A study of the oxygen exchange between chromate ion and water

The kinetics of the isotopic exchange reaction between O¹⁸-enriched chromate ion and solvent water have been measured as a function of pH and chromate ion concentration. The exchange kinetics can be explained in terms of the dimerization equilibria HCrO4̄ + Cr₂O[subscript 7 with double dash above] [double arrows] Cr₂O[subscript 7 with double dash above] + OH⁻ and 2HCrO4̄ [double arrows] Cr₂O[subscript 7 with double dash above] + H₂O except at high pH, where it is independent of pH. Rate constants at 30ºC for the reactions of the dimerization equilibria and the first order reaction at the high pH have been evaluated from the exchange results. The activation energy of the exchange at pH 8.70 and 1.15M̲ chromate ion is 11,400 cal mole⁻¹. The reaction proceeds faster in D₂O with RD/RH equal to 1.64 at pH 7.2. The experimental results are compared with the values obtained by other investigators --Abstract, page ii

The Anodic Dissolution Of Tungsten

The anodic dissolution of tungsten was studied in H2SO4-K2SO4 solutions (pH = -2 to 2.5) and K2SO4-K2CO3-KOH solutions (pH = 11.5 to 14.5) at 25 C. Faradaic efficiency studies in basic solutions showed the metal to be oxidized to the +6 state. In acid solutions, a thick protective film of yellow WO3 was formed. Polarization curves possessed linear Tafel regions (slope ~ 2.3 RT/F) at potentials slightly more positive than the rest potentials. An anodic dissolution mechanism is proposed which involves a surface film of W2O5 that is further oxidized to WO3 and dissolves by hydrolyzation. © 1971, The Electrochemical Society, Inc. All rights reserved

Engineering pulsatile communication in bacterial consortia

Lux-type quorum sensing systems enable communication in bacteria with only two protein components: a signal synthase and an inducible transcription activator. The simplicity of these systems makes them a popular choice for engineering collaborative behaviors in synthetic bacterial consortia, such as photographic edge detection and synchronized oscillation. To add to this body of work, we propose a pulsatile communication circuit that enables dynamic patterning and long-distance communication analogous to action potentials traveling through nerve tissue. We employed a model-driven design paradigm involving incremental characterization of in vivo design candidates with increasing circuit complexity. Beginning with a simple inducible reporter system, we screened a small number of circuits varying in their promoter and ribosomal binding site strengths. From this candidate pool, we selected a candidate to be the seed network for the subsequent round of more complex circuit variants, likewise variable in promoter and RBS strengths. The selection criteria at each level of complexity is tailored to optimize a different desirable performance characteristic. By this approach we individually optimized reporter signal-to-background ratio, pulsatile response to induction, and quiescent basal transcription, avoiding large library screens while ensuring robust performance of the composite circuit

A benchmarking methodology for the centralized-database computer with expandable and parallel database processors and stores

In this paper a benchmarking methodology for a new kind of database computers is introduced. The emergence in the research community and in the commercial world of this kind of database computer (known as the multiple-backed database computers), were each computer system is configured with two or more identical processors and their associated stores for concurrent execution of transactions and for parallel processing of a centralized database spread over separate stores, is evident. The motivation and characterization of the multiple-backend database computer are first given. The need and lack of a methodology for benchmarking the new computer with a variable number of backends for the same database or with a fixed number of backends for different capacities are also evident. The measures (benchmarks) of the new computer are articulated and established and the design of the methodology for conducting the measurements is then given. Because of the novelty of the database computer architecture, the benchmarking methodology is rather elaborate and somewhat complicated. To aid our understanding of the methodology, a concrete sample is given herein. This sample also illustrates the use of the methodology. Meanwhile, a CAD system which computerizes the benchmarking methodology for systematically assisting the design of test databases and test-transaction mixes, for automatically tallying the design data and workloads, and for completely generating the test databases and test-transaction mixes is being implementedPrepared for: Chief of Naval Research Arlington, VAhttp://archive.org/details/benchmarkingmeth00demu61153N; RRO14-0 8-01 N0001485WR24046NAApproved for public release; distribution is unlimited

The Economic Impact on Leisure Activities

This study explores the influence of the economic recession on leisure activities because economic impact is a significant factor that can change people’s travel decisions. A methodology, Ridit analysis, is applied in this study, and it adopts cumulative probability scores instead of ordinal scores. Results show that current economic crisis has had an impact on people’s ability to take time away from work

Examining the relationships between perceived value, service quality, satisfaction, and willingness to revisit a theme park

The purpose of the study is to examine the relationships between satisfaction, perceived value, and quality in their prediction of revisiting intention. Furthermore, this study applies Cronin’s (2000) research model to test the relationships, and a structural model (SEM) is used to examine the hypothesized relationships. The results show that service quality has a direct effect on perceived value and satisfaction, perceived value has direct effect on satisfaction, and satisfaction has strong relation to visitors’ willingness to revisit theme parks

Shape Invariant Coding of Motion Direction in Somatosensory Cortex

Invariant representations of stimulus features are thought to play an important role in producing stable percepts of objects. In the present study, we assess the invariance of neural representations of tactile motion direction with respect to other stimulus properties. To this end, we record the responses evoked in individual neurons in somatosensory cortex of primates, including areas 3b, 1, and 2, by three types of motion stimuli, namely scanned bars and dot patterns, and random dot displays, presented to the fingertips of macaque monkeys. We identify a population of neurons in area 1 that is highly sensitive to the direction of stimulus motion and whose motion signals are invariant across stimulus types and conditions. The motion signals conveyed by individual neurons in area 1 can account for the ability of human observers to discriminate the direction of motion of these stimuli, as measured in paired psychophysical experiments. We conclude that area 1 contains a robust representation of motion and discuss similarities in the neural mechanisms of visual and tactile motion processing.</p