Results Of Cross-correlation Analysis Research Articles

The variability of particulate organic carbon in the northern South China Sea during the 2009–2010 El Niño

The influences of El Niño on the changes of sea surface temperature (SST) and chlorophyll have been well studied, but its impact on changes of particulate organic carbon (POC) remains unclear. In this study, we analyzed the time series of POC and found that from January 2003 to December 2011, the spatially-averaged POC increased at a rate of 0.24 mg/m3 per year. However, during the 2009–2010 El Niño, the spatially-averaged POC increased at a rate of 1.78 mg/m3 per month. This indicated that the increase of POC during 2009–2010 may be related to El Niño. To investigate the relationship between POC and El Niño, we introduced the phase shift time between the POC and the Multivariate ENSO Index (MEI) to characterize the response of POC to El Niño, and calculated the correlation between the time series of the MEI and POC anomalies during El Niño to determine the phase shift time. The results of cross-correlation analysis indicated that changes of POC were delayed from the onset of El Niño by 4 months. Furthermore, a detailed analysis was presented based on a range of in situ observations and satellite-derived datasets available during the 2009–2010 El Niño. The correlation coefficients between POC and chlorophyll, as well as between POC and SST, are 0.9263 and −0.8315, respectively, and the constructed model indicated that chlorophyll and SST had a significant impact on POC. The spatial distribution of POC anomaly maximum occurred in the spring of 2010, because in the winter of 2009, the Rossby-type anomalies were reflected as upwelling Kelvin wave. However, the vertical POC anomaly maximum occurred in the spring of 2011, because the 2009–2010 El Niño experienced a fast phase transition from warm El Niño to cold La Niña, which was associated with oceanic upwelling.

Analysis of the Relationship Between the Economic Sentiment Indicator and GDP Growth

The article analyzes the relationship between aggregate economic sentiment and GDP growth in Russia in the context of the regular large-scale surveys of business and households for the period of 1998–2020. The aim of the study is to prove the empirical value of the opinions of economic agents in expanding macroeconomic information, especially in a time of sudden crisis events, as well as the feasibility of their use in short-term statistics of business cycles. The cyclical sensitivity of aggregate economic sentiment relative to the reference GDP growth dynamics is tested. The authors calculate a composite economic sentiment indicator (ESI) that combines quarterly information on 18 survey-based indicators. The sample used to construct the ESI covers about 24,000 organizations in main economic activities and 5,100 consumers in all Russian regions. Common empirical patterns and cyclical movement are identified using the iterative procedure of visual and statistical analysis of the relationship between the GDP physical volume index and ESI. The results of cross-correlation analysis, Hodrick—Prescott filtering, and dating of cyclical dynamics are described. The significance of the composite survey-based indicator in the sectoral and cross-country analysis of entrepreneurial behavior, including that during the COVID-19-related crisis, is confirmed. The results of the study allow one to record the “cognitive shift” in the level of aggregated entrepreneurial confidence having formed in recent years. After the decline in ESI values during the protracted recession in 2015–2016, its subsequent four-year dynamics are characterized by the lowest potential compared with the recovery periods after all previous crises.

Phenomenon of isoparametricity in reactions of trans-2,3-diaryloxiranes with arenesulfonic acids. Mechanistic interpretation

Nonadditive effects of substituents X and Y are manifested in reactions of symmetrically X-substituted trans-2,3-diaryloxiranes with Y-substituted arenesulfonic acids. The isoparametric point is reached experimentally: close to the point τXIP = 4.73 on substituent Х the rate of the oxirane ring opening of trans-2,3-bis(3-bromo-5-nitrophenyl)oxirane (τX = 4.38) practically does not depend on substituent Y (ρYX = 0.10±0.05). The results of cross correlation analysis of the kinetic data are applied to interpretation of the mechanism of the studied reactions.

Assessment of tissue heterogeneity using diffusion tensor and diffusion kurtosis imaging for grading gliomas.

In this work, we aim to assess the significance of diffusion tensor imaging (DTI) and diffusion kurtosis imaging (DKI) parameters in grading gliomas. Retrospective studies were performed on 53 subjects with gliomas belonging to WHO grade II (n=19), grade III (n=20) and grade IV (n=14). Expert marked regions of interest (ROIs) covering the tumour on T2-weighted images. Statistical texture measures such as entropy and busyness calculated over ROIs on diffusion parametric maps were used to assess the tumour heterogeneity. Additionally, we propose a volume heterogeneity index derived from cross correlation (CC) analysis as a tool for grading gliomas. The texture measures were compared between grades by performing the Mann-Whitney test followed by receiver operating characteristic (ROC) analysis for evaluating diagnostic accuracy. Entropy, busyness and volume heterogeneity index for all diffusion parameters except fractional anisotropy and anisotropy of kurtosis showed significant differences between grades. The Mann-Whitney test on mean diffusivity (MD), among DTI parameters, resulted in the highest discriminability with values of P=0.029 (0.0421) for grade II vs. III and P=0.0312 (0.0415) for III vs. IV for entropy (busyness). In DKI, mean kurtosis (MK) showed the highest discriminability, P=0.018 (0.038) for grade II vs. III and P=0.022 (0.04) for III vs. IV for entropy (busyness). Results of CC analysis illustrate the existence of homogeneity in volume (uniformity across slices) for lower grades, as compared to higher grades. Hypothesis testing performed on volume heterogeneity index showed P values of 0.0002 (0.0001) and 0.0003 (0.0003) between grades II vs. III and III vs. IV, respectively, for MD (MK). In summary, the studies demonstrated great potential towards automating grading gliomas by employing tumour heterogeneity measures on DTI and DKI parameters.

Features of developing motive flairs for boys 6—7 classes

Research aim — to define age-related features of developing motive flairs for boys 6—7 classes. Research methods. In-process used: theoretical analysis of literary data, pedagogical testing, methods of mathematical statistics.Conclusions. Level of motive and functional preparedness of boys 6—7 classes are estimated below the average. The results of cross-correlation analysis testify to the necessity of the accented development of relative force for the boys of sixth class and improvement functional to preparedness boys of seventh class. The worked out standard scale of estimation gives an opportunity to define the level of preparedness of schoolchildren and weak results in separate test exercises, to orientate personally each on self-perfection of motive preparedness.

The Seyfert 1 galaxy Ark 120. Spectral variability in 1992–2005

We have studied the variability of the Hβ line and the adjacent continuum in the spectrum of the Seyfert galaxy Ark 120, based on spectral observations of the galaxy’s nucleus obtained in the Crimea in 1992–2005, supplemented by published data for 1988–1996. Irregular variability on various timescales (years to days) can be accompanied by periodic brightness variations in both the continuum and the Hβ line, with a period of P ∼ 430 days and an amplitude of Δm ∼ 0.2m in the continuum, which were traced for more than 13 cycles. In total, in 1988–2005, the flux variations in the line lag those in the continuum by 55 ± 9 days if calculated from the peak of the cross correlation function, or by 72 ± 7 days, if calculated from the centroid of the CCF. The delay is correlated with the continuum brightness, increasing when the continuum flux increases. The Hβ line profiles indicate both a high degree of diversity and the presence of features that recur after various extended time intervals. Analysis of the evolution of the differences between each individual normalized line profile and the mean normalized profile indicates systematic motion of excesses relative to the average profile from negative to positive radial velocities. In contrast, parts of the Hβ line with low radiation relative to the mean normalized profile evolve in the opposite direction (from the red to the blue Hβ wing). This pattern is also typical for the rotating broad-line region, if this region has the form of a disk. The rotation period exceeds 9000–10000 days, or 25–27 years. The size of the broad-line region calculated form this period corresponds to a reverberation time of no fewer than 30 days, consistent with the results of cross-correlation analysis.

Detecting functional connectivity in the resting brain: a comparison between ICA and CCA

Independent component analysis (ICA) and cross-correlation analysis (CCA) are general tools for detecting resting-state functional connectivity. In this study, we jointly evaluated these two approaches based on simulated data and in vivo functional magnetic resonance imaging data acquired from 10 resting healthy subjects. The influence of the number of independent components (maps) on the results of ICA was investigated. The influence of the selection of the seeds on the results of CCA was also examined. Our results reveal that significant differences between these two approaches exist. The performance of ICA is superior as compared with that of CCA; in addition, the performance of ICA is not significantly affected by structured noise over a relatively large range. The results of ICA could be affected by the number of independent components if this number is too small, however. Converting the spatially independent maps of ICA into z maps for thresholding tends to overestimate the false-positive rate. However, the overestimation is not very severe and may be acceptable in most cases. The results of CCA are dependent on seeds location. Seeds selected based on different criteria will significantly affect connectivity maps.

Modelling the energy dependencies of X-ray quasi-periodic oscillations in accreting compact objects

We have constructed models of the quasi-periodic variability of X-ray emission from accreting compact objects. Assuming a general scenario of a propagation model of variability, with inverse Compton upscattering as the emission mechanism, we have considered a number of cases for the periodic modulation: modulation of the plasma heating rate, cooling rate by external soft photons and the amplitude of the reprocessed component. We have computed various observational characteristics which can be compared to good quality data. These include Fourier-frequency resolved spectra and the results of cross-correlation analysis between light curves at different energies. Each model of modulation predicts specific observational signatures, which help in identifying the physical processes driving quasi-periodic oscillations emission in accreting sources.

Input Parameters for Models of Energetic Electrons Fluxes at the Geostationary Orbit

The results of cross-correlation analysis between electrons fluxes (with energies of ＞ 0.6 MeV,＞ 2.0MeV and ＞ 4.0MeV), geomagnetic indices and solar wind parameters are shown in the paper. It is determined that the electron fluxes are controlled not only by the geomagnetic indices, but also by the solar wind parameters, and the solar wind velocity demonstrates the best relation with the electron fluxes.Numerical value of the relation efficiency of external parameters with the highly energetic electrons fluxes shows a periodicity. It is presented here the preliminary results of daily averaged electrons fluxes forecast for a day ahead on the basis of the model of neuron networks.

Relationship between a drop of sardine and albacore catches and a relaxation of wind, tested by a Superposed Epoch Analysis

Each summer, in the oceanic north-east Atlantic, a drop in the catch of albacore (Thunnus alalunga Bonnaterre, 1788) is observed for 8 to 10 days at the beginning of August. This temporary decrease of catch per unit effort (CPUE) is related to a relaxation of wind for 5 to 8 days during the previous 8 to 15 days. A similar and significant relationship is also observed in the Atlantic sardine (Sardina pilchardus Walbaum) fishery in a coastal area in the north-east of the Bay of Biscay (France). This indicates that a general ecological process is involved in this relationship between wind and CPUE of two pelagic fish, caught at the sea surface.The timing of the response of the sardine and the albacore fishery to a relaxation of wind is interpreted in the light of a productivity model. The lack of wind-driven turbulent mixing provides a progressive decrease of the food organisms in the surface layer about 7 days after the wind event. Thus, fish disperse and become less susceptible to capture.However, particular fertilization processes are involved at the continental shelf-break and the results of the association analysis were not found to be significant for the albacore fishery in this area.The use of Superposed Epoch Analysis seems to provide a suitable method to analyse such a relationship with a daily time scale.Comparison of the results of cross correlation analysis used in a previous work with a Superposed Epoch Analysis suggests that further considerations should be given to the use of the latter method infishery science.