Improved charge injection device and a focal plane interface electronics board for stellar tracking

An improved Charge Injection Device (CID) stellar tracking sensor and an operating sensor in a control/readout electronics board were developed. The sensor consists of a shift register scanned, 256x256 CID array organized for readout of 4x4 subarrays. The 4x4 subarrays can be positioned anywhere within the 256x256 array with a 2 pixel resolution. This allows continuous tracking of a number of stars simultaneously since nine pixels (3x3) centered on any star can always be read out. Organization and operation of this sensor and the improvements in design and semiconductor processing are described. A hermetic package incorporating an internal thermoelectric cooler assembled using low temperature solders was developed. The electronics board, which contains the sensor drivers, amplifiers, sample hold circuits, multiplexer, analog to digital converter, and the sensor temperature control circuits, is also described. Packaged sensors were evaluated for readout efficiency, spectral quantum efficiency, temporal noise, fixed pattern noise, and dark current. Eight sensors along with two tracker electronics boards were completed, evaluated, and delivered

Recent developments in CID imaging

Readout of CID imaging arrays was first performed by injecting and detecting the signal charge from each sensing site in sequence. A new readout method, termed parallel injection, has been developed in which the functions of signal charge detection and injection have been separated. The level of signal charge at each sensing site is detected during a line scan, and during the line retrace interval, all charge in the selected line is injected. The parallel injection technique is well adapted to TV scan formats in that the signal is read out at high speed, line by line. A 244 line by 248 element TV compatible imager, employing this technique and including an on chip preamplifier, has been constructed and operation demonstrated

Design, fabrication, and delivery of a charge injection device as a stellar tracking device

Six 128 x 128 CID imagers fabricated on bulk silicon and with thin polysilicon upper-level electrodes were tested in a star tracking mode. Noise and spectral response were measured as a function of temperature over the range of +25 C to -40 C. Noise at 0 C and below was less than 40 rms carriers/pixel for all devices at an effective noise bandwidth of 150 Hz. Quantum yield for all devices averaged 40% from 0.4 to 1.0 microns with no measurable temperature dependence. Extrapolating from these performance parameters to those of a large (400 x 400) array and accounting for design and processing improvements, indicates that the larger array would show a further improvement in noise performance -- on the order of 25 carriers. A preliminary evaluation of the projected performance of the 400 x 400 array and a representative set of star sensor requirements indicates that the CID has excellent potential as a stellar tracking device

Predictability alters information flow during action observation in human electrocorticographic activity

The action observation network (AON) has been extensively studied using short, isolated motor acts. How activity in the network is altered when these isolated acts are embedded in meaningful sequences of actions remains poorly understood. Here we utilized intracranial electrocorticography to characterize how the exchange of information across key nodes of the AON-the precentral, supramarginal, and visual cortices-is affected by such embedding and the resulting predictability. We found more top-down beta oscillation from precentral to supramarginal contacts during the observation of predictable actions in meaningful sequences compared to the same actions in randomized, and hence less predictable, order. In addition, we find that expectations enabled by the embedding lead to a suppression of bottom-up visual responses in the high-gamma range in visual areas. These results, in line with predictive coding, inform how nodes of the AON integrate information to process the actions of others.</p

Wavelets techniques for pointwise anti-Holderian irregularity

In this paper, we introduce a notion of weak pointwise Holder regularity, starting from the de nition of the pointwise anti-Holder irregularity. Using this concept, a weak spectrum of singularities can be de ned as for the usual pointwise Holder regularity. We build a class of wavelet series satisfying the multifractal formalism and thus show the optimality of the upper bound. We also show that the weak spectrum of singularities is disconnected from the casual one (denoted here strong spectrum of singularities) by exhibiting a multifractal function made of Davenport series whose weak spectrum di ers from the strong one

Multi-technique geochronology of intrusive and explosive activity on Piton des Neiges Volcano, Réunion Island

MD was supported by the AuScope NCRIS2 program, Australian Research Council (ARC) Discovery funding scheme (DP160102427) and Curtin Research Fellowship. CP was supported by the company Austral Energy and by the ANRT CIFRE program (agreement n°2017/1175).The construction of ocean island basaltic volcanoes consists of a succession of eruptions, intrusions, and metamorphism. These events are often temporally ill-constrained because the most widely used radiometric dating methods applicable to mafic volcanic rocks (K-Ar or 40Ar/39Ar on whole rock or groundmass) are prone to inaccuracy when applied to slowly-cooled, altered, or vesicular and aphyric products. Here we adopt a multi-technique geochronology approach (including zircon U-Pb, phlogopite 40Ar/39Ar, zircon and apatite (U-Th)/He, and zircon double-dating) to demonstrate its efficacy when applied to basaltic volcanoes. Taking the main volcano of Réunion Island (Piton des Neiges) as a case study, we establish the time of the major plutonic, metamorphic, and explosive events that had resisted previous dating attempts. We document four stages of pluton emplacement and metamorphism at 2200 - 2000 ka, 1414 ± 8 ka, 665 ± 78 ka, and 150 - 110 ka, all coinciding with volcanism revival after quiescent intervals. We also date a major Plinian eruption at 188.2 ± 10.4 ka, coeval with the formation age of a large caldera, and, finally, we constrain the last eruption of Piton des Neiges to 27 ka, revising a previous estimate of 12 ka. By resolving several conundrums of Réunion's geological history, our multi-technique geochronology approach reveals that endogenous growth of a volcanic island proceeds as pulses at the beginning of renewed volcanism. We also demonstrate that cross-checking eruptions ages by diversified dating techniques is important to better assess the timing and recurrence of basaltic volcanic activity, with implications for hazard prediction.Publisher PDFPeer reviewe

Multifractal Analysis of inhomogeneous Bernoulli products

We are interested to the multifractal analysis of inhomogeneous Bernoulli products which are also known as coin tossing measures. We give conditions ensuring the validity of the multifractal formalism for such measures. On another hand, we show that these measures can have a dense set of phase transitions

Spots & stripes: pleomorphic patterning of stem cells via p-ERK-depenendent cell chemotaxis shown by feather morphogenesis & mathematical simulation

A key issue in stem cell biology is the differentiation of homogeneous stem cells towards different fates which are also organized into desired configurations. Little is known about the mechanisms underlying the process of periodic patterning. Feather explants offer a fundamental and testable model in which multi-potential cells are organized into hexagonally arranged primordia and the spacing between primordia. Previous work explored roles of a Turing reaction–diffusion mechanism in establishing chemical patterns. Here we show that a continuum of feather patterns, ranging from stripes to spots, can be obtained when the level of p-ERK activity is adjusted with chemical inhibitors. The patterns are dose-dependent, tissue stage-dependent, and irreversible. Analyses show that ERK activity-dependent mesenchymal cell chemotaxis is essential for converting micro-signaling centers into stable feather primordia. A mathematical model based on short-range activation, long-range inhibition, and cell chemotaxis is developed and shown to simulate observed experimental results. This generic cell behavior model can be applied to model stem cell patterning behavior at large