Feasibility study for the preparation of certified reference materials part I – mineral oil contaminated soils

The international joint project HYCREF (Contract No. G6RD-CT-2002-00854), funded by the European Commission in the 5th Framework programme, aimed to develop methods to prepare homogeneous and stable reference materials of water, soil, and waste contaminated with mineral oil hydrocarbons and to certify the mineral oil content by gas chromatographic methods. The results of a feasibility study for the preparation of three soil reference materials are discussed in this paper, and for the preparation of three waste reference materials in the second part (Koch et al., Accred Qual Assur submitted for publication). The soil materials were selected to represent different soil types and contamination levels. The project plan set three requirements for these reference materials: uncertainty in the mineral oil content resulting from the certification exercise <5%, a sample inhomogeneity of <3% and a minimum long-term stability of 5 years. For the most part, these requirements were met within this project.     

Reactions on the dimethylphenylbenzacridinones. VI. Hydrogenation of ortho-nitrophenyl derivatives

Catalytic hydrogenation of o-nitrophenylbenz[a], benz[c], dibenz[a,h] and dibenz[a,g]acridinones using Pd/C as catalyst, at 60 psi of pressure, gave the hiterto unknown benzoquinoacridine N-oxides and benzo-pyranonaphthyridine N-oxides. The structure of all products was corroborated by ir, ¹H- and ¹³C-nmr and mass spectra data.     

Densitometric Determination of Embelin in Lysimachia punctata

JPC – Journal of Planar Chromatography – Modern TLC - Athin layer chromatographic method with densitometric UV detection at λ = 285 nm has been developed for quantification of...     

Non-linear advertising capital model with time delayed feedback between advertising and stock of goodwill

According to the classical Nerlove-Arrow model, advertising expenditure can be considered as a capital investment to create present and future demand for the firm's products and, hence, to create present and future revenues for the firm. Advertising is assumed to influence via stock of goodwill which cumulatively counts for the effects of the firm's current and past advertising outlays. The paper presents a time delayed feedback model describing the relations between advertising and goodwill. Three different types of effects of advertising upon the dynamics of goodwill are modelled. The advertising policy of the management is incorporated into the model via a non-linear advertising function. The advertising function controls the advertising outlay e.g. by budget constraint and by the actual and target values of goodwill. The behavior of the model is analysed both analytically and numerically. Special attention is given for deriving the stability conditions for the limiting solution. The cases of repelling or chaotic limiting solutions are analysed by bifurcation and state space diagrams. Several numerical examples are given.     

Middle-ear response in the chinchilla and its relationship to mechanics at the base of the cochlea

The responses of the malleus and the stapes to sinusoidal acoustic stimulation have been measured in the middle ears of anesthetized chinchillas using the M?ssbauer technique. With "intact" bullas (i.e., closed except for venting via capillary tubing), the vibrations of the tip of the malleus reach a maximal peak velocity of about 2 mm/s in responses to 100-dB SPL tones in the frequency range 500-6000 Hz; vibration velocity diminishes toward lower frequencies with a slope of about 6 dB/oct. Opening the bulla widely increases the responses to low-frequency stimuli by as much as 16 dB. At low frequencies, malleus response sensitivity with either open or intact bullas far exceeds all previous measurements in cats and matches or exceeds such measurements in guinea pigs. Whether measured in open or intact bullas, phase-versus-frequency curves closely approximate those predicted from the magnitude-versus-frequency curves by minimum phase theory. The stapes responses are similar to those of the malleus, except that stapes response magnitude is lower, on the average, by 7.5 dB at frequencies below 2 kHz and 10.7 dB at 2 kHz and above. Comparison of the responses of the middle ear with those of the basilar membrane at a site 3.5 mm from the stapes indicates that, at frequencies below 150 Hz, the basilar membrane displacement is proportional to stapes acceleration. At frequencies between 150 and 2000 Hz, basilar membrane displacement is proportional to stapes velocity.     

Cochlear microphonics and the initiation of spikes in the auditory nerve: correlation of single-unit data with neural and receptor potentials recorded from the round window

On the basis of comparisons of responses of guinea pig ganglion cells and inner hair cells to intense low-frequency tones, Sellick et al. [Hear. Res. 7, 199-221 (1982)] have proposed that basal inner hair cells can be depolarized (and thus, VIII-N. spikes generated) by the extracellular microphonic generated during hyperpolarization of outer hair cells. VIII-N. data for the chinchilla have been presented that, to a first approximation, support such a hypothesis [Ruggero and Rich, J. Acoust. Soc. Am. 73, 2096-2108 (1983)]. However, an apparent discrepancy exists in our results, vis à vis Sellick et al.'s hypothesis, in that basal fiber near-threshold responses precede maximal negativity of the round window microphonic (i.e., maximal hyperpolarization of outer hair cells) by up to 90 degrees (but generally less than 45 degrees), depending on frequency. It is shown here that the discrepancy is resolved if certain nonlinear phase changes and overall distortion of the microphonic waveshapes, both of which occur at intense stimulus levels, are taken into account. It is also shown that compound action potentials (AP's), superimposed on the round window microphonics, can be identified at multiple times within each stimulus cycle, closely matching the near-threshold response phases of single-unit excitation. AP1 is nearly synchronous with the negative-to-positive transition of round window microphonics and with the excitation of fibers innervating apical-to-middle cochlear regions. AP2 is synchronous with the positive-to-negative transition of the microphonics and with the excitation of basal fibers. One or two other AP's probably reflect "peak splitting" in the responses of both basal and apical fibers.     

Digital simulation of cyclic voltammetric experiments for non-first-order electrode reactions

Application of the explicit finite-difference simulation method to linear-sweep cyclic voltammetry in the case of non-first-order electrode reactions is described. Reversible, quasi-reversible and totally irreversible electrode reactions with reaction orders > 1 or < 1 are discussed. Simple criteria for evaluating the kinetic parameters are proposed. The accuracy of the proposed method is checked by comparing the results obtained with literature data.     

Convenient synthesis of nucleoside and isonucleoside analogues

[reaction: see text]. A very simple methodology to stereoselectively achieve tricyclic isonucleosides (nucleobase = thymine, uracil, and 5-fluoruracil) and 3'-C-branched nucleosides (nucleobase = theophylline) was performed by means of a DBU-mediated addition process using a readily available 2-bromo sugar. The mechanism for these transformations implies the loss of both substituents at C-2 and C-3 on the sugar moiety, and although it seems that DBU is probably involved, its involvement has not yet been ascertained. Cytosine did not react under these conditions.     

A highly diastereoselective synthesis of 4-octulose and 2-deoxy-4-octulose from a -fructose derivative

Bishydroxylation of methyl

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1 with osmium tetraoxide proceeded with extremed high diastereoselectivity to give only methyl

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2. Configurations of the new stereogenic centers (C-2,3) in 2 were determined by degradation of the C-5,6,7,8 fragment to the well-known methyl

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7. Transformation of 2 into the required

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10, was achieved by a methodology that implied, protection to 8, reduction of the ester group in 8 to a hydroxymethyl group in 9, and finally deprotection to the free

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10. On the other hand, epoxidation reaction on

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11 afforded only the corresponding 2,3-anhydro derivative 12 with configuration, as could be demonstrated by degradation to (S)-1,2,4-trimetoxybutane 16, which synthesis is reported herein.     

Das Schwingungsspektrum von Barium-Divanadat

The infrared and laser-Raman spectra of crystalline Ba₂V₂O₇ are reported and discussed by means of a Site Symmetry analysis.

28. Mitt. der Reihe Orthovanadate und verwandte Verbindungen. 27. Mitt.:E. J. Baran undM. E. Escobar, J. Phys. Chem. Solids, im Druck; 26. Mitt.:E. J. Baran, I. L. Botto, J. F. Ramos undP. J. Aymonino, Mh. Chem.109, 1139 (1978); 25. Mitt.:E. J. Baran, J. Mol. Struct.48, 441 (1978); 24. Mitt.:E. J. Baran undI. L. Botto, J. inorg. nucl. Chem.40, 1603, (1978); 23. Mitt.:M. E. Escobar undE. J. Baran, Z. Anorg. allg. Chem.,441, 273 (1978).