Simultaneous measurement of gamma-rays and neutron fluences</p> using a HPGE detector</o:p></p> </p>

Summary A simultaneous determination of gamma and neutron fluences in a mixed neutron + gamma field can be achieved by gamma-ray spectrometry, optimizing the moderator-converter-detector assembly and measuring both the direct gamma-lines and the neutron induced prompt gammas. For the prompt gamma-lines a combination of high efficiency and low background is the goal, and it can be best achieved if the gamma-energy is in the range above about 1 MeV up to 2.5 MeV. The optimal moderator-converter thickness can be determined experimentally. Most converter elements produce gamma-rays in the low energy range. If chlorine is used as a converter, the 1164.7 keV peak and the 1950-1960 keV peaks seems to be a good choice. A very practical material containing chlorine is PVC. It is an efficient moderator, it is solid, common, and can be handled easily.</p> </p>     

Study of hydrogen adsorption on iridium catalysts

The influence of dispersity on hydrogen adsorption on Ir black and Ir/C catalysts has been studied. It is shown that supported iridium reduces the heat of hydrogen adsorption as compared to Ir black. With decreasing catalyst dispersity, the amount of weakly bound hydrogen increases, while its adsorption heat decreases on all Ir catalysts.

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Ir- Ir/C-. , Ir-. C , Ir-.

     

The glyceride complex of the seed oil ofOnopordum acanthiium

Summary The complex mixture of glycerides of a seed oil containing oxidized aryl radicals in the triglycerides (10 groups of glycerides) has been separated for the first time. New groups of monohydroxyacyl triglycerides (oxoacyl, 0.1% of the oil, and hydroperoxyacyl, 0.1%) and di(oxyacyl)triglycerides (epoxacyl-hydroxyacyl, 0.36%) have been detected and isolated.A new -oxodienoic acid has been found for which the following structural formula is proposed as the most probable: 11-oxooctadeca-cis-9,cis-12-dienoic acid.Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 699–707, November–December, 1978. Original article submitted June 27, 1978.     

Technology for the identification of unusual cis, cis octadecadienoic fatty acids.

In this article methods are presented for the separation and identification of unusual cis, cis dienoic and polygnoic long chain fatty acids. Special emphasis has been laid on the identification of cis, cis octadecadienoic acids. The steps followed are: after transesterification the fatty acid methyl esters are separated by preparative gas chromatography according to chain length followed by argentation chromatography on thin-layer plates. After hydroxylation of the double bonds with osmium tetroxide the polyhydroxy compounds are derivatized to the per-O-trimethylsilyl-ethers. Separation and identification of individual compounds are achieved by combined gas chromatography-mass spectrometry using SCOT columns and low ionization energy.     

Über hexagonale Perowskite mit Kationenfehlstellen. XVII Strukturbestimmung an Ba9Nb6W□2O27 - der ersten Stapel-variante eines rhomboedrischen 27 L-Typs

On Hexagonal Perovskites with Cationic Vacancies. XVII. Structure Determination on Ba₉Nb₆W□₂O₂₇ – the First Stacking Polytype of a Rhombohedral 27 L-Type The hexagonal stacking polytype of rhombohedral 27 L -type, Ba₉Nb₆W□₂O₂₇, crystallizes in the space group R3 m with the sequence (4)1(3)1 ? (hhccchhcc)₃ and three formula units for the trigonal setting. The refined, intensity related, R'-value is 9.7percnt;. The octahedral net consists of blocks of three face connected octahedra which are linked to each other alternately through one or two octahedra connected exclusively by common vertices. The cationic vacancies are located in the centers of the groups of three octahedra. With this distribution direct contact between occupied face-sharing octahedra is avoided. The niobium and tungsten atoms are distributed statistically between the remaining octahedral holes. In the blocks of three octahedra they are displaced by ≈ 0.29 Å from their ideal positions in the direction of the central void. The Ba atoms neighbouring a vacancy (all in hexagonal packed BaO₃ sheets) are dislocated in the direction of the void, while the cubic packed BaO₃ sheets maintain nearly regular form.     

Crystal field parameters and crystal field linewidths in the (REY)Pd3 and (REY)Al2 alloys

The LLW-parametersx andW of dilute rare earth impurities (RE=Pr, Nd, Tb, Dy, Ho, Er, Tm;c0.05), in the cubic matrices YPd₃ and YAl₂ could be determined unequivocally in the crystal field scheme of Lea, Leask and Wolf by inelastic neutron scattering. The crystal field parameters derived fromx andW are not consistent with the point charge model. The ratio of N(E _F)J_ex for the (REY)Pd₃ and (REY)Al₂ extracted from the RE-linewidths correlates with the corresponding ratio extracted from their magnetic ordering temperatures.Supported by Sonderforschungsbereich 125, Deutsche Forschungsgemeinschaft     

Deformation dependence of magnetic moments in the odd transitional nuclei117–125Te

The magnetic moments of the 5/2 ₁ ⁺ state in¹¹⁷Te at 274.4 keV and of the 7/2 ₁ ⁺ state in¹²¹Te at 443.1 keV have been determined asμ _exp(5/2⁺)=?0.75(5)n.m. andμ _exp(7/2⁺)=+0.63(7) n.m., respectively, using the TDPAD method and the reactions^115,119Sn(α,2n)^117,121Te. An evaluation method is described which provides, in case of the normalized time differential patternR(t) exhibits less than half of an oscillation period, a unique value of the Larmor frequency. The comparison of the measured magnetic moments with Nilsson-, soft rotor Coriolis- as well as core-particle coupling calculations gives valuable hints on the shape dependence of magnetic moments and, consequently, on the deformation of different states in the odd transitional nuclei^117–125Te. In the light of the core-particle coupling model the positive parity states of¹¹⁷Te and¹²¹Te are interpreted as the members ofΔJ=1 andΔJ=2 bands built on thes _1/2,d _3/2,d _5/2 and g_7/2 single-particle states, respectively.     

Kinetic theory of adsorption and desorption

In this paper we use stochastic methods to discuss adsorption and desorption. The paper derives generalized coefficients of sticking and accomodation depending on surface temperatureT _s and gas temperatureT _g and shows, that for additive Markov processes, these kinetic coefficients are identical. Furthermore, exact solutions of the kinetic equations for certain simple transition probabilitiesP(, ) are found and an approximation method for more complicatedP(, ) is given. The comparison of the theory with experimental results for noble gas-metal systems indicate a quadratic relationship between the first moment of the transition probabilityP(, ) and the well depth of the physisorption system.     

Experimental beta-decay energies of very neutron-rich Cs isotopes

TheQ _β-values of the very neutron-rich cesium isotopes with mass number 142≤A≤146 have been measured with a plastic scintillation detector telescope at the fission product separator OSTIS. The mass excesses calculated from these decay energies agree well with the values obtained by direct mass determinations.     

General alloy analogs of itinerant magnetic systems

Magnetically disordered, strong correlated itinerant electron systems are studied within the Hubbard model. Following an alloy analogy, the approximated system hamiltonian contains local vectoral magnetic fields at the atomic sites, which can be oriented into all space directions. The statistical system of the localized magnetic moments (due to the fields) is treated by the aid of a generalized CPA-technique. Supposing a macroscopic magnetic structure of sublattice antiferromagnetism, the formation of incomplete antiferromagnetic ordering of the localized moments is examined. The results show, that the electron density plays an essential roll for the question, whether or not it is possible to go beyond the pure (itinerant) antiferromagnetic state. Including the results of earlier papers for homogeneous macroscopic magnetic structure, on the whole scale of electron densities it is summed up (at zero temperature), where the different states (without-, with incomplete- or with complete magnetic order) are able to exist. It is shown, for fixed density respectively, which different phases are passed through on changing the coupling constant.Work supported by the Deutsche Forschungsgemeinschaft