Home About us Contact
|
Home About us Contact | ||
|
|
||
Radiation Energy (radiation + energy)
Selected AbstractsRoot surface roughness following Er:YAG laser irradiation at different radiation energies and working tip angulationsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 7 2002Matthias Folwaczny Abstract Objectives: The determination of roughness of root surfaces following treatment with 2.94 µm Er:YAG laser radiation at different radiation energies and working tip angulations. Materials and methods: The study sample comprised 85 extracted human molars, premolars, canines and incisors (n = 85). The source of laser radiation was an Er:YAG laser device (KAVO-Key II, System Aesculap Meditec) emitting pulsed infrared radiation at a wavelength of 2.94 µm, with a pulse duration of 250 µs, and a pulse repetition rate of 10 pps. The samples were randomly divided into three experimental units, for treatment with a constant amount of 380 laser pulses at a radiation energy of 60 mJ, 100 mJ, and 180 mJ. Each experimental unit was divided into five subgroups of five samples, which were irradiated at a working tip angulations of 15°, 30°, 45°, 60°, and 90°. Five samples were treated mechanically using curettes. Five samples were left untreated as control. The mean (Ra) and maximum (Rmax) surface roughness of each sample was measured using a profilometer. The statistical analysis was undertaken using anova and Scheffé-test at a level of significance of 5% (p < 0.05). Results: Er:YAG laser radiation led to an Ra which ranged from 0.52 µm (± 0.10) to 0.81 µm (± 0.26) and to an Rmax between 3.4 µm (± 0.48) and 9.26 µm (± 3.08). The Ra and Rmax for samples treated with curettes was 0.51 µm (± 0.11) and 5.08 µm (± 4.98), respectively. That for the untreated control samples were 0.53 µm (± 0.15) and 7.07 µm (± 5.48), respectively. Conclusions: The mean and maximum surface roughness of root surfaces following irradiation with Er:YAG laser was not significantly different to that obtained on samples treated with conventional hand instruments or left untreated. Furthermore, the surface roughness does not depend on the radiation energy and the angulation of the working tip. [source] Photoionization of C2F4 in the VUV regionINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 13 2006A. S. Dos Santos Abstract We report calculated cross sections and asymmetry parameters for photoionization out of the outermost valence orbital 2b2u of C2F4 for photon energies ranging from near-threshold to 19 eV. We also report asymmetry parameters for photoionization out of the eight outermost orbitals of C2F4 at the He I radiation energy (21.23 eV). The iterative Schwinger variational method at the exact static-exchange level is used to obtain the continuum photoelectron orbitals. Our calculated results are compared with experimental results available in the literature. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Root surface roughness following Er:YAG laser irradiation at different radiation energies and working tip angulationsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 7 2002Matthias Folwaczny Abstract Objectives: The determination of roughness of root surfaces following treatment with 2.94 µm Er:YAG laser radiation at different radiation energies and working tip angulations. Materials and methods: The study sample comprised 85 extracted human molars, premolars, canines and incisors (n = 85). The source of laser radiation was an Er:YAG laser device (KAVO-Key II, System Aesculap Meditec) emitting pulsed infrared radiation at a wavelength of 2.94 µm, with a pulse duration of 250 µs, and a pulse repetition rate of 10 pps. The samples were randomly divided into three experimental units, for treatment with a constant amount of 380 laser pulses at a radiation energy of 60 mJ, 100 mJ, and 180 mJ. Each experimental unit was divided into five subgroups of five samples, which were irradiated at a working tip angulations of 15°, 30°, 45°, 60°, and 90°. Five samples were treated mechanically using curettes. Five samples were left untreated as control. The mean (Ra) and maximum (Rmax) surface roughness of each sample was measured using a profilometer. The statistical analysis was undertaken using anova and Scheffé-test at a level of significance of 5% (p < 0.05). Results: Er:YAG laser radiation led to an Ra which ranged from 0.52 µm (± 0.10) to 0.81 µm (± 0.26) and to an Rmax between 3.4 µm (± 0.48) and 9.26 µm (± 3.08). The Ra and Rmax for samples treated with curettes was 0.51 µm (± 0.11) and 5.08 µm (± 4.98), respectively. That for the untreated control samples were 0.53 µm (± 0.15) and 7.07 µm (± 5.48), respectively. Conclusions: The mean and maximum surface roughness of root surfaces following irradiation with Er:YAG laser was not significantly different to that obtained on samples treated with conventional hand instruments or left untreated. Furthermore, the surface roughness does not depend on the radiation energy and the angulation of the working tip. [source] Construction of a polymer skeleton that is cut in half by ionizing radiationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2005Takashi Shimizu Abstract Polystyrene with a benzyl ester of carboxylic acid at the center of a polymer skeleton was synthesized by living radical polymerization. The initiator used had two functional groups for 2,2,6,6-tetramethylpiperidinoxyl (TEMPO)-mediated living radical polymerization on the benzyl and the carboxylic sides of the benzyl ester. Introduction of the benzyl ester changed the polystyrene from a crosslink type to a scission type polymer on ,-irradiation. Irradiation of the polymer resulted in a binary change of the molecular weight because of the dissociative capture of secondary electrons by the benzyl ester, as: The binary change of the molecular weight suggests that the polymer can be used as a new type of radiation resist with high sensitivity and spatial resolution to ionizing and high resistivity to plasma etching. The number of scissions per 100 eV radiation energy absorbed was 0.29, which was about one fourth of the yield of secondary electrons. The low efficiency was because of the recombination of polymer radicals generated by the dissociative electron attachment. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1068,1075, 2005 [source] Computer modeling of optical properties of gold ellipsoidal nanoparticles at laser radiation wavelengthsLASER PHYSICS LETTERS, Issue 2 2005V. K. Pustovalov Abstract Processes of laser interaction with metal (gold) nanoparticles are of great interest for laser applications in nanotechnology, engineering, and medicine. Optical properties of nanoparticles determine photophysical and photochemical processes during laser treatment. Computer calculation of efficiency factors of absorption, scattering and extinction of radiation by ellipsoidal gold nanoparticles (two-dimensional ellipsoids of revolution) with small semiaxes in the range 5,100 nm, for some values of aspect ratio and angle of orientation of ellipsoid with respect to direction of laser radiation propagation and for some laser wavelengths is performed. The estimation of absorbed and scattered laser radiation energy by gold ellipsoidal nanoparticles, their maximal temperatures and comparison with experimental data is made. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] A directive dual-band and dual-polarized antenna with zero index metamaterialMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2008Zi-Bin Weng Abstract A novel directive dual-band and dual-polarized microstrip antenna with ZIM is presented. An averaging effect over constituent materials of the metamaterial structure yields an effective permittivity that approaches zero at dual band with different polarizations, and then it results in a metamaterial with zero index of refraction and the radiation energy of this antenna is congregated. The experimental results show that this method is effective, and this structure can greatly increase the gain at dual frequencies. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2902,2904, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23855 [source] A directive patch antenna with metamaterial structureMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2007Zi-bin Weng Abstract A new method to improve the gain of patch antenna with metamaterial composed of ring aperture lattice is presented. The influences of the number of metamaterial layers and a comparison of electromagnetic characteristics between the conventional patch antenna and the new metamaterial patch antenna are studied by using numerical simulation method. Then, a patch antenna with the metamaterial is fabricated and measured. The simulation and experimental results show that this method is effective and this structure can realize congregating the radiation energy, thus the gain of the antenna with metamaterial can greatly increase when compared with the conventional one. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 456,459, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22146 [source] Radiative cooling effect of Hurricane Florence in 2006 and precipitation of Typhoon Matsa in 2005ATMOSPHERIC SCIENCE LETTERS, Issue 2 2009Quanhua Liu Abstract The increasing strength of tropical cyclones may be a response of the Earth's interaction between natural variability and human activities. Negative effects of the severe storms, such as flooding, landslides, damage to properties, and even a number of human casualties, have been reported many times. This study reported other aspects on Hurricanes and Typhoons, which may be beneficial to the world. We found that Hurricane Florence in 2006 decreased radiation energy by , 0.5 × 1020 J to the Earth-atmospheric system, about 10% of the annual global energy consumption. If the amount of energy uniformly distributes over the whole Earth surface and over 1-year time, it corresponds to a power of , 0.003 W m,2 The total forcing power on climate change is 0.24 W m,2, if we only take account for the stored fluxes in water, atmosphere, continents, and heat required to melt glaciers and sea ice. Thus, the shielding effect of solar radiation by tropical storms could contribute to ease global warming. In addition, hurricane and typhoon can ease drought sometimes. This study found that the total rainwater carried by Typhoon Matsa in August 2005 into China's inland amounts to about 135 billion tons. The rainfall over the northern China eased severe drought in summer 2005. Copyright © 2009 Royal Meteorological Society [source] A Novel Class of Antitumor Prodrug, 1-(2,-Oxopropyl)-5-fluorouracil (OFU001), That Releases 5-Fluorouracil upon Hypoxic IrradiationCANCER SCIENCE, Issue 4 2000Yuta Shibamoto We have been developing prodrugs of anticancer agents such as 5-fluorouracil (5-FU) that are activated by irradiation under hypoxic conditions via one-electron reduction. Among them, OFU001 [1-(2,-oxopropyl)-5-fluorouracil] is a prototype radiation-activated prodrug. In this study, we investigated the radiation chemical reactivity and the biological effects of OFU001. This prodrug is presumed to release 5-FU through incorporation of hydrated electrons into the antibonding ,* orbital of the C(1,)-N(1) bond. Hydrated electrons are active species derived from radiolysis of water, but are readily deactivated by O2 into superoxide anion radicals () under conditions of aerobic irradiation. Therefore, 5-FU release occurs highly specifically upon irradiation under hypoxic conditions. OFU001 dissolved in phosphate buffer released 5-FU with a G -value (mol number of molecules that are decomposed or produced by 1 J of absorbed radiation energy) of 1.9×10,7 mol/ J following hypoxic irradiation, while the G -value for 5-FU release was 1.0×10,8 mol/J following aerobic irradiation. However, the G -values for decomposition of OFU001 were almost the same, i.e., 3.4×10,7 mol/J following hypoxic irradiation and 2.5×10,7 mol/J following aerobic irradiation. When hypoxically irradiated (7.5,30 Gy) OFU001 was added to murine SCCVII cells for 1,24 h, a significant cell-killing effect was observed. The degree of this cytotoxicity was consistent with that of authentic 5-FU at the corresponding concentrations. On the other hand, cytotoxicity was minimal when the cells were treated with aerobically irradiated or unirradiated OFU001. This compound had no radiosensitizing effect against SCCVII cells under either aerobic or hypoxic conditions when the drug was removed immediately after irradiation. Since hypoxia is generally most marked in tumors and irradiation is applied at the tumor site, this concept of prodrug design appears to be potentially useful for selective tumor treatment with minimal adverse effects of anticancer agents. [source] | ||||||||||