In this paper we consider a class of partial integro-differential equations of fractional order, motivated by an equation which arises as a result of modeling surface-volume reactions in optical biosensors. We solve these equations by employing techniques from fractional calculus; several examples are discussed. Furthermore, for the first time, we encounter an order of the fractional derivative other than 1 2 in an applied problem. Hence, in this paper we explore the applicability of fractional calculus in real-world applications, further strengthening the true nature of fractional calculus. 1 arXiv:1510.00408v2 [math.CA] 12 Nov 2016 R. M. Evans et al. / Computers & Mathematics with Applications 00 (2016) 1-19 2 [34,35]. The list is by no means complete. It is easy to find hundreds, if not thousands, of new applications in which the fractional calculus approach is more than welcome. This is the first in a series of papers that seeks to find further potential applications of fractional calculus in solving real-world problems, a journey that can benefit both the understanding of profound complexities in the application, and the field of fractional calculus itself. As an application of the theory developed in this paper, we consider the surface-volume reaction problem. The governing equations of the mathematical formulation of such models naturally give rise to a nonlinear equation that contains a fractional integral embedded in it, and which has no solutions to date. Thus, in this paper we both extend the theory of fractional calculus methods by considering equations motivated by modeling the surface-volume reactions, and explore another interpretation of the fractional integral.The remainder of this paper is organized as follows. The definitions and basic results are given in Section 2. In Section 3, we give the main results, which are generalizations of Abel's integral approach to the tautochrone problem. In Section 4, we give illustrative examples to motivate our approaches. One of the main examples is the surface-volume reaction problem that has several very interesting applications in mathematical biology and engineering [36].
Basic Definitions and Preliminary ResultsWe adopt definitions given in [37] or in the encyclopaedic book by Samko et al. [38] here. We begin by introducing the concept of a Riemann-Liouville fractional integral:Definition 2.1 ([37]). Let α > 0 with n − 1 < α ≤ n, n ∈ N, and a < x < b. The left-and right-Riemann-Liouville fractional integrals of order α of a function f are given byThe fractional integrals and derivatives also satisfy the following important properties: fractional operators are linear, that is, if L is a fractional integral or derivative, thenfor any functions f, g ∈ C n [a, b] or f, g ∈ L p (a, b) (as the case may be) and k ∈ R. For any α, β > 0, they also satisfy the following semigroup properties:Equation (5) will be the key property used to prove the main results of this paper. It also says that the Caputo derivative is the left-inverse of the Riemann-Liouville fract...