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Hybrid magnetic arrays embedded in superconducting films are ideal systems to study the competition between different physical (such as the coherence length) and structural length scales such as are available in artificially produ...
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Hybrid magnetic arrays embedded in superconducting films are ideal systems to study the competition between different physical (such as the coherence length) and structural length scales such as are available in artificially produced structures. This interplay leads to oscillation in many magnetically dependent superconducting properties such as the critical currents, resistivity and magnetization. These effects are generally analyzed using two distinct models based on vortex pinning or wire network. In this work, we show that for magnetic dot arrays, as opposed to antidot (i.e. holes) arrays, vortex pinning is the main mechanism for field induced oscillations in resistance R(H), critical current I_c(H), magnetization M(H) and ac-susceptibility χ_(ac)(H) in a broad temperature range. Due to the coherence length divergence at T_c, a crossover to wire network behaviour is experimentally found. While pinning occurs in a wide temperature range up to T_c, wire network behaviour is only present in a very narrow temperature window close to T_c. In this temperature interval, contributions from both mechanisms are operational but can be experimentally distinguished.
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The Little-Parks effect is originally known as a phenomenon, where a critical temperature T-c of the superconducting cylinder oscillates as a function of the applied magnetic field with a period of 450 [R.D. Parks, W.A. Little, Ph...
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The Little-Parks effect is originally known as a phenomenon, where a critical temperature T-c of the superconducting cylinder oscillates as a function of the applied magnetic field with a period of 450 [R.D. Parks, W.A. Little, Phys. Rev. 133 (1964) A97]. It has been well known that a sort of the Little-Parks effect occurs in superconducting network samples, too [B. Pannetier, J. Chaussy, R. Rammal, J.C. Villegier, Phys. Rev. Lett. 53 (1984) 1845]. In this work we intend to prepare fine superconducting networks with the aid of a focused-ion-beam (FIB) microscope. It is very convenient to prepare various kinds of superconducting networks without preparing photo-masks in lithography. The networks thus obtained are examined by using a confocal laser microscope as well as an atomic force microscope. We developed the measurement system to trace a critical temperature T-c as a function of the applied field. The LabVIEW-based system is designed to measure the Little-Parks effect automatically for various sorts of superconducting networks.
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We analyze the timing and extent of Northern European temperature falls during the Little Ice Age, using standard temperature reconstructions. However, we can find little evidence of temporal dependence or structural breaks in Eur...
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We analyze the timing and extent of Northern European temperature falls during the Little Ice Age, using standard temperature reconstructions. However, we can find little evidence of temporal dependence or structural breaks in European weather before the twentieth century. Instead, European weather between the fifteenth and nineteenth centuries resembles uncorrelated draws from a distribution with a constant mean (although there are occasional decades of markedly lower summer temperature) and variance, with the same behavior holding more tentatively back to the twelfth century. Our results suggest that observed conditions during the Little Ice Age in Northern Europe are consistent with random climate variability. The existing consensus about apparent cold conditions may stem in part from a Slutsky effect, where smoothing data gives the spurious appearance of irregular oscillations when the underlying time series is white noise.
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In seasonally dry ecosystems, which are common in sub-Saharan Africa, precipitation after dry periods can cause large pulses of nitrous oxide (N_2O), a greenhouse gas, and of nitric oxide (NO), a precursor to tropospheric ozone po...
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In seasonally dry ecosystems, which are common in sub-Saharan Africa, precipitation after dry periods can cause large pulses of nitrous oxide (N_2O), a greenhouse gas, and of nitric oxide (NO), a precursor to tropospheric ozone pollution. Agricultural practices can change soil characteristics, affecting trace N gas emissions. To evaluate the effects of land use on trace gas pulses at the start of the rainy season, we conducted laboratory measurements of N_2O and NO fluxes from soils collected from four pairs of agricultural and natural savannah sites across the Sudano-Sahelian zone. We also conducted in situ wetting experiments, measuring NO fluxes from fallow sandy soils in Tanzania and NO and N_2O fluxes from clayey soils in Kenya with different histories of fertilizer use. In incubation studies, NO increased by a factor of 7 to 25 following wetting, and N_2O fluxes shifted from negative to positive; cumulative NO fluxes were an order of magnitude larger than cumulative N_2O fluxes. In Kenya and Tanzania, NO increased by 1 to 2 orders of magnitude after wetting, and N_2O increased by a factor of roughly 5 to 10. Cumulative NO fluxes ranged from 87 to 115 g NO-N ha~(-1) across both countries-a substantial proportion of annual emissions-compared to roughly 1 g N_2O-N in Kenya. There were no effects of land use or fertilization history on the magnitude of NO or N_2O pulses, though land use may have been confounded with differences in soil texture potentially limiting the ability to detect land use effects.
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The Donana peridunal lagoons, located in the southwest of Spain, have been well studied, because their conservation is of great interest. Since 1965, they have also been affected by the extraction of underground water for local co...
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The Donana peridunal lagoons, located in the southwest of Spain, have been well studied, because their conservation is of great interest. Since 1965, they have also been affected by the extraction of underground water for local coastal tourist resorts. A reconstruction of the evolution of this series of coastal lagoons reveals that, along with the anthropogenic effect, there was a natural effect resulting from the reactivation of mobile dune fronts that have blocked and filled the original lagoon complex-in the period 1920-1987, the lagoons were reduced by 70.7%. These fronts might have been fed by deposits of marine sand during the climatically driest phases of the Little Ice Age in Andalusia, Spain. Therefore, if the frequency and duration of dry periods increase, as well as droughts as a whole, because of global warming, the desiccation and disappearance of the lagoons could become more widespread, not only at this site in southwestern Europe, but in other Mediterranean coastal ecosystems as well.
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The term 'edge effect' can be defined as an abrupt and local change in the abundance, diversity, composition etc. at the edge of any distinct, spatial patches (structure(s). It usually refers to forest/field, meadow/shrub and othe...
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The term 'edge effect' can be defined as an abrupt and local change in the abundance, diversity, composition etc. at the edge of any distinct, spatial patches (structure(s). It usually refers to forest/field, meadow/shrub and other ecotone environments. This effect in relation to breeding densities and success in birds has been the focus of considerable debate (Manolis et al. 2002). The edge of bird colony is expected to affect similarly on avian population (Krebs 1974). Although such studies can be very useful for management and conservation strategies, they are scarce in the Mediterranean.
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Magnetoresistance measurements in a granular Nb nanoring reveal current-induced crossover between two distinct quantum coherence effects. At low bias currents, Cooper-pair coherence is manifested by Little-Parks oscillations with ...
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Magnetoresistance measurements in a granular Nb nanoring reveal current-induced crossover between two distinct quantum coherence effects. At low bias currents, Cooper-pair coherence is manifested by Little-Parks oscillations with flux periodicity of h/2e. At high bias currents, magnetoresistance oscillations with flux periods of h/e are observed and interpreted as Aharonov-Bohm oscillations, reflecting the phase coherence of individual quasi-particles. The model explaining these data views the ring as a chain of superconducting grains weakly coupled by tunnel junctions. Low bias currents allow coherent tunneling of Cooper pairs between the grains. Increasing the current above the critical current of all the junctions creates a quasi-particles conduction channel along the ring, allowing for quantum interference of quasi-particles.
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The linearized Usadel equations in a generalized form containing both the spin singlet and the odd frequency spin triplet pair amplitudes in an s-wave state are used to study the oscillatory behavior of the superconducting critica...
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The linearized Usadel equations in a generalized form containing both the spin singlet and the odd frequency spin triplet pair amplitudes in an s-wave state are used to study the oscillatory behavior of the superconducting critical temperature T-c due to the influence of an external magnetic field in proximity coaxial cylinders of a ferromagnetic core surrounded by a superconducting shell. Such geometry modifies the pairing wavefunction periodically with the vortex number L. The exchange field in the ferromagnetic core is chosen to be of the spiral type which rotates in the plane with a spiral wave vector Q. The external magnetic field assumes a constant value and is directed perpendicularly to the plane. The switching phenomena of the induced superconductivity in the ferromagnet with various vortex numbers are investigated in detail by solving self-consistently the Usadel equations to determine the Little-Parks effect i.e., the behavior of T-c versus a magnetic flux threading the ferromagnetic core. (C) 2016 Elsevier B.V. All rights reserved.
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The purpose of this study was to elucidate whether the long-term practice of isolated finger movements reduces the enslaved response of the little finger abductor to the index finger abduction. The right-handed participants tonica...
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The purpose of this study was to elucidate whether the long-term practice of isolated finger movements reduces the enslaved response of the little finger abductor to the index finger abduction. The right-handed participants tonically or phasically abducted the index finger, while they maintained at rest or tonic abduction of the little finger. The enslaved response of the tonically contracting little finger abductor to the tonic abduction of the index finger was greater than the response of the same muscle at rest in the nonpianists. This indicates that the tonic contraction of the little finger abductor enhances the enslaving drive from the tonically contracting index finger abductor to the little finger abductor. The enslaved response of the tonically contracting little finger abductor to the tonic abduction of the index finger in the pianists was significantly smaller than that in the nonpianists, but such a significant group difference was absent when the little finger abductor was at rest. This indicates that the inhibitory process on the enslaving drive from the tonically contracting index finger abductor to the tonically active little finger abductor is unmasked through the long-term practice.
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Background Few studies have assessed the effectiveness of the Protected Area networks on the conservation status of target species. Here, we assess the effectiveness of the Portuguese Natura 2000 (the European Union network of pro...
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Background Few studies have assessed the effectiveness of the Protected Area networks on the conservation status of target species. Here, we assess the effectiveness of the Portuguese Natura 2000 (the European Union network of protected areas) in maintaining a species included in the Annex I of the Bird Directive, namely the population of a priority farmland bird, the little bustard Tetrax tetrax. Methods We measured the effectiveness of the Natura 2000 by comparing population trends across time (2003–2006 and 2016) in 51 areas, 21 of which within 12 Special Protection Areas (SPA) that were mostly designated for farmland bird conservation and another 30 areas without EU protection. Results Overall, the national population is estimated to have declined 49% over the last 10–14 years. This loss was found to be proportionally larger outside SPA (64% decline) compared to losses within SPA (25% decline). However, the absolute male density decline was significantly larger within SPA . Discussion In spite of holding higher population densities and having prevented habitat loss, we conclude that Natura 2000 was not effective in buffering against the overall bustard population decline. Results show that the mere designation of SPA in farmland is not enough to secure species populations and has to be combined with agricultural policies and investment to maintain not only habitat availability but also habitat quality.
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