Strange magnetism and the anapole structure of the proton

The violation of mirror symmetry in the weak force provides a powerful tool to study the internal structure of the proton. Experimental results have been obtained that address the role of strange quarks in generating nuclear magnetism. The measurement reported here provides an unambiguous constraint on strange quark contributions to the proton's magnetic moment through the electron-proton weak interaction. We also report evidence for the existence of a parity-violating electromagnetic effect known as the anapole moment of the proton. The proton's anapole moment is not yet well understood theoretically, but it could have important implications for precision weak interaction studies in atomic systems such as cesium.     

Role of the glutathione redox cycle in acquired and de novo multidrug resistance

Drug resistance represents a major obstacle to successful cancer chemotherapy. However, the specific biochemical mechanisms responsible for clinical drug resistance are unknown. In these studies resistance to the antitumor agent adriamycin was found to involve two mechanisms, one that decreased drug accumulation by the P170 mechanism and another that altered the glutathione redox cycle, an important pathway in the detoxification of reactive oxygen. This dual mechanism of drug resistance was demonstrated in cell lines that had acquired the multidrug-resistant phenotype and in human colorectal cancer cells with de novo resistance. These studies support a model of acquired and de novo multidrug resistance that includes alterations in both drug accumulation and the glutathione redox cycle.     

Imaging dopamine receptors in the human brain by positron tomography

Neurotransmitter receptors may be involved in a number of neuropsychiatric disease states. The ligand 3-N-[11C]methylspiperone, which preferentially binds to dopamine receptors in vivo, was used to image the receptors by positron emission tomography scanning in baboons and in humans. This technique holds promise for noninvasive clinical studies of dopamine receptors in humans.     

Templating organic semiconductors via self-assembly of polymer colloids

A route for producing semiconducting polymer blends is demonstrated in which a doped pi-conjugated polymer is forced into a three-dimensionally continuous minor phase by the self-assembly of colloidal particles and block copolymers. The resulting cellular morphology can be viewed as a high-internal phase polymeric emulsion. Compared with traditional blending procedures, this process reduces the percolation threshold for electrical conductivity by a factor of 10, increases the conductivity by several orders of magnitude, and simultaneously improves thermal stability. Following this route, new applications can be envisaged for semiconducting polymer blends that require only minimal concentrations of doped pi-conjugated polymer.     

Transformation of Montmorillonite to Kaolinite during Weathering

Extensive deposits of kaolinite in Florida are formed by transformation of montmorillonite during low-temperature supergene weathering. The transformation occurs by intracrystalline leaching of interlayer cations and tetrahedral silica layers. Interposition of stripped layers within montmorillonite creates a regular 1:1 mixedlayered montmorillonite-kaolinite, a new clay structure. Kaolin-like layers are nourished by lateral epitaxy, as the iron-rich montmorillonite decomposes. Hexagonal outgrowths of new kaolinite develop at the edges of montmorillonite flakes and nucleate new vertical growth. Kaolinitic sands impregnated with goethite are ultimately formed, and the released silica enriches groundwater and forms secondary chert.