Seigniorage, Inflation, and Reputation

This paper derives a reputational equilibrum for inflation in a model in which the government obtains valuable seigniorage by issuing fiat money in echange for real resources. One insightful result is that , with contemporaneous perceptionof actual government behavior and immediate adjustment of real cash balences to new information , the Friedman elasticity solution for maximal seigniorage is the reputatoinal equilibrium. More generally , the analysis shows that the objective of maximal seigniorage produces an equilibrium inflation rate equal either to a generalization of the Friedman elasticity solution or to the rate at which the government discounts future seigniorage adjusted for the growth rate, whichever is larger. Thus, the model formalizes the conjecture that epizodes of inflation rates in excess of the Friedman solution are attributable to high discounts rates for future seigniorage. Adding aversion to high expected inflation to the model, this analysis also rationalizes the observation that inflation rates are usually less than Friedman's elasticity solution.

Sovereign Debt as a Contingent Claim: Excusable Default, Repudiation, and Reputation

History suggests the following stylized facts about default on sovereign debt:(1) Defaults are associated with identifiably bad states of the world. (2) Defaults are usually partial, rather than complete.(3) Sovereign states usually are able to borrow again soon after a default. Motivated by these facts, this paper analyses a reputational equilibrium in a model that interprets sovereign debts as contingent claims that both finance investments and facilitate risk shifting. Loans are a useful device to facilitate risk shifting because they permit the prepayment of indemnities. Nevertheless, because the power to abrogate commitments without having to answer to a higher enforcement authority is an essential aspect of sovereignty, a decision by a sovereign to validate lender expectations about debt servicing depends on the sovereign's concern for its trust worthy reputation. A trustworthy reputationis valuable because it provides continued access to loans. A key aspect of the analysis is that lenders differentiate excusable default, which is associated with implicitly understood contingencies, from unjustifiable repudiation. In the reputational equilibrium, the short-run benefits from repudiation are smaller than the long-run costs from loss of a trustworthy reputation. Thus, although sovereigns sometimes excusably default, they never repudiate their debts. The reputational equilibrium can involve efficient risk shifting and efficient investment or it can involve a binding lending ceiling that limits risk shifting and can also restrict investment. The factors that tend to produce a binding lending ceiling include a high time discount rate for the sovereign, low-risk aversion forthe sovereign, and a low net return from the sovereign's investments.

A Matrix Based Approach for Color Transformations in Reflections

In this thesis, I demonstrate the feasibility of linear regression with 4 × 4 matrices to perform color transformations, specifically looking at the case of color transformations in reflections. I compare and analyze the power and performance linear regression models based on 3 × 3 and 4 × 4 matrices. I conclude that using 4 × 4 matrices in linear regression is more advantageous in power and performance over using 3 × 3 matrices in linear regressions, as 4 × 4 matrices allow for categorically more transformations by including the possibility of translation. This provides more general affine transformations to a color space, rather than being restricted to passing through the origin. I examine the benefits of allowing for negative elements in color transformation matrices. I also touch on the possible differences in application between filled 4 × 4 matrices and diagonal 4 × 4 matrices, and discuss the limitations inherent to linear regression used in any type of matrix operations

An end-to-end software solution for the analysis of high-throughput single-cell migration data

The systematic study of single-cell migration requires the availability of software for assisting data inspection, quality control and analysis. This is especially important for high-throughput experiments, where multiple biological conditions are tested in parallel. Although the field of cell migration can count on different computational tools for cell segmentation and tracking, downstream data visualization, parameter extraction and statistical analysis are still left to the user and are currently not possible within a single tool. This article presents a completely new module for the open-source, cross-platform CellMissy software for cell migration data management. This module is the first tool to focus specifically on single-cell migration data downstream of image processing. It allows fast comparison across all tested conditions, providing automated data visualization, assisted data filtering and quality control, extraction of various commonly used cell migration parameters, and non-parametric statistical analysis. Importantly, the module enables parameters computation both at the trajectory-and at the step-level. Moreover, this single-cell analysis module is complemented by a new data import module that accommodates multiwell plate data obtained from high-throughput experiments, and is easily extensible through a plugin architecture. In conclusion, the end-to-end software solution presented here tackles a key bioinformatics challenge in the cell migration field, assisting researchers in their highthroughput data processing

The XTT cell proliferation assay applied to cell layers embedded in three-dimensional matrix

Abstract Cell proliferation, a main target in cancer therapy, is influenced by the surrounding three-dimensional (3D) extracellular matrix (ECM). In vitro drug screening is, thus, optimally performed under conditions in which cells are grown (embedded or trapped) in dense 3D matrices, as these most closely mimic the adhesive and mechanical properties of natural ECM. Measuring cell proliferation under these conditions is, however, technically more challenging compared with two-dimensional (2D) culture and other "3D culture conditions," such as growth on top of a matrix (pseudo-3D) or in spongy scaffolds with large pore sizes. Consequently, such measurements are only slowly applied on a wider scale. To advance this, we report on the equal quality (dynamic range, background, linearity) of measuring the proliferation of cell layers embedded in dense 3D matrices (collagen, Matrigel) compared with cells in 2D culture using the easy (one-step) and in 2D well-validated, 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT)-assay. The comparison stresses the differences in proliferation kinetics and drug sensitivity of matrix-embedded cells versus 2D culture. Using the specific cell-layer-embedded 3D matrix setup, quantitative measurements of cell proliferation and cell invasion are shown to be possible in similar assay conditions, and cytostatic, cytotoxic, and anti-invasive drug effects can thus be reliably determined and compared in physiologically relevant settings. This approach in the 3D matrix holds promise for improving early-stage, high-throughput drug screening, targeting either highly invasive or highly proliferative subpopulations of cancers or both