PTF11kx: A Type Ia Supernova with Hydrogen Emission Persisting After 3.5 Years

The optical transient PTF11kx exhibited both the characteristic spectral features of Type Ia supernovae (SNe Ia) and the signature of ejecta interacting with circumstellar material (CSM) containing hydrogen, indicating the presence of a nondegenerate companion. We present an optical spectrum at $1342$ days after peak from Keck Observatory, in which the broad component of H$\alpha$ emission persists with a similar profile as in early-time observations. We also present $Spitzer$ IRAC detections obtained $1237$ and $1818$ days after peak, and an upper limit from $HST$ ultraviolet imaging at $2133$ days. We interpret our late-time observations in context with published results - and reinterpret the early-time observations - in order to constrain the CSM's physical parameters and compare to theoretical predictions for recurrent nova systems. We find that the CSM's radial extent may be several times the distance between the star and the CSM's inner edge, and that the CSM column density may be two orders of magnitude lower than previous estimates. We show that the H$\alpha$ luminosity decline is similar to other SNe with CSM interaction, and demonstrate how our infrared photometry is evidence for newly formed, collisionally heated dust. We create a model for PTF11kx's late-time CSM interaction and find that X-ray reprocessing by photoionization and recombination cannot reproduce the observed H$\alpha$ luminosity, suggesting that the X-rays are thermalized and that H$\alpha$ radiates from collisional excitation. Finally, we discuss the implications of our results regarding the progenitor scenario and the geometric properties of the CSM for the PTF11kx system.Comment: 15 pages, 8 figures, 3 tables; submitted to Ap

In vivo Remineralization Using a Sustained Topical Fluoride Delivery System

The efficacy of a new remineralization system was determined in vivo by maintaining a low concentration of approximately 1 ppm fluoride for 48 hrs against a demineralized human tooth. Human subjects were selected who wore removable partial dentures containing two or more of the demineralized teeth with film system. The findings indicate levels of fluoride uptake to 500 ppm at 50 micron depths in experimental sites.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66607/2/10.1177_00220345800590030501.pd

Hedgehog signaling regulates dental papilla formation and tooth size during zebrafish odontogenesis

Intercellular communication by the hedgehog cell signaling pathway is necessary for tooth development throughout the vertebrates, but it remains unclear which specific developmental signals control cell behavior at different stages of odontogenesis. To address this issue, we have manipulated hedgehog activity during zebrafish tooth development and visualized the results using confocal microscopy. Results: We first established that reporter lines for dlx2b, fli1, NF-κB, and prdm1a are markers for specific subsets of tooth germ tissues. We then blocked hedgehog signaling with cyclopamine and observed a reduction or elimination of the cranial neural crest derived dental papilla, which normally contains the cells that later give rise to dentin-producing odontoblasts. Upon further investigation, we observed that the dental papilla begins to form and then regresses in the absence of hedgehog signaling, through a mechanism unrelated to cell proliferation or apoptosis. We also found evidence of an isometric reduction in tooth size that correlates with the time of earliest hedgehog inhibition. Conclusions: We hypothesize that these results reveal a previously uncharacterized function of hedgehog signaling during tooth morphogenesis, regulating the number of cells in the dental papilla and thereby controlling tooth size

Table-driven software architecture for a stitching system

Native code for a CNC stitching machine is generated by generating a geometry model of a preform; generating tool paths from the geometry model, the tool paths including stitching instructions for making stitches; and generating additional instructions indicating thickness values. The thickness values are obtained from a lookup table. When the stitching machine runs the native code, it accesses a lookup table to determine a thread tension value corresponding to the thickness value. The stitching machine accesses another lookup table to determine a thread path geometry value corresponding to the thickness value

Novel topical fluoride-delivery system for remineralization of dental enamel: optimization studies

Further studies have been conducted on a calcium fluoride delivery system with a view to optimizing its ability to remineralize dental enamel. The influence of particle size and load of calcium fluoride used, as well as treatment time, was evaluated in vitro on prior demineralized bovine enamel. Initial studies with the original singlemembrane system did not allow an unambiguous interpretation of efficacy, due to persistent interference from calcium fluoride particles. To overcome this problem, the system was modified to include a second membrane as protection for the enamel surface. This double-membrane system revealed a marked particle size and load effect on fluoride delivery. The performance of a high load of small size calcium fluoride particles was significantly better than previous results obtained with the system and approached the most effective remineralizing conditions established with solution fluoride.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25203/1/0000642.pd

Hydroxyapatite dissolution rates in fluoride/dodecylamine solutions

The influence of fluoride (F) alone and together with dodecylamine hydrochloride (DAC) on the dissolution rate behavior of hydroxyapatite (HAP) crystal suspensions has been studied. The results showed that F and DAC inhibit the dissolution in an additive rather than a synergistic manner. The data suggest that DAC inhibits dissolution from the predominant surface(s) by adsorption physically blocking the HAP surface while F inhibits the same surface by influencing the apparent driving force for dissolution. The existence of a residual component for the dissolution rate at high concentrations that is about 15% of the maximum rate suggests that there are two or more dissolution sites on the HAP crystal. The one associated with the predominant surface(s) is strongly inhibited by both F and DAC whereas the other site(s) is insensitive to F either intrinsically or, in the presence of DAC, because of possible antagonism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24831/1/0000257.pd

Automated gantry-type stitching system

A stitching system includes a gantry that is movable along a material support table. Mounted to the gantry are a plurality of stitching heads and bobbins. The stitching heads are individually controllable in a z-direction, and the bobbins are individually controllable in the z-direction. Each stitching head is paired with a bobbin. Each pair of stitching heads and the bobbins is controlled synchronously in the z-direction. The stitching system is well-suited for stitching preforms of aircraft wing covers and other preforms having variable thickness and compound, contoured three-dimensional surfaces