Metallic nanocrystals near ultrasmooth metallic films for surface-enhanced Raman scattering application

We studied the effect of the substrate on the surface-enhanced Raman scattering (SERS) signals of metallic nanocrystal films by making a direct comparison between cases with metallic and semiconducting substrate surfaces. Ag nanoparticles smaller than 10?nm were synthesized and uniform arrays were formed on both ultrasmooth metallic and Si surfaces. These substrates provide reproducible SERS signals with high enhancement factors over large areas. Moreover, a SERS signal about one order of magnitude higher was obtained in the metallic surface case as compared with the Si substrate case, which is attributed to stronger plasmon coupling between the nanoparticles and their charge-conjugate images in the underlying metallic surface. The interpretation of our experimental results was confirmed by our finite difference time domain calculations. The dependence of the interaction between the nanoparticles and the substrate surface on the direction of the incident electromagnetic field is also discussed.     

Spatial phase shifting for pure in-plane displacement and displacement-derivative measurements in electronic speckle pattern interferometry (ESPI)

Hitherto no method, to our knowledge, was known to incorporate spatial phase shifting for the measurement of pure in-plane displacements. We demonstrate that the modified Duffy two-aperture configuration [Opt. Lett. 22, 1958 (1996)], which is sensitive to only the in-plane displacement component and offers increased sensitivity, lends itself to measurement with spatial phase shifting. The configuration can also be used for obtaining displacement derivatives by the introduction of shear with the tilt of a mirror.     

The Fatality Analysis Reporting System as a tool for investigating racial and ethnic determinants of motor vehicle crash fatalities

The Fatality Analysis Reporting System (FARS) is a Department of Transportation database in the public domain that contains detailed information about fatalities resulting from motor vehicle crashes on public roadways in the United States since 1975. However, data on race and Hispanic ethnicity were not collected by FARS until 1999. Since then, completeness of reported racial and ethnic information has varied from State to State. To assess utility of FARS for investigating race- and ethnicity-specific risk factors associated with motor vehicle crash mortality, we examined yearly national and State-specific reporting rates of race and Hispanic ethnicity for 168,863 motor vehicle crash fatalities from 1999 to 2002. In 1999, national reporting was 85% for race and 78% for Hispanic ethnicity. Over the 4-year study period, a significant linear increase in annual reporting for both race and Hispanic ethnicity was evident at the national level, as reporting by individual States improved over time. In 2002, national reporting rates reached 90% for race and 88% for Hispanic ethnicity. Our findings indicate that FARS has become a valuable resource for population-based studies of motor vehicle crash mortality disparities that exist among racial and ethnic subpopulations in the United States.     

Precise interferometric length and phase-change measurement of gauge blocks based on reproducible wringing

A modern fringe-pattern-analyzing interferometer with a resolution of 1 x 10(-9) and without exclusion of systematic uncertainties owing to optic effects of less than 1 nm was used to test a new method of interferometric length measurement based on a combination of the reproducible wringing and slave-block techniques. Measurements without excessive wringing film error are demonstrated for blocks with nominal lengths of 2-6 mm and with high surface flatness. The uncertainty achieved for these blocks is less than 1 nm. Deformations of steel gauge blocks and reference platens, caused by wringing forces, are investigated, and the necessary conditions for reproducible wringing are outlined. A subnanometer uncertainty level in phase-change-correction measurements has been achieved for gauge blocks as long as 100 mm. Limitations on the accuracy standard method of interferometric length measurements and shortcomings of the present definition of the length of the material artifact are emphasized.     

Statistical search space reduction and two-dimensional data display approaches for UPLC-MS in biomarker discovery and pathway analysis

A new analytical strategy for biomarker recovery from directly coupled ultra-performance liquid chromatography time-of-flight mass spectrometry (UPLC Tof MS) data on biofluids is presented and exemplified using a study on hydrazine-induced liver toxicity. A key step in the strategy involves a novel procedure for reducing the spectroscopic search space by differential analysis of cohorts of normal and pathological samples using an orthogonal projection to latent structures discriminant analysis (O-PLS-DA). This efficiently sorts principal discriminators of toxicity from the background of thousands of metabolic features commonly observed in data sets generated by UPLC-MS analysis of biological fluids and is thus a powerful tool for biomarker discovery.     

Wind-induced dust generation and transport mechanics on a bare agricultural field

Strong atmospheric winds may cause wind erosion and dust emissions on bare, dry, erodible fields. Since these dust emissions may exceed particulate matter limits established by the United States Environmental Protection Agency, information on dust generation and transport mechanics is needed to determine the particulate hazard of dust sources. Measurements of climatic variables and airborne sediment mass and concentration were made during three strong wind events on a bare, fine sandy loam field in west Texas. This study clearly shows that dust flux estimates were very sensitive to dust concentration measurement height. PM10 flux values estimated between heights of 2 and 5m were 2-5 times those estimated between heights of 5 and 10 m. Tower placement in relation to the upwind unerodible boundary produced significant differences in dust flux that varied with storm intensity. During the most intense storm event, the PM10 flux between heights of 2 and 5m measured at the tower 200 m from the unerodible boundary was almost 2.5 times as that measured at the tower 100 m from the unerodible boundary. Vertical PM10 dust flux was closely related with horizontal sediment flux only when the winds came from the same direction during the entire duration of horizontal sediment flux measurements.     

水工隧洞设计和施工

近年来，随着水头高达1000m的不衬砌隧洞的应用，隧洞系统的布置已变得更为灵活，最佳的隧洞设计方案只需考虑不同的施工方法以及其相应的水头损失问题，深入了解和掌握工程地质状况及隧洞支护技术已经成为节省隧洞成本的重要因素。断面仅为相应钻爆隧洞60％的全断面掘进隧洞是一个适当的替代方案，甚至在非常坚硬的岩石中也同样如此，挪威的特色如气垫式调太室、湖泊“水龙头”在某些情况下是替代竖井开挖和大坝建筑的令人关注的方案。