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Purpose: Radical resection of retroperitoneal liposarcoma (RLPS) may necessitate vascular resection and reconstruction. The study was conducted to assess surgical outcomes of surgery for RLPS with major vascular involvement. Methods: Patients with RLPS who underwent surgical resection at the Sarcoma Center of Peking University Cancer Hospital between April 2011 and December 2022 were identified from a prospectively maintained database. Patients were classified into two groups: vascular resection and non-vascular resection groups. A propensity score matching analysis was performed to eliminate baseline differences between the groups. Surgical details and postoperative outcomes were analyzed. Furthermore, prognostic factors for local recurrence-free survival (LRFS) and overall survival (OS) were assessed. Results: Overall, 199 patients were identified and the median follow-up period was 48 (interquartile range [IQR] 45–69) months. Vascular resection was performed in 42 (21%) patients, 25 of whom had vascular infiltration. A total of 39 patients had vascular replacement and 3 patients underwent partial resection (side-wall resection). Vascular resection was burdened by higher rates of major morbidity (38% vs. 14%, p < 0.001) and 30-day mortality (7.1% vs. 1.3%, p = 0.005). After propensity-matched analysis, patients who underwent vascular resection had 5-year LRFS and OS rates comparable to those without vascular involvement. Major vascular resection was not an independent risk factor for LRFS or OS. Conclusions: Although accompanied by increased risks of major morbidity and mortality, the major vascular resection enabled radical resection in patients with advanced RLPS, affording comparable 5-year LRFS and OS rates compared to those who did not. [ABSTRACT FROM AUTHOR]

Background: Multivisceral en bloc resection with the ipsilateral kidney is commonly performed in patients with retroperitoneal liposarcoma (RLPS). We evaluated the effect of nephrectomy on short- and long-term outcomes in patients with RLPS. Methods: Data from a prospectively maintained database of the Peking University Cancer Hospital Sarcoma Center between April 2011 and August 2022 were analyzed. We classified the RLPS patients who underwent surgery into nephrectomy group (NP) and non-nephrectomy group (non-NP). Patients were matched using a 1:1 propensity score to eliminate baseline differences between groups. Postoperative renal function outcomes, major morbidity, and mortality were analyzed to compare short-term outcomes after nephrectomy. Differences in local recurrence-free survival (LRFS) and overall survival (OS) were compared by Kaplan–Meier analysis with respect to oncological benefits. Results: In the matched cohort, patients in the NP group had significantly higher postoperative eGFR and CKD stages, but none required dialysis. Patients between NP and non-NP had a comparable major morbidity (p = 0.820) and 60-day mortality (p = 0.475). Patients in the NP group had a higher 5‐year LRFS rates than those in the non-NP group (34.5 vs. 17.8%, p = 0.015), and similar 5‐year OS rates (52.4 vs. 47.1%, p = 0.401). Nephrectomy was an independent risk factor for LRFS, but not for major morbidity or OS. Conclusions: RLPS resection with nephrectomy is related to a mild progression of renal impairment; however, dialysis is rare. En bloc nephrectomy for complete resection of RLPS is safe and improves local control. [ABSTRACT FROM AUTHOR]

On 31 July 2021, Ningbo, an eastern coast city in China, experienced a severe convective rainstorm, characterized by intense short-duration precipitation extremes with a maximum rainfall rate of 130 mm h−1. In this research, we first analyzed this rainstorm using Doppler radar and precipitation observation and then conducted high-resolution simulation for it. A three-dimensional precipitation diagnostic equation is introduced to quantitatively analyze the microphysical processes during the rainstorm. It is shown that this rainstorm was triggered and developed locally in central Ningbo under favorable large-scale quasi-geostrophic conditions and local conditions. In the early stage, the precipitation increase is mainly driven by the strong convergence of water vapor, and a noticeable increase in both the intensity and spatial extent of uplift promotes the upward transportation of water vapor. As the water vapor flux and associated convergence weaken in the later stage, the precipitation reduces accordingly. Cloud microphysical processes are also important in the entire precipitation process. The early stage updraft supports the escalations in raindrops, with the notable fluctuations in raindrop concentrations directly linked to variations in ground precipitation intensity. The behavior of graupel particles is intricately connected to their melting as they fall below the zero-degree layer. Although cloud water and snow exhibit changes during this period, the magnitudes of these adjustments are considerably less pronounced than those in raindrops and graupels, highlighting the differentiated response of various condensates to the convective dynamics. These results can help deepen the understanding of local severe rainstorms and provide valuable scientific references for practical forecasting. [ABSTRACT FROM AUTHOR]

Plenty of gold deposits related to Late Mesozoic craton destruction are widely distributed in eastern North China Craton. However, significant differences in research degrees, ore-forming characteristics, and proven reserves exist among different regions in the North China Craton. The Liaodong Peninsula has similar regional geological characteristics to those of the Jiaodong Peninsula, with both experiencing craton destruction during Late Mesozoic, but the two areas have substantial differences in terms of gold mineralization and the proven gold resources. Based on regional geology, Mesozoic magmatic-tectonic evolution and ore geology, combined with integrated geophysical exploration and big data AI resource prediction, in this paper, we propose that the ore-forming materials of Late Mesozoic gold deposits in Liaodong were mainly originated from mantle-derived melts and/or fluids induced by craton destruction. The gold deposits were primarily controlled by NE-NNE-trending faults, mainly classified as fracture-controlled altered rock-type and sulfide-bearing quartz vein-type. Moreover, our study predicts that the Yalu River fault zone and its related secondary faults, as well as the periphery and deeper parts of known goldfields, are the important regions for future gold resource exploration. The Yalu River metallogenic belt has an enormous potential for gold resources, and the Liaodong Peninsula has a potential to add thousands of tons of gold resources. [ABSTRACT FROM AUTHOR]

The Yangbajain Geothermal Field in Tibet is located in the fault subsidence basin of the central Yadong-Gulu Rift Valley. The spatial distribution of the field is controlled by mountain-front fault zones on the northwestern and southeastern sides of the basin. Geothermal power has been generated in Yangbajain for more than 40 years. However, owing to the lack of three-dimensional (3D) geophysical exploration data, key geological issues related to the partial melt body of the Yangbajain Geothermal Field, such as its location, burial depth, and geometric form, as well as the ascending channel of the geothermal fluid, have for a long time been controversial. In this study, 3D inversion was performed using measured geo-electromagnetic total impedance tensor data from 47 survey points. The extracted horizontal sections at different depths and profiles, and at different lines, reflect the 3D electrical structure model of the geothermal field in the study area. Subsequently, three findings were obtained. First, the partial melt body, located below the China-Nepal Highway extending along the northeast direction, is the heat source of the Yangbajain Geothermal Field. The burial depth range of the molten body was determined to range between approximately 6.2 and 14 km. Moreover, the geothermal fluid ascended a horn-shaped circulation channel with an up-facing opening, located in the northern section of the sulfur ditch area. The study results revealed that deep rock fissures (>2 km) were not well developed and had poor permeability. In addition, no layered heat reservoirs with high water richness were observed in the northern part of the study area. However, the application of enhanced geothermal system (EGS) technology in the northern region would be essential to improving the power generation capacity of the Yangbajain Geothermal Field. In addition, the study found no deep high-temperature heat storage areas in the southern region of the study area. [ABSTRACT FROM AUTHOR]

This article discusses recent advancements in transient electromagnetic (TEM) methods, specifically focusing on data acquisition, denoising and processing, imaging, inversion, and interpretation techniques. The collection of 13 papers covers various subtopics, including the use of drones in survey methods, the detection of geological boulders in tunnels, and the development of neural network architectures for data processing. The article also includes case studies on topics such as identifying ore-bearing strata, detecting coal-mining goaf areas, and uncovering buried historical harbors. While 3D inversion is a widely discussed topic in TEM research, this special issue does not include any articles specifically addressing this aspect. [Extracted from the article]

The concept of a "smoke ring" in electromagnetic fields can be used to describe the spatial distribution and diffusion of electromagnetic fields with either frequency or time. This provides an intuitive basis for the qualitative interpretation of artificial-source electromagnetic measurement results. The existing discussions regarding this field of study have mainly focused on the smoke rings of a magnetic dipole or loop source. In the present work, smoke rings of other commonly used grounded-wire sources in the time domain are investigated. The results show that the smoke ring of grounded-wire sources is more complex than that of magnetic sources. A grounded-wire source can generate an induced current in both horizontal and vertical directions. The horizontal induced current includes positive and negative parts. Both parts of the horizontal induced current maximum diffuse downward perpendicular to the surface, but the diffusion velocity of the negative part is faster, approximately 5.6 times that of the positive part. The vertical induced current maximum diffuses at 45° from the grounded surface with a velocity approximately 5 times that of the positive horizontal induced current. The smoke ring of the horizontal induced current closely resembles a basin, while that of the vertical induced current is more similar to two separate cylinders. Finally, the imaging depth based on horizontal and vertical induced currents is obtained by the statistical relationship between the induced current maximums and the diffusion depth, which are equal to 1.4 times and 1.25 times the diffusion depth, respectively. [ABSTRACT FROM AUTHOR]

This study focuses on the integrated application of the frequency-domain terrain conductivity (TC) and transient electromagnetic (TEM) methods to map an ancient riverine harbour (port) at the Egyptian archaeological site of Tell el-Rub'a (prehistoric Mendes). Fifty-one TC profiles were measured using six EM frequencies and 16 TEM soundings were performed at the selected site. The apparent conductivity maps derived from the TC survey enabled defining the lateral extension of the harbour basin and its edges to penetration depths ranging between 12 and 30 m. The vertical extension of the harbour basin was determined using the TEM inversion. Three layers were defined: the topsoil, the conductive silty clay infill and the resistive sand bedrock. The bedrock is found at depths ranging from 19 to 31 m. The TC and TEM results were combined to form a 3D image of the harbour basin. This study confirms the existence of Mendes harbour and demonstrates the effectiveness of the TC and TEM methods for such archaeological studies. [ABSTRACT FROM AUTHOR]

Using multigeophysical exploration techniques is a common way for deep targets to be explored in complex survey areas. How to locate an unknown underground target using multiple datasets is a great challenge. The useful information in the multisource geophysical model can be extracted and fused with the help of data fusion, which also works well to correct the interpretation divergence brought on by expert experience, with image feature extraction being the key step in the fusion of the geophysical models. Traditionally, this method is often used for these kinds of geophysical images, but it significantly reduces the efficiency of feature extraction. As a result, we propose a novel method based on a transfer learning method to extract the features of multisource images. First, the ResNet50 network is used to extract the initial features of the images. Owing to the problems of feature redundancy and fuzzy features in initial features, Spearman and zero phase component analysis can be used to achieve feature reduction and enhancement, which can further improve the computational efficiency and fusion accuracy in fusion. Finally, the fusion image is obtained using fusion rules that we designed based on the current state. The algorithm's reliability is tested using field data from the Iliamna Volcano. The case study demonstrates the effectiveness of the proposed strategy, which also offers a novel way to locate subsurface targets. [ABSTRACT FROM AUTHOR]

Crustal structure and fluid or melt originating in the deep crust and mantle are critical in regional magmatic mineral systems. However, the crustal structure and the processes that entrain and focus fluids from a deep-source region to a metallogenic belt remain relatively undisclosed. We present a magnetotelluric (MT) study of the eastern Qimantagh Metallogenic Belt (QMB) in the northern Tibetan Plateau. Data from 33 MT stations in two sections and 7 dispersed stations are acquired using a surface electromagnetic prospecting (SEP) system in frequency band ranges from 320 Hz to 0.00034 Hz. Data are converted by Bostick conversion and two-dimensional (2D) nonlinear conjugate gradient inversion. Our MT results reveal the geoelectrical crustal structure of the QMB, which consists of a southern low-resistivity domain that reflects the Kumukuri rift, a high-resistivity middle domain that represents the southern QMB in the central Kunlun belt, and a northern low-resistivity domain that covers the northern QMB and southwestern Qaidam block. We present a comprehensive tectonic and geophysical model of QMB based on the MT interpretation and geological analysis. We infer the high-resistivity domain as a reflection of a rigid crust and detached lithospheric mantle, this belt separate the QMB into northern and southern QMB. Most of the mineral deposits are found in the northern low-resistivity domain of QMB. Our study and findings provide an understanding of the tectonic evolution of the northern Tibetan Plateau, the crustal structure that controls the temporal and spatial distribution of magmatic rocks, and the geological signature associated with mineral deposits. [ABSTRACT FROM AUTHOR]

The article discusses the recent growth in research on the geophysical electromagnetic method (EM) and its applications in mineral exploration, engineering, and environmental studies. The article highlights the challenges in accurately modeling EM responses for complex earth systems and recovering electrical models from EM configurations. The article proposes a special issue on advances in forward modeling and inversion of geophysical electromagnetic data, which includes eight articles on topics such as numerical modeling, signal processing, and case studies. The article concludes that while 3D inversion is a widely discussed topic, it is not yet practical for real-life situations. [Extracted from the article]

A near-source electromagnetic method known as the short-offset transient electromagnetic (SOTEM) method was proposed. Compared with the traditional far-source methods, the offset of the SOTEM method is greatly reduced, to only 0.3~2 times of the maximum depth. Therefore, the SOTEM can obtain the signal with higher signal-to-noise ratio and sensitivity. Application in the Xiaoshan Mine of Henan Province showed that the SOTEM method is an effective method for deep ore exploration, especially in mountainous areas. [ABSTRACT FROM AUTHOR]

Circular RNA circSLC8A1 is one of the cancer-related circRNAs that is implicated in various cancers. However, studies focusing on the role of circSLC8A1 in glioma is rare. Here we attempted to evaluate the biological function of circSLC8A1 in glioma and explore the potential mechanism. The relative expression of circSLC8A1, miR-214-5p and CDC27 in tissues and cell lines was determined by qRT-PCR. Cell proliferation and invasion were respectively measured by CCK-8 and transwell assays. Protein level of CDC27 was analyzed by western blot. Luciferase reporter assay was performed to confirm the regulatory interaction of cirRNA-miRNA-mRNA. Lowly expressed circSLC8A1 was observed in both glioma tissues and cell lines. Further biological analyses showed that circSLC8A1 inhibits the cell proliferation and invasion of glioma cells. CircSLC8A1 directly sponged miR-214-5p and inhibited miR-214-5p expression in glioma cells. CDC27 was a direct target of miR-214-5p and could be regulated by miR-214-5p. Moreover, miR-214-5p mimics and CDC27 knockdown reversed the inhibitory effects of circSLC8A1 on cell proliferation and invasion. Taken together, our results demonstrated a tumor suppressive role of circSLC8A1 in glioma through regulation of glioma cells proliferation and invasion. The effects of circSLC8A1 were mediated by miR-214-5p/CDC27 axis. Our study provided a new understanding of the occurrence and development of glioma. [ABSTRACT FROM AUTHOR]

Semi-airborne transient electromagnetics (SATEM) is a geophysical survey tool known for its ability to perform three-dimensional (3D) observations and collect high-density data in large volumes. However, SATEM data processing is presently restricted to 3D model-driven inversion, which is not conducive to detailed surveys. This paper presents a new 3D model- and data-driven inversion algorithm using the particle swarm optimization (PSO) and gradient descent (GD) algorithms. PSO is used to suppress the multiplicity of solutions associated with inverse problems, and the GD algorithm is employed to accelerate the convergence of the inversion process. For the PSO-GD algorithm, a new model-updating equation is established and a cosine probability function is introduced as a weighting term for PSO and GD algorithms to ensure a smooth transition between the two algorithms in the iterative process. The α-trimmed filter function is used as a regularization constraint to smooth the model. The stability and reliability of the PSO-GD algorithm are verified through numerical simulations. Finally, the new algorithm is applied to the processing of SATEM measurements of the Qinshui coal mine in Jincheng, Shanxi Province, China. [ABSTRACT FROM AUTHOR]

Because of the relatively weak useful signal and noises with complex characteristics, the data processing of airborne electromagnetic observation is very difficult. As the downstream of data processing, inversion generally cannot further distinguish whether there are residual noises in the processed data. That is, in the current processing flow, the signal‐noise distinguishing is isolated from the signal‐model mapping. The reliability of the estimated earth resistivity model will be seriously affected due to the probable disadvantages in the denoising process. To this end, we propose a manifold assumption, and so establish one "feedback" mechanism between signal‐noise distinguishing and signal‐model mapping. On this basis, we propose a deep learning method: through simultaneous optimal training the network parts for signal‐noise distinguishing and earth resistivity model estimation respectively, the entire neural network can perform the denoising and inversion in the traditional sense at the same time, so as to obtain more objective and reliable estimation results of earth resistivity model. We use the Stacked Auto‐encoder neural network structure to implement the proposed method, and test the network performance with simulation and measured data. The results show that the proposed method can obtain a more reliable earth resistivity model directly from the noisy data. Plain Language Summary: The Transient Electromagnetic (TEM) method is a geophysical method based on the law of electromagnetic induction. The traditional TEM method has low efficiency because of the ground observation. The airborne TEM (ATEM) was introduced to overcome this limitation. However, due to the flight‐movement observation, the useful signal in ATEM data is relatively weak, while the characteristics of noises are complex. So far the denoising process generally consists of many steps, and each step deals with one kind of noise, so the requirements placed on the processing personnel will be very high. After the denoising is completed, the data will be brought into the inversion to obtain an estimate of the earth resistivity model. The inversion generally cannot further distinguish whether there are residual noises in the processed data. Therefore, the reliability of the estimated earth resistivity model will be seriously affected due to the probable disadvantages in the denoising process. So we proposed a Manifold assumption and an alternative approach based on this assumption. The concept of the new approach is similar to adding one more "force" to achieve a more effective separation of the signal and noises, so as to obtain more objective and reliable detection results. Key Points: In the traditional processing flow of the Airborne Transient Electromagnetic data, denoising and inversion are independent of each otherA manifold assumption is proposed, and a "feedback" mechanism is established between signal‐noise distinguishing and signal‐model mappingAn extensible stacked auto‐encoder neural network is used to realize the direct estimation of the earth resistivity model from noisy data [ABSTRACT FROM AUTHOR]

Subsurface geoelectric structures and resources can be detected based on the propagation of the electromagnetic field. Near‐source electromagnetic methods have recently become the most popular survey mode. However, calculation of the electromagnetic field in the near‐source region with artificial sources has always been performed based on far‐source dipole approximation. Owing to the introduction of artificial sources in the near‐source region, it is challenging to obtain accurate solution of the electromagnetic field based on the relationship between the observation point and the source, thereby affecting the detection accuracy. Specifically, the main problem lies in the position vector of the transmitting source, which is generally neglected in the response calculation based on the plane‐wave theory. Moreover, only far‐source data can be observed in the plane‐wave theory. However, near‐source data have been collected in a near‐source survey, with the dipole approximation resulting in a large error. We introduce a point charge element to decrease or eliminate the error caused by the dipole approximation. The non‐homogeneous Helmholtz equation is first solved using the Green's function. Then, the response expression of the real source, including the source position vector, is obtained by integrating the response of the harmonic point charge element. The substitution of the dipole elements with the point‐charge elements not only reduces the dipole approximation errors but also displays the electromagnetic characteristics of the entire zone, which are verified by the forward modeling and field survey results. The near‐source (offset is 0.8 of the target depth) survey can be realized based on the point charge element. Key Points: A point charge element is introduced to decrease or eliminate the error caused by dipole approximationThe response expression of the real source, including the source position vector, is derivedThe electromagnetic characteristics of the entire zone are displayed [ABSTRACT FROM AUTHOR]

Transient electromagnetic method (TEM) is one of the major tools to image the subsurface resistivity. The gradient-based inversion of TEM data only provides a unique solution using a subjectively defined regularization penalty, leaving the uncertainty of the solution unaddressed. The Bayesian method can be used to estimate the model parameters, as well as quantify their uncertainty. However, it requires far higher computational costs than gradient-based inversion, which limits the Bayesian inversion of TEM data to 1-D assumptions. We propose an accelerated Bayesian method based on Markov chain Monte Carlo (MCMC) subposteriors to perform full 2-D inversion of TEM data. A robust scheme is designed to divide the model space of a TEM profile into subspaces so that independent MCMC chains can be used to update the parameters in each subspace in parallel. The division is based on the coverage of the source loops using a cumulative sensitivity matrix. Then, the subposteriors obtained at each subspace are merged to approximate the full posterior of the model space using a weighting strategy. A numerical test of a 2-D valley model is used to validate the proposed method. The Bayesian inversion successfully obtained posterior that converges to the true model. The median model makes a good inference of the model parameters, while the probability density function gives their uncertainty estimates. The statistical model of interest can be further extracted from the model ensemble. The proposed method provides an effective framework for Bayesian inversion of TEM data with a multidimensional forward operator. [ABSTRACT FROM AUTHOR]

Skywave refers to the electromagnetic wave reflected or refracted from the ionosphere and propagated in the form of a guided wave between the ionosphere and the Earth's surface. Since the skywave can propagate over large distances, it has been widely used in long-distance communication. This paper explores and demonstrates the feasibility of skywave for deep resource and energy exploration at depths of up to 10 km. Theoretical and technical advancements were accomplished in furthering skywave applications. A new solution method based on Green's function has been developed to study skywave propagation in a fully coupled lithosphere-air-ionosphere full space model. For the first time, the model allows one to study skywave distribution characteristics in the lithosphere containing inhomogeneity such as ore deposits or oil and gas reservoirs. This model also lays a foundation for skywave data processing and interpretation. On a parallel line, we have developed a multi-channel, broadband, low-noise, portable data acquisition system suitable for receiving skywave signals. Using the skywave field excited by a high-power fixed source located in central China, actual field surveys have been carried out in some areas in China including the Biyang depression of Henan Province. The initial results appear encouraging—the interpreted resistivity models prove to be consistent with those of seismic exploration and known geological information, and the exploration cost is only ∼1/4 to 1/10 that of seismic surveys. These initial successful applications of the skywave theory lay a solid foundation for further verification of the new method. [ABSTRACT FROM AUTHOR]

Geophysics offers an important means to investigate the physical processes occurring inside the earth. In particular, since the 1960s, electromagnetic (EM) methods have played important roles in mineral exploration and engineering investigation. Such investigation requires extensive data acquisition and experimental analysis based on geophysical techniques. However, high-performance geophysical equipment, particularly EM exploration equipment, has been dominated by large geophysical companies from the United States, Canada, Germany, and other European countries for decades. This has limited the development of deep exploration technology in China. Recently, we have developed a high-resolution acquisition system with a wireless control unit and a high-power transmitting system for surface EM prospecting (SEP). The new system has been tested in the high-intensity, noisy environment in Jian-sanjiang area, Heilongjiang Province. We then conducted a field survey on the western edge of Qaidam Basin, Qinghai Province. A highly conductive anomaly was found in the upper mantle below the Qinmantage Mountains, which indicates a possible northward fluid channel that runs from below the Qinmantage Mountains to the bottom of the western crust of the Qaidam Basin. Identification of this significant feature was made possible by the new SEP for its better resolution than the previous systems. Also, geophysical analysis confirmed that the thick Cenozoic sediments of the Qaidam Basin are underlain by rigid Precambrian basement rocks and are characterized by a series of folds. The resistivity profile indicates that the Qaidam Basin was formed due to the folding structures in the northern part of the Qinghai-Tibet Plateau which provided an additional evidence for the uplifting of the Qinghai-Tibet Plateau. [ABSTRACT FROM AUTHOR]

The North China Craton is the oldest continental block, and has suffered from large-scale lithospheric thinning and destruction, which in turn led to gold deposits in northern China. The decratonic gold deposits in the North China Craton became the most important gold deposits in China, and geophysical methods are key means to detect and discover gold deposits there. In this paper, based on the geological and petrophysical characteristics of the North China Craton, the geological model of the decratonic gold deposits is transformed into a geophysical model. At present, two methods of geophysical exploration of decratonic gold deposits are in use: rapid and efficient exploration on the scale of the ore concentration area, and large depth exploration on the scale of the deposit area. In detail, the airborne electromagnetic, magnetic and gravity methods are used to detect the shallow (1,500 m) anomaly area on the scale of the ore concentration area. Through the ground-controlled source electromagnetic and ground magnetotelluric methods, explorations for targets at significant depth (5,000 m) are carried out in the mining area. Then, taking the Liaodong ore concentration area as an example, geophysical methods are used to discover two prospecting areas around the Jianshanzi Fault in the Qingchengzi ore concentration area, Baiyun-Xiaotongjiapuzi deep prospecting area, and Qingchengzi deep prospecting area. Next, three prospecting areas are delineated around the Jixingou Fault in the Wulong mining area, Wulong deep prospecting area, Weishagou deep prospecting area, and Chang'an deep prospecting area. The anomalies in the ore concentration area and mining area are revealed by means of three-dimensional exploration methods, thereby providing technical support for the exploration of metal minerals such as decratonic gold deposits. [ABSTRACT FROM AUTHOR]

The Fengtai Pb–Zn metallogenic deposits located in China's western region have good minerogenetic conditions and exploration potential. However, the Fengtai mining area passed through complex orogenic process zones, such as subduction, collision, and integration between the Yangtze Plate and the North China Plate. Existing geological research and drilling results showed that the ore bodies of large‐scale Pb–Zn deposits in the ore‐gathering area were steeply inclined, and the detection depths of the majority of the metal deposits were generally less than 300 m. Deep ore‐controlling structures at approximately 500–1,000 m are not well understood. Therefore, high‐precision and large‐depth geophysical detection techniques are necessary to achieve the required accurate detection results. This study revealed that the resistivity values of the ore and host rocks were quite different, which is essential for effective and efficient geophysical prospecting. Based on the petrophysical result, the grounded‐wire transient electromagnetic method system has been found to be one of the better choices for the deep prospecting of the metal deposits and was applied to detect Pb–Zn deposits in the Bafangshan‐Erlihe area. First, the grounded‐wire transient electromagnetic method's effectiveness was verified using results from survey line 1 at a known ore deposit verified by the drilling result. Then, the technique was used to identify deposits in an unexplored area. A deep anticline and ore body were successfully imaged. Most lead‐zinc ore bodies are controlled by the hinge and two wings of the tight anticline, and distributed in the contact zone between limestone and phyllite. The results provide a critical basis for deep prospecting and drilling design. [ABSTRACT FROM AUTHOR]

Background: Local recurrence is the most difficult postoperative challenge and the leading cause of death in patients with retroperitoneal liposarcoma (RLPS). We aimed to establish a postoperative nomogram exclusively focused on RLPS for predicting local recurrence-free survival (LRFS). Methods: A cohort of 124 patients after surgical resection with curative intent in the Peking University Cancer Hospital Sarcoma Center were included in the study. Demographic, clinicopathologic, and treatment variables were analyzed using the Cox regression model. Significant clinically relevant variables in multivariable analysis were incorporated into the RLPS-specific nomogram. The discriminative ability and predictive accuracy of the nomogram were assessed by calculating the concordance index and drawing a calibration plot. Results: At a median follow-up of 26.5 (interquartile range 10.9–39.4) months, 71 patients had recurrent disease. The 3-year and 5-year LRFS rates were 35.6% (95% confidence interval, 27.0–46.9%) and 28.2% (95% CI 15.8–38.6%), respectively. Multivariate analysis identified the French Federation of Cancer Centers Sarcoma Group (FNCLCC) grade and completeness of resection as independent predictors of LRFS. Variables included in our nomogram were: presentation status, multifocality, completeness of resection, histologic subtypes, and FNCLCC grade. The concordance index of our nomogram was 0.732 (95% CI 0.667–0.797) and the calibration plot was excellent. Conclusions: Our novel nomogram for patients with resected RLPS could improve recurrence risk stratification to explore molecular analysis associated with recurrence. [ABSTRACT FROM AUTHOR]

Transient electromagnetic method (TEM) is an important tool for mapping the subsurface resistivity. As the electromagnetic fields with different frequencies reach different depth of the Earth, the resolution of TEM method is closely related to the spectrum properties of its source signal. The pseudorandom binary sequence (PRBS) is a recently applied source signal and is thought to be superior to the conventional square wave for its adjustable frequency range and density. However, to invert the response from this optimized source, the pure secondary field needs to be extracted from the full waveform response in which parts of useful information is lost inevitably. We thus propose to directly invert the full waveform TEM response from the excitation of PRBS using a transdimensional framework. We use the reverse-jump Markov chain Monte Carlo (RJ-MCMC) sampler to get the model ensemble so that the posterior of the model can be obtained. The PRBS source is convolved with the impulse response of the Earth to fit the recorded full waveform response. The 2-D model space is discretized using a two-stage binary tree and updates in parallel, which dramatically improve the sampling efficiency. The synthetic examples compare the results from the conventional time-domain step response and the full waveform response and demonstrate that the proposed method obtains higher resolution and can better resolve the interface in the shallow and moderate depth. Furthermore, the real data example recovers the model structure that is consistent with the geologic inference, providing alternate evidence for the conjecture of the Sanshandao fault. [ABSTRACT FROM AUTHOR]

The surface-to-borehole transient electromagnetic (TEM) method, which uses a rectangular loop as its source, has shown great potential in mineral exploration at greater depth. However, recent studies have demonstrated that a grounded-wire source can resolve the resistive targets and provide detection at greater depths than the loop source. Thus, we propose a surface-to-borehole TEM method using a grounded wire as a transmitter at short offsets. We conducted numerical experiments to explain the variation of different parameters and its comparable effects on the TEM transients. Similarly, a systematic comparison of the cross-sectional electric field distribution maps, borehole profiles of the time derivatives of the magnetic field, qualitatively reveal that the proposed method induces detectable responses for conductive and resistive targets at greater depths. In the present study, unlike the loop source configuration, the time derivative of an underground magnetic field in horizontal direction showed high sensitivity to resistive bodies. Furthermore, 1-D inversion was performed to provide quantitative interpretation of the borehole data. The 1-D inversion of the surface and borehole data was realized using an Occam-type inversion scheme. The results of both synthetic and field data indicate that inverting the surface or borehole data separately resulted in degraded resolution in both shallow and deep earth. Thus, we also compared the results from the inversions of surface and borehole data in order to explore the merits of joint inversion in resolving shallow and deep structures. [ABSTRACT FROM AUTHOR]

As an important branch of geophysical exploration method, the electromagnetic method with artificial source has advanced rapidly in the past decade. These methods are classified as airborne electromagnetic method, ground-air electromagnetic method, ground electromagnetic method, and marine electromagnetic method. Over the years, researchers in China have made significant improvement to the fundamental theory, forward modeling and inverse for series of electromagnetic detection methods. Conversely, significant progress was made in the development of corresponding equipment. The researched techniques and their developed equipment have been successfully utilized to detect underground targets as deep as 10 km. However, there is increasing need for deep resources exploration, urban subsurface study, and prediction, monitoring and detection of geological hazards. To meet the increasing need and catch up with the advanced international level of exploration technologies and developed equipment, there is urgent necessity and requirement to continue developing geophysical methods and the corresponding equipment. [ABSTRACT FROM AUTHOR]

Previously, the multi‐channel transient electromagnetic (MTEM) system has been successfully developed and applied to hydrocarbon reservoirs exploration on land and offshore environments in France. In order to explore the mineral resources buried at the depths up to 2,000 m in China, we developed a new MTEM system. In this paper, we present the components of the system, methods, principles, the parameters of the system, and the data interpretation method. To validate the effectiveness of the methodology and the developed system, we carried out an MTEM survey to locate the controlling faults of a gold deposit in the east of China. The survey contains 30 receivers distributed over 12‐km survey. By comparing the MTEM interpretation results with the known geological background, we find that MTEM methods can provide a good estimation of the ore‐controlling faults and this method could be a potential tool for the future deep mineral exploration. [ABSTRACT FROM AUTHOR]

Xiaoshan gold–polymetallic concentrated area is located in Henan Province, central China. The area is principally underlain by typical metamorphic core complexes (MCCs), along with essential components of the basins and ranges of western Henan. Mineralization occurs in the regions where the geochemical anomalies of Au and related elements are widely distributed and consist predominantly of mineralized altered rocks and auriferous quartz veins, both of which are hosted within shear zones or fractures of varying sizes and orientations. Several small‐ to medium‐sized gold–polymetallic ore deposits, along with numerous clustered occurrences, have been found in the area in recent years. However, despite the fact that the Xiaoshan District has traditionally been deemed as an excellent geological endowment area with enormous potential for large‐sized deposits, no significant discoveries have been made to date. It is suggested that the main reason responsible for the present exploration situation could be the scarcity of applications of deep‐penetration geophysical prospecting in the area. It is anticipated that integrating geological and geophysical data would be crucial to enhance the successful mineral explorations. In this contribution, a conceptual geological model for the study area was initially reviewed so that the corresponding electromagnetic responses could then be modelled, which would simulate a geophysical type of survey, with appropriate uncertainties added into the analyses. Then, based on such an integrated approach, the required precision of detecting deep‐buried deposits could then be evaluated. In addition, by employing supplementary geophysical data acquired over known deposits, it is possible to gain more instructive insights into the practical geological model. The viabilities of this approach were demonstrated through a case study in which a hidden gold deposit in the studied area was successfully detected. Geophysical surveys were carried out by employing a grounded‐wire short‐offset TEM (SOTEM) technique and revealed two new anomalies (one of which was subsequently tested by drilling). The drilling then confirmed that this anomaly was caused by an ore body 30 m in thickness occurring at about 550 m below surface. [ABSTRACT FROM AUTHOR]

China is facing many challenges in the area of high‐precision exploration for deep mineral resources, and also in environmental and engineering fields. It has become an urgent task to realize geophysical explorations with high precision and high efficiency in complex environments. It has been found that the traditional transient electromagnetic method (TEM) had a series of problems related to theory, method, and instrument, as well as data interpretation. Based on the reviews of present TEM achievements, three new improved measurements are introduced. The central‐loop system was improved by a large fixed‐loop system; the long‐offset system was changed to the short‐offset one; the resistivity profile was transformed into a virtual wave‐field profile. Finally, this paper points out that the future research direction of the TEM method is in terms of equipment, data processing, and big data information. [ABSTRACT FROM AUTHOR]

Trimethyltin (TMT) is widely used as a plastic heat stabilizer and can cause severe toxicity. Here, the effects of TMT on testosterone production by adult Leydig cells and the related mechanisms of action were investigated. Eighteen adult male Sprague Dawley rats (56 days old) were randomly divided into 3 groups and given intraperitoneal injection of TMT for 21 consecutive days at the doses of 0 (vehicle control), 5, or 10 mg/kg/d. After treatment, trunk blood was collected for hormonal analysis. In addition, related gene and protein expression in testes was detected. At 10 mg/kg, TMT significantly reduced serum testosterone levels but increased serum luteinizing and follicle-stimulating hormone levels. The messenger RNA and protein levels of luteinizing hormone/chorionic gonadotropin receptor, steroidogenic acute regulatory protein, cytochrome P450 17-hydroxylase/17,20-lyase, follicle-stimulating hormone receptor, and SRY box 9 were significantly lower in the TMT-treated testes than in controls. Immunohistochemical study showed that TMT decreased adult Leydig cell number. In conclusion, these findings indicate that TMT reduced adult Leydig cell testosterone production in vivo by directly downregulating the expression of steroidogenic enzymes and decreasing adult Leydig cell number in the testis. [ABSTRACT FROM AUTHOR]

Three emerging techniques for surface electromagnetic (EM) exploration with high detection accuracy and large depth of investigation, namely, WEM (wireless electromagnetic method), MTEM (multi‐channel transient electromagnetic method) and SOTEM (short‐offset grounded‐wire TEM), are introduced. In detail, we proposed a newly developed sky‐wave theory in which EM wave can propagate in full space of ionosphere‐atmosphere‐lithosphere. Correspondingly, we developed the WEM recording system to measure the sky‐wave to obtain the structures down to ∼10 km depth. We then introduced MTEM as a highly effective method for mineral exploration with target depth of 3km. Using self‐developed MTEM system, we presented the results obtained from mineral exploration study carried out in China. Lastly, we proposed the SOTEM method for a greater detection depth (1.5km) than traditional loop source TEM (500m) with a small offset and high resolution. [ABSTRACT FROM AUTHOR]

A strategy to quantitatively evaluate the water content of aquifers was developed using transient electromagnetic (TEM) geo-electrical data and a database of generalized specific capacities obtained by pumping tests. Through regression analysis, a local (site-dependent) relationship was established between the generalized specific capacity and the aquifer's average resistivity. According to the relationship, the quasi-generalized specific capacity can be obtained using TEM data from across the entire survey area. The methodology was tested in a thick composite coal seam aquifer system with abundant water. By using the generalized specific capacities of 11 pumping wells and the average resistivities derived from TEM, a negative power function was established between the aquifer water volume and the area's resistivity. Using the quasi-generalized specific capacity provided a clearer understanding. [ABSTRACT FROM AUTHOR]

In northern China, thick loess strata with low resistivity are widely present and can shield the deep induced electromagnetic field signal and influence the accuracy of deep targets while electromagnetic prospecting is being performed. To achieve deep target exploration with high resolution, a new technique known as the short offset transient electromagnetic method (SOTEM) is applied in this research area. This method can be used to perform near-source configuration surveys, but shows no obvious difference between the deep magnetite deposit and low-resistivity layer in this survey area. Therefore, it cannot explore the magnetite deposit directly using the traditional magnetic component (Hz) of SOTEM. The Ex component, which can more effectively distinguish the high-resistivity surrounding rock and overlying low-resistivity layer than the Hz component, is used for exploration. First, 2D forward modeling and sensitivity analysis of the high-resistivity body are carried out to determine the different responses of the Ex and Hz components, respectively. Moreover, to better determine the interface between the surrounding rock and low-resistivity layer, 1D Occam inversion and the generalized inverse matrix inversion method are used. Furthermore, aiming at the static effect of the Ex component in field exploration, joint inversion of the Ex and Hz components is carried out for comprehensive interpretation. Finally, a field test is conducted, and the drilling results are used for verification. The research results can provide an effective geophysical model for the exploration of contact metasomatic magnetite deposits. [ABSTRACT FROM AUTHOR]

The detection accuracy of the grounded-wire transient electromagnetic method is affected by the incorrect geoelectric structure and burial depth due to shadow and source overprint effects. To better understand these effects, the three conditions under which these effects are present are analyzed separately. First, the analytical expressions are derived for computing the response of the formative wave and the surface wave in homogenous earth. The effects of the formative wave at the anomaly’s location and at the receiving site are analyzed. Then, the response variation due to the presence of an anomaly between the transmitter and the receiver is quantitatively analyzed using the finite-difference method. Finally, the effects of shadow and source overprint on the data inversion are investigated, which is verified by a case study. The wrong geoelectric information is caused by the shadow and source overprint effects. To avoid this, multisource observation can be used to weaken and utilize the shadow and source overprint effects. [ABSTRACT FROM AUTHOR]

Huoqiu iron deposit is a typical Precambrian banded iron-formation (BIF) field which is located in the North China Craton (NCC). To detect the deep ore bodies around Dawangzhuang Village in Yingshang County, north of the Huoqiu deposit field, electromagnetic methods were tested. As the ore bodies are buried under very thick conductive Quaternary sediments, the use of EM methods is a great challenge. Short-offset transient electromagnetic method (SOTEM) was applied in the area as we wanted to test due to its detection depth and resolution. A 2D model was first built according to the geology information and magnetic measurement results. Then, 2D forward and 1D inversion were carried out using FDTD and Occam's algorithm, respectively. The synthetic modeling results helped us with the survey design and interpretation. Two 1400-m-long survey lines with offset of 500 and 1000 m were laid perpendicular to the BIF's strike, and the transmitting parameters were selected by a test measurement at the vicinity of a local village. Finally, the structure of survey area and BIF bodies were determined based on the 1D inversion results of real data, and showed a consistency with the subsequent drill results. Our application of SOTEM in detecting hidden BIF buried under very thick conductive layer has shown that the method is capable of penetrating great depth more than 1000 m even in a very conductive environment and will be an effective tool for deep resources investigation. [ABSTRACT FROM AUTHOR]

The North China-type coalfield is the most important coalfield in China. With the development of Chinese economy, shallow coal resources (<600 m) have been exhausted and large-depth detection is being conducted. Water-inrush is disastrous for coal mining. However, large-depth (600-1200 m) detection of water-filled zones in the North China-type coalfield is a difficult geophysical task due to its low-resistivity coverage. The traditional loop-source transient electromagnetic method (TEM) cannot realize large-depth detection. On the other hand, high-resolution detection of LOTEM is limited by the problem of recording points and large volume effect. To explore the large-depth targets with high-resolution, Short-offset grounded TEM (SOTEM) was applied in the North China-type coalfield. SOTEM is one branch of grounded-wire TEM. The response of SOTEM is calculated using superposing-dipole method rather than the direct-dipole approximation, which is used in the calculation of the response of LOTEM. This paper analyzes the comparison of the resolution and detection depth between SOTEM and loop-source TEM at first. Compared to the loop-source TEM with frequently used parameters, the detection depth of SOTEM with the usual setup parameters is about twice of magnitude, and the resolution capability of SOTEM at large depth is higher than that of loop-source TEM. Then, the resolution capability and detection depth between LOTEM and SOTEM are analyzed. For the grounded-wire TEM, offsets are strictly related to the detection depth. So, the detection depth of LOTEM with larger receiver-transmitter offset will be greater. However, at the depth of 600-1200 m, the resolution capability to conductive targets of SOTEM is higher than that of LOTEM. At last, SOTEM with a 1000-m long source and 1000-2000 m offset is applied to the 1200 m-depth exploration of water-filled zones in the North China-type coalfield. The induced voltage is observed and transformed into magnetic field. Then, the data is inverted using the least mean fourth algorithm. The distribution of water on the top and bottom surface of the large-depth No. 4 coal seam is given, and is verified by the drilling result. [ABSTRACT FROM AUTHOR]

The North China Craton is one of China's major gold-producing areas. Breakthroughs have been continually made in deep prospecting at depths of 500–2000 m in the Jiaodong Peninsula, and geophysical methods have played an important role. Given that the geophysical signals of deep-seated gold deposits are difficult to detect, due to their thick overburden layers, conventional geophysical methods are not suitable for deep prospecting. Therefore, this study upgrades the geological-geophysical prospecting model, which is based on the deep metallogenic model and geophysical method of large exploration depths. Based on the analysis of the metallogenic geological factors of the altered-rock-type gold deposits in the fracture zones of the Jiaodong Peninsula, this study proposes that the gold deposits are controlled by large-scale faults, generally occur near the contact interfaces between the Early Precambrian metamorphic rock series and Mesozoic granitoids, and exhibit a stepped metallogenic model. This model then becomes the prerequisite and basic condition for deep prospecting by geophysical methods. For this reason, the traditional geophysical model, which focuses on the exploration of shallow mineralization anomalies, is transformed into a comprehensive multi-parameter geological-geophysical qualitative prospecting model highlighting the exploration of ore-controlling structural planes. The model adopts various frequency domain methods (e.g., CSAMT, AMT, WFEM), reflection seismology, and other methods to detect the deep geological structure. The characteristics of parameters such as gravity and magnetism, resistivity, polarizability, and the seismic reflection spectrum are applied to identify the ore-controlling fault location and dip angle change, and to estimate the ore-bearing location according to the stepped metallogenic model. The prospecting demonstration of deep-seated gold deposits in the Shuiwangzhuang mining area indicates the effectiveness of the comprehensive model. The comprehensive deep prospecting model effectively solves the problem of deep prospecting of gold deposits controlled by faults, promotes the great breakthrough of deep prospecting in the Jiaodong Peninsula, and provides an important technology demonstration for deep prospecting throughout China. [ABSTRACT FROM AUTHOR]

Combining the adaptive shrinkage genetic algorithm in the feasible region with the imaging of apparent vertical conductance differential, we have inverted the TEM conductive thin layer. The result of the inversion demonstrates that by adaptive shrinkage in the feasible region, the calculation speed accelerates and the calculation precision improves. To a certain extent, in this method we surmount the transient electromagnetic sounding equivalence and reduced equivalence scope. Comparison of the inverted result with the forward curve clearly shows that we can image the conductive thin layer. [ABSTRACT FROM AUTHOR]

Simulation performance comparison of various linear multiuser and parallel interference cancellation (PIC) detectors in the presence of imperfect power control and channel estimation is presented. Results show that imperfect power control degrades even the performance of a single-user detector. Therefore, tight power control is highly indispensable for suboptimal detectors to maintain a good performance. When power control is not perfect, interference cancellation detectors can outperform linear multiuser detectors. Among cancellation detectors, the conventional [1] and partial PIC [2] detectors are fairly sensitive to channel estimation error, while the LMS PIC [3] is quite robust in this regard. [ABSTRACT FROM AUTHOR]