Oral bacteria directly affect the disease status of dental caries and periodontal diseases. The dynamic oral microbiota cooperates with the host to reflect the information and status of immunity and metabolism through...Oral bacteria directly affect the disease status of dental caries and periodontal diseases. The dynamic oral microbiota cooperates with the host to reflect the information and status of immunity and metabolism through two-way communication along the oral cavity and the systemic organs. The oral cavity is one of the most important interaction windows between the human body and the environment.The microenvironment at different sites in the oral cavity has different microbial compositions and is regulated by complex signaling,hosts, and external environmental factors. These processes may affect or reflect human health because certain health states seem to be related to the composition of oral bacteria, and the destruction of the microbial community is related to systemic diseases. In this review, we discussed emerging and exciting evidence of complex and important connections between the oral microbes and multiple human systemic diseases, and the possible contribution of the oral microorganisms to systemic diseases. This review aims to enhance the interest to oral microbes on the whole human body, and also improve clinician’s understanding of the role of oral microbes in systemic diseases. Microbial research in dentistry potentially enhances our knowledge of the pathogenic mechanisms of oral diseases,and at the same time, continuous advances in this frontier field may lead to a tangible impact on human health.展开更多
BACKGROUND Massive pulmonary haemorrhage can spoil the entire lung and block the airway in a short period of time due to severe bleeding,which quickly leads to death.Alveolar lavage is an effective method for haemosta...BACKGROUND Massive pulmonary haemorrhage can spoil the entire lung and block the airway in a short period of time due to severe bleeding,which quickly leads to death.Alveolar lavage is an effective method for haemostasis and airway maintenance.However,patients often cannot tolerate alveolar lavage due to severe hypoxia.We used extracorporeal membrane oxygenation(ECMO)to overcome this limitation in a patient with massive pulmonary haemorrhage due to severe trauma and succeeded in saving the life by repeated alveolar lavage.CASE SUMMARY A 22-year-old man sustained multiple injuries in a motor vehicle accident and was transferred to our emergency department.On admission,he had a slight cough and a small amount of bloody sputum;computed tomography revealed multiple fractures and mild pulmonary contusion.At 37 h after admission,he developed severe chest tightness,chest pain,dizziness and haemoptysis.His oxygen saturation was 68%.Emergency endotracheal intubation was performed,and a large amount of bloody sputum was suctioned.After transfer to the intensive care unit,he developed refractory hypoxemia and heparin-free venovenous ECMO was initiated.Fibreoptic bronchoscopy revealed diffuse and profuse blood in all bronchopulmonary segment.Bleeding was observed in the trachea and right bronchus,and repeated alveolar lavage was performed.On day 3,the patient’s haemoptysis ceased,and ECMO support was terminated 10 d later.Tracheostomy was performed on day 15,and the patient was weaned from the ventilator on day 21.CONCLUSION Alveolar lavage combined with ECMO can control bleeding in trauma-induced massive pulmonary haemorrhage,is safe and can be performed bedside.展开更多
Distinguishing between aplastic anemia(AA)and hypoblastic myelodysplastic syndrome(hMDS)with a low percentage of bone marrow(BM)blasts(<5%)can be difficult due to the overlap in clonality and a spectrum of genetic ...Distinguishing between aplastic anemia(AA)and hypoblastic myelodysplastic syndrome(hMDS)with a low percentage of bone marrow(BM)blasts(<5%)can be difficult due to the overlap in clonality and a spectrum of genetic alternations between the two subtypes of diseases.However,due to recent advances in DNA sequencing technology,both spectnim and frequency of mutations can be accurately determined and monitored by next-generation sequencing(NGS)at initial diagnosis and during immunosuppressive therapy(1ST)in patients with AA or hMDS.This improvement in acquiring a patient's genetic status and clonal evolution can provide more proper,precise,and on-time information to guide disease management,which is especially helpful in the absence of traditional morphologic/cytogenetic evidence.展开更多
Many debris flows have occurred in the areas surrounding the epicenter of the Wenchuan earthquake. Susceptibility assessment of debris flows in this area is especially important for disaster prevention and mitigation....Many debris flows have occurred in the areas surrounding the epicenter of the Wenchuan earthquake. Susceptibility assessment of debris flows in this area is especially important for disaster prevention and mitigation. This paper studies one of the worst hit areas, the Subao river valley, and the susceptibility assessment of debris flows is performed based on field surveys and remote sensing interpretation. By investigating the formation conditions of debris flows in the valley, the following assessment factors are selected: mixture density of landslides and rock avalanches, distance to the seismogenic fault, stratum lithology, ground roughness, and hillside angle. The weights of the assessment factors are determined by the analytic hierarchy process (AHP) method. Each of the assessment factors is further divided into five grades. Then, the assessment model is built using the multifactor superposition method to assess the debris flow susceptibility. Based on the assessment results, the Subao river valley is divided into three areas: high susceptibility areas, medium susceptibility areas, and low susceptibility areas. The high susceptibility areas are concentrated in the middle of the valley, accounting for 17.6%of the valley area. The medium susceptibility areas are in the middle and lower reaches, most of which are located on both sides of the high susceptibility areas and account for 45.3% of the valley area. The remainders are clas-sified as low susceptibility areas. The results of the model are in accordance with the actual debris flow events that occurred after the earthquake in the valley, confirming that the proposed model is capable of assessing the debris flow susceptibility. The results can also provide guidance for reconstruction planning and debris flow prevention in the Subao river valley.展开更多
The load varies periodically, but the peak current of power cable is controlled by its continuous ampacity in China, resulting in the highest conductor temperature is much lower than90℃, the permitted long-term worki...The load varies periodically, but the peak current of power cable is controlled by its continuous ampacity in China, resulting in the highest conductor temperature is much lower than90℃, the permitted long-term working temperature of XLPE. If the cable load is controlled by its cyclic ampacity, the cable transmission capacity could be used sufficiently. To study the 10 kV XLPE cable cyclic ampacity and its factor, a three-core cable cyclic ampacity calculation software is developed and the cyclic ampacity experiments of direct buried cable are undertaken in this paper. Experiments and research shows that the software calculation is correct and the circuit numbers and daily load factor have an important impact on the cyclic ampacity factor. The cyclic ampacity factor of 0.7 daily load factor is 1.20, which means the peak current is the 1.2 times of continuous ampacity. If the continuous ampacity is instead by the cyclic ampacity to control the cable load, the transmission capacity of the cable can be improved greatly without additional investment.展开更多
BACKGROUND Graft-vs-host disease (GVHD) is a major cause of mortality after allogeneic hematopoietic stem cell transplantation.Some patients have steroid-refractory(SR) GVHD.AIM To evaluate the effect and safety of ru...BACKGROUND Graft-vs-host disease (GVHD) is a major cause of mortality after allogeneic hematopoietic stem cell transplantation.Some patients have steroid-refractory(SR) GVHD.AIM To evaluate the effect and safety of ruxolitinib add-on in the treatment of patients with SR acute (a) and chronic (c) GVHD.METHODS We retrospectively analyzed 38 patients administered ruxolitinib add-on to standard immunosuppressive therapy for SR-aGVHD or SR-cGVHD following allogeneic hematopoietic stem cell transplantation.Ruxolitinib was administered5-10 mg/d depending on disease severity,patient status,and the use of antifungal drugs.Overall response rate,time to best response,malignancy relapse rate,infection rate,and treatment-related adverse events were assessed.RESULTS The analysis included 10 patients with SR-aGVHD (gradeⅢ/Ⅳ,n=9) and 28patients with SR-cGVHD (moderate/severe,n=24).For the SR-aGVHD and SRcGVHD groups,respectively:Median number of previous GVHD therapies was 2(range:1-3) and 2 (1-4);median follow-up was 2.5 (1.5-4) and 5 (1.5-10) mo;median time to best response was 1 (0.5-2.5) and 3 (1-9.5) mo;and overall response rate was 100%(complete response:80%) and 82.1%(complete response:10.7%) with a response observed in all GVHD-affected organs.The malignancy relapse rates for the SR-aGVHD and SR-cGVHD groups were 10.0%and 10.7%,respectively.Reactivation rates for cytomegalovirus,Epstein-Barr virus,and varicella-zoster virus,respectively,were 30.0%,10.0%,and 0%for the SR-aGVHD group and 0%,14.3%,and 7.1%for the SR-cGVHD group.CONCLUSION Ruxolitinib add-on was effective and safe as salvage therapy for SR-GVHD.展开更多
Discontinuation of tyrosine kinase inhibitor(TKI)therapy after achieving a persistent deep molecular response(DMR)is an urgently needed treatment goal for chronic myeloid leukemia(CML)patients and has been included in...Discontinuation of tyrosine kinase inhibitor(TKI)therapy after achieving a persistent deep molecular response(DMR)is an urgently needed treatment goal for chronic myeloid leukemia(CML)patients and has been included in the National Comprehensive Cancer Network(NCCN)guidelines(version 2.2017)for CML.Indeed,various studies have confirmed the feasibility of discontinuing TKI therapy.In this study,we analyzed data from 45 CML patients who had discontinued TKI therapy.Univariate analysis was performed to predict factors that were potentially related to treatment-free remission(TFR)and identify the differences between early relapse and late relapse.Out of the 45 patients,20 exhibited molecular relapse after a median follow-up of 18 months(range,1-54 months),and the estimated TFR at 24 months was 40%.The univariate analysis revealed that a high Sokal score and interruptions or dose reductions during TKI treatment were the only baseline factors associated with poor outcomes.Our results indicate that TKI discontinuation could be successfully put into practice in China.展开更多
Although the advent of tyrosine kinase inhibitors(TKIs)has dramatically improved the survival of patients with chronic myeloid leukaemia(CML),acquired drug resistance and TKI-insensitive leukaemic stem cells(LSCs)rema...Although the advent of tyrosine kinase inhibitors(TKIs)has dramatically improved the survival of patients with chronic myeloid leukaemia(CML),acquired drug resistance and TKI-insensitive leukaemic stem cells(LSCs)remain major obstacles to a CML cure.In recent years,the reprogramming of mitochondrial metabolism has emerged as a hallmark of cancers,including CML,and in turn may be exploited for therapeutic purposes.Here,we investigated the effects of several drugs on the mitochondrial function of the CML cell line K562 and found that 5-aminoimidazole-4-carboxamide ribotide(AICAR)and decitabine could effectively increase the ATP content and mitochondrial biogenesis.In addition,these two drugs induced cell cycle arrest and a decrease in colony-forming capacity and promoted K562 cell differentiation.Moreover,we demonstrated that treatment with AICAR or decitabine enhanced the sensitivity o f K562 cells to imatinib,as evidenced by a combination treatment assay.Altogether,our findings indicate that TKIs combined with mitochondrial regulation may provide a therapeutic strategy for the treatment of CML.展开更多
With the benefits of small turning radius and high trafficability, the articulated steering half-track tractor had been widely utilized in orchard and small spaced farmland. To study the dynamic performance of the art...With the benefits of small turning radius and high trafficability, the articulated steering half-track tractor had been widely utilized in orchard and small spaced farmland. To study the dynamic performance of the articulated steering half-track tractor and provide a model basis for studying the path tracking control, an accurate multi-body dynamic model of the tractor was required. In this study, the crucial parameters in the dynamic model construction of the tractor were investigated. Firstly, the topology model of the components of the half-track tractor was built by RecurDyn, in which the movement subs and driver functions were given. Secondly, considering the difference of dynamic characteristic of the articulated steering tractor with respect to different pavement hardnesses, the soft and hard pavement models were constructed by employing the harmonic superposition method. Finally, the simulations of the half-track tractor under straight-line and swerve had been conducted on the two types of pavements, and the simulation results were compared with the experimental and theoretical results. The results indicated that the average speed error of the dynamic model on hard pavement and farmland soft pavement were 2.7% and 2.1% compared with the real tractor tests. At the same time, the straight-line driving offset errors of the dynamic model on the two pavements were 1.6% and 3.8% for the front wheels and the rear wheels offset errors were 3.9% and 2.4%, respectively. Furthermore, the turning radius error under front wheel steering was 8.2% and the error under articulated steering was 5.3%. It is proved that the established dynamic model had high accuracy, which provides an efficient approach to analyze the dynamic features of the half-track tractor.展开更多
Low dielectric in terlayer films have become an important element to ensure the development of the microelectr onics industry.A kind of flexible interlayer dielectrics,polyarylene ether nitrile/bisphenol A cyanate est...Low dielectric in terlayer films have become an important element to ensure the development of the microelectr onics industry.A kind of flexible interlayer dielectrics,polyarylene ether nitrile/bisphenol A cyanate ester(PEN/BADCy)film,with good thermal stability and low frequency dependence,has been developed by solution casting method.Herein,materials were designed to incorporate bisphenol A cyanate ester as a part of blend,contributing to the frequency stability and structural integrity.The morphological study combined with electron microscopy revealed the uniform and flexible microstructure information with controllable morphology through self-polymerization of cyanate esters with different prepolymerization time and curing temperatures.The dielectric films could present high thermal stability with Tg>180℃.Significant improvement in the dielectric properties was achieved for the dielectric constant and loss was much stabler than neat PEN over the frequency range from 100 Hz to 5 MHz.When the prepolymerization time was 3h and final curing temperature reached 230℃,the dielectric constant and dielectric loss of the films were 3.36 and 0.013 at 100 kHz,respectively.The dimensional stability(CTE=53.67×10^-6 K^-1)was confirmed and con sidered beneficial to use as an in terlayer dielectrics.展开更多
The reaction of 2-pyridylacetates andα,β-unsaturated pyrazolamides with DBU as the catalyst has been developed.A range of unexplored multisubstituted 2,3-dihydro-4H-quinolizin-4-ones are obtained with satisfactory y...The reaction of 2-pyridylacetates andα,β-unsaturated pyrazolamides with DBU as the catalyst has been developed.A range of unexplored multisubstituted 2,3-dihydro-4H-quinolizin-4-ones are obtained with satisfactory yields(up to 94%)and excellent diastereoselectivities(all cases>20:1 dr)via a dearomative[3+3]annulation process.This practical method also features transition metal free,mild reaction conditions,wide functional group tolerance,easy scale-up synthesis,and versatile further derivatization.展开更多
文摘Oral bacteria directly affect the disease status of dental caries and periodontal diseases. The dynamic oral microbiota cooperates with the host to reflect the information and status of immunity and metabolism through two-way communication along the oral cavity and the systemic organs. The oral cavity is one of the most important interaction windows between the human body and the environment.The microenvironment at different sites in the oral cavity has different microbial compositions and is regulated by complex signaling,hosts, and external environmental factors. These processes may affect or reflect human health because certain health states seem to be related to the composition of oral bacteria, and the destruction of the microbial community is related to systemic diseases. In this review, we discussed emerging and exciting evidence of complex and important connections between the oral microbes and multiple human systemic diseases, and the possible contribution of the oral microorganisms to systemic diseases. This review aims to enhance the interest to oral microbes on the whole human body, and also improve clinician’s understanding of the role of oral microbes in systemic diseases. Microbial research in dentistry potentially enhances our knowledge of the pathogenic mechanisms of oral diseases,and at the same time, continuous advances in this frontier field may lead to a tangible impact on human health.
文摘BACKGROUND Massive pulmonary haemorrhage can spoil the entire lung and block the airway in a short period of time due to severe bleeding,which quickly leads to death.Alveolar lavage is an effective method for haemostasis and airway maintenance.However,patients often cannot tolerate alveolar lavage due to severe hypoxia.We used extracorporeal membrane oxygenation(ECMO)to overcome this limitation in a patient with massive pulmonary haemorrhage due to severe trauma and succeeded in saving the life by repeated alveolar lavage.CASE SUMMARY A 22-year-old man sustained multiple injuries in a motor vehicle accident and was transferred to our emergency department.On admission,he had a slight cough and a small amount of bloody sputum;computed tomography revealed multiple fractures and mild pulmonary contusion.At 37 h after admission,he developed severe chest tightness,chest pain,dizziness and haemoptysis.His oxygen saturation was 68%.Emergency endotracheal intubation was performed,and a large amount of bloody sputum was suctioned.After transfer to the intensive care unit,he developed refractory hypoxemia and heparin-free venovenous ECMO was initiated.Fibreoptic bronchoscopy revealed diffuse and profuse blood in all bronchopulmonary segment.Bleeding was observed in the trachea and right bronchus,and repeated alveolar lavage was performed.On day 3,the patient’s haemoptysis ceased,and ECMO support was terminated 10 d later.Tracheostomy was performed on day 15,and the patient was weaned from the ventilator on day 21.CONCLUSION Alveolar lavage combined with ECMO can control bleeding in trauma-induced massive pulmonary haemorrhage,is safe and can be performed bedside.
基金the National Natural Science Foundation of China(No.81470009).
文摘Distinguishing between aplastic anemia(AA)and hypoblastic myelodysplastic syndrome(hMDS)with a low percentage of bone marrow(BM)blasts(<5%)can be difficult due to the overlap in clonality and a spectrum of genetic alternations between the two subtypes of diseases.However,due to recent advances in DNA sequencing technology,both spectnim and frequency of mutations can be accurately determined and monitored by next-generation sequencing(NGS)at initial diagnosis and during immunosuppressive therapy(1ST)in patients with AA or hMDS.This improvement in acquiring a patient's genetic status and clonal evolution can provide more proper,precise,and on-time information to guide disease management,which is especially helpful in the absence of traditional morphologic/cytogenetic evidence.
基金supported by the National Natural Science Foundation of China (Grant No. 41372301)the National Science and Technology Support Program (Grant No. 2012BAC06B02)
文摘Many debris flows have occurred in the areas surrounding the epicenter of the Wenchuan earthquake. Susceptibility assessment of debris flows in this area is especially important for disaster prevention and mitigation. This paper studies one of the worst hit areas, the Subao river valley, and the susceptibility assessment of debris flows is performed based on field surveys and remote sensing interpretation. By investigating the formation conditions of debris flows in the valley, the following assessment factors are selected: mixture density of landslides and rock avalanches, distance to the seismogenic fault, stratum lithology, ground roughness, and hillside angle. The weights of the assessment factors are determined by the analytic hierarchy process (AHP) method. Each of the assessment factors is further divided into five grades. Then, the assessment model is built using the multifactor superposition method to assess the debris flow susceptibility. Based on the assessment results, the Subao river valley is divided into three areas: high susceptibility areas, medium susceptibility areas, and low susceptibility areas. The high susceptibility areas are concentrated in the middle of the valley, accounting for 17.6%of the valley area. The medium susceptibility areas are in the middle and lower reaches, most of which are located on both sides of the high susceptibility areas and account for 45.3% of the valley area. The remainders are clas-sified as low susceptibility areas. The results of the model are in accordance with the actual debris flow events that occurred after the earthquake in the valley, confirming that the proposed model is capable of assessing the debris flow susceptibility. The results can also provide guidance for reconstruction planning and debris flow prevention in the Subao river valley.
文摘The load varies periodically, but the peak current of power cable is controlled by its continuous ampacity in China, resulting in the highest conductor temperature is much lower than90℃, the permitted long-term working temperature of XLPE. If the cable load is controlled by its cyclic ampacity, the cable transmission capacity could be used sufficiently. To study the 10 kV XLPE cable cyclic ampacity and its factor, a three-core cable cyclic ampacity calculation software is developed and the cyclic ampacity experiments of direct buried cable are undertaken in this paper. Experiments and research shows that the software calculation is correct and the circuit numbers and daily load factor have an important impact on the cyclic ampacity factor. The cyclic ampacity factor of 0.7 daily load factor is 1.20, which means the peak current is the 1.2 times of continuous ampacity. If the continuous ampacity is instead by the cyclic ampacity to control the cable load, the transmission capacity of the cable can be improved greatly without additional investment.
文摘BACKGROUND Graft-vs-host disease (GVHD) is a major cause of mortality after allogeneic hematopoietic stem cell transplantation.Some patients have steroid-refractory(SR) GVHD.AIM To evaluate the effect and safety of ruxolitinib add-on in the treatment of patients with SR acute (a) and chronic (c) GVHD.METHODS We retrospectively analyzed 38 patients administered ruxolitinib add-on to standard immunosuppressive therapy for SR-aGVHD or SR-cGVHD following allogeneic hematopoietic stem cell transplantation.Ruxolitinib was administered5-10 mg/d depending on disease severity,patient status,and the use of antifungal drugs.Overall response rate,time to best response,malignancy relapse rate,infection rate,and treatment-related adverse events were assessed.RESULTS The analysis included 10 patients with SR-aGVHD (gradeⅢ/Ⅳ,n=9) and 28patients with SR-cGVHD (moderate/severe,n=24).For the SR-aGVHD and SRcGVHD groups,respectively:Median number of previous GVHD therapies was 2(range:1-3) and 2 (1-4);median follow-up was 2.5 (1.5-4) and 5 (1.5-10) mo;median time to best response was 1 (0.5-2.5) and 3 (1-9.5) mo;and overall response rate was 100%(complete response:80%) and 82.1%(complete response:10.7%) with a response observed in all GVHD-affected organs.The malignancy relapse rates for the SR-aGVHD and SR-cGVHD groups were 10.0%and 10.7%,respectively.Reactivation rates for cytomegalovirus,Epstein-Barr virus,and varicella-zoster virus,respectively,were 30.0%,10.0%,and 0%for the SR-aGVHD group and 0%,14.3%,and 7.1%for the SR-cGVHD group.CONCLUSION Ruxolitinib add-on was effective and safe as salvage therapy for SR-GVHD.
基金the National Natural Science Foundation of China(No.81500136 and No.81670145).
文摘Discontinuation of tyrosine kinase inhibitor(TKI)therapy after achieving a persistent deep molecular response(DMR)is an urgently needed treatment goal for chronic myeloid leukemia(CML)patients and has been included in the National Comprehensive Cancer Network(NCCN)guidelines(version 2.2017)for CML.Indeed,various studies have confirmed the feasibility of discontinuing TKI therapy.In this study,we analyzed data from 45 CML patients who had discontinued TKI therapy.Univariate analysis was performed to predict factors that were potentially related to treatment-free remission(TFR)and identify the differences between early relapse and late relapse.Out of the 45 patients,20 exhibited molecular relapse after a median follow-up of 18 months(range,1-54 months),and the estimated TFR at 24 months was 40%.The univariate analysis revealed that a high Sokal score and interruptions or dose reductions during TKI treatment were the only baseline factors associated with poor outcomes.Our results indicate that TKI discontinuation could be successfully put into practice in China.
文摘Although the advent of tyrosine kinase inhibitors(TKIs)has dramatically improved the survival of patients with chronic myeloid leukaemia(CML),acquired drug resistance and TKI-insensitive leukaemic stem cells(LSCs)remain major obstacles to a CML cure.In recent years,the reprogramming of mitochondrial metabolism has emerged as a hallmark of cancers,including CML,and in turn may be exploited for therapeutic purposes.Here,we investigated the effects of several drugs on the mitochondrial function of the CML cell line K562 and found that 5-aminoimidazole-4-carboxamide ribotide(AICAR)and decitabine could effectively increase the ATP content and mitochondrial biogenesis.In addition,these two drugs induced cell cycle arrest and a decrease in colony-forming capacity and promoted K562 cell differentiation.Moreover,we demonstrated that treatment with AICAR or decitabine enhanced the sensitivity o f K562 cells to imatinib,as evidenced by a combination treatment assay.Altogether,our findings indicate that TKIs combined with mitochondrial regulation may provide a therapeutic strategy for the treatment of CML.
基金supported by the National Key R&D Program of China (Grant No.2022YFD2202102).
文摘With the benefits of small turning radius and high trafficability, the articulated steering half-track tractor had been widely utilized in orchard and small spaced farmland. To study the dynamic performance of the articulated steering half-track tractor and provide a model basis for studying the path tracking control, an accurate multi-body dynamic model of the tractor was required. In this study, the crucial parameters in the dynamic model construction of the tractor were investigated. Firstly, the topology model of the components of the half-track tractor was built by RecurDyn, in which the movement subs and driver functions were given. Secondly, considering the difference of dynamic characteristic of the articulated steering tractor with respect to different pavement hardnesses, the soft and hard pavement models were constructed by employing the harmonic superposition method. Finally, the simulations of the half-track tractor under straight-line and swerve had been conducted on the two types of pavements, and the simulation results were compared with the experimental and theoretical results. The results indicated that the average speed error of the dynamic model on hard pavement and farmland soft pavement were 2.7% and 2.1% compared with the real tractor tests. At the same time, the straight-line driving offset errors of the dynamic model on the two pavements were 1.6% and 3.8% for the front wheels and the rear wheels offset errors were 3.9% and 2.4%, respectively. Furthermore, the turning radius error under front wheel steering was 8.2% and the error under articulated steering was 5.3%. It is proved that the established dynamic model had high accuracy, which provides an efficient approach to analyze the dynamic features of the half-track tractor.
基金the National Natural Science Foundation of China(Nos.51603029 and 51773028)China Postdoctoral Science Foundation(No.2017M623001)National Postdoctoral Program for Innovative Talents(No.BX201700044).
文摘Low dielectric in terlayer films have become an important element to ensure the development of the microelectr onics industry.A kind of flexible interlayer dielectrics,polyarylene ether nitrile/bisphenol A cyanate ester(PEN/BADCy)film,with good thermal stability and low frequency dependence,has been developed by solution casting method.Herein,materials were designed to incorporate bisphenol A cyanate ester as a part of blend,contributing to the frequency stability and structural integrity.The morphological study combined with electron microscopy revealed the uniform and flexible microstructure information with controllable morphology through self-polymerization of cyanate esters with different prepolymerization time and curing temperatures.The dielectric films could present high thermal stability with Tg>180℃.Significant improvement in the dielectric properties was achieved for the dielectric constant and loss was much stabler than neat PEN over the frequency range from 100 Hz to 5 MHz.When the prepolymerization time was 3h and final curing temperature reached 230℃,the dielectric constant and dielectric loss of the films were 3.36 and 0.013 at 100 kHz,respectively.The dimensional stability(CTE=53.67×10^-6 K^-1)was confirmed and con sidered beneficial to use as an in terlayer dielectrics.
基金the National Natural Science Foundation of China(No.22171029,21901024,21871252,21801024,and 21801026)the Sichuan Science and Technology Program(2021YFS0315)the Talent Program of Chengdu University(2081919035 and 2081921038).
文摘The reaction of 2-pyridylacetates andα,β-unsaturated pyrazolamides with DBU as the catalyst has been developed.A range of unexplored multisubstituted 2,3-dihydro-4H-quinolizin-4-ones are obtained with satisfactory yields(up to 94%)and excellent diastereoselectivities(all cases>20:1 dr)via a dearomative[3+3]annulation process.This practical method also features transition metal free,mild reaction conditions,wide functional group tolerance,easy scale-up synthesis,and versatile further derivatization.