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PubMed2005

Outcomes of 532 nm frequency-doubled Nd:YAG laser use in the treatment of port-wine stains.

BACKGROUND: Port-wine stains (PWSs) are congenital dermal malformations involving venules, capillaries, and, probably, perivascular nerves. The primary morbidities of PWS are psychological disturbances that adversely affect the development of personality. Lasers have been the treatment of choice for PWS. However, only one type of laser is not a panacea for all PWS malformations. For the treatment of PWSs, carbon dioxide, argon, krypton, copper bromide, frequency-doubled neodymium:yttrium-aluminum-garnet (Nd:YAG), flashlamp pumped pulsed dye laser, and also intense pulsed light sources can be used. OBJECTIVE: To determine the efficacy and the frequency of side effects of the frequency-doubled Nd:YAG laser for the treatment of PWSs. PATIENTS AND METHODS: In this study, 532 nm frequency-doubled Nd:YAG laser with a 2 to 6 mm spot size, 15- to 50-millisecond pulse width, and a 9.5 to 20 J/cm2 fluence was applied for 89 patients (62 female, 27 male; age range 3-49 years) with PWSs on the face and/or neck for 1 to 12 sessions, with 2-month treatment-free intervals. Improvement rates were considered a failure (< 25%), mild (25-49%), moderate (50-74%), good (75-94%), and excellent (> 95%). RESULTS: Excellent (n = 12; 13%), good (n = 34; 38%), moderate (n = 39; 44%), and mild (n = 4; 5%) improvement of lesions was obtained after an average of 5.6, 5.5, 4.4, and 3.8 therapy sessions, respectively. No treatment failure was observed for any patient. As adverse effects, transient hyperpigmentation (n = 2; 2.25%), hypopigmentation (n = 1; 1.12%), and hypotrophic scarring (n = 1; 1.12%) were noted. CONCLUSIONS: The results obtained asserted that the frequency-doubled Nd:YAG laser is a quick, safe, and effective treatment modality for PWS malformations and can be appreciated as a useful alternative therapy that can raise the rates of success in cases with PWSs refractory to other laser therapies.

Adolescent↗
PubMed1989

Fluorescence spectra in lung with porphyrin injection.

The fluorescence emission spectra from human bronchial mucosa and tumors, before and after injection of dihematoporphyrin ether/ester, have been measured with an optical multichannel analyzer from 500 to 750 nm. Fluorescence was excited with a violet krypton ion laser (average wavelength 410 nm). The autofluorescence spectra decrease monotonically with increasing wavelength except for a small broad peak near 600 nm. The spectra from tumor sites, after injection of the fluorescent porphyrin, exhibit the characteristic fluorescence emission at 630 and 690 nm, added to the autofluorescence spectrum. The spectra from control or nontumor sites are similar but the magnitude of the component due to the injected porphyrin is smaller than at a tumor site. The magnitude ratio of tumor to control site fluorescence depends on concentration of the porphyrin, tumor thickness, and time after injection. Autofluorescence degrades contrast and thus makes very thin tumors difficult to image. Subtraction of the autofluorescence background is desirable.

Humans↗
PubMed1983

Management of juvenile disciform lesions of the macula.

Fourteen eyes with a juvenile disciform lesion of unknown aetiology in the macula were followed up for 1-6 years. Eyes with inflammatory signs, pre-existing chorioretinal scars in the macula, or myopia of more than -5.0 dioptres were not included. Seven eyes in which the subretinal neovascular membrane ws within 200 mu from the foveola were followed-up without treatment. Of these, in 4 the new vessels underwent regression, and the result was good central vision in 3, whereas in 3 eyes the lesion progressed. Seven eyes were treated with photocoagulation: 5 with argon, 2 with krypton laser. In the treated eyes, the neovascular membrane was 200-500 mu from the foveola. New vessels were occluded by photocoagulation in 6 eyes. In the 3 treated eyes in which the new vessels were 350 mu or more from the foveola, the visual acuity improved or remained good (0.8-1.0), whereas in the remaining 4 the vision deteriorated. In the eyes with good initial result the vision has remained stable in spite of remarkable late pigmentary changes in and around the scar.

Adult↗
PubMed1985

Fluorescein angiography in the long-term follow-up of choroidal melanoma after conservative treatment.

Three patients showed a growing choroidal melanoma, of them 2 in the only eye. The tumours were treated with Ru106/Rh106 plaques and surrounded by argon or krypton photocoagulation. The patients were followed up for 34-36 months by regular fluorescein angiography. In areas in which the radiation effect was optimal most choroidal and retinal vessels disappeared within 3-6 months. Outside this area occlusion of the vasculature as well as progressing atrophy of the tumour and the overlying retinal pigment epithelium were seen to continue for more than 12 months after treatment. Disappearance of the leaking vessels of the tumour may be the most reliable fluorescein angiographic sign of tumour regression following conservative treatment.

Aged↗
PubMed1985

Treatment of senile macular degeneration by laser photocoagulation.

117 eyes of 103 patients among 476 patients with senile macular degeneration fulfilled a criterion for treatment with blue-green Argon (n = 20 eyes), green Argon (n = 15 eyes) Krypton-red (n = 58 eyes) and combined treatment (24 eyes). In 50 consecutive treated eyes (= 50 patients) with an observation time exceeding one year a visual acuity greater than or equal to 6/18 was preserved in 34 eyes. This post-laser course differs from the spontaneous course of the disease reported in literature indicating that about 70% of eyes with perifoveal neovascular lesion will develop legal blindness within 2 years. Even though the spontaneous course in this material is unknown, and the comparability to patient material in literature is questionable, it might be concluded that a considerable part of the patients with senile macular degeneration with neovascular lesions might benefit from laser-treatment.

Aged↗
PubMed1988

Treatment of age-related macular degeneration by laser photocoagulation. Visual results 2-8 weeks and 2-4 years after initial laser treatment.

Laser treatment with blue-green argon, green argon and/or krypton red was performed on 578 eyes in 443 patients with neovascular age-related macular degeneration (AMD). The visual acuity was examined in all eyes 2 to 8 weeks after initial treatment and in 204 eyes in 167 patients 2 to 4 years after initial treatment. The short term results were as follow: 91/578 eyes (16%) had improved (greater than or equal to 2 lines on Snellen's charge or equivalent steps), 445/578 eyes (77%) remained unchanged and 42/578 eyes (7%) had deteriorated visual acuity (greater than or equal to 2 lines on Snellen's chart or equivalent steps). The reduction in visual acuity, may in about half of the 42 eyes be caused by too intensive laser application in the beginning of this study in 1983 and 1984 where treatment was applied with blue-green argon, which has now been abandoned. In the group with an observation time of 2 to 4 years, 42/204 eyes (21%) had improved, 119/204 eyes (58%) remained unchanged and 43/204 eyes (21%) had a deteriorated visual acuity. In the 204 eyes the subretinal neovascular lesion(s) were located extrafoveally in 52 eyes, juxtafoveally in 114 eyes and subfoveally in 38 eyes. It is to be pointed out, that even patients with a pre-laser visual acuity of 6/60 or worse obtained an improvement of visual acuity in 12/27 eyes. About 40% of the eyes needed re-treatment from 1 to 8 times. It is unknown whether the obtained results are to be considered marginal or more substantial.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1994

Interferon alpha-2a in the treatment of exudative senile macular degeneration.

We performed a pilot study of 10 patients with the objective to determine the efficacy of interferon alpha-2a in the treatment of age-related macular degeneration with freshly diagnosed choroidal neovascular membrane. Interferon was given at a dose of 3 MIU/m2 three times a week for 8 weeks. Mean age of the patients was 74 years. In 3 patients we combined laser photocoagulation of extrafoveal part of the choroidal neovascular membrane to interferon therapy. The patients were followed up for 1 year after termination of interferon treatment. In 1 patient a visual improvement of two Snellen lines was noted, while in 7 patients visual acuity remained the same during the treatment (includes 3 patients treated with combined Krypton-laser photocoagulation). In 2 patients there was a decrease in acuity of one line. Six months later visual acuity had deteriorated in 7 patients and 1 year later all the patients had visual acuity < or = 20/200. We did not find any regression of choroidal neovascular membrane in fluorescein angiography in any of the patients during the treatment except the laser-treated area. At the 6-month follow-up there was still leakage or choroidal neovascular membrane growth in 6 patients. Combined interferon-laser therapy did not prove to be more effective in preventing the membrane growth. Side-effects included weakness, apathy, and fatigue in this elderly population. Our results indicate that treatment with 3 MIU/m2 interferon for 8 weeks is not an effective treatment for subfoveal choroidal neovascular membranes.

Aged↗
PubMedDate not supplied

Resonance Raman spectroscopy of optically trapped functional erythrocytes.

We introduce a novel setup combining a micro-Raman spectrometer with external optical tweezers, suitable for resonance Raman studies of single functional trapped cells. The system differs from earlier setups in that two separate laser beams used for trapping and Raman excitation are combined in a double-microscope configuration. This has the advantage that the wavelength and power of the trapping and probe beam can be adjusted individually to optimize the functionality of the setup and to enable the recording of resonance Raman profiles from a single trapped cell. Trapping is achieved by tightly focusing infrared (IR) diode laser radiation (830 nm) through an inverted oil-immersion objective, and resonance Raman scattering is excited by the lines of an argon:krypton ion laser. The functionality of the system is demonstrated by measurements of trapped single functional erythrocytes using different excitation lines (488.0, 514.5, and 568.2 nm) in resonance with the heme moiety and by studying spectral evolution during illumination. We found that great care has to be taken in order to avoid photodamage caused by the visible Raman excitation, whereas the IR trapping irradiation does not seem to harm the cells or alter the hemoglobin Raman spectra. Stronger photodamage is induced by Raman excitation using 488.0- and 514.5-nm irradiation, compared with excitation with the 568.2-nm line.

Cells, Immobilized↗
PubMedDate not supplied

Fluorescence bronchoscopy for localization of carcinoma in situ.

A fluorescence bronchoscope system has been developed for imaging lung tumors by fluorescence of a previously injected, tumor-specific agent hematoporphyrin derivative. Carcinoma in situ has been localized, but there are too many false positives and negatives. A new system has been implemented which allows rapid switching between viewing of fluorescence, and viewing of the same area under white light illumination as in conventional bronchoscopy. The excitation source is a violet krypton ion laser coupled to a fused quartz fiber light conductor, with a diverging microlens to spread the light uniformly. A third-generation, microchannel plate image intensifier amplifies the weak fluorescence for viewing and video display, recording, and analysis. A movable mirror and periscope bypasses the intensifier for normal color viewing and video display and recording, with the laser shutter closed and the white light shutter open. This facilitates accurate localization, comparison of the color and fluorescence images, and precise sampling during biopsy. The improved system should reduce the false positive rate due to biopsy sampling error, and together with the video analyzer should reduce indeterminate results.

Bronchoscopes↗
PubMed2002

Prandtl number and thermoacoustic refrigerators.

From kinetic gas theory, it is known that the Prandtl number for hard-sphere monatomic gases is 2/3. Lower values can be realized using gas mixtures of heavy and light monatomic gases. Prandtl numbers varying between 0.2 and 0.67 are obtained by using gas mixtures of helium-argon, helium-krypton, and helium-xenon. This paper presents the results of an experimental investigation into the effect of Prandtl number on the performance of a thermoacoustic refrigerator using gas mixtures. The measurements show that the performance of the refrigerator improves as the Prandtl number decreases. The lowest Prandtl number of 0.2, obtained with a mixture containing 30% xenon, leads to a coefficient of performance relative to Carnot which is 70% higher than with pure helium.

Journal Article↗
PubMed2001

X-ray pulses approaching the attosecond frontier.

Single soft-x-ray pulses of approximately 90-electron volt (eV) photon energy are produced by high-order harmonic generation with 7-femtosecond (fs), 770-nanometer (1.6 eV) laser pulses and are characterized by photoionizing krypton in the presence of the driver laser pulse. By detecting photoelectrons ejected perpendicularly to the laser polarization, broadening of the photoelectron spectrum due to absorption and emission of laser photons is suppressed, permitting the observation of a laser-induced downshift of the energy spectrum with sub-laser-cycle resolution in a cross correlation measurement. We measure isolated x-ray pulses of 1.8 (+0.7/-1.2) fs in duration, which are shorter than the oscillation cycle of the driving laser light (2.6 fs). Our techniques for generation and measurement offer sub-femtosecond resolution over a wide range of x-ray wavelengths, paving the way to experimental attosecond science. Tracing atomic processes evolving faster than the exciting light field is within reach.

Journal Article↗
PubMed2005

Deep-ultraviolet quantum interference metrology with ultrashort laser pulses.

Precision spectroscopy at ultraviolet and shorter wavelengths has been hindered by the poor access of narrow-band lasers to that spectral region. We demonstrate high-accuracy quantum interference metrology on atomic transitions with the use of an amplified train of phase-controlled pulses from a femtosecond frequency comb laser. The peak power of these pulses allows for efficient harmonic upconversion, paving the way for extension of frequency comb metrology in atoms and ions to the extreme ultraviolet and soft x-ray spectral regions. A proof-of-principle experiment was performed on a deep-ultraviolet (2 x 212.55 nanometers) two-photon transition in krypton; relative to measurement with single nanosecond laser pulses, the accuracy of the absolute transition frequency and isotope shifts was improved by more than an order of magnitude.

Journal Article↗
PubMed1996

The Galileo probe mass spectrometer: composition of Jupiter's atmosphere.

The composition of the jovian atmosphere from 0.5 to 21 bars along the descent trajectory was determined by a quadrupole mass spectrometer on the Galileo probe. The mixing ratio of He (helium) to H2 (hydrogen), 0.156, is close to the solar ratio. The abundances of methane, water, argon, neon, and hydrogen sulfide were measured; krypton and xenon were detected. As measured in the jovian atmosphere, the amount of carbon is 2.9 times the solar abundance relative to H2, the amount of sulfur is greater than the solar abundance, and the amount of oxygen is much less than the solar abundance. The neon abundance compared with that of hydrogen is about an order of magnitude less than the solar abundance. Isotopic ratios of carbon and the noble gases are consistent with solar values. The measured ratio of deuterium to hydrogen (D/H) of (5 +/- 2) x 10(-5) indicates that this ratio is greater in solar-system hydrogen than in local interstellar hydrogen, and the 3He/4He ratio of (1.1 +/- 0.2) x 10(-4) provides a new value for protosolar (solar nebula) helium isotopes. Together, the D/H and 3He/4He ratios are consistent with conversion in the sun of protosolar deuterium to present-day 3He.

Ammonia↗
PubMed2000

Cool glacial temperatures and changes in moisture source recorded in oman groundwaters

Concentrations of atmospheric noble gases (neon, argon, krypton, and xenon) dissolved in groundwaters from northern Oman indicate that the average ground temperature during the Late Pleistocene (15,000 to 24,000 years before present) was 6.5 degrees +/- 0.6 degrees C lower than that of today. Stable oxygen and hydrogen isotopic groundwater data show that the origin of atmospheric water vapor changed from a primarily southern, Indian Ocean source during the Late Pleistocene to a dominantly northern, Mediterranean source today. The reduced northern water vapor source is consistent with a drier Last Glacial Maximum through much of northern Africa and Arabia.

Journal Article↗
PubMed2000

The nature of pristine noble gases in mantle plumes

High-precision noble gas data show that the Hawaiian and Icelandic mantle plume sources contain uniquely primitive neon that is composed of moderately nucleogenic neon-21 and a primordial component indistinguishable from the meteoritic occurrence of solar neon. This suggests that Earth's solar-type rare gas inventory was acquired during accretion from small planetesimals previously irradiated by solar wind from the early sun. However, nonradiogenic argon, krypton, and xenon isotopes derived from the mantle display nonsolar compositions and indicate an atmosphere-like fingerprint that is not due to recent subduction.

Journal Article↗
PubMed1984

Microbial growth modification by compressed gases and hydrostatic pressure.

Studies of the growth-modifying actions for Escherichia coli, Saccharomyces cerevisiae, and Tetrahymena thermophila of helium, nitrogen, argon, krypton, xenon, and nitrous oxide led to the conclusion that there are two definable classes of gases. Class 1 gases, including He, N(2), and Ar, are not growth inhibitors; in fact, they can reverse the growth inhibitory action of hydrostatic pressures. Class 2 gases, including Kr, Xe, and N(2)O, are potent growth inhibitors at low pressures. For example, at 24 degrees C, 50% growth-inhibitory pressures of N(2)O were found to be ca. 1.7 MPa for E. coli, 1.0 MPa for S. cerevisiae, and 0.5 MPa for T. thermophila. Class 1 gases could act as potentiators for growth inhibition by N(2)O, O(2), Kr, or Xe. Hydrostatic pressure alone is known to reverse N(2)O inhibition of growth, but we found that it did not greatly alter oxygen toxicity. Therefore, potentiation by class 1 gases appeared to be a gas effect rather than a pressure effect. The temperature profile for growth inhibition of S. cerevisiae by N(2)O revealed an optimal temperature for cell resistance of ca. 24 degrees C, with lower resistance at higher and lower temperatures. Overall, it appeared that microbial growth modification by hyperbaric gases could not be related to their narcotic actions but reflected definably different physiological actions.

Journal Article↗
PubMed1973

Effects of various gases on the survival of dried bacteria during storage.

Salmonella newport and Pseudomonas fluorescens were dried together in papain digest broth and sucrose-glutamate, and stored in several gases at various water activities (a(w)) between 0.00 and 0.40 at 25 C for various periods up to 81 weeks. Both S. newport and P. fluorescens, dried in papain digest broth and stored in air, died rapidly if the conditions were very dry (0.00 a(w)) or moist (0.40 a(w)). Storage in carbon dioxide and argon gave greater survival than storage in air but lower survival than did storage in nitrogen or in vacuo. When the organisms were dried in a sucrose-glutamate mixture the differences between the gases were very small, and variations in residual water were less important. Of the inert gases, argon gave the best survival when the organisms were dried in papain digest broth, especially at 0.00 a(w); the survival in neon and krypton was lower and in xenon and helium it was much lower.

Air↗