Statistical Theory of Spin Relaxation and Diffusion in Solids

A comprehensive theoretical description is given for the spin relaxation and diffusion in solids. The formulation is made in a general statistical-mechanical way. The method of the nonequilibrium statistical operator (NSO) developed by D. N. Zubarev is employed to analyze a relaxation dynamics of a spin subsystem. Perturbation of this subsystem in solids may produce a nonequilibrium state which is then relaxed to an equilibrium state due to the interaction between the particles or with a thermal bath (lattice). The generalized kinetic equations were derived previously for a system weakly coupled to a thermal bath to elucidate the nature of transport and relaxation processes. In this paper, these results are used to describe the relaxation and diffusion of nuclear spins in solids. The aim is to formulate a successive and coherent microscopic description of the nuclear magnetic relaxation and diffusion in solids. The nuclear spin-lattice relaxation is considered and the Gorter relation is derived. As an example, a theory of spin diffusion of the nuclear magnetic moment in dilute alloys (like Cu-Mn) is developed. It is shown that due to the dipolar interaction between host nuclear spins and impurity spins, a nonuniform distribution in the host nuclear spin system will occur and consequently the macroscopic relaxation time will be strongly determined by the spin diffusion. The explicit expressions for the relaxation time in certain physically relevant cases are given.Comment: 41 pages, 119 Refs. Corrected typos, added reference

Molecular mechanisms of epidermal growth factor receptor overexpression in patients with cervical cancer

The epidermal growth factor receptor is overexpressed in 70-90% of cervical cancers. Previously, we have shown that epidermal growth factor receptor overexpression independently predicts poor prognosis in cervical cancer patients, which makes it a potential therapeutic target. The aim of this study was to systematically analyze the molecular mechanism leading to epidermal growth factor receptor overexpression in cervical cancer. All experiments were performed on archival paraffin-embedded material. In 166 cervical cancer patients, cytoplasmic, membrane and phosphorylated epidermal growth factor receptor protein expression were studied in association with patient survival. Membrane epidermal growth factor receptor overexpression was associated with poor disease-specific survival (P=0.027). This association was particularly present in human papillomavirus 16-positive patients (P=0.029). We analyzed whether epidermal growth factor receptor overexpression was caused by gene amplification using fluorescence in situ hybridization. Epidermal growth factor receptor gene copy number was linked to chromosome 7 ploidy, as no gene amplification could be detected when corrected for chromosome 7 centromeric signals. Chromosome 7 aneuploidy was associated with membrane epidermal growth factor receptor overexpression (P=0.013). Additional mutation analysis was performed by sequencing pure, flow-sorted tumor cells, but no mutations were detected. Furthermore, human papillomavirus 16 E5 and E6 oncogene mRNA expression was measured, using quantitative real-time polymerase chain reaction, to determine the association between the human papillomavirus and epidermal growth factor receptor overexpression. High human papillomavirus 16 E5 and E6 mRNA expression were associated with decreased survival (P=0.045 and 0.047, respectively). High human papillomavirus 16 E6 mRNA expression was associated with membrane epidermal growth factor receptor overexpression (P=0.013). This is the first study performed on cancer patient material showing that chromosome 7 aneuploidy and high human papillomavirus 16 E6 mRNA expression lead to membrane epidermal growth factor receptor overexpression in cervical cancer.Modern Pathology advance online publication, 21 January 2011; doi:10.1038/modpathol.2010.239.Cervix cance

Autocrine expression of the epidermal growth factor receptor ligand heparin-binding EGF-like growth factor in cervical cancer

Molecular tumour pathology - and tumour genetic