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Imaging-guided percutaneous microwave ablation (MWA) with high thermal efficiency comprises rapid, successful management of small renal cell carcinomas (RCCs) in selected patients. Ultrasound Committee of Chinese Medical Association, Interventional Oncology Committee of Chinese Research Hospital Association developed evidence-based guidelines for MWA of RCCs after systematically reviewing the 1969–2019 literature. Systematic reviews, meta-analyses, randomized controlled trials, cohort, and case–control studies reporting MWA of RCCs were included and levels of evidence assessed. Altogether, 146 articles were identified, of which 35 reported percutaneous MWA for T1a RCCs and 5 articles for T1b RCCs. Guidelines were established based on indications, techniques, safety, and effectiveness of MWA for RCCs, with the goal of standardizing imaging-guided percutaneous MWA treatment of RCCs.Key points Microwave ablation is recommended for managing small renal cell carcinoma in selected patients. Imaging protocols are tailored based on the procedural plan, guidance, and evaluation. Patient’s selection evaluation, updated technique information, clinical efficacy, and complications are recommended to standardize management. A joint task force (multidisciplinary team) summarized the key elements of the standardized report.

A novel strategy involving warm rolling and tempering-annealing was introduced to optimize the strength-ductility balance of Fe-10.2Mn-2.2Al-0.41C-0.6 V (wt. %) steel. The V- and κ-carbide particles produced during the tempering are critical for tailoring the austenite characteristics during the subsequent annealing. Austenite that nucleates on Mn-rich κ-carbides inherit their high Mn content and fine grain size. Quantitative calculations suggest that the pinning effect exerted by the V-carbide particles strongly resists grain boundary motion and recrystallization grain growth, further refining the final microstructure. Moreover, the dual nano-sized particles induce abnormal variations in the grain size and fraction of austenite, influencing the deformation mechanisms. In the absence of deformation twins, the fresh martensite develops into “separating walls” to refine the microstructure and further enhances the work hardening in addition to the complex dislocation mobile. Finally, the tempered-annealed sample demonstrated a simultaneous increase in the yield and tensile strengths from 1166 to 1452 MPa and 1507–1727 MPa, but a slight decrease in the total elongation from 18.6% to 16.8% compared to annealed sample, achieving a good strength-ductility balance.

High-strength steels support the rapid development of modern automobile industry. Especially quenching-partitioning (QP) steels have presented the considerable potential thanks to their excellent mechanical properties. In recent years, quenching-partitioning-tempering (QPT), as well as other processes developed from QP process (DF-QP processes), have received much attention. Numerous QP and QPT steels have been widely used in automobile body materials. This paper summarizes the design principles of QP, QPT, and DF-QP processes of the latest research progress on microstructures and mechanical properties of the high-strength and toughness steels. Furthermore, three key aspects, involving of (i) the carbon (C) partitioning behavior during heat-treatment process and its influence on austenite stability, (ii) the internal relationship between austenite stability and deformation mechanism, and (iii) the influence of micro-alloying elements on microstructure, are summarized in the QPT steels. Finally, the service performances of above-mentioned steels are evaluated and their development prospects are forecasted.

Accurate prediction of deformation behavior of metal plate in deformation zone is the key point for rolling cladding process. At present, there is a lack of accurate analytical model about the deformation of metal plate in deformation zone. Therefore, an analytical model of the deformation characteristics in deformation zone for the two-layered metal clad plate produced by asymmetric rolling is established according to the practical requirements. Firstly, the stream function field model of the clad plate in the deformation zone is founded by using the stream function method. Based on the stream function field, the velocity field model of the clad plate in the deformation zone is established, and the precision of the velocity field model is demonstrated by the comparison between the finite element and the model analytical results. Based on upper bound theory, the layer thickness of the clad plate after rolling and the ratio of deformation power, friction power and shear power to the total power were calculated by minimizing the total rolling power. Finally, based on the thickness of clad plate after rolling and velocity field model, an analytical model is established to calculate the equivalent strain of the clad plate in the deformation zone. The accuracy of the analytical model is tested by the rolling cladding experiments and the finite element simulations. The results indicate that the analytical model has high precision and which makes it useful to predict the deformation behavior in the clad plate rolling process.

The rapid development of automotive industry results in a series of increasingly serious problems such as energy consumption and environmental pollution, so that developing the automotive steels with high-strength and low-density is of great significance for energy conservation and emission reduction. Recently, Fe–Mn–C–Al system steel is favored by numerous researchers because of its low density and excellent combination of strength and ductility. However, too much Al addition inevitably triggers various changes of microstructure, deformation mechanism, and mechanical properties. In this paper, the composition design, production process, strengthening and strain hardening mechanism, and microstructure evolution are systematically expounded. The discussion mainly focuses on various strengthening (solid solution strengthening, grain refinement strengthening and precipitation strengthening) and strain hardening mechanisms (phase transformation-induced-plasticity (TRIP), twinning-induced-plasticity (TWIP), microband-induced-plasticity (MBIP), shear-band-induced-plasticity (SIP) and dynamic slip band refinement (DSBR), etc.). Also, the existing problems and future challenges in Fe–Mn–Al–C low-density steels are pointed out via analyzing the service performance (cryogenic performance, impact toughness, fatigue performance, hydrogen embrittlement, wear performance, and tensile properties). Finally, we look forward to the future development direction of Fe–Mn–Al–C low-density steels and provide the valuable ideas.

Abstract When plates with edge cracks in the rolling process is straightened by cyclic tensile and compressive stress, the tip of edge crack always accompanied by stress concentration, which leads to crack propagation. In this paper, damage parameters are imported into the plate straightening model based on determining the GTN damage parameters of magnesium alloy materials by inverse finite element calibration method, the influence of different straightening process schemes and prefabricated V-shaped crack geometry on crack growth is analyzed through the way of the combination of simulation and straightening experiment. The results show that the peak values of equivalent stress and equivalent strain under each straightening roll appear at the crack tip. The value of longitudinal stress and equivalent stain decrease with the distance to crack tip becomes larger. The peak value of longitudinal stress appears when the crack circumferential angle is about 100°, and the crack tip is easy to form crack propagation; when the plate passes roll 2 and roll 4, the equivalent stress and strain concentration at the crack tip are most obvious; when the reduction reaches a certain degree, the void volume fraction (VVF) reaches the VVF of the material breaking; with the increase of the entrance reduction, the number of VVF at the crack tip which reaches the material fracture increases, and the length of crack propagation increases; the stress concentration at the tip of V-shaped crack with large length–width ratio is obvious, and the VVF is more likely to reach the VVF at the time of material fracture, crack initiates and propagates easily.

ObjectiveTo compare the diagnostic value of cytobrush, ERCP-guided biopsy, SpyGlass direct visual impression and SpyGlass-guided biospy (SpyBite) in the differential diagnosis of benign and malignant bile duct strictures.MethodsThe data of 1,008 patients who were clinically diagnosed with indeterminate biliary strictures and underwent ERCP-guided biopsy, cytobrush, SpyGlass direct visual impression or SpyBite at the First Affiliated Hospital of Nanchang University between January 2010 and December 2019 were collected and analyzed retrospectively. The final diagnose was determined by surgical pathological specimen or follow-up (Malignant stricture can be identified if the stricture showed malignant progression during one year of follow-up). The differential diagnostic value of the above endoscopic diagnostic methods was evaluated by means of sensitivity, specificity, accuracy, positive predictive value, negative predictive value, etc. and safety was evaluated by the incidence rate of adverse events.ResultsIn terms of sensitivity, standard biopsy group (48.6%) and SpyBite group (61.5%) were significantly higher than cytobrush group (32.0%), and visual impression group (100%) was significantly higher than any other group. As far as specificity was concerned, cytobrush group (99.0%), standard biopsy group (99.3%) and the SpyBite group (100%) were significantly higher than visual impression (55.6%), but there was no statistical difference among the three groups above. As far as accuracy was concerned, standard biopsy group (65.3%), and SpyBite group (80.0%) were significantly higher than cytobrush group (44.4%), and SpyBite group (80.0%) was significantly higher than visual impression group (54.8%). In terms of safety, visual impression group and SpyBite group were significantly higher than cytobrush group and standard biopsy group in post-ERCP cholangitis.ConclusionSpyBite combined with SpyGlass-guided visual impression was better for differential diagnosis of benign and malignant bile duct strictures in terms of sensitivity and accuracy compared with conventional endoscopic diagnostic methods such as cytobrush and standard biopsy. Furthmore, the incidence rates of adverse events after SpyGlass examination was similar to those after conventional endoscopic diagnostic methods except for higher cholangitis, which could be controlled by antibiotics and might be avoided by adequate biliary drainage.

Higher-order topological insulators hosting intriguing topologically protected hinge or corner states are of significant research interest. However, materials that possess higher-order topological hinge states associated with gapless bulk Dirac phases still need to be explored. Using first-principles calculations with hybrid exchange functional, we explore the electronic structure and topological properties of Y _3 InC and a few of its sister compounds, totaling 16 bulk materials. A symmetry-protected triple point phase, with dominated d-t _2 _g character, is observed in Y _3 InC without spin–orbit coupling (SOC). Interestingly, the SOC induces a twin Dirac node phase in the bulk Y _3 InC. Furthermore, the computed Z _4 topological invariant reveals the higher-order topological nature of investigated materials. To demonstrate the gapless hinge states, we conduct edge state calculations using a rod-shaped geometry of Y _3 InC. Remarkably, Y _3 InC is identified to host multi-Dirac nodes in the bulk and surface phases together with the higher-order hinge states. These results lay the groundwork for further experimental and theoretical investigations into cubic antiperovskite materials for higher-order topological phases.

Abstract Topological Dirac materials are attracting a lot of attention because they offer exotic physical phenomena. An exhaustive search coupled with first-principles calculations was implemented to investigate 10 Zintl compounds with a chemical formula of CaM2X2 (M = Zn or Cd, X = N, P, As, Sb, or Bi) under three crystal structures: CaAl2Si2-, ThCr2Si2-, and BaCu2S2-type crystal phases. All of the materials were found to energetically prefer the CaAl2Si2-type structure based on total ground state energy calculations. Symmetry-based indicators are used to evaluate their topological properties. Interestingly, we found that CaM2Bi2 (M = Zn or Cd) are topological crystalline insulators. Further calculations under the hybrid functional approach and analysis using k · p model reveal that they exhibit topological Dirac semimetal (TDSM) states, where the four-fold degenerate Dirac points are located along the high symmetry line in-between Г to A points. These findings are verified through Green's function surface state calculations under HSE06. Finally, phonon spectra calculations revealed that CaCd2Bi2 is thermodynamically stable. The Zintl phase of AM2X2 compounds have not been identified in any topological material databases, thus can be a new playground in the search for new topological materials.

Single-atomic impurities may induce novel quantum state, but they are unexplored in topological magnets. Here, the authors report spin-down polarized bound states which further interact with neighboring states to form spin-orbit split quantized orbitals in a topological magnet Co3Sn2S2.

Abstract We report a new graphene allotrope named HOT graphene containing carbon hexagons, octagons, and tetragons. A corresponding series of nanotubes are also constructed by rolling up the HOT graphene sheet. Ab initio calculations are performed on geometric and electronic structures of the HOT graphene and the HOT graphene nanotubes. Dirac cone and high Fermi velocity are achieved in a non-hexagonal structure of HOT graphene, implying that the honeycomb structure is not an indispensable condition for Dirac fermions to exist. HOT graphene nanotubes show distinctive electronic structures depending on their topology. The (0,1) n (n ≥ 3) HOT graphene nanotubes reveal the characteristics of semimetals, while the other set of nanotubes (1,0) n shows continuously adjustable band gaps (0~ 0.51 eV) with tube size. A competition between the curvature effect and the zone-folding approximation determines the band gaps of the (1,0) n nanotubes. Novel conversion between semimetallicity and semiconductivity arises in ultra-small tubes (radius

Rolling experiments of TRCed AZ31 magnesium alloy with different cryogenic treatment time were carried out to study the evolution mechanism of its microstructure and mechanical properties. The experimental results showed that with the increase in cryogenic time, the grain size of the sheets after cryogenic rolling was significantly refined, and the dislocation density and texture strength were greatly weakened. The combined effect led to a significant increase in the elongation and tensile strength of the sheet after cryogenic rolling. The tensile strength, elongation and average hardness of the sheet increased from 282.6 MPa, 8.2%, and 54.6 HV to 305.4 MPa, 16.3%, and 62.8 HV, respectively. Therefore, when the cryogenic treatment time was 60 s, the performance of the rolled sheet was the best. At the same time, the appearance of dimples after cryogenic rolling led to a change of the fracture mechanism, which was also the key to the improvement of the sheet elongation.

Abstract Currently, when magnesium alloy sheet is rolled, the method of controlling roll temperature is simple and inaccurate. Furthermore, roll temperature has a large influence on the quality of magnesium alloy sheet; therefore, a new model using circular fluid flow control roll temperature has been designed. A fluid heat transfer structure was designed, the heat transfer process model of the fluid heating roll was simplified, and the finite difference method was used to calculate the heat transfer process. Fluent software was used to simulate the fluid-solid coupling heat transfer, and both the trend and regularity of the temperature field in the heat transfer process were identified. The results show that the heating efficiency was much higher than traditional heating methods (when the fluid heat of the roll and temperature distribution of the roll surface was more uniform). Moreover, there was a bigger temperature difference between the input and the output, and after using reverse flow the temperature difference decreased. The axial and circumferential temperature distributions along the sheet were uniform. Both theoretical calculation results and numerical simulation results of the heat transfer between fluid and roll were compared. The error was 1.8%–12.3%, showing that the theoretical model can both forecast and regulate the temperature of the roll (for magnesium alloy sheets) in the rolling process.

Abstract The abounding possibilities of discovering novel materials has driven enhanced research effort in the field of materials physics. Only recently, the quantum anomalous hall effect (QAHE) was realized in magnetic topological insulators (TIs) albeit existing at extremely low temperatures. Here, we predict that MPn (M =Ti, Zr, and Hf; Pn =Sb and Bi) honeycombs are capable of possessing QAH insulating phases based on first-principles electronic structure calculations. We found that HfBi, HfSb, TiBi, and TiSb honeycomb systems possess QAHE with the largest band gap of 15 meV under the effect of tensile strain. In low-buckled HfBi honeycomb, we demonstrated the change of Chern number with increasing lattice constant. The band crossings occurred at low symmetry points. We also found that by varying the buckling distance we can induce a phase transition such that the band crossing between two Hf d-orbitals occurs along high-symmetry point K2. Moreover, edge states are demonstrated in buckled HfBi zigzag nanoribbons. This study contributes additional novel materials to the current pool of predicted QAH insulators which have promising applications in spintronics.

X. Deng et al. proved Chvátal’s conjecture on maximal stable sets and maximal cliques in graphs. G. Ding made a conjecture to generalize Chvátal’s conjecture. The purpose of this paper is to prove this conjecture in planar graphs and the complement of planar graphs. [ABSTRACT FROM AUTHOR]

Freshwater Microcystis may form dense blooms in eutrophic lakes. It is known to produce a family of related cyclic hepatopeptides (microcystins, MC) that constitute a threat to aquatic ecosystems. Most toxicological studies of microcystins have focused on aquatic animals and plants, with few examining the possible effects of microcystins on phytoplankton. In this study we chose the unicellular Synechococcus elongatus (one of the most studied and geographically most widely distributed cyanobacteria in the picoplankton) as the test material and investigated the biological parameters: growth, pigment (chlorophyll-a, phycocyanin), photosynthetic activity, nitrate reductase activity, and protein and carbohydrate content. The results revealed that microcystin-RR concentrations above 100 g L-1 significantly inhibited the growth of Synechococcus elongatus. In addition, a change in color of the toxin-treated algae (chlorosis) was observed in the experiments. Furthermore, MC-RR markedly inhibited the synthesis of the pigments chlorophyll-a and phycocyanin. A drastic reduction in photochemical efficiency of PSII (Fv/Fm) was found after a 96-h incubation. Changes in protein and carbohydrate concentrations and in nitrate reductase activity also were observed during the exposure period. This study aimed to evaluate the mechanisms of microcystin toxicity on a cyanobacterium, according to the physiological and biochemical responses of Synechococcus elongatus to different doses of microcystin-RR. The ecological role of microcystins as an allelopathic substance also is discussed in the article. 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 571577, 2004. [ABSTRACT FROM AUTHOR]

Among the families of transition metal dichalcogenides (TMDs), Pd-based TMDs have been one of the less explored materials. In this study, we investigate the electronic properties of PdX _2 (X = S, Se, or Te) bulk and thin films. The analysis of structural stability shows that the bulk and thin film (1 to 5 layers) structures of PdS _2 exhibit pyrite, while PdTe _2 exhibits 1T. Furthermore, PdSe _2 exhibits pyrite in bulk and thin films down to the bilayer. Most surprisingly, PdSe _2 monolayer transits to 1T phase. For the electronic properties of the stable bulk configurations, pyrite PdS _2 and PdSe _2 , and 1T PdTe _2 , demonstrate semi-metallic features. For monolayer, on the other hand, the stable pyrite PdS _2 and 1T PdSe _2 monolayers are insulating with band gaps of 1.399 eV and 0.778 eV, respectively, while 1T PdTe _2 monolayer remains to be semi-metallic. The band structures of all the materials demonstrate a decreasing or closing of indirect band gap with increasing thickness. Moreover, the stable monolayer band structures of PdS _2 and PdSe _2 exhibit flat bands and diverging density of states near the Fermi level, indicating the presence of van Hove singularity. Our results show the sensitivity and tunability of the electronic properties of PdX _2 for various potential applications.

We discuss two-dimensional (2D) topological insulators (TIs) based on planar Bi/Sb honeycombs on a SiC(0001) substrate using first-principles computations. The Bi/Sb planar honeycombs on SiC(0001) are shown to support a nontrivial band gap as large as 0.56 eV, which harbors a Dirac cone lying within the band gap. Effects of hydrogen atoms placed on either just one side or on both sides of the planar honeycombs are examined. The hydrogenated honeycombs are found to exhibit topologically protected edge states for zigzag as well as armchair edges, with a wide band gap of 1.03 and 0.41 eV in bismuth and antimony films, respectively. Our findings pave the way for using planar bismuth and antimony honeycombs as potential new 2D-TI platforms for room-temperature applications.

We have investigated topological electronic properties of freestanding bilayers of group IV (C, Si, Ge, Sn, and, Pb) and V (As, Sb, and, Bi) elements of the periodic table in the buckled and planar honeycomb structures under isotropic strain using first-principles calculations. Our focus is on mapping strain driven phase diagrams and identifying topological phase transitions therein as a pathway for guiding search for suitable substrates to grow two-dimensional (2D) topological insulators (TIs) films. Bilayers of group IV elements, excepting Pb, generally transform from trivial metal $\to $ topological metal $\to $ TI $\to $ topological metal $\to $ trivial metal phase with increasing strain from negative (compressive) to positive (tensile) values. Similarly, among the group V elements, As and Sb bilayers transform from trivial metal $\to $ trivial insulator $\to $ TI phase, while Bi transforms from a topological metal to TI phase. The band gap of 0.5 eV in the TI phase of Bi is the largest we found among all bilayers studied, with the band gap increasing further under tensile strain. Differences in the topological characteristics of bilayers of group V elements reflect associated differences in the strength of the spin–orbit coupling (SOC). We show, in particular, that the topological band structure of Sb bilayer becomes similar to that of a Bi bilayer when the strength of the SOC in Sb is artificially enhanced by a factor of 4. This study provides the first report that As can be a 2D TI under tensile strain. Notably, we found the existence of TI phases in all elemental bilayers we studied, except Pb.

Using thickness-dependent first-principles electronic structure calculations, we predict that hydrogenated ultra-thin films of tin harbor a new class of two-dimensional (2D) topological insulators (TIs). A single bilayer (BL) tin film assumes a 2D-TI phase, but it transforms into a trivial insulator after hydrogenation. In contrast, tin films with 2 and 3 BLs are found to be trivial insulators, but hydrogenation of 2 to 4 BL films results in a non-trivial TI phase. For 1 to 3 BLs, H-passivation converts the films from being metallic to insulating. Moreover, we examined iodine-terminated tin films up to 3 BLs, and found these to be non-trivial, with the films becoming semi-metallic beyond 1 BL. In particular, the large band gap of 340 meV in an iodine-terminated tin BL is not sustained in the iodine-terminated 2 BL and 3 BL tin films.

The patient was a 62-year-old man diagnosed as having prostatic extra-gastrointestinal stromal tumor (EGIST) who was treated with imatinib. No recurrence or metastasis was found after a 6-month follow-up. We identified 14 cases of prostatic primary EGIST in PubMed and summarized these cases with our case. The patients’ ages ranged from 31 to 78 years (average: 53.6 years), and most patients’ prostate-specific antigen (PSA) concentrations were within normal limits (92.9%, 13/14). All patients underwent imaging examinations; prostatic masses measured 6 to 14.2 cm (mean: 9.43 cm), and imaging excluded secondary prostatic masses from the intestinal tract. By immunohistochemical staining, the tumors were positive for cluster of differentiation (CD)117 (71.4%, 10/14), DOG1 (100%, 7/7), and CD34 (100%, 14/14), and negative for smooth muscle actin (SMA) (71.4%, 10/14), desmin (100%, 11/11), and S100 (100%, 12/12). Treatment depended on the results of the gene mutation detection as well as the risk estimation according to tumor size and microscopic mitotic rates (>5 per 50 high-power fields: 60%, 6/10). Among the 12 patients with reported outcomes, nine achieved good results (no recurrence or metastasis), one achieved reduced mass volume, one experienced recurrence, and one died.