A-PHOT: a new, versatile code for precision aperture photometry

Aims. We present A-PHOT, a new publicly available code for performing aperture photometry on astronomical images, that is particularly well suited for multi-band extragalactic surveys. Methods.A-PHOT estimates the fluxes emitted by astronomical objects within a chosen set of circular or elliptical apertures. Unlike other widely used codes, it runs on predefined lists of detected sources, allowing for repeated measurements on the same list of objects on different images. This can be very useful when forced photometric measurement on a given position is needed. A-PHOT can also estimate morphological parameters and a local background flux, and compute on-the-fly individual optimized elliptical apertures, in which the signal-to-noise ratio is maximized. Results. We check the performance of A-PHOT on both synthetic and real test datasets: we explore a simulated case of a space-based high-resolution imaging dataset, investigating the input parameter space to optimize the accuracy of the performance, and we exploit the CANDELS GOODS-South data to compare the A-PHOT measurements with those from the survey legacy catalogs, finding good agreement overall. Conclusions.A-PHOT proves to a useful and versatile tool for quickly extracting robust and accurate photometric measurements and basic morphological information of galaxies and stars, with the advantage of allowing for various measurements of fluxes at any chosen position without the need of a full detection run, and for determining the basic morphological features of the sources.

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3D super-resolved imaging in live cells using sub-diffractive plasmonic localization of hybrid nanopillar arrays

Nanophotonics ◽

10.1515/nanoph-2020-0105 ◽

2020 ◽

Vol 9 (9) ◽

pp. 2847-2859

Author(s):

Soojung Kim ◽

Hyerin Song ◽

Heesang Ahn ◽

Seung Won Jun ◽

Seungchul Kim ◽

...

Keyword(s):

Signal To Noise Ratio ◽

Imaging Techniques ◽

Optical Loss ◽

Super Resolution ◽

Living Cells ◽

Live Cells ◽

Complex Biological System ◽

Observation Volume ◽

Resolution Imaging ◽

Nanopillar Arrays

AbstractAnalysing dynamics of a single biomolecule using high-resolution imaging techniques has been had significant attentions to understand complex biological system. Among the many approaches, vertical nanopillar arrays in contact with the inside of cells have been reported as a one of useful imaging applications since an observation volume can be confined down to few-tens nanometre theoretically. However, the nanopillars experimentally are not able to obtain super-resolution imaging because their evanescent waves generate a high optical loss and a low signal-to-noise ratio. Also, conventional nanopillars have a limitation to yield 3D information because they do not concern field localization in z-axis. Here, we developed novel hybrid nanopillar arrays (HNPs) that consist of SiO2 nanopillars terminated with gold nanodisks, allowing extreme light localization. The electromagnetic field profiles of HNPs are obtained through simulations and imaging resolution of cell membrane and biomolecules in living cells are tested using one-photon and 3D multiphoton fluorescence microscopy, respectively. Consequently, HNPs present approximately 25 times enhanced intensity compared to controls and obtained an axial and lateral resolution of 110 and 210 nm of the intensities of fluorophores conjugated with biomolecules transported in living cells. These structures can be a great platform to analyse complex intracellular environment.

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3D phonon microscopy with sub-micron axial-resolution

Scientific Reports ◽

10.1038/s41598-021-82639-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Richard J. Smith ◽

Fernando Pérez-Cota ◽

Leonel Marques ◽

Matt Clark

Keyword(s):

Signal To Noise Ratio ◽

Single Cells ◽

Optical Resolution ◽

Acquisition Time ◽

Label Free ◽

Axial Resolution ◽

Force Microscopy ◽

Atomic Force ◽

Accuracy And Precision ◽

Good Agreement

AbstractBrillouin light scattering (BLS) is an emerging method for cell imaging and characterisation. It allows elasticity-related contrast, optical resolution and label-free operation. Phonon microscopy detects BLS from laser generated coherent phonon fields to offer an attractive route for imaging since, at GHz frequencies, the phonon wavelength is sub-optical. Using phonon fields to image single cells is challenging as the signal to noise ratio and acquisition time are often poor. However, recent advances in the instrumentation have enabled imaging of fixed and living cells. This work presents the first experimental characterisation of phonon-based axial resolution provided by the response to a sharp edge. The obtained axial resolution is up to 10 times higher than that of the optical system used to take the measurements. Validation of the results are obtained with various polymer objects, which are in good agreement with those obtained using atomic force microscopy. Edge localisation, and hence profilometry, of a phantom boundary is measured with accuracy and precision of approximately 60 nm and 100 nm respectively. Finally, 3D imaging of fixed cells in culture medium is demonstrated.

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The Balloon-Borne Investigation of Temperature and Speed of Electrons in the Corona (BITSE): Mission Description and Preliminary Results

Solar Physics ◽

10.1007/s11207-020-01751-8 ◽

2021 ◽

Vol 296 (1) ◽

Author(s):

N. Gopalswamy ◽

J. Newmark ◽

S. Yashiro ◽

P. Mäkelä ◽

N. Reginald ◽

...

Keyword(s):

Heliocentric Distance ◽

Signal To Noise Ratio ◽

Flow Speed ◽

Science Data ◽

Uncertainty Interval ◽

Heliospheric Observatory ◽

Flash Storage ◽

Goddard Space Flight Center ◽

Good Agreement ◽

Polarization Camera

AbstractWe report on the Balloon-borne Investigation of Temperature and Speed of Electrons in the corona (BITSE) mission launched recently to observe the solar corona from $\approx 3$ ≈ 3 Rs to 15 Rs at four wavelengths (393.5, 405.0, 398.7, and 423.4 nm). The BITSE instrument is an externally occulted single stage coronagraph developed at NASA’s Goddard Space Flight Center in collaboration with the Korea Astronomy and Space Science Institute (KASI). BITSE used a polarization camera that provided polarization and total brightness images of size $1024 \times 1024$ 1024 × 1024 pixels. The Wallops Arc Second Pointer (WASP) system developed at NASA’s Wallops Flight Facility (WFF) was used for Sun pointing. The coronagraph and WASP were mounted on a gondola provided by WFF and launched from the Fort Sumner, New Mexico station of Columbia Scientific Balloon Facility (CSBF) on September 18, 2019. BITSE obtained 17,060 coronal images at a float altitude of $\approx \mbox{128,000}$ ≈ 128,000 feet ($\approx 39$ ≈ 39 km) over a period of $\approx 4$ ≈ 4 hrs. BITSE flight software was based on NASA’s core Flight System, which was designed to help develop flight quality software. We used EVTM (Ethernet Via Telemetry) to download science data during operations; all images were stored on board using flash storage. At the end of the mission, all data were recovered and analyzed. Preliminary analysis shows that BITSE imaged the solar minimum corona with the equatorial streamers on the east and west limbs. The narrow streamers observed by BITSE are in good agreement with the geometric properties obtained by the Solar and Heliospheric Observatory (SOHO) coronagraphs in the overlapping physical domain. In spite of the small signal-to-noise ratio ($\approx 14$ ≈ 14 ) we were able to obtain the temperature and flow speed of the western steamer. In the heliocentric distance range 4 – 7 Rs on the western streamer, we obtained a temperature of $\approx 1.0\pm 0.3$ ≈ 1.0 ± 0.3 MK and a flow speed of $\approx 260$ ≈ 260 km s−1 with a large uncertainty interval.

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Physical AWGN Channel Emulator for Bit Error Rate Test of Digital Baseband Communication

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.241-244.2491 ◽

2012 ◽

Vol 241-244 ◽

pp. 2491-2495 ◽

Cited By ~ 5

Author(s):

Antonio Boscolo ◽

Francesca Vatta ◽

Francesco Armani ◽

Emanuele Viviani ◽

Daniele Salvalaggio

Keyword(s):

Bit Error Rate ◽

Error Rate ◽

Signal To Noise Ratio ◽

Error Correcting Codes ◽

Noise Sources ◽

Channel Emulator ◽

Physical Channel ◽

Rate Test ◽

Data Signal ◽

Good Agreement

This paper presents a physical channel emulator solution for applications such as Bit Error Rate Testing of Error Correcting Codes. The solution relies on an analog White Gaussian Noise Generator coupled additively with an analog data signal to emulate the communication channel. This is interfaced to a computer through a USB connection, allowing the use of programs in different environments, such as Matlab and Labview. This solution can allow different types of channels to be emulated and with different noise sources. A software-based method to measure Signal to Noise Ratio and to characterize the channel is also presented. The system has been validated using a Matlab interface implementing multiple error correcting codes and showed good agreement with the theoretical model.

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Continuing the MODIS Dark Target Aerosol Time Series with VIIRS

Remote Sensing ◽

10.3390/rs12020308 ◽

2020 ◽

Vol 12 (2) ◽

pp. 308 ◽

Cited By ~ 8

Author(s):

Virginia Sawyer ◽

Robert C. Levy ◽

Shana Mattoo ◽

Geoff Cureton ◽

Yingxi Shi ◽

...

Keyword(s):

Near Infrared ◽

Infrared Imaging ◽

Retrieval Algorithm ◽

Spatial And Temporal Variability ◽

Imaging Spectrometer ◽

Standard Data ◽

Moderate Resolution ◽

Resolution Imaging ◽

Infrared Wavelengths ◽

Good Agreement

For reflected sunlight observed from space at visible and near-infrared wavelengths, particles suspended in Earth’s atmosphere provide contrast with vegetation or dark water at the surface. This is the physical motivation for the Dark Target (DT) aerosol retrieval algorithm developed for the Moderate Resolution Imaging Spectrometer (MODIS). To extend the data record of aerosol optical depth (AOD) beyond the expected 20-year lifespan of the MODIS sensors, DT must be adapted for other sensors. A version of the DT AOD retrieval for the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi-National Polar-Orbiting Partnership (SNPP) is now mature enough to be released as a standard data product, and includes some upgraded features from the MODIS version. Differences between MODIS Aqua and VIIRS SNPP lead to some inevitable disagreement between their respective AOD measurements, but the offset between the VIIRS SNPP and MODIS Aqua records is smaller than the offset between those of MODIS Aqua and MODIS Terra. The VIIRS SNPP retrieval shows good agreement with ground-based measurements. For most purposes, DT for VIIRS SNPP is consistent enough and in close enough agreement with MODIS to continue the record of satellite AOD. The reasons for the offset from MODIS Aqua, and its spatial and temporal variability, are investigated in this study.

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Application of Taguchi method in the optimization of geometric parameters for double pin joint configurations made from glass–epoxy nanoclay laminates

Journal of Composite Materials ◽

10.1177/0021998316678920 ◽

2016 ◽

Vol 51 (19) ◽

pp. 2689-2706 ◽

Cited By ~ 8

Author(s):

Manjeet Singh ◽

J S Saini ◽

H Bhunia ◽

Paramdeep Singh

Keyword(s):

Taguchi Method ◽

Signal To Noise Ratio ◽

Characteristic Curve ◽

Free Edge ◽

Geometric Parameters ◽

Signal To Noise ◽

Bearing Strength ◽

Significant Parameter ◽

Numerical Predictions ◽

Good Agreement

In the present work, Taguchi method was used for the optimization of geometric parameters for double pin joint configurations. The orthogonal array, the signal-to-noise ratio, and analysis of variance were employed to study the effect of geometric parameters on the bearing strength of the joints. Geometric parameters, i.e. the distance from the free edge of the specimen to the diameter of the first hole (E/D) ratio, width of the specimen to the diameter of the hole (W/D) ratio, the distance between the two holes to the diameter of the hole (P/D) ratio and side width to the diameter of the hole (K/D) ratio were investigated for the serial and parallel hole configurations. The results demonstrate that the E/D ratio is the most significant parameter to increase the bearing strength in both serial and parallel pin joint configurations. Its percentage contribution is about 84.5% and 64.23% in serial and parallel pin joint configurations, respectively. Characteristic curve with Tsai–Wu failure criterion was used for the prediction of the bearing strength in the joints numerically. A good agreement was obtained between experimental results and numerical predictions.

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Compilation and evaluation of gas phase diffusion coefficients of halogenated organic compounds

Royal Society Open Science ◽

10.1098/rsos.171936 ◽

2018 ◽

Vol 5 (7) ◽

pp. 171936 ◽

Cited By ~ 3

Author(s):

Wenjun Gu ◽

Peng Cheng ◽

Mingjin Tang

Keyword(s):

Gas Phase ◽

Diffusion Coefficients ◽

Input Parameter ◽

Empirical Method ◽

Trace Gas ◽

Temperature And Pressure ◽

Organic Halogens ◽

Semi Empirical ◽

Method Show ◽

Good Agreement

Organic halogens are of great environmental and climatic concern. In this work, we have compiled their gas phase diffusivities (pressure-normalized diffusion coefficients) in a variety of bath gases experimentally measured by previous studies. It is found that diffusivities estimated using Fuller's semi-empirical method agree very well with measured values for organic halogens. In addition, we find that at a given temperature and pressure, different molecules exhibit very similar mean free paths in the same bath gas, and then propose a method to estimate mean free paths in different bath gases. For example, the pressure-normalized mean free paths are estimated to be 90, 350, 90, 80, 120 nm atm in air (and N 2 /O 2 ), He, argon, CO 2 and CH 4 , respectively, with estimated errors of around ±25%. A generic method, which requires less input parameter than Fuller's method, is proposed to calculate gas phase diffusivities. We find that gas phase diffusivities in He (and air as well) calculated using our method show fairly good agreement with those measured experimentally and estimated using Fuller's method. Our method is particularly useful for the estimation of gas phase diffusivities when the trace gas contains atoms whose diffusion volumes are not known.

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Snow Depth Estimation on Slopes Using GPS-Interferometric Reflectometry

Sensors ◽

10.3390/s19224994 ◽

2019 ◽

Vol 19 (22) ◽

pp. 4994

Author(s):

Haohan Wei ◽

Xiufeng He ◽

Yanming Feng ◽

Shuanggen Jin ◽

Fei Shen

Keyword(s):

Time Series ◽

Snow Depth ◽

Water Cycle ◽

Signal To Noise Ratio ◽

Plate Boundary ◽

Depth Estimation ◽

Tilted Surface ◽

Global Water Cycle ◽

Gps Antenna ◽

Good Agreement

Snow is one of the most critical sources of freshwater, which influences the global water cycle and climate change. However, it is difficult to monitor global snow variations with high spatial–temporal resolution using traditional techniques due to their costly and labor-intensive nature. Nowadays, the Global Positioning System Interferometric Reflectometry (GPS-IR) technique can measure the average snow depth around a GPS antenna using its signal-to-noise ratio (SNR) data. Previous studies focused on the use of GPS data at sites located in flat areas or on very gentle slopes. In this contribution, we propose a strategy called the Tilted Surface Strategy (TSS), which uses the SNR data reflected only from the flat quadrants to estimate the snow depth instead of the conventional strategy, which employs all the SNR data reflected from the whole area around a GPS antenna. Three geodetic GPS sites from the Plate Boundary Observatory (PBO) project were chosen in this experimental study, of which GPS sites p683 and p101 were located on slopes with their gradients up to 18% and the site p025 was located on a flat area. Comparing the snow depths derived with the GPS-IR TSS method with the snow depth results provided with the GPS-PBO, i.e., GPS-IR with the conventional strategy, the Snowpack Telemetry (SNOTEL) network measurements and gridded Snow Data Assimilation System (SNODAS) estimates, it was found that the snow depths derived with the four methods had a good agreement, but the snow depth time series with the GPS-IR TSS method were closer to the SNOTEL measurements and the SNODAS estimates than those with GPS-PBO method. Similar observations were also obtained from the cumulative snowfall time series. Results generally indicated that for those GPS sites located on slopes, the TSS strategy works better.

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Single drop square wave polarography

Canadian Journal of Chemistry ◽

10.1139/v81-493 ◽

1981 ◽

Vol 59 (24) ◽

pp. 3326-3333 ◽

Cited By ~ 9

Author(s):

Louis Ramaley ◽

Wee Tee Tan

Keyword(s):

Square Wave Voltammetry ◽

Signal To Noise Ratio ◽

Single Drop ◽

Plane Model ◽

Square Wave ◽

Electrode Reactions ◽

Wave Voltammetry ◽

Average Current ◽

The Times ◽

Good Agreement

The theory of square wave voltammetry for reversible electrode reactions is expanded to include average currents and currents flowing to a growing drop (single drop square wave polarography) using an expanding plane model. Excellent agreement between theory and experiment was found for the reduction of Fe(III), good agreement for the reduction of Cd(II). The expanding plane model proved superior, but not greatly superior to the simpler theory. For the case of average current the effect on the polarogram of the times at which integration is started and stopped is discussed. Integration decreases sensitivity but increases signal-to-noise ratio. The conditions for maximum analytical usefulness are presented.

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Low-Dosage Maximum-A-Posteriori Focusing and Stigmation

Microscopy and Microanalysis ◽

10.1017/s1431927612013852 ◽

2013 ◽

Vol 19 (1) ◽

pp. 38-55 ◽

Cited By ~ 11

Author(s):

Jonas Binding ◽

Shawn Mikula ◽

Winfried Denk

Keyword(s):

Low Dose ◽

Signal To Noise Ratio ◽

Three Dimensions ◽

Maximum A Posteriori ◽

A Posteriori ◽

Electron Dose ◽

Secondary Electrons ◽

Block Face ◽

Resolution Imaging ◽

Low Dosage

AbstractRadiation damage is often an issue during high-resolution imaging, making low-dose focusing and stigmation essential, in particular when no part of the sample can be “sacrificed” for this. An example is serial block-face electron microscopy, where the imaging resolution must be kept optimal during automated acquisition that can last months. Here, we present an algorithm, which we call “Maximum-A-Posteriori Focusing and Stigmation (MAPFoSt),” that was designed to make optimal use of the available signal. We show that MAPFoSt outperforms the built-in focusing algorithm of a commercial scanning electron microscope even at a tenfold reduced total dose. MAPFoSt estimates multiple aberration modes (focus and the two astigmatism coefficients) using just two test images taken at different focus settings. Using an incident electron dose density of 2,500 electrons/pixel and a signal-to-noise ratio of about one, all three coefficients could be estimated to within <7% of the depth of focus, using 19 detected secondary electrons per pixel. A generalization to higher-order aberrations and to other forms of imaging in both two and three dimensions appears possible.

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