Many soft and complex materials exhibit rheological behaviour that evolve spatially in response to changes in their chemical environment, particularly at interfaces. Examples include biopolymer coatings, food products during digestion and personal care products. However, conventional rheological techniques typically operate under static conditions, limiting their ability to capture these coupled time and spatial effects. This presents a significant challenge for understanding processes such as gelation, transport-driven structuring, and interfacial material evolution. Here, we present rheodialysis as an experimental platform that enables in situ rheological measurements under dynamically controlled chemical conditions. The approach integrates a modified rheometer geometry with a membrane-separated flow system, allowing reagents to be introduced non-invasively via diffusion while continuously monitoring rheological properties. This configuration provides precise control over the local chemical environment without disrupting the sample structure. Using alginate hydrogels as a model systems undergoing chemically induced transformations, we demonstrate how rheodialysis can resolve both time-dependent rheological evolution. This work highlights the potential of rheodialysis as a versatile tool for studying soft matter in non-equilibrium conditions. The approach is broadly applicable to systems where external stimuli drive changes in structure and mechanics, offering new opportunities to investigate and optimise processes relevant to formulations, biological systems, and advanced materials.

An increase in cytoplasmic Ca2+ concentration activates multiple cellular activities, including cell division, metabolism, growth, contraction and death. In smooth muscle Ca2+ entry via voltage-dependent Ca2+ channels leads to a relatively uniform increase in cytoplasmic Ca2+ levels that facilitates co-ordinated contraction throughout the cell. However certain functions triggered by voltage-dependent Ca2+ channels require periodic, pulsatile Ca2+ changes. The mechanism by which Ca2+ entry through voltage-dependent channels supports both co-ordinated contraction and distinct cellular responses driven by pulsatile Ca2+ changes is unclear. Here in intact resistance arteries we show that Ca2+ entry via voltage-dependent Ca2+ channels evokes Ca2+ release via inositol triphosphate receptors (IP3Rs), generating repetitive Ca2+ oscillations and waves. We also show that mitochondria play a vital role in regulating Ca2+ signals evoked by voltage-dependent Ca2+ entry by selectively modulating Ca2+ release via IP3Rs. Depolarizing the mitochondrial membrane inhibits Ca2+ release from internal stores, reducing the overall signal-generated Ca2+ influx without altering the signal resulting from voltage-dependent Ca2+ entry. Notably neither Ca2+ entry via voltage-dependent Ca2+ channels nor Ca2+ release via IP3Rs alters mitochondrial location or mitochondrial membrane potential in intact smooth muscle cells. Collectively these results demonstrate that activation of voltage-dependent Ca2+ channels drives Ca2+ entry, which subsequently triggers Ca2+ release from the internal store in smooth muscle cells. Mitochondria selectively regulate this process by modulating IP3R-mediated amplification of Ca2+ signals, ensuring that different cellular responses are precisely controlled. KEY POINTS: In smooth muscle Ca2⁺ entry via voltage-dependent channels produces a uniform Ca2⁺ increase, enabling co-ordinated contraction in each cell. Certain functions, however, require large, pulsatile Ca2⁺ changes rather than a uniform increase. Using advanced imaging in intact arteries, we discovered that voltage-dependent Ca2⁺ entry triggers internal store Ca2⁺ release via IP₃ receptors, generating repetitive Ca2⁺ oscillations and waves. Mitochondria selectively modulate these signals by regulating only IP₃ receptor-mediated release; neither mitochondrial location nor membrane potential is altered by either type of Ca2+ signal. These findings demonstrate how voltage-dependent Ca2⁺ entry supports both co-ordinated contraction and pulsatile Ca2⁺-driven biological responses.

VasoTracker 2 is a collection of open-source tools for blood vessel diameter measurement and vascular physiology research, featuring automated diameter tracking software and low-cost myography hardware components. This blood vessel analysis platform addresses the need for accessible alternatives to expensive commercial vascular imaging systems by providing comprehensive tools for studying vessel reactivity and endothelial function. The software enables multipoint diameter tracking in branched vessels using advanced edge detection algorithms, supporting brightfield microscopy, fluorescence imaging and ultrasound recordings. Automated pressure protocols enable standardized myogenic tone experiments, and both real-time and offline analysis of pre-recorded data are supported. The platform's versatility allows researchers to study vascular dynamics across diverse experimental conditions, from isolated vessel preparations to in vivo imaging applications. For ex vivo applications, VasoTracker 2 includes modular, low-cost open-source pressure myograph hardware: a confocal-compatible vessel chamber and a programmable pressure controller, VasoMoto. These components enable construction of a complete pressure myograph system at a significantly reduced cost compared to commercial alternatives. The hardware integrates seamlessly with the diameter measurement software.VasoTracker 2 provides free software and low-cost hardware for vessel diameter analysis, broadening access to advanced vascular research tools. The platform's open-source nature allows researchers to modify and extend the system for specific applications. This flexibility, combined with significant cost savings, benefits vascular researchers worldwide. KEY POINTS: VasoTracker 2 is an open-source platform that combines versatile vessel diameter tracking software with modular low-cost hardware components for vascular physiology research. The software enables multipoint diameter analysis across brightfield, fluorescence and ultrasound imaging modalities. The hardware includes a confocal-compatible vessel chamber and programmable pressure controller (VasoMoto) that can be assembled into a complete pressure myograph system. The open-source approach provides researchers with accessible tools for advanced vascular physiology experiments.

VasoTracker 2 is an open-source platform for studying blood vessel dynamics, featuring versatile diameter-tracking software and complementary low-cost hardware components. This system surpasses existing tools through accessible, high-resolution analysis across multiple imaging modalities, enabling comprehensive assessment of vascular dynamics in both real-time and pre-recorded experiments. Advanced algorithms enable multi-point diameter tracking in branched vessels, automated pressure-response protocols, and reliable edge detection. The software can assess vessels imaged by brightfield microscopy, fluorescence imaging, and in ultrasound recordings, supporting diverse applications from isolated vessel studies to in vivo assessment. For ex vivo applications, VasoTracker 2 includes modular open-source hardware components that can be used to create a low-cost pressure myograph system: a confocal-compatible vessel chamber and a programmable pressure controller, VasoMoto. By combining powerful analytical capabilities with an open-access approach, VasoTracker 2 provides free software and low-cost hardware alternatives to commercial systems, democratizing access to advanced vascular research tools for scientists worldwide. ### Competing Interest Statement The authors have declared no competing interest.

Our recent THz imaging system performs full-frame high-speed imaging (12000 fps) by exploiting efficient THz-to-optical conversion in an excited Caesium atomic vapour. Structured Illumination Microscopy (SIM) has revolutionized optical microscopy pushing beyond the diffraction limit. At THz frequencies the diffraction limit is measured on the sub-mm scale therefore would benefit from improvement. Implementing Structured Illumination Super Resolution at the THz regime has previously been unattractive due to the long acquisition times of conventional THz detectors, compounded by the requirement of multiple images for super-resolution image reconstruction. Using our high-speed THz imaging system, we investigate the application of Structured Illumination Super Resolution Imaging as a method to improve spatial resolution, while maintaining the high penetrating properties and high detection sensitivity at 0.55THz.

BACKGROUND: Endothelial cell TRPV4 (transient receptor potential vanilloid 4) channels provide a control point that is pivotal in regulating blood vessel diameter by mediating the Ca 2+ -dependent release of endothelial-derived vasoactive factors. In hypertension, TRPV4-mediated control of vascular function is disrupted, but the underlying mechanisms and precise physiological consequences remain controversial. METHODS: Here, using a comprehensive array of methodologies, endothelial TRPV4 channel function was examined in intact mesenteric resistance arteries from normotensive Wistar-Kyoto and spontaneously hypertensive rats. RESULTS: Our results show there is a notable shift in vascular reactivity in hypertension characterized by enhanced endothelium-dependent vasodilation at low levels of TRPV4 channel activation. However, at higher levels of TRPV4 activity, this vasodilatory response is reversed, contributing to the aberrant vascular tone observed in hypertension. The change in response, from dilation to constriction, was accompanied by a shift in intracellular Ca 2+ signaling modalities arising from TRPV4 activity. Oscillatory TRPV4-evoked IP 3 (inositol triphosphate)-mediated Ca 2+ release, which underlies dilation, decreased, while the contraction inducing sustained Ca 2+ rise, arising from TRPV4-mediated Ca 2+ influx, increased. Our findings also reveal that while the sensitivity of endothelial cell TRPV4 to activation was unchanged, expression of the channel is upregulated and IP 3 receptors are downregulated in hypertension. CONCLUSIONS: These data highlight the intricate interplay between endothelial TRPV4 channel expression, intracellular Ca 2+ signaling dynamics, and vascular reactivity. Moreover, the data support a new unifying hypothesis for the vascular impairment that accompanies hypertension. Specifically, endothelial cell TRPV4 channels play a dual role in modulating blood vessel function in hypertension.

Reactive oxygen species (ROS) are naturally produced compounds that play important roles in cell signaling, gene regulation, and biological defense, including involvement in the oxidative burst that is central to the anti-microbial actions of macrophages. However, these highly reactive, short-lived radical species also stimulate cells to undergo programmed cell death at high concentrations, as well as causing detrimental effects such as oxidation of macromolecules at more moderate levels. Imaging ROS is highly challenging, with many researchers working on the challenge over the past 10-15 years without producing a definitive method. We report a new fluorescence microscopy-based technique, Bullseye Analysis. This methodology is based on concepts provided by the FRAP (Fluorescence Recovery after Photobleaching) technique and refined to evidence the spatiotemporal production of ROS, and the subsequent consequences, on a subcellular scale. To exemplify the technique, we have used the ROS-reporter dye, CellROX, and the ROS-inducing photosensitizer, LightOx58, a potent source of ROS compared with UV irradiation alone. Further validation of the technique was carried out using differing co-stains, notably Mitotracker and JC-1.

Significance:Postoperative surgical wound infection is a serious problem around the globe, including in countries with advanced healthcare systems, and a method for early detection of infection is urgently required.Aim:We explore spatial frequency domain imaging (SFDI) for distinguishing changes in surgical wound healing based on the tissue scattering properties and surgical wound width measurements.Approach:A comprehensive numerical method is developed by applying a three-dimensional Monte Carlo simulation to a vertical heterogeneous wound model. The Monte Carlo simulation results are validated using resin phantom imaging experiments.Results:We report on the SFDI lateral resolution with varying reduced scattering value and wound width and discuss the partial volume effect at the sharp vertical boundaries present in a surgical incision. The detection sensitivity of this method is dependent on spatial frequency, wound reduced scattering coefficient, and wound width.Conclusions:We provide guidelines for future SFDI instrument design and explanation for the expected error in SFDI measurements.

This chapter summarizes the entire book and points out some perspectives to the field of OCT applied to dentistry. With the growing importance of noninvasive images for diagnostics, and the need of those methods to arrive at point of care, the subjects treated in this book give the necessary background for the basic and applied research, including clinical uses, of OCT in dentistry. After a brief introduction, each chapter's subject is then reviewed

Light has always been the dentist's first diagnostic tool. Visual inspection of both the teeth and gums is still the first method used by all dental practitioners around the world. A skilled dentist can distinguish between direct reflection from the tooth's surface and light scattered back from the deeper tissue structure and evaluate if mineral is being lost through the caries process. This chapter presents, in basic terms, the way that light can interact with a range of materials covering effects such as reflection, scattering, polarization and fluorescence. These physical processes are then placed into the context of the detection, and subsequent diagnosis, of dental disease. The chapter then explores the technical advances that have been made to help use the effects of the interaction of light with oral tissue, both hard and soft, to aid the dentist. Methods covered include the use of transillumination, fluorescence imaging, near infrared imaging, depth profiling through a lesion and spectroscopic inspection. Some ideas on what features a perfect instrument might provide are discussed and where the dental imaging field may progress to in the future.

Recent studies apparently finding deleterious effects of radiation exposure on cataract formation in birds and voles living near Chernobyl represent a major challenge to current radiation protection regulations. This study conducted an integrated assessment of radiation exposure on cataractogenesis using the most advanced technologies available to assess the cataract status of lenses extracted from fish caught at both Chernobyl in Ukraine and Fukushima in Japan. It was hypothesised that these novel data would reveal positive correlations between radiation dose and early indicators of cataract formation.The structure, function and optical properties of lenses were analysed from atomic to millimetre length scales. We measured the short-range order of the lens crystallin proteins using Small Angle X-Ray Scattering (SAXS) at both the SPring-8 and DIAMOND synchrotrons, the profile of the graded refractive index generated by these proteins, the epithelial cell density and organisation and finally the focal length of each lens.The results showed no evidence of a difference between the focal length, the epithelial cell densities, the refractive indices, the interference functions and the short-range order of crystallin proteins (X-ray diffraction patterns) in lens from fish exposed to different radiation doses. It could be argued that animals in the natural environment which developed cataract would be more likely, for example, to suffer predation leading to survivor bias. But the cross-length scale study presented here, by evaluating small scale molecular and cellular changes in the lens (pre-cataract formation) significantly mitigates against this issue.

Protease‐activated receptor‐1 & ‐2 (PAR1 and PAR2) are expressed widely in cardiovascular tissues including endothelial and smooth muscle cells. PAR1 and PAR2 may regulate blood pressure via changes in vascular contraction or relaxation mediated by endothelial Ca 2+ signaling, but the mechanisms are incompletely understood. By using single‐cell Ca 2+ imaging across hundreds of endothelial cells in intact blood vessels, we explored PAR‐mediated regulation of blood vessel function using PAR1 and PAR2 activators. We show that PAR2 activation evoked multicellular Ca 2+ waves that propagated across the endothelium. The PAR2‐evoked Ca 2+ waves were temporally distinct from those generated by muscarinic receptor activation. PAR2 activated distinct clusters of endothelial cells, and these cells were different from those activated by muscarinic receptor stimulation. These results indicate that distinct cell clusters facilitate spatial segregation of endothelial signal processing. We also demonstrate that PAR2 is a phospholipase C‐coupled receptor that evokes Ca 2+ release from the IP 3 ‐sensitive store in endothelial cells. A physiological consequence of this PAR2 signaling system is endothelium‐dependent relaxation. Conversely, PAR1 activation did not trigger endothelial cell Ca 2+ signaling nor relax or contract mesenteric arteries. Neither did PAR1 activators alter the response to PAR2 or muscarinic receptor activation. Collectively, these results suggest that endothelial PAR2 but not PAR1 evokes mesenteric artery relaxation by evoking IP 3 ‐mediated Ca 2+ release from the internal store. Sensing mediated by PAR2 receptors is distributed to spatially separated clusters of endothelial cells.

The endothelium is the innermost layer of all blood vessels and it controls a host of cardiovascular functions including vascular contractility, hemostasis, inflammation and the exchange of nutrients and waste products between circulating blood and tissue. The importance of the endothelium is clear since changes in the behaviour of this single layer of cells underlies almost all cardiovascular disease. To control each cardiovascular function, the endothelium processes and responds to endless streams of information that originate from multiple sources (i.e. blood cells, hormones, neighboring endothelial cells or underlying smooth muscle cells). To process so much information, the endothelium utilises distributed sensing on spatially-distinct populations of cells that are primed to detect specific activators. These spatially-distinct populations communicate across the endothelial network to coordinate vascular responses. The nature of the endothelial network, and how communication is achieved, is currently not understood. Here, by examining the Ca responses in thousands of endothelial cells in intact arteries, we show how the endothelial network operates. Network organization controls overall system behaviour by determining the signal propagation speed, the robustness of the system to failures and attack, and the degree of synchronizability in the system. To determine the endothelial network structure, we used network (graph) theory. Graph theory has gained much attention due to its ability to quantify social, technological and biological systems, especially the connectivity and synchronisation of the nervous system. However, no studies have examined the network structure employed by the endothelium in the control of cardiovascular function. We analysed muscarinic- and histaminergic-evoked Ca activity from ~1000 endothelial cells from intact resistance arteries. Ca signals were separately analysed in each of the 1000 individual endothelial cells using a custom-written Python algorithm. Ca activity in active cells was cross-correlated and compared to a stochastic model to statistically quantify network connections. We show highly-correlated Ca activities occurred in multiple, separate, cell clusters for each agonist. The network communication links between the clusters exhibited unexpectedly short path-lengths, i.e. the number of links between active cells was significantly shorter than expected when active cells were randomly positioned. The number of connections between active cells (degree distribution) followed a power-law relationship, revealing a scale-free network topology. The path-length and degree distribution reveal an endothelial network with a 'small-world' configuration. The small-world configuration confers particularly dynamic endothelial properties including high signal-propagation speed, stability and a high degree of synchronizability. These findings show that endothelial network design is effective for local and global efficiency in the interaction of cells, and for rapid and robust communication to efficiently control cardiovascular activity. The network organization explains how coordinated cell activity occurs across large regions of endothelium, despite sensing being distributed on spatially-distinct populations of cells.

Remote sensing using passive solar illumination in the Short-Wave Infrared spectrum is exposed to strong intensity variation in the spectral bands due to atmospheric changing conditions and spectral absorption. More robust spectral analysis methods, insensitive to these effects, are increasingly required to improve the accuracy of the data analysis in the field and extend the use of the system to “non ideal” illumination condition. A computational hyperspectral image analysis method (named HIAM) for deriving optimal reflectance indices for use in remote sensing of soil moisture content is detailed and demonstrated. Using histogram analysis of hyperspectral images of wet and dry soil, contrast ratios and wavelength pairings were tested to find a suitable spectral index to recover soil moisture content. Measurements of local soil samples under laboratory and field conditions have been used to demonstrate the robustness of the index to varying lighting conditions, while publicly available databases have been used to test across a selection of soil classes. In both cases, the moisture was recovered with RMS error better than 5%. As the method is independent of material type, this method has the potential to also be applied across a variety of biological and man-made samples.

We present an integrated fiber optic spectrally resolved downwelling irradiance sensor for pushbroom hyperspectral imagers. The system comprises of a cosine corrector and custom fiber patch cables, collecting the ambient light in a large solid angle and feeding it directly to the entrance slit of the spectrometer. The system enables simultaneous measurement of downwelling and upwelling irradiance using the main hyperspectral camera sensor. As a demonstration, the spectral reflectance of a soil sample was measured with a RMSE of 8.4%, a significant improvement on the RMSE of 54% found without correction. At a weight of approximately 10 grams, this system provides a substantial weight saving over standalone incident light sensing instruments.

Every blood vessel is lined by a single layer of highly specialized, yet adaptable and multifunctional endothelial cells. These cells, the endothelium, control vascular contractility, hemostasis, and inflammation and regulate the exchange of oxygen, nutrients, and waste products between circulating blood and tissue. To control each function, the endothelium processes endlessly arriving requests from multiple sources using separate clusters of cells specialized to detect specific stimuli. A well-developed but poorly understood communication system operates between cells to integrate multiple lines of information and coordinate endothelial responses. Here, the nature of the communication network has been addressed using single-cell Ca2+ imaging across thousands of endothelial cells in intact blood vessels. Cell activities were cross-correlated and compared to a stochastic model to determine network connections. Highly correlated Ca2+ activities occurred in scattered cell clusters, and network communication links between them exhibited unexpectedly short path lengths. The number of connections between cells (degree distribution) followed a power-law relationship revealing a scale-free network topology. The path length and degree distribution revealed an endothelial network with a "small-world" configuration. The small-world configuration confers particularly dynamic endothelial properties including high signal-propagation speed, stability, and a high degree of synchronizability. Local activation of small clusters of cells revealed that the short path lengths and rapid signal transmission were achieved by shortcuts via connecting extensions to nonlocal cells. These findings reveal that the endothelial network design is effective for local and global efficiency in the interaction of the cells and rapid and robust communication between endothelial cells in order to efficiently control cardiovascular activity.

Arteries and veins are lined by non-proliferating endothelial cells that play a critical role in regulating blood flow. Endothelial cells also regulate tissue perfusion, metabolite exchange, and thrombosis. It is thought that endothelial cells rely on ATP generated via glycolysis to fuel each of these energy-demanding processes. However, endothelial metabolism has mainly been studied in the context of proliferative cells in angiogenesis, and little is known about energy production in endothelial cells within the fully-formed vascular wall. Using intact arteries isolated from rats and mice, we show that inhibiting mitochondrial oxidative phosphorylation at mitochondrial complex V disrupts calcium-dependent, nitric oxide-mediated endothelial cell control of vascular tone. Basal, mechanically-activated, and agonist-evoked calcium activity in intact artery endothelial cells are each prevented by inhibiting mitochondrial ATP synthesis. This effect is mimicked by blocking the transport of pyruvate, the master fuel for mitochondrial energy production, through the mitochondrial pyruvate carrier. The role for endothelial cell energy production is independent of species, sex, or vascular bed. These data show that mitochondrial ATP is necessary for the obligatory role of endothelial cells in the control of blood vessel diameter, and validate the idea of targeting endothelial cell metabolism to treat endothelial cell dysfunction in cardiovascular disease.

Arteries and veins are lined by nonproliferating endothelial cells that play a critical role in regulating blood flow. Endothelial cells also regulate tissue perfusion, metabolite exchange, and thrombosis. It is thought that endothelial cells rely on ATP generated via glycolysis, rather than mitochondrial oxidative phosphorylation, to fuel each of these energy-demanding processes. However, endothelial metabolism has mainly been studied in the context of proliferative cells, and little is known about energy production in endothelial cells within the fully formed vascular wall. Using intact arteries isolated from rats and mice, we show that inhibiting mitochondrial respiration disrupts endothelial control of vascular tone. Basal, mechanically activated, and agonist-evoked calcium activity in intact artery endothelial cells are each prevented by inhibiting mitochondrial ATP synthesis. Agonist-evoked calcium activity was also inhibited by blocking the transport of pyruvate, the master fuel for mitochondrial energy production, through the mitochondrial pyruvate carrier. The role for mitochondria in endothelial cell energy production is independent of species, sex, or vascular bed. These data show that a mitochondrial ATP supply is necessary for calcium-dependent, nitric oxide-mediated endothelial control of vascular tone, and identifies the critical role of endothelial mitochondrial energy production in fueling perfused blood vessel function.