Edge effects resulting from adjacent land uses are poorly understood in agroecosystems yet understanding above and belowground edge effects is crucial for maintaining ecosystem function. The aim of ...our study was to examine impacts of land management on aboveground and belowground edge effects, measured by changes in plant community, soil properties, and soil microbial communities across agroecosystem edges. We measured plant composition and biomass, soil properties (total carbon, total nitrogen, pH, nitrate, and ammonium), and soil fungal and bacterial community composition across perennial grassland-annual cropland edges. Edge effects due to land management were detected both aboveground and belowground. The plant community at the edge was distinct from the adjacent land uses, where annual, non-native, plant species were abundant. Soil total nitrogen and carbon significantly decreased across the edge (P < 0.001), with the highest values in the perennial grasslands. Both bacterial and fungal communities were different across the edge with clear changes in fungal communities driven directly and indirectly by land management. A higher abundance of pathogens in the more heavily managed land uses (i.e. crop and edge) was detected. Changes in plant community composition, along with soil carbon and nitrogen also influenced the soil fungal community across these agroecosystems edges. Characterizing edge effects in agroecosystem, especially those associated with soil microbial communities, is an important first step in ensuring soil health and resilience in these managed landscapes.
The emerging work on understanding open source software has questioned what leads to effectiveness in OSS development teams in the absence of formal controls, and it has pointed to the importance of ...ideology. This paper develops a framework of the OSS community ideology (including specific norms, beliefs, and values) and a theoretical model to show how adherence to components of the ideology impacts effectiveness in OSS teams. The model is based on the idea that the tenets of the OSS ideology motivate behaviors that enhance cognitive trust and communication quality and encourage identification with the project team, which enhances affective trust. Trust and communication in turn impact OSS team effectiveness. The research considers two kinds of effectiveness in OSS teams: the attraction and retention of developer input and the generation of project outputs. Hypotheses regarding antecedents to each are developed. Hypotheses are tested using survey and objective data on OSS projects. Results support the main thesis that OSS team members' adherence to the tenets of the OSS community ideology impacts OSS team effectiveness and reveal that different components impact effectiveness in different ways. Of particular interest is the finding that adherence to some ideological components was beneficial to the effectiveness of the team in terms of attracting and retaining input, but detrimental to the output of the team. Theoretical and practical implications are discussed.
Polyaniline (PANI) and two copolymers, poly(aniline-co-o-toluidine) (PoTOL-50) and poly(aniline-co-o-anisidine) (PoANI-50) were synthesized with equal input ratios (1:1) to enhance PANI as sensing ...material for the sensing of various heavy metal analytes in aqueous solutions. The polymers were evaluated for both their sensitivity and selectivity toward four heavy metals (Ba2+, Cd2+, Cu2+, and Ni2+) and two common matrix interferents (Ca2+ and Mg2+) at 10 and 40 ppm. The effect of pH and ionic strength of the aqueous solutions on the sensitivity and selectivity was also evaluated. All three polymers showed high sensitivity and selectivity to Ba2+. Varying the pH and ionic strength of solutions did not show significant differences in either the selectivity or the sensitivity of the polymers.
Diversity is a defining characteristic of global collectives facilitated by the Internet. Though substantial evidence suggests that diversity has profound implications for a variety of outcomes ...including performance, member engagement, and withdrawal behavior, the effects of diversity have been predominantly investigated in the context of organizational workgroups or virtual teams. We use a diversity lens to study the success of nontraditional virtual work groups exemplified by open source software (OSS) projects. Building on the diversity literature, we propose that three types of diversity (separation, variety, and disparity) influence two critical outcomes for OSS projects: community engagement and market success. We draw on the OSS literature to further suggest that the effects of diversity on market success are moderated by the application development stage. We instantiate the operational definitions of three forms of diversity to the unique context of open source projects. Using archival data from 357 projects hosted on SourceForge, we find that disparity diversity, reflecting variation in participants' contribution-based reputation, is positively associated with success. The impact of separation diversity, conceptualized as culture and measured as diversity in the spoken language and country of participants, has a negative impact on community engagement but an unexpected positive effect on market success. Variety diversity, reflected in dispersion in project participant roles, positively influences community engagement and market success. The impact of diversity on market success is conditional on the development stage of the project. We discuss how the study's findings advance the literature on antecedents of OSS success, expand our theoretical understanding of diversity, and present the practical implications of the results for managers of distributed collectives.
Soil invertebrates are an integral part of Arctic ecosystems through their roles in the breakdown of litter, soil formation, and nutrient cycling. However, studies examining soil invertebrates in the ...Arctic are limited and our understanding of the abiotic and biotic drivers of these invertebrate communities remains understudied. We examined differences in soil invertebrate taxa (mites, collembolans, enchytraeids) among several undisturbed upland tundra heath sites in Nunavut Canada and identified the drivers (vegetation and substrate cover, soil nutrients and pH) of the soil invertebrate community across these sites. Soil invertebrate densities were similar to that of other Arctic studies. While invertebrate communities were relatively consistent between our sites, cover of rocks, woody litter, and the lichen Alectoria nigricans had significant, positive influences on the density of all invertebrates studied. Mites and collembolans were more closely associated with cover of lichens, whereas enchytraeids were more closely associated with woody litter and rocks. Our results suggest that anthropogenic (e.g., resource exploration and extraction) and/or natural (e.g., climate change) disturbances that result in changes to the vegetation community and woody litter inputs will likely impact soil invertebrates and the ecosystem services they provide.
The removal and detection of toxic analytes, including monomers and plasticizers, is important for both health and the environment. Potential absorbents and/or sensing materials are successfully made ...from polyaniline (PANI) and PANI doped with 10 wt.% of aluminum oxide (PANI‐Al2O3) and titanium dioxide (PANI‐TiO2). The amount of metal oxide incorporated into the surface layers of the polymer and the total amount incorporated are confirmed by energy dispersive X‐rays (EDX) and microwave plasma‐ atomic emission spectroscopy (MP‐AES), respectively. All three materials are evaluated as potential sensing materials and/or absorbents for styrene, monobutyl phthalate (MBP), and dibutyl phthalate (DBP) at 100 ppm in aqueous solutions. It is found that incorporating TiO2 into PANI improved both the sensitivity and selectivity to styrene, making PANI‐TiO2 a good absorbent and potential sensing material for styrene. Additionally, incorporating Al2O3 into PANI improved the sorption to MBP, but reduced the selectivity. As a proof‐of‐concept, the responses of the polymeric nanocomposites are combined and analyzed using principal component analysis (PCA) as such an algorithm. The output reveals good separation of the responses to each analyte, thereby demonstrating how sensing materials with poorer selectivity can be used together to overcome limitations in selectivity.
Polyaniline doped with TiO2 and Al2O3 nanoparticles is evaluated for their sorption of styrene and phthalates in aqueous media. The sensing mechanisms and proof‐of‐concept demonstration of a sensing array is also included.
Geckos, which are capable of walking on walls and hanging from ceilings with the help of micro-/nano-scale hierarchical fibrils (setae) on their toe pads, have become the main prototype in the design ...and fabrication of fibrillar dry adhesives. As the unique fibrillar feature of the toe pads of geckos allows them to develop an intimate contact with the substrate the animal is walking on or clinging to, it is expected that the toe setae exchange significant numbers of electric charges with the contacted substrate via the contact electrification (CE) phenomenon. Even so, the possibility of the occurrence of CE and the contribution of the resulting electrostatic interactions to the dry adhesion of geckos have been overlooked for several decades. In this study, by measuring the magnitude of the electric charges, together with the adhesion forces, that gecko foot pads develop in contact with different materials, we have clarified for the first time that CE does contribute effectively to gecko adhesion. More importantly, we have demonstrated that it is the CE-driven electrostatic interactions which dictate the strength of gecko adhesion, and not the van der Waals or capillary forces which are conventionally considered as the main source of gecko adhesion.
Abstract
While humans lack sufficient capacity to undergo cardiac regeneration following injury, zebrafish can fully recover from a range of cardiac insults. Over the past two decades, our ...understanding of the complexities of both the independent and co-ordinated injury responses by multiple cardiac tissues during zebrafish heart regeneration has increased exponentially. Although cardiomyocyte regeneration forms the cornerstone of the reparative process in the injured zebrafish heart, recent studies have shown that this is dependent on prior neovascularization and lymphangiogenesis, which in turn require epicardial, endocardial, and inflammatory cell signalling within an extracellular milieu that is optimized for regeneration. Indeed, it is the amalgamation of multiple regenerative systems and gene regulatory patterns that drives the much-heralded success of the adult zebrafish response to cardiac injury. Increasing evidence supports the emerging paradigm that developmental transcriptional programmes are re-activated during adult tissue regeneration, including in the heart, and the zebrafish represents an optimal model organism to explore this concept. In this review, we summarize recent advances from the zebrafish cardiovascular research community with novel insight into the mechanisms associated with endogenous cardiovascular repair and regeneration, which may be of benefit to inform future strategies for patients with cardiovascular disease.
Graphical Abstract
Graphical Abstract
Zebrafish and human injury response linking-diagrams to represent the effects of tissues on one another. Epicardium: light green, Endocardium: dark green, Vasculature: blue, Myocardium: red, Lymphatics: purple, Inflammation: yellow, and Extracellular Matrix: orange. Zebrafish follow a highly integrated cardiac regenerative programme involving all cardiac tissues, illustrated above by the Zebrafish Injury Response linking diagram. This is in direct contrast to humans where ischaemic injury is predominantly followed by inflammation and extracellular matrix deposition, as illustrated in the Human Injury Response linking diagram, leading to permanent scarring. It is interesting to consider whether a full understanding of the efficient regenerative programme of the zebrafish could inform future heart regeneration studies in humans (Krzywinski MI, Schein JE, Birol I, Connors J, Gascoyne R, Horsman D, Jones SJ, Marra MA. Circos: An information aesthetic for comparative genomics. Genome Res 2009; 31:1639-1645).
High‐density polyethylene (HDPE) and polypropylene (PP) blends of varying composition have been evaluated in an effort to establish a mixing rule for melt flow index (MFI). In addition, a previously ...established relationship between MFI and Mw¯ for linear polymers was also evaluated for these blends. It was found that a parabolic relationship existed between the composition (by weight fraction) and MFI and that the MFI and Mw¯ relationship held for this set of polymeric materials. Additionally, all properties and relationships were evaluated over five extrusion cycles, which showed minimal to no deviations over the five cycles.
Identifying the key drivers of nitrogen cycling processes that influence gaseous N exchanges in arctic ecosystems is essential for predicting the response of northern systems to changes in climatic ...conditions. In this review we examine pathways of N input (atmospheric N deposition and biological N2-fixation), cycling (N mineralization, immobilization and nitrification) and output (denitrification and nitrifier denitrification) found across the Arctic with a focus upon gaseous N exchanges in these ecosystems. Cyanobacteria are ubiquitous in the Arctic where they can be found in association with lichen or bryophytes and also as free-living components of biological soil crusts. N2-fixation by cyanobacteria in arctic ecosystems provides significant landscape-scale N inputs, and is an important N source for annual plant N uptake. The activity and extent of these cyanobacterial associations is driven primarily by moisture gradients associated with topography that determine nutrient availability. N2-fixation rates tend to be highest in relatively low topographical or microtopographical positions that are associated with soils of higher total N, mineralizable N, total carbon and organic carbon compared to higher topographical positions. Topography is also a key landscape-level driver of N mineralization, nitrification and denitrification processes through its control on factors such as soil moisture, soil temperature and nutrient availability. In general, while N mineralization rates are also higher in relatively low topographical or microtopographical positions, net nitrification and immobilization tend to be inhibited in these locations. This higher mineralization is linked to relatively high N2O emissions in lower lying areas in arctic landscapes since moisture and NH4 levels tend to be higher in those locations and are important controls on denitrification and nitrifier denitrification respectively. These soil topographical controls are modulated by arctic plants which may also have a direct, light-dependent role in N2O emissions, and undoubtedly play important indirect roles in gaseous N cycling via evapotranspiration effects. Our review indicates that arctic microscale and field topographic variation dominate patterns of atmospheric N inputs and losses in arctic ecosystems. However, further studies are needed to provide a better understanding of the associated driving factors on the multitude of processes that influence gaseous N exchange.
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•We examine pathways of atmospheric N input and output across the Arctic.•Arctic microscale and field topography dominate patterns of atmospheric N exchange.•Topography establishes gradients in resource availability influencing N transformations.•Predicting arctic response to climate changes requires knowledge of nitrogen cycling processes.
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