Anatomical variability, multi-modal coordinate systems, and precision targeting in the marmoset brain

Localising accurate brain regions needs careful evaluation in each experimental species due to their individual variability. However, the function and connectivity of brain areas is commonly studied using a single-subject cranial landmark-based stereotactic atlas in animal neuroscience. Here, we address this issue in a small primate, the common marmoset, which is increasingly widely used in systems neuroscience. We developed a non-invasive multi-modal neuroimaging-based targeting pipeline, which accounts for intersubject anatomical variability in cranial and cortical landmarks in marmosets. This methodology allowed creation of multi-modal templates (MarmosetRIKEN20) including head CT and brain MR images, embedded in coordinate systems of anterior and posterior commissures (AC-PC) and CIFTI grayordinates. We found that the horizontal plane of the stereotactic coordinate was significantly rotated in pitch relative to the AC-PC coordinate system (10 degrees, frontal downwards), and had a significant bias and uncertainty due to positioning procedures. We also found that many common cranial and brain landmarks (e.g., bregma, intraparietal sulcus) vary in location across subjects and are substantial relative to average marmoset cortical area dimensions. Combining the neuroimaging-based targeting pipeline with robot-guided surgery enabled proof-of-concept targeting of deep brain structures with an accuracy of 0.2 mm. Altogether, our findings demonstrate substantial intersubject variability in marmoset brain and cranial landmarks, implying that subject-specific neuroimaging-based localization is needed for precision targeting in marmosets. The population-based templates and atlases in grayordinates, created for the first time in marmoset monkeys, should help bridging between macroscale and microscale analyses

Characterization Experiments of Secondary Arcs on Solar Arrays: Threshold and Duration

An electrostatic discharge test performed on a solar array panel is one of the important tests carried out before spacecraft launch to ensure spacecraft reliability in orbit. In this study, the effects of secondary arcs on the solar array, which can cause catastrophic accidents, are considered. The sustained-arc threshold of multijunction and silicon solar arrays was investigated to establish the design guidelines for ensuring the safety of satellite solar arrays. In this experimental study, the string voltage, string current, gap length, and solar-cell type were selected as test parameters. Gap lengths were 0.5, 0.8, 1.0, and 2.0 mm. For 0.5 and 0.8mmof gap length, a permanent sustained arc occurred under the condition of 1.5 A of string current for 50, 70, 90, and 110 V of string voltage. Furthermore, temporary sustained-arc duration exponentially increased with increasing string current. Temporary sustained-arc duration longer than 1 ms can serve as a practical alarm for the imminent permanent sustained-arc inception

Statistical Number of Primary Discharges Required for Solar Array Secondary Arc Tests

In the present paper, we propose a method to assess the risk of a secondary arc on a solar array in orbit based on statistical theory. Ground experiments have been carried out to investigate the statistics of temporary-sustained-arc duration. We have found that secondary-arc duration can be modeled as a combination of multiple Poisson distributions. Once we know the formula of the Poisson distribution, we can easily calculate the probability of a secondary arc lasting longer than an acceptable limit. The quantity of secondary-arc-duration data needed to define the Poisson distribution formula has been discussed. Assuming that thousands or tens of thousands of primary arcs occur in orbit, if the average duration of secondary arcs in the test is less than 5% of the acceptable limit for secondary-arc duration, we can greatly reduce the number of experimental trials to 10 or less in most cases

Towards HCP-Style macaque connectomes: 24-Channel 3T multi-array coil, MRI sequences and preprocessing

© 2020 The Author(s) Macaque monkeys are an important animal model where invasive investigations can lead to a better understanding of the cortical organization of primates including humans. However, the tools and methods for noninvasive image acquisition (e.g. MRI RF coils and pulse sequence protocols) and image data preprocessing have lagged behind those developed for humans. To resolve the structural and functional characteristics of the smaller macaque brain, high spatial, temporal, and angular resolutions combined with high signal-to-noise ratio are required to ensure good image quality. To address these challenges, we developed a macaque 24-channel receive coil for 3-T MRI with parallel imaging capabilities. This coil enables adaptation of the Human Connectome Project (HCP) image acquisition protocols to the in-vivo macaque brain. In addition, we adapted HCP preprocessing methods to the macaque brain, including spatial minimal preprocessing of structural, functional MRI (fMRI), and diffusion MRI (dMRI). The coil provides the necessary high signal-to-noise ratio and high efficiency in data acquisition, allowing four- and five-fold accelerations for dMRI and fMRI. Automated FreeSurfer segmentation of cortex, reconstruction of cortical surface, removal of artefacts and nuisance signals in fMRI, and distortion correction of dMRI all performed well, and the overall quality of basic neurobiological measures was comparable with those for the HCP. Analyses of functional connectivity in fMRI revealed high sensitivity as compared with those from publicly shared datasets. Tractography-based connectivity estimates correlated with tracer connectivity similarly to that achieved using ex-vivo dMRI. The resulting HCP-style in vivo macaque MRI data show considerable promise for analyzing cortical architecture and functional and structural connectivity using advanced methods that have previously only been available in studies of the human brain

Spectroscopic Measurement of Secondary Arc Plasma on Solar Array

As the power level of Geostationary satellites increases, discharge phenomena on solar array are becoming serious threat to safe operation. Arcs on solar array can short-circuit the satellite circuit, decrease the satellite power, and then cause the satellite permanent failure. To prevent the failure caused by charging and arcing, it is necessary to investigate the mechanism of satellite charging and arcing phenomenon. The purpose of this paper is to investigate the occurrence condition of a secondary arc by measuring arc plasma characteristics in ground test. We measured the arc plasma temperature and identified the materials emitted using spectrometer at arbitrary time during arc occurring. We investigated the difference of secondary arcs occurrence condition during secondary arcs. From the spectroscopic measurement results, we found that it was necessary for shifting to the secondary arc that the metallic vapor same as the cathode material was emitted. In case of primary arc (PA) dimension changes, the probability of secondary arc and TSA occurrence became high. And plasma temperature was not affected by PA dimension, however the metallic vapor emission of silver was greatly affected. Thus, secondary arc occurrence greatly depends on metallic vapor emission from cathode.ISTS Special Issue: Selected papers from the 26th International Symposium on Space Technology and Scienc

Crystallization and preliminary X-ray analysis of mitochondrial presequence receptor Tom20 in complexes with a presequence from aldehyde dehydrogenase

A presequence peptide derived from rat aldehyde dehydrogenase was tethered to the cytosolic domain of rat Tom20 protein via an intermolecular disulfide bond. Two crystal forms were obtained with different linker designs and diffracted to 2.1 and 1.9 Å

On-Orbit Operations of A Power System For Japan’s Venus Explorer Akatsuki

This paper describes on-orbit operations of a power system for Japan’s Venus explorer Akatsuki. It was launched on May 20, 2010, and approached Venus on December 7, 2010, but orbit insertion failed because of a propulsion system malfunction. After the failure, the spacecraft stayed on an orbit nearer to the sun than Venus for 5 years before successfully entering an orbit around Venus in 2015. Telemetry data that show radiation degradation of the solar arrays, and here analytical results by the relative damage coefficients method are presented. The capacity loss of the batteries was successfully suppressed by lowering the state of charge and temperature. We plan to extend the mission period from 4.5 years to longer than 9 years to obtain more fruitful scientific results

On-Orbit Operations of A Power System For Japan’s Venus Explorer Akatsuki

This paper describes on-orbit operations of a power system for Japan’s Venus explorer Akatsuki. It was launched on May 20, 2010, and approached Venus on December 7, 2010, but orbit insertion failed because of a propulsion system malfunction. After the failure, the spacecraft stayed on an orbit nearer to the sun than Venus for 5 years before successfully entering an orbit around Venus in 2015. Telemetry data that show radiation degradation of the solar arrays, and here analytical results by the relative damage coefficients method are presented. The capacity loss of the batteries was successfully suppressed by lowering the state of charge and temperature. We plan to extend the mission period from 4.5 years to longer than 9 years to obtain more fruitful scientific results