Teaching Design to Freshmen: Style and Content

This paper describe a freshman course in engineering design that stresses the open-ended and ill-structured nature of design in a project-based context. The projects are chosen in part for their social context and utility. The projects are supplemented by lectures on design methodology and other topics related to engineering practice. Among the deliverables required of the students are proposals, progress reports, and written and oral presentations—the latter to an external design jury as part of a design competition.     

An accurate block-trimming device for ultramicrotomy of selected cells

A small instrument is described which is operated on the stage of a light microscope to trim resin-embedded specimens to precise levels for subsequent ultramicrotomy and to cut thin pilot sections for light microscopy. The operating procedure and examples of results are given.     

Electron Thermalization in Metallic Islands Probed by Coulomb Blockade Thermometry

We describe a systematic series of experiments on thermalization of electrons in lithographic metallic thin films at millikelvin temperatures using Coulomb blockade thermometry (CBT). Joule dissipation due to biasing of the CBT sensor tends to drive the electron system into non-equilibrium. Under all experimental conditions tested, the electron-electron relaxation is fast enough to ensure thermal electron distribution, which is also in agreement with the theoretical arguments we present. On the other hand, poor electron-phonon relaxation plays a dominant role in lifting the electron temperature above that of the bath. From a comparison of the results with the theoretical current-voltage characteristics of the thermometers we precisely determine the electron-phonon coupling constant for the common metals used. Our experiments show that it is a formidable task to attain thermal equilibrium with the bath using single-electron devices under non-zero bias conditions at 20–50 mK temperatures that are typically encountered in experiments. The conclusion concerning Coulomb blockade thermometry is more optimistic and two-fold: (1) One can now correct the errors due to bias heating in a satisfactory manner based on known material properties and the size of the metal films in the sensor. (2) Reliable thermometry down to 20 mK requires islands whose volumes are >10^?15 m³, which is still acceptable both from the parameter (capacitance) and fabrication points of view.     

The L5178Y/tk+/- mouse lymphoma specific gene and chromosomal mutation assay a phase III report of the U.S. Environmental Protection Agency Gene-Tox Program

The L5178Y/tk+/- (-)3.7.2C mouse lymphoma assay (MLA) which detects mutations affecting the heterozygous thymidine kinase (tk) locus is capable of responding to chemicals acting as clastogens as well as point mutagens. Improvements in the assay to enhance detection of this spectrum of genetic events are summarized, and criteria for evaluating the data are defined. Using these criteria, the Phase III Work Group reviewed and evaluated literature containing MLA results published from 1976 through 1993. The data base included 602 chemicals of which 343 were evaluated as positive, 44 negative, 18 equivocal, 54 apparently inappropriate for evaluation in this test system with the published protocols, and 142 that were inadequately tested, and thus a definitive call could not be made. The overall performance of the assay is summarized by chemical class, and the outcome of testing 260 chemicals in the MLA is compared with Gene-Tox and National Toxicology Program evaluations of rodent carcinogenesis bioassay results for the same chemicals. Based on the Work Group's evaluation of published MLA data for chemicals that were considered adequately tested, it is concluded that for most chemicals the L5178Y/tk+/- mouse lymphoma assay is eminently well suited for genotoxicity testing and for predicting the potential for carcinogenicity.     

Automatic generation of IDEF0 models

This paper looks into a new area for knowledge-based system application, that of manufacturing modelling. Manual generation of IDEF0 models of manufacturing systems is time-consuming and inconsistent. However, the process can be automated to improve timeliness and consistency. In this paper, a knowledge-based manufacturing modelling system for the automatic generation of IDEF0 models is proposed. The system will not only greatly reduce the IDEF0 modelling time but will also eliminate the inconsistency problem of conventional IDEF0 modelling systems. The paper explains the knowledge-based approach and identifies the kinds of domain knowledge that are required for the construction of the knowledge-based manufacturing modelling system.     

Homophily of Network Ties and Bonding and Bridging Social Capital in Computer-Mediated Distributed Teams

This research studied homophily of network ties in distributed teams in both task-related instrumental networks and non-task related expressive networks. Homophily of network ties was examined in terms of demographic and social characteristics, including gender, race, geographic location, and group assignment. Social network data were collected from 32 students enrolled in a distance learning class from two universities. MQAP regression analysis showed that homophily in gender and in race had no significant impact on the development of either instrumental or expressive ties. In instrumental networks, both homophily in group assignment and in location had significant impact on the development of network ties. In expressive networks, homophily in location had significant impact on the development of network ties, but the impact of homophily in group membership was only marginally significant. Further analysis of bonding ties with people of the same group and bridging ties with people from different groups showed that bonding social capital can exert significant influence on performance.     

Part II: An example of the use of the comsis software: simulation of an optical network which uses wavelength multiplexing,fsk modulation format and direct detection

This second article deals with using the Comsis software for a particular application. Simulation is used to determine the maximum channel density in presence of crosstalk. In a first part, the modelling of the system is described. The simulation parameters of different optical elements are given. The results show that in the case of channels modulated at 500 Mbitls using fsk modulation format, and a direct detection operation at 1,5 μm, a minimum spacing of 6 GHz can be obtained with a 2 dB penalty. Thus if only the bandwidth of the erbium doped fibre amplifier is taken into account, the maximum number of channels which can be used is 250. However if the fsr (free spectral range) of optical filter is taken into account, the maximun number of channels is limited to 30.     

Citrullinemia: management and clinical course. Apropos of a familial case

The authors report two cases of citrullinemia in siblings which add to 68 observations from the literature. They overview the clinical presentation, diagnosis and therapeutic management of the disease. The prognosis of severe neonatal form remains poor but an early adequate management may contribute to an acceptable outcome.