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The ground state structure of NiTi martensite in experiments and existing theoretical calculations is the focus of ongoing disagreements. Based on Waitz et al.’s (2004, 2007) ...experiments, we use the first principle calculations to investigate the effect of (001) twin interface and thickness on the stability of NiTi martensite. Moreover, we determine the interface of the (001) martensitic twins observed in the experiment as the interface of twinned supercell-1 (TSC-1), in which the lattice parameters of individual unit cells are close to the experimental measurements of B19′. Furthermore, the energy per atom for TSC-1 is always between that of B19′ and B33 and does not vary with the twin thickness. Considering the structural similarity of TSC-1 and B33, an energy barrier between TSC-1 and B33 via the minimum enthalpy pathways was demonstrated. The influence of the (001) twin interface could proves the rationality of the existence of B19′ in experiments.
Micro-ejecta, an instability growth process, occurs at metal/vacuum or metal/gas interface when compressed shock wave releases from the free surface that contains surface defects. We present ...molecular dynamics (MD) simulations to investigate the ejecta production from tin surface shocked by supported and unsupported waves with pressures ranging from 8.5 to 60.8 GPa. It is found that the loading waveforms have little effect on spike velocity while remarkably affect the bubble velocity. The bubble velocity of unsupported shock loading remains nonzero constant value at late time as observed in experiments. Besides, the time evolution of ejected mass in the simulations is compared with the recently developed ejecta source model, indicating the suppressed ejection of unmelted or partial melted materials. Moreover, different reference positions are chosen to characterize the amount of ejecta under different loading waveforms. Compared with supported shock case, the ejected mass of unsupported shock case saturates at lower pressure. Through the analysis on unloading path, we find that the temperature of tin sample increases quickly from tensile stress state to zero pressure state, resulting in the melting of bulk tin under decaying shock. Thus, the unsupported wave loading exhibits a lower threshold pressure causing the solid-liquid phase transition on shock release than the supported shock loading.
Owing to the unique properties of aluminum nanoparticles, these nanoadditives show promise in improving the combustion performance of traditional hydrocarbon fuels. Here, the ignition and combustion ...processes of the simplest hydrocarbon, methane, with the addition of aluminum nanoparticles, were investigated using ReaxFF molecular dynamics simulations. The oxidation of the initially unoxidized aluminum nanoparticles is a microexplosive violent combustion process. The simulation results revealed that the presence of such aluminum nanoparticles reduces the ignition delay of methane and improves its combustion efficiency. The activation energy of methane dissociation is significantly reduced by ∼47% in the presence of aluminum nanoparticles compared to the pure methane system. It is found that the mechanism of this combustion enhancement is from the significant increase in the number of atomic oxygen with the addition of aluminum nanoparticles, which accounts for the decomposition of methane by more than 60%. Moreover, the formation of atomic oxygen is mainly caused by the instability of low-coordination atoms on the surface of the Al x O y cluster. Further simulations of aluminum particles with oxide shells show that such particles can also promote the production of atomic oxygen to a small extent. It is believed that the findings presented here provide an important perspective on understanding the influence of aluminum nanoparticles on the combustion of hydrocarbon fuels at an atomic scale, and have an instructive significance in improving combustion efficiency.
Acute heart failure (AHF) is a common disease in the emergency departments. Its occurrence is often accompanied by electrolyte disorders, but little attention is paid to chloride ion. Recent studies ...have shown that hypochloremia was associated with poor prognosis of AHF. Therefore, this meta-analysis aimed to assess the incidence of hypochloremia and the impact of the reduction of serum chloride on the prognosis of AHF patients.
We searched Cochrane Library, Web of science, PubMed, Embase databases and searched the relevant studies on chloride ion and AHF prognosis. The search time is from the establishment of the database to December 29, 2021. Two researchers screened the literature and extracted data independently. The quality of the included literature was evaluated using Newcastle-Ottawa Scale (NOS) scale. The effect amount is expressed as hazard ratio (HR) or relative risk (RR) and 95% confidence interval (CI). Review Manager 5.4.1 software for was used to perform the meta-analysis.
Seven studies involving 6787 AHF patients were included in meta-analysis. Meta-analysis revealed that the incidence of hypochloremia in AHF patients at admission was 17% (95% CI: 0.11–0.22); One mmol /L decrease in serum chloride at admission was associated with 6% increased risk of all-cause death of AHF patients (HR = 1.06, 95% CI: 1.04–1.08, P < 0.00001); Compared with the non-hypochloremia group, the risk of all-cause death in the hypochloremia group increased by 1.71 times (RR = 1.71, 95% CI: 1.45–2.02, P < 0.00001), the risk of all-cause death in the progressive hypochloremia(development of hypochloremia after admission) group increased by 2.24 times (HR = 2.24, 95% CI: 1.72–2.92, P < 0.00001), and the risk of all-cause death in the persistent hypochloremia (hypochloremia both on admission and at discharge) group increased by 2.80 times (HR = 2.80, 95% CI: 2.10–3.72, P < 0.00001).
The available evidence shows that the decrease of chloride ion at admission is associated with poor prognosis of AHF patients, and the prognosis of persistent hypochloremia is worse.Some outcome indicators(progressive hypochloremia, persistent hypochloremia, and composite of death + HF hospitalization)are as few as 2 studies in the literature, and the results should be interpreted carefully.
Intravenous diltiazem and metoprolol are both commonly used to treat atrial fibrillation (AF) with rapid ventricular rate (RVR) in the emergency department (ED), but the advantages and disadvantages ...of these drugs cannot be verified. This meta-analysis aimed to assess the efficacy and safety of intravenous diltiazem versus metoprolol for AF with RVR.
We systematically searched PubMed, Web of Science, Embase, Cochrane library, the China National Knowledge Infrastructure (CNKI), Wanfang, China Biology Medicine disc (CBM) and the WeiPu (VIP). Meta-analysis was performed using weighted mean difference (WMD), relative risk (RR) and 95% confidence interval (CI). Statistical analysis was performed using Review Manager 5.4.1.
Seventeen studies involving 1214 patients in nine randomized controlled trials (RCTs) and eight cohort studies were included in meta-analysis, including 643 patients in the intravenous diltiazem group and 571 patients group in the intravenous metoprolol. The results of the meta-analysis showed that compared with intravenous metoprolol, intravenous diltiazem was found higher efficacy (RR =1.11; 95% CI = 1.06 to 1.16, p < 0.00001), shorter average onset time (RR = −1.13; 95% CI = −1.97 to −0.28, p = 0.009), lower ventricular rate (RR = −9.48; 95% CI = −12.13 to −6.82, p<0.00001), less impact on systolic blood pressure (WMD = 3.76; 95% CI: 0.20 to 7.33, P = 0.04), and no significant difference in adverse events (RR = 0.80, 95% CI = 0.55 to 1.14, P = 0.22) and diastolic blood pressure (WMD = −1.20; 95% CI: −3.43 to 1.04, P = 0.29) was found between intravenous diltiazem and metoprolol.
Intravenous diltiazem has higher efficacy, shorter average onset time, lower ventricular rate, less impact on blood pressure, and with no increase in adverse events compared to intravenous metoprolol.
Robust metallic surface states (MSS) of topological insulators (TIs) against imperfections and perturbations are important in broad applications such as chemical catalysis and quantum computing. ...Unfortunately, they suffer from the narrow band gap that can be accessed. Searching for MSS with a large bulk band gap beyond conventional TIs becomes a quest. In this work, inspired by the adiabatic connection principle in real space, we identify that all electrides, a new class of emerging materials, must host robust and universal MSS that resist any disturbances, in spite of the fact that some of them could be classified as trivial in standard topology theory. This counterintuitive property is traced to the specific charge localization-delocalization change intrinsic to the electride when approaching the crystalline surface or interface, which is a kind of interstice-centered to atom-centered transition in the real-space topology of the charge density distribution, and is sharply different from the band inversion in the standard topology theory. The new mechanism circumvents the obstacle that limits the band gap of TI. Robust and universal MSS in an electride conventionally determined as trivial but with a colossal band gap beyond 6.13 eV are demonstrated. This gap size is about 6-fold larger than the highest record of known “wide-gap” TIs, thus opening up new avenues to universal MSS with gigantic bulk gap.
Shape memory alloys are emerging functional materials in various fields due to their unique mechanical properties. In this work, plate-impact experiments have been performed to study the dynamic ...behavior of near-equiatomic NiTi shape memory alloys with different initial phases, i.e., the single austenite (B2) and the mixed phase of austenite and martensite (B19′). A Doppler pin system and soft-recovery cylinder are employed to in-situ probe the macroscopic response and catch the shocked sample for postmortem characterizations, respectively. The observed bilinear behavior of the Hugoniot data, combined with the X-ray diffraction analysis of recovered samples, suggests that the B2 austenite undergoes a martensitic transformation at ∼5 GPa. Such a phase transition affects not only the spall damage but also the deformation mechanism of NiTi alloys. Specifically, it is identified that, in association with the B2 to B19’ transformation, the spall strength is reduced by ∼7% and the austenite twinning disappears in the recovered NiTi sample. These results thus indicate that the deformation and fracture behaviors of NiTi shape memory alloys under shock compression are strongly coupled with the martensitic transformation.
Valsalva maneuver (VM) is a simple and easy method for acute termination of supraventricular tachycardia (SVT), while a postural modification to the VM has been suggested to be superior to the ...standard VM (SVM). The objective of this meta-analysis is to explore the efficacy and safety of the modified VM (MVM) to terminate SVT compared with the SVM.
Extensive literature was conducted using the database such as PubMed, Embase, Web of Science, Cochrane library and included randomized controlled trials (RCTs) assessing the efficacy and safety of the MVM and SVM for SVT. Meta-analysis was performed using mean difference (MD), relative risk (RR) and 95% confidence interval (CI). Statistical analysis was performed using Review Manager 5.4.1 software. The quality of the published studies was evaluated using the Oxford quality scoring system (Jadad scale).
Six RCTs involving 1208 patients were reviewed, including 603 patients in the MVM group and 605 patients in the SVM group. The results of the meta-analysis showed that MVM was found to significantly increase the success rate of the sinus rhythm after single VM (RR = 2.83; 95% CI = 2.19 to 3.66; P < 0.00001), sinus rhythm after multiple VM (RR = 3.83; 95% CI = 2.26 to 6.50; P < 0.00001), and single and multiple VM (RR = 2.85, 95% CI = 2.35 to 3.45; P < 0.00001). MVM also decreased the emergency anti-arrhythmic treatments (RR = 0.70; 95% CI = 0.62 to 0.79; P < 0.00001), and use of adenosine and verapamil (RR = 0.69; 95% CI = 0.61 to 0.78; P < 0.00001). There was no significant difference in adverse events (RR = 1.48; 95% CI = 0.91 to 2.42; P = 0.11) and time in emergency department (ED) (RR = 0.03; 95% CI = −0.17 to 0.23, P = 0.79) between MVM and SVM.
Compared with MVM, the conversion rate of SVT to sinus rhythm was more effective than SVM. MVM also reduced the use of anti-arrhythmic measures and drugs, and had no increased time in ED and adverse events.
The laser powder bed fusion (LPBF) process is renowned for producing metal parts with exceptional mechanical properties, attributed to their unique microstructures. However, there is a lack of ...discussion in the literature regarding the plastic deformation mechanism at wide strain rates. To address this research gap, this study employs both quasi-static tensile (QST) tests and dynamic Split-Hopkinson tensile bar (SHTB) experiments to investigate the tensile properties and deformation mechanisms of a well-characterized material, 316L stainless steel (SS), across an extensive range of strain rates spanning from 10−3 s−1 to 103 s−1. Our results reveal the superior quasi-static and dynamic stretching behavior exhibited by LPBF specimen in comparison to the wrought 316L counterpart. This enhanced behavior can be primarily attributed to the cellular and hierarchical structures inherent to LPBF specimen. Notably, the cellular structure emerges as the primary controlling factor in mechanical deformation due to its capacity for increasing the critical strain required for deformed twinning and martensite transition. Consequently, under quasi-static loading, twinning and martensite transition act as the dominant deformation mechanism, while dynamic loading conditions are characterized by a prevalence of dislocation interactions. This comprehensive understanding of the deformation mechanism and strain rate-dependent behavior of LPBF 316L SS provides valuable insight for optimizing its mechanical properties under a wide range of loading conditions.
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