Chemical composition of clay minerals from ODP Leg 168 sites

The exchangeable cation compositions of organic-poor terrigenous sediments containing smectite as primary ion exchanger from a series of holes along ODP Leg 168 transect on the eastern flank of the Juan de Fuca Ridge have been examined as a function of distance from the ridge axis and burial depth. The total cation exchange capacity (CEC) values of the sediments ranged from 2 to 59 meq/100 g, increasing with increases in the wt.% smectite. At the seafloor, the exchangeable cation compositions involving Na, K, Mg, and Ca, expressed in terms of equivalent fraction, are nearly constant regardless of the different transect sites: XNa = 0.21 ± 0.04, XK = 0.08 ± 0.01, XMg = 0.33 ± 0.09, and XCa = 0.38 ± 0.09. The calculated selectivity coefficients of the corresponding quaternary exchange reactions, calculated using porewater data, are in log units -5.45 ± 0.39 for Na, 1.97 ± 0.49 for K, 0.42 ± 0.41 for Mg, and 3.06 ± 0.69 for Ca. The exchangeable cation compositions below the seafloor change systematically with distance from the ridge crest and burial depth, conforming to the trends of the same cations in the porewaters. The selectivities for Na and Mg are roughly constant at temperatures from 2 to 66°C, indicating that the equivalent fractions of these two cations are independent of sediment alteration taking place on the ridge flank. Unlike Na and Mg, the temperature influence is significant for K and Ca, with Ca-selectivity decreases being coupled with increases in K-selectivity. Although potentially related to diagenetic and/or hydrothermal mineral precipitation or recrystallization, no evidence of such alteration was detected by XRD and TEM. In sites where upwelling of hydrothermal fluids from basement is occurring, the K-selectivity of the sediment is appreciably higher than at the other sites and corresponds to the formation of (Fe, Mg) rich smectite and zeolites. Our study indicates that local increases in K-selectivity at hydrothermal sites are caused by the formation of these authigenic minerals.

Chemistry and age determination of basement fluids from Juan de Fuca Ridge

The geochemical implications of thermally driven flow of seawater through oceanic crust on the mid-ocean ridge flank have been examined on a well-studied 80 km transect across the eastern flank of the Juan de Fuca Ridge at 48°N, using porewater and basement fluid samples obtained on ODP Leg 168. Fluid flow is recognised by near-basement reversals in porewater concentration gradients from altered values in the sediment section to seawater-like values in basaltic basement. In general, the basement fluids become more geochemically evolved with distance from the ridge and broadly follow basement temperature which ranges from not, vert, similar16° to 63°C. Although thermal effects of advective heat exchange are only seen within 20 km east of where basement is exposed near the ridge crest, chemical reactivity extends to all sites. Seawater passing through oceanic crust has reacted with basement rocks leading to increases in Ca2+ and decreases in alkalinity, Mg2+, Na+, K+, SO42- and delta18O. Sr isotope exchange between seawater and oceanic crust off axis is unequivocally demonstrated with endmember 87Sr/86Sr ~ 0.707. Evidence of more evolved fluids is seen at sites where rapid upwelling of fluids through sediments occurs. Chlorinities of the basement fluids are consistent with post-glacial seawater and thus a short residence time in the crust. Rates of lateral flow have been by estimated by modelling porewater sulphate gradients, using Cl as a glacial chronometer, and from radiocarbon dating of basal fluids. All three methods reveal fluid flow with 14C ages less than 10,000 yr and particle velocities of ~1-5 m/yr, in agreement with thermally constrained volumetric flow rates through a ~600 m thick permeable layer of ~10% porosity. Delta(element)/Delta(heat) extraction ratios are similar to values for ridge-crest hydrothermal systems.

Ordinary and duplicate analysis from major and trace elements of ODP Holes 146-888B and 168-1027B

Oceanic sediments deposited at high rate close to continents are dominated by terrigenous material. Aside from dilution by biogenic components, their chemical compositions reflect those of nearby continental masses. This study focuses on oceanic sediments coming from the juvenile Canadian Cordillera and highlights systematic differences between detritus deriving from juvenile crust and detritus from old and mature crust. We report major and trace element concentrations for 68 sediments from the northernmost part of the Cascade forearc, drilled at ODP Sites 888 and 1027. The calculated weighted averages for each site can then be used in the future to quantify the contribution of subducted sediments to Cascades volcanism. The two sites have similar compositions but Site 888, located closer to the continent, has higher sandy turbidite contents and displays higher bulk SiO2/Al2O3 with lower bulk Nb/Zr, attributed to the presence of zircons in the coarse sands. Comparison with published data for other oceanic sedimentary piles demonstrates the existence of systematic differences between modern sediments deriving from juvenile terranes (juvenile sediments) and modern sediments derived from mature continental areas (cratonic sediments). The most striking systematic difference is for Th/Nb, Th/U, Nb/U and Th/Rb ratios: juvenile sediments have much lower ratios than cratonic sediments. The small enrichment of Th over Nb in cratonic sediments may be explained by intracrustal magmatic and metamorphic differentiation processes. In contrast, their elevated Th/U and Nb/U ratios (average values of 6.87 and 7.95, respectively) in comparison to juvenile sediments (Th/U ~ 3.09, Nb/U ~ 5.15) suggest extensive U and Rb losses on old cratons. Uranium and Rb losses are attributed to long-term leaching by rain and river water during exposure of the continental crust at the surface. Over geological times, the weathering effects create a slow but systematic increase of Th/U with exposure time.

Sapientia, 1988, Vol. XLIII, nº 167-168 (número completo)

Contenido: El tema de la libertad en Santo Tomás : fuentes y desarrollo / Gustavo E. Ponferrada – Emergencia y sentido del hombre en la reflexión ética de la Suma contra Gentiles / Julio R. Méndez – Azar y contingencia / Juan J. Sanguineti – Indeterminismo y racionalidad : en torno al problema de la causalidad en física / Ramón Queraltó – La tridimensionalidad crítica de la reflexión completa / Stanislavs Ladusans – Humanismo y humanismos / Iulio Brandao – Limitación de la antropología filosófica / José M. de Estrada – Afectividad, obrar humano, moralidad / María C. Donadío de Gandolfi – Naturaleza y ética en Hobbes y Tomás de Aquino / María L. Lukac de Stier – Derecho, pensamiento y lenguaje / Carlos I. Massini-Correas – Derecho natural y positivismo jurídico / Ylves J. de Miranda Guimaraes – La verdad política es el ideal de una sociedad participativa / José P. Galvao de Sousa – Hombre y moral : la “pietas” patriótica / Héctor H. Hernández – Filosofía, teología y cultura cristiana en el pensamiento de San Agustín / Battista Mondin – Amor Ruibal, genial renovador de la filosofía cristiana / Emilio Silva de Castro – La problemática filosófica de las ciencias humanas / Edgardo J. Castro

Diário da Constituinte [gravação de vídeo] : [programa n. 168]

A Mesa da Assembleia Nacional Constituinte (ANC) alerta o governo sobre a necessidade de responder os pedidos de informação dos parlamentares sobre atos administrativos. O Deputado Amaury Muller (PDT-RS) cobra do governo a resposta ao pedido de informação que fez há cinco meses. José Reinaldo Tavares, Ministro dos Transportes, explica a demora na resposta aos pedidos de informação. Parlamentares afirmam que o silêncio do Poder Executivo pode atrapalhar os trabalhos da Constituinte. O Deputado Nelton Friedrich (PMDB-PR) declara que, num momento em que se desejam mudanças profundas e a volta das prerrogativas do Poder Legislativo, não é possível que o Executivo continue se comportando como no período autoritário. O Deputado Ruy Nedel (PMDB-RS) afirma que os membros da Constituinte precisam de dados do governo para que possam ter mais base de sustentação nos seus argumentos em matéria constitucional. Em Plenário, constituintes discutem o sistema de governo. O Deputado Bonifácio de Andrada (PDS-MG) é a favor do parlamentarismo por ser o sistema do diálogo e da responsabilidade política, enquanto que o presidencialismo é o regime do monólogo e da irresponsabilidade política. Para o Deputado Vivaldo Barbosa (PDT-RJ) a melhor forma no Brasil de hoje é o presidencialismo, no sentido de buscar a democracia e uma sociedade mais justa. Na sessão O Povo Pergunta, cidadã quer saber o que está sendo feito para acabar com a dívida externa. O Deputado Raimundo Bezerra (PMDB-CE) responde que está sendo feita uma auditoria da dívida externa do Brasil.

On new or insufficiently-known Chytridinae [Translation from: Archiv fur Protistenkunde 54 168-173 + pl.9, 1926]

This partial translation of a larger paper provides taxonomic descriptions of 5 fungal zoospores species: Olpidium vampyrellae, 0. pseudosporearum, 0. leptophrydis, Rhizophidium leptophrydis and Chytridium lateoperculatum.

双奇核~(168)Ta高自旋态能级结构

用能量为140MeV的27Al束流轰击145Nd氧化靶,通过145Nd(27Al,4nγ)168Ta熔合蒸发反应对双奇核168Ta的高自旋态进行了实验研究.扩展了基于πh11/2νi13/2和π5/2+[402]ν5/2+[642]准粒子组态下的转动带能级纲图.根据实验测量结果,对两转动带的准粒子顺排特征作了分析.通过B(M1)/B(E2)的理论与实验值比较以及168Ta相邻双奇核能级间隔系统性,进一步确定了两转动带的准粒子组态和能级的自旋宇称.

Model 1027连续测氡仪测量室内氡浓度若干问题的探讨

本文探讨Model 1027 连续测氡仪测量室内氡浓度的方法。用两台仪器对一房间内氡浓度在不同情况下进行近一个月的测量后,得出以下结论:仪器操作简便,测量结果稳定;仪器处于DISABLE(数字显示关闭) 状态所测氡浓度高于ENABLE(数字显示开启) 状态测量氡浓度;测量结果表达方式有两类,即氡浓度总平均值和美国环保局推荐平均值,多点比较测量应采用同一类氡浓度;仪器连续测量时间不得少于24h ,最好为48h 或更长;本次所测房间氡浓度平均值为9215 Bq/ m3 ,符合国家标准。

C 168 INST-D 2013. 349 Escenas clásicas del procesos del tejido y secado de la paja toquilla en Sandoná (Sandoná, Nariño)

10 fotografías, nueve a color.

Robert Morin, « Les Pensées philosophiques de Diderot devant leurs principaux contradicteurs au XVIIIe siècle » (Paris 1975), 168 p.

info:eu-repo/semantics/published