Detection of partially resolved carbon-13–proton couplings with selective population inversion (SPI)

In a heteronuclear ¹³C? {¹H} selective population inversion ¹³C NMR spectrum a splitting, resulting from a (CH) coupling over more than one bond, can be detected even when no splitting is observed in the single-frequency ¹³C NMR spectrum. The relationship between the observed splitting, coupling constant and line width is discussed. A method is proposed from which the value of the coupling constant can be estimated, and its application illustrated by the splittings observed in the ¹³C NMR spectra of the mycotoxin, ochratoxin A.     

1H and 13C nuclear magnetic resonance study of (D3)-trishomocuban-4-ol and (D3)-trishomocubanone

The complete assignments of the ¹H and ¹³C NMR spectra for (D₃)-trishomocuban-4-ol (3) and (D₃)-trishomocubanone (4) are reported. The difference between the ¹H and ¹³C chemical shifts of 3 and 4 and those of the hydrocarbon (D₃)-trishomocubane, and the substituent effect of the hydroxy group, can be adequately explained by the unique stereochemistry of these compounds.     

The use of the selective population inversion technique in the assignment of carbon-13 n.m.r. resonances in 3,6-epoxy-pentacyclo[6.2.1.02,7.04,10.05,9]undecane

Different applications of the selective population inversion technique in an n.m.r. study of 3,6-epoxypentacyclo-[6.2.1.0^2,7.0^4,10.0^5,9] undecane have been demonstrated. The intensity gain accompanying heteronuclear ¹³C—{¹H} experiments allowed the detection of fine structure due to long range C? H couplings otherwise hidden in normal proton coupled ¹³C spectra. Definite assignments of two very similar, directly bonded, C? H couplings within a methylene group have been made.     

Synthesis and characterization of HgBa2Can−1CunO2n+2+δ (n = 1, 2, and 3)

We have successfully prepared the first three members of the mercury-based superconducting compounds Hg--- Ba₂Ca_n−1Cu_nO_2n+2+δ, namely Hg---1201, Hg---1212 and Hg---1223 with high purity and very good quality. T he influence of the synthesis parameters is studied in detail. Using the sealed quartz tube method, very simple procedures are found to ensure a 100% reproducibility of nearly 100% pure Hg---1201 and 85–90% Hg---1212 and Hg---1223. Oxygen annealing of the sample Hg---1201 at 300°C for 18 h results in an enhancement of its critical temperature up to 97 K. The symmetry of the first and second members is tetragonal with lattice parameters

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, respectively. X-ray diffraction lines of Hg---1223 can be indexed in a tetragonal cell with

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as well as in an orthorhombic cell with lattice parameters

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.     

Structures of a tetradentate ferrocenyl ligand and its oxorhenium(V) complex in solution and in the solid state

The novel ferrocenyl ligand rac-1,6-diferrocenyl-N,N'-bis(2-hydroxypropyl)-2,5-diazahexane (1, H(2)L) was synthesized from ferrocenylcarboxaldehyde and ethylenediamine followed by the reduction of the Schiff base with LiAlH(4) and subsequent N-alkylation with 1,2-propyleneoxide. The dianion of H(2)L reacted with [ReO(PPh(3))(2)Cl(3)], and the product was treated with NH(4)PF(6) to afford the complex [ReO(L-N(2)O(2))PPh(3)]PF(6) (2). Both the ferrocenyl ligand and the complex were characterized in solution by NMR spectroscopy and in the solid state by single-crystal X-ray diffraction studies. NMR investigations reveal two solvent-dependent isomers for the ferrocenyl ligand in solution of which the major form is the more ordered one. The cation of 2 displays a nonsymmetrically coordinated N(2)O(2) ligand.     

Design aspects of acoustic sensor networks for environmental noise monitoring

An increase in public awareness of noise pollution and the impact of noise on human health has led to the need for enhanced insight in complex noise situations. This insight is commonly obtained either by brief measurements or by evaluation of a simplified acoustic model. Both of these approaches however have limitations in complex noise situations. Noise monitoring can be an appropriate and cost efficient measure to obtain more insight, for it allows to measure at many locations for long periods of time. Monitoring can for example be used to improve the accuracy of models or to assess and respond to changes in the acoustic situation. Several monitoring approaches, for various applications, have been developed or are under development. In the first part of this paper an overview is given of current developments in acoustic monitoring networks and their key aspects. Sensor networks for environmental noise monitoring are here divided into four different categories, distinguished by five aspects: hardware costs, scalability, flexibility, reliability and accuracy. These five aspects determine the range of applications for which a network is suited. In the second part of this paper a monitoring network developed in-house is used to further illustrate the relevance of these aspects. This network was designed to facilitate research into the field of acoustic monitoring networks and is used to experiment with and learn from a broad field of applications.