Monitoring children’s developmental progress using augmented toys and activity recognition

Previous research has established the connection between the way in which children interact with objects and the potential early identification of children with autism. Those findings motivate our own work to develop "smart toys," objects embedded with wireless sensors that are safe and enjoyable for very small children, that allow detailed interaction data to be easily recorded. These sensor-enabled toys provide opportunities for autism research by reducing the effort required to collect and analyze a child’s interactions with objects. In the future, such toys may be a useful part of clinical and in-home assessment tools. In this paper, we discuss the design of a collection of smart toys that can be used to automatically characterize the way in which a child is playing. We use statistical models to provide objective, quantitative measures of object play interactions. We also developed a tool to view rich forms of annotated play data for later analysis. We report the results of recognition experiments on more than fifty play sessions conducted with adults and children as well as discuss the opportunities for using this approach to support video annotation and other applications.     

Effect of stress-strain-law transients on formability

The effect of work-hardening changes, of the type that follow a rapid change of strain state or strain rate, on formability has been investigated using finite element modeling (FEM). A standard sheet tensile test was chosen as an arbitrary forming operation and a rigid-viscoplastic FEM program was employed for analysis. In each case, a transitional region of true strains between 0.1 and 0.2 was modeled. Transients involving lowered work-hardening rates (negative value of An) promoted increased strain localization and premature failure while transients with increased work-hardening rates enhanced formability. Total engineering elongations (50 mm gage length) varied between 20 pct and 46 pct, illustrating the importance of the transient far beyond the transient region. The controlling factor is the effective work-hardening rate in the transient region rather than the change in strength coefficient or flow stressper se. A direct stress offset of the flow curve { } also affects strain localization through a change in effective work-hardening rate.     

The Role of Rigid Residues in Modulating TEM-1 β-Lactamase Function and Thermostability

The relationship between protein motions (i.e., dynamics) and enzymatic function has begun to be explored in β-lactamases as a way to advance our understanding of these proteins. In a recent study, we analyzed the dynamic profiles of TEM-1 (a ubiquitous class A β-lactamase) and several ancestrally reconstructed homologues. A chief finding of this work was that rigid residues that were allosterically coupled to the active site appeared to have profound effects on enzyme function, even when separated from the active site by many angstroms. In the present work, our aim was to further explore the implications of protein dynamics on β-lactamase function by altering the dynamic profile of TEM-1 using computational protein design methods. The Rosetta software suite was used to mutate amino acids surrounding either rigid residues that are highly coupled to the active site or to flexible residues with no apparent communication with the active site. Experimental characterization of ten designed proteins indicated that alteration of residues surrounding rigid, highly coupled residues, substantially affected both enzymatic activity and stability; in contrast, native-like activities and stabilities were maintained when flexible, uncoupled residues, were targeted. Our results provide additional insight into the structure-function relationship present in the TEM family of β-lactamases. Furthermore, the integration of computational protein design methods with analyses of protein dynamics represents a general approach that could be used to extend our understanding of the relationship between dynamics and function in other enzyme classes.     

Micron-Scale Soft Actuators Fabricated from Multi-Shell Polystyrene Particle-Gold Nanoparticle Nanohybrids

Actuators made of soft matter are needed for a variety of fields ranging from biomedical devices to soft robotics to microelectromechanical systems. While there are a variety of excellent methods of soft actuation known, the field is still an area of intense research activity as new niches and needs emerge with new technology development. Here, a soft actuation system is described, based on a core-multi-shell particle, which moves via photothermal expansion. The system consists of a novel polystyrene-based thermally expandable microsphere, with a secondary shell of a silicate-silane graft copolymer, to which gold nanoparticles are covalently linked. The gold nanoparticles act as photothermal nano-transducers, converting light energy into the thermal energy necessary for microsphere expansion, which in turn results in material movement. Actuation is shown in isolated particles in thermal and photothermal regimes using metal ceramic heaters or 520 nm laser illumination, respectively. Macroscale actuation is demonstrated by making a composite material of particles suspended in the transparent elastomer polydimethylsiloxane. The sample demonstrates an inchworm-like movement by starting from an arched geometry. Overall, this work describes a new particle-based actuation method for soft materials, and demonstrates its utility in driving the movement of a composite elastomer.     

Processing,microstructure, and mechanical properties of hot-pressed ZrB2 ceramics with a complex Zr/Si/O-based additive

Densification behavior, microstructure, and mechanical properties of zirconium diboride (ZrB₂) ceramics modified with a complex Zr/Si/O-based additive were studied. ZrB₂ ceramics with 5–20 vol.% additions of Zr/Si/O-based additive were densified to >95% relative density at temperatures as low as 1400°C by hot-pressing. Improved densification behavior of ZrB₂ was observed with increasing additive content. The most effective additive amount for densification was 20 vol.%, hot-pressed at 1400°C (∼98% relative density). Microstructural analysis revealed up to 7 vol.% of residual second phases in the final ceramics. Improved densification behavior was attributed to ductility of the silicide phase, liquid phase formation at the hot-pressing temperatures, silicon wetting of ZrB₂ particles, and reactions of surface oxides. Room temperature strength ranged from 390 to 750 MPa and elastic modulus ranged from 440 to 490 GPa. Vickers hardness ranged from 15 to 16 GPa, and indentation fracture toughness was between 4.0 and 4.3 MPa·m^1/2. The most effective additive amount was 7.5 vol.%, which resulted in high relative density after hot-pressing at 1600°C and the best combination of mechanical properties.     

Low‐velocity impact of nanocomposite and polymer plates

Nanocomposites are more widely studied today because of higher stiffness, decreased permeability, thermal stability, and many other properties superior to those of regular polymers. However, manufacturers are concerned about implementing nanocomposites because of their lower impact properties with respect to the base polymer. This study focused on low‐velocity impact tests of a thermoplastic olefin by itself and with 5 wt % nanoclay. The impact tests were conducted at ?40, 23.9, and 65.6°C until the polymer and nanocomposite plates experienced complete striker penetration. The force–time and force–deflection responses obtained from the impact testing provided a means of comparing the impact performances of the two materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2309–2315, 2005     

A Glass–Ceramic Derived from High TiO2-Containing Slag: Microstructural Development and Mechanical Behavior

A novel glass–ceramic material was developed from the melt of a TiO₂-containing iron-making slag with additional waste glass. The high percentage (∼20 wt% TiO₂) of this network-modifying oxide has promoted a crystallization of the parent glass, resulting in a fine-grained, homogeneous polycrystalline material with high mechanical properties ( E =120 GPa, flexural strength=∼180 MPa, and Vickers hardness=7 GPa) after a heat treatment at 1100°C for 2 h. The room temperature and elevated temperature fracture toughness were also studied. The main crystalline phases of the glass–ceramic material were of the pyroxene series until heat-treatment temperature reached 1000°C, at which titanium-rich perovskite and armalcolite crystals became the dominant phases. The end material is high-strength, aesthetically acceptable (metallic gray or opaque brown colored), and suitable for structural and architectural applications.     

Over-production of 5-enolpyruvylshikimate-3-phosphate synthase in Escherichia coli: use of the T7 promoter

5-Enolpyruvylshikimate-3-phosphate (EPSP) synthase, the productof the Escherichia coli aroA gene, has been overproduced inE.coli BL21(DE3) under the control of the T7 gene 10 promoterand ribosome binding site, to a level of {small tilde}50% oftotal cell protein. EPSP synthase is the primary target of thepost-emergence herbicide, glyphosate, commonly known as Roundup^TM.A simple two step purification is described, which results in99% pure homogeneous protein (as determined by PAGE). The integrityof the protein has been compared with previously characterizedprotein from .E.coli AB2829(pKD501) by determination of itskinetic parameters, N-terminal protein and DNA sequences, aminoacid analysis and ¹³C-NMR spectroscopy. This new overproducingstrain readily provides the gram quantities of highly pure proteinrequired for NMR studies of the active site and the developmentof novel time-resolved solid-state NMR techniques currentlyunderway in this laboratory.     

Using a conductive sphere as a probe to characterize the sensitivity of soft piezoresistive films

Flexible piezoresistive films, such as, carbon black/polydimethylsiloxane (C-PDMS) composites, are often used as skin analogs and integrated into complex array sensors for tactile sensing. The uniformity of the sensor characteristics heavily depends on the homogeneity of the composite. Therefore, the ability to locally characterize a film that will be integrated into a complex force sensor could be critical. Here, a method to characterize the local sensitivity of flexible piezoresistive films is presented. Using a conductive sphere, which was chosen over a flat probe to eliminate misalignment issues, the surface of a thin film composite is indented to characterize the change in resistivity in terms of average strain. Experiments were performed with 15 and 18 wt% carbon black C-PDMS films of varying thickness. The contact radius of the probe with the piezoresistive film was estimated using the Johnson-Roberts-Kendall contact theory. Theoretical contact area estimates were found to agree with contact radius measurements carried out using optically transparent PDMS films observed through an optical microscope. Results show that C-PDMS with 15 wt% carbon black exhibit a higher rate if change of resistivity and gauge factor than films of same thickness with 18 wt% carbon black. On the other hand, thicker films exhibit higher gauge factors for the two tested carbon black contents. Tests carried out at multiple locations yielded consistent sensitivity values, making these types of composites suitable for array type force sensors.