Foliar δ15N values characterize soil N cycling and reflect nitrate or ammonium preference of plants along a temperate grassland gradient

The natural abundance of stable 15N isotopes in soils and plants is potentially a simple tool to assess ecosystem N dynamics. Several open questions remain, however, in particular regarding the mechanisms driving the variability of foliar δ15N values of non-N2 fixing plants within and across ecosystems. The goal of the work presented here was therefore to: (1) characterize the relationship between soil net mineralization and variability of foliar Δδ15N (δ15Nleaf − δ15Nsoil) values from 20 different plant species within and across 18 grassland sites; (2) to determine in situ if a plant’s preference for NO3− or NH4+ uptake explains variability in foliar Δδ15N among different plant species within an ecosystem; and (3) test if variability in foliar Δδ15N among species or functional group is consistent across 18 grassland sites. Δδ15N values of the 20 different plant species were positively related to soil net mineralization rates across the 18 sites. We found that within a site, foliar Δδ15N values increased with the species’ NO3− to NH4+ uptake ratios. Interestingly, the slope of this relationship differed in direction from previously published studies. Finally, the variability in foliar Δδ15N values among species was not consistent across 18 grassland sites but was significantly influenced by N mineralization rates and the abundance of a particular species in a site. Our findings improve the mechanistic understanding of the commonly observed variability in foliar Δδ15N among different plant species. In particular we were able to show that within a site, foliar δ15N values nicely reflect a plant’s N source but that the direction of the relationship between NO3− to NH4+ uptake and foliar Δδ15N values is not universal. Using a large set of data, our study highlights that foliar Δδ15N values are valuable tools to assess plant N uptake patterns and to characterize the soil N cycle across different ecosystems

Immediate thoracotomy for penetrating injuries: Ten years' experience at a Dutch level I trauma center

Background: An emergency department thoracotomy (EDT) or an emergency thoracotomy (ET) in the operating theater are both beneficial in selected patients following thoracic penetrating injuries. Since outcome-descriptive European studies are lacking, the aim of this retrospective study was to evaluate ten years of experience at a Dutch level I trauma center. Method: Data on patients who underwent an immediate thoracotomy after sustaining a penetrating thoracic injury between October 2000 and January 2011 were collected from the trauma registry and hospital files. Descriptive and univariate analyses were performed. Results: Among 56 patients, 12 underwent an EDT and 44 an ET. Forty-six patients sustained one or multiple stab wounds, versus ten with one or multiple gunshot wounds. Patients who had undergone an EDT had a lower GCS (p < 0. 001), lower pre-hospital RTS and hospital triage RTS (p < 0. 001 and p = 0. 009, respectively), and a lower SBP (p = 0. 038). A witnessed loss of signs of life generally occurred in EDT patients and was accompanied by 100 % mortality. Survival following EDT was 25 %, which was significantly lower than in the ET group (75 %; p = 0. 002). Survivors had lower ISS (p = 0. 011), lower rates of pre-hospital (p = 0. 031) and hospital (p = 0. 003) hemodynamic instability, and a lower prevalence of concomitant abdominal injury (p = 0. 002). Conclusion: The overall survival rate in our study was 64 %. The outcome of immediate thoracotomy performed in this level I trauma center was similar to those obtained in high-incidence regions like the US and South Africa. This suggests that trauma units where immediate thoracotomies are not part of the daily routine can achieve similar results, if properly trained

Use of communities of practice in business and health care sectors: A systematic review

<p>Abstract</p> <p>Background</p> <p>Since being identified as a concept for understanding knowledge sharing, management, and creation, communities of practice (CoPs) have become increasingly popular within the health sector. The CoP concept has been used in the business sector for over 20 years, but the use of CoPs in the health sector has been limited in comparison.</p> <p>Objectives</p> <p>First, we examined how CoPs were defined and used in these two sectors. Second, we evaluated the evidence of effectiveness on the health sector CoPs for improving the uptake of best practices and mentoring new practitioners.</p> <p>Methods</p> <p>We conducted a search of electronic databases in the business, health, and education sectors, and a hand search of key journals for primary studies on CoP groups. Our research synthesis for the first objective focused on three areas: the authors' interpretations of the CoP concept, the key characteristics of CoP groups, and the common elements of CoP groups. To examine the evidence on the effectiveness of CoPs in the health sector, we identified articles that evaluated CoPs for improving health professional performance, health care organizational performance, professional mentoring, and/or patient outcome; and used experimental, quasi-experimental, or observational designs.</p> <p>Results</p> <p>The structure of CoP groups varied greatly, ranging from voluntary informal networks to work-supported formal education sessions, and from apprentice training to multidisciplinary, multi-site project teams. Four characteristics were identified from CoP groups: social interaction among members, knowledge sharing, knowledge creation, and identity building; however, these were not consistently present in all CoPs. There was also a lack of clarity in the responsibilities of CoP facilitators and how power dynamics should be handled within a CoP group. We did not find any paper in the health sector that met the eligibility criteria for the quantitative analysis, and so the effectiveness of CoP in this sector remained unclear.</p> <p>Conclusion</p> <p>There is no dominant trend in how the CoP concept is operationalized in the business and health sectors; hence, it is challenging to define the parameters of CoP groups. This may be one of the reasons for the lack of studies on the effectiveness of CoPs in the health sector. In order to improve the usefulness of the CoP concept in the development of groups and teams, further research will be needed to clarify the extent to which the four characteristics of CoPs are present in the mature and emergent groups, the expectations of facilitators and other participants, and the power relationship within CoPs.</p

Does geographic origin dictate ecological strategies in Acacia senegal (L.) Willd.?: evidence from carbon and nitrogen stable isotopes

Background and aims: Acacia senegal, a leguminous dryland tree, is economically and ecologically important to sub-Saharan Africa.Water-use efficiency (WUE) and biological nitrogen fixation (BNF) are fundamental to plant productivity and survival.We quantify provenance differences in WUE, BNF, photosynthesis, biomass and gum arabic production from A. senegal assessing genetic improvement potential. Methods: Using stable isotope ratios, we determined WUE (δ13C) and BNF (δ15N) from provenances of mature A. senegal in field-trials (Senegal), sampling leaves at the beginning (wet) and end (dry) of the rainy season. Seedling provenance trials (UK) determined photosynthesis, and biomass and δ13C in relation to water table. Environmental data were characterised for all provenances at their sites of origin. Results: Provenances differed in both δ13C and δ15N. Gum yield declined with increasing WUE. Virtually no BNF was detected during the dry season and seedlings and mature trees may have different WUE strategies. Wind speed and soil characteristics at provenance origin were correlated with isotope composition and gum production. Conclusion: Provenance differences suggest that selection for desirable traits, e.g., increased gum production, may be possible. As ecological strategies relate to native locality, the environmental conditions at plantation site and provenance origin are important in assessing selection criteria

Simvastatin Treatment Highlights a New Role for the Isoprenoid/Cholesterol Biosynthetic Pathway in the Modulation of Emotional Reactivity and Cognitive Performance in Rats.

The aim of the present work was to shed light on the role played by the isoprenoid/cholesterol biosynthetic pathway in the modulation of emotional reactivity and memory consolidation in rodents through the inhibition of the key and rate-limiting enzyme 3-hydroxy 3-methylglutaryl Coenzyme A reductase (HMGR) both in vivo and in vitro with simvastatin. Three-month-old male Wistar rats treated for 21 days with simvastatin or vehicle were tested in the social interaction, elevated plus-maze, and inhibitory avoidance tasks; after behavioral testing, the amygdala, hippocampus, prefrontal cortex, dorsal and ventral striatum were dissected out for biochemical assays. In order to delve deeper into the molecular mechanisms underlying the observed effects, primary rat hippocampal neurons were used. Our results show that HMGR inhibition by simvastatin induces anxiogenic-like effects in the social interaction but not in the elevated plus maze test, and improves memory consolidation in the inhibitory avoidance task. These effects are accompanied by imbalances in the activity of specific prenylated proteins, Rab3 and RhoA, involved in neurotransmitter release and synaptic plasticity, respectively. Taken together, the present findings indicate that the isoprenoid/cholesterol biosynthetic pathway is critically involved in the physiological modulation of both emotional and cognitive processes in rodents.Neuropsychopharmacology accepted article preview online, 10 October 2013. doi:10.1038/npp.2013.284