18 research outputs found
Profiling the educational value of computer games
There are currently a number of suggestions for educators to include computer games in formal teaching and learning contexts. Educational value is based on claims that games promote the development of complex learning. Very little research, however, has explored what features should be present in a computer game to make it valuable or conducive to learning. We present a list of required features for an educational game to be of value, informed by two studies, which integrated theories of Learning Environments and Learning Styles. A user survey showed that some requirements were typical of games in a particular genre, while other features were present across all genres. The paper concludes with a proposed framework of games and features within and across genres to assist in the design and selection of games for a given educational scenari
SSAGES : Software Suite for Advanced General Ensemble Simulations
Molecular simulation has emerged as an essential tool for modern-day research, but obtaining proper results and making reliable conclusions from simulations requires adequate sampling of the system under consideration. To this end, a variety of methods exist in the literature that can enhance sampling considerably, and increasingly sophisticated, effective algorithms continue to be developed at a rapid pace. Implementation of these techniques, however, can be challenging for experts and non-experts alike. There is a clear need for software that provides rapid, reliable, and easy access to a wide range of advanced sampling methods and that facilitates implementation of new techniques as they emerge. Here we present SSAGES, a publicly available Software Suite for Advanced General Ensemble Simulations designed to interface with multiple widely used molecular dynamics simulations packages. SSAGES allows facile application of a variety of enhanced sampling techniques—including adaptive biasing force, string methods, and forward flux sampling—that extract meaningful free energy and transition path data from all-atom and coarse-grained simulations. A noteworthy feature of SSAGES is a user-friendly framework that facilitates further development and implementation of new methods and collective variables. In this work, the use of SSAGES is illustrated in the context of simple representative applications involving distinct methods and different collective variables that are available in the current release of the suite. The code may be found at: https://github.com/MICCoM/SSAGES-public
Molecular Mechanism of Specific Recognition of Cubic Pt Nanocrystals by Peptides and of the Concentration-Dependent Formation from Seed Crystals
Metal nanocrystals enable new functionality in sensors, biomarkers, and catalysts while mechanisms of shape-control in synthesis remain incompletely understood. This study explains mechanisms of biomolecule recognition and ligand-directed growth of cubic platinum nanocrystals in atomic detail using molecular dynamics simulation (MD), synthesis, and characterization. Peptide T7 is shown to selectively recognize {100} bounded nanocubes through preferential adsorption near the edges as opposed to facet centers. Spatial preferences in peptide binding are related to differences in the binding of water molecules and conformational matching of polarizable atoms in the peptide to {100} epitaxial sites. Changes in peptide concentration also have profound impact on attraction versus repulsion on a given surface. As an example, the selective synthesis of cubes in the presence of peptide T7 demonstrates that only intermediate T7 concentration leads to high yield. High-resolution transmission electron microscopy (HRTEM) shows concentration-dependent changes in crystal shape, yield, and size. Large-scale MD simulations explain associated differences in facet coverage and in adsorption energies of T7 peptides on cuboctahedral seed crystals, supporting a growth mechanism of adatom deposition. A similar analysis using a different peptide S7 is presented as well. Emerging computational opportunities to predict ligand binding to metal nanocrystals and rationalize growth preferences are summarized
A Rational Biomimetic Approach to Structure Defect Generation in Colloidal Nanocrystals
Controlling the morphology of nanocrystals (NCs) is of paramount importance for both fundamental studies and practical applications. The morphology of NCs is determined by the seed structure and the following facet growth. While means for directing facet formation in NC growth have been extensively studied, rational strategies for the production of NCs bearing structure defects in seeds have been much less explored. Here, we report mechanistic investigations of high density twin formation induced by specific peptides in platinum (Pt) NC growth, on the basis of which we derive principles that can serve as guidelines for the rational design of molecular surfactants to introduce high yield twinning in noble metal NC syntheses. Two synergistic factors are identified in producing twinned Pt NCs with the peptide: (1) the altered reduction kinetics and crystal growth pathway as a result of the complex formation between the histidine residue on the peptide and Pt ions, and (2) the preferential stabilization of {111} planes upon the formation of twinned seeds. We further apply the discovered principles to the design of small organic molecules bearing similar binding motifs as ligands/surfactants to create single and multiple twinned Pd and Rh NCs. Our studies demonstrate the rich information derived from biomimetic synthesis and the broad applicability of biomimetic principles to NC synthesis for diverse property tailoring
Water Flux Induced Reorientation of Liquid Crystals
It is well understood
that the adsorption of solutes at the interface
between a bulk liquid crystal phase and an aqueous phase can lead
to orientational or anchoring transitions. A different principle is
introduced here, whereby a transient reorientation of a thermotropic
liquid crystal is triggered by a spontaneous flux of water across
the interface. A critical water flux can be generated by the addition
of an electrolyte to the bulk aqueous phase, leading to a change in
the solvent activity; water is then transported through the liquid
crystal phase and across the interface. The magnitude of the spontaneous
water flux can be controlled by the concentration and type of solutes,
as well as the rate of salt addition. These results present new, previously
unappreciated fundamental principles that could potentially be used
for the design of materials involving transient gating mechanisms,
including biological sensors, drug delivery systems, separation media,
and molecular machines
Understanding Atomic-Scale Behavior of Liquid Crystals at Aqueous Interfaces
The ordered environment
presented by liquid crystals at interfaces
enables a range of novel functionalities that is only now beginning
to be exploited in applications ranging from light focusing devices
to biosensors. One key feature of liquid crystals is that molecular
events occurring at an interface propagate over large distances through
the bulk. In spite of their importance, our fundamental understanding
of liquid crystal–water and liquid crystal–air interfaces remains limited.
In this work, we present results from large-scale atomistic molecular
dynamics simulations on the organization of the nematic and isotropic
phases of the nitrile-containing mesogenic molecule 4-cyano-4′-pentylbiphenyl
(5CB) in the vicinity of vacuum and aqueous interfaces. Hybrid boundary
conditions are imposed by confining 5CB films between vacuum and an
aqueous medium to examine how those two types of interfaces influence
the specific structural arrangement and ordering of 5CB. Consistent
with experiments, our results indicate that 5CB exhibits homeotropic
anchoring at the vacuum interface, and planar alignment at aqueous
interfaces. Two-dimensional molecular dynamics potential of mean force
calculations and average polarization densities show that the polar
nitrile group of 5CB remains hydrated near the aqueous interface,
where it modulates the orientation of water molecules. Estimates of
the anchoring strength reveal an oscillatory decay and a semilinear
decay with distance from the interface in vacuum and water, respectively
Exploiting Localized Surface Binding Effects to Enhance the Catalytic Reactivity of Peptide-Capped Nanoparticles
Peptide-based methods represent new
approaches to selectively produce
nanostructures with potentially important functionality. Unfortunately,
biocombinatorial methods can only select peptides with target affinity
and not for the properties of the final material. In this work, we
present evidence to demonstrate that materials-directing peptides
can be controllably modified to substantially enhance particle functionality
without significantly altering nanostructural morphology. To this
end, modification of selected residues to vary the site-specific binding
strength and biological recognition can be employed to increase the
catalytic efficiency of peptide-capped Pd nanoparticles. These results
represent a step toward the <i>de novo</i> design of materials-directing
peptides that control nanoparticle structure/function relationships