Time Resolution Research Articles

Systematic approach to measure the performance of microchannel-plate photomultipliers

In this paper, we present our approach to systematically measure numerous performance parameters of microchannel plate photomultiplier tubes. The experimental setups, the analyses and selected results are discussed. Although the techniques used may be different in other locations, the document is intended as a guide for comparable measurements with other types of microchannel plate photomultiplier tubes. Measurements are shown for the following performance parameters: spectral and spatial quantum efficiency, collection efficiency, gain as a function of voltage, position and magnetic field, time resolution, rate capability and lifetime. By using a dedicated 3-axis stepper and an FPGA-based data acquisition system, also inner PMT parameters are measured as a function of the active area, such as relative detection efficiency, dark count rate, time resolution, recoil electron and afterpulse distributions, as well as charge sharing and electronic crosstalk. In addition, some of the parameters are investigated inside a strong magnetic field. For many of these measurements, the change of most setup parameters and the subsequent analysis can be controlled semi-automatically by software scripts.

Correction: Wu et al. Accumulatively Increasing Sensitivity of Ultrawide Instantaneous Bandwidth Digital Receiver with Fine Time and Frequency Resolution for Weak Signal Detection. Electronics 2022, 11, 1018

In the original publication [...]

A high-precision view of intercompartmental drug transport via simultaneous, seconds-resolved, in situ measurements in the vein and brain.

The ability to measure specific molecules at multiple sites within the body simultaneously, and with a time resolution of seconds, could greatly advance our understanding of drug transport and elimination. As a proof-of-principle demonstration, here we describe the use of electrochemical aptamer-based (EAB) sensors to measure transport of the antibiotic vancomycin from the plasma (measured in the jugular vein) to the cerebrospinal fluid (measured in the lateral ventricle) of live rats with temporal resolution of a few seconds. In our first efforts, we made measurements solely in the ventricle. Doing so we find that, although the collection of hundreds of concentration values over a single drug lifetime enables high-precision estimates of the parameters describing intracranial transport, due to a mathematical equivalence, the data produce two divergent descriptions of the drug's plasma pharmacokinetics that fit the in-brain observations equally well. The simultaneous collection of intravenous measurements, however, resolves this ambiguity, enabling high-precision (typically of ±5 to ±20% at 95% confidence levels) estimates of the key pharmacokinetic parameters describing transport from the blood to the cerebrospinal fluid in individual animals. The availability of simultaneous, high-density 'in-vein' (plasma) and 'in-brain' (cerebrospinal fluid) measurements provides unique opportunities to explore the assumptions almost universally employed in earlier compartmental models of drug transport, allowing the quantitative assessment of, for example, the pharmacokinetic effects of physiological processes such as the bulk transport of the drug out of the CNS via the dural venous sinuses.

Remaining useful life prediction of machinery based on improved Sample Convolution and Interaction Network

Remaining useful life (RUL) prediction is significant in ensuring the safe and reliable operation of machinery and reducing maintenance costs. There are currently numerous deep learning-based methods for machinery RUL prediction. However, some studies overlook the differences in the contributions of data from different sensors or different time points of the same sensor, and most research only extracts information from feature or sequence dimensions, which inevitably affects the efficiency and accuracy of RUL prediction. Therefore, we proposed a method based on a multi-dimensional attention mechanism and feature-sequence dimensional sample convolution and interaction network (MFSSCINet) to predict the machinery RUL effectively, which includes a Feature-Sequence Dimension Attention Module to capture information interactions in feature dimension and learn the impact weights of various time steps in sequence dimension. Then, a Multi-Source Information Fusion Module was constructed to extract helpful information from features of different dimensions and time resolutions and fuse them. Finally, a RUL Prediction Module was built to estimate the machine RUL effectively. The method’s effectiveness is validated in C-MAPSS and XJTU-SY datasets. Experimental results show that the MFSSCINet model has higher accuracy in machine RUL prediction tasks than other advanced computational methods.

Free-breathing 3D whole-heart joint T1/T2 mapping and water/fat imaging at 0.55 T.

To develop and validate a highly efficient motion compensated free-breathing isotropic resolution 3D whole-heart joint T1/T2 mapping sequence with anatomical water/fat imaging at 0.55 T. The proposed sequence takes advantage of shorter T1 at 0.55 T to acquire three interleaved water/fat volumes with inversion-recovery preparation, no preparation, and T2 preparation, respectively. Image navigators were used to facilitate nonrigid motion-compensated image reconstruction. T1 and T2 maps were jointly calculated by a dictionary matching method. Validations were performed with simulation, phantom, and in vivo experiments on 10 healthy volunteers and 1 patient. The performance of the proposed sequence was compared with conventional 2D mapping sequences including modified Look-Locker inversion recovery and T2-prepared balanced steady-SSFP sequence. The proposed sequence has a good T1 and T2 encoding sensitivity in simulation, and excellent agreement with spin-echo reference T1 and T2 values was observed in a standardized T1/T2 phantom (R2 = 0.99). In vivo experiments provided good-quality co-registered 3D whole-heart T1 and T2 maps with 2-mm isotropic resolution in a short scan time of about 7 min. For healthy volunteers, left-ventricle T1 mean and SD measured by the proposed sequence were both comparable with those of modified Look-Locker inversion recovery (640 ± 35 vs. 630 ± 25 ms [p = 0.44] and 49.9 ± 9.3 vs. 54.4 ± 20.5 ms [p = 0.42]), whereas left-ventricle T2 mean and SD measured by the proposed sequence were both slightly lower than those of T2-prepared balanced SSFP (53.8 ± 5.5 vs. 58.6 ± 3.3 ms [p < 0.01] and 5.2 ± 0.9 vs. 6.1 ± 0.8 ms [p = 0.03]). Myocardial T1 and T2 in the patient measured by the proposed sequence were in good agreement with conventional 2D sequences and late gadolinium enhancement. The proposed sequence simultaneously acquires 3D whole-heart T1 and T2 mapping with anatomical water/fat imaging at 0.55 T in a fast and efficient 7-min scan. Further investigation in patients with cardiovascular disease is now warranted.

Investigation of intra-fractionated range guided adaptive proton therapy: (Part I) on-line PET imaging and range measurement.

Develop a prototype on-line PET scanner and evaluate its capability of on-line imaging and intra-fractionated proton-induced radioactivity range measurement.&#xD;Approach: Each detector consists of 32×32 array of 2×2×30 mm3 Lutetium-Yttrium Oxyorthosilicate scintillators with single-scintillator-end readout through a 20×20 array of 3×3 mm2 Silicon Photomultipliers. The PET can be configurated with a full-ring of 20 detectors for conventional PET imaging or a partial-ring of 18 detectors for on-line imaging and range measurement. All detector-level readout and processing electronics are attached to the backside of the system gantry and their output signals are transferred to a Field-Programable-Gate-Array based system electronics and data acquisition that can be placed 2 meters away from the gantry. The PET imaging performance and radioactivity range measurement capability were evaluated by both the offline study that placed a radioactive source with known intensity and distribution within a phantom and the online study that irradiated a phantom with proton beams under different radiation and imaging conditions.&#xD;Main results: The PET has 32 cm diameter and 6.5 cm axial length field-of-view (FOV), ~2.3 to 5.0 mm spatial resolution within FOV, 3% sensitivity at the FOV center, 18% to 30% energy resolution, and ~9 ns coincidence time resolution. The offline study shows the PET can determine the shift of distal falloff edge position of a known radioactivity distribution with the accuracy of 0.30.3 mm even without attenuation and scatter corrections, and online study shows the PET can measure the shift of proton-induced positron radioactive range with the accuracy of 0.60.3 mm from the data acquired with a short-acquisition (60 second) and low-dose (5 MU) proton radiation to a human head phantom.&#xD;Significance: This study demonstrated the capability of intra-fractionated PET imaging and radioactivity range measurement and will enable the investigation on the feasibility of intra-fractionated, range-shift compensated adaptive proton therapy.

Scour-depth variability controls channel-scale stratigraphy in experimental braided rivers

ABSTRACT Braided rivers distribute sediment across landscapes, often forming wide channel belts that are preserved in stratigraphy as coarse-grained deposits. Theoretical work has established quantitative links between the depth distribution of formative channels in a braided river and the geometry of their preserved strata. However, testing these predictive relationships between geomorphic process and stratigraphic product requires examining how braided rivers and their deposits coevolve, with high resolution in both space and time. Here, using a series of four runs of a physical experiment, we examine the controls of water discharge and slope on the resulting geometry of preserved deposits. Specifically, we focus on how a twofold variation in water discharge and initial riverbed slope affects the spatiotemporal distribution of channel depths and the geometry of preserved deposits of a braided river. We find that the channel depths in the laboratory experiment are described by a two-parameter gamma distribution and the deepest scours correspond to zones of erosion at channel-belt margins and channel-thread confluences in the channel belt. We use a reduced-complexity flow model to reconstruct flow depths, which were shallower compared to channel thalweg depths. Synthetic stratigraphy built from timeseries of topographic surfaces shows that the distribution of cut-and-fill-unit thickness is invariant across the experiments and is determined by the variability in scour depths. We show that the distribution of cut-and-fill-unit thickness can be used to reconstruct formative-channel-depth distributions and that the mean thickness of these units is 0.31 to 0.62 times the mean formative flow depth across all experiments. Our results suggest that variations in discharge and slope do not translate to measurable differences in preserved cut-and-fill-unit thickness, suggesting that changes in external forcings are likely to be preserved in braided river deposits only when they exceed a certain threshold of change.

The effects of back-projection variants in BPF-like TOF PET reconstruction using CNN filtration - Based on simulated and clinical brain data.

The back-projection strategies such as confidence weighting (CW) and most likely annihilation position (MLAP) have been adopted into back-projection-and-filtering-like (BPF-like) deep reconstruction model and shown great potential on fast and accurate PET reconstruction. Although the two methods degenerate to an identical model at the time resolution of 0ps, they represent two distinct approaches at the realistic time resolutions of current commercial systems. There is a lack of a systematic and fair assessment on these differences. This work aims to analyze the impact of back-projection variants on CNN-based PET image reconstruction to find the most effective back-projection model, and ultimately contribute to accurate PET reconstruction. Different back-projection strategies (CW and MLAP) and different angular view processing methods (view-summed and view-grouped) were considered, leading to the comparison of four back-projection variants integrated with the same CNN filtration model. Meanwhile, we investigated two strategies of physical effect compensation, either introducing pre-corrected data as the input or adding a channel of attenuation map to the CNN model. After training models separately on Monte-Carlo-simulated BrainWeb phantoms with full dose (events=3×107), we tested them on both simulated phantoms and clinical brain scans with two dosage levels. For the performance assessment, peak signal-to-noise ratio (PSNR) and root mean square error (RMSE) were used to evaluate the pixel-wise error, structural similarity index (SSIM) to evaluate the structural similarity, and contrast recovery coefficient (CRC) in manually selected ROI to compare the region recovery. Compared to two MLAP-based histo-image reconstruction models, two CW-based back-projected image methods produced clearer, sharper, and more detailed images, from both simulated and clinical data. For angular view processing methods, view-grouped histo-image improved image quality, while view-grouped cwbp-image showed no advantage except for contrast recovery. Quantitative analysis on simulated data demonstrated that the view-summed cwbp-image model achieved the best PSNR, RMSE, SSIM, while the 8-view cwbp-image model achieved the best CRC in lesions and the white matter. Additionally, the multi-channel input model including the back-projection image and attenuation map was proved to be the most efficient and simplest method for compensating for physical effects for brain data. Applying Gaussian blur to the histo-image yielded images with limited improvement. All above results hold for both the half-dose and the full-dose cases. For brain imaging, the evaluation based on metrics PSNR, RMSE, SSIM, and CRC indicates that the view-summed CW-based back-projection variant is the most effective input for the BPF-like reconstruction model using CNN filtration, which can involve the attenuation map through an additional channel to effectively compensate for physical effects.

Utilization of Spontaneous Alkyne-Gold Self-Assembly Chemistry as an Alternative Method for Fabricating Electrochemical Aptamer-Based Sensors.

Electrochemical aptamer-based (E-AB) sensors are a promising class of biosensors which use structure-switching redox-labeled oligonucleotides (aptamers) codeposited with passivating alkanethiol monolayers on electrode surfaces to specifically bind and detect target analytes. Signaling in E-AB sensors is an outcome of aptamer conformational changes upon target binding, with the sequence of the aptamer imparting specificity toward the analyte of interest. The change in conformation translates to a change in electron transfer between the redox label attached to the aptamer and the underlying electrode and is related to analyte concentration, allowing specific electrochemical detection of nonelectroactive analytes. E-AB sensor measurements are reagentless with time resolutions of seconds or less and may be miniaturized into the submicron range. Traditionally these sensors are fabricated using thiol-on-gold chemistry. Here we present an alternate immobilization chemistry, gold-alkyne binding, which results in an increase in sensor lifetimes under ideal conditions by up to ∼100%. We find that gold-alkyne binding is spontaneous and supports efficient E-AB sensor signaling with analytical performance characteristics similar to those of thiol generated monolayers. The surface modification differs from gold-thiol binding only in the time and aptamer concentration required to achieve similar aptamer surface coverages. In addition, alkynated aptamers differ from their thiolated analogues only by their chemical handle for surface attachment, so any existing aptamers can be easily adapted to utilize this attachment strategy.

RoPod, a customizable toolkit for non-invasive root imaging, reveals cell type-specific dynamics of plant autophagy

Arabidopsis root is a classic model system in plant cell and molecular biology. The sensitivity of plant roots to local environmental perturbation challenges data reproducibility and incentivizes further optimization of imaging and phenotyping tools. Here we present RoPod, an easy-to-use toolkit for low-stress live time-lapse imaging of Arabidopsis roots. RoPod comprises a dedicated protocol for plant cultivation and a customizable 3D-printed vessel with integrated microscopy-grade glass that serves simultaneously as a growth and imaging chamber. RoPod reduces impact of sample handling, preserves live samples for prolonged imaging sessions, and facilitates application of treatments during image acquisition. We describe a protocol for RoPods fabrication and provide illustrative application pipelines for monitoring root hair growth and autophagic activity. Furthermore, we showcase how the use of RoPods advanced our understanding of plant autophagy, a major catabolic pathway and a key player in plant fitness. Specifically, we obtained fine time resolution for autophagy response to commonly used chemical modulators of the pathway and revealed previously overlooked cell type-specific changes in the autophagy response. These results will aid a deeper understanding of the physiological role of autophagy and provide valuable guidelines for choosing sampling time during end-point assays currently employed in plant autophagy research.

RRER: A refined registration method based on contrast minimum for event and RGB cameras

AbstractThe precise perception of the surrounding environment in traffic scenes is an important part of an intelligent transportation system. The event camera could provide complementary information to traditional frame‐based cameras, such as high dynamic range, and high time resolution, in the perception of traffic targets. To improve the precision and reliability of perception as well as facilitate lots of RGB camera‐based studies introduced to event cameras directly, a refined registration method for event‐based cameras and RGB cameras on the basis of pixel‐level region segmentation is proposed, to provide a fusion method at pixel level. A total of eight sequences and a dataset containing 260 typical traffic scenes are contained in the experiment dataset, both selected from DSEC, a traffic event‐based dataset. The registered event image shows a better spatial consistency with RGB images visually. Compared to the baseline, the evaluation indicators, such as the performance of the contrast, the proportion of overlapping pixels, and average registration accuracy have been improved. In the traffic object segmentation task, the average boundary displacement error of our method has decreased and the max decline value has reached 79.665%, compared to the boundary displacement error between ground truth and baseline. These results indicate prospective applications in the perception of intelligent transportation systems combined with event and RGB cameras. The traffic dataset with pixel‐level semantic annotations will be provided soon.

Sweet syndrome in the setting of breast cancer: A literature review.

e24044 Background: Sweet syndrome (SS) or acute febrile neutrophilic dermatosis typically present as patients with pyrexia, neutrophilia and rash with dermal neutrophilic dominance on biopsy. While the association of SS with malignancy is well-documented, the connection of sweet syndrome and solid tumors especially breast cancers is not explored enough. It is important to understand these associations better understand the disease course of SS in the setting of breast cancer. We aim to examine the different triggers, subtypes of breast cancer associated with SS, and differences in presentation and resolution time. Methods: A literature review from 1/1950-11/2023 was conducted for co-existing diagnoses of BC and SS in the PubMed Database. Search terms included Sweet Syndrome or Acute febrile neutrophilic dermatosis with Breast Cancer with subtypes. Key outcomes included: trigger identification, breast cancer subtypes, and treatment options. Findings were analyzed via a thematic lens. Results: A total of 34 cases of female BC patients with SS were identified with triggers divided into subtypes of surgery (47%), medication (20%), paraneoplastic (20%), and radiation therapy (11%). Depending on the trigger, average time to presentation varied with drug-triggered being the shortest (3.3 months) followed by radiation (8.5 months) while surgery (50 months) and paraneoplastic- associated (57 months) had similar presentation times. Although the time to presentation time for paraneoplastic-associated SS was the longest, 50% of these cases were associated with underlying progression of cancer. Regarding treatment and resolution time, 26 cases of SS resolved after treatment with treatment mainstay including oral (65%) and topical (12%) steroids. Analyzing triggers specific treatment outcomes, drug (2.7 days) and radiation-induced SS (7 days) had shorter average resolution times while paraneoplastic- associated (10.5 days) and surgery-associated SS (18.5 days) had longer resolution times. 5 cases that documented initial relapse or recurrence of SS after initial treatment were associated with paraneoplastic –induced sweet syndrome. On further analysis, among the 15 cases mentioned the BC type associated with SS- the most common breast cancer subtype was invasive ductal carcinoma of the breast (47%) followed by metastatic carcinoma (20%), adenocarcinoma (13%) and invasive lobular carcinoma (6%), canalicular breast carcinoma (6%) and unspecified malignant tumor of the breast (6%) regardless of the trigger mentioned. Conclusions: Oncologists should always consider SS on the differential for BC patients presenting with fever and rash given the varied presentation times depending on type of trigger. Treatment should be started promptly and continued for an adequate amount of time depending on the trigger to better mitigate complications in breast cancer patients.

Deformation-encoding Deep Learning Transformer for High-Frame-Rate Cardiac Cine MRI.

Purpose To develop a deep learning model for increasing cardiac cine frame rate while maintaining spatial resolution and scan time. Materials and Methods A transformer-based model was trained and tested on a retrospective sample of cine images from 5840 patients (mean age, 55 years ± 19 [SD]; 3527 male patients) referred for clinical cardiac MRI from 2003 to 2021 at nine centers; images were acquired using 1.5- and 3-T scanners from three vendors. Data from three centers were used for training and testing (4:1 ratio). The remaining data were used for external testing. Cines with downsampled frame rates were restored using linear, bicubic, and model-based interpolation. The root mean square error between interpolated and original cine images was modeled using ordinary least squares regression. In a prospective study of 49 participants referred for clinical cardiac MRI (mean age, 56 years ± 13; 25 male participants) and 12 healthy participants (mean age, 51 years ± 16; eight male participants), the model was applied to cines acquired at 25 frames per second (fps), thereby doubling the frame rate, and these interpolated cines were compared with actual 50-fps cines. The preference of two readers based on perceived temporal smoothness and image quality was evaluated using a noninferiority margin of 10%. Results The model generated artifact-free interpolated images. Ordinary least squares regression analysis accounting for vendor and field strength showed lower error (P < .001) with model-based interpolation compared with linear and bicubic interpolation in internal and external test sets. The highest proportion of reader choices was "no preference" (84 of 122) between actual and interpolated 50-fps cines. The 90% CI for the difference between reader proportions favoring collected (15 of 122) and interpolated (23 of 122) high-frame-rate cines was -0.01 to 0.14, indicating noninferiority. Conclusion A transformer-based deep learning model increased cardiac cine frame rates while preserving both spatial resolution and scan time, resulting in images with quality comparable to that of images obtained at actual high frame rates. Keywords: Functional MRI, Heart, Cardiac, Deep Learning, High Frame Rate Supplemental material is available for this article. © RSNA, 2024.

Study of Sudden Magnetic Storm Commencement from Observations with Second Time Resolution

Study of Sudden Magnetic Storm Commencement from Observations with Second Time Resolution

Microfluidic paper-based chemiluminescence sensing platform based on functionalized CaCO3 for time-resolved multiplex detection of avian influenza virus biomarkers

Multiplex detection can enhance diagnostic precision and improve diagnostic efficiency, providing important assistance for epidemiological investigation and epidemic prevention. There is a great need for multi-detection sensing platforms to accurately diagnose diseases. Herein, we reported a μPAD-based chemiluminescence (CL) assay for ultrasensitive multiplex detection of AIV biomarkers, based on three DNAzyme/Lum/PEI/CaCO3. Three time-resolved CL signals were sequentially generated with detection limits of 0.32, 0.34, and 0.29 pM for H1N1, H7N9, and H5N1, respectively, and with excellent selectivity against interfering DNA. The recovery test in human serum displayed satisfactory analysis capabilities for complex biological samples. The μPAD-based CL assay achieved multiplex detection within 70 s, with a high time resolution of 20 s. The proposed strategy has the advantages of low cost, high sensitivity, good selectivity, and wide time resolution, the μPAD-based CL assay has shown great potential in the early and accurate diagnosis of diseases.

Detailed cool star flare morphology with CHEOPS and TESS

Context. White-light stellar flares are proxies for some of the most energetic types of flares, but their triggering mechanism is still poorly understood. As they are associated with strong X and ultraviolet emission, their study is particularly relevant to estimate the amount of high-energy irradiation onto the atmospheres of exoplanets, especially those in their stars’ habitable zone. Aims. We used the high-cadence, high-photometric capabilities of the CHEOPS and TESS space telescopes to study the detailed morphology of white-light flares occurring in a sample of 130 late-K and M stars, and compared our findings with results obtained at a lower cadence. Methods. We employed dedicated software for the reduction of 3 s cadence CHEOPS data, and adopted the 20 s cadence TESS data reduced by their official processing pipeline. We developed an algorithm to separate multi-peak flare profiles into their components, in order to contrast them to those of single-peak, classical flares. We also exploited this tool to estimate amplitudes and periodicities in a small sample of quasi-periodic pulsation (QPP) candidates. Results. Complex flares represent a significant percentage (≳30%) of the detected outburst events. Our findings suggest that high-impulse flares are more frequent than suspected from lower-cadence data, so that the most impactful flux levels that hit close-in exoplanets might be more time-limited than expected. We found significant differences in the duration distributions of single and complex flare components, but not in their peak luminosity. A statistical analysis of the flare parameter distributions provides marginal support for their description with a log-normal instead of a power-law function, leaving the door open to several flare formation scenarios. We tentatively confirmed previous results about QPPs in high-cadence photometry, report the possible detection of a pre-flare dip, and did not find hints of photometric variability due to an undetected flare background. Conclusions. The high-cadence study of stellar hosts might be crucial to evaluate the impact of their flares on close-in exoplanets, as their impulsive phase emission might otherwise be incorrectly estimated. Future telescopes such as PLATO and Ariel, thanks to their high-cadence capability, will help in this respect. As the details of flare profiles and of the shape of their parameter distributions are made more accessible by continuing to increase the instrument precision and time resolution, the models used to interpret them and their role in star-planet interactions might need to be updated constantly.

Access to the full three-dimensional Brillouin zone with time resolution, using a new tool for pump-probe angle-resolved photoemission spectroscopy.

Here, we report the first time- and angle-resolved photoemission spectroscopy (TR-ARPES) with the new Fermiologics "FeSuMa" analyzer. The new experimental setup has been commissioned at the Artemis laboratory of the UK Central Laser Facility. We explain here some of the advantages of the FeSuMa for TR-ARPES and discuss how its capabilities relate to those of hemispherical analyzers and momentum microscopes. We have integrated the FeSuMa into an optimized pump-probe beamline that permits photon-energy (i.e., kz)-dependent scanning, using probe energies generated from high harmonics in a gas jet. The advantages of using the FeSuMa in this situation include the possibility of taking advantage of its "fisheye" mode of operation.

Fresnel lens three-dimensionally printed on the facet of a single mode fiber for trapping, manipulation, and spectrum.

Fiber optical tweezers (FOTs) provide a functionality for micro-/nanoparticle manipulation with a slim and flexible optical fiber setup. An added in situ spectroscopic functionality can achieve characterization of the trapped particle, potentially useful for endoscopic, in-vivo studies in an inherently heterogeneous environment if the applicator end is all-fiber-built. Here, we demonstrate all-fiber optical tweezers (a-FOTs) for the trapping and in situ spectral measurement of a single, cell-sized microparticle. The key to ensure the simultaneous bifunctionality is a high numerical aperture (NA) Fresnel lens fabricated by two-photon direct laser writing (DLW) corrected by grid-correction methods. We demonstrate trapping and time-resolved, in situ spectroscopy of a single upconversion particle (UCP), a common fluorescent biomarker in biophotonics. The system achieves a 0.5-s time resolution in the in situ spectral measurement of a trapped UCP. The all-fiber designed system preserves the advantages of flexibility and robustness of the fiber, potentially useful for in-vivo biomedical studies such as cell-to-cell interactions, pH and temperature detection, and nucleic acids detection.

High-energy pacing inhibits slow-wave dysrhythmias in the small intestine.

The motility of the gastrointestinal tract is coordinated in part by rhythmic slow waves, and disrupted slow-wave patterns are linked to functional motility disorders. At present, there are no treatment strategies that primarily target slow-wave activity. This study assessed the use of pacing to suppress glucagon-induced slow-wave dysrhythmias in the small intestine. Slow waves in the jejunum were mapped in vivo using a high-resolution surface-contact electrode array in pigs (n = 7). Glucagon was intravenously administered to induce hyperglycemia. Slow-wave propagation patterns were categorized into antegrade, retrograde, collision, pacemaker, and uncoupled activity. Slow-wave characteristics such as period, amplitude, and speed were also quantified. Postglucagon infusion, pacing was applied at 4 mA and 8 mA and the resulting slow waves were quantified spatiotemporally. Antegrade propagation was dominant throughout all stages with a prevalence of 55 ± 38% at baseline. However, glucagon infusion resulted in a substantial and significant increase in uncoupled slow waves from 10 ± 8% to 30 ± 12% (P = 0.004) without significantly altering the prevalence of other slow-wave patterns. Slow-wave frequency, amplitude, and speed remained unchanged. Pacing, particularly at 8 mA, significantly suppressed dysrhythmic slow-wave patterns and achieved more effective spatial entrainment (85%) compared with 4 mA (46%, P = 0.039). This study defined the effect of glucagon on jejunal slow waves and identified uncoupling as a key dysrhythmia signature. Pacing effectively entrained rhythmic activity and suppressed dysrhythmias, highlighting the potential of pacing for gastrointestinal disorders associated with slow-wave abnormalities.NEW & NOTEWORTHY Glucagon was infused in pigs to induce hyperglycemia and the resulting slow-wave response in the intact jejunum was defined in high resolution for the first time. Subsequently, with pacing, the glucagon-induced dysrhythmias were suppressed and spatially entrained for the first time with a success rate of 85%. The ability to suppress slow-wave dysrhythmias through pacing is promising in treating motility disorders that are associated with intestinal dysrhythmias.

Association of Symptoms and Viral Culture Positivity for SARS‐CoV‐2—Tennessee, April–July 2020

ABSTRACTBackgroundUnderstanding how symptoms are associated with SARS‐CoV‐2 culture positivity is important for isolation and transmission control guidelines.MethodsIndividuals acutely infected with SARS‐CoV‐2 in Tennessee and their household contacts were recruited into a prospective study. All participants self‐collected nasal swabs daily for 14 days and completed symptom diaries from the day of illness onset through day 14 postenrollment. Nasal specimens were tested for SARS‐CoV‐2 using RT‐qPCR. Positive specimens with cycle threshold values &lt; 40 were sent to the Centers for Disease Control and Prevention (CDC) for viral culture. First, we modeled the association between symptoms and the risk of culture positivity using an age‐adjusted generalized additive model (GAM) accounting for repeated measurements within participants and a symptom‐day spline. Next, we investigated how timing of symptom resolution was associated with the timing of culture resolution.ResultsIn a GAM restricted to follow‐up days after symptoms began, the odds of a specimen being culture positive was significantly increased on days when wheezing, loss of taste or smell, runny nose, nasal congestion, sore throat, fever, or any symptom were reported. For all symptoms except sore throat, it was more common for participants to have culture resolution before symptom resolution than for culture to resolve after or on the same day as symptom resolution.ConclusionsOverall, symptomatic individuals were more likely to be SARS‐CoV‐2 viral culture positive. For most symptoms, culture positivity was more likely to end before symptoms resolved. However, a proportion of individuals remained culture positive after symptom resolved, across all symptoms.