2,000 research outputs found
Multiple plant-wax compounds record differential sources and ecosystem structure in large river catchments
Š The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geochimica et Cosmochimica Acta 184 (2016): 20-40, doi:10.1016/j.gca.2016.04.003.The concentrations, distributions, and stable carbon isotopes (δ13C) of plant waxes carried
by fluvial suspended sediments contain valuable information about terrestrial ecosystem
characteristics. To properly interpret past changes recorded in sedimentary archives it is crucial
to understand the sources and variability of exported plant waxes in modern systems on seasonal
to inter-annual timescales. To determine such variability, we present concentrations and δ13C
compositions of three compound classes (n-alkanes, n-alcohols, n-alkanoic acids) in a 34-month
time series of suspended sediments from the outflow of the Congo River.
We show that exported plant-dominated n-alkanes (C25 â C35) represent a mixture of C3
and C4 end members, each with distinct molecular distributions, as evidenced by an 8.1 Âą 0.7â°
(Âą1Ď standard deviation) spread in δ13C values across chain-lengths, and weak correlations
between individual homologue concentrations (r = 0.52 â 0.94). In contrast, plant-dominated n-alcohols (C26 â C36) and n-alkanoic acids (C26 â C36) exhibit stronger positive correlations (r =
0.70 â 0.99) between homologue concentrations and depleted δ13C values (individual
homologues average ⤠-31.3â° and -30.8â°, respectively), with lower δ13C variability across
chain-lengths (2.6 Âą 0.6â° and 2.0 Âą 1.1â°, respectively). All individual plant-wax lipids show
little temporal δ13C variability throughout the time-series (1Ď â¤ 0.9â°), indicating that their stable
carbon isotopes are not a sensitive tracer for temporal changes in plant-wax source in the Congo
basin on seasonal to inter-annual timescales.
Carbon-normalized concentrations and relative abundances of n-alcohols (19 â 58% of
total plant-wax lipids) and n-alkanoic acids (26 â 76%) respond rapidly to seasonal changes in
runoff, indicating that they are mostly derived from a recently entrained local source. In contrast,
a lack of correlation with discharge and low, stable relative abundances (5 â 16%) indicate that
n-alkanes better represent a catchment-integrated signal with minimal response to discharge
seasonality. Comparison to published data on other large watersheds indicates that this
phenomenon is not limited to the Congo River, and that analysis of multiple plant-wax lipid
classes and chain lengths can be used to better resolve local vs. distal ecosystem structure in river
catchments.J.D.H. was supported by the National Science Foundation
Graduate Research Fellowship under Grant No. 2012126152. V.V.G. was partly supported by
the US National Science Foundation, grants OCE-0851015 and OCE-0928582. Parts of this work
were supported by the DFG Research Center/Cluster of Excellence âThe Ocean in the Earth
Systemâ at MARUM - Center for Marine Environmental Science, University of Bremen.2017-04-0
'Nature or nurture': survival rate oviposition interval, and possible gonotrophic discordance among South East Asian anophelines
Background: Mosquito survival, oviposition interval and gonotrophic concordance are important determinants of vectorial capacity. These may vary between species or within a single species depending on the environment. They may be estimated by examination of the ovaries of host-seeking mosquitoes.
Methods: Landing collections, Furvela tent-trap and CDC light-trap collections were undertaken sequentially in four locations in Cambodia between February 2012 and December 2013 and samples from the collected mosquitoes were dissected to determine parity, sac stage (indicative of time spent prior to returning to feed) and egg stage.
Results: A total of 27,876 Anopheles from 15 species or species groups were collected in the four locations and 2883 specimens were dissected. Both the density and predominant species collected varied according to location and trapping method. Five species were dissected in sufficient numbers to allow comparisons between locations. Estimated oviposition interval differed markedly between species but less within species among different locations. Anopheles aconitus had the shortest cycle, which was 3.17 days (95 % CI 3â3.64), and Anopheles barbirostris had the longest cycle, which took four days (95 % CI 3.29â4). Anopheles minimus had a higher sac rate in weeks leading up to a full moon but there was apparently little effect of moon phase on Anopheles dirus. Despite the fact that many of the species occurred at very low densities, there was no evidence of gonotrophic dissociation in any of them, even during sustained hot, dry periods. The principal Cambodian malaria vector, An. dirus, was only common in one location where it was collected in miniature light-traps inside houses. It did not appear to have an exceptional survival rate (as judged by the low average parous rate) or oviposition cycle.
Conclusions: Differences in the oviposition interval were more pronounced among species within locations than within species among ecologically diverse locations. A nationwide survey using CDC light-traps for the collection of An. dirus inside houses may help in determining patterns of malaria transmission in Cambodia
Using practice development methodology to develop childrenâs centre teams: Ideas for the future
The Childrenâs Centre Programme is a recent development in the UK and brings together
multi-agency teams to work with disadvantaged families. Practice development methods
enable teams to work together in new ways. Although the term practice development
remains relatively poorly defined, its key properties suggest that it embraces engagement,
empowerment, evaluation and evolution. This paper introduces the Childrenâs Centre
Programme and practice development methods and aims to discuss the relevance of using
this method to develop teams in childrenâs centres through considering the findings from an
evaluation of a two-year project to develop inter-agency public health teams.
The evaluation showed that practice development methods can enable successful team
development and showed that through effective facilitation, teams can change their practice to
focus on areas of local need. The team came up with their own process to develop a strategy
for their locality
Planning and Leveraging Event Portfolios: Towards a Holistic Theory
This conceptual paper seeks to advance the discourse on the leveraging and legacies of events by examining the planning, management, and leveraging of event portfolios. This examination shifts the common focus from analyzing single events towards multiple events and purposes that can enable cross-leveraging among different events in pursuit of attainment and magnification of specific ends. The following frameworks are proposed: (1) event portfolio planning and leveraging, and (2) analyzing events networks and inter-organizational linkages. These frameworks are intended to provide, at this infancy stage of event portfolios research, a solid ground for building theory on the management of different types and scales of events within the context of a portfolio aimed to obtain, optimize and sustain tourism, as well as broader community benefits
Colloidal stability of tannins: astringency, wine tasting and beyond
Tannin-tannin and tannin-protein interactions in water-ethanol solvent
mixtures are studied in the context of red wine tasting. While tannin
self-aggregation is relevant for visual aspect of wine tasting (limpidity and
related colloidal phenomena), tannin affinities for salivary proline-rich
proteins is fundamental for a wide spectrum of organoleptic properties related
to astringency. Tannin-tannin interactions are analyzed in water-ethanol
wine-like solvents and the precipitation map is constructed for a typical grape
tannin. The interaction between tannins and human salivary proline-rich
proteins (PRP) are investigated in the framework of the shell model for
micellization, known for describing tannin-induced aggregation of beta-casein.
Tannin-assisted micellization and compaction of proteins observed by SAXS are
described quantitatively and discussed in the case of astringency
Titan's gravity field and interior structure after Cassini
Since its arrival at Saturn in 2004, Cassini performed nine flybys devoted to the determination of Titan's gravity field and its tidal variations. Here we present an updated gravity solution based on the final data set collected during the gravity-dedicated passes, before Cassini's plunge into Saturn's atmosphere. The data set includes an additional flyby (T110, March 2015, primarily devoted to imaging Titan's north polar lakes) carried out with the low-gain antenna. This flyby was particularly valuable because the closest approach occurred at a high latitude (75°N), over an area not previously sampled.
Previously published gravity results (Iess et al., 2012) indicated that Titan is subject to large eccentricity tides in response to the time varying perturbing potential exerted by Saturn. The magnitude of the response quadrupole field, expressed in the tidal Love number k_2, was used to infer the existence of an internal ocean. The new gravity field determination provides an improved estimate of k_2 of about 0.62, accurate to a level of a few percent. The value is higher than the simplest models of Titan suggest and the interpretation is unclear; possibilities include a high density ocean (as high as 1300âŻkg/m^3), a partially viscous response of the deeper region, or a dynamic contribution to the tidal response. The new solution includes higher degree and order harmonic coefficients (up to 5) and offers an improved map of gravity anomalies. The geoid is poorly correlated with the topography, implying strong compensation. In addition, the updated geoid and its associated uncertainty could be used to refine the gravity-altimetry correlation analysis and for improved interpretation of radar altimetric data
- âŚ