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The optimal defence hypothesis predicts that increased plant defence capabilities, lower levels of damage, and lower investment in vegetative biomass will occur more frequently in sexual forms with higher resource-demanding tissue production and/or younger plant parts. We aimed to examine the effects of sexual form, cladode, and flower age on growth rate, herbivore damage, and 4-hydroxybenzoic acid (4-HBA), chlorogenic acid, and quercetin (QUE) concentrations in Opuntia robusta plants in central Mexico. Our findings demonstrated that hermaphrodite flowers showed faster growth and lesser damage than female flowers. The effect of cladode sexual forms on 4-HBA and QUE occurrence was consistent with the predictions of the optimal defence hypothesis. However, chlorogenic acid occurrences were not significantly affected by sexual forms. Old cladodes exhibited higher QUE and 4-HBA occurrences than young cladodes, and hermaphrodites exhibited higher 4-HBA concentrations than females. Resource allocation for reproduction and secondary metabolite production, and growth was higher and lower, respectively, in females, compared to hermaphrodites, indicating a trade-off between investment in reproduction, growth, and secondary metabolite production. Secondary metabolite concentrations in O. robusta plants were not negatively correlated with herbivore damage, and the two traits were not accurate predictors of plant reproductive output. [ABSTRACT FROM AUTHOR]

We examine a fractional discrete nonlinear Schrodinger dimer, where the usual first-order derivative in the time evolution is replaced by a non integer-order derivative. The dimer is nonlinear (Kerr) and PT -symmetric, and for localized initial conditions we examine the exchange dynamics between both sites. By means of the Laplace transformation technique, the linear PT dimer is solved in closed form in terms of Mittag–Leffler functions, while for the nonlinear regime, we resort to numerical computations using the direct explicit Grunwald algorithm. In general, we see that the main effect of the fractional derivative is to produce a monotonically decreasing time envelope for the amplitude of the oscillatory exchange. In the presence of PT symmetry, the oscillations experience some amplification for gain/loss values below some threshold, while beyond threshold, the amplitudes of both sites grow unbounded. The presence of nonlinearity can arrest the unbounded growth and lead to a selftrapped state. The trapped fraction decreases as the nonlinearity is increased past a critical value, in marked contrast with the standard (non-fractional) case. [ABSTRACT FROM AUTHOR]

We study the transport properties of an initially localized excitation in several flat band lattices, in the presence of nonlinear (Kerr) disorder. In the weak nonlinearity regime, the dynamics is controlled by the degeneracy of the bands leading to a linear form of selftrapping. In the strong nonlinearity regime, the dynamics of the excitations depends strongly on the local environment around the initial excitation site that leads to a highly fluctuating selfrapping profile. For a binary nonlinear disorder, it is shown that the spreading of the flat band fundamental mode, is completely inhibited for a finite fraction of all cases. This fraction corresponds to the fraction of times the same value of (random) nonlinearity is assigned to all sites of the fundamental mode. [ABSTRACT FROM AUTHOR]

We investigate the drivers of systemic risk and contagion among banks in the Latin American financial sector. First, a systemic risk measure analysing tail co-movements of daily stock returns of all Latin American banks is derived. We then run panel regressions for our systemic risk measure using idiosyncratic bank characteristics and macroeconomic control variables. Our results include various significant drivers of systemic importance of banks in Latin America like bank size, market concentration and high government indebtedness. Interestingly, we empirically prove that during the financial/economic crisis (2006-2011) systemic risk was driven by banks with low earning prospects and relatively sound deposit management whereas poor capital regulation drove systemic risk of banks during the stable periods before (2003-2005) and after the crisis (2012-2014). [ABSTRACT FROM AUTHOR]

The freezing of aqueous solutions and reciprocal distribution of ice and a freeze-concentrated solution (FCS) are poorly understood in spite of their importance in fields ranging from biotechnology and life sciences to geophysics and climate change. Using an optical cryo-miscroscope and differential scanning calorimetry, we demonstrate that upon cooling of citric acid and sucrose solutions a fast freezing process results in a continuous ice framework (IF) and two freeze-concentrated solution regions of different concentrations, FCS1 and FCS2. The FCS1 is maximally freeze-concentrated and interweaves with IF. The less concentrated FCS2 envelops the entire IF/FCS1.We find that upon further cooling, the FCS1 transforms to glass, whereas the slow freezing of FCS2 continues until it is terminated by a FCS2-glass transition. We observe the resumed slow freezing of FCS2 upon subsequent warming. The net thermal effect of the resumed freezing and a reverse glass-FCS1 transition produces the Ttr2-transition which before has only been observed upon warming of frozen hydrocarbon solutions and which nature has remained misunderstood for decades. [ABSTRACT FROM AUTHOR]

Over the past century, the total material wealth of humanity has been enhanced. However, in the twenty-first century, we face scarcity in critical resources, the degradation of ecosystem services, and the erosion of the planet's capability to absorb our wastes. Equity issues remain stubbornly difficult to solve. This situation is novel in its speed, its global scale and its threat to the resilience of the Earth System. The advent of the Anthropence, the time interval in which human activities now rival global geophysical processes, suggests that we need to fundamentally alter our relationship with the planet we inhabit. Many approaches could be adopted, ranging from geo-engineering solutions that purposefully manipulate parts of the Earth System to becoming active stewards of our own life support system. The Anthropocene is a reminder that the Holocene, during which complex human societies have developed, has been a stable, accommodating environment and is the only state of the Earth System that we know for sure can support contemporary society. The need to achieve effective planetary stewardship is urgent. As we go further into the Anthropocene, we risk driving the Earth System onto a trajectory toward more hostile states from which we cannot easily return. [ABSTRACT FROM AUTHOR]

Polar stratospheric clouds (PSCs) are extremely efficient at catalysing the transformation of photostable chlorine reservoirs into photolabile species, which are actively involved in springtime ozone-depletion events. Why PSCs are such efficient catalysts, however, is not well understood. Here, we investigate the freezing behaviour of ternary HNO3–H2SO4–H2O droplets of micrometric size, which form type II PSC ice particles. We show that on freezing, a phase separation into pure ice and a residual solution coating occurs; this coating does not freeze but transforms into glass below ∼150 K. We find that the coating, which is thicker around young ice crystals, can still be approximately 30 nm around older ice crystals of diameter about 10 µm. These results affect our understanding of PSC microphysics and chemistry and suggest that chlorine-activation reactions are better studied on supercooled HNO3–H2SO4–H2O solutions rather than on a pure ice surface. [ABSTRACT FROM AUTHOR]

The Panel on Educational Technology was organized in April 1995 under the auspices of the President's Committee of Advisers on Science and Technology (PCAST) to provide advice to the President on matters related to the application of information technologies to K–12 education in the United States. Its findings and recommendations were set forth in March 1997 in the Report to the President on the Use of Technology to Strengthen K–12 Education in the United States. This report was based on a review of the research literature and on written submissions and oral briefings from a number of academic and industrial researchers, practicing educators, software developers, governmental agencies, and professional and industry organizations involved in various ways with the application of technology to education. Its most important finding is that a large-scale program of rigorous, systematic research on education in general and educational technology in particular will ultimately prove necessary to ensure both the efficacy and cost-effectiveness of technology use within our nation's K–12 schools. Finding that less than 0.1 percent of our nation's expenditures for elementary and secondary education are currently invested to determine which educational techniques actually work, and to find ways to improve them—an extremely low level relative to comparable ratios within the private sector—the Panel recommended that this figure be increased over a period of several years to at least 0.5 percent, and sustained at that level on an ongoing basis. Further, because no one state, municipality, or private firm could hope to capture more than a small fraction of the benefits associated with a significant advance in our understanding of how best to educate K–12 students, the Panel concluded that such funding will have to be provided largely at the federal level in order to avoid a systematic underinvestment (attributable to a classical form of economic externality) relative to the level that would be optimal for the nation as a whole. This paper originally appeared as Section 8 of the report. [ABSTRACT FROM AUTHOR]

We propose a generalization of the Su-Schrieffer-Heeger (SSH) model of the bipartite lattice, consisting of a periodic array of domain walls. The low-energy description is governed by the superposition of localized states at each domain wall, forming an effective mono-atomic chain at a larger scale. When the domain walls are dimerized, topologically protected edge states can appear, just like in the original SSH model. These new edge states are formed exclusively by soliton-like states and therefore, the new topological states are qualitatively different from the regular SSH edge states. They posses a much longer localization length and are more resistant to on-site disorder, in marked contrast to the standard SSH case. [ABSTRACT FROM AUTHOR]

The transition to democratic governments in Central America over thepast decade, and the subsequent emergence of institutional mechanisms for regional cooperation have greatly increased the frequency and productivity of efforts for preservation of cultural patrimony. Both the archaeological and colonial data bases overlap modern political boundaries and regional collaboration in training, pubic education, curation and research is essential. Natural forces continually impact, and human economic forces (especially international tourism) increasingly impact cultural resources. Regional cooperation in the utilization of human resources is necessary to confront the management and salvage demands of major economic development projects, and rescue efforts following natural disasters. The development of policies and programs will be effective only if matched by the growth of cultural preservation professionals in each of the Central American republics. Finally, other art consuming nations in addition to the United States mustbegin to respect the cultural heritage of the Central American countries and develop policies to deter abuses by diplomatic staff and employees of NGO's (nongovernment organizations).NGO's (nongovernment organizations). [ABSTRACT FROM AUTHOR]