Biomedical subjects

John Clarke

Publications and source records attributed to John Clarke.

21 records · Page 2Linked to original sources

PubMed2002

Liquid-state NMR and scalar couplings in microtesla magnetic fields.

We obtained nuclear magnetic resonance (NMR) spectra of liquids in fields of a few microtesla, using prepolarization in fields of a few millitesla and detection with a dc superconducting quantum interference device (SQUID). Because the sensitivity of the SQUID is frequency independent, we enhanced both signal-to-noise ratio and spectral resolution by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. In the absence of chemical shifts, proton-phosphorous scalar (J) couplings have been detected, indicating the presence of specific covalent bonds. This observation opens the possibility for "pure J spectroscopy" as a diagnostic tool for the detection of molecules in low magnetic fields.

Magnetic Resonance Imaging↗

PubMed2002

Laser-polarized (129)Xe NMR and MRI at ultralow magnetic fields.

Laser-polarized (129)Xe and a high-T(c)superconducting quantum interference device (SQUID) are used to obtain magnetic resonance images in porous materials at a magnetic field of 2.3 mT, corresponding to a Larmor frequency of 27 kHz. Image resolution of 1 mm is obtained with gradients of only 1 mT/m. The resolution of xenon chemical shifts in different physicochemical environments at ultralow fields is also demonstrated. Details of the circulating flow optical pumping apparatus and the SQUID spectrometer are presented.

Journal Article↗

PubMedDate not supplied

Panel 2.14: contribution of non-governmental actors.

This is a summary of the presentations and discussion of Panel 2.14, Contribution of Non-Governmental Actors, of the Conference, Health Aspects of the Tsunami Disaster in Asia, convened by the World Health Organization (WHO) in Phuket, Thailand, 04-06 May 2005. The topics discussed included issues related to the role of media and communication as pertaining to the responses to the damage created by the Tsunami. It is presented in six sections: (1) Background; (2) Key questions; (3) Discussion; (4) What have we learned?; (5) Conclusions; and (6) Recommendations. The what have we learned section is presented in the categories of: (1) needs assessments; (2) coordination; (3) filling gaps; and (4) capacity building.

Disasters↗