Microbial Degradation of the Leachable and Lignocellulosic Components of Leaves and Wood from \u3cem\u3eRhizophora mangle\u3c/em\u3e in a Tropical Mangrove Swamp

Preparations of uniformly [14C] labeled mangrove leaves and specifically radiolabeled [14C-lignin] lignocelluloses and [14C -polysaccharide]lignocelluloses from mangrove leaves and wood were used in experiments to determine the microbial rates of mineralization of the leachable and lignocellulosic components of mangrove detritus in aerobic and anaerobic sediments of a tropical mangrove swamp. The bulk of the leachable fraction from mangrove leaves was mineralized relatively rapidly and was assimilated into microbial biomass with high efficiency (30 %). In contrast, rates of mineralization of the lignocellulosic component of mangrove leaves and wood were 10fold lower than mineralization rates of the leachable fraction. The polysaccharide component of the lignocelluloses was mineralized at rates 2 times higher than rates of mineralization of the lignin component, indicating that mangrove detritus becomes relatively enriched in lignin-derived carbon with time. Anaerobic rates of mineralization of the leachable and lignocellulosic components of mangrove leaves and wood were 10 to 30 times lower than respective aerobic mineralization rates, suggesting a very long residence time for mangrove detritus in anaerobic sediments. Comparison of the rates of degradation of mangrove detritus in sediments from a mangrove swamp and a salt marsh demonstrated that the lignocellulolytic potential in sediments of the two marine ecosystems are similar, but that lignocellulose from mangroves is less biodegradable than lignocellulose from the salt-marsh plants, Spartina alterniflora and Juncus roemerianus

Error Mitigation of Point-to-Point Communication for Fault-Tolerant Computing

Fault tolerant systems require the ability to detect and recover from physical damage caused by the hardware s environment, faulty connectors, and system degradation over time. This ability applies to military, space, and industrial computing applications. The integrity of Point-to-Point (P2P) communication, between two microcontrollers for example, is an essential part of fault tolerant computing systems. In this paper, different methods of fault detection and recovery are presented and analyzed

Distribution of Terrestrially Derived Dissolved Organic Matter on the Southeastern United States Continental Shelf

Dissolved lignin-derived compounds in seawater indicate the presence of organic matter originating from vascular plants and therefore from terrestrial (upland and coastal marsh) ecosystems. We used a hydrophobic resin to concentrate lignin-rich humic substances and to determine concentrations of lignin oxidation products (vanillyl lignin phenols) for waters of the continental shelf of the southeastern U.S. Lignin phenol concentrations ranged from 0.05 to 4.2µg liter‒1 and accounted for 0.002–0.13% of the total dissolved organic carbon (DOC) pool in continental shelf waters. Dissolved lignin concentrations were generally highest near the shore and in those areas receiving greatest river and marsh discharge. Concentrations varied on both short-term (weekly) and seasonal time scales, however, indicating that the contribution of terrestrially derived dissolved organic matter to the C budget of the shelf is quite variable. Salinity (\u3e 31‰) was significantly correlated (negatively) with lignin phenol concentrations during three of four cruises, suggesting largely conservative mixing of lignin-derived material on the shelf In selected rivers and salt marshes contributing terrestrially derived organic matter to the continental shelf, lignin phenol C accounted for 0.14–1.0% of the DOC. A simple mixing model which assumes no biological or physical sinks of lignin-derived material during transport from terrestrial sources to the shelf predicts that an average of 6–36% of nearshore DOC derives from terrestrial ecosystems, depending on whether the terrestrial end-member (lignin source) is assumed to be a river or a salt marsh, while 5–26% of inner shelf DOC and 3–18% of mid- to outer-shelf DOC is of terrestrial origin

Coupled climate response to Atlantic Multidecadal Variability in a multi-model multi-resolution ensemble

North Atlantic sea surface temperatures (SSTs) underwent pronounced multidecadal variability during the twentieth and early twenty-first century. We examine the impacts of this Atlantic Multidecadal Variability (AMV), also referred to as the Atlantic Multidecadal Oscillation (AMO), on climate in an ensemble of five coupled climate models at both low and high spatial resolution. We use a SST nudging scheme specified by the Coupled Model Intercomparision Project’s Decadal Climate Prediction Project Component C (CMIP6 DCPP-C) to impose a persistent positive/negative phase of the AMV in the North Atlantic in coupled model simulations; SSTs are free to evolve outside this region. The large-scale seasonal mean response to the positive AMV involves widespread warming over Eurasia and the Americas, with a pattern of cooling over the Pacific Ocean similar to the Pacific Decadal Oscillation (PDO), together with a northward displacement of the inter-tropical convergence zone (ITCZ). The accompanying changes in global atmospheric circulation lead to widespread changes in precipitation. We use Analysis of Variance (ANOVA) to demonstrate that this large-scale climate response is accompanied by significant differences between models in how they respond to the common AMV forcing, particularly in the tropics. These differences may arise from variations in North Atlantic air-sea heat fluxes between models despite a common North Atlantic SST forcing pattern. We cannot detect a widespread effect of increased model horizontal resolution in this climate response, with the exception of the ITCZ, which shifts further northwards in the positive phase of the AMV in the higher resolution configuratio

Shallow and Deep Groundwater Moderate Methane Dynamics in a High Arctic Glacial Catchment

Glacial groundwater can mobilize deep-seated methane from beneath glaciers and permafrost in the Arctic, leading to atmospheric emissions of this greenhouse gas. We present a temporal, hydro-chemical dataset of methane-rich groundwater collected during two melt seasons from a high Arctic glacial forefield to explore the seasonal dynamics of methane emissions. We use methane and ion concentrations and the isotopic composition of water and methane to investigate the sources of groundwater and the origin of the methane that the groundwater transports to the surface. Our results suggest two sources of groundwater, one shallow and one deep, which mix, and moderate methane dynamics. During summer, deep methane-rich groundwater is diluted by shallow oxygenated groundwater, leading to some microbial methane oxidation prior to its emergence at the surface. Characterization of the microbial compositions in the groundwater shows that microbial activity is an important seasonal methane sink along this flow-path. In the groundwater pool studied, we found that potential methane emissions were reduced by an average of 29% (±14%) throughout the summer due to microbial oxidation. During winter, deep groundwater remains active while many shallow systems shut down due to freezing, reducing subsurface methane oxidation, and potentially permitting larger methane emissions. Our results suggest that ratios of the different groundwater sources will change in the future as aquifer capacities and recharge volumes increase in a warming climate

Circulating Fatty Acids and Prostate Cancer Risk: Individual Participant Meta-Analysis of Prospective Studies

Background: Individual studies have suggested that some circulating fatty acids are associated with prostate cancer risk, but have not been large enough to provide precise estimates of associations, particularly by stage and grade of disease. Methods: Principal investigators of prospective studies on circulating fatty acids and prostate cancer were invited to collaborate. Investigators provided individual participant data on circulating fatty acids (weight percent) and other characteristics of prostate cancer cases and controls. Prostate cancer risk by study-specific fifths of 14 fatty acids was estimated using multivariable-adjusted conditional logistic regression. All statistical tests were two-sided. Results: Five thousand and ninety-eight case patients and 6649 control patients from seven studies with an average follow-up of 5.1 (SD = 3.3) years were included. Stearic acid (18:0) was inversely associated with total prostate cancer (odds ratio [OR] Q5 vs Q1 = 0.88, 95% confidence interval [CI] = 0.78 to 1.00, P trend = .043). Prostate cancer risk was, respectively, 14% and 16% greater in the highest fifth of eicosapentaenoic acid (20:5n-3) (OR = 1.14, 95% CI = 1.01 to 1.29, P trend = .001) and docosapentaenoic acid (22:5n-3) (OR = 1.16, 95% CI = 1.02 to 1.33, P trend = .003), but in each case there was heterogeneity between studies (P = .022 and P < .001, respectively). There was heterogeneity in the association between docosapentaenoic acid and prostate cancer by grade of disease (P = .006); the association was statistically significant for low-grade disease but not high-grade disease. The remaining 11 fatty acids were not statistically associated with total prostate cancer risk. Conclusion: There was no strong evidence that circulating fatty acids are important predictors of prostate cancer risk. It is not clear whether the modest associations of stearic, eicosapentaenoic, and docosapentaenoic acid are causal

Towards an Economy of Higher Education

This paper draws a distinction between ways thinking and acting, and hence of policy and practice in higher education, in terms of different kinds of economy: economies of exchange and economies of excess. Crucial features of economies of exchange are outlined and their presence in prevailing conceptions of teaching and learning is illustrated. These are contrasted with other possible forms of practice, which in turn bring to light the nature of an economy of excess. In more philosophical terms, and to expand on the picture, economies of excess are elaborated with reference, first, to the understanding of alterity in the work of Emmanuel Levinas and, second, to the idea of Dionysian intensity that is to be found in Nietzsche. In the light of critical comment on some current directions in policy and practice, the implications of these ways of thinking for the administrator, the teacher and the student in higher education are explored

‘Lower than a Snake’s Belly’ : Discursive Constructions of Dignity and Heroism in Low-Status Garbage Work

In this paper, we consider how dignity is discursively constructed in the context of work dominated by physicality and dirt. Based on semi-structured interviews with garbage workers, our analysis considers how the deprivations they experience are cast through discourses intended to construct their individual and collective worth. We consider the manner in which dignity maybe denied to such workers through popular repudiations of individuality and status. We demonstrate how this positioning arises from contact with physical dirt, and associations with socially dirty work based on ascriptions of servility, abuse and ambivalence. We go on to consider how garbage workers respond to this positioning through discourses of ‘everyday heroism’. Heroism is evoked through three interrelated narratives that speaks to a particular type of masculinity. The first takes the form of a classic process of reframing and recalibration through which workers not only renegotiate their public position and status, but also point to the inherent value to be had in working with dirt as part of that which we identify as a process of ‘affirmation’. The second narrative arises from the imposition of favourable social and occupational comparisons that effectively elevate garbage collectors’ social position. The third discourse—and previously unobserved in respect of garbage work—centres on paternalistic practices of care. Combined, these discourses disrupt the generally held view that dirty work is antithetical to heroism and wounds dignity

A land-to-ocean perspective on the magnitude, source and implication of DIC flux from major Arctic rivers to the Arctic Ocean

Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 26 (2012): GB4018, doi:10.1029/2011GB004192.A series of seasonally distributed measurements from the six largest Arctic rivers (the Ob', Yenisey, Lena, Kolyma, Yukon and Mackenzie) was used to examine the magnitude and significance of Arctic riverine DIC flux to larger scale C dynamics within the Arctic system. DIC concentration showed considerable, and synchronous, seasonal variation across these six large Arctic rivers, which have an estimated combined annual DIC flux of 30 Tg C yr−1. By examining the relationship between DIC flux and landscape variables known to regulate riverine DIC, we extrapolate to a DIC flux of 57 ± 9.9 Tg C yr−1for the full pan-arctic basin, and show that DIC export increases with runoff, the extent of carbonate rocks and glacial coverage, but decreases with permafrost extent. This pan-arctic riverine DIC estimate represents 13–15% of the total global DIC flux. The annual flux of selected ions (HCO3−, Na+, Ca2+, Mg2+, Sr2+, and Cl−) from the six largest Arctic rivers confirms that chemical weathering is dominated by inputs from carbonate rocks in the North American watersheds, but points to a more important role for silicate rocks in Siberian watersheds. In the coastal ocean, river water-induced decreases in aragonite saturation (i.e., an ocean acidification effect) appears to be much more pronounced in Siberia than in the North American Arctic, and stronger in the winter and spring than in the late summer. Accounting for seasonal variation in the flux of DIC and other major ions gives a much clearer understanding of the importance of riverine DIC within the broader pan-arctic C cycle.Funding for this work was provided through NSF-OPP-0229302 and NSF-OPP-0732985. Additional support to SET was provided by an NSERC Postdoctoral Fellowship.2013-06-1