Coupling between spin, lattice, and charge at the surface of complex transition metal compounds

Understanding and controlling the complexity that develops in complex transition metal compounds such as high-Tc superconductivity, colossal magnetoresistance in manganites, and heavy-fermion compounds, is one of the grand challenges of the 21st century. The exotic properties displayed by these compounds are closely related to the coexistence of nearly degenerate states, coupling simultaneously several active degrees of freedom such as the charge, lattice, orbital, and spin. In this work, we have focused on two systems, one is the newly discovered Fe-based superconducting compounds ((Ba, Ca)(Fe1-xCox)2As2, FeTe1-xSex) and the other one is the doped Ruddleden-Popper (RP) ruthenates (Sr3(Ru1-xMnx)2O7). The materials community was astonished by the discovery of superconductivity with a critical temperature exceeding 55 K in the iron-based superconductors in 2008. This new family of high Tc superconductors with layered structure without Cu has opened up a completely new venue for understanding not only high Tc superconductors but in general the coupling between lattice, charge, orbital and spin. While ruthenates is a prototype of strong correlated electron materials (CEMs) and Mn-doping in Sr3(Ru1-xMnx)2O7 have induced a rich coupled phase diagrams. We approach from the surface to study their geometric and electronic structure because the symmetry breaking offers great opportunities to tune the balance of the coupling. We applied Low energy electron diffraction (LEED) and its Intensity-voltage (I-V) analysis to quantitatively characterize the detail surface structure from momentum space. Then we used low and variable temperature scanning tunneling microscopy/spectroscopy (STM/S) to study surface electronic structure from real space. At last, spin-polarized density functional theory (DFT) calculations were utilized to enhance our understanding of the experimental data, thus providing a new prospective of our discovery. Our results on the domain surface of BaFe2As2 show that the strong spin-lattice coupling at the surface results in the coexistence of structure and spin antiphase domain boundaries with C2 symmetry. For the stripe surface of (Ba, Ca)(Fe1-xCox)2As2, we determined the surface structure which is proved to be stabilized by bulk spin ordering through spin-lattice-charge coupling. Superconductivity has also been observed on stripe surface indicating a spatial-resolved coexisting of anti-ferromagnetic and superconducting order. On FeTe1-xSex system, we observed a nano-scale chemical phase separation of Te and Se atoms thus the optimally doped superconductor is chemically inhomogeneous but electronically homogeneous, in contrast to many CEMs. However, using STM on a different system, Mn-dopants in Sr3(Ru1-xMnx)2O7 were shown to homogeneously (random) distribute on the surface in micro-scale but maybe phase separated in macro-scale.We also discovered a left- and right- chirality of the structural rotation of MnO6, thus to understand the correlation between the magnetic dopants. Our approach of using state-of-the-art surface techniques to study the manifestation of broken symmetry in these complex transition metal compounds, especially the iron pnictides and ruthernate offered the community a fresh look at the underlying physics

Antioxidant and anti-inflammatory effects of rhamnazin on lipopolysaccharide-induced acute lung injury and inflammation in rats

Background: Acute Lung Injury (ALI) results into severe inflammation and oxidative stress to the pulmonary tissue. Rhamnazin is a natural flavonoid and known for its antioxidant and anti-inflammatory properties.Materials and methods: The antioxidative and anti-inflammatory properties rhamnazin were tested for protection against the acute lung injury. We investigated whether rhamnazin improves the lipopolysaccharide (LPS)-induced ALI in an animal model (rat). We also studied the probable molecular mechanism of action of rhamnazin. Rhamnazin was injected intraperitoneally (i.p.) (5, 10 and 20 mg/kg) two days before intratracheal LPS challenge (5mg/kg). The changes in lung wet-to-dry weight ratio, LDH activity, pulmonary histopathology, BALF protein concentration, MPO activity, oxidative stress, cytokine production were estimated.Results: The results showed a significant attenuation of all the inflammatory parameters and a marked improvement in the pulmonary histopathology in the animal groups pretreated with rhamnazin. The rhamnazin pretreated group also showed activation of Nrf2 pathway and attenuation of ROS such as H2O2, MDA and hydroxyl ion. These results indicated that rhamnazin could attenuate the symptoms of ALI in rats due to its strong antioxidant and anti-inflammatory properties.Conclusion: The results strongly demonstrated that rhamnazin provides protection against LPS-induced ALI. The underlying mechanisms of its anti-inflammatory action may include inhibition of Nrf2 mediated antioxidative pathway.Keywords: acute lung injury, inflammation, cytokine, BALF, flavonoi

A theoretical study on the mechanism of the addition reaction between cyclopropenylidene and ethylene

The reaction mechanism between cyclopropenylidene and ethylene has been systematically investigated employing the MP2/6-311+G* level of theory to better understand the cyclopropenylidene reactivity with unsaturated hydrocarbons. Geometry optimization, vibrational analysis, and energy property for the involved stationary points on the potential energy surface have been calculated. Energies of all the species are also further refined by the CCSD(T)/6-311+G* single-point calculations. Firstly, one important reaction intermediate (INTa) has been located via a transition state (TSa). After that, the common intermediate (INTb) for the two pathways (1) and (2) has been formed via TSb. At last, two different products possessing three- and four-membered ring characters have been obtained through two reaction pathways. In the reaction pathway (1), a three-membered ring alkyne compound has been obtained. As for the reaction pathway (2), a four-membered ring conjugated diene compound has been formed, which is the most favorable reaction to occur from the kinetic and thermodynamic viewpoints

Brucellosis in ruminants in two counties of Yunnan, China and the use of an integrated approach for effective control

Brucellosis is an increasing production and public health concern in many countries of Asia including China. Challenges for an effective control include lack of collaboration between sectors or uncontrolled animal movement (among others). Yunnan might be at particular risk as ruminants are increasingly introduced from other parts of China e.g. Inner Mongolia, a known high prevalence area in a response to a higher demand for milk. To face this challenges, new integrated approaches are needed such as Ecohealth to support transdisciplinary collaboration versus silo thinking, the latter rather common in the top down animal health control system of China. In the presented research, which was part of an IDRC funded ILRI-Ecozd project, veterinary, public health, animal science experts from five provincial institutions, practitioners from the project sites, and policy authorities worked together to achieve a more effective control of brucellosis. The research was carried out between 2011 and 2013 in two counties of Yunnan, Mangshi and Yiliang and consisted of a historical data review, biological sampling (milk) in herds/households with dairy ruminants and people at risk (serum). Questionnaires were used to collect management data (N=192) from farmers; focus group discussions (villagers) and in depth interviews (village vets and human doctors) gained information on perception and awareness on zoonoses in general and more specifically on the targeted disease. Results from the biological sampling indicate brucellosis as an existing and potentially emerging public health concern depending on the production system. Risk factors for the spread of brucellosis were reported and included risky handling of aborted fetus among others. Awareness and perception on zoonoses (including brucellosis) of all interviewed groups was in general low. The use of a “learning by doing” EcoHealth approach led to improve team member's capacity on Ecohealth and its practical realisation in a field study, e.g. by building up collaboration between those institutions but also stakeholders. Crucial was the support by the Agriculture Department and Health Department of Yunnan. Outcome mapping indicated a change of behaviour in the targeted groups in particular on zoonoses knowledge and willingness to share of information between sectors (vet and public health)

Marcinkiewicz multipliers associated with the Kohn Laplacian on the Shilov boundary of the product domain in C2n\mathbb C ^{2n}

Let $M^{(k)}$, $k=1,2,\ldots, n$, be the boundary of an unbounded polynomial domain $\Omega^{(k)}$ of finite type in $\mathbb C ^2$, and let $\Box_b^{(k)}$ be the Kohn Laplacian on $M^{(k)}$. In this paper, we study multivariable spectral multipliers $m(\Box_b^{(1)},\ldots, \Box_b^{(n)})$ acting on the Shilov boundary $\widetilde{M}=M^{(1)} \times\cdots\times M^{(n)}$ of the product domain $\Omega^{(1)}\times\cdots\times \Omega^{(n)}$. We show that if a function $F(\lambda_1, \ldots ,\lambda_n)$ satisfies a Marcinkiewicz-type differential condition, then the spectral multiplier operator $m(\Box_b^{(1)}, \ldots, \Box_b^{(n)})$ is a product Calder\'on--Zygmund operator of Journ\'e type