Repair Zone Research Articles

Inferior Healing Rate in Isolated Meniscal Repair than that in Meniscal Repair with Concomitant ACL Reconstruction Evaluated with MRI.

Isolated meniscal repair has been suggested as one of the contributing factors in unhealed meniscal repair. The purpose of this study was to compare the healing rate between isolated meniscal repair and meniscal repair with concomitant anterior cruciate ligament reconstruction (ACLR) using a standardised assessment method after propensity score matching. Accuracy of the Crues' grading system for meniscal healing was validated using second-look arthroscopy as the reference standard in 17 patients. Propensity score matching (one-to-one) was performed between 26 patients who underwent isolated meniscal repair and 98 patients who underwent meniscal repair with concomitant ACLR. Patients were matched for sex, age, side and zone of the meniscal repair, and number of sutures. Healing rates at one year which were evaluated with magnetic resonance imaging (MRI) were compared between the two groups. The sensitivity and specificity of the Crues' grading system on multiple plane MRI for meniscal healing were 100% and 83.3%, respectively. Both the isolated meniscal repair group and the meniscal repair with concomitant ACLR group included 21 patients after propensity score matching. Baseline characteristics did not differ significantly between the two groups. The healing rate was significantly lower in the isolated meniscal repairs group (14.3%) than in the meniscal repair concomitant with ACLR group (47.6%, P=0.04). The healing rate for isolated meniscal repair using a standardised MRI assessment method was inferior to that of meniscal repair with concomitant ACLR after propensity score matching.

PROBABILISTIC MODELS FOR RELIABILITY ASSESSMENT OF PIPELINE SYSTEMS

The issues of functional reliability assessment within the framework of the pipeline system reliability diagnostics subsystem are considered. The basis for the development of the functional reliability diagnostics subsystem is the breakdown of the pipeline system into emergency repair zones, as well as the replacement of the structure with the macro structure of emergency repair zones, which completely inherits the functional reliability of the system. A mathematical model is formed for each consumer Oi of the pipeline system, where and is the total number of consumers. If several consumers receive the target product from only one zone, then the corresponding mathematical models of functional reliability coincide. The following initial data are used to form a mathematical model of functional reliability in relation to the consumer Oi: calculation model of functional reliability in relation to all consumers. On the basis of emergency repair zones probabilistic models for calculating the functional reliability of pipeline systems have been developed, which are used in the algorithm for calculating the reliability of the entire system. The reliability of pipeline systems at the operational stage is supported by timely prevention and elimination of failures. A probabilistic model has been developed that makes it possible to assess the characteristics of the process of prevention and elimination of failures, to select the optimal parameters. Corresponding numerical calculations have been carried out. From the standpoint of a specialized organization that serves pipeline system, you need to minimize costs, while adhering to certain restrictions, namely: the deviation of the actual time of repair from the normative should not exceed the value, and all requests to eliminate accidents must be fulfilled. This means that the organization has a certain margin of capacity to service emergency calls. Minimize costs within the developed model can be solely due to the number of teams nmin, aiming at their maximum loading. So, we got the mathematical programming problem, which is: to find nmin, which maximizes the load function when the relevant restrictions are met. Keywords: model, subsystem, diagnostics, reliability, pipeline system.

Influence of production specialisation level on efficiency of technical service and safety of buses operation

Introduction. The focus is on improving the maintenance and repair system of city buses on the scale of large cities in particular and regions in general. Due to the increase in the number of rolling stock, the load on the existing technical service organisations increases, which in turn leads to their overload. Consequently, the efficiency and safety indicators of bus operation are reduced. The proposed solution is to develop a system of centralised specialised production.Materials and methods. The system of maintenance and repair is considered from the point of view of the marginal utility theory. Dependences of total and marginal utility on the quantity of goods (services) are presented. The term ‘specialization’ is described from the point of view of the motor transport industry. The necessity of combining universal and specialised posts is justified.Results. The results of the experimental study on ten passenger enterprises are presented. The results of calculations of the efficiency indicators of the current repair area are given. The dependence of annual costs and profit of the current repair zone of ten posts on the level of specialisation is reflected. The dependence of the coefficient of technical readiness of buses on the scale of parks in Russia is analysed. The natural factors, influencing the coefficient of technical readiness are presented. An adequate mathematical model with physical variables of the dependence of the coefficient of technical availability on the scale of the enterprise and the level of specialisation was obtained with further processing and verification of the results.Discussion and conclusions. The results of the study are intended for the enterprises of passenger transport. The data obtained will allow to develop a system of cooperation of technical service production facilities in order to improve the performance of requests for maintenance and repair of rolling stock.

8861 Enhancing Laparoscopic Metroplasty Results in Patients with Scar Defects after Caesarean Section

<h3>Study Objective</h3> Enhancing the results of laparoscopic metroplasty (LM) in patients with the c-section scar defects. <h3>Design</h3> Level I, Canadian Task Force. A 4-year randomized prospective study evaluating two methods of LM. <h3>Setting</h3> National Center for Obstetrics, Gynecology, and Perinatology, named after V.I. Kulakov, Moscow, Russia. <h3>Patients</h3> The study includes 83 patients of reproductive age (18 – 45 years) with c-section scar defects/niches, who are interested in pregnancy. The first group – 49 patients: LM. The second group – 34 patients: LM with plication of round ligaments and injection of platelet-riched autoplasma (PRP). <h3>Interventions</h3> Standard for both groups laparoscopic metroplasty included hysteroscopic niche exploration and cervical dilation. Laparoscopic exploration of the scar zone; excision of fibrotic tissue using a monopolar hook; myometrial approximation in two layers. The second group also included 5 ml of PRP injection into the myometrial repair zone and plication of the round ligaments. The ultrasound measurement of the scar was carried out before the operation and 6 months following it. <h3>Measurements and Main Results</h3> The original scar thickness in Group 1 was 2.1 (±0.9) mm, and after surgery – 5.0 (±2.4) mm, p = 0.00001; three patients had an unsatisfactory outcome with scar thickness of less than 2.5 mm, which required a repeated operation. In Group 2 the thickness of the scar was originally 2.1 (±0.6) mm before surgery, and 5.6 (±1.3) mm after surgery, p = 0.00001, no unsatisfactory results were noted. When comparing the two methods, a significant difference was found in the increase in the newly formed scar thickness in the second group compared to the first – by 3.9 mm and 2.9 mm, respectively, p = 0.029. <h3>Conclusion</h3> Tissue tension reduction in the area of a newly formed suture on the uterus as well as use of PRP provides for the most favorable conditions for tissue repair after LM.

The effect of laser energy density on microstructural evolution and mechanical properties of laser clad 316L stainless steel for repair

Laser energy density can affect the powder forming state in laser metal deposition (LMD), ultimately altering the evolution pattern and mechanical properties of formed structures. This work uses high-speed LMD technology to repair the 316L austenitic stainless steel plate with a trapezoidal groove. By analyzing the microstructural evolution and mechanical properties of repaired specimens under different laser energy densities, we revealed the effects of density on LMD shaping. Results indicated that the microstructure in the repair zone developed alternately in forms of columnar, branch, and isometric crystals in the opposite direction of heat flow. Increased laser energy density could enlarge crystal grains in formed structures. Meanwhile, γ-Fe tended to transform into δ phase that was distributed among crystal grains in γ-Fe. When the density reached its peak, the number of the δ phase plummeted. The average microhardness of specimens first increased and then decreased in the repair zone, with its distribution fluctuating repeatedly, and the values in this zone were 1.5–1.7 times that of the substrate. The mechanical properties of repaired specimens were superior to those of the rolled steel substrate at room temperature, and these specimens' ultimate tensile strength (UTS) and elongation at this temperature were positively correlated with the laser energy density. There were dimples and typical cleavage patterns around the fracture of tensile specimens, indicating that the fracture mechanism at room temperature was of quasi-cleavage type. As the density rose, the UTS first increased and then reduced in a tensile test conducted at 500 °C, during which the strain kept growing. Simultaneously, numerous dimples with congregate micropores but without typical cleavage patterns were observed in the fracture, which revealed that all specimens exhibited ductile fracture at high temperatures.

The self-healing of marine concrete cracks based on the synergistic effect of microorganisms and inorganic minerals

To achieve the goal of self-healing of marine concrete cracks and fixation of harmful ions invading the cracks, researches on the synergy of microbial mineralization and inorganic mineral hydration were carried out. The fixation effects of Cl−, SO42− and OH− in simulated solution with different inorganic mineral dosages were tested by experiments. Further, the growth performances of microorganisms in the modified simulated solution were also tested. Finally, the self-healing effect of cracks in cement-based materials was experimentally verified. The results showed that the Cl− and SO42− in the simulated solution can be effectively fixed by the double metal hydroxide, and combined with a part of H2O to form hydration products that accumulated in the deep region of the crack. A large amount of OH− were also consumed for the formation of double metal hydroxides, which greatly lowered the pH of the simulated solution. Thus, the chemical environment of the simulated solution became suitable for the growth of microorganisms, and the number of microorganisms in the solution increased significantly. Eventually, the hydration product and the mineralization product area were connected to form a superimposed repair zone, thereby expanding the repair scope. The test results could provide reference for concrete crack self-healing and anti-corrosion of buildings applied on marine environment.

Effect of Preheat Temperature and Welding Sequence on the Temperature Distribution and Residual Stress in the Weld Overlay Repair of Hydroturbine Runner.

The hydroturbine runner is the core of the whole hydroelectric generating unit, which is employed to transform water energy into mechanical energy. In the process of service, the runner frequently suffers from abrasion due to erosion and cavitation. Defects are usually repaired by welding. To acquire suitable weld cladding repair process parameters, a combination of experimental and numerical simulation was applied to investigate the temperature and weld residual stress distribution in the repair zone under the different welding repair approaches. The results illustrate that the temperature and welding residual stress distribution of the blade and the shroud are out of symmetry, the temperature conduction rate is faster on the blade side, and the high-stress zone is predominantly concentrated in the weld and its adjacent area. When the preheating temperature is up to 150 °C, the peak value of welding residual stress reaches a minimum of 796.29 MPa. The welding sequence can adjust the distribution trend of welding residual stresses. The welding sequence of three-stage welding can effectively reduce the welding residual stresses near the shroud at the water outlet side of the blade. The results of the study will provide theoretical guidance for the welding repair of hydraulic turbine runners.

Method of substantiating operational and production plan for ongoing repair of city buses to improve their operation safety

The article presents the organization factor (use of working time), which takes into account the factors of equipping posts with mechanization tools, the level of organization of post work, the qualifications of repairmen, etc. Operational and production planning tasks are described. The initial information for planning is presented. A generalized algorithm for developing an operational and production plan and evaluating its effectiveness has been developed. The method of evaluation of efficiency of the compiled operational-production plan is presented according to the following indicators: the coefficient of output from the current repair zone, the coefficient of load of the zone, the coefficient of downtime, the coefficient of equipment load, etc. Keywords: bus, routine repair, operational and production plan, application, post, labor intensity, efficiency

Performance of repaired concrete piles partially embedded in Sulfate-Bearing soil

Physical salt attack (PSA) is a key damage mechanism of concrete in salt-bearing environments. Multiple case studies were reported throughout literature on PSA of concrete; yet, without any case on the performance of repaired concrete elements. The current paper presents a case study analyzing the condition of repaired concrete piles in 47-year-old administrative building in Winnipeg, MB, Canada, after 22 years from repair works. Deterioration of the concrete piles was visually observed above the ground level and repair zones, in the form of scaling, crumbling and reduction of cross section. In addition to fluid transport and pore structural features tests, mineralogical, thermal and microscopy analyses were performed on concrete chunks/cores extracted from the piles to elucidate the underlying mechanisms of damage. The repair concrete was capable of mitigating chemical and physical sulfate attacks; however, it could not stop the progress of PSA on the concrete above it, urging for careful design of repair strategies for elements subjected to PSA. Recommendations for future repair in this case are also presented.

The effect of a gap concept on peripheral nerve recovery in modified epineurial neurorrhaphy: An experimental study in rats.

Several factors such as surgical approach that only consider topographic anatomy; inadequate fascicular alignment, extraepineurial sprouting in the repair zone; contact of axons with the suture area are the disadvantages of epineurial neurorrhaphy. Accordingly, axonal mismatch, neuroma, and unfavorable nerve recovery become inevitable. Neurotropism is the theory clarifying appropriate matching of the nerve fibers independently without needing surgical approach. The studies comparing the primary nerve repair with the nerve defects bridged in different ways demonstrated better outcomes of nerve recovery in the groups with a nerve gap. In this study, we aimed to demonstrate the effects of the gap concept in primary nerve repair bridged by own epineurium. We hypothesized that this technique will provide better results in terms of peripheral nerve recovery and will significantly eliminate the occurrence of a neuroma, which is quite possible in epineurial neurorrhaphy. A total of 35 Wistar female rats weighing 200 ~ 250 g were randomly divided into five groups each with seven rats. Sham controls constituted Group 1, while the rats with epineural neurorrhaphy were included in Group 2. The remaining three groups were the study groups. In Group 3, after the sciatic nerve transection, epineurium of the distal segment was sleeved and preserved. A 2-mm axonal segment was removed from the epineurium free distal ending and no any procedure was applied to the proximal ending of the transected sciatic nerve. Epineuriums of the both sides were approximated and repaired. In Group 4, a 2-mm axonal segment was removed from the proximal ending of the sciatic nerve after preservation of epineurium and no any procedure was applied to the distal part of sciatic nerve. Epineuriums of the both sides were approximated and repaired. In addition, in Group 5, after epineuriums were sleeved in the both distal and proximal stumps, a 1-mm nerve segment was removed from both endings and epineuriums were repaired in the middle bridging a 2-mm axonal gap again. After a 3months follow-up period Sciatic Functional Index (SFI) was measured by walking track analysis; the area under the evoked compound muscle action potential (CMAP) and latency periods were calculated via electromyographic (EMG) analysis; and histopathological evaluation were performed to compare the parameters of edema, fibrosis, inflammation, vascularization, axonal degeneration, axonal density, myelination, disorganization, and neuroma occurrence. Vascular structures and nerve fibers were counted at ×200 magnification: +1, +2, and +3 indicated the presence of 0-15, 16-30, and >30 structures, respectively. For uncountable parameters (edema, disorganization, myelination, fibrosis, and inflammation): +1 indicated mild, +2 indicated moderate, and +3 indicated severe. The differences between the groups with axonal gap repair and epineural neurorrhaphy were not significant regarding to SFI. The areas under CMAP were as follows: 27.9 ± 5.9 (Δ=12.1%) in Group 1; 16.5 ± 5.5 (Δ=6.3%) in Group 2; 14.1 ± 6.2 (Δ=4.8%) in group 3; 13.8 ± 2.3 (Δ=9.2%) in Group 4, and 22.5 ± 18.3 (Δ=2.2%) in Group 5. Group 5 (1 mm gap in the distal +1 mm gap in the proximal segments) had a significantly better result in terms of the area under CMAP with the value of 22.5 ± 18.3m/Mv (p=.031). Axonal density was 0.9 ± 0.6 (Δ=2.2%) in Group 2, 2.4 ± 0.3 (Δ=5.1%) in Group 3, 2.8 ± 0.1 (Δ=7.7%) in Group 4, and 2.8 ± 0.2 (Δ=4.8%) in Group 5. Myelination was 1.1 ± 0.5 (Δ=3.4%) in group 2, 2.2 ± 0.2 (Δ=6.7%) in group 3, 2.4 ± 0.4 (Δ=6.0%) in Group 4, and 2.7 ± 0.3 (Δ=4.6%) in Group 5. Disorganization was 2.3 ± 0.4 (Δ=4.1%) in Group 2, 1.2 ± 0.2 (Δ=7.7%) in Group 3, 1.3 ± 0.2 (Δ=6.5%) in Group 4, and 1 ± 0.3 (Δ=5.9%) in Group 5. And, neuroma occurrence was found 2.2 ± 0.6 (Δ=2.8%) in Group 2 and 0.3 ± 0.2 (Δ=0.1%) in Group 4 while neuroma was not encountered in Group 3 and Group 5. Comparison between the epineurial neurorrhaphy group and the groups with axonal defect revealed the statistically significant results in the factors of axonal density (p=.001), myelination (p=.028), disorganization (p=.016) and neuroma (p=.001). Creating axonal gap bridged by own epineurium showed favorable results comparing with epineurial neurorrhaphy. Resection of a 1 mm axonal segment from the proximal and distal stumps following the epineurial sleeve procedure and performing the epineurium- only repair can facilitate the nerve regeneration. The feasibility of the described technique has been demonstrated in a small rat model and must be further validated in larger animals before clinical testing.

Efficacy of non-obstructive aortic angioscopy for detecting a thoracic aortic graft rupture: a case report

BackgroundNon-anastomotic thoracic aortic graft rupture is extremely rare and difficult to diagnose. Non-obstructive general angioscopy can help monitor the aortic intima and detect the locations of abnormal findings, while aortic angioscopy can detect vulnerable plaques in the aorta, which are difficult to visualize using conventional diagnostic methods. Herein, we report the case of a patient with non-anastomotic thoracic aortic graft rupture diagnosed using non-obstructive aortic angioscopy.Case presentationAn 85-year-old man who had undergone total arch replacement 5 years prior complained of chest pain. Emergent contrast-enhanced computed tomography (CT) revealed an intra-mediastinal hematoma around the vascular graft of the ascending aorta and angiography revealed pooling of contrast medium on the dorsal side of the vascular graft. We suspected extravasation of the thoracic vascular graft. Aortic angioscopic examination revealed a red vascular graft defect that matched extravasation at the contralateral level of the prosthetic left common carotid artery branch. Subsequently, non-anastomotic thoracic aortic graft rupture was diagnosed. The patient underwent a two-debranching thoracic endovascular aortic repair (Zone 0) with a right subclavian artery-left common carotid artery-left subclavian artery bypass. Postoperative angiography revealed disappearance of the extravasation from the graft rupture site, patent grafted vessels with flow, and no endoleak. Follow-up CT at 6 months postoperatively showed no extravasation.ConclusionsTo our knowledge, this is the first report of non-anastomotic thoracic aortic graft rupture detected using non-obstructive aortic angioscopy. Aortic angioscopy can help establish a definitive diagnosis in patients with aortic graft rupture.

MicroRNA Expression in the Infarcted Heart Following Neonatal Cardiovascular Progenitor Cell Transplantation in a Sheep Model of Stem Cell–Based Repair

Myocardial infarctions affect approximately 735,000 people annually in the United States and have a substantial impact on quality of life. Neonates have an enhanced capability of repairing cardiovascular damage, while adults do not. The mechanistic basis for this age-dependent difference in regenerative capacity remains unknown. Recent studies have shown that microRNAs (miRNAs) play a significant role in regulating the regenerative ability of cardiovascular cells. This report defines the alterations in miRNA expression within the cardiovascular repair zone of infarcted sheep hearts following intracardiac injection of neonatal islet-1+ cardiovascular progenitor cells. Sheep were infarcted via left anterior descending coronary artery ligation. After 3 to 4 weeks of infarction, sheep neonatal islet-1+ cardiovascular progenitor cells were injected into the infarcted area for repair. Cell-treated sheep were euthanized 2 months following cell injection, and their hearts were harvested for the analysis of miRNA and gene expression within the cardiovascular repair zone. Ten miRNAs were differentially regulated in vivo, including miR-99, miR-100, miR-302a, miR-208a, miR-665, miR-1, miR-499a, miR-34a, miR-133a, and miR-199a. These miRNAs promote stemness, cell division, and survival. Several signaling pathways are regulated by these miRNAs, including Hippo, Wnt, and Erythroblastic Leukemia Viral Oncogene B (ERBB). Transcripts encoding Wnt, ERBB, and Neuregulin 1 (NRG1) were elevated in vivo in the infarct repair zone. Wnt5a signaling and ERBB/NRG1 transcripts contribute to activation of Yes-Associated Protein 1. MiRNAs that impact proliferation, cell survival, and signaling pathways that promote regeneration were induced during cardiovascular repair in the sheep model. This information can be used to design new approaches for the optimization of miRNA-based treatments for the heart.

Priority decision of road repair zone using the drive data of ambulances

Priority decision of road repair zone using the drive data of ambulances

The Danger Zone for Iatrogenic Neurovascular Injury in All-Inside Lateral Meniscal Repair in Relation to the Popliteal Tendon: An MRI Study.

Background:Lateral meniscal repair can endanger the nearby neurovascular structure (peroneal nerve or popliteal artery). To our knowledge, there have been no studies to evaluate the danger zone of all-inside meniscal repair through the anteromedial (AM) and anterolateral (AL) portals in relation to the medial and lateral edges of the popliteal tendon (PT).Purpose:To establish the risk of neurovascular injury and the danger zone in repairing the lateral meniscus in relation to the medial and lateral edges of the PT.Study Design:Descriptive laboratory study.Methods:Using axial magnetic resonance imaging (MRI) studies at the level of the lateral meniscus, lines were drawn to simulate a straight, all-inside meniscal repair device, drawn from the AM and AL portals to both the medial and lateral edges of the PT. In cases in which the line passed through the neurovascular structure, a risk of iatrogenic neurovascular injury was deemed, and measurements were made to determine the danger zones of neurovascular injury in relation to the medial or lateral edges of the PT.Results:Axial MRI images of 240 adult patients were reviewed retrospectively. Repairing the body of the lateral meniscus through the AM portal had a greater risk of neurovascular injury than repairs made through the AL portal in relation to the medial edge of the PT (P = .006). The danger zone in repairing the lateral meniscus through the AM portal extended 1.82 ± 1.68 mm laterally from the lateral edge of the PT and 3.13 ± 2.45 mm medially from the medial edge of the PT. Through the AL portal, the danger zone extended 2.81 ± 1.94 mm laterally from the lateral edge of the PT and 1.39 ± 1.53 mm medially from the medial edge of the PT.Conclusion:Repairing the lateral meniscus through either the AM or the AL portals in relation to the PT can endanger the peroneal nerve or popliteal artery.Clinical Relevance:The surgeon can minimize the risk of iatrogenic neurovascular injury in lateral meniscal repair by avoiding using the all-inside meniscal device in the danger zone area as described in this study.

Evaluation of flexor tendon repair (zone II) with Wide Awake Anesthesia

Abstract Background Recent advances in hand surgery has been the movement away from tourniquet surgery, which often requires sedation or GA and the patient will be awake and cooperative. Wide awake approach depends on the safety of adrenaline which is now well established. This review will evaluate the role of the wide awake approach in reducing rupture and tenolysis rate after flexor tendon repair zone 2. Objective To evaluate the functional outcome of flexor tendon repair zone II (most challengeable) under wide awake anesthesia. Patients and Methods After approval of local ethical committee of faculty of medicine Ain Shams University, this Prospective study has been conducted targeting patients with acute zone II flexor tendon injuries admitted at El Sahel Teaching Hospital within the period from September 2019 till January 2020, and their follow up for minimum three months at outpatient clinic. A Written informed consent explaining the whole procedure under study in this research has been obtained from all patients and absolute confidentiality as regard the patients’ names and addresses was given special care and attention. Final outcome evaluated by Original Strickland evaluation system. Results Using the wide awake technique provides an optimal opportunity to test repair strength through Intra-operative Total Active Movement (ITAM) making the surgeon much more comfortable to initiate early active motion. Besides, rising trend toward using early active rehabilitation protocol in case of strong repair using four or more strands repairs is recently supported in literature. This study adopted early active rehabilitation protocol with slight differences among them Conclusion This preliminary study assessing the outcomes of primary tendon repair in flexor tendon injuries in zone II using the wide-awake technique demonstrates encouraging results, being satisfactory for both surgeons and patients that makes this new approach a competitive to the other approaches of flexor tendon repair implemented under conventional methods of anesthesia.

The Effect of Plug Rotation Speed on Micro-Structure of Nugget Zone of Friction Plug Repair Welding Joint for 6082 Aluminum Alloy.

This paper carried out the friction plug repair welding of 6082 aluminum alloy keyhole defects by using the method of friction heating between shaft shoulder and base material. In addition, a well-formed friction plug welding joint was obtained at different plug rotation speeds. In order to study the influence mechanism of plug rotation speeds on the microstructure of the weld nugget zone, EBSD technology was used to analyze the grain morphology, grain size and grain boundary characteristics of the weld nugget zone under different rotation speeds of the plug rod. The results show that in the nugget zone, the grain was fine and equated crystals refinement, and there was a preferred orientation. The deformation texture components in the welded nugget zone increased with the plug rotation speed from 1600 to 2000 rpm. However, the grain size first decreased and then increased, while the components in the High-Angle Boundary first increased and then decreased.

A Preliminary Study of Laser Directional Solidification for Potential Use in the Repair of Damaged Aviation Turbine Blades

To achieve directional solidification repair of damaged aviation turbine blades, the directional growth repair layer was prepared using a Nd:YAG laser on the surface of superalloy DZ-22. A scanning electron microscope (SEM) was used to observe the microstructure. The element distribution was analyzed and the microhardness of the sample was measured. The results showed that primary dendrite size was proportional to the current and the pulse-width, and inversely proportional to the scanning speed. No obvious macrosegregation of the repair zone was evident. The zone exhibited a finer microstructure than the substrate and had a smaller columnar crystal size, which was approximately two orders of magnitude smaller than the substrate. The micro-segregation between the centers and the edges of the dendrites and in between adjacent dendrites and a decrease in microhardness from the repair zone (455 HV) to the substrate also were observed.

Microstructures and mechanical properties of Ti6Al4V alloy repaired by the technology of point-mode forging and laser repairing

In this experiment, the technology of point-mode forging and laser repairing (PF-LR) has been employed for the repair of rolled Ti6Al4V Alloy. Three subtransus heat treatment regimes were used to investigate the microstructure and mechanical properties of the Ti6Al4V repaired parts before and after heat treatment. The results showed that the macrostructure of the repaired zone (RZ) of PF-LRed Ti6Al4V repaired part was equiaxed prior β grains with an average size of 150–350 μm, while the microstructure consistsed of basketweave microstructure. The yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) of PF-LRed Ti6Al4V repaired part with 50% repair volume fraction in X-axis direction and Z-axis direction samples exceeded the ASTM B381-2013 standard. After heat treatment 550 °C/4h/air cooling (AC), the microstructure of the RZ and RSZ did not change significantly, but the mechanical properties tended to be similar. After heat treatment at 850 °C/2h/AC, the α laths in the RZ were coarsened or spheroidized, and the EL in the RZ and RSZ decreased dramatically. After heat treatment 940 °C/2h/AC + 550 °C/4h/AC, the microstructure of the RZ was trimodal structure consisting of globular α, lath α and transformed β, the EL of the RZ and RSZ almost disappeared. PF-LRed Ti-6Al-4 V repaired parts are not supposed to choose a heat treatment regime with too high temperature. The 50% PL-LR (i.e. the volume fraction of the RZ was set to 50%) tensile specimen sampled in the Z-axis direction was prepared and the phenomenon for its EL reduction was discussed and analyzed.

Dynamics of Renewal of Cell Populations of the Bone Tissue on the Surface of Titanium Implants with Bioactive Coating during Fracture Modeling in Rats.

Localization of PCNA, CD44, osteocalcin, Mdm2, p53, and caspase-3 on the surface of implant with calcium phosphate and hydroxyapatite coating was studied by immunocytochemical method in a model of femur fracture in rats. PCNA+, Ost+, CD44+, and Mdm2+ cells were found in the periosteum, in the layer of the outer surrounding plates, and in the connective tissue of the Haversian canals. Cell density increased on day 7 after fracture and then decreased by day 30. The number of p53+ and CASP3+ cells reached a maximum on day 14 (they were predominantly located in the periosteum and bone plates adjacent to it) and decreased by day 30. Calcium phosphate coating stimulated proliferative activity of cells at the early stages of the regeneration phase and apoptotic death at the later stages. Components of coating can be viewed as a positioning clue for differentiation of mesenchymal stromal cells. The effectiveness of reparative osteogenesis is determined by the balance of proliferative and destructive factors at the site of the fracture healing. This process can be optimized with various nanostructured materials with osteoinductive properties, in particular bioresorbable calcium phosphate coatings on titanium implants. However, the influence of these components on the state of cambial cells, their differentiation, and positioning in the repair zone is unknown.

Experimental and numerical analysis of the effects of different repair mortars on the controlling factors of macro-cell corrosion in concrete patch repair

In reinforced concrete structures, the increase in the corrosion rate in the vicinity of the repair zone, due to galvanic cell formation, is known as the incipient anode effect. This study aims to investigate the effect of different repair mortars on the controlling factors of macro-cell corrosion current, induced by patch repair. Therefore, slab samples with different repair mortars, including mortar with ordinary Portland cement (OPC), repair mortar containing 5 and 9% micro-silica, and latex-modified cementitious mortar are investigated. Moreover, corrosion potential and macro-cell current between the substrate concrete and repair mortar are measured in this study, followed by determining the driving force, anodic and cathodic polarization resistance, and the ohmic drop. Using numerical simulation, a more extensive range of repair mortar resistivity and the driving force has been applied to evaluate their effects on the controlling factors of the macro-cell current. As demonstrated in the experimental results, despite the change in resistivity of the repair mortar, cathodic polarization resistance is always controlling the macro-cell current. An ohmic drop of approximately 5% will have the lowest contribution to controlling macro-cell current. In addition, simulation results illustrate that by increasing the resistivity of the repair mortars to 500 Ω m and the driving force to 500 mV, the ohmic drop contribution does will not increase significantly, while the cathodic polarization is always dominant.