A new physical phenomenon in ultra-high energy collisions

We show that combining the published Pierre Auger Observatory measurements of the longitudinal_and_ lateral properties of UHE atmospheric showers, points to an unforeseen change in the nature of particle interactions at ultrahigh energy. A "toy model" of UHE proton-air interactions is presented which provides the first fully consistent description of air shower observations. It demonstrates that the observed energy dependence of the depth-of-shower-maximum distribution may not indicate a transition to a heavier composition, as commonly assumed. While fundamentally phenomenological, the model is based on considerations of how the normal vacuum of QCD might be vaporized and chiral symmetry restored by the extreme energy densities produced in UHE collisions. Whatever its origin, understanding this unexpected phenomenon opens exciting directions in particle physics and may impact Early Universe cosmology.Comment: Based on talk given Feb. 14, 2012 at UHECR 2012 - International Symposium on Future Directions in UHECR Physics, CERN, Genev

Methods of digital classification accuracy assessment

Landcover classification of remotely sensed data has found many useful applications in industries such as forestry, agriculture, and defense. With the push toward end users, class maps are often incorporated directly into geographical information systems for use in solving large, complex problems. However, errors are inherent in the classification process. The importance of assessing the thematic accuracy of data derived from remote sensing platforms is universally recognized and has motivated much research. Classification accuracy assessment is often required to determine the fitness of use or suitability of a data set for a particular application. Failure to identify the magnitude of inaccuracies in classified data can result in errors cascading into subsequent exploitation and eventually result in false conclusions or flawed products. Many different techniques have been developed and utilized by the remote sensing community for performing thematic accuracy assessment. To date, no one procedure has been adopted as an industry-wide standard. The purpose of this research was to evaluate the effectiveness and compare the results of several state-of-the-art assessment techniques. Synthetically generated imagery, along with real multispectral line scanner data, served as the baseline for the comparison. Synthetic imagery is uniquely suited for this task because the exact classification accuracy can be determined

The effect of extreme response and non-extreme response styles on testing measurement invariance

Extreme and non-extreme response styles (RSs) are prevalent in survey research using Likert-type scales. Their effects on measurement invariance (MI) in the context of confirmatory factor analysis are systematically investigated here via a Monte Carlo simulation study. Using the parameter estimates obtained from analyzing a 2007 Trends in International Mathematics and Science Study data set, a population model was constructed. Original and contaminated data with one of two RSs were generated and analyzed via multi-group confirmatory factor analysis with different constraints of MI. The results indicated that the detrimental effects of response style on MI have been underestimated. More specifically, these two RSs had a substantially negative impact on both model fit and parameter recovery, suggesting that the lack of MI between groups may have been caused by the RSs, not the measured factors of focal interest. Practical implications are provided to help practitioners to detect RSs and determine whether RSs are a serious threat to MI

Tuning density profiles and mobility of inhomogeneous fluids

Density profiles are the most common measure of inhomogeneous structure in confined fluids, but their connection to transport coefficients is poorly understood. We explore via simulation how tuning particle-wall interactions to flatten or enhance the particle layering of a model confined fluid impacts its self-diffusivity, viscosity, and entropy. Interestingly, interactions that eliminate particle layering significantly reduce confined fluid mobility, whereas those that enhance layering can have the opposite effect. Excess entropy helps to understand and predict these trends.Comment: 5 pages, 3 figure

Flatness optimization of micro-injection moulded parts: The case of a PMMA microfluidic component

Micro-injection moulding (µ-IM) has attracted a lot of interest because of its potential for the production of low-cost, miniaturized parts in high-volume. Applications of this technology are, amongst others, microfluidic components for lab-on-a-chip devices and micro-optical components. In both cases, the control of the part flatness is a key aspect to maintaining the component's functionality. The objective of this work is to determine the factors affecting the flatness of a polymer part manufactured by µ-IM and to control the manufacturing process with the aim of minimizing the in-process part deformation. As a case study, a PMMA microfluidic substrate with overall dimensions of 10 mm diameter and 1 mm thickness was investigated by designing a µ-IM experiment having flatness as the experimental response. The part flatness was measured using a micro-coordinate measuring machine. Finite elements analysis was also carried out to study the optimal ejection pin configuration. The results of this work show that the control of the µ-IM process conditions can improve the flatness of the polymer part up to about 15 µm. Part flatness as low as 4 µm can be achieved by modifying the design of the ejection system according to suggested guideline

The Effects of Explicit Code-Switching Instruction on Student Writing Performance for Students Who Speak Non-Standard Forms of English

This research project began by asking how explicit code-switching instruction would impact the writing performance of non-standard English speaking students. Participants included twelve sixth grade students and twelve teachers. The data collected was teacher interviews, anecdotal notes, writing samples, teacher questionnaires, student work samples, and audio recorded code-switching practice sessions. Findings revealed that students were not able to translate their knowledge of and proficiency with oral code-switching and dialect variance to written code-switching. In addition, James Prep’s implementation of code-switching pedagogy is not adequate. The data implied that without valuing the home languages of students and building a culture of natural style shifting, it is difficult to create a culture fit for code-switching and critical conversations about language

Composition and concentration anomalies for structure and dynamics of Gaussian-core mixtures

We report molecular dynamics simulation results for two-component fluid mixtures of Gaussian-core particles, focusing on how tracer diffusivities and static pair correlations depend on temperature, particle concentration, and composition. At low particle concentrations, these systems behave like simple atomic mixtures. However, for intermediate concentrations, the single-particle dynamics of the two species largely decouple, giving rise to the following anomalous trends. Increasing either the concentration of the fluid (at fixed composition) or the mole fraction of the larger particles (at fixed particle concentration) enhances the tracer diffusivity of the larger particles, but decreases that of the smaller particles. In fact, at sufficiently high particle concentrations, the larger particles exhibit higher mobility than the smaller particles. Each of these dynamic behaviors is accompanied by a corresponding structural trend that characterizes how either concentration or composition affects the strength of the static pair correlations. Specifically, the dynamic trends observed here are consistent with a single empirical scaling law that relates an appropriately normalized tracer diffusivity to its pair-correlation contribution to the excess entropy.Comment: 5 pages, 4 figure

The Asymptotic Optimal Partition and Extensions of the Nonsubstitution Theorem

The data describing an asymptotic linear program rely on a single parameter, usually referred to as time, and unlike parametric linear programming, asymptotic linear programming is concerned with the steady state behavior as time increases to infinity. The fundamental result of this work shows that the optimal partition for an asymptotic linear program attains a steady state for a large class of functions. Consequently, this allows us to define an asymptotic center solution. We show that this solution inherits the analytic properties of the functions used to describe the feasible region. Moreover, our results allow significant extensions of an economics result known as the Nonsubstitution Theorem

The Asymptotic Optimal Partition and Extensions of the Nonsubstitution Theorem

The data describing an asymptotic linear program rely on a single parameter, usually referred to as time, and unlike parametric linear programming, asymptotic linear programming is concerned with the steady state behavior as time increases to infinity. The fundamental result of this work shows that the optimal partition for an asymptotic linear program attains a steady state for a large class of functions. Consequently, this allows us to define an asymptotic center solution. We show that this solution inherits the analytic properties of the functions used to describe the feasible region. Moreover, our results allow significant extensions of an economics result known as the Nonsubstitution Theorem