115 resultados para TRYPTOPHAN SIDE-CHAINS
Resumo:
The experience of border crossing for refugees and irregular migrants challenges global border and migration controls in multiple contexts. Using qualitative field research in Tanzania, Spain, Morocco and Australia, Heather Johnson asks how a global regime of migration management and control can be perceived through the dynamics of particular border spaces: refugee camps, border zones and detention centres. She explores how irregular migrants are impacted by the increasingly security-oriented practices of border control, and how they confront these practices. Johnson rejects the characterization of border spaces as exceptional, abject and exclusionary, arguing instead for an understanding of politics as everyday contestation that reveals a radical political agency, re-imagining the global non-citizen as a transgressive and powerful figure. Building on recent scholarship that rethinks irregularity and non-citizenship, her conclusions have broad implications for how we understand irregular migration from a position of dialogue and solidarity.
Resumo:
The Aquivion short-side-chain (SSC) perfluorosulfonic acid (PFSA) ionomer was adopted in catalyst layers (CL) of polymer electrolyte membrane water electrolysers (PEMWE) instead of long-side-chain (LSC) Nafion ionomer. The effects of SSC ionomer content in CL for oxygen evolution reaction were studied in half cell with cyclic voltammetry and steady state linear sweep. In a single cell test the MEA with SSC-PFSA Aquivion ionomer exhibited better thermal stability than the one with LSC-PFSA Nafion ionomer at 90 °C. The cell voltage at a current density of 1 A cm was 1.63 V at 90 °C using the SSC-PFSA Aquivion ionomer binder, Nafion 117 membrane, and without back pressurizing. In a continuous operation the cell voltage degradation rate of the MEA using Aquivion ionomer binder was only about 0.82 mV h.
Resumo:
Conjugated polymers have attracted considerable attention in the last few decades due to their potential for optoelectronic applications. A key step that needs optimisation is charge carrier separation following photoexcitation. To understand better the dynamics of the exciton prior to charge separation, we have performed simulations of the formation and dynamics of localised excitations in single conjugated polymer strands. We use a nonadiabatic molecular dynamics method which allows for the coupled evolution of the nuclear degrees of freedom and of multiconfigurational electronic wavefunctions. We show the relaxation of electron-hole pairs to form excitons and oppositely charged polaron pairs and discuss the modifications to the relaxation process predicted by the inclusion of the Coulomb interaction between the carriers. The issue of charge photogeneration in conjugated polymers in dilute solution is also addressed. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3600404]
Resumo:
An unusual application of hydrological understanding to a police search is described. The lacustrine search for a missing person provided reports of bottom-water currents in the lake and contradictory indications from cadaver dogs. A hydrological model of the area was developed using pre-existing information from side scan sonar, a desktop hydrogeological study and deployment of water penetrating radar (WPR). These provided a hydrological theory for the initial search involving subaqueous groundwater flow, focused on an area of bedrock surrounded by sediment, on the lake floor. The work shows the value a hydrological explanation has to a police search operation (equally to search and rescue). With hindsight, the desktop study should have preceded the search, allowing better understanding of water conditions. The ultimate reason for lacustrine flow in this location is still not proven, but the hydrological model explained the problems encountered in the initial search.
Resumo:
Due to the intermittent nature of renewable generation it is desirable to consider the potential of controlling the demand-side load to smooth overall system demand. The architecture and control methodologies of such a system on a large scale would require careful consideration. Some of these considerations are discussed in this paper; such as communications infrastructure, systems architecture, control methodologies and security. A domestic fridge is used in this paper as an example of a controllable appliance. A layered approach to smart-grid is introduced and it can be observed how each smart-grid component from physical cables, to the end-devices (or smart-applications) can be mapped to these set layers. It is clear how security plays an integral part in each component of the smart-grid so this is also an integral part of each layer. The controllable fridge is described in detail and as one potential smart-grid application which maps to the layered approach. A demonstration system is presented which involves a Raspberry Pi (a low-power, low-cost device representing the appliance controller).
Resumo:
We study the dynamics of the entanglement spectrum, that is the time evolution of the eigenvalues of the reduced density matrices after a bipartition of a one-dimensional spin chain. Starting from the ground state of an initial Hamiltonian, the state of the system is evolved in time with a new Hamiltonian. We consider both instantaneous and quasi adiabatic quenches of the system Hamiltonian across a quantum phase transition. We analyse the Ising model that can be exactly solved and the XXZ for which we employ the time-dependent density matrix renormalisation group algorithm. Our results show once more a connection between the Schmidt gap, i.e. the difference of the two largest eigenvalues of the reduced density matrix and order parameters, in this case the spontaneous magnetisation.
Resumo:
A string of repulsively interacting particles exhibits a phase transition to a zigzag structure, by reducing the transverse trap potential or the interparticle distance. Based on the emergent symmetry Z2 it has been argued that this instability is a quantum phase transition, which can be mapped to an Ising model in transverse field. An extensive Density Matrix Renormalization Group analysis is performed, resulting in an high-precision evaluation of the critical exponents and of the central charge of the system, confirming that the quantum linear-zigzag transition belongs to the critical Ising model universality class. Quantum corrections to the classical phase diagram are computed, and the range of experimental parameters where quantum effects play a role is provided. These results show that structural instabilities of one-dimensional interacting atomic arrays can simulate quantum critical phenomena typical of ferromagnetic systems.
Resumo:
This paper presents a new method for online determination of the Thèvenin equivalent parameters of a power system at a given node using the local PMU measurements at that node. The method takes into account the measurement errors and the changes in the system side. An analysis of the effects of changes in system side is carried out on a simple two-bus system to gain an insight of the effect of system side changes on the estimated Thévenin equivalent parameters. The proposed method uses voltage and current magnitudes as well as active and reactive powers; thus avoiding the effect of phase angle drift of the PMU and the need to synchronize measurements at different instances to the same reference. Applying the method to the IEEE 30-bus test system has shown its ability to correctly determine the Thévenin equivalent even in the presence of measurement errors and/or system side changes.
Resumo:
Context Medical students can have difficulty in distinguishing left from right. Many infamous medical errors have occurred when a procedure has been performed on the wrong side, such as in the removal of the wrong kidney. Clinicians encounter many distractions during their work. There is limited information on how these affect performance.
Objectives Using a neuropsychological paradigm, we aim to elucidate the impacts of different types of distraction on left–right (LR) discrimination ability.
Methods Medical students were recruited to a study with four arms: (i) control arm (no distraction); (ii) auditory distraction arm (continuous ambient ward noise); (iii) cognitive distraction arm (interruptions with clinical cognitive tasks), and (iv) auditory and cognitive distraction arm. Participants’ LR discrimination ability was measured using the validated Bergen Left–Right Discrimination Test (BLRDT). Multivariate analysis of variance was used to analyse the impacts of the different forms of distraction on participants’ performance on the BLRDT. Additional analyses looked at effects of demographics on performance and correlated participants’ self-perceived LR discrimination ability and their actual performance.
Results A total of 234 students were recruited. Cognitive distraction had a greater negative impact on BLRDT performance than auditory distraction. Combined auditory and cognitive distraction had a negative impact on performance, but only in the most difficult LR task was this negative impact found to be significantly greater than that of cognitive distraction alone. There was a significant medium-sized correlation between perceived LR discrimination ability and actual overall BLRDT performance.
Conclusions
Distraction has a significant impact on performance and multifaceted approaches are required to reduce LR errors. Educationally, greater emphasis on the linking of theory and clinical application is required to support patient safety and human factor training in medical school curricula. Distraction has the potential to impair an individual's ability to make accurate LR decisions and students should be trained from undergraduate level to be mindful of this.