Depicting Defects in Metallic Glasses by Atomic Vibrational Entropy.

Due to the chaotic structure of amorphous materials, it is challenging to identify defects in metallic glasses. Here we tackle this problem from a thermodynamic point of view using atomic vibrational entropy, which represents the inhomogeneity of atomic contributions to vibrational modes. We find that the atomic vibrational entropy is correlated to the vibrational mean-square displacement and polyhedral volume of atoms, revealing the critical role of vibrational entropy in bridging dynamics, thermodynamics, and structure. On this method, the local vibrational entropy obtained by coarse-graining the atomic vibrational entropy in space can distinguish more effectively between liquid-like and solid-like atoms in metallic glasses and establish the correlation between the local vibrational entropy and the structure of metallic glasses, offering a route to predict the plastic events from local vibrational entropy. The local vibration entropy is a good indicator of thermally activated and stress-driven plastic events, and its predictive ability is better than that of the structural indicators.

Heparin anticoagulation versus regional citrate anticoagulation for membrane therapeutic plasma exchange in patients with increased bleeding risk.

Background Heparin anticoagulation (HA) is commonly employed for membrane therapeutic plasma exchange (mTPE). However, for patients with increased bleeding risk, there were controversial opinions on the use of HA versus regional citrate anticoagulation (RCA) for mTPE. Our present study aimed to evaluate the efficacy and safety of HA vs. RCA for mTPE in patients with increased bleeding risk.Methods Patients with increased bleeding risk who underwent mTPE between 2014 and 2021 in our center were screened. Observations of anticoagulation efficacy and safety were used as the study endpoints.Results A total of 108 patients with 368 mTPE sessions were included. Of the included patients, 38 and 70 received HA and RCA mTPE, respectively. There was no significant difference in the clotting of extracorporeal circuits between the HA and RCA groups (4.1% vs. 4.4%, p = 0.605). More bleeding episodes were observed in the HA group compared to the RCA group (16.4% vs. 4.4% mTPE sessions, p < 0.001). The frequency of postoperative transfusion within 24 h (11% vs. 3.4%, p = 0.007) was significantly different in the HA and RCA group. Anticoagulation strategy (HA vs. RCA; OR 5.659, 95%CI 2.266-14.129; p < 0.001), and mean arterial pressure (prior treatment, OR 1.052, 95%CI 1.019-1.086; p = 0.002) were independent risk factors of bleeding episodes. At the end of mTPE treatment, the incidence of metabolic alkalosis (16.7% vs. 54.1%, p = 0.027) and hypocalcemia (41.7% vs. 89.2%, p = 0.001) was significantly different in the HA (n = 5, 12 sessions) and RCA (n = 22, 74 sessions) groups, respectively.Conclusion RCA is as effective as HA for mTPE. However, for patients with increased bleeding risk, RCA is associated with a lower risk of bleeding, compared with HA. With careful monitoring and timely adjustment, RCA most likely is a safe and effective anticoagulation option for mTPE in patients with increased bleeding risk.

Uncovering the bridging role of slow atoms in unusual caged dynamics and ß-relaxation of binary metallic glasses.

The origin of ß-relaxation in metallic glasses is still not fully understood, and the guidance of slow atoms for caged dynamics and ß-relaxation is rarely mentioned. Using molecular dynamics simulations, we reveal the bridging role of slow atoms on unusual caged dynamics and ß-relaxation. In the stage of unusual caged dynamics, slow atoms are bounded by neighboring atoms. It is difficult for the slow atoms to break the cage, producing more high-frequency vibration, which causes more atoms to jump out of the cage randomly in the next stage. Precisely, the movement of the slow atoms changes from individual atoms vibrating inside the cage and gradually breaking out of the cage into a string-like pattern. The string-like collective atomic jumps cause decay of the cages, inducing ß-relaxation. This situation generally exists in binary systems with the large atomic mass difference. This work offers valuable insights for understanding the role of slow atoms in unusual caged dynamics and ß-relaxation, complementing studies on the origin of ß-relaxation in metallic glasses and their glass-forming liquids.

Long-term arteriovenous fistula prognosis for maintenance hemodialysis patients who accepted PIRRT by using arteriovenous fistula.

BACKGROUND: Maintenance hemodialysis (MHD) patients are often admitted to the hospital for severe morbidities. Prolonged intermittent renal replacement therapy (PIRRT) is required during the hospital staying. There are controversial opinions on the use of arteriovenous fistula (AVF) as vascular access for PIRRT in MHD patients. METHODS: Patients with AVF who accepted PIRRT in our center between January 2014 and June 2021 were retrospectively screened. AVF dysfunction and patient mortality were assessed as endpoints. Univariate and multivariate regression models were employed to identify the risk factors of AVF dysfunction. RESULTS: About 162 patients were included in our present study. Twenty-six experienced AVF dysfunction, of whom 53.8%, 19.2%, and 27.0% had percutaneous transluminal balloon angioplasty, surgical revision, and AVF reconstruction, respectively. The accumulated AVF dysfunction rates were 11.8%, 16.2%, and 21.0% in 1, 2, and 3 years, respectively. Multivariate analysis revealed that smoking (HR 2.750, 95% CI 1.181-6.402, p = 0.019), higher platelet (PLT, HR 1.009, 95% CI 1.000-1.017, p = 0.047), higher prothrombin activity (PTA, HR 1.039, 95% CI 1.012-1.066, p = 0.004), and lower diastolic blood pressure (DBP, HR 0.963, 95% CI 0.932-0.996, p = 0.026) were independent risk factors for AVF dysfunction. During the follow-up period, 37 patients died. CONCLUSIONS: Overall, the use of AVF for PIRRT might not dramatically increase the incidence of AVF dysfunction. And, Smoking, lower DBP, higher PLT, and higher PTA were associated with increased AVF dysfunction.

New Interpretation of Glass Formation in Isomeric Substances: Shifting from Melting-Point to Melting-Entropy.

Revealing the critical thermodynamic parameters determining the glass formation of substances is of great significance for understanding the glass transition and guiding the composition design of glass-forming materials. Nevertheless, the direct access to glass-forming ability (GFA) by thermodynamics for various substances remains to be substantiated. The strategy to seek the fundamental properties of glass formation is explored several decades ago, as pioneered by Angell, arguing that the GFA in isomeric xylenes depends on the low lattice energy manifested by the low melting point. Here, an in-depth study is advanced using two more isomeric systems. Surprisingly, the results do not constantly support the reported relationship between the melting point and glass formation among isomeric molecules. Instead, molecules with enhanced glass formability are featured by the properties of low melting entropy without exception. Comprehensive studies of isomeric molecules find that the low melting entropy is roughly accompanied by the low melting point, explaining the apparent link between melting point and glass formation. Progressively, the viscosity measurements of the isomers uncover a strong dependence of the melting viscosity on melting entropy. These results emphasize the significance of the melting entropy in governing the glass formability of substances.

Understanding the difference in the stretched structural relaxations probed by dielectric and enthalpic studies of glass forming substances.

We investigated the stretched dynamics of the structural relaxation in molecular glass formers by using dielectric and thermal (or enthalpic) relaxations. The dielectric stretching exponents ßdie are determined by the Havriliak-Negami function, while the enthalpic ßTNMH is quantified by using the Tool-Narayanaswamy-Moynihan-Hodge formalism. We found ßTNMH is anticorrelated with the degree of freedom, a molecule addressed by the concept of beads. Referring to the reported relation of ßdie to the dipole moment µ, we proposed a combined parameter of µ2*beads, which can rationalize the difference in stretching exponents obtained by dielectric and enthalpic relaxations. For the majority of glass-forming molecules, the difference is trivial, but for those molecules with both unusually high dipole moments and flexibility, a large difference is obvious. The interplay of the degree of freedom and dielectric dipole-dipole interaction in molecular dynamics is addressed.

Identifying the structural relaxation dynamics in a strongly asymmetric binary glass former.

Here, we provide calorimetric and dielectric studies in asymmetric binary mixtures constituted by 2-picoline and triphenylethylene. Extreme broadening of the calorimetric glass transition is observed in the mixtures, which is accompanied by a large mismatch of the glass transition temperatures defined by the two techniques. As large broadening in the relaxation dispersion is identified in the mixtures of intermediate concentrations, strong temperature dependence of the relaxation dispersion is detected. The relation between the stretching exponent and non-linear factor derived from the Tool-Narayanaswamy-Moynihan-Hodge model shows a remarkable shift from the one established by pure molecular glass formers and symmetric mixtures. The unusual behaviors suggest an extreme dynamical decoupling mode imposed by the occurrence of strong concentration fluctuation.

Unveiling the strong dependence of the α-relaxation dispersion on mixing thermodynamics in binary glass-forming liquids.

Structural α-relaxation dispersion in binary molecular glass forming mixtures with distinct mixing enthalpy ΔHmix was investigated using enthalpic and dielectric relaxation measurements across the entire composition range. This study focused on the dependence of the relaxation dispersion on the mixing thermodynamics by determining the non-exponential exponent ß, and its composition dependence. The ß values determined by the enthalpic and dielectric relaxations agree well. Remarkably, it is found that the systems with positive enthalpy of mixing (exothermic, ΔHmix >0) have positive deviations in the composition dependence of ß from the linear averaging of the two ß values of the pure components, while negative deviations are observed for the systems with negative enthalpy of mixing (endothermic, ΔHmix <0). Furthermore, the relation between the non-exponential behaviors and entropy of mixing is discussed, revealing that the positive or negative deviation of ß in its composition dependence on mixing is accompanied by the same sign of the excess entropy of mixing relative to the ideal one.

Experimental evidence of co-existence of equilibrium and nonequilibrium in two-glass-transition miscible mixtures.

Two glass-transitions have been observed in some miscible molecular mixtures with notable differences in geometry or chemistry of constituents. The explanation of the phenomena has been puzzling with diverse structural models. Here, we present detailed studies on two glass-transition mixtures composed of tripropyl phosphate (TPP) and polystyrene (PS) by using calorimetric and dielectric measurements. We found that ageing between the two transitions always generates endothermic peaks at temperatures ∼4 K higher than the ageing temperatures and, subsequent thermal cycles around the peaks can remove the ageing effect and restore the systems, confirming the co-existence of nonequilibrium and equilibrium states in the regions. We also found that the broad glass transition thermogram is associated with highly stretched relaxation dynamics. The results allow us to draw a conclusion of continuous mobility gradient spanning the two TPP-PS glass-transitions, rather than complete phase separation.

Isochronal Superposition of the Structural α-Relaxation and Invariance of Its Relation to the ß-Relaxation to Changes of Thermodynamic Conditions in Methyl m-Toluate.

The dielectric spectra of methyl m-toluate (MMT) in supercooled liquid and glassy states were measured over wide ranges of temperature T at ambient and elevated pressures P. We found that the frequency dispersion of the loss peak contributed by the structural α-relaxation is invariant to changes of P and T, while keeping the loss peak frequency fα(T,P) constant. This isochronal superposition property of the α-relaxation holds for different choices of fα(T,P). The invariant frequency dispersions for the same fα(T,P) are also indicated by the fractional exponent ßKWW in the Fourier transform of the Kohlrausch-Williams-Watts (KWW) function. Similarly, the fragility m index of MMT keeps approximately constant on varying pressure, largely different from H-bonded glass formers. The secondary ß-relaxation at a frequency higher than fα(T,P) is found to shift to lower frequencies by elevating pressure in concert with the α-relaxation. The ratio τα(T,P)/τß(T,P) is approximately unchanged to variations of T and P while keeping τα(T,P) constant. These properties observed in MMT offer experimental evidence of the dynamic correlation between α- and ß-relaxations in pure small-molecule glass-formers.

Entropic Nature of the Debye Relaxation in Glass-Forming Monoalcohols.

The dynamics and thermodynamics of the Debye and structural (α) relaxations in isomeric monoalcohols near the glass transition temperature Tg are explored using dielectric and calorimetric techniques. The α relaxation strength at Tg is found to correlate with the heat capacity increment, but no thermal signals can be detected to link to the Debye relaxation. We also observed that the activation energy of the Debye relaxation in monoalcohols is quantitatively correlated with that of the α relaxation at the kinetic Tg, sharing the dynamic behavior of the Rouse modes found in polymers. The experimental results together with the analogy to the Rouse modes in polymers suggest that the Debye process in monoalcohols is an entropic process manifested by the total dipole fluctuation of the supramolecular structures, which is triggered and driven by the α relaxation.

Molecular Dynamics Simulation of Structural Signals of Shear-Band Formation in Zr46Cu46Al8 Metallic Glasses.

The evolution from initiation to formation of a shear band in Zr46Cu46Al8 metallic glasses is presented via molecular dynamics simulation. The increase in number and the decrease in average size of clusters with the quasi-nearest atoms being 0 correspond to the shear-band evolution from initiation to formation. When the shear band is completely formed, the distribution of the bond orientational order q6 reaches a minimum. The maximum of the number of the polyhedral loss of Cu-centered <0, 0, 12, 0> and the minimum of the number of the polyhedral loss of Zr-centered <0, 2, 8, 5> correspond to the shear-band formation. These findings provide a strong foundation for characterizing the evolution from initiation to formation of shear bands.

Related Structure Characters and Stability of Structural Defects in a Metallic Glass.

Structural defects were investigated by a recently proposed structural parameter, quasi-nearest atom (QNA), in a modeled Zr50Cu50 metallic glass through molecular dynamics simulations. More QNAs around an atom usually means that more defects are located near the atom. Structural analysis reveals that the spatial distribution of the numbers of QNAs displays to be clearly heterogeneous. Furthermore, QNA is closely correlated with cluster connections, especially four-atom cluster connections. Atoms with larger coordination numbers usually have less QNAs. When two atoms have the same coordination number, the atom with larger five-fold symmetry has less QNAs. The number of QNAs around an atom changes rather frequently and the change of QNAs might be correlated with the fast relaxation metallic glasses.

A structural signature of the breakdown of the Stokes-Einstein relation in metallic liquids.

The breakdown of the Stokes-Einstein relation (SER) in three model metallic liquids is investigated via molecular dynamics simulations. It is found that the breakdown of SER is closely correlated with the clustering behavior of well-packed atoms. When the SER breaks down, many cluster properties have almost the same value in these metallic liquids. At the breakdown temperature of SER, the temperature dependence of the number of clusters begins to deviate from a linear increase and the average number of well-packed atoms in the clusters reaches about 2, which indicates an increase in structure heterogeneity. Moreover, the size of the largest cluster shows a direct correlation with the SER. Therefore, our study provides a possible structural origin for the breakdown of SER in metallic liquids.

The MicroRNA-199a/214 Cluster Targets E-Cadherin and Claudin-2 and Promotes High Glucose-Induced Peritoneal Fibrosis.

Serum response factor (SRF) was found to be involved in the phenotypic transition and fibrosis of the peritoneal membrane during treatment with peritoneal dialysis (PD), but the exact mechanism remains unclear. SRF regulates microRNAs (miRNAs) that contain the SRF-binding consensus (CArG) element in the promoter region. Therefore, we investigated whether the miR-199a/214 gene cluster, which contains a CArG element in its promoter, is directly regulated by SRF. High-glucose (HG) treatment significantly unregulated the expression of the miR-199a-5p/214-3p gene cluster in human peritoneal mesothelial cells (HPMCs). By chromatin immunoprecipitation and reporter assays, we found that SRF binds to the miR-199a-5p/214-3p gene cluster promoter after HG stimulation. In vitro, in HPMCs, silencing of miR-199a-5p or miR-214-3p inhibited the HG-induced phenotypic transition and cell migration but enhanced cell adhesion, whereas ectopic expression of mimic oligonucleotides had the opposite effects. Both miR-199a-5p and miR-214-3p targeted claudin-2 and E-cadherin mRNAs. In a PD rat model, treatment with an SRF inhibitor silenced miR-199a-5p and miR-214-3p and alleviated HG-PD fluid-induced damage and fibrosis. Overall, this study reveals a novel SRF-miR-199a/miR-214-E-cadherin/claudin-2 axis that mediates damage and fibrosis in PD.

[C1q/tumor necrosis factor related protein 6 (CTRP6) is involved in gentamicin-induced acute kidney injury in rats].

Objective To explore the role of the anti-inflammatory cytokine C1q/tumor necrosis factor related protein 6 (CTRP6) in gentamicin-induced acute kidney injury in rats. Methods SD rats were divided into 5 groups including control group, model group and the other 3 experimental groups. The rats in model group and experimental groups were subcutaneously injected with gentamicin at the dose of 400 mg/(kg.d) for consecutive 2 days to induce acute renal injury. Two days before gentamicin injection, the rats in the 3 experimental groups were given pAd-CTRP6 at the doses of 0.5, 5 and 50 mg/kg, respectively. The serum levels of blood urea nitrogen (BUN) and creatinine (Cr) were respectively assayed with picric acid colorimetry and ultraviolet spectrophotometry; ELISA was used to detect serum CTRP6 content and the production of interleukin 1ß (IL-1ß) and tumor necrosis factor α (TNF-α) in the kidney homogenate; Western blotting was performed to detect the expressions of CTRP6, caspase-1 and pyrin domain containing 3 (NLRP3) proteins in the renal tissues of rats. Results Compared with control group, serum BUN and Cr contents increased in the model rats; the secretion of inflammatory factors IL-1ß and TNF-α, as well as the expressions of caspase-1 and NLRP3 were also enhanced in the model group. Compared with the model group, serum BUN and Cr contents decreased in the experimental groups; the secretion of IL-1ß and TNF-α, as well as the expressions of caspase-1 and NLRP3 were also attenuated in the experimental groups. Moreover, with the increase of the injection dosage of pAd-CTRP6, the suppressive effect was gradually strengthened. Conclusion CTRP6 can attenuate gentamicin-induced acute renal injury in rats in a dose-dependent manner.

Role of γ-glutamyl cyclotransferase as a therapeutic target for colorectal cancer based on the lentivirus-mediated system.

Human GGCT (γ-glutamyl cyclotransferase) has been shown to be upregulated in most tumors, but its role in colorectal cancer (CRC) is poorly understood. Thus, CRC cell lines, including HCT116 and SW1116, were chosen to investigate the role of GGCT by constructing a GGCT silencing cells model using lentivirus-mediated RNA interference. The knockdown efficiency was confirmed by reverse transcription-quantitative PCR and a western blot assay. Then, a set of biological functions of GGCT silencing on CRC cell was assessed by MTT, colony-formation assay, and flow cytometry analysis. Further, western blot and Pathscan intracellular signaling were used to detect intracellular signaling associated with cell growth and apoptosis induced by GGCT knockdown. In addition, the clinical chemotherapeutic drug 5-fluorouracil was used to investigate the impact of GGCT silencing on drug sensitivity by an Annexin V/7-AAD double-staining assay. The results of the analysis indicated that GGCT silencing significantly suppressed cell proliferation and arrested cell cycle at the G0/G1 phase by regulating the expression of p21, p27, and cyclin E. Moreover, GGCT silencing triggered the apoptosis of CRC cells by activating caspase-3 and cleaved poly-ADP-ribose polymerase pathways and downregulating the phosphorylation proline-rich Akt substrate of 40 kDa (PRAS40) expression levels. Furthermore, GGCT silencing combined with 5-fluorouracil treatment further induced the apoptotic rate of CRC cells. These findings suggest that GGCT may be a promising diagnostic and therapeutic target for CRC by activating the apoptotic pathway.

Structural disorder in metallic glass-forming liquids.

We investigated structural disorder by a new structural parameter, quasi-nearest atom (QNA), in atomistic configurations of eight metallic glass-forming systems generated through molecular dynamics simulations at various temperatures. Structural analysis reveals that the scaled distribution of the number of QNA appears to be an universal property of metallic liquids and the spatial distribution of the number of QNA displays to be clearly heterogeneous. Furthermore, the new parameter can be directly correlated with potential energy and structural relaxation at the atomic level. Some straightforward relationships between QNA and other properties (per-atom potential energy and α-relaxation time) are introduced to reflect structure-property relationship in metallic liquids. We believe that the new structural parameter can well reflect structure disorder in metallic liquids and play an important role in understanding various properties in metallic liquids.

Crystallization pathways of liquid-bcc transition for a model iron by fast quenching.

We report simulations on the local structural evolution in the liquid-bcc transition of a model iron. Fourteen main Voronoi polyhedra are chosen as the representatives of short-range orders (SROs) and their transformations during crystallization are also investigated. Thus, the crystallization pathways for the main SROs are drawn. Our results also show that the transformations between two SROs in the crystallization pathways can be classified into two categories, first the enlargement of coordination number, second the transformation of local symmetry from five-fold to four-fold. The former reduces the potential energy while the latter increases it. It is found that the potential energy cannot decease monotonously whatever crystallization pathway is chosen to transform the icosahedral SRO to bcc SRO. Therefore, the latter transformation might provide the energy barrier of crystallization. We propose two transformation styles among SROs. All the transformations in the crystallization pathways can be achieved according to the styles. Moreover, the two transformation styles indicates that the bcc structure is more similar to liquid than other crystals. That might be the reason why the first phase nucleated during a rapid cooling process should be bcc crystal.