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Positive fixed points and fourth-order equations
This work presents sufficient conditions for the existence of at least one positive solution for a nonlinear fourth-order beam equation under Lidstone boundary conditions. The main tool used is aExpand
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Heteroclinic solutions for non-autonomous boundary value problems withsingular $\Phi$-Laplacian operators
We prove the solvability of the following boundary value problem on the real line $\Phi(u'(t))'=f(t,u(t),u'(t))$ on $\mathbb{R}$, $u(-\infty)=-1,$ $u(+\infty)=1,$ with a singularExpand
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Determination of Organophosphorus Compounds in Mediterranean Coastal Waters and Biota Samples Using Gas Chromatography with Nitrogen-Phosphorus and Chemical Ionization Mass Spectrometric Detection
Abstract An analytical method is described for the determination of organophosphorus compounds in water and biota samples. This includes solvent extraction, a clean up procedure using silica gel andExpand
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Computation of Green's functions for boundary value problems with Mathematica
Abstract This paper is devoted to construct an algorithm that allows us to calculate the explicit expression of the Green’s function related to a n th-order linear ordinary differential equation,Expand
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Positivity and lower and upper solutions for fourth order boundary value problems
Abstract This paper is devoted to the study the boundary value problem { u ( 4 ) ( t ) = f ( t , u ( t ) ) for all  t ∈ I = [ 0 , 1 ] , u ( 0 ) = u ( 1 ) = u ″ ( 0 ) = u ″ ( 1 ) = 0 . We prove theExpand
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On first-order ordinary differential equations with nonnegative right-hand sides
Existence of extremal solutions for scalar initial value problems is investigated. We shall concentrate upon nonlinearities having constant sign, which lead to new existence results.
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On uniqueness criteria for systems of ordinary differential equations
Abstract We present some new uniqueness criteria for the Cauchy problem x′(t)=f t,x(t) , x(t 0 )=x 0 , based on the local equivalence with another initial value problem.
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Green's functions and spectral theory for the Hill's equation
The aim of this paper is to show certain properties of the Green's functions related to the Hill's equation coupled with various two point boundary value conditions. We will obtain the expression ofExpand
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Does Lipschitz with Respect to x Imply Uniqueness for the Differential Equation y' = f(x,y)?
Of course, the answer to the question posed in the title is no, in general, but, surprisingly enough, yes in a significant situation to be detailed later. This paper aims to bring to the attention ofExpand
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Existence of infinitely many solutions for second-order singular initial value problems with an application to nonlinear massive gravity
Abstract We prove the existence of infinitely many solutions for a second-order singular initial value problem between given lower and upper solutions. Our study is motivated by a singular problemExpand
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