Nano-perforated graphene sheets have emerged as exciting two-dimensional materials for a broad range of scientific and commercial purposes, due to their modified physicochemical properties as ...compared to native graphene materials. Nanoporous graphene sheets as a class of two-dimensional materials with thicknesses ranging from sub-nanometre to few tens of nanometres, possess high specific surface areas and porous mesh structures with tuneable porosity levels. These properties lead to high densities of unsaturated carbon edges around the pores, making them attractive candidates for applications such as energy storage, separation, sensing or catalysis. Several perforation methodologies have been reported to sculpt pores across graphene structures via etching or guided growth mechanisms. This review focuses on current and emerging nano-perforation methodologies for the two-dimensional graphene materials, and discusses controllable porosity parameters in terms of physical pore size and surface pore density across 2D materials. The relationship between perforation methodology and the achieved porosity level is also discussed and related to electronic or surface reactivity properties. Suggestions towards perforation methodologies in relation to targeted pore size and density, as well as the current challenges hindering scalability of engineering the nanoporous graphene and other similar two-dimensional materials are also highlighted.
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Pain is considered a multidimensional experience that embodies not merely sensation, but also emotion and perception. As is appropriate for this complexity, pain is represented and processed by an ...extensive matrix of cortical and subcortical structures. Of these structures, the cerebellum is gaining increasing attention. Although association between the cerebellum and both acute and chronic pain have been extensively detailed in electrophysiological and neuroimaging studies, a deep understanding of what functions are mediated by these associations is lacking. Nevertheless, the available evidence implies that lobules IV-VI and Crus I are especially pertinent to pain processing, and anatomical studies reveal that these regions connect with higher-order structures of sensorimotor, emotional, and cognitive function. Therefore, we speculate that the cerebellum exerts a modulatory role in pain via its communication with sites of sensorimotor, executive, reward, and limbic function. On this basis, in this review, we propose numerous ways in which the cerebellum might contribute to both acute and chronic pain, drawing particular attention to emotional and cognitive elements of pain. In addition, we emphasise the importance of advancing our knowledge about the relationship between the cerebellum and pain by discussing novel therapeutic opportunities that capitalize on this association.
Chronic Neuropathic Pain: It's about the Rhythm Alshelh, Zeynab; Di Pietro, Flavia; Youssef, Andrew M ...
The Journal of neuroscience,
2016-Jan-20, 2016-01-20, 20160120, Letnik:
36, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The neural mechanisms underlying the development and maintenance of chronic neuropathic pain remain unclear. Evidence from human investigations suggests that neuropathic pain is associated with ...altered thalamic burst firing and thalamocortical dysrhythmia. Additionally, experimental animal investigations show that neuropathic pain is associated with altered infra-slow (<0.1 Hz) frequency oscillations within the dorsal horn and somatosensory thalamus. The aim of this investigation was to determine whether, in humans, neuropathic pain was also associated with altered infra-slow oscillations within the ascending "pain" pathway. Using resting-state functional magnetic resonance imaging, we found that individuals with orofacial neuropathic pain have increased infra-slow oscillatory activity throughout the ascending pain pathway, including within the spinal trigeminal nucleus, somatosensory thalamus, thalamic reticular nucleus, and primary somatosensory cortex. Furthermore, these infra-slow oscillations were temporally coupled across these multiple sites and occurred at frequencies similar to calcium waves in activated astrocytes. The region encompassing the spinal trigeminal nucleus also displayed increased regional homogeneity, consistent with a local spread of neural activity by astrocyte activation. In contrast, no increase in oscillatory behavior within the ascending pain pathway occurred during acute noxious stimuli in healthy individuals. These data reveal increased oscillatory activity within the ascending pain pathway that likely underpins increased thalamocortical oscillatory activity, a self-sustaining thalamocortical dysrhythmia, and the constant perception of pain. Significance statement: Chronic neuropathic pain is associated with altered thalamic firing and thalamocortical dysrhythmia. The mechanisms responsible for these changes remain unknown. In this study, we report in individuals with neuropathic pain increased oscillatory neural activity within the ascending pain pathway with evidence that these changes result from altered neural-astrocyte coupling. We propose a series of neural and glial events after nerve injury that result in the generation of altered thalamocortical activity and a persistent neuropathic pain state. Defining the underlying mechanisms responsible for neuropathic pain is critical if we are to develop more effective treatment regimens.
Translation of the highly promising electrogenerated chemiluminescence (ECL) properties of Ir(
iii
) complexes (with tri-
n
-propylamine (TPrA) as a co-reactant) into a new generation of ECL labels ...for ligand binding assays necessitates the introduction of functionality suitable for bioconjugation. Modification of the ligands, however, can affect not only the photophysical and electrochemical properties of the complex, but also the reaction pathways available to generate light. Through a combined theoretical and experimental study, we reveal the limitations of conventional approaches to the design of electrochemiluminophores and introduce a new class of ECL label, Ir(C^N)
2
(pt-TOxT-Sq)
+
(where C^N is a range of possible cyclometalating ligands, and pt-TOxT-Sq is a pyridyltriazole ligand with trioxatridecane chain and squarate amide ethyl ester), which outperformed commercial Ir(
iii
) complex labels in two commonly used assay formats. Predicted limits on the redox potentials and emission wavelengths of Ir(
iii
) complexes capable of generating ECL
via
the dominant pathway applicable in microbead supported ECL assays were experimentally verified by measuring the ECL intensities of the parent luminophores at different applied potentials, and comparing the ECL responses for the corresponding labels under assay conditions. This study provides a framework to tailor ECL labels for specific assay conditions and a fundamental understanding of the ECL pathways that will underpin exploration of new luminophores and co-reactants.
A new strategy to create iridium(
iii
)-based ECL labels reveals limitations of conventional approaches.
We review our approach to functionally identifying cortical and subcortical areas involved in the generation of spontaneous fluctuations in sympathetic outflow to muscle or skin. We record muscle ...sympathetic nerve activity (MSNA) or skin sympathetic nerve activity (SSNA), via a tungsten microelectrode inserted percutaneously into the common peroneal nerve, at the same time as performing functional magnetic resonance imaging (fMRI) of the brain. By taking advantage of the neurovascular coupling delay associated with BOLD (blood oxygen level dependent) fMRI, and the delay associated with conduction of a burst of sympathetic impulses to the peripheral recording site, we can identify structures in which BOLD signal intensity covaries with MSNA or SSNA. Using this approach, we found MSNA-coupled increases in BOLD signal intensity in the mid-insula and dorsomedial hypothalamus on the left side, and in dorsolateral prefrontal cortex, posterior cingulate cortex, precuneus, ventromedial hypothalamus and rostral ventrolateral medulla on both sides. Conversely, spontaneous bursts of SSNA were positively correlated with BOLD signal intensity in the ventromedial thalamus and posterior insula on the left side, and in the anterior insula, orbitofrontal cortex and frontal cortex on the right side, and in the mid-cingulate cortex and precuneus on both sides. Inverse relationships were observed between MSNA and BOLD signal intensity in the right ventral insula, nucleus tractus solitarius and caudal ventrolateral medulla, and between SSNA and signal intensity in the left orbitofrontal cortex. These results emphasize the contributions of cortical regions of the brain to sympathetic outflow in awake human subjects, and the extensive interactions between cortical and subcortical regions in the ongoing regulation of sympathetic nerve activity to muscle and skin in awake human subjects.
Brain regulation of autonomic function in obstructive sleep apnea (OSA) is disrupted in a sex-specific manner, including in the insula, which may contribute to several comorbidities. The insular gyri ...have anatomically distinct functions with respect to autonomic nervous system regulation; yet, OSA exerts little effect on the organization of insular gyral responses to sympathetic components of an autonomic challenge, the Valsalva. We further assessed neural responses of insular gyri in people with OSA to a static handgrip task, which principally involves parasympathetic withdrawal.
We measured insular function with blood oxygen level dependent functional MRI. We studied 48 newly-diagnosed OSA (age mean±std:46.5±9 years; AHI±std:32.6±21.1 events/hour; 36 male) and 63 healthy (47.2±8.8 years;40 male) participants. Subjects performed four 16s handgrips (1 min intervals, 80% subjective maximum strength) during scanning. fMRI time trends from five insular gyri-anterior short (ASG); mid short (MSG); posterior short (PSG); anterior long (ALG); and posterior long (PLG)-were assessed for within-group responses and between-group differences with repeated measures ANOVA (p<0.05) in combined and separate female-male models; age and resting heart-rate (HR) influences were also assessed.
Females showed greater right anterior dominance at the ASG, but no differences emerged between OSA and controls in relation to functional organization of the insula in response to handgrip. Males showed greater left anterior dominance at the ASG, but there were also no differences between OSA and controls. The males showed a group difference between OSA and controls only in the ALG. OSA males had lower left activation at the ALG compared to control males. Responses were mostly influenced by HR and age; however, age did not impact the response for right anterior dominance in females.
Insular gyri functional responses to handgrip differ in OSA vs controls in a sex-based manner, but only in laterality of one gyrus, suggesting anterior and right-side insular dominance during sympathetic activation but parasympathetic withdrawal is largely intact, despite morphologic injury to the overall structure.
Using fMRI (functional magnetic resonance imaging), we explored the effect of transcranial photobiomodulation on four major resting-state brain networks, namely the sensorimotor, salience, default ...mode and central executive networks, in normal young subjects. We used a vielight transcranial device (810 nm) and compared the scans in 20 subjects (mean age 30.0 ± 2.8 years) after active- and sham-photobiomodulation sessions. Four sets of analysis—independent components, network connectivity, infra-slow oscillatory power and arterial spin labelling—were undertaken. Our results showed that when comparing pre- with post-active and pre- with post-sham photobiomodulation scans, there were no substantial differences in activity across any of the four resting-state networks examined, indicating no clear photobiomodulation effect. When taken together with previous findings, we suggest that the impact of photobiomodulation becomes much clearer only after brain circuitry is altered, for example, after a neurone undergoes some change in its equilibrium or homeostasis, either during pathology or ageing, or during a change in functional activity when individuals are engaged in a specific task (e.g. evoked brain activity).
Complex regional pain syndrome (CRPS) is a painful condition commonly accompanied by movement disturbances and often affects the upper limbs. The basal ganglia motor loop is central to movement, ...however, non‐motor basal ganglia loops are involved in pain, sensory integration, visual processing, cognition, and emotion. Systematic evaluation of each basal ganglia functional loop and its relation to motor and non‐motor disturbances in CRPS has not been investigated. We recruited 15 upper limb CRPS and 45 matched healthy control subjects. Using functional magnetic resonance imaging, infraslow oscillations (ISO) and resting‐state functional connectivity in motor and non‐motor basal ganglia loops were investigated using putamen and caudate seeds. Compared to controls, CRPS subjects displayed increased ISO power in the putamen contralateral to the CRPS affected limb, specifically, in contralateral putamen areas representing the supplementary motor area hand, motor hand, and motor tongue. Furthermore, compared to controls, CRPS subjects displayed increased resting connectivity between these putaminal areas as well as from the caudate body to cortical areas such as the primary motor cortex, supplementary and cingulate motor areas, parietal association areas, and the orbitofrontal cortex. These findings demonstrate changes in basal ganglia loop function in CRPS subjects and may underpin motor disturbances of CRPS.
This study is the first systematic evaluation of functional connectivity of basal ganglia motor and non‐motor territories in CRPS. In CRPS, there is increased ISOs and resting functional connectivity in motor but not in non‐motor basal ganglia territories (except caudate body functional connectivity) compared to controls.
Surface initiated electro-polymerization of acrylamide on carbon fiber with methodically varied amounts of acrylamide monomer and N,N′-methylene bis-acrylamide crosslinker is explored in this study. ...The effect of the polymer coating on tensile strength, Young's modulus, and interfacial properties of carbon fibre in an epoxy resin was determined. A significant improvement in tensile strength, tensile modulus, and interfacial shear strength (IFSS) across all modified samples was observed, with the most notable improvements to tensile strength, tensile modulus and IFSS being 38%, 15% and 192.5%, respectively. This covalently bound polymer coating provides the best kind of solution for the two most crucial limitations of carbon fibre, with the minimum amount of effort, time, and cost.
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