HPLC isolation and NMR structure elucidation of the most prominent octabromo isomer in technical octabromo diphenyl ether

The major octabromo isomer of technical octabromo diphenyl ether mixture (technical octaBDE) DE-79 was isolated by RP-HPLC. Three serially coupled columns (each 250 mm long) enabled a good separation of the target compound from other congeners using 100% ACN as eluent. Approximately 100 microg of the target compound was isolated with a purity of >90% and investigated by MS for confirmation of the degree of bromination. 1H-NMR and 2-D 1H-13C correlation NMR spectra unequivocally clarified that the octaBDE in question is 2,2',3,3',4,4',6,6'-octabromodiphenyl ether (BDE 197). Based on annual production rates of technical BDE products (1999/2001), approximately 380 tons of BDE 197 were annually produced which, on the long term, may enter the environment. Compared with other individual BDE congeners, BDE 197 has the seventh highest application rate. Reductive debromination of BDE 197 can lead to four hepta-, 15 hexa-, 23 penta-, and 28 tetra-BDE isomers, respectively. This variety includes all known major BDEs of environmental concern (BDE 47, 85, 99, 100, 153, 154, and 183). The identification of BDE 197 in technical octaBDE DE-79 strongly suggests that research on the environmental fate of BDEs should include this key-BDE congener.     

Electronic structure and reactivity of high-spin iron--alkyl- and--pterinperoxo complexes

The spectroscopic properties and electronic structure of the four-coordinate high-spin [FeIII(L3)(OOtBu)]+ complex (1; L3 = hydrotris(3-tert-butyl-5-isopropyl-1-pyrazolyl)borate; tBu = tert-butyl) are investigated and compared to the six-coordinated high-spin [Fe(6-Me3TPA)(OHx)(OOtBu)]x+ system (TPA = tris(2-pyridylmethyl)amine, x = 1 or 2) studied earlier [Lehnert, N.; Ho, R. Y. N.; Que, L., Jr.; Solomon, E. I. J. Am. Chem. Soc. 2001, 123, 12802-12816]. Complex 1 is characterized by Raman features at 889 and 830 cm-1 which are assigned to the O-O stretch (mixed with the symmetric C-C stretch) and a band at 625 cm-1 that corresponds to nu(Fe-O). The UV-vis spectrum shows a charge-transfer (CT) transition at 510 nm from the alkylperoxo pi v* (v = vertical to C-O-O plane) to a d orbital of Fe(III). A second CT is identified from MCD at 370 nm that is assigned to a transition from pi h* (h = horizontal to C-O-O plane) to an Fe(III) d orbital. For the TPA complex the pi v* CT is at 560 nm while the pi h* CT is to higher energy than 250 nm. These spectroscopic differences between four- and six-coordinate Fe(III)-OOR complexes are interpreted on the basis of their different ligand fields. In addition, the electronic structure of Fe-OOPtn complexes with the biologically relevant pterinperoxo ligand are investigated. Substitution of the tert-butyl group in 1 by pterin leads to the corresponding Fe(III)-OOPtn species (2), which shows a stronger electron donation from the peroxide to Fe(III) than 1. This is related to the lower ionization potential of pterin. Reduction of 2 by one electron leads to the Fe(II)-OOPtn complex (3), which is relevant as a model for potential intermediates in pterin-dependent hydroxylases. However, in the four-coordinate ligand field of 3, the additional electron is located in a nonbonding d orbital of iron. Hence, the pterinperoxo ligand is not activated for heterolytic cleavage of the O-O bond in this system. This is also evident from the calculated reaction energies that are endothermic by at least 20 kcal/mol.     

On the Purely Longitudinal Space Charge Wave of an Extended Electromagnetic Theory

An extended electromagnetic theory has earlier been developed, as being based on the hypothesis of a nonzero electric field divergence in vacuo and the requirement of Lorentz invariance. This basis is supported by the commonly accepted fact that the vacuum is not merely an empty space, but has a ground state of nonzero energy and can become electrically polarized. The vacuum is thereby considered as electrically polarizable in the sense of being capable of supporting charge motion in the form of, e.g., space-charge waves. One result of the dynamic states of the present theory is the prediction of a purely longitudinal electric space-charge wave (S-wave) having no induced magnetic field. The behaviour of this wave type is demonstrated for a number of geometrical configurations. Some preliminary proposals are finally made for generation and detection of S waves. These waves are expected to have features which differ from those of the conventional transverse electromagnetic waves. If the S wave would come out to be physically realizable, it may thus form the basis of a new principle for telecommunication without or with very small magnetic induction effects.     

Monolithic carrier-envelope phase-stabilization scheme

A new scheme for stabilizing the carrier-envelope (CE) phase of a few-cycle laser pulse train is demonstrated. Self-phase modulation and difference-frequency generation in a single periodically poled lithium niobate crystal that transmits the main laser beam allows CE phase locking directly in the usable output. The monolithic scheme obviates the need for splitting off a fraction of the laser output for CE phase control, coupling into microstructured fiber, and separation and recombination of spectral components. As a consequence, the output yields 6-fs, 800-nm pulses with an unprecedented degree of short- and long-term reproducibility of the electric field waveform.     

Vacuum Cerenkov radiation

Within the classical Maxwell-Chern-Simons limit of the standard-model extension, the emission of light by uniformly moving charges is studied confirming the possibility of a Cerenkov-type effect. In this context, the exact radiation rate for charged magnetic point dipoles is determined and found in agreement with a phase-space estimate under certain assumptions.     

Adaptive tuning of feedback gain in time-delayed feedback control

We demonstrate that time-delayed feedback control can be improved by adaptively tuning the feedback gain. This adaptive controller is applied to the stabilization of an unstable fixed point and an unstable periodic orbit embedded in a chaotic attractor. The adaptation algorithm is constructed using the speed-gradient method of control theory. Our computer simulations show that the adaptation algorithm can find an appropriate value of the feedback gain for single and multiple delays. Furthermore, we show that our method is robust to noise and different initial conditions.     

Many years of experiences in internal quality control in the toxicological analysis of biological material in the field of occupational medicine

Summary Toxicological analysis in blood and urine for biological monitoring of occupationally exposed persons must be carried out in the Federal Republic of Germany under an internal and external quality control scheme. The results of many years of experiences with 5 commercially available control specimens (1 blood, 1 serum, 3 urine samples) from three companies for internal quality assurance are presented. Precision and accuracy were evaluated by comparison of our results with the data of the initial period (within day precision of the methods) and the assigned values. Over years the commercially available control specimens show good comparable results. Except in a few cases, there was a good agreement between our results and the assigned values. An expected worldwide increase of the importance of biological monitoring makes the availability of control specimens for everyday use a prerequisite in effective internal quality control. This is especially valid for the determination of organic compounds, e.g. solvents and pesticides in blood and urine samples.     

Fischer–Tropsch Chemistry at Room Temperature?

The unique catalytic activity of vanadium nitrogenase suggests a new direction for the direct production of biofuels from CO with either synthetic catalysts or nitrogenase-containing bacteria. The reduction of CO by V?nitrogenase to light hydrocarbons shows striking similarities to the established Fischer-Tropsch process; however, the enzyme does not use H(2) directly for this reaction. ADP=adenosine diphosphate, ATP= adenosine triphosphate.