Minutes Of Irradiation Research Articles

Inactivation of phage Qß by 254nm UV light and titanium dioxide photocatalyst

The disinfection efficacy of UV light irradiation at wavelength of 254 nm over a titanium dioxide (TiO2) suspension was compared to that of UV alone. Bacteriophage Qß was used as a model virus for the study. Qß in sterilized pure water and TiO2 suspension was irradiated by a 0.4 mW/cm2 intensity of 254nm UV light. The UV light over TiO2 was more effective than 254nm UV alone in inactivating Qß. 3.5‐log10 Qß inactivation was achieved by UV irradiation over TiO2 suspension (103 mg/L) after 2 minutes of irradiation, while UV alone inactivated 2‐log10. Using a MPN‐PCR method, a ca. 1‐log10‐unit decrease in Qß RNA concentration was detected after 3 minutes of photocatalytic irradiation. The decrease was explained by damage to nucleic acid of phage Qß due to radical oxidation, which is generated by photocatalysis.

Preparation of HNaY zeolite by ion exchange under microwave treatment. A preliminary study

Acidic samples of Y zeolite were prepared by ion exchange promoted using microwave irradiation. Interesting exchange levels were obtained with only a few minutes of irradiation. The catalytic properties of these samples were evaluated using the transformation of iso‐octane; the observed conversions lie in the same range as those for the samples prepared by the conventional ion‐exchange method of stirring the mixture of the sodium form with an ammonium salt solution for several hours; the deactivation with time‐on‐stream was significantly reduced for the catalysts prepared by the irradiation method in the cases of highest activity.

Radiation Induced Polymerization of N,N'-Methylenebisacrylamide in Aqueous Solution

Gamma ray induced polymerization of N,N'-methylenebisacrylamide (MBA) in aqueous solution has been studied. Rates of polymerization have been determined as a function of dose, dose rate, and monomer concentration. Polymerization mechanism was found to be free radical with chain propagation step involving ring formation. About 90% conversion was achieved in 25 minutes of irradiation (dose rate 1.54 × 1018 eV dm−3 s−1) of MBA solution (36 mmol). The polymerization rates were found to vary from 1.9 × 10 4 to 5.6 × 10−4 mol dm−3 s−1 when the monomer concentrations were varied between 80–164 mmols. The value of the constant kp/kt 1/2 was calculated to be 9.85 for the dose rate of 1.54 × 1018 eV dm−3 s−1. The precipitated polymer showed mono disperse particles of diameter of about 170 nm. The polymer was found to be highly crosslinked and insoluble in any solvent.

EFFECTS OF LOW LEVEL LASER IRRADIATION (LLLI) WITH 904 nm PULSED DIODE LASER ON STAPHYLOCOCCUS AUREUS

Many studies using low level laser irradiation (LLLI) have been performed to investigate the influence of laser irradiation on the healing process of wounds. It has been proposed that LLLI may stimulate the growth of bacterial cells and normal tissue cells. This study was performed to determine whether LLLI also has positive effects on the proliferation of Staphylococcus arueus, known as a common cause of skin infections, and to obtain basic data for a future in vivo experiment to study the effect of LLLI on wounds infected with S. aureus. This study includes 3 experiments: experiments for the proliferation of S. Aaureus according to (a) the LLLI pulse type, (b) the interirradiation interval and (c) the irradiation time. The experiment assessing the effect of LLLI by pulse type and energy density, pulse 13 ( P13, 6000 Hz, 14 mW of average output power) was most effective in increasing the proliferation of S. Aureus. As for the interirradiation interval (also using P13), the 4 hour interval was the most effective; 2 minutes of irradiation had a significant effect on the proliferation of S. arueus using P13 and 4 hour interval ( energy density of 14.8 mJ/cm2 ).

Electron beam-induced fullerite structure transformation

Auger spectra of thin fullerite (C60) films have been measured under the conditions precluding their electrostatic charging and destruction. The Auger line of these subjects, Ef=268.3±0.2 eV, turned out to lie considerably lower in energy than that of the ion-beam amorphized graphite (EAG=272.3±0.2 eV) and of pyrographite (EPG=271.8±0.5 eV). Fullerite was found to convert to a graphitic form under irradiation by low-intensity electron beams used customarily in AES, reflection EELS, and inverse photoemission spectroscopy. It has been established that such beams produce noticeable changes in the fullerite structure already in a few minutes of irradiation.

The effect of molecular singlet oxygen 1O2(1∆g) on detergent proteases

The effect of 1 O 2 on the detergent proteases Alcalase®, Savinase® and Durazym (endoproteases of the serine-type, classified as subtilisines) was investigated using methylene blue and TPP-iodide (meso-tetra-(4-methylpyridyl) porphine-tetraiodide) as 1 O 2 -sensitizer Irradiation of the enzyme solution by a He-Ne-Laser at 633 nm in the presence of methylene blue as 1 O 2 -sensitizer led to a dramatic decrease of enzyme activity. As a measure of the activity the rate constant k of the cleavage of the substrate succinyl-ala-ala-pro-phe-p-nitroaniline (suc-AAPF-pNA) by the different enzymes was used. The rate was determined spectrophotometrically at 440nm observing the formation of p-nitroaniline. Alcalase® was most sensitive to irradiation: it took only five minutes of irradiation to destroy more than half its activity. For Savinase® this required more than 10 minutes, for Durazym slightly less than 10 minutes of irradiation time. Furthermore the rate constant k Q E which is the sum of physical and chemical quenching of 1 O 2 by the enzymes, was determined by time-resolved measurement of the 1 O 2 -phosphorescence at 1276 nm in D 2 O using TPP-iodide as 1 O 2 -sensitizer The rate constant was measured at room temperature and at an optimum temperature for the protease in question. This is 45,5 °C for Alcalase® 60°C, for Savinase® 55°C and for Durazym. Generally speaking, the investigated enzymes show high rate constants compared to other biomolecules. At room temperature the k Q E of Alcalase® amounts 5 x 10 8 M -1 s -1 , those of the other proteases are about 1 x 10 9 M -1 s -1 . The change of activity caused by irradiation enables k C E to be evaluated (chemical quenching) and thus separation of k Ph E (physical quench-ing). The physical quenching k Ph E at the optimum temperature of highest activity dominates in the reaction of 1 O 2 with the proteases and is about 1-3 x 10 9 M -1 s -1 .

THE EFFECTS OF DIODE LASER LLLT ON FLAP SURVIVAL: MEASUREMENT OF FLAP MICROCIRCULATION WITH LASER SPECKLE FLOWMETRY

A laser speckle flowmetry technique has been developed to enable visualization of the distribution of skin blood flow and has been used to measure the microcirculation in various angiopathies as well as to monitor blood flow changes and other haemodynamics in skin flaps. The principal author's institute has recently acquired such a laser speckle flowmetry system. The present preliminary study was designed to test the efficacy of the gallium aluminium arsenide (GaAlAs) diode laser on flap survival in the rat model using laser speckle flowmetry. Caudal-based random pattern flaps were raised on the back of two groups of Wistar rats, 10 rats in each group. The first group served as the control and underwent sham irradiation, otherwise they were handled in exactly the same way as the second group. The blood flow in all flaps was measured with laser blood flowmetry using the laser speckle method. Blood flow was measured in the flaps of the experimental animals and the unirradiated controls preirradiation, and the flaps were sutured back in place. The experimental group received laser irradiation from a GaAlAs diode laser (60 mW, 830 nm, continuous wave) for one minute on a point at the centre of the flap base (energy density ≅ 36 J/cm2). Laser speckle flowmetry was then performed on all animals immediately postirradiation and 30 minutes postirradiation. The following points were noted. There was no significant change in the flow rate of the flaps in the unirradiated animals. Immediately following the one minute irradiation in the experimental animals a decrease in the blood flow rate was seen compared with the unirradiated controls, but at 30 minutes postirradiation the blood flow rate in the flaps increased in the irradiated animals compared with controls. Five days postirradiation the survival area of the diode laser irradiated flaps was greater than the control flaps (≅1.12 : 1). It was concluded that GaAlAs diode LLLT increased early perfusion of the experimental flaps, thereby possibly accelerating early stage wound repair while at the same time controlling the inflammatory response, thus giving the irradiated flaps a better and earlier ‘take’.

Electronic Irradiation Effect on Bi-Mo-O Catalysts Observed in a Hrtem Study

AbstractWe studied by high resolution transmission electron microscopy (HRTEM) unsupported bismuth-molybdenum-oxide catalysts. The microscope utilized was a JEOL 4000 EX electron microscope with a resolution better than 0.19 nm (point to point). The image simulation were performed on a personal computer with the aid of a commercial program. With the aid of image simulation it is possible to identify γ-Bi2MoO6 and X-Mo4O11 phases, among several other possibilities that fit the interplanar spacings and angles.A very important aspect, thermal instability, was proved indirectly in the microscope, by the changes of the particles under the electron beam irradiation at 400 kV. After several minutes of irradiation, the amorphous surface layer was totally reconstructed to crystalline phases.The fact that we observe many phases in this sample, is certainly deleterious to the catalytic properties, since not all of them are active. Also the sensitivity to the beam indicates that minimum exposure microscopy has to be applied in order to prevent unecessary complications for phase identification.

Optical Probing of Single Molecules of Terrylene in a Shpol'kii Matrix: A Two-State Single-Molecule Switch

We report fluorescence excitation spectra of individual impurity molecules in a new system: terrylene in a Shpol'skii matrix of hexadecan, Studies of optical incoherent saturation, fluorescence microscope images, and resonance frequency changes are reported for the 0-0 electronic transition at 1.7 K. For four stable molecules, the low-power optical line width at 1.7 K is 40 +/- 2 MHz full width at half-maximum, the saturation intensity is near 1 W/cm(2), and the peak detected count rate can reach 11000 counts per second. Most single molecules either are stable or require many minutes of irradiation before the resonance frequency changes suddenly, but some show spectral changes on a time scale of seconds. Since higher laser power increases the average rate of frequency shifts, this effect represents a light-driven change in the local environment analogous to nonphotochemical hole-burning in large ensembles. Several two-state molecules have been observed, and a preliminary characterization of this light-driven ''molecular switch'' has been completed. Multistate behavior also occurs. This work demonstrates that Shpol'skii matrices should provide fertile ground for the generation of a large number of new materials in which single-molecule spectra can be obtained.

Evidence for Induced Radioresistance from Survival and Other End Points: An Introduction

A substantial body of data published during the past 30 years makes a strong case for the existence of cellular radioprotective mechanisms that can be up-regulated in response to exposure to small doses of ionizing radiation. Either these "induced" mechanisms can protect against a subsequent exposure to radiation that may be substantially larger than the initial "priming" or "conditioning" dose, or they may influence the shape of the survival response to single doses so that small radiation exposures are more effective per unit dose than larger exposures above a threshold where the induced radioprotection is triggered. Evidence for these effects comes from studies in vitro with protozoa, algae, higher plant cells, insect cells, mammalian and human cells, and studies on animal models in vivo. Work at the molecular level is now confirming that changes in levels of some cytoplasmic and nuclear proteins, and the increased expression of some genes, may occur within a few hours or even minutes of irradiation. This would be sufficiently quick to explain the phenomenon of induced radioresistance although the precise mechanism, whether by repair, cell cycle control or some other process, remains yet undefined.

ULTRASTRUCTURAL CHANGES OF THE MOUSE PERIODONTIUM AFTER HeNe LASER RADIATION:

Helium-neon (HeNe) laser radiation is usually utilized in dentistry for diagnostic and therapeutic purposes, principally in Europe. No studies on the ultrastructural effects of HeNe laser irradiation of the periodontal tissues have been reported. This study shows the ultrastructural effects of HeNe laser radiation in mouse periodontium in two different conditions of irradiation. Twenty-four forty days old albino mice were irradiated with a HeNe laser source. They were divided into two groups according to dosage and time (two and six minutes of irradiation. 10.50566J/cm2 and 51.51698 J/cm2 respectively . Each group was subdivided depending on the time of animal sacrifice (immediately after irradiation or 10 days later, respectively). A further 12 mice served as controls using the same handling procedures and times as the experimental groups, but without radiation. In transmission electron microscopy (T.E.M.) ultrathin sections showed epithelial alterations only in the group irradiated for six minutes, and was more manifested in the sacrificed animals ten days after the irradiation. In the low dose irradiated animals, the bone showed two osteocyte populations according to their response to radiation. The connective tissue also showed two types of fibroblast population. This study showed abnormal cellular effects after HeNe laser irradiation in healthy rat periodontium, being more predominant at higher doses, although also present at doses usually utilized in clinical practice.

Modification of a Superficial X-Ray Therapy Machine for Rectal Contact Therapy: Preliminary results

X-ray therapy of superficial rectal cancers using a hand-held 50kV contact unit (Philips RT-50) in a technique first described by Papillon had reached a point of widening clinical acceptability when the manufacturer of this equipment discontinued its production. To pursue this endocavitary approach to rectal therapy, technical modifications have to be made to conventional superficial x-ray therapy machines. Advantages over the original Papillon method include remote viewing of the lesion through the proctoscopic cone and a lower radiation exposure for the operator. We have evaluated a Bucky Combination Therapy Unit under conditions in which the operating voltage (65kV), target skin distance (23.6cm), and added filtration (0.39mm Al) were selected in order to match as closely as possible the beam penetration characteristics of the “standard” (Papillon) technique. With this equipment, the thermal characteristics of the tube anode and housing limit the amount of radiation that can be delivered before a “rest period” for the machine is needed. In practice, 3 minutes of irradiation at an exposure rate of 500R/min can be performed followed by an interval of 3 minutes before irradiation can be resumed.

Continuous flow photocatalytic degradation of carbaryl in aqueous media

Abstract The photocatalytic degradation of carbaryl, present in aqueous solutions containing suspended TiO2 particles, has been studied in a continuous flow system, using a polytetrafluoroethylene photochemical reactor, equipped with an UV lamp. In order to optimize the process the effect of pH, catalyst and pesticide concentration, and irradiation time have been evaluated, working in the best conditions, the measured half‐life of carbaryl was 26 seconds. More than 99% of carbaryl present in solutions containing 0.2 mgL‐1 of pesticide decomposes after less than 1 minute irradiation.

High resolution depth profiling of light elements

An elastic recoil detection analysis technique with swift heavy ions has been developed to measure high resolution depth profiles of light elements in thin films and multilayer systems. A depth resolution of 1 nm was achieved with a Q3D magnetic spectrograph using a high quality 120 MeV 197Au 12 beam. The depth resolution was tested with 12C recoil ions from 12C/ 11B multilayers. Due to the large solid angle used (2 msr) and large scattering cross sections only low ion currents ( ≈ 10 9 ions s ) are necessary for good statistics within a few minutes of irradiation. The method was applied to depth profile analysis of light elements in a-Si:H/a-SiC:H multilayer systems. Alterations in the multilayers induced by the heavy ion beam have been observed during long lasting irradiations and might limit the depth resolution when profiling small elemental concentrations.

Comparison between two INAA methods applied to chemical characterization of ancient ceramics

Two different instrumental neutron activation analysis (INAA) methods were applied to characterize chemically 74 ceramic roof tile samples, found in the town of Pella, Greece and dated back to the Hellenistic Period (3rd century B. C.). The samples were first analyzed for 17 elements with a 4 hour irradiation and two counts and then re-analyzed for 9 elements with a 1 minute irradiation and two counts of short-lived radioisotopes. The results of both methods were very similar, showing the validity of the rapid INAA method (1 min irradiation) in the study of ancient ceramics. All samples were divided into 4 chemical groups, each one representing a different tiling.

Successful treatment of a case of hepatocellular carcinoma with tumor necrosis factor and local hyperthermia

A case of unresectable hepatocellular carcinoma which responded favorably to combined therapy with tumor necrosis factor (TNF) and local hyperthermia is reported. A 58-year-old man was admitted to our hospital in June 1988 for treatment of hepatocellular carcinoma affecting S4 and S8. After three sessions of transcatheter arterial embolization (TAE) therapy, the serum alpha 1-fetoprotein level decreased, and a reduction in the size of the lesions was also noted. Thereafter, the patient received local hyperthermia once a week (60 minutes of irradiation from a Thermotron-RF8 at 1,100W), but the alpha 1-fetoprotein level increased again in February 1989. On examination, enlargement of the S8 lesion and a new nodule in S7 were recognized. Since TAE was contraindicated due to liver dysfunction, human recombinant TNF (1 x 10(6)U) was given by intravenous infusion together with local hyperthermia once a week. Eight sessions of the combined therapy reduced the serum alpha 1-fetoprotein level markedly (7,512.0 to 2,782.0 pg/ml) and after eighteen sessions, 58.1% regression of tumor size (partial response) on computed tomography scans was observed. This anecdotal case supports previous experimental evidence suggesting that TNF plus hyperthermia may be effective for treating unresectable hepatocellular carcinoma.

An XPS investigation of the radiation induced degradation reactions of cellulose nitrate: Part 1—Argon plasma induced surface reactions

Some surface aspects of the argon plasma induced degradation reactions of cellulose nitrate have been investigated by X-ray Photoelectron Spectroscopy (XPS). It is shown that plasma treatment results in an initial decrease in the surface nitrogen and oxygen concentrations, the creation of highly oxidized carbon environments (as observed by a broadening in the C1s spectra of the treated materials) and the creation of new ‘reduced’ nitrogen functionalities (which appear at lower binding energies [398–402 eV]). Whilst little change is noted in the surface nitrogen and oxygen concentrations after the first minute of treatment, plasma irradiation continues to produce changes in the C1s and N1s core level spectra. In the N1s core level there is a slow but continued conversion of nitrate esters to the new nitrogen functionalities. However, the rate of this conversion is much faster in the first minute of irradiation than afterwards and consequently even after 40-min plasma treatment there is still a significant concentration of nitrate esters remaining in the top 50 Å of the treated materials. The observed changes in surface chemistry of cellulose nitrate with plasma treatment are correlated with the depth to which direct and indirect energy transfer processes are known to induce degradation in polymers.

Sm-Co permanent magnets: effects of fast neutron irradiation

Radiation-induced decay of remanence is investigated for Sm-Co5 and Sm2Co17 magnets irradiated with fast neutrons at temperatures below ambient with and without a bucking field. It is shown that most of the remanence is lost during the first minute of irradiation,i.e., at fluences of ≈2.5 × 1014 n/cm2. Also, different magnet materials, even with the same Co:Sm ratio, show markedly different decay rates. The effect of an applied bucking field and a low length-to-diameter ratio of the magnet is to increase the decay rate for a given neutron fluence. These remanence losses obtained with radiation are compared to results due to either an applied bucking field or annealing above 350 K.

Action of Light on Frog Pigment Cells in Culture

Solar radiation induces numerous biologic effects in skin but the mechanism underlying these responses is poorly understood. To study the etiology of these phenomena, we investigated the effect of light on cultured Xenopus laevis melanophores. Visible light stimulated a marked increase in intracellular cAMP levels within the first minute of irradiation. This light-induced elevation in cAMP was blocked by melatonin and was not seen in fibroblasts irradiated in a similar manner. These data show that the photoresponse of pigment cells from amphibian skin can be mediated by a cAMP-dependent mechanisms and suggest that a unique member of the rhodopsin family is involved in this process.

Induction of the Escherichia coli lactose operon selectively increases repair of its transcribed DNA strand

Nucleotide excision repair helps to ameliorate the lethal and mutagenic consequences of DNA damage by removing helix-distorting lesions from cellular genomes. We have previously analysed the removal of ultraviolet-induced cyclobutane pyrimidine dimers from specific DNA sequences in mammalian cells and demonstrated that transcriptionally active genes are preferentially repaired. Additionally, we found that in rodent and human cells only the transcribed strand of the dihydrofolate reductase gene is selectively repaired. Transcription is blocked by pyrimidine dimers in template DNA and the selective removal of these lesions seems to be important for cell survival after irradiation with ultraviolet light. To determine whether this feature of repair is common to prokaryotes and eukaryotes and better to understand its mechanism, we have investigated repair in the two separate DNA strands of the lactose operon of ultraviolet-irradiated Escherichia coli. We find a dramatic difference in the repair of the two strands only when transcription is induced. Most dimers are removed from the transcribed strand of the induced operon within five minutes of irradiation. In the nontranscribed strand, repair is significantly slower and resembles that found in both strands of the uninduced operon. Thus there seems to be a mechanism that couples nucleotide excision repair and transcription.