Epileptic events initiate a large focal increase in metabolism and cerebral blood flow (CBF) to the ictal focus. In contrast, decreases in CBF have been demonstrated surrounding the focus, the etiology of which is unknown i.e. arising either from active shunting of blood or passive steal. The relationship between these events and neuronal activity and metabolism are also unknown. We investigated neurovascular and neurometabolic coupling in the ictal surround using optical imaging of light scattering and cerebral blood volume, autofluorescence imaging (AFI) of flavoproteins, direct measurements of CMRO2 and two-photon imaging of blood vessel diameter in a rat model of ictal events elicited with focal injection of 4-aminopyridine. We discovered a novel phenomenon, in which ictal events are preceded by pre-ictal vasoconstriction of blood vessels in the surround, occurring 1–5 s before seizure onset, which may serve to actively shunt oxygenated blood to the imminently hypermetabolic focus or may be due to small local decreases in metabolism in the surround. Early ictal hypometabolism, transient decreases in cell swelling and CBV in the surround are consistent with early ictal surround inhibition as a precipitating event in seizure onset as well as shaping the evolving propagating ictal wavefront, although the exact mechanism of these cerebraovascular and metabolic changes is currently unknown. AFI was extremely sensitive to the ictal onset zone and may be a useful mapping technique with clinical applications.

Abstract. Frequent monitoring of early-stage burns is necessary for deciding optimal treatment and management. Both superficial and full thickness burns are relatively easy to diagnose based on clinical observation. In between these two extremes are superficial-partial thickness and deep-partial thickness burns. These burns, while visually similar, differ dramatically in terms of clinical treatment and are known to progress in severity over time. The objective of this study was to determine the potential of spatial frequency domain imaging (SFDI) for noninvasively mapping quantitative changes in chromophore and optical properties that may be an indicative of burn wound severity. A controlled protocol of graded burn severity was developed and applied to 17 rats. SFDI data was acquired at multiple near-infrared wavelengths over a course of 3 h. Burn severity was verified using hematoxylin and eosin histology. From this study, we found that changes in water concentration (edema), deoxygenated hemoglobin concentration, and optical scattering (tissue denaturation) to be statistically significant at differentiating superficial partial-thickness burns from deep-partial thickness burns.

In general, fabrication of 2D electronic systems involves transferring the 2D material from one substrate to another in a process called transfer printing. [ 12,13 ] This process relies heavily on the interactions between the 2D material and the various surfaces that it contacts. Adhesion values must allow for the transfer from one substrate to another. By gaining a better understanding of the adhesion energy between 2D materials and the various substrates involved, the transfer process can be improved to allow for the picking up and printing of 2D materials onto arbitrary fl exible and stretchable substrates.Adhesion of 2D materials is also a controlling parameter for device mechanics. As a component in an integrated device, a 2D material will have to make secure contact with supporting substrates, metallic interconnects, other 2D materials, encapsulation layers, and other elements of a complete system. The mechanical interaction between 2D materials and their neighbors is an important parameter that governs the mechanical integrity of the device during thermal and mechanical loadings. Mechanical loading is often prominent during the operation of fl exible 2D devices. For example, strain engineering of 2D materials on polymer substrates can be achieved by deforming the substrate, [ 14 ] but any slippage between 2D materials and the substrate would weaken the strain transfer to the 2D materials and hence limit the tunability. Moreover, slippage between 2D materials and their polymer substrates when the substrate is deformed may lead to buckle delaminations or wrinkles when the substrate is unloaded, [ 15 ] resulting in device degradation.Because of the signifi cance of adhesion, many experimental studies have been carried out to measure the adhesion energy between graphene and stiff substrates, as summarized in a recent review paper. [ 16 ] For example, adhesion energy between exfoliated monolayer graphene and SiO 2 has been measured to be 450 mJ m −2 by a pressurized blister method, [ 17 ] while adhesion of chemical vapor deposited (CVD) monolayer graphene to Si measured by double cantilever peeling method is found to be 357 mJ m −2 . Adhesion between CVD graphene and seed copper has been measured to be 720 mJ m −2 using cantilever method [ 18 ] whereas after transferring CVD graphene to a foreign copper surface, the interface adhesion was found to be only 510 mJ m −2 using a blister test. [ 19 ] 2D systems have great promise as next generation electronic materials but require intimate knowledge of their interactions with their neighbors for device fabrication and mechanical manipulation. Although adhesion between 2D materials and stiff substrates such as silicon and copper has been measured, adhesion between 2D materials and soft polymer substrates remains diffi cult to characterize due to the large deformability of the polymer substrates. In this work, a buckling-based metrology for measuring the adhesion energy between few layer molybdenum disulfi de (MoS 2 ) and soft elastomeric substrates is proposed and de...

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The accumulation of small strokes has been linked to cognitive dysfunction. Although most animal models have focused on the impact of arteriole occlusions, clinical evidence indicates that venule occlusions may also be important. We used two-photon excited fluorescence microscopy to quantify changes in blood flow and vessel diameter in capillaries after occlusion of single ascending or surface cortical venules as a function of the connectivity between the measured capillary and the occluded venule. Clotting was induced by injuring the target vessel wall with femtosecond laser pulses. After an ascending venule (AV) occlusion, upstream capillaries showed decreases in blood flow speed, high rates of reversal in flow direction, and increases in vessel diameter. Surface venule occlusions produced similar effects, unless a collateral venule provided a new drain. Finally, we showed that AVs and penetrating arterioles have different nearest-neighbor spacing but capillaries branching from them have similar topology, which together predicted the severity and spatial extent of blood flow reduction after occlusion of either one. These results provide detailed insights into the widespread hemodynamic changes produced by cortical venule occlusions and may help elucidate the role of venule occlusions in the development of cognitive disorders and other brain diseases.