1,956 research outputs found
High temperature ferromagnetism of Li-doped vanadium oxide nanotubes
The nature of a puzzling high temperature ferromagnetism of doped
mixed-valent vanadium oxide nanotubes reported earlier by Krusin-Elbaum et al.,
Nature 431 (2004) 672, has been addressed by static magnetization, muon spin
relaxation, nuclear magnetic and electron spin resonance spectroscopy
techniques. A precise control of the charge doping was achieved by
electrochemical Li intercalation. We find that it provides excess electrons,
thereby increasing the number of interacting magnetic vanadium sites, and, at a
certain doping level, yields a ferromagnetic-like response persisting up to
room temperature. Thus we confirm the surprising previous results on the
samples prepared by a completely different intercalation method. Moreover our
spectroscopic data provide first ample evidence for the bulk nature of the
effect. In particular, they enable a conclusion that the Li nucleates
superparamagnetic nanosize spin clusters around the intercalation site which
are responsible for the unusual high temperature ferromagnetism of vanadium
oxide nanotubes.Comment: with some amendments published in Europhysics Letters (EPL) 88 (2009)
57002; http://epljournal.edpsciences.or
A wetting and drying scheme for ROMS
This paper is not subject to U.S. copyright. The definitive version was published in Computers & Geosciences 58 (2013): 54-61, doi:10.1016/j.cageo.2013.05.004.The processes of wetting and drying have many important physical and biological impacts on shallow water systems. Inundation and dewatering effects on coastal mud flats and beaches occur on various time scales ranging from storm surge, periodic rise and fall of the tide, to infragravity wave motions. To correctly simulate these physical processes with a numerical model requires the capability of the computational cells to become inundated and dewatered. In this paper, we describe a method for wetting and drying based on an approach consistent with a cell-face blocking algorithm. The method allows water to always flow into any cell, but prevents outflow from a cell when the total depth in that cell is less than a user defined critical value. We describe the method, the implementation into the three-dimensional Regional Oceanographic Modeling System (ROMS), and exhibit the new capability under three scenarios: an analytical expression for shallow water flows, a dam break test case, and a realistic application to part of a wetland area along the Georgia Coast, USA.We
acknowledge support for studies demonstrated in this manuscript
that were supported by the National Science Foundation,Division
of Industrial Innovation and Partnerships (IIP)under the 3470Z.
Defne etal./ Renewable Energy 36(2011)3461e3471 Partnerships
for Innovation Program Grant IIP-0332613,and from the Strategic
Energy Institute at Georgia Institute of Technology via a Creating
Energy Options grant and the 104B Georgia Water Resources
Institute Funding Program,and also by the Department of Energy,Wind and Hydropower Technologies Program award number
DE-FG36-08GO18174 and by the state of Georgia
Magnetic properties of the low-dimensional spin-1/2 magnet \alpha-Cu_2As_2O_7
In this work we study the interplay between the crystal structure and
magnetism of the pyroarsenate \alpha-Cu_2As_2O_7 by means of magnetization,
heat capacity, electron spin resonance and nuclear magnetic resonance
measurements as well as density functional theory (DFT) calculations and
quantum Monte Carlo (QMC) simulations. The data reveal that the magnetic Cu-O
chains in the crystal structure represent a realization of a quasi-one
dimensional (1D) coupled alternating spin-1/2 Heisenberg chain model with
relevant pathways through non-magnetic AsO_4 tetrahedra. Owing to residual 3D
interactions antiferromagnetic long range ordering at T_N\simeq10K takes place.
Application of external magnetic field B along the magnetically easy axis
induces the transition to a spin-flop phase at B_{SF}~1.7T (2K). The
experimental data suggest that substantial quantum spin fluctuations take place
at low magnetic fields in the ordered state. DFT calculations confirm the
quasi-one-dimensional nature of the spin lattice, with the leading coupling J_1
within the structural dimers. QMC fits to the magnetic susceptibility evaluate
J_1=164K, the weaker intrachain coupling J'_1/J_1 = 0.55, and the effective
interchain coupling J_{ic1}/J_1 = 0.20.Comment: Accepted for publication in Physical Review
Entanglement and Timing-Based Mechanisms in the Coherent Control of Scattering Processes
The coherent control of scattering processes is considered, with electron
impact dissociation of H used as an example. The physical mechanism
underlying coherently controlled stationary state scattering is exposed by
analyzing a control scenario that relies on previously established entanglement
requirements between the scattering partners. Specifically, initial state
entanglement assures that all collisions in the scattering volume yield the
desirable scattering configuration. Scattering is controlled by preparing the
particular internal state wave function that leads to the favored collisional
configuration in the collision volume. This insight allows coherent control to
be extended to the case of time-dependent scattering. Specifically, we identify
reactive scattering scenarios using incident wave packets of translational
motion where coherent control is operational and initial state entanglement is
unnecessary. Both the stationary and time-dependent scenarios incorporate
extended coherence features, making them physically distinct. From a
theoretical point of view, this work represents a large step forward in the
qualitative understanding of coherently controlled reactive scattering. From an
experimental viewpoint, it offers an alternative to entanglement-based control
schemes. However, both methods present significant challenges to existing
experimental technologies
Bioaccumulation and physiological responses of Festuca arundinacea (Poaceae) to zn(ii) excess
Fil: Gonzalez, Matías A. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto de Fisiología Vegetal (INFIVE-CCT-La Plata). La Plata. Buenos Aires, Argentina.Fil: Ruscitti, Marcela F. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto de Fisiología Vegetal (INFIVE-CCT-La Plata). La Plata. Buenos Aires, Argentina.Fil: Ruscitti, Marcela F. Universidad Nacional del Noroeste de la Provincia de Buenos Aires. Departamento de Ciencias Básicas y Experimentales. Junín, Buenos Aires, Argentina.Fil: Plaza Cazón, Josefina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas Centro de Investigación y Desarrollo en Fermentaciones Industriales (CINDEFI-CCT-La Plata). La Plata. Buenos Aires, Argentina.Fil: Arango, María C. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto de Fisiología Vegetal (INFIVE-CCT-La Plata). La Plata. Buenos Aires, Argentina.Existe evidencia que demuestra que las plantas de Festuca arundinacea pueden absorber y acumular altas cantidades de Zn(II), superiores a las consideradas fitotóxicas, sin afectar el crecimiento de las plantas. Para determinar la utilidad de esta especie como planta fitorremediadora, se realizó un experimento en macetas para determinar las estrategias fisiológicas empleadas por F. arundinacea ‘Malma’ Schreb, que crecen en ambientes con exceso de Zn(II) para determinar su utilidad como especie fitorremediadora. Las plantas crecieron hasta alcanzar una biomasa adecuada para la aplicación de tres concentraciones crecientes de Zn(II). Tres meses después se determinaron parámetros de crecimiento (biomasa total y área foliar), parámetros fisiológicos (conductividad relativa de la membrana, contenido de clorofila y carotenos, malondialdehído en raíces y proteínas solubles) y contenido de Zn(II). La biomasa total, área foliar, contenido de clorofila, caroteno y proteínas en la parte aérea mostraron una disminución con el aumento de la concentración de Zn(II), mientras que la conductividad relativa, contenido de proteínas y malondialdehído en las raíces mostraron un patrón opuesto. Nuestros resultados sugieren que esta especie puede ser utilizada para la fitoestabilización de suelos contaminados con concentraciones moderadas de Zn(II).tbls., grafs
A quantitative approach to neuropsychiatry: The why and the how
The current nosology of neuropsychiatric disorders allows for a pragmatic approach to treatment choice, regulation and clinical research. However, without a biological rationale for these disorders, drug development has stagnated. The recently EU-funded PRISM project aims to develop a quantitative biological approach to the understanding and classification of neuropsychiatric diseases to accelerate the discovery and development of better treatments. By combining clinical data sets from major worldwide disease cohorts and by applying innovative technologies to deeply phenotype stratified patient groups, we will define a set of quantifiable biological parameters for social withdrawal and cognitive deficits common to Schizophrenia (SZ), Major Depression (MD), and Alzheimer's Disease (AD). These studies aim to provide new classification and assessment tools for social and cognitive performance across neuropsychiatric disorders, clinically relevant substrates for treatment development, and predictive, preclinical animal systems. With patients and regulatory agencies, we seek to provide clear routes for the future translation and regulatory approval for new treatments and provide solutions to the growing public health challenges of psychiatry and neurology
Antifungal Activity of Amphiphilic Perylene Bisimides
[EN] Perylene-based compounds, either naturally occurring or synthetic, have shown interesting biological activities. In this study, we report on the broad-spectrum antifungal properties of two lead amphiphilic perylene bisimides, compounds 4 and 5, which were synthesized from perylene-3,4,9,10-tetracarboxylic dianhydride by condensation with spermine and an ammonium salt formation. The antifungal activity was evaluated using a collection of fungal strains and clinical isolates from patients with onychomycosis or sporotrichosis. Both molecules displayed an interesting antifungal profile with MIC values in the range of 2-25 mu M, being as active as several reference drugs, even more potent in some particular strains. The ammonium trifluoroacetate salt 5 showed the highest activity with a MIC value of 2.1 mu M for all tested Candida spp., two Cryptococcus spp., two Fusarium spp., and one Neoscytalidium spp. strain. Therefore, these amphiphilic molecules with the perylene moiety and cationic ammonium side chains represent important structural features for the development of novel antifungals.This study was supported by grant 201680I008 (awarded to M.A.G.-C.) from the Spanish Government (Consejo Superior de Investigaciones Cientificas) and grant 3756 of the University of Antioquia.Roa-Linares, VC.; Mesa-Arango, AC.; Zaragoza, RJ.; González-Cardenete, MA. (2022). Antifungal Activity of Amphiphilic Perylene Bisimides. Molecules. 27(20):1-12. https://doi.org/10.3390/molecules27206890112272
Metacognition as Evidence for Evidentialism
Metacognition is the monitoring and controlling of cognitive processes. I examine the role of metacognition in ‘ordinary retrieval cases’, cases in which it is intuitive that via recollection the subject has a justified belief. Drawing on psychological research on metacognition, I argue that evidentialism has a unique, accurate prediction in each ordinary retrieval case: the subject has evidence for the proposition she justifiedly believes. But, I argue, process reliabilism has no unique, accurate predictions in these cases. I conclude that ordinary retrieval cases better support evidentialism than process reliabilism. This conclusion challenges several common assumptions. One is that non-evidentialism alone allows for a naturalized epistemology, i.e., an epistemology that is fully in accordance with scientific research and methodology. Another is that process reliabilism fares much better than evidentialism in the epistemology of memory
Multi-class classification based on quantum state discrimination
We present a general framework for the problem of multi-class classification using classification functions that can be interpreted as fuzzy sets. We specialize these functions in the domain of Quantum-inspired classifiers, which are based on quantum state discrimination techniques. In particular, we use unsharp observables (Positive Operator-Valued Measures) that are determined by the training set of a given dataset to construct these classification functions. We show that such classifiers can be tested on near-term quantum computers once these classification functions are “distilled” (on a classical platform) from the quantum encoding of a training dataset. We compare these experimental results with their theoretical counterparts and we pose some questions for future research
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