Selective alkyne hydrogenation in the presence of carbon-carbon double bond compounds, for which Pd is an excellent catalyst, is a strategically important large-scale industrial process. Although in palladium, functionality and structure are closely interrelated, knowledge of the structure of Pd is insufficient as the interaction with the chemical environment causes drastic compositional changes near the subsurface region: while unselective hydrogenation proceeds in the presence of a β-hydride phase, selective hydrogenation can be achieved only in the presence of a near-surface Pd-C phase. Here, we show from a combination of in situ prompt gamma activation analysis and ab initio simulations based on density functional theory that (i) the presence of the Pd-C phase created under selective conditions implies a strong change in the surface and subsurface stability of hydrogen, (ii) there is still a slower exchange of bulk and surface hydrogen, and (iii) the reaction rate for selective hydrogenation is independent of the bulk H/Pd ratio

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In this paper we present results from the first high-precision prompt-γ-ray spectral measurements from the reaction 241 Pu(n th , f). Apart from one recent experiment, no data are reported in the literature for this fissioning system, which motivated a new dedicated experiment. We have measured prompt-fission γ rays with three cerium-doped LaBr 3 (two 5.08 cm × 5.08 cm and one 7.62 cm × 7.62 cm) and one CeBr 3 (5.08 cm × 5.08 cm) scintillation detectors, which all exhibit excellent timing and good energy resolution. The average γ-ray multiplicity was determined to be ν γ = (8.21 ± 0.09) per fission, the average energy to be γ = (0.78 ± 0.01) MeV, and the total energy to be E γ,tot = (6.41 ± 0.06) MeV as the weighted average from all detectors. Since the results from all detectors are in excellent agreement, and the total released γ energy is modestly higher than the one in the present evaluated nuclear data files, we suspect that the underestimation of the prompt-γ heating in nuclear reactors is due to fast-neutron-induced fission on 238 U or rather from fission induced by γ rays from neutron capture in the construction material.

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in 50 ml Aceton wurden mit 0,3 ml 3~ Salzsaure 4 Std. untcr Ruckfluss gekocht. Das Losungsmittel wurde im Vakuum weitgehend abgedampft. Nach Zusatz von Natriumhydrogencarbonat extrahierte man mit Chloroform. Der Chloroformauszug wurde ahgedampft und der Ruckstand mit Chloroform/Methanol = 5/1 dunnschichtchromatographisch gereinigt. Ausheute : 10 mg, die nicht kristallisierten, aher sich in allen anderen untersuchten Eigenschaften als identisch mit der in Versuch 13.1. beschriebenen Base erwiesen (UV.-, 1R.-, Massenspektrum, CR. und Rf-Werte; 1R.-Spektrum (CHC1,) : 3367, 1675, 1610). LITERATURVERZEICHNIS [l] H .Summary. The structure of panepoxydone (1) and some related products, produced by two species of Panus (basidiomycetes), are proposed on the basis of chemical transformations and physical measurements.The absolute configurations of the main products are deduced b y the interpretation of CD.studies and compared with those of the structurally related compounds epoxydone (lo), terreic acid (11) and terremutin (12).Die Gattung P a w s gehort zur Klasse der Basidiomyceten, Familie Agaricaleae, Unterfamilie Leukosporae. Unseres Wissens sind bisher keine antibiotisch oder cytostatisch wirksamen Metaboliten bei dieser Gattung gefunden worden.