7,101 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 firstâorder character and involves both the outâofâplane and the inâplane spin components (magnetic modes gx and gxcyfz, respectively). A second magnetic transition having also a firstâorder 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 outâofâphase component of Ïac shows a peak around 30 K which reflects the coexistence of both magnetic configurations in a wide temperature interval. Finally, two fieldâinduced transitions have been observed at 4.2 K when the field is directed along the c axis. We propose that the highâfield anomaly arises from a metamagnetic transition of the weak ferromagnetic component, similarly to La2CuO4
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&
Structure-function mapping of a heptameric module in the nuclear pore complex.
The nuclear pore complex (NPC) is a multiprotein assembly that serves as the sole mediator of nucleocytoplasmic exchange in eukaryotic cells. In this paper, we use an integrative approach to determine the structure of an essential component of the yeast NPC, the ~600-kD heptameric Nup84 complex, to a precision of ~1.5 nm. The configuration of the subunit structures was determined by satisfaction of spatial restraints derived from a diverse set of negative-stain electron microscopy and protein domain-mapping data. Phenotypic data were mapped onto the complex, allowing us to identify regions that stabilize the NPC's interaction with the nuclear envelope membrane and connect the complex to the rest of the NPC. Our data allow us to suggest how the Nup84 complex is assembled into the NPC and propose a scenario for the evolution of the Nup84 complex through a series of gene duplication and loss events. This work demonstrates that integrative approaches based on low-resolution data of sufficient quality can generate functionally informative structures at intermediate resolution
A hybrid analysis of LBSN data to early detect anomalies in crowd dynamics
Undoubtedly, Location-based Social Networks (LBSNs) provide an interesting source of geo-located data that we have previously used to obtain patterns of the dynamics of crowds throughout urban areas. According to our previous results, activity in LBSNs reflects the real activity in the city. Therefore, unexpected behaviors in the social media activity are a trustful evidence of unexpected changes of the activity in the city. In this paper we introduce a hybrid solution to early detect these changes based on applying a combination of two approaches, the use of entropy analysis and clustering techniques, on the data gathered from LBSNs. In particular, we have performed our experiments over a data set collected from Instagram for seven months in New York City, obtaining promising results.This work is funded by: the European Regional Development Fund (ERDF) and the Galician Regional Government under agreement for funding the Atlantic Research Center for Information and Communication Technologies (AtlantTIC), Spain, the Spanish Ministry of Economy and Competitiveness under the National Science Program (TEC2014-54335-C4-3-R, TEC2014-54335-C4-2-R, TEC2017-84197-C4-3-R and TEC2017-84197-C4-2-R), and by the Madrid Regional Government eMadrid Excellence Network, Spain (S2013/ICE-2715)
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
Pulsatile flow in coronary bifurcations for different stenting techniques
The objective of this work is to analyze the local hem
odynamic changes caused in a coronary bifurcation by three different stenting techniques: simple stenting of the main vessel, simple stenting of the main vessel with kissing balloon in the side branch and culotte. To carry out this study an idealized geometry of a coronary bifurcation is
used, and two bifurcation angles, 45Âș and 90Âș, are chosen as representative of the wide variety of re
al configurations. In order to quantify the influence of the stenting technique on the local blood flow, both numeri-
cal simulations and experimental measurements are performed. First, steady simulations are carried out with the commercial code ANSYS-Fluent, and then, experimental measurements with PIV (Particle Image Velocimetry) obtained
in the laboratory are used to validate the numerical simulation. The steady computational simulations show a good overall agreement with the experimental data. Second, pulsatile flow is considered to take into account the tran-
sient effects. The time averaged wall shear stress, scillatory shear index and pressure drop obtained numerically are used to compare the behavior of the stenting techniques
Treatment with interferon-alpha delays disease in swine infected with a highly virulent CSFV strain
AbstractInterferon-alpha (IFNα) can effectively inhibit or abort a viral infection within the host. It has been reported that IFN induction and production is hindered during classical swine fever virus (CSFV) infection. Most of those studies have been performed in vitro, making it difficult to elucidate the actual role of IFNs during CSFV infection in swine. Here, we report the effect of IFNα treatment (delivered by a replication defective recombinant human adenovirus type 5, Ad5) in swine experimentally infected with highly virulent CSFV strain Brescia. Treatment with two different subtypes of IFNα delayed the appearance of CSF-related clinical signs and virus replication although it did not prevent lethal disease. This is the first report describing the effect of IFNα treatment during CSFV infection in swine
Fermented Goatâs Milk Consumption Improves Duodenal Expression of Iron Homeostasis Genes during Anemia Recovery
Despite the crucial roles of duodenal cytochrome b (Dcytb), divalent metal transporter 1 (DMT1), ferritin light chain (Ftl1), ferroportin 1 (FPN1), transferrin receptor 1 (TfR1), and hepcidin antimicrobial peptide (Hamp) in Fe metabolism, no studies have investigated the modulations of these genes during Fe repletion with fermented milks. Analysis included Fe status markers and gene and protein expression in enterocytes of control and anemic animals fed fermented milks. Fermented goatâs milk up-regulated enterocyte Dcytb, DMT1, FPN1, and Ftl1 and down-regulated TfR1 and Hamp gene expression in control and anemic animals. Anemia decreased Dcytb, DMT1, and Ftl1 in animals fed fermented cowâs milk and up-regulated TfR1 and Hamp expression. Fe overload down-regulated Dcytb and TfR1 in animals fed fermented cowâs milk and up-regulated DMT1 and FPN1 gene expression. Fermented goatâs milk increased expression of duodenal Dcytb, DMT1, and FPN1 and decreased Hamp and TfR1, improving Fe metabolism during anemia recovery
Crystal and magnetic structure of the LaCaMnO compound
We studied the crystal and magnetic structure of the
LaCaMnO compound for and . At T=300 K both
samples are paramagnetic with crystallographic symmetry . At low
temperatures they undergo a monoclinic distortion from orthorhombic -type
structure with to a monoclinic
structure with (,
) and space group below . The
onset of the structural transformation coincides with the development of the
-type long range antiferromagnetic order with propagation vector . The monoclinic unit cell allowed us to determine the
direction of the Mn magnetic moment with respect to the crystallographic axes:
it is perpendicular to the propagation vector, . The amplitude of the ordered magnetic moment at K
is found to be and for and 0.85,
respectively.Comment: In press (Phys. Rev B 01 Feb 2002
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