Analysis of the ST-segment in terms of principal components: application on multichannel magnetocardiographic recordings

Parameterization of the ST-segment is used as a tool for risk stratification for patients to suffer from ventricular tachycardia. This parameterization is performed in terms of Principal Component Analysis (PCA) applied on multichannel magnetocardiographic (MCG) recordings. 55-channel MCG was recorded from 14 normal persons, 10 patients with CHD, 14 patients with MI, and six patients with VT. We found a significantly (p < 0.05) lower PCA-score in patients with MI compared to normals. The lowest PCA-score was found in VT patients. Significant differences can be found between VT patients and normals and also between VT patients and CHD patients.     

On the variability of QRS time-duration in magnetocardiographic recordings

High resolution electrocardiography (HRECG) recordings have already shown an increased beat-to-beat microvariability of the QRS duration of the terminal QRS in patients with a history of ventricular tachycardia (VT). The purpose of this study is to detect QRS-duration microvariability with magnetocardiographic (MCG) recordings in normals, patients with coronary heart disease (CHD), patients with a history of myocardial infarction (MI), and VT patients. QRS microvariability is calculated as the variance of time-shifts of single beats respectively to the average of all beats. The average over all channels of the MCG is performed. QRS microvariability was evaluated from 55-channel MCG in 15 normal persons, in 12 patients with CHD, in 13 patients with MI, and in 10 patients with VT. We found a significantly higher microvariability in patients with MI compared to normals. The highest microvariability was found in VT patients.     

On the variability of QRS time-duration in magnetocardiographic recordings

High resolution electrocardiography (HRECG) recordings have already shown an increased beat-to-beat microvariability of the QRS duration of the terminal QRS in patients with a history of ventricular tachycardia (VT). The purpose of this study is to detect QRS-duration microvariability with magnetocardiographic (MCG) recordings in normals, patients with coronary heart disease (CHD), patients with a history of myocardial infarction (MI), and VT patients. QRS microvariability is calculated as the variance of time-shifts of single beats respectively to the average of all beats. The average over all channels of the MCG is performed. QRS microvariability was evaluated from 55-channel MCG in 15 normal persons, in 12 patients with CHD, in 13 patients with MI, and in 10 patients with VT. We found a significantly higher microvariability in patients with MI compared to normals. The highest microvariability was found in VT patients.     

Effect of the principal blood components on lung surfactant

The action of the principal blood components on surface activity of substrates containing lung surfactant was investigated. Mixing blood hemolysate, serum, albumin, and fibrinogen with extracts and washings from the lungs, application as a monolayer, or their injection into the hypophase of a monolayer of washings increased the surface tension (ST) of these substrates. Hemoglobin, serum lipids, and cholesterol had the opposite action. Contact of all these blood components, exhibiting opposite effects on ST of medium containing surfactant, with bubbles from the lungs during determination of their coefficient of stability (CS), by Pattle's method, led to an increase in CS.Department of Pathological Physiology, Karaganda Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR P. D. Gorizontov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 88, No. 12, pp. 648–650, December, 1979.     

Effect of aerobic conditioning on ventricular activation: A principal components analysis approach to high-resolution electrocardiogram

Background

The athlete's heart represents a reversible structural and functional adaptations of myocardial tissue developed through physical conditioning. Surface electrocardiogram (ECG) has the capability to detect myocardial hypertrophy but has limited performance in monitoring physical conditioning-induced myocardial remodeling. The aim of this study was to develop an ECG-derived test for detecting incipient myocardial hypertrophy in well-conditioned athletes based on a principal components (PC) analysis.

Methods

Two groups of study composed of 14 sedentary healthy volunteers (Control group) and 14 professional long distance runners (Athlete group) had their maximal metabolic equivalents (MET) estimated (mean±SD: Control group: 9±2 METs vs. Athlete group: 20±1 METs, p<0.05). All participants had their high-resolution ECG (HRECG) recorded, and a 120 ms segment starting at the QRS complex onset and ending in the ST segment was extracted to build a data matrix for PC analysis. The Mahalanobis distance was evaluated by a logistic regression model to determine the optimal separation threshold between groups. HRECG was also analyzed using the classical time domain approach. The comparison of areas under the receiver operating characteristic curve (c-statistic) in 10,000 bootstrap re-samplings measured how well each method detected physical conditioning (α<0.05).

Results

Average bootstrap c-statistic for PC analysis and time domain approaches were 0.98 and 0.79 (p<0.05), respectively. PC analysis and maximal oxygen consumption exhibited comparable performances to distinguish between groups.

Discussion

The PC analysis method applied to HRECG signals appropriately discriminates well-conditioned athletes from healthy, sedentary subjects.     

Intracerebral recordings of the Bereitschaftspotential demonstrate the heterogeneity of its components

Though consisting of early and late components, the evoked potential preceding a voluntary movement (Bereitschaftspotential — BP) is often considered as a unitary phenomenon. By analyzing intracerebrally recorded BP we attempted to demonstrate that the components are electrophysiological correlates of separate operations. The BPs recorded in 42 epilepsy surgery candidates (28 men, 14 women; aged from 18 to 49 years) during self-paced clenching movements of the hand opposite to the explored hemisphere were investigated in the study. Microdeep intracerebral 5 to15-contact electrodes were used. The averaged curves were calculated from approximately 30 trials in each case. All the records were taken with a binaural reference. The total number of explored brain regions was 235; the event-related premovement potentials were observed in 121 of them. Three types of premovement responses were observed: (i) the BP with both components; (ii) the BP with the early component only; and (iii) the BP with the late component only. The generators of the early one-component BP were demonstrated in two frontal cortical areas (precentral and middle frontal gyri) and in the parietal area known to be involved in action planning and decision making (precuneus). Some structures generating the early one-component BP were activated during movement; the others were without motor responsiveness. The results suggest a separate elaboration of functional task items in some and their integration in other brain structures, and the existence of volitional mechanisms of different hierarchical character.     

Personalized medicine based on genomic information: the present status in terms of clinical application

Molecular-genetic tests clinically available in Japan are mainly for the analysis of microbial nucleic acids. Genetic tests targeting the human genome have been limited to research purposes, although a few tests are available for clinical use. In April 2006, reimbursement was readjusted and four molecular-genetic tests were added to those with national insurance coverage: Major bcr-abl mRNA nucleic acid amplification assay, genetic analysis of progressive muscular dystrophy, genetic analysis of rearranged immunoglobulin gene, and genetic analysis of malignant tumor. Under Japan's healthcare system, only laboratory tests catalogued in the reimbursement can be clinically applied. Otherwise, the costs won't be reimbursed. Since most molecular-genetic tests are not given insurance reimbursement points, the costs are charged to the patients themselves. This is one of the reasons why molecular-genetic tests are not used in clinics. Other reasons are that such tests are based on the home-brew method, and that standardized assay methods are not available. I reviewed and discussed the following issues: the present status of medicine based on genomic information in Japan, and the significance of the standardization of molecular-genetic testing in clinical application. I also introduced the JMCoE (Japan Molecular Center of Excellence) program for the promotion of molecular-genetic testing in clinics.     

Assessment of the principal components of the equivalent cardiac generator on recorded electrocardiographic potentials

The relative contribution of the various multipolar components to the total surface potential was determined in experiments on the isolated heart located in a spherical volume conductor. These contributions were calculated for distances from the electrodes to the center of the cardiac ventricles that corresponded to the placement of standard and thoracic ECG recording electrodes in different age groups. On the basis of these results the optimal model of an equivalent cardiac generator can be chosen for a given electrocardiographic recording system.     

Comparison of principal components computed with principal factor analysis on the basis of averaged and single-trial ERPs using the Fischer-Roppert procedure

Averaged and single-trial event-related potentials (ERPs) were analysed using the Principal Factor Analysis (PFA) with following varimax rotation, and the results were compared. The correspondence between the matrices of factor loadings was tested by means of the Fischer-Roppert-procedure. For the application of PFA, a preceding averaging to improve the signal to noise ratio is not necessary. If the group of subjects is homogeneous enough, the analysis of the single-trial ERPs provides results sufficient to investigate the component structure of the ERP. The ERPs from all subjects can be described with one common component structure.     

Influence of the distal femoral resection angle on the principal stresses in ceramic total knee components

PurposeA certain failure mode using a newly developed cemented ceramic femoral component in total knee replacement was observed in clinical application, i.e. fracture of the femoral component during intraoperative impaction. This may be caused by unintentional deflection of the saw blades during cutting with consecutive higher resection angle of the distal femur than desired, leading to bending of the femoral component during implantation. A finite-element-analysis was carried out to simulate implantation of the femoral component and to evaluate the influence of distal femur preparation on implant stress.ScopeWe developed and validated a numerical model of the ceramic femoral component including a contact formulation which allowed calculating the principal stresses of the implant during implantation onto the resected femur. The analysis considered different anterior and posterior resection angles with a total of 17 variations. By increasing the femoral resection angle in the finite-element-model it could be shown that a deviation of three degrees from the intended resection angle can cause critical stress amounts during implantation.ConclusionsWhen implanting the ceramic component in total knee arthroplasty, the femoral resection angles should be prepared very precisely, in particular anterior saw blade deflection has to be avoided. The implant manufacturer increased implant safety through an additional resection template. Moreover, the impaction of the ceramic femoral component during cementing was not further recommended by using a hammer.     

Comparison of dimension reduction-based logistic regression models for case-control genome-wide association study: principal components analysis vs. partial least squares

With recent advances in biotechnology, genome-wide association study (GWAS) has been widely used to identify genetic variants that underlie human complex diseases and traits. In case-control GWAS, typical statistical strategy is traditional logistical regression (LR) based on single-locus analysis. However, such a single-locus analysis leads to the well-known multiplicity problem, with a risk of inflating type I error and reducing power. Dimension reduction-based techniques, such as principal component-based logistic regression (PC-LR), partial least squares-based logistic regression (PLS-LR), have recently gained much attention in the analysis of high dimensional genomic data. However, the performance of these methods is still not clear, especially in GWAS. We conducted simulations and real data application to compare the type I error and power of PC-LR, PLS-LR and LR applicable to GWAS within a defined single nucleotide polymorphism (SNP) set region. We found that PC-LR and PLS can reasonably control type I error under null hypothesis. On contrast, LR, which is corrected by Bonferroni method, was more conserved in all simulation settings. In particular, we found that PC-LR and PLS-LR had comparable power and they both outperformed LR, especially when the causal SNP was in high linkage disequilibrium with genotyped ones and with a small effective size in simulation. Based on SNP set analysis, we applied all three methods to analyze non-small cell lung cancer GWAS data.     

Empowerment in terms of theoretical perspectives: Exploring a typology of the process and components across disciplines

A variety of studies on empowerment has been conducted, but there has been no overarching framework available for practitioners and researchers hoping to grasp the process and components of empowerment in a comprehensive manner. This study was designed to provide the overarching framework across theories and disciplines for both academics and practitioners in the field of empowerment. A method of theoretical synthesis was employed in this study. Studies were chosen for review in the article based on the two criteria. First, both books and articles were not limited as long as they included theories on the steps toward empowerment and the cognitive element of empowerment. Second, disciplines were not bounded as they provided ideas for the empowerment process and its cognitive elements. It was found that empowerment might be synthesized into five progressive stages and four cognitive elements in both personal and collective empowerment. © 2006 Wiley Periodicals, Inc.     

多通道局部场电位独立分量能量编码工作记忆事件的研究

目的 基于大鼠前额叶皮层多通道局部场电位（LFPs）的独立分量分析（ICA）,研究LEPs的各个独立分量（ICs）的能量如何编码工作记忆过程中的事件.方法 以事件发生点为零点,分别将±500 ms内在大鼠记忆皮层记录的15通道LEPs,通过ICA分解为15个ICs,计算各分量在窗宽为50 ms的窗口内的能量.以步长为25ms移动窗口,获得15个ICs能量的动态分布.选择在±200 ms内能量明显增高（即其能量改变编码了事件）的ICs,通过ICA逆变换可知ICs对应的记录通道.结果 在对同一段实验数据进行多次重复分析时,由于ICA算法分解结果的不确定性,在±200 ms内能量明显增高的ICs不尽相同,但其对应的空间位置均为同一通道处,表明该通道所在位置即为LFPs编码该次事件的主要功能区域;而对多段实验数据的分析结果显示,实验数据与分析所得的主要功能区域具有较为理想的一一对应性.结论 多通道LFPs独立分量的能量可以编码工作记忆过程中的事件;ICA对于识别多通道LFPs对工作记忆事件的编码模式是有效的;ICA可以对编码事件的主要功能区域进行空间定位,且鲁棒性较为理想.     

留学生掌握解剖学名词难度分析

随着中国国力的增强和国际影响力的提升,来中国学医的外国留学生数量逐年递增.海军军医大学对临床医学六年制本科留学生实施"同班施训"培育模式,即将外军留学生与中国学员置于同等的教学环境之中,与中国学员同受教、同受训、同实习.第一年为预科阶段,课程围绕汉语综合课展开,同时开设听力课、口语课、汉字课和汉语水平考试专项突破课.     

A principal components analysis of the dissociative experiences scale in a substance abuse population

A principal components analysis with a varimax rotation was performed on the Dissociative Experiences Scale using a substance abuse population. Results based on a combination of the eigenvalue greater than 1 criterion and factor interpretability indicated that a four-factor solution best fit the data. Implications for interpreting the Dissociative Experiences Scale with substance abusers were discussed.     

惯量主轴在桡骨粗隆精确定位中的应用研究

目的　根据CT图像测定水平面上桡骨粗隆相对于桡骨长轴的旋转角度。 方法　44例桡骨标本（左侧17例,右侧27例）CT扫描图像,观察桡骨粗隆形态,选择标志点。根据CT原始图像信息应用Mimics21.0构建桡骨三维模型,分别计算生成桡骨的惯量主轴,建立惯量主轴参考坐标系。统计每例标本桡骨粗隆后侧嵴标志点在水平面上相对桡骨长轴的旋转角度。 结果　桡骨粗隆后侧嵴普遍存在。桡骨的惯量主轴与桡骨的相对位置是稳定的。桡骨粗隆后侧嵴在该水平面坐标参考系上相对桡骨主旋转轴的角度为（82.93 ± 5.55）°。 结论　基于惯量主轴建立的解剖参考坐标系稳定性好,可精确定位桡骨粗隆。     

The effects of EEG data transformations on the solution accuracy of principal component analysis

Principal component analysis (PCA) is a commonly used multivariate procedure that reduces the dimensionality of a data set. When applied to quantitative electroencephalogram (qEEG) data, PCA produces components that may represent functional systems within the brain. Unfortunately, qEEG, like many other physiological measures, produce distributions that are positively skewed. In response, researchers often transform qEEG data prior to conducting a PCA, which does not require univariate or multivariate normality. Despite this, researchers continue to transform qEEG data with limited knowledge of how such transformations will affect the accuracy (precision) of their component solutions. The purpose of the present investigation was to examine the effects of several commonly used data transformation procedures on PCA solution accuracy.     

Confounding factors in water EMG recordings: an approach to a definitive standard

This work presents a study on the influence of the aqueous environment on the surface EMG (sEMG) signal recorded in bipolar montage from the abductor pollicis brevis muscle, when only the forearm is immersed in water. Ten men, 30.1±4.0 (mean ± SD) years old, performed ten 2-s 40% MVC isometric contractions of the abductor pollicis brevis muscle in two controlled environments (air and water, at a temperature of 32°C). They were always equipped with electrodes protected with a waterproof adhesive tape. No significant variations (paired Wilcoxon test) due to the environments were observed in the median frequency of the power spectrum (MDF) and in the root mean square (RMS) value of the sEMG signal. These results allow us to assess the methodological criteria to properly record sEMG signals in water and provide the basis to explain different findings obtained by other authors.During part of the development of this work, W. H. Veneziano and A. F. Rocha were with LISiN.     

Analysis of single-unit firing patterns in multi-unit intrafascicular recordings

A system for extracting single-unit activity patterns from multi-unit neural recordings was tested using real and simulated neural data. The system provided reliable estimates of firing frequency for individual units in simulated multi-unit data and allowed reliable determinations of the responses of individual cutaneous mechanoreceptor units to ‘natural’ stimuli such as brushing or pressing on the skin. An implementation of the system, which operated online and in real time, was used to obtain estimates of multiple, single-unit responses from multi-unit intrafascicular electrode recordings. The pattern of activity across the population of units in a given recording gave a reliable indication of the type of stimulus that had evoked the activity. It was concluded that this system, used in combination with intrafascicular peripheral nerve recordings, could be used to provide online, real-time information about peripheral stimuli.