Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 3

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Hydrothermal metasomatism of a peralkaline granite pegmatite, Khaldzan Buragtag massif, Mongolian Altai; complex evolution of REE-Nb minerals

Bagiński B., Jokubauskas P., Domańska-Siuda J., Kartashov P., Macdonald R.

Acta Geologica Polonica

2016

Vol. 66, no. 3

473--491

The low-temperature hydrothermal alteration of certain rare-metal minerals is recorded in a quartz-epidote metasomatite from the Tsakhirin Khuduk occurrence in the Khaldzan-Buragtag Nb-REE-Zr deposit, Mongolian Altai. A peralkaline granitic pegmatite was metasomatized by hydrothermal fluids released from associated intrusions, with the formation of, inter alia, chevkinite-(Ce), fergusonite-(Nd) and minerals of the epidote group. The textural pattern indicates recrystallization and coarsening of these phases. Later, low-temperature alteration byfluids resulted in the chevkinite-(Ce) being replaced by complex titanite-TiO2-cerite-(Ce)-hingganite-hydroxylbastnäsite-(Ce) assemblages. Calcite formed late-stage veins and patches. The hydrous fluids were poor in F and CO2 but had high Ca contents.

Cerebral perfusion in acute stroke monitored by time-domain near-infrared reflectometry

Steinkellner O., Wabnitz H., Jelzow A., Macdonald R., Gruber C., Steinbrink J., Obrig H.

Biocybernetics and Biomedical Engineering

2012

Vol. 32, no. 1

3-16

Though potentially relevant for monitoring of acute stroke, even specialized stroke units do not provide continuous methods to determine cerebral perfusion at the bedside. We present patient measurements on cerebral perfusion in ischemic stroke applying optical bolus tracking. To this end, our portable time-domain near-infrared reflectometer has been optimized and technically approved for clinical studies by a notified body. We used data analysis based on statistical moments of measured time-of-flight distributions of photons. Selective sensitivity to deep absorption changes and a suitable representation of cerebral signals is associated with the suppression of movement artifacts in severely affected patients. The proposed technique offers a unique possibility for a frequently repeatable monitoring of cerebral blood flow during acute and subacute cerebral ischemia directly at the bedside.

Detection and characterization of breast tumours by time-domain scanning optical mammography

Rinneberg H., Grosenick D., Moesta K. T., Wabnitz H., Mucke J., Wübbeler G., Macdonald R., Schlag P.

Opto-Electronics Review

2008

Vol. 16, No. 2

147-162

The paper gives a short overview of various methods of optical mammography, emphasizing scanning time-domain mammography. The results of a clinical study on time-domain optical mammography are reviewed, comprising 154 patients carrying a total of 102 carcinomas validated by histology. A visibility score attributed to each carcinoma as qualitative measure of tumour detectability indicates acceptable sensitivity but poor specificity for discrimination between malignant and benign lesions. Likewise, a multi-variate statistical analysis yields sensitivity and specificity between 80% and 85% for tumour detection and discrimination with respect to normal (healthy) breast tissue, but values less than 70% for discrimination between malignant and benign breast lesions, being too low to be of clinical relevance. For 87 of the 88 tumours detected retrospectively in both projection optical mammograms, optical properties and tissue parameters were derived based on the diffraction of photon density waves by a spherical inhomogeneity as forward model. Following injection of a bolus of indocyanine green as non-targeted absorbing contrast agent, dynamic contrast-enhanced time-domain optical mammography was carried out on a small number of patients, but no differences in wash-out kinetics of indocyanine green between tumours and healthy breast tissue were observed.