Calcareous nannofossil bioevents of early-middle Pleistocene sediments from the Mediterranean Sea and the Noth Atlantic

Quantitative distributions of calcareous nannofossils are analysed in the early-middle Pleistocene at the small Gephyrocapsa and Pseudoemiliania lacunosa zone transition in deep-sea cores from the Mediterranean Sea and North Atlantic Ocean (Ocean Drilling Program [ODP] Sites 977, 964 and 967, Deep Sea Drilling Project [DSDP] Site 607). The temporal and spatial mode of occurrence of medium-sized gephyrocapsids and reticulofenestrids has been examined to refine biostratigraphic constraints and evaluate possible relationships of stratigraphic patterns to environmental changes during a period of global climatic deterioration. The timing of bioevents has been calibrated using high-resolution sampling and correlation to the delta18O record in chronologically well-constrained sections. Newly identified events and ecostratigraphical signals enhance the stratigraphic resolution at the early-middle Pleistocene. The first occurrence (FO) of intermediate morphotypes between Pseudoemiliania and Reticulofenestra (Reticulofenestra sp.) is proposed as a reliable event within marine isotope stage (MIS) 35 or at the MIS 35/34 transition. The distribution of Reticulofenestra asanoi is characterized by rare and scattered occurrences in its lowest range, but the first common occurrence (FCO) is consistently identified at MIS 32 or 32/31; the last common occurrence (LCO) of the species is a distinctive event at MIS 23. In the studied interval, Gephyrocapsa omega dominates among medium-sized Gephyrocapsa. The FO of G. omega and contemporaneous re-entry of medium-sized gephyrocapsids at the lower-middle Pleistocene transition are diachronous between the Atlantic Ocean and Mediterranean Sea and from the western to eastern Mediterranean. In the Mediterranean, the LO of G. omega falls at MIS 15, insolation cycle 54 and is isochronous among the sites. Abundance fluctuations of G. omega show notable relations to early-middle Pleistocene climate changes; they considerably increase in abundance at the interglacial stages, suggesting warm water preferences. Gephyrocapsa omega temporarily disappears during the glacial MIS 22 and MIS 20. Above MIS 20, an impoverishment in G. omega and in the total abundance of medium-sized gephyrocapsids occurs. A decrease in abundance of G. omega is observed between the western Site 977 and the easternmost Site 967 in the Mediterranean Sea, as a possible response to high salinity and/or low nutrient content. Possible environmental influences on the distribution of R. asanoi and of Reticulofenestra sp. are discussed.

Late Pliocene carbonate mineralogy of ODP Hole 133-818B

Shedding of shallow carbonate material toward the deep slopes and basin floors is clearly tied to the position of the carbonate bank tops relative to the photic zone. The onset of bank shedding in periplatform sediments can record either the flooding of the bank tops within the photic zone during a rise in sea level following a period of exposure, referred to in the literature as the "highstand shedding" scenario, or the reentry of the bank tops into the photic zone during a lowering of sea level following a period of drowning, referred to as the "lowstand shedding" scenario. Results from Leg 133 post-cruise research on the Pliocene sequences, drilled in six sites within different slope settings of the Queensland Plateau, seem to point out that the latter "lowstand shedding" scenario can be applied to this particular carbonate system. At the Queensland Plateau sites, the early Pliocene (5.2-3.5 Ma) and the earliest part of the late Pliocene (3.5-2.9 Ma) age sequences were characterized, especially in the ��deep�� Sites 811 and 817, by pelagic sediments (foraminifers and coccoliths) and by typically pelagic sedimentation rates not exceeding 20 mm/k.y. The earliest part of the late Pliocene age section was characterized by well-developed hardgrounds in the "shallow" Sites 812 and 814 and by normal pelagic sediments mixed with reworked phosphatized planktonic foraminifers in Site 813. Finally, the early part of the late Pliocene (2.9-2.4 Ma) section was characterized by high sedimentation rates, related to the shedding and admixture into the pelagic sediments of bank-derived materials. These bank-derived materials consist of either diagenetically unaltered fine aragonite with traces of dolomite in Site 818 or micritic calcite resulting from seafloor and/or shallow burial alteration in the deepest Sites 817 and 811. The highest sedimentation rates (163 mm/k.y.) were recorded in Site 818, drilled nearest the modern carbonate bank of Tregrosse Reef. The sedimentation rates decrease with increasing distance from Tregrosse Reef - 120 mm/k.y. in Site 817 and 47.5 mm/k.y. in Site 811. The initial appearance of fine aragonite in Site 818, corresponding to the transition from pelagic to periplatform sedimentation rates, has been dated at 2.9 Ma. This Pliocene sediment pattern on the Queensland Plateau is different from the pattern observed in sediments from two earlier ODP legs (i.e., Leg 101 in the Bahamas and in Leg 115 in the Maldives), where aragonite-rich sediments, characterized by high periplatform sedimentation rates, were observed in the lower Pliocene section (5.2-3.5 Ma), whereas the upper Pliocene (3.5-1.6 Ma) sediments are more pelagic in nature and are characterized by low sedimentation rates or major hiatuses. These Pliocene periplatform sequences in the Bahamas and in the Maldives and late Quaternary age periplatform sequences worldwide have pointed out that "highstand shedding" was the typical response of carbonate platforms to fluctuations in sea level, just opposite to a "lowstand shedding" response to sea-level fluctuations, typical of siliciclastic shelves. Assuming that the envelope of Haq et al.'s (1987) sea-level curve, showing a well-defined lowering of sea level between 3.5 and 2.9 Ma, can also be applied to the southwest Pacific Ocean, based on a high-resolution Pliocene d18O record from the Ontong Java Plateau recently published by Jansen et al. (1993, doi:10.2973/odp.proc.sr.130.028.1993), the Pliocene periplatform sequences on the Queensland Plateau would have recorded the reentry of the bank tops into the photic zone during a general lowering of sea level, following an interval characterized by high sea level, during which the shallow carbonate system on the Queensland Plateau was drowned. The early Pliocene age (5.2-3.5 Ma) sediments deposited on the Queensland Plateau, an established interval of eustatic sea-level highstand, are typically pelagic in character. In addition, relatively cold surface temperatures (estimated to have ranged from 18�� to 20��C by Isern et al. [this volume]) might have also stressed the reefs during early Pliocene time and contributed to the drowning of the Queensland Plateau carbonate system during the late Miocene and early Pliocene. Differential and relatively high subsidence rates, inferred by variations in paleodepth of water (based upon benthic foraminifer assemblages; Katz and Miller, this volume) may also have influenced the drowning of the carbonate bank tops on the Queensland Plateau during the late Miocene and early Pliocene. The sediments of early late Pliocene age (2.9-2.4 Ma), a well-established interval of lowering of sea level, are clearly periplatform and cyclic in nature. High-frequency (~40 k.y.) aragonite cycles, well-developed between 2.9 and 2.45 Ma, correlate with the planktonic high-resolution Pliocene d18O record from the Ontong Java Plateau, a good sea-level proxy (Jansen et al., in press). Contrary to late Quaternary age aragonite cycles from the Bahamas, the Nicaragua Rise, the Maldives, and the Queensland Plateau, the late Pliocene aragonite cycles in Hole 818B display high levels of aragonite during glacial stages and, therefore, lowstands of sea level. In addition, sediments deposited during the earliest part of the late Pliocene (3.5-2.9 Ma), transition between the early Pliocene highstand and the late Pliocene lowering in sea level, have recorded the first evidence of a fall in sea level, by (1) the occurrence of synchronous submarine hardgrounds in the two shallowest sites (Sites 812 and 814), (2) the deposition of reworked material from the shallower part of the slope into the intermediate Sites 813 and 818, and (3) the deposition of pelagic sediments in the deepest Sites 817 and 817. In summary, contrary to previous findings, the Pliocene periplatform sediments on the Queensland Plateau appear to have recorded a regional shedding of shallow carbonate bank tops during an interval of sea-level lowering, a good illustration of the "carbonate lowstand shedding" scenario, occurring during the reentry of previously drowned carbonate bank tops into the photic zone related to a decrease in sea level.

(Table 1) Geochemistry of basalts of Nauru Basin

Leg 61 of the Deep Sea Drilling Project (DSDP) was concerned with drilling a single continuously cored multiple re-entry hole at site 462 in the Central Nauru Basin (Fig. 1). Preliminary results of this drilling, which penetrated more than 1 km beneath the sea floor, were presented earlier. One major result was the discovery of a late Cretaceous off-ridge volcanic/intrusive complex of basaltic composition and great thickness (>500 m). We now present trace element abundance data for these basalts. Results of the drilling provide further support for a relatively long-lived thermal and magmatic event in the late Cretaceous resulting in voluminous and widespread magmatism in the central and western Pacific consistent with earlier suggestions. The trace element data show that most of the rocks produced during this event have trace element characteristics intermediate between those of normal and transitional mid-ocean ridge basalts (N- and T-type MORB) and different from Hawaiian basalts. These results indicate that basalts which are depleted in light rare earth elements (LREE) relative to the heavy REE may, in certain conditions, be erupted as voluminous intra-plate eruptions far from active ridge crests.

Trace-element geochemistry of tholeiitic basalts from DSDP Hole 55-433C

Hole 433C, a multiple re-entry hole drilled in 1862 meters of water on Suiko Seamount in the central Emperor Seamounts, penetrated 387.5 meters of lava flows overlain by 163.0 meters of sediments. The recovered volcanic rocks consist of three flow units (1-3) of alkalic basalt underlain by more than 105 flows or flow lobes (Flow Units 4-67) of tholeiitic basalt. This study reports trace-element, including rare-earth element (REE), data for 25 samples from 24 of the least altered tholeiitic flows. These data are used to evaluate the origin and evolution of tholeiitic basalts from Suiko Seamount and to evaluate changes in the mantle source between the time when Suiko Seamount formed, 64.7 �� 1.1 m.y. ago (see Dalrymple et al., 1980), and the present day. Stearns (1946), Macdonald and Katsura (1964) and Macdonald (1968) have established that chemically distinct lavas erupt during four eruptive stages of development of a Hawaiian volcano. These stages, from initial to final, are shield-building, caldera-filling, post-caldera, and post-erosional. The lavas of the shield-building stage are tholeiitic basalts, which erupt rapidly and in great volume. The shield-building stage is quickly followed by caldera collapse and by the caldera-filling stage, during which the caldera is filled by tholeiitic and alkalic lavas. During the post-caldera stage, a relatively thin veneer of alkalic basalts and associated differentiated lavas are erupted, sometimes accompanied by minor eruptions of tholeiitic lava. After a period of volcanic quiescence and erosion, lavas of the nephelinitic suite, which include both alkalic basalts and strongly SiO2-undersaturated nephelinitic basalts, may erupt from satellite vents during the post-erosional stage. Many Hawaiian volcanoes develop through all four stages; but individual volcanoes have become extinct before the cycle is complete. We interpret the tholeiitic lavas drilled on Suiko Seamount to have erupted during either the shield-building or the caldera-filling stage, and the overlying alkalic flows to have erupted during either the caldera-filling or the post-caldera stage (see Kirkpatrick et al., 1980).

Calcareous nannofossils of ODP Hole 177-1090D

Calcareous nannofossil assemblages have been investigated at Ocean Drilling Program (ODP) Site 1090 located in the modern Subantarctic Zone, through the Pleistocene Marine Isotope Stages (MIS) 34-29, between 1150 and 1000 ka. A previously developed age model and new biostratigraphic constraints provide a reliable chronological framework for the studied section and allow correlation with other records. Two relevant biostratigraphic events have been identified: the First Common Occurrence of Reticulofenestra asanoi, distinctly correlated to MIS 31-32; the re-entry of medium Gephyrocapsa at MIS 29, unexpectedly similar to what was observed at low latitude sites. The composition of the calcareous nannofossil assemblage permits identification of three intervals (I-III). Intervals I and III, correlated to MIS 34-32 and MIS 30-29 respectively, are identified as characteristic of water masses located south of the Subtropical Front and reflecting the southern border of Subantarctic Zone, at the transition with the Polar Front Zone. This evidence is consistent with the hypothesis of a northward shift of the frontal system in the early Pleistocene with respect to the present position and therefore a northernmost location of the Subantarctic Front. During interval II, which is correlated to MIS 31, calcareous nannofossil assemblages display the most significant change, characterized by a distinct increase of Syracosphaera spp. and Helicosphaera carteri, lasting about 20 ky. An integrated analysis of calcareous nannofossil abundances and few mineralogical proxies suggests that during interval II, Site 1090 experienced the influence of subtropical waters, possibly related to a southward migration of the Subtropical Front, coupled with an expansion of the warmer Agulhas Current at the core location. This pronounced warming event is associated to a minimum in the austral summer insolation. The present results provide a broader framework on the Mid-Pleistocene dynamic of the ocean frontal system in the Atlantic sector of the Southern Ocean, as well as additional evidence on the variability of the Indian-Atlantic ocean exchange.

Mineralogy and geochemistry of sedimentary deposits at DSDP Leg 55 Holes

The four holes (including a re-entry hole) drilled at Site 433 allow determination of the sedimentary sequence of Suiko Seamount in the Emperor chain. The holes are in a small graben basin situated within a lateral lagoon on the seamount. The sedimentary deposits range from the Paleocene to the upper Pliocene and are not uniform and continuous. A major hiatus exists at the top of the lower Eocene reef sediment, below the lower and upper Miocene pelagic sediments. The depositional history and succession of environments are shown by mineralogical and geochemical changes in the sediments.

Recubrimientos autolubricantes cuasicristalinos tipo composite depositados mediante proyecci��n t��rmica para aplicaciones espaciales y de alta temperatura

Los recubrimientos lubricantes s��lidos son requeridos para reducir la fricci��n y prevenir el desgaste en componentes que operan a altas temperaturas o en vac��o (veh��culos espaciales, industria qu��mica, motores di��sel, turbinas aeron��uticas y de generaci��n de energ��a���). Los lubricantes l��quidos pierden sus caracter��sticas cuando las condiciones de presi��n, temperatura o ambientales son severas (oxidaci��n, inestabilidad t��rmica, volatilidad,���), por ejemplo los aceites minerales convencionales se descomponen a temperaturas pr��ximas a 200 ��C. Por tanto, la ��nica manera de poder conseguir una adecuada lubricaci��n a temperaturas extremas es por medio de s��lidos, que cada vez m��s, se aplican en forma de recubrimientos. Estos recubrimientos podr��an ser empleados en componentes de veh��culos espaciales reutilizables, donde se pueden alcanzar, en la reentrada en la atm��sfera, temperaturas de 700 ��C (bisagras, rodamientos, articulaciones y zonas de sellado en las superficies de control, y rodamientos de las turbobombas y las cajas de engranajes). Dichos recubrimientos tambi��n deber��an ser capaces de proporcionar una lubricaci��n efectiva a bajas temperaturas para las operaciones en tierra, para las operaciones de arranque en fr��o, incluso en el espacio. El conjunto de requisitos que tendr��an que satisfacer las capas tribol��gicas relacionadas con estas condiciones extremas es muy diverso, lo que hace que el concepto de capas tipo composite (aqu��llas constituidas por varios componentes) sea, en principio, muy adecuado para estas aplicaciones. Recubrimientos composite proyectados t��rmicamente constituidos por una matriz dura y conteniendo lubricantes s��lidos pueden ser una buena soluci��n desde el punto de vista tribol��gico. El ���Lewis Research Centre��� de la NASA ha estado desarrollando recubrimientos autolubricantes tipo composite, constituidos por la combinaci��n de materiales duros como el carburo de cromo, junto con lubricantes s��lidos como plata o la eut��ctica de fluoruros de calcio y bario, en una matriz de NiCr, para su uso en aplicaciones terrestres a alta temperatura. Estos recubrimientos han sido aplicados mediante proyecci��n t��rmica, siendo denominados como series PS100, PS200, PS300 y PS400, reduciendo de forma significativa el coeficiente de fricci��n y mejorando la resistencia al desgaste en un amplio margen de temperaturas. Otra nueva familia de materiales con comportamiento tribol��gico prometedor son las aleaciones cuasicristalinas (QC). Presentan caracter��sticas muy atractivas: alta dureza, baja fricci��n, alto l��mite el��stico de compresi��n... Son muy fr��giles como materiales m��sicos, por lo que se intentan aplicar en forma de recubrimientos. Se pueden depositar mediante proyecci��n t��rmica. Algunos de estos materiales cuasicristalinos, como AlCoFeCr, poseen coeficientes de dilataci��n pr��ximos al de los materiales met��licos, alta estabilidad t��rmica, baja conductividad t��rmica y una elevada resistencia a la oxidaci��n y a la corrosi��n en caliente. En esta tesis se han desarrollado recubrimientos tipo composite conteniendo cuasicristales como componente antidesgaste, NiCr como componente tenaz, y Ag y la eut��ctica de BaF2-CaF2, como lubricantes s��lidos. Estos recubrimientos han sido depositados con diferentes composiciones (denominadas TH100, TH103, TH200, TH400, TH600���) mediante distintos procesos de proyecci��n t��rmica: plasma en aire (PS), plasma en baja presi��n (LPPS) y combusti��n a alta velocidad (HVOF). Los recubrimientos se han generado sobre el sustrato X-750, una superaleaci��n base n��quel, endurecible por precipitaci��n, con muy buena resistencia mec��nica y a la oxidaci��n hasta temperaturas de 870 ��C y, adem��s, es empleada en aplicaciones aeroespaciales e industriales. Los recubrimientos han sido caracterizados microestructuralmente en INTA (Instituto Nacional de T��cnica Aeroespacial), mediante SEM-EDS (Scanning Electronic Microscopy-Energy Dispersive Spectroscopy) y XRD (X-Ray Diffraction), y tribol��gicamente mediante medidas de microdureza y ensayos en trib��metro POD (Pin On Disc) para determinar los coeficientes de fricci��n y de desgaste. Los recubrimientos han sido ensayados tribol��gicamente a alta temperatura en INTA y en vac��o en AMTTARC (Aerospace and Space Materials Technology Testhouse ��� Austrian Research Centres), en Seibersdorf (Austria). Se ha estudiado la influencia de la carga normal aplicada, la velocidad lineal y el material del pin. De entre las diferentes series de recubrimientos cuasicristalinos tipo composite desarrolladas, dos de ellas, TH100 y TH103 han presentado una excelente calidad microestructural (baja porosidad, distribuci��n uniforme de fases���) y se han mostrado como excelentes recubrimientos antidesgaste. Sin embargo, estas capas presentan un pobre comportamiento como autolubricantes a temperatura ambiente, aunque mejoran mucho a alta temperatura o en vac��o. Los resultados del trabajo presentado en esta tesis han proporcionado nuevo conocimiento respecto al comportamiento tribol��gico de recubrimientos autolubricantes cuasicristalinos tipo composite depositados por proyecci��n t��rmica. Sin embargo, dichos resultados, aunque son muy prometedores, no han puesto de manifiesto el adecuado comportamiento autolubricante que se pretend��a y, adem��s, como ocurre en cualquier trabajo de investigaci��n, durante el desarrollo del mismo siempre aparecen nuevas dudas por resolver. Se proponen nuevas l��neas de trabajo futuro que complementen los resultados obtenidos y que puedan encaminar hacia la obtenci��n de un recubrimiento que mejore su comportamiento autolubricante. ABSTRACT Solid lubricant coatings are required to reduce friction and prevent wear in components that operate at high temperatures or under vacuum (space vehicles, chemical industry, diesel engines, power generation turbines and aeronautical turbines, for instance). In these cases neither greases nor liquid lubricants can be employed and the only practicable approach to lubrication in such conditions is by means of solids. These are increasingly applied in the form of coatings which should exhibit low shear strength, whilst maintaining their chemical stability at extremes temperatures and in the space environment. In the space field, these coatings would be employed in re-usable space plane applications, such as elevon hinges, where temperatures of 700 ��C are reached during re-entry into the Earth���s atmosphere. These coatings should also be capable of providing effective lubrication at lower temperatures since ���cold start��� operation may be necessary, even in the space environment. The diverse and sometimes conflictive requirements in high temperature and space-related tribological coatings make the concept of composite coatings highly suitable for these applications. Thermal-sprayed composites containing solid lubricants in a hard matrix perform well tribologically. NASA���s Lewis Research Centre had developed self-lubricating composite coatings for terrestrial use, comprising hard materials like chromium carbide as well as solid lubricant additives such as silver and BaF2-CaF2 eutectic on a Ni-Cr matrix. These coatings series, named PS100, PS200, PS300 and PS400, are applied by thermal spray and significantly reduce friction coefficients, improving wear resistance over a wide temperature range. Quasicrystalline alloys (QC) constitute a new family of materials with promising tribological behaviour. Some QC materials exhibit a combination of adequate antifriction properties: low friction coefficient, high hardness and high yield strength under compression, and can be easily produced as coatings on top of metallic and non-metallic materials. Among these QC alloys, AlCoFeCr has high hardness (700 HV0.1), a thermal expansion coefficient close to that of metals, high thermal stability, low thermal conductivity and good oxidation and hot corrosion resistance. However most QC materials have the disadvantage of being very brittle. In order to take advantage of the excellent tribological properties of QCs, thick composite lubricant coatings were prepared containing them as the hard phase for wear resistance, Ag and BaF2-CaF2 eutectic as lubricating materials and NiCr as the tough component. These coatings were deposited in different composition mixtures (named TH100, TH103, TH200, TH400, TH600���) by different thermal spray processes: air plasma spray (PS), low pressure plasma spray (LPPS) and high velocity oxy-fuel (HVOF), on X-750 substrates. X-750 is an age-hardenable nickel-base superalloy with very good strength and a good resistance to oxidising combustion gas environments at temperatures up to about 870 ��C and it is widely used in aerospace and industrial applications. Coatings have been characterized microstructurally, at INTA (National Institute for Aerospace Technology), by means of SEM-EDS (Scanning Electronic Microscopy- Energy Dispersive Spectroscopy) and XRD (X-Ray Diffraction), and tribologically by microhardness measurements and pin-on-disc testing to determine friction coefficients as well as wear resistance. The coatings were tested tribologically at high temperature at INTA and under vacuum at AMTT-ARC (Aerospace and Space Materials Technology Testhouse ��� Austrian Research Centres), in Seibersdorf (Austria). Different loads, linear speeds and pin materials were studied. TH100 and TH103 QC alloy matrix composite coatings were deposited by HVOF with excellent microstructural quality (low porosity, uniform phase distribution) and showed to be excellent wear resistant coatings. However these QC alloy matrix composite coatings are poor as a self-lubricant at room temperature but much better at high temperature or in vacuum. The results from the work performed within the scope of this thesis have provided new knowledge concerning the tribological behavior of self-lubricating quasicrystalline composite coatings deposited by thermal spraying. Although these results are very promising, they have not shown an adequate self-lubricating behavior as was intended, and also, as in any research, the results have in addition raised new questions. Future work is suggested to complement the results of this thesis in order to improve the selflubricating behaviour of the coatings.

Development of the DORI-TBI: An Investigation to Develop a New Screening Measure to Determine Consultation with a School-Based Brain Injury Resource Team

Brain injury is the leading cause of disability and death in children in the United States. Student re-entry into the school setting following a traumatic brain injury is crucial to student success. Multidisciplinary teams within the school district comprised of individuals with expertise in brain injury are ideal in implementing student specific treatment plans given their specialized training and wide range of expertise addressing student needs. Therefore, the purpose of this study is to develop and initially validate a quantitative instrument that school personnel can use to determine if a student, identified as having a traumatic brain injury, will benefit from district-level consultation from a brain injury team. Three studies were designed to investigate the research questions. In study one, the planning and construction of the DORI-TBI was completed. Study two addressed the content validity of the DORI-TBI through a comparison analysis with other referral forms, content review with experts in the field of TBI, and cognitive interviews with professionals to test the usability of the new screening tool. In study three, a field administration was conducted using vignettes to measure construct validity. Results produced a valid and reliable new screening instrument that can aid school-based teams to more efficiently utilize district level consultation with a brain injury support team.

Electrogram analysis and pacing are complimentary for recognition of abnormal conduction and far-field potentials during substrate mapping of infarct-related ventricular tachycardia.

BACKGROUND Mapping to identify scar-related ventricular tachycardia re-entry circuits during sinus rhythm focuses on sites with abnormal electrograms or pace-mapping findings of QRS morphology and long stimulus to QRS intervals. We hypothesized that (1) these methods do not necessarily identify the same sites and (2) some electrograms are far-field potentials that can be recognized by pacing. METHODS AND RESULTS From 12 patients with coronary disease and recurrent ventricular tachycardia undergoing catheter ablation, we retrospectively analyzed electrograms and pacing at 546 separate low bipolar voltage (<1.5 mV) sites. Electrograms were characterized as showing evidence of slow conduction if late potentials (56%) or fractionated potentials (76%) were present. Neither was present at (13%) sites. Pacing from the ablation catheter captured 70% of all electrograms. Higher bipolar voltage and fractionation were independent predictors for pace capture. There was a linear correlation between the stimulus to QRS duration during pacing and the lateness of a capturing electrogram (P<0.001), but electrogram and pacing markers of slow conduction were discordant at 40% of sites. Sites with far-field potentials, defined as those that remained visible and not captured by pacing stimuli, were identified at 48% of all pacing sites, especially in areas of low bipolar voltage and late potentials. Initial radiofrequency energy application rendered 74% of targeted sites electrically unexcitable. CONCLUSIONS Far-field potentials are common in scar areas. Combining analysis of electrogram characteristics and assessment of pace capture may refine identification of substrate targets for radiofrequency ablation.

Peronismo, dictadura y universidades privadas en la Argentina de los a��os 70

A partir del an��lisis de normativas universitarias, bibliograf��a especializada y fundamentalmente fuentes documentales y testimoniales, este art��culo aborda la trama del sector universitario privado durante el complejo interregno que significaron los a��os setentas para la historia reciente Argentina. Observaremos que tras el reingreso del peronismo al poder del Estado en 1973, la alta sustentabilidad adquirida por el sector en a��os anteriores fue puesta en jaque: conflictos estudiantiles, intervenciones pol��ticas y un crecimiento institucional refrenado, fueron algunos de sus rasgos distintivos. En cuanto a la ��ltima dictadura militar (1976-1983), abri�� una contradictoria etapa de desarrollo para las universidades privadas. Pese a la alternancia de cat��licos conservadores en el ��rea educativa y al sesgo privatista identificado como un hito del modelo econ��mico implementado, el sector privado result�� contra��do en el marco del avasallamiento m��s brutal del sistema universitario en su conjunto. Sin embargo, algunas universidades cat��licas resultaron beneficiadas con importantes est��mulos econ��micos.

Carbon-carbon process variations /

Inserted Report documentation page designates E.R. Stover as "author."

Job-exits and job-to-job transitions in the U.S. : an empirical analysis using SIPP /

Includes bibliographical references (p. 17).

Signal processing and information fusing algorithms for the synthesis of an alternative electromyogram/eye gaze tracking computer cursor control system

This research pursued the conceptualization and real-time verification of a system that allows a computer user to control the cursor of a computer interface without using his/her hands. The target user groups for this system are individuals who are unable to use their hands due to spinal dysfunction or other afflictions, and individuals who must use their hands for higher priority tasks while still requiring interaction with a computer. ^ The system receives two forms of input from the user: Electromyogram (EMG) signals from muscles in the face and point-of-gaze coordinates produced by an Eye Gaze Tracking (EGT) system. In order to produce reliable cursor control from the two forms of user input, the development of this EMG/EGT system addressed three key requirements: an algorithm was created to accurately translate EMG signals due to facial movements into cursor actions, a separate algorithm was created that recognized an eye gaze fixation and provided an estimate of the associated eye gaze position, and an information fusion protocol was devised to efficiently integrate the outputs of these algorithms. ^ Experiments were conducted to compare the performance of EMG/EGT cursor control to EGT-only control and mouse control. These experiments took the form of two different types of point-and-click trials. The data produced by these experiments were evaluated using statistical analysis, Fitts' Law analysis and target re-entry (TRE) analysis. ^ The experimental results revealed that though EMG/EGT control was slower than EGT-only and mouse control, it provided effective hands-free control of the cursor without a spatial accuracy limitation, and it also facilitated a reliable click operation. This combination of qualities is not possessed by either EGT-only or mouse control, making EMG/EGT cursor control a unique and practical alternative for a user's cursor control needs. ^

Peronismo, dictadura y universidades privadas en la Argentina de los a��os 70

A partir del an��lisis de normativas universitarias, bibliograf��a especializada y fundamentalmente fuentes documentales y testimoniales, este art��culo aborda la trama del sector universitario privado durante el complejo interregno que significaron los a��os setentas para la historia reciente Argentina. Observaremos que tras el reingreso del peronismo al poder del Estado en 1973, la alta sustentabilidad adquirida por el sector en a��os anteriores fue puesta en jaque: conflictos estudiantiles, intervenciones pol��ticas y un crecimiento institucional refrenado, fueron algunos de sus rasgos distintivos. En cuanto a la ��ltima dictadura militar (1976-1983), abri�� una contradictoria etapa de desarrollo para las universidades privadas. Pese a la alternancia de cat��licos conservadores en el ��rea educativa y al sesgo privatista identificado como un hito del modelo econ��mico implementado, el sector privado result�� contra��do en el marco del avasallamiento m��s brutal del sistema universitario en su conjunto. Sin embargo, algunas universidades cat��licas resultaron beneficiadas con importantes est��mulos econ��micos.

Analysis of Poverty Dynamics in Canada (Working Paper 9)

While we know much about poverty (or ���low income���) in Canada in a static context, our understanding of the underlying dynamics remains very limited. This is particularly problematic from a policy perspective and the country has been increasingly left out on an international level in this regard. The contribution of this paper is to report the results of an empirical analysis of low income (���poverty���) dynamics in Canada using the recently available ���LAD��� tax-based database. The paper first describes the general nature of individuals��� poverty profiles (how many are short-term versus longterm, etc.)., the breakdown of the poor population in any given year amongst these different types, and the characterisation of poverty profiles by sex and family type. It then reports the estimation of various econometric models, starting with a set which specifies entry into and exit from poverty in any given year as a function of a variety of personal attributes and situational characteristics, including family status and changes therein, province of residence, inter-provincial mobility, language, area size of residence and calendar year (to capture trend effects). A set of proper hazard models then adds duration effects to these specifications to see how exit and re-entry probabilities shift with the amount of time spent in a poverty spell or after having exited a previous spell. A final set of specifications then investigates ���occurrence dependence��� effects by including past poverty spells first in an entry model and then with respect to the probability of being poor in a given year. Policy implications are discussed.