A Study of the Superplastic Deformation Behavior of Low-Cost Ti-2Fe-0.1B Alloys.

Titanium alloys have high specific strength and corrosion resistance, which have promising applications in industry. However, the machinability of titanium alloys is limited due to their crystal lattice and physical properties. Thus, in recent years, the superplastic forming of titanium alloys has been intensively developing, in particular, forming at low temperatures and/or high strain rates. In this work, a tensile test of low-cost Ti-2Fe-0.1B alloys was carried out at a temperature of 550~750 °C and a strain rate of 1 × 10-3 s-1~1 × 10-2 s-1. The results showed that the alloy exhibited good superplasticity even at a high strain rate (1 × 10-2 s-1) and a low deformation temperature of 550 °C; the elongation of the alloy in this state reached 137.5%. The high strain rate sensitivity coefficient m (0.3) and the maximum elongation (452%) were obtained at a strain rate of 1 × 10-3 s-1 and a temperature of 750 °C. Characteristics of the microstructure showed that during superplastic deformation, the recrystallization and grain boundary sliding of the alloy phases were accelerated, which could be ascribed to the effect of the element Fe. At the same time, the TiB phase located around the primary elongated α grains could also induce dynamic recrystallization and dynamic globularization during deformation.

Biaxial tensile behavior of stainless steel 316L manufactured by selective laser melting.

In this study, miniaturized cruciform biaxial tensile specimens were optimized by finite element simulation software Ansys to vary five geometric parameters. The optimized specimens were utilized to characterize the biaxial tensile properties of 316L stainless steel fabricated through selective laser melting (SLM), with the two loading directions being vertical (X) and parallel (Y) to the building direction. It was discovered that at load ratios of 4:2 and 2:4, the yield strengths along X and Y orientations reached their respective maxima. By comparing the experimentally obtained yield loci against predictions by theoretical criteria including Mises, Hill48 and Hosford, it was found that the Hill48 anisotropic criterion corresponded most closely with the experimental results, while the other two criteria exhibited considerably larger deviations. Therefore, Hill48 was concluded to most accurately describe the yielding behaviors of SLM 316L under complex loading conditions.

Effect of Heat Treatment on Microstructure and Mechanical Behavior of Ultrafine-Grained Ti-2Fe-0.1B.

In the present study, a novel Ti-2Fe-0.1B alloy was processed using equal channel angular pressing (ECAP) via route Bc for four passes. The isochronal annealing of the ultrafine-grained (UFG) Ti-2Fe-0.1B alloy was conducted at various temperatures between 150 and 750 °C with holding times of 60 min. The isothermal annealing was performed at 350-750 °C with different holding times (15 min-150 min). The results indicated that no obvious changes in the microhardness of the UFG Ti-2Fe-0.1B alloy are observed when the annealing temperature (AT) is up to 450 °C. Compared to the UFG state, it was found that excellent strength (~768 MPa) and ductility (~16%) matching can be achieved for the UFG Ti-2Fe-0.1B alloy when annealed at 450 °C. The microstructure of the UFG Ti-2Fe-0.1B alloy before and after the various annealing treatments was characterized using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). It was found that the average grain size remained at an ultrafine level (0.91-1.03 µm) when the annealing temperature was below 450 °C. The good thermal stability of the UFG Ti-2Fe-0.1B alloy could be ascribed to the pinning of the TiB needles and the segregation of the Fe solute atoms at the grain boundaries, which is of benefit for decreasing grain boundary energy and inhibiting the mobility of grain boundaries. For the UFG Ti-2Fe-0.1B alloy, a recrystallization activation energy with an average value of ~259.44 KJ/mol was analyzed using a differential scanning calorimeter (DSC). This is much higher than the lattice self-diffusion activation energy of pure titanium.

[Combined therapy of acute and recurrent cystitis in women].

Lower urinary tract infection (LUTI) is one of the most common causes for a large number of females of different ages to visit a urologist and other physicians. LUTI is often a chronic condition, and its symptoms can sometimes persist throughout live, leading to a serious deterioration in the quality of life. Three clinical cases of the effective treatment of women with recurrent UTI with Phytolysin paste* and Phytolysin capsules as part of combined therapy are presented in the article.

[Kidney transplantation from Covid-19 positive deceased donor: what are the consequences for recipients?]

INTRODUCTION: In recent months, with the spread of COVID 19, the number of kidney transplants from deceased donors has declined significantly in most countries. One of the reasons is the possibility of infection of the recipient with SARS-CoV-2. Determining the risk of transmission of COVID 19 with a donor organ is very important for developing a kidney transplantation policy during a pandemic. MATERIAL AND METHOD: We present cases of kidney transplantation from COVID 19 positive deceased donor to two dialysis patients in single center. Deceased donor: a 45 years old man with diabetes, who had a major hemorrhagic stroke resulting in brain death. He had normal urine output and serum creatinine level for last 24 hours before kidney harvesting. For a few hours after organ harvesting, the donor was diagnosed COVID 19 (retrospective nasopharyngeal swab rRT-PCR which was confirmed by morphological examination and RNA-PCR of specimens from the trachea and bronchus). Recipient 1: a 49 years old man with polycystic kidney disease had been on hemodialysis for 28 months. He was in urgent list because of problems with vascular access. So non identical ABO (0-donor, B-recipient) kidney transplantation from this deceased donor was done in May 2020. Recipient 2: a 45 years old man with polycystic kidney disease on continuous ambulatory peritoneal dialysis (CAPD). was registered on urgent waiting list because of low transport capacity of peritoneum. Kidney transplantation from the same deceased donor was done at the same time. In both cases we completely abandoned any antilymphocytic agents for induction, despite non ABO identical transplantation in one of the recipients and the delayed graft function. Both patients received only basic immunosuppression, including tacrolimus, methylprednisolone and a mycophenolic acid. RESULTS: In first case cold ischemia time was 22 hours. The recipient had delayed graft function with increasing of urine output on day 8 post-transplant. No other deviations from the usual course were seen during hospital stay. The patient was discharge from hospital with serum creatinine level 122 mkmol/L. The cold ischemia time was 21 hours in another patient. Graft function was immediate with a decrease serum creatinine to 92.5 mkmol/L at discharge. Both patients had no febrile and no other symptoms of acute respiratory disease during all hospital stay. No abnormalities on chest X-ray were seen. No serum anti-SARS-CoV-2 IgM and IgG were detected before and during 6 weeks after surgery. Repeated nasopharyngeal swabs rRT-PCR were negative during all the period. Both recipients were discharged for 5 weeks after surgery to prevent out-of-hospital contamination of COVID 19, which would be difficult to differentiate from transmission infection. After 9 months both patients are doing well with no clinical or laboratory signs of COVID-19. CONCLUSION: Today we have no evidence of the possibility of transmission of COVID-19 from a SARS-Cov-2 positive donor to a kidney recipient. We also have no reason to suspect kidney damage by COVID-19 in a deceased donor at normal serum creatinine level. Avoiding the use of anti-lymphocyte drugs for induction of immunosuppression may also reduce the risk of developing COVID19 after transplantation. A careful collection and analysis of such dates is necessary to develop modern practical recommendations for transplant centers.

Impact of Equal Channel Angular Pressing on Mechanical Behavior and Corrosion Resistance of Hot-Rolled Ti-2Fe-0.1B Alloy.

In the present study, the unique bimodal grain size distribution microstructure with the ultrafine substrate and embedded macro grains was fabricated by a traditional hot-rolling process in a novel low-cost Ti-2Fe-0.1B titanium alloy, which possesses a good combination of strength (around 663 MPa) and ductility (around 30%) without any post heat treatment. Meanwhile, the mechanical behavior and corrosion resistance of hot-rolled Ti-2Fe-0.1B alloy after equal channel angular pressing (ECAP) deformation were studied. Results indicated that the average grain size decreased to 0.24 µm after 4 passes ECAP deformation, which led to the enhancement of tensile strength to around 854 MPa and good ductility to around 15%. In addition, corrosion resistance was also improved after ECAP due to the rapid self-repairing and thicker passivation film. Our study revealed that the novel low-cost titanium alloy after hot-rolling and ECAP could be used instead of Ti-6Al-4V in some industrial applications due to similar mechanical behavior and better corrosion resistance.

[Laparoscopic radical cystectomy: novel technique with late dividing of the ureters].

INTRODUCTION: Despite considerable progress during last decade, laparoscopic radical cystectomy (LRC) still remains a complex and time-demanding procedure. The number of patients with baseline chronic kidney diseases has gradually increased. AIM: to compare the results of our novel technique of LRC with late dividing of the ureters with conventional procedure. MATERIALS AND METHODS: A total of 50 patients with bladder cancer, who underwent to LRC in a single clinic between April 2013 and January 2017, were included in the study. A conventional LRC was performed in 25 patients, while in other 25 cases, a novel technique of LRC was used. In all cases, LRC was done with fully intracorporeal urinary diversion. Statistical analysis was performed using the Shapiro-Wilk test for parametric testing. In order to compare two groups, Student t-test was used for independent samples. RESULTS: There were no significant differences between two groups in average length of procedure, blood loss volume and length of hospital stay. Major intraoperative complications (injury of the rectum) occurred in two patients, one in each group. Both cases were successfully managed intraoperatively. In addition, there were two postoperative complications in each group that required repeat intervention. The mean serum creatinine level on the 2nd day after surgery was significantly higher after conventional LRC (171.6 and 147.7 mol/L), while glomerular filtration rate was significantly lower (58 and 72 ml/min/1.73 m2), compared to group of novel technique of LRC with late dividing of the ureters. A total of four patients in group of conventional LRC and two patients in group of novel technique had cancer progression. Two patients (one in each group) died because of cancer progression after 15 and 34 months after surgery. The mean follow-up was 25.6 (12-39) months after LRC with late dividing of the ureters and 33.2 (18-48) months in group of standard LRC. CONCLUSION: LRC with late dividing of the ureters allow to prevent prolonged contact of hyperosmolar and, in some cases, non-sterile urine with peritoneum and decrease inflammation and risk of postoperative adhesions. Using of novel technique may decrease rate of perioperative nephropathy, which is especially important in patients with decreased renal function (single functioning kidney, hydronephrosis, diabetes, renal failure, adjuvant chemotherapy). However, more procedures and longer follow-up period are necessary in order to evaluate ontological results of the novel technique.

Experimental development of new surgical suturing materials with complex biological activities.

New surgical suturing materials with complex biological activities (antibacterial and stimulating tissue regeneration) have been developed. In vitro studies demonstrated pronounced and prolonged (up to 10-12 days) antibacterial activity. Experiments on 108 male albino rats proved the positive effect of the materials on the wound process: shortening of the inflammation period, more rapid transformation of the granulation tissue, more rapid epithelialization of the wound and its pronounced contraction.

Passive and active target delivery of drugs to ischemic myocardium.

Silica nanoparticles as carriers for targeted drug delivery to the heart were studied. Studies of hemodynamic parameters of rats after intravenous infusion of silica nanoparticles showed no acute toxicity. Intravenous infusion of silica nanoparticles to animals with ischemia-reperfusion of the myocardium led to accumulation of the nanoparticles in the focus of injury, which attests to possibility of passive targeted drug delivery to the myocardium.