Biomedical Applications of Proton Induced X-Ray Emission

Apart from studies on aerosols, the majority of applications of proton induced X-ray emission (PIXE) with a normal beam or a microprobe (micro-PIXE) is found in biology and medicine. Two aspects of broad beam PIXE are often decisive for the choice of this analytical technique. Compared to other techniques capable of analysis down beyond the ppm level, PIXE can be carried out with a very small amount of material and minute fractions of the composite samples, even in the scale of micrometers and quite often with minimal sample preparation, which are important requirements for biomedical investigations. Secondly, the speed of the total analysis opens the possibility to analyze large numbers of samples in a reasonable time, which is often necessary in biomedical studies in order to obtain sufficiently significant correlations between trace element concentrations and biomedical phenomena. Few, if any, techniques can compete with micro-PIXE; quantitative trace element analysis on a micrometer scale still represent a challenging problem. The electron microprobe normally lacks the sensitivity while the laser induced techniques suffer as yet from quantification problems. This paper describes recent developments especially in micro-PIXE in biomedical research

Implementation of Asymmetric Yielding in Case Specific Finite Element Models improves the Prediction of Femoral Fracture Risk

Item does not contain fulltextAlthough asymmetric yielding in bone is widely shown in experimental studies, previous case-specific non-linear finite element (FE) studies have mainly adopted material behaviour using the Von Mises yield criterion (VMYC), assuming equal bone strength in tension and compression. In this study, it was verified that asymmetric yielding in FE models can be captured using the Drucker-Prager yield criterion (DPYC), and can provide better results than simulations using the VMYC. A sensitivity analysis on parameters defining the DPYC (i.e. the degree of yield asymmetry and the yield stress settings) was performed, focusing on the effect on bone failure. In this study, the implementation of a larger degree of yield asymmetry improved the prediction of the fracture location; variations in the yield stress mainly affected the predicted failure force. We conclude that the implementation of asymmetric yielding in case-specific FE models improves the prediction of femoral bone strength

Heavy-traffic limits for Polling Models with Exhaustive Service and non-FCFS Service Order Policies

We study cyclic polling models with exhaustive service at each queue under a variety of non-FCFS local service orders, namely Last-Come-First-Served (LCFS) with and without preemption, Random-Order-of-Service (ROS), Processor Sharing (PS), the multi-class priority scheduling with and without preemption, Shortest-Job-First (SJF) and the Shortest Remaining Processing Time (SRPT) policy. For each of these policies, we rst express the waiting-time distributions in terms of intervisit-time distributions. Next, we use these expressions to derive the asymptotic waiting-time distributions under heavy-trac assumptions, i.e., when the system tends to saturate. The results show that in all cases the asymptotic wait

Algebraic equations of state for the liquid crystalline phase behavior of hard rods

Based on simplifications of previous numerical calculations [Graf and L\"{o}wen, Phys. Rev. E \textbf{59}, 1932 (1999)], we propose algebraic free energy expressions for the smectic-A liquid crystal phase and the crystal phases of hard spherocylinders. Quantitative agreement with simulations is found for the resulting equations of state. The free energy expressions can be used to straightforwardly compute the full phase behavior for all aspect ratios and to provide a suitable benchmark for exploring how attractive interrod interactions mediate the phase stability through perturbation approaches such as free-volume or van der Waals theory.Comment: 12 pages,accepted for publication in Phys. Rev.

Згадав Василя Черниха чи Василя Черних?

Anafylactische reacties ten gevolge van chemotherapeutische medicatie komen soms voor en kunnen ernstig zijn. De diversiteit aan oorzaken maakt het optreden van een dergelijke overgevoeligheidsreactie moeilijk te voorspellen. Een 60-jarige vrouw ontwikkelde na toediening van een tweede chemotherapie etoposide ter behandeling van een kleincellig longcarcinoom een anafylactische reactie. Tijdens het vervolg van de behandeling werd etoposide vervangen door paclitaxel, waarna zij kort na het starten van de paclitaxel een tweede, ernstige anafylactische reactie kreeg. Opname op de intensivecareafdeling volgde, waarna de patiënte weer herstelde. Van zowel etoposide als paclitaxel is bekend dat een allergische reactie kan ontstaan bij intraveneuze toediening. Het mechanisme dat ten grondslag ligt aan deze reactie is niet bekend. Gezien het verschil in structuur is kruisovergevoeligheid tussen etoposide en paclitaxel niet waarschijnlijk. Om de oplosbaarheid van beide middelen te verhogen, worden respectievelijk de hulpstoffen polysorbaat 80 en Cremophor® EL gebruikt. Intradermale testen met beide middelen gaven een positieve reactie. De anafylactische reacties op beide cytostatica kunnen waarschijnlijk worden verklaard op grond van kruisovergevoeligheid voor de hulpstoffen