Tracer studies on f-actin fluctuations

We present a study on the fluctuations of semiflexible actin filaments using fluorescence videomicroscopy, focusing on the end-to-end fluctuations of single filaments. In order to specifically measure the position of the polymer's ends, we developed a novel noninvasive method that consists of annealing short end tags to the filaments. This allows us to probe polymer fluctuations to a very high accuracy. We compared the distribution of the end-to-end distance with recent theoretical results, and found excellent agreement. We also studied the dynamics of the mean-square end-to-end distance deltaR2(t) and orientation of the ends, deltaTheta(2)(t), finding power laws t(3/4) and t(1/4), respectively. Scaling behavior for deltaR2(t) is observed over several decades in relaxation time in agreement with theoretical results.     

Hyperpolarization of 13C through order transfer from parahydrogen: a new contrast agent for MRI

The order within proton pairs in organic molecules, resulting from hydrogenation with parahydrogen, can be transferred in great part to nearby carbon 13 spins through adequate field manipulations. The molecules with hyperpolarized 13C thus obtained can be used as new contrast agents of high efficiency in MRI. After a brief presentation of the hydrogenation process and apparatus, in relatively low magnetic field, we describe the procedure of order transfer to the 13C spins through a sudden drop from the initial field to zero field followed by an adiabatic remagnetization. The expected final polarizations in the absence of relaxation are given for several compounds. Finally, we show an example of MR images observed in vivo on animals as an illustration of the contrast capacity of this new method.     

Zum Nachweis von Blut

Ohne Zusammenfassung     

Über die Reduktion und die Darstellungen positiver quaternärer quadratischer Formen

Ohne Zusammenfassung     

Die cubische Involution und die Dreitheilung und Transformation dritter Ordnung der elliptischen Functionen

Ohne Zusammenfassung     

Über das isoperimetrische Problem auf einer gegebenen Fläche

Ohne ZusammenfassungDie folgenden Bemerkungen sind durch zwei vor kurzem veröffentlichte Lösungen dieses Problems veranlaßt: Kneser, Lehrbuch der Variationsrechnung, §34, und Whittemore, Annals of Mathematics (2) II, pag. 176. Die folgende Lösung scheint mir einfacher und zugleich freier von einschränkenden Voraussetzungen zu sein, insofern sie die auftretenden Kurven in Parameterdarstellung annimmt, während Kneser die gegebene, Whittemore die gegebene und die gesuchte Kurve in der Formv=f(u), annimmt.