The effects of asset specificity on maintenance financial performance: An empirical application of Transaction Cost Theory to the medical device maintenance field

This study uses multivariate regression analysis to examine the effects of asset specificity on the financial performance of both external and internal governance structures for medical device maintenance, and investigates how the financial performance of external governance structures differs depending on whether a hospital is private or public. The hypotheses were tested using information on 764 medical devices and 62 maintenance service providers, resulting in 1403 maintenance transactions. As such, our data sample is significantly larger than those used in previous studies in this area. The results empirically support our core theoretical argument that governance financial performance is influenced by assets specificity.     

Effective equations describing the flow of a viscous incompressible fluid through a long elastic tubeEquations efficaces décrivant l'écoulement d'un fluide visqueux incompressible dans un tuyau long et élastique

We study the flow of a viscous incompressible fluid through a long and narrow elastic tube whose walls are modeled by the Navier equations for a curved, linearly elastic membrane. The flow is governed by a given small time dependent pressure drop between the inlet and the outlet boundary, giving rise to creeping flow modeled by the Stokes equations. By employing asymptotic analysis in thin, elastic, domains we obtain the reduced equations which correspond to a Biot type viscoelastic equation for the effective pressure and the effective displacement. The approximation is rigorously justified by obtaining the error estimates for the velocity, pressure and displacement. Applications of the model problem include blood flow in small arteries. We recover the well-known Law of Laplace and provide a new, improved model when shear modulus of the vessel wall is not negligible. To cite this article: S. ?ani?, A. Mikeli?, C. R. Mecanique 330 (2002) 661–666.     

1H and 13C assignments of cyclo[N-(Lys-Phe)-Orn-Val], a semicyclic imide tetrapeptide from Burkholderia cepacia

The rhizobacteria Burkholderia cepacia biosynthesized the new tetrapeptide Cyclo[N-(Lys-Phe)-Orn-Val] (1), a 2,5-diketopiperazine, and the known siderophore azurechelin (salicylic acid). The structure of 1 was established by means of IR, UV, 1H and 13C NMR, double dimension experiments and MS.     

Glasslike structure of globular proteins and the boson peak

Vibrational spectra of proteins and topologically disordered solids display a common anomaly at low frequencies, known as boson peak. We show that such feature in globular proteins can be deciphered in terms of an energy landscape picture, as it is for glassy systems. Exploiting the tools of Euclidean random matrix theory, we clarify the physical origin of such anomaly in terms of a mechanical instability of the system. As a natural explanation, we argue that such instability is relevant for proteins in order for their molecular functions to be optimally rooted in their structures.     

Headspace solid-phase microextraction of oil matrices heated at high temperature and phthalate esters determination by gas chromatography multistage mass spectrometry

A solvent-free analytical approach based on headspace solid-phase microextraction (SPME) of oil matrices heated at high temperatures coupled to gas chromatography with mass spectrometry detector (GC-ion trap) has been developed for the determination of phthalic acid esters (PAEs) in oil matrices without sample manipulation. For this study, three fibers, i.e., 85 μm-polyacrylate (PA), 50/30 μm-divinylbenzene-carboxen-polydimethylsiloxane (DVB/CAR/PDMS) and 100 μm-polydimethylsiloxane (PDMS) were tested. Variables affecting the SPME headspace composition such as incubation sample temperature, sample incubation time and fiber exposition time were optimized. The optimal values found were 250 °C for sample incubation temperature and 30 min for incubation and extraction time. PA fiber was not suitable for the lightest polar phthalates which showed poor extraction and repeatability values. PDMS fiber had very poor response for some of the heavier and non-polar phthalates, whereas DVB/CAR/PDMS fiber showed the best response and repeatability values for the majority of the phthalates studied. The main benefit of the analytical method proposed is the absence of sample manipulation and hence avoidance of possible contamination coming from glassware, environment, solvents and samples.     

Design and application of a molecular mechanics force field for alkyl iodides including an electrostatic polarization model

We describe a force field extending Boyd and Kesner's molecule mechanics treatment of alkyl chlorides, fluorides and bromides to alkyl iodides: accordingly, as well as parameters for the potential energy of bond stretching and bending and for interactions between nonbonded atoms, the field includes parameters taking into account permanent and induced C-I dipoles, whose values have been estimated by fitting the model to experimental dipole moment data. The results of applying this force field to 22 organic iodides comprising several substitution series are reported, and the structural and energy trends in the various series are discussed. These results agree satisfactorily with available experimental data and with those obtained by A. Y. Meyer using a different kind of force field.     

Automatic determination of cobalt at the submicrogram per millilitre level using a flowthrough spectrophotometric sensor

A flowthrough spectrophotometric sensor for the determination of cobalt at the nanogram per millilitre level using pyridoxal 4-phenylthiosemicarbazone as reagent and integrated preconcentration and detection in the flow cell is proposed. The method is highly selective for cobalt(II); it features detection and determination limits of 0.02 and 0.06 mug ml(-1) respectively, and a linear range of at least 0.04-18 mug ml(-1). The method is subject to very few interferences because the strongly acidic medium used prevents the formation of most complexes of the reagent with other metal ions. The method was applied to the determination of cobalt in pharmaceutical preparations.     

Synthesis of n-chloroquinolines and n-ethynylquinolines (n=2, 4, 8): homo and heterocoupling reactions

The n-(ethynyl)quinolines were satisfactorily prepared by heterocoupling reaction between the appropriate n-chloroquinoline and 2-methyl-3-butyn-2-ol, catalyzed by palladium, followed by treatment with a catalytic amount of powdered sodium hydroxide in toluene. The n-(ethynyl)quinolines were transformed in the corresponding conjugate 1,4-bis[n′-(quinolyl)]buta-1,3-diynes by oxidative dimerization, catalyzed by cuprous chloride, with excellent yields. Moreover, the heterocoupling between n′-haloquinoline and n′-(ethynyl)quinoline (n′, 2′ or 3′), catalyzed by palladium, gives 2′,2′-bis(quinoline) or 1,2-di(3′-quinolyl)ethyne, respectively. The same coupling reaction with zerovalent nickel complexes, gives a mixture of 1,2,4- and 1,3,5-tri(n′-quinolyl)benzene.