Adsorption of carbonyles on zeolites - evaluation of infrared spectra using principal component analysis

Principal Component Analysis (PCA) is a useful tool to find the number and the individual spectra of the different species in a set of IR spectra of an adsorption system. On the narrow-pore zeolites PCA detects the presence of physisorbed carbonyl in addition to gaseous carbonyl and decomposition products. it shows two different species of chemisorbed Ni (CO)₄ on Y zeolites.     

Detection of multiple conformations of the E-domain of 5S rRNA from Escherichia coli in solution and in crystals by NMR spectroscopy

NMR spectroscopy of the E-domain fragment of Escherichia coli 5S rRNA indicates that this molecule exists in solution as either a stem-loop or as a duplex with two U-U base pairs in the bulge region. At temperatures below 27 degrees C, interconversion between the monomeric and dimeric forms in solution occurs on a time scale of weeks and allows the preparation of samples on which NMR structure determinations can be carried out on predominantly monomeric or dimeric species. The NMR results obtained provide comparison data for the distinction between A- and B-form E.coli 5S rRNA and for the possible kinetics of conversion between these forms. NMR evidence is presented that the duplex form also exists in crystals and suggestions are made for means to obtain stem-loop conformations of E-domain and other small RNA stem-loop sequences in crystals.     

Enantioselective inotropic actions of the Na+-channel activators BDF 9148, BDF 9196 and BDF 9167 in human failing and nonfailing myocardium

Our study investigated the inotropic effect of the novel Na+-channel activator BDF 9148 and its enantiomeres [S(-)BDF 9169, R(+)BDF 9167] in human failing [New York Heart Association Class (NYHA IV) heart transplants, n = 15] and nonfailing myocardium (NF, donor hearts, n = 5). We studied the effect of BDF 9148 (BDF, 0.03-10 micromol/liter) and of its enantiomeres [S(-) BDF 9196; R(+)BDF 9167] on isometric force of contraction (1 Hz) as well as on the force-frequency-relationship (0.5-3 Hz) in electrically driven (37 degrees C) left ventricular papillary muscle strips, BDF and S-BDF, but not R-BDF, increased force of contraction in a dose-dependent manner in NYHA IV and NF. The effectiveness of BDF, S-BDF and Ca2+ (15 mmol/liter) to increase force of contraction was similar in human nonfailing and failing myocardium. The potency of BDF and S-BDF to increase force of contraction was significantly higher in NYHA IV compared to NF. Carbachol (1 mmol/liter) did not affect the positive inotropic response of the studied compounds. In the presence of 3 micromol/liter BDF or S-BDF force of contraction increased after an increase in stimulation frequency only from 0.5 to 1 Hz in NYHA IV and human nonfailing myocardium. At frequencies above 1 Hz the force-frequency-relationship was negative in human nonfailing myocardium and NYHA IV in the presence of high concentrations of BDF or S-BDF. These results suggest that the racemic Na+-channel activator BDF 9148 and the S(-) BDF-enantiomere, but not the R(+) BDF-enantiomere, are effective to increase force development maximally in NYHA IV and in nonfailing myocardium. Human failing myocardium exerts an enhanced sensitivity toward the Na+-channel activator BDF 9148 and its S(-) enantiomere to increase force of contraction when compared to nonfailing tissue. As Na+-channel activators increase force in a frequency-dependent mode of action the force-frequency-relationship may depend on the intracellular Ca2+- and Na+- homeostasis.     

Beam-propagation in magnetooptic waveguides

The propagation of modes in magnetooptic waveguides distinguishes between the forward and the backward direction. This effect is applied to the realization of integrated optical isolators and circulators. The paper presents a finite-difference beam propagation simulation of such devices. Two different directions of the waveguide magnetization are considered. Finally, some consequences with respect to the practical realization of nonreciprocal integrated optical components are discussed     

Möglichkeiten und Probleme der Prozeß-Synthese

Possibilities and problems of process design. In times of economic constraint the necessity of optimization of processes means that process design becomes increasingly important as methodical and automated approach to process developments. The present contibution considers some examples of process design, together with their methodological realization and also examines the attendant, partly unsolved problems.     

Methods for the Determination of Inorganic Constituents in Water

Methods used for determining inorganic constituents in natural waters have undergone considerable change in the last decade. A majority of metal constituents are now determined by atomic absorption spectrophotometry (AAS). Various chelation and extraction procedures when used with AAS have lowered the detection limits to the microgram-per-liter range for many metal constituents. Aeration techniques have been developed which utilize AAS to determine such constituents as mercury, arsenic, and selenium. Vaporization techniques using graphite furnaces and similar devices linked with atomic absorption spectrophotometers provide for still lower detection limits and greater simplicity. These vaporization procedures require more research to limit interferences before they can be widely applied to the mass analysis of natural waters. Automated equipment is routinely used to analyze water samples. Colorimetric procedures have proven most useful but several potentiometric methods have recently been developed which also adapt themselves well to an automated approach. A procedure for determining fluoride using a potentiometric method has proven especially beneficial. An atomic absorption spectrophotometer has been joined with sampler and proportioning pump modules to produce automated determinations. Further potential development of the already mentioned instrumental techniques as well as anodic stripping voltammetry, X-ray fluorescence spectroscopy, emission spectroscopy, neutron activation analysis, and mass spectroscopy are described.