心电图频谱分析的快速付里叶变换方法

本文第一部分简短地讨论了如何使快速付里叶变换方法适用于心电图频谱分析的若干问题,包括基2付里叶变换(FFT)、混合基FFT及当样本点数不为2的整次幂时实现FFT的几种方法。 第二部分讨论了心电图的频谱分析。给出了由三角波及钟形波合成的心电图的数学模型及根据数学模型计算心电图理论频谱的方法。并把理论频谱和由FFT算出的实际频谱作了比较,目的是对实际心电图频谱进行定量分析,并找出心电图频谱结构的一般特征。     

基于多窗口时频重排的巴克频谱系数心音分类算法研究

多窗口时频重排有助于提升对心音进行巴克频谱系数（BFSC）分析的时频分辨率。为此,本文提出一种基于多窗口时频重排的BFSC特征提取与深度学习结合的心音分类新算法。首先,对随机截取的心音片段进行幅值归一化等预处理,然后分别用多个正交窗口对心音做分帧处理,及计算基于短时傅里叶变换的时频重排,将得到的各独立频谱通过算术平均计算出平稳的频谱估计。最后,通过巴克滤波器组提取该重排频谱的BFSC作为特征。本文采用卷积网络与循环神经网络作为分类器,对提取的特征进行模型比较与性能评估。最终,多窗口时频重排改进BFSC的方法提取了更具有辨别力的特征,二分类准确率达到0.936,灵敏度为0.946,特异度为0.922。研究结果表明,本文所提算法无需分割心音,随机截取心音片段,大大简化了计算流程,有望用于先天性心脏病筛查。     

脑电意识任务分类的研究

目的:脑电意识任务分类.方法:本文将脑电信号中事件去同步化/相同步化现象作为特征信息,讨论了运用多变量参数AAR模型算法(MVAAR)提取脑电信号特征后,采用线性分析、基于马氏距离分类和留一法三种分类器分别进行脑电意识任务识别.引入正确率,互信息,kappa值,ROC曲线下面积值的概念对分类效果进行性能评价.结果:传统的线性分类、基于马氏距离的二次分类,留一法分类效果都较好.结论:但当两类的协方差矩阵差别较大时,MDA方法有更好的结果.当实验数据庞大时,留一法的分类时间将随着数据量的增大而延长,分类效果受到影响.     

用付里叶变换技术提取超声血流速度谱

本文提出了用复数付里叶变换(FFT)技术同时提取超声血流速度大小和方向信息的原理和方法。作者用Z80微处理器制作了一个实时频谱分析系统。采取脉冲多普勒空间取样技术,配合超声M型心动图仪确定血流取样部位,血流频谱直接显示在M型声像图的同一荧光屏上。     

1024点高速FFT处理器的FPGA设计与实现

目的 设计满足高速实时信号处理需要的快速傅里叶变换(FFT)处理器。方法采取基-2按频率抽取( DIF)FFT算法,蝶形运算单元采用流水线方式,接收数据采用乒乓操作的方法设计基于现场可编程门阵列(FPGA)的1 024点、32位字长、定点复数FFT处理器。结果在时钟100 MHz下,计算1次1 024点定点FFT耗时约...     

基于时变频谱相干的工作记忆过程中海马-前额叶皮层局部场电位的同步特征模式研究

目的基于时变频谱相干研究工作记忆过程中海马(HPC)和前额叶皮层(PFC)局部场电位的同步特征模式,为研究工作记忆的信息处理机制提供支持。方法采集6只SD大鼠在执行Y迷宫空间工作记忆任务过程中的腹侧海马(vHPC)和内侧前额叶皮层(mPFC)的局部场电位(LFPs)信号,应用短时傅里叶变换(STFT)计算vHPC和mPFC LFPs的时频分布,确定工作记忆的特征频段,进而基于时变频谱相干研究vHPC和mPFC LFPs特征频段的同步特征模式,最后应用支持向量机探索应用频谱相干值预测工作记忆的可行性。结果大鼠正确执行工作记忆时,HPC和PFC的theta频段(4~12 Hz)能量均增加(均P<0.01),且HPC-PFC theta频段的频谱相干值增加(P<0.05)。以正确和错误执行工作记忆时的平均频谱相干峰值和峰值与起始点的差值作为特征,进行支持向量机的训练和预测,准确率达89%,精确率达90%,召回率为88%,F1分数为88%,与随机打乱标签数据重排结果相比差异均有统计学意义(均P<0.05)。结论 HPC-PFC theta频段的同步协同是正确执行工作记忆时信息处理的潜在机制之一。     

雷达式生命探测仪中人体数量识别技术的研究

针对雷达式生命探测仪穿墙检测到人体的呼吸信号的非平稳特性,采用短时傅里叶变换、频谱图,对单人、多人的呼吸信号进行分析,并通过奇异值分解有效地提取特征矢量进行模式识别,能够成功地识别单人和多人.实验结果表明,基于短时傅里叶变换的奇异值分解法能够稳定、有效地提取特征矢量,从而达到对雷达式生命探测仪中人体数量的较准确地识别.     

意识任务识别中事件相关脑电的时频域信息熵表达

事件相关脑电的量化表征对于研究意识任务识别和认识大脑思维机制具有重要意义.本研究对左右手想象意识任务的脑电信号进行小波包分析,提取出时频域信息熵用来表征事件相关脑电的变化;进而,分析了时频域信息熵特征的事件相关去同步/同步的变化时程,应用互信息评价时频域信息熵对事件相关脑电的表征能力,将相同步理论应用于导联间的脑电信号分析;设计时变线性分类器实现左右手想象运动意识任务识别,获得了满意的结果,最小分类错误率为9%.结果表明,时频域信息熵与频带能量具有一致的变化时程;时频域信息熵具有比频带能量更好的分离性,是事件相关去同步,同步的一个敏感的量化参数;时频域信息熵结合相同步相干性指数.能够提供更多反映大脑意识任务的状态信息.     

视觉工作记忆多通道脑电θ分量因果流的研究

目的 工作记忆是一种在认知活动中对信息进行瞬时加工和贮存的记忆系统.笔者通过研究健康受试者在视觉工作记忆模式多通道脑电(multi-channel EEGs)的因果流(CF)分布模式,从信息传递特征角度为研究工作记忆机制提供支持.方法 记录8例健康受试者共80次Sternberg视觉工作记忆实验中的16通道EEGs.对原始EEGs进行预处理后,应用快速傅里叶变换(FFT)分别计算每个通道EEG的能量,选取能量值最大的通道为特征通道,对这个特征通道EEG进行时频分析,确定工作记忆特征频段.计算EEGs特征频段分量的定向传递函数(DTF)以及因果流.结果 工作记忆EEG能量集中在Fz通道的θ频段(4～8 Hz).EEG θ频段因果流的特征模式:Fz通道因果流为最大的正值,C3、C4、C5、C6通道因果流为前4个绝对值最大的负值.结论 θ频段为工作记忆EEG的特征频段.额叶(Fz)是工作记忆信息流出的关键脑区(因果源),C3、C4、C5、C6为信息流入的主要脑区(因果汇).     

基于矩估计的生物序列模体的贝叶斯检验

针对生物序列模体的显著性检验问题,提出了一种基于矩估计的贝叶斯检验方法.将模体的显著性检验转化为多项分布的检验问题,选取Dirichlet分布作为多项分布的先验分布,并采用矩估计方法估计Dirichlet的超参数,最后应用贝叶斯定理得到一个贝叶斯因子,用于评价模体检验的统计显著性,这种方法克服了传统多项分布检验中构造检验统计量并计算其在零假设下确切分布中的困难.选择JASPAR数据库中107个转录因子结合位点和100组随机模拟数据进行实验,采用皮尔逊积矩相关系数作为评价检验质量的一个标准,实验结果优于传统的模体检验的一些方法,例如快速傅里叶方法.     

Renal dysplasia and asplenia in two sibs

A family is reported in which two sibs, one male and the other female, both died within 24 hours of birth with enlarged polycystic kidneys. Postmortem histology in the second child showed gross renal dysplasia. In both children the pancreas was enlarged, nodular and cystic but the liver appeared macroscopically normal. In the second child, histological examination confirmed pancreatic fibrosis with cystic dilation of ducts, but showed portal fibrosis with bile duct proliferation in the liver.
This combination of findings is very reminiscent of those in a girl and her brother reported by Ivemark et al. (1959). The children reported here also showed absence or hypoplasia of the spleen, cardiac anomalies and other features of the Ivemark syndrome (Ivemark 1955), a quite different, usually sporadic, congenital disorder. It is suggested that the children described here have a distinct lethal congenital disorder, probably inherited in an autosomal recessive manner.     

Schizophrenia in a North Swedish geographical isolate, 1900–1977. Epidemiology, genetics and biochemistry

Over 200 schizophrenic patients belonging to three major and interrelated pedigree complexes have been investigated over the past 30 years in a North Swedish geographically isolated population, presently numbering about 6,000. An intensive investigation of a number of biochemical correlates and genetic markers in a few selected families belonging to one of the major pedigrees has indicated new strategies for the current research program.
Schizophrenia, as defined operationally, is significantly associated with decreased activities of two enzymes (1) blood platelet monoamine oxidase, (2) plasma dopamine-β-hydroxylase, and (3) with the genetic marker Gc² (group specific antigen). Both enzymes are subject to genetic variation. A positive score for linkage between schizophrenia and low plasma DBH activity has been calculated, but, so far, available data are insufficient for discrimination between linkage and partial contribution of genetically controlled low plasma DBH to the pathogenesis of the disease. Alternatively, both mechanisms could be involved.
As a model for continued research, schizophrenia is explained as based on a double dominant-recessive genotype (Aabb), representing a vulnerability which in about 50 % of cases develops into clinical schizophrenia. It is suggested that the dominant mutation (A) operates on or affects MAO activity, and that the recessive genotype (bb) is instrumental in low variates of DBH activity and very likely such variates within the normal range of physiological variation. Moreover, it is suggested that the combined effects of MAO- and DBH-reduced efficiency on the metabolism of e.g. dopamine could be an essential pathogenic mechanism for the schizophrenic illness which is segregating in this population.     

The dominant diseases of modernized societies as omega-3 essential fatty acid deficiency syndrome: Substrate beriberi

About 1900, modern food selection and processing caused widespread $\text{epidemics}$ of the B vitamin deficiency diseases of beriberi and pellagra which, for genetic reasons, often expressed as different diseases ranging from bowel and heart disease to dermatoses and psychoses. But the B vitamins merely help convert essential fatty acids (EFA) into the prostaglandin (PG) tissue regulators and it now turns out that, through hydrogenation, milling and selection of w3-poor southern foods, we have also been systematically depleting, by as much as 90%, a newly discovered trace Nordic EFA (w3) of special importance to primates and sole precursor of the PG3(4) series, even as a concurrent fiber deficiency increases body demand for EFA. Since substrate EFA is processed by many B vitamin catalysts, an EFA deficiency will mimic a $\text{panh}$ypovitaminosis B, i.e., a mixture of $\text{substrate}$ beriberi and $\text{substrate}$ pellagra resembling vitamin beriberi and pellagra but exhibiting as even more diverse $\text{endemic}$ disease. This would consitute a second stage of the Modern Malnutrition and explain why some workers now hold the dominant diseases of modermized societies to be new, nutritionally based, pellagraform yet lipid-related and to range, once again, from heart disease to psychosis. It is an assumption that our dominant diseases are unrelated to each other or are merely revealed by our diagnostic acumen and therapeutic success; and that hydrogenating millions of tons of food oils annually, to destroy the rancidity producing w3-EFA, is safe for $\text{primates}$. Extensive beriberiform disease is reported here in 32 typical cases taken from medical practice which responds strikingly to linseed oil supplements (60% w3-EFA) in confirmation of identical results in Capuchins.     

What will studies of Fulani individuals naturally exposed to malaria teach us about protective immunity to malaria?

There are an estimated over 200 million yearly cases of malaria worldwide. Despite concerted international effort to combat the disease, it still causes approximately half a million deaths every year, the majority of which are young children with Plasmodium falciparum infection in sub-Saharan Africa. Successes are largely attributed to malaria prevention strategies, such as insecticide-treated mosquito nets and indoor spraying, as well as improved access to existing treatments. One important hurdle to new approaches for the treatment and prevention of malaria is our limited understanding of the biology of Plasmodium infection and its complex interaction with the immune system of its human host. Therefore, the elimination of malaria in Africa not only relies on existing tools to reduce malaria burden, but also requires fundamental research to develop innovative approaches. Here, we summarize our discoveries from investigations of ethnic groups of West Africa who have different susceptibility to malaria.     

'Very sore nights and days': the child's experience of illness in early modern England, c.1580-1720

Sick children were ubiquitous in early modern England, and yet they have received very little attention from historians. Taking the elusive perspective of the child, this article explores the physical, emotional, and spiritual experience of illness in England between approximately 1580 and 1720. What was it like being ill and suffering pain? How did the young respond emotionally to the anticipation of death? It is argued that children’s experiences were characterised by profound ambivalence: illness could be terrifying and distressing, but also a source of emotional and spiritual fulfilment and joy. This interpretation challenges the common assumption amongst medical historians that the experiences of early modern patients were utterly miserable. It also sheds light on children’s emotional feelings for their parents, a subject often overlooked in the historiography of childhood. The primary sources used in this article include diaries, autobiographies, letters, the biographies of pious children, printed possession cases, doctors’ casebooks, and theological treatises concerning the afterlife.     

Guidelines for the Validation and Use of Immunoassays for Determination of Introduced Proteins in Biotechnology Enhanced Crops and Derived Food Ingredients

Recent advancements in agricultural biotechnology have created a need for analytical techniques to determine introduced proteins in crops enhanced through modern biotechnology techniques. These proteins are expressed in plant tissues and may be present in food ingredients. Immunoassays are ideally suited for protein detection and may be used as both quantitative and threshold methods. Microplate ELISA and lateral flow devices are two of the most commonly used immunoassay formats for agricultural biotechnology applications. This paper provides general background information and a discussion of criteria for the validation and application of immunochemical methods to the analysis of proteins introduced into plants and food ingredients using biotechnology methods. It is the result of a collaborative effort of members of the Analytical Environmental Immunochemical Consortium. This collaborative effort represents the combined expertise of several organizations to reach consensus on establishing guidelines for the validation and use of immunoassays. Further, the paper offers developers and users a consistent approach to adopting the technology as well as aid in producing accurate and meaningful results.     

Ultracryotomy: development and application (with examples from the yeast cytology) (author's transl)

The preparation steps usually necessary for obtaining ultrathin frozen sections of biological material (chemical prefixation, enclosing, cryoprotective treatment, freezing, sectioning, and post-staining the sections for transmission electron microscopy) are submitted to a critical analysis. The application of cryo-ultramicrotomy, in particularly for cytochemical purposes, is reviewed. Fundamental considerations of chemical prefixation and poststaining are supported by examples from yeast cytology. Furthermore, the efficiency of the cryo-ultramicrotomy (electron optical resolution of ultrastructural details) is demonstrated on yeast cells and protoplasts.     

HLA in North Colombia Chimila Amerindians

HLA-A,-B,-C,-DRB1 and -DQB1 alleles have been studied in Chimila Amerindians from Sabana de San Angel (North Colombian Coast) by using high resolution molecular typing. A frequent extended haplotype was found:HLA-A*24:02-B*51:10-C*15:02-BRB1*04:07-DQB1*03:02 (28.7%) which has also been described in Amerinndian Mayos Mexican population (Mexico, California Gulf, Pacific Ocean). Other haplotypes had already been found in Amerindians from Mexico (Pacific and Atlantic Coast), Peru (highlands and Amazon Basin), Bolivia and North USA. A geographic pattern according to HLA allele or haplotype frequencies is lacking in Amerindians, as already known. Also, five new extended haplotypes were found in Chimila Amerindians. Their HLA-A*24:02 high frequencies characteristic is shared with aboriginal populations of Taiwan; also, HLA-C*01:02 high frequencies are found in New Zealand Maoris, New Caledonians and Kimberly Aborigines from Australia. Finally, this study may show a model of evolutionary factors acting and rising one HLA allele frequency (-A*24:02), but not in others that belong to the same or different HLA loci.     

The case for allele‐specific recognition by the TCR

There is a sharp difference in how one views TCR structure–function–behaviour dependent on whether its recognition of major histocompatibility complex‐encoded restriction elements (R) is germline selected or somatically generated. The generally accepted or Standard model is built on the assumption that recognition of R is by the V regions of the αβ TCR, which is not driven by allele specificity, whereas the competing model posits that recognition of R is allele‐specific. The establishing of allele‐specific recognition of R by the TCR would rule out the Standard model and clear the road to a consideration of a competing construct, the Tritope model. Here, the case for allele‐specific recognition (germline selected) is detailed making it obvious that the Standard model is untenable.