The hyperbolic-oriented efficiency measure as a remedy to infeasibility of super efficiency models

The infeasibility problem in traditional super efficiency models has been well established. A generalization of traditional input- or output-oriented super efficiency models, the directional distance function also suffers from infeasibility and related problems. The hyperbolic-oriented efficiency measure provides an alternative to the input-oriented, output-oriented, and directional efficiency measures in super efficiency models and it has the distinct advantage of eliminating the infeasibility problem for positive input/output data. We also show that using a hyperbolic orientation in a super efficiency model allows us to find feasible solutions for certain cases when the requirement for all data to be positive is relaxed. Further we demonstrate the hyperbolic orientated super efficiency method in an outlier detection application. Together, these results establish the use of the hyperbolic orientation in super efficiency analysis as a realistic alternative in practice.     

On the planes of Suetake

The Suetake planes and the simple full non-square André planes are shown to be exactly those finite translation planes that are coupled with a semifield plane. Also, the Suetake planes are never generalized André planes.     

Solubility of CO2 in CO2-philic oligomers; COSMOtherm predictions and experimental results

We report the solubility of carbon dioxide in four physical solvents and compare our data to predicted phase behavior using the conductor-like screening model for real solvents (COSMO-RS) formalism. The solubility data are presented in pressure-composition (Px) diagrams as well as Henry's law coefficients on a wt% basis at 298.15 K. The oligomers presented in this study are poly ethylene glycol di-methyl ether (PEGDME), perfluoro polyether (PFPE), poly di-methyl siloxane (PDMS), and poly propylene glycol di-methyl ether (PPGDME), which is a new solvent designed for this application by our group. These oligomers had 2–5 repeat units. We assess these four oligomers for capturing CO₂ from high-pressure streams. The COSMO-RS formalism is able to qualitatively and to some extent quantitatively describe solubilities of CO₂ in each of the oligomers.     

A new bio-based nanocomposite: fibrillated TEMPO-oxidized celluloses in hydroxypropylcellulose matrix

Utilization of TEMPO-oxidized celluloses in bio-based nanocomposites is reported for the first time. TEMPO-oxidized wood pulps (net carboxylate content 1.1 mmol/g cellulose) were fibrillated to varying degrees using a high intensity ultrasonic processor. The degree of fibrillation was controlled by varying sonication time from 1 to 20 min. The sonication products were then characterized independently and as fillers (5 wt% loading) in hydroxypropyl cellulose nanocomposite films. Nanofibril yields ranging from 11 to 98 wt% (on fiber weight basis) were obtained over the range of sonication times used. Suspension viscosities increased initially with sonication time, peaked with gel-like behavior at 10 min of sonication and then decreased with further sonication. The thermal degradation temperature of unfibrillated oxidized pulps was only minimally affected (6 °C decrease) by the fibrillation process. Dynamic mechanical analysis of the nanocomposites revealed strong fibril-matrix interactions as evidenced by remarkable storage modulus retention at high temperatures and a suppression of matrix glass transition at “high” (~5 wt%) nanofibril loadings. Creep properties likewise exhibited significant (order of magnitude) suppression of matrix flow at high temperatures. It was also believed, based on morphologies of freeze-fracture surfaces that the nanocomposites may be characterized by high fracture toughness. Direct fracture testing will however be necessary to verify this suspicion.     

The impact of integrated STEM professional development on teacher quality

This study of a state‐funded, 3‐year implementation of an integrated STEM professional development (PD) program for teachers from two middle schools in the midwestern U.S. examined if participants in the PD were enabled to transform their practice and perceptions of STEM. An integrated STEM approach includes a focus on the STEM disciplines, along with leveraging social studies/history and English/language arts as important context and tools for solving society’s biggest challenges. Findings in this study indicated that teachers implemented more effective STEM teaching strategies and had more positive perceptions regarding STEM overall. Further, participants became more aware of their personal needs for resources and support to teach through integrated STEM. Implications for research and practice are discussed.     

Spreading behaviour of aqueous trisiloxane solutions over hydrophobic polymer substrates

The kinetics of spreading of aqueous trisiloxane solutions over different solid hydrophobic substrates has been investigated experimentally. Two pure trisiloxane surfactants with 6 and 8 oxyethylene groups at concentrations close to the critical aggregation concentration and the critical wetting concentration were used in the spreading experiments. Three hydrophobic substrates (Teflon AF, Parafilm, and polystyrene) having different surface properties were used. It was found that the spreading behaviour depends on the hydrophobic/roughness properties of substrates. The rapid spreading and complete wetting were observed for both trisiloxane surfactant solutions at the critical wetting concentration on a substrate with a moderate hydrophobicity. For both highly hydrophobic Teflon AF and Parafilm substrates only partial wetting was found. The experiments have shown that the spreading behaviour over all substrates proceeds at two stages. At the critical aggregation concentration for both trisiloxanes on all substrates the time lag of the spreading was detected. The article is published in the original.     

Nucleation and Growth Synthesis of Siloxane Gels to Form Functional,Monodisperse, and Acoustically Programmable Particles

Nucleation and growth methods offer scalable means of synthesizing colloidal particles with precisely specified size for applications in chemical research, industry, and medicine. These methods have been used to prepare a class of silicone gel particles that display a range of programmable properties and narrow size distributions. The acoustic contrast factor of these particles in water is estimated and can be tuned such that the particles undergo acoustophoresis to either the pressure nodes or antinodes of acoustic standing waves. These particles can be synthesized to display surface functional groups that can be covalently modified for a range of bioanalytical and acoustophoretic sorting applications.     

The size of a hyperbolic Coxeter simplex

We determine the covolumes of all hyperbolic Coxeter simplex reflection groups. These groups exist up to dimension 9. the volume computations involve several different methods according to the parity of dimension, subgroup relations and arithmeticity properties.