Bibliothek

Notizen: Analogous to the localization of the wave function of an electron in a random potential (Anderson localization), in the macroscopic system of magnetoelastic waves (MEWs) propagating in a highly magnetostrictive string exhibiting the giant ΔE effect, the piling-up of MEWs into a wave-packet in a restricted small region of the string is expected. This wave-packet is subject to hopping in a discontinuous wave by applying a magnetic field due to the change in the local elastic states caused by the ΔE effect. From this expectation, a theoretical analysis was performed focusing on the derivation of localization conditions of MEWs. The analysis was carried out using a one-dimensional string model having high magnetostriction. The string is assumed to be composed of random chains with (1) alloy-type disorder (random weights of masses with equal spacings) and (2) liquid-type disorder (random spacings of masses with equal weights). For the elastic and magnetoelastic constants of the string, the value of Fe78Si10B12 amorphous wire (Unitika) were used in the calculations. No substantial changes in the localization states were not recognized in both modes. The analysis revealed that, when the change of the apparent Young's modulus with magnetic field ΔE is 28%, the localized MEWs are subject to hopping conserving their wave identities (eigenfrequencies and eigenstates). This result in considered to originate from the changes in the disorder conditions to support the localization of MEWs. To confirm the above theoretical prediction experimentally, MEW properties have been measured by using Fe78Si10B12 amorphous wires connecting weights made of leads to form the random chain structure. The localized MEWs are, indeed, observed by detecting the local vibrations of the wires. Theoretical and experimental results will be presented in detail at the conference. © 1997 American Institute of Physics.

Notizen: We present a new method to evaluate the photo-oxidative activity of sunscreening agents based on the photodynamic oxidation of uric acid. Uric acid was selected as the oxidant probe for its high reactivity to singlet oxygen and oxygen radicals, high sensitivity of detection using electrochemical (EC) techniques, low light absorptivity and high photochemical stability in the UVA/B region of interest, and stability to autoxidation. The method is demonstrated by the photodynamic oxidation of uric acid on co-irradiation with Rose Bengal, a highly efficient photosensitizing dye for the production of singlet oxygen (1O2). Using this assay we found that the relative photodynamic oxidation rates of UVB-absorbing sunscreens in 80% methanol on irradiation with 〉290 nm light decreased in the order 2-ethylhexyl 4-dimethylaminobenzoate (DMABA-2EH) ≫ 2-ethylhexyl 4-methoxycinnamate (MCA-2EH) and the experimental sunscreens, 1-(1,1-dimethylethyl)-3-octanoyl-4,4-dimethyl- 1,4,5,6,-tetrahydropyridine (ICI-319) and 1-(2-methylpropyl)-3-propionyl-4,4-dimethyl-1,4,5,6-tetrahydropyridine (ICI-855). The relative photodynamic oxidation rates of UVA-absorbing sunscreens decreased in the order 4-tert-butyl-4'-methoxydibenzoylmethane (BMDBM) and 4-(2-propyl)benzophenone (PB) 〉 2-hydroxy-4'-methoxy-benzophenone (HMB) and 2,2'-dihydroxy-4-methoxybenzophenone (DHMB). We have confirmed the photodynamic activity of DMABA-2EH for the production of singlet oxygen (1O2) using electron paramagnetic resonance (EPR) spectroscopy and the reagent 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TEMP). We failed to detect the photodynamic production of the oxyradicals, superoxide (O2.-) and hydroxyl radical (HO.) using N-tert-butyl-a-phenylnitrone (PBN) and 5,5-dimethyl-1-pyrrolidine-1-oxide (DMPO) as a result of photochemical interference caused by these spin-trapping reagents. The uric acid photo-oxidation assay was also used to compare the photodynamic reactivity of light-reflective, microfine oxides TiO2, ZnO and ZrO2 suspended in aqueous 80% methanol. All of the microfine oxides (uncoated) showed greater photodynamic reactivity in equimolar dispersion than did any of the organic UVA- and UVB-absorbing sunscreens in homogeneous solution. In this assay the photodynamic oxidation rates for the microfine oxides decreased in the order ZnO ≫ TiO2 (anatase) 〉 ZrO2 〉 TiO2 (rutile). Resume Nous presentons un nouveau procede d'evaluation de l'activite photooxydante d'agents pour ecrans solaires base sur l'oxydation photodynamique de l'acide urique. L'acide urique a ete choisi comme test a l'oxydation en raison de sa forte reactivite a l'oxygene singulet et aux radicaux oxygene, sa haute sensibilite a la detection par les techniques electrochimiques (EC), sa faible capacite d'absorption de la lumiere, sa stabilite photochimique elevee dans le domaine UVA/UVB concerne, et sa stabilite a l'autooxydation. La demonstration du procede est effectuee au travers de l'oxydation photodynamique de l'acide urique co-irradie avec du Rose du Bengale, colorant phosensibilisateur tres efficace pour generer de l'oxygene singulet (1O2). En mettant ce test en oeuvre nous avons trouve que les vitesses relatives d'oxydation photodynamique d'ecrans solaires aux UVB dans due methanol a 80%, irradies avec une lumiere 〉 290nm, diminuent dans l'ordre: 2-ethylhexyl 4-dimethylamino-benzoate (DMABA-2EH) ≫ 2-ethylhexyl 4-methoxycinnamate (MCA-2EH) et les ecrans a l'essai: la 1-(1,1-dimethylethyl)-3-octanoyl-4,4-dimethyl-1,4,5,6-tetrahydopyridine (ICI-319) et la 1-(2-methylpropyl)-3-propionyl-4,4-dimethyl-1,4,5,6-tetrahydropyridine (ICI-855). les vitesses relatives d'oxydation photodynamique d'ecrans solaires aux UVA diminuent dans l'ordre: 4-tert-butyl-4'-methoxydibenzoylmethane (BMDBM) et 4-(2-propyl) benzophenone (PB) 〉 2-hydroxy-4'-methoxybenzophenone (HMB) et 2'2'-dihydroxy-4-methoxybenzophenone (DHMB). Nous avons confirme l'activite photdynamique du DMABA-2EH pour la production d'oxygene singulet (1O2) en utilisant la spectroscopie par resonance paramagnetique electronique et le reactif 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TEMP). Nous n'avons pas pu detecter la production photodynamique des oxyradicaux du superoxyde (O2.) et du radical hydroxyle (HO.) a l'aide de la N-ter-butyl-a- phenylnitrone (PBN) en raison d'interferences photochimiques causees par ces reactifs spin-Bloquants. Le test de photooxydation de l'acide urique a aussi ete utilise pour comparer la reactivite photodynamique d'oxydes microfins reflechisseurs de lumiere TiO2, ZnO et ZrO2 en suspension dans du methanol aqueux a 80%. Tous ces oxydes microfins (non enrobes) ont montre une meilleure reactivite photodynamique en dispersion equimolaire que ne l'a fait aucun des ecrans solaires aux UVA et UVB en solution homogene. Lors de ce test les vitesses d'oxydation photodynamique des oxydes microfins ont diminue dans l'ordre ZnO ≫ TiO2 (anatase) 〉 ZrO2 〉 TiO2 (rutile).

Notizen: Magnetic properties of multilayer films composed of FeRhIr (or FeRh), Ag and Fe layers were investigated in detail. The results showed that the multilayer film with (FeRhIr/Ag/Fe/Ag)×9/FeRhIr/Ag/Fe structure exhibits a very unique magnetic phase transition, where the transition temperature was subject to change from 40 to 170 °C by the application of a magnetic field ranging from 250 to 150 Oe. The change in pinning strength of magnetization in antiferromagnetic and ferromagnetic phases of FeRhIr layers with a magnetic field is considered to be responsible for the unique properties. Associated with the magnetic phase transition of FeRhIr layers, magnetostrictive response of the film was actually obtained by applying a magnetic field up to 100 Oe. © 1999 American Institute of Physics.

Notizen: We have developed a longitudinal emittance monitor for a 7 MeV proton beam provided by the 433 MHz linac at the Institute for Chemical Research, Kyoto University. In the present system, the beam first hits a thin gold target on the beam line, and a fraction of the scattered protons comes into a small cavity. After deflected by a rf electric field in the cavity, the protons finally reach a position sensitive detector (PSD). The PSD gives the information of the energy and position of the individual scattered proton, which enables us to reconstruct the longitudinal distribution of the beam before colliding with the target. The phase and energy resolution of the system are estimated to be 13° and 23 keV full width at half-maximum, respectively. The longitudinal rms emittance measured was 0.39±0.07 π deg MeV under the nominal operating condition of the linac. © 1996 American Institute of Physics.

Notizen: The x-ray energy responses of silicon semiconductor detectors, including surface-barrier and photodiode-type detectors, have been investigated, using synchrotron radiation from a 2.5 GeV positron storage ring at the Photon Factory (KEK) in order to study the fundamental physics mechanism of the output signals. These studies are essential to obtain the principles of the future designs of plasma x-ray detectors, as well as of their plasma data analyses. The characterization experiments and their physics interpretations were made using (i) a group of fully depleted detectors and (ii) another group of partially depleted detectors characterized by obviously different depletion-layer thicknesses and minority-carrier diffusion lengths, but with the same wafer thickness. Both results are well interpreted by our newly proposed formula for a semiconductor x-ray-detector response. The importance of these investigations for the plasma x-ray diagnostics is highlighted by significant errors for the estimation of plasma-electron temperatures when the commonly utilized conventional theory is employed for the plasma data analyses. © 1995 American Institute of Physics.

Notizen: Vanadium ion (V+) implantation has been successfully applied to the formation of semiinsulating 6H-SiC layers. The resistivity of V+-implanted layers strongly depended on the conduction type of initial 6H-SiC crystals. The resistivity at room temperature exceeded 1012 Ω cm and 106 Ω cm for p- and n-type samples, respectively. Compensation mechanism is discussed based on the temperature dependence of resistivity. This technique will be useful for device isolation, edge termination, and reduction of parasitic impedance of SiC devices. © 1996 American Institute of Physics.

Notizen: Temporal decay characteristics of dislocation-related luminescence bands (D1–D4) were explored in strain-relieved epitaxial SiGe/Si(100). Close similarity of the decay profiles was observed not only between D1 and D2 bands but also between D3 and D4 bands. The decay transients of the D1 and D2 bands at low temperatures are characterized by long decay times, τ(approximately-greater-than)200 ns, whereas the D3 and D4 bands exhibit even sharper transients with τ〈60 ns. Temperature dependence of "radiative'' lifetimes implies a free-to-bound nature of the D1 and D2 bands, while a bound-to-bound character of the luminescence origins for the D3, D4 bands. © 1996 American Institute of Physics.

Notizen: Despite high primary response rates with cisplatin-based combination chemotherapy, the overall survival rate for advanced ovarian cancers remains dismal. We designed a new systematic treatment approach with a combination chemotherapy consisting of cisplatin, doxorubicin and cyclophosphamide (cyclic PAC chemotherapy), with the aim of improving survival rates with minimal disturbance of quality of life. Cyclic PAC chemotherapy is a three-step chemotherapy with three courses of the PAC regimen in each step. A total of nine courses with a 3-month drug-free period between each step were administered over a 15-month period to patients with clinical stage IC-IV ovarian cancer who had undergone cytoreductive surgery. Forty-eight patients with stage IC-IV disease (34 patients with stage III and IV disease) were treated with cyclic PAC chemotherapy. Thirty-four patients with stage IC-IV disease (23 patients with stage III and IV disease) were treated by a brief course of PAC chemotherapy. Long-term survival and toxicity were evaluated for both treatment groups. Cyclic PAC chemotherapy improved the overall outcome of patients (66.6% 3-year and 56.5% 5-year survival rates) compared to brief PAC (41.2% 3-year and 23.5% 5-year survival rates) (P 〈 0.01). The outcome of patients with stage III-IV ovarian cancer of the cyclic PAC group (52.6% 3-year and 37.2% 5-year survival rates) was also superior to that of the brief PAC group (21.7% 3-year and 8.7% 5-year survival rates). Generally, the treatment was well tolerated. The toxicity was similar in both groups, although myelosuppresion and neurotoxicity were rather prominent in the cyclic PAC group. Cyclic PAC chemotherapy may lead to improved survival in advanced ovarian cancer, and merits further investigation in a randomized study.