Fast sample preparation involving MASE and coupled column normal phase liquid chromatography for the rapid trace analysis of dioxins in air-dust samples from fire catastrophe emissions.

A new approach has been developed and tested for the urgent analysis of dioxins in samples of air-dust filters originating from catastrophe emissions. The procedure consists of a fast extraction of the sample with microwave solvent extraction (MASE) and acetone as solvent followed by a fast cleanup of the extract with normal phase coupled column liquid chromatography (LC/LC). The multi-dimensional LC/LC system employs a 50 mm x4.

Interaction between visual and vestibular signals for the control of rapid eye movements.

To investigate interactions between voluntary and reflexive eye movements, five subjects were asked to make pro- or anti-saccades to various oblique locations cued by a head-fixed flash while being rotated sinusoidally in yaw (0.17 Hz; 73 degrees /s peak velocity) in complete darkness. Eye movements were recorded with the coil technique.

Collicular microstimulation during passive rotation does not generate fixed gaze shifts.

We investigated whether saccades evoked by electrical stimulation (E-saccades) in the superior colliculus can compensate for passive sinusoidal head rotation in yaw so as to keep the rapid gaze shift constant. After accounting for variations in E-saccade onset position, we found significant horizontal metric changes, proportional to head velocity, in 31 of 37 experiments in 2 monkeys. Vertical effects were small.

The subjective vertical and the sense of self orientation during active body tilt.

Previous testing of the ability to set a luminous line to the direction of gravity in passively-tilted subjects, in darkness, has revealed a remarkable pattern of systematic errors at tilts beyond 60 degrees, as if body tilt is undercompensated or underestimated (Aubert or A-effect). We investigated whether these consistent deviations from orientation constancy can be avoided during active body tilt, where more potential cues about body tilt (e.g.

Properties of the internal representation of gravity inferred from spatial-direction and body-tilt estimates.

One of the key questions in spatial perception is whether the brain has a common representation of gravity that is generally accessible for various perceptual orientation tasks. To evaluate this idea, we compared the ability of six tilted subjects to indicate earth-centric directions in the dark with a visual and an oculomotor paradigm and to estimate their body tilt relative to gravity. Subjective earth-horizontal and -vertical data were collected, either by adjusting a visual line or by making saccades, at 37 roll-tilt angles across the entire range.

Determination of organochlorine compounds in fatty matrices. Application of rapid off-line normal-phase liquid chromatographic clean-up.

A clean-up method for organochlorine compounds in fatty samples based on normal-phase liquid chromatography (NPLC) is described. To this end, an existing clean-up procedure which uses column switching for the separation of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) from the fat matrix was simplified to a single silica LC column procedure. The use of an LC column packed with 3 microns silica enables complete fat/OCP separation in a total fraction volume of 12 ml, and results in a fully automated clean-up procedure that takes only 32 min per sample.

Bulge-out structures in the single-stranded trimer AUA and in the duplex (CUGGUGCGG).(CCGCCCAG). A model-building and NMR study.

Model-building studies were carried out on the trimer AUA. Bulge-out structures which allow incorporation into a continuous RNA helix were generated and energy-minimized. All geometrical features obtained by previous NMR studies on purine-pyrimidine-purine sequences are accounted for in these models.

Extra thymidine stacks into the d(CTGGTGCGG).d(CCGCCCAG) duplex. An NMR and model-building study.

NMR and model-building studies were carried out on the duplex d(CTGGTGCGG).d(CCGCCCAG), referred to as (9+8)-mer, which contains an unpaired thymidine residue. Resonances of the base and of several sugar protons of the (9+8)-mer were assigned by means of a NOESY experiment.

Conformational and model-building studies of the hairpin form of the mismatched DNA octamer d(m5C-G-m5C-G-T-G-m5C-G).

The hairpin form of the mismatched octamer d(m5C-G-m5C-G-T-G-m5C-G) was studied by means of NMR spectroscopy. In a companion study it is shown that the hairpin form of this DNA fragment consists of a structure with a stem of three Watson-Crick-type base pairs and a loop consisting of only two nucleotides. The non-exchangeable proton resonances were assigned by means of two-dimensional correlation spectroscopy and two-dimensional nuclear Overhauser effect spectroscopy.