Magnetostructural coupling, magnetic ordering, and cobalt spin reorientation in metallic P r0.5 S r0.5Co O3 cobaltite

In half-doped Pr0.50A0.50CoO3 metallic perovskites, the spin-lattice coupling brings about distinct magnetostructural transitions for A=Ca and A=Sr at temperatures close to ~100 K. However, the ground magnetic properties of Pr0.50Sr0.50CoO3 (PSCO) strongly differ from Pr0.50Ca0.50CoO3 ones, where a partial Pr3+ to Pr4+ valence shift and Co spin transition makes the system insulating below the transition. This paper investigates and describes the relationship between the Imma¿I4/mcm symmetry change [Padilla-Pantoja, García-Muñoz, Bozzo, Jirák, and Herrero-Martín, Inorg. Chem. 53, 12297 (2014)] and the original magnetic behavior of PSCO versus temperature and external magnetic fields. The FM1 and FM2 ferromagnetic phases, above and below the magnetostructural transition (TS1~120K) have been investigated. The FM2 phase of PSCO is composed of [100] FM domains, with magnetic symmetry Im'm'a (mx¿0, mz=0). The magnetic space group of the FM1 phase is Fm'm'm (with mx=my). Neutron data analyses in combination with magnetometry and earlier reports results agrees with a reorientation of the magnetization axis by 45° within the ab plane across the transition, in which the system retains its metallic character. The presence below TS1 of conjugated magnetic domains, both of Fm'm'm symmetry but having perpendicular spin orientations along the diagonals in the xy plane of the tetragonal unit cell, is at the origin of the anomalies observed in the macroscopic magnetization. A relatively small field µ0H[¿z]¿30mT is able to reorient the magnetization within the ab plane, whereas a higher field (µ0H[¿z]¿1.2T at 2 K) is necessary to align the Co moments perpendicular to the ab plane. Such a spin reorientation, in which the orbital and spin components of the Co moment rotate joined by 45°, was not observed previously in analogous cobaltites without praseodymium

Cosmic acceleration from asymmetric branes

We consider a single 3-brane sitting in between two different five dimensional spacetimes. On each side of the brane, the bulk is a solution to Gauss-Bonnet gravity, although the bare cosmological constant, funda mental Planck scale, and Gauss-Bonnet coupling can differ. This asymmetry leads to weighted junction conditions across the brane and interesting brane cosmology. We focus on two special cases: a generalized Randall-Sundrum model without any Gauss-Bonnet terms, and a stringy model, without any bare cosmological constants, and positive Gauss-Bonnet coupling. Even though we assume there is no vacuum energy on the brane, we find late time de Sitter cosmologies can occur. Remarkably, in certain parameter regions, this acceleration is preceded by a period of matter/radiation domination, with $H^2 \propto \rho$, all the way back to nucleosynthesis.Comment: Version appearing in CQ

Impact of uterine manipulator on oncological outcome in endometrial cancer surgery

Background: There are limited data available to indicate whether oncological outcomes might be influenced by the uterine manipulator, which is used at the time of hysterectomy for minimally invasive surgery in patients with endometrial cancer. The current evidence derives from retrospective studies with limited sample sizes. Without substantial evidence to support its use, surgeons are required to make decisions about its use based only on their personal choice and surgical experience. Objective: To evaluate the use of the uterine manipulator on oncological outcomes after minimally invasive surgery, for apparent early-stage endometrial cancer. Study Design: We performed a retrospective multicentric study to assess the oncological safety of uterine manipulator use in patients with apparent early-stage endometrial cancer, treated with minimally invasive surgery. The type of manipulator, surgical staging, histology, lymphovascular space invasion, International Federation of Gynecology and Obstetrics stage, adjuvant treatment, recurrence, and pattern of recurrence were evaluated. The primary objective was to determine the relapse rate. The secondary objective was to determine recurrence-free survival, overall survival, and the pattern of recurrence. Results: A total of 2661 women from 15 centers were included; 1756 patients underwent hysterectomy with a uterine manipulator and 905 without it. Both groups were balanced with respect to histology, tumor grade, myometrial invasion, International Federation of Gynecology and Obstetrics stage, and adjuvant therapy. The rate of recurrence was 11.69% in the uterine manipulator group and 7.4% in the no-manipulator group (P<.001). The use of the uterine manipulator was associated with a higher risk of recurrence (hazard ratio, 2.31; 95% confidence interval, 1.27–4.20; P=.006). The use of uterine manipulator in uterus-confined endometrial cancer (International Federation of Gynecology and Obstetrics [FIGO] I–II) was associated with lower disease-free survival (hazard ratio, 1.74; 95% confidence interval, 0.57–0.97; P=.027) and higher risk of death (hazard ratio, 1.74; 95% confidence interval, 1.07–2.83; P=.026). No differences were found regarding the pattern of recurrence between both groups (chi-square statistic, 1.74; P=.63). Conclusion: In this study, the use of a uterine manipulator was associated with a worse oncological outcome in patients with uterus-confined endometrial cancer (International Federation of Gynecology and Obstetrics I–II) who underwent minimally invasive surgery. Prospective trials are essential to confirm these results

Decreased Time to Treatment Initiation for Multidrug-Resistant Tuberculosis Patients after Use of Xpert MTB/RIF Test, Latvia

Few studies have examined whether the Xpert MTB/RIF test improves time to treatment initiation for persons with multidrug-resistant tuberculosis (MDR TB). We determined the impact of this test in Latvia, where it was introduced in 2010. After descriptive analyses of pulmonary MDR TB patients in Latvia during 2009–2012, time to treatment initiation was calculated, and univariate and multivariable accelerated failure time models were constructed. Univariate results showed strong evidence of an association between having rifampin-resistant TB detected by Xpert MTB/RIF and reduced time to treatment initiation versus the test not being used. A multivariable model stratifying by previous TB showed similar results. Our finding that in Latvia, time to treatment initiation was decreased for MDR TB cases that were rifampin-resistant TB by XpertMTB/RIF has implications for the use of this test in other settings with a high burden of MDR TB in which rifampin resistance is highly predictive of MDR TB

Magnetostructural transition and cobalt spin behavior in metallic Pr0.50Sr0.50CoO3 perovskite

Trabajo presentado a la 61st Annual Conference on Magnetism and Magnetic Materials (MMM) celebrada en New Orleans (USA) del 31 de octubre al 4 de noviembre de 2016.We thank financial support from MINECO under projects MAT2012-38213-C02 and MAT2015-68760-C2, cofunded by ERDF from EU.Peer Reviewe

Role of Pr cations and the low temperature transition in Pr0.50Sr0.50CoO3: A comparison to Pr0.50Ca0.50CoO3

The low temperature properties of Pr0.50Sr0.50CoO3 are studied in comparison to Pr0.50Ca0.50CoO3, which is known to exhibit a Pr3+/Pr4+ valence shift below TMI∼80 K. The evolution of the Pr-O network strongly differs in the Sr and Ca compounds, but both have in common a prominent and sudden contraction of some Pr-O bonds. The structural phase transition that accompanies the so-called magnetocrystalline anisotropy transition at TS∼120 K in Pr0.50Sr0.50CoO3 brings about a notable contraction of some Pr-O2 bonds. The observations give support to the active participation of Pr-4f electrons at the intriguing magnetostructural transition (TS) in Pr0.50Sr0.50CoO3. In addition, we have confirmed that (in absence of praseodymium) the magnetostructural transition is suppressed in (Nd2/3La1/3)0.50Sr0.50CoO3, a perovskite with the same average cationic size at the A-site than Pr0.50Sr0.50CoO3.We thank MINECO (Spanish Government) for financial support under Projects MAT2009-09308, MAT2012-38213-C02-02 and CSD2007-00041 (NANOSELECT), and the ILL for granting beamtime. J. P-P thanks CSIC for JAE‐Pre contract.Peer Reviewe

The low temperature magnetostructural transition in Pr0.50Sr0.50CoO3: Bulk versus thin film behavior

Under the terms of the license Creative Commons Attribution 3.0 Unported License to their work.We present a comparative study of the magnetic transitions in metallic Pr0.50Sr0.50CoO3 (PSCO) perovskites prepared in polycrystalline and thin film forms. As the bulk system, the strained epitaxial PSCO (010) film grown on LAO (100) is metallic in all the temperature range, with a ferromagnetic transition at 225 K, close to Tc ∼ 235 K in the ceramic PSCO specimen. Unlike the bulk system, the PSCO film does not show the second magnetic transition on cooling. In the ceramic sample, the second magnetic transition is coupled to an orthorhombic-to-monoclinic symmetry change. There is a contraction of the average ⟨Pr-O⟩ bond distance in the monoclinic phase below Ta, but the ⟨Co-O⟩ bond length is not modified across the transition. The orthorhombic to monoclinic structural transition stabilizes four short Pr-O2 bonds to basal oxygens in CoO6 octahedra. A strong hybridization of Pr 4f and O 2p orbitals in these bonds can be activated at Ta and probably assist the magnetostructural transition.We thank financial support from MICINN (Spanish government) under Projects MAT2009-09308, MAT2012-38213-C02-02, and CSD2007-00041 (NANOSELECT), and the ILL for granting beamtime. J.P-P thanks CSIC for JAE-Pre contract.Peer reviewe

Neutron investigation of the spin-state crossover in the distorted ErCoO3 cobaltite

Poster presented at the VI European Conference on Neutron Scattering, held in Zaragoza (Spain) from August 30th to September 4th, 2015. Magnetism, Superconductivity and other Electronic Phenomena.The spin-state nature across the two electronic transitions in LaCoO3 has been matter of controversy for many years. Two competing pictures in LaCoO3 involve the spin transitions either LS→(HS+LS)→IS or LS→IS→(HS+IS). The ground and thermally excited states of LnCoO3 perovskites (Ln:lanthanide or rare earth) with heavy rare-earths and more distorted structures are also attracting great interest. We present neutron powder diffraction (NPD) studies aimed to characterize the electronic phenomena associated with the spin-state of Co3+ ions in the highly distorted ErCoO3 cobaltite. NPD measurements carried out on the high-resolution D2B diffractometer up to 1000 K were combined with low temperature measurements using several ILL diffractometers (which confirmed the ordering of Er moments below 2 K). To our knowledge, ErCoO3 (prepared under moderate pressure conditions) is the smallest Co3+ simple perovskite investigated so far in a temperature range up to 1000 K. The orthorhombic Pbnm symmetry was confirmed in this range, but the lattice evolution proves a remarkable occupation of excited magnetic states on heating above TSS≈575 K. The spin-state crossover extends over a broad temperature interval and can be monitored by an atypical augmentation of the rthorhombic strain (s). The anomalous contributions to the lattice above that temperature are clearly visible in the evolution of the anisotropic or global linear thermal expansion coefficients. The occupation of excited magnetic states (S=1 or 2) is activated at TSS≈575 K but it develops progressively along the interval 575-780 K. Above ~800 K the progression decreases. An estimation of the anomalous volume expansion accumulated at 1000 K due to spin state excitations gives ~2 %. Several correlated structural modifications above TSS are driven by the anomalous expansion of the CoO6 octahedra, which is partially anisotropic. The activation of IS or HS spin states brings about the augmentation of the Co-O distances in the a-b plane respect to the distance along the c-axis. This fact produces a non monotonous evolution of the tilting between adjacent octahedra and the intensification of the orthorhombic distortion. In spite of this, some evidences suggest the stabilization of a metallic state in the thermally excited phase

Structural effects of the spin-state crossover at high temperature in the distorted ErCoO3 cobaltite

Paper presented at the 7th Meeting of the Spanish Neutron Scattering Association (SETN) held on 22-25th June 2014, Pamplona, Spain.We present a neutron powder diffraction study reporting structural evidences of a spin- state crossover beginning at Tss≈575 K in the highly distorted ErCoO3 cobaltite, based on measurements in the temperature range 100 K - 1000 K. Different interrelated changes in the structural evolution upon heating have been described, which are driven by an anomalous expansion of the octahedra. The activation of IS or HS spin states brings about an expansion of the CoO6 octahedra (increase of Co-O bond lengths), and the augmentation of the Co-O distances in the a-b plane respect to that along the c-axis. The spin-state crossover extends over a broad temperature interval and can be monitored by an atypical augmentation of the orthorhombic strain.We thank financial support from MINECO (Spanish government) under projects MAT2009-09308, MAT2012-38213-C02-02 and MAT2013-41099-R, and to the ILL for granting beamtime. J. P.-P. thanks the CSIC for a JAE-Predoc contract.Peer reviewe