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151.
Dr. L. Claudia Gómez‐Aguirre Dr. Breogán Pato‐Doldán Dr. Alessandro Stroppa Dr. Li‐Ming Yang Prof. Thomas Frauenheim Prof. Jorge Mira Dr. Susana Yáñez‐Vilar Dr. Ramón Artiaga Dr. Socorro Castro‐García Dr. Manuel Sánchez‐Andújar Prof. María Antonia Señarís‐Rodríguez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(23):7863-7870
The perovskite azido compound [(CH3)4N][Mn(N3)3], which undergoes a first‐order phase change at Tt=310 K with an associated magnetic bistability, was revisited in the search for additional ferroic orders. The driving force for such structural transition is multifold and involves a peculiar cooperative rotation of the [MnN6] octahedral as well as order/disorder and off‐center shifts of the [(CH3)4N]+ cations and bridging azide ligands, which also bend and change their coordination mode. According to DFT calculations the latter two give rise to the appearance of electric dipoles in the low‐temperature (LT) polymorph, the polarization of which nevertheless cancels out due to their antiparallel alignment in the crystal. The conversion of this antiferroelectric phase to the paraelectric phase could be responsible for the experimental dielectric anomaly detected at 310 K. Additionally, the structural change involves a ferroelastic phase transition, whereby the LT polymorph exhibits an unusual and anisotropic thermal behavior. Hence, [(CH3)4N][Mn(N3)3] is a singular material in which three ferroic orders coexist even above room temperature. 相似文献
152.
C. Aguirre D. Campos P. Pascual L. Vázquez 《The European physical journal. Special topics》2007,146(1):169-176
In this work we study the formation of patterns of neuronal activity
when some input are presented to the network. For this task a recently
developed model of neuron is utilized. This model requires a very low
computational effort but presents many characteristics of more complex
models such as, spiking, bursting and sub-threshold oscillations, and therefore the
realistic study of the behavior of big ensembles of neurons can be aborded,
even under real time conditions.
New results of the application of the wavelet transform technique to
the analysis of pattern formation and the possible encoding of rhythms
are presented; they show that this simple, low-computational, neuron
model behaves much like more complex ones. 相似文献
153.
Federico Martínez Ramos Manuel Soriano-García Gerardo Aguirre Hernández 《Analytical sciences》2003,19(6):965-966
C14H10O2Se2 is monoclinic, P2(1)/c. The unit-cell dimensions at 293 K are a = 12.795(2), b = 12.126(2), c = 9.0179(13)A, beta = 107.074(6)degrees, V = 1337.5(3)A3, and Z = 4. The R value is 0.048 for 2319 observed reflections. The dihedral angle between the plane C4-C7(O2)-Se1 and C9-C8(O1)-Se2 is 85.6(2)degrees, keeping the Se atom unshared electron pairs in a more stable configuration with the rest of the molecule. The packing in the crystal is entirely due to van der Waals forces. 相似文献
154.
The Raman and IR. spectra of solid diamminediiodidezinc (II) with 15N and 2H isotopic substitution have been measured. The spectra have been interpreted assuming C2v symmetry for the Zn(NH3)2I2 complex structure. The skeletal stretching metal-ligand modes vs(ZnN), vas(ZnN), vs(ZnI), vas(ZnI) as well as the three bending modes δ(NZnN), δ(IZnI) and δ(IZnN) were assigned by comparison with the spectra of Zn(NH3)2C12 and Zn(NH3)2Br2, and by the observed isotopic shifts of the frequencies. A normal coordinate analysis for the whole complex was carried out using the Local Symmetry Force Field Model. 相似文献
155.
Abraham J Abreu P Aglietta M Aguirre C Allard D Allekotte I Allen J Allison P Alvarez-Muñiz J Ambrosio M Anchordoqui L Andringa S Anzalone A Aramo C Argirò S Arisaka K Armengaud E Arneodo F Arqueros F Asch T Asorey H Assis P Atulugama BS Aublin J Ave M Avila G Bäcker T Badagnani D Barbosa AF Barnhill D Barroso SL Baughman B Bauleo P Beatty JJ Beau T Becker BR Becker KH Bellido JA Benzvi S Berat C Bergmann T Bernardini P Bertou X Biermann PL Billoir P Blanch-Bigas O Blanco F Blasi P Bleve C 《Physical review letters》2008,101(6):061101
The energy spectrum of cosmic rays above 2.5 x 10;{18} eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J proportional, variantE;{-gamma}, at energies between 4 x 10;{18} eV and 4 x 10;{19} eV is 2.69+/-0.02(stat)+/-0.06(syst), steepening to 4.2+/-0.4(stat)+/-0.06(syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations. The data are consistent with the prediction by Greisen and by Zatsepin and Kuz'min. 相似文献
156.
Abraham J Abreu P Aglietta M Aguirre C Allard D Allekotte I Allen J Allison P Alvarez-Muñiz J Ambrosio M Anchordoqui L Andringa S Anzalone A Aramo C Argirò S Arisaka K Armengaud E Arneodo F Arqueros F Asch T Asorey H Assis P Atulugama BS Aublin J Ave M Avila G Bäcker T Badagnani D Barbosa AF Barnhill D Barroso SL Bauleo P Beatty JJ Beau T Becker BR Becker KH Bellido JA BenZvi S Berat C Bergmann T Bernardini P Bertou X Biermann PL Billoir P Blanch-Bigas O Blanco F Blasi P Bleve C Blümer H 《Physical review letters》2008,100(21):211101
The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from nu(tau) charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and 31 August 2007 are used to place an upper limit on the diffuse flux of nu(tau) at EeV energies. Assuming an E(nu)(-2) differential energy spectrum the limit set at 90% C.L. is E(nu)(2)dN(nu)(tau)/dE(nu)<1.3 x 10(-7) GeV cm(-2) s(-1) sr(-1) in the energy range 2 x 10(17) eV< E(nu)< 2 x 10(19) eV. 相似文献
157.
Blood oxygenation level dependent (BOLD) contrast has been widely used for visualizing regional neural activation. Temporal filtering and parameter estimation algorithms are generally used to account for the intrinsic temporal autocorrelation present in BOLD data. Arterial spin labeling perfusion imaging is an emerging methodology for visualizing regional brain function both at rest and during activation. Perfusion contrast manifests different noise properties compared with BOLD contrast, represented by the even distribution of noise power and spatial coherence across the frequency spectrum. Consequently, different strategies are expected to be employed in the statistical analysis of functional magnetic resonance imaging (fMRI) data based on perfusion contrast. In this study, the effect of different analysis methods upon signal detection efficacy, as assessed by receiver operator characteristic (ROC) measures, was examined for perfusion fMRI data. Simulated foci of neural activity of varying amplitude and spatial extent were added to resting perfusion data, and the accuracy of each analysis was evaluated by comparing the results with the known distribution of pseudo-activation. In contrast to the BOLD fMRI, temporal smoothing or filtering reduces the power of perfusion fMRI data analyses whereas spatial smoothing is beneficial to the efficacy of analyses. 相似文献
158.
Variation of the complex permeability with frequency of Ni1−xZnxFe2O4 (x=0.5, 0.6 and 0.7) prepared by a combustion method has been measured over a wide range of frequency, up to 1.8 GHz. Zn content improves permeability but moves the onset of resonance to lower frequencies.
The influence on some properties of samples prepared by the insertion of small amounts of Ruthenium, Yttrium and rare-earth cations into the Ni0.5Zn0.5MxFe2−xO4 ferrite has been also investigated. Relative losses and Curie temperature of all the samples have been measured. Ferrites substituted with Ru and Gd improve microwave behavior compared to non-substituted samples. 相似文献
159.
Leonardo Aguirre Giovanni Felder Alexander P. Veselov 《Selecta Mathematica, New Series》2016,22(3):1057-1071
Gaudin Hamiltonians form families of r-dimensional abelian Lie subalgebras of the holonomy Lie algebra of the arrangement of reflection hyperplanes of a Coxeter group of rank r. We consider the set of principal Gaudin subalgebras, which is the closure in the appropriate Grassmannian of the set of spans of Gaudin Hamiltonians. We show that principal Gaudin subalgebras form a smooth projective variety isomorphic to the De Concini–Procesi compactification of the projectivized complement of the arrangement of reflection hyperplanes. 相似文献
160.
The solid particle dispersion in saltating motion is studied in an homogeneous turbulence and in a turbulent boundary layer. The fluid velocity along the particle trajectory is estimated using a continuous stochastic differential equation in which the correlation integral time takes into account gravity and inertia effects. As far as the boundary layer is concerned, the aerodynamic entrainment of particles and the rebound are modelised as random variables with Gaussian probability density functions. Compared with experimental results, the numerical results show good agreement for dispersion, although velocity fluctuations are slightly under evaluated. To cite this article: C. Aguirre et al., C. R. Mecanique 332 (2004). 相似文献