In vivo study of porous NiTi cryotweezers for bone tissue cryotherapy.

This study examined the effects of liquid nitrogen vapor on osteogenesis in the rabbit femur. Cryotweezers made of porous nickel titanium alloy (nitinol or NiTi) obtained by self-propagating high temperature synthesis were used in this experiment. The porous structure of the cryotweezers allows them to hold up to 10 g of liquid nitrogen after being immersed for 2 min, which completely evaporates after 160 s. To study the effects of liquid nitrogen evaporation on osteogenesis, a rabbit femur was perforated. The formed holes were subjected to cryotherapy with varying exposure times. It was found that a 3 s exposure time stimulates osteogenesis, which was manifested in a greater number of osteoblasts in the regenerate compared to the control sample without liquid nitrogen. It was observed that increasing the exposure to 6, 9 or 12 s had a destructive effect, to varying degrees. The most severe damage was exerted by a 12 s exposure, which resulted in the formation of osteonecrosis areas. In the samples exposed to 6 and 9 s of cryotherapy, destruction of the cytoplasm of osteocytes and osteoclasts was observed.

Engineered Fibrous NiTi Scaffolds with Cultured Hepatocytes for Liver Regeneration in Rats.

At present, the use of alternative systems to replenish the lost functions of hepatic metabolism and partial replacement of liver organ failure is relevant, due to an increase in the incidence of various liver disorders, insufficiency, and cost of organs for transplantation, as well as the high cost of using the artificial liver systems. The development of low-cost intracorporeal systems for maintaining hepatic metabolism using tissue engineering, as a bridge before liver transplantation or completely replacing liver function, deserves special attention. In vivo applications of intracorporeal fibrous nickel-titanium scaffolds (FNTSs) with cultured hepatocytes are described. Hepatocytes cultured in FNTSs are superior to their injections in terms of liver function, survival time, and recovery in a CCl4-induced cirrhosis rats' model. 232 animals were divided into 5 groups: control, CCl4-induced cirrhosis, CCl4-induced cirrhosis followed by implantation of cell-free FNTSs (sham surgery), CCl4-induced cirrhosis followed by infusion of hepatocytes (2 mL, 107 cells/mL), and CCl4-induced cirrhosis followed by FNTS implantation with hepatocytes. Restoration of hepatocyte function in the FNTS implantation with the hepatocytes group was accompanied by a significant decrease in the level of aspartate aminotransferase (AsAT) in blood serum compared to the cirrhosis group. A significant decrease in the level of AsAT was noted after 15 days in the infused hepatocytes group. However, on the 30th day, the AsAT level increased and was close to the cirrhosis group due to the short-term effect after the introduction of hepatocytes without a scaffold. The changes in alanine aminotransferase (AlAT), alkaline phosphatase (AlP), total and direct bilirubin, serum protein, triacylglycerol, lactate, albumin, and lipoproteins were similar to those in AsAT. The survival time of animals was significantly longer in the FNTS implantation with hepatocytes group. The obtained results showed the scaffolds' ability to support hepatocellular metabolism. The development of hepatocytes in FNTS was studied in vivo using 12 animals using scanning electron microscopy. Hepatocytes demonstrated good adhesion to the scaffold wireframe and survival in allogeneic conditions. Mature tissue, including cellular and fibrous, filled the scaffold space by 98% in 28 days. The study shows the extent to which an implantable "auxiliary liver" compensates for the lack of liver function without replacement in rats.

Thickness Effects on the Martensite Transformations and Mechanical Properties of Nanocrystalline NiTi Wires.

This paper studied the features of the martensitic transformations and mechanical properties of 40, 60, and 90 µm thick NiTi wires with nanocrystalline B2 structures. It was established that the wires were composites and consisted of a TiNi matrix and a TiO2 + TiNi3 surface layer. Structural methods showed that the wire matrix was formed by grains of up to 20 nm in size. The method of measuring the electrical resistivity during cooling and heating revealed a two-stage nature of the martensitic transformation. Cyclic loading-unloading demonstrated that all the samples exhibited superelasticity effects and completely restored their shape when unloaded from a 4-8% relative strain at room temperature. An increase in mechanical characteristics with respect to the wire thickness was experimentally established. This was due to the change in the composition of the TiNi matrix during drawing.

Softening Effects in Biological Tissues and NiTi Knitwear during Cyclic Loading.

Samples of skin, tendons, muscles, and knitwear composed of NiTi wire are studied by uniaxial cyclic tension and stretching to rupture. The metal knitted mesh behaves similar to a superelastic material when stretched, similar to soft biological tissues. The superelasticity effect was found in NiTi wire, but not in the mesh composed of it. A softening effect similar to biological tissues is observed during the cyclic stretching of the mesh. The mechanical behavior of the NiTi mesh is similar to the biomechanical behavior of biological tissues. The discovered superelastic effects allow developing criteria for the selection and evaluation of mesh materials composed of titanium nickelide for soft tissue reconstructive surgery.

Recording, Storage, and Reproduction of Information on Polyvinyl Chloride Films Using Shape Memory Effects.

Partial dissolution and plasticization are used for recording, storing, and reproducing information with modified industrial screen-printing equipment and aqueous solutions of colorless organic liquids on small surface area shape memory polymer films. To justify the choice of "ink" and evaluate the effectiveness of using organic liquids as high-speed polymer solvents, the new method for recording hidden information uses the calculation of the solubility parameter, differential scanning calorimetry, and the method of one-sided swelling of films under isometric conditions. Using the example of tactile marking of shrink labels made of polyvinyl chloride, the optimal conditions for recording hidden information on a film are established in terms of the concentration of an aqueous solution of tetrahydrofuran, the contact time, and the processing temperature of the polymer using screen printing equipment.

Microstructure Evolution in Cu-Ni-Co-Si-Cr Alloy During Hot Compression by Ce Addition.

Cu-Ni-Si alloys are widely used in lead frames and vacuum devices due to their high electrical conductivity and strength. In this paper, a Cu-Ni-Co-Si-Cr-(Ce) alloy was prepared by vacuum induction melting. Hot compression tests of the Cu-Ni-Co-Si-Cr and Cu-Ni-Co-Si-Cr-Ce alloys were carried out using a Gleeble-1500 simulator at 500-900 °C deformation temperatures and 0.001-10 s-1 strain rates. The texture change was analyzed by electron backscatter diffraction. The <110> fiber component dominated the texture after compression, and the texture intensity was reduced during recrystallization. Moreover, the average misorientation angle φ for Cu-Ni-Co-Si-Cr-Ce (11°) was lower than that of Cu-Ni-Co-Si-Cr (16°) under the same conditions. Processing maps were developed to determine the optimal processing window. The microstructure and precipitates of the Cu-Ni-Co-Si-Cr and Cu-Ni-Co-Si-Cr-Ce alloys were also analyzed. The average grain size of the Cu-Ni-Co-Si-Cr-Ce alloy (48 µm) was finer than that of the Cu-Ni-Co-Si-Cr alloy (80 µm). The average size of precipitates in the Cu-Ni-Co-Si-Cr alloy was 73 nm, while that of the Cu-Ni-Co-Si-Cr-Ce alloy was 27 nm. The addition of Ce delayed the occurrence of dynamic recrystallization.

Thermodynamics Analysis of Multiple Microelements' Coupling Behavior in High Fatigue Resistance 50CrVA Spring Steel with Nanoparticles.

Solid solution and coupling precipitation behavior of multiple microelements in 50CrVA spring steel under different temperatures were analyzed based on thermodynamics. Quantitative relationships between the multiple microelements' contents and secondary phases, and their effects on fatigue life, were systematically studied in conjunction with the secondary phase microstructure characterization using scanning and transmission electron microscopy, etc. The solid solution contents of different microelements decreased as the temperature decreased, especially N and Ti, but the number of compounds gradually increased when the temperature decreased. Carbonitride constitutional liquation occurred in 50CrVA-S1# spring steel-containing microparticles, and without carbonitrides, constitutional liquation occurred in 50CrVA-S2# spring steel-containing nanoparticles. The experimental results indicate that the fatigue life reduces by about an order of magnitude when the secondary phase size changes from nanometers to microns, and the corresponding relationship among multiple microelements, microstructure of secondary phases, and fatigue life, was established in this spring steel.

Long-term in vivo study of biodegradable Zn-Cu stent: A 2-year implantation evaluation in porcine coronary artery.

In the present study, a novel biodegradable Zn-0.8Cu coronary artery stent was fabricated and implanted into porcine coronary arteries for up to 24 months. Micro-CT analysis showed that the implanted stent was able to maintain structural integrity after 6 months, while its disintegration occurred after 9 months of implantation. After 24 months of implantation, approximately 28 ±â€¯13 vol% of the stent remained. Optical coherence tomography and histological analysis showed that the endothelialization process could be completed within the first month after implantation, and no inflammation responses or thrombosis formation was observed within 24 months. Cross-section analysis indicated that the subsequent degradation products had been removed in the abluminal direction, guaranteeing that the strut could be replaced by normal tissue without the risk of contaminating the circulatory system, causing neither thrombosis nor inflammation response. The present work demonstrates that the Zn-0.8Cu stent has provided sufficient structural supporting and exhibited an appropriate degradation rate during 24 months of implantation without degradation product accumulation, thrombosis, or inflammation response. The results indicate that the Zn-0.8Cu coronary artery stent is promising for further clinical applications. STATEMENT OF SIGNIFICANCE: Although Zn and its alloys have been considered to be potential candidates of biodegradable metals for vascular stent use, by far, no Zn-based stent with appropriate medical device performance has been reported because of the low mechanical properties of zinc. The present work presents promising results of a Zn-Cu biodegradable vascular stent in porcine coronary arteries. The Zn-Cu stent fabricated in this work demonstrated adequate medical device performance both in vitro and in vivo and degraded at a proper rate without safety problems induced. Furthermore, large animal models have more cardiovascular similarities as humans. Results of this study may provide further information of the Zn-based stents for translational medicine research.

Editorial for the Special Issue on Small-Scale Deformation using Advanced Nanoindentation Techniques.

Nanoindentation techniques have been used to reliably characterize mechanical properties at small scales for the past 30 years [...].

Initial formation of corrosion products on pure zinc in saline solution.

Corrosion product formed on zinc sample during 2 weeks immersion in saline solution has been investigated. The corrosion layer morphology as well as its chemical composition, was analyzed using scanning electron microscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Electrochemical measurement was used to analyze the corrosion behavior. Zinc oxide, zinc hydroxide and zinc hydroxide chloride were formed on zinc surface in saline solution. The thickness of corrosion layer increased with the time increased. The pure Zn has an estimated corrosion rate of 0.063 mm y-1 after immersion for 336 h. Probable mechanisms of zinc corrosion products formation are presented.

Recording digital color information on transparent polyethylene films by thermal treatment.

This study characterizes the use of transparent low-density polyethylene laminate films for the purpose of recording digital information in the form of linear and color two-dimensional matrix codes that are distinguishable in polarized light. Color characteristics of multilayer laminated materials made from polyethylene and heat treatment methods for changing their coloring are examined. The contribution of the number of multilayer film interfaces to the lightness and color of the laminate is shown. Melt-extruded industrial polyethylene film heat treatment methods by convection, conduction, and radiation, to control their optical characteristics and color in polarized light, are studied.

Cu-Doped ZnO Electronic Structure and Optical Properties Studied by First-Principles Calculations and Experiments.

The band structure, the density of states and optical absorption properties of Cu-doped ZnO were studied by the first-principles generalized gradient approximation plane-wave pseudopotential method based on density functional theory. For the Zn1-xCuxO (x = 0, x = 0.0278, x = 0.0417) original structure, geometric optimization and energy calculations were performed and compared with experimental results. With increasing Cu concentration, the band gap of the Zn1-xCuxO decreased due to the shift of the conduction band. Since the impurity level was introduced after Cu doping, the conduction band was moved downwards. Additionally, it was shown that the insertion of a Cu atom leads to a red shift of the optical absorption edge, which was consistent with the experimental results.

Proton Irradiation Effects on Hardness and the Volta Potential of Welding 308L Duplex Stainless Steel.

308L welding duplex stainless steel has been irradiated at 360 °C with 2 MeV protons, corresponding to a dose of 3 dpa at the maximum depth of 20 µm. Microhardness of the δ-ferrite and austenite phases was studied before and after proton irradiation using in situ nanomechanical test system (ISNTS). The locations of the phases for indentations placement were obtained by scanning probe microscopy from the ISNTS. The hardness of the δ-ferrite had a close relationship with the vacancy distribution obtained from the Stopping and Range of Ions in Matter (SRIM) Monte Carlo simulation code. However, the hardness of the austenite phase in the maximum damage region (17⁻20 µm depth) from the SRIM simulation was decreasing sharply, and a hardness transition region (>20 µm and <55 µm depth) was found between the maximum damage region (17⁻20 µm depth) and the unirradiated region (>20 µm depth). However, the δ-ferrite hardness behavior was different. A hardness of the two phases increased on the irradiated surface and the interior due to different hardening mechanisms in the austenite and δ-ferrite phases after a long time high-temperature irradiation. A transition region (>20 µm and <55 µm depth) of the Volta potential was also found, which was caused by the deeper transfer of implanted protons measured by scanning Kelvin probe force microscopy.

Thermodynamic Analysis of Ti3O5Nanoparticles Formed in Melt and Their Effects on Ferritic Steel Microstructure.

Based on the Wagner's formalism combined with mass conservation, a thermodynamic analysis method has been developed previously. This method enables the calculation of the equilibrium matrix composition, precipitate composition and precipitate total molar fraction for TixOy(s) in molten metal, which can be determined at any appropriate temperature. In this present study, the Ti3O5 phase precipitation and the quantitative relationship between the addition of Ti, O and Ti3O5 in the molten steel were studied using the thermodynamic model. Using the combined multipoint dispersion supply method, electromagnetic stirring and well-dispersed 5-nm Ti3O5 nanoparticles were fabricated in the ferrite matrix of the as-cast high-strength steel with 0.05 wt % Ti-0.002 wt % O. The as-cast microstructure was improved by the homogeneously dispersed Ti3O5 nanoparticles through heterogeneous nucleation and grain refinement.

Study of oxygen evolution reaction on amorphous Au13@Ni120P50 nanocluster.

The pursuit of catalysts to promote effective water oxidization to produce oxygen has become a research subject of high priority for water splitting. Here, first-principles calculations are employed to study the water-splitting oxygen evolution reaction (OER) on ∼1.5 nm diameter Au13@Ni120P50 core-shell nanoclusters. Water splitting to produce oxygen proceeds in four intermediate reaction steps (OH*, O*, OOH* and O2). Adsorption configurations and adsorption energies for the species involved in OER on both Au13@Ni120P50 cluster and Ni12P5(001) supported by Au are presented. In addition, thermodynamic free energy diagrams and kinetic potential energy changes are systematically discussed. We show that the third intermediate reaction (O* reacting with H2O to produce OOH*) of the four elementary steps is the reaction-determining step, which accords with previous results. Also, the catalytic performance of OER for Au13@Ni120P50 is better than that for Ni12P5(001) supported by Au in terms of reactive overpotential (0.74 vs. 1.58 V) and kinetic energy barrier (2.18 vs. 3.17 eV). The optimal kinetic pathway for OER is further explored carefully for the Au13@Ni120P50 cluster. The low thermodynamic overpotential and kinetic energy barrier make Au13@Ni120P50 promising for industrial applications as a good OER electrocatalyst candidate.

Antibacterial activity and inflammation inhibition of ZnO nanoparticles embedded TiO2 nanotubes.

Titanium (Ti) with nanoscale structure on the surface exhibits excellent biocompatibility and bone integration. Once implanted, the surgical implantation may lead to bacterial infection and inflammatory reaction, which cause the implant failure. In this work, irregular and nanorod-shaped ZnO nanoparticles were doped into TiO2 nanotubes (TNTs) with inner diameter of about 50 nm by electro-deposition. The antibacterial properties of ZnO incorporated into TiO2 nanotubes (TNTs/ZnO) were evaluated using Staphylococcus aureus (S. aureus). Zn ions released from the nanoparticles and the morphology could work together, improving antibacterial effectiveness up to 99.3% compared with the TNTs. Macrophages were cultured on the samples to determine their respective anti-inflammatory properties. The proliferation and viability of macrophages were evaluated by the CCK-8 method and Live&Dead stain, and the morphology of the cells was observed by scanning electron microscopy. Results indicated that TNTs/ZnO has a significant inhibitory effect on the proliferation and adhesion of macrophages, which could be used to prevent chronic inflammation and control the inflammatory reaction. Besides, the release of Zn ions from the ZnO nanoparticles is a long-term process, which could be beneficial for bone integration. Results demonstrate that ZnO deposited into TNTs improved the antibacterial effectiveness and weakened the inflammatory reaction of titanium-based implants, which is a promising approach to enhance their bioactivity.

A Statistical Study on the Effect of Hydrostatic Pressure on Metastable Pitting Corrosion of X70 Pipeline Steel.

Hydrostatic pressure effects on pitting initiation and propagation in X70 steel are investigated by evaluating metastable pitting probability using electrochemical methods and immersion corrosion tests in containing chlorine ion solution. Potentiodynamic tests indicated that hydrostatic pressure can decrease the breakdown potential and lead to a reduced transpassivity region. Metastable test results revealed that hydrostatic pressure can increase metastable pitting formation frequency and promote stabilization of metastable pitting growth. Electrochemical impedance spectroscopy (EIS) results indicate that Hydrostatic pressure decreases the charge transfer resistance and increases the dissolution rate within the cavities. Corrosion test results also indicated that pitting initiation and propagation are accelerated by hydrostatic pressure. Result validity was verified by evaluating metastable pitting to predict pitting corrosion resistance.

Pitting Initiation and Propagation of X70 Pipeline Steel Exposed to Chloride-Containing Environments.

Inclusion-induced pitting initiation mechanisms in X70 steel were investigated by scanning electron microscopy, scanning Kelvin probe force microscopy (SKPFM), immersion and electrochemical polarization tests in chloride-containing ion solutions. There are three inclusion types in the X70 steel. Corrosion test results indicated that pitting corrosion resistance of type A inclusion < type C inclusion < type B inclusion, i.e., (Mn, Ca)S < matrix < (Al, Ca)O. SKPFM test results show that the type A inclusion exhibited both lower and higher potentials than the matrix, while the type B inclusion exhibited higher potential than the matrix. The corrosion test and the SKPFM potential test results are consistent. Potentiodynamic polarization results indicate that the type A and C are active inclusions, while the type B is an inactive inclusion. Three kinds of possible mechanisms of inclusion-induced pitting corrosion are established for the X70 steel.

Effect of Hydrogen Exposure on Mechanical and Tribological Behavior of CrxN Coatings Deposited at Different Pressures on IN718.

In the current study, the properties of the CrxN coatings deposited on the Inconel 718 superalloy using direct current reactive magnetron sputtering are investigated. The influence of working pressure on the microstructure, mechanical, and tribological properties of the CrxN coatings before and after high-temperature hydrogen exposure is studied. The cross-sectional scanning electron micrographs indicate the columnar structure of the coatings, which changes from dense and compact columns to large columns with increasing working pressure. The Cr/N ratio increases from 1.4 to 1.9 with increasing working pressure from 300 to 900 mPa, respectively. X-ray diffraction analysis reveals a change from mixed hcp-Cr2N and fcc-CrN structure to approximately stoichiometric Cr2N phase. After gas-phase hydrogenation, the coating deposited at 300 mPa exhibits the lowest hydrogen absorption at 600 °C of all investigated coatings. The results indicate that the dense mixed cubic and hexagonal structure is preferential for hydrogen permeation resistance due to the presence of cubic phase with higher packing density in comparison to the hexagonal structure. After hydrogenation, no changes in phase composition were observed; however, a small amount of hydrogen is accumulated in the coatings. An increase of coating hardness and elastic modulus was observed after hydrogen exposure. Tribological tests reveal that hydrogenation leads to a decrease of the friction coefficient up to 20%-30%. The best value of 0.25 was reached for hydrogen exposed CrxN coating deposited at 300 mPa.

Modified Qigong Breathing Exercise for Reducing the Sense of Hunger on an Empty Stomach.

BACKGROUND: The aims of this study were to determine whether a modified Qigong breathing exercise can reduce the sense of hunger and identify possible mechanisms. METHODS: The results from the test group, which performed the exercise, are compared with the control group, which performed deep breathing. Intestinal pressure measurements, stomach pH monitoring, and participant surveys were used for assessment. RESULTS: Stomach pH was increased by 3 (0.2) and intestinal pressure was reduced by 12 (0.5) mm Hg in the experimental group and did not change significantly in the control group. The study provides strong evidence that the exercise can significantly reduce, or even suppress the sense of hunger on an empty stomach. CONCLUSION: This breathing exercise provides comfort in different circumstances, such as lack of regular meals, limited volume or caloric diet, and even during temporary complete absence of food in therapeutic fasting.