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Short wavelength infrared (SWIR) and near-infrared (NIR) imaging methods have been in development for almost two decades for dental use. Due to the high transparency of enamel in the NIR, separate novel imaging configurations such as occlusal transillumination and cross-polarization reflectance imaging have been discovered to be useful in imaging interproximal and occlusal lesions, respectively. Novel clinical probes capable of acquiring simultaneous SWIR reflectance and occlusal transillumination images of lesions on tooth proximal and occlusal surfaces have recently been developed at UCSF. The dual probe is 3D-printed, and the imaging system uses a SWIR camera and fiber-optic light sources that use SWIR light at 1300-nm for occlusal transillumination and SWIR 1450-nm light for reflectance measurements. Previously, this dual probe was used to image extracted teeth with proximal and occlusal lesions, showing promising results verifying false positives using micro-CT images as a gold standard to assess performance. The purpose of this study is to determine the sensitivity and specificity of this novel probe on 40 human test subjects each with 2-4 premolars scheduled for extraction due to orthodontic purposes. In addition to imaging with the dual probe, visible intraoral photos of the teeth were taken prior to extraction. After extraction, radiographs of the teeth were taken, and samples were imaged using microradiography serving as the gold standard. The visible digital images and radiographs were assessed, and all samples were scored with the standardized ICDAS criteria. For the short-wave infrared images, contrast calculations were performed. The sensitivity and specificity were then calculated for visual examination, radiography, individual SWIR reflectance and occlusal transillumination and for combined SWIR reflectance and occlusal transillumination. Our study demonstrates for the first time that near simultaneous transillumination (1300-nm) and reflectance (1600-nm) video can be successfully acquired of lesions in real-time. Both imaging modalities had markedly higher sensitivity for lesions on proximal and occlusal surfaces compared to conventional methods (visual and radiographic images). Reflectance imaging at 1600-nm had significantly higher specificity than transillumination at 1300-nm.

Abstract: Here I investigate the rates of preserved original organic tissue and their quality within vertebrate bones that were preserved during the late Cretaceous of Alberta. Specimens recovered from the Dinosaur Park Formation provide a baseline for comparison to four other Alberta Formations (Brazeau, Foremost, Horseshoe Canyon, and Wapiti). Formations are all limited to approximately 13 MYA of one another, in order to eliminate excessive temporal variation in specimens. The formations studied were also chosen to cover a virtual transect of depositional settings from upland near source, to upper shoreface marine environments. This provides the opportunity to investigate if the general depositional environments play a major role in the preservation of original organic tissues in vertebrate remains from deep time. In addition to depositional environment, other previously proposed preservational factors are addressed, including the associated depositional matrix and amount of weathering before burial (degree of articulation). Findings reveal a general trend of greater tissue degradation across the terrestrial transect of depositional environments from upland to coastal plains. A marked increase in the preservation frequency and quality of tissues in upper shoreface facies reveals the potential of further investigations into tissues of extinct marine reptiles. Although groundwater quality during deposition of each of the formations has not been addressed in the literature, evidence addressed herein indicates that slight alkaline conditions were present in upland environments and slightly acidic conditions were present in those of coastal plains. Research done in an archaeological context has shown that groundwater pH plays the most significant role in the preservation of bone and its organic component. Findings made during this research indicate that initial pH levels not only have short term effects on the mineral and organic phases of bone, but also play a major role in preserving them into deep time.

Bone can achieve high strength and toughness simultaneously through its composite structure and multiple structural hierarchies, which are revealed from the nanoscale to macroscale. While numerous studies have been published on hierarchical structure of bone, the nanostructure is still a topic of debate. To date, there are three main models of bone at the nanoscale. The first and most widely accepted is the staggered crystal model which states that hydroxyapatite (HA) crystals are generally confined to the gap regions in the collagen matrix. Another model states that mineral is primarily extrafibrillar, surrounding collagen fibrils as curved lamellae. Finally, we propose that bone is an interpenetrating phase composite with a continuous mineral phase. This doctoral dissertation explores whether bone is an interpenetrating composite by isolating the component phases in bone through either deproteinization to remove the organic phase (collagen) or demineralization to remove the mineral phase (non-stoichiometric hydroxyapatite). In these studies, the most efficient chemical treatments that also preserve residual phases was found. Quality of the remaining phases was examined using techniques such as Raman spectroscopy, Fourier transform infrared spectroscopy, x-ray diffraction, and scanning electron microscopy. Mineral was found to form a continuous phase in bone from the deproteinization study, and demineralized bone was used to make a collagen scaffold with biomedical applications.Next, the effect of geometrical arrangement of phases on mechanical properties was explored through 3D printing and finite element modeling. The geometrical arrangements tested include a discontinuous phase composite, a matrix inclusion composite with a stiff or soft frame, and an interpenetrating composite with a stiff or soft phase representing the mineral and protein phases of bone, respectively. A continuous stiff phase was found to increase composite stiffness. The soft phase functioned to redistribute stress. Size effects of 3D print features on mechanical properties of composites are also discussed, showing that imperfections in additive manufacturing have a large effect on mechanical properties. Finally, drawing inspiration from two collagen-hydroxyapatite composites (porcupine fish spines and bone), synthetic scaffolds are designed and created using freeze casting. The effect of microstructure and hydration on mechanical properties is discussed for the topics, respectively.

ABSTRACTBackground and Objectives: For decades there has been an effort to develop alternative optical methods of imaging dental decay utilizing non-ionizing radiation methods. The purpose of this in-vivo study was to demonstrate whether NIR can be used as a diagnostic tool to evaluate dental caries and to compare the sensitivity and specificity of this method with that of conventional methods, including bitewing x-rays and visual inspection.Materials and Methods: 31 test subjects (n=31) from the UCSF orthodontic clinic undergoing orthodontic treatment with planned premolar extractions were recruited. Calibrated examiners performed caries detection examinations using conventional methods: bitewing radiographs and visual inspection. These findings were compared with the results from NIR examinations: transillumination and reflectance. To confirm the results found in the two different detection methods, a gold standard was used. After teeth were extracted, polarized light microscopy and transverse microradiography were performed. Results: A total of 87 premolars were used in the study. NIR identified the occlusal lesions with a sensitivity of 71% and a specificity of 77%, whereas, the visual examination had a sensitivity of only 40% and a specifity of 39%. For interproximal lesions < halfway to DEJ, both NIR and x-rays were comparable. For lesions > halfway to DEJ, specificity remained constant, but sensitivity improved to 100% for NIR and 75% for x-rays. Conclusions: The results of this preliminary study demonstrate that NIR is just as effective at detecting enamel interproximal lesions as standard dental x-rays. NIR was more effective at detecting occlusal lesions than visual examination alone. NIR shows promise as an alternative diagnostic tool to the conventional methods of x-rays and visual examination and provides a non-ionizing radiation technique.

Direct carbon fuel cell (DCFC) is a high temperature fuel cell (around 700 "C) that produces electrical energy from the direct conversion of the chemical energy of carbon. DCFC has a higher achievable efficiency of 80% compared to other fuel cells and the corresponding CO2 emission is very low compared to conventional coal-burning power plants. Moreover, a DCFC can use diversified fuel resources even waste material, which is advantageous compared to other types of fuel cells which are limited to specific fuels. DCFCs are still under development due to a number of fundamental and technological challenges such as the efficiency of carbon fuels and the effect of impurities on the performance and lifetime of the DCFC. These are key factors for the development and commercialization of these devices. In this study, three biochars obtained from the pyrolysis of poultry litters (PL) collected from Tunisian and US farmers, were characterized to see whether they can be potential anode fuels for DCFC or not. PL biochars have low fixed carbon contents (19-35 wt%) and high ash contents (32.5-63 wt%). These ashes contain around 40 wt% catalytic oxides for carbon oxidation reaction, however, these oxides have very low electrical conductivities, which resulted in the very low (negligible) electrical conductivity of the PL biochars (7.7x10-9-70.56x10-9 S/cm) at room temperature. Moreover, the high ash contents resulted in low surface areas (3.34-4.2 m"/g). These findings disqualified PL biochar from being a potential anode fuel for DCFCs. Chemical demineralization in the sequence HF/HCl followed by carbonization at 950" C of the PL biochars will result in higher fixed carbon content, higher surface area, and higher electrical conductivities. Moreover, the treated PL biochars would contain a potential catalyst (Calcium in the form of CaF2) for carbon oxidation. All these criteria would qualify the treated PL biochars to be potential fuels for DCFC.

Enamel demineralization in the form of white spot lesions (WSLs) is a pervasive problem in orthodontics. These lesions can result in long-term aesthetic compromises and increased susceptibility to caries. Though detection by eyesight has traditionally been the most common way of diagnosing these lesions, the defect by then is often irreversible. Our aim is to reduce the prevalence of these lesions by exploring tools for earlier detection and by substantiating the salient effects of fluoride. To this end, we used Polarization Sensitive--Optical Coherence Tomography (PS-OCT) to investigate the long-term potential of a fluoride-releasing glass ionomer primer for minimizing prevalence of these lesions. We devised a split-mouth protocol for this study: the control tooth bracket was bonded with conventional composite, while the experimental tooth bracket was bonded with glass ionomer. We used PS-OCT to scan each tooth every 3 months for 1 year, and then analyzed the integrated reflectivity and lesion depth for each image. We obtained high-quality images of the enamel gingival to the bracket, and were able to track and quantify enamel integrity over time. Our results indicate that glass ionomer cements do not result in less demineralization when compared to composite controls over an extended period of time. Our study also highlights the important advantages PS-OCT has over traditional techniques for assessing enamel demineralization. These scans are capable of revealing how deep and severe white spot lesions are, thus making PS-OCT an attractive tool for future use in dental imaging.

Various regions around the world are confronted with dwindling water supplies and thus the need for exploiting non-traditional inland brackish water resource, as well as reclamation and reuse of municipal wastewater and agricultural drainage (AD) water. Reverse osmosis (RO) membrane desalination is the primary technology for inland brackish water desalting. However, successful implementation of RO technology requires operation at high product water recovery (>85%) in order to minimize the volume of generated concentrate (i.e., brine). Brine management is a key factor governing the economics of inland water desalination. Therefore, brine volume reduction is critical to enabling various brine residual management options. At high water recovery, dissolved mineral salts (e.g., CaSO4, BaSO4, CaCO3) may become concentrated above their solubility limits and may crystallize in the bulk and onto the surface of the RO membranes. Mineral crystallization leads to membrane scaling and hence leads to flux decline, increased process costs, and shortening of membrane life. Therefore, the attainable desalination water recovery is limited by mineral scaling. Many inland brackish water sources contain high concentrations of sparingly soluble mineral salts. In certain areas, such as in California's San Joaquin Valley (SJV), brackish water is near saturation with respect to calcium sulfate and barium sulfate. Based on the current work, single-stage RO desalination in SJV would generally be limited to ~50-70%.In order to desalt brackish water of high mineral scaling propensity at a high recovery level (>85%), the feasibility of intermediate concentrate demineralization (ICD) of primary RO (PRO) concentrate, as a means of enabling secondary RO (SRO) desalting, was investigated with a focus on brackish water having high concentrations of gypsum salt precursor ions (i.e., calcium and sulfate). Accordingly, a two-step chemically-enhanced seeded precipitation (CESP) ICD process was developed in which the PRO concentrate is treated prior to further SRO desalting. The first step is lime precipitation softening (PS) which serves to induce sufficient CaCO3 crystallization in order to remove residual antiscalant (AS), a PRO feed treatment additive (generally polymeric) used for scale control, that would otherwise inhibit precipitation (in the ICD) of the target mineral salt scalants. Subsequently, gypsum seeded precipitation (GSP) is carried out to reduce the level of calcium sulfate saturation.The CESP process was evaluated experimentally, in a batch crystallizer, using synthetic PRO concentrate and also PRO concentrate generated in the field, from AD water, using a spiral-wound RO pilot plant. The effect of residual AS (from the PRO stage) on retardation of mineral salt precipitation (in the ICD) was evaluated using both a generic (polyacrylic acid) and a commercial AS. Laboratory batch CESP studies were carried out in which the CESP process conditions were first optimized with respect to the required lime and gypsum seed doses. For raw brackish water that was about 98% saturated with respect to gypsum, PRO desalination at 52%-62% recovery yielded a brine stream 70-150% above saturation. CESP treatment, at lime doses of 0.25-0.35 mg/L and gypsum seeding of 4-5 g/L, enabled reduction of gypsum concentration to only 10-15% above its saturation. In general, the sequential processes of lime treatment for 10-20 minutes followed by ~1 hr of GSP were sufficient to achieve the above level of gypsum desupersaturation. GSP alone reduced gypsum saturation by only ~5%. PRO brine desupersaturation via CESP was feasible due to the effectiveness of AS removal (up to 90% for AS content of up to 10 mg/L in the PRO brine). Analysis of AS removal using a fundamental AS adsorption model, along with measurements of the size distribution of precipitating CaCO3 crystals, indicated that the area for AS adsorption provided by lime-induced nucleation of CaCO3 crystals is the key factor governing AS removal. In order to establish the feasibility of deploying CESP as a continuous process, a numerical model was developed for a fluidized bed reactor for the GSP stage. Model simulations indicated that the required level of calcium sulfate desupersaturation could be maintained by solids recycling leading to a steady-state particle size distribution. Process simulations and economic analysis were carried out for the integrated process of PRO, CESP and SRO (PRO-CESP-SRO) demonstrating the existence of an optimal recovery (with respect to product water treatment cost). For the evaluated SJV brackish AD water source, the optimal recovery was about 93%. Overall brackish water treatment cost, when considering the disposal cost of high salinity AD water, was lower for PRO-CESP-SRO relative to a similar process based on conventional PS or utilizing a single stage RO which would be of limited recovery (

Aims: The aims of this study were to test the hypothesis that PS-OCT can be used to nondestructively measure and quantify the severity of the early demineralization of buccal and occlusal enamel surfaces and assess the effect of fluoride varnish in inhibiting demineralization in vivo.Material & Methods: Twenty subjects requiring bilateral premolar extractions were used. A cariogenic challenge was introduced by cementing orthodontic bands with a buccal window to these premolars and by making incisions on their occlusal surface. Bands were removed after 30 days and PS-OCT scans were acquired in vivo of occlusal and buccal areas. A split mouth design was used to test the effects of fluoride varnish. Teeth were extracted, serial sectioned and analyzed using Polarized Light Microscopy and Microradiography for comparison with the PS-OCT images.Results: High quality PS-OCT images were acquired in vivo, with excellent optical penetration through the sound enamel to the dentin. Both occlusal and buccal surfaces showed a significant difference between the "sound" and "carious" enamel groups. The "sound" group had an average ΔR = 67.72 dB * μm, and the "carious" group had an average ΔR = 206.64 dB * μm. Both PLM and PS-OCT lesion depth measurements showed a significant difference between the "sound" and "carious" enamel groups for the occlusal surface, but not for the buccal surface, when calculated with PS-OCT. There was not a significant difference between the fluoride varnish and control groups in both TMR and PS-OCT tests.Conclusion: This is the first clinical study to show the great potential of PS-OCT as a clinical tool, to nondestructively measure the depth and severity of early enamel demineralization including the high risk areas of occlusal surfaces and around orthodontic appliances, and to assess the efficacy of chemical intervention. With further studies, PS-OCT can prove to be valuable in the clinical setting due to its: ease of use, high contrast of early detection compared to traditional x rays or visual evaluation, and value of early detection in taking preventive action. This work was supported by NIDCR Grant# R01-17869.

The purpose of this study was to develop a base of understanding regarding the remineralization behavior of dental enamel in acidic fluoride solutions. The approach was to investigate the reminerali- zation behavior of synthetic hydroxyapatite powders under similar experimental conditions and to relate these findings to those obtained with bovine dental enamel. Crystal suspension experiments were designed to investigate the influences of varying the hydroxyapatite (HAP) seed prepara- tions and seed concentrations (slurry densities) upon the extent of remineralization and the nature of depositing phase (chemical stoi- chiometry and transmission electron microscopy). These studies were conducted at pkFAP = 108 (where pkFAP is minus the loga- rithm of the ion activity product, a(,Ca)2+('10) a(,PO(,4))3-('6) a(,OH)-('2)), Ca/P (molar ratio) = 1.0 and fluoride (F) = 10 ppm at pH 4.5 in 0.10 M acetate buffers. These solution conditions were known to give relatively rapid and complete remineralization of artificial lesions in bovine teeth and HAP pellets. It was concluded from these experiments that, at pkFAP = 108, the remineralization behavior was comparable for the different seed preparations studied. The results were consistent with fluorapatite (FAP) deposition upon the seeds being the predominant process and all crystal dimensions were observed to grow substan- tially. In a second set of studies the kinetics of HAP powder reminer- alization provided data for developing a quantitative understanding of the tooth remineralization behavior. These data directly related the crystal suspension remineralization behavior with changes in the tooth lesion chemistry and mineral densities with time, and deductions were made regarding possible ion activity product gradients within the lesion and how these may change with time. The principal outcomes were that the HAP powder remineralization kinetics data can explain or can help explain the essentially com- plete remineralization of bovine tooth when pkFAP = 108 and the phenomenon of simultaneous demineralization/remineralization which takes place in the bovine tooth when pkFAP > 112. Finally, the influence of the presence of carbonate in apatite on the crys- tal dissolution behavior was assessed. The dissolution rate of carbonate containing HAP (C-HAP) in the presence of fluoride was controlled by an apparent solubility corresponding to an ion activity product that is 4 to 5 orders of magnitude greater than that for HAP.