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1
Burgess, M., M. E. Carrington y G. Kunstatter. "Covariant approach to equilibration in effective field theories". Canadian Journal of Physics 80, n.º 2 (1 de febrero de 2002): 97–107. http://dx.doi.org/10.1139/p01-136.
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The equilibration of two coupled reservoirs is studied using a Green function approach that is suitable for future development with the closed time path method. The problem is solved in two parameterizations, to demonstrate the nontrivial issues of parameterization in both the intermediate steps and the interpretation of physical quantities. We use a covariant approach to find self-consistent solutions for the statistical distributions as functions of time. We show that by formally introducing covariant connections, one can rescale a slowly varying nonequilibrium theory so that it appears to be an equilibrium one, for the purposes of calculation. We emphasize the importance of properly tracking variable redefinitions to correctly interpret physical quantities. PACS Nos.: 11.10-z, 03.70+k, 05.70ln
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Galligari, Alessandro y Marco Sciandrone. "A convergent and fast path equilibration algorithm for the traffic assignment problem". Optimization Methods and Software 33, n.º 2 (15 de junio de 2017): 354–71. http://dx.doi.org/10.1080/10556788.2017.1332621.
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Shkliarevsky, Gennady. "Understanding the Process of Creation: A New Approach". Management:Journal of Sustainable Business and Management Solutions in Emerging Economies 22, n.º 3 (31 de octubre de 2017): 1. http://dx.doi.org/10.7595/management.fon.2017.0021.
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Our contemporary civilization increasingly relies on creative approaches and solutions. This growing dependence makes issues of control, regulation, and management of the process of creation ever more important. This article finds two major current theoretical perspectives on creativity and the process of creation to be vulnerable in one important respect: their explanation of the production of disequilibrium, which plays a singularly important role in the process of creation, does not pass the test of rational justification. This article suggests that the production of disequilibrium is intimately related to equilibration—the essential operation of rational thought processes. The emphasis on the role equilibration makes a rational justification of the production of disequilibrium possible. The new theoretical perspective opens the path toward a comprehensive and objective understanding of the process of creation, which is the main condition for regulating, controlling, and managing this process.
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Cruciani, Gabriele, Marcello Franceschelli y Norma Brogioni. "Mineral re-equilibration and P-T path of metagabbros, Sierra de San Luis, Argentina: insights into the exhumation of a mafic-ultramafic belt". European Journal of Mineralogy 23, n.º 4 (24 de octubre de 2011): 590–607. http://dx.doi.org/10.1127/0935-1221/2011/0023-2118.
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Thompson, Andrew F. y Alberto C. Naveira Garabato. "Equilibration of the Antarctic Circumpolar Current by Standing Meanders". Journal of Physical Oceanography 44, n.º 7 (1 de julio de 2014): 1811–28. http://dx.doi.org/10.1175/jpo-d-13-0163.1.
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Abstract The insensitivity of the Antarctic Circumpolar Current (ACC)’s prominent isopycnal slope to changes in wind stress is thought to stem from the action of mesoscale eddies that counterbalance the wind-driven Ekman overturning—a framework verified in zonally symmetric circumpolar flows. Substantial zonal variations in eddy characteristics suggest that local dynamics may modify this balance along the path of the ACC. Analysis of an eddy-resolving ocean GCM shows that the ACC can be broken into broad regions of weak eddy activity, where surface winds steepen isopycnals, and a small number of standing meanders, across which the isopycnals relax. Meanders are coincident with sites of (i) strong eddy-induced modification of the mean flow and its vertical structure as measured by the divergence of the Eliassen–Palm flux and (ii) enhancement of deep eddy kinetic energy by up to two orders of magnitude over surrounding regions. Within meanders, the vorticity budget shows a balance between the advection of relative vorticity and horizontal divergence, providing a mechanism for the generation of strong vertical velocities and rapid changes in stratification. Temporal fluctuations in these diagnostics are correlated with variability in both the Eliassen–Palm flux and bottom speed, implying a link to dissipative processes at the ocean floor. At larger scales, bottom pressure torque is spatially correlated with the barotropic advection of planetary vorticity, which links to variations in meander structure. From these results, it is proposed that the “flexing” of standing meanders provides an alternative mechanism for reducing the sensitivity of the ACC’s baroclinicity to changes in forcing, separate from an ACC-wide change in transient eddy characteristics.
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Stutter, M. I., S. M. Dunn y D. G. Lumsdon. "Dissolved organic carbon dynamics in a UK podzolic moorland catchment: linking storm hydrochemistry, flow path analysis and sorption experiments". Biogeosciences Discussions 9, n.º 1 (5 de enero de 2012): 209–51. http://dx.doi.org/10.5194/bgd-9-209-2012.
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Abstract. Better knowledge of spatial and temporal delivery of dissolved organic Carbon (DOC) in small catchments is required to understand the mechanisms behind reported long-term changes in C fluxes from some peatlands. We monitored two storms with contrasting seasons and antecedent conditions in a small upland UK moorland catchment. We examined DOC concentrations and specific UV absorbance (SUVA at 285 nm), together with solute concentrations required to undertake end member mixing analyses to define dominant flow paths contributing to streamflow. This was combined with laboratory soil-solution equilibrations. We aimed to resolve how seasonal biogeochemical processing of DOC and flowpath changes in organo-mineral soils combine to affect DOC exported via the stream. An August storm following a dry period gave maximum DOC concentration of 10 mg l−1. Small DOC:DON ratios (16–28) and SUVA (2.7–3.6 l mg−1 m−1) was attributed to filtration of aromatic compounds associated with up to 53% B horizon flow contributions. This selective filtration of high SUVA DOC was reproduced in the experimental batch equilibration system. For a November storm, wetter antecedent soil conditions led to enhanced soil connectivity with the stream and seven times greater DOC stream-load (maximum concentration 16 mg l−1). This storm had a 63% O horizon flow contribution at its peak, limited B horizon buffering and consequently more aromatic DOC (SUVA 3.9–4.5 l mg−1 m−1 and DOC:DON ratio 35–43). We suggest that simple mixing of waters from different flow paths cannot alone explain the differences in DOC compositions between August and November and biogeochemical processing of DOC is required to fully explain the observed stream DOC dynamics. This is in contrast to other studies proposing hydrological controls and provides evidence that DOC biogeochemistry must be incorporated in modelling to predict the impacts of changes in DOC delivery to aquatic systems.
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Assanelli, Matteo, Pietro Luoni, Gisella Rebay, Manuel Roda y Maria Iole Spalla. "Tectono-Metamorphic Evolution of Serpentinites from Lanzo Valleys Subduction Complex (Piemonte—Sesia-Lanzo Zone Boundary, Western Italian Alps)". Minerals 10, n.º 11 (5 de noviembre de 2020): 985. http://dx.doi.org/10.3390/min10110985.
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In the upper Tesso Valley the folded contact between Piemonte Zone ophiolites and Sesia-Lanzo Zone continental crust is exposed. Here serpentinites, metabasites, calcschists and fine-grained gneisses are deformed by four ductile superposed groups of structures, associated with different mineral assemblages. Different serpentinite lithologies have been recognized and studied in detail. Mylonitic D2 structures are pervasive and mineral assemblages point to re-equilibration at T of 450 ± 50 ∘C and P of 0.8 ± 0.3 GPa, under blueschist/epidote amphibolite-facies conditions. Pre-D2 structures and mineral assemblages are relics within S2 and indicate a re-equilibration under eclogite-facies conditions, at T of 570 ± 50 ∘C and P > 1.8 GPa. Post-D2 occurs under greenschist-facies conditions. Numerical modeling of a subduction zone allows exploration of the geodynamic context in which such PT path could have developed, and to make hypotheses about the possible timing of such a scenario, in agreement with the timing generally proposed for the Alpine subduction and collision. Model predictions indicate that pre-D2 mineral assemblages may have developed during Paleocene at 60–90 km depth and 115–145 km from the trench, or, alternatively, during lower Eocene at ca. 70–90 km depth, and 135–160 km from the trench.
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Gao, Wenyuan, Cristiana L. Ciobanu, Nigel J. Cook, Ashley Slattery, Fei Huang y Dan Song. "Nanoscale Study of Titanomagnetite from the Panzhihua Layered Intrusion, Southwest China: Multistage Exsolutions Record Ore Formation". Minerals 9, n.º 9 (26 de agosto de 2019): 513. http://dx.doi.org/10.3390/min9090513.
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Titanomagnetite from Fe-Ti-V ores of the Lanjiahuoshan deposit, Panzhihua layered intrusion, Southwest China, was investigated at the nanoscale. The objectives were to establish the composition of exsolution phases and their mutual relationships in order to evaluate the sequence of exsolution among oxide phases, and assess mechanisms of ore formation during magma emplacement. At the micron-scale, titanomagnetite shows crosscutting sets of exsolutions with ilmenite and Al-Mg-Fe-spinel (pleonaste), as well as overprint, both in terms of phase re-equilibration and remobilization of trace elements. Most complex textures were found in titanomagnetite surrounded by ilmenite and this was selected for high-angle annular dark field scanning transmission electron microscopy (HAADF STEM) imaging and STEM energy-dispersive X-ray spectrometry (EDS) spot analysis and mapping on a thin foil prepared in situ on a focused ion beam scanning electron microscope platform. Titanomagnetite revealed two sequential sets of exsolutions, {111} crosscutting {100}, which are associated with changes in phase speciation and trace element distribution patterns. Qandilite is the dominant spinel phase inside titanomagnetite; magnesioferrite is also identified. In contrast, Fe-poor, Al-rich, Mg-bearing spinel is present within ilmenite outside the grain. Vanadium enrichment in newly-formed magnetite lamellae is clear evidence for trace element remobilization. This V-rich magnetite shows epitaxial relationships with ilmenite at the contact with titanomagnetite. Two-fold super-structuring in ilmenite is evidence for non-redox re-equilibration between titanomagnetite and ilmenite, supporting published experimental data. In contrast, the transformation of cubic Ti-rich spinel into rhombohedral ilmenite imaged at the nanoscale represents the “oxy-exsolution” model of titanomagnetite–ilmenite re-equilibration via formation of a transient ulvöspinel species. Nanoscale disorder is encountered as vacancy layers in Ti-rich spinel, and lower symmetry in the Fe-poor, Al-Mg phase, suggesting that slow cooling rates can preserve small-scale phase equilibration. The cooling history of titanomagnetite ore can be reconstructed as three distinct stages, concordant with published models for the magma plumbing system: equilibrium crystallization of Al-rich, Mg-bearing titanomagnetite from cumulus melts at ~55 km, with initial exsolutions occurring above 800 °C at moderate fO2 conditions (Stage 1); crosscutting {111} exsolutions resulting in formation of qandilite, attributable to temperature increase due to emplacement of another batch of melt affecting the interstitial cumulus during uplift. Formation of 2-fold superstructure ilmenite + V-rich magnetite exsolution pairs representing non-redox equilibration indicates resetting of the cooling path at this stage (Stage 2); and ilmenite formation from pre-existing Ti-rich spinel and ulvöspinel, illustrative of redox-driven cooling paths at <10 km (Stage 3). HAADF STEM provides direct imaging of atomic arrangements, allowing recognition of processes not recognizable at the micron-scale, and can thus be used to constrain exsolution models during ore formation.
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Stutter, M. I., S. M. Dunn y D. G. Lumsdon. "Dissolved organic carbon dynamics in a UK podzolic moorland catchment: linking storm hydrochemistry, flow path analysis and sorption experiments". Biogeosciences 9, n.º 6 (18 de junio de 2012): 2159–75. http://dx.doi.org/10.5194/bg-9-2159-2012.
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Abstract. Better knowledge of spatial and temporal delivery of dissolved organic carbon (DOC) in small catchments is required to understand the mechanisms behind reported long-term changes in C fluxes from some peatlands. We monitored two storms with contrasting seasons and antecedent conditions in a small upland UK moorland catchment. We examined DOC concentrations and specific UV absorbance (SUVA at 285 nm), together with solute concentrations required to undertake end-member mixing analyses to define dominant flow paths contributing to streamflow. This was combined with laboratory soil-solution equilibrations. We aimed to resolve how seasonal biogeochemical processing of DOC and flowpath changes in organo-mineral soils combine to affect DOC exported via the stream. An August storm following a dry period gave maximum DOC concentration of 10 mg l−1. Small DOC:DON ratios (16–28) and SUVA (2.7–3.6 l mg−1 m−1) was attributed to filtration of aromatic compounds associated with up to 53% B horizon flow contributions. This selective filtration of high SUVA DOC was reproduced in the experimental batch equilibration system. For a November storm, wetter antecedent soil conditions led to enhanced soil connectivity with the stream and seven times greater DOC stream-load (maximum concentration 16 mg l−1). This storm had a 63% O horizon flow contribution at its peak, limited B horizon buffering and consequently more aromatic DOC (SUVA 3.9–4.5 l mg−1 m−1 and DOC:DON ratio 35–43). We suggest that simple mixing of waters from different flow paths cannot alone explain the differences in DOC compositions between August and November and biogeochemical processing of DOC is required to fully explain the observed stream DOC dynamics. This preliminary evidence is in contrast to other studies proposing hydrological controls on the nature of DOC delivered to streams. Although our study is based only on two storms of very different hydrological and biogeochemical periods, this should promote wider study of DOC biogeochemical alteration in headwaters so that this be better incorporated in modelling to predict the impacts of changes in DOC delivery to, and fate in, aquatic systems.
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Cruciani, G., M. Franceschelli y H. J. Massonne. "Low-temperature metamorphic evolution of a pre-Variscan gabbro: a case study from the Palaeozoic basement of northwest Sardinia, Italy". Mineralogical Magazine 75, n.º 6 (diciembre de 2011): 2793–812. http://dx.doi.org/10.1180/minmag.2011.075.6.2793.
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AbstractA lenticular metagabbro crops out in an early Palaeozoic metasedimentary sequence at Nurra, northwest Sardinia. The metagabbro consists of variable proportions of early-formed coarse-grained albite, chlorite, epidote and apatite, later biotite and amphibole, and late stilpnomelane. Clinopyroxene and ilmenite are rare relict igneous minerals; albite has completely replaced primary plagioclase.The metamorphic evolution of the Nurra metagabbro has been investigated by pseudosection modelling for a fixed bulk-rock composition in the Na2O—CaO—K2O—FeO—MgO—A12O3—SiO2—H2O (NCKFMASH) model system with added Ti and Mn in the P-T range 1-11 kbar and 150-450°C. The P—T path of the metagabbro is a loop with a prograde segment overprinted by later metamorphic re-equilibration. The pressure peak was at ⩽7 kbar and ∼400°C. The subsequent temperature peak, at ∼440°C, was accompanied by a decrease in pressure to ∼3 kbar. The final P—T evolution of the metagabbro is characterized by near-isobaric cooling to 250—300°C, with the formation of stilpnomelane. The P—T path of the Nurra gabbro is typical of continental orogenic belts that have undergone crustal thickening.
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Ogilvie, Paula y Roger L. Gibson. "Arrested development – a comparative analysis of multilayer corona textures in high-grade metamorphic rocks". Solid Earth 8, n.º 1 (6 de febrero de 2017): 93–135. http://dx.doi.org/10.5194/se-8-93-2017.
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Abstract. Coronas, including symplectites, provide vital clues to the presence of arrested reaction and preservation of partial equilibrium in metamorphic and igneous rocks. Compositional zonation across such coronas is common, indicating the persistence of chemical potential gradients and incomplete equilibration. Major controls on corona mineralogy include prevailing pressure (P), temperature (T) and water activity (aH2O) during formation, reaction duration (t) single-stage or sequential corona layer growth; reactant bulk compositions (X) and the extent of metasomatic exchange with the surrounding rock; relative diffusion rates for major components; and/or contemporaneous deformation and strain. High-variance local equilibria in a corona and disequilibrium across the corona as a whole preclude the application of conventional thermobarometry when determining P–T conditions of corona formation, and zonation in phase composition across a corona should not be interpreted as a record of discrete P–T conditions during successive layer growth along the P–T path. Rather, the local equilibria between mineral pairs in corona layers more likely reflect compositional partitioning of the corona domain during steady-state growth at constant P and T. Corona formation in pelitic and mafic rocks requires relatively dry, residual bulk rock compositions. Since most melt is lost along the high-T prograde to peak segment of the P–T path, only a small fraction of melt is generally retained in the residual post-peak assemblage. Reduced melt volumes with cooling limit length scales of diffusion to the extent that diffusion-controlled corona growth occurs. On the prograde path, the low melt (or melt-absent) volumes required for diffusion-controlled corona growth are only commonly realized in mafic igneous rocks, owing to their intrinsic anhydrous bulk composition, and in dry, residual pelitic compositions that have lost melt in an earlier metamorphic event. Experimental work characterizing rate-limiting reaction mechanisms and their petrogenetic signatures in increasingly complex, higher-variance systems has facilitated the refinement of chemical fractionation and partial equilibration diffusion models necessary to more fully understand corona development. Through the application of quantitative physical diffusion models of coronas coupled with phase equilibria modelling utilizing calculated chemical potential gradients, it is possible to model the evolution of a corona through P–T–X–t space by continuous, steady-state and/or sequential, episodic reaction mechanisms. Most coronas in granulites form through a combination of these endmember reaction mechanisms, each characterized by distinct textural and chemical potential signatures with very different petrogenetic implications. An understanding of the inherent petrogenetic limitations of a reaction mechanism model is critical if an appropriate interpretation of P–T evolution is to be inferred from a corona. Since corona modelling employing calculated chemical potential gradients assumes nothing about the sequence in which the layers form and is directly constrained by phase compositional variation within a layer, it allows far more nuanced and robust understanding of corona evolution and its implications for the path of a rock in P–T–X space.
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Vezinet, Adrien, Emilie Thomassot, Yan Luo, Chiranjeeb Sarkar y D. Graham Pearson. "Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane". Geosciences 12, n.º 1 (12 de enero de 2022): 36. http://dx.doi.org/10.3390/geosciences12010036.
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In metamorphic rocks, mineral species react over a range of pressure–temperature conditions that do not necessarily overlap. Mineral equilibration can occur at varied points along the metamorphic pressure–temperature (PT) path, and thus at different times. The sole or dominant use of zircon isotopic compositions to constrain the evolution of metamorphic rocks might then inadvertently skew geological interpretations towards one aspect or one moment of a rock’s history. Here, we present in-situ U–Pb/Sm–Nd isotope analyses of the apatite crystals extracted from two meta-igneous rocks exposed in the Saglek Block (North Atlantic craton, Canada), an Archean metamorphic terrane, with the aim of examining the various signatures and events that they record. The data are combined with published U–Pb/Hf/O isotope compositions of zircon extracted from the same hand-specimens. We found an offset of nearly ca. 1.5 Gyr between U-Pb ages derived from the oldest zircon cores and apatite U–Pb/Sm–Nd isotopic ages, and an offset of ca. 200 Ma between the youngest zircon metamorphic overgrowths and apatite. These differences in metamorphic ages recorded by zircon and apatite mean that the redistribution of Hf isotopes (largely hosted in zircon) and Nd isotopes (largely hosted in apatite within these rocks), were not synchronous at the hand-specimen scale (≤~0.001 m3). We propose that the diachronous redistribution of Hf and Nd isotopes and their parent isotopes was caused by the different PT conditions of growth equilibration between zircon and apatite during metamorphism. These findings document the latest metamorphic evolution of the Saglek Block, highlighting the role played by intra-crustal reworking during the late-Archean regional metamorphic event.
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Cruciani, Gabriele, Marcello Franceschelli, Chiara Groppo, Giacomo Oggiano y Maria Elena Spano. "Re-equilibration history and P–T path of eclogites from Variscan Sardinia, Italy: a case study from the medium-grade metamorphic complex". International Journal of Earth Sciences 104, n.º 3 (11 de noviembre de 2014): 797–814. http://dx.doi.org/10.1007/s00531-014-1095-5.
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Castillo-García, Alvaro, Andreas W. Hauser, María Pilar de Lara-Castells y Pablo Villarreal. "A Path Integral Molecular Dynamics Simulation of a Harpoon-Type Redox Reaction in a Helium Nanodroplet". Molecules 26, n.º 19 (24 de septiembre de 2021): 5783. http://dx.doi.org/10.3390/molecules26195783.
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We present path integral molecular dynamics (PIMD) calculations of an electron transfer from a heliophobic Cs2 dimer in its (3Σu) state, located on the surface of a He droplet, to a heliophilic, fully immersed C60 molecule. Supported by electron ionization mass spectroscopy measurements (Renzler et al., J. Chem. Phys.2016, 145, 181101), this spatially quenched reaction was characterized as a harpoon-type or long-range electron transfer in a previous high-level ab initio study (de Lara-Castells et al., J. Phys. Chem. Lett.2017, 8, 4284). To go beyond the static approach, classical and quantum PIMD simulations are performed at 2 K, slightly below the critical temperature for helium superfluidity (2.172 K). Calculations are executed in the NVT ensemble as well as the NVE ensemble to provide insights into real-time dynamics. A droplet size of 2090 atoms is assumed to study the impact of spatial hindrance on reactivity. By changing the number of beads in the PIMD simulations, the impact of quantization can be studied in greater detail and without an implicit assumption of superfluidity. We find that the reaction probability increases with higher levels of quantization. Our findings confirm earlier, static predictions of a rotational motion of the Cs2 dimer upon reacting with the fullerene, involving a substantial displacement of helium. However, it also raises the new question of whether the interacting species are driven out-of-equilibrium after impurity uptake, since reactivity is strongly quenched if a full thermal equilibration is assumed. More generally, our work points towards a novel mechanism for long-range electron transfer through an interplay between nuclear quantum delocalization within the confining medium and delocalized electronic dispersion forces acting on the two reactants.
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ZANCHETTA, S., N. MALASPINA, A. ZANCHI, L. BENCIOLINI, S. MARTIN, H. R. JAVADI y M. KOUHPEYMA. "Contrasting subduction–exhumation paths in the blueschists of the Anarak Metamorphic Complex (Central Iran)". Geological Magazine 155, n.º 2 (3 de abril de 2017): 316–34. http://dx.doi.org/10.1017/s0016756817000218.
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AbstractThe Anarak Metamorphic Complex, localized in Central Iran, is a fossil accretionary wedge composed of several tectonometamorphic units. Some of these, the Chah Gorbeh, the Morghab and the Ophiolitic complexes, contain mafic rocks that have been metamorphosed at high-pressure–low-temperature conditions. Such units have been stacked together and later refolded during the final stages of exhumation. Structural analysis at the mesoscale recognized at least three deformation events. Microstructural analyses, mineral chemistry and thermodynamic modelling reveal that the mafic schists followed contrasting P–T paths during their tectonometamorphic evolutions. In the schists of the Chah Gorbeh and Ophiolitic complexes an early greenschist-facies stage was later overprinted by blueschist-facies phase assemblages with suggested peak conditions of 390–440°C at 0.6–0.9 GPa for the meta-basalt within the Ophiolitic Complex and 320–380°C at 0.6–0.9 GPa for the blueschists of the Chah Gorbeh Complex. P–T conditions at metamorphic peak were 410–450°C at 0.78–0.9 GPa for the Morghab blueschists, but they are reached before a greenschist-facies re-equilibration. Compositional zoning of amphiboles and epidotes of this greenschist-facies stage suggests a renewed pressure increase at the end of this metamorphic stage. Based on these data we reconstructed a clockwise P–T path for the Morghab mafic schists and a counter-clockwise path for the Chah Gorbeh blueschists and ophiolitic meta-basalts. Such contrasting metamorphic evolutions of tectonic units that were later accreted to the same wedge are indicative of the complex tectonic dynamics that occur within accretionary–subduction complexes.
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Gaff, Donald F. y Melvin Oliver. "The evolution of desiccation tolerance in angiosperm plants: a rare yet common phenomenon". Functional Plant Biology 40, n.º 4 (2013): 315. http://dx.doi.org/10.1071/fp12321.
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In a minute proportion of angiosperm species, rehydrating foliage can revive from airdryness or even from equilibration with air of ~0% RH. Such desiccation tolerance is known from vegetative cells of some species of algae and of major groups close to the evolutionary path of the angiosperms. It is also found in the reproductive structures of some algae, moss spores and probably the aerial spores of other terrestrial cryptogamic taxa. The occurrence of desiccation tolerance in the seed plants is overwhelmingly in the aerial reproductive structures; the pollen and seed embryos. Spatially and temporally, pollen and embryos are close ontogenetic derivatives of the angiosperm microspores and megaspores respectively. This suggests that the desiccation tolerance of pollen and embryos derives from the desiccation tolerance of the spores of antecedent taxa and that the basic pollen/embryo mechanism of desiccation tolerance has eventually become expressed also in the vegetative tissue of certain angiosperm species whose drought avoidance is inadequate in micro-habitats that suffer extremely xeric episodes. The protective compounds and processes that contribute to desiccation tolerance in angiosperms are found in the modern groups related to the evolutionary path leading to the angiosperms and are also present in the algae and in the cyanobacteria. The mechanism of desiccation tolerance in the angiosperms thus appears to have its origins in algal ancestors and possibly in the endosymbiotic cyanobacteria-related progenitor of chloroplasts and the bacteria-related progenitor of mitochondria. The mechanism may involve the regulation and timing of the accumulation of protective compounds and of other contributing substances and processes.
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SPALLA, CARMINATI, CERIANI, OLIVA y BATTAGLIA. "Influence of deformation partitioning and metamorphic re-equilibration on P-T path reconstruction in the pre-Alpine basement of central Southern Alps (Northern Italy)". Journal of Metamorphic Geology 17, n.º 3 (25 de diciembre de 2001): 319–36. http://dx.doi.org/10.1046/j.1525-1314.1999.00199.x.
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Bazˇant, Zdeneˇk P. "Softening Instability: Part II—Localization Into Ellipsoidal Regions". Journal of Applied Mechanics 55, n.º 3 (1 de septiembre de 1988): 523–29. http://dx.doi.org/10.1115/1.3125824.
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Extending the preceding study of exact solutions for finite-size strain-softening regions in layers and infinite space, exact solution of localization instability is obtained for the localization of strain into an ellipsoidal region in an infinite solid. The solution exploits Eshelby’s theorem for eigenstrains in elliptical inclusions in an infinite elastic solid. The special cases of localization of strain into a spherical region in three dimensions and into a circular region in two dimensions are further solved for finite solids — spheres in 3D and circles in 2D. The solutions show that even if the body is infinite the localization into finite regions of such shapes cannot take place at the start of strain-softening (a state corresponding to the peak of the stress-strain diagram) but at a finite strain-softening slope. If the size of the body relative to the size of the softening region is decreased and the boundary is restrained, homogeneous strain-softening remains stable into a larger strain. The results also can be used as checks for finite element programs for strain-softening. The present solutions determine only stability of equilibration states but not bifurcations of the equilibrium path.
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Nasrabady, M., F. Rossetti, T. Theye y G. Vignaroli. "Metamorphic history and geodynamic significance of the Early Cretaceous Sabzevar granulites (Sabzevar structural zone, NE Iran)". Solid Earth Discussions 3, n.º 1 (19 de mayo de 2011): 477–526. http://dx.doi.org/10.5194/sed-3-477-2011.
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Abstract. The Iranian ophiolites are part of the vast orogenic suture zones that mark the Alpine-Himalayan convergence zone. Few petrological and geochronological data are available from these ophiolitic domains, hampering a full assessment of the timing and regimes of subduction zone metamorphism and orogenic construction in the region. This paper describes texture, geochemistry and the pressure-temperature path of the Early Cretaceous granulites that occur within the Tertiary Sabzevar suture zone of NE Iran. The geochemical data set document that the granulites are remnants of a MORB-type oceanic crust and thus of a (Early Cretaceous ?) back-arc basin formed in the upper plate of the Neotethyan subduction and thus interpreted as portions of a dismembered dynamothermal sole formed during oceanic subduction. The metamorphic history of the granulites suggests an anticlockwise pressure-temperature loop, compatible with burial in a hot subduction zone followed by cooling during exhumation. This is interpreted as the evidence of a nascent subduction zone formed at the expenses of hot and hence young oceanic lithosphere. These data point to diachronous and independent tectonic evolutions of the different ophiolitic domains of central Iran, for which a growing heterogeneity in the timing of metamorphic equilibration and of pressure-temperature paths can be expected with further investigations.
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O'Beirne-Ryan, A. M., R. A. Jamieson y Y. D. Gagnon. "Petrology of garnet–clinopyroxene amphibolites from Mont Albert, Gaspé, Quebec". Canadian Journal of Earth Sciences 27, n.º 1 (1 de enero de 1990): 72–86. http://dx.doi.org/10.1139/e90-006.
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The Mont Albert mafic–ultramafic complex of central Gaspé, Quebec, is generally regarded as a partial ophiolite with an underlying metamorphic sole. The metamorphic rocks include a number of mineralogical and textural varieties of amphibolite, including some migmatite, as well as minor metasedimentary and quartzo-feldspathic gneisses. The most intriguing rocks in the complex are mafic to ultramafic garnet- and clinopyroxene-bearing amphibolites that are restricted to the vicinity of the peridotite contact. These rocks have unusual Fe-rich, Si-poor bulk compositions and may represent tholeiites chemically modified by interaction with fluid or melt before or during metamorphism. These amphibolites are not retrograde eclogites, since andesine was present throughout the metamorphic history, and the clinopyroxene is not omphacitic. Coexisting mineral compositions and temperature estimates overlap for core, rim, and matrix grains of all the major phases in the garnet–clinopyroxene amphibolites, implying equilibration in the range 750–800 °C at 8–9 kbar (1 kbar = 100 MPa). Garnet amphibolites lacking clinopyroxene yielded somewhat lower P–T estimates of 600–700 °C and 6–7 kbar. Owing to complex field relationships, it is not clear whether or not these P–T conditions resulted from evolution along a single P–T–t path.
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Kryza, R., A. P. Willner, H. J. Massonne, A. Muszyński y H. P. Schertl. "Blueschist-facies metamorphism in the Kaczawa Mountains (Sudetes, SW Poland) of the Central-European Variscides: P-T constraints from a jadeite-bearing metatrachyte". Mineralogical Magazine 75, n.º 1 (febrero de 2011): 241–63. http://dx.doi.org/10.1180/minmag.2011.075.1.241.
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AbstractSodic pyroxene is reported from an Ordovician metatrachyte of the Kaczawa Mountains, SW Poland. Its composition ranges from Jd0.98Ae0.02 to Jd0.15Ae0.85. Relict jadeite and phengite (up to 3.75 Si atoms per fomula unit) belong to the peak-pressure assemblage of an early HP-LT event. Later greenschist-facies stages are represented by riebeckite, biotite, chlorite, low-Si potassic white mica and actinolite. P-T pseudosections calculated for the range 200–450°C, 3–13 kbar allow evaluation of the conditions of formation of jadeite in the metatrachyte and derivaton of a P-T path. Considering the position of prograde, peak and retrograde metamorphic assemblages and respective mineral compositions, we can derive the following equilibration stages: 8.5±0.5 kbar, 270±20°C for the pressure maximum, 6.0±1.0 kbar, 310±20°C for the temperature maximum and 3.5±0.5 kbar, 280±20°C as well as <3.5 kbar, <280°C for the retrograde stages.The metamorphic gradient for the peak-pressure is estimated at ∼10°C/km, which is typical of a subduction setting involving subducted continental crust, in particular of an exhumation channel within a collision zone of a microplate. Based on earlier structural observations, the ESE-oriented subduction in the NE Bohemian Massif was confined with WNW thrusting and followed by extension and ESE backward normal faulting during Devonian–Early Carboniferous times.
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Nasrabady, M., F. Rossetti, T. Theye y G. Vignaroli. "Metamorphic history and geodynamic significance of the Early Cretaceous Sabzevar granulites (Sabzevar structural zone, NE Iran)". Solid Earth 2, n.º 2 (11 de noviembre de 2011): 219–43. http://dx.doi.org/10.5194/se-2-219-2011.
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Abstract. The Iranian ophiolites are part of the vast orogenic suture zones that mark the Alpine-Himalayan convergence zone. Few petrological and geochronological data are available from these ophiolitic domains, hampering a full assessment of the timing and regimes of subduction zone metamorphism and orogenic construction in the region. This paper describes texture, geochemistry, and the pressure-temperature path of the Early Cretaceous mafic granulites that occur within the Tertiary Sabzevar ophiolitic suture zone of NE Iran. Whole rock geochemistry indicates that the Sabzevar granulites are likely derived from a MORB-type precursor. They are thus considered as remnants of a dismembered dynamo-thermal sole formed during subduction of a back-arc basin (proto-Sabzevar Ocean) formed in the upper-plate of the Neotethyan slab. The metamorphic history of the granulites suggests an anticlockwise pressure-temperature loop compatible with burial in a hot subduction zone, followed by cooling during exhumation. Transition from a nascent to a mature stage of oceanic subduction is the geodynamic scenario proposed to accomplish for the reconstructed thermobaric evolution. When framed with the regional scenario, results of this study point to diachronous and independent tectonic evolutions of the different ophiolitic domains of central Iran, for which a growing disparity in the timing of metamorphic equilibration and of pressure-temperature paths can be expected to emerge with further investigations.
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HUET, BENJAMIN, LOÏC LABROUSSE, PATRICK MONIÉ, BENJAMIN MALVOISIN y LAURENT JOLIVET. "Coupled phengite 40Ar–39Ar geochronology and thermobarometry: P-T-t evolution of Andros Island (Cyclades, Greece)". Geological Magazine 152, n.º 4 (21 de noviembre de 2014): 711–27. http://dx.doi.org/10.1017/s0016756814000661.
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AbstractAndros is a key island for understanding both the timing of high-pressure–low-temperature (HP-LT) metamorphism and the dynamics of crustal-scale detachment systems exhuming high-grade units in the Cyclades (Greece). Using phengite 40Ar–39Ar geochronology coupled with thermobarometry, as well as data from literature, we constrain the pressure–temperature–time (P-T-t) paths of the Makrotantalon and Attic–Cycladic Blueschist units on Andros. Peak conditions of the HP-LT episode in the Makrotantalon unit are 550°C and 18.5 kbar, dated at 116 Ma. We correlate this episode with Early Cretaceous blueschist facies metamorphism recognized in the Pelagonian zone of continental Greece. This is a new argument favouring a Pelagonian origin for the Makrotantalon unit. In the Attic–Cycladic Blueschist unit, the P-T-t path is characterized by: (1) exhumation after peak conditions in HP-LT conditions between 55 and 35 Ma; (2) isobaric heating at 7 kbar until 30 Ma; and (3) isothermal decompression until 21 Ma. This thermal evolution and timing are similar to those of the neighbouring Tinos Island, emphasizing major thermal re-equilibration at the transition between stable and retreating subduction. Modifications of the crustal thermal state played a major role in the evolution of the North Cycladic Detachment System, below which Andros HP-LT units were exhumed.
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Harris, J. P., J. L. Edwards, L. A. Rispoli, N. R. Rorhbach, T. M. Prado, A. M. Saxton y F. N. Schrick. "13 MOTILITY CHARACTERISTICS OF SPERMATOZOA FROM BULLS GRAZING TALL FESCUE PASTURES". Reproduction, Fertility and Development 26, n.º 1 (2014): 121. http://dx.doi.org/10.1071/rdv26n1ab13.
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Fertilisation is less than expected with spermatozoa from bulls consuming toxic endophyte-infected (E+) tall fescue. The objective of this study was to evaluate motility characteristics of spermatozoa from bulls grazing tall fescue pastures using computer-assisted sperm analysis (CASA). Semen was collected from six Angus bulls (average age = 15.1 ± 0.04 months) during a three-month grazing study. Bulls grazed Kentucky 31 tall fescue (Festuca arundinacea Schreb.) infected with Neotyphodium coenophialum, an ergot alkaloid-producing endophyte (n = 3), or Jesup tall fescue with Max-Q™ (NTE), a non-ergot alkaloid producing endophyte (n = 3), and grouped by body weight and scrotal circumference to graze pastures from April 18 to June 26. Semen was collected once per week between 0600–0800 h beginning in mid-May and ending the last week of June. Gross motility and morphology was evaluated before extending with Bioxcell® animal protein-free formula (IMV, Aigle, France) and antibiotics (CSS 100, 2% of total volume). Extended semen was then evaluated using CASA to determine final dilution and packaged into straws (20 million sperm/straw), where equilibration occurred over 3 h in a cold room at 4°C. Straws were frozen for 7 min in static vapor of liquid nitrogen and plunged into goblets filled with liquid nitrogen. Semen was thawed and assessed using CASA at 0 and 3 h post-thaw. Data were analysed as a randomised block design with the fixed effects of treatment, blocking on semen collection date, utilising the mixed models procedure of SAS 9.2 (SAS Institute Inc., Cary, NC, USA). Data were tested for normality (Shapiro-Wilk W ≥ 0.90), and treatment differences were determined using F-protected least significant differences. Path velocity (P = 0.001) and progressive velocity (P = 0.003) were lower in spermatozoa from bulls grazing E+ during the last 2 weeks of collection in June independent of time of assessment post-thaw. Sperm head area decreased in size in spermatozoa from E+ grazing bulls at 3 h post-thaw (P = 0.04) compared with NTE grazing bulls. Percent of rapid (progressive % with path velocity >50 μm s–1) and medium (progressive % with path velocity <50 μm s–1 but > 30μm s–1) velocity spermatozoa was decreased for E+ grazing bulls compared to NTE grazing bulls (P < 0.0001 and P = 0.004, respectively) and was accompanied by an increase in static (immobile) spermatozoa from E+ bulls (P < 0.0001). These findings indicate that spermatozoa movement and velocity are impaired in bulls grazing E+ tall fescue pastures compared to bulls grazing NTE tall fescue pastures after the freeze and thaw process, which may explain decreased fertilisation and cleavage rates of oocytes co-incubated with these spermatozoa.
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Miraz, Md Faizul Hossain, Gautam Kumar Deb, SM Jahangir Hossain y Shahrina Akter. "Motion characteristics and plasma integrity evaluation of Murrah buffalo semen". Asian-Australasian Journal of Bioscience and Biotechnology 7, n.º 2 (29 de agosto de 2022): 75–81. http://dx.doi.org/10.3329/aajbb.v7i2.61097.
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Buffalo semen collected from Murrah bull were cryopreserved and evaluated for different motility parameter, kinematics and plasma membrane integrity. Buffalo bulls were maintained uniform standard management and nutritional practices. Semen was collected regularly twice a week semen collection schedule from four (04) Murrah bull. Collected semen was immediately transported to laboratory and evaluated for different macroscopic parameter (color, volume and thickness). Fresh semen was then diluted with saline solution and evaluated for sperm concentration, motility, sperm kinematics and morphology. Semen samples that fill all the standard were selected for freezing and diluted with Tris-egg yolk citrate diluter. Diluted semen was equilibrated, cryopreserved and finally evaluated for post thaw sperm quality. Different motility parameter (total, progressive, static and slow motility) varied significantly (p<0.01) irrespective of different freezing stages. Significantly higher progressive sperm motility and viability of buffalo spermatozoa were observed at fresh semen whereas lower progressive sperm motility and viability was found at post thaw stage. Total and progressive motility reduced by 2.5 and 2.12% following equilibration, whereas following cryopreservation, total and progressive motility reduced by 35.7 and 28.51% and static motility increases accordingly (35.4%). Significantly higher plasma membrane integrity of sperm was observed at fresh semen followed by pre freeze and post thaw semen. Following freezing, integrity of plasma membrane reduces at the rate of 10.81% and 26.7% at pre freezing and post thaw stages. Significantly higher average path velocity (VAP), straight line velocity (VSL), curvilinear velocity (VCL), straightness (STR), amplitude of lateral head displacement (ALH) and beat cross frequency (BCF) were found for fresh semen followed by pre-freeze and post-thaw semen. Frozen buffalo semen with higher progressive motility and motion characteristics may be produced if motility losses can be reduced during freezing stage as this stage results higher motility losses. Asian Australas. J. Biosci. Biotechnol. 2022, 7(2), 75-81
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ENGVIK, A. K. y S. ELVEVOLD. "Pan-African extension and near-isothermal exhumation of a granulite facies terrain, Dronning Maud Land, Antarctica". Geological Magazine 141, n.º 6 (noviembre de 2004): 649–60. http://dx.doi.org/10.1017/s0016756804009859.
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The Mühlig-Hofmann- and Filchnerfjella in central Dronning Maud Land, Antarctica, consist of series of granitoid igneous rocks emplaced in granulite and upper amphibolite facies metamorphic rocks. The area has experienced high-temperature metamorphism followed by near-isothermal decompression, partial crustal melting, voluminous magmatism and extensional exhumation during the later phase of the late Neoproterozoic to Cambrian Pan-African event. Remnants of kyanite–garnet–ferritschermakite–rutile assemblages indicate an early higher-pressure metamorphism and crustal overthickening. The gneisses experienced peak granulite facies temperatures of 800–900 °C at intermediate pressures. Breakdown of garnet + sillimanite + spinel-bearing assemblages to cordierite shows subsequent re-equilibration to lower pressures. An E–W foliation dominating the gneisses illustrates transposition of migmatites and leucocratic melts which evolved during the near-isothermal decompression. Occurrence of extensional shear bands and shear zones evolving from the ductile partial melting stage through semiductile towards brittle conditions, shows that the uplift persisted towards brittle crustal conditions under tectonic W/SW-vergent extension. Late-orogenic Pan-African quartz syenites intruded after formation of the main gneiss fabric contain narrow semiductile to brittle shear zones, illustrating that the extensional exhumation continued also after their emplacement. The latest record of the Pan-African event is late-magmatic fluid infiltration around 350–400 °C and 2 kbar. At this stage the Pan-African crust had undergone 15–20 km exhumation from the peak granulite facies conditions. We conclude that the later phase of the Pan-African event in central Dronning Maud Land is characterized by a near-isothermal decompression P–T path and extensional structures indicating tectonic exhumation, which is most likely related to a late-orogenic collapsing phase of the Pan-African orogen.
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Mphaphathi, M. L., M. M. Seshoka, T. R. Netshirovha, Z. C. Raphalalani, T. C. Chokoe, M. Nkadimeng, N. L. Kanuya, J. P. C. Greyling y T. L. Nedambale. "37 DOUBLE FREEZING AND THAWING OF NGUNI BULL SEMEN". Reproduction, Fertility and Development 28, n.º 2 (2016): 148. http://dx.doi.org/10.1071/rdv28n2ab37.
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Indigenous bulls semen are important for conservation programs. The objectives of this study were to evaluate the effects of repeated freezing and thawing on sperm motility characteristics. Semen was collected from 4 Nguni bulls by means of electro ejaculator and stored in a thermo flask (37°C). Sperm total motility, progressive and nonprogressive motility, and velocity were assessed using computer-aided sperm analysis before and after freezing. Semen was then diluted with egg yolk citrate extender (fraction A), then followed by 12% of glycerol + egg yolk citrate extender (fraction B, Seshoka et al. 2012). Diluted semen samples were equilibrated for 4 h at 5°C. After the equilibration period, samples were loaded into 0.25-mL straws and transferred into a controlled rate programmable freezer. After the target temperature of –130°C was reached, semen straws were stored in a LN tank (–196°C). After 3 months of storage, straws were thawed at 15°C (first and second freezing and thawing followed the same process) for 5 min and further evaluated post-thawed at 0 and 15 min during incubation at 15°C. Treatment means were separated using Fisher’s protected t-test least. No significant differences were recorded between the raw semen total sperm motility percentage (93.2%) and first frozen-thawed at 0 min (82.6%), with the total sperm motility rate recovery of 88.6%. In addition, there was a marked decline recorded in sperm total motility during the first frozen-thawed at 15 min (77.6%), second frozen-thawed at 0 min (31.3%), and second frozen-thawed at 15 min (30.1%; P < 0.05). The sperm curvilinear velocity and average path velocity was reduced following first frozen-thawed (P < 0.05) but remained constant and stable between the treatment groups (P > 0.05). In conclusion, the freezing-thawing process did not reduce the Nguni bull total sperm motility during the first freezing and thawing process, compared with raw semen. However, a drastic decline was recorded during the second freezing-thawing processes, compared with raw semen.
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Pathak, P. K., A. J. Dhami y D. V. Chaudhari. "Correlations of Motion Characteristics and KinematicAttributes of Fresh and Frozen-thawed Spermatozoaof Gir Bulls". INDIAN JOURNAL OF VETERINARY SCIENCES AND BIOTECHNOLOGY 15, n.º 01 (25 de julio de 2019): 9–13. http://dx.doi.org/10.21887/ijvsbt.15.1.2.
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This investigation was carried out on semen of three healthy mature breeding bulls of Gir breed to evaluate the interrelationships among sperm quality attributes of fresh and frozen-thawed semen assessed by Biovis CASA. The ejaculates (n = 24) having >75% initial motility were diluted @80 million sperm/mL using TFYG extender, filled in French mini straws, and were frozen using a programmable bio freezer after 4 hours of equilibration. The straws were thawed in a water bath at 37°C for 30 sec. The freshly diluted and frozenthawed samples were assessed for routine subjective tests and various motion characteristics/kinematics by Biovis CASA. The Pearson’s correlations for sperm motility and velocity/kinematic parameters of total motile sperm as well as of progressively motile sperm were studied in freshly diluted and frozen-thawed semen. In fresh semen, total motile sperm assessed by CASA had significant (p less than 0.05, 01) correlations with rapid progressive motile sperm (r = 0.46), wobbling index (r = 0.52) and dancing frequency (r = -0.43) in fresh semen. In frozen-thawed semen, it was significantly correlated only with linearity (r = 0.46). The rapid progressive motile sperm in both fresh (r = 0.41 to 0.92) and frozen-thawed (r = 044 to 0.88) semen, however, had significant correlations with most of their velocity traits. Further, the average path velocity (VAP), curvilinear velocity (VCL), straight line velocity (VSL), linearity (LIN), straightness (STR), wobbling (WOB), beat-cross frequency (BCF), amplitude of lateral head displacement (ALH), and dancing mean (DNM) of sperm showed significant positive or negative interrelationships among each other in both fresh (r = 0.41 to 0.91) as well as post-thawed (r = 0.44 to 0.90) semen. Moreover, the correlations of motility and kinematics parameters of total motile sperm in both fresh and frozen-thawed semen were highly significant with velocity/kinematics traits of only progressively motile sperm, and the velocity traits among only motile sperm were highly significantly interrelated in both fresh (r = 0.46 to 0.98) and frozen-thawed (r = 0.43 to 0.93) semen of Girbulls, though the magnitudes of correlations were lower in frozen-thawed semen as compared to fresh semen. Thus, CASA analysis offresh semen for motility and velocity traits could predict the post-thawed sperm motility and velocity/kinematics of bovine semen.
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Volkmann, T. H. M. y M. Weiler. "Continual in-situ monitoring of pore water stable isotopes in the subsurface". Hydrology and Earth System Sciences Discussions 10, n.º 11 (5 de noviembre de 2013): 13293–331. http://dx.doi.org/10.5194/hessd-10-13293-2013.
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Abstract. The stable isotope signature of pore water provides an integral fingerprint of water origin, flow path, transport processes, and residence times and can thus serve as a powerful tracer of hydrological processes in the unsaturated and saturated zone. However, the full potential of stable isotopes to quantitatively characterize subsurface water dynamics is yet unfolded due to the difficulty in obtaining extensive detailed and continual measurements of spatiotemporally variable pore water signatures. With the development of field-deployable laser-based isotope analyzers, such measurements are now becoming feasible. This study presents the development and application of a functional, automatable, and cost-efficient system for non-destructive continual in-situ monitoring of pore water stable isotope signatures with high resolution. The monitoring system uses automatic-controllable valve arrays to continuously extract diluted soil air water vapor via a branching network of multiple small microporous probes into a commercial isotope analyzer. Soil temperature observations are used to convert obtained vapor phase into liquid phase water isotope signatures, but these can also be obtained based on vapor concentration measurements. In-situ sampling was conducted at six depths for each of three plots planted with varying vegetation on an experimental site in SW Germany. Two different methods based on advective and diffusive soil water vapor probing were employed suitable under unsaturated and all (including saturated) moisture conditions, respectively. The advective sampling method was applied using multiple permanently installed probes (continual mode) and using a single probe subsequently inserted to sample the various locations (push-in mode), while the diffusive sampling method was applied in push-in mode only. Using a specific identical treatment onsite calibration approach along with basic corrections for instrument bias and temperature dependent free water-vapor isotopic equilibrium fractionation, the monitoring system facilitated inference of normalized liquid pore water isotopic composition with sufficiently high accuracy and precision at sampling intervals of less than four minutes and resolved the isotopic variability along natural depth profiles. Comparison indicated that the presented in-situ approaches may be used interchangeably with each other and with concurrent laboratory-based direct equilibration measurements of destructively collected samples, such that the choice of method will depend upon the task and anticipated conditions of sampling. The introduced sampling techniques provide powerful tools towards a detailed quantitative understanding of dynamic and heterogeneous shallow subsurface and vadose zone processes.
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Karanassou, Marika y Dennis J. Snower. "Unemployment Invariance". German Economic Review 5, n.º 3 (1 de agosto de 2004): 297–317. http://dx.doi.org/10.1111/j.1465-6485.2004.00110.x.
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Abstract This paper provides a critique of the ‘unemployment invariance hypothesis’, according to which the behavior of the labor market, by itself, ensures that the long-run unemployment rate is independent of the size of the capital stock, productivity and the labor force. In the context of an endogenous growth model, we show that the labor market alone need not contain all the equilibrating mechanisms to ensure unemployment invariance; in particular, other markets may perform part of the equilibrating process as well. By implication, policies that raise the growth path of capital or increase the effective working-age population may influence the long-run unemployment rate.
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Pardo, Paula Conde, Bronte Tilbrook, Clothilde Langlais, Thomas William Trull y Stephen Rich Rintoul. "Carbon uptake and biogeochemical change in the Southern Ocean, south of Tasmania". Biogeosciences 14, n.º 22 (21 de noviembre de 2017): 5217–37. http://dx.doi.org/10.5194/bg-14-5217-2017.
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Abstract. Biogeochemical change in the water masses of the Southern Ocean, south of Tasmania, was assessed for the 16-year period between 1995 and 2011 using data from four summer repeats of the WOCE–JGOFS–CLIVAR–GO-SHIP (Key et al., 2015; Olsen et al., 2016) SR03 hydrographic section (at ∼ 140° E). Changes in temperature, salinity, oxygen, and nutrients were used to disentangle the effect of solubility, biology, circulation and anthropogenic carbon (CANT) uptake on the variability of dissolved inorganic carbon (DIC) for eight water mass layers defined by neutral surfaces (γn). CANT was estimated using an improved back-calculation method. Warming (∼ 0.0352 ± 0.0170 °C yr−1) of Subtropical Central Water (STCW) and Antarctic Surface Water (AASW) layers decreased their gas solubility, and accordingly DIC concentrations increased less rapidly than expected from equilibration with rising atmospheric CO2 (∼ 0.86 ± 0.16 µmol kg−1 yr−1 versus ∼ 1 ± 0.12 µmol kg−1 yr−1). An increase in apparent oxygen utilisation (AOU) occurred in these layers due to either remineralisation of organic matter or intensification of upwelling. The range of estimates for the increases in CANT were 0.71 ± 0.08 to 0.93 ± 0.08 µmol kg−1 yr−1 for STCW and 0.35 ± 0.14 to 0.65 ± 0.21 µmol kg−1 yr−1 for AASW, with the lower values in each water mass obtained by assigning all the AOU change to remineralisation. DIC increases in the Sub-Antarctic Mode Water (SAMW, 1.10 ± 0.14 µmol kg−1 yr−1) and Antarctic Intermediate Water (AAIW, 0.40 ± 0.15 µmol kg−1 yr−1) layers were similar to the calculated CANT trends. For SAMW, the CANT increase tracked rising atmospheric CO2. As a consequence of the general DIC increase, decreases in total pH (pHT) and aragonite saturation (ΩAr) were found in most water masses, with the upper ocean and the SAMW layer presenting the largest trends for pHT decrease (∼ −0.0031 ± 0.0004 yr−1). DIC increases in deep and bottom layers (∼ 0.24 ± 0.04 µmol kg−1 yr−1) resulted from the advection of old deep waters to resupply increased upwelling, as corroborated by increasing silicate (∼ 0.21 ± 0.07 µmol kg−1 yr−1), which also reached the upper layers near the Antarctic Divergence (∼ 0.36 ± 0.06 µmol kg−1 yr−1) and was accompanied by an increase in salinity. The observed changes in DIC over the 16-year span caused a shoaling (∼ 340 m) of the aragonite saturation depth (ASD, ΩAr = 1) within Upper Circumpolar Deep Water that followed the upwelling path of this layer. From all our results, we conclude a scenario of increased transport of deep waters into the section and enhanced upwelling at high latitudes for the period between 1995 and 2011 linked to strong westerly winds. Although enhanced upwelling lowered the capacity of the AASW layer to uptake atmospheric CO2, it did not limit that of the newly forming SAMW and AAIW, which exhibited CANT storage rates (∼ 0.41 ± 0.20 mol m−2 yr−1) twice that of the upper layers.
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Norberg, N., D. Harlov, G. Neusser, R. Wirth, D. Rhede y L. Morales. "Experimental development of patch perthite from synthetic cryptoperthite: Microstructural evolution and chemical re-equilibration". American Mineralogist 98, n.º 8-9 (1 de agosto de 2013): 1429–41. http://dx.doi.org/10.2138/am.2013.4412.
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Żaba, Mariusz y Piotr Garbaczewski. "Thermalization of Lévy Flights: Path-Wise Picture in 2D". International Journal of Statistical Mechanics 2013 (3 de octubre de 2013): 1–11. http://dx.doi.org/10.1155/2013/738345.
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We analyze two-dimensional (2D) random systems driven by a symmetric Lévy stable noise which in the presence of confining potentials may asymptotically set down at Boltzmann-type thermal equilibria. In view of the Eliazar-Klafter no-go statement, such dynamical behavior is plainly incompatible with the standard Langevin modeling of Lévy flights. No explicit path-wise description has been so far devised for the thermally equilibrating random motion we address, and its formulation is the principal goal of the present work. To this end we prescribe a priori the target pdf ρ∗ in the Boltzmann form ~exp[] and next select the Lévy noise (e.g., its Lévy measure) of interest. To reconstruct random paths of the underlying stochastic process we resort to numerical methods. We create a suitably modified version of the time honored Gillespie algorithm, originally invented in the chemical kinetics context. A statistical analysis of generated sample trajectories allows us to infer a surrogate pdf dynamics which sets down at a predefined target, in consistency with the associated kinetic (master) equation.
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Pallotta, B. S., J. R. Hepler, S. A. Oglesby y T. K. Harden. "A comparison of calcium-activated potassium channel currents in cell-attached and excised patches." Journal of General Physiology 89, n.º 6 (1 de junio de 1987): 985–97. http://dx.doi.org/10.1085/jgp.89.6.985.
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Single channel currents from Ca-activated K channels were recorded from cell-attached patches, which were then excised from 1321N1 human astrocytoma cells. Cells were depolarized with K (110 mM) so that the membrane potential was known in both patch configurations, and the Ca ionophore A23187 or ionomycin (20-100 microM) was used to equilibrate intracellular and extracellular [Ca] (0.3 or 1 microM). Measurements of intracellular [Ca] with the fluorescent Ca indicator quin2 verified that [Ca] equilibration apparently occurred in our experiments. Under these conditions, where both membrane potential and intracellular [Ca] were known, we found that the dependence of the channel percent open time on membrane potential and [Ca] was similar in both the cell-attached and excised patch configuration for several minutes after excision. Current-voltage relations were also similar, and autocorrelation functions constructed from the single channel currents revealed no obvious change in channel gating upon patch excision. These findings suggest that the results of studies that use excised membrane patches can be extrapolated to the K-depolarized cell-attached configuration, and that the relation between [Ca] and channel activity can be used to obtain a quantitative measure of [Ca] near the membrane intracellular surface.
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Miyashita, Tomofumi. "(Digital Presentation) Additional Voltage Loss in Terms of Electromagnetic Potential Related to Jarzynski’s Equality Using Sm-Doped Ceria Electrolytes in Wagner’s Equation for SOFCs". ECS Meeting Abstracts MA2022-01, n.º 41 (7 de julio de 2022): 2398. http://dx.doi.org/10.1149/ma2022-01412398mtgabs.
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A solid oxide fuel cell (SOFC) converts chemical energy from a fuel gas, such as hydrogen or methane, to electrical energy. Yttria-stabilized zirconia (YSZ) films are often used as electrolytes in which only oxygen ions are carriers. In such cases, the open circuit voltage (OCV = 1.15 V at 1073 K) is equal to the Nernst voltage (Vth = 1.15 V at 1073 K). Samaria-doped ceria (SDC) have higher ionic conductivity. Therefore, SDC films are possible electrolyte candidates. However, when SDC electrolytes are used in SOFCs, the OCV is only 0.80 V at 1073 K. The voltage loss has been explained by Wagner’s equation. Numerous subsequent models have been created based on Wagner’s equation. Using the Riess model, the current-voltage relationship can be calculated with the cathode and anode polarization voltage losses [1]. Furthermore, a nonlinear model was created by Duncan and Wachsman [2]. This model can also be used to explain the equilibrium process. According to the Riess model, the OCV should decrease during electrode degradation. However, experimentally, the OCV does not change during electrode degradation [3]. The change in the equilibration of thick SDC electrolytes in response to a change in the anode gas has never been explained using the model defined by Duncan and Wachsman. Experimentally, when a very thick (6.6 mm) SDC electrolyte is used, the OCV can reach 0.80 V in only 5 minutes [4]. According to Weppner, the corresponding delay in the electron diffusion current should be more than 2080 minutes [5]. We proposed a current-independent anode voltage loss (0.35 V = 1.15 V- 0.80 V) [6]. Since we disproved the existence of large leakage currents in SDC electrolytes, our explanations seem to disregard and disprove Wagner’s equation. However, we noticed that the dismissal of this idea regarding large leakage currents in SDC electrolytes is nothing more than a side effect. When SDC electrolytes experience a large anode voltage loss (0.35 V), the leakage currents are very small. This is called the “anode shielding effect” [7]. The ionic activation energy (Ea) of SDC electrolytes is 0.7 eV (= 0.35 V ×2e). During ion hopping processes in SDC electrolytes, the work done by ions on the surrounding lattice structure is 0.7 eV. The ions should regain the 0.7 eV after hopping. However, when there are many electrons in the hopping path, hopping processes are very complex, and calculating the loss of work is challenging. Jarzynski’s equality is a very useful method of calculating the loss of work only from the first equilibrium state to the second equilibrium state. Because the distribution of hopping ions always should be a canonical ensemble, the loss of work can be calculated. When there are enough electrons, the ions cannot regain the 0.7 eV, and voltage loss (0.35 V) occurs [8]. To assist the above explanation, we use the electromagnetic potential to explain the voltage loss that occurs during ion hopping. We noticed that the potential of ions during hopping can be calculated from the Lorenz gauge condition. Reference: [1] I. Riess, J. Phys. Chem. Solids., 47(2), 129 (1986). doi: 10.1016/0022-3697(86)90121-6. [2] K. L. Duncan and E. D. Wachsman, J. Electrochem. Soc., 156, B1030 (2009). doi: 10.1149/1.315851. [3] T. Miyashita, J. Mater. Sci., 41(10), 3183 (2006). doi: 10.1007/s10853-006-6371-8. [4] T. Miyashita, J. Electrochem. Soc., 164(11) 3190 (2017). doi: 10.1149/2.0251711jes [5] J. Liu and W. Weppner, Ionics, 5(1–2), 115 (1999). doi: 10.1007/BF02375914. [6] T. Miyashita, J. Mater. Sci., 40(22), 6027 (2005). doi: 10.1007/s10855-005-4560-2. [7] B. Dalslet, P. Blennow, P. V. Hendriksen, N. Bonanos, D. Lybye, and M. Mogensen, J. Solid State Electrochem., 10(8), 547 (2006). doi: 10.1007/s10008-006-0135-x. [8] T. Miyashita, Miyashita, ECSarXiv (2020) “Open-Circuit Voltage Anomalies in Yttria-Stabilized Zirconia and Samaria-Doped Ceria Bilayered Electrolytes”, https://ecsarxiv.org/xhn73/
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Shin, E. y D. A. Streit. "Harmonic Synthesis Theory for Dynamic Spring Balancing". Journal of Dynamic Systems, Measurement, and Control 119, n.º 1 (1 de marzo de 1997): 61–68. http://dx.doi.org/10.1115/1.2801216.
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At resonance, a small excitation force amplitude results in a relatively large amplitude system response. Although typically viewed as undesirable, operating a machine near resonance can sometimes be advantageous. A new approach to dynamic spring balancing, called harmonic synthesis, tunes a system so that the desired dynamic motion is approximated by the linear superposition of resonant mode shapes. Large amplitude machine motions are achieved with minimum energy required from system actuators. Machine motion is first approximated using a Fourier series expansion about a mean operating configuration. Equilibrators are then synthesized such that resulting machine natural frequencies and mode shapes are commensurate with the harmonics of the Fourier series expansion. Harmonic synthesis examples include one and two mode approximations to the motion of a two degree-of-freedom planar robot manipulator. Results show that equilibrator parameters are determined explicitly whether a path is specified at a number of points or described over the whole range of motion.
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Wagner, J. J. y B. E. Alger. "GTP modulates run-up of whole-cell Ca2+ channel current in a Ca(2+)-dependent manner". Journal of Neurophysiology 71, n.º 2 (1 de febrero de 1994): 814–16. http://dx.doi.org/10.1152/jn.1994.71.2.814.
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1. Whole-cell voltage-clamp recordings were obtained from CA1 neurons acutely dissociated from rat hippocampus to study the effects of guanosine 5'-triphosphate (GTP) on the gradual increase in Ca2+ channel current amplitude that takes place over several minutes after breaking in to whole-cell mode ("run-up"). 2. Including GTP (500 microM) in the patch pipette significantly prolonged the duration of run-up of peak Ca2+ channel current to its maximum value compared with controls without GTP when the recording solutions contained Ca2+. On the other hand, GTP significantly enhanced run-up when Mg2+ and Ba2+ were substituted for intracellular and extracellular Ca2+, respectively. 3. The enhancement of run-up of the current in the Mg/Ba condition appeared to be due both to an initial increase in current amplitude that was complete within 30 s after break in and to a more rapid initial rate of run-up when compared with the Ca2+ condition. GTP did not affect the absolute maximum amplitudes of the currents in either Ca2+ or Ba2+ conditions. 4. We conclude that an early GTP-dependent modulation of Ca2+ channel current is qualitatively altered, depending on whether Ca2+ or Ba2+ is used as the charge carrier. Evidence of this modulation is apparent within seconds after rupture of the membrane patch. Conceivably, influences occurring during the period of "equilibration" with electrode contents could alter subsequent regulatory steps.
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Bader, Annika y Eric Beitz. "Transmembrane Facilitation of Lactate/H+ Instead of Lactic Acid Is Not a Question of Semantics but of Cell Viability". Membranes 10, n.º 9 (15 de septiembre de 2020): 236. http://dx.doi.org/10.3390/membranes10090236.
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Transmembrane transport of monocarboxylates is conferred by structurally diverse membrane proteins. Here, we describe the pH dependence of lactic acid/lactate facilitation of an aquaporin (AQP9), a monocarboxylate transporter (MCT1, SLC16A1), and a formate–nitrite transporter (plasmodium falciparum FNT, PfFNT) in the equilibrium transport state. FNTs exhibit a channel-like structure mimicking the aquaporin-fold, yet act as secondary active transporters. We used radiolabeled lactate to monitor uptake via yeast-expressed AQP9, MCT1, and PfFNT for long enough time periods to reach the equilibrium state in which import and export rates are balanced. We confirmed that AQP9 behaved perfectly equilibrative for lactic acid, i.e., the neutral lactic acid molecule enters and passes the channel. MCT1, in turn, actively used the transmembrane proton gradient and acted as a lactate/H+ co-transporter. PfFNT behaved highly similar to the MCT in terms of transport properties, although it does not adhere to the classical alternating access transporter model. Instead, the FNT appears to use the proton gradient to neutralize the lactate anion in the protein’s vestibule to generate lactic acid in a place that traverses the central hydrophobic transport path. In conclusion, we propose to include FNT-type proteins into a more generalized, function-based transporter definition.
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Himeno, Yukiko, Futoshi Toyoda, Hiroyasu Satoh, Akira Amano, Chae Young Cha, Hiroshi Matsuura y Akinori Noma. "Minor contribution of cytosolic Ca2+ transients to the pacemaker rhythm in guinea pig sinoatrial node cells". American Journal of Physiology-Heart and Circulatory Physiology 300, n.º 1 (enero de 2011): H251—H261. http://dx.doi.org/10.1152/ajpheart.00764.2010.
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The question of the extent to which cytosolic Ca2+ affects sinoatrial node pacemaker activity has been discussed for decades. We examined this issue by analyzing two mathematical pacemaker models, based on the “Ca2+ clock” (C) and “membrane clock” (M) hypotheses, together with patch-clamp experiments in isolated guinea pig sinoatrial node cells. By applying lead potential analysis to the models, the C mechanism, which is dependent on potentiation of Na+/Ca2+ exchange current via spontaneous Ca2+ release from the sarcoplasmic reticulum (SR) during diastole, was found to overlap M mechanisms in the C model. Rapid suppression of pacemaker rhythm was observed in the C model by chelating intracellular Ca2+, whereas the M model was unaffected. Experimental rupturing of the perforated-patch membrane to allow rapid equilibration of the cytosol with 10 mM BAPTA pipette solution, however, failed to decrease the rate of spontaneous action potential within ∼30 s, whereas contraction ceased within ∼3 s. The spontaneous rhythm also remained intact within a few minutes when SR Ca2+ dynamics were acutely disrupted using high doses of SR blockers. These experimental results suggested that rapid disruption of normal Ca2+ dynamics would not markedly affect spontaneous activity. Experimental prolongation of the action potentials, as well as slowing of the Ca2+-mediated inactivation of the L-type Ca2+ currents induced by BAPTA, were well explained by assuming Ca2+ chelation, even in the proximity of the channel pore in addition to the bulk cytosol in the M model. Taken together, the experimental and model findings strongly suggest that the C mechanism explicitly described by the C model can hardly be applied to guinea pig sinoatrial node cells. The possible involvement of L-type Ca2+ current rundown induced secondarily through inhibition of Ca2+/calmodulin kinase II and/or Ca2+-stimulated adenylyl cyclase was discussed as underlying the disruption of spontaneous activity after prolonged intracellular Ca2+ concentration reduction for >5 min.
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Kim, Kyungtae, Akash Arora, Ronald M. Lewis, Meijiao Liu, Weihua Li, An-Chang Shi, Kevin D. Dorfman y Frank S. Bates. "Origins of low-symmetry phases in asymmetric diblock copolymer melts". Proceedings of the National Academy of Sciences 115, n.º 5 (18 de enero de 2018): 847–54. http://dx.doi.org/10.1073/pnas.1717850115.
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Cooling disordered compositionally asymmetric diblock copolymers leads to the formation of nearly spherical particles, each containing hundreds of molecules, which crystallize upon cooling below the order–disorder transition temperature (TODT). Self-consistent field theory (SCFT) reveals that dispersity in the block degrees of polymerization stabilizes various Frank–Kasper phases, including the C14 and C15 Laves phases, which have been accessed experimentally in low-molar-mass poly(isoprene)-b-poly(lactide) (PI-PLA) diblock copolymers using thermal processing strategies. Heating and cooling a specimen containing 15% PLA above and below the TODT from the body-centered cubic (BCC) or C14 states regenerates the same crystalline order established at lower temperatures. This memory effect is also demonstrated with a specimen containing 20% PLA, which recrystallizes to either C15 or hexagonally ordered cylinders (HEXC) upon heating and cooling. The process-path–dependent formation of crystalline order shapes the number of particles per unit volume, n/V, which is retained in the highly structured disordered liquid as revealed by small-angle X-ray scattering (SAXS) experiments. We hypothesize that symmetry breaking during crystallization is governed by the particle number density imprinted in the liquid during ordering at lower temperature, and this metastable liquid is kinetically constrained from equilibrating due to prohibitively large free energy barriers for micelle fusion and fission. Ordering at fixed n/V is enabled by facile chain exchange, which redistributes mass as required to meet the multiple particle sizes and packing associated with specific low-symmetry Frank–Kasper phases. This discovery exposes universal concepts related to order and disorder in self-assembled soft materials.
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Lasave, J., S. Koval, A. Laio y E. Tosatti. "Proton strings and rings in atypical nucleation of ferroelectricity in ice". Proceedings of the National Academy of Sciences 118, n.º 1 (21 de diciembre de 2020): e2018837118. http://dx.doi.org/10.1073/pnas.2018837118.
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Ordinary ice has a proton-disordered phase which is kinetically metastable, unable to reach, spontaneously, the ferroelectric (FE) ground state at low temperature where a residual Pauling entropy persists. Upon light doping with KOH at low temperature, the transition to FE ice takes place, but its microscopic mechanism still needs clarification. We introduce a lattice model based on dipolar interactions plus a competing, frustrating term that enforces the ice rule (IR). In the absence of IR-breaking defects, standard Monte Carlo (MC) simulation leaves this ice model stuck in a state of disordered proton ring configurations with the correct Pauling entropy. A replica exchange accelerated MC sampling strategy succeeds, without open path moves, interfaces, or off-lattice configurations, in equilibrating this defect-free ice, reaching its low-temperature FE order through a well-defined first-order phase transition. When proton vacancies mimicking the KOH impurities are planted into the IR-conserving lattice, they enable standard MC simulation to work, revealing the kinetics of evolution of ice from proton disorder to partial FE order below the transition temperature. Replacing ordinary nucleation, each impurity opens up a proton ring generating a linear string, an actual FE hydrogen bond wire that expands with time. Reminiscent of those described for spin ice, these impurity-induced strings are proposed to exist in doped water ice too, where IRs are even stronger. The emerging mechanism yields a dependence of the long-time FE order fraction upon dopant concentration, and upon quenching temperature, that compares favorably with that known in real-life KOH doped ice.
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Hawryluk, J. M., L. L. Ferrari, S. A. Keating y E. Arrigoni. "Adenosine inhibits glutamatergic input to basal forebrain cholinergic neurons". Journal of Neurophysiology 107, n.º 10 (15 de mayo de 2012): 2769–81. http://dx.doi.org/10.1152/jn.00528.2011.
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Adenosine has been proposed as an endogenous homeostatic sleep factor that accumulates during waking and inhibits wake-active neurons to promote sleep. It has been specifically hypothesized that adenosine decreases wakefulness and promotes sleep recovery by directly inhibiting wake-active neurons of the basal forebrain (BF), particularly BF cholinergic neurons. We previously showed that adenosine directly inhibits BF cholinergic neurons. Here, we investigated 1) how adenosine modulates glutamatergic input to BF cholinergic neurons and 2) how adenosine uptake and adenosine metabolism are involved in regulating extracellular levels of adenosine. Our experiments were conducted using whole cell patch-clamp recordings in mouse brain slices. We found that in BF cholinergic neurons, adenosine reduced the amplitude of AMPA-mediated evoked glutamatergic excitatory postsynaptic currents (EPSCs) and decreased the frequency of spontaneous and miniature EPSCs through presynaptic A1 receptors. Thus we have demonstrated that in addition to directly inhibiting BF cholinergic neurons, adenosine depresses excitatory inputs to these neurons. It is therefore possible that both direct and indirect inhibition may synergistically contribute to the sleep-promoting effects of adenosine in the BF. We also found that blocking the influx of adenosine through the equilibrative nucleoside transporters or inhibiting adenosine kinase and adenosine deaminase increased endogenous adenosine inhibitory tone, suggesting a possible mechanism through which adenosine extracellular levels in the basal forebrain are regulated.
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Shepherd, Neal y Holly B. McDonough. "Ionic diffusion in transverse tubules of cardiac ventricular myocytes". American Journal of Physiology-Heart and Circulatory Physiology 275, n.º 3 (1 de septiembre de 1998): H852—H860. http://dx.doi.org/10.1152/ajpheart.1998.275.3.h852.
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We have estimated the rate of diffusion of calcium ions in the transverse tubules of isolated cardiocytes by recording changes in peak calcium current ( I Ca) caused by rapid changes of the extracellular calcium concentration ([Ca]o) at various intervals just preceding activation of I Ca. Isolated ventricular cells of guinea pig heart and atrial cells from rabbit heart were voltage-clamped (whole cell patch), superfused at a high flow rate, and stimulated continuously with depolarizing pulses (0.5 Hz, 200- or 20-ms pulses from a holding potential of −45 or −75 mV to 0 mV). In ventricular cells, the change in peak I Ca following a sudden change of [Ca]oincreased rapidly as the delay between the solution change and depolarization was increased, up to a delay of ∼75 ms [time constant (τ) ≈ 20 ms, 30–40% of total current change), and then increased more slowly (τ ≈ 200 ms, 60–70% of total current change); 400–500 ms were needed to achieve 90% of the total current increase. In atrial cells, a clear separation into two phases was not possible and 90% of the current change occurred within 85 ms. The slow phase of current change, which was unique to the ventricular cells, presumably reflects the slow equilibration of ions between the bulk perfusate and the lumina of the transverse tubules. If the lengths of the transverse tubules were equal to the cell thickness, the slow rate of change of current would be consistent with an apparent diffusion coefficient for calcium ions of 0.95 × 10−6cm2/s, considerably smaller than the value in bulk solution (7.9 × 10−6cm2/s). Most likely, this discrepancy is due to a high degree of tortuosity in the transverse tubular system in guinea pig ventricular cells or possibly to ion binding sites within the tubular membranes and glycocalyx.
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Stachenfeld, Nina S., Loretta Dipietro, Steven F. Palter y Ethan R. Nadel. "Estrogen influences osmotic secretion of AVP and body water balance in postmenopausal women". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 274, n.º 1 (1 de enero de 1998): R187—R195. http://dx.doi.org/10.1152/ajpregu.1998.274.1.r187.
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To determine if estrogen upregulates osmotic secretion of arginine vasopressin (AVP) and alters body water balance, we infused hypertonic (3% NaCl) saline in 6 women (68 ± 3 yr) after 14 days of 17β-estradiol (transdermal patch, ∼0.1 mg/day, E2) and placebo (control) administration. Hypertonic saline was infused at 0.1 ml ⋅ kg−1⋅ min−1for 120 min, and after a 30-min equilibration period, the subjects drank water ad libitum for 180 min. E2increased basal plasma estradiol concentration from ≤12 to 80 ± 12 pg/ml and plasma AVP concentration (P[AVP]) from 2.1 ± 0.7 to 3.1 ± 0.8 pg/ml ( P< 0.05), but not plasma osmolality (Posm, 288 ± 1 and 287 ± 1, for control and E2, respectively). Hypertonic saline infusion increased Posmby 18 ± 1 and 17 ± 1 mosmol/kgH2O and P[AVP]by 5.2 ± 0.5 and 4.9 ± 0.4 pg/ml for control and E2treatments, respectively. The P[AVP]-Posmrelationship shifted upward after E2, with no change in sensitivity (slope, 0.36 ± 0.02 and 0.33 ± 0.03 pg ⋅ ml−1⋅ mosmol−1for control and E2, respectively). Water intake was similar between control and E2(24 vs. 22 ml/kg), but by 180 min of drinking, urine output and free water clearance ([Formula: see text]) were reduced by 5.6 ± 2.3 ml/kg and 2.6 ± 2.0 ml/min, respectively ( P < 0.05) after E2. Plasma aldosterone concentration was unaffected by E2, but fractional sodium excretion was reduced from 2.7 ± 0.5 to 1.7 ± 0.4% ( P < 0.05) at 180 min of drinking. Our data suggest that E2augments osmotic AVP secretion, thereby implicating elevated AVP as a contributor to water retention in high E2states; however, an increase in renal sodium reabsorption was a major component of the enhanced fluid retention.
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Lepore, Amedeo. "Dal divario Nord-Sud alla convergenza: il modelo dell'intervento straordinario a l'azione della Cassa per in Mezzogiorno, durante e oltre la golden age = From the North-South gap to the convergence: The model of the extraordinary intervention and the..." Pecvnia : Revista de la Facultad de Ciencias Económicas y Empresariales, Universidad de León, n.º 15 (10 de julio de 2012): 79. http://dx.doi.org/10.18002/pec.v0i15.805.
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<p>La storiografia incentrata sul tema della Cassa per il Mezzogiorno è molto ampia e si sviluppa in relazione non solo alle questioni generali riguardanti l’intervento straordinario, ma anche alle molteplici forme di articolazione settoriale e territoriale dell’iniziativa pubblica per la ripresa e lo sviluppo del Sud. Una ricostruzione puntuale delle vicende della Cassa, che per oltre un quarantennio– anche se con diversità di impostazione nelle varie fasi –ha operato come strumento delle strategie per lo sviluppo del Mezzogiorno, richiede un impegno molto approfondito. Tuttavia, anche senza effettuare una dettagliata cronistoria dell’attività dell’Ente, si può ricomporre una visione d’insieme, attraverso l’interpretazione di un modello di intervento pubblico collegato strettamente agli eventi economici concreti e all’andamento dei processi di industrializzazione che hanno interessato i territori meridionali.</p><p>La scelta di una prospettiva di lungo periodo, imperniata sull’analisi dell’intervento straordinario nel suo complesso, ha permesso un giudizio più equilibrato su tutta l’epoca dell’azione “aggiuntiva” dello Stato per il recupero del divario meridionale, superando eccessive semplificazioni nella valutazione di quell’esperienza e confutando pareri sommari sui suoi risultati, spesso privi di fondamento. Al tempo stesso, una visione ampia ha fatto emergere un percorso in grado di associare il caso della Cassa per il Mezzogiorno, controverso e difficile, ma considerato anche un modello tra i più avanzati a livello internazionale, a un tema di grande importanza, come quello delle politiche di sviluppo adottate per affrontare i problemi dell’arretratezza economica e per avviare a soluzione i dilemmi del dualismo.</p><p>L’analisi effettuata ha provato l’esistenza di un indiscutibile progresso economico nel periodo della <em>golden age</em>. Durante quell’epoca di prosperità non solo si realizzò un notevole avanzamento delle aree del Paese che già possedevano un’armatura industriale, ma si ottenne, contemporaneamente, il risultato, per nulla scontato, di una modernizzazione della struttura economica del Mezzogiorno –attraverso la politica delle opere pubbliche, prima, e dell’industrializzazione vera e propria, poi– nonché, di un recupero del divario accumulato con le regioni settentrionali. In questo modo, l’intervento straordinario, indirizzato verso obiettivi macroeconomici e guidato da una tecnostruttura come quella della Cassa, al tempo stesso autonoma e reattiva alle scelte strategiche del governo, si dimostrò lo strumento più efficace e innovativo per fare dell’Italia intera una potenza industriale. L’allontanamento da questi esiti, nella fase successiva dominata dalla crisi petrolifera e dalle politiche di ristrutturazione industriale, pur determinando una netta inversione di tendenza, non ha messo in discussione il valore dell’esperienza iniziale della Cassa per il Mezzogiorno, capace di aprire la strada alla crescita economica italiana negli anni del <em>boom</em>.</p><p>Historiography focusing on the Cassa per il Mezzogiorno is indeed vast and developed not only in regard to the main issues concerning the extraordinary intervention, but also to the various sectorial and territorial articulations public interventions for the recovery of Southern Italy undertook. Achieving a punctual reconstruction of the goings-on of the Cassa, an istitution that, for more than forty years –despite some differences in planning during its various phases– operated as an instrument to implement the strategies focusing on developing Southern Italy, requires a very deep commitment. However, an effective overall view can be reconstructed by interpreting a public intervention model strictly linked to the concrete economic events and to the trends of those industrial processes implemented in Southern Italy, even without going through a detailed chronicle of this entity.</p><p>The choice of a long-term perspective, focused on the analysis of the extraordinary intervention in its entirety, allowed for a more balanced evaluation of all the era regarding the “supplementary” actions the Italian State carried out to bridge the gap of its Southern regions, going beyond the exaggerated simplifications plaguing the evaluations of such an experience and confuting those hasty, often baseless, judgments on the results it achieved. At the same time, a wide viewpoint on the matter let a research path emerge, able to link the specific case of the Cassa per il Mezzogiorno, itself difficult and controversial, while being considered one of the most advanced models internationally, with a very significant theme, such as the development policies implemented to tackle the problems of economic backwardness and to begin solving the dilemmas brought by the dualism.</p><p>The analysis which was carried out proved the existence of an unquestionable economic progress during the <em>golden age</em>. In that era of prosperity, not only did the areas in Italy already possessing a significant industrial presence experience significant advancement, all the while, the result, by no means granted, of a modernized economic structure in Southern Italy was achieved –first through a policy focused on public works and then by true forms of industrialization– and of a significant recovery of the gap the area had towards the Northern regions of Italy. Thus, the extraordinary intervention, focused on macroeconomic goals and driven by a technical structure such as the Cassa, itself autonomous and reacting towards governmental choices at the same time, revealed itself to be the most effective and innovative tool in turning the whole of Italy into an industrial power. The departure from such results in the following phase, dominated by the oil crisis and by the policies of industrial reconstruction, despite triggering a significant trend inversion, never questioned the value of the Cassa per il Mezzogiorno’s initial experience, which was able to open and show the way to economical growth, during the Italian <em>boom </em>years.</p>
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Hoy, Robert S. y Mark O. Robbins. "Effect of equilibration on primitive path analyses of entangled polymers". Physical Review E 72, n.º 6 (16 de diciembre de 2005). http://dx.doi.org/10.1103/physreve.72.061802.
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King, Andrew D., Jack Raymond, Trevor Lanting, Sergei V. Isakov, Masoud Mohseni, Gabriel Poulin-Lamarre, Sara Ejtemaee et al. "Scaling advantage over path-integral Monte Carlo in quantum simulation of geometrically frustrated magnets". Nature Communications 12, n.º 1 (18 de febrero de 2021). http://dx.doi.org/10.1038/s41467-021-20901-5.
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AbstractThe promise of quantum computing lies in harnessing programmable quantum devices for practical applications such as efficient simulation of quantum materials and condensed matter systems. One important task is the simulation of geometrically frustrated magnets in which topological phenomena can emerge from competition between quantum and thermal fluctuations. Here we report on experimental observations of equilibration in such simulations, measured on up to 1440 qubits with microsecond resolution. By initializing the system in a state with topological obstruction, we observe quantum annealing (QA) equilibration timescales in excess of one microsecond. Measurements indicate a dynamical advantage in the quantum simulation compared with spatially local update dynamics of path-integral Monte Carlo (PIMC). The advantage increases with both system size and inverse temperature, exceeding a million-fold speedup over an efficient CPU implementation. PIMC is a leading classical method for such simulations, and a scaling advantage of this type was recently shown to be impossible in certain restricted settings. This is therefore an important piece of experimental evidence that PIMC does not simulate QA dynamics even for sign-problem-free Hamiltonians, and that near-term quantum devices can be used to accelerate computational tasks of practical relevance.
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Hopkins, Patrick E. y Pamela M. Norris. "Contribution of Ballistic Electron Transport to Energy Transfer During Electron-Phonon Nonequilibrium in Thin Metal Films". Journal of Heat Transfer 131, n.º 4 (20 de febrero de 2009). http://dx.doi.org/10.1115/1.3072929.
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With the ever decreasing characteristic lengths of nanomaterials, nonequilibrium electron-phonon scattering can be affected by additional scattering processes at the interface of two materials. Electron-interface scattering would lead to another path of energy flow for the high-energy electrons other than electron-phonon coupling in a single material. Traditionally, electron-phonon coupling in transport is analyzed with a diffusion (Fourier) based model, such as the two temperature model (TTM). However, in thin films with thicknesses less than the electron mean free path, ballistic electron transport could lead to electron-interface scattering, which is not taken into account in the TTM. The ballistic component of electron transport, leading to electron-interface scattering during ultrashort pulsed laser heating, is studied here by a ballistic-diffusive approximation of the Boltzmann transport equation. The results for electron-phonon equilibration times are compared with calculations with TTM based approximations and experimental data on Au thin films.
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Gordijn, A., J. Francke, L. Hodakova, J. K. Rath y R. E. I. Schropp. "Influence of Pressure and Plasma Potential on High Growth Rate Microcrystalline Silicon Grown by Vhf Pecvd". MRS Proceedings 862 (2005). http://dx.doi.org/10.1557/proc-862-a10.3.
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AbstractMicrocrystalline silicon (μc-Si) based single junction solar cells are deposited by VHF PECVD using a showerhead cathode at high pressures in depletion conditions. At a deposition rate of 4.5 nm/s, a stabilized conversion efficiency of 6.7 % is obtained for a single junction solar cell with a μc-Si i-layer of 1 μm. The i-layer is made near the transition from amorphous to crystalline. In order to control the material properties in the growth direction, the hydrogen dilution of silane in the gas phase is graded following different profiles with a parabolic shape. It is observed that the performance of solar cells deposited at high rate improves under light soaking conditions at 50 °C, which we attribute to post deposition equilibration of a fast deposited transition material.The performance is lower at higher rates due to poorer i-layer quality (higher defect density), which may be attributed to smaller relaxation times for growth precursors at the growth surface and the higher energy ion bombardment at higher plasma power. High process pressures can be used to reduce the ion energy by decreasing the mean free path. We have introduced an additional method to limit the ion energy by controlling the DC self bias voltage using an external power source. In this way the quality of the μc-Si layers and the performance of the solar cells is further improved.
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Corno, Alberto, Chiara Groppo, Pietro Mosca, Alessandro Borghi y Marco Gattiglio. "Eclogitic metamorphism in the Alpine far-west: petrological constraints on the Banchetta-Rognosa tectonic unit (Val Troncea, Western Alps)". Swiss Journal of Geosciences 114, n.º 1 (16 de septiembre de 2021). http://dx.doi.org/10.1186/s00015-021-00393-7.
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AbstractThe Banchetta-Rognosa tectonic unit (BRU), covering an area of 10 km2 in the upper Chisone valley, consists of two successions referred to a continental margin (Monte Banchetta succession) and a proximal oceanic domain (Punta Rognosa succession) respectively. In both successions, Mesozoic meta-sedimentary covers discordantly lie on their basement. This paper presents new data on the lithostratigraphy and the metamorphic evolution of the continental basement of the Monte Banchetta succession. It comprises two meta-sedimentary sequences with minor meta-intrusive bodies preserving their original lithostratigraphic configuration, despite the intense Alpine deformation and metamorphic re-equilibration. Phase equilibrium modeling points to a metamorphic eclogitic peak (D1 event) of 20–23 kbar and 440–500 °C, consistent among three different samples, analyzed from suitable lithologies. The exhumation P–T path is characterized by a first decompression of at least 10 kbar, leading to the development of the main regional foliation (i.e. tectono-metamorphic event D2). The subsequent exhumation stage (D3 event) is marked by a further decompression of almost 7–8 kbar associated with a significant temperature decrease (cooling down to 350–400 °C), implying a geothermal gradient compatible with a continental collision regime. These data infer for this unit higher peak P–T conditions than previously estimated with conventional thermobarometry. The comparison of our results with the peak P–T conditions registered by other neighboring tectonic units allows to interpret the BRU as one of the westernmost eclogite-facies unit in the Alps.