This article presents a retrospective analysis of Team IHMC's experience throughout the DARPA Robotics Challenge (DRC), where we took first or second place overall in each of the three phases. As an ...extremely demanding challenge typical of DARPA, the DRC required rapid research and development to push the boundaries of robotics and set a new benchmark for complex robotic behavior. We present how we addressed each of the eight tasks of the DRC and review our performance in the Finals. While the ambitious competition schedule limited extensive experimentation, we will review the data we collected during the approximately three years of our participation. We discuss some of the significant lessons learned that contributed to our success in the DRC. These include hardware lessons, software lessons, and human‐robot integration lessons. We describe refinements to the coactive design methodology that helped our designers connect human–machine interaction theory to both implementation and empirical data. This approach helped our team focus our limited resources on the issues most critical to success. In addition to helping readers understand our experiences in developing on a Boston Dynamics Atlas robot for the DRC, we hope this article will provide insights that apply more widely to robotics development and design of human–machine systems.
Abstract
The trajectory and orbit of the
LL
7 ordinary chondrite Dishchii'bikoh are derived from low‐light video observations of a fireball first detected at 10:56:26
UTC
on June 2, 2016. Results ...show a relatively steep ~21° inclined orbit and a short 1.13
AU
semimajor axis. Following entry in Earth's atmosphere, the meteor luminosity oscillated corresponding to a meteoroid spin rate of 2.28 ± 0.02 rotations per second. A large fragment broke off at 44 km altitude. Further down, mass was lost to dust during flares at altitudes of 34, 29, and 25 km. Surviving meteorites were detected by Doppler weather radar and several small 0.9–29 g meteorites were recovered under the radar reflection footprint. Based on cosmogenic radionuclides and ground‐based radiometric observations, the Dishchii'bikoh meteoroid was 80 ± 20 cm in diameter assuming the density was 3.5 g/cm
3
. The meteoroid's collisional history confirms that the unusual petrologic class of
LL
7 does not require a different parent body than three previously observed
LL
chondrite falls. Dishchii'bikoh was ejected 11 Ma ago from parent body material that has a 4471 ± 6 Ma U‐Pb age, the same as that of Chelyabinsk (4452 ± 21 Ma). The distribution of the four known pre‐impact
LL
chondrite orbits is best matched by dynamical modeling if the source of
LL
chondrites is in the inner asteroid belt in a low inclined orbit, with the highly inclined Dishchii'bikoh being the result of interactions with Earth before impacting.
SIPHRA is a low-power (30 mW) application specific integrated circuit (ASIC) recently developed by IDEAS, Norway for readout of photomultiplier tubes (PMTs) and silicon photomultipliers (SiPMs). The ...ASIC has 16 input channels and one summing channel. Each channel can be used for timing and pulse height spectroscopy with a programmable shaping time of 200 ns, 400 ns, 800 ns, or 1600 ns. The current mode input stage (CMIS) is designed for large negative charge (-16 nC, -8 nC, -4 nC, and 0.4 nC), depending on the programmable attenuation. The ASIC contains a 12-bit ADC for pulse-height digitization. SIPHRA's performance has been tested using a 4 \times4 array of 6 mm Jseries SiPMs from SensL and a number of scintillator crystals (BGO, LYSO, LaBr_{3}:Ce and CeBr_{3}). The LaBr_{3}:Ce detector has shown energy resolution (FWHM) of 3.4% at 662 keV and 2.5% at 1274 keV. In further measurements with a light emitting diode, the SiPMs have demonstrated the same energy resolution as obtained using discrete readout electronics.
The Impact and Recovery of Asteroid 2018 LA Jenniskens, Peter; Gabadirwe, Mohutsiwa; Yin, Qing-Zhu ...
Meteoritics & planetary science,
04/2021, Letnik:
56, Številka:
4
Journal Article
Recenzirano
The June 2, 2018 impact of asteroid 2018 LA over Botswana is only the second asteroid detected in space prior to impacting over land. Here, we report on the successful recovery of meteorites. ...Additional astrometric data refine the approach orbit and define the spin period and shape of the asteroid. Video observations of the fireball constrain the asteroid’s position in its orbit and were used to triangulate the location of the fireball’s main flare over the Central Kalahari Game Reserve. Twenty-three meteorites were recovered. A consortium study of eight of these classifies Motopi Pan as an HED polymict breccia derived from howardite, cumulate and basaltic eucrite, and diogenite lithologies. Before impact, 2018 LA was a solid rock of ~156 cm diameter with high bulk density ~2.85 g cm(exp -3), a relatively low albedo p(sub v) ~0.25, no significant opposition effect on the asteroid brightness, and an impact kinetic energy of ~0.2 kt. The orbit of 2018 LA is consistent with an origin at Vesta (or its Vestoids) and delivery into an Earth-impacting orbit via the m6 resonance. The impact that ejected 2018 LA in an orbit toward Earth occurred 22.8 ± 3.8 Ma ago. Zircons record a concordant U-Pb age of 4563 ± 11 Ma and a consistent 207Pb/206Pb age of 4563 ± 6 Ma. A much younger Pb-Pb phosphate resetting age of 4234 ± 41 Ma was found. From this impact chronology, we discuss what is the possible source crater of Motopi Pan and the age of Vesta’s Veneneia impact basin.
Two chromatographically distinct stress‐activated protein kinase kinases (SAPKKs) have been identified in several mammalian cells, termed SAPKK2 and SAPKK3, which activate the MAP kinase family ...member RK/p38 but not JNK/SAPK in vitro. Here we demonstrate that SAPKK2 is identical or very closely related to the MAP kinase kinase family member MKK3. However, under our assay conditions, SAPKK3 was the major activator of RK/p38 detected in extracts prepared from stress‐ or interleukin‐1‐stimulated epithelial (KB) cells, from bacterial lipopolysaccharide and tumour necrosis factor alpha‐stimulated THP1 monocytes or from rabbit skeletal muscle. The activated form of SAPKK3 was purified from muscle to near homogeneity, and tryptic peptide sequences were used to clone human and murine cDNAs encoding this enzyme. Human SAPKK3 comprised 334 amino acids and was 78% identical to MKK3. The murine and human SAPKK3 were 97% identical in their amino acid sequences. We also cloned a different murine cDNA that appears to encode a SAPKK3 protein truncated at the N‐terminus. SAPKK3 is identical to the recently cloned MKK6.
Due to the growing volume of remote sensing data and the low latency required for safe marine navigation, machine learning (ML) algorithms are being developed to accelerate sea ice chart generation, ...currently a manual interpretation task. However, the low signal-to-noise ratio of the freely available Sentinel-1 Synthetic Aperture Radar (SAR) imagery, the ambiguity of backscatter signals for ice types, and the scarcity of open-source high-resolution labelled data makes automating sea ice mapping challenging. We use Extreme Earth version 2, a high-resolution benchmark dataset generated for ML training and evaluation, to investigate the effectiveness of ML for automated sea ice mapping. Our customized pipeline combines ResNets and Atrous Spatial Pyramid Pooling for SAR image segmentation. We investigate the performance of our model for: i) binary classification of sea ice and open water in a segmentation framework; and ii) a multiclass segmentation of five sea ice types. For binary ice-water classification, models trained with our largest training set have weighted F1 scores all greater than 0.95 for January and July test scenes. Specifically, the median weighted F1 score was 0.98, indicating high performance for both months. By comparison, a competitive baseline U-Net has a weighted average F1 score of ranging from 0.92 to 0.94 (median 0.93) for July, and 0.97 to 0.98 (median 0.97) for January. Multiclass ice type classification is more challenging, and even though our models achieve 2% improvement in weighted F1 average compared to the baseline U-Net, test weighted F1 is generally between 0.6 and 0.80. Our approach can efficiently segment full SAR scenes in one run, is faster than the baseline U-Net, retains spatial resolution and dimension, and is more robust against noise compared to approaches that rely on patch classification.
Single particle tracking (SPT) of transmembrane receptors in the plasma membrane often reveals heterogeneous diffusion. A thorough interpretation of the displacements requires an extensive analysis ...suited for discrimination of different motion types present in the data. Here the diffusion pattern of the homomeric alpha3-containing glycine receptor (GlyR) is analyzed in the membrane of HEK 293 cells. More specifically, the influence of the alpha3 RNA splice variants alpha3K and alpha3L on lateral membrane diffusion of the receptor is revealed in detail. Using a combination of ensemble and local SPT analysis, free and anomalous diffusion parameters are determined. The GlyR alpha3 free diffusion coefficient is found to be 0.13 +/- 0.01 microm2/s and both receptor variants display confined motion. The confinement probability level and residence time are significantly elevated for the alpha3L variant compared to the alpha3K variant. Furthermore, for the alpha3L GlyR, the presence of directed motion was also established, with a velocity matching that of saltatory vesicular transport. These findings reveal that alpha3 GlyRs are prone to different types of anomalous diffusion and reinforce the role of RNA splicing in determining lateral membrane trafficking.
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