Characterization of minimum impeller speed for suspension of solids in liquid at high solid concentration, using gamma-ray densitometry

The successful design and operation of Liquid-Solid (LS) and Gas-Liquid-Solid (GLS) stirred tank reactors requires an accurate determination of the level of solid suspension needed for the process at hand. A poor design of the stirred tank to achieve optimum conditions and maintain the system under these conditions during operation may cause significant drawbacks concerning product quality (selectivity and yield) and cost. In this paper, the limitations of applying conventional measurement techniques for the accurate characterization of critical impeller speed for just off-bottom suspension (NJS) at high solid concentrations are described. Subsequently, the Gamma-Ray Densitometry technique for characterizing NJS is introduced, which can overcome the limitations of previous experimental techniques. The theoretical concept of this method is explained, and experimental validation is presented to confirm the accuracy of the Gamma-Ray Densitometry technique. The effects of clearance, scale, and solid loading on NJS for several impellers are discussed. Experimental NJS values are compared with correlations proposed in the literatures, and modifications are made to improve the prediction. Finally, by utilizing the similarity to the incipient movement of solid particles in other systems, a theoretical model for NJS prediction is presented

Extensional viscosity of coating colors and its relation with jet coating performance

Résumé: Un rhéomètre à orifice a été utilisé pour mesurer la viscosité extensionnelle de plusieurs fluides non pigmentés et de sauces de couchage prépareés à base de carbonate de calcium dans le cadre d’une application de couchage par jet. Le rhéomètre à orifice a été tout d’abord étalonné en utilisant une courbe du nombre d’Euler en fonction du nombre de Reynolds avec des fluides newtoniens. Cette courbe d’étalonnage a par la suite été utilisée pour déterminer la viscosité extensionnelle apparente des sauces de couchage. Dans l’intervalle des vitesses de déformation étudié, tous les fluides ont montré une rhéofluidifiance en extension, le rapport de Trouton des sauces de couchage étant compris entre 5 et 20. Des essais de couchage par jet ont été aussi menés dans le but d’évaluer l’effet de la viscosité extensionnelle des sauces de couchage sur la performance du jet. Il s’est avéré que la viscosité extensionnelle est un paramètre clé déterminant la configuration du ménisque en aval de la région de contact sur le substrat. ---------- Abstract: An orifice flowmeter was used to measure the extensional viscosity of several non-pigmented fluids and paper coating colors containing calcium carbonate as pigment in the context of a jet coating application. The orifice flowmeter was first calibrated in terms of a dimensionless Euler number versus Reynolds number curve with Newtonian fluids. The calibration curve was then used to determine the apparent extensional viscosity of coating colors. In the strain rate range investigated, all the fluids were found to exhibit strain-thinning and the Trouton ratio of the coating colors was in the range 5 to 20. Jet coating tests were also carried out in order to evaluate the effect of the extensional viscosity on the jet performance. The extensional viscosity was shown to be a key parameter determining the configuration of the downstream meniscus in the web contact region

Circulating Secretory Phospholipase A2 Activity Predicts Recurrent Events in Patients With Severe Acute Coronary Syndromes

ObjectivesThe purpose of this study was to determine the prognostic value of circulating secretory phospholipase A2 (sPLA2) activity in patients with acute coronary syndromes (ACS).BackgroundThe plasma level of type IIA sPLA2 is a risk factor for coronary artery disease (CAD) and is associated with adverse outcomes in patients with stable CAD. The prognostic impact of sPLA2 in patients with ACS is unknown.MethodsSecretory phospholipase A2 antigen levels and activity were measured in plasma samples of 446 patients with ACS, obtained at the time of enrollment.ResultsBaseline sPLA2 activity was associated with the risk of death and myocardial infarction (MI). The unadjusted rate of death and MI increased in a stepwise fashion with increasing tertiles of sPLA2 activity (p < 0.0001). The association remained significant in the subgroup of patients who had MI with ST-segment elevation (p = 0.014) and the subgroup of patients who had unstable angina or non–ST-segment elevation MI (p < 0.002). After adjustment for clinical and biological variables, the hazard ratios for the combined end point of death or MI in the third tertile of sPLA2 compared with the first and second tertiles was 3.08 (95% confidence interval, 1.37 to 6.91, p = 0.006).ConclusionsA single measurement of plasma sPLA2 activity at the time of enrollment provides strong independent information to predict recurrent events in patients with ACS

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file

Non-local rheology in dense granular flows -- Revisiting the concept of fluidity

Granular materials belong to the class of amorphous athermal systems, like foams, emulsion or suspension they can resist shear like a solid, but flow like a liquid under a sufficiently large applied shear stress. They exhibit a dynamical phase transition between static and flowing states, as for phase transitions of thermodynamic systems, this rigidity transition exhibits a diverging length scales quantifying the degree of cooperatively. Several experiments have shown that the rheology of granular materials and emulsion is non-local, namely that the stress at a given location does not depend only on the shear rate at this location but also on the degree of mobility in the surrounding region. Several constitutive relations have recently been proposed and tested successfully against numerical and experimental results. Here we use discrete elements simulation of 2D shear flows to shed light on the dynamical mechanism underlying non-locality in dense granular flows

Insights into the innate immunity of the Mediterranean mussel Mytilus galloprovincialis

<p>Abstract</p> <p>Background</p> <p>Sessile bivalves of the genus <it>Mytilus </it>are suspension feeders relatively tolerant to a wide range of environmental changes, used as sentinels in ecotoxicological investigations and marketed worldwide as seafood. Mortality events caused by infective agents and parasites apparently occur less in mussels than in other bivalves but the molecular basis of such evidence is unknown. The arrangement of Mytibase, interactive catalogue of 7,112 transcripts of <it>M. galloprovincialis</it>, offered us the opportunity to look for gene sequences relevant to the host defences, in particular the innate immunity related genes.</p> <p>Results</p> <p>We have explored and described the Mytibase sequence clusters and singletons having a putative role in recognition, intracellular signalling, and neutralization of potential pathogens in <it>M. galloprovincialis</it>. Automatically assisted searches of protein signatures and manually cured sequence analysis confirmed the molecular diversity of recognition/effector molecules such as the antimicrobial peptides and many carbohydrate binding proteins. Molecular motifs identifying complement C1q, C-type lectins and fibrinogen-like transcripts emerged as the most abundant in the Mytibase collection whereas, conversely, sequence motifs denoting the regulatory cytokine MIF and cytokine-related transcripts represent singular and unexpected findings. Using a cross-search strategy, 1,820 putatively immune-related sequences were selected to design oligonucleotide probes and define a species-specific Immunochip (DNA microarray). The Immunochip performance was tested with hemolymph RNAs from mussels injected with <it>Vibrio splendidus </it>at 3 and 48 hours post-treatment. A total of 143 and 262 differentially expressed genes exemplify the early and late hemocyte response of the <it>Vibrio</it>-challenged mussels, respectively, with AMP trends confirmed by qPCR and clear modulation of interrelated signalling pathways.</p> <p>Conclusions</p> <p>The Mytibase collection is rich in gene transcripts modulated in response to antigenic stimuli and represents an interesting window for looking at the mussel immunome (transcriptomes mediating the mussel response to non-self or abnormal antigens). On this basis, we have defined a new microarray platform, a mussel Immunochip, as a flexible tool for the experimental validation of immune-candidate sequences, and tested its performance on <it>Vibrio</it>-activated mussel hemocytes. The microarray platform and related expression data can be regarded as a step forward in the study of the adaptive response of the <it>Mytilus </it>species to an evolving microbial world.</p