High spatial resolution nanoslit SERS for single-molecule nucleobase sensing

Solid-state nanopores promise a scalable platform for single-molecule DNA analysis. Direct, real-time identification of nucleobases in DNA strands is still limited by the sensitivity and the spatial resolution of established ionic sensing strategies. Here, we study a different but promising strategy based on optical spectroscopy. We use an optically engineered elongated nanopore structure, a plasmonic nanoslit, to locally enable single-molecule surface enhanced Raman spectroscopy (SERS). Combining SERS with nanopore fluidics facilitates both the electrokinetic capture of DNA analytes and their local identification through direct Raman spectroscopic fingerprinting of four nucleobases. By studying the stochastic fluctuation process of DNA analytes that are temporarily adsorbed inside the pores, we have observed asynchronous spectroscopic behavior of different nucleobases, both individual and incorporated in DNA strands. These results provide evidences for the single-molecule sensitivity and the sub-nanometer spatial resolution of plasmonic nanoslit SERS

Characterization of PECVD Silicon Nitride Photonic Components at 532 and 900 nm Wavelength

Low temperature PECVD silicon nitride photonic waveguides have been fabricated by both electron beam lithography and 200 mm DUV lithography. Propagation losses and bend losses were both measured at 532 and 900 nm wavelength, revealing sub 1dB/cm propagation losses for cladded waveguides at both wavelengths for single mode operation. Without cladding, propagation losses were measured to be in the 1-3 dB range for 532 nm and remain below 1 dB/cm for 900 nm for single mode waveguides. Bend losses were measured for 532 nm and were well below 0.1 dB per 90 degree bend for radii larger than 10 mu m

Relationship between freight accessibility and logistics employment in US counties

This paper analyzes the relationship between freight accessibility and logistics employment in the US. It develops an accessibility measure relevant for logistics companies based on a gravity model. This allows for an analysis of the accessibility of US counties focusing on four different modes of transportation: road, rail, air, and maritime. Using a Partial Least Squares model, these four different freight accessibility measures are combined into two constructs, continental and intercontinental freight accessibility, and related to logistics employment. Results show that highly accessible counties attract more logistics employment than other counties. The analyses show that it is very important to control for the effect of the county population on both freight accessibility and logistics employment. While county population explains the most variation in the logistics employment per county, there is a significant relationship between freight accessibility and logistics employment, when controlling for this effect

A method to evaluate equitable accessibility: combining ethical theories and accessibility-based approaches

In this paper, we present the case that traditional transport appraisal methods do not sufficiently capture the social dimensions of mobility and accessibility. However, understanding this is highly relevant for policymakers to understand the impacts of their transport decisions. These dimensions include the distribution of mobility and accessibility levels over particular areas or for specific population groups, as well as how this may affect various social outcomes, including their levels of participation, social inclusion and community cohesion. In response, we propose a method to assess the socially relevant accessibility impacts (SRAIs) of policies in some of these key dimensions. The method combines the use of underlying ethics principles, more specifically the theories of egalitarianism and sufficientarianism, in combination with accessibility-based analysis and the Lorenz curve and Gini index. We then demonstrate the method in a case study example. Our suggestion is that policymakers can use these ethical perspectives to determine the equity of their policies decisions and to set minimum standards for local transport delivery. This will help them to become more confident in the development and adoption of new decision frameworks that promote accessibility over mobility and which also disaggregate the costs and benefits of transport policies over particular areas or for specific under-served population groups

3D surface-based morphometrics used to determine the intraspecific differences within the tail of syngnathid fishes

Neutens C., De Dobbelaer B., Claes P., Adriaens D., ''3D surface-based morphometrics used to determine the intraspecific differences within the tail of syngnathid fishes'', Integrative and comparative biology, vol. 55, pp. E133, 2015 (The Society for Integrative and Comparative Biology annual meeting - SICB 2015, January 3-7, 2015, West Palm Beach, Florida, USA).status: publishe

Understanding the mechanics of tail grasping in seahorses using a parametrized computer model

Seahorses are intriguing fishes for several reasons, one being their prehensile tail. Syngnathid fishes, to which seahorses, pipefish, seadragons and pipehorses belong, are characterised by a body armour of bony plates. They form a serially articulated system that encloses the vertebral column and its musculature. In the ancestral condition, as in pipefish, the tail is straight with limited flexibility, and mainly used for steering (pectorals and dorsal used for swimming). During evolution, the tail became modified into a grasping apparatus multiple times independently within the syngnathid family. Less known than the seahorse prehensile capabilities, pipehorses also show different morphologies related to grasping performance. To better understand the structural basis of tail grasping mechanics, a parameterized model of the seahorse tail was developed. By combining multibody dynamics analysis with finite element analysis, we analysed the implication of partial contribution of epaxial and hypaxial muscles, versus ventral median muscle, as well as that of the bony plate geometry. Natural bending postures, as observed in living seahorses, can be obtained up to some degree. The analyses showed particular relations between morphology and bending kinematics. Using this seahorse model, functional implications of evolutionary changes in in syngnathid tails can be further analysed, as well as to develop biomimetic designs of serially articulated systems that meet particular application demands