Flood Forecasting and Decision Making in the new Millennium. Where are We?

This paper reviews the development of real time flood forecasting systems from the early 1970 approaches to the recent probabilistic ones. A preliminary discussion on the motivations for developing real time flood forecasting systems is introduced to explain their evolution in the last four to five decades. It will be shown how recent probabilistic flood forecasts are more robust and effective than the traditional deterministic ones. In particular, when combined with Bayesian decision approaches, probabilistic forecasts are the most appropriate tools for rational decision making in flood warning and flood management.Moreover, they allow taking into account the information from several models to be taken into account by combining into a unique predictive density the deterministic predictions of several hydrological or hydraulic models of a different nature, while in the multi-temporal forecasting extensions, they provide to answers questions such as: Which is the probability of overtopping a dyke in the next 24 h? When will this event be more likely to occur during the next 24 h?The work concludes with a discussion on the still unresolved problems, namely how decisions makers can fully take advantage of the probabilistic forecasts and how these forecasts must be communicated to them in order to meet this objective.     

Absolute rate constants for radical-monomer reactions

Summary A method is described for determining the absolute rate constants for the first few propagation steps in radical polymerization. The procedure involves a product analysis of the oligomeric alkoxyamines formed when an initiator is decomposed in monomer containing a very low concentration of a nitroxide radical scavenger. The method is illustrated with analysis of data for methyl acrylate. The rate constants for the first two propagation steps for polymerization of this monomer,k _p(1) andk _p(2), are at least an order of magnitude greater thank _p(average). Values of the absolute rate constants for reactions of phenyl and primary alkyl radicals with methyl acrylate are also estimated.     

2 1/2 D Visual Servoing with Respect to Unknown Objects Through a New Estimation Scheme of Camera Displacement

Classical visual servoing techniques need a strong a priori knowledge of the shape and the dimensions of the observed objects. In this paper, we present how the 2 1/2 D visual servoing scheme we have recently developed, can be used with unknown objects characterized by a set of points. Our scheme is based on the estimation of the camera displacement from two views, given by the current and desired images. Since vision-based robotics tasks generally necessitate to be performed at video rate, we focus only on linear algorithms. Classical linear methods are based on the computation of the essential matrix. In this paper, we propose a different method, based on the estimation of the homography matrix related to a virtual plane attached to the object. We show that our method provides a more stable estimation when the epipolar geometry degenerates. This is particularly important in visual servoing to obtain a stable control law, especially near the convergence of the system. Finally, experimental results confirm the improvement in the stability, robustness, and behaviour of our scheme with respect to classical methods.     

Physical,dynamic-mechanical and thermogravimetric analysis of aromatic and cycloaliphatic-based poly(urethaneurea)s

Experimental batches of linear rubber-like polyurethanes characterized by the presence of chemically different hard segments are studied and their thermal and dynamic-mechanical properties are related to the differences in chemical compositions. Interesting correlations are found between the development of crystallinity in such elastomeric poly(urethaneurea)s and the aromatic or alicyclic nature of the diisocyanate. Moreover, for a fixed ratio between hard and soft segments, and for a given composition of the soft segment, the results seem to indicate a better degree of phase separation in cycloaliphatic-based hard segment poly(urethaneurea)s than in aromatic-based hard segment poly(urethaneurea)s.     

Involvement of Clostridium gasigenes and C. algidicarnis in 'blown pack' spoilage of Brazilian vacuum-packed beef

The objectives of this study were to isolate psychrotrophic clostridia from Brazilian vacuum-packed beef cuts (spoiled or not) and to identify the isolates by using 16S rRNA gene sequencing. Anaerobic psychrotrophic microorganisms were also enumerated and samples were collected to verify the incidence of psychrotrophic clostridia in the abattoir environment. Vacuum-packed beef cuts (n = 8 grossly distended and n = 5 non-spoiled) and environmental samples were obtained from a beef packing plant located in the state of São Paulo, Brazil. Each sample was divided in three subsamples (exudate, beef surface and beef core) that were analyzed for vegetative forms, total spore-forming, and sulfide reducing spore-forming, both activated by alcohol and heat. Biochemical profiles of the isolates were obtained using API20A, with further identification using 16S rRNA gene sequencing. The growth temperature and the pH range were also assessed. Populations of psychrotrophic anaerobic vegetative microorganisms of up to 10¹⁰ CFU/(g, mL or 100 cm²) were found in ‘blown pack’ samples, while in non-spoiled samples populations of 10⁵ CFU/(g, CFU/mL or CFU/100cm²) was found. Overall, a higher population of total spores and sulfide reducing spores activated by heat in spoiled samples was found. Clostridium gasigenes (n = 10) and C. algidicarnis (n = 2) were identified using 16S rRNA gene sequencing. Among the ten C. gasigenes isolates, six were from spoiled samples (C1, C2 and C9), two were isolated from non-spoiled samples (C4 and C5) and two were isolated from the hide and the abattoir corridor/beef cut conveyor belt. C. algidicarnis was recovered from spoiled beef packs (C2). Although some samples (C3, C7, C10 and C14) presented signs of ‘blown pack’ spoilage, Clostridium was not recovered. C. algidicarnis (n = 1) and C. gasigenes (n = 9) isolates have shown a psychrotrophic behavior, grew in the range 6.2-8.2. This is the first report on the isolation of psychrotrophic Clostridium (C. gasigenes and C. algidicarnis) in Brazil. This study shows that psychrotrophic Clostridium may pose a risk for the stability of vacuum-packed beef produced in tropical countries during shelf-life and highlights the need of adopting control measures to reduce their incidence in abattoir and the occurrence of ‘blown pack’ spoilage.     

High Performance, Low-Dose Radiography Systems for Space and Remote Site Applications

Medical imaging applications using X- and gamma-rays have reached outstanding levels of complexity and performance, thanks to technology achievements in the fields of radiography, tomography and high resolution synchrotron devices. The operability of the related instrumentation resides in the availability of highly qualified specialists, as well as of medical doctors for diagnoses and treatment. This is a problem for personnel working in difficult ambient conditions as can be found in remote sites like Arctica, Antarctica and under-populated, desolated or mountainous regions on Earth. Astronauts, during long permanence at the Space Station or on future mission to Mars are potentially subject to risks such as traumas, fractures or diseases which would require semi-automated, easy-to-handle application of X-ray radiographic devices. For this purpose, the possible use of imaging instrumentation based on solid state detectors is discussed with special regard to CdZnTe pixel devices, now available with sub-mm resolution. The use of these semiconductor detectors will also allow to perform image diagnostics at much lower doses compared to the current plate-based radiographic techniques.