Diameter Percentiles Research Articles

A Diameter Distribution Yield Prediction for Teak Stands in Taungoo District, Bago Region of Myanmar

A parameter recovery procedure was applied to characterize the parameters for the Weibull distribution function based on four percentile methods and two hybrid methods which were the combination of diameter percentiles and moment methods. The procedure was used to develop a diameter distribution yield prediction for teak stands in Taungoo District of Myanmar. All the methods were evaluated by using independent observed data and calculating error indices. Among them, method 1 which involved the 31st and 63rd diameter percentiles produced the lowest error index. Therefore, method 1 was considered to predict yield based on diameter distribution and selected to construct a yield table for the study area. An example was also provided to show users how to apply this kind of yield prediction.

Ultrasound in labor admission to predict need for emergency cesarean section: a prospective, blinded cohort study

Objective To assess whether assessment with ultrasound could improve the detection of emergency cesarean section (ECS) in laboring women. Methods Women who presented with symptoms of active labor or women in need of labor induction were invited to participate in the study. Women included in the study were evaluated with ultrasonography for fetal biometry and vaginal examinations for Bishop score assessment. The main aim in this study was determining factors associated with ECS due to fetal distress and obstructed labor. Results No fetal biometry variable was associated with ECS due to any indication (fetal distress and obstructed labor combined) in the univariate analysis. In multivariate analyses, biometry variables were adjusted for Bishop score at admission and only abdominal circumference percentile showed a significant association with the odds of ECS due to any indication (OR:1.02, 95% CI: 1.01–1.03). Biparietal diameter and abdominal circumference variables were associated with the odds of ECS due to obstructed labor in both univariate and multivariate analyses (p < .05 for all). However, the predictive accuracy of biparietal diameter percentile (area under the curve (AUC): 0.55, 95% CI: 0.46–0.63) and abdominal circumference percentile (AUC: 0.56, 95% CI: 0.48–0.64) without adjunct variables were poor. Moreover, the addition of fetal biometry parameters to Bishop score did not improve the predictive accuracy of Bishop score. Conclusion Ultrasound assessment at admission, in addition to Bishop score assessment, did not significantly improve the prediction of ECS. Also, the fetal biometry alone had poor predictive capability for ECS. Routine ultrasound assessment at labor admission appears to be ineffective for predicting ECS. Precis Fetal biparietal diameter and abdominal circumference showed an association with emergency cesarean due to obstructed labor but the predictive accuracy of fetal biometry was low. Routine ultrasound examination at admission, in addition to Bishop score assessment, may not useful for assessing the risk of emergency section in unselected populations.

Measurements in First-Trimester Abortion Products: A Pathologic Study.

Related to the advances in prenatal diagnosis and the emergence of medically challenging situations, there has been an increased interest in conducting a pathologic study of first-trimester abortion products. To evaluate measurements across a large group of first-trimester spontaneous abortion specimens. Potential goals include a validation of prenatal embryo and gestational-sac measurements as a function of gestational age (GA). A retrospective case study of first-trimester spontaneous abortions between June 2015 and April 2017 in Centro de Genética Clínica Embryo-Fetal Pathology Laboratory, Porto, Portugal. Considering the inclusion criteria, 585 complete gestational sacs, 182 embryos, and 116 umbilical cords were selected. We recorded the weight of the gestational sacs and embryos and measurements of gestational sacs, umbilical cords, and embryo crown-rump length. Models were computed using regression techniques. Gestational-sac diameter percentiles 5, 25, 50, 75 and 95 were calculated according to GA, and at each 1-week interval the diameter increased an average of 3 mm. Umbilical cord length percentiles 5, 25, 50, 75 and 95 were calculated according to GA, and at each 1-week interval, the length increased an average of 1.35 mm. Embryo crown-rump length estimated mean ± SD values were GA 6 weeks, 5.3 ± 2.3 mm; GA 7 weeks, 9.4 ± 4.8 mm; GA 8 weeks, 13.7 ± 8.2 mm; GA 9 weeks, 20.8 ± 9.1 mm; GA 10 weeks, 22.6 ± 13.4 mm; GA 11 weeks, 29.4 ± 12.9 mm; and GA 12 weeks, 52 mm. Pathologic measurements obtained should be compared to expected measurements and correlated with ultrasound findings, clinical information, and microscopic findings. Deviations from expected values could lead to an understanding of early pregnancy loss.

Eucalyptus growth and yield system: Linking individual-tree and stand-level growth models in clonal Eucalypt plantations in Brazil

Linking individual-tree and stand-level growth models is required for estimating future forest stand structure, while maintaining the desired accuracy for forest management decision making. There is a scarcity of studies addressing this issue for clonal Eucalypt stands in Brazil. Thus, this paper aims to develop a compatible individual-tree and stand-level growth and yield system for clonal Eucalypt stands in Brazil. The dataset used in this study is derived from remeasurement information of sixteen TECHS sites. At every site, eleven Eucalypt clones were planted in single block plots, while extra plots under a rainfall exclusion regime were also installed in fourteen sites. Prediction and projection diameter percentile equations were developed, as well as an individual-tree mortality equation and a generalized height-diameter equation. In addition, a detailed explanation of the structural architecture of the developed compatible growth and yield system is provided. Differences when forecasting forest afforestation and updating forest inventories were highlighted in order to provide the proper use of the developed growth and yield system. Finally, the individual-tree equations were validated through the use of the rainfall exclusion regime plots as was the growth and yield system when applied for prediction and projection purposes. The individual-tree level equations provided accurate estimates. The newly developed compatible growth and yield system also displayed unbiased and accurate estimates. The system achieved full compatibility between individual-tree and stand-level estimates and produced accurate stand table estimates. The growth and yield system presented is a powerful analytical tool that can serve to update inventory data in tropical Brazil and also to provide estimates for expected forest afforestation. The system has the capability of providing detailed outputs, which allows forest managers to consider merchandizing the clonal Eucalypt stands into multiple products.

Ice Crystal Sizes in High Ice Water Content Clouds. Part II: Statistics of Mass Diameter Percentiles in Tropical Convection Observed during the HAIC/HIWC Project

AbstractHigh ice water content (IWC) regions in mesoscale convective systems (MCSs) are a potential threat to commercial aviation, as they are suspected to cause in-service engine power-loss events and air data probe malfunctions. To investigate this, the high-altitude ice crystals (HAIC)/high ice water content (HIWC) projects set up a first field campaign in Darwin (Australia) in 2014. The airborne instrumentation was selected to provide the most accurate measurements of both the bulk total water content (TWC), using a specially developed isokinetic evaporator, and the individual ice crystals properties, using particle imaging probes.This study focuses on determining the size ranges of ice crystals responsible for the mass in high IWC regions, defined here as cloud regions with IWC greater than 1.5 g m−3. It is shown that for high IWC areas in most of the encountered MCSs, median mass diameters (MMDs) of ice crystals range from 250 to 500 μm and decrease with increasing TWC and decreasing temperature. At the same time, the mass contribution of the smallest crystals (below 100 μm) remains generally low (below 15%).In contrast, data from two flight missions in a long-lasting quasi-stationary tropical storm reveal that high IWC values can also be associated with MMDs in the range 400–800 μm and peak values of up to 2 mm. Ice crystal images suggest a major growth contribution by vapor deposition (columns, capped columns) even for such larger MMD values.

The Roles of Formaldehyde Exposure and Oxidative Stress in Fetal Growth in the Second Trimester

ObjectiveTo examine the relationship between formaldehyde exposure and fetal growth in the second trimester and the potential mediating role of oxidative stress in this relationship. DesignA cross-sectional study was conducted. SettingThe participants were recruited from one university-related clinic and two private obstetrics and gynecology offices in the Southeastern United States. ParticipantsA convenience sample of 140 healthy pregnant women in the second trimester of pregnancy was enrolled from November 2013 through June 2014. MethodsFormaldehyde exposure was measured via vapor monitors worn by the participants for 24 hours. One-time urine samples were collected during a routine prenatal visit to measure the level of 15-isoprostane F2t and cotinine as biomarkers of oxidative stress and tobacco smoking, respectively. Urine creatinine was measured to standardize the cotinine and 15-isoprostane F2t levels. ResultsEighty-eight participants (63%) returned their formaldehyde monitors. The linear regression model showed that the dichotomized level of formaldehyde exposure (<0.03 and >0.03 ppm) was a significant predictor of biparietal diameter percentile after controlling for maternal race (p < .006). The relationship between 15-isoprostane F2t and fetal growth was nonsignificant, and the mediating role of oxidative stress in the relationship between formaldehyde exposure and biparietal diameter was not confirmed. ConclusionA relationship was found between formaldehyde exposure and biparietal diameter in the second trimester. Although further research is necessary to confirm the results of this study, nurses may consider advising pregnant women to limit their exposure to formaldehyde during pregnancy.

Performance of Weibull function as a diameter distribution model for Pinus thunbergii stands in the eastern coast of South Korea

This study was carried out to determine the performance of percentile-based Weibull diameter distribution model for Pinus thunbergii stands thriving along the eastern coast of South Korea. The parameter recovery technique was used to estimate the three parameters of the Weibull model. The analysis demonstrated satisfactory results based on the following test statistics for the principal percentile models: fit index (FI) range from 0.501 (minimum diameter) to 0.932 (50th diameter percentiles) and root mean square error (RMSE) range from 0.112 (quadratic mean diameter) to 3.572 (minimum diameter). The developed model was further evaluated by determining the mean bias (Ē) in trees per ha (TPH) for each diameter class, and the results showed highest over-prediction in the 20 cm, and under-prediction in the 16 cm and 24 cm diameter classes. The goodness of fit tested by Kolmogorov-Smirnov (KS) test showed no significant differences (p>0.05) between the observed and predicted diameter distributions for almost all plots. Using site index and aboveground biomass (AGB) models developed for P. thunbergii in South Korea, a model to predict the AGB per ha for each diameter class and subsequently the total AGB of the stand was created. An application guide was also created, which will serve as a decision-support tool for forest managers in quantifying the future total AGB in P. thunbergii stands located in the eastern coast of South Korea and, subsequently, the quantification of potential carbon stocks aside from being a vital input in designing efficient management and protection strategies for these stands.

Percentile-based Weibull diameter distribution model for Pinus kesiya stands in Benguet province, Philippines

This study was conducted to develop a diameter distribution model for Pinus kesiya stands in Benguet province, Philippines, using the percentile-based Weibull model. The performance of the different equations was examined using evaluation statistics such as the fit index (FI) and root mean square error (RMSE). Results showed a FI range from 0.48799 (minimum diameter) to 0.94071 (95th diameter percentiles) and a RMSE range from 0.12622 (quadratic mean diameter) to 5.06882 (25th diameter percentile). To further evaluate the developed Weibull diameter distribution model, mean bias (Ē) in trees per hectare for each diameter class was determined, and the results showed that the highest over-prediction was found in the 18 cm diameter class, and that the highest under-prediction was found in the 12 cm diameter class. Using a site index equation and stem volume model developed for Pinus kesiya in the Philippines, a yield prediction system was created to predict the volume per ha (VPH) for each diameter class and, subsequently, the total volume of a stand. To evaluate the yield prediction system, the predicted mean VPH for each diameter class was compared to the observed mean VPH. Results showed that most of the under-predictions of the model were found in the 32–38 cm, 44–48 cm and 60 cm diameter classes. To assist forest managers in using this yield prediction system, an application guide was also created to predict the future yield of Pinus kesiya stands in Benguet, Philippines.

Comparing parametric and non-parametric modelling of diameter distributions on independent data using airborne laser scanning in a boreal conifer forest

This study used two different approaches to model diameter distributions on data from 201 field plots in a boreal conifer forest in south eastern Norway using airborne laser scanning. These two methods were a non-parametric most similar neighbour (MSN) approach and a parametric seemingly unrelated regression (SUR) approach to predict diameter percentiles, and their accuracies were compared by validation with an independent dataset. Based on calculated differences between predicted and observed number of stems on the entire validation dataset, we found that SUR gave unbiased results and that MSN slightly underestimated total number of stems. However, both methods overpredicted the number of stems per hectare in the range of 15.6‐61.5 stems in the smallest diameter classes (between 4 and 12 cm). If the predicted diameter distributions were converted into basal area per hectare (G), both methods gave unbiased results. The average difference for G was 1.9 per cent of the observed value for the MSN approach. The corresponding number for the SUR model was 12.4 per cent. Neither of these differences were statistically significant (P . 0.05). We concluded that the even though both methods overall yielded accurate results, the MSN approach was more reliable in terms of predicting the number of large trees.

Umbilical cord diameter percentile curves and their correlation to birth weight and placental pathology

ObjectiveThe aims of this study were to develop a nomogram of umbilical cord diameter (UCD) for pathologic examination of the placenta, to identify the umbilical cord components responsible for variations in UCD, and to examine the relationship between UCD and other placental pathologic features and perinatal outcome. Study designWe prospectively collected 497 umbilical cords between 18 and 41 weeks' gestation over a 1-year period. Fresh-tissue UCD were grouped according to gestational age and compared to sonographic and histological measurements. Associations between UCD percentile and placental pathologic findings or obstetrical outcomes were examined. ResultsMean UCD increased with gestational age until a plateau at 1.0 cm in the third trimester, a value that was 0.56 cm less than sonographic measurements prior to delivery and 0.17 cm greater than UCD measured histologically. Umbilical cord components varied with UCD percentile, with umbilical vessel area increased in thick cords (p < 0.001) and Wharton's jelly area reduced in thin cords (p = 0.002). Thin umbilical cords were associated with at least one pathologic histological placental finding (p = 0.02), low placental weight (p < 0.001), single umbilical artery (p = 0.02), marginal cord insertion (p = 0.01), and low infant birth weight (p < 0.001). ConclusionsThis study provides reference curves for post-delivery UCD from 18 to 41 weeks' gestation for use by perinatal pathologists. We show that increased UCD is a function of increased umbilical blood vessel volume and decreased UCD is a function of decreased Wharton's jelly volume. UCD shows a strong association with placental and infant birth weight.

Hamburger high in total, saturated andtrans-fatty acids decreases HDL cholesterol and LDL particle diameter, and increases TAG, in mildly hypercholesterolaemic men

The consumption of high-fat hamburger enriched with SFA and trans-fatty acids may increase risk factors for coronary vascular disease, whereas hamburger enriched with MUFA may have the opposite effect. Ten mildly hypercholesterolaemic men consumed five, 114 g hamburger patties per week for two consecutive phases. Participants consumed high-SFA hamburger (MUFA:SFA = 0.95; produced from pasture-fed cattle) for 5 weeks, consumed their habitual diets for 3 weeks and then consumed high-MUFA hamburger (MUFA:SFA = 1.31; produced from grain-fed cattle) for 5 weeks. These MUFA:SFA ratios were typical of ranges observed for retail ground beef. Relative to habitual levels and levels during the high-MUFA phase, the high-SFA hamburger: increased plasma palmitic acid, palmitoleic acid and TAG (P < 0.01); decreased HDL cholesterol (HDL-C) and LDL particle diameter percentile distributions (P < 0.05); and had no effect on LDL cholesterol or plasma glucose (P>0.10). Plasma palmitoleic acid was positively correlated with TAG (r 0.90), VLDL cholesterol (r 0.73) and the LDL:HDL ratio (r 0.45), and was negatively correlated with plasma HDL-C (r - 0.58), whereas plasma palmitic, stearic and oleic acids were negatively correlated with LDL particle diameter (all P <or= 0.05). Because plasma palmitoleic acid was derived from Delta9 desaturation of palmitic acid in liver, we conclude that alterations in hepatic stearoyl-CoA desaturase activity may have been responsible the variation in HDL-C and TAG caused by the high-SFA and high-MUFA hamburgers.

Comparing strategies for modeling tree diameter percentiles from remeasured plots

AbstractIn many situations, including forest management planning, the underlying diameter distribution of a forest stand needs to be predicted. One alternative for predicting diameter distribution involves modeling diameter percentiles. We introduce a quantile regression (QR) approach for predicting diameter percentiles, and compare it with customary linear fixed‐effect and linear mixed‐effects models. The customary methods involve first estimating plot‐specific sample percentiles and then regressing them on stand characteristics, whereas QR directly models percentiles. We compared two prediction situations: a conditional one where a previously measured diameter sample is available from the stand of interest, and a marginal one where only some stand‐specific characteristics are known. To compare the predictions to the true underlying percentiles, we conducted a simulation study. The QR approach led to slight improvements in the marginal prediction situation. In the conditional situation, the mixed‐effect model led to clearly better predictions and should be preferred until QR methods have been developed for hierarchical data. It is extremely important to filter out the highly correlated sampling error from conditional predictions in order that the models predict underlying population percentiles rather than the realized sample percentiles. Copyright © 2007 John Wiley &amp; Sons, Ltd.

A regionalised growth model for Eucalyptus globulus plantations in south-eastern Australia

Summary A whole-stand distribution growth and yield model was developed for Eucalyptus globulus plantations in south-eastern Australia. The model was developed and parameterised using growth measurements from permanent sample or experimental plots established within plantation estates across the Gippsland, Central Victorian and Green Triangle regions. Regional variation of stand height and basal area growth, and mortality, was statistically tested using selected base models and indicator variables. Stand-level component models were constructed for projecting the stand heights, basal areas and stockings sampled in inventories into the future. Tree-level component models were developed for estimating the relationship between height and diameter, stem taper, and bark thickness at 1.3 m height from ground. To derive the diameter distributions of trees at any age, models were developed for predicting the 0th, 25th, 50th and 95th percentiles of cumulative diameter distributions. The Weibull distribution-based diameter distributions are estimated using the diameter percentiles and quadratic mean diameter predicted at the ages of interest (parameter recovery). In general, the developed models represent the mean growth of the E. globulus plantations in the three regions, and the observed and predicted yield trajectories agreed well for stand height, basal area and stocking. The accuracy of the developed stand models was evaluated using an independent data set. In general, for a prediction interval of 5 y or less, average bias in stand height, basal area and volume predictions is within ±1.0 m, ±0.5 m2 ha−1 and ±1.0 m3 ha−1 respectively. The models are reliable for projecting the stand parameters sampled in inventories at ages 5 or 6 y to the end of the rotation at about age 10 y. The developed growth model is particularly useful for strategic planning and wood flow analysis.

Localizing a Predicted Diameter Distribution Using Sample Information

Abstract This study presents a new method for predicting the diameter distribution of a stand, utilizing the percentile-based diameter distribution. The expected diameter percentiles are first predicted using stand measurements. Subsequently, the distribution is calibrated (localized) for the stand using sample order statistics, which consist of one or more diameters of sample trees and their ranks on the sample plot(s). These measurements can be quickly carried out in the field, because the rank can be assessed visually. The sample order statistics can be interpreted as measured sample percentiles. The expectations, variances, and covariances of the measured sample order statistics are derived using the theory of order statistics. Regression models are used to predict the conditional expectations of predefined percentiles, which are then combined with the measured percentiles using the best linear unbiased predictor. The method was tested in a real data set using simulated sample plots. The test showed that, even with a small number of sample measurements, the relative root mean square error and bias of volume per hectare could be decreased remarkably. Furthermore, increasing the number of measurements steadily improved the prediction. The proposed method seems to be a promising tool in the prediction of diameter distributions of various forms, including those found in complex stands. FOR. SCI. 51(4):292–303.

Stand level pine response to occupancy of woody shrub and herbaceous vegetation

The relationship between age-5 pine height and vegetation cover was estimated for loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) stands using regression analysis. This paper utilizes results from four locations of a vegetation control study that included herbicide treatments to control woody shrub and herbaceous vegetation. Age-5 average dominant height was predicted from first-year herbaceous cover, untreated first-year shrub cover, and fifth-year shrub cover. Dominant height increased 0.5 m for each decrease of about 30% in either first year herbaceous cover, untreated first-year shrub cover, or year-5 shrub cover. Lack of vegetation control on beds where vegetation was allowed to recolonize before planting reduced dominant height an additional 0.5 m. A competition index was constructed that estimates the difference between "potential" and actual age-5 pine height. Stand-level models were developed to link age-5 pine height and occupancy of competing vegetation to quadratic mean DBH, specific DBH percentiles, and stand basal area. The effects of interspecific competition on stand basal area and diameter percentiles could be accounted for through the effects of competing vegetation on dominant height except for treatments that did not control woody shrubs.

Incorporating the effects of interspecific competition and vegetation management treatments in diameter distribution models for Douglas-fir saplings

A parameter recovery procedure for the Weibull distribution function, based on diameter percentiles, was modified to incorporate the effects of interfering vegetation in young Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco var. menziesii) plantations. The applicability of the system was tested by using data from sites in the Coast Ranges of Oregon and Washington and in the Siskiyou Mountains of southwestern Oregon. Four percentiles (0, 25th, 50th, 95th) of the cumulative probability distribution were predicted as functions of quadratic mean diameter and age. In the Siskiyou study, cover and total vegetation control affected quadratic mean diameter and all four percentiles; intensity of the vegetation treatments affected the 0 and 25th percentiles, and the interaction between intensity and timing of treatment affected quadratic mean diameter. In the Coast Ranges study, only quadratic mean diameter was affected by cover of woody vegetation, while quadratic mean diameter and the 25th percentile were significantly affected by total vegetation control. The predicted distributions showed decreasing variance with increasing cover, particularly in the Siskiyou Mountains. In the Coast Ranges study, the coefficient of variation increased with increasing cover, indicating that the variance of stem diameters was affected by average size. On xeric sites in the Siskiyou Mountains, high diameter variability in plots with total vegetation control suggests that interspecific competition may inhibit the expression of microsite variation.

Compatible Basal Area and Diameter Distribution Models for Thinned Loblolly Pine Plantations in Santa Catarina, Brazil

Abstract A simultaneous basal area growth and yield model based on diameter percentiles is developed. It is suggested that the diameter distribution percentiles essentially provide a description of the past stand history. The subsequent growth of a thinned or unthinned stand is affected by the shape and position of the diameter distribution percentiles. A noniterative technique is demonstrated for recovering the Weibull distribution parameters and generating a diameter distribution consistent with basal area. For. Sci. 33(1):43-51.