Reconstruction of Ultra-High Vacuum Mass Spectra Using Genetic Algorithms

In ultra-high vacuum systems, obtaining the composition of a mass spectrum is often a challenging task due to the highly overlapping nature of the individual profiles of the gas species that contribute to that spectrum, as well as the high differences in terms of degree of contribution (several orders of magnitude). This problem is even more complex when not only the presence but also a quantitative estimation of the contribution (partial pressure) of each species is required. This paper aims at estimating the relative contribution of each species in a target mass spectrum by combining a state-of-the-art machine learning method (multilabel classifier) to obtain a pool of candidate species based on a threshold applied to the probability scores given by the classifier with a genetic algorithm that aims at finding the partial pressure at which each one of the species contributes to the target mass spectrum. For this purpose, we use a dataset of synthetically generated samples. We explore different acceptance thresholds for the generation of initial populations, and we establish comparative metrics against the most novel method to date for automatically obtaining partial pressure contributions. Our results show a clear advantage in terms of the integral error metric (up to 112 times lower for simpler spectra) and computational times (up to 4 times lower for complex spectra) in favor of the proposed method, which is considered a substantial improvement for this task.

Measurement of cross-sections for charge pickup by 12C on elemental targets at 290MeV/n

The nuclear charge pickup cross-sections of [Formula: see text]C on CH2, C, Al, Cu and Pb targets at the highest energy of 288[Formula: see text]MeV/n were investigated using CR-39 nuclear track detector. The cross-section for H was calculated from those measured on C and CH2 targets. The dependence of charge pickup cross-section on target mass was investigated. It was found that the nuclear charge pickup cross-section of [Formula: see text]C at our studied beam energies seems to exponentially depend on the target mass with the fitting exponent [Formula: see text], which can be well explained by the peripheral and the surface collisions of the nuclear charge pickup reactions.

A Low Cost Inkjet-Printed Mass Sensor Using a Frequency Readout Strategy

The development of low-cost mass sensors is of unique interest for the scientific community due to the wide range of fields requiring these kind of devices. In this paper, a full inkjet-printed mass sensor is proposed. The device is based on a PolyEthylene Terephthalate (PET) cantilever beam (operating in its first natural frequency) where a strain-sensor and a planar coil have been realized by a low-cost InkJet Printing technology to implement the sensing and actuation strategies, respectively. The frequency readout strategy of the sensor presents several advantages, such as the intrinsic robustness against instabilities of the strain sensor, the residual stress of the cantilever beam, the target mass material, and the distance between the permanent magnet and the actuation coil (which changes as a function of the target mass values). However, the frictionless actuation mode represents another shortcoming of the sensor. The paper describes the sensor design, realization, and characterization while investigating its expected behavior by exploiting dedicate models. The working span of the device is 0–0.36 g while its resolution is in the order of 0.001 g, thus addressing a wide range of potential applications requiring very accurate mass measurements within a narrow operating range.

On-Orbit Robotic Grasping of a Spent Rocket Stage: Grasp Stability Analysis and Experimental Results

The increased complexity of the tasks that on-orbit robots have to undertake has led to an increased need for manipulation dexterity. Space robots can become more dexterous by adopting grasping and manipulation methodologies and algorithms from terrestrial robots. In this paper, we present a novel methodology for evaluating the stability of a robotic grasp that captures a piece of space debris, a spent rocket stage. We calculate the Intrinsic Stiffness Matrix of a 2-fingered grasp on the surface of an Apogee Kick Motor nozzle and create a stability metric that is a function of the local contact curvature, material properties, applied force, and target mass. We evaluate the efficacy of the stability metric in a simulation and two real robot experiments. The subject of all experiments is a chasing robot that needs to capture a target AKM and pull it back towards the chaser body. In the V-REP simulator, we evaluate four grasping points on three AKM models, over three pulling profiles, using three physics engines. We also use a real robotic testbed with the capability of emulating an approaching robot and a weightless AKM target to evaluate our method over 11 grasps and three pulling profiles. Finally, we perform a sensitivity analysis to demonstrate how a variation on the grasping parameters affects grasp stability. The results of all experiments suggest that the grasp can be stable under slow pulling profiles, with successful pulling for all targets. The presented work offers an alternative way of capturing orbital targets and a novel example of how terrestrial robotic grasping methodologies could be extended to orbital activities.

Online μSEC2-nRPLC-MS for improved sensitivity of intact protein detection of IEF separated non-human primate cerebrospinal fluid proteins

Proteoform-resolved information, obtained by top-down (TD) ″intact protein″ proteomics, is expected to contribute substantially to the understanding of molecular pathogenic mechanisms and in turn, identify novel therapeutic and diagnostic targets. However, the robustness of mass spectrometry analysis of intact proteins in complex mixtures is hindered by high dynamic range in protein concentration and mass, protein instability, and the chemical complexity of biological samples. Here, we describe an evolutionary step for intact protein investigations through the online implementation of tandem microflow size exclusion chromatography with nanoflow reversed-phase liquid chromatography and mass spectrometry (μSEC2-nRPLC-MS). Online serial high- and low-pass SEC filtration overcomes the aforementioned hurdles to intact proteomic analysis through automated sample desalting/cleanup and enrichment of target mass ranges prior to nRPLC-MS analysis. The coupling of μSEC to nRPLC is achieved through a novel injection volume control (IVC) strategy of inserting protein trap columns pre- and post-μSEC columns to enable injection of dilute samples in high volumes without loss of sensitivity or resolution. Critical characteristics of the approach are tested via rigorous investigations on samples of varied complexity and chemical background. Application to cerebrospinal fluid (CSF) samples pre-fractionated by OFFGEL isoelectric focusing demonstrates that the platform drastically increases the number of intact mass tags detected within the target mass range (< 30 kDa) in comparison to one-dimensional nRPLC-MS starting from approximately 100x less CSF than previous studies. Furthermore, the modular design of the μSEC2-nRPLC-MS platform is robust and promises significant flexibility for large-scale TDMS analysis of diverse samples either directly or in concert with other multidimensional fractionation steps.

A High-Resolution Fully Inkjet Printed Resonant Mass Sensor

The rapid prototyping of low-cost sensors is assuming strategic importance in several application fields. In this paper, a fully inkjet printed mass sensor is proposed. The device consists of a poly-ethylene terephthalate (PET) cantilever beam, which is driven to its resonant mode by an electromagnetic actuation mechanism, implemented through the interaction between a current impulse flowing through a planar coil (inkjet printed on the PET beam), and a permanent magnet, facing the actuation coil. Target masses are positioned close to the beam end. The sensing methodology, based on the relationship between the beam first natural frequency and the target mass, is implemented through a strain gauge (inkjet printed across the fixed end of the cantilever). The resonant operating mode of the sensor confers intrinsic robustness against instabilities of the strain sensor structure (e.g., the residual stress of the cantilever beam), the target mass material and the magnet–coil distance. The latter indeed changes as a function of the target mass values. The friction-less actuation mode is another shortcoming of the sensor, as well as the low-cost feature arising from the adopted technology. As far as we know, the solution proposed is the first example of a low-cost fully printed mass sensor. The operating range of the device is 0–0.36 g while its resolution is in the order of 1.0 mg, thus addressing crucial application fields. A Q factor around 35 has been estimated, which confirms the suitable performances of the sensor in term of selectivity and resolution.