Inorganic hydrophobic coatings: Surfaces mimicking the nature

Added value products are being developed in ceramic industry. Different optical effects as bright metallic shine or new functionalities as hydrophobicity or bactericide characteristics are the new properties searched on the tiles. In this study, we prepare glassy coatings for tiles based on copper pigment by a conventional industrial process. The obtained coatings present different aesthetical aspects, including bright metallic aspect which confers a high decorative value to the tile. Furthermore, these metallic coatings present hydrophobic properties with contact angles with water as high as 115 degrees and also bactericide characteristics. Superficial microstructure and nanoparticles were found in the bactericide-hydrophobic samples, resembling the surface of hydrophobic leaf surfaces. This structure was formed by the crystallization of CuO nanoparticles as Tenorite due to the copper saturation of the glassy matrix at the surface of the coatings.

The radiation impedance of orbiting conductors

The dispersion relation for waves in a cold, magnetized plasma is discussed using the potential for the longitudinal part of the electric field. This clarifies wave emission from a conductor in low Earth orbit and should be useful in considering the far field and both hot plasma and nonlinear, near-field effects. General formulas for radiation impedance are directly obtained. For tethers a fundamental dependence on contactor size is discussed. Spherical and ellipsoidal contactors and an (anodcless) bare tether are considered. Simple arguments on nonlinear contactor effects lead to a surprisingly simple result for impedances off the Alfven branch.

Optically Induced Reorientation in Nematic Cylindrical Structures

Cyclindrical structures of nematics give rise to several opto-optical effects related to molecular reorientation. One of these effects is the formation of diffraction ring patterns similar to the ones observed in planar cells, but differing in shape. Another effect has been observed, namely a quasi-chaotic motion of rings with a very large angular spread; this motion can be obtained using a cw laser and high power densities. The phenomenon could be attributed to thermal motion, however, there are some features that cannot be explained by a purely thermal effect, e.g., a wavelength dependence of the threshold and the frequencies of the ring motion.

Pulse-Shape Analysis of PDM-QPSK Modulation Formats for 100 and 200 Gb/s DWDM transmissions

Advanced optical modulation format polarization-division multiplexed quadrature phase shift keying (PDM-QPSK) has become a key ingredient in the design of 100 and 200-Gb/s dense wavelength-division multiplexed (DWDM) networks. The performance of this format varies according to the shape of the pulses employed by the optical carrier: non-return to zero (NRZ), return to zero (RZ) or carrier-suppressed return to zero (CSRZ). In this paper we analyze the tolerance of PDM-QPSK to linear and nonlinear optical impairments: amplified spontaneous emission (ASE) noise, crosstalk, distortion by optical filtering, chromatic dispersion (CD), polarization mode dispersion (PMD) and fiber Kerr nonlinearities. RZ formats with a low duty cycle value reduce pulse-to-pulse interaction obtaining a higher tolerance to CD, PMD and intrachannel nonlinearities.

V-substituted In2S3: an intermediate band material with photocatalytic activity in the whole visible light range

We proposed in our previous work V-substituted In2S3 as an intermediate band (IB) material able to enhance the efficiency of photovoltaic cells by combining two photons to achieve a higher energy electron excitation, much like natural photosynthesis. Here this hyper-doped material is tested in a photocatalytic reaction using wavelength-controlled light. The results evidence its ability to use photons with wavelengths of up to 750 nm, i.e. with energy significantly lower than the bandgap (=2.0 eV) of non-substituted In2S3, driving with them the photocatalytic reaction at rates comparable to those of non-substituted In2S3 in its photoactivity range (λ ≤ 650 nm). Photoluminescence spectra evidence that the same bandgap excitation as in V-free In2S3 occurs in V-substituted In2S3 upon illumination with photons in the same sub-bandgap energy range which is effective in photocatalysis, and its linear dependence on light intensity proves that this is not due to a nonlinear optical property. This evidences for the first time that a two-photon process can be active in photocatalysis in a single-phase material. Quantum calculations using GW-type many-body perturbation theory suggest that the new band introduced in the In2S3 gap by V insertion is located closer to the conduction band than to the valence band, so that hot carriers produced by the two-photon process would be of electron type; they also show that the absorption coefficients of both transitions involving the IB are of significant and similar magnitude. The results imply that V-substituted In2S3, besides being photocatalytically active in the whole visible light range (a property which could be used for the production of solar fuels), could make possible photovoltaic cells of improved efficiency.

Electro y dielectroforesis de nanopartículas por efecto fotovoltaico

El objetivo de esta tesis doctoral es la investigación del nuevo concepto de pinzas fotovoltaicas, es decir, del atrapamiento, ordenación y manipulación de partículas en las estructuras generadas en la superficie de materiales ferroeléctricos mediante campos fotovoltaicos o sus gradientes. Las pinzas fotovoltaicas son una herramienta prometedora para atrapar y mover las partículas en la superficie de un material fotovoltaico de una manera controlada. Para aprovechar esta nueva técnica es necesario conocer con precisión el campo eléctrico creado por una iluminación específica en la superficie del cristal y por encima de ella. Este objetivo se ha dividido en una serie de etapas que se describen a continuación. La primera etapa consistió en la modelización del campo fotovoltaico generado por iluminación no homogénea en substratos y guías de onda de acuerdo al modelo de un centro. En la segunda etapa se estudiaron los campos y fuerzas electroforéticas y dielectroforéticas que aparecen sobre la superficie de substratos iluminados inhomogéneamente. En la tercera etapa se estudiaron sus efectos sobre micropartículas y nanopartículas, en particular se estudió el atrapamiento superficial determinando las condiciones que permiten el aprovechamiento como pinzas fotovoltaicas. En la cuarta y última etapa se estudiaron las configuraciones más eficientes en cuanto a resolución espacial. Se trabajó con distintos patrones de iluminación inhomogénea, proponiéndose patrones de iluminación al equipo experimental. Para alcanzar estos objetivos se han desarrollado herramientas de cálculo con las cuales obtenemos temporalmente todas las magnitudes que intervienen en el problema. Con estas herramientas podemos abstraernos de los complicados mecanismos de atrapamiento y a partir de un patrón de luz obtener el atrapamiento. Todo el trabajo realizado se ha llevado a cabo en dos configuraciones del cristal, en corte X ( superficie de atrapamiento paralela al eje óptico) y corte Z ( superficie de atrapamiento perpendicular al eje óptico). Se ha profundizado en la interpretación de las diferencias en los resultados según la configuración del cristal. Todas las simulaciones y experimentos se han realizado utilizando como soporte un mismo material, el niobato de litio, LiNbO3, con el f n de facilitar la comparación de los resultados. Este hecho no ha supuesto una limitación en los resultados pues los modelos no se limitan a este material. Con respecto a la estructura del trabajo, este se divide en tres partes diferenciadas que son: la introducción (I), la modelización del atrapamiento electroforético y dielectroforético (II) y las simulaciones numéricas y comparación con experimentos (III). En la primera parte se fijan las bases sobre las que se sustentarán el resto de las partes. Se describen los efectos electromagnéticos y ópticos a los que se hará referencia en el resto de los capítulos, ya sea por ser necesarios para describir los experimentos o, en otros casos, para dejar constancia de la no aparición de estos efectos para el caso en que nos ocupa y justificar la simplificación que en muchos casos se hace del problema. En esta parte, se describe principalmente el atrapamiento electroforético y dielectroforético, el efecto fotovoltaico y las propiedades del niobato de litio por ser el material que utilizaremos en experimentos y simulaciones. Así mismo, como no debe faltar en ninguna investigación, se ha analizado el state of the art, revisando lo que otros científicos del campo en el que estamos trabajando han realizado y escrito con el fin de que nos sirva de cimiento a la investigación. Con el capítulo 3 finalizamos esta primera parte describiendo las técnicas experimentales que hoy en día se están utilizando en los laboratorios para realizar el atrapamiento de partículas mediante el efecto fotovoltaico, ya que obtendremos ligeras diferencias en los resultados según la técnica de atrapamiento que se utilice. En la parte I I , dedicada a la modelización del atrapamiento, empezaremos con el capítulo 4 donde modelizaremos el campo eléctrico interno de la muestra, para a continuación modelizar el campo eléctrico, los potenciales y las fuerzas externas a la muestra. En capítulo 5 presentaremos un modelo sencillo para comprender el problema que nos aborda, al que llamamos Modelo Estacionario de Separación de Carga. Este modelo da muy buenos resultados a pesar de su sencillez. Pasamos al capítulo 6 donde discretizaremos las ecuaciones que intervienen en la física interna de la muestra mediante el método de las diferencias finitas, desarrollando el Modelo de Distribución de Carga Espacial. Para terminar esta parte, en el capítulo 8 abordamos la programación de las modelizaciones presentadas en los anteriores capítulos con el fn de dotarnos de herramientas para realizar las simulaciones de una manera rápida. En la última parte, III, presentaremos los resultados de las simulaciones numéricas realizadas con las herramientas desarrolladas y comparemos sus resultados con los experimentales. Fácilmente podremos comparar los resultados en las dos configuraciones del cristal, en corte X y corte Z. Finalizaremos con un último capítulo dedicado a las conclusiones, donde resumiremos los resultados que se han ido obteniendo en cada apartado desarrollado y daremos una visión conjunta de la investigación realizada. ABSTRACT The aim of this thesis is the research of the new concept of photovoltaic or optoelectronic tweezers, i.e., trapping, management and manipulation of particles in structures generated by photovoltaic felds or gradients on the surface of ferroelectric materials. Photovoltaic tweezers are a promising tool to trap and move the particles on the surface of a photovoltaic material in a monitored way. To take advantage of this new technique is necessary to know accurately the electric field created by a specifc illumination in the crystal surface and above it. For this purpose, the work was divided into the stages described below. The first stage consisted of modeling the photovoltaic field generated by inhomogeneous illumination in substrates and waveguides according to the one-center model. In the second stage, electrophoretic and dielectrophoretic fields and forces appearing on the surface of substrates and waveguides illuminated inhomogeneously were studied. In the third stage, the study of its effects on microparticles and nanoparticles took place. In particular, the trapping surface was studied identifying the conditions that allow its use as photovoltaic tweezers. In the fourth and fnal stage the most efficient configurations in terms of spatial resolution were studied. Different patterns of inhomogeneous illumination were tested, proposing lightning patterns to the laboratory team. To achieve these objectives calculation tools were developed to get all magnitudes temporarily involved in the problem . With these tools, the complex mechanisms of trapping can be simplified, obtaining the trapping pattern from a light pattern. All research was carried out in two configurations of crystal; in X section (trapping surface parallel to the optical axis) and Z section (trapping surface perpendicular to the optical axis). The differences in the results depending on the configuration of the crystal were deeply studied. All simulations and experiments were made using the same material as support, lithium niobate, LiNbO3, to facilitate the comparison of results. This fact does not mean a limitation in the results since the models are not limited to this material. Regarding the structure of this work, it is divided into three clearly differentiated sections, namely: Introduction (I), Electrophoretic and Dielectrophoretic Capture Modeling (II) and Numerical Simulations and Comparison Experiments (III). The frst section sets the foundations on which the rest of the sections will be based on. Electromagnetic and optical effects that will be referred in the remaining chapters are described, either as being necessary to explain experiments or, in other cases, to note the non-appearance of these effects for the present case and justify the simplification of the problem that is made in many cases. This section mainly describes the electrophoretic and dielectrophoretic trapping, the photovoltaic effect and the properties of lithium niobate as the material to use in experiments and simulations. Likewise, as required in this kind of researches, the state of the art have been analyzed, reviewing what other scientists working in this field have made and written so that serve as a foundation for research. With chapter 3 the first section finalizes describing the experimental techniques that are currently being used in laboratories for trapping particles by the photovoltaic effect, because according to the trapping technique in use we will get slightly different results. The section I I , which is dedicated to the trapping modeling, begins with Chapter 4 where the internal electric field of the sample is modeled, to continue modeling the electric field, potential and forces that are external to the sample. Chapter 5 presents a simple model to understand the problem addressed by us, which is called Steady-State Charge Separation Model. This model gives very good results despite its simplicity. In chapter 6 the equations involved in the internal physics of the sample are discretized by the finite difference method, which is developed in the Spatial Charge Distribution Model. To end this section, chapter 8 is dedicated to program the models presented in the previous chapters in order to provide us with tools to perform simulations in a fast way. In the last section, III, the results of numerical simulations with the developed tools are presented and compared with the experimental results. We can easily compare outcomes in the two configurations of the crystal, in section X and section Z. The final chapter collects the conclusions, summarizing the results that were obtained in previous sections and giving an overview of the research.

Método da propagação de feixe de ângulo largo para análise de guias de ondas ópticos não-lineares

Este trabalho propõe uma extensão do método de propagação de feixe (BPM - Beam Propagation Method) para a análise de guias de ondas ópticos e acopladores baseados em materiais não-lineares do tipo Kerr. Este método se destina à investigação de estruturas onde a utilização da equação escalar de Helmholtz (EEH) em seu limite paraxial não mais se aplica. Os métodos desenvolvidos para este fim são denominados na literatura como métodos de propagação de feixe de ângulo largo. O formalismo aqui desenvolvido é baseado na técnica das diferenças finitas e nos esquemas de Crank-Nicholson (CN) e Douglas generalizado (GD). Estes esquemas apresentam como característica o fato de apresentarem um erro de truncamento em relação ao passo de discretização transversal, Δx, proporcional a O(Δx2) para o primeiro e O(Δx4). A convergência do método em ambos esquemas é otimizada pela utilização de um algoritmo interativo para a correção do campo no meio não-linear. O formalismo de ângulo largo é obtido pela expansão da EEH para os esquemas CN e GD em termos de polinômios aproximantes de Padé de ordem (1,0) e (1,1) para CN e GD, e (2,2) e (3,3) para CN. Os aproximantes de ordem superior a (1,1) apresentam sérios problemas de estabilidade. Este problema é eliminado pela rotação dos aproximantes no plano complexo. Duas condições de contorno nos extremos da janela computacional são também investigadas: 1) (TBC - Transparent Boundary Condition) e 2) condição de contorno absorvente (TAB - Transparent Absorbing Boundary). Estas condições de contorno possuem a facilidade de evitar que reflexões indesejáveis sejam transmitidas para dentro da janela computacional. Um estudo comparativo da influência destas condições de contorno na solução de guias de ondas ópticos não-lineares é também abordada neste trabalho.

Toward better outcomes with tacrolimus therapy: Population pharmacokinetics and individualized dosage prediction in adult liver transplantation

Patient outcomes in transplantation would improve if dosing of immunosuppressive agents was individualized. The aim of this study is to develop a population pharmacokinetic model of tacrolimus in adult liver transplant recipients and test this model in individualizing therapy. Population analysis was performed on data from 68 patients. Estimates were sought for apparent clearance (CL/F) and apparent volume of distribution (V/F) using the nonlinear mixed effects model program (NONMEM). Factors screened for influence on these parameters were weight, age, sex, transplant type, biliary reconstructive procedure, postoperative day, days of therapy, liver function test results, creatinine clearance, hematocrit, corticosteroid dose, and interacting drugs. The predictive performance of the developed model was evaluated through Bayesian forecasting in an independent cohort of 36 patients. No linear correlation existed between tacrolimus dosage and trough concentration (r(2) = 0.005). Mean individual Bayesian estimates for CL/F and V/F were 26.5 8.2 (SD) L/hr and 399 +/- 185 L, respectively. CL/F was greater in patients with normal liver function. V/F increased with patient weight. CL/F decreased with increasing hematocrit. Based on the derived model, a 70-kg patient with an aspartate aminotransferase (AST) level less than 70 U/L would require a tacrolimus dose of 4.7 mg twice daily to achieve a steady-state trough concentration of 10 ng/mL. A 50-kg patient with an AST level greater than 70 U/L would require a dose of 2.6 mg. Marked interindividual variability (43% to 93%) and residual random error (3.3 ng/mL) were observed. Predictions made using the final model were reasonably nonbiased (0.56 ng/mL), but imprecise (4.8 ng/mL). Pharmacokinetic information obtained will assist in tacrolimus dosing; however, further investigation into reasons for the pharmacokinetic variability of tacrolimus is required.

Population pharmacokinetics of metformin in late pregnancy

The pharmacokinetic disposition of metformin in late pregnancy was studied together with the level of fetal exposure at birth. Blood samples were obtained in the third trimester of pregnancy from women with gestational diabetes or type 2 diabetes, 5 had a previous diagnosis of polycystic ovary syndrome. A cord blood sample also was obtained at the delivery of some of these women, and also at delivery of others who had been taking metformin during pregnancy but from whom no blood had been taken. Plasma metformin concentrations were assayed by a new, validated, reverse-phase HPLC method, A 2-compartment, extravascular maternal model with transplacental partitioning of drug to a fetal compartment was fitted to the data. Nonlinear mixed-effects modeling was performed in'NONMEM using FOCE with INTERACTION. Variability was estimated using logarithmic interindividual and additive residual variance models; the covariance between clearance and volume was modeled simultaneously. Mean (range) metformin concentrations in cord plasma and in maternal plasma were 0.81 (range, 0.1-2.6) mg/L and 1.2 (range, 0. 1-2.9) mg/L, respectively. Typical population values (interindividual variability, CV%) for allometrically scaled maternal clearance and volume of distribution were 28 L/h/70 kg (17.1%) and 190 L/70 ka (46.3%), giving a derived population-wide half-life of 5.1 hours. The placental partition coefficient for metformin was 1.07 (36.3%). Neither maternal age nor weight significantly influenced the pharmacokinetics. The variability (SD) of observed concentrations about model-predicted concentrations was 0.32 mg/L. The pharmacokinetics were similar to those in nonpregnant patients and, therefore, no dosage adjustment is warranted. Metformin readily crosses the placenta, exposing the fetus to concentrations approaching those in the maternal circulation. The sequelae to such exposure, ea, effects on neonatal obesity and insulin resistance, remain unknown.

Development of a dosage strategy in patients receiving enoxaparin by continuous intravenous infusion using modelling and simulation

Aim To develop an appropriate dosing strategy for continuous intravenous infusions (CII) of enoxaparin by minimizing the percentage of steady-state anti-Xa concentration (C-ss) outside the therapeutic range of 0.5-1.2 IU ml(-1). Methods A nonlinear mixed effects model was developed with NONMEM (R) for 48 adult patients who received CII of enoxaparin with infusion durations that ranged from 8 to 894 h at rates between 100 and 1600 IU h(-1). Three hundred and sixty-three anti-Xa concentration measurements were available from patients who received CII. These were combined with 309 anti-Xa concentrations from 35 patients who received subcutaneous enoxaparin. The effects of age, body size, height, sex, creatinine clearance (CrCL) and patient location [intensive care unit (ICU) or general medical unit] on pharmacokinetic (PK) parameters were evaluated. Monte Carlo simulations were used to (i) evaluate covariate effects on C-ss and (ii) compare the impact of different infusion rates on predicted C-ss. The best dose was selected based on the highest probability that the C-ss achieved would lie within the therapeutic range. Results A two-compartment linear model with additive and proportional residual error for general medical unit patients and only a proportional error for patients in ICU provided the best description of the data. Both CrCL and weight were found to affect significantly clearance and volume of distribution of the central compartment, respectively. Simulations suggested that the best doses for patients in the ICU setting were 50 IU kg(-1) per 12 h (4.2 IU kg(-1) h(-1)) if CrCL < 30 ml min(-1); 60 IU kg(-1) per 12 h (5.0 IU kg(-1) h(-1)) if CrCL was 30-50 ml min(-1); and 70 IU kg(-1) per 12 h (5.8 IU kg(-1) h(-1)) if CrCL > 50 ml min(-1). The best doses for patients in the general medical unit were 60 IU kg(-1) per 12 h (5.0 IU kg(-1) h(-1)) if CrCL < 30 ml min(-1); 70 IU kg(-1) per 12 h (5.8 IU kg(-1) h(-1)) if CrCL was 30-50 ml min(-1); and 100 IU kg(-1) per 12 h (8.3 IU kg(-1) h(-1)) if CrCL > 50 ml min(-1). These best doses were selected based on providing the lowest equal probability of either being above or below the therapeutic range and the highest probability that the C-ss achieved would lie within the therapeutic range. Conclusion The dose of enoxaparin should be individualized to the patients' renal function and weight. There is some evidence to support slightly lower doses of CII enoxaparin in patients in the ICU setting.

A D-optimal designed population pharmacokinetic study of itraconazole capsules and solution in adults with cystic fibrosis

Background: Oral itraconazole (ITRA) is used for the treatment of allergic bronchopulmonary aspergillosis in patients with cystic fibrosis (CF) because of its antifungal activity against Aspergillus species. ITRA has an active hydroxy-metabolite (OH-ITRA) which has similar antifungal activity. ITRA is a highly lipophilic drug which is available in two different oral formulations, a capsule and an oral solution. It is reported that the oral solution has a 60% higher relative bioavailability. The influence of altered gastric physiology associated with CF on the pharmacokinetics (PK) of ITRA and its metabolite has not been previously evaluated. Objectives: 1) To estimate the population (pop) PK parameters for ITRA and its active metabolite OH-ITRA including relative bioavailability of the parent after administration of the parent by both capsule and solution and 2) to assess the performance of the optimal design. Methods: The study was a cross-over design in which 30 patients received the capsule on the first occasion and 3 days later the solution formulation. The design was constrained to have a maximum of 4 blood samples per occasion for estimation of the popPK of both ITRA and OH-ITRA. The sampling times for the population model were optimized previously using POPT v.2.0.[1] POPT is a series of applications that run under MATLAB and provide an evaluation of the information matrix for a nonlinear mixed effects model given a particular design. In addition it can be used to optimize the design based on evaluation of the determinant of the information matrix. The model details for the design were based on prior information obtained from the literature, which suggested that ITRA may have either linear or non-linear elimination. The optimal sampling times were evaluated to provide information for both competing models for the parent and metabolite and for both capsule and solution simultaneously. Blood samples were assayed by validated HPLC.[2] PopPK modelling was performed using FOCE with interaction under NONMEM, version 5 (level 1.1; GloboMax LLC, Hanover, MD, USA). The PK of ITRA and OH‑ITRA was modelled simultaneously using ADVAN 5. Subsequently three methods were assessed for modelling concentrations less than the LOD (limit of detection). These methods (corresponding to methods 5, 6 & 4 from Beal[3], respectively) were (a) where all values less than LOD were assigned to half of LOD, (b) where the closest missing value that is less than LOD was assigned to half the LOD and all previous (if during absorption) or subsequent (if during elimination) missing samples were deleted, and (c) where the contribution of the expectation of each missing concentration to the likelihood is estimated. The LOD was 0.04 mg/L. The final model evaluation was performed via bootstrap with re-sampling and a visual predictive check. The optimal design and the sampling windows of the study were evaluated for execution errors and for agreement between the observed and predicted standard errors. Dosing regimens were simulated for the capsules and the oral solution to assess their ability to achieve ITRA target trough concentration (Cmin,ss of 0.5-2 mg/L) or a combined Cmin,ss for ITRA and OH-ITRA above 1.5mg/L. Results and Discussion: A total of 241 blood samples were collected and analysed, 94% of them were taken within the defined optimal sampling windows, of which 31% where taken within 5 min of the exact optimal times. Forty six per cent of the ITRA values and 28% of the OH-ITRA values were below LOD. The entire profile after administration of the capsule for five patients was below LOD and therefore the data from this occasion was omitted from estimation. A 2-compartment model with 1st order absorption and elimination best described ITRA PK, with 1st order metabolism of the parent to OH-ITRA. For ITRA the clearance (ClItra/F) was 31.5 L/h; apparent volumes of central and peripheral compartments were 56.7 L and 2090 L, respectively. Absorption rate constants for capsule (kacap) and solution (kasol) were 0.0315 h-1 and 0.125 h-1, respectively. Comparative bioavailability of the capsule was 0.82. There was no evidence of nonlinearity in the popPK of ITRA. No screened covariate significantly improved the fit to the data. The results of the parameter estimates from the final model were comparable between the different methods for accounting for missing data, (M4,5,6)[3] and provided similar parameter estimates. The prospective application of an optimal design was found to be successful. Due to the sampling windows, most of the samples could be collected within the daily hospital routine, but still at times that were near optimal for estimating the popPK parameters. The final model was one of the potential competing models considered in the original design. The asymptotic standard errors provided by NONMEM for the final model and empirical values from bootstrap were similar in magnitude to those predicted from the Fisher Information matrix associated with the D-optimal design. Simulations from the final model showed that the current dosing regimen of 200 mg twice daily (bd) would provide a target Cmin,ss (0.5-2 mg/L) for only 35% of patients when administered as the solution and 31% when administered as capsules. The optimal dosing schedule was 500mg bd for both formulations. The target success for this dosing regimen was 87% for the solution with an NNT=4 compared to capsules. This means, for every 4 patients treated with the solution one additional patient will achieve a target success compared to capsule but at an additional cost of AUD $220 per day. The therapeutic target however is still doubtful and potential risks of these dosing schedules need to be assessed on an individual basis. Conclusion: A model was developed which described the popPK of ITRA and its main active metabolite OH-ITRA in adult CF after administration of both capsule and solution. The relative bioavailability of ITRA from the capsule was 82% that of the solution, but considerably more variable. To incorporate missing data, using the simple Beal method 5 (using half LOD for all samples below LOD) provided comparable results to the more complex but theoretically better Beal method 4 (integration method). The optimal sparse design performed well for estimation of model parameters and provided a good fit to the data.

Actively modelocked dual-wavelength fibre laser with ultra-low inter-pulse-stream timing jitter

We demonstrate a novel dual-wavelength erbium-fiber laser that uses a single nonlinear-optical loop mirror modulator to simultaneously modelock two cavities with chirped fiber Bragg gratings as end mirrors. We show that this configuration produces synchronized soliton pulse trains with an ultra-low RMS inter-pulse-stream timing jitter of 620 fs enabling application to multiwavelength systems at data rates in excess of 130 Gb/s.

The use of loop mirrors and chirped fibre Bragg gratings in actively-modelocked fibre lasers

The development of an all-optical communications infrastructure requires appropriate optical switching devices and supporting hardware. This thesis presents several novel fibre lasers which are useful pulse sources for high speed optical data processing and communications. They share several attributes in common: flexibility, stability and low-jitter output. They all produce short (picosecond) and are suitable as sources for soliton systems. The lasers are all-fibre systems using erbium-doped fibre for gain, and are actively-modelocked using a dual-wavelength nonlinear optical loop mirror (NOLM) as a modulator. Control over the operating wavelength and intra-cavity dispersion is obtained using a chirped in-fibre Bragg grating.Systems operating both at 76MHz and gigahertz frequencies are presented, the latter using a semiconductor laser amplifier to enhance nonlinear action in the loop mirror. A novel dual-wavelength system in which two linear cavities share a common modulator is presented with results which show that the jitter between the two wavelengths is low enough for use in switching experiments with data rates of up to 130Gbit/s.

Dispersion aspects of periodically amplified soliton transmission systems

This thesis presents improvements to optical transmission systems through the use of optical solitons as a digital transmission format, both theoretically and experimentally. An introduction to the main concepts and impairments of optical fibre on pulse transmission is included before introducing the concept of solitons in optically amplified communications and the problems of soliton system design. The theoretical work studies two fibre dispersion profiling schemes and a soliton launch improvement. The first provides superior pulse transmission by optimally tailoring the fibre dispersion to better follow the power, and hence nonlinearity, decay and thus allow soliton transmission for longer amplifier spacings and shorter pulse widths than normally possible. The second profiling scheme examines the use of dispersion compensating fibre in the context of soliton transmission over existing, standard fibre systems. The limits for solitons in uncompensated standard fibre are assessed, before the potential benefits of dispersion compensating fibre included as part of each amplifier are shown. The third theoretical investigation provides a simple improvement to the propagation of solitons in a highly perturbed system. By introducing a section of fibre of the correct length prior to the first system amplifier span, the soliton shape can be better coupled into the system thus providing an improved "average soliton" propagation model. The experimental work covers two areas. An important issue for soliton systems is pulse sources. Three potential lasers are studied, two ring laser configurations and one semiconductor device with external pulse shaping. The second area studies soliton transmission using a recalculating loop, reviewing the advantages and draw-backs of such an experiment in system testing and design. One particular example of employing the recirculating loop is also examined, using a novel method of pulse shape stabilisation over long distances with low jitter. The future for nonlinear optical communications is considered with the thesis conclusions.