Calculation of electron-impact rotationally elastic total cross sections for NH₃, H₂S, and PH₃ over the energy range from 0.01 eV to 2 keV

This paper report results of calculation of the total cross section QT for electron impact on NH3, H2S,and PH3 over a wide range of incident energies from 0.01 eV to 2 keV. Total cross sections QT (elastic plus electronic excitation) for incident energies below the ionization threshold of the target were calculated using the UK molecular R-matrix code through the Quantemol-N software package and cross sections at higher energies were derived using the spherical complex optical potential formalism. The two methods are found to give self-consistent values where they overlap. The present results are, in general, found to be in good agreement with previous experimental and theoretical results

An investigation of Martian atmospheric trace species using laboratory and computer-based simulation

The study of trace gas species in the Martian atmosphere has the potential to shed new light on wide-ranging topics such as the search for life and the history of liquid water on the planet. Investigating the way that molecules such as ozone, water and HCl are cycled in the atmosphere will give insights into the interactions taking place between the atmosphere, lithosphere and any potential biosphere. Numerous missions are currently being planned; for example the NASA/ESA Trace Gas Orbiter which will probe the trace constituents of the Martian atmosphere and to try to explain recent observations such as the Tharsis methane plumes and the presence of perchlorate in the North polar plains. Currently there are two Mars General Circulation Models (MGCMs) that have fully coupled photochemistry modules: the 3D Mars Global Multiscale Model (GM3) and the Laboratoire de Météorologie Dynamique (LMD) MGCM. Both modules focus on odd-hydrogen (HOx) and odd-oxygen (Ox) chemistry and are not yet capable of simulating more complex chemical interactions. However, the benefit of fully-coupled MGCMs is that both the chemistry and the global transport of trace species can be investigated. In the current project we plan to study the more exotic chemical reactions occurring in the Martian atmosphere and to constrain their mechanisms and rates using both laboratory analogues and computerbased simulation

Research on Europa's dust cloud at The Open University's HVI Laboratory

Space in the vicinity of Europa is populated by dust originating from its surface. Fragments of the surface are ejected due to meteroid hypervelocity impacts (but also they may originate from the sub-surface such as was found on Enceladus). It is assumed that orbit-based detection and analysis of material ejected from the Europan Surface may provide an alternative method for sampling Europan material without landing on the surface. Rleative impact speeds from these dust sources onto an in-orbit detector would, typically, be about 2 kms.This impact speed is generally too low for complete vapourisation of the impactor/target and the ejecta material could be caputured in-situ for further analysis. Our current work is aimed at the development of a new hybrid dust detector for any Europa orbiter as well as an understanding of Europa's dust cloud by mimicing micrometeoroid impact into simulated European regolith/ice. In this paper we present our latest research as well as the caility we have developed as a new laboratory in the filed of HVI physics

Modeling of nanoparticle coatings for medical applications

Abstract Gold nanoparticles (AuNPs) have been shown to possess properties beneficial for the treatment of cancerous tumors by acting as radiosensitizers for both photon and ion radiation. Blood circulation time is usually increased by coating the AuNPs with poly(ethylene glycol) (PEG) ligands. The effectiveness of the PEG coating, however, depends on both the ligand surface density and length of the PEG molecules, making it important to understand the structure of the coating. In this paper the thickness, ligand surface density, and density of the PEG coating is studied with classical molecular dynamics using the software package MBN Explorer. AuNPs consisting of 135 atoms (approximately 1.4 nm diameter) in a water medium have been studied with the number of PEG ligands varying between 32 and 60. We find that the thickness of the coating is only weakly dependent on the surface ligand density and that the degree of water penetration is increased when there is a smaller number of attached ligands

Theoretical total cross sections for <i>e</i>-SO₂ scattering over a wide energy range (0.1−2000 eV) revealing a 3.4-eV shape resonance

We have used the ab initio R-matrix formalism at low impact energies (below the ionization threshold of the target) and the spherical complex optical potential methodology above the ionization threshold to generate total cross sections for e-SO2 scattering over the energy range from 0.1 to 2000 eV. The eigenphase diagram and total cross section indicate a structure at 3.4 eV which is ascribed to a shape resonance, evidence for which appears in earlier experimental studie

Symmetry breaking by quantum coherence in single electron attachment

Quantum coherence-induced effects in atomic and molecular systems are the basis of several proposals for laser-based control of chemical reactions. So far, these rely on coherent photon beams inducing coherent reaction pathways that may interfere with one another, in order to achieve the desired outcome. This concept has been successfully exploited for removing the inversion symmetry in the dissociation of homonuclear diatomic molecules, but it remains to be seen if such quantum coherent effects can also be generated by interaction of incoherent electrons with such molecules. Here we show that resonant electron attachment to H2 and the subsequent dissociation into H (n=2) + H− is asymmetric about the inter-nuclear axis, while the asymmetry in D2 is far less pronounced. We explain this observation as due to attachment of a single electron resulting in a coherent superposition of two resonances of opposite parity. In addition to exemplifying a new quantum coherent process, our observation of coherent quantum dynamics involves the active participation of all three electrons and two nuclei, which could provide new tools for studying electron correlations as a means to control chemical processes and demonstrates the role of coherent effects in electron induced chemistry

The Personal is still Political: Museums, Participation and Copyright

Copyright is a means of managing the interests of individual authors and those of the ‘public interest’. In a museum context, copyright is a technical practice which illuminates how museums imagine and manage their own organizational legitimacy – a settlement which has often operated through a ‘public interest argument’ (‘we need you to hand over control of your object/story for the benefit of all’). Drawing on interviews with people who work in museums and those who have taken part in a museum participation project, we focus on a digital storytelling project to show how copyright was deployed to make an in-practice argument for the how museums might legitimately relate personal story telling with the ‘public interest’. The project did this through three processes: coming into the public via managing informed consent through evoking future audiences, making an author through creating intentional decisions and ‘responsibilization’ and making an object by transforming a digital story into a ‘finished’ object which is, in turn, transferred into the museum collections. While those involved in the project recognized they had signed over the rights to their story and were, in most cases, broadly happy with this – ‘that’s what the form was for’, as one put it – the personal nature of the story itself (linked to personal memories, friends and family) and the sociality of the process of making it (in a group; through interactions with museum staff) was also emphasized. This sociality was expressed in the sense that participants would like to be told when a story is going to be re-displayed, be sent drafts of interpretation and be invited to the opening of the exhibition – a mode of relationship with the museum consistently described as ‘courtesy’. The article concludes by suggesting that the expectation of courtesy – though it might seem like a very modest claim – does something to museums and makes way for more nuanced asymmetries within the public interest argument. Rather than assuming that ‘the public interest’ lies in treating people (slightly coldly) in the same way, the lens of courtesy might suggest ways of both respecting the importance of the public ethos (for institutions to address themselves to ideas of fairness, inclusion and equality) yet might also work to socialize this impulse and reimagine a responsive public museum from the bottom up

Investigation of the dust environment around Europa

Space in the vicinity of atmosphereless bodies in the Solar system is often populated by dust originating from the surface. Fragments of the surface are ejected mostly due to hypervelocity meteoroid impacts. It is also possible that material from sub-surface layers may be vented through cracks in the ice (as detected near Enceladus). The understanding of Europa's dust cloud (and dust clouds of this sort in general) is done by mimicking micrometeoroid impact into simulated Europan regolith/ice using the light gas gun at the Open University. The research is complemented with impact modelling using the finite element hydrocode, ANSYS Autodyn 3D. The results are implemented in IDL in order to calculate the approximate dust cloud population (size and spatial density) of the surface fragments at different altitudes above Europa’s surface. It is, therefore, investigated whether orbit-based detection and analysis of material ejected from the surface may provide an alternative method for sampling material without landing, both quantitatively and qualitatively. Our current work is aimed at the understanding of the local dust fluxes and geometries at the orbital altitudes and its application to the design of a dust detector for an orbiter

Numerical simulations of the possible atmospheric origin of Martian perchlorate

The first detection of perchlorate salts in the Martian regolith was made by NASA’s Phoenix Mars lander in the northern polar plains. Perchlorate salts are important as they can lead to the formation of brines, are a possible energy source for microbes and can be used as a marker for climate change from wet to dry conditions. There is currently no known mechanism of perchlorate production on Mars though an atmospheric chemical pathway resulting in perchlorate has been proposed

Modelling trace gas chemistry in the Martian atmosphere

Dust-bourne heterogeneous reactions have been modelled using the UK Mars Global Circulation Model (MGCM) coupled with physics and chemistry schemes used in the Laboratoire de Météorologie Dynamique (LMD) MGCM. The seasonal ozone column abundance has been calculated using a number of different dust scenarios. Reactions involving volcanically interesting species such as water vapour, SO2 and HCl have been included and tracer release experiments have been conducted to mimic short and long-term volcanic outgassing. The effect of these new reactions on the bulk chemistry of the Martian atmosphere has been quantified