A new SOLT calibration method for leaky on-wafer measurements using a 10-term error model

We present a new Short-Open-Load-Thru (SOLT) calibration method for on-wafer S-parameter measurements. The new calibration method is based on a 10-term error model which is a simplified version of the 16-term error model. Compared with the latter, the former ignores all signal leakages except the ones between the probes. Experimental results show that this is valid for modern vector network analyzers (VNA). The advantage of using this 10-term error model is that the exact values of all error terms can be obtained by using the same calibration standards as the conventional SOLT method. This avoids not only the singularity problem with approximate methods, such as least squares, but also the usage of additional calibration standards. In this paper, we first demonstrate how the 10-term error model is developed and then the experimental verification of the theory is given. Finally, a practical application of the error model using a 10 dB attenuator from 140 GHz to 220 GHz is presented. Compared with the conventional SOLT calibration method without crosstalk corrections, the new method shows approximately 1 dB improvement in the transmission coefficients of the attenuator at 220 GHz

Landscaping Helen Frankenthaler

There is no abstract art. You must always start with something. Afterward you can remove all traces of reality. There’s no danger then, anyway, because the idea of the object will have left an indelible mark. It is what started the artist off, excited his ideas, and stirred up his emotions. Ideas and emotions will in the end be prisoners in his work. Whatever they do, they can’t escape from the picture. They form an integral part of it, even when their presence is no longer discernible. — Picasso1 Helen Frankenthaler is an Abstract Expressionist painter who seems to prove Picasso’s point of view. She is an Abstract Expressionist painter who employs the techniques of abstraction but with links to the recognizable— particularly to nature. She uses her emotions, aesthetic sense, experiences and artistic training to paint large abstract canvases. Frankenthaler’s abstractions are not meaningless shapes or random paint strokes. Her paintings have a strong link to other sources and inspirations. Helen Frankenthaler uses abstraction and landscape in combination to achieve deeper meanings. However, her paintings are not replications of the natural world. They can be considered “interior landscapes.” Frankenthaler does not consciously begin to paint a landscape, but she allows her thoughts and feelings to guide her work, pouring paint onto a canvas spread on the floor. With this technique Frankenthaler creates environments of paint. Many, if not most, of Frankenthaler’s paintings prove her tie between abstraction and landscape. Mountains and Sea of 1952 is Frankenthaler’s most famous work, and the watershed work from which the rest of her career began. It is not only the work in which she first used her renowned innovation, stain painting, it is also a prime example of her abstract landscapes. Frankenthaler would continue to resolve the apparent dichotomy between landscape and abstraction in the majority of her canvases from 1952 to the present day. This study will consider a selection of works from the 1950s, 1960s, and 1970s, to demonstrate this theme in the work of Helen Frankenthaler. 1 Christian Zervos, “Conversation avec Picasso,” Cahiers d’Art (Paris), 1935. Reprinted in Dore Ashton, Picasso on Art: A Selection of Views in The Documents of 20th-Century Art (Harmondsworth, UK and New York: Penguin Books, Ltd., 1972; rpt. 1977), p. 64

An active interferometric method for extreme impedance on-wafer device measurements

Nano-scale devices and high-power transistors present extreme impedances, which are far removed from the 50-Ω reference impedance of conventional test equipment, resulting in a reduction in the measurement sensitivity as compared with impedances close to the reference impedance. This letter describes a novel method based on active interferometry to increase the measurement sensitivity of a vector network analyzer for measuring such extreme impedances, using only a single coupler. The theory of the method is explained with supporting simulation. An interferometry-based method is demonstrated for the first time with on-wafer measurements, resulting in an improved measurement sensitivity for extreme impedance device characterization of up to 9%

Entorhinal cortex dysfunction in rodent models of dementia

As both the major input and output of the hippocampal formation, the entorhinal cortex (EC) occupies a pivotal position in the medial temporal lobe. The discovery of grid cells in the medial entorhinal cortex (mEC) has led to this region being widely implicated in spatial information processing. Importantly, the EC is also the first area affected by dementia pathology, with neurons appearing particularly susceptible to degeneration. Despite this, little is known about how pathology affects the functional output of mEC neurons, either in their ability to coordinate firing to produce network oscillations, or to represent information regarding the external environment. This thesis will use electrophysiological techniques to examine how dementia pathology contributes to the breakdown of mEC neuronal networks using the rTg4510 mouse model of tauopathy. The first 2 results chapters will show how the anatomical organisation along the dorso-ventral axis of the mEC has profound influence on the network activity that can be observed both in brain slices and awake-behaving mice. It will further show how deficits in network activity in rTg4510 mice occur differentially across this axis, with dorsal mEC appearing more vulnerable to changes in oscillatory function than ventral. The third results chapter will begin to explore the relationship between global network activity and the external environment, showing that rTg4510 mice display clear deficits in the relationship between oscillation properties and locomotor activity. Finally, the underlying basis for these changes will be examined, through the recording of single-unit activity in these mice. It will show a decreased tendency for mEC neurons to display firing rates modulated by running speed, as well as an almost complete breakdown of grid cell periodicity after periods of tau overexpression. Understanding how dementia pathology produces changes to neuronal function and ultimately cognition is key for understanding and treating the disease. This thesis will therefore provide novel insights into the dysfunction of the EC during dementia pathology

The Bauhaus Wall Painting Workshop: Mural Painting to Wallpapering, Art to Product

The wall painting workshop at the Bauhaus was established in fall 1919, the first semester of the famed and influential German school of art, architecture, and design. Over the course of the next thirteen years, the workshop experimented with many techniques, philosophies, and strategies for painting, coloring, and covering wall surfaces. This dissertation analyzes the evolving approaches of the Bauhaus wall painting workshop. Early Masters of Form, Oskar Schlemmer and Wassily Kandinsky, oversaw abstract and figurative murals like those developed for the 1923 Bauhaus exhibition, and the student wall painters used color to form and mold architectural spaces in, for example, Walter Gropius’s colored office and the experimental Haus am Horn. In 1924 Kandinsky identified color as the workshop’s medium, which was applied in a variety of approaches by the former students and later leaders of the workshop, Hinnerk Scheper and Alfred Arndt. Arndt’s painting scheme in Haus Auerbach and Scheper’s supervision of the coloration of the new Bauhaus Dessau school building are central to this dissertation and provide excellent examples of these two wall painters’ approaches and differing philosophies. In 1929, during Hannes Meyer’s directorship at the Bauhaus, a new opportunity arose for the workshop to design mass-produced wall color, which would enable color to be more efficiently, cheaply, and uniformly applied. Subsequently, Bauhaus wallpaper became the most profitable Bauhaus product and was quickly hanging on the walls of large housing estates and in retail stores throughout Germany. Murals, wall painting schemes, and wallpapers beyond the Bauhaus, in the architecture of, for example, Bruno Taut and Le Corbusier, provide comprehensive and international comparisons for the Bauhaus projects. This dissertation explores the many restored and recreated Bauhaus wall paintings, while addressing the frictions inherent in collaborations between architect and wall painter and the tension in merging color with architectural form at the Bauhaus

Emergence: Towards a Historiography of Canadian Defence Research during the Second World War

The Second World War forced Canada to become a nation with effective defence research assets, and these assets were among the nation's many contributions to victory in 1945. The historical literature on these developments has been slow to develop though it is now becoming an increasingly popular field of study. This premier historiography attempts to chart how and why the writings on Canada's defence research efforts during the Second World War have grown, its various forms of discourse, and its major themes, controversies, and deficiencies.La Seconde Guerre mondiale a obligé le Canada à se doter de capacités éprouvées de recherche en matière de défense, des capacités qui, avec de nombreux autres apports du Canada, ont d’ailleurs contribué à la victoire en 1945. Bien que des études historiques de ces questions aient pris du temps à démarrer, elles sont devenues de plus en plus populaires. Cette première historiographie vise à décrire comment et pourquoi des écrits sur les efforts de recherche de défense du Canada pendant la Seconde Guerre ont pris de l’ampleur, ainsi que leurs diverses formes de discours et leurs principaux thèmes, controverses et lacunes

Some two-dimensional markov processes

This thesis is primarily concerned with the mathematical analysis of some Markov processes which take place on a two-dimensional lattice of points in the first two chapters, mathematical models of two biological phenomena are considered, namely the competition for survival between two species, and the effect of an epidemic on a population. These models are obtained by a known method which permits certain random variations in the population sizes. For the model of the competition process, it is found that one of the species almost certainly becomes extinct, and the likelihood of the extinction of a given species is investigated. Also, the expectation of the the time-at which extinction occurs is bounded, irrespective of the initial state, and an estimate is made of the total number of births and deaths that occur before this time. For the epidemic model, it is found that the epidemic almost certainly dies out, and the expectation of the time at which this event first occurs is estimated when the initial population is large. Various questions on the eventual state of the population are also considered. In the third chapter, a class of recurrent two-dimensional random walks in discrete time is considered. A limiting law is found for the probability distribution of first passage times which is identical to the limiting law in the analogous situation for Brownien motion. The method is also applied to certain continuous time random walks and to certain random walks in three dimensions. The last problem considered is the distribution of points at which e simple unsymmetric discrete time random walk makes its first passage through the boundaries of the half and quarter planes. The limiting distribution is found to be a form of either normal distribution or stable distribution of order half

Evaluating the Effect of Using Precision Alignment Dowels on Connection Repeatability of Waveguide Devices at Frequencies from 750 GHz to 1.1 THz

This paper describes an investigation into the effects of using additional precision alignment dowel pins on the connection repeatability performance of waveguide interfaces at submillimeter-wave frequencies. The waveguide interface type that was used for this investigation is an adapted version of the `precision' UG-387 (i.e. based on the MIL-DTL-3922/67 design), manufactured by Virginia Diodes, Inc. The investigation was undertaken in the WM-250 waveguide band (i.e. at frequencies ranging from 750 GHz to 1.1 THz). Connection performance is compared with and without the use of added precision dowel pins in the inner dowel holes of this flange type. The repeatability of the measurements is assessed using statistical techniques, in terms of the experimental standard deviation in both the real and imaginary components of the complex-valued linear reflection coefficient