A Fullerene-Like Ball in a Second Century Roman Mosaic?

A fullerene-like ball is found in a second century mosaic from Porta Marina Roman Baths near Ostia. Although it could be an hexadecahedral ball (28 vertices, 4 hexagonal and 12 pentagonal faces), it is probably an erroneous representation of a dodecahedral ball.     

Towards the automatic generation of software diagrams

The authors formulate the criteria for drawing dataflow diagrams and describe the placement and routing algorithms used in a system called MONDRIAN. A generalized approach to the question of software diagrams is proposed based on the authors' experience with MONDRIAN and a metasystem approach to the creation of CASE (computer-aided software engineering) environments. A formal approach to the definition of software objects and their graphical representation is given. The use of location constraints as a basis for generalized layout algorithms is discussed     

Hybrid Approach for Addressing Uncertainty in Risk Assessments

Parameter uncertainty is a major aspect of the model-based estimation of the risk of human exposure to pollutants. The Monte Carlo method, which applies probability theory to address model parameter uncertainty, relies on a statistical representation of available information. In recent years, other uncertainty theories have been proposed as alternative approaches to address model parameter uncertainty in situations where available information is insufficient to identify statistically representative probability distributions, due in particular to data scarcity. The simplest such theory is possibility theory, which uses so-called fuzzy numbers to represent model parameter uncertainty. In practice, it may occur that certain model parameters can be reasonably represented by probability distributions, because there are sufficient data available to substantiate such distributions by statistical analysis, while others are better represented by fuzzy numbers (due to data scarcity). The question then arises as to how these two modes of representation of model parameter uncertainty can be combined for the purpose of estimating the risk of exposure. This paper proposes an approach (termed a hybrid approach) which combines Monte Carlo random sampling of probability distribution functions with fuzzy calculus. The approach is applied to a real case of estimation of human exposure, via vegetable consumption, to cadmium present in the surficial soils of an industrial site located in the north of France. The application illustrates the potential of the proposed approach, which allows the uncertainty affecting model parameters to be represented in a way that is consistent with the information at hand. Also, because the hybrid approach takes advantage of the “rich” information provided by probability distributions, while retaining the conservative character of fuzzy calculus, it is believed to hold value in terms of a “reasonable” application of the precautionary principle.     

Near-Optimal Signal Preprocessor for Positive Cardiac Arrhythmia Identification

Extremely high reliability of waveform detection is fundamental for computer-assisted identification of cardiac arrhythmias. The problem is formulated in terms of one of the basic aspects in digital signal processing, namely, detection of an unknown deterministic signal in noise. The signal is considered band limited and the noise as Gaussian with zero mean. The theory presented leads to an energy based detector. No a priori assumption is made about the morphology of the waveforms to be detected; only energy thresholding is necessary for event detection. The addition of a linear filter as a front end to the energy detector has resulted in an entire detection process described as suboptimal matched nonlinear filtering. The SNR gain at the input of the energy detector has given performances almost identical to the matched filter. The method has been implemented with an original fast algorithm to allow reasonable execution time for the processing of continuous long-duration signals (1 h). The design of such a fillter is described along with its application to the processing of two simultaneously recorded cardiac signals. The two signals are an auricular electrogram (OEG from an esophageal pill electrode) and an ECG (lead II or III). Systematic evaluation and detection performance results show that the proposed method could be seriously considered as a near-optimal approach to waveform detection, since it is based on proven signal processing theory and is far superior to heuristic methods.     

Optically pumped rubidium as a frequency standard at 196 THz

The performance of 196.0-THz (1529-nm) DFB lasers frequency-locked to absorption lines of a rubidium vapor optically pumped at 384.2 THz (780.2 nm) is studied. The absorption profiles of the pumped vapor are measured under various conditions and compared with theoretical predictions. A bright resonance resulting from the cascade of two cycling transitions is characterized both experimentally and theoretically. The measured frequency stability of a DFB laser frequency-locked to this line reaches a level of 2×10^-10 for an averaging time of 100 s when compared to a similar laser locked to an acetylene line     

Packaging production and consumption in the world and in some industrialized countries

This paper reports on statistics concerning production and consumption of packaging (as a whole or per capita) in Europe, in the USA, in Japan and in the world. Data have been provided by National Trade Associations and by consultants specialized in packaging and in economics. It is estimated that in 1986 the global consumption of packaging reached 150 millions of tonnes valued at 1200 billions of French francs. Consumption could reach 247 million tonnes by the year 2000. Paper and board have the highest consumption rate, but plastics have the highest rate of growth. Nevertheless, consumption per capita in the industrialized countries will be more than 10 times the consumption in underdeveloped countries. The packaging industries take fourth place in the USA, sixth in Western Germany and twelfth in France. In Europe, as in the world, paper and board is the material most used (40%), with glass (a high density material) taking second place and plastics third, i.e. if we consider the quantity of materials and not their value. Some differences appear between the various countries, but the figures for USA and Japan lead to similar conclusions. The survey shows clearly that the USA as compared with Europe has twice the consumption of packaging materials per capita and this difference is even greater compared with the rest of the world.     

Reward prediction in primate basal ganglia and frontal cortex

Reward information is processed in a limited number of brain structures, including fronto-basal ganglia systems. Dopamine neurons respond phasically to primary rewards and reward-predicting stimuli depending on reward unpredictability but without discriminating between rewards. These responses reflect 'errors' in the prediction of rewards in correspondence to learning theories and thus may constitute teaching signals for appetitive learning. Neurons in the striatum (caudate, putamen, ventral striatum) code reward predictions in a different manner. They are activated during several seconds when animals expect predicted rewards. During learning, these activations occur initially in rewarded and unrewarded trials and become subsequently restricted to rewarded trials. This occurs in parallel with the adaptation of reward expectations by the animals, as inferred from their behavioral reactions. Neurons in orbitofrontal cortex respond differentially to stimuli predicting different liquid rewards, without coding spatial or visual features. Thus, different structures process reward information processed in different ways. Whereas dopamine neurons emit a reward teaching signal without indicating the specific reward, striatal neurons adapt expectation activity to new reward situations, and orbitofrontal neurons process the specific nature of rewards. These reward signals need to cooperate in order for reward information to be used for learning and maintaining approach behavior.     

Object-oriented specification of a bandwidth management system for ATM-based virtual private networks

This paper describes the specification of a bandwidth management system for ATM-based virtual private networks (vpn). Such a system allows a vpn customer to dynamically modify the bandwidth allocated to vpn connections. The analysis process focuses on the service management information model and interfaces required to provide that service to the customer. The specification work is performed according to a second generation object-oriented development method called Fusion. The vpn service and management architectures as well as the different actors involved are also described in detail.     

Distributed constraint optimization with MULBS: A case study on collaborative meeting scheduling

This paper introduces MULBS, a new DCOP (distributed constraint optimization problem) algorithm and also presents a DCOP formulation for scheduling of distributed meetings in collaborative environments. Scheduling in CSCWD can be seen as a DCOP where variables represent time slots and values are resources of a production system (machines, raw-materials, hardware components, etc.) or management system (meetings, project tasks, human resources, money, etc). Therefore, a DCOP algorithm must find a set of variable assignments that maximize an objective function taking constraints into account. However, it is well known that such problems are NP-complete and that more research must be done to obtain feasible and reliable computational approaches. Thus, DCOP emerges as a very promising technique: the search space is decomposed into smaller spaces and agents solve local problems, collaborating in order to achieve a global solution. We show with empirical experiments that MULBS outperforms some of the state-of-the-art algorithms for DCOP, guaranteeing high quality solutions using less computational resources for the distributed meeting scheduling task.