Hyperbolic Systems Modeling Currency Hoarding

It is a pleasure to dedicate this paper to Peter Lax, the greatest influence on the research of the second author. His ideas have shaped the subject of hyperbolic partial differential equations in the second part of the twentieth century. At the same time, his qualities as a person serve as a model for all scientists. We introduce and analyse linear systems of hyperbolic partial differential equations that model the replacement and hoarding of currency. The goal is to deduce the hoarding behavior from observations of circulating bills. The large time asymptotics of the models is identified in all cases. The mathematical analysis is novel, partly because of nonstandard boundary conditions. To identify parameters we suggest the measurement of the age histogram of notes, the rate of growth, and the retard in wear of notes due to hoarding. In our models that suffices to identify all but one quantity

The Economics of Counterfeiting

We develop a strategic theory of counterfeiting as a multi-market large game. Bad guys choose whether to counterfeit, and what quality to produce. Opposing them is a continuum of good guys who select a costly verification effort. In equilibrium, counterfeiters produce better quality at higher notes, but verifiers try sufficiently harder that verification still improves. We develop a graphical framework for deducing comparative statics. Passed and counterfeiting rates vanish for low and high notes. Our predictions are consistent with time series and cross-sectional patterns in a unique data set assembled largely from the Secret Servic

Previsione delle emissioni di biossido di azoto e ozono nella città di Livorno

Studio relativo dei principali inquinanti nella città di Livorno che risulta un centro ben definito vista la presenza di aree industriali, di un porto turistico e commerciale, e la relativa vicinanza all'aeroporto di Pisa

Strategically Rational Risk Taking by Age in COVID-19, and the Heterogeneous Agent Behavioral SIR Model

Given the dramatic age variation in COVID death rates, we create a heterogeneous agent version of the Behavioral SIR contagion model of Engle et al. (2020). The Bayes Nash equilibrium of our infection avoidance game yields a simple new log-linear relationship between the case fatality rate (CFR) and COVID incidence: Everyone knows that everyone optimizes vigilance both for the prevalence and their CFR. We explain 2020 CDC incidence data for the USA north-east in terms of the CFR to age-specific COVID death data for Massachusetts. Our model is statistically significant: A 10% higher CFR reduces incidence by about 1%

The Behavioral SI* Model, with Applications to the Swine Flu and COVID-19 Pandemics

The 1927 SIR contagion model is the dynamical system for an infection that passes at a constant rate in random pairwise meetings. Our Behavioral SI* Model assumes that everyone has access to a constant elasticity of avoidance technology. We then derive the passing rate in fully solvable Nash equilibrium of the game where everyone optimizes. The resulting dynamics are log-linear, and incidence is log-linear in prevalence, with slope less than one. The SI* models yields extreme predictions for major contagions, not realized. At breakout, the SI* models capture exponential growth. In our BSI* model, increasing avoidance behavior bends the curve, and induces herd immunity at lower prevalence but a later time. Our model is tractable, and better explains incidence data during the 2009 Swine Flu and the COVID-19 pandemic. In both cases, we statistically reject the SIR model. For Swine Flu, across states, the prevalence elasticity ranges from 0.8 to 0.9. We find a similar slope at breakout in the COVID-19 pandemic, and verify that its curve bending matches our BSI* formula. The BSI* model captures mandated social distancing or lockdowns in downward shifts of the line in log-prevalance - log-incidence space

GENE EXPRESSION TIME-SERIES ANALYSIS OF CAMPTHOTECIN EFFECTS IN U-87-MG AND DBTRG-05 GLIOBLASTOMA CELL LINES

The clinical efficacy of camptothecin (CPT), a drug specifically targetingtopoisomerase I (TopoI), is under evaluation for the treatment of malignant gliomas. Due to thehigh unresponsiveness of these tumours to chemotherapy, it would be very important to study thesignalling network that drives camptothecin outcome in this type of cancer cells. To address thisissue, we had previously compared the expression profile of human U87-MG glioblastoma cellswith that of a CPT-resistant counterpart, giving evidence that the development of a robustinflammatory response was the main transcriptional effect associated with CPT resistance.Here we report time-related changes and cell line specific patterns of gene expression after CPTtreatment by using two p53 wild-type glioblastoma cell lines, U87-MG and DBTRG-05, withdifferent sensitivities to TopoI inhibition

Time zone lines and suicides: west side story

A recent study (1) specifically finds high serotonin loadings in the brain of patients who attempt violent suicide. This is important because it connects to a previous area of research (2) showing that the human brain produces more serotonin when exposed to sunlight for longer periods of time. These two studies jointly suggest that the longer the exposure to sunlight, the higher the concentration of serotonin, and thus the more likely a patient is to attempt suicide. The extent to which sunlight exposure contributes to suicide has long been debated. On the one hand, lack of sunlight during the winter season is linked to seasonal affective disorder, and perhaps suicidal depressive moods (3). On the other hand, suicides peak in the spring and summer months (2) and midday rather than nighttime (4)

Training, Turnover, and Search

This article explores a model of firm-specific training in a job search environment with labor turnover. The main substantive finding is a positive association between training and wages (when dispersed). The article then precisely characterizes how both wage dispersion and firm profitability depend on the flow value b≥ 0 of workers\u27 unmatched time. It is shown that: (i) for all high values b, no equilibrium exists; (ii) for intermediate values b, multiple equilibria arise, where firms earn zero profits, and choose from a general wage distribution; (iii) for all lower values b, there is a unique equilibrium, with firms earning positive profits, and choosing from an atomless set of wages