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The dynamics of normal and leukemic stem cell clones competing for resources in the same bone marrow niche can be modeled in a systems biology approach. We derive three related models describing the time evolution of normal and chronic myelogenous leukemia (CML) stem cells. The approach is based on the idea that stem cell proliferation is regulated by feedback mechanisms. We assume here that the growth of stem cell clones can be approximated by Tsallis functions, which depend on population numbers to ensure the communication between different stem cell strains. Of particular interest is the influence of medication, for example, by the CML drug imatinib, on the stem cell dynamics, which can be simulated by a variation of the parameterization of the differential equation systems. The basic 2D model represents the contest between cycling normal and wild‐type CML stem cells. In addition, extension of the basic model (i) by coupled reservoirs of quiescent stem cells and (ii) by a third stem cell species, which could be interpreted as an imatinib‐resistant mutant, is investigated. We analyze the global dynamics of the corresponding 2D, 3D, and 4D equation systems by analytic means and provide a complete map of the bifurcation landscape that occurs for changing values of the respective signaling strengths and growth or death parameters. This includes a complete classification of equilibria and their linear and non‐linear Lyapunov stability. Copyright © 2014 John Wiley & Sons, Ltd.

PurposeThe purpose of this paper is to gain a better understanding between procurement strategy, organization, processes, methods and tools, human resources, supplier management, and overall procurement success.Design/methodology/approachIn order to achieve the above‐mentioned results, a holistic benchmark with highly recognized companies is conducted. Applying a cohesive questionnaire of open and closed questions, the paper covers all relevant aspects of procurement functions. Regression analysis is used to identify significant correlations.FindingsThe benchmarking (BM) proved the following significant success factors for the overall procurement process: use of cross‐functional teams, high hierarchical positioning of the procurement function within the company, strong cooperation with other functions, training and development of the procurement personnel as well as supplier integration and continuous evaluation.Practical implicationsThe paper provides the reader with sound evidence of how to improve the overall performance of procurement.Originality/valueThe analytical results of the research rely on statistical/mathematical methodology to substantiate qualitative BM results.

In this paper complex powers of the Dedekind eta function are studied. The vanishing of the n-th Fourier coefficients are labeled by the roots of an attached polynomial p n (x). We study these polynomials, and their values and roots distribution. The considered polynomials of degree n ≤ 700 are verified as Hurwitz polynomials. We study the value distribution of the polynomials restricted to the imaginary axis.