Buchbesprechungen

Ohne Zusammenfassung     

Remarks on regularity and uniqueness of the Dirac–Klein–Gordon equations in one space dimension

In recent work, the authors extended the local and global well-posedness theory for the 1D Dirac–Klein–Gordon equations, but the uniqueness of the solutions was only known in the contraction spaces (of Bourgain–Klainerman–Machedon type). Here we prove some unconditional uniqueness results [that is, uniqueness in the larger space C([0,T];X ₀), where X ₀ denotes the data space]. We also prove a result about persistence of higher regularity, which is stronger than the standard version obtained from the contraction argument, since our result allows to independently increase the regularity of the spinor and scalar fields, whereas in the standard result they must be increased by the same amount.     

Buchbesprechungen

Ohne Zusammenfassung     

Electron ionization mass spectrometry of the ryanodine receptor‐based Ca2+‐channel stabilizer S‐107 and its implementation into routine doping control

New insights into the biochemistry of cardiac arrhythmia and skeletal muscle fatigue have yielded new drug candidates to counteract these phenomena. Major biological targets have become ryanodine receptor (RyR)‐based Ca²⁺‐release channels, which tend to ‘leak’ under various circumstances including strenuous exercise and, thus, cause aberrant calcium sparks that entail impaired muscle function. Therapeutics, which are referred to as rycals, are currently being developed to treat cardiac arrhythmia via enhancement of calstabin‐ryanodine affinities that causes a stabilization of the RyR. These therapeutics possess potential for misuse in sports, and an early implementation of target analytes such as the benzothiazepine derivatives S‐107 and JTV‐519 or putative metabolites into doping control screening procedures is recommended. Reference compounds, deuterated analogues, and a putative metabolic product were synthesized, and electron ionization mass spectra of these products were studied and dissociation pathways elucidated by means of tandem mass spectrometry (MS/MS) and accurate mass measurements. The characterized analytes were incorporated into existing sports drug testing assays based on liquid‐liquid extraction and subsequent gas chromatography/mass spectrometry (GC/MS) analysis, and specificity, lower limit of detection (4–6 ng/mL), intraday and interday precision (1.5–17.2%), as well as recovery (63–66%) were determined. The established procedure proved suitable for routine doping control analysis to detect a potential misuse of the drug candidate S‐107 in elite sport. Copyright © 2009 John Wiley & Sons, Ltd.     

Silicon enhanced carbon nanotube growth on nickel films by chemical vapor deposition

Silicon enhances carbon nanotube growth on nickel films by chemical vapor deposition using methane and hydrogen. Nanotube growth characteristic is significantly improved on nickel films patterned by argon plasma etching on silicon oxide layers. Auger electron spectroscopy shows that a reduced silicon phase forms in the surface silicon oxide layer by Ar ion bombardment used for patterning. The enhanced growth of carbon nanotubes could be ascribed to an oxygen removal effect by silicon in the process of synthesis.     

Über ein äskulinspaltendes Enzym und über ein fettspaltendes Enzym in Aesculus Hippocastanum L.

Ohne Zusammenfassung     

Spatial Heterogeneity Length Scales in Carbonate Rocks

Spatially resolved distributions of T ₂ relaxation times in carbonate rocks are measured with slice-selective multiple spin echo magnetic resonance imaging to study the length scales of heterogeneity in these samples. Single-voxel Carr–Purcell–Meiboom–Gill decays are fit to double exponential functions, and the results of those fits are combined into a histogram. We describe a novel qualitative method of assessing the importance of different length scales of heterogeneity, involving comparing various aspects of these histograms to the full-core T ₂ distributions. Using this technique, it is found that almost all individual voxels relax not only with more than one time constant but indeed with a range of relaxation times that approximates the full breadth of relaxation times for the entire core, indicating significant subvoxel heterogeneity. In addition, different voxels are found to exhibit relaxation times that differ by orders of magnitude, indicating significant heterogeneity between the scale of a voxel (1 mm) and that of the entire core (several centimeters). These results reflect the importance of a broad range of length scales of heterogeneity in these carbonate rocks. Authors' address: Yi-Qiao Song, Schlumberger-Doll Research, 36 Old Quarry Road, Ridgefield, CT 06877, USA     

Hole-burning diffusion measurements in high magnetic field gradients

We describe methods for the measurement of translational diffusion in very large static magnetic field gradients by NMR. The techniques use a "hole-burning" sequence that, with the use of fringe field gradients of 42 T/m, can image diffusion along one dimension on a submicron scale. Two varieties of this method are demonstrated, including a particularly efficient mode called the "hole-comb," in which multiple diffusion times comprising an entire diffusive evolution can be measured within the span of a single detected slice. The advantages and disadvantages of these methods are discussed, as well as their potential for addressing non-Fickian diffusion, diffusion in restricted media, and spatially inhomogeneous diffusion.