Endothelial repair process and its relevance to longitudinal neointimal tissue patterns: comparing histology with in silico modelling

Re-establishing a functional endothelium following endovascular treatment is an important factor in arresting neointimal proliferation. In this study, both histology (in vivo) and computational simulations (in silico) are used to evaluate neointimal growth patterns within coronary arteries along the axial direction of the stent. Comparison of the growth configurations in vivo and in silico was undertaken to identify candidate mechanisms for endothelial repair. Stent, lumen and neointimal areas were measured from histological sections obtained from eight right coronary stented porcine arteries. Two re-endothelialization scenarios (endothelial cell (EC) random seeding and EC growth from proximal and distal ends) were implemented in silico to evaluate their influence on the morphology of the simulated lesions. Subject to the assumptions made in the current simulations, comparison between in vivo and in silico results suggests that endothelial growth does not occur from the proximal and distal ends alone, but is more consistent with the assumption of a random seeding process. This may occur either from the patches of endothelium which survive following stent implantation or from attachment of circulating endothelial progenitor cells.     

A miniaturized DNA amplifier: its application in traditional Chinese medicine

A Si-based miniaturized device for the polymerase chain reaction (PCR) has been developed. The device has Pt temperature sensors and heaters integrated on top of the reaction chamber for real-time accurate temperature sensing and control. Reaction temperature of the device is digitally controlled to achieve a temperature accuracy of +/-0.025 degrees C. The effects of PCR protocol optimization on the amplification performance of the surface-passivated chip reactor have been investigated in detail and quantitatively compared with that of the conventional thermal cycler. In this study, four traditional Chinese medicine genes including Fritillaria cirrhosa, Cartharmus tinctorius, Adenophora lobophilla, and Stephania tetrandra are used as model template. With appropriate chamber surface treatment (chlorotrimethylsilane/polyadenylic acid or SiO2 coatings), the device demonstrates amplification as efficient as that in the conventional thermal cycler at optimized MgCl2 concentration. The amplified DNA has concentration higher than 27 ng/microL, which is sufficient for subsequent on-chip analyses and detection. Experimental results reveal the importance of inclusion of BSA for an efficient amplification in the SiO2-passivated device and the excellent reusability of the device with a simple cleaning step.     

Using AVAL-1D to simulate avalanches in the eastern Pyrenees

The two friction parameters used in the numerical avalanche dynamics program AVAL-1D, were calibrated empirically with data from observed avalanches in the Swiss Alps. The implementation of the model with these friction parameters in other regions with different characteristics can lead to considerable uncertainty if a previous calibration is not performed. However, direct calibration for a specific avalanche path is often not possible since the data available are insufficient. Therefore, we back-calculated twelve well-documented avalanche events from the Catalan Pyrenees to calibrate the friction coefficients to be used in this mountain range. The result of the study reveals that there is a good fit between recorded and simulated avalanche events using the friction parameters originally calibrated for the Swiss Alps, despite the difference in snow climate between these two mountain ranges.     

Electrode surface treatments in sludge electro-osmosis dewatering

The sewage sludge dewatering produced by wastewater treatment plants (WWTP) is a multifaceted process due to the presence of colloid fractions. Electro-osmosis could be a suitable technique to reduce the water content of the final sludge. Electric fields of 10, 15, and 20?V/cm have been studied for electro-osmosis tests under the pressure of a static or rotating piston, obtaining a dry solids content up to 40–45%, with respect to 25–30% obtained by mechanical methods. In order to optimize the process, the corrosion behavior and the wear of the anodic material appear to be the main critical aspects, due to the high circulating current density and the use of a rotating electrode. We compared the efficiency and the corrosion resistance of dimensionally stable anodes (DSA) with respect to bare stainless steel (AISI 304) and stainless steel coated by PVD technique with TiN, AlTiN, and DLC. Characterization of the anode surfaces by SEM and potentiodynamic tests show that DSA is the most suitable material for our application. However, efficiencies of the electro-osmosis processes have been found comparable, in terms of developed current densities and total energy consumptions, for short-test duration.     

Evaluation of Carbon Partitioning in New Generation of Quench and Partitioning (Q&P) Steels

Quenching and partitioning (Q&P) and a novel combined process of hot straining (HS) and Q&P (HSQ&P) treatments have been applied to a TRIP-assisted steel in a Gleeble®3S50 thermomechanical simulator. The heat treatments involved intercritical annealing at 800 °C and a two-step Q&P heat treatment with a partitioning time of 100 seconds at 400 °C. The “optimum” quench temperature of 318 °C was selected according to the constrained carbon equilibrium (CCE) criterion. The effects of high-temperature deformation (isothermal and non-isothermal) on the carbon enrichment of austenite, carbide formation, and the strain-induced transformation to ferrite (SIT) mechanism were investigated. Carbon partitioning from supersaturated martensite into austenite and carbide precipitation were confirmed by means of atom probe tomography (APT) and scanning transmission electron microscopy (STEM). Austenite carbon enrichment was clearly observed in all specimens, and in the HSQ&P samples, it was significantly greater than in Q&P, suggesting an additional carbon partitioning to austenite from ferrite formed by the deformation-induced austenite-to-ferrite transformation (DIFT) phenomenon. By APT, the carbon accumulation at austenite/martensite interfaces was observed, with higher values for HSQ&P deformed isothermally (≈ 11 at. pct), when compared with non-isothermal HSQ&P (≈ 9.45 at. pct) and Q&P (≈ 7.6 at. pct). Moreover, a local Mn enrichment was observed in a ferrite/austenite interface, indicating ferrite growth under local equilibrium with negligible partitioning (LENP).

     

Management of acute otitis media caused by resistant pneumococci in infants

OBJECTIVES: To assess the clinical outcome and risk of failure after oral vs. intravenous treatment in otitis media caused by penicillin-resistant pneumococci. To determine the possible correlations between pneumococcal minimal inhibitory concentration (MIC) to penicillin and clinical outcome. DESIGN: Retrospective study of 156 cases collected between 1993 and 1995. Mean follow-up: 5 months. Setting. Two tertiary academic medical centers in Paris, France. PATIENTS AND METHODS: Pneumococcus was isolated from 191 of 570 ear samples obtained from children with otitis media and shown to be penicillin-resistant in 156. Medical history, antibiotic therapy during the previous 3 months and day-care center attendance were reviewed. For the current episode microbiologic characteristics of the isolated strains, type of treatment, therapy efficacy and clinical outcome were analyzed. Patients were predominantly young (76.3% were <1 year old) and bacteriologic samples were taken mainly because of previous treatment failure. RESULTS: Among 156 children with pneumococcal penicillin-resistant otitis media, 72.2% attended day-care centers, 71.8% had been previously treated with aminopenicillin and 52.5% with cephalosporins. Failure of previous empirical oral therapy was noted in 84% (one-third of these had been receiving amoxicillin-clavulanate). Patients treated intravenously had had a more protracted otitis but no greater number of previous episodes of acute otitis media than those receiving oral therapy. Acute mastoiditis occurred in 4 infants resulting in mastoidectomy. Oral treatment (mainly with high dose amoxicillin,120 to 150 mg/kg/day) and intravenous therapy (cephalosporin or glycopeptide) had been used in 59 and 41%, respectively. Mean duration of therapy was 10.7 days. Three failures (1.9%) and 10 recurrences (6.4%, average 28 days) occurred. No statistical difference was found between intravenous and oral therapy with respect to risk of recurrence. A high penicillin MIC value was correlated with previous antibiotic treatment but not with clinical outcome. CONCLUSIONS: Oral therapy appears to be as effective as intravenous therapy for the treatment of penicillin-resistant pneumococcal otitis media. Intravenous treatment should not necessarily be dictated by the penicillin susceptibility value but should be considered in cases of failure to thrive, persistent otitis or other complications.     

A singular element for three-dimensional fracture mechanics analysis

In this article, a singular boundary element for three-dimensional fracture mechanics analysis is presented. It is a nine-node quadratic element with plane geometry. These nodes are located at one quarter of the distance between two opposite sides of the element. Shape functions with a 11/√r singularity at the crack front are used to represent the tractions. The Stress Intensity Factors are computed as system unknowns appearing (except for a constant) as traction nodal values. Special attention is paid to the development of a simple and accurate integration approach for this singular element. The accuracy of the results obtained with the proposed element is demonstrated by solving several crack problems including edge and embedded cracks with different geometries. The element can be easily implemented and incorporated into existing quadratic boundary element codes. In a companion paper the element is formulated and used for fracture mechanics problems in transversely isotropic materials. Extension to other fields for which boundary element formulations exist, is quite simple.