Korean larch(Larix olgensis)is one of the main tree species for aff orestation and timber production in northeast China.However,its timber quality and growth ability are largely infl uenced by crown size,structure and...Korean larch(Larix olgensis)is one of the main tree species for aff orestation and timber production in northeast China.However,its timber quality and growth ability are largely infl uenced by crown size,structure and shape.The majority of crown models are static models based on tree size and stand characteristics from temporary sample plots,but crown dynamic models has seldom been constructed.Therefore,this study aimed to develop height to crown base(HCB)and crown length(CL)dynamic models using the branch mortality technique for a Korean larch plantation.The nonlinear mixed-eff ects model with random eff ects,variance functions and correlation structures,was used to build HCB and CL dynamic models.The data were obtained from 95 sample trees of 19 plots in Meng JiaGang forest farm in Northeast China.The results showed that HCB progressively increases as tree age,tree height growth(HT growth)and diameter at breast height growth(DBH growth).The CL was increased with tree age in 20 years ago,and subsequently stabilized.HT growth,DBH growth stand basal area(BAS)and crown competition factor(CCF)signifi cantly infl uenced HCB and CL.The HCB was positively correlated with BAS,HT growth and DBH growth,but negatively correlated with CCF.The CL was positively correlated with BAS and CCF,but negatively correlated with DBH growth.Model fi tting and validation confi rmed that the mixed-eff ects model considering the stand and tree level random eff ects was accurate and reliable for predicting the HCB and CL dynamics.However,the models involving adding variance functions and time series correlation structure could not completely remove heterogeneity and autocorrelation,and the fi tting precision of the models was reduced.Therefore,from the point of view of application,we should take care to avoid setting up over-complex models.The HCB and CL dynamic models in our study may also be incorporated into stand growth and yield model systems in China.展开更多
<strong>Introduction</strong> <span style="font-family:""><span style="font-family:Verdana;">Accurate pregnancy dating is important for many aspects of </span><...<strong>Introduction</strong> <span style="font-family:""><span style="font-family:Verdana;">Accurate pregnancy dating is important for many aspects of </span><span style="font-family:Verdana;">obstetric care at individual level as well as population level. Traditionally</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> pregnancy</span><span style="font-family:Verdana;"> dating has done by adding 9 months and 7 days to the last menstrual period (LMP) using Naegele’s formula. Determination of gestational age by ultrasound is more precise. Most commonly used parameters are mean sac diameter, gestation sac volume, crown</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">rump length (CRL), biparietal diameter (BPD), head circumference (HC) and femur length (FL). After 24 weeks</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> gestational age cannot be accurately determined by ultrasound scans. The biological variability of CRL is small and growth is very rapid. There are </span><span style="font-family:Verdana;">many factors</span><span style="font-family:"color:red;"> </span><span style="font-family:""><span style="font-family:Verdana;">that</span><span style="color:red;"> </span></span><span style="font-family:""><span style="font-family:Verdana;">can affect CRL such as measurement errors, differences in growth rates between individuals, fetal sex and maternal conditions such as diabetes </span><span style="font-family:Verdana;">mellitus. A correctly performed measurement of CRL is the most accurate way</span><span style="font-family:Verdana;"> of estimating the gestational age in early pregnancy from 8 weeks to 13 weeks + 6 days. </span><b><span style="font-family:Verdana;">Objectives </span></b><span style="font-family:Verdana;">Our study aims were to prepare a new Crown Rump Length chart with Sri Lankan population data and to compare </span><span><span style="font-family:Verdana;">new CRL chart with existing intergrowth CRL chart.</span><b><span style="font-family:Verdana;"> Method </span></b><span style="font-family:Verdana;">Prospective observationa</span></span><span style="font-family:Verdana;">l study with recruitment of subjects by Quota sampling technique was carried out from April 2015 to March 2016. Spontaneously conceived uncomplicated singleton pregnancies with normal Body Mass Index (BMI) 18.5 - 23 kg/m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> were recruited at the time of registration to antenatal care. Consenting woman with known LMP with regular cycles in preceding 3 months were undergone ultrasound examination only once at gestational age (GA) ranging from 8 weeks to 13 weeks + 6 days. If ultrasound dating w</span></span><span style="font-family:Verdana;">as</span><span style="font-family:Verdana;"> different from LMP dating by more than 5 days in pregnancies with POA less than 9 weeks and dating difference</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> more than 7 days in pregnancies between 9 weeks and 14 weeks w</span><span style="font-family:Verdana;">ere</span><span style="font-family:""><span style="font-family:Verdana;"> excluded. Pregnancies complicated with uncertain viability, congenital anomalies and spontaneous miscarriage were excluded from statistical analysis. Data collection done with pre-tested interviewer administered form and analysis was carried out using the Statistical Package for Social Sciences (SPSS) version 21. </span><b><span style="font-family:Verdana;">Results </span></b><span style="font-family:Verdana;">A total of 653 subjects were recruited for the study and 557 turned up for ultrasound dating assessment. Dating discrepancy and multiple pregnancies excluded 31 subjects, uncertain viability and spontaneous miscarriage excluded 15 subjects resulting 511 subjects for final statistical analysis. The mean CRL increased with GA almost linearly from day 56 to 97. </span><b><span style="font-family:Verdana;">Conclusions </span></b><span style="font-family:Verdana;">We have produced new CRL chart based on Sri Lankan data and it can be used for clinical practice in Sri Lanka. There is no statistically significant difference between our CRL chart and intergrowth CRL chart.</span></span>展开更多
Polydioxanone(PDS),one of the bioabsorbable materials for coronary stent,is catching eyes of researchers recently. When designing the geometry of the PDS coronary stent,the length and the height of the crown are quite...Polydioxanone(PDS),one of the bioabsorbable materials for coronary stent,is catching eyes of researchers recently. When designing the geometry of the PDS coronary stent,the length and the height of the crown are quite important. However,rarely literatures have discussed the relationship between the two geometry parameters and the radial force of the bioabsorbable coronary stent. Therefore,a current effective tool of finite element method was applied in the evaluation of the relationship. By simulating 4 groups of models,it was obtained that the radial force of the coronary stent would not definitely increase with the rising value of Lcrownfrom 0. 8 mm to 2. 4mm. Meanwhile,Hcrownand radial force of the coronary stent had no linear relationship with each other.展开更多
基金supported by the National Key Research and Development Program of China(2017YFD0600401)the Fundamental Research Funds for the Central Universities(2572019CP08)
文摘Korean larch(Larix olgensis)is one of the main tree species for aff orestation and timber production in northeast China.However,its timber quality and growth ability are largely infl uenced by crown size,structure and shape.The majority of crown models are static models based on tree size and stand characteristics from temporary sample plots,but crown dynamic models has seldom been constructed.Therefore,this study aimed to develop height to crown base(HCB)and crown length(CL)dynamic models using the branch mortality technique for a Korean larch plantation.The nonlinear mixed-eff ects model with random eff ects,variance functions and correlation structures,was used to build HCB and CL dynamic models.The data were obtained from 95 sample trees of 19 plots in Meng JiaGang forest farm in Northeast China.The results showed that HCB progressively increases as tree age,tree height growth(HT growth)and diameter at breast height growth(DBH growth).The CL was increased with tree age in 20 years ago,and subsequently stabilized.HT growth,DBH growth stand basal area(BAS)and crown competition factor(CCF)signifi cantly infl uenced HCB and CL.The HCB was positively correlated with BAS,HT growth and DBH growth,but negatively correlated with CCF.The CL was positively correlated with BAS and CCF,but negatively correlated with DBH growth.Model fi tting and validation confi rmed that the mixed-eff ects model considering the stand and tree level random eff ects was accurate and reliable for predicting the HCB and CL dynamics.However,the models involving adding variance functions and time series correlation structure could not completely remove heterogeneity and autocorrelation,and the fi tting precision of the models was reduced.Therefore,from the point of view of application,we should take care to avoid setting up over-complex models.The HCB and CL dynamic models in our study may also be incorporated into stand growth and yield model systems in China.
文摘<strong>Introduction</strong> <span style="font-family:""><span style="font-family:Verdana;">Accurate pregnancy dating is important for many aspects of </span><span style="font-family:Verdana;">obstetric care at individual level as well as population level. Traditionally</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> pregnancy</span><span style="font-family:Verdana;"> dating has done by adding 9 months and 7 days to the last menstrual period (LMP) using Naegele’s formula. Determination of gestational age by ultrasound is more precise. Most commonly used parameters are mean sac diameter, gestation sac volume, crown</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">rump length (CRL), biparietal diameter (BPD), head circumference (HC) and femur length (FL). After 24 weeks</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> gestational age cannot be accurately determined by ultrasound scans. The biological variability of CRL is small and growth is very rapid. There are </span><span style="font-family:Verdana;">many factors</span><span style="font-family:"color:red;"> </span><span style="font-family:""><span style="font-family:Verdana;">that</span><span style="color:red;"> </span></span><span style="font-family:""><span style="font-family:Verdana;">can affect CRL such as measurement errors, differences in growth rates between individuals, fetal sex and maternal conditions such as diabetes </span><span style="font-family:Verdana;">mellitus. A correctly performed measurement of CRL is the most accurate way</span><span style="font-family:Verdana;"> of estimating the gestational age in early pregnancy from 8 weeks to 13 weeks + 6 days. </span><b><span style="font-family:Verdana;">Objectives </span></b><span style="font-family:Verdana;">Our study aims were to prepare a new Crown Rump Length chart with Sri Lankan population data and to compare </span><span><span style="font-family:Verdana;">new CRL chart with existing intergrowth CRL chart.</span><b><span style="font-family:Verdana;"> Method </span></b><span style="font-family:Verdana;">Prospective observationa</span></span><span style="font-family:Verdana;">l study with recruitment of subjects by Quota sampling technique was carried out from April 2015 to March 2016. Spontaneously conceived uncomplicated singleton pregnancies with normal Body Mass Index (BMI) 18.5 - 23 kg/m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> were recruited at the time of registration to antenatal care. Consenting woman with known LMP with regular cycles in preceding 3 months were undergone ultrasound examination only once at gestational age (GA) ranging from 8 weeks to 13 weeks + 6 days. If ultrasound dating w</span></span><span style="font-family:Verdana;">as</span><span style="font-family:Verdana;"> different from LMP dating by more than 5 days in pregnancies with POA less than 9 weeks and dating difference</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> more than 7 days in pregnancies between 9 weeks and 14 weeks w</span><span style="font-family:Verdana;">ere</span><span style="font-family:""><span style="font-family:Verdana;"> excluded. Pregnancies complicated with uncertain viability, congenital anomalies and spontaneous miscarriage were excluded from statistical analysis. Data collection done with pre-tested interviewer administered form and analysis was carried out using the Statistical Package for Social Sciences (SPSS) version 21. </span><b><span style="font-family:Verdana;">Results </span></b><span style="font-family:Verdana;">A total of 653 subjects were recruited for the study and 557 turned up for ultrasound dating assessment. Dating discrepancy and multiple pregnancies excluded 31 subjects, uncertain viability and spontaneous miscarriage excluded 15 subjects resulting 511 subjects for final statistical analysis. The mean CRL increased with GA almost linearly from day 56 to 97. </span><b><span style="font-family:Verdana;">Conclusions </span></b><span style="font-family:Verdana;">We have produced new CRL chart based on Sri Lankan data and it can be used for clinical practice in Sri Lanka. There is no statistically significant difference between our CRL chart and intergrowth CRL chart.</span></span>
基金Key Project of Medicine,Shanghai Science and Technical Committee,China(No.10411953300)
文摘Polydioxanone(PDS),one of the bioabsorbable materials for coronary stent,is catching eyes of researchers recently. When designing the geometry of the PDS coronary stent,the length and the height of the crown are quite important. However,rarely literatures have discussed the relationship between the two geometry parameters and the radial force of the bioabsorbable coronary stent. Therefore,a current effective tool of finite element method was applied in the evaluation of the relationship. By simulating 4 groups of models,it was obtained that the radial force of the coronary stent would not definitely increase with the rising value of Lcrownfrom 0. 8 mm to 2. 4mm. Meanwhile,Hcrownand radial force of the coronary stent had no linear relationship with each other.
