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van der Waals materials exhibit naturally passivated surfaces and an ability to form versatile heterostructures to enable an examination of carrier transport mechanisms not seen in traditional materials. Here, we report a new type of homojunction termed a "band-bending junction" whose potential landscape depends solely on the difference in thickness between the two sides of the junction. Using MoS2 on Au as a prototypical example, we find that surface potential differences can arise from the degree of vertical band bending in thin and thick regions. Furthermore, by using scanning ultrafast electron microscopy, we examine the spatiotemporal dynamics of charge carriers generated at this junction and find that lateral carrier separation is enabled by differences in the band bending in the vertical direction, which we verify with simulations. Band-bending junctions may therefore enable new optoelectronic devices that rely solely on band bending arising from thickness variations to separate charge carriers.

Submergence during germination impedes aerobic metabolisms and limits the growth of most higher plants. However, some wetland plants including rice can germinate under submerged conditions. It has long been hypothesized that the first elongating shoot tissue, the coleoptile, acts as a snorkel to acquire atmospheric oxygen (O2) to initiate the first leaf elongation and seminal root emergence. Here, we obtained direct evidence for this hypothesis by visualizing the spatiotemporal O2 dynamics during submerged germination in rice using a planar O2 optode system. In parallel with the O2 imaging, we tracked the anatomical development of shoot and root tissues in realtime using an automated flatbed scanner. Three hours after the coleoptile tip reached the water surface, O2 levels around the embryo transiently increased. At this time, the activity of alcohol dehydrogenase (ADH), an enzyme critical for anaerobic metabolism, was significantly reduced, and the coleorhiza covering the seminal roots in the embryo was broken. Approximately 10 h after the transient burst in O2, seminal roots emerged. A transient O2 burst around the embryo was shown to be essential for seminal root emergence during submerged rice germination. The parallel application of a planar O2 optode system and automated scanning system can be a powerful tool for examining how environmental conditions affect germination in rice and other plants. [ABSTRACT FROM AUTHOR]

Motivated by the image reconstruction in spatiotemporal imaging, we introduce a concept named diffeomorphic optimal transportation (DOT), which combines the Wasserstein distance with Benamouâ€"Brenier formula in optimal transportation and the flow of diffeomorphisms in large deformation diffeomorphic metric mapping. Using DOT, we propose a new variational model for joint image reconstruction and motion estimation, which is suitable for spatiotemporal imaging involving mass-preserving large diffeomorphic deformations. We further get its equivalent PDE-constrained optimal control formulation. The proposed model is easy-to-implement and solved by an alternating gradient descent algorithm, which is compared against existing alternatives theoretically and numerically. The performance is validated by several numerical experiments in spatiotemporal tomography, where the projection data is time-dependent sparse and/or high-noise. Moreover, we present several extensions based on DOT. Under appropriate conditions, the proposed algorithm can be adapted as a new algorithm to solve the models using quadratic Wasserstein distance. [ABSTRACT FROM AUTHOR]

Mechanoresponsive materials have been studied to visualize and measure stresses in various fields. However, the high-sensitive and spatiotemporal imaging remain a challenging issue. In particular, the time evolutional responsiveness is not easily integrated in mechanoresponsive materials. In the present study, high-sensitive spatiotemporal imaging of weak compression stresses is achieved by time-evolutional controlled diffusion processes using conjugated polymer, capsule, and sponge. Stimuli-responsive polydiacetylene (PDA) is coated inside a sponge. A mechanoresponsive capsule is set on the top face of the sponge. When compression stresses in the range of 6.67-533 kPa are applied to the device, the blue color of PDA is changed to red by the diffusion of the interior liquid containing a guest polymer flowed out of the disrupted capsule. The applied strength (F/N), time (t/s), and impulse (F·t/N s) are visualized and quantified by the red-color intensity. When a guest metal ion is intercalated in the layered structure of PDA to tune the responsivity, the device visualizes the elapsed time (τ/min) after unloading the stresses. PDA, capsule, and sponge play the important roles to achieve the time evolutional responsiveness for the high-sensitive spatiotemporal distribution imaging through the controlled diffusion processes., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

We propose a new variational model for joint image reconstruction and motion estimation applicable to spatiotemporal imaging, which is investigated along a general framework that we present with shape theory. This model consists of two parts, one that conducts modified image reconstruction in a static setting and the other that estimates the motion by sequentially indirect image registration. For the latter, we generalize the large deformation diffeomorphic metric mapping framework into the sequentially indirect registration setting. The proposed model is compared theoretically against alternative approaches (optical flow based model and diffeomorphic motion models), and we demonstrate that the proposed model has desirable properties in terms of the optimal solution. The theoretical derivations and efficient algorithms are also presented for a time-discretized scenario of the proposed model, which show that the optimal solution of the time-discretized version is consistent with that of the time-continuous one, and most of the computational components are the easily implemented linearized deformations. The complexity of the algorithm is analyzed as well. This work is concluded by some numerical examples in two-dimensional space + time tomography with very sparse and/or highly noisy data. [ABSTRACT FROM AUTHOR]

Highlights • The method with photocaged probes for imaging was efficient and spatiotemporal. • The two probes NDPPI and NNDPPI could be applied in cells and human tissues with satisfactory results. • This strategy can be used in other modified reagents for controlling biological function with light. Abstract Two compounds with nitrobenzene-derived caging groups were designed and synthesized for cells and tissues imaging. After 350 nm irradiation, the two reagents can realize highly efficient fluorescence turn on with large Stokes shift. As for the two probes can bare out a common functional group of aldehyde group under UV irradiation, it may be used for detection of cysteine, DNA methylation in a spatiotemporal method with selectivity. The idea of design and synthesis might be used in other modified reagents for controlling biological function with light. [ABSTRACT FROM AUTHOR]

Abstract: Diffuse acoustic or seismic waves are highly sensitive to detect changes of mechanical properties in heterogeneous geological materials. In particular, thanks to acoustoelasticity, we can quantify stress changes by tracking acoustic or seismic relative velocity changes in the material at test. In this paper, we report on a small‐scale laboratory application of an innovative time‐lapse tomography technique named Locadiff to image spatiotemporal mechanical changes on a granite sample under biaxial loading, using diffuse waves at ultrasonic frequencies (300 kHz to 900 kHz). We demonstrate the ability of the method to image reversible stress evolution and deformation process, together with the development of reversible and irreversible localized microdamage in the specimen at an early stage. Using full‐field infrared thermography, we visualize stress‐induced temperature changes and validate stress images obtained from diffuse ultrasound. We demonstrate that the inversion with a good resolution can be achieved with only a limited number of receivers distributed around a single source, all located at the free surface of the specimen. This small‐scale experiment is a proof of concept for frictional earthquake‐like failure (e.g., stick‐slip) research at laboratory scale as well as large‐scale seismic applications, potentially including active fault monitoring. [ABSTRACT FROM AUTHOR]

Okadaic acid (OA) has attracted considerable attention in the fields of human health and public safety because it can cause severe virulence and is widely distributed. Therefore, it is of immediate significance to explore a novel method for highly sensitive, low-consumption, efficient, and convenient OA detection. In this study, a triple-helix molecular switch (THMS)-based light-addressable potentiometric aptasensor (LAPA) is proposed for the highly sensitive and selective label-free detection and spatiotemporal imaging of OA. In this method, a THMS containing an OA aptamer served as the recognition element, and a DNA microarray including a light-addressable potentiometric sensor was designed as the transducer. Meanwhile, poly (allylamine hydrochloride) was modified on the chip surface to enhance DNA absorption and signal detection. A detection platform was constructed to measure signals and scan spatiotemporal images. The realized biosensing system enabled the multichannel detection of OA in a linear range of 0.05–100 nM with low sample consumption, a detection limit of 0.03 nM, and a detection time of 27 min/channel and spatiotemporal imaging analysis with a resolution of 400 µm2/pixel and frame duration of 3.2 min/frame. Considering the technical developing of aptamer-based THMS and micro/nano biosensor, the proposed method will provide a promising approach for label-free detection and spatiotemporal analysis of OA with high sensitivity, specificity, and detection efficiency; low sample dosage; and simple operation. • The THMS-based LAPA realizes unlabeled detection and spatiotemporal analysis of OA. • The THMS-based aptamer improves the sensitivity and selectivity of biosensor. • The LAPS implements multi-channel detection and spatiotemporal imaging. • The PAH modification improves the output signal quality of the transducer. • The self-built platform scans the weak photocurrent automatically and efficiently. [ABSTRACT FROM AUTHOR]

Understanding ultrafast electronic dynamics of the interlayer excitonic states in atomically thin transition metal dichalcogenides is of importance in engineering valleytronics and developing excitonic integrated circuits. In this work, we experimentally explored the ultrafast dynamics of indirect interlayer excitonic states in monolayer type II WSe 2 /ReS 2 heterojunctions using time-resolved photoemission electron microscopy, which reveals its anisotropic behavior. The ultrafast cooling and decay of excited-state electrons exhibit significant linear dichroism. The ab initio theoretical calculations provide unambiguous evidence that this linear dichroism result is primarily associated with the anisotropic nonradiative recombination of indirect interlayer excitonic states. Measuring time-resolved photoemission energy spectra, we have further revealed the ultrafast evolution of excited-state electrons in anisotropic indirect interlayer excitonic states. The findings have important implications for controlling the interlayer moiré excitonic effects and designing anisotropic optoelectronic devices.

In this study, we successfully determined spatiotemporal distribution of curcumin in mice via simple and fast fluorescence detection of native curcumin and stabilized curcumin. We used 2-aminoethyl diphenyl borate (DPBA) as a stabilizer of curcumin, which binds to curcumin and enhances its aqueous stability. After intravenous injection, curcumin and DPBA–curcumin complexes showed similar fluorescence intensities in the brain, pancreas, lungs, and kidneys at 15 min. However, stabilized DPBA–curcumin complexes exhibited much stronger fluorescent signals at metabolically active sites such as liver tissues than native curcumin. After incubation for 1–3 h, native curcumin showed significantly rapid reduction of fluorescent signals, compared to DPBA–curcumin complexes, probably due to degradation and reduction. In addition, complicate extraction procedures inhibited precise fluorescent monitoring of unstable curcumin, which result in different biodistribution of curcumin before and after extraction. Direct fluorescent monitoring could allow evaluation of in vivo distribution and fate of curcumin, which could be also applied to diverse natural polyphenols with fluorescent signals. [ABSTRACT FROM AUTHOR]

Submergence during germination impedes aerobic metabolisms and limits the growth of most higher plants. However, some wetland plants including rice can germinate under submerged conditions. It has long been hypothesized that the first elongating shoot tissue, the coleoptile, acts as a snorkel to acquire atmospheric oxygen (O 2 ) to initiate the first leaf elongation and seminal root emergence. Here, we obtained direct evidence for this hypothesis by visualizing the spatiotemporal O 2 dynamics during submerged germination in rice using a planar O 2 optode system. In parallel with the O 2 imaging, we tracked the anatomical development of shoot and root tissues in real-time using an automated flatbed scanner. Three hours after the coleoptile tip reached the water surface, O 2 levels around the embryo transiently increased. At this time, the activity of alcohol dehydrogenase (ADH), an enzyme critical for anaerobic metabolism, was significantly reduced, and the coleorhiza covering the seminal roots in the embryo was broken. Approximately 10 h after the transient burst in O 2 , seminal roots emerged. A transient O 2 burst around the embryo was shown to be essential for seminal root emergence during submerged rice germination. The parallel application of a planar O 2 optode system and automated scanning system can be a powerful tool for examining how environmental conditions affect germination in rice and other plants., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Shiono, Koshide, Iwasaki, Oguri, Fukao, Larsen and Glud.)

As a powerful signal amplification tool, the DNA walker has been widely applied to detect rare microRNA (miRNA) in vivo . Despite the significant advances, a near-infrared (NIR) light controllable DNA walker for signal amplification powered by an endogenous initiator has not been realized, which is crucial for spatiotemporal imaging of miRNA in living cells with high sensitivity. Herein, we constructed a NIR-photoactivatable DNA walker system, which was powered by endogenous adenosine triphosphate (ATP) for in situ miRNA imaging with spatial and temporal resolution. The system was very stable with an extremely low fluorescent background for the bioimaging in living cells. We employed upconversion nanoparticles (UCNPs) as the carriers of the DNA probe and transducers of converting NIR to UV light. Coupled with the DNA walker fueled by intracellular ATP, a smart system based on the NIR light initiated DNA walker was successfully developed for precise spatiotemporal control in living cells. Triggered by NIR light, the DNA walker could autonomously and progressively travel along the track with the assistance of intracellular ATP. The system has been successfully applied for in situ miRNA imaging in different cell lines with highly spatial and temporal resolution. This strategy can expand NIR photocontrol the DNA walker for precise imaging in a biological system.

Black phosphorus (BP) is an elemental layered material with a strong in-plane anisotropic structure. This structure is accompanied by anisotropic optical, electrical, thermal, and mechanical properties. Despite interest in BP from both fundamental and technical aspects, investigation into the structural dynamics of BP caused by strain fields, which are prevalent for two-dimensional (2D) materials and tune the material physical properties, has been overlooked. Here, we report the morphological dynamics of photoexcited BP membranes observed using time-resolved diffractograms and dark-field images obtained via ultrafast electron microscopy. Aided by 4D reconstruction, we visualize the nonequilibrium bulging of thin BP membranes and reveal that the buckling transition is driven by impulsive thermal stress upon photoexcitation in real time. The bulging, buckling, and flattening (on strain release) showed anisotropic spatiotemporal behavior. Our observations offer insights into the fleeting morphology of anisotropic 2D matter and provide a glimpse into the mapping of transient, modulated physical properties upon impulsive excitation, as well as strain engineering at the nanoscale.

A skin-gas cam that allows continuous imaging of transcutaneous blood volatile organic compounds (VOCs) emanated from human skin was developed. The skin-gas cam is able to reveal the relationship between the local skin conditions and transcutaneous blood VOCs in the field of volatile metabolomics (volatolomics). A ring-type ultraviolet (UV) light-emitting diode was mounted around a camera lens as an excitation light source, which enabled the simultaneous excitation and imaging of fluorescence. A nicotinamide adenine dinucleotide (NAD)-dependent alcohol dehydrogenase (ADH) was used to detect ethanol as a model sample. When gaseous ethanol was applied to an ADH-immobilized mesh that was wetted with an oxidized NAD solution placed in front of the camera, a reduced form of NAD (NADH) was produced through an ADH-mediated reaction. NADH emits fluorescence by UV excitation, and thus, the concentration distribution of ethanol was visualized by measuring the distribution of the fluorescence light intensity from NADH on the ADH-immobilized mesh surface. In this study, a new gas application method that mimicked the release mechanism of transcutaneous gas for quantification of the transcutaneous gas concentration was evaluated. Also, spatiotemporal changes of transcutaneous ethanol for various body parts were measured. As a result, we revealed a relationship between local skin conditions and VOCs that could not be observed previously. In particular, we demonstrated the facile measurement of transdermal gases from around the ear where capillaries are densely distributed below a thin stratum corneum.