The State of the Art in Hadron Beam Cooling

Cooling of hadron beams (including heavy-ions) is a powerful technique by which accelerator facilities around the world achieve the necessary beam brightness for their physics research. In this paper, we will give an overview of the latest developments in hadron beam cooling, for which high energy electron cooling at Fermilab's Recycler ring and bunched beam stochastic cooling at Brookhaven National Laboratory's RHIC facility represent two recent major accomplishments. Novel ideas in the field will also be introduced.Comment: 7 pages, 7 figures, ICFA-HB2008 Invited presentatio

Nonequilibrium Fluctuations, Travelling Waves, and Instabilities in Active Membranes

The stability of a flexible fluid membrane containing a distribution of mobile, active proteins (e.g. proton pumps) is shown to depend on the structure and functional asymmetry of the proteins. A stable active membrane is in a nonequilibrium steady state with height fluctuations whose statistical properties are governed by the protein activity. Disturbances are predicted to travel as waves at sufficiently long wavelength, with speed set by the normal velocity of the pumps. The unstable case involves a spontaneous, pump-driven undulation of the membrane, with clumping of the proteins in regions of high activity.Comment: 4 two-column pages, two .eps figures included, revtex, uses eps

Polarity patterns of stress fibers

Stress fibers are contractile actomyosin bundles commonly observed in the cytoskeleton of metazoan cells. The spatial profile of the polarity of actin filaments inside contractile actomyosin bundles is either monotonic (graded) or periodic (alternating). In the framework of linear irreversible thermodynamics, we write the constitutive equations for a polar, active, elastic one-dimensional medium. An analysis of the resulting equations for the dynamics of polarity shows that the transition from graded to alternating polarity patterns is a nonequilibrium Lifshitz point. Active contractility is a necessary condition for the emergence of sarcomeric, alternating polarity patterns.Comment: 5 pages, 3 figure

Escape configuration lattice near the nematic-isotropic transition: Tilt analogue of blue phases

We predict the possible existence of a new phase of liquid crystals near the nematic-isotropic ($NI$) transition. This phase is an achiral, tilt-analogue of the blue phase and is composed of a lattice of {\em double-tilt}, escape-configuration cylinders. We discuss the structure and the stability of this phase and provide an estimate of the lattice parameter.Comment: 5 pages, 6 figures (major revision, typos corrected, references added

Assessing the Educational Environment of a Flipped Physical Therapy Course: Utilization of the Dundee Ready Education Environment Measure (DREEM)

Purpose: Using valid and reliable measures to assess curricula within health professions programs has gained significant attention in recent years. The educational environment is considered a key domain for student success. The primary aim of this study was to measure the educational environment following the addition of a flipped classroom model within a physical therapy course as measured by the Dundee Ready Education Environment Measure. Methods: A first year doctorate of physical therapy course, “Physical Agents”, was redesigned to include a flipped classroom model, incorporating 24 videos that students reviewed independently, prior to hands-on laboratory learning. Following the conclusion of the course, students (n=57) completed the Dundee Ready Education Environment Measure, a valid and reliable survey designed to measure the educational environment within health profession programs. The Dundee Ready Education Environment Measure contains 50 items, rated from 0 to 4 (5-point Likert scale, “0” strongly disagree to “4” strongly agree), assessing five domains: students’ perceptions of learning; perceptions of teachers; academic self-perception; perceptions of atmosphere; and social self-perception. Descriptive statistics included mean global score (out of 200, 151 to 200 being an excellent environment) mean domain scores, and mean item scores. Cumulative grade point average between students in the flipped classroom model (n=58) and those who previously received a traditional teaching model (n=59) for the course were also compared. Student’s t-test was utilized with significance accepted at p\u3c0.05. Results: The mean global score (168 ± 13.3), indicated that the flipped classroom model fostered an excellent educational environment. Additionally, all mean domain scores, including students’ perceptions of learning (41.3 ± 3.9), perceptions of teachers (39.2 ± 2.9), academic self-perception (25.1 ± 2.5) perception of atmosphere (40.1 ± 4.1) and social self-perception (22.1 ± 2.9) fell into the highest rank of each subscale. Individual item analysis demonstrated 26 items (52%) were identified as especially strong areas, five items (10%) were identified as areas that could be improved, and no individual items were identified as requiring particular concern or immediate attention. Further, no significant differences were seen in cumulative course grade point average between the flipped classroom model (3.74 ± 0.44) and the traditional teaching model (3.71 ± 0.46). Conclusions: The flipped classroom model, utilizing an online learning environment, fostered an excellent educational environment for the physical therapy Physical Agents class. No difference in course grade point average between the flipped classroom model and previous traditional teaching model was seen. Further investigations examining performance on didactic and psychomotor activities within the flipped classroom model are recommended

Mechanical Instabilities of Biological Tubes

We study theoretically the shapes of biological tubes affected by various pathologies. When epithelial cells grow at an uncontrolled rate, the negative tension produced by their division provokes a buckling instability. Several shapes are investigated : varicose, enlarged, sinusoidal or sausage-like, all of which are found in pathologies of tracheal, renal tubes or arteries. The final shape depends crucially on the mechanical parameters of the tissues : Young modulus, wall-to-lumen ratio, homeostatic pressure. We argue that since tissues must be in quasistatic mechanical equilibrium, abnormal shapes convey information as to what causes the pathology. We calculate a phase diagram of tubular instabilities which could be a helpful guide for investigating the underlying genetic regulation

Factors Responsible for the Stability and the Existence of a Clean Energy Gap of a Silicon Nanocluster

We present a critical theoretical study of electronic properties of silicon nanoclusters, in particular the roles played by symmetry, relaxation, and hydrogen passivation on the the stability, the gap states and the energy gap of the system using the order-N [O(N)] non-orthogonal tight-binding molecular dynamics and the local analysis of electronic structure.Comment: 26 pages including figure