3,314 research outputs found
Preparation of Translationally Competent tRNA by Direct Chemical Acylation
Nonsense codon suppression for unnatural amino acid incorporation requires the preparation of a suppressor aminoacyl-tRNA. Chemical acylation strategies are general but inefficient and arduous. A recent report (J. Am. Chem. Soc. 2007, 129, 15848) showed acylation of RNA mediated by lanthanum(III) using amino acid phosphate esters. The successful implementation of this methodology to full-length suppressor tRNA is described, and it is shown that the derived aminoacyl-tRNA is translationally competent in Xenopus oocytes
Smeared Impedence Model for Variable Depth Liners
Noise from modern aircraft engines has a significant broadband component, which has motivated the need for broadband acoustic engine liners. A promising broadband design, called a variable depth liner, is composed of groups of resonators tuned for different frequencies. The accuracy of commonly used smeared impedance models, however, has not been thoroughly assessed for this type of liner. Therefore, the purpose of this study is to assess, and if necessary develop, semi-analytical impedance models for variable depth designs. The impedance prediction is complicated by the fact that the radiation loading on individual resonators within the array can be different. While the radiation loading can be neglected on conventional engine liners that consist of a dense array of uniform resonators, the same is not true for variable depth liners. To better understand and model this effect, nine liner samples are tested in the NASA Langley normal incidence tube. Comparisons of predicted and measured data for relatively simple non-uniform samples confirm that the radiation loading can be approximated using mass end correction terms. Semi-analytical impedance models that incorporate the proposed end corrections provide favorable comparisons with measured impedance spectra for variable depth liner samples
Modeling the Psychology of Consumer and Firm Behavior with Behavioral Economics
Marketing is an applied science that tries to explain and influence how firms and
consumers actually behave in markets. Marketing models are usually applications of
economic theories. These theories are general and produce precise predictions, but they
rely on strong assumptions of rationality of consumers and firms. Theories based on
rationality limits could prove similarly general and precise, while grounding theories in
psychological plausibility and explaining facts which are puzzles for the standard
approach.
Behavioral economics explores the implications of limits of rationality. The goal is to
make economic theories more plausible while maintaining formal power and accurate
prediction of field data. This review focuses selectively on six types of models used in
behavioral economics that can be applied to marketing.
Three of the models generalize consumer preference to allow (1) sensitivity to reference
points (and loss-aversion); (2) social preferences toward outcomes of others; and (3)
preference for instant gratification (quasi-hyperbolic discounting). The three models are
applied to industrial channel bargaining, salesforce compensation, and pricing of virtuous
goods such as gym memberships. The other three models generalize the concept of gametheoretic
equilibrium, allowing decision makers to make mistakes (quantal response
equilibrium), encounter limits on the depth of strategic thinking (cognitive hierarchy),
and equilibrate by learning from feedback (self-tuning EWA). These are applied to
marketing strategy problems involving differentiated products, competitive entry into
large and small markets, and low-price guarantees.
The main goal of this selected review is to encourage marketing researchers of all kinds
to apply these tools to marketing. Understanding the models and applying them is a
technical challenge for marketing modelers, which also requires thoughtful input from
psychologists studying details of consumer behavior. As a result, models like these could
create a common language for modelers who prize formality and psychologists who prize
realism
Initial Developments Toward an Active Noise Control System for Small Unmanned Aerial Systems
Small unmanned aerial systems have the potential to expand commercial markets from package delivery to infrastructure inspection. Many missions, however, require the vehicles to operate in close proximity to people, where community noise concerns could ultimately limit vehicle acceptability. Therefore, noise control technologies may be needed to achieve an acceptable noise signature and enable widespread use of these vehicles. The purpose of this paper is to assess the feasibility of using loudspeakers attached to the vehicle to actively reduce noise. More specifically, this initial study explores the possibility of using a single loudspeaker to reduce the noise from an isolated rotor. Tests performed in an anechoic chamber with a 7.6 cm diameter speaker and 23.9 cm diameter rotor are used to demonstrate the potential benefits and limitations of the concept. Results confirm that active noise control can work in this application with measured tonal reductions of over 30 dB in specific directions. However, since the radiation characteristics of the speaker are different than the rotor, amplification is observed in other directions. This technology has the potential to create a cone of silence, which could be steered during flight operations to minimize the impact on noise sensitive areas
Development and Validation of the Colorado Learning Attitudes about Science Survey for Experimental Physics
As part of a comprehensive effort to transform our undergraduate physics
laboratories and evaluate the impacts of these efforts, we have developed the
Colorado Learning Attitudes about Science Survey for Experimental Physics
(E-CLASS). The E-CLASS assesses the changes in students' attitudes about a
variety of scientific laboratory practices before and after a lab course and
compares attitudes with perceptions of the course grading requirements and
laboratory practices. The E-CLASS is designed to give researchers insight into
students' attitudes and also to provide actionable evidence to instructors
looking for feedback on their courses. We present the development, validation,
and preliminary results from the initial implementation of the survey in three
undergraduate physics lab courses.Comment: 8 pages, 4 figures, 1 table, submitted to 2012 PERC Proceeding
SAT Modulo Monotonic Theories
We define the concept of a monotonic theory and show how to build efficient
SMT (SAT Modulo Theory) solvers, including effective theory propagation and
clause learning, for such theories. We present examples showing that monotonic
theories arise from many common problems, e.g., graph properties such as
reachability, shortest paths, connected components, minimum spanning tree, and
max-flow/min-cut, and then demonstrate our framework by building SMT solvers
for each of these theories. We apply these solvers to procedural content
generation problems, demonstrating major speed-ups over state-of-the-art
approaches based on SAT or Answer Set Programming, and easily solving several
instances that were previously impractical to solve
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