Faint Light from Dark Matter: Classifying and Constraining Dark Matter-Photon Effective Operators

Even if Dark Matter (DM) is neutral under electromagnetism, it can still interact with the Standard Model (SM) via photon exchange from higher-dimensional operators. Here we classify the general effective operators coupling DM to photons, distinguishing between Dirac/Majorana fermion and complex/real scalar DM. We provide model-independent constraints on these operators from direct and indirect detection. We also constrain various DM-lepton operators, which induce DM-photon interactions via RG running or which typically arise in sensible UV-completions. This provides a simple way to quickly assess constraints on any DM model that interacts mainly via photon exchange or couples to SM leptons.Comment: 32 pages + appendices, 9 + 1 figures, 2 + 1 tables. v2: some clarifications and references added; conclusions unchanged; version published in JHE

Self-indicating, simultaneous multianalyte recognition using an ionic liquid

Ionic Liquids (ILs) are the subject of increased diverse research worldwide due to many attractive inherent characteristics such as high thermal stability, negligible vapour pressure and physical and chemical diversity due to the many permutations possible1. We have studied the IL [P6,6,6,14][DCA] as a self-indicating, simultaneous, multianalyte recognition system for heavy metal ions such as Cu2+ and Co2+. When incorporated into a polymer membrane, this system maintains all these attractive features with the added bonus of the IL now being self-plasticizing. The optical response is obtained via co-ordination of the heavy metal to the anion [DCA]-.2 A system like this can be viewed as a building block for future chemical sensing platforms; where the system itself is responsive toward an analyte, thereby eliminating the need for a reactive chromophore. The resulting system can also be viewed as an optode containing only two components (polymer and plasticizer) as opposed to a classical 5-component optode (polymer, plasticizer, ionophore, ion-exchanger, dye). This simplification of components shows potential for further studies in electrochemical-based sensors (ISE’s). Our aim will be to present the results obtained thus far from both optical and structural characterization studies. 1. Wilkes, J. S., Green Chemistry, 2002, 4, (2), 73-80. 2. Vangdal, B.; Carranza, J.; Lloret, F.; Julve, M.; Sletten, J., Journal of the Chemical Society-Dalton Transactions 2002, (4), 566-574

A two-component polymeric optode membrane based on a multifunctional ionic liquid

This work details the use of a 2-component optode membrane which is capable of generating three distinct colours in the presence of Cu2+ and Co2+ ions. It has been found that the ionic liquid (IL) trihexyltetradecylphosphonium dicyanamide [P6,6,6,14][DCA] can act as plasticizer, ligand and transducer dye when used in poly(vinylchloride) (PVC) membranes, which significantly simplifies the optode membrane platform. Upon exposure to an aqueous Cu2+ solution, a yellow colour is generated within the membrane, while exposure to aqueous Co2+ solution generates a blue colour. Exposure to a solution containing both ions produces a green colour. Vibrational spectroscopy has been used to investigate molecular basis of the IL-metal binding mechanism. Analytical characteristics of the membranes including the effect of interfering ions, binding constants and the limit of detection for both ions have been estimated. Finally the case of simultaneous dual-analyte recognition is presented based on two distinct absorption maxima

The NSERC Program of University Research Fellowships

In the mid-1970s several analyses warned of an impending crisis in Canadian universities resulting from the age distribution of faculty members and anticipated trends in student enrolments. It was feared that many young Canadians with new doctoral degrees would be unable to enter academic careers and that the universities would suffer from a lack of young research-oriented faculty members. This paper describes the University Research Fellowships program which was introduced by the Natural Sciences and Engineering Research Council in 1980 as a response to this situation. The steps leading up to the launching of the program, the experience with this program to date, and its impact upon the universities are described. Finally, the Council's plans for the future of this program are discussed.Au cours des années 70, plusieurs analyses présageaient une crise imminente dans les universités canadiennes. Cette crise résulterait de la répartition par âge des membres du corps professoral et des tendances prévues du nombre d'étudiants. On craignait que beaucoup de jeunes Canadiens ayant récemment obtenu leur doctorat ne puissent faire carrière dans une université canadienne. Par ailleurs, les universités subiraient les effets d'un manque de jeunes professeurs désirant faire de la recherche. Cet article décrit le programme de chercheurs-boursiers universitaires qui a été crée par le Conseil de recherches en sciences naturelles et en génie en 1980 pour remédier à cette situation. On y décrit les étapes menant au lancement du programme, les résultats de ce programme jusqu'à présent et ses répercussions sur les universités. Enfin, l'article décrit les projets d'avenir du Conseil en ce qui a trait à ce programme

Hunting for exoplanets via magnetic star-planet interactions: geometrical considerations for radio emission

Recent low-frequency radio observations suggest that some nearby M dwarfs could be interacting magnetically with undetected close-in planets, powering the emission via the electron cyclotron maser (ECM) instability. Confirmation of such a scenario could reveal the presence of close-in planets around M dwarfs, which are typically difficult to detect via other methods. ECM emission is beamed, and is generally only visible for brief windows depending on the underlying system geometry. Due to this, detection may be favoured at certain orbital phases, or from systems with specific geometric configurations. In this work, we develop a geometric model to explore these two ideas. Our model produces the visibility of the induced emission as a function of time, based on a set of key parameters that characterise magnetic star-planet interactions. Utilising our model, we find that the orbital phases where emission appears are highly dependent on the underlying parameters, and does not generally appear at the quadrature points in the orbit as is seen for the Jupiter-Io interaction. Then using non-informative priors on the system geometry, we show that untargeted radio surveys are biased towards detecting emission from systems with planets in near face-on orbits. While transiting exoplanets are still likely to be detectable, they are less likely to be seen than those in near face-on orbits. Our forward model serves to be a powerful tool for both interpreting and appropriately scheduling radio observations of exoplanetary systems, as well as inverting the system geometry from observations.Comment: 19 pages, 16 figures. Accepted for publication in MNRA

Light-modulated ion binding: towards calibrationless sensors

Emerging technologies create new application fields but few of them require that we completely rethink our approach in preparation and characterization of sensors. The vision of internet scale wireless sensor networks (WSNs) requires the deployment of enormous numbers of sensors. This necessarily means that the cost of each sensor must be brought down significantly if this vision is to be realized. An ideal solution for this problem would be a sensor that does not interact with its environment in any way until there is a need for measurement. Upon the measurement, the sensor’s surface is completely regenerated and returned into the state as before the measurement. This step is critical as it ensures that the measurement did not any effect on the sensor hence no calibration is necessary. In our work, we use compounds that indeed can be switched between the active and passive state using light. Most commonly used compounds are so called spiropyrans (SP) and spirooxazines (SO). Here we show the recent advance in preparation of reversible, light-modulated sensors using surface immobilised SP/SO derivatives. A further attractive property of these materials is that they are inherently self-indicating through striking colour changes that enable the state to be easily determined (active vs. passive), and the presence of a bound guest to be detected. These spectral changes enable a range of self-diagnostic tests to be incorporated that enable binding events to be controlled at the surface interface, and for real binding events to be distinguished from artefacts arsing from changes in light intensity, or photobleaching of the active component. We have identified most notable problems for utilization of these compounds in “calibrationless” sensors such as relatively weak binding constants, photodegradation, and unfavourable kinetics of switching between the active and passive state and we demonstrate our approach in solving these problems

The art of earth and fire : the aesthetics of Robin George Collingwood and the craft of the studio potter

The purpose of this dissertation is to make a contribution toward a theory of creative craft. The dissertation consists of three major divisions: the first posits the problem of the craft/art distinction in the context of the aesthetics of R. G. Collingwood; the second offers a transition to a more concrete orientation concerning the problem by using the approaches of William Morris, Sir Herbert Read, and Bernard Leach; and in the third, I present a case study and an investigation of doing, making, and creating in the potter's studio. I look on them as studio achievements and activities nestled in the general context of human artistic practices, traditions, and labour. Collingwood makes a clear and deep distinction between craft making and art making. He defined them in such a way that no features of the one could possibly be features of the other, yet he stipulated that craft was a necessary (but not sufficient) condition of great art. He defined craft as the specialized knowledge necessary for the skilled fabrication of preconceived artifacts; he defined art as the expression of emotion, pure and simple. Following Collingwood's lead, I offer a negative criticism of his theory in order to break up a logjam of philosophical debris. I then proceed to a constructive analysis of the case based in the potter's workplace. This setting provides me with the opportunity to propose and develop a new model for exemplifying what craft making is. The thesis asserts that by seeing the studio craftsperson as a member of a human community and communities, we can more readily grasp how skill and originality, excellence and uniqueness, plan and autonomy, imagination and physical labour, and technique and creativity need not be seen as exclusive poles. They may be, and often are, interwoven facets of much human labour in the arts. The activity of the studio potter provides the context, the tradition, the practices, and the broad cultural base within which language about creative making, an important part of the aesthetic aspect of craft, may be intelligently discusse