Light Energy Density Research Articles

Location Control of Large Grain Following Excimer-Laser Melting of Si Thin-Films

We propose a method to locate a large silicon (Si) crystal grain at a predetermined position on a glass substrate following excimer-laser melting of Si thin-film. The thickness of part of the intermediate insulator of the amorphous-Si (a-Si)/insulator/metal/glass structure was increased. After the irradiation by dual-beam light to both the back and front sides of the structure, a Si crystal grain as large as 4 µm was located exactly at the center of the predetermined position, for wide range of diameter of the thick portion and irradiated light energy density.

The Nature of Starburst Galaxies

Utilizing a large sample of infrared-selected starburst galaxies having optical images and long-slit spectra, we explore the interrelationships between the properties of starbursts and relate these properties to those of the galaxy. We find that the half-light radius of the Hα-emitting region (re, Hα) enters into several correlations that suggest it is physically related to the actual starburst radius. Most suggestively, the effective IR surface brightness (LIR/πr2e, Hα) correlates strongly with the far-IR color temperature. This can be reproduced roughly with an idealized model of a surrounding dust screen whose far-IR emissivity is determined by the local energy density of UV starburst light. Typical values for re, Hα are a few hundred pc to a few kpc (with the Ha emission being significantly more compact than the red starlight). This confirms the circumnuclear scales of typical starbursts. We show also that starbursts seem to obey a limiting IR surface brightness of about 1011 L☉ kpc2, corresponding to a maximum star formation rate of about 20 M☉ yr–1 kpc2 for a normal initial mass function. We argue that this upper limit suggests that starbursts are self-regulating in some way.We show that most of these galaxies have relatively normal, symmetric rotation curves. This implies that the galactic disk need not suffer severe dynamical damage in order to fuel a typical starburst. We show also that the starbursts occur preferentially in the inner region of solid-body rotation. This may reflect both bar-driven inflow of gas to the region between the inner Lindblad resonances and the dominance of gravitational instability over tidal shear in this region. Most of the starbursts reside in galaxies with rotation speeds of 120--200 km s–1 (compared to 220 km s–1 for a fiducial L* galaxy like the Milky Way). The lack of a correlation between galaxy rotation speed and starburst luminosity means that even relatively modest galaxies (masses ~10% of the Milky Way) can host powerful starbursts. We argue on the basis of causality that the internal velocity dispersion in a starburst sets an upper limit to the star formation rate. The most extreme starbursts approach this limit, but most are well below. Finally, we show that the relative narrowness of the nuclear emission lines in starbursts (relative to the galaxy rotation speed) arises because the gas in the nuclear bin usually does not sample fully the solid-body part of the rotation curve. The narrow lines do not necessarily imply that the starburst is not in dynamical equilibrium.

Real‐time holographic interferometry using optical phase conjugation in photorefractive materials and direct spatial phase reconstruction

The structure and operation of a holographic interferometer that uses photorefractive Bi12TiO20 crystals as reusable recording mate- rials and computer image processing for rapid and precise interpretation of the fringe patterns are discussed. Different types of two-wave and four-wave mixing were applied to optical testing by double-exposure ho- lographic interferometry. A very convenient matching was found in the phase-conjugation setup for the Bi12TiO20 crystals and usual He-Ne la- sers, when the exposures were of ;10 s for light energy densities of 4310 23 W/cm 2 . Simple algorithms and direct spatial phase reconstruc- tion were used for computer image processing of the fringe patterns. © 1996 Society of Photo-Optical Instrumentation Engineers. Subject terms: real-time holographic interferometry; optical phase conjugation; photorefractive materials; fringe image processing; direct spatial phase demodu- lation.

The killing of Helicobacter pylori by low-power laser light in the presence of a photosensitiser

Helicobacter pylori is associated with various gastrointestinal disorders. Lethal photosensitisation was investigated as a possible technique for killing H. pylori which might offer a better alternative to antibiotics. The susceptibility of H. pylori to lethal photosensitisation was determined by mixing suspensions of H. pylori with various photosensitisers and plating out on blood agar before irradiation with low-power laser light. Five sensitisers were studied further by mixing them with H. pylori in a tissue-culture plate and counting survivors after irradiation as a function of laser exposure time, dye concentration and pre-irradiation time. Crystal violet and thionine were ineffective as sensitisers, but zones of inhibition appeared with methylene blue (MB), protoporphyrin IX (PPIX), haematoporphyrin derivative (HPD), toluidine blue O (TBO) and disulphonated aluminium phthalocyanine (S2). Laser light or sensitiser alone did not affect bacterial viability. S2 (100 microg/ml) with a laser light energy density of 16 J/cm2, HPD (10O microg/ml) with 160 J/cm2, MB (100 microg/ml) with 21 J/cm2, PPIX (150 microg/ml) with 320 J/cm2 and TBO (50 microg/ml) with 160 J/cm2 all reduced bacterial viability by >99%. The killing of sensitised H. pylori by laser light offers a new approach to the treatment of localised infections when all colonised areas are accessible to light.

Adjuvant intraoperative photodynamic therapy for colorectal carcinoma: a clinical study

The local recurrence rate of colorectal carcinoma after surgery is unacceptable in most series, and adjuvant therapies have made only a small impact on this. There is experimental evidence that adjuvant intraoperative photodynamic therapy (AIOPDT) may be effective. AIOPDT involves systemically photosensitizing the patient preoperatively with a drug (HpD) which relatively localizes to tumour and is activated using visible light. At operation the resected tumour bed is illuminated with a predetermined uniform light energy density to eradicate microscopic tumour deposits left at the lateral resection margin. We have previously investigated technical and biological factors leading to this clinical trial. Seventeen patients have received AIOPDT in a potentially effective dose, and safety and technical matters have been investigated. Cutaneous phototoxicity occurred in 3 patients. Three patients had anastomotic breakdown, none considered attributable to PDT. The intraoperative technique was a practical option. AIOPDT carried a low patient morbidity and should be investigated in prospective clinical trials to determine if local recurrence rates can be decreased.

悪性脳腫瘍患者に対する光線力学療法の治療成績

Twenty five patients with malignant brain tumor were treated with photodynamic therapy (PDT). 16 cases were glioblastomas, 4 cases were malignant gliomas, 5 cases were metastatic brain tumors. All patients recieved a 3mg/kg of HpD or HPE 48 hours prior to photoillumination. Photoillumunation was carried out at 630 nm wavelength of argon dye pump laser to glioma. In 15 cases, laser was irradiated interstitially to the tumor bed following tumor resection. In 5 cases, a stereotactic intratumoral photoradiation was carried out. The light energy density was 180 Joules cm2. The total energy ranged from 411 to 3,840 Joules/cm2. The median survival time for 16 glioblastom patients was 20.5 months with al, 2 and 3 year actuarial survival rate of 75%, 50% and 25%.

Scattering and wavelength transduction of diffuse photon density waves.

Experiments are performed that illustrate the scattering and reradiation of damped traveling waves of light energy density from objects within otherwise homogeneous turbid media. We demonstrate that simple diffractive and refractive models can be used to understand the scattering of these waves by absorptive and dispersive spheres. Furthermore, using a fluorescent dye we can reestablish the origin of the diffuse photon density waves, by converting from one optical and diffusive wavelength to another while maintaining phase coherence. The possibilities for precise medical imaging are presented.

Primary production dynamics in seagrass beds of Mississippi Sound: the contributions of seagrass epiphytic algae, sand microflora, and phytoplankton

Primary production rates of 4 autotrophic components in Halodule wrightii Aschers. beds off Horn Island in Mississippi Sound (USA) were measured over an annual cycle. Hourly production rates varied from as little as 0.9 mg C m-' for H, wrightii leaves in winter to as high as 1143 mg C m-' for eplphytic algae during summer. Stepwise multiple regression showed that only 15 % of the variation in hourly epiphytic algal production could be related to a single environmental variable (i.e. light energy). Variations in hourly production rates for the other productivity components were best explained by light energy, water temperature, tidal range and blade density; R2 for these regressions was 0.66 and 0.80 for phytoplankton and seagrass blades respectively. The epiphytic algal assemblage on H. wrightii leaves was dominated by the red alga Acrochaetium flexuosum Vickers and 12 taxa of araphid, monoraphid and biraphid diatoms. Phytoplankton over the beds were virtually all centric diatoms, whereas the microflora associated with the sandy sediments in which H. wrightii was rooted was dominated by small pennate diatoms. Annual production rates (g C were estimated as follows: epiphytic algae (905), phytoplankton (468), sand microflora (339) and Halodule wriyhtij (256). System production was dominated by the microalgae, with the contribution of H. rvrightji blades being only 13 % of the total. Epiphytic algae were the single most important productivity con~ponent, being responsible for 46 and 60 % of total system and benthic production respectively. The high standing crops and production rates of the epiphytic and benthic microalgae are of interest in that recent studies have indicated these algae can be the principal source of organic matter in seagrass food webs.

Photodynamic therapy with chlorin e 6. A morphologic study of tumor damage efficiency in experiment

Morphological changes in rat sarcoma M-1 after photodynamic treatment with chlorin e 6 were studied. The frequency of necrosis appearance and the depth of its spreading in tumor tissue were evaluated after intraperitoneal injection of chlorin e 6 in doses of 1–10 mg kg −1 and subsequent irradiation by a krypton laser with light energy density 22.5–135 J cm −2, using the method of vital staining with Evans blue. It was found that the antitumoral effect of photodynamic treatment was strengthened by increasing the dose of the agent and light and reduced by increasing the time interval between chlorin e 6 injection and light irradiation. The treatment being given in the parameters mentioned produced a depth of tumor necrosis which varied from 4.0 mm to 16.6 mm. The mechanisms of tumor tissue damage after photodynamic treatment in vivo are discussed.

Preliminary studies of photoinactivation of human immunodeficiency virus in blood

The transmission of human immunodeficiency virus (HIV) by blood or blood components is a major concern in blood banking. A photodynamic flow cell system was designed to inactivate cell-free HIV mixed with blood from a healthy donor. Blood containing 4 x 10(3) infectious units of HIV was treated with 10 and 20 micrograms per mL of commercially available dihematoporphyrin ether (DHE) per mL. Aliquots of this mixture were then held in the dark or irradiated in a flow cell illuminated at a light energy density of 5 J per cm2 provided by a xenon light source equipped with a 630 +/- 5 nm band-pass interference filter; the aliquots were subsequently placed in A.301 cells. All infected cultures were assessed for reverse transcriptase (RT) activity for 17 days. RT activity for either concentration of dye was significantly reduced in irradiated samples as compared to that in samples held in the dark. Blood samples from volunteers also were assessed for the effects of the inactivation process on red cells at concentrations of DHE up to 200 micrograms per mL. No effects were observed on red cell 2,3 DPG or ATP, whole blood potassium concentrations, red cell osmotic fragility, or blood cell antigens.

Photodynamic therapy of malignant brain tumours

Experience with intraoperative PDT in 50 patients with malignant supratentorial tumours is reported; in 33 cases the tumour was recurrent. In 45 patients the tumour was a cerebral glioma and in five cases a solitary cerebral metastasis. There were 29 males and 17 females with an age range of 17–73 (mean 48) years. All patients received either haematoporphyrin derivative (HPD) or dihaematoporphyrin ether (DHE) 18–24 h preoperatively. A photoilluminating device, of the authors' design, was coupled to an argon dye pump laser in order to deliver light at 630 nm to a tumour cavity created by radical tumour resection and/or tumour cyst drainage. The total light energy delivered ranged from 440 to 3888 J and the light energy density ranged from 8 to 175 J/cm2. In eight patients a line fibre(s) was used to administer interstitial light as a supplement to the cavitary photoillumination. The additional light dose ranged from 60 to 945 J/cm. There were two postoperative deaths as the consequence of haematoma accumulation in the tumour resection cavity. In three patients neurological function was worse postoperatively and did not recover. Postoperative cerebral oedema was pronounced in some cases and required second craniotomy in two patients (the histology from both showed haemorrhagic necrosis of residual tumour). Four patients developed wound infections; two of these required surgical treatment. Four patients, two of whom were hemiparetic, developed deep vein thrombosis and required anticoagulant therapy. There were no adverse systemic reactions to the administration of either photosensitizer and only three skin photosensitivity reactions. Follow up ranged from 1 to 30 months. In the group of 45 patients with gliomas the death rate per observation year was 0.92 for the interval between PDT and death. For the interval between first diagnosis and death the rate was 0.41 deaths per observation year. The median survival was 8.6 months with a 1 and 2 year actuarial survival rate of 32% and 18%, repectively. In 12 patients a complete or near complete CT scan response was identified post PDT. These patients tended to have a tumour geometry (e.g. cystic) that allowed complete or near complete light distribution to the tumour. The median survival for this group was 17.1 months with a 1 and 2 year actuarial survival of 62% and 38%, respectively. In the 33 cases without a complete response the median survival was 6.5 months with a 1 and 2 year actuarial survival of 22% and 11%, respectively. Photodynamic therapy of malignant brain tumours can be carried out with acceptable risk. Good responses appear to be related to adequate light delivery to the tumour.

Photodynamic Therapy of Malignant Brain Tumours

Fifty patients with malignant supratentorial tumours were treated with intra-operative photodynamic therapy (PDT); in 33 cases the tumour was recurrent. In 45 patients the tumour was a cerebral glioma and in 5 cases a solitary cerebral metastasis. All patients received a porphyrin photosensitizer 18-24 hours pre-operatively. Photoillumination was carried out at 630 nm to a tumour cavity created by radical tumour resection and/or tumour cyst drainage. The light energy density ranged from 8 to 175 J/cm2. In 8 patients additional interstitial light was administered. The operative mortality was 4%. Follow up has ranged from 1 to 30 months. The median survival for the 45 primary malignant tumours was 8.6 months with a 1 and 2 year actuarial survival rate of 32% and 18%, respectively. In 12 patients a complete or near complete CT scan response was identified post PDT. These patients tended to have a tumour geometry (eg. cystic) that allowed complete or near complete light distribution to the tumour. The median survival for this group was 17.1 months with a 1 and 2 year actuarial survival of 62% and 38%, respectively. In the 33 cases who did not have a complete response the median survival was 6.5 months with a 1 and 2 year actuarial survival of 22% and 11%, respectively. Photodynamic therapy of malignant brain tumours can be carried out with acceptable risk. Good responses appear to be related to adequate light delivery to the tumour.

Photosensitized patients and operating lights

Photosensitized patients who receive intra-operative photodynamic therapy are subjected to the intense brightness of operating lights. In order to investigate the potential phototoxic effects of this therapy, light energy densities were measured in non-photosensitized patients undergoing major abdominal surgery. The results show energy densities of 0.14 to 12.51 J cm−2 of polychromatic light for different operative fields. By a consideration of photon absorption numbers, these levels have a photodynamic equivalent of 0.34 to 30.06 J cm−2 of 630 nm light at the surface of tissue. If surgeons are unaware of the possible phototoxic effects of operating lights, some tissues could receive an unacceptably high energy density of polychromatic light. However, operating lights should not give significant phototoxic effects if the surgeon is aware and takes simple precautions.

Pulsed Laser Cleaning of Antimony Single Crystal <111> Surface

ABSTRACTThe<111> face of an antimony single crystal was irradiated under ultra-high-vacuum conditions by the 193 rn radiation of a high-power excimer laser. The effects of the laser beam on the sample as a function of the light Energy Density (ED) and of theannealing Repetition Number are presented.Surface studies by Auger electron spectroscopy, scanning electron microscopy and low energy electron diffraction show that an atomically clean and well ordered surface can be produced by t is method. A strong chemical reduction is induced by pulsed aser annealing above 100 to 130 mI/cm2. Surface analysis shows that, for an ED less than 500 mJ/cm2 the surface evaporates without melting deeper than 200 rim. Evidences for oxide modification and for organic molecule desorption were observed even after irradiations with an ED as low as 45 mJ/cm2.The surface reduction is described by a thermal model involving surface heating and subsequent evaporation of the oxide layer. The desorption and diffusion processes may involve both thermal and photolytic mechanisms.

Photodynamic therapy of malignant primary brain tumours: clinical effects, post-operative ICP, and light penetration of the brain.

Abstract We are reporting our experience with intraoperative PDT in 32 patients with malignant supratentorial gliomas; in 19 cases the tumour was recurrent. There were 20 males and 12 females with an age range of 17‐73 (mean = 45) yr. The first 8 patients in this series received HpD (Photofrin I) and the next 24 received DHE (Photofrin II). A photo‐illuminating device, of the author's design, was coupled to an argon dye pump laser in order to deliver light at 630 nm to a tumour cavity created by radical tumour resection and/or tumour cyst drainage. The total light energy delivered ranged from 440 to 3888 J and the light energy density ranged from 8 to 68 J cm−2.There were two post‐operative deaths as the consequence of hematoma accumulation in an extensive tumour resection cavity. In two patients neurological function was worse post‐operatively and did not recover. Post‐operative cerebral edema was pronounced in eight cases and required emergency craniotomy in two patients (the histology from both showed hemorrhagic necrosis of residual tumour). We have fashioned continuous post‐operative ICP measurements in the last 15 patients treated with PDT and compared the values to those obtained from cases with malignant gliomas who did not have PDT; the mean ICP was significantly greater in the PDT group. Four patients developed wound infections; two of these required surgical treatment. Four patients, two of whom were hemiparetic, developed deep vein thrombosis and required anticoagulant therapy. There were no adverse systemic reactions to the administration of either photosensitizer and only 3 skin photosensitivity reactions.Follow up has ranged from 1 to 26 months at the time of writing; 38% were still alive; in the interval between PDT and death, the deaths per observation year was 1.11 for the whole group and 1.00 when the two post‐operative deaths are excluded. In the interval between first diagnosis and death the rate was 0.45 deaths per observation year. Photodynamic therapy of malignant brain tumours using surface or cavitary photo‐illumination can be carried out with acceptable risk.In eight patients we determined the penetration depth of light in brain tissue in vivo by reading the detected light flux from a fiber passed radially into the brain towards the centre of the irradiation volume. The optical fiber consisted of a single 400 μ.m, cleaved fiber fixed in a 17‐gauge biopsy needle coupled to a photometer. The light penetration depth ranged from 0.8 to 4.9. The mean PD values in the‘tumour’group and the‘brain’group was 2.9 ± 1.5 and 1.5 ± 0.43, respectively. We attribute this significant difference to the differences in the absorption and scattering properties of brain and tumour.

表在性膀胱癌のphotodynamic therapyPhotodynamic Therapy for Superficial Bladder Cancer

Spot and total bladder wall photodynamic therapies (PDT) using argon-dye laser (630 nm) were carried out in 17 patients with Ta-TI lesions and in 22 patients with carcinoma in situ (CIS) or/and multicentric superficial tumors, respectively. The intervals between hematoporphyrin derivative 3 mg/kg i. v. injection and PDT were 48 to 96 hours. Total light energy density was 100 to 200 J/cm2 in spot PDT through a 400 μm quartz fiber and cystoscope, and 10 to 30 J/cm2 in total PDT carried out by a laser light scattering device. There was no recurrence in 4 of the 17 patients with a mean tumor free time of 20.8 months in spot PDT, and in 5 of 22 with a mean tumor free time of 8.2 months in total PDT. The most appropriate patients for PDT will be those with CIS, those withe diffuse Ta-TI lesions, and those with tumor in a bladder diverticulum.

Silicide formation by pulsed-incoherent-light annealing

Nickel silicide formation is studied using a pulsed incoherent light source of variable duration in the range 5-50 μs. The potential advantages of the arc source over other pulsed techniques such as electron (e)-beam and laser annealing are simplicity, higher electrical-conversion efficiency, and larger area processing. The plasma arc provided incident light energy density in the range 5–45 J/cm2, and our results indicate that mixed layers of nickel and silicon can be produced using this source at about 45 J/cm2. It was found that a thin layer of amorphous silicon on the nickel enhanced light absorption and mixing. Rutherford back scattering and scanning Auger microprobe techniques were used to characterize the mixed layers. The incoherent light annealing is believed to be a rapid thermal process, which in our case results either in solid- or liquid-phase epitaxial regrowth depending on the annealing conditions.

Flash-lamp annealing of boron implanted silicon

Abstract Structure and impurity behaviour of silicon doped by B+ ion implantation up to dose of 2 × 1015 ion/cm2 have been investigated after lamp pulse annealing. It has been demonstrated that the implanted layer structure strongly depends on the implantation dose, light energy density, as well as the crystallographic orientation. The optimal annealing result in the structure, which is equivalent to that obtained in the thermal treatment, The impurity diffusive redistribution proved to be rather weaker then in the case of thermal treatment.

Background light from galaxies as a cosmological probe

view Abstract Citations (7) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Background light from galaxies as a cosmological probe Stabell, R. ; Wesson, P. S. Abstract Galaxies emit radiation as a background of intergalactic light whose energy density depends on the epoch during which the galaxies formed, the luminosity evolution undergone by them, and their cosmology. The expected energy density of the extragalactic background light (EBL) was computed for a range of galaxy formation epochs, luminosity-evolution parameters, and Robertson-Walker universe models. It is concluded that the upper limits of the EBL were not more luminous when young than they are at present. Publication: The Astrophysical Journal Pub Date: December 1980 DOI: 10.1086/158478 Bibcode: 1980ApJ...242..443S Keywords: Background Radiation; Cosmology; Galactic Evolution; Galactic Radiation; Luminosity; Elliptical Galaxies; Flux Density; Hubble Constant; Quasars; Spiral Galaxies; Astrophysics full text sources ADS |

The influence of radiative collisions on two-photon atomic ionisation

Investigates theoretically a new aspect of radiative collisions on two-photon ionisation of colliding atoms of different species A and B. The authors derive the main characteristics of the resonance appearing in the two-photon ionisation cross section of atom B when the laser frequency is tuned on a resonance transition of atom A which cannot itself be ionised by two-photon absorption. Under some realistic conditions and for reasonable values of the light energy density flux F ( approximately 1 MW cm-2), the cross section of the process considered varies as F2/5 while its width varies as F1/2. These predictions are in reasonable agreement with a recent observation on the mixture Sr(A)-Cs(B) by Brechignac et al. (1980).