background:   objective: to determine whether different diagnostic criteria of gestational diabetes mellitus (gdm) are suitable for iranian population.   materials and methods: prospective study was performed on 617 pregnant women. 1804 subjects referred for 50 g glucose challenge test (gct) between 24th and 28 th weeks of gestation. 617 women with abnormal gct (blood glucose ≥130 mg/dl) underw...

Consider the first-order linear delay differential equation x′(t) + p(t)x(τ(t)) = 0, t ≥ t0, and the second-order linear delay equation x′′(t) + p(t)x(τ(t)) = 0, t ≥ t0, where p and τ are continuous functions on [t0,∞), p(t) > 0, τ(t) is nondecreasing, τ(t) ≤ t for t ≥ t0 and limt→∞ τ(t) = ∞. Several oscillation criteria are presented for the first-order equation when