The first business computer: a case study in user-driven innovation

In 1949, the world's first business computer application was rolled out. The host for the application was a British catering and food-manufacturing company, which had developed and built its own computer, designed for business data processing. The author traces the endeavour's history and presents an analysis of how and why the company-J. Lyons & Co.-was in a natural position to take on the challenge, the precursor of the information revolution we see toda

Vascular Growth in the Fetal Lung

The structure of the lung is truly remarkable. It is primarily composed of three branched tubular networks (the airway, pulmonary artery and vein, bronchial artery and vein) which supply blood and air to the site of gas exchange and which maintain nutrient supply to supporting tissues. This complex interwoven network is packed into a chest cavity with a volume of 6 litres but yet it services a gas-exchange surface area of 130m2, the floor area of a comfortably sized Mediterranean holiday villa! Weibel (1991) tells us that if this surface area were arranged as a balloon it would possess a radius of 3m and a volume of 113,000 litres, more than 18 thousand times the space available in the chest cavity. The process which drives this exceptional packaging involves repeated cycles of ordered branching to create a fractal network of tubules whose core dimensions decrease at a precise and regular rate with each successive branch. This is a high “gain-of–structure” process. In the airway, 23 generations of branching form a conducting tubular network with 17 million branches and a combined length of more than 7km. This provides convective air flow to 480 million alveoli each of which are located along a path length that is no further than 45cm from the external atmosphere. The pulmonary vasculature forms along side the airway but undergoes an additional five generations of branching to form the capillary network that surrounds each alveolus. If you simply assumed that each alveolus (diameter ~200?m) was serviced by only one blood vessel you would calculate that the alveolar capillary bed alone runs to nearly 100 km in length. Realistic attempts at modelling this structure in three dimensions suggest that it is, in all probability, between 2 and 6 thousand km long (Muhlfield et al., 2010), illustrating the impressive capacity of fractal branching processes to package colossal structures into ever smaller spaces.</p

Discrete Symmetries of Off-Shell Electromagnetism

We discuss the discrete symmetries of the Stueckelberg-Schrodinger relativistic quantum theory and its associated 5D local gauge theory, a dynamical description of particle/antiparticle interactions, with monotonically increasing Poincare-invariant parameter. In this framework, worldlines are traced out through the parameterized evolution of spacetime events, advancing or retreating with respect to the laboratory clock, with negative energy trajectories appearing as antiparticles when the observer describes the evolution using the laboratory clock. The associated gauge theory describes local interactions between events (correlated by the invariant parameter) mediated by five off-shell gauge fields. These gauge fields are shown to transform tensorially under under space and time reflections, unlike the standard Maxwell fields, and the interacting quantum theory therefore remains manifestly Lorentz covariant. Charge conjugation symmetry in the quantum theory is achieved by simultaneous reflection of the sense of evolution and the fifth scalar field. Applying this procedure to the classical gauge theory leads to a purely classical manifestation of charge conjugation, placing the CPT symmetries on the same footing in the classical and quantum domains. In the resulting picture, interactions do not distinguish between particle and antiparticle trajectories -- charge conjugation merely describes the interpretation of observed negative energy trajectories according to the laboratory clock.Comment: 26 page

Scheduling Monotone Moldable Jobs in Linear Time

A moldable job is a job that can be executed on an arbitrary number of processors, and whose processing time depends on the number of processors allotted to it. A moldable job is monotone if its work doesn't decrease for an increasing number of allotted processors. We consider the problem of scheduling monotone moldable jobs to minimize the makespan. We argue that for certain compact input encodings a polynomial algorithm has a running time polynomial in n and log(m), where n is the number of jobs and m is the number of machines. We describe how monotony of jobs can be used to counteract the increased problem complexity that arises from compact encodings, and give tight bounds on the approximability of the problem with compact encoding: it is NP-hard to solve optimally, but admits a PTAS. The main focus of this work are efficient approximation algorithms. We describe different techniques to exploit the monotony of the jobs for better running times, and present a (3/2+{\epsilon})-approximate algorithm whose running time is polynomial in log(m) and 1/{\epsilon}, and only linear in the number n of jobs