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Insects that feed on plants are widely used for studies of host-plant-associated speciation due to their diversity and tractability. The value of these studies necessarily depends upon an accurate understanding of the diet of the focal insects. In North America, the 12 Phytomyza Fallén (Diptera: Agromyzidae) leafmining fly species feeding on hollies (Ilex spp. (Aquifoliaceae: Ilex)) initially appeared to be primarily a host-plant-associated radiation of largely monophagous species. However, our increased collecting efforts found that a majority of the morphospecies are oligophagous, feeding on multiple Ilex species. Patterns of host-associations suggest that colonization of new hosts followed by host-associated speciation may be an important feature of diversification. Analyses of mitochondrial COI data in three oligophagous species found evidence of host-associated genetic structure consistent with processes of host-associated divergence. However, in one of these species, evidence of geographic divergence as well as host-associated divergence was detected, illustrating complexity in factors relating to speciation and host-use evolution in this radiation of leafmining flies.

Evolutionary radiations have been well documented in plants and insects, and natural selection may often underly these radiations. If radiations are adaptive, the diversity of species could be due to ecological speciation in these lineages. Agromyzid flies exhibit patterns of repeated host-associated radiations. We investigated whether host-associated population divergence and evidence of divergent selection exist in the leaf miner Phytomyza glabricola on its sympatric host plants, the holly species, Ilex coriacea and I. glabra. Using AFLPs and nuclear sequence data, we found substantial genetic divergence between host-associated populations of these flies throughout their geographic range. Genome scans using the AFLP data identified 13 loci under divergent selection, consistent with processes of ecological speciation. EF-1α data suggest that I. glabra is the original host of P. glabricola and that I. coriacea is the novel host, but the AFLP data are ambiguous with regard to directionality of the host shift.

Boxwood (Buxus spp.) are commercially important evergreen ornamental plants with an annual market value of over $103 million in the United States. The recent U.S. incursion of boxwood blight disease caused by the fungus Calonectria pseudonaviculata (syn. Cylindrocladium pseudonaviculatum, Cy. buxicola) threatens the health and productivity of boxwood in both landscape plantings and nurseries. The first confirmed U.S. reports of the disease were made from Connecticut and North Carolina in November 2011 (2,4), followed by diagnoses in 10 additional states during 2012 and 2013. By August 2013, symptoms consistent with boxwood blight had been observed from B. sempervirens in Delaware, Maryland, New Jersey, and southeastern New York. Affected plants showed rapid onset of disease symptoms: dark brown to black spots or diffuse dark areas on leaves, followed by defoliation. Narrow, elongate black cankers also formed on current season shoots. Symptomatic stems and leaves were placed in petri dishes with moistened filter paper at 22°C for 3 days under continuous light. Conidiophores were excised, then placed on potato dextrose agar amended with streptomycin and neomycin (0.3 g/l). Resultant colonies showed dark brown pigmentation at the colony center surrounded by tan to reddish brown rings with white mycelia at the advancing edge. Conidia (n = 30 per isolate) were hyaline, cylindrical, rounded at both ends, with a single septum (45 to 76 × 4 to 6 μm; avg. 63 × 5 μm). Conidiophores (n = 20 per isolate) comprised a stipe, a hyaline septate stipe extension (length 119 to 192 μm; avg. 150 μm) and a terminal ellipsoidal vesicle (diameter 4 to 10 μm; avg. 7 μm). Based on morphological characteristics, the causal agent was identified as C. pseudonaviculata (1,4). Voucher specimens were deposited in the U.S. National Fungus Collections (BPI 892698 to 701). To verify morphological diagnosis, genomic DNA was extracted from fungal biomass grown in liquid cultures of yeast extract peptone dextrose media. A portion of the β-tubulin gene (TUB2) was PCR amplified and sequenced bi-directionally using primers Bta/Bt2b (3). BLASTn searches of NCBI GenBank databases using the TUB2 sequences (Accession Nos. KF785808 to 11) demonstrated 96 to 100% sequence identity with other C. pseudonaviculata isolates. To confirm pathogenicity, 5-month-old B. sempervirens and B. microphylla seedlings were spray-inoculated with a spore suspension of 1 × 104 conidia/ml. One isolate from each state was independently tested with four replicates each. Non-inoculated water-sprayed plants served as negative controls. Plants were maintained in growth chambers at 22°C under constant light. Blight symptoms developed 4 to 5 days post inoculation. C. pseudonaviculata was re-isolated from inoculated plants; no symptoms or signs were observed from control plants. To our knowledge, this is the first report of C. pseudonaviculata in the states of Delaware, Maryland, New Jersey, and New York. This report demonstrates that C. pseudonaviculata is now widespread across the United States eastern seaboard, and represents a substantial threat to boxwood plants in North American landscapes and nurseries. References: (1) P. Crous et al. Sydowia 54:23, 2002. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, USDA-ARS. Retrieved from http://nt.ars-grin.gov/fungaldatabases , 30 August 2013. (3) N. L. Glass and G. C. Donaldson. Appl. Environ. Microbiol. 61:1323, 1995. (4) K. L. Ivors et al. Plant Dis. 96:1070, 2012.

Subduction-related transport of water into the mantle has significant dynamical and geochemical implications. Dehydration of hydrous phases within the slab can introduce water into the transition zone and lower mantle, potentially hydrating nominally anhydrous minerals (NAM) and impacting the viscosity and density structure of the mantle over a wide area. We present models of fluid transport and mantle hydration in the vicinity of a deeply subducting slab, focusing on the fate of water released by deep dehydration reaction in the subducted serpentinized mantle. A sharp decrease in water storage capacity across the lower boundary of the transition zone may produce “secondary dehydration” of hydrated NAM, leading to precipitation of a hydrous fluid and heterogeneous hydration of the transition zone. Rapid fluid migration relative to the solid flow field can lead to a broad region of diffuse hydration within the upper mantle wedge and the potential for localized melt regions at the top of the transition zone coincident with fluid pathways. Slower fluid migration instead implies that the fluid phase can be transported deep into the lower mantle. Water stabilized in NAM and as a free fluid can initiate upwelling within and above the transition zone. A less abrupt change in water storage capacity across the base of the transition zone leads to high NAM water contents in a channel adjacent to the slab where viscosity is reduced. However, seismic and electromagnetic observations of hydration in the transition zone are most compatible with a sudden drop of water storage capacity.

This paper describes a two-limb single-pass modeling approach constrained by vent temperature, heat flow, vent geochemistry, active-source seismology, and seismically inferred circulation geometry to provide first-order constraints on crustal permeability, conductive boundary layer thickness, fluid residence times, and magma replenishment rates for the magma-hydrothermal system at the East Pacific Rise (EPR) near 9°50'N. Geochemical data from black smokers and nearby diffuse-flow patches, as well as an estimate of heat flow partitioning, suggest that nearly 90% of the heat output stems from heat supplied by the subaxial magma chamber, even though almost 90% of that output appears as diffuse flow at the seafloor. Estimates of magma replenishment rates are consistent with the evolution of lava chemistry over the eruption cycle between 1991–1992 and 2005–2006. If the recharge surface area is 105 m2, a one-dimensional model of hydrothermal recharge using EPR 9°50'N parameters gives rise to rapid sealing as a result of anhydrite precipitation; however, if the area of recharge widens at depth to ~ 106 m2, sealing by anhydrite precipitation may not significantly affect hydrothermal circulation.

Separated by continents and cultures, survivors of the Asian tsunami and Hurricane Katrina share a common bond in their extreme trauma and ensuing struggles. The authors discuss and illustrate core ideas based on the commonalities derived from the experiences of women survivors of these two disasters. Separados tanto por continentes como culturas, los supervivientes del tsunami asiatico y el huracan Katrina comparten el vinculo comun de su enorme trauma y las dificultades subsiguientes. Los autores discuten e ilustran las ideas fundamentals basandose en las similitudes derivadas a partir de las experiencias de las mujeres que sobrevivieron a ambos desastres.

Using two-dimensional dynamic models of the Northern Izu–Bonin (NIB) subduction zone, we show that a particular localized low-viscosity (η_(LV) = 3.3 × 10^(19) − 4.0 × 10^(20) Pa s), low-density (Δρ ~ −10 kg/m^3 relative to ambient mantle) geometry within the wedge is required to match surface observations of topography, gravity, and geoid anomalies. The hydration structure resulting in this low-viscosity, low-density geometry develops due to fluid release into the wedge within a depth interval from 150 to 350 km and is consistent with results from coupled geochemical and geodynamic modeling of the NIB subduction system and from previous uncoupled models of the wedge beneath the Japan arcs. The source of the fluids can be either subducting lithospheric serpentinite or stable hydrous phases in the wedge such as serpentine or chlorite. On the basis of this modeling, predictions can be made as to the specific low-viscosity geometries associated with geophysical surface observables for other subduction zones based on regional subduction parameters such as subducting slab age.

The GyPSM-S (Geodynamic and Petrological Synthesis Model for Subduction) scheme couples a petrological model with a 2-D thermal and variable viscosity flow model to describe and compare fundamental processes occurring within the subduction mantle wedge, including the development of a low-viscosity channel (LVC) (Hebert et al., 2009, Earth and Planetary Science Letters, v. 278, p. 243–256). Here we supplement the basic coupled model result with more sophisticated treatments of trace element partitioning in the fluid phase and melt transport regimes. We investigate the influences of slab fluid source lithology and fluid transport mechanisms on melt geochemistry, the implications of mantle source depletion related to fluid fluxing, and potential melt migration processes. This study describes two model cases that can be compared to geochemical datasets for the Izu–Bonin intra-oceanic subduction system and the Central Costa Rican part of the Central American arc. We find that there is a progression of geochemical characteristics described in studies of cross-arc and along-arc lavas that can be approximated assuming (i) limited fluid–rock interaction within the mantle wedge and (ii) that melt migration preserves the spatial distinction among melts initiated in different areas of the wedge. Specifically, volcanic front lavas have significant contributions from shallower slab fluid sources, and rear-arc lavas have significant contributions from deeper slab fluid sources. Evidence for limited fluid–rock interaction could imply either a rapid fluid transport mechanism or a fluid-dominated trace element budget within the LVC. Although we do not include a back-arc in these models, interpretations of the results lead to several potential mechanisms to explain hydrous inputs to back-arc source regions.

We use a petrological model (pHMELTS), coupled with a 2D thermal and variable viscosity flow model (ConMan), to describe and compare fundamental processes occurring within subduction zones. We study the thermal state and phase equilibria of the subducting oceanic slab and adjacent mantle wedge and constrain fluid flux. Using a Lagrangian particle distribution to perform thousands of thermodynamically equilibrated calculations, the chemical state of the domain is continuously updated. Compositionally and thermally dependent buoyancy and viscosity terms provide a consistent linkage between the effect of water addition to and flow within the mantle wedge. We present seven model cases that span normal ranges in subducting slab age, convergence velocity, and slab dip angle. In all models, the coupling between chemistry and dynamics results in behavior previously unresolved, including the development of a continuous, slab-adjacent low-viscosity channel (LVC) defined by hydrous mineral stability and higher concentrations of water in nominally anhydrous minerals (NAM). As the LVC evolves to fluid saturation, slab-derived components are able to migrate vertically upwards to the water-saturated solidus, forming a melting region that bounds the top of the LVC. The LVC develops due to fluid ingress into the mantle wedge from the dehydrating slab, and can be responsible for slab decoupling, large-scale changes in the wedge flow field, and a mechanism by which hydrated slab-adjacent mantle material can be transported to the deep mantle. Varying model parameters indicates that slab age and slab dip angle exert primary control over LVC shape and thickness, due to changing fluid release patterns within the slab. Younger slabs tend to have thinner, more uniform LVCs, while older slabs tend to have a thinner LVC at shallow depths with a large increase in LVC thickness at ~100 km depth. Slab convergence velocity appears to have a secondary role in controlling LVC shape.

Special Issue on Coastal Ocean Processes, Observing Technologies and Models, Oceanography, Volume 21, No. 4. December 2008.

Naturally occurring greenish quartz found within the context of amethyst-bearing deposits is not simply the result of the exposure of amethyst to thermal bleaching or exposure to the sun. Rather, it can represent a set of distinct color-varieties resulting from the changing chemical and thermal nature of the precipitating solution. Greenish quartz occurs at the Thunder Bay Amethyst Mine Panorama (TBAMP), Thunder Bay, Ontario, Canada, in several distinct varieties. Yellowish green quartz and dark green quartz with purple hues occur as loose detritus, and pale greenish gray quartz occurs as part of a color-gradational sequence of mineralization involving macrocrystalline quartz of other colors and chalcedony. The TBAMP system contains a number of color varieties of quartz including greenish, amethyst, colorless, and smoky. Spectroscopic, irradiation and controlled heating studies show that changes in salinity and temperature of the hydrothermal system that produced the TBAMP deposit are reflected in the changing coloration of the quartz. The greenish quartz, especially the greenish gray variety, has increased turbidity and fluid inclusions in comparison with the adjacent amethyst. Analysis of different colors on major (r = {101 1}) and minor (z = {011 1}) rhombohedral sectors within the quartz indicates that changes in the growth rate also have influenced color development. As the system evolved, two factors contributed to the color changes. A minor ferric component appears to change position from interstitial to substitutional within specific growth-sectors, and the trace-element composition of the quartz evolved. The samples from the TBAMP deposit are compared to isolated samples of greenish quartz collected from three other amethyst-bearing localities: Farm Kos and Farm Rooisand (Namibia), Kalomo-Mapatiqya (Zambia), and southern Bahia (Brazil). All included similar greenish hues with the exception of the yellowish green variety. Colors within the quartz are consistently correlated with the speciation of hydrous components. Darker green samples incorporate larger amounts of molecular H_2O than either pale greenish gray samples, colorless samples, or amethyst. The appearance of strong hydroxyl peaks in the infrared spectra is limited to amethyst and colorless varieties.

Expanded marine Holocene archives are relatively scarce in the Mediterranean Sea because most of the sediments were trapped in catchment areas during this period. Mud belts are most suitable targets to access expanded Holocene records. These sedimentary bodies represent excellent archives for the study of sea-land interactions and notably the impact of the hydrological activity on sediment accumulation. We retrieved a 7.2 m-long sediment core from the Rhone mud belt in the Gulf of Lions in an area where the average accumulation rate is of ca. 0.70 m/1000 years. This core thus provides a continuous and high-resolution record of the last 10 ka cal BP. A multi-proxy dataset (XRF-core scan, 14C dates, grain size and organic matter analysis) combined with seismic stratigraphic analysis was used to document decadal to centennial changes of the Rhone hydrological activity. Our results show that 1) the Early Holocene was characterized by high sediment delivery likely indicative of local intense (but short duration) rainfall events , 2) important sediment delivery around 7 ka cal BP roughly presumably related to increased river flux, 3) a progressive increase of continental/marine input during the Mid-Holocene despite increased distance from river outlets due to sea-level rise possibly related to higher atmospheric humidity caused by the southward migration of the storm tracks in the North Atlantic, 4) multi-decadal to centennial humid events in the Late Holocene. Some of these events correspond to the cold periods identified in the North Atlantic (Little Ice Age, LIA; Dark Age) and also coincide with time intervals of major floods a in the Northern Alps. Other humid events are also observed during relatively warm periods (Roman Humid Period and Medieval Climate Anomaly).

A sudden change in flow in a confined system results in the formation of a series of pressure pulses known as a water hammer. Pump shutdown or valve closure at the conclusion of a hydraulic fracture treatment frequently generates a water hammer, which sends a pressure pulse down the wellbore that interacts with the created fracture before returning towards the surface. The result is a pressure profile that consists of a series of oscillations that attenuate over time due to friction. Hydraulic fracture treatments have been shown to alter the period, amplitude, and duration of the water hammer signal. The goal of this study was to history match water hammer data from several multi-stage fractured wells with simulations derived from a water hammer model and compare the results to gathered production log and microseismic derived stimulated reservoir volume (SRV) data.Water hammer pressure signals were simulated in this study with a numerical model that combined the continuity and momentum equations of the wellbore with a created hydraulic fracture represented by a circuit with a resistance, capacitance, and inertance (R, C, and I) connected in series. Treatment pressure data from three horizontal fractured wells were history matched with the numerical model by iteratively altering R, C, and I until an appropriate match was obtained. All three horizontal wells had both production log and microseismic data for each stage, and the R, C, and I values obtained from history matching were compared to production log (gas) and microseismic SRV for any correlations.It is shown that the water hammer derived capacitance was directly correlated with the stimulated reservoir volume (SRV) derived from micro-seismic measurements, however, it showed no correlation with gas production obtained from the production log. Inertance also showed a positive correlation with SRV but had no correlation with production log data. Finally, the water hammer derived resistance exhibited no correlation with SRV data, but showed a positive correlation with gas production.The results from this work support the fact that the water hammer signal at the conclusion of a hydraulic fracturing treatment stage, contains diagnostic information about the created fracture network. Since this data can be recorded at very little incremental cost, it may prove to be a very useful and cost effective fracture diagnostic tool.

This research (1) integrated a fluorescent dye injection and monitoring system for measuring the mixing of a fluorescent dye tracer (fluorescein) in permeable (sandy) sediments with a cabled ocean observatory, Kilo Nalu, Oahu, Hawaii, and (2) used this system to conduct remotely controlled in situ measurements of wave-enhanced porewater mixing in a physically well-characterized wave-dominated setting. Laboratory results indicated that the fiber-optic sensor is effective at measuring fluorescence-traced enhanced mixing in sandy sediments. Observed dye mixing, driven by paddle-generated surface waves in a laboratory wave channel was 2–3 orders of magnitude greater than molecular diffusion, and decreased with depth in the sediments. Similarly, field experiments used a remotely controlled submersible syringe pump for fluorescent tracer injection into sediment that was monitored with a fiber-optic sensor. These experiments were carried out at 10 m water depth, with mean wave heights of 0.3–1.5 m and periods of ∼15 s. At 15 cm sediment depth, transport rates of 0–5 cm h−1 were measured, with maximum dispersion coefficients 2–3 orders of magnitude faster than sedimentary molecular diffusion. Hydrodynamic measurements collected simultaneously via Kilo Nalu correlated with porewater transport, with significant wave height and diffusion having the strongest covariation.

The Auger facility was designed, built and installed by Shell, with first oil production on April 15, 1994. It was the first Tension Leg Platform in the Gulf of Mexico, first to support drilling rig, complete production facilities, and world record setting water depth at the time. Auger has continued its strategic role in Shell's Gulf of Mexico portfolio since then with 7 subsea satellite tie-back fields, the most of any in the Shell deep water Gulf of Mexico portfolio. In 2010 and 2011 Auger had 5 recordable injuries per year (TRIF of 6 per million man hours worked). In this same timeframe, Shell also made a major discovery, Deep Cardamom, 6 miles from Auger. The Cardamom field will increase oil and gas production on Auger back to nearly peak facility production rates and give the facility a new lease on life. In order to add one more subsea tieback and onboard Cardamom production, many upgrades and facility changes were required. This scope called for simultaneous production, drilling and brown field construction on the asset for 2 ½ years. From a personnel perspective, this required a 20% increase in personnel capacity at Auger with a full-time construction team of 80 to 100 people, in addition to the normal production crew of 100. Shell recognized that the increase in activity level would increase exposure to individuals at Auger. This fact, coupled with the recent safety performance track record, required a step change in safety culture simultaneous with the increase in personnel capacity and hazard exposure. The Auger/Cardamom team focused on re-invigorating the safety culture offshore; driving visible, vigilant and felt safety leadership; hazard recognition training of the front line work force; improvements in PPE; and improvements in the quality of life and working conditions. The re-invigorated safety program moved beyond compliance to a culture of individual accountability and personal commitment to caring for each other with strong leadership behaviors. This paper describes the efforts to re-invigorate the safety culture on the facility. The team moved safety culture and performance to one of the best in Shell worldwide, including a Goal Zero year in 2013 with no recordable injuries.

In addition to nutrient and light availability, sedimentary biogeochemical processes can play an essential role in seagrass productivity. Previous investigations of the interactions between seagrasses and their underlying sediments have failed to clearly identify the spatio-temporal variability of the major geochemical parameters involved. Dissolved and solid phase chemical parameters in eelgrass vegetated and nearby non-vegetated sediments were investigated in this study to determine their vertical, lateral, and temporal distributions. Solid-state microelectrodes were used to investigate dissolved O2, ΣH2S, Fe2+, and Mn2+ on mm space scales. In this study, spatial heterogeneity was assessed and diurnal “ventilation” by seagrass productivity (i.e., the translocation of photosynthetically produced oxygen to the anoxic sedimentary environment) was not observed probably because benthic infaunal activity (bioturabation and bioirrigation) and microzones established by microbial processes led to highly heterogeneous sediment geochemistry where temporal variability was obscured by small-scale spatial variability. Non-vegetated sediments were less geochemically variable laterally than vegetated sediments, however, in some cases, they had similar vertical variability, possibly because they had been vegetated at an earlier time. This study demonstrates that in vegetated sediments where there is also substantial benthic macrofaunal activity it is difficult to separate the impacts of the two types of biota on sediment geochemistry and their spatial patterns, and it also raises the question of the applicability of traditional one-dimensional diagenetic models for such spatially–temporally complex sediments.

An approach to scaling that has found considerable utility inthe field of physical oceanography is based on theauto-covariance function (ACF). It is demonstrated to alsobe useful in determining the characteristic length scale of thedominant variance of dissolved sulfide and ferrous iron inanoxic pore waters. The method begins with the analysisof a data series in which the measurement sampling intervalis smaller than the expected length scales. A least squarespolynomial fit to the data representing a background field isthen removed from the data series making possible the analysisof the variability superimposed on the background field. Thecharacteristic length scale is then defined as the distancein which the measurements become uncorrelated. This usuallyoccurs at a significance-level or zero-crossing of the ACF.Characteristic lengths obtained for sediments from a varietyof coastal environments are not distinguishable betweensecond and third order polynomial fits with average valuesand standard deviations of, respectively, 7.0 ± 2.7 mm and6.1 ± 2.3 mm. These values are close to the typical burrowdiameter of 7.5 mm used by Aller (1978) in his bioirrigationmodel for sediment diagenesis. These results indicate thatmacrofauna dwelling in the sediment are probably responsiblefor the variability, although in the seagrass meadow rhizomesmay also play a role.

Interactions between seagrasses and associated sediment pore water chemistry in response to light–dark conditions were investigated in this study. Vertical profiling using a solid-state, gold–mercury amalgam made possible the observation of fine-scale (

Recently diverged taxa often show discordance in genetic divergence among genomic loci, where some loci show strong divergence and others show none at all. Genetic studies alone cannot distinguish among the possible mechanisms but experimental studies on other aspects of divergence may provide guidance in the inference of causes of observed discordances. In this study, we used no-choice mating trials to test for the presence of reproductive isolation between host races of the leaf-mining fly, Phytomyza glabricola on its two holly host species, Ilex coriacea and I. glabra. These trials inform our effort to determine the cause of significant differences in the degree of divergence of nuclear and mitochondrial loci of flies collected from the two host plants. We present evidence of reproductive isolation between host races in a controlled greenhouse setting: significantly more mate pairs consisting of flies from the same host plant species produced offspring than inter-host mate pairs, which produced no offspring. We also tested whether the presence of the natal or non-natal host plant affects reproductive success. Flies collected from I. coriacea were more likely to produce offspring when in the presence of the natal host, whereas the presence or absence of either the natal or non-natal host had no effect on flies collected from I. glabra. The results indicate discordant patterns of nuclear and mitochondrial divergence among host races of P. glabricola are likely due to incomplete lineage sorting, and the host races may be well on their way to becoming biological species.

[1] Crustal thickness variations at the ultraslow spreading 10–16°E region of the Southwest Indian Ridge are used to constrain melt migration processes. In the study area, ridge morphology correlates with the obliquity of the ridge axis with respect to the spreading direction. A long oblique “supersegment”, nearly devoid of magmatism, is flanked at either end by robust magmatic centers (Joseph Mayes Seamount and Narrowgate segment) of much lesser obliquity. Plate-driven mantle flow and temperature structure are calculated in 3-D based on the observed ridge segmentation. Melt extraction is assumed to occur in three steps: (1) vertical migration out of the melting region, (2) focusing along an inclined permeability barrier, and (3) extraction when the melt enters a region shallower than ∼35 km within 5 km of the ridge axis. No crust is predicted in our model along the oblique supersegment. The formation of Joseph Mayes Seamount is consistent with an on-axis melt anomaly induced by the local orthogonal spreading. The crustal thickness anomaly at Narrowgate results from melt extracted at a tectonic damage zone as it travels along the axis toward regions of lesser obliquity. Orthogonal spreading enhances the Narrowgate crustal thickness anomaly but is not necessary for it. The lack of a residual mantle Bouguer gravity high along the oblique supersegment can be explained by deep serpentization of the upper mantle permissible by the thermal structure of this ridge segment. Buoyancy-driven upwelling and/or mantle heterogeneities are not required to explain the extreme focusing of melt in the study area.

[1] Throughout the global mid-ocean ridge system, transform faults offset spreading centers. Conductive cooling may be more efficient beneath transform faults, producing a thickened lithosphere that directs melt away from the transform. However, recent observations of thickened crust along transform faults at fast ridges suggest melt redistribution toward transforms, intra-crustal melt production, or efficient extraction of melt. We apply a 3-D model of melt migration and extraction along an oceanic transform domain bounded by ridge segments. Melt is assumed to travel vertically before collecting and migrating beneath a low-permeability boundary inclined towards the ridge axis. A melt extraction zone, which may be geologically interpreted as the presence of faults and/or dikes leading to rapid lateral and vertical melt migration toward plate boundaries, affects the pattern of crustal accretion at segmented ridges. First, we examine a generic ridge-transform-ridge geometry and then a model that represents the Siqueiros transform on the East Pacific Rise. On the basis of crustal thickness variations within the intra-transform spreading centers along the fast-slipping Siqueiros fault, we constrain the presence of a melt extraction zone within 10 km of the transform zone.

Melt focusing at mid-ocean ridges is necessary to explain the narrowness of the zone of crustal accretion and the formation of large but localized on-axis seamounts at slow and ultraslow spreading centers. It has been proposed that melt focusing is facilitated by the presence of a barrier to upward melt migration at the base of the thermal boundary layer (TBL). We assess the development of a melt impermeable boundary by modeling the geochemical evolution and crystallization history of melts as they rise into the TBL of mid-ocean ridges with different spreading rates. A permeability barrier, associated with a crystallization front controlled by the conductive thermal regime, exists for melt trajectories at slow to fast spreading ridges (≥10 mm/yr half rate). The effective lateral scope of the barrier, where the slope of the barrier exceeds a critical value that allows buoyant melt transport to the axis, generally increases with spreading rate. At all distances from the axis at ultraslow ridges and off-axis at slow spreading ridges, the weak crystallization front may prohibit formation of an efficient barrier and lead to the possibility that some fraction of melt may be incorporated into the lithospheric mantle, allowing refertilization. The protracted crystallization history and potential absence of an effective permeability barrier may explain the dearth of volcanism at ultraslow ridges and calls for a revision of lateral melt focusing scenarios at ultraslow spreading rates.

A direct adaptive controller for trajectory tracking of high-speed robots such as a direct-drive SCARA robot is presented. In this robot, nonlinear effects due to centrifugal, Coriolis, and inertial forces are more important than friction and gravity forces, unlike most industrial robots. The control law of the adaptive scheme consists of a PD regulator plus feedforward compensation of full dynamics. The feedforward terms are adjusted by an adaptation law so that the steady-state position errors are zero. With this adaptive controller, the joint acceleration measurement is not required and no inversion of the estimated mass matrix is involved. The tracking performances of the controller applied to a two-degree-of-freedom SCARA is illustrated by a real-time implementation based on a single-chip digital signal processor (DSP). >

The Kilo Nalu Observatory, located on the south shore of the island of Oahu, supplies data and power connections to a suite of instruments over an array of stations extending from 12 to 20 m water depth which enable real-time extended time series observations, as well as individual user-specific interactive and automated experiments. The observatory power backbone includes a central distribution node at 12 m depth which controls DC power for up to four secondary nodes distributed across the reef; each node, in turn, provides isolated power for up to four experiment modules or ‘subnodes’. The shore cable also provides gigabit Ethernet data communications to the central node over optical fiber, with 100 Mb data bandwidth capability routed subsequently to each node. A monitoring system provides real-time diagnostic data on power system performance. Backbone data connections to remote nodes are achieved using underwater mate-able ‘micro-nodes’ that transmit Ethernet over fiber optic cable. Raw observational and diagnostic data are collected and archived at a shore station and transmitted via wireless link to the University of Hawai'i at Manoa campus where a database system provides products to a web interface (www.soest.hawaii. edu/OE/KiloNalu). Baseline observations include water currents and temperature versus depth, directional wave spectra, salinity, acoustic backscatter, turbidity, dissolved oxygen and chlorophyll fluorescence. Meteorological data is collected at the observatory's shore station. Kilo Nalu is part of the broader Hawai'i Ocean Observing System (HIOOS), which includes observational and forecast components across the Hawaiian Islands.

The implementation of a self-tuning regulator for the positioning of a direct-drive servomotor is described. The servo motor is a permanent magnet DC motor in which no speed reducer is used. The auto-tuning regulator consists of two major loops. The inner loop contains a feedback (PD or PID) regulator with additional feedforward terms. The parameters of the feedforward compensation are adjusted by the outer loop, which contains an online parameter estimator. The estimator is based on a recursive least-squares equation, and the estimated parameters are the load inertia and viscous friction. This self-tuning regulator has been simulated with PC.MATLAB, and the results demonstrate the high performance of the scheme. Experimental results obtained with a small DC motor (Electrocraft E-576) are presented, and these results show good agreement with the digital simulation results. There are two innovative aspects to this work. First, parameter estimation is used to adapt the feedforward compensation terms instead of the gains of the feedback controller, as usually is the case in conventional indirect self-tuning regulators. Secondly, the complete adaptive controller has been implemented using a single-chip digital signal processor (DSP), which results in the reduction of system hardware and cost. >

In a 24-month prospective study, 22 patients with documented papillomavirus lesions elsewhere in the lower genital tract underwent biopsy of the urothelium of the urethra. These patients met the accepted criteria for urethral syndrome. The specimens were obtained under colposcopic control with small tissue biopsy forceps inserted through a modified Kelly air cystoscope. Polymerase chain reaction amplification and subsequent DNA primer evaluation failed to reveal the presence of papillomavirus infection in 20 of the 22 patients. Differentiated squamous mucosa was found on morphologic studies from these biopsies in 18 instances (82%). This multicenter study was unable to document the presence of human papillomavirus infection of the proximal urethral vesical neck or bladder trigone.

The authors describe the implementation of a self-tuning regulator for the positioning of a direct-drive servo motor. The servo motor is a permanent magnet DC motor in which no gear reducer is used. The autotuning regulator consists of two major loops. The inner loop contains a feedback (proportional-derivative or proportional-integral-derivative) regulator with additional feedforward terms. The parameters of the regulator are adjusted by the outer loop, which contains an online parameter estimator. The estimated parameters are the load inertia and friction. This self-tuning regulator has been simulated with PC.MATLAB, and the results demonstrate the high performance of the scheme. The influence on the estimator of important factors such as noise, forgetting factor, and converter precision are evaluated. >

The authors present the results of a digital simulation of a smooth positioning system for a self-controlled permanent-magnet synchronous motor. The parameter estimation that is included in the controls is based only on the position feedback. The use of predictive control and parameter estimation enables fast, accurate, and nonoscillatory positioning of a directly driven load varying over a wide range. >

The authors present a hybrid controller that allows simultaneous force tracking in constrained directions and position tracking in unconstrained directions. The controller is an extension of a well-known adaptive position control scheme that exhibits remarkable performance in joint space. The hybrid controller is obtained by adding a commonly used force controller to the Cartesian space version of the adaptive position tracking controller. Analysis and simulation are used to evaluate the hybrid controller's ability to execute trajectories using force and position feedback. The application robot is a four-degree-of-freedom SCARA. >

The traditional approach to understanding early diagenetic processes in sediments has generally been to analyze pore water and solid phases from a single core on depth scales of centimeters. The resulting data is then modeled using the approximations of lateral homogeneity and steady-state conditions. However, the continuing advancement of the field of benthic biogeochemistry and development of new microelectrode analytic techniques are clearly demonstrating that in many sedimentary environments a more sophisticated approach to measure the spatial and temporal variability is necessary. Although no one approach is appropriate for all situations, a scaling method is presented, with examples, in this study for determining appropriate sampling intervals in time and space that has considerable utility for investigating early changes in sediment geochemistry in complex natural systems. This approach is derived from scaling techniques that have been developed by physical oceanographers for the study of processes in the water column where many analogous sampling problems are encountered.

A direct adaptive controller for trajectory tracking of high-speed robots such as a direct-drive SCARA robot is presented. In this robot, nonlinear effects due to centrifugal, Coriolis, and gravity forces are more important than friction forces. The control law of the adaptive scheme consists in a PD regulator and feedforward compensation of full dynamics. The feedforward terms are adjusted by an adaptation law so that the steady-state position errors are zero. The regulator gain matrix can be fixed or time-varying; in the latter case, the adaptive scheme becomes similar to the computed torque scheme. However, with the adaptive controller, joint accelerations measurement is not required and no inversion of the estimated mass matrix is involved. The tracking performances of the controller applied to a 4 d.o.f. SCARA robot are illustrated by a digital simulation. >

A new approach to drilling and completing long horizontal open-hole gravel packed intervals in a subsea West African Field development using oil-based drilling fluid throughout the well trajectory has resulted in significant cost savings and increased well productivity. Without this successful change and the use of horizontal wells, many of the subsea wells drilled in 50’- 2200’ of water would have been uneconomical. Previously, the upper, non-pay portions of the subsea wells were drilled with oil-based drilling fluids while the horizontal reservoir sections were drilled with a sized calcium carbonate-polymer drill-in fluid. To remove filter cake damage following gravel packing, acidization of the entire horizontal interval was required. Operations associated with changing the drill-in fluid and acidizing added significant cost and complexity to well completions. In addition to higher completion costs, the water-based drill-in fluid reduced drilling flexibility in the target channel sands resulting in more sidetracks and in some cases less than optimal completed intervals. It was recognized that continued use of oil-based fluids through the reservoir section would overcome these limitations, however, the damage potential of using oil-based drilling fluids prior to gravel packing was unknown. This paper presents the development, application, and results of the new drilling and completion practice for horizontal, gravel-packed, oil wells offshore West Africa. Large and small scale laboratory testing will be described, including formation damage core testing, development of displacement and cleanup procedures and fluid compatibility. Integration of technical advisors, laboratory personnel, and field operations led to rapid implementation of the new technologies. A pilot hole test was conducted in the field followed by successful application in three wells. The new procedures have resulted in improved drilling, considerable cost savings, and observed PI’s 2–3 times higher than similar wells using water-based drill-in fluids.

Lower levels of plasma total cholesterol have been observed during severe infection, but it is not known whether the minor illnesses encountered in the general population are also associated with reduced cholesterol. This paper examines the relation between minor illness and plasma lipids, using 7- and 10-year follow-up data from more than 3,000 generally healthy participants in the Coronary Artery Risk Development in Young Adults (CARDIA) Study. At both 7 and 10 years, approximately 8.5% of participants stated they had been "ill with cold, flu, fever, or vomiting in the past 24 hours." In both cross-sectional and longitudinal analyses, the plasma total cholesterol was about 5 mg/dl lower (p0.006) and high density lipoprotein cholesterol about 1.2 mg/dl lower (p0.12) in those who reported minor illness than in those who did not. Plasma triglycerides did not vary with minor illness. The authors conclude that reductions in plasma total, low density, and high density lipoprotein cholesterol mark an acute phase response even during minor illness. These reductions may bias surveys over a limited geographic area during a short period because the proportion with minor illness may vary locally. Because this effect should be stronger with more precise illness diagnosis, clinicians should avoid making measurements for cholesterol management when illness may alter plasma lipid levels and the resulting decisions.

Technetium-99m-teboroxime (CardioTec) is a promising new myocardial perfusion imaging agent. The purposes of this study were to define teboroxime clearance kinetics in normal and flow-restricted myocardium over a 1-hr period and to determine whether teboroxime kinetics are useful in detecting myocardial hyperperfusion. Accordingly, the circumflex arteries of 23 dogs were stenosed. By using miniature cadmium-telluride radiation detectors, myocardial teboroxime activities were continuously monitored in both the control and the stenosed zones. Myocardial clearance of teboroxime was modeled and found to be biexponential over 1 hr. A significant difference in myocardial clearance between the normal and stenosed zones (t1/2 = 4.5 +/- 0.9 min versus 10.2 +/- 2.6 min, respectively; p0.05) was observed for the first exponential phase (the first 5 min following initial uptake), but not for the second exponential phase (t1/2 = 160.7 +/- 35.9 min versus 140.4 +/- 27.4 min, respectively; p = ns). One hour fractional teboroxime blood clearance was 0.95 +/- 0.03, with most of the clearance occurring during the first 4 min. Gamma camera images of excellent quality demonstrated an initial defect with significant quantitative differential clearance over 1 hr. Thus, there are two phases of myocardial teboroxime clearance. During the early exponential clearance phase, teboroxime kinetics at rest may be able to differentiate between normal and hypoperfused myocardium.

To quantitatively define the coronary vascular bed in the 21-day-old rat fetus with gestational normoxia and hypoxia; to determine if maternal supplemental oxygen and/or oxygen-carrying perfluorocarbons (PFCs) influence development of coronary vessels; and to compare the results using purified and unpurified PFC treatment.Unilateral uterine artery ligation was introduced on gestational day 17 in pregnant animals. Control fetuses were from unligated uterine horns. Experimental intervention occurred during gestational days 17 to 21, with fetuses recovered on day 21. Developing coronary vessels were analyzed quantitatively via light microscopy.Pregnant Sprague Dawley rats.Following ligation, pregnant rats received no further treatment, supplemental oxygen inhalation alone, or daily intravenous purified PFC treatment, with or without supplemental oxygen.Hypoxia caused an increase in resorptions (P less than 0.001), and decreased fetal body weight (P less than 0.001) and heart weight (P less than 0.05). Although the area occupied by developing coronary vessels (sinusoids) was substantially increased, maturation was unchanged. Oxygen supplementation alone did not appreciably influence fetal resorptions or body weight in ligated horns, but did increase fetal heart weight. Sinusoidal area decreased (P less than 0.01), with no effect on sinusoidal maturity. Purified PFC treatment did not alter maternal weight gain or fetal body weight, and moderately decreased resorptions in ligated horns. Fetal heart weight was augmented with purified perflurochemical, while unpurified perfluorochemical treatment diminished heart weight. Both PFC emulsions substantially decreased sinusoidal area.Perflurocarbon treatment associated with supplemental oxygen is capable of improving the hypoxic effects on fetal heart and coronary vessel development if the emulsion used is appropriately purified.

Many children have struggled to cope with the traumatic experiences brought about by hurricanes Katrina and Rita. This article recounts how the authors intervened in the lives of children and families after the storms.

The use of incremental instead of absolute encoders for servomotor control involves the design of an interface to feed bidirectional counters. A robust method that the authors have implemented with a minimum number of components is presented. The method is also suitable for an all-software version that could be used in microcontroller applications with low CPU overhead. >

To probe the effects of N-glycosylation on the fibrin-dependent plasminogenolytic activity of tissue-type plasminogen activator (t-PA), we have expressed a human recombinant t-PA (rt-PA) gene in Chinese hamster ovary (CHO) cells and in a murine C127 cell line. The resulting rt-PA glycoproteins were isolated and their associated N-linked oligosaccharide structures determined by using a combination of high-resolution Bio-Gel P-4 gel filtration chromatography, sequential exoglycosidase digestion, and methylation analysis. The results show that CHO rt-PA is N-glycosylated differently from murine C127 derived rt-PA. Further, both rt-PA's are N-glycosylated differently from t-PA derived from a human colon fibroblast and the Bowes melanoma cell line (Parekh et al., 1989), confirming that N-glycosylation of the human t-PA polypeptide is cell-type-specific. Both CHO and murine rt-PA were fractionated on lysine-Sepharose chromatography. The N-glycosylation of the major forms was analyzed and their fibrin-dependent plasminogenolytic activity determined by using an indirect amidolytic assay with Glu-plasminogen and a chromogenic plasmin substrate. The results suggest that the various forms of rt-PA differ from one another with respect to the kinetics of their fibrin-dependent activation of plasminogen. Together, these data support the notion (Wittwer et al., 1989) that N-glycosylation influences the fibrin-dependent catalytic activity of t-PA and that t-PA when expressed in different cell lines may consist of kinetically and structurally distinct glycoforms.