Resonant x-ray scattering study on multiferroic BiMnO3

Resonant x-ray scattering is performed near the Mn K-absorption edge for an epitaxial thin film of BiMnO3. The azimuthal angle dependence of the resonant (003) peak (in monoclinic indices) is measured with different photon polarizations; for the $\sigma\to\pi'$ channel a 3-fold symmetric oscillation is observed in the intensity variation, while the $\sigma\to\sigma'$ scattering intensity remains constant. These features are accounted for in terms of the peculiar ordering of the manganese 3d orbitals in BiMnO3. It is demonstrated that the resonant peak persists up to 770 K with an anomaly around 440 K; these high and low temperatures coincide with the structural transition temperatures, seen in bulk, with and without a symmetry change, respectively. A possible relationship of the orbital order with the ferroelectricity of the system is discussed.Comment: 14 pages, 4 figure

Substructural Identification of Flexural Rigidity for Beam-Like Structures

This study proposes a novel substructural identification method based on the Bernoulli-Euler beam theory with a single variable optimization scheme to estimate the flexural rigidity of a beam-like structure such as a bridge deck, which is one of the major structural integrity indices of a structure. In ordinary bridges, the boundary condition of a superstructure can be significantly altered by aging and environmental variations, and the actual boundary conditions are generally unknown or difficult to be estimated correctly. To efficiently bypass the problems related to boundary conditions, a substructural identification method is proposed to evaluate the flexural rigidity regardless of the actual boundary conditions by isolating an identification region within the internal substructure. The proposed method is very simple and effective as it utilizes the single variable optimization based on the transfer function formulated utilizing Bernoulli Euler beam theory for the inverse analysis to obtain the flexural rigidity. This novel method is also rigorously investigated by applying it for estimating the flexural rigidity of a simply supported beam model with different boundary conditions, a concrete plate-girder bridge model with different length of an internal substructure, a cantilever-type wind turbine tower structure with different type of excitation, and a steel box-girder bridge model with internal structural damages.This research was financially supported by the Ministry of Land, Infrastructure and Transport (MOLIT) of the Korea government (code 12 Technology Innovation E09)

Anisotropic strains and magnetoresistance of La_{0.7}Ca_{0.3}MnO_{3}

Thin films of perovskite manganite La_{0.7}Ca_{0.3}MnO_{3} were grown epitaxially on SrTiO_3(100), MgO(100) and LaAlO_3(100) substrates by the pulsed laser deposition method. Microscopic structures of these thin film samples as well as a bulk sample were fully determined by x-ray diffraction measurements. The unit cells of the three films have different shapes, i.e., contracted tetragonal, cubic, and elongated tetragonal for SrTiO_3, MgO, and LaAlO_3 cases, respectively, while the unit cell of the bulk is cubic. It is found that the samples with cubic unit cell show smaller peak magnetoresistance than the noncubic ones do. The present result demonstrates that the magnetoresistance of La_{0.7}Ca_{0.3}MnO_{3} can be controlled by lattice distortion via externally imposed strains.Comment: Revtex, 10 pages, 2 figure

Neurosyphilis in a Non-HIV Patient: More than a Psychiatric Concern

Neurosyphilis is a form of tertiary syphilis infection caused by the spirochete bacterium Treponema pallidum. Patients suffering from this illness can present with neurological manifestations such as headaches, seizures, hearing loss, and ataxia. However, the typical presentation of neurosyphilis is the insidious onset of psychiatric symptoms including personality changes. A good history and clinical work-up is essential in the diagnostic process. There has been a recent increase in the incidence of infectious syphilis in Canada (1). However, in other parts of the world including China, infectious syphilis rates have remained high due to limited access to primary care and affordable treatments (2 Here, we present a case of neurosyphilis in a 40 year old Chinese male residing in China who presents with an 18 month history of personality changes as well as neurological and physical manifestations of the infection

Singlet ground state in the alternating spin-1/21/2 chain compound NaVOAsO4_4

We present the synthesis and a detailed investigation of structural and magnetic properties of polycrystalline NaVOAsO$_4$ by means of x-ray diffraction, magnetization, electron spin resonance (ESR), and $^{75}$As nuclear magnetic resonance (NMR) measurements as well as density-functional band structure calculations. Temperature-dependent magnetic susceptibility, ESR intensity, and NMR line shift could be described well using an alternating spin-$1/2$ chain model with the exchange coupling $J/k_{\rm B}\simeq 52$ K and an alternation parameter $\alpha \simeq 0.65$. From the high-field magnetic isotherm measured at $T=1.5$ K, the critical field of the gap closing is found to be $H_{\rm c}\simeq 16$ T, which corresponds to the zero-field spin gap of $\Delta_0/k_{\rm B}\simeq 21.4$ K. Both NMR shift and spin-lattice relaxation rate show an activated behavior at low temperatures, further confirming the singlet ground state. The spin chains do not coincide with the structural chains, whereas the couplings between the spin chains are frustrated. Because of a relatively small spin gap, NaVOAsO$_4$ is a promising compound for further experimental studies under high magnetic fields.Comment: 14 pages, 10 figures, 2 table

Viability of optical tracking systems for monitoring deformations of a long span bridge

Authors' manuscript. Paper presented at 6th European Conference on Structural Control (EACS 2016); July 11th - July 13th 2016 - Sheffield, England.Characterisation of both dynamic and quasi-static deformations of suspension bridges is essential to manage their serviceability and to appreciate the internal forces due to the various live loads effects of wind, temperature and traffic. GPS is commonly used for the largest, most flexible structures but the limitations are not well understood and accelerometers cannot capture the extreme low frequency movements. Optical displacement tracking has potential to avoid all these errors but has different types of limitation that need to be evaluated and mitigated. In attempt to cross-validate optical tracking technology against GPS data, a commercial optical system the Imetrum ‘Video Gauge’ was used at Humber Bridge, after first initial experiments on a short span bridge to identify the most effective way to deploy it in the field for measurements at very long range. Some results are presented illustrating the character of the observed deformations and the limitations of the various forms of deformation monitoring instrumentation. In particular limitations of GPS were highlighted through comparison with Video Gauge and accelerometer data.The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 330195. The authors would also like to acknowledge the support of the Bridge Design Group of Devon County Council, led by Kevin Dentith, and Humber Bridge Board

A Continuum Model for Soil-Pile-Structure Interactions Under Earthquake Excitation

An exact analytical method for the interaction analysis of a fully coupled soil-pile-structure system under seismic excitation is investigated in this paper. Only horizontal shaking induced by harmonic SH waves was considered. The soil mass, pile and building were all considered as elastic with hysteretic type damping. Geometrically, the soil is modeled as an elastic isotropic homogeneous continuum, and both pile and structures are simplified as beam models. The structure and piles are coupled through a rigid foundation at the ground level. Buildings of various heights in Hong Kong designed to withstand wind load were analyzed using the present model. Only the shaking at the ground level is considered in this study. It was discovered that the maximum shaking of the piled-structures at ground level is generally larger than that of a free field ground shaking except near the first natural frequency of the coupled soil-pile-structure system. This first resonant frequency depends strongly on the natural frequency of the structure

Challenges in design and construction of deep excavation for KVMRT in Kuala Lumpur limestone formation

The Klang Valley Mass Rapid Transit (KVMRT) Sungai Buloh-Kajang Line project is the first Mass Rapid Transit (MRT) project in Malaysia. The KVMRT Project when completed will cover a distance of 51km and comprises of 31 passenger stations. This paper covers the challenges in design and construction of deep excavation works for three underground stations, namely Tun Razak Exchange (TRX) station, Cochrane Station and Maluri Station, as well as one portal (South Portal) all located in Kuala Lumpur limestone formation. The Kuala Lumpur Limestone formation exhibits notorious karstic features with irregular bedrock profiles, variable weathering condition, cavities and slime zones. This paper presents the design principles of temporary earth retaining system together with vertical rock excavation to the final depth of the station in karstic limestone formation. The unique experience (design and construction) gained from this project will be a useful reference for similar excavation works, especially in karstic limestone formation

Diffusion-Limited Annihilation with Initially Separated Reactants

A diffusion-limited annihilation process, A+B->0, with species initially separated in space is investigated. A heuristic argument suggests the form of the reaction rate in dimensions less or equal to the upper critical dimension $d_c=2$. Using this reaction rate we find that the width of the reaction front grows as $t^{1/4}$ in one dimension and as $t^{1/6}(\ln t)^{1/3}$ in two dimensions.Comment: 9 pages, Plain Te

Quantitative Risk Assessment as Applied to Natural Terrain Landslide Hazard Management in a Mid-levels Catchment, Hong Kong

This paper presents a case study of the application of quantitative risk assessment techniques to a site-specific natural terrain hazard study in Hong Kong. The development of the landslide hazard and susceptibility models is described and salient details of the consequence model are given, including the assessment of debris flowpaths and runout using state-of-the-art Geographic Information System (GIS) tools and debris runout computer models. A synthesis of the risk quantification process and schematic design of risk mitigation works is presented