Journal articles: 'Coherence'

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Concha, Soledad, Soledad Aravena, Carmen Julia Coloma, and Verónica Romero. "Escritura expositiva en tres niveles de escolaridad: coherencia y dominio de recursos lingüísticos." Literatura y Lingüística, no. 21 (June 26, 2015): 75. http://dx.doi.org/10.29344/0717621x.21.135.

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ResumenEl estudio explora la capacidad de estudiantes de tres niveles de escolaridad –5° Básico,1° Medio y 4° Medio– para producir textos expositivos coherentes utilizando los recursos lingüísticos con que se construye la coherencia local en la escritura expositiva. Se trabajó con alumnos de dos colegios municipalizados de Santiago, quienes redactaron textos expositivos a partir de un ítem de respuesta abierta extensa. Sus textos fueron codificados con dos rúbricas para medir la coherencia local (CL) y los recursos lingüísticos involucrados en la coherencia local (RCL). Los resultados muestran un ascenso significativo en el desempeño para la medida RCL a lo largo de los tres niveles escolares,pero no para la medida CL.Palabras clave: Producción escrita, texto expositivo, coherencia, recursos lingüísticosAbstractThe study focused on 5th grade, 9th grade and 12th grade students’ ability to produce coherent expository texts and to use the linguistic resources with which local coherenceis achieved in expository writing. Participants belonged to two public schools in Santiago,Chile, and their expository writing was elicited with writing prompts. Products of writing were coded using two different rubrics: Local Coherence (LC) and Local Coherence Resources (LCR). Results reveal a significant improvement for the measure LCR across age groups, but not for LC.Key words: Writing, expository text, coherence, linguistic resources

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Le, Thai-Hoa, and Dong-Anh Nguyen. "TEMPORO-SPECTRAL COHERENT STRUCTURE OF TURBULENCE AND PRESSURE USING FOURIER AND WAVELET TRANSFORMS." ASEAN Journal on Science and Technology for Development 25, no. 2 (November 22, 2017): 405–17. http://dx.doi.org/10.29037/ajstd.271.

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Studying the spatial distribution in coherent fields such as turbulent and turbulent-induced force ones is important to model and evaluate turbulent-induced forces and response of structures on the turbulent flows. Turbulent field-based coherent function is commonly used for the spatial distribution characteristic of induced forces in the frequency domain. This paper will focus to study spectral coherent structure of turbulence and forces in not only the frequency domain using conventional Fourier transform-based coherence, but also temporo-spectral coherent one in the time-frequency plane thanks to wavelet transform-based coherence for more understanding of the turbulence and force coherences and their spatial distributions. Effects of spanwise separations, bluff body flow and flow conditions on coherent structures of turbulence and induced pressure, comparison between turbulence and pressure coherences as well as intermittency of coherent structure in the time-frequency plane will be investigated here.

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Jung, Jungkyo, and Sang-Ho Yun. "Evaluation of Coherent and Incoherent Landslide Detection Methods Based on Synthetic Aperture Radar for Rapid Response: A Case Study for the 2018 Hokkaido Landslides." Remote Sensing 12, no. 2 (January 13, 2020): 265. http://dx.doi.org/10.3390/rs12020265.

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Damage mapping using Synthetic Aperture Radar (SAR) imagery has been studied in recent decades to support rapid response to natural disasters. Many researches have been developing coherent and incoherent change detection. However, their performances can vary depending on the types of the damages, the characteristics of the scatterers and the corresponding capability of algorithms. In particular, the coherence-based methods have been used as promising detectors over urban areas where high coherences are observed, but their detection accuracies still remain controversial over the area where low coherences are mainly observed such as the 2018 Hokkaido landslides. In order to understand the characteristics of landslide (damage) detectors for low-coherence areas and find an alternative and complementary method, we designed the coherence difference, coherence normalized difference, log-ratio, intensity correlation difference, and normalized differences of the intensity correlation assuming limited availability of dataset, and also developed multi-temporal algorithms using the coherence, intensity, and intensity correlation. They were tested and evaluated using multiple polygons extracted from aerial photos. We were able to observe that the multi-temporal intensity correlation method has the potential to detect the landslides over the low coherence region and all types of land uses.

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Zhu, Ruidan, Meixia Ruan, Hao Li, Xuan Leng, Jiading Zou, Jiayu Wang, Hailong Chen, Zhuan Wang, and Yuxiang Weng. "Vibrational and vibronic coherences in the energy transfer process of light-harvesting complex II revealed by two-dimensional electronic spectroscopy." Journal of Chemical Physics 156, no. 12 (March 28, 2022): 125101. http://dx.doi.org/10.1063/5.0082280.

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The presence of quantum coherence in light-harvesting complex II (LHCII) as a mechanism to understand the efficiency of the light-harvesting function in natural photosynthetic systems is still debated due to its structural complexity and weak-amplitude coherent oscillations. Here, we revisit the coherent dynamics and clarify different types of coherences in the energy transfer processes of LHCII using a joint method of the high-S/N transient grating and two-dimensional electronic spectroscopy. We find that the electronic coherence decays completely within 50 fs at room temperature. The vibrational coherences of chlorophyll a dominate over oscillations within 1 ps, whereas a low-frequency mode of 340 cm−1 with a vibronic mixing character may participate in vibrationally assisted energy transfer between chlorophylls a. Our results may suggest that vibronic mixing is relevant for rapid energy transfer processes among chlorophylls in LHCII.

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Fan, Zhaobing, Zewen Shan, and Haitao Ma. "Partial Recovery of Coherence Loss in Coherence-Assisted Transformation." Entropy 25, no. 10 (September 24, 2023): 1375. http://dx.doi.org/10.3390/e25101375.

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Coherence-assisted transformation under incoherent operations is discussed. For transformation from the pure state to the mixed state, we show that the coherence loss can be partially recovered by adding auxiliary coherent states. First, we discuss the coherence-assisted transformation for qubit states and give the sufficient and necessary condition for the partial recovery of coherence loss, and the maximum of the recovery of coherence loss is also studied in this case. Second, the maximally coherent state can be obtained in the above recovery scheme, so we give the full characterization of obtaining the maximally coherent state in a qubit system. Finally, we show that the coherence-assisted transformation for arbitrary finite-dimensional main coherent states and low-dimensional auxiliary coherent states is always possible, and the coherence loss also can be partially recovered in these cases.

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Hájek, Alan. "Is Strict Coherence Coherent?" Dialectica 66, no. 3 (September 2012): 411–24. http://dx.doi.org/10.1111/j.1746-8361.2012.01310.x.

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Qin, Lei, Frank L. Vernon, Christopher W. Johnson, and Yehuda Ben‐Zion. "Spectral Characteristics of Daily to Seasonal Ground Motion at the Piñon Flats Observatory from Coherence of Seismic Data." Bulletin of the Seismological Society of America 109, no. 5 (August 27, 2019): 1948–67. http://dx.doi.org/10.1785/0120190070.

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Abstract We investigate coherences of seismic data recorded during three years (2015–2017) at the Piñon Flats Observatory (PY) array and a collocated 148 m deep borehole station B084, along with oceanic data from a buoy southwest of the PY array. Seismic and barometric recordings at PY stations are analyzed with a multitaper spectral technique. The coherence of signals from seismic sources is >0.6 at 0.05–8 Hz between closely spaced (<65 m) surface stations and decreases to ∼0.2 in frequency bands in which the wavelengths are smaller than interstation distances. There are several local coherence increases at 1–8 Hz between nearby (<65 m) surface stations, whereas large coherence values between a surface and 148 m deep borehole stations are only present at the secondary microseism (∼0.14 Hz). These points to significant modification of seismic recordings in the top crust, and those continual near‐surface failures might produce shallow rapidly attenuating signals at surface stations. Incoherent local atmospheric effects induce incoherent seismic signals in low‐ and high‐frequency ranges through different coupling mechanisms. Between 0.003 and 0.05 Hz, atmospheric loadings generate ground tilts that contaminate the two horizontal seismic recordings and decrease their coherence, whereas the vertical component is less affected. At 1–8 Hz, coupling of atmospheric pressure with surface structures transmits incoherent signals into the ground, degrading the seismic coherence in all three components. The two horizontal coherences show seasonal variations with extended coherent frequency bands in winter and spring, likely to be produced by seasonal variations in microseisms and local ground tilts. The coherences also contain high anomalies between 2 and 4 Hz resulting from anthropogenic activities. The results provide useful information on instrument characteristics and variations in the shallow crustal response to earthquakes, seasonal and ambient sources of seismic energy, along with atmospheric pressure–temperature changes and anthropogenic activities.

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Wang, Bang-Hai, Zi-Heng Ding, Zhihao Ma, and Shao-Ming Fei. "Common Coherence Witnesses and Common Coherent States." Entropy 23, no. 9 (August 31, 2021): 1136. http://dx.doi.org/10.3390/e23091136.

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We show the properties and characterization of coherence witnesses. We show methods for constructing coherence witnesses for an arbitrary coherent state. We investigate the problem of finding common coherence witnesses for certain class of states. We show that finitely many different witnesses W1,W2,⋯,Wn can detect some common coherent states if and only if ∑i=1ntiWi is still a witnesses for any nonnegative numbers ti(i=1,2,⋯,n). We show coherent states play the role of high-level witnesses. Thus, the common state problem is changed into the question of when different high-level witnesses (coherent states) can detect the same coherence witnesses. Moreover, we show a coherent state and its robust state have no common coherence witness and give a general way to construct optimal coherence witnesses for any comparable states.

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Baker, Stuart N., Elizabeth M. Pinches, and Roger N. Lemon. "Synchronization in Monkey Motor Cortex During a Precision Grip Task. II. Effect of Oscillatory Activity on Corticospinal Output." Journal of Neurophysiology 89, no. 4 (April 1, 2003): 1941–53. http://dx.doi.org/10.1152/jn.00832.2002.

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Recordings from primary motor cortex (M1) during periods of steady contraction show oscillatory activity; these oscillations are coherent with the activity of contralateral muscles. We investigated synchronization of corticospinal output neurons with the oscillations, which could provide the pathway for their transmission to the spinal motoneurons. One hundred seventy-six antidromically identified pyramidal tract neurons (PTNs) were recorded from M1 in three macaque monkeys trained to perform a precision grip task. Local field potentials (LFP) were simultaneously recorded. All analysis was confined to the hold period of the task, where our previous work has shown that there is the strongest oscillatory activity. Coherence was calculated between LFP and PTN discharge. Significant coherence was seen in three bands, with frequencies of 10–14, 17–31, and 34–44 Hz. Coherence values were low, with the majority of PTN–LFP coherences having a peak lower than 0.05. The phase of coherence was approximately −π/2 radians for each band (with LFP polarity defined as negative upward), although there was some dispersion of phase across the population of PTNs. Coherence was also calculated between pairs of PTNs that had been simultaneously recorded. Where there was significant coherence, it was also generally smaller than 0.05. The phase of PTN–PTN coherence clustered around zero radians. A computer model was constructed to assist the interpretation of the experimental results. It simulated an integrate-and-fire neuron responding to synaptic inputs. A fraction of the synaptic inputs was synchronized with a simulated LFP; the remainder were uncorrelated with it. The model showed that coherence between the LFP and the output spike train considerably underestimated the fraction of synchronized inputs. Additionally, for a given fraction of synchronized inputs, coherence was smaller for high- compared with low-frequency bins. Cell discharge rate also influenced the spike–LFP coherence: coherence was higher for simulations in which the cell discharged at a faster rate. Thus although levels of PTN–LFP coherence seen experimentally were low, a considerable proportion of the input to the PTN must be synchronized with the global oscillatory activity recorded by the LFP. The low LFP–PTN coherences do however indicate that cortical oscillations are transmitted with only low fidelity in the discharge of a single PTN. Using further computer simulations, it was demonstrated that a small population of PTNs could encode the cortical oscillatory signal effectively, since the action of averaging across the population improves the signal:noise ratio. The oscillations will therefore be effectively transmitted to spinal motoneurons, and this has important consequences for the possible role of oscillations in motor control of the hand.

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LIM, WOOCHANG, and SANG-YOON KIM. "STOCHASTIC SPIKING COHERENCE IN COUPLED SUBTHRESHOLD MORRIS-LECAR NEURONS." International Journal of Modern Physics B 23, no. 05 (February 20, 2009): 703–10. http://dx.doi.org/10.1142/s0217979209049991.

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We consider a large population of globally coupled subthreshold Morris-Lecar neurons. By varying the noise intensity D, we numerically investigate stochastic spiking coherence (i.e., collective coherence between noise-induced neural spikings). As D passes a lower threshold, a transition from an incoherent to a coherent state occurs because of a constructive role of noise to stimulate coherence between noise-induced spikings. However, when passing a higher threshold of D, another transition from a coherent to an incoherent state takes place due to a destructive role of noise to spoil the spiking coherence. Such an incoherence-coherence-incoherence transition is well-described in terms of the order parameter which is just the mean square deviation of the global potential. In the coherent regime, we also characterize the degree of stochastic spiking coherence by using a coherence measure which reflects the degree of "resemblance" of the global potential to the local potential. Thus, stochastic spiking coherence with large coherence measure is found to occur over a large range of intermediate noise intensity.

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Cao, De-Wei, Yixin Zhang, Jicheng Wang, and Zheng-Da Hu. "Quantum coherence in a coupled-cavity array." International Journal of Modern Physics B 30, no. 18 (July 11, 2016): 1650114. http://dx.doi.org/10.1142/s0217979216501149.

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The dynamical properties of quantum coherence in the system of two-coupled-cavities, each of which resonantly interacts with a two-level atom, is investigated via the relative entropy measure. We focus on the coherences for the atom–atom, atom–cavity and cavity–cavity subsystems and find that the dynamical behaviors of these coherences depend largely on the cavity–cavity coupling, which may indicate the Mott insulator-superfluid transition in the thermodynamic limit. We also study the influences of the initial cavity–cavity correlation on the coherences and show that the initial correlation of the cavity–cavity subsystem can enhance the revival ability for the atom–atom and cavity–cavity coherences while reduce that for the atom–cavity coherence. Besides, we demonstrate the qualitative difference of dynamics between coherence and entanglement. Finally, the influences of dissipations including cavity losses and atomic decays on the coherence are explored.

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Lukin, Igor, and Vladimir Lukin. "Propagation of a Partially Coherent Bessel–Gaussian Beam in a Uniform Medium and Turbulent Atmosphere." Photonics 11, no. 6 (June 14, 2024): 562. http://dx.doi.org/10.3390/photonics11060562.

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In this paper, the coherent properties of partially coherent Bessel–Gaussian optical beams propagating through a uniform medium (free space) or a turbulent atmosphere are examined theoretically. The consideration is based on the analytical solution of the equation for the transverse second-order mutual coherence function of the field of partially coherent optical radiation in a turbulent atmosphere. For the partially coherent Bessel–Gaussian beam, the second-order mutual coherence function of the source field is taken as a Gaussian–Schell model. In this approximation, we analyze the behavior of the coherence degree and the integral coherence scale of these beams as a function of the propagation pathlength, propagation conditions, and beam parameters, such as the radius of the Gauss factor of the beam, parameter of the Bessel factor of the beam, topological charge, and correlation width of the source field of partially coherent radiation. It was found that, as a partially coherent vortex Bessel–Gaussian beam propagates through a turbulent atmosphere, there appear not two (as might be expected: one due to atmospheric turbulence and another due to the partial coherence of the source field), but only one ring dislocation of the coherence degree (due to the simultaneous effect of both these factors on the optical radiation). In addition, it is shown that the dislocation of the coherence degree that significantly affects the beam coherence level is formed only for beams, for which the coherence width of the source field is larger than the diameter of the first Fresnel zone.

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Ding Chaoliang, 丁超亮, 亓协兴 Qi Xiexing, and 潘留占 Pan Liuzhan. "时空相干涡旋中的相干开关." Acta Optica Sinica 42, no. 20 (2022): 2026004. http://dx.doi.org/10.3788/aos202242.2026004.

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GÜLERCE, MUSTAFA, and GAZANFER ÜNAL. "FORECASTING OF OIL AND AGRICULTURAL COMMODITY PRICES: VARMA VERSUS ARMA." Annals of Financial Economics 12, no. 03 (September 2017): 1750012. http://dx.doi.org/10.1142/s2010495217500129.

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The aim of this paper is to show that the estimates made with vector autoregressive–moving-average (ARMA) models based on the coherent time intervals of the multiple time series give more precise results than the univariate case. The previous literature on dynamic correlations (co-movement) in between food and energy prices has mixed results and mainly based on parametric approaches. Therefore, partial wavelet coherence (PWC) and multiple wavelet coherence (MWC) methods are used, respectively, to uncover the coherency simultaneously for time and frequency domains. In our study; world oil, corn, soybeans, wheat and sugar prices are examined instead of the return and volatility relationship between oil and agricultural commodities due to model-free approach of wavelet analysis.

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Nopita, Dewi. "CONSTRUCTING COHERENT IDEAS AND USING COHERENCE DEVICES IN WRITTEN DESCRIPTIVE ESSAYS: A Study at the Fourth Grade English Department Students of STBA Haji Agus Salim Bukittinggi." Lingua Didaktika: Jurnal Bahasa dan Pembelajaran Bahasa 4, no. 2 (July 1, 2011): 96. http://dx.doi.org/10.24036/ld.v4i2.1260.

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This paper derived from the research results conducted in 2011, looks into the skill of the fourth grade English department students of STBA Haji Agus Salim Bukittinggi in constructing coherent ideas and in using coherence devices in writing descriptive essays. The students’ skill in constructing coherent ideas concerned the relevance and the order of ideas and in using coherence devices concerned the repetitions of the key words/nouns and the use of pronouns and transitional signals. The research results show that the students had weak skill in constructing coherent ideas and had low average skill in using the coherence devices. In relation to constructing coherent ideas, the relevance and the order of ideas of the students’ descriptive essays were weak. Then, in relation to the use of coherence devices, the students’ skill in repeating the key words/nouns was weak, and in using pronouns and transitional signals were high average. Therefore, the students could not achieve coherence in writing descriptive essays yet. Key words/phrases: writing descriptive essays, coherent ideas, coherence devices

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Fu, Liangxue, Fengli Yan, and Ting Gao. "Block-coherence measures and coherence measures based on positive-operator-valued measures." Communications in Theoretical Physics 74, no. 2 (February 1, 2022): 025104. http://dx.doi.org/10.1088/1572-9494/ac42c2.

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Abstract We study block-coherence measures based on the resource theory of block-coherence and coherence measures based on positive-operator-valued measures (POVM). Several block-coherence measures are presented, including the block-coherence measure based on maximum relative entropy, the one-shot block-coherence cost under maximally block-incoherent operations, and the coherence measure based on coherent rank. Their relationships are obtained. Moreover, we describe the deterministic coherence dilution process by constructing block-incoherent operations. Based on the POVM coherence resource theory, we also propose two coherence measures and analyze their relationship.

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Hammerness, Karen. "From Coherence in Theory to Coherence in Practice." Teachers College Record: The Voice of Scholarship in Education 108, no. 7 (July 2006): 1241–65. http://dx.doi.org/10.1177/016146810610800704.

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Historically, one of the central concerns that has plagued the field of teacher education is the observation that fragmentation characterizes the experience of learning to teach. Too often, university-based teacher education programs consist of a set of disconnected individual courses; separate clinical work from coursework; and lack a vision of teaching and learning. Therefore, some teacher educators have argued that creating structurally and conceptually coherent programs will result in more powerful learning for prospective teachers. Yet, although empirical work on such programs is growing, there is little research on the nature of coherence and on how it might develop. To that end, this article documents one teacher education program's efforts to become more coherent, focusing on the ways in which the program tries to become more coherent and on the challenges of coherence. The article concludes with implications for teacher education program design and evaluation, with a focus on the power, complexity, and problems of coherence.

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Kahnt, Maik, Konstantin Klementiev, Vahid Haghighat, Clemens Weninger, Tomás S. Plivelic, Ann E. Terry, and Alexander Björling. "Measurement of the coherent beam properties at the CoSAXS beamline." Journal of Synchrotron Radiation 28, no. 6 (October 5, 2021): 1948–53. http://dx.doi.org/10.1107/s1600577521009140.

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The CoSAXS beamline at the MAX IV Laboratory is a modern multi-purpose (coherent) small-angle X-ray scattering (CoSAXS) instrument, designed to provide intense and optionally coherent illumination at the sample position, enabling coherent imaging and speckle contrast techniques. X-ray tracing simulations used to design the beamline optics have predicted a total photon flux of 1012–1013 photons s−1 and a degree of coherence of up to 10% at 7.1 keV. The normalized degree of coherence and the coherent flux of this instrument were experimentally determined using the separability of a ptychographic reconstruction into multiple mutually incoherent modes and thus the Coherence in the name CoSAXS was verified. How the beamline can be used both for coherent imaging and XPCS measurements, which both heavily rely on the degree of coherence of the beam, was demonstrated. These results are the first experimental quantification of coherence properties in a SAXS instrument at a fourth-generation synchrotron light source.

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Kahnt, Maik, Konstantin Klementiev, Vahid Haghighat, Clemens Weninger, Tomás S. Plivelic, Ann E. Terry, and Alexander Björling. "Measurement of the coherent beam properties at the CoSAXS beamline." Journal of Synchrotron Radiation 28, no. 6 (October 5, 2021): 1948–53. http://dx.doi.org/10.1107/s1600577521009140.

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The CoSAXS beamline at the MAX IV Laboratory is a modern multi-purpose (coherent) small-angle X-ray scattering (CoSAXS) instrument, designed to provide intense and optionally coherent illumination at the sample position, enabling coherent imaging and speckle contrast techniques. X-ray tracing simulations used to design the beamline optics have predicted a total photon flux of 1012–1013 photons s−1 and a degree of coherence of up to 10% at 7.1 keV. The normalized degree of coherence and the coherent flux of this instrument were experimentally determined using the separability of a ptychographic reconstruction into multiple mutually incoherent modes and thus the Coherence in the name CoSAXS was verified. How the beamline can be used both for coherent imaging and XPCS measurements, which both heavily rely on the degree of coherence of the beam, was demonstrated. These results are the first experimental quantification of coherence properties in a SAXS instrument at a fourth-generation synchrotron light source.

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Cuthbert, John. "Book Review: Coherent about Coherence?" Expository Times 116, no. 6 (March 2005): 208. http://dx.doi.org/10.1177/001452460511600612.

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Kamrath, Matthew J., Vladimir Ostashev, D. Keith Wilson, Michael J. White, Carl R. Hart, and Anthony Finn. "Temporal coherence of sound propagated along vertical paths through the atmosphere." Journal of the Acoustical Society of America 150, no. 4 (October 2021): A336. http://dx.doi.org/10.1121/10.0008493.

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Reductions in signal coherence caused by atmospheric turbulence constrain the performance of signal processing methods. This presentation compares theoretical predictions and measurements of acoustic temporal coherence, which describes the similarity of a signal at two times. Combining sound propagation theory with turbulence models yields the theoretical coherence. To be applicable to vertical and slanted propagation, the turbulence models use height-dependent variances and length scales for the fluctuations in temperature, shear-produced velocity, and buoyancy-produced velocity. Meteorological instruments on a 135-m tower measured the required model input data. The coherence measurements used a ground-based source emitting tones between 0.6 and 3.5 kHz and nine microphones on the same tower at heights 39, 80, and 130 m. In most cases, the predicted coherences accurately approximate the measured temporal coherences. In the two early-morning trials, the measured coherence times were much larger than predicted because the atmospheric turbulence was not fully developed. Excluding these cases, the measured coherence times were in the range 0.1–100 s. For each trial, the coherence times decreased slightly more than an order of magnitude from the smallest to largest frequencies. From the shortest to the longest propagation distances, the coherence times decrease slightly less than an order of magnitude.

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Martínez-Herrero, Rosario, Gemma Piquero, Juan Carlos González de Sande, Massimo Santarsiero, and Franco Gori. "Besinc Pseudo-Schell Model Sources with Circular Coherence." Applied Sciences 9, no. 13 (July 4, 2019): 2716. http://dx.doi.org/10.3390/app9132716.

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Partially coherent sources with non-conventional coherence properties present unusual behaviors during propagation, which have potential application in fields like optical trapping and microscopy. Recently, partially coherent sources exhibiting circular coherence have been introduced and experimentally realized. Among them, the so-called pseudo Schell-model sources present coherence properties that depend only on the difference between the radial coordinates of two points. Here, the intensity and coherence properties of the fields radiated from pseudo Schell-model sources with a degree of coherence of the besinc type are analyzed in detail. A sharpening of the intensity profile is found for the propagated beam by appropriately selecting the coherence parameters. As a possible application, the trapping of different types of dielectric nanoparticles with this kind of beam is described.

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Kobayashi, Yuki, and Stephen R. Leone. "Characterizing coherences in chemical dynamics with attosecond time-resolved x-ray absorption spectroscopy." Journal of Chemical Physics 157, no. 18 (November 14, 2022): 180901. http://dx.doi.org/10.1063/5.0119942.

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Coherence can drive wave-like motion of electrons and nuclei in photoexcited systems, which can yield fast and efficient ways to exert materials’ functionalities beyond the thermodynamic limit. The search for coherent phenomena has been a central topic in chemical physics although their direct characterization is often elusive. Here, we highlight recent advances in time-resolved x-ray absorption spectroscopy (tr-XAS) to investigate coherent phenomena, especially those that utilize the eminent light source of isolated attosecond pulses. The unparalleled time and state sensitivities of tr-XAS in tandem with the unique element specificity render the method suitable to study valence electronic dynamics in a wide variety of materials. The latest studies have demonstrated the capabilities of tr-XAS to characterize coupled electronic–structural coherence in small molecules and coherent light–matter interactions of core-excited excitons in solids. We address current opportunities and challenges in the exploration of coherent phenomena, with potential applications for energy- and bio-related systems, potential crossings, strongly driven solids, and quantum materials. With the ongoing developments in both theory and light sources, tr-XAS holds great promise for revealing the role of coherences in chemical dynamics.

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Zuljan Kumar, Danila. "Strategies for establishing discourse coherence. The case of Slovene dialectal discourse." Dialectologia et Geolinguistica 30, no. 1 (November 1, 2022): 51–68. http://dx.doi.org/10.1515/dialect-2022-0003.

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Abstract A discourse is considered coherent only if all its parts are semantically related to each other and if it makes sense. However, coherence cannot be attributed to a discourse in advance because it depends on how the participants understand what they hear/ read. So we can say that it is not the discourse that establishes coherence, but the participants according to their understanding of a discourse. In practise, this means that for the same discourse there are at least two coherences that may or may not match up. Usually they match up to some extent because participants follow the cooperative principle of mutual willingness to establish coherence in discourse. There are several strategies for establishing and maintaining discourse coherence; among them, repetition and inference form an extensive group. In this paper, however, I will focus only on the strategies that are typical of spontaneous spoken discourse. These are the following: questions, completion, contradiction and polyphonic talk. In the second part of the article I will present each of them in the examples of spontaneous dialectal discourse. The texts were recorded in Brda, a region in the far west of Slovenia. The dialect spoken there is called the Brda dialect. It belongs to the Littoral dialect group of the Slovene language.

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Sweklej, Joanna, Robert Balas, Grzegorz Pochwatko, and Małgorzata Godlewska. "Automatic effects of processing fluency in semantic coherence judgments and the role of transient and tonic affective states." Polish Psychological Bulletin 46, no. 1 (March 1, 2015): 151–58. http://dx.doi.org/10.1515/ppb-2015-0020.

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Abstract Recent literature reported that judgments of semantic coherence are influenced by a positive affective response due to increased fluency of processing. The presented paper investigates whether fluency of processing can be modified by affective responses to the coherent stimuli as well as an automaticity of processes involved in semantic coherence judgments. The studies employed the dyads of triads task in which participants are shown two word triads and asked to solve a semantically coherent one or indicate which of the two is semantically coherent. Across two studies in a dualtask paradigm we show that a) attentional resources moderate insight into semantically coherent word triads, whereas b) judgments of semantic coherence judgments are independent of attentional resources. We discuss implications of our findings for how people might form intuitive judgments of semantic coherence.

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Sinjela, Kwangaika Mwala, Jimmy Kijai, and Josephine Esther Katenga. "Teachers´ Perception of Coherence in High School Biology Textbooks in Zambia." Abstract Proceedings International Scholars Conference 7, no. 1 (December 18, 2019): 1444–68. http://dx.doi.org/10.35974/isc.v7i1.926.

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Introduction: Textbook coherence is an important aspect of effective teacher´s instruction and performance of students. This study involved assessing coherence of senior biology high school textbooks in Zambia (MK Biology10, Longman Biology11 and Pupil´s Biology12) and the extent to which these books are aligned with the biology course syllabus. Methods: Using quantitative research design, coherence was conceptualized as a unit of three constructs: alignment and organization, rigor, focus and relevance of contents and connections among ideas. A questionnaire instrument was developed which teachers in Mufulira and other districts in Zambia (n = 82) used to assess textbook and textbook-syllabus coherence. Data was analyzed using statistical methods, independent t-tests and One-way ANOVA. Results: Teachers were generally uncertain about coherence levels in the textbooks. Concerning textbook-syllabus alignment, Pupil´s Biology12 was viewed as most coherent with the course syllabus and MK Biology10 as the least. Discussion: Assessment of coherence is a complex process but it focuses on few common elements. Identifying these elements may help teachers improve teaching practice, curriculum developers design coherent curricula and educational activities, and authors produce coherent textbooks. Further research studies are recommended that would extend the scope of this study to include teachers in all provinces in Zambia, include a mixed method to explore perceptions about coherence, compare coherence of same grade level textbooks, or evaluate coherence of the syllabus and that of other science or non-science textbooks.

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Chen, Shixian, Xiaojie Li, Kaixuan Wu, and Jiadong Shi. "Quantum coherence in a superconducting circuit coupled with a dissipative cavity field." Laser Physics Letters 19, no. 10 (August 18, 2022): 105202. http://dx.doi.org/10.1088/1612-202x/ac867a.

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Abstract Quantum coherence represents a basic feature of a quantum system that is not present in the classical world. Here, we explore the dynamic behaviors of quantum coherence in two charge qubits who are strongly coupled with a single-mode dissipative cavity field. The results show that quantum coherence is sensitive to the coupled system parameters including qubit dissipation rate, initial qubit distribution angle, and coherent state intensity of the cavity field. Additionally, during the dynamic evolution, quantum coherence behaves periodically in the case of the qubit distribution angle, and this periodicity depends on the qubit dissipation rate. Also, the increasing coherent state intensity of cavity field can enhance the magnitude of quantum coherence, meaning that coherence resource in dissipative solid state quantum system can be controlled to some extent. This controllable coherence resource in engineering applications may quantify the advantage enabled in the superconducting circuit for processing the remarkable quantum information tasks.

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Cheung, Mei-chun, Agnes S. Chan, Yvonne M. Han, and Sophia L. Sze. "Brain Activity During Resting State in Relation to Academic Performance." Journal of Psychophysiology 28, no. 2 (April 1, 2014): 47–53. http://dx.doi.org/10.1027/0269-8803/a000107.

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EEG coherence has been widely used to investigate brain activity and learning. However, relatively little is known about the relationship between resting-state EEG coherence and academic performance. The present study investigated this relationship with 140 healthy, normal participants. EEG was recorded during resting periods, with eyes open for 3 min, and the recordings were analyzed for 64 electrode positions in the theta (4–8 Hz), alpha (8–12 Hz), and beta (12–25 Hz) frequency bands. Coherence, defined as the spectral cross-correlation between two signals normalized by their power spectra, was calculated. Short- and long-range intrahemispheric coherence within each hemisphere and interhemispheric coherence across the left and right hemispheres were then computed and compared for each of the theta, alpha, and beta bands. The results showed that academic performance, as measured by grade point average (GPA), was negatively correlated with short-range intrahemispheric alpha and beta coherences in both hemispheres and with interhemispheric alpha and beta coherences in the temporal cortical regions. Therefore, better academic performers demonstrated more decoupling of brain areas when resting with eyes open. This is consistent with a model that relates decreased coherence to neural efficiency.

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Cong, Haisheng, Jianfeng Sun, Zhiyong Lu, Hongyu He, Weijie Ren, Yuxin Jiang, Lingling Xu, Chaoyang Li, Longkun Zhang, and Zhengwei Zhang. "Intrapulse coherence degradation suppressing method of echo signal in coherent lidar." Chinese Optics Letters 21, no. 7 (2023): 071201. http://dx.doi.org/10.3788/col202321.071201.

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Wright, Michael J., and Kevin N. Gurney. "Coherence and Motion Transparency in Rigid and Nonrigid Plaids." Perception 26, no. 5 (May 1997): 553–67. http://dx.doi.org/10.1068/p260553.

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Under a wide range of conditions, stimuli composed of two superimposed grating components with unequal rotation velocities (differing in sign and/or magnitude) gave a striking percept of a single, coherent, nonrigidly deforming plaid surface. Conversely, component angular velocities of the same sign and magnitude yielded rigidly rotating plaids. Rigidity and motion coherence were shown to be independent percepts, and coherent plaids were categorised unambiguously as rigid or nonrigid. Coherence and motion transparency were found to depend upon the relative orientation of components, and polar plots showed two lobes of high coherence for narrow intercomponent angles. There was a slight tendency for plaids with unequal component rotations to appear less coherent, but this was nonsignificant, once the effect of intercomponent angle was taken into account. Changes in the relative spatial frequency of components, relative contrast of components, and repeated presentation produced equivalent effects on coherence for rigid and nonrigid types of plaid motion. Manipulation of the terminators in the display by making the aperture diameters for the two component gratings unequal reduced coherence and increased transparency. The effect was the same for rigid and nonrigid plaids. Coherence in rigid and nonrigid plaids thus depends primarily on local processes and there is no strong interaction between rigidity and coherence.

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Palato, Samuel, Hélène Seiler, Parmeet Nijjar, Oleg Prezhdo, and Patanjali Kambhampati. "Atomic fluctuations in electronic materials revealed by dephasing." Proceedings of the National Academy of Sciences 117, no. 22 (May 14, 2020): 11940–46. http://dx.doi.org/10.1073/pnas.1916792117.

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The microscopic origin and timescale of the fluctuations of the energies of electronic states has a significant impact on the properties of interest of electronic materials, with implication in fields ranging from photovoltaic devices to quantum information processing. Spectroscopic investigations of coherent dynamics provide a direct measurement of electronic fluctuations. Modern multidimensional spectroscopy techniques allow the mapping of coherent processes along multiple time or frequency axes and thus allow unprecedented discrimination between different sources of electronic dephasing. Exploiting modern abilities in coherence mapping in both amplitude and phase, we unravel dissipative processes of electronic coherences in the model system of CdSe quantum dots (QDs). The method allows the assignment of the nature of the observed coherence as vibrational or electronic. The expected coherence maps are obtained for the coherent longitudinal optical (LO) phonon, which serves as an internal standard and confirms the sensitivity of the technique. Fast dephasing is observed between the first two exciton states, despite their shared electron state and common environment. This result is contrary to predictions of the standard effective mass model for these materials, in which the exciton levels are strongly correlated through a common size dependence. In contrast, the experiment is in agreement with ab initio molecular dynamics of a single QD. Electronic dephasing in these materials is thus dominated by the realistic electronic structure arising from fluctuations at the atomic level rather than static size distribution. The analysis of electronic dephasing thereby uniquely enables the study of electronic fluctuations in complex materials.

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Neupane, Sujaya, Daniel Guitton, and Christopher C. Pack. "Coherent alpha oscillations link current and future receptive fields during saccades." Proceedings of the National Academy of Sciences 114, no. 29 (July 3, 2017): E5979—E5985. http://dx.doi.org/10.1073/pnas.1701672114.

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Oscillations are ubiquitous in the brain, and they can powerfully influence neural coding. In particular, when oscillations at distinct sites are coherent, they provide a means of gating the flow of neural signals between different cortical regions. Coherent oscillations also occur within individual brain regions, although the purpose of this coherence is not well understood. Here, we report that within a single brain region, coherent alpha oscillations link stimulus representations as they change in space and time. Specifically, in primate cortical area V4, alpha coherence links sites that encode the retinal location of a visual stimulus before and after a saccade. These coherence changes exhibit properties similar to those of receptive field remapping, a phenomenon in which individual neurons change their receptive fields according to the metrics of each saccade. In particular, alpha coherence, like remapping, is highly dependent on the saccade vector and the spatial arrangement of current and future receptive fields. Moreover, although visual stimulation plays a modulatory role, it is neither necessary nor sufficient to elicit alpha coherence. Indeed, a similar pattern of coherence is observed even when saccades are made in darkness. Together, these results show that the pattern of alpha coherence across the retinotopic map in V4 matches many of the properties of receptive field remapping. Thus, oscillatory coherence might play a role in constructing the stable representation of visual space that is an essential aspect of conscious perception.

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Díaz, María García, Kun Fang, Xin Wang, Matteo Rosati, Michalis Skotiniotis, John Calsamiglia, and Andreas Winter. "Using and reusing coherence to realize quantum processes." Quantum 2 (October 19, 2018): 100. http://dx.doi.org/10.22331/q-2018-10-19-100.

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Coherent superposition is a key feature of quantum mechanics that underlies the advantage of quantum technologies over their classical counterparts. Recently, coherence has been recast as a resource theory in an attempt to identify and quantify it in an operationally well-defined manner. Here we study how the coherence present in a state can be used to implement a quantum channel via incoherent operations and, in turn, to assess its degree of coherence. We introduce the robustness of coherence of a quantum channel-which reduces to the homonymous measure for states when computed on constant-output channels-and prove that: i) it quantifies the minimal rank of a maximally coherent state required to implement the channel; ii) its logarithm quantifies the amortized cost of implementing the channel provided some coherence is recovered at the output; iii) its logarithm also quantifies the zero-error asymptotic cost of implementation of many independent copies of a channel. We also consider the generalized problem of imperfect implementation with arbitrary resource states. Using the robustness of coherence, we find that in general a quantum channel can be implemented without employing a maximally coherent resource state. In fact, we prove that every pure coherent state in dimension larger than 2, however weakly so, turns out to be a valuable resource to implement some coherent unitary channel. We illustrate our findings for the case of single-qubit unitary channels.

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Xiong, Deyi, and Min Zhang. "A Topic-Based Coherence Model for Statistical Machine Translation." Proceedings of the AAAI Conference on Artificial Intelligence 27, no. 1 (June 30, 2013): 977–83. http://dx.doi.org/10.1609/aaai.v27i1.8566.

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Coherence that ties sentences of a text into a meaningfully connected structure is of great importance to text generation and translation. In this paper, we propose a topic-based coherence model to produce coherence for document translation, in terms of the continuity of sentence topics in a text. We automatically extract a coherence chain for each source text to be translated. Based on the extracted source coherence chain, we adopt a maximum entropy classifier to predict the target coherence chain that defines a linear topic structure for the target document. The proposed topic-based coherence model then uses the predicted target coherence chain to help decoder select coherent word/phrase translations. Our experiments show that incorporating the topic-based coherence model into machine translation achieves substantial improvement over both the baseline and previous methods that integrate document topics rather than coherence chains into machine translation.

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Lukin, I. P. "Coherence of vortex pseudo-Bessel beams in turbulent atmosphere." Computer Optics 43, no. 6 (December 2019): 926–35. http://dx.doi.org/10.18287/2412-6179-2019-43-6-926-935.

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Theoretical research of coherent properties of vortex conic waves propagating in a turbulent atmosphere was developed. The analysis was based on the analytical solution of the equation for the transverse second-order mutual coherence function of a light field. The following characteristics of coherence of vortex conic waves were considered: the coherence degree, the coherence radius, the root-mean-square and the integral scale of coherence degree. Dependence of these characteristics on the parameters of optical radiation and turbulent atmosphere was analyzed. Unlike the coherence radius, the root-mean-square and integral scales of the coherence degree of vortex conic waves were found to be highly sensitive to the influence of atmospheric turbulence.

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Anindita, Widyashanti Kunthara. "Cohesion and Coherence Problems Among Non-Native English Students’ Writing Essays." Lensa: Kajian Kebahasaan, Kesusastraan, dan Budaya 14, no. 1 (June 30, 2024): 58. http://dx.doi.org/10.26714/lensa.14.1.2024.58-79.

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In order to properly organize ideas and express significant information, non-native students sometimes struggle with cohesion and coherence in their essays. This study examines the body of literature to pinpoint frequent problems non-native writers have while trying to make their writing coherent and cohesive. This study aims to assess the literature on cohesion and coherence issues in essays written by non-native students, with a particular focus on a number of components, including referential and relational coherence, theme and rheme, and grammatical and lexical cohesion. The literature study looks at papers that address problems with coherence and cohesiveness in student writing. It groups the results according to several coherence and cohesion criteria, such as referential and relational coherence, theme and rheme, and grammatical and lexical cohesion. An analysis of the essays shows common problems that non-native students face. Accompanying difficulties with collocation and diction are lexical cohesion faults, like as repetition and restricted vocabulary utilization. Issues with conjunction usage and text arrangement are examples of grammatical cohesion issues. Coherence is an issue that students struggle with; they have trouble coming up with thesis statements, topic sentences, introductions, and conclusion that are all coherent. Recognizing these difficulties emphasizes the necessity of focused interventions to improve non-native students' writing abilities. The development of instruments such as Tool for Automatic Cohesion Analysis (TAACO) presents encouraging paths for methodically evaluating and resolving cohesion concerns. These insights can be used by educators to create coherence and cohesiveness-enhancing tactics for non-native essay writers, which will ultimately result in clearer, more coherent writing.

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Santarsiero, M., R. Martínez-Herrero, D. Maluenda, J. C. G. de Sande, G. Piquero, and F. Gori. "Partially coherent sources with circular coherence." Optics Letters 42, no. 8 (April 5, 2017): 1512. http://dx.doi.org/10.1364/ol.42.001512.

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Piquero, G., M. Santarsiero, R. Martínez-Herrero, J. C. G. de Sande, M. Alonzo, and F. Gori. "Partially coherent sources with radial coherence." Optics Letters 43, no. 10 (May 14, 2018): 2376. http://dx.doi.org/10.1364/ol.43.002376.

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Gbur, Greg, and Taco D. Visser. "Coherence vortices in partially coherent beams." Optics Communications 222, no. 1-6 (July 2003): 117–25. http://dx.doi.org/10.1016/s0030-4018(03)01606-7.

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Chriki, Ronen, Slava Smartsev, David Eger, Ofer Firstenberg, and Nir Davidson. "Coherent diffusion of partial spatial coherence." Optica 6, no. 11 (October 29, 2019): 1406. http://dx.doi.org/10.1364/optica.6.001406.

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41

Simmons, James A., Kelsey N. Hom, and Andrea Megela Simmons. "Temporal coherence of harmonic frequencies affects echo detection in the big brown bat, Eptesicus fuscus." Journal of the Acoustical Society of America 154, no. 5 (November 1, 2023): 3321–27. http://dx.doi.org/10.1121/10.0022444.

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Echolocating big brown bats (Eptesicus fuscus) broadcast frequency modulated (FM) ultrasonic pulses containing two prominent harmonic sweeps (FM1, FM2). Both harmonics typically return as echoes at the same absolute time delay following the broadcast, making them coherent. Electronically splitting FM1 and FM2 allows their time delays to be controlled separately, making them non-coherent. Earlier work shows that big brown bats discriminate coherent from split harmonic, non-coherent echoes and that disruptions of harmonic coherence produce blurry acoustic images. A psychophysical experiment on two trained big brown bats tested the hypothesis that detection thresholds for split harmonic, non-coherent echoes are higher than those for coherent echoes. Thresholds of the two bats for detecting 1-glint echoes with coherent harmonics were around 35 and 36 dB sound pressure level, respectively, while thresholds for split harmonic echoes were about 10 dB higher. When the delay of FM2 in split harmonic echoes is shortened by 75 μs to offset neural amplitude-latency trading and restore coherence in the auditory representation, thresholds decreased back down to those estimated for coherent echoes. These results show that echo detection is affected by loss of harmonic coherence, consistent with the proposed broader role of coherence across frequencies for auditory perception.

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Duda, Jaromír. "Coherence and weak coherence in the square of algebras." Czechoslovak Mathematical Journal 42, no. 4 (1992): 613–18. http://dx.doi.org/10.21136/cmj.1992.128370.

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Megawati, Erna. "Coherence Aspects Within Efl Essay." Scope : Journal of English Language Teaching 3, no. 1 (January 30, 2019): 13. http://dx.doi.org/10.30998/scope.v3i1.2720.

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<p>The purpose of this research is to discover Indonesian undergraduate students’ understanding in composing a coherence English essay. The subjects of the research are essay texts written by thirty undergraduate students using theme “Students’ attitude toward Indonesian language” chosen randomly. The analysis has revealed that s coherence aspects have not used properly, more over there is one aspect is not used. The coherence aspects consist of repetition key noun, using consistent pronoun, transition signals and logical order. This research is designed as library research using content analysis method. Data are analyzed to investigated the coherency in students’ essay.</p><p>Key words: essay, coherence</p>

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Koscholke, Jakob, Michael Schippers, and Alexander Stegmann. "New Hope for Relative Overlap Measures of Coherence." Mind 128, no. 512 (September 21, 2018): 1261–84. http://dx.doi.org/10.1093/mind/fzy037.

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Abstract Relative overlap measures of coherence have recently been shown to have two devastating properties: (i) according to the plain relative overlap measure, the degree of coherence of any set of propositions cannot be increased by adding further propositions, and (ii) according to the refined relative overlap measure, no set can be more coherent than its most coherent two-element subset. This result has been taken to rule out relative overlap as a foundation for a probabilistic explication of coherence. The present paper shows that this view is premature: we propose a relative overlap measure that does not fall victim to the two properties. The guiding idea is to employ a well-established recipe for the construction of coherence measures and to adapt it to the idea of relative overlap. We show that this new measure keeps up with, or even outperforms, former overlap measures in a set of desiderata for coherence measures and a collection of popular test cases. This result re-establishes relative overlap as a candidate for a proper formalization of coherence.

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Canrinus, Esther T., Kirsti Klette, and Karen Hammerness. "Diversity in Coherence: Strengths and Opportunities of Three Programs." Journal of Teacher Education 70, no. 3 (December 8, 2017): 192–205. http://dx.doi.org/10.1177/0022487117737305.

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Although teacher educators may perceive their program and courses to be coherent, the question remains to what extent student teachers also are able to perceive the linkages within their programs. Coherence within teacher education programs is important for teacher candidates to build understanding of teaching. Our study draws upon survey data from 269 teacher candidates, in three different teacher education programs, located in three different countries (Norway, Finland, United States [California]) and compares these candidates’ perceptions of the coherence of their teacher education programs. Candidates from a program that has explicitly been working on constructing a coherent program over a period of 15 years do report significantly more coherence, yet, across the programs, there remains room for improvement regarding the coherence between field placement and campus courses. We conclude with the suggestion that potential improvement of program coherence lies within greater communication and collaboration between the various stakeholders within teacher education.

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Kwon, Ji-Hwan, Joohyun Lee, Je In Lee, Byeong-Gwan Cho, and Sooheyong Lee. "Exploring TEM Coherence Properties via Speckle Contrast Analysis in Coherent Electron Scattering of Amorphous Material." Nanomaterials 13, no. 23 (November 24, 2023): 3016. http://dx.doi.org/10.3390/nano13233016.

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We investigate the coherence properties of a transmission electron microscope by analyzing nano-diffraction speckles originating from bulk metallic glass. The spatial correlation function of the coherent diffraction patterns, obtained in the transmission geometry, reveals the highly coherent nature of the electron probe beam and its spatial dimension incident on the sample. Quantitative agreement between the measured speckle contrast and an analytical model yields estimates for the transverse and longitudinal coherence lengths of the source. We also demonstrate that the coherence can be controlled by changing the beam convergence angle. Our findings underscore the preservation of electron beam coherence throughout the electron optics, as evidenced by the high-contrast speckles observed in the scattering patterns of the amorphous system. This study paves the way for the application of advanced coherent diffraction methodologies to investigate local structures and dynamics occurring at atomic-length scales across a diverse range of materials.

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Li, Qing, Kris Vasudevan, and Frederick A. Cook. "3-D coherency filtering." GEOPHYSICS 62, no. 4 (July 1997): 1310–14. http://dx.doi.org/10.1190/1.1444232.

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Coherency filtering is a tool used commonly in 2-D seismic processing to isolate desired events from noisy data. It assumes that phase‐coherent signal can be separated from background incoherent noise on the basis of coherency estimates, and coherent noise from coherent signal on the basis of different dips. It is achieved by searching for the maximum coherence direction for each data point of a seismic event and enhancing the event along this direction through stacking; it suppresses the incoherent events along other directions. Foundations for a 2-D coherency filtering algorithm were laid out by several researchers (Neidell and Taner, 1971; McMechan, 1983; Leven and Roy‐Chowdhury, 1984; Kong et al., 1985; Milkereit and Spencer, 1989). Milkereit and Spencer (1989) have applied 2-D coherency filtering successfully to 2-D deep crustal seismic data for the improvement of visualization and interpretation. Work on random noise attenuation using frequency‐space or time‐space prediction filters both in two or three dimensions to increase the signal‐to‐noise ratio of the data can be found in geophysical literature (Canales, 1984; Hornbostel, 1991; Abma and Claerbout, 1995).

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Akeju, Oluwaseun, M. Brandon Westover, Kara J. Pavone, Aaron L. Sampson, Katharine E. Hartnack, Emery N. Brown, and Patrick L. Purdon. "Effects of Sevoflurane and Propofol on Frontal Electroencephalogram Power and Coherence." Anesthesiology 121, no. 5 (November 1, 2014): 990–98. http://dx.doi.org/10.1097/aln.0000000000000436.

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Abstract Background: The neural mechanisms of anesthetic vapors have not been studied in depth. However, modeling and experimental studies on the intravenous anesthetic propofol indicate that potentiation of γ-aminobutyric acid receptors leads to a state of thalamocortical synchrony, observed as coherent frontal alpha oscillations, associated with unconsciousness. Sevoflurane, an ether derivative, also potentiates γ-aminobutyric acid receptors. However, in humans, sevoflurane-induced coherent frontal alpha oscillations have not been well detailed. Methods: To study the electroencephalogram dynamics induced by sevoflurane, the authors identified age- and sex-matched patients in which sevoflurane (n = 30) or propofol (n = 30) was used as the sole agent for maintenance of general anesthesia during routine surgery. The authors compared the electroencephalogram signatures of sevoflurane with that of propofol using time-varying spectral and coherence methods. Results: Sevoflurane general anesthesia is characterized by alpha oscillations with maximum power and coherence at approximately 10 Hz, (mean ± SD; peak power, 4.3 ± 3.5 dB; peak coherence, 0.73 ± 0.1). These alpha oscillations are similar to those observed during propofol general anesthesia, which also has maximum power and coherence at approximately 10 Hz (peak power, 2.1 ± 4.3 dB; peak coherence, 0.71 ± 0.1). However, sevoflurane also exhibited a distinct theta coherence signature (peak frequency, 4.9 ± 0.6 Hz; peak coherence, 0.58 ± 0.1). Slow oscillations were observed in both cases, with no significant difference in power or coherence. Conclusions: The study results indicate that sevoflurane, like propofol, induces coherent frontal alpha oscillations and slow oscillations in humans to sustain the anesthesia-induced unconscious state. These results suggest a shared molecular and systems-level mechanism for the unconscious state induced by these drugs.

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Anczykowska, A., S. Bartkiewicz, and J. Mysliwiec. "Laser Coherence Meter Based on Nanostructured Liquid Crystals." International Journal of Optics 2013 (2013): 1–3. http://dx.doi.org/10.1155/2013/287506.

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We present the method for coherence length measurement using coherence meter based on hybrid liquid crystal structures doped with gold nanoparticles. The results indicate that the method is able to determine the coherence length of coherent light sources with precision of 0.01 m at wavelength range from 200 to 800 nm for wide range of initial beam powers starting from 1 mW. Given the increasing use of laser technology in industry, military, or medicine, our research may open up a possible route for the development of improved techniques of coherent diagnostic light sources.

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Xu He, 徐荷, 孙迪峰 Sun Difeng, and 李健兵 Li Jianbing. "相干测风激光雷达回波相干性分析." Laser & Optoelectronics Progress 60, no. 14 (2023): 1428003. http://dx.doi.org/10.3788/lop222106.

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Journal articles on the topic 'Coherence'

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