Longitudinal Splitting Research Articles

Distraction of longitudinally split fragments using the Ilizarov method: a series of clinical cases of treating partial bone defects

Background. The Ilizarov method is a recognized technique for treating severe skeletal injuries, allowing for a comprehensive restoration of both bone and soft tissue components. Despite the fact that bone lengthening and transport are widely known techniques, distraction of a longitudinally split fragment is still used extremely rarely. The aim of the study is to describe a series of clinical cases involving patients operated on using this technique. Methods. We present a series of observations of five patients who underwent distraction of a longitudinally split fragment using the Ilizarov method between January 2006 and December 2022. Clinical information was obtained from case histories, all surgical interventions were documented. Postoperative examination was performed using radiography. Results. A case series demonstrates the successful application of this technique for reconstruction of partial bone defects resulting from trauma or osteomyelitis. The study included five patients (4 men and 1 woman) who underwent surgery 4.8-34.0 months after trauma for a partial defect of the proximal tibia ranging from 4 to 8 cm in length. Distraction was performed in different directions along the sagittal and longitudinal axes. The time of external fixation ranged from 3.5 to 4.8 months, the external fixation index ranged from 0.49 to 1.22. The ASAMI (Association for the Study and Application of the Methods of Ilizarov) functional score at the follow-up examination was excellent in all five patients. The ASAMI bone tissue assessment showed excellent results in all patients, except for one patient with residual equinus (good result). No other complications were reported. Conclusions. The Ilizarov method provides a minimally invasive and comprehensive approach to the elimination of partial bone defects, affecting simultaneously the skeletal and soft tissue components. Due to the longitudinal splitting during fragment transport and distraction osteogenesis, this method promotes bone and tissue regeneration and helps to avoid a volumetric bone defect and more complex segmental bone transport. Moreover, the role of transverse transport of the tibial cortex increases in the treatment of peripheral arterial diseases.

Hair fragility (trichorrhexis nodosa) in alopecic Pomeranian dogs.

While alopecia associated with hair cycle arrest (HCA, Alopecia X) is well-recognised in Pomeranian dogs, the authors are unaware of reports of concurrent hair fragility. Following the observation of frequent hair shaft abnormalities in alopecic Pomeranians, we hypothesised that hair fragility events would be more frequent in dogs with a phenotype of HCA when compared to dogs with normal coats. Eight alopecic Pomeranian dogs or crosses with a phenotype of HCA and 36 unaffected Pomeranians with owner-reported normal hair coats. All affected dogs underwent dermatological examination and clinicopathological evaluations. Hair samples, plucked from affected areas or obtained by brushing from unaffected dogs, were examined microscopically for structural abnormalities. Hair fragility events were characterised as trichorrhexis nodosa (TN) or longitudinal splits and were expressed per 10 mg of hair. A reference interval was calculated from the number of hair fragility events in the samples from unaffected dogs. The upper reference limit (with 90% confidence) from samples of 35 unaffected Pomeranians (one outlier excluded) was 9.75 hair fragility events per 10 mg of hair. The median (range) of fragility events in eight dogs with a phenotype of HCA was 66.0 (30.2-166.7) per 10 mg of hair. Clinicians should routinely perform trichography in Pomeranians with HCA because abundant hair abnormalities, particularly TN, may contribute to poor hair coat quality. Further studies are required to establish the pathophysiology of and treatments for these fragility events and to determine their predictive value for HCA.

Shear failure characteristics and stress-strain relationship of Moso bamboo parallel to the fibers

Bamboo is susceptible to longitudinal splitting, which is mainly driven by its shear properties parallel to the fibers. In this work, bowtie tests including 124 Moso bamboo internode and node specimens were conducted to investigate the shear behaviors of Moso bamboo in shear parallel to the fibers. Based on the test results, the difference in shear strength between internode and node specimens using the analysis of variance (ANOVA) was quantitatively evaluated. The distribution of shear strength was fitted using Normal, Log-normal, and Weibull distributions, and the corresponding standard value was calculated using the non-parametric method. The design value was obtained based on reliability analysis. Additionally, prediction formulas for shear strength were fitted using univariate and multiple regression analyses based on outer diameter, wall thickness, and density. Various shear stress-strain constitutive models were established and validated. The research results indicated that there is no statistically significant difference in shear strength between internode and node specimens with the value of 17.17 MPa and 17.48 MPa, respectively. The distribution of shear strength followed the Normal and Log-normal distributions, but not the Weibull distribution. The standard value and design value of shear strength were 14.91 and 9.47 MPa, respectively. The shear strength was found to be negatively correlated with the outer diameter and wall thickness, but positively correlated with the density. The recommended strength prediction formulas and stress-strain constitutive models match well with the test results. This study can serve as a reference for the improvement of bamboo standard and design basis of Moso bamboo.

Experimental study on constitutive relation of coal gangue coarse aggregate concrete under uniaxial compression

As an efficient method for utilizing coal gangue (CG), concrete incorporating coal gangue as coarse aggregate has significantly reduced the reliance on natural aggregates, offering substantial environmental and economic benefits. In this study, coal gangue concrete was prepared with coal gangue replacement rates of 0, 20, 40, 60, 80, and 100%, and mechanical tests under unconfined compression were conducted to evaluate the stress-strain behavior and failure mechanism of coal gangue coarse aggregate concrete (CGC). Utilizing scanning electron microscope (SEM) microscopic characterization, the microscopic failure mechanism of CGC was further elucidated. With increased coal gangue replacement, the CGC's uniaxial compression failure mode shifts from shear to longitudinal splitting failure. The slope, peak stress and elastic modulus of the stress–strain curve's rising section are negatively correlated with the coal gangue content, while the falling section's slope, peak strain and ultimate strain are positively correlated. Next, building upon the classical constitutive model, we adjust the constitutive parameters utilizing the uniaxial compressive strength and coal gangue content. Finally, we introduce a predictive model for the CGC's constitutive compressive behavior across various content levels. There is a notably high agreement between the model and experimental data.

Oil-based drilling cutting pyrolysis residues-recycled fine powder sintered ceramsite: Basic properties, microsintering mechanism, lightweight concrete application and heavy metals solidification

Oil-based Drilling Cutting Pyrolysis Residue (ODPR) is a waste produced during oilfield drilling using oil-based mud. Recycled Fine Powder (RFP) consists of particles less than 0.16 mm, crushed and sieved from waste concrete. China's solid waste is characterized by high production, low utilization rates, and high pollution levels. This study explores the feasibility of preparing ceramsite from ODPR and RFP. By examining the effects of varying temperatures and proportions on the macroscopic and microscopic properties of ODPR-RFP ceramsite (ORC), the optimal process was determined: ODPR: RFP = 7:3, 2 % borax flux, 10 minutes ball milling, 1200℃ sintering temperature, and 30 minutes insulation. The resulting ORC, with a bulk density of 1120 kg/m³, cylinder compression strength of 10.50 MPa, and water absorption rate of 7.8 %, meets the "Lightweight aggregates and its test methods (GT/B17431.2)" standard. Batch production of ORC products of various sizes was conducted to evaluate their practical application in LC30 lightweight aggregate concrete. Replacing the aggregate in lightweight concrete with ORC yielded a concrete with excellent mixing performance, reaching a maximum strength of 31.2 MPa after 7d and 44.8 MPa after 28d. The damage pattern of ORC lightweight concrete is characterized by longitudinal splitting, with varied crack initiation and expansion paths. In the interfacial transition zone of ORC concrete, the ORC form a strong bond with the cement mortar, enhancing the strength of the lightweight concrete. Additionally, the leaching of heavy metals (HMs) from the ORC was examined to assess potential environmental pollution. The results indicated that preparing ORC from these two types of solid waste can effectively immobilize HMs, with a solidification rate of up to 92.10 %. Pb with high content is mainly solidified in the form of solid solution to form (Ba, Pb) SO4. The ecological risk assessment method for HMs shows that using this solid waste and process to prepare ORC does not pose HMs risks and is an environmentally friendly building material.

Simplified medial canthoplasty: Technique and early postoperative complications in 601 dogs (1180 eyes).

To present a novel modified medial canthoplasty (MCP) technique, the application in 601 dogs (1180 eyes), and a review of the early postoperative complications related to the technique. Macroblepharon and nasal entropion is a common presentation in many brachycephalic dog breeds promoting chronic keratitis. The previously described MCP techniques limit the medial shortening of the eyelids to the location of the lacrimal puncta. A novel technique was developed allowing for a more extensive eyelid shortening nasally. The modification of the here described technique includes the longitudinal splitting of the lacrimal canaliculi allowing for an extensive shortening of the lids beyond the lacrimal puncta. Records of 601 dogs which underwent the modified MCP were reviewed regarding breed, indications for surgery, follow-up, and early postoperative surgical complications. Descriptive statistics were applied. Six hundred one dogs (1180 eyes) were included in this study. Twenty-four different breeds underwent the simplified MCP with the Pug (n = 403) being the most represented breed. Indications were macropalpebral fissure, medial entropion, pigmentary keratitis, trichiasis by haired caruncle, strabismus after globe prolapse, and facial nerve paralysis. The overall complication rate was 1.01% (12/1180) and consisted of wound dehiscence 0.59% (7/1180), corneal ulceration caused by suture material 0.25% (3/1180), and wound infection (2/1180). None of the 601 operated dogs developed serious complications related to the surgical technique. The simplified MCP is a novel technique with a very low complication rate.

Comparative assessment of load-bearing capacities in bolted laminated bamboo lumber connections: A study on diverse reinforcement techniques

Laminated bamboo lumber (LBL), a renowned engineered bamboo composite known for its outstanding performance and sustainability, is extensively used in modern bamboo structured buildings. This study focuses on examining the effects of diverse reinforcement techniques, particularly self-tapping screws and tension control bolts, on the load-bearing capacity of bolted LBL connections with steel plates. In total, 24 specimens were categorized into 8 groups and subjected to monotonic loading tests. The test results demonstrate that the non-reinforced group clearly shows longitudinal splitting failure at the bolt position, followed by a decrease in load-bearing capacity after failure. In contrast, the group with self-tapping screws (ST) and tension control bolts (BT) exhibited fiber tearing at the lower part of the midspan, accompanied by section bending and damage. The final load-bearing capacity of the groups reinforced with single-row three-bolt self-tapping screws and tension control bolts showed an increase of 67.30 % and 52.95 %, respectively. Likewise, the groups with single-row four-bolt configurations also demonstrated significant reinforcement effects, with increases of 40.52 % and 29.66 %, respectively. Furthermore, DIC-3D analysis was employed to examine the displacement of the connection bolts, and the van der Put model was utilized to estimate the load-bearing capacity of bolted LBL connections under splitting conditions. Subsequently, finite element models were established and calibrated based on the experimental data. The results confirm that self-tapping screws and tension control bolts can serve as structural enhancements in the design of bolted LBL connections, providing effective reinforcement for existing engineering structures.

Goos–Hänchen shifts on spin representation

We analyze the Goos–Hänchen (GH) shift and longitudinal spin splitting (LSS) at a planar interface between two optical media in the spin representation. While these optical effects have been studied previously, we examine the direct and cross-reflected light fields, and their interference from the spin representation to reveal the physical mechanism of the GH shift and establish a quantitative relationship between it and LSS. Furthermore, we show that angular asymmetric spin splitting occurs under the spin representation when linearly polarized light with a phase difference of 180° and an amplitude ratio angle deviating from 45° impinges on the air–glass interface at Brewster’s angle. Finally, we reveal that the spin component field of the reflected light field for the total reflection case is different from that of the Brewster angle reflection, the most typical manifestation is that the intensity of the two spin component fields is not equal.

Olecranon Osteotomy Exposure for Distal Humeral Fracture Treatment.

Olecranon osteotomy (OO) is commonly utilized to improve exposure when treating intra-articular distal humeral fractures. A chevron-shaped osteotomy facilitates reduction and increases surface area for healing1. Following distal humeral fracture reduction and fixation, the OO fragment is fixed with a precontoured plate. The OO technique yields comparable outcomes to alternative techniques1,2. The technique is performed as follows. (1) Imaging is reviewed and preoperative planning is performed. (2) The patient is positioned in the lateral decubitus position with the operative extremity placed over a bolster. (3) A longitudinal posterior skin incision is centered just medial or lateral to the tip of the olecranon. Full-thickness skin flaps are raised medially and laterally. (4) The ulnar nerve is identified and mobilized for later anterior subcutaneous transposition. (5) An OO is performed at the non-articular "bare area" of the trochlear notch with an oscillating saw and completed with an osteotome. (6) Open reduction and internal fixation of the distal humerus is performed. (7) The osteotomy fragment is reduced, and a precontoured plate is applied. (8) A small longitudinal slit in the distal triceps over the proximal edge of the plate decreases plate prominence and is repaired with suture. (9) The subcutaneous tissues and skin are closed in the usual manner. Alterative techniques include extra-articular OO, triceps splitting, triceps reflecting, and lateral para-olecranon combined with a medial approach. Multiple drill holes and a thin osteotome can help mitigate the kerf created by the oscillating saw. Alternative fixation methods include a predrilled 6.5-mm intramedullary screw, a tension band construct, suture fixation, or a one-third tubular plate. The OO technique provides improved exposure when compared with alternative techniques, enabling accurate reduction and fixation of distal humeral fractures1-3. Wilkinson and Stanley found that OO exposed the distal humeral articular surface to a greater degree than the triceps-splitting and triceps-reflecting approaches3. OO has not been associated with triceps weakness, unlike some of the alternative techniques2. The incidence of good-to-excellent outcomes is similar when comparing the techniques for exposure of intra-articular distal humeral fractures4. Osteotomies united in all patients in 2 reported series, totaling 84 cases1,2. Removal of symptomatic hardware used in OO fragment fixation can occur in a small subset of patients1,2. Provisionally size a precontoured plate and fix it on the olecranon to aid in later reduction and fracture fixation.The bare area is the desired position for the OO because of its natural lack of cartilage5,6. This non-articular bare area is located just distal to the deepest portion of the trochlear notch, approximately 2 to 2.5 cm distal to the olecranon tip5,6.An (apex-distal) chevron osteotomy angle of ∼130° will help to keep the osteotomy within the non-articular bare area6.Beginning on the dorsal surface of the ulna, directly posterior to the bare area, an oscillating saw is utilized to create a chevron osteotomy to subchondral bone, perpendicular to the long axis of the ulna5,6.The OO is completed by fracturing through the osteochondral surface, which leaves an irregular chondral cancellous surface that can accurately interdigitate. This facilitates later reduction and stability of the osteotomy.Anatomic articular reduction of the OO is not solely judged on the dorsal cortical bone because of the kerf removed by the saw blade. Instead, examination of the articular surface of the trochlear notch is the primary assessment of reduction.Placement of suture through the proximal portion of the plate aids in the repair of the longitudinal split of the distal triceps.Successful treatment of distal humeral fractures requires accurate reduction and rigid fixation aided by adequate exposure achieved through OO. ORIF = open reduction and internal fixationOT = occupational therapyHWR = hardware removalK-wire = Kirschner wireROM = range of motion.

Effectiveness of EndoActivator, PATS Vario system, and XP-endo Finisher files on smear layer removal under scanning electron microscope: A comparative study.

The smear layer may harbor many bacteria; hence, alternative methods are used to disrupt and remove biofilm. The aim of the study was to compare the effectiveness of EndoActivator, PATS Vario System, and XP-endo Finisher files on smear layer removal using a scanning electron microscope. Sixty single-rooted extracted premolars with Vertucci Type 1 configuration were decoronated and divided into four groups. The groups were instrumented with the rotary ProTaper file system. All specimens were flushed with 1 ml of 3% sodium hypochlorite. Group 1 was irrigated with a conventional needle and syringe. In Group 2, the irrigant was activated with an EndoActivator. In Group 3, the irrigant was activated with PATS Vario system, and in Group 4, XP-endo Finisher files were used after biomechanical preparation to remove debris and smear layer. All specimens were finally rinsed with 3 ml of 3% sodium hypochlorite. The teeth underwent longitudinal splitting and grooving in the coronal, middle, and apical thirds, and then, the samples were taken for scanning electron microscopy to evaluate the amount of smear layer removal in each third. The middle and coronal thirds Showed that almost similar efficacy to remove smear layer in both Group II and Group III. At the apical third, Group III showed comparatively better results than Group I, II, and IV, respectively. Equal amount of smear layer was seen with EndoActivator and PATS Vario system when used as sonic irrigation devices.

Resection of the entire first rib for giant osteochondroma by trans manubrial approach: a case report and review of the literature

BackgroundFirst rib tumors are extremely rare. Its compression of neurovascularity can easily lead to severe complications such as thoracic outlet syndrome, so early surgical resection is crucial. However, there is no standardized approach to surgery.Case presentationA previously healthy 18-year-old Chinese male undergoes a chest computed tomography (CT) scan that incidentally reveals a raised calcified mass on the right first rib, which is most likely an osteochondroma when combined with magnetic resonance imaging (MRI). We achieved excellent results with resection and thoracic reconstruction by adopting an inverse L-shaped incision in the anterior chest and a longitudinal split of the sternum.ConclusionsOur practice provides great reference for the surgical management of first rib tumors.

Design of novel glass fiber reinforced polypropylene cable-anchor component and its long-term properties exposed in alkaline solution

The high performance and long life of engineering structures can be realized through replacing traditional steel materials with glass fiber reinforced polypropylene composites with high toughness/durability, flexibility design and recycling. In addition, the anchorage problem of composites needs to be solved by developing new anchorage technologies or forms. In the present paper, a new type cable-anchor component was developed to prolong the service life and realize the reliable anchoring of composite. The influence mechanism of arc angle (10°, 20°, and 30°) on the mechanical properties of cable-anchor component was evaluated through the experimental and mechanical simulation. The durability evolution of cable-anchor component exposed to alkali solution environment was investigated through macro-performance test and microstructure analysis. The results showed the tensile strength retention of cable-anchor component was up to 88.7 % at the arc angles of 10° under the circumferential constraint of carbon fiber. Larger arc angle increased the stress concentration and fiber misalignment of transition area between arc and straight segments, leading to the formation and propagation of defects or cracks in transition areas and early fracture failure. The saturated water absorption and diffusion coefficient of glass fiber reinforced polypropylene composites were obtained to be 0.78 % and 4.41×10−14 m2/s, respectively. Compared with nylon 6 and epoxy resin, polypropylene has excellent hydrophobic properties with the diffusion coefficient ratio of 0.0077 and 0.024. At the longest immersion, the tensile strength retentions of cable-anchor component were 61.8 % and the failure mode changed from component longitudinal splitting to brittleness fracture of arc region. The degradation mechanism was attributed to the initial defects of arc section formed and expanded under the complex stress and corrosive medium, which further aggravated the fiber/resin interfacial debonding. Through comparing with other glass fiber reinforced thermoplastic and thermosetting composites, the cable-anchor component has higher tensile strength retention after the immersion of alkaline solution owing to excellent hydrophobicity behavior of polypropylene and efficient preparation process.

Aerial Acrobatics and Pole Sports as Means of Developing Flexibility and Strength Endurance.

The Relevance of the Research topic lies in the current stage of development of physical education in schools, characterized by the need to update content, constant search for effective methods to develop physical qualities, and the integration of innovations into physical education classes and extracurricular activities. One such innovation is aerial acrobatics and pole sports, which have gained popularity as forms of motor activity influencing students' interest in physical exercise and the development of physical qualities. The Purpose and Methods of the Research were to experimentally assess the impact of a comprehensive physical and technical training program in aerial acrobatics and pole sports on flexibility and power endurance development. The study employed analysis and synthesis of literature, pedagogical experimentation, and methods of mathematical statistics. The Results revealed improvements in flexibility indicators during «Bridge» exercises, changing from 45,07±5,42 cm to 37,13±3,79 cm; «Longitudinal split on the right» from -2,53±2,31 cm to 4,33±1,03 cm; «Left longitudinal split» from -4,7±1,47 cm to 4,47±1,17 cm; and «Lumbar split» from -5,6±1,83 cm to -2,73±1,39 cm. A statistically significant difference was observed at p<0.05. Similar improvements were found in power endurance development, with statistically significant differences between experimental group (EG) and control group (CG) indicators. For instance, during the «Bending and extending the arms in a supine position» exercise, EG indicators improved from 21,93±1,2 times to 33,13±1,14 times, and the time of maintaining body position in the supine position changed from 125,33±11,66 s to 288,0±18,18 s (p<0,05). In Conclusion, it has been established that a comprehensive program of physical and technical training incorporating aerial acrobatics and pole sports, which includes general and specialized exercises along with technical training, is more effective and positively impacts the development of flexibility and strength endurance. This is evidenced by the statistically significant improvement in these physical qualities among the experimental group (EG) girls compared to the control group (CG) across all parameters studied.

Simultaneous observation of transverse and longitudinal photonic spin splitting in monolayer WSe2 via quantum weak measurement

Simultaneous observation of transverse and longitudinal photonic spin splitting in monolayer WSe2 via quantum weak measurement

Model characteristics of physical fitness of taekwondo players at the stage of basic training

The purpose of the study was to study the characteristics of physical fitness and develop model characteristics of taekwondo athletes at the stage of basic training. The results. The analysis of the physical fitness of taekwondo athletes showed that the average indicators of physical fitness of taekwondo athletes at the stage of basic training of the 2nd year of training are better than those of athletes of the 1st year from 3.39 to 14.28%. The largest differences between the groups of 14.28% are observed in the pistol test for 30 s on the left leg and 11.56% - swing with the right leg forward for 15 s, and the smallest 3.51% in the 20 m s gait test. Statistically significant differences were established according to the Student's test t=2.25–2.68 at p <0.05, in tests: speed-power index (ratio of jump length to height) t=2.25; left leg swing forward in 15 s, t=2.33; swing with the right leg forward in 15 seconds, t=2.68. The model performance characteristics of flexibility tend to decrease in the range between the ideal and minimum values by 21.75% and 20.92% in the transverse split and longitudinal split tests for the left leg, respectively, but it is found that the indicators for the longitudinal split for the right leg differ by 0.29%

Multiaxial failure behavior and fatigue life prediction of unidirectional composite laminates

Complex coupling mechanisms exist between longitudinal and shear stress on the multiaxial fatigue behavior of composites. A thorough reanalysis of matrix shear failure mechanism under multiaxial fatigue loading is presented. Longitudinal single splitting fracture were analyzed and validated as an independent failure mode under multiaxial loading by analogy to the failure mechanism of natural composites. A new multiaxial fatigue life prediction model was established by double projection on the critical and subcritical fracture planes. Experiments on unidirectional tubular specimens were carried out under combined tension-torsion loadings to separate and identify the multiaxial fatigue failure behavior of composites. The proposed model has been verified using unidirectional laminates subjected to cyclic tension-torsion and off-axis loading, and the results showed that the predicted life is in good agreement with the experimental ones. Applications of three-dimensional digital image correlation (3D-DIC) and microscopy regarding verification in multiaxial damage mechanism are also addressed.

Effects of external loads-induced inclination damage on the seismic performance of traditional straight M-T joints

Under the earthquakes, wind, and other external loads, ancient timber structures have experienced various degrees of damages, in which the inclination damage of mortise and tenon (M-T) joints, induced by the external loads, has an adverse effect on the safety of the whole structure. To study the effect of various degrees of inclination damage on the seismic behavior of straight M-T joints, we fabricated four 1/3.2-scaled ancient straight M-T joint specimens, one without inclination and three with different degrees of inclination, and subjected them to the cyclic loading tests. The inclination of the joint was simulated artificially, i.e., pushing the intact joint to the predetermined inclination rotation and holding the loads, then unloading when the part of tenon entered a nonrecoverable plastic state. The failure modes, initial elastic stiffness, moment-resisting capacity, strength and stiffness degradation laws as well as energy dissipation and deformation capacities of the joints were investigated. The results showed that the plastic deformation of the tenon and mortise edge, tenon pull-out, and longitudinal splitting of the tenon were exhibited in the inclined joint specimens. Compared to the intact joint, the plastic deformation of the tenon and tenon pull-out for the inclined M-T joints were more apparent during the positive loading. The hysteretic curve of each joint exhibited an anti- "Z" shaped, and the greater the inclination degree, the more apparent the negative initial slipping and pinching effect. With an increase in the damage degree, the initial stiffness, ultimate moment-resisting capacity, and hysteretic energy dissipation behavior of the inclined M-T joint gradually degraded. When the damage degree was 3.89%, the positive yielding moment, peak moment, and initial stiffness of the inclined M-T joint degraded to 52.41%, 86.09%, and 67.19% of that of the intact joint. Based on the hysteretic characteristics and test results of the inclined M-T joints, the degradation formulas of the key parameters of seismic behavior for the inclined M-T joints were established, and an improved degraded hysteretic model, which can reflect the hysteretic behaviors of inclined M-T joint, was proposed. Good agreements between the model predictions and the test results were observed.

Experimental Study on the Influence of Real-Time Temperature Cycling on Physical and Mechanical Properties of Granite

In this paper, a self-developed multi-functional high-temperature rock triaxial servo control testing machine was used to carry out uniaxial compression tests on the granite after the cooling and heating cycles under real-time temperature. The physical and mechanical properties of two types of granite damaged by hot and cold cycling under real-time temperature were discussed, and the changes in apparent color, longitudinal wave velocity, elastic modulus, uniaxial compressive strength, and damage characteristics of the specimen were revealed. The research results show the following: (1) With the increase in temperature or the increase in number of cycles, the uniaxial compressive strength, longitudinal wave velocity, and elastic modulus of the samples under the two cooling methods all show a decreasing trend, but the decrease in the range is different. The change range of the sample with temperature is greater than that with the number of cycles. (2) Under the dual action of real-time temperature and cold heat cycle damage, the failure form of granite is very random, but it is mainly shear failure, longitudinal splitting failure, and conical failure, and it is accompanied by a high temperature with the increase in the number of cycles, and the degree of crushing of the test piece gradually increases. For example, the sample under 600 °C water cooling for 25 cycles is crushed and destroyed. (3) As the temperature and the number of cycles increase, the surface of the water-cooled sample becomes rougher with the increase in the temperature and the number of cycles and the higher temperature, along with more cracks and debris; the increase in the temperature cycle, no obvious cracks appeared on the surface. The test results in this paper can provide relevant theoretical guidance for the stability and safety of rock in geothermal mining.

Comparative Evaluation of the Efficacy of Different Ni-Ti Rotary Instruments in Removal of Gutta-Percha During Root Canal Retreatment: An in vitro Study

Aim: An assessment and comparison of three retreatment files was conducted to determine their effectiveness in the retrieval of gutta-percha. Materials and Method: In the investigation, 60 extracted single-rooted human teeth having straight canals and complete apices were used. The ProTaper Universal file system was used to prepare teeth and obturated using gutta-percha with sealant AH Plus utilizing down pack and backfill obturation technique. Removal was performed with ProTaper, D-RaCe files, MTwo, and R-Endo retreatment files. Using a stopwatch, the time needed to take out the GP was also calculated in seconds. We used ANOVA along with the post hoc Tukey’s test to analyze the quantity of obturating material in apical, middle, and coronal third following decoronation and longitudinal splitting. Results: The average percentage of gutta-percha points removed across root levels varied significantly among the ProTaper, D-RaCe MTwo, and R-Endo groups. With the exception of the ProTaper group, when the middle level displayed the most removal, the coronal level showed much higher removal than the mid-root level, while the apical level often exhibited the highest removal. Conclusion: ProTaper retreatment files outperformed MTwo, D-RaCe, and R-Endo among the four groups in terms of removing root canal filling material. However, none of the experimental groups removed gutta-percha completely from root canals.

Mechanical properties of laminated bamboo lumber N-finity according to ISO 23478-2022

This research used the new ISO 23478-2022 standard as a reference for the calculation of mechanical properties of N-finity, and to understand the failure modes in compression. Previous studies have investigated the mechanical properties of laminated bamboo lumber (LBL), however no study has evaluated the mechanical properties of LBL according to the recently published ISO 23478-2022. The compression testing programme in parallel and perpendicular-to-grain directions were conducted. The measured elastic stiffness properties and compressive strengths show anisotropy with higher compressive strength and stiffness parallel-to-grain direction as compared to those at the transversal directions. The observed failure modes at the parallel-to-grain direction exhibited a mixed mode failure, whereas perpendicular-to-grain directions exhibited failure with longitudinal splitting with crack propagation rupture. This finding can be quantified using Hills failure criterion principle to define the failure criterion and to estimate the Hill’s yield failure ratios.