The rates of the exchange reactions between [Gd(DTPA)]2- and the endogenous ions Cu2+ and Zn2+: a kinetic model for the prediction of the in vivo stability of [Gd(DTPA)]2-, used as a contrast agent in magnetic resonance imaging

The kinetic stability of the complex [Gd(DTPA)]2- (H5DTPA = diethylenetriamine-N,N,N',N",N"-pentaacetic acid), used as a contrast-enhancing agent in magnetic resonance imaging (MRI), is characterised by the rates of the exchange reactions that take place with the endogenous ions Cu2+ and Zn2+. The reactions predominantly occur through the direct attack of Cu2+ and Zn2+ on the complex (rate constants are 0.93+/-0.17 M(-1) s(-1) and (5.6+/-0.4) x 10(-2)M(-1) S(-1), respectively). The proton-assisted dissociation of [Gd(DTPA)]2- is relatively slow (k1 = 0.58+/-0.22 M(-1) s(-1)), and under physiological conditions the release of Gd3+ predominantly occurs through the reactions of the complex with the Cu2+ and Zn2+ ions. To interpret the rate data, the rate-controlling role of a dinuclear intermediate was assumed in which a glycinate fragment of DTPA is coordinated to Cu2+ or Zn2+. In the exchange reactions between [Gd-(DTPA)]2- and Eu3+, smaller amounts of Cu2+ and Zn2+ and their complexes with the amino acids glycine and cysteine have a catalytic effect. In a model of the fate of the complex in the body fluids, the excretion and the "dissociation" of [Gd(DTPA)]2- are regarded as parallel first-order processes, and by 10 h after the intravenous administration the ratio of the amounts of "dissociated" and excreted [Gd(DTPA)]2- is constant. From about this time, 1.71% of the injected dose of [Gd(DTPA)]2- is "dissociated". The results of equilibrium calculations indicate that the Gd3+ released from the complex is in the form of Gd3+-citrate.     

Local–Global Minimum Property in Unconstrained Minimization Problems

The main goal of this paper is to prove some new results and extend some earlier ones about functions, which possess the so-called local–global minimum property. In the last section, we show an application of these in the theory of calculus of variations.     

HPLC separation of diastereomers of Ln(III)-ethylenepropylene-triamine-pentaacetate complexes. Direct assessment of their water exchange rate

The diastereomers of two Ln(III)-EPTPA derivatives have been separated by reversed-phase HPLC, and the water exchange rate on their Gd(III) complexes has been directly determined by 17O NMR (H5EPTPA = ethylenepropylene-triamine-pentaacetic acid).     

Characterization of quasi-arithmetic means without regularity condition

Acta Mathematica Hungarica - We show that bisymmetry, which is an algebraic property, has a regularity improving feature. More precisely, we prove that every bisymmetric, partially strictly...     

The equality problem in the class of conjugate means

Let ${I\subset\mathbb{R}}$ be a nonempty open interval and let ${L:I^2\to I}$ be a fixed strict mean. A function ${M:I^2\to I}$ is said to be an L-conjugate mean on I if there exist ${p,q\in{]}0,1]}$ and a strictly monotone and continuous function φ such that $$M(x,y):=\varphi^{-1}(p\varphi(x)+q\varphi(y)+(1-p-q)\varphi(L(x,y)))=:L_\varphi^{(p,q)}(x,y),$$ for all ${x,y\in I}$ . Here L(x, y) is a fixed quasi-arithmetic mean. We will solve the equality problem in this class of means.     

Driving matrix liquid crystal displays

Liquid crystal displays had a humble beginning with wrist watches in the seventies. Continued research and development in this multi-disciplinary field have resulted in displays with increased size and complexity. After three decades of growth in performance, LCDs now offer a formidable challenge to the cathode ray tubes (CRT). A major contribution to the growth of LCD technology has come from the developments in addressing techniques used for driving matrix LCDs. There are several approaches like passive matrix addressing, active matrix addressing and plasma addressing to drive a matrix display. Passive matrix LCD has a simple construction and uses the intrinsic non-linear characteristic of the LCD for driving. Departure from conventional line by line addressing of a passive matrix has resulted in improved performance of the display. Orthogonal functions have played a crucial role in the development of passive matrix addressing. Simple orthogonal functions that are useful for driving a matrix LCD are introduced. The basics of driving several rows simultaneously (multi-line addressing) are discussed by drawing analogies from multiplexing in communication. The impact of multi-line addressing techniques on the performance of the passive matrix LCDs in comparison with the conventional technique will be discussed.     

Necessary and sufficient condition on global optimality without convexity and second order differentiability

The main goal of this paper is to give a necessary and sufficient condition of global optimality for unconstrained optimization problems, when the objective function is not necessarily convex. We use Gâteaux differentiability of the objective function and its bidual (the latter is known from convex analysis).     

EuII-cryptate with optimal water exchange and electronic relaxation: a synthon for potential pO2 responsive macromolecular MRI contrast agents

The cryptate [EuII(2.2.2)(H2O)2]2+ displays several interesting features with respect to pO2 responsive MRI contrast agent applications: it is relatively stable against oxidation, it has two inner sphere water molecules, and the water exchange and electron spin relaxation rates are in the optimal range to attain high proton relaxivities, provided the rotation is also optimized.