Noninvasive assessment of regional ventilation in the human lung using oxygen-enhanced magnetic resonance imaging

The imaging of regional ventilation in the lungs is essential for the evaluation of a variety of pathological conditions, such as emphysema, pneumonia and pulmonary embolism. We propose a novel approach for ventilation scanning, using magnetic resonance imaging (MRI) and inhaled molecular oxygen as a contrast agent, that directly depicts transfer of oxygen across the alveolus into the pulmonary vasculature. Molecular oxygen is only weakly paramagnetic but produces substantial signal changes in the lungs because of their large surface area. Ventilation defects were shown in a patient with bullous emphysema, and ventilation-perfusion mismatches were shown in two patients with pulmonary embolism.     

Stoffwechselwirkungen von ω-3-Fettsäuren

Metabolic Effects of ω-3 Fatty Acids Biological effects of ω-3 fatty acids are related to their properties as structural components of cell membranes, their role as precursors of eicosanoids and their effects on lipoprotein metabolism. This is the basis for a great variety of metabolic effects, many of which of increasing medical interest. Particularly in the cardiovascular field, ω-3 fatty acids have been shown to have a wide spectrum of potentially antiatherogenic effects. Among these are the inhibition of platelet aggregation, reduction of blood viscosity, lowering of blood pressure and suppression of inflammatory reactions in the arteriosclerotic plaque. The principal actions in lipid metabolism are a reduction in triglycerides and a small increase in HDL₂. The effect on LDL-cholesterol is complex and an adverse LDL-increase may occur in particular hyperlipoproteinemias.     

Bemerkungen zum Biot-Savartschen Gesetz

Übersicht Die folgende Arbeit verfolgt u. a. auch didaktische Absichten. Das Biot-Savartsche Gesetz wird oft falsch oder mindestens sehr mißverständlich dargestellt und auch auf unzulässige Weise benutzt. Ausgangspunkt der Mißverständnisse ist die auch in vielen Lehrbüchern anzutreffende unkorrekte Aussage, man könne einem von StromI durchflossenen Linienelement ds ein magnetostatisches Feld dB [entsprechend der Gleichung (32) des folgenden Beitrags] zuordnen. Im folgenden werden derartige Aussagen untersucht und in modifizierter Form korrekt dargestellt.

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Remarks concerning the Law of Biot-Savart

Contents The following paper is at least partly of a didactic nature. The Biot-Savart law of magnetostatics is often interpreted in an illegitimate manner and consequently applied incorrectly. The source of these misunderstandings and errors is the incorrect statement that a magnetic field dB [as given by equation (32) of this paper] is caused by an electric currentI flowing along a line element ds, a statement very popular also in many textbooks. Questions related to this problem are investigated and widespread misleading statements are replaced by correct ones.

     

Categorical ML — Category-theoretic modular programming

We consider an extension of the functional programming language Standard ML with a modular structure based upon concepts in category theory such as categories, functors, natural transformations and adjunctions. In essence, we are following the categorical imperative of considering arrows as well as objects. This is intended to enforce a certain mathematical rigour on the programmer, so that the only programs that can be expressed are those with a categorical significance. The essentially algebraic nature of category theory means that we may generate equational correctness conditions for the modular structure of programs, thus separating the correctness of individual functions from that of modules. We describe this programming language, give examples of its use, and explain how it is implemented in a type system.     

Dry sliding wear response of some bearing alloys as influenced by the nature of microconstituents and sliding conditions

An attempt has been made in this study to examine the dry sliding wear response of a leaded-tin bronze, an aluminum bronze, and a conventional zinc-based alloy under varying applied pressure and speed conditions. Different characteristics of the microconstituents of the alloys have been correlated with that of their wear behavior. The study clearly indicates that the influence of the microstructural features greatly changes with the sliding conditions. It also has been observed that in order to attain good wear characteristics, a material should comprise an optimum level of lubricating, load bearing and ductile microconstituents, and, above all, thermal stability. Room temperature properties in fact play rather a secondary role in this context.     

Direkte und indirekte Randelementmethoden zur Bestimmung der Lage des Schubmittelpunktes beliebig geformter Stabquerschnitte

Zusammenfassung Die Koordinaten des Schubmittelpunktes eines beliebig berandeten Stabquerschnittes werden in dieser Arbeit aus der Torsionsverw?lbung des Querschnittes berechnet. Zur Bestimmung der Querschnittsverw?lbung wird die Randelementmethode (Boundary-Element-Method) herangezogen. Dabei entstehen durch verschiedene Vorgehensweisen mehrere Fredholmsche Integralgleichungen erster und zweiter Art, von denen jedoch nur bestimmte zur L?sung des genannten Problems geeignet sind. Einige direkte und indirekte Integralgleichungen werden hier für beliebig berandete Stabquerschnitte bezüglich ihrer Einsetzbarkeit untersucht und miteinander verglichen. Es zeigt sich dabei, da? auch eine Integralgleichung erster Art problemlos eingesetzt werden kann. Die Randelemente werden bei der numerischen L?sung der Integralgleichungen durch Polynome dritten Grades und die unbekannten Funktionen durch Polynome zweiten Grades approximiert, um eine glatte Berandung und stetigen Funktionenverlauf zu sichern.—Die Methode ist auf dünnwandige, dickwandige, offene und auf geschlossene Profile anwendbar. Numerische Ergebnisse für verschiedene Querschnittsformen aus den DIN-Normen zeigen die Effektivit?t sowohl der direkten als auch der indirekten Methode.     

The occurrence of multiple solutions for the TSD-Euler equation

Summary In a recent paper the TSD-Euler equation for transonic flow has been derived. This equation is similar in some respects to the TSD equation but has both entropy and vorticity terms retained. In this paper the existence of multiple solutions for the TSD-Euler equation is examined and it is found that such solutions exist for a small range of Mach numbers and airfoil thickness. It is found also that the addition of a vorticity flux on the airfoil surface can enhance the appearance of multiple solutions.With 4 Figures     

Guaranteed inclusions for the complex generalized eigenproblem

A method is described which produces guaranteed bounds for a solution of the generalized complex eigenproblem. The method extends a similar approach for general systems of nonlinear equations to the special case of complex pencils, where under weaker assumptions stronger assertions can be proved.