One size fits all: How many default funds does a pension scheme need?

In this paper, we analyse the number of default investment funds appropriate for an occupational defined contribution pension scheme. Using a unique dataset of member risk attitudes and characteristics from a survey of a large UK pension scheme, we apply cluster analysis to identify two distinct groups of members in their 40s and 50s. Further analysis indicated that the risk attitudes of the two groups were not significantly different, allowing us to conclude that a single lifestyle default fund is appropriate

Grouping Individual Investment Preferences in Retirement Savings: A Cluster Analysis of a USS Members Risk Attitude Survey

Cluster analysis is used to identify homogeneous groups of members of USS in terms of risk attitudes. There are two distinct clusters of members in their 40s and 50s. One had previously ‘engaged’ with USS by making additional voluntary contributions. It typically had higher pay, longer tenure, less interest in ethical investing, lower risk capacity, a higher percentage of males, and a higher percentage of academics than members of the ‘disengaged’ cluster. Conditioning only on the attitude to risk responses, there are 18 clusters, with similar but not identical membership, depending on which clustering method is used. The differences in risk aversion across the 18 clusters could be explained largely by differences in the percentage of females and the percentage of couples. Risk aversion increases as the percentage of females in the cluster increases, while it reduces as the percentage of couples increases because of greater risk sharing within the household. Characteristics that other studies have found important determinants of risk attitudes, such as age, income and (pension) wealth, do not turn out to be as significant for USS members. Further, despite being on average more highly educated than the general population, USS members are marginally more risk averse than the general population, controlling for salary, although the difference is not significant

A Latest Carboniferous Warming Spike Recorded by a Fusulinid-Rich Bioherm in Timor Leste: Implications for East Gondwana Deglaciation

During the late Paleozoic and early Mesozoic Timor lay in the northern part of the north–south East Gondwana rift system along which the western margin of Australia later developed. Discovery of a latest Gzhelian bioherm in the central highlands of Timor Leste has implications for latest Carboniferous–earliest Permian climate history and deglaciation in basins further south in the rift system. Limestone outcrop of the Maubisse Formation near the village of Kulau is recognized as a bioherm with a massive lower unit, including reef framework at the base, and a bedded grainstone upper unit. The bioherm developed on a basalt substrate in warm shallow-water, as indicated by photozoan assemblages in the massive lower unit. Foraminifera belonging to 17 genera are recorded from the bioherm. These include representatives of the families Biseriamminidae, Biwaellidae, Bradyinidae, Cornuspiridae, Lasiodiscidae, Palaeotextulariidae, Pseudotaxidae, Ozawainellidae, Schubertellidae, Schwagerinidae, Staffellidae and Textrataxidae. Twenty-one species have been referred to known types and 12 species are left in open nomenclature. The assemblage probably belongs within the uppermost Gzhelian Schwagerina robusta–Ultradaixina bosbytauensis Zone although a possible lowest Asselian correlation cannot be excluded. The bioherm is the oldest carbonate unit so far recorded from the Maubisse Formation, and the oldest sedimentary unit biostratigraphically dated in Timor. The dominantly heterozoan composition of the skeletal component of the limestone (except for the basal photozoan assemblage) and the taxonomic diversity of the larger foraminifera suggest a subtropical environment consistent with a paleolatitude of about 40° S. The late Pennsylvanian was a time of glaciation that in Australia is represented by a significant stratigraphic hiatus in basins to the south of Timor in the East Gondwana rift system. The development of the Kulau bioherm during the latest Gzhelian may have coincided with a global warming spike that led to rapid melting of continental ice sheets and a substantial influx of glacigene sediment (alternating diamictite and mudstone) in the southern basins

Asymmetric masks for large field-of-view and high-energy X-ray phase contrast imaging

We report on a large field of view, laboratory-based X-ray phase-contrast imaging setup. The method is based upon the asymmetric mask design that enables the retrieval of the absorption, refraction and scattering properties of the sample without the need to move any component of the imaging system. This can be thought of as a periodic repetition of a group of three (or more) apertures arranged in such a way that each laminar beam, defined by the apertures, produces a different illumination level when analysed with a standard periodic set of apertures. The sample is scanned through the imaging system, also removing possible aliasing problems that might arise from partial sample illumination when using the edge illumination technique. This approach preserves the incoherence and achromatic properties of edge illumination, removes the problems related to aliasing and it naturally adapts to those situations in clinical, industrial and security imaging where the image is acquired by scanning the sample relative to the imaging system. These concepts were implemented for a large field-of-view set of masks (20 cm × 1.5 cm and 15 cm × 1.2 cm), designed to work with a tungsten anode X-ray source operated up to 80–100 kVp, from which preliminary experimental results are presented

The first large-area, high-X-ray energy phase contrast prototype for enhanced detection of threat objects in baggage screening

X-ray imaging is the most commonly used method in baggage screening. Conventional x-ray attenuation (usually in dual-energy mode) is exploited to discriminate threat and non-threat materials: this is essentially, a method that has seen little changes in decades. Our goal is to demonstrate that x-rays can be used in a different way to achieve improved detection of weapons and explosives. Our approach involves the use of x-ray phase contrast and it a) allows much higher sensitivity in the detection of object edges and b) can be made sensitive to the sample’s microstructure. We believe that these additional channels of information, alongside conventional attenuation which would still be available, have the potential to significantly increase both sensitivity and specificity in baggage scanning. We obtained preliminary data demonstrating the above enhanced detection, and we built a scanner (currently in commissioning) to scale the concept up and test it on real baggage. In particular, while previous X-ray phase contrast imaging systems were limited in terms of both field of view (FOV) and maximum x-ray energy, this scanner overcomes both those limitations and provides FOVs up to 20 to 50 cm2 with x-ray energies up to 100 keV

Large field-of-view asymmetric masks for high-energy x-ray phase imaging with standard x-ray tube

We report on a new approach to large field-of-view laboratory-based X-ray phase-contrast imaging. The method is based upon the asymmetric mask design that enables the retrieval of the absorption, refraction and ultra-small- angle scattering properties of the sample without the need to move any component of the imaging system. The sample is scanned through the imaging system, which also removes possible aliasing problems that might arise from partial sample illumination when using the edge illumination technique. This concept can be extended to any desired number of apertures providing, at the same time, intensity projections at complementary illumination conditions. Experimental data simultaneously acquired at seven different illumination fractions are presented along with the results obtained from a numerical model that incorporates the actual detector performance. The ultimate shape of the illumination function is shown to be significantly dependent on these detector-specific characteristics. Based on this concept, a large field-of-view system was designed, which is also capable to cope with relatively high (100 kVp) X-ray energies. The imaging system obtained in this way, where the asymmetric mask design enables the data to be collected without moving any element of the instrumentation, adapts particularly well to those situations in medical, industrial and security imaging where the sample has to be scanned through the syste

Increased material differentiation through multi-contrast x-ray imaging: a preliminary evaluation of potential applications to the detection of threat materials

Most material discrimination in security inspections is based on dual-energy x-ray imaging, which enables the determination of a material's effective atomic number (Zeff) as well as electron density and its consequent classification as organic or inorganic. Recently phase-based "dark-field" x-ray imaging approaches have emerged that are sensitive to complementary features of a material, namely its unresolved microstructure. It can therefore be speculated that their inclusion in the security-based imaging could enhance material discrimination, for example of materials with similar electron densities and Z eff but different microstructures. In this paper, we present a preliminary evaluation of the advantages that such a combination could bear. Utilising an energy-resolved detector for a phase-based dark-field technique provides dual-energy attenuation and dark-field images simultaneously. In addition, since we use a method based on attenuating x-ray masks to generate the dark-field images, a fifth (attenuation) image at a much higher photon energy is obtained by exploiting the x-rays transmitted through the highly absorbing mask septa. In a first test, a threat material is imaged against a non-threat one, and we show how their discrimination based on maximising their relative contrast through linear combinations of two and five imaging channels leads to an improvement in the latter case. We then present a second example to show how the method can be extended to discrimination against more than one non-threat material, obtaining similar results. Albeit admittedly preliminary, these results indicate that significant margins of improvement in material discrimination are available by including additional x-ray contrasts in the scanning process

Bolocam Survey for 1.1 mm Dust Continuum Emission in the c2d Legacy Clouds. II. Ophiuchus

We present a large-scale millimeter continuum map of the Ophiuchus molecular cloud. Nearly 11 square degrees, including all of the area in the cloud with visual extinction more than 3 magnitudes, was mapped at 1.1 mm with Bolocam on the Caltech Submillimeter Observatory (CSO). By design, the map also covers the region mapped in the infrared with the Spitzer Space Telescope. We detect 44 definite sources, and a few likely sources are also seen along a filament in the eastern streamer. The map indicates that dense cores in Ophiuchus are very clustered and often found in filaments within the cloud. Most sources are round, as measured at the half power point, but elongated when measured at lower contour levels, suggesting spherical sources lying within filaments. The masses, for an assumed dust temperature of 10 K, range from 0.24 to 3.9 solar masses, with a mean value of 0.96 solar masses. The total mass in distinct cores is 42 solar masses, 0.5 to 2% of the total cloud mass, and the total mass above 4 sigma is about 80 solar masses. The mean densities in the cores are quite high, with an average of 1.6 x 10^6 per cc, suggesting short free-fall times. The core mass distribution can be fitted with a power law with slope of 2.1 plus or minus 0.3 for M>0.5 solar masses, similar to that found in other regions, but slightly shallower than that of some determinations of the local IMF. In agreement with previous studies, our survey shows that dense cores account for a very small fraction of the cloud volume and total mass. They are nearly all confined to regions with visual extinction at least 9 mag, a lower threshold than found previously.Comment: 47 pages, 16 figures, accepted for Ap

Savanna in equatorial Borneo during the late Pleistocene

Equatorial Southeast Asia is a key region for global climate change. Here, the Indo-Pacific Warm Pool (IPWP) is a critical driver of atmospheric convection that plays a dominant role in global atmospheric circulation. However, fluctuating sea-levels during the Pleistocene produced the most drastic land-sea area changes on Earth, with the now-drowned continent of Sundaland being exposed as a contiguous landmass for most of the past 2 million years. How vegetation responded to changes in rainfall that resulted from changing shelf exposure and glacial boundary conditions in Sundaland remains poorly understood. Here we use the stable carbon isotope composition (δ13C) of bat guano and High Molecular Weight n-alkanes, from Saleh Cave in southern Borneo to demonstrate that open vegetation existed during much the past 40,000 yrs BP. This location is at the southern equatorial end of a hypothesized ‘savanna corridor’ and the results provide the strongest evidence yet for its existence. The corridor would have operated as a barrier to east-west dispersal of rainforest species, and a conduit for north-south dispersal of savanna species at times of lowered sea level, explaining many modern biogeographic patterns. The Saleh Cave record also exhibits a strong correspondence with insolation and sea surface temperatures of the IPWP, suggesting a strong sensitivity of vegetation to tropical climate change on glacial/interglacial timeframes