scholarly journals Creep Characteristics of Different Saturated States of Red Sandstone after Freeze-Thaw Cycles

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Yongxin Che ◽  
Yongjun Song ◽  
Jianxi Ren ◽  
Jiaxing Chen ◽  
Xixi Guo ◽  
...  
Keyword(s):  
Mechanical Characteristics ◽  
Creep Failure ◽  
Creep Tests ◽  
Red Sandstone ◽  
Freeze Thaw ◽  
Sem Image ◽  
In Series ◽  
Distribution Shifts ◽  
The Right

To investigate the creep mechanical characteristics of rocks in different saturated states after freeze-thaw cycles, samples with different saturations (30%, 50%, 70%, 90%, and 100%) were selected for nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and uniaxial compression creep tests. The internal microscopic damage of the rock sample and mechanical characteristics under long-term loading are analyzed after the action of freeze-thaw cycles. The test results show that, as the saturation increases, the T2 spectrum distribution shifts to the right. The spectrum area gradually increases as the porosity increases. The critical saturation of freeze-thaw damage occurs when the saturation increases from 70% to 90%. It can be seen from the SEM image that the number of pores inside the rock samples gradually increases with increases in saturation, leading to the appearance of cracks. Under long-term loading, the saturation has a significant influence on the time-efficiency characteristics of sandstone freeze-thaw. As the saturation increases, the creep deformation gradually increases. After reaching 70%, the axial creep strain increases significantly. The rate of creep is accelerated, the creep failure stress is reduced, and the creep time under the last level of stress is significantly increased. A modified viscous-plastic body is connected in series to the basic Burgers model, the freeze-thaw-damage viscous element is introduced, and the creep parameters are fitted using test data. The results will provide a reference for long-term antifreeze design for rock engineering in cold areas.

scholarly journals Triaxial Creep Behavior of Red Sandstone in Freeze-Thaw Environments

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Yongjun Song ◽  
Yongxin Che ◽  
Leitao Zhang ◽  
Jianxi Ren ◽  
Shaojie Chen ◽  
...  
Keyword(s):  
Stress Level ◽  
Creep Deformation ◽  
Transverse Shear ◽  
Shear Plane ◽  
Confining Pressure ◽  
Term Strength ◽  
Red Sandstone ◽  
Freeze Thaw ◽  
Viscoelastic Strain

To investigate the time-dependent mechanical properties of rock masses in cold regions under the effects of freeze-thaw cycling and long-term loading, triaxial multilevel loading and unloading creep tests were performed on saturated red sandstone samples subjected to different numbers of freeze-thaw cycles. The effects of freeze-thaw cycles and confining pressure on the creep properties, long-term strength, and creep failure mode of the rock were analyzed. The effect of freeze-thaw cycles on the microstructure of the rock was analyzed using scanning electron microscopy. The results showed that as the number of freeze-thaw cycles increased, the rock particle boundaries became more distinct, and more pores formed. The effect of freeze-thaw cycles on the creep deformation of red sandstone was related to the loading stress level. At low stress levels, the rock viscoelastic strain increased gradually and almost linearly with an increasing number of freeze-thaw cycles; in contrast, at high stress levels, the rock viscoelastic strain increased nonlinearly. The viscoplastic strain increased almost linearly with increasing freeze-thaw cycles. The fourth loading stress level (70% σ c ) corresponded to the transition of the creep deformation of the red sandstone. When the confining pressure was low, a higher stress level caused the confining pressure to have a more significant effect on the creep strain. However, as the confining pressure continued to increase, the effect of the confining pressure on the creep strain eventually disappeared. The long-term strength of the red sandstone decreased approximately linearly with an increase in the number of freeze-thaw cycles. When the number of freeze-thaw cycles and the confining pressure were high, the rock samples formed a transverse shear plane and were more fragmented than those without a transverse shear plane. These results provide a reference for construction in rock mass engineering and long-term stability analysis in cold regions.

scholarly journals The Uniaxial Creep Characteristics of Red Sandstone under Dry-Wet Cycles

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Guangcheng Liu ◽  
Xin Huang ◽  
Jianyong Pang
Keyword(s):  
Elastic Modulus ◽  
Creep Strain ◽  
Failure Modes ◽  
Peak Strength ◽  
Logarithmic Function ◽  
Creep Tests ◽  
Engineering Structures ◽  
Red Sandstone ◽  
Instantaneous Strain

Water is one of the most important factors that affect the long-term stability of geotechnical engineering structures. Rainfall often results in periodic changes in the water content in underground rock, which is subjected to alternating dry-wet cycles. In this paper, in order to study the short-term and long-term mechanical properties of red sandstone under these dry-wet cycles, a series of uniaxial compressive strength (UCS) tests and multistage creep tests have been carried out on specimens of red sandstone after being treated to different numbers of dry-wet cycles. A scanning electron microscope (SEM) was used to image the different groups of specimens. The test results have shown that the peak strength and the elastic modulus of the red sandstone decreased as the number of dry-wet cycles increased. It is worth noting that the first immersion of the specimens decreased their strength the most, and the negative logarithmic function was able to better reflect the peak strength of the red sandstone and the variation of its elastic modulus in relation to the number of dry-wet cycles. The results of the creep tests have shown that the instantaneous strain and creep strain of the sandstone increased significantly with the increase of the number of dry-wet cycles. A linear function and a negative logarithmic function can be used to describe the instantaneous strain and the creep strain, respectively. The creep duration of the red sandstone in its failure stage decreased with the increase of the number of dry-wet cycles, and the creep rate increased with the increase of the number of dry-wet cycles. Lastly, the failure modes of the red sandstone were observed; the results showed that the angle between the main crack and the axis of creep failure gradually increased with the increase of the number of dry-wet cycles and the angle of the internal friction and the cohesion decreased. In addition, the failure mode of the specimens changed from tensile failure to shear failure. The microstructure of the sandstone showed that the surface of the specimen changed from being compact to being loose, and the mineral particles in the specimen changed from being spherical to being flat and curly; this led to a decrease in the macroscopic mechanical parameters of the sandstone.

scholarly journals Clinical Study of 107 Hospitalized Patients with Peritonsillar Abscess

2021 ◽  
Vol 04 (01) ◽  
pp. e11-e16
Author(s):  
Risa Wakisaka ◽  
Takumi Kumai ◽  
Kan Kishibe ◽  
Miki Takahara ◽  
Akihiro Katada ◽  
...  
Keyword(s):  
Clinical Study ◽  
Initial Treatment ◽  
Peritonsillar Abscess ◽  
Laryngeal Edema ◽  
Antibacterial Drugs ◽  
Inferior Pole ◽  
Duration Of Hospitalization ◽  
The Right ◽  
Superior Pole

AbstractWe conducted a retrospective analysis of the data of 107 cases of peritonsillar abscess treated at our hospital between January 2014 and December 2018. Data on age, sex, affected site, duration of hospitalization, method of drainage, presence/absence of laryngeal edema, antibacterial drugs used, and isolated bacteria were analyzed. Of the 107 patients, 71 were males and 36 were females; the median age was 44 years (range: 18–88 years).The left side was affected in 55 patients, the right side in 50 patients, and both sides in two patients. The abscess was localized in the superior pole in 71 patients, and in the inferior pole in 36 patients. Thirty-five patients had laryngeal edema, of which three underwent tracheotomy. Recurrence of the abscess was observed in 15 cases, with the recurrence developing within 3 months in 7 cases, and over a period of 3 years in 4 cases. As for the sensitivity of the causative bacteria to antibacterial drugs, 17% of the causative bacteria showed resistance to clindamycin, while none showed resistance to ampicillin/sulbactam (ABPC/SBT). We concluded that ABPC/SBT might be suitable for the initial treatment of peritonsillar abscess, and that we need to bear in mind the possibility of long-term recurrence.

Physiological Pacing: A New Road to Future

2021 ◽  
pp. 263246362097804
Author(s):  
Vanita Arora ◽  
Pawan Suri
Keyword(s):  
Side Effects ◽  
Fibrous Tissue ◽  
Cardiac Pacing ◽  
His Bundle ◽  
Anatomy And Physiology ◽  
Long Term Follow Up ◽  
Pacing Lead ◽  
The Right

Anatomy and physiology are the basis of human body functioning and as we have progressed in management of various diseases, we have understood that physiological intervention is always better than an anatomical one. For more than 50 years, a standard approach to permanent cardiac pacing has been an anatomical placement of transvenous pacing lead at the right ventricular apex with a proven benefit of restoring the rhythm. However, the resultant ventricular dyssynchrony on the long-term follow-up in patients requiring more than 40% ventricular pacing led to untoward side effects in the form of heart failure and arrhythmias. To counter such adverse side effects, a need for physiological cardiac pacing wherein the electrical impulse be transmitted directly through the normal conduction system was sought. His bundle pacing (HBP) with an intriguing alternative of left bundle branch pacing (LBBP) is aimed at restoring such physiological activation of ventricles. HBP is safe, efficacious, and feasible; however, localization and placement of a pacing lead at the His bundle is challenging with existing transvenous systems due to its small anatomic size, surrounding fibrous tissue, long-learning curve, and the concern remains about lead dislodgement and progressive electrical block distal to the HBP lead. In this article, we aim to take the reader through the challenging journey of HBP with focus upon the hardware and technique, selective versus nonselective HBP, indications and potential disadvantages, and finally the future prospects.

scholarly journals QOL-09. WHOLE-BRAIN WHITE MATTER NETWORK CONNECTIVITY IS DISRUPTED BY PEDIATRIC BRAIN TUMOR TREATMENT

2020 ◽  
Vol 22 (Supplement_3) ◽  
pp. iii432-iii432
Author(s):  
Adeoye Oyefiade ◽  
Kiran Beera ◽  
Iska Moxon-Emre ◽  
Jovanka Skocic ◽  
Ute Bartels ◽  
...  
Keyword(s):  
White Matter ◽  
Pediatric Brain Tumor ◽  
Pediatric Brain Tumors ◽  
Magnetic Resonance Images ◽  
Long Term Effects ◽  
Brain White Matter ◽  
The Right ◽  
Pediatric Brain ◽  
Betweeness Centrality

Abstract INTRODUCTION Treatments for pediatric brain tumors (PBT) are neurotoxic and lead to long-term deficits that are driven by the perturbation of underlying white matter (WM). It is unclear if and how treatment may impair WM connectivity across the entire brain. METHODS Magnetic resonance images from 41 PBT survivors (mean age: 13.19 years, 53% M) and 41 typically developing (TD) children (mean age: 13.32 years, 51% M) were analyzed. Image reconstruction, segmentation, and node parcellation were completed in FreeSurfer. DTI maps and probabilistic streamline generation were completed in MRtrix3. Connectivity matrices were based on the number of streamlines connecting two nodes and the mean DTI (FA) index across streamlines. We used graph theoretical analyses to define structural differences between groups, and random forest (RF) analyses to identify hubs that reliably classify PBT and TD children. RESULTS For survivors treated with radiation, betweeness centrality was greater in the left insular (p < 0.000) but smaller in the right pallidum (p < 0.05). For survivors treated without radiation (surgery-only), betweeness centrality was smaller in the right interparietal sulcus (p < 0.05). RF analyses showed that differences in WM connectivity from the right pallidum to other parts of the brain reliably classified PBT survivors from TD children (classification accuracy = 77%). CONCLUSIONS The left insular, right pallidum, and right inter-parietal sulcus are structurally perturbed hubs in PBT survivors. WM connectivity from the right pallidum is vulnerable to the long-term effects of treatment for PBT.

scholarly journals Long term follow-up of inguinal endometriosis

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
BoRan Mu ◽  
ZhiQiang Zhang ◽  
Chongdong Liu ◽  
Kunning Zhang ◽  
ShuHong Li ◽  
...  
Keyword(s):  
Management Strategies ◽  
Uterosacral Ligament ◽  
Round Ligament ◽  
Pelvic Endometriosis ◽  
Ovarian Endometriosis ◽  
Hernia Sac ◽  
Peritoneal Endometriosis ◽  
Long Term Follow Up ◽  
The Right

Abstract Background Inguinal endometriosis (IEM) is a rare extra pelvic endometriosis. Here, we study the clinical characteristics, management strategies, and long-term gynecological outcomes of IEM patients at Beijing Chaoyang Hospital. Case presentation Three patients presented with a total of four lesions (one on the left side, one on the right side, and one bilaterally). The diameters of the four lesions were 2 cm, 2 cm, 3.5 cm and 1.5 cm, respectively. Two patients were admitted with inguinal hernias. Two patients were admitted with endometrioses—one with ovarian endometriosis and one with pelvic endometriosis. The hernia sac was repaired concomitantly via excision of the round ligament in two patients. One patient underwent a concomitant laparoscopy for gynecologic evaluations, including an ablation to the peritoneal endometriosis, and resection of the left uterosacral ligament endometriosis and pelvic adhesiolysis. All lesions were located on the extraperitoneal portion of the round ligament and were diagnosed histologically. No recurrence was observed in the inguinal region. All patients diagnosed with adenomyosis were treated with medication alone without any complaints. Conclusions Inguinal endometriosis can occur simultaneously with pelvic endometriosis. In most cases, a concomitant hernia sac appears together with groin endometriosis. Clinical management should be individualized and performed in tandem with general practitioners and obstetrics & gynecology experts. Pelvic disease, in particular, should be followed-up by a gynecologist.

scholarly journals Concomitant Partial Achilles Tendon Rupture and Lateral Luxation of the Superficial Digital Flexor Muscle Tendon in a Dog

VCOT Open ◽  
2021 ◽  
Vol 04 (01) ◽  
pp. e37-e40
Author(s):  
Hélène Dosseray ◽  
Claire Deroy-Bordenave
Keyword(s):  
Achilles Tendon ◽  
Achilles Tendon Rupture ◽  
Simultaneous Occurrence ◽  
Flexor Muscle ◽  
Screw Insertion ◽  
Superficial Digital Flexor Tendon ◽  
Fixation Screw ◽  
Pelvic Limb ◽  
The Right

AbstractThe aim of this study was to report a posttraumatic partial Achilles tendon (AT) rupture associated with lateral luxation of the superficial digital flexor tendon (SDFT) in a Whippet. This article is a brief communication. A Whippet was presented with posttraumatic plantigrade stance and non-load-bearing lameness of the right pelvic limb. The objective findings consisted in partial AT rupture and SDFT lateral luxation. Surgical treatment ensued: tenorrhaphy of the torn tendons and calcaneo-tibial screw insertion for tarsal immobilization, followed by suturing of the SDFT retinaculum. A casting bandage was employed for additional immobilization. Nonetheless, a bandage complication prompted the premature removal of the fixation screw and casting wrap. Complete functional recovery was achieved by the 20th postoperative week. The simultaneous occurrence of SDFT luxation and partial AT tear has not been reported in the literature before. The long-term postoperative functional outcome was highly satisfactory.

scholarly journals Large papillary fibroelastoma of right atrium, an unusual case of respiratory distress in a young man

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Yan Le Ho ◽  
Pui Fong Ng ◽  
Sotheenathan Krishinan ◽  
Basheer Ahamed Abdul Kareem
Keyword(s):  
Right Atrium ◽  
Clinical Manifestations ◽  
Clinical Information ◽  
Interatrial Septum ◽  
Papillary Fibroelastoma ◽  
Case Presentation ◽  
Intracardiac Masses ◽  
The Right ◽  
Embolic Risk

Abstract Background Papillary fibroelastomas are rare but benign cardiac tumour that are often found on cardiac valvular surfaces. Their clinical manifestations ranging from clinically asymptomatic to substantial complications that are usually secondary to systemic embolism. Multiple theories have been proposed to explain the pathophysiology of its formation. Case presentation We reported a rare case of large papillary fibroelastoma in the right atrium of a young gentleman which was complicated with pulmonary embolism. Transthoracic echocardiography identified a large pedunculated mass measuring 3.4cmX3.4cmX2cm in right atrium with stalk attached to interatrial septum. The intracardiac mass was resected surgically, which revealed papillary fibroelastoma in histology examination. Conclusion Differential diagnosis of intracardiac masses requires clinical information, laboratory tests and imaging modalities including echocardiography. Incidentally discovered papillary fibroelastomas are treated on the basis of their sizes, site, mobility and potential embolic complications. Due to the embolic risk inherent to intraacardiac masses, surgical resection represents an effective curative protocol in treating both symptomatic and asymptomatic right sided and left sided papillary fibroelastomas, with excellent long term postoperative prognosis.

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