Simulating reinforced concrete members. Part 2: displacement-based analyses

A companion paper described the partial-interaction localised properties that require the development of pseudo properties. If the quantification through experimental testing of these pseudo properties could be removed by the use of mechanics-based models, which is the subject of this paper, then this would: (a) substantially reduce the cost of developing new reinforced concrete products by reducing the amount of testing; (b) increase the accuracy of designing existing and novel reinforced concrete members and structures, bearing in mind that experimentally derived pseudo properties are only applicable within the range of the testing from which they were derived; and (c) reduce the cost and increase the accuracy of developing reinforced concrete design rules. This paper deals with the development of pseudo properties and behaviours directly through mechanics, as opposed to experimental testing, and their incorporation into member global simulations. It also addresses the need for a fundamental shift to displacement-based analyses as opposed to strain-based analyses.

CSI 2264: Simultaneous Optical and Infrared Light Curves of Young Disk-bearing Stars in NGC 2264 with CoRoT and Spitzer—Evidence for Multiple Origins of Variability

We present the Coordinated Synoptic Investigation of NGC 2264, a continuous 30 day multi-wavelength photometric monitoring campaign on more than 1000 young cluster members using 16 telescopes. The unprecedented combination of multi-wavelength, high-precision, high-cadence, and long-duration data opens a new window into the time domain behavior of young stellar objects. Here we provide an overview of the observations, focusing on results from Spitzer and CoRoT. The highlight of this work is detailed analysis of 162 classical T Tauri stars for which we can probe optical and mid-infrared flux variations to 1% amplitudes and sub-hour timescales. We present a morphological variability census and then use metrics of periodicity, stochasticity, and symmetry to statistically separate the light curves into seven distinct classes, which we suggest represent different physical processes and geometric effects. We provide distributions of the characteristic timescales and amplitudes and assess the fractional representation within each class. The largest category (>20%) are optical "dippers" with discrete fading events lasting ~1-5 days. The degree of correlation between the optical and infrared light curves is positive but weak; notably, the independently assigned optical and infrared morphology classes tend to be different for the same object. Assessment of flux variation behavior with respect to (circum)stellar properties reveals correlations of variability parameters with Hα emission and with effective temperature. Overall, our results point to multiple origins of young star variability, including circumstellar obscuration events, hot spots on the star and/or disk, accretion bursts, and rapid structural changes in the inner disk. Based on data from the Spitzer and CoRoT missions. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.

Accountability for Forced Displacement in Democratic Republic of Congo and Uganda before the International Criminal Court

This article examines the challenges of investigating and prosecuting forced displacement in the Central African countries of Democratic Republic of Congo and Uganda, where higher loss of life was caused by forced displacement, than by any other. In the Democratic Republic of Congo, armed groups intentionally attacked civilian populations displacing them from their homes, to cut them off from food and medical supplies. In Northern Uganda, the government engaged in a forced displacement policy as part of its counter-insurgency against the Lord’s Resistance Army, driving the civilian population into “protected villages”, where at one point the weekly death toll was over 1,000 in these camps. This article critically evaluates how criminal responsibility can be established for forced displacement and alternative approaches to accountability through reparations.

ALMA Observations of a Gap and a Ring in the Protoplanetary Disk around TW Hya

We report the first detection of a gap and a ring in dust continuum emission from the protoplanetary disk around TW Hya, using the Atacama Large Millimeter/Submillimeter Array. The gap and ring are located at 25 and 41 AU from the central star, respectively, and are associated with the CO snowline at ~ 30AU. The gap width and depth are 15AU at the maximum and 23% at the minimum, respectively, regarding that the observations are limited to an angular resolution of ~ 15AU. In addition, we detect a decrement in CO line emission down to ~ 10AU, indicating freeze-out of gas-phase CO onto grain surfaces and possible subsequent surface reactions to form larger molecules. According to theoretical studies, the gap could be caused by gravitational interaction between the disk gas and a planet with a mass less than super-Neptune (2 Neptune mass), or result from destruction of large dust aggregates due to the sintering of CO ice.

Forced Displacement, Suffering and the Aesthetics of Loss

This article investigates how artists have addressed shocking experiences of displacement in different political contexts. Drawing on the notion of ‘the aesthetics of loss’ (Köstlin, 2010), it examines and compares the different aims, desires and strategies that have shaped the histories and social lives of paintings, memorial statues, installations and other artefacts. The analysis identifies a mode of artistic engagement with the sense of a ‘loss of homeland’ that has been commonly felt amongst Sudeten German expellees, namely the production and framing of visual images as markers of collective trauma. These aesthetics of loss are contrasted with the approach taken by the Dutch artist Sophie Ernst in her project entitled HOME. Working with displaced people from Pakistan, India, Palestine, Israel and Iraq, she created a mnemonic space to stimulate a more individualistic, exploratory engagement with the loss of home, which aimed, in part, to elicit interpersonal empathy. To simply oppose these two modes of aesthetic engagement, however, would ignore the ways in which artefacts are drawn into different discursive, affective and spatial formations. This article argues for the need to expose such dynamic processes of framing and reframing by focusing on the processual aspects of aestheticisation with attention to the perspective of loss.

First Detection of Gas-phase Methanol in a Protoplanetary Disk

The first detection of gas-phase methanol in a protoplanetary disk (TW Hya) is presented. In addition to being one of the largest molecules detected in disks to date, methanol is also the first disk organic molecule with an unambiguous ice chemistry origin. The stacked methanol emission, as observed with the Atacama Large Millimeter/submillimeter Array, is spectrally resolved and detected across six velocity channels (>3σ), reaching a peak signal-to-noise of 5.5σ, with the kinematic pattern expected for TW Hya. Using an appropriate disk model, a fractional abundance of 3 x 10^-12 – 4 x 10^-11 (with respect to H₂) reproduces the stacked line profile and channel maps, with the favored abundance dependent upon the assumed vertical location (midplane versus molecular layer). The peak emission is offset from the source position, suggesting that the methanol emission has a ring-like morphology: the analysis here suggests it peaks at ≈30 au, reaching a column density ≈3–6 x 10¹² cm⁻². In the case of TW Hya, the larger (up to millimeter-sized) grains, residing in the inner 50 au, may thus host the bulk of the disk ice reservoir. The successful detection of cold gas-phase methanol in a protoplanetary disk implies that the products of ice chemistry can be explored in disks, opening a window into studying complex organic chemistry during planetary system formation.

Fiber optic sensors for the biomechanical study of the intervertebral disc

O presente trabalho teve como objetivo principal estudar o comportamento mecânico do disco intervertebral recorrendo a sensores em fibra ótica. Na expetativa de efetuar o melhor enquadramento do tema foi efetuada uma revisão exaustiva das várias configurações de sensores em fibra ótica que têm vindo a ser utilizadas em aplicações biomédicas e biomecânicas, nomeadamente para medição de temperatura, deformação, força e pressão. Nesse âmbito, procurou-se destacar as potencialidades dos sensores em fibra ótica e apresentá-los como uma tecnologia alternativa ou até de substituição das tecnologias associadas a sensores convencionais. Tendo em vista a aplicação de sensores em fibra ótica no estudo do comportamento do disco intervertebral efetuou-se também uma revisão exaustiva da coluna vertebral e, particularmente, do conceito de unidade funcional. A par de uma descrição anatómica e funcional centrada no disco intervertebral, vértebras adjacentes e ligamentos espinais foram ainda destacadas as suas propriedades mecânicas e descritos os procedimentos mais usuais no estudo dessas propriedades. A componente experimental do presente trabalho descreve um conjunto de experiências efetuadas com unidades funcionais cadavéricas utilizando sensores convencionais e sensores em fibra ótica com vista à medição da deformação do disco intervertebral sob cargas compressivas uniaxiais. Inclui ainda a medição in vivo da pressão intradiscal num disco lombar de uma ovelha sob efeito de anestesia. Para esse efeito utilizou-se um sensor comercial em fibra ótica e desenvolveu-se a respetiva unidade de interrogação. Finalmente apresenta-se os resultados da investigação em curso que tem como objetivo propor e desenvolver protótipos de sensores em fibra ótica para aplicações biomédicas e biomecânicas. Nesse sentido, são apresentadas duas soluções de sensores interferométricos para medição da pressão em fluídos corporais.

HIV positive men as fathers: Accounts of displacement, ir/responsibility and paternal emergence

It is now apparent that socio-cultural constructions of masculinity variously impact men’s experiences of their HIV positive status, yet how being a father can feature in this mix remains under-researched. This study employed in-depth semi-structured interviews and Foucauldian-informed discourse analysis to explore the accounts of six self-identifying heterosexual fathers (four black African migrants, two white European) who had been living with HIV from five to 24 years. While the HIV-related literature calls for the need to subvert ‘traditional’ expressions of masculinity as a means of promoting HIV prevention and HIV health, we argue that the lived experience for HIV positive men as fathers is more socially, discursively and thus more psychologically nuanced. We illustrate this by highlighting ways in which HIV positive men as fathers are not simply making sense of themselves as a HIV positive man for whom the modern (new) man and father positions are useful strategies for adapting to HIV and combating associated stigma. Discourses of modern and patriarchal fatherhoods, a gender-specific discourse of irresponsibility, and the neoliberal conflation of heath and self-responsibility are also at work in the sense making frames that HIV positive men, who are also fathers, can variously deploy. Our analysis shows how this discursive mix can underpin possibilities of often conflicted meaning and identity when living as a man and father with HIV in the UK, and specifically how discourses of fatherhood and HIV ‘positive’ health can complicate these men’s expressions and inhabitations of masculinity.

Octopus Standard Automated Perimetry, Pulsar Perimetry, Moorfields Motion Displacement Test and Heidelberg Retinal Tomography in Glaucoma Detection - A Comparison of Diagnostic Accuracy

Purpose: To investigate the accuracy of 4 clinical instruments in the detection of glaucomatous damage. Methods: 102 eyes of 55 test subjects (Age mean = 66.5yrs, range = [39; 89]) underwent Heidelberg Retinal Tomography (HRTIII), (disc area<2.43); and standard automated perimetry (SAP) using Octopus (Dynamic); Pulsar (TOP); and Moorfields Motion Displacement Test (MDT) (ESTA strategy). Eyes were separated into three groups 1) Healthy (H): IOP<21mmHg and healthy discs (clinical examination), 39 subjects, 78 eyes; 2) Glaucoma suspect (GS): Suspicious discs (clinical examination), 12 subjects, 15 eyes; 3) Glaucoma (G): progressive structural or functional loss, 14 subjects, 20 eyes. Clinical diagnostic precision was examined using the cut-off associated with the p<5% normative limit of MD (Octopus/Pulsar), PTD (MDT) and MRA (HRT) analysis. The sensitivity, specificity and accuracy were calculated for each instrument. Results: See table Conclusions: Despite the advantage of defining glaucoma suspects using clinical optic disc examination, the HRT did not yield significantly higher accuracy than functional measures. HRT, MDT and Octopus SAP yielded higher accuracy than Pulsar perimetry, although results did not reach statistical significance. Further studies are required to investigate the structure-function correlations between these instruments.

Determination of displacement, stress- and strain-distribution in the human heart: a FE-model on the basis of MR imaging.

The determination of characteristic cardiac parameters, such as displacement, stress and strain distribution are essential for an understanding of the mechanics of the heart. The calculation of these parameters has been limited until recently by the use of idealised mathematical representations of biventricular geometries and by applying simple material laws. On the basis of 20 short axis heart slices and in consideration of linear and nonlinear material behaviour we have developed a FE model with about 100,000 degrees of freedom. Marching Cubes and Phong's incremental shading technique were used to visualise the three dimensional geometry. In a quasistatic FE analysis continuous distribution of regional stress and strain corresponding to the endsystolic state were calculated. Substantial regional variation of the Von Mises stress and the total strain energy were observed at all levels of the heart model. The results of both the linear elastic model and the model with a nonlinear material description (Mooney-Rivlin) were compared. While the stress distribution and peak stress values were found to be comparable, the displacement vectors obtained with the nonlinear model were generally higher in comparison with the linear elastic case indicating the need to include nonlinear effects.

A treatment of atomic mean square displacement in higher order perturbation theory

A general derivation of the anharmonic coefficients for a periodic lattice invoking the special case of the central force interaction is presented. All of the contributions to mean square displacement (MSD) to order 14 perturbation theory are enumerated. A direct correspondance is found between the high temperature limit MSD and high temperature limit free energy contributions up to and including 0(14). This correspondance follows from the detailed derivation of some of the contributions to MSD. Numerical results are obtained for all the MSD contributions to 0(14) using the Lennard-Jones potential for the lattice constants and temperatures for which the Monte Carlo results were calculated by Heiser, Shukla and Cowley. The Peierls approximation is also employed in order to simplify the numerical evaluation of the MSD contributions. The numerical results indicate the convergence of the perturbation expansion up to 75% of the melting temperature of the solid (TM) for the exact calculation; however, a better agreement with the Monte Carlo results is not obtained when the total of all 14 contributions is added to the 12 perturbation theory results. Using Peierls approximation the expansion converges up to 45% of TM• The MSD contributions arising in the Green's function method of Shukla and Hubschle are derived and enumerated up to and including 0(18). The total MSD from these selected contributions is in excellent agreement with their results at all temperatures. Theoretical values of the recoilless fraction for krypton are calculated from the MSD contributions for both the Lennard-Jones and Aziz potentials. The agreement with experimental values is quite good.

Molecular dynamics calculation of mean square displacement in alkali metals and rare gas solids and comparison with lattice dynamics

Molec ul ar dynamics calculations of the mean sq ua re displacement have been carried out for the alkali metals Na, K and Cs and for an fcc nearest neighbour Lennard-Jones model applicable to rare gas solids. The computations for the alkalis were done for several temperatures for temperature vol ume a swell as for the the ze r 0 pressure ze ro zero pressure volume corresponding to each temperature. In the fcc case, results were obtained for a wide range of both the temperature and density. Lattice dynamics calculations of the harmonic and the lowe s t order anharmonic (cubic and quartic) contributions to the mean square displacement were performed for the same potential models as in the molecular dynamics calculations. The Brillouin zone sums arising in the harmonic and the quartic terms were computed for very large numbers of points in q-space, and were extrapolated to obtain results ful converged with respect to the number of points in the Brillouin zone.An excellent agreement between the lattice dynamics results was observed molecular dynamics and in the case of all the alkali metals, e~ept for the zero pressure case of CSt where the difference is about 15 % near the melting temperature. It was concluded that for the alkalis, the lowest order perturbation theory works well even at temperat ures close to the melting temperat ure. For the fcc nearest neighbour model it was found that the number of particles (256) used for the molecular dynamics calculations, produces a result which is somewhere between 10 and 20 % smaller than the value converged with respect to the number of particles. However, the general temperature dependence of the mean square displacement is the same in molecular dynamics and lattice dynamics for all temperatures at the highest densities examined, while at higher volumes and high temperatures the results diverge. This indicates the importance of the higher order (eg. ~* ) perturbation theory contributions in these cases.

On the equation of state and atomic mean square displacement of crystals

We have presented a Green's function method for the calculation of the atomic mean square displacement (MSD) for an anharmonic Hamil toni an . This method effectively sums a whole class of anharmonic contributions to MSD in the perturbation expansion in the high temperature limit. Using this formalism we have calculated the MSD for a nearest neighbour fcc Lennard Jones solid. The results show an improvement over the lowest order perturbation theory results, the difference with Monte Carlo calculations at temperatures close to melting is reduced from 11% to 3%. We also calculated the MSD for the Alkali metals Nat K/ Cs where a sixth neighbour interaction potential derived from the pseudopotential theory was employed in the calculations. The MSD by this method increases by 2.5% to 3.5% over the respective perturbation theory results. The MSD was calculated for Aluminum where different pseudopotential functions and a phenomenological Morse potential were used. The results show that the pseudopotentials provide better agreement with experimental data than the Morse potential. An excellent agreement with experiment over the whole temperature range is achieved with the Harrison modified point-ion pseudopotential with Hubbard-Sham screening function. We have calculated the thermodynamic properties of solid Kr by minimizing the total energy consisting of static and vibrational components, employing different schemes: The quasiharmonic theory (QH), ).2 and).4 perturbation theory, all terms up to 0 ().4) of the improved self consistent phonon theory (ISC), the ring diagrams up to o ().4) (RING), the iteration scheme (ITER) derived from the Greens's function method and a scheme consisting of ITER plus the remaining contributions of 0 ().4) which are not included in ITER which we call E(FULL). We have calculated the lattice constant, the volume expansion, the isothermal and adiabatic bulk modulus, the specific heat at constant volume and at constant pressure, and the Gruneisen parameter from two different potential functions: Lennard-Jones and Aziz. The Aziz potential gives generally a better agreement with experimental data than the LJ potential for the QH, ).2, ).4 and E(FULL) schemes. When only a partial sum of the).4 diagrams is used in the calculations (e.g. RING and ISC) the LJ results are in better agreement with experiment. The iteration scheme brings a definitive improvement over the).2 PT for both potentials.