Genesis and Propagation of Fractal Structures During Photoelectrochemical Etching of n-Silicon

The genesis, propagation, and dimensions of fractal-etch patterns that form anodically on front- or back-illuminated n-Si(100) photoelectrodes in contact with 11.9 M NH₄F(aq) has been investigated during either linear-sweep voltammetry or when the electrode was held at a constant potential (E = +6.0 V versus Ag/AgCl). Optical images collected in situ during electrochemical experiments revealed the location and underlying mechanism of initiation and propagation of the structures on the surface. X-ray photoelectron spectroscopic (XPS) data collected for samples emersed from the electrolyte at varied times provided detailed information about the chemistry of the surface during fractal etching. The fractal structure was strongly influenced by the orientation of the crystalline Si sample. The etch patterns were initially generated at points along the circumference of bubbles that formed upon immersion of n-Si(100) samples in the electrolyte, most likely due to the electrochemical and electronic isolation of areas beneath bubbles. XPS data showed the presence of a tensile-stressed silicon surface throughout the etching process as well as the presence of SiO_xF_y on the surface. The two-dimensional fractal dimension D_(f,2D) of the patterns increased with etching time to a maximum observed value of D_(f,2D)=1.82. Promotion of fractal etching near etch masks that electrochemically and electronically isolated areas of the photoelectrode surface enabled the selective placement of highly branched structures at desired locations on an electrode surface

The Continuing of Organicism: An Enviro-organic Form Integrating to the Built Environment

Humans have engaged nature as an ideal paradigm of form and function since time immemorial. Within the organic paradigm, architecture may be seen to constitute an organic relationship with nature in any climatic, cultural and social condition. Though often rejected in canonical modern architecture, organic forms have been manifested, in various forms, and with different purposes. Recently, some modern organic movements have emerged, such as those following principles of biomorphic form and biomimicry. Unfortunately, these movements often fail to more fully embrace organicism in the totality and depth of their relationship to the natural. Following D‘Arcy Thompson‘s On Growth and Form, this research aims at uncovering the key attributes of natural form, in order to allow the design of enviro-organic form. Such form is defined as one that opens to the natural world, facilitating the making of architecture that sustains human life and nature today and in the future. In order to carry this out, the research offers graphic and analytic tools that help aid understanding into what organic architecture is, and how we can undertake a design process leading to enviro-organic form. The research concentrates on the analogies between architectural form and natural forms. The outcomes are, to paraphrase D‘Arcy Thompson, explained by the, “equilibrium resulting from the interaction or balance of forces.” Natural forms result from the fitness of the resolution of inside and outside living forces. Similarly, architectural organic form, as embodied in indigenous or vernacular architecture, result from integrating environmental and socio-cultural forces. Because architecture must adapt to cultural and social changes, human built environments are argued to be functionally more complex than those made by animals, as seen for example in a bird-nest, spider-web, or ant-hill. Since vernacular architecture is largely shaped by instinct, and in response to specific local place and culture, vernacular forms are not typically suited to be applied directly to the needs of contemporary culture. Geometry is proposed as the medium for historical examination of the incidental analogy between nature and organic architecture, for the rational fitness of integrating between natural principles and architecture disciplines, and for the selective transformation of enviro-organic forms that promise to more fully integrate the works of humans into the natural environment

The evaluation of bulbar redness grading scales

The use of grading scales is common in clinical practice and research settings. A number of grading scales are available to the practitioner, however, despite their frequent use, they are only poorly understood and may be criticised for a number of things such as the variability of the assessments or the inequality of scale steps within or between scales. Hence, the global aim of this thesis was to study the McMonnies/Chapman-Davies (MC-D), Institute for Eye Research (IER), Efron, and validated bulbar redness (VBR) grading scales in order to (1) get a better understanding and (2) attempt a cross-calibration of the scales. After verifying the accuracy and precision of the objective and subjective techniques to be used (chapter 3), a series of experiments was conducted. The specific aims of this thesis were as follows: • Chapter 4: To use physical attributes of redness to determine the accuracy of the four bulbar redness grading scales. • Chapter 5: To use psychophysical scaling to estimate the perceived redness of the four bulbar redness grading scales. • Chapter 6: To investigate the effect of using reference anchors when scaling the grading scale images, and to convert grades between scales. • Chapter 7: To grade bulbar redness using cross-calibrated versions of the MC-D, IER, Efron, and VBR grading scales. Methods: • Chapter 4: Two image processing metrics, fractal dimension (D) and % pixel coverage (% PC), as well as photometric chromaticity (u’) were selected as physical measures to describe and compare redness in the four bulbar redness grading scales. Pearson correlation coefficients were calculated between each set of image metrics and the reference image grades to determine the accuracy of the scales. • Chapter 5: Ten naïve observers were asked to arrange printed copies of modified versions of the reference images (showing vascular detail only) across a distance of 1.5m for which only start and end point were indicated by 0 and 100, respectively (non-anchored scaling). After completion of scaling, the position of each image was hypothesised to reflect its perceived bulbar redness. The averaged perceived redness (across observers) for each image was used for comparison to the physical attributes of redness as determined in chapter 4. • Chapter 6: The experimental setup from chapter 5 was modified by providing the reference images of the VBR scale as additional, unlabelled anchors for psychophysical scaling (anchored scaling). Averaged perceived redness from anchored scaling was compared to non-anchored scaling, and perceived redness from anchored scaling was used to cross-calibrate grades between scales. • Chapter 7: The modified reference images of each grading scale were positioned within the 0 to 100 range according to their averaged perceived redness from anchored scaling, one scale at a time. The same 10 observers who had participated in the scaling experiments were asked to represent perceived bulbar redness of 16 sample images by placing them, one at a time, relative to the reference images of each scale. Perceived redness was taken as the measured position of the placed image from 0 and was averaged across observers. Results: • Chapter 4: Correlations were high between reference image grades and all sets of objective metrics (all Pearson’s r’s≥0.88, p≤0.05); each physical attribute pointed to a different scale as being most accurate. Independent of the physical attribute used, there were wide discrepancies between scale grades, with sometimes little overlap of equivalent levels when comparing the scales. • Chapter 5: The perceived redness of the reference images within each scale was ordered as expected, but not all consecutive within-scale levels were rated as having different redness. Perceived redness of the reference images varied between scales, with different ranges of severity being covered by the images. The perceived redness was strongly associated with the physical attributes of the reference images. • Chapter 6: There were differences in perceived redness range and when comparing reference levels between scales. Anchored scaling resulted in an apparent shift to lower perceived redness for all but one reference image compared to non-anchored scaling, with the rank order of the 20 images for both procedures remaining fairly constant (Spearman’s ρ=0.99). • Chapter 7: Overall, perceived redness depended on the sample image and the reference scale used (RM ANOVA; p=0.0008); 6 of the 16 images had a perceived redness that was significantly different between at least two of the scales. Between-scale correlation coefficients of concordance (CCC) ranged from 0.93 (IER vs. Efron) to 0.98 (VBR vs. Efron). Between-scale coefficients of repeatability (COR) ranged from 5 units (IER vs. VBR) to 8 units (IER vs. Efron) for the 0 to 100 range. Conclusions: • Chapter 4: Despite the generally strong linear associations between the physical characteristics of reference images in each scale, the scales themselves are not inherently accurate and are too different to allow for cross-calibration based on physical redness attributes. • Chapter 5: Subjective estimates of redness are based on a combination of chromaticity and vessel-based components. Psychophysical scaling of perceived redness lends itself to being used to cross calibrate the four clinical scales. • Chapter 6: The re-scaling of the reference images with anchored scaling suggests that redness was assessed based on within-scale characteristics and not using absolute redness scores, a mechanism that may be referred to as clinical scale constancy. The perceived redness data allow practitioners to modify the grades of the scale they commonly use so that comparisons of grading estimates between calibrated scales may be made. • Chapter 7: The use of the newly calibrated reference grades showed close agreement between grading estimates of all scales. The between-scale variability was similar to the variability typically observed when a single scale is repeatedly used. Perceived redness appears to be dependent upon the dynamic range of the reference images of the scale. In conclusion, this research showed that there are physical and perceptual differences between the reference images of all scales. A cross-calibration of the scales based on the perceived redness of the reference images provides practitioners with an opportunity to compare grades across scales, which is of particular value in research settings or if the same patient is seen by multiple practitioners who are familiar with using different scales

Genesis and Propagation of Fractal Structures During Photoelectrochemical Etching of n-Silicon

The genesis, propagation, and dimensions of fractal-etch patterns that form anodically on front- or back-illuminated n-Si(100) photoelectrodes in contact with 11.9 M NH₄F(aq) has been investigated during either linear-sweep voltammetry or when the electrode was held at a constant potential (E = +6.0 V versus Ag/AgCl). Optical images collected in situ during electrochemical experiments revealed the location and underlying mechanism of initiation and propagation of the structures on the surface. X-ray photoelectron spectroscopic (XPS) data collected for samples emersed from the electrolyte at varied times provided detailed information about the chemistry of the surface during fractal etching. The fractal structure was strongly influenced by the orientation of the crystalline Si sample. The etch patterns were initially generated at points along the circumference of bubbles that formed upon immersion of n-Si(100) samples in the electrolyte, most likely due to the electrochemical and electronic isolation of areas beneath bubbles. XPS data showed the presence of a tensile-stressed silicon surface throughout the etching process as well as the presence of SiO_xF_y on the surface. The two-dimensional fractal dimension D_(f,2D) of the patterns increased with etching time to a maximum observed value of D_(f,2D)=1.82. Promotion of fractal etching near etch masks that electrochemically and electronically isolated areas of the photoelectrode surface enabled the selective placement of highly branched structures at desired locations on an electrode surface

A Bottom-Up Approach to Building an Artificial Cell by Self-Assembly

Synthetic biology is a rapidly growing field in which recent advances now allow the formation of minimal or artificial cells composed of a minimum number of components, capable of performing specific functions. New developments contributing to the complexity of artificial cells or making their design more cell-like increases the number of possible applications. To-date many processes and chemical reactions have been studied in these cells; many more remain to be explored. However, more sophisticated approaches to artificial cell design and preparation will be required to do this. The results presented here provide insights into how artificial cell development can contribute to our understanding of the self-assembly of biomolecules. The formation of lipid based vesicles is an inherent element of artificial cell development, which requires reliable techniques to prepare vesicles of cell size. The most widely applied methods have been evaluated here based on the size, quality and abundance of vesicles formed as well as the ease of encapsulating biological solutes. The effect of various lipid compositions, particularly cholesterol, has also been analysed. This comparison provides reliable information for tailoring the selection of experimental approach when building a model cell. Functionalisation of the artificial cell surface and its interior is required for many applications. For surface modification, there is growing interest in using glycolipids to fulfil a molecular recognition role. A synthetic glycolipid has been incorporated into the phospholipid membrane of giant unilamellar vesicles at biologically relevant concentrations. The synthetic glycolipid shows concentration-dependent phase behaviour in binary mixtures with DOPC and in ternary mixtures with DOPC and cholesterol. At low concentrations, the glycolipid is fully dispersed in the GUV membrane. At concentrations above 10%, the formation of lipid tubules was observed, consistent with the formation of a columnar lipid phase. Lipid tubules are observed in aqueous and oil solvents, suggesting that both hexagonal and inverted hexagonal lipid arrangements can be formed. The self- assembly of proteins in cells is required for normal biological function and unintended self-assembly also can occur following a change in environmental conditions, in some cases leading to disease. To understand these processes more fully, experiments performed in controlled, but closer to physiological conditions are required. Artificial cells provide an idea platform to do this. Bovine Serum Albumin (BSA) was encapsulated in phospholipid based giant unilamellar vesicles of cell size. The formation of aggregates within the GUV was analysed using a fluorescent dye (Thioflavin T) and various modes of microscopy. While protein aggregation was observed inside the vesicles, harsh environmental conditions were required to induce this aggregation (e.g.heat, low pH). An approach to investigate protein condensation upon in-situ expression in physiologically relevant conditions was also explored. In this case, a protein that aggregates at physiological temperature and pH (the P23T mutant of human gamma D crystallin) was expressed in-situ inside a GUV using a cell-free expression system. The formation of P23T specific aggregates was observed after incubation for several hours at 37°C. These aggregates have a fractal dimension lower than those normally observed for amorphous protein aggregate. Furthermore, we have demonstrated that the self-assembly of P23T can also be induced following transfection in mammalian cells, providing deeper insights into the mechanism by which the genetic cataract associated with this mutation occurs

Atlas of sensations - on sensibilities in a computational design practice

The driving force behind the body of work of SPAN is defined by the application of advanced computational design methodologies. This dissertation can be understood as a cartography (in the best tradition of an atlas) of the work of the practice from its founding year 2003 until 2017 - a period profoundly shaped by the progress made in technological advances. These technological means allow SPAN to discuss architectural project through a series of different lenses such as conceptualization, planning, fabrication to the maintenance of the designed objects, through the use of emerging technical opportunities wither this be the interrogation of novel geometries (Blocks, Ore, Barcelona Recursion), computational methods of rationalization (Expo Façade) or advanced methods of fabrication (Robots, as for example in Plato's Columns). In a parallel move between the necessities and desires of the practice and the ambitious studios and seminars in academia, novel toolsets and design concepts are developed to address contemporary architectural problems. These areas can be understood as different territories of interrogation, forming a landscape of opportunities, or as we describe it internally in our office: a design ecology. The interrogation of these distinct territories, and the unique way in which SPAN assembles those various elements to something larger than its parts, is what constitutes part of SPAN's contribution to the discipline. Apart from projects and visual work, SPAN´s contribution to discourse started early with papers to conferences such as IASS (International Association for Shell and Spatial Structures) in 2007, Design Modeling Symposium in 2008, and ACADIA (Association for Computer Aided Design in Architecture) in 2008, which included ideas such as the application of tissue engineering in architecture, aspects of artifact and affect, fabrication, and considerations on architectural details in complex curved geometries. Within the Atlas of Sensations, a second ecology is defined by the contribution to the paradigm shift in the discourse from the continuous to the hyper-articulated surface, which contains an additional level of information. A surface, which describes architectural properties through the deep pochés, folds, joints, niches, and arches it generates.  The question is: How does this shift in the conception of architecture affect the qualities of the design, and by extension the context these objects construct? To further investigate this question the work focuses on one part of the practice's design ecology: design sensibilities. In order to interrogate this question, the presented work observes these moments in SPAN's practice through the lens of geometrical properties. Ultimately resulting in thoughts on Postdigital design ecologies that discuss aspects of design agency in our contemporary age

Approaches to the Use of Geometry in Architecture: A study of the works of Andrea Palladio, Frank Lloyd Wright, and Frank Gehry

Geometry deals with form, shape, and measurement and is a part of mathematics where visual thought is dominant. Both design and construction in architecture deal with visualization, and architects constantly employ geometry. Today, with the advent of computer software, architects can visualize forms that go beyond our everyday experience. Some architects claim that the complex forms of their works have correlations with non-Euclidean geometry, but the space we experience is still Euclidean. Given this context, I have explored possible correlations that might exist between mathematical concepts of geometry and the employment of geometry in architectural design from a historic perspective. The main focus will be to describe the two phenomena historically, and then investigate any connections that might emerge from the discussion. While discussing the way geometry has been approached in architecture, I have focused on the Renaissance, Modern, and Post-modern phases as they have a distinct style and expression. Andrea Palladio, Frank Lloyd Wright, and Frank Gehry's works will be case studies for the Renaissance, Modern, and Post-modern phases respectively. One of the important conclusions of this study is that architects use geometry in a more subconscious and intuitive manner while designing. Certain approaches to geometry can be determined by the way an architect deals with form and space. From the discussions of the works of Palladio, Wright, and Gehry, it can be concluded that from a two-dimensional simple approach to form and space in architecture, there has been a development of thinking about complex forms three dimensionally. Similarly, in mathematics, geometry has developed from a two-dimensional and abstract description of our surroundings to something that can capture the complex and specific nature of a phenomena. It is also shown that architects rarely come up with new concepts of geometry. Significant developments in geometry have always been in the domain of mathematics. Hence, most correlations between geometry in architecture and geometry in mathematics develop much later than the introduction of those concepts of geometry in mathematics. It is also found that the use of Euclidean geometry persists in architecture and that later concepts like non-Euclidean geometry cannot be used in an instrumental manner in architecture

Rethinking urban lighting: geographies of artificial lighting in everyday life

PhDIn this thesis I study the role of artificial lighting in the everyday urban life of older residents living in the London Borough of Newham. Newham’s light infrastructure is currently undergoing change as the borough’s entire 19,000 street lamps are being re-placed with Light Emitting Diodes and as a range of regeneration projects provide public spaces designed with new lighting. By increasing visibility and encouraging everyday activity into the evening, the Council claims that the changes in public light-ing will provide ‘eyes on the streets’ and encourage ‘eyes from the windows’ of build-ings, contributing to increasing ‘natural surveillance’. The Council’s avowal of every-day practices in streets and in homes, has made me question how lighting affects the way older residents move through streets and carry out domestic practices as dark-ness falls. The study explores how light planning, lighting design and everyday, rou-tine practices in the public realm and inside homes co-produce the urban, lit environ-ment. Two major contributions of the thesis lie in the (post)phenomenological ap-proach I develop to study everyday experiences of urban lighting, and the methodo-logical framework I employ to research such practices, which combines mobile and visual methods. I have conducted 11 in-depth interviews with nine different planners and designers, 12 walk-along interviews with 22 residents between 58 and 79 years old, and a collaborative photography project with 14 residents between 68 and 96 years old. As I show how older residents experiences different lighting technologies, layers of light, and different lit spaces in their neighbourhoods, I discuss how urban lighting makes them see, feel and carry out routine practices in particular ways. Based on my findings, I argue that urban lighting shapes what, and how, people see, but how people see depends on how they negotiate changes in lighting. In a range of examples where residents mould the urban, lit environment or respond to lighting in different ways, I show how they play and active part in co-producing ways of seeing. I argue it is crucial that light planners and lighting designers recognise such co-constitutive role of everyday practices in order to ensure better lighting for our future cities

The herd moves? Emergence and self-organization in collective actors?

The puzzle about collective actors is in the focus of this contribution. The first section enters into the question of the adequateness and inadequateness of reductionist explanations for the description of entities. The considerations in this part do not draw on systems and hence not on principles of self-organisation, because this concept necessitates a systemic view. In other words, the first section discusses reductionism and holism on a very general level. The scope of these arguments goes far beyond self-organising systems. Pragmatically, these arguments will be discussed within the domain of corporative actors. Emergence is a concept embedded in system theory. Therefore, in the second part the previous general considerations about holism are integrated with respect to the concept “emergence”. In order to close the argument by exactly characterising self-organising systems and giving the conceptual link between self-organisation and emergence – which is done in the section four – the third section generally conceptualises systems. This conceptualisation is independent of whether these systems are self-organising or not. Feedback loops are specified as an essential component of systems. They establish the essential precondition of system-theoretic models where causes may also be effects and vice versa. System-theory is essential for dynamic models like ecological models and network thinking. In the fourth part mathematical chaos-theory bridges the gap between the presentation of systems in general and the constricted consideration of self-organising systems. The capability to behave or react chaotically is a necessary precondition of self-organisation. Nevertheless, there are striking differences in the answers given from theories of self-organisation in biology, economics or sociology on the question “What makes the whole more than the sum of its parts?” The fracture seems particularly salient at the borderline between formal-mathematical sciences like natural sciences including economy and other social sciences like sociology, for instance in the understanding and conceptualisation of “chaos” or “complexity”. Sometimes it creates the impression that originally well defined concepts from mathematics and natural science are metaphorically used in social sciences. This is a further reason why this paper concentrates on conceptualisations of self-organisation from natural sciences. The fifth part integrates the arguments from a system-theoretic point of view given in the three previous sections with respect to collective and corporative actors. Due to his prominence all five sections sometimes deal with the sociological system theory by Niklas Luhmann, especially in those parts with rigorous and important differences between his conception and the view given in this text. Despite Luhmann’s undoubted prominence in sociology, the present text strives for a more analytical and formal understanding of social systems and tries to find a base for another methodological approach.