Reflective Collaboration Practices to Explore Personal Belief Systems in Teacher Preparation Courses

The purpose of this article is to examine the need for intentionally designed faith integration conversations to explore the personal belief systems and concerns of teacher candidates through the use of effective reflective collaboration strategies in their preparation courses. The influence of one’s prior experiences and personal belief system cannot be underestimated when working effectively in a pluralistic society. This necessitates that all teachers be cognizant of how their belief system shapes interactions with students and families, as well as how they plan for instruction. Student voice and reflective collaboration techniques are important instructional tools that can be integrated into teacher preparation courses at Christian universities to assist pre-service teachers in reaching this understanding. Practical strategies to address faith integration questions are discussed in this article to assist instructors with incorporating student voice and reflective collaboration practices in their university classrooms

The effect of polydispersity in a turbulent channel flow laden with finite-size particles

We study turbulent channel flows of monodisperse and polydisperse suspensions of finite-size spheres by means of Direct Numerical Simulations using an immersed boundary method to account for the dispersed phase. Suspensions with 3 different Gaussian distributions of particle radii are considered (i.e. 3 different standard deviations). The distributions are centered on the reference particle radius of the monodisperse suspension. In the most extreme case, the radius of the largest particles is 4 times that of the smaller particles. We consider two different solid volume fractions, 2% and 10%. We find that for all polydisperse cases, both fluid and particles statistics are not substantially altered with respect to those of the monodisperse case. Mean streamwise fluid and particle velocity profiles are almost perfectly overlapping. Slightly larger differences are found for particle velocity fluctuations. These increase close to the wall and decrease towards the centerline as the standard deviation of the distribution is increased. Hence, the behavior of the suspension is mostly governed by excluded volume effects regardless of particle size distribution (at least for the radii here studied). Due to turbulent mixing, particles are uniformly distributed across the channel. However, smaller particles can penetrate more into the viscous and buffer layer and velocity fluctuations are therein altered. Non trivial results are presented for particle-pair statistics.Comment: Under review in the European Journal of Mechanics/B - Fluid

Sedimentation of finite-size spheres in quiescent and turbulent environments

Sedimentation of a dispersed solid phase is widely encountered in applications and environmental flows, yet little is known about the behavior of finite-size particles in homogeneous isotropic turbulence. To fill this gap, we perform Direct Numerical Simulations of sedimentation in quiescent and turbulent environments using an Immersed Boundary Method to account for the dispersed rigid spherical particles. The solid volume fractions considered are 0.5-1%, while the solid to fluid density ratio 1.02. The particle radius is chosen to be approximately 6 Komlogorov lengthscales. The results show that the mean settling velocity is lower in an already turbulent flow than in a quiescent fluid. The reduction with respect to a single particle in quiescent fluid is about 12\% and 14\% for the two volume fractions investigated. The probability density function of the particle velocity is almost Gaussian in a turbulent flow, whereas it displays large positive tails in quiescent fluid. These tails are associated to the intermittent fast sedimentation of particle pairs in drafting-kissing-tumbling motions. The particle lateral dispersion is higher in a turbulent flow, whereas the vertical one is, surprisingly, of comparable magnitude as a consequence of the highly intermittent behavior observed in the quiescent fluid. Using the concept of mean relative velocity we estimate the mean drag coefficient from empirical formulas and show that non stationary effects, related to vortex shedding, explain the increased reduction in mean settling velocity in a turbulent environment.Comment: In press on Journal of Fluid Mechanic

Turbulent channel flow of dense suspensions of neutrally-buoyant spheres

Dense particle suspensions are widely encountered in many applications and in environmental flows. While many previous studies investigate their rheological properties in laminar flows, little is known on the behaviour of these suspensions in the turbulent/inertial regime. The present study aims to fill this gap by investigating the turbulent flow of a Newtonian fluid laden with solid neutrally-buoyant spheres at relatively high volume fractions in a plane channel. Direct Numerical Simulation are performed in the range of volume fractions Phi=0-0.2 with an Immersed Boundary Method used to account for the dispersed phase. The results show that the mean velocity profiles are significantly altered by the presence of a solid phase with a decrease of the von Karman constant in the log-law. The overall drag is found to increase with the volume fraction, more than one would expect just considering the increase of the system viscosity due to the presence of the particles. At the highest volume fraction here investigated, Phi=0.2, the velocity fluctuation intensities and the Reynolds shear stress are found to decrease. The analysis of the mean momentum balance shows that the particle-induced stresses govern the dynamics at high Phi and are the main responsible of the overall drag increase. In the dense limit, we therefore find a decrease of the turbulence activity and a growth of the particle induced stress, where the latter dominates for the Reynolds numbers considered here.Comment: Journal of Fluid Mechanics, 201

Transition and self-sustained turbulence in dilute suspensions of finite-size particles

We study the transition to turbulence of channel flow of finite-size particle suspensions at low volume fraction, i.e. $\Phi \approx 0.001$. The critical Reynolds number above which turbulence is sustained reduces to $Re \approx 1675$, in the presence of few particles, independently of the initial condition, a value lower than that of the corresponding single-phase flow, i.e. $Re\approx1775$. In the dilute suspension, the initial arrangement of the particles is important to trigger the transition at a fixed Reynolds number and particle volume fraction. As in single phase flows, streamwise elongated disturbances are initially induced in the flow. If particles can induce oblique disturbances with high enough energy within a certain time, the streaks breakdown, flow experiences the transition to turbulence and the particle trajectories become chaotic. Otherwise, the streaks decay in time and the particles immigrate towards the channel core in a laminar flow.Comment: 12 pages, 3 figure

Continuous Growth of Droplet Size Variance due to Condensation in Turbulent Clouds

We use a stochastic model and direct numerical simulation to study the impact of turbulence on cloud droplet growth by condensation. We show that the variance of the droplet size distribution increases in time as t^{1/2}, with growth rate proportional to the large-to-small turbulent scale separation and to the turbulence integral scales but independent of the mean turbulent dissipation. Direct numerical simulations confirm this result and produce realistically broad droplet size spectra over time intervals of 20 minutes, comparable with the time of rain formation.Comment: 5 pages, 3 figures+Supplemental material 6 pages, 5 figure

Diagnostic and Interventional Radiology in a breast centre

Topic of the thesis is the analysis of three key aspects of diagnostic and interventional radiology in a Breast Center: 1 - monitoring of the radiation dose delivered by mammography; 2 – integrated diagnostic approach conducted together by radiologists and surgeons (joint CORD; 3 - interdisciplinary meetings. Radiation dose monitoring Mammography is still considered the most effective imaging technique for the early detection of breast cancer and for mortality reduction. The parameter for estimating the absorbed dose is the average glandular dose. The purpose of this section of the thesis is to present the data collected from three mammography units in the period from January 1 to May 31. A dose monitoring software (TQM) was used that was able to automatically detect relevant indices from X-ray equipments and to analyze the data in terms of variability of dosimetric behaviours. The “joint CORD” In the period from January 16 to April 11, a weekly session handled by a junior breast surgeon and a senior Radiology resident (joint CORD) was established. The aim of this session was to optimize the path within the Breast Centre of the patients with urgent referral and nonspecific symptoms. In fact, for these patients it is likely that the final diagnosis can be already reached with a clinical breast examination and a breast ultrasonography. Twelve sessions of joint CORD were performed, that included 95 patients (average: 7.9 patients for each session). Of the 95 patients who had access to this service, 33 had an examination performed elsewhere with detection of suspicious nodules or were controls at 6 months of multiple fibroadenomatosis; 20 came for palpable lumps; 16 for unilateral or bilateral breast pain; 5 for mastitis; 5 for swelling / hyperemia or collection after QUART; 4 for secretion (milky); and 12 for various reasons (axillary swelling, screening prior hormonal therapies, skin nodule, adenoma of the nipple). Of the 95 patients, besides ultrasound and clinical breast examination, 24 (25.2%) underwent mammography, 6 (6.3%) underwent MRI, and 2 (2, 1%) underwent stereotactic biopsy. Twentythree US-guided cytological examinations were performed (24.2%): in 21 cases of nodules and in 2 cases of mammary secretions. The results of cytology were: 15 C2 (benign findings) with the conclusion of the diagnostic iter; 2 C3 (probably benign findings); 4 C1 (inadequate sampling). The joint CORD allowed patients to finish their diagnostic workup in a single access, thus dramatically reducing the time they spent in the breast imaging center. Interdisciplinary meetings Were conducted interdisciplinary meetings (with breast radiologists and surgeons) on a weekly basis starting from January 17. This section of the thesis analyzes the period from January 17 to March 27. The cases discussed were tabulated to analyze the most frequent causes of problems, possible solutions and improvements for clinical practice. Eleven meetings were held, discussing a total of 48 cases (average: 4.36 cases discussed per meeting). Of the 48 cases discussed, 11 (22.9%) did not reach a cyto-histological conclusive diagnosis, 9 (18.7%) had an underlying lack of communication between radiologists and surgeons, 8 (16.6%) required a further biopsy, 6 (12.5%) had an improper use of MRI , 5 (10.4%) required additional MRI, 3 (6.25%) required a shared decision between radiologists and surgeons, 2 (4.1%) had a PET inappropriately performed, 2 (4.1%) were considered inappropriate for surgical evaluation, and 1 (2.07%) required a new mammography