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system dynamic model

Zabit Hameed, Saqib Saleem, Jawad Mirza, Muhammad Salman Mustafa, Qamar-Ul-Islam
Epilepsy is a brain disorder characterised by the recurrent and unpredictable interruptions of normal brain function, called epileptic seizures. The present study attempts to derive new diagnostic indices which may delineate between ictal and interictal states of epilepsy. To achieve this, the nonlinear modeling approach of global principal dynamic modes (PDMs) is adopted to examine the functional connectivity of the temporal and frontal lobes with the occipital brain segment using an ensemble of paediatric EEGs having the presence of epileptic seizure...
2018: PloS One
Tobias Zimmermann, Bertram Taetz, Gabriele Bleser
Human body motion analysis based on wearable inertial measurement units (IMUs) receives a lot of attention from both the research community and the and industrial community. This is due to the significant role in, for instance, mobile health systems, sports and human computer interaction. In sensor based activity recognition, one of the major issues for obtaining reliable results is the sensor placement/assignment on the body. For inertial motion capture (joint kinematics estimation) and analysis, the IMU-to-segment (I2S) assignment and alignment are central issues to obtain biomechanical joint angles...
January 19, 2018: Sensors
Enrico Pirotta, Marc Mangel, Daniel P Costa, Bruce Mate, Jeremy A Goldbogen, Daniel M Palacios, Luis A Hückstädt, Elizabeth A McHuron, Lisa Schwarz, Leslie New
Integrating behavior and physiology is critical to formulating new hypotheses on the evolution of animal life-history strategies. Migratory capital breeders acquire most of the energy they need to sustain migration, gestation, and lactation before parturition. Therefore, when predicting the impact of environmental variation on such species, a mechanistic understanding of the physiology of their migratory behavior is required. Using baleen whales as a model system, we developed a dynamic state variable model that captures the interplay among behavioral decisions, energy, reproductive needs, and the environment...
February 2018: American Naturalist
Katherine M Marchetto, Alison G Power
Infections of one host by multiple parasites are common, and several studies have found that the order of parasite invasion can affect both within-host competition and disease severity. However, it is unclear to what extent coinfection timing might be important to consider when modeling parasite impacts on host populations. Using a model system of two viruses infecting barley, we found that simultaneous infections of the two viruses were significantly more damaging to hosts than sequential coinfections. While priority effects were evident in within-host concentrations of sequential coinfections, priority did not influence any parameters (such as virulence or transmission rate) that affect host population dynamics...
February 2018: American Naturalist
N M Gergs, S A Bender, R A Duine, D Schuricht
We develop a theory for spin transport and magnetization dynamics in a quantum dot spin valve, i.e., two magnetic reservoirs coupled to a quantum dot. Our theory is able to take into account effects of strong correlations. We demonstrate that, as a result of these strong correlations, the dot gate voltage enables control over the current-induced torques on the magnets and, in particular, enables voltage-controlled magnetic switching. The electrical resistance of the structure can be used to read out the magnetic state...
January 5, 2018: Physical Review Letters
Katarzyna Pernal
An adiabatic connection (AC) formula for the electron correlation energy is derived for a broad class of multireference wave functions. The AC expression recovers dynamic correlation energy and assures a balanced treatment of the correlation energy. Coupling the AC formalism with the extended random phase approximation allows one to find the correlation energy only from reference one- and two-electron reduced density matrices. If the generalized valence bond perfect pairing model is employed a simple closed-form expression for the approximate AC formula is obtained...
January 5, 2018: Physical Review Letters
Philippe Bun, Serge Dmitrieff, Julio M Belmonte, François J Nédélec, Péter Lénárt
While contraction of sarcomeric actomyosin assemblies is well understood, this is not the case for disordered networks of actin filaments (F-actin) driving diverse essential processes in animal cells. For example, at the onset of meiosis in starfish oocytes a contractile F-actin network forms in the nuclear region transporting embedded chromosomes to the assembling microtubule spindle. Here, we addressed the mechanism driving contraction of this 3D disordered F-actin network by comparing quantitative observations to computational models...
January 19, 2018: ELife
Katharina Witte, Ioanna Mantouvalou, Rocío Sánchez-de-Armas, Heiko Lokstein, Janina Lebendig-Kuhla, Adrian Jonas, Friedrich Roth, Birgit Kanngiesser, Holger Stiel
Using Near-Edge X-ray Absorption Fine Structure Spectroscopy (NEXAFS) the carbon backbone of sodium copper chlorophyllin (SCC), a widely used chlorophyll derivative, and its breakdown products are analyzed to elucidate their electronic structure and physicochemical properties. Using various sample preparation methods and complementary spectroscopic methods (including UV/VIS, X-ray Photoelectron Spectroscopy), a comprehensive insight into the SCC breakdown process is presented. The experimental results are supported by Density Functional Theory (DFT) calculations allowing a detailed assignment of characteristic NEXAFS-features to specific C-bonds...
January 19, 2018: Journal of Physical Chemistry. B
Weiwei Cui, Meihang He, Luye Mu, Zuzeng Lin, Yanyan Wang, Wei Pang, Mark A Reed, Xuexin Duan
Quantitative biomarker detection methods featured with rapidity, high accuracy, and label-free are demonstrated for the development of point-of-care (POC) technologies or "beside" diagnostics. Microbead aggregation via protein-specific linkage provides an effective approach for selective capture of biomarkers from the samples, and can directly readout the presence and amount of the targets. However, sensors or microfluidic analyzers that can accurately quantify the microbead aggrega-tion are scared. In this work, we demonstrate a microwell-based microbeads analyzing system, by which online manipula-tions of microbeads including trapping, arraying, and rotations can be realized, providing a series of microfluidic approaches to layout the aggregated microbeads for further convenient characterizations...
January 19, 2018: ACS Sensors
Angelica I Aviles-Rivero, Samar M Alsaleh, Alicia Casals
PURPOSE: Technical advancements have been part of modern medical solutions as they promote better surgical alternatives that serve to the benefit of patients. Particularly with cardiovascular surgeries, robotic surgical systems enable surgeons to perform delicate procedures on a beating heart, avoiding the complications of cardiac arrest. This advantage comes with the price of having to deal with a dynamic target which presents technical challenges for the surgical system. In this work, we propose a solution for cardiac motion estimation...
January 19, 2018: International Journal of Computer Assisted Radiology and Surgery
Ravi C Dutta, Suresh K Bhatia
We investigate the structure of polyimide (PI) at the surface of a silicalite zeolite (MFI), as part of a model hybrid organic-inorganic mixed matrix membrane system, through equilibrium Molecular Dynamics simulations. Further, we report a comparison of the adsorption and transport characteristics of pure component CO2 and CH4 in PI, MFI and PI-MFI composite membranes. It is seen that incorporation of MFI zeolite into PI results in the formation of densified polymer layers (rigidified region) near the surface, having thickness around 1...
January 19, 2018: ACS Applied Materials & Interfaces
Carla White, Lloyd J Bridge
Evidence suggests that many G protein-coupled receptors (GPCRs) are bound together forming dimers. The implications of dimerisation for cellular signalling outcomes, and ultimately drug discovery and therapeutics, remain unclear. Consideration of ligand binding and signalling via receptor dimers is therefore required as an addition to classical receptor theory, which is largely built on assumptions of monomeric receptors. A key factor in developing theoretical models of dimer signalling is cooperativity across the dimer, whereby binding of a ligand to one protomer affects the binding of a ligand to the other protomer...
January 18, 2018: Bulletin of Mathematical Biology
Li-Fei Ji, Jian-Xun Fan, Shou-Feng Zhang, Ai-Min Ren
2,5-Difluoro-7,7,8,8-tetracyanoquinodimethane (F2-TCNQ) was recently reported to display excellent electron transport properties in single crystal field-effect transistors (FETs). Its carrier mobility can reach 25 cm2 V-1 s-1 in devices. However, its counterparts TCNQ and F4-TCNQ (tetrafluoro-7,7,8,8-tetracyanoquinodimethane) do not exhibit the same highly efficient behavior. To better understand this significant difference in charge carrier mobility, a multiscale approach combining semiclassical Marcus hopping theory, a quantum nuclear enabled hopping model and molecular dynamics simulations was performed to assess the electron mobilities of the Fn-TCNQ (n = 0, 2, 4) systems in this work...
January 19, 2018: Physical Chemistry Chemical Physics: PCCP
Rebecca J Wood, Angelique R Ormsby, Mona Radwan, Dezerae Cox, Abhishek Sharma, Tobias Vöpel, Simon Ebbinghaus, Mikael Oliveberg, Gavin E Reid, Alex Dickson, Danny M Hatters
The pool of quality control proteins (QC) that maintains protein-folding homeostasis (proteostasis) is dynamic but can become depleted in human disease. A challenge has been in quantitatively defining the depth of the QC pool. With a new biosensor, flow cytometry-based methods and mathematical modeling we measure the QC capacity to act as holdases and suppress biosensor aggregation. The biosensor system comprises a series of barnase kernels with differing folding stability that engage primarily with HSP70 and HSP90 family proteins...
January 18, 2018: Nature Communications
Josep Sardanyés, Tomás Alarcón
Tumor cell populations are highly heterogeneous. Such heterogeneity, both at genotypic and phenotypic levels, is a key feature during tumorigenesis. How to investigate the impact of this heterogeneity in the dynamics of tumors cells becomes an important issue. Here we explore a stochastic model describing the competition dynamics between a pool of heterogeneous cancer cells with distinct phenotypes and healthy cells. This model is used to explore the role of demographic fluctuations on the transitions involving tumor clearance...
January 18, 2018: Scientific Reports
Audrey J Sederberg, Jason N MacLean, Stephanie E Palmer
To compensate for sensory processing delays, the visual system must make predictions to ensure timely and appropriate behaviors. Recent work has found predictive information about the stimulus in neural populations early in vision processing, starting in the retina. However, to utilize this information, cells downstream must be able to read out the predictive information from the spiking activity of retinal ganglion cells. Here we investigate whether a downstream cell could learn efficient encoding of predictive information in its inputs from the correlations in the inputs themselves, in the absence of other instructive signals...
January 18, 2018: Proceedings of the National Academy of Sciences of the United States of America
Doris F Wu, Therese Löhrich, Andreas Sachse, Roger Mundry, Roman M Wittig, Sébastien Calvignac-Spencer, Tobias Deschner, Fabian H Leendertz
BACKGROUND: Cross-sectional surveys of chimpanzee (Pan troglodytes) communities across sub-Saharan Africa show large geographical variation in malaria parasite (Plasmodium spp.) prevalence. The drivers leading to this apparent spatial heterogeneity may also be temporally dynamic but data on prevalence variation over time are missing for wild great apes. This study aims to fill this fundamental gap. METHODS: Some 681 faecal samples were collected from 48 individuals of a group of habituated chimpanzees (Taï National Park, Côte d'Ivoire) across four non-consecutive sampling periods between 2005 and 2015...
January 18, 2018: Malaria Journal
G Muñoz-Gil, C Charalambous, M A García-March, M F Garcia-Parajo, C Manzo, M Lewenstein, A Celi
We introduce a model in which a particle performs a continuous-time random walk (CTRW) coupled to an environment with Ising dynamics. The particle shows locally varying diffusivity determined by the geometrical properties of the underlying Ising environment, that is, the diffusivity depends on the size of the connected area of spins pointing in the same direction. The model shows anomalous diffusion when the Ising environment is at critical temperature. We show that any finite scale introduced by a temperature different from the critical one, or a finite size of the environment, cause subdiffusion only during a transient time...
November 2017: Physical Review. E
N Roy, P Sanz-Leon, P A Robinson
The modulation of neural quantities by presynaptic and postsynaptic activities via local feedback processes is investigated by incorporating nonlinear phenomena such as relative refractory period, synaptic enhancement, synaptic depression, and habituation. This is done by introducing susceptibilities, which quantify the response in either firing threshold or synaptic strength to unit change in either presynaptic or postsynaptic activity. Effects on the power spectra are then analyzed for a realistic corticothalamic model to determine the spectral signatures of various nonlinear processes and to what extent these are distinct...
November 2017: Physical Review. E
Stefano S Turzi
I propose a continuum theory for active nematic gels, defined as fluids or suspensions of orientable rodlike objects endowed with active dynamics, that is based on symmetry arguments and compatibility with thermodynamics. The starting point is our recent theory that models (passive) nematic liquid crystals as relaxing nematic elastomers. The interplay between viscoelastic response and active dynamics of the microscopic constituents is naturally taken into account. By contrast with standard theories, activity is not introduced as an additional term of the stress tensor, but it is added as an external remodeling force that competes with the passive relaxation dynamics and drags the system out of equilibrium...
November 2017: Physical Review. E
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