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system theory

Michael M Safaee, Christopher P Ames, Vedat Deviren, Aaron J Clark
BACKGROUND: Traditional approaches for retroperitoneal lumbar plexus schwannomas involve anterior open or laparoscopic resection. For select tumors, the lateral retroperitoneal approach provides a minimally invasive alternative. OBJECTIVE: To describe a minimally invasive lateral transpsoas approach for the resection of retroperitoneal schwannomas. METHODS: A lateral retroperitoneal transpsoas approach was used to resect a 3.1 × 2.7 × 4...
January 17, 2018: Operative Neurosurgery (Hagerstown, Md.)
Jeng-Cheng Liu, Yuang-Tung Cheng, Hsien-Sen Hung
Direction-of-arrival (DOA) and range estimation is an important issue of sonar signal processing. In this paper, a novel approach using Hilbert-Huang transform (HHT) is proposed for joint bearing and range estimation of multiple targets based on a uniform linear array (ULA) of hydrophones. The structure of this ULA based on micro-electro-mechanical systems (MEMS) technology, and thus has attractive features of small size, high sensitivity and low cost, and is suitable for Autonomous Underwater Vehicle (AUV) operations...
January 19, 2018: Sensors
Thomas R Clancy
As systems evolve over time, their natural tendency is to become increasingly more complex. Studies in the field of complex systems have generated new perspectives on the application of management strategies in health systems. Much of this research appears as a natural extension of the cross-disciplinary field of systems theory. This article is the 3rd in a series of articles that focus on why technological complexity is increasing and strategies nurse administrators can use to successfully implement change in the face of it...
February 2018: Journal of Nursing Administration
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
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
Kunpeng Cui, Zhe Ma, Nan Tian, Fengmei Su, Dong Liu, Liangbin Li
Flow-induced crystallization (FIC) is a typical nonequilibrium phase transition and a core industry subject for the largest group of commercially useful polymeric materials: semicrystalline polymers. A fundamental understanding of FIC can benefit the research of nonequilibrium ordering in matter systems and help to tailor the ultimate properties of polymeric materials. Concerning the crystallization process, flow can accelerate the kinetics by orders of magnitude and induce the formation of oriented crystallites like shish-kebab, which are associated with the major influences of flow on nucleation, that is, raised nucleation density and oriented nuclei...
January 19, 2018: Chemical Reviews
Federico Elias-Wolff, Martin Lindén, Alexander P Lyubartsev, Erik G Brandt
Membrane curvature sensing, where the binding free energies of membrane-associated molecules depend on the local membrane curvature, is a key factor to modulate and maintain the shape and organization of cell membranes. However, the microscopic mechanisms are not well understood, partly due to absence of efficient simulation methods. Here, we describe a method to compute the curvature dependence of the binding free energy of a membrane-associated probe molecule that interacts with a buckled membrane, which has been created by lateral compression of a flat bilayer patch...
January 19, 2018: Journal of Chemical Theory and Computation
Cipriano Rangel, Joaquin Espinosa-Garcia
Within the Born-Oppenheimer approximation a full-dimensional analytical potential energy surface, PES-2017, was developed for the gas-phase hydrogen abstraction reaction between the chlorine atom and ethane, which is a nine body system. This surface presents a valence-bond/molecular mechanics functional form dependent on 60 parameters and is fitted to high-level ab initio calculations. This reaction presents little exothermicity, -2.30 kcal mol-1, with a low height barrier, 2.44 kcal mol-1, and intermediate complexes in the entrance and exit channels...
January 19, 2018: Physical Chemistry Chemical Physics: PCCP
Jing Zeng, Ke-Qiu Chen
Although a lot of theoretical studies have designed perfect spin filters using inorganic/organic/organometallic materials, their fabrication methods are not experimentally feasible. This dilemma could be solved by a recent experiment, where porphyrins have been covalently coupled to graphene edges in a precise manner (Y. He et al., Nat. Chem., 2017, 9, 33-38). In particular, experimental results confirmed that the intrinsic features of porphyrins for metallation are preserved after dehydrogenative coupling to graphene edges, paving the way for realizing synthesizable spintronic devices...
January 19, 2018: Physical Chemistry Chemical Physics: PCCP
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
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
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
Zhifeng Jiang, Weiming Wan, Huaming Li, Shouqi Yuan, Huijun Zhao, Po Keung Wong
The challenge in the artificial photosynthesis of fossil resources from CO2 by utilizing solar energy is to achieve stable photocatalysts with effective CO2 adsorption capacity and high charge-separation efficiency. A hierarchical direct Z-scheme system consisting of urchin-like hematite and carbon nitride provides an enhanced photocatalytic activity of reduction of CO2 to CO, yielding a CO evolution rate of 27.2 µmol g-1 h-1 without cocatalyst and sacrifice reagent, which is >2.2 times higher than that produced by g-C3 N4 alone (10...
January 19, 2018: Advanced Materials
Maryse A Wiewel, Brendon P Scicluna, Lonneke A van Vught, Arie J Hoogendijk, Aeilko H Zwinderman, René Lutter, Janneke Horn, Olaf L Cremer, Marc J Bonten, Marcus J Schultz, Tom van der Poll
BACKGROUND: Statins can exert pleiotropic anti-inflammatory, vascular protective and anticoagulant effects, which in theory could improve the dysregulated host response during sepsis. We aimed to determine the association between prior statin use and host response characteristics in critically ill patients with sepsis. METHODS: We performed a prospective observational study in 1060 patients admitted with sepsis to the mixed intensive care units (ICUs) of two hospitals in the Netherlands between January 2011 and July 2013...
January 18, 2018: Annals of Intensive Care
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
Montserrat Manadé, Francesc Viñes, Adrià Gil, Francesc Illas
The attachment of H2 to the full set of transition metal (TM) adatoms supported on graphene is studied by using density functional theory. Methodology validation calculations on the interactions of H2 with benzene and graphene show that any of the vdW corrections under study, the Grimme D2, D3, D3 with Becke-Jonson damping (D3BJ), and Tkatchenko-Scheffler methods, applied on the PBE functional, are similarly accurate in describing such subtle interactions, with an accuracy of almost 2 kJ mol-1 compared to experiments...
January 19, 2018: Physical Chemistry Chemical Physics: PCCP
Bun Chan, John M Simmie
The kinetics of many reactions are critically dependent upon the barrier heights for which accurate determination can be difficult. From the perspective of attaining such quantities using computational quantum chemistry, it is important to appropriately validate routine and efficient methodologies such as density functional theory (DFT) procedures. In the present study, we embark on the journey of establishing diverse databases using a consistent high-level quantum chemistry procedure, against which new and existing methodologies can be assessed...
January 19, 2018: Physical Chemistry Chemical Physics: PCCP
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
Benjamin Seligman, Shripad Tuljapurkar, David Rehkopf
Background: Social and economic factors are important predictors of health and of recognized importance for health systems. However, machine learning, used elsewhere in the biomedical literature, has not been extensively applied to study relationships between society and health. We investigate how machine learning may add to our understanding of social determinants of health using data from the Health and Retirement Study. Methods: A linear regression of age and gender, and a parsimonious theory-based regression additionally incorporating income, wealth, and education, were used to predict systolic blood pressure, body mass index, waist circumference, and telomere length...
April 2018: SSM—Population Health
Nelson Y Dzade, Nora H de Leeuw
Layered transition-metal chalcogenides have emerged as a fascinating new class of materials for catalysis. Here, we present periodic density functional theory (DFT) calculations of the adsorption of thiophene and the direct desulfurization reaction pathways on the (001), (011), and (111) surfaces of layered FeS. The fundamental aspects of the thiophene adsorption, including the initial adsorption geometries, adsorption energies, structural parameters, and electronic properties, are presented. From the calculated adsorption energies, we show that the flat adsorption geometries, wherein the thiophene molecule forms multiple π-bonds with the FeS surfaces, are energetically more favorable than the upright adsorption geometries, with the strength of adsorption decreasing in the order FeS(111) > FeS(011) > FeS(001)...
January 11, 2018: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
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