[en] Effects of dispersity of initial ZrO₂ powder and holding time at high temperature were investigated for the process of zirconium reduction by calcium thermic method. The charge containing zirconium dioxide and metallic calcium chip was heated in argon up to 1100 deg C with holding at heat for 1.5 and 3 h. Calcium oxide obtained then was removed with the help of hydrochloric acid and distilled water. Fragmentation composition of zirconium powder after drying was determined by sedimentation technique. It was found out, that the tendency to universal distribution function with maximum at 5 μm took place indipendently of initial distribution function

[en] Kinetics of catalytic reduction of uranyl species, U(VI) to U(IV) with hydrazine nitrate was studied over Pt/SiO₂ catalyst in nitric acid medium. Experiments were carried out in a stainless-steel autoclave as a function of mixing intensity, temperature, catalyst loading and concentration of nitric acid, hydrazine and uranium. Langmuir-Hinshelwood approach was considered to derive various model equations and each of them was evaluated. Results of the present study indicated that catalytic reduction of U(VI) can be described by surface reaction between adsorbed molecules. The activation energy of the reaction was calculated to be 74.5 kJ/mol, suggesting a chemical reaction controlled process. (author)

No abstract available

[en] Process for reducing the 'pertechnetate' ion TcO₄^-, whereby an aqueous solution of 'pertechnetate' is mixed with tin metal or a tin alloy as 'pertechnetate' reducing agent, and a soluble salt of a metal below tin in the electro-chemical tension scale, as activator for the reducing tin. This reduced 'pertechnetate' is used for forming usable complexes in medical diagnosis exploration

[en] A new material for neutralization of nitrogen oxides is presented. Two or three metals containing catalysts with a good activity and selectivity towards NO_x have been obtained. Preparation of carbon catalysts by deposition of the active phase precursor on the initial carbon material prior to activation is considered as the most promising method. An active carbon-based catalyst (AC/Co) has been synthesized Apricot shells preliminary impregnated with a water-alcohol solution of Co nitrate have been used as initial carbon material. after drying they have been subjected to one-phase steam pyrolysis using a fix-bed reactor. The catalyst thus obtained has a specific surface area (BET) of 53 m²g^-1, a favorable mesopore volume/total volume ratio (about 0.85) determined by nitrogen adsorption, a suitable mesopore distribution, about 70% of the mesopores being characterized by r_p larger than 25 A and a high dispersion of the Co oxide phase. In addition the catalyst possesses the necessary mechanical resistance. The catalyst has exhibited a high activity with respect to NO_x reduction with CO at low temperatures (at 150-250^oC which are the temperatures of industrial flue gases, nO conversion up to 60-95% occurs) and a high selectivity. No presence of H₂O has been established over the whole temperature range (100-300^oC). An additional advantage of the catalyst is the fact that the amount of CO above 150^oC is lower than the stoichiometric which indicates parallel participation in the process of both the active phase and the support (active carbon) It is also important that the presented catalyst has a low price due to the use of waste products from agriculture and the elimination of special thermal treatment of the supported Co nitrate. There are possibilities of using of other organic wastes from agriculture as well as wastes obtained during flotation of coal. (author)

[en] The aluminothermic process for the reduction of vanadium pentoxide is considered. Its thermochemistry features are presented, as well as the heat transfer and the rate phenomena concerning such a reaction system. It is pointed out also the effect of the process parameters on the recovery of metallic vanadium. (Author)

[en] With the development of bio electrochemistry, researches appeared on the enzymes immobilization at the surface of electrodes for the realization of bioreactors and bio sensors. One of the main challenges is the development of host matrix able to immobilize the protein material preserving its integrity. In this framework the authors developed graphite electrodes modified by clay films. These electrodes are examined for two enzyme reactions involving proteins of sulfate-reduction bacteria. Then in the framework of the hydrogen biological production and bioreactors for the environmental pollution de-pollution, the electrochemical behavior of the cytochrome c3 in two different clays deposed at the electrode is examined

[en] Purpose: Evaluation of the emphasis of themes pertaining to radiation dose and dose reduction at the Meeting of the German Radiological Society from 1998-2008 in comparison to international data. Materials and Methods: Retrospective analysis of 9440 abstracts with documentation of study presentation character, type of imaging, and examined body region. Abstracts stating radiation dose or primarily dealing with radiation dose/dose reduction were documented. Results were compared with a Pubmed query. Results: The percentage of purely scientific presentations sank in the observation period from 88 to 66%. While contributions dealing with MRI sank from 48 to 34%, those dealing with CT rose from 30 to 34%. The percentage of abstracts dealing with radiation dose rose from 7 to 10%, while that of work primarily pertaining to dose/dose reduction grew from 4 to 6% and 2 to 4%, respectively. Of all abstracts concerning CT, 15% touched on radiation dose, while 9% and 6% primarily dealt with dose and dose reduction. The respective numbers for cardiac CT, whose relative share of all CT abstracts rose from 3% in 1998 to 12% in 2008, were 10%, 7%, and 5%. An online query produced 137,791 publications on CT, and 2% of these abstracts mentioned radiation dose and 0.5% mentioned dose reduction. Conclusion: The number of presentations dealing with dose at the Meeting of the German Radiological Society has risen with time and is higher than the international number. On the other hand, >90% of all presentations and >85% of all CT abstracts do not mention radiation dose. In light of increasing public concern relating to radiation exposure, more intensive research of these themes is warranted. (orig.)

[en] The electrochemical reduction of some transplutonium elements (Pu - Cf) and rare earths (Eu, Tm) from aqueous complexing solutions to amalgams was studied over a wide range of cathodic potentials in order to get the best separation of californium. The reduction process in acetate media (pH 1.5 - 4.6) at potential around - 1.7, 1.9 V leads to quantitative extractions of californium into the mercury phase, while more negative potentials are required for the reduction of the lighter transuranium elements and lanthanides. Thus, the optimal conditions of the californium purification from the investigated actinides and lanthanides were determined. Separation factors α were found to be 25 - 90 excepted in the case of Cf/Eu, where poor values (α varying from 7 to 12) were observed. Applications of more negative cathodic potentials decrease the selectivity of the reduction process. A similar study with lithium citrate solutions (pH ∼ 6) shows that a good separation of californium from lighter and heavier actinides is achievable. Separation factor of 88 is obtained for Cf/Am at - 1.98 V. The anodic stripping of mixed amalgams (Pu, Am, Cm, Bk, Tm and Cf) Hg in nitric acid and acetic solutions at potentials + 0.1, - 0.7 V proceeds slowly and proved to be uneffective for californium separation from light actinides under described conditions

[en] We consider the reconstruction problem for limited angle tomography using filtered backprojection (FBP) and lambda tomography. We use microlocal analysis to explain why the well-known streak artifacts are present at the end of the limited angular range. We explain how to mitigate the streaks and prove that our modified FBP and lambda operators are standard pseudodifferential operators, and so they do not add artifacts. We provide reconstructions to illustrate our mathematical results. (paper)