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Mia Couto is among the most prominent of contemporary Mozambican writers. Yet he has also enjoyed a career as an environmental biologist and ecologist, having expressed much interest in interrogating the border between what is human and not human through his scientific practice. In this essay I locate the nexus of Couto’s literary and ecological careers in his concern with recovering forms of proximity among humans, environments, and other species. Through an analysis of some of Couto’s recently translated novels, I argue that his work reconceives of the relations between humans and animals through the concept of biosemiotics, an approach attuned to languages conveyed semiotically through embodied and skillful engagement with the larger-than-human world. Couto’s work in turn grounds biosemiotics in segments of African life that find their basis in forms of animism, thus implicating the concept in the postcolonial work of cultural recuperation and decolonization.
We study the damping of collisionless Alfvénic turbulence in a strongly magnetised plasma by two mechanisms: stochastic heating (whose efficiency depends on the local turbulence amplitude
) and linear Landau damping (whose efficiency is independent of
), describing in detail how they affect and are affected by intermittency. The overall efficiency of linear Landau damping is not affected by intermittency in critically balanced turbulence, while stochastic heating is much more efficient in the presence of intermittent turbulence. Moreover, stochastic heating leads to a drop in the scale-dependent kurtosis over a narrow range of scales around the ion gyroscale.
Stochastic heating refers to an increase in the average magnetic moment of charged particles interacting with electromagnetic fluctuations whose frequencies are smaller than the particles’ cyclotron frequencies. This type of heating arises when the amplitude of the gyroscale fluctuations exceeds a certain threshold, causing particle orbits in the plane perpendicular to the magnetic field to become stochastic rather than nearly periodic. We consider the stochastic heating of protons by Alfvén-wave (AW) and kinetic-Alfvén-wave (KAW) turbulence, which may make an important contribution to the heating of the solar wind. Using phenomenological arguments, we derive the stochastic-proton-heating rate in plasmas in which
is the ratio of the proton pressure to the magnetic pressure. (We do not consider the
regime, in which KAWs at the proton gyroscale become non-propagating.) We test our formula for the stochastic-heating rate by numerically tracking test-particle protons interacting with a spectrum of randomly phased AWs and KAWs. Previous studies have demonstrated that at
, particles are energized primarily by time variations in the electrostatic potential and thermal-proton gyro-orbits are stochasticized primarily by gyroscale fluctuations in the electrostatic potential. In contrast, at
, particles are energized primarily by the solenoidal component of the electric field and thermal-proton gyro-orbits are stochasticized primarily by gyroscale fluctuations in the magnetic field.
When a liquid drop is placed on a highly superheated surface, it can be levitated by its own vapour. This remarkable phenomenon is referred to as the Leidenfrost effect. The thermally insulating vapour film results in a severe reduction of the heat transfer rate compared to experiments at lower surface temperatures, where the drop is in direct contact with the solid surface. A commonly made assumption is that this solid surface is isothermal, which is at least questionable for materials of low thermal conductivity, resulting in an overestimation of the surface temperature and heat transfer for such systems. Here we aim to obtain more quantitative insight into how surface cooling affects the Leidenfrost effect. We develop a technique based on Mach–Zehnder interferometry to investigate the surface cooling of a quartz plate by a Leidenfrost drop. The three-dimensional plate temperature field is reconstructed from interferometric data by an Abel inversion method using a basis function expansion of the underlying temperature field. By this method we are able to quantitatively measure the local cooling inside the plate, which can be as strong as 80 K. We develop a numerical model which shows good agreement with experiments and enables extending the analysis beyond the experimental parameter space. Based on the numerical and experimental results we quantify the effect of surface cooling on the Leidenfrost phenomenon. By focusing on the role of the solid surface we provide new insights into the Leidenfrost effect and demonstrate how to adjust current models to account for non-isothermal solids and use previously obtained isothermal scaling laws for the neck thickness and evaporation rate.
More than forty years have passed since Coase's fundamental insight that transaction, coordination, and contracting costs must be considered explicitly in explaining the extent of vertical integration. Starting from the truism that profit-maximizing firms will undertake those activities that they find cheaper to administer internally than to purchase in the market, Coase forced economists to begin looking for previously neglected constraints on the trading process that might efficiently lead to an intrafirm rather than an interfirm transaction. This paper attempts to add to this literature by exploring one particular cost of using the market system – the possibility of postcontractual opportunistic behavior.
Opportunistic behavior has been identified and discussed in the modern analysis of the organization of economic activity. Williamson, for example, has referred to effects on the contracting process of “ex post small numbers opportunism,” and Teece has elaborated:
Even when all of the relevant contingencies can be specified in a contract, contracts are still open to serious risks since they are not always honored. The 1970's are replete with examples of the risks associated with relying on contracts … [O]pen displays of opportunism are not infrequent and very often litigation turns out to be costly and ineffectual.
The particular circumstance we emphasize as likely to produce a serious threat of this type of reneging on contracts is the presence of appropriable specialized quasi rents. After a specific investment is made and such quasi rents are created, the possibility of opportunistic behavior is very real.
To better understand the molecular mechanisms involved in the biodegradation
of hydrocarbon compounds from the “Erika” oil-spill, we have studied the
ability of Marinobacter hydrocarbonoclasticus strain sp 17 to cope with hexadecane
as sole carbon and energy source. Growth kinetics of cultures shifted from acetate to hexadecane
revealed the presence of a 20 hours adaptation phase. Changes in global
protein expression in response to hexadecane was analyzed by two-dimensional
gel electrophoresis. Of the 370 proteins detected 42 had their expression
level altered in presence of hexadecane indicating that alkane adaptation
may involve many cellular functions.
A major advance in economics involves the recognition that contracts adopted by transactors are incomplete. This fundamental insight has produced two main strands of economic research. One strand of research emphasizes the importance of self-enforcement in assuring contractual performance. Building upon Stuart Macaulay's pioneering study documenting that performance is secured in most business relationships not by the threat of court enforcement but by the threat of termination of the relationship, this work develops models of self-enforcement where a termination sanction is sufficient to assure transactor performance.
The other, more extensive, unrelated strand of economic research flowing from incomplete contracts is the principal–agent contract design literature. This work examines the role of contract terms in minimizing transactor malincentives given that performance can only imperfectly be contracted on. The major point of this chapter is that the incomplete contract terms actually used by transactors in the marketplace can be understood only by combining these two strands of research. What follows is a summary of my research on contracts from this perspective of integrating our research on incomplete contracts.
One way to integrate the two lines of research on incomplete contracts is to add self-enforcement considerations to the principal-agent model. The alternative way I have attempted this integration is by extending the simple model of self-enforcement to take account of the role of contract terms in facilitating self-enforcement. Contract terms are used as an aid to self-enforcement because the transactors' reputational capital through which the self-enforcement mechanism operates is limited (in the sense that transactors can credibly promise to pay only a finite maximum future amount to their transacting partners in return for current performance).
A theoretical model of microwave absorption in linear dielectric (non-ferroelectric) ionic crystals that takes into account the presence of point defects was synthesized and verified using NaCl single crystals. In the next stage of this research, we will introduce a controlled density of dislocations into the single crystal NaCl samples and study the effect on the microwave absorption mechanisms (ionic conduction, dielectric relaxation and multi-phonon processes) both theoretically and experimentally. Qualitative outlines of this modified theory are presented. The loss factor ε’ has been measured in the dislocation-free case by a cavity resonator insertion technique and the experimental results are in good agreement with the theoretical model. We describe the sample preparation technique that will be used to produce a controlled dislocation density in single crystal samples that will also be studied in our cavity resonator insertion system.
Richtmyer–Meshkov instability causes spatially periodic perturbations initially imposed on a shock-accelerated, thin gas layer to develop into one of three distinct flow patterns. Planar laser-induced fluorescence imaging of the evolving layer, produced by a perturbed SF6 planar jet in air, shows an apparent flow bifurcation that is observed as mushroom-shaped or sinuous-shaped interfacial patterns. Analysis of this nonlinear instability growth, accomplished by modelling the flow field as a row of line vortices, predicts that the layer thickness grows logarithmically at later times and compares well with our measurements. Because the row of vortices is unstable, the model also provides an explanation for the appearance of the three observed interfacial patterns.
Terms such as “unfair” are foreign to the economic model of voluntary exchange which implies anticipated gains to all transactors. However, much recent statutory, regulatory and antitrust activity has run counter to this economic paradigm of the efficiency properties of “freedom of contract.” The growth of “dealer day in court” legislation, FTC franchise regulations, favorable judicial consideration of “unequal bargaining power,” and unconscionability arguments, are some examples of the recent legal propensity to “protect” transactors. This is done by declaring unenforceable or illegal particular contractual provisions that, although voluntarily agreed upon in the face of significant competition, appear to be one-sided or unfair. Presentation of the standard abstract economic analysis of the mutual gains from voluntary exchange is unlikely to be an effective counterweight to this recent legal movement without an explicit attempt to provide a positive rationale for the presence of the particular unfair contractual term. This paper considers some transaction costs that might explain the voluntary adoption of contractual provisions such as termination at will and long-term exclusive dealing clauses that have been under legal attack.
The “holdup” problem
Given the presence of incomplete contractual arrangements, wealth maximizing transactors have the ability and often the incentive to renege on the transaction by holding up the other party, in the sense of taking advantage of unspecified or unenforceable elements of the contractual relationship. Such behavior is, by definition, unanticipated and not a long-run equilibrium phenomenon. Oliver Williamson  has identified and discussed this phenomenon of “opportunistic behavior,” and my recent paper with Robert Crawford and Armen Alchian  attempted to make operational some of the conditions under which this holdup potential is likely to be large.