Ciliary propulsion of objects in tubes: wall drag on swimming Tetrahymena (Ciliata) in the presence of mucin and other long-chain polymers

The lubrication effect of three long-chain polymers - mucin, methylcellulose and Ficoll - on ciliary propulsion in tubes is measured by plotting the relative velocities of swimming cilitates as a function of the tube bore diameter. Mucin shows the most unequivocal lubrication, which is found at concentrations between 0% and 9.1% (w/v). This observation, coupled with viscometric measurements which show that ciliary tip shear rates are sufficient to solate mucin, serve as the groundwork for a model of mucin lubrication which explains the optimized lubrication behaviour of thixotropic gelating polymers as an expression of the response to shear by the various stages of polymer clustering during the gelatin process. In addition to the lubricative effect, another wall drag reduction effect by mucin was measured in the clearance region beyond the lubrication layer. This apparent viscosity reduction is optimized in the concentration range between 1.7% and 4.1% mucin and may also be explained in terms of the properties of gel clustering

Wall Drag on Free-Moving Ciliated Micro-Organisms

It is generally assumed that wall drag on free-moving, self-propelled or passively moving micro-organisms is not significant under normal observation conditions. Yet the point at which such drag becomes significant has not been determined quantitatively. By comparing the relative velocities of sinking as well as swimming ciliates in tubes of various bore widths it has been determined that wall drag on sinking cells is about 8% significant at 108-132 body radii (or minor semi-axes) from the cell surface while the corresponding range for swimming cells is less than 1-4·2 body radii. These results are compared with the mathematical approximations for Stokes radius R_8 and depth of penetration of diffusing vorticity δ which characterize steady and quasi-steady Stokes flow respectively around a solid body. It is found that the asymptotic nature of the velocity profile of steady flow is reflected in the lack of agreement between R_8 and the measured distance for 8% drag. Conversely, the sharp gradient (or propulsive envelope) of the quasi-steady velocity profile is reflected in the substantial agreement between δ and the measured distance for > 0% drag. It is suggested that the given formula for δ which includes allowance for a propagated wave is a valid measure of the thickness of the quasi-steady region and that observations on motile ciliates be restricted to organisms at least 4 cell radii from the nearest wall if measurements free of wall-drag effects are to be obtained

Spirillum swimming: theory and observations of propulsion by the flagellar bundle

The hydrodynamics and energetics of helical swimming by the bacterium Spirillum sp. is analysed using observations from medium speed cine photomicrography and theory. The photographic records show that the swimming organism's flagellar bundles beat in a helical fashion just as other bacterial flagella do. The data are analysed according to the rotational resistive theory of Chwang & Wu (1971) in a simple-to-use parametric form with the viscous coefficients C_s and C_n calculated according to the method of Lighthill (1975). Results of the analysis show that Spirillum dissipated biochemical energy in performing work against fluid resistance to motion at an average rate of about 6 X 10^(−8) dyne cm s^(-1) with some 62–72% of the power dissipation due to the non-contractile body. These relationships yield a relatively low hydromechanical efficiency which is reflected in swimming speeds much smaller than a representative eukaryote. In addition the C_n/C_s ratio for the body is shown to lie in the range 0–86-1-51 and that for the flagellar bundle in the range 1–46-1-63. The implications of the power calculations for the Berg & Anderson (1973) rotating shaft model are discussed and it is shown that a rotational resistive theory analysis predicts a 5-cross bridge M ring for each flagellum of Spirillum

Interpolating American Method Acting in 1950s Indonesia

Interpolating American Method Acting in 1950s Indonesi

Intravital Microscopic Evidence that Polylactide-Polyglycolide (PLGA) Delays Neo-Osteogenesis and Neo-Angiogenesis in Healing Bone

The bone chamber implant (BCI) has allowed monitoring a healing bone defect as well as the effect of an eroding implant on the healing process. The BCI is a useful tool and intravital microscopy a valuable technique for obtaining quantitative data chronicling osseous wound healing. The physiological parameters that form the initial data base documenting healing are neo-osteogenesis and neo-angiogenesis. This review compares and characterizes osseous wound healing in a BCI loaded with an erodible copolymer, PLGA (polylactide-polyglycolide). To determine if a statistically significant deviation from normal healing had occurred, the results were compared with present and historical controls. In the BCI PLGA erosion was accompanied by a delay in the onset of neo-osteogenesis, as measured by trabecular apposition. Concurrently, neo-angiogenesis was both detained and retarded. The neo-angiogenesis delay was interpreted as a direct consequence of the neo-osteogenesis delay since the major part of the vasculature was carried by the apposing trabeculae. Angiogenesis inhibition is more difficult to interpret until data are further analyzed to determine if apposing trabeculae in the presence of eroding PLGA carry less vasculature

Three Ways In: Approaches to Teaching Visual Rhetoric Through Infographics Programs

In this Kairos PraxisWiki webtext, we use Hill\u27s three-part framework to address concerns like those espoused by Handa about rhetorical illiteracy in relationship to visual rhetoric and design, and we share three assignments of varying scope and sequence that respond to these challenges. Besides learning opportunities to explore and practice visual rhetoric, design, and writing, each assignment offers opportunities for students to explore Piktochart, a web-based drag-and-drop infographic program, which can be used to create infographics, posters, and presentations. Because of its drag-and-drop capabilities, our students generally find it easy to learn. With minimal guidance, students may learn program basics and, by learning through exploration and practice, may develop competence with the program. Each assignment example below increases in scope and stake—from short and ungraded to complex and a significant portion of the grade. With these increases, chances for in-depth teaching of the programs arise, if needed, based on students’ capabilities

Bedeutung von Peergroups in der Prävention illegaler Substanzen : die Relevanz der jugendlichen Peergroup in der Prävention von problematischem Konsum

Die vorliegende Literaturarbeit fragt nach der Relevanz der Peergroup von Jugendlichen in der Prävention von problematischem Konsum illegaler Substanzen. Dazu wird die Lebensphase der Adoleszenz und darin enthaltene Entwicklungsaufgaben sowie die Rolle der Peergroup und aktuelle Studien zu psychoaktiven Substanzkonsum näher beleuchtet. Dabei zeigt sich, dass der Aufbau der Identität ein grundlegendes Thema darstellt. Dies widerspiegelt sich auch in der mehrdimensionalen Betrachtung der Entstehung eines problematischen Konsumverhaltens. Dafür werden bewältigungstheoretische Überlegungen sowie Ansätze aus der Theorie der Subkulturen und des Labeling Approachs miteinbezogen. Weiter werden die Methoden Peer Education, Positive Peer Culture und funktionale Äquivalente vorgestellt, um aufzuzeigen, wie die Peergroup und deren Funktionen in der Prävention eingesetzt werden können. Zum Schluss werden drei Praxisorganisationen der Stadt Zürich auf ihren Einsatz solcher Methoden analysiert. Es zeigt sich, dass besonders bei Präventionsmassnahmen mit Fokus auf illegale Substanzen kaum ein Einbezug der Peergroup bewusst stattfindet. Allerdings lassen sich bei einigen Angeboten Bezüge zu den vor-gestellten Methoden herstellen. Ein zukünftiger Ausbau solcher Projekte wäre auch für wissenschaftliche Wirksamkeitsstudien interessant, um ihre Effektivität zu analysieren und enthaltene Gruppenprozesse nachvollziehen zu können