Attitude maneuver of liquid-filled spacecraft with an appendage as a cantilever beam by momentum wheel is studied. The dynamic equations are derived by conserva- tion of angular momentum and force equilibrium principl...Attitude maneuver of liquid-filled spacecraft with an appendage as a cantilever beam by momentum wheel is studied. The dynamic equations are derived by conserva- tion of angular momentum and force equilibrium principle. A feedback control strategy of the momentum wheel is ap- plied for the attitude maneuver. The residual nutation of the spacecraft in maneuver process changes with some chosen parameters, such as steady state time, locations of the liq- uid container and the appendage, and appendage parame- ters. The results indicate that locations in the second and fourth quadrants of the body-fixed coordinate system and the second quadrant of the wall of the main body are better choices for.placing the liquid containers and the appendage than other locations if they can be placed randomly. Higher density and thicker cross section are better for lowering the residual nutation if they can be changed. Light appendage can be modeled as a rigid body, which results in a larger residual nutation than a flexible model though. The resid- ual nutation decreases with increasing absolute value of the initial sloshing angular height.展开更多
BACKGROUND Cerebral microbleeds(CMBs)may increase the risk of future intracerebral hemorrhage and ischemic stroke.However,It is unclear whether antiplatelet medication is associated with CMBs.This study aimed to inves...BACKGROUND Cerebral microbleeds(CMBs)may increase the risk of future intracerebral hemorrhage and ischemic stroke.However,It is unclear whether antiplatelet medication is associated with CMBs.This study aimed to investigate the association between antiplatelet medication and CMBs in a community-based stroke-free population.METHODS In this cross-sectional study,stroke-free participants aged 18-85 years were recruited from a community in Beijing,China.Demographic,clinical,and antiplatelet medication data were collected through a questionnaire,and all participants underwent blood tests and brain magnetic resonance imaging at 3.0T.The presence,count,and location of CMBs were evaluated using susceptibility-weighted imaging.The association between antiplatelet medication and the presence of CMBs was analyzed using multivariable logistic regression.The associations between antiplatelet medication and CMBs by location(lobar,deep brain or infratentorial,and mixed regions)were also analyzed using multinomial logistic regression.A linear regression analysis was conducted to determine the association between antiplatelet medication and the log-transformed number of CMBs.RESULTS Of the 544 participants(mean age:58.65±13.66 years,217 males),119 participants(21.88%)had CMBs,and 64 participants(11.76%)used antiplatelet medication.Antiplatelet medication was found to be associated with CMBs at any location[odds ratio(OR)=2.39,95%CI:1.24-4.58]and lobar region(OR=2.83,95%CI:1.36-5.86),but not with the number of CMBs(β=0.14,95%CI:-0.21-0.48).Among antiplatelet medications,aspirin use was found to be associated with any CMB(OR=3.17,95%CI:1.49-6.72)and lobar CMBs(OR=3.61,95%CI:1.57-8.26).CONCLUSIONS Antiplatelet medication was associated with CMBs in stroke-free participants,particularly lobar CMBs.Among antiplatelet medications,aspirin use was associated with any CMB and lobar CMBs.Our findings suggest that it might be essential to optimize the management of antiplatelet medication in the stroke-free population with a higher burden of vascular risk factors to reduce the potential risk of CMBs.展开更多
Objective To determine the association of carotid plaque features with collateral circulation status in elderly patients with moderate to severe carotid stenosis.Methods Elderly patients(>60 years)with moderate to ...Objective To determine the association of carotid plaque features with collateral circulation status in elderly patients with moderate to severe carotid stenosis.Methods Elderly patients(>60 years)with moderate to severe carotid stenosis were recruited and categorized into good and poor collateral circulation groups,and underwent magnetic resonance imaging and computed tomography imaging.The carotid plaque features including lipid-rich necrotic core,intraplaque hemorrhage,calcification,and fibrous cap rupture(FCR)were evaluated,and maximum wall thickness,normalized wall index(NWI),and luminal stenosis were measured.The association between these variables and collateral circulation status was analyzed.Results Of the 97 patients(78 males,mean age:69.0±6.1 years),19(19.6%)had poor collaterals.The poor collateral group had a significantly higher NWI(93.7%±5.0%vs.89.0%±7.9%,P=0.011),a greater extent of stenosis(80.0%±11.4%vs.75.3%±9.4%,P=0.036)and FCR(84.2%vs.55.1%,P=0.020)compared with good collateral group.Carotid NWI(OR=3.83,95%CI:1.36–10.82,P=0.011)and more FCR(OR=6.77,95%CI:1.35–33.85,P=0.020)were associated with poor collateral circulation after adjustment for the confounding factors.The combination of NWI,FCR,systolic blood pressure,and triglycerides had the highest area-under-the-curve(AUC=0.85)for detection of poor collaterals.Conclusions Carotid plaque features,specifically NWI and FCR,are independently associated with poor collateral circulation,and the combination of carotid plaque features and traditional risk factors has a stronger predictive value for poor collateral circulation than plaque features alone.展开更多
BACKGROUND Appendiceal mucinous neoplasm (AMN) is extremely rare. Since the disease does not manifest a characteristic profile of clinical symptoms, it is easy to misdiagnose and still difficult to diagnose without op...BACKGROUND Appendiceal mucinous neoplasm (AMN) is extremely rare. Since the disease does not manifest a characteristic profile of clinical symptoms, it is easy to misdiagnose and still difficult to diagnose without operation. Here, we report a case of low-grade AMN (LAMN) and summarize its clinical features, diagnosis, and treatment. CASE SUMMARY A 63-year-old postmenopausal woman presented with a history of right lower abdominal mass. The patient underwent laparotomy, which showed an appendiceal mucocele originating from the apex of the appendix, and a simple appendectomy was performed. The subsequent histological assessment identified an LAMN with no lymph node involvement and negative surgical margin. The patient received six cycles of chemotherapy after surgery, and to date, more than a year after the surgery, the patient remains in good health. CONCLUSION A unified, standardized, detailed, and accurate pathological diagnosis is needed for LAMN, to facilitate selection of an appropriate surgical plan. In addition, the surgeon should record the details of the tumors in the surgical records in order to facilitate follow-up after surgery.展开更多
AIM:To observe the changes in Schlemm’s canal(SC),trabecular meshwork(TM),and anterior chamber relevant parameters after small incision lenticule extraction(SMILE) of myopia patients.METHODS:A total of 58 eyes from 3...AIM:To observe the changes in Schlemm’s canal(SC),trabecular meshwork(TM),and anterior chamber relevant parameters after small incision lenticule extraction(SMILE) of myopia patients.METHODS:A total of 58 eyes from 30 patients who underwent SMILE were divided into a low and moderate myopia group(group A,32 eyes) and a high myopia group(group B,26 eyes).The diameter and area of the SC,the width and thickness of TM obtained by CIRRUS HD-OCT5000,and the related anterior chamber parameters obtained by Pentacam anterior segment analysis system,accommodation amplitude(AMP) were observed pre-and postoperatively.The preoperative intraocular pressure(IOP) and postoperative correction of intraocular pressure(IOPcc) were measured.RESULTS:The diameter and area of the SC in the two groups were significantly increased postoperatively(all P<0.01).The TM width of the patients in the two groups were increased at 1mo after surgery(both P<0.01),but the TM thickness did not change(P>0.05).The corneal curvature,central anterior chamber depth,and anterior chamber volume decreased after SMILE surgery(all P<0.01).There was a weak negative correlation between the SC area change and AMP change in group A(r=-0.362,P<0.01).The postoperative IOP decreased after correction by Shah formula(P<0.05).CONCLUSION:SC and TM in myopia patients change in the early postoperative stage of SMILE and the IOP is decline.展开更多
Dear editor,Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment for severe aortic valve stenosis and aortic regurgitation. Multiple randomized trials have proved its therapeutic advantages ...Dear editor,Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment for severe aortic valve stenosis and aortic regurgitation. Multiple randomized trials have proved its therapeutic advantages in patients at any level of surgical risks.展开更多
The present paper studies the ventilated cavitation over a NACA0015 hydrofoil by numerical methods. The corresponding cavity evolutions are obtained at three ventilation rates by using the level set method. To depict ...The present paper studies the ventilated cavitation over a NACA0015 hydrofoil by numerical methods. The corresponding cavity evolutions are obtained at three ventilation rates by using the level set method. To depict the complicated turbulent flow structure, the filter-based density corrected model（FBDCM） and the modified partially-averaged Navier-Stokes（MPANS） model are applied in the present numerical analyses. It is indicated that the predicted results of the cavitation shedding dynamics by both turbulence models agree fairly well with the experimental data. It is also noted that the shedding frequency and the super cavity length predicted by the MPANS method are closer to the experiment data as compared to that predicted by the FBDCM model. The simulation results show that in the ventilated cavitation, the vapor cavity and the air cavity have the same shedding frequency. As the ventilated rate increases, the vapor cavity is depressed rapidly. The cavitation-vortex interaction in the ventilated cavitation is studied based on the vorticity transport equation（VTE） and the Lagrangian coherent structure（LCS）. Those results demonstrate that the vortex dilatation and baroclinic torque terms are highly dependent on the evolution of the cavitation. In addition, from the LCSs and the tracer particles in the flow field, one may see the process from the attached cavity to the cloud cavity.展开更多
基金supported by the National Natural Science Foundation of China (11072030)
文摘Attitude maneuver of liquid-filled spacecraft with an appendage as a cantilever beam by momentum wheel is studied. The dynamic equations are derived by conserva- tion of angular momentum and force equilibrium principle. A feedback control strategy of the momentum wheel is ap- plied for the attitude maneuver. The residual nutation of the spacecraft in maneuver process changes with some chosen parameters, such as steady state time, locations of the liq- uid container and the appendage, and appendage parame- ters. The results indicate that locations in the second and fourth quadrants of the body-fixed coordinate system and the second quadrant of the wall of the main body are better choices for.placing the liquid containers and the appendage than other locations if they can be placed randomly. Higher density and thicker cross section are better for lowering the residual nutation if they can be changed. Light appendage can be modeled as a rigid body, which results in a larger residual nutation than a flexible model though. The resid- ual nutation decreases with increasing absolute value of the initial sloshing angular height.
基金supported by the National Key Research and Development Program of the Ministry of Science and Technology of China(2017YFC 1307702)the Capital’s Funds for Health Improvement and Research(No.2020-1-2041).
文摘BACKGROUND Cerebral microbleeds(CMBs)may increase the risk of future intracerebral hemorrhage and ischemic stroke.However,It is unclear whether antiplatelet medication is associated with CMBs.This study aimed to investigate the association between antiplatelet medication and CMBs in a community-based stroke-free population.METHODS In this cross-sectional study,stroke-free participants aged 18-85 years were recruited from a community in Beijing,China.Demographic,clinical,and antiplatelet medication data were collected through a questionnaire,and all participants underwent blood tests and brain magnetic resonance imaging at 3.0T.The presence,count,and location of CMBs were evaluated using susceptibility-weighted imaging.The association between antiplatelet medication and the presence of CMBs was analyzed using multivariable logistic regression.The associations between antiplatelet medication and CMBs by location(lobar,deep brain or infratentorial,and mixed regions)were also analyzed using multinomial logistic regression.A linear regression analysis was conducted to determine the association between antiplatelet medication and the log-transformed number of CMBs.RESULTS Of the 544 participants(mean age:58.65±13.66 years,217 males),119 participants(21.88%)had CMBs,and 64 participants(11.76%)used antiplatelet medication.Antiplatelet medication was found to be associated with CMBs at any location[odds ratio(OR)=2.39,95%CI:1.24-4.58]and lobar region(OR=2.83,95%CI:1.36-5.86),but not with the number of CMBs(β=0.14,95%CI:-0.21-0.48).Among antiplatelet medications,aspirin use was found to be associated with any CMB(OR=3.17,95%CI:1.49-6.72)and lobar CMBs(OR=3.61,95%CI:1.57-8.26).CONCLUSIONS Antiplatelet medication was associated with CMBs in stroke-free participants,particularly lobar CMBs.Among antiplatelet medications,aspirin use was associated with any CMB and lobar CMBs.Our findings suggest that it might be essential to optimize the management of antiplatelet medication in the stroke-free population with a higher burden of vascular risk factors to reduce the potential risk of CMBs.
基金supported by the National Natural Science Foundation of China(No.81771825)Peking University Third Hospital(BYSY2015013)+1 种基金Beijing Municipal Science and Technology Commission(D171100003017003)Ministry of Science and Technology of China(2017 YFC1307904).
文摘Objective To determine the association of carotid plaque features with collateral circulation status in elderly patients with moderate to severe carotid stenosis.Methods Elderly patients(>60 years)with moderate to severe carotid stenosis were recruited and categorized into good and poor collateral circulation groups,and underwent magnetic resonance imaging and computed tomography imaging.The carotid plaque features including lipid-rich necrotic core,intraplaque hemorrhage,calcification,and fibrous cap rupture(FCR)were evaluated,and maximum wall thickness,normalized wall index(NWI),and luminal stenosis were measured.The association between these variables and collateral circulation status was analyzed.Results Of the 97 patients(78 males,mean age:69.0±6.1 years),19(19.6%)had poor collaterals.The poor collateral group had a significantly higher NWI(93.7%±5.0%vs.89.0%±7.9%,P=0.011),a greater extent of stenosis(80.0%±11.4%vs.75.3%±9.4%,P=0.036)and FCR(84.2%vs.55.1%,P=0.020)compared with good collateral group.Carotid NWI(OR=3.83,95%CI:1.36–10.82,P=0.011)and more FCR(OR=6.77,95%CI:1.35–33.85,P=0.020)were associated with poor collateral circulation after adjustment for the confounding factors.The combination of NWI,FCR,systolic blood pressure,and triglycerides had the highest area-under-the-curve(AUC=0.85)for detection of poor collaterals.Conclusions Carotid plaque features,specifically NWI and FCR,are independently associated with poor collateral circulation,and the combination of carotid plaque features and traditional risk factors has a stronger predictive value for poor collateral circulation than plaque features alone.
基金Supported by Wu Jieping Medical Foundation of China,No.320.6750.18492the Innovative Talents Fund of Harbin Science and Technology Bureau of China,No.2015RAQYJ103
文摘BACKGROUND Appendiceal mucinous neoplasm (AMN) is extremely rare. Since the disease does not manifest a characteristic profile of clinical symptoms, it is easy to misdiagnose and still difficult to diagnose without operation. Here, we report a case of low-grade AMN (LAMN) and summarize its clinical features, diagnosis, and treatment. CASE SUMMARY A 63-year-old postmenopausal woman presented with a history of right lower abdominal mass. The patient underwent laparotomy, which showed an appendiceal mucocele originating from the apex of the appendix, and a simple appendectomy was performed. The subsequent histological assessment identified an LAMN with no lymph node involvement and negative surgical margin. The patient received six cycles of chemotherapy after surgery, and to date, more than a year after the surgery, the patient remains in good health. CONCLUSION A unified, standardized, detailed, and accurate pathological diagnosis is needed for LAMN, to facilitate selection of an appropriate surgical plan. In addition, the surgeon should record the details of the tumors in the surgical records in order to facilitate follow-up after surgery.
基金Supported by the National Natural Science Foundation of China (No.81974133)。
文摘AIM:To observe the changes in Schlemm’s canal(SC),trabecular meshwork(TM),and anterior chamber relevant parameters after small incision lenticule extraction(SMILE) of myopia patients.METHODS:A total of 58 eyes from 30 patients who underwent SMILE were divided into a low and moderate myopia group(group A,32 eyes) and a high myopia group(group B,26 eyes).The diameter and area of the SC,the width and thickness of TM obtained by CIRRUS HD-OCT5000,and the related anterior chamber parameters obtained by Pentacam anterior segment analysis system,accommodation amplitude(AMP) were observed pre-and postoperatively.The preoperative intraocular pressure(IOP) and postoperative correction of intraocular pressure(IOPcc) were measured.RESULTS:The diameter and area of the SC in the two groups were significantly increased postoperatively(all P<0.01).The TM width of the patients in the two groups were increased at 1mo after surgery(both P<0.01),but the TM thickness did not change(P>0.05).The corneal curvature,central anterior chamber depth,and anterior chamber volume decreased after SMILE surgery(all P<0.01).There was a weak negative correlation between the SC area change and AMP change in group A(r=-0.362,P<0.01).The postoperative IOP decreased after correction by Shah formula(P<0.05).CONCLUSION:SC and TM in myopia patients change in the early postoperative stage of SMILE and the IOP is decline.
文摘Dear editor,Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment for severe aortic valve stenosis and aortic regurgitation. Multiple randomized trials have proved its therapeutic advantages in patients at any level of surgical risks.
基金Project supported by the National Natural Science Foundation of China(Grant No.51536008)
文摘The present paper studies the ventilated cavitation over a NACA0015 hydrofoil by numerical methods. The corresponding cavity evolutions are obtained at three ventilation rates by using the level set method. To depict the complicated turbulent flow structure, the filter-based density corrected model（FBDCM） and the modified partially-averaged Navier-Stokes（MPANS） model are applied in the present numerical analyses. It is indicated that the predicted results of the cavitation shedding dynamics by both turbulence models agree fairly well with the experimental data. It is also noted that the shedding frequency and the super cavity length predicted by the MPANS method are closer to the experiment data as compared to that predicted by the FBDCM model. The simulation results show that in the ventilated cavitation, the vapor cavity and the air cavity have the same shedding frequency. As the ventilated rate increases, the vapor cavity is depressed rapidly. The cavitation-vortex interaction in the ventilated cavitation is studied based on the vorticity transport equation（VTE） and the Lagrangian coherent structure（LCS）. Those results demonstrate that the vortex dilatation and baroclinic torque terms are highly dependent on the evolution of the cavitation. In addition, from the LCSs and the tracer particles in the flow field, one may see the process from the attached cavity to the cloud cavity.
