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The incidence of papillary thyroid carcinoma (PTC) increases significantly after exposure of the head and neck region to ionizing radiation, yet we know neither the steps involved in malignant transformation of thyroid epithelium nor the specific carcinogenic mode of action of radiation. Such increased tumor frequency became most evident in children after the 1986 nuclear accident in Chernobyl, Ukraine. In the twelve years following the accident, the average incidence of childhood PTCs (chPTC) increased over one hundred-fold compared to the rate of about 1 tumor incidence per 10{sup 6} children per year prior to 1986. To study the etiology of radiation-induced thyroid cancer, we formed an international consortium to investigate chromosomal changes and altered gene expression in cases of post-Chernobyl chPTC. Our approach is based on karyotyping of primary cultures established from chPTC specimens, establishment of cell lines and studies of genotype-phenotype relationships through high resolution chromosome analysis, DNA/cDNA micro-array studies, and mouse xenografts that test for tumorigenicity. Here, we report the application of fluorescence in situ hybridization (FISH)-based techniques for the molecular cytogenetic characterization of a highly tumorigenic chPTC cell line, S48TK, and its subclones. Using chromosome 9 rearrangements as an example, we describe a new approach termed ''BAC-FISH'' …

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Batch adsorption/dissolution experiments were conducted toexamine the interactions between 233U(VI) and a synthetic aluminumoxyhydroxide (boehmite, g-AlOOH) in 1.0M NaCl suspensions containing1-hydroxyethane-1,1-diphosphonic acid (HEDPA). In the pH range 4 to 9,complexation of Al(III) by HEDPA significantly enhanced dissolution ofboehmite. This phenomenon was especially pronounced in the neutral pHregion where the solubility of aluminum, in the absence of complexants,is limited by the formation of sparsely soluble aluminum hydroxides. Athigh pH levels, dissolution of synthetic boehmite was inhibited by HEDPA,likely due to sorption of Al(III)/HEDPA complexes. Addition of HEDPA toequilibrated U(VI)-synthetic boehmite suspensions yielded an increase inthe aqueous phase uranium concentration. The concentration of uraniumcontinually increased over 59 days. Partitioning of uranium between thesolid and aqueous phase was found to correlate well with HEDPApartitioning.

Complexation of NpO2+ with oxalic acid (OX),2,2'-oxydiacetic acid (ODA), 2,2'-iminodiacetic acid (IDA) and 2,2'-thiodiacetic acid (TDA), has been studied using spectrophotometry in1 M NaClO4. Both the position and the intensity of the absorption band of NpO2+ at 980 nm are affected by the formation of NpO2+/dicarboxylate complexes, providing useful information on the complexation strength, the coordination mode and the structure of the complexes.

The influence of GaSb substrate surface defects such as native oxides on the crystalline quality of epitaxial layers was investigated using transmission electron microscopy (TEM). Cross sectional TEM imaging showed that there are discrete defects at the GaSb-substrate/epilayer interface. Secondary ion mass spectroscopy (SIMS) results revealed high oxygen concentration at the interface, indicating that the defects are likely oxides and presumed to be native oxides since other impurities were not detected. High resolution TEM micrographs showed that the subsequent growth of the epilayer continues beyond the defects without any additional defect generation or propagation. Tellurium doped AlGaAsSb epitaxial layers were grown lattice-matched on GaSb substrates and lattice-mismatched on semi-insulating GaAs substrates by organometallic vapor phase epitaxy. Secondary ion mass spectroscopy and Hall data showed that the ratio of carrier concentration to Te concentration decreases significantly when the carrier concentration increases from 2.5 x 10{sup 17} cm{sup -3} to 6.5 x 10{sup 17} cm{sup -3}. TEM imaging showed that the material with heavily doped Te generates a high density (about 10{sup 8} cm{sup 2}) of planar defects (stacking fault) located on (111) planes. Most of the Te-related defects originate at the GaSb buffer layer/AlGaAsSb epilayer interface. In addition, discrete precipitates were …

We provide string theory examples where a toy model of a SUSY GUT or the MSSM is embedded in a compactification along with a gauge sector which dynamically breaks supersymmetry. We argue that by changing microscopic details of the model (such as precise choices of flux), one can arrange for the dominant mediation mechanism transmitting SUSY breaking to the Standard Model to be either gravity mediation or gauge mediation. Systematic improvement of such examples may lead to top-down models incorporating a solution to the SUSY flavor problem.

Complexation of Np(V), U(VI) and Nd(III) with dimethyl-3-oxa-glutaramic acid (DMOGA) and tetramethyl-3-oxa-glutaramide (TMOGA) was studied in comparison with the complexation with oxydiacetic acid (ODA). Stability constants and enthalpy of complexation were determined by potentiometry, spectrophotometry and calorimetry. Thermodynamic parameters, in conjunction with structural information of solid compounds, indicate that DMOGA and TMOGA form tridentate complexes with the ether-oxygen participating in bonding with actinide/lanthanide ions. The trends in the stability constants, enthalpy and entropy of complexation are discussed in terms of the difference in the hydration of the amide groups and carboxylate groups and the difference in the charge density of the metal ions.