Development of InAlN HEMTs for space application

This thesis investigates the emerging InAlN high electron mobility transistor (HEMT) technology with respect to its application in the space industry. The manufacturing processes and device performance of InAlN HEMTs were compared to AlGaN HEMTs, also produced as part of this work. RF gain up to 4 GHz was demonstrated in both InAlN and AlGaN HEMTs with gate lengths of 1 ��m, with InAlN HEMTs generally showing higher channel currents (~150 c.f. 60 mA/mm) but also degraded leakage properties (~ 1 x 10-4 c.f. < 1 x 10-8 A/mm) with respect to AlGaN. An analysis of device reliability was undertaken using thermal stability, radiation hardness and off-state breakdown measurements. Both InAlN and AlGaN HEMTs showed excellent stability under space-like conditions, with electrical operation maintained after exposure to 9.2 Mrad of gamma radiation at a dose rate of 6.6 krad/hour over two months and after storage at 250��C for four weeks. Furthermore a link was established between the optimisation of device performance (RF gain, power handling capabilities and leakage properties) and reliability (radiation hardness, thermal stability and breakdown properties), particularly with respect to surface passivation. Following analysis of performance and reliability data, the InAlN HEMT device fabrication process was optimised by adjusting the metal Ohmic contact formation process (specifically metal stack thicknesses and anneal conditions) and surface passivation techniques (plasma power during dielectric layer deposition), based on an existing AlGaN HEMT process. This resulted in both a reduction of the contact resistivity to around 1 x 10-4 ��.cm2 and the suppression of degrading trap-related effects, bringing the measured gate-lag close to zero. These discoveries fostered a greater understanding of the physical mechanisms involved in device operation and manufacture, which is elaborated upon in the final chapter.

Seawater carbonate chemistry and processes during experiments with a coral community, 2008

Ocean acidification represents a key threat to coral reefs by reducing the calcification rate of framework builders. In addition, acidification is likely to affect the relationship between corals and their symbiotic dinoflagellates and the productivity of this association. However, little is known about how acidification impacts on the physiology of reef builders and how acidification interacts with warming. Here, we report on an 8-week study that compared bleaching, productivity, and calcification responses of crustose coralline algae (CCA) and branching (Acropora) and massive (Porites) coral species in response to acidification and warming. Using a 30-tank experimental system, we manipulated CO2 levels to simulate doubling and three- to fourfold increases [Intergovernmental Panel on Climate Change (IPCC) projection categories IV and VI] relative to present-day levels under cool and warm scenarios. Results indicated that high CO2 is a bleaching agent for corals and CCA under high irradiance, acting synergistically with warming to lower thermal bleaching thresholds. We propose that CO2 induces bleaching via its impact on photoprotective mechanisms of the photosystems. Overall, acidification impacted more strongly on bleaching and productivity than on calcification. Interestingly, the intermediate, warm CO2 scenario led to a 30% increase in productivity in Acropora, whereas high CO2 lead to zero productivity in both corals. CCA were most sensitive to acidification, with high CO2 leading to negative productivity and high rates of net dissolution. Our findings suggest that sensitive reef-building species such as CCA may be pushed beyond their thresholds for growth and survival within the next few decades whereas corals will show delayed and mixed responses.

Paleoclimate records from maar Monticchio

Oxygen-isotope records from Greenland ice cores indicate numerous rapid climate fluctuations during the last glacial period. North Atlantic marine sediment cores show comparable variability in sea surface temperature and the deposition of icerafted debris. In contrast, very few continental records of this time period provide the temporal resolution and environmental sensitivity necessary to reveal the extent and effects of these environmental fluctuations on the continents. Here we present high-resolution geochemical, physical and pollen data from lake sediments in Italy and from a Mediterranean sediment core, linked by a common tephrochronology. Our lacustrine sequence extends to the past 102,000 years. Many of its features correlate well with the Greenland ice-core records, demonstrating that the closely coupled ocean-atmosphere system of the Northern Hemisphere during the last glacial extended its influence at least as far as the central Mediterranean region. Numerous vegetation changes were rapid, frequently occurring in less than 200 years, showing that the terrestrial biosphere participated fully in lastglacial climate variability. Earlier than 65,000 years ago, our record shows more climate fluctuations than are apparent in the Greenland ice cores. Together, the multi-proxy data from the continental and marine records reveal differences in the seasonal character of climate during successive interstadials, and provide a step towards determining the underlying mechanisms of the centennial-millennial-scale variability.

Nonlinear soil-structure interaction for buried pressure pipes under differential ground motion

Pipelines extend thousands of kilometers across wide geographic areas as a network to provide essential services for modern life. It is inevitable that pipelines must pass through unfavorable ground conditions, which are susceptible to natural disasters. This thesis investigates the behaviour of buried pressure pipelines experiencing ground distortions induced by normal faulting. A recent large database of physical modelling observations on buried pipes of different stiffness relative to the surrounding soil subjected to normal faults provided a unique opportunity to calibrate numerical tools. Three-dimensional finite element models were developed to enable the complex soil-structure interaction phenomena to be further understood, especially on the subjects of gap formation beneath the pipe and the trench effect associated with the interaction between backfill and native soils. Benchmarked numerical tools were then used to perform parametric analysis regarding project geometry, backfill material, relative pipe-soil stiffness and pipe diameter. Seismic loading produces a soil displacement profile that can be expressed by isoil, the distance between the peak curvature and the point of contraflexure. A simplified design framework based on this length scale (i.e., the Kappa method) was developed, which features estimates of longitudinal bending moments of buried pipes using a characteristic length, ipipe, the distance from peak to zero curvature. Recent studies indicated that empirical soil springs that were calibrated against rigid pipes are not suitable for analyzing flexible pipes, since they lead to excessive conservatism (for design). A large-scale split-box normal fault simulator was therefore assembled to produce experimental data for flexible PVC pipe responses to a normal fault. Digital image correlation (DIC) was employed to analyze the soil displacement field, and both optical fibres and conventional strain gauges were used to measure pipe strains. A refinement to the Kappa method was introduced to enable the calculation of axial strains as a function of pipe elongation induced by flexure and an approximation of the longitudinal ground deformations. A closed-form Winkler solution of flexural response was also derived to account for the distributed normal fault pattern. Finally, these two analytical solutions were evaluated against the pipe responses observed in the large-scale laboratory tests.

Economic impacts of seafood production growth targets in Ireland

This paper examines the potential economic impact of the Irish government strategy for the development of the seafood sector in Ireland, Food Harvest 2020 (FH2020). The seafood industry accounts for a large proportion of income and employment in peripheral coastal areas. Many of these regions are predominantly rural and they are largely dependent on the primary fisheries sector. Moreover, the services and retail businesses in these areas are heavily dependent on direct spending from the fisheries, aquaculture and seafood processing sectors. A social accounting matrix (SAM) approach with (1) set to zero purchase coefficients for all directly impacted industries and (2) changes in output converted to final demand shocks is used to calculate the economic and employment impact on the rest of the economy from an increase in the output in the fisheries, aquaculture and seafood processing sectors in Ireland. The results suggest fisheries sectors have strong links with the rest of the economy hence an important economic impact from a policy perspective.

Full-Duplex Spectrum Sharing in Cooperative Single Carrier Systems

We propose cyclic prefix single carrier full-duplex transmission in amplify-and-forward cooperative spectrum sharing networks to achieve multipath diversity and full-duplex spectral efficiency. Integrating full-duplex transmission into cooperative spectrum sharing systems results in two intrinsic problems: 1) the residual loop interference occurs between the transmit and the receive antennas at the secondary relays and 2) the primary users simultaneously suffer interference from the secondary source (SS) and the secondary relays (SRs). Thus, examining the effects of residual loop interference under peak interference power constraint at the primary users and maximum transmit power constraints at the SS and the SRs is a particularly challenging problem in frequency selective fading channels. To do so, we derive and quantitatively compare the lower bounds on the outage probability and the corresponding asymptotic outage probability for max���min relay selection, partial relay selection, and maximum interference relay selection policies in frequency selective fading channels. To facilitate comparison, we provide the corresponding analysis for half-duplex. Our results show two complementary regions, named as the signal-to-noise ratio (SNR) dominant region and the residual loop interference dominant region, where the multipath diversity and spatial diversity can be achievable only in the SNR dominant region, however the diversity gain collapses to zero in the residual loop interference dominant region.

Physical Layer Security with Threshold-Based Multiuser Scheduling in Multi-antenna Wireless Networks

In this paper, we consider a multiuser downlink wiretap network consisting of one base station (BS) equipped with AA antennas, NB single-antenna legitimate users, and NE single-antenna eavesdroppers over Nakagami-m fading channels. In particular, we introduce a joint secure transmission scheme that adopts transmit antenna selection (TAS) at the BS and explores threshold-based selection diversity (tSD) scheduling over legitimate users to achieve a good secrecy performance while maintaining low implementation complexity. More specifically, in an effort to quantify the secrecy performance of the considered system, two practical scenarios are investigated, i.e., Scenario I: the eavesdropper���s channel state information (CSI) is unavailable at the BS, and Scenario II: the eavesdropper���s CSI is available at the BS. For Scenario I, novel exact closed-form expressions of the secrecy outage probability are derived, which are valid for general networks with an arbitrary number of legitimate users, antenna configurations, number of eavesdroppers, and the switched threshold. For Scenario II, we take into account the ergodic secrecy rate as the principle performance metric, and derive novel closed-form expressions of the exact ergodic secrecy rate. Additionally, we also provide simple and asymptotic expressions for secrecy outage probability and ergodic secrecy rate under two distinct cases, i.e., Case I: the legitimate user is located close to the BS, and Case II: both the legitimate user and eavesdropper are located close to the BS. Our important findings reveal that the secrecy diversity order is AAmA and the slope of secrecy rate is one under Case I, while the secrecy diversity order and the slope of secrecy rate collapse to zero under Case II, where the secrecy performance floor occurs. Finally, when the switched threshold is carefully selected, the considered scheduling scheme outperforms other well known existing schemes in terms of the secrecy performance and complexity tradeoff

Similarity between the in vitro activity and toxicity of two different fungizone��� / lipofundin��� admixtures

Amphotericin B (AmB), an antifungal agent that presents a broad spectrum of activity, remains the gold standard in the antifungal therapy. However, sometimes the high level of toxicity forbids its clinical use. The aim of this work was to evaluate and compare the efficacy and toxicity in vitro of Fungizon��� (AmB-D) and two new different AmB formulations. Methods: three products were studied: Fungizon���, and two Fungizon��� /Lipofundin��� admixtures, which were diluted through two methods: in the first one, Fungizon��� was previously diluted with water for injection and then, in Lipofundin��� (AmB-DAL); the second method consisted of a primary dilution of AmB-D as a powder in the referred emulsion (AmB-DL). For the in vitro assay, two cell models were used: Red Blood Cells (RBC) from human donors and Candida tropicallis (Ct). The in vitro evaluation (K+ leakage, hemoglobin leakage and cell survival rate-CSR) was performed at four AmB concentrations (from 50 to 0.05mg.L-1). Results: The results showed that the action of AmB was not only concentration dependent, but also cellular type and vehicle kind dependent. At AmB concentrations of 50 mg.L-1, although the hemoglobin leakage for AmB-D was almost complete (99.51), for AmB-DAL and AmB-DL this value tended to zero. The p = 0.000 showed that AmB-D was significantly more hemolytic. Conclusion: The Fungizon���- Lipofundin��� admixtures seem to be the more valuable AmB carrier systems due to their best therapeutic index presented

Interpretaci��n metodol��gica de los precios de transferencia en Colombia

El concepto de precios de transferencia es un referente universal donde los pa��ses se han visto afectados por las malas pr��cticas comerciales que tiene las diferentes organizaciones en concentrar sus utilidades en aquellos lugares donde las cargas impositivas sean menores o tiendan a cero. Lo anterior implica que lo que dejo de pagar en una regi��n por las bases tributarias determinadas lo estoy recibiendo como utilidad en otro pa��s, generando ��ndices de pobreza y de inequidad tributaria en los pa��ses de origen y riqueza a los pa��ses destino. Dentro de las directrices que tiene el Gobierno para evitar que se trasladen cargas tributarias entre pa��ses es definir unos criterios normativos vinculantes u obligatorios, que eviten que se tipifiquen estos focos de evasi��n y por el contrario generar una cultura empresarial donde se respete el principio de la plena competencia. Dentro de los criterios normativos est��n los criterios de vinculaci��n, la informaci��n que se debe evidenciar como la comprobatoria y la informativa y las sanciones por incumplir los requisitos vinculantes antes mencionados lo cual nos obliga a profundizar en el mecanismo de control que ejerce el gobierno. De igual forma se establecieron destinos donde se tipifican los precios de transferencia como son los para��sos fiscales, las zonas francas y los vinculados del exterior, donde el destino m��s relevante donde el Gobierno ejerce control son los para��sos fiscales por sus caracter��sticas que las identifican como son las m��nimas cargas tributarias y de igual forma la ausencia de informaci��n. Los contribuyentes del impuesto sobre la renta y complementarios que celebren operaciones con vinculados y/o est��n obligados a la aplicaci��n de las normas que regulen el r��gimen de precios de transferencia, deber��n llevar acabo tales operaciones en cumplimiento del Principio de Plena Competencia, entendido como aquel en el cual las operaciones entre vinculados cumplen con las condiciones que se hubiesen observado en operaciones comparables con o entre partes independientes, lo anterior, a efectos de determinar sus ingresos ordinarios y extraordinarios, costos, deducciones, activos y pasivos para los fines del impuesto sobre la renta y complementarios. En el siguiente contenido el lector encontrara una metodolog��a ilustrativa que le permita interpretar la normatividad contenida en el Estatuto Tributario (Ley 1607 de 2012 y Decreto 3030 de 2013 el cual reglamenta la norma la ley 1607) y su respectiva aplicaci��n para dar cumplimiento a los requerimientos de la Administraci��n de Impuestos y Aduanas Nacionales. Lo anterior significa que el contenido del texto es el contenido normativo el cual es detallado en su contenido en algunos aspectos gr��fico, en otros casos num��ricos y en los dem��s casos narrativos.

Move, for string quartet, piano, percussion and electronics

MOVE is a composition for string quartet, piano, percussion and electronics of approximately 15-16 minutes duration in three movements. The work incorporates electronic samples either synthesized electronically by the composer or recorded from acoustic instruments. The work aims to use electronic sounds as an expansion of the tonal palette of the chamber group (rather like an extended percussion setup) as opposed to a dominating sonic feature of the music. This is done by limiting the use of electronics to specific sections of the work, and by prioritizing blend and sonic coherence in the synthesized samples. The work uses fixed electronics in such a way that allows for tempo variations in the music. Generally, a difficulty arises in that fixed ���tape��� parts don���t allow tempo variations; while truly ���live��� software algorithms sacrifice rhythmic accuracy. Sample pads, such as the Roland SPD-SX, provide an elegant solution. The latency of such a device is close enough to zero that individual samples can be triggered in real time at a range of tempi. The percussion setup in this work (vibraphone and sample pad) allows one player to cover both parts, eliminating the need for an external musician to trigger the electronics. Compositionally, momentum is used as a constructing principle. The first movement makes prominent use of ostinato and shifting meter. The second is a set of variations on a repeated harmonic pattern, with a polymetric middle section. The third is a type of passacaglia, wherein the bassline is not introduced right away, but becomes more significant later in the movement. Given the importance of visual presentation in the Internet age, the final goal of the project was to shoot HD video of a studio performance of the work for publication online. The composer recorded audio and video in two separate sessions and edited the production using Logic X and Adobe Premiere Pro. The final video presentation can be seen at geoffsheil.com/move.

Similarity between the in vitro activity and toxicity of two different fungizone��� / lipofundin��� admixtures

Amphotericin B (AmB), an antifungal agent that presents a broad spectrum of activity, remains the gold standard in the antifungal therapy. However, sometimes the high level of toxicity forbids its clinical use. The aim of this work was to evaluate and compare the efficacy and toxicity in vitro of Fungizon��� (AmB-D) and two new different AmB formulations. Methods: three products were studied: Fungizon���, and two Fungizon��� /Lipofundin��� admixtures, which were diluted through two methods: in the first one, Fungizon��� was previously diluted with water for injection and then, in Lipofundin��� (AmB-DAL); the second method consisted of a primary dilution of AmB-D as a powder in the referred emulsion (AmB-DL). For the in vitro assay, two cell models were used: Red Blood Cells (RBC) from human donors and Candida tropicallis (Ct). The in vitro evaluation (K+ leakage, hemoglobin leakage and cell survival rate-CSR) was performed at four AmB concentrations (from 50 to 0.05mg.L-1). Results: The results showed that the action of AmB was not only concentration dependent, but also cellular type and vehicle kind dependent. At AmB concentrations of 50 mg.L-1, although the hemoglobin leakage for AmB-D was almost complete (99.51), for AmB-DAL and AmB-DL this value tended to zero. The p = 0.000 showed that AmB-D was significantly more hemolytic. Conclusion: The Fungizon���- Lipofundin��� admixtures seem to be the more valuable AmB carrier systems due to their best therapeutic index presented

A bistable reaction-diffusion system in a stretching flow

We examine the evolution of a bistable reaction in a one-dimensional stretching flow, as a model for chaotic advection. We derive two reduced systems of ordinary differential equations (ODEs) for the dynamics of the governing advection-reaction-diffusion partial differential equations (PDE), for pulse-like and for plateau-like solutions, based on a non-perturbative approach. This reduction allows us to study the dynamics in two cases: first, close to a saddle-node bifurcation at which a pair of nontrivial steady states are born as the dimensionless reaction rate (Damkoehler number) is increased, and, second, for large Damkoehler number, far away from the bifurcation. The main aim is to investigate the initial-value problem and to determine when an initial condition subject to chaotic stirring will decay to zero and when it will give rise to a nonzero final state. Comparisons with full PDE simulations show that the reduced pulse model accurately predicts the threshold amplitude for a pulse initial condition to give rise to a nontrivial final steady state, and that the reduced plateau model gives an accurate picture of the dynamics of the system at large Damkoehler number. Published in Physica D (2006)

Adsor����o de cromo (VI) em leito fixo utilizando part��culas de areia recobertas com Quitosana

Neste trabalho foi avaliado o processo de recobrimento de part��culas de areia com quitosana utilizando a t��cnica dip-coating, e analisado o emprego destas part��culas como recheio de uma coluna de leito fixo no processo de adsor����o de cromo (VI) em solu����o aquosa. A quitosana foi obtida a partir de res��duos de camar��o e caracterizada. O estudo avaliou a influ��ncia do tamanho das part��culas e da concentra����o da solu����o de quitosana no recobrimento das part��culas de areia. Foram avaliados par��metros termodin��micos, isotermas de equil��brio e par��metros relacionados ao funcionamento do leito (vaz��o e pH da solu����o, di��metro de part��cula) para o processo de adsor����o de cromo (VI) em solu����o aquosa. No recobrimento das part��culas de areia, o tamanho n��o teve signific��ncia na resposta, enquanto a concentra����o da solu����o de recobrimento mostrou ter grande influ��ncia sobre o resultado, sendo que a menor concentra����o de quitosana dentro da faixa estudada (0,5% p/v) apresentou o melhor desempenho. O processo de cura f��sica para o recobrimento das part��culas de areia mostrou melhor desempenho para a adsor����o de cromo (VI) em leito fixo frente ao processo f��sico-qu��mico. As an��lises de superf��cie (MEV) e de difra����o de raio-X (EDX) comprovaram a mudan��a na superf��cie das part��culas recobertas e a presen��a de cromo ap��s a adsor����o. O modelo de Sips foi o que melhor representou os dados experimentais de equil��brio, com R2 >0,99% e EMR<3,5%, sendo que a capacidade m��xima de adsor����o foi de 46,93 mg g-1 obtida a 298 K. O processo se mostrou espont��neo, exot��rmico e favor��vel, com valores de -4,49 a -4,66kJ mol-1 para e energia livre de Gibbs, -5,97kJ mol-1 para a varia����o de entalpia e -5,17x10-3 kJ mol-1K -1 para varia����o de entropia. O aumento do pH diminuiu a adsor����o de cromo (VI), sendo que a melhor resposta foi obtida em pH 3, sendo que o di��metro de part��cula n��o teve efeito significante. O estudo da vaz��o da solu����o de cromo (VI) no desempenho do leito mostrou que no menor valor (2,5 mL min-1 ) a concentra����o de sa��da do leito foi pr��xima a zero, mantendo-se com concentra����es de sa��da abaixo de 20% por pelo menos 20 min. O estudo da dessor����o do leito mostrou que ap��s cinco ciclos de trabalho o leito manteve 86% da capacidade de adsor����o, com taxas de recupera����o do cromo no processo de dessor����o maiores que 95%.

Desenvolvimento e valida����o de m��todo voltam��trico para determina����o de ferro e sua especia����o qu��mica em ��gua intersticial no sedimento da Lagoa dos Patos-RS

Os sedimentos podem atuar tanto como acumuladores quanto como fontes de poluentes. Em fun����o das atividades portu��rias locais estarem em ritmo de crescimento pela amplia����o do porto de Rio Grande (RS), estudos que mostrem a situa����o do local investigado s��o importantes a fim de prever o aporte do ferro nesse ambiente. Neste trabalho, a especia����o qu��mica do ferro e a determina����o da concentra����o do metal total e dissolvido em amostras de ��guas intersticiais no sedimento do Saco do Mendanha (RS) foram avaliadas, utilizando a Voltametria Adsortiva de Redissolu����o Cat��dica com o ligante 2,3-Dihidroxinaftaleno. O objetivo principal desse trabalho foi validar a metodologia anal��tica para realizar a especia����o qu��mica do ferro em ��guas intersticiais, o que englobou a faixa linear de trabalho, limites de detec����o e de quantifica����o, a exatid��o e precis��o. O Limite de Detec����o encontrado foi de 0,11 nmol L-1 . Foram determinadas as concentra����es de ferro total, dissolvido e l��bil em tr��s fra����es distintas: na interface ��gua/sedimento, entre 0 e -5 cm; e entre -15 e -20 cm de profundidade na coluna sedimentar. Nas amostras analisadas, a concentra����o de ferro l��bil encontrada foi entre 4,64 ��� 135,37 ��mol L-1 ; a concentra����o do metal dissolvido foi de 6,25 ��� 322,70 ��mol L-1 e de ferro total entre 83,36 ��� 390,30 ��mol L-1 . A concentra����o do metal l��bil em compara����o com a fra����o dissolvida e total indica a presen��a de complexos est��veis entre o metal e a mat��ria org��nica natural presente na ��gua intersticial, tornando dessa forma, o metal menos biodispon��vel para a biota local. Durante os meses de amostragem do sedimento, foi observada varia����o da concentra����o do metal, onde no m��s de abril ocorreu o maior aporte do metal da coluna d�����gua para o sedimento. Essa transfer��ncia do metal para o sedimento pode estar relacionada pela forte mudan��a na salinidade no local de amostragem, passando de 16 no m��s de fevereiro para 33 no m��s de abril e para pr��ximo de zero nos meses de agosto e novembro de 2009.

Seasonal changes of heat and moisture fluxes from the Caspian Sea surface and its effect on synoptic systems with heavy rainfalls in southern shores of the sea during 2005-2010

Caspian Sea with its unique characteristics is a significant source to supply required heat and moisture for passing weather systems over the north of Iran. Investigation of heat and moisture fluxes in the region and their effects on these systems that could lead to floods and major financial and human losses is essential in weather forecasting. Nowadays by improvement of numerical weather and climate prediction models and the increasing need to more accurate forecasting of heavy rainfall, the evaluation and verification of these models has been become much more important. In this study we have used the WRF model as a research-practical one with many valuable characteristics and flexibilities. In this research, the effects of heat and moisture fluxes of Caspian Sea on the synoptic and dynamical structure of 20 selective systems associated with heavy rainfall in the southern shores of Caspian Sea are investigated. These systems are selected based on the rainfall data gathered by three local stations named: Rasht, Babolsar and Gorgan in different seasons during a five-year period (2005-2010) with maximum amount of rainfall through the 24 hours of a day. In addition to synoptic analyses of these systems, the WRF model with and without surface flues was run using the two nested grids with the horizontal resolutions of 12 and 36 km. The results show that there are good consistencies between the predicted distribution of rainfall field, time of beginning and end of rainfall by the model and the observations. But the model underestimates the amounts of rainfall and the maximum difference with the observation is about 69%. Also, no significant changes in the results are seen when the domain and the resolution of computations are changed. The other noticeable point is that the systems are severely weakened by removing heat and moisture fluxes and thereby the amounts of large scale rainfall are decreased up to 77% and the convective rainfalls tend to zero.