Academic literature on the topic 'Gradiente di gravità'

An expression for force balance is derived for the general case of gradients in longitudinal and lateral normal stresses and lateral shear stress. In order to consider horizontal glacial mechanics in Newton’s style of actions and reactions, the full stresses are partitioned into lithostatic and resistive, Rij , components. The lithostatic stress is the weight of ice above, and the horizontal gradient in lithostatic force on a vertical column is the familiar driving stress, which accounts for the horizontal effect of body or action forces. The horizontal resistive-stress components describe the reactions to this horizontal action of gravity. Force balance is with horizontal coordinates x 1, x 2 and vertical z. The upper and bottom elevations are h and b, and τ di and τ bi are driving stress and basal drag respectively. This describes net reaction due to normal resistance, lateral shear resistance, and basal drag resistance, and finally the action or driving stress. This equation is exact. Resistive stresses are simply linked to deviatoric stresses, and hence to strain-rates, through the flow law.

Abstract. Since 1981, relative gravity measurements have routinely carried out at the Campi Flegrei caldera, a densely populated area. The gravity network also includes two absolute stations periodically measured with a laboratory absolute gravimeter, which does not permit field measurements. At the end of 2014, the Osservatorio Vesuviano, Section of Napoli of the Istituto Nazionale di Geofisica e Vulcanologia (INGV-OV), acquired a portable absolute gravimeter that allows field operations on outdoor sites. Therefore, in 2015 a dense absolute gravity network was established in Campi Flegrei. This will permit an advanced approach for volcano monitoring. The net consists of 36 stations, 34 of which located inside the caldera and placed upon or very close to gravity stations belonging to the relative network. Five surveys were carried out on June 2015, on February and November 2017, on October 2018 and on October 2019. The comparison with height changes suggests that significant Δg are partly due to the uplift occurred over the same time intervals and mostly to shallow processes associated to the dynamic of the local hydrothermal system. The comparison with the gradients observed during the last large uplift (1982–1984) and the following subsidence (1985–2003) confirms this observation. These results suggest that the present activity may be due to a transient or pulsating phenomenon as the alternating recharge/discharge of fluids in the surface hydrothermal system. Gravity changes detected by absolute measurements are in good agreement with those obtained by relative ones, and confirms the feasibility of this methodology for volcano monitoring. Finally, they also encourage replacing the relative networks with absolute ones, with all the consequent advantages.

Landslides are the process of moving rock periods (soil) due to gravity. On the spatial prediction of landslide occurrence in the District in Central Java based on vegetation index using kriging. The vegetation index is the amount of green vegetation values obtained from the processing of digital signal data of the brightness value of several satellite sensor data channels. Some of the vegetation index algorithms used are SAVI (Soil Adjusted Vegetation Index), OSAVI (Optimized Soil Adjusted Vegetation Index), DVI (Difference Vegetation Index), NDVI (Normalized Difference Vegetation Index). Kriging is one of the prediction and interpolation methods in geostatistika, consisting of two types of ordinary kriging when only one variable and cokriging when there are more than one variable observed. Kriging functioning formation of color gradient pattern on map result of data interpolation. In this research it was found that the occurrence of landslide in the sample area correlated with low, medium, high, DVI vegetation index of DVI, NDVI, SAVI, OSVII. Banjarnegara Regency is prone to landslides in medium category, Wonosobo Regency in High category, Magelang Regency in High category, Kebumen Regency in Low category, Purworejo Regency in Low category. So it can be concluded that landslides are affected or associated with low tree cover seen by NDVI, DVI, SAVI, OSAVI vegetation indices.

Studies of the mechanisms of visual analyzer adaptation in remote space missions are of paramount importance in the domain of space medicine. Pathogenesis of ocular nerve edema, the fundamental symptom of space-flight associated neuro-ocular syndrome (SANS), remains unclear. One of the hypothesized SANS trigger is a change of the pressure gradient in the sclera lattice coat of the membrane due to fluctuations of both the intracranial and intraocular pressures in the absence of gravity. This work extended the previous studies of ocular hydrodynamics during 5-day simulation of the microgravity body effects by dry immersion. We present the results of intraocular hydrobalance analysis after 21-d DI with participation of 8 male subjects at the age of 24 to 35 years. Data of electron tonography and diurnal intraocular pressure measurements were correlated with the fluid balance dynamics. Ocular hydrodynamics disbalance was registered in 80 % of the subjects. Tonography revealed clinically significant changes in 25 % of the subjects. These results enabled determination of the degree and character of ocular hydrodynamics autoregulation in the condition of compensatory body hypohydration.

We present a comparison of possibilities of three methods of magnetic field measurements using the Zeeman effect, namely, method of ”center of gravity”, splitting of Stokes V peaks and analysis of bisectors of I ± V profiles. We note that first method gives very averaged data in form of effective magnetic field Beff which presents the lower limit of local magnetic field in spatially unresolved structures. Splitting of Stokes V peaks DlV can present local magnetic field B, but only in a case when this splitting exceeds considerably the splitting of peaks of the Stokes I gradient dI/dl. Analysis of bisectors of I ± V profiles presents simple method for rapid diagnostics of magnetic field inhomogeneity. In particular, in case of really weak and homogeneous magnetic field, bisectors of I + V and I – V profiles should be parallel to each other. If these bisectors are non-parallel having some extrema, this could be an evidence of hidden presence of strong spatially unresolved magnetic field. Last method is very subtle but needs careful accounting of instrumental effects in line profiles. In this paper, we present also new data related to magnetic fields in limb solar flare of 14 July 2005. Spectral observations of this flare were carried out with the Echelle spectrograph of the Horizontal Solar Telescope of the Astronomical Observatory of Taras Shevchenko National University of Kyiv. In order to measure the magnetic fields in this flare, I ± V profiles of Нa line were studied. It was found that effective magnetic field Вeff in the flare reached 850 ± 100 G on height 16 Mm. However, the spectral evidences to yet stronger local fields of 104 – 105 G range were found. In particular, for several places of the flare, a weak circular polarization of opposite signs was found in line wings on distances of 1.8-2.2 Å from line center. If this polarization to interpret as manifestations of the Zeeman effect, the corresponding magnetic field is » 85–100 kG.

The aim of this work was to study the sensitivity of the visual system in 5-day “dry” immersion with a course of high-frequency electromyostimulation (HFEMS) and without it. “Dry” immersion (DI) is one of the most effective models of microgravity. DI reproduces three basic effects of weightlessness: physical inactivity, support withdrawal and elimination of the vertical vascular gradient. The “dry” immersion included in the use of special waterproof and highly elastic fabric on of immersion in a liquid similar in density to the tissues of the human body. The sensitivity of the visual system was assessed by measuring contrast sensitivity and magnitude of the Müller-Lyer illusion. The visual contrast sensitivity was measured in the spatial frequency range from 0.4 to 10.0 cycles/degree. The strength of visual illusion was assessed by means of motor response using “tracking.” Measurements were carried out before the start of immersion, on the 1st, 3rd, 5th days of DI, and after its completion. Under conditions of “dry” immersion without HFEMS, upon the transition from gravity to microgravity conditions (BG and DI1) we observed significant differences in contrast sensitivity in the low spatial frequency range, whereas in the experiment with HFEMS—in the medium spatial frequency range. In the experiment without HFEMS, the Müller-Lyer illusion in microgravity conditions was absent, while in the experiment using HFEMS it was significantly above zero at all stages. Thus, we obtained only limited evidence in favor of the hypothesis of a possible compensating effect of HFEMS on changes in visual sensitivity upon the transition from gravity to microgravity conditions and vice versa. The study is a pilot and requires further research on the effect of HFEMS on visual sensitivity.

2010/2011
Riassunto: La finalità di questo studio è la caratterizzazione della litosfera sottostante il bacino intracratonico del Paraná. I modelli gravimetrici adottati sono vincolati ai dati geofisici tra i quali quelli sismologici più recenti (Lloyd et al., 2010) e sono corroborati dai modelli petrografici (Bryan & Ernst, 2008). Si offre un approccio che include la comparazione isostatica a quella sismologica al fine di interpretare al meglio la struttura litosferica nell’area del bacino in analisi e di comprendere le variazioni geodinamiche legate alle province geologiche ivi presenti. Il bacino del Paraná (Sud America) è ubicato nella piattaforma stabile del Sud America, ed è circondato da cratoni tra i quali: il cratone amazzonico, il cratone di San Francisco e il Rio de La Plata. La sua genesi in epoca paleozoica è quella di vasto bacino sedimentario, sul quale però durante il Mesozoico (Cretaceo inferiore) si è sviluppata un’intensa attività vulcanica (Capitolo 3). Quest’attività effusiva lo classifica tra le maggiori LIP (Large Igneous Province) mondiali, provincie magmatiche con volume di materiale espulso superiore a 0.1 Mkm3 (Bryan & Ernst, 2008). L’analisi effettuata in questo lavoro è eseguita tramite lo studio del campo gravimetrico da modelli di nuova generazione derivanti dal satellite GOCE (Gravity field and steady state Ocean Circulation Explorer) e GRACE (Gravity Recovery and Climate Experiment). I prodotti gravimetrici satellitari di GOCE possiedono una risoluzione senza precedenti (mezza lunghezza d’onda 80 km): ciò consente di validare i modelli gravimetrici precedenti (280 km, EGM08, Pavlis et al., 2008) che per offrire una maggior dettaglio nelle anomalie integravano ai dati satellitari di GRACE le campagne gravimetriche terrestri, non sempre complete e quindi globalmente precise e di adempire agli indispensabile fini di interpretazione geodinamica. La descrizione dei modelli e la validazione degli stessi sono offerte nel Capitolo 2. I campi potenziali studiati per le principali province geologiche sono illustrati nel Capitolo 5; mentre nel Capitolo 6 si applica la metodologia spettrale sulla seconda derivata verticale del potenziale per discernere le diverse litologie individuate nell’area di studio. L’anomalia di Bouguer calcolata tramite sviluppo in armoniche sferiche viene corretta sia in superficie e in profondità stimando l’effetto di gravità dei sedimenti conosciuti (Capitolo 4) e le conoscenze geofisiche note. Il bacino è composto da: i sedimenti pre-vulcanici paleozoici di spessore pari a circa 3500 m, la Formazione Serra Geral composta principalmente da basalti tholeiitici del cretaceo inferiore (~1500 m di spessore), ed infine i sedimenti post-vulcanici del cretaceo superiore appartenenti al Gruppo Bauru, solo 300 m di spessore (Capitolo 3). Sfruttando i modelli sismologici regionali è stato infine possibile valutare anche il contributo gravimetrico dello spessore crostale stimato con la sismologia. Con questi elementi viene calcolata la Bouguer residua, che è interpretata come anomalia isostatica e quindi correlata alle strutture geologiche locali e regionali. Questo comporta il riconoscimento di una struttura anomala sotto la parte settentrionale del bacino del Paraná comprendente anche parte del settore adiacente Blocco del Guaporé. L’inquadramento a scala maggiore però permette di evidenziare un’area molto più ampia di quanto riconosciuto in prima istanza. Tale anomalia è centrata infatti nel nucleo archeano del cratone amazzonico, di cui quindi il bacino del Paraná risulta solamente il suo braccio più meridionale. In assenza di attività tettonica-magmatica recente (ultima risale 50 Ma) ed in mancanza di grandi anomalie superficiali, tale anomalia positiva potrebbe essere inserita in un contesto regionale e più profondo, rappresentando delle dinamiche di mantello. Infine tramite inversione gravimetrica è stata quantificata numericamente l’anomalia nel bacino di studio utilizzando la geometria semplice di un tronco di cono. La quantità di materiale in presunto underplating che dovrebbe spiegare l’anomalia positiva è compatibile ai modelli petrografici conosciuti. Tali modelli sottolineano come la presenza di un magmatismo noto in superficie rappresenti solo una piccola parte di quello che dovrebbe trovarsi in intrusione: è stato calcolato infatti che il magmatismo superficiale potrebbe rappresentare solo la decima parte di quello associato in profondità.
Abstract: Goal of this study is the characterization of the lithosphere beneath the intracratonic area of Paraná basin. We formulate gravimetric models constrained by geophysical data and new seismological models (Lloyd et al., 2010) and also underpinned by petrographic models (Bryan & Ernst, 2008). Our approach includes isostatic Moho to seismological Moho comparison to better understand lithospheric structures in the area of basin, and geodynamic context of the local geological province. Paraná basin (South America) is located on the stable South American platform, and it is surrounded by some craton areas, as: the Amazon craton, the San Francisco craton and the Rio de La Plata Craton. During Paleozoic epoch the Paraná region was a wide sedimentary basin, while in the Mesozoic (Early Cretaceous) a significant volcanic activity developed on it. This effusive phase classifies the basin between the greatest LIP (Large Igneous Province) worldwide known, where the magmatism volume is greater than 0.1 Mkm3(Bryan & Ernst, 2008). We analyzed gravimetric field using new generation satellite models as GOCE (Gravity field and steady-state Ocean Circulation Explorer) and GRACE (Gravity Recovery and Climate Experiment). GOCE’s products gives unprecedented resolution (half wavelength: 80 km) helping to validate previous global gravity models as EGM08 (Pavlis et al., 2008). The 280 km satellite- only resolution was increased by integration of terrestrial gravity fields data, but this methodology added some problems during processing, where the terrestrial information is not complete or precise. On Chapter 2 some descriptions and validation among models are shown. We calculated potential field for the main geological provinces of Chapter 5; while in Chapter 6, using spectral methodology on the second vertical derivatives of potential field, we identify main lithologic units. The Bouguer anomaly calculated with the spherical harmonics expansion of the potential field is corrected by known stratigraphic units. The basin is made by pre-volcanic sediments of Paleozoic age, with over 3500 m of thickness, Serra Geral Formation, mainly tholeiitic basalts of Early Cretaceous (~1500 m), and post-volcanic sediment of Bauru Group, only 300 m of thickness. We evaluate the effect of crustal thickness variations on the gravity field by using the seismological crustal model. Removing these elements from the Bouguer anomaly, we obtain the residual Bouguer anomaly. Further we calculate the isostatic anomaly and we correlate it to the local and regional geological framework. This helps to recognize a positive residual anomaly on the northern part of the Paraná basin, including the nearby Guaporé Block. Setting a major scale we see the same phenomenon: it is in agreement with the archean nucleus of the Amazon craton, so we can claim that the anomaly on the Paraná is only the southern part of a greater positive area. The relative gravity positive anomaly in the Paraná basin is not very extended and lack of tectonic activity since50 Ma makes us consider that this anomaly is part of a deeper and greater anomaly, maybe due to mantle dynamic effects. We quantified the intracrustal density anomaly using gravity inversion and adopting a truncated cone geometry and volume in accord to petrographic models. It is known that an underplated magmatic body can be up to 10 time larger than the associated extrusive volume and this corroborates our models.
XXIV Ciclo
1979

L’ascomicete Guignardia bidwellii, agente causale del marciume nero della vite, è un patogeno economicamente importante in alcuni areali viticoli. La conoscenza, disponibile sul marciume nero dell’uva, è stata recuperata dalla letteratura, analizzata e sintetizzata per sviluppare un modello meccanicistico del ciclo di vita del patogeno, guidata dalle variabili meteorologiche e dalla fenologia della vite, e basata sull'analisi dei sistemi. Il modello è stato poi valutato per la sua capacità di rappresentare il sistema reale e la sua utilità per la comprensione di epidemie di marciume nero su foglie e grappoli in un vigneto del Nord Italia, nel 2013 al 2015. Successivamente, le mancanze di conoscenza sono state analizzate, studiate e quindi colmate attraverso specifici esperimenti. In un primo passo, le dinamiche dell’inoculo primario e dei modelli di dispersione (di entrambi ascospore e conidi) da mummie svernate sono state studiate in un vigneto sperimentale per tre anni. In un secondo passo, l'effetto della temperatura e dell'umidità sulla formazione di picnidi di G. bidwellii e la successiva estrusione di cirri, nelle lesioni su foglia, la produzione e la germinazione dei conidi (inoculo secondario), e la lunghezza del periodo di latenza sono stati studiati sia in condizioni di campo che in ambiente controllato. In un terzo passo, sono stati condotti studi in ambiente controllato per studiare la produzione di conidi di G. bidwellii sulle lesioni di foglie, influenzata da lavaggi ripetuti e alternando periodi di secco ed umido. Il modello epidemiologico sviluppato in questa tesi può essere utilizzata da viticoltori come strumento predittivo per la pianificazione di trattamenti fungicidi nei vigneti.
The ascomycete Guignardia bidwellii, causal agent of black-rot on grapevines, is an economically important pathogen in some viticultural areas. The available knowledge on black-rot of grape was retrieved from literature, analyzed, and synthesized to develop a mechanistic model of the life cycle of the pathogen, driven by weather and vine phenology, and based on the systems analysis. The model was then evaluated for its ability to represent the real system and its usefulness for understanding black-rot epidemics on leaves and bunches in a vineyard of north Italy, in 2013 to 2015. Thereafter, weaknesses in our knowledge were analysed and studied through specific experiments. In a first step, dynamics of primary inoculum and dispersal patterns (both ascospores and conidia) from overwintered grape mummies were investigated in an experimental vineyard during three years. In a second step, the effect of temperature and humidity on the formation of G. bidwellii pycnidia and the extrusion of cirri in grape leaf lesions, production and germination of conidia (secondary inoculum), and the length of the latency period were studied under both environmental and controlled conditions. In a third step, environmental-controlled studies were conducted to investigate the production course of G. bidwellii conidia on grape leaf lesions as influenced by repeated washing events and alternate dry and wet periods. The model developed in this thesis can be used by vinegrowers as a predictive tool for scheduling fungicide sprays in the vineyards.

L’ascomicete Guignardia bidwellii, agente causale del marciume nero della vite, è un patogeno economicamente importante in alcuni areali viticoli. La conoscenza, disponibile sul marciume nero dell’uva, è stata recuperata dalla letteratura, analizzata e sintetizzata per sviluppare un modello meccanicistico del ciclo di vita del patogeno, guidata dalle variabili meteorologiche e dalla fenologia della vite, e basata sull'analisi dei sistemi. Il modello è stato poi valutato per la sua capacità di rappresentare il sistema reale e la sua utilità per la comprensione di epidemie di marciume nero su foglie e grappoli in un vigneto del Nord Italia, nel 2013 al 2015. Successivamente, le mancanze di conoscenza sono state analizzate, studiate e quindi colmate attraverso specifici esperimenti. In un primo passo, le dinamiche dell’inoculo primario e dei modelli di dispersione (di entrambi ascospore e conidi) da mummie svernate sono state studiate in un vigneto sperimentale per tre anni. In un secondo passo, l'effetto della temperatura e dell'umidità sulla formazione di picnidi di G. bidwellii e la successiva estrusione di cirri, nelle lesioni su foglia, la produzione e la germinazione dei conidi (inoculo secondario), e la lunghezza del periodo di latenza sono stati studiati sia in condizioni di campo che in ambiente controllato. In un terzo passo, sono stati condotti studi in ambiente controllato per studiare la produzione di conidi di G. bidwellii sulle lesioni di foglie, influenzata da lavaggi ripetuti e alternando periodi di secco ed umido. Il modello epidemiologico sviluppato in questa tesi può essere utilizzata da viticoltori come strumento predittivo per la pianificazione di trattamenti fungicidi nei vigneti.
The ascomycete Guignardia bidwellii, causal agent of black-rot on grapevines, is an economically important pathogen in some viticultural areas. The available knowledge on black-rot of grape was retrieved from literature, analyzed, and synthesized to develop a mechanistic model of the life cycle of the pathogen, driven by weather and vine phenology, and based on the systems analysis. The model was then evaluated for its ability to represent the real system and its usefulness for understanding black-rot epidemics on leaves and bunches in a vineyard of north Italy, in 2013 to 2015. Thereafter, weaknesses in our knowledge were analysed and studied through specific experiments. In a first step, dynamics of primary inoculum and dispersal patterns (both ascospores and conidia) from overwintered grape mummies were investigated in an experimental vineyard during three years. In a second step, the effect of temperature and humidity on the formation of G. bidwellii pycnidia and the extrusion of cirri in grape leaf lesions, production and germination of conidia (secondary inoculum), and the length of the latency period were studied under both environmental and controlled conditions. In a third step, environmental-controlled studies were conducted to investigate the production course of G. bidwellii conidia on grape leaf lesions as influenced by repeated washing events and alternate dry and wet periods. The model developed in this thesis can be used by vinegrowers as a predictive tool for scheduling fungicide sprays in the vineyards.

In 2005-2006 in the framework of an INGV-DPC projects, in co-operation with the University of Rome “La Sapienza”, a gravity research started in the Colli Albani Volcanic District aimed: i) to realize a new gravity network to detect gravity changes due to mass redistribution in the underground inferred by the local volcanic activity; ii) to upgrade the already available Bouguer gravity map by means of new stations and to carry out new analyses and interpretations to outline a more detailed structural setting of the area. The gravity network has been designed so as to incorporate an old net of 7 stations, settled in 1981 by the same University group and periodically reoccupied until 2004. The new network is presently formed by 30 stations covering the whole volcanic area and all close to levelling benchmarks to remove the effect of the vertical ground movements. Taking into account the logistic situation of the area, three absolute gravity stations have been settled. Two of them have been located out of the volcanic area to be adopted as references (Sant'Angelo Romano and Palestrina). The third ones has been realized inside the most active part of the volcanic district to calibrate in future (Castel Gandolfo), through its repetition, the gravity changes detected by relative measurements. In the absolute sites the measurements of the vertical gravity gradient have been carried out because g is not directly measured on the ground. Each absolute station is completed with an external satellite ones, then included in the relative network, where the absolute value of g has been also transported through relative measurements. Moreover, 13 selected stations are also sites of vertical gravity gradient measurements. Those measurements helpful to reduce the effect of height changes on gravity variations and their space distribution is useful to reduce the prospecting gravity data. Four surveys of both relative and gradiometric measurements has been carried out (March and June 2006 - January and June 2007). In order to outline a more structural setting of the investigated area, a new set of about 900 new prospecting gravity stations have been settled inside an old survey made by 1500 stations measured partly by the Servizio Geologico d’Italia (SGI) in 1969 and partly by the University of Rome in 1995. Up today, the new stations have been partly measured and all the available data have been reprocessed and uniformed. The results from both the dynamics and the static gravimetry will be presented and discussed. 3-D density model of the Colli Albani Volcanic District was obtained. Based on its volcano-tectonic evolution, we interpret volcanic structures that have never been imaged before.
Dipartimento di Scienze della Terra Università Sapienza di Roma
Unpublished
1V. Storia eruttiva
2V. Struttura e sistema di alimentazione dei vulcani
4V. Dinamica dei processi pre-eruttivi
5V. Dinamica dei processi eruttivi e post-eruttivi
6V. Pericolosità vulcanica e contributi alla stima del rischio
2SR. VULCANI - Servizi e ricerca per la Società