Hypervelocity atomic oxygen source for the study of atom-surface interactions

Planned improvements in an electric discharge heated atomic oxygen beam source are described which will provide 6 to 7 kms(-1) beams of atomic oxygen with a flux of 10(16) cm(-2) s(-1) at 50 cm distance from the source aperture. A major advance will be the use of a zone of silence nozzle-skimmer arrangement which is necessitated by the need for high source flux and performance. It is anticipated that a Phase 2 program would provide for the fabrication of a two stage vacuum system which would be suitable for bolting on to a UHV (ultrahigh vacuum) surface study apparatus

On the Procrustean analogue of individual differences scaling (INDSCAL)

In this paper, individual differences scaling (INDSCAL) is revisited, considering INDSCAL as being embedded within a hierarchy of individual difference scaling models. We explore the members of this family, distinguishing (i) models, (ii) the role of identification and substantive constraints, (iii) criteria for fitting models and (iv) algorithms to optimise the criteria. Model formulations may be based either on data that are in the form of proximities or on configurational matrices. In its configurational version, individual difference scaling may be formulated as a form of generalized Procrustes analysis. Algorithms are introduced for fitting the new models. An application from sensory evaluation illustrates the performance of the methods and their solutions

Factor Analysis of Data Matrices: New Theoretical and Computational Aspects With Applications

The classical fitting problem in exploratory factor analysis (EFA) is to find estimates for the factor loadings matrix and the matrix of unique factor variances which give the best fit to the sample covariance or correlation matrix with respect to some goodness-of-fit criterion. Predicted factor scores can be obtained as a function of these estimates and the data. In this thesis, the EFA model is considered as a specific data matrix decomposition with fixed unknown matrix parameters. Fitting the EFA model directly to the data yields simultaneous solutions for both loadings and factor scores. Several new algorithms are introduced for the least squares and weighted least squares estimation of all EFA model unknowns. The numerical procedures are based on the singular value decomposition, facilitate the estimation of both common and unique factor scores, and work equally well when the number of variables exceeds the number of available observations. Like EFA, noisy independent component analysis (ICA) is a technique for reduction of the data dimensionality in which the interrelationships among the observed variables are explained in terms of a much smaller number of latent factors. The key difference between EFA and noisy ICA is that in the latter model the common factors are assumed to be both independent and non-normal. In contrast to EFA, there is no rotational indeterminacy in noisy ICA. In this thesis, noisy ICA is viewed as a method of factor rotation in EFA. Starting from an initial EFA solution, an orthogonal rotation matrix is sought that minimizes the dependence between the common factors. The idea of rotating the scores towards independence is also employed in three-mode factor analysis to analyze data sets having a three-way structure. The new theoretical and computational aspects contained in this thesis are illustrated by means of several examples with real and artificial data

Testing For Acid Rain Near Cobalt Lake Located Within Glacier National Park

Cobalt Lake located in the southeastern portion of Glacier National Park potentially receives acid rain. Precipitation containing sulfate and having a low pH indicates the possible presence of acid rain

Allan Variance Analysis as Useful Tool to Determine Noise in Various Single-Molecule Setups

One limitation on the performance of optical traps is the noise inherently present in every setup. Therefore, it is the desire of most experimentalists to minimize and possibly eliminate noise from their optical trapping experiments. A step in this direction is to quantify the actual noise in the system and to evaluate how much each particular component contributes to the overall noise. For this purpose we present Allan variance analysis as a straightforward method. In particular, it allows for judging the impact of drift which gives rise to low-frequency noise, which is extremely difficult to pinpoint by other methods. We show how to determine the optimal sampling time for calibration, the optimal number of data points for a desired experiment, and we provide measurements of how much accuracy is gained by acquiring additional data points. Allan variances of both micrometer-sized spheres and asymmetric nanometer-sized rods are considered.Comment: 14 pages, 6 figures, presented at SPIE Optics+Photonics 2009 in San Diego, CA, US

(A)synchronous Communication about TV Series on Social Media: A Multi-Method Investigation of Reddit Discussions

Audiences’ TV series entertainment experiences are increasingly shaped not only by the events on the ‘first screen’ but also by discussions on social media. While an extensive body of research has examined practices of ‘second screening,’ especially on Twitter, online discussions before and after the live broadcast and on other platforms have received less attention. On Reddit—one of the most important platforms for Social TV—discussions often take place in temporally structured threads that allow users to discuss an episode before (pre-premiere thread), during (live premiere thread), and after (post-premiere thread) it airs. In this project, we examine whether these spaces mainly indicate temporal preferences among users or are associated with different usage practices and motives. To do so, we conducted two case studies of the Reddit community r/gameofthrones: a survey about usage motives (n = 417) and an automated content analysis of approximately 1.2 million comments left on the episode discussion threads in which we examined thread use over time, interactions between users, and discussion content. The results revealed differing usage motives and practices for the three thread types, illustrating the distinct function that these communication spaces fulfil for users