Limited Instrumental Resolution Research Articles

Origin of Line Broadening in Fading Granules: Influence of Small-scale Turbulence

In the quiet region of the solar photosphere, turbulent convective motions of the granular flows naturally drive the subgranular-scale flows. However, evaluating such small-scale velocities is challenging because of the limited instrumental resolution. Our previous study, R. T. Ishikawa et al., found line-broadening events during the fading process of granules; however, their physical mechanism has remained unclear. In the present study, we observed the fading granules with the Hinode-SOT/SP and performed spectral line inversions. Moreover, we investigated the broadening events of synthesized spectra in fading granules reproduced by the MURaM simulation. Our results demonstrated that the small-scale turbulent motions are excited in the fading process, and such turbulent flows contribute to line broadening. The spectral line widths can be potential tracers of the photospheric turbulent flows.

Electromagnetic Landau Resonance: Nonlinear Dynamics and Harmonic Generation

AbstractIn situ particle observations provide useful information for determining the significance of nonlinearity in wave‐particle interactions. Here, we examine an electromagnetic Landau resonance event observed by the Magnetospheric Multiscale mission near the dayside magnetopause along this line of thought. During this event, protons with energy 748 eV and pitch angle are observed to resonate with electromagnetic‐ion‐cyclotron waves. Detailed data analysis reveals the existence of a second harmonic signal in proton modulation. Using an observation‐based test particle simulation, this signal is explained as a low‐resolution manifestation of phase space rolled‐up structures, which themselves are not observable due to limited instrument resolution. The presence of these rolled‐up structures suggests that the waves induce significant displacement of the protons in phase space, consequently confirming the nonlinear nature of the observed interaction. Based on the observations, we further discuss the possibility of the nonlinear electromagnetic Landau resonance generating second harmonic waves.

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.

Quantitative collision-induced unfolding differentiates model antibody-drug conjugates.

Antibody-drug conjugates (ADCs) are antibody-based therapeutics that have proven to be highly effective cancer treatment platforms. They are composed of monoclonal antibodies conjugated with highly potent drugs via chemical linkers. Compared to cysteine-targeted chemistries, conjugation at native lysine residues can lead to a higher degree of structural heterogeneity, and thus it is important to evaluate the impact of conjugation on antibody conformation. Here, we present a workflow involving native ion mobility (IM)-MS and gas-phase unfolding for the structural characterization of lysine-linked monoclonal antibody (mAb)-biotin conjugates. Following the determination of conjugation states via denaturing Liquid Chromatography-Mass Spectrometry (LC-MS) measurements, we performed both size exclusion chromatography (SEC) and native IM-MS measurements in order to compare the structures of biotinylated and unmodified IgG1 molecules. Hydrodynamic radii (Rh) and collision cross-sectional (CCS) values were insufficient to distinguish the conformational changes in these antibody-biotin conjugates owing to their flexible structures and limited instrument resolution. In contrast, collision induced unfolding (CIU) analyses were able to detect subtle structural and stability differences in the mAb upon biotin conjugation, exhibiting a sensitivity to mAb conjugation that exceeds native MS analysis alone. Destabilization of mAb-biotin conjugates was detected by both CIU and differential scanning calorimetry (DSC) data, suggesting a previously unknown correlation between the two measurement tools. We conclude by discussing the impact of IM-MS and CIU technologies on the future of ADC development pipelines.

Improving AFM Reveals a Multitude of Hidden Dynamics in the Unfolding of a Membraneprotein

Protein folding occurs as a set of transitions between structural states within an energy landscape. An oversimplified view of the folding process emerges when transiently populated states are undetected because of limited instrumental resolution. Moreover, predicting the structure and stability of membrane proteins significantly lags success with globular protein. Using force spectroscopy optimized for 1-µs resolution, we reexamined the unfolding of individual bacteriorhodopsin (BR) molecules in native lipid bilayers with a 100-fold improvement in time resolution and a 10-fold improvement in force precision. The resulting data revealed the unfolding pathway in unprecedented detail. Numerous newly detected intermediates—many separated by as few as 2-3 amino acids—exhibited complex dynamics, including frequent refolding and state occupancies of <10 µs. To elucidate the detailed dynamics of individual membrane proteins under their most native-likeset of intra- and inter-helix contacts, we labeled BR at its c-terminal with a copper-free click chemistry reagent and then gently but covalently coupled BR to an azide-functionalized, PEG-coated tip. This process suppressed nonspecific adhesion that confounds analysis of the initial unfolding of BR. The resulting force-extension curves revealed rapid near-equilibrium folding dynamics between previously undetected intermediate states. We assigned the first state to the top of the G-helix with the second and third states corresponding to a total unfolding of 5 and 9 amino acids. Interestingly, this assignment placed the third state where BR's retinal binds to lysine 216. We verified this assignment by performing dynamic force spectroscopy on BR with and without its retinal. We also reconstructed the full 1D free-energy landscape underlying the initial 9 amino acid unfolding of BR. Looking forward, this reversible unfolding and refolding assay should provide a platform to precisely quantify the energetics of membrane folding under native-like conditions.

Bayesian approach to the analysis of neutron Brillouin scattering data on liquid metals

When the dynamics of liquids and disordered systems at mesoscopic level is investigated by means of inelastic scattering (e.g., neutron or x ray), spectra are often characterized by a poor definition of the excitation lines and spectroscopic features in general and one important issue is to establish how many of these lines need to be included in the modeling function and to estimate their parameters. Furthermore, when strongly damped excitations are present, commonly used and widespread fitting algorithms are particularly affected by the choice of initial values of the parameters. An inadequate choice may lead to an inefficient exploration of the parameter space, resulting in the algorithm getting stuck in a local minimum. In this paper, we present a Bayesian approach to the analysis of neutron Brillouin scattering data in which the number of excitation lines is treated as unknown and estimated along with the other model parameters. We propose a joint estimation procedure based on a reversible-jump Markov chain Monte Carlo algorithm, which efficiently explores the parameter space, producing a probabilistic measure to quantify the uncertainty on the number of excitation lines as well as reliable parameter estimates. The method proposed could turn out of great importance in extracting physical information from experimental data, especially when the detection of spectral features is complicated not only because of the properties of the sample, but also because of the limited instrumental resolution and count statistics. The approach is tested on generated data set and then applied to real experimental spectra of neutron Brillouin scattering from a liquid metal, previously analyzed in a more traditional way.

Magnetic structure and magnon dispersion in LaSrFeO4

We present elastic and inelastic neutron scattering data on LaSrFeO$_4$. We confirm the known magnetic structure with the magnetic moments lying in the tetragonal basal plane, but contrarily to previous reports our macroscopic and neutron diffraction data do not reveal any additional magnetic phase transition connected to a spin reorientation or to a redistribution of two irreducible presentations. Our inelastic neutron scattering data reveals the magnon dispersion along the main-symmetry directions [0 $\xi$ 0] and [$\xi$ -$\xi$ 0]. The dispersion can be explained within linear spin-wave theory yielding an antiferromagnetic nearest-neighbour interaction parameter $J_{1}=7.4(1)$ meV and a next-nearest neighbour interaction parameter $J_{2}=0.4(1)$ meV. The dispersion is gapped with the out-of-plane anisotropy gap found at $\Delta_{out}=5.26(2)$ meV, while evidence is present that the in-plane anisotropy gap lies at lower energies, where it cannot be determined due to limited instrument resolution.

Resolving the Azimuthal Ambiguity in Vector Magnetogram Data with the Divergence-Free Condition: The Effects of Noise and Limited Spatial Resolution

We investigate how the azimuthal ambiguity in solar vector magnetogram data can be resolved by using the divergence-free property of magnetic fields. In a previous article, by Crouch, Barnes, and Leka (Solar Phys. 260, 271, 2009), error-free synthetic data were used to test several methods that each make a different assumption about how the divergence-free property can be used to resolve the ambiguity. In this paper this testing is continued with an examination of the effects of Poisson photon noise and limited instrumental spatial resolution. We find that all currently available methods based on the divergence-free property can produce undesirable results when photon noise or unresolved structure are present in the data. We perform a series of experiments aimed at improving the performance of the global minimisation method, which is the most promising of the methods. We present a two-step approach that produces reasonable results in tests using synthetic data. The first step of this approach involves the global minimisation of a combination of the absolute value of the approximation for the divergence and a smoothness constraint, which is designed to minimise the difference between the magnetic field in neighbouring pixels. In the second step, pixels with measurements known to be strongly affected by photon noise are revisited with a smoothing algorithm that also seeks to minimise the difference between the magnetic field in neighbouring pixels.

High-Resolution Absorption Studies of the Ã1A2−X̃1A1202401Band of Formaldehyde

Absolute peak absorption cross sections and pressure broadening coefficients have been recorded with sub-Doppler limited instrumental resolution for selected rotational lines in the 2(0)(2)4(0)(1) vibronic band of the formaldehyde A(1)A2-X(1)A1 electronic transition. The measured absorption cross sections range between (0.18 +/- 0.01) and (10.1 +/- 0.08) x 10(-19) cm2 molecule(-1) and are considerably larger than values from the literature recorded using apparatus where instrumental broadening was significant. However, comparisons with spectral simulations with equivalent resolution from Smith et al. (J. Phys. Chem. A 2006, 110, 11645-11653) are in excellent agreement. Pressure broadening was studied for the collision partners CH2O, CO2, N2, O2, Ne, Kr, Ar, and He, and the resulting broadening coefficients were found to be reduced in comparison to equivalent values measured in infrared regions, consistent with the reduced dipole moment of the upper state probed in this work. Cavity-enhanced absorption spectroscopy (CEAS) measurements were undertaken using calibrated low concentration (2.9-4.6 ppmv) samples from a permeation source and demonstrate a noise equivalent absorption of 1.2 x 10(-6) cm(-1) Hz(-1/2). This implies a minimum detectable formaldehyde concentration with the current system in atmospheric air of 172 ppbv Hz(-1/2).

Improving the Numerical Modeling of the OiResonance Triplet in the Solar Spectrum

We present a slight modification to an existing multilevel radiative transfer code that allows us to include the effects of frequency cross redistribution (XRD) between lines sharing the same upper level. With this improved code, we calculate theoretical profiles of the O I resonance triplet lines at 130 nm through a hydrostatic model of the average quiet Sun. The width of the calculated XRD profiles show good agreement with an observed, spatially averaged disk-center spectrum obtained with the high-resolution telescope spectrometer (HRTS) spectrograph. This is in stark contrast to profiles calculated with complete frequency redistribution (CRD) and ordinary partial frequency redistribution (PRD), which have Lorentzian wings that are too broad. We find deep central reversals, contrary to most observed profiles, but we note that this discrepancy is to a large degree the result of limited instrumental spectral resolution.

Slow Diffusion of Molecular Hydrogen in Zeolite 13X

High-resolution quasi-elastic neutron scattering measurements have been performed on molecular hydrogen in zeolite 13X. Previous NMR measurements suggested that the freezing temperature is suppressed from 14 K down to 8 K. In contrast, previous intermediate resolution quasi-elastic neutron scattering studies suggested freezing occurred between 25 and 35 K. Unfortunately, the limited instrumental resolution available in the previous quasi-elastic neutron scattering study was not sufficient to show this point definitively. We report new quasi-elastic neutron scattering measurements with very high resolution that show no evidence of mobile hydrogen below 25 K, which is well above the bulk liquid-solid transition temperature for hydrogen. A quasi-elastic component appears between 25 and 30 K indicating the presence of mobile H2. However, the width and momentum dependence of the quasi-elastic scattering are much different than would be expected for the diffusive motion of liquid hydrogen in this temperature range. Instead, we find that a slow diffusive component representing jumps between well-defined sites appears first at low temperatures. As the temperature is raised, a faster liquid like diffusive component appears.

Characterization of the combined molecular weight and composition distribution of industrial ethylene/α-olefin copolymers

The composition–molecular weight distribution, CD×MWD, of ethylene/α-olefin copolymers was measured quantitatively using two methods: (1) temperature rising elution fractionation (TREF) followed by size-exclusion chromatography (SEC) of each fraction and (2) SEC followed by Fourier-transform infrared spectroscopy (FTIR) of each fraction. TREF-SEC provides a rather complete, accurate, and quantitative representation of the CD×MWD. On the other hand, SEC-FTIR leads to loss of information on some details of the CD×MWD. The extent of the loss depends on the material examined. The main advantage of SEC-FTIR is the much shorter analysis time compared to TREF-SEC.We briefly discuss another method, TREF followed by measurements of the molecular weight of the fractions by light scattering, LS — either off-line or on-line. We point out that this technique also leads to some loss of information on the CD×MWD. However, for linear low density polyethylene-type materials, TREF-LS may be a more useful technique than SEC-FTIR while less time-consuming than TREF-SEC.Finally, we use deconvolution of the SEC-FTIR data into Flory–Stockmayer distributions in an attempt to recover all or part of the information loss inherent in the SEC-FTIR method. The attempt was not successful when applied to the data presented in this work. We discuss several reasons for this failure including limited instrumental resolution and intrinsic limitations of the SEC-FTIR technique.

Diagnostic value of transesophageal versus transthoracic echocardiography in discrete subaortic stenosis

Accurate diagnosis of discrete subaortic stenosis (DSS) is essential because it has unique prognostic and therapeutic implications. Clinical diagnosis is difficult and even angiography has been reported to diagnose only 59% of cases. 1 Conventional echocardiography including M-mode and 2-dimensional sector scanning frequently enable a definitive diagnosis to be made and almost always raise the possibility of DSS. Nevertheless, suboptimal patient imaging and limited instrument resolution, especially where the subaortic membrane is located in close proximity to the aortic valve, limit the sensitivity and specificity of transthoracic imaging (TTE). In this report we evaluate the utility of transesophageal echocardiography (TEE) in patients with DSS.

Anomalous Pressure Dependence of Infrared Spectra Due to the Combination of Collisional Broadening and Instrument Resolution

The combination of collisional line broadening and limited instrumental resolution can have peculiar and unexpected effects on the intensities of infrared spectra. An illustrative example is provided by the series of Q branches in the v7 band of ethane. Conventional FT-IR spectra, with a resolution of ∼0.25 cm−1, show a dramatic increase in the absorbance of these branches as a function of increasing N2 partial pressure, an effect which could be construed as collisional narrowing. In contrast, high-resolution diode laser spectroscopy reveals a monotonie increase in branch width (0.14 cm−1/atm), and a concomitant decrease in intensity, as the N2 pressure is raised. The present work shows that absorption measurement of the inherently very narrow ethane Q branches with limited instrumental resolution and collisional line broadening conspire to give the appearance that the absorbance increases with N2 pressure. This effect in general, as well as its implications for the use of FT-IR spectroscopy to measure molecular concentrations in gaseous mixtures, is discussed.

Emergence of local realism in fuzzy observations of correlated quantum systems

A pair of spin-j particles, prepared in a singlet state, move away from each other and are examined by two distant observers. If the latter are able to discriminate between the2j+1 values of a component ofJ, there are pairs of observables whose correlation strongly violates Bell's inequality, for arbitrarily large j. However, if neighboring values are lumped together because of limited instrumental resolution, the observable correlations tend to those predicted by classical mechanics.

Collinear and helical phases of the monoclinic and rhombohedral antiferromagnet. Application to the α- and β-phases of solid oxygen

Classical spins localised on the sites of a rhombohedral lattice and coupled by nearest-neighbour Heisenberg exchange show infinite degeneracy of the ground state; there are infinite inequivalent isoenergetic helices which minimise the classical ground-state energy. This configuration is referred to as a 'degenerate helix' (DH). A genuine DH configuration provides unusual elastic neutron scattering peaks, owing to the infinite inequivalent helices of the ground state. A DH configuration provides the first example of an elastic neutron scattering peak width not determined by the limited instrumental resolution. The rhombohedral Heisenberg antiferromagnet (RAF) model is suitable for describing the beta -phase of solid oxygen which is stable at intermediate temperatures (24-44 K) while in the low-temperature alpha -phase the lattice is stretched and becomes monoclinic. Recent experimental data for elastic and inelastic neutron scattering by polycrystalline samples of solid oxygen in both the alpha - and the beta -phases are satisfactorily interpreted on the basis of the authors' theoretical results.

Temperature estimation of carbon dioxide by infrared absorption spectrometry at medium resolution

A method for estimating the temperature of a sample of CO 2 gas heated above ambient temperature is evaluated. A nonlinear, least-squares regression fir for the peak absorbance of the rotation-vibration lines of the hot bands of CO 2 was obtained for samples at temperatures from 90 to 190°C and at pressures from 200 to 650 torr. The i.r. spectra of CO 2 gas samples in a 1 m cell were collected using a Fourier-transform i.r. spectrometer. The spectral resolution was sufficient to resolve the rotational fine structure of these bands. However, it was necessary to account for the effect of limited instrument resolution in fitting the data. The temperatures retrieved from the regression were compared with the temperature of the sample. Good agreement was obtained between the directly measured temperature and the value determined spectroscopically. The sensitivity of the fitting program to increased noise in the spectrum was also studied.

Roughening of Si (111) surface under high-temperature thermal cycling

High-resolution low-energy electron diffraction has been used to study the generation of defects on the surface of commercial Si (111) wafers under high-temperature thermal cycling in ultrahigh vacuum. We observed a gradual increase of single-atomic step density from 0.15 to 0.30% after several thermal annealings at ∼1200 °C. However, a reduction of step density, accompanied by a change of step height from single-atomic to double-atomic step height, was observed after the sample was annealed to near melting temperature (∼1400 °C). At the same time, the surface was broken into micrograins having a small mosaic orientation. Due to the limited instrumental resolution, these low-density step structures and the small-angle mosaic structures cannot be resolved by using the conventional low-energy electron diffraction technique.

Light scattering vs. microscopy for measuring average cell size and shape

Light-scattering photometry is compared with electron and light microscopy as a source of information about the average size and shape of cells in population. Examined are the effects of limited instrument resolution, necessary experimental procedures, and cell heterogeneity. Information theory is used to survey the relative amounts of information provided by photometric and microscopic measurements. Then in model exploratory experiments, cell size and shape and changes therein are determined both by microscopy and by photometry for spherical and spheroidal cells. Scattering theory is used to calculate photometrically observed light from cell parameters. It is found that if certain other appropriate information about the morphological property of interest is available, then visible light photometry is the preferred method for obtaining quantitative information. It has good absolute sensitivity (0.01-0.10 micrometers resolution), its results are relatively unaffected by sample heterogeneity, it is nondestructive and compatible with many other techniques, it requires no sample preparation, and it provides its information in real time.