Radionuclide mapping of the Molise region (Central Italy) via gamma-ray spectrometry of soil samples: relationship with geological and pedological parameters

Radionuclide maps of the Molise region were created for the first time using gamma-ray spectrometry analysis of 205 soil samples. The geographical distributions of ⁴⁰K, ²³²Th and ²³⁸U were within the world average values for soils. ⁴⁰K was distributed homogeneously with a slight enhancement along the coastline. The decay chains of ²³⁸U and ²³²Th were in secular equilibrium with their daughters, also showing a homogeneous distribution except for localized areas of enhanced concentrations close to the borders with the Lazio and the Campania regions. Concentrations of all three radionuclides were correlated with geological and pedological characteristics of soils. The measured external gamma-dose rate in the air due to naturally occurring radionuclides in the soil, and the dose rate due to cosmic rays were in agreement with values measured in other Mediterranean regions. Increased ¹³⁷Cs levels from atmospheric nuclear weapons tests and the Chernobyl fallout were found at sites above 1,000 m a.s.l.     

Horizontal and vertical distributions of Biogenic and Anthropogenic Organic compounds in the Ross Sea (Antarctica)

Horizontal and vertical distributions of organic compounds extractable with n-hexane were investigated at five sampling stations (Ross Sea) during the Italian Antarctic Expedition 1997/98. Samples were collected from seven depths under pack ice and from two or three depths at the other stations located at different distances from the coast. The lowest concentrations of biogenic and anthropogenic compounds were found at station Y3, the furthest from the coast, while the highest concentrations were observed under pack ice (B2-2 station) or in the Polynya zone (Y1 station). The levels of organic compounds in the particulate phase were higher than those in the dissolved phase for all the investigated samples. Concentrations of biogenic organic compounds (long-chain aldehydes and alcohols, fatty acid esters and n-alkanes) were well related to fluorescence intensity, which is usually reported as a biological activity index. The odd-to-even carbon-number ratio for n-alkanes was lower than 1 at stations B2-2, Y1, Y5 and Y6 (located less than 150?km far from the coast) with the predominance of n-C16, n-C24 and n-C28, indicative of autochthonous pelagic species. An odd-to-even ratio higher than unity and a different n-alkane profile were observed at station Y3 (about 300?km from the Ross Ice Shelf and 600?km from Terra Nova Bay). Low levels of pollutants (i.e. phthalates) were found, mainly in the particulate phase up to a depth of 50?m, confirming a local source of the phthalates found at significant concentrations during previous expeditions.     

Experimental and theoretical differential cross sections for the N(2D) + H2 reaction

In this paper, we report a combined experimental and theoretical study on the dynamics of the N(2D) + H2 insertion reaction at a collision energy of 15.9 kJ mol(-1). Product angular and velocity distributions have been obtained in crossed beam experiments and simulated by using the results of quantum mechanical (QM) scattering calculations on the accurate ab initio potential energy surface (PES) of Pederson et al. (J. Chem. Phys. 1999, 110, 9091). Since the QM calculations indicate that there is a significant coupling between the product angular and translational energy distributions, such a coupling has been explicitly included in the simulation of the experimental results. The very good agreement between experiment and QM calculations sustains the accuracy of the NH2 ab initio ground state PES. We also take the opportunity to compare the accurate QM differential cross sections with those obtained by two approximate methods, namely, the widely used quasiclassical trajectory calculations and a rigorous statistical method based on the coupled-channel theory.     

Dynamics of the O(3P) + C2H4 reaction: identification of five primary product channels (vinoxy, acetyl, methyl, methylene, and ketene) and branching ratios by the crossed molecular beam technique with soft electron ionization

The crossed molecular beam scattering technique with soft electron ionization (EI) is used to disentangle the complex dynamics of the polyatomic O(3P) + C2H4 reaction, which is of great relevance in combustion and atmospheric chemistry. Exploiting the newly developed capability of attaining universal product detection by using soft EI, at a collision energy of 54.0 kJ mol(-1), five different primary products have been identified, which correspond to the five exoergic competing channels leading to CH2CHO(vinoxy) + H, CH3CO(acetyl) + H, CH3(methyl) + HCO(formyl), CH2(methylene) + HCHO(formaldehyde), and CH2CO(ketene) + H2. From laboratory product angular and velocity distributions, center-of-mass product angular and translational energy distributions and the relative branching ratios for each channel have been obtained, affording an unprecedented characterization of this important reaction.     

Structure of dipotassium 5,6-dihydrouracil-6,6-disulfonate monohydrate

The title compound was synthesized and its crystal structure determined by single crystal X-ray diffraction techniques. It crystallizes in the monoclinic system witha=9.390(1),b=9.688(2),c=13.828(3)Å,=110.16(2)°, space groupP2₁/c,Z=4. The structure was solved by direct methods and refined by full-matrix least-squares calculations toR=0.032 for 1968 reflections withI>3(I) [MoK radiation]. The six-membered ring of the 5,6-dihydrouracil-6,6-disulfonate dianion displays an approximate skew-boat conformation, but the ring puckering differs from that commonly observed in 5,6-dihydrouracil derivatives. The coordination to two crystallographically independent K⁺ ions which exhibit different coordination geometries links anions, cations and water molecules in an infinite three-dimensional network.     

Soft electron impact ionization in crossed molecular beam reactive scattering: the dynamics of the O((3)P)+C(2)H(2) reaction

Soft ionization by low-energy, tunable electrons is implemented for the first time in crossed molecular beam reactive scattering experiments with mass-spectrometric detection. The power of the method, which permits the suppression of the dissociative ionization of interfering species, is exemplified with the study of the O((3)P)+C(2)H(2) multichannel reaction.     

Separation,structural determination and biological evaluation of the thymidylate synthase inhibitor 3,3-Di-(4′-hydroxyphenyl)-6(7)-chloro-1-oxo-1H,3H-naphtho[1,8-cd]pyran

The chloro substituted 3,3-di-(4′-hydroxyphenyl)-1-oxo-1H,3H-naphtho[1,8-cd]pyran was synthesized in a 40/60 mixture of C₆ or C₇ substituted isomers, respectively. The two isomers were separated by hplc. The X-ray crystal structure of the mixture was obtained. Both the mixture and the single isomers were tested against Lactobacillus Casei thymidylate synthase. The X-ray analysis clearly revealed co-crystallization of the two isomeric species. The apparent Ki of the mixture was 0.8 muM, while those of the C₆ and C₇ substituted isomers were 0.42 and 0.52 muM, respectively, thus showing that the position of the chlorine in the naphthalene ring was not critical for enzymatic activity.     

O(3P)+1，2-丁二烯反应的交叉分子束和理论研究：丙烯+CO和亚乙基+乙烯酮反应的主要分子通道

详细了解O(~3P)与不饱和烃的多通道燃烧反应机理需要鉴定所有主要反应产物、确定分支比、评估三重态与单重态势能面之间的系间窜跃.将交叉分子束实验、软电离、质谱、飞行时间分析,以及高级从头算计算三重态/单线态势能面,RRKM/Master方程计算支化比包括系间窜跃,均可以获得最佳效果.最近已经证明这些方法对于含有两个或三个碳原子的最简单的不饱和烃(炔烃,烯烃,二烯)和O(~3P)反应是成功的.本文通过交叉分子束与理论相结合的方法研究O(~3P)和含有四个C原子的二烯类化合物,1,2-丁二烯(甲基芳烃)的反应,探索产物分布、分支比和系间窜跃如何随着分子复杂性的增加而变化,即从O(~3P)和丙二烯反应到O(~3P)1,2-丁二烯的反应变化.尤其关注了最重要的导致链终止的主导分子通道(即形成丙烯+CO(分支≥0.5)和亚乙基+乙烯酮(分支比≥0.15))与导致链传递的自由基形成通道进行对比(分支比≥0.35).