Electron sources in the form of one-dimensional nanotubes and nanowires are an essential tool for investigations in a variety of fields, such as X-ray computed tomography, flexible displays, chemical sensors and electron optics applications. However, field emission instability and the need to work under high-vacuum or high-temperature conditions have imposed stringent requirements that are currently limiting the range of application of electron sources. Here we report the fabrication of a LaB6 nanowire with only a few La atoms bonded on the tip that emits collimated electrons from a single point with high monochromaticity. The nanostructured tip has a low work function of 2.07 eV (lower than that of Cs) while remaining chemically inert, two properties usually regarded as mutually exclusive. Installed in a scanning electron microscope (SEM) field emission gun, our tip shows a current density gain that is about 1,000 times greater than that achievable with W(310) tips, and no emission decay for tens of hours of operation. Using this new SEM, we acquired very low-noise, high-resolution images together with rapid chemical compositional mapping using a tip operated at room temperature and at 10-times higher residual gas pressure than that required for W tips.
The electronic structure and spin asymmetry of metal phthalocyanines (Pcs) (metal = Mn, Fe, Cu, and Mg) and metal-free Pc thin films of 1-monolayer (ML) thickness on an Fe(100) substrate were investigated using spin-polarized metastable deexcitation spectroscopy (SPMDS). The surface density-of-states (SDOS) of these Pcs observed in MDS was almost identical, and thus, insensitivity of the Pc electronic structure to the variation of the central metal atoms is indicated. On the other hand, the spin asymmetry in the SPMDS measurements exhibited noticeable differences among Pcs. These results are discussed from the viewpoint of the Pcs electronic structure calculated by a discrete variational X α method. The fact that differences are found in the spin asymmetry but not in SDOS among Pcs indicates an important role of the central metal atoms for spin polarization.
IQGAP1 is a multifunctional protein involved in actin cytoskeleton assembly and E-cadherin-mediated cell adhesion. We reported previously IQGAP1 overexpression in human colorectal carcinomas especially at the invasion front (IF) and that such overexpression tended to correlate with lymph node metastasis in advanced cases. Thus, in this study, we investigated the clinicopathological significance of IQGAP1 expression in 85 cases of pT2-3 colorectal carcinomas with special reference to its expression pattern and prognosis, followed by analysis of the role of IQGAP1 in cancer invasion in vitro. Quantitative reverse transcription-PCR showed significant upregulation of IQGAP1 in colorectal carcinomas compared with normal mucosa. Immunohistochemically, IQGAP1 expression pattern was classified into diffuse (20%), IF-associated (35.3%) and focal (44.7%). The diffuse pattern was associated with higher rates of distant metastasis. Patients with IQGAP1 overexpression and diffuse pattern had significantly shorter survival (p < 0.0001) than others, and the diffuse pattern was an independent predictor of poor survival by multivariate analysis. In vitro invasion assays using three human colon carcinoma cell lines showed that IQGAP1 siRNA significantly suppressed hepatocyte growth factor (HGF)-stimulated cell invasion. HGF reduced membranous localization of a-catenin, but did not alter localization of E-cadherin, b-catenin and IQGAP1 in membranes. Suppression of IQGAP1 expression by siRNA did not alter membranous localization of a-catenin even in the presence of HGF. Our results indicate that IQGAP1 plays a critical role in colon cancer cell invasion, and therefore diffuse and high expression of IQGAP1 predicts poor prognosis in patients with colorectal carcinoma.Colorectal cancer is the third most common incidence and causes of cancer death in both males and females in the United States, 1 and it is fourth and third most common cause of cancer death in males and females in Japan, respectively.2 The tumor-node-metastasis (TNM) and Dukes staging system for colorectal cancer 3 has been the most widely employed classification that provides useful prognostic information. However, the staging system, based on the extent of the tumor spread at the time of operation, does not always account for the invasive ability and aggressiveness of the tumor itself. 4 With recent progress in effective adjuvant therapy, it is crucial to provide additional prognostic factors within each given stage, as this is often useful for clinicians to tailor the follow-up of patients to accommodate the likelihood of more frequent metastasis that may require aggressive management.Invasion is the key step in tumor progression, leading to metastasis. Based on the nature of the advancing tumor margin (invasion front), colorectal carcinoma is divided into two types; an expanding type and an infiltrating type.5 Invasion or movement of carcinoma cells as nests, tubules or clusters of cells keeping cell-cell contact with each other, occasionally termed collective cel...
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