A Novel Chiral Phase of Achiral Hard Triangles and an Entropy-Driven Demixing of Enantiomers

We investigate the phase behavior of a system of hard equilateral and right-angled triangles in two dimensions using Monte Carlo simulations. Hard equilateral triangles undergo a continuous isotropic-triatic liquid crystal phase transition at packing fraction $\phi=0.7$. Similarly, hard right-angled isosceles triangles exhibit a first-order phase transition from an isotropic fluid phase to a rhombic liquid crystal phase with a coexistence region $\phi \in \left[0.733,0.782\right]$. Both these liquid crystal phases undergo a continuous phase transition to their respective close-packed crystal structures at high pressures. Although the particles and their close-packed crystals are both achiral, the solid phases of equilateral and right-angled triangles exhibit spontaneous chiral symmetry breaking at sufficiently high packing fractions. The colloidal triangles rotate either in clockwise or anti-clockwise direction with respect to one of the lattice vectors for packing fractions higher than $\phi_\chi$. As a consequence, these triangles spontaneously form a regular lattice of left- or right-handed chiral holes which are surrounded by six triangles in the case of equilateral triangles and four or eight triangles for right-angled triangles. Moreover, our simulations show a spontaneous entropy-driven demixing transition of the right- and left-handed "enantiomers".Comment: 9 pages, 10 figure

Investigating impacts of environmental factors on the cycling behavior of bicycle-sharing users

As it is widely accepted, cycling tends to produce health benefits and reduce air pollution. Policymakers encourage people to use bikes by improving cycling facilities as well as developing bicycle-sharing systems (BSS). It is increasingly interesting to investigate how environmental factors influence the cycling behavior of users of bicycle-sharing systems, as users of bicycle-sharing systems tend to be different from regular cyclists. Although earlier studies have examined effects of safety and convenience on the cycling behavior of regular riders, they rarely explored effects of safety and convenience on the cycling behavior of BSS riders. Therefore, in this study, we aimed to investigate how road safety, convenience, and public safety affect the cycling behavior of BSS riders by controlling for other environmental factors. Specifically, in this study, we investigated the impacts of environmental characteristics, including population density, employment density, land use mix, accessibility to point-of-interests (schools, shops, parks and gyms), road infrastructure, public transit accessibility, road safety, convenience, and public safety on the usage of BSS. Additionally, for a more accurate measure of public transit accessibility, road safety, convenience, and public safety, we used spatiotemporally varying measurements instead of spatially varying measurements, which have been widely used in earlier studies. We conducted an empirical investigation in Chicago with cycling data from a BSS called Divvy. In this study, we particularly attempted to answer the following questions: (1) how traffic accidents and congestion influence the usage of BSS; (2) how violent crime influences the usage of BSS; and (3) how public transit accessibility influences the usage of BSS. Moreover, we tried to offer implications for policies aiming to increase the usage of BSS or for the site selection of new docking stations. Empirical results demonstrate that density of bicycle lanes, public transit accessibility, and public safety influence the usage of BSS, which provides answers for our research questions. Empirical results also suggest policy implications that improving bicycle facilities and reducing the rate of violent crime rates tend to increase the usage of BSS. Moreover, some environmental factors could be considered in selecting a site for a new docking station

Technical Change, Income Distribution, and Profitability in Multisector Linear Economies

This paper analyzes the effect of technical change on income distribution and profitability by comparing the long-run outcomes defined by a uniform profit rate in a multisector linear economy. We study three scenarios with (i) fixed real wage; (ii) fixed profit rate; or (iii) fixed wage-profit ratio, and show that any viable capital- using and labor-saving technical change itself (in the absence of power change) would bring about a fall in the rate of profit. Profit rate would not rise unless the technical change is so power-biased against the working-class that the wage-profit ratio can not be maintained. Our result conclusively supports the argument of the falling rate of profit due to a rising organic composition of capital as an underlying economic force

The discourse, governance and configurations of polycentricity in transitional China: a case study of Tianjin

Polycentricity has been identified as a prominent feature of modern landscapes as well as a buzzword in spatial planning at a range of scales worldwide. Since the Reform and Opening-up Policy in 1978, major cities in China have experienced significant polycentric transition manifested by their new spatial policy framework and reshaped spatial structure. The polycentric transformation has provoked academics’ interests on structural and performance analysis in quantitative ways recently. However, little research investigates the nature of (re)formation and implementation of polycentric development policies in Chinese cities from a processual and critical perspective. This research interprets the underlying meanings and rationality of polycentric development strategy in planning discourse and explains how concrete centres within the polycentric system are created, governed and materialized to facilitate the implementation of polycentric policies in the special context of political system, spatial planning system and socio-economic conditions in China. Referring to existing literature of polycentricity and theories of urban space, this research develops a novel theoretical framework, which holds that polycentricity is produced by the articulation of state power, planning profession and produced space. The research is founded on an embedded case study of Tianjin based on empirical data derived from interviews with stakeholders and secondary data. Through a discourse analysis of four Tianjin City Master Plans, discourses of ‘polycentric urban settlements’, ‘functional polycentricity’, ‘polycentric growth nodes’ and ‘nested polycentricity’ are identified, which are deployed in different ways with variegated composition of spatial elements. Moreover, rather than being mere technocratic practice, the production and legitimation of distinct discourses is essentially an articulation of multi-scalar power involving various stakeholders, which is disguised and justified by the planning profession. The findings demonstrate that polycentricity is a malleable concept and its fluidity creates space to accommodate consensus or to allow the play of contested interests and policy experiments. Based on that, this research further selects centres in Tianjin Binhai New Area Core Zone, Wuqing District and Dongli District as embedded cases to explore how the polycentric development policy is implemented in practice. The empirical findings from local perspective show that these centres are created or formed according to different contexts and logics, and they are consolidated by employment of a portfolio of tools and instruments such as new planning and urban design, establishment of financial and development corporations, exclusive preferential policies, manipulation of public sector, land development and institutional innovation. Correspondingly, these centres have experienced distinct development trajectories and shown different spatial outcomes from the perspectives of urban form, functional composition, and spatial identity. It is suggested that significant gaps and contradictions exist between spatial visions and actual development, which poses challenges for sustainable development