Fourier analysis of wing beat signals: assessing the effects of genetic alterations of flight muscle structure in Diptera.

A method for determining and analyzing the wing beat frequency in Diptera is presented. This method uses an optical tachometer to measure Diptera wing movement during flight. The resulting signal from the optical measurement is analyzed using a Fast Fourier Transform (FFT) technique, and the dominant frequency peak in the Fourier spectrum is selected as the wing beat frequency. Also described is a method for determining quantitatively the degree of variability of the wing beat frequency about the dominant frequency. This method is based on determination of a quantity called the Hindex, which is derived using data from the FFT analysis. Calculation of the H index allows computer-based selection of the most suitable segment of recorded data for determination of the representative wing beat frequency. Experimental data suggest that the H index can also prove useful in examining wing beat frequency variability in Diptera whose flight muscle structure has been genetically altered. Examples from Drosophila indirect flight muscle studies as well as examples of artificial data are presented to illustrate the method. This method fulfills a need for a standardized method for determining wing beat frequencies and examining wing beat frequency variability in insects whose flight muscles have been altered by protein engineering methods.     

Assessing the effect of management changes and environmental features on the spatio- temporal pattern of fire in an African Savanna: Fire spatio-temporal pattern

Spatio-temporal variability of the fire regime in the Kruger National Park (KNP) has been analyzed for the 1957–2011 period. Generalized linear mixed models have been used to assess the variability of fire metrics, such as the burnt area, the fire frequency and intensity for the entire area as well as for the main environmental classification systems (geology, soil, vegetation) and fire management zones. This analysis supports the hypothesis that the spatial pattern of fire regime is strongly influenced by the environmental template defined by climatic, geological, pedological and vegetation features. Moreover, contrary to some previous studies, together with the precipitation trend, fire management changes had a significant role in determining the temporal variability of the fire regime at the scale of KNP, particularly regarding the burnt area and the fire frequency.The complex interaction between the environmental template and management in determining the variability of the fire regime, as underscored by our study, defends the merit of adopting an adaptive planning/management based approach supported by quantitative analytic tools.     

New approach to the statistical analysis of cardiovascular data.

Fourier-based approaches to analysis of variability of R-R intervals or blood pressure typically compute power in a given frequency band (e.g., 0.01-0.07 Hz) by aggregating the power at each constituent frequency within that band. This paper describes a new approach to the analysis of these data. We propose to partition the blood pressure variability spectrum into more narrow components by computing power in 0.01-Hz-wide bands. Therefore, instead of a single measure of variability in a specific frequency interval, we obtain several measurements. The approach generates a more complex data structure that requires a careful account of the nested repeated measures. We briefly describe a statistical methodology based on generalized estimating equations that suitably handles this more complex data structure. To illustrate the methods, we consider systolic blood pressure data collected during psychological and orthostatic challenge. We compare the results with those obtained using the conventional methods to compute blood pressure variability, and we show that our approach yields more efficient results and more powerful statistical tests. We conclude that this approach may allow a more thorough analysis of cardiovascular parameters that are measured under different experimental conditions, such as blood pressure or heart rate variability.     

Variability in the performance of the spectrogram correlation detector for North-east Pacific blue whale calls

Spectrogram correlation has been used successfully for automatic detection of baleen whale calls. However, applying this method consistently to long time series can be challenging. To illustrate the potential challenges of the automatic detection process, recordings collected in the Southern California Bight between 2007 and 2012 were used for detection of North-east Pacific blue whale (Balaenoptera musculus) B calls. The effects of the following factors were investigated: blue whale B call frequency shift and appropriate kernel modification, seasonal variability in call abundance, analyst variability and noise. Due to intra- and inter-annual changes in the call frequency of blue whale B calls, seasonal and annual adjustments to the call detection kernel were needed. To account for seasonal variability in call production, evaluation of the detector against ground truth data was performed at multiple times during the year. Analyst variability did not affect overall long-term trends in detection, but it had an impact on the total number of detections, as well as call rate estimation. Noise, particularly from shipping, was negatively correlated with detections at hourly time scales. A detailed analysis of variability in the performance of spectrogram correlation detectors should be performed when applying this method to long-term acoustic data-sets.     

A comparison of the number of chromatid aberrations with dose, estimated from the frequency of dicentrics, in the cytogenetic study of lymphocytes in subjects involved in the accident at the Chernobyl Nuclear Power Station

A study was made of the frequency of chromatid aberrations in lymphocyte culture of subjects affected by the Chernobyl accident as a function of dose estimated by the incidence of dicentrics. The average number of chromatid aberrations was nearly the same within the dose range from 0 to 5 Gy exhibiting a tendency towards growth with dose. A high individual variability of the chromatid aberration frequency was observed.     

Sensitivity of the erythrocyte micronucleus assay: dependence on number of cells scored and inter-animal variability

Until recently, the in vivo erythrocyte micronucleus assay has been scored using microscopy. Because the frequency of micronucleated cells is typically low, cell counts are subject to substantial binomial counting error. Counting error, along with inter-animal variability, limit the sensitivity of this assay. Recently, flow cytometric methods have been developed for scoring micronucleated erythrocytes and these methods enable many more cells to be evaluated than is possible with microscopic scoring. Using typical spontaneous micronucleus frequencies reported in mice, rats, and dogs we calculate the counting error associated with the frequency of micronucleated reticulocytes as a function of the number of reticulocytes scored. We compare this counting error with the inter-animal variability determined by flow cytometric scoring of sufficient numbers of cells to assure that the counting error is less than the inter-animal variability, and calculate the minimum increases in micronucleus frequency that can be detected as a function of the number of cells scored. The data show that current regulatory guidelines allow low power of the test when spontaneous frequencies are low (e.g., < or =0.1%). Tables and formulas are presented that provide the necessary numbers of cells that must be scored to meet the recommendation of the International Working Group on Genotoxicity Testing that sufficient cells be scored to reduce counting error to less than the inter-animal variability, thereby maintaining a more uniform power of detection of increased micronucleus frequencies across laboratories and species.     

Spectrum analysis of the r-r interval using a PC]

Spectral analysis of r-r variability has been recently proposed as a clinical tool to assess the autonomic nervous system function. In this article we present the results obtained using an equipment and an analysis software (based on Maximum Entropy Method) developed in our laboratory. Analyzing the tachograms derived from prolonged ECG registrations of 12 young healthy subjects, 24 to 36 years old (mean 31 +/- 4), we observed the two classic components of the signal: a low frequency component (0.7 +/- 0.2 Hz) and a high frequency component (0.21 +/- 16.6 Hz). As expected, standing, a simple manoeuvre augmenting sympathetic activity, caused a stronger predominance of the low frequency component. We conclude that our method is reliable to evaluate, by means of spectral analysis, rhythmical oscillations of r-r variability.     

The variability characteristics of the arterial pressure in man and animals

The development of computer monitoring methods over haemodynamic parameters has made possible on objective quantitative estimation of blood pressure (BP) variability in humans and animals which can have both periodic and aperiodic feachers. The spectral analysis of spontaneous BP fluctuations reveals presence of several power peaks main of which, as well as in heart rate variability, reflect sympathetic and parasympathetic activity. Both in hypertensive patients and animal models of arterial hyper tension BP variability is higher, but its relationship with BP level is not realized in a simple causal scheme. Observations in prehypertensive period demonstrate an opportunity of dissociation between rates of BP level and variability increase. The pharmacological analysis permisses to suggest the sympathetic activation as the main cause of BP destabilization. Despite a leading role of baroreceptor reflex (BR) in damping of evoked BP fluctuations, its role in regulation of spontaneous variability seems to be ambiguous. The studies excluding episodes of locomotor and other activities from the curve analysis do not confirm a correlation between BP variability and BR gain. The spectral analysis of BP lability in animals with denervated mechanoreceptor zones has revealed BR effective control only of a low and superlow frequency areas (less than 0.07 Hz). The study of the regional blood flows in sinoartic denervated rats has concluded that the increase of their autonomy is the main reason of BP lability. The offset of BR efferent limb by ganglionic blocking agents or desympathization leads to analogical BP lability. Thus, BP variability seems to be a reflection of functional efficiency of BP stabilization mechanisms. Considering that on its origin, connections with other haemodynamic parameters, amplitude and frequency characteristics is a complex phenomenon, no one of mechanisms is an universal instrument of its regulation.     

Sensitivity of the erythrocyte micronucleus assay: Dependence on number of cells scored and inter-animal variability

Until recently, the in vivo erythrocyte micronucleus assay has been scored using microscopy. Because the frequency of micronucleated cells is typically low, cell counts are subject to substantial binomial counting error. Counting error, along with inter-animal variability, limit the sensitivity of this assay. Recently, flow cytometric methods have been developed for scoring micronucleated erythrocytes and these methods enable many more cells to be evaluated than is possible with microscopic scoring. Using typical spontaneous micronucleus frequencies reported in mice, rats, and dogs we calculate the counting error associated with the frequency of micronucleated reticulocytes as a function of the number of reticulocytes scored. We compare this counting error with the inter-animal variability determined by flow cytometric scoring of sufficient numbers of cells to assure that the counting error is less than the inter-animal variability, and calculate the minimum increases in micronucleus frequency that can be detected as a function of the number of cells scored. The data show that current regulatory guidelines allow low power of the test when spontaneous frequencies are low (e.g., ≤0.1%). Tables and formulas are presented that provide the necessary numbers of cells that must be scored to meet the recommendation of the International Working Group on Genotoxicity Testing that sufficient cells be scored to reduce counting error to less than the inter-animal variability, thereby maintaining a more uniform power of detection of increased micronucleus frequencies across laboratories and species.     

Investigation of the Variability of NIR In-line Monitoring of Roller Compaction Process by Using Fast Fourier Transform (FFT) Analysis

The purpose of this research was to investigate the variability of the roller compaction process while monitoring in-line with near-infrared (NIR) spectroscopy. In this paper, a pragmatic method in determining this variability of in-line NIR monitoring roller compaction process was developed and the variability limits were established. Fast Fourier Transform (FFT) analysis was used to study the source of the systematic fluctuations of the NIR spectra. An off-line variability analysis method was developed as well to simulate the in-line monitoring process in order to determine the variability limits of the roller compaction process. For this study, a binary formulation was prepared composed of acetaminophen and microcrystalline cellulose. Different roller compaction parameters such as roll speed and feeding rates were investigated to understand the variability of the process. The best-fit line slope of NIR spectra exhibited frequency dependence only on the roll speed regardless of the feeding rates. The eccentricity of the rolling motion of rollers was identified as the major source of variability and correlated with the fluctuations of the slopes of NIR spectra. The off-line static and dynamic analyses of the compacts defined two different variability of the roller compaction; the variability limits were established. These findings were proved critical in the optimization of the experimental setup of the roller compaction process by minimizing the variability of NIR in-line monitoring.     

Long Recording Sequences: How to Track the Intra-Individual Variability of Acoustic Signals

Recently developed acoustic technologies - like automatic recording units - allow the recording of long sequences in natural environments. These devices are used for biodiversity survey but they could also help researchers to estimate global signal variability at various (individual, population, species) scales. While sexually-selected signals are expected to show a low intra-individual variability at relatively short time scale, this variability has never been estimated so far. Yet, measuring signal variability in controlled conditions should prove useful to understand sexual selection processes and should help design acoustic sampling schedules and to analyse long call recordings. We here use the overall call production of 36 male treefrogs (Hyla arborea) during one night to evaluate within-individual variability in call dominant frequency and to test the efficiency of different sampling methods at capturing such variability. Our results confirm that using low number of calls underestimates call dominant frequency variation of about 35% in the tree frog and suggest that the assessment of this variability is better by using 2 or 3 short and well-distributed records than by using samples made of consecutive calls. Hence, 3 well-distributed 2-minutes records (beginning, middle and end of the calling period) are sufficient to capture on average all the nightly variability, whereas a sample of 10 000 consecutive calls captures only 86% of it. From a biological point of view, the call dominant frequency variability observed in H. arborea (116Hz on average but up to 470 Hz of variability during the course of the night for one male) challenge about its reliability in mate quality assessment. Automatic acoustic recording units will provide long call sequences in the near future and it will be then possible to confirm such results on large samples recorded in more complex field conditions.     

The effect of sinus node depression on heart rate variability in humans using zatebradine, a selective bradycardic agent

Zatebradine is a bradycardic agent with a selective effect on the pacemaker current in the sinus node. The effect of such drugs on heart rate variability is not known. Thirty-six patients without structural heart disease were randomly assigned to receive 10 mg of zatebradine i.v. (n = 24) or isotonic saline (n = 12). Heart rate variability (HRV) was recorded as power in the very low frequency (VLF, 0.003-0.040 Hz), low frequency (LF, 0.040-0.150 Hz), and high frequency (HF, 0.150-0.400 Hz) spectral bands as well as total power (TP, 0.003-0.400 Hz) during 5-min ECG acquisitions at baseline, 30, and 60 min following the start of the infusion. No change in heart rate variability was detected in the control group. Zatebradine significantly reduced heart rate variability at 60 min in all frequency bands: VLF (-12+/-4%, p<0.001), LF (-19+/-4%, p<0.001), and HF (-26+/-5%, p<0.001). The reduction in HRV following zatebradine is due to depression of sinus node response to all external stimuli and underscores the need for documentation of normal sinus node function in HRV research.     

迷走神经在心率变异性中的作用

采用功率谱和近似熵 (approximateentropy ,ApEn)的方法 ,分析清醒家兔在双侧迷走神经保留 ,右、左侧迷走神经切断以及双侧迷走神经同时切断时心搏间期 (RRI)的变化。结果显示 :双侧迷走神经保留时功率谱中高频功率 (HF)、低频功率 (LF)及ApEn值均高于双侧及单侧迷走神经切断时 (P <0 0 5 ) ,LF/HF比值最小 ;切断单侧迷走神经 ,ApEn变小 ,LF/HF比值在右侧迷走神经切断时增大 ,而切断左侧迷走时LF/HF比值无明显变化 ;双侧迷走神经切断后LF/HF比值最大 ,ApEn最低。结果表明 :心率变异主要由迷走神经调节 ,右侧迷走神经起主要作用 ;传统心率变异性测量方法与非线性方法所得结果一致     

Spatial coherence and stationarity of local field potentials in an isolated whole hippocampal preparation <Emphasis Type="Italic">in vitro</Emphasis>

Local field potential (LFP) multielectrode recordings of spontaneous rhythms in an isolated whole hippocampal preparation are characterized with respect to their spatial variability within the hippocampus, and their frequency properties. Using simulated data, we categorize potential relationships between frequency variation over time in LFP recordings and spatial variability between electrodes. We then use data recorded from the intact preparation to distinguish between our theoretical categories. We find that the LFP recordings have a close to spatially invariant frequency distribution (not phase) across the hippocampus, and differ in frequency only in a component that may be seen as physiological noise. From these facts, we conclude that the isolated hippocampal LFP recordings represent a single signal and may be regarded as a unitary circuitry. We additionally examine phase differences across our recording sites. We use our characterization of the hippocampal isolate’s properties to predict its spatial coherence in response to high frequency stimulation. We find that there is a finely tuned inverse relationship between temporal variability in the hippocampal isolate’s LFP recordings and their spatial coherence.     

Assessment of pulse rate variability by the method of pulse frequency demodulation

Background  

Due to its easy applicability, pulse wave has been proposed as a surrogate of electrocardiogram (ECG) for the analysis of heart rate variability (HRV). However, its smoother waveform precludes accurate measurement of pulse-to-pulse interval by fiducial-point algorithms. Here we report a pulse frequency demodulation (PFDM) technique as a method for extracting instantaneous pulse rate function directly from pulse wave signal and its usefulness for assessing pulse rate variability (PRV).     

The nature of very low frequency component of the heart rate variability and the role of sympathetic-parasympathetic interactions

A method of separate monitoring "instant" changes of the VLF, LF and HF power spectral components of heart rate variability, has been developed. The power of the LF and HF spectral components were proved to be continuously changing. The period of these power fluctuations could stay within 15 to 150 sec. Comparison of the heart rate variability spectrum with LF and HF spectral components power fluctuations' spectrums has shown that the frequencies of the LF and HF spectral components power fluctuations stay within the VLF range. The co-operative spectrum form of these fluctuations repeats the form of the VLF peak. In cases when the LF and HF spectral components power fluctuations' periods do not coincide, VLF has two peaks. The frequency of one VLF peak coincides with frequency of the HF power fluctuations, and the frequency of another--with the frequency of LF power fluctuations.     

Genetic components of litter size variability in sheep

Classical selection for increasing prolificacy in sheep leads to a concomitant increase in its variability, even though the objective of the breeder is to maximise the frequency of an intermediate litter size rather than the frequency of high litter sizes. For instance, in the Lacaune sheep breed raised in semi-intensive conditions, ewes lambing twins represent the economic optimum. Data for this breed, obtained from the national recording scheme, were analysed. Variance components were estimated in an infinitesimal model involving genes controlling the mean level as well as its environmental variability. Large heritability was found for the mean prolificacy, but a high potential for increasing the percentage of twins at lambing while reducing the environmental variability of prolificacy is also suspected. Quantification of the response to such a canalising selection was achieved.     

Heart rate variability analysis

The expansion of heart rate variability analysis has been facilitated by the remarkable development of computer sciences and digital signal processing during the last thirty years. The beat-to-beat fluctuation of the heart rate originates from the momentary summing of sympathetic and parasympathetic influences on the sinus node. According to the extensive associations of the autonomic nervous system, several factors affect heart rate and its variability such as posture, respiration frequency, age, gender, physical or mental load, pain, numerous disease conditions, and different drugs. Heart rate variability can be quantitatively measured by time domain and frequency domain methods that are detailed in the paper. Non-linear methods have not spread in the clinical practice yet. Various cardiovascular and other pathologies as well as different forms of mental and physical load are associated with altered heart rate variability offering the possibility of predicting disease outcome and assessing stress.     

Variability of enzyme systems in the coenopopulation of Taraxacum officinale s.l. from the zone of East-Ural- radioactive trace

Levels of soil contamination with 90Sr and 137Cs radionuclides on the plots within the zone of Eastern-Ural radioactive trace exceed values of the global level 4-240 times. We have carried out allozyme analysis of apomict species Taraxacum officinale s.l. from this zone. Zimogrammes were interpreted as allozyme phenotypes. In condition of chronic irradiation the plants had increased phenogenetic variability of majority enzymes systems and high frequency of rare morphs. Thus, in plant coenopopoulations situated in radioactive-polluted zone, genomic recombination processes show higher intensity. High enzymatic variability provides the material for natural selection and increase the adaptive potential of coenopopulations.