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Background Transcranial direct current stimulation (tDCS) is a form of noninvasive brain stimulation whose potential as a cognitive therapy is hindered by our limited understanding of how participant and experimental factors influence its effects. Using functional MRI to study brain networks, we have previously shown in healthy controls that the physiological effects of tDCS are strongly influenced by brain state. We have additionally shown, in both healthy and traumatic brain injury (TBI) populations, that the behavioral effects of tDCS are positively correlated with white matter (WM) structure. Objectives In this study we investigate how these two factors, WM structure and brain state, interact to shape the effect of tDCS on brain network activity. Methods We applied anodal, cathodal and sham tDCS to the right inferior frontal gyrus (rIFG) of healthy (n = 22) and TBI participants (n = 34). We used the Choice Reaction Task (CRT) performance to manipulate brain state during tDCS. We acquired simultaneous fMRI to assess activity of cognitive brain networks and used Fractional Anisotropy (FA) as a measure of WM structure. Results We find that the effects of tDCS on brain network activity in TBI participants are highly dependent on brain state, replicating findings from our previous healthy control study in a separate, patient cohort. We then show that WM structure further modulates the brain-state dependent effects of tDCS on brain network activity. These effects are not unidirectional - in the absence of task with anodal and cathodal tDCS, FA is positively correlated with brain activity in several regions of the default mode network. Conversely, with cathodal tDCS during CRT performance, FA is negatively correlated with brain activity in a salience network region. Conclusions Our results show that experimental and participant factors interact to have unexpected effects on brain network activity, and that these effects are not fully predictable by studying the factors in isolation., Highlights • We replicated the brain state and polarity dependent effects of tDCS. • White matter structure influences tDCS's state-dependent changes in neural activity • The parameters of tDCS may operate under a hierarchy of influence.

New helmet technologies have been developed to improve the mitigation of traumatic brain injury (TBI) in bicycle accidents. However, their effectiveness under oblique impacts, which produce more strains in the brain in comparison with vertical impacts adopted by helmet standards, is still unclear. Here we used a new method to assess the brain injury prevention effects of 27 bicycle helmets in oblique impacts, including helmets fitted with a friction-reducing layer (MIPS), a shearing pad (SPIN), a wavy cellular liner (WaveCel), an airbag helmet (Hövding) and a number of conventional helmets. We tested whether helmets fitted with the new technologies can provide better brain protection than conventional helmets. Each helmeted headform was dropped onto a 45° inclined anvil at 6.3 m/s at three locations, with each impact location producing a dominant head rotation about one anatomical axes of the head. A detailed computational model of TBI was used to determine strain distribution across the brain and in key anatomical regions, the corpus callosum and sulci. Our results show that, in comparison with conventional helmets, the majority of helmets incorporating new technologies significantly reduced peak rotational acceleration and velocity and maximal strain in corpus callosum and sulci. Only one helmet with MIPS significantly increased strain in the corpus collosum. The helmets fitted with MIPS and WaveCel were more effective in reducing strain in impacts producing sagittal rotations and a helmet fitted with SPIN in coronal rotations. The airbag helmet was effective in reducing brain strain in all impacts, however, peak rotational velocity and brain strain heavily depended on the analysis time. These results suggest that incorporating different impact locations in future oblique impact test methods and designing helmet technologies for the mitigation of head rotation in different planes are key to reducing brain injuries in bicycle accidents.

Axonal injury is a key determinant of long-term outcomes after traumatic brain injury (TBI) but has been difficult to measure clinically. Fluid biomarker assays can now sensitively quantify neuronal proteins in blood. Axonal components such as neurofilament light (NfL) potentially provide a diagnostic measure of injury. In the multicenter BIO-AX-TBI study of moderate-severe TBI, we investigated relationships between fluid biomarkers, advanced neuroimaging, and clinical outcomes. Cerebral microdialysis was used to assess biomarker concentrations in brain extracellular fluid aligned with plasma measurement. An experimental injury model was used to validate biomarkers against histopathology. Plasma NfL increased after TBI, peaking at 10 days to 6 weeks but remaining abnormal at 1 year. Concentrations were around 10 times higher early after TBI than in controls (patients with extracranial injuries). NfL concentrations correlated with diffusion MRI measures of axonal injury and predicted white matter neurodegeneration. Plasma TAU predicted early gray matter atrophy. NfL was the strongest predictor of functional outcomes at 1 year. Cerebral microdialysis showed that NfL concentrations in plasma and brain extracellular fluid were highly correlated. An experimental injury model confirmed a dose-response relationship of histopathologically defined axonal injury to plasma NfL. In conclusion, plasma NfL provides a sensitive and clinically meaningful measure of axonal injury produced by TBI. This reflects the extent of underlying damage, validated using advanced MRI, cerebral microdialysis, and an experimental model. The results support the incorporation of NfL sampling subacutely after injury into clinical practice to assist with the diagnosis of axonal injury and to improve prognostication.

The long-term effects of elite contact sports participation on brain health are poorly understood. This clinic aims to provide expert clinical review of retired players with neurocognitive and neuropsychiatric symptoms and, in an integrated research programme, better understand their neurological outcomes.Former professional rugby players aged 30-55 are eligible, expanding to include footballers and control participants shortly. Assessment includes questionnaires documenting head injury exposure (Ohio State Method), substance use, affective, sleep, post-traumatic and post-concussive symptoms, quality of life and behavioural difficulties, including caregiver collateral. 3T MRI is acquired incorporating volumetric T1w, FLAIR, DTI, SWI and resting state-fMRI. Blood markers of neuronal damage and neurodegeneration are taken including neurofilament light and ptau181. Plasma/serum are stored for further research analyses. Neuropsychological performance is assessed including working memory, processing speed, executive functioning and performance validity testing. Participants undergo neurological review, receiving indi- vidual level multidisciplinary assessment and support. Assessment is repeated longitudinally after two and four years.We will test the relationship of head injury exposure, genotype, biomarkers of injury and neurodegenera- tion, cognitive, neuropsychiatric and functional status. Sub-studies incorporating 7T MRI and tau PET are planned to further clarify disease mechanisms. The work is funded by but performed independently of the Rugby Football Union.

BackgroundRugby is a collision sport with high rates of head injury. The effect of rugby participation at the elite level on cerebral grey matter structure is unclear.MethodsData from 44 active professional rugby players, including 21 acquired within one week of mild traumatic brain injury, and 47 healthy controls were analysed. Whole-cortex and region of interest analyses investigating the effects of rugby participation, sub-acute mild traumatic brain injury, and biomarkers of traumatic brain injury (fractional anisotropy, plasma neurofilament light and glial fibrillary acidic protein) on cortical thickness were performed. Plasma neurofilament light and glial fibrillary acidic protein concen- trations were measured using Single molecule array technology.ResultsWhole-cortex analysis revealed evidence of lower right hemisphere precentral cortical thickness in non-injured rugby players compared to controls. In region of interest analyses, there was evidence rugby participation predicted lower cortical thickness in the inferior part of the precentral sulcus (right hemisphere). In the same region, there was evidence sub-acute mild traumatic brain injury predicted higher cortical thickness compared to non-injured players, and that plasma glial fibrillary acidic protein was positively associated with cortical thickness in players with sub-acute mild traumatic brain injury. No associations with neurofilament light concentration were found.ConclusionWe present evidence that elite rugby participation predicts alterations in cortical thickness. Larger scale study with prolonged follow-up to understand the clinical implications of these findings is warranted.

The recognition, diagnosis and management of mild traumatic brain injuries are difficult and confusing. It is unclear how the severity and number of injuries sustained relate to brain injuries, such as diffuse axonal injury, diffuse vascular injury and progressive neurodegeneration. Advances in neuroimaging techniques enable the investigation of neuropathologies associated with acute and long-term effects of injury. Head injuries are the most commonly reported injury seen during professional rugby. There is increased vigilance for the immediate effects of these injuries in matches, but there has been surprisingly little research investigating the longer-term effects of rugby participation. Here, we present a longitudinal observational study investigating the relationship of exposure to rugby participation and sub-acute head injuries in professional adult male and female rugby union and league players using advanced MRI. Diffusion tensor imaging and susceptibility weighted imaging was used to assess white matter structure and evidence of axonal and diffuse vascular injury. We also studied changes in brain structure over time using Jacobian Determinant statistics extracted from serial volumetric imaging. We tested 41 male and 3 female adult elite rugby players, of whom 21 attended study visits after a head injury, alongside 32 non-sporting controls, 15 non-collision-sport athletic controls and 16 longitudinally assessed controls. Eighteen rugby players participated in the longitudinal arm of the study, with a second visit at least 6 months after their first scan. Neuroimaging evidence of either axonal injury or diffuse vascular injury was present in 23% (10/44) of players. In the non-acutely injured group of rugby players, abnormalities of fractional anisotropy and other diffusion measures were seen. In contrast, non-collision-sport athletic controls were not classified as showing abnormalities. A group level contrast also showed evidence of sub-acute injury using diffusion tensor imaging in rugby players. Examination of longitudinal imaging revealed unexpected reductions in white matter volume in the elite rugby players studied. These changes were not related to self-reported head injury history or neuropsychological test scores and might indicate excess neurodegeneration in white matter tracts affected by injury. Taken together, our findings suggest an association of participation in elite adult rugby with changes in brain structure. Further well-designed large-scale studies are needed to understand the impact of both repeated sports-related head impacts and head injuries on brain structure, and to clarify whether the abnormalities we have observed are related to an increased risk of neurodegenerative disease and impaired neurocognitive function following elite rugby participation., Using advanced neuroimaging techniques to study a group of professional rugby players, Zimmerman et al. report evidence of both cross-sectional and longitudinal imaging abnormalities in the white matter. Their findings suggest an association of participation in elite adult rugby with changes in brain structure., Graphical Abstract Graphical Abstract

To further fulfil their missions of promoting teaching, education and research in neurology and related clinical-academic disciplines, the Guarantors of Brain and the Brain journal family invited delegates to the first Brain Conference in Spring of this year. This event aimed to deliver excellent teaching and scientific presentations across a broad spectrum of neuroscience fields, with the key aim of making the content as accessible as possible. We hoped to capitalize on the benefits of an online format, whilst trying to capture a little of the joy of the in-person meeting. This article reports on the approach and practical choices made to achieve these goals, and we hope this will provide some guidance and advice to others organizing their own online conference., Li et al. report on what went on ‘behind the scenes’ of the first Brain Conference, which took place in March 2021. Programming, technology and organizational choices are described, as well as reflections on what went well and what should be improved for future events.

BackgroundTranscranial direct current stimulation (tDCS) is a form of noninvasive brain stimulation whose potential as a cognitive therapy is hindered by our limited understanding of how participant and experimental factors influence its effects. Using functional MRI to study brain networks, we have previously shown in healthy controls that the physiological effects of tDCS are strongly influenced by brain state. We have additionally shown, in both healthy and traumatic brain injury (TBI) populations, that the behavioral effects of tDCS are positively correlated with white matter (WM) structure.ObjectivesIn this study we investigate how these two factors, WM structure and brain state, interact to shape the effect of tDCS on brain network activity.MethodsWe applied anodal, cathodal and sham tDCS to the right inferior frontal gyrus (rIFG) of healthy (n=22) and TBI participants (n=34). We used the Choice Reaction Task (CRT) performance to manipulate brain state during tDCS. We acquired simultaneous fMRI to assess activity of cognitive brain networks and used Fractional Anisotropy (FA) as a measure of WM structure.ResultsWe find that the effects of tDCS on brain network activity in TBI participants are highly dependent on brain state, replicating findings from our previous healthy control study in a separate, patient cohort. We then show that WM structure further modulates the brain-state dependent effects of tDCS on brain network activity. These effects are not unidirectional – in the absence of task with anodal and cathodal tDCS, FA is positively correlated with brain activity in several regions of the default mode network. Conversely, with cathodal tDCS during CRT performance, FA is negatively correlated with brain activity in a salience network region.ConclusionsOur results show that experimental and participant factors interact to have unexpected effects on brain network activity, and that these effects are not fully predictable by studying the factors in isolation.

Jolly et al. develop a diffusion MRI pipeline for the diagnosis of axonal injury in individual patients with traumatic brain injury. They demonstrate the sensitivity of this pipeline for detecting axonal injury, show its relationship to clinical measures, and provide practical guidelines for its use in subacute and chronic TBI., Poor outcomes after traumatic brain injury (TBI) are common yet remain difficult to predict. Diffuse axonal injury is important for outcomes, but its assessment remains limited in the clinical setting. Currently, axonal injury is diagnosed based on clinical presentation, visible damage to the white matter or via surrogate markers of axonal injury such as microbleeds. These do not accurately quantify axonal injury leading to misdiagnosis in a proportion of patients. Diffusion tensor imaging provides a quantitative measure of axonal injury in vivo, with fractional anisotropy often used as a proxy for white matter damage. Diffusion imaging has been widely used in TBI but is not routinely applied clinically. This is in part because robust analysis methods to diagnose axonal injury at the individual level have not yet been developed. Here, we present a pipeline for diffusion imaging analysis designed to accurately assess the presence of axonal injury in large white matter tracts in individuals. Average fractional anisotropy is calculated from tracts selected on the basis of high test-retest reliability, good anatomical coverage and their association to cognitive and clinical impairments after TBI. We test our pipeline for common methodological issues such as the impact of varying control sample sizes, focal lesions and age-related changes to demonstrate high specificity, sensitivity and test-retest reliability. We assess 92 patients with moderate-severe TBI in the chronic phase (≥6 months post-injury), 25 patients in the subacute phase (10 days to 6 weeks post-injury) with 6-month follow-up and a large control cohort (n = 103). Evidence of axonal injury is identified in 52% of chronic and 28% of subacute patients. Those classified with axonal injury had significantly poorer cognitive and functional outcomes than those without, a difference not seen for focal lesions or microbleeds. Almost a third of patients with unremarkable standard MRIs had evidence of axonal injury, whilst 40% of patients with visible microbleeds had no diffusion evidence of axonal injury. More diffusion abnormality was seen with greater time since injury, across individuals at various chronic injury times and within individuals between subacute and 6-month scans. We provide evidence that this pipeline can be used to diagnose axonal injury in individual patients at subacute and chronic time points, and that diffusion MRI provides a sensitive and complementary measure when compared to susceptibility weighted imaging, which measures diffuse vascular injury. Guidelines for the implementation of this pipeline in a clinical setting are discussed.

Mild traumatic brain injury is a relatively common event in contact sports and there is increasing interest in the long-term neurocognitive effects. The diagnosis largely relies on symptom reporting and there is a need for objective tools to aid diagnosis and prognosis. There are recent reports that blood biomarkers could potentially help triage patients with suspected injury and normal CT findings. We have measured plasma concentrations of glial and neuronal proteins and explored their potential in the assessment of mild traumatic brain injury in contact sport. We recruited a prospective cohort of active male rugby players, who had pre-season baseline plasma sampling. From this prospective cohort, we recruited 25 players diagnosed with mild traumatic brain injury. We sampled post-match rugby players without head injuries as post-match controls. We measured plasma neurofilament light chain, tau and glial fibrillary acidic protein levels using ultrasensitive single molecule array technology. The data were analysed at the group and individual player level. Plasma glial fibrillary acidic protein concentration was significantly increased 1-h post-injury in mild traumatic brain injury cases compared to the non-injured group (P = 0.017). Pairwise comparison also showed that glial fibrillary acidic protein levels were higher in players after a head injury in comparison to their pre-season levels at both 1-h and 3- to 10-day post-injury time points (P = 0.039 and 0.040, respectively). There was also an increase in neurofilament light chain concentration in brain injury cases compared to the pre-season levels within the same individual at both time points (P = 0.023 and 0.002, respectively). Tau was elevated in both the non-injured control group and the 1-h post-injury group compared to pre-season levels (P = 0.007 and 0.015, respectively). Furthermore, receiver operating characteristic analysis showed that glial fibrillary acidic protein and neurofilament light chain can separate head injury cases from control players. The highest diagnostic power was detected when biomarkers were combined in differentiating 1-h post-match control players from 1-h post-head injury players (area under curve 0.90, 95% confidence interval 0.79–1.00, P, Neuro-astrocytic proteins are potential blood markers of traumatic brain injury. We report significant increases in glial fibrillary acidic protein and neurofilament light chain in sports-related mild traumatic brain injury compared to post-match controls and demonstrate their potential as biomarkers; total-tau was increased in post-match controls and mild traumatic brain injury., Graphical Abstract Graphical Abstract

Traumatic brain injury is associated with elevated rates of neurodegenerative diseases such as Alzheimer’s disease and chronic traumatic encephalopathy. In experimental models, diffuse axonal injury triggers post-traumatic neurodegeneration, with axonal damage leading to Wallerian degeneration and toxic proteinopathies of amyloid and hyperphosphorylated tau. However, in humans the link between diffuse axonal injury and subsequent neurodegeneration has yet to be established. Here we test the hypothesis that the severity and location of diffuse axonal injury predicts the degree of progressive post-traumatic neurodegeneration. We investigated longitudinal changes in 55 patients in the chronic phase after moderate–severe traumatic brain injury and 19 healthy control subjects. Fractional anisotropy was calculated from diffusion tensor imaging as a measure of diffuse axonal injury. Jacobian determinant atrophy rates were calculated from serial volumetric T1 scans as a measure of measure post-traumatic neurodegeneration. We explored a range of potential predictors of longitudinal post-traumatic neurodegeneration and compared the variance in brain atrophy that they explained. Patients showed widespread evidence of diffuse axonal injury, with reductions of fractional anisotropy at baseline and follow-up in large parts of the white matter. No significant changes in fractional anisotropy over time were observed. In contrast, abnormally high rates of brain atrophy were seen in both the grey and white matter. The location and extent of diffuse axonal injury predicted the degree of brain atrophy: fractional anisotropy predicted progressive atrophy in both whole-brain and voxelwise analyses. The strongest relationships were seen in central white matter tracts, including the body of the corpus callosum, which are most commonly affected by diffuse axonal injury. Diffuse axonal injury predicted substantially more variability in white matter atrophy than other putative clinical or imaging measures, including baseline brain volume, age, clinical measures of injury severity and microbleeds (>50% for fractional anisotropy versus

Traumatic brain injury (TBI) can trigger progressive neurodegeneration, with tau pathology seen years after a single moderate-severe TBI. Identifying this type of posttraumatic pathology in vivo might help to understand the role of tau pathology in TBI pathophysiology. We used flortaucipir positron emission tomography (PET) to investigate whether tau pathology is present many years after a single TBI in humans. We examined PET data in relation to markers of neurodegeneration in the cerebrospinal fluid (CSF), structural magnetic resonance imaging measures, and cognitive performance. Cerebral flortaucipir binding was variable, with many participants with TBI showing increases in cortical and white matter regions. At the group level, flortaucipir binding was increased in the right occipital cortex in TBI when compared to healthy controls. Flortaucipir binding was associated with increased total tau, phosphorylated tau, and ubiquitin carboxyl-terminal hydrolase L1 CSF concentrations, as well as with reduced fractional anisotropy and white matter tissue density in TBI. Apolipoprotein E (APOE) e4 genotype affected the relationship between flortaucipir binding and time since injury, CSF β amyloid 1–42 (Aβ42) concentration, white matter tissue density, and longitudinal Mini-Mental State Examination scores in TBI. The results demonstrate that tau PET is a promising approach to investigating progressive neurodegeneration associated with tauopathy after TBI.

The behavioural effects of non-invasive brain stimulation are highly variable. Li et al. show that the effects of transcranial direct current stimulation on cognitive function after traumatic brain injury are heavily influenced by white matter damage within the stimulated network. A personalized approach to selecting stimulation parameters may therefore be required., Non-invasive brain stimulation has been widely investigated as a potential treatment for a range of neurological and psychiatric conditions, including brain injury. However, the behavioural effects of brain stimulation are variable, for reasons that are poorly understood. This is a particular challenge for traumatic brain injury, where patterns of damage and their clinical effects are heterogeneous. Here we test the hypothesis that the response to transcranial direct current stimulation following traumatic brain injury is dependent on white matter damage within the stimulated network. We used a novel simultaneous stimulation-MRI protocol applying anodal, cathodal and sham stimulation to 24 healthy control subjects and 35 patients with moderate/severe traumatic brain injury. Stimulation was applied to the right inferior frontal gyrus/anterior insula node of the salience network, which was targeted because our previous work had shown its importance to executive function. Stimulation was applied during performance of the Stop Signal Task, which assesses response inhibition, a key component of executive function. Structural MRI was used to assess the extent of brain injury, including diffusion MRI assessment of post-traumatic axonal injury. Functional MRI, which was simultaneously acquired to delivery of stimulation, assessed the effects of stimulation on cognitive network function. Anodal stimulation improved response inhibition in control participants, an effect that was not observed in the patient group. The extent of traumatic axonal injury within the salience network strongly influenced the behavioural response to stimulation. Increasing damage to the tract connecting the stimulated right inferior frontal gyrus/anterior insula to the rest of the salience network was associated with reduced beneficial effects of stimulation. In addition, anodal stimulation normalized default mode network activation in patients with poor response inhibition, suggesting that stimulation modulates communication between the networks involved in supporting cognitive control. These results demonstrate an important principle: that white matter structure of the connections within a stimulated brain network influences the behavioural response to stimulation. This suggests that a personalized approach to non-invasive brain stimulation is likely to be necessary, with structural integrity of the targeted brain networks an important criterion for patient selection and an individualized approach to the selection of stimulation parameters.

American football players are frequently exposed to head impacts, which can cause concussions and may lead to neurodegenerative diseases such as chronic traumatic encephalopathy (CTE). Player position appears to influence the risk of concussion but there is limited work on its effect on the risk of CTE. Computational modelling has shown that large brain deformations during head impacts co-localise with CTE pathology in sulci. Here we test whether player position has an effect on brain deformation within the sulci, a possible biomechanical trigger for CTE. We physically reconstructed 148 head impact events from video footage of American Football games. Players were separated into 3 different position profiles based on the magnitude and frequency of impacts. A detailed finite element model of TBI was then used to predict Green-Lagrange strain and strain rate across the brain and in sulci. Using a one-way ANOVA, we found that in positions where players were exposed to large magnitude and low frequency impacts (e.g. defensive back and wide receiver), strain and strain rate across the brain and in sulci were highest. We also found that rotational head motion is a key determinant in producing large strains and strain rates in the sulci. Our results suggest that player position has a significant effect on impact kinematics, influencing the magnitude of deformations within sulci, which spatially corresponds to where CTE pathology is observed. This work can inform future studies investigating different player-position risks for concussion and CTE and guide design of prevention systems.

Background: Multiple sclerosis (MS) is characterised by a diffuse inflammatory response mediated by microglia and astrocytes. Brain translocator protein (TSPO) positron-emission tomography (PET) and [myo-inositol] magnetic resonance spectroscopy (MRS) were used together to assess this. Objective: To explore the in vivo relationships between MRS and PET [11C]PBR28 in MS over a range of brain inflammatory burden. Methods: A total of 23 patients were studied. TSPO PET imaging with [11C]PBR28, single voxel MRS and conventional magnetic resonance imaging (MRI) sequences were undertaken. Disability was assessed by Expanded Disability Status Scale (EDSS) and Multiple Sclerosis Functional Composite (MSFC). Results: [11C]PBR28 uptake and [ myo-inositol] were not associated. When the whole cohort was stratified by higher [11C]PBR28 inflammatory burden, [ myo-inositol] was positively correlated to [11C]PBR28 uptake (Spearman’s ρ = 0.685, p = 0.014). Moderate correlations were found between [11C]PBR28 uptake and both MRS creatine normalised N-acetyl aspartate (NAA) concentration and grey matter volume. MSFC was correlated with grey matter volume (ρ = 0.535, p = 0.009). There were no associations between other imaging or clinical measures. Conclusion: MRS [ myo-inositol] and PET [11C]PBR28 measure independent inflammatory processes which may be more commonly found together with more severe inflammatory disease. Microglial activation measured by [11C]PBR28 uptake was associated with loss of neuronal integrity and grey matter atrophy.

The last three decades have seen significant improvements in power system protection. With the rise of digital relays, recalibration during maintenance tests became obsolete. The model of one IEEE element per electromechanical relay is not the case anymore. Digital relays build a system of elements freely combinable with programmable logic conditions. Additionally, to be able to protect the increasingly complex power system, these relays communicate with other relays, building an even bigger system. This being said, with few exceptions, like the use of RTDS (real-time-digital simulator) to simulate real world test cases, protection testing has neither changed significantly since the days of one element per electromechanical relay, nor adapted to the new challenges.

This paper describes several commonly applied line protection schemes, including distance schemes, directional comparison schemes using distance and directional elements, and line current differential schemes. Using analysis tools like fault trees, power system studies, and event analysis, we evaluate and compare these protection schemes in terms of speed, sensitivity, dependability, security, and selectivity. The paper considers the use of various communications channels, including direct relay-to-relay fiber-optic channels and multiplexed digital fiber-optic networks. The paper also discusses some practical considerations for evaluating line protection schemes when faced with complications like series compensation, mutual coupling, single-pole tripping and reclosing, three-terminal lines, and short lines.

This simulator experiment compares driver behavior in the Dilemma Zone (DZ) on a 4-lane divided highway using three types of warnings of impending traffic signal end of green to no advance warning (control). The DZ occurs when onset of a yellow signal occurs at a temporal interval before an intersection such that stopping or proceeding through the intersection has roughly equal perceived risk. Two of the systems allowed lane specific warnings and one did not. Sixty-nine participants drove a total of 45 minutes in the right lane of on a multilane highway with 36 intersections. On approach to 10 of the intersections, participants were placed in the DZ. For 6 other intersections drivers (still in the right lane) were exposed to a warning not intended for them but for a driver behind them in the left lane. Participants in all warning conditions received warnings 1.5 s or 3.0 s in advance of the end of green. Drivers in all of the advanced warning conditions stopped at the DZ intersections significantly more often than control condition drivers. When stopping at intersections, drivers given an advanced warning decelerated more gradually than those that had no warning. One exception was when drivers misinterpreted the left lane warning as intended for them and therefore decelerated rapidly to stop at the intersection.

High-speed signalized intersections present a grave hazard to the traveling public. An important component of this hazard is variation in the process of deciding whether to stop or proceed that occurs in the dilemma zone. To mitigate the dilemma zone problem, an innovative vehicle-specific detection, control, and warning system (DCWS) is being developed. To reduce dilemma zone conflicts, DCWS uses detection of individual vehicle speeds to provide unique, speed-specific dilemma zone protection for each vehicle as it approaches a signalized intersection. Although protecting all vehicles would be ideal, under some situations such protection is not possible. To account for these situations, DCWS also uses a vehicle-specific in-pavement system to give advance warning to drivers who are going to be trapped in the dilemma zone. With hardware-in-the-loop simulations, the new DCWS outperforms conventional dilemma zone warning systems in terms of the number of vehicles in the dilemma zone, the number and percentage of vehicles requiring warning, and the number of warning events per hour.

Horizontal curves have been identified as a target area for improving safety on rural two-lane highways in Texas. This study involved the development of multinomial logit models to assess driver injury severity resulting from single-vehicle crashes on such roads. Likelihood ratio tests warranted the development of separate injury severity models for curves of small, medium, and large radius. Various driver, vehicle, roadway, and environmental characteristics were found to affect injury severity among the 10,029 crashes analyzed. Run-off-the-road crashes, particularly those resulting in collisions with roadside objects, were found to increase injury severity significantly. Females were more likely to sustain injury and older drivers to be critically injured, particularly on curves of smaller radius. Various driver actions and behaviors were also significant determinants of injury severity. Unbelted drivers were up to 10 times more likely to suffer fatal injuries, and drivers who were uninsured, fatigued, or under the influence of drugs or alcohol were more likely to be seriously injured. Several of these behavioral factors were more pronounced on sharper curves.

The research on the effects of roadway geometry on truck crashes is relatively limited in comparison with predictive models developed for total vehicle crashes. The most common predictive models currently used are Poisson and negative binomial models. This study uses a negative binomial model but applies the full Bayes’ methods for improving model performance. To use Bayes’ methods successfully, a learning process was used to develop a final model, which was then compared with a separate validation data set to verify its accuracy. The data set used for this study is based on rural two-lane collector and arterial horizontal curves in Ohio, comprising 15,390 observations from crash records between 2002 through 2006. Specific areas of interest in this study include the impact of shoulder width, horizontal curve radius, curve length, and other traffic parameters. The final results indicate a significant increase in truck crashes due to both horizontal curvature and passenger vehicle volumes. The final model's predictions were improved compared with the initial model, indicating that the learning process is a viable tool for future crash model development.

Modern microprocessor-based relays are designed to provide robust and reliable protection even with disruptions in the dc supply, dc control circuits, or interconnected communications system. Noisy battery voltage supplies, interruptions in the dc supply, and communications interference are just a few of the challenges that relays encounter. This paper provides field cases that investigate protection system performance when systems are subjected to unexpected switching or interruptions in dc or communications links. The discussion emphasizes the importance of environmental and design type testing, proper dc control circuit design and application, reliable and safe operating and maintenance practices with respect to dc control circuits and power supplies, and considerations for reliable communications design, installation, and testing. Some practical recommendations are made with regard to engineering design and operations interface with equipment to improve protection reliability and reduce the possibility of undesired operations.

The problem of red light running is widespread and growing; its cost to society is significant. However, the literature is void of quantitative guidelines that can be used to identify and treat problem locations. Moreover, there has been concern voiced over the validity of various methods used to identify problem locations, especially when automated enforcement is being considered. This paper documents the development of a procedure for identifying and ranking intersection approaches with the potential for improvement in the area of crashes related to red lights. One component of this procedure is a safety prediction model. A sensitivity analysis of this model indicates that red light–related crashes decrease with an increase in duration of the yellow interval and a reduction in the speed limit.

An innovative detection–control system was developed for the Texas Department of Transportation to reduce both delay and crash frequency at rural intersections. This system was implemented at several intersections in Texas, and its safety and operational benefits were evaluated. This report documents findings and conclusions reached after a 3-year implementation project. The detection–control system was installed and evaluated at each of five intersections in Texas during the 3-year period. Evaluation of before-and-after data indicates that the new detection–control system was able to reduce approach delay by 14%, stop frequency by 9%, red light violations by 58%, heavy-vehicle red light violations by 80%, and severe crash frequency by 39%.

This paper describes a research effort to determine the time into red of 63 red light–related crashes. From these 63 crashes, the relationship of time into red and the red light–related crash type is explored, as are relationships to other factors. From the red light–related crashes investigated, it was found that red light–related crash type was related to time into red. Other factors were not found to be related to time into red, although the sample size and selection method prevented any definitive findings. A brief discussion of the possible safety effectiveness of the all-red interval is also included. The time into red of red light–related crashes is related to the time into red of red light violations, so a characterization of red light violations and crashes is provided, along with suggested red light violation countermeasure classifications for each type of red light violation.

A procedure that can be used to compare a variety of common interchange types or make decisions about their design is described. The technique is based on the critical movement analysis approach traditionally used for signalized intersection analysis. This approach defines the rules for quantifying the sum of critical flow ratios for various interchange types. The concept of interchange delay is defined, and an equation for quantifying it is described. Simulation data are used to calibrate a series of models that relate the sum of critical flow ratio to interchange delay. A procedure that describes how these models can be used to obtain a quick estimate of the delay associated with a particular interchange type, given specific volume levels, lane assignments, and ramp separation distances, is documented.

Introduction Traumatic brain injury (TBI) disrupts salience (SN) and default mode brain network (DMN) function, causing dysexecutive problems. A possible treatment is to modulate network function using transcranial direct current stimulation (tDCS). Objective To investigate the effects of tDCS on network and cognitive function after TBI. Methods 26 healthy subjects and 15 TBI patients underwent simultaneous MRI-tDCS. They performed the Stop Signal Task (SST) under sham, anodal tDCS or cathodal tDCS of the right inferior frontal gyrus (rIFG). Results Patients had damage to structural connexions within the SN, associated with abnormal DMN activity. rIFG TDCS modulated SN and DMN activity and functional connectivity in a polarity dependent way. An overall effect of stimulation on SST performance was not seen. However, behavioural improvements were seen with anodal stimulation that depended on the network structural integrity. Across all subjects, higher SN structural integrity was associated with improved SST performance during anodal stimulation. Conclusions Our results show that rIFG tDCS modulates SN and DMN function in a polarity dependent manner. The effects of stimulation interact with network structural integrity. This suggests that an understanding the pattern of axonal injury will be important for achieving beneficial behavioural effects of tDCS following TBI.

Objective: We investigated whether intelligent advanced warnings of the end of green traffic signals help drivers negotiate the dilemma zone (DZ) at signalized intersections and sought to identify behavioral mechanisms for any warning-related benefits. Background: Prior research suggested that warnings of end of green can increase slowing and stopping frequency given the DZ, but drivers may sometimes respond to warnings by speeding up. Method: In two simulator studies, we compared six types of roadway or in-vehicle warnings with a no-warning control condition. Using multilevel modeling, we tested mediation models of the behavioral mechanisms underlying the effects of warnings. Results: In both studies, warnings led to more stopping at DZ intersections and milder decelerations when stopping compared with no warning. Drivers’ predominant response to warnings was anticipatory slowing on approaching the intersection, not speeding up. The increased stopping with warning was mediated by increased slowing. In Study 1, anticipatory slowing given warnings generalized to green-light intersections where no warning was given. In Study 2, we found that lane-specific warnings (e.g., LED lights embedded in each lane) sometimes led to fewer unsafe emergency stops than did non-lane-specific roadside warnings. Conclusion: End-of-green warnings led to safer behavior in the DZ and on the early approach to intersections. The main mechanism for the benefits of warnings was drivers’ increased anticipatory slowing on approaching an intersection. Lane-specific warnings may have some benefits over roadside warnings. Application: Applications include performance models of how drivers use end-of-green warnings, control algorithms and warning displays for intelligent intersections, and statistical methodology in human factors research.

Substance P (SP) is an important neurotransmitter in the control of intestinal motility and is found in both the enteric and sympathetic nervous systems. This study examined the effect of celiac ganglionectomy on (1) mechanical properties of the circular muscles of the duodenum, ileum and proximal colon, (2) circular muscle responses to SP and neurokinin A. (3) distribution of substance P-like immunoreactive nerves, and (4) the distribution of neurokinin 1 and neurokinin 2 receptors. Celiac ganglionectomy resulted in an effective sympathectomy as evidenced by a marked decrease in norepinephrine content and tyrosine hydroxylase staining in the duodenum, ileum and proximal colon. The in vitro length/tension characteristics of the circular muscle of the duodenum, ileum and colon were unchanged after ganglionectomy. In all regions of the gut studied, substance P and neurokinin A caused dose-dependent contractions that were unaltered by celiac ganglionectomy. Immunohistochemistry revealed moderate substance P-like immunoreactive fibers in the myenteric plexus, submucosal plexus and circular muscle of the ileum, while in the colon, substance P-like immunoreactivity was intense in the myenteric plexus, and moderate in the circular muscle. In vitro autoradiography showed minimal binding of SP (NK1 receptor) or neurokinin A (NK2 receptor) in the ileum and significantly greater binding in the circular muscle layer of the colon. Celiac ganglionectomy did not affect substance P-like immunoreactivity, or NK1 or NK2 receptor binding. A greater contractile response to neurokinins was seen in the colon than in the duodenum or ileum, which paralleled the receptor density. The studies demonstrate that surgical celiac ganglionectomy, unlike chemical sympathectomy, does not affect the substance P innervation, receptor density or physiological responses of the intestine. The greater contractile response of the colon than the ileum parallels the greater receptor density rather than the peptide content as determined by immunhistochemistry.

Several classic papers explain the fundamentals of capacitive voltage transformer (CVT) design, operation, and transient response. Distance elements can overreach, particularly in high source-to-line impedance ratio (SIR) applications, which can result in undesired Zone 1 operations. Because this continues to be a problem in real applications, this paper revisits documented field cases using event data in hopes of shedding new light on this known problem. Solutions to distance element overreach are shared, from modified reach and time delays to modern solutions such as CVT transient detection logic. How does the protection engineer know what type of CVT is used? How can the protection engineer calculate the SIR from real-world event data? This paper gives practical guidance for the user to answer these fundamental questions. New data and research included in this paper update the topic. We investigate the CVT transient effect on directional element stability, directional overcurrent applications, and various communications-assisted protection schemes. We also share field cases of directional element and directional comparison blocking scheme misoperations and solutions and practical recommendations for mitigating the problems in all cases.

How stable is the frequency of the power system on a given day? How does a microprocessor-based relay track power system frequency? Why is frequency tracking important? This paper reviews the fundamentals of frequency tracking and explains, in practical terms, how and why this is done in digital relays. The performance of protective elements at off-nominal frequencies is of key interest. As with all technical areas, designs have evolved over time. This paper also documents the evolution of different designs, exploring each design's merits and why it was implemented. Real-world power system events are used to highlight scenarios that challenge designs. Lessons learned from event analysis are shared. Practical solutions and application advice are provided for each case study.

In August 1999, a lightning strike caused a misoperation of a relay installed in the late 1980s. The relay misoperation caused a two-minute outage at a petrochemical plant and led to an exhaustive root-cause analysis. The misoperation can be attributed to incorrect fault type selection in a distance element-based, 1980s-era relay. Two separate events in different locations, one in December 2007 and another in March 2009, highlight additional incorrect operations that occurred due to the same problem and root cause. The recent events remind us that this topic is still important and should be reviewed. This paper shares details about three challenging case studies and their root causes. Methodical root-cause analysis techniques are used, including mathematical simulation and testing of old and newer relay designs. This paper contrasts distance and fault identification algorithms, demonstrates methodical analysis techniques, and proposes solutions. Fault type selection logic is discussed, and the evolution and improvement of faulted phase selection logic over several decades is demonstrated. A newer relay design, available since 1993, is proven to have improved performance, namely better security, for these challenging cases.

Phase and ground directional elements are relied on for fast and secure protection throughout the power system. Although directional relays have been applied successfully for many years, several new and unique applications and power system disturbances present challenges. Using field and laboratory data, this paper reviews fundamentals, discusses the limits to sensitivity, and shows how and why directional element designs have progressed. The paper also describes how directional elements are applied during loss of voltage conditions. In addition to design basics, we show several practical field examples that illustrate problems and solutions, while providing guidance on applying and setting modern directional relays.

A reliable electric power supply is critical to the success of any industrial facility. Electrical faults and disturbances cannot always be avoided, but a quick diagnosis of problems can reduce downtime. Using event data from digital relays can provide valuable information to identify the root cause of problems and offer solutions. The data can also assist with commissioning during planned outages. This paper provides real-world examples of industrial applications that demonstrate how to improve electrical power system reliability. These examples include motor protection and starting, transformer and bus protection, main-tie-main applications, and feeder protection.

Commissioning protective relays has changed with the increased use of microprocessor-based relays. Many relays have multiple functions, and logic that used to be contained in wiring diagrams or control schematics now resides in relay settings.

In this paper, we include some important industry definitions of arc flash and ways of measuring arc-flash hazards. We then examine the use of existing technologies, including digital relays and communications capabilities, to implement reduced trip times using instantaneous overcurrent relays, a fast bus trip scheme, differential schemes, and light detection. We use a typical industrial switchgear lineup as an example of how to implement these schemes. Finally, we quantify the levels to which we can reduce arc-flash energy and its impact on safety.

In August 1999, a thunderstorm and lightning strike caused relay misoperations and a two-minute outage at a petrochemical plant. The outage led to an exhaustive root-cause analysis and subsequent litigation. This paper shares details about the event and its root cause, contrasts distance and fault identification algorithms, demonstrates methodical analysis techniques, and proposes solutions. This paper also highlights that engineers face the challenge of always staying current with their experience and understanding of the "state-of-the-art." The paper challenges engineers to do the right thing, find root cause, and solve problems.

In this paper, we include some important industry definitions of arc flash and ways of measuring arc-flash hazards. We then examine the use of existing technologies, including digital relays and communications capabilities, to implement reduced trip times using instantaneous overcurrent relays, a fast bus-trip scheme, and differential schemes. We use a typical industrial switchgear lineup as an example of how to implement these schemes. Finally, we quantify the levels to which we can reduce arc-flash energy and its impact on safety.