Protein functionalized ZnO thin film bulk acoustic resonator as an odorant biosensor

ZnO thin film bulk acoustic resonators (FBARs) with resonant frequency of ∼1.5 GHz have been fabricated to function as an odorant biosensor. Physical adsorption of an odorant binding protein (AaegOBP22 from Aedes aegypti) resulted in frequency down shift. N,N-diethyl-meta-toluamide (DEET) has been selected as a ligand to the odorant binding protein (OBP). Alternate exposure of the bare FBARs to nitrogen flow with and without DEET vapor did not cause any noticeable frequency change. However, frequency drop was detected when exposing the OBP loaded FBAR sensors to the nitrogen flow containing DEET vapor against nitrogen flow alone (control) and the extent of frequency shift was proportional to the amount of the protein immobilized on the FBAR surface, indicating a linear response to DEET binding. These findings demonstrate the potential of binding protein functionalized FBARs as odorant biosensors. © 2012 Elsevier B.V. All rights reserved.

Augmented attribute representations

We propose a new learning method to infer a mid-level feature representation that combines the advantage of semantic attribute representations with the higher expressive power of non-semantic features. The idea lies in augmenting an existing attribute-based representation with additional dimensions for which an autoencoder model is coupled with a large-margin principle. This construction allows a smooth transition between the zero-shot regime with no training example, the unsupervised regime with training examples but without class labels, and the supervised regime with training examples and with class labels. The resulting optimization problem can be solved efficiently, because several of the necessity steps have closed-form solutions. Through extensive experiments we show that the augmented representation achieves better results in terms of object categorization accuracy than the semantic representation alone. © 2012 Springer-Verlag.

Function propagation through nested systems

Concepts of function are central to design but statements about a device's functions can be interpreted in different ways. This raises problems for researchers trying to clarify the foundations of design theory and for those developing design support-tools that can represent and reason about function. By showing how functions relate systems to their sub-systems and super-systems, this article illustrates some limitations of existing function terminology and some problems with existing function statements. To address these issues, a system-relative function terminology is introduced. This is used to demonstrate that systems function not only with respect to their most local super-system, but also with respect to their more global super-systems. © 2012 Elsevier Ltd. All rights reserved.

Quantum dots and nanowires for optoelectronic device applications

InGaAs quantum dots (QDs) and nanowires have been grown on GaAs by metal-organic chemical vapour deposition on GaAs (100) and (111)B substrates, respectively. InGaAs QD lasers were fabricated and characterised. Results show ground-state lasing at about 1150 nm in devices with lengths greater than 2.5 mm. We also observed a strong influence of nanowire density on nanowire height specific to nanowires with high indium composition. This dependency was attributed to the large difference of diffusion length on (111)B surfaces between In and Ga reaction species, with In being the more mobile species. Selective area epitaxy for applications in quantum-dot optoelectronic device integration is also discussed in this paper. ©2006 IEEE.

Sand column impact onto a Kolsky pressure bar

A laboratory-based methodology to launch cylindrical sand slugs at high velocities is developed. The methodology generates well-characterised soil ejecta without the need for detonation of an explosive; this laboratory-based tool thereby allows for the experimental investigation of the soil-structure events. The experimental set-up comprises a launcher with a cylindrical cavity and a piston to push out the sand slug. The apparatus is used to launch both dry and water-saturated sand slugs. High speed photography is used to characterise the evolution of the sand slugs after launch. We find that the diameter of the slugs remains unchanged, and the sand particles possess only an axial component of velocity. However, the sand particles have a uniform spatial gradient of axial velocity and this results in lengthening of the slugs as they travel towards their target. Thus, the density of the sand slugs remains spatially homogenous but decreases with increasing time. The velocity gradient is typically higher in the dry sand slugs than that of the water-saturated slugs. The pressure exerted by the slugs on a rigid-stationary target is measured by impacting the slugs against a direct impact Kolsky bar. After an initial high transient pressure, the pressure reduces to a value of approximately ρv 2 where ρ is the density of the impacting sand slug and v is the particle velocity. This indicates that loading due to the sand is primarily inertial in nature. The momentum transmitted to the Kolsky bar was approximately equal to the incident momentum of the sand slugs, regardless of whether they are dry or water-saturated. © 2013 Elsevier Ltd. All rights reserved.

Deterministic cold cathode electron emission from carbon nanofibre arrays.

The ability to accurately design carbon nanofibre (CN) field emitters with predictable electron emission characteristics will enable their use as electron sources in various applications such as microwave amplifiers, electron microscopy, parallel beam electron lithography and advanced Xray sources. Here, highly uniform CN arrays of controlled diameter, pitch and length were fabricated using plasma enhanced chemical vapour deposition and their individual emission characteristics and field enhancement factors were probed using scanning anode field emission mapping. For a pitch of 10 µm and a CN length of 5 µm, the directly measured enhancement factors of individual CNs was 242, which was in excellent agreement with conventional geometry estimates (240). We show here direct empirical evidence that in regular arrays of vertically aligned CNs the overall enhancement factor is reduced when the pitch between emitters is less than half the emitter height, in accordance to our electrostatic simulations. Individual emitters showed narrow Gaussian-like field enhancement distributions, in excellent agreement with electric field simulations.