Fractional diffusion emulates a human mobility network during a simulated disease outbreak

From footpaths to flight routes, human mobility networks facilitate the spread of communicable diseases. Control and elimination efforts depend on characterizing these networks in terms of connections and flux rates of individuals between contact nodes. In some cases, transport can be parameterized with gravity-type models or approximated by a diffusive random walk. As a alternative, we have isolated intranational commercial air traffic as a case study for the utility of non-diffusive, heavy-tailed transport models. We implemented new stochastic simulations of a prototypical influenza-like infection, focusing on the dense, highly-connected United States air travel network. We show that mobility on this network can be described mainly by a power law, in agreement with previous studies. Remarkably, we find that the global evolution of an outbreak on this network is accurately reproduced by a two-parameter space-fractional diffusion equation, such that those parameters are determined by the air travel network.Comment: 26 pages, 4 figure

Market for Luca Pacioli\u27s Summa de Arithmetica: some comments

This paper explains why Pacioli\u27s exposition of double-entry bookkeeping, published in his Summa of 1494, was neither an effective reference text for merchants nor a satisfactory text for their sons. In doing so, the paper contradicts some of the points made in the interesting and wide-ranging article by Sangster, Stoner, and McCarthy in the June 2008 issue of this journal

Common costs and business decisions: An historical note

Almost contemporaneously with The Wealth of Nations, a treatise on bookkeeping and accounts was published which shows a lucid awareness of several cost issues, especially of the futility of attempting to allocate common or joint cost. This book is Robert Hamilton\u27s An Introduction to Merchandise

Two-currency, nostro and vostro accounts: Historical notes, 1400-1800

Suppose a merchant in country A has dealings with an agent in country B. The indebtedness between the merchant (principal) and his foreign correspondent (agent) has to be settled in terms of B\u27s currency. Fluctuations in the exchange rate give rise to gains or losses, borne by the merchant. This paper discusses one accounting treatment (in the principal\u27s ledger) of the dealings between domestic principal and foreign agent. It also considers the treatment where the merchant serves as agent for a foreign principal. The discussion is illustrated by references to two 15th century Italian ledgers and to passages in several treatises on bookkeeping and accounts published in the period 1400 to 1800

Personal accounts, account books and their probative value: Historical notes, c.1200-c.1800

This paper discusses a number of topics pertaining to personal accounts in account books in the period roughly between 1200 and 1800. The main emphasis is on two topics, namely the use of account books as evidence in courts of law, and bad and doubtful debts and their accounting treatment. Examples from various countries and periods are provided to illustrate the discussion, which is not intended to be exhaustive

Poynting Vector Flow in a Circular Circuit

A circuit is considered in the shape of a ring, with a battery of negligible size and a wire of uniform resistance. A linear charge distribution along the wire maintains an electrostatic field and a steady current, which produces a constant magnetic field. Earlier studies of the Poynting vector and the rate of flow of energy considered only idealized geometries in which the Poynting vector was confined to the space within the circuit. But in more realistic cases the Poynting vector is nonzero outside as well as inside the circuit. An expression is obtained for the Poynting vector in terms of products of integrals, which are evaluated numerically to show the energy flow. Limiting expressions are obtained analytically. It is shown that the total power generated by the battery equals the energy flowing into the wire per unit time.Comment: 19 pages, 8 figure

Is Nigeria Really “Big for Nothing”? Matters Arising from Kevin Nwabugwu Echeruo’s 1969 Propaganda Poster

The audacious declaration “Big for nothing” in Kevin Echeruo’s propaganda poster during the Nigerian civil war offers illumination to the forgotten undercurrents that drove the 30-month war which in the last fifty years has contributed to the setting of agenda for separatist polemics in the Nigeria nation-state. Using largely the iconographic approach to visual description and interpretation, this study examines the cultural codes and representational conventions that inform contemporary artistic representational style as a cultural practice. The illustration not only approximates to one of the early visual indicators on the divisive national challenge rendered in highly coded visual and linguistic rhetoric of hegemonic power struggle by the elite class, but also a significant metaphor of contemporary frustration on nationhood and nationality for most Nigerians. Accordingly, this article broaches on the parameters of patriotism, nationality and self-determination to posit that the illustration represents the extremes of citizen dissatisfaction couched in a radical artistic narrative of a caricature. It submits that the strength of national allegiance and cohesiveness is a function of the reciprocity to its citizens