by Peter D. Hart
Original Research
Purpose: The purpose of this study was to examine the protective effects of different modes of physical activity (PA) on all-cause mortality in adults. Methods: Data for this research came from the 2001-2002 National Health and Nutrition Examination Survey (NHANES). Participants 18+ years of age who were eligible for mortality linkage were used in the analysis. Different modes of PA were determined from a series of questions asking respondents if they participated in transportation (TPA), home/yard (HPA), moderate recreational (MPA), vigorous recreational (VPA), or muscle strengthening (MSPA) physical activity. Those respondents answering “yes” to either question were considered participating in that PA mode. Cox proportional hazards regression was used to model the effects of PA mode on mortality while controlling for age, sex, race, and income. Results: Adults were at less risk of mortality if they participated in TPA (Hazard Ratio (HR) =0.72, 95% CI: 0.57, 0.90), HPA (HR=0.43, 95% CI: 0.33-0.55), VPA (HR=0.30, 95% CI: 0.23-0.38), MPA (HR=0.53, 95% CI: 0.45-0.62), and MSPA (HR=0.44, 95% CI: 0.32-0.60). The adjusted model showed a 24.0% decrease in mortality (HR=0.76, 95% CI: 0.67-0.85) for each additional PA mode adopted. Conclusions: Results from this study indicate that various types of PA protect adults from all-cause mortality. Additionally, a dose-response relationship exists between the number of PA modes adopted and risk of mortality.
American Journal of Applied Mathematics and Statistics. 2017, 5(4), 154-158. DOI: 10.12691/ajams-5-4-6
Pub. Date: November 27, 2017
9930 Views3040 Downloads
by Mahdy I. Aljazzaf
Original Research
Teenagers in Kuwait and elsewhere spend a lot of their time using various types of social media applications (SMA). This study surveyed Kuwaiti teenagers, males and females at different educational levels, the usage intensity, purpose of use of these applications and quantitatively assessed the effect it has on many dimensions of their life. Many interesting results are highlighted and can be extrapolated to teens in the Arab World and beyond. The most outstanding results are that Kuwait teenagers spend a lot of time using social media applications, use WhatsApp and Snapchat in particular for communicating with others and for entertainment, it has negatively affected their sleeping hours, consider it a very useful learning resource, by in large trust the information received on social media, do not seem to be over concerned about how it affects their privacy, use it quite often to buy products and services, and they are satisfied with such purchases. To achieve these goals, a special questionnaire has been prepared especially for this purpose has been met from a random sample of Kuwait teens from different schools in Kuwait. Appropriate statistical analysis tools were used in this study.
American Journal of Applied Mathematics and Statistics. 2017, 5(4), 145-153. DOI: 10.12691/ajams-5-4-5
Pub. Date: November 21, 2017
17819 Views2625 Downloads
by Isaac Anthony. A, Tim Itoro M, Ikpang Ikpang N and Nsikak S
Original Research
This study investigated the goodness of four (4) different types of organic fertilizers on crop (maize) yield. Data on kilograms of maize yield for the 2014/2015 planting season from four separate farms in which the four (4) different types of organic fertilizer (poultry droppings, piggery manure, extract from farm product and cassava sediment) were applied were collected from the Department of Soil Science, Akwa Ibom State University. SPLIT PLOT DESIGN and TWO-WAY ANOVA WITH INTERACTIONS models were used in carrying out the analysis. Hypothesis that was tested to ascertain whether there was a significant effect of the four types of organic fertilizer on maize yield indicated that, for both models, there was significant effect. When a pair-wise comparison via Least Significant Difference (LSD) was carried out to determine which of the four types of organic fertilizer was the best. For both models, results showed that extract from farm product was the best.
American Journal of Applied Mathematics and Statistics. 2017, 5(4), 136-144. DOI: 10.12691/ajams-5-4-4
Pub. Date: November 20, 2017
11814 Views2165 Downloads
by Mezbahur Rahman and Han Wu
Original Research
The exponential distribution is considered in situtations where intervals between events are considered as well as where a skewed distribution is appropriate. The exponential distribution also plays key role in survival analysis. Goodness-of-fit for exponentiality is crucial as, in the natural sciences, some of the commonly used distributions such as gamma and Weibull distributions are just translated versions of the exponential distributions. Several well known exponentiality tests are reviewed. A power comparison is performed using simulation.
American Journal of Applied Mathematics and Statistics. 2017, 5(4), 125-135. DOI: 10.12691/ajams-5-4-3
Pub. Date: November 15, 2017
11232 Views2257 Downloads2 Likes
by Terman Frometa-Castillo
Original Research
This document provides probabilistic-mechanistic models for describing the cell kill (K) and cell sub-lethal damage (SL) for one fraction with a dose of radiation that is absorbed by a living tissue; also this provides the K and SL formalisms for fractioned irradiation regimens. These models and formalisms are based on real mean behavior of cell survival (S) - a complement of K- and strong probabilistic-radiobiological foundations. The K and SL formalisms include all possible factors affecting the biological radiation effects: dose (d), fractionations (n), SL, and the temporal factors: cell repair and cell repopulation. It is discussed some aspects about the widely used linear-quadratic (LQ) S(d) model and LQ S(n,d) formalism, and one of its derivations, the BED (biologically effective dose). The SMp K(d) parameters can be obtained from S data, or using graphical/analytical tools developed by this study. These new formalisms will be useful for simulations of treatments, and together regional damage distribution for optimizations of the treatment planning.
American Journal of Applied Mathematics and Statistics. 2017, 5(4), 119-124. DOI: 10.12691/ajams-5-4-2
Pub. Date: November 10, 2017
8360 Views2669 Downloads
by Terman Frometa-Castillo
Original Research
We provide the most current results of the statistical models project (SMp) related to probabilistic-mechanistic NTCP models for evaluating radiation injury (RI), and discuss some problems of the current radiobiological concepts and models, The SMp NTCP models in function of dose of reference (Dref) were formulated. The SMp (Dref) were used two QUANTEC studies. The SMp will provide of less complex and advantageous models and parameters. Given their unquestionable common elements with the Lyman-Kutcher-Burman (LKB) and sigmoid models derived from logistic functions, they will be applicable; and according to negative remarks pointed out, the well-established, clinically validated, NTCP models in clinical radiobiology, even the SMp NTCP models could replace to these. Until date for fitting real datasets concerning radiation injuries have been used mathematical models that have some similarities with the probabilistic models. All datasets, which have been fitted with mathematical models that have similarities with probabilistic functions (PFs) can also be fitted with PFs.
American Journal of Applied Mathematics and Statistics. 2017, 5(4), 115-118. DOI: 10.12691/ajams-5-4-1
Pub. Date: November 07, 2017
7979 Views2299 Downloads1 Likes