Validation of the Factor Structure of the Health Professionals’ Attitudes Toward the Homeless Inventory (HPATHI)

Background - Considerable stigma exists toward persons experiencing homelessness (PEH)—a vulnerable population at greater risk for health disparities.1, 2 - Many healthcare students begin their programs without interacting with PEH and with preconceived notions influenced by societal stigma. - Interprofessional education programs, such as the Enhancing Services for People Experiencing Homelessness program below, have incorporated experiential learning into curricula to address student biases and develop understanding and compassion. Educating students to understand issues that PEH face can help mitigate healthcare disparities. - Evaluating the effectiveness of these interprofessional educational experiences requires valid assessment of the attitudes, interest, and confidence of students from various professions about working with PEH. - The Health Professional Attitudes Toward the Homeless Inventory (HPATHI) is frequently used for this purpose, including for ESHP, but has several limitations: Developed with a sample of medical students, overgeneralizing its validity for other health professions Standard-practice psychometric approaches were not used to support its validity. Final solution included several cross-loaded items.https://jdc.jefferson.edu/jcipeposters/1012/thumbnail.jp

Photoprocessing of formamide ice: route towards prebiotic chemistry in space

Aims. Formamide (HCONH2) is the simplest molecule containing the peptide bond first detected in the gas phase in Orion-KL and SgrB2. In recent years, it has been observed in high temperature regions such as hot corinos, where thermal desorption is responsible for the sublimation of frozen mantles into the gas phase. The interpretation of observations can benefit from information gathered in the laboratory, where it is possible to simulate the thermal desorption process and to study formamide under simulated space conditions such as UV irradiation. Methods. Here, two laboratory analyses are reported: we studied formamide photo-stability under UV irradiation when it is adsorbed by space relevant minerals at 63 K and in the vacuum regime. We also investigated temperature programmed desorption of pure formamide ice in the presence of TiO2 dust before and after UV irradiation. Results. Through these analyses, the effects of UV degradation and the interaction between formamide and different minerals are compared.We find that silicates, both hydrates and anhydrates, offer molecules a higher level of protection from UV degradation than mineral oxides. The desorption temperature found for pure formamide is 220 K. The desorption temperature increases to 250 K when the formamide desorbs from the surface of TiO2 grains. Conclusions. Through the experiments outlined here, it is possible to follow the desorption of formamide and its fragments, simulate the desorption process in star forming regions and hot corinos, and constrain parameters such as the thermal desorption temperature of formamide and its fragments and the binding energies involved. Our results offer support to observational data and improve our understanding of the role of the grain surface in enriching the chemistry in space.Comment: In press Astronomy and Astrophysics, 13 pages, 12 figure

Influence of drag and turbulence modelling on CFD predictions of solid liquid suspensions in stirred vessels

Suspensions of solid particles into liquids within industrial stirred tanks are frequently carried out at an impeller speed lower than the minimum required for complete suspension conditions. This choice allows power savings which usually overcome the drawback of a smaller particle-liquid interfacial area. Despite this attractive economical perspective, only limited attention has been paid so far to the modelling of the partial suspension regime. In the present work two different baffled tanks stirred by Rushton turbines were simulated by employing the Eulerian-Eulerian Multi Fluid Model (MFM) along with either the Sliding Grid algorithm (transient simulations) or the Multiple Reference Frame technique (steady state simulations). In particular, a comparison of alternative modelling approaches for inter-phase drag force and turbulence closure is presented. The results are evaluated against a number of experimental data concerning sediment features (amount and shape) and local axial profiles of solids concentration, with emphasis on the partial suspension regime. Results show that some of the approaches commonly adopted to account for dense particle effects or turbulent fluctuations of the volumetric fractions may actually lead to substantial discrepancies from the experimental data. Conversely simpler models which do not include such additional effects give the best overall predictions in the whole range of partial to complete suspension conditions

Dense Solid-Liquid Off-Bottom Suspension Dynamics: Simulation and Experiment

Dense solid-liquid off-bottom suspension inside a baffled mechanically agitated stirred tank equipped with a standard Rushton turbine is investigated. Dynamic evolution of the suspension from start up to steady state conditions has been inspected by both visual experiments and computational fluid dynamics. A classical Eulerian-Eulerian Multi Fluid Model along with the “homogeneous” k-epsilon turbulence model is adopted to simulate suspension dynamics. In these systems the drag inter-phase force affects both solids suspension and distribution. Therefore, different computational approaches are tested in order to compute this term. Simulation results are compared with images acquired on the real system and a good agreement is found

CFD prediction of solid particle distribution in baffled stirred vessels under partial to complete suspension conditions

Solid-liquid mixing within tanks agitated by stirrers can be easily encountered in many industrial processes. It is common to find an industrial tank operating at an impeller speed N lower than the minimum agitation speed for the suspension of solid particles: under such conditions the distribution of solid-particles is very far from being homogeneous and very significant concentration gradients exist. The present work evaluates the capability of a Computational Fluid Dynamics (CFD) model to reliably predict the particle distribution throughout the tank under either partial or complete suspension conditions. A flat bottomed baffled tank stirred by a Rushton turbine was investigated. Both transient and steady state RANS simulations of the stirred tank were performed with the commercial code CFX4.4. The Eulerian-Eulerian Multi Fluid Model along with the k-ε turbulence model was adopted. Either the Sliding Grid or the Multiple Reference Frame technique was employed to simulate the impeller to baffle relative rotation. Inter-phase momentum exchange terms were approximated only by the inter-phase drag forces. Literature experimental data were used for the model validation. Results show that the model along with the Sliding Grid technique can reliably predict the experimental particle distribution at all investigated impeller speeds. Radial gradients of solids concentration, usually neglected in the literature, where found to be significant in the presence of unsuspended solid particles (partial suspension conditions)

Power requirements for complete suspension and aeration in an unbaffled bioslurry reactor

Remediation of contaminated soils is spreading as a matter of crucial importance nowadays. Bioremediation via bioslurry reactors of sites polluted by recalcitrant pollutants has been proved to be a valuable option, although optimization is needed to reduce process costs. Free-surface unbaffled stirred tanks (with central air vortex) have been recently proposed as a promising alternative to the more common systems provided with baffles. In a bioslurry reactor solid-liquid interfacial area, oxygen supply, solid loading per reactor unit volume should be maximized, and, at the same time, operation costs have to be kept low. In this regard, the minimum impeller speeds for complete suspension Njs (suspension of all solid particles) and aeration Nca (air vortex ingested by the turbine and dispersed as bubbles in the system) represents a reasonable compromise between process yield and power requirements. To this purpose, a flat bottomed unbaffled tank with diameter T=0.19 m was investigated. The tank was filled with water up to a height H=T. It was stirred by a radial sixbladed Rushton turbines (RT) with diameter D=T/3 and H=T/3. Mono-dispersed particles with diameter dp=250-300μm and density p≈2500 kg/m3 were employed. Solid loadings B% ranging from 2.5% (weight of solid/weight of liquid) up to the very high 160% w/w were tested. The visual Zwietering criterion along with the aid of a digital camera was employed to evaluate Njs values. An acoustic criterion was adopted to assess Nca. A static frictionless granite turntable was employed to measure the impeller torque at Njs and Nca and to assess the relevant specific power requirements js and ca. Results show that the dependence of Njs and Nca on B% is much lower at low solids loading (B30%). The relevant specific powers per unit mass of solids (i.e. js and ca) were found to exhibit a minimum, at B≈20% for js and B≈60% for ca. On overall, data collected suggest that operating a radially stirred unbaffled bioslurry reactor loaded with a concentration B≈30% could be the best compromise to minimize the costs for achieving complete suspension and aeration conditions

Poly-Left-Lactic Acid tubular scaffolds via Diffusion Induced Phase Separation (DIPS): control of morphology

n this work, tubular poly-left-lactic acid scaffolds for vascular tissue engineering applications were produced by an innovative two-step method. The scaffolds were obtained by performing a dip-coating around a nylon fiber, followed by a diffusion induced phase separation process. Morphological analysis revealed that the internal lumen of the as-obtained scaffold is equal to the diameter of the fiber utilized; the internal surface is homogeneous with micropores 1–2 μm large. Moreover, a porous open structure was detected across the thickness of the walls of the scaffold. An accurate analysis of the preparation process revealed that it is possible to tune up the morphology of the scaffold (wall thickness, porosity, and average pore dimension), simply by varying some experimental parameters. Preliminary in vitro cell culture tests were carried out inside the scaffold. The results showed that cells are able to grow within the internal surface of the scaffolds and after 3 weeks they begin to form a “primordial” vessel-like structure. Modeling predictions of the dip-coating process display always an underestimate of experimental data (dependence of wall thickness upon extraction rate).In this work, tubular poly-left-lactic acid scaffolds for vascular tissue engineering applications were produced by an innovative two-step method. The scaffolds were obtained by performing a dip-coating around a nylon fiber, followed by a diffusion induced phase separation process. Morphological analysis revealed that the internal lumen of the as-obtained scaffold is equal to the diameter of the fiber utilized; the internal surface is homogeneous with micropores 1–2 lm large. Moreover, a porous open structure was detected across the thickness of the walls of the scaffold. An accurate analysis of the preparation process revealed that it is possible to tune up the morphology of the scaffold (wall thickness, porosity, and average pore dimension), simply by varying some experimental parameters. Preliminary in vitro cell culture tests were carried out inside the scaffold. The results showed that cells are able to grow within the internal surface of the scaffolds and after 3 weeks they begin to form a ‘‘primordial’’ vessel-like structure. Modeling predictions of the dipcoating process display always an underestimate of experimental data (dependence of wall thickness upon extraction rate)

CFD MODELLING OF PARTICLE SUSPENSION IN STIRRED TANKS

Mixing of solid particles into liquids in mechanically agitated vessels is a topic of primary importance for several industrial applications. A great deal of research efforts has been devoted so far to the assessment of the minimum impeller speed (Njs) able to guarantee that all particles are suspended. Conversely, only little attention has been paid to the evaluation of the amount of solid particles that are suspended at impeller speeds N lower than Njs, despite the fact that in a number of industrial applications agitation speeds smaller than Njs are actually adopted [1,2]. The present work deals with dense solid-liquid partial suspensions in baffled stirred tanks and particularly focuses on the prediction of the amount of suspended particles at a number of angular velocities by means of Computational Fluid Dynamics. An Eulerian-Eulerian Multi Fluid Model coupled with a standard k-epsilon turbulence model is adopted for CFD simulations. Both Sliding Grid and Multiple Reference Frame approaches are employed to simulate the impeller-tank relative rotation. The computational model is validated by comparison with purposely collected experimental data. 1.Oldshue, J. Y., (1983). Fluid Mixing Technology, Chapter 5, McGraw-Hill, New York, NY. 2.Rieger, F., Ditl, P., Havelkova, O., (1988). Suspension of solid particles–concentration profiles and particle layer on the vessel bottom. Proceedings of the 6th European Conference on Mixing, Pavia, Italy, 24-26 May, 251-258

Oxygen Transfer Performances of Unbaffled Bio-Reactors with Various Aspect Ratios

Cultivation of microorganisms, plants or animal cells requires liquid agitation in order to ensure oxygen and nutrient transfer and to maintain cell suspension. Many studies on animal cell damage due to mechanical agitation and sparging aeration have shown that mechanical damage of freely suspended animal cells is in most cases associated with bursting bubbles at the air–liquid interface (Barrett et al., 2010). Gas bubbles are usually generated by direct air sparging aimed at supplying oxygen to the culture medium. Mechanical agitation may also introduce gas bubbles in the culture medium via vortexing entrainment from the free surface. In this work oxygen transfer performance of an unbaffled stirred bioreactor, with various aspect ratios, is presented in view of its use as a biochemical reactor for animal cell growth. In practice oxygen mass transfer occurs through the (more or less deep) free surface vortex which takes place when agitation is started in unbaffled vessels. If this vortex is not allowed to reach impeller blades, bubble formation and subsequent bursting at the free-surface is avoided. Experimental results show that this kind of bioreactor can provide sufficient oxygen mass transfer for animal cell growth, so resulting in a viable alternative to the more common sparged reactors. The mass transfer performance observed with the different aspect ratio configurations is also presented and discussed