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Shabbir Muhammad, Abdullah G Al-Sehemi, Zhongmin Su, Hongliang Xu, Ahmad Irfan, Aijaz Rasool Chaudhry
Using first-principle methods, several key electronic, optical and nonlinear optical properties are calculated for two recently synthesized chalcone derivatives i.e. (2E)-3-(4-methylphenyl)-1-(3-nitrophenyl)prop-2-en-1-one (comp.1) and (2E)-3-[4-(dimethylamino)phenyl]-1-(3-nitrophenyl)prop-2-en-1-one (comp.2). The calculation of dipole moment, polarizability <α>, anisotropy of polarizability as well as second hyperpolarizability (usually considered as a signature for two photon absorption phenomenon) are performed using density functional theory methods at PBE0/6-311G** level of theory...
December 14, 2016: Journal of Molecular Graphics & Modelling
J Vieira, R M G M Trines, E P Alves, R A Fonseca, J T Mendonça, R Bingham, P Norreys, L O Silva
We identify and explore a high orbital angular momentum (OAM) harmonics generation and amplification mechanism that manipulates the OAM independently of any other laser property, by preserving the initial laser wavelength, through stimulated Raman backscattering in a plasma. The high OAM harmonics spectra can extend at least up to the limiting value imposed by the paraxial approximation. We show with theory and particle-in-cell simulations that the orders of the OAM harmonics can be tuned according to a selection rule that depends on the initial OAM of the interacting waves...
December 23, 2016: Physical Review Letters
A A Fedorov, A S Berdnikov, D G Sochivko, D A Varlamov, V E Kurochkin, R V Petrov
Development of methods for obtaining approximate analytical solutions of nonlinear differential equations and their systems is a rapidly developing field of mathematical physics. Earlier, an approximate solution of the simplest system of kinetic enzymatic equations for calculating dynamics of complementary strands of nucleic acids was obtained. In this study, we consider an alternative approach to selecting the basic linear approximation of the used method, which makes it possible to obtain more accurate analytical solutions of the set problem...
November 2016: Doklady. Biochemistry and Biophysics
Xueshu Xie, Roman A Zubarev
Isotopic compositions of reactants affect the rates of chemical and biochemical reactions. Usually it is assumed that heavy stable isotope enrichment leads to progressively slower reactions. Yet the effect of stable isotopes may be nonlinear, as exemplified by the "isotopic resonance" phenomenon. Since the isotopic compositions of other planets of Solar system, including Mars and Venus, are markedly different from terrestrial (e.g., deuterium content is ≈5 and ≈100 times higher, respectively), it is far from certain that terrestrial life will thrive in these isotopic conditions...
2017: PloS One
Laura E R Buckley, Benjamin J Coe, Daniela Rusanova, Sergio Sánchez, Michael Jirásek, Vishwas D Joshi, Jan Vávra, Dushant Khobragade, Lubomír Pospíšil, Šárka Ramešová, Ivana Císařová, David Šaman, Radek Pohl, Koen Clays, Nick Van Steerteghem, Bruce S Brunschwig, Filip Teplý
Three new dipolar cations have been synthesised, containing ferrocenyl (Fc) electron donor groups attached to helquat (Hq) acceptors. These organometallic Hq derivatives have been characterised as their TfO(-) salts by using various techniques including NMR and electronic absorption spectroscopies and electrochemical measurements. UV-vis spectra show multiple intense low energy absorptions attributable to intramolecular charge-transfer (ICT) excitations. Each compound displays a reversible Fc(+/0) redox process, together with two reversible one-electron reductions of the Hq fragment...
January 4, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
F Settles, E Ripley, D Shengwen, G Clarke
PURPOSE: Skeletal muscle energetics were studied by phosphorus-31 MRS ((31) P-MRS) during exercise. The reproducibility of work performed and the MRS parameters were investigated. METHODS: Reproducibility of the (31) P-MRS exercise parameters was validated in five healthy volunteers (2 M/3 F, age 39.2 ± 21.9 yr, BMI 25.1 ± 4.8 kg/m(2) ). Five minute exercise of the vastus lateralis (VL) was performed on two separate occasions during MRS in a 3 Tesla MRI system...
June 2016: Medical Physics
W Liu, A Sawant, D Ruan
PURPOSE: The development of high dimensional imaging systems (e.g. volumetric MRI, CBCT, photogrammetry systems) in image-guided radiotherapy provides important pathways to the ultimate goal of real-time volumetric/surface motion monitoring. This study aims to develop a prediction method for the high dimensional state subject to respiratory motion. Compared to conventional linear dimension reduction based approaches, our method utilizes manifold learning to construct a descriptive feature submanifold, where more efficient and accurate prediction can be performed...
June 2016: Medical Physics
W Cao, K Randeniya, P Yepes, D Grosshans, R Mohan
PURPOSE: To investigate the impact of a new approach for calculating relative biological effectiveness (RBE) in intensity-modulated proton therapy (IMPT) optimization on RBE-weighted dose distributions. This approach includes the nonlinear RBE for the high linear energy transfer (LET) region, which was revealed by recent experiments at our institution. In addition, this approach utilizes RBE data as a function of LET without using dose-averaged LET in calculating RBE values. METHODS: We used a two-piece function for calculating RBE from LET...
June 2016: Medical Physics
Radoslaw Martin Cichy, Santani Teng
In natural environments, visual and auditory stimulation elicit responses across a large set of brain regions in a fraction of a second, yielding representations of the multimodal scene and its properties. The rapid and complex neural dynamics underlying visual and auditory information processing pose major challenges to human cognitive neuroscience. Brain signals measured non-invasively are inherently noisy, the format of neural representations is unknown, and transformations between representations are complex and often nonlinear...
February 19, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Hafez Asgharzadeh, Iman Borazjani
The explicit and semi-implicit schemes in flow simulations involving complex geometries and moving boundaries suffer from time-step size restriction and low convergence rates. Implicit schemes can be used to overcome these restrictions, but implementing them to solve the Navier-Stokes equations is not straightforward due to their non-linearity. Among the implicit schemes for nonlinear equations, Newton-based techniques are preferred over fixed-point techniques because of their high convergence rate but each Newton iteration is more expensive than a fixed-point iteration...
February 15, 2017: Journal of Computational Physics
Alvaro Diaz-Ruelas, Henrik Jeldtoft Jensen, Duccio Piovani, Alberto Robledo
It is well known that low-dimensional nonlinear deterministic maps close to a tangent bifurcation exhibit intermittency and this circumstance has been exploited, e.g., by Procaccia and Schuster [Phys. Rev. A 28, 1210 (1983)], to develop a general theory of 1/f spectra. This suggests it is interesting to study the extent to which the behavior of a high-dimensional stochastic system can be described by such tangent maps. The Tangled Nature (TaNa) Model of evolutionary ecology is an ideal candidate for such a study, a significant model as it is capable of reproducing a broad range of the phenomenology of macroevolution and ecosystems...
December 2016: Chaos
Andrés G Rolhauser, Eduardo R Pucheta
How plant functional traits (e.g. seed mass) drive species abundance within communities remains an unsolved question. Borrowing concepts from natural selection theory, we propose that trait-abundance relationships can generally correspond to one of three modes of trait selection: directional (a rectilinear relationship, where species at one end of a trait axis are most abundant), stabilizing (an n-shaped relationship), and disruptive (a u-shaped relationship). Stabilizing selection (i.e. the functional convergence of abundant species) would result from positive density-dependent interactions (e...
December 30, 2016: Ecology
Nolan Ferral, Kyara Holloway, Mingzhong Li, Zhaozheng Yin, Chen Hou
Increasing evidence has shown that the energy use of ant colonies increases sublinearly with colony size so that large colonies consume less per capita energy than small colonies. It has been postulated that social environment (e.g., in the presence of queen and brood) is critical for the sublinear group energetics, and a few studies of ant workers isolated from queens and brood observed linear relationships between group energetics and size. In this paper, we hypothesize that the sublinear energetics arise from the heterogeneity of activity in ant groups, i...
December 26, 2016: Insect Science
W P E M Op 't Root, G J H Brussaard, P W Smorenburg, O J Luiten
Terahertz (THz) pulses are applied in areas as diverse as materials science, communication and biosensing. Techniques for subwavelength concentration of THz pulses give access to a rapidly growing range of spatial scales and field intensities. Here we experimentally demonstrate a method to generate intense THz pulses on a metal wire, thereby introducing the possibility of wave-guiding and focussing of the full THz pulse energy to subwavelength spotsizes. This enables endoscopic sensing, single-shot subwavelength THz imaging and study of strongly nonlinear THz phenomena...
December 23, 2016: Nature Communications
David O Oluwole, Alexey V Yagodin, Nhlakanipho C Mhkize, Kutloano E Sekhosana, Alexander G Martynov, Yulia Germanovna Gorbunova, Aslan Yu Tsivadze, Tebello Nyokong
We report the original selective and efficient approaches to novel nonlinear optical (NLO) materials, namely homoleptic double- and triple-decker europium(III) complexes 2 and 3 with A3B-type phthalocyanine ligand bearing two anchoring diethyleneglycol chains terminated with OH-groups. Their covalently linked nanoconjugates with mercaptosuccinic acid-capped ternary CdSeTe/CdTeS/ZnSeS quantum dots were prepared in the presence of ethyl(dimethylaminopropyl)carbodiimide activating agent. Optical limiting (OL) properties of the obtained low-symmetry complexes and their conjugates with quantum dots (QDs) were measured for the first time by open aperture Z-scan technique (532 nm laser and pulse rate of 10 ns)...
December 21, 2016: Chemistry: a European Journal
Huan Yang, Hil G E Meijer, Jan R Buitenweg, Stephan A van Gils
Healthy or pathological states of nociceptive subsystems determine different stimulus-response relations measured from quantitative sensory testing. In turn, stimulus-response measurements may be used to assess these states. In a recently developed computational model, six model parameters characterize activation of nerve endings and spinal neurons. However, both model nonlinearity and limited information in yes-no detection responses to electrocutaneous stimuli challenge to estimate model parameters. Here, we address the question whether and how one can overcome these difficulties for reliable parameter estimation...
2016: Frontiers in Psychology
S Budday, G Sommer, C Birkl, C Langkammer, J Haybaeck, J Kohnert, M Bauer, F Paulsen, P Steinmann, E Kuhl, G A Holzapfel
: Mechanics are increasingly recognized to play an important role in modulating brain form and function. Computational simulations are a powerful tool to predict the mechanical behavior of the human brain in health and disease. The success of these simulations depends critically on the underlying constitutive model and on the reliable identification of its material parameters. Thus, there is an urgent need to thoroughly characterize the mechanical behavior of brain tissue and to identify mathematical models that capture the tissue response under arbitrary loading conditions...
October 27, 2016: Acta Biomaterialia
Vivek Raj Senthivel, Marc Sturrock, Gabriel Piedrafita, Mark Isalan
Nonlinear responses to signals are widespread natural phenomena that affect various cellular processes. Nonlinearity can be a desirable characteristic for engineering living organisms because it can lead to more switch-like responses, similar to those underlying the wiring in electronics. Steeper functions are described as ultrasensitive, and can be applied in synthetic biology by using various techniques including receptor decoys, multiple co-operative binding sites, and sequential positive feedbacks. Here, we explore the inherent non-linearity of a biological signaling system to identify functions that can potentially be exploited using cell genome engineering...
December 16, 2016: Scientific Reports
Edward J Zuperku, Astrid G Stucke, Francis A Hopp, Eckehard A E Stuth
The role of the dorsolateral pons in the control of expiratory duration (TE) and breathing frequency is incompletely understood. A subregion of the pontine parabrachial/Kölliker-Fuse (PB-KF) complex of dogs was identified via microinjections, in which localized pharmacologically-induced increases in neuronal activity increased breathing rate, while decreases in neural activity decreased breathing rate. This subregion is very sensitive to local and systemic opioids. The object of this study was to precisely characterize the relationship between the PB-KF subregion pattern of altered neuronal activity and the control of respiratory phase timing and the time-course of the phrenic nerve activity/neurogram (PNG)...
December 14, 2016: Journal of Neurophysiology
Eun-Jin Kim, Rainer Hollerbach
We report time-dependent probability density functions (PDFs) for a nonlinear stochastic process with a cubic force using analytical and computational studies. Analytically, a transition probability is formulated by using a path integral and is computed by the saddle-point solution (instanton method) and a new nonlinear transformation of time. The predicted PDF p(x,t) in general involves a time integral, and useful PDFs with explicit dependence on x and t are presented in certain limits (e.g., in the short and long time limits)...
November 2016: Physical Review. E
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