Search for a 33.9 MeV/c(2) neutral particle in pion decay

The E815 (NuTeV) neutrino experiment has performed a search for a 33. 9 MeV/c(2) weakly interacting neutral particle produced in pion decay. Such a particle may be responsible for an anomaly in the timing distribution of neutrino interactions in the KARMEN experiment. E815 has searched for this particle's decays in an instrumented decay region; no evidence for this particle was found. The search is sensitive to pion branching ratios as low as 10(-13).     

Hydrolysis of dinuclear ruthenium complexes [{CpRu(PPh3)2}2(micro,eta(1:1)-L)][CF3SO3]2 (L=P4, P4S3): simple access to metal complexes of P2H4 and PH2SH

The reaction of [CpRu(PPh(3))(2)Cl] (1) with half an equivalent of P(4) or P(4)S(3) in the presence of AgCF(3)SO(3) as chloride scavenger affords the stable dimetal complexes [{CpRu(PPh(3))(2)}(2)(micro,eta(1:1)-P(4))][CF(3)SO(3)](2).3 CH(2)Cl(2) (2) and [{CpRu(PPh(3))(2)}(2)(micro,eta(1:1)-P(apical)-P(basal)-P(4)S(3))][CF(3)SO(3)](2).0.5 C(7)H(8) (3), in which the tetrahedral P(4) and mixed-cage P(4)S(3) molecules are respectively bound to two CpRu(PPh(3))(2) fragments through two phosphorus atoms. The coordinated cage molecules, at variance with the free ligands, readily react with an excess of water in THF under mild conditions. Among the hydrolysis products, the new, remarkably stable complexes [{CpRu(PPh(3))(2)}(2)(micro,eta(1:1)-P(2)H(4))][CF(3)SO(3)](2) (4) and [CpRu(PPh(3))(2)(eta(1)-PH(2)SH)]CF(3)SO(3) (8) were isolated. In the former, diphosphane, P(2)H(4), is coordinated to two CpRu(PPh(3))(2) fragments, and in the latter thiophosphinous acid, H(2)PSH, is coordinated to the metal centre through the phosphorus atom. All compounds were characterised by elemental analyses and IR and NMR spectroscopy. The crystal structures of 2, 3, 4 and 8 were determined by X-ray diffraction.     

d- and l-amino acids in Antarctic lakes: assessment of a very sensitive HPLC-MS method

Amino acids represent a fraction of organic matter in marine and freshwater ecosystems, and a source of carbon, nitrogen and energy. l-Amino acids are the most common enantiomers in nature because these chiral forms are used during the biosynthesis of proteins and peptide. To the contrary, the occurrence of d-amino acids is usually linked to the presence of bacteria. We investigated the distribution of l- and d-amino acids in the lacustrine environment of Terra Nova Bay, Antarctica, in order to define their natural composition in this area and to individuate a possible relationship with primary production. A simultaneous chromatographic separation of 40 l- and d-amino acids was performed using a chiral stationary phase based on teicoplainin aglycone (chirobiotic tag). The chromatographic separation was coupled to two different mass spectrometers—an LTQ-Orbitrap XL (Thermo Fisher Scientific) and an API 4000 (ABSciex)—in order to investigate their quantitative performance. High-performance liquid chromatography coupled with mass spectrometry methods were evaluated through the estimation of their linear ranges, repeatability, accuracy and detection and quantification limits. The high-resolution mass spectrometer LTQ-Orbitrap XL presented detection limits between 0.4 and 7 μg?l ^?1, while the triple quadrupole mass spectrometer API 4000 achieved the best detection limits reported in the literature for the quantification of amino acids (between 4 and 200 ng?l ^?1). The most sensitive method, HPLC-API 4000, was applied to lake water samples. Figure

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Iodine Activation of Coordinated White Phosphorus: Formation and Transformation of 1,3-Dihydride-2-iodidecyclotetraphosphane

Double stabilization: Previously unknown polyphosphorus compounds are obtained by activation of white phosphorus (P(4) ) coordinated between two CpRu(PPh(3) )(2) moieties with iodine, and subsequent hydrolysis. The polyphosphorus compounds (P(4) H(2) I, P(4) H(2) , P(3) H(5) ; see scheme, Cp=cyclopentadienyl) are all stabilized by coordination to two ruthenium centers.     

Hydrogenation of arenes over silica-supported catalysts that combine a grafted rhodium complex and palladium nanoparticles: evidence for substrate activation on Rh(single-site)-Pd(metal) moieties

The complex Rh(cod)(sulfos) (Rh(I); sulfos = (-)O(3)S(C(6)H(4))CH(2)C(CH(2)PPh(2))(3); cod = cycloocta-1,5-diene), either free or supported on silica, does not catalyze the hydrogenation of benzene in either homogeneous or heterogeneous phase. However, when silica contains supported Pd metal nanoparticles (Pd(0)/SiO(2)), a hybrid catalyst (Rh(I)-Pd(0)/SiO(2)) is formed that hydrogenates benzene 4 times faster than does Pd(0)/SiO(2) alone. EXAFS and DRIFT measurements of in situ and ex situ prepared samples, batch catalytic reactions under different conditions, deuterium labeling experiments, and model organometallic studies, taken together, have shown that the rhodium single sites and the palladium nanoparticles cooperate with each other in promoting the hydrogenation of benzene through the formation of a unique entity throughout the catalytic cycle. Besides decreasing the extent of cyclohexa-1,3-diene disproportionation at palladium, the combined action of the two metals activates the arene so as to allow the rhodium sites to enter the catalytic cycle and speed up the overall hydrogenation process by rapidly reducing benzene to cyclohexa-1,3-diene.