The effect of the number of response cycles on the behaviour of reinforced concrete elements subject to cyclic loading

The development of damage in reinforced concrete (RC) structures is a cumulative process. Some damage indices used to quantify damage make use of the number of response cycles as an Engineering Demand Parameter (EDP) relating with damage development. Other indices make use of deformation in terms of displacement or chord rotation. These functions are generally a function of whether the response is monotonic or cyclic, and are insensitive to the number of major deflection cycles leading to that state of damage. Many such relations are derived from experimental data from low-cycle fatigue tests performed on RC elements. The loading in such tests generally consists of either a monotonic increase in load or a gradually increasing cyclic load. Since damage development is a cumulative process, and hence depends on the load history, the loading pattern in low-cycle fatigue tests for assessment purposes should reflect the response of an earthquake. This paper will discuss a procedure to determine a loading history for cyclic tests, based on earthquake demands. The preliminary results of a campaign of low-cycle fatigue tests on RC elements to investigate the effect of using different load histories are also discussed

Low cycle fatigue tests of reinforced concrete columns and joints built with ribbed reinforcement and plain stirrups

The majority of existing reinforced concrete (RC) buildings were built prior to the introduction of seismic codes. As observed in various recent earthquakes, due to their lack of structural capacity and ductility such structures are very vulnerable and have suffered considerable damage. The number of cyclic tests that have been carried out to investigate the behaviour of RC components with detailing typical of these buildings is very limited. Such tests are very relevant for seismic vulnerability assessment purposes. In this paper, a low-cycle fatigue testing campaign on RC columns and connections specifically devised to investigate various physical parameters that affect damage development, is presented. The campaign consists of 19 columns and 7 beam-column connections. Some of the preliminary results and observations are presented and discussed

Seronegative spondyloarthropathies : a review : part I: classification and differential diagnosis

The seronegative spondyloarthropathies comprise a group of non-rheumatoid disorders with similar clinical, laboratory and genetic features. Recognition of new clinical features has supported the notion that they all form part of a clinical spectrum. These features and the classification of the seronegative spondyloarthropathies are discussed in the review.peer-reviewe

Escherichia coli O157:H7 in Malta for the first time

The emergence of E coli O157:H7 in Malta is a sign of the times. It represents one of the newly emerging infections associated with food. The first two documented cases of E coli 0157:H7 infection in Malta occurred in July and August, 1996. Food types classically incriminated were surveyed by the Department of Public Health. Epidemiological investigation aimed to trace the environmental sources of infection.• Microbiology was performed jointly by diagnostic and public health laboratories. Facts about infection and control of the disease are highlighted with a view to alerting local practitioners to the condition.peer-reviewe

Seronegative spondyloarthropathies : a review : part II: genetics and pathogenesis

In none of the spondyloarthropathies is the pathogenesis well understood. Much of the investigation into the aetio-pathogenesis of these diseases has focused on the association with HLA-B27 and the known triggering potential of certain infectious agents. In this article the author describes that the HLA linked genes which is subdivided into three groups, class I, class II and class III, which are structurally and functionally distinct from each other.peer-reviewe

Aortic coarctation : never too late to diagnose, never too late to treat

We present two cases of severe aortic coarctation detected in adulthood and who underwent successful relief by transcatheter stent deployment using a new covered stent, Optimus® stent (AndraTec GmbH Koblenz, Germany). One patient is a 46-year old female with resistant arterial hypertension, in whom coarctation was suspected on a follow-up transthoracic echocardiogram for bicuspid aortic valve disease and subsequently confirmed on magnetic resonance imaging. The second patient is a 68-year old male whose coarctation was diagnosed incidentally at coronary angiography being performed as part of the preoperative work-up for severe aortic stenosis. Suprasternal views to assess aortic arch and flows in the proximal descending aorta should be a standard part of every transthoracic echocardiogram. Treatment of aortic coarctation should be considered irrespective of patient’s age.peer-reviewe

Scale Free Cluster Distributions from Conserving Merging-Fragmentation Processes

We propose a dynamical scheme for the combined processes of fragmentation and merging as a model system for cluster dynamics in nature and society displaying scale invariant properties. The clusters merge and fragment with rates proportional to their sizes, conserving the total mass. The total number of clusters grows continuously but the full time-dependent distribution can be rescaled over at least 15 decades onto a universal curve which we derive analytically. This curve includes a scale free solution with a scaling exponent of -3/2 for the cluster sizes.Comment: 4 pages, 3 figure

Can perceptual indices estimate physiological strain across a range of environments and metabolic workloads when wearing explosive ordnance disposal and chemical protective clothing?

Objective Explosive ordnance disposal (EOD) often requires technicians to wear multiple protective garments in challenging environmental conditions. The accumulative effect of increased metabolic cost coupled with decreased heat dissipation associated with these garments predisposes technicians to high levels of physiological strain. It has been proposed that a perceptual strain index (PeSI) using subjective ratings of thermal sensation and perceived exertion as surrogate measures of core body temperature and heart rate, may provide an accurate estimation of physiological strain. Therefore, this study aimed to determine if the PeSI could estimate the physiological strain index (PSI) across a range of metabolic workloads and environments while wearing heavy EOD and chemical protective clothing. Methods Eleven healthy males wore an EOD and chemical protective ensemble while walking on a treadmill at 2.5, 4 and 5.5 km·h− 1 at 1% grade in environmental conditions equivalent to wet bulb globe temperature (WBGT) 21, 30 and 37 °C. WBGT conditions were randomly presented and a maximum of three randomised treadmill walking trials were completed in a single testing day. Trials were ceased at a maximum of 60-min or until the attainment of termination criteria. A Pearson's correlation coefficient, mixed linear model, absolute agreement and receiver operating characteristic (ROC) curves were used to determine the relationship between the PeSI and PSI. Results A significant moderate relationship between the PeSI and the PSI was observed [r = 0.77; p < 0.001; mean difference = 0.8 ± 1.1 a.u. (modified 95% limits of agreement − 1.3 to 3.0)]. The ROC curves indicated that the PeSI had a good predictive power when used with two, single-threshold cut-offs to differentiate between low and high levels of physiological strain (area under curve: PSI three cut-off = 0.936 and seven cut-off = 0.841). Conclusions These findings support the use of the PeSI for monitoring physiological strain while wearing EOD and chemical protective clothing. However, future research is needed to confirm the validity of the PeSI for active EOD technicians operating in the field

Attitudes of a sample of English, Maltese and German teachers towards media education

Media education forms part of the National Minimum Curriculum of England, Malta and Germany. Teacher training courses differ greatly in how teachers are prepared to teach media education. In this paper we shall investigate the attitudes of a sample of teachers trained in England, Malta and in Germany towards their perceived importance of media education and the teachers’ preparedness to teach the subject. This preliminary study had a sample of 132 participants, 33 teachers from England, 47 from Germany and 52 teachers from Malta. The tool used to collect data was an online questionnaire. The results show that teachers taking part in this study were not given enough training, or any training at all to be able to teach media education with the result that they do not feel sufficiently prepared to teach the subject. It is suggested by the authors that media education becomes a compulsory component of the initial teacher training courses as well as advanced training for teachers.peer-reviewe

Human subjective response to steering wheel vibration caused by diesel engine idle

This study investigated the human subjective response to steering wheel vibration of the type caused by a four-cylinder diesel engine idle in passenger cars. Vibrotactile perception was assessed using sinusoidal amplitude-modulated vibratory stimuli of constant energy level (r.m.s. acceleration, 0.41 m/s(2)) having a carrier frequency of 26 Hz (i.e. engine firing frequency) and modulation frequency of 6.5 Hz (half-order engine harmonic). Evaluations of seven levels of modulation depth parameter m (0.0, 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0) were performed in order to define the growth function of human perceived disturbance as a function of amplitude modulation depth. Two semantic descriptors were used (unpleasantness and roughness) and two test methods (the Thurstone paired-comparison method and the Borg CR-10 direct evaluation scale) for a total of four tests. Each test was performed using an independent group of 25 individuals. The results suggest that there is a critical value of modulation depth m = 0.2 below which human subjects do not perceive differences in amplitude modulation and above which the stimulus-response relationship increases monotonically with a power function. The Stevens power exponents suggest that the perceived unpleasantness is non-linearly dependent on modulation depth m with an exponent greater than 1 and that the perceived roughness is dependent with an exponent close to unity