According to the authors, time-modified confounding occurs when the causal relation between a time-fixed or time-varying confounder and the treatment or outcome changes over time. A key difference between previously described time-varying confounding and the proposed time-modified confounding is that, in the former, the values of the confounding variable change over time while, in the latter, t...

In this paper, we prove the existence of twelve small (local) limit cycles in a planar system with third-degree polynomial functions. The best result so far in literature for a cubic order planar system is eleven limit cycles. The system considered in this paper has a saddle point at the origin and two focus points which are symmetric about the origin. This system was studied by the authors and...

We analyse a simple model of the heat transfer to and from a small satellite orbiting round a solar system planet. Our approach considers the satellite isothermal, with external heat input from the environment and from internal energy dissipation, and output to the environment as black-body radiation. The resulting nonlinear ordinary differential equation for the satellite’s temperature is anal...

The present paper measures natural radioactivity in different areas of Wassit governorate, using (HPGe) detector. Gamma spectrum analysis for each sample along with caululated specific activity show that the average concentrations of U-238, Th-232, and K-40 have been 19.420±4.7 Bq/kg, 18.487±5.05 Bq/kg, and 204.266±46.9 Bq/kg respectively, which is lower than the worldwide average value. While ...

The present paper measures natural radioactivity in different areas of Wassit governorate, using (HPGe) detector. Gamma spectrum analysis for each sample along with caululated specific activity show that the average concentrations of U-238, Th-232, and K-40 have been 19.420±4.7 Bq/kg, 18.487±5.05 Bq/kg, and 204.266±46.9 Bq/kg respectively, which is lower than the worldwide average value. While ...

Abstract: In the present work, it is shown that the problem of the cosmological constant (CC) is practically the consequence of the inadequacy of general relativity to take into account the quantum property of the space. The equations show that the cosmological constant naturally emerges in the hydrodynamic formulation of quantum gravity and that it does not appear in the classical limit becaus...

We give a classical confidence belt construction which unifies the treatment of upper confidence limits for null results and two-sided confidence intervals for non-null results. The unified treatment solves a problem (apparently not previously recognized) that the choice of upper limit or two-sided intervals leads to intervals which are not confidence intervals if the choice is based on the dat...

To expedite the timely creation of medical practice guidelines, a meta-analytic method was developed to combine both dichotomous survival data and continuous physiologic data from multiple studies of differing experimental design, which compare the same innovative clinical intervention to standard care. An aggregate ratio, R*, of the observed treatment effect to a clinically optimal treatment e...

We derive constraints on the fluctuation amplitude σ8 and the cosmological density parameter Ω0 in cold dark matter (CDM) universes from the observed logN -logS relation of X-ray clusters. The 95 percent confidence limits on σ8 in the CDM models with n = 1 and h = 0.7 are expressed as (0.52± 0.02)Ω −0.35−0.90Ω0+0.76Ω20 0 (Ω0 < 0.75; λ0 = 1 − Ω0) and (0.52 ± 0.02)Ω −0.29−0.91Ω0+0.73Ω20 0 (Ω0 < 0...

Phylogenetic analyses of large data sets pose special challenges, including the apparent tendency for the bootstrap support for a clade to decline with increased taxon sampling of that clade. We document this decline in data sets with increasing numbers of taxa in Astragalus, the most species-rich angiosperm genus. Support for one subclade, Neo-Astragalus, declined monotonically with increased ...