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Antenna-pattern measurements obtained from a double-metal supra-terahertz-frequency (supra-THz) quantum cascade laser (QCL) are presented. The QCL is mounted within a mechanically micro-machined waveguide cavity containing dual diagonal feedhorns. Operating in continuous-wave mode at 3.5 THz, and at an ambient temperature of ~60 K, QCL emission has been directed via the feedhorns to a supra-THz detector mounted on a multi-axis linear scanner. Comparison of simulated and measured far-field antenna patterns shows an excellent degree of correlation between beamwidth (full-width-half-maximum) and sidelobe content and a very substantial improvement when compared with unmounted devices. Additionally, a single output has been used to successfully illuminate and demonstrate an optical breadboard arrangement associated with a future supra-THz Earth observation space-borne payload. Our novel device has therefore provided a valuable demonstration of the effectiveness of supra-THz diagonal feedhorns and QCL devices for future space-borne ultra-high-frequency Earth-observing heterodyne radiometers.
Analyzing audiovisual communication is challenging because its content is highly symbolic and less rule-governed than verbal material. But audiovisual messages are important to understand: they amplify, enrich, and complicate the meaning of textual information. We describe a fully-reproducible approach to analyzing video content using minimally—but systematically—trained online workers. By aggregating the work of multiple coders, we achieve reliability, validity, and costs that equal those of traditional, intensively trained research assistants, with much greater speed, transparency, and replicability. We argue that measurement strategies relying on the “wisdom of the crowd” provide unique advantages for researchers analyzing complex and intricate audiovisual political content.
Evolutionary economics sees the economy as always in motion with change being driven largely by continuing innovation. This approach to economics, heavily influenced by the work of Joseph Schumpeter, saw a revival as an alternative way of thinking about economic advancement as a result of Richard Nelson and Sidney Winter's seminal book, An Evolutionary Theory of Economic Change, first published in 1982. In this long-awaited follow-up, Nelson is joined by leading figures in the field of evolutionary economics, reviewing in detail how this perspective has been manifest in various areas of economic inquiry where evolutionary economists have been active. Providing the perfect overview for interested economists and social scientists, readers will learn how in each of the diverse fields featured, evolutionary economics has enabled an improved understanding of how and why economic progress occurs.
There is now a clear focus on incorporating, and integrating, multiple levels of analysis in developmental science. The current study adds to research in this area by including markers of the immune and neuroendocrine systems in a longitudinal study of temperament in infants. Observational and parent-reported ratings of infant temperament, serum markers of the innate immune system, and cortisol reactivity from repeated salivary collections were examined in a sample of 123 infants who were assessed at 6 months and again when they were, on average, 17 months old. Blood from venipuncture was collected for analyses of nine select innate immune cytokines; salivary cortisol collected prior to and 15 min and 30 min following a physical exam including blood draw was used as an index of neuroendocrine functioning. Analyses indicated fairly minimal significant associations between biological markers and temperament at 6 months. However, by 17 months of age, we found reliable and nonoverlapping associations between observed fearful temperament and biological markers of the immune and neuroendocrine systems. The findings provide some of the earliest evidence of robust biological correlates of fear behavior with the immune system, and identify possible immune and neuroendocrine mechanisms for understanding the origins of behavioral development.
The motion of two small bodies orbiting each other whose barycenter is orbiting around a massive body is studied. The equations of motion are integrated considering the secular part of the disturbing function.
Research organizations face challenges in creating infrastructures that cultivates and sustains interdisciplinary team science. The objective of this paper is to identify structural elements of organizations and training that promote team science.
We qualitatively analyzed the National Institutes of Health’s Building Interdisciplinary Research Careers in Women’s Health, K12 using organizational psychology and team science theories to identify organizational design factors for successful team science and training.
Seven key design elements support team science: (1) semiformal meta-organizational structure, (2) shared context and goals, (3) formal evaluation processes, (4) meetings to promote communication, (5) role clarity in mentoring, (6) building interpersonal competencies among faculty and trainees, and (7) designing promotion and tenure and other organizational processes to support interdisciplinary team science.
This application of theory to a long-standing and successful program provides important foundational elements for programs and institutions to consider in promoting team science.
This chapter presents a “history-friendly” model of the evolution of the pharmaceutical industry, and in particular of the so-called golden age. This industry is an ideal subject for such an analysis, especially because it has characteristics and problems that provide both contrasts and similarities with the computer industry. Like computers, the pharmaceutical industry has traditionally been a highly R&D and marketing-intensive sector and it has undergone a series of radical technological and institutional “shocks.” However, despite these shocks, the core of the leading innovative firms and countries has remained stable for a very long period of time. Entry by new firms has been a rather rare occurrence until the advent of biotechnology. However, while the evolution of computers coincides largely with the history of very few firms, that of pharmaceuticals involves at least a couple of dozens of companies. Further, the degree of concentration has been consistently low at the aggregate level and the industry has never experienced a shakeout of producers.
We argue that the observed patterns of the evolutionary dynamics were shaped by three main factors, related both to the nature of the relevant technological regime and the structure of demand:
(1) The nature of the process of drug discovery, in terms of the properties of the space of technological opportunities and of the search procedures by which firms explore it. Specifically, innovation processes were characterized for a long time by “quasi-random” search procedures (random screening), with little positive spillovers from one discovery to the next (low cumulativeness).
(2) The type of competition and the role of patents and imitation in shaping gains from innovation. Patents gave temporary monopoly power to the innovator, but competition remained strong nevertheless, sustained by processes of “inventing around” and – after a patent expires – by imitation.
(3) The fragmented nature of the relevant markets. The industry comprises many independent submarkets, which correspond broadly to different therapeutic classes. For example, cardiovascular products do not compete with antidepressants. And, given the quasi-random nature of the innovative process, innovation in one therapeutic class typically does little to enhance innovation opportunities in other markets.
This book is about technological progress and its relationships with competition and the evolution of industry structures. It presents a new approach to the analysis of these issues, which we have labeled “history-friendly” modeling. This research stream began more than a decade ago and various papers have been published over the years. Here, we build on those initial efforts to develop a comprehensive and integrated framework for a systematic analysis of innovation and industry evolution.
The relationships among technological change, competition and industry evolution are old and central questions in industrial economics and the economics of innovation, a subject matter that dates back to Marshall and of course to Schumpeter. We authors are indeed Schumpeterians in that we believe the hallmark feature of modern capitalism is that it induces, even compels, firms to be innovative in industries where technological opportunities exist and customers are responsive to new or improved products. The evolution of these industries – like computers or semiconductors – is often characterized by the emergence of a monopolist or of a few dominant firms. The speed at which concentration develops varies drastically, however, across sectors and over time, and, often, monopoly power is not durable. In other significant industries – e.g. pharmaceuticals – no firm actually succeeded in achieving such an undisputed leadership. In some cases, the characteristic drift toward concentration is interrupted by significant exogenous change, such as new technologies appearing from outside the sector.
Long ago, Schumpeter proposed that the turning-over of industrial leadership was a common feature in industries where technological innovation was an important vehicle of competition. In recent years economists studying technological change have come to recognize a number of other important connections between the evolution of technologies and the dynamics of industries’ structure. Progress in this area has come from different sources. The availability of large longitudinal databases at a very high level of disaggregation has allowed researchers to unveil robust stylized facts in industrial dynamics and to conduct thorough statistical analyses, which show strong inter-industry regularities, but also deep and persistent heterogeneity across and within industries. New sophisticated models have been created that attempt to explain the regularities.
The formal representation of the history-friendly models presented some notable issues, first of all because of the huge amount of variables and parameters defining the models: some of these elements were common or at least analogous across the models, while others referred to completely different domains. In order to reduce the number of the main symbols to a manageable size, we adapted from computer programming languages the idea of overloading notation: a main symbol can have slightly different meanings according to the presence or absence of further details, such as superscripts and subscripts. For example, the symbol T indicates the total number of periods of a simulation, Tk indicates the period of introduction of technology k, and TI the minimum number of periods a firm has to stay integrated after its decision to switch to internal production of components. In general, we use as subscripts the indices for elements (products, firms, markets, technologies) that take different values, without changing the meaning of the main symbol. Instead, we use as superscripts further identifiers of the main symbols that are not instances of a general category: for example, PT is the symbol of patents and E is the symbol of exit. In a very limited number of cases an identifier can be used both as a subscript identifier (TR and MP in most of the cases are used as instances of component technology k) and as a superscript identifier (TR and MP are used as superscripts of the main symbol α, as they refer to different parts of the same equation).
Upper and lowercase letters are considered as different, although whenever it is possible they take related meanings: for example, i indicates the propensity to integrate and I the corresponding probability. The symbols used for specific variables and parameters are not used across models, unless these variables and parameters have the same or a very similar meaning and role in the different models. The values that parameters take and the range of values that heterogeneous parameters and variables can take are indicated in the tables in the Appendices.
As we reach the end of our explorations, it is instructive to look back at the assessment of formal modeling that Alfred Marshall offered many years ago:
It would be possible to extend the scope of such systems of equations as we have been considering … But while a mathematical illustration of the mode of action of a definite set of causes may be complete in itself, and strictly accurate within its clearly defined limits, it is otherwise with any attempt to grasp the whole of a complex problem of real life, or even any considerable part of it, in a series of equations. For many important considerations, especially those connected with the manifold influences of the element of time, do not lend themselves to mathematical expression; they must either be omitted altogether, or clipped and pruned till they resemble the conventional birds and animals of decorative art. And hence arises a tendency to assigning wrong portions to economic forces; those elements being most emphasized which lend themselves most easily to analytical methods.
(Marshall, 1890, p. 850)
We have been concerned in this book with grasping the decidedly complex real-life problems of innovation and industrial evolution. We have sought to capture in our dynamic models at least some of those “manifold influences of the element of time” of which Marshall spoke – though, of course, we do not make much progress on the full list. In choosing the “influences” to emphasize, we have tried in particular to bring to the fore the mechanisms that shape outcomes in ways that, while highlighted in many appreciative accounts of technological and industrial dynamics, are quite often ignored in highly stylized, static models. These are mechanisms that, first of all, take some time to operate. They also tend to involve substantial momentum effects, and path dependence. That our models reflect those mechanisms and aspects forms the foundation of their claim to being called “history-friendly models.” They portray the dynamic features of real economic causation, as described in empirical studies.
The constraints on mathematical analysis have obviously been relaxed a good deal since Marshall was turning out the successive editions of his Principles, roughly a century ago.