男性新生儿血红蛋白正常参考值与中国地理因素

目的:为制定中国男性新生儿血红蛋白正常参考值的统一标准提供科学依据。方法:收集了中国78个单位用氰化高铁血红蛋白(HiCN)法测定的5169例男性新生儿血红蛋白正常参考值,运用相关分析和回归分析的方法,研究了其与地理因素的关系。结果:发现男性新生儿血红蛋白正常参考值与中国地理因素之间有很显著的相关关系(F=17.93)。用逐步回归分析的方法推导出了一个回归方程:Y=156.8+0.01670X1+0.4140X3-0.008596X5±25.1。结论:如果知道了中国某地的地理因素,就可以用回归方程估算这个地区的血红蛋白正常参考值。依据血红蛋白正常参考值与地理因素的依赖关系把中国分为青藏区、西南区、西北区、东南区、华北区、东北区等六个区。     

中国健康中年男性全血比粘度参考值与海拔高度的关系

为制定中国健康中年男性全血比粘度参考值的统一标准提供科学依据,本文收集了中国各地用毛细管法测定的健康中年男性全血比粘度参考值,并对其与海拔高度的关系进行了研究,发现随着海拔高度的逐渐增高,健康中年男性全血比粘度参考值也在逐渐的增大,相关性很显著,用一元回归分析的方法推导出了一个回归方程,如果知道了中国某地的海拔高度,就可以用回归方程估算这个地区的健康中年男性全血比粘度参考值。     

Verification of predicted specimen-specific natural and implanted patellofemoral kinematics during simulated deep knee bend

Verified computational models represent an efficient method for studying the relationship between articular geometry, soft-tissue constraint, and patellofemoral (PF) mechanics. The current study was performed to evaluate an explicit finite element (FE) modeling approach for predicting PF kinematics in the natural and implanted knee. Experimental three-dimensional kinematic data were collected on four healthy cadaver specimens in their natural state and after total knee replacement in the Kansas knee simulator during a simulated deep knee bend activity. Specimen-specific FE models were created from medical images and CAD implant geometry, and included soft-tissue structures representing medial–lateral PF ligaments and the quadriceps tendon. Measured quadriceps loads and prescribed tibiofemoral kinematics were used to predict dynamic kinematics of an isolated PF joint between 10° and 110° femoral flexion. Model sensitivity analyses were performed to determine the effect of rigid or deformable patellar representations and perturbed PF ligament mechanical properties (pre-tension and stiffness) on model predictions and computational efficiency.Predicted PF kinematics from the deformable analyses showed average root mean square (RMS) differences for the natural and implanted states of less than 3.1° and 1.7 mm for all rotations and translations. Kinematic predictions with rigid bodies increased average RMS values slightly to 3.7° and 1.9 mm with a five-fold decrease in computational time. Two-fold increases and decreases in PF ligament initial strain and linear stiffness were found to most adversely affect kinematic predictions for flexion, internal–external tilt and inferior–superior translation in both natural and implanted states. The verified models could be used to further investigate the effects of component alignment or soft-tissue variability on natural and implant PF mechanics.     

Leg kinematics and muscle activity during treadmill running in the cockroach, Blaberus discoidalis : I. Slow running

We have combined high-speed video motion analysis of leg movements with electromyogram (EMG) recordings from leg muscles in cockroaches running on a treadmill. The mesothoracic (T2) and metathoracic (T3) legs have different kinematics. While in each leg the coxa-femur (CF) joint moves in unison with the femur-tibia (FT) joint, the relative joint excursions differ between T2 and T3 legs. In T3 legs, the two joints move through approximately the same excursion. In T2 legs, the FT joint moves through a narrower range of angles than the CF joint. In spite of these differences in motion, no differences between the T2 and T3 legs were seen in timing or qualitative patterns of depressor coxa and extensor tibia activity. The average firing frequencies of slow depressor coxa (Ds) and slow extensor tibia (SETi) motor neurons are directly proportional to the average angular velocity of their joints during stance. The average Ds and SETi firing frequency appears to be modulated on a cycle-by-cycle basis to control running speed and orientation. In contrast, while the frequency variations within Ds and SETi bursts were consistent across cycles, the variations within each burst did not parallel variations in the velocity of the relevant joints. Accepted: 24 May 1997     

中国健康老年前期人全血比粘度参考值与地理因素的关系

目的为制定中国健康老年前期人全血比粘度参考值的统一标准提供科学依据。方法收集了全国各地用毛细管法测定的健康老年前期人全血比粘度参考值,并对其与地理因素的关系进行了研究。结果发现海拔高度是影响健康老年前期人全血比粘度参考值最主要的因素,随着海拔高度的逐渐增大,健康老年前期人全血比粘度参考值也在逐渐的增大,相关性很显著。用逐步回归分析的方法推导出了二个回归方程。结论如果知道了中国某地的地理因素,就可以用这二个回归方程估算这个地区的健康老年前期人全血比粘度参考值。依据健康老年前期人全血比粘度参考值与地理因素的依赖关系把中国分为青藏区,西南区,西北区,东南区,华北区,东北区等六个区。     

Procedures for selecting composites based on prediction methods

Summary Procedures for selecting among parental varieties to be used in the synthesis of composites are discussed. In addition to the criterion based on the mean and variance of composites of the same size (k) proposed by Cordoso (1976), we suggest the index I_j=w₁v_j+w_{2 j} or I_j=(2/k) I_j for a preliminary selection among parental varieties. We show that by increasing k (size of the composite) I_j tends to g_j, the general combining ability effect. Such a criterion is particularly important when n, the number of parental varieties, is large, so that the number of possible composites (N_c=2ⁿ–n–1) becomes too large to be handled when using the common prediction procedures. Yield data from a 9 × 9 variety diallel cross were used for illustration.     

Goodness-of-Fit Testing for the Logistic Regression Model when the Estimated Probabilities are Small

The distribution of the Hosmer-Lemeshow chi-square type goodness-of-fit tests (?_g, ?_g) for the logistic regression model are examined via simulations designed to examine their behavior when most of the estimated probabilities are small or are expected to fall in a few deciles. The results of the simulations show statistic ?_g should be used when the two outcome groups (y = 0, 1) are not well separated, Δ≤2, where Δ² is the Mahalanobis distance. Statistic ?_g should be used when Δ ≥ 8. Either statistic may be used when 2 ≦ Δ ≦ 8. All tests should be used with caution when the proportion in the sample with y = 1 is less than 0.1.     

The position of the rotation center of the glenohumeral joint

To validate the assumption that the center of rotation in the glenohumeral (GH) joint can be described based on the geometry of the joint, two methods for calculation of the GH rotation center were compared. These are a kinematic estimation based on the calculation of instantaneous helical axes, and a geometric estimation based on a spherical fit through the surface of the glenoid. Four fresh cadaver arms were fixed at the scapula and fitted with electromagnetic sensors. Each arm was moved in different directions while at the same time the orientation of the humerus was recorded. Subsequently, each specimen was dissected and its glenoid and humeral head surfaces were digitized. Results indicate no differences between the methods. It is concluded that the method to estimate the GH center of rotation as the center of a sphere through the glenoid surface, with the radius of the humeral head, appears to be valid.     

P-Values as Measures of Predictive Validity

A predictive P-value is proposed to measure the difference between an actual and predicted outcome in assessing the validity of an hypothesized prediction model. The concept is illustrated by applications to multiple regression prediction and to the validation of forecast models.     

Correlation and Linear Regression if the Random Variables are Subject to Errors or Fluctuations

For the model x=a+e, y=b+d estimators of Pearson's coefficient of correlation and of the line of regression between a and b are presented. The problem of prediction is dealt with.     

Variation in patellofemoral kinematics due to changes in quadriceps loading configuration during in vitro testing

This study investigated changes in patellofemoral (PF) kinematics for different loading configurations of the quadriceps muscle: single line of action (SL), physiological-based multiple lines of action (ML), weak vastus medialis (WVM), and weak vastus lateralis (WVL). Fourteen cadaveric knees were flexed from 15° to 120° knee flexion using a loading rig with the ability to load different heads of the quadriceps and hamstring muscles in their anatomical orientation. PF rotation in the sagittal plane) and medial lateral translation were significantly different (p<0.05) for SL and ML, with maximum differences of 2.8° and 0.9 mm at 15° and 45° knee flexion, respectively. Compared to the ML, the WVM induced an average lateral shift of 1.5 mm and an abduction rotation of 0.8°, whereas a 0.9 mm medial shift and 0.6° adduction rotation was seen when simulating a WVL. The difference in the sagittal plane resultant force orientation of 26° between SL and ML was the major contributor to the change in PF rotation in the sagittal plane, while the difference in the frontal plane resultant force orientation of both the WVM and WVL from the ML (17° medial and 8° lateral, respectively) were the primary reasons for the change in PF frontal plane rotation and medial lateral translation. The two PF kinematic were significantly different from the ML for WVM and WVL (p<0.05). The results suggest that quadriceps muscle loading configuration can have a large influence on PF kinematics during full extension but less in deeper flexion. Therefore, using quadriceps single line loading for simulating activities with low flexion angles might not be sufficient to accurately replicate the physiological condition.     

A motion analysis marker-based method of determining centre of pressure during two-legged hopping

The fixed position of force plates has led researchers to pursue alternative methods of determining centre of pressure (CoP) location. To date, errors reported using alternative methods to the force plate during dynamic tasks have been high. The aim of this study was to investigate the accuracy of a motion analysis marker-based system to determine CoP during a two-legged hopping task. Five markers were attached to the left and right feet of eight healthy adults (5 females, 3 males, age: 25.0±2.8 years, height: 1.75±0.07 m, mass: 71.3±11.3 kg). Multivariate forward stepwise and forced entry linear regression was used with data from five participants to determine CoP position during quiet standing and hopping at various frequencies. Maximum standard error of the estimate of CoP position was 12 mm in the anteroposterior direction and 8 mm in the mediolateral. Cross-validation was performed using the remaining 3 participants. Maximum root mean square difference between the force plate and marker method was 14 mm for mediolateral CoP and 20 mm for anteroposterior CoP during 1.5 Hz hopping. Differences reduced to a maximum of 7 mm (mediolateral) and 14 mm (anteroposterior) for the other frequencies. The smallest difference in calculated sagittal plane ankle moment and timing of maximum moment was during 3.0 Hz hopping, and largest at 1.5 Hz. Results indicate the marker-based method of determining CoP may be a suitable alternative to a force plate to determine CoP position during a two-legged hopping task at frequencies greater than 1.5 Hz.