724 research outputs found
The end of the line: competitive exclusion and the extinction of historical entities
Identifying competitive exclusion at the macroevolutionary scale has typically relied on demonstrating a reciprocal, contradictory response by two co-occurring, functionally similar clades. Finding definitive examples of such a response in fossil time series has proven challenging, however, as has controlling for the effects of a changing physical environment. We take a novel approach to this issue by quantifying variation in trait values that capture almost the entirety of function for steam locomotives (SL), a known example of competitive exclusion from material culture, with the goal of identifying patterns suitable for assessing clade replacement in the fossil record. Our analyses find evidence of an immediate, directional response to the first appearance of a direct competitor, with subsequent competitors further reducing the realized niche of SLs, until extinction was the inevitable outcome. These results demonstrate when interspecific competition should lead to extinction and suggest that clade replacement may only occur when niche overlap between an incumbent and its competitors is near absolute and where the incumbent is incapable of transitioning to a new adaptive zone. Our findings provide the basis for a new approach to analyse putative examples of competitive exclusion that is largely free of a priori assumptions
Living Faith in a Culture of Fear: Love as the Key to a Culture of Connection
Fear carves a path of self-destruction. Fear of not being lovable grounds the seemingly contradictory vices of pride and self-negation. Pride needs endless adulation to counter what arrogance most fears: "I'm really worthless." If there is a unity of the virtues, it is love
Discrete Three-dimensional Representation of Macromolecular Motion from eNOE-based Ensemble Calculation
Three-dimensional structural data and description of dynamics are fundamental to infer and understand protein function. Structure determination by NMR follows well-established protocols while NMR relaxation phenomena provide insights into local molecular dynamics. However, methods to
detect concerted motion were not pursued until very recently. Here, we present an ensemble-based structure determination protocol using ensemble-averaged distance restraints obtained from exact NOE (eNOE) rate constants. An application of our protocol to the model protein GB3 established an
ensemble of structures that reveals correlated motion across the ?-sheet and concerted motion between the backbone and side chains localized in the core. Furthermore, the data repudiate concerted conformational exchange between the ?-sheet and the ?-helix
Management of a capital stock by Strotz's naive planner
http://dx.doi.org/10.1016/j.jedc.2007.09.01
Fermionic Molecular Dynamics for nuclear dynamics and thermodynamics
A new Fermionic Molecular Dynamics (FMD) model based on a Skyrme functional
is proposed in this paper. After introducing the basic formalism, some first
applications to nuclear structure and nuclear thermodynamics are presentedComment: 5 pages, Proceedings of the French-Japanese Symposium, September
2008. To be published in Int. J. of Mod. Phys.
TI-games I: An Exploration of Type Indeterminacy In Strategic Decision-Making
The Type Indeterminacy model is a theoretical framework that formalizes the
constructive preference perspective suggested by Kahneman and Tversky. In this
paper we explore an extention of the TI-model from simple to strategic
decision-making. A 2X2 game is investigated. We first show that in a one-shot
simultaneaous move setting the TI-model is equivalent to a standard incomplete
information model. We then let the game be preceded by a cheap-talk promise
exchange game. We show in an example that in the TI-model the promise stage can
have impact on next following behavior when the standard classical model
predicts no impact whatsoever. The TI approach differs from other behavioral
approaches in identifying the source of the effect of cheap-talk promises in
the intrinsic indeterminacy of the players' type.Comment: 18
Recent Advances
Although often depicted as rigid structures, proteins are highly dynamic
systems, whose motions are essential to their functions. Despite this, it is
difficult to investigate protein dynamics due to the rapid timescale at which
they sample their conformational space, leading most NMR-determined structures
to represent only an averaged snapshot of the dynamic picture. While NMR
relaxation measurements can help to determine local dynamics, it is difficult
to detect translational or concerted motion, and only recently have
significant advances been made to make it possible to acquire a more holistic
representation of the dynamics and structural landscapes of proteins. Here, we
briefly revisit our most recent progress in the theory and use of exact
nuclear Overhauser enhancements (eNOEs) for the calculation of structural
ensembles that describe their conformational space. New developments are
primarily targeted at increasing the number and improving the quality of
extracted eNOE distance restraints, such that the multi-state structure
calculation can be applied to proteins of higher molecular weights. We then
review the implications of the exact NOE to the protein dynamics and function
of cyclophilin A and the WW domain of Pin1, and finally discuss our current
research and future directions
Time consistent discounting
A possibly immortal agent tries to maximise its summed discounted rewards over time, where discounting is used to avoid infinite utilities and encourage the agent to value current rewards more than future ones. Some commonly used discount functions lead to time-inconsistent behavior where the agent changes its plan over time. These inconsistencies can lead to very poor behavior. We generalise the usual discounted utility model to one where the discount function changes with the age of the agent. We then give a simple characterisation of time-(in)consistent discount functions and show the existence of a rational policy for an agent that knows its discount function is time-inconsistent
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