1,721,101 research outputs found
Expected sensitivity of GOCE satellite to detect basement and Moho undulations
No full textThe GOCE satellite is the first mission to carry a gravity gradiometer on board with the goal to improve knowledge of the global Earth gravity field. It has been launched on March 17, 2009 and has been acquiring data since that date, including a several month lasting calibration phase. The satellite is designed to produce a global satellite-only gravity field model in the spherical harmonic expansion up to degree and order n=200-250. Previous missions, including the GRACE satellite, contribute to a maximum degree and order of n=120. Up to now the global field with the highest degree and order of the expansion is EGM2008 (Pavlis et al., 2008), complete to n=2159. The goal of our work is to estimate the geologically relevant structures which can be studied with the GOCE-data and for which we can expect to obtain an improved knowledge with respect to existing models. We base our study on the degree error variances of two existing gravity models (EGM2008 and EIGEN5C) and on simulated errors of the GOCE mission. The error degree variances are tied to the spherical harmonic expansion and consequently we perform the sensitivity study in the spectral domain. We consider in detail two density discontinuities, which can be found everywhere in the crust, and which are the top basement and the Moho. The density discontinuity is expressed as a sheet mass which we can expand in spherical harmonics. We use the relations that tie the sheet mass to the disturbing potential field to determine the smallest mass that can be detected, given the error corresponding to a certain degree of the field. We obtain thus the smallest boundary oscillation that can be detected at the level of the crust-mantle boundary, and at the level of the basement. In our solution available constraints on the Moho stemming from seismic or receiver functions are taken into account. We show under which conditions the GOCE gravity field is bound to improve present knowledge on the boundaries. Our study is accomplished in the frame of different projects as the GOCE-Italy project supported by the Italian Space Agency, responsible Prof. F. Sansò , the FAPESP project, responsible Prof. I. Vittorello, and is part of the ESA GOCE EO project ID 4323, responsible Prof. C. Braitenber
Il settore della componentistica per apparecchi domestici in Italia: aspetti strategici nelle operations e nelle relazioni cliente-fornitore
No full textFattori critici di successo nel settore della componentistica per tecnologia domestica in Italia
No full textDIY adapting SEM for low-voltage TEM imaging
Full text linkElectron microscopy is essential for examining materials and biological samples at microscopic levels, providing detailed insights. Achieving high-quality imaging is often challenged by the potential damage high-energy beams can cause to sensitive samples. This study compares scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to evaluate image quality, noise levels, and the ability to preserve delicate specimens. We used a modified SEM system with a transmitted electrons conversion accessory, allowing it to operate like a TEM but at lower voltages, thereby reducing sample damage. Our analysis included quantitative assessments of noise levels and texture characteristics such as entropy, contrast, dissimilarity, homogeneity, energy, and correlation. This comprehensive evaluation directly compared traditional TEM and the adapted SEM system across various images. The results showed that TEM provided images with higher clarity and significantly lower noise levels, reinforcing its status as the preferred method for detailed studies. However, the modified SEM system also produced high-quality images at very low acceleration voltages, which is crucial for imaging samples sensitive to high-energy exposure. The texture metrics analysis highlighted the strengths and limitations of each method, with TEM images exhibiting lower entropy and higher homogeneity, indicating smoother and more uniform textures. This study emphasizes the importance of selecting the appropriate electron microscopy method based on research needs, such as sample sensitivity and required detail level. With its conversion accessory, the modified SEM system is a versatile and valuable tool, offering a practical alternative to TEM for various applications. This research enhances our understanding of the capabilities and limitations of SEM and TEM. It paves the way for further innovations in electron microscopy techniques, improving their applicability for studying sensitive materials. Research Highlights: Our study introduces a modified SEM adapter enabling TEM-like imaging at reduced voltages, effectively minimizing sample damage without compromising image resolution. Through comparative analysis, we found that images from the modified SEM closely match the quality of traditional TEM, showcasing significantly lower noise levels. This advancement underscores the SEM's enhanced capability for detailed structural analysis of sensitive materials, broadening its utility across materials science and biology. © 2024 The Author(s). Microscopy Research and Technique published by Wiley Periodicals LL
The GOCE estimated Moho beneath the Tibetan Plateau and Himalaya
No full textA better understanding of the physics of the Earth's interior is one of the key objectives of the ESA Earth Explorer missions. This work is focused on the GOCE mission and presents a numerical experiment for the Moho estimation under the Tibet-
Quinghai Plateau and the Himalayan range by exploiting the gravity data collected by this mission. The gravity observations, at satellite level, are rst reduced for the topography, oceans and known sediments and then the residual eld is inverted to
determine the crust-mantle interface. The uniqueness of the solution is guaranteed using this simplied two-layer model by making assumptions on the density contrast. Our inversion algorithm is based on the linearization of the Newton's gravitational law around an approximate constant Moho depth. The resulting equations are inverted by exploiting the Wiener-Kolmogorov theory in the frequency domain and treating the
Moho depth as a random signal with zero mean and its own covariance function. As for the input gravity observations, we considered grids of the anomalous gravitational potential and its second radial derivative at satellite altitude, as computed by applying the so called space-wise approach to eight months of GOCE data. Errors of these grids are available by means of Monte Carlo simulations. Taking a lateral density variations
for granted, the Moho beneath the Tibetan Plateau and Himalaya is computed on a grid covering the whole area with an accuracy of few kilometers and an estimated resolution of about 250 km. Taking into account this resolution, the estimated Moho
generally shows a good agreement with existing local seismic proles. The areas where this agreement is not so good can be clearly attributed to the presence of anomalies in the crust-mantle separation, such as subduction zones. The GOCE-only solution is nally improved by using seismic proles as additional observations, locally increasing its accuracy and resolution
Expression of p53, bcl-2 oncoprotein and proliferating cell nuclear antigen in the human placenta
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