Temporal Resolution Measurements Research Articles

Understanding and modeling of gas puff injection for diagnostic purposes.

This article presents an experimental setup capable of providing high spatial and temporal resolution measurements of neutral gas puff injection using a glow discharge to excite the neutral gas and an ultra-high-speed camera to record the emitted light. Using the proposed setup, the shape and propagation velocity of a thermal deuterium gas puff at 1bar have been measured. The cloud has a conical shape and a propagation velocity of vprop = 1870 ± 270m/s. Furthermore, a code has been developed with the aim of studying the relation between the propagation velocity and the initial injection velocity of the gas. The simulations show that an initial injection velocity in the range of vinj ∼ 1650-1950m/s can reproduce a propagation velocity of vprop = 1870 ± 270m/s.

Modification of an Automated Precision Farming Robot for High Temporal Resolution Measurement of Leaf Angle Dynamics using Stereo Vision

Modification of an Automated Precision Farming Robot for High Temporal Resolution Measurement of Leaf Angle Dynamics using Stereo Vision

Correction of Sensible Heat Flux from Flux-Gradient Method to Eddy Covariance Method Based on Multi-Layer Perceptron

Abstract. Understanding surface-atmosphere interactions is critical for environmental and meteorological studies. Sensible heat flux, a key component in this interaction, is typically measured using methods such as Eddy Covariance (EC) and Flux-Gradient (FG). The EC method, known for its high temporal resolution and direct measurement capabilities of wind speed, temperature, and humidity changes, requires the use of expensive and complex equipment, making it costly and challenging to implement. On the contrary, the FG method is more accessible and economical, relying on simpler instruments, but often lacks the precision of the EC method. To harness the benefits of both methods, this article uses the Multi-Layer Perceptron (MLP) machine learning method to enhance the accuracy of the FG method's sensible heat flux calculations. Through the MLP model, this paper aims to determine the optimal parameter settings for the specific measurement environment, thereby improving the FG methods accuracy. The data was measured from Guandu Village, Anhui Province, China. This research seeks to demonstrate that the trained MLP model can be applied to similar measurement environments, thus enhancing the FG method's applicability and precision.

Small-Scale Biophysical Interactions and Dinophysis Blooms: Case Study in a Strongly Stratified Chilean Fjord

Diarrhetic shellfish poisoning (DSP) toxins and pectenotoxins (PTXs) produced by endemic species of Dinophysis, mainly D. acuta and D. acuminata, threaten public health and negatively impact the shellfish industry worldwide. Despite their socioeconomic impact, research on the environmental drivers of DSP outbreaks in the Chilean fjords is scanty. From 22 to 24 March 2017, high spatial–temporal resolution measurements taken in Puyuhuapi Fjord (Northern Patagonia) illustrated the short-term (hours, days) response of the main phytoplankton functional groups (diatoms and dinoflagellates including toxic Dinophysis species) to changes in water column structure. Results presented here highlight the almost instantaneous coupling between time–depth variation in density gradients, vertical shifts of the subsurface chlorophyll maximum, and its evolution to a buoyancy-driven thin layer (TL) of diatoms just below the pycnocline the first day. A second shallower TL of dinoflagellates, including Dinophysis acuta, was formed on the second day in a low-turbulence lens in the upper part of the pycnocline, co-occurring with the TL of diatoms. Estimates of in situ division rates of Dinophysis showed a moderate growth maximum, which did not coincide with the cell density max. This suggests that increased cell numbers resulted from cell entrainment of off-fjord populations combined with in situ growth. Toxin profiles of the net tow analyses mirrored the dominance of D. acuminata/D. acuta at the beginning/end of the sampling period. This paper provides information about biophysical interactions of phytoplankton, with a focus on Dinophysis species in a strongly stratified Patagonian fjord. Understanding these interactions is crucial to improv predictive models and early warning systems for toxic HABs in stratified systems.

Feasibility of capturing vessel expansion with 4D-CTA: Phantom study to determine reproducibility, spatial and temporal resolution.

Dynamic Computed Tomography Angiography (4D CTA) has the potential of providing insight into the biomechanical properties of the vessel wall, by capturing motion of the vessel wall. For vascular pathologies, like intracranial aneurysms, this could potentially refine diagnosis, prognosis, and treatment decision-making. The objective of this research is to determine the feasibility of a 4D CTA scanner for accurately measuring harmonic diameter changes in an in-vitro simulated vessel. A silicon tube was exposed to a simulated heartbeat. Simulated heart rates between 40 and 100 beats-per-minute (bpm) were tested and the flow amplitude was varied, resulting in various changes of tube diameter. A 320-detector row CT system with ECG-gating captured three consecutive cycles of expansion. Image registration was used to calculate the diameter change. A vascular echography set-up was used as a reference, using a 9MHz linear array transducer. The reproducibility of 4D CTA was represented by the Pearson correlation (r) between the three consecutive diameter change patterns, captured by 4D CTA. The peak value similarity (pvs) was calculated between the 4D CTA and US measurements for increasing frequencies and was chosen as a measure of temporal resolution. Spatial resolution was represented by the Sum of the Relative Percentual Difference (SRPD) between 4D CTA and US diameter change patterns for increasing amplitudes. The reproducibility of 4D CTA measurements was good (r ≥ 0.9) if the diameter change was larger than 0.3mm, moderate (0.7 ≤ r<0.9) if the diameter change was between 0.1 and 0.3mm, and low (r<0.7) if the diameter change was smaller than 0.1mm. Regarding the temporal resolution, the amplitude of 4D CTA was similar to the US measurements (pvs ≥ 90%) for the frequencies of 40 and 50bpm. Frequencies between 60 and 80bpm result in a moderate similarity (70% ≤ pvs<90%). A low similarity (pvs<70%) is observed for 90 and 100bpm. Regarding the spatial resolution, diameter changes above 0.30mm result in SRPDs consistently below 50%. In a phantom setting, 4D CTA can be used to reliably capture reproducible tube diameter changes exceeding 0.30mm. Low pulsation frequencies (40 or 50bpm) provide an accurate measurement of the maximum tube diameter change.

Quantitative Optical Imaging of Oxygen in Brain Vasculature.

The intimate relationship between neuronal activity and cerebral oxygenation underpins fundamental brain functions like cognition, sensation, and motor control. Optical imaging offers a noninvasive approach to assess brain oxygenation and often serves as an indirect proxy for neuronal activity. However, deciphering neurovascular coupling─the intricate interplay between neuronal activity, blood flow, and oxygen delivery─necessitates independent, high spatial resolution, and high temporal resolution measurements of both microvasculature oxygenation and neuronal activation. This Perspective examines the established optical techniques employed for brain oxygen imaging, specifically functional near-infrared spectroscopy, photoacoustic imaging, optical coherence tomography, and two-photon phosphorescent lifetime microscopy, highlighting their fundamental principles, strengths, and limitations. Several other emerging optical techniques are also introduced. Finally, we discuss key technological challenges and future directions for quantitative optical oxygen imaging, paving the way for a deeper understanding of oxygen metabolism in the brain.

Extension Of Spatial Filtering Technique Using Kalman Filters For Real-Time Pipe Flow Profile Measurements

Spatial filtering is used for real-time velocity measurement due to its computational efficiency. However, this method can be noisy in real measurement environments, requiring the averaging of a substantial number of measurements to achieve reliable results, which compromises temporal resolution. This study proposes enhancing the spatial filtering algorithm by implementing Kalman filtering for pipe flow profile measurements. Kalman filtering is expected to mitigate the noise issue more effectively than traditional methods like low-pass filtering while maintaining or improving the temporal resolution of measurements.

Quantifying Impacts of Local Traffic Policies on PM Concentrations Using Low Cost Sensors in Berlin

Urban air pollution remains a challenge in European cities, despite decades of improvement, especially with respect to recent updates to the World Health Organization’s (WHO) air quality guidelines in 2021. At the same time, a new generation of small sensors for air pollution measurement have opened up new avenues for understanding air pollution in cities. In this study, we use Plantower PMS 5003 sensors to measure PM2.5 alongside three local traffic policies implemented in 2020 and 2021. These measures include a new bike-lane and a temporary community space, as well as the creation of a pedestrian zone through the closure of a street to through-traffic. The measurement campaign used the sensors in both mobile and stationary deployments, utilizing their small size and lower cost to increase spatial and temporal resolution measurements. We calibrate the Plantower sensors using Schmitz et al.’s (2021b) methodology and test three different models: multiple linear regression (MLR), gradient-boosting machines (GBM), and support vector machines (SVM). Results show that sensors are useful for measuring PM2.5. We also find no significant effect of any of the local transport policies on local concentrations of PM2.5, despite previous studies of these policies showing reductions in local NO2 concentrations. This indicates that larger-scale policies tackling urban and regional emissions of PM will be needed to improve PM concentrations and meet WHO standards.

Mid-infrared dual-comb spectroscopy with quantum cascade lasers

Since its invention in 1994, the quantum cascade laser (QCL) has emerged as a versatile light source of wavelength 4–12 µm, covering most of the mid- and long-wavelength infrared spectral ranges. Its application range has widened even further since frequency comb operation and its use as a light source for dual-comb spectroscopy (DCS) was demonstrated. In this tutorial, we introduce the unique properties of QCL frequency combs, such as high optical power, multi-GHz repetition rate, and narrow optical linewidths. Implemented in a dual-comb spectroscopy setup, this allows for broadband, low-noise measurements of strongly absorbing samples with sub-microsecond time resolution, and spectral resolution better than 10−3 cm−1/30 MHz. The advantages of QCL DCS will be discussed in the context of its broad range of applications. The high optical power (both total and per comb tooth) is leveraged for measurements in aqueous solution or at large stand-off distances. Microsecond temporal resolution measurements address the demand for probing rapid protein dynamics and combustion diagnostics. MHz-level spectral resolution, in turn, facilitates accurate line parameter studies in low pressure and cold molecular gases. Future development directions of the technology are discussed, including sub-microsecond response DCS, instrument miniaturization, or its expansion toward THz frequencies. Overall, the tutorial aims at giving a broad introduction to QCL DCS and its applications.

Temporal variability of air-water gas exchange of carbon dioxide in clam and fish aquaculture ponds

The growing trend of land-based aquaculture has heightened the significance of comprehensively assessing air-water carbon dioxide (CO2) gas exchange in these inland waters, given their potential impact on carbon neutral strategies. However, temporal variations of partial pressure of CO2 (pCO2) and CO2 flux in clam and fish aquaculture ponds were barely investigated. We assessed the water surface pCO2 in one to five months intervals by deploying a lab-made buoy in three clam ponds and three fishponds located in tropical and subtropical climates. Measurements were conducted over a 24 h period each time, spanning from April 2021 to June 2022, covering the stocking, middle, and harvesting stages of the culture cycle. Diurnal pCO2 variations were dominantly controlled by biologically driven changes in dissolved inorganic carbon and total alkalinity (~97 %), while temperature and salinity effects were minor (~3 %). Clam ponds acted as a sink of atmospheric CO2 during stocking stages and transitioned to a source during middle to harvesting stages. In contrast, fishponds acted as a source of atmospheric CO2 throughout culture cycles and CO2 flux strengthened when reaching harvesting stages. Overall, clam ponds acted as a weak sink for atmospheric CO2 (−2.8 ± 17.3 mmol m−2 d−1), whereas fishponds acted as a source (16.8 ± 21.7 mmol m−2 d−1). CO2 emission was stronger during daytime coinciding with higher windspeeds compared to nighttime in fishponds. We suggest incorporating high temporal resolution measurements to account for diurnal and culture-stage variations, enabling more accurate estimates of air-water CO2 flux in aquaculture ponds. Moreover, the findings of this study highlight the importance of feeding, aeration, and biological activities (photosynthesis, remineralization, and calcification) in controlling the air-water CO2 flux in aquaculture ponds and such information can be used in implementing better strategies to achieve carbon neutral goals.

Yttrium-Iron Garnet Film Magnetometer for Registration of Magnetic Nano- and Submicron Particles: In Vitro and In Vivo Studies.

In the current article, we present a new kind of magnetometer for quantitative detection of magnetic objects (magnetic nano- and submicron particles) in biological fluids and tissues. The sensor is based on yttrium-iron garnet film with optical signal registration system. Inheriting the working principle of a fluxgate magnetometers, the sensor works at a room-temperature, its wide dynamic range allows the measurements in an unshielded environment. A small size of sensitive element combined with a short recovery time after the excitation coils are off provide us with a potentially high spatial and temporal resolution of measurements. We show the feasibility of the developed devices by sensing the remanent magnetization of magnetic nanoparticles (MNPs) both in vitro (test tubes, dry MNPs) and in vivo (local injection of the MNPs into mice).

Investigating methods to quantifying uncertainty in PM2.5 emission rates from cooking by toasting bread

Exposure to airborne fine particulate matter (PM2.5) is linked to multiple negative health effects and indoor sources are important contributors to personal exposure. Cooking is a common indoor source, but reported emission rates have high variability. Methods to quantify uncertainty in PM2.5 cooking emission rates are investigated so that they can be used in probabilistic exposure models to evaluate interventions. Controlled tests were conducted to measure emission rates from the toasting of bread because it is simple and repeatable. Two methods were compared: residential kitchen field tests and large chamber tests. The theoretical peak calculation method was used to determine emission rates from time-resolved PM2.5 concentration measurements. The large chamber tests produced more consistent results than the residential field tests, with a coefficient of variance almost an order of magnitude lower due to the improved control of variables. Then, the emission rates were normally distributed with mean 0.23mg/min and standard deviation 0.067mg/min. However, this distribution may be less representative of normal behaviour. The resulting dataset can be combined with other sources to represent housing stock exposures in probabilistic models, enabling the exploration of exposure uncertainties and interventions. More generally, key recommendations when measuring PM2.5 emission rates include: high temporal resolution measurements; custom calibration factors; identifying periods for emissions, mixing, and decay; constant ventilation rates; quantifying mixing conditions; and ensuring high quality decay data.

Spectral Grouping of Electrically Encoded Sound Predicts Speech-in-Noise Performance in Cochlear Implantees

ObjectivesCochlear implant (CI) users exhibit large variability in understanding speech in noise. Past work in CI users found that spectral and temporal resolution correlates with speech-in-noise ability, but a large portion of variance remains unexplained. Recent work on normal-hearing listeners showed that the ability to group temporally and spectrally coherent tones in a complex auditory scene predicts speech-in-noise ability independently of the audiogram, highlighting a central mechanism for auditory scene analysis that contributes to speech-in-noise. The current study examined whether the auditory grouping ability also contributes to speech-in-noise understanding in CI users.DesignForty-seven post-lingually deafened CI users were tested with psychophysical measures of spectral and temporal resolution, a stochastic figure-ground task that depends on the detection of a figure by grouping multiple fixed frequency elements against a random background, and a sentence-in-noise measure. Multiple linear regression was used to predict sentence-in-noise performance from the other tasks.ResultsNo co-linearity was found between any predictor variables. All three predictors (spectral and temporal resolution plus the figure-ground task) exhibited significant contribution in the multiple linear regression model, indicating that the auditory grouping ability in a complex auditory scene explains a further proportion of variance in CI users’ speech-in-noise performance that was not explained by spectral and temporal resolution.ConclusionMeasures of cross-frequency grouping reflect an auditory cognitive mechanism that determines speech-in-noise understanding independently of cochlear function. Such measures are easily implemented clinically as predictors of CI success and suggest potential strategies for rehabilitation based on training with non-speech stimuli.

NEXT GENERATION GRAVITY MISSIONS: STUDYING THE POSSIBILITIES OF MULTIPLE CONSTELLATION

We study potential possibilities of space constellation consisting of two pairs of spacecraft moving in different orbits, the so-called next generation gravity missions, aimed at increasing the spatial and temporal resolution of measurements and improving the accuracy of the recovery of the Earth’s gravity field. As a result of numerical simulation of the orbital motion of the multiple spacecraft constellation and solving the inverse problem of recovering the Earth’s gravitational field based on model measurements performed in this constellation, a multiple configuration with orbital parameters \(h = 370\) km, \(i = 90.5^\circ \) and \(h = 370\) km, \(i = 70.0^\circ \), was found. Such a multiple constellation makes possible to increase both the spatial and temporal resolution of the Earth’s gravity field models with a significant refinement of zonal, sectorial and tesseral harmonics compared to the one-pair near-polar configuration.

Properties of the mixing layer height retrieved from ceilometer measurements in Slovakia and its relationship to the air pollutant concentrations.

Mixing layer height (MLH) is an important meteorological parameter for air quality since it significantly affects ground-level pollution in the atmosphere. This study examined the properties of the MLH on diurnal and seasonal timescales over a 3-year period (2020-2022) using high temporal resolution measurements from eight Vaisala CL31 ceilometers situated around Slovakia. Hourly averaged MLH data was retrieved from the BL-View software using merged method. The highest daily maxima for the MLH occurred mostly in summer and spring, while the lowest values occurred predominantly during winter and autumn. The average MLH daily maximum in summer was 2229m, and just 859m in winter. During summer, the spatial distribution of the MLH daily maxima was more uniform compared to winter, when the air masses within the individual valleys did not mix well. Correlations between ground-level pollutant concentrations and hourly mean/daily mean MLH were analyzed. The highest correlation, R≈0.6, was found for O3. For PM10, PM2.5, and NOx, the anticorrelations with MLH were found with maximum in winter (R ≈ - 0.3 for hourly data and R ≈ - 0.5 for daily mean data) but no relation in summer. Lastly, the ceilometer MLH was compared to the radiosonde retrieved MLH for various cloud covers. Our analysis is based on an extensive set of empirical data, which can improve the accuracy and effectiveness of meteorological and atmospheric chemistry models. The findings can support air pollution forecasting and warning systems, providing valuable insights for policymakers and researchers.

Micropollutant concentration fluctuations in combined sewer overflows require short sampling intervals

Combined sewer overflows (CSOs) are an important pathway of organic micropollutants from urban areas to open water bodies. Understanding the temporal dynamics of these micropollutants during overflow events is crucial for applying appropriate sampling methods and implementing effective management strategies. Yet, little is known about the dynamics of micropollutants in CSOs, because most studies report concentrations from single grab samples or event mean concentrations (EMCs). With unique high temporal resolution measurements (3 min), we show the real dynamics of polar organic micropollutants in CSOs of one small (2,700 people: P) and one large (159,000 P) urban catchment, for two micropollutant categories: (i) 33 micropollutants in municipal wastewater and (ii) 13 micropollutants from urban surface runoff. The concentration dynamics depend on the substance source and the catchment size. Indoor substances such as pharmaceuticals show high temporal dynamics with changes of 1 to 2 orders of magnitude within 9 min in the CSO of the small catchment. In contrast, outdoor substances at the small catchment and all substances at the large catchment display considerably lower variation. We tested various time-proportional sampling strategies to assess the range of error when estimating EMCs. We recommend an interval of 3 min to capture the dynamics of indoor substances in CSOs from small catchments. The results highlight that both future monitoring campaigns and the planning and management of urban wet-weather treatment systems will benefit from high temporal sampling resolutions, not only to understand dynamics but also to minimize errors of estimated EMCs.

Saline bolus for negative contrast perfusion imaging in magnetic particle imaging.

Objective.Magnetic particle imaging (MPI) is capable of high temporal resolution measurements of the spatial distribution of magnetic nanoparticles and therefore well suited for perfusion imaging, which is an important tool in medical diagnosis. Perfusion imaging in MPI usually requires a fresh bolus of tracer material to capture the key signal dynamics. Here, we propose a method to decouple the imaging sequence from the injection of additional tracer material, without further increasing the administered iron dose in the body with each image.Approach.A bolus of physiological saline solution without any particles (negative contrast) diminishes the steady-state concentration of a long-circulating tracer during passage. This depression in the measured concentration contributes to the required contrast dynamics. The presence of a long-circulating tracer is therefore a prerequisite to obtain the negative contrast. As a quantitative tracer based imaging method, the signal is linear in the tracer concentration for any location that contains nanoparticles and zero in the surrounding tissue which does not provide any intrinsic signal. After tracer injection, the concentration over time (positive contrast) can be utilized to calculate dynamic diagnostic parameters like perfusion parameters in vessels and organs. Every acquired perfusion image thus requires a new bolus of tracer with a sufficiently large iron dose to be visible above the background.Main results.Perfusion parameters are calculated based on the time response of the proposed negative bolus and compared to a positive bolus. Results from phantom experiments show that normalized signals from positive and negative boli are concurrent and deviations of calculated perfusion maps are low.Significance.Our method opens up the possibility to increase the total monitoring time of a future patient by utilizing a positive-negative contrast sequence, while minimizing the iron dose per acquired image.

An in situ benthic chamber system for improved temporal and spatial resolution measurement of sediment oxygen demand

AbstractIn shallow coastal systems, sediments are exposed to dramatic and complex variability in environmental conditions that influences sediment processes on short timescales. Sediment oxygen demand (SOD), or consumption of oxygen by sediment‐dwelling organisms and chemical reactions within sediments, is one such process and an important metric of aquatic ecosystem functioning and health. The most common instruments used to measure SOD in situ are batch‐style benthic chambers, which generally require long measurement periods to resolve fluxes and thus do not capture the high temporal variability in SOD that can be driven by dynamic coastal processes. These techniques also preclude linking changes in SOD through time to specific features of the sediment, for example, shifts in sediment faunal activities which can vary on short time scales and can also be affected by ambient oxygen concentrations. Here we present an in situ semi‐flow through instrument to repeatedly measure SOD in discrete areas of sediment. The system isolates patches of sediment in replicate benthic chambers, and measures and records oxygen decrease for a short time before refreshing the overlying water in the chamber with water from the external environment. This results in a sawtooth pattern in which each tooth is an incubation, providing an automated method to produce direct measurements of in situ SOD that can be directly linked to an area of sediment and related to rapid shifts in environmental conditions.

Hydrosedimentary behavior of a field combining surface drains and tile drains

In agricultural fields, soil erosion is usually associated to surface runoff. However, in drained fields, tile drains are additional pathways for soil particles. Few studies have quantified erosion in drained fields and they mainly focused on tile drained fields, without considering fields combining surface and tile drainage. These studies show high inter-site and inter-annual variabilities that highlight the need for more annual quantifications of erosion in drained fields. Consequently, it is still difficult to quantify the relative importance of the factors affecting soil erosion in drained fields. In addition to a comprehensive review of the existing studies of erosion through drainage, this study aims at quantifying surface and subsurface erosion in a 5 ha cultivated field combining surface and tile drainage. Suspended sediments (SS) and water fluxes have been monitored during two years (2019–2020 and 2020–2021) at a high temporal resolution (1 min), both at the outlet of the tile drain network and at the outlet of the surface drainage rill. SS yield was 0.49 t ha−1 and 1.08 t ha−1 in 2019–2020 and 2020–2021, respectively. During 2019–2020 and 2020–2021, tile drainage contribution to the total runoff was 46% and 21%, respectively and its contribution to SS yield was 9% and 11%, respectively. High temporal resolution measurements of runoff and SS concentrations showed the suspended sediment concentration in the surface drain runoff only increase by 17% from the first to the second study year. Conversely, for tile drainage, average suspended sediment concentrations increased by 260%. These variations and the increase of surface runoff rate suggest a shift in water and sediment connectivity at the field scale. Cropping practices could have generated a slumping of the soil surface during the second year and, at the same time, the development of a macropore network in the subsoil. Cropping practices induced changes of surface horizon characteristics and their impact on the hydrosedimentary behavior of drained soils need to be further studied. This study confirms previous results concerning the temporal dynamics of SS exports in a drained context under temperate climate and adds a new quantification of hydrosedimentary fluxes in a surface and tile drained field separating surface drains and tile drains contributions.

80 Hz auditory steady state responses (ASSR) elicited by silent gaps embedded within a broadband noise.

Although auditory temporal processing plays an important role in speech comprehension, it cannot be measured by pure tone audiometry. Auditory temporal resolution is often assessed by behavioral gaps-in-noise test. To evaluate whether auditory temporal resolution could be objectively assessed, we measured the auditory steady state response (ASSR) elicited by silent gaps embedded within broadband noises at 80 Hz. We prepared six sound types as test stimuli. One was a continuous broadband noise without a silent interval as a control stimulus and the others were broadband noises with 80 Hz silent intervals of 0.4, 0.8, 1.6, 3.1, and 6.3 ms. Significant ASSRs were recorded only when the gap length was longer than the behavioral thresholds and the ASSR amplitude increased as the gap length increased. Eighty Hertz gap-evoked ASSR appears to reflect the neural activity related to the auditory gap processing and may be used as an objective measure of auditory temporal resolution in humans.