Journal articles on the topic 'Crest distribution'
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1
Kriebel, D. L., and T. H. Dawson. "Distribution of Crest Amplitudes in Severe Seas With Breaking." Journal of Offshore Mechanics and Arctic Engineering 115, no. 1 (February 1, 1993): 9–15. http://dx.doi.org/10.1115/1.2920097.
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A theoretical model is presented for the probability distribution of wave crest amplitudes in severe seas states with wave breaking. As the severity of a sea state increases, nonlinearities cause an increase in the amplitudes of the largest wave crests with a subsequent modification of the distribution of wave crest amplitudes from the linear Rayleigh theory. In this paper, a theory for the probabilities of these nonlinear crest amplitudes is first reviewed based on earlier work. The further limitations on these nonlinear crest amplitudes by wave breaking are then considered. As a result, a theoretical model is presented to account for both: 1) the nonlinear increase in the highest wave crests, and 2) the selective reduction of some fraction of these high crests due to wave breaking. This model is then verified using several sets of laboratory data for severe breaking seas having approximate JONSWAP wave spectra.
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Forristall, George Z., Stephen F. Barstow, Harald E. Krogstad, Marc Prevosto, Paul H. Taylor, and Peter S. Tromans. "Wave Crest Sensor Intercomparison Study: An Overview of WACSIS." Journal of Offshore Mechanics and Arctic Engineering 126, no. 1 (February 1, 2004): 26–34. http://dx.doi.org/10.1115/1.1641388.
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The Wave Crest Sensor Intercomparison Study (WACSIS) was designed as a thorough investigation of the statistical distribution of crest heights. Measurements were made in the southern North Sea during the winter of 1997–1998 from the Meetpost Noordwijk in 18 m water depth. The platform was outfitted with several popular wave sensors, including Saab and Marex radars, an EMI laser, a Baylor wave staff and a Vlissingen step gauge. Buoys were moored nearby to obtain directional spectra. Two video cameras viewed the ocean under the wave sensors and their signals were recorded digitally. The data analysis focused on comparisons of the crest height measurements from the various sensors and comparisons of the crest height distributions derived from the sensors and from theories. Some of the sensors had greater than expected energy at high frequencies. Once the measurements were filtered at 0.64 Hz, the Baylor, EMI and Vlissingen crest height distributions matched quite closely, while those from the other sensors were a few percent higher. The Baylor and EMI crest distributions agreed very well with the statistics from second order simulations, while previous parameterizations of the crest height distribution were generally too high. We conclude that crest height distributions derived from second order simulations can be used with confidence in engineering calculations. The data were also used in investigations of crest and trough shapes and the joint height/period distribution.
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Wang, Yongfei, Junru Li, Zhenyu Wu, Jiankang Chen, Chuan Yin, and Kang Bian. "Dynamic Risk Evaluation and Early Warning of Crest Cracking for High Earth-Rockfill Dams through Bayesian Parameter Updating." Applied Sciences 10, no. 21 (October 29, 2020): 7627. http://dx.doi.org/10.3390/app10217627.
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Crest cracking is one of the most common damage types for high earth-rockfill dams. Cracking risk of dam crest is closely related to the duration of abnormal deformation state. In this paper, a methodology for dynamic risk evaluation and early warning of crest cracking for high earth-rockfill dams is proposed and mainly consists of: (a) The discrimination of abnormal deformation state related to crest cracking, which is implemented by comparing the crest settlement inclination with the threshold value. (b) Computation of crest cracking probability and estimation of cracking time. The exponential distribution is adopted to represent the probability distribution of the duration TAS of abnormal state before crest cracking. Then the crest cracking probability in a given time can be computed by integration with respect to TAS. Inversely, the cracking time corresponding to a given probability can be estimated. (c) Determination of the values of probability adopted to early warn crest cracking, which are suggested to be selected by statistical analysis of the calculated probabilities at the observed cracking times. (d) Bayesian estimation and updating of probability distribution of the parameter λ in the PDF of TAS, according to observed durations of abnormal state before crest cracking. The methodology is illustrated and verified by the case study for an actual earth-rockfill dam, of which crest cracking and recracking events were observed during the periods of high reservoir level. According to the observed values of TAS, the probability distribution for λ is progressively updated and the dispersion of the distributions of λ gradually decreases. The crest cracking probability increases with the duration of abnormal state and the width of confidence interval of the estimated cracking probability progressively contracts with the updating of the distribution for λ. Finally, the early warning of crest cracking for the dam is investigated by estimating the lower limit of cracking time. It is shown that early warning of crest cracking can be issued from at least 20 days ahead of the occurrence of crest cracking event. The idea of using duration of abnormal state of crest settlement to evaluate crest cracking risk of the earth-rockfill dam in this paper may be applicable to other dams.
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Duband, J. L., and J. P. Thiery. "Distribution of laminin and collagens during avian neural crest development." Development 101, no. 3 (November 1, 1987): 461–78. http://dx.doi.org/10.1242/dev.101.3.461.
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The distribution of type I, III and IV collagens and laminin during neural crest development was studied by immunofluorescence labelling of early avian embryos. These components, except type III collagen, were present prior to both cephalic and trunk neural crest appearance. Type I collagen was widely distributed throughout the embryo in the basement membranes of epithelia as well as in the extracellular spaces associated with mesenchymes. Type IV collagen and laminin shared a common distribution primarily in the basal surfaces of epithelia and in close association with developing nerves and muscle. In striking contrast with the other collagens and laminin, type III collagen appeared secondarily during embryogenesis in a restricted pattern in connective tissues. The distribution and fate of laminin and type I and IV collagens could be correlated spatially and temporally with morphogenetic events during neural crest development. Type IV collagen and lamin disappeared from the basal surface of the neural tube at sites where neural crest cells were emerging. During the course of neural crest cell migration, type I collagen was particularly abundant along migratory pathways whereas type IV collagen and laminin were distributed in the basal surfaces of the epithelia lining these pathways but were rarely seen in large amounts among neural crest cells. In contrast, termination of neural crest cell migration and aggregation into ganglia were correlated in many cases with the loss of type I collagen and with the appearance of type IV collagen and laminin among the neural crest population. Type III collagen was not observed associated with neural crest cells during their development. These observations suggest that laminin and both type I and IV collagens may be involved with different functional specificities during neural crest ontogeny. (i) Type I collagen associated with fibronectins is a major component of the extracellular spaces of the young embryo. Together with other components, it may contribute to the three-dimensional organization and functions of the matrix during neural crest cell migration. (ii) Type III collagen is apparently not required for tissue remodelling and cell migration during early embryogenesis. (iii) Type IV collagen and laminin are important components of the basal surface of epithelia and their distribution is consistent with tissue remodelling that occurs during neural crest cell emigration and aggregation into ganglia.
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FEDELE, FRANCESCO, and M. AZIZ TAYFUN. "On nonlinear wave groups and crest statistics." Journal of Fluid Mechanics 620 (February 10, 2009): 221–39. http://dx.doi.org/10.1017/s0022112008004424.
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We present a second-order stochastic model of weakly nonlinear waves and develop theoretical expressions for the expected shape of large surface displacements. The model also leads to an exact theoretical expression for the statistical distribution of large wave crests in a form that generalizes the Tayfun distribution (Tayfun, J. Geophys. Res., vol. 85, 1980, p. 1548). The generalized distribution depends on a steepness parameter given by μ = λ3/3, where λ3 represents the skewness coefficient of surface displacements. It converges to the Tayfun distribution in narrowband waves, where both distributions describe the crests of all waves well. In broadband waves, the generalized distribution represents the crests of large waves just as well whereas the Tayfun distribution appears as an upper bound and tends to overestimate them. However, the theoretical nature of the generalized distribution presents practical difficulties in oceanic applications. We circumvent these by adopting an appropriate approximation for the steepness parameter. Comparisons with wind-wave measurements from the North Sea suggest that this approximation allows both distributions to assume an identical form with which we can describe the distribution of large wave crests fairly accurately. The same comparisons also show that third-order nonlinear effects do not appear to have any discernable effect on the statistics of large surface displacements or wave crests.
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Cho, Yong Jun. "Joint Distribution of the Wave Crest and Its Associated Period for Nonlinear Random Waves of Finite Bandwidth." Journal of Marine Science and Engineering 8, no. 9 (August 25, 2020): 654. http://dx.doi.org/10.3390/jmse8090654.
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The theoretical treatment of statistical properties relevant to nonlinear random waves of finite bandwidth, such as the joint distribution of wave crest and its associated wave period, is an overdue task hampered by the complicated form of the analytical model for sea surface elevation. In this study, we first derive the wave crest distribution based on the simplified version of the Longuet-Higgins’ wave model and proceed to derive the joint distribution of the wave crest and its associated period, and the conditional wave period distribution with a given wave crest, which are of great engineering value. It is shown that the bandwidth of the wave spectrum has a significant influence on the crest distribution, and the significant wave crest is getting larger in an increasing manner as nonlinearity is increased as expected. It also turns out that the positive correlation of wave crest height with its associated period is extended to more massive waves as nonlinearity is enhanced contrary to the general perception in the coastal engineering community that the wave crest is a statistically independent random process with wave period over large waves. The peak period decreases due to the destructive interference of second-order free harmonics.
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Mackie, E. J., R. P. Tucker, W. Halfter, R. Chiquet-Ehrismann, and H. H. Epperlein. "The distribution of tenascin coincides with pathways of neural crest cell migration." Development 102, no. 1 (January 1, 1988): 237–50. http://dx.doi.org/10.1242/dev.102.1.237.
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The distribution of the extracellular matrix (ECM) glycoprotein, tenascin, has been compared with that of fibronectin in neural crest migration pathways of Xenopus laevis, quail and rat embryos. In all species studied, the distribution of tenascin, examined by immunohistochemistry, was more closely correlated with pathways of migration than that of fibronectin, which is known to be important for neural crest migration. In Xenopus laevis embryos, anti-tenascin stained the dorsal fin matrix and ECM along the ventral route of migration, but not the ECM found laterally between the ectoderma and somites where neural crest cells do not migrate. In quail embryos, the appearance of tenascin in neural crest pathways was well correlated with the anterior-to-posterior wave of migration. The distribution of tenascin within somites was compared with that of the neural crest marker, HNK-1, in quail embryos. In the dorsal halves of quail somites which contained migrating neural crest cells, the predominant tenascin staining was in the anterior halves of the somites, codistributed with the migrating cells. In rat embryos, tenascin was detectable in the somites only in the anterior halves. Tenascin was not detectable in the matrix of cultured quail neural crest cells, but was in the matrix surrounding somite and notochord cells in vitro. Neural crest cells cultured on a substratum of tenascin did not spread and were rounded. We propose that tenascin is an important factor controlling neural crest morphogenesis, perhaps by modifying the interaction of neural crest cells with fibronectin.
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Lioutas, Anestis, Gregory M. Smith, and Henk Jan Verhagen. "SPATIAL DISTRIBUTION OF OVERTOPPING." Coastal Engineering Proceedings 1, no. 33 (December 14, 2012): 63. http://dx.doi.org/10.9753/icce.v33.structures.63.
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The scope of this research is to find an empirical formula to describe the distribution of wave overtopping in the region behind the crest. A physical model was set up in which irregular waves were generated. In order to find a formula which adequately describes the test observations, the influence of several parameters has been analysed. The proper determination of the crest freeboard, which is a dominant factor, has been investigated. Finally, the test results have been used to assess and compare the existing relevant computational methods.
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Perris, R., D. Krotoski, T. Lallier, C. Domingo, J. M. Sorrell, and M. Bronner-Fraser. "Spatial and temporal changes in the distribution of proteoglycans during avian neural crest development." Development 111, no. 2 (February 1, 1991): 583–99. http://dx.doi.org/10.1242/dev.111.2.583.
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In this study, we describe the distribution of various classes of proteoglycans and their potential matrix ligand, hyaluronan, during neural crest development in the trunk region of the chicken embryo. Different types of chondroitin and keratan sulfate proteoglycans were recognized using a panel of monoclonal antibodies produced against specific epitopes on their glycosaminoglycan chains. A heparan sulfate proteoglycan was identified by an antibody against its core protein. The distribution of hyaluronan was mapped using a biotinylated fragment that corresponds to the hyaluronan-binding region of cartilage proteoglycans. Four major patterns of proteoglycan immunoreactivity were observed. (1) Chondroitin-6-sulfate-rich proteoglycans and certain keratin sulfate proteoglycans were absent from regions containing migrating neural crest cells, but were present in interstitial matrices and basement membranes along prospective migratory pathways such as the ventral portion of the sclerotome. Although initially distributed uniformly along the rostrocaudal extent of the sclerotome, these proteoglycans became rearranged to the caudal portion of the sclerotome with progressive migration of neural crest cells through the rostral sclerotome and their aggregation into peripheral ganglia. (2) A subset of chondroitin/keratan sulfate proteoglycans bearing primarily unsulfated chondroitin chains was observed exclusively in regions where neural crest cells were absent or delayed from entering, such as the perinotochordal and subepidermal spaces. (3) A subset of chondroitin/keratan sulfate proteoglycans was restricted to the perinotochordal region and, following gangliogenesis, was arranged in a metameric pattern corresponding to the sites where presumptive vertebral arches form. (4) Certain keratan sulfate proteoglycans and a heparan sulfate proteoglycan were observed in basement membranes and in an interstitial matrix uniformly distributed along the rostrocaudal extent of the sclerotome. After gangliogenesis, the neural crest-derived dorsal root and sympathetic ganglia contained both these proteoglycan types, but were essentially free of other chondroitin/keratan-proteoglycan subsets. Hyaluronan generally colocalized with the first set of proteoglycans, but also was concentrated around migrating neural crest cells and was reduced in neural crest-derived ganglia. These observations demonstrate that proteoglycans have diverse and dynamic distributions during times of neural crest development and chondrogenesis of the presumptive vertebrae. In general, chondroitin/keratan sulfate proteoglycans are abundant in regions where neural crest cells are absent, and their segmental distribution inversely correlates with that of neural crest-derived ganglia.
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Thomson, Jim, and Andrew T. Jessup. "A Fourier-Based Method for the Distribution of Breaking Crests from Video Observations." Journal of Atmospheric and Oceanic Technology 26, no. 8 (August 1, 2009): 1663–71. http://dx.doi.org/10.1175/2009jtecho622.1.
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Abstract A Fourier-based method is presented to process video observations of water waves and calculate the speed distribution of breaking crest lengths. The method has increased efficiency and robust statistics compared with conventional algorithms that assemble distributions from tracking individual crests in the time domain. The method is tested using field observations (video images of whitecaps) of fetch-limited breaking waves during case studies with low (6.7 m s−1), moderate (8.5 m s−1), and high (12.6 m s−1) wind speeds. The method gives distributions consistent with conventional algorithms, including breaking rates that are consistent with direct observations. Results are applied to obtain remote estimates of the energy dissipation associated with wave breaking.
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Perris, R., D. Krotoski, and M. Bronner-Fraser. "Collagens in avian neural crest development: distribution in vivo and migration-promoting ability in vitro." Development 113, no. 3 (November 1, 1991): 969–84. http://dx.doi.org/10.1242/dev.113.3.969.
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This study examines the spatiotemporal distribution of collagen (Col) types I-V and IX during neural crest development in vivo and their ability to support neural crest cell movement in vitro. Col I, III and IV were widespread throughout the embryo, including the neural crest migratory pathways, whereas Col II, V and IX preferentially localized to regions from which migrating neural crest cells were absent. Col I-IV and IX occurred both in association with basement membranes and within interstitial matrices, whereas Col V only was detected in juxtaposition to basement membranes. Although initially distributed throughout the rostrocaudal extent of the somitic sclerotome, Col I and III rearranged to the caudal portion with progressive neural crest cell migration through the rostral portion of the sclerotome. This rearrangement does not occur in neural crest-ablated embryos, suggesting that it is a direct consequence of neural crest cell migration. The perinotochordal matrix, avoided by neural crest cells, contained a metameric Col II/IX immunoreactivity along the rostrocaudal axis which alternated with that of Col I and III. In contrast, Col IV and V were not observed in this matrix, but lined the basement membranes of the notochord and ventrolateral neural tube. To determine their functional significance for neural crest cell migration in vivo, purified collagens were tested for their ability to promote neural crest cell motility in vitro. Neural crest cell migration on isolated collagens was most pronounced on Col I and IV, whereas Col II, V and the triple-helical fragment of Col VII were unable to support cell motility. Substrata created by copolymerization of Col I and fibronectin, or Col I and laminin-nidogen, supported cell motility better than Col I alone, whereas both Col V and a cartilage-type chondroitin sulfate proteoglycan reduced cell movement on Col I. Fibronectin bound to pre-immobilized monomeric Col I, II or V had a reduced ability to support neural crest cell movement when compared to fibronectin alone. A similar reduction was seen for Col IV bound to the low density heparan sulfate proteoglycan from the EHS mouse tumor. The results demonstrate that Col I-IX are differentially distributed in the early avian embryo. During neural crest development several of these collagens undergo dynamic reorganizations that correlate with the migration of neural crest cells. Furthermore, various collagens possess distinct abilities to support neural crest cell migration in vitro, and their migration-promoting activity can be modulated by their conformation and/or association with other matrix components.
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Stilmant, Frédéric, Sebastien Erpicum, Yann Peltier, Pierre Archambeau, Benjamin Dewals, and Michel Pirotton. "Flow at an Ogee Crest Axis for a Wide Range of Head Ratios: Theoretical Model." Water 14, no. 15 (July 28, 2022): 2337. http://dx.doi.org/10.3390/w14152337.
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The discharge coefficient of an ogee crest is a function of the ratio of the effective head to the design head. The purpose of the present study is to derive a theoretical model of this relation, which does not depend on empirical coefficients and whose predictions over a wide range of head ratios are accurate enough for practical use. The developments consider unsubmerged ogee crests without approach flow or lateral contraction effects, heads large enough to enable surface tensions to be neglected, and heads small enough to avoid flow separation. The method is based on potential flow theory, depth integration in a curvilinear reference frame, and critical flow theory. The characteristics of the crest shape are defined by the trajectory of a free jet passing over the crest at the design head. The dimensionless equations show that the position of the critical section is not at the apex of the crest. Nevertheless, they also suggest an approximate equation at the apex of the crest from which the discharge coefficient is derived, together with the local water depth, velocity, and pressure distribution. The results compare well with experimental data for head ratios between 0 and 5, which validates the underlying assumptions of the theoretical model.
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Prado-Irwin, Sofia R., Liam J. Revell, and Kristin M. Winchell. "Variation in tail morphology across urban and forest populations of the crested anole (Anolis cristatellus)." Biological Journal of the Linnean Society 128, no. 3 (August 28, 2019): 632–44. http://dx.doi.org/10.1093/biolinnean/blz111.
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AbstractAnolis lizards are well known for their specialist ecomorphs characterized by the convergent evolution of suites of traits linked to the use of particular microhabitats. Many of these same traits evolve rapidly in response to novel selection pressures and have been very well studied. In contrast, the tail crest, a feature present in a subset of lineages, has been almost entirely overlooked. Variation in tail crest morphology within and among species remains largely unstudied, as does the function of the trait. Here, we use the natural experiment provided by urbanization to ask whether tail crest size differs between urban and forest populations of the crested anole (Anolis cristatellus) across the Caribbean island of Puerto Rico. We find that tail crest size differs primarily between regions; however, within regions, crests are invariably larger in urban than in forest environments. This difference in size is correlated with the hotter, drier conditions and sparser distribution of perches that typify urban sites, leading to the intriguing possibility that the tail crest might be under differential natural selection for signalling and/or because of the thermoregulatory challenge of urban habitats. Further study is required to shed light on the functional significance and evolution of this under-studied trait.
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ÁVILA, ROBSON W., ANDRÉ PANSONATO, and CHRISTINE STRÜSSMANN. "A new species of the Rhinella margaritifera group (Anura: Bufonidae) from Brazilian Pantanal." Zootaxa 2339, no. 1 (January 20, 2010): 57. http://dx.doi.org/10.11646/zootaxa.2339.1.3.
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We describe adult morphology, advertisement call and some natural history traits of a new species of toad from the Pantanal, western Brazil. Rhinella paraguayensis sp. nov. belongs to the Rhinella margaritifera group, and is characterized by medium size, snout rounded in dorsal view, with a vertical apical ridge, supraorbital crests weakly developed, parietal crest not well developed, postorbital crest prominent, presence of a dorsolateral line of tubercles, tympanum evident, bony protrusions at angle of jaws, absence of vertebral apophyses and of projections on upper eyelids, and parotoid glands small. The new species is distinguished from other species of the group by geographic distribution and by the use of floating mats of vegetation as reproductive site.
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Zhang, Yangyang, Qingfu Huang, Shizhuang Chen, Fudong Chi, Huachen Wang, and Weiya Xu. "Spatial and Temporal Distribution Characteristics of Landslide Surge Based on Large-Scale Physical Modeling Experiment." Applied Sciences 14, no. 5 (March 3, 2024): 2104. http://dx.doi.org/10.3390/app14052104.
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Surge is a common secondary disaster caused by reservoir landslides. The study of its spatial and temporal distribution characteristics is important since it affects not only the normal operation of reservoirs but also the safety of people residing along the river. This paper presents a large-scale three-dimensional physical modeling experiment using a near-dam high-position landslide project as a prototype. It investigated the relationships between the river course characteristics, the landslide volume, the head wave velocity of the landslide surge, the waveform of surges, and the head wave crest of the wave along the course in depth. The results indicate that the head wave velocity of the landslide surge is basically unchanged during the propagation process, and it is minimally affected by the landslide volume. The waveform distribution characteristics and head wave crests change considerably in the diversion area and the curved areas but remain mostly unchanged in the topographic similarity area. In addition, there is a negative correlation between the head wave crest and the cross-sectional area of the river course. Furthermore, under conditions of a large landslide volume, the influence of the cross-sectional area of the river channel on the wave height of landslide surges becomes more significant. Finally, the maximum wave height along the course may not necessarily occur in the head wave crest; it could occur in the second wave or even the subsequent ones.
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Li, Cuilin, Dingyong Yu, Yangyang Gao, and Junxian Yang. "Crest-height distribution of nonlinear random waves." Journal of Ocean University of China 9, no. 1 (January 27, 2010): 31–36. http://dx.doi.org/10.1007/s11802-010-0031-y.
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Du, Ana, Li Li, Zhaoshuang Jiao, Gaochun Zhu, Ting Peng, and He Li. "Protein expression pattern of calcium-responsive transactivator in early postnatal and adult testes." Histochemistry and Cell Biology 155, no. 4 (January 4, 2021): 491–502. http://dx.doi.org/10.1007/s00418-020-01942-1.
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AbstractCalcium-responsive transactivator (CREST), a nuclear protein highly expressed in postmitotic neurons, is involved in the regulation of cell cycle, differentiation and dendritic development of neuronal cells. Its mRNA has been detected in the testis of adult rat, whilst its protein expression and distribution pattern in the testis remain to be elucidated. In this study, we examined the distribution of CREST in the adult testes of both rats and human as well as the expression pattern of CREST in the testes of postnatal developing rats. In the adult testes of both human and rats, immunohistochemical analysis revealed that CREST was selectively distributed in the mature Sertoli cells but not in the spermatogenic cells. In the testes of postnatal developmental rats, CREST was expressed not only in Sertoli cells but also in the gonocytes and spermatogenic cells at the initial stage of spermatogenic cell differentiation. CREST immunoreactivity continued to increase in Sertoli cells during differentiation, reaching its peak in adulthood. However, CREST immunostaining intensity dramatically decreased as the spermatogenic cells differentiate, disappearing in the post-differentiation stage. Furthermore, Brg1 and p300, two CREST-interacting proteins ubiquitously expressed in the body, are found to be colocalized with CREST in the spermatogenic epithelial cells including Sertoli cells. The unique expression pattern of CREST in developing testis suggests that CREST might play regulatory roles in the differentiation of spermatogenic epithelial cells. The Sertoli cell-specific expression of CREST in the adulthood hints that CREST might be a novel biomarker for the mature Sertoli cells.
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Wang, Ying-Guang. "Efficient Computation of Nonlinear Crest Distributions for Irregular Stokes Waves." Communications in Computational Physics 19, no. 4 (April 2016): 881–903. http://dx.doi.org/10.4208/cicp.191214.071215a.
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AbstractThis paper concerns the computation of nonlinear crest distributions for irregular Stokes waves, and a numerical algorithm based on the Fast Fourier Transform (FFT) technique has been developed for carrying out the nonlinear computations. In order to further improve the computational efficiency, a new Transformed Rayleigh procedure is first proposed as another alternative for computing the nonlinear wave crest height distributions, and the corresponding computer code has also been developed. In the proposed Transformed Rayleigh procedure, the transformation model is chosen to be a monotonic exponential function, calibrated such that the first three moments of the transformed model match the moments of the true process. The numerical algorithm based on the FFT technique and the proposed Transformed Rayleigh procedure have been applied for calculating the wave crest distributions of a sea state with a Bretschneider spectrum and a sea statewith the surface elevation datameasured at the Poseidon platform. It is demonstrated in these two cases that the numerical algorithm based on the FFT technique and the proposed Transformed Rayleigh procedure can offer better predictions than those from using the empirical wave crest distribution models. Meanwhile, it is found that our proposed Transformed Rayleigh procedure can compute nonlinear crest distributions more than 25 times faster than the numerical algorithm based on the FFT technique.
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Duband, J. L., and J. P. Thiery. "Spatial and temporal distribution of vinculin and talin in migrating avian neural crest cells and their derivatives." Development 108, no. 3 (March 1, 1990): 421–33. http://dx.doi.org/10.1242/dev.108.3.421.
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Neural crest cells express different adhesion modes at each phase of their development starting with their separation from the neural tube, followed by migration along definite pathways throughout the embryo, and finally to settlement and differentiation in elected embryonic regions. In order to determine possible changes in the cytoskeleton organization and function during these processes, we have studied the in situ distribution of two major cytoskeleton-associated elements involved in the membrane anchorage of actin microfilaments, i.e. vinculin and talin, during the ontogeny of the neural crest and its derivatives in the avian embryo. Prior to emigration, neural crest cells exhibited both vinculin and talin at levels similar to the neighbouring neural epithelial cells, and this expression apparently did not change as cells became endowed with migratory properties. However, vinculin became selectively enhanced in neural crest cells as they further migrated towards their final destination. This increase in vinculin amount was particularly striking in vagal and truncal neural crest cells entering cellular environments, such as the sclerotome and the gut mesenchyme. Talin was also expressed by neural crest cells but, in contrast to vinculin, staining was not conspicuous compared to neighbouring mesenchymal cells. High levels of vinculin persisted throughout embryogenesis in almost all neural derivatives of the neural crest, including the autonomous and sensory ganglia and Schwann cells along the peripheral nerves. In contrast, the non-neural derivatives of the neural crest rapidly lost their prominent vinculin staining after migration. The pattern of talin in the progeny of the neural crest was complex and varied with the cell types: for example, some cranial sensory ganglia expressed high amounts of the molecule whereas autonomic ganglia were nearly devoid of it. Our results suggest that (i) vinculin and talin may follow independent regulatory patterns within the same cell population, (ii) the level of expression of vinculin and talin in neural crest cells may be consistent with the rapid, constant modulations of their adhesive properties, and (iii) the expression patterns of the two molecules may also be correlated with the genesis of the peripheral nervous system.
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Krotoski, D. M., C. Domingo, and M. Bronner-Fraser. "Distribution of a putative cell surface receptor for fibronectin and laminin in the avian embryo." Journal of Cell Biology 103, no. 3 (September 1, 1986): 1061–71. http://dx.doi.org/10.1083/jcb.103.3.1061.
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The cell substratum attachment (CSAT) antibody recognizes a 140-kD cell surface receptor complex involved in adhesion to fibronectin (FN) and laminin (LM) (Horwitz, A., K. Duggan, R. Greggs, C. Decker, and C. Buck, 1985, J. Cell Biol., 101:2134-2144). Here, we describe the distribution of the CSAT antigen along with FN and LM in the early avian embryo. At the light microscopic level, the staining patterns for the CSAT receptor and the extracellular matrix molecules to which it binds were largely codistributed. The CSAT antigen was observed on numerous tissues during gastrulation, neurulation, and neural crest migration: for example, the surface of neural crest cells and the basal surface of epithelial tissues such as the ectoderm, neural tube, notochord, and dermomyotome. FN and LM immunoreactivity was observed in the basement membranes surrounding many of these epithelial tissues, as well as around the otic and optic vesicles. In addition, the pathways followed by cranial neural crest cells were lined with FN and LM. In the trunk region, FN and LM were observed surrounding a subpopulation of neural crest cells. However, neither molecule exhibited the selective distribution pattern necessary for a guiding role in trunk neural crest migration. The levels of CSAT, FN, and LM are dynamic in the embryo, perhaps reflecting that the balance of surface-substratum adhesions contributes to initiation, migration, and localization of some neural crest cell populations.
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OCA-AGUILAR, ANA CELIA MONTES DE, OSCAR MIKERY-PACHECO, ALFREDO CASTILLO, EDUARDO A. REBOLLAR-TÉLLEZ, PETER M. PIERMARINI, and SERGIO IBÁÑEZ-BERNAL. "Morphology variation of Lutzomyia cruciata eggs (Diptera: Psychodidae: Phlebotominae) in southern Mexico." Zootaxa 4258, no. 5 (May 2, 2017): 477. http://dx.doi.org/10.11646/zootaxa.4258.5.5.
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The sand fly Lutzomyia cruciata has been associated with the transmission of Leishmania mexicana to humans in Mexico. This species has a wide distribution in Mexico occupying different microhabitats and environments. In this work comparisons of the egg exochorion of Lu. cruciata from different physiographic areas are presented. Study sites are from different states of southern Mexico. Exochorion analysis was carried out using scanning electron microscopy (SEM). Results show differences in the exochorionic pattern among samples from Veracruz (AVER), Yucatán (HOYU) and Chiapas (TACH). The morphotype “Chiapas” has a polygonal crest pattern, the morphotype “Veracruz” shows parallel and longitudinal crests with some or few connections, and the morphotype “Yucatán” has weak connections between crest ridges. These morphological differences could be the result of local adaptations or evidence of divergence within the nominal unit Lutzomyia cruciata.
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Epperlein, H. H., W. Halfter, and R. P. Tucker. "The distribution of fibronectin and tenascin along migratory pathways of the neural crest in the trunk of amphibian embryos." Development 103, no. 4 (August 1, 1988): 743–56. http://dx.doi.org/10.1242/dev.103.4.743.
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It is generally assumed that in amphibian embryos neural crest cells migrate dorsally, where they form the mesenchyme of the dorsal fin, laterally (between somites and epidermis), where they give rise to pigment cells, and ventromedially (between somites and neural tube), where they form the elements of the peripheral nervous system. While there is agreement about the crest migratory routes in the axolotl (Ambystoma mexicanum), different opinions exist about the lateral pathway in Xenopus. We investigated neural crest cell migration in Xenopus (stages 23, 32, 35/36 and 41) using the X. laevis-X. borealis nuclear marker system and could not find evidence for cells migrating laterally. We have also used immunohistochemistry to study the distribution of the extracellular matrix (ECM) glycoproteins fibronectin (FN) and tenascin (TN), which have been implicated in directing neural crest cells during their migrations in avian and mammalian embryos, in the neural crest migratory pathways of Xenopus and the axolotl. In premigratory stages of the crest, both in Xenopus (stage 22) and the axolotl (stage 25), FN was found subepidermally and in extracellular spaces around the neural tube, notochord and somites. The staining was particularly intense in the dorsal part of the embryo, but it was also present along the visceral and parietal layers of the lateral plate mesoderm. TN, in contrast, was found only in the anterior trunk mesoderm in Xenopus; in the axolotl, it was absent. During neural crest cell migration in Xenopus (stages 25–33) and the axolotl (stages 28–35), anti-FN stained the ECM throughout the embryo, whereas anti-TN staining was limited to dorsal regions. There it was particularly intense medially, i.e. in the dorsal fin, around the neural tube, notochord, dorsal aorta and at the medial surface of the somites (stage 35 in both species). During postmigratory stages in Xenopus (stage 40), anti-FN staining was less intense than anti-TN staining. In culture, axolotl neural crest cells spread differently on FN- and TN-coated substrata. On TN, the onset of cellular outgrowth was delayed for about 1 day, but after 3 days the extent of outgrowth was indistinguishable from cultures grown on FN. However, neural crest cells in 3-day-old cultures were much more flattened on FN than on TN. We conclude that both FN and TN are present in the ECM that lines the neural crest migratory pathways of amphibian embryos at the time when the neural crest cells are actively migrating. FN is present in the embryonic ECM before the onset of neural crest migration.(ABSTRACT TRUNCATED AT 400 WORDS)
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Romero, Leonel, and W. Kendall Melville. "Spatial Statistics of the Sea Surface in Fetch-Limited Conditions." Journal of Physical Oceanography 41, no. 10 (October 1, 2011): 1821–41. http://dx.doi.org/10.1175/2011jpo4535.1.
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Abstract An analysis of airborne wave observations collected in the Gulf of Tehuantepec is presented. The data include lidar measurements of the surface displacement as a function of two horizontal dimensions in fetch-limited conditions, with fetches between 20 and 500 km and winds between 10 and 20 m s−1. The spatial data have an advantage over the commonly used single-point time series measurements, allowing direct estimates of the wavelength and wave slope, including spatial information such as the lengths of crests exceeding various thresholds. This study presents an analysis of several statistical wind wave parameters, including the joint probability distribution function (pdf) of wave amplitudes and wavelengths; the pdf of wave heights, wavenumber vectors, and wave slopes; as well as the statistics of the lengths of crests exceeding threshold wave heights and slopes. The empirical findings from the lidar data are compared against analytical theories in the literature, including some that had not been tested previously with field data such as the work by M. S. Longuet-Higgins describing the length of contours surrounding large wave heights per unit surface area. The effect of second-order nonlinearities on the distribution of crest lengths per unit surface area is investigated with analytical approximations and stochastic numerical simulations from computed directional wavenumber spectra. The results show that second-order nonlinearities can increase the crest-length distribution of large waves by a factor of 2 or more.
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Kriebel, D. L., and T. H. Dawson. "Nonlinear Effects on Wave Groups in Random Seas." Journal of Offshore Mechanics and Arctic Engineering 113, no. 2 (May 1, 1991): 142–47. http://dx.doi.org/10.1115/1.2919910.
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Laboratory simulations of extreme random seas reveal that high wave crests occur more frequently than predicted by the Rayleigh distribution. In this paper, a theory is presented to account for nonlinearities in the sea state to second order resulting in a non-Rayleigh distribution of wave crest and trough amplitudes based on the narrow-band assumption. The resulting probability density functions are then used to predict average wave group characteristics through a modification of linear wave envelope theory which accounts, for example, for a significant decrease in the time intervals between successive runs of high crests compared to linear theory. The nonlinear theory is then verified based on a laboratory data set on deep water wave group statistics for severe seas described by Bretschneider and JONSWAP spectra.
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Sadaghiani, Bahram, Bruce J. Crawford, and Juergen R. Vielkind. "Changes in the distribution of extracellular matrix components during neural crest development in Xiphophorus spp. embryos." Canadian Journal of Zoology 72, no. 7 (July 1, 1994): 1340–53. http://dx.doi.org/10.1139/z94-177.
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The changes in distribution of chondroitin sulfate proteoglycans (CSs) and fibronectin (FN), two major components of the extracellular matrix (ECM), are described during the development and migration of neural crest cells in two Xiphophorus species offish, X. helleri (swordtail) and X. maculatus (platyfish), using immunohistochemistry. A detailed description of the developmental changes in HNK-1-positive ECM components is also provided and compared with those of CSs and FN. HNK-1 antigen was also used as a marker for the neural crest cells. Weak staining for CSs, FN, and HNK-1-positive ECM was present in the neural crest cell migration pathways prior to migration of the cells. The level of staining increased dramatically during migration of these cells and decreased again after migration was nearly completed. Staining for CSs was more widespread than staining for FN, while the HNK-1 staining pattern was more clearly restricted to the migratory pathways than those seen with the other two antibodies. The correlation between the spatiotemporal relationship of these ECM components and the segregation and migration of neural crest cells suggests that these ECM molecules may be involved in both initiating and guiding the migration of neural crest cells in these fish. The HNK-1-positive ECM may play a more critical role than CSs and FN.
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Wang, Yingguang. "Nonlinear crest distribution for shallow water Stokes waves." Applied Ocean Research 57 (April 2016): 152–61. http://dx.doi.org/10.1016/j.apor.2016.03.006.
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Laface, Valentina, Giovanni Malara, Ioannis A. Kougioumtzoglou, Alessandra Romolo, and Felice Arena. "Nonlinear wave crest distribution on a vertical breakwater." Coastal Engineering 138 (August 2018): 227–34. http://dx.doi.org/10.1016/j.coastaleng.2018.04.018.
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Chan, W. Y., and P. P. Tam. "A morphological and experimental study of the mesencephalic neural crest cells in the mouse embryo using wheat germ agglutinin-gold conjugate as the cell marker." Development 102, no. 2 (February 1, 1988): 427–42. http://dx.doi.org/10.1242/dev.102.2.427.
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The distribution of the mesencephalic neural crest cells in the mouse embryo was studied by mapping the colonization pattern of WGA-gold labelled cells following specific labelling of the neuroectoderm and grafting of presumptive neural crest cells to orthotopic and heterotopic sites. The result showed that (1) there were concomitant changes in the morphology of the neural crest epithelium during the formation of neural crest cells, in the 4- to 7-somite-stage embryos, (2) the neural crest cells were initially confined to the lateral subectodermal region of the cranial mesenchyme and there was minimal mixing with the paraxial mesoderm underneath the neural plate, (3) labelled cells from the presumptive crest region colonized the lateral cranio-facial mesenchyme, the developing trigeminal ganglion and the pharyngeal arch, (4) the formation of neural crest cells was facilitated by the focal disruption of the basal lamina and the cell-cell interaction specific to the neural crest site and (5) the trigeminal ganglion was colonized not only by neural crest cells but also by cells from the ectodermal placode.
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Meister, R. "Influence of Strong Winds on Snow Distribution and Avalanche Activity." Annals of Glaciology 13 (1989): 195–201. http://dx.doi.org/10.3189/s0260305500007886.
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In a local range, crest winds were compared with winds at lower stations to make it possible to initiate a drift-transport model which would predict snow accumulation patterns on leeward slopes. Corrections to the model input were made after consideration of detailed drift-flux measurements in the lowest 2 m above snow surface. Good agreement was found between the total length of large avalanches in a path near the crest, the appropriate wind reading and the corrected snow-depth increments in the rupture zone. Control of medium-sized avalanches likely to cause injury to skiers can be improved with the proposed method.
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Meister, R. "Influence of Strong Winds on Snow Distribution and Avalanche Activity." Annals of Glaciology 13 (1989): 195–201. http://dx.doi.org/10.1017/s0260305500007886.
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In a local range, crest winds were compared with winds at lower stations to make it possible to initiate a drift-transport model which would predict snow accumulation patterns on leeward slopes. Corrections to the model input were made after consideration of detailed drift-flux measurements in the lowest 2 m above snow surface. Good agreement was found between the total length of large avalanches in a path near the crest, the appropriate wind reading and the corrected snow-depth increments in the rupture zone. Control of medium-sized avalanches likely to cause injury to skiers can be improved with the proposed method.
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Wakamatsu, Y., M. Mochii, K. S. Vogel, and J. A. Weston. "Avian neural crest-derived neurogenic precursors undergo apoptosis on the lateral migration pathway." Development 125, no. 21 (November 1, 1998): 4205–13. http://dx.doi.org/10.1242/dev.125.21.4205.
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Neural crest cells of vertebrate embryos disperse on distinct pathways and produce different derivatives in specific embryonic locations. In the trunk of avian embryos, crest-derived cells that initially migrate on the lateral pathway, between epidermal ectoderm and somite, produce melanocytes but no neuronal derivatives. Although we found that melanocyte precursors are specified before they disperse on the lateral pathway, we also observed that a few crest-derived neuronal cells are briefly present on the same pathway. Here, we show that neuronal cells are removed by an episode of apoptosis. These observations suggest that localized environmental factor(s) affect the distribution of fate-restricted crest derivatives and function as a ‘proof-reading mechanism’ to remove ‘ectopic’ crest-derived cells.
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Greenhow, Martin. "A probability distribution of breaking wave crest height based on a crest-acceleration threshold method." Ocean Engineering 16, no. 5-6 (January 1989): 537–44. http://dx.doi.org/10.1016/0029-8018(89)90051-6.
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Sadaghiani, B., and J. R. Vielkind. "Distribution and migration pathways of HNK-1-immunoreactive neural crest cells in teleost fish embryos." Development 110, no. 1 (September 1, 1990): 197–209. http://dx.doi.org/10.1242/dev.110.1.197.
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Whole mounts and cross-sections of embryos from three species of teleost fish were immunostained with the HNK-1 monoclonal antibody, which recognizes an epitope on migrating neural crest cells. A similar distribution and migration was found in all three species. The crest cells in the head express the HNK-1 epitope after they have segregated from the neural keel. The truncal neural crest cells begin to express the epitope while they still reside in the dorsal region of the neural keel; this has not been observed in other vertebrates. The cephalic and anterior truncal neural crest cells migrate under the ectoderm; the cephalic cells then enter into the gill arches and the anterior truncal cells into the mesentery of the digestive tract where they cease migration. These cephalic and anterior trunk pathways are similar to those described in Xenopus and chick. The neural crest cells of the trunk, after segregation, accumulate in the dorsal wedges between the somites, however, unlike in chick and rat, they do not migrate in the anterior halves of the somites but predominantly between the neural tube and the somites, the major pathway observed in carp and amphibians; some cells migrate over the somites. The HNK-1 staining of whole-mount embryos revealed a structure resembling the Rohon-Beard and extramedullary cells, the primary sensory system in amphibians. Such a system has not been described in fish.
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Sechrist, J., G. N. Serbedzija, T. Scherson, S. E. Fraser, and M. Bronner-Fraser. "Segmental migration of the hindbrain neural crest does not arise from its segmental generation." Development 118, no. 3 (July 1, 1993): 691–703. http://dx.doi.org/10.1242/dev.118.3.691.
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The proposed pathways of chick cranial neural crest migration and their relationship to the rhombomeres of the hindbrain have been somewhat controversial, with differing results emerging from grafting and DiI-labelling analyses. To resolve this discrepancy, we have examined cranial neural crest migratory pathways using the combination of neurofilament immunocytochemistry, which recognizes early hindbrain neural crest cells, and labelling with the vital dye, DiI. Neurofilament-positive cells with the appearance of premigratory and early-migrating neural crest cells were noted at all axial levels of the hindbrain. At slightly later stages, neural crest cell migration in this region appeared segmented, with no neural crest cells obvious in the mesenchyme lateral to rhombomere 3 (r3) and between the neural tube and the otic vesicle lateral to r5. Focal injections of DiI at the levels of r3 and r5 demonstrated that both of these rhombomeres generated neural crest cells. The segmental distribution of neural crest cells resulted from the DiI-labelled cells that originated in r3 and r5 deviating rostrally or caudally and failing to enter the adjacent preotic mesoderm or otic vesicle region. The observation that neural crest cells originating from r3 and r5 avoided specific neighboring domains raises the intriguing possibility that, as in the trunk, extrinsic factors play a major role in the axial patterning of the cranial neural crest and the neural crest-derived peripheral nervous system.
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Kallel, Ahmed Yahia, and Olfa Kanoun. "Crest Factor Optimization for Multisine Excitation Signals with Logarithmic Frequency Distribution Based on a Hybrid Stochastic-Deterministic Optimization Algorithm." Batteries 8, no. 10 (October 12, 2022): 176. http://dx.doi.org/10.3390/batteries8100176.
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For diagnosis of batteries and fuel cells based on impedance spectroscopy, excitation signals are required, including low frequencies down to the mHz range. This leads to a long measurement time and compromises the stability condition for impedance spectroscopy. Multisine excitation signals with logarithmic frequency distribution can significantly reduce the measurement time but need optimization of the crest factor to realize a high signal-to-noise ratio at all excitation frequencies and maintain at the same time the linearity and stability conditions of impedance spectroscopy. Crest factor optimization is challenging, as the obtained results strongly depend on the initial phase values and many trials are necessary. It takes a very long time and can not be easily performed automatically up to now. In this paper, we propose a time-efficient hybrid stochastic-deterministic crest factor optimization method for multisine signals with logarithmic frequency distribution. A sigmoid transform on the multisine signal gradually transforms the multi-frequency signal into a binary-alike signal. The crest factor is significantly decreased, but the phases of the singular frequency signals remain sub-optimal. Further optimization based on the Gauss-Newton algorithm can determine the final phases, realizing a lower crest factor. The proposed method is less sensitive to initial phase values and provides more reasonable results in a reasonable time. The validation on a Samsung INR-18650-25R Lithium-ion battery cell shows that the crest factor of the optimized multisine signals has a median of 3.62 ± 0.7 within 6 min of run time, which is significantly better than the best previous work in the state-of-the-art of 3.85 ± 0.11 for the same run time.
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Springer, Emilie Grønbæk, Jan Audun Rasmussen, Lars Stemmerik, and Jan Audun Rasmussen. "Distribution and significance of foraminiferal biofacies on an aphotic Danian bryozoan mound, Karlstrup, Denmark." Bulletin of the Geological Society of Denmark 64 (April 12, 2016): 57–67. http://dx.doi.org/10.37570/bgsd-2016-64-02.
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In this study, the distribution of benthic foraminifers across a Danian bryozoan mound in Karlstrup quarry, Denmark, is analysed in 22 samples using multivariate analysis. Three foraminiferal biofacies are established, each representing a distinct part of the mound. The Anomalinoides-Cibicides- Osangularia Biofacies is characteristic of the relatively pure carbonate sediments on the crest and flanks of the bryozoan mound. The Patellina Biofacies occurs at the mound flanks and is particularly common in marly sediments. The Spirillina Biofacies characterises the crest of the bryozoan mound in both marly and pure carbonate sediments. Variations in the plankton/benthos ratio indicate that the benthic foraminifers prefer the marly sediments to pure limestone and mound flanks relative to the mound top. It is likely that the benthic foraminifers avoided the more powerful currents at the mound crest. The common occurrence of spirillinids on the mound top may represent the remnant of a rich, siliceous sponge community.
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Luxmoore, Jamie F., Suzana Ilic, and Nobuhito Mori. "On kurtosis and extreme waves in crossing directional seas: a laboratory experiment." Journal of Fluid Mechanics 876 (August 8, 2019): 792–817. http://dx.doi.org/10.1017/jfm.2019.575.
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We examine the statistical properties of extreme and rogue wave activity in crossing directional seas, to constrain the probabilistic distributions of wave heights and wave crests in complex sea states; such crossing seas alter the statistical structure of surface waves and are known to have been involved in several marine accidents. Further, we examine the relationship between the kurtosis as an indicator of nonlinearity in the spectrum and the directionality and crossing angles of the sea-state components. Experimental tests of two-component directionally spread irregular waves with varying frequency, directional spreading and component crossing angles were carried out at the Ocean Basin Laboratory in Trondheim, Norway. The results from the experiments show that wave heights are well described by a first-order (linear) statistical distribution, while for the wave crest heights several cases exceed a second-order distribution. The number of rogue waves is relatively low overall, which agrees with previous findings in directionally spread seas. The kurtosis and wave and crest height exceedance probabilities were more affected by varying the directional spreading of the components than by varying the crossing angles between components; reducing the component directional spreading increases the kurtosis and increases the exceedance probabilities. The kurtosis can be estimated quite well for two-component seas from the directional spreading using an empirical relationship based on the two-dimensional Benjamin–Feir index when the effects of bound modes are included. This result may allow forecasting of the probability of extreme waves from the directional spreading in complex sea states.
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Ranscht, B., and M. Bronner-Fraser. "T-cadherin expression alternates with migrating neural crest cells in the trunk of the avian embryo." Development 111, no. 1 (January 1, 1991): 15–22. http://dx.doi.org/10.1242/dev.111.1.15.
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Trunk neural crest cells and motor axons move in a segmental fashion through the rostral (anterior) half of each somitic sclerotome, avoiding the caudal (posterior) half. This metameric migration pattern is thought to be caused by molecular differences between the rostral and caudal portions of the somite. Here, we describe the distribution of T-cadherin (truncated-cadherin) during trunk neural crest cell migration. T-cadherin, a novel member of the cadherin family of cell adhesion molecules was selectively expressed in the caudal half of each sclerotome at all times examined. T-cadherin immunostaining appeared graded along the rostrocaudal axis, with increasing levels of reactivity in the caudal halves of progressively more mature (rostral) somites. The earliest T-cadherin expression was detected in a small population of cells in the caudal portion of the somite three segments rostral to last-formed somite. This initial T-cadherin expression was observed concomitant with the invasion of the first neural crest cells into the rostral portion of the same somite in stage 16 embryos. When neural crest cells were ablated surgically prior to their emigration from the neural tube, the pattern of T-cadherin immunoreactivity was unchanged compared to unoperated embryos, suggesting that the metameric T-cadherin distribution occurs independent of neural crest cell signals. This expression pattern is consistent with the possibility that T-cadherin plays a role in influencing the pattern of neural crest cell migration and in maintaining somite polarity.
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Kumar, V. Sanil, S. Harikrishnan, and Sourav Mandal. "Wave crest height distribution during the tropical cyclone period." Ocean Engineering 197 (February 2020): 106899. http://dx.doi.org/10.1016/j.oceaneng.2019.106899.
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Naess, Arvid. "On the distribution of crest to trough wave heights." Ocean Engineering 12, no. 3 (January 1985): 221–34. http://dx.doi.org/10.1016/0029-8018(85)90014-9.
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Gani, Yarnelly, and Louise Luckenbill-Edds. "Quantitative distribution of chick neural crest cells during gangliogenesis." Cell and Tissue Research 263, no. 1 (January 1991): 107–14. http://dx.doi.org/10.1007/bf00318405.
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Anderson, R. Scott, Susan J. Smith, and Peter A. Koehler. "Distribution of Sites and Radiocarbon Dates in the Sierra Nevada: Implications for Paleoecological Prospecting." Radiocarbon 39, no. 2 (1997): 121–37. http://dx.doi.org/10.1017/s0033822200051973.
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The number of paleoecological records for the Sierra Nevada of California has increased substantially since the compilation of Adam (1985). We examine here the geographical and temporal distribution of records within the range in order to identify areas for which “gaps” exist in our paleoecological knowledge. Seventy-two sites with paleoecological information are identified; these sites are dated with 234 radiocarbon dates. Sites occur primarily between ca. 36°N and 38°30'N latitudes, and from ca. 1000 m to over 3000 m elevation on both sides of the Sierran crest, although more sites have been analyzed on the west side of the crest than the east side. In general, packrat (Neotoma) midden series are located at the lowest elevations, meadow and marsh cores originate from mid-elevations, and lake sediments have been analyzed from the highest elevations. Significant gaps in our knowledge occur for much of the east side of the crest, for both sides of the range above modern treeline, and for time periods older than the latest Pleistocene.
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Myrhaug, D., and H. Rue. "Joint Distribution of Successive Wave Steepness Parameters." Journal of Offshore Mechanics and Arctic Engineering 115, no. 3 (August 1, 1993): 191–95. http://dx.doi.org/10.1115/1.2920111.
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A joint distribution of wave steepness parameters associated with two successive waves is presented. The wave steepness parameters considered herein are the crest front steepness and the total wave steepness. This joint distribution is represented by a two-dimensional Weibull distribution with the parameters α = 0.84 and β = 1.40. The application of the results is illustrated by an example.
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Rowe, A., J. M. Richman, and P. M. Brickell. "Development of the spatial pattern of retinoic acid receptor-beta transcripts in embryonic chick facial primordia." Development 114, no. 3 (March 1, 1992): 805–13. http://dx.doi.org/10.1242/dev.114.3.805.
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Retinoic acid causes a range of embryonic defects, including craniofacial abnormalities, in both birds and mammals and is believed to have a number of roles in normal development. We have previously shown that the distribution of retinoic acid receptor-beta (RAR-beta) transcripts is spatially restricted within the neural-crest-derived upper beak primordia of the chick embryo. We have now used in situ hybridisation to trace the distribution of RAR-beta transcripts during the migration of cranial neural crest cells and during formation of these primordia. RAR-beta transcripts were present in a subset of migrating neural-crest-derived cells in the head of the stage 10 embryo. These cells were situated in pathways followed by cells that migrate from the neural crest overlying the posterior prosencephalic/anterior mesencephalic region of the developing brain. Cells containing RAR-beta transcripts accumulated around the developing eyes and in the regions of the ventral head from which the upper beak primordia later develop. We mapped the distribution of RAR-beta transcripts as the facial primordia were forming, with particular reference to the development of the maxillary primordia. We found that these form in a region of the ventral head that includes the boundary between regions of high and low levels of RAR-beta transcripts. The boundary between these two groups of cells persisted as the maxillary primordia developed.(ABSTRACT TRUNCATED AT 250 WORDS)
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Blanchon, Paul, Alexis E. Medina-Valmaseda, Eduardo Islas-Domínguez, Edlin Guerra-Castro, David Blakeway, Joaquín Rodrigo Garza Pérez, Adan Guillermo Jordan-Garza, Ismael Mariño-Tapia, and Paula A. Zapata-Ramírez. "Linear breakwater reefs of the greater Caribbean: Classification, distribution & morphology." PLOS ONE 17, no. 11 (November 23, 2022): e0270053. http://dx.doi.org/10.1371/journal.pone.0270053.
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Geomorphic differences among Caribbean reefs have long been noted. These differences are considered to reflect the presence of reefs in different stages of development, following an incomplete recovery from rapid deglacial sea-level rise. But the possibility that these reflect real developmental differences caused by variation in wind, wave, and climate regime, has never been fully considered. Here, for the first time, we quantify the geomorphology and distribution of Greater Caribbean reefs using satellite images in Google Earth and public-domain bathymetry. To do this, we first standardise their classification based on shallow geomorphology, substrate depth, and physiographic setting, and then count and categorise the total number of reefs. These data show a total of 1023 linear breakwater reefs with a combined length of 2237 km. Of this total length, 80% are fringing reefs, 16% are barriers and 4% are faros and atolls. In terms of categories, there are 16 reef subtypes present, but only 9 are common. Their distribution, however, is not uniform. In particular, flat-subtypes form 60% of breakwater reefs in southern regions, but are less common in northern regions where crest-subtypes dominate (80%). To distinguish the geomorphology of these common reef subtypes, we collect size- and length-related morphometric data from their main reef zones. These data reveal that flat and crest subtypes also have morphometric differences: flat subtypes have well-constrained morphologies with statistically consistent unimodal morphometrics characterised by large back-reef zones, smaller and steeper reef fronts, and more sinuous and persistent crestlines. Crest subtypes, by contrast, have multimodal morphometrics suggesting less consistent morphologies (or unresolved subtypes), and are characterised by crestlines with lower sinuosity, more variable back-reef and reef-front areas, and slopes. These differences in geomorphology and distribution imply that flat- and crest-subtypes are neither successional stages of a single reef type, nor a genetically related sequence of types, but distinct reefal geoforms with different modes of development. In subsequent work we will explore what controls these differences.
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Skourup, J., N. E. O. Hansen, and K. K. Andreasen. "Non-Gaussian Extreme Waves in the Central North Sea." Journal of Offshore Mechanics and Arctic Engineering 119, no. 3 (August 1, 1997): 146–50. http://dx.doi.org/10.1115/1.2829061.
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The area of the Central North Sea is notorious for the occurrence of very high waves in certain wave trains. The short-term distribution of these wave trains includes waves which are far steeper than predicted by the Rayleigh distribution. Such waves are often termed “extreme waves” or “freak waves.” An analysis of the extreme statistical properties of these waves has been made. The analysis is based on more than 12 yr of wave records from the Mærsk Olie og Gas AS operated Gorm Field which is located in the Danish sector of the Central North Sea. From the wave recordings more than 400 freak wave candidates were found. The ratio between the extreme crest height and the significant wave height (20-min value) has been found to be about 1.8, and the ratio between extreme crest height and extreme wave height has been found to be 0.69. The latter ratio is clearly outside the range of Gaussian waves, and it is higher than the maximum value for steep nonlinear long-crested waves, thus indicating that freak waves are not of a permanent form, and probably of short-crested nature. The extreme statistical distribution is represented by a Weibull distribution with an upper bound, where the upper bound is the value for a depth-limited breaking wave. Based on the measured data, a procedure for determining the freak wave crest height with a given return period is proposed. A sensitivity analysis of the extreme value of the crest height is also made.
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Krogstad, Harald E., and Stephen F. Barstow. "Analysis and Applications of Second-Order Models for Maximum Crest Height." Journal of Offshore Mechanics and Arctic Engineering 126, no. 1 (February 1, 2004): 66–71. http://dx.doi.org/10.1115/1.1641798.
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Expressions for the maximum crest height are reviewed and tested on data from five different sensors in the WACSIS data set. The overall agreement is good and the analysis supports that second-order models give accurate expressions for the distribution of the maximum crest height for varying water depth and wave steepness. In the second part of the paper, the expressions are combined with the existing extreme crest and wave height framework and applied to sets of time series and long term wave data. It is concluded that the second-order models represent a definite improvement over earlier empirical parametrizations.
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Gemmrich, Johannes. "Strong Turbulence in the Wave Crest Region." Journal of Physical Oceanography 40, no. 3 (March 1, 2010): 583–95. http://dx.doi.org/10.1175/2009jpo4179.1.
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Abstract High-resolution vertical velocity profiles in the surface layer of a lake reveal the turbulence structure beneath strongly forced waves. Dissipation rates of turbulence kinetic energy are estimated based on centered second-order structure functions at 4-Hz sampling. Dissipation rates within nonbreaking wave crests are on average 3 times larger than values found at the same distance to the free surface but within the wave trough region. This ratio increases to 18 times for periods with frequent wave breaking. The depth-integrated mean dissipation rate is a function of the wave field and correlates well with the mean wave saturation in the wave band ωp ≤ ω ≤ 4ωp. It shows a clear threshold behavior in accordance with the onset of wave breaking. The initial bubble size distribution is estimated from the observed distribution of energy dissipation rates, assuming the Hinze scale being the limiting size. This model yields the slope of the size distribution, , consistent with laboratory results reported in the literature, and implies that bubble fragmentation associated with intermittent high dissipation rates is a valid mechanism for the setup of bubble size spectra.
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Gemmrich, Johannes R., Michael L. Banner, and Chris Garrett. "Spectrally Resolved Energy Dissipation Rate and Momentum Flux of Breaking Waves." Journal of Physical Oceanography 38, no. 6 (June 1, 2008): 1296–312. http://dx.doi.org/10.1175/2007jpo3762.1.
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Abstract Video observations of the ocean surface taken from aboard the Research Platform FLIP reveal the distribution of the along-crest length and propagation velocity of breaking wave crests that generate visible whitecaps. The key quantity assessed is Λ(c)dc, the average length of breaking crests per unit area propagating with speeds in the range (c, c + dc). Independent of the wave field development, Λ(c) is found to peak at intermediate wave scales and to drop off sharply at larger and smaller scales. In developing seas breakers occur at a wide range of scales corresponding to phase speeds from about 0.1 cp to cp, where cp is the phase speed of the waves at the spectral peak. However, in developed seas, breaking is hardly observed at scales corresponding to phase speeds greater than 0.5 cp. The phase speed of the most frequent breakers shifts from 0.4 cp to 0.2 cp as the wave field develops. The occurrence of breakers at a particular scale as well as the rate of surface turnover are well correlated with the wave saturation. The fourth and fifth moments of Λ(c) are used to estimate breaking-wave-supported momentum fluxes, energy dissipation rate, and the fraction of momentum flux supported by air-entraining breaking waves. No indication of a Kolmogorov-type wave energy cascade was found; that is, there is no evidence that the wave energy dissipation is dominated by small-scale waves. The proportionality factor b linking breaking crest distributions to the energy dissipation rate is found to be (7 ± 3) × 10−5, much smaller than previous estimates.
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Xu, X., W. E. I. Li, G. Y. Huang, R. Meyer, T. Chen, Y. Luo, M. P. Thomas, G. L. Radice, and C. W. Lo. "Modulation of mouse neural crest cell motility by N-cadherin and connexin 43 gap junctions." Journal of Cell Biology 154, no. 1 (July 9, 2001): 217–30. http://dx.doi.org/10.1083/jcb.200105047.
Full textAbstract:
Connexin 43 (Cx43α1) gap junction has been shown to have an essential role in mediating functional coupling of neural crest cells and in modulating neural crest cell migration. Here, we showed that N-cadherin and wnt1 are required for efficient dye coupling but not for the expression of Cx43α1 gap junctions in neural crest cells. Cell motility was found to be altered in the N-cadherin–deficient neural crest cells, but the alterations were different from that elicited by Cx43α1 deficiency. In contrast, wnt1-deficient neural crest cells showed no discernible change in cell motility. These observations suggest that dye coupling may not be a good measure of gap junction communication relevant to motility. Alternatively, Cx43α1 may serve a novel function in motility. We observed that p120 catenin (p120ctn), an Armadillo protein known to modulate cell motility, is colocalized not only with N-cadherin but also with Cx43α1. Moreover, the subcellular distribution of p120ctn was altered with N-cadherin or Cx43α1 deficiency. Based on these findings, we propose a model in which Cx43α1 and N-cadherin may modulate neural crest cell motility by engaging in a dynamic cross-talk with the cell's locomotory apparatus through p120ctn signaling.