Huge increase of therapeutic window at a bioactive silver/titania nanocomposite coating surface compared to solution

A silver containing coating used in the human body, e.g., on an implant should be both effectively antimicrobial and non-cytotoxic to human cells. It is generally believed that the biologic effect originates from silver ions released from the coating. Nanocomposites with well controlled Ag filling factor were prepared by co-sputtering, and the silver surface concentration and the silver release were determined by XPS and ICP-MS, respectively. Here we show that only a small therapeutic window exists for dissolved silver but the therapeutic window is largely increased at the surface. While the toxicity observed for mammalian cells in contact with the bioactive Ag/TiO₂ nanocomposite surface and for silver ions in solution is rather similar the antimicrobial activity is drastically enhanced at the surface. A model is proposed to explain the strong increase of the antimicrobial activity at the surface. The present results not only question well-established tests for antimicrobial activity but they are also important for the design of antimicrobial coatings, e.g., for biomedical devices.     

Assessing stationarity in web analytics: A study of bounce rates

Evidence-based methods for evaluating marketing interventions such as A/B testing have become standard practice. However, the pitfalls associated with the misuse of this decision-making instrument are not well understood by managers and analytics professionals. In this study, we assess the impact of stationarity on the validity of samples from conditioned time series, which are abundant in web metrics. Such a prominent metric is the bounce rate, which is prevalent in assessing engagement with web content as well as the performance of marketing touchpoints. In this study, we show how to control for stationarity using an algorithmic transformation to calculate the optimum sampling period. This distance is based on a novel stationary ergodic process that considers that a stationary series presents reversible symmetric features and is calculated using a dynamic time warping algorithm in a self-correlation procedure. This study contributes to the expert and intelligent systems literature by demonstrating a robust method for sub-sampling time-series data, which are critical in decision making.     

The effect of layered silicates on the crosslinking reaction of silanol‐terminated polysiloxane

The effect of incorporation of clay nanoparticles on the vulcanization reaction of silanol‐terminated polysiloxane was studied. Three different types of commercial clays were investigated as reinforcement, namely: Cloisite 20 A (organically modified with nonpolar aliphatic chains), Cloisite 30B (modified with aliphatic chains containing hydroxyl‐end groups) and Nanofil 116, an unmodified montmorillonite as a reference. Nanoclays were found to increase the rate of curing, assessed by viscosity measurements, in all the examined systems and the acceleration rate is proportional to the content of the additive. Moreover, an increase of the area of peaks corresponding to the formation of Si? O? Si bonds (900–1200 cm^?1) was recorded by FTIR spectroscopy for pure and reinforced poly(dimethylsiloxane) (PDMS). Temperature modulated differential scanning calorimetry was also used for accurately monitoring the curing reaction of organoclay/PDMS hybrids, through the heat capacity and the enthalpy of cold crystallization measurements. For pure PDMS low reaction rate was observed during the first 200 min, followed by fast acceleration. A linear increase of the reaction rate as a function of time was observed for the organoclay/PDMS hybrids. POLYM. ENG. SCI., 55:957–965, 2015. © 2014 Society of Plastics Engineers     

The effect of pigments on the stability of silicone/montmorillonite prosthetic nanocomposites

The purpose of this investigation was to evaluate the protection provided to silicone by pigments, such as dry earth pigments. In addition, the effect of nanostructured and organically modified montmorillonite fillers on the overall behavior of reinforced systems was explored. To obtain relevant data and, furthermore, to reveal possible mechanisms of structural changes that could influence silicone stability, pure and reinforced silicon elastomers were mixed with various colorants and studied for their stability to accelerating aging, during the exposure to UV radiation and humidity. A number of tests were run such as, Attenuated Total Reflectance, Fourier Transform Infrared Spectroscopy (ATR‐FTIR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Tensile measurements. Swelling in toluene and color tests were also carried out. The experimental results showed that the UV aging of silicone elastomers results in chain scission and cross‐linking rather than formation of oxygen containing groups. The main conclusion of this work is montmorillonite acts as a significant reinforcement and protects silicone against degradation during exposure to UV irradiation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A non-linear index to evaluate a journal’s scientific impact

The purpose of this study is to define a bibliometric indicator of the scientific impact of a journal, which combines objectivity with the ability to bridge many different bibliometric factors and in particular the side factors presented along with celebrated ISI impact factor. The particular goal is to determine a standard threshold value in which an independent self-organizing system will decide the correlation between this value and the impact factor of a journal. We name this factor “Cited Distance Factor (CDF)” and it is extracted via a well-fitted, recurrent Elman neural network. For a case study of this implementation we used a dataset of all journals of cell biology, ranking them according to the impact factor from the Web of Science Database and then comparing the rank according to the cited distance. For clarity reasons we also compare the cited distance factor with already known measures and especially with the recently introduced eigenfactor of the institute of scientific information (ISI).