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Chemists have created molecular machines and switches with specific mechanical responses that were typically demonstrated in solution, where mechanically relevant motion is dissipated in the Brownian storm. The next challenge consists of designing specific mechanisms through which the action of individual molecules is transmitted to a supramolecular architecture, with a sense of directionality. Cellular microtubules are capable of meeting such a challenge. While their capacity to generate pushing forces by ratcheting growth is well known, conversely these versatile machines can also pull microscopic objects apart through a burst of their rigid tubular structure. One essential feature of this disassembling mechanism is the accumulation of strain in the tubules, which develops when tubulin dimers change shape, triggered by a hydrolysis event. We envision a strategy toward supramolecular machines generating directional pulling forces by harnessing the mechanically purposeful motion of molecular switches in supramolecular tubules. Here, we report on wholly synthetic, water-soluble, and chiral tubules that incorporate photoswitchable building blocks in their supramolecular architecture. Under illumination, these tubules display a nonlinear operation mode, by which light is transformed into units of strain by the shape changes of individual switches, until a threshold is reached and the tubules unleash the strain energy. The operation of this wholly synthetic and stripped-down system compares to the conformational wave by which cellular microtubules disassemble. Additionally, atomistic simulations provide molecular insight into how strain accumulates to induce destabilization. Our findings pave the way toward supramolecular machines that would photogenerate pulling forces, at the nanoscale and beyond.

A key goal of nanotechnology is the development of artificial machines capable of converting molecular movement into macroscopic work. Although conversion of light into shape changes has been reported and compared to artificial muscles, real applications require work against an external load. Here, we describe the design, synthesis and operation of spring-like materials capable of converting light energy into mechanical work at the macroscopic scale. These versatile materials consist of molecular switches embedded in liquid-crystalline polymer springs. In these springs, molecular movement is converted and amplified into controlled and reversible twisting motions. The springs display complex motion, which includes winding, unwinding and helix inversion, as dictated by their initial shape. Importantly, they can produce work by moving a macroscopic object and mimicking mechanical movements, such as those used by plant tendrils to help the plant access sunlight. These functional materials have potential applications in micromechanical systems, soft robotics and artificial muscles. Helices are found at every level of natural systems, where their dynamic potential is exploited to achieve a variety of functions. Here, liquid-crystalline molecular switches embedded in a polymer are used to prepare biomimetic spring-like materials that can convert molecular motion into macroscopic work.

Michael Porter (1990) declared that entrepreneurship is \"at the heart of national advantage.\" Edward Lazear (2002) more recently proclaimed that, \"the entrepreneur is the single most important player in a modern economy.\" Audretsch and Thurik (2001) explain that the shifting emphasis on entrepreneurship can be explained by comparative advantage that now lies in knowledge-based economic activities. This growing literature has presented local, state, and federal policy makers with a compelling way through entrepreneurship programs to gain back jobs lost to globalization and outsourcing (Audretsch et al., 2006). While the effects of entrepreneurs on growth have been studied, the benefits of cities for new firms is less researched. We consider how cities encourage entrepreneurship, support entrepreneur survival, and enhance new firm financing. Chapter 1 analyzes the effect of cities on the individual decision to start a firm. Specifically, we consider how several agglomeration theories may encourage individuals to launch a new firm. We contribute to the expanding literature on entrepreneurship by using the Kauffman Index of Entrepreneurial Activity (KIEA) for 1998-2011, considering individual startup decisions, while controlling for individual motivations, and examining the importance of the local industry conditions to new firm launches across several industries. We find that individuals in regions with entrepreneurial social and institutional structures are more likely to launch a new firm, while industry concentration and diversity are only significant in denser locations. The presence of small and new firms in a region creates an environment conducive to entry and is consistent across industry sectors. Chapter 2 explores the effect of local industrial conditions on a startup's probability of shutdown using the Kauffman Firm Survey (KFS). We contribute to the expanding literature on entrepreneurship by considering shutdowns and positive-exits separately, using a comprehensive model including firm and local industry conditions, and estimating shutdown determinants for high-tech and manufacturing startups. We find strong evidence that the determinants of shutdown are significantly affected along these three dimensions. We test the effect of cluster, Jacobs, and Chinitz agglomerations on new firm shutdowns, but find that new firm shutdowns are not prevented by any source of agglomeration. While concentrated clusters and dense regions promote persistence for manufacturing firms, a regional structure with a large share of small firms (i.e. Chinitz hypothesis) promotes survival for non-manufacturing startups. An environment with a large share of small firms also decreases the risk of shutdown for low-tech startups, while higher industry MES and research expenditures decrease the risk of shutdown. Finally, chapter 3 considers the effects of local industry conditions on external capital acquisition of new firms, using the Kauffman Firm Survey (KFS). While survival and growth has been the predominant measure of performance, Gompers and Lerner (2001) emphasize that access to external finance is necessary for entrepreneurs to establish a competitive advantage. We contribute to the entrepreneurial financing literature by accounting for heterogeneity in financing methods and repeated transactions, exploring how local industry conditions affect new firm financing, and considering how the determinants of financing differ for high-tech and low-tech firms. We find that the region in which a firm operates significantly affects the funding chances of new firms. New firms are at a greater risk of external equity and debt infusions in regions that specialize in certain industries and in industries with lower wages. While the chance of equity financing is greater in regions with an entrepreneurial culture and small supplier network (Landier model and Chinitz hypothesis), the probability of debt financing is greater in regions with concentrated clusters (Porter) and lower university research expenditures. Interestingly, these effects are mirrored for low-tech startups, while high-tech startups are only affected by the industry's wage and region's specialization.

Here is the mission statement of CPW; \"The mission of Colorado Parks and Wildlife is to perpetuate the wildlife resources of the state, to provide a quality state parks system, and to provide enjoyable and sustainable outdoor recreation opportunities that educate and inspire current and future generations to serve as active stewards of Colorado's natural resources.\" According to CPW, hunting revenue was roughly $70 million in 2015.

MATTHEW and Karen Benjamin from Crookwell Squash and Fitness recently held their six week Junior Squash Development Clinic no.1. There were nine children who trained on Wednesday afternoons for six...