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system theory

Suzanne Grant, Bruce Guthrie
Patient safety is an increasing concern for health systems internationally. The majority of administrative work in UK general practice takes place in the context of organisational routines such as repeat prescribing and test results handling, where high workloads and increased clinician dependency on administrative staff have been identified as an emerging safety issue. Despite this trend, most research to date has focused on the redistribution of the clinical workload between doctors, nurses and allied health professionals within individual care settings...
March 2, 2018: Social Science & Medicine
Christine Prouty, Shima Mohebbi, Qiong Zhang
Given the increasing vulnerability of communities to the negative impacts of untreated wastewater, resource recovery (RR) systems provide a paradigm shift away from a traditional approach of waste separation and treatment towards a productive recovery of water, energy and nutrients. The aim of this research is to understand the relationships between factors that influence the adoption and sustainability of wastewater-based RR systems to inform technology implementation strategies. The study presents a theory-informed, community-influenced system dynamics (SD) model to provide decision-makers with an adaptable tool that simulates system-level responses to the strategies that are developed for the coastal town of Placencia, Belize...
March 7, 2018: Water Research
Qiang Zhang, Tianyuan Xin, Xiaoke Lu, Yuexia Wang
We exploited novel two-dimensional (2D) carbon selenide (CSe) with a structure analogous to phosphorene, and probed its electronics and optoelectronics. Calculating phonon spectra using the density functional perturbation theory (DFPT) method indicated that 2D CSe possesses dynamic stability, which made it possible to tune and equip CSe with outstanding properties by way of X-doping (X = O, S, Te), i.e., X substituting Se atoms. Then systematic investigation on the structural, electronic, and optical properties of pristine and X-doped monolayer CSe was carried out using the density functional theory (DFT) method...
March 16, 2018: Materials
Audrey M Bernstein, Robert Ritch, J Mario Wolosin
Exfoliation syndrome (XFS) is an age-related disease involving the deposition of aggregated fibrillar material (XFM) at extracellular matrices in tissues that synthesize elastic fibers. Its main morbidity is in the eye, where XFM accumulations form on the surface of the ciliary body, iris and lens. Exfoliation glaucoma (XFG) occurs in a high proportion of persons with XFS and can be a rapidly progressing disease. Worldwide, XFG accounts for about 25% of open-angle glaucoma cases. XFS and XFG show a sharp age-dependence, similarly to the many age-related diseases classified as aggregopathies...
March 15, 2018: Journal of Glaucoma
Chang-Hwan Yi, Julius Kullig, Jan Wiersig
One of the interesting features of open quantum and wave systems is the non-Hermitian degeneracy called an exceptional point, where not only energy levels but also the corresponding eigenstates coalesce. We demonstrate that such a degeneracy can appear in optical microdisk cavities by deforming the boundary extremely weakly. This surprising finding is explained by a semiclassical theory of dynamical tunneling. It is shown that the exceptional points come in nearly degenerated pairs, originating from the different symmetry classes of modes...
March 2, 2018: Physical Review Letters
Chun-Yu Wang, Shuai Jiang, Yi-Rong Liu, Hui Wen, Zhongquan Wang, Ya-Juan Han, Teng Huang, Wei Huang
Ammonia and amines are important common trace atmospheric species that can enhance new particle formation (NPF) in the Earth's atmosphere. However, the synergistic effect of these two bases involving nucleation is still lacking. We studied the most stable geometric structures and thermodynamics of quaternary (NH3)(CH3NH2)(H2SO4)m(H2O)n (m = 1-3, n = 0-4) clusters at the PW91PW91/6-311++G(3df,3pd) level of theory for the first time. We find that the proton transfer from H2SO4 molecule to CH3NH2 molecule is easier than to NH3 molecule in the free or hydrated H2SO4-base clusters, and thus leads to the stability...
March 16, 2018: Journal of Physical Chemistry. A
Li-Hui Mou, Qing-Yu Liu, Ting Zhang, Zi-Yu Li, Sheng-Gui He
Dinitrogen activation/fixation is one of the most important and challenging subjects in synthetic as well as theoretical chemistry. In this study, the adsorption reactions of N2 onto TaCn - ( n = 1-4) cluster anions have been investigated by means of mass spectrometry in conjunction with density functional theory calculations. Following the experimental results that only TaC4 - was observed to adsorb N2 , theoretical calculations predicted that TaC4 - reaction system (TaC4 - + N2 → TaC4 N2 - ) has a negligible barrier on the approach of N2 molecule while insurmountable barriers are located on the reaction pathways of TaC1-3 - /N2 reaction systems...
March 16, 2018: Journal of Physical Chemistry. A
Joseph M Kasper, David B Williams-Young, Eugene Vecharynski, Chao Yang, Xiaosong Li
The time-dependent Hartree-Fock (TDHF) and time-dependent density functional theory (TDDFT) equations allow one to probe electronic resonances of a system quickly and cheaply. However, the iterative solution of the eigenvalue problem can be challenging or impossible to converge with standard methods such as the Davidson algorithm for spectrally dense regions in the interior of the spectrum as are common in X-ray absorption spectroscopy (XAS). More robust solvers such as the generalized preconditioned locally harmonic residual (GPLHR) method can alleviate this problem, but at the expense of higher average computational cost...
March 16, 2018: Journal of Chemical Theory and Computation
Raphaël Le Bouc, Mathias Pessiglione
Motivation can be defined as the function that orients and activates the behavior. Motivation deficits such as apathy are pervasive in both neurological and psychiatric diseases, and are currently assessed with clinical scales that do not give any mechanistic insight. Here, we present another approach that consists in phenotyping the behaviour of patients in motivation tests, using computational models. These formal models impose a precise and operational definition of motivation that is embedded in decision theory...
March 2018: Médecine Sciences: M/S
Julia Tesch, Fabian Paschke, Mikhail Fonin, Marko Wietstruk, Stefan Böttcher, Roland J Koch, Aaron Bostwick, Chris Jozwiak, Eli Rotenberg, Anna Makarova, Beate Paulus, Elena Voloshina, Yuriy Dedkov
The implementation of graphene in semiconducting technology requires precise knowledge about the graphene-semiconductor interface. In our work the structure and electronic properties of the graphene/n-Ge(110) interface are investigated on the local (nm) and macro (from μm to mm) scales via a combination of different microscopic and spectroscopic surface science techniques accompanied by density functional theory calculations. The electronic structure of freestanding graphene remains almost completely intact in this system, with only a moderate n-doping indicating weak interaction between graphene and the Ge substrate...
March 16, 2018: Nanoscale
P Alex Smith, Yaxin Wang, Ralph W Metcalfe, Luiz C Sampaio, Daniel L Timms, William E Cohn, O H Frazier
PURPOSE: A minimally invasive, partial-assist, intra-atrial blood pump has been proposed, which would unload the left ventricle with a flow path from the left atrium to the arterial system. Flow modulation is a common strategy for ensuring washout in the pump, but it can increase power consumption because it is typically achieved through motor-speed variation. However, if a pump's performance curve had the proper gradient, flow modulation could be realized passively. To achieve this goal, we propose a pump performance operating curve as an alternative to the more standard operating point...
March 2018: International Journal of Artificial Organs
Guoqi Li, Lei Deng, Gaoxi Xiao, Pei Tang, Changyun Wen, Wuhua Hu, Jing Pei, Luping Shi, H Eugene Stanley
Complex networks characterize the nature of internal/external interactions in real-world systems including social, economic, biological, ecological, and technological networks. Two issues keep as obstacles to fulfilling control of large-scale networks: structural controllability which describes the ability to guide a dynamical system from any initial state to any desired final state in finite time, with a suitable choice of inputs; and optimal control, which is a typical control approach to minimize the cost for driving the network to a predefined state with a given number of control inputs...
March 15, 2018: Scientific Reports
A G Ramos, V J García-Garrido, A M Mancho, S Wiggins, J Coca, S Glenn, O Schofield, J Kohut, D Aragon, J Kerfoot, T Haskins, T Miles, C Haldeman, N Strandskov, B Allsup, C Jones, J Shapiro
Transoceanic Gliders are Autonomous Underwater Vehicles (AUVs) for which there is a developing and expanding range of applications in open-seas research, technology and underwater clean transport. Mature glider autonomy, operating depth (0-1000 meters) and low energy consumption without a CO2 footprint enable evolutionary access across ocean basins. Pursuant to the first successful transatlantic glider crossing in December 2009, the Challenger Mission has opened the door to long-term, long-distance routine transoceanic AUV missions...
March 15, 2018: Scientific Reports
Ketan Shankardass, Carles Muntaner, Lauri Kokkinen, Faraz Vahid Shahidi, Alix Freiler, Goldameir Oneka, Ahmed M Bayoumi, Patricia O'Campo
BACKGROUND: There has been a renewed interest in broadening the research agenda in health promotion to include action on the structural determinants of health, including a focus on the implementation of Health in All Policies (HiAP). Governments that use HiAP face the challenge of instituting governance structures and processes to facilitate policy coordination in an evidence-informed manner. Due to the complexity of government institutions and the policy process, systems theory has been proposed as a tool for evaluating the implementation of HiAP...
March 15, 2018: Health Research Policy and Systems
Salvador Vargas-Salfate, Dario Paez, James H Liu, Felicia Pratto, Homero Gil de Zúñiga
This study tests specific competing hypotheses from social dominance theory/realistic conflict theory (RCT) versus system justification theory about the role of social status. In particular, it examines whether system justification belief and effects are stronger among people with low socioeconomic status, and in less socially developed and unequal nations than among better-off people and countries. A cross-national survey was carried out in 19 nations from the Americas, Western and Eastern Europe, Asia, and Oceania using representative online samples ( N = 14,936, 50...
March 1, 2018: Personality & Social Psychology Bulletin
Zelig Chernia, Yoav Tsori
Phase separation in substituted pyridines in water is usually described as an interplay between temperature-driven breakage of hydrogen bonds and the associating interaction of the van der Waals force. In previous quantum-chemical studies, the strength of hydrogen bonding between one water and one pyridine molecules (the 1:1 complex) was assigned a pivotal role. It was accepted that the disassembly of the 1:1 complex at a critical temperature leads to phase separation and formation of the miscibility gap. Yet, for over two decades, notable empirical data and theoretical arguments were presented against that view, thus revealing the need in a revised quantum-mechanical description...
March 14, 2018: Journal of Chemical Physics
Giovanni Rillo, Miguel A Morales, David M Ceperley, Carlo Pierleoni
We performed simulations for solid molecular hydrogen at high pressures (250 GPa ≤ P ≤ 500 GPa) along two isotherms at T = 200 K (phase III) and at T = 414 K (phase IV). At T = 200 K, we considered likely candidates for phase III, the C2c and Cmca12 structures, while at T = 414 K in phase IV, we studied the Pc48 structure. We employed both Coupled Electron-Ion Monte Carlo (CEIMC) and Path Integral Molecular Dynamics (PIMD). The latter is based on Density Functional Theory (DFT) with the van der Waals approximation (vdW-DF)...
March 14, 2018: Journal of Chemical Physics
Igor Poltavsky, Robert A DiStasio, Alexandre Tkatchenko
Nuclear quantum effects (NQE), which include both zero-point motion and tunneling, exhibit quite an impressive range of influence over the equilibrium and dynamical properties of molecules and materials. In this work, we extend our recently proposed perturbed path-integral (PPI) approach for modeling NQE in molecular systems [I. Poltavsky and A. Tkatchenko, Chem. Sci. 7, 1368 (2016)], which successfully combines the advantages of thermodynamic perturbation theory with path-integral molecular dynamics (PIMD), in a number of important directions...
March 14, 2018: Journal of Chemical Physics
Yining Han, Jaehyeok Jin, Jacob W Wagner, Gregory A Voth
Coarse-grained (CG) models serve as a powerful tool to simulate molecular systems at much longer temporal and spatial scales. Previously, CG models and methods have been built upon classical statistical mechanics. The present paper develops a theory and numerical methodology for coarse-graining in quantum statistical mechanics, by generalizing the multiscale coarse-graining (MS-CG) method to quantum Boltzmann statistics. A rigorous derivation of the sufficient thermodynamic consistency condition is first presented via imaginary time Feynman path integrals...
March 14, 2018: Journal of Chemical Physics
Ali Mirzaeinia, Farzaneh Feyzi, Seyed Majid Hashemianzadeh
Based on Wertheim's second order thermodynamic perturbation theory (TPT2), equations of state (EOSs) are presented for the fluid and solid phases of tangent, freely jointed spheres. It is considered that the spheres interact with each other through the Weeks-Chandler-Anderson (WCA) potential. The developed TPT2 EOS is the sum of a monomeric reference term and a perturbation contribution due to bonding. MC NVT simulations are performed to determine the structural properties of the reference system in the reduced temperature range of 0...
March 14, 2018: Journal of Chemical Physics
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