Lehigh University

About: Lehigh University is a education organization based out in Bethlehem, Pennsylvania, United States. It is known for research contribution in the topics: Catalysis & Fracture mechanics. The organization has 12684 authors who have published 26550 publications receiving 770061 citations.

The role of photochemical degradation of dissolved organic carbon in regulating the UV transparency of three lakes on the Pocono Plateau

Abstract: The role of photochemical degradation of dissolved organic carbon (DOC) on UV transparency (280–400 nm) was investigated in three Pocono Plateau lakes. Diffuse attenuation coefficients (KdUV) in the epilimnia of these lakes varied seasonally (39–81% decline from maximum Kd320nm), with minimum KdUV values occurring near summer solstice. Declines in KdUV corresponded to reductions in UV absorbance by dissolved material (adUV), caused by declines in both DOC concentration and UV (ad : [DOC]). The seasonal decline in KdUV was also accompanied by substantial increases in an absorption coefficient ratio (ad250nm : ad365nm) and decreases in spectral slopes (S). Experimental studies of photochemical degradation were also performed using filtered lake water and natural sunlight. Exposure to solar radiation produced a number of changes in optical parameters and DOC that resembled those observed in the water column: adUV (−35 to −52%), UV absorptivity (−31 to −48%), ad250nm : ad365nm (0 to +39%), spectral slope, S (0 to −27%), and DOC concentration (0 to −20%). Changes in adUV were correlated with absorbed UV dose. The derived rate constants were used in a model to estimate the contribution of photochemical degradation of DOC to water column declines in KdUV. Results suggest that rates of photochemical degradation were sufficient to account for the summer reductions in KdUV observed in the three lakes.

The Role of the Posterior Fusiform Gyrus in Reading

Abstract: Studies of skilled reading [Price, C. J., & Mechelli, A. Reading and reading disturbance. Current Opinion in Neurobiology, 15, 231--238, 2005], its acquisition in children [Shaywitz, B. A., Shaywitz, S. E., Pugh, K. R., Mencl, W. E., Fulbright, R. K., Skudlarski, P., et al. Disruption of posterior brain systems for reading in children with developmental dyslexia. Biological Psychiatry, 52, 101--110, 2002; Turkeltaub, P. E., Gareau, L., Flowers, D. L., Zeffiro, T. A., & Eden, G. F. Development of neural mechanisms for reading. Nature Neuroscience, 6, 767--773, 2003], and its impairment in patients with pure alexia [Leff, A. P., Crewes, H., Plant, G. T., Scott, S. K., Kennard, C., & Wise, R. J. The functional anatomy of single word reading in patients with hemianopic and pure alexia. Brain, 124, 510--521, 2001] all highlight the importance of the left posterior fusiform cortex in visual word recognition. We used visual masked priming and functional magnetic resonance imaging to elucidate the specific functional contribution of this region to reading and found that (1) unlike words, repetition of pseudowords (“solst-solst”) did not produce a neural priming effect in this region, (2) orthographically related words such as “corner-corn” did produce a neural priming effect, but (3) this orthographic priming effect was reduced when prime-target pairs were semantically related (“teacher-teach”). These findings conflict with the notion of stored visual word forms and instead suggest that this region acts as an interface between visual form information and higher order stimulus properties such as its associated sound and meaning. More importantly, this function is not specific to reading but is also engaged when processing any meaningful visual stimulus.

Experimental Evaluation of Earthquake Resistant Posttensioned Steel Connections

Abstract: Nine large-scale subassembly tests were conducted to investigate the behavior of an innovative posttensioned wide flange beam-to-column connection for steel moment resisting frames subjected to seismic loading conditions. The connection includes top and seat angles bolted to the beam and column. Strands are placed along the length of the beam, passing through the column and posttensioned to provide a precompression of the beam against the column. The parameters investigated in the study include the angle thickness, angle gage length, beam flange reinforcing plates, connection shim plates, and posttensioning force. The test results demonstrate that posttensioned connections provide excellent elastic stiffness, strength, and ductility under cyclic loading, with energy dissipation occurring primarily in the angles. The connection initial elastic stiffness is comparable to that of a fully restrained welded connection. In addition, the connection has essentially no residual deformation following several cycles...