Contract Adjustment under Uncertainty

Consider a contract over trade in continuous time between two players, according to which one player makes a payment to the other, in exchange for an exogenous service. At each point in time, either player may unilaterally require an adjustment of the contract payment, involving adjustment costs for both players. Players’ payoffs from trade under the contract, as well as from trade under an adjusted contract, are exogenous and stochastic. We consider players’ choice of whether and when to adjust the contract payment. It is argued that the optimal strategy for each player is to adjust the contract whenever the contract payment relative to the outcome of an adjustment passes a certain threshold, depending among other things of the adjustment costs. There is strategic substitutability in the choice of thresholds, so that if one player becomes more aggressive by choosing a threshold closer to unity, the other player becomes more passive. If players may invest in order to reduce the adjustment costs, there will be over-investment compared to the welfare maximizing levels.

Adaptive independent Metropolis--Hastings

We propose an adaptive independent Metropolis--Hastings algorithm with the ability to learn from all previous proposals in the chain except the current location. It is an extension of the independent Metropolis--Hastings algorithm. Convergence is proved provided a strong Doeblin condition is satisfied, which essentially requires that all the proposal functions have uniformly heavier tails than the stationary distribution. The proof also holds if proposals depending on the current state are used intermittently, provided the information from these iterations is not used for adaption. The algorithm gives samples from the exact distribution within a finite number of iterations with probability arbitrarily close to 1. The algorithm is particularly useful when a large number of samples from the same distribution is necessary, like in Bayesian estimation, and in CPU intensive applications like, for example, in inverse problems and optimization.Comment: Published in at http://dx.doi.org/10.1214/08-AAP545 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Sediment and particulate carbon removal by pipe erosion increase over time in blanket peatlands as a consequence of land drainage

Land drainage is common in peatlands. Artificially drained blanket peat catchments have been shown to have a significantly greater soil pipe density than intact catchments. This paper investigates the role of surface land drains in the enhancement of soil piping in blanket peats. The density of piping was found to significantly increase in a linear fashion with the age of the drainage. Thirty-five years after drains were cut, slopes would be expected to have twice the density of soil piping than would an undrained blanket peat catchment. The rate of pipe erosion increases exponentially over time, so that particulate carbon loss from subsurface pipes is greatest where drains are oldest

A Comparison of Cryptography Courses

The author taught two courses on cryptography, one at Duke University aimed at non-mathematics majors and one at Rose-Hulman Institute of Technology aimed at mathematics and computer science majors. Both tried to incorporate technical and societal aspects of cryptography, with varying emphases. This paper will discuss the strengths and weaknesses of both courses and compare the differences in the author's approach.Comment: 14 pages; to appear in Cryptologi

Geospatial aspects of catchment hydrology

The catchment is a fundamental unit of study in hydrology. It is normally well defined topographically, can be studied as a series of nested units (larger catchments are made of many smaller sub-catchments), and is an open system for measuring inputs and outputs of mass and energy. Catchments are usually delineated by land-surface topography and are made of hillslopes and channels. The proportion of hillslope area to channel density or total channel length may determine how efficiently water can be removed from a catchment since water in channels tends to move much more quickly than water across and through hillslopes. Thus the spatial layout of hillslopes and channels is important. This article describes some basic principles of catchment hydrology and illustrates how determining spatial factors involved is fundamental for understanding how environmental change may impact on runoff production and resulting river flow

Piping and woody plants in peatlands: Cause or effect?

This paper presents, for the first time, evidence to show that Calluna species are one causative factor of piping in blanket peat catchments. Ground-penetrating radar survey on 960 plots illustrated that piping was prevalent throughout blanket peats. However, soil pipe occurrence was significantly higher where bare peat (149 pipes/km) or Calluna (87 pipes/km) were present compared to other species (67 pipes/km). A case study catchment where there was an altitudinal limit to Calluna provided some control over potential factors that may lead to an association between piping and Calluna. Under the controlled conditions of topographic index, peat depth, and water table, piping was greater under the Calluna-covered peat than under other vegetation covers. Laboratory experiments demonstrated that 10 years worth of rainfall was enough to almost double the proportion of macropore flow occurring in recently colonized Calluna peatlands. This suggests that given enough water and time, the woody Calluna plants result in water being preferentially channeled through the upper peat. Improvements are therefore required in our understanding of the relationships between peatland plant nutrient and water supply and the feedbacks between ecosystem functioning and landform development. These results are also important given the propensity to encourage Calluna growth for game bird enhancement in many northern peatlands

Complex dynamics of the biological rhythms: gallbladder and heart cases

A theoretical analysis of the mechanisms underlying the dynamics of gallbladder and heart pulsation could clarify the question regarding the classification as chaotic of the associated behaviour, eventually related to a normal and healthy beat; this analysis is particularly relevant in view of the control of dynamics bifurcations arising in situations of disease. In this work is presented a summary of the DFA method applied to gallbladder volume data for a modest number of healthy and ill patients: the presence of signal correlation is found in both cases, but the fit shapes differ from some critical values.Comment: 3 pages, 8 figures, to appear on Physica

Women Judges and Women\u2019s Rights in Pakistan

Although the first appointment of women judges in Pakistan dates back to 1974, the massive appointment of &ldquo;lady judges&rdquo; in the past decade has caused a jump in female representation in the judiciary to more than one third &ndash; a quiet move that sends a message of adherence to the principle of gender equality as per the international treaties to which Pakistan is signatory. By investigating the everyday interactions and preoccupations of women-judges in their daily management of justice, this paper explores the socio-legal reception of the human rights discourse from the perspective of the female judges. The challenge in this scenario lies, on the one hand, in whether this change will be only formal or will also lead to substantial and accountable justice and, on the other hand, how the global agenda impacts local expectations and conceptualizations of rights within and beyond the state. A pesar de que la designaci&oacute;n de juezas en Pakist&aacute;n se remonta a 1974, la significativa designaci&oacute;n de "se&ntilde;oras juezas" en la pasada d&eacute;cada ha provocado que la representaci&oacute;n de las mujeres en la judicatura haya pasado a m&aacute;s de un tercio en juzgados de familia -un cambio silencioso que env&iacute;a un mensaje de adhesi&oacute;n al principio de igualdad de sexos consagrado por los tratados internacionales de los que Pakist&aacute;n es firmante. Mediante la investigaci&oacute;n de las interacciones y preocupaciones cotidianas de las juezas en su gesti&oacute;n habitual de la justicia, este art&iacute;culo analiza la recepci&oacute;n sociojur&iacute;dica del discurso de los derechos humanos desde la perspectiva de las mujeres que ejercen la judicatura. En tal estado de cosas, cabe preguntarse si este cambio se limitar&aacute; a las formas o si, por el contrario, alcanzar&aacute; a la justicia sustancial y comprobable. Los hallazgos permiten tambi&eacute;n elucidar la forma en que la agenda global afecta las expectativas y conceptos locales sobre los derechos, dentro y fuera del estado. DOWNLOAD THIS PAPER FROM SSRN: https://ssrn.com/abstract=3034280</p