Tunable uptake of poly(ethylene oxide) by graphite-oxide-based materials

We investigate the role of structure and chemical composition on the uptake of poly(ethylene oxide) by a series of graphite oxides (GOs) and thermally reduced GOs, leading to the formation of polymer-intercalated GO and polymer-adsorbed graphene nanostructures. To this end, a series of poly(ethylene oxide) (PEO) - GO hybrid materials exhibiting a variable degree of GO oxidation and exfoliation has been investigated in detail using a combination of techniques including X-ray photoelectron spectroscopy, X-ray diffraction, thermogravimetry, scanning-electron microscopy, and nitrogen adsorption. Intercalation of the polymer phase into well-defined GO galleries is found to correlate well with both the degree of GO oxidation and with the presence of hydroxyl groups. The latter feature is an essential prerequisite to optimize polymer uptake owing to the predominance of hydrogen-bonding interactions between intercalant and host. Unlike the bulk polymer, these intercalation compounds show neither crystallisation nor glass-transition associated with the polymer phase. Exfoliation and reduction of GO result in high-surface-area graphene layers exhibiting the highest polymer uptake in these GO-based materials. In this case, PEO undergoes surface adsorption, where we observe the recovery of glass and melting transitions associated with the polymer phase albeit at significantly lower temperatures than the bulk.     

Optimization and Parallelization of Monaural Source Separation Algorithms in the openBliSSART Toolkit

We describe the implementation of monaural audio source separation algorithms in our toolkit openBliSSART (Blind Source Separation for Audio Recognition Tasks). To our knowledge, it provides the first freely available C+ + implementation of Non-Negative Matrix Factorization (NMF) supporting the Compute Unified Device Architecture (CUDA) for fast parallel processing on graphics processing units (GPUs). Besides integrating parallel processing, openBliSSART introduces several numerical optimizations of commonly used monaural source separation algorithms that reduce both computation time and memory usage. By illustrating a variety of use-cases from audio effects in music processing to speech enhancement and feature extraction, we demonstrate the wide applicability of our application framework for a multiplicity of research and end-user applications. We evaluate the toolkit by benchmark results of the NMF algorithms and discuss the influence of their parameterization on source separation quality and real-time factor. In the result, the GPU parallelization in openBliSSART introduces double-digit speedups with respect to conventional CPU computation, enabling real-time processing on a desktop PC even for high matrix dimensions.     

Infrared matrix-assisted laser desorption/ionization orthogonal-time-of-flight mass spectrometry employing a cooling stage and water ice as a matrix

Although water ice has been utilized in the past as a matrix for infrared matrix-assisted laser desorption/ionization mass spectrometry (IR-MALDI-MS), it has not found a wider use due to limitations in the analytical performance and technical demands on the employment of the necessary cooling stage. Here, we developed a temperature-controlled sample stage for use with an orthogonal time-of-flight mass spectrometer (MALDI-o-TOF-MS). The stage utilizes a combination of liquid nitrogen cooling and counterheating with a Peltier element. It allows adjustment of the sample temperature between ~-120 °C and room temperature. To identify optimal irradiation conditions for IR-MALDI with the water ice matrix, we first investigated the influence of excitation wavelength, varied between 2.7 and 3.1 μm, and laser fluence on the signal intensities of molecular substance P ions. These data suggest the involvement of transient melting of the ice during the laser pulse and primary energy deposition into liquid water. As a consequence, the best analytical performance is obtained at a wavelength corresponding to the absorption maximum of liquid water of about 2.94 μm. The current data significantly surpass the previously reported analytical features. The particular softness of the method is, for example, exemplified by the analysis of noncovalently bound holo-myoglobin and of ribonuclease B. This is also the first report demonstrating the analysis of an IgG monoclonal antibody (MW ~ 150 kDa) from a water ice matrix. Untypical for MALDI-MS, high charge states of multiply protonated species were moreover observed for some of the investigated peptides and even for lacto-N-fucopentaose II oligosaccharides. Using water ice as matrix is of particular interest for MALDI MS profiling and imaging applications since matrix-free spectra are produced. The MS and tandem MS analysis of metabolites directly from frozen food samples is demonstrated with the example of a strawberry fruit.     

A cross-country model of contextual factors impacting cloud computing adoption at universities in sub-Saharan Africa

Cloud computing is a new computing paradigm that is revolutionizing the way we access and use computer infrastructure and services. Universities in developing countries lag behind their Western counterparts due to lack of cutting edge technology required for teaching, collaboration, and research. The purpose of this study was to investigate the factors that impact diffusion, adoption, and usage of cloud computing at universities in sub-Saharan Africa (SSA). An adoption model was developed focusing on contextual factors and constructs from two technology adoption theories. Structural equation modelling was used for data analysis and model validation. Results from 355 valid responses to a survey of information and communication technology (ICT) experts and decision makers at universities in SSA indicated that socio-cultural factors, results demonstrability, usefulness, and data security significantly impact their propensity to recommend adoption of cloud computing in the universities. The implications of the findings and practical contributions are discussed.     

Use of an Optical–Mechanical Test Combined with Acoustic-Emission Techniques to Study Adhesion in Filled Polymeric Composites

The use of acoustic-emission (AE) techniques integrated with single-particle composite (SPC) mechanical–optical testing is proposed to evaluate and characterize adhesion in particle-filled polymeric composites. It is shown that not only can an intrinsic interfacial strength be determined but also that different types of adhesion mechanisms may be distinguished in terms of straightforward criteria using the wavelet transform (WT) of the acoustic signature, once problems with internal reflections in the test coupon are resolved. The validity of the proposed method is demonstrated with a study of the adhesion of a commercial poly(vinylbutyral) (PVB) to bare and aminosilane-treated glass beads.