Significant performance improvement of a terahertz photoconductive antenna using a hybrid structure

Design of a photoconductive terahertz antenna based on a distributed Bragg reflector, recessed nanoplasmonic grating and recessed electrodes.

Improved measurement of polarization state in terahertz polarization spectroscopy

A calibration scheme is presented for improved polarization state measurement of terahertz pulses. In this scheme the polarization response of a two-contact terahertz photoconductive detector is accurately measured, and is used to correct for the impact of the nonidealities of the detector. Experimental results show excellent subdegree angular accuracy and at least 60% error reduction with this scheme.

An inhibitor of mTOR reduces neoplasia and normalizes p70/S6 kinase activity in Pten+/- mice

PTEN phosphatase acts as a tumor suppressor by negatively regulating the phosphoinositide 3-kinase (PI3K) signaling pathway. It is unclear which downstream components of this pathway are necessary for oncogenic transformation. In this report we show that transformed cells of PTEN(+/-) mice have elevated levels of phosphorylated Akt and activated p70/S6 kinase associated with an increase in proliferation. Pharmacological inactivation of mTOR/RAFT/FRAP reduced neoplastic proliferation, tumor size, and p70/S6 kinase activity, but did not affect the status of Akt. These data suggest that p70/S6K and possibly other targets of mTOR contribute significantly to tumor development and that inhibition of these proteins may be therapeutic for cancer patients with deranged PI3K signaling.

A DNA repair abnormality specific for rearranged immunoglobulin variable genes in germinal center B cells

The somatic hypermutation mechanism produces high-rate mutagenesis specifically targeted to rearranged immunoglobulin (Ig) variable (V) gene segments during the germinal center (GC) stage of B lymphocyte differentiation. The mechanism of this process remains uncertain, partly due to the lack of a direct assay for hypermutation activity. In this study, a gene-specific DNA repair assay was used to compare the rate and quality of DNA repair in the mantle zone (MZ) and GC B cells at rearranged and unrearranged Ig V genes. GC B cells were distinguished from MZ B cells by a retarded repair rate specific for rearranged Ig V genes. In addition, a unique feature of GC cells after DNA repair was the appearance of predominant mutations in rearranged Ig VH5 gene PCR products. These predominant mutations also occurred in natural mutants of VH5 genes. However, repair-associated mutations reflected, at least in part, "template-jumping" during amplification of the residually damaged genomic template. Overall, these findings reflect a repair abnormality associated with the hypermutation process by the criteria of sequence- and B cell stage-specificity. We conclude that locus-specific retardation of DNA repair is a component of the hypermutation mechanism. RFLP or SSCP analysis provides a simple assay to monitor this repair abnormality as a surrogate biochemical marker for hypermutation during B cell differentiation.