121 results on '"Shepherd, Simon"'
Search Results
2. Quantitative assessment of the oral microvasculature using optical coherence tomography angiography.
- Author
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Tianyu Zhang, Yilong Zhang, Jinpeng Liao, Shepherd, Simon, Zhihong Huang, Macluskey, Michaelina, and Chunhui Li
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- 2024
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3. Scenarios for New Mobility Policies and Automated Mobility in Beijing.
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Harrison, Gillian, Shepherd, Simon, Pfaffenbichler, Paul, Xu, Meng, Tian, Hang, and Mao, Wei
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SYSTEM dynamics ,AUTOMATED guided vehicle systems ,SUSTAINABILITY ,MEGALOPOLIS - Abstract
In this study, we consider the introduction of new mobility services and technologies into the megacity of Beijing, China, as per developed strategy and action plans, in order to investigate their potential contribution to sustainable mobility. This includes population relocation (decentralization), the construction of new rail lines, the introduction of shared bike services as a feeder to subway stations, the electrification of passenger vehicles and the adoption of automated and shared vehicles. The well-established, system dynamics-based MARS model is adapted to Beijing and further improved via the inclusion of these new services, technologies and policies. We find that decentralization can have a profound effect on overall sustainability if not considered in conjunction with other policies and that new rail lines and shared bikes may only have benefits in specific zones. Shared and automated vehicles could increase VKT by 60% and reduce active and public transport trips by a quarter. As such, nuanced integrated policy approaches will be required that are similar to those currently in place, such as imposed car shedding and taxi fleet control. [ABSTRACT FROM AUTHOR]
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- 2024
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4. Effect of Mifepristone on Migration and Proliferation of Oral Cancer Cells.
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Iftikhar, Anem, Shepherd, Simon, Jones, Sarah, and Ellis, Ian
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HEAD & neck cancer ,GLUCOCORTICOID receptors ,CELL morphology ,MITOGEN-activated protein kinases ,PHOSPHATIDYLINOSITOL 3-kinases - Abstract
Glucocorticoid receptor (GR) overexpression has been linked to increased tumour aggressiveness and treatment resistance. GR antagonists have been shown to enhance treatment effectiveness. Emerging research has investigated mifepristone, a GR antagonist, as an anticancer agent with limited research in the context of oral cancer. This study investigated the effect of mifepristone at micromolar (µM) concentrations of 1, 5, 10 and 20 on the proliferation and migration of oral cancer cells, at 24 and 48 h. Scratch and scatter assays were utilised to assess cell migration, MTT assays were used to measure cell proliferation, Western blotting was used to investigate the expression of GR and the activation of underlying Phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) and mitogen-activated protein kinase (MAPK) signalling pathways, and immunofluorescence (IF) was used to determine the localisation of proteins in HaCaT (immortalised human skin keratinocytes), TYS (oral adeno squamous cell carcinoma), and SAS-H1 cells (squamous cell carcinoma of human tongue). Mifepristone resulted in a dose-dependent reduction in the proliferation of HaCaT, TYS, and SAS-H1 cells. Mifepristone at a concentration of 20 µM effectively reduced collective migration and scattering of oral cancer cells, consistent with the suppression of the PI3K-Akt and MAPK signalling pathways, and reduced expression of N-Cadherin. An elongated cell morphology was, however, observed, which may be linked to the localisation pattern of E-Cadherin in response to mifepristone. Overall, this study found that a high concentration of mifepristone was effective in the suppression of migration and proliferation of oral cancer cells via the inhibition of PI3K-Akt and MAPK signalling pathways. Further investigation is needed to define its impact on epithelial–mesenchymal transition (EMT) markers. [ABSTRACT FROM AUTHOR]
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- 2024
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5. A Comparison of Models for Teaching Suturing and Surgical Skills to Dental Students.
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Macluskey, Michaelina, Revie, Gavin, and Shepherd, Simon D.
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DENTAL students ,SUTURING ,SURGICAL education ,TEACHING models ,SUTURES ,MEDICAL cadavers - Abstract
Learning suturing skills is an important area of the undergraduate curriculum and ideally requires realistic and anatomically accurate surgical training models to prepare students for treating patients. Little is currently understood regarding which model might be perceived by students to be the best or which might most effectively facilitate their learning. The aim of this study was to compare four teaching models: a tabletop silicon dental model, a restricted access tabletop model, a traditional phantom head mounted model, and a Thiel cadaver. Student preferences were explored for each of the models. Following lecture and video-based teaching 67 fourth-year students attended a practical suturing teaching session followed by the second session more focused on the experience of cutting and suturing mucoperiosteal flaps. Forty-six students (67%) gave online anonymous feedback on the first session. The majority (95%) felt prepared to place a simple interrupted suture on a patient, and 88% felt confident to do so. Twenty-eight students (40%) provided feedback on the second session with 82% agreeing that they were prepared to cut a mucoperiosteal flap and 48% felt confident to do this for a patient. The cadaver model was rated as the best of the four models for both suturing and mucoperiosteal flap skills. These results support its use for teaching students to suturing and surgical skills. However, despite this teaching student-rated confidence to cut and suture flaps for a patient remains poor. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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6. Machine learning assisted 5-part tooth segmentation method for CBCT-based dental age estimation in adults.
- Author
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Boedi, Rizky Merdietio, Shepherd, Simon, Oscandar, Fahmi, Franco, Ademir, and Mânica, Scheila
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DENTAL maturity ,MACHINE learning ,TEETH ,CONE beam computed tomography ,DENTIN ,AMELOBLASTS ,MAXILLA - Abstract
Background: The utilization of segmentation method using volumetric data in adults dental age estimation (DAE) from cone-beam computed tomography (CBCT) was further expanded by using current 5-Part Tooth Segmentation (SG
t 5 ) method. Additionally, supervised machine learning modelling--namely support vector regression (SVR) with linear and polynomial kernel, and regression tree -- was tested and compared with the multiple linear regression model. Material and Methods: CBCT scans from 99 patients aged between 20 to 59.99 was collected. Eighty eligible teeth including maxillary canine, lateral incisor, and central incisor were used in this study. Enamel to dentine volume ratio, pulp to dentine volume ratio, lower tooth volume ratio, and sex was utilized as independent variable to predict chronological age. Results: No multicollinearity was detected in the models. The best performing model comes from maxillary lateral incisor using SVR with polynomial kernel (Radj ² = 0.73). The lowest error rate achieved by the model was given also by maxillary lateral incisor, with 4.86 years of mean average error and 6.05 years of root means squared error. However, SGt 5 demands a complex approach to segment the enamel volume in the crown section and a lengthier labour time of 45 minutes per tooth. [ABSTRACT FROM AUTHOR]- Published
- 2024
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7. Dental age estimation using the Kvaal method—an evaluation of length and width ratios: a systematic review.
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Kazmi, S., Zaidi, Syed Jaffar Abbas, Reesu, Gowri Vijay, and Shepherd, Simon
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DENTAL maturity ,AGE ,RESEARCH personnel ,ETHNIC groups ,SCIENTIFIC observation - Abstract
This study aimed to systematically review the correlational accuracy between width ratios and length ratios based on the Kvaal methodology with chronological age. This systematic review followed Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). The search strategy included ProQuest, PubMed, Science Direct, and Taylor and Francis and Willey online without time or language restriction using Kvaal method of age estimation as key words for the search up to December 2021. A team of two researchers independently selected the studies and extracted the data. The Covidence platform was used to systematically organize all titles. The full texts of eligible studies were analyzed. Risk of bias (RoB) was assessed using a modified (to the specific characteristics of this systematic review) checklist based on Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement checklist for observational studies. A total of 658 articles were initially reviewed, but 22 were selected for inclusion. The risk of bias was estimated to be unclear to low overall. Among the length ratios, ratio R showed a strong association with chronological age, followed by ratio P. For the width ratios, ratio B demonstrated a close association with chronological age, followed by ratio C. The results suggest that width ratios correlate better with chronological age than length ratios. This systematic review suggests the width ratios are more strongly associated with chronological age than the length ratios. Using a width ratio could serve as a convenient and rapid way to estimate dental age. Our results apply equally to all types of ethnic groups. [ABSTRACT FROM AUTHOR]
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- 2024
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8. Preferences for electric motorcycle adoption in Bandung, Indonesia.
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Balijepalli, Chandra, Shepherd, Simon, Dit Sourd, Romain Crastes, Farda, Muhammad, Praesha, Tryas, and Lubis, Harun Al-Rasyid
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ELECTRIC motorcycles ,MOTORCYCLES ,ELECTRIC vehicles ,CHOICE of transportation ,AIR pollution ,CONSUMER preferences - Abstract
Due to an alarming threat of air pollution and climate change, governments around the world are now actively promoting electric vehicles. The case for vehicle electrification is even more important in big cities of developing countries, where motorcycle is a dominant mode of travel. To promote electric motorcycles successfully, we need to understand the factors that would drive the consumer choices when buying a motorcycle. This study chose Bandung in Indonesia as the case study location, where nearly 75% of vehicles are motorcycles. This study conducted a survey of preferences from over 700 residents and included battery charging methods such as plug-in/battery swap at home/office, superfast charging at stations, and deployed an innovative modelling approach constraining the mixture of distributions for monetary attributes. The study found that quick recharge in 10 minutes and battery swap at station are preferred over the base method of plugin at home/work. The battery swap at home has been perceived the same as plug-in home/work and the respondents are indifferent to this option. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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9. 3D segmentation of dental crown for volumetric age estimation with CBCT imaging.
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Merdietio Boedi, Rizky, Shepherd, Simon, Oscandar, Fahmi, Mânica, Scheila, and Franco, Ademir
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CONE beam computed tomography ,DENTAL crowns ,INCISORS ,DENTAL pulp cavities ,DENTAL maturity - Abstract
In adult dental age estimation, segmentation of dental volumetric information from different tooth parts using cone-beam computed tomography (CBCT) has proven beneficial in improving the regression model reliability. This segmentation method can be expanded in the crown part since the volumetric information in the crown is affected by attrition in the enamel and secondary dentine in the dentine and pulp chamber. CBCT scans from 99 patients aged between 20 and 60 were collected retrospectively. A total of 80 eligible teeth for each tooth type were used in this study. The enamel to dentine volume ratio (EDVR), pulp to dentine volume ratio (PDVR) and sex were used as independent variables to predict chronological age (CA). The EDVR was not affected by PDVR. The highest R
2 was calculated from the maxillary canine (R2 = 0.6). The current approach in crown segmentation has proven to improve model performance in anterior maxillary teeth. [ABSTRACT FROM AUTHOR]- Published
- 2023
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10. Metal-Hydride-Based Hydrogen Storage as Potential Heat Source for the Cold Start of PEM FC in Hydrogen-Powered Coaches: A Comparative Study of Various Materials and Thermal Management Techniques.
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Gkanas, Evangelos I., Wang, Chongming, Shepherd, Simon, and Curnick, Oliver
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HEAT storage ,PROTON exchange membrane fuel cells ,HYDROGEN storage ,HYDROGEN as fuel ,MATERIALS management ,HYDRIDES - Abstract
The successful and fast start-up of proton exchange membrane fuel cells (PEMFCs) at subfreezing temperatures (cold start) is very important for the use of PEMFCs as energy sources for automotive applications. The effective thermal management of PEMFCs is of major importance. When hydrogen is stored in hydride-forming intermetallics, significant amounts of heat are released due to the exothermic nature of the reaction. This excess of heat can potentially be used for PEMFC thermal management and to accelerate the cold start. In the current work, this possibility is extensively studied. Three hydride-forming intermetallics are introduced and their hydrogenation behavior is evaluated. In addition, five thermal management scenarios of the metal hydride beds are studied in order to enhance the kinetics of the hydrogenation. The optimum combination of the intermetallic, hydrogenation behavior, weight and complexity of the thermal management system was chosen for the study of thermal coupling with the PEMFCs. A 1D GT-SUITE model was built to stimulate the thermal coupling of a 100 kW fuel cell stack with the metal hydride. The results show that the use of the heat from the metal hydride system was able to reduce the cold start by up to 8.2%. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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11. Exploring the relationship between age and the pulp and tooth size in canines. A CBCT analysis.
- Author
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Kazmi, Shakeel, Shepherd, Simon, Revie, Gavin, Hector, Mark, and Mânica, Scheila
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CONE beam computed tomography ,CUSPIDS ,DENTAL pulp ,DENTAL pulp cavities ,AGE - Abstract
Radiographic methods using pulp-tooth volume ratio (PTVR) are important for dental age estimation. According to previous studies, using PTVR possesses different relationships with age in males and females but none of the studies have used a homogenous (approximately equal numbers of individuals in each age range) age distribution to assess this relationship and the effect of sex as a predictor on age estimation. This study was performed on Cone-beam computed tomography (CBCT)images of 521 left maxillary and 681 left mandibular canines of 719 subjects of Pakistani origin (368 females and 349 males) aged from 15 to 65 years. Planmeca Romexis® software was used to trace the outline of the pulp cavity and tooth and to calculate respective volumes. Subsequently, Microsoft® Office Excel 2016 was used to calculate the ratios. Regression analysis was performed to assess the relationship between PTVR factoring sex as apredictor for age estimation. The obtained results showed that including sex as predictor with maxillary PTVR (R
2 = 0.46) have the highest predictive power. The relationship between maxillary PTVR including sex with chronological age demonstrates anon-linear relationship. The conclusion is that including sex as predictor with maxillary PTVR produced the best estimate of chronological age. [ABSTRACT FROM AUTHOR]- Published
- 2022
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12. The Impact of a 1-Year COVID-19 Extension on Undergraduate Dentistry in Dundee: Final Year Students' Perspectives of Their Training in Oral Surgery.
- Author
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Macluskey, Michaelina, Anderson, Angela S., and Shepherd, Simon D.
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STUDENT attitudes ,ORAL surgery ,DENTAL education ,DENTAL schools ,SURGICAL education ,PSYCHOLOGY of students ,COVID-19 - Abstract
Background: The detrimental impact of the COVID-19 pandemic on dental education prompted the Scottish Government to fund an additional year to the dental course to ensure that the students had the necessary clinical experience. The aim of the study was to better understand the final year student perceptions of this extension on their oral surgery experience at the University of Dundee. Methods: This mixed methods study consisted of an anonymous online questionnaire and a focus group. Results: Forty-one students (69.3%) completed the questionnaire and ten students participated in the focus group. Thirty-six (88.8%) students agreed that the oral surgery teaching provided sufficient knowledge to undertake independent practice. All of the students felt confident to carry out an extraction, and the majority of them (n = 40, 95%) felt confident to remove a retained root, however, their confidence with surgery was lower. Conclusion: The extension gave the students sufficient experience in oral surgery to gain confidence in clinical skills and an appropriate level of knowledge in preparation for the next phase of their career. Most of the students agreed that the extension was necessary and beneficial. This cohort graduated with more oral surgery experience than any of the students did in the previous 4 years from Dundee and with experience that was comparable with the students at other schools in the pre-COVID-19 era. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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13. Geospace Concussion: Global Reversal of Ionospheric Vertical Plasma Drift in Response to a Sudden Commencement.
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Shi, Xueling, Lin, Dong, Wang, Wenbin, Baker, Joseph B. H., Weygand, James M., Hartinger, Michael D., Merkin, Viacheslav G., Ruohoniemi, J. Michael, Pham, Kevin, Wu, Haonan, Angelopoulos, Vassilis, McWilliams, Kathryn A., Nishitani, Nozomu, and Shepherd, Simon G.
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IONOSPHERIC plasma ,ELECTRIC currents ,THERMOSPHERE ,VERTICAL motion ,ELECTRIC fields ,BRAIN concussion ,GEOMAGNETISM - Abstract
An interplanetary shock can abruptly compress the magnetosphere, excite magnetospheric waves and field‐aligned currents, and cause a ground magnetic response known as a sudden commencement (SC). However, the transient (<∼1 min) response of the ionosphere‐thermosphere system during an SC has been little studied due to limited temporal resolution in previous investigations. Here, we report observations of a global reversal of ionospheric vertical plasma motion during an SC on 24 October 2011 using ∼6 s resolution Super Dual Auroral Radar Network ground scatter data. The dayside ionosphere suddenly moved downward during the magnetospheric compression due to the SC, lasting for only ∼1 min before moving upward. By contrast, the post‐midnight ionosphere briefly moved upward then moved downward during the SC. Simulations with a coupled geospace model suggest that the reversed E⃗×B⃗ $\vec{E}\times \vec{B}$ vertical drift is caused by a global reversal of ionospheric zonal electric field induced by magnetospheric compression during the SC. Plain Language Summary: It is well‐known that a shock wave can suddenly compress objects they directly interact with. In this study, we report a special case in the geospace environment in which an interplanetary shock produced a concussion‐like response in the ionosphere that was tens of thousands of kilometers away from the location where the shock first impacted. The ionized part of the atmosphere, or the ionosphere, was remotely connected to the magnetosphere‐the region of geospace dominated by the Earth's magnetic field‐via electric currents. When the magnetosphere was abruptly compressed after the shock arrival, a pair of electric currents flowing along the geomagnetic field lines was generated in the dayside mid‐latitudes. The newly generated currents flipped the dayside ionospheric electric field from eastward to westward, leading to a downward motion of dayside ionospheric charged particles. Within 1 minute, the vertical motion and zonal electric field flipped again to the direction before the compression due to the generation of another pair of electric currents with an opposite sense to the first pair. This study depicts a global picture of the transient ionospheric response using multi‐point high‐resolution measurements and simulations with a state‐of‐the‐art fully coupled geospace model. Key Points: Dayside ionospheric plasma undergoes a transient motion from downward to upward during a sudden commencement (SC)Both observations and simulations show that the reversed vertical drift is a global response of the ionosphere to the SCThe transient response is caused by a reversal of induced zonal electric field during the SC [ABSTRACT FROM AUTHOR]
- Published
- 2022
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14. What is behind the lifestyle risk factors for head and neck cancer?
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Iftikhar, Anem, Islam, Mohammad, Shepherd, Simon, Jones, Sarah, and Ellis, Ian
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HEAD & neck cancer ,DISEASE risk factors ,ETIOLOGY of diseases ,ALCOHOL drinking ,UNHEALTHY lifestyles - Abstract
Lifestyle factors are known to be influential determinants of health. According to the World Health Organization (WHO), approximately one third of deaths involve unhealthy lifestyle habits. Among lifestyle risk factors for head and neck cancers (HNC), alcohol consumption and smoking have an undeniable role in the multifactorial aetiology of the disease. In recent years, the promotion of healthy lifestyle choices has gained significant attention as contributory to improving health and disease prevention. Interventions to tackle these risk factors are vitally important in disease prevention and progression. However, in order to effectively prevent the disease and reduce the risk factors, it is crucial to identify what upstream reasons lead to the adoption of these lifestyle risk factors in the first place. Stress being a constant aspect of modern-day life is known to contribute to alcohol and smoking practices. In this review paper, relevant literature was searched in PubMed database for stress, lifestyle factors, HNC and cancer to explore the role of stress and its associated biological pathways as an upstream factor in the adoption of lifestyle risk factors that cause HNC. It highlights the importance of stress pathways and the Hypothalamus Pituitary Adrenal (HPA) axis as a locus of interaction between stress, alcohol, smoking and cancer. Despite their widely accepted harmful effects, alcohol and smoking remain deeply rooted in contemporary life. A greater understanding of the impact of stress on lifestyle choices and an exploration of the mechanisms resulting in stress, alcohol- and smoking-related cancer may highlight opportunities for improved prevention measures through the modification of unhealthy lifestyle choices. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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15. Regressive changes of crown‐root morphology and their volumetric segmentation for adult dental age estimation.
- Author
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Merdietio Boedi, Rizky, Shepherd, Simon, Oscandar, Fahmi, Mânica, Scheila, and Franco, Ademir
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DENTAL maturity ,CONE beam computed tomography ,INCISORS ,TOOTH roots ,INDEPENDENT variables - Abstract
Cone‐beam computed tomography (CBCT) enables the assessment of regressive morphological changes in teeth, which can be used to predict chronological age (CA) in adults. As each tooth region is known to have different correlations with CA, this study aimed to segment and quantify the sectional volumes of the tooth crown and root from CBCT scans to test their correlations with the chronological age (CA). Seventy‐five CBCT scans from individuals with age between 20 and 60 years were collected retrospectively from an existing database. A total of 192 intact maxillary anterior teeth fulfilled the eligibility criteria. The upper tooth volume ratio (UTVR), lower tooth volume ratio (LTVR), and sex were used as predictor variables. The UTVR and LTVR parameters were both found to be differently correlated to CA and independent from each other. Regression models were derived from each tooth, with the highest R2 being the maxillary lateral incisor (R2 = 0.67). Additional single predictor models using each ratio were capable of reliably predicting the CA. The segmentation approach in volumetric adult dental age estimation proved to be beneficial in enhancing the reliability of the regression model. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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16. Combining Tradable Credit Schemes with a New Form of Road Pricing: Producing Liveable Cities and Meeting Decarbonisation Goals.
- Author
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Pattinson, Jo-Ann, Harrison, Gillian, Mullen, Caroline, and Shepherd, Simon
- Abstract
This paper considers how the implementation of a tradable credit scheme (TCS) may be used to reduce road traffic and to contribute to the formation of liveable cities and global climate change commitments. The concept of applying TCS to individual road transport is familiar to transport researchers as a measure to regulate congestion and reduce transport-related emissions. Yet, it is not a strategy currently being considered by policy makers in the UK, despite the electrification of the road vehicle fleet and the associated loss of tax revenue presenting a rare opportunity to alter the economic instruments, which apply to road traffic. We consider how transport researchers can capitalise on this unique moment in transport history to shape transport policy. Our study uses qualitative methods, including a thematic analysis of semi-structured interviews with transport stakeholders and experts, in addition to a literature review and document analysis. Data analysis is inductive, permitting the formation of new ideas about the potential benefits of TCS and the barriers to the application of TCS to real-world policy. Building upon the results of TCS experiments and the results of our analysis, we propose a novel potential form of TCS combined with road pricing to maintain government revenue, which incentivises road users to decrease road vehicle kilometres travelled and reduce pollution and congestion. The proposal contributes to the discussion on the governance of road transport and taxation. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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17. An Educational Evaluation of Thiel Cadavers as a Model for Teaching Suturing Skills to Dental Students during the COVID-19 Pandemic.
- Author
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Macluskey, Michaelina, Anderson, Angela S., Gribben, Mark, and Shepherd, Simon D.
- Subjects
DENTAL students ,COVID-19 pandemic ,EDUCATIONAL evaluation ,MEDICAL cadavers ,TEACHING models ,DENTAL education - Abstract
Suturing is an essential skill in dentistry and not one easily acquired. The COVID-19 pandemic prompted a change to the use of Thiel cadavers and online resources with the aim of improving skill acquisition using the best model available. This study investigated the utility of the Thiel cadaver for teaching suturing skills and the potential impact of the lockdown. Fifty-seven year 4 students attended a teaching session. Student views on this teaching were explored via a questionnaire survey and qualitative data collected from a focus group. Data were analysed using an inductive approach. The response rate was 53% (30 students) for the questionnaire with 9 students participating in the focus group. Independent feedback was provided by two members of the teaching staff. Online video resources were very well received by the students with 97% agreeing that it was useful preparation. Ninety percent (90%) thought that the cadaveric model was suitable for this teaching and realistic. Positive emergent themes from the focus group centred on the use of the cadaveric model and the positive and relaxed teaching and learning environment. Staff perceived this model as superior to previously used models. There were no reported negative pandemic impacts and the cadaver model was well received. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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18. CBCT in dental age estimation: A systematic review and meta analysis.
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Merdietio Boedi, Rizky, Shepherd, Simon, Mânica, Scheila, and Franco, Ademir
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DENTAL maturity ,CONE beam computed tomography ,SCIENTIFIC literature ,INTRACLASS correlation ,VOLUMETRIC analysis - Abstract
This study aimed to investigate the reproducibility of dental age estimation methods in cone beam computed tomography (CBCT) and the correlation between dental (DA) and chronological (CA) ages. The scientific literature was searched in six databases (PubMed, Scopus, LILACS, Web of Science, SciELO, and OATD). Only observational studies were selected. Within each study, the outcomes of interest were (I) the quantified reproducibility of the method (κ statistics and Intraclass correlation coefficient); and (II) the correlation (r) between the dental and chronological ages. A random-effect three-level meta-analysis was conducted alongside moderator analysis based on methods, arch (maxillary/mandibular), population, and number of roots. From 671 studies, 39 fulfilled the inclusion criteria, with one study reporting two different methods. The methods used in the studies were divided into metric (n = 17), volumetric (n = 20), staging (n = 2), and atlas (n = 1). All studies reported high examiner reproducibility. Group 1 (metric and volumetric) provided a high inverse weighted r ( δ ^ = −0.71, CI [-0.79,–0.61]), and Group 2 (staging) provided a medium-weighted r ( δ ^ = 0.49, CI [0.44, 0.53]). Moderator analysis on Group one did not show statistically significant differences between methods, tooth position, arch, and number of roots. An exception was detected in the analysis based on population (Southeast Asia, δ ^ = −0.89, CI [-0.94,–0.81]). There is high evidence that CBCT methods are reproducible and reliable in dental age estimation. Quantitative metric and volumetric analysis demonstrated better performance in predicting chronological age than staging. Future studies exploring population-specific variability for age estimation with metric and volumetric CBCT analysis may prove beneficial. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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19. Effects of Subauroral Polarization Streams on the Upper Thermospheric Winds During Non‐Storm Time.
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Zou, Ying, Lyons, Larry R., Shi, Xueling, Liu, Jiang, Wu, Qian, Conde, Mark, Shepherd, Simon G., Mende, Stephen, Zhang, Yongliang, and Coster, Antea
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GPS receivers ,PLASMA flow ,WIND speed ,PLASMA density ,THERMOSPHERE ,STORM surges - Abstract
Intense sunward (westward) plasma flows, named Subauroral Polarization Stream (SAPS), have been known to occur equatorward of the electron auroras for decades, yet their effect on the upper thermosphere has not been well understood. On the one hand, the large velocity of SAPS results in large momentum exchange upon each ion‐neutral collision. On the other hand, the low plasma density associated with SAPS implies a low ion‐neutral collision frequency. We investigate the SAPS effect during non‐storm time by utilizing a Scanning Doppler Imager (SDI) for monitoring the upper thermosphere, SuperDARN radars for SAPS, all‐sky imagers and DMSP Spectrographic Imager for the auroral oval, and GPS receivers for the total electron content. Our observations suggest that SAPS at times drives substantial (>50 m/s) westward winds at subauroral latitudes in the dusk‐midnight sector, but not always. The occurrence of the westward winds varies with AE index, plasma content in the trough, and local time. The latitudinally averaged wind speed varies from 60 to 160 m/s, and is statistically 21% of the plasma. These westward winds also shift to lower latitude with increasing AE and increasing MLT. We do not observe SAPS driving poleward wind surges, neutral temperature enhancements, or acoustic‐gravity waves, likely due to the somewhat weak forcing of SAPS during the non‐storm time. Key Points: Subauroral Polarization Stream (SAPS) at times drives substantial (>; 50‐m/s) westward winds at subauroral latitudes in the dusk‐midnight sector, but not alwaysThe occurrence of the SAPS‐driven winds varies with AE index, plasma content in the trough, and the local timeThe wind speed is 21% of SAPS flow, implying a weaker ion‐neutral coupling during non‐storm than active time [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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20. The impact of wrong‐site surgery on dental undergraduate teaching: a survey of UK dental schools.
- Author
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Dargue, Anna, Fyfe, Eithne, French, Kathryn, Ali, Kamran, Bailey, Edmund, Bell, Aileen, Bolt, Robert, Bulsara, Yogesh, Carey, James, Emanuel, Charlotte, Green, Rachel, Khawaja, Nadine, Kushnerev, Evgeny, Patel, Neil, Shepherd, Simon, Smart, Binthan, Smyth, Joanna, Taylor, Kate, and Varma Datla, Kumar
- Subjects
DENTAL schools ,OPERATIVE dentistry ,DENTAL extraction ,PATIENT safety ,DENTAL surveys ,DENTAL education ,UNDERGRADUATES - Abstract
Introduction: Patient safety within dental education is paramount. Wrong‐site surgery (WSS) tooth extraction is not uncommon and is a significant never event (NE) in dentistry. This study aimed to explore dental schools' undergraduate experience of NEs, safety interventions implemented and the impact on student experience. Methods: All 16 UK dental schools were surveyed via email. Results: The response rate was 100%. A modified World Health Organization (WHO) checklist was used within institutions (94%) including pre‐operative briefings and recording teeth on whiteboards (81%, respectively). Students were directly supervised performing extractions (63%) utilising a 1:4 staff: student ratio. WSS by students was reported in 69% of schools, with student experience being impacted by an increased patient safety focus. Discussion: This study demonstrated an increased utilisation of an adapted WHO checklist. Modification of practices to ensure patient safety was demonstrated at all schools, irrespective of student WSS occurrences. Institutions experiencing student NEs commonly implemented WHO checklists and recording teeth for extraction on whiteboards. Other strategies included direct staff supervision and pre‐operative briefings. Conclusion: UK dental schools have increased the emphasis on patient safety by the implementation of national healthcare models, for example WHO checklists and pre‐operative briefings. These strategies both aim to improve communication and teamwork. Increased levels of staff supervision foster greater quality of teaching; however, this has resulted in reduced student clinical experience. A proposed minimum standard for undergraduate surgery is suggested to ensure safe and competent dental practitioners of the future. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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- View/download PDF
21. Study of the spectral composition of waves in the lower ionospheric layers according to the data of the SuperDARN and SEKIRA radars using the ARIMA model.
- Author
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Lavygin, Ivan A., Berngardt, Oleg I., and Shepherd, Simon G.
- Published
- 2024
- Full Text
- View/download PDF
22. Tourism, transport, and land use: a dynamic impact assessment for Kaohsiung's Asia New Bay Area.
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Man, Chun-Yin, Shyr, Oliver F., Hsu, Yi-Ya, Shepherd, Simon, Lin, Han-Liang, and Tu, Chien-Hung
- Abstract
This paper proposes a hybrid methodology for analysing the causal relations between public transportation development, tourism and land use by combining System Dynamics (SD) with Geographical Information Systems (GIS) and agent-based modelling (ABM). It is applied to illustrate the quantitative and spatial effect of the two phases Light Rail Transit (LRT) development in Asia New Bay Area, Kaohsiung, Taiwan. This paper also furthers the application of the ABM spatial information as interactive variables in the stocks-flow model. The simulation results support that development policies of LRT are significant to the future tourism in Asia New Bay Area, while the under debate second phase of LRT is estimated to raise the number of visitors in long term by alleviating the deteriorating road traffic congestion. This policy-oriented simulation can serve as a reference to the decision-makers towards the future management of LRT. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
23. An Autonomous Host-Based Intrusion Detection System for Android Mobile Devices.
- Author
-
Ribeiro, José, Saghezchi, Firooz B., Mantas, Georgios, Rodriguez, Jonathan, Shepherd, Simon J., and Abd-Alhameed, Raed A.
- Subjects
SUPERVISED learning ,MOBILE operating systems ,MALWARE prevention ,PERSONAL computers ,MACHINE learning ,MALWARE - Abstract
Intrusion Detection System (IDS) is crucial to protect smartphones from imminent security breaches and ensure user privacy. Android is the most popular mobile Operating System (OS), holding above 85% market share. The traffic generated by smartphones is expected to exceed the one generated by personal computers by 2021. Consequently, this prevalent mobile OS will stay one of the most attractive targets for potential attacks on fifth generation mobile networks (5G). Although Android malware detection has received considerable attention, offered solutions mostly rely on performing resource intensive analysis on a server, assuming a continuous connection between the device and the server, or on employing supervised Machine Learning (ML) algorithms for profiling the malware's behaviour, which essentially require a training dataset consisting of thousands of examples from both benign and malicious profiles. However, in practice, collecting malicious examples is tedious since it entails infecting the device and collecting thousands of samples in order to characterise the malware's behaviour and the labelling has to be done manually. In this paper, we propose a novel Host-based IDS (HIDS) incorporating statistical and semi-supervised ML algorithms. The advantage of our proposed IDS is two folds. First, it is wholly autonomous and runs on the mobile device, without needing any connection to a server. Second, it requires only benign examples for tuning, with potentially a few malicious ones. The evaluation results show that the proposed IDS achieves a very promising accuracy of above 0.9983, reaching up to 1. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
24. Age estimation using canine pulp volumes in adults: a CBCT image analysis.
- Author
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Kazmi, Shakeel, Mânica, Scheila, Revie, Gavin, Shepherd, Simon, and Hector, Mark
- Subjects
FORENSIC anthropology ,IMAGE analysis ,AGE ,AGE distribution ,PANORAMIC radiography ,CONE beam computed tomography ,DENTAL pulp ,DENTAL maturity - Abstract
Secondary dentine deposition is responsible for the decrease in the volume of the pulp cavity with age. Therefore, the volume of the pulp cavity can be considered as a predictor for estimating age. The aims of this study were to investigate the relationship strength between canine pulp volumes and chronological age from homogenous (approximately equal numbers of individuals in each age range) age distribution and to assess the effect of sex as predictor in age estimation. This study was performed on 719 subjects of Pakistani origin. Cone beam computed tomography images of 521 left maxillary and 681 left mandibular canines were collected from 368 females and 349 males aged from 15 to 65 years. Planmeca Romexis® software was used to trace the outline of the pulp cavity and to calculate pulp volumes. Regression analysis was performed to assess the correlation between pulp volumes considering with and without sex as a predictor with chronological age. The obtained results showed that mandibular canine pulp volume and sex have the highest predictive power (R
2 = 0.33). The relationship between mandibular canine pulp volume and sex with chronological age demonstrates an odd S-shaped non-linear relationship. A statistically significant difference in volumes of pulp was found (p = 0.000) between males and females. The conclusion was that predictions using the pulp volume of the mandibular canine and sex produced the best estimates of chronological age. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
25. The smart grid as commons: Exploring alternatives to infrastructure financialisation.
- Author
-
O'Brien, Peter, O'Neill, Phillip, Pike, Andy, Hall, Stephen, Jonas, Andrew EG, Shepherd, Simon, and Wadud, Zia
- Subjects
INFRASTRUCTURE financing ,SMART power grids ,ELECTRIC power distribution grids ,ECONOMIC development projects ,SUSTAINABILITY - Abstract
This article explores a tension between financialisation of electricity infrastructures and efforts to bring critical urban systems into common ownership. Focusing on the emerging landscape of electricity regulation and e-mobility in the United Kingdom (UK), it examines how electricity grid ownership has become financialised, and why the economic assumptions that enabled this financialisation are being called into question. New technologies, such as smart electricity meters and electric vehicles, provide cities with new tools to tackle poor air quality and greenhouse gas emissions. Electricity grids are key enabling infrastructures but the companies that run them do not get rewarded for improving air quality or tackling climate change. UK government regulation of electricity grids both enables financialisation and forecloses opportunities to manage the infrastructure for wider environmental and public benefit. Nonetheless, the addition of smart devices to this network – the 'smart grid' – opens up an opportunity for common ownership of the infrastructure. Transforming the smart grid into commons necessitates deep structural reform to the entire architecture of infrastructure regulation in the UK. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
26. Multi‐instrument Observations of Mesoscale Enhancement of Subauroral Polarization Stream Associated With an Injection.
- Author
-
Wang, Zihan, Zou, Shasha, Shepherd, Simon G., Liang, Jun, Gjerloev, Jesper W., Ruohoniemi, J. Michael, Kunduri, Bharat, and Wygant, John R.
- Subjects
MESOSCALE eddies ,GEOMAGNETIC indexes ,VAN Allen radiation belts ,RING currents ,INTERPLANETARY magnetic fields - Abstract
Subauroral polarization streams (SAPS) prefer geomagnetically disturbed conditions and strongly correlate with geomagnetic indexes. However, the temporal evolution of SAPS and its relationship with dynamic and structured ring current and particle injection are still not well understood. In this study, we performed detailed analysis of temporal evolution of SAPS during a moderate storm on 18 May 2013 using conjugate observations of SAPS from the Van Allen Probes (VAP) and the Super Dual Auroral Radar Network (SuperDARN). The large‐scale SAPS (LS‐SAPS) formed during the main phase of this storm and decayed due to the northward turning of the interplanetary magnetic field. A mesoscale (approximately several hundreds of kilometers zonally) enhancement of SAPS was observed by SuperDARN at 0456 UT. In the conjugate magnetosphere, a large SAPS electric field (∼8 mV/m) pointing radially outward, a local magnetic field dip, and a dispersionless ion injection were observed simultaneously by VAP‐A at L shell = 3.5 and MLT = 20. The particle injection observed by VAP‐A is likely associated with the particle injection observed by the Geostationary Operational Environmental Satellite 15 near 20 MLT. Magnetic perturbations observed by the ground magnetometers and flow reversals observed by SuperDARN reveal that this mesoscale enhancement of SAPS developed near the Harang reversal and before the substorm onset. The observed complex signatures in both space and ground can be explained by a two‐loop current wedge generated by the perturbed plasma pressure gradient and the diamagnetic effect of the structured ring current following particle injection. Key Points: Mesoscale enhancement of SAPS was observed by VAP and SuperDARN on top of the existing large‐scale SAPSMesoscale enhancement is associated with energetic ion flux increase, energetic electron flux decrease, and local magnetic field dipMesoscale enhancement of SAPS and equatorward flow burst developed near the Harang reversal [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
27. Temporal and Spatial Variations of Storm Time Midlatitude Ionospheric Trough Based on Global GNSS‐TEC and Arase Satellite Observations.
- Author
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Shinbori, Atsuki, Otsuka, Yuichi, Tsugawa, Takuya, Nishioka, Michi, Kumamoto, Atsushi, Tsuchiya, Fuminori, Matsuda, Shoya, Kasahara, Yoshiya, Matsuoka, Ayako, Ruohoniemi, J. Michael, Shepherd, Simon G., and Nishitani, Nozomu
- Abstract
Abstract: Temporal and spatial variations of the midlatitude ionospheric trough during a geomagnetic storm on 4 April 2017 have been investigated using Global Navigation Satellite System total electron content data together with Arase satellite observations. After the geomagnetic storm commencement, the trough minimum location moves equatorward from 60 to 48° in geomagnetic latitude within 4 hr. The trough minimum location identified from the Global Navigation Satellite System total electron content data is located near the footprint of an abrupt drop of electron density detected by the Arase High‐Frequency Analyzer instrument. The longitudinal variation of the trough minimum location shows a significant variation with a scale of 1,000–2,500 km during both storm and quiet times. This phenomenon has not yet been reported by previous studies. After the onset of the storm recovery phase, the trough minimum location rapidly moves poleward back to the quiet time location within 4 hr. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
28. Interinstrument comparison of remote-sensing devices and a new method for calculating on-road nitrogen oxides emissions and validation of vehicle-specific power.
- Author
-
Rushton, Christopher E., Tate, James E., Shepherd, Simon P., and Carslaw, David C.
- Subjects
NITRIC oxide & the environment ,REMOTE sensing ,GLOBAL Positioning System ,LINEAR statistical models ,SYNCHRONIZATION - Abstract
Emissions of nitrogen oxides (NOx) by vehicles in real driving environments are only partially understood. This has been brought to the attention of the world with recent revelations of the cheating of the type of approval tests exposed in the dieselgate scandal. Remote-sensing devices offer investigators an opportunity to directly measure in situ real driving emissions of tens of thousands of vehicles. Remote-sensing NO2measurements are not as widely available as would be desirable. The aim of this study is to improve the ability of investigators to estimate the NO2emissions and to improve the confidence of the total NOx results calculated from standard remote-sensing device (RSD) measurements. The accuracy of the RSD speed and acceleration module was also validated using state-of-the-art onboard global positioning system (GPS) tracking. Two RSDs used in roadside vehicle emissions surveys were tested side by side under off-carriageway conditions away from transient pollution sources to ascertain the consistency of their measurements. The speed correlation was consistent across the range of measurements at 95% confidence and the acceleration correlation was consistent at 95% confidence intervals for all but the most extreme acceleration cases. VSP was consistent at 95% confidence across all measurements except for those at VSP ≥ 15 kW t−1, which show a small underestimate. The controlled distribution gas nitric oxide measurements follow a normal distribution with 2σ equal to 18.9% of the mean, compared to 15% observed during factory calibration indicative of additional error introduced into the system. Systematic errors of +84 ppm were observed but within the tolerance of the control gas. Interinstrument correlation was performed, with the relationship between the FEAT and the RSD4600 being linear with a gradient of 0.93 and anR2of 0.85, indicating good correlation. A new method to calculate NOx emissions using fractional NO2combined with NO measurements made by the RSD4600 was constructed, validated, and shown to be more accurate than previous methods. Implications: Synchronized remote-sensing measurements of NO were taken using two different remote-sensing devices in an off-road study. It was found that the measurements taken by both instruments were well correlated. Fractional NO2measurements from a prior study, measurable on only one device, were used to create new NOxemission factors for the device that could not be measured by the second device. These estimates were validated against direct measurement of total NOxemission factors and shown to be an improvement on previous methodologies. Validation of vehicle-specific power was performed with good correlation observed. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
- View/download PDF
29. A novel application of PageRank and user preference algorithms for assessing the relative performance of track athletes in competition.
- Author
-
Beggs, Clive B., Shepherd, Simon J., Emmonds, Stacey, and Jones, Ben
- Subjects
TRACK & field athletes ,ALGORITHMS ,RANKING ,SPORTS competitions ,DECISION making - Abstract
Ranking enables coaches, sporting authorities, and pundits to determine the relative performance of individual athletes and teams in comparison to their peers. While ranking is relatively straightforward in sports that employ traditional leagues, it is more difficult in sports where competition is fragmented (e.g. athletics, boxing, etc.), with not all competitors competing against each other. In such situations, complex points systems are often employed to rank athletes. However, these systems have the inherent weakness that they frequently rely on subjective assessments in order to gauge the calibre of the competitors involved. Here we show how two Internet derived algorithms, the PageRank (PR) and user preference (UP) algorithms, when utilised with a simple ‘who beat who’ matrix, can be used to accurately rank track athletes, avoiding the need for subjective assessment. We applied the PR and UP algorithms to the 2015 IAAF Diamond League men’s 100m competition and compared their performance with the Keener, Colley and Massey ranking algorithms. The top five places computed by the PR and UP algorithms, and the Diamond League ‘2016’ points system were all identical, with the Kendall’s tau distance between the PR standings and ‘2016’ points system standings being just 15, indicating that only 5.9% of pairs differed in their order between these two lists. By comparison, the UP and ‘2016’ standings displayed a less strong relationship, with a tau distance of 95, indicating that 37.6% of the pairs differed in their order. When compared with the standings produced using the Keener, Colley and Massey algorithms, the PR standings appeared to be closest to the Keener standings (tau distance = 67, 26.5% pair order disagreement), whereas the UP standings were more similar to the Colley and Massey standings, with the tau distances between these ranking lists being only 48 (19.0% pair order disagreement) and 59 (23.3% pair order disagreement) respectively. In particular, the UP algorithm ranked ‘one-off’ victors more highly than the PR algorithm, suggesting that the UP algorithm captures alternative characteristics to the PR algorithm, which may more suitable for predicting future performance in say knockout tournaments, rather than for use in competitions such as the Diamond League. As such, these Internet derived algorithms appear to have considerable potential for objectively assessing the relative performance of track athletes, without the need for complicated points equivalence tables. Importantly, because both algorithms utilise a ‘who beat who’ model, they automatically adjust for the strength of the competition, thus avoiding the need for subjective decision making. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
30. 9 August 1967/the pyjamas.
- Author
-
Shepherd, Simon
- Subjects
BIOGRAPHY (Literary form) ,MEMORIALS - Abstract
Commemoration of the anniversary of the deaths of Joe Orton and Kenneth Halliwell brings centre-stage an event which has caused difficulties for those writing about Orton. These difficulties mainly originate in John Lahr's biography, which used the deaths as a frame for viewing Orton's life and work. This essay attempts to think afresh about those deaths by drawing on texts that pre-date the biography, namely the news reports of witness evidence at the inquest. These texts have very different tone and detail from the biography but get lost under the memory- and archive-management which characterises the early Orton industry. In following where the news reports lead us, the essay takes the opportunity to ask questions about the concept of anniversary. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
31. Alcohol and the Dental Team: Relevance, Risk, Role and Responsibility.
- Author
-
Shepherd, Simon and Ogden, Graham
- Published
- 2017
- Full Text
- View/download PDF
32. A Versatile and Ubiquitous Secret Sharing.
- Author
-
Adeka, Muhammad, Shepherd, Simon, Abd-Alhameed, Raed, and Ahmed, Nuredin A. S
- Published
- 2015
- Full Text
- View/download PDF
33. Nigeria: Cyber Space Security Vis a Vis Computerisation, Miniaturisation and Location-Based Authentication.
- Author
-
Adeka, Muhammad, Ngala, Mohammad, Bin-Melha, Mohammad, Ibrahim, E., Shepherd, Simon J., Elfergani, Issa T. E., Hussaini, Ash S., Elmegri, Fauzi, and Abd-Alhameed, Raed
- Published
- 2015
- Full Text
- View/download PDF
34. A Multi-service Cluster-Based Decentralized Group Key Management Scheme for High Mobility Users.
- Author
-
Mapoka, Trust T., AlSabbagh, Haider M., Dama, Yousef A.S., Shepherd, Simon J., Abd-Alhameed, Raed, Bin-Melha, Mohammad, and Anoh, Kelvin O.
- Published
- 2015
- Full Text
- View/download PDF
35. Cordon tolls and competition between cities with symmetric and asymmetric interactions.
- Author
-
Balijepalli, Chandra and Shepherd, Simon
- Subjects
TOLLS ,CITIES & towns ,TRAFFIC congestion ,TRANSPORTATION ,TRANSPORTATION research ,CONTESTS - Abstract
The aim of this paper is to model the impacts of competition between cities on both the optimal welfare generating tolls and upon longer-term decisions such as business and residential location choices. The research uses a dynamic land use transport interaction model of two neighbouring cities and analyses the impacts by setting up a game between the two cities to maximise the welfare of their own residents. The work builds on our earlier research which studied competition in a small network using a static equilibrium approach for private car traffic without accounting for the land use responses to the change in accessibility. This paper extends the earlier work by setting up a dynamic model which includes active modes of travel and the more usual car and public transport in a realistic twin city setting and assesses the longer term relocation responses. This paper firstly sets out the competition between two hypothetical identical cities i.e. the symmetric case; and then sets out the real world asymmetric case in which the cities are of different size representative of Leeds and Bradford in the UK but equally applicable elsewhere too. We found that the level of interaction between the two cities is a key determinant to the optimal tolls and welfare gains. Our findings show that the competition between cities could lead to a Nash Trap at which both cities are worse off in terms of welfare gains. On the other hand, we found that cities, if regulated, would gain in terms of welfare and yet charge only half the toll compared with tolls under competition. We then show that the effect of competition increases with increased interaction between cities. In terms of residential location, cities with higher charges benefit from an increase in residents, though as with other studies, the relative change in population in response to cordon charging is small. The policy implications are threefold-(i) while there is an incentive to cooperate at local authority level, this is not achieved due to competition; (ii) where cities compete they may fall into a Nash Trap where both cities will be worse off compared to the regulated solution; and (iii) regulation is recommended when there is a strong interaction between the cities but that the benefits of regulation decrease as interaction between cities decreases and the impact of competition is lessened. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
36. A model of the free surface dynamics of shallow turbulent flows.
- Author
-
NICHOLS, ANDREW, TAIT, SIMON J., HOROSHENKOV, KIRILL V., and SHEPHERD, SIMON J.
- Subjects
GEOPHYSICAL fluid dynamics ,TURBULENT flow ,HARMONIC motion - Abstract
Understanding the dynamic free surface of geophysical flows has the potential to enable direct inference of the flow properties based on measurements of the free surface. An important step is to understand the inherent response of free surfaces in depth-limited flows. Here a model is presented to demonstrate that free surface oscillatory spatial correlation patterns result from individual surface features oscillating vertically as they advect over space and time. Comparison with laboratory observations shows that these oscillating surface features can be unambiguously explained by simple harmonic motion, whereby the oscillation frequency is controlled by the root-mean-square water surface fluctuation, and to a lesser extent the surface tension. This demonstrates that the observed "complex" wave pattern can be simply described as an ensemble of spatially and temporally distributed oscillons. Similarities between the oscillon frequency and estimated frequency of near-bed bursting events suggest that oscillon behaviour is linked with the creation of coherent flow structures. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
37. Optimal Charging Strategies under Conflicting Objectives for the Protection of Sensitive Areas: A Case Study of the Trans-Pennine Corridor.
- Author
-
Gühnemann, Astrid, Koh, Andrew, and Shepherd, Simon
- Subjects
ELECTRIC vehicle charging stations ,ENVIRONMENTALLY sensitive areas ,POLLUTION ,AIR quality management - Abstract
This paper analyses the application of road user charging for the reduction of local pollution in environmentally sensitive areas. The key question is to investigate the interdependencies between the price setting strategies of neighbouring institutions with conflicting objectives and what the optimal strategy would be if environmental considerations are included. The analysis is carried out using a large network case study with two transport sensitive areas of different type in the Trans-Pennine corridor: the Peak District National Park, as a sensitive ecosystem and area of high recreational value, and the Sheffield Air Quality Management Area (AQMA), as an area with very high population density. Different combinations of user charging between both areas and the surrounding motorways have been analysed. For each combination, cordon charges and distance based motorway tolls have been determined that optimise the welfare gains under the objectives given in that scenario. The overall welfare of the region would be maximised under a global co-operative regulation scenario including all players. However, left to their own devices, the authorities might be tempted to play a Nash game and set the tolls at a level that results in a positive outcome for the local area but reduces the net welfare for the entire network compared to a co-ordinated introduction of charges. If motorways are not tolled, overall welfare can even be reduced due to wide diversion of traffic in the area. Regarding environmental impacts, substantial improvements within the sensitive areas and on the motorways for which charges have been applied can be achieved, although the reductions in environmental costs over the case study region are small. In conclusion, a charging instrument can be successful in reducing local environmental problems but implementation in isolation of surrounding areas needs to be avoided. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
38. Dirty-Appearing White Matter in the Brain is Associated with Altered Cerebrospinal Fluid Pulsatility and Hypertension in Individuals without Neurologic Disease.
- Author
-
Beggs, Clive B., Magnano, Christopher, Shepherd, Simon J., Belov, Pavel, Ramasamy, Deepa P., Hagemeier, Jesper, and Zivadinov, Robert
- Subjects
BRAIN imaging ,WHITE matter (Nerve tissue) ,CEREBROSPINAL fluid ,HYPERTENSION ,LEUKOARAIOSIS - Abstract
Background and Purpose: Aging of the healthy brain is characterized by focal or nonfocal white matter (WM) signal abnormality (SA) changes, which are typically detected as leukoaraiosis (LA). Hypertension is a risk factor for WM lesion formation. This study investigated whether LA might be associated with increased cerebrospinal fluid (CSF) pulsatility linked to arterial hypertension.Methods: A total of 101 individuals without neurologic diseases (53 females and 48 males) aged between 18 and 75 years underwent 3T brain MRI with cine phase contrast imaging for CSF flow estimation, after providing their informed consent. LA was defined as the presence of focal T2 WM SA changes and/or nonfocal uniform areas of signal increase termed dirty appearing white matter (DAWM). Relevant information relating to cardiovascular risk factors was also collected.Results: When controlled for age and hypertension, significant partial correlations were observed between: DAWM volume and: net negative flow (r = -.294, P = .014); net positive flow (NPF) (r = .406, P = .001); and peak positive velocity (r = .342, P = .004). Multiple linear regression analysis revealed DAWM volume to be significantly correlated with CSF NPF (P = .019) and hypertension (P = .007), whereas T2 WM SA volume was only significantly correlated with age (P = .002). Combined DAWM and T2 WM SA volumes were significantly related with age (P = .001) and CSF peak negative velocity (P = .041).Conclusions: Rarefaction of WM leading to LA is a multifactorial process, in which formation of DAWM induced by hypertension and increased aqueductal CSF pulsatility, may play a contributory role. These two factors appear to act independently of each other in a process that is independent of age. [ABSTRACT FROM AUTHOR]- Published
- 2016
- Full Text
- View/download PDF
39. Efficient authenticated multi-service group key management for secure wireless mobile multicast.
- Author
-
Mapoka, Trust T., Shepherd, Simon J., Abd-Alhameed, Raed, and Anoh, Kelvin O. O.
- Published
- 2014
- Full Text
- View/download PDF
40. Novel rekeying approach for secure multiple multicast groups over wireless mobile networks.
- Author
-
Mapoka, Trust Tshepo, Shepherd, Simon, Abd-Alhameed, Raed, and Anoh, Kelvin O. O.
- Published
- 2014
- Full Text
- View/download PDF
41. The use of kurtosis de-noising for EEG analysis of patients suffering from Alzheimer's disease.
- Author
-
Gang Wang, Shepherd, Simon J., Beggs, Clive B., Nini Rao, and Ying Zhang
- Subjects
ELECTROENCEPHALOGRAPHY ,ALZHEIMER'S patients ,BIOMECHANICS ,BIOMEDICAL engineering ,BIOMEDICAL materials - Abstract
The use of electroencephalograms (EEGs) to diagnose and analyses Alzheimer's disease (AD) has received much attention in recent years. The sample entropy (SE) has been widely applied to the diagnosis of AD. In our study, nine EEGs from 21 scalp electrodes in 3 AD patients and 9 EEGs from 3 age-matched controls are recorded. The calculations show that the kurtoses of the AD patients' EEG are positive and much higher than that of the controls. This finding encourages us to introduce a kurtosis-based de-noising method. The 21-electrode EEG is first decomposed using independent component analysis (ICA), and second sort them using their kurtoses in ascending order. Finally, the subspace of EEG signal using back projection of only the last five components is reconstructed. SE will be calculated after the above de-noising preprocess. The classifications show that this method can significantly improve the accuracy of SE-based diagnosis. The kurtosis analysis of EEG may contribute to increasing the understanding of brain dysfunction in AD in a statistical way. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
42. A New Multiple Service Key Management Scheme for Secure Wireless Mobile Multicast.
- Author
-
Mapoka, Trust T., Shepherd, Simon J., and Abd-Alhameed, Raed A.
- Subjects
MOBILE communication systems ,MULTICASTING (Computer networks) ,WIRELESS communications ,CELL phone security measures ,CRYPTOGRAPHY ,MOBILE computing - Abstract
Addressing key management in mobile multicast communication is currently a booming topic due to the convergence of wireless and mobile technologies. With the proliferation of multiple group based services that are possible to co-exist within a single network, mobile subscribers could subscribe to these services concurrently while ubiquitous. However, the existing group key management (GKM) protocols intend to secure group communication for just a single group service. The GKM approaches involve inefficient use of keys and huge rekeying overheads, hence unsuitable for multiple multicast group environments. In this paper, we propose a novel GKM protocol for multiple multicast groups, called slot based multiple group key management (SMGKM) scheme. SMGKM supports the movement of single and multiple members across a homogeneous or heterogeneous wireless network while participating in multiple group services with minimized rekeying transmission overheads. Unlike conventional GKM protocols, SMGKM protocol can mitigate one-affect-n phenomenon, single point of failure and investment pressure of signaling load caused by rekeying at the core network. Numerical analysis and simulation results of the proposed protocol show significant resource economy in terms of communication bandwidth overhead, storage overheads at the Domain Key Distributor (DKD), mobile receiver and Area Key Distributors while providing intense security. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
43. Resolving the password security purgatory in the contexts of technology, security and human factors.
- Author
-
Adeka, Muhammad, Shepherd, Simon, and Abd-Alhameed, Raed
- Published
- 2013
- Full Text
- View/download PDF
44. Clustering Gene Expression Data for Periodic Genes Based on INMF.
- Author
-
De-Shuang Huang, Kang Li, Irwin, George William, Rao, Nini, and Shepherd, Simon J.
- Abstract
In this paper, we have explored the use of improved non - negative matrix factorization (INMF) to analyze gene expression data. Firstly, the mathematical principle of INMF algorithm is analyzed; Secondly, we proposed an INMF - based method for clustering periodic genes, which can provide valuable information for gene network research. Using simulated data, our approach is able to extract periodic genes subsets even when the signal-to-noise ratio is low. Subsequently, our approach is tested by real gene expression datasets from Yeast and is compared with the related other approaches. Our results showed that our scheme is feasible and effective. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
45. Aqueductal Cerebrospinal Fluid Pulsatility in Healthy Individuals Is Affected by Impaired Cerebral Venous Outflow.
- Author
-
Beggs, Clive B., Magnano, Christopher, Shepherd, Simon J., Marr, Karen, Valnarov, Vesela, Hojnacki, David, Bergsland, Niels, Belov, Pavel, Grisafi, Steven, Dwyer, Michael G., Carl, Ellen, Weinstock‐Guttman, Bianca, and Zivadinov, Robert
- Abstract
Purpose: To investigate cerebrospinal fluid (CSF) dynamics in the aqueduct of Sylvius (AoS) in chronic cerebrospinal venous insufficiency (CCSVI)-positive and - negative healthy individuals using cine phase contrast imaging. Materials and Methods: Fifty-one healthy individuals (32 CCSVI-negative and 19 age-matched CCSVI-positive subjects) were examined using Doppler sonography (DS). Diagnosis of CCSVI was established if subjects fulfilled ⩾2 venous hemodynamic criteria on DS. CSF flow and velocity measures were quantified using a semiautomated method and compared with clinical and routine 3T MRI outcomes. Results: CCSVI was associated with increased CSF pulsatility in the AoS. Net positive CSF flow was 32% greater in the CCSVI-positive group compared with the CCSVInegative group (P = 0.008). This was accompanied by a 28% increase in the mean aqueductal characteristic signal (ie, the AoS cross-sectional area over the cardiac cycle) in the CCSVI-positive group compared with the CCSVI-negative group (P = 0.021). Conclusion: CSF dynamics are altered in CCSVI-positive healthy individuals, as demonstrated by increased pulsatility. This is accompanied by enlargement of the AoS, suggesting that structural changes may be occurring in the brain parenchyma of CCSVI-positive healthy individuals. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
46. Jugular Venous Reflux and White Matter Abnormalities in Alzheimer's Disease: A Pilot Study.
- Author
-
Chung, Chih-Ping, Beggs, Clive, Wang, Pei-Ning, Bergsland, Niels, Shepherd, Simon, Cheng, Chun-Yu, Ramasamy, Deepa P., Dwyer, Michael G., Hu, Han-Hwa, and Zivadinov, Robert
- Subjects
WHITE matter (Nerve tissue) ,CENTRAL nervous system ,ALZHEIMER'S disease ,BASAL ganglia diseases ,DOPPLER ultrasonography - Abstract
To determine whether jugular venous reflux (JVR) is associated with cerebral white matter changes (WMCs) in individuals with Alzheimer's disease (AD), we studied 12 AD patients 24 mild cognitive impairment (MCI) patients, and 17 elderly age- and gender-matched controls. Duplex ultrasonography and 1.5T MRI scanning was applied to quantify cerebral WMCs [T2 white matter (WM) lesion and dirty-appearing-white-matter (DAWM)]. Subjects with severe JVR had more frequently hypertension (p = 0.044), more severe WMC, including increased total (p = 0.047) and periventricular DAWM volumes (p = 0.008), and a trend for increased cerebrospinal fluid volumes (p = 0.067) compared with the other groups. A significantly decreased (65.8%) periventricular DAWM volume (p = 0.01) in the JVR-positive AD individuals compared with their JVR-negative counterparts was detected. There was a trend for increased periventricular and subcortical T2 WMC lesion volumes in the JVR-positive AD individuals compared with their JVR-negative counterparts (p = 0.073). This phenomenon was not observed in either the control or MCI groups. In multiple regression analysis, the increased periventricular WMC lesion volume and decreased DAWM volume resulted in 85.7% sensitivity and 80% specificity for distinguishing between JVR-positive and JVR-negative AD patients. These JVR-WMC association patterns were not seen in the control and MCI groups. Therefore, this pilot study suggests that there may be an association between JVR and WMCs in AD patients, implying that cerebral venous outflow impairment might play a role in the dynamics of WMCs formation in AD patients, particularly in the periventricular regions. Further longitudinal studies are needed to confirm and validate our findings. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
47. An interdisciplinary study to explore impacts from policies for the introduction of low carbon vehicles.
- Author
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Harrison, Gillian and Shepherd, Simon
- Subjects
ELECTRIC motors ,TRANSPORTATION policy ,CARBON dioxide mitigation ,CLIMATE change ,DYNAMIC models ,GREENHOUSE gas mitigation - Abstract
Driven by concerns of climate change, governments across the world are introducing a number of policies to accelerate the uptake of low carbon vehicles (LCVs), with a specific focus on electric motors. However, there is uncertainty in the effectiveness of such policies and technology pathways, which are inherently interlinked. This article considers the short-term situation to 2020 and focuses on the concern that these policies may bring about some disproportionate impacts in society due to changes in mobility. An ethical framework is established that seeks to balance obligations to reduce greenhouse gas (GHG) emissions and rights to car ownership, then selected policies are modelled within this framework to assess acceptability of implementation. Although these policies are successful in introducing LCVs and reducing GHG emissions, findings also indicate uneven cost burdens and reduced affordability of car ownership. Following this, recommendations for policy amendments and model improvements are made. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
- Full Text
- View/download PDF
48. Jugular venous reflux and white matter abnormalities in Alzheimer's disease: a pilot study.
- Author
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Chung, Chih-Ping, Beggs, Clive, Wang, Pei-Ning, Bergsland, Niels, Shepherd, Simon, Cheng, Chun-Yu, Ramasamy, Deepa P, Dwyer, Michael G, Hu, Han-Hwa, and Zivadinov, Robert
- Abstract
To determine whether jugular venous reflux (JVR) is associated with cerebral white matter changes (WMCs) in individuals with Alzheimer's disease (AD), we studied 12 AD patients 24 mild cognitive impairment (MCI) patients, and 17 elderly age- and gender-matched controls. Duplex ultrasonography and 1.5T MRI scanning was applied to quantify cerebral WMCs [T2 white matter (WM) lesion and dirty-appearing-white-matter (DAWM)]. Subjects with severe JVR had more frequently hypertension (p = 0.044), more severe WMC, including increased total (p = 0.047) and periventricular DAWM volumes (p = 0.008), and a trend for increased cerebrospinal fluid volumes (p = 0.067) compared with the other groups. A significantly decreased (65.8%) periventricular DAWM volume (p = 0.01) in the JVR-positive AD individuals compared with their JVR-negative counterparts was detected. There was a trend for increased periventricular and subcortical T2 WMC lesion volumes in the JVR-positive AD individuals compared with their JVR-negative counterparts (p = 0.073). This phenomenon was not observed in either the control or MCI groups. In multiple regression analysis, the increased periventricular WMC lesion volume and decreased DAWM volume resulted in 85.7% sensitivity and 80% specificity for distinguishing between JVR-positive and JVR-negative AD patients. These JVR-WMC association patterns were not seen in the control and MCI groups. Therefore, this pilot study suggests that there may be an association between JVR and WMCs in AD patients, implying that cerebral venous outflow impairment might play a role in the dynamics of WMCs formation in AD patients, particularly in the periventricular regions. Further longitudinal studies are needed to confirm and validate our findings. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
49. Jugular venous reflux and brain parenchyma volumes in elderly patients with mild cognitive impairment and Alzheimer's disease.
- Author
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Beggs, Clive, Chih-Ping Chung, Bergsland, Niels, Pei-Ning Wang, Shepherd, Simon, Chun-Yu Cheng, Dwyer, Michael G., Han-Hwa Hu, and Zivadinov, Robert
- Subjects
JUGULAR vein ,NECK blood-vessels ,DIAGNOSIS of brain diseases ,MILD cognitive impairment ,ALZHEIMER'S disease diagnosis ,ALZHEIMER'S patients ,DISEASES ,DIAGNOSIS - Abstract
Background To determine whether or not jugular venous reflux (JVR) is associated with structural brain parenchyma changes in individuals with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Methods 16 AD patients (mean (SD): 81.9 (5.8) years), 33 MCI patients (mean (SD): 81.4 (6.1) years) and 18 healthy elderly controls (mean (SD): 81.5 (3.4) years) underwent duplex ultrasonography and magnetic resonance imaging scans to quantify structural brain parenchyma changes. Normalized whole brain (WB), gray matter (GM) and white matter (WM) volumes were collected, together with CSF volume. Results JVR was strongly associated with increased normalized WB (p = 0.014) and GM (p = 0.002) volumes across all three subject groups. There was a trend towards increased WB and GM volumes, which was accompanied by decreased CSF volume, in the JVR-positive subjects in both the MCI and AD groups. When the MCI and AD subjects were aggregated together significant increases were observed in both normalized WB (p = 0.009) and GM (p = 0.003) volumes for the JVR-positive group. No corresponding increases were observed for the JVRpositive subjects in the control group. Through receiver operating characteristic analysis of the brain volumetric data it was possible to discriminate between the JVR-positive and negative AD subjects with reasonable accuracy (sensitivity = 71.4%; specificity = 88.9%; p = 0.007). Conclusions JVR is associated with intracranial structural changes in MCI and AD patients, which result in increased WB and GM volumes. The neuropathology of this unexpected and counterintuitive finding requires further investigation, but may suggest that JVR retrogradely transmits venous hypertension into the brain and leads to brain tissues swelling due to vasogenic edema. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
50. Early Detection of Oral Cancer: How Do I Ensure I Don't Miss a Tumour?
- Author
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Ogden, Graham, Lewthwaite, Rowena, and Shepherd, Simon D.
- Published
- 2013
- Full Text
- View/download PDF
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