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[en] Dielectrophoresis (DEP) has been widely used to focus and separate cells and particles in microfluidic devices. This work first demonstrates negative and positive dielectrophoretic focusing of particles in a serpentine microchannel by changing only the electric conductivity of the suspending fluid. Due to the channel turn-induced dielectrophoretic force, particles are focused to either the centerline or the sidewalls of the channel when their electric conductivity is lower (i.e. negative DEP) or higher (i.e. positive DEP) than that of the fluid. These distinctive dielectrophoretic focusing phenomena in a serpentine microchannel are then combined to implement a continuous separation between particles of different sizes and electric conductivities. Such separation eliminates the fabrication of in-channel microelectrodes or micro-insulators that are typically required in DEP-based separation techniques. A numerical model is also developed to predict the particle motion, and the simulation results agree reasonably with the observed particle focusing and separation behaviors.
[en] While higher plant communities found on ultramafics are known to display peculiar characteristics, the distinguishability of any peculiarity in lichen communities is still a matter of contention. Other biotic or abiotic factors, rather than substrate chemistry, may contribute to differences in species composition reported for lichens on adjacent ultramafic and non-ultramafic areas. This work examines the lichen biota of ultramafics, at global and regional scales, with reference to species-specific functional traits. An updated world list of lichens on ultramafic substrates was analyzed to verify potential relationships between diversity and functional traits of lichens in different Köppen–Geiger climate zones. Moreover, a survey of diversity and functional traits in saxicolous communities on ultramafic and non-ultramafic substrates was conducted in Valle d’Aosta (North-West Italy) to verify whether a relationship can be detected between substrate and functional traits that cannot be explained by other environmental factors related to altitude. Analyses (unweighted pair group mean average clustering, canonical correspondence analysis, similarity-difference-replacement simplex approach) of global lichen diversity on ultramafic substrates (2314 reports of 881 taxa from 43 areas) displayed a zonal species distribution in different climate zones rather than an azonal distribution driven by the shared substrate. Accordingly, variations in the frequency of functional attributes reflected reported adaptations to the climate conditions of the different geographic areas. At the regional scale, higher similarity and lower species replacement were detected at each altitude, independent from the substrate, suggesting that altitude-related climate factors prevail over putative substrate–factors in driving community assemblages. In conclusion, data do not reveal peculiarities in lichen diversity or the frequency of functional traits in ultramafic areas.
[en] The 'EMMA' Non-Scaling Fixed Field Alternating Gradient (ns-FFAG) international project is currently being commissioned at Daresbury Laboratory, UK. This accelerator has been equipped with a number of diagnostic systems to facilitate this. These systems include a novel time-domain-multiplexing BPM system, moveable screen systems, a time-of-flight instrument, Faraday cups, and injection/extraction tomography sections to analyze the single bunch beams. An upgrade still to implement includes the installation of wall current monitors. This paper gives an overview of these systems and shows some data and results from the diagnostics that have contributed to the successful demonstration of a serpentine acceleration by this novel accelerator.
[en] Many of the plants found in serpentine areas are endemics and they may accumulate Ni at high concentration. High accumulation of Cr is rare, or in some views, never properly demonstrated. Generally, a very small proportion of any serpentine flora shows high accumulation of Ni, in some serpentine areas Ni accumulators are completely absent. There are approximately 570 hyperaccumulator plant species found on earth, 450 of them are Ni hyperaccumulators. A few of the Ni accumulators have potential for phytoremediation or phytomining. In the present study, 19 different Brassicaceae members growing in serpentine habitats in the district of Yahyalı, Kayseri province, Turkey viz., members of genera Aethionema, Alyssum, Arabis, Heldreichia, Hesperis, Iberis, Isatis, Microthlaspi, Odontarrhena, Pseudosempervivum and Thlaspi were investigated. Nickel concentrations in the soil and underground and aboveground parts of plants were determined by using ICP-OES. It was observed that Ni concentrations of seven taxa (Odontarrhena muralis, O. oxycarpa, Isatis cappadocica subsp. cappadocica, Microthlaspi perfoliatum, Pseudosempervivum sempervivum, Thlaspi triangulare, Thlaspi rosulare) reach the threshold criterion of 1,000 mg kg−1 for Ni hyperaccumulation. In this study Ni concentrations in aboveground tissues of I. cappadocica subsp. cappadocica are determined as 5,587 mg kg−1 (in dry weight). Accordingly, it is suggested that this taxon be added to the list of Ni hyperaccumulator plants.
[en] Serpentine, a chemically extreme substrate with a discontinuous distribution, supports a high proportion of endemic plant species. The evolutionary pathway of edaphic endemics in isolated areas may be of parallel origin (convergence), but this can be difficult to detect due to similar sets of phenotypic traits repeatedly selected for by the extreme conditions of serpentine environments. Testing the alternative histories of single origin vs. parallel evolution in serpentine plant populations provides insight into the ability of plants to adapt to extreme serpentine environments and to disperse between isolated serpentine areas. In this study, we focused on the herb Picris hieracioides L. (Asteraceae), which includes early-flowering serpentine populations surrounded by later flowering, non-serpentine populations on Hokkaido Island, Japan. We performed population genetic analysis based on genome-wide SNPs markers and quantified temporal overlap of flowering times under natural conditions. Phylogeographic analysis confirmed the occurrence of two genetic groups, corresponding to the serpentine and non-serpentine races. Although the two races were found to occur in close parapatry over multiple paired soil sites, little evidence for hybridization was detected. The flowering times of the two races showed significant divergence, with flowering peaks separated by more than 1 month. Overall, this study supported the single origin of serpentine Picris populations, and showed the role of divergent flowering time as a strong prezygotic barrier to maintain the edaphic races over short spatial distances.
[en] Hyperaccumulation has been proposed as an elemental defense against herbivores; however, few studies have examined seed defense. This study included two annual Streptanthus species (Brassicaceae) from California serpentine soils: a non-hyperaccumulator (S. insignis) and three populations (representing Y, P, and U morphs) of a Ni hyperaccumulator (S. polygaloides). Adults of the generalist seed herbivore Tribolium confusum (Coleoptera: Tenebrionidae) were fed either whole or cut seeds, survival was recorded for 7 weeks, and Ni concentrations of both beetles and seeds were determined using ICP-OES. Survival analysis showed significantly more rapid mortality for beetles consuming S. polygaloides seeds compared to those consuming S. insignis. Mortality of beetles fed whole S. polygaloides seeds was more rapid than those fed cut S. polygaloides seeds. Seeds of the S. polygaloides populations contained approximately 300 µg Ni g−1 whereas S. insignis contained approximately 5 µg Ni g−1. Beetles fed whole S. polygaloides seeds contained more than 2.5-fold greater Ni concentrations than those fed cut seeds (approximately 60 and 25 µg Ni g−1, respectively), whereas beetles fed either cut or whole S. insignis seeds contained < 0.3 µg Ni g−1. An artificial diet study, using Ni-amended cornmeal, confirmed that diet Ni concentrations greater than 240 µg Ni g−1 were toxic to T. confusum. We conclude that Ni in S. polygaloides seeds can act as an elemental defense against seed herbivores even at 300 µg Ni g−1, a level below the 1000 µg Ni g−1 hyperaccumulation threshold concentration.
[en] Pursuits of wearable electronics include the features of flexible, self-powered, and even being ultrathin and transparent for a better fit on different curved surfaces in an imperceptible way. In this paper, by stacking two graphene-covered parylene films layer by layer and introducing serpentine structures in one parylene film as the spacer, ultraflexible triboelectric nanogenerators (TENGs) with a total thickness of 5.5 μm and a transmittance of 80% were achieved. Under the stimulation of vertical impacts at frequencies of 0.5 Hz, 1 Hz, 1.5 Hz, 2 Hz, and 2.5 Hz, an open-circuit (OC) voltage of 3 V was maintained in a TENG measuring 2 × 2 cm2 throughout all the cases, which indicated a good mechanical stability of the device. When the TENG was bent, there was an increase in OC voltage and short-circuit current in response to an increased curvature. Due to its ultrathin nature and being sensitive to curvature, the TENG was demonstrated to serve as a self-powered curvature sensor for movement monitoring when conformably attached on the finger joint. (paper)
[en] We studied a type of Californian ultramafic chaparral to determine functional groups which can help reduce the complexity of ecosystem management. The study was realized in McLaughlin Reserve, State of California, USA. We analysed the species of a serpentine plant association previously phytosociologically described in the area: Ceanotho albiflori-Quercetum duratae for their functional traits and functional groups. Traits per species were measured building a trait database. We used Principal Component Analysis to identify the combination of functional traits with major weight and a neighbor-joining clustering to define functional groups for this vegetation association. Our results indicated that the studied association is dominated by phanerophytes, with low degree of spinescence. Leaves were mainly malacophyllous with high degree of tomentosity, reduced size and a partial shedding of leaves was observed during summer. We considered six functional groups as the optimum number of clusters in a total of 18 species. The two first functional groups were composed of chamaephytes with brachyblasts and dolichoblasts with differences in the degree of tomentosity. The rest of the functional groups were composed of phanerophytes where the differences between them were based on traits in relation to the branches, leaf size and the horizontal development of the root system. The functional groups obtained show that this serpentine chaparral is composed of species with a wide range of functional traits. The study of other Mediterranean serpentine ecosystems in California and elsewhere could contribute to create new perspectives of functional ecology and help in the management of these valuable ecosystems.
[en] In a fixed-field alternating-gradient (FFAG) accelerator, eliminating pulsed magnet operation permits rapid acceleration to synchrotron energies, but with a much higher beam-pulse repetition rate. Conceived in the 1950s, FFAGs are enjoying renewed interest, fuelled by the need to rapidly accelerate unstable muons for future high-energy physics colliders. Until now a 'scaling' principle has been applied to avoid beam blow-up and loss. Removing this restriction produces a new breed of FFAG, a non-scaling variant, allowing powerful advances in machine characteristics. We report on the first non-scaling FFAG, in which orbits are compacted to within 10?mm in radius over an electron momentum range of 12-18 MeV/c. In this strictly linear-gradient FFAG, unstable beam regions are crossed, but acceleration via a novel serpentine channel is so rapid that no significant beam disruption is observed. This result has significant implications for future particle accelerators, particularly muon and high-intensity proton accelerators.
[en] The functionality of flexible electronics relies on stable performance of thin film micro-electrodes. This letter investigates the behavior of gold thin films on polyimide, a prevalent combination in flexible devices. The dynamic behavior of gold micro-electrodes has been studied by subjecting them to stress while monitoring their resistance in situ. The shape of the electrodes was systematically varied to examine resistive strain sensitivity, while an additional encapsulation was applied to characterize multilayer behavior. The realized designs show remarkable tolerance to repetitive strain, demonstrating that curvature and encapsulation are excellent approaches for minimizing resistive strain sensitivity to enable durable flexible electronics