Organolanthanide-catalyzed hydroamination

Organolanthanides are highly efficient catalysts for inter- and intramolecular hydroamination of various C-C unsaturations such as alkenes, alkynes, allenes, and dienes. Attractive features of organolanthanide catalysts include very high turnover frequencies and excellent stereoselectivities, rendering this methodology applicable to concise synthesis of naturally occurring alkaloids and other polycyclic azacycles. The general hydroamination mechanism involves turnover-limiting C-C multiple bond insertion into the Ln-N bond, followed by rapid protonolysis by other amine substrates. Sterically less encumbered ligand designs have been developed to improve reaction rates, and metallocene and nonmetallocene chiral lanthanide complexes have been synthesized for enantioselective hydroamination.     

Splittings, Satellites and Fine Structure in the Soft X-ray Spectroscopy of the Actinides

Perhaps the most demanding and powerful actinide spectroscopy is that using soft X-ray and VUV photons. Because of the relatively low energy and fairly small sampling depths of these photons and the corresponding electrons, it is necessary to use un-encapsulated samples with highly cleaned and well-prepared surfaces. This causes a myriad of sample containment problems for these radioactive materials. Despite these hindrances and difficulties, the soft-X-ray and ultra-violet spectroscopy of the actinides can provide an amazing level of detailed information, particularly having to do with 5f electronic structure. In this paper, the splittings, satellites and fine structure of the following actinide soft X-ray spectroscopies will be discussed: X-ray photoelectron spectroscopy; X-ray absorption spectroscopy; and inverse photoelectron spectroscopy, including Bremstrahlung isochromat spectroscopy and resonant inverse photoelectron spectroscopy.     

Agreeableness, empathy, and helping: A person × situation perspective.

This research program explored links among prosocial motives, empathy, and helping behavior. Preliminary work found significant relations among components of self-reported empathy and personality (N = 223). In Study 1, the authors examined the generality of prosocial behavior across situations and group memberships of victims (N = 622). In Study 2, empathic focus and the victim's outgroup status were experimentally manipulated (N = 87). Study 3 (N = 245) replicated and extended Study 2 by collecting measures of prosocial emotions before helping. In Study 4 (N = 244), empathic focus and cost of helping as predictors of helping behavior were experimentally manipulated. Overall, prosocial motivation is linked to (a) Agreeableness as a dimension of personality, (b) proximal prosocial cognition and motives, and (c) helping behavior across a range of situations and victims. In persons low in prosocial motivation, when costs of helping are high, efforts to induce empathy situationally can undermine prosocial behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Connecting levels of activity with classroom network technology

Classroom activity traditionally takes one of three forms, variously oriented toward the levels of individual students, small groups, or the whole class. CSCL systems, however, may enable novel ways to facilitate instruction within or sequence activity across these different levels. Drawing on theoretical accounts of learning at and across different scales of social interaction, this paper examines episodes of classroom activity featuring two learning environment designs that leverage networked digital devices to support face-to-face collaboration. Analysis of these episodes focused on two questions: When did activity shift between small and whole-group levels, and what mechanisms enabled or supported those shifts? Findings suggest that classroom activity in these environments was sometimes characterized by frequent, rapid shifts between levels, as well as instances that suggested hybrid forms of small-group and whole-class interaction. These shifts between and overlaps across levels were enabled and sustained through mechanisms including teacher orchestration, mediating roles played by virtual mathematical objects, learners’ appropriation of shared artifacts and resources, and emergent properties of these complex interactions among classroom participants.     

Radial Basis Function Interpolation on Irregular Domain through Conformal Transplantation

In this paper, Radial Basis Function (RBF) method for interpolating two dimensional functions with localized features defined on irregular domain is presented. RBF points located inside the domain and on its boundary are chosen such that they are the image of conformally mapped points on concentric circles on a unit disk. On the disk, a fast RBF solver to compute RBF coefficients developed by Karageorghis et al. (Appl. Numer. Math. 57(3):304–319, 2007) is used. Approximation values at desired points in the domain can be computed through the process of conformal transplantation. Some numerical experiments are given in a style of a tutorial and MATLAB code that solves RBF coefficients using up to 100,000 RBF points is provided.     

Exploring quadrilaterals in a small group computing environment

Though cooperative learning has been a topic of considerable interest in educational research, there has been little study specific to learning in the mathematics content area of geometry. This paper seeks to address that gap through a design experiment featuring a novel small-group computing environment for supporting student learning about quadrilaterals. In this design, each student controls a unique point in a shared geometric space, and those points are linked such that a group of four students collectively forms a quadrilateral. We first present results from pre- and post-measures to show how the students learned from the activities and developed in terms of geometric reasoning. We then present three episodes, elaborated with the notion of appropriation, to explain how students took up ways of using the technological tools and of talking about geometric concepts from one another in the interactive environment. Our study found that students achieved learning gains in this novel environment, that the environment provided rich opportunities for peer interaction around geometric objects, and that student learning opportunities and interactions were characterized by processes of appropriating ways of talking about and using software features.     

Dynamic Network User Equilibrium with State-Dependent Time Lags

This paper recasts the Friesz et al. (1993) measure theoretic model of dynamic network user equibrium as a controlled variational inequality problem involving Riemann integrals. This restatement is done to make the model and its foundations accessible to a wider audience by removing the need to have a background in functional analysis. Our exposition is dependent on previously unavailable necessary conditions for optimal control problems with state-dependent time lags. These necessary conditions, derived in an Appendix, are employed to show that a particular variational inequality control problem has solutions that are dynamic network user equilibria. Our analysis also shows that use of proper flow propagation constraints obviates the need to explicitly employ the arc exit time functions that have complicated numerical implementations of the Friesz et al. (1993) model heretofore. We close by describing the computational implications of numerically determining dynamic user equilibria from formulations based on state-dependent time lags.     

Code talk: Student discourse and participation with networked handhelds

This study explores the potential of networked handheld computers to support collaborative problem solving in small groups. Drawing on data from a middle school mathematics classroom equipped with a wireless handheld network, I argue that the sharing of mathematical objects through interactive devices broadens the ‘bandwidth’ of classroom collaboration, expanding the range of participatory forms through which students might contribute to the work of a group and enhance their own learning. The analysis focuses on the participation strategies of those students in two focus groups who were most able to demonstrate posttest score gains from relatively low scores on a pretest. In particular, the device network provided those students with a set of collective, dynamic objects through which they supplemented and coordinated discursive forms of participation in the joint work of their respective groups.     

Maxsim2—Real-time interactive simulations for computer-assisted teaching of pharmacokinetics and pharmacodynamics

We developed a computer program for use in undergraduate and graduate courses in pharmacology, pharmacokinetics and pharmacodynamics. This program can also be used in environmental and toxicological studies and preclinical simulation, to facilitate communication between modeling pharmacokineticists and project leaders or other decision-makers in the pharmaceutical industry. The program simulates the drug delivery and transport by means of (I) a six-compartment physiological pharmacokinetic flow model, (II) a system of traditional compartment models, or (III) a target-mediated drug disposition system. The program also can be used to simulate instantaneous equilibria between concentration and pharmacodynamic response, or as temporal delays between concentration and response. The latter is done by means of turnover models (indirect response models). Drug absorption, distribution, and elimination are represented by differential equations, which are described by organ and tissue volumes or other volumes of distribution, blood flows, clearance terms, and tissue-to-blood partition coefficients. The user can control and adjust these parameters by means of a slider in real time. By interactively changing the parameter values and simultaneously displaying the resulting concentration–time and/or response–time profiles, users can understand the major mechanisms that govern the disposition or the pharmacological response of the drug in the organism in real time. Schedule dependence is typically seen in clinical practice with a non-linear concentration–response relationship, and is difficult to communicate except via simulations. Here, we sought to illustrate the potential advantages of this approach in teaching pharmacology, pharmacokinetics, and pharmacodynamics to undergraduate pharmacy-, veterinary-, and medical students or to project teams in drug discovery/development.