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| 2. |
- Challis, K, et al.
(författare)
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Gestational diabetes mellitus and fetal death in Mozambique: an incident case-referent study
- 2002
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Ingår i: Acta Obstetricia et Gynecologica Scandinavica. - : Wiley. - 1600-0412 .- 0001-6349. ; 81:6, s. 560-563
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Tidskriftsartikel (refereegranskat)abstract
- Background. Third trimester fetal death is a common problem in Mozambique, occurring in approximately 5% of parturient women. Objective. To elucidate the magnitude of the gestational diabetes mellitus problem, and to estimate its prevalence in a group of women with unexplained late fetal deaths and in women with live fetuses (referents). Methods. An incident case-referent study of 109 pregnant Mozambican women with fetal deaths and 110 women delivering liveborns, regarding fasting B-glucose, oral glucose tolerance test and glycosylated hemoglobin. Result. The difference in gestational diabetes mellitus prevalence in the two groups is not significant. The prevalence of gestational diabetes mellitus was high in both groups: 11% and 7%, respectively.
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| 3. |
- de Melo, J S, et al.
(författare)
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Time-resolved and steady-state fluorescence studies of hydrophobically modified water-soluble polymers
- 2003
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Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 107:46, s. 12605-12621
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Tidskriftsartikel (refereegranskat)abstract
- A comprehensive study of the photophysical behavior of poly(acrylic acids) randomly labeled with pyrene using steady-state and time-resolved fluorescence spectroscopy is presented. The influence of external factors, such as different solvents and pH in the aqueous solution, on the polymer photophysics has been investigated. These factors induce major changes in the polymer conformation, which are reflected in the fluorescence experiments. The random introduction of the hydrophobic pyrene groups along the macromolecule favors the coexistence of static (preformed dimers) and dynamic (excimers) monomer quenching phenomena together with a fraction of isolated monomers (not able to form excimer), as revealed by time-resolved and steady-state fluorescence data. In dioxane and methanol solvents, the global analysis of the fluorescence time profiles shows a rise time of similar to21-32 ns followed by a decay of similar to90-138 ns with an additional long r decay component with a low preexponential factor. This is consistent with the fact that in organic solvents such as methanol and dioxane, which are considered to be good solvents, the fraction of preassociated and isolated chromophores is highly reduced and excimer formation is essentially due to a dynamic mechanism. A kinetic scheme involving two types of monomers (M-A and M-B) and one excimer (E) is proposed. From the fluorescence decays it was possible to extract quantitatively the percentage of ground-state preformed dimers along with the percentage of isolated chromophores at room temperature. In addition, it is shown that the fraction of associated ground-state chromophores that can be excited is always larger than that of the isolated chromophores. The rate constants for excimer formation (k(a)), dissociation (k(d)), and deactivation (k(E)) were determined considering the absence and presence of preformed dimers. Additional photophysical and spectroscopic data consisting of wavelength shifts, peak- o-valley ratios and differences (obtained both from absorption and from excitation spectra collected at the monomer and excimer emission region), and the vibronic I-1/I-3 ratio in the pyrene monomer emission were found to be pH-dependent for the polymers in aqueous solution. Hence, by combining the results from steady-state fluorescence measurements with time-resolved fluorescence data, information is provided on how the chain conformation of the labeled PAA polymers changes depending on the solvent (water at different pH values or organic solvents). In water, the conformation changes from compact at low pH to an open polymer coil at high pH, whereas the polymers are in an extended state when in dioxane and methanol.
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| 4. |
- Santos, Olga, et al.
(författare)
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Modified stainless steel surfaces targeted to reduce fouling - surface characterization
- 2004
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774. ; 64:1, s. 63-79
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Tidskriftsartikel (refereegranskat)abstract
- The surface properties of several modified stainless steel samples were characterized according to their chemical composition, roughness, topography and wettability. The modifications tested were SiF3+ and MoS22+ ion implantation; diamond-like carbon (DLC) sputtering: DLC. DLC-Si-O and SiOx, plasma enhanced chemical vapor deposition (PECVD); autocatalytic Ni-P-PTFE and silica coating. X-ray photoelectron spectroscopy (XPS) and X-ray microanalysis were applied to determine the surface chemical composition. Atomic force microscopy (AFM) and stylus-type instruments were used for roughness determination, and the surface topography was imaged with AFM and scanning electron microscopy (SEM). The contact angle and surface tension were measured with the Wilhelmy plate method and the sessile drop method. For thick modified layers, only the elements of the coating were detected at the surface, whereas for thin layers the surface composition determined was that of the stainless steel substrate. The roughness of the 2R (cold rolled and annealed in a protective atmosphere) Surfaces was not altered by the modification techniques (except for the Ni-P-PTFE coating), while for the 2B (cold rolled. heat treated, pickled and skinpassed) surfaces an increase in roughness was observed. The silica coating produced surfaces with consistent roughness, independent of which steel substrate was used. DLC sputtering and Ni-P-PTFE coating produced surfaces with the highest roughness. All modified surfaces revealed a similar surface topography with the exception of the Ni-P-PTFE coating, for which the coating masked the underlying steel topography. In terms of wettability, the SiOx-plasmaCVD and NiP-PTFE coating, techniques produced the most hydrophilic and hydrophobic surfaces, respectively. (C) 2003 Elsevier Ltd. All rights reserved.
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