Neutron activation and gamma spectrometry are usable also for the determination of cross-sections of different neutron reactions. We have studied the cross-section of yttrium (n,xn) threshold ...reactions using quasi mono-energetic neutron source based on the reaction on 7Li target at Nuclear Physics Institute of ASCR in Rez. Yttrium (n,xn) threshold reactions are suitable candidates for fast neutron field measurement by activation detectors. Fast neutron field monitoring is necessary already today at a wide range of accelerator facilities and will gain on importance in future fast reactors of generation IV, accelerator transmutation systems or fusion reactors. The knowledge of the cross-sections is crucial for such purpose. Unfortunately, the cross-section is sufficiently known only for 89Y(n,2n)88Y reaction. For higher orders of reactions there are almost no experimental data. Special attention was paid to the 89Y(n,3n)87Y reaction. The nuclei are produced, both in the ground state with half-life 79.8hours and in the isomeric state with half-life 13.38hours. The isomer decays mainly through the gamma transition to the ground state, the beta decay of the excited state is negligible within our accuracy. The cross-sections of both 87Y productions were analyzed.
An extended U/Pb-assembly was irradiated with an extracted beam of 2.52 GeV deuterons from the Nuclotron accelerator of the Laboratory of High Energies within the JINR in Dubna, Russia. The lay-out ...of this experiment and first results are reported. The Pb-target (diameter 8.4 cm, length 45.6 cm) is surrounded by a
nat
U-blanket (206.4 kg) and used for transmutation studies of hermetically sealed radioactive samples of
129
I,
237
Np,
238
Pu and
239
Pu. Estimates of transmutation rates were obtained as result of measurements of gamma-activities of the samples. Information about the spatial and energy distribution of neutrons in the volume of the lead target and the uranium blanket was obtained with sets of activation threshold detectors (Al, Y and Au) and solid state nuclear track detectors (SSNTD). An electronic
3
He neutron detector was tested on-line. A comparison of experimental data with theoretical model calculations using the MCNPX program was performed yielding satisfactory results.
A recent review of the literature revealed more than 20 methods of correction of protruding ears. Pitanguy's cartilage island flap technique is still not widespread. However, it is extraordinarily ...versatile and effective from our own experience. The aim of this study is to present our own experience in the correction of prominent ears using this method. According to Pitanguy's cartilage island flap technique, 80 patients were operated on at the Private Plastic Surgery Clinic from 1992 to 1999. There were 45 (56%) female and 35 (44%) male patients, aged from 9 to 37 years (22 years on average). All procedures were performed under local anesthesia. In the follow-up period of 1 to 8 years the final aesthetic results were estimated as very good in 68 (85%) patients and good in 12 (15%) patients. Early complications in the form of bleeding occurred in three (3.75%) patients. Asymmetry in the ears' position was qualified as a late complication and occurred in four (5%) patients.
In our department from 1995 to 1998, 30 patients were operated on under general anesthesia via tracheosubmental intubation (TSI). No local or general complications were observed. Operating in the ...field free from the intubation tube is very comfortable for a surgeon, while for an anesthesiologist the safety of the tube and efficiency of ventilation are very important. TSI, as a technically simple, safe, and efficient procedure, is extremely helpful in the surgical treatment of patients with simultaneous multifragmentaric and comminuted fractures of the maxilla and mandible, and in orthognathic and aesthetic plastic surgery of the face, where assessment of facial symmetry and occlusion is especially important.
Immunohistochemical demonstration of S100 protein was performed in 56 cases of malignant melanoma of the facial skin and oral cavity. The depth of invasion was measured comparatively in HE sections ...and in sections stained for S100 protein. Comparison of measured melanoma invasion depth in S100-and HE-stained sections revealed a deeper invasion of the tumor in S100-stained slides than in slides stained routinely with HE according to Breslow's melanoma staging procedure. A reverse relationship between the intensity of immunohistochemical staining for S100 protein and survival rate was found in both melanomas of the facial skin and oral cavity. Although the presence of S100 protein has been demonstrated previously in skin melanomas, no similar investigations concerning the oral mucosa have been performed up to now.
The development of cancer is associated with high oxidative stress and at the same time with immune system activation. Tumors develop efficient mechanisms of protection against the immune response, ...which allow them to escape the immune surveillance. Simultaneously, key events in the process of carcinogenesis are related to oxidative stress. The relationship between the two remains unknown. Novel understanding of oxidative stress shows that discrete changes of activities of certain enzyme systems such as NADPH oxidases or nitric oxide synthases may be more important than the overall balance of production and removal of reactive oxygen species. Such imbalance of nitric oxide and superoxide production could modify inflammation and immune regulation. We studied superoxide anion production (by lucigenin enhanced chemiluminescence - 5 microM), NADPH oxidase activity and nitric oxide synthase (NOS) dysfunction. In parallel mRNA expression of immunomodulatory markers such as FoxP3 (T regulatory cell marker), CCR6 (mucosal homing effector T cell marker) and CD85j (NK cell/CD8 T cell Ig-like MHC class I inhibitory receptor) was determined. Basal superoxide production and NADPH oxidase activity are increased in oral squamous cell carcinoma. Tumor superoxide production was inhibited by NADPH oxidase inhibitor apocynin and by NOS inhibitor L-NAME. This indicates, for the first time, that oral squamous cell carcinoma is characterized by dysregulated nitric oxide synthase, which apart from increased NADPH oxidase activity contributes to oxidative stress and may be related to the immuno-pathology of these tumors. Studied tumors were infiltrated by CCR6+, but showed lower expression of both CD85j and FoxP3 mRNA. Finally, the CD85j mRNA expression was inversely correlated to oxidative stress parameters. These preliminary studies indicate that tumor oxidative stress, related to NADPH oxidase activity and NOS activity could be related to immune responses to cancer, thus therapeutic modification of oxidative stress, which could include the correction of NOS dysfunction, could facilitate immune surveillance.
Results of two experiments with Yttrium-89 samples on U/Pb-assembly “Energy plus Transmutation” 1 are presented. The assembly is a lead cylindrical target (8.4 cm diameter, 45.6 cm length) with ...natural uranium blanket (206.4 kg). The lead target was irradiated with JINR Dubna NUCLOTRON with 1.60 and 2.52 GeV deuteron beam. The final purpose of the experiments was to measure neutron field inside the assembly. Yttrium-89 activation detectors were located throughout the entire U/Pb-assembly. Irradiated sample gamma activity was measured with HPGe spectrometer. The gamma spectra were analyzed and the net peak areas were calculated using the DEIMOS program 2. After short presentation of the activation results neutron spectrum determination method is proposed and its results presented. Assuming reaction model through compound nucleus and using some mathematical tricks Yttrium isotope “k ” production rate discrete formula
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$$I_k = N\int\limits_{E_{thr,k} }^\infty {\phi \left( E \right)\sigma _k \left( {E,E_{thr} } \right)} dE$$
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was transformed into Volterra's integral equation of the first kind and then solved. The method and its applicability still to be discussed. The results as the preliminary ones are for illustrative purpose only.
The experiment described in this communication is a part of the scientific program "Investigations of physical aspects of electronuclear method of energy production and transmutation of radioactive ...waste of atomic energetic using relativistic beams from the JINR Synchrophasotron/Nuclotron" - the project "Energy plus Transmutation". The performing of the first experiment at deuteron beam with energy 2.52 GeV at the electronuclear setup which consists of Pb-target with U-blanket (206.4 kg of natural uranium) and transmutation samples and its preliminary results are described. The hermetic samples of isotopes of I-129, Np-237, Pu-238 and Pu-239 which are produced in atomic reactors and industry setups which use nuclear materials and nuclear technologies were irradiated in the field of electronuclear neutrons produced in the Pb-target surrounded with the U-blanket setup "Energy plus transmutation". The estimations of its transmutations (radioecological aspect) were obtained in result of measurements of gamma activities of these samples. The information about space-energy distribution of neutrons in the volume of the Pb-target and the U-blanket was obtained with help of sets of activation threshold detectors (Al, V, Cu, Co, Y, In, I, Ta, Au, W, Bi and other), solid state nuclear track detectors, He-3 neutron detectors and nuclear emulsions. PUBLICATION ABSTRACT
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