Turbulent Transport and Mixing of Unconfined and Sloped Fire-Induced Flows Using a Laser-Assisted Saltwater Modeling Technique

The present work investigates turbulent, buoyant fire-induced flows using an experimental scaling technique known as saltwater modeling — a methodology enabling quantitative analysis of fire plumes built upon the analogy with saltwater (plume) flowing into the ambient water (air). The investigation, conducted by means of velocimetry (PIV) and concentration (PLIF) laser-based techniques, concerns unconfined plume mixing and transport, characterization of ceiling jet flows under sloped ceilings and activation of suppression devices in these sloped configurations. Flow imaging provides detailed measurements of velocity and saltwater concentration within the entire spatial and temporal domain of a planar section of the plume. In analogy with low-pass filtering in large eddy simulation (LES), a virtual, pixel-binning grid of varying size is overlaid on images to compute statistical moments representative of the larger and smaller scales. By leveraging actual measurements, converged statistics (first, second, higher-order) enables selection of cutoff resolutions, useful for validation and development of computational fluid dynamics (CFD) simulations. The saltwater plume's subsequent impingement onto a sloped plate generates a ceiling jet flowing both streamwise (up- and downslope) and spanwise with respect to the impingement point. Such flow is investigated to first build correlations predicting velocity and temperature along a sloped ceiling and second to analyze slope-related suppression device (sprinkler) activation. For the first task, single-planar, streamwise measurements are employed; for the second, multiple orthogonal laser sheets crossing the plate are used to generate a virtual grid of measured points. Transport characteristics are implemented into an activation model, modified to predict a dimensionless response time spatial distribution. At increasing slopes, the delay in the activation between upslope (faster) and downslope (delayed) devices progressively increases at increasing ceiling angles. This also occurs between sprinklers symmetrically located upslope and spanwise. From the response spatial distribution, the streamwise-to-spanwise correlation for the delay time (thermal responsiveness) is determined using the saltwater front arrival times. The analysis for the lag time reveals that the delay in thermal responsiveness between two sprinklers with the same activation time located up- and downslope, respectively, increases exponentially compared to that found for sprinklers located spanwise, at a quadratic rate with increasing angles

Particle Image Velocimetry Applications Using Fluorescent Dye-Doped Particles

Polystyrene latex sphere particles are widely used to seed flows for velocimetry techniques such as Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV). These particles may be doped with fluorescent dyes such that signals spectrally shifted from the incident laser wavelength may be detected via Laser Induced Fluorescence (LIF). An attractive application of the LIF signal is achieving velocimetry in the presence of strong interference from laser scatter, opening up new research possibilities very near solid surfaces or at liquid/gas interfaces. Additionally, LIF signals can be used to tag different fluid streams to study mixing. While fluorescence-based PIV has been performed by many researchers for particles dispersed in water flows, the current work is among the first in applying the technique to micron-scale particles dispersed in a gas. A key requirement for such an application is addressing potential health hazards from fluorescent dyes; successful doping of Kiton Red 620 (KR620) has enabled the use of this relatively safe dye for fluorescence PIV for the first time. In this paper, basic applications proving the concept of PIV using the LIF signal from KR620-doped particles are exhibited for a free jet and a twophase flow apparatus. Results indicate that while the fluorescence PIV techniques are roughly 2 orders of magnitude weaker than Mie scattering, they provide a viable method for obtaining data in flow regions previously inaccessible via standard PIV. These techniques have the potential to also complement Mie scattering signals, for example in multi-stream and/or multi-phase experiments

Characterization of Fluorescent Polystyrene Microspheres for Advanced Flow Diagnostics

Fluorescent dye-doped polystyrene latex microspheres (PSLs) are being developed for velocimetry and scalar measurements in variable property flows. Two organic dyes, Rhodamine B (RhB) and dichlorofluorescence (DCF), are examined to assess laser-induced fluorescence (LIF) properties for flow imaging applications and single-shot temperature measurements. A major interest in the current research is the application of safe dyes, thus DCF is of particular interest, while RhB is used as a benchmark. Success is demonstrated for single-point laser Doppler velocimetry (LDV) and also imaging fluorescence, excited via a continuous wave 2 W laser beam, for exposures down to 10 ms. In contrast, when exciting with a pulsed Nd:YAG laser at 200 mJ/pulse, no fluorescence was detected, even when integrating tens of pulses. We show that this is due to saturation of the LIF signal at relatively low excitation intensities, 4-5 orders of magnitude lower than the pulsed laser intensity. A two-band LIF technique is applied in a heated jet, indicating that the technique effectively removes interfering inputs such as particle diameter variation. Temperature measurement uncertainties are estimated based upon the variance measured for the two-band LIF intensity ratio and the achievable dye temperature sensitivity, indicating that particles developed to date may provide about +/-12.5 C precision, while future improvements in dye temperature sensitivity and signal quality may enable single-shot temperature measurements with sub-degree precision

Il trattamento delle discromie da tetracicline

Scopo del lavoro è stato quello di verificare la validità del perossido di carbammide, a diverse concentrazioni, e del perossido di idrogeno, nel trattamento dei vari gradi di discromie da tetracicline. La sperimentazione è stata condotta su 44 soggetti (18 maschi e 26 femmine), intenzionati a risolvere il loro problema estetico. I pazienti, dopo un'attenta anamnesi, sono stati divisi in 3 gruppi, secondo la gravità della discromia. i trattamenti sono stati eseguiti per circa 6 settimane, mediante l'applicazione di perossido sulla superficie degli elementi dentari, in modo sia professionale che domiciliare

A Food-Grade Method for Enhancing the Levels of Low Molecular Weight Proanthocyanidins with Potentially High Intestinal Bioavailability

: Proanthocyanidins (PACs) are a group of bioactive molecules found in a variety of plants and foods. Their bioavailability depends on their molecular size, with monomers and dimers being more bioavailable than those that have a higher polymerization degree. This study aimed to develop a method to convert high-molecular-weight PACs to low-molecular-weight ones in a grape seed extract (GSE) from Vitis vinifera L. Therefore, GSE was subjected to alkaline treatment (ATGSE), and its difference in chemical composition, compared to GSE, was evaluated using a molecular networking (MN) approach based on results obtained from HPLC-ESI HRMS/MS characterization analysis. The network analysis mainly noted the PAC cluster with about 142 PAC compounds identified. In particular, the obtained results showed a higher content of monomeric and dimeric PACs in ATGSE compared to GSE, with 58% and 49% monomers and 31% and 24% dimers, respectively. Conversely, trimeric (9%), polymeric (4%), and galloylated PACs (14%) were more abundant in GSE than in ATGSE (6%, 1%, and 4%, respectively). Moreover, in vitro antioxidant and anti-inflammatory activities were investigated, showing the high beneficial potential of both extracts. In conclusion, ATGSE could represent an innovative natural matrix rich in bioavailable and bioaccessible PACs for nutraceutical applications with potential beneficial properties

Indexes of temporal myocardial repolarization dispersion and risk of sudden cardiac death in chronic heart failure: any difference?

Background The QT variability index, calculated between Q- and the T-wave end (QTendVI), is an index of temporal myocardial repolarization lability associated with sudden cardiac death (SCD) in chronic heart failure (CHF). Little is known about temporal variability in the other two temporal myocardial repolarization descriptors obtained from Q-Tpeak and Tpeak-Tend intervals. We therefore investigated differences between these indexes in patients with CHF who died suddenly and in those who survived with a left ventricular ejection fraction (LVEF) ≤35% or >35%. Methods and Results We selected 127 ECG and systolic blood pressure (SPB) recordings from outpatients with CHF all of whom had been followed up for 30 months. We calculated RR and SPB variability by power spectral analysis and QTendVI, QTpeakVI, TpeakTendVI. We then subdivided data patients into three groups SCD, LVEF ≤ 35%, and LVEF > 35%. The LVEF was higher in the SCD than in the LVEF ≤ 35% group, whereas no difference was found between the SCD and LVEF > 35% groups. QTendVI, QTpeakVI, and TpeakTendVI were higher in the SCD and LVEF ≤ 35% groups than in the LVEF > 35% group. Multivariate analysis detected a negative relationship between all repolarization variability indexes, low frequency obtained from RR intervals and LVEF. Conclusions Our data show that variability in the first (QT peakVI) and second halves of the QT interval (Tpeak-T endVI) significantly contributes to the QTendVI in patients with CHF. Further studies should investigate whether these indexes might help stratify the risk of SCD in patients with a moderately depressed LVEF