4,043 research outputs found

    Chalcophile Element Constraints on the Sulfur Content of the Martian Mantle

    Get PDF
    The sulfur content of the Martian mantle is critical to understanding volcanic volatiles supplied to the surface of Mars and possibly climate. In the absence of Martian mantle rocks, sulfur content of the mantle has been inferred from S contents of Martian meteorites or from sedimentary sulfate abundances. Estimates of the sulfur content of the Martian mantle vary from 390-2,000 ppm, all of which are higher than that of the terrestrial mantle (~250 ppm;). Residual sulfide in the Martian mantle controls the distribution of chalcophile elements during partial melting. In this study, we report new analyses of Martian meteorites, and use the incompatible behavior of As, Tl and Pb to infer the sulfide mode of the Martian mantle using a different set of assumptions than those of prior studies

    Key Issues Generated from the XI International Rangeland Congress 2021: Summary and Way Forward

    Get PDF
    The important issues, knowledge gaps, and evolving research approaches for the global rangelands are summarised in this review of submissions to the Joint XXIV International Grasslands and XI International Rangelands Congress (IGC/IRC). In the big picture, it is concluded that stand-alone studies of livestock production are becoming rare compared to that of the past International Rangelands Congresses (IRC). Rather, added effort is now being directed at understanding the fuller context of social-ecological systems (SESs) on rangelands in a quest to improve the prospects for sustainable resource management as well as the enhancement of human welfare. Although climate change is upon us, there was still a dearth of papers that dealt with broad- scaled climate-adaptation per se; opportunities to improve local drought response were the default topics here with a focus on implementing better drought early warning systems and integrating perspectives among producers and scientists. Invasive species challenges remain as prominent global concerns, and woody encroachment is viewed as a major contributor to rangeland degradation. Treatments to combat rangeland degradation can involve innovative layering methods incorporating grazing management and use of prescribed fire. While there is an important backdrop concerning ecosystem services from rangelands, research in this area is still in its infancy. Analysing trade-offs between production and conservation for services such as carbon sequestration loom large going forward. There were relatively few papers concerning wildlife, tourism, and associated issues; successes and challenges for natural resource conservancies were noted, in particular. These are topics that merit more creative research and development attention in the future. Some contributions highlighted the important issue of landscape conversion from rangelands to cultivation; in conjunction with human population growth, loss of such key resources can be very negative for wildlife and associated values. In terms of pastoralism and related sub-themes, while it was noted that the majority of studies now embrace SESs and integrated, participatory, action- oriented approaches, there is little effort to standardize methodologies. A focus on repeatable methods can help grow sustainability science on rangelands, and this is a challenge for research and outreach education. The volume of studies submitted overall indicated a decided numerical advantage for the Global South over the Global North. Why this is the case remains unclear, however. Disciplinary research traditions in wealthier nations may not yet provide the incentives needed to spur innovative SES work. Finally, policy makers are seen by many investigators as being ignorant of rangeland development issues. It is argued, however, that this view has not changed for 40 years. How to better engage policy makers in comprehensive SES projects is an important future goal. Policy makers themselves can then also become human research subjects in the overall process. Based on our review the future for IRC stakeholders is clear: Continue the expansion of interdisciplinary SES and action-based approaches and increase attention to climate-change adaptation/mitigation, ecosystem services, community-based development, human empowerment, market development, poverty mitigation, and creation of effective policy frameworks

    Tin Abundances Require that Chassignites Originated from Multiple Magmatic Bodies Distinct from Nakhlites

    Get PDF
    Meteorites from Mars lack field context but chemical and chronologic studies have revealed remarkable links between nakhlites and chassignites. A widely held consensus is that nakhlites and chassignites originated from a large, single differentiated flow or shallow intrusive [1-5]. An Ar-Ar study assumed multiple flows based on resolvable age differences between meteorites [6], but did not address the possibility of differential cooling in a large, shallowly emplaced intrusion [1]. REE abundances in pyroxenes from nakhlites and Chassigny led [7] to argue for derivation of these rocks from distinct magmas. Volatile abundances (F, Cl, OH) in chlorapatites indicated that the entire suite of nakhlites and chassignites experienced hydrothermal interaction with a single fluid supporting a single body origin [4]. The discovery of a new chassignite, NWA 8694, extended the Mg# range from 80-54, providing a closer link to nakhlites but revealed the petrological difficulty of fractionating a single body of liquid to yield a series of olivine cumulates with such a large Mg# range [8]. When mafic magmas are emplaced into the crust, crustal assimilation can impart distinct elemental signatures if the country rock has experienced sedimentary or hydrothermal processing [9]. In this work, we used Sn abundances of nakhlites and chassignites to show that these rocks were crystallized from distinct magma batches, providing vital contextual clues to their origin

    Colchicine for pericarditis

    Get PDF
    Pericarditis is the inflammation of the pericardium, the membranous sac surrounding the heart. Recurrent pericarditis is the most common complication of acute pericarditis, causing severe and disabling chest pains. Recurrent pericarditis affects one in three patients with acute pericarditis within the first 18 months. Colchicine has been suggested to be beneficial in preventing recurrent pericarditis

    First Scientific Results From The Infrared Astronomical Satellite (IRAS)

    Get PDF
    The Infrared Astronomical Satellite (IRAS) was successfully launched on 25 January 1983 and terminated science data acquisition on 22 November 1983. The in-orbit performance of the telescope has been described in two previous papers in these proceedings. A previous description of very preliminary scientific results from the mission has been given in these proceedings, while far more extensive reports have been given elsewhere. In this paper we will summarize some of the results obtained to date from the IRAS data. The work to date has sampled only a small fraction of the IRAS data; the study of the data from the IRAS survey will continue for many years to come
    • …
    corecore