Relaxation into equilibrium under pure Schr\"odinger dynamics

We consider bipartite quantum systems that are described completely by a state vector $|\Psi(t)>$ and the fully deterministic Schr\"odinger equation. Under weak constraints and without any artificially introduced decoherence or irreversibility, the smaller of the two subsystems shows thermodynamic behaviour like relaxation into an equilibrium, maximization of entropy and the emergence of the Boltzmann energy distribution. This generic behaviour results from entanglement.Comment: 5 pages, 9 figure

On the concept of pressure in quantum mechanics

Heat and work are fundamental concepts for thermodynamical systems. When these are scaled down to the quantum level they require appropriate embeddings. Here we show that the dependence of the particle spectrum on system size giving rise to a formal definition of pressure can, indeed, be correlated with an external mechanical degree of freedom, modelled as a spatial coordinate of a quantum oscillator. Under specific conditions this correlation is reminiscent of that occurring in the classical manometer.Comment: 7 pages, 3 figure

Project-based science instruction for general-education undergraduates and seventh graders: Practices, proficiency, and pitfalls

For three semesters we conducted a general-education course designed for both undergraduates and seventh-graders in which students investigated contaminant sources and water quality of a local stream. The middle school students attend a local, county school that draws its students from disadvantaged areas of the town of Richmond, Kentucky. Undergraduates were general-education honors students with little predilection toward science. The instructors guided undergraduates through the project, and our honors students then mentored the middle-schoolers in their scientific endeavors. Both sets of students serially investigated the chemical and biological properties of a typical upland stream (Tates Creek, Madison County, Kentucky) impacted by anthropogenic activities as dictated by land use. Students measured water properties such as temperature, conductivity, pH, and oxygen content then sampled stream waters to quantify dissolved nutrient concentration, fecal microbes (Escherichia coli), and stream macroinvertebrates. Nutrients (ammonium, NH4+; nitrate, NO3-; phosphate, PO43-) were measured by colorimetry and E. coli were counted using rapid-assay, IDEXX methods. Students also assessed water quality by classifying and counting macroinvertebrates, and using an established water quality index. Students then summarized their findings with group presentations. Middle-schoolers researched aspects of anthropogenic contamination and stream ecology to present their work as poster projects at an event on the campus of Eastern Kentucky University. Undergraduates gave group presentations in class following the format of an oral presentation at a scientific conference. Courses with embedded projects are challenging from logistical, fiscal, and pedagogical standpoints. Assessment of overall course effectiveness continues, but several aspects emerge. The course seemed most effective for middle-schoolers where teachers saw students actively engage in all aspects of the project, even those students who are generally disinterested in science. Results from undergraduates were mixed. Honors students enjoyed mentoring the seventh graders, but did not fully grasp the impact and nuances of project finding

Non-point sources and point sources for nutrient and fecal microbe contamination in a typical upland stream: Tates Creek, Madison County, Kentucky

Tates Creek (Madison County, Kentucky) is characterized by an oversupply of nutrients and fecal microbe contamination. Its watershed is dominated by pastureland and immature woodlands with scattered settlements served by septic systems, whereas, 5% of the watershed drains urban areas of Richmond, Kentucky. Creek waters are eutrophic and commonly display levels of Escherichia coli deemed unfit for human contact by United States Environmental Protection Agency standards. Both point and non-point sources existed for stream contaminants. A secondary sewage treatment plant (STP) discharged effluent into the creek until mid-2011 and was a point source for nitrate and phosphate. Pastureland likely contributes dissolved nutrients as well. High ammonium levels occurred sporadically, only sometimes related to plant discharge. After plant shutdown, nutrient levels downstream of the former STP decreased markedly for nitrate and phosphate, but phosphate then became the principal nutrient contaminant, suggesting that nitrogen may be the limiting nutrient within the stream ecosystem. Fecal microbes enter the stream from the sewer system serving the town of Richmond, from cattle farming, and from large developments served by septic systems. We cannot demonstrate any fecal contamination from single residence septic systems. KEY WORDS: stream, water quality, nutrient, ammonium, nitrate, phosphorus, E. col

Predictions from a stochastic polymer model for the MinDE dynamics in E.coli

The spatiotemporal oscillations of the Min proteins in the bacterium Escherichia coli play an important role in cell division. A number of different models have been proposed to explain the dynamics from the underlying biochemistry. Here, we extend a previously described discrete polymer model from a deterministic to a stochastic formulation. We express the stochastic evolution of the oscillatory system as a map from the probability distribution of maximum polymer length in one period of the oscillation to the probability distribution of maximum polymer length half a period later and solve for the fixed point of the map with a combined analytical and numerical technique. This solution gives a theoretical prediction of the distributions of both lengths of the polar MinD zones and periods of oscillations -- both of which are experimentally measurable. The model provides an interesting example of a stochastic hybrid system that is, in some limits, analytically tractable.Comment: 16 page

Localisation of the human hSuv3p helicase in the mitochondrial matrix and its preferential unwinding of dsDNA

We characterised the human hSuv3p protein belonging to the family of NTPases/helicases. In yeast mitochondria the hSUV3 orthologue is a component of the degradosome complex and participates in mtRNA turnover and processing, while in Caenorhabditis elegans the hSUV3 orthologue is necessary for viability of early embryos. Using immunofluorescence analysis, an in vitro mitochondrial uptake assay and sub‐fractionation of human mitochondria we show hSuv3p to be a soluble protein localised in the mitochondrial matrix. We expressed and purified recombinant hSuv3p protein from a bacterial expression system. The purified enzyme was capable of hydrolysing ATP with a Km of 41.9 µM and the activity was only modestly stimulated by polynucleotides. hSuv3p unwound partly hybridised dsRNA and dsDNA structures with a very strong preference for the latter. The presented analysis of the hSuv3p NTPase/helicase suggests that new functions of the protein have been acquired in the course of evolution

Project-based science for general education college students and seventh graders: Pitfalls and pointers

We teach a general-education science course for honors students, who in turn mentor disadvantaged seventh graders through a water quality investigation of a local stream. Activities for both groups involve all aspects of a scientific project: scientific background, local context, project design, data collection and analysis, and communication of scientific results. On successive weeks, we first lead our college students through each step in the process then the honors students mentor middle school students through those same steps. College and middle school teachers act as facilitators, and each honors student is responsible for about 6 to 8 middle schoolers. The college students and 7th graders often form strong bonds during their work together. The project explores nutrient (ammonium, NH4; nitrate, NO3, phosphate, PO4) and fecal microbe (Escherichia coli) contamination within the stream, as well as macroinvertebrate distribution and abundance, which is affected by overall water quality. Both student groups are responsible for documenting project activities in a project notebook. Once we establish background principles and context, both college and middle school students sample stream water and fauna. Selected students measure nutrient and E. coli concentrations in water samples, whereas all students pick and identify macroinvertebrates from 4 stations. Students then analyze all data to identify probable contamination sources and to assess water quality using established macroninvertebrate indices. Honors students give oral group presentations on their project findings in class. The project culminates when the 7th graders come to campus and present their work with oral and poster presentations. We invite parents, interested water-quality experts, and local dignitaries to the presentation event. Coordination of supporting college class content, supporting middle school class content, and project activities for both student groups - especially the middle school sampling trip to the stream - requires careful planning, shuffling of middle school schedules, and enthusiastic support by all instructors and administrative educators. Also, preparatory instruction and practice for college students in project activities is key, so they feel more comfortable in mentoring 7th graders