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In recent years the plethora of ‘weird wonders,’ the vernacular for the apparently extinct major body plans documented in many of the Cambrian Lagerstätten, has been dramatically trimmed. This is because various taxa have been either assigned to known phyla or accommodated in larger monophyletic assemblages. Nevertheless, a number of Cambrian taxa retain their enigmatic status. To this intriguing roster we add Dakorhachis thambus n. gen. n. sp. from the Miaolingian (Guzhangian) Weeks Formation Konservat-Lagerstätte of Utah. Specimens consist of an elongate body that lacks appendages but is apparently segmented. A prominent feeding apparatus consists of a circlet of triangular teeth, while posteriorly there are three distinct skeletal components. D. thambus is interpreted as an ambush predator and may have been partially infaunal. The wider affinities of this new taxon remain conjectural, but it is suggested that it may represent a stem-group member of the Gnathifera, today represented by the gnathostomulids, micrognathozoans, and rotifers and possibly with links to the chaetognaths.
Southern range extensions of the tropical Australian heterobranch sea slug fauna may be symptomatic of climate change, particularly in south-eastern Australia, a recognized climate change hot-spot. In the Solitary Islands Marine Park, northern New South Wales, the presence of biogeographic mixing means that the southern coastal distribution limit of several tropical marine species and the northern limit of some temperate species overlap. During a year-long series of monthly surveys of sea slug communities on intertidal rocky shores, we observed four species beyond their previously recorded range – Colpodaspis thompsoni, Elysia pusilla, Phidiana bourailli and Herviella claror. The southern migration of species is an anticipated response to warming seas and we note an apparent extension of the southern limit for these taxa.
Patterns in radar-detected internal layers in glaciers and ice streams can be tracked hundreds of kilometers downstream. We use distinctive patterns to delineate flowbands of Thwaites Glacier in the Amundsen Sea sector of West Antarctica. Flowbands contain information for the past century to millennium, the approximate time for ice to flow through the study region. GPS-detected flow directions (acquired in 2007/08) agree within uncertainty (~4°) with the radar-detected flowlines, indicating that the flow direction has not changed significantly in recent centuries. In contrast, InSAR-detected directions (from 1996) differ from the radar- and GPS-detected flowlines in all but the middle tributary, indicating caution is needed when using InSAR velocities to define flow directions. There is agreement between all three datasets in the middle tributary. We use two radar-detected flowlines to define a 95 km long flowband and perform a flux balance analysis using InSAR-derived velocities, radar-detected ice thickness, and estimates of the accumulation rate. Inferred thinning of 0.49 ± 0.34 m a–1 is consistent with satellite altimetry measurements, but has higher uncertainty due mainly to the velocity uncertainty. The uncertainty is underestimated because InSAR velocities often differ from GPS velocities by more than the stated uncertainties.
It has long been recognised that the Neolithic spread across Europe via two separate routes, one along the Mediterranean coasts, the other following the axis of the major rivers. But did these two streams have a common point of origin in south-west Asia, at least with regard to the principal plant and animals species that were involved? This study of barley DNA shows that the domesticated barley grown in Neolithic Europe falls into three separate types (groups A, B and C), each of which may have had a separate centre of origin in south-west Asia. Barley was relatively rarely cultivated by the early Linearbandkeramik farmers of Central and Northern Europe, but became more common during the fifth and fourth millennia BC. The analysis reported here indicates that a genetic variety of barley more suitable for northern growing conditions was introduced from south-west Asia at this period. It also suggests that the barley grown in south-eastern Europe at the very beginning of the Neolithic may have arrived there by different routes from two separate centres of domestication in south-west Asia. The multiple domestications that this pattern reveals imply that domestication may have been more a co-evolutionary process between plants and people than an intentional human action.
We have determined the influence of the severity of retinopathy of prematurity (ROP) on development at 3 years of age in infants <29 weeks gestation from a population-based cohort. Primary analysis of surviving infants born <29 weeks gestational age (GA) from 1998 to 2001 in New South Wales and the Australian Capital Territory were grouped according to stage of ROP. Infants with periventricular leukomalacia, Grade III or IV intraventricular haemorrhage, hydrocephalus, major congenital abnormalities, Stage 4 or 5 ROP, cerebral palsy or a severe hearing impairment were excluded. Infants with Stage 3 ROP were matched for GA, birthweight and gender to those with no ROP, Stage 1 and Stage 2 ROP. The four groups were then compared for their 3-year-old developmental outcome, using the Griffiths Mental Development Scale. Development was also compared for those infants with Stage 3 ROP who were either treated or not treated with laser therapy. A secondary multivariate regression analysis on developmental outcome was performed with all infants included in the analysis. In neurologically comparable groups and in the multivariate analysis, there was no association between ROP and developmental outcome. There was also no difference in the Griffiths assessment at 3 years between those who were or were not treated for severe ROP. Neither severity of ROP nor treatment for severe ROP were related to developmental outcome at 3 years of age in a large population-based cohort of infants born <29 weeks gestation.
Garnets, A3B2C3O12, are considered to be potential host phases for the immobilization of high-level nuclear waste as they can accommodate a number of elements of interest, including Zr, Ti and Fe. The naturally occurring garnet, kimzeyite, Ca3(Zr,Ti)2(Si,Al,Fe)3O12, can contain ˜30wt% Zr. An understanding of the radiation tolerance of these materials is crucial to their potential use in nuclear waste immobilization. In this study two synthetic analogues of kimzeyite of composition Ca3Zr2FeAlSiO12 and Ca3Hf2FeAlSiO12 were monitored in situ during irradiation with 1.0 MeV Kr ions using the intermediate voltage electron microscope-Tandem User Facility (IVEM) at Argonne National Laboratory. The structure of these materials was previously determined by neutron diffraction and 57Fe Mössbauer spectroscopy. Ca3Zr2FeAlSiO12 and Ca3Hf2FeAlSiO12 have very similar structural properties with cubic Ia3d symmetry, the only significant difference being the presence of Zr and Hf, respectively, on the 6 coordinated B sites.
Thin crystals of rutile, brookite, and anatase were irradiated in-situ with 1.0 MeV Kr using the IVEM-TANDEM facility. Synthetic rutile and cassisterite (SnO2, rutile structure) remained crystalline up to 5 × 1015 ion cm-2 at 50 K. Natural brookite and anatase with low impurity levels became amorphous at 8.1 ± 1.8 × 1014 and 2.3 ± 0.2 × 1014 ions cm-2, respectively, at 50 K. Irradiation at higher temperature revealed Tc = 170 K for brookite and 242 K for anatase. Natural rutile with about 2 wt% impurities became amorphous at 9.4 ± 1.8 × 1014 ions cm-2 at 50 K and has a Tc = 207 K. The available data reveal both a structural effect in the polymorphs with low levels of chemical impurities and a chemical effect in natural rutile specimens containing up to about 1.7 wt% impurities.
The gerbil Meriones unguiculatus, infected with three species of nematodes, each located in a separate part of the gastrointestinal tract, provided a reliable laboratory assay for the evaluation of broad-spectrum anthelmintic activity. Gerbils harbouring 6-day-old infections of Haemonchus contortus, Trichostrongylus colubriformis and T. sigmodontis were given selected broad-spectrum anthelmintics by gavage. Three benzimidazoles, thiabendazole, oxfendazole and albendazole, a tetrahydropyrimidine, morantel, an imidazothiazole, levamisole hydrochloride, a macrocyclic lactone, ivermectin and an experimental natural product, paraherquamide, were active against all three nematodes at various dosages. Trichostrongylus colubriformis was most sensitive to levamisole hydrochloride, morantel, thiabendazole and paraherquamide whereas ivermectin, oxfendazole and albendazole were more effective against H. contortus. All compounds were active against the caecal nematode T. sigmodontis although it was less sensitive than T. colubriformis. Haemonchus contortus was more sensitive than T. sigmodontis to all anthelmintics tested except thiabendazole.
The introduction of invasive species may be the most profound modern threat to biological communities in high-latitude regions. In the Southern Ocean, the natural transport mechanism for shallow-water marine organisms provided by kelp rafts is being increasingly augmented by plastic debris and shipping activity. Plastic debris provide additional opportunities for dispersal of invasive organisms, but dispersal routes are passive, dependent on ocean currents, and already established. In contrast, ships create novel pathways, moving across currents and often visiting many locations over short periods of time. Transportation of hull-fouling communities by vessel traffic thus poses the most likely mechanism by which exotic species may be introduced to the Southern Ocean.
Electron-optical aberration correction has recently progressed from a promising concept to a powerful research tool. 100–120 kV scanning transmission electron microscopes (STEMs) equipped with spherical aberration (Cs) correctors now achieve sub-Å resolution in high-angle annular dark field (HAADF) imaging, and a 300 kV Cs-corrected STEM has reached 0.6 Å HAADF resolution. Moreover, the current available in an atom-sized probe has grown by about 10x, allowing electron energy loss spectroscopy (EELS) to detect single atoms. We summarize the factors that have made this possible, and outline likely future progress.
This article reports on the latest experiments in the series of
Richtmyer–Meshkov instability (RMI) shock-tube experiments.
Previous work described a double-bump experiment that evidenced some
degree of unrepeatability. The present work features an enlarged
perturbation introduced to improve repeatability. In common with the
previous work, the experiments were conducted at shock Mach number 1.26
(70 kPa overpressure), using the Atomic Weapons Establishment 200
× 100 mm shock tube with a three-zone test cell arrangement of
air/sulphur hexafluoride/air. The sulphur hexafluoride gas
(SF6) was chosen for its high density (5.1 relative to air)
providing an Atwood number of 0.67. Gas separation was by means of
microfilm membranes, supported by fine wire meshes. A double-bump
perturbation of two-dimensional geometry was superimposed on the
downstream membrane representing a 0.6% addition to the dense gas
volume. Visualization of the turbulent gas mixing was by laser sheet
illumination of the seeded SF6 gas using a copper vapor
laser pulsing at 12.5 kHz. Mie scattered light was recorded using a
35-mm rotating drum camera to capture a sequence of 50 images per
experiment. Sample experimental results shown alongside corresponding
three-dimensional hydrocode calculations highlight the problems in both
analysis and comparison caused by multiple scattering arising from the
necessary use of a high seeding concentration. Included is a
demonstration of the effectiveness of introducing into the hydrocode a
Monte Carlo-based simulation of the multiple scattering process. The
results so derived yield greatly improved qualitative agreement with
the experimental images. Quantitative analysis took the form of
deriving relative intensity data from line-outs through experimental
images and their code equivalents. A comparison revealed substantial
agreement on major features.
This article reports the first Richtmyer–Meshkov instability
experiments using an improved version of the Atomic Weapons
Establishment convergent shock tube. These investigate the
shock-induced turbulent mixing across the interfaces of an
air/dense gas/air region. Multipoint ignition of a detonatable
gas mixture produces a cylindrically convergent shock that travels into
a test cell containing the dense gas region. The mixing process is
imaged with shadowgraphy. Sample results are presented from an
unperturbed experiment and one with a notch perturbation imposed on one
of the dense gas interfaces. The unperturbed experiment shows the
mixing across the dense gas boundaries and the motion of the bulk dense
gas region. Imposition of the notch perturbation produces a
mushroom-shaped air void penetrating the dense gas region.
Three-dimensional simulations performed using the AWE TURMOIL3D code
are presented and compared with the sample experimental results. A very
good agreement is demonstrated. Conducting these first turbulent mixing
experiments has highlighted a number of areas for future development of
the convergent shock-tube facility; these are also presented.
T helper cell (Th1 and Th2) associated responses were examined following a primary infection with the gastrointestinal nematode Heligmosomoides polygyrus in five inbred strains of mice with different resistance phenotypes. Levels of (i) mast cell protease, (ii) specific IgE, (iii) nitric oxide and (iv) specific IgG2a, as markers of Th2 and Th1 associated responses, respectively, were determined in sera and intestinal fluids and correlated with worm burdens. The ‘fast’ responder (resistant) strains SWR and SJL produced strong Th2 and Th1 associated responses respectively in a mutually exclusive fashion. The F1 hybrid (SWR×SJL) F1, showed rapid expulsion of the parasite and expressed both intense Th1 and Th2 responses, suggesting synergism between Th1 and Th2 activity in these mice. The results indicate that both Th2 and Th1 responses operate in mice following a primary infection with H. polygyrus and that each Th response may be involved to a greater or lesser degree within certain strains. Resistance to H. polygyrus was found to correlate only to the intensity of either the gut-associated mastocytosis or nitric oxide production in these strains but not to either specific IgE or IgG2a titres. Chronic infections in the ‘slow’ response phenotype mouse strains CBA and C57BL/10, were associated with both poor Th2 and poor Th1-associated responses attributed to a general parasite-mediated immunosuppression of the host immune response to infection.
The shore environments of most sub-Antarctic islands have been described in a number of
previous studies. However, there have been few attempts to quantify the variation in population and
community patterns over different spatial scales. The objectives of this study were to provide an analysis of
differences in the community structure of the biota of three exposed shore zones and of the macrofauna
inhabiting holdfasts of the kelp Durvillaea antarctica across spatial scales of hundreds of metres, kilometres,
and between a sheltered and exposed coast. Data were collected using a combination of quadrat, transect and
direct sampling methods over the 1994–95 summer season. The results indicated that there were significant
differences between coasts for some of the biotic variables in most of the habitats examined but that
differences at the smaller spatial scales were more often significant. Thus, although wave exposure exerts an
obvious effect on the shore biota of Macquarie Island, these effects are modified by other factors operating at
smaller spatial scales. For the holdfast macrofauna, the overall patterns of community structure are likely to
be due to the differential response of the component taxa to variation in holdfast volume and holdfast
sediment content as well as other, currently undetermined factors.
A project to develop an Accounting Standard for Insurance, with the aim of enhancing understandability, relevance, reliability and comparability of general purpose financial reporting for insurance worldwide, is being progressed by the International Accounting Standards Board. The basis of the proposals is that assets and liabilities be shown at fair values (market values for quoted instruments). This paper, prepared by a Working Party established by the Life Board of the United Kingdom actuarial profession, summarises and comments upon a number of the principal features of the proposals, as they have emerged up to September 2001. The paper goes on to consider how a system of reporting for prudential regulatory purposes might be built upon a fair value general reporting base, summarising the thinking of a number of other bodies, proposing certain principles and suggesting lines of development. The appendices to the paper discuss a number of issues in further depth and present some illustrative results of some investigations into applying fair value methods in practice. The emphasis of the paper is on reporting for life assurance business, although many of the principles apply equally to general insurance.
The family Chrysopidae contains some 90 genera or subgenera and almost 2000 species (New, 1984) of predaceous insects, including some commercially available species that are widely used in augmentative biological control. These predators feed on a variety of slowmoving, soft-bodied arthropods (Hydorn, 1971; Hydorn & Whitcomb, 1979). Hunter (1997) lists 65, 20, and 54 North American suppliers of Chrysoperla carnea (Stephens), C. comanche (Banks), and C. rufilabris (Burmeister), respectively. Also, C. carnea is used in Europe and C. sinica (Tjeder) is used in China (Wang & Nordlund, 1994). Large numbers of chrysopids are required for augmentative biological control programmes. Thus cost-effective mass-rearing systems for lacewings are necessary for their successful use. An effective artificial diet and/or innovations that will facilitate rearing process automation are the first steps to development of an effective mass-rearing system. Current methods for commercial rearing of lacewings use, primarily, Sitotroga or Ephestia eggs for larval diet. An artificial diet (Cohen & Smith, 1998) for larvae, which we expect will replace the expensive insect eggs, has been developed. The rearing process, though, still consists of labour-intensive operations. Automation of one or more of these processes could considerably decrease the cost of rearing large numbers (i.e. millions to trillions) of lacewings. Effective release systems must also be available to fulfil the objective of augmentative biological control programs. Success in periodic release programs requires that agents of sufficient quality be available in sufficient numbers at a reasonable cost.
Mass-rearing techniques for Chrysoperla spp. were reviewed recently by Nordlund & Morrison (1992).
The latest deep ultra-violet (DUV) photomask technology requires macroscopic properties such as optical transmission, reflectance, and chemical reactivity to be precisely controlled. Therefore, a fundamental understanding of the relationship between atomic bonding and nanometer scale property variation is required. Thin films of Cr-OC-N are compositionally graded to produce specific attenuation and phase shift of optical radiation. A combination of techniques was used to relate the local atomic bonding to macroscopic properties. Sputtered neutral mass spectroscopy was used to resolve local composition, and variable angle spectroscopic ellipsometry was used to determine local optical properties (on nm scale) that are then related to local composition. Core level shifts in X-ray photoelectron spectroscopy characterize changes in the Cr environment associated with changes in composition. A model is suggested in which bonding at the atomic level is controlled within different 10-100 nm sized regions which can be combined to produce arbitrary optical properties.
Excavations at two sites in Gwynedd have produced new evidence for highland zone rural settlement during the Romano-British period. At Bryn Eryr this activity was the culmination of a long sequence of development during the Iron Age. At Bush Farm, similarly, a Romano-British phase succeeded earlier, probably late prehistoric occupation of the site. At both locations significant structural changes took place during the Romano-British period as small stone-walled houses replaced larger, clay-walled buildings. Changes in the local farming economy have been identified and the proximity of the vicus at Segontium provided access to Roman pottery vessels. The quality and range of pottery from Bryn Eryr and Bush Farm are considerable in comparison with other ‘Highland Zone’ settlements and the material is discussed in detail.