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Diffusion Models

C Li, Y N Wang, M Wang, Y Peng, J T Wu, X F Luo
Objective: To evaluate the feasibility of diffusion parameters obtained from mono-exponential and stretched exponential diffusion-weighted imaging models in staging of nonalcoholic fatty liver disease and compare the diagnosis ability of nonalcoholic steatohepatitis. Methods: Thirty-two 12 -week-old male New Zealand rabbits, about 2.5 kg of each, were randomly divided into five groups. To obtained different severity groups of NAFLD, a variety of diet (from standard to high-fat, high cholesterol chow) were feed for different periods before liver diffusion imaging was performed by using 3...
February 19, 2019: Zhonghua Yi Xue za Zhi [Chinese medical journal]
Alison N Leonard, Eric Wang, Viviana Monje-Galvan, Jeffery B Klauda
The amphipathic nature of the lipid molecule (hydrophilic head and hydrophobic tails) enables it to act as a barrier between fluids with various properties and to sustain an environment where the processes critical to life may proceed. While computer simulations of biomolecules primarily investigate protein conformation and binding to drug-like molecules, these interactions often occur in the context of a lipid membrane. Chemical specificity of lipid models is essential to accurately represent the complex environment of the lipid membrane...
February 20, 2019: Chemical Reviews
Christopher D Williams, Paola Carbone, Flor R Siperstein
Graphene oxide (GO) membranes offer exceptional promise for certain aqueous separation challenges, such as desalination. Central to unlocking this promise and optimising performance for a given separation is the establishment of a detailed molecular-level understanding of how the membrane's composition affects its structural and transport properties. This understanding is currently lacking, in part due to the fact that, until recently, molecular models with a realistic distribution of oxygen-functionalities and interlayer flake structure were unavailable...
February 20, 2019: ACS Nano
D Merrill Dane, Cuneyt Yilmaz, Dipendra Gyawali, Roshni Iyer, Jyothi U Menon, Kytai T Nguyen, Priya Ravikumar, Aaron S Estrera, Connie C W Hsia
Paracrine erythropoietin (EPO) signaling in the lung recruits endothelial progenitor cells, promotes cell maturation and angiogenesis , and is upregulated during canine post-pneumonectomy (PNX) compensatory lung growth. To determine whether inhalational delivery of exogenous EPO augments endogenous post-PNX lung growth, adult canines underwent right PNX and received, via a permanent tracheal stoma, weekly nebulization of recombinant human EPO-containing nanoparticles or empty nanoparticles (control) for 16 weeks...
February 20, 2019: American Journal of Physiology. Lung Cellular and Molecular Physiology
Can Wu, Yunyun Xu, Si Xu, Jingwei Tu, Chen Tian, Zhang Lin
In this work, zinc ferrite spinel with different zinc contents (Znx Fe3-x O4 ) was synthesized by a hydrothermal method and used for removing As(V) in aqueous solution. X-ray diffraction (XRD) results indicated that in the crystal structure of Znx Fe3-x O4 , the zinc atoms tended to occupy the octahedral sites for x < 0.6 and diffused into the tetrahedral sites gradually with x > 0.6. The size of Znx Fe3-x O4 crystallites increased with the increasing zinc content. Batch adsorption experiments showed that the adsorption isotherms could be well described by the Langmuir model, while the adsorption kinetics followed the pseudo-second-order kinetic model...
May 2019: Journal of Environmental Sciences (China)
Tania Deis, Louise Balling, Kasper Rossing, Emil Wolsk, Michael Perch, Finn Gustafsson
AIMS: Patients with heart failure (HF) are known to have a reduced pulmonary diffusion capacity for carbon monoxide (DLCO ), but little is known about how lung function relates to central haemodynamics. The aim of this study was to investigate the association between haemodynamic variables and pulmonary diffusion capacity adjusted for alveolar volume in congestive HF patients and to analyse how predicted DLCO /VA affects mortality in relation to the haemodynamic status. METHODS AND RESULTS: We retrospectively studied right heart catheterization (RHC) and lung function data on 262 HF patients (mean age 51 ± 13 years) with a left ventricular ejection fraction < 45% referred non-urgently for evaluation for heart transplantation (HTX) or left ventricular assist device (LVAD)...
February 19, 2019: ESC Heart Failure
Gabriel Maciel, Chris Cosner, Robert Stephen Cantrell, Frithjof Lutscher
Many types of organisms disperse through heterogeneous environments as part of their life histories. For various models of dispersal, including reaction-advection-diffusion models in continuously varying environments, it has been shown by pairwise invasibility analysis that dispersal strategies which generate an ideal free distribution are evolutionarily steady strategies (ESS, also known as evolutionarily stable strategies) and are neighborhood invader strategies (NIS). That is, populations using such strategies can both invade and resist invasion by populations using strategies that do not produce an ideal free distribution...
February 19, 2019: Journal of Mathematical Biology
Taihei Fujimori, Akihiko Nakajima, Nao Shimada, Satoshi Sawai
Despite their central role in multicellular organization, navigation rules that dictate cell rearrangement remain largely undefined. Contact between neighboring cells and diffusive attractant molecules are two of the major determinants of tissue-level patterning; however, in most cases, molecular and developmental complexity hinders one from decoding the exact governing rules of individual cell movement. A primordial example of tissue patterning by cell rearrangement is found in the social amoeba Dictyostelium discoideum where the organizing center or the "tip" self-organizes as a result of sorting of differentiating prestalk and prespore cells...
February 19, 2019: Proceedings of the National Academy of Sciences of the United States of America
Wang-Sheng Chen, Lan Hong, Fei Wang, Jian-Jun Li
BACKGROUND: Glioma is one of the most epidemic and obstinate types of cancer in the central nervous system with poor survival rate. Dacomitinib inhibited cell viability and proliferation of  EGFR -amplified glioma. In the present study, the regional effects of Dacomitinib on tumor necrosis was investigated. METHODS: A C6 rat glioma model was evaluated using proton magnetic resonance spectroscopy (1H-MRS), diffusion weighted imaging (DWI), morphological T2-weighted imaging (T2W)...
February 19, 2019: Bioscience Reports
Michael D N Stolle, Cécile Fradin
Using fluorescence correlation spectroscopy (FCS) to distinguish between different types of diffusion processes is often a perilous undertaking because the analysis of the resulting autocorrelation data is model dependant. Two recently introduced strategies, however, can help move toward a model-independent interpretation of FCS experiments: 1) the obtention of correlation data at different length scales and 2) their inversion to retrieve the mean-squared displacement associated with the process under study...
January 30, 2019: Biophysical Journal
José F Costa, Paula Bompastor-Ramos, Marco Marques, Jorge Henriques, João Póvoa, Conceição Lobo, Jorge L Alió, Liliana Werner, Joaquim Murta
PURPOSE: To determine the prevalence and risk factors related to the opacification of the LS-502-1 intraocular lens. METHODS: Cross-sectional study including patients submitted to cataract surgery between January 2010 and March 2012, with implantation of the LS-502-1 intraocular lens. Past medical history was registered and a complete ophthalmologic evaluation, that included best-corrected visual acuity, slit-lamp examination and fundoscopy, was performed. Anterior segment photographs were taken whenever intraocular lens opacification was present...
February 19, 2019: European Journal of Ophthalmology
Leonardo Campiotti, Diego De Palma, Luigina Guasti, Ilaria Proserpio, Sabrina Casagrande, Ilaria Schiorlin, Elena Bolzacchini, Matteo Suter, Francesca Ogliari, Alessandro Squizzato
BACKGROUND: International guidelines support performing baseline positron emission tomography (PET) in lymphoma. Metabolic tumor volume (MTV) measurement has been proposed as a good measurement of disease burden. We investigated if MTV at baseline PET can be predictive of complete response (CR) to first line standard chemotherapy in diffuse large B-cell lymphoma (DLBCL) and in follicular lymphoma (FL) grade 3b. METHODS: We retrospectively analyzed data on54 consecutive patients with DLBCL and FL grade 3b treated in our institution...
February 14, 2019: Quarterly Journal of Nuclear Medicine and Molecular Imaging
Afiq Izzudin A Rahim, Mohd Ismail Ibrahim, Faizul Nizam A Salim, Mohd Ariff Ikram Ariffin
Health organizations have widely adopted social media for health promotion, public health communication conveyance, and organizational promotion activities. However, little published data exists on the factors that facilitate health information diffusion in South East Asia, especially Malaysia compared with Western countries. This study aimed to investigate factors associated with good engagement rates among internet users on the Facebook (FB) page of Ministry of Health Malaysia. In this observational study, 2123 FB posts were randomly selected...
February 18, 2019: International Journal of Environmental Research and Public Health
Yajian Wang, Yuyou Yang, Mingjiang Tao
Understanding the underlying processes associated with the viscoelasticity performance of ethylene-propylene-diene monomer (EPDM) during its service life is essential for assessing and predicting its waterproofing performance in underground infrastructure. The viscoelasticity of the polymer is closely related to its free volume, and both of these properties depend on multiple factors, such as temperature, stress magnitude, and strain level. To explore the fundamental viscoelastic behavior of EPDM using free volume as a proxy for viscoelasticity, this article investigates the influence of temperature, stress magnitude, and strain level, as well as their combined effect, on the free volume through molecular dynamics (MD) simulations...
February 18, 2019: Materials
Xiao Xing, Jiayu Zhou, Shouxin Zhang, Hao Zhang, Zili Li, Zhenjun Li
The effects of temperature on bulk hydrogen concentration and diffusion have been tested with the Devanathan⁻-Stachurski method. Thus, a model based on hydrogen potential, diffusivity, loading frequency, and hydrostatic stress distribution around crack tips was applied in order to quantify the temperature's effect. The theoretical model was verified experimentally and confirmed a temperature threshold of 320 K to maximize the crack growth. The model suggests a nanoscale embrittlement mechanism, which is generated by hydrogen atom delivery to the crack tip under fatigue loading, and rationalized the Δ K dependence of traditional models...
February 15, 2019: Materials
Fabrizio Croccolo, Loreto García-Fernández, Henri Bataller, Alberto Vailati, José María Ortiz de Zárate
Nonequilibrium temperature and concentration fluctuations inside a binary liquid mixture under the action of a temperature gradient relax back to equilibrium either due to conduction and diffusion at large wave numbers, or due to the quenching determined by gravity at small wave numbers. We investigate the dynamics of nonequilibrium fluctuations in a binary liquid mixture of polystyrene and toluene heated from above under stationary conditions in a thermodiffusion experiment. We show that the strong gravitational stabilization at small wave numbers determines the appearance of propagating modes of nonequilibrium fluctuations as detected through the structure function of shadowgraph images...
January 2019: Physical Review. E
Romain Bachelard, Nicola Piovella, Shamik Gupta
Inspired by one-dimensional light-particle systems, the dynamics of a non-Hamiltonian system with long-range forces is investigated. While the molecular dynamics does not reach an equilibrium state, it may be approximated in the thermodynamic limit by a Vlasov equation that does possess stable stationary solutions. This implies that on a macroscopic scale the molecular dynamics evolves on a slow timescale that diverges with the system size. At the single-particle level, the evolution is driven by incoherent interaction between the particles, which may be effectively modeled by a noise, leading to a Brownian-like dynamics of the momentum...
January 2019: Physical Review. E
Davide Vergni, Stefano Berti, Angelo Vulpiani, Massimo Cencini
Standard reaction-diffusion systems are characterized by infinite velocities and no persistence in the movement of individuals, two conditions that are violated when considering living organisms. Here we consider a discrete particle model in which individuals move following a persistent random walk with finite speed and grow with logistic dynamics. We show that, when the number of individuals is very large, the individual-based model is well described by the continuous reactive Cattaneo equation (RCE), but for smaller values of the carrying capacity important finite-population effects arise...
January 2019: Physical Review. E
R Salgado-García
We consider the motion of overdamped particles over random potentials subjected to a Gaussian white noise and a time-dependent periodic external forcing. The random potential is modeled as the potential resulting from the interaction of a point particle with a random polymer. The random polymer is made up, by means of some stochastic process, from a finite set of possible monomer types. The process is assumed to reach a nonequilibrium stationary state, which means that every realization of a random polymer can be considered as an out-of-equilibrium structure...
January 2019: Physical Review. E
Daniele Colognesi, Ubaldo Bafile, Milva Celli, Martin Neumann, Eleonora Guarini, Manh Duc Le
We have measured the dynamic structure factor of liquid neon-hydrogen mixtures (T=30.1 K) at two different H_{2} concentration levels (namely, 3.4% and 10%) making use of inelastic neutron scattering. This system has been selected since the presence of heavy Ne atoms strongly influences the self-dynamics of the H_{2} centers of mass via the formation of short-lived cages, which act both on the vibrational and the diffusive parts of the single-particle motion. After operating a standard data reduction and the subtraction of the Ne signal, experimental neutron spectra were analyzed through a generalization of the Young and Koppel model, and the H_{2} center-of-mass self-dynamic structure factor was finally extracted for the two liquid samples...
January 2019: Physical Review. E
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