Journal articles: 'Locally coherent'

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Saorín, Manuel. "On locally coherent hearts." Pacific Journal of Mathematics 287, no. 1 (February 6, 2017): 199–221. http://dx.doi.org/10.2140/pjm.2017.287.199.

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Chauris, Hervé, Mark S. Noble, Gilles Lambaré, and Pascal Podvin. "Migration velocity analysis from locally coherent events in 2‐D laterally heterogeneous media, Part I: Theoretical aspects." GEOPHYSICS 67, no. 4 (July 2002): 1202–12. http://dx.doi.org/10.1190/1.1500382.

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We present a new method based on migration velocity analysis (MVA) to estimate 2‐D velocity models from seismic reflection data with no assumption on reflector geometry or the background velocity field. Classical approaches using picking on common image gathers (CIGs) must consider continuous events over the whole panel. This interpretive step may be difficult—particularly for applications on real data sets. We propose to overcome the limiting factor by considering locally coherent events. A locally coherent event can be defined whenever the imaged reflectivity locally shows lateral coherency at some location in the image cube. In the prestack depth‐migrated volume obtained for an a priori velocity model, locally coherent events are picked automatically, without interpretation, and are characterized by their positions and slopes (tangent to the event). Even a single locally coherent event has information on the unknown velocity model, carried by the value of the slope measured in the CIG. The velocity is estimated by minimizing these slopes. We first introduce the cost function and explain its physical meaning. The theoretical developments lead to two equivalent expressions of the cost function: one formulated in the depth‐migrated domain on locally coherent events in CIGs and the other in the time domain. We thus establish direct links between different methods devoted to velocity estimation: migration velocity analysis using locally coherent events and slope tomography. We finally explain how to compute the gradient of the cost function using paraxial ray tracing to update the velocity model. Our method provides smooth, inverted velocity models consistent with Kirchhoff‐type migration schemes and requires neither the introduction of interfaces nor the interpretation of continuous events. As for most automatic velocity analysis methods, careful preprocessing must be applied to remove coherent noise such as multiples.

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Armstrong, Thomas E., and William D. Sudderth. "Locally Coherent Rates of Exchange." Annals of Statistics 17, no. 3 (September 1989): 1394–408. http://dx.doi.org/10.1214/aos/1176347278.

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Belaid, Karim, Othman Echi, and Riyadh Gargouri. "Two classes of locally compact sober spaces." International Journal of Mathematics and Mathematical Sciences 2005, no. 15 (2005): 2421–27. http://dx.doi.org/10.1155/ijmms.2005.2421.

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We deal with two classes of locally compact sober spaces, namely, the class of locally spectral coherent spaces and the class of spaces in which every point has a closed spectral neighborhood (CSN-spaces, for short). We prove that locally spectral coherent spaces are precisely the coherent sober spaces with a basis of compact open sets. We also prove that CSN-spaces are exactly the locally spectral coherent spaces in which every compact open set has a compact closure.

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Odabaşı, Sinem. "Locally torsion-free quasi-coherent sheaves." Journal of Pure and Applied Algebra 218, no. 9 (September 2014): 1760–70. http://dx.doi.org/10.1016/j.jpaa.2014.02.002.

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HAGHANY, A., M. MAZROOEI, and M. R. VEDADI. "PURE PROJECTIVITY AND PURE INJECTIVITY OVER FORMAL TRIANGULAR MATRIX RINGS." Journal of Algebra and Its Applications 11, no. 06 (November 14, 2012): 1250107. http://dx.doi.org/10.1142/s0219498812501071.

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Over a formal triangular matrix ring we study pure injective, pure projective and locally coherent modules. Some applications are then given, in particular the (J-)coherence of the ring [Formula: see text] is characterized whenever BM is flat.

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Aghasi, Mansour, and Hamidreza Nemati. "Absolute purity in the category of quasi coherent sheaves." Filomat 29, no. 7 (2015): 1663–69. http://dx.doi.org/10.2298/fil1507663a.

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In this paper we consider the class of absolutely pure and Fp-injective quasi-coherent sheaves. We show that these two classes of quasi-coherent sheaves over a locally coherent scheme are equivalent. As a corollary we will show that the class of absolutely pure quasi-coherent sheaves over such a scheme is an enveloping and a covering class. It is proved that over a locally coherent scheme, the pair (?(Abs(X),Abs(X)) is a cotorsion theory. The existence of a duality between absolutely pure envelopes and flat covers is proved as expected.

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Krause, Henning. "The spectrum of a locally coherent category." Journal of Pure and Applied Algebra 114, no. 3 (January 1997): 259–71. http://dx.doi.org/10.1016/s0022-4049(95)00172-7.

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Lu, Wenkai, Wenpo Zhang, and Dongqi Liu. "Local linear coherent noise attenuation based on local polynomial approximation." GEOPHYSICS 71, no. 6 (November 2006): V163—V169. http://dx.doi.org/10.1190/1.2335873.

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We propose a new technique for the attenuation of locally coherent noise. We assume that the moveout of the noise is locally linear and approximate its amplitude variations with offset using piecewise (local) polynomial models. Thus, our method consists of three steps: detection of the noise (locally linear coherent noise, LLCN), amplitude estimation by a local polynomial approximation (LPA), and subtraction of the estimated coherent noise from the original data. Applying the proposed method to synthetic data and to a field data set shows that the LPA filter has good ability to model LLCN and is insensitive to the filter parameters. Comparisons of the results obtained by our method with those from the traditional frequency-wavenumber filter and the localized 2D filter in the Fourier projection domain (FPF) show that the new method outperforms both traditional methods in situations with complex coherent noise.

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Child, M. S., and D. V. Shalashilin. "Locally coupled coherent states and Herman–Kluk dynamics." Journal of Chemical Physics 118, no. 5 (February 2003): 2061–71. http://dx.doi.org/10.1063/1.1531997.

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Timofeeva, N. V. "Locally Free Resolution of Coherent Sheaves in Arbitrary Dimension." Mathematical Notes 110, no. 3-4 (September 2021): 632–37. http://dx.doi.org/10.1134/s0001434621090340.

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Herzog, I. "The Ziegler Spectrum of a Locally Coherent Grothendieck Category." Proceedings of the London Mathematical Society 74, no. 3 (May 1997): 503–58. http://dx.doi.org/10.1112/s002461159700018x.

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Mirrahimi, Mazyar, Gabriel Turinici, and Pierre Rouchon. "Reference Trajectory Tracking for Locally Designed Coherent Quantum Controls." Journal of Physical Chemistry A 109, no. 11 (March 2005): 2631–37. http://dx.doi.org/10.1021/jp0472461.

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Li, Xueqi, Youming Lei, and Dibakar Ghosh. "Taming non-stationary chimera states in locally coupled oscillators." Chaos: An Interdisciplinary Journal of Nonlinear Science 32, no. 9 (September 2022): 093152. http://dx.doi.org/10.1063/5.0118034.

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The imperfect traveling chimera (ITC) state is a novel non-stationary chimera pattern in which the incoherent domain of oscillators spreads into the coherent domain. We investigate the ITC state in locally coupled pendulum oscillators with heterogeneous driving forces. We introduce the heterogeneous phase value in the driving forces by two different ways, namely, the random phase from uniform distribution and random phase directions with identical amplitude. We discover two transition mechanisms from ITC to coherent state through traveling chimera-like state by taking the two different phase heterogeneity. The transition phenomena are investigated using cylindrical and polar coordinate phase spaces. In the numerical study, we propose a quantitative measurement named “spatiotemporal consistency” strength for distinguishing the ITC from the traveling one. Our research facilitates the exploration of potential applications of heterogeneous interactions in neuroscience.

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Sugawara, M., S. Yoshizawa, and S. Yabushita. "Coherent control of wavepacket dynamics by locally designed external field." Chemical Physics Letters 350, no. 3-4 (December 2001): 253–59. http://dx.doi.org/10.1016/s0009-2614(01)01259-3.

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Hornbostel, Scott. "Spatial prediction filtering in the t-x and f-x domains." GEOPHYSICS 56, no. 12 (December 1991): 2019–26. http://dx.doi.org/10.1190/1.1443014.

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The predictability of seismic signals from nearby traces can be a powerful tool for reducing random or locally coherent noise. The choice of algorithm to reduce noise for a given application is a function of the data signal and noise characteristics. When the signal and noise are relatively consistent over a given design window, an f-x domain Wiener‐filter approach can be used. For cases in which the data are time‐ or space‐varying, a new approach using 2-D adaptive filtering in the t-x domain can be very effective. In either of these approaches, a prediction trace‐gap can often be successfully used to remove locally coherent noise when lateral signal changes are not too rapid.

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NITSURE, NITIN. "SCHEMATIC HARDER–NARASIMHAN STRATIFICATION." International Journal of Mathematics 22, no. 10 (October 2011): 1365–73. http://dx.doi.org/10.1142/s0129167x11007264.

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For any flat family of pure-dimensional coherent sheaves on a family of projective schemes, the Harder–Narasimhan type (in the sense of Gieseker semistability) of its restriction to each fiber is known to vary semicontinuously on the parameter scheme of the family. This defines a stratification of the parameter scheme by locally closed subsets, known as the Harder–Narasimhan stratification. In this paper, we show how to endow each Harder–Narasimhan stratum with the structure of a locally closed subscheme of the parameter scheme, which enjoys the universal property that under any base change the pullback family admits a relative Harder–Narasimhan filtration with a given Harder–Narasimhan type if and only if the base change factors through the schematic stratum corresponding to that Harder–Narasimhan type. The above schematic stratification induces a stacky stratification on the algebraic stack of pure-dimensional coherent sheaves. We deduce that coherent sheaves of a fixed Harder–Narasimhan type form an algebraic stack in the sense of Artin.

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18

Hu, Xianghong, Shuning Sun, and Yujun Zheng. "Witnessing localization of a quantum state via quantum speed limits in a driven avoided-level crossing system." Journal of Chemical Physics 156, no. 13 (April 7, 2022): 134113. http://dx.doi.org/10.1063/5.0078207.

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In this work, we investigate the witnessing of the localization of quantum states through quantum speed limits (QSLs) in a two-level driven avoided-level crossing system. As the characteristic natures of the localized quantum states, the QSL presents the periodic oscillations and coherence. The coherence partition of QSL is much bigger than the population partition of QSL. Our study gives us the possibilities to manipulate dynamics of quantum states locally by employing the coherent destruction of tunneling, which is significant in quantum information process. In addition, we analyze the effects of the rotating-wave approximation and the generalized Van Vleck approach on QSL and show that they wipe out the quantum coherence.

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Meister, Clara, Tiago Pimentel, Gian Wiher, and Ryan Cotterell. "Locally Typical Sampling." Transactions of the Association for Computational Linguistics 11 (2023): 102–21. http://dx.doi.org/10.1162/tacl_a_00536.

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Abstract Today’s probabilistic language generators fall short when it comes to producing coherent and fluent text despite the fact that the underlying models perform well under standard metrics (e.g., perplexity). This discrepancy has puzzled the language generation community for the last few years. In this work, we posit that the abstraction of natural language generation as a discrete stochastic process—which allows for an information-theoretic analysis—can provide new insights into the behavior of probabilistic language generators, for example, why high-probability texts can be dull or repetitive. Humans use language as a means of communicating information, aiming to do so in a simultaneously efficient and error-minimizing manner; in fact, psycholinguistics research suggests humans choose each word in a string with this subconscious goal in mind. We formally define the set of strings that meet this criterion: Those for which each word has an information content close to the expected information content, namely, the conditional entropy of our model. We then propose a simple and efficient procedure for enforcing this criterion when generating from probabilistic models, which we call locally typical sampling. Automatic and human evaluations show that, in comparison to nucleus and top-k sampling, locally typical sampling offers competitive performance (in both abstractive summarization and story generation) in terms of quality while consistently reducing degenerate repetitions.

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Dow, Alan, and Franklin D. Tall. "Normality Versus Paracompactness in Locally Compact Spaces." Canadian Journal of Mathematics 70, no. 1 (February 1, 2018): 74–96. http://dx.doi.org/10.4153/cjm-2017-006-x.

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AbstractThis note provides a correct proof of the result claimed by the second author that locally compact normal spaces are collectionwise Hausdorff in certain models obtained by forcing with a coherent Souslin tree. A novel feature of the proof is the use of saturation of the non-stationary ideal on ω1, as well as of a strong form of Chang's Conjecture. Together with other improvements, this enables the consistent characterization of locally compact hereditarily paracompact spaces as those locally compact, hereditarily normal spaces that do not include a copy of ω1.

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Enochs, Edgar, Sergio Estrada, and Sinem Odabaşi. "Pure Injective and Absolutely Pure Sheaves." Proceedings of the Edinburgh Mathematical Society 59, no. 3 (November 20, 2015): 623–40. http://dx.doi.org/10.1017/s0013091515000462.

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AbstractWe study two notions of purity in categories of sheaves: the categorical and the geometric. It is shown that pure injective envelopes exist in both cases under very general assumptions on the scheme. Finally, we introduce the class of locally absolutely pure (quasi-coherent) sheaves with respect to the geometrical purity, and characterize locally Noetherian closed subschemes of a projective scheme in terms of the new class.

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Kaasalainen, Sanna, Karri Muinonen, and Jukka Piironen. "Modelling of the Coherent Backscattering Opposition Effect: Comparison to Planetary Phase Curves." Highlights of Astronomy 12 (2002): 649. http://dx.doi.org/10.1017/s1539299600014532.

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AbstractWe study the opposition effect of icy planetary satellites by means of a Monte Carlo simulation of the coherent backscattering opposition effect for spherical objects covered with locally plane parallel media.

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Sugawara, M. "General formulation of locally designed coherent control theory for quantum system." Journal of Chemical Physics 118, no. 15 (April 15, 2003): 6784–800. http://dx.doi.org/10.1063/1.1559680.

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Edwards, Stephen D., David J. Edwards, and Richard Honeycutt. "HeartMath as an Integrative, Personal, Social, and Global Healthcare System." Healthcare 10, no. 2 (February 15, 2022): 376. http://dx.doi.org/10.3390/healthcare10020376.

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COVID-19 is a recent major event, adding to planet Earth’s contexts of chaos, crime, injustice, illness, and violence. The HeartMath system has produced research evidence for scientific interventions that alter contexts characterized by chaos and stress, promoting health, coherence, and interconnectedness. This study provides an updated overview of HeartMath as an interdisciplinary, scientific, coherent, integral heart-based healthcare system, operated locally through various initiatives and globally through the Global Coherence Initiative. The HeartMath approach integrates ancient and contemporary, indigenous and mainstream, popular and folk, Eastern, Western, and African forms of healing. The HeartMath interdisciplinary, personal, social, and global vision and mission have considerable theoretical and practical potential for promoting planetary health, education, and development.

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Laucht, Arne, Juha T. Muhonen, Fahd A. Mohiyaddin, Rachpon Kalra, Juan P. Dehollain, Solomon Freer, Fay E. Hudson, et al. "Electrically controlling single-spin qubits in a continuous microwave field." Science Advances 1, no. 3 (April 2015): e1500022. http://dx.doi.org/10.1126/sciadv.1500022.

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Large-scale quantum computers must be built upon quantum bits that are both highly coherent and locally controllable. We demonstrate the quantum control of the electron and the nuclear spin of a single31P atom in silicon, using a continuous microwave magnetic field together with nanoscale electrostatic gates. The qubits are tuned into resonance with the microwave field by a local change in electric field, which induces a Stark shift of the qubit energies. This method, known asA-gate control, preserves the excellent coherence times and gate fidelities of isolated spins, and can be extended to arbitrarily many qubits without requiring multiple microwave sources.

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AREFIJAMAAL, A. A., and R. A. KAMYABI-GOL. "ON CONSTRUCTION OF COHERENT STATES ASSOCIATED WITH SEMIDIRECT PRODUCTS." International Journal of Wavelets, Multiresolution and Information Processing 06, no. 05 (September 2008): 749–59. http://dx.doi.org/10.1142/s021969130800263x.

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Most of the interesting groups encountered in the physics literature are semidirect product groups. These groups are of the general form G = H ×τ K, where H and K are locally compact groups. In this paper, we consider the quasi regular representation on such a group G and investigate when it is possible to construct a family of coherent states associated to this representation.

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Mesablishvili, B. "More on Descent Theory for Schemes." gmj 11, no. 4 (December 2004): 783–800. http://dx.doi.org/10.1515/gmj.2004.783.

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Abstract In this paper we continue the investigation of some aspects of descent theory for schemes that was begun in [Mesablishvili, Appl. Categ. Structures]. Let 𝐒𝐂𝐇 be a category of schemes. We show that quasi-compact pure morphisms of schemes are effective descent morphisms with respect to 𝐒𝐂𝐇-indexed categories given by (i) quasi-coherent modules of finite type, (ii) flat quasi-coherent modules, (iii) flat quasi-coherent modules of finite type, (iv) locally projective quasicoherent modules of finite type. Moreover, we prove that a quasi-compact morphism of schemes is pure precisely when it is a stable regular epimorphism in 𝐒𝐂𝐇. Finally, we present an alternative characterization of pure morphisms of schemes.

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Tian, Hai Ping, Shao Qiong Yang, and Nan Jiang. "Topological Characteristics of Coherent Structures in the Turbulent Boundary Layer Measured by Tomo-PIV." Advanced Materials Research 718-720 (July 2013): 801–6. http://dx.doi.org/10.4028/www.scientific.net/amr.718-720.801.

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Database of time series of the instantaneous three-dimensional three-component (3D-3C) velocity vector field, measured by tomographic time-resolved PIV(Tomo-PIV) in a water tunnel, was analyzed to investigate spatial topologies of coherent structures in the turbulent boundary layer (TBL). A new concept of spatial locally averaged velocity structure function of turbulence is put forward to describe the spatial dilation or compression of the multi-scale coherent structures in the TBL. According to the physical mechanism of dilation or compression of multi-scale coherent vortex structures in the turbulent flow, a new conditional sampling method was proposed as well to extract the spatial topological characteristics of physical quantities of coherent structures, such as fluctuating velocities, velocity gradients, velocity strain rates and vorticity during the bursting process in the Tomo-PIV database. Furthermore, the anti-symmetric structures are the typical spatial topologies characteristics for the velocity gradients and vorticity during coherent structures burst.

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Driscoll, Erin, Mark Bocko, and Sarah R. Smith. "Analysis of partially coherent acoustic wavefields from multichannel sound reproduction systems." Journal of the Acoustical Society of America 150, no. 4 (October 2021): A349. http://dx.doi.org/10.1121/10.0008545.

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This work analyzes the performance of multichannel sound reproduction systems using the theory of partially coherent wavefields to model the acoustic velocity vector at the listener’s location. In this framework, the original signal is modelled as a narrowband, locally stationary random process, defined by a coherence time. The system model incorporates attenuation and delays from both positioning of the listener relative to the loudspeakers and any processing used in the reproduction system (e.g., panning). Given the finite coherence time of the signal, the magnitude and direction of the resultant velocity vector fluctuates in time. The location and spread of the virtual source that a human listener infers is determined by the distribution of velocity vector directions and a psychoacoustic averaging time associated with the precedence effect. Using this framework, we demonstrate the relative importance of three time constants in forming a stable image of the source location: the signal coherence time, the acoustic decay time, and the perceptual averaging time. This framework can be extended to incorporate early reflections in the listening environment and generalized to encompass natural sounds, such as speech or music, which can be modelled as a sum of narrowband components.

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Alsop, Richard J., Sebastian Himbert, Alexander Dhaliwal, Karin Schmalzl, and Maikel C. Rheinstädter. "Aspirin locally disrupts the liquid-ordered phase." Royal Society Open Science 5, no. 2 (February 2018): 171710. http://dx.doi.org/10.1098/rsos.171710.

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Local structure and dynamics of lipid membranes play an important role in membrane function. The diffusion of small molecules, the curvature of lipids around a protein and the existence of cholesterol-rich lipid domains (rafts) are examples for the membrane to serve as a functional interface. The collective fluctuations of lipid tails, in particular, are relevant for diffusion of membrane constituents and small molecules in and across membranes, and for structure and formation of membrane domains. We studied the effect of aspirin (acetylsalicylic acid, ASA) on local structure and dynamics of membranes composed of dimyristoylphosphocholine (DMPC) and cholesterol. Aspirin is a common analgesic, but is also used in the treatment of cholesterol. Using coherent inelastic neutron scattering experiments and molecular dynamics (MD) simulations, we present evidence that ASA binds to liquid-ordered, raft-like domains and disturbs domain organization and dampens collective fluctuations. By hydrogen-bonding to lipid molecules, ASA forms ‘superfluid’ complexes with lipid molecules that can organize laterally in superlattices and suppress cholesterol’s ordering effect.

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Gross, Philipp. "The resolution property of algebraic surfaces." Compositio Mathematica 148, no. 1 (November 9, 2011): 209–26. http://dx.doi.org/10.1112/s0010437x11005628.

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AbstractWe prove that on separated algebraic surfaces every coherent sheaf is a quotient of a locally free sheaf. This class contains many schemes that are neither normal, reduced, quasiprojective nor embeddable into toric varieties. Our methods extend to arbitrary two-dimensional schemes that are proper over an excellent ring.

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Zhang, Zhengyuan, and Liming Dai. "Effects of Synaptic Pruning on Phase Synchronization in Chimera States of Neural Network." Applied Sciences 12, no. 4 (February 12, 2022): 1942. http://dx.doi.org/10.3390/app12041942.

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This research explores the effect of synaptic pruning on a ring-shaped neural network of non-locally coupled FitzHugh–Nagumo (FHN) oscillators. The neurons in the pruned region synchronize with each other, and they repel the coherent domain of the chimera states. Furthermore, the width of the pruned region decides the precision and efficiency of the control effect on the position of coherent domains. This phenomenon gives a systematic comprehension of the relation between pruning and synchronization in neural networks from a new aspect that has never been addressed. An explanation of this mechanism is also given.

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Braunling, Oliver. "K-Theory of Locally Compact Modules over Rings of Integers." International Mathematics Research Notices 2020, no. 6 (April 27, 2018): 1748–93. http://dx.doi.org/10.1093/imrn/rny083.

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Abstract We generalize a recent result of Clausen; for a number field with integers $\mathcal{O}$, we compute the K-theory of locally compact $\mathcal{O}$-modules. For the rational integers this recovers Clausen’s result as a special case. Our method of proof is quite different; instead of a homotopy coherent cone construction in $\infty$-categories, we rely on calculus of fraction type results in the style of Schlichting. This produces concrete exact category models for certain quotients, a fact that might be of independent interest. As in Clausen’s work, our computation works for all localizing invariants, not just K-theory.

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Patel, Deepam, Tobias Schmidt, and Matthias Strauch. "LOCALLY ANALYTIC REPRESENTATIONS OF VIA SEMISTABLE MODELS OF." Journal of the Institute of Mathematics of Jussieu 18, no. 1 (January 12, 2017): 125–87. http://dx.doi.org/10.1017/s1474748016000396.

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In this paper we study certain sheaves of $p$-adically complete rings of differential operators on semistable models of the projective line over the ring of integers in a finite extension $L$ of $\mathbb{Q}_{p}$. The global sections of these sheaves can be identified with (central reductions of) analytic distribution algebras of wide open congruence subgroups. It is shown that the global sections functor furnishes an equivalence between the categories of coherent module sheaves and finitely presented modules over the distribution algebras. Using the work of M. Emerton, we then describe admissible representations of $\text{GL}_{2}(L)$ in terms of sheaves on the projective limit of these formal schemes. As an application, we show that representations coming from certain equivariant line bundles on Drinfeld’s first étale covering of the $p$-adic upper half plane are admissible.

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Perrinet, Laurent U., and Guillaume S. Masson. "Motion-Based Prediction Is Sufficient to Solve the Aperture Problem." Neural Computation 24, no. 10 (October 2012): 2726–50. http://dx.doi.org/10.1162/neco_a_00332.

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In low-level sensory systems, it is still unclear how the noisy information collected locally by neurons may give rise to a coherent global percept. This is well demonstrated for the detection of motion in the aperture problem: as luminance of an elongated line is symmetrical along its axis, tangential velocity is ambiguous when measured locally. Here, we develop the hypothesis that motion-based predictive coding is sufficient to infer global motion. Our implementation is based on a context-dependent diffusion of a probabilistic representation of motion. We observe in simulations a progressive solution to the aperture problem similar to physio-logy and behavior. We demonstrate that this solution is the result of two underlying mechanisms. First, we demonstrate the formation of a tracking behavior favoring temporally coherent features independent of their texture. Second, we observe that incoherent features are explained away, while coherent information diffuses progressively to the global scale. Most previous models included ad hoc mechanisms such as end-stopped cells or a selection layer to track specific luminance-based features as necessary conditions to solve the aperture problem. Here, we have proved that motion-based predictive coding, as it is implemented in this functional model, is sufficient to solve the aperture problem. This solution may give insights into the role of prediction underlying a large class of sensory computations.

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Behzadan, A., and M. Holst. "On the Space of Locally Sobolev-Slobodeckij Functions." Journal of Function Spaces 2022 (July 18, 2022): 1–30. http://dx.doi.org/10.1155/2022/9094502.

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The study of certain differential operators between Sobolev spaces of sections of vector bundles on compact manifolds equipped with rough metric is closely related to the study of locally Sobolev functions on domains in the Euclidean space. In this paper, we present a coherent rigorous study of some of the properties of locally Sobolev-Slobodeckij functions that are especially useful in the study of differential operators between sections of vector bundles on compact manifolds with rough metric. The results of this type in published literature generally can be found only for integer order Sobolev spaces W m , p or Bessel potential spaces H s . Here, we have presented the relevant results and their detailed proofs for Sobolev-Slobodeckij spaces W s , p where s does not need to be an integer. We also develop a number of results needed in the study of differential operators on manifolds that do not appear to be in the literature.

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Chikishev, Leonid M., Dmitriy K. Sharaborin, Aleksei S. Lobasov, Artem A. Dekterev, Roman V. Tolstoguzov, Vladimir M. Dulin, and Dmitriy M. Markovich. "LES Simulation of a Model Gas-Turbine Lean Combustor: Impact of Coherent Flow Structures on the Temperature Field and Concentration of CO and NO." Energies 15, no. 12 (June 15, 2022): 4362. http://dx.doi.org/10.3390/en15124362.

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The present paper reports on the numerical simulation of flow dynamics in a model gas-turbine combustor by large eddy simulation in order to evaluate the effect of coherent flow structures on the local fluctuations of gas temperature and local concentrations of NO and CO. The simulations were performed for a generic swirler, based on the design by Turbomeca, for a Reynolds number of 15,000 at normal and elevated inlet temperature and pressure (up to 500 K and 3.4 atm). The simulation data were validated based on the velocity measurements by stereoscopic particle image velocimetry. In order to reveal coherent flow structures, the velocity snapshots were processed by the proper orthogonal method. The temporal coefficients of the decomposition were used to evaluate the conditional sampled spatial distributions of the temperature and species concentration. It is shown that the coherent fluctuations of temperature can locally reach up to 200 K with the fluctuations of NO up to 20%. Thus, the results demonstrate that coherent flow structures in a lean swirl combustor can sufficiently contribute to NOx emission.

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GARBACZEWSKI, PIOTR. "CANONICAL ACTION-ANGLE FORMALISM FOR QUANTIZED NONLINEAR FIELDS." International Journal of Modern Physics A 02, no. 01 (February 1987): 223–48. http://dx.doi.org/10.1142/s0217751x87000090.

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The canonical quantizations of field and action-angle coordinates which (locally) parametrize the phase manifold for the same nonlinear field theory model (e.g. sine-Gordon and nonlinear Schrödinger with the attractive coupling) are reconciled on the common for both cases state space. The classical-quantum relationship is maintained in the mean: coherent state expectation values of operators give rise to classical objects.

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Deguchi, K., and P. Hall. "Canonical exact coherent structures embedded in high Reynolds number flows." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, no. 2020 (July 28, 2014): 20130352. http://dx.doi.org/10.1098/rsta.2013.0352.

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The applications and implications of two recently addressed asymptotic descriptions of exact coherent structures in shear flows are discussed. The first type of asymptotic framework to be discussed was introduced in a series of papers by Hall & Smith in the 1990s and was referred to as vortex–wave interaction theory (VWI). New results are given here for the canonical VWI problem in an infinite region; the results confirm and extend the results for the infinite problem inferred the recent VWI computation of plane Couette flow. The results given define for the first time exact coherent structures in unbounded flows. The second type of canonical structure described here is that recently found for asymptomatic suction boundary layer and corresponds to freestream coherent structures (FCS), in boundary layer flows. Here, it is shown that the FCS can also occur in flows such as Burgers vortex sheet. It is concluded that both canonical problems can be locally embedded in general shear flows and thus have widespread applicability.

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da SILVA, C. B., and O. MÉTAIS. "On the influence of coherent structures upon interscale interactions in turbulent plane jets." Journal of Fluid Mechanics 473 (December 10, 2002): 103–45. http://dx.doi.org/10.1017/s0022112002002458.

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The influence of the coherent structures on grid/subgrid-scale (GS/SGS) interactions in free shear layers is analysed through the application of a top-hat filter to several plane jet direct numerical simulations (DNS). The Reynolds number based on the plane jet inlet slot width is Reh = 3000. The study deals with energy containing (Kelvin–Helmholtz) and inertial range (streamwise) vortices, from the far field of the turbulent plane jet. The most intense kinetic energy exchanges between GS and SGS occur near these structures and not randomly in the space. The GS kinetic energy is dominated by GS advection and GS pressure/velocity interactions which appear located next to the Kelvin–Helmholtz rollers. Surprisingly, GS/SGS transfer is not very well correlated with the coherent vortices and GS/SGS diffusion plays an important role in the local dynamics of both GS and SGS kinetic energy. The so-called ‘local equilibrium assumption’ holds globally but not locally as most viscous dissipation of SGS kinetic energy takes place within the vortex cores whereas forward and backward GS/SGS transfer occurs at quite different locations. Finally, it was shown that SGS kinetic energy advection may be locally large as compared to the other terms of the SGS kinetic energy transport equation.

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Tall, Franklin D. "PFA(S)[S]: More Mutually Consistent Topological Consequences of PFA and V = L." Canadian Journal of Mathematics 64, no. 5 (October 1, 2012): 1182–200. http://dx.doi.org/10.4153/cjm-2012-010-0.

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Abstract Extending the work of Larson and Todorcevic, we show that there is a model of set theory in which normal spaces are collectionwise Hausdorff if they are either first countable or locally compact, and yet there are no first countable L-spaces or compact S-spaces. The model is one of the form PFA(S)[S], where S is a coherent Souslin tree.

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Dias, F. M. "Data processing of electric probe data acquired under locally close-to-coherent noise conditions." Journal of Physics: Conference Series 207 (January 1, 2010): 012003. http://dx.doi.org/10.1088/1742-6596/207/1/012003.

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LABBI, ABDERRAHIM, RUGGERO MILANESE, and HOLGER BOSCH. "ASYMPTOTIC SYNCHRONIZATION IN NETWORKS OF LOCALLY CONNECTED OSCILLATORS." International Journal of Bifurcation and Chaos 09, no. 12 (December 1999): 2279–84. http://dx.doi.org/10.1142/s0218127499001759.

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In this paper, we describe the asymptotic behavior of a network of locally connected oscillators. The main result concerns asymptotic synchronization. The presented study is stated in the framework of neuronal modeling of visual object segmentation using oscillatory correlation. The practical motivations of the synchronization analysis are based on neurophysiological experiments which led to the assumptions that existence of temporal coding schemes in the brain by which neurons, with oscillatory dynamics, coding for the same coherent object synchronize their activities, while neurons coding for different objects oscillate with nonzero phase lags. The oscillator model considered is the FitzHugh–Nagumo neuron model. We restrict our study to the mathematical analysis of a network of such neurons. We firstly show the motivations and suitability of choosing FitzHugh–Nagumo oscillator, mainly for stimulus coding purposes, and then we give sufficient conditions on the coupling parameters which guarantee asymptotic synchronization of oscillators receiving the same external stimulation (input). We have used networks of such oscillators to design a layered architecture for object segmentation in gray-level images. Due to space limitations, description of this architecture and simulation results are briefly referred to by the end of the paper.

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DUGUET, Y., A. P. WILLIS, and R. R. KERSWELL. "Transition in pipe flow: the saddle structure on the boundary of turbulence." Journal of Fluid Mechanics 613 (October 1, 2008): 255–74. http://dx.doi.org/10.1017/s0022112008003248.

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The laminar–turbulent boundary Σ is the set separating initial conditions which relaminarize uneventfully from those which become turbulent. Phase space trajectories on this hypersurface in cylindrical pipe flow appear to be chaotic and show recurring evidence of coherent structures. A general numerical technique is developed for recognizing approaches to these structures and then for identifying the exact coherent solutions themselves. Numerical evidence is presented which suggests that trajectories on Σ are organized around only a few travelling waves and their heteroclinic connections. If the flow is suitably constrained to a subspace with a discrete rotational symmetry, it is possible to find locally attracting travelling waves embedded within Σ. Four new types of travelling waves were found using this approach.

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SINIORA, DAOUD, and SŁAWOMIR SOLECKI. "COHERENT EXTENSION OF PARTIAL AUTOMORPHISMS, FREE AMALGAMATION AND AUTOMORPHISM GROUPS." Journal of Symbolic Logic 85, no. 1 (May 6, 2019): 199–223. http://dx.doi.org/10.1017/jsl.2019.32.

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AbstractWe give strengthened versions of the Herwig–Lascar and Hodkinson–Otto extension theorems for partial automorphisms of finite structures. Such strengthenings yield several combinatorial and group-theoretic consequences for homogeneous structures. For instance, we establish a coherent form of the extension property for partial automorphisms for certain Fraïssé classes. We deduce from these results that the isometry group of the rational Urysohn space, the automorphism group of the Fraïssé limit of any Fraïssé class that is the class of all ${\cal F}$-free structures (in the Herwig–Lascar sense), and the automorphism group of any free homogeneous structure over a finite relational language all contain a dense locally finite subgroup. We also show that any free homogeneous structure admits ample generics.

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Billette, Frederic, Soazig Le Bégat, Pascal Podvin, and Gilles Lambaré. "Practical aspects and applications of 2D stereotomography." GEOPHYSICS 68, no. 3 (May 2003): 1008–21. http://dx.doi.org/10.1190/1.1581072.

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Stereotomography is a new velocity estimation method. This tomographic approach aims at retrieving subsurface velocities from prestack seismic data. In addition to traveltimes, the slope of locally coherent events are picked simultaneously in common offset, common source, common receiver, and common midpoint gathers. As the picking is realized on locally coherent events, they do not need to be interpreted in terms of reflection on given interfaces, but may represent diffractions or reflections from anywhere in the image. In the high‐frequency approximation, each one of these events corresponds to a ray trajectory in the subsurface. Stereotomography consists of picking and analyzing these events to update both the associated ray paths and velocity model. In this paper, we describe the implementation of two critical features needed to put stereotomography into practice: an automatic picking tool and a robust multiscale iterative inversion technique. Applications to 2D reflection seismic are presented on synthetic data and on a 2D line extracted from a 3D towed streamer survey shot in West Africa for TotalFinaElf. The examples demonstrate that the method requires only minor human intervention and rapidly converges to a geologically plausible velocity model in these two very different and complex velocity regimes. The quality of the velocity models is verified by prestack depth migration results.

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Polishchuk, A. "Simple Helices on Fano Threefolds." Canadian Mathematical Bulletin 54, no. 3 (September 1, 2011): 520–26. http://dx.doi.org/10.4153/cmb-2010-106-x.

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AbstractBuilding on the work of Nogin, we prove that the braid groupB4acts transitively on full exceptional collections of vector bundles on Fano threefolds withb2= 1 andb3= 0. Equivalently, this group acts transitively on the set of simple helices (considered up to a shift in the derived category) on such a Fano threefold. We also prove that on threefolds withb2= 1 and very ample anticanonical class, every exceptional coherent sheaf is locally free.

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Langer, Adrian. "Fano 4-Folds with scroll structure." Nagoya Mathematical Journal 150 (June 1998): 135–76. http://dx.doi.org/10.1017/s0027763000025095.

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Abstract.We classify smooth Fano 4-folds with second betti number b2 = 2, possesing adjunction theoretic scroll structure. These manifolds occur to be projectivisations of coherent sheaves over Fano manifolds. The paper deals mainly with projectivisations of non-locally free rank 2 Fano sheaves over Fano 3-folds with b2 = 1, using Mori theory. By the way, we classify nef and big rank 2 bundles over P2 with the first Chern class (3).

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Waldron, Kim, Ian Parsons, and William L. Brown. "Solution-redeposition and the orthoclase-microcline transformation: evidence from granulites and relevance to 18O exchange." Mineralogical Magazine 57, no. 389 (December 1993): 687–95. http://dx.doi.org/10.1180/minmag.1993.057.389.13.

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AbstractThe Or-rich part of optically blebby to lamellar mesoperthite crystals from an Adirondack granulite has been shown by TEM to be a lamellar cryptoperthite, composed dominantly of tweed orthoclase. A fluid-absent, two-stage thermal history is proposed to explain the coarse and fine textures, with the cryptoperthite forming by coherent exsolution below ∼350°C probably during uplift. The mechanism was most probably homogeneous coherent nucleation rather than spinodal decomposition. However, cutting the orthoclase cryptoperthite are thin (<1 μm) seams of tartan microcline with sharp boundaries, often defined locally by {110} planes, and micropores. The microcline has replaced orthoclase by solution-redeposition along narrow planes infiltrated by fluid during minor retrogression at T < 350°C Solution-redeposition is a common process in feldspars at T < 500°C potentially accompanied by 18O exchange, because release of elastic strain energy in coherent perthite lamellar boundaries and twin-domain walls, followed by Si, Al ordering, provide driving forces for dissolution and reprecipitation of unstrained, more ordered phases.

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Bekara, Maïza, and Mirko Van der Baan. "Local singular value decomposition for signal enhancement of seismic data." GEOPHYSICS 72, no. 2 (March 2007): V59—V65. http://dx.doi.org/10.1190/1.2435967.

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Singular value decomposition (SVD) is a coherency-based technique that provides both signal enhancement and noise suppression. It has been implemented in a variety of seismic applications — mostly on a global scale. In this paper, we use SVD to improve the signal-to-noise ratio of unstacked and stacked seismic sections, but apply it locally to cope with coherent events that vary with both time and offset. The local SVD technique is compared with [Formula: see text] deconvolution and median filtering on a set of synthetic and real-data sections. Local SVD is better than [Formula: see text] deconvolution and median filtering in removing background noise, but it performs less well in enhancing weak events or events with conflicting dips. Combining [Formula: see text] deconvolution or median filtering with local SVD overcomes the main weaknesses associated with each individual method and leads to the best results.

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Journal articles on the topic 'Locally coherent'

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