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Multi-terminal HVDC grids facilitate the integration of various renewable resources from distant locations; in addition, they enhance the reliability and stability of the grid. Protection is one of the major obstacles in realizing reliable and secure multi-terminal HVDC grids. This paper presents a comprehensive review of the existing protection schemes for multi-terminal HVDC grids. First, DC fault current stages are demonstrated; in addition, fault analysis studies and the existing fault current calculation methods are reviewed. Then, HVDC grid protection requirements including multi-vendor interoperability conditions are extensively discussed. Furthermore, primary protection algorithms are classified into single- and double-ended schemes, and a detailed comparison between each category is presented such that the distinctive algorithms from each group are highlighted. Moreover, the recent DC reclosing schemes are reviewed highlighting their role in enhancing grid stability and ensuring supply continuity. Finally, available standards for HVDC protection systems alongside their design considerations and procedures are thoroughly outlined. This paper focuses on the recently proposed methods to design reliable protection schemes for multi-terminal HVDC grids and highlights the main advantages and disadvantages associated with them; thus, it offers a beneficial guide for researchers in the HVDC protection field.

The large integration of inverter-based resources will significantly alter grid dynamics, leading to pronounced stability challenges due to fundamental disparities between inverter-based and traditional energy systems. While grid-following inverters (GFLIs) dominate current inverter configurations, their increased penetration into the grid can result in major stability issues. In contrast, grid-forming inverters (GFMIs) excel over GFLIs by offering features like standalone operation, frequency support, and adaptability in weak grid scenarios. GFMIs, unlike GFLIs, control the AC voltage and frequency at the common coupling point, impacting the inverter dynamic response to grid disturbances and overall stability. Despite the existing literature highlighting differences between GFLIs and GFMIs and their control strategies, a comprehensive review of GFMIs’ stability and the effects of their control schemes on grid stability is lacking. This paper provides an in-depth evaluation of GFMIs’ stability, considering various control schemes and their dynamics. It also explores different types of power system stability, introduces new stability concepts that correspond to power grids with integrated inverters, i.e., resonance and converter-driven stability, and reviews small-signal and transient stability analyses, which are the main two types of GFMI stability studied in the literature. The paper further assesses existing studies on GFMI stability, pinpointing research gaps for future investigations.

Modular multilevel converters (MMCs) based on half-bridge submodules (HBSMs) are unable to prevent the AC side contribution to DC side fault currents, thus necessitating circuit breakers (CBs) for protection. A solution to this problem is using submodules (SMs) that are capable of blocking the flow of current from the AC grid to feed the DC side fault. The full-bridge submodule (FBSM) is one type of fault blocking SM where the presence of two extra switches ensures that in the event of a DC fault, the reverse voltage from the FBSM capacitor is placed in the path of the AC side current feeding the DC side fault through the antiparallel diodes. However, the additional semiconductor switches in the FBSMs increase the converter cost, complexity, and losses. Several SM configurations have been proposed in recent years that provide DC fault blocking capability with lower losses and device counts than those of FBSMs. Besides, many of the proposed hybrid converter configurations that combine different topologies to optimize converter performance are also capable of providing DC fault blocking. Furthermore, certain SM topologies are capable of riding through DC faults by remaining deblocked and operating in static synchronous compensator (STATCOM) mode to provide reactive power support to the AC grid. In this paper, noteworthy SM and MMC configurations capable of DC fault blocking and ride-through are reviewed and compared in terms of component requirements, semiconductor losses, and DC fault handing capability. The review also includes a discussion on control strategies for MMC arm/leg energy balancing during STATCOM operation.

In the event of a DC side fault in modular multilevel converters (MMCs), the fault current contributions are initially made by submodule (SM) capacitor discharge, which occurs before the fault is detected, followed by the AC side contribution to the DC side fault. While the AC side currents can be regulated using fault blocking SMs, the initial discharge of the SM capacitors results in high DC fault currents, which can take several milliseconds to be brought under control. This paper presents a method to actively control the rate of rise of the DC fault current by regulating the discharge of SM capacitors and accelerating the suppression of fault current oscillations during fault ride-through (FRT) in a full-bridge (FB)-MMC system. In the proposed method, the discharge direction of the FBSM capacitors is reversed following the detection of a DC side fault, which leads to a reversal in the fault current direction and a fast drop-off towards the zero-crossing. Immediately after the zero-crossing of the DC fault current, the DC fault is cleared by adjusting the arm voltage references and operating the MMC as a static synchronous compensator (STATCOM) to provide voltage support to the AC grid. The proposed control scheme provides faster fault current suppression, more effective SM capacitor voltage regulation, low AC side and MMC arm current transient peaks, and an overall superior DC-FRT performance compared to methods in which the conventional fault ride-through operation is initiated immediately upon DC fault detection.

Sparing the periprostatic neurovascular bundles during robot-assisted radical prostatectomy (RARP) improves postoperative erectile function and early urinary continence recovery. The NeuroSAFE technique, a standardised frozen section analysis, enables accurate real-time detection of positive surgical margins during nerve-sparing, increasing the likelihood of successful nerve preservation. However, the impact of the technique on patient outcomes remains uncertain. We aimed to assess the effect of NeuroSAFE-guided RARP versus standard RARP on erectile function and urinary continence. NeuroSAFE PROOF was a multicentre, patient-blinded, randomised, controlled phase 3 trial done at five National Health Service hospitals in the UK. Key eligibility criteria were a diagnosis of non-metastatic prostate cancer deemed suitable to undergo RARP, good erectile function (defined as a score of ≥22 on the first 5 items of the International Index of Erectile Function [IIEF]) without medical erectile function assistance, and no previous prostate cancer treatment. No age limits were applied. Participants were randomly assigned (1:1) to standard RARP or NeuroSAFE-guided RARP using block randomisation, stratified by site. Masking of participants to allocation was maintained throughout, but patients were informed of their nerve-sparing status after the operation. Due to the nature of the intervention, operating teams were aware of treatment group. Nerve-sparing was guided by a preoperative plan in the standard RARP group and by intraoperative NeuroSAFE assessment in the NeuroSAFE group. The primary outcome was erectile function at 12 months, assessed using the IIEF-5 score, in the modified intention-to-treat population, which included all randomly assigned participants who had surgery. Secondary endpoints were urinary continence scores at 3 and 6 months, evaluated using the International Consultation on Incontinence Questionnaire (ICIQ), and the erectile function domain of the IIEF (IIEF-6) scores at 12 months. The trial is registered at ClinicalTrials.gov, NCT03317990. Between Jan 6, 2019, and Dec 6, 2022, 407 patients were recruited, of whom 381 had surgery (190 participants in the NeuroSAFE group and 191 participants in the standard RARP group), and were included in the modified intention-to-treat population. Data for the primary outcome (IIEF-5 score at 12 months) were available for 344 participants (173 in the NeuroSAFE group and 171 participants in the standard RARP group). Median follow-up was 12·3 months (IQR 11·8–12·7). At 12 months, the mean IIEF-5 score was 12·7 (SD 8·0) in the NeuroSAFE group versus 9·7 (7·5) in the standard RARP group (adjusted mean difference 3·18 [95% CI 1·62 to 4·75]; p<0·0001). At 3 months, the ICIQ score was significantly lower in the NeuroSAFE group than the standard RARP group (adjusted mean difference –1·41 [95% CI –2·42 to –0·41]; p=0·006). At 6 months, no significant difference in ICIQ score was observed between groups (adjusted mean difference –0·37 [95% CI –1·35 to 0·62]; p=0·46). At 12 months, the mean IIEF-6 score was higher in the NeuroSAFE group than in the standard RARP group (15·3 [SD 9·7] vs 11·5 [SD 9·0]; adjusted mean difference 3·92 [95% CI 2·01 to 5·83]; p<0·0001). Serious adverse events occurred in six (3%) of 190 patients in the NeuroSAFE group, and and in five (3%) of 191 patients in the standard RARP group. All adverse events were postoperative complications; no serious adverse events or deaths were attributed to the study intervention. The use of NeuroSAFE to guide nerve-sparing during RARP improves patient-reported IIEF-5 scores at 12 months and short-term urinary continence. The erectile function benefit is enhanced in patients who would not otherwise have undergone bilateral nerve-sparing by standard practice. National Institute of Healthcare Research, JP Moulton Charitable Foundation, UCLH Charity, St Peters Trust, and Rosetrees Trust.

Introduction. Enterococcus faecalis (E. faecalis) is the most important species in dentistry and plays a significant role in the etiology of persistent apical lesions after root canal treatment. Up to date, the intracanal application of 2% chlorhexidine for 7 days is the best way to eliminate E. faecalis. However, due to the ability of this bacterium to persist and survive in harsh environments, many studies have been directed towards finding an alternative strategy for prevention or eradication of it. This study was conducted to investigate the effect of bismuth nanoparticles on E. faecalis, as an etiologic factor in recurrent root canal infections. Methods. Forty patients, referred to Endodontic Ward of Shiraz University of Medical Science for endodontic pretreatment, provided root canal samples. First, all samples were transferred in Enterococcosel broth and incubated. Then, samples which showed growth were plated on blood agar plates and incubated for further PCR procedure. Nanoparticle powder was dissolved in high-purity water, and the final concentration of bismuth nanoparticles (BiNPs) was measured by the spectrophotometer. Minimum inhibitory concentration (MIC) of BiNPs against E. faecalis was determined by microbroth dilution method according to methods for antimicrobial susceptibility tests. Also, bactericidal assays were conducted in Mueller-Hinton broth medium and reported as the concentration of BiNPs that reduced the viable bacterial count by 99.9%. Results. Of all samples, 77.5% revealed the presence of E. faecalis by PCR. Also, E. faecalis growth inhibition was observed at concentrations ranging from 0.625 μg/ml to 20 μg/ml (geometric mean: 2.337 μg/ml), and the MBC values were between 1.25 μg/ml and 40 μg/ml (geometric mean: 4.781 μg/ml), which in comparison with chlorhexidine, these values were about one-eighth of chlorhexidine. Conclusion. The experimental data suggest that bismuth nanoparticles could be an interesting alternative to combat E. faecalis, which, in view of the advantages mentioned for bismuth nanoparticle like inhibiting Streptococcus mutans biofilm formation and higher antibacterial activity compared to chlorhexidine, can be suggested to be used in different fields of dentistry.

This study evaluated the distribution pattern, species diversity index (richness, diversity, and evenness), importance value index (IVI), and family importance value (FIV) of all vascular plant species and various plant community life-form spectra along the Moghan Plain–Sabalan Mountain rangelands, Ardabil province, Iran. Sampling was conducted in 11 elevation classes at 300-m elevation intervals (100–3300 masl). In each elevation interval, 30 quadrats (1 × 1 m) were laid to collect vegetation data. Different vegetation attributes (density, frequency, and canopy cover) were measured for each quadrat. Regression analyses were employed to explore the interrelation of elevation with diversity, species richness, evenness, and IVI. In total, 251 species (143 genera, 38 families) were recorded across the study area. Poaceae, Fabaceae, and Asteraceae were most dominant families according to the FIV. According to the IVI, Poa bulbosa, Festuca ovina, Medicago minima, and Artemisia austriaca were the dominant species along the elevation gradient. Total diversity and species richness showed a normal distribution along the elevation gradient. Overall, hemicryptophytes and therophytes were the dominant life forms, while chamaephytes and geophytes were less frequent forms. The life-form patterns changed along elevation gradients. While the diversity and species richness values of therophytes and chamaephytes showed a decreasing trend, hemicryptophytes increased with increasing elevation. Diversity, species richness, and evenness of geophytes were not significantly different across the elevation gradient. Class I (highly palatable) and class II (mostly palatable) species declined as the elevation increased and then increased, while class III (hardly or unpalatable) species showed a reverse trend. The difference in the abundance and distribution of species in elevation classes could be related to resource availability, overlap of habitats, habitat patchiness, land area, degree of human influence, or biotic disturbances.

Energy has a strategic role in the economic and social development of countries. In the last few decades, energy demand has been increasing exponentially across the world, and predicting energy demand has become one of the main concerns in many countries. The residential and commercial sectors constitute about 34.7% of global energy consumption. Anticipating energy demand in these sectors will help governments to supply energy sources and to develop their sustainable energy plans such as using renewable and non-renewable energy potentials for the development of a secure and environmentally friendly energy system. Modeling energy consumption in the residential and commercial sectors enables identification of the influential economic, social, and technological factors, resulting in a secure level of energy supply. In this paper, we forecast residential and commercial energy demands in Iran using three different machine learning methods, including multiple linear regression, logarithmic multiple linear regression methods, and nonlinear autoregressive with exogenous input artificial neural networks. These models are developed based on several factors, including the share of renewable energy sources in final energy consumption, gross domestic production, population, natural gas price, and the electricity price. According to the results of the three machine learning methods applied in our study, by 2040, Iranian residential and commercial energy consumption will be 76.97, 96.42 and 128.09 Mtoe, respectively. Results show that Iran must develop and implement new policies to increase the share of renewable energy supply in final energy consumption.

The diameters and heights of trees are two of the most important components in a forest inventory. In some circumstances, the heights of trees need to be estimated due to the time and cost involved in measuring them in the field. Artificial intelligence models have many advantages in modeling nonlinear height–diameter relationships of trees, which sometimes make them more useful than empirical models in estimating the heights of trees. In the present study, the heights of trees in uneven-aged and mixed stands in the high elevation forests of northern Iran were estimated using an artificial neural network (ANN) model, an adaptive neuro-fuzzy inference system (ANFIS) model, and empirical models. A systematic sampling method with a 150 × 200 m network (0.1 ha area) was employed. The diameters and heights of 516 trees were measured to support the modeling effort. Using 10 nonlinear empirical models, the ANN model, and the ANFIS model, the relationship between height as a dependent variable and diameter as an independent variable was analyzed. The results show, according to R2, relative root mean square error (RMSE), and other model evaluation criteria, that there is a greater consistency between predicted height and observed height when using artificial intelligence models (R2 = 0.78; RMSE (%) = 18.49) than when using regression analysis (R2 = 0.68; RMSE (%) = 17.69). Thus, it can be said that these models may be better than empirical models for predicting the heights of common, commercially-important trees in the study area.

Recurrence in hepatocellular carcinoma (HCC) after conventional treatments is a crucial challenge. Despite the promising progress in advanced targeted therapies, HCC is the fourth leading cause of cancer death worldwide. Radionuclide therapy can potentially be a practical targeted approach to address this concern. Rhenium-188 (188Re) is a β-emitting radionuclide used in the clinic to induce apoptosis and inhibit cell proliferation. Although adherent cell cultures are efficient and reliable, appropriate cell-cell and cell-extracellular matrix (ECM) contact is still lacking. Thus, we herein aimed to assess 188Re as a potential therapeutic component for HCC in 2D and 3D models. The death rate in treated Huh7 and HepG2 lines was significantly higher than in untreated control groups using viability assay. After treatment with 188ReO4, Annexin/PI data indicated considerable apoptosis induction in HepG2 cells after 48 h but not Huh7 cells. Quantitative RT-PCR and western blotting data also showed increased apoptosis in response to 188ReO4 treatment. In Huh7 cells, exposure to an effective dose of 188ReO4 led to cell cycle arrest in the G2 phase. Moreover, colony formation assay confirmed post-exposure growth suppression in Huh7 and HepG2 cells. Then, the immunostaining displayed proliferation inhibition in the 188ReO4-treated cells on 3D scaffolds of liver ECM. The PI3-AKT signaling pathway was activated in 3D culture but not in 2D culture. In nude mice, Huh7 cells treated with an effective dose of 188ReO4 lost their tumor formation ability compared to the control group. These findings suggest that 188ReO4 can be a potential new therapeutic agent against HCC through induction of apoptosis and cell cycle arrest and inhibition of tumor formation. This approach can be effectively combined with antibodies and peptides for more selective and personalized therapy.