Harmonic hopping, and both punctuated and gradual evolution of acoustic characters in Selasphorus hummingbird tail-feathers.

Models of character evolution often assume a single mode of evolutionary change, such as continuous, or discrete. Here I provide an example in which a character exhibits both types of change. Hummingbirds in the genus Selasphorus produce sound with fluttering tail-feathers during courtship. The ancestral character state within Selasphorus is production of sound with an inner tail-feather, R2, in which the sound usually evolves gradually. Calliope and Allen's Hummingbirds have evolved autapomorphic acoustic mechanisms that involve feather-feather interactions. I develop a source-filter model of these interactions. The 'source' comprises feather(s) that are both necessary and sufficient for sound production, and are aerodynamically coupled to neighboring feathers, which act as filters. Filters are unnecessary or insufficient for sound production, but may evolve to become sources. Allen's Hummingbird has evolved to produce sound with two sources, one with feather R3, another frequency-modulated sound with R4, and their interaction frequencies. Allen's R2 retains the ancestral character state, a ∼1 kHz "ghost" fundamental frequency masked by R3, which is revealed when R3 is experimentally removed. In the ancestor to Allen's Hummingbird, the dominant frequency has 'hopped' to the second harmonic without passing through intermediate frequencies. This demonstrates that although the fundamental frequency of a communication sound may usually evolve gradually, occasional jumps from one character state to another can occur in a discrete fashion. Accordingly, mapping acoustic characters on a phylogeny may produce misleading results if the physical mechanism of production is not known

Simple and Effective Multi-Paragraph Reading Comprehension

We consider the problem of adapting neural paragraph-level question answering models to the case where entire documents are given as input. Our proposed solution trains models to produce well calibrated confidence scores for their results on individual paragraphs. We sample multiple paragraphs from the documents during training, and use a shared-normalization training objective that encourages the model to produce globally correct output. We combine this method with a state-of-the-art pipeline for training models on document QA data. Experiments demonstrate strong performance on several document QA datasets. Overall, we are able to achieve a score of 71.3 F1 on the web portion of TriviaQA, a large improvement from the 56.7 F1 of the previous best system.Comment: 11 pages, updated a referenc

The Effect of Historical Entitlements in Cooperative Bargaining Over Evironment Policy: An Experimental Test

Collaborative policy making has been an increasingly popular method of solving use conflicts on public lands. Representatives of interested groups are authorized to negotiate land use policy in the shadow of a government imposed backstop policy. This process can be modeled using cooperative game theory over multiple goods in an Edgeworth Box framework, and its outcomes predicted using axiomatic bargaining theories (e.g. Pareto efficiency or the Nash bargain). A challenge for collaborative policymaking arises when users’ historical land use entitlements differ from the backstop the government will impose if negotiations fail. A challenge for the predictive power of axiomatic bargaining theory arises when the government’s backstop policy (and the Nash bargain it generates) creates substantial inequality of benefits among users. In this paper, we use laboratory experiments to test the effect on bargaining of 1) the divergence of historical entitlements from the prospective backstop and 2) the divergence of the Nash bargain generated by the backstop policy from the outcome that equalizes benefits. We examine the effects of both types of divergence on agreement rates, and on the likelihood that parties settle inside the bargaining lens, on the contract curve, and at the Nash bargain. We find that divergence of historical entitlements from the backstop significantly changes bargaining outcomes when the historical benefits were equally distributed and the benefits at the backstop and Nash are not. At the same time, historical entitlements do not affect outcomes when they were unequal but the backstop and Nash bargain generate equal benefits. We also find the outcomes parties reach are affected by the divergence of equality from the Nash bargain, independent of historical entitlement.Historical entitlements; Collaborative policy making; Land use conflicts

The Effect of Entitlements and Equality on Cooperative Bargaining with Private, Unverifiable Information

In many bargaining situations a third party is authorized to impose a backstop position on the bargainers. Prominent examples include governments who use collaborative policymaking between stakeholders to set public policy, but also compulsory arbitration in labour negotiations. Axiomatic models of cooperative bargaining, such as the Nash bargain, presume that the status quo allocation will have no effect on the outcome parties reach if it differs from the backstop set by the third party. In contrast, experimental findings have suggested that both equality of outcomes and entitlement (where the status quo establishes a focal point) may affect the agreements bargainers reach, at least under full information. This paper extends the investigation of the effect of equality and entitlement on cooperative bargaining to the case where parties have private, unverifiable information concerning the value of outcomes. We use a two-party, two-attribute experimental design in which subjects take part in unstructured, face-to-face bargaining to jointly select from among approximately 200 potential outcomes. We find that, relative to full information, parties who bargain under private information are almost as likely to reach agreements as those under full information, and that these agreements are still approximately Pareto efficient. Further, the effect of the status quo (rather than backstop) allocation seems amplified under private information, while the effect of equality is dampened, but not eliminated.cooperative bargaining; private information; Nash bargain; egalitarian; entitlement; fairness; focal points

The Efficiency of Direct Public Involvement in Environmental Policymaking: An Experimental Test

In one of the most ambitious forms of environmental decision-making, representatives of interested parties – environmentalists, developers, farmers, loggers, miners, etc. - are charged with the responsibility of developing a set of public policies that is acceptable to all of them. Although this approach has become increasingly popular, and has been widely discussed in the academic literature, little is known about the characteristics of the outcomes that are reached in this type of negotiation. We do not know, for example, whether these outcomes meet the standard criteria for efficiency or equity. In this paper, we use laboratory experiments to test whether a number of axiomatic models of bargaining can predict the behavior of the parties to environmental decision making. In recognition of the multi-dimensional aspect of most public land use conflicts, we ask pairs of subjects to negotiate over two goods, without the possibility of cash side payments. We thus provide one of the first experimental tests of a prediction associated with the Edgeworth Box: that parties with an initial endowment that is Pareto inefficient will make trades until they reach a Pareto efficient allocation. We further test whether parties in particular reach the Nash bargain when it coincides with or conflicts with outcomes that maximise the parties’ joint payoffs and with outcomes at which the parties’ receive equal payoffs. Finally, the effect of providing parties with full or partial information regarding payoffs is also examined.Axiomatic models of bargaining; Experimental tests; Land use conflicts; Collaborative policymaking

Novel polyoxometalates: Is antimony the new molybdenum?

Polyoxometalates based on Mo, W or V have been known for a long time and present a diverse range of structures, with the [XMo₁₂O₄₀]ⁿ⁻ Keggin ions (X = P, Si ,…) perhaps the best known.¹ They are still subject to intense research with >4000 papers published in the past five years. Following on from our study² of aryl arsonic acids RAsO₃H₂, which are straightforward molecular species based on four-coordinate As(V), we became interested in the corresponding antimony compounds. Although aryl stibonic acids of nominal formula RSbO₃H₂ have been known for over 100 years,³ their composition has remained uncertain, as they form only amorphous solids, have complicated titration behaviour and only limited solubility. The presumption has been that they are polymeric, based on 5- or 6-coordinate Sb with Sb-O-Sb linkages, though direct evidence is sparse.⁴ Recently, it has been shown by Beckman that if very bulky R groups are used, then relatively simple dimers such as (2,6-Mes₂C₆H₃Sb₂O₂(OH)₄(Mes=mesityl) can be isolated, but these represent a special case.

ECOLABELS AND ECONOMIC EFFICIENCY: SOME PRELIMINARY RESULTS

The public provision of information about the environmental performance of firms and products has generated considerable enthusiasm and become a common instrument of environmental regulation, even though the economic analysis of the social welfare properties of these policies is quite limited. This paper proposes a model for examining these properties.Research Methods/ Statistical Methods,