Nathan Shettell, Kai Sheng Lee, Fong En Oon
et al.
Absolute gravimeters deliver drift-free, high-precision measurements but are typically bulky and difficult to deploy, whereas relative gravimeters are lightweight and mobile but intrinsically limited by time-dependent drift. We demonstrate a hybrid quantum-enabled gravimetry approach in which an on-site atomic gravimeter provides routine, $μ$Gal-level calibration of two mobile spring gravimeters during a field survey spanning 24 km$^2$ of dense tropical terrain. The atomic reference enables high-precision, asynchronous cross-comparison of relative measurements acquired over seven days, effectively suppressing instrumental drift to a level required for demanding geophysical applications. This deployment captures regional gravity gradients with high fidelity under challenging environmental conditions, illustrating how field-operable quantum sensors can extend quantum-grade gravimetry beyond laboratory settings and serve as scalable calibration backbones for large-area, high-precision geophysical surveys in remote or logistically constrained environments.
Jean-Louis Le Mouël, Dominique Gibert, Jean-Baptiste Boulé
et al.
In this paper, we revisit old electrical measurements conducted on a poplar tree in 2003 (Gibert et al. 2006), which showed the presence of a diurnal electrical signal, attributed to an electrokinetic phenomenon correlated with sap flow, even in winter. We reanalyze these data using the singular spectrum analysis method and demonstrate that the electrical signal measured at various locations (roots, trunk, and branches) on the poplar tree can be decomposed to over 80\% into a sum of 7 pseudo-periods, all linked to luni-solar tides. The precision of the extracted periods exceeds that of models. To validate these old measurements, we have reproduced the 2003 protocol since 2018 at the Jardin des Plantes in Paris, on 3 oak trees and 3 hornbeams. The electrical signals today exhibit the same characteristics as those of 2003. Tidal forces could be a driving force of sap flow in trees.
Ken'yo Uh, Masanori Kameyama, Gaku Nishiyama
et al.
We develop a 2-D numerical model of magmatism and mantle convection to understand the volcanism on the Procellarum KREEP terrane (PKT) of the Moon, which continued for billions of years with two peaks of activities at 3.5-4 Gyr ago and around 2 Gyr ago. In our model, the effects of the PKT on lunar evolution are considered by initially imposing a region of localized radioactive enrichment. The calculated volcanism has two peaks induced by different mechanisms. The first peak occurs at 3.5-4 Gyr ago when magma generated in the deep mantle by internal heating ascends to the surface as partially molten plumes. The basaltic blocks in the uppermost mantle formed by this magmatism, then, sink to the deep mantle, triggering further plumes that cause the resurgence of volcanism at $\sim$2 Gyr ago. Our model shows that localized radioactive enrichment is important for the long-lasting volcanism with a couple of peaks.
AbstractRock cuttability has great influence on the rock excavation efficiency of TBM (tunnel boring machine). In order to evaluate rock cuttability in real time, quickly, accurately and efficiently during TBM excavating, the relevant excavation parameters of Zagros, Kerman and Bazideraz tunnels were first collected. Then, the regression analyses between excavation parameters and rock cuttability were carried out. The two-dimensional regression analyses studied the relationship between operating parameters (thrust F and rotation speed RPM) and the characterization parameters (torque T and penetration rate PR). The three-dimensional regression analyses were utilized to create the PR and specific energy SE models based on operating parameters. The result shows that the established three-dimensional regression models have good prediction performance, and its performance is superior to two-dimensional models. Moreover, the prediction model of uniaxial compressive strength UCS and the classification model of rock cuttability were founded based on SE. The rock cuttability is divided into three levels, namely, easy (level 1), medium (level 2), and poor (level 3), in which the corresponding SE ranges are 0 to 6, 6 to 10 and exceeds 10 kWh·m−3, respectively. Finally, the intelligent algorithms, combined with excavation parameters, were introduced to establish UCS prediction model and rock cuttability classification model, and the good prediction performance was achieved. The above studies can provide necessary references and ideas for real-time, rapid, accurate and effective evaluation of rock cuttability based on TBM excavation parameters, and has certain guiding significance for engineering application.
Jefferson G. Filgueiras, Matheus S. J. de Miranda, Carla S. Semiramis
et al.
Clay minerals are important components of sandstone rocks, due to their significant role in petrophysical properties like porosity and permeability. These minerals have a particular impact on Nuclear Magnetic Resonance measurements since the iron inside clays generates internal gradients that impact the transverse relaxation directly. Here, we apply a methodology recently developed to a set of 20 sandstones with diverse clay content and mineralogy to estimate the total clay content. This estimation relies on the effect of internal gradients and restricted diffusion on transverse relaxation. Our analysis revealed a linear correlation between the total clay content and the displacement of the peak of the T$_2$ distribution as a function of $τ$, which is half the echo time in the CPMG sequence. Based on these measurements, we propose a geochemical rock typing from quantities determined by our measurements, namely total clay content and porosity.
The general circulation of the atmosphere determines the long-term variability of weather processes. This circulation is driven by the temperature differences between the poles and the equator, causing air to move along the Earth's surface. However, this requires enhanced pressure at the poles, which is not observed. To sustain the circulation, an additional non-hydrostatic pressure gradient is required. In my research, I propose the emergence of an additional non-hydrostatic pressure gradient resulting from the centrifugal force generated by the Earth's rotation. This centrifugal force creates a non-hydrostatic vertical pressure gradient, which is essential for the closed circulation of unequally heated air in the meridional direction. The circulation is composed of three distinct streams flowing in opposite directions, with the polar and tropical tropopause acting as boundaries. The temperature in the atmosphere decreases from the surface to the polar tropopause and remains constant above it.
During the propagation of a tsunami, gravity and sound waves can be produced, spreading from its source to the ionosphere's upper layers, thus generating perturbed electron densities in its E and F regions. These ionospheric disturbances can be studied in detail using measurements of the ionosphere's Total Electron Content (TEC), registered by permanent GNSS stations. In this contribution, the foundations of the VARION method (Variometric Approach for Real-time Ionosphere Observation) are described in order to obtain TEC's temporal variations with the aim of detecting such ionospheric disturbances. Moreover, the numerical results obtained after applying this method to real cases of tsunamis monitored by those satellites whose Ionospheric Pierce Points (IPPs) are closest to the tsunami source are presented. Lastly, based on these ionospheric perturbations reflected in the signals emitted by the satellites, a preliminary design is described for its potential integration into a Tsunami early Warning System (TWS) for the Iberian Peninsula.
L. Alonso-Llanes, G. Sánchez-Colina, A J Batista-Leyva
et al.
We study the behavior of cylindrical objects as they sink into a drygranular bed fluidized due to lateral oscillations. Somewhat unexpectedly, we have found that, within a large range of lateral shaking powers,cylinders with flat bottoms sink vertically, while those with a''foundation'' consisting in ashallow ring attached to their bottom, tilt besides sinking. Thelatter scenario seems to dominate independently from the nature ofthe foundation when strong enough lateral vibrations are applied. Weare able to explain the observed behavior by quasi-2D numericalsimulations, which also demonstrate the influence of the intruder's aspect ratio. The vertical sink dynamics is explained with the help of a Newtonian equation of motion for the intruder. Our findings may shed light on the behavior of buildings and other man-made constructions during earthquakes.
Daria Holdenried-Chernoff, David A. King, Bruce A. Buffett
Variations in the geomagnetic field occur on a vast range of time scales, from milliseconds to millions of years. The advent of satellite measurements has allowed for detailed studies of the short timescale geomagnetic field behaviour, but understanding the long timescale evolution remains challenging due to the sparsity of the paleomagnetic record. This paper introduces a field theory framework for studying magnetic field generation as a result of stochastic fluid motions. By constructing a stochastic kinematic dynamo model, we derive statistical properties of the magnetic field that may be compared to observations from the paleomagnetic record. The fluid velocity is taken to act as a random forcing obeying Gaussian statistics. Using the Martin-Siggia-Rose-Janssen-de Dominicis (MSRJD) formalism, we compute the average magnetic field response function. From this we obtain an estimate for the turbulent contribution to the magnetic diffusivity, and find that it is consistent with results from mean-field dynamo theory. This framework presents much promise for studying the geomagnetic field in a stochastic context.
Recent progress in extraction of unconventional hydrocarbon resources has ignited the interest in the studies of nanoporous media. Since many thermodynamic and mechanical properties of nanoscale solids and fluids differ from the analogous bulk materials, it is not obvious whether wave propagation in nanoporous media can be described using the same framework as in macroporous media. Here we test the validity of Gassmann equation using two published sets of ultrasonic measurements for a model nanoporous medium, Vycor glass, saturated with two different fluids, argon and n-hexane. Predictions of the Gassmann theory depend on the bulk and shear moduli of the dry samples, which are known from ultrasonic measurements, and the bulk moduli of the solid and fluid constituents. The solid bulk modulus can be estimated from adsorption-induced deformation or from elastic effective medium theory. The fluid modulus can be calculated according to the Tait-Murnaghan equation at the solvation pressure in the pore. Substitution of these parameters into the Gassmann equation provides predictions consistent with measured data. Our findings set up a theoretical framework for investigation of fluid-saturated nanoporous media using ultrasonic elastic wave propagation.
Grain feeding often causes a decrease in ruminal pH, and experiments were conducted to define the role of pH in regulating the acetate to propionate ratio and production of CH4. Cows that were fed 90% concentrate had lower ruminal pH values (6.22 vs. 6.86), higher VFA concentrations (85 vs. 68 mM), and lower acetate to propionate ratios (2.24 vs. 4.12) than did cows that were fed forage only. When mixed ruminal bacteria from cows that were fed 90% concentrate or 100% forage were incubated (48 h) with hay (10 g/L) or cracked corn (5 g/L) in a medium containing bicarbonate (38 mM) and tricarballylate (50 mM), the final pH values were less than 0.3 units lower than the initial pH. At final pH values less than 5.7, hay fermentation was inhibited, the acetate to propionate ratio and CH4 production declined more than twofold, and the inoculum source was without effect. Small amounts of H2 were detected at pH values less than 5.5. Total VFA production from cracked corn decreased when pH declined, but only if the inoculum was obtained from cows that were fed 90% concentrate. The acetate to propionate ratio of cracked corn incubations declined from 1.2 to 0.6 when final pH was decreased from 6.5 to 5.3, and CH4, as a percentage of total VFA production, also decreased. At pH values less than 5.3, the acetate to propionate ratio of cracked corn increased more than fourfold, and large amounts of H2 could be detected. Over the final pH range of 6.5 to 5.3, CH4 production was highly correlated with acetate to propionate ratio, which was dependent on pH and substrate (CH4 = 0.02 + 0.05 pH; r2 = 0.80). Calculations based on the differences between pH 6.5 and 5.8 indicated that as much as 25% of the decrease in acetate to propionate ratio could be explained by the effect of pH alone.