Biomedical subjects

T-C Chiang

Publications and source records attributed to T-C Chiang.

4 recordsLinked to original sources

PubMed2003

Alternating layer and island growth of Pb on Si by spontaneous quantum phase separation.

Real-time in situ x-ray studies of continuous Pb deposition on Si(111)-(7x7) at 180 K reveal an unusual growth behavior. A wetting layer forms first to cover the entire surface. Then islands of a fairly uniform height of about five monolayers form on top of the wetting layer and grow to fill the surface. The growth then switches to a layer-by-layer mode upon further deposition. This behavior of alternating layer and island growth can be attributed to spontaneous quantum phase separation based on a first-principles calculation of the system energy.

Journal Article↗

PubMed2002

Large electron-phonon coupling at an interface.

The strength of electron-phonon coupling in atomically uniform films of Ag on Fe is determined by angle-resolved photoemission from quantum well states in these films over a wide temperature range. As the film thickness is reduced, contributions from the surface and interface should become more important, and, experimentally, a large enhancement with superimposed quantum oscillations is observed. An analysis of the quantum oscillations indicates that this large enhancement is an interface effect.

Journal Article↗

PubMed2002

Electron-hole coupling and the charge density wave transition in TiSe2.

Angle-resolved photoemission is employed to measure the band structure of TiSe2 in order to clarify the nature of the ( 2 x 2 x 2) charge density wave transition. The results show a very small indirect gap in the normal phase transforming into a larger indirect gap at a different location in the Brillouin zone. Fermi surface topology is irrelevant in this case. Instead, electron-hole coupling together with a novel indirect Jahn-Teller effect drives the transition.

Journal Article↗

PubMed2002

The 13C-urea breath test to detect Helicobacter pylori infection: a validated simple methodology with 50 mg 13C-urea.

BACKGROUND: Several modifications of the 13C-urea breath test have been published. For reasons of cost efficiency and practicability, the urea dose and measurement duration should be reduced while still maintaining excellent diagnostic accuracy. AIMS: To establish a validated simple protocol for the urea breath test with 50 mg 13C-urea and to compare this protocol with the conventional urea breath test with 100 mg 13C-urea. METHODS: Conventional urea breath test with 100 mg 13C-urea was performed on 152 dyspeptic patients. Full-cream cow's milk was used as the test meal. Breath tests were repeated using 50 mg 13C-urea and the breath samples were collected at baseline and at 10 (protocol t10), 15 (protocol t15) and 30 min (protocol t30). Helicobacter pylori status was assessed by rapid urease test, histology and conventional urea breath test with 100 mg 13C-urea. RESULTS: With protocol t15, the best combination of sensitivity (99.1%), specificity (97.3%) and accuracy (98.7%) was obtained with a cut-off of 2.5 per thousand. There was an extremely high correlation coefficient between the three protocols and conventional 13C-urea breath test (all P < 0.001). CONCLUSIONS: A urea breath test with 50 mg 13C-urea using a simple test meal and a 15-min sampling interval with a low cut-off seems to be cost-effective and convenient. In a well-standardized laboratory, this modification is not associated with any loss of diagnostic accuracy.

Adolescent↗