Intact Specimen Research Articles

Creep and permeability evolution behavior of red sandstone containing a single fissure under a confining pressure of 30\u2009MPa

The long-term deformation and permeability evolution with time are key issues for geo-engineering applications such as radioactive waste disposal. Rock permeability concurrent with deformation is significantly influenced by cracking. This study investigated the creep-permeability evolution behavior of red sandstone specimens containing a single fissure under a confining pressure of 30 MPa. First, the effects of stress ratio (SR) and fissure dip angle on the creep behavior of rock were investigated. The more loading/unloading cyclic numbers, the larger the irrecoverable axial deformation. The instant elastic strains and visco-elastic strains linearly increased with SR for both the intact and fissured specimens, whereas the instant plastic strains showed different results. The visco-plastic strains nonlinearly increased. For fissured and intact specimens, the creep strains and the steady-state creep rates nonlinearly increased as SR increased. The instantaneous strains, instant elastic strains, and visco-elastic strains slightly varied when the fissure dip angle was less than 45° but notably decreased with increasing fissure dip angle beyond 45°. However, the fissure dip angle had no obvious effects on the plastic and creep strains. Damage (D) was defined using the ratio of non-elastic strains to the total strain. D increased approximately linearly with SR, but the fissure dip angle had no obvious influences. Subsequently, the long-term strength (LTS) of the red sandstone was determined using two different methods. The LTS first decreased when the fissure dip angle increased from 0 to 45° but increased with increasing dip angle. The triaxial and creep failure modes were mainly shear along anti-wing cracks for the fissured specimens but shear failure occurred for the intact specimen. Moreover, the permeability of the fissured red sandstone was governed by SR and deformation or time. During the multi-step loading/unloading creep process, the permeability first decreased and then had a sudden rise when tertiary creep occurred.

Evaluation of an Ultrasonic Method for Damage Characterization of Brittle Rocks

An intact rock specimen, when subjected to uniaxial compression, experiences multiple stages of deformation. This begins with the nucleation of microcracks at low stresses (crack initiation—CI) and their subsequent transition into unstable crack propagation (crack damage—CD) close to the ultimate strength. In the present study, an active ultrasonic monitoring method was used during uniaxial compression testing of Lyons sandstone specimens to evaluate the potential of the technique for damage characterization. The sensitivity of ultrasonic monitoring in relation to the input excitation frequency was also analyzed using four ultrasonic transducers with different central frequencies. A LabVIEW-controlled active ultrasonic system was used to acquire active seismic waveforms, which were made to propagate perpendicular to the direction of uniaxial stress. With increasing deformation, the corresponding changes in amplitude, frequency, and velocity of the active seismic signals were analyzed to characterize the CI and CD stress thresholds. Using statistical analysis, it was concluded that the changes in the amplitude and frequency of the active signals could be potential indicators of CI and CD. The comparison of wave characteristics corresponding to different input excitations also indicated that appropriate selection of transducer frequency is crucial for a representative interpretation of damage processes.

Numerical investigation on cracking behavior of granite with intersecting two-flaws: A flat-joint modeling method

Abstract In practical rock engineering, it is of considerable significance for the study of mechanical behavior of rock containing flaws. The uniaxial compression failure mechanism of granite containing intersecting two-flaws is investigated through the flat-joint modeling approach. The flat-joint model is introduced briefly, and numerical models of intact granite specimens are established. After that, a series of micro-parameters are confirmed by comparison with the laboratory tests of intact granite specimen. Then uniaxial compression simulations are conducted on granites with intersecting two-flaws. The numerically simulated results show good consistency with laboratory tests, including the strength properties, deformation properties, and failure modes. The strength and deformation characteristics of the granites are dependent on the relative position length. Furthermore, the relationship between the crack evolution process and the stress-strain curves for the specimens is studied concerning the relative position length. Finally, the crack propagation mechanism and cracking type of granite specimens are revealed by analyzing the micro-force field.

Numerical Test Research on Loading Rate Effect of Rock Mass with Transfixion Sawtooth Structural Plane

In this paper, numerical test research is carried out on the loading rate effect of a numerical specimen (sample C) with a transfixion sawtooth structural plane by using the rock failure process analysis (RFPA) 2D software. In order to study the mechanical characteristics difference between the rock mass with this kind of structural plane and other rock masses, the intact numerical specimen (sample A) of no structural plane and the numerical specimen (sample B) with smooth structural plane are also simulated. The uniaxial compression tests were carried out for each specimen under five loading rates of 0.002, 0.005, 0.008, 0.02, and 0.05 mm/s. The following several conclusions are obtained by the numerical test. When the loading rate is 0.002 or 0.005 mm/s, the failure mode of the numerical specimen C is an inclined linear fracture zone located in the middle and lower part of the rock mass; however, when the loading rate rises to 0.008, 0.02, and 0.05 mm/s, the fracture zone of the numerical specimen C is located in the middle and upper part of the rock mass, and its inclination angle is about 60 degrees. The peak strength, residual strength, and stress drop of the specimens A, B, and C increase with the addition of loading rate; the peak strength and stress drop of the sample C are higher than those of the other two samples. When the loading rate is 0.002 mm/s, the residual strength of sample C is lower than that of samples A and B, and the other four kinds of loading conditions are higher than those of specimens A and B. Based on the acoustic emission (AE) information, it can be seen that the failure modes of the numerical specimen C under five loading conditions are tensile failure. The AE accumulated energy decreases with the increase of loading rate, but the change law of AE accumulated number is opposite.

Investigation on the Effects of Prefabricated Crack and Strain Rate on Uniaxial Compressive Properties of Frozen Silty Soil

To investigate the uniaxial compressive strength and deformation properties of frozen silty soil with prefabricated crack under various strain rates, the static uniaxial compressive tests were conducted for frozen silty soil using three kinds of binder materials to select the suitable prefabricated crack manufacturing method. Afterward, the static and dynamic stress‐strain curves of frozen silty soil with different prefabricated crack numbers were obtained based on static and splitting Hopkinson pressure bar (SHPB) tests. In addition, the high‐speed camera was employed to record the fracturing process of frozen silty soil under impact loads. Results indicated that the frozen silty soil specimens with no binder showed higher static strength compared with other two binder materials (plaster and Vaseline). The strength growth rate of frozen silty soil showed three‐stage (fast‐slow‐rapid) change characteristics. The peak strain of frozen silty soil under static loads scope was higher compared with that under dynamic loads, while its dynamic peak strain with various prefabricated crack numbers was remarkably rate‐dependent. The absorbed energy density of frozen silty soil was subject to a negative (positive) relationship with the prefabricated crack numbers (strain rate). The dominated crack of intact frozen silty soil specimen finally presented Y‐shaped shear failure. However, tensile cracks parallel to stress wave propagation direction were observed for the frozen silty soil specimen with prefabricated crack.

Производственные участки на поселении ранней бронзы Старый Тартас-5 (Барабинская лесостепь)

В статье представлены результаты исследования участков со следами бронзолитейного производства на поселении одиновской культуры Старый Тартас-5 в Барабинской лесостепи. Рассмотрены два участка: один — на территории жилища № 1 — с очагом и ямами, расположенными вблизи теплотехнического устройства, другой — за пределами этого жилища — с плавильным горном. Даются характеристика объектов и информация об археологическом контексте находок. В работе приведены полные описания каждого предмета литейного комплекта производственной оснастки, аналоги этих находок, результаты бинокулярного анализа формовочных масс. На основе данных термогравиметрических исследований установлены функциональная принадлежность обломков технической керамики и кратность использования различных предметов литейного комплекта. Отмечено, что тигли в виде прямостенных баночек известны только по одному целому изделию из погр. № 286 могильника Тартас-1; в составе поселенческих комплексов одиновской культуры они ранее не встречались. Определены специализация жилища № 1 указанного поселения на бронзолитейном производстве и специфика организации данного производства как индивидуально-семейного. Подчеркнуто, что традиции бронзового литья одиновской культуры сохранились в традициях кротовской культуры и пополнились новациями: типичные для одиновской культуры тигли в виде овальных чашечек носители кротовской культуры в соответствии с особенностями своего производственного процесса делали с более толстым дном. Одиновские комплексы Барабинской лесостепи датируются в пределах первой половины III тыс. до н.э. Сделан вывод о том, что свидетельства бронзолитейного производства, выявленные на памятнике Старый Тартас-5, являются самыми ранними для данного региона, уровень этого производства у носителей одиновской культуры был высоким.

Evaluation of bipolar transurethral en-bloc resection in patients with primary non-muscle invasive bladder cancer

Background Conventional TURBT includes tumour fragmentation; this impairs pathological examination and is associated with a high risk of residual disease, tumour understaging and early recurrence. En-bloc TURBT (eTURBT) is supposed to overcome these major drawbacks. It includes uprooting of the whole tumour in one piece, providing an intact specimen for accurate pathological evaluation with a low risk of scattering malignant cells. Aim This study aimed to evaluate the efficacy, safety and oncological outcomes of bipolar eTURBT in resection of a small primary bladder mass. Patients and methods This prospective study included 63 patients with a primary bladder mass suspected to be non-muscle invasive bladder cancer (NMIBC). All patients underwent bipolar eTURBT using a mushroom loop electrode. All operations were performed by one experienced uro-oncologist and all the procedures were successfully completed. The patients included were scheduled for follow-up cystoscopy at 3, 6 and 12 months. Results The mean (SD) operative time was 37.01 (±5.50) min, enucleation time was 23.11 (± 6.26) min and obturator nerve jerk occurred only in three cases (4.76%); the mean (SD) postoperative irrigation time was 1.21 (±3.32) h, haemoglobin drop was 0.3 (± 0.57) g/dl, with no need for blood transfusion at all, and the mean (SD) hospital stay was 2.30 (±0.53) days. There were no other perioperative complications. Conclusion Bipolar eTURBT is effective and safe for managing NMIBC as it preserves well-intact specimens, with negligible perioperative complications.

Biomechanical contribution of the alar ligaments to upper cervical stability

Acute and chronic whiplash-associated disorders pose a significant healthcare burden due to chronic pain, which is associated with upper cervical instability resulting from ligamentous injury. No standard measure exists for diagnosing alar ligament injury and imaging findings vary widely. Multiple physical examination maneuvers are used to diagnose alar ligament injury including the C2 Spinous Kick, Flexion-Rotation, and Bending-Rotation tests. The objective of the current study was to determine the mechanical contribution of the alar ligaments to upper cervical stability and quantify the biomechanical changes seen during simulated clinical examinations after alar ligament injury. Eight cadaveric C0-C3 specimens were evaluated using a robotic testing system. Range of motion and moment at the end of intact specimen replay were the primary outcomes. Clinical examinations were simulated by rotation through two axes as performed during physical examination. Intact, unilateral and bilateral alar ligament injury states were tested. Unilateral alar ligament injury led to significant increases in lateral bending (12.0 ± 7.2%, p < 0.05), axial rotation (4.1 ± 2.4%, p < 0.05), and flexion-extension (5.3 ± 4.3%, p < 0.05) compared with intact specimens. The alar ligaments also contributed to resistance to intact motion in extension (13.4 ± 6.6%, p < 0.05), flexion (4.4 ± 2.2%, p < 0.05), axial rotation (19.3 ± 2.7%, p < 0.05), and lateral bending (16.0 ± 2.8%, p < 0.05). The C2 Spinous Kick Test showed the largest percentage change (−23.0 ± 14.8%), and the Bending-Rotation Test towards the side of injury significantly increased axial rotation by the largest absolute magnitude (5.5° ± 5.1°). Overall, quantifiable changes to motion measured during simulated physical examinations were found, but the ability of a clinician to feel these changes remains unknown.

Non-destructive DNA extraction from herbarium specimens: a method particularly suitable for plants with small and fragile leaves.

Protocols for DNA extraction from plants generally involve physical and chemical destruction of tissues. Use of these conventional methods precludes preservation of morphological information from herbarium specimens, especially for small plants with few leaves, and reduces the voucher value of specimens. Here, we developed a new, non-destructive DNA extraction protocol (Protocol 1) that only needs a small piece of leaf (< 25mm2) to obtain DNA suitable for DNA sequencing from fragile herbarium specimens. The protocol was very simple and rapid; an extraction buffer was placed on the leaf surface of an intact specimen for 30min at room temperature (20°C). The quality of extracted DNA was checked by PCR amplification of two standard plant DNA barcode regions, the maturase K gene (matK, ca. 850 bp) and the ribulose-1,5-bisphosphatecarboxylase/oxygenase gene (rbcL, ca. 550 bp), for 14 vascular plant species encompassing various taxonomic groups. The protocol retrieved sequences from 80.0% of specimens for matK and 46.2% of specimens for rbcL. Placing of the extraction buffer onto specimens did not cause any tears or deformation, but caused discoloration in some plants. To improve DNA yield for specimens incompatible with Protocol 1, we developed an alternative protocol for DNA extraction with minimally invasive destruction of specimens (Protocol 2). In this protocol, a cut leaf was immersed in the extraction buffer for 30min and stored subsequently in a fragment pocket on the specimen sheet. This alternative method retrieved matK sequences from 80.0% of specimens and rbcL sequences from 92.8% of specimens. The combination of Protocols 1 and 2 enabled us to obtain matK sequences from 90.0% of specimens and rbcL sequences form 92.8% of specimens. The new protocols facilitate the use of museum specimens for use of DNA of museum specimens while still preserving morphological information.

Freeze-thaw damage evolution of fractured rock mass using nuclear magnetic resonance technology

Taking sandstone as a research object, this study investigated the damage evolution law of rock mass with different macroscopic and microscopic defects under freeze–thaw cycles. For the first time, macroscopic defects were simulated by prefabricating 0°, 45°, and 90° fractures in real rock materials. Initial microscopic damage was caused by applying prestressing forces equal to 0%, 30%, 50%, and 70% of the ultimate compressive strength of the specimen. The microstructure changes of samples during freeze–thaw cycles were tracked by nuclear magnetic resonance (NMR) technology, and the characteristic parameters such as porosity, aperture distribution, and T2 spectral distribution were obtained. Through freeze–thaw cycle tests and uniaxial compression tests on specimens undergoing 0, 20, 40, and 60 freeze–thaw cycles, the influence of different damage levels on the changes in the surface, mass, volume, compressive strength, and elastic modulus of rock mass was investigated. The experimental results show that the porosity of the intact specimen is greater than that of the fractured specimen during freeze-thaw cycles. The mechanical properties of the intact specimen and the 90° fractured specimen are controlled by the pore distribution, and the strength drop increases first and then decreases during freeze-thaw cycles, while the mechanical properties of the 0° fractured specimen and the 45° fractured specimen are affected by the prefabricated fracture, and the strength drop increases with the increase of the fracture damage. The initial damage can accelerate the damage degradation of the rock mass, and when the damage level exceeds a certain threshold, which is between 30% and 50%, the deterioration effect will be more significant.

Partially corroded reinforced concrete piers under axial compression and cyclic loading: An experimental study

Twelve reinforced concrete (RC) pier specimens were developed and partially corroded to simulate severe corrosion in splash and tidal zones. Six target corrosion levels were applied to rebars and stirrups using an electrochemical accelerated corrosion technique. Axial compression loading and cyclic loading tests were carried out with six specimens per group. The test results showed that mechanical parameters of pier specimens degraded with an increase in corrosion. The ultimate load, ductility factor, energy dissipation decreased by 29.96%, 9.26%, 67.44% for axial compression specimen with 15.82% rebar mass loss compared to those of intact specimen; for cyclic loading specimens, they decreased by 10.69%, 21.47%, 57.46% with 15.71% rebar mass loss, respectively. Comparative analysis showed that the difference for the degradation level of dimensionless parameters was not obvious between axial compression loading and cyclic loading tests. Findings also showed that for severely corroded specimens, the plastic hinge zone transferred from the bottom of RC piers to the splash and tidal zones. Although the extent of the degradation of the results between the published paper and this test shows significant variations; degradation of dimensionless energy dissipation was always the most serious one.

Effect of incremental increase in radial neck height on coronoid and capitellar contact pressures.

Over-lengthening of the radial neck has been shown to affect ulnohumeral kinematics and has been proposed to affect radiocapitellar pressures. We hypothesized that an incremental increase in radial neck height increases the capitellar contact pressure and reduces the coronoid contact pressure. Knowledge of the effects of over-lengthening is clinically important in preventing pain and degenerative changes due to overstuffing. Six human cadaveric elbows were prepared on a custom-designed apparatus simulating muscle loads and passive flexion from 0° to 90° under gravity valgus torque while measuring joint contact pressures in this biomechanical study. Each elbow was tested sequentially starting with the intact specimen followed by insertion of a radial head prosthesis with 0, +2, and +4 mm of radial neck height, respectively. Capitellar mean contact pressures significantly increased after insertion of +2 and +4 mm radial head prostheses (p < 0.03). The capitellar mean contact pressure with a 0 mm radial head prosthesis was 97 KPa. Insertion of +2 mm and +4 mm radial heads increased mean contact pressures to 391 KPa (p = 0.001) and 619 KPa (p = 0.001), respectively, with 90° of elbow flexion. Increasing radial prosthesis height by 2 mm significantly increases capitellar contact pressures and reduces coronoid contact pressures.

2538 Current Methods of Tissue Extraction in Minimally Invasive Surgical Treatment of Uterine Fibroids

Study Objective Since the 2014 Food and Drug Administration warnings regarding the use of power morcellation, gynecologists have adopted multiple alternative tissue extraction strategies. The objective of this study is to investigate the current techniques used by minimally invasive gynecologic surgeons for tissue extraction following minimally invasive hysterectomy for fibroids. Design Web-based survey. Setting N/a Patients or Participants Current AAGL members were sent a link to access the survey, which was available from March 26, 2019 to April 17, 2019. Interventions N/a. Measurements and Main Results 420 respondents completed the survey. The most common methods of tissue extraction were manual morcellation through the colpotomy (72.4%) and mini-laparotomy (66.9%). 31.7% of all participants endorsed the use of power morcellation. Intact specimen removal through a laparotomy was reported by 10% of respondents. Other methods of tissue extraction, such as intra-abdominal manual morcellation with a laparoscopic scalpel, were reported by 1.4%. Use of containment bags was reported by 43.4% during vaginal morcellation, 83.6% during mini-laparotomy, and 56.8% during power morcellation. Mini-laparotomies were on average 3.5cm and most commonly located at the umbilicus. Geographic differences were seen with respect to power morcellation, with 18.4% of US-based surgeons reporting its use compared to 56.9% of non-US-based surgeons. Conclusion Minimally invasive gynecologic surgeons are currently employing a variety of tissue extraction strategies for hysterectomy for fibroids. A large majority of practitioners are performing manual morcellation through the colpotomy and/or mini-laparotomy; use of containment bags is more common with during mini-laparotomy than via colpotomy. Power morcellation is still in use, less commonly in the United States than in other countries, and usually within a containment system.

RNA isolation from corals and other cnidarian species using urea-LiCl as a denaturant

A method of RNA isolation using a solution of urea-LiCl as a denaturing agent was tested on stony coral. As the method does not require homogenization of tissues prior to their incubation in the denaturant, specimen collected in the field can be immediately transferred to the urea-LiCl solution. The method was also tested on tissues of other cnidarian species. RNA was isolated from fresh tissues of jellyfish and sea anemones using two protocols – that is, incubations in the urea-LiCl solution were either performed on homogenized tissues or on intact tissues or specimen. RNA quality was evaluated on a bioanalyser.

Suprapubic-assisted laparoendoscopic single-site surgery in nephroureterectomy A case series of 4 patients

Objective: To evaluate the feasibility and clinical value of suprapubic-assisted laparoendoscopic single-site surgery (SA-LESS) in nephroureterectomy using method of transvaginal natural orifice specimen extraction (NOSE) (SA-LESS+TV-NOSE NU). Methods: Four patients (three cases of renal pelvic carcinoma and one case of ureteral carcinoma) undergoing SA-LESS+TV-NOSE NU were enrolled between April 2015 and January 2016. After general anesthesia, the patients were placed in the lithotomy position with the affected side elevated by 60°. Two trocars were inserted at the medial margin of umbilicus, and the third one was inserted into abdominal cavity at the superior margin of pubic symphysis. The operation was performed under a direct vision with a 5.4 mm 0° flexible-tip laparoscope. Firstly, the distal ureter was isolated completely and blocked by a Hem-O-lok clip. Then, the laparoscopic nephrectomy was performed according to the standard method. Finally, the bladder cuff excision was executed and the incision was sutured. The intact specimen was placed inside a homemade bag and removed through the incision at posterior vaginal fornix. Results: All the procedures were successfully performed. The median operative time was 150 (range: 120 to 210) minutes, and the median estimated blood loss was 180 (range: 80 to 350) ml. No major perioperative complications occurred. The mean visual analogue score (VAS) of 24 hours and 48 hours after operation were 3.25 (range: 2 to 5) and 2.25 (range: 2 to 3). All the patients resumed ambulation on postoperative day 1. Pelvic drainage tube was removed on postoperative day 2-4. On postoperative day 7, urethral catheter was removed. The patients were discharged on postoperative day 7-9. During the follow-up of 20-29 months, the patient recovered well with no case of incisional hernia and pelvic, abdominal infections. The vaginal fornix incision healed well, and the umbilical and suprapubic puncture scars were not obvious. All the patients completed the patient-assessed acromegaly symptom questionnaire PASQ. The average PSAQ score of 3 months after surgery was 34.5. Three of them restarted their sex lives, with an average female sexual function index score of 16.0, which was not significantly different with that of preoperation (15.6). There was no tumor recurrence, metastasis and implantation in all cases. Conclusion: SA-LESS+TV-NOSE NU is safe and feasible for upper tract urothelial carcinoma with faster postoperative recovery, less pain, shorter hospitalization time, better cosmetic results, and does not cause negative effect on the female sexual function.

6. Biomechanical investigation of the potential development and prevention of scoliosis following various sizes of chest wall resection

BACKGROUND CONTEXT Chest wall resection is used to treat several thoracic disorders including tumor removals. A well-known problematic sequela of chest wall resections is development of scoliosis. Literature shows that the degree of the induced curvature correlates to the number of resected ribs. Despite the seriousness and frequency of scoliosis following chest well resection, the etiology and biomechanical information needed to understand this deformity development are not well-known. PURPOSE The objective of the present study was to investigate the effect of chest wall resections, ranging in size from 1 to 6 ribs, on the biomechanical stability of the spine. Further, the study compared anterior-only fixation with a combined anterior-posterior approach in reducing range of motion (ROM) following chest wall resection. STUDY DESIGN/SETTING Biomechanics/laboratory. METHODS The range of motion (ROM) of six specimens (C7–L2) was captured using a custom-built six degrees-of-freedom machine in each of three physiological rotation axes: flexion extension (FE), lateral bending (LB), and axial rotation (AR). Left posterior ribs were sequentially resected 7 cm from the rib head, starting at the 5th rib and continuing until the 10th rib. Injured specimens were instrumented first with unilateral anterior rod fixation (UA) and then with additional unilateral posterior fixation (UA+UP), each starting at T4 and then extended distally as ribs were resected. Relative motion between the proximal and distal ends of the construct was measured in all three axes for the intact, injured, UA, and UA+UP constructs. RESULTS Raw ROM of the injured specimen increased in a stepwise manner as additional ribs were resected, with an average increase of 0.90°±0.52° in FE, 0.98°±0.40° in LB, and 2.75°±1.50° in AR. No statistically significant differences in ROM normalized to the intact specimen were found between operative constructs for any injury size (p>.05). Across all injury sizes, the UA construct reduced motion, and the UA+UP construct further reduced motion in all FE (22.0±12.3% vs 58.4±13.2%), LB (51.0±9.8% vs 74.4±9.0%), and AR (25.4±9.0% vs 58.7±11.2%). The impact of fixation was slightly greater as more ribs were resected. CONCLUSIONS The stepwise ROM increase for the injured model as more ribs were resected can likely be attributed to the additional motion segment, suggesting that the etiology of scoliosis following chest wall resection may not be purely biomechanical in nature. Overall, the UA+UP construct may be a more optimal construct than UA in reducing motion and potentially assisting in limiting the risk of scoliosis development. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

5. A biomechanical investigation of the sacroiliac joint in the setting of lumbosacral fusion: the impact of pelvic fixation vs sacroiliac joint fixation

BACKGROUND CONTEXT The sacroiliac (SI) joint is a known source of lower back pain. Randomized clinical trials support sacroiliac fusion over conservative management for sacroiliac joint dysfunction. Clinical experience suggests degeneration of the sacroiliac joint in the setting of lumbosacral fusions. However, there are limited biomechanical studies to understand the effect of lumbosacral fusion on the sacroiliac joint. This study is a biomechanical investigation to understand the effect of pelvic vs sacroiliac joint fixation on the sacroiliac joint in lumbosacral fusion. Furthermore, researchers studied the effect of lumbosacral fixation on the SI joint in the absence of pelvic and SI joint fixation. PURPOSE To determine the immediate stability of various lumbopelvic fixation constructs. STUDY DESIGN/SETTING In-vitro biomechanical range of motion testing. METHODS Seven fresh-frozen human cadaver specimens were used. There was one intact and 6 operative constructs: (1) posterior pedicle screws and rods from T10–S1 (PS); (2) PS+bilateral iliac screw fixation (BIS); (3) PS+unilateral iliac screw fixation (UIS); (4) PS+UIS+3 contralateral unilateral SIJ screws (UIS+3SIJ); (5) PS+3 unilateral SIJ screws (3SIJ); and (6) PS+6 bilateral SIJ screws (6SIJ). A custom-built 6 degrees-of-freedom (6DOF) testing apparatus was used to simulate 3 bending modes: flexion extension (FE), lateral bending (LB), axial rotation (AR). Range of motion was recorded at L5–S1 and sacroiliac joint. RESULTS All 6 operative constructs had significantly reduced ROM at L5–S1 compared to the intact specimen in all 3 bending modes (p CONCLUSIONS This biomechanical investigation demonstrated the effects of various fusion constructs using pelvic and sacroiliac fixation in lumbosacral fusion. It adds biomechanical evidence to the literature showing adjacent segment stress in the SIJ in fusion constructs to S1. Unilateral pelvic fixation or SIJ fusion led to appreciable but nonsignificant reduction to the unfused contralateral SIJ. Finally, bilateral pelvic fixation showed the greatest significant reduction of movement at L5–S1 and was equivalent to bilateral sacroiliac fusion in reducing SIJ motion. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Investigation on Properties of Rock Joint in Compression Dynamic Test

This paper is devoted to investigate rock joint interaction with stress waves by split Hopkinson pressure bar (SHPB) during wave propagation on dynamic loading. Taking two different specimens from the intact specimen (Series N) and the joint specimen (Series J), this study focused on three aspects: the influence of joint specimens on waveform propagation, inversion analysis of rock joint parameters using the waveform transmission coefficient, and the influence of the joint on rock specimens. With an increase in impact air pressure, compared with the intact sample, the transmittance and reflectance of joint specimens showed the opposite change rule; the closure rate change process of rock joint was converted from an exponential function to a linear function; the peak strength of the intact specimens was higher than the joint specimens at the same impact pressure above 19.58%, 21.21%, 21.56%, and 22.68% (mean values), respectively; and the strain rates (mean value) of the intact specimens were respectively 1.61, 1.31, 1.20, and 1.09 times that of the joint specimens.

Damage and residual bending strength in glass-polyester molded grating composite panels after low-velocity impact

Glass-polyester molded grating composites (MGC) are brittle and sensitive to the damage caused by the impact. In this study, a finite element model has been proposed to predict the strength of the molded grating composite panels against low-velocity impact loads. Molded grating composites have unidirectional reinforcement fibers, except in the intersections where behave as a blocked bidirectional reinforced materials. Hashin failure criteria and a proposed sudden degradation model have been employed to distinguish damage initiation and formulate damage evolution, respectively. The proposed degradation rule basically is Tserpes model with a small modification for shear dominant tension-compression degradation. In order to validate the results a series of experimental impact tests were carried out by means of a drop weight tower in different states of the height and mass of the drop weight. Three-point bending tests on the intact specimen and impacted specimens were performed in order to determine the reduction of strength and stiffness after impact. The results show that the numerical analysis based on the proposed modified Tserpes model predicts the ultimate force and the slope of the load-displacement diagram with a reasonable accuracy that correlate well with the experimental results.

Numerical simulation of crack propagation behavior of a semi-cylindrical specimen under dynamic loading

To design and evaluate the analytical crack propagation of a specimen under dynamic load, measurement of dynamic fracture parameters is necessary. However, analytical methods have significant complexity, and experimental methods are also time-consuming that require high precision and considerable funding. Therefore, numerical methods can be used to solve these problems. The Extended Finite Element Method (X-FEM) as a powerful and efficient tool can be used for this purpose. In this paper, X-FEM code in ABAQUS software was used in order to simulate crack growth in a semi-circular specimen with pre-existed crack and also intact specimen to determine dynamic stress intensity factor (DSIF) using displacement extrapolation method. To verify the numerical modeling output, the curve of crack surface opening displacement (CSOD) in X-FEM model has been compared with the experimental curve. Moreover, concrete damage plastic (CDP) model was used to validate X-FEM simulation results. The results show that the DSIF for a cracked sample under a maximum dynamic load 3000 N is equal to 0.5 Mpa . Comparison between the CDP and X-FEM results showed that in both approaches, the same area for crack propagation was also determined.