160keV 26Al-AMS with a single-stage accelerator mass spectrometer

Proof-of-principle 26Al-AMS analysis is achieved with a single-stage accelerator mass spectrometer (SSAMS) utilising very low ion energy. The SSAMS operates by discriminating against atomic isobar interference in a negative ion source and suppressing molecules with thick gas stripper. Resulting 1+ ions counting is with a surface barrier detector. The NEC designed SSAMS for 14C analysis is a popular model accelerator mass spectrometer and the developed further capability might be a significant addition to established 26Al-AMS capacity. Measurements at these energies should also be sufficient for alternative 26Al positive-ion mass spectrometry (PIMS)

Radiocarbon positive-ion mass spectrometry

Proof-of-principle of a new mass spectrometric technique for radiocarbon measurement is demonstrated. Interfering nitrogen and hydrocarbon molecules are largely eliminated in a charge-exchange cell operating on non-metallic gas. The positive-to-negative ion conversion is the reverse of that conventionally used in accelerator mass spectrometry (AMS) and is compatible with plasma ion sources that may be significantly more efficient and capable of greater output than are AMS sputter ion sources. The Nanogan electron cyclotron resonance (ECR) ion source employed exhibited no sample memory and the >50 kyrs age range of AMS was reproduced. A bespoke prototype new instrument is now required to optimise the plasma and cell physics and to realise hypothetical performance gains over AMS

Storage and hydrolysis of seawater samples for inorganic carbon isotope analysis

Preservation of seawater samples was tested for total inorganic carbon (ΣCO2), stable carbon isotope (δ13C), and radiocarbon (14C) applications using foil bags and storage by refrigeration and freezing. The aim was to preserve representative samples with minimal storage effects but without using toxic methods such as mercuric chloride poisoning. Hydrolysis of samples to CO2 was based on existing methods. Results of IAEA-C2 standard used with deionized water stored in the foil bags showed complete reaction yields, 14C results within 2σ of the consensus value, and δ13C that were internally consistent, indicating that there were no procedural effects associated with the foil bags. 14C results were statistically indistinguishable across the storage times, for frozen and refrigerated seawater samples from a coastal site, Elie Ness, Fife, UK. The scatter of ΣCO2 concentrations and δ13C was within scatter observed in other studies for lake- and seawater samples preserved by acidification or using mercuric chloride. However, both ΣCO2 and δ13C were less variable for frozen samples compared with refrigerated samples. The foil bags are lighter, safer to transport, and similar in cost to glass bottles and allow sample collection in the field and transfer to the hydrolysis vessel without exposure of the sample to atmosphere. Storage of seawater samples in the foil bags was considered a reliable, alternative method to poisoning for ΣCO2, δ13C, and 14C, and freezing the samples is recommended for storage time beyond a week

An empirical study of electricity and gas demand drivers in large food retail buildings of a national organisation

AbstractFood retail buildings account for a measurable proportion of a country's energy consumption and resultant carbon emissions so energy-operating costs are key business considerations. Increased understanding of end-use energy demands in this sector can enable development of effective benchmarking systems to underpin energy management tools. This could aid identification and evaluation of interventions to reduce operational energy demand. Whilst there are a number of theoretical and semi-empirical benchmarking and thermal modelling tools that can be used for food retail building stocks, these do not readily account for the variance of technical and non-technical factors that can influence end-use demands.This paper discusses the various drivers of energy end-uses of typical UK food retail stores. It reports on an empirical study of one organisation's hypermarket stock to evaluate the influence of various factors on annual store electricity and gas demands. Multiple regression models are discussed in the context of the development and application of a methodology for estimating annual energy end-use demand in food retail buildings. The established models account for 75% of the variation in electricity demand, 50% of the variation in gas demand in stores without CHP and 77% of the variation in gas demand in stores with CHP

Performance of the rebuilt SUERC single-stage accelerator mass spectrometer

The SUERC bipolar single-stage accelerator mass spectrometer (SSAMS) has been dismantled and rebuilt to accommodate an additional rotatable pre-accelerator electrostatic spherical analyser (ESA) and a second ion source injector. This is for the attachment of an experimental positive-ion electron cyclotron resonance (ECR) ion source in addition to a Cs-sputter source. The ESA significantly suppresses oxygen interference to radiocarbon detection, and remaining measurement interference is now thought to be from 13C injected as 13CH molecule scattering off the plates of a second original pre-detector ESA

Late Quaternary glaciation in the Hebrides sector of the continental shelf : cosmogenic nuclide dating of glacial events on the St Kilda archipelago

The authors thank NERC-CIAF for funding analysis of the 10Be and 36Cl exposure ages (Allocation 9116/0412), the Carnegie Trust for the Universities of Scotland for a grant towards travel expenses.The St Kilda archipelago lies ~65 km west of the Outer Hebrides and ~60 km east of the Atlantic shelf break, and represents a key site for testing the assertion that during the Last Local Glacial Maximum (LLGM; c. 27 ka) the British–Irish Ice Sheet (BIIS) extended to near the shelf edge in all sectors. Two consistent cosmogenic 36Cl exposure ages averaging (≥) 81.6±7.8 ka for perched boulders at 290 m altitude demonstrate that the last ice sheet failed to over-run high ground on the largest island, Hirta. 36Cl and 10Be exposure ages for glacially emplaced boulders on low ground indicate deposition by small, locally nourished glaciers that last occupied a north-facing valley (Gleann Mòr) at c. 30.9±3.2 ka, prior to extension of the last ice sheet to the outer shelf, and a south-facing valley (Village Bay) at c. 19.2±2.3 ka, several millennia after the LLGM. Our dating evidence is consistent with previous interpretations of lithostratigraphical, seismostratigraphical and geomorphological evidence and confirms that the last ice sheet failed to encroach on St Kilda. A simple ice-flow model demonstrates that even if thin, low-gradient ice lobes encircled the archipelago during the LLGM, the ice margin can only have reached the outermost moraine banks, ~40 km west of St Kilda, under extremely low (<2 kPa) driving stresses, implying either surge-like transient streaming behaviour at the ice-sheet margin or that the moraine banks relate to an earlier, more extensive ice sheet. The final glaciation of the Village Bay area at c. 19.2±2.3 ka was out of phase with the behaviour of the BIIS, which was undergoing net retreat during this period.PostprintPeer reviewe

Energy consumption prediction models for the retail sector

The ability to analyse and accurately forecast future events is becoming increasingly important as most management decisions depend on them. This is especially evident for the retail sector, mainly because of the small margins that the sector is working within, alongside the increasing prices of electricity and gas. Tesco, as the market leader, wishes to be at the forefront of research and make a step change in their ability to forecast and reduce the energy consumption of their buildings. This work presents the various benchmarking methods available in the UK, Europe and the US, including CIBSE TM46, ISA, and ASHRAE benchmarks. The mathematical techniques employed to access the predictions obtained using these benchmarking and forecasting methods are discussed as well as the analysis and forecasting methods used by the industry. The research reported throughout this paper uses energy data obtained from the Tesco estate to draw correlations with weather, sales’ floor area, sales and other factors that might affect the energy consumption. Initial results regarding the effect these factors have on the energy consumption of buildings in the Tesco estate are presented

Kinetics and mechanism of microtubule length changes by dynamic instability.

Microtubules at steady state were found to undergo dramatic changes in length, with only very little change in number concentration and mean length. This result is accounted for by a mechanism in which microtubules are capped at ends by tubulin-GTP subunits; loss of the tubulin-GTP cap at one end results in disassembly of all the tubulin-GDP subunits, so that the medial edge of the distal tubulin-GTP cap is exposed; the exposed tubulin-GTP cap is sufficiently stable, so that microtubule regrowth from the cap rather than loss of the cap occurs. This mechanism predicts that a bell-shaped length distribution of sheared microtubules will be transiently bimodal, with peaks of short and moderate length microtubules, in rearranging to an exponential length distribution. We have observed the predicted transient bimodal length distribution experimentally and in a Monte Carlo simulation. Dynamic instability has recently been accounted for by assuming that microtubule ends are capped with only a single tubulin-GTP subunit at each end of the five helices that serve as elongation sites. Such a minimal tubulin-GTP cap is apparently ruled out by our observations, which require that the remnant tubulin-GTP cap generated from disassembly be able to serve as nucleating site; we do not expect that a stable nucleating site can be generated from five tubulin-GTP subunits, oriented as the five helices that serve as elongation sites

Fall Faculty Conference: The Future of the University

This was the first fall of President Robert Eckley\u27s time in office. The first part of the recording is an open Q&A session, followed by division-based reports. There are frequent references to a recent North Central reaccreditation visit in this meeting. In a memo distributed a day later President Eckley notes that the North Central visit and the recent changes in the general education requirements indicate the importance of a re-assessment of our departmental-divisional-university structural relationships. His proposal formed a structure with three colleges: Liberal Arts, Fine Arts and Applied Arts. Speakers include President Robert Eckley; Robert Harrington, Business & Economics; Justus Pearson, Humanities; Wayne Wantland, Natural Sciences; Emily Dale, Social Sciences; John Ficca, Art & Drama; Richard Hishman, Music; and Mary Shanks, Nursing