The Effect on the Lifetime of an Atom Undergoing a Dipole Transition Due to the Presence of a Resonating Atom

First order perturbation analysis of atom lifetime undergoing dipole transition due to presence of resonating ato

Development of a high power microwave thruster, with a magnetic nozzle, for space applications

This paper describes the current development of a high-power microwave electrothermal thruster (MET) concept at the NASA Lewis Research Center. Such a thruster would be employed in space for applications such as orbit raining, orbit maneuvering, station change, and possibly trans-lunar or trans-planetary propulsion of spacecraft. The MET concept employs low frequency continuous wave (CW) microwave power to create and continuously pump energy into a flowing propellant gas at relative high pressure via a plasma discharge. The propellant is heated to very high bulk temperatures while passing through the plasma discharge region and then is expanded through a throat-nozzle assembly to produce thrust, as in a conventional rocket engine. Apparatus, which is described, is being assembled at NASA Lewis to test the MET concept to CW power levels of 30 kW at a frequency of 915 MHz. The microwave energy is applied in a resonant cavity applicator and is absorbed by a plasma discharge in the flowing propellant. The ignited plasma acts as a lossy load, and with optimal tuning, energy absorption efficiencies over 95 percent (based on the applied microwave power) are expected. Nitrogen, helium, and hydrogen will be tested as propellants in the MET, at discharge chamber pressures to 10 atm

Measuring Uncertainty in Games: Design and Preliminary Validation

Uncertainty is an important element of game play, which is widely believed to act as a precondition for player experience (PX). To investigate the concept and examine its relation to other PX concepts, we should be able to measure it. We present the design and preliminary results of the validation of the Player Uncertainty in Games (PUG) questionnaire. Based on various sources from games user research and work done with regards to searching digital archives, we designed a questionnaire that measures the experience of uncertainty in games. The scale was refined down to 66 items via interviews with players and expert reviews, which was then validated and further refined based on data gathered from gamers in an online survey. The Principal Component Analysis showed high level of internal consistency for the scale and each of its four factors: Disorientation, Exploration, Prospect, and Randomness. This work demonstrates the initial findings towards a validated tool for measuring uncertainty of players in digital games

Rigidity of Frameworks Supported on Surfaces

A theorem of Laman gives a combinatorial characterisation of the graphs that admit a realisation as a minimally rigid generic bar-joint framework in \bR^2. A more general theory is developed for frameworks in \bR^3 whose vertices are constrained to move on a two-dimensional smooth submanifold \M. Furthermore, when \M is a union of concentric spheres, or a union of parallel planes or a union of concentric cylinders, necessary and sufficient combinatorial conditions are obtained for the minimal rigidity of generic frameworks.Comment: Final version, 28 pages, with new figure

European sea bass (Dicentrarchus labrax) skin and scale transcriptomes

Fish skin and their appendages, the mineralized scales, are important organs for protection and homeostasis, but little is known about their specific transcript or protein repertoire. This study used RNA-seq to generate transcriptome data for skin and scales in the European sea bass (Dicentrarchus labrax), an important species for fisheries and aquaculture. RNA was extracted from the pectoral skin and from scales collected above the midline of immature one-year old sea bass. More than 20 x 10(6) reads were obtained for each tissue, using RNA-seq Illumina technology. De novo assembly resulted in 31,842 transcripts (of 500 base pairs or greater) for skin and 20,423 transcripts for scale. This dataset provides a useful resource for both aquaculture and fish conservation studies and for research into the physiology and molecular biology of fish skin and scales. (C) 2017 Elsevier B.V. All rights reserved.Foundation for Science and Technology of Portugal (FCT) [PTDC/AAG-GLO/4003/2012, CCMAR/Multi/04326/2013, SFRH/BPD/84033/2012

Microscopic Theory of Spontaneous Decay in a Dielectric

The local field correction to the spontanous dacay rate of an impurity source atom imbedded in a disordered dielectric is calculated to second order in the dielectric density. The result is found to differ from predictions associated with both "virtual" and "real" cavity models of this decay process. However, if the contributions from two dielectric atoms at the same position are included, the virtual cavity result is reproduced.Comment: 12 Page