Statistical Tests of Taylor’s Hypothesis: An Application to Precipitation Fields

2009 ◽  
Vol 10 (1) ◽  
pp. 254-265 ◽  
Author(s):  
Bo Li ◽  
Aditya Murthi ◽  
Kenneth P. Bowman ◽  
Gerald R. North ◽  
Marc G. Genton ◽  
...  
Keyword(s):  
Correlation Analysis ◽  
Time Scale ◽  
Statistical Tests ◽  
Spatial Scales ◽  
Statistical Significance ◽  
Time Lag ◽  
Mean Flow ◽  
Spatial Covariance ◽  
Simple Correlation ◽  
Taylor’S Hypothesis

Abstract The Taylor hypothesis (TH) as applied to rainfall is a proposition about the space–time covariance structure of the rainfall field. Specifically, it supposes that if a spatiotemporal precipitation field with a stationary covariance Cov(r, τ) in both space r and time τ moves with a constant velocity v, then the temporal covariance at time lag τ is equal to the spatial covariance at space lag r = vτ that is, Cov(0, τ) = Cov(vτ, 0). Qualitatively this means that the field evolves slowly in time relative to the advective time scale, which is often referred to as the frozen field hypothesis. Of specific interest is whether there is a cutoff or decorrelation time scale for which the TH holds for a given mean flow velocity v. In this study, the validity of the TH is tested for precipitation fields using high-resolution gridded Next Generation Weather Radar (NEXRAD) reflectivity data produced by the WSI Corporation by employing two different statistical approaches. The first method is based on rigorous hypothesis testing, while the second is based on a simple correlation analysis, which neglects possible dependencies between the correlation estimates. Radar reflectivity values are used from the southeastern United States with an approximate horizontal resolution of 4 km × 4 km and a temporal resolution of 15 min. During the 4-day period from 2 to 5 May 2002, substantial precipitation occurs in the region of interest, and the motion of the precipitation systems is approximately uniform. The results of both statistical methods suggest that the TH might hold for the shortest space and time scales resolved by the data (4 km and 15 min) but that it does not hold for longer periods or larger spatial scales. Also, the simple correlation analysis tends to overestimate the statistical significance through failing to account for correlations between the covariance estimates.

scholarly journals Correlation analysis of epicardial adipose tissue thickness, C-reactive protein, interleukin-6, visfatin, juxtaposed with another zinc finger protein 1, and type 2 diabetic macroangiopathy

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Yuan-Yuan Gong ◽  
Hai-Ying Peng
Keyword(s):  
Correlation Analysis ◽  
Zinc Finger Protein ◽  
Pearson Correlation ◽  
Statistical Significance ◽  
Healthy Control Group ◽  
Control Group ◽  
Diabetes Group ◽  
Reactive Protein ◽  
Healthy Control

Abstract Background To investigate the correlation between the thickness of epicardial adipose tissue (EAT), C-reactive protein (CRP), interleukin (IL) -6, visfatin, juxtaposed with another zinc finger protein 1 (JAZF1) and type 2 diabetic mellitus (T2DM) macroangiopathy. Methods The study enrolled 82 patients with T2DM with macroangiopathy (the Complication Group), and 85 patients with T2DM (the Diabetes Group) who were admitted to Shandong Provincial Third Hospital from February 2018 to February 2020. In addition, 90 healthy people who underwent physical examination at the same hospital during the same period were enrolled (the Healthy Control Group). Age, gender, height, weight, waist circumference (WC), hip circumference (HC), diabetic course and therapeutic drugs, waist hip ratio (WHR), and body mass index (BMI) were recorded and calculated. Results The baseline characteristics of the three groups were comparable, and the diabetic course of the Complication Group and the Diabetes Group was not significantly different (P > 0.05). The WHR of the Complication Group was higher than that of the Diabetes Group and the Healthy Control Group, with statistical significance (P < 0.05). The FPG, 2hPG, HbA1C, CRP, IL-6, Visfatin, JAZF1, HOMA-IR, EAT thickness, and baPWV of the Complication Group were all higher than those of the Diabetes Group and the Healthy Control Group (P < 0.05, respectively). The JAZF1 and FIns of the Complication Group and Diabetes Group were lower than those of the Healthy Control Group, and JAZF1 of the Complication Group was lower than the Diabetes Group with statistical significance (P<0.05, respectively). Pearson correlation analysis showed that the EAT thickness was positively correlated with CRP, IL-6, visfatin, and JAZF1 (r = 0.387, 0.451, 0.283, 0.301, respectively, all P<0.001). Pearson correlation analysis showed that baPWV was positively correlated with EAT thickness, CRP, IL-6, visfatin, and JAZF1 (r = 0.293, 0.382, 0.473, 0.286, respectively, all P < 0.001). Multivariate stepwise regression analysis showed that FPG, 2hPG, HbA1C, CRP, IL-6, visfatin, JAZF1, and EAT thickness were independent risk factors that affected T2DM macroangiopathy. Conclusions Clinical monitoring and treatment of T2DM macroangiopathy can use CRP, IL-6, Visfatin, JAZF1, and EAT thickness as new targets to delay the progression of the disease. Further research on the relationship between the above factors and the pathogenesis of T2DM macroangiopathy may be helpful provide new treatment strategies.

scholarly journals Gamma entrainment frequency affects mood, memory and cognition: an exploratory pilot study

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Ryan L. S. Sharpe ◽  
Mufti Mahmud ◽  
M. Shamim Kaiser ◽  
Jianhui Chen
Keyword(s):  
Pilot Study ◽  
Correlation Analysis ◽  
Negative Correlation ◽  
Cognitive Abilities ◽  
Statistical Significance ◽  
Assessment Scores ◽  
Frequency Group ◽  
Before And After ◽  
Mood Score ◽  
40 Hz

AbstractHere we provide evidence with an exploratory pilot study that through the use of a Gamma 40 Hz entrainment frequency, mood, memory and cognition can be improved with respect to a 9-participant cohort. Participants constituted towards three binaural entrainment frequency groups: the 40 Hz, 25 Hz and 100 Hz. Participants attended a total of eight entrainment frequency sessions twice over the duration of a 4-week period. Additionally, participants were assessed based on their cognitive abilities, mood as well as memory, where the cognitive and memory assessments occurred before and after a 5-min binaural beat stimulation. The mood assessment scores were collected from sessions 1, 4 and 8, respectively. With respect to the Gamma 40 Hz entrainment frequency population, we observed a mean improvement in cognitive scores, elevating from 75% average to 85% average upon conclusion of the experimentation at weak statistical significance ($$\alpha$$ α = 0.10, p = 0.076). Similarly, memory score improvements at a greater significance ($$\alpha$$ α = 0.05, p = 0.0027) were noted, elevating from an average of 87% to 95%. In pertinence to the mood scores, a negative correlation across all populations were noted, inferring an overall increase in mood due to lower scores correlating with elevated mood. Finally, correlation analysis revealed a stronger R$$^2$$ 2 value (0.9838) within the 40 Hz group between sessions as well as mood score when compared across the entire frequency group cohort.

On the irreversibility of internal-wave dynamics due to wave trapping by mean flow inhomogeneities. Part 1. Local analysis

1993 ◽  
Vol 251 ◽  
pp. 21-53 ◽  
Author(s):  
Sergei I. Badulin ◽  
Victor I. Shrira
Keyword(s):  
Shear Flow ◽  
Internal Wave ◽  
Wave Field ◽  
Large Scale ◽  
Spatial Scales ◽  
Energy Concentration ◽  
Local Analysis ◽  
Mean Flow ◽  
Wave Trapping ◽  
Wave Dynamics

The propagation of guided internal waves on non-uniform large-scale flows of arbitrary geometry is studied within the framework of linear inviscid theory in the WKB-approximation. Our study is based on a set of Hamiltonian ray equations, with the Hamiltonian being determined from the Taylor-Goldstein boundary-value problem for a stratified shear flow. Attention is focused on the fundamental fact that the generic smooth non-uniformities of the large-scale flow result in specific singularities of the Hamiltonian. Interpreting wave packets as particles with momenta equal to their wave vectors moving in a certain force field, one can consider these singularities as infinitely deep potential holes acting quite similarly to the ‘black holes’ of astrophysics. It is shown that the particles fall for infinitely long time, each into its own ‘black hole‘. In terms of a particular wave packet this falling implies infinite growth with time of the wavenumber and the amplitude, as well as wave motion focusing at a certain depth. For internal-wave-field dynamics this provides a robust mechanism of a very specific conservative and moreover Hamiltonian irreversibility.This phenomenon was previously studied for the simplest model of the flow non-uniformity, parallel shear flow (Badulin, Shrira & Tsimring 1985), where the term ‘trapping’ for it was introduced and the basic features were established. In the present paper we study the case of arbitrary flow geometry. Our main conclusion is that although the wave dynamics in the general case is incomparably more complicated, the phenomenon persists and retains its most fundamental features. Qualitatively new features appear as well, namely, the possibility of three-dimensional wave focusing and of ‘non-dispersive’ focusing. In terms of the particle analogy, the latter means that a certain group of particles fall into the same hole.These results indicate a robust tendency of the wave field towards an irreversible transformation into small spatial scales, due to the presence of large-scale flows and towards considerable wave energy concentration in narrow spatial zones.

scholarly journals Isotopic Composition of Precipitation in a Southeastern Region of Brazil during the Action of the South Atlantic Convergence Zone

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 418
Author(s):  
Cleber Santos ◽  
Rayonil Carneiro ◽  
Camilla Borges ◽  
Didier Gastmans ◽  
Laura Borma
Keyword(s):  
Isotopic Composition ◽  
Hydrological Cycle ◽  
Statistical Tests ◽  
Spatial Scales ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Southeastern Brazil ◽  
Convergence Zone ◽  
The South ◽  
Hysplit Model

The use of stable isotopes of hydrogen and oxygen is a tool widely used to trace water paths along the hydrological cycle, providing support for understanding climatic conditions in different spatial scales. One of the main synoptic scale events acting in southeastern Brazil is the South Atlantic Convergence Zone (SACZ), which causes a large amount of precipitation from southern Amazonia to southeastern Brazil during the southern summer. In order to determine the isotopic composition of precipitation during the action of SACZ in São Francisco Xavier in southeastern Brazil, information from the Weather Forecasting and Climate Studies Center of the National Institute for Space Research (CPTEC) was used regarding SACZ performance days, the retrograde trajectories of the HYSPLIT model, and images from the GOES-16 satellite, in addition to the non-parametric statistical tests by Spearman and Kruskal–Wallis. A high frequency of air mass trajectories from the Amazon to southeastern Brazil was observed when the SACZ was operating. During the SACZ events, the average isotopic composition of precipitation was more depleted, with a δ18O of −9.9‰ (±2.1‰), a δ2H of −69.3‰ (±17.9‰), and d-excess of 10.1‰ (±4.0‰). When disregarding the SACZ performance, the annual isotopic composition can present an enrichment of 1.0‰ for δ18O and 8.8‰ for the δ2H. The long-term monitoring of trends in the isotopic composition of precipitation during the SACZ events can assist in indicating the evapotranspiration contribution of the Amazon rainforest to the water supply of southeastern Brazil.

Variation terminologique en francophonie. Élaboration d’un modèle d’analyse des facteurs d’implantation terminologique

2017 ◽  
Author(s):  
◽  
Minchai Kim
Keyword(s):  
Correlation Analysis ◽  
Statistical Tests ◽  
Rank Correlation ◽  
Decisive Role ◽  
European Countries ◽  
French Language ◽  
Hypothetical Model ◽  
Moderator Variables ◽  
Spearman’S Rank Correlation ◽  
Significant Difference

Our research aims to elucidate the factors that influence the terminological implantation of a term by proposing a new typology of those factors with a method revealing how their mechanism causes terminological variation in French-language ICT. We accomplish this through an analysis of four Francophone communities: France, Quebec, Belgium, and Switzerland. After establishing a new typology, which encompasses the terminological, socio-terminological, psycho-terminological, and extra-terminological factors, we propose a hypothetical model of their mechanism by introducing three statistical concepts—dependent, independent, and moderator variables—to elucidate these factors’ relationships. We verify our model in two steps. First, for the analysis of terminological and socio- terminological factors, we examine the relations between each factor and terminological implantation of 256 French ICT terms. For this, we begin by coding the terms according to a criterion established for each factor. We then carry out a correlation analysis with Spearman’s rank correlation. Second, we analyse the psycho-terminological and extra-terminological factors with statistical tests on the answers to our questionnaire, which show significant differences between these four linguistic communities. Our analysis confirms a significant difference between the three European countries and Quebec in the mechanism of the terminological implantation factors and we conclude that the psycho-terminological and extra-terminological factors play a decisive role in this difference, which we identify as diatopic.

scholarly journals Use of a Simple Anthropometric Measurement to Identify Low-Birth-Weight Infants in Enugu, Nigeria

2018 ◽  
Vol 5 ◽  
pp. 2333794X1878817
Author(s):  
Ndubuisi Kennedy Chukwudi ◽  
Huldah Ijeoma Nwokeukwu ◽  
Gilbert Nwadiakanma Adimorah
Keyword(s):  
Birth Weight ◽  
Low Birth Weight ◽  
Statistical Tests ◽  
Statistical Significance ◽  
Linear Regression Analysis ◽  
Cutoff Point ◽  
Chest Circumference ◽  
Anthropometric Measurement ◽  
Suitable Alternative ◽  
Study Population

Background. This prospective study was conducted to identify a suitable alternative to birth weight and establish its cutoff point to facilitate the identification of low-birth-weight (LBW) infants in Enugu, Southeast Nigeria. Methods. The study involved newborn babies within the first 48 hours of life. Five anthropometric measurements (head, chest, mid-arm and calf circumferences, as well as abdominal girth) were taken using a tape measure while supine length was measured with an aluminum infantometer. Birth weight was also recorded. Linear regression analysis was done to identify the measurement with the highest coefficient of determination with birth weight while its cutoff point was defined using a receiver operating characteristic curve. Standard statistical tests were used to determine the statistical significance of the findings. Results. The LBW prevalence for the study population was 21.41%. Chest circumference had the highest R2 value of 0.83 for the general study population and 0.72 for the LBW infants. The identified cutoff point for chest circumference is ⩽30 cm. Conclusion. Chest circumference is the best alternative to birth weight in identifying LBW babies within the first 48 hours of life in this environment.

scholarly journals Six-year analysis of traumatic injuries of the craniomaxillofacial area: relation between maxillofacial and traumatic brain injuries

2021 ◽  
Vol 105 (1) ◽  
pp. 56-60
Author(s):  
E. Shuminsky ◽  
◽  
A. Kopchak ◽  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Correlation Analysis ◽  
Brain Injuries ◽  
Statistical Significance ◽  
Maxillofacial Trauma ◽  
Traumatic Injuries ◽  
The Face ◽  
The Difference ◽  
Panfacial Fractures

Summary. Craniofacial trauma is one of the most difficult types of injuries. There is disagreement among various authors about the relationship between maxillofacial trauma (MFT) and traumatic brain injury (TBI). Purpose. Retrospectively evaluate the epidemiology of traumatic injuries of the craniomaxillofacial area and determine whether there is a relationship between different isolated or combined fractures of the facial bones and brain damage. Materials and methods. The case histories of three groups of patients with isolated fractures of the mandible (I group), isolated fractures of the midface zone (II group) and combined fractures of all areas of the face (III group), who were hospitalized in the period from 2012 to 2017, were analyzed. The main epidemiological indicators were determined. The analysis of indicators of severity of MFT and TBI is carried out. Correlation analysis of indicators, analysis using the Kruskal- Wallis test and Steel-Dwass test for pairwise comparisons was performed. Results. Were treated519 patients. 457 men (88 %) and 62 women (12 %). The main causes of injuries were assaults (40 %). Correlation analysis did not reveal the dependence of MFT and TBI. The difference in severity of isolated fractures of the mandible and midface bones was statistically significant, and there is a statistical significance between the severity of TBI in case of isolated fractures of midface bones and panfacial fractures (p < 0.05). Conclusions. The severity of maxillofacial trauma in the case of panfacial fractures is on average 3 times higher than in the case of isolated fractures of the lower jaw or midface bones. The severity of TBI is largely consistent with concussion in all groups, but in the group with panfacial fractures, the median rate is lower comparing to other groups. Key words: Glasgow coma scale, fracture, Le Fort, traumatic brain injury

scholarly journals The DO-climate events are noise induced: statistical investigation of the claimed 1470 years cycle

2006 ◽  
Vol 2 (6) ◽  
pp. 1277-1292
Author(s):  
P. D. Ditlevsen ◽  
K. K. Andersen ◽  
A. Svensson
Keyword(s):  
Time Scale ◽  
Statistical Significance ◽  
Ice Cores ◽  
Statistical Investigation ◽  
Significance Tests ◽  
Recurrence Times ◽  
Annual Layer ◽  
Random Occurrence ◽  
Triggering Mechanisms ◽  
Climate Events

Abstract. The significance of the apparent 1470 years cycle in the recurrence of the Dansgaard-Oeschger (DO) events, observed in the Greenland ice cores, is debated. Here we present statistical significance tests of this periodicity. The detection of a periodicity relies strongly on the accuracy of the dating of the DO events. Here we use both the new NGRIP GICC05 time scale based on multi-parameter annual layer counting and the GISP2 time scale where the periodicity is most pronounced. For the NGRIP dating the recurrence times are indistinguishable from a random occurrence. This is also the case for the GISP2 dating, except in the case where the DO9 event is omitted from the record. Whether or not the record shows a truly periodic beating has strong implications for identifying the underlying cause. If the recurrence is periodic it suggests an external cause. If the recurrence of DO events is not periodic it points to triggering mechanisms internal to the climate system being manifested at the millennial timescale.

scholarly journals Dominant Anomaly Patterns in the Near-Surface Baroclinicity and Accompanying Anomalies in the Atmosphere and Oceans. Part II: North Pacific Basin

2010 ◽  
Vol 23 (24) ◽  
pp. 6445-6467 ◽  
Author(s):  
Mototaka Nakamura ◽  
Shozo Yamane
Keyword(s):  
Heat Flux ◽  
North Pacific ◽  
Spatial Scales ◽  
Baroclinic Instability ◽  
Lower Troposphere ◽  
Pacific Basin ◽  
Mean Flow ◽  
Near Surface ◽  
Eddy Heat Flux ◽  
North Pacific Basin

Abstract Variability in the monthly-mean flow and storm track in the North Pacific basin is examined with a focus on the near-surface baroclinicity. Dominant patterns of anomalous near-surface baroclinicity found from empirical orthogonal function (EOF) analyses generally show mixed patterns of shift and changes in the strength of near-surface baroclinicity. Composited anomalies in the monthly-mean wind at various pressure levels based on the signals in the EOFs show accompanying anomalies in the mean flow up to 50 hPa in the winter and up to 100 hPa in other seasons. Anomalous eddy fields accompanying the anomalous near-surface baroclinicity patterns exhibit, broadly speaking, structures anticipated from simple linear theories of baroclinic instability, and suggest a tendency for anomalous wave fluxes to accelerate–decelerate the surface westerly accordingly. However, the relationship between anomalous eddy fields and anomalous near-surface baroclinicity in the midwinter is not consistent with the simple linear baroclinic instability theories. Composited anomalous sea surface temperature (SST) accompanying anomalous near-surface baroclinicity often exhibits moderate values and large spatial scales in the basin, rather than large values concentrated near the oceanic fronts. In the midsummer and in some cases in cold months, however, large SST anomalies are found around the Kuroshio–Oyashio Extensions. Accompanying anomalies in the net surface heat flux, SST in the preceding and following months, and meridional eddy heat flux in the lower troposphere suggest active roles played by the ocean in generating the concomitant anomalous large-scale atmospheric state in some of these cases.

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