Aaron Crawford

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The ability of pathogenic microorganisms to assimilate sufficient nutrients for growth within their hosts is a fundamental requirement for pathogenicity. However, certain trace nutrients, including iron, zinc and manganese, are actively withheld from invading pathogens in a process called nutritional immunity. Therefore, successful pathogenic species must(More)
The present study examines gender differences in the mechanisms that explain the association between PTSD symptoms and substance use frequency in a sample of 182 urban substance users. Specifically, the current study examined gender differences in the role of two potential explanatory variables, namely, difficulties controlling impulsive behavior when(More)
The Knowledge Network (www.knowledge.scot.nhs.uk) is Scotland's online knowledge service for health and social care. It is designed to support practitioners to apply knowledge in frontline delivery of care, helping to translate knowledge into better health-care outcomes through safe, effective, person-centred care. The Knowledge Network helps to combine the(More)
The findings and opinions expressed in this report are those of the authors and do not necessarily reflect the positions or policies of the Center for Advance Technology in Schools Abstract A major issue in the study of learning progressions (LPs) is linking student performance on assessment tasks to the progressions. This report describes the challenges(More)
As the world becomes more digital, data Science is the successful study that incorporates varying techniques and theories from distinct fields. Among all fields, the domain knowledge might be the most important since all data science researchers need to start with the domain problem, and end with useful information within the domain. Identifying new(More)
A central challenge in using learning progressions (LPs) in practice is modeling the relationships that link student performance on assessment tasks to students' levels on the LP. On the one hand, there is a progression of theoretically defined levels, each defined by a configuration of knowledge, skills, and/or abilities (KSAs). On the other hand, there(More)
For the past twenty years, protein tertiary structure research has been given much attention. Unfortunately, each approach has significant shortcomings, such as necessary time, capital, or restrictions imposed by the method, limiting the resolution or novelty of produced tertiary structures. This work proposes the Adaptively-Branching Fuzzy Greedy(More)
In this paper we describe the specification of evidence models within the evidence-centered design (ECD) framework for the Packet Tracer digital learning environment of the Cisco Networking Academy. In the environment learners design, configure, and troubleshoot computer networks within an interactive interface. This leads to product data, which are the(More)
For the past twenty years, protein tertiary structure research has been given much attention, with solutions existing for both wet lab procedures (x-ray crystallography and NMR spectroscopy) and bioinformatics approaches (threading, homology-modeling, and de novo). Unfortunately, each approach has significant shortcomings, such as necessary time, capital,(More)
Previous studies have established a positive association between organizational volunteering and well-being. In the current study, we examined whether the relations between organizational volunteering and positive affect, negative affect, and resilience are modified by respondents' age and number of chronic health conditions. This study used cross-sectional(More)