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[en] CO adsorption on small Aun (n = 1 — 7) clusters which are supported by a partially reduced rutile TiO2(110) surface has been investigated by the first-principles method. The low coordinated sites of Au clusters are favorable for CO adsorption. CO—Aun—TiO2 system displays surface magnetism. There is a strong interaction between the adsorbed CO molecule and the supported Au clusters. (condensed matter: structural, mechanical, and thermal properties)
[en] Objective: To investigate the clinical application of 'V + Pad' point plaster in hemostasis of femoral artery puncturing point after interventional therapy. Methods: A total of 320 patients who underwent interventional treatment were divided into 5 F sheath group (n = 180) and 7 F sheath group (n = 140). The patients of each group were randomly and equally subdivided into control subgroup and observation subgroup. Conventional hemostasis by compression was performed in the patients of control groups, while 'V + Pad' hemostasis point plaster was employed in the patients of observation groups. The compression time, immobilization time, time of staying in bed, subcutaneous hemorrhage, subcutaneous hematoma, lumbodorsal aching pain, the necessity incidence of urethral catheterization, etc. were documented, and the results were compared between the subgroups of 5 F and 7 F groups separately. Results: In the 5 F sheath group, the compression time, immobilization time, time of staying in bed, the occurrence of lumbodorsal aching pain and the necessity incidence of urethral catheterization in control subgroup were (8.1 ± 2.2)min, (8.3 ± 0.5) h, (20.3 ± 2.6) h, 41.1% and 4.4%, respectively, while those in observation subgroup were (5.1 ± 0.3) min, (2.3 ± 0.4) h, (7.5 ± 1.6) h and 10% and 0%, respectively. Statistically significant differences in the above items existed between the two subgroups (P < 0.05). The occurrences of subcutaneous hemorrhage and subcutaneous hematoma in control subgroup were 2.2% and 1.1%, respectively, while those in observation subgroup were 1.1% and 0%, respectively. The differences between the two subgroups were not significant (P > 0.05). In the 7 F sheath group, the compression time, immobilization time, time of staying in bed, subcutaneous hemorrhage, subcutaneous hematoma, the occurrence of lumbodorsal aching pain and the necessity incidence of urethral catheterization in control subgroup were (16.4 ± 6.8 ) min, (8.8 ± 1.3 ) h, (22.6 ± 4.3) h, 30.0%, 8.6%, 47.1% and 5.7%, respectively, while those in observation subgroup were (9.1 ± 3.7) min, (4.7 ± 0.7) h and (9.1 ± 1.7 ) h, 12.9%, 2.9%, 11.4% and 0%, respectively. The differences in the above items between the two subgroups were statistically significant (P < 0.05). Conclusion: The use of 'V + Pad' point plaster can quickly stop the bleeding with reliable effect. Moreover, it can improve the patient's comfortableness and acceptability as well. (authors)
[en] Objective: To discuss the diagnosis and treatment of iatrogenic abdominal wall implantation and metastasis from malignant tumors. Methods: Combined with literature review, the clinical data, including diagnosis, treatment course and outcomes, of five patients with iatrogenic abdominal wall implantation and metastasis from malignant tumors were retrospectively analyzed. Results: The primary malignancies in the five patients included cholangiocarcinoma (n = 1) and hepatic carcinoma (n = 4). The abdominal wall implantation and metastasis from the primary malignant tumors occurred in the period varying from 42 to 94 days after the operative management. One patient died six months later due to cachexia, with the metastatic lesions becoming a little bit larger than before. TACE was employed in two patients with hepatic carcinoma to deal with the primary tumor as well as the abdominal wall implantation and metastasis lesions. Local radiotherapy was used in two patients for the abdominal wall implantation and metastasis lesions. All the metastasis lesions in the four patients were kept in stable condition. Local skin injury was seen in two patients. Conclusion: Clinical operative management carries a certain degree of risk in producing iatrogenic abdominal wall implantation and metastasis from primary malignant tumors. The diagnosis can be easily clarified when the medical history, imaging features, cytological and pathological findings are altogether taken into account. Local therapy has certain advantages. For patients in terminal stage with metastasis lesions that do not affect the living quality, the temporal measure of simple observation is recommended. (authors)
[en] The effects of the alloying element Re on the ideal strength of γ'-Ni3Al under tensile and shear stresses are investigated using the first-principles method. Results for the stress-strain relationships, ideal tensile and shear strengthes with and without Re addition are presented and explained. Re is found to be effective in improving the strength of Ni3Al. The electronic mechanism underlying the strengthening effects of Re is also elucidated.
[en] We address the problem of encoding entanglement-assisted (EA) quantum error-correcting codes (QECCs) and of the corresponding complexity. We present an iterative algorithm from which a quantum circuit composed of CNOT, H, and S gates can be derived directly with complexity O(n2) to encode the qubits being sent. Moreover, we derive the number of each gate consumed in our algorithm according to which we can design EA QECCs with low encoding complexity. Another advantage brought by our algorithm is the easiness and efficiency of programming on classical computers. (general)
[en] A size-dependent transition of deformation mechanism is revealed in Ni3Al nanowire under atomistic uniaxial tension. Deformation twinning is replaced by phase transformation when the diameter of Ni3Al nanowire reduces to a critical value near 4 nm. Enhanced size-dependent nonlinear elasticity is observed in the nanowires, in comparison to their bulk counterpart which is benchmarked by combined density functional and atomistic study. This study provide fundamental understanding on the size-dependent deformation mechanisms of nanostructured alloys.
[en] The polycrystalline Ni_3Al is brittle since the notorious intergranular fracture mode hinders its applications. Here we perform molecular dynamics to highlight the unique role of nanotwin boundary in the plastic deformation and failure mechanisms of Ni_3Al via an atomistic cracking model. Surprisingly, the strength, ductility and fracture toughness of the nanotwinned Ni_3Al are revealed to increase simultaneously with reducing twin size, possibly evading a traditional tradeoff between ductility/toughness and strength. A possible quasi-brittle fracture mode in single crystalline Ni_3Al is recognized as nucleating twinning partials from crack tip. However, the pre-existing twin boundaries can suppress the emission and propagation of successive twinning dislocations. Instead, dislocation avalanches happen and serve as a crack blunting mechanism which leads to the ductile fracture pattern of the nanotwinned Ni_3Al. A size-dependent transition of fracture mode from dislocation nucleation to shear localization is observed as twin becomes very small. A physical model combined with energetics analysis is provided to rationalize the transition. Our atomistic insights are in qualitative agreement with recent observations of improved strength and ductility of Ni_3Al with disordered nanotwinned structure after severe plastic deformation.
[en] Direct atomic-scale evidence is presented for the shear–dilatation correlation in metallic glasses via molecular dynamics and first-principles calculations. A quantitative parabolic relationship is established between the atomic local shear and hydrostatic volumetric strains by carrying out statistical analysis on a deformed glass model. The correction is further verified by density functional theory. Our atomistic demonstration of shear–dilatation correlation collaborates with the experimentally observed a few percent volume change in shear bands. It brings quantitative insights into the unique correlation between shear transformation and cavitation in metallic glasses. - Graphical abstract: A statistical analysis on the atomic-scale strains of a deformed metallic glass model reveals a parabolic relationship between the atomic local shear strain and hydrostatic volumetric strain, bridging the unique shear transformation and dilatation-induced cavitation mechanisms of amorphous solids.
[en] In the present work, stress relaxation tests, high-resolution transmission electron microscopy (HRTEM), and molecular dynamics (MD) simulations were conducted on coarse-grained (cg), nanograined (ng), and nanotwinned (nt) copper at temperatures of 22 °C (RT), 30 °C, 40 °C, 50 °C, and 75 °C. The comprehensive investigations provide sufficient information for the building-up of a formula to describe the time, stress, and temperature-dependent deformation and clarify the relationship among the strain rate sensitivity parameter, stress exponent, and activation volume. The typically experimental curves of logarithmic plastic strain rate versus stress exhibited a three staged relaxation process from a linear high stress relaxation region to a subsequent nonlinear stress relaxation region and finally to a linear low stress relaxation region, which only showed-up at the test temperatures higher than 22 °C, 22 °C, and 30 °C, respectively, in the tested cg-, ng-, and nt-Cu specimens. The values of stress exponent, stress-independent activation energy, and activation volume were determined from the experimental data in the two linear regions. The determined activation parameters, HRTEM images, and MD simulations consistently suggest that dislocation-mediated plastic deformation is predominant in all tested cg-, ng-, and nt-Cu specimens in the initial linear high stress relaxation region at the five relaxation temperatures, whereas in the linear low stress relaxation region, the grain boundary (GB) diffusion-associated deformation is dominant in the ng- and cg-Cu specimens, while twin boundary (TB) migration, i.e., twinning and detwinning with parallel partial dislocations, governs the time, stress, and temperature-dependent deformation in the nt-Cu specimens.
[en] Graphical abstract: Fig. 1 shows temperature dependence of the normalized loss modulus of La_6_0Ni_1_5Al_2_5 bulk metallic glass (heating rate: 3 K/min and driving frequency: 3 K/min): (1) As-cast, (2) annealed one (annealing temperature: 448 K and annealing time: 16 h). A pronounced β relaxation process was observed at lower temperature (∼360 K). In addition, the α relaxation was detected at a higher temperature (∼500 K). - Abstract: The β relaxation typically plays an important role in the plastic deformation of glassy materials. Compared with amorphous polymers, most of the metallic glasses do not show evident β relaxation based on mechanical spectroscopy. However, La_6_0Ni_1_5Al_2_5 bulk metallic glass (BMG) exhibits a prominent β relaxation process, which could be an ideal model alloy to investigate the correlation between the β relaxation and mechanical behavior of metallic glasses. In this work, compressive properties and stress relaxation at high temperature (below glass transition temperature T_g) were studied. Stress relaxation of La_6_0Ni_1_5Al_2_5 BMG was measured by uniaxial compressive tests and mechanical spectroscopy around both α and β relaxation temperature domain. At higher temperatures and sufficiently low strain rate, the flow behavior of the La_6_0Ni_1_5Al_2_5 BMG could be simulated by a master curve, showing that the behavior is independent of temperature, especially on the proximity of the β relaxation process. Because the existence of the β relaxation, a high value of the activation volume for the plastic deformation could be ascribed to the existence of a specific atomic arrangement in the La_6_0Ni_1_5Al_2_5 BMG. It is found that compressive stress relaxation kinetics parameter remains temperature independent below T_g