Ultra-narrow gap welding （UNGW） process with high stabilization, reliability and without spatter can be achieved with constricted arc by molten slag wall, which is made from melted flux. The experiments are carried ...Ultra-narrow gap welding （UNGW） process with high stabilization, reliability and without spatter can be achieved with constricted arc by molten slag wall, which is made from melted flux. The experiments are carried out by changing voltage under different currents. The results indicate voltage range being fit for UNGW is about 22 -31 V under the current range of 200 -320 A. With the increasing of voltage, weld formation of UNGW has the law of lack of fusion on sidewall, good weld and undercut in turn under a certain current. In addition, the action relationships among arc, molten slag wall and sidewalls can be improved by properly adjusting voltage and current of arc, which makes cathode spot properly distribute in ultra-narrow gap. Therefore, the effective control of weld formation of UNGW has been achieved.展开更多
Cell migration through narrow interstitial space in tissues is commonly seen in both physiological and pathological conditions. For example, immune cells have to squeeze through vasculature and extracellular matrix to...Cell migration through narrow interstitial space in tissues is commonly seen in both physiological and pathological conditions. For example, immune cells have to squeeze through vasculature and extracellular matrix to reach the wound or diseased sites, and similarly cancer cells need to crawl through porous space in tissues to invade surrounding tumor-free regions. Therefore, the bulky stiff nucleus in the cell becomes a barrier during constricted migration making such process pore-size dependent with smaller pores exponentially alleviate the passage capability. However, in some cases, cells can actively deform their nuclei to squeeze through constrictions although some price needs to be paid. In this review, we focus on:(1) nuclear structures and morphological regulations,(2) proposed mechanisms that drive constricted migration,(3) short-term consequences such as nuclear envelope (NE) rupture and DNA damage during such process,(4) biophysical factors that facilitate NE rupture, and (5) long term consequences such as genomic variation caused by repetitive NE rupture. Both experimental results and modeling are provided with the intention to better understand the constricted migration.展开更多
The magnetically constricted arc technique was implemented to mitigate the heat input related metallurgical problems in Gas Tungsten Arc Welding(GTAW)of Inconel 718 alloy particularly Nb segregation and subsequent lav...The magnetically constricted arc technique was implemented to mitigate the heat input related metallurgical problems in Gas Tungsten Arc Welding(GTAW)of Inconel 718 alloy particularly Nb segregation and subsequent laves phase evolution in fusion zone.This paper reports the direct effect of magnetically constricted arc traverse speed(MCATS)on bead profile,tensile properties and microstructural evolution of Inconel 718 alloy sheets joined by Gas Tungsten Constricted Arc Welding(GTCAW)process.The mechanism amenable for the microstructural modification and corresponding influence on the tensile properties of joints is investigated both in qualitative and quantitative manner related to the mechanics of arc constriction and pulsing.It is correlated to the solidification conditions during welding.The relationship between MCATS and Arc Constriction Current(ACC)was derived.Its interaction effect on the magnetic arc constriction and joint performance was analysed.Results showed that the joints fabricated using CATS of 70 mm/min exhibited superior tensile properties(98.39% of base metal strength with 31.50% elongation).It is attributed to the grain refinement in fusion zone microstructure leading to the evolution of finer,discrete laves phase in interdendritic areas.展开更多
The transition from a spark discharge to a constricted glow discharge in atmospheric air was studied with a capacitor coupled pin-to-water plasma reactor. The reason of the transition is considered to be of various fa...The transition from a spark discharge to a constricted glow discharge in atmospheric air was studied with a capacitor coupled pin-to-water plasma reactor. The reason of the transition is considered to be of various factors, namely the change of the air gap due to the polarization of water molecules by the electric field, the feedback effect of the capacitors, and the ion trapping mechanism. The effects of the frequency of the power supply, inter-electrode gap, and coupled capacitance on the discharge transition were also investigated.展开更多
The main theme of the current article is to investigate the heat transfer in the pulsatile flow of an electrically conducting viscous fluid in a constricted channel under the effect of the magnetic field and thermal r...The main theme of the current article is to investigate the heat transfer in the pulsatile flow of an electrically conducting viscous fluid in a constricted channel under the effect of the magnetic field and thermal radiation.The unsteady governing equations simplified for low conducting fluids are solved numerically by finite difference method using stream-vorticity function formulation.The influence of the flow parameters such as the Hartmann number(magnetic parameter),Strouhal number(flow pulsation parameter),Prandtl number,and radiation parameter is studied on the relevant flow profiles.The influence of different emerging parameters on the skin friction coefficient and Nusselt number are examined,as well.In general,the profiles are observed to exhibit a relatively more regular pattern upstream of the construction than that downstream of the constriction.展开更多
One viable approach to the study of haemodynamics is to numerically model this flow behavior in normal and stenosed arteries.The blood is either treated as Newtonian or non-Newtonian fluid and the flow is assumed to b...One viable approach to the study of haemodynamics is to numerically model this flow behavior in normal and stenosed arteries.The blood is either treated as Newtonian or non-Newtonian fluid and the flow is assumed to be pulsating,while the arteries can be modeled by constricted tubes with rigid or elastic wall.Such a task involves formulation and development of a numerical method that could at least handle pulsating flow of Newtonian and non-Newtonian fluid through tubes with and without constrictions where the boundary is assumed to be inelastic or elastic.As a first attempt,the present paper explores and develops a time-accurate finite difference lattice Boltzmann method(FDLBM)equipped with an immersed boundary(IB)scheme to simulate pulsating flow in constricted tube with rigid walls at different Reynolds numbers.The unsteady flow simulations using a time-accurate FDLBM/IB numerical scheme is validated against theoretical solutions and other known numerical data.In the process,the performance of the time-accurate FDLBM/IB for a model blood flow problem and the ease with which the no-slip boundary condition can be correctly implemented is successfully demonstrated.展开更多
Hemodynamics is a complex problem with several distinct characteristics;fluid is non-Newtonian,flow is pulsatile in nature,flow is three-dimensional due to cholesterol/plague built up,and blood vessel wall is elastic....Hemodynamics is a complex problem with several distinct characteristics;fluid is non-Newtonian,flow is pulsatile in nature,flow is three-dimensional due to cholesterol/plague built up,and blood vessel wall is elastic.In order to simulate this type of flows accurately,any proposed numerical scheme has to be able to replicate these characteristics correctly,efficiently,as well as individually and collectively.Since the equations of the finite difference lattice Boltzmann method(FDLBM)are hyperbolic,and can be solved using Cartesian grids locally,explicitly and efficiently on parallel computers,a program of study to develop a viable FDLBM numerical scheme that can mimic these characteristics individually in any model blood flow problem was initiated.The present objective is to first develop a steady FDLBM with an immersed boundary(IB)method to model blood flow in stenoic artery over a range of Reynolds numbers.The resulting equations in the FDLBM/IB numerical scheme can still be solved using Cartesian grids;thus,changing complex artery geometry can be treated without resorting to grid generation.The FDLBM/IB numerical scheme is validated against known data and is then used to study Newtonian and non-Newtonian fluid flow through constricted tubes.The investigation aims to gain insight into the constricted flow behavior and the non-Newtonian fluid effect on this behavior.展开更多
Left atrial aneurysm is an exceptionally rare condition,particularly in the pediatric population,and even more so as a sequela of bacterial pericarditis.We present the case of a 16-month-old girl who developed a left ...Left atrial aneurysm is an exceptionally rare condition,particularly in the pediatric population,and even more so as a sequela of bacterial pericarditis.We present the case of a 16-month-old girl who developed a left atrial aneurysm following isolated Staphylococcus aureus pericarditis.She initially presented in decompensated shock and was later diagnosed with constrictive pericarditis.Despite undergoing pericardiectomy,she subsequently developed a left atrial aneurysm,necessitating surgical closure.This case highlights the aggressive nature of bacterial pericarditis and its potential to cause rare structural cardiac complications.展开更多
Non-typhoid Salmonella is a common foodborne infection.[1]In the setting of immunosuppression,the classical symptom of diarrhea,that is an immune defense mechanism,may be absent,[2,3]allowing the bacteria to hematogen...Non-typhoid Salmonella is a common foodborne infection.[1]In the setting of immunosuppression,the classical symptom of diarrhea,that is an immune defense mechanism,may be absent,[2,3]allowing the bacteria to hematogenous spread and settle in other organs.[4,5]As a result,in the setting of acute pericarditis in immunosuppressed patients,a bacterial etiology must always be considered,which requires pericardiocentesis to complete drainage and pathogen identification.展开更多
BACKGROUND Neuralgic amyotrophy(NA)is a rare disease with sudden upper limb pain followed by affected muscle weakness.The most commonly affected area in NA is the upper part of the brachial plexus,and the paraspinal m...BACKGROUND Neuralgic amyotrophy(NA)is a rare disease with sudden upper limb pain followed by affected muscle weakness.The most commonly affected area in NA is the upper part of the brachial plexus,and the paraspinal muscles are rarely affected(1.5%),making these cases difficult to distinguish from cervical radiculopathy.CASE SUMMARY A 76-year-old male presented to the emergency department with left hip pain post-fall.After undergoing left femoral neck fracture surgery,he experienced sudden left shoulder pain for 10 days with subsequent left arm weakness.Cervical spine computed tomography revealed mild right asymmetric intervertebral disc bulging with a decreased C5-6disc space.Three weeks later,an electrodiagnostic study confirmed brachial plexopathy findings involving the cervical root.Magnetic resonance neurography was performed for a differential diagnosis.Contrast enhancement was identified at the upper trunk of the brachial plexus,including the C5 nerve root.A suprascapular nerve hourglass-like focal constriction(HLFC)was also identified,confirming NA.After being diagnosed with NA,the patient received 15 mg prednisolone,twice daily,for 3 weeks.Physical therapy was initiated,including left arm strengthening exercises and electrical stimulation therapy.Left shoulder muscle strength significantly improved one CONCLUSION NA's unique features like HLFC and paraspinal involvement are crucial for accurate diagnosis,avoiding confusion with cervical radiculopathy.展开更多
Rationale:Synthetic cannabinoids are increasingly used as recreational drugs and have been associated with adverse cardiovascular effects.However,reports of synthetic cannabinoids accompanied by constrictive pericardi...Rationale:Synthetic cannabinoids are increasingly used as recreational drugs and have been associated with adverse cardiovascular effects.However,reports of synthetic cannabinoids accompanied by constrictive pericarditis are limited.Patient’s concern:A 28-year-old male with a history of synthetic cannabinoid(Bonzai)abuse presented with chest discomfort,dyspnea,and lower extremity edema.Investigations revealed reduced left ventricular ejection fraction,elevated inflammatory markers,low electrocardiogram voltages,and atrial fibrillation.Diagnosis:Chest spiral computerized tomography scan and chest X-ray demonstrated pericardial calcification.Cardiac magnetic resonance imaging and right heart catheterization were done to confirm the possibility of constrictive pericarditis.Based on the patient’s addiction history and exclusion of rheumatologic and infectious causes,it was supposed that constrictive pericarditis and cardiomyopathy may be accompanied by synthetic cannabinoid use.Interventions:The patient received standard medical therapy,including loop diuretics for cardiomyopathy and constrictive pericarditis.Catheter ablation was recommended for his rhythm control,and he was planned for close monitoring of clinical and echocardiographic response and evaluation of the need for surgical pericardiectomy in the future.Outcomes:After 6 months follow-up,echocardiographic exam revealed no significant improvement in ventricular function.However,due to the high surgical risk,the patient’s poor compliance,and the continuation of drug abuse,he was not a good candidate for surgery according to our heart team’s decision.Lessons:Synthetic cannabinoids can trigger constrictive pericarditis,and clinicians should consider them when evaluating patients with compatible symptoms and exposure history.Further research on the cardiovascular effects of synthetic cannabinoids is needed and public education on potential harms is warranted.展开更多
Centered or striped wick structures have been used to develop ultrathin heat pipes.Differing from traditional heat pipes,the centered or striped wick structures leave noncontact container surfaces with the wick struct...Centered or striped wick structures have been used to develop ultrathin heat pipes.Differing from traditional heat pipes,the centered or striped wick structures leave noncontact container surfaces with the wick structure.In this study,experiments andnumerical analyseswere conductedtoinvestigate the influenceof thesenoncontact surfaces.In the experiments,a strip-shaped wick structure was placed vertically,the top was sandwiched between wider rods and the bottom was immersed in a working fluid.The rod width was greater than the wick width;thus,noncontact surfaces were left between the rod and the wick structure.The heat was applied from the rod to the wick structure,and the evaporation heat transfer characteristics of the working fluid from the wick structure were evaluated.Water was used as the working fluid.The experiments were conducted by varying the rod and wick widths.The experimental results were obtained when the wick structures were placed separately.In the numerical analyses,the temperature and heat flux distributions in the rod were obtained.From the experimental and numerical results,it was confirmed that the noncontact surfaces caused the heat flux in the rod near both surfaces of the wick structure to concentrate,which increased the evaporation thermal resistance of the wick structure.A reduction in the noncontact surface area by increasing the wick width was found to be effective in decreasing the evaporation thermal resistance and increasing themaximumheat transfer rate of the wick structure.The separation of the wick structure increased the evaporation surface area.However,its effectiveness was limited when the heat transfer rate was small.展开更多
BACKGROUND Endoscopic management is the first-line therapy for post-liver-transplant anas-tomotic strictures.Although the optimal duration of treatment with plastic stents has been reported to be 8-12 months,data on s...BACKGROUND Endoscopic management is the first-line therapy for post-liver-transplant anas-tomotic strictures.Although the optimal duration of treatment with plastic stents has been reported to be 8-12 months,data on safety and duration for metal stents in this setting is scarce.Due to limited access to endoscopic retrograde cholan-giopancreatography(ERCP)during the coronavirus disease 2019 pandemic in our centre,there was a change in practice towards increased usage and length-of-stay of the Kaffes biliary intraductal self-expanding stent in patients with suitable anatomy.This was mainly due to the theoretical benefit of Kaffes stents allowing for longer indwelling periods compared to the traditional plastic stents.METHODS Adult liver transplant recipients aged 18 years and above who underwent ERCP were retrospectively identified during a 10-year period through a database query.Unplanned admissions post-Kaffes stent insertion were identified manually through electronic and scanned medical records.The main outcome was the incidence of complications when stents were left indwelling for 3 months vs 6 months.Stent efficacy was calculated via rates of stricture recurrence between patients that had stenting courses for≤120 d or>120 d.RESULTS During the study period,a total of 66 ERCPs with Kaffes insertion were performed in 54 patients throughout their stenting course.In 33 ERCPs,the stent was removed or exchanged on a 3-month interval.No pancreatitis,perfor-ations or deaths occurred.Minor post-ERCP complications were similar between the 3-month(abdominal pain and intraductal migration)and 6-month(abdominal pain,septic shower and embedded stent)groups-6.1%vs 9.1%respectively,P=0.40.All strictures resolved at the end of the stenting course,but the stenting course was variable from 3 to 22 months.The recurrence rate for stenting courses lasting for up to 120 d was 71.4%and 21.4%for stenting courses of 121 d or over(P=0.03).There were 28 patients that were treated with a single ERCP with Kaffes,21 with removal after 120 d and 7 within 120 d.There was a significant improvement in stricture recurrence when the Kaffes was removed after 120 d when a single ERCP was used for the entire stenting course(71.0%vs 10.0%,P=0.01).CONCLUSION Utilising a single Kaffes intraductal fully-covered metal stent for at least 4 months is safe and efficacious for the management of post-transplant anastomotic strictures.展开更多
The main objective of this investigation is to study the influence of arc constriction current frequency(ACCF)on tensile properties and microstructural evolution of aerospace Alloy 718 sheets(2 mm in thickness)joined ...The main objective of this investigation is to study the influence of arc constriction current frequency(ACCF)on tensile properties and microstructural evolution of aerospace Alloy 718 sheets(2 mm in thickness)joined by constricted arc TIG(CA-TIG)welding process.One variable at a time approach of design of experiments(DOE)was used,in which ACCF was varied from 4 to 20 kHz at an interval of 5 levels while other parameters were kept constant.The joints welded using ACCF of 4 kHz exhibited superior tensile properties extending joint efficiency up to 99.20%.It is attributed to the grain refinement in fusion zone leading to the evolution of finer,discrete Laves phase in interdendritic areas.An increase of ACCF above 12 kHz caused severe grain growth and evolution of coarser Laves phase in fusion zone.Alloy 718 welds showed more obvious tendency for Nb segregation and Laves phase formation at higher levels of ACCF due to the slower cooling rate.The volume fraction of Laves phase was increased by 62.31%at ACCF of 20 kHz compared to that at 4 kHz,thereby reducing the tensile properties of joints.This is mainly due to the stacking of heat input in weld thermal cycles at increased levels of ACCF.展开更多
This paper investigates the effect of porosity on active damping of geometrically nonlinear vibrations(GNLV)of the magneto-electro-elastic(MEE)functionally graded(FG)plates incorporated with active treatment constrict...This paper investigates the effect of porosity on active damping of geometrically nonlinear vibrations(GNLV)of the magneto-electro-elastic(MEE)functionally graded(FG)plates incorporated with active treatment constricted layer damping(ATCLD)patches.The perpendicularly/slanted reinforced 1-3 piezoelectric composite(1-3 PZC)constricting layer.The constricted viscoelastic layer of the ATCLD is modeled in the time-domain using Golla-Hughes-Mc Tavish(GHM)technique.Different types of porosity distribution in the porous magneto-electro-elastic functionally graded PMEE-FG plate graded in the thickness direction.Considering the coupling effects among elasticity,electrical,and magnetic fields,a three-dimensional finite element(FE)model for the smart PMEE-FG plate is obtained by incorporating the theory of layer-wise shear deformation.The geometric nonlinearity adopts the von K arm an principle.The study presents the effects of a variant of a power-law index,porosity index,the material gradation,three types of porosity distribution,boundary conditions,and the piezoelectric fiber’s orientation angle on the control of GNLV of the PMEE-FG plates.The results reveal that the FG substrate layers’porosity significantly impacts the nonlinear behavior and damping performance of the PMEE-FG plates.展开更多
The constriction factor method (CFM) is a new variation of the basic particle swarm optimization (PSO), which has relatively better convergent nature. The effects of the major parameters on CFM were systematically inv...The constriction factor method (CFM) is a new variation of the basic particle swarm optimization (PSO), which has relatively better convergent nature. The effects of the major parameters on CFM were systematically investigated based on some benchmark functions. The constriction factor, velocity constraint, and population size all have significant impact on the per- formance of CFM for PSO. The constriction factor and velocity constraint have optimal values in practical application, and im- proper choice of these factors will lead to bad results. Increasing population size can improve the solution quality, although the computing time will be longer. The characteristics of CFM parameters are described and guidelines for determining parameter values are given in this paper.展开更多
Acupuncture has been used to treat neuropathic pain for a long time, but its mechanisms of action remain unknown. In this study, we observed the effects of electroacupuncture and manual acu- puncture on neuropathic pa...Acupuncture has been used to treat neuropathic pain for a long time, but its mechanisms of action remain unknown. In this study, we observed the effects of electroacupuncture and manual acu- puncture on neuropathic pain and on ephrin-B/EphB signaling in rats models of chronic constriction injury-induced neuropathic pain. The results showed that manual acupuncture and electroacu- puncture significantly reduced mechanical hypersensitivity following chronic constriction injury, es- pecially electroacupuncture treatment. Real-time PCR results revealed that ephrin-B1/B3 and EphB1/B2 mRNA expression levels were significantly increased in the spinal dorsal horns of chronic constriction injury rats. Electroacupuncture and manual acupuncture suppressed the high expres- sion of ephrin-B1 mRNA, and elevated EphB3/B4 mRNA expression. Electroacupuncture signifi- cantly enhanced the mRNA expression of ephrin-B3 and EphB3/B6 in the dorsal horns of neuro- pathic pain rats. Western blot results revealed that electroacupuncture in particular, and manual acupuncture, significantly up-regulated ephrin-B3 protein levels in rat spinal dorsal horns. The re- sults of this study suggest that acupuncture could activate ephrin-B/EphB signaling in neuropathic pain rats and improve neurological function.展开更多
This article describes a case we experienced in which good postsurgical facial profiles were obtained for a patient with jaw deformities associated with facial asymmetry,by implementing surgical planning with SimPlant...This article describes a case we experienced in which good postsurgical facial profiles were obtained for a patient with jaw deformities associated with facial asymmetry,by implementing surgical planning with SimPlant OMS.Using this method,we conducted LF1 osteotomy,intraoral vertical ramus osteotomy（IVRO）,sagittal split ramus osteotomy（SSRO）,mandibular constriction and mandibular border genioplasty.Not only did we obtain a class I occlusal relationship,but the complicated surgery also improved the asymmetry of the frontal view,as well as of the profile view,of the patient.The virtual operation using three-dimensional computed tomography（3D-CT）could be especially useful for the treatment of patients with jaw deformities associated with facial asymmetry.展开更多
基金The work was supported by National Natural Science Foundation of China （51105185） and Advanced Project Foundation of Jinchuan Company（420032）.
文摘Ultra-narrow gap welding （UNGW） process with high stabilization, reliability and without spatter can be achieved with constricted arc by molten slag wall, which is made from melted flux. The experiments are carried out by changing voltage under different currents. The results indicate voltage range being fit for UNGW is about 22 -31 V under the current range of 200 -320 A. With the increasing of voltage, weld formation of UNGW has the law of lack of fusion on sidewall, good weld and undercut in turn under a certain current. In addition, the action relationships among arc, molten slag wall and sidewalls can be improved by properly adjusting voltage and current of arc, which makes cathode spot properly distribute in ultra-narrow gap. Therefore, the effective control of weld formation of UNGW has been achieved.
基金the National Institutes of Health National Cancer Institute under Physical Sciences Oncology Center Award U54 CA193417National Heart Lung and Blood Institute Award R21 HL128187the US-Israel Binational Science Foundation, and National Science Foundation grant agreement CMMI 15-48571.
文摘Cell migration through narrow interstitial space in tissues is commonly seen in both physiological and pathological conditions. For example, immune cells have to squeeze through vasculature and extracellular matrix to reach the wound or diseased sites, and similarly cancer cells need to crawl through porous space in tissues to invade surrounding tumor-free regions. Therefore, the bulky stiff nucleus in the cell becomes a barrier during constricted migration making such process pore-size dependent with smaller pores exponentially alleviate the passage capability. However, in some cases, cells can actively deform their nuclei to squeeze through constrictions although some price needs to be paid. In this review, we focus on:(1) nuclear structures and morphological regulations,(2) proposed mechanisms that drive constricted migration,(3) short-term consequences such as nuclear envelope (NE) rupture and DNA damage during such process,(4) biophysical factors that facilitate NE rupture, and (5) long term consequences such as genomic variation caused by repetitive NE rupture. Both experimental results and modeling are provided with the intention to better understand the constricted migration.
基金funded by Indian Space Research Organization (ISRO) India. Project No. ISRO/RES/3/728/16e17
文摘The magnetically constricted arc technique was implemented to mitigate the heat input related metallurgical problems in Gas Tungsten Arc Welding(GTAW)of Inconel 718 alloy particularly Nb segregation and subsequent laves phase evolution in fusion zone.This paper reports the direct effect of magnetically constricted arc traverse speed(MCATS)on bead profile,tensile properties and microstructural evolution of Inconel 718 alloy sheets joined by Gas Tungsten Constricted Arc Welding(GTCAW)process.The mechanism amenable for the microstructural modification and corresponding influence on the tensile properties of joints is investigated both in qualitative and quantitative manner related to the mechanics of arc constriction and pulsing.It is correlated to the solidification conditions during welding.The relationship between MCATS and Arc Constriction Current(ACC)was derived.Its interaction effect on the magnetic arc constriction and joint performance was analysed.Results showed that the joints fabricated using CATS of 70 mm/min exhibited superior tensile properties(98.39% of base metal strength with 31.50% elongation).It is attributed to the grain refinement in fusion zone microstructure leading to the evolution of finer,discrete laves phase in interdendritic areas.
基金supported by National Natural Science Foundation of China (Nos.50177002,10475014)
文摘The transition from a spark discharge to a constricted glow discharge in atmospheric air was studied with a capacitor coupled pin-to-water plasma reactor. The reason of the transition is considered to be of various factors, namely the change of the air gap due to the polarization of water molecules by the electric field, the feedback effect of the capacitors, and the ion trapping mechanism. The effects of the frequency of the power supply, inter-electrode gap, and coupled capacitance on the discharge transition were also investigated.
文摘The main theme of the current article is to investigate the heat transfer in the pulsatile flow of an electrically conducting viscous fluid in a constricted channel under the effect of the magnetic field and thermal radiation.The unsteady governing equations simplified for low conducting fluids are solved numerically by finite difference method using stream-vorticity function formulation.The influence of the flow parameters such as the Hartmann number(magnetic parameter),Strouhal number(flow pulsation parameter),Prandtl number,and radiation parameter is studied on the relevant flow profiles.The influence of different emerging parameters on the skin friction coefficient and Nusselt number are examined,as well.In general,the profiles are observed to exhibit a relatively more regular pattern upstream of the construction than that downstream of the constriction.
基金funding support in the form of a PhD studentship awarded him by the Hong Kong Polytechnic Universitysupport received as Co-PI from the NSF Grant CBET-0854411 awarded to New Mexico State University.
文摘One viable approach to the study of haemodynamics is to numerically model this flow behavior in normal and stenosed arteries.The blood is either treated as Newtonian or non-Newtonian fluid and the flow is assumed to be pulsating,while the arteries can be modeled by constricted tubes with rigid or elastic wall.Such a task involves formulation and development of a numerical method that could at least handle pulsating flow of Newtonian and non-Newtonian fluid through tubes with and without constrictions where the boundary is assumed to be inelastic or elastic.As a first attempt,the present paper explores and develops a time-accurate finite difference lattice Boltzmann method(FDLBM)equipped with an immersed boundary(IB)scheme to simulate pulsating flow in constricted tube with rigid walls at different Reynolds numbers.The unsteady flow simulations using a time-accurate FDLBM/IB numerical scheme is validated against theoretical solutions and other known numerical data.In the process,the performance of the time-accurate FDLBM/IB for a model blood flow problem and the ease with which the no-slip boundary condition can be correctly implemented is successfully demonstrated.
基金funding support in the form of a PhD studentship awarded him by the Hong Kong Polytechnic Universitysupport received as Co-PI from the NSF Grant CBET-0854411 awarded to New Mexico State University.
文摘Hemodynamics is a complex problem with several distinct characteristics;fluid is non-Newtonian,flow is pulsatile in nature,flow is three-dimensional due to cholesterol/plague built up,and blood vessel wall is elastic.In order to simulate this type of flows accurately,any proposed numerical scheme has to be able to replicate these characteristics correctly,efficiently,as well as individually and collectively.Since the equations of the finite difference lattice Boltzmann method(FDLBM)are hyperbolic,and can be solved using Cartesian grids locally,explicitly and efficiently on parallel computers,a program of study to develop a viable FDLBM numerical scheme that can mimic these characteristics individually in any model blood flow problem was initiated.The present objective is to first develop a steady FDLBM with an immersed boundary(IB)method to model blood flow in stenoic artery over a range of Reynolds numbers.The resulting equations in the FDLBM/IB numerical scheme can still be solved using Cartesian grids;thus,changing complex artery geometry can be treated without resorting to grid generation.The FDLBM/IB numerical scheme is validated against known data and is then used to study Newtonian and non-Newtonian fluid flow through constricted tubes.The investigation aims to gain insight into the constricted flow behavior and the non-Newtonian fluid effect on this behavior.
文摘Left atrial aneurysm is an exceptionally rare condition,particularly in the pediatric population,and even more so as a sequela of bacterial pericarditis.We present the case of a 16-month-old girl who developed a left atrial aneurysm following isolated Staphylococcus aureus pericarditis.She initially presented in decompensated shock and was later diagnosed with constrictive pericarditis.Despite undergoing pericardiectomy,she subsequently developed a left atrial aneurysm,necessitating surgical closure.This case highlights the aggressive nature of bacterial pericarditis and its potential to cause rare structural cardiac complications.
文摘Non-typhoid Salmonella is a common foodborne infection.[1]In the setting of immunosuppression,the classical symptom of diarrhea,that is an immune defense mechanism,may be absent,[2,3]allowing the bacteria to hematogenous spread and settle in other organs.[4,5]As a result,in the setting of acute pericarditis in immunosuppressed patients,a bacterial etiology must always be considered,which requires pericardiocentesis to complete drainage and pathogen identification.
文摘BACKGROUND Neuralgic amyotrophy(NA)is a rare disease with sudden upper limb pain followed by affected muscle weakness.The most commonly affected area in NA is the upper part of the brachial plexus,and the paraspinal muscles are rarely affected(1.5%),making these cases difficult to distinguish from cervical radiculopathy.CASE SUMMARY A 76-year-old male presented to the emergency department with left hip pain post-fall.After undergoing left femoral neck fracture surgery,he experienced sudden left shoulder pain for 10 days with subsequent left arm weakness.Cervical spine computed tomography revealed mild right asymmetric intervertebral disc bulging with a decreased C5-6disc space.Three weeks later,an electrodiagnostic study confirmed brachial plexopathy findings involving the cervical root.Magnetic resonance neurography was performed for a differential diagnosis.Contrast enhancement was identified at the upper trunk of the brachial plexus,including the C5 nerve root.A suprascapular nerve hourglass-like focal constriction(HLFC)was also identified,confirming NA.After being diagnosed with NA,the patient received 15 mg prednisolone,twice daily,for 3 weeks.Physical therapy was initiated,including left arm strengthening exercises and electrical stimulation therapy.Left shoulder muscle strength significantly improved one CONCLUSION NA's unique features like HLFC and paraspinal involvement are crucial for accurate diagnosis,avoiding confusion with cervical radiculopathy.
文摘Rationale:Synthetic cannabinoids are increasingly used as recreational drugs and have been associated with adverse cardiovascular effects.However,reports of synthetic cannabinoids accompanied by constrictive pericarditis are limited.Patient’s concern:A 28-year-old male with a history of synthetic cannabinoid(Bonzai)abuse presented with chest discomfort,dyspnea,and lower extremity edema.Investigations revealed reduced left ventricular ejection fraction,elevated inflammatory markers,low electrocardiogram voltages,and atrial fibrillation.Diagnosis:Chest spiral computerized tomography scan and chest X-ray demonstrated pericardial calcification.Cardiac magnetic resonance imaging and right heart catheterization were done to confirm the possibility of constrictive pericarditis.Based on the patient’s addiction history and exclusion of rheumatologic and infectious causes,it was supposed that constrictive pericarditis and cardiomyopathy may be accompanied by synthetic cannabinoid use.Interventions:The patient received standard medical therapy,including loop diuretics for cardiomyopathy and constrictive pericarditis.Catheter ablation was recommended for his rhythm control,and he was planned for close monitoring of clinical and echocardiographic response and evaluation of the need for surgical pericardiectomy in the future.Outcomes:After 6 months follow-up,echocardiographic exam revealed no significant improvement in ventricular function.However,due to the high surgical risk,the patient’s poor compliance,and the continuation of drug abuse,he was not a good candidate for surgery according to our heart team’s decision.Lessons:Synthetic cannabinoids can trigger constrictive pericarditis,and clinicians should consider them when evaluating patients with compatible symptoms and exposure history.Further research on the cardiovascular effects of synthetic cannabinoids is needed and public education on potential harms is warranted.
文摘Centered or striped wick structures have been used to develop ultrathin heat pipes.Differing from traditional heat pipes,the centered or striped wick structures leave noncontact container surfaces with the wick structure.In this study,experiments andnumerical analyseswere conductedtoinvestigate the influenceof thesenoncontact surfaces.In the experiments,a strip-shaped wick structure was placed vertically,the top was sandwiched between wider rods and the bottom was immersed in a working fluid.The rod width was greater than the wick width;thus,noncontact surfaces were left between the rod and the wick structure.The heat was applied from the rod to the wick structure,and the evaporation heat transfer characteristics of the working fluid from the wick structure were evaluated.Water was used as the working fluid.The experiments were conducted by varying the rod and wick widths.The experimental results were obtained when the wick structures were placed separately.In the numerical analyses,the temperature and heat flux distributions in the rod were obtained.From the experimental and numerical results,it was confirmed that the noncontact surfaces caused the heat flux in the rod near both surfaces of the wick structure to concentrate,which increased the evaporation thermal resistance of the wick structure.A reduction in the noncontact surface area by increasing the wick width was found to be effective in decreasing the evaporation thermal resistance and increasing themaximumheat transfer rate of the wick structure.The separation of the wick structure increased the evaporation surface area.However,its effectiveness was limited when the heat transfer rate was small.
文摘BACKGROUND Endoscopic management is the first-line therapy for post-liver-transplant anas-tomotic strictures.Although the optimal duration of treatment with plastic stents has been reported to be 8-12 months,data on safety and duration for metal stents in this setting is scarce.Due to limited access to endoscopic retrograde cholan-giopancreatography(ERCP)during the coronavirus disease 2019 pandemic in our centre,there was a change in practice towards increased usage and length-of-stay of the Kaffes biliary intraductal self-expanding stent in patients with suitable anatomy.This was mainly due to the theoretical benefit of Kaffes stents allowing for longer indwelling periods compared to the traditional plastic stents.METHODS Adult liver transplant recipients aged 18 years and above who underwent ERCP were retrospectively identified during a 10-year period through a database query.Unplanned admissions post-Kaffes stent insertion were identified manually through electronic and scanned medical records.The main outcome was the incidence of complications when stents were left indwelling for 3 months vs 6 months.Stent efficacy was calculated via rates of stricture recurrence between patients that had stenting courses for≤120 d or>120 d.RESULTS During the study period,a total of 66 ERCPs with Kaffes insertion were performed in 54 patients throughout their stenting course.In 33 ERCPs,the stent was removed or exchanged on a 3-month interval.No pancreatitis,perfor-ations or deaths occurred.Minor post-ERCP complications were similar between the 3-month(abdominal pain and intraductal migration)and 6-month(abdominal pain,septic shower and embedded stent)groups-6.1%vs 9.1%respectively,P=0.40.All strictures resolved at the end of the stenting course,but the stenting course was variable from 3 to 22 months.The recurrence rate for stenting courses lasting for up to 120 d was 71.4%and 21.4%for stenting courses of 121 d or over(P=0.03).There were 28 patients that were treated with a single ERCP with Kaffes,21 with removal after 120 d and 7 within 120 d.There was a significant improvement in stricture recurrence when the Kaffes was removed after 120 d when a single ERCP was used for the entire stenting course(71.0%vs 10.0%,P=0.01).CONCLUSION Utilising a single Kaffes intraductal fully-covered metal stent for at least 4 months is safe and efficacious for the management of post-transplant anastomotic strictures.
基金This work was supported by the Indian Space Research Organization(ISRO),Department of Space,India,under ISRO RESPOND scheme(Project No.ISRO/RES/3/728/16-17).
文摘The main objective of this investigation is to study the influence of arc constriction current frequency(ACCF)on tensile properties and microstructural evolution of aerospace Alloy 718 sheets(2 mm in thickness)joined by constricted arc TIG(CA-TIG)welding process.One variable at a time approach of design of experiments(DOE)was used,in which ACCF was varied from 4 to 20 kHz at an interval of 5 levels while other parameters were kept constant.The joints welded using ACCF of 4 kHz exhibited superior tensile properties extending joint efficiency up to 99.20%.It is attributed to the grain refinement in fusion zone leading to the evolution of finer,discrete Laves phase in interdendritic areas.An increase of ACCF above 12 kHz caused severe grain growth and evolution of coarser Laves phase in fusion zone.Alloy 718 welds showed more obvious tendency for Nb segregation and Laves phase formation at higher levels of ACCF due to the slower cooling rate.The volume fraction of Laves phase was increased by 62.31%at ACCF of 20 kHz compared to that at 4 kHz,thereby reducing the tensile properties of joints.This is mainly due to the stacking of heat input in weld thermal cycles at increased levels of ACCF.
文摘This paper investigates the effect of porosity on active damping of geometrically nonlinear vibrations(GNLV)of the magneto-electro-elastic(MEE)functionally graded(FG)plates incorporated with active treatment constricted layer damping(ATCLD)patches.The perpendicularly/slanted reinforced 1-3 piezoelectric composite(1-3 PZC)constricting layer.The constricted viscoelastic layer of the ATCLD is modeled in the time-domain using Golla-Hughes-Mc Tavish(GHM)technique.Different types of porosity distribution in the porous magneto-electro-elastic functionally graded PMEE-FG plate graded in the thickness direction.Considering the coupling effects among elasticity,electrical,and magnetic fields,a three-dimensional finite element(FE)model for the smart PMEE-FG plate is obtained by incorporating the theory of layer-wise shear deformation.The geometric nonlinearity adopts the von K arm an principle.The study presents the effects of a variant of a power-law index,porosity index,the material gradation,three types of porosity distribution,boundary conditions,and the piezoelectric fiber’s orientation angle on the control of GNLV of the PMEE-FG plates.The results reveal that the FG substrate layers’porosity significantly impacts the nonlinear behavior and damping performance of the PMEE-FG plates.
基金Project (No. 20276063) supported by the National Natural Sci-ence Foundation of China
文摘The constriction factor method (CFM) is a new variation of the basic particle swarm optimization (PSO), which has relatively better convergent nature. The effects of the major parameters on CFM were systematically investigated based on some benchmark functions. The constriction factor, velocity constraint, and population size all have significant impact on the per- formance of CFM for PSO. The constriction factor and velocity constraint have optimal values in practical application, and im- proper choice of these factors will lead to bad results. Increasing population size can improve the solution quality, although the computing time will be longer. The characteristics of CFM parameters are described and guidelines for determining parameter values are given in this paper.
基金supported by the China Postdoctoral Science Foundation,No.20100480643the Program of Shanghai Municipal Education Commission,No.2011JW13
文摘Acupuncture has been used to treat neuropathic pain for a long time, but its mechanisms of action remain unknown. In this study, we observed the effects of electroacupuncture and manual acu- puncture on neuropathic pain and on ephrin-B/EphB signaling in rats models of chronic constriction injury-induced neuropathic pain. The results showed that manual acupuncture and electroacu- puncture significantly reduced mechanical hypersensitivity following chronic constriction injury, es- pecially electroacupuncture treatment. Real-time PCR results revealed that ephrin-B1/B3 and EphB1/B2 mRNA expression levels were significantly increased in the spinal dorsal horns of chronic constriction injury rats. Electroacupuncture and manual acupuncture suppressed the high expres- sion of ephrin-B1 mRNA, and elevated EphB3/B4 mRNA expression. Electroacupuncture signifi- cantly enhanced the mRNA expression of ephrin-B3 and EphB3/B6 in the dorsal horns of neuro- pathic pain rats. Western blot results revealed that electroacupuncture in particular, and manual acupuncture, significantly up-regulated ephrin-B3 protein levels in rat spinal dorsal horns. The re- sults of this study suggest that acupuncture could activate ephrin-B/EphB signaling in neuropathic pain rats and improve neurological function.
文摘This article describes a case we experienced in which good postsurgical facial profiles were obtained for a patient with jaw deformities associated with facial asymmetry,by implementing surgical planning with SimPlant OMS.Using this method,we conducted LF1 osteotomy,intraoral vertical ramus osteotomy（IVRO）,sagittal split ramus osteotomy（SSRO）,mandibular constriction and mandibular border genioplasty.Not only did we obtain a class I occlusal relationship,but the complicated surgery also improved the asymmetry of the frontal view,as well as of the profile view,of the patient.The virtual operation using three-dimensional computed tomography（3D-CT）could be especially useful for the treatment of patients with jaw deformities associated with facial asymmetry.
