Photophysics of Carbon Nanotubes: from Dispersion to Supramolecular Systems

The aim of this PhD thesis is the investigation of the photophysical properties of materials that can be exploited in solar energy conversion. In this context, my research was mainly focused on carbon nanotube-based materials and ruthenium complexes. The first part of the thesis is devoted to carbon nanotubes (CNT), which have unique physical and chemical properties, whose rational control is of substantial interest to widen their application perspectives in many fields. Our goals were (i) to develop novel procedures for supramolecular dispersion, using amphiphilic block copolymers, (ii) to investigate the photophysics of CNT-based multicomponent hybrids and understand the nature of photoinduced interactions between CNT and selected molecular systems such as porphyrins, fullerenes and oligo (p-phynylenevinylenes). We established a new protocol for the dispersion of SWCNTs in aqueous media via non-covalent interactions and demonstrated that some CNT-based hybrids are suitable for testing in PV devices. The second part of the work is focussed on the study of homoleptic and heteroleptic Ru(II) complexes with bipyridine and extended phenanthroline ligands. Our studies demonstrated that these compounds are potentially useful as light harvesting systems for solar energy conversion. Both CNT materials and Ru(II) complexes have turned out to be remarkable examples of photoactive systems. The morphological and photophysical characterization of CNT-based multicomponent systems allowed a satisfactory rationalization of the photoinduced interactions between the individual units, despite several hurdles related to the intrinsic properties of CNTs that prevent, for instance, the utilization of laser spectroscopic techniques. Overall, this work may prompt the design and development of new functional materials for photovoltaic devices.

VHL-gene deletion in single renal tubular epithelial cells and renal tubular cysts: further evidence for a cyst-dependent progression pathway of clear cell renal carcinoma in von Hippel-Lindau disease

Inheritance of a mutant allele of the von Hippel-Lindau tumor suppressor gene predisposes affected individuals to develop renal cysts and clear cell renal cell carcinoma. Von Hippel-Lindau gene inactivation in single renal tubular cells has indirectly been showed by immunohistochemical staining for the hypoxia-inducible factor alpha target gene product carbonic anhydrase IX. In this study we were able to show von Hippel-Lindau gene deletion in carbonic anhydrase IX positive nonneoplastic renal tubular cells, in epithelial cells lining renal cysts and in a clear cell renal cell carcinoma of a von Hippel-Lindau patient. This was carried out by means of laser confocal microscopy and immunohistochemistry in combination with fluorescence in situ hybridization. Carbonic anhydrase IX negative normal renal tubular cells carried no von Hippel-Lindau gene deletion. Furthermore, recent studies have indicated that the von Hippel-Lindau gene product is necessary for the maintenance of primary cilia stability in renal epithelial cells and that disruption of the cilia structure by von Hippel-Lindau gene inactivation induces renal cyst formation. In our study, we show a significant shortening of primary cilia in epithelial cells lining renal cysts, whereas, single tubular cells with a von Hippel-Lindau gene deletion display to a far lesser extent signs of cilia shortening. Our in vivo results support a model in which renal cysts represent precursor lesions for clear cell renal cell carcinoma and arise from single renal tubular epithelial cells owing to von Hippel-Lindau gene deletion.

Tissue fusion, a new opportunity for sutureless bypass surgery

Microsurgical suturing is the standard for cerebral bypass surgery, a technique where temporary occlusion is usually necessary. Non-occlusive techniques such as excimer laser-assisted non-occlusive anastomosis (ELANA) have certainly widened the spectrum of treatment of complex cerebrovascular situations, such as giant cerebral aneurysms, that were otherwise non-treatable. Nevertheless, the reduction of surgical risks while widening the spectrum of indications, such as a prophylactic cerebral bypass, is still a main aim, that we would like to pursue with our sutureless tissue fusion research. The primary concern in sutureless tissue fusion- and especially in tissue fusion of cerebral vessels- is the lack of reproducibility, often caused by variations in the thermal damage of the vessel. This has prevented this novel fusion technique from being applicable in daily surgical use. In this overview, we present three ways to further improve the laser tissue soldering technique.In the first section entitled "Laser Tissue Soldering Using a Biodegradable Polymer," a porous polymer scaffold doped with albumin (BSA) and indocyanine green (ICG) is presented, leading to strong and reproducible tensile strengths in tissue soldering. Histologies and future developments are discussed.In the section "Numerical Simulation for Improvement of Laser Tissue Soldering," a powerful theoretical simulation model is used to calculate temperature distribution during soldering. The goal of this research is to have a tool in hand that allows us to determine laser irradiation parameters that guarantee strong vessel fusion without thermally damaging the inner structures such as the intima and endothelium.In a third section, "Nanoparticles in Laser Tissue Soldering," we demonstrate that nanoparticles can be used to produce a stable and well-defined spatial absorption profile in the scaffold, which is an important step towards increasing the reproducibility. The risks of implanting nanoparticles into a biodegradable scaffold are discussed.Step by step, these developments in sutureless tissue fusion have improved the tensile strength and the reproducibility, and are constantly evolving towards a clinically applicable anastomosis technique.

Geochemical and Strontium Isotope Characterization of Produced Waters from Marcellus Shale Natural Gas Extraction

Extraction of natural gas by hydraulic fracturing of the Middle Devonian Marcellus Shale, a major gas-bearing unit in the Appalachian Basin, results in significant quantities of produced water containing high total dissolved solids (TDS). We carried out a strontium (Sr) isotope investigation to determine the utility of Sr isotopes in identifying and quantifying the interaction of Marcellus Formation produced waters with other waters in the Appalachian Basin in the event of an accidental release, and to provide information about the source of the dissolved solids. Strontium isotopic ratios of Marcellus produced waters collected over a geographic range of ∼375 km from southwestern to northeastern Pennsylvania define a relatively narrow set of values (εSr SW = +13.8 to +41.6, where εSr SW is the deviation of the 87Sr/86Sr ratio from that of seawater in parts per 104); this isotopic range falls above that of Middle Devonian seawater, and is distinct from most western Pennsylvania acid mine drainage and Upper Devonian Venango Group oil and gas brines. The uniformity of the isotope ratios suggests a basin-wide source of dissolved solids with a component that is more radiogenic than seawater. Mixing models indicate that Sr isotope ratios can be used to sensitively differentiate between Marcellus Formation produced water and other potential sources of TDS into ground or surface waters.

Effect of a plasmaelectrolytic coating on the strength retention of in vivo and in vitro degraded magnesium implants

The strength decrease in magnesium implants was studied in vitro and in vivo, with and without a protective plasmaelectrolytic coating. In vivo, degradation was examined by implanting rectangular plates on top of the nasal bone of miniature pigs. The presence of gas pockets in the soft tissue surrounding the implants was evaluated with intermediate X-rays and computed X-ray tomography scans before euthanasia. After 12 and 24weeks of in vivo degradation, the large rectangular plates were removed and mechanically tested in three-point bending. In vitro, identical plates were immersed in simulated body fluid for 4, 8 and 12weeks. In vitro and in vivo results showed that onset of gas release can be delayed by the plasmaelectrolytic coating. Mass loss and strength retention during in vivo degradation is about four times slower than during in vitro degradation for the chosen test conditions. Despite the slow degradation of the investigated WE43 alloy, the occurrence of gas pockets could not be completely avoided. Nevertheless, uniformity of degradation and reliable strength retention make this alloy a prime candidate for the use of magnesium in cranio-maxillofacial surgery.

Automated optimization of polymer extrusion dies using finite element analysis

An extrusion die is used to continuously produce parts with a constant cross section; such as sheets, pipes, tire components and more complex shapes such as window seals. The die is fed by a screw extruder when polymers are used. The extruder melts, mixes and pressures the material by the rotation of either a single or double screw. The polymer can then be continuously forced through the die producing a long part in the shape of the die outlet. The extruded section is then cut to the desired length. Generally, the primary target of a well designed die is to produce a uniform outlet velocity without excessively raising the pressure required to extrude the polymer through the die. Other properties such as temperature uniformity and residence time are also important but are not directly considered in this work. Designing dies for optimal outlet velocity variation using simple analytical equations are feasible for basic die geometries or simple channels. Due to the complexity of die geometry and of polymer material properties design of complex dies by analytical methods is difficult. For complex dies iterative methods must be used to optimize dies. An automated iterative method is desired for die optimization. To automate the design and optimization of an extrusion die two issues must be dealt with. The first is how to generate a new mesh for each iteration. In this work, this is approached by modifying a Parasolid file that describes a CAD part. This file is then used in a commercial meshing software. Skewing the initial mesh to produce a new geometry was also employed as a second option. The second issue is an optimization problem with the presence of noise stemming from variations in the mesh and cumulative truncation errors. In this work a simplex method and a modified trust region method were employed for automated optimization of die geometries. For the trust region a discreet derivative and a BFGS Hessian approximation were used. To deal with the noise in the function the trust region method was modified to automatically adjust the discreet derivative step size and the trust region based on changes in noise and function contour. Generally uniformity of velocity at exit of the extrusion die can be improved by increasing resistance across the die but this is limited by the pressure capabilities of the extruder. In optimization, a penalty factor that increases exponentially from the pressure limit is applied. This penalty can be applied in two different ways; the first only to the designs which exceed the pressure limit, the second to both designs above and below the pressure limit. Both of these methods were tested and compared in this work.

CHARACTERIZATION OF ELECTRODEPOSITED POLYANILINE BIOSENSOR PLATFORM FOR ESCHERICHIA COLI O157:H7 DETECTION

Amperometric electrodeposition has been used to obtain uniform, conductive, and repeatable polyaniline (PANi) thin films for use in nano scaled biochemical sensors. This report describes the characterization of these films. Techniques such as ellipsometry were used to test repeatability of the deposition and the uniformity of the deposited thin films. Raman spectroscopy was utilized to confirm the composition of the deposited PANi thin films. Fluorescence microscopy was used to determine the immobilization of antibodies to the PANi thin films using biotin-avidin interactions, as well as the density of active binding sites. Ellipsometry results demonstrated that biomolecules could be immobilized on PANi films as thin as 9nm. Evidence from the Raman spectroscopy demonstrated the conductive nature of the PANi films. The fluorescence microscopy demonstrated that antibodies could be immobilized on PANi films, although the experiment also demonstrated a low density of binding sites. The characterization demonstrates the utility of the PANi thin films as a conductive interface between the inorganic sensor platform and biochemical molecules.

A Measurement System Experiment to Evaluate the Nosing-to-nosing Method for Measuring Dimensions of Steps

Non-uniformity of steps within a flight is a major risk factor for falls. Guidelines and requirements for uniformity of step risers and tread depths assume the measurement system provides precise dimensional values. The state-of-the-art measurement system is a relatively new method, known as the nosing-to-nosing method. It involves measuring the distance between the noses of adjacent steps and the angle formed with the horizontal. From these measurements, the effective riser height and tread depth are calculated. This study was undertaken for the purpose of evaluating the measurement system to determine how much of total measurement variability comes from the step variations versus that due to repeatability and reproducibility (R&R) associated with the measurers. Using an experimental design quality control professionals call a measurement system experiment, two measurers measured all steps in six randomly selected flights, and repeated the process on a subsequent day. After marking each step in a flight in three lateral places (left, center, and right), the measurers took their measurement. This process yielded 774 values of riser height and 672 values of tread depth. Results of applying the Gage R&R ANOVA procedure in Minitab software indicated that the R&R contribution to riser height variability was 1.42%; and to tread depth was 0.50%. All remaining variability was attributed to actual step-to-step differences. These results may be compared with guidelines used in the automobile industry for measurement systems that consider R&R less than 1% as an acceptable measurement system; and R&R between 1% and 9% as acceptable depending on the application, the cost of the measuring device, cost of repair, or other factors.

Support for the predictions of the pollinator-mediated stabilizing selection hypothesis

Aims Floral traits are frequency used in traditional plant systematics because Of their assumed constancy. One potential reason for the apparent constancy of flower size is that effective pollen transfer between flowers depends oil the accuracy of the physical fit between the flower and pollinator. Therefore, dowels are likely to he under stronger stabilizing selection for uniform size than vegetative plant parts. Moreover, as predicted by the pollinator-mediated stabilizing selection (PMSS) hypothesis, all accurate fit between flowers and their pollinators is likely to he more important for specialized pollination systems as found in many species with bilaterally symmetric (zygomorphic) flowers than for species, with radially symmetric (actinomorphic) flowers. Methods In a comparative study of 15 zygomorphic and 13 actinomorphic species ill Switzerland, we tested whether variation in flower size, among and within individuals, is smaller than variation ill leaf size and whether variation in flower size is smaller ill zygomorphic compared to actinomorphic species. Important findings Indeed, variation ill leaf length was significantly larger than variation in flower length and width. Within-individual variation ill flower and leaf sizes did not differ significantly between zygomorphic and actinomorphic species. In line with the predictions of the PMSS, among-individual variation ill flower length and flower width was significantly smaller for zygomorphic species than for actinomorphic species, while the two groups did not differ in leaf length variation. This suggests that plants with zygomorphic flowers have undergone stronger selection for uniform flowers than plants with actinomorphic flowers. This supports that the uniformity of flowers compared to vegetative structures within species, as already observed in traditional plant systematics, is, at least in part, a consequence of the requirement for effective pollination.

Variation of cell and matrix morphologies in articular cartilage among locations in the adult human knee

OBJECTIVE: Understanding of articular cartilage physiology, remodelling mechanisms, and evaluation of tissue engineering repair methods requires reference information regarding normal structural organization. Our goals were to examine the variation of cartilage cell and matrix morphology in different topographical areas of the adult human knee joint. METHODS: Osteochondral explants were acquired from seven distinct anatomical locations of the knee joints of deceased persons aged 20-40 years and prepared for analysis of cell, matrix and tissue morphology using confocal microscopy and unbiased stereological methods. Differences between locations were identified by statistical analysis. RESULTS: Medial femoral condyle cartilage had relatively high cell surface area per unit tissue volume in the superficial zone. In the transitional zone, meniscus-covered lateral tibia cartilage showed elevated chondrocyte densities compared to the rest of the knee while lateral femoral condyle cartilage exhibited particularly large chondrocytes. Statistical analyses indicated highly uniform morphology throughout the radial zone (lower 80% of cartilage thickness) in the knee, and strong similarities in cell and matrix morphologies among cartilage from the femoral condyles and also in the mediocentral tibial plateau. Throughout the adult human knee, the mean matrix volume per chondron was remarkably constant at approximately 224,000 microm(3), corresponding to approximately 4.6 x 10(6) chondrons per cm(3). CONCLUSIONS: The uniformity of matrix volume per chondron throughout the adult human knee suggests that cell-scale biophysical and metabolic constraints may place limitations on cartilage thickness, mechanical properties, and remodelling mechanisms. Data may also aid the evaluation of cartilage tissue engineering treatments in a site-specific manner. Results indicate that joint locations which perform similar biomechanical functions have similar cell and matrix morphologies; findings may therefore also provide clues to understanding conditions under which focal lesions leading to osteoarthritis may occur.

Algorithms For Automatic And Robust Registration Of 3D Head Scans

wo methods for registering laser-scans of human heads and transforming them to a new semantically consistent topology defined by a user-provided template mesh are described. Both algorithms are stated within the Iterative Closest Point framework. The first method is based on finding landmark correspondences by iteratively registering the vicinity of a landmark with a re-weighted error function. Thin-plate spline interpolation is then used to deform the template mesh and finally the scan is resampled in the topology of the deformed template. The second algorithm employs a morphable shape model, which can be computed from a database of laser-scans using the first algorithm. It directly optimizes pose and shape of the morphable model. The use of the algorithm with PCA mixture models, where the shape is split up into regions each described by an individual subspace, is addressed. Mixture models require either blending or regularization strategies, both of which are described in detail. For both algorithms, strategies for filling in missing geometry for incomplete laser-scans are described. While an interpolation-based approach can be used to fill in small or smooth regions, the model-driven algorithm is capable of fitting a plausible complete head mesh to arbitrarily small geometry, which is known as "shape completion". The importance of regularization in the case of extreme shape completion is shown.

Facts and myths regarding the maxillary midline frenum and its treatment: a systematic review of the literature

OBJECTIVE To systematically review the current literature on the maxillary midline frenum and associated conditions and complications, as well as the recommended treatment options. METHOD AND MATERIALS A detailed MEDLINE database search was carried out to provide evidence about the epidemiology, associated pathologies, and treatment options regarding the maxillary frenum. Of the 206 initially identified articles, 48 met the inclusion criteria. RESULTS The maxillary frenum is highly associated with a number of syndromes and developmental abnormalities. A hypertrophic frenum may be involved in the etiology of the midline diastema. There is also a tendency by orthodontists to suggest posttreatment removal of the frenum (frenectomy). Studies on the cause of gingival recession due to the maxillary frenum are inconclusive. An injured frenum in combination with other traumas and doubtful history might point to child abuse. The involvement of hyperplastic frena in the pathogenesis of peri-implant diseases remains uncertain. There seems to be a clinical interest regarding lasers for surgery for treatment of maxillary frena. The superiority of laser treatment in relation to conventional surgical methods has not yet been demonstrated in the literature. CONCLUSION A maxillary frenum is a clinical symptom in numerous syndromic conditions and plays a role in the development of the median midline diastema. Nevertheless, the contribution to gingival recession and peri-implant diseases in the region of the maxillary incisors is rather controversial. Laser techniques are reported as the method of choice for the surgical removal of frena; however, this needs to be substantiated by appropriate prospective controlled studies.

Characterization of Optically Stimulated Luminescent Detectors in Photon & Proton Beams for Use in Anthropomorphic Phantoms

This study investigated characteristics of optically stimulated luminescent detectors (OSLDs) in protons, allowing comparison to thermoluminescent detectors, and to be implemented into the Radiological Physics Center’s (RPC) remote audit quality assurance program for protons, and for remote anthropomorphic phantom irradiations. The OSLDs used were aluminum oxide (Al2O3:C) nanoDots from Landauer, Inc. (Glenwood, Ill.) measuring 10x10x2 mm3. A square, 20(L)x20(W)x0.5(H) cm3 piece of solid water was fabricated with pockets to allow OSLDs and TLDs to be irradiated simultaneously and perpendicular to the beam. Irradiations were performed at 5cm depth in photons, and in the center of a 10 cm SOBP in a 200MeV proton beam. Additionally, the Radiological Physics Center’s anthropomorphic pelvic phantom was used to test the angular dependence of OSLDs in photons and protons. A cylindrical insert in the phantom allows the dosimeters to be rotated to any angle with a fixed gantry angle. OSLDs were irradiated at 12 angles between 0 and 360 degrees. The OSLDs were read out with a MicroStar reader from Landauer, Inc. Dose response indicates that at angles where the dosimeter is near parallel with the radiation beam response is reduced slightly. Measurements in proton beams do not show significant angular dependence. Post-irradiation fading of OSLDs was studied in proton beams to determine if the fading was different than that of photons. The fading results showed no significant difference from results in photon beams. OSLDs and TLDs are comparable within 3% in photon beams and a correction factor can be posited for proton beams. With angular dependence characteristics defined, OSLDs can be implemented into multiple-field treatment plans in photons and protons and used in the RPC’s quality assurance program.

The Role of Cell Sterilization in Population Based Studies of Radiogenic Second Cancers Following Radiation Therapy

Advances in radiotherapy have generated increased interest in comparative studies of treatment techniques and their effectiveness. In this respect, pediatric patients are of specific interest because of their sensitivity to radiation induced second cancers. However, due to the rarity of childhood cancers and the long latency of second cancers, large sample sizes are unavailable for the epidemiological study of contemporary radiotherapy treatments. Additionally, when specific treatments are considered, such as proton therapy, sample sizes are further reduced due to the rareness of such treatments. We propose a method to improve statistical power in micro clinical trials. Specifically, we use a more biologically relevant quantity, cancer equivalent dose (DCE), to estimate risk instead of mean absorbed dose (DMA). Our objective was to demonstrate that when DCE is used fewer subjects are needed for clinical trials. Thus, we compared the impact of DCE vs. DMA on sample size in a virtual clinical trial that estimated risk for second cancer (SC) in the thyroid following craniospinal irradiation (CSI) of pediatric patients using protons vs. photons. Dose reconstruction, risk models, and statistical analysis were used to evaluate SC risk from therapeutic and stray radiation from CSI for 18 patients. Absorbed dose was calculated in two ways: with (1) traditional DMA and (2) with DCE. DCE and DMA values were used to estimate relative risk of SC incidence (RRCE and RRMA, respectively) after proton vs. photon CSI. Ratios of RR for proton vs. photon CSI (RRRCE and RRRMA) were then used in comparative estimations of sample size to determine the minimal number of patients needed to maintain 80% statistical power when using DCE vs. DMA. For all patients, we found that protons substantially reduced the risk of developing a second thyroid cancer when compared to photon therapy. Mean RRR values were 0.052±0.014 and 0.087±0.021 for RRRMA and RRRCE, respectively. However, we did not find that use of DCE reduced the number of patents needed for acceptable statistical power (i.e, 80%). In fact, when considerations were made for RRR values that met equipoise requirements and the need for descriptive statistics, the minimum number of patients needed for a micro-clinical trial increased from 17 using DMA to 37 using DCE. Subsequent analyses revealed that for our sample, the most influential factor in determining variations in sample size was the experimental standard deviation of estimates for RRR across the patient sample. Additionally, because the relative uncertainty in dose from proton CSI was so much larger (on the order of 2000 times larger) than the other uncertainty terms, it dominated the uncertainty in RRR. Thus, we found that use of corrections for cell sterilization, in the form of DCE, may be an important and underappreciated consideration in the design of clinical trials and radio-epidemiological studies. In addition, the accurate application of cell sterilization to thyroid dose was sensitive to variations in absorbed dose, especially for proton CSI, which may stem from errors in patient positioning, range calculation, and other aspects of treatment planning and delivery.

ANALYTICAL MODELS OF EXOPLANETARY ATMOSPHERES. I. ATMOSPHERIC DYNAMICS VIA THE SHALLOW WATER SYSTEM

Within the context of exoplanetary atmospheres, we present a comprehensive linear analysis of forced, damped, magnetized shallow water systems, exploring the effects of dimensionality, geometry (Cartesian, pseudo-spherical, and spherical), rotation, magnetic tension, and hydrodynamic and magnetic sources of friction. Across a broad range of conditions, we find that the key governing equation for atmospheres and quantum harmonic oscillators are identical, even when forcing (stellar irradiation), sources of friction (molecular viscosity, Rayleigh drag, and magnetic drag), and magnetic tension are included. The global atmospheric structure is largely controlled by a single key parameter that involves the Rossby and Prandtl numbers. This near-universality breaks down when either molecular viscosity or magnetic drag acts non-uniformly across latitude or a poloidal magnetic field is present, suggesting that these effects will introduce qualitative changes to the familiar chevron-shaped feature witnessed in simulations of atmospheric circulation. We also find that hydrodynamic and magnetic sources of friction have dissimilar phase signatures and affect the flow in fundamentally different ways, implying that using Rayleigh drag to mimic magnetic drag is inaccurate. We exhaustively lay down the theoretical formalism (dispersion relations, governing equations, and time-dependent wave solutions) for a broad suite of models. In all situations, we derive the steady state of an atmosphere, which is relevant to interpreting infrared phase and eclipse maps of exoplanetary atmospheres. We elucidate a pinching effect that confines the atmospheric structure to be near the equator. Our suite of analytical models may be used to develop decisively physical intuition and as a reference point for three-dimensional magnetohydrodynamic simulations of atmospheric circulation.