Optimal allocation in a multiresources graduated tariff communication environment

The designer of computer networks is often confronted with the problem of the optimal allocation of multiple communications resources, subject to a graduated tariff. Such optimality criteria for the correct mix of facilities for use in system design are obtained. The paper gives examples from data communications.     

Studies on the transformation of intact yeast cells by the LiAc/SS-DNA/PEG procedure

An improved lithium acetate (LiAc)/single-stranded DNA (SS-DNA)/polyethylene glycol (PEG) protocol which yields >1 × 10⁶ transformants/μg plasmid DNA and the original protocol described by Schiestl and Gietz (1989) were used to investigate aspects of the mechanism of LiAc/SS-DNA/PEG transformation. The highest transformation efficiency was observed when 1 × 10⁸ cells were transformed with 100 ng plasmid DNA in the presence of 50 μg SS carrier DNA. The yield of transformants increased linearly up to 5 μg plasmid per transformation. A 20-min heat shock at 42°C was necessary for maximal yields. PEG was found to deposit both carrier DNA and plasmid DNA onto cells. SS carrier DNA bound more effectively to the cells and caused tighter binding of ³²P-labelled plasmid DNA than did double-stranded (DS) carrier. The LiAc/SS-DNA/PEG transformation method did not result in cell fusion. DS carrier DNA competed with DS vector DNA in the transformation reaction. SS plasmid DNA transformed cells poorly in combination with both SS and DS carrier DNA. The LiAc/SS-DNA/PEG method was shown to be more effective than other treatments known to make cells transformable. A model for the mechanism of transformation by the LiAc/SS-DNA/PEG method is discussed.     

[PSI] and [URE3] as yeast prions

[URE3] is a non-Mendelian genetic element that mimics recessive mutations in the chromosomal URE2 gene making cells derepressed for nitrogen catabolic enzymes. [PSI] is a non-Mendelian enhancer of readthrough of translational termination similar in its effects to some mutations in the chromosomal SUP35 gene. Three lines of evidence led to the proposal⁷⁵ that both [URE3] and [PSI] are prions, infectious proteins analogous to the scrapie agent mediating transmissible spongiform encephalopathies of mammals. (1) Both [PSI] and [URE3] are reversibly curable. (2) [PSI] propagation requires SUP35 and [URE3] propagation requires URE2 with recessive chromosomal mutants having the same phenotypes as the presence of the respective dominant non-Mendelian element. (3) Overproduction of Sup35p and Ure2p increases the frequency of cells acquiring [PSI] or [URE3], respectively.     

Stimulus-response compatibility for moving stimuli: Perception of affordances or directional coding?

C. F. Michaels (1988) reported a compatibility effect in which responses were fastest at the destination of a moving stimulus; this "destination" compatibility effect was interpreted in terms of catching actions "afforded" by the stimulus motion. The present study evaluated implications of the catching-affordance account and compared them with those of an account based on spatial coding or relative direction. The destination compatibility effect was obtained when the responses were keypresses rather than catching movements of a joystick and regardless of whether the stimulus expanded, contracted, or only changed location. This effect was a function of relative rather than absolute location of the responses. A similar compatibility effect was obtained when destinations were designed by static arrow stimuli. The results are inconsistent with the catching-affordance account and are best explained by the coding of relative direction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Toward a theory of verification and validation: Artifacts

This article uses the notion of artifacts to generate a theory for the verification and validation of intelligent systems. This theory has a number of applications. First, it provides a language and a way of thinking about verification and validation. Second, it suggests that we examine not the processes used in the design and development of systems, but instead the tangible artifacts generated by those processes. Third, it broadens the base of the set of artifacts encompassed by the typical verification and validation processes to include more than just specifications and prototypes. Fourth, the use of artifacts leads to a redefinition of verification and validation in terms of artifacts. Fifth, verification and validation tests are tied to artifacts, so that the choice of a set of artifacts can be used as a means of generating a portfolio of tests to investigate each artifact and the interaction of artifacts. Sixth, relationships between artifacts can be defined as “operators” which can be isolated and investigated for their individual quality. Seventh, standards can be generated for specific artifacts and operators rather than for entire development processes. © 1994 John Wiley & Sons, Inc.     

Monte Carlo simulations of very low pressure chemical vapor deposition

Summary Simulation strategies for chemical vapor deposition (CVD) of thin solid films are presented, with emphasis on direct simulation Monte Carlo methods for analyzing and predicting physical phenomena occurring at low pressures and in micron-sized substrate features. The Monte Carlo approach is placed in perspective, relative to standard continuum mechanics-based strategies for modeling of CVD systems. Design issues that may be addressed through the developed methods are exemplified with computations for a new, technologically important CVD process for epitaxy of Si and Si_xGe_1-x alloys. Specifically, radiative heat transfer, rarefied gas-flow characteristics, species separation caused by pressure and thermal diffusion, growth-rate uniformity vs. surface reactivity, and deposition in microscopic features are addressed as parts of the overall CVD reactor-design approach. Process implications of rarefied transport effects unique to very low pressure CVD conditions are described. A new profile evolution technique is also introduced which predicts film topology, as well as the microstructure of the film.     

Visual comparability of 3D regular sampling and reconstruction

The Body-Centered Cubic (BCC) and Face-Centered Cubic (FCC) lattices have been analytically shown to be more efficient sampling lattices than the traditional Cartesian Cubic (CC) lattice, but there has been no estimate of their visual comparability. Two perceptual studies (each with N = 12 participants) compared the visual quality of images rendered from BCC and FCC lattices to images rendered from the CC lattice. Images were generated from two signals: the commonly used Marschner-Lobb synthetic function and a computed tomography scan of a fish tail. Observers found that BCC and FCC could produce images of comparable visual quality to CC, using 30-35 percent fewer samples. For the images used in our studies, the L(2) error metric shows high correlation with the judgement of human observers. Using the L(2) metric as a proxy, the results of the experiments appear to extend across a wide range of images and parameter choices.