Soft systems methodology: a context within a 50-year retrospective of OR/MS

Soft systems methodology (SSM) has been used in the practice of operations research and management science OR/MS) since the early 1970s. In the 1990s, it emerged as a viable academic discipline. Unfortunately, its proponents consider SSM and traditional systems thinking to be mutually exclusive. Despite the differences claimed by SSM proponents between the two, they have been complementary. An extensive sampling of the OR/MS literature over its entire lifetime demonstrates the richness with which the non-SSM literature has been addressing the very same issues as does SSM

Tetranuclear d-f Metallostars: Synthesis, Relaxometric, and Luminescent Properties

International audienceA novel ditopic ligand DTPA-ph-phen, based on 1,10-phenanthroline and diethylenetriaminepentaacetic acid (DTPA) units, has been designed and fully characterized by (1)H, (13)C, and 2D-COSY NMR spectroscopy, IR and electrospray ionization mass spectrometry (ESI-MS) techniques. The DTPA core of the ligand specifically binds Ln(III) ions (Ln = Eu, Gd) resulting in formation of the [Ln{DTPA-ph-phen}(H(2)O)](-) complex. The photophysical properties of the Eu(III) compound have been investigated, and the complex shows characteristic red luminescence with an overall quantum yield of 2.2%. Reaction of [Gd{DTPA-ph-phen}(H(2)O)](-) with Ru(II) leads to further self-assembly into a heterobimetallic metallostar complex containing Gd(III) and Ru(II) in a 3:1 ratio. This tetranuclear [(Gd{DTPA-ph-phen})(3)(H(2)O)(3)Ru](-) complex (Gd(3)Ru), formed by the coordination of Ru(II) to the 1,10-phenanthroline unit, has been characterized by a range of experimental techniques and evaluated toward its feasibility as a potential bimodal optical/MRI agent. The Gd(3)Ru metallostar shows intense metal-to-ligand charge transfer (MLCT) transition resulting in intense light absorption in the visible spectral region. Upon irradiation into this MLCT band at 450 nm, the Gd(3)Ru complex exhibits red broad-band luminescence in the range of 550-800 nm centered at 610 nm with a quantum yield of 4.8%. Proton nuclear magnetic relaxation dispersion (NMRD) measurements indicate that the Gd(3)Ru complex exhibits an enhanced relaxivity value r(1) of 36.0 s(-1) mM(-1) per metallostar molecule at 20 MHz and 310 K. The ability of the complex to noncovalently bind to human serum albumin (HSA) was investigated, but no significant interaction was detected