Reference Curves Research Articles

Comparison of singleton and twin birth weight reference percentile curves by gestational age and sex in extremely preterm infants: a population-based study

BackgroundWith the increasing survival rate of smaller newborns and twins, previous growth curves may not accurately assess the growth of extremely preterm infants (EPIs). Our study aimed to establish birth...

First trimester maternal tryptophan metabolism and embryonic and fetal growth: the Rotterdam Periconceptional Cohort (Predict Study).

What is the association between first trimester maternal tryptophan (TRP) metabolites and embryonic and fetal growth? Higher 5-hydroxytryptophan (5-HTP) concentrations are associated with reduced embryonic growth and fetal growth and with an increased risk of small-for-gestational age (SGA), while higher kynurenine (KYN) concentrations are associated with a reduced risk of SGA. The maternal TRP metabolism is involved in many critical processes for embryonic and fetal growth, including immune modulation and regulation of vascular tone. Disturbances in TRP metabolism are associated with adverse maternal and fetal outcomes. This study was embedded within the Rotterdam Periconceptional Cohort (Predict Study), an ongoing prospective observational cohort conducted at a tertiary hospital from November 2010 onwards. A total of 1115 women were included before 11 weeks of gestation between November 2010 and December 2020. Maternal serum samples were collected between 7 and 11 weeks of gestation, and TRP metabolites (TRP, KYN, 5-HTP, 5-hydroxytryptamine, and 5-hydroxyindoleacetic acid) were determined using a validated liquid chromatography (tandem) mass spectrometry method. Serial 3D ultrasound scans were performed at 7, 9, and 11 weeks of gestation to accurately assess features of embryonic growth, including crown-rump length (CRL) and embryonic volume (EV) offline using virtual reality systems. Fetal growth parameters were retrieved from medical records and standardized according to Dutch reference curves. Mixed models were used to assess associations between maternal TRP metabolites and CRL and EV trajectories. Linear and logistic regression models were utilized to investigate associations with estimated fetal weight (EFW) and birthweight, and with SGA, respectively. All analyses were adjusted for potential confounders. Maternal 5-HTP concentrations and the maternal 5-HTP/TRP ratio were inversely associated with embryonic growth (5-HTP, √CRL: β = -0.015, 95% CI = -0.028 to -0.001; 5-HTP 3√EV: β = -0.009, 95% CI = -0.016 to -0.003). An increased maternal 5-HTP/TRP ratio was also associated with lower EFW and birthweight, and with an increased risk of SGA (odds ratio (OR) = 1.006, 95% CI = 1.00-1.013). In contrast, higher maternal KYN concentrations were associated with a reduced risk of SGA in the unadjusted models (OR = 0.548, 95% CI = 0.320-0.921). Residual confounding cannot be ruled out because of the observational design of this study. Moreover, this study was conducted in a single tertiary hospital, which assures high internal validity but may limit external validity. The novel finding that maternal 5-HTP concentrations are associated with a smaller embryo and fetus implies that disturbances of the maternal serotonin pathway in the first trimester of pregnancy are potentially involved in the pathophysiology of fetal growth restriction. The association between higher maternal KYN concentrations and a reduced risk of SGA substantiate the evidence that the KYN pathway has an important role in fetal growth. More research is needed to delve deeper into the potential role of the maternal TRP metabolism during the periconception period and pregnancy outcome for mother and offspring. This study was funded by the Department of Obstetrics and Gynecology and the Department of Clinical Chemistry of the Erasmus MC, University Medical Center, Rotterdam, the Netherlands. The authors have no competing interests to disclose. N/A.

Quality Index for Assessment of the Mechanical Condition of Transformers’ Active Part with Frequency Response and Vibroacoustic Measurements

The paper describes the application of the numerical tool quality index for an objective evaluation of complementary frequency response analysis (FRA) and vibroacoustic method (VM) test methods. These diagnostic methods are used in the industrial practice of transformer diagnostics for the assessment of the mechanical condition of windings and a core. The quality index is based on a numerical comparison of the curve obtained from measurements and the reference curve in a frequency domain. The quality index is based on estimators for the covariance, variance, and expected values. First, both methods of analysis were applied to a group of transformers of similar construction, leading conclusions on quality index values being quickly drawn. Next, it was applied to another transformer’s FRA and VM measurement results. The results showed problems with its mechanical condition, thus confirming that the proposed methods can be used in the practical assessment of transformers with these two diagnostic methods. The assessment of transformer’s active-part mechanical condition with complementary FRA and VM methods can be performed much more easily with the proposed quality indices.

Swimming behavior as a potential metric to detect satiation levels of European seabass in marine cages

Aquaculture is anticipated to contribute to two-thirds of the world’s fish consumption by 2030, emphasizing the need for innovative methods to optimize practices for economic viability, social responsibility, and environmental sustainability. Feeding practices play a pivotal role in aquaculture success and the feeding requirements are dynamic, influenced by factors like fish size, environmental conditions, and health status necessitating ongoing improvements in feeding practices. This study addresses a critical gap in feeding control systems in sea cages. It introduces a continuous, real-time monitoring system for analyzing the feeding behavior of European seabass, employing advanced AI models (YOLO and DEEPSORT) and computer vision techniques. The investigation focuses on key parameters, including speed and the newly defined feeding behavior index (FBI), to evaluate swimming responses under varying feeding scenarios exploring meal frequency, feeding time, and feeding quantity. The findings reveal a sensitivity of fish speed and the feeding behavior index (FBI) to different feeding scenarios, elucidating distinct behavioral patterns in response to varying frequencies, times, and quantities of feeding, such as increased activity in the morning relative to later times and the emergence of asymmetric activity patterns when fish are underfed or overfed. Notably, this study is one of the few in the field, presenting the development of a continuous, real-time monitoring system for feeding control in sea cages. Simultaneously, it explores reference curves and threshold values to enhance the overall efficacy of feeding control measures.

Marine Strontium Isotope Evolution at the Triassic‐Jurassic Transition Links Transient Changes in Continental Weathering to Volcanism of the Central Atlantic Magmatic Province

AbstractThe end‐Triassic extinction (ETE) is one of the most severe biotic crises in the Phanerozoic. This event was synchronous with volcanism of the Central Atlantic Magmatic Province (CAMP), the ultimate cause of the extinction and related environmental perturbations. However, the continental weathering response to CAMP‐induced warming remains poorly constrained. Strontium isotope stratigraphy is a powerful correlation tool that can also provide insights into the changes in weathering regime, but the scarcity of 87Sr/86Sr data across the Triassic‐Jurassic boundary (TJB) hindered the use of this method. Here we present new high‐resolution 87Sr/86Sr data from bulk carbonates at Csővár, a continuous marine section that spans 2.5 Myrs across the TJB. We document a continuing decrease in 87Sr/86Sr ratio from the late Rhaetian to the ETE, terminated by a 300 kyr interval of a flat trend and followed by a transient increase in the early Hettangian that levels off. We suggest that the first in the series of perturbations is linked to the influx of non‐radiogenic Sr from the weathering of freshly erupted CAMP basalts, leading to a delay in the radiogenic continental weathering response. The subsequent rise in 87Sr/86Sr after the TJB is explained by intensified continental crustal weathering from elevated CO2 levels and reduced mantle‐derived Sr flux. Using Sr flux modeling, we also find support for such multiphase, prolonged continental weathering scenarios. Aggregating the new data set with published records employing an astrochronological age model results in a highly resolved Sr isotope reference curve for an 8.5 Myr interval around the TJB.

Longitudinal Quantiles of Frailty Trajectories Considering Death: New Insights into Sex and Cohort Differences in the Reference Curves for Frailty Progression of Older European.

Most previous studies of frailty trajectories in older adults focus on the average trajectory and ignore death. Longitudinal quantile analysis of frailty trajectories permits the definition of reference curves, and the application of mortal cohort inference provides more realistic estimates than models that ignore death. Using data from individuals aged 65 or older (n = 25446) from the Survey of Health, Ageing, and Retirement in Europe (SHARE) from 2004 to 2020, we derived repeated values of the Frailty Index (FI) based on the accumulation of health deficits. We applied weighted Generalized Estimating Equations to estimate the quantiles of the FI trajectory, adjusting for sample attrition due to death, sex, education, and cohort. The FI quantiles increased with age and progressed faster for those with the highest level of frailty (β^a0.9 = 0.0229, p < .001; β^a0.5 = 0.0067, p < .001; H0: βa0.5=βa0.9, p < .001). Education was consistently associated with a slower progression of the FI in all quantiles (β^ae0.1 = -0.0001, p < .001; β^ae0.5 =-0.0004, p < .001; β^ae0.9 = -0.0003, p < .001) but sex differences varied across the quantiles. Women with the highest level of frailty showed a slower progression of the FI than men when considering death. Finally, no cohort effects were observed for the FI progression. Quantile FI trajectories varied by age, sex, education, and cohort. These differences could inform the practice of interventions aimed at older adults with the highest level of frailty.

Kinetic Modeling of Brain [18-F]FDG Positron Emission Tomography Time Activity Curves with Input Function Recovery (IR) Method.

Accurate positron emission tomography (PET) data quantification relies on high-quality input plasma curves, but venous blood sampling may yield poor-quality data, jeopardizing modeling outcomes. In this study, we aimed to recover sub-optimal input functions by using information from the tail (5th-100th min) of curves obtained through the frequent sampling protocol and an input recovery (IR) model trained with reference curves of optimal shape. Initially, we included 170 plasma input curves from eight published studies with clamp [18F]-fluorodeoxyglucose PET exams. Model validation involved 78 brain PET studies for which compartmental model (CM) analysis was feasible (reference (ref) + training sets). Recovered curves were compared with original curves using area under curve (AUC), max peak standardized uptake value (maxSUV). CM parameters (ref + training sets) and fractional uptake rate (FUR) (all sets) were computed. Original and recovered curves from the ref set had comparable AUC (d = 0.02, not significant (NS)), maxSUV (d = 0.05, NS) and comparable brain CM results (NS). Recovered curves from the training set were different from the original according to maxSUV (d = 3) and biologically plausible according to the max theoretical K1 (53//56). Brain CM results were different in the training set (p < 0.05 for all CM parameters and brain regions) but not in the ref set. FUR showed reductions similarly in the recovered curves of the training and test sets compared to the original curves (p < 0.05 for all regions for both sets). The IR method successfully recovered the plasma inputs of poor quality, rescuing cases otherwise excluded from the kinetic modeling results. The validation approach proved useful and can be applied to different tracers and metabolic conditions.

Overpressure Estimation Based on Velocity Data Analysis in The Subduction Zone of Hyuga-nada at Western Nankai Trough, Japan

Subduction zone is one of the areas which has great potential of earthquake. Nankai trough in Japan is such an area with subduction zone where earthquake records are well archived, despite its complexity. Also, slow earthquakes have been detected in this zone over the past 20 years, so that there are many opportunities to understand the dynamics and deformation in such an active setting. To expand the knowledge about slow earthquake which might occur and trigger a bigger earthquake, this study wants to infer the relationship between overpressure, one of the states and properties of seismogenic zone, and tremors. To carry out this research, 4 velocity models of seismicity line taken in Hyuga-nada are used. And the recorded tremor data placed around the lines came from Yamashita. In correlating the overpressure and tremors, this research is started by converting the Vp model to porosity model using Wyllie equation to predict the pore pressure conditions in the area. Then, the model will be used for fitting the actual data. Assuming there is an exact location following the normal compaction curve as a function of effective stress, it can be used for estimating the overpressure. Overpressure is economized by comparing the observed porosity and the reference curve at the same depth below seafloor. Potential overpressure occurred may be associated with areas of low Vp. The estimated overpressure is in the range of 1.2 to 12 MPa in the depth range of 700 to 4000mbsf. This study also concludes that the overpressure zone overlaps with the tremor location, although the overpressure value estimated is also still uncertain due to the uncertainty of the density value used.

Design of Unplasticized Polyamide 12 Oilfield Line Pipe Based on Published Regression Curves and ASTM F3524

The long-term strength of unplasticized polyamide 12 (PA-U12) has been characterized using standard methods for plastic pressure pipe during the qualification process for use in buried piping systems for natural gas delivery operating at low ambient temperatures, usually less than 20 to 30°C at pressures previously served only by steel pipe. The high strength characteristics of the material also made it interesting as a steel substitute for buried and above-ground industrial pressure pipe applications. So far, typical geometries are diameters up to 6 inch (162 mm) with wall thicknesses up to DR9. Assuming a design factor of 0.63 applied to the PPI TR-4 listed HDB, DR9 PA-U12 pipes have a maximum pressure at 23°C of 496 psig (3.4 MPa), although design pressures will typically be lower. These industrial systems can operate at much higher temperatures, up to ~ 50°C for above-ground installations in pipe supports or up to ~ 65°C for surface-laid oilfield pipes. Design engineers need the temperature dependent strength curves to properly design a thermoplastic pressure piping system. Therefore, the regression curves have been extended by LTHS tests up to 120°C. Corresponding test durations enabled to define the location of knees with determination of second branches. These branches are caused by hydrolytic degradation of the polymer resulting in brittleness of the polyamide after long times at elevated temperature in sufficiently wet environments or services. The first appearance of a knee is at 60° C and approximately 44 years. This paper describes various standards to which PA-U line pipe and materials must conform, and the development of standardized, temperature dependent, long-term strength reference curves for PA-U12 pressure pipe, including the transition from ductile to brittle behavior at long times and high temperatures. These curves have been standardized first in DVS and followed by ISO based on the combined LTHS data of pipes made from two different PA-U12 180 compounds and one PA-U11 180 compound. An example of a typical PA-U12 180 pipe design is presented, applying chemical resistance derating factors for oil and gas applications in the design process. Short Summary: Oilfield pipeline design engineers need temperature dependent strength curves to properly design a thermoplastic pressure piping system for use at temperatures often far above the typical range for natural gas distribution. Therefore, LTHS regression curves have been experimentally developed at temperatures up to 120°C to define the location of knees and characterization of second branches. In this paper we describe various standards to which PA-U line pipe and materials must conform, and the development of standardized, temperature dependent, long-term strength reference curves for PA-U12 pressure pipe, including the transition from ductile to brittle behavior at long times and high temperatures. These curves have been standardized in ISO and DVS and apply to both PA-U12 and PA-U11 [1,2]. For PA-U12 line pipe we also present an example for a typical pipe design, where chemical resistance derating factors are applied for oil and gas applications in the design process.

Reference centiles of bone mineral density, and body composition of lower limbs in children and adolescents for Hologic DXA Discovery model A.

Background: Regional Dual-energy X-ray absorptiometry (DXA) assessments are useful for patients where whole body measurements are not feasible due to positioning difficulties because of anatomic anomalies (e.g. severe scoliosis) and artifacts due to neuroorthopedic hardware. Until now, there is a lack of reference centiles of bone mineral density and body composition of lower limbs for the DXA device Hologic Discovery model A densitometer. The study aimed to generate age-and sex specific reference centiles of bone mineral content (BMC), bone mineral density (BMD), lean body mass (LBM), and fat mass (FM) of the lower limbs of children and adolescents of Hologic DXA system (Discovery model A). Methodology: Data from children and adolescents aged 8-20 years of the National Health and Nutrition Examination Survey (NHANES) of the years 2015-2018 were used to create age-specific and sex-specific reference centiles. Study population was subdivided into three ethnic groups (non-Hispanic Black, non-Hispanic White and Mexican-American). The LMS method was used to calculate the reference centiles. Study population was adjusted concerning the BMI. Results: A total of DXA scans of 769 non-Hispanic Black children (386 females), 937 non-Hispanic White children (447 females) and 692 Mexican-American children (370 females) were used to calculate age-specific and sex-specific reference curves. 881 DXA scans had to be excluded because of extreme BMI values of the study population, leaving 513 non-Hispanic Black (205 females), 346 Mexican-American children (179 females), 658 Non-Hispanic White (282 females) for statistical analysis and creating age-and sex specific reference centiles after BMI adjustment. Conclusions: We presented pediatric reference centiles for regional bone mineral density, bone mineral content, lean body mass and fat mass of the lower limbs which were age-and sex-specific for three ethnic groups (Mexican-American, non-Hispanic Black and non-Hispanic-White). The reference centiles can be used for the Hologic DXA system Discovery model A with the software version 3.2.

Paediatric dominant and non-dominant handgrip reference curves and the association with body composition

Background Lack of paediatric reference data limits the utility of handgrip strength as a measure of fitness and well-being. Aim To develop paediatric handgrip reference curves and evaluate associations with body size and composition and race/ethnicity group. Subjects and methods Handgrip, body size and composition data were obtained from National Health and Nutrition Examination Survey 2011–2014 participants aged 6–20 years. Densitometry-derived fat and appendicular lean soft tissue mass index Z-scores (FMIZ, ALSTMIZ) were generated in participants >8 years. Dominant and non-dominant handgrip reference curves were created using the LMS method. Analyses included sample weights to produce nationally representative estimates. Results Differences in handgrip strength according to hand dominance increased with age. Handgrip strength was associated with height and arm length Z-scores (R = 0.42 to 0.47) and ALSTMIZ (R = 0.54). Handgrip strength was higher in the non-Hispanic Black group and lower in the Mexican American compared to non-Hispanic White group. Group differences were attenuated when adjusted for height, arm length or ALSTMIZ. Conclusion Paediatric handgrip reference curves were generated from which individual Z-scores can be calculated separately for dominant versus non-dominant hand and adjusted for body size. Association with ALSTMIZ suggests handgrip Z-score may be used as a measure of functional body composition.

Age-stratified Assessment of Brain Volumetric Segmentation on the Indian Population Using Quantitative Magnetic Resonance Imaging.

Automated methods for quantifying brain tissue volumes have gained clinical interest for their objective assessment of neurological diseases. This study aimed to establish reference curves for brain volumes and fractions in the Indian population using Synthetic MRI (SyMRI), aquantitative imaging technique providing multiple contrast-weighted images through fast postprocessing. The study included acohort of 314 healthy individuals aged 15-65years from multiple hospitals/centers across India. The SyMRI-quantified brain volumes and fractions, including brain parenchymal fraction (BPF), gray matter fraction (GMF), white matter fraction (WMF), and myelin. Normative age-stratified quantification curves were created based on the obtained data. The results showed significant differences in brain volumes between the sexes, but not after normalization by intracranial volume. The findings provide normative data for the Indian population and can be used for comparative analysis of brain structure values. Furthermore, our data indicate that the use of fractions rather than absolute volumes in normative curves, such as BPF, GMF, and WMF, can mitigate sex and population differences as they account for individual differences in head size or brain volume.

An archaeomagnetic study of the Ishtar Gate, Babylon.

Data from the marriage of paleomagnetism and archaeology (archaeomagnetism) are the backbone of attempts to create geomagnetic field models for ancient times. Paleointensity experimental design has been the focus of intensive efforts and the requirements and shortcomings are increasingly well understood. Some archaeological materials have excellent age control from inscriptions, which can be tied to a given decade or even a specific year in some cases. In this study, we analyzed fired mud bricks used for the construction of the Ishtar Gate, the entrance complex to the ancient city of Babylon in Southern Mesopotamia. We were able to extract reliable intensity data from all three phases of the gate, the earliest of which includes bricks inscribed with the name of King Nebuchadnezzar II (605 to 562 BCE). These results (1) add high quality intensity data to a region relatively unexplored so far (Southern Mesopotamia), (2) contribute to a better understanding of paleosecular variation in this region, and the development of an archaeomagnetic dating reference for one of the key regions in the history of human civilizations; (3) demonstrate the potential of inscribed bricks (glazed and unglazed), a common material in ancient Mesopotamia, to archaeomagnetic studies; and (4) suggest that the gate complex was constructed some time after the Babylonian conquest of Jerusalem, and that there were no substantial chronological gaps in the construction of each consecutive phase. The best fit of our data (averaging 136±2.1 ZAm2) with those of the reference curve (the Levantine Archaeomagnetic Curve) is 569 BCE.

Simplified vented acoustic window with broadband sound transmission loss

A vented window design is presented allowing for air ventilation and improved sound reduction for urban traffic noise. The window design aims to be of simple construction, consisting of double-glass cells with a two-sided vent opening and a single internal division that splits the inner cavity into two resonators tuned at about 200 and 400 Hz. The basic window cell is modeled by means of a transmission matrix model, as well as through a finite element simulation. These provide an insight into the physical performance principles of the device, and produce results comparable with the acoustic measurements. Preliminary experiments showed the convenience of covering the resonator openings with flow-resistive absorbing material. This helps in raising the spectral sound transmission dips, improving the single number rating according to ISO 717-1:2020 with a measured weighted sound reduction index Rw(C,Ctr)=18(0;0) dB. The comparative performance of the window related to other windows reported in the literature is shown in a graph relating sound reduction and open ventilation area ratio. A reference performance curve is proposed corresponding to the maximum sound transmission loss of a pure constriction with the same open area. The sound reductions offered by different windows can be compared depending on how much their performance, according to Rw, departs above or below this reference curve. The window design performs according to the reference curve.

Faults detection and diagnosis of PV systems based on machine learning approach using random forest classifier

Accurate and reliable fault detection procedures are crucial for optimizing photovoltaic (PV) system performance. Establishing a trustworthy PV array model is the primary step and a vital tool for monitoring and diagnosing PV systems. This paper outlines a two-step approach for creating a reliable PV array model and implementing a fault detection procedure using Random Forest Classifiers (RFCs).Firstly, we extracted the five unknown parameters of the one-diode model (ODM) by combining the current–voltage translation method to predict the reference curve and employing the modified grey wolf optimization (MGWO) algorithm. In the second step, we simulated the PV array to obtain maximum power point (MPP) coordinates and construct operational databases through co-simulations in PSIM/MATLAB. We developed two RFCs: one for fault detection (a binary classifier) and another for fault diagnosis (a multiclass classifier).Our results confirmed the accuracy of the PV array modeling approach. We achieved a root mean square error (RMSE) value of 0.0122 for the ODM parameter extraction and RMSEs lower than 0.3 in dynamic PV array output current simulations under cloudy conditions. Regarding the fault detection procedure, our results demonstrate exceptional classification accuracy rates of 99.4% for both fault detection and diagnosis, surpassing other tested models like Support Vector Machines (SVM), K-Nearest Neighbors (KNN), Neural Networks (MLP Classifier), Decision Trees (DT), and Stochastic Gradient Descent (SGDC).

Monitoring of sugars adsorption breakthrough curves with online Raman spectroscopy

We introduce a new application for online Raman spectroscopy to monitor adsorption breakthrough curves of a glucose and xylose mixtures. Univariate and multivariate Partial Least Squares (PLS) calibration models are developed for each sugar when they are dissolved in water and in the case of the ethanol addition as a cosolvent. The models are validated by performing actual breakthrough experiments in a liquid phase using a column packed with a zeolite adsorbent. The first statistical moments of predicted curves are compared to the reference curves obtained with offline High-Performance Liquid Chromatography (HPLC). Glucose and xylose univariate predictions in the presence or absence of ethanol in the mixture are accurate and no improvements are found with the PLS models. Spectral subtraction coupled with the first derivative proved to be effective pretreatments to develop robust univariate models.

Prediction of deciduous teeth eruption in Brazilian children: A cross-sectional study nested in a prospective birth cohort (BRISA)

BackgroundDental eruption is part of a set of children´s somatic growth phenomena. The worldwide accepted human dental eruption chronology is still based on a small sample of European children. However, evidence points to some population variations with the eruption at least two months later in low-income countries, and local standards may be useful. So, this study aimed to predict deciduous teeth eruption from 12 months of age in a Brazilian infant population.MethodsWe developed a cross-sectional study nested in four prospective cohorts – the Brazilian Ribeirão Preto and São Luís Cohort Study (BRISA) – in a sample of 3,733 children aged 12 to 36 months old, corrected by gestational age. We made a reference curve with the number of teeth erupted by age using the Generalized Additive Models for location, scale, and shape (GAMLSS) technique. The explanatory variable was the corrected children´s age. The dependent variable was the number of erupted teeth, by gender, evaluated according to some different outcome distributional forms. The generalized Akaike information criterion (GAIC) and the model residuals were used as the model selection criterion.ResultsThe Box-Cox Power Exponential method was the GAMLSS model with better-fit indexes. Our estimation curve was able to predict the number of erupted deciduous teeth by age, similar to the real values, in addition to describing the evolution of children’s development, with comparative patterns. There was no difference in the mean number of erupted teeth between the sexes. According to the reference curve, at 12 months old, 25% of children had four erupted teeth or less, while 75% had seven or fewer and 95% had 11 or fewer. At 24 months old, 5% had less than 12, and 75% had 18 or more. At 36 months old, around 50% of the population had deciduous dentition completed (20 teeth).ConclusionThe adjusted age was an important predictor of the number of erupted deciduous teeth. This outcome can be a variable incorporated into children’s growth and development curves, such as weight and height curves for age to help dentists and physicians in the monitoring the children’s health.

Chinese Population Reference Curves for Ultrasound-Measured Amniotic Fluid Deepest Vertical Pocket in Dichorionic Twin Pregnancies, and Their Associations With Pregnancy Outcomes

Abstract Objective To establish the Chinese population's amniotic fluid deepest vertical pocket (DVP) reference curves for dichorionic twin pregnancies and to investigate DVP links with adverse perinatal outcomes. Methods This retrospective cohort study, conducted at Peking University Third Hospital from August 2011 to December 2020, used data from 375 women aged 20 to 45 years who had dichorionic twin pregnancies that were confirmed through first-trimester ultrasound. After exclusions, reference curves were developed using 318 women with 3,299 DVP scans, and the data analyzed included maternal demographics, pregnancy outcomes, ultrasound measurements, and neonatal information. DVPs were assessed via ultrasound at regular intervals and grouped by gestational age (GA) for analyses. Linear mixed models were used to create amniotic fluid reference curves. Associations between abnormalities and adverse perinatal outcomes were examined using Chi-squared or Fisher's exact tests. Logistic regression provided both crude and adjusted odds ratios, adjusting for pre-pregnancy weight, age, ethnicity, parity, and conception mode. Significance was set at P &lt; 0.05 with 95% confidence intervals (CI), and the analyses were conducted using SPSS ver. 26.0 (IBM Corp., Armonk, NY) and SAS ver. 9.4 (SAS Institute Inc., Cary, NC, USA) software. Results DVP increased from the first trimester to a maximum at 26 weeks (95% confidence interval (CI), 2.7–8.3 cm for twin 1 and 2.8–7.9 cm for twin 2) and then decreased gradually toward term. Differences between twins 1 and 2 were significant after 26 weeks (95% CI for twin 1: 5.3, 5.5; 95% CI for twin 2: 4.4, 4.5; P &lt; 0.010). Polyhydramnios of twin 1 increased the risk of large for GA. Oligohydramnios of twin 1 increased the risk of small for GA. Polyhydramnios of twin 2 increased the risk of small for GA, premature birth, and neonatal complications. Oligohydramnios of twin 2 increased the risk of preeclampsia, hypertensive disorder complicating pregnancy, and premature rupture of membranes. Conclusion Reference curves for twin amniotic fluid volumes vary by GA and differ between twins, with potential implications for pregnancy outcomes.

Two-sample survival tests based on control arm summary statistics.

The one-sample log-rank test is the preferred method for analysing the outcome of single-arm survival trials. It compares the survival distribution of patients with a prefixed reference survival curve that usually represents the expected outcome under standard of care. However, classical one-sample log-rank tests assume that the reference curve is known, ignoring that it is frequently estimated from historical data and therefore susceptible to sampling error. Neglecting the variability of the reference curve can lead to an inflated type I error rate, as shown in a previous paper. Here, we propose a new survival test that allows to account for the sampling error of the reference curve without knowledge of the full underlying historical survival time data. Our new test allows to perform a valid historical comparison of patient survival times when only a historical survival curve rather than the full historic data is available. It thus applies in settings where the two-sample log-rank test is not applicable as method of choice due to non-availability of historic individual patient survival time data. We develop sample size calculation formulas, give an example application and study the performance of the new test in a simulation study.

Colorimetric analysis in Secondary Education, a simulation with portable electronic devices and food coloring substances

Due to the widespread availability of smartphones with strong cameras and decent computing power, teachers are able to create innovative, experimental lesson plans. This study's primary goal was to use digital technologies, such cellphones, to the scientific process of colorimetry in chemistry and the Beer-Lambert law. Students made solutions using candy colors in varying quantities for this lab practice. They recorded the Hue (H) value on a white background using a cell phone that has soft-ware installed to measure color using the HSV model. They plotted the H color pa-rameter against the quantity of droplets per 100 milliliters using these values. The outcome was a straight line, which effectively validated the method's underlying premise that is, the Beer-Lambert law. The solution used for the most recent meas-urement had an unknown concentration. The groups were able to accurately calcu-late the concentration of the unknown solution by using the reference curve they had generated. Students produced solutions, measured particulars, used software and smartphones as scientific instruments, made graphs, evaluated data, and came to scientific findings during this lab exercise.