During the supersonic re-entry of multi-nozzle heavy rockets into the atmosphere,the basic flow state becomes increasingly complex due to the coupling effect between the retropropulsion plumes and the freestream.A num...During the supersonic re-entry of multi-nozzle heavy rockets into the atmosphere,the basic flow state becomes increasingly complex due to the coupling effect between the retropropulsion plumes and the freestream.A numerical method using the hybrid Reynolds-Averaged Navier-Stokes and Large Eddy Simulation(RES)method and discrete coordinate method is developed to accurately estimate the thermal environment.In addition,finite rate chemical kinetics is used to calculate the afterburning reactions.The numerical results agree well with wind tunnel data,which confirms the validity and accuracy of the numerical method.Computations are conducted for the heavy carrier rocket re-entry from 53.1 km to 39.5 km altitude with 180°angle of attack by using three different Supersonic Retro-Propulsion(SRP)modes.The numerical results reveal that these three SRP flow fields are all Short Penetration Models(SPM).As the re-entry altitudes decrease,both the plume-plume interaction and the plume-freestream interaction become weaker.The highest temperatures in the plume shear layers of the three SRP modes increase by 8.36%,7.33%and 6.92%respectively after considering afterburning reactions,and all occur at a reentry altitude of 39.5 km.As the rocket re-enters the atmosphere,the maximum heat flux on the rocket base plate of three SRP modes stabilizes at 290,170 and 200 kW/m^(2) respectively,but the maximum heat flux on the side wall increases significantly.When the altitude declines to 39.5 km,the extreme heat flux of the three modes increase by 84.16%,49.45%and 62.97%respectively compared to that at 53.1 km.展开更多
Traditionally, perivaterian duodenal perforation can be managed conservatively or surgically. If a large volume of leakage results in fluid collection in the retroperitoneum, surgery may be necessary. Our case met the...Traditionally, perivaterian duodenal perforation can be managed conservatively or surgically. If a large volume of leakage results in fluid collection in the retroperitoneum, surgery may be necessary. Our case met the surgical indication for perivaterian duodenal perforation after endoscopic retrograde cholangiopancreatography(ERCP) with sphincterotomy and endoscopic papillary balloon dilatation. The patient developed a retroperitoneal abscess after the procedures, and a perivaterian perforation was suggested on computed tomography(CT). CT-guided abscess drainage was performed immediately. We unsuccessfully attempted to close the perforation with hemoclips initially. Subsequently, we used fibrin sealant(Tisseel) injection to occlude the perforation. Fibrin sealant injections have been previously used during endoscopy for wound closure and fistula repair. Based on our report, fibrin sealant injection can be considered as an alternative method for the treatment of ERCPrelated type Ⅱ perforations.展开更多
Objectives: To study the epidemiological profile and the prognosis of the retro-placental hematoma (HRP) at the maternity ward at Kolda Regional Hospital Center. Materials and methods: This was a retrospective descrip...Objectives: To study the epidemiological profile and the prognosis of the retro-placental hematoma (HRP) at the maternity ward at Kolda Regional Hospital Center. Materials and methods: This was a retrospective descriptive cross-sectional study conducted over a period of 11 years: from January 1st, 2006 to December 31st, 2016, at Kolda Regional Hospital Center. It included all patients admitted for HRP during this period. The studied parameters concerned sociodemographic characteristics, gynecological obstetrical history;clinical, therapeutic and prognostic data (non-inclusion or exclusion criteria). The data were collected from medical records, the delivery room and the surgery room registers using a collection sheet developed for this purpose. The statistical analysis of the variables studied was done with the software Epi-info 3.5. For the qualitative variables, we calculated the frequencies and for the quantitative variables, we studied the distributions. Results: During the study period, 15,343 were recorded deliveries and we carried out the diagnosis of HRP in 301 patients (1.97%). The average age of the patients was 24 years with an average parity of 4.8 deliveries. Almost all the patients (87.5%) were evacuated and half had delivered by caesarean section. Maternal and fetal deaths were 7% and 72.1%, respectively. Uterine atony accounted for 21.2% of complications. One third of the cases of uterine atony had resulted in a hysterectomy. The average duration of hospitalization was 6 days. Conclusion: The retro-placental hematoma is a serious medico-obstetric emergency. It is burdened with high maternal and fetal morbidity and mortality in developing countries.展开更多
This paper proposes the novel concept of retrofitting damaged reinforced concrete frame with self-centering and energy-dissipating rocking wall.Parametric studies were carried out base on pushover and time-history anal...This paper proposes the novel concept of retrofitting damaged reinforced concrete frame with self-centering and energy-dissipating rocking wall.Parametric studies were carried out base on pushover and time-history analysis.In both pushover and time-history analysis,the soft-story mechanism was effectively mitigated through the rocking wall retrofit of the damaged structures.The results demonstrated that the stiffness and bearing capacity of the retrofitted system were improved compare to its intact state.Additionally,the seismic response of the damaged frame retrofitted using rocking wall in combination with post-tension and shear-type damper fell within the relevant design limits.Pushover analysis of the rocking wall indicated that there is a linear relationship between the wall thickness and the initial stiffness of the retrofitted system.The addition of post-tension tendon to the rocking wall system enables the wall to self-center and increases lateral stiffness and bearing capacity of the retrofitted system.When the shear-type damper was installed,the energy dissipation of the system was increased,and the stiffness and bearing capacity of the retrofitted system were also improved.In the time-history analysis,it was found that the thickness of the rocking wall is directly related to the maximum inter-story drift and the distribution patterns of inter-story drift of the frame.As the post-tension was added to the system,the maximum inter-story drift under rare earthquake excitation improved significantly.With the addition of shear-type dampers,the overall drift magnitude of the retrofitted system was fundamentally decreased.展开更多
Retro reflective beamforming technique has the potential of enabling efficient wireless power transmission over long distance(on the order of meters and even kilometers).In retro reflective beamforming,wireless power ...Retro reflective beamforming technique has the potential of enabling efficient wireless power transmission over long distance(on the order of meters and even kilometers).In retro reflective beamforming,wireless power transmission is guided by pilot signal:Based upon pilot signal broadcasted by a wireless power receiver,a wireless power transmitter delivers focused microwave power beam(s)onto the location of wireless power receiver.When the wireless power receiver’s location is not fixed or when the wireless power receiver’s location is unknown to the wireless power transmitter,the microwave power beam would follow the wireless power receiver’s location dynamically as long as the wireless power receiver broadcasts pilot signal periodically.This paper reviews our research endeavors in recent years on retro reflective beamforming technique targeting three applications:(1)wireless charging for low power mobile/portable electronic devices,(2)space solar power satellites(SSPS)application,and(3)wireless charging in fully enclosed space.The feasibility and potential of retro reflective beamforming technique with applications in wireless power transmission are demonstrated by some preliminary experimental results.展开更多
Via case analysis and literature retrospect,a kind of active design style at present is initially explored: retro-futurism,and the design method of realizing this style and its artistic value are discussed.By reviewin...Via case analysis and literature retrospect,a kind of active design style at present is initially explored: retro-futurism,and the design method of realizing this style and its artistic value are discussed.By reviewing and analyzing the modeling element and spatial form of futurism in the space age,designers can refine the special formal language of this period,adjust these formal languages according to the need,and then place these formal languages in the context of the new era,thereby obtaining style of retrofuture.Retro-futurism design can create a strong visual style,arouse people’s nostalgia and trigger double associations about history and the future.By shaping model and space,people’s attention is directed to the perception of time,thereby stimulating people to reflect on technology and modern life.Its intrinsic complexity brings strong visual impact,makes it have wide application prospects in architecture,plane,clothing,products and other different design areas,and brings people richer visual experience.展开更多
Liposomes effectively transport fatty proteins to targeted tissues. Laboratory experiments use multiple methods to administer liposomes, but comparison of these methods is not available. In this retrospective study, w...Liposomes effectively transport fatty proteins to targeted tissues. Laboratory experiments use multiple methods to administer liposomes, but comparison of these methods is not available. In this retrospective study, we characterized and compared four intravenous administration routes (tail vein, jugular catheter, femoral vein and percutaneous retro-orbital injections) in murine models. ApoE<sup>-/-</sup> mice were used to compare administration routes. Results indicate that the jugular catheter route delivered the highest amount of liposomes to tissues due to longer period of injections compared to other routes;however, this route failed to remain patent for 8/10 animals. Delivery via tail vein, femoral vein and percutaneous retro-orbital injections resulted in similar accumulation in the organs. When including technical difficulty and expense, percutaneous retro-orbital injections of liposomes are the most convenient and efficacious approach.展开更多
Background: Mesh expansion and fixation at retro-rectus plane through multiples stabs produces good results. But these stabs cause cosmetic disorders for the patients and doctors. So, we find some modification to do t...Background: Mesh expansion and fixation at retro-rectus plane through multiples stabs produces good results. But these stabs cause cosmetic disorders for the patients and doctors. So, we find some modification to do this procedure without these stabbing wounds in midline hernial repair. Patients and methods: This technique was used to fix the mesh at retro-rectus plane in 50 patients suffering from midline hernias, from January 2008 through January 2010 at Zagazig university Hospital, Egypt. Laparotomy incision was done over the hernial sac or at old incision;the contents were then released and reduced into peritoneal cavity without much subcutaneous dissection. The suitable sheet of polypropylene mesh to cover the hernial defect and any weak area was prepared and fixed at retro-rectus plane percutaneously without stabbing wounds by using redirecting suture hook. The mean period of follow up was 26 months. Results: There was no recurrence during the period of follow up. Five patients developed subcutaneous bluish discoloration at the site of some stitches, which disappear within two weeks with conservative treatment. Conclusion: Percutaneous mesh expansion and fixation at retro-rectus plane by using redirecting suture hook procedure has good results in recurrence rate and cosmetic appearance.展开更多
<strong>Introduction:</strong><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">The majority...<strong>Introduction:</strong><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">The majority of pregnancies and births go off without incident even though they all present risks. Retro-placental hematoma (RPH) is an extreme obstetric emergency. The aim of our study was to assess the maternal-fetal prognosis of this pathology in our patients. </span><b><span style="font-family:Verdana;">Patients and Methods:</span></b></span><b><span style="font-family:""> </span></b><span style="font-family:Verdana;">This is a retrospective descriptive and analytical study over 5 years ranging from the period from January 1st, 2015 to December 31st, 2019. The study</span><span style="font-family:Verdana;">’</span><span style="font-family:Verdana;">s population consisted of pregnant women, in the 3rd trimester, who </span><span style="font-family:Verdana;">were </span><span style="font-family:Verdana;">presented with the retro-placental</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">hematoma during the pregnancy or childbirth and taken care of in the maternity ward of the Centre Hospitalier Universitaire Communautaire. </span><b><span style="font-family:Verdana;">Results:</span></b></span><b><span style="font-family:""> </span></b><span style="font-family:Verdana;">During our study period, we recorded 87 cases of retro-placental hematoma</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">and 40</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;">763 deliveries. The frequency of retro-placental hematoma was</span><span style="font-family:""> </span><span style="font-family:Verdana;">0.21% at delivery. The average maternal age was 26.4 years with extremes of 16 and 40 years. The parity</span><span style="font-family:Verdana;">’</span><span style="font-family:Verdana;">s average was 3.8 with extremes of 1 and 13. The mean gestational age at the time of the onset of the accident was 35.9 amenorrhea</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">weeks (AW) with extremes of 28 and 40 AW. We performed 4 cases of hysterectomy (4.5%). We recorded 8 maternal deaths (9.2%) and 60 newborn deaths (69%). The causes of maternal death were dominated by afibrinogenemia 62.5%, followed by renal failure in 25%. </span><b><span style="font-family:Verdana;">Conclusion:</span></b><span style="font-family:Verdana;"> Retro-placental hematoma is a serious pathology during the pregnancy.</span></span>展开更多
Approximately 5% of goitres extend below the thoracic inlet and can potentially become life threatening due to compression of the airway and major vessels. Approximately 7% of these goitres which require surgical rese...Approximately 5% of goitres extend below the thoracic inlet and can potentially become life threatening due to compression of the airway and major vessels. Approximately 7% of these goitres which require surgical resection will need an additional sternotomy to deliver the intra-thoracic component. Massive retrosternal toxic goitres presenting acutely are rare and are described infrequently in literature. We hereby present two cases of massive retrosternal thyrotoxic goitres presenting with acute respiratory failure, requiring non-invasive ventilation, as well as significant head and neck venous compression. Surgery on the thyrotoxic patient with a goitre, even if not significantly enlarged, is associated with a high peri-operative mortality due to cardiac instability and hemorrhage. We discuss the challenges of surgical intervention in these patients with particular emphasis on the timing of surgery to relieve compressive symptoms and the time needed to achieve a euthyroid state. We also emphasize the need for meticulous hemostasis, use of a cell-saver, transfusion protocols, adjuncts to hemostasis, as well as careful monitoring and continuous adjustments to the coagulation profile.展开更多
For an effective thermoplastic pavement marking replacement strategy, the rate at which the marking’s retro-reflectivity deteriorates in service must be well established in order to avoid re-stripping that is too soo...For an effective thermoplastic pavement marking replacement strategy, the rate at which the marking’s retro-reflectivity deteriorates in service must be well established in order to avoid re-stripping that is too soon or too late. Against this background, this paper undertook a review of models that deal with degradation of thermoplastic pavement markings under different traffic and environmental conditions in order to establish service life and the terminal retro-reflectivity levels that have informed re-striping. Service life in the context of this paper is the time taken for a newly-installed marking to degrade to some minimum retro-reflectivity level below which motorists would find it difficult to navigate on the carriageway under night-time and poor visibility conditions. It was established that the minimum retro-reflectivity requiring re-stripping intervention reported varied, although commonly-adopted values tended to range from 50 mcd/m2/lx to 150 mcd/m2/lx. A number of empirical models, based on site specific conditions, have been developed by researchers using field data, to estimate marking retro-reflectivity at any time since placement. Whereas some of the models used time as the only independent variable, others used a combination of time, traffic level and a few other parameters to estimate retro-reflectivity. Even though degradation of marking retro-reflectivity is a reflection, among other things of material degeneration impacted by environmental and service conditions, almost all the models reviewed failed to consider environmental factors. Additionally, for some of the models, non-inclusion of the initial retro-reflectivity level and their generally low coefficient of determination statistic erode the confidence in their reliability.展开更多
The grazing-incidence hard X-ray retro-reflector (GIRR) is a novel optical element, which completely suppresses the conventional mirror beam in the retro-reflection mode, and, at the same time, totally reflects the pr...The grazing-incidence hard X-ray retro-reflector (GIRR) is a novel optical element, which completely suppresses the conventional mirror beam in the retro-reflection mode, and, at the same time, totally reflects the primary grazing incident X-radiation backwards to its source in strictly anti-parallel direction with minimal scattering. The GIRR is a good alternative to hard X-ray normal-incidence Bragg mirror, and has a high potential for applications in various X-ray optical devices and techniques, such as, hard X-ray optical noise (or background) filters, high-quality hard X-ray waveguides, low-gain hard X-ray free electron laser resonators (XFELRs), X-ray holography, coherent X-ray diffraction imaging, phase-contrast imaging, as well as in hard X-ray optical data storage devices and deep space hard X-ray communications. The proposed optical element consists of single-crystal wafer covered by a thin, non-diffracting layer of low-absorbing material.展开更多
To study the intramolecular Diels-Alder cycloadditon of 2H-chromen-2-one as a diene, a series of chiral N-allyl-N-benzylamides that contain a 2H-chrornen-2-one moiety were designed for the synthesis of benzo[f]isoindo...To study the intramolecular Diels-Alder cycloadditon of 2H-chromen-2-one as a diene, a series of chiral N-allyl-N-benzylamides that contain a 2H-chrornen-2-one moiety were designed for the synthesis of benzo[f]isoindol-1-ones via an intrarnolecular Diels-Alder and a subsequent retro-Diels-Alder cycloaddition with the expulsion of CO2. Both the yield （80%-89%） and absolute stereocontrol of the tandem reaction were high when an electron-withdrawing group was attached to the dienophile. The double bond in the styrene substructure remained in the products could be further derivatized by dihydroxylation.展开更多
A new guidance law, called biased retro proportional navigation(BRPN), is proposed. The guidance law is designed to intercept high-speed targets with angular constraint, which can be used for ballistic target intercep...A new guidance law, called biased retro proportional navigation(BRPN), is proposed. The guidance law is designed to intercept high-speed targets with angular constraint, which can be used for ballistic target interception. BRPN guidance law is defined, and the exact time-varying bias for a required impact angle is derived. Furthermore, the simulation results(trajectory, variation of navigation ratio, capture region, etc) are compared with those of biased proportional navigation(BPN), proportional navigation and retro-proportional navigation. The results show that,at the cost of a higher intercept time, BRPN demands lower terminal lateral acceleration and has larger capture region compared to BPN.展开更多
High-reflectivity micro-glass bead, as a kind of retro-reflective material, is widely used in reflective fabric or film and other reflective coatings. But it is rarely used in coated paper. The retro-reflective theory...High-reflectivity micro-glass bead, as a kind of retro-reflective material, is widely used in reflective fabric or film and other reflective coatings. But it is rarely used in coated paper. The retro-reflective theory of micro-bead is described. Also the effect of size of micro-bead, dosage of binder and different color layers on reflective properties of coated paper are discussed in this article. The results show that its retro-reflective efficiency is good, equally to reflective fabric or film when the micro-glass bead is used in coated paper.展开更多
To the Editor:Living donor liver transplantation continues to be a widely ac-cepted treatment for end-stage liver diseases[1].However,biliary complications remain a significant challenge,attributable to both surgical ...To the Editor:Living donor liver transplantation continues to be a widely ac-cepted treatment for end-stage liver diseases[1].However,biliary complications remain a significant challenge,attributable to both surgical and nonsurgical factors.These complications include bile leakage,biliary stricture,and choledocholithiasis,with a reported incidence of biliary stricture in pediatric living donor liver recip-ients ranging from 10%to 35%[2].Commonly employed thera-peutic approaches for biliary complications are endoscopic retro-grade cholangiopancreatography(ERCP),percutaneous transhepatic cholangioscopic lithotomy(PTCSL),and surgery,with ERCP often being the preferred initial treatment.展开更多
基金co-supported by the National Level Project,China and Shanghai Municipal Major Science and Technology Project,China.In addition,the authors gratefully acknowledge the guidance on English writing and numerical methods of Professor Junfeng ZHANG from the Faculty of Engineering at Laurentian University.
文摘During the supersonic re-entry of multi-nozzle heavy rockets into the atmosphere,the basic flow state becomes increasingly complex due to the coupling effect between the retropropulsion plumes and the freestream.A numerical method using the hybrid Reynolds-Averaged Navier-Stokes and Large Eddy Simulation(RES)method and discrete coordinate method is developed to accurately estimate the thermal environment.In addition,finite rate chemical kinetics is used to calculate the afterburning reactions.The numerical results agree well with wind tunnel data,which confirms the validity and accuracy of the numerical method.Computations are conducted for the heavy carrier rocket re-entry from 53.1 km to 39.5 km altitude with 180°angle of attack by using three different Supersonic Retro-Propulsion(SRP)modes.The numerical results reveal that these three SRP flow fields are all Short Penetration Models(SPM).As the re-entry altitudes decrease,both the plume-plume interaction and the plume-freestream interaction become weaker.The highest temperatures in the plume shear layers of the three SRP modes increase by 8.36%,7.33%and 6.92%respectively after considering afterburning reactions,and all occur at a reentry altitude of 39.5 km.As the rocket re-enters the atmosphere,the maximum heat flux on the rocket base plate of three SRP modes stabilizes at 290,170 and 200 kW/m^(2) respectively,but the maximum heat flux on the side wall increases significantly.When the altitude declines to 39.5 km,the extreme heat flux of the three modes increase by 84.16%,49.45%and 62.97%respectively compared to that at 53.1 km.
基金Supported by Shin Kong Wu Ho-Su Memorial HospitalTaipeiTaiwan
文摘Traditionally, perivaterian duodenal perforation can be managed conservatively or surgically. If a large volume of leakage results in fluid collection in the retroperitoneum, surgery may be necessary. Our case met the surgical indication for perivaterian duodenal perforation after endoscopic retrograde cholangiopancreatography(ERCP) with sphincterotomy and endoscopic papillary balloon dilatation. The patient developed a retroperitoneal abscess after the procedures, and a perivaterian perforation was suggested on computed tomography(CT). CT-guided abscess drainage was performed immediately. We unsuccessfully attempted to close the perforation with hemoclips initially. Subsequently, we used fibrin sealant(Tisseel) injection to occlude the perforation. Fibrin sealant injections have been previously used during endoscopy for wound closure and fistula repair. Based on our report, fibrin sealant injection can be considered as an alternative method for the treatment of ERCPrelated type Ⅱ perforations.
文摘Objectives: To study the epidemiological profile and the prognosis of the retro-placental hematoma (HRP) at the maternity ward at Kolda Regional Hospital Center. Materials and methods: This was a retrospective descriptive cross-sectional study conducted over a period of 11 years: from January 1st, 2006 to December 31st, 2016, at Kolda Regional Hospital Center. It included all patients admitted for HRP during this period. The studied parameters concerned sociodemographic characteristics, gynecological obstetrical history;clinical, therapeutic and prognostic data (non-inclusion or exclusion criteria). The data were collected from medical records, the delivery room and the surgery room registers using a collection sheet developed for this purpose. The statistical analysis of the variables studied was done with the software Epi-info 3.5. For the qualitative variables, we calculated the frequencies and for the quantitative variables, we studied the distributions. Results: During the study period, 15,343 were recorded deliveries and we carried out the diagnosis of HRP in 301 patients (1.97%). The average age of the patients was 24 years with an average parity of 4.8 deliveries. Almost all the patients (87.5%) were evacuated and half had delivered by caesarean section. Maternal and fetal deaths were 7% and 72.1%, respectively. Uterine atony accounted for 21.2% of complications. One third of the cases of uterine atony had resulted in a hysterectomy. The average duration of hospitalization was 6 days. Conclusion: The retro-placental hematoma is a serious medico-obstetric emergency. It is burdened with high maternal and fetal morbidity and mortality in developing countries.
基金support received from National Key R&D Program of China(2019YFC1509304)Natural Science Foundation of China Grant No.52121005 and Natural Science Foundation of China Grant No.52108459.
文摘This paper proposes the novel concept of retrofitting damaged reinforced concrete frame with self-centering and energy-dissipating rocking wall.Parametric studies were carried out base on pushover and time-history analysis.In both pushover and time-history analysis,the soft-story mechanism was effectively mitigated through the rocking wall retrofit of the damaged structures.The results demonstrated that the stiffness and bearing capacity of the retrofitted system were improved compare to its intact state.Additionally,the seismic response of the damaged frame retrofitted using rocking wall in combination with post-tension and shear-type damper fell within the relevant design limits.Pushover analysis of the rocking wall indicated that there is a linear relationship between the wall thickness and the initial stiffness of the retrofitted system.The addition of post-tension tendon to the rocking wall system enables the wall to self-center and increases lateral stiffness and bearing capacity of the retrofitted system.When the shear-type damper was installed,the energy dissipation of the system was increased,and the stiffness and bearing capacity of the retrofitted system were also improved.In the time-history analysis,it was found that the thickness of the rocking wall is directly related to the maximum inter-story drift and the distribution patterns of inter-story drift of the frame.As the post-tension was added to the system,the maximum inter-story drift under rare earthquake excitation improved significantly.With the addition of shear-type dampers,the overall drift magnitude of the retrofitted system was fundamentally decreased.
基金supported in part by the National Natural Science Foundations of China (Nos. 61871220, 61471195, 61628106)the United States National Science Foundation (Nos. ECCS 1303142, ECCS 1503600)
文摘Retro reflective beamforming technique has the potential of enabling efficient wireless power transmission over long distance(on the order of meters and even kilometers).In retro reflective beamforming,wireless power transmission is guided by pilot signal:Based upon pilot signal broadcasted by a wireless power receiver,a wireless power transmitter delivers focused microwave power beam(s)onto the location of wireless power receiver.When the wireless power receiver’s location is not fixed or when the wireless power receiver’s location is unknown to the wireless power transmitter,the microwave power beam would follow the wireless power receiver’s location dynamically as long as the wireless power receiver broadcasts pilot signal periodically.This paper reviews our research endeavors in recent years on retro reflective beamforming technique targeting three applications:(1)wireless charging for low power mobile/portable electronic devices,(2)space solar power satellites(SSPS)application,and(3)wireless charging in fully enclosed space.The feasibility and potential of retro reflective beamforming technique with applications in wireless power transmission are demonstrated by some preliminary experimental results.
文摘Via case analysis and literature retrospect,a kind of active design style at present is initially explored: retro-futurism,and the design method of realizing this style and its artistic value are discussed.By reviewing and analyzing the modeling element and spatial form of futurism in the space age,designers can refine the special formal language of this period,adjust these formal languages according to the need,and then place these formal languages in the context of the new era,thereby obtaining style of retrofuture.Retro-futurism design can create a strong visual style,arouse people’s nostalgia and trigger double associations about history and the future.By shaping model and space,people’s attention is directed to the perception of time,thereby stimulating people to reflect on technology and modern life.Its intrinsic complexity brings strong visual impact,makes it have wide application prospects in architecture,plane,clothing,products and other different design areas,and brings people richer visual experience.
文摘Liposomes effectively transport fatty proteins to targeted tissues. Laboratory experiments use multiple methods to administer liposomes, but comparison of these methods is not available. In this retrospective study, we characterized and compared four intravenous administration routes (tail vein, jugular catheter, femoral vein and percutaneous retro-orbital injections) in murine models. ApoE<sup>-/-</sup> mice were used to compare administration routes. Results indicate that the jugular catheter route delivered the highest amount of liposomes to tissues due to longer period of injections compared to other routes;however, this route failed to remain patent for 8/10 animals. Delivery via tail vein, femoral vein and percutaneous retro-orbital injections resulted in similar accumulation in the organs. When including technical difficulty and expense, percutaneous retro-orbital injections of liposomes are the most convenient and efficacious approach.
文摘Background: Mesh expansion and fixation at retro-rectus plane through multiples stabs produces good results. But these stabs cause cosmetic disorders for the patients and doctors. So, we find some modification to do this procedure without these stabbing wounds in midline hernial repair. Patients and methods: This technique was used to fix the mesh at retro-rectus plane in 50 patients suffering from midline hernias, from January 2008 through January 2010 at Zagazig university Hospital, Egypt. Laparotomy incision was done over the hernial sac or at old incision;the contents were then released and reduced into peritoneal cavity without much subcutaneous dissection. The suitable sheet of polypropylene mesh to cover the hernial defect and any weak area was prepared and fixed at retro-rectus plane percutaneously without stabbing wounds by using redirecting suture hook. The mean period of follow up was 26 months. Results: There was no recurrence during the period of follow up. Five patients developed subcutaneous bluish discoloration at the site of some stitches, which disappear within two weeks with conservative treatment. Conclusion: Percutaneous mesh expansion and fixation at retro-rectus plane by using redirecting suture hook procedure has good results in recurrence rate and cosmetic appearance.
文摘<strong>Introduction:</strong><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">The majority of pregnancies and births go off without incident even though they all present risks. Retro-placental hematoma (RPH) is an extreme obstetric emergency. The aim of our study was to assess the maternal-fetal prognosis of this pathology in our patients. </span><b><span style="font-family:Verdana;">Patients and Methods:</span></b></span><b><span style="font-family:""> </span></b><span style="font-family:Verdana;">This is a retrospective descriptive and analytical study over 5 years ranging from the period from January 1st, 2015 to December 31st, 2019. The study</span><span style="font-family:Verdana;">’</span><span style="font-family:Verdana;">s population consisted of pregnant women, in the 3rd trimester, who </span><span style="font-family:Verdana;">were </span><span style="font-family:Verdana;">presented with the retro-placental</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">hematoma during the pregnancy or childbirth and taken care of in the maternity ward of the Centre Hospitalier Universitaire Communautaire. </span><b><span style="font-family:Verdana;">Results:</span></b></span><b><span style="font-family:""> </span></b><span style="font-family:Verdana;">During our study period, we recorded 87 cases of retro-placental hematoma</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">and 40</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;">763 deliveries. The frequency of retro-placental hematoma was</span><span style="font-family:""> </span><span style="font-family:Verdana;">0.21% at delivery. The average maternal age was 26.4 years with extremes of 16 and 40 years. The parity</span><span style="font-family:Verdana;">’</span><span style="font-family:Verdana;">s average was 3.8 with extremes of 1 and 13. The mean gestational age at the time of the onset of the accident was 35.9 amenorrhea</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">weeks (AW) with extremes of 28 and 40 AW. We performed 4 cases of hysterectomy (4.5%). We recorded 8 maternal deaths (9.2%) and 60 newborn deaths (69%). The causes of maternal death were dominated by afibrinogenemia 62.5%, followed by renal failure in 25%. </span><b><span style="font-family:Verdana;">Conclusion:</span></b><span style="font-family:Verdana;"> Retro-placental hematoma is a serious pathology during the pregnancy.</span></span>
文摘Approximately 5% of goitres extend below the thoracic inlet and can potentially become life threatening due to compression of the airway and major vessels. Approximately 7% of these goitres which require surgical resection will need an additional sternotomy to deliver the intra-thoracic component. Massive retrosternal toxic goitres presenting acutely are rare and are described infrequently in literature. We hereby present two cases of massive retrosternal thyrotoxic goitres presenting with acute respiratory failure, requiring non-invasive ventilation, as well as significant head and neck venous compression. Surgery on the thyrotoxic patient with a goitre, even if not significantly enlarged, is associated with a high peri-operative mortality due to cardiac instability and hemorrhage. We discuss the challenges of surgical intervention in these patients with particular emphasis on the timing of surgery to relieve compressive symptoms and the time needed to achieve a euthyroid state. We also emphasize the need for meticulous hemostasis, use of a cell-saver, transfusion protocols, adjuncts to hemostasis, as well as careful monitoring and continuous adjustments to the coagulation profile.
文摘For an effective thermoplastic pavement marking replacement strategy, the rate at which the marking’s retro-reflectivity deteriorates in service must be well established in order to avoid re-stripping that is too soon or too late. Against this background, this paper undertook a review of models that deal with degradation of thermoplastic pavement markings under different traffic and environmental conditions in order to establish service life and the terminal retro-reflectivity levels that have informed re-striping. Service life in the context of this paper is the time taken for a newly-installed marking to degrade to some minimum retro-reflectivity level below which motorists would find it difficult to navigate on the carriageway under night-time and poor visibility conditions. It was established that the minimum retro-reflectivity requiring re-stripping intervention reported varied, although commonly-adopted values tended to range from 50 mcd/m2/lx to 150 mcd/m2/lx. A number of empirical models, based on site specific conditions, have been developed by researchers using field data, to estimate marking retro-reflectivity at any time since placement. Whereas some of the models used time as the only independent variable, others used a combination of time, traffic level and a few other parameters to estimate retro-reflectivity. Even though degradation of marking retro-reflectivity is a reflection, among other things of material degeneration impacted by environmental and service conditions, almost all the models reviewed failed to consider environmental factors. Additionally, for some of the models, non-inclusion of the initial retro-reflectivity level and their generally low coefficient of determination statistic erode the confidence in their reliability.
文摘The grazing-incidence hard X-ray retro-reflector (GIRR) is a novel optical element, which completely suppresses the conventional mirror beam in the retro-reflection mode, and, at the same time, totally reflects the primary grazing incident X-radiation backwards to its source in strictly anti-parallel direction with minimal scattering. The GIRR is a good alternative to hard X-ray normal-incidence Bragg mirror, and has a high potential for applications in various X-ray optical devices and techniques, such as, hard X-ray optical noise (or background) filters, high-quality hard X-ray waveguides, low-gain hard X-ray free electron laser resonators (XFELRs), X-ray holography, coherent X-ray diffraction imaging, phase-contrast imaging, as well as in hard X-ray optical data storage devices and deep space hard X-ray communications. The proposed optical element consists of single-crystal wafer covered by a thin, non-diffracting layer of low-absorbing material.
基金supported by the research grant from the National Natural Science Foundation of China (No. 21172191)
文摘To study the intramolecular Diels-Alder cycloadditon of 2H-chromen-2-one as a diene, a series of chiral N-allyl-N-benzylamides that contain a 2H-chrornen-2-one moiety were designed for the synthesis of benzo[f]isoindol-1-ones via an intrarnolecular Diels-Alder and a subsequent retro-Diels-Alder cycloaddition with the expulsion of CO2. Both the yield （80%-89%） and absolute stereocontrol of the tandem reaction were high when an electron-withdrawing group was attached to the dienophile. The double bond in the styrene substructure remained in the products could be further derivatized by dihydroxylation.
文摘A new guidance law, called biased retro proportional navigation(BRPN), is proposed. The guidance law is designed to intercept high-speed targets with angular constraint, which can be used for ballistic target interception. BRPN guidance law is defined, and the exact time-varying bias for a required impact angle is derived. Furthermore, the simulation results(trajectory, variation of navigation ratio, capture region, etc) are compared with those of biased proportional navigation(BPN), proportional navigation and retro-proportional navigation. The results show that,at the cost of a higher intercept time, BRPN demands lower terminal lateral acceleration and has larger capture region compared to BPN.
文摘High-reflectivity micro-glass bead, as a kind of retro-reflective material, is widely used in reflective fabric or film and other reflective coatings. But it is rarely used in coated paper. The retro-reflective theory of micro-bead is described. Also the effect of size of micro-bead, dosage of binder and different color layers on reflective properties of coated paper are discussed in this article. The results show that its retro-reflective efficiency is good, equally to reflective fabric or film when the micro-glass bead is used in coated paper.
文摘To the Editor:Living donor liver transplantation continues to be a widely ac-cepted treatment for end-stage liver diseases[1].However,biliary complications remain a significant challenge,attributable to both surgical and nonsurgical factors.These complications include bile leakage,biliary stricture,and choledocholithiasis,with a reported incidence of biliary stricture in pediatric living donor liver recip-ients ranging from 10%to 35%[2].Commonly employed thera-peutic approaches for biliary complications are endoscopic retro-grade cholangiopancreatography(ERCP),percutaneous transhepatic cholangioscopic lithotomy(PTCSL),and surgery,with ERCP often being the preferred initial treatment.
