A new stabilized least-squares imaging condition

Vivas, Flor A.; Pestana, Reynam C.; Ursin, Bjørn

doi:10.1088/1742-2132/6/3/005

Cited by 12 publications

(15 citation statements)

References 12 publications

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“…Since the real point-spread function of the microscope setup was lacking, the convolution kernel was estimated by a general Gaussian function (the width of the Gaussian is empirically set to 2 pixels), which is a reasonable guess in the general case of isotropic blur. The actual deconvolution was done with a damped least squares method (see [27]).…”

Section: Methodsmentioning

confidence: 99%

Phosphodiesterase 2 Inhibitors Promote Axonal Outgrowth in Organotypic Slice Co-Cultures

et al. 2013

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The development of appropriate models assessing the potential of substances for regeneration of neuronal circuits is of great importance. Here, we present procedures to analyze effects of substances on fiber outgrowth based on organotypic slice co-cultures of the nigrostriatal dopaminergic system in combination with biocytin tracing and tyrosine hydroxylase labeling and subsequent automated image quantification. Selected phosphodiesterase inhibitors (PDE-Is) were studied to identify their potential growth-promoting capacities. Immunohistochemical methods were used to visualize developing fibers in the border region between ventral tegmental area/substantia nigra co-cultivated with the striatum as well as the cellular expression of PDE2A and PDE10. The quantification shows a significant increase of fiber density in the border region induced by PDE2-Is (BAY60-7550; ND7001), comparable with the potential of the nerve growth factor and in contrast to PDE10-I (MP-10). Analysis of tyrosine hydroxylase-positive fibers indicated a significant increase after treatment with BAY60-7550 and nerve growth factor in relation to dimethyl sulfoxide. Additionally, a dose-dependent increase of intracellular cGMP levels in response to the applied PDE2-Is in PDE2-transfected HEK293 cells was found. In summary, our findings show that PDE2-Is are able to significantly promote axonal outgrowth in organotypic slice co-cultures, which are a suitable model to assess growth-related effects in neuro(re)generation.

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Section: Methodsmentioning

confidence: 99%

Phosphodiesterase 2 Inhibitors Promote Axonal Outgrowth in Organotypic Slice Co-Cultures

et al. 2013

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“…However, this imaging condition becomes unstable for small values of the up-going wavefield. On the one hand, least-square imaging condition involving a division of the cross-correlation of the up-going and down-going wavefields by the autocorrelation of the up-going wavefields at each extrapolation depth [4,5,17,21,22] has been shown to be robust [21]:…”

Section: Imaging Conditionmentioning

confidence: 99%

“…Wavefield separation in 3D (e.g., [15][16][17][18][19][20]) is then applied to the modeled dual-sensor data to recover the up-going and down-going pressure fields. Subsequently, the separated wavefields are extrapolated upwards in small steps, and an imaging condition [5,6,17,21,22] is applied at every step in order to recover the modeled 3D sea surface. The depth positions of the maximum image values define the sea surface.…”

Section: Introductionmentioning

confidence: 99%

Imaging 3D Sea Surfaces from 3D Dual-Sensor Towed Streamer Data

Orji

Söllner

Gelius

2013

International Journal of Geophysics

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3D realistic sea surface imaging from 3D dual-sensor towed streamer data is presented. The technique is based on separating data acquired by collocated dual-sensors into up-going and down-going wavefields. Subsequently, these wavefields are extrapolated upwards in order to image the sea surface. This approach has previously been demonstrated using 2D data examples. Here, the focus is on 3D data. Controlled 3D data based on the Kirchhoff-Helmholtz algorithm is generated, and the 3D sea surface imaging technique is applied. For coarsely spaced streamers from 3D field data, the technique is applied streamerwise (i.e., 2D wavefield separation, extrapolation, and imaging). In the latter case, the resulting sea surface profiles corresponding to each time frame are interpolated to demonstrate that the main sea surface characteristics are preserved, and artefacts due to 2D processing of 3D data are mainly limited to areas corresponding to large angles of incidence. Time-varying sea surfaces from two different 3D field data are imaged. The data examples were acquired under different weather conditions. The imaged sea surfaces show realistic wave heights, and their spectra suggest plausible speeds and directions.

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“…Alternatively, the least-squares imaging condition estimates the reflection coefficient by adding crosscorrelations of the upgoing and downgoing wavefields for all frequencies and sources available and dividing it by the total energy of the downgoing wavefield ͑Schle-icher et al, Vivas et al, 2009͒. Many authors ͑among them are Vivas et al, 2009, Chattopadhyay and McMechan, 2008 have shown that the least-squares imaging condition ͑also known as a source illumination map͒ is more robust and gives an improved image.…”

Section: Imaging Conditionmentioning

confidence: 99%

“…Many authors ͑among them are Vivas et al, 2009, Chattopadhyay and McMechan, 2008 have shown that the least-squares imaging condition ͑also known as a source illumination map͒ is more robust and gives an improved image. Nevertheless, unconditional division by the autocorrelation can cause instabilities.…”

Section: Imaging Conditionmentioning

confidence: 99%

Imaging the sea surface using a dual-sensor towed streamer

2010

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Sea-surface profile and reflection coefficient estimates are vital input parameters to various seismic data processing applications. The common assumption of a flat sea surface when processing seismic data can lead to misinterpretations and mislocations of events. A new method of imaging the sea surface from decomposed wavefields has been developed. Wavefield separation is applied to the data acquired by a towed dual-sensor streamer containing collocated pressure and vertical particle velocity sensors to obtain upgoing and downgoing wavefields of the related sensors. Time-gated upgoing and downgoing wavefields corresponding to a given sensor are then extrapolated to the sea surface where an imaging condition is applied so that the time-invariant shape of the sea surface can be recovered. By sliding the data time-window, the temporal changes of the sea surface can be correspondingly estimated. Ray tracing and finite-difference methods were used to generate different controlled data sets used in this feasibility study to demonstrate the imaging principle and to test the image accuracy. The method was also tested on a first field data example of a marginal weather line from the North Sea.

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A new stabilized least-squares imaging condition

Cited by 12 publications

References 12 publications

Phosphodiesterase 2 Inhibitors Promote Axonal Outgrowth in Organotypic Slice Co-Cultures

Phosphodiesterase 2 Inhibitors Promote Axonal Outgrowth in Organotypic Slice Co-Cultures

Imaging 3D Sea Surfaces from 3D Dual-Sensor Towed Streamer Data

Imaging the sea surface using a dual-sensor towed streamer

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