Instrumental Resolution Research Articles

Intra-annual variations of regional total column ozone, aerosol optical depth, and water vapor from ground-based, satellite-based and model-based observations

Abstract The Microtops II ozonometer has been deployed to continuously measure the total column ozone (TCO), precipitable water content (PWC) and aerosol optical thickness (AOT) at Atigre village (16.74° N, 74.37° E, 604 m above sea level, masl) located on the southeastern slope of Indian western Ghats. The Microtops II ozonometer measurements during the period from September 2017 to June 2018 were analyzed along with the retrieved products of Ozone Monitoring Instrument (OMI) and Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASA's Terra satellites and also the ERA-interim reanalysis model. We found that the TCO (or PWC) data from the OMI (or MODIS) and the ERA reanalysis model data products are in good agreement. The measurements showed strong seasonal variability such that TCO was lowest in the winter season but increased in the summer season, and both PWC and AOT were lowest in the post-monsoon season and increased in the summer season. In continuous ERA-interim reanalysis TCO observations, we found the three types of periodicities in the daily mean TCO as well as PWC (i) The weekly (7 days), (ii) quasi-biweekly (14 to 16 days), (iii) Madden Julian Oscillations (MJO) (30–60 days) oscillations. These oscillations depend on the periodic weather changes in the troposphere. We also observe that the average day to day variability in daily mean TCO observations in the observational period is about 1.4%, 1.1%, 2.62% in the Microtops II ozonometer, ERA-interim reanalysis, and OMI data respectively. We found the positive correlation between daily mean AOT and PWC in all seasons (except monsoon), which is maximum in the winter season, showing the hygroscopic nature of aerosols. The sources of water vapor and aerosol at our location are also studied using back-trajectory analysis.

Image quality guided smart rotation improves coverage in microscopy

Fluorescence microscopy is an essential tool for biological discoveries. There is a constant demand for better spatial resolution across a larger field of view. Although strides have been made to improve the theoretical resolution and speed of the optical instruments, in mesoscopic samples, image quality is still largely limited by the optical properties of the sample. In Selective Plane Illumination Microscopy (SPIM), the achievable optical performance is hampered by optical degradations encountered in both the illumination and detection. Multi-view imaging, either through sample rotation or additional optical paths, is a popular strategy to improve sample coverage. In this work, we introduce a smart rotation workflow that utilizes on-the-fly image analysis to identify the optimal light sheet imaging orientations. The smart rotation workflow outperforms the conventional approach without additional hardware and achieves a better sample coverage using the same number of angles or less and thereby reduces data volume and phototoxicity.

Nuclear magnetic resonance and x-ray microtomography pore-scale analysis of oil recovery in mixed-porosity carbonates

With the recognition that carbonate reservoir rocks commonly contain a significant microporosity component (pore sizes ∼1 μm), there has been an ongoing effort to understand how this affects hydrocarbon recovery. This work reports x-ray microtomography (XMT) and nuclear magnetic resonance (NMR) data on two characteristic rock types. One is micropore dominated, and the other exhibits mixed-pore sizes. Several new techniques are introduced to accommodate investigation of full-sized core-plug samples having preserved wettability and to perform such studies with native fluids. First, the uses of high-field NMR techniques are demonstrated to determine porosity, overall oil and water content, and how these fluids are distributed between micro- and macropores. It is found that microporosity values agree with those obtained by optical (total pore system) analysis. Second, the use of xenon gas to tag the native oil phase for XMT imaging is demonstrated, showing how this helps determine contributions from pores that are smaller than the instrument resolution. Finally, a new method that uses NMR measurements of oil and water saturations to constrain the image analysis is demonstrated. The analysis shows the extent to which oil recovery occurs from the different pore systems. In both rock types, oil in the macroporosity is preferentially swept. Nevertheless, in agreement with a recent theory, oil recovery from the microporosity is significant. For the 70% microporosity sample, approximately one-third of the total oil recovery comes from the micropores, a factor that agrees well with theory.

Новая оценка линейного инструментального разрешения на местности космических аппаратов дистанционного зондирования Земли для совершенного проектирования их оптико-электронной аппаратуры

Новая оценка линейного инструментального разрешения на местности космических аппаратов дистанционного зондирования Земли для совершенного проектирования их оптико-электронной аппаратуры

Experience in synchronous observation of seismic-strain oscillations of the Earth by the spaced laser interferometers

The first results of unique experiments on the synchronous registration of seismic-strain oscillations of the Earth’s surface by three laser interferometers-deformographs (strainmeters) spaced 6740 km apart are presented. Two 100-meter laser interferometers at the Fryazino site (Moscow Region) and the 18-meter laser strainmeter at the observation point of Karymshina (Kamchatka Peninsula) were applied. The frequency-stabilized and thermally controlled lasers and the interferogram registration systems of compensation and modulation types providing an absolute instrumental resolution of 0.1-0.01 nm were used. The results of data analysis in sessions of synchronous operation of these instruments during 2016-2020 were obtained and discussed.

Spectropolarimetric Insight into Plasma Sheet Dynamics of a Solar Flare

Abstract We examine spectropolarimetric data from the Coronal Multi-channel Polarimeter (CoMP) instrument, acquired during the evolution of the 2017 September 10 X8.2 solar flare on the western solar limb. CoMP captured linearly polarized light from two emission lines of Fe xiii at 1074.7 and 1079.8 nm, from 1.03 to 1.5 solar radii. We focus here on the hot plasma sheet lying above the bright flare loops and beneath the ejected coronal mass ejection. The polarization has a striking and coherent spatial structure, with unexpectedly small polarization aligned with the plasma sheet. By elimination, we find that small-scale magnetic field structure is needed to cause such significant depolarization, and suggest that plasmoid formation during reconnection (associated with the tearing-mode instability) creates magnetic structure on scales below instrument resolution of 6 Mm. We conclude that polarization measurements with new coronagraphs, such as the upcoming Daniel K. Inouye Solar Telescope, will further enhance our understanding of magnetic reconnection and development of turbulence in the solar corona.

Frequency stabilization of dual-mode microchip laser by means of beat frequency stabilization

The stabilization of the laser oscillation frequency of a dual-mode microchip laser was demonstrated by stabilizing the beat frequency generated by the two simultaneously oscillating longitudinal modes. In the experiment, a beat frequency of 101 GHz was stabilized to ± 50 kHz using negative feedback control. As a result, the fluctuation of the laser oscillation frequency was finally stabilized to ± 50 MHz or less within the resolution of the measurement instrument with an estimated short-term fluctuation of ± 3.3 MHz. Furthermore, using this technique, the initial drift of the laser oscillation frequency was significantly reduced, and the linear sweep operation of the laser oscillation frequency was successfully demonstrated by linearly sweeping the beat frequency over 30 MHz while maintaining locking. Our technique is essentially robust and suitable for the miniaturization of the system in the future.

Evaluation of Lateral Resolution for Confocal Raman Microscopy Using Gold Nano‐Lines Made by Electron Beam Lithography

Assessing the instrumental resolution of confocal Raman microscopy is a key aspect in 2D or 3D imaging in various applications. An important issue in this regard is the experimental measurement of a lateral resolution for the Raman microscope system. Several methods have been proposed for the resolution measurement in fluorescence microscopy; however, these methods have rather limited applications. In this paper, we demonstrate an experimental approach for evaluating the lateral resolution with well‐defined nano‐patterns in confocal Raman microscopy and discuss the factors that can improve estimation of instrumental resolution. This study contributes to the further understanding of the assessment of instrumental resolution in confocal scanning Raman microscopy.

Resolution verification sensing device for a stereo digital image correlation system based on dual-frequency laser interference.

Digital image correlation (DIC) is widely used in materials mechanics, nondestructive testing, and other fields due to its advantages of noncontact, full-field measurement, and simple experimental setup. As an optical measurement method to measure the three-dimensional shape and deformation of an object, measurement accuracy is one of the most important technical indicators of DIC. If DIC is made into a measuring instrument, the resolution is an important parameter that must be provided. In general, the higher the measurement accuracy of the instrument, the higher the resolution of the instrument. At present, the research on DIC focuses on the analysis of factors affecting measurement accuracy, the noise reduction of measurement results, and the improvement of correlation algorithms. There are few reports on the verification of the resolution of DIC measurement instruments. However, accuracy analysis and resolution verification of the measurement instrument is a vital technical task to ensure the credibility of the measurement data. In this paper, a high-precision dual-frequency laser interferometer principle is used to design a sensing device to verify the measurement resolution of the DIC instrument. The accuracy and resolution of the self-made stereo DIC instrument were tested and evaluated using this sensing device.

Ultrastructural modeling of small angle scattering from photosynthetic membranes

The last decade has seen a range of studies using non-invasive neutron and X-ray techniques to probe the ultrastructure of a variety of photosynthetic membrane systems. A common denominator in this work is the lack of an explicitly formulated underlying structural model, ultimately leading to ambiguity in the data interpretation. Here we formulate and implement a full mathematical model of the scattering from a stacked double bilayer membrane system taking instrumental resolution and polydispersity into account. We validate our model by direct simulation of scattering patterns from 3D structural models. Most importantly, we demonstrate that the full scattering curves from three structurally typical cyanobacterial thylakoid membrane systems measured in vivo can all be described within this framework. The model provides realistic estimates of key structural parameters in the thylakoid membrane, in particular the overall stacking distance and how this is divided between membranes, lumen and cytoplasmic liquid. Finally, from fitted scattering length densities it becomes clear that the protein content in the inner lumen has to be lower than in the outer cytoplasmic liquid and we extract the first quantitative measure of the luminal protein content in a living cyanobacteria.

High-Throughput Onboard Hyperspectral Image Compression With Ground-Based CNN Reconstruction

Compression of hyperspectral images onboard of spacecrafts is a tradeoff between the limited computational resources and the ever-growing spatial and spectral resolution of the optical instruments. As such, it requires low-complexity algorithms with good rate-distortion performance and high throughput. In recent years, the Consultative Committee for Space Data Systems (CCSDS) has focused on lossless and near-lossless compression approaches based on predictive coding, resulting in the recently published CCSDS 123.0-B-2 recommended standard. While the in-loop reconstruction of quantized prediction residuals provides excellent rate-distortion performance for the near-lossless operating mode, it significantly constrains the achievable throughput due to data dependencies. In this paper, we study the performance of a faster method based on prequantization of the image followed by a lossless predictive compressor. While this is well known to be suboptimal, one can exploit powerful signal models to reconstruct the image at the ground segment, recovering part of the suboptimality. In particular, we show that convolutional neural networks can be used for this task and that they can recover the whole SNR drop incurred at a bitrate of 2 bits per pixel.

Analysis and Sorting of Individual HSV-1 Particles by Flow Virometry.

Flow cytometry has been instrumental in characterizing normal and infected cells. However, until recently, it was not possible to use such an approach to analyze small entities such as bacteria, let alone viruses, owing to the 0.5μm resolution of most instruments. To circumvent this limitation, some laboratories decorate pathogens with antibodies or nanoparticles. Our laboratory instead exploits an alternative approach that relies on the staining of internal viral constituents with permeable SYTO dyes or the fluorescent tagging of individual viral proteinaceous components, whether capsid, tegument or glycoproteins. This opens up a range of new research avenues and, for example, enabled us to characterize individual herpes simplex virus type 1 particles, discern their different subpopulations, measure the heterogeneity of mature virions in terms of protein content, sort these viral particles with >90% purity and, for the first time, directly address the impact of this heterogeneity on viral fitness. This approach, coined flow virometry or nanoscale flow cytometry, allows for the study of a wide variety of pathogens with high statistical significance and the potential discovery of novel virulence factors.

Photon-limited ptychography of 3D objects via Bayesian reconstruction

We introduce a Bayesian framework for the ptychotomographic imaging of 3D objects under photon-limited conditions. This approach is significantly more robust to measurement noise by incorporating prior information on the probabilities of the object features and the measurement process into the reconstruction problem, and it can improve both the temporal and spatial resolution of current and future ptychography instruments. We use the alternating direction method of multipliers to solve the proposed optimization problem, where the ptychography and tomography subproblems are both solved using the conjugate-gradient method. The effectiveness of the framework is demonstrated by reconstructing a synthetic 3D integrated chip with a significantly reduced photon-budget for the simulated experiment.

Broadening of van Hove Singularities Measured by Photoemission Spectroscopy of Single- and Mixed-Chirality Single-Walled Carbon Nanotubes

The occupied valence electronic states of single-walled carbon nanotubes (SWCNTs) are responsible for their optoelectronic properties and are unique for each SWCNT chirality. Photoemission spectroscopy (PES) is one of the few methods capable of directly measuring the electron density in the valence states of materials, but there are only a few reports which have observed the valence states of SWCNTs and no examples for single-chirality SWCNTs. Here, we prepare single- and mixed-chirality SWCNT films and characterize their valence states using PES. Chirality-pure SWCNTs were isolated using both gel permeation chromatography and single-stranded DNA-facilitated aqueous two-phase extraction from starting materials consisting of mixed-chirality species. Chirality separation and purity was confirmed with UV-vis-NIR absorption spectroscopy. SWCNT films were prepared for the single-chirality species (10,3), (7,6), (7,3), (6,5), (8,3), (9,1) along with SWCNT chirality mixture of metallic and semiconducting SWCNTs, and as-synthesized mixtures possessing a range of SWCNT diameter. PES using synchrotron radiation was completed for all samples with survey and C 1s core-level spectra obtained to confirm SWCNT coverage, defect level, and purity. Valence band PES was obtained to characterize the valence electronic states and showed significant broadening of the signal, in comparison to calculated density of states, which could not be accounted for by instrument resolution. An inverse diameter dependence of the broadening was observed with greater broadening for smaller-diameter SWCNTs. The broadening is hypothesized to be related to the photohole lifetime, which was found to be significantly longer for wide-diameter SWCNTs. The diameter dependence of the broadening and photohole lifetimes is discussed in terms of both Tomonaga-Luttinger and Landau theories of Fermi liquids.

Intersensor Remote Sensing Image Registration Using Multispectral Semantic Embeddings

This letter presents a novel intersensor registration framework specially designed to register Sentinel-3 (S3) operational data using the Sentinel-2 (S2) instrument as a reference. The substantially higher resolution of the Multispectral Instrument (MSI), on-board S2, with respect to the Ocean and Land Color Instrument (OLCI), carried by S3, makes the former sensor a suitable spatial reference to finely adjust OLCI products. Nonetheless, the important spectral–spatial differences between both instruments may constrain traditional registration mechanisms to effectively align data of such different nature. In this context, the proposed registration scheme advocates the use of a topic model-based embedding approach to conduct the intersensor registration task within a common multispectral semantic space, where the input imagery is represented according to their corresponding spectral feature patterns instead of the low-level attributes. Thus, the OLCI products can be effectively registered to the MSI reference data by aligning those hidden patterns that fundamentally express the same visual concepts across the sensors. The experiments, conducted over four different S2 and S3 operational data collections, reveal that the proposed approach provides performance advantages over six different intersensor registration counterparts.

Super-resolution energy spectra from neutron direct-geometry spectrometers

Neutron direct-geometry time-of-flight chopper spectroscopy is instrumental in studying fundamental excitations of vibrational and/or magnetic origin. We report here that techniques in super-resolution optical imagery (which is in real-space) can be adapted to enhance resolution and reduce noise for a neutron spectroscopy (an instrument for mapping excitations in reciprocal space). The procedure to reconstruct super-resolution energy spectra of phonon density of states relies on a realization of multiframe registration, accurate determination of the energy-dependent point spread function, asymmetric nature of instrument resolution broadening, and iterative reconstructions. Applying these methods to phonon density of states data for a graphite sample demonstrates contrast enhancement, noise reduction, and ∼5-fold improvement over nominal energy resolution. The data were collected at three different incident energies measured at the wide angular-range chopper spectrometer at the Spallation Neutron Source.

Optimization of a phase-space beam position and size monitor for low-emittance light sources.

The recently developed vertical phase-space beam position and size monitor (ps-BPM) system has proven to be able to measure the electron-source position, angle, size and divergence simultaneously in the vertical plane at a single location of a beamline. The optimization of the ps-BPM system is performed by ray-tracing simulation to maximize the instrument sensitivity and resolution. The contribution of each element is studied, including the monochromator, the K-edge filter, the detector and the source-to-detector distance. An optimized system is proposed for diffraction-limited storage rings, such as the Advanced Photon Source Upgrade project. The simulation results show that the ps-BPM system can precisely monitor the source position and angle at high speed. Precise measurements of the source size and divergence will require adequate resolution with relatively longer integration time.

Quantifying the Chain Folding in Polymer Single Crystals by Single-Molecule Force Spectroscopy.

Chain folding is a motif of polymer crystallization, which is essential for determining the crystallization kinetics. However, the experimental quantification of the chain folding remains a challenge because of limited instrumental resolution. Here, we quantify chain folding in solution-grown single crystals by using atomic force microscopy (AFM)-based single-molecule force spectroscopy. The fingerprint spectrum of force-induced chain motion allows us to decipher the adjacent and nonadjacent re-entry folding with spatial resolution of subnanometers. The average fractions of adjacent re-entry folds ⟨f⟩ are in the range 91-95% for polycaprolactone, poly-l-lactic acid, and polyamide 66, which is higher than the values determined by other classical technologies. The established single-molecule method is applicable to a broad range of crystalline polymer systems with different chain conformations or compositions.

A Partial Inventory of Observational Anisotropies in Single-dish Line-intensity Mapping

Abstract Line-intensity mapping, being an imperfect observation of the line-intensity field in a cosmological volume, will be subject to various anisotropies introduced in observation. Existing literature in the context of CO and [C ii] line-intensity mapping often predicts only the real-space, spherically averaged line-intensity power spectrum, with some works considering anisotropies while examining projection of interloper emission. We explicitly consider a simplified picture of redshift-space distortions and instrumental effects due to limited resolution, and how these distort an isotropic line-intensity signal in real space and introduce strong apparent anisotropies. The results suggest that while signal loss due to limited instrumental resolution is unavoidable, measuring the quadrupole power spectrum in addition to the monopole would still break parameter degeneracies present in monopole-only constraints, even without a measurement of the full anisotropic power spectrum.

Polarized inelastic neutron scattering of nonreciprocal spin waves in MnSi

We report spin-polarized inelastic neutron scattering of the dynamical structure factor of the conical magnetic helix in the cubic chiral magnet MnSi. We find that the spectral weight of spin-flip scattering processes is concentrated on single branches for wavevector transfer parallel to the helix axis as inferred from well-defined peaks in the neutron spectra. In contrast, for wavevector transfers perpendicular to the helix the spectral weight is distributed among different branches of the magnon band structure as reflected in broader features of the spectra. Taking into account the effects of instrumental resolution, our experimental results are in excellent quantitative agreement with parameter-free theoretical predictions. Whereas the dispersion of the spin waves in MnSi appears to be approximately reciprocal at low energies and small applied fields, the associated spin-resolved spectral weight displays a pronounced non-reciprocity that implies a distinct non-reciprocal response in the limit of vanishing uniform magnetization at zero magnetic field.