Experimental Resolution Research Articles

On using ab initio calibration to fit temperature from AlO B-X emission

Aluminum Oxide (AlO) emission can be an important indicator of reaction and temperature in combustion and explosion systems. The Δv=-1 and particularly Δv=-2 sequences are attractive for temperature measurement, but have presented some challenges in modelling, especially for high vibrational energy transitions. Recent studies and ab initio simulations have offered parameters for the simulation of high resolution AlO spectra (Patrascu et.al. Mon. Not. R. Astron. Soc., 2015). In this paper we compare simulated spectra with high resolution emissions of AlO, both from laser induced breakdown spectroscopy and carefully calibrated shock tube experiments (3000<T<5000 K). In this manner, we assess the spectral model and its capacity for temperature assignment, rather than assume model accuracy and a best-fit-temperature. The experimental and modeled spectra agree below 0.1 Å resolution, and line features agree within our experimental resolution, in some regions down to 3 pm. Least squares fitting was performed on the experimental spectra, resulting in temperatures in agreement with calibration temperatures. The Δv=-2 sequence fits with residuals less than 4%. Our analysis suggests that experimental measurements with a resolution of 0.2 nm in this sequence can reliably fit the temperature within 100 K. Because of the apparently accurate fits to temperature, apparent accuracy of line position list, and reasonableness of line width model, we assess that the line strengths are likely also accurate and that ab initio simulated calibrations are useful for measuring temperature in AlO.

Mass distributions of dijet resonances from excited quarks at proton-proton colliders

We study the expected experimental mass distributions of dijet resonances from excited quarks in proton-proton collisions at energies s = 13, 14, 27, 100, 300, and 500 TeV. We explore in detail the expected shapes at both the generator and experimental levels, and identify within the distributions the effects of the excited quark natural width, parton momentum distributions of the proton, radiation, and experimental resolution. We present both differential and cumulative probability distributions as a function of dijet mass, and the signal acceptance of a window in dijet mass centered on each resonance. We find that for a range of resonance masses, between 10% and 50% of s, the dijet mass distributions and window acceptance are practically universal, approximately invariant under changes in resonance mass and s. This universality is violated when the resonance mass reaches 60% of s, because the steepness of the parton momentum distributions of the proton produces a significant tail at low dijet mass. This work supports our Snowmass 2021 study on the sensitivity to dijet resonances at proton-proton colliders.

Effect of static mixer on optical properties of plastic injection molded parts

AbstractThe effect of an in‐mold static mixer on the optical properties of polystyrene (PS) parts was explored within the injection molding process. Several mixers were assessed via simulation and molding trials to identify the mixing ability and effect on optical properties including retardation and birefringence. It was found that the static mixers within the runner could successfully mix the polymer and disrupt property distributions including temperature but that there was only a slight improvement in retardation with some of the mixer cases. The experiments and simulations showed relatively good correlation in results although there were slight differences in the trends that could be due to the experimental measurement resolution or unaccounted‐for variables between the experiments and simulations. The retardation was experimentally measured using a custom‐made polariscope using photography and image processing. These experiments indicated that the use of a static mixer within the runner system of a mold could be used for homogenizing the polymer melt after the plasticizing unit. However, its effect on improving the optical performance of injection molded parts could be offset by the melt flow downstream of the static mixer and the potential increase of residual stresses due to flow restriction, suggesting the importance of mixer location and geometry.

Compact neutron source from head-on collision of high energy density plasma jets

We propose a new scheme to generate a neutron source with a short duration, and the scheme is validated in two-dimensional radiation hydrodynamic simulations. When a laser beam irradiates a deuterated polystyrene cone with a half-opening angle of 60°, high energy density plasma jets are produced due to the converging effect. As two laser-driven counter-propagating jets collide in a head-on configuration, the kinetic energy converts into internal energy efficiently, inducing a significant increase in density and temperature. Then, deuteron–deuteron thermonuclear reactions are triggered, and plenty of neutrons are released. The simulation results show that the total neutron yield is as high as 6.6×108 with a duration of 103 ps, providing a new way to achieve ultrafast diagnosis with high resolution in experiments.

Explainable machine learning for breakdown prediction in high gradient rf cavities

The occurrence of vacuum arcs or radio frequency (rf) breakdowns is one of the most prevalent factors limiting the high-gradient performance of normal conducting rf cavities in particle accelerators. In this paper, we search for the existence of previously unrecognized features related to the incidence of rf breakdowns by applying a machine learning strategy to high-gradient cavity data from CERN's test stand for the Compact Linear Collider (CLIC). By interpreting the parameters of the learned models with explainable artificial intelligence (AI), we reverse-engineer physical properties for deriving fast, reliable, and simple rule-based models. Based on 6 months of historical data and dedicated experiments, our models show fractions of data with a high influence on the occurrence of breakdowns. Specifically, it is shown that the field emitted current following an initial breakdown is closely related to the probability of another breakdown occurring shortly thereafter. Results also indicate that the cavity pressure should be monitored with increased temporal resolution in future experiments, to further explore the vacuum activity associated with breakdowns.

The Effect of Time Resolution on Apparent Transition Path Times Observed in Single-Molecule Studies of Biomolecules.

Single-molecule experiments have now achieved a time resolution allowing observation of transition paths, the brief trajectory segments where the molecule undergoing an unfolding or folding transition enters the energetically or entropically unfavorable barrier region from the folded/unfolded side and exits to the unfolded/folded side, thereby completing the transition. This resolution, however, is yet insufficient to identify the precise entrance/exit events that mark the beginning and the end of a transition path: the nature of the diffusive dynamics is such that a molecular trajectory will recross the boundary between the barrier region and the folded/unfolded state, multiple times, at a time scale much shorter than that of the typical experimental resolution. Here we use theory and Brownian dynamics simulations to show that, as a result of such recrossings, the apparent transition path times are generally longer than the true ones. We quantify this effect using a simple model where the observed dynamics is a moving average of the true dynamics and discuss experimental implications of our results.

Asymmetry of wetting and de-wetting on high-friction surfaces originates from the same molecular physics

Motion of three-phase contact lines is one of the most relevant research topics of micro- and nano-fluidics. According to many hydrodynamic and molecular models, the dynamics of contact lines is assumed overdamped and dominated by localized liquid–solid friction, entailing the existence of a mobility relation between contact line speed and microscopic contact angle. We present and discuss a set of non-equilibrium atomistic molecular dynamics simulations of water nanodroplets spreading on or confined between silica-like walls, showing the existence of the aforementioned relation and its invariance under wetting modes (“spontaneous” or “forced”). Upon changing the wettability of the walls, it has been noticed that more hydrophilic substrates are easier to wet rather than de-wet; we show how this asymmetry can be automatically captured by a contact line friction model that accounts for the molecular transport between liquid layers. A simple examination of the order and orientation of near-contact-line water molecules corroborates the physical foundation of the model. Furthermore, we present a way to utilize the framework of multicomponent molecular kinetic theory to analyze molecular contributions to the motion of contact lines. Finally, we propose an approach to discriminate between contact line friction models which overcomes the limitations of experimental resolution. This work constitutes a stepping stone toward demystifying wetting dynamics on high-friction hydrophilic substrates and underlines the relevance of contact line friction in modeling the motion of three-phase contact lines.

Enhanced Understanding of Groundwater Storage Changes under the Influence of River Basin Governance Using GRACE Data and Downscaling Model

The low spatial resolution of Gravity Recovery and Climate Experiment (GRACE) data limits their application in practical groundwater resource management. To overcome this limitation, this study developed a dynamic downscaling method based on a model using groundwater storage anomaly (GWSA) data to study groundwater storage changes in an inland arid region. The groundwater storage model was calibrated using publicly accessible data at a spatial resolution of 1°. The constructed model had a satisfactory fitting effect in both the calibration and validation periods, with correlation coefficients over 0.60, in general, and a root mean square error of less than 1.00 cm equivalent water height (EWH). It was found that the hydraulic gradient coefficient was the most sensitive parameter, whereas the boundary condition had an obvious influence on the simulated GWSA compared to the different forcing data. The model was then refined at a higher resolution (0.05°) using driving data to obtain downscaled GWSA data. The downscaled results had a similar pattern to the GRACE-derived GWSA and reflected the spatial heterogeneity across the basin scale and subregion scales. The downscaled GWSA shows that the groundwater storage had an overall downward trend during the period from 2003 to 2019 and the annual decline rates ranged from 0.22 to 0.32 cm/year in four subregions. A four-month time lag between the field-observed and downscaled GWSA was observed downstream of the study area. This study provides an applicable method for assessing groundwater storage changes for groundwater management at the local scale.

Pharmacological reduction of coagulation factor XI reduces macrophage accumulation and accelerates deep vein thrombosis resolution in a mouse model of venous thrombosis

BackgroundDeep vein thrombosis (DVT) and post‐thrombotic syndrome (PTS) remain highly prevalent despite modern medical therapy. Contact activation is a promising target for safe antithrombotic anticoagulation. The anti‐factor XI (FXI) monoclonal antibody 14E11 reduces circulating levels of FXI without compromising hemostasis. The human recombinant analog, AB023, is in clinical development. The role of FXI in mediation of inflammation during DVT resolution is unknown. ObjectivesInvestigate the effects of pharmacological targeting of FXI with 14E11 in an experimental model of venous thrombosis. MethodsAdult wild‐type CD1 mice were treated with subcutaneous anti‐FXI antibody (14E11, 5 mg/kg) versus saline prior to undergoing surgical constriction of the inferior vena cava (IVC). Mice were evaluated at various time points to assess thrombus weight and volume, as well as histology analysis, ferumoxytol enhanced magnetic resonance imaging (Fe‐MRI), and whole blood flow cytometry. Results14E11‐treated mice had reduced thrombus weights and volumes after IVC constriction on day 7 compared to saline‐treated mice. 14E11 treatment reduced circulating monocytes by flow cytometry and macrophage content within thrombi as evaluated by histologic staining and Fe‐MRI. Collagen deposition was increased at day 3 while CD31 and smooth muscle cell actin expression was increased at day 7 in the thrombi of 14E11‐treated mice compared to saline‐treated mice. ConclusionPharmacologic targeting of FXI enhances the early stages of experimental venous thrombus resolution in wild‐type CD1 mice, and may be of interest for future clinical evaluation of the antibody in DVT and PTS.

Mechanical response during bending of Ni–Mn–Ga-based melt-spun ribbons

In this paper, we report on mechanical properties observed during bending experiments conducted on quinary Ni–Mn–Ga–Co–Cu melt-spun ribbons. Depending on the ribbon’s side to which force is applied, different mechanical response is noted. Substantially larger mechanical instabilities are observed when force is applied to the “free side” than to the “wheel side” of ribbons. When force is applied to the latter, much lower force fluctuations are recorded and the amplitude of the force–displacement response remains within the experimental resolution limit. It is also shown that the character of the force–displacement curve changes upon cycling; mainly by decreasing the maximum force and mechanical hysteresis. These results are important for materials design and optimization of the magnetic field-induced bending effect recently shown in Ni–Mn–Ga-based melt-spun ribbons.

High-fidelity denoising for differential pulse-width pair brillouin optical time domain analyzer based on block-matching and 3D filtering

In the field of structural deformation and strain measurement for civil structural health monitoring, Brillouin optical time-domain analyzer (BOTDA) system with sub-meter high spatial resolution is required. Differential pulse-width pair Brillouin optical time-domain analyzer (DPP-BOTDA) is an excellent method to achieve the goal without the need to modify the system structure. But the signal-to-noise ratio (SNR) of DPP-BOTDA is poor due to the differential operation, which limits its practical applications. Here, we propose to use Block-Matching and 3D filtering (BM3D) algorithm to improve the SNR of DPP-BOTDA with less degradation of measurement accuracy and spatial resolution. The influence of each BM3D parameter on the denoising performance is fully analyzed in detail for the first time which helps the optimization of the algorithm. Three pulse pairs of 50/47 ns, 50/45 ns and 50/43 ns are used for the demonstration with a sensing range of 9.9 km. With the optimized BM3D, the experimental spatial resolution only degrades by 0.08 m, 0.05 m and 0.04 m after denoising when the SNR improvement is 9 dB, respectively. And the temperature uncertainty for the three cases is improved to be 0.79 °C, 0.36 °C and 0.24 °C, respectively. We believe that this research will improve the efficiency of the parameter optimization when using the BM3D method for noise reduction and contribute to the practical application of the DPP-BOTDA system.

(Keynote) Developments in Visualizing Electrochemistry in Action with Liquid Cell Electron Microscopy

In situ transmission electron microscopy (TEM) can provide unparalleled structural and compositional information with high spatial and temporal resolution and is a standard tool for understanding and quantifying electrochemical nucleation and growth processes. Both solid state reactions and processes involving liquids can be examined. However, liquid phase reactions require particular care since the liquid needs to be confined in a thin layer and protected from the vacuum in the microscope. This problem is solved in the technique of electrochemical liquid cell TEM by confining the liquid between microfabricated electron transparent membranes on which the electrodes are patterned. Electrochemical liquid cell TEM has enabled quantification of nucleation and growth phenomena, dendrite formation, additive effects on morphology and SEI formation. Recent experimental developments have broadened the application space, but many more opportunities remain to be explored. Here we discuss how the existing strategies for electrochemical liquid cell TEM experiments can be adapted to allow quantitative data acquisition under an expanded range of electrochemical conditions. We first discuss the control of temperature, an important parameter in electrochemical systems such as batteries and fuel cells. Increasing the temperature while simultaneously applying a bias is achieved by customizing liquid cell chips to incorporate an electrically isolated heater strip beneath the electrodes. We find, as expected, that elevated temperature increases the rates of deposition and etching reactions and we discuss potential applications in electrocatalysis and codeposition. We then address the limitations of image resolution in liquid cell experiments. For nucleation and growth processes that take place on the surface of the electrode, the electrode materials such as Au or Pt often used in microfabricated liquid cells contribute strongly to electron scattering and thereby reduce the signal to noise ratio in the images. We show how few-layer graphene can be added to liquid cell chips to produce electrodes with minimal scattering, resulting in nucleation and growth movies with improved discrimination between nucleus shapes. We next consider the exciting consequences of instrumental improvements in microscopy - aberration correction, energy filtering and efficient electron detectors - in improving the resolution and lowering the dose required for imaging. Electron beam effects are unavoidable, however, and we discuss how the chemical changes caused by the beam can be modeled and perhaps mitigated for different electrolyte compositions and as a function of temperature. More speculative developments in liquid cell technique may allow us to measure stress, electrolyte composition and even the electrochemical double layer. Although a lot of work remains to be done, I hope to convince you that electrochemical TEM of liquids can address grand challenge questions in nucleation and growth through its unique view of electrochemical processes.

LigninGraphs: lignin structure determination with multiscale graph modeling

Lignin is an aromatic biopolymer found in ubiquitous sources of woody biomass. Designing and optimizing lignin valorization processes requires a fundamental understanding of lignin structures. Experimental characterization techniques, such as 2D-heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectra, could elucidate the global properties of the polymer molecules. Computer models could extend the resolution of experiments by representing structures at the molecular and atomistic scales. We introduce a graph-based multiscale modeling framework for lignin structure generation and visualization. The framework employs accelerated rejection-free polymerization and hierarchical Metropolis Monte Carlo optimization algorithms. We obtain structure libraries for various lignin feedstocks based on literature and new experimental NMR data for poplar wood, pinewood, and herbaceous lignin. The framework could guide researchers towards feasible lignin structures, efficient space exploration, and future kinetics modeling. Its software implementation in Python, LigninGraphs, is open-source and available on GitHub.Graphical abstract

Assessment of AlphaFold2 for Human Proteins via Residue Solvent Exposure.

As only 35% of human proteins feature (often partial) PDB structures, the protein structure prediction tool AlphaFold2 (AF2) could have massive impact on human biology and medicine fields, making independent benchmarks of interest. We studied AF2's ability to describe the backbone solvent exposure as a functionally important and easily interpretable "natural coordinate" of protein conformation, using human proteins as test case. After screening for appropriate comparative sets, we matched 1818 human proteins predicted by AF2 against 7585 unique experimental PDBs, and after curation for sequence overlap, we assessed 1264 comparative pairs comprising 115 unique AF2 structures and 652 unique experimental structures. AF2 performed markedly worse for multimers, whereas ligands, cofactors, and experimental resolution were interestingly not very important for performance. AF2 performed excellently for monomer proteins. Challenges relating to specific groups of residues and multimers were analyzed. We identified larger deviations for lower-confidence scores (pLDDT), and exposed residues and polar residues (e.g., Asp, Glu, Asn) being less accurately described than hydrophobic residues. Proline conformations were the hardest to predict, probably due to a common location in dynamic solvent-accessible parts. In summary, using solvent exposure as a metric, we quantified the performance of AF2 for human proteins and provided estimates of the expected agreement as a function of ligand presence, multimer/monomer status, local residue solvent exposure, pLDDT, and amino acid type. Overall performance was found to be excellent.

Nested mirror optics for neutron extraction, transport, and focusing

Neutron scattering is a well-established tool for the investigation of the static and dynamic properties of condensed matter systems over a wide range of spatial and temporal scales. Many studies of high interest, however, can only be performed on small samples and typically require elaborate environments for variation of parameters such as temperature, magnetic field and pressure. To improve the achievable signal-to-background ratio, focusing devices based on elliptic or parabolic neutron guides or Montel mirrors have been implemented. Here we report an experimental demonstration of a nested mirror optics (NMO), which overcomes some of the disadvantages of such devices. While even simpler than the original Wolter design, our compact assembly of elliptic mirrors images neutrons from a source to a target, reducing geometric aberrations, gravitational effects and waviness-induced blurring. Experiments performed at MIRA at FRM-II demonstrate the expected focusing properties and a beam transport efficiency of 72% for our first prototype. NMO seem particularly well-suited to (i) extraction of neutrons from compact high-brilliance neutron moderators, (ii) general neutron transport, and (iii) focusing and polarizing neutrons. The phase space of the neutrons hitting a sample can be tailored on-line to the needed experimental resolution, resulting in small scattering backgrounds. As additional benefits, NMO situated far away from both the moderator and the sample are less susceptible to radiation damage and can easily be replaced. NMO enable a modular and physically transparent realization of beam lines for neutron physics similar to setups used in visible light optics.

Stress Component Decoupling Analysis Based on Large Numerical Aperture Objective Lens, an Impractical Approach.

Micro Raman spectroscopy is an effective method to quantitatively analyse the internal stress of semiconductor materials and structures. However, the decoupling analysis of the stress components for {100} monocrystalline silicon (c-Si) remains difficult. In the work outlined, physical and simulation experiments were combined to study the influence of the objective lens numerical aperture (NA) on the Raman stress characterization. The physical experiments and simulation experiments show that the spectral results obtained by using lenses with different NAs can accurately obtain the principal stress sum but cannot decouple the components of the in-plane stress. Even if the spectral resolution of the simulated experiment is ideal (The random errors of the polarization directions of less than ±1° and the systematic random errors of less than ±0.02 cm−1). The analysis based on the theoretical model demonstrates that the proportion of the principal stress sum in the Raman shift obtained in an actual experiment exceeded 98.7%, while the proportion of the principal stress difference part was almost negligible. This result made it difficult to identify the variable effects of different stress states from the experimental results. Further simulation experiments in this work verify that when the principal stress sum was identical, the differences in the Raman shifts caused by different stress states were much smaller than the resolution of the existing Raman microscope system, which was hardly possible to identify in the experimental results. It was proven that decoupling analysis of stress components using the large-NA objective lens lacked actual practicability.

Uncertainty quantification of multi-source hydrological data products for the improvement of water budget estimations in small-scale Sakarya basin, Turkey

ABSTRACT The present study aims to improve the efficacy of water budget (WB) estimations from various hydrological data products, by (1) evaluating the uncertainties of hydrological data products, (2) merging four precipitation and six evapotranspiration products using their error variances, and (3) employing the constrained Kalman filter (CKF) method to distribute residual errors among water budget components based on their relative uncertainties. The results show that applying bias correction before the merging process improved estimations of precipitation products with decreasing root mean square error (RMSE), except Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN). Variable Infiltration Capacity (VIC) and bias-corrected Climate Prediction Center Morphing Technique (CMORPH) products outperformed other evapotranspiration and bias-corrected precipitation products, respectively, in terms of mean merging weights. The terrestrial water storage change is the primary reason for non-closure errors, mainly caused by the coarse resolution of Gravity Recovery and Climate Experiment (GRACE). The CKF results were insensitive to variations in uncertainties of runoff. Precipitation derived from the CKF was the best precipitation output, with the highest correlation coefficient (CC) and smallest root mean square deviation (RMSD).

3D deep geoelectrical exploration in the Larderello geothermal sites (Italy)

The paper describes a new experimental deep electrical resistivity acquisition (down to 1600 m) for exploring deep and shallow geothermal systems. The test site is located in the Larderello geothermal area, the oldest geothermal field in the world under exploitation for power production. In this area, many data have been acquired in the frame of previous exploration projects but nowadays several critical issues are still matter of debate: permeability distribution, depth and volume of the magmatic heat source, supercritical fluid condition at depth, and the occurrence of low resistivity anomalies in a dry-steam crystalline and carbonate reservoir. In order to develop new methods for contributing to the hydrothermal reservoir issues, an experimental high resolution 3D Surface-Hole Deep Electrical Resistivity Tomography (SH-DERT) was designed and the Venelle2 well in the Larderello geothermal site, hosted in the crystalline units, was used for the experiment. The design of the in-hole experiment and the results of the deep geoelectrical survey are hereby presented. SH-DERT was properly designed to face extreme conditions at depth characterizing the geothermal well. It provided a 3D resistivity distribution. Transmitting and receiving electrodes were distributed on a large surface (6 km2) and in the Venelle2 well (down to 1600 m). The in-hole electrical cable was equipped to be able to operate in very high temperature conditions. The experiment represents a challenge and an opportunity for the applied geophysics in geothermal areas, where a lowest resistivity is highlighted in a zone above the reservoir and the resistivity of the reservoir is higher. Moreover, the relationship between temperature, clay alteration and resistivity can define a challenger to enable better prediction of reservoir temperature distribution from resistivity measurements. It is a potential improvement of the reservoir knowledge and a useful success for exploration drilling.

Discrimination of edge orientation by bumblebees.

Simple feature detectors in the visual system, such as edge-detectors, are likely to underlie even the most complex visual processing, so understanding the limits of these systems is crucial for a fuller understanding of visual processing. We investigated the ability of bumblebees (Bombus terrestris) to discriminate between differently angled edges. In a multiple-choice, “meadow-like” scenario, bumblebees successfully discriminated between angled bars with 7° differences, significantly exceeding the previously reported performance of eastern honeybees (Apis cerana, limit: 15°). Neither the rate at which bees learned, nor their final discrimination performance were affected by the angular orientation of the training bars, indicating a uniform performance across the visual field. Previous work has found that, in dual-choice tests, eastern honeybees cannot reliably discriminate between angles with less than 25° difference, suggesting that performance in discrimination tasks is affected by the training regime, and doesn’t simply reflect the perceptual limitations of the visual system. We used high resolution LCD monitors to investigate bumblebees’ angular resolution in a dual-choice experiment. Bumblebees could still discriminate 7° angle differences under such conditions (exceeding the previously reported limit for Apis mellifera, of 10°, as well as that of A. cerana). Bees eventually reached similar levels of accuracy in the dual-choice experiment as they did under multiple-choice conditions but required longer learning periods. Bumblebees show impressive abilities to discriminate between angled edges, performing better than two previously tested species of honeybee. This high performance may, in turn, support complex visual processing in the bumblebee brain.

Understanding the complex rheology of human blood plasma

Blood plasma (BP) is a borderline non-Newtonian fluid. Few studies have characterized the rheology of BP and even less focused on understanding its subtle viscoelastic traits, which were only somewhat recently acknowledged. We use passive microrheology to measure the bulk response of human plasma samples under shear at body and ambient temperatures. Evidence of subdiffusive behavior in the mean-squared displacement is observed at the highest frequencies probed, which we attribute to the stress relaxation of protein molecules or chains. Jeffreys-like complex shear moduli were computed thereof. The microenvironments of albumin, fibrinogen, and gamma-globulin solutions (key plasma proteins) were probed as well. Single proteins in an aqueous buffer showed no signs of viscoelasticity within experimental resolution. Conversely, mixed together, they appear to promote the same kind of short-term elastic behavior seen in plasma. All in all, a fresh look at the shear rheology of BP is presented.