Search results for "crossover"
showing 10 items of 658 documents
An evolutionary approach to multi-objective scheduling of mixed model assembly lines
1999
In this paper a multi-objective genetic algorithm for the scheduling of a mixed model assembly line is proposed, pursuing the line stop time minimisation together with the component usage smoothing. Specific features of the developed GA are step by step random selection of diversified crossover and mutation operators, population control for the substitution of duplicate chromosomes, and in-process updating of GA control parameters. Three different formulation of the fitness function were been tested with some distinct line configurations.
Spin crossover of ferric complexes with catecholate derivatives. Single-crystal X-ray structure, magnetic and Mössbauer investigations.
2005
Complexes of general formula [(TPA)Fe(R-Cat)]X·nS were synthesised with different catecholate derivatives and anions (TPA = tris(2-pyridylmethyl)amine, R-Cat2− = 4,5-(NO2)2-Cat2− denoted DNC2−; 3,4,5,6-Cl4-Cat2− denoted TCC2−; 3-OMe-Cat2−; 4-Me-Cat2− and X = BPh4−; NO3−; PF6−; ClO4−; S = solvent molecule). Their magnetic behaviours in the solid state show a general feature along the series, viz., the occurrence of a thermally-induced spin crossover process. The transition curves are continuous with transition temperatures ranging from ca. 84 to 257 K. The crystal structures of [(TPA)Fe(DNC)]X (X = PF6−; BPh4−) and [(TPA)Fe(TCC)]X·nS (X = PF6−; NO3− and n = 1, S = H2O; ClO4− and n = 1, S = H…
Vibrational spectrum of the spin crossover complex [Fe(phen)(2)(NCS)(2)] studied by IR and Raman spectroscopy, nuclear inelastic scattering and DFT c…
2006
The vibrational modes of the low-spin and high-spin isomers of the spin crossover complex [Fe(phen)(2)(NCS)(2)] (phen = 1,10-phenanthroline) have been measured by IR and Raman spectroscopy and by nuclear inelastic scattering. The vibrational frequencies and normal modes and the IR and Raman intensities have been calculated by density functional methods. The vibrational entropy difference between the two isomers, DeltaS(vib), which is--together with the electronic entropy difference DeltaS(el)--the driving force for the spin-transition, has been determined from the measured and from the calculated frequencies. The calculated difference (DeltaS(vib) = 57-70 J mol(-1) K(-1), depending on the m…
Reversible Chemisorption of Sulfur Dioxide in a Spin Crossover Porous Coordination Polymer
2013
The chemisorption of sulfur dioxide (SO2) on the Hofmann-like spin crossover porous coordination polymer (SCO-PCP) {Fe(pz)[Pt(CN)4]} has been investigated at room temperature. Thermal analysis and adsorption-desorption isotherms showed that ca. 1 mol of SO2 per mol of {Fe(pz)[Pt(CN)4]} was retained in the pores. Nevertheless, the SO2 was loosely attached to the walls of the host network and completely released in 24 h at 298 K. Single crystals of {Fe(pz)[Pt(CN)4]}·nSO2 (n ≈ 0.25) were grown in water solutions saturated with SO2, and its crystal structure was analyzed at 120 K. The SO2 molecule is coordinated to the Pt(II) ion through the sulfur atom ion, Pt-S = 2.585(4) Å. This coordination…
Spin Crossover in a Supramolecular Fe4II [2×2] Grid Triggered by Temperature, Pressure, and Light
2000
A multiplex electronic switch on the molecular level has been realized by using a tetranuclear FeII complex of the [2×2] grid type. The four metal ions can be switched stepwise between their high-spin and low-spin states by temperature, pressure, and light, thus representing a triple level, triple switch system as illustrated in the picture.
Synthesis and immobilization of molecular switches onto titaniumdioxide nanowires
2009
Abstract The precursor [Fe III (L)Cl (L = N , N ′-bis(2′-hydroxy-3′-methyl-benzyliden)-1,7-diamino-4-azaheptane) is combined with [Mo(CN) 8 ] 4− yields a star shaped nona-nuclear cluster, [Mo IV {(CN)Fe III (L)} 8 ]Cl 4 . This Fe 8 Mo molecule is a high-spin system at room temperature. On cooling to 20 K some of the iron(III) centres in the molybdenum(IV)-star switch to the low-spin state as proven by Mossbauer spectroscopy. This molecule was deposited on TiO 2 nanowires by electrostatic interactions between the cluster cations and the surface functionalized titanium oxide nanowire. The synthesis and surface binding of the multistable molecular switch was demonstrated using IR and UV–Vis s…
Dinuclear Iron(II) Spin Crossover Compounds: Singular Molecular Materials for Electronics
2006
Dinuclear spin crossover molecules can adopt three different spin-pair states: a fully diamagnetic low spin state, [LS–LS], with both iron(II) atoms in the LS state; a paramagnetic mixed spin-pair state [LS–HS]; and an antiferromagnetically coupled [HS–HS] state. Stabilisation of the [LS–HS] state depends on a subtle balance between intra- and inter-molecular interactions in the solid state, consequently, the thermal dependence of the physical and structural properties can present one-step or two-step spin transitions. The former case involves the [LS–LS] ↔ [HS–HS] transformation while in the latter case the intermediate stage responsible for the plateau, at 50% conversion between the two s…
Spin crossover in a catenane supramolecular system.
1995
The compound [Fe(tvp)(2)(NCS)(2)] . CH(3)OH, where tvp is 1,2-di-(4-pyridyl)-ethylene, has been synthesized and characterized by x-ray single-crystal diffraction. It consists of two perpendicular, two-dimensional networks organized in parallel stacks of sheets made up of edge-shared [Fe(II)](4) rhombuses. The fully interlocked networks define large square channels in the [001] direction. Variable-temperature magnetic susceptibility measurements and Mossbauer studies reveal that this compound shows low-spin to high-spin crossover behavior in the temperature range from 100 to 250 kelvin. The combined structural and magnetic characterization of this kind of compound is fundamental for the inte…
Dynamics at the Temperature Crossover in Dilute Polymer Solutions Investigated by Neutron Spin-Echo Spectroscopy
1980
Applying ultrahigh-resolution neutron spin-echo spectroscopy the existence of a $q$-dependent temperature crossover in the dynamics of dilute polymer solutions was proved. It is associated with the transition from $\ensuremath{\theta}$ to good solvent conditions. At small momentum transfers $q$ a nearly stepwise increase of the reduced quasielastic linewidth versus the reduced temperature was observed. With increasing $q$, both the sharpness of the transition and the step height decrease.
l-Carnitine l-tartrate supplementation favorably affects biochemical markers of recovery from physical exertion in middle-aged men and women.
2009
The purpose of this study was to examine the effects of Carnipure tartrate (Lonza, Allendale, NJ) supplementation (total dose of 2 g/d of l-carnitine) on markers of performance and recovery from physical exertion in middle-aged men and women. Normally active and healthy men (n = 9, 45.4 +/- 5.3 years old) and women (n = 9, 51.9 +/- 5.0 years old) volunteered to participate in the investigation. Double-blind, placebo, balanced treatment presentation and crossover design were used with 3 weeks and 3 days of supplementation followed by a 1-week washout period before the other counterbalanced treatment was initiated. After 3 weeks of each supplementation protocol, each participant then performe…