GENI Ants for the Traveling Salesman Problem

In this paper, the probabilistic nearest neighbor heuristic, which is at the core of classical ant colony systems for the Traveling Salesman Problem, is replaced by an alternative insertion procedure known as the GENI heuristic. The benefits provided by GENI-based ants are empirically demonstrated on a set of benchmark problems, through a comparison with the classical ant colony system and an iterated GENI heuristic.     

An Exchange Heuristic for Routeing Problems with Time Windows

In this paper, we compare different exchange heuristics for vehicle routeing problems with time windows. We also introduce a new 2-opt* exchange heuristic, and show that a hybrid approach, based on Or-opt and 2-opt* exchanges, is particularly powerful for problems with time windows. Computational results are reported for randomly generated problems and for a standard test set.     

Biomedical Engineering Education: Enrollment, Courses, Degrees, and Employment

During the 1979-1980 academic year a two-page questionnaire on biomedical engineering education was sent to 251 engineering schools. 71 schools indicated that they had degree programs and an additional 35 indicated that they had official minor or option programs, 107 did not have a program, and 38 did not respond. For schools offering degrees in biomedical engineering, there were 2859 students enrolled in 37 B.S. programs, 830 students in 48 M.S. programs, and 469 students in 41 Ph.D. programs. Options or minors in biomedical engineering with a degree in another engineering discipline were available at the B.S. level at 41 schools, at the M.S. level at 42 schools, and at the Ph.D. level at 34 schools. Over the past two years, schools offered 109 courses in biomedical instrumentation, 74 in computers in medicine, 162 in physiological systems/modeling, 60 in biomechanics, 47 in biomaterials, 33 in hospital internship, 23 in clinical engineering, 9 in biomedical engineering lab, and 67 in other areas. During the academic year 1978-1979, schools awarded 464 B.S. degrees, 249 M.S. degrees, and 107 Ph.D. degrees in biomedical engineering. Of these graduates, 253 found jobs in industry, 23 in government, 35 in academia, and 66 in hospitals or clinics; 100 went to medical school, 96 to biomedical engineering graduate schools, and 57 to other graduate or professional schools.     

Electrostatic bubbles and supramolecular assistance of photosensitization by carboxylated Ru(II) complexes

The paper examines the supramolecular effects at play during photosensitization by carboxylated Ru(II) sensitizers, both by experiment and by modeling. Experimentally, twelve Ru(II) complexes of pyrazolylpyridine and polypyridine ligands, including two benchmark complexes and two new species, were assessed as photosensitizers by measurement of the kinetics of methyl viologen cation radical (MV(*)(+)) generation through an oxidative, photoinduced electron transfer (PET) to methyl viologen (MV(2+)) under continuous irradiation in the presence of a sacrificial reductant. All complexes, luminescent or not, produced measurable amounts of MV(*)(+) in CH(3)CN. The assessment protocol was found to be useful with sensitizers of widely varying excited-state lifetimes (tau) as well as being easier and faster than conventional approaches. The seven sensitizers bearing peripheral COOH groups were found to be significantly more active than their non-carboxylated analogues, which is consistent with ionization of the COOH groups and electrostatic promotion of PET. Only the luminescent complexes were active in aqueous solvents, where tau appears to be the dominant effector. The benefits are exemplified by the singly carboxylated [Ru(H1)(bpy)(2)](2+) (H1 is 1-(4-carboxyphenyl)-3-(2-pyridyl)-4,5,6,7-tetrahydroindazole), a weakly luminescent sensitizer that was less active in aqueous solvents than [Ru(bpy)(3)](2+) (bpy is 2,2'-bipyridine), but which became the better sensitizer in CH(3)CN. Computationally, electrostatic field and dissociation energy calculations demonstrated that even a single peripheral COO(-) substituent suffices to provide supramolecular assistance: it defines a spheric "bubble" of electrostatically attractive space that is sufficiently large to allow the supramolecular preassociation of MV(2+), which provides an entropic advantage to PET that reduces the importance of tau in organic solvent. Calculations also show that the PET is electrostatically favored over its reverse (BET) even with cationic sensitizers because the "bubble" contracts after PET while the bulk medium becomes more repulsive, and favorable cation exchanges can occur to effect post-PET dissociation. Two peripheral COO(-) groups can define a two-point binding site for MV(2+) in an attractive sector of space that contracts to a kidney-shaped "bubble" after PET. This enables unimolecular PET while the reverse reaction remains bimolecular. The resultant benefits are illustrated with [Ru(Na1)(2)(bpy)](2+), a very weakly luminescent sensitizer that was totally inactive in H(2)O but appreciably active in CH(3)CN, despite the need to displace Na(+) in order to derive any electrostatic benefit. The Marcus free energies of activation for PET and BET corroborate the benefits of carboxylation, solvent, and other factors and correlated with the experimental rate constants.     

Measurement of the 11B(11B, 10Be)12C proton transfer reaction at low energies

Differential cross sections for the ¹¹B(¹¹B,¹⁰Be)¹²C proton transfer reaction leading to the ¹⁰Be(g.sO+¹²C(4.43 MeV) $\text{(Q = 0.289}\text{MeV}\text{)}\text{and}{}^{10}\text{(3.37}\text{MeV}\text{) +}{}^{12}\text{C}\text{(g.s.) (Q = 1.36}\text{Me V}\text{)}$ final channels have been measured at E_c.m. = 5.5 MeV by coincident detection of the ¹⁰Be and ¹²C nuclei. The integrated cross sections for the ¹⁰Be + ¹²C(4.43 MeV) channel have been obtained for incident energies between E_c.m. = 2.66 and 3.64 MeV from the yields of the 4.43 MeV γ-ray emitted in the ¹²C 4.43 MeV → g.s. transition. The cross-section magnitudes compare well with the DWBA calculations. The sub-barrier transfer cross sections exhibit an unusual energy dependence: their ratio to the total reaction cross section is decreasing with decreasing incident energy.     

Complexes olefiniques du ruthenium : IV. Etude des complexes [RuClH(diène)(amine)2], structure cristalline de [RuClH(cod)(pipéridine)2]

The polymer [RuCl₂(diene)]_n undergoes bridge cleavage reaction with amines giving, at temperatures dependant on the nature of the diene moiety, the monomer [RuClH(diene)(amine)₂]. The crystal structure of the compound [RuClH(cod)(pip)₂] has been determined from three dimensional X-ray data.The complex crystallizes in space group Pmcn of the orthorhombic system, a 16.808(4), b 11.520(2), c 9.744(2) Å D_m 1.44 D_c 1.46 g cm^?3; Z 4. The structure was solved by standard heavy atom methods and has been refined by least squares to a conventional R factor of 0.039 based on 3280 refections. The complex has a crystallographically C_s imposed symmetry. The coordination geometry around the ruthenium atom is octahedrally distorted with cis amine ligands, the chloro and the hydrido ligands being trans to each other and the cyclooctadiene moiety bound through the two double bonds. The CC distances of the olefinic bonds are longer (1.394(4) Å) than was to be expected according to the Dewar—Chatt—Duncanson model. Principal bond lengths are: RuH 1.57(4); RuCl 2.555(1) (demonstrating a high structural trans influence of the hydrido ligand); RuN, 2.240(2) Å. An order of increasing structural trans influence for RuCl distances is proposed. In the IR spectrum ν(RuH) was observed at 2040 cm^?1. Decomposition of the complexes in chlorinated solvents prevented NMR studies.     

Die Bestimmung von Chloriden in Nahrungsmitteln

Ohne Zusammenfassung