Rosina - Rosetta Orbiter Spectrometer for Ion and Neutral Analysis

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) will answer important questions posed by the mission's main objectives. After Giotto, this will be the first time the volatile part of a comet will be analyzed in situ. This is a very important investigation, as comets, in contrast to meteorites, have maintained most of the volatiles of the solar nebula. To accomplish the very demanding objectives through all the different phases of the comet's activity, ROSINA has unprecedented capabilities including very wide mass range (1 to >300 amu), very high mass resolution (m/Δ m > 3000, i.e. the ability to resolve CO from N2 and 13C from 12CH), very wide dynamic range and high sensitivity, as well as the ability to determine cometary gas velocities, and temperature. ROSINA consists of two mass spectrometers for neutrals and primary ions with complementary capabilities and a pressure sensor. To ensure that absolute gas densities can be determined, each mass spectrometer carries a reservoir of a calibrated gas mixture allowing in-flight calibration. Furthermore, identical flight-spares of all three sensors will serve for detailed analysis of all relevant parameters, in particular the sensitivities for complex organic molecules and their fragmentation patterns in our electron bombardment ion source

Ultrafiltration of Natural Organic Matter

Increasingly stringent regulations for drinking water quality have stimulated the application of ultrafiltration to water treatment. In addition to removing particulate materials from water (including microorganisms, bacteria and viruses), the use of membrane treatment also meets purification requirements. However, irreversible fouling curtails the economic viability of such a process. Experiments in stirred-cells were conducted to evaluate the effects of surface water composition on rejection and fouling of two ultrafiltration membranes with different molecular weight cut-offs (10kDa and 100kDa). Experimental solutions consisted of natural organic matter or humic substances in a background electrolyte. The effect of calcium concentration decreased rejection of humic acid under certain circumstances. This is believed due to reduced molecular size with an initial increase in calcium concentration. However, at about 2.5mM CaCl2, IHSS humic acid aggregates. This aggregation increased rejection, and also caused irreversible fouling of the 100kDa membrane, presumably as a result of pore size reduction due to internal deposition of aggregates. This was confirmed by blocking law analysis. The variation of transmembrane pressure indicated the importance of a ‘critical flux’ effect. The organics and their various fractions showed differences both in rejection and flux decline. The larger and more UV-absorbing fraction of humic acid was shown to be responsible for irreversible pore adsorption and plugging. The fulvic acid and the hydrophilic fraction showed a smaller and mostly reversible flux decline

Simulation of motor unit action potential recordings from intramuscular multichannel scanning electrodes

Multi-channel intramuscular EMG (iEMG) provides information on motor neuron behavior, muscle fiber (MF) innervation geometry and, recently, has been proposed as a means to establish a human-machine interface. Objective: to provide a reliable benchmark for computational methods applied to such recordings, we propose a simulation model for iEMG signals acquired by intramuscular multi-channel electrodes. Methods: we propose several modifications to the existing motor unit action potentials (MUAPs) simulation methods, such as farthest point sampling (FPS) for the distribution of motor unit territory centers in the muscle cross-section, accurate fiber-neuron assignment algorithm, modeling of motor neuron action potential propagation delay, and a model of multi-channel scanning electrode. Results: we provide representative applications of this model to the estimation of motor unit territories and the iEMG decomposition evaluation. Also, we extend it to a full multi-channel iEMG simulator using classic linear EMG modeling. Conclusions: altogether, the proposed models provide accurate MUAPs across the entire motor unit territories and for various electrode configurations. Significance: they can be used for the development and evaluation of mathematical methods for multi-channel iEMG processing and analysis

On-line recursive decomposition of intramuscular EMG signals using GPU-implemented bayesian filtering

Objective: Real-time intramuscular electromyography (iEMG) decomposition, which is needed in biofeedback studies and interfacing applications, is a complex procedure that involves identifying the motor neuron spike trains from a streaming iEMG recording. Methods: We have previously proposed a sequential decomposition algorithm based on a Hidden Markov Model of EMG, which used Bayesian filter to estimate unknown parameters of motor unit (MU) spike trains, as well as their action potentials (MUAPs). Here, we present a modification of this original model in order to achieve a real-time performance of the algorithm as well as a parallel computation implementation of the algorithm on Graphics Processing Unit (GPU). Specifically, the Kalman filter previously used to estimate the MUAPs, is replaced by a least-mean-square filter. Additionally, we introduce a number of heuristics that help to omit the most improbable decomposition scenarios while searching for the best solution. Then, a GPU-implementation of the proposed algorithm is presented. Results: Simulated iEMG signals containing up to 10 active MUs, as well as five experimental fine-wire iEMG signals acquired from the tibialis anterior muscle, were decomposed in real time. The accuracy of decompositions depended on the level of muscle activation, but in all cases exceeded 85%. Conclusion: The proposed method and implementation provide an accurate, real-time interface with spinal motor neurons. Significance: The presented real time implementation of the decomposition algorithm substantially broadens the domain of its application