Observation of topologically protected helical edge modes in Kagome elastic plates

The investigation of topologically protected waves in classical media has opened unique opportunities to achieve exotic properties like one-way phonon transport, protection from backscattering and immunity to imperfections. Contrary to acoustic and electromagnetic domains, their observation in elastic solids has so far been elusive due to the presence of both shear and longitudinal modes and their modal conversion at interfaces and free surfaces. Here we report the experimental observation of topologically protected helical edge waves in elastic media. The considered structure consists of an elastic plate patterned according to a Kagome architecture with an accidental degeneracy of two Dirac cones induced by drilling through holes. The careful breaking of symmetries couples the corresponding elastic modes which effectively emulates spin orbital coupling in the quantum spin Hall effect. The results shed light on the topological properties of the proposed plate waveguide and opens avenues for the practical realization of compact, passive and cost-effective elastic topological waveguides

"Stakeholder Orientation" and Capital Structure: Social Entrerprises versus For-Profit Firms in the Italian Social Residencial Service Sector

In this paper, we investigate whether capital structure differs between for-profit and nonprofit sectors by focusing on two key aspects of the latter: the non-distribution constraint and the stakeholder oriented governance system. We develop a theoretical model and show that the former negatively affects leverage, defined as the amount borrowed over the total investment, whilst the latter has a positive effect. We then analyze a longitudinal data set of balance sheets of 800 firms operating in the social residential sector in Italy and show that, once controlled for observable characteristics, for-profit companies have a leverage 18% higher than nonprofit enterprises, even if the latter face lower credit costs. We explain this finding by arguing that the effect of the non-distribution constraint prevails over the effect of stakeholder orientation

Financial Risk Aversion, Economic Crises and Past Risk Perception

We use a panel dataset from the Dutch Household Survey, covering annually the period 1993-2011, to analyze whether individual risk aversion changes over time with the background economic conditions. Considering six different measures of self-assessed risk aversion, which cover different aspects of risk, our preliminary results show that risk aversion is not stable over time. Its dynamics, however, depends on the type of investor. Those who made no investment in the previous year showed higher risk aversion at the end of the 90s; those who invested, in contrast, showed a steadily constant or decreasing pattern. The gap between the risk aversion of investors and noninvestors was the largest between the end of the 90s and the beginning of the 00s, when the stock market experienced exceptionally high volatility

Household Portfolios and Risk Taking over Age and Time

We exploit the US Survey of Consumer Finances (SCF) from 1998 to 2007 to provide new insights on the evolution of US households’ willingness to undertake portfolio risk. Specifically, we consider four alternative measures of portfolio risk, based on two definitions of portfolio - a narrow one, including financial assets, and a broad one, also including human capital, real estate, business wealth and related debt. The four measures consistently show that risk taking peaked in 2001, many households are willing to undertake only limited risk, and that risk taking increases with wealth, income and financial sophistication. Each measure, nevertheless, provides a different ranking of household risk taking; in addition, the age profile of risk is sensitive to the definition of portfolio. However, risk taking turns out to be constant for a large part of the life cycle, and in particular during the ages 40-60, keeping all the other variables constant

Energy affordability and the benefits system in Italy

In this paper, we discuss a number of ways to define and measure the affordability of energy consumption, and we examine the emergence of energy poverty in Italy in the period from 1998 to 2011. The paper examines the eligibility criteria for claiming the benefits available to support energy consumption for vulnerable families and it identifies the potential beneficiaries. The study assesses the appropriateness of the eligibility criteria by comparing the population targeted by the policy with the population actually facing affordability problems. A simulation exercise, using the hypothetical scenario most likely to result in energy benefits made available, shows that, regardless of the affordability index adopted, the provision of state energy benefits has little impact on fuel poverty

Debt Shifting in Europe

This article aims to analyze the link between subsidiary capital structure and taxation in Europe. First we have introduced a trade-off model, which looks at a MNC???s financial strategy and in particular debt shifting from low-tax to high-tax jurisdictions. By letting the MNC choose both leverage and the debt shifting percentage, we depart from the relevant literature which has mainly focused on the latter. Using the AMADEUS dataset we show that: (i) in line with the relevant literature, subsidiary leverage increases with its tax rate; (ii) contrary to previous work, the parent company tax rate does not have a negative effect on subsidiary leverage. More specifically, its effect is estimated to be nil when statutory tax rates are used. When, however, effective marginal tax rates (EMTRs), accounting for cross-border effects, are used, the impact of parent company taxation on subsidiary leverage is positive

Temporal stability, cross-validity, and external validity of risk preferences measures: experimental evidence from a UK representative sample

We conduct an “artefactual” field experiment to incorporate three different risk preferences measures within the Innovation Panel (IP) of the UK Household Longitudinal Survey (UKHLS). We randomly allocate to an experimental module a nationally representative sample of 661 adult respondents to the IP Wave 6 (IP6). These subjects respond to the incentive-compatible tasks by Holt and Laury (2002) (HL), and by Binswanger (1980, 1981) and Eckel and Grossman (2008) (B-EG), and to the SOEP survey questions by Dohmen et al. (2011) for self-reported willingness to take risks in general (SOEP-G), in finance (SOEP-F), and in health (SOEP-H). One year later (IP7) the same measures are repeated for 413 of these respondents. This design allows us to systematically test, for a UK representative sample, the validity of the three measures along three dimensions. First, we look at cross-validity by testing how responses at one point in time correlate across the three tasks, assuming a Constant Relative Risk Aversion (CRRA) utility function. Second, we look at temporal stability by comparing the responses across IP6 and IP7. Third, we look at external validity by considering a range of risky health and financial behaviors in the UKHLS. We have three main findings. First, concerning cross-validity, we find evidence that the different measures generally correlate and map into each other, although their associations are not perfect. Second, concerning temporal stability, there are significant and positive correlations of the B-EG, HL, and SOEP measures across IP6 and IP7. Finally, we find mixed evidence concerning external validity

Bio-inspired non self-similar hierarchical elastic metamaterials

Hierarchy provides unique opportunities for the design of advanced materials with superior properties that arise from architecture, rather than from constitutive material response. Contrary to the quasi-static regime, where the potential of hierarchy has been largely explored, its role in vibration mitigation and wave manipulation remains elusive. So far, the majority of the studies concerning hierarchical elastic metamaterials have proposed a selfsimilar repetition of a specific unit cell at multiple scale levels, leading to the activation of the same bandgap mechanism at different frequencies. On the contrary, here, we show that by designing non self-similar hierarchical geometries allows us to create periodic structures supporting multiple, highly attenuative and broadband bandgaps involving (independently or simultaneously) different scattering mechanisms, namely, Bragg scattering, local resonance and/or inertial amplification, at different frequencies. The type of band gap mechanism is identified and discussed by examining the vibrational mode shapes and the imaginary component of the wavenumber in the dispersion diagram of the unit cell. We also experimentally confirm this by performing measurements in the lowest frequency regime on a 3D printed structure. Hierarchical design strategies may find application in vibration mitigation for civil, aerospace and mechanical engineering

Integration of Long-Term-Memory-Related Synaptic Plasticity Involves Bidirectional Regulation of Gene Expression and Chromatin Structure

AbstractExcitatory and inhibitory inputs converge on single neurons and are integrated into a coherent output. Although much is known about short-term integration, little is known about how neurons sum opposing signals for long-term synaptic plasticity and memory storage. In Aplysia, we find that when a sensory neuron simultaneously receives inputs from the facilitatory transmitter 5-HT at one set of synapses and the inhibitory transmitter FMRFamide at another, long-term facilitation is blocked and synapse-specific long-term depression dominates. Chromatin immunoprecipitation assays show that 5-HT induces the downstream gene C/EBP by activating CREB1, which recruits CBP for histone acetylation, whereas FMRFa leads to CREB1 displacement by CREB2 and recruitment of HDAC5 to deacetylate histones. When the two transmitters are applied together, facilitation is blocked because CREB2 and HDAC5 displace CREB1-CBP, thereby deacetylating histones