First principles investigation of the electronic structure of La2MnNiO6: A room-temperature insulating ferromagnet

Using first principles calculations within DFT based on the full potential APW+lo method, we calculated the electronic and magnetic structures for the ferromagnetic and antiferromagnetic states of La2MnNiO6 and analyzed the site projected density of states and electronic band structures. Our calculations show that the ground state of La2MnNiO6 is ferromagnetic insulating with the magnetization in agreement with Hund's first rule and experimental findings.Comment: 10 pages, 3 figure

Interplay of Chemical Bonding and Magnetism in Fe_4N, Fe_3N, Fe_2N

Using spin density functional theory we have carried out a comparative study of chemical bonding and magnetism in Fe_4N, Fe_3N and Fe_2N. All of these compounds form close packed Fe lattices, while N occupies octahedral interstitial positions. High spin fcc Fe and hypothetical FeN with rock salt structure have been included in our study as reference systems. We find strong, covalent Fe-N bonds as a result of a substantial \sigma-type p-d hybridisation, with some charge transfer to N. Those Fe d orbitals which contribute to the p-d bonds, do no longer participate in the exchange splitting of the Fe d bands. Because of the large exchange fields, the majority spin d bands are always fully occupied, while the minority spin d bands are close to half-filling, thus optimizing the Fe d-d covalent bonding. As a consequence, in good approximation the individual Fe moments decrease in steps of 0.5 \mu_B from fcc iron (2.7 \mu_B) via Fe_4N (2.7 and 1.97 mu_B}), \chem{Fe_3N} (1.99 \mu_B) to \zeta - Fe_2N (1.43 \mu_B).Comment: 16 pages, 15 figure

First principles study of the electronic and magnetic structures of the tetragonal and orthorhombic phases of Ca3Mn2O7

On the basis of density functional theory electronic band structure calculations using the augmented spherical wave method, the electronic and magnetic properties of the orthorhombic and tetragonal phases of Ca3Mn2O7 were investigated and the spin exchange interactions of the orthorhombic phase were analyzed. Our calculations show that the magnetic insulating states are more stable than the non-magnetic metallic state for both polymorphs of Ca3Mn2O7, the orthorhombic phase is more stable than the tetragonal phase, and the ground state of the orthorhombic phase is antiferromagnetic. The total energies calculated for the three spin states of the orthorhombic phase of Ca3Mn2O7 led to estimates of the spin exchange interactions Jnn = -3.36 meV and Jnnn = -0.06 meV. The accuracy of these estimates were tested by calculating the Curie-Weiss temperature within the mean-field approximation.Comment: 11 pages, 7 figure

Hybrid in vitro diffusion cell for simultaneous evaluation of hair and skin decontamination: temporal distribution of chemical contaminants

Most casualty or personnel decontamination studies have focused on removing contaminants from the skin. However, scalp hair and underlying skin are the most likely areas of contamination following airborne exposure to chemicals. The aim of this study was to investigate the interactions of contaminants with scalp hair and underlying skin using a hybrid in vitro diffusion cell model. The in vitro hybrid test system comprised “curtains” of human hair mounted onto sections of excised porcine skin within a modified diffusion cell. The results demonstrated that hair substantially reduced underlying scalp skin contamination and that hair may provide a limited decontamination effect by removing contaminants from the skin surface. This hybrid test system may have application in the development of improved chemical incident response processes through the evaluation of various hair and skin decontamination strategies.Peer reviewedFinal Published versio

‘Some glimpses of an Asian PhD journey in tourism’ – An ethnodrama

By combining three different genres – academic writing, theatrical playwriting and performing – this article presents different ways of knowing and representing realities for tourism scholars. More specifically, drawing upon social scientists\u27 influential work on performance texts and an ethnodramatic script written by the authors based on dramatized ethnographic and autoethnographic fieldwork, it portrays a tourism PhD journey in an Asian institution. As an attempt of representing the power structures underpinning academia (and tourism academia), namely postcolonial, gendered, global, regional, institutional, and socio-cultural forces, among others, the 8 scenes constituting the script (one of which is enacted and presented in a video) discuss how Asian PhD journeys are shaped by specific approaches to supervision, issues of authorship, gendered dynamics and postcolonial legacies. The main rationale behind this work lies in the recognition of the powerful/performative role of embodied texts and performances in producing, shaping and re-presenting realities. More specifically, the ethnodrama presented in this paper and its embodied representation act as vehicles that are both political and entertaining in producing meanings

Transition to elasto-capillary thinning dynamics in viscoelastic jets

We perform simulations of an impulsively-started, axisymmetric viscoelastic jet exiting a nozzle and entering a stagnant gas phase using the open-source code Basilisk. This code allows for efficient computations through an adaptively-refined volume-of-fluid technique that can accurately capture the deformation of the liquid-gas interface. We use the FENE-P constitutive equation to describe the viscoelasticity of the liquid and employ the log-conformation transformation, which provides stable solutions for the evolution of the conformation tensor as the jet thins down under the action of interfacial tension. For the first time, the entire jetting and breakup process of a viscoelastic fluid is simulated, including the pre-shearing flow through the nozzle, which results in an inhomogeneous initial radial stress distribution in the fluid thread that affects the subsequent breakup dynamics. The evolution of the velocity field and the elastic stresses in the nozzle are validated against analytical solutions where possible, and the early-stage dynamics of the jet evolution are compared favourably to the predictions of linear stability theory. We study the effect of the flow inside the nozzle on the thinning dynamics of the viscoelastic jet (which develops distinctive "beads-on-a-string" structures) and on the spatio-temporal evolution of the polymeric stresses in order to systematically explore the dependence of the filament thinning and breakup characteristics on the initial axial momentum of the jet and the extensibility of the dissolved polymer chains

Application of global and regional myocardial deformation using cardiovascular magnetic resonance: an assessment of feature tracking in vivo and using numerical simulation

PhDCardiovascular diseases are responsible for approximately a third of all death worldwide, with hypertension being a major risk factor for many of those. Hypertension can lead to left ventricle hypertrophy and diastolic and systolic dysfunction. Myocardial deformation parameters have been shown to have high sensitivity at the early stage of contractile dysfunction. They can be derived from myocardial tagging, considered to be the goldstandard method, or from routinely acquired cine images using feature tracking (FT) techniques. This work aimed to validate FT as a post processing technique. Three FT software packages were used to measure strain parameters in healthy subjects and hypertensive patients in order to assess agreement. Intra- and inter-observer reproducibility was also investigated. The CVI42 software was found to have the best reproducibility. Good agreement across the three software packages and both groups was also observed for circumferential strain calculated from mid-ventricle short axis and longitudinal strain parameters. CVI42 was also compared to the reference tagging analysis by applying both techniques to a healthy and hypertensive patient cohort. Although tagging could discriminate between the two populations (longitudinal strain), no statistically significant differences were found by CVI42. The final validation step was to generate simulation models mimicking simplified cardiac views to compare the experimental results against a true gold-standard for which strain values are known. Two commercial FT software packages were used to analyze the simulated cine images with increasing complexity levels. Both showed inaccurate tracking and high errors compared to analytical values. This indicated that more realistic and complex numerical models should be investigated. Although FT is a relatively new and promising technique, the results demonstrated that it still requires going through standardization to better understand inter-vendor variability.Government of Saudi Arabia

Dynamics of long gas bubbles rising in a vertical tube in a cocurrent liquid flow

© 2019 American Physical Society. When a confined long gas bubble rises in a vertical tube in a cocurrent liquid flow, its translational velocity is the result of both buoyancy and mean motion of the liquid. A thin film of liquid is formed on the tube wall and its thickness is determined by the interplay of viscous, inertial, capillary and buoyancy effects, as defined by the values of the Bond number (Bo≡ρgR2/σ with ρ being the liquid density, g the gravitational acceleration, R the tube radius, and σ the surface tension), capillary number (Cab≡μUb/σ with Ub being the bubble velocity and μ the liquid dynamic viscosity), and Reynolds number (Reb≡2ρUbR/μ). We perform experiments and numerical simulations to investigate systematically the effect of buoyancy (Bo=0-5) on the shape and velocity of the bubble and on the thickness of the liquid film for Cab=10-3-10-1 and Reb=10-2-103. A theoretical model, based on an extension of Bretherton's lubrication theory, is developed and utilized for parametric analyses; its predictions compare well with the experimental and numerical data. This study shows that buoyancy effects on bubbles rising in a cocurrent liquid flow make the liquid film thicker and the bubble rise faster, when compared to the negligible gravity case. In particular, gravitational forces impact considerably the bubble dynamics already when B

Detection of a highly prevalent and potentially virulent strain of Pseudomonas aeruginosa from nosocomial infections in a medical center

BACKGROUND: We correlated genotypes, virulence factors and antimicrobial susceptibility patterns of nosocomially identified Pseudomonas aeruginosa isolates from clinical specimens to those of environmental isolates encountered in the same units of a medical center. Antibiotic susceptibility testing, RAPD analysis and detection of enzymatic activities of extracellular virulence factors, were done on these isolates. RESULTS: Data showed that most of the clinical and environmental isolates were susceptible to tested antimicrobial agents. RAPD analysis determined the presence of 31 genotypes, with genotype 1 detected in 42% of the clinical isolates and 43% of the environmental isolates. Enzymatic activity testing showed that genotype 1 produced all virulence factors tested for. CONCLUSION: In conclusion, our data demonstrated the predominant prevalence of a potentially virulent P. aeruginosa genotype, circulating in a number of units of the medical center and emphasize the need to reinforce infection control measures