Post-CMOS wafer level growth of carbon nanotubes for low-cost microsensors--a proof of concept.

Here we demonstrate a novel technique to grow carbon nanotubes (CNTs) on addressable localized areas, at wafer level, on a fully processed CMOS substrate. The CNTs were grown using tungsten micro-heaters (local growth technique) at elevated temperature on wafer scale by connecting adjacent micro-heaters through metal tracks in the scribe lane. The electrical and optical characterization show that the CNTs are identical and reproducible. We believe this wafer level integration of CNTs with CMOS circuitry enables the low-cost mass production of CNT sensors, such as chemical sensors.

Integration of holographic sensors into microfluidics for the real-time pH sensing of L. casei metabolism

We describe developments in the integration of analyte specific holographic sensors into PDMS-based microfluidic devices for the purpose of continuous, low-impact monitoring of extra-cellular change in micro-bioreactors. Holographic sensors respond to analyte concentration via volume change, which makes their reduction in size and integration into spatially confined fluidics difficult. Through design and process modification many of these constraints have been addressed, and a microfluidics-based device capable of real-time monitoring of the pH change caused by Lactobacillus casei fermentation is presented as a general proof-of-concept for a wide array of possible devices.

Laser micromachining of thin films for optoelectronic devices and packages

Focused laser micromachining in an optical microscope system is used to prototype packages for optoelectronic devices and to investigate new materials with potential applications in packaging. Micromachined thin films are proposed as mechanical components to locate fibres and other optical and electrical components on opto-assemblies. This paper reports prototype structures which are micromachined in silicon carbide to produce beams 5 μm thick by (i) laser cutting a track in a SiC coated Si wafer, (ii) undercutting by anisotropic silicon etching using KOH in water, and (iii) trimming if necessary with the laser system. This approach has the advantage of fast turn around and proof of concept. Mechanical test data are obtained from the prototype SiC beam package structures by testing with a stylus profilometer. The Youngs modulus obtained for chemical vapour deposited silicon carbide is 360 +/- 50 GPa indicating that it is a promising material for packaging applications.

Field of view expansion for 3-D holographic display using a single spatial light modulator with scanning reconstruction light

Increasing the field of view of a holographic display while maintaining adequate image size is a difficult task. To address this problem, we designed a system that tessellates several sub-holograms into one large hologram at the output. The sub-holograms we generate is similar to a kinoform but without the paraxial approximation during computation. The sub-holograms are loaded onto a single spatial light modulator consecutively and relayed to the appropriate position at the output through a combination of optics and scanning reconstruction light. We will review the method of computer generated hologram and describe the working principles of our system. Results from our proof-of-concept system are shown to have an improved field of view and reconstructed image size. ©2009 IEEE.

In vivo regulation of the Vi antigen in Salmonella and induction of immune responses with an in vivo-inducible promoter.

Salmonella enterica serovar Typhi, the agent of typhoid fever in humans, expresses the surface Vi polysaccharide antigen that contributes to virulence. However, Vi expression can also be detrimental to some key steps of S. Typhi infectivity, for example, invasion, and Vi is the target of protective immune responses. We used a strain of S. Typhimurium carrying the whole Salmonella pathogenicity island 7 (SPI-7) to monitor in vivo Vi expression within phagocytic cells of mice at different times after systemic infection. We also tested whether it is possible to modulate Vi expression via the use of in vivo-inducible promoters and whether this would trigger anti-Vi antibodies through the use of Vi-expressing live bacteria. Our results show that Vi expression in the liver and spleen is downregulated with the progression of infection and that the Vi-negative population of bacteria becomes prevalent by day 4 postinfection. Furthermore, we showed that replacing the natural tviA promoter with the promoter of the SPI-2 gene ssaG resulted in sustained Vi expression in the tissues. Intravenous or oral infection of mice with a strain of S. Typhimurium expressing Vi under the control of the ssaG promoter triggered detectable levels of all IgG subclasses specific for Vi. Our work highlights that Vi is downregulated in vivo and provides proof of principle that it is possible to generate a live attenuated vaccine that induces Vi-specific antibodies after single oral administration.

A novel ultra-fast optical router using time-slot switching

We present a novel optical routing scheme scalable to greater than 50×50 channels with a potential aggregate bit-rate of 1Tbps. The proof-of-principle experiment demonstrates the feasibility of the router with a de-multiplexed Q-factor of 6.35. © 2004 Optical Society of America.

A novel scalable photonic analog switch architecture based on semiconductor optical amplifiers

We propose a novel semiconductor optical amplifier (SOA) based switch architecture for analog applications. Proof-of-principle experiments show that the system is very linear with an SFDR of approximately 100dB·Hz 2/3 for a switching time of 50μs. The port number of this switch is scalable and can be expanded to 80 × 80.

Projective Limit Random Probabilities on Polish Spaces

A pivotal problem in Bayesian nonparametrics is the construction of prior distributions on the space M(V) of probability measures on a given domain V. In principle, such distributions on the infinite-dimensional space M(V) can be constructed from their finite-dimensional marginals---the most prominent example being the construction of the Dirichlet process from finite-dimensional Dirichlet distributions. This approach is both intuitive and applicable to the construction of arbitrary distributions on M(V), but also hamstrung by a number of technical difficulties. We show how these difficulties can be resolved if the domain V is a Polish topological space, and give a representation theorem directly applicable to the construction of any probability distribution on M(V) whose first moment measure is well-defined. The proof draws on a projective limit theorem of Bochner, and on properties of set functions on Polish spaces to establish countable additivity of the resulting random probabilities.

IMPORTANCE OF TRACK DESIGN IN GROUND TRANSPORTATION SYSTEMS.

The development of the tracks for the Tracked Hovercraft and Bliss Pendair Systems is described. Comment is made on the relative importance of track and suspension costs and of the need for tracks that are weather, vandal and noise proof. It is argued that the beam section required for a suspended air cushion is more likely to fit these requirements than that for beam riding vehicles, either air-cushion or magnetically suspended.

Appraisal of PD6493:1991 fracture assessment procedures

PD6493:1991 fracture assessment have been performed for a range of large-scale fracture mechanics tests conducted at TWI in the past. These tests cover several material groups, including pressure vessel steels, pipeline steels, stainless steels and aluminium alloys, including parent material and weldments. Ninety-two wide plate and pressure vessel tests have been assessed, following Levels 1, 2 and 3 PD6493:1991 procedures. In total, over 400 assessments have been performed, examining many features of the fracture assessment procedure including toughness input, proof testing, residual stress assumptions and stress state (tension, bending and biaxial). In all cases the large scale tests have been assessed as one would actual structures: i.e., based on lower bound toughness values obtained from small scale fracture toughness specimens.

Polymer-based board-level optical interconnects

This paper provides an overview of the rationale behind the significant interest in polymer-based on-board optical links together with a brief review of recently reported work addressing certain challenges in this field. Polymer-based optical links have garnered considerable research attention due to their important functional attributes and compelling cost-benefit advantages in on-board optoelectronic systems as they can be cost-effectively integrated on conventional printed circuit boards. To date, significant work on the polymer materials, their fabrication process and their integration on standard board substrates have enabled the demonstration of numerous high-speed on-board optical links. However, to be deployed in real-world systems, these optoelectronic printed circuit boards (OE PCBs) must also be cost-effective. Here, recent advances in the integration process focusing on simple direct end-fire coupling schemes and the use of low-cost FR4 PCB substrates are presented. Performance of two proof-of-principle 10 Gb/s systems based on this integration method are summarised while work in realising more complex yet compact planar optical components is outlined. © 2011 IEEE.