Comparison between Fast Fourier Transform and Autoregressive Model on Analysis of Autonomic Nervous Function after Food Intake in Women

Purpose: Heart rate variability (HRV) is acknowledged as a useful tool to estimate autonomic function. Fast Fourier transform (FFT) and autoregressive model (AR) are used for power spectral analysis of HRV. However, there is little evidence of agreement between FFT and AR in relation to HRV following food intake in females. In the present study, we applied both FFT and AR after food intake during the follicular and luteal phases, and compared raw low-frequency (LF) and high- frequency (HF) powers, and LF/HF ratio obtained with the two power-spectral analytical methods. Methods: All subjects participated in two sessions: follicular phase session and luteal phase session. In each session, R-R intervals were continuously recorded before and after meals, and power spectral analysis of heart rate variability was performed. We analyzed low-frequency power (LF: 0.04 - 0.15 Hz) and high-frequency power (HF: 0.15 - 0.40 Hz) by using FFT and AR. LF and HF power were computed for each 30 sec, 1 min, 2.5 min, and 5 min of the 5-min R-R data before meal intake and at 20, 40, 60 and 80 min after meal intake. The LF/HF ratio was calculated as an index of sympathovagal balance. Results: In the present study, after 30 sec and 1 min of segment analysis, there was little interchangeability between AR and FFT in LF, HF, and LF/HF ratio in both follicular and luteal phases. In 2.5 min or 5 min of segment analysis, there was interchangeability between FFT and AR in LF and HF, but not in the LF/HF ratio in both follicular and luteal phases. Additionally, FFT underestimated HRV compared with AR, and the extent of underestimation increased with increasing AR value. Conclusion: FFT underestimated HRV compared with AR, and FFT correlated poorly with AR when the analysis segment was shortened.

AFM Analysis of TiN, TiAlN, and TiAlSiN Coatings Prepared by Cathodic Arc Ion Plating

The TiN, TiAlN, and TiAlSiN coatings were prepared on YT14 cutting tool surface with CAIP（cathode arc ion plating）, the surface morphologies and phases were analyzed with FESEM（field emission scanning electron microscopy）, and XRD（X-ray diffraction）, respectively, and the coating parameters such as 3D surface micro-topography, grain size, surface height, hierarchy, profile height, and power spectral density, etc, were measured with AFM（atomic force microscope）. The results show that the phases of TiN, TiAlN, and TiAlSiN coatings are TiN, TiN＋TiAlN, TiN＋Si_3N_4＋TiAlN, respectively, while the surface roughness Sa of TiN, TiAlN, and TiAlSiN coatings is 75.3, 98.9, and 42.1 nm, respectively, and the roughness depth Sk is 209, 389, and 54 nm, respectively, the sequence of average grain sizes is TiAlN〉TiN〉TiAlSiN. The surface bearing index Sbi of TiN, TiAlN, and TiAlSiN coatings is 0.884, 1.01, and 0.37, respectively, and the sequence of surface bearing capability is TiAlN〉TiN〉TiAlSiN. At the lower wavelength（102-103 nm）, the power spectral densities have a certain correlation, and the sequence of TiN〉TiAlN〉TiAlSiN, while the correlation is low at the higher wavelength（〉103 nm）.

Paraspinal strength and electromyographic fatigue in patients with sub-acute back pain and controls:Reliability,clinical applicability and between-group differences

BACKGROUND Paraspinal muscle strength and fatigue are considered important in low back pain(LBP)prevention and rehabilitation.High reliability of paraspinal strength and electromyographic(EMG)-fatigue parameters has not been universally reported.Moreover,the discriminative validity of these parameters requires further exploration,under the threat of potentially poor reliability of the methods examined.AIM To investigate the reliability and discriminative validity of paraspinal strength and EMG-related fatigue in subjects with recurrent LBP and healthy participants.METHODS Test-retest measurements were performed in 26 healthy and 66 LBP volunteers,for reliability.Paraspinal isometric maximal and mean strength were determined with a maximum voluntary isometric contraction(MVIC)protocol,performed in a custom-made device.For the fatigue test,participants performed a 60% MIVC level continuous isometric contraction of the paraspinals,in conjunction with EMG analysis from 4 muscle sites of the lumbar spine.Initial median frequency(IMF),the median frequency slope(MFslope),as well as the root mean square(RMS)slope EMG parameters were used as fatigue measures.Data were analysed with repeated measures ANOVA for test-retest differences.For reliability,the intraclass correlation coefficient(ICC3,1),standard error of the measurement(SEM)and the smallest detectable difference(SDD)were reported.Group-related differences for fatigue measures were analysed with a Multivariate Analysis of Covariance,with age,weight and strength as covariates.RESULTS Isometric strength presented statistically significant between-day differences(P<0.01),however these did not exceed 10%(healthy:7.2%/LBP-patients:9.7%)and ICC reliability values were excellent,yet test-retest error was increased for the patient group(healthy:ICC3,1:0.92-0.96,SEM:5.72-5.94 Hz,SDD:18.51%-18.57%/LBP-patients:ICC3,1:0.91-0.96,SEM:6.49-6.96,SDD:30.75%-31.61%).For the frequency data,IMF reliability was excellent(healthy:ICC3,1:0.91-0.94,SEM:3.45-7.27 Hz,SDD:9.56%-20.14%/patients:ICC3,1:0.90-0.94,SEM:6.41-7.59 Hz,SDD:17.75%-21.02%)and of MF raw and normalised slopes was good(healthy:ICC3,1:0.78-0.82,SEM:4.93-6.02 Hz,SDD:13.66-16.67%/LBP-patients:ICC3,1:0.83-0.85,SEM:6.75-7.47 Hz,SDD:18.69%-20.69%).However,the reliability for RMS data presented unacceptably high SDD values and were not considered further.For discriminative validity,less MVIC and less steep MFslopes were registered for the patient group(P<0.01).CONCLUSION Reliability and discriminative ability of paraspinal strength and EMG-related frequency parameters were demonstrated in healthy participants and patients with LBP.

Bathymetry predicting using the altimetry gravity anomalies in South China Sea

In South China Sea(112°E-119°E, 12°N-20°N), 81159 ship soundings published by NGDC(National Geophysics Data Center) and the altimetry gravity anomalies published by SIO(Scripps Institute of Oceanography) were used to predict bathymetry by GGM(gravity-geologic method) and SAS(Smith and Sandwell) method respectively. The residual 40576 ship soundings were used to estimate precisions of the predicted bathymetry models. Results showed that: the standard deviation of difference between the GGM model and ship soundings was 59.75 m and the relative accuracy was 1.86%. The SAS model is60.07 m and 1.87%. The power spectral densities of the ETOPO1, SIO, GGM and SAS models were also compared and analyzed. At last, we presented an integrated bathymetry model by weighted averaging method, the weighted factors were determined by precisions of the ETOPO1, SIO, GGM, and SAS model respectively.