Understanding the application of Raman spectroscopy to the detection of traces of life

This is the publisher's version, also available electronically from "http://online.liebertpub.com".Investigating carbonaceous microstructures and material in Earth's oldest sedimentary rocks is an essential part of tracing the origins of life on our planet; furthermore, it is important for developing techniques to search for traces of life on other planets, for example, Mars. NASA and ESA are considering the adoption of miniaturized Raman spectrometers for inclusion in suites of analytical instrumentation to be placed on robotic landers on Mars in the near future to search for fossil or extant biomolecules. Recently, Raman spectroscopy has been used to infer a biological origin of putative carbonaceous microfossils in Early Archean rocks. However, it has been demonstrated that the spectral signature obtained from kerogen (of known biological origin) is similar to spectra obtained from many poorly ordered carbonaceous materials that arise through abiotic processes. Yet there is still confusion in the literature as to whether the Raman spectroscopy of carbonaceous materials can indeed delineate a signature of ancient life. Despite the similar nature in spectra, rigorous structural interrogation between the thermal alteration products of biological and nonbiological organic materials has not been undertaken. Therefore, we propose a new way forward by investigating the second derivative, deconvolution, and chemometrics of the carbon first-order spectra to build a database of structural parameters that may yield distinguishable characteristics between biogenic and abiogenic carbonaceous material. To place Raman spectroscopy as a technique to delineate a biological origin for samples in context, we will discuss what is currently accepted as a spectral signature for life; review Raman spectroscopy of carbonaceous material; and provide a historical overview of Raman spectroscopy applied to Archean carbonaceous materials, interpretations of the origin of the ancient carbonaceous material, and a future way forward for Raman spectroscopy

Microwave Power Transmission System Studies. Volume 1: Executive Summary

A study of microwave power generation, transmission, reception and control was conducted as a part of a program to demonstrate the feasibility of power transmission from geosynchronous orbit. A summary is presented of results concerning design approaches, estimated costs (ROM), critical technology, associated ground and orbital test programs with emphasis on dc to rf conversion, transmitting antenna, phase control, mechanical systems, flight operations, ground power receiving-rectifying antenna with systems analysis, and evaluation. Recommendations for early further in-depth studies complementing the technology program are included

Microwave power transmission system studies. Volume 2: Introduction, organization, environmental and spaceborne systems analyses

Introduction, organization, analyses, conclusions, and recommendations for each of the spaceborne subsystems are presented. Environmental effects - propagation analyses are presented with appendices covering radio wave diffraction by random ionospheric irregularities, self-focusing plasma instabilities and ohmic heating of the D-region. Analyses of dc to rf conversion subsystems and system considerations for both the amplitron and the klystron are included with appendices for the klystron covering cavity circuit calculations, output power of the solenoid-focused klystron, thermal control system, and confined flow focusing of a relativistic beam. The photovoltaic power source characteristics are discussed as they apply to interfacing with the power distribution flow paths, magnetic field interaction, dc to rf converter protection, power distribution including estimates for the power budget, weights, and costs. Analyses for the transmitting antenna consider the aperture illumination and size, with associated efficiencies and ground power distributions. Analyses of subarray types and dimensions, attitude error, flatness, phase error, subarray layout, frequency tolerance, attenuation, waveguide dimensional tolerances, mechanical including thermal considerations are included. Implications associated with transportation, assembly and packaging, attitude control and alignment are discussed. The phase front control subsystem, including both ground based pilot signal driven adaptive and ground command approaches with their associated phase errors, are analyzed

An Interim Investigation of the Potential of Vibrational Spectroscopy for the Dating of Cultural Objects in Ivory

Radiocarbon dating of ivory requires destructive sampling on a scale not always compatible with the requirements of the preservation and curation of cultural objects. The development of a minimally-destructive dating technique is urgently needed. Raman spectroscopy can detect the changes in the organic and inorganic molecular components of ivory that occur with time. It has been suggested that these vibrational spectroscopic changes could be used to assess the relative date of mammoth ivories, assuming that the state of preservation of the ivory is directly related to its age. This paper tests this assumption with specimens of mammoth ivory of known date and burial environment and concludes that the vibrational spectra of ivory cannot in general be used to deduce the age of the specimen.La datation au radiocarbone de l’ivoire exige un échantillonnage destructif d’une taille qui n’est pas toujours compatible avec les exigences de la préservation et la conservation des objets du patrimoine culturel. Le développement d’une technique de datation la moins destructive possible est devenue une nécessité. La spectroscopie Raman peut détecter les changements dans les composants moléculaires organiques et inorganiques d’ivoire, qui se produisent avec le temps. Il a été suggéré que ces changements pourraient servir à estimer une datation relative des ivoires de mammouths, en supposant que l’état de conservation de l’ivoire est directement lié à son âge. Cet article teste cette hypothèse avec des spécimens d’ivoire de mammouth d’âge connu qui ont subi un enfouissement dans des conditions également connues. Cette étude montre que les spectres vibrationnels d’ivoire ne peuvent pas, en général, être utilisés pour en déduire l’âge d’un spécimen d’ivoire

Green's function probe of a static granular piling

We present an experiment which aim is to investigate the mechanical properties of a static granular assembly. The piling is an horizontal 3D granular layer confined in a box, we apply a localized extra force at the surface and the spatial distribution of stresses at the bottom is obtained (the mechanical Green's function). For different types of granular media, we observe a linear pressure response which profile shows one peak centered at the vertical of the point of application. The peak's width increases linearly when increasing the depth. This green function seems to be in -at least- qualitative agreement with predictions of elastic theory.Comment: 9 pages, 3 .eps figures, submitted to PR

Packing of Compressible Granular Materials

3D Computer simulations and experiments are employed to study random packings of compressible spherical grains under external confining stress. Of particular interest is the rigid ball limit, which we describe as a continuous transition in which the applied stress vanishes as (\phi-\phi_c)^\beta, where \phi is the (solid phase) volume density. This transition coincides with the onset of shear rigidity. The value of \phi_c depends, for example, on whether the grains interact via only normal forces (giving rise to random close packings) or by a combination of normal and friction generated transverse forces (producing random loose packings). In both cases, near the transition, the system's response is controlled by localized force chains. As the stress increases, we characterize the system's evolution in terms of (1) the participation number, (2) the average force distribution, and (3) visualization techniques.Comment: 4 pages, 7 figures, to appear in Phys. Rev. Let

Detection of reduced carbon in a basalt analogue for martian nakhlite : a signpost to habitat on Mars

C. W. Taylor and J. Still are thanked for skilled technical support. J. Parnell, H.G.M. Edwards, I. Hutchinson and R. Ingley acknowledge the support of the UKSA and the STFC Research Council in the UK ExoMars programme. L. V. Harris and S. McMahon acknowledge STFC studentship funding.Peer reviewedPublisher PD

Dorures des céramiques et tesselles anciennes : technologies et accrochage

Les technologies de dorures des céramiques et verres et leurs évolutions historiques sont très mal documentées. Des échantillons d'époques et de technologies différentes (tesselles d'époque omeyyade, début VIIIe s., Qusayr 'Amra, Jordanie ; porcelaine de type « Kinran-de », épave de Cu Lao Cham, XVe s. Vietnam ; porcelaine phosphatique de Rockingham, début XIXe s., Angleterre) ont été analysés par PIXE et RBS sur l'accélérateur AGLAE et par micro-spectrométrie Raman. Dans tous ces cas, l'or est un alliage Au-Ag dont la teneur en argent va de ~5 % en poids pour les deux céramiques à ~ 15 % pour les tesselles. Les épaisseurs des « dorures » sont de 3-5 µm pour la céramique vietnamienne et de 1 µm pour les autres. Une couche d'argent, bien accrochée, est observée à l'interface alliage Au-Ag/céramique et il est probable qu'elle résulte de la diffusion à la cuisson. De ce travail on peut conclure que la dorure des tesselles du VIIIe s. a été réalisée à partir d'une feuille d'or alliée recouverte de verre fondu, que celle de la céramique du XVe s. a été cuite avec les émaux et brunie à la pierre dure, alors que la porcelaine du XIXe s. a été décorée à l'or « liquide ».To date, the ancient gilding technologies of glasses and ceramics, and their history, are not well documented. In this paper three examples, Umayyad tesserae (beginning of the 8th century, Qusayr 'Amra, Jordan), a “Kinran-de” Vietnamese porcelain (Cu Lao Cham shipwreck, middle 15th century) and an English Bone China (Rockingham, beginning 19th century) have been analysed by optical microscopy, µ-Raman scattering, PIXE and RBS (AGLAE). In all cases the gold coating consists of an Au-Ag alloy, -5 % wt for both the ceramics and 15 % wt for the glass tesserae. A silver film is observed at the interface between the gold film and the silicate substrate, which remains partly when the gilding has been eliminated. Film formation is assigned to a segregation at the interface during the firing. It can be conclude that the 8th c. tesserae gold foil has been covered by molten glass, the 15thc. ceramic gold have been fired with the glaze and then burnished and the 19th c. Bone China has been decorated using liquid gold

South African NGOs and the public sphere: between popular movements and partnerships for development.

This article examines the widespread notion that post-apartheid democracy can be deepened and civil society strengthened by NGO activities in the sphere of public debate and participation. I focus on a number of interrelated processes which I argue may compromise NGOs' ability to expand the public sphere: first, donors' overwhelming focus on NGOs as the sole representative of civil society may contribute to a homogenous and institutionalised public sphere; second, the tendency for NGOs to be drawn into partnerships with government bodies and corporate sponsors casts doubt on their ability to open up spaces for critical public debate. By directing attention to popular movements as potentially offering a site for the production of critique, NGOs' relationships to such movements are examined. It is argued that attention must be paid to the processes of NGO-isation and reformism by which NGOs themselves come to define what civil society should be and may consequently contain counterpublic spheres

Continuum theory of partially fluidized granular flows

A continuum theory of partially fluidized granular flows is developed. The theory is based on a combination of the equations for the flow velocity and shear stresses coupled with the order parameter equation which describes the transition between flowing and static components of the granular system. We apply this theory to several important granular problems: avalanche flow in deep and shallow inclined layers, rotating drums and shear granular flows between two plates. We carry out quantitative comparisons between the theory and experiment.Comment: 28 pages, 23 figures, submitted to Phys. Rev.