BACKGROUND: Implants have been widely used in the medical field. It was adopted in dentistry, offering patients replacement of missing teeth. Researchers have been investigating techniques to improve implants’ survival. Among these techniques is plasma glow discharge. Radio-frequency Glow discharge (RGD) is a surface treatment and sterilization technique with the aim to improve the titanium oxide layer for better osseointegration. Previous studies have evaluated its effect on non-human cell lines with promising results. Up to date, there is no report on how RGD surface treatment of titanium affects normal human osteoblasts. MATERIAL AND METHODS: Human bone fragments were obtained from dental extraction sites and were processed to culture normal human osteoblasts. Cells were seeded on three different surfaces at a concentration of 1x105 cells per plate; Titanium discs with and without Argon RGD (ARGD), and tissue culture plates (TCP). Dishes were allocated to 3 timelines: 16 hours, 7 days and 14 days. The outcome measures were cell attachment, cell number, alkaline phosphatase and osteocalcin levels. RESULTS: Data was analyzed using a one-way ANOVA test. Mean cell proliferation percentage for the ARGD group at 7 days was the highest (167.966%). The difference in means among the three groups at 7 days was statistically significant (p=0.0022). At 14 days, the highest mean of cell proliferation percentage was highest for the ARGD group. When testing all pairs, at 7 days the differences in means were statistically significant between (ARGD vs. no ARGD, and ARGD vs. TCP) (p=0.0018, and p=0.0286), respectively. At 14 days, the differences in means were statistically significant between (ARGD vs. TCP, p= 0.0003) and (no ARGD vs. TCP, p=0.0007). There was a significant difference in means for alkaline phosphatase and osteocalcin at 7 and 14 days between TCP and ARGD, and TCP and no ARGD groups (p < 0.05). CONCLUSIONS: The results of this study on normal human osteoblasts indicated that ARGD significantly enhanced cell proliferation. There was no significant difference in osteogenic behavior between with and without ARGD treatment on titanium surfaces within the time studied. A prolonged phase of cell proliferation was observed in ARGD treated groups.

<p>An improved understanding of colloid transport in fractured media is required to assess the potential for microorganisms to contaminate groundwater, to develop groundwater management/protection plans, to design remedial action strategies based on the application of microorganisms, and to quantify colloid-facilitated transport of many organic and inorganic contaminants. Although colloid transport has been investigated to an extent in porous media environments, this field is still in its infancy in fractured media environments.</p> <p>Colloid transport in fractured media involves a host of complex and interacting processes, including (among others): advection, hydrodynamic dispersion, attachment and detachment, straining, size/ charge exclusion, and gravitational settling. These processes are, in turn, influenced by the physicochemical properties of fractured media, the geochemical properties of groundwater, hydrodynamics, and the colloid properties. This research program focused on investigating the effects of aperture field variability, specific discharge, and ionic strength on colloid transport in saturated, variable-aperture, single fractures. An extensive literature review was first conducted, and a combination of physical model experiments and numerical simulations were then employed to achieve this goal.</p> <p> Three transparent fracture replicas were fabricated, and the light transmission method was employed to obtain a direct measurement of each of the three aperture fields. A systematic series of hydraulic and tracer tests was conducted on each of the three experimental fractures, and the cubic law, mass balance and frictional loss apertures were calculated. Additionally, the experimental breakthrough curves were fit to the one-dimensional advection-dispersion equation. The results clearly demonstrate that the mass balance aperture is the only appropriate 'equivalent aperture' for describing transport in a single variable-aperture fracture, and that the mass balance aperture is an excellent approximation ofthe arithmetic mean aperture.</p> <p>A 3^3 factorial experimental design was then implemented to numerically investigate the interactive effect of the arithmetic mean (μb), standard deviation (σb), and anisotropic ratio (AR=λ^b x/ λ^b,y where λ^b x and λ^b y is the correlation length of the aperture field along x- and y- direction respectively) of single fracture apertures on dispersion regimes (specifically Taylor dispersion and geometric dispersion) and dispersivity. The simulation results show that: (1) for a fixed hydraulic gradient: (a) the dominant dispersion regime is controlled by μb, and to a lesser degree, σb, and (b) geometric dispersion becomes more dominant as the coefficient of variation (CoV = σb/μb) increases; (2) for a fixed mean aperture, the dispersivity and the spread in dispersivity for varying ARs increase with the CoV; and (3) the AR has a significant effect on dispersivity only when the CoV is large (>0.2).</p> <p> Numerical simulations investigating colloid and solute transport in single parallel-plate fractures, conducted using the Random Walk Particle Tracking (RWPT) method, demonstrated that: 1) There exists a threshold value, δo , of the aspect ratio, δ (δ= 2rc/b, where rc and b represent the colloid radius and fracture aperture respectively), where the average transport velocities of colloids and solutes are similar. When δ> δo , the Taylor Aris assumption is satisfied, and tp (tp = tc/ts, where tc and ts represent colloid and solute retention times respectively) decreases as δ increases, as is well documented in the hydrodynamic chromatography literature. However, when δ < δo , the Taylor-Aris assumption is violated, and tp increases as δ increases. This has never been documented before, and it helps to explain some seemingly contradictory work in the literature. 2) The Taylor dispersion coefficient and its extension by James and Chrysikopoulos (2003) will overestimate the colloid dispersion coefficient significantly when the Taylor-Aris assumption is violated. Additionally, these simulations demonstrated that tp and DL,coll/DL,solute (where DL,coll and DL,solute represent the dispersion coefficients of colloids and solutes respectively) decrease with increasing CoV, and that the anisotropy ratio, AR, only plays a minor role on these two ratios compared to the CoV. These observations have never been documented before to the knowledge of these authors, and have important implications towards the interpretation of colloid transport in both porous and fractured media.</p> <p> A combination of physical experiments, numerical simulations and visualization techniques was employed to investigate the impact of aperture variability, specific discharge, and ionic strength on colloid transport processes. The mean colloid transport velocity and colloid dispersion coefficient were obtained by fitting the analytical solution of the one-dimensional advection-dispersion equation (ADE) to the measured breakthrough curves. Two significant observations were made from the colloid transport experiment images: (1) colloids migrate along preferential pathways, and bypass some aperture regions; and (2) the colloid plume is irregular in shape, and becomes more irregular with increasing specific discharge, indicating non-Fickian transport. It is therefore postulated that the dispersivity cannot be completely determined by the aperture field characteristics alone; it is also a function of specific discharge. The colloid recovery in all fractures was found to increase with increasing specific discharge. For each specific discharge, it was found that the colloid recoveries in F2 and F3 were similar, and were always larger than the recovery in F1. This is consistent with the fact that the arithmetic mean apertures of F2 and F3 were similar (μb,F2= 1.57 mm, /μb,F3= 1.75 mm), and larger than that of F1 (μb,F1 = 0.88 mm). This suggests that it is the transport step (the step in which the colloids are transported from the bulk fluid to the vicinity of the fracture wall), and not the attachment step, that plays the dominant role in the colloid sorption process. It was also found that the mean transport velocity and dispersion coefficient of colloids are larger than those of solutes in F3 (CoV = 0.29), but similar to those of solutes in F1 (CoV = 0.78) and F2 (CoV = 0.71). This confirms the numerical simulation results from this work indicating that tp and DL,coll/DL,solute decrease with increasing CoV. These findings have significant implications on the interpretation of colloid transport data.</p> / Thesis / Doctor of Philosophy (PhD)

<p> This report deals with the design of an electrode system which utilizes the double dis- charge technique to achieve a Uniform discharge between two continuous electrodes with the intent of using this electrode system as the excitation unit for a TEA CO2 laser. The particular electrode configuration dealt with in this report involves a continous cathode and a similar continuous anode which has a set of rounded tip, rod, preionization electrodes set into holes in it. Also included in this report is a preliminary measure of the gain of the resultant double discharge TEA CO2 laser. </p> / Thesis / Master of Science (MSc)

Alternate bars are large-scale bedforms characterised by an ordered sequence of scour zones and depositional diagonal fronts alternating along channel banks, which are typical of straight channelized rivers. Due to their high relief and migration properties, they represent a problem in river management, because they affect navigation, increase the flooding risk and interact with instream structures. For this reason, in the last decades many studies took the challenge of defining suitable criteria able to describe their morphometric properties. Theoretical, experimental and numerical works have clearly demonstrated that bar occurrence is a threshold process governed by the width-to-depth ratio of the channel, β. If this parameter exceeds a critical threshold, βcr, an instability mechanism amplifies the riverbed perturbations occurring due to the effect of the turbulent flow on the cohesionless riverbed, leading to the spontaneous growth of finite amplitude bars. Under steady flow conditions, alternate bars achieve an equilibrium configuration, whose amplitude value is related to the difference β-βcr. Much less information is available to describe bar characteristics under variable flow conditions, when the width-to-depth ratio changes in time and the amplitude of bars evolves depending on the duration and the shape of the hydrograph. The effect of a single idealized flood on bar amplitude evolution was successfully described by the weakly nonlinear model of Tubino (1991), which was able to capture the trajectory of bar amplitude during different stages of the flood. Supported by experimental results, he found that the response of bars crucially depends on the ratio between the flood duration and the bar-growth timescale. Nevertheless, the effect of a complex flow regime, characterised by a sequence of flow events, is to a large extent unexplored. Specifically, (i) the definition of a criterion to predict the average response of alternate bars in a river reach subject to an hydrological flow regime and (ii) the quantification of bar amplitude evolution due to a complex flow regime are still to a large extent unexplored. The goals of this work are: (i) to investigate the dependence of bar properties to variable discharge conditions; (ii) to analyse the effect of flow unsteadiness in terms of duration and sequencing of flood events and derive the main hydrological characteristics that primarily control the average response of bar amplitude; (iii) to determine the long-term bar geometry and define the "bar-forming'' discharge, which is the theoretical discharge that if maintained indefinitely would produce the same long-term bar response as the natural hydrograph; (iv) to analyse the effect that a sequence of flood events composing a complex flow series has on the evolution of bar amplitude. To pursue these purposes, we adopted a methodology primary based on theoretical models, then supported and validated through the analysis of laboratory experiments and field data. The methodology and the key results for the different parts of this thesis can be summarized as follows: 1. First, the response of bar topography to different flow stages has been investigated both theoretically and through the analysis of experimental data, observing the dependence of alternate bars to peculiar threshold conditions. The validity of weakly nonlinear model of Colombini et al. (1987), originally defined in the neighborhood of the critical condition βcr, has been extended taking into account the emersion of bars for low flows. 2. Subsequently, the average response of bars to idealized flow series has been analysed, exploring their dependence on the duration and sequencing of flood events. The probability density function has been found to be the essential hydrological information of the flow series required to determine the long-term response of bar amplitude, while the integral scale of flow sequence is a suitable metric to quantify the unsteadiness of a flow regime. 3. Then, an innovative approach has been introduced to define an occurrence criterion for alternate bars in straightened river reaches that accounts for the hydrological regime, and to determine the average bar state, with the corresponding "bar-forming'' discharge. The key novelty with respect to the classical methods adopted so far to predict the long-term equilibrium channel geometry is that in this case the morphodynamical work acted on river bars by relatively low-flow stages enhancing their formation can be reversed by high-flow stages that suppress them. Therefore, both the occurrence criterion and the average state are found from a balance between the cumulative effects of bar-forming and bar-suppressing events. 4. Finally, the weakly nonlinear model of Colombini et al. (1987), originally defined to predict the evolution of bars under steady flow conditions, has been extended to reproduce a natural flow series by considering the basic flow varying in time. This approach allows us to (i) statistically investigate the effect of flood magnitude and duration on the variations of bar amplitude and (ii) to simulate the morphological response of a river to alterations of the hydrological regime.The long-term analysis of bar amplitude, as such as its evolution subject to the hydrological flow regime, have been applied to four different study cases, each of them characterised by a distinctive average bar response: two reaches of the Alpine Rhine River, upstream and downstream the confluence of the River Ill (Switzerland), respectively, the Adige River near Trento (Italy) and the Isère River near Montmèlian (France). The theoretical model is able to capture both qualitatively and quantitatively the observed bed response. Specifically, it predicts the occurrence of high-relief bars for the upstream reach of the Alpine Rhine River and for the Isère River, while a plane configuration is predicted for the Adige River. Also the intermediate response of the downstream reach of the Alpine Rhine River is reproduced, showing a predominant flat bed morphology with sporadic low-relief bars.

Thesis (M.S.)--Boston University / The chronically ill patient in a general hospital designated for the treatment of the acutely ill presents serious problems to the medical team. With the advancements made in the medical profession, together with improved hospital facilities, more people today can benefit from hospitalization. Because of this fact, more people utilize hospital facilities today than in the past, with the results that hospitals are often overcrowded and cannot accommodate all who require treatment. Consequently, it is extremely important that the period of hospitalization be as short as possible, and consistent with the patient's condition, both for the chronically and the acutely ill if these services are to be available to all.

京都大学 / 新制・課程博士 / 博士(社会健康医学) / 甲第24844号 / 社医博第133号 / 新制||社医||13(附属図書館) / 京都大学大学院医学研究科社会健康医学系専攻 / (主査)教授 近藤, 尚己, 教授 川上, 浩司, 教授 平井, 豊博 / 学位規則第4条第1項該当 / Doctor of Public Health / Kyoto University / DFAM

Partial discharge testing is a nondestructive method of identifying possible premature insulation breakdown. Magnet wires are used in various electrical equipment like injection coils, solenoids, small transformers and motors. Winding wires used in high voltage systems are subjected to several stresses during operation, which considerably lowers their lifetime. A prolonged combined effect of these stresses causes aging of the wires, inception of partial discharge activity, and degradation of the organic material in the enamel coating and varnish used by the manufacturer. The tests were conducted for AWG 30 and AWG 31 twisted magnet wire samples. The samples are aged under accelerated conditions of high frequency, temperature, and pulsed voltages. As well as conventional sinusoidal voltages. This thesis is focused on the results of voltage, frequency, and temperature stresses on the magnet wires. The partial discharge inception voltage (PDIV) and breakdown voltages are measured for different twisted wire samples. A software tool is utilized to study these partial discharge patterns. Evaluation of the parameters charge intensity, pulse count, and pulse phase position are presented in 2- and 3-dimensional plots.

The Sand Creek watershed, Choctaw County, Mississippi, constitutes a proposed site for a recreational and water management reservoir. Prior to the development of the site, the geology and hydrogeology of the watershed must be investigated to determine suitability for impoundment. Geological cross sections derived from geophysical logs and field exploration provides information regarding facies distributions within the proposed site area. Discharge characteristics of streams provide data concerning surface runoff that can then be related to the amount of water that is beneficial to the reservoir filling and remaining filled. All data collected and the characteristics of the reservoir are mapped using ArcGIS 9.1 software. The amount of sand located near the abutment of the levee and possible thin ridge with prospect of faulting to the southeast of the abutment is cause for concern. Analysis of the study area suggests that the proposed site is suitable for location of a reservoir.

During the fabrication of solid electrical insulation, small cavities known as micro voids may form in the material. As electrical stress increases in this micro void, the breakdown probability also increases. This type of electrical breakdown is commonly known as partial discharge. Magnitudes of partial discharge currents are typically small but enough to cause degradation of the electrical insulation. To study degradation for fast-rise time voltage square pulse train, partial discharge measurement is needed. In current studies, partial discharge pulse widths have been measured in the range of nanoseconds. The best approach for measurement at ultra wide band frequencies is a bridge type measurement system, to reduce external noise and improve sensitivity to PD currents. The bridge configuration can be used with samples instead of one sample and one coupling capacitor. Identically created samples will have a close match for impedance and frequency response. This type of bridge also helps to reduce other sources of measured current such as the high displacement currents due to fast rise time square pulse voltage on the samples. Further improvement includes simultaneous measurements using a “linked” bridge configuration, where bridges share a common sample. A directly connected measurement current shunt should be used for high sensitivity with a uniform ultra wide band frequency response. Post-measurement digital signal processing (DSP) algorithms will perform the task of pulse discrimination and time delay from the pulse front. This research presents a method to improve the measurement of partial discharge when applied voltage is non-sinusoidal, with high frequency components. The improvements are apparent when square pulse voltage rise times are less than 50 ns. Ultra wide band measurements of physical samples will be performed for short time duration with a digital storage oscilloscope. A DSP algorithm is used to filter residual noise from the partial discharge current. The presented measurement technique for samples for this study is an original approach. Sample results demonstrate the effectiveness of the technique.

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