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We have measured the absolute doubly differential angular sputtering yield for 20 keV Kr+ impacting a polycrystalline Cu slab at an incidence angle of θi = 45° relative to the surface normal. Sputtered Cu atoms were captured using collectors mounted on a half dome above the sample, and the sputtering distribution was measured as a function of the sputtering polar, θs, and azimuthal, ϕs, angles. Absolute results of the sputtering yield were determined from the mass gain of each collector, the ion dose, and the solid angle subtended, after irradiation to a total fluence of ∼1 × 1018 ions/cm2. Our approach overcomes shortcomings of commonly used methods that only provide relative yields as a function of θs in the incidence plane (defined by the ion velocity and the surface normal). Our experimental results display an azimuthal variation that increases with increasing θs and is clearly discrepant with simulations using binary collision theory. We attribute the observed azimuthal anisotropy to ion-induced formation of micro- and nano-scale surface features that suppress the sputtering yield through shadowing and redeposition effects, neither of which are accounted for in the simulations. Our experimental results demonstrate the importance of doubly differential angular sputtering studies to probe ion sputtering processes at a fundamental level and to explore the effect of ion-beam-generated surface roughness. [ABSTRACT FROM AUTHOR]

Digital Badges--icons that can represent skills and achievements at a more fine-grained level than a degree--give colleges and universities a new way to document learning outcomes and to map the pathways students follow to earn a degree. They also provide a common currency to denote learning outcomes and give employers a visual representation and evidence of an applicant's skills and abilities. Badges, unlike degrees, can capture and show granular details that the broader view represented by a degree cannot. The question then becomes whether a badge system and a degree can be combined to illustrate what a person knows and can do. The idea seems to be catching on. Badges are now in use or in development at institutions such as MIT, Carnegie Mellon, the University of California-Davis and Seton Hall. Organizations outside of higher education are issuing badges, too, including NASA, the National Oceanic and Atmospheric Administration, the US Departments of Veterans Affairs and Education, the Corporation for Public Broadcasting, and animated film icon Disney-Pixar.

Microblogging is a popular technology in social networking applications that lets users publish online short text messages (e.g., less than 200 characters) in real time via the web, SMS, instant messaging clients, etc. Microblogging can be an effective tool in the classroom and has lately gained notable interest from the education community. This paper proposes a novel application of text categorization for two types of microblogging questions asked in a classroom, namely relevant (i.e., questions that the teacher wants to address in the class) and irrelevant questions. Empirical results and analysis show that using personalization together with question text leads to better categorization accuracy than using question text alone. It is also beneficial to utilize the correlation between questions and available lecture materials as well as the correlation between questions asked in a lecture. Furthermore, empirical results also show that the elimination of stopwords leads to better correlation estimation between questions and leads to better categorization accuracy. On the other hand, incorporating students' votes on the questions does not improve categorization accuracy, although a similar feature has been shown to be effective in community question answering environments for assessing question quality. (Contains 5 tables and 1 figure.)

Despite their flaws as teaching and learning environments, large lectures remain a standard teaching approach because of their relatively low cost, ease of preparation, and long tradition in education. Research shows that active inquiry yields positive results in learning outcomes, and one way to make the large lecture class more active and participatory is to create and leverage a backchannel. Hotseat is a backchannel management tool developed to connect students to each other and their instructors in these large lecture conditions. In this article, the authors describe Hotseat and the features designed to make it useful in instructional situations. They then describe how it was implemented at Purdue University and how it affected the large lecture learning environment. (Contains 12 figures, 2 tables and 12 endnotes.)

We report absolute integral cross section (ICS) measurements using a dual-source merged-fast-beams apparatus to study the titular reactions over the relative translational energy range of Er ∼ 0.01–10 eV. We used photodetachment of C− to produce a pure beam of atomic C in the ground electronic 3P term, with statistically populated fine-structure levels. The H2+ and D2+ were formed in an electron impact ionization source, with well known vibrational and rotational distributions. The experimental work is complemented by a theoretical study of the CH2+ electronic system in the reactant and product channels, which helps to clarify the possible reaction mechanisms underlying the ICS measurements. Our measurements provide evidence that the reactions are barrierless and exoergic. They also indicate the apparent absence of an intermolecular isotope effect, to within the total experimental uncertainties. Capture models, taking into account either the charge-induced dipole interaction potential or the combined charge-quadrupole and charge-induced dipole interaction potentials, produce reaction cross sections that lie a factor of ∼4 above the experimental results. Based on our theoretical study, we hypothesize that the reaction is most likely to proceed adiabatically through the 14A′ and 14A′′ states of CH2+via the reaction C(3P) + H2+(2Σ +g) → CH+(3Π) + H(2S). We also hypothesize that at low collision energies only H2+(v ≤ 2) and D2+(v ≤ 3) contribute to the titular reactions, due to the onset of dissociative charge transfer for higher vibrational v levels. Incorporating these assumptions into the capture models brings them into better agreement with the experimental results. Still, for energies ≲0.1 eV where capture models are most relevant, the modified charge-induced dipole model yields reaction cross sections with an incorrect energy dependence and lying ∼10% below the experimental results. The capture cross section obtained from the combined charge-quadrupole and charge-induced dipole model better matches the measured energy dependence but lies ∼30–50% above the experimental results. These findings provide important guidance for future quasiclassical trajectory and quantum mechanical treatments of this reaction. [ABSTRACT FROM AUTHOR]

The article discusses Purdue University in Indiana's released of Mixable Web and mobile application system that allows students to build and share their personal learning environments with the use of social tools such as Facebook and Twitter. Some features of the system are status updates, document sharing and bookmarking. Details of how the system works are provided. It concludes that the system provides a simple way to connect students in the same learning community.

The article explores the development of the Hotseat tool at Purdue University in Lafayette, Indiana as a way to include and improve on existing backchannel solutions for learning environments such as large lectures. Four core challenges were identified that are needed to be overcome in order to create an open backchannel within the classroom, which include technology, access, social and assessment challenges. Hotseat has several differences from clickers and Twitter. Results of student perception and social presence surveys are discussed.

We report absolute integral cross section (ICS) measurements using a dual-source merged-fast-beams apparatus to study the titular reactions over the relative translational energy range of Er ∼ 0.01-10 eV. We used photodetachment of C- to produce a pure beam of atomic C in the ground electronic 3P term, with statistically populated fine-structure levels. The H2+ and D2+ were formed in an electron impact ionization source, with well known vibrational and rotational distributions. The experimental work is complemented by a theoretical study of the CH2+ electronic system in the reactant and product channels, which helps to clarify the possible reaction mechanisms underlying the ICS measurements. Our measurements provide evidence that the reactions are barrierless and exoergic. They also indicate the apparent absence of an intermolecular isotope effect, to within the total experimental uncertainties. Capture models, taking into account either the charge-induced dipole interaction potential or the combined charge-quadrupole and charge-induced dipole interaction potentials, produce reaction cross sections that lie a factor of ∼4 above the experimental results. Based on our theoretical study, we hypothesize that the reaction is most likely to proceed adiabatically through the 14A' and 14A'' states of CH2+via the reaction C(3P) + H2+(2Σ+g) → CH+(3Π) + H(2S). We also hypothesize that at low collision energies only H2+(v ≤ 2) and D2+(v ≤ 3) contribute to the titular reactions, due to the onset of dissociative charge transfer for higher vibrational v levels. Incorporating these assumptions into the capture models brings them into better agreement with the experimental results. Still, for energies ⪅0.1 eV where capture models are most relevant, the modified charge-induced dipole model yields reaction cross sections with an incorrect energy dependence and lying ∼10% below the experimental results. The capture cross section obtained from the combined charge-quadrupole and charge-induced dipole model better matches the measured energy dependence but lies ∼30-50% above the experimental results. These findings provide important guidance for future quasiclassical trajectory and quantum mechanical treatments of this reaction.