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1
Li, Z., W. Lynn, R. Chambers, Ken Larner, and Ray Abma. "Enhancements to prestack frequency‐wavenumber (f-k) migration." GEOPHYSICS 56, no. 1 (January 1991): 27–40. http://dx.doi.org/10.1190/1.1442955.
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Prestack frequency‐wavenumber (f-k) migration is a particularly efficient method of doing both full prestack time migration and migration velocity analysis. Conventional implementations of the method, however, can encounter several drawbacks: (1) poor resolution and spatial aliasing noise caused by insufficient sampling in the offset dimension, (2) poor definition of steep events caused by insufficient sampling in the velocity dimension, and (3) inadequate handling of ray bending for steep events. All three of these problems can be mitigated with modifications to the prestack f-k algorithm. The application of linear moveout (LMO) in the offset dimension prior to migration reduces event moveout and hence increases the bandwidth of non‐spatially aliased signals. To reduce problems of interpolation for steep events, the number of constant‐velocity migrations can be economically increased by performing residual poststack migrations. Finally, migration with a dip‐dependent imaging velocity addresses the issue of ray bending and thereby improves the positioning of steep events. None of these enhancements substantially increases the computational effort of f-k migration. Prestack f-k migration possesses a limitation for which no solution is readily available. Where lateral velocity variation is modest, steep events (such as fault‐plane reflections in sediments) may not be imaged as well as by other migration approaches. This shortcoming results from the restriction that, in the prestack f-k approach, a single velocity field must serve to perform two different functions: imaging and stacking. Nevertheless, in areas of strong velocity variation and gentle to moderate dip, the detailed velocity control afforded by the prestack f-k method is an excellent source of geologic information.
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Beasley, Craig J., Walt Lynn, Ken Larner, and Hung Nguyen. "Cascaded f-k migration: Removing the restrictions on depth‐varying velocity." GEOPHYSICS 53, no. 7 (July 1988): 881–93. http://dx.doi.org/10.1190/1.1442525.
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Stolt’s frequency‐wavenumber (f-k) method is computationally efficient and has unlimited dip accuracy for constant‐velocity media. Although the f-k method can handle moderate vertical velocity variations, errors become unacceptable for steep dips when such variations are large. This paper describes an extension to the f-k method that removes its restrictions on vertical velocity variation, yielding accuracy comparable to phase‐shift migration at only a fraction of the computational time. This extension of the f-k method is based on partitioning the velocity field, just as in cascaded finite‐difference migration, and performing a number of stages of f-k migration. In each stage, the migration‐velocity field is closer to a constant—the ideal situation for the f-k migration method—than when the migration is done conventionally (i.e., in just one stage). Empirical results and error analyses show that, at most, four stages of the cascaded f-k algorithm are sufficient to migrate steep events as accurately as by the phase‐shift method for virtually any vertically inhomogeneous velocity field. Given its accuracy and efficiency, cascaded f-k migration can become the method of choice for 2-D, two‐pass 3-D, and single‐pass 3-D time migrations.
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Stolt, Robert H. "A prestack residual time migration operator." GEOPHYSICS 61, no. 2 (March 1996): 605–7. http://dx.doi.org/10.1190/1.1443987.
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Larner and Beasley (1987) present cascaded migration as a way to increase the power and effectiveness of relatively simple migration methods. In particular, f-k migration (Stolt, 1978) can be made to accommodate a depth‐dependent velocity as a cascade of constant‐velocity migrations. The core concept is that data which have been migrated with an approximate velocity can be effectively migrated to their true velocity by migrating with a velocity that is equal to the square root of the difference between the squares of the true and approximate velocities.
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Garcia, D., L. L. Tarnec, S. Muth, E. Montagnon, J. Poree, and G. Cloutier. "Stolt's f-k migration for plane wave ultrasound imaging." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 60, no. 9 (September 2013): 1853–67. http://dx.doi.org/10.1109/tuffc.2013.2771.
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Pai, David M. "Generalized f-k (frequency‐wavenumber) migration in arbitrarily varying media." GEOPHYSICS 53, no. 12 (December 1988): 1547–55. http://dx.doi.org/10.1190/1.1442436.
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Migration requires one‐way wave continuation. In the spatial domain, one‐way wave equations are derived based on various approximations to an assumed dispersion relation. In the frequency‐wavenumber domain, the well known f-k method and the phase‐shift method are strictly valid only within homogeneous models and layered models, respectively. In this paper, a frequency‐wavenumber domain method is presented for one‐way wave continuation in arbitrarily varying media. In the method, the downward continuation is accomplished, not with plane waves individually as in the f-k or the phase‐shift method, but with the whole spectrum of plane waves simultaneously in order to account for the coupling among the plane waves due to lateral inhomogeneity. The method is based on a matrix integral equation. The method has the following merits: (1) The method is a generalization of the f-k and the phase‐shift methods, valid in arbitrarily varying models. (2) The method has physical interpretations in terms of upgoing and downgoing plane waves, and as such the method has well defined steps leading from full‐wave continuation (two‐way wave) to one‐way wave continuation for migration. (3) The method is rigorous; the only approximations in the method—other than the one‐way wave approximation necessary for migration—are the discretization of a continuous system (which is necessary in computer methods) and imperfections associated with the limited spatial aperture of the data; as such, the method can achieve high solution accuracy. (4) The method can be fast, since computations are mainly matrix‐vector multiplications, which are easily vectorizable. In particular, compared to spatial domain methods, I contend that the method is (1) more rigorous in one‐way wave theory, (2) more accurate in migration of high‐dip events, and (3) faster for smooth models. I applied the method to a few examples of zero‐offset data migration, including imaging a point diffractor below a dipping interface, migration with sharp lateral variations in velocity, and migration with smooth lateral variations in velocity.
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Kim, Y. C., R. Gonzalez, and J. R. Berryhill. "Recursive wavenumber‐frequency migration." GEOPHYSICS 54, no. 3 (March 1989): 319–29. http://dx.doi.org/10.1190/1.1442657.
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There are many approaches for migrating seismic data using velocities varying only with depth. These methods are capable of accommodating quasi‐continuous vertical velocity variation at the expense of a considerably larger amount of computation than with the Stolt method, which assumes a constant velocity for the subsurface of the earth. However, the errors involved in estimating migration velocities from seismic data are often too large to justify such a large amount of computational effort. Furthermore, because there is a resolution limit in velocity estimation, a time‐depth curve based on the velocity estimates may be represented by a series of line segments that typically are much larger than the migration step size. For a time‐depth curve segmented in this way, we may successively apply the fast Stolt method interleaved with phase shift for downward continuation. This approach, recursive wavenumber‐frequency (k-f ) migration, retains the speed of the Stolt method and produces from seismic data a subsurface image as good as that from the phase‐shift method. The recursive k-f method is a powerful tool, particularly for the migration of 3-D data.
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Subari, Achmad, Syamsurijal Rasimeng, and Nando Liven Konstanta. "PENGHILANGAN SWELL NOISE DAN LINIER NOISE PADA DATA SEISMIK 2D MARINE HIGH RESOLUTION PADA LINTASAN “AF” MENGGUNAKAN METODE SWNA, F-K FILTER DAN TAU-P TRANSFORM." Jurnal Geofisika Eksplorasi 4, no. 1 (January 17, 2020): 3–18. http://dx.doi.org/10.23960/jge.v4i1.3.
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Research have been done about noise removal caused by environment (swell noise) and linear noise on high frequency 2D seismic data on line “AF” using swell noise attenuation (SWNA) method, f-k filter and tau-p transformation. Based on obtained result, swell noise succeed removed from data using velocity limited filter that is 1000 m/s on frequency 25 Hz applied to swell noise attenuation process. Applied SWNA data, then created input f-k filter process. In f-k filter process, used polygon design having a minimum frequency limit around 5 Hz maximum high frequency around 450 Hz. The results f-k filter giving a good output with linear noise removal to time 1500 ms. F-k filter output obtained, then processed again using tau-p transformation method. Application of tau-p transformation transformed data into (τ-p) domain. Transformed data on (τ-p) domain, linear noise made on moveout 600 ms. Then the data muted using surgical mute. Based on obtained result, tau-p result can removing linear noise on data. Linear noise removed dominating on time 1500 ms-2500 ms. That matter caused by linear noise on time 0-1500 ms succeed removed using previous process. After the method succesfully applied , data processing continued doing the stack and migration process. Applied migration is postack kirchoff time migration, migration do with migration angel around 300 and aperture around 600 m.
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Jin, Yang, and Yunling Duan. "2D Wavelet Decomposition and F-K Migration for Identifying Fractured Rock Areas Using Ground Penetrating Radar." Remote Sensing 13, no. 12 (June 10, 2021): 2280. http://dx.doi.org/10.3390/rs13122280.
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The quality of the surrounding rock is crucial to the stability of underground caverns, thereby requiring an effective monitoring technology. Ground-penetrating radar (GPR) can reconstruct the subterranean profile by electromagnetic waves, but two significant issues, called clutter and hyperbola tails, affect the signal quality. We propose an approach to identify fractured rocks using 2D Wavelet transform (WT) and F-K migration. F-K migration can handle the hyperbola using Fourier analysis. WT can mitigate clutter, distinguish signal discontinuity, and provide signals with a good time-frequency resolution for F-K migration. In the simulation, the migration result from horizontal detail coefficients highlight the crack locations and reduce the scattering signals. Noise has been separated by 2D WT. Hyperbola tails are decomposed to vertical and diagonal detail coefficients. Similar promising results have been achieved in the field measurement. Therefore, the proposed approach can process GPR signals for identifying fractured rock areas.
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Huo, Jianjian, Binzhong Zhou, Qing Zhao, and Iain M. Mason. "Reconstruction of borehole radar images by a modified f–k migration." Geophysical Journal International 221, no. 3 (February 27, 2020): 1626–34. http://dx.doi.org/10.1093/gji/ggaa094.
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SUMMARY Borehole radar (BHR) is an effective imaging tool. It can be used to detect and map faults, fractures, folds, domes, partings and mine workings. Most BHRs have azimuthally omnidirectional radiation patterns. The echoes sensed by such BHRs may come from any direction. Considering a radar in a straight borehole that passes through a stack of flat reflection planes, V-shaped events or crosses appear on the time section. One of the arms of each cross is a real image while the other is an ambiguity of known origin. Directional ambiguities such as these obstruct efforts to interpret the data. In this paper, we address this difficulty by using a modified f–k migration algorithm to translate crosses into lines on the final section that are consistent with a priori information about for example bedding. Compared with conventional strategies, for example migration + f–k dip filter, this approach integrates the two separated processes into one and is straightforward, computationally effective and simple to implement. The method is demonstrated using a synthetic model and a real BHR field data set. It allows the interpreter to use a priori information about fault swarms or plausible bedding planes at an early stage. The reconstructed BHR image helps the search for geological anomalies such as fractures, partings, domes and rolls that could be a hazard for mining.
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Kostecki, Andrzej, and Anna Półchłopek. "Stable depth extrapolation of seismic wavefields by a Neumann series." GEOPHYSICS 63, no. 6 (November 1998): 2063–71. http://dx.doi.org/10.1190/1.1444499.
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Several migration methods fail to work when applied to complex geological structures with strong lateral heterogeneity. The generalized migration in the frequency‐wavenumber (f-k) domain based on a convolution with a slowness- (inverse of velocity) dependent operator is capable of downward continuation of wavefield in media with strong vertical and lateral variations of velocity. Unfortunately, this method, as presented in the literature, is potentially unstable. We propose a new, stable extrapolator based on the solution of the integral Fredholm equation, which describes a one‐way wave equation in the form of a Neumann series. The resulting algorithm of depth migration is implemented in both the frequency‐wavenumber (f-k) and frequency‐space (f-x) domains and takes into account arbitrary lateral gradients of velocity, using a low‐frequency filter (in x-f domain) that is the sum of the power series. The computation time of depth migration by a Neumann series is slightly longer than for split‐step Fourier migration. The examples presented suggest that the depth migration by Neumann’s series method can be used to map complex structures with strong lateral gradients of velocity.
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Lindell, David B., Gordon Wetzstein, and Matthew O'Toole. "Wave-based non-line-of-sight imaging using fast f-k migration." ACM Transactions on Graphics 38, no. 4 (July 12, 2019): 1–13. http://dx.doi.org/10.1145/3306346.3322937.
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Margrave, Gary F. "Direct Fourier migration for vertical velocity variations." GEOPHYSICS 66, no. 5 (September 2001): 1504–14. http://dx.doi.org/10.1190/1.1487096.
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The Stolt f‐x migration algorithm is a direct (i.e. nonrecursive) Fourier‐domain technique based on a change of variables, or equivalently a mapping, that converts the unmigrated spectrum to the migrated spectrum. The algorithm is simple and efficient but limited to constant velocity. A v(z) f‐k migration method, capable of very high accuracy for vertical velocity variations, can be formulated as a nonstationary filter that avoids the change of variables. The result is a direct Fourier‐domain process that, for each wavenumber, applies a nonstationary migration filter to a vector of input frequency samples to create a vector of output frequency samples. The filter matrix is analytically specified in the mixed domain of input frequency and migrated time. It can be moved to the full‐Fourier domain of input frequency and output frequency by a fast Fourier transform. When applied for constant velocity, the v(z) f‐k algorithm is slower than the Stolt method but without the usual artifacts related to complex‐valued frequency‐domain interpolation. Vertical velocity variations, through an rms‐velocity (straight‐ray) assumption, are handled by the v(z) f‐k method with no additional cost. Greater accuracy at slight additional expense is obtained by extending the method to a WKBJ phase‐shift integral. This has the same accuracy as recursive phase shift and is similar in cost. For constant velocity, the full‐Fourier domain migration filter is a discrete approximation to a Dirac delta function whose singularity tracks along a hyperbola determined by the migration velocity. For variable velocity, the migration filter has significant energy between hyperbolic trajectories determined by the minimum and maximum instantaneous velocities. The full‐Fourier domain offers interesting conceptual parallels to Stolt’s algorithm. However, unless a more efficient method of calculating the Fourier filter matrix can be found, the mixed‐domain method will be faster. The mixed‐domain nonstationary filter moves the input data from the Fourier domain to the migrated time domain as it migrates. It is faster because the migration filter is known analytically in the mixed domain.
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Gureli, O., T. Kayiran, and G. B. Ecevitoglu. "3D true-amplitude constant-offset migration and DMO for F-K and integral methods." Journal of Geophysics and Engineering 6, no. 2 (May 19, 2009): 189–203. http://dx.doi.org/10.1088/1742-2132/6/2/010.
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Sakamoto, Takuya, Toru Sato, Pascal J. Aubry, and Alexander G. Yarovoy. "Ultra-Wideband Radar Imaging Using a Hybrid of Kirchhoff Migration and Stolt F-K Migration With an Inverse Boundary Scattering Transform." IEEE Transactions on Antennas and Propagation 63, no. 8 (August 2015): 3502–12. http://dx.doi.org/10.1109/tap.2015.2431725.
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Salvati, Dalilla da Silva, Júlia Fernandes Perroca, Sabrina Morilhas Simões, Antonio Leão Castilho, and Rogerio Caetano da Costa. "Variation in size distribution of juvenile pink shrimps Farfantepenaeus brasiliensis and F. paulensis in the estuarine-adjacent ocean area of Cananéia, south-eastern coast of Brazil." Journal of the Marine Biological Association of the United Kingdom 101, no. 1 (February 2021): 117–29. http://dx.doi.org/10.1017/s0025315420001393.
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AbstractThe study characterized the structure of juveniles and sub-adults of Farfantepenaeus brasiliensis and F. paulensis in the Cananéia-Iguape estuarine lagoon system and its adjacent coastal area by evaluating the period of juvenile recruitment, sex ratio, growth, longevity, natural mortality, and development time until the late juvenile phase. Samples were collected from July 2012 to June 2014. Shrimps were identified by species and sex, and measured (carapace length – CL mm); 889 individuals of F. brasiliensis and 848 of F. paulensis were analysed. Females were more abundant than males for both species. The growth parameters of F. brasiliensis were: CL∞ = 45.5 mm, k = 1.8 year−1 for males and CL∞ = 55.2 mm, k = 1.6 year−1 for females; longevity of 2.52 years (males) and 2.88 years (females); and natural mortality of 1.71 (males) and 1.55 (females). For F. paulensis, the following values were observed: CL∞ = 40.7 mm, k = 2.3 year−1 for males and CL∞ = 56.5 mm, k = 1.9 year−1 for females; longevity of 2.04 years (males) and 2.37 years (females); and natural mortality of 2.39 (males) and 2.05 (females). The juvenile recruitment of both species peaked in January 2014. The development time until late juvenile phase was ~7 months (F. brasiliensis) and ~5 months (F. paulensis). Even though the highest abundance of juveniles did not occur in the closed season, fishing is forbidden in the estuarine area and the migration towards the adult population occurred close to or even during the closed season.
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Witt, Colleen M., and Ellen A. Robey. "The Ins and Outs of CCR7 in the Thymus." Journal of Experimental Medicine 200, no. 4 (August 16, 2004): 405–9. http://dx.doi.org/10.1084/jem.20041110.
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Although it is widely supposed that chemokines play a role in the thymus, most existing evidence is circumstantial. In this issue, two groups provide direct evidence that the chemokine receptor CCR7 is required for normal thymocyte migration (Ueno, T., F. Saito, D. Gray, S. Kuse, K. Hieshima, H. Nakano, T. Kakiuchi, M. Lipp, R. Boyd, and Y. Takahama. 2004. J. Exp. Med. 200:493–505; Misslitz, A., O. Pabst, G. Hintzen, L. Ohl, E. Kremmer, H. T. Petrie, and R. Forster. 2004. J. Exp. Med. 200:481–491). The two papers focus on distinct and opposite migration events, an early outward migration and a later inward migration. Together these papers provide a fascinating picture of the complex role of CCR7 in orchestrating thymocyte migration.
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Xue, Mei Gui, and Shuang Fei Wang. "Correlation between Partition Coefficients Food Simulant/Paper, KF, P, and Octanol/Water, KO,W - A New Approach in Support of Migration Modeling and Compliance Testing." Applied Mechanics and Materials 469 (November 2013): 440–43. http://dx.doi.org/10.4028/www.scientific.net/amm.469.440.
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An investigation on the migration of various migrants from paper (board) into solid food simulants was undertaken to determine the correlation of partition coefficients between food simulants / paper, KF,P, and octanol/water, KO,W. The migration tests were carried out using four solid food simulants (rice powder, milk powder, white sugar and rice) in contact with a kind paper which was spiked with 5 compounds. These model migrants cover a wide range of potential migrants in paper (board) food packaging materials and can be characterized by octanol/water partition coefficients ranging from log KO,W= 2.293 to 4.496. In all simulants a correlation of increasing log KO, Wwith increasing log KF,Pwas found. Using the correlation line as a calibration curve, log KF, Pcan be predicted from the log KO, Wvalues of the migrants for a given food stimulant. This approach is a new estimation procedure to obtain KF, Pvalues from easily accessible KO,Wvalues which can significantly reduce the efforts for compliance assessment by minimizing time and costs to be spent compared to carrying out an enormous number of specific migration test. Furthermore, this approach will support experimental migration testing since it provides a method to determine which simulant is appropriate for a given foodstuff.
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Bruce, Michael I., Brian W. Skelton, Natasha N. Zaitseva, and Allan H. White. "Temperature Dependence of the Crystal Structure of Ru4(µ4-C2H2)(CO)9(η-PhMe)." Australian Journal of Chemistry 52, no. 7 (1999): 681. http://dx.doi.org/10.1071/ch99035.
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The thermal reaction between Ru4(µ4-C2H2)(CO)12 and toluene afforded Ru4(µ4-C2H2)(CO)9(η-PhMe), whose crystal and molecular structures, determined at c. 300 and 153 K, are reported [triclinic, P 1; a ≈ 8 . 0; b ≈ 10 . 4; c ≈ 13 . 7 Å, a ≈ 87; b ≈ 89 . 7; γ ≈ 70°, Z = 2; conventional R values on |F| at convergence were 0 . 027 (300 K), 0 . 020 (153 K) for 4561, 4761 independent ‘observed’ [F >4σ(F)] reflections, respectively]. At low temperature, the structure is a nicely ordered Ru4 butterfly with a C2H2 ligand sitting between the wing tips and an η6 -PhMe ligand attached to one of the wing-tip atoms along the extension of the axis between them. At 300 K, a disordered component is evident, 9% occupancy of the wing-tip atom appended to toluene being displaced by 0 . 701(8) Å so that the bonding to the toluene approaches η2; this is accompanied by a counterpart displacement of one of the hinge Ru atoms. It is suggested that this is the first stage of a putative migration of the arene from wing-tip to hinge Ru atoms.
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Sun, Yimin, and Tong W. Fei. "Flank-preserving deprimary reverse time migration." GEOPHYSICS 86, no. 1 (December 16, 2020): S1—S15. http://dx.doi.org/10.1190/geo2019-0844.1.
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Deprimary reverse time migration (RTM) is a newly proposed technology aiming at removing false structures in images computed by RTM. However, a side effect of this new technology is an inability to image steeply dipping structures. We first introduce how to obtain a composite wavefield, including a complete downgoing wavefield and a partial upgoing wavefield, using the combination of an f-k filter and a spatial-wavenumber filter. We next thoroughly analyze the root cause leading to this side effect in the deprimary RTM technology. By using a modified imaging condition accommodating a composite wavefield, we propose a novel flank-preserving deprimary RTM method to maintain the capability of removing false structures and preserve steeply dipping subsurface structures in the final image. We demonstrate the success of this new technology via several examples. Furthermore, we study different perspectives in depth to show that flank-preserving deprimary RTM is a trade-off solution between RTM and deprimary RTM.
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Meinardus, Hans A., and Karl L. Schleicher. "3-D time‐variant dip moveout by the f-k method." GEOPHYSICS 58, no. 7 (July 1993): 1030–41. http://dx.doi.org/10.1190/1.1443479.
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The standard seismic imaging sequence consists of normal moveout (NMO), dip moveout (DMO), stack, and zero‐offset migration. Conventional NMO and DMO processes remove much of the effect of offset from prestack data, but the constant velocity assumption in most DMO algorithms can compromise the ultimate results. Time‐variant DMO avoids the constant velocity assumption to create better stacks, especially for steeply dipping events. Time‐variant DMO can be implemented as a 3-D, f-k domain process using the dip decomposition method. Prestack data are moved out with a set of NMO velocities corresponding to discrete values of in‐line and crossline dips. The dip‐dependent NMO velocity is computed to remove the trace offset and azimuth dependence of event times for an arbitrary velocity function of depth. After stacking the moved out CMP gathers, a three‐dimensional (3-D) dip filter is applied to select the particular in‐line and crossline dip. The final zero‐offset image is obtained by summing all the dip‐filtered sections. This process generates a saddle‐shaped 3-D impulse response for a constant velocity gradient. The impulse response is more complicated for a general depth‐variable velocity function, where the response exhibits secondary branches, or triplications, at steeper dips. These complicated impulse responses, including amplitude and phase effects, are implicitly produced by the f-k process. The dip‐decomposition method of 3-D time‐variant DMO is an efficient and accurate process to correct for the effect of offset in the presence of an arbitrary velocity variation with depth. The impulse response of this process implicitly contains complex features like a 3-D saddle shape, triplications, amplitude, and phase. Field data from the Gulf of Mexico shows significant improvement on a steep salt flank event.
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Kawski, A., and J. Kamiński. "Depolarization of Photoluminescence of Isotropic Solutions Produced by Excitation Energy Migration." Zeitschrift für Naturforschung A 42, no. 8 (August 1, 1987): 813–18. http://dx.doi.org/10.1515/zna-1987-0808.
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A theory of the excitation energy transfer between like molecules in isotropic solution based on a centre or shell model of a primarily excited luminescent molecule and on the extended Förster “excitation master equation” has been elaborated. Fluorescence and phosphorescence depolarization are shown to be governed by singlet-singlet energy migration and described by the same expression. The comparison of the theoretical curve with the experimental data obtained by Gondo et al. (1975) for benzo[f]quinoline in ethanol glass at 77 K results in the following critical distance R0 for the excitation energy migration: 21.5 Å for fluorescence and phosphorescence, respectively.
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Mikulich, Weston, and Dave Hale. "Steep‐dip v(z) imaging from an ensemble of Stolt‐like migrations." GEOPHYSICS 57, no. 1 (January 1992): 51–59. http://dx.doi.org/10.1190/1.1443188.
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Stolt migration is often performed with many different velocities, creating a cube (or ensemble) of migrated constant‐velocity sections. With this ensemble, an interpreter can quickly, even interactively, carve out a single, variable‐velocity time migration. Unfortunately, the variable‐velocity section obtained in this way cannot image steep dips correctly. Phase‐shift (i.e., Gazdag) migration accurately images reflections from steep interfaces where velocity varies with depth. However, it is computationally slow compared to Stolt’s f-k migration, its constant‐velocity counterpart. Similarities between the Gazdag and Stolt methods allow a mapping between the two to be derived. This new mapping, which replaces the constant‐velocity Stolt mapping, defines a new Stolt‐like migration. Stolt‐like migration can then be performed to create an ensemble of migrated data, from which a Gazdag‐equivalent migration can be carved. All dips can be imaged properly, even where velocity varies significantly with depth, while the advantages of working with the ensemble of migrated sections are preserved.
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Jenssen, Rolf Ole R., and Svein K. Jacobsen. "Measurement of Snow Water Equivalent Using Drone-Mounted Ultra-Wide-Band Radar." Remote Sensing 13, no. 13 (July 2, 2021): 2610. http://dx.doi.org/10.3390/rs13132610.
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The use of unmanned aerial vehicle (UAV)-mounted radar for obtaining snowpack parameters has seen considerable advances over recent years. However, a robust method of snow density estimation still needs further development. The objective of this work is to develop a method to reliably and remotely estimate snow water equivalent (SWE) using UAV-mounted radar and to perform initial field experiments. In this paper, we present an improved scheme for measuring SWE using ultra-wide-band (UWB) (0.7 to 4.5 GHz) pseudo-noise radar on a moving UAV, which is based on airborne snow depth and density measurements from the same platform. The scheme involves autofocusing procedures with the frequency–wavenumber (F–K) migration algorithm combined with the Dix equation for layered media in addition to altitude correction of the flying platform. Initial results from field experiments show high repeatability (R > 0.92) for depth measurements up to 5.5 m, and good agreement with Monte Carlo simulations for the statistical spread of snow density estimates with standard deviation of 0.108 g/cm3. This paper also outlines needed system improvements to increase the accuracy of a snow density estimator based on an F–K migration technique.
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O'Connor, Kathleen L., Leslie M. Shaw, and Arthur M. Mercurio. "Release of cAMP Gating by the α6β4 Integrin Stimulates Lamellae Formation and the Chemotactic Migration of Invasive Carcinoma Cells." Journal of Cell Biology 143, no. 6 (December 14, 1998): 1749–60. http://dx.doi.org/10.1083/jcb.143.6.1749.
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The α6β4 integrin promotes carcinoma in-vasion by its activation of a phosphoinositide 3-OH (PI3-K) signaling pathway (Shaw, L.M., I. Rabinovitz, H.H.-F. Wang, A. Toker, and A.M. Mercurio. Cell. 91: 949–960). We demonstrate here using MDA-MB-435 breast carcinoma cells that α6β4 stimulates chemotactic migration, a key component of invasion, but that it has no influence on haptotaxis. Stimulation of chemotaxis by α6β4 expression was observed in response to either lysophosphatidic acid (LPA) or fibroblast conditioned medium. Moreover, the LPA-dependent formation of lamellae in these cells is dependent upon α6β4 expression. Both lamellae formation and chemotactic migration are inhibited or “gated” by cAMP and our results reveal that a critical function of α6β4 is to suppress the intracellular cAMP concentration by increasing the activity of a rolipram-sensitive, cAMP-specific phosphodiesterase (PDE). This PDE activity is essential for lamellae formation, chemotactic migration and invasion based on data obtained with PDE inhibitors. Although PI3-K and cAMP-specific PDE activities are both required to promote lamellae formation and chemotactic migration, our data indicate that they are components of distinct signaling pathways. The essence of our findings is that α6β4 stimulates the chemotactic migration of carcinoma cells through its ability to influence key signaling events that underlie this critical component of carcinoma invasion.
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Zhou, Huilin, Xing Wan, Wei Li, and Yuling Jiang. "Combining F-K Filter with Minimum Entropy Stolt Migration Algorithm for Subsurface Object Imaging and Background Permittivity Estimation." Procedia Engineering 23 (2011): 636–41. http://dx.doi.org/10.1016/j.proeng.2011.11.2558.
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Young, J. A. "Diffraction tomography applied to crosshole and VSP seismic data." Exploration Geophysics 20, no. 2 (1989): 169. http://dx.doi.org/10.1071/eg989169.
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Diffraction tomography is an approach to seismic inversion which is analogous to f-k migration. It differs from f-k migration in that it attempts to obtain a more quantitative rather than qualitative image of the Earth's subsurface. Diffraction tomography is based on the generalized projection-slice theorem which relates the scattered wave field to the Fourier spectrum of the scatterer. Factors such as the survey geometry and the source bandwidth determine the data coverage in the spatial Fourier domain which in turn determines the image resolution. Limited view-angles result in regions of the spatial Fourier domain with no data coverage, causing the solution to the tomographic reconstruction problem to be nonunique. The simplistic approach is to assume the missing samples are zero and perform a standard reconstruction but this can result in images with severe artefacts. Additional a priori information can be introduced to the problem in order to reduce the nonuniqueness and increase the stability of the reconstruction. This is the standard approach used in ray tomography but it is not commonly used in diffraction tomography applied to seismic data.This paper shows the application of diffraction tomography to crosshole and VSP seismic data. Using synthetic data, the effects on image resolution of the survey geometry and the finite source bandwidth are examined and techniques for improving image quality are discussed.
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Nguyen, Van Thi Thanh, Kim Hoang Le, Trung Hoang Dang, and Thuan Van Nguyen. "Determining velocities in high frequency electromagnetic prospecting by phase shift plus interpolation migration." Science and Technology Development Journal 19, no. 1 (March 31, 2016): 74–82. http://dx.doi.org/10.32508/stdj.v19i1.546.
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Phase Shift Plus Interpolation (PSPI) Migration is one of the most popular migration methods that is used not only in Seismic Data Processing but also in interpreting high frequency electromagnetic prospecting [Ground Penetrating Radar (GPR) data]. Based on the similarities between the principle of the propagation of electromagnetic wave and the mechanical wave, migration methods could be applied to interpreting GPR data as a particular step to calculate the medium’s velocity, estimate the depth, shape and size of buried objects. Noticeably, there are two kinds of velocities usually used in migration methods: root mean square (RMS) velocity, which is used in F – K, Finite Difference and Kirchhoff Migration, and interval velocity, which is used in PSPI Migration. RMS velocity is the average velocity taken into account by considering the influence of the upper layer’s instantaneous velocity; whereas the interval velocity only reflect the practical velocity of one layer. In this paper, the problem of how to apply PSPI Migration to interpret GPR data will be presented. Some results of model datum and real datum were also examined. Besides, we made a comparison of using RMS velocity and interval velocity, and then explain how these two types of velocity could be combined to receive the best result.
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Sidiq, Aditya P., Henry M. Manik, and Tumpal B. Nainggolan. "STUDI KOMPARASI METODE MIGRASI SEISMIK DALAM MENGKARAKTERISASI RESERVOIR MIGAS DI BLOK KANGEAN, LAUT BALI MENGGUNAKAN INVERSI IMPEDANSI AKUSTIK BERBASIS MODEL." Jurnal Ilmu dan Teknologi Kelautan Tropis 11, no. 1 (April 1, 2019): 205–19. http://dx.doi.org/10.29244/jitkt.v11i1.23028.
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ABSTRAK Karakterisasi reservoir menjadi penting dalam tahapan eksplorasi minyak dan gas bumi. Salah satu hal yang dibutuhkan untuk mencapai keakuratan dalam mengkarakterisasi reservoir adalah penampang seismik yang sesuai dengan penampang aslinya. Struktur lapisan bumi yang kompleks mengakibatkan gelombang terdifraksi, sehingga penampang seismik mengalami pembelokan dari posisi sebenarnya. Penelitian ini menerapkan metode migrasi seismik Kirchhoff dan Stolt (F-K) untuk mengembalikan posisi reflektor pada waktu dan kedalaman yang sebenarnya pada data seismik 2D di Perairan Utara Bali. Data seismik diintegrasikan dengan data sumur APS-1 sebagai kontrol untuk diinversikan dengan teknik inversi berbasis model sehingga dapat mengkarakterisasi reservoir. Penelitian ini bertujuan membandingkan hasil migrasi seismik yaitu migrasi Stolt dan migrasi Kirchhoff untuk diinversikan menggunakan metode inversi berbasis model sehingga dapat diketahui sejauh mana kualitas data seismik mempengaruhi proses karakterisasi reservoir. Nilai korelasi dari hasil analisis regresi antara log impedansi inversi dengan log impedansi data sumur pada migrasi Kirchhoff sebesar 0,739 dan galat regresi sebesar 873,54, sedangkan pada migrasi Stolt memiliki nilai korelasi sebesar 0,698 dan nilai galat sebesar 1236,17. Hal ini menunjukkan bahwa migrasi Kirchhoff lebih baik dari migrasi Stolt baik secara kualitatif maupun kuantitatif dalam mengkarakterisasi reservoir hidrokarbon. ABSTRACTReservoir characterization is an important method in gas and oil exploration. In order to obtain accuracy for defining reservoir, required seismic image that similar to the actual seismic image. The complexity of earth structure could cause diffracted waves, therefore, seismic image was diffracted from its actual position. This study applies Kirchhoff and Stolt (F-K) seismic migration methods to restore the position of the reflector at the actual time and depth seismic data in North Bali. Seismic data is integrated with APS-1 well data as controls to be converted with model-based inversion techniques so as to characterize the reservoir. This study aims to compare the results of seismic migration namely Stolt and Kirchhoff migration to be converted using a model-based inversion method so that it can be seen to what extent the quality of seismic data influences the reservoir characterization process. Correlation value from the results of regression analysis between inversion log impedance and well impedance log data in Kirchhoff migration is 0.739 and regression error is 873.54, while the Stolt migration has a correlation value of 0.698 and an error value of 1236.17. This shows that Kirchhoff's migration is better than Stolt migration both qualitatively and quantitatively in characterizing hydrocarbon reservoirs.
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Mork, Kjell Arne, John Gilbey, Lars Petter Hansen, Arne J. Jensen, Jan Arge Jacobsen, Marianne Holm, Jens Christian Holst, et al. "Modelling the migration of post-smolt Atlantic salmon (Salmo salar) in the Northeast Atlantic." ICES Journal of Marine Science 69, no. 9 (June 13, 2012): 1616–24. http://dx.doi.org/10.1093/icesjms/fss108.
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Abstract Mork, K. A., Gilbey, J., Hansen, L. P., Jensen, A. J., Jacobsen, J. A., Holm, M., Holst, J. C., Ó Maoiléidigh, N., Vikebø, F., McGinnity, P., Melle, W., Thomas, K., Verspoor, E., and Wennevik, V. 2012. Modelling the migration of post-smolt Atlantic salmon (Salmo salar) in the Northeast Atlantic. – ICES Journal of Marine Science, 69: 1616–1624. The migration of post-smolt Atlantic salmon (Salmo salar) during their first 4 months at sea in the Northeast Atlantic was simulated using an individual-based model that combined a particle-tracking scheme with growth and behaviour routines. The migration was decomposed into both passive pelagic drift with the surface currents, provided by an ocean model, and active horizontal swimming behaviour. The active swimming direction was aligned with the surface current. Swimming speed was a function of body length and calculated from recaptured tagged salmon. Releases of particles in the model were made to the west of Ireland and to the southwest of Norway. The modelled post-smolt distributions were compared with the observed distributions, and a sensitivity analysis using different swimming speeds was performed. The strength and direction of the flow can transport the post-smolts towards areas with favourable feeding conditions. However, in some areas, the direction of migration was sensitive to interannual changes in the windforcing, leading the post-smolts to areas with a different environment and prey. Inclusion in the swimming behaviour of a preference for water with higher temperature and salinity displaced the northward migration more offshore, away from coastal areas.
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Uren, N. F., G. H. F. Gardner, and J. A. McDonald. "The migrator’s equation for anisotropic media." GEOPHYSICS 55, no. 11 (November 1990): 1429–34. http://dx.doi.org/10.1190/1.1442789.
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The migrator’s equation, which gives the relationship between real and apparent dips on a reflector in zero‐offset reflection seismic sections, may be readily implemented in one step with a frequency‐domain migration algorithm for homogeneous media. Huygens’ principle is used to derive a similar relationship for anisotropic media where velocities are directionally dependent. The anisotropic form of the migrator’s equation is applicable to both elliptically and nonelliptically anisotropic media. Transversely isotropic media are used to demonstrate the performance of an f-k implementation of the migrator’s equation for anisotropic media. In such a medium SH-waves are elliptically anisotropic, while P-waves are nonelliptically anisotropic. Numerical model data and physical model data demonstrate the performance of the algorithm, in each case recovering the original structure. Isotropic and anisotropic migration of anisotropic physical model data are compared experimentally, where the anisotropic velocity function of the medium has a vertical axis of symmetry. Only when anisotropic migration is used is the original structure recovered.
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Gamper, Coralie, Caroline Spenlé, Sonia Boscá, Michael van der Heyden, Mathieu Erhardt, Gertraud Orend, Dominique Bagnard, and Manfred Heinlein. "Functionalized Tobacco Mosaic Virus Coat Protein Monomers and Oligomers as Nanocarriers for Anti-Cancer Peptides." Cancers 11, no. 10 (October 22, 2019): 1609. http://dx.doi.org/10.3390/cancers11101609.
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Components with self-assembly properties derived from plant viruses provide the opportunity to design biological nanoscaffolds for the ordered display of agents of diverse nature and with complementing functions. With the aim of designing a functionalized nanoscaffold to target cancer, the coat protein (CP) of Tobacco mosaic virus (TMV) was tested as nanocarrier for an insoluble, highly hydrophobic peptide that targets the transmembrane domain of the Neuropilin-1 (NRP1) receptor in cancer cells. The resulting construct CPL-K (CP-linker-“Kill”) binds to NRP1 in cancer cells and disrupts NRP1 complex formation with PlexA1 as well as downstream Akt survival signaling. The application of CPL-K also inhibits angiogenesis and cell migration. CP was also fused to a peptide that targets the extracellular domain of NRP1 and this fusion protein (CPL-F, CP-Linker-“Find”) is shown to bind to cultured cancer cells and to inhibit NRP1-dependent angiogenesis as well. CPL-K and CPL-F maintain their anti-angiogenic properties upon co-assembly to oligomers/nanoparticles together with CPL. The observations show that the CP of TMV can be employed to generate a functionalized nanoparticle with biological activity. Remarkably, fusion to CPL allowed us to solubilize the highly insoluble transmembrane NRP1 peptide and to retain its anti-angiogenic effect.
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Margrave, Gary F., John C. Bancroft, and Hugh D. Geiger. "Fourier prestack migration by equivalent wavenumber." GEOPHYSICS 64, no. 1 (January 1999): 197–207. http://dx.doi.org/10.1190/1.1444516.
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Fourier prestack migration is reformulated through a change of variables, from offset wavenumber to a new equivalent wavenumber, which makes the migration phase shift independent of horizontal wavenumber. After the change of variables, the inverse Fourier transform over horizontal wavenumber can be performed to create unmigrated, but fully horizontally positioned, gathers at each output location. A complete prestack migration then results by imaging each gather independently with a poststack migration algorithm. This equivalent wavenumber migration (EWM) is the Fourier analog of the space‐time domain method of equivalent offset migration (EOM). The latter is a Kirchhoff time‐migration technique which forms common scatterpoint (CSP) gathers for each migrated trace and then images those gathers with a Kirchhoff summation. These CSP gathers are formed by trace mappings at constant time, and migration velocity analysis is easily done after the gathers are formed. Both EWM and EOM are motivated by the algebraic combination of a double square root equation into a single square root. This result defines equivalent wavenumber or offset. EWM is shown to be an exact reformulation of prestack f-k migration. The EWM theory provides explicit Fourier integrals for the formation of CSP gathers from the prestack data volume and the imaging of those gathers to form the final prestack migrated result. The CSP gathers are given by a Fourier mapping, at constant frequency, of the unmigrated spectrum followed by an inverse Fourier transform. The mapping requires angle‐dependent weighting factors for full amplitude preservation. The imaging expression (for each CSP gather) is formally identical to poststack migration with the result retained only at zero equivalent offset. Through a numerical simulation, the impulse responses of EOM and EWM are shown to be kinematically identical. Amplitude scale factors, which are exact in the constant velocity EWM theory, are implemented approximately in variable velocity EOM.
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Loewenthal, Dan, Paul L. Stoffa, and Eduardo L. Faria. "Suppressing the unwanted reflections of the full wave equation." GEOPHYSICS 52, no. 7 (July 1987): 1007–12. http://dx.doi.org/10.1190/1.1442352.
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In many instances in exploration geophysics we are interested in the so‐called one‐way wave equation. This equation allows the wave fields to propagate in the positive depth direction, but not in the reverse (−Z) direction. Some modeling and migration methods, such as the f-k method (Stolt, 1978) and the phase‐shift method (Gazdag, 1978), produce in a natural way the one‐way wave equation. The main advantage of the one‐way wave equation is that it does not give rise to multiples or interlayer reverberations and enables the observation of primary events only.
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KAZEMPOUR, ALI. "POTENTIAL ENERGY SURFACES OF OXYGEN VACANCIES IN RUTILE TiO2: CONFIGURATION COORDINATE AND MIGRATION BARRIER SCHEMES." Modern Physics Letters B 27, no. 24 (September 11, 2013): 1350173. http://dx.doi.org/10.1142/s021798491350173x.
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Applying the screened hybrid functional Heyd–Scuseria–Ernzerhof (HSE) method, we studied the polaronic degree of freedom of different charged oxygen vacancies V o in rutile TiO 2. The HSE method not only corrects the band gap, but also allows for correct polaron localization. Due to the important role of phonon in oxygen vacancy associated levels in the gap, we calculated configuration coordinate (CC) potential energy surfaces for all charged V o 's. Our calculated CC diagrams with effective impression on host states, show significant improvement of electron–lattice interaction compared to semi(local) DFT methods. The obtained values of stokes shifts for sequential transitions of charged vacancies agree well with experimental evidences which confirm Ti 3+ centers are responsible for photoluminescence. In addition, we explored the effect of polaron localization on diffusive mechanism of V o along most open [001] direction. Calculated values of migration barriers for [Formula: see text] are found to be in quantitative agreement with experimental migration energy [E. Iguchi and K. Yajima, J. Phys. Soc. Jpn.32 (1971) 1415] of 2.4 eV. These results highlight the small polaronic behavior of V o 's and is consistent with studies suggest the polaronic hopping model for electron transport of n-type conductivity in reduced TiO 2 [J.-F. Baumard and F. Gervais, Phys. Rev. B15 (1977) 2316–2323].
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Cho, Daeheum, Jérémy R. Rouxel, Markus Kowalewski, JinYong Lee, and Shaul Mukamel. "Imaging of transition charge densities involving carbon core excitations by all X-ray sum-frequency generation." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, no. 2145 (April 2019): 20170470. http://dx.doi.org/10.1098/rsta.2017.0470.
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X-ray diffraction signals from the time-evolving molecular charge density induced by selective core excitation of chemically inequivalent carbon atoms are calculated. A narrowband X-ray pulse selectively excites the carbon K-edge of the –CH 3 or –CH 2 F groups in fluoroethane (CH 3 –CH 2 F). Each excitation creates a distinct core coherence which depends on the character of the electronic transition. Direct propagation of the reduced single-electron density matrix, using real-time time-dependent density functional theory, provides the time-evolving charge density following interactions with external fields. The interplay between partially filled valence molecular orbitals upon core excitation induces characteristic femtosecond charge migration which depends on the core–valence coherence, and is monitored by the sum-frequency generation diffraction signal. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.
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Vianna Gallinaro, Julia, Claudia Mirian de Godoy Marques, Fernando Mendes de Azevedo, and Daniela Ota Hisayasu Suzuki. "Mathematical Modeling of Melanoma Cell Migration with an Elastic Continuum Model for the Evaluation of the Influence of Tumor Necrosis Factor-Alpha on Migration." Journal of Computational Medicine 2013 (September 25, 2013): 1–8. http://dx.doi.org/10.1155/2013/534073.
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An elastic continuum mathematical model was implemented to study collective C8161 melanoma cell migration during a “scratch wound” assay, in control and under the influence of the proinflammatory cytokine tumour necrosis factor-alpha (TNF-α). The model has four constants: force that results from lamellipod formation (F), adhesion constant between cells and extracellular matrix (ECM) (b), cell layer elasticity modulus (k), and growth rate (ρ). A nonlinear regression routine was used to obtain the parameters of the model with data from an experiment made with C8161 melanoma cells, with and without TNF-α. Coefficient of determination for both situations was R2=0.89 and R2=0.92, respectively. The parameters values obtained were similar to the ones found in the literature. However, the adhesion constant value decreased with the introduction of TNF-α, which is not in accordance with expected since the presence of TNF-α is associated with an increased expression of integrins that would promote an enhanced adhesion among cells. The model was used in a study relating to the adhesion constant and cell migration, and the results suggested that cell migration decreases with higher adhesion, which is also not in accordance with expected. These differences would not occur if it was considered that TNF-α increases the elasticity modulus of the cell layer.
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Ceyhan, Tevfik, Okan Akyol, Adnan Ayaz, and Francis Juanes. "Age, growth, and reproductive season of bluefish (Pomatomus saltatrix) in the Marmara region, Turkey." ICES Journal of Marine Science 64, no. 3 (March 29, 2007): 531–36. http://dx.doi.org/10.1093/icesjms/fsm026.
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AbstractCeyhan, T., Akyol, O., Ayaz, A., and Juanes, F. 2007. Age, growth, and reproductive season of bluefish (Pomatomus saltatrix) in the Marmara region, Turkey. – ICES Journal of Marine Science, 64: 531–536. Bluefish (Pomatomus saltatrix) are distributed widely along the Turkish coasts, and are regularly captured, especially in the Sea of Marmara during their spawning migration to the Black Sea from the Mediterranean in spring and during their return migration south in early autumn. Age, growth, and reproductive season are reported. The ages of 1114 bluefish were determined from otoliths. The age groups ranged from 0 to III, and mean fork lengths (and weights) were 14.4 ± 0.12 cm (38.2 ± 1.02 g), 19.5 ± 0.06 cm (93.7 ± 0.86 g), 27.5 ± 0.48 cm (238.5 ± 11.3 g), and 33.3 ± 0.50 cm (431.9 ± 17.08 g) for each age group, respectively. The von Bertalanffy growth parameters were L∞ = 51 cm, K = 0.228, and t0 = −1.26 y. The reproductive period, evaluated from gonadosomatic indices, began in early spring and extended until August.
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Кашницкий, Илья Савельевич, Софья Ахманаева, Анна Бежанишвили, Никита Ганжа, Юлия Лонщикова, and Вадим Хрюков. "Демографический дайджест." Демографическое обозрение 5, no. 1 (April 28, 2018): 165–85. http://dx.doi.org/10.17323/demreview.v5i1.7713.
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Zhang, J. The Evolution of China's One-Child Policy and Its Effects on Family Outcomes
Tropf, F. C., & Mandemakers, J. J. Is the Association Between Education and Fertility Postponement Causal? The Role of Family Background Factors.
Bongaarts, J., Mensch, B. S., & Blanc, A. K. Trends in the age at reproductive transitions in the developing world: The role of education
Wright, D. M., Rosato, M., & O'Reilly, D. Influence of Heterogamy by Religion on Risk of Marital Dissolution: A Cohort Study of 20,000 Couples
Reher, D., & Requena, M. Elderly women living alone in Spain: the importance of having children
Garcia-Roman, J., Flood, S., & Genadek, K. Parents' time with a partner in a cross-national context: A comparison of the United States, Spain, and France
Wahrendorf, M., Akinwale, B., Landy, R., Matthews, K., & Blane, D. Who in Europe Works beyond the State Pension Age and under which Conditions? Results from SHARE
Faggian, A., Rajbhandari, I., & Dotzel, K. R. The interregional migration of human capital and its regional consequences: a review
Xu, X., Li, Y., Liu, X., & Gan, W. Does religion matter to corruption? Evidence from China
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Szathmary, Emoke. ": Isolation, Migration and Health: 33rd Symposium Volume of the Society for the Study of Human Biology . D. F. Roberts, N. Fujiki, K. Torizuka." American Anthropologist 96, no. 1 (March 1994): 188–89. http://dx.doi.org/10.1525/aa.1994.96.1.02a00330.
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Sun, M., B. Réthi, A. Krishnamurthy, V. Joshua, A. Circiumaru, M. Engström, C. Grönwall, et al. "FRI0005 DIVERSITY OF ANTI-CITRULLINATED PROTEIN ANTIBODY COMPOSITIONS INFLUENCE SYNOVIAL FIBROBLAST REACTIVITY." Annals of the Rheumatic Diseases 79, Suppl 1 (June 2020): 573.2–574. http://dx.doi.org/10.1136/annrheumdis-2020-eular.5343.
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Background:Anti-citrullinated protein antibodies (ACPAs) play an important role in rheumatoid arthritis (RA) pathogenesis. We hypothesized that the effect of these antibodies is mediated by their binding to synovial fibroblasts and inducing an increased mobility of fibroblasts1.Objectives:In our study, we analyzed and compared fibroblast modulation by ACPA pools obtained from different patients or by a set of monoclonal ACPAs with different fine specificity that were obtained from different tissue sites.Methods:Synovial fibroblasts were isolated from RA patients synovial tissue biopsies. Individual polyclonal ACPA and control IgGs were purified from sera of four ACPA-positive RA patients by affinity purification on protein G and CCP-2 columns. Monoclonal antibodies were derived from memory B cell isolated from blood2, synovial fluid or bronchoalveolar lavage of RA patients. Whole antibodies and F(ab’)2 fragments were tested in fibroblast migration using IncuCyte live-cell analysis. Blocking experiments were performed with soluble citrullinated proteins in SF migration. Cross-reactivity of the antibodies to citrullinated and acetylated epitopes was tested using PAD inhibitors (Cl-amidine and GSK199), histone acetyltransferases (anacardic acid) and deacetylases (trichostatin A). Binding patterns of monoclonal ACPAs, both whole and F(ab’)2 fragments were analyzed in synovial biopsies obtained from both healthy donors and RA patients.Results:Three out of four tested individual ACPA were able to promote fibroblast migration. Five out of nine tested monoclonal ACPAs stimulated fibroblast migration. One of these antibodies, clone 1325:01B09 is characterized by cross-reactivity to citrullinated, homocitrullinated and acetylated targets. The effect of 1325:01B09 on fibroblast migration was completely abolished by Cl-amidine or by pre-incubating the antibody with citrullinated fibrinogen or histone but not citrullinated enolase or vimentin. Despite the cross-reactivity to acetylated epitopes, neither anacardic acid nor trichostatin A could modulate the 1325:01B09 effect on fibroblast migration. F(ab’)2 fragments of this antibody stimulated fibroblast migration and labelled podoplanin-positive fibroblasts in inflamed RA synovium similarly to the intact antibody, indicating an Fc-independent effect.Conclusion:The effect on fibroblast mobility was likely to be mediated by binding to citrullinated epitopes but not through Fc receptors. Detection of fibroblast modulating ACPAs in majority of RA patients indicated that fibroblasts might be key cellular targets in disease pathogenesis, although individual variability might exist in the composition of ACPA cellular targets.References:[1]Sun M, Rethi B, Krishnamurthy A, et al. Anticitrullinated protein antibodies facilitate migration of synovial tissue-derived fibroblasts. Ann Rheum Dis 2019;78(12):1621-31. doi: 10.1136/annrheumdis-2018-214967 [published Online First: 2019/09/05][2]Amara K, Lena Israelsson, Ragnhild Stålesen, et al. A Refined Protocol for Identifying Citrulline-specific Monoclonal Antibodies from Single Human B Cells from Rheumatoid Arthritis Patient Material. Bio-protocol 2019;9(16)Disclosure of Interests:Meng Sun: None declared, Bence Réthi: None declared, Akilan Krishnamurthy: None declared, Vijay Joshua: None declared, Alexandra Circiumaru: None declared, Marianne Engström: None declared, Caroline Grönwall: None declared, Vivianne Malmström Grant/research support from: VM has had research grants from Janssen Pharmaceutica, Khaled Amara: None declared, Lars Klareskog: None declared, Heidi Wähämaa: None declared, Anca Catrina: None declared
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Black, James L., Karl L. Schleicher, and Lin Zhang. "True‐amplitude imaging and dip moveout." GEOPHYSICS 58, no. 1 (January 1993): 47–66. http://dx.doi.org/10.1190/1.1443351.
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True‐amplitude seismic imaging produces a three dimensional (3-D) migrated section in which the peak amplitude of each migrated event is proportional to the reflectivity. For a constant‐velocity medium, the standard imaging sequence consisting of spherical‐divergence correction, normal moveout (NMO), dip moveout (DMO), and zero‐offset migration produces a true‐amplitude image if the DMO step is done correctly. There are two equivalent ways to derive the correct amplitude‐preserving DMO. The first is to improve upon Hale’s derivation of F-K DMO by taking the reflection‐point smear properly into account. This yields a new Jacobian that simply replaces the Jacobian in Hale’s method. The second way is to calibrate the filter that appears in integral DMO so as to preserve the amplitude of an arbitrary 3-D dipping reflector. This latter method is based upon the 3-D acoustic wave equation with constant velocity. The resulting filter amounts to a simple modification of existing integral algorithms. The new F-K and integral DMO algorithms resulting from these two approaches turn out to be equivalent, producing identical outputs when implemented in nonaliased fashion. As dip increases, their output become progressively larger than the outputs of either Hale’s F-K method or the integral method generally associated with Deregowski and Rocca. This trend can be observed both on model data and field data. There are two additional results of this analysis, both following from the wave‐equation calibration on an arbitrary 3-D dipping reflector. The first is a proof that the entire imaging sequence (not just the DMO part) is true‐amplitude when the DMO is done correctly. The second result is a handy formula showing exactly how the zero‐phase wavelet on the final migrated image is a stretched version of the zero‐phase deconvolved source wavelet. This result quantitatively expresses the loss of vertical resolution due to dip and offset.
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Grasmueck, Mark, Ralf Weger, and Heinrich Horstmeyer. "Full-resolution 3D GPR imaging." GEOPHYSICS 70, no. 1 (January 2005): K12—K19. http://dx.doi.org/10.1190/1.1852780.
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Noninvasive 3D ground-penetrating radar (GPR) imaging with submeter resolution in all directions delineates the internal architecture and processes of the shallow subsurface. Full-resolution imaging requires unaliased recording of reflections and diffractions coupled with 3D migration processing. The GPR practitioner can easily determine necessary acquisition trace spacing on a frequency-wavenumber (f-k) plot of a representative 2D GPR test profile. Quarter-wavelength spatial sampling is a minimum requirement for full-resolution GPR recording. An intensely fractured limestone quarry serves as a test site for a 100-MHz 3D GPR survey with 0.1 m × 0.2 m trace spacing. This example clearly defines the geometry of fractures in four different orientations, including vertical dips to a depth of 20 m. Decimation to commonly used half-wavelength spatial sampling or only 2D migration processing makes most fractures invisible. The extra data-acquisition effort results in image volumes with submeter resolution, both in the vertical and horizontal directions. Such 3D data sets accurately image fractured rock, sedimentary structures, and archeological remains in previously unseen detail. This makes full-resolution 3D GPR imaging a valuable tool for integrated studies of the shallow subsurface.
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Anderson, John, Tariq Alkhalifah, and Ilya Tsvankin. "Fowler DMO and time migration for transversely isotropic media." GEOPHYSICS 61, no. 3 (May 1996): 835–45. http://dx.doi.org/10.1190/1.1444008.
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The main advantage of Fowler’s dip‐moveout (DMO) method is the ability to perform velocity analysis along with the DMO removal. This feature of Fowler DMO becomes even more attractive in anisotropic media, where imaging methods are hampered by the difficulty in reconstructing the velocity field from surface data. We have devised a Fowler‐type DMO algorithm for transversely isotropic media using the analytic expression for normal‐moveout velocity. The parameter‐estimation procedure is based on the results of Alkhalifah and Tsvankin showing that in transversely isotropic media with a vertical axis of symmetry (VTI) the P‐wave normal‐moveout (NMO) velocity as a function of ray parameter can be described fully by just two coefficients: the zero‐dip NMO velocity [Formula: see text] and the anisotropic parameter η (η reduces to the difference between Thomsen parameters ε and δ in the limit of weak anisotropy). In this extension of Fowler DMO, resampling in the frequency‐wavenumber domain makes it possible to obtain the values of [Formula: see text] and η by inspecting zero‐offset (stacked) panels for different pairs of the two parameters. Since most of the computing time is spent on generating constant‐velocity stacks, the added computational effort caused by the presence of anisotropy is relatively minor. Synthetic and field‐data examples demonstrate that the isotropic Fowler DMO technique fails to generate an accurate zero‐offset section and to obtain the zero‐dip NMO velocity for nonelliptical VTI models. In contrast, this anisotropic algorithm allows one to find the values of the parameters [Formula: see text] and η (sufficient to perform time migration as well) and to correct for the influence of transverse isotropy in the DMO processing. When combined with poststack F-K Stolt migration, this method represents a complete inversion‐processing sequence capable of recovering the effective parameters of transversely isotropic media and producing migrated images for the best‐fit homogeneous anisotropic model.
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Nardone, Lucia, Roberta Esposito, Danilo Galluzzo, Simona Petrosino, Paola Cusano, Mario La Rocca, Mauro Antonio Di Vito, and Francesca Bianco. "Array and spectral ratio techniques applied to seismic noise to investigate the Campi Flegrei (Italy) subsoil structure at different scales." Advances in Geosciences 52 (October 28, 2020): 75–85. http://dx.doi.org/10.5194/adgeo-52-75-2020.
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Abstract. The purpose of this work is to study the subsoil structure of the Campi Flegrei area using both spectral ratios and array techniques applied to seismic noise. We have estimated the dispersion curves of Rayleigh waves by applying the Frequency–Wavenumber (f–k hereinafter) and Modified Spatial Autocorrelation (MSPAC) techniques to the seismic noise recorded by the underground short period seismic Array “ARF”, by the broadband stations of the UNREST experiment and by the broadband stations of the seismic monitoring network of INGV – Osservatorio Vesuviano. We have performed the inversion of a dispersion curve (obtained averaging the f–k and MSPAC dispersion curves of seismic noise and single phase velocity values of coherent transient signals) jointly with the H∕V spectral ratio of the broadband station CELG, to obtain a shear wave velocity model up to 2000 m depth. The best-fit model obtained is in a good agreement with the stratigraphic information available in the area coming from shallow boreholes and deep wells drilled for geothermal exploration. In active volcanic areas, such as Campi Flegrei, the definition of the velocity model is a crucial issue to characterize the physical parameters of the medium. Generally, a high quality characterization of the medium properties helps to separate the contributions of the volcanic source, path and site in the geophysical observables. Therefore, monitoring possible variations in time of such properties in general can help to recognize anomalies due to the volcano dynamics, i.e. fluid migration connected to the volcanic activity.
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Nie, Changsheng, Pedro Almeida, Yaxiong Jia, Haigang Bao, Zhonghua Ning, and Lujiang Qu. "Genome-Wide Single-Nucleotide Polymorphism Data Unveil Admixture of Chinese Indigenous Chicken Breeds with Commercial Breeds." Genome Biology and Evolution 11, no. 7 (July 1, 2019): 1847–56. http://dx.doi.org/10.1093/gbe/evz128.
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Abstract The conservation and development of chicken have received considerable attention, but the admixture history of chicken breeds, especially Chinese indigenous breeds, has been poorly demonstrated. In this study, we aimed to evaluate the genetic diversity and population structure of eight chicken breeds (including conserved chicken breeds) from different geographic origin and to identify admixture within these breeds using a 600-K single-nucleotide polymorphism panel for genotyping. Using the genotype of 580,961 single-nucleotide polymorphism markers scored in 1,200 animals, we evaluated the genetic diversity (heterozygosity and proportion of polymorphic markers), linkage disequilibrium decay, population structure (principal component analysis and neighbor-joining tree), genetic differentiation (FST and genetic distance), and migration events (TreeMix and f-statistics) of the eight domesticated chicken breeds. The results of population analytical methods revealed patterns of hybridization that occurred after divergence in Tibetan chicken. We argue that chicken migration and admixture, followed by trade, have been important forces in shaping the genomic variation in modern Chinese chicken. Moreover, isolation by distance might play a critical role in shaping the genomic variation within Eurasia continent chicken breeds. Moreover, genetic information provided in this study is valuable resources for production applications (genomic prediction, and breeding strategy) and scientific research (genetic basis detection, studying evolution, or domestication).
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Kean, William F., Muriel Jennings Waller, and H. Richard Layson. "REPLY TO the preceding Discussion by R. K. Frohlich, C. D. Parke, and W. F. Kelly of "Monitoring Moisture Migration in the Vadose Zone with Resistivity"." Ground Water 26, no. 3 (May 1988): 362–63. http://dx.doi.org/10.1111/j.1745-6584.1988.tb00403.x.
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Schoenberg, Michael A., and Maarten V. de Hoop. "Approximate dispersion relations for qP-qSV-waves in transversely isotropic media." GEOPHYSICS 65, no. 3 (May 2000): 919–33. http://dx.doi.org/10.1190/1.1444788.
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To decouple qP and qSV sheets of the slowness surface of a transversely isotropic (TI) medium, a sequence of rational approximations to the solution of the dispersion relation of a TI medium is introduced. Originally conceived to allow isotropic P-wave processing schemes to be generalized to encompass the case of qP-waves in transverse isotropy, the sequence of approximations was found to be applicable to qSV-wave processing as well, although a higher order of approximation is necessary for qSV-waves than for qP-waves to yield the same accuracy. The zeroth‐order approximation, about which all other approximations are taken, is that of elliptical TI, which contains the correct values of slowness and its derivative along and perpendicular to the medium’s axis of symmetry. Successive orders of approximation yield the correct values of successive orders of derivatives in these directions, thereby forcing the approximation into increasingly better fit at the intervening oblique angles. Practically, the first‐order approximation for qP-wave propagation and the second‐order approximation for qSV-wave propagation yield sufficiently accurate results for the typical transverse isotropy found in geological settings. After only slight modification to existing programs, the rational approximation allows for ray tracing, (f-k) domain migration, and split‐step Fourier migration in TI media—with little more difficulty than that encountered presently with such algorithms in isotropic media.
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Zolfaghari, M. R., F. Salimpour, F. Sharifnia, and S. J. Marandi. "Analysis of genetic diversity among Iranian populations of Ficus carica L. (Moraceae)." Acta Biologica Sibirica 5, no. 3 (September 29, 2019): 131–38. http://dx.doi.org/10.14258/abs.v5.i3.6534.
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Ficus carica L. is a species of Moraceae family that has been cultivated in different parts of the world from ancient time. Its fruit is eaten by human and has several medicinal properties. This species widely grows and cultivated in various parts of Iran. For this, in the current study, we investigated infraspecific genetic variation and population structure of F. carica in the country. 14 natural populations of F. carica were collected and their genomic DNA were extracted and tested with RAPD molecular technique. Parameters of population’s genetic diversity varied among the studied populations. In addition, AMOVA test revealed significant variations among the populations. The studied populations clustered separately in UPGMA tree of RAPD data, moreover PCA and MDS plots produced similar results. STRUCTURE analysis revealed the best number of k = 9. Based on Nei’s genetic distance, we had nine distinct groups. Genetic clustering patterns according to UPGMA trees of RAPD data and Nei’s genetic distance were more similar with the results of STRUCTURE analysis. The small amount of Nm) the product of the effective size of individual populations (N) and the rate of migration among them (m) (value showed limited gene flow among the studied populations, therefore it seems that high genetic variations among these populations may be related less or few amount of gene exchange among populations.
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Manuessa, Bonifácio, Eurico Morais, Teresa Cerveira Borges, Maria Teodósio, and Francisco Leitão. "First Assessment of the Thryssa vitrirostris (Engraulidae) Beach Seine Fishery in Northeastern Mozambique." J 1, no. 1 (October 15, 2018): 116–32. http://dx.doi.org/10.3390/j1010012.
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Monthly length-frequency data, from 2009 to 2014, was used to estimate the growth parameters, mortality, and spawning season, and to assess the exploitation status of Thryssa vitrirostris (Engraulidae) fisheries in Pebane. The von Bertalanffy asymptotic length (L∞) and growth rate (K) were 25.1 cm (standard length) and 0.41 per year (standard length), respectively. Two proxy recruitment peaks were found: the first peak of recruitment occurs from April to July, and the second recruitment peak from September to October. The total estimated mortality rates (Z), natural mortality (M), and fishing mortality (F) were Z = 1.31, M = 0.92, and F = 0.39. For the beach seine gear, the size at first catch of T. vitrirostris was Lc25 = 4.43 cm. The 50% retention size of the catch was Lc50 = 5.39 cm. The retention probability analyses revealed a large rate of juvenile fishing mortality (54.2%). The estimated exploitation rate (0.30) was below the maximum exploitation rate (0.48), and above the optimal sustainable exploitation rate (E50 = 0.28), evidencing a sustainable fishery. However, under such an exploitation regime, it is advised that a continuously monitoring-survey of T. vitrirostris is maintained. An increase in migration of fishermen has been recently recorded in Pebane, due to its rich fisheries, which can increase the fishing effort and the risk of overexploitation if management measures (such as mesh size increase) are not taken in advance.
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Karimov, Denis N., Irina I. Buchinskaya, Natalia A. Arkharova, Anna G. Ivanova, Alexander G. Savelyev, Nikolay I. Sorokin, and Pavel A. Popov. "Growth Peculiarities and Properties of KR3F10 (R = Y, Tb) Single Crystals." Crystals 11, no. 3 (March 14, 2021): 285. http://dx.doi.org/10.3390/cryst11030285.
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Cubic KR3F10 (R = Y, Tb) single crystals have been successfully grown using the Bridgman technique. Growth of crystals of this type is complicated due to the hygroscopicity of potassium fluoride and melt overheating. The solution to the problem of oxygen-incorporated impurities has been demonstrated through the utilization of potassium hydrofluoride as a precursor. In this study, the crystal quality, structure features, and optical, thermal and electrophysical properties of KR3F10 were examined. Data on the temperature dependences of conductivity properties of KTb3F10 crystals were obtained for the first time. These crystals indicated thermal conductivity equal to 1.54 ± 0.05 Wm−1K−1 at room temperature caused by strong phonon scattering in the Tb-based crystal lattice. Ionic conductivities of KY3F10 and KTb3F10 single crystals were 4.9 × 10−8 and 1.2 × 10−10 S/cm at 500 K, respectively, and the observed difference was determined by the activation enthalpy of F− ion migration. Comparison of the physical properties of the grown KR3F10 crystals with the closest crystalline analog from the family of Na0.5−xR0.5+xF2+2x (R = Tb, Y) cubic solid solutions is reported.