Signal processing of the surface electromyogram to gain insight into neuromuscular physiology

A surface electromyogram (sEMG) contains information about physiological and morphological characteristics of the active muscle and its neural strategies. Because the electrodes are situated on the skin above the muscle, the sEMG is an easily obtainable source of information. However, different combinations of physiological and morphological characteristics can lead to similar sEMG signals and sEMG recordings contain noise and other artefacts. Therefore, many sEMG signal processing methods have been developed and applied to allow insight into neuromuscular physiology. This paper gives an overview of important advances in the development and applications of sEMG signal processing methods, including spectral estimation, higher order statistics and spatio-temporal processing. These methods provide information about muscle activation dynamics and muscle fatigue, as well as characteristics and control of single motor units (conduction velocity, firing rate, amplitude distribution and synchronization).     

Ultra-small graphene oxide functionalized with polyethylenimine (PEI) for very efficient gene delivery in cell and zebrafish embryos

Efficient DNA delivery is essential for introducing new genes into living cells. However, effective virus-based systems carry risks and efficient synthetic systems that are non-toxic remain to be discovered. The bottle-neck in synthetic systems is cytotoxicity, caused by the high concentration of DNA-condensing compounds required for efficient uptake of DNA. Here we report a polyethyleneimine (PEI) grafted ultra-small graphene oxide (PEI-g-USGO) for transfection. By removing the free PEI and ensuring a high PEI density on small sized graphene, we obtained very high transfection efficiencies combined with very low cytotoxicity. Plasmid DNA could be transfected into mammalian cell lines with up to 95% efficiency and 90% viability. Transfection in zebrafish embryos was 90%, with high viability, compared to efficiencies of 30% or lower for established transfection technologies. This result suggests a novel approach to the design of synthetic gene delivery vehicles for research and therapy.      

Sorption concentration of IO<Subscript>3</Subscript><Superscript>−</Superscript> and I<Superscript>−</Superscript> on anion exchangers AV-17 and silicas modified with tertiary ammonium groups

We have studied the possibility of using new anion exchangers based on silica with covalently-immobilized trimethyl ammonium propyl and dimethyloctadecyl ammonium propyl groups for sorption concentration of trace amounts of iodine iodide ions followed by their spectrophotometric determination. Sorption properties of new anion exchangers were compared with the properties of the industrial anion exchangers AV-17.     

Dependence of thermoelectric behaviour on severe plastic deformation parameters: A case study on p-type skutterudite DD0.60Fe3CoSb12

High-pressure torsion (HPT), a severe plastic deformation technique, can effectively improve the thermoelectric performance of skutterudites, resulting in ZT values higher than for ball-milled and hot-pressed (BMHP) samples. In this paper the influence of the HPT parameters, i.e. the number of revolutions (equivalent to the applied strain), the processing temperature and the hydrostatic pressure on the microstructural and thermoelectric properties of the skutterudite DD_0.60Fe₃CoSb₁₂ are evaluated and compared with the BMHP samples before HPT processing. Whilst the three parameters have specific effects on (i) the crystallite size, (ii) the density of lattice defects and (ii) the density of cracks, a suitable combination thereof allows for an increase of the figure of merit by at least 20%.     

Effect of High-Pressure Torsion on Texture,Microstructure, and Raman Spectroscopy: Case Study of Fe- and Te-Substituted CoSb3

Fe_0.05Co_0.95Sb_2.875Te_0.125, a double-element-substituted skutterudite, was prepared by induction melting, annealing, and hot pressing (HP). The hot-pressed sample was subjected to high-pressure torsion (HPT) with 4 GPa pressure at 673 K. X-ray diffraction was performed before and after HPT processing of the sample; the skutterudite phase was observed as a main phase, but an additional impurity phase (CoSb₂) was observed in the HPT-processed sample. Surface morphology was determined by high-resolution scanning electron microscopy. In the HP sample, coarse grains with sizes in the range of approximately 100 nm to 300 nm were obtained. They changed to fine grains with a reduction in grain size to 75 nm to 125 nm after HPT due to severe plastic deformation. Crystallographic texture, as measured by x-ray diffraction, indicated strengthening of (112), (102) poles and weakening of the (123) pole of the HPT-processed sample. Raman-active vibrational modes showed a peak position shift towards the lower energy side, indicating softening of the modes after HPT. The distortion of the rectangular Sb–Sb rings leads to broadening of Sb–Sb vibrational modes due to local strain fluctuation. In the HPT process, a significant effect on the shorter Sb–Sb bond was observed as compared with the longer Sb–Sb bond.     

Cluster Analysis of Biomedical Image Time-Series

In this paper, we present neural network clustering by deterministic annealing as a powerful strategy for self-organized segmentation of biomedical image time-series data identifying groups of pixels sharing common properties of local signal dynamics. After introducing the theoretical concept of minimal free energy vector quantization and related clustering techniques, we discuss its potential to serve as a multi-purpose computer vision strategy to image time-series analysis and visualization for many fields of medicine ranging from biomedical basic research to clinical assessment of patient data. In particular, we present applications to (i) functional MRI data analysis for human brain mapping, (ii) dynamic contrast-enhanced perfusion MRI for the diagnosis of cerebrovascular disease, and (iii) magnetic resonance mammography for the analysis of suspicious lesions in patients with breast cancer. This wide scope of completely different medical applications illustrates the flexibility and conceptual power of neural network vector quantization in this context. Although there are obvious methodological similarities, each application requires specific careful consideration w.r.t. data preprocessing, postprocessing and interpretation. This challenge can only be managed by close interdisciplinary cooperation of medical doctors, engineers, and computer scientists. Hence, this field of research can serve as an example for lively cross-fertilization between computer vision and related research.     

Azocoupling of Quaternary 1,2,4-Triazolium Salts to form 5-p-N,N-dimethylaminophenylazo-1,2,4-triazolium salts

Quaternary 1,2,4-triazolium salts 1 couple easily with p-N,N-dimethylamino-benzenediazonium salts to form azodyes 3 (5-N,N-dimethylaminophenylazo-1,2,4-triazolium salts), preferably under solid-liquid phase transfer conditions using chloroform or methylene chloride and triethylamine or DABCO. Zwitterionic 1,2,4-triazolium salts anhydro mercapto hydroxide, anhydro hydroxy hydroxide, and anhydro anilido hydroxide („nitron”︁) couple as well. The azodyes — as also well known from industrially used types — absorb in the region of 500 nm and have high extinction coefficients. Substituents in 1-, 3- or 4-position of the triazolium ring exert no clear substituent effects. The quaternary 1,2,4-triazolium salts were synthesized according to standard procedures.     

Crust and alumina powder dissolution in aluminum smelting electrolytes

Modern smelter potlines often undergo process excursions, which are attributed to “solubility problems” of the alumina used. Assigning the problem to a specific property is, however, a challenge, compounded by the fact that the alumina has usually undergone secondary treatments through a dry scrubbing system prior to arrival at the cell. With a better understanding there is the potential for avoiding some of the troubles experienced in these “alumina solubility” problems but there is a need to clarify what are the relevant chemical and physical properties of the alumina that are having the impact. Published and unpublished data are drawn together here to provide further insight into the alumina solubility issues.     

Einfluß von Additiven und Verunreinigungen auf Kristallisationsprozesse

Influence of additives and contaminants on crystallisation processes. The presence of additives and contaminants in a crystallising solution can have a considerable influence on the crystallisation properties of the products, such as nucleation and growth kinetics, agglomeration or dispersion of the crystals, and the incorporation of foreign ions into the crystal lattice. These influences are caused by various mechanisms, depending upon the type of additive or contaminant. Tailor-made and multifunctional additives are distinguished. Trace amounts of metal ions can also modify the kinetics of crystallisation. The metal ions can be incorporated to a greater or lesser extent in the crystal, depending upon thermodynamic and kinetic factors.