The MoS2 Nanotubes with Defect-Controlled Electric Properties

We describe a two-step synthesis of pure multiwall MoS₂ nanotubes with a high degree of homogeneity in size. The Mo₆S₄I₆ nanowires grown directly from elements under temperature gradient conditions in hedgehog-like assemblies were used as precursor material. Transformation in argon-H₂S/H₂ mixture leads to the MoS₂ nanotubes still grouped in hedgehog-like morphology. The described method enables a large-scale production of MoS₂ nanotubes and their size control. X-ray diffraction, optical absorption and Raman spectroscopy, scanning electron microscopy with wave dispersive analysis, and transmission electron microscopy were used to characterize the starting Mo₆S₄I₆ nanowires and the MoS₂ nanotubes. The unit cell parameters of the Mo₆S₄I₆ phase are proposed. Blue shift in optical absorbance and metallic behavior of MoS₂ nanotubes in two-probe measurement are explained by a high defect concentration.     

Synergistic mechanical response of Nylon 6/Trogamid® T blends

Blends of semicrystalline Nylon 6 with a varying ratios of amorphous Nylon are studied for their morphological, thermal, dielectric, and mechanical behavior. Thermal analysis indicated a compositional dependant decrease in the melting and crystallization temperatures of Nylon 6. The blends exhibited a single compositional dependant glass transition temperature in dynamic mechanical thermal analysis and dielectrical relaxation spectroscopy over entire mixing ratio indicating miscibility between the blend components. The values of flexural modulus and tensile modulus of the blends are found to increase without significant loss in the impact properties. The water absorption of the blends is also lower than the values calculated by rule of mixtures. The observed synergistic behavior of the mechanical properties of the blends is indicative of presence of strong interactions in the blends components. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Distance between behaviours

In this paper we endow the set of controllable behaviours with a distance function and produce a metric space. We link it with the subspace gap metric in the case of state-space linear systems.     

Preparation and characterization of elastin-like polypeptide scaffolds for local delivery of antibiotics and proteins

Tissue engineering applications could benefit from simultaneous release of growth factors, signaling molecules, and antibiotics to obtain optimal healing of tissues. Elastin-like polypeptides (ELPs) are genetically engineered polymers that possess good biocompatibility, are biodegradable, and exhibit mechanical properties similar to natural elastin. In addition, ELPs exhibit a characteristic inverse phase transition temperature (T_t). This T_t behavior is widely exploited in hyperthermia mediated drug delivery. The objectives of this research were to prepare ELP hydrogel scaffolds using a novel ultrasonication method and to investigate the release of a model protein (bovine serum albumin, BSA) and a commonly used antibiotic in periodontal therapy (doxycycline) from the scaffolds at two different temperatures (25?°C <T_t vs. 37?°C >T_t). Both BSA and doxycycline showed a gradual time dependent release and showed a trend of higher release fractions with higher loading doses. Based on the comparison between the release profiles at the two selected temperatures, the release was higher at 37?°C compared to that at 25?°C for both the loading concentrations of doxycycline (0.05 and 0.1?% v/v) and only one of the loading concentrations of BSA (0.5?% v/v) studied, while the release was higher at 25?°C compared to that at 37?°C only for the other loading concentration of BSA (1?% v/v) studied. These results suggested that the drug molecular weight and loading concentration were significant factors that affected the release kinetics. The experiments in this study demonstrated that the ELP hydrogel scaffolds can successfully release proteins and antibiotics critical to tissue engineering.     

Simultaneous analysis of glycosylated and sialylated prostate-specific antigen revealing differential distribution of glycosylated prostate-specific antigen isoforms in prostate cancer tissues

Aberrant protein glycosylation has been shown to be associated with disease progression and can be potentially useful as a biomarker if disease-specific glycosylation can be identified. However, high-throughput quantitative analysis of protein glycosylation derived from clinical specimens presents technical challenges due to the typically high complexity of biological samples. In this study, a mass spectrometry-based analytical method was developed to measure different glycosylated forms of glycoproteins from complex biological samples by coupling glycopeptide extraction strategy for specific glycosylation with selected reaction monitoring (SRM). Using this method, we monitored glycosylated and sialylated prostate-specific antigen (PSA) in prostate cancer and noncancer tissues. Results of this study demonstrated that the relative abundance of glycosylated PSA isoforms were not correlated with total PSA protein levels measured in the same prostate cancer tissue samples by clinical immunoassay. Furthermore, the sialylated PSA was differentially distributed in cancer and noncancer tissues. These data suggest that differently glycosylated isoforms of glycoproteins can be quantitatively analyzed and may provide unique information for clinically relevant studies.     

Confined compression of dental composites for Class I restorations

This study focuses on the mechanical response of a particle-reinforced restorative dental composite (Renew?) under proportional transverse confinement to understand the effects of stress multiaxiality on its mechanical and failure behaviors. We describe the confining ring technique as an experimental tool to introduce multiaxial compressive stress states in dental composites that realistically mimic three-dimensional stress states commonly experienced by dental restorations in the oral cavity. Effect of initial radial misfit between confining ring and specimen is analyzed through computational finite element simulations, and an analytical treatment of problem is also provided to compute the confining stress during elasto-plastic expansion of confining ring. Experimental results suggest that inelastic response of Renew composite is significantly influenced by hydrostatic stress component, and pressure-dependent yield functions are required to analyze plastic deformations and internal damage accumulation process.     

Forecasting time-to-failure of machine using hybrid Neuro-genetic algorithm – a case study in mining machinery

Forecasting of time-to-failure is an important aspect of a mining machine for the performance assessment, fault detection and schedule maintenance. The knowledge of failure time allows more defined arrangement of preventive maintenance. Traditional methods, including lifetime distribution models, fault tree analysis and Markov models, have a limitation of assuming a specific statistical distribution function to fit the failure time data. In this study, a hybrid data-driven method using neural network and genetic algorithm is proposed to forecast failure time. The forecasting model was developed using neural network algorithm and all the neural network parameters, i.e. input nodes, hidden nodes and the learning algorithms, are selected automatically using the genetic algorithm. The developed model was validated using the failure data of a mining machine. A case study was conducted investigating a load-haul-dump machine (LHD) in the mining industry. Failure historical data for the LHD machine were collected, and cumulative failure time was calculated for time-to-failure forecasting. Study results demonstrate that the developed model performs satisfactory in the prediction of next failure time. A comparative study reveals that the proposed method performs better than existing methods.     

On the evaluation of agent behaviors

This work focuses on robot behaviors which use minimal communication and rely mostly on changes in the environment as their cue for action. The behavior-based paradigm for building autonomous robots has become very popular because of its successes, use of the world as an external memory and replacement of classical planning by agent-environment dynamics. However there are no criteria for evaluating and improving behavior sets. Our aim here is to bridge this gap. We define several criteria (power, usefulness, flexibility, modularity, and, reliability) and investigate the properties of behavior sets using them. We use these criteria to present results on modifications to individual behaviors and addition of new behaviors to the behavior sets. We show how computations related to these criteria can be carried out. We report on guidelines to improve a behavior set.     

Equivalence of a behavioral distance and the gap metric

In this article it is shown that for the class of stable linear state space systems with a fixed MacMillan degree, the topology of the gap between the graphs of the systems is equivalent to the topology of the gap between the extended graphs of the systems.     

A comparative study on liquid phase alkylation of 2-methylnaphthalene with long chain olefins using different solid acid catalysts

A comparative study has been made over a variety of solid acid catalysts, which include isopoly and heteropoly ions supported on various supports such as zirconia, titania, a large variety of zeolites and a couple of mesoporous materials for liquid phase alkylation of 2-methylnaphthalene with 1-octene. All the catalyst systems were characterized by nitrogen sorption analysis, X-ray diffraction and NH₃-TPD. Inspite of their high acid amounts zeolites gave poor catalytic performance due to their diffusional constraints; on the other hand mesoporous materials lacked diffusional constraints but due to their low acid amounts resulted in poor conversions. Isopoly and heteropoly ions supported on zirconia and titania were found to be catalytically active for the reaction due to total surface acidity. Among them, isopolytungstate supported on zirconia exhibited the best catalytic activity and was used for further optimization of reaction conditions. Excellent conversions of all olefins (>92%) with high selectivity of monoalkylmethylnaphthalene (>95%) was obtained under optimized reaction conditions. The catalyst could be recycled for several times without any obvious loss of its activity.