Paired T-test For Differences Research Articles

Understanding Factors Impacting Coronavirus Disease 2019 Vaccine Hesitancy in a Rural Surgical Clinic.

Objective: Evaluate patient hesitancy about the coronavirus disease 2019 (COVID-19) vaccine. Patients and Methods: English and Spanish pre-and post-video surveys were completed by patients at rural surgery clinics. The surveys consisted of 25 or 21 five-point Likert statements, respectively. Paired difference t-tests and independent sample t-tests were performed. Results: Ninety-four patients completed the surveys: 137 females (73%) and 51 (27%) males; 113 patients were Hispanic (64%); 63 patients were white (36%). The pre-video survey showed that the top two factors influencing patients were: preference for wearing masks over vaccination (n = 185; = 3.55) and not trusting the effectiveness of the vaccine (n = 186; = 3.01). Patients agreed that the video made them want to talk to their family about getting vaccinated (n = 176; = 3.14) and made them appreciate that they can get really sick from COVID-19 (n = 177; = 3.14). After watching the video, women of childbearing age (WCBA; n = 65; = 3.20) agreed more that the video made them want to get the COVID-19 vaccine than non-WCBA (n = 59; = 2.37; p = 0.0123). Women of childbearing age (n = 66; = 3.32) also agreed more that the video made them appreciate that they can get really sick from the COVID virus than non-WCBA (n = 60; = 2.58; p = 0.0254). Post-video statements showed that patients agreed that the video was easy to understand, they liked the video, and the video was helpful. Conclusions: There is room to better inform patients in a rural setting, especially WCBA, about COVID-19 illness and vaccination through video testimonies. Surgeons are uniquely positioned to offer effective recommendations, to increase vaccination rates, and address vaccine hesitancy.

Schematic Analysis and Fiducial Point of Tooth for Root Canal Therapy

The purpose of this study is to identify schematic relationships between root canal axis, the cementoenamel junction (CEJ), and the contour of the clinical crown’s facial surface in maxillary central incisors. 72 radiographic images of extracted maxillary central incisors with previous root canal treatment were collected. Angles (tangent angle) between the root canal axis and lines tangent to fiducial points on the facial surface 3.5 mm, 4.0 mm, 4.5 mm, 5.0 mm, and 5.5 mm cervical to the incisal edge were measured using ImageJ software. Facial-palatal CEJ widths were measured and divided into facial and palatal CEJ by the root canal axis. Generalized linear models were used to assess any relationship between CEJ widths and the constructed tangent angles. The Paired Difference T-test was performed to determine the ratio of palatal CEJ to facial CEJ widths. The correlation between CEJ width and angle measurements was statistically significant except at 3.5 mm (P < 0.05). The tangent angle values decreased from the most incisal point (22.8°) to the most cervical point (18.4°). The average value of total CEJ widths was 7.44 mm. Palatal CEJ was on average 0.22 mm greater than facial CEJ widths (P = 1.61e-6). Using CEJ width and the tangent angle at the fiducial point, the root canal axis of the maxillary central incisor can be predicted.

복합운동 프로그램이 여자 중학생의 성장호르몬 및 칼시토닌에 미치는 영향

The purpose of this study is to investigate the effect of the Combined exercise program on growth hormones and calcitonin in female middle school students. The subjects of the study were female middle school students, and a total of 20 students were classified into an exercise group (10) and a control group (10), and a combined exercise program was conducted three times a week for 50 minutes for 12 weeks at a 50 to 70 percent HRR intensity. Measurements were performed twice before and after. For the analysis of all data, SPSS (Ver. 23.0) was used, and the average value (M) and standard deviation (SD) were calculated Two-way repeated measures ANOVA were used to verify the interaction between groups and measurement periods, paired t-test for differences within groups, and independent t-test for differences between groups. As a result, growth hormones increased significantly in the exercise group in the change by period within the group, and calcitonin did not show any significant differences in the interaction effect between the group and the group.BR Taken together, the 12-week combined exercise program shows a positive effect on the growth hormone and calcitonin of female middle school students, requiring the development of various programs for overweight middle school girls.

Behavioral Activation, Mindfulness Exercises, and Loving-Kindness Meditation Exercises as Effective Therapies to Reduce Stress among Nursing Students’ during COVID-19 Pandemic

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic could increase stress which will impact the student’s achievement during the pandemic situation. AIM: The purpose of the study was to analyze stress among Indonesian nursing students’ after giving the interventions of behavioral activation (BA), mindfulness exercises (ME), and loving-kindness meditation exercise (LKME) during the COVID-19 pandemic. METHODS: This study was a quasi-experimental study with a one-group pre-test-post-test design. Data collection has been conducted in 4 weeks’ period on April–May 2021 using consecutive sampling. The sample of this study was 83 respondents in Level II of Indonesian nursing students at Stikes Kesdam IV/Diponegoro who have fulfilled the inclusion criteria. The instrument used was the Perceived Stress Scale. RESULTS: The majority of respondents are women, namely, 64 respondents (77.1%). After being given the intervention of BA, ME, and LKME, respondents decreased their stress with a mean of 16.66 became 14.76. The dependent t-test showed that the p value was 0.000 (p &lt; 0.05), which means that there was a significance difference in stress pre- and post-intervention. The mean difference was 1.90 and the paired difference t-test was 0.000 (p &lt; 0.05). CONCLUSION: BA, MEs, and LKME are recommended as stress coping mechanisms for Indonesian nursing students during the COVID-19 pandemic.

The FACT : Use of a novel intermittent pneumatic compression device to promote pre-surgery arm vein dilation in patients with chronic renal failure.

Arteriovenous fistula (AVF) creation and maturation for hemodialysis is globally a topic of importance given the poor results and high costs associated with renal care. Successful AVF (surgical or endovascular) creation requires appropriate superficial veins and quality arteries. Many procedures fail due to initial small veins with limited blood flow capacity and distensibility. Intermittent pneumatic compression has previously shown success in trials to increase superficial veins in patients with end stage renal disease post AVF. The objective of this study is to investigate the role of an intermittent pneumatic device, the Fist Assist®, to dilate cephalic arm veins in patients with advanced chronic kidney disease (CKD) prior to AVF placement. Three centers enrolled subjects from June 2019 through July 2021. Baseline Doppler measurements of the cephalic vein in standard locations the forearm and upper arm with and without a blood pressure cuff were recorded. Patients were instructed and used Fist Assist® on their non-dominant arm for up to 4 h daily for 90 days. At approximately 3 months, Doppler measurements were repeated. The primary endpoint was cephalic vein enlargement with secondary endpoints based on percentage of veins approaching 2.5 mm in the forearm and 3.5 mm in the upper arm. Thirty-seven subjects with CKD (mean eGFR 13.8 mL/min) were enrolled and completed the trial. Paired-difference t-tests (one tail) for aggregate data showed significant venous dilation of the cephalic vein in both the forearm and upper arm after use with the Fist Assist® (p < 0.05). Mean differences in the forearm veins were approximately 0.6 and 1.1 mm in the upper arm cephalic vein after Fist Assist® application. There were no major complications reported by any subject during the trial. Fist Assist® use in patients with CKD is effective to enhance vein dilation. Forearm and upper arm cephalic veins increased on average 0.6 and 1.1 mm respectively after Fist Assist® application. This is the first trial to evaluate the effect of intermittent, focal pneumatic compression on pre-surgery vein diameter in patients with advanced CKD before AVF creation.

The impact of creative drama activities on aggressive behaviour of preschool children

This article presents the findings of a research study examining the impact of creative puppetry activities on aggressive behaviour in preschool children. The aim of creative drama was to allow for experiences that help children understand interpersonal relations, put themselves in another’s shoes and see alternative possibilities of behaving or acting in given situations. Play with a puppet in small groups offers children opportunities to establish pro-social peer interactions and learn socialisation skills including solving minor conflicts. The research was conducted with 22 preschool teachers in Slovenian preschools and first grades of elementary schools (including 460 children aged 4–7). The teachers completed a scale of social behaviour for each child in the group before introducing the puppetry activities and after concluding them, i.e. after three months of intense, daily creative work with puppets. The paired difference t-test showed that according to the teachers’ assessments after the three-month conduct of creative puppetry activities in the group, the frequency of the occurrence of aggressive behaviour in the total population was diminished, especially in the children who had the lowest scores in the initial assessment.

Prostatic Enucleovaporization Using GreenLight™ Laser for Treatment of Benign Prostatic Hyperplasia: 12-Month Results

Introduction: Treatment options for benign prostatic hyperplasia (BPH) include an open approach, transurethral resection of the prostate (TURP), and newer energy-driven modalities. TURP has been the preferred technique for many decades; however, it carries a significant risk of bleeding, hyponatremia, and reoperation.1,2 Newer modalities are growing in popularity but face limitations on prostate size and risk causing irritative bladder symptoms.3 Enucleovaporization of the prostate (EVP) using the Greenlight™ laser (American Medical Systems, Minnetonka, MN) is a new technique that is suitable for larger prostates while potentially minimizing postoperative morbidity. We present our initial experience with the first 10 consecutive patients to undergo Greenlight EVP by a single surgeon at a large academic medical center with 1 year follow-up. Materials and Methods: A retrospective review was conducted on 10 consecutive patients undergoing EVP by a single surgeon between March 2013 and March 2014. Descriptive statistical analysis was conducted, including paired difference t-test, to examine intraoperative variables and clinical outcomes. The EVP technique employs the GreenLight XPS™ laser and the Moxy™ fiber. First, the prostate is enucleated by subcapsular dissection using low energy settings. Prostatic glandular tissue is then directionally vaporized to reduce energy transfer to the prostatic capsule and underlying nervous plexus. Results: Our first 10 patients who underwent Greenlight EVP were with an average age of 65 years (52–81 years) at the time of procedure and a mean prostate volume of 57 cc (35–70 cc). Total length of procedure averaged 72 minutes (50–100 minutes) with 61 minutes of laser time (45–85 minutes) and an average energy use of 339 kJ (150–550 kJ). At 1 year postprocedure, patients experienced improved urinary flow from preoperative Qmax of 7.3 to 17.6 mL/sec (p<0.00001), decreased postvoid residual volumes from 108 to 39 cc (p=0.005), and improved International Prostate Symptom Survey scores from 25.5 to 7.5 (p=0.00001). Conclusions: EVP is an effective treatment option for BPH with notable improvement in urinary flow and lower urinary tract symptoms over the early learning curve. It offers distinct promise in reducing complications such as capsular perforation or injury to the prostatic nervous plexus through energy transfer. Previous studies have also noted improvement for large-volume glands.4 The EVP technique merits further study to establish longer term safety and efficacy. No competing financial interests exist. Runtime of video: 6 mins 44 secs

Making Use of Big Data to Evaluate the Effectiveness of Selective Law Enforcement in Reducing Crashes

State departments of transportation across the nation fund selective enforcement campaigns aimed at intensifying law enforcement at certain locations to improve traffic safety. At the same time, many states passively collect large data sets, such as officer GPS location tracks. To evaluate the effectiveness of selective enforcement, an approach was developed to employ structured query language (SQL) and geographic information system (GIS) technology to mine and integrate police patrol patterns, citations issued, crash occurrences, and selective enforcement periods. This information was analyzed in a relational database within a spatial and temporal analysis framework. The intent was to use solely GIS technology; however, the size of the data sets was prohibitive, and SQL was used as a big data analytic. The SQL techniques successfully turned more than 37 million points of GPS data into 1.3 million points of selective enforcement location information, enabled the geolocation of 72.6% of electronic citations, and identified 21 selective enforcement areas across the state of Alabama. With big data analytics, GIS technology was reestablished as useful for the evaluation of changes in crash and citation frequencies before and during selective enforcement. Paired difference t-tests confirmed the decrease of crash frequency with 85% confidence at urban and rural locations. The analysis of the number of citations at the locations confirmed that citations increased during selective enforcement by an average of 254%. The developed methodology is a successful approach using large data sets for an unintended purpose to make valuable engineering conclusions and data-driven discoveries.

Tractography of Meyer's Loop asymmetries

The purpose of the current study was to use diffusion tensor imaging (DTI) to conduct tractography of the optic radiations (OR) and its component bundles and to assess both the degree of hemispheric asymmetry and the inter-subject variability of Meyer's Loop (ML). We hypothesized that there are significant left versus right differences in the anterior extent of ML to the temporal pole (TP) in healthy subjects. DTI data were acquired on a 3T Siemens MRI system using a single-shot Spin Echo EPI sequence. The dorsal, central and ML bundles of the OR were tracked and visualized in forty hemispheres of twenty healthy volunteers. The uncinate fasciculus (UF) was also tracked in these subjects so that it could be used as a distinct anatomical reference. Measurements were derived for the distance between ML-TP, ML and the temporal horn (ML-TH) and ML and the uncinate fasciculus (ML-UF). Paired difference t-tests were carried out with SPSS 14.0. ML and the UF were successfully tracked and visualized in all 20 volunteers. Significant hemispheric asymmetries were found for all measurements with left distances shorter than the right (P<0.005). In 50% of the subjects the left ML-UF distance was ≤1.9 mm. The results support our hypothesis and demonstrate that left ML-TP distances are significantly shorter than right ML-TP distances. These asymmetries are also reflected in shorter left distances between ML-TH and ML-UF. Moreover, these results are of interest to left-sided temporal lobe epilepsy surgery because it is not only more likely to disturb the anterior extent of ML but also renders the often closely located posterior aspect of the left UF more vulnerable to potential surgical impact.

Safety and efficacy of a high-adhesion whitening strip under extended wear regimen

ObjectivesThis randomized, parallel group, single centre clinical trial was conducted to evaluate the safety and compare the whitening efficacy for an extended wear of an experimental 9.5% H2O2 high-adhesion whitening strip, relative to a marketed 10% H2O2 control strip. MethodsTwenty-nine eligible adult volunteers were randomly assigned to either a treatment series with an experimental 9.5% H2O2 high-adhesion whitening strip at home for 2h, once a day, for 8 days; or a marketed 10% H2O2 whitening strip for 30min, on a similar daily regimen. Tooth color/whitening progression was recorded under standardized lighting conditions at baseline, day 3, day 5, and day 9, via digital imaging. Outcomes were reported using the CIELAB system. Usage safety was also assessed at each follow-up visit. Whitening efficacy for each group was investigated using a paired-difference t-test. The treatment groups were compared among each other using the analysis of covariance, with the baseline value and age as the covariates. ResultsBoth treatment groups demonstrated statistically significant mean color improvement from baseline for b* (yellowness) and L* (lightness) at each post-baseline visit. In addition, the 2-h high-adhesion strips demonstrated significantly greater improvement in b* and L* relative to the 30-min strip group at each follow-up visit. ConclusionsThe 2-h regimen for the 9.5% H2O2 high-adhesion whitening strip was more efficient for tooth whitening than the 30-min regimen of 10% H2O2 whitening strip. Both treatments were well tolerated and the use of the test products during the study time frame was considered safe. Clinical relevanceExtending the daily wear time of whitening strips can improve the efficacy of the treatment and ultimately shorten the length of the treatment without any significant adverse effects.

Quantification of White Spot Lesions around Orthodontic Brackets with Image Analysis

To investigate the use of image analysis for diagnosis and quantification of artificial white spot lesions on digital photographs before and after removal of orthodontic brackets. Enamel demineralization was artificially induced on the labial surface of 20 teeth bonded with orthodontic brackets. Standardized digital photographs were taken at angles of 90 degrees and 110 degrees to the labial surface, before and after bracket removal. All images were analyzed by two observers using image-processing software, and the area of the white spot lesion was calculated. Reproducibility was assessed by the Pearson correlation coefficient for interobserver reliability and by the paired t-test for differences between observers. Differences between the known and the measured demineralization area were tested using the t-test. Differences between both stages and angles were assessed by application of the paired t-test. Reproducibility was very good for all measurements. For the photographs taken at an angle of 110 degrees , there was a statistically significant but clinically irrelevant difference between the observers. The difference between the surface measured and the true surface was dependent on the stages and angles but was always <1 mm2. Image analysis is a reproducible and reliable method for quantification of artificial enamel demineralization around orthodontic brackets.

Applying statistical tests to empirically compare tabu search parameters for MAX 3-SATISFIABILITY: A case study

The application of stochastic heuristic, like tabu search or simulated annealing, to address hard discrete optimization problems has been an important advance for efficiently obtaining good solutions in a reasonable amount of computing time. A challenge when applying such heuristics is assessing when a particular set of parameter values yields better performance compared to other such sets of parameter values. For example, it can be difficult to determine the optimal mix of memory types to incorporate into tabu search. This in turn prompts users to undertake a trial and error phase to determine the best combination of parameter settings for the problem under study. Moreover, for a given problem instance, one set of heuristic parameter settings may yield a better solution than another set of parameters, for a given initial solution. However, the performance of this heuristic on this instance for a single heuristic execution is not sufficient to assert that the first set of parameter settings will always produce superior results than the second set of parameters, for all initial solutions. This paper looks at three known statistical procedures (one of which is a basic statistical test procedure and two of which were developed for discrete event simulation (discrete) optimization) to assess and compare the computational performance of tabu search for MAX 3-SATISFIABILITY. The statistical procedures designed for application within the domain of discrete event simulation output analysis (a paired difference t-test and two multiple comparison procedures developed and studied by Nelson and others) are adapted for this new purpose. An empirical case study is reported by computationally studying MAX 3-SATISFIABILITY instances across 32 variations of tabu search.

Nitrate content and potential microbial signature of rock glacier outflow, Colorado Front Range

AbstractHere we characterize the nutrient content in the outflow of the Green Lake 5 rock glacier, located in the Green Lakes Valley of the Colorado Front Range. Dissolved organic carbon (DOC) was present in all samples with a mean concentration of 0·85 mg L−1 . A one‐way analysis of variance test shows no statistical difference in DOC amounts among surface waters (p = 0·42). Average nitrate concentrations were 69 µmoles L−1 in the outflow of the rock glacier, compared to 7 µmoles L−1 in snow and 25 µmoles L−1 in rain. Nitrate concentrations from the rock glacier generally increased with time, with maximum concentrations of 135 µmoles L−1 in October, among the highest nitrate concentrations reported for high‐elevation surface waters. These high nitrate concentrations appear to be characteristic of rock glacier outflow in the Rocky Mountains, as a paired‐difference t‐test shows that nitrate concentrations from the outflow of 7 additional rock glaciers were significantly greater compared to their reference streams (p = 0·003). End‐member mixing analysis suggest that snow was the dominant source of nitrate in June, ‘soil’ solution was the dominant nitrate source in July, and base flow was the dominant source in September. Fluoresence index values and PARAFAC analyses of dissolved organic matter (DOM) are also consistent with a switch from terrestrial DOM in the summer time period to an increasing aquatic‐like microbial source during the autumn months. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Role of exercise to prevent fatigue and improve quality of life in localized prostate cancer patients undergoing radiation therapy

Materials/Methods: A prospective IRB approved randomized study. Twenty-one patients were assigned to a structured exercise group (n-11) or a control no exercise group (n 10). Assessments were carried out prior to starting and at the completion of radiotherapy. Instruments used included: Cardiac Fitness as measured by Metabolic Equivalents (METS); Piper Fatigue Scale (PFS); Beck Depression Inventory (BDI); and Functional Assessment of Cancer Therapy-Prostate (FACT-P). Lower extremity strength and flexibility also were assessed. Post-Pre changes within each group were assessed using paired-difference t-tests. These changes were compared between the two groups using two-sample t-tests. Each comparison was intended to stand on its own, so P-values were not adjusted for the large number of comparisons performed.

Dialyzable free cortisol after stimulation with Synacthen®

Objectives To compare the changes in free vs. total serum cortisol concentrations after acute stimulation of the adrenal cortex. Design and methods Paired serum samples of ten individuals taken immediately before and 1 h after stimulation with 250 μg ACTH (1–24) (Synacthen®) given i.v. were analyzed. Total cortisol was quantified using liquid chromatography tandem-mass spectrometry with an online sample extraction system and tri-deuterated cortisol as the internal standard. Free cortisol was measured with the same method after equilibrium dialysis. Concentrations of the corticosteroid-binding globulin (CBG) were determined by radioimmuno assay. Results Total cortisol increased by a mean of 106% (mean basal cortisol 312 nmol/L (SD 140 nmol/L), stimulated 686 nmol/L (SD 163 nmol/L); p < 0.001, paired t-test for differences); no significant change of CBG concentrations was found (874 nmol/L (SD 179 nmol/L) before stimulation, 869 nmol/L (SD 225 nmol/L) after stimulation). The mean increase of free cortisol was 263% (mean basal free cortisol 20.3 nmol/L (SD 13.2 nmol/L), stimulated 73.8 nmol/L (SD 26.7 nmol/L); p < 0.001) and thus substantially more pronounced compared to the increase of total cortisol ( p < 0.01). The ratio of free to total serum cortisol was significantly increased after stimulation (6.1% (SD 1.7%) before stimulation, 10.6% (SD 1.9%) after stimulation; p < 0.001). Conclusions After acute neuroendocrine stimulation of the adrenal cortex the relative increase of free bioactive cortisol concentrations is substantially more pronounced than the increase of total cortisol concentrations.

Serum cortisol/cortisone ratio after Synacthen stimulation

Objectives: 11β-Hydroxysteroid dehydrogenase (11β-HSD) enzymes interconvert active cortisol and inactive cortisone. There is growing evidence that local tissue concentrations of cortisol are generally modulated by site specific different 11β-HSD actions. While 11β-HSD type 2 unidirectionally inactivates cortisol, type 1 isoform acts bidirectionally. 11β-HSD type 1 is mainly localized in the liver and may thus restore circulating biologically inactive cortisone to active cortisol thereby modulating systemic glucocorticoid action; such a mechanism might be of importance in stressful situations. To study this hypothesis we investigated the influence of exogenous ACTH on serum cortisol/cortisone ratio. Design and Methods: Paired serum samples that were submitted for routine analysis of cortisol before and 1 h after stimulation with 250 μg ACTH (1–24) (Synacthen) were collected prospectively if the routine tests indicated normal adrenal function; 40 patients were included in the study, 29 patients were female, 11 male, median age was 31 yr (range 14–70). Serum cortisol and cortisone were determined using LC-ESI/MS/MS with an online sample extraction system and tri-deuterated cortisol as the internal standard. Results: While mean serum cortisol increased by 109% (mean basal concentration 373 nmol/L (SD 151 nmol/L), stimulated 781 nmol/L (SD 194 nmol/L)), mean serum cortisone significantly decreased after ACTH administration by 31% ( p < 0.001, paired t-test for differences). Mean serum cortisone was 70 nmol/L (SD 16 nmol/L) before and 48 nmol (SD 16 nmol/L) after ACTH administration; decrease in serum cortisone was observed in 34 (85%) of the patients. The ratio of serum cortisol/cortisone increased in all subjects (mean 5.4 (SD 1.9) before ACTH, and 16.2 (SD 6.2) after ACTH; p < 0.001). Conclusions: The data of our observational study suggest a modulation of peripheral metabolism of cortisol by ACTH with a stimulation of systemic 11β-HSD type 1 activity, leading to restoration of inactive cortisone to biologically active cortisol.

Goniometry of the proximal and distal interphalangeal joints, part II: Placement preferences, interrater reliability, and concurrent validity

The purposes of this repeated-measures single-case-design study were to describe goniometric placement preferences and their effect on the measurement of the proximal and distal interphalangeal joints, to determine interrater reliability, and to determine concurrent validity. Thirty-nine therapists measured one patient dorsally and laterally with the DeVore and the 6″ clear goniometers. No significant differences were found between the two goniometers used in the study. Comparison of the means of lateral and dorsal measurements revealed that the only joint associated with a significant difference was the contracted index proximal interphalangeal joint (p = 0.0347). Preferences did affect the standard deviations and ranges but not the means of the measurements. Interrater reliability was high (ICC 2,1: 0.99 and 0.86). Clinical and radiographic measurements were markedly different from each other (paired-difference t-tests), leading to inconclusive concurrent validity.

Automated Spectral Manipulation and Data Analysis for EPR Dosimetry of Teeth

A method for automating the spectral manipulation and data analysis procedures for EPR dosimetry of teeth is presented. The method is shown to correlate with conventional spectral peak-to-peak values to within 10 mGy for the reconstructed doses. Paired difference t-test data show that definitive systematic differences exist but that these effects on the reconstructed dose accuracy and precision are negligible for typical applications in tooth enamel EPR dosimetry. The algorithm is written in Hypercard© script for Macintosh computers but could be -implemented on other platforms.

The effect of fetal neck position on nuchal translucency measurement.

To determine the influence of the position of the fetal neck on nuchal translucency measurement. A prospective cross-sectional study. One hundred and ninety-six. Nuchal translucency was measured in the mid-sagittal plane, with the fetal neck in the flexed, neutral and extended positions. Measurements were made to the nearest 0.1 mm. Statistical analysis used the paired t-test for differences between the extended and neutral positions, [delta extended nuchal translucency] and the flexed and neutral positions [delta flexed nuchal translucency]. The mean extended nuchal translucency was 0.62 mm greater than the mean neutral nuchal translucency value [95% confidence interval 0.53 to 0.70, T = 14.33, P < or = 0.00001]. The mean flexed nuchal translucency was 0.40 mm less than the mean neutral nuchal translucency value [95% CI 0.34 to 0.47, T = 11.99; P = < 0.00001]. The repeatability coefficient was lower in the case of neutral nuchal translucency measurements [0.48] and was higher in the other groups [extended = 1.04, flexed = 0.70]. Fetal neck position can make a significant difference to nuchal translucency measurements. Repeatability of measurements are more accurate with the fetal neck in the neutral position. These findings have important implications for clinicians using nuchal translucency to screen the general obstetric population.

SIZE OF POINTERS FOR RESIDUE COVER MEASUREMENT

Comprehensive models for agrichemical transport necessarily include runoff predictions to partition rainfallbetween infiltration and runoff, as this ability is fundamental to predictions of chemical runoff and leaching. We compared GLEAMS, Opus, and PRZM-2 model runoff predictions with runoff measured in a precisely controlled field site used for chemical runoff studies. In 1992 and 1993, two 14.5 m 42.9 m corn (Zea mays, L.) field plots with 3% slope on Tifton loamy sand (fine-loamy, siliceous, thermic Plinthic Kandiudult) received six severe, artificial rainfall events over the growing season with each event consisting of a 25 mm hC1 rainfall for 2 h. Runoff was monitored continuously using a collector and flume. Model performance criteria included sensitivity analysis, graphical comparison and statistical analysis including mean, ratio of means, root mean square error (RMSE), and a paired difference t-test. Observed runoff averaged 20% of added rainfall. Lowest values occurred with freshly plowed soil or full canopy cover, while 24 to 34% runoff occurred when nearly bare soils had crusted over. Using an initial moisture condition-II curve number (CN) of 85, GLEAMS and Opus predicted runoff within 10%, overall, and produced a pattern of high and low runoff that closely followed observed. PRZM-2 overpredicted runoff by 90%, overall, and predicted its highest runoff when observed runoffwas lowest. Paired difference t-tests indicated a significant difference between measured and predicted runoff for PRZM-2 (p<0.001 at = 0.05), but none for GLEAMS (p = 0.761) or Opus (p = 0.194). Mean, ratio of means, and RMSE showed that GLEAMS and Opus performed better than PRZM-2. All three models were very sensitive to CN values which were empirical and subjective, but less sensitive to measurable soil physical properties. With careful parameterization, GLEAMS and Opus could be used to simulate runoff from similar row-crop and soil conditions.