SM Journal of Biometrics & Biostatistics

Archive Articles

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Statistical Analysis and Inter Comparison of Albedo for Athalassa and Larnaca, Cyprus

A statistical analysis and inter-comparison of the reflected radiation at two sites in Cyprus representing two different climate regimes of the island (Athalassa-inland plain vs Larnaca-coastal location) covering the period January 2013-December 2015 is presented. Mean annual and mean monthly daily totals of the reflected radiation and ground albedo as well as their frequency distribution are computed and discussed. The monthly means of reflected irradiance range from 50 to 120 W m-2 at Athalassa, while at Larnaca they range between 50 and 140 W m-2. The mean annual albedo for Athalassa is 0.202 which coincides with the most common value given in the literature, while for Larnaca it is higher (0.221). The higher value at Larnaca is attributed to its alluvial (silty sandy) soil which has higher reflectivity compared to the calcarenite (calcium carbonate) soil at Athalassa. The lowest values of albedo at Athalassa, are observed around noon and the higher values in the morning and afternoon. The highest values are obtained in January and February and the lowest in May and June when global solar irradiance have its higher values. On the other hand, we observe an increasing trend from the morning towards the afternoon hours at Larnaca throughout the year. The maximum of daily reflected irradiation is about 6.5 MJ m-2 at Athalassa and about 7.5 MJ m-2 at Larnaca. The monthly mean daily values of albedo at Athalassa range between 0.175 to 0.224, while at Larnaca they are higher ranging from 0.198 to 0.239. As a result of the differences of the global and reflected radiation of the two sites, the net shortwave irradiation at Larnaca is slightly higher than that at Athalassa, almost throughout the year.

Pashiardis S1, Kalogirou SA1* and Pelengaris A2


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T hermal Spectroscopy, Photothermal Spectroscopy, Thermal Microspectroscopy, Photothermal Microspectroscopy, Thermal Macrospectroscopy and Photothermal Macrospectroscopy Comparative Study on Malignant and Benign Human Cancer Cells and Tissues with the Passage of Time under Synchrotron Radiation

In the current study, we have experimentally and comparatively investigated and compared malignant human cancer cells and tissues before and after irradiating of synchrotron radiation using T hermal Spectroscopy, Photothermal Spectroscopy, Thermal Microspectroscopy, Photothermal Microspectroscopy, Thermal Macrospectroscopy and Photothermal Macrospectroscopy. It is clear that malignant human cancer cells and tissues have gradually transformed to benign human cancer cells and tissues under synchrotron radiation with the passage of time (Figures 1-6) [1-123]. It can be concluded that malignant human cancer cells and tissues have gradually transformed to benign human cancer cells and tissues under synchrotron radiation with the passage of time (Figures 1-6) [1-123].

Alireza Heidari*


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Bayesian Bent-Cable Tobit Models for Longitudinal and Survival Data: Application to AIDS Studies

This paper presents a new methodology for jointly identifying bent cable phasic patterns and mixture of progressors and non-progressors of human immunodeficiency virus infection and acquired immune deficiency syndrome (HIV/AIDS) patients based on longitudinal and time-to-event data. Using the longitudinal data, the bentcable model gives an estimate of a gradual transition period for the development of drug resistance to Antiretroviral (ARV) drug for treating HIV patients. In addition to finding such an estimate (phasic pattern identification), a two-part modeling is carried out to incorporate a relatively large percentage of left-censored data in the framework of joint analysis of time to event and longitudinal data. Even though there are some methods for separately analyzing time to event and longitudinal data, those methods may not be appropriate when time to event is dependent on the longitudinal outcome. A better approach is to extend a bent-cable To bit model that jointly incorporates patients who are potentially progressors to AIDS from those patients who do not, phasic changes of trajectories of viral load, and the association between the time to a decline of CD4/CD8 ratio and rates of change in viral load. The proposed methods are illustrated using real data from an AIDS clinical study.

Getachew A Dagne*


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Different Statistical Methods Studying the Nature Relationships between Climatic Variables and Cotton Production

Cotton yield is a function of growth rates, flower production rates and flower and boll retention during the fruiting period. This study, predicting effects of climatic factors during different convenient intervals (in days) on cotton flower and boll production compared with daily observations and collect information about the nature of the relationship between various climatic factors and cotton boll development and the 15-day period both prior to and after initiation of individual bolls. Evaporation, sunshine duration, relative humidity, surface soil temperature at 1800 h and maximum air temperature, are the important climatic factors that significantly affect flower and boll production. Evaporation; minimum humidity and sunshine duration were the most effective climatic factors during preceding and succeeding periods on boll production and retention. There was a negative correlation between f lower and boll production and either evaporation or sunshine duration, while that correlation with minimum relative humidity was positive.

Zakaria M Sawan*


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Practical Issues in Sample Size Determination for Correlation Coefficient Inference

Determination of the appropriate sample size to use when performing inference for a single Pearson correlation coefficient ρ is usually based on achieving sufficient power for the test of H0 : ρ = 0. However, sample sizes found using this method can yield confidence intervals that are so wide that they provide very little useful information about the magnitude of the population correlation. Alternative approaches for determining the appropriate sample size are proposed and compared to the "usual" method.

Stephen W Looney*