186,913 research outputs found
Metastatic deposits in Paget's disease of bone
No full textArticle first published online: 6 APR 2002G. S. Keene, P. Stavrou, R. Clarnette and S. E. Grave
Intermetatarsal coalition: a delayed complication of hallux valgus surgery
No full textArticle first published online: 29 OCT 2013Nicholas Russell, Peter Stavrou, George Dracopoulo
Asymptotic Reverse Waterfilling Algorithm of NRDF for Certain Classes of Vector Gauss-Markov Processes [Elektronisk resurs]
No full textIn this paper, we revisit the asymptotic reverse-waterfilling characterization of the nonanticipative rate distortion function (NRDF) derived for a time-invariant multidimensional Gauss-Markov processes with mean-squared error (MSE) distortion in \cite{stavrou:2018cdc}. We show that for certain classes of time-invariant multidimensional Gauss-Markov processes, the specific characterization behaves as a reverse-waterfilling algorithm obtained in {\it matrix form} ensuring that the numerical approach of \cite[Algorithm 1]{stavrou:2018cdc} is optimal. In addition, we give an equivalent characterization that utilizes the {\it eigenvalues of the involved matrices} reminiscent of the well-known reverse-waterfilling algorithm in information theory. For the latter, we also propose a novel numerical approach to solve the algorithm optimally. The efficacy of our proposed iterative scheme compared to similar existing schemes is demonstrated via experiments. Finally, we use our new results to derive an analytical solution of the asymptotic NRDF for a correlated time-invariant two-dimensional Gauss-Markov process.</p
Nicéphore Blemmydès, Œuvres théologiques. Tome 1. Introduction, texte critique, traduction et notes par Michel Stavrou (coll. Sources chrétiennes, 517). 2007
No full textAuwers Jean-Marie. Nicéphore Blemmydès, Œuvres théologiques. Tome 1. Introduction, texte critique, traduction et notes par Michel Stavrou (coll. Sources chrétiennes, 517). 2007. In: Revue théologique de Louvain, 41ᵉ année, fasc. 1, 2010. p. 123
Bilateral functional popliteal artery entrapment in a young athlete
No full textPopliteal artery entrapment syndrome is a frequent cause of intermittent claudication in young patients. We present a case of a bilateral functional entrapment, where static imaging did not demonstrate the occlusion until the patient's feet were placed in forced plantar flexion. A high index of clinical suspicion and dynamic tests with provocative manoeuvres are needed to diagnose this condition.Panagiotis D. Symeonidis, Peter Stavrou and David Kin
Inertial microfluidic circuits for investigating receptor activation dynamics
No full textThe ErbB family of receptor tyrosine kinases members comprises epidermal growth factor receptor (EGFR), ErbB2, ErbB3 and ErbB4. These receptors recognize external cues (ligands) and subsequently undergo signal transduction that direct the downstream activation of other proteins such as GRB2 and Shc in the signalling cascade and ultimately direct cell fate. Ligand binding induces conformational changes, receptor dimerization and autophosphorylation. Current techniques lack the temporal resolution required to observe receptor activation dynamics that occur over sub-second timescales. Traditionally, quench flow analysis has been used. However, this approach involves turbulent flows that disrupt the cell membrane. Microfluidics involves gentle, laminar flow and has been used for rapid whole cell quench flow analysis to reveal new insights into EGFR autophosphorylation dynamics (Chiang Y. and West J. Lab Chip, 2013, p.1031). In my PhD, I have developed a novel platform based on inertial microfluidics coupled with Dean flow principles. High velocities (m/s) transport within microfluidic channels was used to focus cells to lateral positions within the ligand streams in less than a millisecond (0.5 ms), followed by a curved incubation channel where Dean forces drove cells to a common position, to produce a uniform cell velocity and thus uniform incubation times (CV = <5%). The cells were transported to a second inertial focusing channel and were laterally focused into a quench buffer in order to preserve the receptor intermediates for analysis by multiplexed flow cytometry. The novel microfluidic device successfully monitored the early dynamics of EGFR signalling (25-2000 ms) and unravelled new information on the phosphorylation of two important tyrosine residues, Y1068 and Y1173, found on the EGF receptor. The Y1068 was characterized by high levels of phosphorylation compared to the levels of Y1173 in the sub-second time window. These findings can be used for identifying potential therapeutic targets
Vision, functional and cognitive determinants of motor vehicle incidents in older drivers
No full textBackground: The proportion of older individuals in the driving population is predicted to increase in the next 50 years. This has important implications for driving safety as abilities which are important for safe driving, such as vision (which accounts for the majority of the sensory input required for driving), processing ability and cognition have been shown to decline with age. The current methods employed for screening older drivers upon re-licensure are also vision based. This study, which investigated social, behavioural and professional aspects involved with older drivers, aimed to determine: \ud
(i) if the current visual standards in place for testing upon re-licensure are effective in reducing the older driver fatality rate in Australia; \ud
(ii) if the recommended visual standards are actually implemented as part of the testing procedures by Australian optometrists; and\ud
(iii) if there are other non-standardised tests which may be better at predicting the on-road incident-risk (including near misses and minor incidents) in older drivers than those tests recommended in the standards.\ud
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Methods: For the first phase of the study, state-based age- and gender-stratified numbers of older driver fatalities for 2000-2003 were obtained from the Australian Transportation Safety Bureau database. Poisson regression analyses of fatality rates were considered by renewal frequency and jurisdiction (as separate models), adjusting for possible confounding variables of age, gender and year. \ud
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For the second phase, all practising optometrists in Australia were surveyed on the vision tests they conduct in consultations relating to driving and their knowledge of vision requirements for older drivers. \ud
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Finally, for the third phase of the study to investigate determinants of on-road incident risk, a stratified random sample of 600 Brisbane residents aged 60 years and were selected and invited to participate using an introductory letter explaining the project requirements. In order to capture the number and type of road incidents which occurred for each participant over 12 months (including near misses and minor incidents), an important component of the prospective research study was the development and validation of a driving diary. The diary was a tool in which incidents that occurred could be logged at that time (or very close in time to which they occurred) and thus, in comparison with relying on participant memory over time, recall bias of incident occurrence was minimised. Association between all visual tests, cognition and scores obtained for non-standard functional tests with retrospective and prospective incident occurrence was investigated.\ud
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Results: In the first phase,rivers aged 60-69 years had a 33% lower fatality risk (Rate Ratio [RR] = 0.75, 95% CI 0.32-1.77) in states with vision testing upon re-licensure compared with states with no vision testing upon re-licensure, however, because the CIs are wide, crossing 1.00, this result should be regarded with caution. However, overall fatality rates and fatality rates for those aged 70 years and older (RR=1.17, CI 0.64-2.13) did not differ between states with and without license renewal procedures, indicating no apparent benefit in vision testing legislation. \ud
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For the second phase of the study, nearly all optometrists measured visual acuity (VA) as part of a vision assessment for re-licensing, however, 20% of optometrists did not perform any visual field (VF) testing and only 20% routinely performed automated VF on older drivers, despite the standards for licensing advocating automated VF as part of the vision standard. This demonstrates the need for more effective communication between the policy makers and those responsible for carrying out the standards. It may also indicate that the overall higher driver fatality rate in jurisdictions with vision testing requirements is resultant as the tests recommended by the standards are only partially being conducted by optometrists. Hence a standardised protocol for the screening of older drivers for re-licensure across the nation must be established.\ud
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The opinions of Australian optometrists with regard to the responsibility of reporting older drivers who fail to meet the licensing standards highlighted the conflict between maintaining patient confidentiality or upholding public safety. Mandatory reporting requirements of those drivers who fail to reach the standards necessary for driving would minimise potential conflict between the patient and their practitioner, and help maintain patient trust and goodwill. \ud
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The final phase of the PhD program investigated the efficacy of vision, functional and cognitive tests to discriminate between at-risk and safe older drivers. Nearly 80% of the participants experienced an incident of some form over the prospective 12 months, with the total incident rate being 4.65/10 000 km. Sixty-three percent reported having a near miss and 28% had a minor incident. \ud
The results from the prospective diary study indicate that the current vision screening tests (VA and VF) used for re-licensure do not accurately predict older drivers who are at increased odds of having an on-road incident. However, the variation in visual measurements of the cohort was narrow, also affecting the results seen with the visual functon questionnaires. Hence a larger cohort with greater variability should be considered for a future study. A slightly lower cognitive level (as measured with the Mini-Mental State Examination [MMSE]) did show an association with incident involvement as did slower reaction time (RT), however the Useful-Field-of-View (UFOV) provided the most compelling results of the study. Cut-off values of UFOV processing (>23.3ms), divided attention (>113ms), selective attention (>258ms) and overall score (moderate/ high/ very high risk) were effective in determining older drivers at increased odds of having any on-road incident and the occurrence of minor incidents. \ud
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Discussion: \ud
The results have shown that for the 60-69 year age-group, there is a potential benefit in testing vision upon licence renewal. However, overall fatality rates and fatality rates for those aged 70 years and older indicated no benefit in vision testing legislation and suggests a need for inclusion of screening tests which better predict on-road incidents.\ud
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Although VA is routinely performed by Australian optometrists on older drivers renewing their licence, VF is not. Therefore there is a need for a protocol to be developed and administered which would result in standardised methods conducted throughout the nation for the screening of older drivers upon re-licensure. Communication between the community, policy makers and those conducting the protocol should be maximised. By implementing a standardised screening protocol which incorporates a level of mandatory reporting by the practitioner, the ethical dilemma of breaching patient confidentiality would also be resolved.\ud
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The tests which should be included in this screening protocol, however, cannot solely be ones which have been implemented in the past. In this investigation, RT, MMSE and UFOV were shown to be better determinants of on-road incidents in older drivers than VA and VF, however, as previously mentioned, there was a lack of variability in visual status within the cohort. Nevertheless, it is the recommendation from this investigation, that subject to appropriate sensitivity and specificity being demonstrated in the future using a cohort with wider variation in vision, functional performance and cognition, these tests of cognition and information processing should be added to the current protocol for the screening of older drivers which may be conducted at licensing centres across the nation
Recensions / Book Reviews: CONSTAS DIMITRI AND STAVROU THEOFANIS G., Editors, Greece Prepares for the Twenty-first Century
No full textCONSTAS DIMITRI AND STAVROU THEOFANIS G., Editors, Greece Prepares for the Twenty-first CenturyWashington, D.C.: The Woodrow Wilson Center Press and Baltimore and London: the Johns Hopkins University Press, 1995 (Published in cooperation with the lnstitute of International Relations, Panteion University). XI + 319 p.CONSTAS DIMITRI AND STAVROU THEOFANIS G., Editors, Greece Prepares for the Twenty-first CenturyWashington, D.C.: The Woodrow Wilson Center Press and Baltimore and London: the Johns Hopkins University Press, 1995 (Published in cooperation with the lnstitute of International Relations, Panteion University). XI + 319 p
Providing users' anonymity in mobile hybrid networks
No full textWe present a novel hybrid communication protocol that guarantees mobile users' anonymity against a wide-range of adversaries by exploiting the capability of handheld devices to connect to both WiFi and cellular networks. Unlike existing anonymity schemes, we consider all parties that can intercept communications between a mobile user and a server as potential privacy threats. We formally quantify the privacy exposure and the protection of our system in the presence of malicious neighboring peers, global WiFi eavesdroppers, and omniscient mobile network operators, which possibly collude to breach user's anonymity or disrupt the communication. We also describe how a micropayment scheme that suits our mobile scenario can provide incentives for peers to collaborate in the protocol. Finally, we evaluate the network overhead and attack resiliency of our protocol using a prototype implementation deployed in Emulab and Orbit, and our probabilistic model
Functional losses in type 2 diabetes mellitus
No full textAims: \ud
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Psychophysical tests such as Letter contrast sensitivity (CS) and flicker perimetry have been used to detect early functional losses in ocular disease such as age-related maculopathy (ARM) and in vascular disorders such as migraine. This study set out to determine the ability of these tests to detect early functional losses in type 2 diabetics with minimal or early diabetic retinopathy (DR).\ud
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Methods: \ud
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Subjects consisted of 20 patients with type 2 diabetes (duration, following diagnosis, ranging from 6 months to 18 years) and 24 age-matched normal controls.\ud
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Letter CS, using the Pelli-Robson cha.ii, visual acuity (VA) using the standard high contrast Bailey-Lovie chart and monocular visual fields (VF) were measured. Static and flicker VF were measured using the Medmont M600 perimeter (MFA) and SIT A-standard fields using the Humphrey Field Analyser (HFA) were tested.\ud
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Results: \ud
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Letter CS was able to discriminate those diabetic subjects with none or early DR and those with and without ME from the control group, whereas VA was not able to detect any significant differences in visual function in these diabetic sub-groups compared to the control group.\ud
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In terms of visual fields, both the pattern defect (PD) index and hill-ofvision profiles were analysed. In those with early onset of diabetes and in those with none/minimal DR, only the PD index obtained with the flicker technique was significantly worse than the control group. The hill-of-vision profiles showed that the PD loss in those with minimal DR when flicker perimetry was used, was due to a central depression close to fixation, whereas the MFA static and HFA profiles consisted of a general depression across the field. This indicated that the flicker technique is a more sensitive test than the static technique in determining central visual field defects in those with minor observable retinal changes.\ud
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The inability of the HFA to detect changes to the macula region was thought to be due to the large grid spacing of the stimuli, as when the severity of retinopathy increased to a moderate level, the MFA static technique produced central losses which were not evident with the HFA.\ud
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Conclusion: \ud
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For diabetic patients who had either, a duration of diabetes of less than five years, or displayed only minimal or no DR or no ME, VF defects were only elicited with the use of the MFA flicker technique. Further functional losses in those with no or early, clinically detectable changes, were revealed by measuring Pelli-Robson Letter CS
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