Pb isotopes in Cenozoic sediments of ODP Site 177-1090

Nd and Pb isotopic compositions extracted from bulk deep sea sediments have been shown to be robust proxies for deep water circulation as well as weathering provenance and intensity over geologically young time scales. In this study we evaluated ten deep sea samples from Ocean Drilling Program (ODP) site 1090 ranging in age from mid Eocene to early-Miocene to test whether Pb isotopic compositions extracted from geologically older sediments record reliable seawater isotopic ratios and to evaluate the source of the extracted Pb. The sequential extraction protocol used in this study is similar to protocols reported for previous studies and produces acetic acid, hydroxylamine hydrochloride (HH) and residue fractions. Each extracted fraction was analyzed for Pb isotopes, rare earth elements (REEs), and a suite of major elements. Similar 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios are recorded from the acetic acid and HH fractions for ~70-80% of the samples, suggesting that either the acetic acid dissolves Fe-Mn oxides or multiple phases are recording the same seawater isotopic value. Several indirect tests, such as Al mass balance, comparison of Sr isotopes in HH extracts to contemporaneous seawater Sr isotopes, and comparison of Nd isotopic compositions in HH extracts to published fossil fish teeth values, provide evidence that Pb isotopic compositions measured in our bulk HH extracts record bottom water values. The relationship between Pb, Mn and Ca concentrations in HH fractions indicates that Fe-Mn oxides and a Mn-bearing carbonate are the dominant phases contributing seawater Pb. Comparison of REE patterns derived from the HH fraction and total digestions of Fe-Mn nodule standards reveals that the trivalent REEs exhibit patterns consistent with the parent archive, but Ce can be fractionated during extraction. Ratios of REEs also produce unique fields for each fraction and can be used to test the purity of the seawater signal of the extraction protocol. Finally, an initial evaluation of Pb isotopic compositions in fossil fish indicates that this archive is not suitable for bottom water Pb isotope studies.

Sapientia, 1992, Vol. XLVII, nº 183 (número completo)

Contenido: La persona y su mundo : la cultura, la moral, el derecho y la sociedad familiar y política (I) / Octavio Nicolás Derisi – Ciencia y filosofía en el tomismo / Gustavo E. Ponferrada – Conocimiento y concepto / Víctor Velarde Mayol – Spinoza : presencia de la tradición en la modernidad / Augusto Furlán – Notas y comentarios -- Bibliografía

Nuclear hyperfine interactions in W^(182), W^(183), and Pt^(195) as studies by the Mossbauer effect

The Mössbauer technique has been used to study the nuclear hyperfine interactions and lifetimes in W¹⁸² (2⁺ state) and W¹⁸³ (3/2^- and 5/2^- states) with the following results: g(5/2^-)/g(2⁺) = 1.40 ± 0.04; g(3/2^- = -0.07 ± 0.07; Q(5/2^-)/Q(2⁺) = 0.94 ± 0.04; T_1/2(3/2^-) = 0.184 ± 0.005 nsec; T_1/2(5/2^-) >̰ 0.7 nsec. These quantities are discussed in terms of a rotation-particle interaction in W¹⁸³ due to Coriolis coupling. From the measured quantities and additional information on γ-ray transition intensities magnetic single-particle matrix elements are derived. It is inferred from these that the two effective g-factors, resulting from the Nilsson-model calculation of the single-particle matrix elements for the spin operators ŝ_z and ŝ₊, are not equal, consistent with a proposal of Bochnacki and Ogaza.

The internal magnetic fields at the tungsten nucleus were determined for substitutional solid solutions of tungsten in iron, cobalt, and nickel. With g(2⁺) = 0.24 the results are: |H_eff(W-Fe)| = 715 ± 10 kG; |H_eff(W-Co)| = 360 ± 10 kG; |H_eff(W-Ni)| = 90 ± 25 kG. The electric field gradients at the tungsten nucleus were determined for WS₂ and WO₃. With Q(2⁺) = -1.81b the results are: for WS₂, eq = -(1.86 ± 0.05) 10¹⁸ V/cm²; for WO₃, eq = (1.54 ± 0.04) 10¹⁸ V/cm² and ƞ = 0.63 ± 0.02.

The 5/2^- state of Pt¹⁹⁵ has also been studied with the Mössbauer technique, and the g-factor of this state has been determined to be -0.41 ± 0.03. The following magnetic fields at the Pt nucleus were found: in an Fe lattice, 1.19 ± 0.04 MG; in a Co lattice, 0.86 ± 0.03 MG; and in a Ni lattice, 0.36 ± 0.04 MG. Isomeric shifts have been detected in a number of compounds and alloys and have been interpreted to imply that the mean square radius of the Pt¹⁹⁵ nucleus in the first-excited state is smaller than in the ground state.

~(183)Au核高自旋态转动带结构研究

通过重离子熔合蒸发反应和在束核谱学实验方法研究了奇A核183Au的高自旋态能级结构.扩展并更新了183Au的能级纲图.首次建立了183Au的πi13/2转动带的能量非优先带.分析并讨论了183Au中πh9/2转动带的能量非优先带和πf7/2转动带间的相互作用.

W-183 NMR characterization of rare earth heteropolymetalates in aqueous solution

W-183 NMR spectra were obtained for [La(AsW11O39)(2)](11-), [La(As2W17O61)(2)](17-), [La(SiW9Mo2O39)(2)](13-), [LaSb9W21O86](16-), [LaAs4W40O140](25-) and alpha-, beta-[(CeO)(3) . (SiW9O34)(2)](14-) complexes, Tungsten NMR studies showed that the C-s symmetry of the square antiprism for [La(ASW(11)O(39))(2)](11-) and [La(As2W17O61)(2)](17-) anions keep constant in aqueous solution; the lanthanide accupied the central S-1 site in [LnSb(9)W(21)O(86)](16-) and [LnAs(4)W(40)O(140)](25-) complexes, respectively, and lanthanide metal cations gave [(CeO)(3) . (SiW9O34)(3)](14-) type of complexes with SiW9O3410-.

稀土杂多化合物在溶液中的￣（183）W核磁共振表征

~（１８３）Ｗ核磁共振研究确认，Ｌａ（ＡｓＷ_（１１））_２、Ｌａｍ（Ａｓ_２Ｗ_（１７））_２在溶液中仍保持其四方反棱柱的Ｃ_３结构，Ｌａ（ＳｉＷ_９ＭＯ_２）_２阴离子中，２个Ｍｏ原子取代了２个等价的Ｗ原子，在穴状杂多阴离子ＬｎＡｓ_４Ｗ_（１０）和ＬｎＳｂ_９Ｗ_（２１）中，稀土离子占据中心Ｓ_１位置，ＳｉＷ_９与稀土离子生成（ＬｎＯ）_３（ＳｉＷ_９）_２型杂多阴离子。

Dawson结构钨铌磷杂多配合物~（183）WNMR谱的研究

Ｄａｗｓｏｎ结构钨铌磷杂多配合物~（１８３）ＷＮＭＲ谱的研究龚剑，瞿伦玉，陈亚光，李宝利（东北师范大学化学系，长春１３００２４）张建国（中国科学院长春应用化学研究所，长春１３００２２）关键词：Ｄａｗｓｏｎ结构杂多配合物，钨铌磷杂多配合物，~（１８３）Ｗ...

Dawson结构杂多阴离子~（183）W NMR谱的研究──“极位”W原子~（183）W NMR谱化学位移值的预测

本文研究了Ｄａｗｓｏｎ结构取代原子数与相应的１８３ＷＮＭＲ谱中“极位’Ｗ原子的化学位移值间的关系，预测广α－１，２－［Ｐ２Ｗ１６Ｎｂ２Ｏ６２］８－α－１－２，３－［Ｐ２Ｗ１５ＭｏＮｂ２Ｏ６２］８－“极位”Ｗ原子１８３ＷＮＭＲ谱化学位移们，结果α－１，２－［Ｐ２Ｗ１６Ｎｂ２Ｏ６２］８－中与取代Ｎｂ相连“极位”Ｗ原子的化学位移值为－８８ｐｐｍ，与取代Ｎｂ书对称“极位”Ｗ原了的化学位移值为－１４４．７ｐｐｍ，与取代Ｎｂ不对称“极位”Ｗ原子的化学位移值为－１３０．５ｐｐｍ，α－１－２，３－［Ｐ２Ｗ１５ＭｏＮｂ２Ｏ６２］８－中与取代Ｍｏ对称“极位”Ｗ原子的化学位移值为－１３４．７ｐｐｍ，与取代Ｎｂ对称“极位”Ｗ原子的化学位移值为－１４５．６ｐｐｍ．

Dawson结构钨铌磷杂多配合物~(183)W NMR谱的研究

过渡金属离子取代的杂多钨酸盐,具有金属叶啉的类似结构,在烯烃环氧化反应中具有比金属叶啉更优异的催化活性和选择性,特别重要的是其抗氧化性能强,在烯烃基质存在下比金属叶啉稳定,催化寿命持久,并称其为无机金属叶啉,因而引起人们的极大关注.

C 183 INST-D 2013. 364 Ilustración de procesos de elaboración de telas y hamacas en telares horizontales y verticales.

32 fotografías, treinta y una a color.

Annotation of Case C-183/91, Commission v Hellenic Republic, ECR 1993 I-3131

State aid - Tax exemption on earnings from exports - Recovery