Combinatorial simplex algorithms can solve mean payoff games

A combinatorial simplex algorithm is an instance of the simplex method in which the pivoting depends on combinatorial data only. We show that any algorithm of this kind admits a tropical analogue which can be used to solve mean payoff games. Moreover, any combinatorial simplex algorithm with a strongly polynomial complexity (the existence of such an algorithm is open) would provide in this way a strongly polynomial algorithm solving mean payoff games. Mean payoff games are known to be in NP and co-NP; whether they can be solved in polynomial time is an open problem. Our algorithm relies on a tropical implementation of the simplex method over a real closed field of Hahn series. One of the key ingredients is a new scheme for symbolic perturbation which allows us to lift an arbitrary mean payoff game instance into a non-degenerate linear program over Hahn series.Comment: v1: 15 pages, 3 figures; v2: improved presentation, introduction expanded, 18 pages, 3 figure

Characterization of carbon nanotubes produced by arc discharge: Effect of the background pressure

Single walled carbon nanotubes (SWNT) produced by the anodic arc discharge over a range of constant background pressures of helium (100–1000 Torr) were examined under a high-resolution transmission electron microscope, and a Raman spectrometer. It was found that the average SWNT diameter is about 2 nm and fairly independent of the background pressure. Analysis of the relative purity of SWNTs samples suggests that highest SWNT relative concentration can be obtained at background pressure of about 200–300 Torr. Measured anode ablation rate increases linearly with background pressure. The model of the anodic arc discharge was developed. It was found that the predicted anode ablation rate agrees well with experiment suggesting that electron temperature in the anodic arc is about 0.5 eV. © 2004 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69876/2/JAPIAU-95-5-2749-1.pd

The Planning Process: Lessons of the Past and a Model for the Future

SUMMARY Development planning, as practised over the last 25 years, has been technocratic, politically isolated and naive. Planners have entered a blind alley, described as ‘narrow?planning’, where professionalisation and division of labour have led to a concentration on documents rather than real?world changes. Narrow?planning is contrasted with ‘broad?planning’, where data collection, the consultation of relevant interest groups, forecasting, the definition of objectives, plan construction, authorisation, implementation, monitoring, and evaluation, are linked, providing a model of a continuous, integrated planning process. The preconditions for the success of this model are discussed, and it is emphasised that planning is essentially a political process. RESUME Le processus de planification: leçons du passé et modele pour I'avenir. La planification du développement, telle que pratiquée au cours des 25 dernières années, a été technocratique, isolée politiquement et naïive. Les planificateurs se sont engagés dans une impasse, qualifiée de “planification étroite”, où la professionalisation et la division du travail a résulté en une concentration sur les documents plutôt que sur les changements du monde concret. A cette forme de planification étroite, l'auteur oppose une “planification large”, où le rassemblement des données, la consultation des groupes d'intérêt appropriés, les prévisions, la définition des objectifs, la mise au point des projets, l'autorisation, la mise en oeuvre, le contrôle et l'évaluation sont des activités liées les unes aux autres, fournissant le modèle d'un processus de planification continu et intégré. L'auteur examine les conditions préalables nécessaires au succès de ce modèle, en soulignant que la planification est essentiellement un processus politique. RESUMEN El Proceso de Planif icación: Las lecciones del pasado y un modelo para el futuro La planificación del desarrollo, según se ha venido practicando durante los ultimos 25 años, ha sido tecnocrático, políticamente aislado y ingenuo. Los planificadores han entrado en un callejón sin salida, que se conoce como “planificación estrecha”, en que el profesionalismo y la división de trabajos han resultado en una acumulación de documentos, pero sin producir cambios reales y prácticos. Se compara la “planificación estrecha” con la “planificación amplia”, en que van unidas la recopilación de datos, la consultación con los diferentes grupos afectados, previsión, la defición de objetivos, la formulación de planes, autorización, implementación, control y evaluación, resultando en un modelo de planificación integrada y continua. Se comenta sobre las condiciones previas para que este modelo resulte un éxito, y se hace hincapié para que la planificación sea básicamente un proceso político

Continuous Nanoclimate Data (1985-1988) from the Ross Desert (McMurdo Dry Valleys) Cryptoendolithic Microbial Ecosystem

We have collected year-round nanoclimate data for the cryptoendolithic microbial habitat in sandstones of the Ross desert, Antarctica, obtained with an Argos satellite data system. Data for two sites in the McMurdo Dry Valleys are available: Linnaeus Terrace, January 1985 to June 1988, and Battleship Promontory, 1986-1987. The focus of this research is ecological, and hence year-round environmental data have been obtained for the ambient environment as well as for conditions within the rock. Using data from the summer, we compare the conditions inside the rock to the outside weather. This demonstrates how the rock provides a shelter for the endolithic microbial community. The most important property of the rock is that it absorbs the summer sunlight, thereby warming up to temperatures above freezing. This warming allows snowmelt to seep into the rock, and the moisture level in the rocks can remain high for weeks against loss to the dry environment

Exploring opportunities around climate-smart breeding for future food and nutrition security

There is a 95% chance that warming will exceed 2°C by the end of the century (Raftery et al. 2017). Global crop productivity is projected to fall by 5-10 % per degree of warming (Challinor et al. 2014), with even greater losses likely for some crops in some areas. The challenge of meeting future food demand is increasing, and climate change is already diminishing our ability to adapt through crop breeding (Challinor et al. 2016; Aggarwal et al. 2019). Recent research is suggesting that increases in climate variability are already affecting the number of food-insecure people, and that increasing atmospheric CO2 concentrations may affect the nutrient content of some food staples, with serious implications for food and nutrition security (Smith and Myers 2018). New crop varieties will be needed that can deliver higher yields as well as possessing the ability to withstand heat and greater tolerances for the secondary effects of a warmer world, such as increased pressures from drought, water-logging, pests and diseases, and reduced nutritional quality due to higher levels of CO2. The systems for accelerated delivery of climate-resilient varieties into food producers’ hands need to be massively upgraded (Cramer 2018). Innovative holistic breeding strategies for multiple traits will be needed that embrace the full pipeline from trait discovery to varietal deployment and seed system development

Entwurf und Implementierung von CSSA - Beschreibung der Sprache, des Compilers und des Mehrrechnersimulationssystems : Teil E II: Programmdokumentation Teil II

CSSA (Computing System for Societies of Agents) is an interactive programming language for asynchronous multiprocessor systems. Computations are done by concurrently working sequential modules, called agents which implement objects of data and control abstractions. Communication is done by passing messages to acquainted agents. The receiving agent creates an instance of an operation capability referred to in the message. Since agents can be created during the computation and acquaintances can be transmitted in messages the heterarchical agent-net may dynamically change. The language described in volume B of the CSSA-documentation has been successfully implemented for a multiprocessor simulation system running on a general purpose computer. This system allows the execution of CSSA-applications on a wide range of simulated multicomputer configurations. The use of the system is described in volume C. This volume contains the documentation of the different system-components including program sceletons and complete source-listings. Portability problems are discussed in the description of the program development system which is realized in the Siemens BS2000 command language. The reader is expected to have a certain knowledge of this language. Compiler and runtime system are written in SIMULA using to a large degree the more sophisticated language concepts of SIMULA, such as CLASS SIMULATION, hierarchical class definitions, virtual attributes of classes and prefix blocks. Therefore extensive knowledge of the SIMULA language is necessary for reading this volume

Design and Implementation of CSSA -Description of the Language, the Compiler and the Multiprocessor Simulation System: Volume C: User's Guide

CSSA (Computing System for Societies of Agents) is an interactive programming language for asynchronous multiprocessor systems. Computations are done by concurrently working sequential modules, called agents which implement objects of data and control abstractions. Communication is done by passing messages to acquainted agents. The receiving agent creates an instance of an operation capability referred to in the message. Since agents can be created during the computation and acquaintances can be transmitted in messages the heterarchical agent-net may dynamically change. The language described in volume B of the CSSA-documentation has been successfully implemented for a multiprocessor simulation system running on a general purpose computer. This system allows the execution of CSSA-applications on a wide range of simulated multicomputer configurations. This manual describes the use of the CSSA-system consisting of the compiler, the multiprocessor-simulation system, the commandinterpreter and the interactive debugging-system. All systemcomponents are integrated in-a menue-driven program-development system. A detailed discussion of the language concepts and the simulation system can be found in other volumes of the CSSA-documentation