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This paper introduces a new formulation of limit analysis based on nodal integrations for calculating static and seismic collapse loads in geotechnical engineering. Unlike the classical kinematic limit analysis, our newly proposed formulation of upper-bound limit analysis using mixed elements is expressed in terms of the stress fields rather than displacement fields. The numerical framework approximates stress and velocity fields using low-order triangular elements with a strain smoothing technique. Subsequently, the weak form of the equilibrium conditions and flow rule are imposed over nodal smoothing cells rather than elements. The final form of stress mixed formulation is established on nodal smoothing cells and is cast as a set of conic constraints, allowing the stress fields to be directly determined using conic programming algorithms. Additionally, the determination of kinematically admissible displacement fields is achieved through duality theory. We demonstrate the robustness and accuracy of our numerical scheme through benchmark examples involving static and seismic collapse loads, such as bearing capacity and tunnel stability, showcasing its practical application. Although the proposed scheme outperforms other traditional numerical schemes and smoothed limit analysis in terms of accuracy and efficiency, the gain in performance is offset by a loss of rigour. Furthermore, we incorporate a simple non-associated plasticity scheme into the analyses to assess dilation-dependent collapse loads. The newly proposed numerical scheme of the stress-based upper-bound limit analysis is then utilised to assess the influence of the dilation on the static and seismic collapse loads and their failure mechanism, giving some valuable insights into the dilation-dependent collapse loads under seismic conditions. [ABSTRACT FROM AUTHOR]

Dicer substrate interfering RNAs (DsiRNAs) destroy targeted transcripts using the RNA-Induced Silencing Complex (RISC) through a process called RNA interference (RNAi). This process is ubiquitous among eukaryotes. Here we report the utility of DsiRNA in embryos of the sea urchin Lytechinus variegatus (Lv). Specific knockdowns phenocopy known morpholino and inhibitor knockdowns, and DsiRNA offers a useful alternative to morpholinos. Methods are described for the design of specific DsiRNAs that lead to destruction of targeted mRNA. DsiRNAs directed against pks1 , an enzyme necessary for pigment production, show how successful DsiRNA perturbations are monitored by RNA in situ analysis and by qPCR to determine relative destruction of targeted mRNA. DsiRNA-based knockdowns phenocopy morpholino- and drug-based inhibition of nodal and lefty. Other knockdowns demonstrate that the RISC operates early in development as well as on genes that are first transcribed hours after gastrulation is completed. Thus, DsiRNAs effectively mediate destruction of targeted mRNA in the sea urchin embryo. The approach offers significant advantages over other widely used methods in the urchin in terms of cost, and ease of procurement, and offers sizeable experimental advantages in terms of ease of handling, injection, and knockdown validation. • DsiRNA provides an RNAi approach for perturbation of sea urchin embryos. • A dilution series of DsiRNA oligos reveals properties of the Nodal gradient in establishing the Dorsal-Ventral axis. [ABSTRACT FROM AUTHOR]

Electrical circuits are present in a variety of technologies, making their design an important part of computer aided engineering. The growing number of parameters that affect the final design leads to a need for new approaches to quantify their impact. Machine learning may play a key role in this regard; however, current approaches often make suboptimal use of existing knowledge about the system at hand. In terms of circuits, their description via modified nodal analysis is well‐understood. This particular formulation leads to systems of differential‐algebraic equations (DAEs), which bring with them a number of peculiarities, for example, hidden constraints that the solution needs to fulfill. We use the recently introduced dissection index that can decouple a given system of DAEs into ordinary differential equations, only depending on differential variables, and purely algebraic equations, that describe the relations between differential and algebraic variables. The idea is to then only learn the differential variables and reconstruct the algebraic ones using the relations from the decoupling. This approach guarantees that the algebraic constraints are fulfilled up to the accuracy of the nonlinear system solver, and it may also reduce the learning effort as only the differential variables need to be learned. [ABSTRACT FROM AUTHOR]

The diagnosis of schizophrenia is associated with a complex psychopathology related to disrupted brain circuitry causing a failure in coordinating information across brain sites with no consensus regarding the mechanisms. Although schizophrenia is well-studied, the great majority of studies investigated pre-selected ROIs or Seed-based connectivity. Whole brain ROI-wise studies that consider all ROIs available simultaneously are lacking. This technique helps understand large- and local-scale dynamics of information exchange across the whole brain. We investigated ROI-wise whole brain networks in 35 participants diagnosed with schizophrenia and 41 control participants. To unveil dysfunctions in brain subnetworks and to characterize network topology, we applied a statistical tool specially developed for network comparison called network-based statistic and graph theory. We observed a hyperconnected thalamo-cortico-cerebellar subnetwork in participants with schizophrenia; nodal analysis revealed higher number of thalamic connections. Our results suggest disruptions at the local level of the subnetwork rather than globally spread across the brain and driven by hyperconnectivity. Importantly, this subnetwork emerged from an exploratory analysis directly comparing ROI-wise whole brain network. This fact makes it an important contribution to the field as additional evidence, demonstrating the high reliability of malfunction in the local thalamo-cortico-cerebellar network. [ABSTRACT FROM AUTHOR]

Most simulations of electric field driven bioeffects have considered spherical cellular geometries or probed symmetrical structures for simplicity. This work assesses cellular transmembrane potential build-up and electroporation in a Jurkat cell that includes the endoplasmic reticulum (ER) and mitochondria, both of which have complex shapes, in response to external nanosecond electric pulses. The simulations are based on a time-domain nodal analysis that incorporates membrane poration utilizing the Smoluchowski model with angular-dependent changes in membrane conductivity. Consistent with prior experimental reports, the simulations show that the ER requires the largest electric field for electroporation, while the inner mitochondrial membrane (IMM) is the easiest membrane to porate. Our results suggest that the experimentally observed increase in intracellular calcium could be due to a calcium induced calcium release (CICR) process that is initiated by outer cell membrane breakdown. Repeated pulsing and/or using multiple electrodes are shown to create a stronger poration. The role of mutual coupling, screening, and proximity effects in bringing about electric field modifications is also probed. Finally, while including greater geometric details might refine predictions, the qualitative trends are expected to remain. [ABSTRACT FROM AUTHOR]

Copyright of Elektronik Industrie is the property of Hüthig GmbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A simplified technique has been developed for accurately evaluating the steady-state performance of self-excited induction generator (SEIG). This proposed technique employs nodal analysis of the equivalent circuit of SEIG, taking the core loss resistance (Rm) also into consideration. This circuit has no voltage or current source and hence the net value of its complex nodal admittance becomes zero. The real and imaginary parts of this admittance, are then individually equated to zero and a closed-form expression for per unit (pu) speed (b), without involving the magnetizing reactance (Xm), is easily obtained in a few steps, for the specified pu frequency (a). Then, the expressions for Xm and Rm are also obtained. Subsequently, the complete performance of the SEIG is evaluated using the equivalent circuit. It is also shown that the proposed technique does not require lengthy complex derivations and it takes much less computational time, compared to the other commonly used methods for the analysis of SEIG. Test results, obtained on a three-phase, 4-pole, 3.7 kW, 230 V SEIG very closely agree with the computed values. The formulated technique is also slightly modified to make it applicable, if the performance evaluation is needed for a given pu speed. [ABSTRACT FROM AUTHOR]

Copyright of Special Oil & Gas Reservoirs is the property of Special Oil & Gas Reservoirs Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract The gas lift technique applies gas bubble injection into the vertical wells to raise production. Gas and liquid rates, shifts in flow regimes, and system equilibrium influence this process. This study explores the efficient implementation of gas lift techniques to maximize production from the Asmari Formation in the Abu Ghirab Field, southeastern Iraq, using a continuous gas lift for maximum production rate by PIPESIM TM software. The results of the gas lift design for the four wells (AGCS-33, 26, 28, and 36) show that the Vogel method provided the best results for the gas lift design, and faults and facies distribution impact the gas lift injection and oil production rates. These will become evident with wells AGCS-33 and 36 as their proximity to faults will increase oil production rates with a gas injection rate limit of 7 MMSCF/d. Conversely, for wells 26 and 28, the limit will marginally rise, starting at 5 MMSCF/d. In addition, the effect of gas lift is clearly in the middle western of the crest, which shows an increasing percentage of oil production of 136.6% at minimum rate and 198.5% at maximum for the well AGCS-26, 89.7% and 105.7% for the well AGCS-36. Wellhead pressure has a significant impact on gas-lift performance, and improving gas-lift efficiency can be accomplished using an electric control valve. The feasibility of implementing gas lift in the Asmari Formation depends on the water cut, well location, and water saturation distribution within the Formation.

Many students who enroll in a first course in linear algebra major in STEM disciplines other than mathematics. Teachers who serve such students may find it difficult to provide authentic problems from these broader areas that ignite students' interest in linear algebra. In this paper, we highlight an interdisciplinary learning activity that engages students in using linear systems of equations to model the behavior of practical electric circuits. This exercise fits nicely into standard introductory linear algebra curricula and is designed to excite students majoring in engineering, physics, or applied mathematics. We also include references to a collection of open-access resources to support instructors who want to use this material in project-based, flipped-learning, inquiry-oriented, or independent-study environments. [ABSTRACT FROM AUTHOR]

The gas lift technique applies gas bubble injection into the vertical wells to raise production. Gas and liquid rates, shifts in flow regimes, and system equilibrium influence this process. This study explores the efficient implementation of gas lift techniques to maximize production from the Asmari Formation in the Abu Ghirab Field, southeastern Iraq, using a continuous gas lift for maximum production rate by PIPESIM TM software. The results of the gas lift design for the four wells (AGCS-33, 26, 28, and 36) show that the Vogel method provided the best results for the gas lift design, and faults and facies distribution impact the gas lift injection and oil production rates. These will become evident with wells AGCS-33 and 36 as their proximity to faults will increase oil production rates with a gas injection rate limit of 7 MMSCF/d. Conversely, for wells 26 and 28, the limit will marginally rise, starting at 5 MMSCF/d. In addition, the effect of gas lift is clearly in the middle western of the crest, which shows an increasing percentage of oil production of 136.6% at minimum rate and 198.5% at maximum for the well AGCS-26, 89.7% and 105.7% for the well AGCS-36. Wellhead pressure has a significant impact on gas-lift performance, and improving gas-lift efficiency can be accomplished using an electric control valve. The feasibility of implementing gas lift in the Asmari Formation depends on the water cut, well location, and water saturation distribution within the Formation. [ABSTRACT FROM AUTHOR]

Copyright of Iraqi Journal of Chemical & Petroleum Engineering is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Iraqi Journal of Chemical & Petroleum Engineering is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Various analytical solutions for computing production and injection-induced pressure changes in aquifers and oil reservoirs have been derived over the past century. All prior solutions assumed a constant well rate as the boundary condition. However, in many practical situations, the fluid withdrawal from and/or injection into such subsurface reservoirs occurs with the aid of pump devices that maintain a constant bottomhole pressure in the well. Until now, how the well rate will decline over time, based on the pressure difference in the well relative to the initial reservoir pressure, could not be rapidly computed analytically (using the diffusivity as the key governing system parameter), because no concise expression had been derived with the boundary condition of a constant bottomhole pressure. The present study shows how the pressure diffusion equation can be readily solved for wells acting as sinks and sources with a constant bottomhole pressure condition. We consider both fractured and unfractured completions, as well as injection and production modes. The new solutions do not require an elaborate time-stepped pressure-matching procedure as in nodal analysis, the only other physics-based analytical method currently available to compute the well rate decline when a constant bottomhole pressure production system is used, which unlike our new method proposed here is limited to single well systems. [ABSTRACT FROM AUTHOR]

We propose a Neurosimilator, novel analog neuron circuit and mathematical model of its dynamics that both simulate with high precision the spiking behavior of known types of excitable cells. The analog circuit is compact and can be built using off-the-shelf components. This could facilitate its use in teaching neuroscience and biophysics. The circuit is scalable down to the pF-valued capacitors, presenting an advantage in research on the analog nerve fiber networks. The equations of circuit dynamics contain exponential non-linearities and Heaviside functions, so that the model combines features from the generalized adapting exponential integrate-and-fire neuron model and from the intermittent feedback Hindmarsh-Rose model, but it is not directly related to them. Our four-dimensional system (4D-Neurosimilator) simulates most of excitable cells' spiking, bursting and chaotic behavior depending on only fewer predefined parameters. In bursting and chaotic oscillatory patterns, the model demonstrates self-adaptive energy flow redistribution. The energy expenditure amounts to ≈36 µJ per one spiking event in original model and to ≈0.63 pJ in its down-scaled version. The model has computational cost comparable to that of the Hodgkin–Huxley model, but it tends to handle noisy input stimulations more efficiently. Our work provides novel insights to the simulation of neuron's non-linear dynamics and may constitute another choice of available model in computational neuroscience research that expands the limits of a tradeoff between accuracy, biological explainability, noise-resistance and computing time. [ABSTRACT FROM AUTHOR]

Currently, most of the wells in X Oilfield are self-flowing wells. In order to adjust the production system of oil wells in time according to the production requirements of oilfields, it is necessary to predict the ceasing-flowing time. Therefore, how to accurately predict the ceasing-flowing time is the main problem faced by the self-flowing well. As the conventional prediction methods only consider the influence of a single variable, the prediction results are not ideal. Combining the production prediction based on the long short-term memory (LSTM) neural network and the inflow and outflow dynamic curves, this study proposes a comprehensive method for predicting the ceasing-flowing time of a flowing well by considering multiple factors. Using the minimum wellhead pressure prediction method, the changes in bottom hole flowing pressure and reservoir pressure are also considered. The practical application results in X Oilfield show that the calculated and predicted results are highly consistent with the actual production data, verifying the reliability of this method. This study can provide a reference for the prediction of oil well ceasing-flowing in other oilfields. [ABSTRACT FROM AUTHOR]

Background: Skip metastases, node metastases in the lateral neck sparing the ipsilateral central neck, challenge the current concept of central-to-lateral lymphatic spread. This study sought to delineate patterns of central and lateral neck involvement in unilateral papillary thyroid cancer (PTC) and medullary thyroid cancer (MTC). Methods: This was a retrospective correlative analysis of nodal patterns in surgical specimens from patients with unilateral PTC or MTC who had undergone thyroidectomy with at least ipsilateral central neck dissection between November 1994 and January 2024 at a tertiary referral center. Results: Included were 833 patients with unilateral PTC and 640 patients with unilateral MTC. Simultaneous presence or absence of node metastases was noted in ipsilateral central and lateral neck compartments in 76.6–78.1% of patients with PTC (both node positive in 27.0–54.7% and both node negative in 23.4–49.6%) and 77.3–80.0% of patients with MTC (both node positive in 26.6–33.2% and both node negative in 44.1–53.4%). Only one ipsilateral neck compartment was node positive in 21.9–23.4% of patients with PTC and 20.0–22.7% of patients with MTC. The ipsilateral central, but not the ipsilateral lateral compartment, was node positive in 8.8–16.9% with PTC and 8.6–8.8% of patients with MTC, whereas the ipsilateral lateral, but not the ipsilateral central compartment, was node positive in 6.5–13.1% with PTC and 11.3–14.1% with MTC. Ipsilateral lateral neck involvement sparing the ipsilateral central neck was 1.5–2 times more frequent in patients with node positive MTC than patients with node positive PTC (24.2–25.2% vs. 12.9–17.1%). Greater numbers of node metastases in the ipsilateral central neck compartment were associated with more frequent involvement of the ipsilateral lateral, contralateral central, and contralateral lateral neck compartments. Thyroid tumor diameter intensified nodal spread without changing nodal spread patterns. Conclusions: These histopathological findings, which need to be interpreted in light of the respective tumor biology, offer an unprecedented glimpse at the metastatic patterns of unilateral PTC and MTC. Customizing neck dissection to the patterns of nodal spread, considering operative status (initial vs. reoperative surgery) and experience with neck dissection, may require more frequent concomitant dissections of ipsilateral central and ipsilateral lateral neck compartments. [ABSTRACT FROM AUTHOR]

Copyright of Artnodes is the property of Universitat Oberta de Catalunya and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mibale oil field considered a mature oil field, located offshore in the coastal basin of the DR Congo and discovered in 1973, has seen an evolution in its production since it began operation in 1976, starting from an initial rate of 10,000 BOPD with 3 producing wells to the current production of 5,905 BOPD from 14 wells. In 2021, the field had 393 MMstb of oil reserves in the reservoir. A thorough study of the production system was carried out, focusing on the five best producing wells, including well MIB-02. Despite traversing layers of the reservoir with high oil potential, the well is underperforming with a respective flow rate of 351 BOPD and a 60% WOR using an electric submersible pump. Following this low production, various studies were conducted, including the study on converting the activation method by proceeding with nodal analysis technique. The use of nodal analysis proved crucial in identifying the shortcomings of the production system, combining field history with analysis of production, well test, pressure, and completion data. The IPM Prosper software enabled a thorough analysis, revealing that MIB-02 had a production potential greater than its current performance. This performance was revealed after evaluation and interpretation of IPR, VLP curves and sensitivities of variables such as water cut and pressure at the first node. After interpreting these curves, the MIB-02 well had the production capacity of 4100.62 BOPD and 12463.9 BWPD. By converting the submersible electric pump activation mode to gas-lift and exploring various scenarios, production was improved with an oil flow rate of 1244.9 BOPD, water flow of 2539 BWPD, to a gas flow of 0.37346 MMscf/day and 67.1% water cut. Despite these improvements, excessive water production remains a challenge while also highlighting the complexity of the production system and the limitations of the analysis technique. Therefore, further studies can be envisaged by modeling and simulating the reservoir, considering well interventions and quantifying the remaining reserves today. This more comprehensive approach will enable a clearer vision and help decide the best optimization strategies for the Mibale field production system.

Background: Parkinson's disease (PD) is a common neurodegenerative disorder that is predominantly known for its motor symptoms but is also accompanied by non-motor symptoms, including anxiety. Objective: The underlying neurobiological substrates and brain network changes associated with comorbid anxiety in PD require further exploration. Methods: An analysis of oscillation-specific nodal properties in patients with and without anxiety was conducted using resting-state functional magnetic resonance imaging (rs-fMRI) and graph theory. We used a band-pass filtering approach to differentiate oscillatory frequency bands for subsequent functional connectivity (FC) and graph analyses. Results: The study included 68 non-anxiety PD (naPD) patients, 62 anxiety PD (aPD) patients, and 64 healthy controls (NC). Analyses of nodal betweenness centrality (BC), degree centrality (DC), and efficiency were conducted across multiple frequency bands. The findings indicated no significant differences in BC among naPD, aPD, and NC within the 0.01–0.08 Hz frequency range. However, we observed a specific reduction in BC at narrower frequency ranges in aPD patients, as well as differing patterns of change in DC and efficiency, which are believed to reflect the neurophysiological bases of anxiety symptoms in PD. Conclusions: Differential oscillation-specific nodal characteristics have been identified in PD patients with anxiety, suggesting potential dysregulations in brain network dynamics. These findings emphasize the complexity of brain network alterations in anxiety-associated PD and identify oscillatory frequencies as potential biomarkers. The study highlights the importance of considering oscillatory frequency bands in the analysis of brain network changes. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Integrated Coastal Zone Management / Revista de Gestão Costeira Integrada is the property of Associacao Portuguesa dos Recursos Hidricos and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The reliable diagnosis of electrical submersible pump (ESP) failure is a vital process for establishing of the optimal production strategies and achieving minimum development costs. Although traditional ammeter charts and nodal analysis are commonly used for ESP failure diagnosis, the techniques have limitations, as it requires manpower and is difficult to diagnose the failure in real-time. Therefore, in this study, ESP failure diagnosis was performed using the principal component analysis (PCA). First, 11 types of 9,955 pieces of data were acquired from a newly constructed ESP experimental system for 300 days. During the experimental period, ESP failure occurred twice with a significant drop in performance: first on day 112 and second on day 271. The PCA model was constructed with the 8,928 pieces of normal status data and tested with the 1,027 pieces of normal and failure status data. Three principal components were extracted from the measured data to identify the patterns of the normal and failure status. Based on the logistic regression method to analyze the efficiency of the PCA model, it was found out that the developed PCA model showed an accuracy of 93.3%. Therefore, the PCA model was found to be reliable and effective for the ESP failure diagnosis and performance analysis. [ABSTRACT FROM AUTHOR]

Copyright of Iraqi Journal of Chemical & Petroleum Engineering is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the context of power systems with a high proportion of renewable energy, energy storage plays a significant role in facilitating the consumption of renewable energy and ensuring the operational safety of power systems. However, the current power spot market's predominant power bidding model does not fully consider the physical and cost-operational characteristics of energy storage, which is not conducive to further incentivizing investment and construction of energy storage, and may indirectly affect the flexibility of energy storage in peak shaving and valley filling. This paper summarizes the key issues that need to be addressed for energy storage to participate in the spot market from two aspects: the power bidding model does not meet the requirements of the physical and cost-operational characteristics of energy storage, and the real-time market under this model cannot achieve optimal allocation of energy storage. Considering the energy constraints and cost characteristics of energy storage, a charge and discharge bidding model is proposed, which is based on the stored energy value of energy storage and is in line with the physical and cost-operational characteristics and real-time optimization needs of energy storage. Subsequently, a market clearing model for energy storage participation in the spot market under the state of energy bidding method is constructed, and based on the IEEE 39-bus test case, a comparative analysis of the nodal electricity prices, energy storage revenue, and total system costs under the proposed market participation model and the traditional power bidding model is conducted. Simulation results show that the proposed energy storage participation model in the spot market can better utilize the value of energy storage in peak shaving and valley filling compared to the conventional power bidding model, reducing the extreme electricity prices by up to 10%, increasing single cycle revenue of energy storage by 46%, and reducing the total operating costs of the system in scenarios with significant deviations in system load in the day-ahead and real-time markets. [ABSTRACT FROM AUTHOR]

Extensive use of petroleum as fuel causes some negative developments such as; variation of climate, pollution of environment, degeneration of some living thinks, increase of some catastrophic events etc. In order to prevent these negative developments, the use of clean and endless energies such as solar energy, nuclear energy, geothermal energy, hydrogen energy etc. is needed. For the use of these energies, the development of an engine able to convert all of the heat energies into mechanical energy is needed. One of the machines being developed for this purpose is the Stirling engine. Despite that Stirling engine is not a machine being used in industrial areas, it is one of the machines on which too much investigations are ongoing. In this study, the thermodynamic performance of an alpha type Stirling engine, having a Crank-Shifted Piston Driving Mechanism, is investigated. The work, power, mean pressure and thermal efficiency are optimized with respect to cylinder length, the amount of crank shifting, relative position of cylinders, length of connecting rods, temperature of hot end and mass of the helium used as working fluid. The mathematical model used in the study consists of kinematic relations, the first law of thermodynamics, the equation of state of ideal gases, the law of conservation of mass, and the Schmidt formula. Corresponding to 3.5 g helium mass, 800 K heater temperature, 328.5 mm distance between cylinder top and crank center, 171 mm connecting rod length and 40 mm crank shifting; the analysis provided 223 J work, 24.9 bar mean pressure, 3.55 kW power and 52% thermal efficiency. [ABSTRACT FROM AUTHOR]

Introduction. Adjuvant durvalumab has become a standard treatment protocol for patients with locally advanced non-small cell lung cancer (LA-NSCLC). However, there is still limited knowledge about prognostic factors in a real-world setting across this specific patient group. Materials and methods. In our single-center retrospective study, we evaluated 45 patients to identify predictors of overall survival (OS) in LA-NSCLC. We utilized the univariable Cox proportional hazards models, and we developed multivariable Cox models after adjusting for the known clinical predictors. Results. In univariable analysis nodal status, the percentage of basophils in peripheral blood before treatment and D-dimers were associated with OS. Multivariable analysis, adjusted for age, sex, T characteristics, and nodal status revealed that the percentage of basophils is a significant predictor of OS. A higher percentage of basophils was associated with improved OS (HR = 0.077, 95% CI: 0.007-0.853, p = 0.037). Conclusions. Our study indicates that a lower serum percentage of basophils may be associated with better OS in patients with LA-NSCLC. These findings should be validated in larger cohorts. [ABSTRACT FROM AUTHOR]

Background: Nodal T-follicular helper cell lymphomas (nTFHLs) represent a new family of peripheral T-cell lymphomas (PTCLs), and comparative studies of their constituents are rare. Methods: This study retrospectively enrolled 10 patients with nTFHL-F and 30 patients with nTFHL-NOS diagnosed between December 2017 and October 2023 at six large comprehensive tertiary hospitals; 188 patients with nTFHL-AI were diagnosed during the same period at the First Affiliated Hospital of Zhengzhou University for comparison. Results: Compared with nTFHL-AI, nTFHL-NOS patients exhibited better clinical manifestations, lower TFH expression levels, and a lower Ki-67 index. However, no differences in clinicopathological features were observed between nTFHL-F and nTFHL-AI patients as well as nTFHL-NOS patients. According to the survival analysis, the median OS for patients with nTFHL-NOS, nTFHL-AI, and nTFHL-F were 14.2 months, 10 months, and 5 months, respectively, whereas the median TTP were 14 months, 5 months, and 3 months, respectively. Statistical analysis revealed differences in TTP among the three subtypes(P=0.0173). Among the population of patients receiving CHOP-like induction therapy, there were significant differences in the OS and TTP among the nTFHL-NOS, nTFHL-AI, and nTFHL-F patients (P=0.0134, P=0.0205). Both the GDPT and C-PET regimens significantly improved the ORR, OS, and PFS in nTFHL patients. Conclusion: There are significant differences in the clinical manifestations, pathology, and survival outcomes among the three subtypes of nTFHLs. However, further research with a larger sample size, and involving clinical pathology and molecular genetics is needed to determine the distinctive biological characteristics of these tumors. [ABSTRACT FROM AUTHOR]

Background: pregnancy-associated breast cancer (PABC) affects one in 3000 pregnancies, often presenting with aggressive features. Methods: We retrospectively evaluated a cohort of 282 young BC patients (≤45 years old) treated between 1995 and 2019, dividing them into three groups: nulliparous women, women with PABC (diagnosed within 2 years since last pregnancy) and women with BC diagnosed > 2 years since last pregnancy. This last group was further stratified according to the time between pregnancy and BC. The analysis encompassed histological factors (tumor size, histotype, grading, nodal involvement, multifocality, lympho-vascular invasion, hormone receptor expression, Ki-67 index, and HER2 expression), type of surgery and recurrence. Results: Age at diagnosis was younger in nulliparous than in parous women (p < 0.001). No significant differences were noticed regarding histological characteristics and recurrences. At univariate analysis, nodal involvement (OR = 2.4; p < 0.0001), high tumor grade (OR = 2.6; p = 0.01), and lympho-vascular invasion (OR = 2.3; p < 0.05), but not pregnancy (OR = 0.8; p = 0.30), influenced DFS negatively. Multivariate analysis confirmed nodal involvement as the only negative independent prognostic factor for a worse DFS (OR = 2.4; p = 0.0001). Conclusions: in our experience, pregnancy is not an independent adverse prognostic factor for BC DFS. [ABSTRACT FROM AUTHOR]

The intake plugging of an electrical submersible pump (ESP) has presented a formidable challenge to conventional ESP wells. Attention to cumulative solid deposition is essential since it intensifies the intake plugging severity and impedes ESP performance. We present a new approach to evaluate the ESP performance degradation during increased intake plugging severity. In particular, we employ the intake plugging factor, rate-derating factor, and affinity law to calculate the new ESP speed at different plugging conditions. We used Schlumberger PIPESIM software to perform nodal analysis of the newly calculated ESP speed. The result was validated using the actual field data and compared to the field cases that reported the intake plugging issue. The nodal analysis showed a steady maximum ESP head with zero rate derating at the shut-in point. The intake plugging factor caused a significant reduction in the ESP operating rate and increased pump intake pressure and annulus liquid level. Based on the existing intake plugging field data, we established the quantitative standard for the normal and abnormal intake plugging factor range. The observed results agreed with the field downhole data recorded during the intake plugging problem. We identified that regulating the ESP speed to the reduced operating rate could minimize unexpected pump stoppage. It is also possible to carefully monitor the intake plugging problem by combining the annulus liquid level, the signature of pump intake pressure, and a deadhead test. [ABSTRACT FROM AUTHOR]

In the context of oil and gas extraction, a dead well refers to a well that has ceased to produce hydrocarbons. The major problems that account for this are: the reservoir has been depleted, the pressure has dropped too low to allow for extraction, or there are technical issues such as blockages or equipment failure. The main objective of this paper is to analyze the performance of a dead well called K88 (for confidential reasons) activated by the progressive cavity pump (PCP) in order to improve and maximize the oil flow rate produced. The completion, reservoir, production pressure, volume, and temperature (PVT) data are processed under Excel and Prosper software by using nodal analysis, sensitive analysis, economic analysis, and decline curve methods to obtain the results. The results showed that well K88 activated by the PCP has an oil flow rate of 1600.9 STB/day. The optimization makes it possible to obtain a net oil flow rate of 2005 STB/day associated with a head pressure of 45 psig. According to the economic calculation results, a gain in production is noticed during 10 years of production and a return on investment at the latest 39 days of production.

The hydraulic fracturing technique is a widely used technique worldwide, making it interesting to study. This technique was applied for the first time in Iraq on a tight carbonate reservoir in the Halfaya oil field. In this field, the oil production rates, and flowing pressure were low during production periods reflecting a problem for the development plan designed to increase production using a hydraulic fracture technique. Initially, the hydraulic fracture well showed high oil-producing rates, but then, quickly experienced a high decline failing to keep a stable production rate. To address this problem, it is important to describe and analyze the behavior of pilot hydraulic fracturing wells during their production period, study the inflow performance relationship (IPR), and determine the optimum wellhead pressure above the bubble point pressure (Pb) to avoid loss of lifting energy. Furthermore, it identifies the allowable flow rate to keep stable production, investigates the effect of selecting internal tubing size, and reveals a future production procedure for hydraulic fracture wells. This study reveals that the transient inflow performance relationship observed in the production history of hydraulic fracture well in the tight carbonate reservoir and traditional inflow performance relationship concepts are not applicable. The optimum wellhead pressure for stability in production for Wells w-5 and w-55 is determined to be 750 and 580 psi with optimum rates of 800 and 450 Bbl/D, respectively. The results also showed that producing at a high flow rate may cause a depletion in the fracture potential storage without giving an opportunity for a reservoir to compensate for the produced fluid into fracturing potential storage. The internal tubing size has a passive effect on the hydraulic fracture well, as an increase in size causes an unstable flow zone. Lastly, future production procedures emphasize keeping wellhead pressures stable or increasing them if they drop. This can be accomplished by re-adjusting the choke size according to any changes observed.

Currently, most of the wells in X Oilfield are self-flowing wells. In order to adjust the production system of oil wells in time according to the production requirements of oilfields, it is necessary to predict the ceasing–flowing time. Therefore, how to accurately predict the ceasing–flowing time is the main problem faced by the self-flowing well. As the conventional prediction methods only consider the influence of a single variable, the prediction results are not ideal. Combining the production prediction based on the long short-term memory (LSTM) neural network and the inflow and outflow dynamic curves, this study proposes a comprehensive method for predicting the ceasing–flowing time of a flowing well by considering multiple factors. Using the minimum wellhead pressure prediction method, the changes in bottom hole flowing pressure and reservoir pressure are also considered. The practical application results in X Oilfield show that the calculated and predicted results are highly consistent with the actual production data, verifying the reliability of this method. This study can provide a reference for the prediction of oil well ceasing–flowing in other oilfields.

Abstract The intake plugging of an electrical submersible pump (ESP) has presented a formidable challenge to conventional ESP wells. Attention to cumulative solid deposition is essential since it intensifies the intake plugging severity and impedes ESP performance. We present a new approach to evaluate the ESP performance degradation during increased intake plugging severity. In particular, we employ the intake plugging factor, rate-derating factor, and affinity law to calculate the new ESP speed at different plugging conditions. We used Schlumberger PIPESIM software to perform nodal analysis of the newly calculated ESP speed. The result was validated using the actual field data and compared to the field cases that reported the intake plugging issue. The nodal analysis showed a steady maximum ESP head with zero rate derating at the shut-in point. The intake plugging factor caused a significant reduction in the ESP operating rate and increased pump intake pressure and annulus liquid level. Based on the existing intake plugging field data, we established the quantitative standard for the normal and abnormal intake plugging factor range. The observed results agreed with the field downhole data recorded during the intake plugging problem. We identified that regulating the ESP speed to the reduced operating rate could minimize unexpected pump stoppage. It is also possible to carefully monitor the intake plugging problem by combining the annulus liquid level, the signature of pump intake pressure, and a deadhead test.

This work introduces a novel data‐driven model‐free modified nodal analysis (MNA) circuit solver. The solver is capable of handling circuit problems featuring elements for which solely measurement data are available. Rather than utilizing hard‐coded phenomenological model representations, the data‐driven MNA solver reformulates the circuit problem such that the solution is found by minimizing the distance between circuit states that fulfill Kirchhoff's laws, and states belonging to the measurement data. In this way, the formerly inevitable demand for model representations is eliminated, thus avoiding the introduction of related modeling errors and uncertainties. The proposed solver is applied to linear and nonlinear RC‐circuits and to a half‐wave rectifier. [ABSTRACT FROM AUTHOR]

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In this study, we determine the stress release from the 2003 Bam earthquake (Mw 6.6) by applying the stress inversion technique to focal mechanisms of 199 aftershocks. There is no evidence of significant surface faulting that can be used to study the faulting pattern of the Bam fault zone. Therefore, we applied two independent methods for identifying the faulting pattern in this zone: the instability criterion based on the analysis of orientations of nodal planes of focal mechanisms with respect to the regional stress, and the Fry method based on the analysis of spatial clustering of aftershock foci. The results show that the fault associated with the 2003 Bam earthquake is well oriented for shearing under the present-day regional stress. We identified four sets of faults with a close angular relation to the maximum horizontal compression (SHmax) that have been (re)activated. These faults include strike-slip (right lateral and left lateral), thrust, and normal faults that are oriented approximately oblique, perpendicular, and parallel relative to the SHmax, respectively. The direction of the SHmax is N31° E. Based on the results, we propose to apply the instability criterion and the Fry method to seismic data as two valuable and independent techniques in order to constrain the kinematic and active faulting in the area. [ABSTRACT FROM AUTHOR]

The neck control strategies of early-stage oral squamous cell carcinoma (OSCC) patients with clinical node-negative neck remain uncertain. These patients could be benefit from elective neck dissection (END) alongside primary tumor excision; but current evidence on END versus observation for OSCC of stage I only is not yet analyzed collectively in detail. Herein, this short communication aimed to evaluate the neck control strategies of stage I OSCC, mainly END versus observation. A total of 740 patients with stage I OSCC, comprising 434 underwent END and 306 received observation, were identified from literature. The results showed that stage I OSCC patients would not be benefit from END based on the analysis of neck nodal recurrence and overall survival. An ideal strategy would likely be to avoid neck dissection for stage I OSCC patients with N0 neck. Immune checkpoint therapy is such a potential strategy, which aims at eliciting potent antitumor immune responses within lymph nodes hold promise for treating patients with early-stage OSCC and may prove more efficacious than lymphadenectomy in a variety of scenarios. Consequently, neck dissection for stage I OSCC could be approached with caution, particularly in patients receiving immune checkpoint therapy. [ABSTRACT FROM AUTHOR]

Various analytical solutions for computing production and injection-induced pressure changes in aquifers and oil reservoirs have been derived over the past century. All prior solutions assumed a constant well rate as the boundary condition. However, in many practical situations, the fluid withdrawal from and/or injection into such subsurface reservoirs occurs with the aid of pump devices that maintain a constant bottomhole pressure in the well. Until now, how the well rate will decline over time, based on the pressure difference in the well relative to the initial reservoir pressure, could not be rapidly computed analytically (using the diffusivity as the key governing system parameter), because no concise expression had been derived with the boundary condition of a constant bottomhole pressure. The present study shows how the pressure diffusion equation can be readily solved for wells acting as sinks and sources with a constant bottomhole pressure condition. We consider both fractured and unfractured completions, as well as injection and production modes. The new solutions do not require an elaborate time-stepped pressure-matching procedure as in nodal analysis, the only other physics-based analytical method currently available to compute the well rate decline when a constant bottomhole pressure production system is used, which unlike our new method proposed here is limited to single well systems.

This study investigates the well named X (for confidential reasons) of the field called Y which initially was productive with the natural energy of the reservoir of the oil in the absence of water. After a few years of production, water began to overflow excessively in the well. The goal of this paper is to maximize the oil production in an oil well X by reducing water ingress. The Pressure Volume Temperature (PVT) data, completion data, and reservoir data are analyzed via PIPESIM and Excel software by using the nodal analysis method to get the well performance and decline curve for predictions. Two scenarios are considered: firstly, to install an electric submersible pump (ESP) to activate the X well and secondly to make a new perforation. The ESP is installed at 11300 ft where the water production flow rate is 5586.264 STB/d and the oil production flow rate is 1396.566 STB/d. The new perforation is installed at 12038 ft where the water production flow rate is 277.1693 STB/d and the oil production flow rate is 5543.387 STB/d. To have the optimal parameters, the sensitivity analysis is applied to the flowline diameter and the wellhead pressure. The optimal parameter values obtained are 308.6128 STB/d for the water production flow rate and 5863.643 STB/d for the oil production flow rate. The new perforation is appropriate because this scenario allows water reduction, oil production maximization, profitability of 98086854 $, and a return on investment in 5 months during 16 years of production.

Single‐phase loads and photovoltaic generation cause three‐phase imbalance in distribution systems, and prospective growth of normal chargers of electric vehicles may even increase the imbalance. The analysis of such unbalanced systems requires the three‐phase power‐flow calculation. Since existing methods require the admittance matrices of three‐phase transformers, they must be derived for all possible winding connection patterns in advance to its computer‐code implementation. This paper proposes a three‐phase power‐flow calculation method which formulates circuit equations using the modified nodal analysis, making it possible to automatically handle any winding connection. The power‐flow constraints are then embedded into the circuit equations using a fixed‐point iteration. Newton‐Raphson, backward/forward sweep and fixed‐point iteration methods are the existing three categories of solution methods. Newton‐Raphson methods may show convergence problems due to the high R/X ratios of distribution lines. Backward/forward sweep methods cannot be used, because loops are temporarily formed in a distribution system during circuit switching. These justify the use of a fixed‐point iteration. In this paper, the proposed method is validated by practical examples. [ABSTRACT FROM AUTHOR]