Dinoflagellate contributions to the deep sea

For the first time, sediment trap samples from several depths in the deep sea were analyzed to estimate both the types and amounts of mineral contributed by dinoflagellates to the deep sea sediment flux. Thecal remains of dinoflagellate motile stages were almost entirely restricted to the upper few hundred meters of the water column, supporting the generally accepted explanation of their absence in the fossil record (i.e., theca are composed of cellulosic material which is destroyed before they may be incorporated into bottom sediments). The main contribution to the sediment flux is composed of resting cysts routinely produced in the life cycles of just a few of the more obscure oceanic dinoflagellates, probably species of Scrippsiella or Ensiculifera. The cyst assemblage sedimenting out from plankton at present is overwhelmingly dominated by a few small calcareous types (up to several thousands/m2/day). If not dissolved, these may accumulate in paleontologically significant amounts in bottom sediments to give the most representative fossil record of oceanic dinoflagellates. "Oceanic assemblages" of organic-walled cysts from Recent deep-sea sediments previously described by palynologists probably represent long distance transport from more coastal regions rather than oceanic dinoflagellate production

Bioleaching of Transition Metals From Limonitic Laterite Deposits and Reassessment of the Multiple Roles of Sulfur-Oxidizing Acidophiles in the Process

Using acidophilic bacteria to catalyze the reductive dissolution of oxidized minerals is an innovative process that facilitates the extraction of valuable base metals (principally cobalt and nickel) from limonites, which are otherwise often regarded as waste products of laterite mining. The most appropriate conditions required to optimize reductive mineral dissolution are unresolved, and the current work has reassessed the roles of Acidithiobacillus spp. in this process and identified novel facets. Aerobic bio-oxidation of zero-valent sulfur (ZVS) can generate sufficient acidity to counterbalance that consumed by the dissolution of oxidized iron and manganese minerals but precludes the development of low redox potentials that accelerate the reductive process, and although anaerobic oxidation of sulfur by iron-reducing species can achieve this, less acid is generated. Limited reduction of soluble iron (III) occurs in pure cultures of Acidithiobacillus spp. (Acidithiobacillus thiooxidans and Acidithiobacillus caldus) that do not grow by iron respiration. This phenomenon (“latent iron reduction”) was observed in aerated cultures and bioreactors and was independent of electron donor used (ZVS or hydrogen). Sufficient ferrous iron was generated in the presence of sterilized hydrophilic sulfur (bio-ZVS) to promote the effective reductive dissolution of Mn (IV) minerals in limonite and the solubilization of cobalt in the absence of viable acidophiles

Human prostaglandin EP3 receptor isoforms show different agonist-induced internalization patterns

AbstractThe human prostaglandin EP3 receptor comprises eight isoforms that differ in carboxyl-tail. We show here that the isoforms are trafficked differently. When expressed in HEK293 cells, the isoforms located to the cell surface, although a fraction of some remained in the cell. Upon prostaglandin E2 stimulation, EP3.I internalized almost completely, EP3.II, EP3.V, EP3.VI and EP3.f internalized to a lesser extent and EP3.III and EP3.IV did not internalize. Both EP3.I and EP3.f internalized with β-arrestin and internalization were blocked by a dominant negative form of Eps15, a clathrin-associated protein. Although EP3.II internalized, β-arrestin did not translocate with the receptor and internalization was not blocked by mutant Eps15. EP3.V and EP3.VI internalized to discrete areas of the cell with β-arrestin

GEM/POPs: a global 3-D dynamic model for semi-volatile persistent organic pollutants ? Part 2: Global transports and budgets of PCBs

International audienceGlobal transports and budgets of three PCBs were investigated with a 3-D dynamic model for semi-volatile persistent organic pollutants ? GEM/POPs. Dominant pathways were identified for PCB transports in the atmosphere with a transport flux peaking below 8 km for gaseous and 14 km for particulate PCB28, and peaking below 4 km for gaseous and 6 km for particulate PCB180. The inter-continental transports of PCBs in the Northern Hemisphere (NH) are dominated in the zonal direction with their route changes regulated seasonally by the variation of westerly jet. The transport pathways from Europe and North Atlantic contributed the most PCBs to the Arctic. Inter-hemispheric transports of PCBs originated from the regions of Europe, Asia and North America in three different flow-paths, accompanying with easterly jet, Asian monsoon winds and trade winds. PCBs from the Southern Hemisphere (SH) could also be exported into the NH. According to the PCB emissions of year 2000, Europe, North America and Asia are the three largest sources of the three PCBs, contributing to the global background concentrations in the atmosphere, soil and water. Globally, PCB28 in soil and water has become a comparable source to the anthropogenic emissions while heavier PCBs such as PCB153 and 180 are still transporting into soil and water. For all three congeners, particulate PCBs are concentrated in the higher levels than gaseous PCBs. More than half of the particulate PCB28 could reach up to the stratosphere, while most of the heavier counter-parts (PCB153 and PCB180) are stored in the troposphere including boundary layer with more than 99% gaseous PCB180 below 6 km

Toward Defining Literacy

Literacy is a topic much on the public\u27s mind these days. It is one of those subjects on which all laypersons think they are experts. When it comes time, however, to establish measures of illiteracy rates or to set policies, it becomes apparent that we know less than we thought we did. It is small comfort to know that specialists also have their differences

An in vivo analysis of safe laparoscopic grasping thresholds for colorectal surgery

Background Analysis of safe laparoscopic grasping thresholds for the colon has not been performed. This study aimed to analyse tissue damage thresholds when the colon is grasped laparoscopically, correlating histological changes to mechanical compressive forces. Methods An instrumented laparoscopic grasper was used to measure the forces applied to porcine colon, with data captured and plotted as a force–time (f–t) curve. Haematoxylin and eosin histochemistry of tissue subjected to 10, 20, 40, 50 and 70 N for 5, 30 and 60 s was performed, and the area of colonic circular and longitudinal muscle was compared in grasped and un-grasped regions. The area under the f–t curve was calculated as a measure of the accumulated force applied, known as the force–time product (FTP). Results FTP ranged from 55.7 to 3793 N.s. Significant differences were observed between the muscle area of the grasped and un-grasped regions in both longitudinal and circular muscle at 50 N and above for all grasping times. For the longitudinal muscle, significant differences were observed between grasped and un-grasped areas at 20 N force for 30 s (mean difference = 59 mm2, 95% CI 41–77 mm2, P = 0.04), 20 N force for 60 s (mean difference = 31 mm2, 95% CI 21.5–40.5 mm2, P = 0.006) and 40 N force for 30 s (mean difference 37 mm2, 95% CI 27–47 mm2, P = 0.006). Changes in histology correlated with mechanical forces applied to the longitudinal muscle at a FTP over 300 N s. Conclusions This study characterizes the grasping forces that result in histological changes to the colon and correlates these with a mechanical measurement of the applied force. The findings will contribute to the development of smart laparoscopic graspers with active constraints to prevent excessive grasping and tissue injury

Textile composite fuselage structures development

Phase 2 of the NASA ACT Contract (NAS1-18888), Advanced Composite Structural Concepts and Materials Technology for Transport Aircraft Structures, focuses on textile technology, with resin transfer molding or powder coated tows. The use of textiles has the potential for improving damage tolerance, reducing cost and saving weight. This program investigates resin transfer molding (RTM), as a maturing technology for high fiber volume primary structures and powder coated tows as an emerging technology with a high potential for significant cost savings and superior structural properties. Powder coated tow technology has promise for significantly improving the processibility of high temperature resins such as polyimides

The rheology of carbon black dispersions

The interaction of carbon black with an acrylic resin in aqueous solution has been investigated by rheology. Two carbon blacks Raven L and Raven M, with similar particle size and surface characteristics but quite different particle morphologies, have been examined. In the absence of polymer, stable aqueous dispersions could not be obtained. Stable dispersions could be obtained however upon addition of polymer to a level corresponding to a ratio of 50mg of polymer per 13m2 of surface area (i.e.l5wt% particles). These stable dispersions exhibit flow typical of concentrated dispersions - Newtonian behaviour up to some apparent 'yield' or critical value. Above which shear thinning is observed. This critical stress increases with increasing polymer concentration. At low polymer concentrations, the dispersions are predominantly viscous at low shear stresses. The phase angle decreases significantly over a narrow shear stress range and the rheology tends to more elastic behaviour. At higher shear stresses, the dependence on particle morphology is weak. Furthermore, increasing the pH of the aqueous dispersions has little effect, but changing the adsorbent does alter the rheology somewhat. In addition to Raven L and Raven M, other carbon blacks were also investigated in which the surface chemistry had been modified by ozonolysis. In addition to aqueous systems, a selection of oil based systems have also been investigated. Here, four carbon blacks were used with a bitumen binder: the low-medium structured fine particle (Raven L), the medium-high structured fine particle (Raven M), a low-medium structured coarse particle (N772) and a medium-high structured coarse particle (N660). For these systems, the rheology and the dispersion colour properties have been investigated. Finally, a rheology study on the effect of bimodal dispersions was undertaken

Modeling sea-salt aerosols in the atmosphere: 2. Atmospheric concentrations and fluxes

Atmospheric sea-salt aerosol concentrations are studied using both long-term observations and model simulations of Na+ at seven stations around the globe. Good agreement is achieved between observations and model predictions in the northern hemisphere. A stronger seasonal variation occurs in the high-latitude North Atlantic than in regions close to the equator and in high-latitude southern hemisphere. Generally, concentrations are higher for both boreal and austral winters. With the model, the production flux and removal flux at the atmosphere-ocean interface was calculated and used to estimate the global sea-salt budget. The flux also shows seasonal variation similar to that of sea-salt concentration. Depending on the geographic location, the model predicts that dry deposition accounts for 60–70% of the total sea-salt removed from the atmosphere while in-cloud and below-cloud precipitation scavenging accounts for about 1% and 28–39% of the remainder, respectively. The total amount of sea-salt aerosols emitted from the world oceans to the atmosphere is estimated to be in the vicinity of 1.17×1016 g yr−1. Approximately 99% of the sea-salt aerosol mass generated by wind falls back to the sea with about 1–2% remaining in the atmosphere to be exported from the original grid square (300×300 km). Only a small portion of that exported (∼4%) is associated with submicron particles that are likely to undergo long-range transport