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  • 1
    Electronic Resource
    Electronic Resource
    Fracture-frequency prediction from borehole wireline logs using artificial neural networks [Received J] (1999)
    Oxford BSL : Blackwell Science Ltd
    Geophysical prospecting 47 (1999), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Borehole-wall imaging is currently the most reliable means of mapping discontinuities within boreholes. As these imaging techniques are expensive and thus not always included in a logging run, a method of predicting fracture frequency directly from traditional logging tool responses would be very useful and cost effective. Artificial neural networks (ANNs) show great potential in this area. ANNs are computational systems that attempt to mimic natural biological neural networks. They have the ability to recognize patterns and develop their own generalizations about a given data set. Neural networks are trained on data sets for which the solution is known and tested on data not previously seen in order to validate the network result. We show that artificial neural networks, due to their pattern recognition capabilities, are able to assess the signal strength of fracture-related heterogeneity in a borehole log and thus fracture frequency within a borehole. A combination of wireline logs (neutron porosity, bulk density, P-sonic, S-sonic, deep resistivity and shallow resistivity) were used as input parameters to the ANN. Fracture frequency calculated from borehole televiewer data was used as the single output parameter. The ANN was trained using a back-propagation algorithm with a momentum learning function. In addition to fracture frequency within a single borehole, an ANN trained on a subset of boreholes in an area could be used for prediction over the entire set of boreholes, thus allowing the lateral correlation of fracture zones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2478.1999.00156.x
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  • 2
    Electronic Resource
    Electronic Resource
    Meiotic pairing and imprinted X chromatin assembly in Caenorhabditis elegans (2004)
    [s.l.] : Nature Publishing Group
    Nature genetics 36 (2004), S. 100-105 
    Details
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] The genetic imprinting of individual loci or whole chromosomes, as in imprinted X-chromosome inactivation in mammals, is established and reset during gametogenesis; defects in this process in the parent can result in disease in the offspring. We describe a sperm-specific chromatin-based imprinting ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/ng1283
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  • 3
    Electronic Resource
    Electronic Resource
    Alphoid variant-specific FISH probes can distinguish autosomal meiosis I from meiosis II non-disjunction in human sperm (1997)
    Springer
    Human genetics 〈Berlin〉 101 (1997), S. 61-66 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Over the past few years, several groups have used fluorescence in situ hybridization (FISH) to study aneuploidy in human sperm. Several important observations have derived from these studies, including the demonstration of chromosome-specific variation in non-disjunction frequencies, and the possible association of aneuploidy with environmental agents and with increasing paternal age. However, an important technical limitation of these studies has been the inability to distinguish between autosomal non-disjunction occurring at meiosis I and meiosis II. In the present report, we describe a simple FISH-based approach designed to overcome this limitation. Using oligonucleotide probes capable of distinguishing subtle differences in the alpha satellite sequences of chromosome 17, we demonstrate that (in appropriate heterozygotes) it is possible to simultaneously identify disomic sperm and to determine the meiotic stage of origin of the additional chromosome. This novel approach has important implications for future FISH sperm studies, since the ability to distinguish between meiosis I and meiosis II non-disjunction will make it possible to determine whether putative etiological agents affect chromosome segregation at both, or only one, of the two meiotic stages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004390050587
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  • 4
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    Amplitude and recurrence time analysis of LP activity at Mount Etna, Italy (2020)
    Details
    Publication Date: 2020-11-23
    Description: The aim of this work is to improve our understanding of the long‐period (LP) source mechanism at Mount Etna (Italy) through a statistical analysis of detailed LP catalogues. The behavior of LP activity is compared with the empirical laws governing earthquake recurrence, in order to investigate whether any relationships exist between these two apparently different earthquake classes. We analyzed a family of 8894 events detected during a temporary experiment in August 2005. For that time interval, the LP activity is sustained in time and the volcano did not exhibit any evident sign of unrest. The completeness threshold of the catalogue is established through a detection test based on synthetic waveforms. The retrieved amplitude distribution differs significantly from the Gutenberg‐Richter law, and the interevent times distribution does not follow the typical γ law, expected for tectonic activity. In order to compare these results with a catalogue for which the source mechanism is well established, we applied the same procedure to a data set from Stromboli Volcano, where recurrent LP activity is closely related to very‐long‐period pulses, in turn associated with the summit explosions. Our results indicate that the two catalogues exhibit similar behavior in terms of amplitude and interevent time distributions. This suggests that the Etna's LP signals are most likely driven by stress changes caused by an intermittent degassing process occurring at depth, similar to that which drives the summit explosions at Stromboli Volcano.
    Description: Published
    Description: 6474– 6486
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    2D Synthetic dataset of numerical simulations of long-period seismicity in a volcanic edifice and related sensitivity kernels (2022)
    Elsevier
    Details
    Publication Date: 2022-02-11
    Description: This work describes the data used in the EPSL research article "Quantifying strong seismic propagation effects in the upper volcanic edifice using sensitivity kernels". The dataset is generated in order to investigate to what extent the seismic signals recorded on volcanoes are affected by near surface velocity structure. Data were calculated using the computational spectral elements scheme SPECFEM2D, where the wave propagation beneath Mount Etna volcano, Italy, was simulated in both homogeneous and heterogeneous models. The heterogeneous model comprises a low-velocity superficial structure (top several hundred meters) based on the previously published studies. Several different source mechanisms and locations were used in the simulations. The seismic wavefield was "recorded" by 15 surface receivers distributed along the surface of the volcano. The associated sensitivity kernels were also computed. These kernels highlight the region of the velocity model that affects the recorded seismogram within a desired time window. The text files describing the velocity models used in the simulations are also provided. The data may be of interest to volcano seismologists, as well as earthquake seismologists studying path effects and wave propagation through complex media.
    Description: European Union Seventh Framework Programme (FP7/2007 2013) under the project NEMOH, grand agreement no. 289976.
    Description: Published
    Description: 106673
    Description: 4V. Processi pre-eruttivi
    Description: JCR Journal
    Keywords: Near surface velocity structure; Numerical simulations; Sensitivity kernels; Specfem2d; Volcanic edifice; Volcano seismic sources
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    Quantifying strong seismic propagation effects in the upper volcanic edifice using sensitivity kernels (2022)
    Elsevier
    Details
    Publication Date: 2022-02-11
    Description: In volcanic environments, the correct interpretation of the signals recorded by a seismic station is critical for a determination of the internal state of the volcano. Those signals contain information about both the seismic source and the properties of the path travelled by the seismic wave. Therefore, understanding the path effect is necessary for both source inversions and geophysical investigation of the volcanoes' properties at depth. We present an application of the seismic adjoint methodology and sensitivity kernel analysis to investigate seismic wave propagation effects in the upper volcanic edifice. We do this by performing systematic numerical simulations to calculate synthetic seismograms in two-dimensional models of Mount Etna, Italy, considering different wave velocity properties. We investigate the relationship between different portions of a seismogram and different parts of the structural volcano model. In particular, we examine the influence of known near-surface low-velocity volcanic structure on the recorded seismic signals. Results improve our ability to understand path effects highlighting the importance of the shallowest velocity structure in shaping the recorded seismograms and support recent studies that show that, although long-period seismic events are commonly associated with magma movements in resonant conduits, these events can be reproduced without the presence of fluids. We conclude that edifice heterogeneities impart key signatures on volcano seismic traces that must be considered when investigating volcano seismic sources.
    Description: Published
    Description: 116683
    Description: 4V. Processi pre-eruttivi
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Volcanic Tremor Tracks Changes in Multi‐Vent Activity at Mt. Etna, Italy: Evidence From Analyses of Seismic Array Data (2023)
    Wiley-Agu
    Details
    Publication Date: 2023-02-28
    Description: Abstract The mild degassing and effusion that characterizes open-vent volcanoes can be interrupted by episodes of sustained explosive activity known as paroxysms. Here, we present observations from a seismic array deployment during the 2021 eruption of Mt. Etna, Italy. During the observation period, degassing dominated surface activity at the central and northeast summit craters; lava flows, Strombolian explosions, and fire fountaining, accompanied by ash plumes, characterized eruption in the southeast sector of Mt. Etna. Seismic array locations showed changes associated with shifts in the style and location of activity across multiple craters at Mt. Etna. We observed changes in array locations between the north-northeast and southeast directions that consistently anticipated the onset of paroxysmal activity in the southeast sector. Our results demonstrate the potential of seismic arrays to resolve vent-specific activity and shed light on precursory patterns leading up to paroxysmal activity.
    Description: Published
    Description: e2022GL100056
    Description: 4V. Processi pre-eruttivi
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
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    Publisher Correction: Seismic ground vibrations give advanced early-warning of subglacial floods (2020)
    Springer Nature
    Details
    Publication Date: 2020-07-21
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 9
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    Meiotic pairing and imprinted X chromatin assembly in Caenorhabditis elegans (2003)
    Springer Nature
    Details
    Publication Date: 2003-12-21
    Print ISSN: 1061-4036
    Electronic ISSN: 1546-1718
    Topics: Biology , Medicine
    Published by Springer Nature
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  • 10
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    Helicopter location and tracking using seismometer recordings (2017)
    Oxford University Press
    Details
    Publication Date: 2017-02-07
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Royal Astronomical Society.
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