Exchange systems and style in the Central Mediterranean. 4500-1700 b.c..:Unpublished PhD. Cambridge University Library

Malone, C.A.T., 1986, Unpublished PhD, Cambridge University, Cambridge.

Interpreting A-level Mathematics grades – as easy as A, B, C?

Many concerns have been expressed that students’ basic mathematical skills have deteriorated during the 1990s and there has been disquiet that current A-level grading does not distinguish adequately between the more able students. This study reports the author’s experiences of teaching maths to large classes of first-year engineering students and aims to enhance understanding of levels of mathematical competence in more recent years. Over the last four years, the classes have consisted of a very large proportion of highly qualified students – about 91% of them had at least grade B in A-level Mathematics. With a small group of students having followed a non-traditional route to university (no A-level maths) and another group having benefitted through taking A-level Further Mathematics at school, the classes have contained a very wide range of mathematical backgrounds. Despite the introductory maths course at university involving mainly repetition of A-level material, students’ marks were spread over a very wide range – for example, A-level Mathematics grade B students have scored across the range 16 – 97%. Analytical integration is the topic which produced the largest variation in performance across the class but, in contrast, the A-level students generally performed well in differentiation. Initial analysis suggests some stability in recent years in the mathematical proficiency of students with a particular A-level Mathematics grade. Allowing choice of applied maths modules as part of the A-level maths qualification increases the variety of students’ mathematical backgrounds and their selection from mechanics, statistics or decision maths is not clear from the final qualification.

Synthesis of a neodymium-quinolate complex for near-infrared electroluminescence applications

A structurally pure, near-infrared emissive Nd-(5,7-dichloro-8-hydroxyquinoline)4 tetrakis complex has been synthesized. When incorporated as a dopant in the blue emissive, hole conducting polymer poly(N-vinylcarbazole), PVK, sensitized neodymium ion emission was observed following photo-excitation of the polymer host. OLED devices were fabricated by spin-casting layers of the doped polymer onto glass/indium tin oxide (ITO)/3,4-polyethylene-dioxythiophene-polystyrene sulfonate (PEDOT) substrates. An external quantum efficiency of 1 x 10(-3)% and a near-infrared irradiance of 2.0 nW/mm(2) at 25 mA/mm(2) and 20 V was achieved using glass/ITO/PEDOT/ PVK:Nd-(5,7-dichloro-8-hydroxyquinoline)(4)/Ca/Al devices. (C) 2007 Elsevier B.V. All rights reserved.

Near infrared electroluminescence from neodymium complex-doped polymer light emitting diodes

Organic light emitting diode devices employing organometallic Nd(9-hydroxyphenalen-1-one)(3) complexes as near infrared emissive dopants dispersed within poly(N-vinylcarbazole) (PVK) host matrices have been fabricated by spin-casting layers of the doped polymer onto glass/indium tin oxide (ITO)/3,4-polyethylene-dioxythiophene-polystyrene sulfonate (PEDOT) substrates. Room temperature electroluminescence, centered at similar to 1065 nm. was observed from devices top contacted by evaporated aluminum or calcium metal cathodes and was assigned to transitions between the F-4(3/2) -> I-4(11/2) levels of the Nd3+ ions. In particular, a near infrared irradiance of 8.5 nW/mm(2) and an external quantum efficiency of 0.007% was achieved using glass/ITO/PEDOT/PVK:Nd(9-hydroxyphenalen-1-one)(3)/Ca/Al devices. (c) 2005 Elsevier B.V. All rights reserved.

Rapid climate change did not cause population collapse at the end of the European Bronze Age

The impact of rapid climate change on contemporary human populations is of global concern. To contextualize our understanding of human responses to rapid climate change it is necessary to examine the archeological record during past climate transitions. One episode of abrupt climate change has been correlated with societal collapse at the end of the northwestern European Bronze Age. We apply new methods to interrogate archeological and paleoclimate data for this transition in Ireland at a higher level of precision than has previously been possible. We analyze archeological 14C dates to demonstrate dramatic population collapse and present high-precision proxy climate data, analyzed through Bayesian methods, to provide evidence for a rapid climatic transition at ca. 750 calibrated years B.C. Our results demonstrate that this climatic downturn did not initiate population collapse and highlight the nondeterministic nature of human responses to past climate change.

Chaotropicity: a key factor in product tolerance of biofuel-producing microorganisms

Fermentation products can chaotropically disorder macromolecular systems and induce oxidative stress, thus inhibiting biofuel production. Recently, the chaotropic activities of ethanol, butanol and vanillin have been quantified (5.93, 37.4, 174kJkg(-1)m(-1) respectively). Use of low temperatures and/or stabilizing (kosmotropic) substances, and other approaches, can reduce, neutralize or circumvent product-chaotropicity. However, there may be limits to the alcohol concentrations that cells can tolerate; e.g. for ethanol tolerance in the most robust Saccharomyces cerevisiae strains, these are close to both the solubility limit (<25%, w/v ethanol) and the water-activity limit of the most xerotolerant strains (0.880). Nevertheless, knowledge-based strategies to mitigate or neutralize chaotropicity could lead to major improvements in rates of product formation and yields, and also therefore in the economics of biofuel production.

Dilute acid hydrolysis of Lignocellulosic biomass

The overall aim of this work was to establish the optimum conditions for acid hydrolysis of hemicellulosic biomass in the form of potato peel. The hydrolysis reaction was undertaken in a 1l high pressure pilot batch reactor using dilute phosphoric acid. Analysis of the decomposition rate of hemicellulosic biomass (namely Cellulose, Hemicellulose and lignin) was undertaken using HPLC of the reaction products namely, 5 and 6 carbon sugars. Process parameters investigated included, reactor temperature (from 135 degrees C to 200 degrees C) and acid concentration (from 2.5% (w/w) to 10% (w/w)). Analysis of the reactor products indicated that high conversion of cellulose to glucose was apparent although arabinose conversion was quite low due to thermally un-stability. However, an overall sugar yield is 82.5% was achieved under optimum conditions. This optimum yield was obtained at 135 degrees C and 10% (w/w) acid concentration. 55.2 g sugar/100 g dry potato peel is produced after a time of 8 min. The work indicates that the use of potato peel may be a feasible option as a feed material for the production of sugars for biofuel synthesis, due its low cost and high sugar yields. (C) 2009 Elsevier B.V. All rights reserved.

Interaction of water, hydrogen and their mixtures with SnO2 based materials: the role of surface hydroxyl groups in detection mechanisms

DRIFTS, TGA and resistance measurements have been used to study the mechanism of water and hydrogen interaction accompanied by a resistance change (sensor signal) of blank and Pd doped SnO2. It was found that a highly hydroxylated surface of blank SnO2 reacts with gases through bridging hydroxyl groups, whereas the Pd doped materials interact with hydrogen and water through bridging oxygen. In the case of blank SnO2 the sensor signal maximum towards H-2 in dry air (R-0/R-g) is observed at similar to 345 degrees C, and towards water, at similar to 180 degrees C, which results in high selectivity to hydrogen in the presence of water vapors (minor humidity effect). In contrast, on doping with Pd the response to hydrogen in dry air and to water occurred in the same temperature region (ca. 140 degrees C) leading to low selectivity with a high effect of humidity. An increase in water concentration in the gas phase changes the hydrogen interaction mechanism of Pd doped materials, while that of blank SnO2 is unchanged. The interaction of hydrogen with the catalyst doped SnO2 occurs predominantly through hydroxyl groups when the volumetric concentration of water in the gas phase is higher than that of H-2 by a factor of 1000.

DECOMPOSITION PRODUCTS OF TRINUCLEAR RUTHENIUM COMPLEXES AS EFFECTIVE CATALYSTS OF WATER OXIDATION

Ruthenium red, a di-mu-oxo-bridged ruthenium complex, and its oxidised form, ruthenium brown, have been studied as possible homogeneous redox catalysts for the oxidation of water to O2 by Ce(IV) ions in H2SO4 and HCIO4. In both media the Ce(IV) ions oxidised the ruthenium red to brown and, with excess of Ce(IV), decomposed the ruthenium brown irreversibly to product(s) with three weak absorption bands at 390, 523 and 593 nm. Only in HCIO4 did the decomposition product(s) appear to act as a stable O2 catalyst. Spectral evidence tentatively suggests that the active catalyst may be a hydrolysed Ru(IV) polymeric species. The rate of catalysis was proportional to the initial concentration of ruthenium red/brown and the activation energy was determined as 36 +/- 1 kJ mol-1 over the temperature range ambient to ca. 50-degrees-C. At temperatures greater than 50-degrees-C the O2 catalyst undergoes an irreversible thermal decomposition reaction.

A 50,000-year record of Late Pleistocene tropical vegetation and human impact in lowland Borneo.

There has been considerable uncertainty about the nature of Pleistocene environments colonised by the first modern humans in Island SE Asia, and about the vegetation of the Last Glacial Maximum (LGM) in the region. Here, the palynology from a series of exposures in the Great Cave of Niah, Sarawak, Malaysian Borneo, spanning a period from ca. 52,000 to 5000 BP is described. Vegetation during this period was climate-driven and often highly unstable. Interstadials are marked by lowland forest, sometimes rather dry and at times by mangroves. Stadials are indicated by taxa characteristic of open environments or, as at the LGM, by highly disturbed rather open forest. Stadials are also characterised by taxa now restricted to 1000-1600 m above sea level, suggesting temperature declines of ca 7-9 C relative to present, by comparison with modern lapse rates. The practice of biomass burning appears associated with the earliest human activity in the cave.