Millisecond Rates Research Articles

Understanding Human Reactions Looking at Facial Microexpressions With an Event Camera

With the establishment of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Industry 4.0</i> , machines are now required to interact with workers. By observing biometrics they can assess if humans are authorized, or mentally and physically fit to work. Understanding body language, makes human–machine interaction more natural, secure, and effective. Nonetheless, traditional cameras have limitations; low frame rate and dynamic range hinder a comprehensive human understanding. This poses a challenge, since faces undergo frequent instantaneous microexpressions. In addition, this is privacy-sensitive information that must be protected. We propose to model expressions with event cameras, bio-inspired vision sensors that have found application within the Industry 4.0 scope. They capture motion at millisecond rates and work under challenging conditions like low illumination and highly dynamic scenes. Such cameras are also privacy-preserving, making them extremely interesting for industry. We show that using event cameras, we can understand human reactions by only observing facial expressions. Comparison with red-green-blue (RGB)-based modeling demonstrates improved effectiveness and robustness.

Single-molecule imaging of non-equilibrium molecular ensembles on the millisecond timescale.

Molecular recognition is often driven by transient processes beyond the reach of detection. Single-molecule fluorescence microscopy methods are uniquely suited for detecting such non-accumulating intermediates, yet achieving the time resolution and statistics to realize this potential has proven challenging. Here, we present a single-molecule fluorescence resonance energy transfer (smFRET) imaging and analysis platform leveraging advances in scientific complementary metal-oxide semiconductor (sCMOS) detectors that enable the imaging of more than 10,000 individual molecules simultaneously at millisecond rates. The utility of this advance is demonstrated through quantitative measurements of previously obscured processes relevant to the fidelity mechanism in protein synthesis.

Cryogenic cooling for high power laser amplifiers

Using DPSSL (Diode Pumped Solid State Lasers) as pumping technology, PW-class lasers with enhanced repetition rates are developed. Each of the Yb YAG amplifiers will be diode-pumped at a wavelength of 940 nm. This is a prerequisite for achieving high repetition rates (light amplification duration 1 millisecond and repetition rate 10 Hz). The efficiency of DPSSL is inversely proportional to the temperature, for this reason the slab amplifier have to be cooled at a temperature in the range of 100 K–170 K with a heat flux of 1 MW*m−2 . This paper describes the thermo-mechanical analysis for the design of the amplification laser head, presents a preliminary proposal for the required cryogenic cooling system and finally outlines the gain of cryogenic operation for the efficiency of high pulsed laser.

MILLISECOND IMAGING OF RADIO TRANSIENTS WITH THE POCKET CORRELATOR

We demonstrate a signal processing concept for imaging the sky at millisecond rates with radio interferometers. The Pocket Correlator (PoCo) correlates the signals from multiple elements of a radio interferometer fast enough to image brief, dispersed pulses. By the nature of interferometry, a millisecond correlator functions like a large, single-dish telescope, but with improved survey speed, spatial localization, calibration, and interference rejection. To test the concept, we installed PoCo at the Allen Telescope Array (ATA) to search for dispersed pulses from the Crab pulsar, B0329+54, and M31 using total-power, visibility-based, and image-plane techniques. In 1.7 hours of observing, PoCo detected 191 giant pulses from the Crab pulsar brighter than a typical 5 sigma sensitivity limit of 60 Jy over pulse widths of 3 milliseconds. Roughly 40% of pulses from pulsar B0329+54 were detected by using novel visibility-based techniques. Observations of M31 constrain the rate of pulses brighter than 190 Jy in a three degree region surrounding the galaxy to <4.3/hr. We calculate the computational demand of various visibility-based pulse search algorithms and demonstrate how compute clusters can help meet this demand. Larger implementations of the fast imaging concept will conduct blind searches for millisecond pulses in our Galaxy and beyond, providing a valuable probe of the interstellar/intergalactic media, discovering new kinds of radio transients, and localizing them to constrain models of their origin.

Lunar occultations of 184 stellar sources in two crowded regions toward the Galactic bulge

Lunar occultations (LO) provide a unique combination of high angular resolution and sensitivity at near-infrared wavelenghts. At the ESO Very Large Telescope, it is possible to achieve about 1 milliarcsecond (mas) resolution and detect sources as faint as K$\approx$12\,mag. We have taken advantage of a passage of the Moon over two crowded and reddened regions in the direction of the inner part of the galactic bulge, in order to obtain a high number of occultation light curves over two half nights. Our goal was to detect and characterize new binary systems, and to investigate highly extincted and relatively unknown infrared sources in search of circumstellar shells and similar peculiarities. Our target list included a significant number of very late-type stars, but in fact the majority of the sources was without spectral classification. A LO event requires the sampling of the light curve at millisecond rates in order to permit a detailed study of the diffraction fringes. For this, we used the so-called burst mode of the ISAAC instrument at the Melipal telescope. Our observing efficiency was ultimately limited by overheads for telescope pointing and data storage, to about one event every three minutes. We could record useful light curves for 184 sources. Of these, 24 were found to be binaries or multiples, all previously unknown. The projected separations are as small as 7.5\,mas, and the magnitude differences as high as $\Delta$K=6.5\,mag. Additionally we could establish, also for the first time, the resolved nature of at least two more stars, with indication of circumstellar emission. We could also put upper limits on the angular size of about 165 unresolved stars, an information that combined with previous and future observations will be very helpful in establishing a list of reliable calibrators for long baseline interferometers.

New high-sensitivity, milliarcsecond resolution results from routine observations of lunar occultations at the ESO VLT

(Abridged) Lunar occultations (LO) are a very efficient and powerful technique, that achieves the best combination of high angular resolution and sensitivity possible today at near-infrared wavelengths. Given that the events are fixed in time, that the sources are occulted randomly, and that the telescope use is minimal, the technique is very well suited for service mode observations. We have established a program of routine LO observations at the VLT observatory, especially designed to take advantage of short breaks available in-between other programs. We have used the ISAAC instrument in burst mode, capable of producing continuous read-outs at millisecond rates on a suitable subwindow. Given the random nature of the source selection, our aim has been primarily the investigation of a large number of stellar sources at the highest angular resolution in order to detect new binaries. Serendipitous results such as resolved sources and detection of circumstellar components were also anticipated. We have recorded the signal from background stars for a few seconds, around the predicted time of occultation by the Moon's dark limb. At millisecond time resolution, a characteristic diffraction pattern can be observed. Patterns for two or more sources superimpose linearly, and this property is used for the detection of binary stars. The detailed analysis of the diffraction fringes can be used to measure specific properties such as the stellar angular size and the presence of extended light sources such as a circumstellar shell. We present a list of 191 stars for which LO data could be recorded and analyzed. Results include the detection of 16 binary and 2 triple stars, all but one of which were previously unknown. The projected angular separations are as small as 4 milliarcseconds and magnitude differences as high as ?K=5.8 mag...

Intrinsic Domain and Loop Dynamics Commensurate with Catalytic Turnover in an Induced-Fit Enzyme

Arginine kinase catalyzes reversible phosphoryl transfer between ATP and arginine, buffering cellular ATP concentrations. Structures of substrate-free and -bound enzyme have highlighted a range of conformational changes thought to occur during the catalytic cycle. Here, NMR is used to characterize the intrinsic backbone dynamics over multiple timescales. Relaxation dispersion indicates rigid-body motion of the N-terminal domain and flexible dynamics in the I182-G209 loop, both at millisecond rates commensurate with k(cat), implying that either might be rate limiting upon catalysis. Lipari-Szabo analysis indicates backbone flexibility on the nanosecond timescale in the V308-V322 loop, while the rest of the enzyme is more rigid in this timescale. Thus, intrinsic dynamics are most prominent in regions that have been independently implicated in conformational changes. Substrate-free enzyme may sample an ensemble of different conformations, of which a subset is selected upon substrate binding, with critical active site residues appropriately configured for binding and catalysis.

Structural Basis of the Broad Specificity of a General Odorant-Binding Protein from Honeybee

General odorant-binding proteins (GOBPs) are believed to transport a wide range of volatile hydrophobic molecules across the aqueous sensillum lymph toward olfactory receptors in insects. GOBPs are involved in the first step of odorant recognition, which has a great impact in agriculture and in insect-mediated human disease control. We report here the first structural study of a GOBP, the honeybee ASP2, in complex with a small hydrophilic ligand. The overall fold of the NMR structure of ASP2 consists of the packing of six alpha-helices creating an internal cavity and closely resembles that of the related pheromone-binding proteins (PBPs). The predominantly hydrophobic internal cavity of ASP2 provides additional possible interactions (pi-stacking, electrostatic contact) for ligand binding. We also show that the internal cavity of ASP2 has the ability to bind ligands of different structures and properties, including a hydrophobic component of the floral scent [2-isobutyl-3-methoxypyrazine (IBMP)] and a small hydrophilic ligand. We further demonstrate that IBMP binds ASP2 with two stable alternative conformations inside the ASP2 binding pocket. The (15)N NMR relaxation study suggests that significant backbone mobility occurs at the ligand entry site at the millisecond rate, which likely plays a role in the recognition and the uptake-release mechanism of ligands by ASP2. We propose that the broad ligand specificity of GOBPs compared with PBPs is conferred by the cumulative effects of weak nonspecific protein-ligand interactions and of enhanced protein internal dynamics at the ligand entry site.

A P2X receptor from the tardigrade species Hypsibius dujardini with fast kinetics and sensitivity to zinc and copper.

BackgroundOrthologs of the vertebrate ATP gated P2X channels have been identified in Dictyostelium and green algae, demonstrating that the emergence of ionotropic purinergic signalling was an early event in eukaryotic evolution. However, the genomes of a number of animals including Drosophila melanogaster and Caenorhabditis elegans, both members of the Ecdysozoa superphylum, lack P2X-like proteins, whilst other species such as the flatworm Schistosoma mansoni have P2X proteins making it unclear as to what stages in evolution P2X receptors were lost. Here we describe the functional characterisation of a P2X receptor (HdP2X) from the tardigrade Hypsibius dujardini demonstrating that purinergic signalling is preserved in some ecdysozoa.ResultsATP (EC50 ~44.5 μM) evoked transient inward currents in HdP2X with millisecond rates of activation and desensitisation. HdP2X is antagonised by pyridoxal-phosphate-6-azophenyl-2',4' disulfonic acid (IC50 15.0 μM) and suramin (IC50 22.6 μM) and zinc and copper inhibit ATP-evoked currents with IC50 values of 62.8 μM and 19.9 μM respectively. Site-directed mutagenesis showed that unlike vertebrate P2X receptors, extracellular histidines do not play a major role in coordinating metal binding in HdP2X. However, H306 was identified as playing a minor role in the actions of copper but not zinc. Ivermectin potentiated responses to ATP with no effect on the rates of current activation or decay.ConclusionThe presence of a P2X receptor in a tardigrade species suggests that both nematodes and arthropods lost their P2X genes independently, as both traditional and molecular phylogenies place the divergence between Nematoda and Arthropoda before their divergence from Tardigrada. The phylogenetic analysis performed in our study also clearly demonstrates that the emergence of the family of seven P2X channels in human and other mammalian species was a relatively recent evolutionary event that occurred subsequent to the split between vertebrates and invertebrates. Furthermore, several characteristics of HdP2X including fast kinetics with low ATP sensitivity, potentiation by ivermectin in a channel with fast kinetics and distinct copper and zinc binding sites not dependent on histidines make HdP2X a useful model for comparative structure-function studies allowing a better understanding of P2X receptors in higher organisms.

CCD drift-scan imaging lunar occultations: A feasible approach for sub-meter class telescopes

A CCD drift-scanning technique for lunar occultation (LO) observations is presented. While this ap- proach has been addressed before by Sturmann (1994) for the case of large telescopes, the technical validity has never been discussed for sub-meter class telescopes. In contrast to Sturmann's scheme, the proposed technique places the CCD in the image plane of the telescope. This does not represent a problem in the case of small telescopes, where the practical angular resolution attainable by LO is not limited by aperture smoothing. Photon- generated charge is read out at millisecond rates on a column by column basis, as the diraction pattern of the occulted star is being tracked. Two LO events (SAO 79031 and SAO 77911) were observed to demonstrate the feasibility of the method. Data analysis was carried out, yielding unresolved angular diameters for both objects. We show, however, that the technique could be useful for close binary detections with small telescopes. A dis- cussion of the limiting resolution and magnitude imposed by our instrumentation is carried out, showing that the drift-scanning technique could be extended to 1{2 m telescopes for stellar diameter determination purposes. Finally, we point out that the technical demands required by this technique can be easily met by most small professional observatories and advanced amateurs.

Achieving variation of the optical path length by a few millimeters at millisecond rates for imaging of turbid media and optical interferometry: a new technique

A new technique that offers very high stability and repeatability in varying the optical path length by a few millimeters at a millisecond rate is demonstrated. The technique is simply based on a rotating optical cube with parallel facets. The optical path length is varied at a nonlinear rate, and the data can be presented in the frequency or the spatial domain.

The Biophysics of Visual Photoreception

Vision is awe inspiring. The wondrous nature of this sensory process becomes clear when we consider just a few of its features. In the terminology of today's technology, the human visual system has a set of stereoscopic foreoptics that are instantly and automatically focusable to a few centimeters and are fully corrected for geometric aberrations, a servo-controlled two-axis scanning mechanism, a millisecond framing rate, sensitivity to brightnesses varying by a factor of 100 billion, the ability to detect a single photon, nearly 100% quantum efficiency and a spatial as well as temporal image processor that could not be matched by the fastest supercomputer.