Polyelectrolyte Networks: Elasticity, Swelling, and the Violation of the Flory - Rehner Hypothesis

This paper discusses the elastic behavior of polyelectrolyte networks. The deformation behavior of single polyelectrolyte chains is discussed. It is shown that a strong coupling between interactions and chain elasticity exists. The theory of the complete crosslinked networks shows that the Flory - Rehner - Hypothesis (FRH) does not hold. The modulus contains contributions from the classical rubber elasticity and from the electrostatic interactions. The equilibrium degree of swelling is estimated by the assumption of a $c^{*}$-network.Comment: submitted to Computational and Theoretical Polymer Scienc

Elasticity in strongly interacting soft solids: polyelectrolyte network

This paper discusses the elastic behavior of a very long crosslinked polyelectrolyte chain (Debye-H\"uckel chain), which is weakly charged. Therefore the response of the crosslinked chain (network) on an external constant force $f$ acting on the ends of the chain is considered. A selfconsistent variational computation of an effective field theory is employed. It is shown, that the modulus of the polyelectrolyte network has two parts: the first term represents the usual entropy elasticity of connected flexible chains and the second term takes into account the electrostatic interaction of the monomers. It is proportional to the squared crosslink density and the Debye - screening parameter.Comment: submitted for publication to PR

The Influence Attitude Has on Student Achievement in a Developmental College Algebra Course.

Faced with unacceptable failure rates in introductory mathematics courses, institutions of higher learning are incorporating methods of placing students into their math courses based upon the students\u27 preexisting math knowledge or skills. West Virginia University is no exception and is currently incorporating a combination of ACT/SAT scores with an internal placement exam to properly place students in the appropriate math course. This method is not working in that failure rates continue to rise in spite of continual increases in placement requirements. Based upon anecdotal evidence by experienced faculty over a ten year period it became clear that factors other than prerequisite math knowledge were influencing the success of students. This study researched the influence which attitude has upon developmental algebra students at West Virginia University. A quantitative research tool in the form of a scannable attitude survey was devised and piloted the semester before the actual study was conducted. Access was granted to all aspects of the student\u27s course grades allowing all types of classroom behavior to be tracked and monitored. The attitude survey was administered twice during the semester to all enrolled students (approx. 200), attitudes were quantified, recorded and correlated with overall exam grades. Concurrently a special grouping procedure was utilizes to study the correlations within specific subgroups within the main course population. To further triangulate the determination of attitude, a qualitative interview process was developed and also piloted the semester before this study. The qualitative interview protocol addressed documented factors of attitude. The interview process was performed concurrently with a sample population from within the same main group of students as was the attitude survey. All interviews were audio recorded and transcribed. Statistical reliability analysis and all correlations were run using established procedures within the field of survey statistics. Quantitative results were compared to qualitative interviews for specific students. This study found that there exists a strong correlation between observed attitude and course outcomes in this developmental course, for particular subsets of students within the main course population

University of Illinois Biological Station

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Photoacoustic Imaging for Noninvasive Periodontal Probing Depth Measurements.

The periodontal probe is the gold standard tool for periodontal examinations, including probing depth measurements, but is limited by systematic and random errors. Here, we used photoacoustic ultrasound for high-spatial resolution imaging of probing depths. Specific contrast from dental pockets was achieved with food-grade cuttlefish ink as a contrast medium. Here, 39 porcine teeth (12 teeth with artificially deeper pockets) were treated with the contrast agent, and the probing depths were measured with novel photoacoustic imaging and a Williams periodontal probe. There were statistically significant differences between the 2 measurement approaches for distal, lingual, and buccal sites but not mesial. Bland-Altman analysis revealed that all bias values were < ±0.25 mm, and the coefficients of variation for 5 replicates were <11%. The photoacoustic imaging approach also offered 0.01-mm precision and could cover the entire pocket, as opposed to the probe-based approach, which is limited to only a few sites. This report is the first to use photoacoustic imaging for probing depth measurements with potential implications to the dental field, including tools for automated dental examinations or noninvasive examinations

Over-wintering Characteristics of West-Central Wisconsin Blanding's Turtles, Emydoidea blandingii

Hibernation of adult-sized Blanding's Turtles was studied at two west-central Wisconsin sites between 1991 and 2008. Turtles arrived at hibernacula from mid September to early October, spending 126 to 216 days at these sites, and generally emerged in early April yearly. Sixty percent of females and 30 percent of males hibernated in natural over man-made structures as hibernation sites. Anoxic conditions near five hibernation sites ranged from 78 to 100 days. Shell temperatures of three turtles monitored over five winters remained at <1°C a mean of 2,274 hours each winter. Over the same period, four turtles' temperatures were between 0° and -1°C a mean of 302 hours. During the course of our study, hibernating west-central Wisconsin Blanding's Turtles demonstrated a remarkable degree of both cold and anoxia-tolerance similar to that observed among Painted Turtles (Chrysemys picta) and Snapping Turtles (Chelydra serpentina)

On the elasticity of a single polyelectrolyte chain

This paper discusses the elastic behavior of a single polyelectrolyte chain. A simple scaling analysis as in self avoiding walk chains are not possible, because three interplaying relevant length scales are involved, i.e., the Debye screening length and the Pincus blob size. Therefore a selfconsistent computation of an effective variational propagator is employed. It is shown that the elastic force f is proportional to the end to end distance R for small f. For larger forces we find a new regime, characterized by deformations larger than a computed electrostatic "blob size". These results are supported by simulations and intuitive physical arguments.Comment: to be published in J. de Phys. I