Considering Transmission Impairments in Wavelength Routed Networks

Abstract — We consider dynamically reconfigurable wavelength routed networks in which lightpaths carrying IP traffic are on demand established. We face the Routing and Wavelength Assignment problem considering as constraints the physical impairments that arise in all-optical wavelength routed networks. In particular, we study the impact of the physical layer when establishing a lightpath in transparent optical network. Because no signal transformation and regeneration at intermediate nodes occurs, noise and signal distortions due to non-ideal transmission devices are accumulated along the physical path, and they degrade the quality of the received signal. We propose a simple yet accurate model for the physical layer which consider both static and dynamic impairments, i.e., nonlinear effects depending on the actual wavelength/lightpath allocation. We then propose a novel algorithm to solve the RWA problem that explicitly considers the physical impairments. Simulation results show the effectiveness of our approach. Indeed, when the transmission impairments come into play, an accurate selection of paths and wavelengths which is driven by physical consideration is mandatory. I

Quantitative immunohistochemical analysis of matrilysin 1 (MMP-7) in various renal cell carcinoma subtypes.

The role of matrilysin 1 or matrix metalloproteinase-7 (MMP-7) in cancer is extremely complex and poorly understood. In this study we investigated differential expression of MMP-7 in the epithelium and stroma of 95 paraffin-embedded renal tumor samples by immunohistochemistry and compared tumoral with normal peritumoral renal tissue. We also determined a possible correlation of the immunohistochemical findings with histological subtype, tumor grade and stage of RCC. In all areas examined MMP-7 protein expression was significantly higher in epithelium than in stroma (P<.01). MMP-7 was more less expressed in peritumoral normal areas than in benign epithelial neoplasias (renal papillary and oncocytomas) and RCC carcinomas, reaching the highest immunopositive reaction in chromophobe RCC subtypes, followed by conventional clear-cell and chromophilic-papillary RCC histological subtypes and the lowest levels in more aggressive RCC histotypes (spindle-cell and collecting-duct RCCs). MMP-7 reached their highest levels in high-grade and high-stage RCCs. Our observation suggests an important role of MMP-7 in the development and progression of renal cancer. The differential expression of MMP-7 in the various histological RCC subtypes may reflect the malignant phenotype and more aggressive behavior of RCCs

Action Concepts in the Brain: An Activation Likelihood Estimation Meta-Analysis

Many recent neuroimaging studies have investigated the representation of semantic memory for actions in the brain. We used activation likelihood estimation (ALE) meta-analyses to answer two outstanding questions about the neural basis of action concepts. First, on an “embodied” view of semantic memory, evidence to date is unclear regarding whether visual motion or motor systems are more consistently engaged by action concepts. Second, few studies have directly investigated the possibility that action concepts accessed verbally or nonverbally recruit different areas of the brain. Because our meta-analyses did not include studies requiring the perception of dynamic depictions of actions or action execution, we were able to determine whether conceptual processing alone recruits visual motion and motor systems. Significant concordance in brain regions within or adjacent to visual motion areas emerged in all meta-analyses. By contrast, we did not observe significant concordance in motor or premotor cortices in any analysis. Neural differences between action images and action verbs followed a gradient of abstraction among representations derived from visual motion information in the left lateral temporal and occipital cortex. The consistent involvement of visual motion but not motor brain regions in representing action concepts may reflect differences in the variability of experience across individuals with perceiving versus performing actions

Deconstructing Events: The Neural Bases for Space, Time, and Causality

Space, time, and causality provide a natural structure for organizing our experience. These abstract categories allow us to think relationally in the most basic sense; understanding simple events requires one to represent the spatial relations among objects, the relative durations of actions or movements, and the links between causes and effects. The present fMRI study investigates the extent to which the brain distinguishes between these fundamental conceptual domains. Participants performed a 1-back task with three conditions of interest (space, time, and causality). Each condition required comparing relations between events in a simple verbal narrative. Depending on the condition, participants were instructed to either attend to the spatial, temporal, or causal characteristics of events, but between participants each particular event relation appeared in all three conditions. Contrasts compared neural activity during each condition against the remaining two and revealed how thinking about events is deconstructed neurally. Space trials recruited neural areas traditionally associated with visuospatial processing, primarily bilateral frontal and occipitoparietal networks. Causality trials activated areas previously found to underlie causal thinking and thematic role assignment, such as left medial frontal and left middle temporal gyri, respectively. Causality trials also produced activations in SMA, caudate, and cerebellum; cortical and subcortical regions associated with the perception of time at different timescales. The time contrast, however, produced no significant effects. This pattern, indicating negative results for time trials but positive effects for causality trials in areas important for time perception, motivated additional overlap analyses to further probe relations between domains. The results of these analyses suggest a closer correspondence between time and causality than between time and space