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Complexity theory

Efrath Barta
Long-chain fatty acids cross a few membranes on their way from the capillary blood to the cardiomyocyte cytosol, where they are utilized as an essential source of energy. Details of the transport mechanism across those membranes remained elusive despite decades of laboratory and theoretical work. Here we inspect several optional scenarios for the crossing of the luminal membrane of the endothelial cell, the first barrier that should be crossed: a passive diffusion, facilitation by receptors for albumin and facilitation by fatty acids transporters...
December 3, 2016: Journal of Membrane Biology
Rüdiger Kunow
In this paper, I will present a reading of senior life through the lens of postcolonial theory. Even while this body of theory is as varied as the life experience summarized under the label "old age", such a project promises mutually fruitful results. Postcolonialism's preoccupation with positional difference, subalternity and the abiding influence of the hegemon over what it discards as other can be helpful in overcoming the often merely chronological or individualized understanding of the last stages of the life course...
December 2016: Journal of Aging Studies
Po-Jen Hsu, Kun-Lin Ho, Sheng-Hsien Lin, Jer-Lai Kuo
The potential energy surface (PES), structures and thermal properties of methanol clusters (MeOH)n with n = 8-15 were explored by replica-exchange molecular dynamics (REMD) simulations with an empirical model and refined using density functional theory (DFT) methods. For a given size, local minima structures were sampled from REMD trajectories and archived by a newly developed molecular database via a two-stage clustering algorithm (TSCA). Our TSCA utilizes both the topology of O-HO hydrogen bonding networks and the similarity of the shapes to filter out duplicates...
December 2, 2016: Physical Chemistry Chemical Physics: PCCP
Isaac Sugden, Claire S Adjiman, Constantinos C Pantelides
The global search stage of crystal structure prediction (CSP) methods requires a fine balance between accuracy and computational cost, particularly for the study of large flexible molecules. A major improvement in the accuracy and cost of the intramolecular energy function used in the CrystalPredictor II [Habgood et al. (2015). J. Chem. Theory Comput. 11, 1957-1969] program is presented, where the most efficient use of computational effort is ensured via the use of adaptive local approximate model (LAM) placement...
December 1, 2016: Acta Crystallographica Section B, Structural Science, Crystal Engineering and Materials
Arkadiusz Sitek
The origin ensemble (OE) algorithm is a new method used for image reconstruction from nuclear tomographic data. The main advantage of this algorithm is the ease of implementation for complex tomographic models and the sound statistical theory. In this comment, the author provides the basics of the statistical interpretation of OE and gives suggestions for the improvement of the algorithm in the application to prompt gamma imaging as described in Polf et al (2015 Phys. Med. Biol. 60 7085).
December 21, 2016: Physics in Medicine and Biology
Qi Wang, Zhijie Lian, Jianming Wang, Qingliang Chen, Yukuan Sun, Xiuyan Li, Xiaojie Duan, Ziqiang Cui, Huaxiang Wang
Electrical impedance tomography (EIT) reconstruction is a nonlinear and ill-posed problem. Exact reconstruction of an EIT image inverts a high dimensional mathematical model to calculate the conductivity field, which causes significant problems regarding that the computational complexity will reduce the achievable frame rate, which is considered as a major advantage of EIT imaging. The single-step method, state estimation method, and projection method were always used to accelerate reconstruction process. The basic principle of these methods is to reduce computational complexity...
November 2016: Review of Scientific Instruments
Dominic A Boardman, Jacinta Jacob, Lesley A Smyth, Giovanna Lombardi, Robert I Lechler
Direct allorecognition is the process by which donor-derived major histocompatibility complex (MHC)-peptide complexes, typically presented by donor-derived 'passenger' dendritic cells, are recognised directly by recipient T cells. In this review, we discuss the two principle theories which have been proposed to explain why individuals possess a high-precursor frequency of T cells with direct allospecificity and how self-restricted T cells recognise allogeneic MHC-peptide complexes. These theories, both of which are supported by functional and structural data, suggest that T cells recognising allogeneic MHC-peptide complexes focus either on the allopeptides bound to the allo-MHC molecules or the allo-MHC molecules themselves...
2016: Current Transplantation Reports
Muriah D Wheelock, Nathaniel G Harnett, Kimberly H Wood, Tyler R Orem, Douglas A Granger, Sylvie Mrug, David C Knight
Contemporary theory suggests that prefrontal cortex (PFC) function is associated with individual variability in the psychobiology of the stress response. Advancing our understanding of this complex biobehavioral pathway has potential to provide insight into processes that determine individual differences in stress susceptibility. The present study used functional magnetic resonance imaging to examine brain activity during a variation of the Montreal Imaging Stress Task (MIST) in 53 young adults. Salivary cortisol was assessed as an index of the stress response, trait anxiety was assessed as an index of an individual's disposition toward negative affectivity, and self-reported stress was assessed as an index of an individual's subjective psychological experience...
2016: Frontiers in Human Neuroscience
Eszter Makkos, Andrew Kerridge, Jonathan Austin, Nikolas Kaltsoyannis
Density functional theory (DFT) at the generalised gradient approximation level is employed within the periodic electrostatic embedded cluster method (PEECM) to model the brucite (0001) surface. Three representative studies are then used to demonstrate the reliability of the PEECM for the description of the interactions of various ionic species with the layered Mg(OH)2 structure, and its performance is compared with periodic DFT, an approach known to be challenging for the adsorption of charged species. The adsorption energies of a series of s block cations, including Sr(2+) and Cs(+) which are known to coexist with brucite in nuclear waste storage ponds, are well described by the embedded cluster model, provided that basis sets of triple-zeta quality are employed for the adsorbates...
November 28, 2016: Journal of Chemical Physics
Thomas-C Jagau
The theory and implementation of the complex-scaled coupled-cluster method with singles and doubles excitations (cs-CCSD) for studying resonances induced by static electric fields are presented. Within this framework, Stark shifts and ionization rates are obtained directly from the real and imaginary parts of the complex energy. The method is applied to the ground states of hydrogen, helium, lithium, beryllium, neon, argon, and carbon at varying field strengths. Complex-scaled Hartree-Fock, second-order many-body perturbation theory, and CCSD results are reported and analyzed with a focus on the impact of electron correlation on the ionization process...
November 28, 2016: Journal of Chemical Physics
Christopher C Ballard, C Clark Esty, David A Egolf
Equilibrium statistical mechanics allows the prediction of collective behaviors of large numbers of interacting objects from just a few system-wide properties; however, a similar theory does not exist for far-from-equilibrium systems exhibiting complex spatial and temporal behavior. We propose a method for predicting behaviors in a broad class of such systems and apply these ideas to an archetypal example, the spatiotemporal chaotic 1D complex Ginzburg-Landau equation in the defect chaos regime. Building on the ideas of Ruelle and of Cross and Hohenberg that a spatiotemporal chaotic system can be considered a collection of weakly interacting dynamical units of a characteristic size, the chaotic length scale, we identify underlying, mesoscale, chaotic units and effective interaction potentials between them...
November 2016: Chaos
Osvaldo A Rosso, Raydonal Ospina, Alejandro C Frery
We present a new approach for handwritten signature classification and verification based on descriptors stemming from time causal information theory. The proposal uses the Shannon entropy, the statistical complexity, and the Fisher information evaluated over the Bandt and Pompe symbolization of the horizontal and vertical coordinates of signatures. These six features are easy and fast to compute, and they are the input to an One-Class Support Vector Machine classifier. The results are better than state-of-the-art online techniques that employ higher-dimensional feature spaces which often require specialized software and hardware...
2016: PloS One
Robert Lickliter
Biologists and psychologists are re-thinking the long-standing premise of genes as the primary cause of development, a view widely embraced in 20th-century biology. This shift in thinking is based in large part on: (1) the growing appreciation of the complex, distributed regulatory dynamics of gene expression; and (2) the growing appreciation of the probabilistic, contingent, and situated nature of development. We now appreciate that what actually unfolds during individual development represents only one of many possibilities...
December 1, 2016: Wiley Interdisciplinary Reviews. Cognitive Science
Hana D'Souza, Annette Karmiloff-Smith
Recent technological advances allow us to measure how the infant brain functions in ways that were not possible just a decade ago. Although methodological advances are exciting, we must also consider how theories guide research: what we look for and how we explain what we find. Indeed, the ways in which research findings are interpreted affects the design of policies, educational practices, and interventions. Thus, the theoretical approaches adopted by scientists have a real impact on the lives of children with neurodevelopmental disorders (NDDs) and their families, as well as on the wider community...
December 1, 2016: Wiley Interdisciplinary Reviews. Cognitive Science
Fabio Pavanello, Xiaoge Zeng, Mark T Wade, Miloš A Popović
We propose ring modulators based on interdigitated p-n junctions that exploit standing rather than traveling-wave resonant modes to improve modulation efficiency, insertion loss and speed. Matching the longitudinal nodes and antinodes of a standing-wave mode with high (contacts) and low (depletion regions) carrier density regions, respectively, simultaneously lowers loss and increases sensitivity significantly. This approach permits further to relax optical constraints on contacts placement and can lead to lower device capacitance...
November 28, 2016: Optics Express
Mathias Perrin
We derive a quasi-normal mode theory for three-dimensional scatterers, taking care to remove an hypothesis of weakly dispersive materials implicitely used in previous works. In our approach, the normalized modes remain unchanged, but the analytic expansion coefficients onto the set of QNM are modified. In particular, we take into account in a simple way the non-orthogonality of the modes, and we set up a rigourous frame, to treat the case where several QNMs are excited. Eventally, the complex concept of PML integration, previously introduced, becomes unnecessary, even to compute the QNM mode volume...
November 28, 2016: Optics Express
Victor V Kotlyar, Alexey A Kovalev, Alexey P Porfirev
We derived exact analytical relationships to describe the complex amplitude of a perfect optical vortex generated by means of three different optical elements, namely, (i) an amplitude-phase element with a transmission function proportional to a Bessel function, (ii) an optimal phase element with a transmission equal to the sign function of a Bessel function, and (iii) a spiral axicon. The doughnut intensity was shown to be highest when using an optimal phase element. The spiral-axicon-aided diffraction ring was found to be twice as wide as when generated using two other elements...
December 1, 2016: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Ole Bernt Fasmer, Espen Borgå Johansen
BACKGROUND: Increased motor activity is a defining characteristic of patients with ADHD, and spontaneously hypertensive rats have been suggested to be an animal model of this disorder. In the present study, we wanted to use linear and non-linear methods to explore differences in motor activity patterns in SHR/NCrl rats compared to Wistar Kyoto (WKY/NHsd) rats. METHODS: A total number of 42 rats (23 SHR/NCrl and 19 WKY/NHsd, male and female) were tested. At PND 51, the animals' movements were video-recorded during an operant test procedure that lasted 90 min...
December 1, 2016: Behavioral and Brain Functions: BBF
Selina C Wang, Dean J Tantillo
The results of density functional theory calculations on thiyl radical-promoted polycyclization to form dodecahedrane are described. On the basis of these results, the proposed polycyclization is predicted to be both highly exergonic and fast. These results showcase the potential power of radical polycyclization reactions in constructing complex molecular architectures.
December 1, 2016: Organic & Biomolecular Chemistry
Fabiola E Medina, Rui P P Neves, Maria J Ramos, Pedro A Fernandes
Human fatty acid synthase (hFAS) is a multifunctional enzyme involved in a wide diversity of biological functions. For instance, it is a precursor of phospholipids and other complex processes such as the de novo synthesis of long chain fatty acid. Human FAS is also a component of biological membranes and it is implicated in the overexpression of several types of cancers. In this work, we describe the catalytic mechanism of β-ketoreductase (KR), which is a catalytic domain of the hFAS enzyme that catalyzes the reduction of β-ketoacyl to β-hydroxyacyl with the concomitant oxidation of the NADPH cofactor...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
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