupled plasma on the ions within the non-relativistic as well as the relativistic framework. Time dependent perturbation theory has been applied for obtaining the linear response properties of the ions in the non-relativistic approximation. The effects of the plasma environment on such properties of the ions under the Debye screening model with suitable cut off radii have also been considered for comparing the data with those obtained from the IS model of the plasma. These results show that the IS model seems to be a viable method for predicting the data obtained from experiments involving strongly coupled plasmas generated in laser produced Icf plasmas

  16. Spectra of heliumlike carbon, aluminium and argon under strongly coupled plasma

    Energy Technology Data Exchange (ETDEWEB)

    Sil, A. [Heidelberg Univ., Theoretische Chemie (Germany); Anton, J. [Ulm Univ., Institut fur Elektrochemie (Germany); Fritzsche, S. [Gesellschaft fur Schwerionenforschung Darmstadt, Darmstadt (Germany); Mukherjee, P.K. [Indian Association for the Cultivation of Science, Jadavpur, Kolkata (India); Ramakrishna Mission Vivekananda Univ., West Bengal (India); Fricke, B. [Kassel Univ., Institut fur Physik (Germany)

    2009-12-15

    Spectral line positions for the highly stripped helium like carbon, aluminium and argon embedded in intense plasma environments have been calculated theoretically to compare with the existing data available from laser plasma experiments. The changes in the ionization potentials for such ions have been determined and the excitation energies, oscillator strengths and transition probabilities for the transitions 1s{sup 2} 1S -> 1snp {sup 1}P (n 2-5) have been evaluated for the diagnostic determination of such plasmas. The ion sphere (IS) model was used for estimating the effect of strongly coupled plasma on the ions within the non-relativistic as well as the relativistic framework. Time dependent perturbation theory has been applied for obtaining the linear response properties of the ions in the non-relativistic approximation. The effects of the plasma environment on such properties of the ions under the Debye screening model with suitable cut off radii have also been considered for comparing the data with those obtained from the IS model of the plasma. These results show that the IS model seems to be a viable method for predicting the data obtained from experiments involving strongly coupled plasmas generated in laser produced Icf plasmas

  17. Development of cryogenic installations for large liquid argon neutrino detectors

    CERN Document Server

    Adamowski, M; Geynisman, M; Hentschel, S; Montanari, D; Nessi, M; Norris, B

    2015-01-01

    A proposal for a very large liquid argon (68,000 kg) based neutrino detector is being studied. To validate the design principles and the detector technology, and to gain experience in the development of the cryostats and the cryogenic systems needed for such large experiments, several smaller scale installations will be developed and implemented, at Fermilab and CERN. The cryogenic systems for these installations will be developed, constructed, installed and commissioned by an international engineering team. These installations shall bring the required cooling power under specific conditions to the experiments for the initial cool-down and the long term operation, and shall also guarantee the correct distribution of the cooling power within the cryostats to ensure a homogeneous temperature distribution within the cryostat itself. The cryogenic systems shall also include gaseous and liquid phase argon purification devices to be used to reach and maintain the very stringent purity requirements needed for these...

  18. Measurement of longitudinal electron diffusion in liquid argon

    Science.gov (United States)

    Li, Yichen; Tsang, Thomas; Thorn, Craig; Qian, Xin; Diwan, Milind; Joshi, Jyoti; Kettell, Steve; Morse, William; Rao, Triveni; Stewart, James; Tang, Wei; Viren, Brett

    2016-04-01

    We report the measurement of longitudinal electron diffusion coefficients in liquid argon for electric fields between 100 and 2000 V/cm with a gold photocathode as a bright electron source. The measurement principle, apparatus, and data analysis are described. In the region between 100 and 350 V/cm, our results show a discrepancy with the previous measurement [1]. In the region between 350 and 2000 V/cm, our results represent the world's best measurement. Over the entire measured electric field range, our results are systematically higher than the calculation of Atrazhev-Timoshkin [2]. The quantum efficiency of the gold photocathode, the drift velocity and longitudinal diffusion coefficients in gas argon are also presented.

  19. Evaporation and condensation at a liquid surface. I. Argon

    Science.gov (United States)

    Yasuoka, Kenji; Matsumoto, Mitsuhiro; Kataoka, Yosuke

    1994-11-01

    Molecular dynamics computer simulations were carried out to investigate the dynamics of evaporation and condensation for argon at the temperature of 80 and 100 K. From the decrease of the survival probability of vapor molecules, the ratio of self reflection to collision is estimated to be 12%-15%, only weakly dependent on the temperature. This suggests that argon vapor molecules are in the condition of almost complete capture, and the condensation is considered to be a barrierless process. The total ratio of reflection which is evaluated with the flux correlation of condensation and evaporation is 20% at both temperature. The difference between these two ratios of reflection is ascribed to a phenomenon that vapor molecules colliding with the surface drive out other liquid molecules. This molecule exchange at the surface is as important as the self-reflection, and the conventional picture of condensation as a unimolecular chemical reaction is not appropriate.

  20. Trimming a Metallic Biliary Stent Using an Argon Plasma Coagulator

    International Nuclear Information System (INIS)

    Background. Distal migration is one of the common complications after insertion of a covered metallic stent. Stent repositioning or removal is not always possible in every patient. Therefore, trimming using an argon plasma coagulator (APC) may be a good alternative method to solve this problem. Methods. Metallic stent trimming by APC was performed in 2 patients with biliary Wallstent migration and in another patient with esophageal Ultraflex stent migration. The power setting was 60-100 watts with an argon flow of 0.8 l/min. Observations. The procedure was successfully performed and all distal parts of the stents were removed. No significant collateral damage to the nearby mucosa was observed. Conclusions. In a patient with a distally migrated metallic stent, trimming of the stent is possible by means of an APC. This new method may be applicable to other sites of metallic stent migration