Plastic instability,including both the discontinuous yielding and stress serrations,has been frequently observed during the tensile deformation of medium-Mn steels(MMnS)and has been intensively studied in recent years...Plastic instability,including both the discontinuous yielding and stress serrations,has been frequently observed during the tensile deformation of medium-Mn steels(MMnS)and has been intensively studied in recent years.Unfortunately,research results are controversial,and no consensus has been achieved regarding the topic.Here,we first summarize all the possible factors that affect the yielding and flow stress serrations in MMnS,including the morphology and stability of austenite,the feature of the phase interface,and the deformation parameters.Then,we propose a universal mechanism to explain the conflicting experimental results.We conclude that the discontinuous yielding can be attributed to the lack of mobile dislocation before deformation and the rapid dislocation multiplication at the beginning of plastic deformation.Meanwhile,the results show that the stress serrations are formed due to the pinning and depinning between dislocations and interstitial atoms in austenite.Strain-induced martensitic transformation,influenced by the mechanical stability of austenite grain and deformation parameters,should not be the intrinsic cause of plastic instability.However,it can intensify or weaken the discontinuous yielding and the stress serrations by affecting the mobility and density of dislocations,as well as the interaction between the interstitial atoms and dislocations in austenite grains.展开更多
Background: Surgical drains are used in at least half of all surgical operations world-wide. The gold standard for the fixation of drains to the skin is currently the “Roman garter” (RG) technique, which involves kn...Background: Surgical drains are used in at least half of all surgical operations world-wide. The gold standard for the fixation of drains to the skin is currently the “Roman garter” (RG) technique, which involves knotting a suture around the drain. Its disadvantages include the time to perform the technique, possible loosening and accidental removal, and bacterial infection with biofilm formation if left in place for weeks. Methods: The Elist Drain Retainer (EDR) has been developed, and it consists of a short plastic tube bent to 90° with a side slit for the drain, fixed to a mounting patch with adhesive and an antiseptic. Results: In a clinical trial comparing 25 drain attachments with the RG versus 25 drain attachments with the new EDR, the former took an average of five minutes and the EDR took an average of one minute to place. Loosening occurred in five (20%) drains and accidental removal occurred in four (16%) for the RG group versus no incidences of loosening or accidental removal in the EDR group. Self-removal of the EDR was possible for seven (28%) patients. Conclusion: The EDR demonstrated a clear advantage over the RG in all tested parameters. The lack of instruments and the possibility of self-removal of the EDR when a drain is needed are particularly advantageous features.展开更多
Background: The integration of the current technology of CBCT and 3D CAD/CAM technology has great potential in the field of orthodontics, which is not yet fully investigated. The purpose of this article is to evaluate...Background: The integration of the current technology of CBCT and 3D CAD/CAM technology has great potential in the field of orthodontics, which is not yet fully investigated. The purpose of this article is to evaluate the accuracy of 3D printed retainers in comparison to vacuum formed retainers. Methods: Alginate impressions were taken for ten patients who have a CBCT scan. A 3D printed retainer and vacuum formed retainer were fabricated. Linear measure-ments were measured by two assessors using digital caliper. Every measure-ment on the 3D printed retainer was compared to the corresponding measure-ment on the thermoformed retainer. The linear measurements were Inter-canine width, Inter-premolar width (first and second premolars), Inter-molar width, Canine-midline length (both sides) and Canine-molar length (both sides). Intra-observer, and inter-observer reliability measurements were done. Results: Results showed excellent intra-observer reliability for the thermoformed retainer and the 3D printed retainer. Inter-observer measurements showed strong agreement between the measurements of the two assessors, for both retainers. The comparison of the thermoformed retainer to the 3D printed retainer showed high statistical agreement, except for the canine-molar on the right side, but with no clinical significance, p value of 0.038 and mean difference 0.19. Conclusions: The new method for fabricating a 3D printed retainer is accurate and reliable in comparison to the vacuum formed retainer (conventional method). CBCT proved to be efficient for fabrication of a custom made appliances.展开更多
The effects of carbon distribution on the microstructure and thermal conductivity of ductile iron were investigated in the present study.The microstructure of as-cast and quenched ductile iron were characterized by OM...The effects of carbon distribution on the microstructure and thermal conductivity of ductile iron were investigated in the present study.The microstructure of as-cast and quenched ductile iron were characterized by OM and SEM.Results showed that the microstructure of as-cast ductile iron was composed of spheroidal graphite,ferrite with the volume of 80%,and a small amount of pearlite,and quenched ductile iron was composed of spheroidal graphite,coarse/fine acicular martensite(α_(M)phase)and high-carbon retained austenite(γphase).The volume fraction of retained austensite and its carbon content for direct quenched ductile iron and tepmered ductile iron were quantitatively analysed by XRD.Results revealed that carbon atoms diffused fromα_(M)phase toγphase during tempering at low temperatures,which resulted in carbon content in retainedγphase increasing from 1.2 wt%for the direct quenched sample to about 1.9 wt%for the tempered samples.Consequently,the lattice distortion was significantly reduced and gave rise to an increase of thermal conductivity for ductile iron.展开更多
Introduction and importance: In the surgical field, we utilize gauze and surgical instruments daily, and the complications can be divided into avoidable versus nonavoidable. The term Gossypioma in the literature indic...Introduction and importance: In the surgical field, we utilize gauze and surgical instruments daily, and the complications can be divided into avoidable versus nonavoidable. The term Gossypioma in the literature indicates a retained surgical sponge or gauze. It can be there for years and be dormant or discovered within days as the patient starts to reveal symptoms. This makes diagnosing challenging pre-operatively as the radiological findings might not be as specific. Case presentation: A 75 male Moroccan patient with Normal Body mass index, Medically free. His main complaint was Abdominal pain in the epigastric area. His past surgical history was positive for a left open inguinal hernia repair with mesh three months ago that went uneventfully And an open appendectomy before 20 years. The Abdomen X-ray: multiple air-fluid levels with dilated small bowel as well as perfectly rounded calcifications at the right lower quadrant. Conclusion: It’s a devastating medical error, but it can be avoidable. Communication between the surgical team and operation staff is a crucial and straightforward tactic to prevent these complications. As the sequel will reveal itself at any time and the patient will pay the price.展开更多
基金support from the National Natural Science Foundation of China(Nos.51831002,51904028,and 52233018)the Beijing Municipal Natural Science Foundation(No.2242048)the Fundamental Research Funds for the Central Universities,China(No.FRF-EYIT-23-08).
文摘Plastic instability,including both the discontinuous yielding and stress serrations,has been frequently observed during the tensile deformation of medium-Mn steels(MMnS)and has been intensively studied in recent years.Unfortunately,research results are controversial,and no consensus has been achieved regarding the topic.Here,we first summarize all the possible factors that affect the yielding and flow stress serrations in MMnS,including the morphology and stability of austenite,the feature of the phase interface,and the deformation parameters.Then,we propose a universal mechanism to explain the conflicting experimental results.We conclude that the discontinuous yielding can be attributed to the lack of mobile dislocation before deformation and the rapid dislocation multiplication at the beginning of plastic deformation.Meanwhile,the results show that the stress serrations are formed due to the pinning and depinning between dislocations and interstitial atoms in austenite.Strain-induced martensitic transformation,influenced by the mechanical stability of austenite grain and deformation parameters,should not be the intrinsic cause of plastic instability.However,it can intensify or weaken the discontinuous yielding and the stress serrations by affecting the mobility and density of dislocations,as well as the interaction between the interstitial atoms and dislocations in austenite grains.
文摘Background: Surgical drains are used in at least half of all surgical operations world-wide. The gold standard for the fixation of drains to the skin is currently the “Roman garter” (RG) technique, which involves knotting a suture around the drain. Its disadvantages include the time to perform the technique, possible loosening and accidental removal, and bacterial infection with biofilm formation if left in place for weeks. Methods: The Elist Drain Retainer (EDR) has been developed, and it consists of a short plastic tube bent to 90° with a side slit for the drain, fixed to a mounting patch with adhesive and an antiseptic. Results: In a clinical trial comparing 25 drain attachments with the RG versus 25 drain attachments with the new EDR, the former took an average of five minutes and the EDR took an average of one minute to place. Loosening occurred in five (20%) drains and accidental removal occurred in four (16%) for the RG group versus no incidences of loosening or accidental removal in the EDR group. Self-removal of the EDR was possible for seven (28%) patients. Conclusion: The EDR demonstrated a clear advantage over the RG in all tested parameters. The lack of instruments and the possibility of self-removal of the EDR when a drain is needed are particularly advantageous features.
文摘Background: The integration of the current technology of CBCT and 3D CAD/CAM technology has great potential in the field of orthodontics, which is not yet fully investigated. The purpose of this article is to evaluate the accuracy of 3D printed retainers in comparison to vacuum formed retainers. Methods: Alginate impressions were taken for ten patients who have a CBCT scan. A 3D printed retainer and vacuum formed retainer were fabricated. Linear measure-ments were measured by two assessors using digital caliper. Every measure-ment on the 3D printed retainer was compared to the corresponding measure-ment on the thermoformed retainer. The linear measurements were Inter-canine width, Inter-premolar width (first and second premolars), Inter-molar width, Canine-midline length (both sides) and Canine-molar length (both sides). Intra-observer, and inter-observer reliability measurements were done. Results: Results showed excellent intra-observer reliability for the thermoformed retainer and the 3D printed retainer. Inter-observer measurements showed strong agreement between the measurements of the two assessors, for both retainers. The comparison of the thermoformed retainer to the 3D printed retainer showed high statistical agreement, except for the canine-molar on the right side, but with no clinical significance, p value of 0.038 and mean difference 0.19. Conclusions: The new method for fabricating a 3D printed retainer is accurate and reliable in comparison to the vacuum formed retainer (conventional method). CBCT proved to be efficient for fabrication of a custom made appliances.
基金Funded by China Postdoctoral Science Foundation(Nos.2019M653703 and 2020T130523)Xi’an University of Technology Youth Nova Fund(No.101-451320005)。
文摘The effects of carbon distribution on the microstructure and thermal conductivity of ductile iron were investigated in the present study.The microstructure of as-cast and quenched ductile iron were characterized by OM and SEM.Results showed that the microstructure of as-cast ductile iron was composed of spheroidal graphite,ferrite with the volume of 80%,and a small amount of pearlite,and quenched ductile iron was composed of spheroidal graphite,coarse/fine acicular martensite(α_(M)phase)and high-carbon retained austenite(γphase).The volume fraction of retained austensite and its carbon content for direct quenched ductile iron and tepmered ductile iron were quantitatively analysed by XRD.Results revealed that carbon atoms diffused fromα_(M)phase toγphase during tempering at low temperatures,which resulted in carbon content in retainedγphase increasing from 1.2 wt%for the direct quenched sample to about 1.9 wt%for the tempered samples.Consequently,the lattice distortion was significantly reduced and gave rise to an increase of thermal conductivity for ductile iron.
文摘Introduction and importance: In the surgical field, we utilize gauze and surgical instruments daily, and the complications can be divided into avoidable versus nonavoidable. The term Gossypioma in the literature indicates a retained surgical sponge or gauze. It can be there for years and be dormant or discovered within days as the patient starts to reveal symptoms. This makes diagnosing challenging pre-operatively as the radiological findings might not be as specific. Case presentation: A 75 male Moroccan patient with Normal Body mass index, Medically free. His main complaint was Abdominal pain in the epigastric area. His past surgical history was positive for a left open inguinal hernia repair with mesh three months ago that went uneventfully And an open appendectomy before 20 years. The Abdomen X-ray: multiple air-fluid levels with dilated small bowel as well as perfectly rounded calcifications at the right lower quadrant. Conclusion: It’s a devastating medical error, but it can be avoidable. Communication between the surgical team and operation staff is a crucial and straightforward tactic to prevent these complications. As the sequel will reveal itself at any time and the patient will pay the price.
