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A quantum protective mechanism in photosynthesis
https://cds.cern.ch/record/2129344
Since the emergence of oxygenic photosynthesis, living systems have developed protective mechanisms against reactive oxygen species. During charge separation in photosynthetic reaction centres, triplet states can react with molecular oxygen generating destructive singlet oxygen. The triplet product yield in bacteria is observed to be reduced by weak magnetic fields. Reaction centres from plants' photosystem II share many features with bacterial reaction centres, including a high-spin iron whose function has remained obscure. To explain observations that the magnetic field effect is reduced by the iron, we propose that its fast-relaxing spin plays a protective role in photosynthesis by generating an effective magnetic field. We consider a simple model of the system, derive an analytical expression for the effective magnetic field and analyse the resulting triplet yield reduction. The protective mechanism is robust for realistic parameter ranges, constituting a clear example of a quantum effect playing a macroscopic role vital for life.Marais, AdrianaSinayskiy, IlyaPetruccione, Francescovan Grondelle, RienkSat, 06 Feb 2016 06:37:33 GMT04 Feb 2016arXiv:1602.01689https://cds.cern.ch/record/2129344['arXiv:1602.01689']arXiv:1602.01689Four-wave mixing in long wavelength III-nitride QD-SOAs
https://cds.cern.ch/record/2129328
Four wave mixing analysis is stated for quantum dot semiconductor optical amplifiers (QD SOAs) using the propagation equations (including nonlinear propagation contribution) coupled with the QD rate equations under the saturation assumption. Long wavelength III-nitride InN and AlInN QD SOAs are simulated. Asymmetric behavior due to linewidth enhancement factor is assigned. P-doping increases efficiency. Lossless efficiency for InAlN QDs for longer radii is obtained. Carrier heating is shown to have a considerable effect and a detuning dependence is expected at most cases. InN QD SOAs shown to have higher efficiency.Al-Khursan, Amin HJbara, Ahmed SAbood, H ISat, 06 Feb 2016 06:37:32 GMT03 Feb 2016arXiv:1602.01546https://cds.cern.ch/record/2129328['arXiv:1602.01546']arXiv:1602.01546New Astrophysical Reaction Rate for the $^{12}\textrm{C}(\alpha,\gamma)^{16}\textrm{O}$ Reaction
https://cds.cern.ch/record/2129317
A new astrophysical reaction rate for $^{12}$C($\alpha,\gamma$)$^{16}$O has been evaluated on the basis of a global R-matrix fitting to the available experimental data. The reaction rates of $^{12}$C($\alpha,\gamma$)$^{16}$O for stellar temperatures between 0.04 $\leq$ $T_9$ $\leq$ 10 are provided in a tabular form and by an analytical fitting expression. At $T_9$ = 0.2, the reaction rate is (7.83 $\pm$ 0.35)$\times10^{15}$ $\rm{cm^3 mol^{-1} s^{-1}}$, where stellar helium burning occurs.An, Z DMa, Y GFan, G TLi, Y JChen, Z PSun, Y YSat, 06 Feb 2016 06:36:51 GMT04 Feb 2016arXiv:1602.01692https://cds.cern.ch/record/2129317['arXiv:1602.01692']arXiv:1602.01692Detection of binary and multiple systems among rapidly rotating K and M dwarf stars from Kepler data
https://cds.cern.ch/record/2129254
From an examination of ~18,000 Kepler light curves of K- and M-stars we find some 500 which exhibit rotational periods of less than 2 days. Among such stars, approximately 50 show two or more incommensurate periodicities. We discuss the tools that allow us to differentiate between rotational modulation and other types of light variations, e.g., due to pulsations or binary modulations. We find that these multiple periodicities are independent of each other and likely belong to different, but physically bound, stars. This scenario was checked directly by UKIRT and adaptive optics imaging, time-resolved Fourier transforms, and pixel-level analysis of the data. Our result is potentially important for discovering young multiple stellar systems among rapidly rotating K- and M-dwarfs.Oláh, KatalinRappaport, SaulJoss, MatthewSat, 06 Feb 2016 06:32:21 GMT04 Feb 2016arXiv:1602.01713https://cds.cern.ch/record/2129254['arXiv:1602.01713']arXiv:1602.01713Very Hight Energy Observationa of Shell-Type Supernova Remnants with SHALON Mirror Cherenkov Telescopes
https://cds.cern.ch/record/2129251
The investigation of VHE gamma-ray sources by any methods, including mirror Cherenkov telescopes, touches on the problem of the cosmic ray origin and, accordingly, the role of the Galaxy in their generation. The SHALON observations have yielded the results on Galactic shell-type supernova remnants (SNR) on different evolution stages. Among them are: SNRs Tycho's SNR, Cas A, IC 443, $\gamma$Cygni SNR and classical nova GK Per (Nova 1901). For each of SNRs the observation results are presented with spectral energy distribution by SHALON in comparison with other experiment data and images by SHALON. The collected experimental data have confirmed the prediction of the theory about the hadronic generation mechanism of very high energy 800 GeV - 100 TeV $\gamma$-rays in Tycho's SNR, Cas A and IC443.Sinitsyna, Vera GSinitsyna, Vera YSat, 06 Feb 2016 06:32:21 GMT04 Feb 2016arXiv:1602.01694https://cds.cern.ch/record/2129251['arXiv:1602.01694']arXiv:1602.01694Indication of the High Mass-Transfer Ratio in S-type Symbiotic Binaries
https://cds.cern.ch/record/2129246
By modelling H$^0$ column densities in eclipsing S-type symbiotic stars EG And and SY Mus, we derived the wind velocity profile and the corresponding mass-loss rate from their giants. Our analysis revealed a strong enhancement of the wind at the orbital plane.Shagatova, NataliaSkopal, AugustinSat, 06 Feb 2016 06:32:21 GMT04 Feb 2016arXiv:1602.01668https://cds.cern.ch/record/2129246['arXiv:1602.01668']arXiv:1602.01668Slender-ribbon theory
https://cds.cern.ch/record/2128909
Ribbons are long narrow strips possessing three distinct material length scales (thickness, width, and length) which allow them to produce unique shapes unobtainable by wires or filaments. For example when a ribbon has half a twist and is bent into a circle it produces a M\"obius strip. Significant effort has gone into determining the structural shapes of ribbons but less is know about their behavior in viscous fluids. In this paper we determine, asymptotically, the leading-order hydrodynamic behavior of a slender ribbon in Stokes flows. The derivation, reminiscent of slender-body theory for filaments, assumes that the length of the ribbon is much larger than its width, which itself is much larger than its thickness. The final result is an integral equation for the force density on a mathematical ruled surface, termed the ribbon plane, located inside the ribbon. A numerical implementation of our derivation shows good agreement with the known hydrodynamics of long flat ellipsoids, and successfully captures the swimming behavior of artificial microscopic swimmers recently explored experimentally. We also study the asymptotic behavior of a ribbon bent into a helix, that of a twisted ellipsoid, and we investigate how accurately the hydrodynamics of a ribbon can be effectively captured by that of a slender filament. Our asymptotic results provide the fundamental framework necessary to predict the behavior of slender ribbons at low Reynolds numbers in a variety of biological and engineering problems.Koens, LyndonLauga, EricThu, 04 Feb 2016 07:25:21 GMT03 Feb 2016arXiv:1602.01268https://cds.cern.ch/record/2128909['arXiv:1602.01268']arXiv:1602.01268Closed form expression for the Goos-Haenchen lateral displacement
https://cds.cern.ch/record/2128903
The Artmann formula provides an accurate determination of the Goos-Haenchen lateral displacement in terms of the light wavelength, refractive index and incidence angle. In the total reflection region, this formula is widely used in the literature and confirmed by experiments. Nevertheless, for incidence at critical angle, it tends to infinity and numerical calculations are needed to reproduce the experimental data. In this paper, we overcome the divergence problem at critical angle and find, for Gaussian beams, a closed formula in terms of modified Bessel functions of the first kind. The formula is in excellent agreement with numerical calculations and reproduces, for incidence angles greater than critical ones, the Artmann formula. The closed form also allows one to understand how the breaking of symmetry in the angular distribution is responsible for the difference between measurements done by considering the maximum and the mean value of the beam intensity. The results obtained in this study clearly show the Goos-Haenchen lateral displacement dependence on the angular distribution shape of the incoming beam. Finally, we also present a brief comparison with experimental data and other analytical formulas found in the literature.Araujo, Manoel PDe Leo, StefanoMaia, Gabriel GThu, 04 Feb 2016 07:25:21 GMT03 Feb 2016arXiv:1602.01247https://cds.cern.ch/record/2128903['arXiv:1602.01247']arXiv:1602.01247Probing QED and fundamental constants through laser spectroscopy of vibrational transitions in HD+
https://cds.cern.ch/record/2128886
The simplest molecules in nature, molecular hydrogen ions in the form of H2+ and HD+, provide an important benchmark system for tests of quantum electrodynamics in complex forms of matter. Here, we report on such a test based on a frequency measurement of a vibrational overtone transition in HD+ by laser spectroscopy. We find that the theoretical and experimental frequencies are equal to within 0.6(1.1) parts per billion, which represents the most stringent test of molecular theory so far. Our measurement not only confirms the validity of high-order quantum electrodynamics in molecules, but also enables the long predicted determination of the proton-to-electron mass ratio from a molecular system, as well as improved constraints on hypothetical fifth forces and compactified higher dimensions at the molecular scale. With the perspective of comparisons between theory and experiment at the 0.01 part-per-billion level, our work demonstrates the potential of molecular hydrogen ions as a probe of fundamental physical constants and laws.Biesheuvel, JKarr, J -PhHilico, LEikema, K S EUbachs, WKoelemeij, J C JThu, 04 Feb 2016 07:25:19 GMT02 Feb 2016arXiv:1602.01048https://cds.cern.ch/record/2128886['arXiv:1602.01048']arXiv:1602.01048Kernel Architecture of the Genetic Circuitry of the Arabidopsis Circadian System
https://cds.cern.ch/record/2128854
A wide range of organisms features molecular machines, circadian clocks, which generate endogenous oscillations with ~24 h periodicity and thereby synchronize biological processes to diurnal environmental fluctuations. Recently, it has become clear that plants harbor more complex gene regulatory circuits within the core circadian clocks than other organisms, inspiring a fundamental question: are all these regulatory interactions between clock genes equally crucial for the establishment and maintenance of circadian rhythms? Our mechanistic simulation for Arabidopsis thaliana demonstrates that at least half of the total regulatory interactions must be present to express the circadian molecular profiles observed in wild-type plants. A set of those essential interactions is called herein a kernel of the circadian system. The kernel structure unbiasedly reveals four interlocked negative feedback loops contributing to circadian rhythms, and three feedback loops among them drive the autonomous oscillation itself. Strikingly, the kernel structure, as well as the whole clock circuitry, is overwhelmingly composed of inhibitory, rather than activating, interactions between genes. We found that this tendency underlies plant circadian molecular profiles which often exhibit sharply-shaped, cuspidate waveforms. Through the generation of these cuspidate profiles, inhibitory interactions may facilitate the global coordination of temporally-distant clock events that are markedly peaked at very specific times of day. Our systematic approach resulting in experimentally-testable predictions provides insights into a design principle of biological clockwork, with implications for synthetic biology.Foo, MathiasSomers, David EKim, Pan-JunThu, 04 Feb 2016 07:25:16 GMT01 Feb 2016arXiv:1602.00776https://cds.cern.ch/record/2128854['arXiv:1602.00776']arXiv:1602.00776Low-frequency electromagnetic field in a Wigner crystal
https://cds.cern.ch/record/2128849
Long-wave low-frequency oscillations are described in a Wigner crystal by generalization of the reverse continuum model for the case of electronic lattice. The internal self-consistent long-wave electromagnetic field is used to describe the collective motions in the system. The eigenvectors and eigenvalues of the obtained system of equations are derived. The velocities of longitudinal and transversal sound waves are found.Stupka, AntonThu, 04 Feb 2016 07:25:15 GMT29 Jan 2016arXiv:1602.00718https://cds.cern.ch/record/2128849['arXiv:1602.00718']arXiv:1602.00718Focusing of world-lines in Weyl gravity
https://cds.cern.ch/record/2128742
We study the evolution of time-like congruences in the vacuum solutions of Weyl conformal theory of gravity. Using the Raycaudhuri equation, we show that for positive values of the coeffcient of the linear term in the solution and in the absence of the cosmological constant, the incoming rays converge. The evolution of the congruence for negative values is investigated for different values of the parameters. The behavior of the congruence under conformal transformations is also studied.Mohseni, MortezaFathi, MohsenThu, 04 Feb 2016 07:18:45 GMT02 Feb 2016arXiv:1602.01043https://cds.cern.ch/record/2128742['arXiv:1602.01043']arXiv:1602.01043A Numerical Model for Accretion in Intermediate Polars with Dipolar Magnetic Fields
https://cds.cern.ch/record/2128719
A three-dimensional numerical model for an accretion process investigation in the magnetosphere of a white dwarf in magnetic cataclysmic variables is developed. The model assumes that the white dwarf has a dipole magnetic field with its symmetry axis inclined to the rotation axis. The model is based on the equations of modified MHD, that describe the mean flow parameters in the wave MHD turbulence. Diffusion of the magnetic field and radiative heating and cooling are taken into account. The suitability of the model is confirmed by modeling the accretion in a typical intermediate polar. The computations show that a magnetosphere forms around the accretor, with the accretion occurring via columns. The accretion columns have a curtain-like shape, and arc-shaped zones of energy release form on the surface of the white dwarf in the magnetic poles area as a result of the matter infall.Isakova, P BZhilkin, A GBisikalo, D VThu, 04 Feb 2016 07:15:31 GMT03 Feb 2016arXiv:1602.01315https://cds.cern.ch/record/2128719['arXiv:1602.01315']arXiv:1602.01315Eta Carinae's Thermal X-ray Tail Measured with XMM-Newton and NuSTAR
https://cds.cern.ch/record/2128706
The evolved, massive highly eccentric binary system, eta Carinae, underwent a periastron passage in the summer of 2014. We obtained two coordinated X-ray observations with XMM-Newton and NuSTAR during the elevated X-ray flux state and just before the X-ray minimum flux state around this passage. These NuSTAR observations clearly detected X-ray emission associated with eta Car extending up to ~50 keV for the first time. The NuSTAR spectrum above 10 keV can be fit with the bremsstrahlung tail from a kT ~6 keV plasma. This temperature is Delta kT ~2 keV higher than those measured from the iron K emission line complex, if the shocked gas is in collisional ionization equilibrium. This result may suggest that the companion star's pre-shock wind velocity is underestimated. The NuSTAR observation near the X-ray minimum state showed a gradual decline in the X-ray emission by 40% at energies above 5 keV in a day, the largest rate of change of the X-ray flux yet observed in individual eta Car observations. The column density to the hardest emission component, NH ~1e24 cm-2, marked one of the highest values ever observed for eta Car, strongly suggesting increased obscuration of the wind-wind colliding X-ray emission by the thick primary stellar wind prior to superior conjunction. Neither observation detected the power-law component in the extremely hard band that INTEGRAL and Suzaku observed prior to 2011. If the non-detection by NuSTAR is caused by absorption, the power-law source must be small and located very near the WWC apex. Alternatively, it may be that the power-law source is not related to either eta Car or the GeV gamma-ray source.Hamaguchi, KenjiCorcoran, Michael FGull, Theodore RTakahashi, HiromitsuGrefenstette, Brian WYuasa, TakayukiStuhlinger, MartinRussell, Christopher M PMoffat, Anthony F JSharma, NeetikaMadura, Thomas IRichardson, Noel DGroh, JosePittard, Julian MOwocki, StanleyThu, 04 Feb 2016 07:15:29 GMT02 Feb 2016arXiv:1602.01148https://cds.cern.ch/record/2128706['arXiv:1602.01148']arXiv:1602.01148Gravitation Field Dynamics in Jeans Theory
https://cds.cern.ch/record/2128680
Closed system of time equations for nonrelativistic gravitation field and hydrodynamic medium was obtained by taking into account binary correlations of the field, which is the generalization of Jeans theory. Distribution function of the systemwas built on the basis of the Bogolyubov reduced description method. Calculations were carried out up to the first order of a perturbation theory in interaction. Adiabatic and enthropic types of perturbations were corrected and two new types of perturbations were found.Stupka, A AThu, 04 Feb 2016 07:15:25 GMT02 Feb 2016arXiv:1602.01041https://cds.cern.ch/record/2128680['arXiv:1602.01041']arXiv:1602.01041Relativistic Signatures at the Galactic Center
https://cds.cern.ch/record/2128656
Studies of the inner few parsecs at the Galactic Centre provide evidence of a supermassive black hole, associated with the unusual, variable radio and infrared source Sgr A*. Our major aim is the study and analysis of the physical processes responsible for the variable emission from the compact radio source Sgr A*. In order to understand the physics behind the observed variability, we model the time evolution of the flare emitting region by studying light curves and spectra of emission originating at the surface of the accretion disk, close to the event horizon, near the marginally stable orbit of a rotating black hole. Here we discuss the methods used in the analysis of the time-variable spectral features and subsequently present preliminary modeling results.Howard, E MThu, 04 Feb 2016 07:15:20 GMT02 Feb 2016arXiv:1602.00818https://cds.cern.ch/record/2128656['arXiv:1602.00818']arXiv:1602.00818Les composantes obscures de l'Univers
https://cds.cern.ch/record/2128644
This article is the detailed version of a paper on dark matter, dark energy, and modified gravity, published in the December 2015-January 2016 special issue of "La Recherche" (in French)Blanchet, LucFamaey, BenoitThu, 04 Feb 2016 07:15:16 GMT01 Feb 2016arXiv:1602.00711https://cds.cern.ch/record/2128644['arXiv:1602.00711']arXiv:1602.00711Qualitative evolution in f(R) cosmologies
https://cds.cern.ch/record/2128632
We investigate the qualitative evolution of (D+1)-dimensional cosmological models in f(R) gravity for the general case of the function f(R). The analysis is specified for various examples, including the (D+1)-dimensional generalization of the Starobinsky model, models with polynomial and exponential functions. The cosmological dynamics are compared in the Einstein and Jordan representations of the corresponding scalar-tensor theory. The features of the cosmological evolution are discussed for Einstein frame potentials taking negative values in certain regions of the field space.Avagyan, R MChubaryan, E VHarutyunyan, G HSaharian, A AThu, 04 Feb 2016 07:15:11 GMT01 Feb 2016arXiv:1602.00685https://cds.cern.ch/record/2128632['arXiv:1602.00685']arXiv:1602.00685Hidden beauty in $N$ = 4 supersymmetric Gauge theory
https://cds.cern.ch/record/2128592
Sokatchev, EWed, 03 Feb 2016 15:04:42 GMThttps://cds.cern.ch/record/2128592['']Composite weak Bosons at the LHC
https://cds.cern.ch/record/2128588
Fritzsch, HaraldWed, 03 Feb 2016 14:53:11 GMThttps://cds.cern.ch/record/2128588['']Electric-magnetic duality and supersymmetry
https://cds.cern.ch/record/2128564
Ferrara, SergioMarrani, AlessioAschieri, PaoloWed, 03 Feb 2016 14:36:45 GMThttps://cds.cern.ch/record/2128564['']The Pandora Software Development Kit for Pattern Recognition
https://cds.cern.ch/record/2128422
The development of automated solutions to pattern recognition problems is important in many areas of scientific research and human endeavour. This paper describes the implementation of the Pandora Software Development Kit, which aids the process of designing, implementing and
running pattern recognition algorithms. The Pandora Application Programming Interfaces ensure simple specification of the building-blocks defining a pattern recognition problem. The logic required to solve the problem is implemented in algorithms. The algorithms request operations to create or modify data structures and the operations are performed by the Pandora framework. This design promotes an approach using many decoupled algorithms, each addressing specific topologies. Details of algorithms addressing two pattern recognition problems in High Energy Physics are presented: reconstruction of events at a high-energy e+e- linear collider and reconstruction of cosmic ray or neutrino events in a liquid argon time projection chamber.Marshall, J. S.Thomson, M. A.Tue, 02 Feb 2016 10:45:22 GMT2015-09-18AIDA-2020-PUB-2015-001https://cds.cern.ch/record/21284222015001Emergence of core-peripheries in networks
https://cds.cern.ch/record/2128389
A number of important transport networks, such as the airline and trade networks of the world, exhibit a characteristic core-periphery structure, wherein a few nodes are highly interconnected and the rest of the network frays into a tree. Mechanisms underlying the emergence of core-peripheries, however, remain elusive. Here, we demonstrate that a simple pruning process based on removal of underutilized links and redistribution of loads can lead to the emergence of core-peripheries. Links are assumed beneficial if they either carry a sufficiently large load or are essential for global connectivity. This incentivized redistribution process is controlled by a single parameter which balances connectivity and profit. The obtained networks exhibit a highly resilient and connected core with a frayed periphery. The balanced network shows a higher resilience than the World Airline Network or the World Trade Network, revealing a pathway towards robust structural features through pruning.Verma, TRussmann, FAraújo, N A MNagler, JHerrmann, H JTue, 02 Feb 2016 06:38:46 GMT01 Feb 2016arXiv:1602.00667https://cds.cern.ch/record/2128389['arXiv:1602.00667']arXiv:1602.00667Dynamical prediction of flu seasonality driven by ambient temperature: influenza vs. common cold
https://cds.cern.ch/record/2128369
This work presents a comparative analysis of Influenzanet data for influenza itself and common cold in the Netherlands during the last 5 years, from the point of view of modelling by linearised SIRS equations parametrically driven by the ambient temperature. It is argued that this approach allows for the forecast of common cold, but not of influenza in a strict sense. The difference in their kinetic models is discussed with reference to the clinical background.Postnikov, Eugene BTue, 02 Feb 2016 06:38:43 GMT01 Feb 2016arXiv:1602.00536https://cds.cern.ch/record/2128369['arXiv:1602.00536']arXiv:1602.00536LES of the Sandia Flame D Using an FPV Combustion Model
https://cds.cern.ch/record/2128368
The simulation of turbulent combustion phenomena is still an open problem in modern fluid dynamics. Considering the economical importance of hydrocarbon combustion in energy production processes, it is evident the need of an accurate tool with a relatively low computational cost for the prediction of this kind of reacting flows. In the present work, a comparative study is carried out among large eddy simulations, performed with various grid resolutions, a Reynolds averaged Navier-Stokes simulation, and experimental data concerning the well-known Sandia D flame test case. In all the simulations, a flamelet progress variable model has been employed using various hypotheses for the joint probability density function closure. The filtered approach proved to be more accurate than the averaged one, even for the coarser grid used in this work. In fact both approaches have shown poorly accurate predictions in the first part of the combustion chamber, but only by the large eddy simulation one is capable to recover the inlet discrepancies with respect to the experimental data going along the streamwise direction.Di Renzo, MarioCoclite, Alessandrode Tullio, Marco DonatoDe Palma, PietroPascazio, GiuseppeTue, 02 Feb 2016 06:38:43 GMT01 Feb 2016arXiv:1602.00535https://cds.cern.ch/record/2128368['arXiv:1602.00535']arXiv:1602.00535