James Webb Space Telescope (JWST) transmission and emission spectra will provide invaluable glimpses of transiting exoplanet atmospheres, including possible biosignatures. This promising science from ...JWST, however, will require exquisite precision and understanding of systematic errors that can impact the time series of planets crossing in front of and behind their host stars. Here, we provide estimates of the random noise sources affecting JWST Near-Infrared Camera (NIRCam) time-series data on the integration-to-integration level. We find that 1/ f noise can limit the precision of grism time series for two groups (230–1000 ppm depending on the extraction method and extraction parameters) but will average down like the square root of N frames/reads. The current NIRCam grism time-series mode is especially affected by 1/ f noise because its GRISMR dispersion direction is parallel to the detector fast-read direction, but could be alleviated in the GRISMC direction. Care should be taken to include as many frames as possible per visit to reduce this 1/ f noise source: thus, we recommend the smallest detector subarray sizes one can tolerate, four output channels, and readout modes that minimize the number of skipped frames (RAPID or BRIGHT2). We also describe a covariance-weighting scheme that can significantly lower the contributions from 1/ f noise as compared to sum extraction. We evaluate the noise introduced by preamplifier offsets, random telegraph noise, and high dark current resistor capacitor (RC) pixels and find that these are correctable below 10 ppm once background subtraction and pixel masking are performed. We explore systematic error sources in a companion paper.
Spontaneous activity represents an early, primitive form of motor activity within zebrafish embryos, providing a potential readout for identification of neuroactive compounds. However, despite use as ...an endpoint in chemical screens around the world, the predictive power and limitations of assays relying on spontaneous activity remain unclear. Using an improved high-content screening assay that increased throughput from 384 to 3072 wells per week, we screened a well-characterized library of 1280 pharmacologically active compounds (LOPAC{sup 1280}) – 612 of which target neurotransmission – to identify which targets are detected using spontaneous activity as a readout. Results from this screen revealed that (1) 8% of the LOPAC{sup 1280} library was biologically active; (2) spontaneous activity was affected by compounds spanning a broad array of targets; (3) only 4% of compounds targeting neurotransmission impacted spontaneous activity; and (4) hypoactivity was observed for 100% of hits detected, including those that exhibit opposing mechanisms of action for the same target. Therefore, while this assay was able to rapidly identify potent neuroactive chemicals, these data suggest that spontaneous activity may lack the ability to discriminate modes of action for compounds interfering with neurotransmission, an issue that may be due to systemic uptake following waterborne exposure, persistent control variation, and/or interference with non-neurotransmission-related mechanisms. - Highlights: • Assay throughput was increased from 384 to 3072 wells per week. • 8% of the LOPAC{sup 1280} library was biologically active within zebrafish embryos. • Spontaneous activity was affected by compounds spanning a broad array of targets. • Only 4% of compounds targeting neurotransmission impacted spontaneous activity. • Hypoactivity was observed for 100% of hits detected.
Abstract
We describe a new instrument capable of high-precision (10
−5
) polarimetric observations simultaneously in three passbands (
BVR
). The instrument utilizes electron-multiplying ...charge-coupled device (EM CCD) cameras for high efficiency and fast image readout. The key features of the Double Image Polarimeter—Ultra Fast (DIPol-UF) are: (i) the optical design with high throughput and inherent stability; (ii) great versatility, which makes the instrument optimally suitable for observations of bright and faint targets; and (iii) a control system, which allows the use of the polarimeter remotely. Examples are given of the first results obtained from high signal-to-noise observations of bright nearby stars and of fainter sources such as X-ray binaries in their quiescent states.
This article presents two adaptive biasing techniques for comparators to achieve ultralow-power and high dynamic range in readout circuits for resistive gas sensors. The first technique is based on ...an on-demand biasing that generates a bias current up to <inline-formula> <tex-math notation="LaTeX">3 \mu \text{A} </tex-math></inline-formula> when the differential input voltage is close to zero, while minimizing the bias current when a comparison is not imminent. The second technique takes advantage of the correlation between sensor current and delay requirements to bias the comparator with the appropriate current for each situation. These techniques were applied to two readout circuits, demonstrating a reduction of the energy per measurement to less than a fifth for the largest input resistance in comparison to fixed biasing without affecting SNR. The input range is above five decades in both cases, from 2.4 <inline-formula> <tex-math notation="LaTeX">\text{k}\Omega </tex-math></inline-formula> up to 1 <inline-formula> <tex-math notation="LaTeX">\text{G}\Omega </tex-math></inline-formula> and from 1 <inline-formula> <tex-math notation="LaTeX">\text{k}\Omega </tex-math></inline-formula> up to 270 <inline-formula> <tex-math notation="LaTeX">\text{M}\Omega </tex-math></inline-formula>. The signal to noise ratio ranges from 55 dB up to 70 dB which provides enough margin to interface a wide range of gas sensors. Lastly, one of the designs was successfully employed to measure varying concentrations of ammonia with a polypyrrole (PPy) gas sensor.
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