Coupling-of-modes analysis and modeling of polymer-coated surface acoustic wave resonators for chemical sensors

The analysis and modeling of SAW resonator devices based on the coupling-of-modes (COM) theory are described, integrating the effect of polymer coating so that the sensor effects can be accounted for in the device transfer function. Based on the perturbation method, the effects of film coating are included in determining the parameters for the model. The COM parameters are, therefore, modified and its simple analytical approaches are presented. The model is validated using the experimental data of a two-port SAW resonator device fabricated on ST-X quartz substrate. The experimental results for a device coated with Parylene C are compared with the simulation results of the proposed model. The comparative results of the electrical characteristics and the frequency sensitivity to film thickness show a good agreement which proves the validity of the model. This analysis and model will provide insight into the influence of the device design parameters on the sensor performance and help in practical design and optimization of SAW-based chemical sensor systems.     

Nanostructured polymeric scaffolds for orthopaedic regenerative engineering

Successful regeneration necessitates the development of three-dimensional (3-D) tissue-inducing scaffolds that mimic the hierarchical architecture of native tissue extracellular matrix (ECM). Cells in nature recognize and interact with the surface topography they are exposed to via ECM proteins. The interaction of cells with nanotopographical features such as pores, ridges, groves, fibers, nodes, and their combinations has proven to be an important signaling modality in controlling cellular processes. Integrating nanotopographical cues is especially important in engineering complex tissues that have multiple cell types and require precisely defined cell-cell and cell-matrix interactions on the nanoscale. Thus, in a regenerative engineering approach, nanoscale materials/scaffolds play a paramount role in controlling cell fate and the consequent regenerative capacity. Advances in nanotechnology have generated a new toolbox for the fabrication of tissue-specific nanostructured scaffolds. For example, biodegradable polymers such as polyesters, polyphosphazenes, polymer blends and composites can be electrospun into ECM-mimicking matrices composed of nanofibers, which provide high surface area for cell attachment, growth, and differentiation. This review provides the fundamental guidelines for the design and development of nanostructured scaffolds for the regeneration of various tissue types in human upper and lower extremities such as skin, ligament, tendon, and bone. Examples focusing on the collective work of our laboratory in those areas are discussed to demonstrate the regenerative efficacy of this approach. Furthermore, preliminary strategies and significant challenges to integrate these individual tissues into one complex organ through regenerative engineering-based integrated graft systems are also discussed.     

Position-dependent absorption-dispersion spectrum of a Λ-type three-level atom embedded in a defective photonic crystal

The position-dependent optical spectra of a Λ-type three-level atom embedded in a photonic crystal are studied by considering the double-band photonic band gap reservoir with defect modes in the band gap. It is shown that the number of absorption peaks, transparency windows and the slope of the dispersion curve can be modulated by adjusting the position of the embedded atom.     

New functional copolymers of <Emphasis Type="Italic">N</Emphasis>-acryloyl-<Emphasis Type="Italic">N</Emphasis>′-methyl piperazine and 2-hydroxyethyl methacrylate: synthesis,determination of reactivity ratios and swelling characteristics of gels

Copolymers of N-acryloyl-N′-methylpiperazine (AcrNMP) and 2-hydroxyethyl methacrylate (HEMA) were synthesized by free radical solution polymerization in dioxane at 70 ± 1 °C, using 2,2′-azobisisobutyronitrile (AIBN) as initiator. The copolymer compositions were analyzed by the methods of FTIR spectroscopy and elemental analysis. Both the method of analysis yielded results that agreed reasonably well. The monomer reactivity ratios of the copolymerization were determined by the linearization methods of Finemann–Ross (FR) and Kelen–Tüdös (KT). The reactivity parameter results derived using FTIR analysis showed that the copolymerization yielded mainly alternating structure with reactivity ratios, r ₁(AcrNMP) = 0.263 ± 0.011 and r ₂(HEMA) = 0.615 ± 0.097 by F–R method and r ₁ = 0.227 ± 0.074 and r ₂ = 0.53 ± 0.15 by KT method. Microstructure data calculated by the method of Igarashi also supports the alternating structure (tendency) of the copolymer. Crosslinked polymer gels of this system exhibited remarkably high swelling of more than 500% in water at ambient temperature.     

Space-Filling Designs for Robustness Experiments

To identify the robust settings of the control factors, it is very important to understand how they interact with the noise factors. In this article, we propose space-filling designs for computer experiments that are more capable of accurately estimating the control-by-noise interactions. Moreover, the existing space-filling designs focus on uniformly distributing the points in the design space, which are not suitable for noise factors because they usually follow nonuniform distributions such as normal distribution. This would suggest placing more points in the regions with high probability mass. However, noise factors also tend to have a smooth relationship with the response and therefore, placing more points toward the tails of the distribution is also useful for accurately estimating the relationship. These two opposing effects make the experimental design methodology a challenging problem. We propose optimal and computationally efficient solutions to this problem and demonstrate their advantages using simulated examples and a real industry example involving a manufacturing packing line. Supplementary materials for the article are available online.     

Bayesian optimization of functional output in inverse problems

Optimization and Engineering - Motivated by the parameter identification problem of a reaction-diffusion transport model in a vapor phase infiltration processes, we propose a Bayesian optimization...     

Recent evolution of modern datasets for human activity recognition: a deep survey

Multimedia Systems - Human activity recognition has been a significant goal of computer vision since its inception and has developed considerably in the last years. Recent approaches to this...     

A randomized trial of a self-help smoking cessation intervention in a nonvolunteer female population: Testing the limits of the public health model.

2,786 smokers among 15,004 female members of a health maintenance organization who completed a routine needs assessment were invited into a preventive health behavior study, consisting of 5 telephone interviews over 2 yrs assessing health practices. 1,396 participants were randomized into experimental or control conditions of an unsolicited, mailed, self-help smoking cessation program. Ss were not alerted to the link between the program and the health study. Smoking status was assessed at 1, 6, 12, and 18 mo. Although quit rates were higher than in the general population and were comparable to volunteer samples in self-help smoking cessation trials, there was no differential effect of the targeted intervention on the experimental group compared with the control group. Data indicate that mass mailing of cessation materials is not a useful form of cessation intervention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fracture and fatigue performance of textile commingled yarn composites

The response to mechanical loads of unidirectional commingled warp knitted and woven glass fibre reinforced polyethylene terephthalate laminates has been characterized. The mechanical properties of the two materials were determined under tension, in-plane shear and flexure. The flexural fatigue properties were determined for the woven laminates by means of three-point bending tests with a loading ratio of R=0.1 at stress levels of 50–90% of the ultimate static strength. The Mode I, Mode II and mixed mode (Mode I : II ratios 4 : 1, 1 : 1 and 1 : 4) interlaminar fracture toughnesses of the laminates were determined by means of the double cantilever beam and mixed mode bending tests, respectively. The main fractographic features, as determined by a scanning electron microscopy examination, of the Mode I dominated failures were a brittle matrix failure and larger amounts of fibre pull-out. As the Mode II loading component increased, the amount of fibre pull-out was reduced and the features of the matrix appeared to be more sheared. Cusps were found on the fracture surfaces of specimens tested in pure Mode II and mixed mode I : II=1 : 4. Cusps are normally not found in thermoplastic matrix composites. © 1998 Kluwer Academic Publishers