Molecular dynamics simulations of enantiomeric separations as an interfacial process in HPLC

Since chromatographic separation is a dynamic process, with the interactions between the drug and the chiral stationary phase mediated by the solvent, no single interacting structure, such as could be found by minimizing the energy, could possibly describe and account for the ratio of residence times in the chromatographic column for the enantiomeric pair. We describe the use of explicit-solvent fully atomistic molecular dynamics simulations, permitting all the interactions between the atoms constituting the chiral stationary phase, solvent molecules and the drug molecule. This allows us to better understand the molecular dynamic chiral recognition that provides the discrimination, which results in the separation of enantiomers by high performance liquid chromatography. It also provides a means of predicting, for a given set of conditions, which enantiomer elutes first and an estimate of the expected separation factor. In this review, we consider the use of molecular dynamics toward this understanding and prediction.     

Awareness of Organizational Expertise

Comprehension of computer programs involves identifying important program parts and inferring relationships between them. The ability to comprehend a computer program is a skill that begins its development in the novice programmer and reaches maturity in the expert programmer. This research examined the beginning of this process, that of comprehension of computer programs by novice programmers. The mental representations of the program text that novices form, which indicate the comprehension strategies being used, were examined. In the first study, 80 novice programmers were tested on their comprehension of short program segments. The results suggested that novices form detailed, concrete mental representations of the program text, supporting work that has previously been done with novice comprehension. Their mental representations were primarily procedural in nature, with little or no modeling using real‐world referents. In a second study, the upper and lower quartile comprehenders from Study 1 were tested on their comprehension of a longer program. Results supported the conclusions from Study 1 in that the novices tended towards detailed representations of the program text with little real‐world reference. However, the comprehension strategies used by high comprehenders differed substantially from those used by low comprehenders. Results indicated that the more advanced novices were using more abstract concepts in their representations, although their abstractions were detailed in nature.     

Factors impacting the perceived organizational support of IT employees

Organizations today face shortages of IT personnel. We investigated workplace factors in one state government in hope of identifying factors that influence perceived organizational support (POS) within an IT work environment. A combination of job characteristics (challenging job and perceived workload), job stressors (work exhaustion, role conflict, and role ambiguity), and the organization’s discretionary actions (pay-for-performance and mentoring opportunities) were measured and hierarchical regression was used to determine the relationships. Four control variables were also included (age, gender, organizational tenure, and professional versus administrator status). Role ambiguity, role conflict, work exhaustion, career mentoring, and pay-for-performance together explained 62% of the variance in the IT employees’ POS. Career mentoring and role ambiguity explained most of the variance.     

An artificial life approach to dense stereo disparity

This article presents an adaptive approach to improving the infection algorithm that we have used to solve the dense stereo matching problem. The algorithm presented here incorporates two different epidemic automata along a single execution of the infection algorithm. The new algorithm attempts to provide a general behavior of guessing the best correspondence between a pair of images. Our aim is to provide a new strategy inspired by evolutionary computation, which combines the behaviors of both automata into a single correspondence problem. The new algorithm will decide which automata will be used based on the transmission of information and mutation, as well as the attributes, texture, and geometry, of the input images. This article gives details about how the rules used in the infection algorithm are coded. Finally, we show experiments with a real stereo pair, as well as with a standard test bed, to show how the infection algorithm works.     

Electrochemical studies of octadecanethiol and octanethiol films on variable surface area mercury sessile drops

Octadecanethiol (ODT) and octanethiol (OT) films at the mercury-electrolyte interface are examined using cyclic voltammetry and differential capacitance measurements at a single frequency. A mercury flow-system is used to alter the volume, and therefore, the surface area and surface pressure of the mercury electrode. Manipulation of the mercury electrode's volume enables the introduction and removal of defects in the insulating thiol films. OT and ODT film behavior are contrasted under conditions of expansion and contraction. ODT forms extremely impermeable layers that allow 1000 time less redox probe current than seen on uncoated drops. Expansion of the mercury electrode to increase the electrode surface area produces defects and pinholes in the thiol film. These defects are almost completely removed when the drop is compressed back to its initial surface area. OT also forms insulating films on mercury sessile drops, however these films contain more defects than ODT films. While expansion of an OT-coated mercury drop increases redox probe current, recompression of the drop does not return the film to its initial condition. Pinholes and defects in the OT and ODT films can also be produced by cycling to negative potentials, which produce abrupt stripping peaks.     

Manipulation of matter by electric and magnetic fields: Toward novel synthesis and processing routes of inorganic materials

The use of external electric and magnetic fields for the synthesis and processing of inorganic materials such as metals and ceramics has seen renewed interest in recent years. Electromagnetic energy can be utilized in different ways to improve or accelerate phase formation and stabilization, chemical ordering, densification and coarsening of particle-based materials (pore elimination and grain growth), and mechanical deformation (plasticity and creep). In these new synthesis and processing routes, the resulting microstructures and macroscopic material behavior are determined by the interaction of the applied fields with defects such as single or clustered point defects, dislocation networks, and interfaces. Multiscale experimental investigations and modeling are necessary to unveil the mechanisms underlying this field-assisted manipulation of matter.     

TreePlus: interactive exploration of networks with enhanced tree layouts

Despite extensive research, it is still difficult to produce effective interactive layouts for large graphs. Dense layout and occlusion make food Webs, ontologies and social networks difficult to understand and interact with. We propose a new interactive visual analytics component called TreePlus that is based on a tree-style layout. TreePlus reveals the missing graph structure with visualization and interaction while maintaining good readability. To support exploration of the local structure of the graph and gathering of information from the extensive reading of labels, we use a guiding metaphor of "plant a seed and watch it grow." It allows users to start with a node and expand the graph as needed, which complements the classic overview techniques that can be effective at (but often limited to) revealing clusters. We describe our design goals, describe the interface and report on a controlled user study with 28 participants comparing TreePlus with a traditional graph interface for six tasks. In general, the advantage of TreePlus over the traditional interface increased as the density of the displayed data increased. Participants also reported higher levels of confidence in their answers with TreePlus and most of them preferred TreePlus