More Harvard humbug.

Replies to J. Sonnenfeld's (1982) critique of D. Bramel and R. Friend's (see record 1982-08638-001) article on the studies performed at the Hawthorne plant of Western Electric. Sonnenfeld fails to recognize the unique aspects of Bramel and Friend's reinterpretation of what happened at Hawthorne. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Three-dimensional finite-element analysis of laminated composites

A three-dimensional finite-element analysis treating the mechanical response of thick laminated composite plates in bending is presented. An isoparametric solid element with a cubic displacement expansion in planform and a linear variation through the thickness is used to model each layer of the laminate. The degrees-of-freedom of the element are retained at its boundaries so that interconnections between lamina with different fiber orientations can be made at their interfaces. An incore version of the conjugate gradient technique, which does not have bandwidth restrictions, is used to minimize the total potential energy of the system with the number of iterations to convergence being about one-fifth the total global degrees-of-freedom. Because a three-dimensional analysis is used, the effects of thickness-stretching, transverse shear, extension, and bending deformations are obtained. Comparisons with three-dimensional elasticity solutions are in excellent agreement and show the necessity of having individual elements for each layer when they have different fiber orientations and when the plates are thick.     

Comparative psychometric analysis of vector and isochrone cardiac activation maps

Isochronal cardiac activation maps can be constructed from local activation times associated with spatial locations, and are frequently used to study cardiac arrhythmias. Cardiac velocity vector mapping has been proposed as an alternative method to study cardiac activation in both clinical and research environments. Velocity vectors inherently contain more information than scalar measures of latency, but it is unknown how vector maps and isochronal maps compare when they are used to identify patterns and features associated with arrhythmias. In order to quantitatively compare these two visualization methods, eight cardiologists were asked to complete forced-choice tasks in which they selected ablation sites based on synthetic vector or isochronal maps. Maps varied in arrhythmia complexity, number of vectors or activation times included, and errors in magnitude or angle for maps of velocity vectors. Quantitative comparison was achieved by using psychometric functions to characterize the learning curve and the total number of measurements needed in order to choose a correct ablation site. For simple arrhythmias, performance with vector maps was superior to isochronal maps. Subjects required fewer measurements, and learned more rapidly by studying vector maps. For more complex arrhythmias, there was no significant difference in performance between vector and isochronal maps. However, arrhythmia features were clearer with vector maps, even though this clarity did not necessarily change the ablation site choice. When errors were added to vector maps, performance was satisfactory for angle errors < 55 degrees, and speed errors did not affect performance.     

Deformation-induced release of ATP from erythrocytes in a poly(dimethylsiloxane)-based microchip with channels that mimic resistance vessels

The ability of nitric oxide to relax smooth muscle cells surrounding resistance vessels in vivo is well documented. Here, we describe a series of studies designed to quantify amounts of adenosine triphosphate (ATP), a known stimulus of NO production in endothelial cells, released from erythrocytes that are mechanically deformed as these cells traverse microbore channels in lithographically patterned microchips. Results indicate that micromolar amounts of ATP are released from erythrocytes flowing through channels having cross sectional dimensions of 60 x 38 micron (2.22 +/- 0.50 microM ATP). Microscopic images indicate that erythrocytes, when being pumped through the microchip channels, migrate toward the center of the channels, leaving a cell-free or skimming layer at the walls of the channel, a profile known to exist in circulatory vessels in vivo. A comparison of the amounts of ATP released from RBCs mechanically deformed in microbore tubing (2.54 +/- 0.15 microM) vs a microchip (2.59 +/- 0.32 microM) suggests that channels in microchips may serve as functional biomimics of the microvasculature. Control studies involving diamide, a membrane-stiffening agent, suggest that the RBC-derived ATP is not due to cell lysis but rather physical deformation.     

Molecular-level description of proteins from saccharomyces cerevisiae using quadrupole FT hybrid mass spectrometry for top down proteomics

For improved detection of diverse posttranslational modifications (PTMs), direct fragmentation of protein ions by top down mass spectrometry holds promise but has yet to be achieved on a large scale. Using lysate from Saccharomyces cerevisiae, 117 gene products were identified with 100% sequence coverage revealing 26 acetylations, 1 N-terminal dimethylation, 1 phosphorylation, 18 duplicate genes, and 44 proteolytic fragments. The platform for this study combined continuous-elution gel electrophoresis, reversed-phase liquid chromatography, automated nanospray coupled with a quadrupole-FT hybrid mass spectrometer, and a new search engine for querying a custom database. The proteins identified required no manual validation, ranged from 5 to 39 kDa, had codon biases from 0.93 to 0.083, and were primarily associated with glycolysis and protein synthesis. Illustrations of gene-specific identifications, PTM detection and subsequent PTM localization (using either electron capture dissociation or known PTM data stored in a database) show how larger scale proteome projects incorporating top down may proceed in the future using commercial Q-FT instruments.     

Conditioned suppression of humoral immunity in the rat.

180 Charles River rats were conditioned by pairing consumption of a novel sodium saccharin drinking solution with the effects of an ip injection of 75 mg/kg cyclophosphamide, an immunosuppressive drug. Five and 10 days after conditioning, an experimental group (Group CS) was reexposed to the saccharin drinking solution. Control Ss (Group CSo) were conditioned but were not reexposed to saccharin. On Days 10, 15, or 25 after conditioning, Ss were injected ip with sheep erythrocytes, and independent subgroups were sampled for hemagglutinating antibody titer 4, 6, or 8 days later. Antibody titers 4 days after immunization were lower than values observed 6 and 8 days after immunization, and CS Ss had an attenuated antibody response. There were no significant differences between Group CSo and a group of placebo-treated Ss, but CS Ss had lower antibody titers than placebo-treated animals 4, 6, and 8 days after antigenic stimulation. Results suggest that reexposure to a CS may have long-lasting effects, and provide further documentation of conditioned immunopharmacologic effects and the impact of behavioral factors in modifying immunologic reactivity. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Designing mobile technologies to support co-present collaboration

Mobile technologies offer new opportunities for childrens educational activities in that they can be used across different locations and times. Naturally, some instances of mobile technology use will necessitate, or be enhanced by, the sharing of information. Social interaction is important for sharing ideas, constructing and shaping understanding and fundamental for educational development. However the physical size of mobile technologies presents interesting challenges when designing for collaborative activities. When designing mobile technologies the importance of collaborative tasks has often been overlooked. The replacement of low-tech artefacts with digital devices, for supporting multiple users, can inhibit the shareability of information. We present three projects where mobile technologies have been used as part of a larger mixed reality experience. Novel technologies were used to support childrens collaborative activities in storytelling, an adventure game and during an outdoor field trip. Interaction with mobile devices within each project is reviewed and the authors highlight important considerations for their design and use across multiple contexts.     

A miniature photorefractive circuit for principal component extraction

The optical feature extractor is a photorefractive ring oscillator that can identify the strongest spatiotemporal component of its input space. The theoretical sections discuss the design and performance limitations of the signal extractor. A simple model of the filter's nonlinear functioning enables the reader to go directly to the experimental section that describes the making of the filter and experimental results. The device, also called the auto-tuning filter, is 5 cm2 in size, has a 3 GHz processing bandwidth, and requires less than 5 mW of continuous optical power to operate.     

Microchip-based purification of DNA from biological samples

A microchip solid-phase extraction method for purification of DNA from biological samples, such as blood, is demonstrated. Silica beads were packed into glass microchips and the beads immobilized with sol-gel to provide a stable and reproducible solid phase onto which DNA could be adsorbed. Optimization of the DNA loading conditions established a higher DNA recovery at pH 6.1 than 7.6. This lower pH also allowed for the flow rate to be increased, resulting in a decrease in extraction time from 25 min to less than 15 min. Using this procedure, template genomic DNA from human whole blood was purified on the microchip platform with the only sample preparation being mixing of the blood with load buffer prior to loading on the microchip device. Comparison between the microchip SPE (microchipSPE) procedure and a commercial microcentrifuge method showed comparable amounts of PCR-amplifiable DNA could be isolated from cultures of Salmonella typhimurium. The greatest potential of the microchipSPE device was illustrated by purifying DNA from spores from the vaccine strain of Bacillus anthracis, where eventual integration of SPE, PCR, and separation on a single microdevice could potentially enable complete detection of the infectious agent in less than 30 min.     

The hardness of the Expected Decision Depth problem

Given a function f over n binary variables, and an ordering of the n variables, we consider the Expected Decision Depth problem. Namely, what is the expected number of bits that need to be observed until the value of the function is determined, when bits of the input are observed according to the given order. Our main finding is that this problem is (essentially) #P-complete. Moreover, the hardness holds even when the function f is represented as a decision tree.