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"Georges, A"
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Key Enablers of and Barriers to the Uptake and Implementation of Nature-Based Solutions in Urban Settings: A Review
Climate change and urbanization have resulted in several societal challenges for urban areas. Nature-based solutions (NBS) have been positioned as solutions for enhancing urban resilience in the face of these challenges. However, the body of conceptual and practical knowledge regarding NBS remains fragmented. This study addresses this gap by means of a systematic review of the literature, to define NBS as a theoretical concept; its broader significance with respect to societal challenges; the key stakeholders in NBS planning, implementation and management; and major barriers to and enablers of NBS uptake. The results of this review reveal that, despite a lack of consensus about the definition of NBS, there is a shared understanding that the NBS concept encompasses human and ecological benefits beyond the core objective of ecosystem conservation, restoration or enhancement. Significant barriers to and enablers of NBS are discussed, along with a proposed strategic planning framework for successful uptake of NBS.
Journal Article
Telecommuting and sustainable travel
Existing research has concluded that shares of telecommuting are low but stable, increase with distance from the workplace and that telecommuting may reduce commuting-related travel. Its effect on work and non-work travel are subject to rebound effects and, thus, still debated. Additionally, telecommuting does not necessarily occur entirely at home. The paper studies telecommuting’s potential as a sustainable mobility tool in Canada to reduce overall travel time and peak hour travel, and to increase non-motorised travel. Do types of telecommuting arrangements have varying relationships with these studied travel patterns? Using time use data from the 2005 Canadian General Social Survey, studied outcomes are regressed on telecommuting arrangements (all day home working, part-day home working and a combination of other locations and home and/or workplace) and other personal characteristics. Depending on telecommuting arrangements and travel outcomes, results vary. Working from home is associated with decreases in overall travel time by 14 minutes and increases in odds of non-motorised travel by 77%. Other forms of telecommuting yield different results. Telecommuters may be more likely to avoid peak hours when they do take trips. Types of telecommuting arrangements have different impacts on sustainable travel outcomes that should be considered depending on policy priorities.
现有研宄得出结论：远程办公的份额小但稳定，随着与工作场所的距离拉远而增加，并且远程 办公可能减少与通勤相关的出行。它对工作出行和非工作出行的影响受反弹效应制约，因此仍 然受到争论。此外，远程办公不必然完全是在家里。本文研宄了远程办公作为加拿大一项可持 续流动工具的潜力，可减少总体出行时间和高峰期出行，并增加非机动车出行。不同类型的远 程办公安排与这些研宄的出行模式有着不同关系吗？我们运用2005年“加拿大综合社会调查” 的用时数据，根据远程办公安排（全天在家办公、半天在家办公、其他地点以及家庭或工作场 所相结合）和其他个人特征对研宄结果做了回归分析。根据远程办公安排和出行结果的不同， 分析结果也呈现差异化。在家办公总体出行时间减少14 分钟，非机动车出行几率增加 77%。其他形式的远程办公得到了不同的结果。远程办公者在出行时更可能避开高峰期。不同 的远程办公类型对可持续的出行结果有不同的影响，这一点应根据政策重点做适当考虑。
Journal Article
Mott insulators with boundary zeros
The topological classification of electronic band structures is based on symmetry properties of Bloch eigenstates of single-particle Hamiltonians. In parallel, topological field theory has opened the doors to the formulation and characterization of non-trivial phases of matter driven by strong electron-electron interaction. Even though important examples of topological Mott insulators have been constructed, the relevance of the underlying non-interacting band topology to the physics of the Mott phase has remained unexplored. Here, we show that the momentum structure of the Green’s function zeros defining the “Luttinger surface\" provides a topological characterization of the Mott phase related, in the simplest description, to the one of the single-particle electronic dispersion. Considerations on the zeros lead to the prediction of new phenomena: a topological Mott insulator with an inverted gap for the bulk zeros must possess gapless zeros at the boundary, which behave as a form of “topological antimatter” annihilating conventional edge states. Placing band and Mott topological insulators in contact produces distinctive observable signatures at the interface, revealing the otherwise spectroscopically elusive Green’s function zeros.
Topological classification of interacting electronic states has emerged as an important topic recently. Wagner at al. show that the momentum structure of the zeros of the electron Green’s function can be used to identify a topological Mott insulator phase, similarly to the single-particle dispersion.
Journal Article
Nonlinear lattice dynamics as a basis for enhanced superconductivity in YBa2Cu3O6.5
Femtosecond X-ray diffraction and
ab initio
density functional theory calculations are used to determine the crystal structure of YBa
2
Cu
3
O
6.5
undergoing optically driven, nonlinear lattice excitation above the transition temperature of 52 kelvin, under which conditions the electronic structure of the material changes in such a way as to favour superconductivity.
Structure of superconducting YBa
2
Cu
3
O
6+
x
Andrea Cavalleri and colleagues use femtosecond X-ray diffraction measurements and
ab initio
density functional theory calculations to determine the crystal structure of YBa
2
Cu
3
O
6+
x
undergoing optically driven, nonlinear lattice excitation at 100 kelvin. In this exotic non-equilibrium state, the electronic structure of the material changes in such a way as to favour superconductivity. The results reveal that in the driven state the superconducting planes are displaced closer and away from one another in a staggered manner, explaining how superconducting coupling can be enhanced or reduced, inside and between the bilayers.
Terahertz-frequency optical pulses can resonantly drive selected vibrational modes in solids and deform their crystal structures
1
,
2
,
3
. In complex oxides, this method has been used to melt electronic order
4
,
5
,
6
, drive insulator-to-metal transitions
7
and induce superconductivity
8
. Strikingly, coherent interlayer transport strongly reminiscent of superconductivity can be transiently induced up to room temperature (300 kelvin) in YBa
2
Cu
3
O
6+
x
(refs
9
,
10
). Here we report the crystal structure of this exotic non-equilibrium state, determined by femtosecond X-ray diffraction and
ab initio
density functional theory calculations. We find that nonlinear lattice excitation in normal-state YBa
2
Cu
3
O
6+
x
at above the transition temperature of 52 kelvin causes a simultaneous increase and decrease in the Cu–O
2
intra-bilayer and, respectively, inter-bilayer distances, accompanied by anisotropic changes in the in-plane O–Cu–O bond buckling. Density functional theory calculations indicate that these motions cause drastic changes in the electronic structure. Among these, the enhancement in the
character of the in-plane electronic structure is likely to favour superconductivity.
Journal Article
Higher-Order Correlations Between Thermodynamic Fluctuations in Compressible Aerodynamic Turbulence
This paper studies the exact and approximate relations between fluctuations in thermodynamic variables (pressure, density and temperature) that are imposed by the dilute-gas (Z=1) equation-of-state (EoS), which is a satisfactory approximation of air thermodynamics for a wide range of pressures and temperatures. It focuses on triple- and higher-order correlations, extending previous studies that concentrated on second-order moments, with emphasis on the mathematical relations, which are generally valid independently of the particular flow configuration. Exact equations are developed both involving only single-variable moments and relating the correlations between variables. These contain nonlinear terms generated by the density-temperature fluctuation product in the fluctuating EoS. The importance of the nonlinear terms in the 6 exact equations between the 10 third-order moments is assessed using DNS (direct numerical simulation) data for compressible turbulent plane channel (TPC) flows and analyzed using general statistical inequalities involving third-order and fourth-order moments. The corresponding linearized system between third-order moments is studied to determine approximate relations and 4-tuples of linearly independent moments. These mathematical tools are then used to analyze TPC flow DNS data on the triple correlations between the thermodynamic variables.
Journal Article