scholarly journals Advances and Perspectives in Chemical Imaging in Cellular Environments Using Electrochemical Methods

2018 ◽  
Author(s):  
Robert A. Lazenby ◽  
Ryan J. White
Keyword(s):  
Spatial Resolution ◽  
Chemical Imaging ◽  
Active Species ◽  
Electrochemical Methods ◽  
High Time Resolution ◽  
Spatiotemporal Resolution ◽  
Cellular Processes ◽  
Significant Research ◽  
Technological Developments ◽  
Multiple Frame

This review discusses a broad range of recent advances (2013-2017) of chemical imaging using electrochemical methods, with a particular focus on techniques that have been applied to study cellular processes, or techniques that show promise for use in this field in the future. Non-scanning techniques such as microelectrode arrays (MEAs) offer high time-resolution (< 10 ms) imaging, however at reduced spatial resolution. In contrast, scanning electrochemical probe microscopies (SEPMs) offer higher spatial resolution (as low as a few nm per pixel) imaging, with images collected typically over many minutes. Recent significant research efforts to improve the spatial resolution of SEPMs using nanoscale probes, and to improve the temporal resolution using fast scanning have resulted in movie (multiple frame) imaging with frame rates as low as a few seconds per image. Many SEPM techniques lack chemical specificity or have poor selectivity (defined by the choice of applied potential for redox-active species). This can be improved using multifunctional probes, ion-selective electrodes and tip-integrated biosensors, although additional effort may be required to preserve sensor performance after miniaturization of these probes. We discuss advances to the field of electrochemical imaging, and technological developments which are anticipated to extend the range of processes that can be studied. This includes imaging cellular processes with increased sensor selectivity and at much improved spatiotemporal resolution than has been previously customary.

Generalized Heterodyne Configurations for Photo-induced Force Microscopy

2019 ◽  
Author(s):  
Le Wang ◽  
Devon Jakob ◽  
Haomin Wang ◽  
Alexis Apostolos ◽  
Marcos M. Pires ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Repetition Rate ◽  
Modulation Frequency ◽  
High Harmonic ◽  
Chemical Imaging ◽  
Heterodyne Detection ◽  
Force Microscopy ◽  
Wide Range ◽  
The Difference ◽  
Afm Cantilever

<div>Infrared chemical microscopy through mechanical probing of light-matter interactions by atomic force microscopy (AFM) bypasses the diffraction limit. One increasingly popular technique is photo-induced force microscopy (PiFM), which utilizes the mechanical heterodyne signal detection between cantilever mechanical resonant oscillations and the photo induced force from light-matter interaction. So far, photo induced force microscopy has been operated in only one heterodyne configuration. In this article, we generalize heterodyne configurations of photoinduced force microscopy by introducing two new schemes: harmonic heterodyne detection and sequential heterodyne detection. In harmonic heterodyne detection, the laser repetition rate matches integer fractions of the difference between the two mechanical resonant modes of the AFM cantilever. The high harmonic of the beating from the photothermal expansion mixes with the AFM cantilever oscillation to provide PiFM signal. In sequential heterodyne detection, the combination of the repetition rate of laser pulses and polarization modulation frequency matches the difference between two AFM mechanical modes, leading to detectable PiFM signals. These two generalized heterodyne configurations for photo induced force microscopy deliver new avenues for chemical imaging and broadband spectroscopy at ~10 nm spatial resolution. They are suitable for a wide range of heterogeneous materials across various disciplines: from structured polymer film, polaritonic boron nitride materials, to isolated bacterial peptidoglycan cell walls. The generalized heterodyne configurations introduce flexibility for the implementation of PiFM and related tapping mode AFM-IR, and provide possibilities for additional modulation channel in PiFM for targeted signal extraction with nanoscale spatial resolution.</div>

scholarly journals PERSIANN-CCS-CDR, a 3-hourly 0.04° global precipitation climate data record for heavy precipitation studies

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Mojtaba Sadeghi ◽  
Phu Nguyen ◽  
Matin Rahnamay Naeini ◽  
Kuolin Hsu ◽  
Dan Braithwaite ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Heavy Precipitation ◽  
Climate Data ◽  
Spatiotemporal Resolution ◽  
Data Record ◽  
Precipitation Estimation ◽  
Precipitation Estimates ◽  
Global Precipitation ◽  
Climate Data Record

AbstractAccurate long-term global precipitation estimates, especially for heavy precipitation rates, at fine spatial and temporal resolutions is vital for a wide variety of climatological studies. Most of the available operational precipitation estimation datasets provide either high spatial resolution with short-term duration estimates or lower spatial resolution with long-term duration estimates. Furthermore, previous research has stressed that most of the available satellite-based precipitation products show poor performance for capturing extreme events at high temporal resolution. Therefore, there is a need for a precipitation product that reliably detects heavy precipitation rates with fine spatiotemporal resolution and a longer period of record. Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Cloud Classification System-Climate Data Record (PERSIANN-CCS-CDR) is designed to address these limitations. This dataset provides precipitation estimates at 0.04° spatial and 3-hourly temporal resolutions from 1983 to present over the global domain of 60°S to 60°N. Evaluations of PERSIANN-CCS-CDR and PERSIANN-CDR against gauge and radar observations show the better performance of PERSIANN-CCS-CDR in representing the spatiotemporal resolution, magnitude, and spatial distribution patterns of precipitation, especially for extreme events.

scholarly journals Microscale dynamics of electrophysiological markers of epilepsy

2020 ◽  
Author(s):  
Jimmy C. Yang ◽  
Angelique C. Paulk ◽  
Sang Heon Lee ◽  
Mehran Ganji ◽  
Daniel J. Soper ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
High Frequency ◽  
Time Windows ◽  
List Type ◽  
Spatiotemporal Resolution ◽  
Similar Time ◽  
Human Epilepsy ◽  
High Frequency Oscillations ◽  
Peak Tracking ◽  
Interictal Discharges

AbstractObjectiveInterictal discharges (IIDs) and high frequency oscillations (HFOs) are neurophysiologic biomarkers of epilepsy. In this study, we use custom poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) microelectrodes to better understand their microscale dynamics.MethodsElectrodes with spatial resolution down to 50µm were used to record intraoperatively in 30 subjects. For IIDs, putative spatiotemporal paths were generated by peak-tracking, followed by clustering. For HFOs, repeating patterns were elucidated by clustering similar time windows. Fast events, consistent with multi-unit activity (MUA), were covaried with either IIDs or HFOs.ResultsIIDs seen across the entire array were detected in 93% of subjects. Local IIDs, observed across <50% of the array, were seen in 53% of subjects. IIDs appeared to travel across the array in specific paths, and HFOs appeared in similar repeated spatial patterns. Finally, microseizure events were identified spanning 50-100µm. HFOs covaried with MUA, but not with IIDs.ConclusionsOverall, these data suggest micro-domains of irritable cortex that form part of an underlying pathologic architecture that contributes to the seizure network.SignificanceMicroelectrodes in cases of human epilepsy can reveal dynamics that are not seen by conventional electrocorticography and point to new possibilities for their use in the diagnosis and treatment of epilepsy.HighlightsPEDOT:PSS microelectrodes with at least 50µm spatial resolution uniquely reveal spatiotemporal patterns of markers of epilepsyHigh spatiotemporal resolution allows interictal discharges to be tracked and reveal cortical domains involved in microseizuresHigh frequency oscillations detected by microelectrodes demonstrate localized clustering on the cortical surface

Spatial bootstrapping for model-free estimation of subcatchment parameter uncertainty for a semi-distributed rainfall runoff model

2021 ◽  
Author(s):  
Everett Snieder ◽  
Usman Khan
Keyword(s):  
Spatial Heterogeneity ◽  
Spatial Resolution ◽  
Parameter Uncertainty ◽  
Spatial Uncertainty ◽  
Performance Criteria ◽  
Rainfall Runoff ◽  
Spatiotemporal Resolution ◽  
Computational Expense ◽  
Model Free ◽  
Uncertainty Estimates

&lt;p&gt;Semi-distributed rainfall runoff models are widely used in hydrology, offering a compromise between the computational efficiency of lumped models and the representation of spatial heterogeneity offered by fully distributed models. In semi-distribute models, the catchment is divided into subcatchments, which are used as the basis for aggregating spatial characteristics. During model development, uncertainty is usually estimated from literature, however, subcatchment uncertainty is closely related to subcatchment size and level of spatial heterogeneity. Currently, there is no widely accepted systematic method for determining subcatchment size. Typically, subcatchment discretisation is a function of the spatiotemporal resolution of the available data. In our research, we evaluate the relationship between lumped parameter uncertainty and subcatchment size. Models with small subcatchments are expected to have low spatial uncertainty, as the spatial heterogeneity per subcatchment is also low. As subcatchment size increases, as does spatial uncertainty. Our objectives are to study the trade-off between subcatchment size, parameter uncertainty, and computational expense, to outline a systematic and precise framework for subcatchment discretisation. A proof of concept is presented using the Stormwater Management Model (EPA-SWMM) platform, to study a semi-urban catchment in Southwestern Ontario, Canada. Automated model creation is used to create catchment models with varying subcatchment sizes. For each model variation, uncertainty is estimated using spatial statistical bootstrapping. Applying bootstrapping to the spatial parameters directly provides a model free method for calculating the uncertainty of sample estimates. A Monte Carlo simulation is used to propagate uncertainty through the model and spatial resolution is assessed using performance criteria including the percentage of observations captured by the uncertainty envelope, the mean uncertainty envelope width, and rank histograms. The computational expense of simulations is tracked across the varying spatial resolution, achieved through subcatchment discretisation. Initial results suggest that uncertainty estimates often disagree with typical values listed in literature and vary significantly with respect to subcatchment size; this has significant implications on model calibration.&lt;/p&gt;

scholarly journals Multi-beam Synchrotron FTIR Chemical Imaging: Impacts of Schwarzschild Objective and Spatial Oversampling on Spatial Resolution

2013 ◽  
Vol 425 (14) ◽  
pp. 142001 ◽  
Author(s):  
Eric C Mattson ◽  
Miriam Unger ◽  
Binod Manandhar ◽  
Zahrasadat Alavi ◽  
Carol J Hirschmugl
Keyword(s):  
Spatial Resolution ◽  
Chemical Imaging

Simultaneous Determination of E, G and ν of Soft Hydrogels Using Theory of Elasticity

2009 ◽  
Author(s):  
Uday Chippada ◽  
Xue Jiang ◽  
Lulu Li ◽  
Rene Schloss ◽  
Bernard Yurke ◽  
...  
Keyword(s):  
Poisson’S Ratio ◽  
Theory Of Elasticity ◽  
Complete Characterization ◽  
Poisson's Ratio ◽  
Force Microscopy ◽  
Cellular Processes ◽  
Atomic Force ◽  
Significant Research

Hydrogels have been used as substrates by many researchers in the study of cellular processes. The mechanical properties of these gels play a significant role in the growth of the cells. Significant research using several methods like compression, indentation, atomic force microscopy and manipulation of beads has been performed in the past to characterize the stiffness of these substrates. However, most of the methods employed assume the gel to be incompressible, with a Poisson’s ratio of 0.5. However, Poisson’s ratio can differ from 0.5. Hence, a more complete characterization of the elastic properties of hydrogels requires that one experimentally obtain the value of at least two of the three quantities: Poisson’s ratio, shear modulus, and elastic modulus.

scholarly journals Recent Development of the Nobeyama 17GHz Interferometer and Some Initial Results

1980 ◽  
Vol 86 ◽  
pp. 123-126
Author(s):  
Keizo Kai
Keyword(s):  
Spatial Resolution ◽  
Time Resolution ◽  
Solar Radio ◽  
High Time Resolution ◽  
The Sun ◽  
Radio Observatory ◽  
Time Calibration ◽  
Drift Scan ◽  
Time Variations ◽  
Initial Results

We have constructed a 17GHz interferometer of a multi-correlator type at the Nobeyama Solar Radio Observatory. Novel features of the new interferometer are summarized as (i) high time-resolution up to 0.8 s and (ii) “real-time” calibration of the whole system with an accuracy of ~ 2% for amplitudes and ~ 2° for phases. With the aid of these advantages over an interferometer of a conventional drift-scan type we are able to detect and follow rapid time variations of even a faint source (say, ~ 0.5 s.f.u.) on the Sun with a spatial resolution of ~ 40″. The interferometer has been put in operation since July 1978. We have recorded hundreds of bursts at 17GHz in a year including some tens of rapidly changing sources which would not precisely be measured so far. We present here some preliminary results of observations such as polarization structures of both rapidly changing and GRF bursts.

Nanoscale chemical imaging of solid–liquid interfaces using tip-enhanced Raman spectroscopy

Nanoscale ◽  
2018 ◽  
Vol 10 (4) ◽  
pp. 1815-1824 ◽  
Author(s):  
Naresh Kumar ◽  
Weitao Su ◽  
Martin Veselý ◽  
Bert M. Weckhuysen ◽  
Andrew J. Pollard ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Spatial Resolution ◽  
Chemical Imaging ◽  
Liquid Interfaces ◽  
New Approach ◽  
Immersed Surfaces ◽  
Nanoscale Chemical Imaging ◽  
Tip Enhanced Raman Spectroscopy ◽  
Solid Liquid

New approach to TERS probe coating enables chemical imaging of liquid-immersed surfaces with nanoscale spatial resolution.

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