Advancing atomic nanolithography: cold atomic Cs beam exposure of alkanethiol self-assembled monolayers

We report the results of a study into the quality of functionalized surfaces for nanolithographic imaging. Self-assembled monolayer (SAM) coverage, subsequent post-etch pattern definition and minimum feature size all depend on the quality of the Au substrate used in atomic nanolithographic experiments. We find sputtered Au substrates yield much smoother surfaces and a higher density of {111} oriented grains than evaporated Au surfaces. A detailed study of the self-assembly mechanism using molecular resolution AFM and STM has shown that the monolayer is composed of domains with sizes typically of 5-25 nm, and multiple molecular domains can exist within one Au grain. Exposure of the SAM to an optically-cooled atomic Cs beam traversing a two-dimensional array of submicron material masks ans also standing wave optical masks allowed determination of the minimum average Cs dose (2 Cs atoms per SAM molecule) and the realization of < 50 nm structures. The SAM monolayer contains many non-uniformities such as pin-holes, domain boundaries and monoatomic depressions which are present in the Au surface prior to SAM adsorption. These imperfections limit the use of alkanethiols as a resist in atomic nanolithography experiments. These studies have allowed us to realize an Atom Pencil suitable for deposition of precision quantities of material at the microand nanoscale to an active surface.

Enhancing the Visualization of the Peripheral Retina with Wide Field-of-View Optical Coherence Tomography

The goal of my Ph.D. thesis is to enhance the visualization of the peripheral retina using wide-field optical coherence tomography (OCT) in a clinical setting.

OCT has gain widespread adoption in clinical ophthalmology due to its ability to visualize the diseases of the macula and central retina in three-dimensions, however, clinical OCT has a limited field-of-view of 300. There has been increasing interest to obtain high-resolution images outside of this narrow field-of-view, because three-dimensional imaging of the peripheral retina may prove to be important in the early detection of neurodegenerative diseases, such as Alzheimer's and dementia, and the monitoring of known ocular diseases, such as diabetic retinopathy, retinal vein occlusions, and choroid masses.

Before attempting to build a wide-field OCT system, we need to better understand the peripheral optics of the human eye. Shack-Hartmann wavefront sensors are commonly used tools for measuring the optical imperfections of the eye, but their acquisition speed is limited by their underlying camera hardware. The first aim of my thesis research is to create a fast method of ocular wavefront sensing such that we can measure the wavefront aberrations at numerous points across a wide visual field. In order to address aim one, we will develop a sparse Zernike reconstruction technique (SPARZER) that will enable Shack-Hartmann wavefront sensors to use as little as 1/10th of the data that would normally be required for an accurate wavefront reading. If less data needs to be acquired, then we can increase the speed at which wavefronts can be recorded.

For my second aim, we will create a sophisticated optical model that reproduces the measured aberrations of the human eye. If we know how the average eye's optics distort light, then we can engineer ophthalmic imaging systems that preemptively cancel inherent ocular aberrations. This invention will help the retinal imaging community to design systems that are capable of acquiring high resolution images across a wide visual field. The proposed model eye is also of interest to the field of vision science as it aids in the study of how anatomy affects visual performance in the peripheral retina.

Using the optical model from aim two, we will design and reduce to practice a clinical OCT system that is capable of imaging a large (800) field-of-view with enhanced visualization of the peripheral retina. A key aspect of this third and final aim is to make the imaging system compatible with standard clinical practices. To this end, we will incorporate sensorless adaptive optics in order to correct the inter- and intra- patient variability in ophthalmic aberrations. Sensorless adaptive optics will improve both the brightness (signal) and clarity (resolution) of features in the peripheral retina without affecting the size of the imaging system.

The proposed work should not only be a noteworthy contribution to the ophthalmic and engineering communities, but it should strengthen our existing collaborations with the Duke Eye Center by advancing their capability to diagnose pathologies of the peripheral retinal.

Math 412 - Topology with Applications

Highlights of Data Expedition: • Students explored daily observations of local climate data spanning the past 35 years. • Topological Data Analysis, or TDA for short, provides cutting-edge tools for studying the geometry of data in arbitrarily high dimensions. • Using TDA tools, students discovered intrinsic dynamical features of the data and learned how to quantify periodic phenomenon in a time-series. • Since nature invariably produces noisy data which rarely has exact periodicity, students also considered the theoretical basis of almost-periodicity and even invented and tested new mathematical definitions of almost-periodic functions. Summary The dataset we used for this data expedition comes from the Global Historical Climatology Network. “GHCN (Global Historical Climatology Network)-Daily is an integrated database of daily climate summaries from land surface stations across the globe.” Source: https://www.ncdc.noaa.gov/oa/climate/ghcn-daily/ We focused on the daily maximum and minimum temperatures from January 1, 1980 to April 1, 2015 collected from RDU International Airport. Through a guided series of exercises designed to be performed in Matlab, students explore these time-series, initially by direct visualization and basic statistical techniques. Then students are guided through a special sliding-window construction which transforms a time-series into a high-dimensional geometric curve. These high-dimensional curves can be visualized by projecting down to lower dimensions as in the figure below (Figure 1), however, our focus here was to use persistent homology to directly study the high-dimensional embedding. The shape of these curves has meaningful information but how one describes the “shape” of data depends on which scale the data is being considered. However, choosing the appropriate scale is rarely an obvious choice. Persistent homology overcomes this obstacle by allowing us to quantitatively study geometric features of the data across multiple-scales. Through this data expedition, students are introduced to numerically computing persistent homology using the rips collapse algorithm and interpreting the results. In the specific context of sliding-window constructions, 1-dimensional persistent homology can reveal the nature of periodic structure in the original data. I created a special technique to study how these high-dimensional sliding-window curves form loops in order to quantify the periodicity. Students are guided through this construction and learn how to visualize and interpret this information. Climate data is extremely complex (as anyone who has suffered from a bad weather prediction can attest) and numerous variables play a role in determining our daily weather and temperatures. This complexity coupled with imperfections of measuring devices results in very noisy data. This causes the annual seasonal periodicity to be far from exact. To this end, I have students explore existing theoretical notions of almost-periodicity and test it on the data. They find that some existing definitions are also inadequate in this context. Hence I challenged them to invent new mathematics by proposing and testing their own definition. These students rose to the challenge and suggested a number of creative definitions. While autocorrelation and spectral methods based on Fourier analysis are often used to explore periodicity, the construction here provides an alternative paradigm to quantify periodic structure in almost-periodic signals using tools from topological data analysis.

Circuit-aware design of energy-efficient massive MIMO systems

Densification is a key to greater throughput in cellular networks. The full potential of coordinated multipoint (CoMP) can be realized by massive multiple-input multiple-output (MIMO) systems, where each base station (BS) has very many antennas. However, the improved throughput comes at the price of more infrastructure; hardware cost and circuit power consumption scale linearly/affinely with the number of antennas. In this paper, we show that one can make the circuit power increase with only the square root of the number of antennas by circuit-aware system design. To this end, we derive achievable user rates for a system model with hardware imperfections and show how the level of imperfections can be gradually increased while maintaining high throughput. The connection between this scaling law and the circuit power consumption is established for different circuits at the BS.

Autoavaliação institucional na dimensão do SINAES comunicação com a sociedade : estudo de múltiplos casos em instituições de ensino superior do Rio Grande do Norte

This study is about the institutional self-evaluation in Dimension 4, "Communication with Society", from the National System of Higher Education Evaluation SINAES, mandatory for all universities in Brazil. A multiple cases study was conducted with three institutions from Rio Grande do Norte, and the goal was to know how this evaluation is made, describing the concept for the evaluation of communication proposed by them, identifying controllers or emancipator aspects, categorizing methodological procedures and discussing the difficulties reported in the communication evaluation process. Coordinators of the institutions Evaluating Committees were interviewed and data categorized by means of qualitative content analysis. It was noted characteristics of the current controller, emancipator and hybrid designs in the three institutions for evaluation of communication, revealing the lack of a theoretical corpus that transits in accordance with the systemic perspective and epistemology of complexity from SINAES. It was found that the most frequently reported difficulties in the evaluation processes of communication are in the preparation stage, especially in the definition of indicators and tools and awareness work. The weakness in planning makes their own activities in the sector of communication become targets of assessment, forming goals poorly related with broader organizational goals. It was also concluded that the technical evaluation cannot override the issues associated with the broader issue of the complexity surrounding the assessment paradigm proposed by SINAES because contradictions and imperfections are part of the evaluation process and several references are current in the literature to support this view. Finally, it is said that objectives such as transparency and behavioral changes can rely on methodologies and techniques for research on the question of the construction of meaning

Análise do licenciamento ambiental como instrumento de política do meio ambiente no Rio Grande do Norte Período 1992-2003

This analysis on the ambient licensing is based on a research that identifies the fragilities and advances of the application of this instrument of politics of the environment in the ambient politics of the Rio Grande do Norte, in the period of 1992 the 2003. The isolated urban area of Búzios, situated in the City of Nísia Floresta/RN, situated in the eastern coast of the State, where concentrates the boarding of the ambient question as a matter in the Brazilian process of urbanization, over all the institutionalization and implementation of the ambient licensing. They are distinguished in the used methodology in consultation to the diverse involved social segments with the ambient subject in study, the example of the managers, technician and specialists, as well as the application of the legislation and norms techniques, the forms of appropriation of the common wealth and the procedures of ambient licensing of the competent agencies. The results of the research designate that the ambient licensing while instrument of the ambient politics is one of the alternatives more efficient as techniques in the process of sustainable development, since it is beyond the prerogatives to conciliate the activities and enterprises with the conservation of the environmental resources and natural benefits to the societies. In the RN one evidenced progress in the ambient legislation and the instructions techniques, and that the imperfections and limitations in the system of ambient licensing are not directly on to the instruments, but in the implementation of mechanisms of the ambient agencies. This because they do not make use of operational structure to apply in practical and established abilities, as an ambient management, institutional joint and deliberations of the State Counselor for Environment

Análise dos efeitos da legislação urbanística na formação e crescimento do Bairro de Lagoa Nova: planos diretores de 1974, 1984 e 1994

To Analyze the Managing Plans of Natal in the decades of 1970, 1980 and 1990, identifying elements that had contributed for the growth of the Lagoa Nova quarter, capital one of the Rio Grande do Norte state. Ahead of the sped up growth of the urban centers, many times is not given to analyze which law had taken care of to its objective, and which the imperfections that had appeared during the application of these laws. To make the comparisons in you square them chosen at there distantinct times made possible to analyze the form as the ground of Lagoa Nova absorbed the proposals laws.Therefore toanalyze influences it of the Managing Plans, to make comparatives analyses between the urbanistics condicion, made possible to understand that the fabric urban of the quarter of Lagoa Nova is a true granary of information that it makes possible to the dedicated ones to the urban studies, a true field of analysis

Possibilities of advanced MAG-welding processes in shipbuilding

In shipbuilding industry welding of primer coated and tack welded steel products cause different issues. Primer coated steel products are commonly used at shipyards to ensure corrosion free storage of products in outdoor conditions. However usage of primer can cause imperfections to welds. To prevent porosity primed steel products are usually welded with tubular welding wires. Tack welds cause commonly interferences in mechanized welding when over welded, which increases costs related to welding due to increased need of preparing and repairing. The aim of this study is to research possibilities of advanced solid wire MAG-welding processes to deal with these two previously mentioned problems. This study concentrates to examine possibilities of MAG-welding, pulse MAG-welding, double pulse MAG-welding, RapidArc and ForceArc processes. Large amount of experiments were made to find out the produced porosity and the ability to over weld tack welds with each process in different circumstances. In welding of primed steel products porosity is caused mainly by hydrogen, CO, CO2, nitrous gases and zinc fumes. It was found in experiments that porosity of MAG-welding can be greatly decreased by using pulse MAG-welding instead. Also reduction of welding speed, usage of air gap and usage of solid wire product with higher amount of alloying elements reduces porosity. Researched advanced MAG-welding processes did not have an improvement into over welding of tack welds. With studied throat thicknesses and welding positions conventional MAG-welding managed better over welding of tack welds than the four studied advanced MAG-welding processes. Studied solid wire MAG-welding processes would be best suited at shipyard for mechanized welding in welding position PB. In welding positions PD and PG tubular welding wires are clearly more productive.

A noise simulator for eLISA: Migrating LISA Pathfinder knowledge to the eLISA mission

We present a new technical simulator for the eLISA mission, based on state space modeling techniques and developed in MATLAB. This simulator computes the coordinate and velocity over time of each body involved in the constellation, i.e. the spacecraft and its test masses, taking into account the different disturbances and actuations. This allows studying the contribution of instrumental noises and system imperfections on the residual acceleration applied on the TMs, the latter reflecting the performance of the achieved free-fall along the sensitive axis. A preliminary version of the results is presented.

Effect of Geometric Uncertainties on the Aerodynamic Characteristic of Offshore Wind Turbine Blades

Offshore wind turbines operate in a complex unsteady flow environment which causes unsteady aerodynamic loads. The unsteady flow environment is characterized by a high degree of uncertainty. In addition, geometry variations and material imperfections also cause uncertainties in the design process. Probabilistic design methods consider these uncertainties in order to reach acceptable reliability and safety levels for offshore wind turbines. Variations of the rotor blade geometry influence the aerodynamic loads which also affect the reliability of other wind turbine components. Therefore, the present paper is dealing with geometric uncertainties of the rotor blades. These can arise from manufacturing tolerances and operational wear of the blades. First, the effect of geometry variations of wind turbine airfoils on the lift and drag coefficients are investigated using a Latin hypercube sampling. Then, the resulting effects on the performance and the blade loads of an offshore wind turbine are analyzed. The variations of the airfoil geometry lead to a significant scatter of the lift and drag coefficients which also affects the damage-equivalent flapwise bending moments. In contrast to that, the effects on the power and the annual energy production are almost negligible with regard to the assumptions made.

Influence of applied uniaxial stress upon the ultraviolet absorption bands in KBr and KI

The influence of uniaxial stress upon three types of imperfections occurring in the alkali halide crystal lattice has been investigated. The imperfections are the interstitial atom, the interstitial ion, and the negative ion vacancy. The interstitial atom, or H center, is a paraelastic defect which assumes a preferential crystal orientation in the field of an external mechanical stress. From the results of the reorientation kinetics - studies, it was possible to show that H centers are not stable in the KBr crystal lattice above 2SoK. At temperatures higher than 2SoK, the H centers are transformed into two new paraelastic defects, H(ii) and H(iii), possessing the same optical absorption band as the H center but differing both from the H' center and from each other in their reorientation kinetics. A study of the wavelength dependence of the H, H(ii), and VI (Na+) centers s~owed the 'existence of three similar-polarized transitions for each of these defects. One of these transitions, located at 230 run for all of the defects studied, was determined to be too high in energy to be explained by the simple X2 - level scheme. In addition, a comparison of various properties of the four defects indicates that the last three can be described as perturbed H centers. Dichroism measurements, performed as a function of temperature and wavelengt, h on the 230-nm I band in KBr, showed this band to be a composite of a band at 234 nm due to the I center and a band at 230 nm attributed to the H center. The I center dichroism was isolated and was observed under various experimental conditions. The results of these observations are consistent with a body-centered model for the I center in which the I-center absorption band is attributed to the excitation of a p-like electron on the interstitial Br- ion. Similar measurements were also perfonned on the a band in KI. The a-band dichroism measurements were found to be consistent with an electronic transition from an s-like ground state to a p-like excited state, indicating that the a center is best described as a quasi-molecule.

O processo de adopção em crianças adoptadas tardiamente

Dissertação de Mestrado apresentada ao ISPA - Instituto Universitário

Autoavaliação institucional na dimensão do SINAES comunicação com a sociedade : estudo de múltiplos casos em instituições de ensino superior do Rio Grande do Norte

This study is about the institutional self-evaluation in Dimension 4, "Communication with Society", from the National System of Higher Education Evaluation SINAES, mandatory for all universities in Brazil. A multiple cases study was conducted with three institutions from Rio Grande do Norte, and the goal was to know how this evaluation is made, describing the concept for the evaluation of communication proposed by them, identifying controllers or emancipator aspects, categorizing methodological procedures and discussing the difficulties reported in the communication evaluation process. Coordinators of the institutions Evaluating Committees were interviewed and data categorized by means of qualitative content analysis. It was noted characteristics of the current controller, emancipator and hybrid designs in the three institutions for evaluation of communication, revealing the lack of a theoretical corpus that transits in accordance with the systemic perspective and epistemology of complexity from SINAES. It was found that the most frequently reported difficulties in the evaluation processes of communication are in the preparation stage, especially in the definition of indicators and tools and awareness work. The weakness in planning makes their own activities in the sector of communication become targets of assessment, forming goals poorly related with broader organizational goals. It was also concluded that the technical evaluation cannot override the issues associated with the broader issue of the complexity surrounding the assessment paradigm proposed by SINAES because contradictions and imperfections are part of the evaluation process and several references are current in the literature to support this view. Finally, it is said that objectives such as transparency and behavioral changes can rely on methodologies and techniques for research on the question of the construction of meaning

Análise mecânica e microestrutural das ligas de cobalto-cromo de uso odontológico após sucessivas refundições

The cobalt-chromium alloy is extensively used in the Odontology for the confection of metallic scaffolding in partial removable denture. During the last few years, it has been reported an increasing number of premature imperfections, with a few months of prosthesis use. The manufacture of these components is made in prosthetic laboratories and normally involves recasting, using parts of casting alloy and parts of virgin alloy. Therefore, the objective of the present study was to analyze the mechanical properties of a commercial cobalt-chromium alloy of odontological use after successive recasting, searching information to guide the dental prosthesis laboratories in the correct manipulation of the cobalt-chromium alloy in the process of casting and the possible limits of recasting in the mechanical properties of this material. Seven sample groups were confectioned, each one containing five test bodies, divided in the following way: G1: casting only with virgin alloy; G2: casting with 50% of the alloy of the G1 + 50% of virgin alloy; G3: casting with 50% of the alloy of the G2 + 50% of virgin alloy; G4: casting with 50% of the alloy of the G3 + 50% of virgin alloy; G5: 50% of alloy of the G4 + 50% of virgin alloy; G6: 50% of alloy of the G5 + 50% of virgin alloy and finally the G7, only with recasting alloy. The modifications in the mechanical behavior of the alloy were evaluated. Moreover, it was carried the micro structural characterization of the material by optic and electronic scanning microscopy, and X ray diffraction.and fluorescence looking into the correlatation of the mechanical alterations with structural modifications of the material caused by successive recasting process. Generally the results showed alterations in the fracture energy of the alloy after successive recasting, resulting mainly of the increasing presence of pores and large voids, characteristic of the casting material. Thus, the interpretation of the results showed that the material did not reveal significant differences with respect to the tensile strength or elastic limit, as a function of successive recasting. The elastic modulus increased from the third recasting cycle on, indicating that the material can be recast only twice. The fracture energy of the material decreased, as the number of recasting cycles increased. With respect to the microhardness, the statistical analyses showedno significant differences. Electronic scanning microscopy revealed the presence of imperfections and defects, resulting of the recasting process. X ray diffraction and fluorescence did not show alterations in the composition of the alloy or the formation of crystalline phases between the analyzed groups. The optical micrographs showed an increasing number of voids and porosity as the material was recast. Therefore, the general conclusion of this study is that the successive recasting of of Co-Cr alloys affects the mechanical properties of the material, consequently leading to the failure of the prosthetic work. Based on the results, the best recommendadition is that the use of the material should be limited to two recasting cycles

An analysis of the effects of preferential trade policies through the estimation of quantitative models: the case of Portugal.

Doutoramento em Economia.