CERN Document Server
https://cds.cern.ch
CERN Document Server latest documentsenSat, 30 Apr 2016 11:15:38 GMTInvenio 1.1.3.1106-62468cds.support@cern.ch3601273495125https://cds.cern.ch/img/site_logo_rss.pngCERN Document Server
https://cds.cern.ch
Search Search this site:p
https://cds.cern.ch/search
Available free energy under local phase space diffusion
https://cds.cern.ch/record/2149594
The free energy associated with the birth distribution of alpha particles in DT fusion reactors is an enormous resource that can be tapped with waves. An interesting academic question is the maximum energy that can be extracted from the alpha particle birth distribution in the quasilinear (diffusive) limit of wave-particle interaction. In the nonlocal problem, particles may be diffused from high energy to any lower energy; in the local diffusion problem, particles may only be diffused to incrementally smaller energies. It is shown that the discrete version of the nonlocal problem corresponds to diffusion on the complete graph $K_n$, whereas the local problem is a solvable case defined on the path graph $P_n$. We further discuss the extension of the solution to arbitrary subgraphs of $K_n$.Hay, M JSchiff, JFisch, N JSat, 30 Apr 2016 06:39:22 GMT28 Apr 2016arXiv:1604.08573https://cds.cern.ch/record/2149594['arXiv:1604.08573']arXiv:1604.08573Stored energies for electric and magnetic current densities
https://cds.cern.ch/record/2149593
Electric and magnetic current densities are an essential part of electromagnetic theory. The goal of the present paper is to define and investigate stored energies that are valid for structures that can support both electric and magnetic current densities. Stored energies normalized with the dissipated power give us the Q factor, or antenna Q, for the structure. Lower bounds of the Q factor provide information about the available bandwidth for passive antennas that can be realized in the structure. The definition that we propose is valid beyond the leading order small antenna limit. Our starting point is the energy density with subtracted far-field form which we obtain an explicit and numerically attractive current density representation. This representation gives us the insight to propose a coordinate independent stored energy. Furthermore, we find here that lower bounds on antenna Q for structures with e.g. electric dipole radiation can be formulated as convex optimization problems. We determine lower bounds on both open and closed surfaces that support electric and magnetic current densities. The here derived representation of stored energies has in its electrical small limit an associated Q factor that agrees with known small antenna bounds. These stored energies have similarities to earlier efforts to define stored energies. However, one of the advantages with this method is the above mentioned formulation as convex optimization problems, which makes it easy to predict lower bounds for antennas of arbitrary shapes. The present formulation also gives us insight into the components that contribute to Chu's lower bound for spherical shapes. We utilize scalar and vector potentials to obtain a compact direct derivation of these stored energies. Examples and comparisons end the paper.Jonsson, B L GGustafsson, MatsSat, 30 Apr 2016 06:39:22 GMT28 Apr 2016arXiv:1604.08572https://cds.cern.ch/record/2149593['arXiv:1604.08572']arXiv:1604.08572Single Particle Dynamics in a Quasi-Integrable Nonlinear Accelerator Lattice
https://cds.cern.ch/record/2149592
Fermilab is constructing the Integrable Optics Test Accelerator (IOTA) as the centerpiece of the Accelerator R&D; Program towards high-intensity circular machines. One of the factors limiting the beam intensity in present circular accelerators is collective instabilities, which can be suppressed by a spread of betatron frequencies (tunes) through the Landau damping mechanism or by an external damper, if the instability is slow enough. The spread is usually created by octupole magnets, which introduce the tune dependence on the amplitude and, in some cases, by a chromatic spread (tune dependence on particle's momentum). The introduction of octupoles usually lead to a resonant behavior and a reduction of the dynamic aperture. One of the goals of the IOTA research program is to achieve a high betatron tune spread, while retaining a large dynamic aperture using conventional octupole magnets in a special but realistic accelerator configuration. In this report, we present results of computer simulations of an electron beam in the IOTA by particle tracking and the Frequency Map Analysis. The results show that the ring's octupole magnets can be configured to provide a betatron tune shift of 0.08 (for particles at large amplitudes) with the dynamical aperture of over 20 beam sigma for a 150-MeV electron beam. The influence of the synchrotron motion, lattice errors, and magnet imperfections is insignificant for the parameters and levels of tolerances set by the design of the ring. The described octupole insert could be beneficial for suppression of space-charge induced instabilities in high intensity machines.Antipov, Sergey ANagaitsev, SergeiValishev, AlexanderSat, 30 Apr 2016 06:39:22 GMT28 Apr 2016arXiv:1604.08565https://cds.cern.ch/record/2149592['arXiv:1604.08565']arXiv:1604.08565Generalized Fick Jacobs Approach for describing Adsorption Desorption Kinetics in Irregular Pores under Non Equilibrium Conditions
https://cds.cern.ch/record/2149591
We present a study exploring the range of applicability of a generalized Fick Jacobs equation in the case when diffusive mass transport of a fluid along a pore includes chemical reactions in the bulk and pore surface. The study contemplates nonequilibrium boundary conditions and makes emphasis on the comparison between the predictions coming from the projected Fick Jacobs description and the corresponding predictions of the original two dimensional mass balance equation, establishing a simple cuantitative criterion of validity of the projected description. For the adsorption desorption process, we demonstrate that the length and the local curvature of the pore are the relevant geometric quantities for its description, allowing for giving very precise predictions of the mass concentration along the pore. Some schematic cases involving adsorption and chemical reaction are used to quantify with detail the concentration profiles in transient and stationary states involving equilibrium and nonequilibrium situations. Our approach provides novel and important insights in the study of diffusion and adsorption in confined geometries.Ledesma-Durán, AldoHernández-Hernández, Saúl IvánSantamaría-Holek, IvánSat, 30 Apr 2016 06:39:22 GMT28 Apr 2016arXiv:1604.08549https://cds.cern.ch/record/2149591['arXiv:1604.08549']arXiv:1604.08549Numerical methods for interface coupling of compressible and almost incompressible media
https://cds.cern.ch/record/2149590
Many experiments in biomedical applications and other disciplines use a shock tube. These experiments often involve placing an experimental sample within a fluid-filled container, which is then placed inside the shock tube. The shock tube produces an initial shock that propagates through gas before hitting the container with the sample. In order to gain insight into the shock dynamics that is hard to obtain by experimental means, computational simulations of the shock wave passing from gas into a thin elastic solid and into a nearly incompressible fluid are developed. It is shown that if the solid interface is very thin, it can be neglected, simplifying the model. The model uses Euler equations for compressible fluids coupled with a Tammann equation of state (EOS) to model both compressible gas and almost incompressible materials. A three-dimensional (2D axisymmetric) model of these equations is solved using high-resolution shock-capturing methods, with newly developed Riemann solvers and limiters. The methods are extended to work on a mapped grid to allow more complicated interface geometry, and they are adapted to work with adaptive mesh refinement (AMR) for higher resolution and faster computations. The Clawpack software is used to implement the method. These methods were initially inspired by shock tube experiments to study the injury mechanisms of traumatic brain injury (TBI).Del Razo, Mauricio JLeVeque, Randall JSat, 30 Apr 2016 06:39:22 GMT28 Apr 2016arXiv:1604.08544https://cds.cern.ch/record/2149590['arXiv:1604.08544']arXiv:1604.08544Calculation of differential cross section for dielectronic recombination with two-electron uranium
https://cds.cern.ch/record/2149589
Calculation of the differential cross section for the dielectronic recombination with two-electron uranium within the framework of QED is presented. The polarization of the emitted photon is investigated. The contributions of the Breit interaction and the interference of the photon multipoles are studied.Lyashchenko, Konstantin NAndreev, Oleg YuSat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08541https://cds.cern.ch/record/2149589['arXiv:1604.08541']arXiv:1604.08541Rydberg atom mediated non-destructive readout of collective rotational states in polar molecule arrays
https://cds.cern.ch/record/2149588
We analyze in detail the possibility to use charge-dipole interaction between a single polar molecule or a 1D molecular array and a single Rydberg atom to read out rotational populations. The change in the Rydberg electron energy is conditioned on the rotational state of the polar molecules, allowing for realization of a CNOT quantum gate between the molecules and the atom. Subsequent readout of the atomic fluorescence results in a non-destructive measurement of the rotational state. We study the interaction between a 1D array of polar molecules and an array or a cloud of atoms in a Rydberg superatom (blockaded) state and calculate the resolved energy shifts of Rb(60s) with KRb and RbYb molecules, with N=1, 3, 5 molecules. We show that collective molecular rotational states can be read out using the conditioned Rydberg energy shifts.Kuznetsova, ElenaRittenhouse, Seth TSadeghpour, H RYelin, Susanne FSat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08535https://cds.cern.ch/record/2149588['arXiv:1604.08535']arXiv:1604.08535A Modest View of Bell's Theorem
https://cds.cern.ch/record/2149587
In the 80 years since the seminal Einstein, Podolsky, and Rosen (EPR) paper, physicists and philosophers have mused about the `spooky action at a distance' aspect of quantum mechanics that so bothered Einstein. In his formal analysis of EPR-type entangled quantum states, Bell (1964) concluded that any hidden variable theory designed to reproduce the predictions of quantum mechanics must necessarily be nonlocal and allow superluminal interactions. This doesn't immediately imply that nonlocality is a characteristic feature of quantum mechanics let alone a fundamental property of nature; however, many physicists and philosophers of science do harbor this belief. Experts in the field often use the term `nonlocality' to designate particular non-classical aspects of quantum entanglement and do not confuse the term with superluminal interactions. However, many physicists seem to take the term more literally. I endeavor to disabuse the latter of this notion by emphasizing that the correlations of Bell-type entanglement are a result of ordinary quantum superposition with no need to introduce nonlocality. The conclusion of the EPR paper wasn't that quantum mechanics is nonlocal but rather that it is an incomplete description of reality. For different reasons, many physicists, including me, agree with Einstein that quantum mechanics is necessarily an incomplete description of reality.Boughn, StephenSat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08529https://cds.cern.ch/record/2149587['arXiv:1604.08529']arXiv:1604.08529The local dayside reconnection rate for oblique interplanetary magnetic fields
https://cds.cern.ch/record/2149586
We present an analysis of local properties of magnetic reconnection at the dayside magnetopause for various interplanetary magnetic field (IMF) orientations in global magnetospheric simulations. This has heretofore not been practical because it is difficult to locate where reconnection occurs for oblique IMF, but new techniques make this possible. The approach is to identify magnetic separators, the curves separating four regions of differing magnetic topology, which map the reconnection X-line. The electric field parallel to the X-line is the local reconnection rate. We compare results to a simple model of local two-dimensional asymmetric reconnection. To do so, we find the plasma parameters that locally drive reconnection in the magnetosheath and magnetosphere in planes perpendicular to the X-line at a large number of points along the X-line. The global magnetohydrodynamic simulations are from the three-dimensional Block-Adaptive, Tree Solarwind Roe-type Upwind Scheme (BATS-R-US) code with a uniform resistivity, although the techniques described here are extensible to any global magnetospheric simulation model. We find that the predicted local reconnection rates scale well with the measured values for all simulations, being nearly exact for due southward IMF. However, the absolute predictions differ by an undetermined constant of proportionality, whose magnitude increases as the IMF clock angle changes from southward to northward. We also show similar scaling agreement in a simulation with oblique southward IMF and a dipole tilt. The present results will be an important component of a full understanding of the local and global properties of dayside reconnection.Komar, Colin MCassak, Paul ASat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08528https://cds.cern.ch/record/2149586['arXiv:1604.08528']arXiv:1604.08528Bounds for convection between rough boundaries
https://cds.cern.ch/record/2149585
We consider Rayleigh-B\'enard convection in a layer of fluid between no-slip rough boundaries, where the top and bottom boundary heights are functions of the horizontal coordinates with bounded gradients. We use the background method to derive an upper bound on mean heat flux across the layer for all admissible boundary geometries. This flux, normalized by the temperature difference between the boundaries, can grow with the Rayleigh number ($Ra$) no faster than $Ra^{1/2}$ as $Ra \rightarrow \infty$. Coefficients of the bound are given explicitly in terms of the geometry, and evaluation of the coefficients is illustrated for sinusoidal boundaries.Goluskin, DavidDoering, Charles RSat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08515https://cds.cern.ch/record/2149585['arXiv:1604.08515']arXiv:1604.08515Numerical assessments of ocean energy extraction from western boundary currents using a quasi-geostrophic ocean circulation model
https://cds.cern.ch/record/2149584
A single-layer, quasi-geostrophic (QG), large-scale ocean circulation model is developed in this paper to study available ocean current energy potentials harnessed by using the ocean current turbines. Power extraction is modeled by adding a parameterized Rayleigh friction term in the barotropic vorticity equation. Numerical assessments are performed by simulating a set of mid-latitude ocean basins in the beta plane, which are standard prototypes of more realistic ocean dynamics considering inter-decadal variability in turbulent equilibrium. A sensitivity analysis with respect to the turbine parameters is performed for various physical conditions. Results show that the proposed model captures the quasi-stationary ocean dynamics and provides the four-gyre circulation patterns in time mean. After an initial spin-up process, the proposed model reaches a statistically steady state at an average maximum speed between 1.5 m/s and 2.5 m/s, which is close to the observed maximum zonal velocities in the western boundary currents. The probability density function of the available power over a long time period is computed for a wide range of parameters. Numerical results shows that 10 GW mean power can be extracted from the turbines distributed over a length scale of 100 km along the western boundaries. However, it is demonstrated that bigger turbine areas would alter the flow patterns and energetics due to excessive dissipation. An increase in the turbine area results in an increase in the available power ranging from 8 to 22 GW depending on the values of turbine modeling parameters. This first step in the numerical assessment of the proposed QG model shows that the present framework could represent a viable tool for evaluating energy potentials in a highly turbulent flow regime.San, OmerSat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08486https://cds.cern.ch/record/2149584['arXiv:1604.08486']arXiv:1604.08486Comparison of Coherent Smith-Purcell radiation and Coherent Transition Radiation
https://cds.cern.ch/record/2149583
Smith-Purcell radiation and Transition Radiation are two radiative phenomenon that occur in charged particles accelerators. For both the emission can be significantly enhanced with sufficiently short pulses and both can be used to measure the form factor of the pulse. We compare the yield of these phenomenon in different configurations and look at their application as bunch length monitors, including background filtering and rejection. We apply these calculations to the specific case of the CLIO Free Electron laser.Khodnevych, VitaliiDelerue, NicolasBezshyyko, OlegSat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08474https://cds.cern.ch/record/2149583['arXiv:1604.08474']arXiv:1604.08474Solution of the square lid-driven cavity flow of a Bingham plastic using the finite volume method
https://cds.cern.ch/record/2149582
We investigate the performance of the finite volume method in solving viscoplastic flows. The creeping square lid-driven cavity flow of a Bingham plastic is chosen as the test case and the constitutive equation is regularised as proposed by Papanastasiou [J. Rheol. 31 (1987) 385-404]. It is shown that the convergence rate of the standard SIMPLE pressure-correction algorithm, which is used to solve the algebraic equation system that is produced by the finite volume discretisation, severely deteriorates as the Bingham number increases, with a corresponding increase in the non-linearity of the equations. It is shown that using the SIMPLE algorithm in a multigrid context dramatically improves convergence, although the multigrid convergence rates are much worse than for Newtonian flows. The numerical results obtained for Bingham numbers as high as 1000 compare favourably with reported results of other methods.Syrakos, AlexandrosGeorgiou, Georgios CAlexandrou, Andreas NSat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08461https://cds.cern.ch/record/2149582['arXiv:1604.08461']arXiv:1604.08461Study of Short Bunches at the Free Electron Laser CLIO
https://cds.cern.ch/record/2149581
CLIO is a Free Electron Laser based on a thermionic electron gun. In its normal operating mode it delivers electron 8 pulses but studies are ongoing to shorten the pulses to about 1 ps. We report on simulations showing how the pulse can be shortened and the expected signal yield from several bunch length diagnostics (Coherent Transition Radiation, Coherent Smith Purcell Radiation).Delerue, NicolasJenzer, StéphaneKhodnevych, VitaliiBerthet, Jean-PaulGlotin, FrancoisOrtega, Jean-MichelPrazeres, RuiSat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08458https://cds.cern.ch/record/2149581['arXiv:1604.08458']arXiv:1604.08458Monte Carlo model for electron degradation in xenon gas
https://cds.cern.ch/record/2149580
We have developed a Monte Carlo model for studying the local degradation of electrons in the energy range 9-10000 eV in xenon gas. Analytically fitted form of electron impact cross sections for elastic and various inelastic processes are fed as input data to the model. Two dimensional numerical yield spectrum, which gives information on the number of energy loss events occurring in a particular energy interval, is obtained as output of the model. Numerical yield spectrum is fitted analytically, thus obtaining analytical yield spectrum. The analytical yield spectrum can be used to calculate electron fluxes, which can be further employed for the calculation of volume production rates. Using yield spectrum, mean energy per ion pair and efficiencies of inelastic processes are calculated. The value for mean energy per ion pair for Xe is 22 eV at 10 keV. Ionization dominates for incident energies greater than 50 eV and is found to have an efficiency of 65% at 10 keV. The efficiency for the excitation process is 30% at 10 keV.Mukundan, VrindaBhardwaj, AnilSat, 30 Apr 2016 06:39:21 GMT12 Mar 2016arXiv:1604.08449https://cds.cern.ch/record/2149580['arXiv:1604.08449']arXiv:1604.08449Generation of topologically diverse acoustic vortex beams using a compact metamaterial aperture
https://cds.cern.ch/record/2149579
Vortex waves, which carry orbital angular momentum, have found use in a range of fields from quantum communications to particle manipulation. Due to their widespread influence, significant attention has been paid to the methods by which vortex waves are generated. For example, active phased arrays generate diverse vortex modes at the cost of electronic complexity and power consumption. Conversely, analog apertures, such as spiral phase plates, metasurfaces, and gratings require separate apertures to generate each mode. Here we present a new class of metamaterial-based acoustic vortex generators, which are both geometrically and electronically simple, and topologically tunable. Our metamaterial approach generates vortex waves by wrapping an acoustic leaky wave antenna back upon itself. Exploiting the antennas frequency-varying refractive index, we demonstrate experimentally and analytically that this analog structure generates both integer, and non-integer vortex modes. The metamaterial design makes the aperture compact and can thus be integrated into high-density systems.Naify, Christina JRohde, Charles AMartin, Theodore PNicholas, MichaelGuild, Matthew DOrris, Gregory JSat, 30 Apr 2016 06:39:21 GMT05 Apr 2016arXiv:1604.08447https://cds.cern.ch/record/2149579['arXiv:1604.08447']arXiv:1604.08447On the hyperfine structures of the ground state(s) in the ${}^{6}$Li and ${}^{7}$Li atoms
https://cds.cern.ch/record/2149578
Hyperfine structure of the ground $2^{2}S-$states of the three-electron atoms and ions is investigated. By using our recent numerical values for the doublet electron density at the atomic nucleus we determine the hyperfine structure of the ground (doublet) $2^{2}S-$state(s) in the ${}^{6}$Li and ${}^{7}$Li atoms.Frolov, Alexei MSat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08436https://cds.cern.ch/record/2149578['arXiv:1604.08436']arXiv:1604.08436Crowdsourcing the Robin Hood effect in cities
https://cds.cern.ch/record/2149577
Socioeconomic inequalities in cities are embedded in space and result in neighborhood effects, whose harmful consequences have proved very hard to counterbalance efficiently by planning policies alone. Considering redistribution of money flows as a first step toward improved spatial equity, we study a bottom-up approach that would rely on a slight evolution of shopping mobility practices. Building on a database of anonymized credit card transactions in Madrid and Barcelona, we quantify the mobility effort required to reach a reference situation where commercial income is evenly shared among neighborhoods. The redirections of shopping trips preserve key properties of human mobility, including travel distances. Surprisingly, for both cities only a small fraction ($\sim 5 \%$) of trips need to be altered to reach equity situations, improving even other sustainability indicators. The method could be implemented in mobile applications that would assist individuals in reshaping their shopping practices, to promote the spatial redistribution of opportunities in the city.Louail, ThomasLenormand, MaximeArias, Juan MurilloRamasco, José JSat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08394https://cds.cern.ch/record/2149577['arXiv:1604.08394']arXiv:1604.08394Judo Biomechanical Optimization
https://cds.cern.ch/record/2149576
In this paper, for the first time, there is comprehensively tackling the problem of biomechanical optimization of a sport of situation such as judo. Starting from the optimization of more simple sports, optimization of this kind of complex sports is grounded on a general physics tool such as the analysis of variation. The objective function is divided for static and dynamic situation of Athletes couple, and it is proposed also a sort of dynamic programming problem Strategic Optimization. A dynamic programming problem is an optimization problem in which decisions have to be taken sequentially over several time periods linked in some fashion. A strategy for a dynamic programming problem is just a contingency plan, a plan that specifies what is to be done at each stage as a function of all that has transpired up to that point. It is possible to demonstrate, under some conditions, that a Markovian optimal strategy is an optimal strategy for the dynamic programming problem under examination. At last we try to approach the optimization of couple of athletes motion. Shifting s Trajectories study is a very hard and complex work, because falls among fractal, self similar trajectories produced by Chaotic, irregular, Dynamics. It is possible to Optimize Athletes motion planning. Motion planning could be defined as the problem of finding a collision free trajectory from the start configuration to the goal configuration. It is possible to treat motion as an optimization problem, to search the trajectory that drive adversary into a final broken symmetry position, where it is possible to collide and apply one of the two throwing tools: Couple or Lever.Sacripanti, AttilioSat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08390https://cds.cern.ch/record/2149576['arXiv:1604.08390']arXiv:1604.08390Floquet-Weyl and Floquet-topological-insulator phases in a stacked two-dimensional ring-network lattice
https://cds.cern.ch/record/2149575
We show the presence of Floquet-Weyl and Floquet-topological-insulator phases in a stacked two-dimensional ring-network lattice. The Weyl points in the three-dimensional Brillouin zone and Fermi-arc surface states are clearly demonstrated in the quasienergy spectrum of the system in the Weyl phase. In addition, chiral surface states coexist in this phase. The Floquet-topological-insulator phase is characterized by the winding number of two in the reflection matrices of the semi-infinite system and resulting two gapless surface states in the quasienergy g ap of the bulk. The phase diagram of the system is derived in the two-parameter space of hopping S-matrices among the rings. We also discuss a possible optical realization of the system together with the introduction of synthetic gauge fields.Ochiai, TetsuyukiSat, 30 Apr 2016 06:39:21 GMT28 Apr 2016arXiv:1604.08368https://cds.cern.ch/record/2149575['arXiv:1604.08368']arXiv:1604.08368Angular momentum and topological dependence of Kepler's Third Law in the Broucke-Hadjidemetriou-H\'enon family of periodic three-body orbits
https://cds.cern.ch/record/2149574
We use 57 recently found topological satellites of Broucke-Hadjidemetriou-Henon's periodic orbits with values of the topological exponent $k$ ranging from $k$ = 3 to $k$ = 58 to plot the angular momentum $L$ as a function of the period $T$, with both $L$ and $T$ rescaled to energy $E=-\frac12$. Upon plotting $L(T/k)$ we find that all our solutions fall on a curve that is virtually indiscernible by naked eye from the $L(T)$ curve for non-satellite solutions. The standard deviation of the satellite data from the sixth-order polynomial fit to the progenitor data is $\sigma = 0.13$. This regularity supports Henon's 1976 conjecture that the linearly stable Broucke-Hadjidemetriou-Henon orbits are also perpetually, or Kolmogorov-Arnold-Moser stable.Janković, Marija RDmitrašinović, VeljkoSat, 30 Apr 2016 06:39:20 GMT28 Apr 2016arXiv:1604.08358https://cds.cern.ch/record/2149574['arXiv:1604.08358']arXiv:1604.08358Characterization of specific nuclear reaction channels by deconvolution in the energy space of the total nuclear cross-section of protons - applications to proton therapy and technical problems
https://cds.cern.ch/record/2149573
The total nuclear cross-section Qtot(E) resulting from the interaction of protons with nuclei is decomposed in 3 different contributions: 1. elastic scatter at the complete nucleus, which adopts a part of the proton kinetic energy; 2. inelastic scatter at a nucleus, which changes its quantum numbers by vibrations, rotations, transition to highly excited states; 3. proper nuclear reactions with change of the mass and/or charge number. Then different particles leave the hit nucleus (neutrons, protons, etc.), which is now referred to as 'heavy recoil' nucleus. The scatter parts of Qtot(E) according to points 1 and 2 can be removed by a deconvolution acting at Qtot(E) in the energy space. The typical nuclear reaction channels are mainly characterized by resonances of a reduced cross-section function Qred(E). The procedure is applied to cross-sections of therapeutic protons and also to Cs55137 as an example with technical relevance (transmutations with the goal to drastically reduce its half-time).Ulmer, WSat, 30 Apr 2016 06:39:20 GMT28 Apr 2016arXiv:1604.08356https://cds.cern.ch/record/2149573['arXiv:1604.08356']arXiv:1604.08356Inferring interaction partners from protein sequences
https://cds.cern.ch/record/2149572
Specific protein-protein interactions are crucial in the cell, both to ensure the formation and stability of multi-protein complexes, and to enable signal transduction in various pathways. Functional interactions between proteins result in coevolution between the interaction partners. Hence, the sequences of interacting partners are correlated. Here we exploit these correlations to accurately identify which proteins are specific interaction partners from sequence data alone. Our general approach, which employs a pairwise maximum entropy model to infer direct couplings between residues, has been successfully used to predict the three-dimensional structures of proteins from sequences. Building on this approach, we introduce an iterative algorithm to predict specific interaction partners from among the members of two protein families. We assess the algorithm's performance on histidine kinases and response regulators from bacterial two-component signaling systems. The algorithm proves successful without any a priori knowledge of interaction partners, yielding a striking 0.93 true positive fraction on our complete dataset, and we uncover the origin of this surprising success. Finally, we discuss how our method could be used to predict novel protein-protein interactions.Bitbol, Anne-FlorenceDwyer, Robert SColwell, Lucy JWingreen, Ned SSat, 30 Apr 2016 06:39:20 GMT28 Apr 2016arXiv:1604.08354https://cds.cern.ch/record/2149572['arXiv:1604.08354']arXiv:1604.08354Formation of high-order acoustic Bessel beams by spiral diffraction gratings
https://cds.cern.ch/record/2149571
The formation of high-order Bessel beams by a passive acoustic device consisting of an Archimedes' spiral diffraction grating is theoretically, numerically and experimentally reported in this work. These beams are propagation-invariant solutions of the Helmholtz equation and are characterized by an azimuthal variation of the phase along its annular spectrum producing an acoustic vortex in the near field. In our system, the scattering of plane acoustic waves by the spiral grating leads to the formation of the acoustic vortex with zero pressure on-axis and the angular phase dislocations characterized by the spiral geometry. The order of the generated Bessel beam and, as a consequence, the size of the generated vortex can be fixed by the number of arms in the spiral diffraction grating. The obtained results allow to obtain Bessel beams with controllable vorticity by a passive device, which has potential applications in low-cost acoustic tweezers and acoustic radiation force devices.Jiménez, NoéPicó, RubénSánchez-Morcillo, VíctorRomero-García, VicentGarcía-Raffi, Lluis MStaliunas, KestutisSat, 30 Apr 2016 06:39:20 GMT28 Apr 2016arXiv:1604.08353https://cds.cern.ch/record/2149571['arXiv:1604.08353']arXiv:1604.08353Group velocity locked vector dissipative solitons in a high repetition rate fiber laser
https://cds.cern.ch/record/2149570
Vectorial nature of dissipative solitons (DSs) with high repetition rates is studied for the first time in a normal-dispersion fiber laser. Despite the fact that the formed DSs are strongly chirped and the repetition rate is greater than 100 MHz, polarization locked and polarization rotating group velocity locked vector DSs can be formed under 129.3 MHz fundamental mode-locking and 258.6 MHz harmonic mode-locking of the fiber laser, respectively. The two orthogonally polarized components of these vector DSs possess distinctly different central wavelengths and travel together at the same group velocity in the laser cavity, resulting in a gradual spectral edge and small steps on the optical spectra, which can be considered as an auxiliary indicator of the group velocity locked vector DSs.Luo, YiyangLiu, DemingLi, LeiSun, QizhenWu, ZhichaoXu, ZhilinFu, SongnianZhao, LumingSat, 30 Apr 2016 06:39:20 GMT28 Apr 2016arXiv:1604.08344https://cds.cern.ch/record/2149570['arXiv:1604.08344']arXiv:1604.08344