9,524 research outputs found
Magnetic transitions in Pr2NiO4 single crystal
The magnetic properties of a stoichiometric Pr2NiO4 single crystal have been examined by means of the temperature dependence of the complex ac susceptibility and the isothermal magnetization in fields up to 200 kOe at T=4.2 K. Three separate phases have been identified and their anisotropic character has been analyzed. A collinear antiferromagnetic phase appears first between TN = 325 K and Tc1 = 115 K, where the Pr ions are polarized by an internal magnetic field. At Tc1 a first modification of the magnetic structure occurs in parallel with a structural phase transition (Bmab to P42/ncm). This magnetic transition has a first‐order character and involves both the out‐of‐plane and the in‐plane spin components (magnetic modes gx and gxcyfz, respectively). A second magnetic transition having also a first‐order character is also clearly identified at Tc2 = 90 K which corresponds to a spin reorientation process (gxcyfz to cxgyaz magnetic modes). It should be noted as well that the out‐of‐phase component of χac shows a peak around 30 K which reflects the coexistence of both magnetic configurations in a wide temperature interval. Finally, two field‐induced transitions have been observed at 4.2 K when the field is directed along the c axis. We propose that the high‐field anomaly arises from a metamagnetic transition of the weak ferromagnetic component, similarly to La2CuO4
A 80 OBS and and 30 Land 3-component seismometers array encompassing the 280 km segment of the Lesser Antilles subduction megathrust seismogenic zone : view of current seismicity
The exotic weevil Stenopelmus rufinasus Gyllenhal, 1835 (Coleoptera: Curculionidae) across a "host-free" pond network
The presence of the exotic weevil Stenopelmus rufinasus (Coleoptera: Curculionidae) is closely related to the occurrence of
the exotic red water fern, Azolla filiculoides. In this paper, we present the first records of S. rufinasus in Doñana National
Park (SW Spain), based on sampling of macroinvertebrates in 91 temporary ponds, including monthly samples of 22 ponds,
during two successive years (2005-2007). The exotic weevil was present in 21% of the sampled ponds where the host plant, A.
filiculiodes, was not detectable. Because A. filiculoides can reach high densities in an adjacent area of marsh, we suggest that
the occurrence of the exotic weevil in these ponds is a consequence of dispersal from nearby marshes. Our study demonstrates
that S. rufinasus adults can occur at relatively high densities in ponds where the host plant is not present, suggesting that such
apparently “host-free” sites may act as stepping stones for the spread of this speciesLa presencia de la especie de gorgojo exótico Stenopelmus rufinasus (Coleoptera: Curculionidae) está íntimamente rela-
cionada con la planta acuática exótica Azolla filiculoides. En este estudio se registró por primera vez la presencia de S.
rufinasus en el Parque Nacional de Doñana (SO España) tras realizar un muestreo de macroinvertebrados en 91 lagunas
que incluye muestreos mensuales de 22 de las mismas durante dos años consecutivos (2005-2007). El gorgojo exótico estuvo
presente en el 21% de las lagunas muestreadas a pesar de que su supuesto hospedador, A. filiculiodes, no fue detectado.
Dado que A. filiculiodes puede alcanzar grandes densidades en la marisma adyacente, sugerimos que la presencia del gor-
gojo exótico en las lagunas temporales se debe a su dispersión desde la marisma. Este estudio demuestra que individuos
adultos de S. rufinasus pueden aparecer con densidades relativamente altas en lagunas donde su hospedador potencial no
está presente, lo que sugiere que estos sitios libres de hospedador podrían actuar como zonas de paso para la dispersión de
la especiePeer reviewe
Microenvironmental cooperation promotes early spread and bistability of a Warburg-like phenotype
We introduce an in silico model for the initial spread of an aberrant phenotype with Warburg-like overflow metabolism within a healthy homeostatic tissue in contact with a nutrient reservoir (the blood), aimed at characterizing the role of the microenvironment for aberrant growth. Accounting for cellular metabolic activity, competition for nutrients, spatial diffusion and their feedbacks on aberrant replication and death rates, we obtain a phase portrait where distinct asymptotic whole-tissue states are found upon varying the tissue-blood turnover rate and the level of blood-borne primary nutrient. Over a broad range of parameters, the spreading dynamics is bistable as random fluctuations can impact the final state of the tissue. Such a behaviour turns out to be linked to the re-cycling of overflow products by non-aberrant cells. Quantitative insight on the overall emerging picture is provided by a spatially homogeneous version of the model
Crystal and magnetic structure of the oxypnictide superconductor LaO(1-x)FxFeAs: evidence for magnetoelastic coupling
High-resolution and high-flux neutron as well as X-ray powder-diffraction
experiments were performed on the oxypnictide series LaO(1-x)FxFeAs with
0<x<0.15 in order to study the crystal and magnetic structure. The magnetic
symmetry of the undoped compound corresponds to those reported for ReOFeAs
(with Re a rare earth) and for AFe2As2 (A=Ba, Sr) materials. We find an ordered
magnetic moment of 0.63(1)muB at 2 K in LaOFeAs, which is significantly larger
than the values previously reported for this compound. A sizable ordered
magnetic moment is observed up to a F-doping of 4.5% whereas there is no
magnetic order for a sample with a F concentration of x=0.06. In the undoped
sample, several interatomic distances and FeAs4 tetrahedra angles exhibit
pronounced anomalies connected with the broad structural transition and with
the onset of magnetism supporting the idea of strong magneto-elastic coupling
in this material.Comment: 8 pages, 7 figures, regular articl
Millimagnitude Photometry for Transiting Extrasolar Planetary Candidates. V. Follow-up of 30 OGLE Transits. New Candidates
We used VLT/VIMOS images in the V band to obtain light curves of extrasolar
planetary transits OGLE-TR-111 and OGLE-TR-113, and candidate planetary
transits: OGLE-TR-82, OGLE-TR-86, OGLE-TR-91, OGLE-TR-106, OGLE-TR-109,
OGLE-TR-110, OGLE-TR-159, OGLE-TR-167, OGLE-TR-170, OGLE-TR-171. Using
difference imaging photometry, we were able to achieve millimagnitude errors in
the individual data points. We present the analysis of the data and the light
curves, by measuring transit amplitudes and ephemerides, and by calculating
geometrical parameters for some of the systems. We observed 9 OGLE objects at
the predicted transit moments. Two other transits were shifted in time by a few
hours. For another seven objects we expected to observe transits during the
VIMOS run, but they were not detected. The stars OGLE-TR-111 and OGLE-TR-113
are probably the only OGLE objects in the observed sample to host planets, with
the other objects being very likely eclipsing binaries or multiple systems. In
this paper we also report on four new transiting candidates which we have found
in the data.Comment: 11 pages, 17 figures, accepted for publication in A&
Pipeline for recording datasets and running neural networks on the Bela embedded hardware platform
Deploying deep learning models on embedded devices is an arduous task: oftentimes, there exist no platform-specific instructions, and compilation times can be considerably large due to the limited computational resources available on-device. Moreover, many music-making applications de- mand real-time inference. Embedded hardware platforms for audio, such as Bela, offer an entry point for beginners into physical audio computing; however, the need for cross- compilation environments and low-level software develop- ment tools for deploying embedded deep learning models imposes high entry barriers on non-expert users. We present a pipeline for deploying neural networks in the Bela embedded hardware platform. In our pipeline, we include a tool to record a multichannel dataset of sen- sor signals. Additionally, we provide a dockerised cross- compilation environment for faster compilation. With this pipeline, we aim to provide a template for programmers and makers to prototype and experiment with neural networks for real-time embedded musical applications
Interactive Neural Resonators
In this work, we propose a method for the controllable synthesis of real-time contact sounds using neural resonators. Previous works have used physically inspired statistical methods and physical modelling for object materials and excitation signals. Our method incorporates differentiable second-order resonators and estimates their coefficients using a neural network that is conditioned on physical parameters. This allows for interactive dynamic control and the generation of novel sounds in an intuitive manner. We demonstrate the practical implementation of our method and explore its potential creative applications
Crystal structure and phonon softening in Ca3Ir4Sn13
We investigated the crystal structure and lattice excitations of the ternary
intermetallic stannide Ca3Ir4Sn13 using neutron and x-ray scattering
techniques. For T > T* ~ 38 K the x-ray diffraction data can be satisfactorily
refined using the space group Pm-3n. Below T* the crystal structure is
modulated with a propagation vector of q = (1/2, 1/2, 0). This may arise from a
merohedral twinning in which three tetragonal domains overlap to mimic a higher
symmetry, or from a doubling of the cubic unit cell. Neutron diffraction and
neutron spectroscopy results show that the structural transition at T* is of a
second-order, and that it is well described by mean-field theory. Inelastic
neutron scattering data point towards a displacive structural transition at T*
arising from the softening of a low-energy phonon mode with an energy gap of
Delta(120 K) = 1.05 meV. Using density functional theory the soft phonon mode
is identified as a 'breathing' mode of the Sn12 icosahedra and is consistent
with the thermal ellipsoids of the Sn2 atoms found by single crystal
diffraction data
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