Beschreibung: Phaeocystis globosa (Prymnesiophyceae) is an ecologically dominating phytoplankton species in many areas around the world. It plays an important role in both the global sulfur and carbon cycles, by the production of dimethylsulfide (DMS) and the drawdown of inorganic carbon. Phaeocystis globosa has a polymorphic life cycle and is considered to be a harmful algal bloom (HAB) forming species. All these aspects make this an interesting species to study the effects of increasing carbon dioxide (CO2) concentrations, due to anthropogenic carbon emissions. Here, the combined effects of three different dissolved carbon dioxide concentrations (CO2(aq)) (low: 4 µmol/kg, intermediate: 6-10 µmol/kg and high CO2(aq): 21-24 µmol/kg) and two different light intensities (low light, suboptimal: 80 µmol photons/m**2/s and high light, light saturated: 240 µmol photons/m**2/s) are reported. The experiments demonstrated that the specific growth rate of P. globosa in the high light cultures decreased with increasing CO2(aq) from 1.4 to 1.1 /d in the low and high CO2 cultures, respectively. Concurrently, the photosynthetic efficiency (Fv/Fm) increased with increasing CO2(aq) from 0.56 to 0.66. The different light conditions affected photosynthetic efficiency and cellular chlorophyll a concentrations, both of which were lower in the high light cultures as compared to the low light cultures. These results suggest that in future inorganic carbon enriched oceans, P. globosa will become less competitive and feedback mechanisms to global change may decrease in strength.

Beschreibung: A subseafloor replacement-style barite and sulfide occurrence was drilled in shallow waters at the Palinuro volcanic complex, the northernmost Aeolian arc volcano in the Tyrrhenian Sea, Italy. Using a lander-type drilling device, 11 successful drill holes yielded a total of 13.5 m of core from a sediment-filled depression located at a water depth of 630 to 650 m. The longest continuous drill core recovered consists of 4.84 m of massive to semimassive barite and sulfides with abundant late, native sulfur overprint. Seafloor observations suggest that the hydrothermal system associated with the formation of the subseafloor barite and sulfide ore zone is still active, although black smoker activity does not occur on the seafloor. The recovered drill core shows that the subseafloor deposit is zoned with depth. The top of the mineralized zone is comprised of a variably silicified vuggy barite-sulfide facies that shows notable polymetallic metal enrichment, while the deeper portion of the mineralized zone is dominated by massive pyrite having distinctly lower base and precious metal grades. Metal zonation of the barite and sulfide deposit is related to the evolution of the hydrothermal fluids in space and time. The barite cap and the massive pyrite present in the deeper portion of the mineralized zone appear to have formed early in the paragenesis. During the main stage of the mineralization, the barite cap was brecciated and cemented by a polymetallic assemblage of barite and pyrite with minor chalcopyrite and tetrahedrite, trace famatinite, and rare cinnabar. Lower temperature precipitates formed during the main stage of mineralization include sphalerite, galena, pyrite, opal-A, and barite, which are associated with traces of Pb-Sb-As sulfosalts such as bournonite-seligmannite, or semseyite. A distinct mineral assemblage of fine-grained anhedral enargite, hypogene covellite, chalcopyrite, and galena is commonly associated with colloform sphalerite, galena, and pyrite as a late phase of this main stage. Colloform pyrite and marcasite are the last sulfides formed in the paragenetic sequence. The deposit is interpreted to have formed from fluids having an intermediate-sulfidation state, although excursions to high- and very high sulfidation states are indicated by the presence of abundant enargite and hypogene covellite. Laser ablation and conventional sulfur isotope analyses show that pyrite formed close to the seafloor within the zone of polymetallic metal enrichment has a variable sulfur isotope composition (δ34S = −39 to +3‰), whereas a more narrow range is observed in the massive pyrite at depth (δ34S = −10 to 0‰). Similar variations were also documented for the late native sulfur overprint. Overall, the negative sulfur isotope ratios at depth, the intermediate- to very high sulfidation conditions during mineralization, and the abundance of native sulfur suggest contributions of magmatic volatiles to the mineralizing fluids from a degassing magma chamber at depth. Biological processes are interpreted to have played a major role during late stages of ore formation. The combination of a subseafloor replacement deposit with a massive to semimassive barite cap rock overlying massive pyrite, the intermediate- to high-sulfidation characteristics, and the strong biological influence on the late stages of mineralization are distinct from other modern seafloor massive sulfide deposits and represents a style of submarine mineralization not previously recognized in a modern volcanic arc environment. The barite and sulfide occurrence at Palinuro shares many characteristics with porphyry-related base metal veins and intermediate-sulfidation epithermal deposits, suggesting that metallogenic processes associated with arc-related magmatic-hydrothermal systems are not restricted to the subaerial environment.

Beschreibung: R. Bader, L. Sarraf-Zadeh, M. Peters, N. Moderau, H. Stocker, K. Kohler, M. J. Pankratz, and E. Hafen

Beschreibung: [1]  Previous studies suggest that a large part of the variability in the atmospheric ratio of 13 CO 2 / 12 Co 2 originates from carbon exchange with the terrestrial biosphere rather than with the oceans. Since this variability is used to quantitatively partition the total carbon sink, we here investigate the contribution of interannual variability (IAV) in biospheric exchange to the observed atmospheric 13 C variations. We use the SiBCASA biogeochemical model, including a detailed isotopic fractionation scheme, separate 12 C and 13 C biogeochemical pools, and satellite-observed fire disturbances. This model of 12 CO 2 and 13 CO 2 thus also produces return fluxes of 13 CO 2 from its differently aged pools, contributing to the so-called disequilibrium flux. Our simulated terrestrial 13 C budget closely resembles previously published model results for plant discrimination and disequilibrium fluxes, and similarly suggests that variations in C 3 discrimination and year-to-year variations in C 3 and C 4 productivity are the main drivers of their IAV. But the year-to-year variability in the isotopic disequilibrium flux is much lower (1 σ  = ± 1.5 PgC ‰ yr –1 ) than required (± 12.5 PgC ‰ yr –1 ) to match atmospheric observations, under the common assumption of low variability in net ocean CO 2 fluxes. This contrasts with earlier published results. It is currently unclear how to increase IAV in these drivers suggesting that SIBCASA still misses processes that enhance variability in plant discrimination and relative C 3 /C 4 productivity. Alternatively, 13 C budget terms other than terrestrial disequilibrium fluxes, including possibly the atmospheric growth rate, must have significantly more IAV in order to close the atmospheric 13 C budget on a year-to-year basis.

Beschreibung: The importance of the health of medical workforces is increasingly recognised, and poor health can compromise performance and adversely affect standards of care.1 As demands on doctors continue to...

Beschreibung: Interferon lambda 4 protein can be generated in IFNL4 -G carriers but not IFNL4 -TT homozygotes. We studied 890 anti–hepatitis C virus (HCV)–positive participants in the Women's Interagency HIV Study. Among blacks (n = 555), HCV was more often cleared for those with genotype IFNL4 -TT/TT (32.6%; odds ratio [OR], 3.59; P = 3.3 x 10 –5 ) than IFNL4 -TT/G (11.3%; OR, 0.95; P = .86) or IFNL4 -G/G (11.9%; referent). Pooling these data with published results in blacks (n = 1678), ORs were 3.84 ( P = 8.6 x 10 –14 ) for IFNL4 -TT/TT and 1.44 ( P = .03) IFNL4 -TT/G, and the area under the curve was 0.64 for IFNL4 -G genotype and 0.61 for rs12979860 ( IL28B ). IFNL4 -G is strongly associated with impaired spontaneous HCV clearance.

Beschreibung: Background.  Few studies have examined the relationship of human immunodeficiency virus (HIV) monoinfection and its associated perturbations with liver fibrosis. Methods.  Using multivariable linear regression, we examined the demographic, behavioral, metabolic and viral factors associated with transient elastography–measured liver stiffness in 314 participants (165 HIV positive/hepatitis C virus [HCV] negative, 78 HIV positive/HCV positive, 14 HIV negative/HCV positive, 57 HIV negative/HCV negative) in the Women's Interagency HIV Study. Results.  Compared with HIV negative/HCV negative women, HIV positive/HCV positive women had higher median liver stiffness values (7.1 vs 4.4 kPa; P 〈 .001); HIV positive/HCV negative and HIV negative/HCV negative women had similar liver stiffness values (both 4.4 kPa; P = .94). HIV/HCV coinfection remained associated with higher liver stiffness values (74% higher; 95% confidence interval [CI], 49–104) even after multivariable adjustment. Among HCV positive women, waist circumference (per 10-cm increase) was associated with 18% (95% CI, 7.5%–30%) higher liver stiffness values after multivariable adjustment; waist circumference showed little association among HIV positive/HCV negative or HIV negative/HCV negative women. Among HIV positive/HCV negative women, history of AIDS (13%; 95% CI, 4% –27%) and HIV RNA (7.3%; 95% CI, 1.59%–13.3%, per 10-fold increase) were associated with greater liver stiffness. Conclusions.  HCV infection but not HIV infection is associated with greater liver stiffness when infected women are compared with those with neither infection. Our finding that waist circumference, a marker of central obesity, is associated with greater liver stiffness in HIV/HCV-coinfected but not HIV-monoinfected or women with neither infection suggests that in the absence of HCV-associated liver injury the adverse effects of obesity are lessened.

Beschreibung: Author(s): A. J. M. Giesbers, K. Uhlířová, M. Konečný, E. C. Peters, M. Burghard, J. Aarts, and C. F. J. Flipse We show ferromagnetic properties of hydrogen-functionalized epitaxial graphene on SiC. Ferromagnetism in such a material is not directly evident as it is inherently composed of only nonmagnetic constituents. Our results nevertheless show strong ferromagnetism with a saturation of 0.9 μ B /hexagon proje... [Phys. Rev. Lett. 111, 166101] Published Wed Oct 16, 2013