Kendall's Rank Correlation Analysis Research Articles

Enhancing undergraduate research talents: the role of tutors in dental basic research education.

This study endeavors to investigate ways to optimize the role of teachers in undergraduate dental basic research education (UDBRE) with the aim of nurturing the research potential of undergraduate students. We conducted a cross-sectional study among medical undergraduates enrolled at the School of Stomatology, Guangzhou Medical University. Descriptive statistics were employed to comprehensively analyze UDBRE's fundamental aspects. Kendall rank correlation analysis was performed to evaluate the relationship between the quality of feedback provided by tutors to undergraduates and the students' scientific research abilities. Additionally, multivariate logistic regression analysis was employed to uncover the factors influencing the effectiveness of UDBRE. A total of 168 medical students were surveyed with a valid response rate of 93.85%. The effectiveness of UDBRE was demonstrated by undergraduates' self-rated research abilities, active participation in scientific research projects, and a certain amount of academic outputs. Significant and positive correlations (𝓣b> 0.5, p < 0.001) were identified between the tutor-undergraduate feedback quality and students' self-rated scores for scientific research abilities. These abilities included developing scientific questions, designing research projects, retrieving and reading literature, academic writing, experiment operation, and analyzing and evaluating experimental results. Positive effects on students' academic performance (p < 0.05) were observed when higher-quality feedback, an authoritative tutoring style and tutors with middle-career experience were present. This study underscores the pivotal role of UDBRE in fostering the scientific research aptitude of medical undergraduates. It emphasizes the constructive influence of tutor-undergraduate feedback, authoritative teaching styles, providing valuable insights for establishing an effective mentorship framework.

Immediate Impact of the COVID-19 Pandemic on Heart and Kidney Transplantation andtheRecovery Trends in 30 Developed andLess-Developed Countries.

BACKGROUND The COVID-19 pandemic had multifaceted and disproportionate impacts on various countries. We investigated the decline of heart and kidney transplantation in 2020 and recovery trends in 2020, 2021, and 2022 in 30 developed and developing countries, considering COVID-19 incidence and mortality and pandemic-time economic variables. MATERIAL AND METHODS Data were obtained from reliable open databases. Nations were grouped by hierarchical cluster analysis into high-gross domestic product (GDP), mid-GDP, and low-GDP countries. Expected transplant numbers for 2020 to 2021 were estimated by the artificial neural network method using data from 2015 to 2019. Effect size and its inference were determined through the Hodges-Lemann estimate and Wilcoxon signed-rank test, respectively. The possible disproportionate effect was estimated by the Jonckheere-Tersptra test. Associations between transplantation and economic variables, COVID-19 caseload, and mortality were examined using Kendall rank correlation analysis. RESULTS All nations experienced a decline in 2020 and some real recovery in 2020 to 2022. For high-GDP countries, decline was insignificant and recovery was marginal; for mid-GDP countries, decline was significant for heart and deceased kidneys and recovery was modest; for low-GDP countries, decline was significant for heart, live kidneys, and deceased kidneys and recovery was marginal. The low-GDP countries were disproportionally negatively impacted, although the associations between the impact and economic variables, COVID-19 incidence, and COVID-19 mortality were statistically insignificant. CONCLUSIONS More inclusive studies of socioeconomic and cultural factors that affected the impact of the COVID-19 pandemic in different countries can be useful for better preparedness and reducing disruption in healthcare in future global pandemics.

A computational model of surface electromyography signal alterations after spinal cord injury

Objective. Spinal cord injury (SCI) can cause significant impairment and disability with an impact on the quality of life for individuals with SCI and their caregivers. Surface electromyography (sEMG) is a sensitive and non-invasive technique to measure muscle activity and has demonstrated great potential in capturing neuromuscular changes resulting from SCI. The mechanisms of the sEMG signal characteristic changes due to SCI are multi-faceted and difficult to study in vivo. In this study, we utilized well-established computational models to characterize changes in sEMG signal after SCI and identify sEMG features that are sensitive and specific to different aspects of the SCI. Approach. Starting from existing models for motor neuron pool organization and motor unit action potential generation for healthy neuromuscular systems, we implemented scenarios to model damages to upper motor neurons, lower motor neurons, and the number of muscle fibers within each motor unit. After simulating sEMG signals from each scenario, we extracted time and frequency domain features and investigated the impact of SCI disruptions on sEMG features using the Kendall Rank Correlation analysis. Main results. The commonly used amplitude-based sEMG features (such as mean absolute values and root mean square) cannot differentiate between injury scenarios, but a broader set of features (including autoregression and cepstrum coefficients) provides greater specificity to the type of damage present. Significance. We introduce a novel approach to mechanistically relate sEMG features (often underused in SCI research) to different types of neuromuscular alterations that may occur after SCI. This work contributes to the further understanding and utilization of sEMG in clinical applications, which will ultimately improve patient outcomes after SCI.

EPH97 Application of Self-Protective Behaviors in Balancing Objective and Subjective COVID-19 Risk Assessments Among Residents in an Urban Setting

We examined the association between self-perceived and Latent Class Analysis (LCA) assessed risk of COVID-19 infection and evaluated their relationships with sociodemographic and modifiable behavioral factors among residents of Onitsha, an urban city in Nigeria. We analyzed data from a cross-sectional survey (n=140) conducted in March 2020. The survey elicited information on the participants’ demographic characteristics, COVID-19 knowledge, attitude, preventive practice, level of preparedness, misconceptions, and COVID-19 information gaps. Participants were classified as being “not at risk” or “at risk” based on self-perceived risk of COVID-19 infection (subjective) and LCA-segmented risk clusters (objective). We applied the Chi-square test and used Kendall rank correlation analysis to determine the relationship between demographic characteristics and self-protective behaviors by the risk assessment methods. There was a significant association between subjective (32.4%) and objective (50.7%) assessments of COVID-19 risk (X2=5.38, p<0.05) among the survey participants. However, those who perceived themselves at risk of COVID-19 were 58% less likely to be classified as such when assessed objectively (OR: 0.42, 95%CI: 0.20-0.88, p<0.05). In contrast, those who perceived themselves to be at no risk were 2.38 times (OR: 2.38, 95%CI: 1.13-4.99, p<0.05) more likely to be at risk when assessed objectively. Significantly negative and low correlation was observed between subjective and objective assessments ((Kendall's tau-b (τb)= -0.193,p<0.05). Relationship between knowledge and attitude of residents toward COVID-19 were in opposite direction (τb= 0.431,p<0.01 (subjective) and τb= -0.339,p<0.01 (objective)). Adoption of preventive practices was negatively correlated with information gap among persons assessed both subjectively (τb= -0.379,p<0.01) and objectively (τb= -0.404,p<0.001) for COVID-19 risks. Objective assessment allowed for the integration of self-protective behaviors in the model, making it a reliable framework for identifying at risk group and tailoring intervention program aimed at curbing the devastating impact of COVID-19 among the city residents.

Multiple logistic regression based prediction of heat flow direction in an intake incline of shallow depth by integrating thermal flywheel effect: A case study

The diurnal changes of psychrometric conditions in a shallow intake incline of an Indian coal mine were investigated. On different days spread over thirteen months, 24-hour studies were conducted. Based on the findings, the cyclic behavior of the heat load was documented. The Kendall rank correlation analysis between heat parameters of surface air and the airway reveals that the wet-bulb depression of inlet air is the most important factor for air to rock heat transfer, while sensible heat of inlet air is dominating factor for rock to air heat transfer. A multiple logistic regression-based model was proposed for predicting the direction of heat flow. Using Youden's index, the optimal cut-off value for the model was determined to be 0.478. Performance evaluation of the proposed model on the testing dataset shows an F-score of 0.8182 and an accuracy of 80%.

Are there correlations between the levels of fluctuating asymmetry in Pelophylax ridibundus (Anura: Ranidae) meristic morphological traits and morphological parameters used for assessing their physical fitness (health status)?

The degree of developmental stability of individuals and populations is most often estimated by their level of fluctuating asymmetry (FA) - the random deviations from perfect symmetry. In our previous work, we recorded high levels of FA (FAMI index: frequency of asymmetric manifestation of an individual) in Pelophylax ridibundus populations that inhabit biotopes at Sazliyka River, south Bulgaria with high levels of anthropogenic pollution (domestic sewage pollution). At the same time, in the biotopes located in the upper reaches of the river (less disrupted habitats), the populations showed low levels of FA. Currently, we present the results of the study of the values of several morphological parameters: snout-vent length (SVL), body weight (BW), and body condition factor (CF) in the same populations of P. ridibundus. In addition, we evaluate the correlation between the values of these morphological parameters and the values of fluctuating asymmetry (the FAMI index), using the Kendall rank correlation analysis. The analysis of the relationships between the parameters characterizing the physical fitness of frogs and the indicator of developmental stability - the FAMI index - did not establish statistically significant correlations in the analyses in the whole groups of P. ridibundus from each site and in the correlations between sexes. We believe that the approaches to the study of developmental stability (analysis of fluctuating asymmetry levels) and those related to the assessment of physical fitness (health status) of frogs should be applied independently of each other.

Factors influencing emergency medical competencies of health centers and fire stations in areas that are vulnerable to earthquakes.

ObjectiveThis study aimed to investigate the factors influencing the emergency medical competency (EMC), perceived by the fire station and health center staff, in the areas where of emergency medical vulnerability where earthquakes had occurred.MethodsThis study was conducted between December 2019 and February 2020. A proper questionnaire was created to evaluate EMC in disaster situations and administered to the fire station and the health center groups. Descriptive variables of each group were calculated. The Kendall rank correlation analysis was used to measure the relationships between the demographic variables, disaster-related variables, and EMC. The factors influencing the EMC for both groups were investigated in the linear regression analysis.ResultsFor a total of 200 respondents, the mean scores of EMC were 99.85±21.24 and 95.24±20.05 for the fire station (n=96) and the health center (n=104) groups, respectively (P=0.121). EMC was significantly correlated with age, years of service, job position, natural disaster experience, disaster relief service experience, and joint disaster response exercise (P<0.050). Linear regression analysis revealed that the duration of joint disaster response exercise (β=0.640, t=11.696) in Model 1 (F=136.806, P<0.001), the duration of joint disaster response exercise (β=0.627, P<0.001), and disaster rescue service experience (β=0.124, P<0.001) in Model 2 (F=72.431, P<0.001) were independently associated with EMC improvement.ConclusionOur findings indicate that the disaster preparedness program with a longer duration of joint disaster response exercise and more frequent disaster rescue service experience is necessary for improved and systematic response to a disaster.

The relation between left ventricular systolic function parameters and preceding or prepreceding beat-to-beat distance in patients with atrial fibrillation: an echocardiographic study.

We aimed at investigating the relation between left ventricle (LV) systolic parameters and beat-to-beat distances and also whether this relation is different in heart failure with reduced ejection fraction (HFrEF) patients with atrial fibrillation (AF). The relation between peak velocity in left ventricular outflow (VLVOT), left atrioventricular plane displacement (LAVPD) or peak systolic tissue Doppler velocity of lateral mitral annulus (Lateral S') and preceding beat-to-beat distance (RR1) or prepreceding beat-to-beat distance (RR2) were analyzed by linear regression analysis. From this analysis, three parameters were obtained: slope of regression line, constant of regression line, and square of regression coefficient (r2) of linear relation. In the group with HFrEF, the slope and r2 values of the regression line showing the relationship between the RR1 interval and VLVOT, LAVPD, and Lateral S' values were higher and the constants were lower. In the Kendall rank correlation analysis, the slope, constant, and r2 values of the regression analysis between RR1 interval and VLVOT or Lateral S' were in significant correlation with LVEF. The r2 of VLVOT-RR1 analysis, slope of this analysis, and slope of Lateral S'-RR1 regression line values were mostly predictive for detecting HFrEF. It was concluded that the novel parameters obtained by linear regression analysis between LV systolic function parameters and RR1 interval, but not RR2, might be beneficial for evaluating systolic heart failure in patients with AF. They might have potential for future research about the physiopathology of heart and prognosis in patient with AF.

Sunlight ultraviolet radiation dose is negatively correlated with the percent positive of SARS-CoV-2 and four other common human coronaviruses in the U.S.

Human coronaviruses are RNA viruses that are sensitive to ultraviolet (UV) radiation. Sunlight contains UVA (320–400 nm), UVB (260–320 nm) and UVC (200–260 nm) action spectra. UVC can inactivate coronaviruses, including severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). The incidence and mortality of coronavirus disease 2019 (COVID-19) are considered to be correlated with vitamin D levels. Vitamin D synthesis in human skin is closely related to exposure to UVB radiation. Therefore, the incidence and mortality of COVID-19 are also considered to be correlated with Vitamin D levels. In this study, Spearman and Kendall rank correlation analysis tests were used to analyze the correlation between the average percent positive of five human coronaviruses (SARS-CoV-2, CoVHKU1, CoVNL63, CoVOC43, and CoV229E) in the U.S. and the corresponding sunlight UV radiation dose The results indicated that the monthly average percent positive of four common coronaviruses was significantly negatively correlated with the sunlight UV radiation dose. The weekly percent positive of SARS-CoV-2 during April 17, 2020 to July 10, 2020 showed a significant negative correlation with the sunlight UV radiation dose in census regions 1 and 2 of the U.S. while no statistical significance in the other regions. Additionally, sunlight UV radiation also showed some negative effects with respect to the early SARS-CoV-2 transmission.

Gallbladder sizes in patients with arterial hypertension, obesity and hypothyroidism: correlation analysis

Our previous studies showed that patients with arterial hypertension and excessive weight or obesity presented with the significantly enlarged gallbladder, both fasting and after taking cholekinetic. The gallbladder ejection fraction was below the normal range, and poor blood pressure control was accompanied by further gallbladder over distension, reduction of its contractility and increased risk of gallstone formation. This needs further research, especially considering hypothyreoidism. The aim is to establish correlations of the sonographically estimated gallbladder sizes in patients with arterial hypertension, obesity and hypothyreoidism.&#x0D; Materials and methods. The cohort of 40 patients (females 90%, males 10%) with arterial hypertension, body overweight/obesity and h underlying hypothyroidism was examined; sonographically estimated gallbladder sizes are compared with clinical, laboratory and instrumental data. Kendall's rank correlation method was applied; significance threshold was taken as р &lt; 0,05.&#x0D; Results. In patients with arterial hypertension and overweight/obesity, the sizes of GB are enlarged both in cases of hypothyreoidism 64,4 mm (56–87) and 25 mm (21,2–28) and without it 67 mm (60–72) and 24 mm (22–29) with a significantly larger interquartile range (31 vs 12 mm) for hypothyroidism. According to Kendall's rank correlation analysis, gallbladder was enlarged in the older patients with a higher body mass index, and this statistically correlated with the advancement of stage and degree of arterial hypertension, cardiovascular risk, neutrophilic inflammationactivationandimmuneinflammation suppression, thinned renal parenchyma, increased echogenicity of the pancreas, and cardioselective aspartataminotransferase cytolysis. These connections can be based on the common spinal innervation of the heart and gallbladder, dysregulated beta 3-adrenoceptor activity and disturbed nitrite mediated vasorelaxation.

Using network analysis to identify keystone species in the food web of Haizhou Bay, China

Keystone species play critical roles in ecological communities and ecosystem functions by interacting directly or indirectly with other species. Studies on keystone species will contribute to the understanding of community stability and mechanisms underlying ecosystem degradation. Based on a survey in Haizhou Bay and adjacent waters in 2011, the food web was constructed according to the predator–prey relationships of species. The binary network was analysed to calculate 11 network indices to identify keystone species, and removal analysis was conducted to examine the effects of the extinction of keystone species on the food web. Kendall rank correlation analysis showed that there were significant correlations between most pairs of the 11 network indices (P&amp;lt;0.05). According to the results of principal component analysis of all these indices, several species, namely Leptochela gracilis, Loligo sp., Larimichthys polyactis, Alpheus japonicus and Oratosquilla oratoria, were identified as keystone species in the Haizhou Bay food web. Removal analysis suggested that the absence of keystone species may have considerable effects on the complexity and stability of the food web in Haizhou Bay. It is suggested that priority is given to the protection of keystone species in the marine ecosystem.

Multiscale Analysis of the Polymeric Insulators Degradation in Simulated Arid Environment Conditions: Cross-Correlation Assessment

The aim of this study is to highlight the joint evolution of the chemical, morphological, thermal and dielectric behaviors upon the UV weathering of an industrial ethylene-propylene-diene monomer (EPDM) rubber. This latter is used as a housing of composite high voltage insulators which are installed in the Algerian desert. This material was submitted to photochemical aging by irradiating UVA rays (λ = 340 nm) at a temperature of 45 °C in order to simulate the witnessed site conditions. It was shown that the degradation process leading to the formation of oxygenated species and the depolymerization of the material are responsible of the coupling which may appear between the realized measurements. Using Kendall rank correlation analysis, joint evolution models were established. Those models introduce a novel assessment approach of the chemical and morphological status of the aged rubber using electrical and dielectric measurements.

Prolonged wait time is associated with increased mortality for Chilean waiting list patients with non-prioritized conditions

BackgroundMost data on mortality and prognostic factors of universal healthcare waiting lists come from North America, Australasia, and Europe, with little information from South America. We aimed to determine the relationship between medical center-specific waiting time and waiting list mortality in Chile.MethodUsing data from all new patients listed in medical specialist waitlists for non-prioritized health problems from 2008 to 2015 in three geographically distant regions of Chile, we constructed hierarchical multivariate survival models to predict mortality risk at two years after registration for each medical center. Kendall rank correlation analysis was used to measure the association between medical center-specific mortality hazard ratio and waiting times.ResultThere were 987,497 patients waiting for care at 77 medical centers, including 33,546 (3.40%) who died within two years after registration. Male gender (hazard ratio [HR] = 1.17, 95% confidence interval [CI] 1.1–1.24), older age (HR = 2.88, 95% CI 2.72–3.05), urban residence (HR = 1.19, 95% CI 1.09–1.31), tertiary care (HR = 2.2, 95% CI 2.14–2.26), oncology (HR = 3.57, 95% CI 3.4–3.76), and hematology (HR = 1.6, 95% CI 1.49–1.73) were associated with higher risk of mortality at each medical center with large region-to-region variations. There was a statistically significant association between waiting time variability and death (Z = 2.16, P = 0.0308).ConclusionPatient wait time for non-prioritized health conditions was associated with increased mortality in Chilean hospitals.

Prolonged Wait Time is Associated with Increased Mortality for Chilean Waiting List Patients with Non-Prioritized Conditions

Background: Most data on mortality and prognostic factors of universal healthcare waiting lists come from North America, Australasia, and Europe, with little information from South America. We aimed to determine the relationship between medical center-specific waiting time and waiting list mortality in Chile. Methods: Using data from all new patients listed in medical specialist waitlists for non-prioritized health problems from 2008 to 2015 in three geographically distant regions of Chile, we constructed hierarchical multivariate survival models to predict mortality risk at two years after registration for each medical center. Kendall rank correlation analysis was used to measure the association between medical center-specific mortality hazard ratio and waiting times. Findings: There were 987,497 patients waiting for care at 77 medical centers, including 33,546 (3‧ 40%) who died within two years after registration. Male gender (hazard ratio [HR]=1‧ 17, 95% confidence interval [CI] 1‧ 1-1‧ 24), older age (HR=2‧ 88, 95% CI 2‧ 72-3‧ 05), urban residence (HR=1‧ 19, 95% CI 1‧ 09-1‧ 31), tertiary care (HR=2‧ 2, 95% CI 2‧ 14-2‧ 26), oncology (HR=3‧ 57, 95% CI 3‧ 4-3‧ 76), and hematology (HR=1‧ 6, 95% CI 1‧ 49-1‧ 73) were associated with higher risk of mortality at each medical center with large region-to-region variations. There was a statistically significant association between prolonged waiting and death (Z = 2‧ 16, P = 0‧ 0308). Interpretation: Patient wait time for non-prioritized health conditions was associated with increased mortality in Chilean hospitals. Funding Statement: The work was supported by the Johns Hopkins Alliance for a Healthier World. DM is also supported by the U.S. Centers for Disease Control and Prevention, U.S. Agency for Healthcare Research and Quality, and the Emergency Medicine Foundation. DP is also supported by the U.S. National Science Foundation. FF is also supported by the Comision Nacional de Investigacion Cientifica y Tecnologica de Chile. JH is also supported by the U.S. National Institutes of Health, U.S. Agency for Healthcare Research and Quality, and the Emergency Medicine Foundation. SL is also supported by the U.S. National Science Foundation, U.S. National Institutes of Health, and the U.S. Agency for Healthcare Research and Quality. Declaration of Interests: FF is the founder and co-owner of a start-up company with a focus on data analytics for process improvement. SL is the founder and co-owner of a start-up company with a focus on data-driven improvement of emergency department and hospital operations. DM, DP, HZ, JH, JD, MB, and RM have no competing interests.

Serum HBsAg and HBeAg levels are associated with liver pathological stages in the immune clearance phase of hepatitis B virus chronic infection.

The association between hepatitis B surface antigen (HBsAg) and hepatitis B 'e' antigen (HBeAg) levels and liver inflammation and fibrosis in patients with chronic hepatitis B (CHB) in the immune clearance (IC) remains elusive. The aim of the present study was to investigate whether HBsAg and HBeAg levels were associated with liver inflammation and fibrosis in CHB patients during the IC phase. Kendall's rank correlation analysis and receiver operating characteristic curves were used to determine the correlation between HBsAg, HBeAg and liver pathological stages. Multivariate analysis by forward logistic regression was used to analyze significant predictors of cirrhosis. A liver pathology‑predicting model (IC model), which used routinely assessed markers in combination with HBsAg and HBeAg levels, was constructed. There were significantly positive correlations between the HBsAg and HBeAg levels (γ=0.317, P<0.001), and between the HBsAg and HBV‑DNA levels (γ=0.489, P<0.001). However, there was no correlation between the HBsAg and alanine aminotransferase levels. HBsAg and HBeAg levels differed significantly at various liver pathological stages and declined progressively in advanced liver pathological stages. Multivariate logistic regression analysis showed that age, HBsAg and HBeAg levels as well as the international normalized ratio (INR) were independent predictors of liver fibrosis during the IC phase. The IC model had a specificity and sensitivity of 88.64 and 78.24%, respectively, a positive predictive value of 48.15% and negative predictive value of 96.79%. In conclusion, HBsAg and HBeAg levels were negatively and indirectly correlated with liver inflammation and fibrosis in CHB patients in the IC phase. The IC model reliably predicted the probability of liver cirrhosis.

Prostate-specific antigen density as a parameter for the prediction of positive lymph nodes at radical prostatectomy.

Objective:The aim was to determine the prognostic ability of Partin's tables for a patient collective undergoing radical prostatectomy (RP) and to evaluate the association of prostate-specific antigen (PSA) density (PSAD) and postoperative lymph node status.Methods:From 1999 to 2006, 393 consecutive patients underwent RP at our Urology department. Patients with Gleason scores < 6, clinical stages >T2c or neoadjuvant hormonal therapy were excluded. Preoperative PSA, biopsy results, digital rectal examination, and prostate size at transrectal ultrasound were recorded. Risk stratification according to the Partin scoring system was performed. Postoperative results were compared with preoperative risk estimation. Univariate and multivariate statistical analysis about prediction of postoperative lymph node status was performed.Results:Lymph node invasion (LNI) was found in 36 patients (9.16%). Kendall's rank correlation analysis revealed a significant association between the number of removed LN and LNI (P = 0.016). Patients with LNI had a significantly higher preoperative PSA and PSAD. Preoperative Gleason score was a significant predictor of LNI. The Partin tables' prediction of organ confined stages, extraprostatic extension, and seminal vesicle invasion was in line with the pathological findings in our collective. PSAD was a significant predictor of LNI in univariate and multivariate analysis.Conclusion:The most widely used nomogram is of high value in therapy decision-making, although it remains an auxiliary means. Considering the performance of lymph node dissection, surgeons should be aware of the specifics of the applied nomogram. PSAD appears as a useful adjunctive parameter for preoperative prostate risk estimation and warrants further evaluation.

A Comparison of Computed Tomography Scans and Digital Periapical Radiographs Ridge Height Measurements

To investigate the agreement between computerized tomography scans (CT) and intraoral periapical digital radiographs (PA) alveolar ridge height measurements in maxillary and mandibular posterior regions. We reviewed 100 implant patient radiographic records and identified 27 mandibular sites in 19 patients and 23 maxillary sites in 13 patients with available CT scans and matching PA radiographs. The distance from the crest of the ridge to the floor of the maxillary sinus or to the superior border of the inferior alveolar canal was measured. PAs were measured with Dexis software v. 8.0 and CTs were measured with Simplant software v. 11.02. Two examiners (RJ and MM) recorded the measurements separately; each examiner recorded two readings. The average of the 4 readings was used for data analysis. Absolute agreement: Paired t test comparing ridge-height measurements between the two imaging methods showed no differences for maxillary sites (P > 0.2) and significant differences for the mandibular sites (CT > PA, P = 0.0009). Relative agreement: Kendall rank correlation analysis of ridge-height measurements between the 2 imaging methods showed a high positive correlation for maxillary sites (Kendall's tau = 0.76, P = 0.0001) and moderate correlation for the mandibular sites (Kendall's tau = 0.46, P = 0.001). Maxillary PAs tend to approximate CT ridge-height measurements. By contrast mandibular PAs tend to underestimate the distance from the crest of the ridge to the inferior alveolar canal.

Relativity among starch quantity, polysaccharides content and total alkaloid content of Dendrobium loddigesii

To find out the relativity among starch quantity, polysaccharides content and total alkaloid content of Dendrobium loddigesii. Microscopy-counting process was applied to starch quantity statistics, sulfuric acid-anthrone colorimetry was used to assay polysaccharides content and bromocresol green colorimetry was used to assay alkaloid content. Pearson product moment correlation analysis, Kendall's rank correlation analysis and Spearman's concordance coefficient analysis were applied to study their relativity. Extremely significant positive correlation was found between starch quantity and polysaccharides content, and significant negative correlation between alkaloid content and starch quantity was discovered, as well was between alkaloid content and polysaccharides content.

Temporal correlations and clustering of landslides

AbstractThis paper examines temporal correlations and temporal clustering of a proxy historical landslide time series, 2255 reported landslides 1951–2002, for an area in the Emilia‐Romagna Region, Italy. Landslide intensity is measured by the number of reported landslides in a day (DL) and in an ‘event’ (Sevent) of consecutive days with landsliding. The non‐zero values in both time series DL and Sevent are unequally spaced in time, and have heavy‐tailed frequency‐size distributions. To examine temporal correlations, we use power‐spectral analysis (Lomb periodogram) and surrogate data analysis, confronting our original DL and Sevent time series with 1000 shuffled (uncorrelated) versions. We conclude that the landslide intensity series DL has strong temporal correlations and Sevent has likely temporal correlations. To examine temporal clustering in DL and Sevent, we consider extremes over different landslide intensity thresholds. We first examine the statistical distribution of interextreme occurrence times, τ, and find Weibull distributions with parameter γ &lt;&lt; 1·0 [DL] and γ &lt; 1·0 [Sevent]; thus DL and Sevent each have temporal correlations, but Sevent to a lesser degree. We next examine correlations between successive interextreme occurrence times, τ. Using autocorrelation analysis applied to τ, combined with surrogate data analysis, we find for DL linear correlations in τ, but for Sevent inconclusive results. However, using Kendall's rank correlation analysis we find for both DL and Sevent the series of τ are strongly correlated. Finally, we apply Fano Factor analysis, finding for both DL and Sevent the timings of extremes over a given threshold exhibit a fractal structure and are clustered in time. In this paper, we provide a framework for examining time series where the non‐zero values are strongly unequally spaced and heavy‐tailed, particularly important in the Earth Sciences due to their common occurrence, and find that landslide intensity time series exhibit temporal correlations and clustering. Many landslide models currently are designed under the assumption that landslides are uncorrelated in time, which we show is false. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Estimation from PET data of transient changes in dopamine concentration induced by alcohol: support for a non-parametric signal estimation method

We previously developed a model-independent technique (non-parametric ntPET) for extracting the transient changes in neurotransmitter concentration from paired (rest & activation) PET studies with a receptor ligand. To provide support for our method, we introduced three hypotheses of validation based on work by Endres and Carson (1998 J. Cereb. Blood Flow Metab. 18 1196–210) and Yoder et al (2004 J. Nucl. Med. 45 903–11), and tested them on experimental data. All three hypotheses describe relationships between the estimated free (synaptic) dopamine curves (FDA(t)) and the change in binding potential (ΔBP). The veracity of the FDA(t) curves recovered by nonparametric ntPET is supported when the data adhere to the following hypothesized behaviors: (1) ΔBP should decline with increasing DA peak time, (2) ΔBP should increase as the strength of the temporal correlation between FDA(t) and the free raclopride (FRAC(t)) curve increases, (3) ΔBP should decline linearly with the effective weighted availability of the receptor sites. We analyzed regional brain data from 8 healthy subjects who received two [11C]raclopride scans: one at rest, and one during which unanticipated IV alcohol was administered to stimulate dopamine release. For several striatal regions, nonparametric ntPET was applied to recover FDA(t), and binding potential values were determined. Kendall rank-correlation analysis confirmed that the FDA(t) data followed the expected trends for all three validation hypotheses. Our findings lend credence to our model-independent estimates of FDA(t). Application of nonparametric ntPET may yield important insights into how alterations in timing of dopaminergic neurotransmission are involved in the pathologies of addiction and other psychiatric disorders.