A study of a plume induced separation shock wave, including effects of periodic plume unsteadiness

A wind tunnel investigation was conducted to study the flow field in which separation is caused by an expanding plume, with emphasis on effects associated with periodic unsteadiness in the plume. The separation shock was photographed with high speed motion pictures, from which mean shock position and excursion data were reported. Pressure fluctuations were measured beneath the separation shock. A response of the separation shock to plume periodic unsteadiness was identified, and the magnitude of a corresponding transfer function was defined. Small harmonic effects in plume response to periodic unsteadiness were noted. The stabilizing effect of a lateral surface protuberance near the separation shock wave was investigated. The protuberance configuration was a lateral circular cylinder, and various diameters, all less than the boundary layer thickness, were employed

Effects of periodic unsteadiness of a rocket engine plume on the plume-induced separation shock wave

A wind tunnel investigation was conducted to study the flow field in which separation is caused by an expanding plume, with emphasis on effects associated with periodic unsteadiness in the plume. The separation shock was photographed with high speed motion pictures, from which mean shock position and excursion data are reported. Pressure fluctuations were measured beneath the separation shock and statistics of the results are reported. A response of the separation shock to plume periodic unsteadiness was identified, and the magnitude of a corresponding transfer function was defined and is reported

Factors in Long-Term Algal Composition of Cayman Reefs: Determining Effects of Natural Disturbance and Grazer Pressures

Abstract. Current research shows a worldwide shift in the population dynamics of reefs attributed to increasing human disturbance. With increasing nutrient additions, competitive populations of turf and macroalgae bloom and dominate coral reefs leading to decreased health of the reef as a whole. Unfortunately, few studies have been done showing the long-term changes in algae composition on reefs. In order to find the significant factors in the long-term composition of algae on reefs, algae and fish abundance data were collected through the Lawrence University Marine Program and analyzed for this study. Algae were split into three functional groups: encrusting, turf and macroalgae, and relative abundance for each was compared for significance against fish and level of natural disturbance at a site. This study found that the level of natural disturbance was likely an important factor in long-term algal abundance with the highly protected sites hosting high levels of macroalgae and less protected sites hosting high levels of turf algae. Two herbivores, blue tangs (Acanthurus coeruleus) and stoplight parrotfish (Sparisoma viride) were also found to significantly control turf algae. Future studies on fishing pressures in the region could more fully assess the long-term effects of herbivores on reef algae composition

Assessing Learning Outcomes in Middle-Division Classical Mechanics: The Colorado Classical Mechanics/Math Methods Instrument

Reliable and validated assessments of introductory physics have been instrumental in driving curricular and pedagogical reforms that lead to improved student learning. As part of an effort to systematically improve our sophomore-level Classical Mechanics and Math Methods course (CM 1) at CU Boulder, we have developed a tool to assess student learning of CM 1 concepts in the upper-division. The Colorado Classical Mechanics/Math Methods Instrument (CCMI) builds on faculty consensus learning goals and systematic observations of student difficulties. The result is a 9-question open-ended post-test that probes student learning in the first half of a two-semester classical mechanics / math methods sequence. In this paper, we describe the design and development of this instrument, its validation, and measurements made in classes at CU Boulder and elsewhere.Comment: 11 pages, 6 figures, 1 tabl

Optimal psycholinguistic environments for distance foreign langauge learning

Rational choices among the numerous technological options available for foreign language teaching need to be based, in part, on psycholinguistic considerations. Which technological advances help create an optimal psycholinguistic environment for language learning, and which may be innovative but relatively unhelpful? One potential source of guidance is offered by the ten methodological principles of Task-Based Language Teaching (Long, 1985, and elsewhere), each realizable by a variety of pedagogic procedures. Interest in TBLT derives from several sources, including its responsiveness to learners’ precisely specified communicative needs, the potential it offers for developing functional language proficiency without sacrificing grammatical accuracy, and its attempt to harmonize the way languages are taught with what SLA research has revealed about how they are learned. TBLT’s ten methodological principles are briefly defined and motivated, and illustrations provided of how the principles can inform choices among technological options in the particular case of distance education for the less commonly taught languages

A Golgi and tonoplast localized S-acyl transferase is involved in cell expansion, cell division, vascular patterning and fertility in Arabidopsis

S‐acylation of eukaryotic proteins is the reversible attachment of palmitic or stearic acid to cysteine residues, catalysed by protein S‐acyl transferases that share an Asp‐His‐His‐Cys (DHHC) motif. Previous evidence suggests that in Arabidopsis S‐acylation is involved in the control of cell size, polarity and the growth of pollen tubes and root hairs. Using a combination of yeast genetics, biochemistry, cell biology and loss of function genetics the roles of a member of the protein S‐acyl transferase PAT family, AtPAT10 (At3g51390), have been explored. In keeping with its role as a PAT, AtPAT10 auto‐S‐acylates, and partially complements the yeast akr1 PAT mutant, and this requires Cys192 of the DHHC motif. In Arabidopsis AtPAT10 is localized in the Golgi stack, trans‐Golgi network/early endosome and tonoplast. Loss‐of‐function mutants have a pleiotropic phenotype involving cell expansion and division, vascular patterning, and fertility that is rescued by wild‐type AtPAT10 but not by catalytically inactive AtPAT10C192A. This supports the hypothesis that AtPAT10 is functionally independent of the other Arabidopsis PATs. Our findings demonstrate a growing importance of protein S‐acylation in plants, and reveal a Golgi and tonoplast located S‐acylation mechanism that affects a range of events during growth and development in Arabidopsis