Low Gradient Research Articles

Adaptive control for downhole nuclear magnetic resonance excitation

Nuclear magnetic resonance (NMR) measurements are performed with the pulse sequence and acquisition parameters set by the operator, which cannot be adjusted in real time according to sample characteristics. In one acquisition cycle, usually thousands of high-power pulses are transmitted and thousands of echo points are acquired. The power consumption cause the RF amplifier to overheat, and large amounts of acquired data may be invalid. Therefore, the optimization of excitation and acquisition processes is necessary to improve measurement efficiency. We explore a scheme for the real-time measurement of the samples by adaptively regulating the pulse sequence, which adapts the variable TE pulse sequence as the reconnaissance mode. The appropriate pulse sequence and reasonable parameters (NE, TE) can be selected according to the relaxation characteristics of the samples.This adaptive control strategy has great significance in guiding both dynamic and static measurements, and it is especially suitable for occasions where low magnetic field gradients and diffusion terms can be ignored. We also design a test circuit for adaptive control, which has the function of automatic parameter adjustment. By adjusting parameters such as the number of refocusing pulses, echo spacing, etc., the effective measurement of the samples can be achieved in practice.

Strategies for Prevention of Downhole Tool Failure Caused by High Bottomhole Temperature in Geothermal and High-Pressure/High-Temperature Oil and Gas Wells

Summary High bottomhole temperature can lead to decreased downhole tool life in geothermal and high-pressure/high-temperature (HPHT) oil and gas wells. The temperature increase is exacerbated when circulation stops (e.g., during connection, tripping, and well control situations). While continuous circulation technology is an appropriate solution for managing temperature, it is not yet widely adopted in HPHT and geothermal drilling practices. This work investigates factors that impact downhole temperature (DHT) and recommends strategies to better manage the temperature when continuous circulation is not available. An integrated thermo-hydraulic model was developed to capture the transient behavior of DHT and was applied here to study the transient temperature profile when there is no fluid circulation. The model was validated using the open-source FORGE field data set, with the mean absolute percentage error between 1% and 4%. In addition, hundreds of case scenarios were numerically studied to investigate the impact of several key factors on the DHT. The evaluated factors include the pumps-off time, type and physical properties of the drilling fluid, wellbore hydraulic diameter, reservoir temperature, geothermal gradient, total wellbore depth and profile, and operational parameters before stopping the circulation. The cooling effects of different drilling parameters were compared to a benchmark case of continuous circulation. A correlation map was generated to visualize the impact of those parameters on the DHT distribution when circulation stops. A logarithmic relationship between the pump stop time and the DHT was observed. For the FORGE case scenario, the DHT increases by 27°C and 48°C after the pump stops for 30 minutes and 60 minutes, respectively. It was observed that water-based mud (WBM) with a high viscosity increases fluid convection heat resistance between the formation and wellbore. Also, drilling with a higher flow rate before stopping the pump can cool the near-wellbore formation faster and reduce the DHT even after circulation ceases. Wells with high geothermal gradients, like FORGE wells, have a higher temperature buildup during circulation stoppage than wells with low geothermal gradients targeting the same reservoir (formation) in-situ temperature. This study investigates the efficacy of different cooling strategies to avoid DHT buildup when there is no circulation. It thereby facilitates the optimization of geothermal and HPHT well design and construction to prevent downhole tool failures. The developed correlation map can aid drilling engineers in understanding the impact of different drilling conditions on the DHT.

Field development of Posidonia oceanica seedlings changes under predicted acidification conditions

Ocean acidification has been consistently evidenced to have profound and lasting impacts on marine species. Observations have shown seagrasses to be highly susceptible to future increased pCO2 conditions, but the responses of early life stages as seedlings are poorly understood. This study aimed at evaluating how projected Mediterranean Sea acidification affects the survival, morphological and biochemical development of Posidonia oceanica seedlings through a long-term field experiment along a natural low pH gradient. Future ocean conditions seem to constrain the morphological development of seedlings. However, high pCO2 exposures caused an initial increase in the degree of saturation of fatty acids in leaves and then improved the fatty acid adjustment increasing unsaturation levels in leaves (but not in seeds), suggesting a nutritional compound translocation. Results also suggested a P. oceanica structural components remodelling which may counteract the effects of ocean acidification but would not enhance seagrass seedling productivity.

Irreversible and Large‐Scale Heavy Metal Pollution Arising From Increased Damming and Untreated Water Reuse in the Nile Delta

AbstractEgypt observes one of the highest water budget deficits in Africa that is mainly compensated by intensive reuse of untreated agricultural drainage water in the Nile Delta. The implications of untreated water reuse on increasing soil pollution levels remain poorly characterized; however, a large‐scale pollution can compromise crop production and water quality. To address this deficiency, we evaluate the level of heavy metal pollution in the Nile Delta, identify its sources and explore the implications of damming on heavy metal concentration using integrated pollution indicators and statistical modeling. Pollution indicators show moderate to very high contamination by Pb, Ni, Cr, Cd, Cu, and Zn, with unprecedented Cd levels in the sediments (up to 72.0 ppm) and a northward increase in pollution levels. Statistical modeling and historical datasets reveal the association of Cd and Fe on both Nile branches and the clustering of Pb, Ni, Cu, Zn and Cr, which attribute the heavy metal concentrations to the cumulative addition of untreated agricultural drainage water (9.5 BCM/yr) and wastewater. These processes introduced an accelerated pollution in the Nile Delta system. Though, conservation measures are crucial to reverse this degradation, yet the increasingly engineered Nile flow, the low gradient of the delta and the active silting impede heavy metal flushing causing irreversible pollution. Our findings alarm future increase in heavy metal pollution in response to increased untreated drainage water reuse to mitigate the impacts of ongoing upstream damming and call for implementing international cooperative agreements for integrated water management along the Nile River.

Effective optimization strategy for large optimization volume object, remaining volume at risk (RVR): α-value selection and usage from generalized equivalent uniform dose (gEUD) curve deviation perspective

Objective. A large optimization volume for intensity-modulated radiation therapy (IMRT), such as the remaining volume at risk (RVR), is traditionally unsuitable for dose-volume constraint control and requires planner-specific empirical considerations owing to the patient-specific shape. To enable less empirical optimization, the generalized equivalent uniform dose (gEUD) optimization is effective; however, the utilization of parameter a-values remains elusive. Our study clarifies the a-value characteristics for optimization and to enable effective a-value use. Approach. The gEUD can be obtained as a function of its a-value, which is the weighted generalized mean; its curve has a continuous, differentiable, and sigmoid shape, deforming in its optimization state with retained curve characteristics. Using differential geometry, the gEUD curve changes in optimization is considered a geodesic deviation intervened by the forces between deforming and retaining the curve. The curvature and gradient of the curve are radically related to optimization. The vertex point (a = a k ) was set and the a-value roles were classified into the following three parts of the curve with respect to the a-value: (i) high gradient and middle curvature, (ii) middle gradient and high curvature, and (iii) low gradient and low curvature. Then, a strategy for multiple a-values was then identified using RVR optimization. Main results. Eleven head and neck patients who underwent static seven-field IMRT were used to verify the a-value characteristics and curvature effect for optimization. The lower a-value (i) (a = 1–3) optimization was effective for the whole dose-volume range; in contrast, the effect of higher a-value (iii) (a = 12–20) optimization addressed strongly the high-dose range of the dose volume. The middle a-value (ii) (around a = a k ) showed intermediate but effective high-to-low dose reduction. These a-value characteristics were observed as superimpositions in the optimization. Thus, multiple gEUD-based optimization was significantly superior to the exponential constraints normally applied to the RVR that surrounds the PTV, normal tissue objective (NTO), resulting in up to 25.9% and 8.1% improvement in dose-volume indices D2% and V10Gy, respectively. Significance. This study revealed an appropriate a-value for gEUD optimization, leading to favorable dose-volume optimization for the RVR region using fixed multiple a-value conditions, despite the very large and patient-specific shape of the region.

Petrology and phase equilibria of HP/LT eclogite at Gaoqiao, western Dabie and implications for lawsonite development in continental subduction zones

Lawsonite is of great significance for understanding fluid activity, element migration and crust–mantle interactions in subduction zones. Though studies have predicted lawsonite to be present under theP–Tregime during continental subduction, no lawsonite has been documented from natural (U) HP rocks in continental orogenic belt. In this study, we work on HP–LT eclogite (GQ–1 and GQ–2) at Gaoqiao, western Dabie to explore lawsonite formation and preservation during continental subduction and exhumation. Both samples have ubiquitous polymineralic aggregates of epidote/clinozoisite + paragonite/albite ± other minerals showing distinct rectangular or rhombic shapes developed as inclusions in garnet or in the matrix. Combined with recalculated bulk compositions similar to that of ideal lawsonite, we interpret these polymineralic aggregates to be pseudomorphs after lawsonite. Phase equilibrium modelling combined with compositional isopleth thermobarometry have constrained a segment of the prograde to peak stages to evolve from 19.0 to 19.5 kbar, ∼470°C to ∼20.0 kbar, 500C–505°C, then to ∼25 kbar, 530C–555°C in lawsonite stability fields. The progradeP–Tpath shows a two-stageP–Tevolution, with the first stage following a geothermal gradient of ∼7°C/km and the second stage decreasing to ∼6°C/km. Initial exhumation was inferred to follow an isothermal decompression process leading to lawsonite breakdown to form epidote/clinozosite ± paragoniteviathe reaction lawsonite + omphacite→ epidote + glaucophane ± paragonite + H2O at ∼19 kbar, 550°C. ModeledP/T–Xpseudosections calculated atT= 550°C andp= 25 kbar show that, when H2O content in bulk composition is more than 1.1 wt%, a certain amount of lawsonite (>13 mode%) should be present in eclogite. On the other hand, in the compositional range of natural intracontinental plate basalts, variations on O (Fe3+),XMgO[MgO/(MgO+FeO)],XCaO[CaO/(CaO+MgO+FeO+MnO+Na2O)],XNa2O[(Na2O/(CaO+Na2O)] andXAl2O3[Al2O3/(Al2O3+CaO+Na2O)] in bulk compositions have little influence on lawsonite development. In combination with previous studies, we conclude that during continent subduction along low geothermal gradient (<8°C/km), lawsonite could be formed under H2O present conditions. The absence of lawsonite in natural eclogite might be ascribed to retrograde overprint during exhumation.

Nanotechnology for purifying nematic liquid crystals based on magnetic separation accompanied by phase transition

Free ions are generally unfavorable in liquid crystal (LC) displays, and LC purification technologies are critically important. The colloidal γ-Fe2O3 magnetic nanoparticles coated with oleic acid (γ-Fe2O3@OA MNPs) have a high ratio of surface to volume, which may adsorb more free ions and are uniform in the LC at room temperature. In this work, the precipitation and separation of the doped colloidal γ-Fe2O3@OA MNPs resulting from the magnetic field accompanied by an isotropic-nematic phase transition are more efficient than in the single case of the phase transition or the magnetic field. The residual ion concentrations have decreased distinctly using the low gradient magnetic field (∇ B ∼ 2 T/m) with the phase transition. In addition, when the doped colloidal γ-Fe2O3@OA MNPs are 0.4 % and 0.2 % by weight, the former concentrations of the residual ions and γ-Fe2O3@OA MNPs are lower than the latter. As a result, the commercial nematic LC can be purified by this approach based on nanotechnology in our study.

Application of Thermoelectric Generators for Low-Temperature-Gradient Energy Harvesting

Thermoelectric generators (TEGs) convert a temperature difference into useful direct current (DC) power. TEGs are solid-state semiconductor devices that are generating a lot of interest for energy harvesting purposes in Internet of Things (IoT) applications. This paper analyzes the behavior of state-of-the-art TEGs designed for low temperature gradient operation, with special emphasis on IoT systems for health monitoring for high-voltage alternating current (AC) and DC applications. In such applications, the energy harvesting unit plays a leading role in supplying wireless sensors (WSs). An application example is also presented with the aim to monitor the health condition of devices installed in the tubular busbars found in electrical substations. Since substation busbars heat up due to the Joule effect, there is a small thermal gradient between the busbar and the ambient, so the TEG can convert this heat flow into useful DC energy to supply low-power WSs. This paper assesses the performance of different TEG devices for this application, where very low temperature gradients are expected. The results presented show that with temperature gradients as low as 5 °C it is possible to supply WSs.

Design of a Fast Molten Salt Reactor for Space Nuclear Electric Propulsion

The French National Center for Scientific Research (CNRS) is carrying out design studies on a nuclear electric propulsion (NEP) engine based on a molten salt reactor (MSR). A NEP engine based on liquid nuclear fuel could allow developing a core design with relatively high power densities and temperatures while using simple reactivity control systems and keeping low pressure and temperature gradients in the fuel. Nevertheless, the design work of such an engine poses significant technical challenges and requires the use of advanced numerical simulation tools. Different MSRs for space are currently being studied. In this work, a MSR concept using a fast neutron spectrum is investigated using a multiphysics tool based on a numerical coupling between the OpenFOAM (computational fluid dynamics) and SERPENT 2 (Monte Carlo neutronics) codes. The analysis of this paper is focused on the reactor core coupled neutronic and thermal-hydraulic phenomena. Steady state full-power conditions are calculated for two different fast MSR designs using low-enriched uranium (LEU) and highly enriched uranium. The results show that the proposed core layout and materials allow obtaining a satisfactory temperature distribution in the core (maximal values and gradients) without significant penalization of the reactor operating conditions. A reactivity control strategy excluding the use of control rods is studied for the LEU concept. Transient and safety studies are also performed and show acceptable performance.

Lithological controls influence river form in contrasting sub‐catchments: The Scamander and Avenue Rivers, Tasmania

AbstractBedrock influence on river channel form is difficult to assess, with many catchments dominated by glacial erosion and with blanketing sediments from both pluvial and fluvial sources. The Scamander catchment in Tasmania lacks glacial history and features two bedrock‐confined sub‐catchments of similar area and maximum flow length, but one dominated by Mathinna Group sedimentary rocks, and the other with large areas in granite lithology. Lithology types, stream network parameters and near stream slope angles were analysed using geographical information systems, and results of stream cross sections, channel form and planforms were compared for each lithology. Results showed that granite features low gradient, shallow streams with channel slope cross sections of <10°. Granite channels are irregular and dominated by large boulders that create channel roughness and resist incision. Weathering products of coarse quartz sand provide anchorages for in‐channel vegetation. By contrast, sedimentary Mathinna Group rocks feature steeply incised trough‐like channels, with near‐channel hillslope gradients mostly between 30° and 50°. Rectangular blocks disintegrate to gravel cobbles on the channel bed, providing poor anchorage for vegetation. Mathinna lithology influences steep, low roughness channels, and stable, incised recurved meanders formed by river interaction with vertical layers of resistant rock. The resistant bedrock lithology is demonstrated in this study to influence varied river planforms, near‐channel slope gradients, channel sediments and cross sections.

Temporal Diffusion Ratio (TDR) for imaging restricted diffusion: Optimisation and pre-clinical demonstration

Temporal Diffusion Ratio (TDR) is a recently proposed dMRI technique (Dell'Acqua et al., proc. ISMRM 2019) which provides contrast between areas with restricted diffusion and areas either without restricted diffusion or with length scales too small for characterisation. Hence, it has a potential for informing on pore sizes, in particular the presence of large axon diameters or other cellular structures. TDR employs the signal from two dMRI acquisitions obtained with the same, large, b-value but with different diffusion gradient waveforms. TDR is advantageous as it employs standard acquisition sequences, does not make any assumptions on the underlying tissue structure and does not require any model fitting, avoiding issues related to model degeneracy. This work for the first time introduces and optimises the TDR method in simulation for a range of different tissues and scanner constraints and validates it in a pre-clinical demonstration. We consider both substrates containing cylinders and spherical structures, representing cell soma in tissue. Our results show that contrasting an acquisition with short gradient duration, short diffusion time and high gradient strength with an acquisition with long gradient duration, long diffusion time and low gradient strength, maximises the TDR contrast for a wide range of pore configurations. Additionally, in the presence of Rician noise, computing TDR from a subset (50% or fewer) of the acquired diffusion gradients rather than the entire shell as proposed originally further improves the contrast. In the last part of the work the results are demonstrated experimentally on rat spinal cord. In line with simulations, the experimental data shows that optimised TDR improves the contrast compared to non-optimised TDR. Furthermore, we find a strong correlation between TDR and histology measurements of axon diameter. In conclusion, we find that TDR has great potential and is a very promising alternative (or potentially complement) to model-based approaches for informing on pore sizes and restricted diffusion in general.

Measuring Sediment Transport Capacity of Concentrated Flow with Erosion Feeding Method

Sediment transport capacity in rills is an important parameter for erosion modeling on hillslopes. It is difficult to measure, especially at gentle slopes with limited rill length. In this study, a special flume with variable slope gradients in upper and lower sections was implemented to measure the sediment transport capacity. The upper flume section with a higher slope gradient generates faster water flow that could scout more sediment to feed the water flow in the rill. The rest of the flume is set at the designated slopes to measure the transport capacity in different slope and runoff conditions. A series of flume experiments were conducted with silt-loam soil to verify the method. The sediment transport capacity was measured under slope gradients of 5°, 10°, 15°, 20°, and 25° and a flow rate of 2, 4, 8, and 16 L min−1. The measured sediment transport capacity values were compared with reference measurements from other rill erosion experiments with similar materials and setups. At high slope gradients of 15°, 20°, and 25°, the newly suggested method produced almost the same transport capacity values. Under the low slope gradients of 5° and 10°, the maximum sediment concentrations from the 8 m long flume with the uniform gradients in the previous experiments, rill erosion with an 8 m long flume produced were about 36% lower than the values measured with the new method, which is insufficient to make the flow reach sediment transport capacity. The sediment transport capacities at lower slopes measured with the new method followed the same trend as those at higher slopes. The new method can supply enough sediments to ensure the flow approach transport capacity measurement and, therefore, provides a feasible approach for estimating sediment transport capacity for conditions with relatively gentle slopes.

Characterization of dextran-coated magnetic nanoparticles (Fe3O4) conjugated with monoclonal antibody through low gradient magnet and centrifugation-based buffer separation processes

Conjugation of magnetic nanoparticles (MNPs) with biomolecules can be achieved through covalent or non-covalent bonding and chemisorption. By glutaraldehyde cross-linking, we successfully conjugated mouse monoclonal antibody (Ab) with amine-functionalized dextran-coated MNPs of diameter 50 nm. We aim to characterize the antibody-conjugated MNPs (Ab-MNPs) after buffer separation through low-gradient magnet and centrifugation. The magnetic separation/washing was achieved throughout the conjugation process by attaching the MNPs solution to a natural magnet for about 12 h. The centrifugation-based separation steps were done at 15,000×g for 30 min. The transmission electron microscope (TEM) data showed the flower-shaped core MNPs and their increased diameter after conjugation with Abs. The nanoparticle tracking analysis (NTA) also revealed the size distribution and drift velocities in MNPs and Ab-MNPs. The size distribution and concentration data showed an increased size and a lower value after conjugation, respectively. The drift velocities of Ab-MNPs prepared by the centrifugation method were significantly reduced than magnetic separation and standard MNPs.

Gas kinematics around filamentary structures in the Orion B cloud

Context. Understanding the initial properties of star-forming material and how they affect the star formation process is key. From an observational point of view, the feedback from young high-mass stars on future star formation properties is still poorly constrained. Aims. In the framework of the IRAM 30m ORION-B large program, we obtained observations of the translucent (2 ≤ AV < 6 mag) and moderately dense gas (6 ≤ AV < 15 mag), which we used to analyze the kinematics over a field of 5 deg2 around the filamentary structures. Methods. We used the Regularized Optimization for Hyper-Spectral Analysis (ROHSA) algorithm to decompose and de-noise the C18O(1–0) and 13CO(1–0) signals by taking the spatial coherence of the emission into account. We produced gas column density and mean velocity maps to estimate the relative orientation of their spatial gradients. Results. We identified three cloud velocity layers at different systemic velocities and extracted the filaments in each velocity layer. The filaments are preferentially located in regions of low centroid velocity gradients. By comparing the relative orientation between the column density and velocity gradients of each layer from the ORION-B observations and synthetic observations from 3D kinematic toy models, we distinguish two types of behavior in the dynamics around filaments: (i) radial flows perpendicular to the filament axis that can be either inflows (increasing the filament mass) or outflows and (ii) longitudinal flows along the filament axis. The former case is seen in the Orion B data, while the latter is not identified. We have also identified asymmetrical flow patterns, usually associated with filaments located at the edge of an H II region. Conclusions. This is the first observational study to highlight feedback from H II regions on filament formation and, thus, on star formation in the Orion B cloud. This simple statistical method can be used for any molecular cloud to obtain coherent information on the kinematics.

Surface heat transfer coefficients in building envelopes: Uncertainty levels in experimental methods

There are several research methods for the on-site assessment of U-values that aim to avoid the use of surface heat flux measurements and rely on tabulated or empirically developed correlations to define this parameter. This works performs a detailed process to estimate indoor surface heat transfer coefficients based on several experimental campaigns over building walls. Data is filtered out to remove periods with large temperature variations and/or unstable convective conditions due to HVAC. A statistical analysis is conducted, and the outcomes used to test the validity of U-value estimation approaches. The outcomes show that the actual surface heat transfer coefficients are in the range of reference works, but variations in the range of up to 2 W/m2 K are found. Uncertainty levels associated to the estimation of surface heat transfer coefficient are in the range 60% for instantaneous values while this is reduced down to 12%–20% for 8-h averages. Variations and uncertainty levels are higher for low temperature gradient situations, which are considered to be very likely for modern insulation levels. It is concluded that methods seeking to avoid the use of surface heat flux measurements need to develop much deeper knowledge in this field to gain accuracy and reliability.

Species niche and interspecific associations alter flora structure along a fertilization gradient in an alpine meadow of Tianshan Mountain, Xinjiang

The niche breadth, niche overlap, and interspecific associations of species in Bayinbuluke alpine meadow were investigated using ecology statistics to explore the competitive connection between the species and restricted resources in the community and the stable coexistence relationships among populations under different nitrogen addition gradients in the short term. The findings demonstrate the following. (1) The importance value of species shifted, with the fertilization samples Festuca ovina and Poa annua becoming the species with the highest importance value. Species richness fell gradually as fertilization gradient progressed, while the number of species grew initially and subsequently decreased. (2) Under different fertilization methods, the niche width and niche overlap values of the principal species changed. A positive link was found between niche width values and critical values under fertilization treatment compared with the controls. (3) By using the variance ratio approach, Pearson’s correlation, and the association coefficient test, a positive correlation was discovered among species under low fertilization gradient treatment. However, a negative correlation was found under other gradients.

Sediment degradation experiments for a low gradient stream suggest the watershed’s connectivity regime exhibits control on stream biogeochemistry

Knowledge is lacking for sediment organic matter degradation and its influence on water quality for low gradient agriculturally impacted streams despite their importance for freshwater biogeochemical cycles and ecological restoration. We hypothesized degradation rates vary across sediment type and are a function of the connectivity regimes for low gradient systems. We carried out aerobic incubation experiments to assess oxidation and mineralization-nitrification rates and changes in stable isotopic ratios for sediment and dissolved organic matter and nitrate. Sediment originated from erosion across the watershed’s surface shows higher carbon oxidation rates (k = 3.9 × 10−3 d−1) and lower nitrogen mineralization-nitrification rates (k = 7.9 × 10−4 d−1) compared to sediment originated from the creek’s streambed that integrates algae and other autotrophic matter (k = 1.6 × 10−3 d−1 and k = 3.4 × 10−3 d−1). Differences are attributed to sediment transport of humified and plant matter during storms of high watershed connectivity and sediment transport of autochthonous sediment for low connectivity. Results support our hypothesis and suggest that the sediment connectivity regime of the watershed exhibits control on biogeochemical cycling of the stream network. Cumulatively, sediment degradation rates were one to two orders magnitude higher than previously assumed. Sediment rates reflect aerobic waters and place the organic matter as active and comparable to reported turnover of algae and fine sized leaf litter. Stable isotopic ratios of sediment change marginally for the two sediment types for carbon (ε = 0.4 ‰ and 1.3 ‰) and nitrogen (ε = 3.5 ‰ and 1.5 ‰). Dissolved organic nitrogen of stream water degraded similarly across all experiments (k = 1.8 × 10−2 d−1), and turnover rates were an order of magnitude higher than recent rates reported for lake water. Nitrate concentration in the solute increased by an average 35 % during experiments and the nitrogen stable isotopic ratio of nitrate decreased by over 1 ‰ showing the potential of sediment and dissolved organic matter degradation to influence nitrate flux and its isotopic signal.

Integration of Geophysical Survey Data for the Identification of New Archaeological Remains in the Subsoil of the Akrai Greek Site (Sicily, Italy)

For more than a decade now, geophysical prospecting has been considered an integral part of archaeological research; the ability to quickly investigate large areas and locate objects buried in the ground without directly interacting with it is a key feature that makes such surveys essential for identifying and locating, with good accuracy, buried archaeological remains. In this study, two extensive magnetic and electromagnetic surveys were carried out in two different areas of the Akrai archaeological site, where given the distribution of archaeological remains already found at the site, it was likely that additional buried remains were present. The surveys were performed using a proton precession magnetometer and a multifrequency electromagnetic device with a frequency range of 2.5–250 kHz. By processing the data, the vertical magnetic gradient and electrical conductivity maps were obtained. Furthermore, 3D models of electrical conductivity distribution were reconstructed. On comparing the results, it was notable that many anomalies characterized by low vertical gradient values were identified within areas characterized by low electrical conductivity values. These anomalies detected by both surveys can be associated with good probability with buried archaeological remains made up of limestones. In fact, they exhibit shapes and sizes comparable to those of the wall remains already found at the site.

LCZ method is more effective than traditional LUCC method in interpreting the relationship between urban landscape and atmospheric particles

Landscape classification methods significantly impact the exploration of the mechanism of the relationship between landscapes and atmospheric particulate matter. This study compared the local climate zones (LCZs) and traditional land use/cover change (LUCC) landscape classification methods in explaining spatial differences in concentrations of atmospheric particulate matter (PM2.5 and PM10) and explored the mechanisms involved in how landscape elements affect atmospheric particulate matter. This was done by establishing a PM2.5 and PM10 land use regression (LUR) model of LCZ and LUCC landscapes under low, typical, and high particle concentration gradients in urban and suburban areas. The results show that under an LCZ classification system, the number of patches in the urban area of Shanghai was 548 times higher than that of a LUCC system. Moreover, LCZs were successfully established for LUR models in 12 scenarios, while only five models were established for LUCC, all of which were suburban models. The R2 of the LUR model based on the LCZ landscape and atmospheric particulate matter was mostly higher than that of the LUCC. For unnatural landscapes, the LUCC demonstrated that an urbanized environment positively affects the concentration of atmospheric particles. However, the LCZ analysis found that areas with high-density buildings have a positive effect on atmospheric particles, while most areas with low-density buildings significantly reduced the number of atmospheric particles present. Generally, compared with the traditional LUCC landscape classification method, LCZ integrates Shanghai's physical structure and classifies the urban landscape more accurately, which is closely related to the urban atmospheric particulate matter, especially in the urban area. Because the low-density building area has the same effect on the particulate matter as the natural landscape, the use of low-density buildings is recommended when planning new towns.

Does valve size impact hemodynamic, left ventricular mass regression, and prosthetic valve deterioration with a sutureless aortic valve?

ObjectiveTo assess the mid-term clinical outcomes, hemodynamics, left ventricular (LV) mass regression, and structural valve deterioration (SVD) in patients implanted with the Perceval aortic sutureless valve across valve sizes. MethodsData were obtained from a multicenter European trial and a US Investigational Device Exemption trial. Echocardiography data were analyzed by an echocardiography core lab. A mixed-effects regression model was used to assess relationships between hemodynamic outcomes, time from the procedure, and valve sizes. The Valve Academic Research Consortium (VARC)-3 definition for bioprosthetic valve failure was applied. ResultsA Perceval sutureless valve was implanted in 970 patients. The median patient age was 77.8 years, 57.2% were female, the median Society of Thoracic Surgeons predicated risk of mortality was 3.3% (range, 2.1%-6.2%), and 33.4% had a concomitant procedure. The median clinical follow-up was 45.7 months (range, 28.2-76.1 months). Small and medium valves were implanted more commonly in women than in men (16.9% vs 1.9% for small and 55.1% vs 19.5% for medium; P < .001). The mean aortic valve gradients decreased significantly postimplantation and remained stable across all valve sizes throughout the follow-up period. All patients were free from severe patient–prosthesis mismatch (with an effective orifice area/m2 of >0.8). Significant LV mass regression was documented regardless valve sizes, plateaued at -9.1% at 5 years. Freedom from SVD and reintervention were 95.2% and 96.3%, respectively, at 5 years and were independent of implanted valve size (P = .22). The VARC-3 stage 3 bioprosthetic valve failure rate was low, 2.8% at 5 years. ConclusionsThe Perceval valve demonstrated low and stable mean gradients, significant LV mass regression, and low SVD and reintervention rates across all valve sizes.