Aims In ecology and conservation biology,the number of species counted in a biodiversity study is a key metric but is usually a biased underestimate of total species richness because many rare species are not detected...Aims In ecology and conservation biology,the number of species counted in a biodiversity study is a key metric but is usually a biased underestimate of total species richness because many rare species are not detected.Moreover,comparing species richness among sites or samples is a statistical challenge because the observed number of species is sensitive to the number of individuals counted or the area sampled.For individual-based data,we treat a single,empirical sample of species abundances from an investigator-defined species assemblage or community as a reference point for two estimation objectives under two sampling models:estimating the expected number of species(and its unconditional variance)in a random sample of(i)a smaller number of individuals(multinomial model)or a smaller area sampled(Poisson model)and(ii)a larger number of individuals or a larger area sampled.For sample-based incidence(presence–absence)data,under a Bernoulli product model,we treat a single set of species incidence frequencies as the reference point to estimate richness for smaller and larger numbers of sampling units.Methods The first objective is a problem in interpolation that we address with classical rarefaction(multinomial model)and Coleman rarefaction(Poisson model)for individual-based data and with sample-based rarefaction(Bernoulli product model)for incidence frequencies.The second is a problem in extrapolation that we address with sampling-theoretic predictors for the number of species in a larger sample(multinomial model),a larger area(Poisson model)or a larger number of sampling units(Bernoulli product model),based on an estimate of asymptotic species richness.Although published methods exist for many of these objectives,we bring them together here with some new estimators under a unified statistical and notational framework.This novel integration of mathematically distinct approaches allowed us to link interpolated(rarefaction)curves and extrapolated curves to plot a unified species accumulation curve for empirical examp展开更多
Background： Sacroiliac （SI） screw fixation is a demanding technique, with a high rate of screw malposition due to the complex pelvic anatomy. TiRobot- is an orthopedic surgery robot which can be used for SI screw f...Background： Sacroiliac （SI） screw fixation is a demanding technique, with a high rate of screw malposition due to the complex pelvic anatomy. TiRobot- is an orthopedic surgery robot which can be used for SI screw fixation. This study aimed to evaluate the accuracy of robot-assisted placement of SI screws compared with a freehand technique. Methods：Thirty patients requiring posterior pelvic ring stabilization were randomized to receive freehand or robot-assisted SI screw fixation, between January 2016 and June 2016 at Beijing Jishuitan Hospital. Forty-five screws were placed at levels S1 and S2. In both methods, the primary end point screw position was assessed and classified using postoperative computed tomography. Fisher＇s exact probability test was used to analyze the screws＇positions. Secondary end points, such as duration of trajectory planning, surgical time after reduction of the pelvis, insertion time for guide wire, number of guide wire attempts, and radiation exposure without pelvic reduction, were also assessed. Results： Twenty-three screws were placed in the robot-assisted group and 22 screws in the freehand group; no postoperative complications or revisions were reported. The excellent and good rate of screw placement was 100% in the robot-assisted group and 95% in the freehand group. The P value （0.009） showed the same superiority in screw distribution. The fluoroscopy time after pelvic reduction in the robot-assisted group was significantly shorter than that in the freehand group （median [Q1, Q3]： 6.0 [6.0, 9.0] s vs. median [Q1, Q3]： 36.0 [21.5, 48.0] s; χ2 = 13.590, respectively, P 〈 0.001）; no difference in operation time after reduction of the pelvis was noted （χ2 = 1.990, P = 0.158）. Time for guide wire insertion was significantly shorter for the robot-assisted group than that for the freehand group （median [Q1, Q3]： 2.0 [2.0, 2.7] min vs. median [Q1, Q3]： 19.0 [15.5, 45.0] min; χ2 = 20.952, respectively, P 〈 0.001）. The number of guide wire attempts展开更多
AIM To assess the effect of polyglycolic acid(PGA) plus stent placement compared with stent placement alone in the prevention of post-endoscopic submucosal dissection(ESD) esophageal stricture in early-stage esophagea...AIM To assess the effect of polyglycolic acid(PGA) plus stent placement compared with stent placement alone in the prevention of post-endoscopic submucosal dissection(ESD) esophageal stricture in early-stage esophageal cancer(EC) patients. METHODS Seventy EC patients undergoing ESD were enrolled in this randomized, controlled study. Patients were allocated randomly at a 1:1 ratio into two groups as follows:(1) PGA plus stent group(PGA sheet-coated stent placement was performed); and(2) Stent group(only stent placement was performed). This study was registered on http://www.chictr.org.cn(No. chictrinr-16008709). RESULTS The occurrence rate of esophageal stricture in the PGA plus stent group was 20.5%(n = 7), which was lower than that in the stent group(46.9%, n = 15)(P = 0.024). The mean value of esophageal stricture time was 59.6 ± 16.1 d and 70.7 ± 28.6 d in the PGA plus stent group and stent group(P = 0.174), respectively. Times of balloon dilatation in the PGA plus stent group were less than those in the stent group [4(2-5) vs 6(1-14), P = 0.007]. The length(P = 0.080) and diameter(P = 0.061) of esophageal strictures were numerically decreased in the PGA plus stent group, whereas no difference in location(P = 0.232) between the two groups was found. Multivariate logistic analysis suggested that PGA plus stent placement(P = 0.026) was an independent predictive factor for a lower risk of esophageal stricture, while location in the middle third(P = 0.034) and circumferential range = 1/1(P = 0.028) could independently predict a higher risk of esophageal stricture in EC patients after ESD. CONCLUSION PGA plus stent placement is more effective in preventing post-ESD esophageal stricture compared with stent placement alone in EC patients with earlystage disease.展开更多
Quantifying trends in soil microbial biomass carbon (SMBC) undercontrasting management conditions is important in understanding thedynamics of soil organic matter (SOM) in soils and in ensuring theirsustainable use. A...Quantifying trends in soil microbial biomass carbon (SMBC) undercontrasting management conditions is important in understanding thedynamics of soil organic matter (SOM) in soils and in ensuring theirsustainable use. Against such a background, a 60-day greenhousesimulation experiment was carried out to study the effects of strawplacement, mineral N source, and tillage on SMBC dynamics in twocontrasting soils, red sol (Ferrasol) and black soil (Acrisol). Thetreatments included straw addition + buried (T1); straw addition +mineral N (T2); and straw addition + tillage (T3).展开更多
By decoupling control plane and data plane,Software-Defined Networking(SDN) approach simplifies network management and speeds up network innovations.These benefits have led not only to prototypes,but also real SDN dep...By decoupling control plane and data plane,Software-Defined Networking(SDN) approach simplifies network management and speeds up network innovations.These benefits have led not only to prototypes,but also real SDN deployments.For wide-area SDN deployments,multiple controllers are often required,and the placement of these controllers becomes a particularly important task in the SDN context.This paper studies the problem of placing controllers in SDNs,so as to maximize the reliability of SDN control networks.We present a novel metric,called expected percentage of control path loss,to characterize the reliability of SDN control networks.We formulate the reliability-aware control placement problem,prove its NP-hardness,and examine several placement algorithms that can solve this problem.Through extensive simulations using real topologies,we show how the number of controllers and their placement influence the reliability of SDN control networks.Besides,we also found that,through strategic controller placement,the reliability of SDN control networks can be significantly improved without introducing unacceptable switch-to-controller latencies.展开更多
基金US National Science Foundation(DEB 0639979 and DBI 0851245 to R.K.C.DEB-0541936 to N.J.G.+4 种基金DEB-0424767 and DEB-0639393 to R.L.C.DEB-0640015 to J.T.L.)the US Department of Energy(022821 to N.J.G.)the Taiwan National Science Council(97-2118-M007-MY3 to A.C.)and the University of Connecticut Research Foundation(to R.L.C.).
文摘Aims In ecology and conservation biology,the number of species counted in a biodiversity study is a key metric but is usually a biased underestimate of total species richness because many rare species are not detected.Moreover,comparing species richness among sites or samples is a statistical challenge because the observed number of species is sensitive to the number of individuals counted or the area sampled.For individual-based data,we treat a single,empirical sample of species abundances from an investigator-defined species assemblage or community as a reference point for two estimation objectives under two sampling models:estimating the expected number of species(and its unconditional variance)in a random sample of(i)a smaller number of individuals(multinomial model)or a smaller area sampled(Poisson model)and(ii)a larger number of individuals or a larger area sampled.For sample-based incidence(presence–absence)data,under a Bernoulli product model,we treat a single set of species incidence frequencies as the reference point to estimate richness for smaller and larger numbers of sampling units.Methods The first objective is a problem in interpolation that we address with classical rarefaction(multinomial model)and Coleman rarefaction(Poisson model)for individual-based data and with sample-based rarefaction(Bernoulli product model)for incidence frequencies.The second is a problem in extrapolation that we address with sampling-theoretic predictors for the number of species in a larger sample(multinomial model),a larger area(Poisson model)or a larger number of sampling units(Bernoulli product model),based on an estimate of asymptotic species richness.Although published methods exist for many of these objectives,we bring them together here with some new estimators under a unified statistical and notational framework.This novel integration of mathematically distinct approaches allowed us to link interpolated(rarefaction)curves and extrapolated curves to plot a unified species accumulation curve for empirical examp
文摘Background： Sacroiliac （SI） screw fixation is a demanding technique, with a high rate of screw malposition due to the complex pelvic anatomy. TiRobot- is an orthopedic surgery robot which can be used for SI screw fixation. This study aimed to evaluate the accuracy of robot-assisted placement of SI screws compared with a freehand technique. Methods：Thirty patients requiring posterior pelvic ring stabilization were randomized to receive freehand or robot-assisted SI screw fixation, between January 2016 and June 2016 at Beijing Jishuitan Hospital. Forty-five screws were placed at levels S1 and S2. In both methods, the primary end point screw position was assessed and classified using postoperative computed tomography. Fisher＇s exact probability test was used to analyze the screws＇positions. Secondary end points, such as duration of trajectory planning, surgical time after reduction of the pelvis, insertion time for guide wire, number of guide wire attempts, and radiation exposure without pelvic reduction, were also assessed. Results： Twenty-three screws were placed in the robot-assisted group and 22 screws in the freehand group; no postoperative complications or revisions were reported. The excellent and good rate of screw placement was 100% in the robot-assisted group and 95% in the freehand group. The P value （0.009） showed the same superiority in screw distribution. The fluoroscopy time after pelvic reduction in the robot-assisted group was significantly shorter than that in the freehand group （median [Q1, Q3]： 6.0 [6.0, 9.0] s vs. median [Q1, Q3]： 36.0 [21.5, 48.0] s; χ2 = 13.590, respectively, P 〈 0.001）; no difference in operation time after reduction of the pelvis was noted （χ2 = 1.990, P = 0.158）. Time for guide wire insertion was significantly shorter for the robot-assisted group than that for the freehand group （median [Q1, Q3]： 2.0 [2.0, 2.7] min vs. median [Q1, Q3]： 19.0 [15.5, 45.0] min; χ2 = 20.952, respectively, P 〈 0.001）. The number of guide wire attempts
文摘AIM To assess the effect of polyglycolic acid(PGA) plus stent placement compared with stent placement alone in the prevention of post-endoscopic submucosal dissection(ESD) esophageal stricture in early-stage esophageal cancer(EC) patients. METHODS Seventy EC patients undergoing ESD were enrolled in this randomized, controlled study. Patients were allocated randomly at a 1:1 ratio into two groups as follows:(1) PGA plus stent group(PGA sheet-coated stent placement was performed); and(2) Stent group(only stent placement was performed). This study was registered on http://www.chictr.org.cn(No. chictrinr-16008709). RESULTS The occurrence rate of esophageal stricture in the PGA plus stent group was 20.5%(n = 7), which was lower than that in the stent group(46.9%, n = 15)(P = 0.024). The mean value of esophageal stricture time was 59.6 ± 16.1 d and 70.7 ± 28.6 d in the PGA plus stent group and stent group(P = 0.174), respectively. Times of balloon dilatation in the PGA plus stent group were less than those in the stent group [4(2-5) vs 6(1-14), P = 0.007]. The length(P = 0.080) and diameter(P = 0.061) of esophageal strictures were numerically decreased in the PGA plus stent group, whereas no difference in location(P = 0.232) between the two groups was found. Multivariate logistic analysis suggested that PGA plus stent placement(P = 0.026) was an independent predictive factor for a lower risk of esophageal stricture, while location in the middle third(P = 0.034) and circumferential range = 1/1(P = 0.028) could independently predict a higher risk of esophageal stricture in EC patients after ESD. CONCLUSION PGA plus stent placement is more effective in preventing post-ESD esophageal stricture compared with stent placement alone in EC patients with earlystage disease.
基金Project (No. G1999011809) supported by the National Key Basic Research Support Foundation (NKBRSF) of China.
文摘Quantifying trends in soil microbial biomass carbon (SMBC) undercontrasting management conditions is important in understanding thedynamics of soil organic matter (SOM) in soils and in ensuring theirsustainable use. Against such a background, a 60-day greenhousesimulation experiment was carried out to study the effects of strawplacement, mineral N source, and tillage on SMBC dynamics in twocontrasting soils, red sol (Ferrasol) and black soil (Acrisol). Thetreatments included straw addition + buried (T1); straw addition +mineral N (T2); and straw addition + tillage (T3).
基金supported in part by the National High Technology Research and Development Program(863 Program)of China under Grant No.2011AA01A101the National High Technology Research and Development Program(863 Program)of China under Grant No.2013AA01330the National High Technology Research and Development Program(863 Program)of China under Grant No.2013AA013303
文摘By decoupling control plane and data plane,Software-Defined Networking(SDN) approach simplifies network management and speeds up network innovations.These benefits have led not only to prototypes,but also real SDN deployments.For wide-area SDN deployments,multiple controllers are often required,and the placement of these controllers becomes a particularly important task in the SDN context.This paper studies the problem of placing controllers in SDNs,so as to maximize the reliability of SDN control networks.We present a novel metric,called expected percentage of control path loss,to characterize the reliability of SDN control networks.We formulate the reliability-aware control placement problem,prove its NP-hardness,and examine several placement algorithms that can solve this problem.Through extensive simulations using real topologies,we show how the number of controllers and their placement influence the reliability of SDN control networks.Besides,we also found that,through strategic controller placement,the reliability of SDN control networks can be significantly improved without introducing unacceptable switch-to-controller latencies.
