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  • 1
    ISSN: 1432-1327
    Keywords: Key words Iron complexes ; Chelating agents ; Iron metabolism ; Oxidative dehydrogenation ; Cytotoxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The interaction of Fe(II) and Fe(III) with the novel Fe(II) chelator N,N′N″-tris(2-pyridylmethyl)-cis,cis-1,3,5-triaminocyclohexane (referred to as tachpyr) gives rise to six-coordinate, low-spin, cationic complexes of Fe(II). Tachpyr also displays a cytotoxicity toward cultured bladder cancer cells that is believed to involve coordination of intracellular iron. The anaerobic reaction of tachpyr with Fe(II) salts affords the Fe(II)-tachpyr2+ complex, but in presence of oxygen, oxidative dehydrogenation of one or two of the aminomethylene group(s) of the ligand occurs, with formal loss of H2: R—N(H)—C(H)2—(2-py) → R—N=C(H)—(2-py)+H2. The resulting mono- and diimino Fe(II) complexes (denoted as [Fe(tachpyr-H2)]2+ and [Fe(tachpyr-2H2)]2+) are an inseparable mixture, but they may be fully oxidized by H2O2 to the known tris(imino) complex Fe(II)[cis,cis-1,3,5-tris(pyridine-2-carboxaldimino)cyclohexane]2+ (or [Fe(tachpyr-3H2)]2+). Cyclic voltammetry of the imino complex mixture reveals an irreversible anodic wave at +0.78 V vs. NHE. Tachpyr acts as a reducing agent toward Fe(IIII) salts, affording the same two Fe(II) imino complexes as products. Tachpyr also reductively removes Fe(III) from an Fe(III)(ATP)3 complex (which is a putative form of intracellular iron), producing the two Fe(II) imino complexes. Novel N-alkylated derivatives of tachpyr have been synthesized. N-Alkylation has two effects on tachpyr: lowering metal affinity through increased steric hindrance, and preventing Fe(III) reduction because oxidative dehydrogenation of nitrogen is blocked. The N-methyl tachpyr derivative binds Fe(II) only weakly as a high-spin complex, and no complexation or reduction of Fe(III) is observed. Corresponding to their inability to bind iron, the N-alkylated chelators are nontoxic to cultured bladder cancer cells. A tach-based chelator with three N-propyleneamino arms is also synthesized. Studies of the chemical and biochemical properties of this chelator further support a relationship between intracellular iron chelation, iron reduction, and cytotoxicity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 14 (1969), S. 48-54 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Im Rahmen der Mullikenschen Theorie wird eine Frequenzverschiebung im NQR-Spektrum untersucht. Es wird gezeigt, da\ in der MO-LCAO-NÄherung die Frequenzverschiebung proportional dem Grad des “charge transfer” ist. Für Pikrylchlorid-Komplexe wird die LinearitÄt dieser AbhÄngigkeit bestÄtigt. Experimentell wurde gezeigt, da\ die Verschiebung stark durch sterische Effekte beeinflu\t wird.
    Abstract: Résumé Dans le cadre de la théorie de Mulliken on a étudié le déplacement de. fréquence dans le spectre NQR. Il a été montré que dans l'approximation MO LCAO le déplacement de fréquence est proportionnel à l'importance du transfert de charge. Pour les complexes du chlorure de picryle cette proportionalité a été confirmée par l'expérience. Le déplacement est affecté par ailleurs par les interactions stériques.
    Notes: Abstract In the framework of Mulliken's theory a frequency shift in NQR spectra has been considered. It has been shown that in MO LCAO approximation the frequency shift is proportional to the degree of the charge transfer. For the picrylchloride complexes the linearity of this dependence has been confirmed. It has been shown experimentally that the shift is appreciably affected by steric interactions.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-601X
    Keywords: 25.85
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The fission-fragment mass distributions for3He-induced reactions on162Dy,169Tm,176Hf,181Ta, and180W were measured at a bombarding energy of 60–65 MeV. The parameters of stability of the saddle-point configurations with respect to the mass-asymmetric deformationsQ have been estimated from the data on the distribution variances and compared with the LDM predictions. Quantitative analysis of the fission barriers andQ(X)-dependence has shown inconsistencies in the modern description of the mass and energy macroscopic component.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The variances of the fission-fragment mass distributions,σ M 2 , were measured for (α,f) and (3He,f) reactions in the interval between Os and At. The analysis of the experimental data suggests that the properties of symmetric fission aroundx-0.7 are mainly determined by the barrier passing stage. This conclusion is in discrepancy with results of dynamic calculations.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Refractories and industrial ceramics 3 (1962), S. 171-172 
    ISSN: 1573-9139
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Conclusions Tips for immersion thermocouples were made from a mixture of kaolin and aluminum powder, fired in a nitrogen stream, under laboratory conditions. The tests in melted steel, pig iron, melted aluminum, zinc, cadmium, lead, tin and bismuth showed the good working properties of the tips. The production technique put forward is simple and the initial materials are inexpensive.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This is the first systematic study of air pollution from heavy metals and other trace elements throughout several industrialized areas and national parks of Eastern Romanian Carpathians using the moss biomonitoring technique. Samples ofHylocomium splendens collected at 120 sites were analyzed by epithermal neutron activation analysis at the pulsed fast reactor IBR-2 at JINR, Dubna, for a wide range of elements including heavy metals and rare earths (Na, Mg, Al, Cl,K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni (by (n,p) reaction), Cu, Zn, As, Se, Br, Rb, Sr, Zr, Mo, Ag, Sn, Sb, I, Cs, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Yb, Hf, Ta, W, Au, Th, and U). Copper, lead and cadmium were determined by AAS. Certified Reference Standards of mosses produced for interlaboratory comparisons in the European moss-survey 1995 were used to ensure the quality of the measurements. To present results in the form of coloured contour maps the geographical information system GIS-INTEGRO was used. The regional extent of pollution with specific metals was determined. Results reported are well consistent with those obtained in numerous recent projects carried out in Germany, the Netherlands, Poland, Bulgaria and other countries.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mining science 36 (2000), S. 452-461 
    ISSN: 1573-8736
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A calculated scheme is developed for the explosion action of a spherical charge in brittle rock taking account of the ejection of stemming and penetration of gaseous detonation products through the charge borehole into broken rock mass. The influence of stemming parameters on operating efficiency is determined. Estimates are given for the dimensions of breaking zones when the gas finds its way into cracks.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mining science 36 (2000), S. 462-475 
    ISSN: 1573-8736
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The deformation and failure of brittle monolithic rocks under the action of confined explosion of a concentrated charge are examined. A calculated scheme is suggested for determining the dynamics of breaking zone development. Features of the increase in radial crack area are considered.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-8973
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Conclusions 1. TMT of the nickel-base alloys, investigated even under conditions in which the recrystallizations is not completely suppressed, leads to a noticeable gain in strength characteristics at room temperature, and to a considerable gain in ductility. 2. The observed strengthening may be related to an increase in the amount of the carbide phase, to a change of the sub-crystal structure of the material, and to some textural properties. 3. The strong increase in ductility of the alloys investigated apparently results from the attainment of crystal plasticity by eliminating intercrystal-line fracture.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Metal science and heat treatment 4 (1962), S. 141-143 
    ISSN: 1573-8973
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Conclusions 1. The reason for brittle failure of hot rolled EI652 alloy is slow cooling at 700–600°. During slow cooling there is decomposition of the solid solution and precipitation of an intermetallide phase of the type Ni3Al. The amount of phase precipitated depends on the length of time the metal remains within the danger on temperature range. Coupled with the stresses produced by work hardening and also the thermal stresses, the precipitation of this phase leads to the formation of cracks. 2. To prevent the metal cracking, the sheets should be cooled in staggered fashion after rolling.
    Type of Medium: Electronic Resource
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