Final Chamber Research Articles

Drawing potential of fiber metal laminates in hydromechanical forming: A numerical and experimental study

It is known that fiber metal laminates as one of hybrid materials with thin metal sheets and fiber/resin layers have limited formability in conventional forming methods. This paper presents an experimental and numerical study for drawability of glass fiber-reinforced aluminum laminates under hydromechanical drawing technique. Fiber metal laminates comprised of a layer of woven glass fiber-reinforced prepreg, sandwiched between two layers of aluminum alloy. In order to produce fiber metal laminates, the laminates were subjected to a sufficient squeezing pressure under a controlled heating time and temperature by using a hydraulic hot press. A hydromechanical tooling equipped with blank-holder force and fluid pressure control system was used to form the initial circular fiber metal laminate blank. Finally, the effect of parameters such as pre-bulging pressure, final chamber pressure, and drawing ratio on process variables was evaluated. Also, the characteristic curve of hydromechanical drawing of fiber metal laminate i.e. chamber pressure in terms of drawing ratio was achieved by means of experimental tests and numerical simulations. The results showed that the maximum drawing ratio of defect-free fiber metal laminates, namely without any tearing, wrinkling, and delamination was obtained at pre-bulging and chamber pressure of 35 and 80 bar, respectively.

Comparison of δ18O analyses on individual planktic foraminifer (Orbulina universa) shells by SIMS and gas-source mass spectrometry

Abstract The oxygen isotope (δ18O) compositions of final chamber fragments of individual shells of the planktic foraminifer Orbulina universa were measured in situ via secondary ion mass spectrometry (SIMS) and by traditional gas-source mass spectrometry (GSMS) entailing acid digestion of sampled calcite. The paired SIMS-GSMS analyses were performed on final chamber fragments of fossil shells taken from the top of a sediment core (Holocene) as well as shells grown in laboratory culture. Multiple iterations of SIMS-GSMS analyses were conducted on final chamber fragments treated with a variety of cleaning protocols. The series of paired analyses yielded an average SIMS-GSMS δ18O offset (Δ18OSIMS-GSMS) of −0.9 ± 0.1‰ (±2 SE). The volume of material analyzed in 10-μm SIMS spots is ~105 times smaller than that analyzed by GSMS; hence, the extent to which these Δ18OSIMS-GSMS values represent real differences in analyte vs. instrumental factors remains unclear. Possible contributing factors to the SIMS-GSMS δ18O difference include sample-standard mismatch by SIMS, differences in standardization of SIMS and GSMS, and non-calcite contaminants in samples. Although the two datasets are consistently offset, SIMS values reproduce inter-shell δ18O variability delineated by shell fragment GSMS values. This strong positive covariance proved useful for bringing the two datasets into agreement (i.e. Δ18OSIMS-GSMS = 0), and confirms that SIMS-based foraminifer δ18O values record changes in calcification temperature and/or δ18O of seawater. Whether shells of foraminifer taxa with differing microcrystalline structures, chemical composition, and/or preservation histories register a similar Δ18OSIMS-GSMS value is a subject of ongoing testing.

Intracameral ketorolac concentration at the beginning and end of cataract surgery following preoperative topical ketorolac administration

PurposeTo evaluate the intracameral concentration of ketorolac tromethamine (ketorolac) at the beginning and end of cataract surgery following preoperative topical administration.SettingSanta Barbara Surgery Center, Santa Barbara, CA, USA.DesignThis was a pre–post, interventional, single-arm study.Patients and methodsPatients undergoing cataract extraction and lens replacement (CELR) were eligible. Written informed consent was obtained from 14 patients who were prescribed topical ophthalmic ketorolac according to the surgeon’s usual practice beginning the day prior to surgery. The surgeon withdrew 100 μL of aqueous humor from the operative eye immediately prior to the initial surgical incision and again just prior to final anterior chamber reinflation and wound closure. Ketorolac concentrations in the intracameral fluid samples were measured.ResultsThirteen of 14 patients used four doses of ketorolac the day prior to surgery as directed, and one patient used three doses. On the day of surgery, all 14 patients administered one drop of topical ketorolac on awakening and one drop after arriving at the surgery center. Preoperative ketorolac concentrations for the 12 patients from whom samples were collected ranged from 4.9 to 369 ng/mL. End-of-procedure sample concentrations ranged from <1.0 (the lower limit of quantification [LLOQ]) to 6.32 ng/mL, with eight of 12 patients having ketorolac levels below the LLOQ.ConclusionAt-home compliance with topical ketorolac was good, with 92.9% of patients using it as directed. Following CELR, levels of ketorolac in the aqueous humor were low, and 66.7% of patients had undetectable levels.

On the Taxonomic Identity of the Planktonic Foraminiferal Species Globorotalia Barisanensis Le Roy, 1939

Abstract Examination of the holotype of Globorotalia barisanensis Le Roy, 1939, has revealed that this species from the Middle Miocene of central Sumatra is non-keeled, contradicting the synonymizing of G. barisanensis with Globorotalia fohsi. Because the type sample is untraceable, we examined the available type specimens (holotype and eight paratypes), notes and data presented by previous researchers, and material from the near-topotype locality of Paragloborotalia siakensis, to clarify Le Roy's concept of G. barisanensis. Our investigation has revealed that the Middle Miocene of central Sumatra contains two different groups of globorotaliids: the Globorotalia menardii group and the G. fohsi group, and that G. barisanensis belongs to the latter. The paratypes examined belong to Globorotalia peripheroacuta and to forms transitional between G. peripheroacuta and Globorotalia praefohsi. The holotype, as described by Le Roy, is included in G. peripheroacuta as well, despite the observation that it differs from the paratypes in the abnormally inflated final chamber. In retrospect, the specimen selected as the holotype was an unfortunate choice as it has long been misinterpreted and used to denominate the earliest representatives of the G. fohsi group (viz. G. fohsi barisanensis) until G. barisanensis was reinterpreted as a junior synonym of G. fohsi based on a flawed redrawing of a fully keeled holotype of G. barisanensis. We conclude that Le Roy's concept of G. barisanensis was broad and may have included G. fohsi and Globorotalia peripheroronda as well. Remarkably, after 67 years of misinterpretation since Bolli (1950), G. barisanensis appears to be a valid name and a senior synonym of G. peripheroacuta. However, we recommend that it will be more practical to conserve the latter name, which is well established in the literature.

Link between light-triggered Mg-banding and chamber formation in the planktic foraminifera Neogloboquadrina dutertrei

The relationship between seawater temperature and the average Mg/Ca ratios in planktic foraminifera is well established, providing an essential tool for reconstructing past ocean temperatures. However, many species display alternating high and low Mg-bands within their shell walls that cannot be explained by temperature alone. Recent experiments demonstrate that intrashell Mg variability in Orbulina universa, which forms a spherical terminal shell, is paced by the diurnal light/dark cycle. Whether Mg-heterogeneity is also diurnally paced in species with more complex shell morphologies is unknown. Here we show that high Mg/Ca-calcite forms at night in cultured specimens of the multi-chambered species Neogloboquadrina dutertrei. Our results demonstrate that N. dutertrei adds a significant amount of calcite, and nearly all Mg-bands, after the final chamber forms. These results have implications for interpreting patterns of calcification in N. dutertrei and suggest that diurnal Mg-banding is an intrinsic component of biomineralization in planktic foraminifera.

A Customizable Chamber for Measuring Cell Migration.

Cell migration is a vital part of immune responses, growth, and wound healing. Cell migration is a complex process that involves interactions between cells, the extracellular matrix, and soluble and non-soluble chemical factors (e.g., chemoattractants). Standard methods for measuring the migration of cells, such as the Boyden chamber assay, work by counting cells on either side of a divider. These techniques are easy to use; however, they offer little geometric modification for different applications. In contrast, microfluidic devices can be used to observe cell migration with customizable concentration gradients of soluble factors1,2. However, methods for making microfluidics based assays can be difficult to learn. Here, we describe an easy method for creating cell culture chambers to measure cell migration in response to chemical concentration gradients. Our cell migration chamber method can create different linear concentration gradients in order to study cell migration for a variety of applications. This method is relatively easy to use and is typically performed by undergraduate students. The microchannel chamber was created by placing an acrylic insert in the shape of the final microchannel chamber well into a Petri dish. After this, poly(dimethylsiloxane) (PDMS) was poured on top of the insert. The PDMS was allowed to harden and then the insert was removed. This allowed for the creation of wells in any desired shape or size. Cells may be subsequently added to the microchannel chamber, and soluble agents can be added to one of the wells by soaking an agarose block in the desired agent. The agarose block is added to one of the wells, and time-lapse images can be taken of the microchannel chamber in order to quantify cell migration. Variations to this method can be made for a given application, making this method highly customizable.

A Customizable Chamber for Measuring Cell Migration

Cell migration is a vital part of immune responses, growth, and wound healing. Cell migration is a complex process that involves interactions between cells, the extracellular matrix, and soluble and non-soluble chemical factors (e.g., chemoattractants). Standard methods for measuring the migration of cells, such as the Boyden chamber assay, work by counting cells on either side of a divider. These techniques are easy to use; however, they offer little geometric modification for different applications. In contrast, microfluidic devices can be used to observe cell migration with customizable concentration gradients of soluble factors1,2. However, methods for making microfluidics based assays can be difficult to learn. Here, we describe an easy method for creating cell culture chambers to measure cell migration in response to chemical concentration gradients. Our cell migration chamber method can create different linear concentration gradients in order to study cell migration for a variety of applications. This method is relatively easy to use and is typically performed by undergraduate students. The microchannel chamber was created by placing an acrylic insert in the shape of the final microchannel chamber well into a Petri dish. After this, poly(dimethylsiloxane) (PDMS) was poured on top of the insert. The PDMS was allowed to harden and then the insert was removed. This allowed for the creation of wells in any desired shape or size. Cells may be subsequently added to the microchannel chamber, and soluble agents can be added to one of the wells by soaking an agarose block in the desired agent. The agarose block is added to one of the wells, and time-lapse images can be taken of the microchannel chamber in order to quantify cell migration. Variations to this method can be made for a given application, making this method highly customizable.

A user-centred design process of new cold-protective clothing for offshore petroleum workers operating in the Barents Sea.

Petroleum operations in the Barents Sea require personal protective clothing (PPC) to ensure the safety and performance of the workers. This paper describes the accomplishment of a user-centred design process of new PPC for offshore workers operating in this area. The user-centred design process was accomplished by mixed-methods. Insights into user needs and context of use were established by group interviews and on-the-job observations during a field-trip. The design was developed based on these insights, and refined by user feedback and participatory design. The new PPC was evaluated via field-tests and cold climate chamber tests. The insight into user needs and context of use provided useful input to the design process and contributed to tailored solutions. Providing users with clothing prototypes facilitated participatory design and iterations of design refinement. The group interviews following the final field test showed consensus of enhanced user satisfaction compared to PPC in current use. The final cold chamber test indicated that the new PPC provides sufficient thermal protection during the 60 min of simulated work in a wind-chill temperature of −25°C. Conclusion: Accomplishing a user-centred design process contributed to new PPC with enhanced user satisfaction and included relevant functional solutions.

Power-Augmented Steam Power Plant in a Cogeneration Cement Factory

AbstractCement factories have more potential to generate power from waste heat compared to other industries. Pressurized water flashing into wet steam at the end of a boiler’s economizer augments 15% of the plant’s output by increasing waste heat recovery compared to a regular steam power plant (Rankine cycle with a deaerator). A double-flash steam power plant is considered for theoretical demonstration of power augmentation with a cement factory’s waste heat recovery compared to a regular steam power plant. The hot water from the final flash chamber is used for feedwater heating and the saturated steam from the two flash chambers is supplied to the turbine. The current work is focused on selection of heat-recovery steam generator’s (HRSG) pressure and location of the high-pressure flasher (HPF) and low-pressure flasher (LPF). The flash fluid mass can be analyzed for better heat recovery as it influences the exhaust gas temperature. A low pressure has been recommended for the HRSG as it increases the heat...

Morphometric and stable isotopic differentiation of Orbulina universa morphotypes from the Cariaco Basin, Venezuela

Abstract Biometric characteristics of Orbulina universa (d'Orbigny) were used to differentiate two morphotypes present in sediment trap samples collected from the Cariaco Basin, Venezuela. Specifically, wall thickness and weight–area relationships were used to separate shells into thin (Mthin) and thick (Mthick) morphotypes. Mthick (mean thickness = 19–41 μm) comprises 75% of the total O. universa in these samples and has morphometric characteristics similar to that of the previously described Type I Caribbean genotype, whereas Mthin (mean thickness = 6–22 μm) is comparable to the Type III Mediterranean genotype. The flux of Mthick increases during periods of upwelling, whereas Mthin flux shows no systematic relationship with changing hydrographic regimes in the basin. The δ18O and δ13C of Mthick are on average 0.34‰ higher and 0.38‰ lower, respectively, than those of Mthin, suggesting that they calcify their final spherical chamber at different depths in the water column and/or differ in their vital effects on shell geochemistry. Additionally, the absolute offset in the stable isotopic compositions of the two morphotypes varies as a function of surface ocean stratification. During periods of upwelling, the δ18O and δ13C absolute offsets between Mthin and Mthick are on average − 0.15 and 0.25‰, whereas average δ18O and δ13C absolute offsets between these two morphotypes increase to − 0.54 and 0.41‰ during non-upwelling periods. We attribute the higher δ18O and δ13C offsets during non-upwelling periods to a difference in final chamber calcification depth and the combined effects of temperature (δ18O), δ13CDIC (δ13C), irradiance (δ13C) and [CO32 −] (δ18O and δ13C). These data provide field evidence that thin and thick morphotypes of O. universa likely experience different environmental conditions during the formation of their final chamber and, therefore, should not be combined in geochemical analyses for reconstructing past surface ocean conditions. Finally, we introduce a new proxy for reconstructing past surface ocean stratification changes via the use of Mthin and Mthick δ18O and δ13C offsets.

Comparative morpho-physiology of the metapleural glands of two Atta leaf-cutting ant queens nesting in clayish and organic soils

Queens of leaf-cutting ants found their nests singly, each consisting of a vertical tunnel and a final horizontal chamber. Because of the claustral mode of nest founding, the queen and/or her initial fungus garden are exposed to threats imposed by several soil pathogens, and the antibiotic secretions produced by their metapleural glands are considered a main adaptation to deal with them. Nests of two Atta leaf-cutting ant species, Atta vollenweideri and Atta sexdens rubropilosa, occur in different soil types, alfisols and oxisols. Their queens are known to excavate the initial nest in different soil horizons, clayish and organic, respectively, which differ in their fertility and associated microbiota. The aim of the present study was to comparatively investigate the morpho-physiology of the metapleural glands in queens of A. vollenweideri and A. sexdens rubropilosa, addressing the question whether the distinct selective pressure imposed by the microbiota in the two different soil types led to morpho-physiological differences in the metapleural glands that were consistent with their antiseptic function. The results revealed that metapleural glands of A. sexdens rubropilosa have a larger number of secretory cells, and consequently a higher production of antibiotic secretions, which may have been selected to allow nest founding at the superficial horizon of oxisols rich in organic matter and microorganisms. Glands of A. vollenweideri, on the contrary, presented fewer secretory cells, suggesting less production of antibiotic secretions. We argue that the excavation of deep founding nests in A. vollenweideri was primarily selected for during evolution to avoid the risk posed by flooding, and further hypothesize that a reduced number of cells in their metapleural glands occurred because of a weak pathogen-driven selective pressure at the preferred soil depth.

Traceability of Ground-Based Air-Temperature Measurements: A Case Study on the Meteorological Observatory of Moncalieri (Italy)

The robustness and reliability of any climatic assessment, especially those analyzing climate variability and change, depend crucially on the soundness of data and uncertainty associated with measurements. The metrological traceability to national standards of the measurements involved in climate change is a necessary step. This work describes the first attempt to define a fully traceable procedure for the calibration of air-temperature sensors in a special chamber manufactured for this purpose. The facility was designed to calibrate automatic weather stations by comparison with embedded reference standards traceable to temperature and pressure primary standards as maintained in a national metrology institute. The results shown in this paper were obtained through a prototype of the final calibration chamber. An application example of the calibration process is described for the temperature sensor working in the Meteorological Observatory of Moncalieri (Italy) of the Societa Meteorologica Italiana where a continuous climate record has been kept since 1865. As result, the data of the historical data series have now associated calibration uncertainties as contributions from the instrument capability, resolution, and calibration procedure adopted. Finally, the possibility of improving climatic analysis, for evaluating climatic trend, by applying calibration corrections to data recorded has been evaluated. The in situ calibration campaign and the resulting differences between the corrected and uncorrected data for the most important quantities considered in the climate analysis, the maximum, minimum, and mean temperatures, are reported. The analysis carried out on a one-year-long observation period shows that the application of the calibration function has an impact on the recorded data. The differences between corrected and uncorrected data are outside the expanded calibration uncertainty, and in a winter season, this effect is more evident.

Photothermal desorption of single-walled carbon nanotubes and coconut shell-activated carbons using a continuous light source for application in air sampling.

Many techniques exist to measure airborne volatile organic compounds (VOCs), each with differing advantages; sorbent sampling is compact, versatile, has good sample stability, and is the preferred technique for collecting VOCs for hygienists. Development of a desorption technique that allows multiple analyses per sample (similar to chemical desorption) with enhanced sensitivity (similar to thermal desorption) would be helpful to field hygienists. In this study, activated carbon (AC) and single-walled carbon nanotubes (SWNT) were preloaded with toluene vapor and partially desorbed with light using a common 12-V DC, 50-W incandescent/halogen lamp. A series of experimental chamber configurations were explored starting with a 500-ml chamber under static conditions, then with low ventilation and high ventilation, finally a 75-ml high ventilation chamber was evaluated. When preloaded with toluene and irradiated at the highest lamp setting for 4min, AC desorbed 13.9, 18.5, 23.8, and 45.9% of the loaded VOC mass, in each chamber configuration, respectively; SWNT desorbed 25.2, 24.3, 37.4, and 70.5% of the loaded VOC mass, respectively. SWNT desorption was significantly greater than AC in all test conditions (P = 0.02-<0.0001) demonstrating a substantial difference in sorbent performance. When loaded with 0.435mg toluene and desorbed at the highest lamp setting for 4min in the final chamber design, the mean desorption for AC was 45.8% (39.7, 52.0) and SWNT was 72.6% (68.8, 76.4) (mean represented in terms of 95% confidence interval). All desorption measurements were obtained using a field grade photoionization detector; this demonstrates the potential of using this technique to perform infield prescreening of VOC samples for immediate exposure feedback and in the analytical lab to introduce sample to a gas chromatograph for detailed analysis of the sample.

Potential Utilization of Catalyst for the Combustion of Wood in Households

The application of stricter requirements on combustion devices is placing more pressure especially on the manufacturers of such devices. They can improve the emission parameters of their products e.g. by primary technical measures (modification of combustion air supply, modification of combustion chamber, introduction of a final combustion chamber, etc.) or by secondary technical measures, e.g. introduction of a catalyst into the exhaust route.

Morphological variability of menardiform globorotalids in the Atlantic Ocean during Mid-Pliocene

Abstract The morphological variation of the planktonic foraminifera plexus of Globorotalia ( Menardella ) (Bandy, 1972) has been studied in a Pliocene time-slice at 3.2 Ma. Using a combination of size, linear shell measurements and shape analysis, an extended morphological protocol is explored in order to define morphological subgroups within the Menardella subgenus (Bandy, 1972). Isochronous samples at 3.2 Ma have been selected at five ODP/IODP Sites in the low latitude Atlantic Ocean, in which up to 600 specimens per sample have been oriented, imaged and analyzed using a new automated prototype for morphological analysis called AMOR. Multimodal size frequency distribution is related to the occurrence of several distinct populations. Three main ubiquitous populations of such menardellids are isolated, next to two additional biogeographically limited subgroups. These populations strongly differ in abundance and size. Using morphological classifiers, subpopulations are distinguished among these populations, leading to the establishment of seven different morphotypes informally named: MA, MB, MC1, MC2, MC3, SH1 and SH2. These morphotypes are assigned to formal species, i.e., MA corresponds to Globorotalia ( Menardella ) menardii , MB to G. ( M. ) limbata , SH1 to G. ( M. ) exilis , and SH2 to G. ( M. ) pertenuis . In contrast, the species G. ( M. ) multicamerata is interpreted as being composed of three distinct morphotypes, sharing a similar size range, but differing in shell morphology. Morphotype MC1 shows thin and elongated chambers, whereas morphotype MC2 is characterized by a thick and robust test. MC3 is inflated with a distinct flexure in the final chamber. Size differences are linked to variations in habitat temperature and oxygenation, with the exception of G. ( M. ) multicamerata morphotypes, which are probably adapted to a productivity gradient.

New insights into Troglotella incrustans WERNLI and FOOKES, 1992, a fascinating Upper Jurassic-Upper Cretaceous foraminifer

New data about the highly variable test morphology of the benthic foraminifer Troglotella incrustans WERNLI & FOOKES (Oxfordian-Lower Cenomanian) are presented, permitting an emended species/genus diagnosis. This concerns mainly the existence of a large final chamber with fistulose extensions that may follow the uniserial or the irregular-branching test part. The way of life of T. incrustans (cryptoendolithic vs. euendolithic) is discussed against the background of different existing models in the literature. The study is based on material (thin-sections and provided photographs) mainly from the Upper Jurassic of Austria, Italy, Romania, Ukraine, and also the type-locality of France.

Low-Resource Method for Extracting the Malarial Biomarker Histidine-Rich Protein II To Enhance Diagnostic Test Performance

We have demonstrated the utility of a self-contained extraction device for the selective isolation, purification, and concentration of the malaria diagnostic protein biomarker Plasmodium falciparum histidine-rich protein II (pfHRPII) from human plasma and whole blood. The extraction cassette consists of a small-diameter tube containing a series of preloaded processing solutions separated by mineral oil valves. Nickel(II) nitrilotriacetic acid-functionalized magnetic particles are added to a parasite-spiked sample contained within the loading chamber of the device for capture of pfHRPII. The biomarker-bound magnetic particles are then entrained by an external magnetic field and transported through three wash solutions. Processing removes sample interfering agents, and the biomarker target is concentrated in the final chamber for subsequent analysis. At parasitemias of 200 parasites/μL, purification and concentration of pfHRPII with extraction efficiencies in excess of 70% total protein target are achieved. The concentration of nonspecific protein interfering agents was reduced by more than 2 orders of magnitude in the final extracted sample without the need for hours of processing time and specialized laboratory equipment. We have demonstrated an application of this low-resource technology by coupling extraction and concentration of pfHRPII within the cassette to a commonly employed rapid diagnostic test. Sample preprocessing improved the visual limit of detection of this test by over 8-fold, suggesting that the combination of both low-resource technologies could prove to be useful in malaria eradication efforts.

The determination of nest depth in founding queens of leaf-cutting ants (Atta vollenweideri): idiothetic and temporal control

Leaf-cutting ant queens excavate a founding nest consisting of a vertical tunnel and a final horizontal chamber. Nest foundation is very time consuming, and colony success depends on the excavated depth. Although shallow nests may be energetically cheaper to dig, queens may be more exposed to the changing environment. Deeper chambers, in contrast, may be climatically more stable, but are more expensive to dig. We investigated the mechanisms underlying the control of nest depth in queens of the leaf-cutting ant Atta vollenweideri. We focused on the use of internal information for the control of nest depth, and therefore maintained the soil and environmental conditions invariant during the different laboratory experiments. We compared the tunnel lengths excavated by queens that were able to complete their nests earlier, faster or slower than under standard conditions. An earlier and faster nest completion was obtained by offering queens either pre-excavated tunnels of different lengths, soils at different temperatures, or soft sandy soils. A slower nest excavation was induced by offering queens harder dry soils, and by delaying the start of digging several days after the nuptial flight. Results indicate that the determination of nest depth was a regulated process involving the use of internal references: queens excavated their tunnels either until a particular depth was reached or for some predetermined length of time. Queens appear to monitor their movements while walking up und down the tunnel, and to compare this sensory information with a motor command that represents a preset tunnel length to be excavated before switching to chamber digging. In addition to this form of idiothetic control, results indicate that the elapsed digging time also feeds back onto the control system. It is argued that the determination of nest depth, i.e. the transition from tunnel to chamber digging, is initiated either after a preset tunnel length is reached, or as soon as a maximal time interval has elapsed, irrespective of the excavated tunnel length. A control system using both idiothetic and temporal information, as demonstrated in the present study, allows queens to flexibly react to different soil conditions, and therefore avoid excessive time and energy investments. Possible mechanisms underlying the control of chamber size are also discussed.

Geochemical assessment of the palaeoecology, ontogeny, morphotypic variability and palaeoceanographic utility of “Dentoglobigerina” venezuelana

To better understand the links between the carbon cycle and changes in past climate over tectonic timescales we need new geochemical proxy records of secular change in silicate weathering rates. A number of proxies are under development, but some of the most promising (e.g. palaeoseawater records of Li and Nd isotope change) can only be employed on such large samples of mono-specific foraminifera that application to the deep sea sediment core archive becomes highly problematic. “Dentoglobigerina” venezuelana presents a potentially attractive target for circumventing this problem because it is a typically large (> 355 μm diameter), abundant and cosmopolitan planktic foraminifer that ranges from the early Oligocene to early Pliocene. Yet considerable taxonomic and ecological uncertainties associated with this taxon must first be addressed. Here, we assess the taxonomy, palaeoecology, and ontogeny of “D.” venezuelana using stable isotope (oxygen and carbon) and Mg/Ca data measured in tests of late Oligocene to early Miocene age from Ocean Drilling Program (ODP) Site 925, on Ceara Rise, in the western equatorial Atlantic. To help constrain the depth habitat of “D.” venezuelana relative to other species we report the stable isotope composition of selected planktic foraminifera species within Globigerina , Globigerinoides , Paragloborotalia and Catapsydrax . We define three morphotypes of “D.” venezuelana based on the morphology of the final chamber and aperture architecture. We determine the trace element and stable isotope composition of each morphotype for different size fractions, to test the validity of pooling these morphotypes for the purposes of generating geochemical proxy datasets and to assess any ontogenetic variations in depth habitat. Our data indicate that “D.” venezuelana maintains a lower thermocline depth habitat at Ceara Rise between 24 and 21 Ma. Comparing our results to published datasets we conclude that this lower thermocline depth ecology for the Oligo-Miocene is part of an Eocene-to-Pliocene evolution of depth habitat from surface to sub-thermocline for “D.” venezuelana . Our size fraction data advocate the absence of photosymbionts in “D.” venezuelana and suggest that juveniles calcify higher in the water column, descending into slightly deeper water during the later stages of its life cycle. Our morphotype data show that δ 18 O and δ 13 C variation between morphotypes is no greater than within-morphotype variability. This finding will permit future pooling of morphotypes in the generation of the “sample hungry” palaeoceanographic records. ► A broad taxonomic concept can be applied to “ D.” venezuelana for proxy records. ► “D.” venezuelana maintained a lower thermocline depth habitat from 24 to 21 Ma. ► “D.” venezuelana descended through the water column during its life cycle. ► Possible instability of the tropical Atlantic thermocline during the early Miocene.

Physics-based models of ground deformation and extrusion rate at effusively erupting volcanoes

[1] We present a model of effusive silicic volcanic eruptions which relates magma chamber and conduit physics to time-dependent data sets, including ground deformation and extrusion rate. The model involves a deflating chamber which supplies Newtonian magma through a cylindrical conduit. Solidification is approximated as occurring at fixed depth, producing a solid plug that slips along its margins with rate-dependent friction. Changes in tractions acting on the chamber and conduit walls are used to compute surface deformations. Given appropriate material properties and initial conditions, the model predicts the full evolution of an eruption, allowing us to examine the dependence of observables on initial chamber volume, overpressure, and volatile content. Employing multiple data sets in combination with a physics-based model allows for better constraints on these parameters than is possible using kinematic idealizations. Modeling posteruptive deformation provides an improved constraint on the rate of influx into the magma chamber from deeper sources. We compare numerical results to analytical approximations and to data from the 2004–2008 eruption of Mount St. Helens. For nominal parameters the balance between magma chamber pressure and frictional resistance of the solid plug controls the evolution of the eruption, with little contribution from the fluid magma below the idealized crystallization depth. While rate-dependent plug friction influences the time-dependent evolution of the eruption, it has no control on the final chamber pressure or extruded volume.