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- Pfaller, M.A., et al.
(författare)
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Twelve years of fluconazole in clinical practice : Global-trends in species distribution and fluconazole susceptibility of bloodstream isolates of Candida
- 2004
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Ingår i: Clinical Microbiology and Infection. - : Elsevier BV. - 1198-743X .- 1469-0691. ; 10:SUPPL. 1, s. 11-23
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Tidskriftsartikel (refereegranskat)abstract
- We determined the species distribution and in-vitro susceptibility of 6082 bloodstream infection (BSI) isolates of Candida spp. collected from 250 medical centres in 32 nations over a 10-year period from 1992 through 2001. The species included 3401 C. albicans, 984 C. glabrata, 796 C. parapsilosis, 585 C. tropicalis, 153 C. krusei, 67 C. lusitaniae, 48 C. guilliermondii, 10 C. famata, 10 C. kefyr, six C. pelliculosa, five C. rugosa, four C. lipolytica, three C. dubliniensis, three C. inconspicua, two C. sake and one isolate each of C. lambica, C. norvegensis and C. zeylanoides. Minimum inhibitory concentration determinations were made using the National Committee for Clinical Laboratory Standards reference broth microdilution method. Variation in the rank order and frequency of the different species of Candida was observed over time and by geographic area. The proportion of BSI due to C. albicans and C. glabrata increased and C. parapsilosis decreased over time in Canada, the USA and Europe. C. glabrata was an infrequent cause of BSI in Latin America and the Asia-Pacific region. Very little variation in fluconazole susceptibility was observed among isolates of C. albicans, C. tropicalis and C. parapsilosis. These species accounted for 78% of all BSI and remained highly susceptible (91-100% susceptible) to fluconazole from 1992 to 2001 irrespective of geographic origin. The prevalence of fluconazole resistance among C. glabrata isolates was variable both over time and among the various countries and regions. Resistance to fluconazole among C. glabrata isolates was greatest in the USA and varied by US census region (range 0-23%). These observations are generally encouraging relative to the sustained usefulness of fluconazole as a systemically active antifungal agent for the treatment of candida BSI. © 2004 Copyright by the European Society of Clinical Microbiology and Infectious Diseases.
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- Casellas, D., et al.
(författare)
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On the transformation toughening of Y-ZrO2 ceramics with mixed Y-TZP/PSZ microstructures
- 2001
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Ingår i: Journal of the European Ceramic Society. - 0955-2219 .- 1873-619X. ; 21:6, s. 765-777
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Tidskriftsartikel (refereegranskat)abstract
- Heat treatment of Y-TZP at high temperatures produces materials with a mixed Y-TZP/PSZ phase assemblage, which exhibit a unique combination of high mechanical strength and fracture toughness, uncommon in zirconia ceramics. The microstructure and crack growth resistance of the Y-TZP/PSZ materials developed by treating at 1650°C in air a fine-grained Y-TZP was studied. XRD as well as Raman spectroscopy results indicate that the obtained microstructure allow the retention of large tetragonal grains (up to ˜4 μm), resulting in both phase transformability enhancement and pronounced R-curve behavior. The large transformation zone, discerned from accurate measurements with Raman microprobe spectroscopy, sustains the above assessment and points out tetragonal to monoclinic phase transformation as the main toughening mechanism in the investigated Y-TZP/PSZ microstructures. This was confirmed by satisfactory agreement between the transformation toughening estimated from numerical analysis and the crack shielding experimentally determined from the R-curve measurements.
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- Casellas, Nicolas M., et al.
(författare)
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Resistive switching in an organic supramolecular semiconducting ferroelectric
- 2019
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Ingår i: Chemical Communications. - : ROYAL SOC CHEMISTRY. - 1359-7345 .- 1364-548X. ; 55:60, s. 8828-8831
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Tidskriftsartikel (refereegranskat)abstract
- The combination of switchable dipolar side groups and the semiconducting core of the newly synthetized C-3-symmetric benzotrithiophene molecule (BTTTA) leads to an ordered columnar material showing continuous tunability from injection- to bulk-limited conductivity modulation.
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- Frómeta, D., et al.
(författare)
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Assessing edge cracking resistance in AHSS automotive parts by the Essential Work of Fracture methodology
- 2017
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Ingår i: Journal of Physics, Conference Series. - : Institute of Physics (IOP). - 1742-6588 .- 1742-6596. ; 896
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Tidskriftsartikel (refereegranskat)abstract
- Lightweight designs and demanding safety requirements in automotive industry areincreasingly promoting the use of Advanced High Strength Steel (AHSS) sheets. Such steelspresent higher strength (above 800 MPa) but lower ductility than conventional steels. Their greatproperties allow the reduction of the thickness of automobile structural components withoutcompromising the safety, but also introduce new challenges to parts manufacturers. Thefabrication of most cold formed components starts from shear cut blanks and, due to the lowerductility of AHSS, edge cracking problems can appear during forming operations, forcing thestop of the production and slowing down the industrial process.Forming Limit Diagrams (FLD) and FEM simulations are very useful tools to predict fractureproblems in zones with high localized strain, but they are not able to predict edge cracking. Ithas been observed that the fracture toughness, measured through the Essential Work of Fracture(EWF) methodology, is a good indicator of the stretch flangeability in AHSS and can help toforesee this type of fractures.In this work, a serial production automotive component has been studied. The componentshowed cracks in some flanged edges when using a dual phase steel. It is shown that theconventional approach to explain formability, based on tensile tests and FLD, fails in theprediction of edge cracking. A new approach, based on fracture mechanics, help to solve theproblem by selecting steel grades with higher fracture toughness, measured by means of EWF.Results confirmed that fracture toughness, in terms of EWF, can be readily used as a materialparameter to rationalize cracking related problems and select AHSS with improved edgecracking resistance.
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| 16. |
- Lara, A., et al.
(författare)
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Effect of Sandblasting on Low and High-Cycle Fatigue Behaviour after Mechanical Cutting of a Twinning-Induced Plasticity Steel
- 2018
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Ingår i: MATEC Web of Conferences. - : EDP Sciences.
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Konferensbidrag (refereegranskat)abstract
- In the last years, car bodies are increasingly made with new advanced high-strength steels, for both lightweighting and safety purposes. Among these new steels, high-manganese or TWIP steels exhibit a promising combination of strength and toughness, arising from the austenitic structure, strengthened by C, and from the twinning induced plasticity effect. Mechanical cutting such as punching or shearing is widely used for the manufacturing of car body components. This method is known to bring about a very clear plastic deformation and therefore causes a significant increase of mechanical stress and micro-hardness in the zone adjacent to the cut edge. To improve the cut edge quality, surface treatments, such as sandblasting, are often used. This surface treatment generates a compressive residual stress layer in the subsurface region. The monotonic tensile properties and deformation mechanisms of these steels have been extensively studied, as well as the effect of grain size and distribution and chemical composition on fatigue behaviour; however, there is not so much documentation about the fatigue performance of these steels cut using different strategies. Thus, the aim of this work is to analyse the fatigue behaviour of a TWIP steel after mechanical cutting with and without sandblasting in Low and High-Cycle Fatigue regimes. The fatigue behaviour has been determined at room temperature with tensile samples tested with a load ratio of 0.1 and load amplitude control to analyse High-Cycle Fatigue behaviour; and a load ratio of -1 and strain amplitude control to determine the Low-Cycle Fatigue behaviour. Samples were cut by shearing with a clearance value of 5%. Afterwards, a part of the cut specimens were manually blasted using glass microspheres of 40 to 95 microns of diameter as abrasive media. The results show a beneficial effect of the sandblasting process in fatigue behaviour in both regimes, load amplitude control (HCF) and strain amplitude control (LCF) tests, when these magnitudes are low, while no significant differences are observed with higher amplitudes. low-cycle fatigue, high-cycle fatigue, mechanical cutting, sandblasting, high manganese steel, TWIP steel.
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| 17. |
- Lara, A., et al.
(författare)
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Sheared edge formability characterization of cold-rolled advanced high strength steels for automotive applications
- 2022
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Ingår i: IOP Conference Series: Materials Science and Engineering. - : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- Edge cracking has become a limiting factor in the use of some advanced high strength steels (AHSS) for high-performance automotive applications. This fact has motivated the development of a multitude of experimental tests for edge formability prediction over the last years. In this sense, the Hole Expansion Test (HET) according to ISO16630 has been established in the automotive industry as a standard procedure for edge cracking sensitivity ranking. However, whereas it may be useful for rapid material screening, the results are often not accurate and reliable enough. Consequently, alternative methods based on Digital Image Correlation (DIC) have been proposed aimed at improving the prediction of edge cracking occurrence during forming and obtaining useful strain data that can be implemented in forming simulations. This paper explores the applicability of different DIC-based methods, such as Half-Specimen Dome Tests, Sheared Edge Tensile Tests, and KWI hole expansion tests with a flat nosed punch, for characterizing the edge formability of three cold-rolled AHSS sheets. The results obtained from the different testing methods are compared and validated with a laboratory-scale demonstrator. Finally, the limitations and advantages of the different methods are discussed.
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| 18. |
- Pujante, J., et al.
(författare)
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Investigations into wear and galling mechanism of aluminium alloy-tool steel tribopair at different temperatures
- 2013
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 308:1-2, s. 193-198
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Tidskriftsartikel (refereegranskat)abstract
- Aluminium alloys show poor formability at room temperature, and the production of complex components requires a series of high temperature forming processes, such as warm and hot forging, extrusion and hot sheet metal forming. Forming aluminium in these conditions subjects the tools to severe adhesive wear and galling, leading to increased energy needs, shorter tool life, lower part quality and increased cost. In this work, the wear mechanisms generated by aluminium alloys on forming tools have been studied by means of linear reciprocating sliding tests. Aluminium alloy AA2017 balls were slid against DIN 1.2344 (AISI H13) tool steel samples with various surface finishes at temperatures up to 450 °C. The main results show that the observed wear mechanisms are extremely dependent on the system temperature, ranging from pure abrasive wear to formation of layers of compacted aluminium debris and gross aluminium transfer in the form of lumps. On the other hand, tool surface finish has a limited effect on gross material transfer, but does affect the material transfer micromechanisms
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| 19. |
- Tornatore, M., et al.
(författare)
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Guest Editorial Latest Advances in Optical Networks for 5G Communications and beyond
- 2021
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Ingår i: IEEE Journal on Selected Areas in Communications. - 0733-8716 .- 1558-0008. ; 39:9, s. 2667-2671
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Forskningsöversikt (refereegranskat)abstract
- This Special Issue contains a collection of outstanding papers covering several recent advances in optical networks for 5G communications and beyond. Papers are organized into four categories: network resource planning; optical access networks; optical fronthaul solutions; and autonomous and data-driven network management. In this introduction, a brief overview of the field is given, followed by a summary of the seventeen papers of this Special Issue, and a discussion of future directions in the field.
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