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https://www.readbyqxmd.com/read/28108037/a-semi-analytical-method-for-simulating-matrix-diffusion-in-numerical-transport-models
#1
Ronald W Falta, Wenwen Wang
A semi-analytical approximation for transient matrix diffusion is developed for use in numerical contaminant transport simulators. This method is an adaptation and extension of the heat conduction method of Vinsome and Westerveld (1980) used to simulate heat losses during thermally enhanced oil recovery. The semi-analytical method is used in place of discretization of the low permeability materials, and it represents the concentration profile in the low permeability materials with a fitting function that is adjusted in each element at each time-step...
January 11, 2017: Journal of Contaminant Hydrology
https://www.readbyqxmd.com/read/28106156/tunable-multifunctional-thermal-metamaterials-manipulation-of-local-heat-flux-via-assembly-of-unit-cell-thermal-shifters
#2
Gwanwoo Park, Sunggu Kang, Howon Lee, Wonjoon Choi
Thermal metamaterials, designed by transformation thermodynamics are artificial structures that can actively control heat flux at a continuum scale. However, fabrication of them is very challenging because it requires a continuous change of thermal properties in materials, for one specific function. Herein, we introduce tunable thermal metamaterials that use the assembly of unit-cell thermal shifters for a remarkable enhancement in multifunctionality as well as manufacturability. Similar to the digitization of a two-dimensional image, designed thermal metamaterials by transformation thermodynamics are disassembled as unit-cells thermal shifters in tiny areas, representing discretized heat flux lines in local spots...
January 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28098559/lattice-boltzmann-simulations-of-the-bead-spring-microswimmer-with-a-responsive-stroke-from-an-individual-to-swarms
#3
Kristina Pickl, Jayant Pande, Harald Köstler, Ulrich Rüde, Ana-Suncana Smith
Propulsion at low Reynolds numbers is often studied by defining artificial microswimmers which exhibit a particular stroke. The disadvantage of such an approach is that the stroke does not adjust to the environment, in particular the fluid flow, which can diminish the effect of hydrodynamic interactions. To overcome this limitation, we simulate a microswimmer consisting of three beads connected by springs and dampers, using the self-developed waLBerla and <i>pe</i> framework based on the lattice Boltzmann method and the discrete element method...
January 18, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28068948/women-s-preferences-for-childbirth-experiences-in-the-republic-of-ireland-a-mixed-methods-study
#4
Patricia Larkin, Cecily M Begley, Declan Devane
BACKGROUND: How women experience childbirth is acknowledged as critical to the postnatal wellbeing of mother and baby. However there is a knowledge deficit in identifying the important elements of these experiences in order to enhance care. This study elicits women's preferences for the most important elements of their childbirth experiences. METHODS: A mixed methods design was used. An initial qualitative phase (reported previously) was followed by a second quantitative one using a discrete choice experiment (DCE), which is reported on here...
January 10, 2017: BMC Pregnancy and Childbirth
https://www.readbyqxmd.com/read/28048443/su-g-201-06-directional-low-dose-rate-brachytherapy-determination-of-the-tg-43-dose-rate-constant-analog-for-a-new-pd-103-source
#5
M Aima, W Culberson, C Hammer, J Micka, L DeWerd
PURPOSE: The aim of this work is to determine the TG-43 dose-rate constant analog for a new directional low-dose rate brachytherapy source based on experimental methods and comparison to Monte Carlo simulations. The CivaSheet™ is a new commercially available planar source array comprised of a variable number of discrete directional source elements called "CivaDots". Given the directional nature and non-conventional design of the source, modifications to the AAPM TG-43 protocol for dosimetry are required...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047701/th-ab-bra-09-stability-analysis-of-a-novel-dose-calculation-algorithm-for-mri-guided-radiotherapy
#6
O Zelyak, B Fallone, J St Aubin
PURPOSE: To determine the iterative deterministic solution stability of the Linear Boltzmann Transport Equation (LBTE) in the presence of magnetic fields. METHODS: The LBTE with magnetic fields under investigation is derived using a discrete ordinates approach. The stability analysis is performed using analytical and numerical methods. Analytically, the spectral Fourier analysis is used to obtain the convergence rate of the source iteration procedures based on finding the largest eigenvalue of the iterative operator...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047410/tu-ab-brc-01-spherical-harmonic-based-finite-element-method-shfem-a-new-angular-discretization-of-linear-boltzmann-transport-equation-for-accurate-dose-calculation
#7
X Hong, G Chen, H Gao
PURPOSE: As a deterministic method for dose calculation, the linear Boltzmann transport equation (LBTE) can reach the same accuracy as the Monte Carlo method (MC). In terms of speed, LBTE can be significantly accelerated through various state-of-art numerical techniques. The angular discretization is crucial since the accuracy of LBTE highly depends on it and the computational time of LBTE is quadratic with respect to number of discretized angles. This work proposes a new angular discretization scheme that synergizes spherical harmonics method and finite element method...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046743/su-f-t-111-investigation-of-the-attila-deterministic-solver-as-a-supplement-to-monte-carlo-for-calculating-out-of-field-radiotherapy-dose
#8
M Mille, C Lee, G Failla
PURPOSE: To use the Attila deterministic solver as a supplement to Monte Carlo for calculating out-of-field organ dose in support of epidemiological studies looking at the risks of second cancers. Supplemental dosimetry tools are needed to speed up dose calculations for studies involving large-scale patient cohorts. METHODS: Attila is a multi-group discrete ordinates code which can solve the 3D photon-electron coupled linear Boltzmann radiation transport equation on a finite-element mesh...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046330/su-g-tep1-15-toward-a-novel-gpu-accelerated-deterministic-solution-to-the-linear-boltzmann-transport-equation
#9
R Yang, B Fallone, J St Aubin
PURPOSE: To develop a Graphic Processor Unit (GPU) accelerated deterministic solution to the Linear Boltzmann Transport Equation (LBTE) for accurate dose calculations in radiotherapy (RT). A deterministic solution yields the potential for major speed improvements due to the sparse matrix-vector and vector-vector multiplications and would thus be of benefit to RT. METHODS: In order to leverage the massively parallel architecture of GPUs, the first order LBTE was reformulated as a second order self-adjoint equation using the Least Squares Finite Element Method (LSFEM)...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28040003/solving-transient-acoustic-boundary-value-problems-with-equivalent-sources-using-a-lumped-parameter-approach
#10
John B Fahnline
An equivalent source method is developed for solving transient acoustic boundary value problems. The method assumes the boundary surface is discretized in terms of triangular or quadrilateral elements and that the solution is represented using the acoustic fields of discrete sources placed at the element centers. Also, the boundary condition is assumed to be specified for the normal component of the surface velocity as a function of time, and the source amplitudes are determined to match the known elemental volume velocity vector at a series of discrete time steps...
December 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28018540/development-of-a-comprehensive-communication-skills-curriculum-for-pediatrics-residents
#11
Eleanor B Peterson, Kimberly A Boland, Kristina A Bryant, Tara F McKinley, Melissa B Porter, Katherine E Potter, Aaron W Calhoun
BACKGROUND : Effective communication is an essential element of medical care and a priority of medical education. Specific interventions to teach communication skills are at the discretion of individual residency programs. OBJECTIVE : We developed the Resident Communication Skills Curriculum (RCSC), a formal curriculum designed to teach trainees the communication skills essential for high-quality practice. METHODS : A multidisciplinary working group contributed to the development of the RCSC, guided by an institutional needs assessment, literature review, and the Accreditation Council for Graduate Medical Education core competencies...
December 2016: Journal of Graduate Medical Education
https://www.readbyqxmd.com/read/27992333/continuous-subresolution-displacements-in-finite-difference-simulations-of-ultrasound-propagation-and-imaging
#12
Gianmarco Pinton
Time domain finite difference simulations are used extensively to simulate wave propagation. They approximate the wave field on a discrete domain with a grid spacing that is typically on the order of a tenth of a wavelength. The smallest displacements that can be modeled by this type of simulation are thus limited to discrete values that are integer multiples of the grid spacing. This paper presents a method to represent continuous and subresolution displacements by varying the impedance of individual elements in a multi-element scatterer...
December 12, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27986476/micro-feeding-and-dosing-of-powders-via-a-small-scale-powder-pump
#13
M O Besenhard, S Fathollahi, E Siegmann, E Slama, E Faulhammer, J G Khinast
Robust and accurate powder micro-feeding (<100mg/s) and micro-dosing (<5mg) are major challenges, especially with regard to regulatory limitations applicable to pharmaceutical development and production. Since known micro-feeders that yield feed rates below 5mg/s use gravimetric feeding principles, feed rates depend primarily on powder properties. In contrast, volumetric powder feeders do not require regular calibration because their feed rates are primarily determined by the feeder's characteristic volume replacement...
December 13, 2016: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/27967124/localized-fluidization-in-granular-materials-theoretical-and-numerical-study
#14
E P Montellà, M Toraldo, B Chareyre, L Sibille
We present analytical and numerical results on localized fluidization within a granular layer subjected to a local injection of fluid. As the injection rate increases the three different regimes previously reported in the literature are recovered: homogeneous expansion of the bed, fluidized cavity in which fluidization starts developing above the injection area, and finally the chimney of fluidized grains when the fluidization zone reaches the free surface. The analytical approach is at the continuum scale, based on Darcy's law and Therzaghi's effective stress principle...
November 2016: Physical Review. E
https://www.readbyqxmd.com/read/27915232/quantitative-profiling-of-selective-sox-pou-pairing-on-hundreds-of-sequences-in-parallel-by-coop-seq
#15
Yiming K Chang, Yogesh Srivastava, Caizhen Hu, Adam Joyce, Xiaoxiao Yang, Zheng Zuo, James J Havranek, Gary D Stormo, Ralf Jauch
Cooperative binding of transcription factors is known to be important in the regulation of gene expression programs conferring cellular identities. However, current methods to measure cooperativity parameters have been laborious and therefore limited to studying only a few sequence variants at a time. We developed Coop-seq (cooperativity by sequencing) that is capable of efficiently and accurately determining the cooperativity parameters for hundreds of different DNA sequences in a single experiment. We apply Coop-seq to 12 dimer pairs from the Sox and POU families of transcription factors using 324 unique sequences with changed half-site orientation, altered spacing and discrete randomization within the binding elements...
December 2, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/27882468/discrete-element-modelling-of-sediment-falling-in-water
#16
Dong Wang, Dao Ho-Minh, Danielle S Tan
The Discrete Element Method (DEM) is a discrete, particle-based method commonly used in studies involving granular media, e.g. sediment transport, and geomechanics. It is heavily dependent on particle properties, and one important component is the force model, which relates the relative positions and velocities of the simulated particles to the forces they experience. In this paper we model a collection of lightly compacted granular material, released at a short distance above a flat base in a quiescent fluid --similar to the process whereby sediment tailings are released back into the sea during nodule harvesting...
November 2016: European Physical Journal. E, Soft Matter
https://www.readbyqxmd.com/read/27865921/community-detection-in-weighted-brain-connectivity-networks-beyond-the-resolution-limit
#17
Carlo Nicolini, Cécile Bordier, Angelo Bifone
Graph theory provides a powerful framework to investigate brain functional connectivity networks and their modular organization. However, most graph-based methods suffer from a fundamental resolution limit that may have affected previous studies and prevented detection of modules, or "communities", that are smaller than a specific scale. Surprise, a resolution-limit-free function rooted in discrete probability theory, has been recently introduced and applied to brain networks, revealing a wide size-distribution of functional modules (Nicolini and Bifone, 2016), in contrast with many previous reports...
November 16, 2016: NeuroImage
https://www.readbyqxmd.com/read/27855228/the-devil-is-in-the-details-incomplete-reporting-in-preclinical-animal-research
#18
Marc T Avey, David Moher, Katrina J Sullivan, Dean Fergusson, Gilly Griffin, Jeremy M Grimshaw, Brian Hutton, Manoj M Lalu, Malcolm Macleod, John Marshall, Shirley H J Mei, Michael Rudnicki, Duncan J Stewart, Alexis F Turgeon, Lauralyn McIntyre
Incomplete reporting of study methods and results has become a focal point for failures in the reproducibility and translation of findings from preclinical research. Here we demonstrate that incomplete reporting of preclinical research is not limited to a few elements of research design, but rather is a broader problem that extends to the reporting of the methods and results. We evaluated 47 preclinical research studies from a systematic review of acute lung injury that use mesenchymal stem cells (MSCs) as a treatment...
2016: PloS One
https://www.readbyqxmd.com/read/27853896/discrete-mesh-approach-in-morphogenesis-modelling-the-example-of-gastrulation
#19
J Demongeot, A Lontos, E Promayon
Morphogenesis is a general concept in biology including all the processes which generate tissue shapes and cellular organizations in a living organism. Many hybrid formalizations (i.e., with both discrete and continuous parts) have been proposed for modelling morphogenesis in embryonic or adult animals, like gastrulation. We propose first to study the ventral furrow invagination as the initial step of gastrulation, early stage of embryogenesis. We focus on the study of the connection between the apical constriction of the ventral cells and the initiation of the invagination...
December 2016: Acta Biotheoretica
https://www.readbyqxmd.com/read/27845929/electroencephalography-eeg-forward-modeling-via-h-div-finite-element-sources-with-focal-interpolation
#20
S Pursiainen, J Vorwerk, C H Wolters
The goal of this study is to develop focal, accurate and robust finite element method (FEM) based approaches which can predict the electric potential on the surface of the computational domain given its structure and internal primary source current distribution. While conducting an EEG evaluation, the placement of source currents to the geometrically complex grey matter compartment is a challenging but necessary task to avoid forward errors attributable to tissue conductivity jumps. Here, this task is approached via a mathematically rigorous formulation, in which the current field is modeled via divergence conforming H(div) basis functions...
December 21, 2016: Physics in Medicine and Biology
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