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1
Dove, Justin, and Jeffrey H. Shapiro. "Speckled speckled speckle." Optics Express 28, no. 15 (July 10, 2020): 22105. http://dx.doi.org/10.1364/oe.398226.
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Wubalem, Azemeraw, Chiara Caselle, Battista Taboni, and Gessica Umili. "Effects of Rock Texture on Digital Image Correlation." Geosciences 15, no. 4 (April 10, 2025): 145. https://doi.org/10.3390/geosciences15040145.
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Digital image correlation (DIC) is a non-contact optical method that can provide high-resolution strain and displacement measurements, but its effectiveness depends on surface texture contrast. This study investigates the effects of surface characteristics on the quality of DIC results in tonalite and marble samples under Brazilian tests. Tonalite samples have a coarse texture with a heterogeneous mineral composition; therefore, DIC analysis was conducted without artificial speckle patterns. Marble, instead, poses a challenge due to its uniform fine texture and composition. Thus, using point and line grids to enhance surface contrast, artificial speckle patterns were applied to marble samples. A total of 39 disk samples (12 tonalite and 27 marble) were tested with video frames recorded during loading and analyzed using Ncorr software. The results confirmed that tonalite’s natural texture allows accurate strain mapping without artificial speckle patterns. In contrast, marbles without speckles are not effective in strain evolution mapping due to a lack of surface contrast. Marble with both point- and line-speckled patterns effectively mapped the strain evolution except for some distortion and directionality along speckles in displacement fields. This result suggests that the preparation of speckled surfaces need special attention for effective deformation evolution mapping in homogeneous materials.
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Alexander, Katherine A., Ruofan Yu, Christine Faunce, Nicolas Skuli, Nathan Coffey, Son Nguyen, Nicholas Biddle, et al. "Abstract PR010: In-“speck”-ting the nucleus: Nuclear speckles are a critical layer of gene regulation that predict outcomes in clear cell renal cell carcinoma." Cancer Research 83, no. 16_Supplement (August 15, 2023): PR010. http://dx.doi.org/10.1158/1538-7445.kidney23-pr010.
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Abstract Nuclear speckles are dynamic substructures within the nucleus that contain a myriad of factors involved in gene activation. While nuclear speckles were discovered over 100 years ago, how they vary in human health and disease and the consequences of such variation remain enigmatic. Using RNA-seq data to estimate nuclear speckle content, we found that nuclear speckle phenotypes vary reproducibly in >20 cancer types. Of these cancers, nuclear speckle variation predicted patient outcomes specifically in clear cell renal cell carcinoma (ccRCC). This ccRCC speckle sensitivity was confirmed in a separate cohort using immunofluorescence to independently assess speckle phenotypes, and was specific to ccRCC with VHL mutation or copy number loss, suggesting involvement of the VHL-degraded HIF stress-responsive transcription factors. Given our previous findings linking nuclear speckles to another stress-responsive transcription factor, p53, we hypothesized that the speckle sensitivities we observed in ccRCC may be a consequence of as-of-yet uncharacterized speckle functions of HIF1A or HIF2A. Previously, we found that p53 drives DNA-speckle contacts of a subset of target genes to boost expression, revealing a novel method of transcription-factor-based gene regulation. However, the extent that DNA-speckle positioning is regulated by transcription factors other than p53, including the HIF transcription factors, is currently unclear. Critically, p53 and HIF2A, but not HIF1A, share a homologous protein motif, now coined the speckle targeting motif, that precisely overlaps with the region where we had mapped p53 DNA-speckle targeting abilities. Using genomic and imaging-based methods, we identified HIF2A as a second transcription factor that drives association between a subset of its target genes and nuclear speckles. Deletion of the HIF2A speckle targeting motifs ablated its DNA-speckle targeting functions, led to lower induction of speckle-associating genes, and resulted in a HIF2A-mediated gene expression program that more closely resembled the better-outcome ccRCC speckle patient group. Beyond p53 and HIF2A, we found that the speckle targeting motif occurs within hundreds of proteins and is specifically enriched among transcriptional regulators. These findings suggest that DNA-speckle targeting by transcription factors is potentially a wide-spread mechanism of gene regulation that may be manipulated by changing speckle-targeting abilities of transcription factors or by altering speckles themselves. For ccRCC, our findings reveal nuclear speckle phenotypes as novel prognostic indicators and illuminate nuclear speckles and HIF2A speckle-targeting abilities as new avenues for therapeutic development. Citation Format: Katherine A. Alexander, Ruofan Yu, Christine Faunce, Nicolas Skuli, Nathan Coffey, Son Nguyen, Nicholas Biddle, Catherine Li, Eric Joyce, Arjun Raj, M. Celeste Simon, Shelley Berger. In-“speck”-ting the nucleus: Nuclear speckles are a critical layer of gene regulation that predict outcomes in clear cell renal cell carcinoma [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr PR010.
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Ulyanov, Sergey S. "Speckle-interferometry and speckle-correlometry of GB-speckles." Frontiers in Bioscience 24, no. 4 (2019): 700–711. http://dx.doi.org/10.2741/4744.
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Blagova, T. V., and I. Sh Khasanov. "Contribution of wave aberrations represented by Zernike polynomials to the cross-correlation function between distorted and actual speckle patterns." Journal of Physics: Conference Series 2091, no. 1 (November 1, 2021): 012009. http://dx.doi.org/10.1088/1742-6596/2091/1/012009.
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Abstract Speckles are sensitive to the slightest inhomogeneities of the medium, which is used in optical research methods such as speckle interferometry. However, the stochastic nature of propagation of speckle fields complicates their accurate detection and processing. For example, aberrations in the optical system result in the decorrelation of the image of speckles with the actual speckles that are observed in free space. The report will consider the main types of wave aberrations of optical system and their influence on the correlation properties of speckle patterns. The research results can be used to optimize optical systems in which speckles play a significant role, for example, in classical ghost imaging.
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Freund, Isaac, and David A. Kessler. "Singularities in speckled speckle." Optics Letters 33, no. 5 (February 27, 2008): 479. http://dx.doi.org/10.1364/ol.33.000479.
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Hu, Yan, Matt Plutz, and Andrew S. Belmont. "Hsp70 gene association with nuclear speckles is Hsp70 promoter specific." Journal of Cell Biology 191, no. 4 (November 8, 2010): 711–19. http://dx.doi.org/10.1083/jcb.201004041.
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Many mammalian genes localize near nuclear speckles, nuclear bodies enriched in ribonucleic acid–processing factors. In this paper, we dissect cis-elements required for nuclear speckle association of the heat shock protein 70 (Hsp70) locus. We show that speckle association is a general property of Hsp70 bacterial artificial chromosome transgenes, independent of the chromosome integration site, and can be recapitulated using a 2.8-kilobase HSPA1A gene fragment. Association of Hsp70 transgenes and their transcripts with nuclear speckles is transcription dependent, independent of the transcribed sequence identity, but dependent on the Hsp70 promoter sequence. Transgene speckle association does not correlate with the amount of transcript accumulation, with large transgene arrays driven by different promoters showing no speckle association, but smaller Hsp70 transgene arrays with lower transcript accumulation showing high speckle association. Moreover, despite similar levels of transcript accumulation, Hsp70 transgene speckle association is observed after heat shock but not cadmium treatment. We suggest that certain promoters may direct specific chromatin and/or transcript ribonucleoprotein modifications, leading to nuclear speckle association.
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Waterman-Storer, C. M., and W. C. Salmon. "Fluorescent Speckle Microscopy in Studies of Cytoskeletal Dynamics During Cell Motility." Microscopy and Microanalysis 7, S2 (August 2001): 6–7. http://dx.doi.org/10.1017/s1431927600026106.
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We have discovered a new method, Fluorescent Speckle Microscopy (FSM), for analyzing the dynamic movement and turnover of macromolecular protein assemblies, such as the cytoskeleton, in living cells (Waterman-Storer et al., 1998). FSM compliments or replaces the techniques of fluorescence recovery after photobleaching or photoactivation of fluorescence for measuring protein dynamics in vivo. For FSM, cells are microinjected with a very low fraction of fluorescently labeled subunits that co-assemble with unlabeled subunits to give a structure with a fluorescent speckled appearance in diffraction-limited wide-field or confocal digital fluorescence images. At low fractions of fluorescent subunits relative to unlabeled subunits, fluorescent speckles vary randomly in intensity according to the number of fluorescent subunits within a diffraction-limited region. in time-lapse FSM image series, movement of the fluorescent speckle pattern indicates translocation of structures, while changes in speckle intensity indicate subunit turnover. We have used FSM to study microtubule and actin behavior in interphase and mitotic cells. We use kymograph analysis to quantitate the movement of speckled structures (Fig 1) and are currently developing analysis procedures to quantify subunit turnover in structures.We have applied these methods to the study of microtubule and actin cytoskeletal dynamics in migrating vertebrate cells in culture. Interactions between the microtubule and actin cytoskeletons underlie fundamental cellular processes such as cytokinesis and cell locomotion, but are poorly understood.
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Desai, K. M., C. R. Gwinn, J. Reynolds, E. A. King, D. Jauncey, G. Nicholson, C. Flanagan, R. A. Preston, and D. L. Jones. "Speckles in Interstellar Radio-Wave Scattering." International Astronomical Union Colloquium 131 (1991): 238–41. http://dx.doi.org/10.1017/s0252921100013385.
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AbstractObservations of speckles in the scattering disk of the Vela pulsar are presented and speckle techniques for studying and circumventing scattering of radio waves by the turbulent interstellar plasma are discussed. The speckle pattern contains, in a hologrammatic fashion, complete information on the structure of the radio source as well as the distribution of the scattering material. Speckle observations of interstellar scattering of radio waves are difficult because of their characteristically short timescales (≈seconds) and narrow bandwidths (≈kHz). Here, we present first observations, taken at 13 cm wavelength with elements of the SHEVE VLBI network, of speckles in interstellar scattering.
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Ulianova, Onega, Yury Saltykov, Sergey Ulyanov, Sergey Zaytsev, Alexander Ulyanov, and Valentina Feodorova. "Discrimination of the SARS–CoV-2 strains using of coloured s-LASCA-imaging of GB-speckles, developed for the gene “S” nucleotide sequences." F1000Research 10 (June 22, 2022): 503. http://dx.doi.org/10.12688/f1000research.53214.4.
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Background: A recent bioinformatics technique involves changing nucleotide sequences into 2D speckles. This technique produces speckles called GB-speckles (Gene Based speckles). All classical strategies of speckle-optics, namely speckle-interferometry, subtraction of speckle-images as well as speckle-correlometry have been inferred for processing of GB-speckles. This indicates the considerable improvement in the present tools of bioinformatics. Methods: Colour s-LASCA imaging of virtual laser GB-speckles, a new method of high discrimination and typing of pathogenic viruses, has been developed. This method has been adapted to the detecting of natural mutations in nucleotide sequences, related to the spike glycoprotein (coding the gene «S») of SARS–CoV-2 gene as the molecular target. Results: The rate of the colouring images of virtual laser GB-speckles generated by s-LASCA can be described by the specific value of R. If the nucleotide sequences compared utilizing this approach the relevant images are completely identical, then the three components of the resulting colour image will be identical, and therefore the value of R will be equal to zero. However, if there are at least minimal differences in the matched nucleotide sequences, then the value of R will be positive. Conclusion: The high effectiveness of an application of the colour images of GB-speckles that were generated by s-LASCA- has been demonstrated for discrimination between different variants of the SARS–CoV-2 spike glycoprotein gene.
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Ulianova, Onega, Yury Saltykov, Sergey Ulyanov, Sergey Zaytsev, Alexander Ulyanov, and Valentina Feodorova. "Discrimination of the SARS–CoV-2 strains using of coloured s-LASCA-imaging of GB-speckles, developed for the gene “S” nucleotide sequences." F1000Research 10 (November 8, 2021): 503. http://dx.doi.org/10.12688/f1000research.53214.3.
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Background: A recent bioinformatics technique involves changing nucleotide sequences into 2D speckles. This technique produces speckles called GB-speckles (Gene Based speckles). All classical strategies of speckle-optics, namely speckle-interferometry, subtraction of speckle-images as well as speckle-correlometry have been inferred for processing of GB-speckles. This indicates the considerable improvement in the present tools of bioinformatics. Methods: Colour s-LASCA imaging of virtual laser GB-speckles, a new method of high discrimination and typing of pathogenic viruses, has been developed. This method has been adapted to the detecting of natural mutations in nucleotide sequences, related to the spike glycoprotein (coding the gene «S») of SARS–CoV-2 gene as the molecular target. Results: The rate of the colouring images of virtual laser GB-speckles generated by s-LASCA can be described by the specific value of R. If the nucleotide sequences compared utilizing this approach the relevant images are completely identical, then the three components of the resulting colour image will be identical, and therefore the value of R will be equal to zero. However, if there are at least minimal differences in the matched nucleotide sequences, then the value of R will be positive. Conclusion: The high effectiveness of an application of the colour images of GB-speckles that were generated by s-LASCA- has been demonstrated for discrimination between different variants of the SARS–CoV-2 spike glycoprotein gene.
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Ulianova, Onega, Yury Saltykov, Sergey Ulyanov, Sergey Zaytsev, Alexander Ulyanov, and Valentina Feodorova. "Discrimination of the SARS–CoV-2 strains using of coloured s-LASCA-imaging of GB-speckles, developed for the gene “S” nucleotide sequences." F1000Research 10 (September 6, 2021): 503. http://dx.doi.org/10.12688/f1000research.53214.2.
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Background: A recent bioinformatics technique involves changing nucleotide sequences into 2D speckles. This technique produces speckles called GB-speckles (Gene Based speckles). All classical strategies of speckle-optics, namely speckle-interferometry, subtraction of speckle-images as well as speckle-correlometry have been inferred for processing of GB-speckles. This indicates the considerable improvement in the present tools of bioinformatics. Methods: Colour s-LASCA imaging of virtual laser GB-speckles, a new method of high discrimination and typing of pathogenic viruses, has been developed. This method has been adapted to the detecting of natural mutations in nucleotide sequences, related to the spike glycoprotein (coding the gene «S») of SARS–CoV-2 gene as the molecular target. Results: The rate of the colouring images of virtual laser GB-speckles generated by s-LASCA can be described by the specific value of R. If the nucleotide sequences compared utilizing this approach the relevant images are completely identical, then the three components of the resulting colour image will be identical, and therefore the value of R will be equal to zero. However, if there are at least minimal differences in the matched nucleotide sequences, then the value of R will be positive. Conclusion: The high effectiveness of an application of the colour images of GB-speckles that were generated by s-LASCA- has been demonstrated for discrimination between different variants of the SARS–CoV-2 spike glycoprotein gene.
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Ulianova, Onega, Yury Saltykov, Sergey Ulyanov, Sergey Zaytsev, Alexander Ulyanov, and Valentina Feodorova. "Discrimination of the SARS–CoV-2 strains using of coloured s-LASCA-imaging of GB-speckles, developed for the gene “S” nucleotide sequences." F1000Research 10 (June 25, 2021): 503. http://dx.doi.org/10.12688/f1000research.53214.1.
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Background: A recent bioinformatics technique involves changing nucleotide sequences into 2D speckles. This technique produces speckles called GB-speckles (Gene Based speckles). All classical strategies of speckle-optics, namely speckle-interferometry, subtraction of speckle-images as well as speckle-correlometry have been inferred for processing of GB-speckles. This indicates the considerable improvement in the present tools of bioinformatics. Methods: Colour s-LASCA imaging of virtual laser GB-speckles, a new method of high discrimination and typing of pathogenic viruses, has been developed. This method has been adapted to the detecting of natural mutations in nucleotide sequences, related to the spike glycoprotein (coding the gene «S») of SARS–CoV-2 gene as the molecular target. Results: The rate of the colouring images of virtual laser GB-speckles generated by s-LASCA can be described by the specific value of R. If the nucleotide sequences compared utilizing this approach the relevant images are completely identical, then the three components of the resulting colour image will be identical, and therefore the value of R will be equal to zero. However, if there are at least minimal differences in the matched nucleotide sequences, then the value of R will be positive. Conclusion: The high effectiveness of an application of the colour images of GB-speckles that were generated by s-LASCA- has been demonstrated for discrimination between different variants of the SARS–CoV-2 spike glycoprotein gene.
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Dong, Lihua, Dabo Guo, and Guang Yuan. "P‐17.2: Study on speckle suppression of RGB color semiconductor laser driven by high frequency current." SID Symposium Digest of Technical Papers 55, S1 (April 2024): 1546–49. http://dx.doi.org/10.1002/sdtp.17422.
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The suppression of laser speckle has always been a crucial research topic in the field of laser display. At present, many methods of laser speckle suppression have been proposed. In this paper, we present a method for reducing speckle in high‐frequency current driven RGB semiconductor lasers. The RGB monochromatic speckle contrast in direct current (DC) driving mode and 100 Hz to 50 MHz pulse modulation frequency driving mode, and the color luminosity speckle contrast of composite light in 1 KHz to 45 MHz pulse modulation frequency driving mode were measured. Red laser speckle contrast is reduced from 47.12% to 38.5%, Green laser speckle contrast is reduced from 35.69% to 21%, and blue laser speckle contrast is reduced from 31.5% to 25.09%. Additionally, the photometric speckle contrast of composite light decreased by approximately 6%. Experimental results demonstrate that high‐frequency current driving mode disrupts the coherence of lasers and effectively suppresses both monochromatic and color‐based laser speckles.
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Salmon, E. D., and Clare M. Waterman. "How we discovered fluorescent speckle microscopy." Molecular Biology of the Cell 22, no. 21 (November 2011): 3940–42. http://dx.doi.org/10.1091/mbc.e11-07-0646.
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Fluorescent speckle microscopy (FSM) is a method for measuring the movements and dynamic assembly of macromolecular assemblies such as cytoskeletal filaments (e.g., microtubules and actin) or focal adhesions within large arrays in living cells or in preparations in vitro. The discovery of the method depended on recognizing the importance of unexpected fluorescence images of microtubules obtained by time-lapse recording of vertebrate epithelial cells in culture. In cells that were injected with fluorescent tubulin at ∼10% of the cytosol pool, microtubules typically appeared as smooth threads with a nearly constant fluorescence intensity. One day, when an unusually low concentration of fluorescent tubulin was injected into cells, the images from a sensitive cooled charge-coupled detector camera showed microtubules with an unusual “speckled” appearance—there were fluorescent dots with variable intensity and spacing along the microtubules. A first thought was that the speckles were an artifact. With further thought, we surmised that the speckles could be telling us something about stochastic association of tubulin dimers with the growing end of a microtubule. Numerous experiments confirmed the latter hypothesis. Subsequently the method we call FSM has proven to be very valuable. The speckles turned out not to be a meaningless artifact, but rather a serendipitous find.
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Reu, Phillip. "All about Speckles: Speckle Density." Experimental Techniques 39, no. 3 (April 23, 2015): 1–2. http://dx.doi.org/10.1111/ext.12161.
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Kessler, David A., and Isaac Freund. "Singularities in speckled speckle: screening." Journal of the Optical Society of America A 25, no. 12 (November 5, 2008): 2932. http://dx.doi.org/10.1364/josaa.25.002932.
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Freund, Isaac, and David A. Kessler. "Singularities in speckled speckle: Statistics." Optics Communications 281, no. 24 (December 2008): 5954–67. http://dx.doi.org/10.1016/j.optcom.2008.09.029.
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Pereira, António J., Paulo Aguiar, Michael Belsley, and Helder Maiato. "Inducible fluorescent speckle microscopy." Journal of Cell Biology 212, no. 2 (January 18, 2016): 245–55. http://dx.doi.org/10.1083/jcb.201506128.
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The understanding of cytoskeleton dynamics has benefited from the capacity to generate fluorescent fiducial marks on cytoskeleton components. Here we show that light-induced imprinting of three-dimensional (3D) fluorescent speckles significantly improves speckle signal and contrast relative to classic (random) fluorescent speckle microscopy. We predict theoretically that speckle imprinting using photobleaching is optimal when the laser energy and fluorophore responsivity are related by the golden ratio. This relation, which we confirm experimentally, translates into a 40% remaining signal after speckle imprinting and provides a rule of thumb in selecting the laser power required to optimally prepare the sample for imaging. This inducible speckle imaging (ISI) technique allows 3D speckle microscopy to be performed in readily available libraries of cell lines or primary tissues expressing fluorescent proteins and does not preclude conventional imaging before speckle imaging. As a proof of concept, we use ISI to measure metaphase spindle microtubule poleward flux in primary cells and explore a scaling relation connecting microtubule flux to metaphase duration.
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Ruocco, A., G. Duchateau, and V. T. Tikhonchuk. "Self-focusing of a spatially modulated beam within the paraxial complex geometrical optics framework in low-density plasmas." Plasma Physics and Controlled Fusion 63, no. 12 (November 9, 2021): 125019. http://dx.doi.org/10.1088/1361-6587/ac2e43.
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Abstract Accurate modelling of ponderomotive laser self-focusing may represent a key for the success of inertial confinement fusion, especially within the shock ignition approach. From a numerical point of view, implementation of a paraxial complex geometrical optics (PCGO) method has improved the performance of the hydrodynamics code CHIC, but (1) overestimating ponderomotive speckle self-focusing in reduced two-dimensional geometry, and (2) not accounting for speckle intensity statistics. The first issue was addressed in our previous work (Ruocco et al 2019 Plasma Phys. Control. Fusion 61 115009). Based on those results, here we propose a novel PCGO scheme for modelling spatially modulated laser beams by (1) creating Gaussian speckles, and (2) emulating the realistic speckle intensity statistics. Self-focusing of spatially modulated beams in a homogeneous stationary plasma with this method is studied. This investigation evidences that plasma smoothing does not reduce the speckle intensity enhancement at long time scales when the average beam intensity is twice above the speckle critical intensity. Comparison against electromagnetic simulations confirms that this approach improves the description of self-focusing of high-intensity speckles within the PCGO model.
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Zimnyakov, Dmitry, Marina Alonova, Ekaterina Ushakova, Sergey Volchkov, Olga Ushakova, Daniil Klimov, Ilya Slavnetskov, and Anna Kalacheva. "Speckle-Based Sensing of Microscopic Dynamics in Expanding Polymer Foams: Application of the Stacked Speckle History Technique." Sensors 21, no. 20 (October 9, 2021): 6701. http://dx.doi.org/10.3390/s21206701.
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Microscopic structural rearrangements in expanding polylactide foams were probed using multiple dynamic scattering of laser radiation in the foam volume. Formation and subsequent expansion of polylactide foams was provided by a rapid or slow depressurization of the “plasticized polylactide–supercritical carbon dioxide” system. Dynamic speckles induced by a multiple scattering of laser radiation in the expanding foam were analyzed using the stacked speckle history technique, which is based on a joint mapping of spatial–temporal dynamics of evolving speckle patterns. A significant decrease in the depressurization rate in the case of transition from a rapid to slow foaming (from 0.03 MPa/s to 0.006 MPa/s) causes dramatic changes in the texture of the synthesized stacked speckle history maps. These changes are associated with transition from the boiling dynamics of time-varying speckles to their pronounced translational motions and are manifested as significant slopes of individual speckle traces on the recovered stacked speckle history maps. This feature is interpreted in terms of the actual absence of a new cell nucleation effect in the expanding foam upon slow depressurization on the dynamic scattering of laser radiation.
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Abramovich, N. D., and S. K. Dick. "DEPENDENCE OF THE SPECKLE-PATTERNS SIZE AND THEIR CONTRAST ON THE BIOPHYSICAL AND STRUCTURAL PARAMETERS OF BIOLOGICAL TISSUES." Devices and Methods of Measurements 8, no. 2 (June 9, 2017): 177–87. http://dx.doi.org/10.21122/2220-9506-2017-8-2-177-187.
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Speckle fields are widely used in optical diagnostics of biotissues and evaluation of the functional state of bioobjects. The speckle field is formed by laser radiation scattered from the object under study. It bears information about the average dimensions of the scatterers, the degree of surface roughness makes it possible to judge the structural and biophysical characteristics of individual tissue cells (particles), on the one hand, and the integral optical characteristics of the entire biological tissue. The aim of the study was – the determination of connections between the biophysical and structural characteristics of the biotissue and the light fields inside the biotissues.The model developed of the medium gives a direct relationship between the optical and biophysical parameters of the biotissue. Calculations were carried out using known solutions of the radiation transfer equation, taking into account the multilayer structure of the tissue, multiple scattering in the medium, and multiple reflection of irradiation between the layers.With the increase wavelength, the size of speckles formed by the non-scattered component (direct light) of laser radiation increases by a factor of 2 from 400 to 800 μm in the stratum corneum and 5 times from 0.6 to 3 μm for the epidermis and from 0.27 to 1.4 μm to the dermis. Typical values of sizes of speckles formed by the diffraction component of laser radiation for the stratum corneum and epidermis range from 0.02 to 0.15 μm. For the dermis typical spot sizes are up to 0.03 μm. The speckle-spot size of the diffusion component in the dermis can vary from ±10 % at 400 nm and up to ±23 % for 800 nm when the volume concentration of blood capillaries changes. Characteristic dependencies are obtained and biophysical factors associated with the volume concentration of blood and the degree of it’s oxygenation that affect the contrast of the speckle structure in the dermis are discussed.The of speckles׳ size in the layers of tissue varies from a share of micrometer to millimeter. The established dependence makes it possible to determine the depth of penetration of light into the biotissue based on the dimensions of speckles. Calculation of the contrast of the speckle structure of scattered light in visible spectral range at different depths in the biotissue made it possible to establish the dependence of the contrast value of the interference pattern on the degree of oxygenation of the blood and the volume concentration of capillaries in the dermis.
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Carminati, Rémi. "Hidden statistics in speckle patterns." Photoniques, no. 110 (October 2021): 32–35. http://dx.doi.org/10.1051/photon/202111032.
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Scattering of coherent light from a disordered material produces a complex distribution of intensity known as a speckle pattern. Speckle patterns are not as random as they appear at first glance. Their statistical properties exhibit universal features, as already recognized in the first paper on laser speckle. The existence of short-range and long-range spatial correlations in speckles has been shown to be fundamental in wave physics. It has also led to the emergence of novel approaches for imaging through scattering media.
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Fan, Ji Jun, and Nan Hui Yu. "Velocities of Starch Particles in ER Fluids Measured with Laser Speckle." Advanced Materials Research 287-290 (July 2011): 2781–84. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.2781.
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In this paper, the principle of measuring infinitesimal displacement by laser speckle is proposed to measure the velocities of particles in ER fluids. It is verified that speckles can be formed by illuminating laser beam on the starch ER fluids. The speckle patterns was recorded with high speed CCD camera, and the speckle patterns sequences with short time intervals was obtained by intercepting laser speckle video. Displacements parallel to the direction of electric field and that perpendicular to the direction of electric field were obtained by processing the two consecutive speckle patterns. The experimental results showed that the velocities of particles decreased oscillatorily with time. There is a critical electric field and a critical sample concentration, when lower than this critical electric field (concentration), the mean particle velocity increased; otherwise, it decreased.
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Wang, Xijun. "The Magnetic Nanoparticle Movement in Magnetic Fluid Characterized by the Laser Dynamic Speckle Interferometry." Journal of Nanomaterials 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/287813.
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A dual scanning laser speckle interferometry experiment was designed to observe the dynamic behavior of the magnetic fluid actuated by a magnetic field. In order to improve the spatial resolution of the dynamic speckle measurement, the phase delay scanning was used to compensate the additional phase variation which was caused by the transverse scanning. The correlation coefficients corresponding to the temporal dynamic speckle patterns within the same time interval scattering from the nanoparticles were calculated in the experiment on nanoscale magnetic clusters. In the experiment, the speckle of the magnetic nanoparticle fluid movement has been recorded by the lens unmounted CCD within the interferometry strips, although the speckle led to the distinguished annihilation of the light coherence. The results have showed that the nanoparticle fluid dynamic properties appeared synergistically in the fringe speckles. The analyses of the nanoparticle's relative speed and the speckle pattern moving amount in the fringes have proved the nanoparticle’s movement in a laminar flow in the experiment.
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Song, Haoyang, Feiyu Sun, Yunxu Sun, and Wei Liu. "The Optimization of Multimode Fiber Speckle Sensor for Microvibration." International Journal of Optics 2023 (February 17, 2023): 1–9. http://dx.doi.org/10.1155/2023/3356849.
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A vibration sensing system with optical fiber speckles is demonstrated and optimized with different optical fiber diameters and speckle statistical algorithms. The types of fiber diameter and material lead to a different performance of fiber specklegram sensor (FSS), which has been experimentally explored. The signal intensity, demodulated from the speckles, is different when using multimode fibers with different diameters. At the same time, the sensing effect of different fibers depends on the speckle statistical algorithms. Accordingly, we use different statistical methods in theory and experiment to analyze the influence of fiber diameter and speckle statistical methods on the sensing performance. A vibration sensing system with optimized performance is achieved by the optimized types of optical fiber and the corresponding optimized algorithms, which are promising for sensing weak vibration, such as detecting.
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Masthan Reddy, V. V., and S. Vidhyalakshmi. "Critical Evaluation of Reinforced Concrete Beams Using Digital Image Correlation Technique." IOP Conference Series: Earth and Environmental Science 1086, no. 1 (September 1, 2022): 012001. http://dx.doi.org/10.1088/1755-1315/1086/1/012001.
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Abstract Digital Image Correlation technique (DIC) is a non-contact optical method for rapid structural health monitoring of critical infrastructure. DIC is used to extract Moment (M) – Curvature (κ) relationships using random speckle patterns. The random speckle pattern is evaluated for 2D DIC measurements and shows an improved correlation with conventional measurements. Characteristics of random speckle patterns are quantified and their applicability to DIC is explored. The ultimate moment-curvature values computed from the random speckled pattern are found to be in good agreement with conventional measurements.
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Chen, Yanyu, Huang Tan, and Gaofeng Wu. "Self-Reconstruction Property of a Special Speckle Pattern after Obstructing by an Opaque Obstruction." Advances in Condensed Matter Physics 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/9625206.
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Numerical simulation of random optical field with special autocorrelation is performed. It can be seen that the speckle pattern with special autocorrelation is different from the general speckle pattern whose autocorrelation is a Gaussian function. Furthermore, we study the propagation property of the special speckle in free space after blocking by an opaque obstruction and find the self-healing effect of speckle. In particular, we investigate the influence of size and shape of obstruction and the coherence of speckle on the speckle’s reconstruction process. We find that it is affected by the size of obstruction and the coherence of the speckle but is almost not affected by the shape of obstruction. Our results can be applied to the imaging, optical communication, and so on.
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D.Sachin, Kumar, P.R.Seshadri, N.Vaishnav, and Janaki Dr.Saraswathi. "Real Time Speckle Image De-Noising." Advances in Vision Computing: An International Journal (AVC) 1, no. 1 (March 27, 2014): 39–46. https://doi.org/10.5281/zenodo.3362094.
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The paper presents real time speckle de-noising based on activity computation algorithm and wavelet transform. Speckles arise in an image when laser light is reflected from an illuminated surface. The process involves detection of speckles in an image by obtaining a number of frames of the same object under different illumination or angle and comparing the frames for the granular computation and de-noising the same on presence of greater activity index. The project can be implemented in FPGA (Field Programmable Gate Array) technology. The results can be shown that the used activity computation algorithm and wavelet transform has better accuracy in the process of speckle detection and de-noising.
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D.Sachin, Kumar, P.R.Seshadri, N.Vaishnav, and Janaki Dr.Saraswathi. "Real Time Speckle Image De-Noising." Advances in Vision Computing: An International Journal (AVC) 1, no. 1 (March 27, 2014): 39–46. https://doi.org/10.5281/zenodo.3561357.
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The paper presents real time speckle de-noising based on activity computation algorithm and wavelet transform. Speckles arise in an image when laser light is reflected from an illuminated surface. The process involves detection of speckles in an image by obtaining a number of frames of the same object under different illumination or angle and comparing the frames for the granular computation and de-noising the same on presence of greater activity index. The project can be implemented in FPGA (Field Programmable Gate Array) technology. The results can be shown that the used activity computation algorithm and wavelet transform has better accuracy in the process of speckle detection and de-noising.
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Singh, Prabhishek, and Raj Shree. "Statistical Quality Analysis of Wavelet Based SAR Images in Despeckling Process." Asian Journal of Electrical Sciences 6, no. 2 (November 5, 2017): 1–18. http://dx.doi.org/10.51983/ajes-2017.6.2.2001.
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Synthetic aperture radar (SAR) images are mainly denoised by multiplicative speckle noise, which is due to the consistent behavior of scattering phenomenon known as speckle noise. This paper presents the basic concept, role and importance of Discrete Wavelet Transform (DWT) in the field of despeckling SAR images and also offers a study of SAR image quality on applying DWT on the speckled image and log transformed speckled image. Log transform operation plays a decisive and comfortable role in despeckling SAR images as this operation changes the multiplicative behavior of the speckle noise to an additive which enables to use the additive noise restoration model efficiently. Wavelet transform has now become important in the field of image restoration although being in practice for a decade. Wavelet transform allows both time and frequency analysis simultaneously around a particular time. This transform is most appropriate for the non-stationary signals, so it deals with satellite imagery in a more efficient manner. The major part of this paper is revolving around DWT image decomposition with its role and practical implementation on the speckled image and log transformed speckled image. All the experimental results are performed on the SAR images.
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Reu, Phillip. "All about speckles: Speckle Size Measurement." Experimental Techniques 38, no. 6 (October 26, 2014): 1–2. http://dx.doi.org/10.1111/ext.12110.
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Aghdam, Milad Z., and Nasser Soltani. "Effect of speckle size on surface crack detection via digital image correlation." JUSTC 52 (2022): 1. http://dx.doi.org/10.52396/justc-2021-0160.
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Digital image correlation (DIC) is an experimental stress analysis technique used in nondestructive tests. The accuracy of DIC in crack detection depends on various factors such as the sizes of speckles and pixels. In the current study, a speckle pattern based on the spreading of nanoparticles with small speckles is compared with a conventional sprayed pattern to understand whether crack detection via DIC is improved by reducing the sizes of speckles and pixels. Owing to the small size of nanoparticles, an optical microscope is used for magnification. The spreading method for crack detection is first investigated experimentally. Results show that cracks can be detected easily when a 250 nm opening appears in the crack edges. Subsequently, the spreading method is compared with the conventional DIC, in which spraying method is used for patterning, in terms of crack detection. Results show that by reducing the speckle size and closely analyzing the speckle pattern, the DIC technique is considerably better than the conventional technique in detecting small cracks. Moreover, the conventional method is more suitable for detecting large cracks.
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Lee, Yujin, Sangjun Byun, Changyoon Yi, Jaewoo Jung, and Seung Ah Lee. "Rolling shutter speckle plethysmography for quantitative cardiovascular monitoring." Biomedical Optics Express 15, no. 3 (February 9, 2024): 1540. http://dx.doi.org/10.1364/boe.511755.
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We propose a new speckle-based plethysmography technique, termed rolling shutter speckle plethysmography (RSSPG), which can quantitatively measure the velocity and volume fluctuations of blood flow during the cardiac cycle. Our technique is based on the rolling shutter speckle imaging, where the short row-by-row time differences in the rolling shutter image sensors are used to measure the temporal decorrelation behavior of vertically elongated speckles from a single image capture. Temporal analysis of the speckle field provides rich information regarding the dynamics of the scattering media, such as both the dynamic scattering fraction and the speckle decorrelation time. Using a sequence of images, RSSPG can monitor fluctuations in the blood flow dynamics while separating velocity and volume changes in blood vessels and obtaining high-quality plethysmography waveforms compared to regular photoplethysmography. We demonstrate the quantitative RSSPG based on accurate fitting of the speckle dynamics model, as well as the qualitative RSSPG based on simple row-by-row correlation (RIC) calculation for fast and robust analysis. Based on exploratory in vivo experiment, we show that RSSPG can reliably measure pulsatile waveforms and heart rate variations in various conditions, potentially providing physiologically relevant information for cardiovascular monitoring.
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Jia, Mianqian. "Smooth Surface Defect Detection of Metal Workpiece Based on Digital Speckle Pattern Interferometry." Journal of Physics: Conference Series 2403, no. 1 (December 1, 2022): 012015. http://dx.doi.org/10.1088/1742-6596/2403/1/012015.
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Abstract When the existing defect detection methods are used to detect the defects on the smooth surface of metal workpieces, there is a big difference between the detection results and the actual results, and the detection accuracy is low. Therefore, the digital speckle pattern interferometry (DSPI) technology is introduced in this paper to study the design of the detection method of smooth surface defects of the metal workpieces. In this paper, the smooth surface of metal workpiece is measured by using digital speckle interferometry. The speckle on the measurement image is processed by the Laplace algorithm, and the speckled area is automatically extracted; The defects on the smooth surface of the metal workpiece are detected and located according to the speckled area. The comparative experiments show that the detection errors of the two new detection methods are less than 0.1 µm in practical application, and the detection accuracy is high, which can realize the high-precision detection of smooth surface defects of metal workpieces.
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Sjödahl, Mikael. "Practical limits and opportunities with speckle metrology." EPJ Web of Conferences 266 (2022): 10022. http://dx.doi.org/10.1051/epjconf/202226610022.
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In this presentation, the role of speckles as a carrier of information in phase-based optical metrology is re-visited. Starting with the fundamental mechanisms for speckle decorrelation it is shown that information about the state of an object is transferred through the modified mutual coherence function and can be detected either through the phase, speckle movement, speckle decorrelation or as a combination. The presentation is focusing on practical scale laws that set the limit for what is possible to achieve with present day technology and is demonstrated with a few examples incorporating measurements of microstructural changes, strain, shape, lenses and other refractive index objects.
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Fugger, Sif, Jonathan Gow, Hongfeng Ma, Villads Egede Johansen, and Ulrich J. Quaade. "Measured and Predicted Speckle Correlation from Diffractive Metasurface Diffusers." Photonics 11, no. 9 (September 5, 2024): 845. http://dx.doi.org/10.3390/photonics11090845.
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Speckles are inherent in structured laser-based light projection using diffractive optics such as metasurfaces or diffractive optical elements (DOEs). One application of structured light is to provide illumination for machine vision and depth sensing. This is particularly attractive for mobile or low-power applications, where metasurfaces provide a compact, customizable solution, which can furthermore reach extreme field of illuminations. However, the speckles might limit detection capabilities by, e.g., lowering the detection range or providing false results. In this work, we present a series of measurements with matching simulations on a 70 × 50 degrees diffractive diffuser using different light sources (varying divergence angles + VCSEL array) to quantify the impact of speckles. We observe a qualitative agreement in speckle correlation between the measurements and the simulations and explain, in part using cross-correlation for analysis, why we do not observe the same speckle pattern between the measurements and the simulations. By performing extra simulations, we conclude that by only changing the light source, there is a limit to the reduction of the speckle contrast which, we can achieve, and, to reduce it further, alternative approaches such as changing the design method of the diffractive diffuser must be harnessed.
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Acosta-Cárdenas, Jeniffer, Luis Felipe Jiménez-García, Sarai de Jesús Cruz-Gómez, Ana Paulina Mendoza-von der Borch, and María de Lourdes Segura-Valdez. "Microscopic Analysis of Nuclear Speckles in a Viviparous Reptile." International Journal of Molecular Sciences 25, no. 10 (May 12, 2024): 5281. http://dx.doi.org/10.3390/ijms25105281.
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Nuclear speckles are compartments enriched in splicing factors present in the nucleoplasm of eucaryote cells. Speckles have been studied in mammalian culture and tissue cells, as well as in some non-mammalian vertebrate cells and invertebrate oocytes. In mammals, their morphology is linked to the transcriptional and splicing activities of the cell through a recruitment mechanism. In rats, speckle morphology depends on the hormonal cycle. In the present work, we explore whether a similar situation is also present in non-mammalian cells during the reproductive cycle. We studied the speckled pattern in several tissues of a viviparous reptile, the lizard Sceloporus torquatus, during two different stages of reproduction. We used immunofluorescence staining against splicing factors in hepatocytes and oviduct epithelium cells and fluorescence and confocal microscopy, as well as ultrastructural immunolocalization and EDTA contrast in Transmission Electron Microscopy. The distribution of splicing factors in the nucleoplasm of oviductal cells and hepatocytes coincides with the nuclear-speckled pattern described in mammals. Ultrastructurally, those cell types display Interchromatin Granule Clusters and Perichromatin Fibers. In addition, the morphology of speckles varies in oviduct cells at the two stages of the reproductive cycle analyzed, paralleling the phenomenon observed in the rat. The results show that the morphology of speckles in reptile cells depends upon the reproductive stage as it occurs in mammals.
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Smith, Stephen W., Gregg E. Trahey, Sylvia M. Hubbard, and Robert F. Wagner. "Properties of Acoustical Speckle in the Presence of Phase Aberration Part II: Correlation Lengths." Ultrasonic Imaging 10, no. 1 (January 1988): 29–51. http://dx.doi.org/10.1177/016173468801000103.
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In recent years, analysis of the second order statistics of ultrasound speckle has led to accurate prediction and measurements of the average speckle size in the transducer focal zone. In this paper, that work has been extended to the average speckle size as determined by the normalized autocovariance in the presence of transducer phase aberrations. In general, a phase aberration causes a narrowing of the main lobe of the normalized autocovariance in the lateral direction. However, the lateral speckle autocovariance also showed significant side lobes in the presence of phase aberrations, indicating that individual speckles in a region of interest are not independent but are correlated so that less information is present for the task of signal detection when a transducer phase aberration exists. The same evidence of correlated speckle was found in the near field of a transducer in the region of fine speckle texture. This explanation satisfies the quandary of poor detectability in the near field region where the speckle is fine but the lateral resolution is quite degraded. The axial speckle in the presence of phase aberrations showed a small increase in main lobe widths and no evidence of side lobes. Beginning in 1978, the analysis of the second order statistics of speckle images for the purpose of spatial compounding led to accurate measurement and prediction of the cross-correlation curve as a function of transducer aperture translation for purposes of spatial compounding. In this paper, that work has been extended to the presence of transducer phase aberrations. The existence of transducer phase aberrations causes significant increases in the rate of decorrelation of speckle interference patterns as a transducer is translated. This indicates that spatial compounding will result in quite significant improvements in area-wise SNR and low contrast lesion detection for the case of severe random aberrators or focal point errors.
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Iwai, Toshiaki, and Kazuyuki Shigeta. "Experimental Study on the Spatial Correlation Properties of Speckled Speckles Using Digital Speckle Photography." Japanese Journal of Applied Physics 29, Part 1, No. 6 (June 20, 1990): 1099–102. http://dx.doi.org/10.1143/jjap.29.1099.
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Sutton, M., Y. Li, J. D. Brock, and R. E. Thorne. "X-ray intensity fluctuation spectroscopy measurements of the charge density wave phases of NbSe3." Journal de Physique IV 12, no. 9 (November 2002): 3–8. http://dx.doi.org/10.1051/jp4:20020342.
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An introduction to X-ray Intensity Fluctuation Spectroscopy (XIFS) is given by describing its relationship to speckle from coherent sources. A brief description of the relationship of XIFS measurements to the underlying equations of motion is given. Preliminary results for the charge density wave (CDW) system NbSe3 are then presented. Static speckle patterns are shown for the $\overrightarrow {Q}_1 = (0 .76$ 0) CDW peak showing that XIFS experiments are possible in this systom provided time constants are long enough. For electrical currents below threshold, a static speckle pattern is observed but for currents above threshold the speckles are smeared out showing movement of the CDW. It is also shown that above threshold, the longitudinal correlation length decreases.
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Zimnyakov, Dmitry, Valerij Tuchin, and Alexei Mishin. "Imaging of the biotissues fractal structures using spatial speckle-correlometry technique." Izvestiya VUZ. Applied Nonlinear Dynamics 4, no. 1 (June 5, 1996): 49–59. https://doi.org/10.18500/0869-6632-1996-4-1-49-59.
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Far-zone speckles formation due to coherent beam diffraction on fractal structures is discussed using the random phase screen approach. Relationship between parameters of the structure functions of boundary field phase and speckle intensity fluctuations has been analyzed. Biotissues structure imaging technique using local estimations of the intensity exponential factor has been developed. Experiments with psoriasis human epidermis using scanning speckle-correlometer have shown the adequacy of the obtained 2Dimages to structure evolution character caused by disease progress.
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Lallena, M. J., and I. Correas. "Transcription-dependent redistribution of nuclear protein 4.1 to SC35-enriched nuclear domains." Journal of Cell Science 110, no. 2 (January 15, 1997): 239–47. http://dx.doi.org/10.1242/jcs.110.2.239.
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Protein 4.1, originally identified as a component of the membrane-skeleton of the red blood cell, has also been localized in the nucleus of mammalian cells. To learn more about nuclear 4.1 protein, we have analyzed the nature of its association with the nuclear structure in comparison with SC35 and snRNP antigens, splicing proteins of the nuclear speckle domains. When MDCK or HeLa cells were digested with DNase I and washed in the presence of high salt (2 M NaCl), snRNP antigens were extracted whereas protein 4.1 and SC35 remained colocalizing in nuclear speckles. In cells treated with RNase A or heat shocked, nuclear 4.1 distribution also resembled that of SC35. Experiments carried out in transcriptionally active nuclei showed that protein 4.1 distributed in irregularly shaped speckles which appeared to be interconnected. During transcriptional inhibition, protein 4.1 accumulated in rounded speckles lacking interconnections. When cells were released from transcriptional inhibition, protein 4.1 redistributed back to the interconnected speckle pattern of transcriptionally active cells, as it was also observed for SC35. Finally, coprecipitation of 4.1 and SC35 proteins from RNase A digested HeLa nuclei further indicates that these two proteins are associated, forming part of the nuclear speckle domains to which they attach more tightly than snRNP antigens.
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Jin, Ming, Kun-Shan Chen, and Dengfeng Xie. "On the Very High-Resolution Radar Image Statistics of the Exponentially Correlated Rough Surface: Experimental and Numerical Studies." Remote Sensing 10, no. 9 (August 28, 2018): 1369. http://dx.doi.org/10.3390/rs10091369.
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The aim of this study is to investigate, by means of experimental measurements and full-wave simulations, the dominant factors for the very high-resolution (VHR) radar image speckles from exponentially correlated rough surfaces. A Ka-band radar system was used to collect the return signal from such a surface sample fabricated by 3D printing and that signal was further processed into images at different resolution scales, where the image samples were obtained by horizontally turning around the surface sample. To cross-validate the results and to further discuss the VHR speckle properties, full wave simulations by full 3D Finite Difference Time Domain (FDTD) method were conducted with 1600 realizations for the speckle analysis. At the considered very high resolution, speckle statistics show divergence from the fully developed Rayleigh distribution. The factors that impact on the high-resolution speckle properties from exponentially correlated rough surface, are analyzed in views of the equivalent number of scatterers theory and scattering scales, respectively. From the data results and extended discussions, it is evident that both of the above factors matter for VHR speckle of backscattering, from the exponentially correlated rough surface as a good representative for the ground surface.
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Nishikawa, Jun. "The Coherent Differential Imaging on Speckle Area Nulling (CDI-SAN) Method for High-contrast Imaging under Speckle Variation." Astrophysical Journal 930, no. 2 (May 1, 2022): 163. http://dx.doi.org/10.3847/1538-4357/ac5f44.
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Abstract Differential imaging is a postprocessing method to obtain high contrast, often used for exoplanet searches. The coherent differential imaging on speckle area nulling (CDI-SAN) method was developed to detect a faint exoplanet lying beneath residual speckles of a host star. It utilizes image acquisitions faster than the stellar speckle variation synchronized with five shapes of a deformable mirror repeatedly. By using only the integrated values of each of the five images and square differences for a long interval of observations, the light of the exoplanet could be separated from the stellar light. The achievable contrast would reach almost the photon-noise limit of the residual speckle intensities under appropriate conditions. CDI-SAN can be applied to both ground-based and space telescopes.
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Bos, S. P. "Vector speckle grid: instantaneous incoherent speckle grid for high-precision astrometry and photometry in high-contrast imaging." Astronomy & Astrophysics 638 (June 2020): A118. http://dx.doi.org/10.1051/0004-6361/202037957.
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Context. Photometric and astrometric monitoring of directly imaged exoplanets will deliver unique insights into their rotational periods, the distribution of cloud structures, weather, and orbital parameters. As the host star is occulted by the coronagraph, a speckle grid (SG) is introduced to serve as astrometric and photometric reference. Speckle grids are implemented as diffractive pupil-plane optics that generate artificial speckles at known location and brightness. Their performance is limited by the underlying speckle halo caused by evolving uncorrected wavefront errors. The speckle halo will interfere with the coherent SGs, affecting their photometric and astrometric precision. Aims. Our aim is to show that by imposing opposite amplitude or phase modulation on the opposite polarization states, a SG can be instantaneously incoherent with the underlying halo, greatly increasing the precision. We refer to these as vector speckle grids (VSGs). Methods. We derive analytically the mechanism by which the incoherency arises and explore the performance gain in idealised simulations under various atmospheric conditions. Results. We show that the VSG is completely incoherent for unpolarized light and that the fundamental limiting factor is the cross-talk between the speckles in the grid. In simulation, we find that for short-exposure images the VSG reaches a ∼0.3–0.8% photometric error and ∼3−10 × 10−3λ/D astrometric error, which is a performance increase of a factor ∼20 and ∼5, respectively. Furthermore, we outline how VSGs could be implemented using liquid-crystal technology to impose the geometric phase on the circular polarization states. Conclusions. The VSG is a promising new method for generating a photometric and astrometric reference SG that has a greatly increased astrometric and photometric precision.
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Trapani, Vittorio Di, Sara Savatović, Fabio De Marco, Ginevra Lautizi, Marco Margini, and Pierre Thibault. "Speckle-based imaging (SBI) applications with spectral photon counting detectors at the newly established OPTIMATO (OPTimal IMAging and TOmography) laboratory." Journal of Instrumentation 19, no. 01 (January 1, 2024): C01018. http://dx.doi.org/10.1088/1748-0221/19/01/c01018.
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Abstract Speckle-based imaging (SBI) is an advanced X-ray imaging technique that measures phase and dark-field signals, in addition to absorption signals. SBI uses random wavefront modulators to generate speckles and requires two images: one with a speckle pattern alone, and one with both the sample and speckles. SBI reconstruction algorithms retrieve three signals (transmission, refraction, and dark-field) by comparing the two images. In SBI, speckle visibility plays a crucial role in the retrieval of the three signals. When translating the technique from synchrotron sources to compact laboratory setups, the reduced coherence of the source and limitations in the available resolution yield lower speckle visibility, hampering the retrieval of phase and dark-field signals. In this context, direct-detection CdTe X-ray photon-counting detectors (XPCDs) provide an attractive solution, as they allow for a high detection efficiency and optimal spatial resolution enhancing speckle visibility. In this work, we present the newly established OPTIMATO (OPTimal IMAging and TOmography) laboratory for X-ray imaging hosted at the Elettra synchrotron (Trieste, Italy). The setup for SBI with resolutions up to 15 µm including an XPCD and a charge-integrating flat-panel detector (FPD) has been used to acquire SBI data. The main limiting factors when moving SBI applications from synchrotron facilities to compact laboratory setups are summarized. The advantages of XPCDs over FPDs are discussed by comparing the SBI images obtained using both detectors. The potential of the spectral decomposition approach via multi-threshold acquisitions using XPCDs is briefly introduced. The results shown in this work represent the first step toward the realization of a multimodal and multiresolution X-ray facility.
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Maire, Jérôme, Jonathan Gagné, David Lafrenière, James R. Graham, and René Doyon. "High-fidelity photometry and astrometry of high-contrast imaged companions using LOCI processing." Proceedings of the International Astronomical Union 8, S299 (June 2013): 44–45. http://dx.doi.org/10.1017/s1743921313007795.
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RésuméDirect imaging and spectroscopy of exoplanets is a key element for understanding planet formation and migration. Such direct detections and characterizations remains technologically challenging, since a very high contrast ratio and small angular separation are involved, and futhermore speckle noise limits the high-contrast imaging performance. We further discuss a speckle subtraction and suppression technique that fully takes advantage of spectral and time-domain information on quasi-static speckles to measure the highest-fidelity photometry as well as accurate astrometry of detected companions.
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Ulianova, Onega, Sergey Ulyanov, Sergey Zaytsev, Yuriy Saltykov, Alexander Ulyanov, and Valentina Feodorova. "Could LASCA-imaging of GB-speckles be applied for a high discrimination and typing of pathogenic bacteria?" PLOS ONE 16, no. 1 (January 28, 2021): e0245657. http://dx.doi.org/10.1371/journal.pone.0245657.
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In this article, the method of analysis of GB-speckles (gene-based speckles) has been adapted to the problem of detecting the differences in a group of genes (usually 5–7), used in Multi Locus Sequence Typing (MLST). This method is based on s-LASCA imaging (spatial Laser Speckle Contrast Analysis) of virtual GB-speckle and on the technique of RGB coordinates for GB-speckles, processed by the s-LASCA method. A very high sensitivity and accuracy of the new method for detecting gene polymorphism as a great alternative to classical MLST has been demonstrated. The analysis of GB-speckles, obtained for the concatenated sequences of seven genes (gatA, gidA, enoA, fumC, hemN, hflX, oppA) of three different Chlamydia trachomatis strains (E/Bour, ST94; G/9301, ST95; G/11222, ST94) has been applied as the model. The high efficiency of usage of s-LASCA-imaging of GB-speckles has been shown. The data obtained represent a significant progress in digital biology as a whole and improvements in the bio-digitalization of bacterial DNA.
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Hüller, S., and A. Porzio. "Order statistics and extreme properties of spatially smoothed laser beams in laser-plasma interaction." Laser and Particle Beams 28, no. 3 (September 2010): 463–77. http://dx.doi.org/10.1017/s0263034610000418.
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AbstractThe order statistics of intense speckles or “laser hot spots” are studied in the context of the so-called “optically smoothed” light beams of laser-matter interaction. We investigate theoretically and by means of numerical simulations the distribution function for the k-th most intense speckle maxima in the upper tail speckle distribution. From these distributions for each order k, a distribution function for the intense speckles as a function of their peak intensity can be established, which allows to compute their impact on nonlinear processes, like parametric instabilities. This is done for the example of stimulated Brillouin scattering, using the so-called independent hot spot model, for which the backscatter reactivity level is computed, which proves to be in very good agreements with numerical simulations. This result is of great interest for nonlinear processes, like instabilities, where extreme speckles play an important role.