Connection between Mechanical Relaxation and Equilibration Kinetics in a High-Entropy Metallic Glass.

The slow transition from an out-of-equilibrium glass towards a supercooled liquid is a complex relaxation phenomenon. In this Letter, we study the correlation between mechanical relaxation and equilibration kinetics in a Pd_{20}Pt_{20}Cu_{20}Ni_{20}P_{20} high-entropy metallic glass. The evolution of stress relaxation with aging time was obtained with an unprecedented detail, allowing us to pinpoint new interesting features. The long structural relaxation towards equilibrium contains a wide distribution of activation energies, instead of being just associated to the ß relaxation as commonly accepted. The stress relaxation time can be correlated with the equilibration rate and we observe a decrease of microstructural heterogeneity which contrasts with an increase of dynamic heterogeneity. These results significantly enhance our insight of the interplay between relaxation dynamics and thermodynamics in metallic glasses.

Erratum: Intrinsic Correlation between the Fraction of Liquidlike Zones and the ß Relaxation in High-Entropy Metallic Glasses [Phys. Rev. Lett. 129, 175501 (2022)].

This corrects the article DOI: 10.1103/PhysRevLett.129.175501.

Intrinsic Correlation between the Fraction of Liquidlike Zones and the ß Relaxation in High-Entropy Metallic Glasses.

Lacking the structural information of crystalline solids, the origin of the relaxation dynamics of metallic glasses is unclear. Here, we report the evolution of stress relaxation of high-entropy metallic glasses with distinct ß relaxation behavior. The fraction of liquidlike zones, determined at each temperature by the intensity of stress decay, is shown to be directly related to both the aging process and the spectrum of relaxation modes obtained by mechanical spectroscopy. The results shed light on the intrinsic correlation between the static and dynamic mechanical response in high-entropy and conventional metallic glasses, pointing toward a sluggish diffusion high-entropy effect in the liquid dynamics.

A highly distorted ultraelastic chemically complex Elinvar alloy.

The development of high-performance ultraelastic metals with superb strength, a large elastic strain limit and temperature-insensitive elastic modulus (Elinvar effect) are important for various industrial applications, from actuators and medical devices to high-precision instruments1,2. The elastic strain limit of bulk crystalline metals is usually less than 1 per cent, owing to dislocation easy gliding. Shape memory alloys3-including gum metals4,5 and strain glass alloys6,7-may attain an elastic strain limit up to several per cent, although this is the result of pseudo-elasticity and is accompanied by large energy dissipation3. Recently, chemically complex alloys, such as 'high-entropy' alloys8, have attracted tremendous research interest owing to their promising properties9-15. In this work we report on a chemically complex alloy with a large atomic size misfit usually unaffordable in conventional alloys. The alloy exhibits a high elastic strain limit (approximately 2 per cent) and a very low internal friction (less than 2 × 10-4) at room temperature. More interestingly, this alloy exhibits an extraordinary Elinvar effect, maintaining near-constant elastic modulus between room temperature and 627 degrees Celsius (900 kelvin), which is, to our knowledge, unmatched by the existing alloys hitherto reported.

Determination of the thermodynamic potentials of metallic glasses and their relation to the defect structure.

We performed calorimetric and shear modulus measurements on four bulk metallic glasses upon heating up to the temperature of the complete crystallization as well as in the fully crystallized state. On the basis of calorimetric experiments, we calculated the excess thermodynamic potentials with respect to the crystalline state-the enthalpy ΔH, entropy ΔSand Gibbs free energy ΔΦ-as functions of temperature. Using high-frequency shear modulus measurements we show that calorimetric determination of ΔH, ΔSand ΔΦ is consistent with the calculation of these potentials within the framework of the interstitialcy theory (IT) within a 15% uncertainty in the worst case for all MGs under investigation. It is concluded that the physical origin of the excess thermodynamic potentials in MGs can be related to a system of interstitial-type defects frozen-in from the liquid state upon melt quenching as suggested by the IT. The estimates of the defect formation enthalpyHfand entropySfshow thatHfscales with the shear modulus whileSfis quite large (10kBto 20kB), in line with the basic assumptions of the IT.

Relation of the fragility and heat capacity jump in the supercooled liquid region with the shear modulus relaxation in metallic glasses.

Fragility constitutes a major parameter of supercooled liquids. The phenomenological definition of this quantity is related to the rate of a change of the shear viscosityηat the glass transition temperature. Although a large number of correlations of the fragility with different properties of metallic glasses were reported, an adequate understanding of its physical nature is still lacking. Attempting to uncover this nature, we performed the calculation of the fragility within the framework of the interstitialcy theory (IT) combined with the elastic shoving model. We derived an analytical expression for the fragility, which shows its relation with the high-frequency shear modulusGin the supercooled liquid state. To verify this result, specially designed measurements ofηandGwere performed on seven Zr-, Cu- and Pd-based metallic glasses. It was found that the fragility calculated from shear modulus relaxation data is in excellent agreement with the fragility derived directly from shear viscosity measurements. We also calculated the heat capacity jump ΔCsqlat the glass transition and showed that it is related to the fragility and, consequently, to shear modulus relaxation. The ΔCsql-value thus derived is in a good agreement with experimental data. It is concluded that the fragility and heat capacity jump in the supercooled liquid state can be determined by the evolution of the system of interstitial-type defects frozen-in from the melt upon glass production, as suggested by the IT. This connection is mediated by the high-frequency shear modulus.

[The effect of standardized lymphectomy and sampling of resected lymph nodes on TNM staging of resectable pancreatic head cancer].

Objective: To examine the effect of standardized lymphectomy and sampling of resected lymph nodes (LN) on TNM staging of resectable pancreatic head cancer. Methods: Consecutive patients with resectable pancreatic head cancer who received standard pancreatoduodenctomy at Department of General Surgery in Beijing Hospital from December 2017 to November 2018 were recruited as study group. After operation, the surgeon sampled lymph nodes from the fresh specimen following the Japanese Gastric Cancer Guidelines.Thirty-three cases were recruited in the study group and the mean age was (59.8±15.2) years.Pathologic reports from December 2015 to November 2016 were taken as control group, containing 29 cases with age of (57.0±13.0) years. Number of lymph nodes, standard-reaching ratio and positive nodes ratio were compared between two groups. According to the seventh edition and eighth edition of TNM staging, the changes of N staging and TNM staging were analysed. The quantitative data conforming to normal distribution were tested by independent sample t test, the quantitative data not conforming to normal distribution were tested by rank sum test, and the enumeration data were analysed by χ(2) test. Results: The basal data of the two groups were comparable (all P>0.05) . The number of lymph nodes sampled in the study group was 23.27±8.87, significantly more than in control group (12.86±5.90, t=0.653, P=0.000) .Ratio of cases with more than 15 nodes was 81.8% (27/33) in the study group and 34.5% (10/29) in the control group with statistical significance (χ(2)=14.373, P=0.000) . In the study group, the positive lymph node ratios of No. 17a+17b, 14a+14b, 8a+8p LN were 36.4% (12/33) , 30.3% (10/33) and 9.1% (3/33) respectively. The positive lymph node ratio in No.14a+14b LN was higher than in No.8 LN (χ(2)=4.694, P=0.030) . According to the change in N staging system in the AJCC eighth edition, 2 cases (6.1%, 2/33) changed from ⅠB to ⅡA, 7 cases (21.2%, 7/33) from ⅡA to ⅠB and 5 cases (15.2%, 5/33) changed from ⅡB to Ⅲ (25.0%, 5/20) . Conclusions: No.14 LN should be treated as the first station rather than second station because of the anatomic character and higher metastatic ratio. Standardised lymphectomy and sampling may increase the number of LN resected and improve the TNM staging of resectable pancreatic head cancer.

Liver transplantation in an adult patient with situs inversus: a case report and overview of the literature.

Liver transplantation (OLT) in an adult with situs inversus (SI) is extremely rare and considered a contraindication because of the anatomic difficulties. A 45-year-old male patient with complete SI, suffering from progressive hepatic failure secondary to hepatolithiasis, obstructive jaundice, and liver cirrhosis, underwent transplantation in July 2004. Preoperatively the liver anatomy was determined by computed tomography scan, three-dimensional liver reconstruction, and angiography. OLT was performed using a modified piggyback technique, the donor right lobe was rotated 45 degrees to the left, making the donor left lobe point into the left paracolic sulcus and the donor right lobe in the recipient hepatic fossa. The donor's suprahepatic vena cava was sewn end to side to the recipient vena cava, and the infrahepatic vena cava oversewn. The patient recovered uneventfully, and transplant perfusion and function were stable at a follow-up of 40 months. The present study showed OLT in adult patients with SI to be feasible. The knowledge of exact anatomy, meticulous preoperative planning, and optimization of the recipients condition are essential.

Experimental low-level direct current therapy in liver metastases: influence of polarity and current dose.

Several authors recently reported on the successful local treatment of malignant disease with low-level direct current therapy. However, antitumoral effects in colorectal metastases has not been investigated experimentally. The aim of the present study was to assess the effectiveness of this therapy and the influence of polarity and current dose. Colorectal metastases were established in BD IX rats by the injection of colon cancer cells under the liver capsule. After three weeks, the liver tumor volumes were determined by magnetic resonance imaging of the liver. Low-level direct current therapy was applied via five platinum electrodes. Four different applications were used: 60 C/cm(3), anode at the center; 60 C/cm(3), cathode at the center; 80 C/cm(3), anode at the center; and 80 C/cm(3), cathode at the center. In the control group, five electrodes were placed without applying any direct current. All animals were sacrificed on postoperative day 7. Liver metastases were histologically examined for vital tumor cells. Statistical analysis was performed with chi(2)-test. The mean initial tumor diameter before treatment was 3.6 +/- 1.4 mm (volume: 25.2 +/- 9.7 mm(3)). Histological examination of the removed livers revealed significant destruction of the metastases with localized necroses in all treatment groups; 37% had a complete response rate and 63% a partial response rate. There were no significant necroses in the control group (P < 0.0001). The best treatment results were obtained in the group with an anode at the center and a current dose of 80 C/cm(3). Direct current therapy offers a new and safe method for the local treatment of liver metastases. We were able to observe that tumor damage is related to current dose but not to the polarity of the central electrode.

Local treatment of hepatic metastases with low-level direct electric current: experimental results.

BACKGROUND: Several authors have recently reported encouraging results from low-level direct current therapy in easily accessible malignant tumors. However, antitumoral effects in colorectal metastases have not been investigated experimentally. METHODS: Using an animal model with induced hepatic metastases, we analyzed the effectiveness and the tumor growth dynamics after direct current application. Three weeks after induction tumor volumes were estimated with magnetic resonance imaging (MRI). Then direct current (80 C/cm3) was applied in the treatment group by means of one anode in the tumor center and four cathodes peripherally. In the control group electrodes were placed without applying current. Tumor growth dynamics was analyzed with MRI after 3 and 5 weeks. After this all animals were killed, and the livers histologically examined. RESULTS: After 5 weeks MRI showed a 1.6-fold tumor enlargement in the treatment group versus a 2.9-fold enlargement in the control group (Student t test, P=0.0051). The histopathologic analysis of the treated livers yielded a 21% complete response rate and a 78% partial response rate. No necroses were found in the control group. CONCLUSIONS: These results confirm the effectiveness of low-level direct current application as a potential modality for the treatment of hepatic metastases.

[Pilot study of effectiveness of electrotherapy in the experimental liver metastasis model]. / Pilotstudie zur Wirksamkeit der Gleichstromtherapie im experimentellen Lebermetastasenmodell.

The aim of the present was to assess the effectiveness of low level direct current therapy in liver metastases and the influence of polarity (anode or cathode in the center of the tumor) or current dose (60 or 80 C/cm3). Colorectal metastases were established in 25 BD IX rats by injection of DHD/K12 colon cancer cells under the liver capsule. After 3 weeks the tumors were treated by low level direct current therapy (applied with five platinum electrodes). Histological examination of the removed livers on postoperative day 7 revealed significant destruction of the metastases with localized necroses. The best treatment results were obtained in the group with an anode in the center and a current dose of 80 C/cm3. We conclude that low level direct current therapy may offer an alternative minimal invasive method in the treatment of liver metastases.