MBS Vehicle-Crossing Model for Crossing Structural Health Monitoring.

This paper presents the development of a multi-body system (MBS) vehicle-crossing model and its application in the structural health monitoring (SHM) of railway crossings. The vehicle and track configurations in the model were adjusted to best match the real-life situation. By using the measurement results obtained from an instrumented crossing and the simulation results from a finite element (FE) model, the MBS model was validated and verified. The results showed that the main outputs of the MBS model correlated reasonably well with those from both the measurements and the FE model. The MBS and FE models formed the basis of an integrated analysis tool, which can be applied to thoroughly study the performance of railway crossings. As part of the SHM system for railway crossings developed at Delft University of Technology, the MBS model was applied to identify the condition stage of a monitored railway crossing. The numerical results confirmed the highly degraded crossing condition. By using the measured degradation as the input in the MBS model, the primary damage sources were further verified. Through identifying the crossing condition stage and verifying the damage source, necessary and timely maintenance can be planned. These actions will help to avoid crossing failure and unexpected traffic interruptions, which will ultimately lead to sustainable railway infrastructure.

Train Hunting Related Fast Degradation of a Railway Crossing-Condition Monitoring and Numerical Verification.

This paper presents the investigation of the root causes of the fast degradation of a railway crossing. The dynamic performance of the crossing was assessed using the sensor-based crossing instrumentation, and the measurement results were verified using the multi-body system (MBS) vehicle-crossing model. Together with the field inspections, the measurement and simulation results indicate that the fast crossing degradation was caused by the high wheel-rail impact forces related to the hunting motion of the passing trains. Additionally, it was shown that the train hunting was activated by the track geometry misalignment in front of the crossing. The obtained results have not only explained the extreme values in the measured responses, but also shown that crossing degradation is not always caused by the problems in the crossing itself, but can also be caused by problems in the adjacent track structures. The findings of this study were implemented in the condition monitoring system for railway crossings, using which timely and correctly aimed maintenance actions can be performed.

Improving the performance of finite element simulations on the wheel-rail interaction by using a coupling strategy.

Over the past few years, a number of implicit/explicit finite element models have been introduced for the purpose of tackling the problems of wheel-rail interaction. Yet, most of those finite element models encounter common numerical difficulties. For instance, initial gaps/penetrations between two contact bodies, which easily occur when realistic wheel-rail profiles are accounted for, would trigger the problems of divergence in implicit finite element simulations. Also, redundant, insufficient or mismatched mesh refinements in the vicinity of areas in contact can lead to either prohibitive calculation expenses or inaccurate implicit/explicit finite element solutions. To address the abovementioned problems and to improve the performance of finite element simulations, a novel modelling strategy has been proposed. In this strategy, the three-dimensional explicit finite element analysis is seamlessly coupled with the two-dimensional geometrical contact analysis. The contact properties in the three-dimensional finite element analyses, such as the initial "Just-in-contact" point, the exact wheel local rolling radius, etc., which are usually a priori unknown, are determined using the two-dimensional geometrical contact model. As part of the coupling strategy, a technique has been developed for adaptive mesh refinement. The mesh and mesh density of wheel-rail finite element models change adaptively depending on the exact location of the contact areas and the local geometry of contact bodies. By this means, a good balance between the calculation efficiency and accuracy can be achieved. Last, but not least, the advantage of the coupling strategy has been demonstrated in studies on the relationship between the initial slips and the steady frictional rolling state. Finally, the results of the simulations are presented and discussed.

Effect of wheel-rail interface parameters on contact stability in explicit finite element analysis.

It is widely recognized that the accuracy of explicit finite element simulations is sensitive to the choice of interface parameters (i.e. contact stiffness/damping, mesh generation, etc.) and time step sizes. Yet, the effect of these interface parameters on the explicit finite element based solutions of wheel-rail interaction has not been discussed sufficiently in literature. In this paper, the relation between interface parameters and the accuracy of contact solutions is studied. It shows that the wrong choice of these parameters, such as too high/low contact stiffness, coarse mesh, or wrong combination of them, can negatively affect the solution of wheel-rail interactions which manifest in the amplification of contact forces and/or inaccurate contact responses (here called "contact instability"). The phenomena of "contact (in)stabilities" are studied using an explicit finite element model of a wheel rolling over a rail. The accuracy of contact solutions is assessed by analyzing the area of contact patches and the distribution of normal pressure. Also, the guidelines for selections of optimum interface parameters, which guarantee the contact stability and therefore provide an accurate solution, are proposed. The effectiveness of the selected interface parameters is demonstrated through a series of simulations. The results of these simulations are presented and discussed.

Kerosene lighting contributes to household air pollution in rural Uganda.

The literature on the contribution of kerosene lighting to indoor air particulate concentrations is sparse. In rural Uganda, kitchens are almost universally located outside the main home, and kerosene is often used for lighting. In this study, we obtained longitudinal measures of particulate matter 2.5 microns or smaller in size (PM2.5 ) from living rooms and kitchens of 88 households in rural Uganda. Linear mixed-effects models with a random intercept for household were used to test the hypotheses that primary reported lighting source and kitchen location (indoor vs outdoor) are associated with PM2.5 levels. During initial testing, households reported using the following sources of lighting: open-wick kerosene (19.3%), hurricane kerosene (45.5%), battery-powered (33.0%), and solar (1.1%) lamps. During follow-up testing, these proportions changed to 29.5%, 35.2%, 18.2%, and 9.1%, respectively. Average ambient, living room, and kitchen PM2.5 levels were 20.2, 35.2, and 270.0 µg/m3 . Living rooms using open-wick kerosene lamps had the highest PM2.5 levels (55.3 µg/m3 ) compared to those using solar lighting (19.4 µg/m3 ; open wick vs solar, P=.01); 27.6% of homes using open-wick kerosene lamps met World Health Organization indoor air quality standards compared to 75.0% in homes using solar lighting.

Cardiopoietic cell therapy for advanced ischaemic heart failure: results at 39 weeks of the prospective, randomized, double blind, sham-controlled CHART-1 clinical trial.

AIMS: Cardiopoietic cells, produced through cardiogenic conditioning of patients' mesenchymal stem cells, have shown preliminary efficacy. The Congestive Heart Failure Cardiopoietic Regenerative Therapy (CHART-1) trial aimed to validate cardiopoiesis-based biotherapy in a larger heart failure cohort. METHODS AND RESULTS: This multinational, randomized, double-blind, sham-controlled study was conducted in 39 hospitals. Patients with symptomatic ischaemic heart failure on guideline-directed therapy (n = 484) were screened; n = 348 underwent bone marrow harvest and mesenchymal stem cell expansion. Those achieving > 24 million mesenchymal stem cells (n = 315) were randomized to cardiopoietic cells delivered endomyocardially with a retention-enhanced catheter (n = 157) or sham procedure (n = 158). Procedures were performed as randomized in 271 patients (n = 120 cardiopoietic cells, n = 151 sham). The primary efficacy endpoint was a Finkelstein-Schoenfeld hierarchical composite (all-cause mortality, worsening heart failure, Minnesota Living with Heart Failure Questionnaire score, 6-min walk distance, left ventricular end-systolic volume, and ejection fraction) at 39 weeks. The primary outcome was neutral (Mann-Whitney estimator 0.54, 95% confidence interval [CI] 0.47-0.61 [value > 0.5 favours cell treatment], P = 0.27). Exploratory analyses suggested a benefit of cell treatment on the primary composite in patients with baseline left ventricular end-diastolic volume 200-370 mL (60% of patients) (Mann-Whitney estimator 0.61, 95% CI 0.52-0.70, P = 0.015). No difference was observed in serious adverse events. One (0.9%) cardiopoietic cell patient and 9 (5.4%) sham patients experienced aborted or sudden cardiac death. CONCLUSION: The primary endpoint was neutral, with safety demonstrated across the cohort. Further evaluation of cardiopoietic cell therapy in patients with elevated end-diastolic volume is warranted.

Persistent Atrial Fibrillation And Atrial Flutter Complicated By Tachycardiomyopathy Because Of Intermittent Conduction Through Accessory Pathway.

The term tachycardiomyopathy refers to a specific form of tachycardia-related cardiomyopathy caused by supraventricular or ventricular tachyarrhytmias that are both associated with ventricular rates higher than 120 bpm. The arrhythmias which are most frequently associated with these forms of heart disease are atrial fibrillation and atrial flutter, particularly found in the elderly population. The most frequent clinical manifestation is heart failure. In this case we are reporting a clinical case of a patient that came to our attention because of an episode of heart failure associated with atrial fibrillation and atrial flutter. The patient had also prolonged and repetitive strips of rapid conduction with wide QRS morphology. We don't know if the cause is pre excitation or ectopia. We showed that those strips of tachycardia with wide QRS, particularly when they were associated with atrial flutter, were so fast and consistent to determine the left ventricular contractile dysfunction; we showed also that those strips of wide complex tachycardia were caused by pre-excitation through an accessory right posteroseptal pathway and supported by the reentry circuit of common atrial flutter. The block of conduction through the accessory pathway and the elimination of atrial arrhythmia allowed the regression of left ventricular contractile dysfunction. We believe that this case is interesting because it shows that there is a strict continuity between sophisticated electrophysiological mechanisms and clinical manifestation.

Comparison between immunoradiometric and fluorimetric brain natriuretic peptide determination in patients with congestive heart failure.

UNLABELLED: This study compared two different methods, namely the immunoradiometric (IRMA) and fluorimetric (FIA), in order to determine plasma brain natriuretic peptide (BNP) in congestive heart failure (CHF) patients. METHODS: CHF in-patients underwent echocardiography and plasma BNP determination using both two methods. The echocardiograms analysed left ventricular end-systolic (LVESV) and end-diastolic (LVEDV) volumes and systolic dysfunction [left ventricular ejection fraction (LVEF) <50%]. RESULTS: Seventy-three (71% males, age 67 ± 9.6 yr) patients were enrolled, 31.5% affected by valvular heart disease. The mean LVEF was 39.8 ± 14.1%; in 26 (35%) a hypertensive etiology emerged. The immunoradiometric assay (IRMA) BNP was found to be significantly lower than the FIA determination 116.5 ± 149 pg/ml vs 267.3 ± 285.6 pg/ml; p=0.0001) and the two methods were closely correlated (r=0.89; p=0.00001). Logistic regression demonstrated a significant correlation between BNP, LVEF, and LVESV/LVEDV (r=-0.45, p=0.0003; r=-0.48, p=0.00001; r=0.22 p=0.003; r=0.34 p=0.0001; r=0.13 p=0.02; r=0.28 p=0.001 IRMA and FIA, respectively). IRMA BNP and FIA BNP significantly increased according to the worsening functional class [from 34.3 ± 60.2 pg/ml in NYHA (New York Heart Association) I to 555.5 ± 273.1 pg/ml in NYHA IV; from 86.1 ± 162.1 pg/ml in NYHA I to 1070 ± 42.2 pg/ml in NYHA IV, respectively]. In severe systolic dysfunction (LVEF<30%), receiver operating characteristic analysis revealed a satisfactorily sensitivity and specificity using a cut-off point of 50.6 pg/ml with IRMA and 243 pg/ml with FIA. In mild systolic dysfunction (LVEF<50%), a good sensitivity and specificity using a cut-off point of 42 pg/ml with IRMA and 182 pg/ml with FIA emerged. CONCLUSIONS: In CHF patients both BNP methods correlated with NYHA class, LVEF, and ventricular volumes.

Melatonin attenuates metabolic disorders due to streptozotocin-induced diabetes in rats.

Enhanced oxidative stress and impairments in nitric oxide synthesis and bioavailability are of considerable importance in the pathogenesis of diabetic vascular diseases. The aim of the present work was to evaluate the metabolic effects of pharmacological doses of the melatonin, a known antioxidant, on streptozotocin-induced diabetic damage in rats. We investigated the indolamine's influence on the cellular redox-balance, nitric oxide (NO) level, and the activities of antioxidative defence enzymes, as well as the activities of enzymes involved in phase II detoxication and NADPH-generating pentose phosphate pathway. Blood glucose, glycated hemoglobin, bilirubin, as well as plasma alanine aminotransferase activities increased and body weight was reduced in rats with streptozotocin-induced (60 mg/kg, i.p.) diabetes (25 days). The NO level was markedly increased in diabetic plasma (by 50%) and aortic tissue (by 30%). The hyperglycemia resulted in reduced activities of glutathione peroxidase (by 25%), catalase (by 20%), glucose-6-phosphate dehydrogenase (by 55%) and transketolase (by 40%) in liver tissue of diabetic animals. Melatonin treatment (10 mg/kg, 18 days) did not influence the level of hyperglycemia or glycated hemoglobin and it had little effect on the activities of antioxidative enzymes. However, melatonin markedly reversed the activities of glucose-6-phosphate dehydrogenase and transketolase in liver tissue of diabetic rats. The most pronounced effect of the melatonin administration was the prevention of an increase in nitric oxide levels in blood plasma and aortic tissue during diabetes. In in vitro experiments, nitrosomelatonin formation in the presence of nitrosodonors was observed. This implies that melatonin might operate as an NO scavenger and carrier. Thus, melatonin treatment may have some beneficial effects in controlling diabetic vascular complications.

Reliability and validity of the Cognitive Slippage Scale in two populations.

Analyses of responses from a clinical sample of 120 patients (primarily schizophrenics) and from 158 college students to the Cognitive Slippage Scale, a scale designed by Miers and Raulin to identify speech deficits and confused thinking in schizophrenic and schizotypal personality disorders showed high internal reliability; Cronbach's coefficients alpha were .89 and .86 in the clinical and college student samples, respectively. The mean scale scores significantly differentiated the two samples. Also, change scores over 4 wk. showed adequate stability for both samples. Item analysis indicated Items 11, 20, 21, and 28 may not reliably discriminate between schizophrenic and college student samples. Over-all, these preliminary results are consistent with the reliability and validity of the scale.

Comparison of traditional gas chromatography (GC), headspace GC, and the microbial identification library GC system for the identification of Clostridium difficile.

Three gas chromatography (GC) methods were compared for the identification of 52 clinical Clostridium difficile isolates, as well as 17 non-C. difficile Clostridium isolates. Headspace GC and Microbial Identification System (MIS) GC, an automated system which utilizes a software library developed at the Virginia Polytechnic Institute to identify organisms based on the fatty acids extracted from the bacterial cell wall, were compared against the reference method of traditional GC. Headspace GC and MIS were of approximately equivalent accuracy in identifying the 52 C. difficile isolates (52 of 52 versus 51 of 52, respectively). However, 7 of 52 organisms required repeated sample preparation before an identification was achieved by the MIS method. Both systems effectively differentiated C. difficile from non-C. difficile clostridia, although the MIS method correctly identified only 9 of 17. We conclude that the headspace GC system is an accurate method of C. difficile identification, which requires only one-fifth of the sample preparation time of MIS GC and one-half of the sample preparation time of traditional GC.

Quantitative evaluation of spleen haemodynamics from radiocolloidal dynamic scintigraphy.

Quantitative information on spleen perfusion may be obtained as a byproduct of liver studies using 99Tcm colloids, by means of model analysis of dynamic data collected with a large field-of-view computerized gamma camera for about 4 min after intravenous administration of the tracer. Spleen extraction efficiency, vascular transit time, and parameters related to spleen blood flow, splenic clearance and volume of distribution of the tracer were computed, the latter three being expressed in arbitrary units. Results in 14 normal subjects and 78 patients with liver cirrhosis show good agreement with known physiopathological data. Results in five splenectomised patients and one patient undergoing ligation of the splenic artery provided further confirmation of the physiopathological meaning of the estimated parameters. Accuracy was found to be poor for spleens of small (normal) size, but was acceptable for enlarged spleens. Reproducibility of the results appears to be within 20%. It is concluded that this method, when associated with the study of liver function using a single 3-4 mCi dose of radiocolloids, may provide valuable additional information for routine assessment of splanchnic haemodynamics in patients with portal hypertension and splenomegaly.

A new approach to non-invasive quantitative study of hepatic haemodynamics using radiocolloids in vivo.

A non-invasive radioisotopic method for the study of liver haemodynamics is described. Data collected by means of a computerised gamma camera for about 4 min after intravenous administration of 99Tcm human serum albumin colloids were analysed using a new mathematical model formulated on a physiopathological basis. Several quantities of possible clinical interest were determined, namely parameters related to liver blood flows, intrahepatic shunts, the intrahepatic space of distribution of the tracer, transit times and extraction efficiency. Results are not affected, within certain limits, by the shape of the radioactive bolus and, with the exception of extraction efficiency, they appear to be independent of the size of the radiocolloidal particle. The dose employed (3-4 mCi) is comparable with that used in liver scintigraphy. Results in 19 subjects with normal liver function, 45 patients with liver cirrhosis and 7 patients with focal liver lesions were in good agreement, from a quantitative viewpoint, with known physiopathological data, thus validating this method in comparison with other more traumatic and/or less practical techniques, which provide less complete information on liver haemodynamics. The method proposed appears to be sufficiently accurate, reproducible, safe and practical, and may thus be considered suitable for routine use in the assessment of functional aspects of liver perfusion for clinical purposes.

Familiar clustering and spreading of hepatitis delta virus infection.

The prevalence of hepatitis delta virus (HDV) infection was significantly higher among the relatives of 79 carriers of HBsAg with antibody to HDV (index cases) than among relatives of 111 carriers without serological evidence of HDV infection (controls). Antibody to HDV was found in 45 of the 80 (56%) carriers of HBsAg in families of index cases but only in 2 of 59 (3%) carriers in families of controls (P less than 0.0001). During follow-up new HDV infection developed in 31% of 13 susceptible carriers in families of index cases, but only in 1.2% of 162 susceptible carriers in families of controls (P less than 0.001). None of the family members previously unexposed to the hepatitis B virus had HDV markers in serum or developed this infection during the follow-up. Familial clustering shows that HDV is transmitted by personal contacts, presumably through the inapparent permucosal or percutaneous passage of virus during close or intimate contact. The family model indicates that endemic HDV is maintained and spread through the network of carriers in the community, and that HBsAg carriers in contact with HBsAg/HDV carriers are at high risk of contracting HDV.