Ultrastructural Variation in Enamel of Australian Marsupials

This paper initiates a survey of the enamel of fossil and extant Australian marsupials by scanning electron microscopy. Enamel was examined from 17 extant and 11 extinct marsupials. Assessment was made of prism packing pattern, prism course, tubule presence, tubule size and distribution. Values calculated were: prism diameter; prism axis ratio; cross-sectional prism area; cross-sectional ameloblast area; and numerical prism density. Three different prism packing arrangements were found for extant and fossil marsupials within the classical Pattern 2. The Pattern 1 arrangement found in three extant species was relatively unexpected given the general acceptance of Marsupialia as having Pattern 2 enamel. Attention is drawn to the variable loss of prism demarcation towards the outer enamel surface. The majority of both extant and fossil marsupials exhibited a simple radial prism course. Prism diameters were small ranging from 1.4 μm to 3.9 μm and prism densities were high, compared to those for human and multituberculate enamel. A significant inter-species variation was noted in the presence and size of enamel tubules. The absence of enamel tubules in the incisors of D. optatum, N. tedfordi and T. rostratus and the molar of W. wakefieldi was confirmed. Large bulbous spaces were found either along or at the termination of enamel tubules in some teeth of five fossil species: these spaces may represent the resting place of an ameloblast. We have found: a greater variation in prism packing patterns; a greater difference in characteristics studied between incisor and molar teeth; and a greater variety of tubule morphology than anticipated. There are signs that useful enamel ultrastructural characters are emerging to help ultimately with taxonomic investigations of Australian marsupials

Marsupial and Monotreme Enamel Structure

We present some recent developments in our understanding of two basic questions: the origin, extent, nature and course of marsupial enamel tubules; and the characterisation of monotreme enamel, more particularly, the prismatic nature of platypus enamel. Methods used included SEM of methacrylate casts of marsupial enamel tubules, worn and cut surfaces of whole marsupial teeth, developing and erupted platypus teeth, and a well-developed molar of the newly discovered Miocene ornithorhynchid Obdurodon sp., and tandem scanning reflected light microscopy of intact marsupial teeth. We conclude that there are significant species differences with respect to prism shape, row formation and tubule disposition in marsupials and, moreover, that these features change in a consistent way through the thickness of the enamel. Consideration of enamel prism course in incisor and molar enamel of Macropus eugenii, together with the tubule casts, enables us to conclude that there is a fundamental relationship of tubule to prism in the body of marsupial enamel. This and previously reported data put beyond dispute the essential relationship of the marsupial tubule to the formative ameloblast. The enamel of Ornithorhynchus anatinus is shown to be prismatic only in part, with well-formed regular prisms not being a primary structural feature. The enamel of the fossil monotreme is prismatic and tubular and displays large areas of Pattern 2 prism packing. Monotreme enamel has been interpreted as representing a structural stage intermediate between that of known multituberculates and extant tribosphenid mammals

Enamel of Yalkaparidon Coheni: Representative of a Distinctive Order of Tertiary Zalambdodont Marsupials

The enamel of an incisor and a premolar of Yalkaparidon coheni was examined by scanning electron microscopy in fractured and in sectioned, polished surfaces. The enamel of both teeth demonstrated: complete, ovoid and horse-shoe shaped prisms in a Pattern 2 arrangement; a simple parallel prism course; and, enamel tubules in abundance in the premolar but restricted to the innermost enamel in the incisor. Overall, the enamel ultrastructure supports the marsupial affiliation proposed for Yalkaparidon coheni but does not unambiguously ally it with any other order of marsupials. The observation of a significant ultrastructural difference between the anterior and posterior teeth of a marsupial emphasizes the need to sample both if available. In pursuing this, we report here also the lack of tubules in the anterior teeth of the extant Tarsipes rostratus. This together with a similar absence of typical marsupial tubules from the incisor of the extinct Yalkaparidon coheni, would suggest that the wombat is not the only surviving marsupial to have experimented so extensively with this particular structural feature. It is likely that further study will demonstrate an unexpected and relative lack of tubules in the incisor enamel of other fossil Australian marsupials

Massive pericardial hematoma simulating constrictive pericarditis: a complication of radiofrequency catheter ablation

AbstractJ Thorac Cardiovasc Surg 1998;115:726-

Aerodynamic CFD Based Optimization of Police Car Using Bezier Curves

This paper investigates the optimization of the aerodynamic design of a police car, BMW 5-series which is popular police force across the UK. A Bezier curve fitting approach is proposed as a tool to improve the existing design of the warning light cluster in order to reduce drag. A formal optimization technique based on Computational Fluid Dynamics (CFD) and moving least squares (MLS) is used to determine the control points for the approximated curve to cover the light-bar and streamline the shape of the roof. The results clearly show that improving the aerodynamic design of the roofs will offer an important opportunity for reducing the fuel consumption and emissions for police vehicles. The optimized police car has 30% less drag than the non-optimized counter-part

Isotopic and geologic studies to identify the sources of sulfate in groundwater containing high barium concentrations

"Final report, project no. A-100-I11.""November 1981"--P. 1 of cover.Bibliography: p. 36-39."UILU-WRC-81-0165"--P. 1 of cover

Tribo-oxidation of a brake friction couple under varying sliding conditions

This study explores a common parameter that is used to describe the energy input into a friction pairing in pin-on-disc investigations, the pv-value. The impacts of multiple sliding speed, v, and contact pressure, p, combinations were investigated while keeping their product, the pv-value at a constant level. The chosen tests for this study consisted of steady-state drag braking applications on a small-scale test bench. The actual contact area on the friction material's surface was measured after the tests and correlated to the steady-state temperature, T, that was reached during testing. The tribological interface showed sensitivity towards the different sliding and loading conditions including a shift in oxidising states of the iron contents of the friction couples. The sliding and loading conditions were reversed after the transition of oxidising states in order to investigate their impact. The results show that the oxidising states dynamically react to the operating conditions, but the overall frictional performance of the system can remain at an altered level due to enduring changes in the actual contact area and the thermal response of the friction couple with the transition in oxidising states

Evaluation of left ventricular ejection fraction using through-time radial GRAPPA

BACKGROUND: The determination of left ventricular ejection fraction using cardiovascular magnetic resonance (CMR) requires a steady cardiac rhythm for electrocardiogram (ECG) gating and multiple breathholds to minimize respiratory motion artifacts, which often leads to scan times of several minutes. The need for gating and breathholding can be eliminated by employing real-time CMR methods such as through-time radial GRAPPA. The aim of this study is to compare left ventricular cardiac functional parameters obtained using current gold-standard breathhold ECG-gated functional scans with non-gated free-breathing real-time imaging using radial GRAPPA, and to determine whether scan time or the occurrence of artifacts are reduced when using this real-time approach. METHODS: 63 patients were scanned on a 1.5T CMR scanner using both the standard cardiac functional examination with gating and breathholding and the real-time method. Total scan durations were noted. Through-time radial GRAPPA was employed to reconstruct images from the highly accelerated real-time data. The blood volume in the left ventricle was assessed to determine the end systolic volume (ESV), end diastolic volume (EDV), and ejection fraction (EF) for both methods, and images were rated for the presence of artifacts and quality of specific image features by two cardiac readers. Linear regression analysis, Bland-Altman plots and two-sided t-tests were performed to compare the quantitative parameters. A two-sample t-test was performed to compare the scan durations, and a two-sample test of proportion was used to analyze the presence of artifacts. For the reviewers´ ratings the Wilcoxon test for the equality of the scores’ distributions was employed. RESULTS: The differences in EF, EDV, and ESV between the gold-standard and real-time methods were not statistically significant (p-values of 0.77, 0.82, and 0.97, respectively). Additionally, the scan time was significantly shorter for the real-time data collection (p<0.001) and fewer artifacts were reported in the real-time images (p<0.01). In the qualitative image analysis, reviewers marginally preferred the standard images although some features including cardiac motion were equivalently rated. CONCLUSION: Real-time functional CMR with through-time radial GRAPPA performed without ECG-gating under free-breathing can be considered as an alternative to gold-standard breathhold cine imaging for the evaluation of ejection fraction in patients

Stroke Severity Predicted by Aortic Atheroma Detected by Ultra-Fast and Cardiac-Gated Chest Tomography†

Background and Purpose: The presence of aortic atherosclerosis is an independent risk factor for secondary stroke. The present study was designed to have an initial exploration of the correlation between the load and extent of aortic atheroma (AA) and initial stroke severity or clinical outcome 3 months after stroke. Methods: Cardiac-gated chest tomography (CGCT) was used to detect and measure AA in patients with acute ischemic stroke as shown by our group in prior prospective studies and this is part four sub-exploratory study of the same cohort. The National Institute of Health Stroke Scale (NIHSS) was used to assess the initial stroke severity, and the modified Rankin Scale (mRS) was used to assess 3-month outcome. Results: Thirty-two patients underwent CGCT for evaluation of AA, and 21 were found to have AA. AA was more prevalent in patient with NIHSS >6 (14/17 versus 7/15, p-value 0.03). Applying the multiple logistic regression and propensity score adjustment (using the propensity of having AA given the baseline features as covariates) showed a non-significant trend that AA is three times more likely to be associated with NIHSS >6 (p = 0.08, OR 3.08, 95% CI 0.94–13.52). There was no evidence of association of AA with 3-month functional outcome (mRS): 11/14 (78.6%) mRS >1 had AA, and 10/18 (55.5%) of those with mRS ≤1 had AA (p = 0.27). Conclusion: In our current study with limited sample number and exploratory nature, the presence of AA on CGCT with acute ischemic stroke patients may be associated with worse neurological deficit at presentation. There was no evidence of association with 3-month functional outcome using the mRS

Effect of Iron Chelation Therapy on Recovery From Deep Coma in Children With Cerebral Malaria

Cerebral malaria is a severe complication of Plasmodium falciparum infection in children, with a mortality rate of 15 to 50 percent despite antimalarial therapy. To determine whether combining iron chelation with quinine therapy speeds the recovery of consciousness, we conducted a randomized, double-blind, placebo-controlled trial of the iron chelator deferoxamine in 83 Zambian children with cerebral malaria. To be enrolled, patients had to be less than six years old, have P. falciparum parasitemia, have normal cerebrospinal fluid without evidence of bacterial infection, and be in a coma from which they could not be aroused. Deferoxamine (100 mg per kilogram of body weight per day, infused intravenously for 72 hours) or placebo was added to standard therapy with quinine and sulfadoxine—pyrimethamine. The time to the recovery of full consciousness, time to parasite clearance, and mortality were examined with Cox proportional-hazards regression analysis. The rate of recovery of full consciousness among the 42 patients given deferoxamine was 1.3 times that among the 41 given placebo (95 percent confidence interval, 0.7 to 2.3); the median time to recovery was 20.2 hours in the deferoxamine group and 43.1 hours in the placebo group (P = 0.38). Among 50 patients with deep coma, the rate of recovery of full consciousness was increased 2.2-fold with deferoxamine (95 percent confidence interval, 1.1 to 4.7), decreasing the median recovery time from 68.2 to 24.1 hours (P = 0.03). Among 69 patients for whom data on parasite clearance were available, the rate of clearance with deferoxamine was 2.0 times that with placebo (95 percent confidence interval, 1.2 to 3.6). Among all 83 patients, mortality was 17 percent in the deferoxamine group and 22 percent in the placebo group (P = 0.52). Iron chelation therapy may hasten the clearance of parasitemia and enhance recovery from deep coma in cerebral malaria. (N Engl J Med 1992; 327:1473–7.), CEREBRAL malaria, one of the most severe complications of infection with Plasmodium falciparum, is especially common among young children. Despite therapy with parenteral antimalarial agents and attentive management of complications, the mortality rate is 15 to 50 percent and gross neurologic sequelae persist in about 10 percent of the children who survive.1 2 3 It is estimated that in sub-Saharan Africa alone, over 1 million children die from severe forms of malaria annually.4 , 5 Cerebral malaria is diagnosed when asexual forms of P. falciparum are found in the blood of a patient with signs of an acute, diffuse symmetric encephalopathy not attributable to