An error analysis for visioplasticity data processing

The conducted investigations are concerned with the effect of data errors on the calculations of stress and strain components according to the visioplasticity method. The error analysis was based on an evaluating process suitable both experimentally and theoretically for exact calculations. Longitudinal sectional areas of rod drawing stock were marked photochemically with measuring grids with a line spacing of 0.1–1 mm. Specimens thus prepared were partially drawn and the deformation patterns were registered by means of a measuring microscope. The measured data were evaluated with the aid of a smoothing and calculating procedure based on cubic spline approximations. This procedure was checked with a flow model and proved to be suitable for exact visioplasticity calculations. Error investigations were carried out in order to examine the influence of a measured data scatter on the visioplasticity calculation results and an error size was defined and used to establish an error curve according to three different methods. By means of this function it is possible to quantify – as has been indicated by means of an example – the calculation error for a given quantity of data or, depending on the accuracy and aim of the calculations, the demands on the measuring grid and the data quality can be derived. By the example of the calculation of frictional stresses it has been demonstrated that the spacing of the measuring grid lines must be adjusted to suit the inhomogeneity of the plastic flow. If need be, a special more sophisticated method of evaluation is necessary – as described in ⁵) – to determine accurately such inhomogenous strain patterns.     

The clinical estimation of liver size: a comparison of techniques and an analysis of the source of error

The clinical estimation of liver size using radioisotope scintiscans as a standard of reference has been shown to be very inaccurate. The main source of error is in the location of the upper border of the liver. Physical characteristics of the patients influence this measurement.     

Covariate measurement error and the estimation of random effect parameters in a mixed model for longitudinal data

We explore the effects of measurement error in a time-varying covariate for a mixed model applied to a longitudinal study of plasma levels and dietary intake of beta-carotene. We derive a simple expression for the bias of large sample estimates of the variance of random effects in a longitudinal model for plasma levels when dietary intake is treated as a time-varying covariate subject to measurement error. In general, estimates for these variances made without consideration of measurement error are biased positively, unlike estimates for the slope coefficients which tend to be 'attenuated'. If we can assume that the residuals from a longitudinal fit for the time-varying covariate behave like measurement errors, we can estimate the original parameters without the need for additional validation or reliability studies. We propose a method to test this assumption and show that the assumption is reasonable for the example data. We then use a likelihood-based method of estimation that involves a simple extension of existing methods for fitting mixed models. Simulations illustrate the properties estimators.     

A model of synchronization of motor acts to a stimulus sequence. II. Stability analysis, error estimation and simulations

In Part I (Mates 1994), a linear model of timing and error-corrections was constructed that aims at an explanation of the mechanisms underlying a subject's performance in an experimental paradigm, in which the task is to synchronize a sequence of motor acts to a sequence of stimuli. The model consists of two error-corrective mechanisms: (1) corrections of period (inverted frequency) of the sequence of responses; (2) corrections of phase shift of that sequence (synchronization error). In this paper, the influence of the physiologically justifiable model variables and of initial conditions on the steady-state response sequence as well as the stability of performance of the model are analyzed. The model is stable for error-correction gains in the range from 0 to 2. Comparison with known empirical data supports the assumption that reasonable values are less than 1. Furthermore, an alternative to the basic linear model is introduced in which the possible character of the process of subjective acquisition of the synchronization error is discussed. On the basis of findings from other experimental paradigms (fusion and order threshold) it can be assumed that the subjective estimate is a nonlinear function of the difference between the temporal central availability of internal representations of the stimulus and response-feedback events. Some other known synchronization data are simulated by the nonlinear modification of the model in this paper. A good fit of the simulation results achieved further justifies the model structure proposed. Finally, the possible effect of the subjective synchronization-error estimation on empirical data is discussed.     

Type I error rates for moderated multiple regression analysis.

The method of moderated multiple regression is increasingly being applied in the search for moderator variables in industrial and organizational psychology. Because of frequent failures of the method in revealing moderator effects in empirical studies—in which such effects are strongly expected—it has been suggested that the procedure may lack statistical power with respect to hypothesis tests about moderating effects and, therefore, is inappropriate for the purposes of conventional moderator analyses. We evaluated this conclusion with computer simulation data. Our study indicated that the method is not overly conservative and that the Type I error rate of moderated multiple regression is approximately .05 at α?=?.05. Moreover, a proposed alternative multivariate procedure, principal component regression, is shown to have a Type I error rate that approaches unity under ordinary conditions when applied to the evaluation of moderator effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling hemodynamic response for analysis of functional MRI time-series

The standard Gaussian function is proposed for the hemodynamic modulation function (HDMF) of functional magnetic resonance imaging (fMRI) time-series. Unlike previously proposed parametric models, the Gaussian model accounts independently for the delay and dispersion of the hemodynamic responses and provides a more flexible and mathematically convenient model. A suboptimal noniterative scheme to estimate the hemodynamic parameters is presented. The ability of the Gaussian function to represent the HDMF of brain activation is compared with Poisson and Gamma models. The proposed model seems valid because the lag and dispersion values of hemodynamic responses rendered by the Gaussian model are in the ranges of their previously reported values in recent optical and fMR imaging studies. An extension of multiple regression analysis to incorporate the HDMF is presented. The detected activity patterns exhibit improvements with hemodynamic correction. The proposed model and efficient parameter estimation scheme facilitated the investigation of variability of hemodynamic parameters of human brain activation. The hemodynamic parameters estimated over different brain regions and across different stimuli showed significant differences. Measurement of hemodynamic parameters over the brain during sensory or cognitive stimulation may reveal vital information on physiological events accompanying neuronal activation and functional variability of the human brain, and should lead to the investigation of more accurate and complex models.     

Shaping of the cat paw for food taking and object manipulation: an X-ray analysis

The kinematics of the cat distal forelimb during food-taking were analysed to obtain information on the movement processes within the paw before and during object taking in a species without monosynaptic corticomotoneuronal projections. The behaviour was investigated with two tests: either the table test (TT, food offered on a table located at ground level in a reaching distance of 22 and 28 cm) or the horizontal test (HT, food offered in a small container located at shoulder level, height 18-25 cm, reaching distance 6-12 cm). In five animals, the changes in configuration and the conjoint actions of the wrist, the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints were assessed with three-dimensional X-ray cinematography (time resolution 20 ms, spatial resolution 1 mm) and video analysis. While approaching the target, the digits were first extended and subsequently abducted. This 'preshaping' consisted of combined angular changes in the MCP and PIP joints, thereby attaining an adequate grip aperture. Each cat used a stable strategy, but different cats used different strategies. In the TT, preshaping involved an MCP extension and a PIP flexion. In the HT, predominant extension of the MCP, predominant extension of the PIP, or a combination of both were used, followed by MCP flexion and PIP flexion. The grip aperture started to decrease before object contact, earlier in the TT, later in the HT. Grasping was achieved by flexion of first the PIP and later the MCP. The X-ray analysis gave evidence for individuated digit movements. Correlation analysis of the angular position of the joints between the different phalanges showed that digits 3 and 4 acted in concert, as did digits 2 and 5, but with clear independence between the different pairs. Furthermore, the different phalanges served different purposes during the grasp. Digits 3, 4 established object contact, digits 2, 5 were mainly used to stabilize the paw onto the surface. The cat distal forelimb displays a refined movement repertoire during the preshaping and grasping phase of food-taking. During the preshaping phase, the kinematics resembled in some aspects the situation in humans. The results demonstrate the ability of the polysynaptic projections from the cortico-motoneuronal system to organize differentiated distal limb movements, including individuated movements of the digits.     

项目投资绩效审计评估探析

从项目建设全过程角度探讨分析投资绩效内部审计、评估的有效途径。     

A systems analysis approach to medical error

Using decerebrate frogs (Rana catesbeiana), we investigated the role of vagal and laryngeal sensory feedback in controlling motor activation of the larynx. Vagal and laryngeal nerve afferents were activated by electrical stimulation of the intact vagal and laryngeal nerves. Pulmonary afferents were activated by lung inflation. Reflex responses were recorded by measuring efferent activity in the laryngeal branch of the vagus (Xl) and changes in glottal aperture. Two glottic closure reflexes were identified, one evoked by lung inflation or electrical stimulation of the main branch of the vagus (Xm), and the other by electrical stimulation of Xl. Lung inflation evoked a decrementing burst of Xl efferent activity and electrical stimulation of Xm resulted in a brief burst of Xl action potentials. Electrical stimulation of Xl evoked a triphasic mechanical response, an abrupt glottal constriction followed by glottal dilatation followed by a long-lasting glottal constriction. The first phase was inferred to be a direct (nonreflex) response to the stimulus, whereas the second and third represent reflex responses to the activation of laryngeal afferents. Intracellular recordings of membrane potential of vagal motoneurons of lung and nonlung types revealed EPSPs in both types of neurons evoked by stimulation of Xm or Xl, indicating activation of glottal dilator and constrictor motoneurons. In summary, we have identified two novel reflexes producing glottic closure, one stimulated by activation of pulmonary receptors and the other by laryngeal receptors. The former may be part of an inspiratory terminating reflex and the latter may represent an airway protective reflex.     

"Exact" and approximate methods for analysis of total error in radiation measurements

BACKGROUND: It is documented that truncal vagotomy and Billroth II gastroenterostomy disturbs the emptying of the gallbladder. The aim of the present prospective study was to assess the emptying of the gallbladder after Roux-en-Y gastroenterostomy. STUDY DESIGN: There were 34 patients, who had undergone either truncal vagotomy with pyloroplasty (TVP, 14 instances) or Billroth II gastrectomy (20 instances), and were subsequently subjected to Roux-en-Y gastroenterostomy. The emptying of the gallbladder was assessed before and after the Roux-en-Y procedure, by milk-technetium-99m labeled hepatoiminodiacetic acid (milk-99mTc-HIDA) scintigraphy. Milk-99mTc-HIDA scintigraphy was also performed on twenty-eight healthy subjects, who served as the control group. RESULTS: After excluding the subjects having spontaneous gallbladder evacuation before milk ingestion, there remained 26 subjects in the control group, 12 patients with TVP, and 19 with Billroth II gastrectomy. Truncal vagotomy with pyloroplasty was associated with delayed onset (p < 0.001) and decreased rate (p < 0.01) of emptying of the gallbladder compared with the control group. Truncal vagotomy with pyloroplasty also changed the normal pattern of emptying in two patients (sequential emptying and refilling events). Billroth II gastrectomy was associated with decreased extent and abnormal pattern of emptying compared with subjects in the control group (p < 0.0001) and patients having TVP. Roux-en-Y gastroenterostomy, performed upon patients with TVP, significantly increased lag phase duration (p < 0.001), decreased ejection fraction (p < 0.01), and changed the pattern of emptying of the gallbladder (p < 0.01). Roux-en-Y procedure performed upon patients with Billroth II gastrectomy significantly increased lag phase duration (p < 0.0001). CONCLUSIONS: Roux-en-Y gastroenterostomy severely disturbs all parameters of the emptying of the gallbladder.     

Image analysis for grain shape characterization in lamp filaments

Algorithms have been developed for appraising the quality of tungsten lamp filament wire microstructure with respect to its resistance to sag. They allow a numerical determination of grain aspect ratio, grain boundary contour, angle of boundary with wire diameter, and degree of grain boundary surface convolution. These values are combined algebraically to give a grain shape parameter (GSP) which reliably predicts how resistant the filament is to grain boundary sliding. Measurements are made of thermally etched grain boundaries on scanning electron microscopy (SEM) images of the surfaces on coiled filaments. Data are recorded and parameters computed by means of an image analyzer. The technique has been tested on samples made from the same wire modified in process to have varying strain after the last anneal. It has also been tested on samples purchased from various vendors. These applications indicate that the computed GSP is a sensitive predictor of filament creep resistance and reliably reflects variation in wire drawing strain after the last anneal.     

NOMAD: a versatile strategy for in vitro DNA manipulation applied to promoter analysis and vector design

Molecular analysis of complex modular structures, such as promoter regions or multi-domain proteins, often requires the creation of families of experimental DNA constructs having altered composition, order, or spacing of individual modules. Generally, creation of every individual construct of such a family uses a specific combination of restriction sites. However, convenient sites are not always available and the alternatives, such as chemical resynthesis of the experimental constructs or engineering of different restriction sites onto the ends of DNA fragments, are costly and time consuming. A general cloning strategy (nucleic acid ordered assembly with directionality, NOMAD; WWW resource locator http:@Lmb1.bios.uic.edu/NOMAD/NOMAD.htm l) is proposed that overcomes these limitations. Use of NOMAD ensures that the production of experimental constructs is no longer the rate-limiting step in applications that require combinatorial rearrangement of DNA fragments. NOMAD manipulates DNA fragments in the form of "modules" having a standardized cohesive end structure. Specially designed "assembly vectors" allow for sequential and directional insertion of any number of modules in an arbitrary predetermined order, using the ability of type IIS restriction enzymes to cut DNA outside of their recognition sequences. Studies of regulatory regions in DNA, such as promoters, replication origins, and RNA processing signals, construction of chimeric proteins, and creation of new cloning vehicles, are among the applications that will benefit from using NOMAD.     

Multivariate analysis and the problem of Type I error.

Discusses the recommendation by M. R. Leary and E. M. Altmaier (see record 1981-02539-001) that MANOVA should be used with several dependent variables in order to control for overall Type I error rate. This paper calls attention to limitations and dangers in routine application of MANOVA, describes some alternative procedures, and laments the necessarily pervasive character of the problem of statistical error. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

数控滚齿机热变形误差分析与补偿新方法

为了对数控滚齿机的热变形误差进行补偿,提高齿轮加工精度,利用聚类回归分析方法,优化选择了热误差补偿过程中的温度测量点.采用最小二乘回归方法建立了热误差模型,实验结果验证,该模型精度高.提出了一种热误差差动螺旋补偿方法,该方法完全采用外部硬件补偿,能够独立地实现对热变形误差的实时补偿.与其他补偿方法对比,该方法不受限于数控系统的开放性,通用性较强.     

7种不同物质标定EDTA标准滴定溶液的条件控制及误差分析

本文通过CaCO3,MgO,FeNH4(SO4)2.12H2O、锌粒、铜粒、铅粒、铋粒等7种物质在不同条件下对EDTA标准滴定溶液的标定对比试验,研究了酸效应、水解效应、温度、光照、空气浮力、基准物质溶液的配制和酸度的初调、缓冲溶液、指示剂的种类和用量等多种因素对标定误差的影响及其消除办法。实验结果表明,只要选择和控制好测定条件,标定方法之间的误差是可以减小或消除的。在本实验条件下,用上述7种物质标定0.020015mol/LEDTA标准滴定溶液,相对误差均小于0.20%。     

Electrophysiological analysis of error monitoring in schizophrenia.

In this study, the authors sought to determine whether abnormalities exhibited by schizophrenia patients in event-related potentials associated with self-monitoring--the error-related negativity (ERN) and the correct response negativity (CRN)--persist under conditions that maximize ERN amplitude and to examine relationships between the ERN and behavior in schizophrenia. Participants performed a flanker task under 2 contingencies: one encouraging accuracy and another emphasizing speed. Compared with healthy participants, in schizophrenia patients the ERN was reduced in the accuracy condition, and the CRN was enhanced in the speed condition. The amplitude of a later ERP component, the error positivity, did not differ between groups in either task condition. Reduced self-correction and increased accuracy following errors were associated with larger ERNs in both groups. Thus, ERN generation appears to be abnormal in schizophrenia patients even under conditions demonstrated to maximize ERN amplitude; however, functional characteristics of the ERN appear to be intact. (PsycINFO Database Record (c) 2010 APA, all rights reserved)