In-line phosphate pre-concentration in a flow injection method platform for monitoring fertilizers excess in soil leachates

info:eu-repo/semantics/publishedVersio

A review on sequential injection methods for water analysis

The development of fast, automatic and less expensive methods of analysis has always been the main aim of flowmethodologies. The search for newprocedures that still maintain the reliability and accuracy of the reference procedures is an ever growing challenge. Newrequirements are continually added to analytical methodologies, such as lower consumption of samples and reagents, miniaturisation and portability of the equipment, computer interfaces for full decision systems and so on. Therefore, the development of flow methodologies meeting the extra requirements of water analysis is a challenging work. Sequential injection analysis (SIA) presents a set of characteristics that make it highly suitable for water analysis. With sequential injection analysis, most routine determinations in waters can be performed more quickly with much lower reagent consumption when compared to reference procedures. Additionally, SIA can be a valuable tool for analyte speciation and multiparametric analysis. This paper critically reviews the overall work in this area.info:eu-repo/semantics/acceptedVersio

Reconstruction of velopharyngeal sphincter in secondary Cleft Palate: surgical alternative

Cir Pediatr. 2006 Apr;19(2):106-10. [Reconstruction of velopharyngeal sphincter in secondary Cleft Palate: surgical alternative] [Article in Spanish] Recamán M, Bonet B, Leitão J, Mesquita A. Hospital Central e Especializado de Crianças Maria Pia, Serviço de Cirurgía Plástica. [email protected] Abstract There are numerous surgical procedures for the repair of Cleft Palate (CP). Since 1998, in children with CP we use a modified Wardill-Kilner technique, with a large section of the nasal mucous layer at the level of the muscular insertion on the hard palate and lateral nasopharingeal wall, obtaining a push-back and reorientation of the muscular fibres without dissection, diminishing this way the risks of haemorrhages and fibrosis, simplifying the intervention. It allows a lower operative time and a short internment. The aim of our study was to evaluate the results of this operative procedure specially in the development of the speech in 73 children operated on from 1998 until 2000 in our hospital. We verify a competence of the velopharingeal sphincter with ideal results in speech in 88,8% of the cases. PMID: 16846134 [PubMed - indexed for MEDLIN

Towards absolute calibration of optical tweezers

Aiming at absolute force calibration of optical tweezers, following a critical review of proposed theoretical models, we present and test the results of MDSA (Mie-Debye-Spherical Aberration) theory, an extension of a previous (MD) model, taking account of spherical aberration at the glass/water interface. This first-principles theory is formulated entirely in terms of experimentally accessible parameters (none adjustable). Careful experimental tests of the MDSA theory, undertaken at two laboratories, with very different setups, are described. A detailed description is given of the procedures employed to measure laser beam waist, local beam power at the transparent microspheres trapped by the tweezers, microsphere radius and the trap transverse stiffness, as a function of radius and height in the (inverted microscope) sample chamber. We find generally very good agreement with MDSA theory predictions, for a wide size range, from the Rayleigh domain to large radii, including the values most often employed in practice, and at different chamber heights, both with objective overfilling and underfilling. The results asymptotically approach geometrical optics in the mean over size intervals, as they should, and this already happens for size parameters not much larger than unity. MDSA predictions for the trapping threshold, position of stiffness peak, stiffness variation with height, multiple equilibrium points and `hopping' effects among them are verified. Remaining discrepancies are ascribed to focus degradation, possibly arising from objective aberrations in the infrared, not yet included in MDSA theory.Comment: 15 pages, 20 figure

Finite element analysis of steel beams with web apertures under fire condiction

This work is intended to analyse the behaviour steel beams with apertures under high temperatures rise due to fire using finite elements simulations with ANSYS software. It includes a structural fire analysis and a comparative study of cellular and castellated steel beams which takes into account transient temperature effect, material and geometric non-linear behaviour. FE models which estimate limiting time, mid-span deflection and failure temperature are presented for hexagonal and circular types of web opening shapes under several uniform load levels. The study shows that for any beam with closely spaced openings failure in fire will in most cases be caused by failure of the steel web. The numbers of web-openings and cells as well as their shapes are critical for the behaviour of castellated sections and cellular beams under fire condition.info:eu-repo/semantics/publishedVersio

Finite element analysis of steel beams with web apertures under fire condiction

This work is intended to analyse the behaviour steel beams with apertures under high temperatures rise due to fire using finite elements simulations with ANSYS software. It includes a structural fire analysis and a comparative study of cellular and castellated steel beams which takes into account transient temperature effect, material and geometric non-linear behaviour. FE models which estimate limiting time, mid-span deflection and failure temperature are presented for hexagonal and circular types of web opening shapes under several uniform load levels. The study shows that for any beam with closely spaced openings failure in fire will in most cases be caused by failure of the steel web. The numbers of web-openings and cells as well as their shapes are critical for the behaviour of castellated sections and cellular beams under fire condition.info:eu-repo/semantics/publishedVersio

Numerical analysis of lateral torsional buckling of steel i-beams with and without web-openings under fire

Steel structures are being widely used in construction industry owing to their excellent structural flexibility and to their high ductility to withstand lateral forces. However, for the case of solid and cellular steel beams, high temperature effect may result in different fire response for each case due to a great reduction of yield stress and Young’s modulus. Moreover, when the beams are not restrained, lateral torsional bending phenomenon which are bound to take place is made worse in the case of fire. The aim of this study is to analyse the behaviour of steel beams with and without web openings when taking into account the effect of geometry and material imperfections. The results from the finite element models produced lateral and vertical displacements as well as the buckling moments.info:eu-repo/semantics/publishedVersio