Biomedical subjects

T Mildner

Publications and source records attributed to T Mildner.

At least 19 recordsLinked to original sources

PubMed2003

Impaired hemodynamics and neural activation? A fMRI study of major cerebral artery stenosis.

Functional MRI motor mapping was performed in two women with unilateral high-grade stenosis of the middle cerebral artery (MCA) to determine the influence of impaired hemodynamics on the blood oxygenation level dependent (BOLD) response. In both patients no structural lesions were present in primary motor pathways. A redistribution of the motor network to the healthy hemisphere was the main indicator of chronic hemodynamic compromise.

Adult↗

PubMed2001

A qualitative test of the balloon model for BOLD-based MR signal changes at 3T.

The aim of this study was to adapt the balloon model for BOLD-based MR signal changes to a magnetic field strength of 3T and to examine its validity. The simultaneous measurement of BOLD and diffusion-weighted BOLD responses was performed. The amplitude of the BOLD peak was found to be similar for all subjects when a short visual stimulus of 6 sec was used. The rise-time to the BOLD peak and the shape and depth of the poststimulus undershoot varied significantly. A fit of the experimental BOLD responses was found to be possible by use of parameters within a reasonable physiological range. The relations between these parameters and their influence on the modeled BOLD responses is discussed. A prediction of the balloon model is the occurrence of a BOLD overshoot, i.e., a lag between the changes of the blood volume and the blood flow after the start of the stimulation. Experimental evidence for the existence of a BOLD overshoot is presented.

Brain↗

PubMed1996

Laser-supported high-temperature MAS NMR for time-resolved in situ studies of reaction steps in heterogeneous catalysis.

The temperature of zeolite samples containing various adsorbed molecules was rapidly changed (within 15 s) from room temperature to 600 K by means of a laser beam. The location of the sealed glass ampoule in a boron nitride container decreases the temperature gradient in the sample and avoids laser-induced reactions. The technique facilitates time-dependent magic-angle-spinning (MAS) NMR spectroscopy of high-temperature reactions which take place within 60 s. The H-D exchange in the hydrogen form of zeolites loaded with fully deuterated molecules, the methanol-to-gasoline conversion and the catalytic ethylbenzene disproportionation in zeolites were monitored by 13C and 1H MAS NMR by means of a "stop and go" method.

Benzene Derivatives↗

PubMed1995

207Pb NMR detection of spinning-induced temperature gradients in MAS rotors.

The position of the 207Pb MAS NMR resonance from Pb(NO3)2 at a given inlet temperature of the spinning air depends on the rotation frequency, the diameter and geometry of the rotor, the position of the sample in the rotor, and the bearing air pressure. Taking these effects into consideration, the use of Pb(NO3)2 as a chemical shift thermometer gives a temperature accuracy of (0.1 K for a very small sample and a MAS-induced temperature gradient of 4 K for a 4 mm sample spun at 10 kHz.

Lead↗

PubMed1975