Comparisons of z values between fine-grained titanomagnetites within interstitial glass and large-grained titanomaghemtes in older ocean-floor basalts

Transmission electron microscopy observations and rock magnetic measurements reveal that alteration of fine- and large-grained iron-titanium oxides can occur at different rates. Fine-grained titanomagnetite occurs as a crystallization product within interstitial glass that originated as an immiscible liquid within a fully differentiated melt; in several samples with ages to 32 Ma it displays very little or no oxidation (z = ca. 0). In contrast, samples with ages of 10 Ma or older are observed to also contain highly oxidized (z >/= 0.66) large-grained titanomaghemite. These large grains, having originated by direct crystallization from melt, are associated with pore space. Such pore space can serve as a conduit for fluids that promote alteration, whereas fine grains may have been "armored" against alteration by the glass matrix in which they are embedded. Apparently, alteration of oceanic crust is a heterogeneous process on a microscopic scale. The existence of pristine, fine-grained titanomagnetite in the interstitial glass of older ocean-floor basalts that have undergone significant alteration implies that such glassy material is capable of carrying original thermal remanent magnetization and may be suitable for paleointensity determinations.

14C ages of core top samples from Ontong-Java Plateau

Radiocarbon measurements on core tops from the Ontong-Java plateau confirm a previous finding by Berger and Killingley [1982] that at any given water depth, cores taken on the equator have higher accumulation rates and younger core top ages than their off-equator counterparts. Further, these new results fortify the conclusion by Broecker et al. [1991] that the increase in core top radiocarbon age with water depth rules out homogeneous dissolution within the pore waters as the dominant mechanism. Either most of the dissolution must occur prior to burial or it must occur during the first pass through the respiration-CO2-rich upper pore waters after which the calcite grains become armored against further dissolution. A puzzling aspect of this new data set is that despite the sizable difference in accumulation rate, the extent of dissolution as measured by either the CaCO3 content or the ratio of CaCO3 in the >150-µm size fraction to that in the < 63-µm fraction is no different off than on the equator. In order to reconcile the results of this study with those obtained by Hales and Emerson [1996] using in situ electrodes, it is necessary to call upon calcite armoring.

(Table 1) Typical trace-fossil occurrences in DSDP Holes 56-436 and 56-435A

Trace fossils are in places abundant in cores from DSDP Leg 56 sites. They are particularly rich in the pelagic-clay sequence at Site 436. Some significant trace fossils, including Zoophycos, Teichichnus, Chondrites, rind and solid burrows, and pellet-armored rods, are described. The ichnofauna, except for pellet-armored rods in diatomaceous mudstone of the landward trench slope, is characterized by cosmopolitan bathyal to abyssal forms.

Reengenharia de sistemas na recuperação e modernização de produtos: proposta de um modelo baseado em risco.

Produtos com um tempo considerável de utilização podem ser objeto de um processo de manutenção mais amplo e profundo, que visa prolongar a sua vida útil. O termo recuperação é aplicado a este tipo de manutenção, que visa à substituição de peças defeituosas, desgastadas, e/ou com a vida útil encerrada. O surgimento de novos paradigmas e de um novo conjunto de doutrinas operacionais pode mudar as expectativas e necessidades das partes interessadas de modo que o produto pode ser proposto para uma modernização. Assim, o produto pode ser reengenheirado durante a sua recuperação. Para realizar um projeto de recuperação e modernização, propõe-se uma abordagem em seis passos centrada numa decisão baseada no risco para classificar os componentes de acordo com a ação a ser realizada. A análise do produto é desenvolvida com base em técnicas de desmontagem e uma análise da fase operacional é realizada para as tomadas de decisões. Deste modo, um componente pode sofrer manutenção, ser modernizado, ser excluído, ser inserido ou permanecer fora do escopo dos trabalhos. O processo da gestão baseada em risco também inclui duas fases de monitoramento de risco continuado: durante a produção e na fase de operação. As decisões podem ser revistas pelo uso da análise bayesiana. Um estudo de caso é proposto para ilustrar o modelo num programa de recuperação e modernização de veículos blindados realizada numa unidade do Exército Brasileiro. A aplicação da metodologia permitiu a seleção de uma alternativa de modernização, considerando riscos e benefícios. O desdobramento das análises no projeto detalhado permitiu a definição final do escopo de recuperação e modernização, observando efeitos de propagação de alterações de engenharia. A principal contribuição deste trabalho é a formalização de um estudo da recuperação e modernização como projeto específico, descrevendo suas características de uma forma a permitir a aplicação de um modelo baseado em risco.

Soviet/Russian armor and artillery design practices : 1945-1995.

"MCIA-1141-001-96."

Our modern navy; illustrations of battleships, cruisers, monitors, gunboats and torpedo boats with full detail description of the material, displacement, dimensions, horse-power, speed, armor, batteries, caliber and firing capacity of the guns, and the cost of the principal vessels in the United States navy and like details of the great navies of the world.

Mode of access: Internet.

[Naval vessels. General. : pamphlet collection]

Mode of access: Internet.

Organizational, direct support, and general support maintenance repair parts and special tools list for combat vehicle, anti-tank, improved TOW vehicle, M901A1, NSN 2350-01-103-5641 (EIC: AEV).

"October 1992."

Direct support and general support maintenance : fighting vehicle, infantry, M2 (2350-01-048-5920) and fighting vehicle, cavalry, M3 (2350-01-049-2695), hull.

Includes index.

Hand receipt covering contents of Components of End Item (COEI), Basic Issued Items (BII), and Additional Authorization List (AAL) for combat vehicle, anti-tank : improved tow vehicle, M901 (2350-01-045-1123).

"April 1983."

Direct support and general support maintenance : fighting vehicle, Infantry, M2 (2350-01-048-5920) and fighting vehicle, Cavalry, M3 (2350-01-049-2695) turret.

Includes index.

Operator's manual for combat vehicle, anti-tank, improved tow vehicle, M901, NSN 2350-01-045-1123.

"June 1979."

Organizational maintenance manual for combat vehicle, anti-tank, improved tow vehicle, M901, SN 2350-01-045-1123.

"June 1979."

Unit maintenance : fighting vehicle, infantry, M2, (2350-01-048-5920), M2A1 (2350-01-179-1027), and fighting vehicle, cavalry, M3 (2350-01-049-2695), M3A1 (2350-01-179-1028), turret.

"December 1986"--Vol. 3.

Operator's manual : carrier, ammunition, tracked, M992 (2350-01-110-4660).

"Current as of September 1985."