<strong>Objective: </strong>To explore the value of real-time bedside ultrasonography in the etiologic diagnosis of acute dyspnea.<strong> Methods:</strong> Sixty-two patients with acute dyspne...<strong>Objective: </strong>To explore the value of real-time bedside ultrasonography in the etiologic diagnosis of acute dyspnea.<strong> Methods:</strong> Sixty-two patients with acute dyspnea who were treated in our hospital from January 2016 to December 2020 were randomly selected and their clinical data were retrospectively analyzed. All patients were randomly divided into a control group for routine examinations (n = 31) and an observation group for real-time beside ultrasonography (n = 31). The costs of medical examinations, examination duration, and diagnostic results of severe pneumonia, acute cardiogenic pulmonary edema, pulmonary embolism, chronic obstructive pulmonary disease, and pneumothorax (including sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy) of the two groups of patients were compared and analyzed. <strong>Results:</strong> Compared with the control group, the observation group had significantly shorter examinations (P < 0.05). Although the cost of medical examinations of the observation group tended to be higher, the difference between groups was not significant (P > 0.05). Moreover, there were no significant differences in left ventricular ejection fraction, left ventricular end-diastolic diameter, or brain natriuretic peptide between the two groups (P > 0.05). Comparison of the etiologic diagnosis results between the two groups showed that the observation group had significantly higher diagnostic sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy for various causes compared with the control group (P < 0.05). <strong>Conclusion:</strong> Real-time bedside ultrasonography for the etiologic diagnosis of patients with acute dyspnea was quicker and had higher diagnostic accuracy;thus providing accurate guidance for the disease treatment, and having a higher promotional value in clinical practice compared with routine examinations.展开更多
Habitats with different features such as soil depth and soil/rock conditions can provide favorable environments for species with different requirements, while anthropogenic disturbances normally exert additional effec...Habitats with different features such as soil depth and soil/rock conditions can provide favorable environments for species with different requirements, while anthropogenic disturbances normally exert additional effects on species composition. However, specific studies have rarely been conducted in the degraded karst regions of Southwest China despite the high heterogeneity of karst habitats and past human disturbances. In this study, woody species richness and composition on rocky outcrops on a typical karst hillslope were investigated and compared with those of nearby matrices on shallow and rocky soil. Our results showed that matrix vegetation was more diverse in genera and species than vegetation on rocky outcrops. This might relate to the contrasting substrate features and different disturbance histories of these two habitats. Unlike the significant effect of slope on species richness of the matrix vegetation, rocky outcrops exhibited no significant differences between upper and lower slope positions, largely because their microhabitats were similar in different slope positions. Although the study area has been reforested naturally for about 30 years, woody species of the matrix vegetation were still dominated by pioneer shrub species. Rocky outcrops were dominated by late-successional tree species, which was primarily related to their isolated features and resistance to certain disturbances. Most of these late-successional species were not habitat endemics, indicating the possibility for their encroachment into surrounding the matrix. From this aspect, further studies will be necessary to identify and address the limiting factors for the encroachment of these late-successional species into the surrounding environment.展开更多
Background:Old-growth forests are irreplaceable with respect to climate change mitigation and have considerable carbon(C)sink potential in soils.However,the relationship between the soil organic carbon(SOC)turnover ra...Background:Old-growth forests are irreplaceable with respect to climate change mitigation and have considerable carbon(C)sink potential in soils.However,the relationship between the soil organic carbon(SOC)turnover rate and forest development is poorly understood,which hinders our ability to assess the C sequestration capacity of soil in old-growth forests.Methods:In this study,we evaluated the SOC turnover rate by calculating the isotopic enrichment factor β(defined as the slope of the regression between ^(13)C natural abundance and log-transformed C concentrations)along 0-30 cm soil profiles in three successional forests in subtropical China.A lower β(steeper slope)is associated with a higher turnover rate.The three forests were a 60-year-old P.massoniana forest(PF),a 100-year-old coniferous and broadleaved mixed forest(MF),and a 400-year-old monsoon evergreen broadleaved forest(BF).We also analyzed the soil physicochemical properties in these forests to examine the dynamics of SOC turnover during forest succession and the main regulators.Results:The β value for the upper 30-cm soils in the BF was significantly(p<0.05)higher than that in the PF,in addition to the SOC stock,although there were nonsignificant differences between the BF and MF.The β value was significantly(p<0.05)positively correlated with the soil recalcitrance index,total nitrogen,and available nitrogen contents but was significantly(p<0.01)negatively correlated with soil pH.Conclusions:Our results demonstrate that SOC has lower turnover rates in old-growth forests,accompanied by higher soil chemical recalcitrance,nitrogen status,and lower soil pH.This finding helps to elucidate the mechanism underlying C sequestration in old-growth forest soils,and emphasizes the important value of old-growth forests among global C sinks.展开更多
The 4.2 ka event that occurred during the period from 4 500–3 900 a BP was characterized by cold and dry climates and resulted in the collapse of civilizations around the world. The cause of this climatic event, howe...The 4.2 ka event that occurred during the period from 4 500–3 900 a BP was characterized by cold and dry climates and resulted in the collapse of civilizations around the world. The cause of this climatic event, however, has been under debate. We collected four corals(Porites lutea) from Yongxing Island, Xisha Islands, South China Sea, dated them with the U-series method, and measured the annual coral growth rates using X-ray technology. The dating results showed that the coral growth ages were from 4 500–3 900 a BP, which coincide well with the period of the4.2 ka event. We then reconstructed annual sea surface temperature anomaly(SSTA) variations based on the coral growth rates. The growth rate-based SSTA results showed that the interdecadal SSTA from 4 500–3 900 a BP was lower than that during modern times(1961–2008 AD). A spectral analysis showed that the SSTA variations from4 500–3 900 a BP were under the influence of El Nino-Southern Oscillation(ENSO) activities. From 4 500–4 100 a BP, the climate exhibited La Nina-like conditions with weak ENSO intensity and relatively stable and lower SSTA amplitudes. From 4 100–3 900 a BP, the climate underwent a complicated period of ENSO variability and showed alternating El Nino-or La Nina-like conditions at interdecadal time scales and large SSTA amplitudes. We speculate that during the early and middle stages of the 4.2 ka event, the cold climate caused by weak ENSO activities largely weakened social productivity. Then, during the end stages of the 4.2 ka event, the repeated fluctuations in the ENSO intensity caused frequent extreme weather events, resulting in the collapse of civilizations worldwide. Thus, the new evidence obtained from our coral records suggests that the 4.2 ka event as well as the related collapse of civilizations were very likely driven by ENSO variability.展开更多
This study used a novel combination of in vivo and in vitro experiments to show that Braintone had neuroprotective effects and clarified the molecular mechanisms underlying its efficacy. The Chinese herbal extract Bra...This study used a novel combination of in vivo and in vitro experiments to show that Braintone had neuroprotective effects and clarified the molecular mechanisms underlying its efficacy. The Chinese herbal extract Braintone is composed of Radix Rhodiolase Essence, Radix Notoginseng Essence, Folium Ginkgo Essence and Rhizoma Chuanxiong. In vivo experiments showed that cerebral infarction volume was reduced, hemispheric water content decreased, and neurological deficits were alleviated in a rat model of permanent middle cerebral artery occlusion after administration of 87.5, 175 or 350 mg/kg Braintone for 7 consecutive days. Western blot analysis showed that Braintone enhanced the expression of hypoxia-inducible factor 1α, heme oxygenase-1 and vascular endothelial growth factor in the ischemic cortex of these rats. The 350 mg/kg dose of Braintone produced the most dramatic effects. For the in vitro experiments, prior to oxygen-glucose deprivation, rats were intragastrically injected with 440, 880 or 1 760 mg/kg Braintone to prepare a Braintone-containing serum, which was used to pre-treat human umbilical vein endothelial cells for 24 hours. Human umbilical vein endothelial cell injury was alleviated with this pre-treatment. Western blot and real-time PCR analysis showed that the Braintone-containing serum increased the levels of hypoxia-inducible factor 1α mRNA and protein, heme oxygenase-1 protein and vascular endothelial growth factor mRNA in oxygen-glucose deprived human umbilical vein endothelial cells. The 1 760 mg/kg dose produced the greatest increases in expression. Collectively, these experimental findings suggest that Braintone has neuroprotective effects on ischemia-induced brain damage via the up-regulation of hypoxia-inducible factor 1α, heme oxygenase-1 and vascular endothelial growth factor expression in vascular endothelial cells.展开更多
On average,five to six storms occur in the Qiongzhou Strait every year,causing significant damage to coastal geomorphology and several property losses.Tropical Storm Bebinca is the most unusual and complex storm event...On average,five to six storms occur in the Qiongzhou Strait every year,causing significant damage to coastal geomorphology and several property losses.Tropical Storm Bebinca is the most unusual and complex storm event that has occurred in this region over the last 10 years.To detect the high-frequency beachface responses to the storm,a pressure sensor was deployed in the surf zone to record the free sea surface height,and the heights of grid pile points on the beachface were measured manually to determine beach elevation changes during this storm.Empirical Mode Decomposition and related analysis techniques were used to analyze the high-frequency topography and wave data.The results showed that:(1)the beachface response process occurred in three stages.The first stage was the rapid response stage,wherein the spring tide berm began to erode significantly,and the front edge of the beach berm reacted closely.The two beach sections resisted the harmful energy of the main storm.In the second stage,the beach slope increased after a large sediment loss on the beach berm and its front edge.To adapt to the storm energy,the beach at the low tide line began to erode,and the beach slope decreased.In the third stage,after the storm turned,the wave energy was significantly attenuated,and the beach berm eroded to resist the residual wave energy.The beachface began to oscillate and recover.(2)The main wave surface was the superimposed product of a few internal mode functions.Similar results were observed in beachface changes.High-frequency driving factors determine the local characteristics of beach evolution,and low-frequency driving factors determine the beach evolution trend.(3)The response of sediment to the storm was not a single sea-transportation,but a single-or two-way conversion driven by factors such as wave energy,swash flow,and secondary wave breaking.(4)TheΩ-RTR model is not completely applicable to beach states that undergo rapid changes during storms.Therefore,it is necessary to carry out further research on beach state identification during storms.展开更多
In order to reveal the intrinsic fluid-dynamic mechanisms of a pressure-swirl nozzle used for Si3N4 dry granulation,and effectively predict its external spray characteristics,the dynamics of air-atomized liquid two-p...In order to reveal the intrinsic fluid-dynamic mechanisms of a pressure-swirl nozzle used for Si3N4 dry granulation,and effectively predict its external spray characteristics,the dynamics of air-atomized liquid two-phase flow is analyzed using a VOF(Volume of Fraction)method together with the modified realizable k-εturbulence model.The influence of nozzle orifice shape on velocity distribution,pressure distribution is studied.The results show that the pressure difference in a convergent conical nozzle is the largest with a hollow air core being formed in the nozzle.The corresponding velocity of atomized liquid at nozzle orifice is the largest.Using a self-designed atomization experiment platform,the velocity and pressure of atomized liquid and the spray cone angle are measured for three nozzles with different orifice shapes.The micro-morphology of Si3N4 particles is also determined.These data confirm the correctness of numerical simulation.Considering atomization performance of the nozzle,the contraction conical nozzle is more suitable for the atomization of Si3N4 in practical production based on the dry granulation approach.展开更多
Ananas comosus var.bracteatus is an important ornamental plant because of its green/white chimeric leaves.The accumulation of anthocyanin makes the leaf turn to red especially in the marginal part.However,the red fade...Ananas comosus var.bracteatus is an important ornamental plant because of its green/white chimeric leaves.The accumulation of anthocyanin makes the leaf turn to red especially in the marginal part.However,the red fades away in summer and winter.Light intensity is one of the most important factors affecting leaf color along the seasons.In order to understand the effects of light intensity on the growth and coloration of the chimeric leaves,Ananas comosus var.bracteatus was grown under full sunlight,50%shade and 75%shade for 75 days to evaluate the concentration of pigments,the color parameters(values L^(*),a^(*),b^(*))and the morpho-anatomical variations of chimeric leaves.The results showed that a high irradiance was beneficial to keep the chimeric leaves red.However,prolonged exposure to high irradiance caused a damage,some of the leaves wrinkled and even burned.Shading instead decreased the concentration of anthocyanin and increased the concentration of chlorophyll,especially in the white marginal part of the leaves.Numerous chloroplasts were observed in the mesophyll cells of the white marginal part of the chimeric leaves under shading for 75 days.The increase in chlorophyll concentration resulted in a better growth of plants.In order to balance the growth and coloration of the leaves,approximately 50%shade is suggested to be the optimum light irradiance condition for Ananas comosus var.bracteatus in summer.展开更多
Map Reduce is a programming model for processing large data sets,and Hadoop is the most popular open-source implementation of MapReduce.To achieve high performance,up to 190 Hadoop configuration parameters must be man...Map Reduce is a programming model for processing large data sets,and Hadoop is the most popular open-source implementation of MapReduce.To achieve high performance,up to 190 Hadoop configuration parameters must be manually tunned.This is not only time-consuming but also error-pron.In this paper,we propose a new performance model based on random forest,a recently developed machine-learning algorithm.The model,called RFMS,is used to predict the performance of a Hadoop system according to the system's configuration parameters.RFMS is created from 2000 distinct fine-grained performance observations with different Hadoop configurations.We test RFMS against the measured performance of representative workloads from the Hadoop Micro-benchmark suite.The results show that the prediction accuracy of RFMS achieves 95% on average and up to 99%.This new,highly accurate prediction model can be used to automatically optimize the performance of Hadoop systems.展开更多
AIDS is a chronic infectious disease caused by human immunodeficiency virus.Due to the infectiousness of AIDS and the lack of specific drugs to treat AIDS,the majority of people still have the psychology of rejection ...AIDS is a chronic infectious disease caused by human immunodeficiency virus.Due to the infectiousness of AIDS and the lack of specific drugs to treat AIDS,the majority of people still have the psychology of rejection and discrimination against AIDS patients.Under the influence of various factors such as themselves,families and the public,AIDS patients are prone to be negative,inferior and even world-weary.Among them,the mental health status of adolescent AIDS patients is even less optimistic due to their unique psychological characteristics.The living conditions and mental health of this particular group deserve social attention;Psychological nursing is an important way to promote the mental health of adolescent patients.Improving the long-term psychological coping ability of young AIDS patients is beneficial to their own health,family stability and social harmony.This paper studies the current situation of psychological care for AIDS patients in adolescents,analyzes its importance and puts forward some suggestions.展开更多
Objectives To study the depressive effect of the antisense oligonuceotides (ASODN) of c-myc and proliferating cell nuclear antigen (PCNA) on the proliferation of VSMC. Methods Taking the VSMC obtained from rat aorta t...Objectives To study the depressive effect of the antisense oligonuceotides (ASODN) of c-myc and proliferating cell nuclear antigen (PCNA) on the proliferation of VSMC. Methods Taking the VSMC obtained from rat aorta thoracalis cultured 4～8 generation as research object. The objects were divided into three groups to carry out control study: control group, PCNA ASODN group and c-myc ASODN group. The ASODNs' working concentration all were 1:50. The depressive effect of ASODN on VSMC proliferation was investigated by cell counting, MTT and 3H-TdR incorporation assay; PCNA and c-myc expression were detected by immunohistochemical method after transferring PCNA and c-myc ASODN into VSMC. Results PCNA and c-myc ASODN could inhibit the proliferation of VSMC significantly, compared with control group (P<0.05). ② Transferring PCNA and c-myc ASODN into VSMC obtained successfully; the corresponding gene was inhibited obviously; compared with control group (P<0.05). Conclusions PCNA and c-myc might play a considerable role in the VSMC proliferation process. The corresponding gene could be depressed successfully after transferring PCNA and c-myc ASODN into VSMC, and then the proliferation of VSMC was slowed down. This study presented a beneficial proposal and theoretical fundament for atherosclerotic treatment.展开更多
AIDS is spreading faster and faster in China.Strengthening health education is an important way to prevent the spread of AIDS,and is also the main means to control the growth of AIDS population.From the current situat...AIDS is spreading faster and faster in China.Strengthening health education is an important way to prevent the spread of AIDS,and is also the main means to control the growth of AIDS population.From the current situation of health education on prevention and treatment of AIDS among adolescents,there are still many problems,which is also the main reason for the increase of AIDS infected young students year by year.Therefore,it is necessary to formulate corresponding solutions to the problems existing in the current health education on AIDS prevention and control among adolescents,so as to further improve the effectiveness of AIDS prevention and control education for adolescents,strengthen the health education for adolescents,and reduce the HIV infection rate of adolescents.展开更多
In this work,Eu^(3+)-doped CsPbCl_(2)Br_(1) in borosilicate glass was successfully synthesized by the melt quenching annealing technique and crystallization method.This work reports a novel Eu^(3+)-doped CsPbCl_(2)Br_...In this work,Eu^(3+)-doped CsPbCl_(2)Br_(1) in borosilicate glass was successfully synthesized by the melt quenching annealing technique and crystallization method.This work reports a novel Eu^(3+)-doped CsPbCl_(2)Br_(1) perovskite quantum dots(QDs)glass with high sensitivity for optical temperature sensing.The relation of fluorescence intensity ratio(FIR)with the temperature was studied in the temperature range of 80-440 K.Notably,the maximum absolute temperature sensitivity(Sa)and relative temperature sensitivity(Sr)of Eu^(3+)-doped CsPbCl_(2)Br_(1) perovskite QDs glass can reach as high as 0.0315 K-1 and3.097%/K,respectively.Meanwhile,Eu^(3+)-doped CsPbCl_(2)Br_(1) QDs glass demonstrates good water resistance,excellent thermal and cold cycling stability performance,The Eu^(3+)-doped QDs glass materials can bring inspiration to the future exploration of rare earth ion-doped QDs glass material on the application of optical temperature sensing in the future.展开更多
Simultaneous and continuous measurements of visibility, meteorological parameters and air pollutants were carried out at a suburban site in Ningbo from June 1, 2013 to May 31,2015. The characteristics of visibility an...Simultaneous and continuous measurements of visibility, meteorological parameters and air pollutants were carried out at a suburban site in Ningbo from June 1, 2013 to May 31,2015. The characteristics of visibility and their relationships with air pollutants and meteorological factors were investigated using multiple statistical methods. Daily visibility ranged from 0.6 to 34.1 km, with a mean value of 11.8 km. During the 2-year experiment,43.4% of daily visibility was found to be less than 10.0 km and only 9.2% was greater than 20.0 km. Visibility was lower in winter with a frequency of 53.4% in the range of 0.0–5.0 km.Annual visibility had an obvious diurnal variation, with the lowest and highest visibility being 7.5 km at approximately 06:00 local time and 15.6 km at approximately 14:00 local time, respectively. Multiple correspondence analysis(MCA) indicated that the different ranges of visibility were significantly affected by different levels of pollutants and meteorological conditions. Based on the analyses, visibility was found to be an exponential function of PM_(2.5) concentrations within a certain range of relative humidity. Thus, nonlinear models combining multiple linear regressions with exponential regression were subsequently developed using the data collected from June 2014 to May 2015, and the data from June 2013 to May 2014 was used to evaluate the performance of the model. It was demonstrated that the derived models can quantitatively describe the relationships between visibility, air quality and meteorological parameters in Ningbo.展开更多
Sequence-based protein tertiary structure prediction is of fundamental importance because the function of a protein ultimately depends on its 3 D structure.An accurate residue-residue contact map is one of the essenti...Sequence-based protein tertiary structure prediction is of fundamental importance because the function of a protein ultimately depends on its 3 D structure.An accurate residue-residue contact map is one of the essential elements for current ab initio prediction protocols of 3 D structure prediction.Recently,with the combination of deep learning and direct coupling techniques,the performance of residue contact prediction has achieved significant progress.However,a considerable number of current Deep-Learning(DL)-based prediction methods are usually time-consuming,mainly because they rely on different categories of data types and third-party programs.In this research,we transformed the complex biological problem into a pure computational problem through statistics and artificial intelligence.We have accordingly proposed a feature extraction method to obtain various categories of statistical information from only the multi-sequence alignment,followed by training a DL model for residue-residue contact prediction based on the massive statistical information.The proposed method is robust in terms of different test sets,showed high reliability on model confidence score,could obtain high computational efficiency and achieve comparable prediction precisions with DL methods that relying on multi-source inputs.展开更多
To improve the uniformity of the flow field and the poor axial velocity in the chamber of Si3N4 dry granulation, the influence of geometric parameters at open turbinecombined structure on the flow field distribution ...To improve the uniformity of the flow field and the poor axial velocity in the chamber of Si3N4 dry granulation, the influence of geometric parameters at open turbinecombined structure on the flow field distribution is studied. The Euler–Euler gas-solidtwo-phase flow model is established and the physical model of dry granulation chamberunder the combined structure is simplified. Under the same radial structure, the volumedistribution and velocity field of Si3N4 particles in the granulation chamber with a different number and angle of the axial structure at the open turbine are analyzed by theCFD method. The influence of the axial structure at the open turbine on the flow fielddistribution of Si3N4 particles under different geometric parameters is compared. Theresults show that the axial structure of the open turbine in the granulation chamber isthe most uniform when the number of blades is 6 and the inclination angle is 45◦, andthe circulating flow of the upper and lower parts of Si3N4 powder is strong.展开更多
文摘<strong>Objective: </strong>To explore the value of real-time bedside ultrasonography in the etiologic diagnosis of acute dyspnea.<strong> Methods:</strong> Sixty-two patients with acute dyspnea who were treated in our hospital from January 2016 to December 2020 were randomly selected and their clinical data were retrospectively analyzed. All patients were randomly divided into a control group for routine examinations (n = 31) and an observation group for real-time beside ultrasonography (n = 31). The costs of medical examinations, examination duration, and diagnostic results of severe pneumonia, acute cardiogenic pulmonary edema, pulmonary embolism, chronic obstructive pulmonary disease, and pneumothorax (including sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy) of the two groups of patients were compared and analyzed. <strong>Results:</strong> Compared with the control group, the observation group had significantly shorter examinations (P < 0.05). Although the cost of medical examinations of the observation group tended to be higher, the difference between groups was not significant (P > 0.05). Moreover, there were no significant differences in left ventricular ejection fraction, left ventricular end-diastolic diameter, or brain natriuretic peptide between the two groups (P > 0.05). Comparison of the etiologic diagnosis results between the two groups showed that the observation group had significantly higher diagnostic sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy for various causes compared with the control group (P < 0.05). <strong>Conclusion:</strong> Real-time bedside ultrasonography for the etiologic diagnosis of patients with acute dyspnea was quicker and had higher diagnostic accuracy;thus providing accurate guidance for the disease treatment, and having a higher promotional value in clinical practice compared with routine examinations.
基金supported by the National Key Research and Development Program of China(2016YFC0502402)the National Natural Science Foundation of China(31570428)+1 种基金the Young Scholars of Western China,Chinese Academy of Sciences(for Y.N.)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2018397)
文摘Habitats with different features such as soil depth and soil/rock conditions can provide favorable environments for species with different requirements, while anthropogenic disturbances normally exert additional effects on species composition. However, specific studies have rarely been conducted in the degraded karst regions of Southwest China despite the high heterogeneity of karst habitats and past human disturbances. In this study, woody species richness and composition on rocky outcrops on a typical karst hillslope were investigated and compared with those of nearby matrices on shallow and rocky soil. Our results showed that matrix vegetation was more diverse in genera and species than vegetation on rocky outcrops. This might relate to the contrasting substrate features and different disturbance histories of these two habitats. Unlike the significant effect of slope on species richness of the matrix vegetation, rocky outcrops exhibited no significant differences between upper and lower slope positions, largely because their microhabitats were similar in different slope positions. Although the study area has been reforested naturally for about 30 years, woody species of the matrix vegetation were still dominated by pioneer shrub species. Rocky outcrops were dominated by late-successional tree species, which was primarily related to their isolated features and resistance to certain disturbances. Most of these late-successional species were not habitat endemics, indicating the possibility for their encroachment into surrounding the matrix. From this aspect, further studies will be necessary to identify and address the limiting factors for the encroachment of these late-successional species into the surrounding environment.
基金jointly supported by the China Postdoctoral Science Foundation(No.2020 M682951)the National Natural Science Foundation of China(No.NSFC41773088)the Key Research Program of the Chinese Academy of Sciences(No.QYZDJ-SSW-DQC003).
文摘Background:Old-growth forests are irreplaceable with respect to climate change mitigation and have considerable carbon(C)sink potential in soils.However,the relationship between the soil organic carbon(SOC)turnover rate and forest development is poorly understood,which hinders our ability to assess the C sequestration capacity of soil in old-growth forests.Methods:In this study,we evaluated the SOC turnover rate by calculating the isotopic enrichment factor β(defined as the slope of the regression between ^(13)C natural abundance and log-transformed C concentrations)along 0-30 cm soil profiles in three successional forests in subtropical China.A lower β(steeper slope)is associated with a higher turnover rate.The three forests were a 60-year-old P.massoniana forest(PF),a 100-year-old coniferous and broadleaved mixed forest(MF),and a 400-year-old monsoon evergreen broadleaved forest(BF).We also analyzed the soil physicochemical properties in these forests to examine the dynamics of SOC turnover during forest succession and the main regulators.Results:The β value for the upper 30-cm soils in the BF was significantly(p<0.05)higher than that in the PF,in addition to the SOC stock,although there were nonsignificant differences between the BF and MF.The β value was significantly(p<0.05)positively correlated with the soil recalcitrance index,total nitrogen,and available nitrogen contents but was significantly(p<0.01)negatively correlated with soil pH.Conclusions:Our results demonstrate that SOC has lower turnover rates in old-growth forests,accompanied by higher soil chemical recalcitrance,nitrogen status,and lower soil pH.This finding helps to elucidate the mechanism underlying C sequestration in old-growth forest soils,and emphasizes the important value of old-growth forests among global C sinks.
基金The National Natural Science Foundation of China under contract No.91428203the Guangxi Scientific Projects under contract Nos AD17129063 and AA17204074the Bagui Fellowship from Guangxi of China
文摘The 4.2 ka event that occurred during the period from 4 500–3 900 a BP was characterized by cold and dry climates and resulted in the collapse of civilizations around the world. The cause of this climatic event, however, has been under debate. We collected four corals(Porites lutea) from Yongxing Island, Xisha Islands, South China Sea, dated them with the U-series method, and measured the annual coral growth rates using X-ray technology. The dating results showed that the coral growth ages were from 4 500–3 900 a BP, which coincide well with the period of the4.2 ka event. We then reconstructed annual sea surface temperature anomaly(SSTA) variations based on the coral growth rates. The growth rate-based SSTA results showed that the interdecadal SSTA from 4 500–3 900 a BP was lower than that during modern times(1961–2008 AD). A spectral analysis showed that the SSTA variations from4 500–3 900 a BP were under the influence of El Nino-Southern Oscillation(ENSO) activities. From 4 500–4 100 a BP, the climate exhibited La Nina-like conditions with weak ENSO intensity and relatively stable and lower SSTA amplitudes. From 4 100–3 900 a BP, the climate underwent a complicated period of ENSO variability and showed alternating El Nino-or La Nina-like conditions at interdecadal time scales and large SSTA amplitudes. We speculate that during the early and middle stages of the 4.2 ka event, the cold climate caused by weak ENSO activities largely weakened social productivity. Then, during the end stages of the 4.2 ka event, the repeated fluctuations in the ENSO intensity caused frequent extreme weather events, resulting in the collapse of civilizations worldwide. Thus, the new evidence obtained from our coral records suggests that the 4.2 ka event as well as the related collapse of civilizations were very likely driven by ENSO variability.
基金supported by grants from the National Natural Science Foundation of China, No.30973510Scientific Research Foundation for Returned Overseas Chinese Scholars, State Education Ministry, No. K513400110a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘This study used a novel combination of in vivo and in vitro experiments to show that Braintone had neuroprotective effects and clarified the molecular mechanisms underlying its efficacy. The Chinese herbal extract Braintone is composed of Radix Rhodiolase Essence, Radix Notoginseng Essence, Folium Ginkgo Essence and Rhizoma Chuanxiong. In vivo experiments showed that cerebral infarction volume was reduced, hemispheric water content decreased, and neurological deficits were alleviated in a rat model of permanent middle cerebral artery occlusion after administration of 87.5, 175 or 350 mg/kg Braintone for 7 consecutive days. Western blot analysis showed that Braintone enhanced the expression of hypoxia-inducible factor 1α, heme oxygenase-1 and vascular endothelial growth factor in the ischemic cortex of these rats. The 350 mg/kg dose of Braintone produced the most dramatic effects. For the in vitro experiments, prior to oxygen-glucose deprivation, rats were intragastrically injected with 440, 880 or 1 760 mg/kg Braintone to prepare a Braintone-containing serum, which was used to pre-treat human umbilical vein endothelial cells for 24 hours. Human umbilical vein endothelial cell injury was alleviated with this pre-treatment. Western blot and real-time PCR analysis showed that the Braintone-containing serum increased the levels of hypoxia-inducible factor 1α mRNA and protein, heme oxygenase-1 protein and vascular endothelial growth factor mRNA in oxygen-glucose deprived human umbilical vein endothelial cells. The 1 760 mg/kg dose produced the greatest increases in expression. Collectively, these experimental findings suggest that Braintone has neuroprotective effects on ischemia-induced brain damage via the up-regulation of hypoxia-inducible factor 1α, heme oxygenase-1 and vascular endothelial growth factor expression in vascular endothelial cells.
基金The National Natural Science Foundation of China under contract Nos 42176167 and 41676079the Project of Enhancing School with Innovation,Guangdong Ocean University under contract No.Q18307.
文摘On average,five to six storms occur in the Qiongzhou Strait every year,causing significant damage to coastal geomorphology and several property losses.Tropical Storm Bebinca is the most unusual and complex storm event that has occurred in this region over the last 10 years.To detect the high-frequency beachface responses to the storm,a pressure sensor was deployed in the surf zone to record the free sea surface height,and the heights of grid pile points on the beachface were measured manually to determine beach elevation changes during this storm.Empirical Mode Decomposition and related analysis techniques were used to analyze the high-frequency topography and wave data.The results showed that:(1)the beachface response process occurred in three stages.The first stage was the rapid response stage,wherein the spring tide berm began to erode significantly,and the front edge of the beach berm reacted closely.The two beach sections resisted the harmful energy of the main storm.In the second stage,the beach slope increased after a large sediment loss on the beach berm and its front edge.To adapt to the storm energy,the beach at the low tide line began to erode,and the beach slope decreased.In the third stage,after the storm turned,the wave energy was significantly attenuated,and the beach berm eroded to resist the residual wave energy.The beachface began to oscillate and recover.(2)The main wave surface was the superimposed product of a few internal mode functions.Similar results were observed in beachface changes.High-frequency driving factors determine the local characteristics of beach evolution,and low-frequency driving factors determine the beach evolution trend.(3)The response of sediment to the storm was not a single sea-transportation,but a single-or two-way conversion driven by factors such as wave energy,swash flow,and secondary wave breaking.(4)TheΩ-RTR model is not completely applicable to beach states that undergo rapid changes during storms.Therefore,it is necessary to carry out further research on beach state identification during storms.
基金the National Natural Science Foundation of China(Grant:51964022).
文摘In order to reveal the intrinsic fluid-dynamic mechanisms of a pressure-swirl nozzle used for Si3N4 dry granulation,and effectively predict its external spray characteristics,the dynamics of air-atomized liquid two-phase flow is analyzed using a VOF(Volume of Fraction)method together with the modified realizable k-εturbulence model.The influence of nozzle orifice shape on velocity distribution,pressure distribution is studied.The results show that the pressure difference in a convergent conical nozzle is the largest with a hollow air core being formed in the nozzle.The corresponding velocity of atomized liquid at nozzle orifice is the largest.Using a self-designed atomization experiment platform,the velocity and pressure of atomized liquid and the spray cone angle are measured for three nozzles with different orifice shapes.The micro-morphology of Si3N4 particles is also determined.These data confirm the correctness of numerical simulation.Considering atomization performance of the nozzle,the contraction conical nozzle is more suitable for the atomization of Si3N4 in practical production based on the dry granulation approach.
基金This work was funded by the National Natural Science Foundation of China(Grant Nos.31971704,31770743).
文摘Ananas comosus var.bracteatus is an important ornamental plant because of its green/white chimeric leaves.The accumulation of anthocyanin makes the leaf turn to red especially in the marginal part.However,the red fades away in summer and winter.Light intensity is one of the most important factors affecting leaf color along the seasons.In order to understand the effects of light intensity on the growth and coloration of the chimeric leaves,Ananas comosus var.bracteatus was grown under full sunlight,50%shade and 75%shade for 75 days to evaluate the concentration of pigments,the color parameters(values L^(*),a^(*),b^(*))and the morpho-anatomical variations of chimeric leaves.The results showed that a high irradiance was beneficial to keep the chimeric leaves red.However,prolonged exposure to high irradiance caused a damage,some of the leaves wrinkled and even burned.Shading instead decreased the concentration of anthocyanin and increased the concentration of chlorophyll,especially in the white marginal part of the leaves.Numerous chloroplasts were observed in the mesophyll cells of the white marginal part of the chimeric leaves under shading for 75 days.The increase in chlorophyll concentration resulted in a better growth of plants.In order to balance the growth and coloration of the leaves,approximately 50%shade is suggested to be the optimum light irradiance condition for Ananas comosus var.bracteatus in summer.
基金supported by the cooperation project of Research on Green Cloud IDC Resource Scheduling with ZTE Corporation
文摘Map Reduce is a programming model for processing large data sets,and Hadoop is the most popular open-source implementation of MapReduce.To achieve high performance,up to 190 Hadoop configuration parameters must be manually tunned.This is not only time-consuming but also error-pron.In this paper,we propose a new performance model based on random forest,a recently developed machine-learning algorithm.The model,called RFMS,is used to predict the performance of a Hadoop system according to the system's configuration parameters.RFMS is created from 2000 distinct fine-grained performance observations with different Hadoop configurations.We test RFMS against the measured performance of representative workloads from the Hadoop Micro-benchmark suite.The results show that the prediction accuracy of RFMS achieves 95% on average and up to 99%.This new,highly accurate prediction model can be used to automatically optimize the performance of Hadoop systems.
文摘AIDS is a chronic infectious disease caused by human immunodeficiency virus.Due to the infectiousness of AIDS and the lack of specific drugs to treat AIDS,the majority of people still have the psychology of rejection and discrimination against AIDS patients.Under the influence of various factors such as themselves,families and the public,AIDS patients are prone to be negative,inferior and even world-weary.Among them,the mental health status of adolescent AIDS patients is even less optimistic due to their unique psychological characteristics.The living conditions and mental health of this particular group deserve social attention;Psychological nursing is an important way to promote the mental health of adolescent patients.Improving the long-term psychological coping ability of young AIDS patients is beneficial to their own health,family stability and social harmony.This paper studies the current situation of psychological care for AIDS patients in adolescents,analyzes its importance and puts forward some suggestions.
文摘Objectives To study the depressive effect of the antisense oligonuceotides (ASODN) of c-myc and proliferating cell nuclear antigen (PCNA) on the proliferation of VSMC. Methods Taking the VSMC obtained from rat aorta thoracalis cultured 4～8 generation as research object. The objects were divided into three groups to carry out control study: control group, PCNA ASODN group and c-myc ASODN group. The ASODNs' working concentration all were 1:50. The depressive effect of ASODN on VSMC proliferation was investigated by cell counting, MTT and 3H-TdR incorporation assay; PCNA and c-myc expression were detected by immunohistochemical method after transferring PCNA and c-myc ASODN into VSMC. Results PCNA and c-myc ASODN could inhibit the proliferation of VSMC significantly, compared with control group (P<0.05). ② Transferring PCNA and c-myc ASODN into VSMC obtained successfully; the corresponding gene was inhibited obviously; compared with control group (P<0.05). Conclusions PCNA and c-myc might play a considerable role in the VSMC proliferation process. The corresponding gene could be depressed successfully after transferring PCNA and c-myc ASODN into VSMC, and then the proliferation of VSMC was slowed down. This study presented a beneficial proposal and theoretical fundament for atherosclerotic treatment.
文摘AIDS is spreading faster and faster in China.Strengthening health education is an important way to prevent the spread of AIDS,and is also the main means to control the growth of AIDS population.From the current situation of health education on prevention and treatment of AIDS among adolescents,there are still many problems,which is also the main reason for the increase of AIDS infected young students year by year.Therefore,it is necessary to formulate corresponding solutions to the problems existing in the current health education on AIDS prevention and control among adolescents,so as to further improve the effectiveness of AIDS prevention and control education for adolescents,strengthen the health education for adolescents,and reduce the HIV infection rate of adolescents.
基金Project supported by the National Natural Science Foundation of China(51872207,51672192)。
文摘In this work,Eu^(3+)-doped CsPbCl_(2)Br_(1) in borosilicate glass was successfully synthesized by the melt quenching annealing technique and crystallization method.This work reports a novel Eu^(3+)-doped CsPbCl_(2)Br_(1) perovskite quantum dots(QDs)glass with high sensitivity for optical temperature sensing.The relation of fluorescence intensity ratio(FIR)with the temperature was studied in the temperature range of 80-440 K.Notably,the maximum absolute temperature sensitivity(Sa)and relative temperature sensitivity(Sr)of Eu^(3+)-doped CsPbCl_(2)Br_(1) perovskite QDs glass can reach as high as 0.0315 K-1 and3.097%/K,respectively.Meanwhile,Eu^(3+)-doped CsPbCl_(2)Br_(1) QDs glass demonstrates good water resistance,excellent thermal and cold cycling stability performance,The Eu^(3+)-doped QDs glass materials can bring inspiration to the future exploration of rare earth ion-doped QDs glass material on the application of optical temperature sensing in the future.
基金supported by the National Natural Science Foundation of China(No.31300435,U1405235)Science and Technology Plan Project of Ningbo City(No.2015C110001)+1 种基金Natural Science Foundation of Ningbo City(No.2015A610247)Knowledge Innovation Program of the Chinese Academy of Sciences(No.IUEQN-2012-03)
文摘Simultaneous and continuous measurements of visibility, meteorological parameters and air pollutants were carried out at a suburban site in Ningbo from June 1, 2013 to May 31,2015. The characteristics of visibility and their relationships with air pollutants and meteorological factors were investigated using multiple statistical methods. Daily visibility ranged from 0.6 to 34.1 km, with a mean value of 11.8 km. During the 2-year experiment,43.4% of daily visibility was found to be less than 10.0 km and only 9.2% was greater than 20.0 km. Visibility was lower in winter with a frequency of 53.4% in the range of 0.0–5.0 km.Annual visibility had an obvious diurnal variation, with the lowest and highest visibility being 7.5 km at approximately 06:00 local time and 15.6 km at approximately 14:00 local time, respectively. Multiple correspondence analysis(MCA) indicated that the different ranges of visibility were significantly affected by different levels of pollutants and meteorological conditions. Based on the analyses, visibility was found to be an exponential function of PM_(2.5) concentrations within a certain range of relative humidity. Thus, nonlinear models combining multiple linear regressions with exponential regression were subsequently developed using the data collected from June 2014 to May 2015, and the data from June 2013 to May 2014 was used to evaluate the performance of the model. It was demonstrated that the derived models can quantitatively describe the relationships between visibility, air quality and meteorological parameters in Ningbo.
基金supported by the Strategic Priority CAS Project (No. XDB38050100)the National Key Research and Development Program of China (No. 2018YFB0204403)+4 种基金the National Natural Science Foundation of China (No. U1813203)the Shenzhen Basic Research Fund (Nos. RCYX2020071411473419,JCYJ20200109114818703,and JSGG20201102163800001)CAS Key Lab (No. 2011DP173015)Hong Kong Research Grant Council (No. GRF-17208019)the Outstanding Youth Innovation Fund (Doctoral Students) of CAS-SIAT (No. Y9G054)。
文摘Sequence-based protein tertiary structure prediction is of fundamental importance because the function of a protein ultimately depends on its 3 D structure.An accurate residue-residue contact map is one of the essential elements for current ab initio prediction protocols of 3 D structure prediction.Recently,with the combination of deep learning and direct coupling techniques,the performance of residue contact prediction has achieved significant progress.However,a considerable number of current Deep-Learning(DL)-based prediction methods are usually time-consuming,mainly because they rely on different categories of data types and third-party programs.In this research,we transformed the complex biological problem into a pure computational problem through statistics and artificial intelligence.We have accordingly proposed a feature extraction method to obtain various categories of statistical information from only the multi-sequence alignment,followed by training a DL model for residue-residue contact prediction based on the massive statistical information.The proposed method is robust in terms of different test sets,showed high reliability on model confidence score,could obtain high computational efficiency and achieve comparable prediction precisions with DL methods that relying on multi-source inputs.
文摘To improve the uniformity of the flow field and the poor axial velocity in the chamber of Si3N4 dry granulation, the influence of geometric parameters at open turbinecombined structure on the flow field distribution is studied. The Euler–Euler gas-solidtwo-phase flow model is established and the physical model of dry granulation chamberunder the combined structure is simplified. Under the same radial structure, the volumedistribution and velocity field of Si3N4 particles in the granulation chamber with a different number and angle of the axial structure at the open turbine are analyzed by theCFD method. The influence of the axial structure at the open turbine on the flow fielddistribution of Si3N4 particles under different geometric parameters is compared. Theresults show that the axial structure of the open turbine in the granulation chamber isthe most uniform when the number of blades is 6 and the inclination angle is 45◦, andthe circulating flow of the upper and lower parts of Si3N4 powder is strong.
