Native and generic parallel programming environments on a transputer and a PowerPC platform

Genericity of parallel programming environments, enabling development of portable parallel programs, is expected to result in performance penalties. Furthermore, programmability and tool support of programming environments are important issues if a choice between programming environments has to be made. In this paper we propose a methodology to compare native and generic parallel programming environments, taking into account such competing issues as portability and performance. As a case study, this paper compares the Iserver-Occam, Parix, Express and PVM parallel programming environments on a 512-node Parasytec GCel. Furthermore, we apply our methodology to compare Parix and PVM on a new architecture, a 32-node Parsytec PowerXplorer, which is based on the PowerPC chip. In our approach we start with a representative application and isolate the basic (environment)-dependent building blocks. These basic building blocks, which depend on floating-point performance and communication capabilities of the environments, are analysed independently. We have measured point-to-point communication times, global communication times and floating-point performance. All information is combined into a time complexity analysis, allowing comparison of the environments on different degrees of functionality. Together with demands for portability of the code and development time (i.e. programmability), an overall judgement of the environments is given.     

POOSS: A Parallel Object-Oriented Stable Storage

This article describes the design and implementation of a parallel object-oriented stable storage (POOSS) system in the context of the PRISMA project.

The main issues of the POOSS system include atomic access of generic objects, fault tolerance, parallelism, and the issues in designing a fast disk file system. These issues are approached by constructing the POOSS system as a hierarchical one, with each layer attacking different issues, resulting in a system which is easier to understand, implement and maintain.

The multiple layers of the POOSS system are interfaced by a restricted set of UNIX compatible routines. By exposing the internal interfaces of different layers to external users, the POOSS system is able to provide the application programs with multiple services of a different nature: the normal local file service, the parallel global file service, the parallel stable file service, and the parallel object-oriented stable file service. Implemented in a 100-node parallel machine environment, the POOSS system could not only process multiple files simultaneously, but also be partitioned into multiple independent subsystems.

The performance measurement of the current implementation has shown good results for the system and also identified bottlenecks, candidates for further optimizations.     

A hierarchical view on modeling the reliability of a DSRC link for ETC applications

For electronic payments, the communication link has to be reliable. Dedicated short-range communication (DSRC) is a proposed solution for the automatic debiting of vehicles in an electronic toll collection (ETC) system without disturbing the traffic flow. The requirements on the reliability of such a system are high, which implies that only large-scale simulations with a lot of detail are effective for analyzing occasional errors. In this paper, a hierarchical approach is worked out that allows such simulations of the communication link, with a 80% reduction of the computational effort compared to simulation with full detail.     

Evaluating automatic debiting systems by modelling and simulationof virtual sensors

The Dutch government is considering placing Automatic Debiting Systems (ADS) for electronic fee collection (EFC) on the highways. These systems would interact via a transponder in each passing car, and subtract a fee from the driver's credit card. Nonpayers would be photographed and fined. The ultimate goal is to use these systems to influence road usage. It is shown how the concept of virtual sensors, designed for goal-directed sensing in (robotic) autonomous systems, can be used in the design of the simulation. It is also shown how this forces the choice for a discrete event simulation, which in turn affects the implementation of the virtual sensor concept     

Genetic Elements Orchestrating Lactobacillus crispatus Glycogen Metabolism in the Vagina

Glycogen in the female lower reproductive tract is a major carbon source for colonization and acidification by common vaginal Lactobacillus species, such as Lactobacillus crispatus. Previously, we identified the amylopullulanase encoding gene pulA of Lactobacillus crispatus to correlate with the ability to autonomously utilize glycogen for growth. Here, we further characterize genetic variation and differential regulation of pulA affecting the presence of its gene product on the outer surface layer. We show that alpha-glucan degrading activity dissipates when Lactobacillus crispatus is grown on glucose, maltose and maltotriose, in agreement with carbon catabolite repression elements flanking the pulA gene. Proteome analysis of the S-layer confirmed that the amylopullulanase protein is highly abundant in an S-layer enriched fraction, but not in a strain with a defective amylopullulanase variant or in an amylopullulanase-sufficient strain grown on glucose. In addition, we provide evidence that Lactobacillus crispatus pulA mutants are relevant in vivo, as they are commonly observed in metagenome datasets of human vaginal microbial communities. Analysis of the largest publicly available dataset of 1507 human vaginal metagenomes indicates that among the 270 samples that contain a Lactobacillus crispatus pulA gene, 62 samples (23%) had a defective variant of this gene. Taken together, these results demonstrate that both environmental, as well as genetic factors explain the variation of Lactobacillus crispatus alpha-glucosidases in the vaginal environment.     

Progress in the fifth generation inference architectures

In an earlier article, the architecture of the FGCS sequential inference machines PSI and SIM and the parallel inference machine PIM were described. This article gives a progress report concerning these developments. Moreover, the relational database machine (DELTA) and the connection of DELTA with PSI to form a first prototype of a Knowledge Base Machine (KBM) are discussed. Most of the information is based on the 1984 research report on the Fifth Generation Computer Systems.     

The dutch parallel reduction machine project

In November 1984 three research groups at the universities of Amsterdam, Nijmegen and Utrecht started a cooperative project sponsored by the Dutch Ministry of Science and Education (Science Council). The first phase lasting until the end of 1987 is a pilot study and has as aim to answer the following question. Is it possible and realistic to construct an efficient parallel reduction machine? The present paper gives an outline of the problems concerning parallel reduction machines and of our research towards their solutions.     

Significant reduction in post-lumbar puncture headache using an atraumatic needle. A double-blind, controlled clinical trial

A characteristic headache occurs in about 36-55% of patients after lumbar puncture, and many of these patients need bed rest for one or more days to get relief. In a double-blind randomized trial we compared a new 22-gauge atraumatic puncture needle with the most widely used 20-gauge "conventional" needle. In 49 patients randomized to the atraumatic needle, post-lumbar puncture headache occurred in 6%, whereas in the 50 patients randomized to the conventional needle this occurred in 32% (p = 0.001). On the basis of these results we recommend use of the atraumatic needle in order to diminish the frequency of post-lumbar puncture headache.     

罗马小学及初中，罗马，意大利

在罗马郊区,一个小学与初中结合的建筑项目正在建设中。它由重复的建筑单元组成．每一个单元由2组4个相连的教室构成一个街区。每一个单元围绕一个天井布置,仿效一种传统的罗马住宅的设计。由于意大利的气候温和．天井在一年当中的大部分时间里都可以当作一种附加的用于教学的室外空间。