Permeability due to the Increase of Damage in Concrete: From Diffuse to Localized Damage Distributions

Experimental tests exhibit a strong interaction between material damage and transport properties of concrete. There are at least two asymptotic cases where some theoretical modeling exists: in the case of diffuse cracking, the material permeability should be controlled by damage, e.g., by the decrease of average stiffness due to microcracking. In the case of localized microcracking, and after a macrocrack has formed, permeability should be controlled by a power function of the crack opening (Poiseuille flow). For quasi-brittle materials with evolving microstructure due to mechanical loads, a transition regime on the evolution of permeability between these two asymptotic cases is expected. In this contribution, we define a relationship between permeability and damage that is consistent with the two above configurations. One of the key issues is to relate the crack opening to the state variables in the continuum approach, so that the two asymptotic cases are expressed in the same variable system and can be matched. A simplified approach is used for this purpose. The permeability law is then derived using a mixing formula that weights each asymptotic regime with damage. To illustrate the influence of the matching law on structural response, finite-element simulations of a Brazilian splitting test and a comparison with existing test data are presented.     

Wedge type creep damage in low cycle fatigue

A model is proposed to quantify the accumulation of wedge type creep damage in low cycle fatigue. It is proposed that such damage is produced primarily during the ramp periods of the cycle. Equations are developed for estimating incremental accumulation of damage per cycle in fully reversed, multiaxial loading. The rate of accumulation of damage depends on the strain-rate, the temperature, and the microstructure. The analysis is kept simple by making physically reasonable assumptions. Cycles to failure are predicted by invoking a fracture criterion. The model is applied to two sets of data; one set is a well characterized life test data on an aluminum alloy, and the other is phenomenological data on austenitic stainless steels. In both cases the predictions are good enough to prompt further experimental evaluation of the model. This paper deals with only one mechanism of creep-fatigue interaction. Other mechanisms of failure,e.g., ‘r’ type cavitation, or fatigue crack initiation and propagation, are also viable. The model described here may be expected to apply only under those conditions when wedge damage is the dominant failure mechanism.     

Use of liver allografts from carbon monoxide poisoned cadaveric donors

Carbon monoxide (CO) inhalation leads to cerebral, cardiac, and, more rarely, liver damage. The use of liver allografts from CO poisoned donors with evidence of liver damage has not previously been reported. In this report we describe two recipients, both in fulminant hepatic failure, who received liver grafts from such donors. One donor had markedly abnormal liver function tests (LFTS), and in the other LFTS were mildly abnormal. In both, the liver appeared normal at procurement. There was satisfactory early function of both allografts, although marked patchy necrosis was seen on the postreperfusion biopsy (case 1), and on a 10 day postoperative biopsy (case 2). In both cases the changes were considered to be related to damage sustained from CO inhalation. Both allografts soon achieved normal function and both recipients are well. We conclude that CO poisoning can cause liver damage that can recover completely following liver transplantation.     

Review: the overviews of contrast echocardiography in cardiovascular disorders

Damage to clothing is commonly encountered in serious crimes of violence such as homicide and rape. Examination of damage to clothing and other textiles may provide valuable information as to the possible implement that caused the damage and the manner in which it was caused. Damage analysis may corroborate or refute a particular crime scenario. This report describes two recent cases examined at the Victoria Forensic Science Centre laboratory where opposing views as to the origin of the damage to the clothing of the victim were proposed. The results confirm the value of simulation experiments mimicking each case scenario. They also demonstrate that it may not be possible to unequivocally choose between opposing scenarios because of limitations inherent in damage analysis.     

Methylmercury poisoning, Clinical follow-up and sensory nerve conduction studies

Methylmercury poisoning occurred in four cases after passage of methylmercury through the food chain. The neurological damage in all four cases was severe. The damage was greater at younger ages with maximum involvement in the case of transplacental poisoning. Significant recovery occurred in two cases, but on six-year follow-up two cases remained severely impaired. Clinical and electrophysiological evidence suggests that damage to peripheral sensory nerves may not be the cause of the late sensory symptomatology.     

Late-onset cutis laxa (generalized elastolysis)

Cutis laxa is a heterogeneous disease of elastic fibres, divided into three congenital and two acquired forms. Its aetiology is unknown except for the X-linked recessive form. A late form with slow progression in a 52-year-old woman and a probably postinflammatory form in a 29-year-old woman are reported. In both cases histological examination revealed severe damage of the elastic fibres of the skin, in the first one also calcium deposits and (electronmicroscopically) damage to collagen fibres. Treatment is entirely symptomatic, but in severe cases plastic surgery may help cosmetically.     

Hilbert-Huang Based Approach for Structural Damage Detection

When measured data contain damage events of the structure, it is important to extract the information of damage as much as possible from the data. In this paper, two methods are proposed for such a purpose. The first method, based on the empirical mode decomposition (EMD), is intended to extract damage spikes due to a sudden change of structural stiffness from the measured data thereby detecting the damage time instants and damage locations. The second method, based on EMD and Hilbert transform is capable of (1) detecting the damage time instants, and (2) determining the natural frequencies and damping ratios of the structure before and after damage. The two proposed methods are applied to a benchmark problem established by the ASCE Task Group on Structural Health Monitoring. Simulation results demonstrate that the proposed methods provide new and useful tools for the damage detection and evaluation of structures.     

Iodixanol in cardioangiography in patients with coronary artery disease. Tolerability, cardiac and renal effects

PURPOSE: Complications following transvaginal ultrasound-directed follicle aspiration are rare, making it difficult to assess their true incidence. During a 4-year prospective study the complications arising from a series of 2670 consecutive procedures were monitored. RESULTS: Vaginal hemorrhage occurred in 229 (8.6%) of the cases, with a significant loss (> 100 ml) in 22 (0.8%). Postoperative pelvic infection occurred in 18 (0.6%) of the cases. Hemorrhage from the ovary with hemoperitoneum formation was seen on two occasions and necessitated emergency laparotomy in one instance. A single case of pelvic haematoma formation from a punctured iliac vessel was also recorded; this settled without intervention. Of the 18 cases with infection, 9 were severe with pelvic abscess formation; microbiological examination of the pus from these cases suggests that the most common route of infection in such cases is probably by direct inoculation of vaginal organisms into the peritoneal cavity by the collecting needle. CONCLUSION: The low incidence of pelvic infection questions the value of using prophylactic antibiotics. No increased risk of infection was demonstrated in cases with preexisting peritoneal damage.     

High prevalence of acute myocardial damage in a hospital necropsy series, shown by C9 immunohistology

AIMS: To use a sensitive test of acute myocardial damage--immunohistological detection of complement component C9--to assess the prevalence of damage in an unselected series of hearts taken at necropsy in adults. METHODS: Sections of formalin fixed and paraffin wax embedded myocardium were cut from 128 consecutive necropsy cases on which a block of heart had been taken. These were stained with an immunohistological method for C9. Necropsy findings were reviewed and clinical risk factors for myocardial damage noted. The extent of C9 immunostaining was correlated with clinical and pathological findings. RESULTS: There was immunostaining for C9 in 109 heart sections (85%). Most had conventional evidence of coronary artery disease or acute or chronic myocardial abnormality, but necrosis was identified by orthodox microscopy in only 12 (11% of C9 positive cases). In 29 cases, orthodox examination showed no abnormality, but C9 was detected. These cases had clinical risk factors for damage such as hypoxia and hypotension. Increasing age, heart weight, and total number of risk factors and pathological findings were associated with increasing extent of C9 immunostaining. CONCLUSIONS: Acute myocardial damage was common in a hospital necropsy series and its prevalence was underestimated by conventional pathological techniques. Immunostaining for C9 was a simple and useful way of detecting such damage.     

Morphological changes in traumatized skeletal muscle: the appearance of 'opaque fibers' of cervical muscles as evidence of compression of the neck

Cervical muscles of 15 cases of compression of the neck and the other traumatized skeletal muscles from 54 autopsy cases were examined histologically and immunohistochemically. Round and thick fibers, that is, opaque fibers were observed in the muscles beneath the compression marks on the neck, whereas in areas where no force had been applied, such fibers did not exist. Furthermore, opaque changes appeared around cavities, which formed within severely compressed injured muscle tissue. The pattern of appearance of opaque fibers in the cases of compression of the neck were mainly divided into two types, 'diffuse' pattern and 'focal' pattern. In both blunt and sharp force injuries, the production of opaque fibers were common in the area directly where damage had been inflicted. In stab wounds especially, the appearance of opaque fibers and wavelike fibers, which fanned out and showed a different color from the other areas, was limited to the marginal zone. These results suggest that there is a close relationship between opaque changes and force. Opaque fibers are probably produced by damage to muscles due to extremely applied force. The high incidence of opaque fibers beneath compression marks on the neck should be regarded as a useful indication of strangulation and/or hanging. Furthermore, the distribution and direction of force to the neck might be presumed by the pattern of opaque fibers in cervical muscles, to a certain extent.     

Vulnerability Assessment of Cable-Stayed Bridges in Probabilistic Domain

Vulnerability of a structure under terrorist attack can be regarded as the study of its behavior against blast-induced loads. A structure is vulnerable if a small damage can trigger a disproportionately large consequence and lead to a cascade of failure events or even collapse. The performance of structural vulnerability depends upon factors such as external loading condition and structural properties. As many of these factors are random in nature, it is necessary to develop a vulnerability assessment technique in the probabilistic domain. In this study, one such assessment framework is proposed for cable-stayed bridges. The framework consists of two stages of analysis: determining the probability of direct damage due to blast loads and assessing the subsequent probability of collapse due to component damage. In the first stage assessment, damage of the bridge component is defined as the exceedance of a predefined limit state such as displacement or yielding. The damage probability is obtained through a stochastic finite-element analysis and the first-order second-moment reliability method. The second stage assessment further calculates the probability of collapse due to direct damage of some component via an event tree approach. The proposed assessment methods are illustrated on a hypothetical single-tower cable-stayed bridge. It is seen that the proposed methods provide a quantitative tool for analyzing the vulnerability performance of cable-stayed bridges under terrorist attack.     

Structural Health Monitoring and Damage Assessment Using Frequency Response Correlation Criteria

Two frequency response correlation criteria, namely the global shape correlation (GSC) function and the global amplitude correlation (GAC) function, are established tools to quantify the correlation between predictions from a finite-element (FE) model and measured data for the purposes of FE model validation and updating. This paper extends the application of these two correlation criteria to structural health monitoring and damage detection. In addition, window-averaged versions of the GSC and GAC, namely WAIGSC and WAIGAC, are defined as effective damage indicators to quantify the change in structural response. An integrated method of structural health monitoring and damage assessment, based on the correlation functions and radial basis function neural networks, is proposed and the technique is applied to a bookshelf structure with 24 measured responses. The undamaged and damaged states, single and multiple damage locations, as well as damage levels, were successfully identified in all cases studied. The ability of the proposed method to cope with incomplete measurements is also discussed.     

Brain imaging in neonatal hypoglycaemia

Magnetic resonance imaging studies in two cases of neonatal hypoglycaemia showed cortical and white matter cerebral damage that was most obvious in the occipital lobes. Both cases showed oedema in the parieto-occipital cortex and underlying white matter in the acute phase, with profound atrophy of these regions in the chronic phase. These findings support those of pathological studies which suggest that hypoglycaemia induces cerebral damage by a mechanism separate from the effects of cerebral hypoxia-ischaemia caused by secondary seizures.     

Intrarenal reflux

Seventy-six children with a total of 123 ureters showing vesico-ureteric reflux were reviewed in order to detect intrarenal reflux (pyelotubular backflow) occuring during micturating cystourethrography. This was found in 7 patients (9.2%). Five patients had unilateral and two bilateral intrarenal reflux. In only 7 out of the 9 kidneys with intrarenal reflux was it possible to outline the kidney contour precisely on excretion urography. In 3 cases renal damage corresponded exactly to the areas with intrarenal reflux. One kidney showed damage which did not correspond to the location of intrarenal reflux and 3 were without signs of damage. Renal damage of varying localization was found in 54 of the 123 kidneys with vesico-ureteric reflux and intrarenal reflux was present in 6 of these (11%). The significance of intrarenal reflux as a cause of renal damage and whether intrarenal reflux might be primary or secondary to the renal damage are discussed, and it is concluded that presence of intrarenal reflux is a definite indication for operation.     

Intravenous gentamicin therapy in bilateral Menière disease

BACKGROUND: The treatment of severe forms of bilateral Menière's disease remains an especially challenging task. Similar problems also occur in debilitating Menière's disease in the only hearing ear. The intramuscular titration therapy with streptomycin has been the means of choice since 1984 to minimize the risk of total hearing loss in cases of severe bilateral disease. METHOD: Since 1989 we have treated six out of 21 cases of bilateral Menière's disease by intravenous application of 2 x 120 mg gentamicin in Ringer's solution for several days. Additionally we reported on two cases in 1988. Only minor amounts of gentamicin were applied to sedate the function of both vestibular organs while avoiding damage to the cochlea. RESULTS: In two cases hearing approved approximately about 10 dB, in two cases hearing remained stable, and in two cases hearing worsened about 10 dB. Five of six patients showed minor excitability in caloric tests on both sides, they did not complain of vertigo attacks one to five years after therapy. CONCLUSION: Given that only very small amounts of gentamicin are applied to sedate the function of the vestibular organ while causing almost no damage to the cochlea, this method seems to be an excellent means for treatment of bilateral Menière's disease. Patients do not experience severe problems with equilibrium afterwards, and the treatment can be repeated as often as necessary.     

Side effects of anticonvulsants in the treatment of idiopathic generalized epilepsy

This investigation was ainced on detection of frequency and main features of side effects of anticonvulsants in therapy of idiopathic generalized epilepsy. There were observed 190 patients aged 5-29 years suffering from different forms of idiopathic generalized epilepsy. Side effects were revealed in 48.4% of patients as a result of the investigation. Almost half of patients (49.0%) who were administered valproic acid developed side effects. Neuroendocrine dysfunctions and digestive disturbances were the most frequent. Side effects were revealed within the first two months after administration of valproats. Only in 13.2% of cases the treatment and to be stopped at the expense of severeness of side effects. Barbiturates caused side effects in 39.6% of cases. Toxic damage of CNS was the most significant. Hyperkinetic syndrome with lack of attention was observed 37.9% of cases. Succinimides caused side effects in 37.9% of cases. Toxic damage of CNS was the most frequent--in 22.4% of cases, digestive disturbances was in 15.5% of cases. There are no really effective means for correction of above mentioned side effects.     

Fatal neonatal liver failure and mitochondrial cytopathy (oxidative phosphorylation deficiency): a light and electron microscopic study of the liver

Mitochondrial cytopathies are multisystemic disorders of extremely variable expression due to a deficiency in oxidative phosphorylation. Cases have recently been reported in which fatal liver failure with neonatal onset was the major clinical and biochemical syndrome. In this series we reviewed the liver histology of 10 such patients who died in the first weeks of life (from 3 days to 6 mo). In six cases the diagnosis was confirmed by study of the mitochondrial respiratory chain in the muscle, liver or both; in the other four, appropriate tests were not available for diagnosis but symptoms were identical and all other diagnoses were ruled out. In all 10 cases we noted significant steatosis, mostly microvesicular; widespread hepatocytic, canalicular and bile duct cholestasis with bile thrombi and cholangiolar proliferation; and different degrees of hepatosiderosis and glycogen depletion. Fibrosis took varying forms: perisinusoidal, periportal with the formation of septa, even precirrhosis. In the two cases of infants who died, one at 5 and one 6 mo, micronodular cirrhosis was also present. Mitochondria, either densely or loosely packed, were abnormal-pleiomorphic with few or no cristae and a granular fluffy matrix. Dense, large granules were seen in two cases. The association of neonatal liver failure and hyperlactacidemia should lead to immediate examination of the respiratory chain. The expression of this mitochondrial cytopathy can be lethal, associated with severe liver damage due to the deficiency in oxidative phosphorylation.     

Skin disease

Skin disease is one of the common causes of illness in most tropical countries and tropical skin diseases are often regarded as exotic. Most patients presenting with lesions acquired abroad however have either developed a condition common in their own environment or one that has been aggravated by the climatic conditions. Sun exposure in particular is a major source of skin damage. Specific disorders seen in visitors to the tropics are often infective in aetiology. They include specific fungal infections as well as parasitic disease, such as leishmaniasis and onchocerciasis. In many of such cases the infections are more readily acquired by those visiting rural areas but this is not always the case.     

Structural Damage Detection Using Empirical Mode Decomposition: Experimental Investigation

This paper presents an experimental investigation on the applicability of the empirical mode decomposition (EMD) for identifying structural damage caused by a sudden change of structural stiffness. A three-story shear building model was constructed and installed on a shaking table with two springs horizontally connected to the first floor of the building to provide additional structural stiffness. Structural damage was simulated by suddenly releasing two pretensioned springs either simultaneously or successively. Various damage severities were produced using springs of different stiffness. A series of free vibration, random vibration, and earthquake simulation tests were performed on the building with sudden stiffness changes. Dynamic responses including floor accelerations and displacements, column strains, and spring releasing time instants were measured. The EMD was then applied to measured time histories to identify damage time instant and damage location for various test cases. The comparison of identified results with measured ones showed that damage time instants could be accurately detected in terms of damage spikes extracted directly from the measurement data by EMD. The damage location could be determined by the spatial distribution of the spikes along the building. The influence of damage severity, sampling frequency, and measured quantities on the performance of EMD for damage detection was also discussed.