61 research outputs found
The Signal in the Noise: Understanding and Mitigating Decorrelation in Particle Image Velocimetry
No full textParticle image velocimetry (PIV) has become one of the most important tools for experimentally investigating the physics of fluid flows. In PIV, image-processing algorithms estimate flow velocity by measuring the displacements of flow-tracer particles suspended in a fluid. The fundamental operation in PIV is the cross correlation (CC), which measures the displacement between two similar patterns. These measurements can fail under circumstances that arise due to the nature of the underlying flow field (e.g., vortices and boundary layers, where particle patterns not only translate but also rotate, stretch, and shear) or of the images (e.g., X-ray images, with comparatively low signal to noise ratios). Despite these shortcomings, fairly little attention has been paid to fundamentally improving measurements at the level of the CC. The objective of this dissertation is to demonstrate specific modifications to the correlation kernel of PIV that increase its accuracy and in certain cases extend its utility to classes of flows and image types that were previously unresolvable. First, we present a new PIV correlation algorithm called the Fourier-Mellin correlation (FMC) that reduces velocity errors by an order of magnitude in rotating flows (chapter 1). Second, we develop a model of PIV cross correlations that explains the fundamental sources of several major drivers of error in these measurements. We show how the shapes of the tracer particles and the distributions of their individual displacements affect the correlation signal to noise ratio (SNR), whose effects have previously been described only heuristically. We use this insight to create an algorithm that automatically creates a Fourier-based weighting filter, and demonstrate that our algorithm reduces bias and RMS errors in multiple types of PIV experiments (chapter 2). Finally, we apply principles from our insights to measure blood flows in the hearts of grasshoppers using X-ray PIV, and discovered flow kinematics that were unexpected according to the current prevailing understanding of the heart as a peristaltic pump that produces directional flows. Our results suggest that flow production in insect hearts may be more complex than once thought (chapter 3).Ph. D.Particle image velocimetry (PIV) is a tool for measuring the motion of fluid flows. In PIV, reflective particles are suspended in a flowing fluid, and cameras record their motion. Computer algorithms measure the motion of the particles in those images to estimate the velocity of the fluid. This dissertation is about the theory, algorithms, and experiments of particle image velocimetry. We explain from a theoretical standpoint the reasons that PIV can fail to provide reliable measurements for several types of flows that are commonly encountered in the research of fluid physics and engineering, such as swirling vortices or eddies, jets, turbulence, and microscopic flows. We apply this understanding to create new algorithms that improve PIV measurements in these kinds of challenging scenarios. Lastly, we use PIV and high-speed Xray imaging to measure flow patterns within the tubular hearts of living grasshoppers. From these experiments, we discovered flow behaviors that were strikingly different from what we expected according to the current prevailing presumption that the insect heart is a peristaltic pump. If the heart is proven to function other than by peristalsis, then this could imply that a previously overlooked flow mechanism could in fact be among the most prevalent among animals
A RAMAN/SANS/XRD STUDY ON THE STRUCTURE-PROPERTY RELATIONSHIP OF OUTDOOR AND INDOOR ROMAN WALL PAINTINGS
No full textDetermination of the chemical composition of different parts of the wall paintings (pigments, mortars and binders) allows extracting information about technology of preparation of the artefact. Herein we present a multimethodological characterization of wall paintings from a Roman Archeological sites from Cuma, focusing on differences between indoor (domus) and outdoor (Temple) fabrication. Both pigments, binders and mortars were studied via a combination of destructive/microdestructutive (mass spectrometry, ionic chromatography, ICP-based techniques) and non-destructive (Raman microscopy, X-ray diffraction and SANS) methodologies. Particularly, the systematic presence of dolomite only in temple mortars suggests an intentional use of such limestone for outdoor fabrication. Differences between temple and domus extends also to binder composition: proteinaceous binders in domus (possibly egg [3] and animal glue), whereas in TCP no protein was detected but some fat acids (probably from animal fat). Ultimately, the multimethodological study allowed an overall picture of the components and technology of the paintings from fabrications with different use, proposing distinct engineering choices for indoor and outdoor walls.
References
[1] Cartechini L., Pucci P., Sgamellotti A., Marino G., Birolo L., “Proteomic strategies for the identification of proteinaceous binders in paintings” Analytical & Bioanalytical Chemistry 395(7), 2009, 2269-2280.
[2] Gelzo M., Grimaldi M., Vergara A., Severino V., Chambery A., Dello Russo A., Piccioli C., Corso G,. Arcari P. "Comparison of binder composition in Pompeian wall painting styles from Insula Occidentalis" Chemistry Central J. 8(65), 2014, 1-10.
[3] Vinciguerra R, Galano E, Vallone F, Greco G, Vergara A, Bonaduce I, Marino G, Pucci P, Amoresano A, Birolo L, “Deglycosylation Step to Improve the Identification of Egg Proteins in Art Samples”
Analytical Chemistry 87 (20), 2015, 10178-10182.
Acknowledgements
This work was financially supported by Distretto ad Alta Tecnologia dei Beni Culturali (DATABENC scarl), progetto SNECS. “Soprintendenza Speciale per i Beni Archeologici di Napoli e Pompei” – Ufficio Archeologico di Cuma - Dr Paolo Caputo is also acknowledged
Comparative toxicity of seven rare earth elements in sea urchin early life stages
No full textThe widespread use of rare earth elements (REEs)
in a number of technological applications raises unanswered
questions related to REE-associated adverse effects. We have
previously reported on the multiple impact of some REEs on
the early life stages of the sea urchin Paracentrotus lividus.
The present investigation was to evaluate REE toxicity to
early life stages in two unrelated sea urchin species,
Sphaerechinus granularis and Arbacia lixula. The comparative
toxicities were tested of seven REEs, namely yttrium,
lanthanum, cerium, neodymium, samarium, europium and
gadolinium as chloride salts at concentrations ranging from
10−7 to 10−4 M. The evaluated endpoints included developmental
defects and cytogenetic anomalies in REE-exposed
embryos/larvae, and decreased fertilization success and offspring
damage following sperm exposure. The results showed
different toxicity patterns for individual REEs that varied according
to test species and to treatment protocol, thus showin
Fluid dynamics characterization of biomedical implantable devices: experimental measurements and numerical simulation
No full textMechanical heart valves, specifically bileaflet valves, are widely applied to take place of diseased native valves. These prosthetic valve replacements exhibit good long-term mechanical durability. However, mechanical loading of blood is associated to complications (hemolysis and thrombogenicity), which represent important safety requirements for this kind of valves.
In this thesis work, Particle Image Velocimetry (PIV) was applied as experimental tool for evaluating fluid dynamics characterization of biomedical implantable devices, especially for bileaflet mechanical heart valves (BMHVs). The procedures of PIV measurement of same target were repeatedly executed for multiple experimental validations of numerical data. The reproducibility of experimental data from PIV multiple measurements was proved reliable with the coefficients of variation for hemodynamic properties below 5%. These hemodynamic parameters such as velocity, turbulence shear stress (TSS) and hemolysis index (HI) did not only supply a good research basis for numerical simulation, but also directly analyze the potential risks for blood damages due to the artificial implantations. The maximum TSS captured in leakage jets of valve type 1 was around 40 Pa and that of valve type 2 was 20 Pa.
The simulations using computational fluid dynamics (CFD) were carried out based on the physical parameters of experimental conditions. Good agreements between PIV and CFD were observed according to the comparisons in near-hinge regions. Furthermore, CFD data were used to investigate the hemodynamic properties inside of hinge region, where PIV measurements cannot be carried out due to optical inaccessibility. The experimental work was carried out entirely at the Istituto Superiore di Sanita (ISS) in Rome, Italy, whereas the simulation work was based on the cooperation between ISS and the Technical University of Cluj-Napoca (TuCN) in Cluj-Napoca, Romania.
The final object of our cooperation is to take use of experimental and simulation methodologies to define a standard procedure for obtaining sufficient reliability in risk evaluation and mitigation of prosthetic heart valves
Double production in pion-nucleon scattering at COMPASS
No full textWe present the study of the production of double mesons using
COMPASS data collected with a 190 GeV/ beam scattering off NH,
Al and W targets. Kinematic distributions of the collected double
events are analysed, and the double production cross section is
estimated for each of the COMPASS targets. The results are compared to
predictions from single- and double-parton scattering models as well as the
pion intrinsic charm and the tetraquark exotic resonance hypotheses. It is
demonstrated that the single parton scattering production mechanism gives the
dominant contribution that is sufficient to describe the data. An upper limit
on the double intrinsic charm content of pion is evaluated. No significant
signatures that could be associated with exotic tetraquarks are found in the
double mass spectrum.Comment: 12 pages, 4 figure
Geospatial pattern of topsoil pollution and multi-endpoint toxicity in the petrochemical area of Augusta-Priolo (eastern Sicily, Italy)
No full textThe present study was aimed at identifying geospatial patterns of pollutants including concentrations and toxicity as complex environmental mixtures, in topsoil samples close to petrochemical facilities in the heavily industrialized area of Augusta and Priolo in south-eastern Sicily (Italy). Elemental analysis of soil was conducted by ICP-MS for 23 metals and 16 rare earth elements (REEs). Organic analyses were primarily focused on polycyclic aromatic hydrocarbons (PAHs) (16 parent homologs) and total aliphatic hydrocarbons (C10 - C40). Topsoil samples were tested for toxicity in multiple bioassay models including: 1) developmental defects and cytogenetic anomalies in sea urchin Sphaerechinus granularis early life stages; 2) growth inhibition of diatom Phaeodactylum tricornutum; 3) mortality in nematode Caenorhabditis elegans; and 4) induction of mitotic abnormalities in onion Allium cepa. Samples collected at sites closest to defined petrochemical facilities were highest in select pollutants and correlated with biological effects in different toxicity endpoints. A noteworthy finding was the increased level of total REEs in sites closest to petrochemical facilities, suggesting their contributions to identifying petrochemical sources of pollutants to the environment. The combined data obtained in the different bioassays allowed exploration of geospatial patterns of effect in biota as a function of contaminant levels. In conclusion, this study provides consistent data of soil toxicity, metal and REE contamination at Augusta-Priolo sampling sites, and may provide an appropriate baseline for epidemiological studies on high incidences of congenital birth defects in the area and identification of at-risk localities
Exotic meson with and its decay into
No full textWe study the spin-exotic JPC=1-+ amplitude in single-diffractive dissociation of 190 GeV/c pions into π-π-π+ using a hydrogen target and confirm the π1(1600)→ρ(770)π amplitude, which interferes with a nonresonant 1-+ amplitude. We demonstrate that conflicting conclusions from previous studies on these amplitudes can be attributed to different analysis models and different treatment of the dependence of the amplitudes on the squared four-momentum transfer and we thus reconcile these experimental findings. We study the nonresonant contributions to the π-π-π+ final state using pseudodata generated on the basis of a Deck model. Subjecting pseudodata and real data to the same partial-wave analysis, we find good agreement concerning the spectral shape and its dependence on the squared four-momentum transfer for the JPC=1-+ amplitude and also for amplitudes with other JPC quantum numbers. We investigate for the first time the amplitude of the π-π+ subsystem with JPC=1-- in the 3π amplitude with JPC=1-+ employing the novel freed-isobar analysis scheme. We reveal this π-π+ amplitude to be dominated by the ρ(770) for both the π1(1600) and the nonresonant contribution. These findings largely confirm the underlying assumptions for the isobar model used in all previous partial-wave analyses addressing the JPC=1-+ amplitude.We study the spin-exotic amplitude in single-diffractive dissociation of 190 GeV pions into using a hydrogen target and confirm the amplitude, which interferes with a nonresonant amplitude. We demonstrate that conflicting conclusions from previous studies on these amplitudes can be attributed to different analysis models and different treatment of the dependence of the amplitudes on the squared four-momentum transfer and we thus reconcile their experimental findings. We study the nonresonant contributions to the final state using pseudo-data generated on the basis of a Deck model. Subjecting pseudo-data and real data to the same partial-wave analysis, we find good agreement concerning the spectral shape and its dependence on the squared four-momentum transfer for the amplitude and also for amplitudes with other quantum numbers. We investigate for the first time the amplitude of the subsystem with in the amplitude with employing the novel freed-isobar analysis scheme. We reveal this amplitude to be dominated by the for both the and the nonresonant contribution. We determine the resonance parameters within the three-pion final state. These findings largely confirm the underlying assumptions for the isobar model used in all previous partial-wave analyses addressing the amplitude
Search for muoproduction of at COMPASS and indication of a new state
No full textWe have searched for exclusive production of exotic charmonia in the reaction μ+N→μ+(J/ψπ+π−)π±N′ using COMPASS data collected with incoming muons of 160 GeV/ c and 200 GeV/ c momentum. In the J/ψπ+π− mass distribution we observe a signal with a statistical significance of 4.1 σ . Its mass and width are consistent with those of the X(3872) . The shape of the π+π− mass distribution from the observed decay into J/ψπ+π− shows disagreement with previous observations for X(3872) . The observed signal may be interpreted as a possible evidence of a new charmonium state. It could be associated with a neutral partner of X(3872) with C=−1 predicted by a tetraquark model. The product of cross section and branching fraction of the decay of the observed state into J/ψπ+π− is determined to be 71±28(stat)±39(syst) pb.We have observed exclusive production of the exotic hadron in the reaction using COMPASS data collected with incoming muons of 160~GeV/ and 200~GeV/ momentum. The statistical significance of the signal is 6. The shape of the two-pion mass distribution shows disagreement with previous observations. The product of cross section and branching fraction of the decay into is determined to be 7128(stat)39(syst)~pb
Spectroscopy of Strange Mesons and First Observation of a Strange Crypto-Exotic State with
No full textInternational audienceWe measured the strange-meson spectrum in the scattering reaction with the COMPASS spectrometer at CERN. Using the world's largest sample of this reaction, we performed a comprehensive partial-wave analysis of the mesonic final state. It substantially extends the strange-meson spectrum covering twelve states with masses up to 2.4 GeV/. We observe the first candidate for a crypto-exotic strange meson with and find and states consistent with predictions for the ground states
Spectroscopy of Strange Mesons and First Observation of a Strange Crypto-Exotic State with
No full textWe measured the strange-meson spectrum in the scattering reaction with the COMPASS spectrometer at CERN. Using the world's largest sample of this reaction, we performed a comprehensive partial-wave analysis of the mesonic final state. It substantially extends the strange-meson spectrum covering twelve states with masses up to 2.4 GeV/. We observe the first candidate for a crypto-exotic strange meson with and find and states consistent with predictions for the ground states
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