Strategies for Enhancing the Performance of Chemical Sensors Based on Microcantilever Sensors

Microcantilever (MC) based chemical sensors have become more widely used during the past 10 years due to the advantages they possess over other chemical sensors. One of the most significant characteristics is their extremely high surface to volume ratio. This key facet allows surface forces that can be ignored on a macroscale to become a significant sensing transduction mechanism. MC based sensors also exhibit a higher mass sensitivity to adsorbates than do many other chemical sensor platforms. Under many conditions, MC based sensors directly translate changes in Gibbs free energies due to analyte-surface interactions into mechanical responses. However, the widespread application of MCs in the field of sensors has yet to be fully realized. This is primarily due to the lack of a unifying methodology and instrumentation that would allow various research groups to benefit from a combined wealth of knowledge on the subject. The underlying goal of this research is to broaden the depth and scope of knowledge of MC based chemical sensors. By working on several areas in a coherent order, the limitations of MC based sensors have been determined and largely overcome. The information gathered in all aspects of this project will be useful to present and future researchers in this field. The initial research was focused on the application of various chemical films to MC sensors to be able to measure a wide range of chemical species. In one case, thin films of polymeric gas chromatography (GC) phases were deposited onto V-shaped MCs. A main strength to using GC phases was that the responses of the analytes could be predicted before hand by using the McReynolds constants of the phases used. This allowed for the detection and quantification of various chemical species using these moderately selective phases. vi During this phase of research it was discovered that methods for enhancing MC response were needed to overcome some of the traditional problems facing MC based sensors. By employing a new type of underlying nanostructured metallic film, MC response was greatly enhanced. This resulted in a better limit of detection and wider dynamic range relative to previous results with smooth surface MCs. In addition to advances resulting from nanostructuring, important advances were made in MC coating strategies. The widely used and well-characterized process of physical vapor deposition was used to deposit both organic and polymeric materials onto the MC surface. This process allowed for uniform films to be deposited with tailored thicknesses and for individual MCs on a single chip to be coated selectively. Another approach involving the immersion of MCs into fused silica capillaries containing solutions of thiolated materials was also developed. This method also allowed for individual MCs in an array to be selectively coated. Finally, out of these results and a developing trend of using sensor arrays came the need to increase the robustness and selectivity of MC based systems. Two different systems for achieving these goals were developed. First, a simple differential system based upon dual diode lasers was constructed in order to eliminate common sources of noise and non-specific interactions that decrease the dynamic range of these sensors. This system was also applied to the quantification of individual components in a binary mixture. While this system has met only limited success, it has been a beneficial first step towards MC systems of higher order. Towards that goal, a system designed to measure multiple MCs simultaneously using an array of vertical cavity surface emitting lasers was also used. This system measures the responses of multiple MCs exposed to an vii analyte in a single run and provides unique response patterns for that analyte. This allowed for the qualitative analysis of a simple mixture to be performed

Editorial

Following publication of the Conference Proceedings of the International Art Therapy Conference 2013 in the last issue of ATOL (5,1) we now return to our regular content of peer reviewed articles and other items of interest

Hearing through your eyes: neural basis of audiovisual cross-activation, revealed by transcranial alternating current stimulation

Some people experience auditory sensations when seeing visual flashes or movements. This prevalent synaesthesia-like ‘visual-evoked auditory response’ (vEAR) could result either from over-exuberant cross-activation between brain areas, and/or reduced inhibition of normally-occurring cross-activation. We have used transcranial alternating current stimulation (tACS) to test these theories. We applied tACS at 10Hz (alpha-band frequency) or 40Hz (gamma-band), bilaterally either to temporal or occipital sites, while measuring same/different discrimination of paired auditory (A) versus visual (V) 'Morse code' sequences. At debriefing, participants were classified as vEAR or non-vEAR depending on whether they reported 'hearing' the silent flashes. In non-vEAR participants, temporal 10Hz tACS caused impairment of A performance, which correlated with improved V; conversely under occipital tACS, poorer V performance correlated with improved A. This reciprocal pattern suggests that sensory cortices are normally mutually inhibitory, and that alpha-frequency tACS may bias the balance of competition between them. vEAR participants showed no tACS effects, consistent with reduced inhibition, or enhanced cooperation between modalities. In addition, temporal 40Hz tACS impaired V performance, specifically in individuals who showed a performance advantage for V (relative to A). Gamma-frequency tACS may therefore modulate the ability of these individuals to benefit from recoding flashes into the auditory modality, possibly by disrupting cross-activation of auditory areas by visual stimulation. Our results support both theories, suggesting that vEAR may depend on disinhibition of normally-occurring sensory cross-activation, which may be expressed more strongly in some individuals. Furthermore, endogenous alpha and gamma-frequency oscillations may function respectively to inhibit or promote this cross-activation

Open Studio Group

Robin volunteered to run the open studio group because, in part, he felt that in open groups it could easier for members and the conductor to manage anxiety, the situation was less anxiety provoking. He remembered open groups that he had been a part of, in learning disability settings, where the numbers ranged from 15 to 20 clients, depending on the demand that day. There were usually two therapists and a helper. Here clients came and used the space and materials as they felt inclined to do. There was not a lot of pressure to interact with others, other members of the group or the therapists. Many of the clients returned to the same part of the room each day, personalising the space in some way. Anxiety levels were lower in this environment and a culture of respect was inculcated over time, respect in relation to personal space and the work that others produced. Significant exchanges did take place in this group but they were not generated through any overt structures, rather they represented spontaneous communications, sharing of work, thought, emotions, and wishes. Robin wanted something like this in the conference, but without the territorial element, a space where individuals could access a range of art materials and work quietly, or sit quietly as they wished. Interaction, sharing and exchanges with others would be, of course, permitted but there would be no obligation in this respect

Insight into ortho-boronoaldehyde conjugation via a FRET-based reporter assay

Ortho-boronoaldehydes react with amine-based nucleophiles with dramatically increased rates and product stabilities, relative to unfunctionalised benzaldehydes, leading to exciting applications across biological and material chemistry. We have developed a novel Förster resonance energy transfer (FRET)-based assay to provide key new insights into the reactivity of these boronoaldehydes, allowing us to track conjugation with unprecedented sensitivity and accuracy under standardised conditions. Our results highlight the key role played by reaction pH, buffer additives, and boronoaldehyde structure in controlling conjugation speed and stability, providing design criteria for further innovations and applications in the field

Evaluating US drone strikes in Yemen and Pakistan

This dissertation seeks to evaluate the effectiveness of drone strikes in Pakistan and Yemen using the theoretical framework of hard, soft and smart power. The first chapter will define and analyse this theoretical framework, providing a foundation and structure in which this dissertation takes place. The subsequent chapter analyses the drone strikes through the theoretical lens of hard power, emphasising their effectiveness in satisfying the drone campaign's objective to punish terrorist organisations. Following this, the soft power effectiveness of the drone strikes will be evaluated, focusing on how targeted drone killings produce a counterproductive soft power effect, resulting in terrorist organisations being able to absorb their losses through increased recruitment. However, these new recruits are shown to be led by an increasingly inexperienced leadership, hampering the ability of terrorist organisations. Consequently, the drone strikes are argued to be effective through relying of their hard power success, as the hard power effectiveness of the targeted drone killings are shown to be successful enough to overcome the soft power failures of the drone campaign. The final chapter analyses the overall effectiveness of the drone strikes and the known policies the US can implement to increase the soft power effectiveness of the drone campaign. Accordingly, this dissertation concludes that although the drone strikes are effective, this effectiveness is sub-optimal and not 'smart', as the drone strikes are shown to not combine soft power tools with its hard power success to punish terrorist organisations.Master of Science (International Political Economy

Integration of paper spray ionization high‐field asymmetric waveform ion mobility spectrometry for forensic applications

Rationale: Paper spray ionization (PSI) is an attractive ambient ionization source for mass spectrometry (MS) since it allows the combination of surface sampling and ionization. The minimal sample preparation inherent in this approach greatly reduces the time needed for analysis. However, the ions generated from interfering compounds in the sample and the paper substrate may interfere with the analyte ions. Therefore, the integration of PSI with high‐field asymmetric ion mobility spectrometry (FAIMS) is of significant interest since it should reduce the background ions entering the mass analyzer without complicating the analysis or increasing analysis time. Here we demonstrate the integration of PSI with FAIMS/MS and its potential for analysis of samples of forensic interest. Methods: In this work, the parameters that can influence the integration, including sampling and ionization by paper spray, the FAIMS separation of analytes from each other and background interferences, and the length of time that a usable signal can be observed for explosives on paper, were evaluated with the integrated system. Results: In the negative ion analysis of 2,4,6‐trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX), and 1,3,5‐trinitroperhydro‐1,3,5‐ triazine (RDX), amounts as low as 1 ng on paper were readily observed. The successful positive ion separation of a set of illicit drugs including heroin, methamphetamine, and cocaine was also achieved. In addition, the positive ion analysis of the chemical warfare agent simulants dimethyl methylphosphonate (DMMP) and diisopropyl methylphosphonate (DIMP) was evaluated. Conclusions: The integration of PSI‐FAIMS/MS was demonstrated for the analyses of explosives in negative ion mode and for illicit drugs and CW simulants in positive mode. Paper background ions that could interfere with these analyses were separated by FAIMS. The compensation voltage of an ion obtained by FAIMS provided an additional identification parameter to be combined with the mass spectrum for each analyte

Insight into ortho-boronoaldehyde conjugation via a FRET-based reporter assay

Ortho-boronoaldehydes react with amine-based nucleophiles with dramatically increased rates and product stabilities, relative to unfunctionalised benzaldehydes, leading to exciting applications across biological and material chemistry. We have developed a novel Förster resonance energy transfer (FRET)-based assay to provide key new insights into the reactivity of these boronoaldehydes, allowing us to track conjugation with unprecedented sensitivity and accuracy under standardised conditions. Our results highlight the key role played by reaction pH, buffer additives, and boronoaldehyde structure in controlling conjugation speed and stability, providing design criteria for further innovations and applications in the field

someunconsciousthings Goldsmiths Art Psychotherapy Exhibition

Art practice in art therapy is given shape by its simultaneous involvement of artist, viewer and curator and its boundaries of time, space and materials. The drama takes place within contexts such as hospitals, schools, prisons and hospices; the players are positioned in relationships of power and unconscious and conscious processes can be explored. Tutors on the MA Art Psychotherapy, Goldsmiths, University of London, have used aspects of an art therapy practice to explore their individual and collective understanding of the ‘unconscious’. This exhibition, created in response to the centenary of Freud’s essays on the unconscious, is part of an on-going research project, which uses art-making and writing to explore the theme. Freud's essays were in part written as a rejoinder to scepticism of the concept; our research explores its contested relevance to contemporary art therapy practice. Christopher Brown, Kristen Catchpole, Annamaria Cavaliero, Diana Kagiafa, Jon Martyn, Lesley Morris, Lisa Rimmer, Susan Rudnik, Sally Skaife, Robin Tipple, Diana Velada, Jill Westwood