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System dynamics

Marzena Rydygier, Marcin Jastrzab, Dawid Krzempek, Tomasz Nowak, Leszek Grzanka, Piotr Bednarczyk, Liliana Stolarczyk
Proton radiotherapy requires precise knowledge of the volumetric dose distribution. In proton beam delivery systems, based on narrow pencil beams, a contribution from small doses in low-intensity regions, consisting mainly of scattered protons, may have not negligible influence on total dose delivered to patient. Insufficient information about dose profile can cause underestimation of dose and potential delivery of inflated dose during hadrontherapy treatment. Presented work aims to verify applicability of diamond detectors, produced by Chemical Vapor Deposition method, for therapeutic proton beam profilometry at large fields...
January 17, 2018: Radiation Protection Dosimetry
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
Lucie Gerber, Frank B Jensen, Steffen S Madsen
Recent research has shown that nitric oxide (NO) produced by nitric oxide synthases (Nos) is an inhibitor of ion transporter activity and a modulator of epithelial ion transport in fish but little is known on changes in the Nos/NO system during osmotic stress. We hypothesized that the Nos/NO system responds to salinity changes as an integrated part of the acclimation process. Expression and localization of nos1/Nos1 and nos2/Nos2 were investigated in gill, kidney and intestine of FW- and SW-transferred trout using qPCR, Western blotting and immunohistochemistry, along with expressional changes of major ion transporters in the gill...
December 20, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Iyad Aqra, Tutut Herawan, Norjihan Abdul Ghani, Adnan Akhunzada, Akhtar Ali, Ramdan Bin Razali, Manzoor Ilahi, Kim-Kwang Raymond Choo
Designing an efficient association rule mining (ARM) algorithm for multilevel knowledge-based transactional databases that is appropriate for real-world deployments is of paramount concern. However, dynamic decision making that needs to modify the threshold either to minimize or maximize the output knowledge certainly necessitates the extant state-of-the-art algorithms to rescan the entire database. Subsequently, the process incurs heavy computation cost and is not feasible for real-time applications. The paper addresses efficiently the problem of threshold dynamic updation for a given purpose...
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
Paul Romatschke
Fluid dynamics is traditionally thought to apply only to systems near local equilibrium. In this case, the effective theory of fluid dynamics can be constructed as a gradient series. Recent applications of resurgence suggest that this gradient series diverges, but can be Borel resummed, giving rise to a hydrodynamic attractor solution which is well defined even for large gradients. Arbitrary initial data quickly approaches this attractor via nonhydrodynamic mode decay. This suggests the existence of a new theory of far-from-equilibrium fluid dynamics...
January 5, 2018: Physical Review Letters
Zijian Zheng, Fanzhu Li, Jun Liu, Raffaele Pastore, Guido Raos, Youping Wu, Liqun Zhang
The dispersion of solid nanoparticles within polymeric materials is widely used to enhance their performance. Many scientific and technological aspects of the resulting polymer nanocomposites have been studied, but the role of the structural and chemical heterogeneity of the nanoparticles has just started to be appreciated. For example, simulations of polymer films on planar heterogeneous surfaces revealed unexpected, non-monotonic activation energy to diffusion on varying the surface composition. Motivated by these intriguing results, here we simulate via molecular dynamics a different, fully three-dimensional system, in which the heterogeneous nanoparticles are incorporated in a polymer melt...
January 19, 2018: Soft Matter
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
Claire C Berton-Carabin, Leonard Sagis, Karin Schroën
Emulsions, i.e., the dispersion of liquid droplets in a nonmiscible liquid phase, are overwhelmingly present in food products. In such systems, both liquid phases (generally, oil and water) are separated by a narrow region, the oil-water interface. Despite the fact that this interface is very thin (in the nanometer range), it represents a large surface area and controls to a great extent the physicochemical stability of emulsions. This review provides an overview of the aspects that govern the composition, structure, and mechanical properties of interfaces in food emulsions, taking into account the complexity of such systems (presence of numerous surface-active molecules, influence of processing steps, and dynamic evolution due to chemical changes)...
January 18, 2018: Annual Review of Food Science and Technology
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
Shuguang Chen, YanHo Kwok, GuanHua Chen
Photovoltaic devices, electrochemical cells, catalysis processes, light emitting diodes, scanning tunneling microscopes, molecular electronics, and related devices have one thing in common: open quantum systems where energy and matter are not conserved. Traditionally quantum chemistry is confined to isolated and closed systems, while quantum dissipation theory studies open quantum systems. The key quantity in quantum dissipation theory is the reduced system density matrix. As the reduced system density matrix is an O(M! × M!) matrix, where M is the number of the particles of the system of interest, quantum dissipation theory can only be employed to simulate systems of a few particles or degrees of freedom...
January 19, 2018: Accounts of Chemical Research
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
Mao Mao, Jiankang He, Yongjie Lu, Xiao Li, Tianjiao Li, Wenxing Zhou, Dichen Li
As an alternative to conventional cell culture and animal testing, organ-on-a-chip is applied to study the biological phenomena of organ development and disease, as well as the interactions between human tissues and external stimuli such as chemicals, forces and electricity. The pattern design of microfluidic channel is one of the key approaches to regulate cell growth and differentiation, because these channels work as a crucial vasculature system to control the fluidic flow throughout the organ-on-a-chip device...
January 19, 2018: Biofabrication
Frigyes Samuel Racz, Peter Mukli, Zoltan Nagy, Andras Eke
Brain function is organized as a network of functional connections between different neuronal populations with connection strengths dynamically changing in time and space. Studies investigating functional connectivity (FC) usually follow a static approach when describing FC by considering the connectivity strengths constant, however a dynamic approach seems more reasonable, as this way the spatio-temporal dynamics of the underlying system can also be captured. Objective: The scale-free, i.e. fractal nature of neural dynamics is an inherent property of the nervous system...
January 19, 2018: Physiological Measurement
Enyuan Hu, Xuelong Wang, Xiqian Yu, Xiao-Qing Yang
The rechargeable lithium-ion battery (LIB) is the most promising energy storage system to power electric vehicles with high energy density and long cycling life. However, in order to meet customers' demands for fast charging, the power performances of current LIBs need to be improved. From the cathode aspect, layer-structured cathode materials are widely used in today's market and will continue to play important roles in the near future. The high rate capability of layered cathode materials during charging and discharging is critical to the power performance of the whole cell and the thermal stability is closely related to the safety issues...
January 19, 2018: Accounts of Chemical Research
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