High potential for weathering and climate effects of non-vascular vegetation in the Late Ordovician

It has been hypothesized that predecessors of today’s bryophytes significantly increased global chemical weathering in the Late Ordovician, thus reducing atmospheric CO2 concentration and contributing to climate cooling and an interval of glaciations. Studies that try to quantify the enhancement of weathering by non-vascular vegetation, however, are usually limited to small areas and low numbers of species, which hampers extrapolating to the global scale and to past climatic conditions. Here we present a spatially explicit modelling approach to simulate global weathering by non-vascular vegetation in the Late Ordovician. We estimate a potential global weathering flux of 2.8 (km3 rock) yr−1, defined here as volume of primary minerals affected by chemical transformation. This is around three times larger than today’s global chemical weathering flux. Moreover, we find that simulated weathering is highly sensitive to atmospheric CO2 concentration. This implies a strong negative feedback between weathering by non-vascular vegetation and Ordovician climate

Interferon β-1a in relapsing multiple sclerosis: four-year extension of the European IFNβ-1a Dose-C omparison Study

Background: Multiple sclerosis (MS) is a chronic disease requiring long-term monitoring of treatment. Objective: To assess the four-year clinical efficacy of intramuscular (IM) IFNb-1a in patients with relapsing MS from the European IFNb-1a Dose-C omparison Study. Methods: Patients who completed 36 months of treatment (Part 1) of the European IFNb-1a Dose-C omparison Study were given the option to continue double-blind treatment with IFNb-1a 30 mcg or 60 mcg IM once weekly (Part 2). Analyses of 48-month data were performed on sustained disability progression, relapses, and neutralizing antibody (NA b) formation. Results: O f 608/802 subjects who completed 36 months of treatment, 493 subjects continued treatment and 446 completed 48 months of treatment and follow-up. IFNb-1a 30 mcg and 60 mcg IM once weekly were equally effective for up to 48 months. There were no significant differences between doses over 48 months on any of the clinical endpoints, including rate of disability progression, cumulative percentage of patients who progressed (48 and 43, respectively), and annual relapse rates; relapses tended to decrease over 48 months. The incidence of patients who were positive for NAbs at any time during the study was low in both treatment groups. Conclusion: C ompared with 60-mcg IM IFNb-1a once weekly, a dose of 30 mcg IM IFNb-1a once weekly maintains the same clinical efficacy over four years

Toward catchment hydro-biogeochemical theories

Headwater catchments are the fundamental units that connect the land to the ocean. Hydrological flow and biogeochemical processes are intricately coupled, yet their respective sciences have progressed without much integration. Reaction kinetic theories that prescribe rate dependence on environmental variables (e.g., temperature and water content) have advanced substantially, mostly in well-mixed reactors, columns, and warming experiments without considering the characteristics of hydrological flow at the catchment scale. These theories have shown significant divergence from observations in natural systems. On the other hand, hydrological theories, including transit time theory, have progressed substantially yet have not been incorporated into understanding reactions at the catchment scale. Here we advocate for the development of integrated hydro-biogeochemical theories across gradients of climate, vegetation, and geology conditions. The lack of such theories presents barriers for understanding mechanisms and forecasting the future of the Critical Zone under human- and climate-induced perturbations. Although integration has started and co-located measurements are well under way, tremendous challenges remain. In particular, even in this era of "big data," we are still limited by data and will need to (1) intensify measurements beyond river channels and characterize the vertical connectivity and broadly the shallow and deep subsurface; (2) expand to older water dating beyond the time scales reflected in stable water isotopes; (3) combine the use of reactive solutes, nonreactive tracers, and isotopes; and (4) augment measurements in environments that are undergoing rapid changes. To develop integrated theories, it is essential to (1) engage models at all stages to develop model-informed data collection strategies and to maximize data usage; (2) adopt a "simple but not simplistic," or fit-for-purpose approach to include essential processes in process-based models; (3) blend the use of process-based and data-driven models in the framework of "theory-guided data science." Within the framework of hypothesis testing, model-data fusion can advance integrated theories that mechanistically link catchments' internal structures and external drivers to their functioning. It can not only advance the field of hydro-biogeochemistry, but also enable hind- and fore-casting and serve the society at large. Broadly, future education will need to cultivate thinkers at the intersections of traditional disciplines with hollistic approaches for understanding interacting processes in complex earth systems.This article is categorized under:Science of Water > Method

Processus électroniques dans le tellurure de fer γ

Le choix de la phase haute température du système fer-tellure pour une étude systématique de l’influence de la composition stœchiométrique sur les propriétés semiconductrices des composés d’éléments de transition a été déterminé par les 3 points suivants : son caractère semiconducteur semblait certain, le domaine d’homogénéité de la phase était large et, pour la première fois, un paramagnétisme de Pauli était signalé dans un cristal semiconducteur. Les mesures électriques et optiques s’accordent sur une hauteur de bande interdite de l’ordre de 0,6 eV, avec un niveau d’impuretés accepteur à 0,08 eV au-dessus de la bande de valence. Les mesures magnétiques, par contre, mettent en évidence le paramagnétisme de Pauli d’électrons d entièrement délocalisés, dont le nombre est minimum pour la composition Fe2Te3. La présence d’une bande 3 d possédant un minimum de densité d’états en son milieu et située dans la bande interdite rend compte de cette « composante métallique ». La délocalisation dans la bande 3 d est confirmée par l’étude du déplacement isomérique de la résonance Mössbauer du noyau Fe57 ainsi que celle de la chaleur spécifique électronique du cristal. La première met en évidence, pour la première fois, l’influence des électrons libres sur le déplacement isomérique. On discute enfin de la nature des liaisons interatomiques

Correlation between an early sexual debut, and reproductive health and behavioral factors: A multinational European study

Objective: To investigate whether women who made an early sexual debut differ from those with a later debut regarding genital signs and symptoms. Methods: The study included women who considered themselves gynecologically healthy and who attended 17 family planning centers in 13 European countries for contraceptive advice. There were 629 women who made their sexual debut at the age of 16 years or earlier (study population) and 927 women who had their first sexual intercourse at the age of 19 years or later (comparison group). Genital symptoms and signs, contraceptive use, smoking, and genital hygiene habits and previous genital infections were recorded on a structured patient record form. Detection of Chlamydia trachomatis was made by means of a polymerase chain reaction on first-void urine. The study was made, on average, 7-10 years after the women's sexual debut. Results: The mean age of first intercourse was 15.3 years for the study group versus 20.7 years for the control group (p < 0.001). The study population had significantly more symptoms, such as vaginal discharge and pruritus, and signs, such as abnormal discharge, erythema of the vaginal mucosa and lower genital tract infections, than the comparison group. Twice as many women in the study group were smokers and there was a ten-fold increase among these subjects of using low-pH solutions for genital hygiene. The prevalence of C. trachomatis infection did not differ between the two groups (p = 0.22). Conclusion: Age at first intercourse is not only a predictor of sexual risk behavior, but also a predictor, regarding both signs and symptoms, of future gynecological problems

Modelled glacial and non-glacial HCO3-, Si and Ge fluxes since the LGM: little potential for impact on atmospheric CO2 concentrations and a potential proxy of continental chemical erosion, the marine Ge:Si ratio

The runoff and riverine fluxes of HCO3-, Si and Ge that arise from chemical erosion in non-glaciated terrain are modelled at 6 time steps from the Last Glacial Maximum (LGM) to the present day. The fluxes that arise from the Great Ice Sheets are also modelled. Terrestrial HCO3- fluxes decrease during deglaciation, largely because of the reduction in the area of the continental shelves as sea level rises. The HCO3- fluxes, and the inferred consumption of atmospheric CO2 are used as inputs to a carbon cycle model that estimates their impact on atmospheric CO2 concentrations (atmsCO2). A maximum perturbation of atmsCO2 by ~5.5 ppm is calculated. The impact of solutes from glaciated terrain is small in comparison to those from non-glaciated terrain. Little variation in terrestrial Si and Ge fluxes is calculated (<10%). However, the global average riverine Ge:Si ratio may be significantly perturbed if the glacial Ge:Si ratio is high. At present, variations in terrestrial chemical erosion appear to have only a reduced impact on atmsCO2, and only little influence on the global Si and Ge cycle and marine Ge:Si ratios during deglaciation