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Eugenia stipitata occurs along rivers in Western Amazonia and produces berry-type fruits with economic potential. Its large recalcitrant (i.e. desiccation-intolerant) seeds have been proposed as a model to study seed stress response, as no apparent differentiation between the embryonic axis and the fused cotyledons are visible. Here, the longevity of submerged seeds was analysed with a view to understanding adaptive mechanisms to seasonal flooding. Submerged seeds began germinating after 2 months. After 1 year, 87 and 96% total germination was reached when seeds were submerged under a water column of 6 cm (where seedlings could emerge from under the water) and 26 cm (where seedlings could not reach the water surface), respectively. Seedling morphology was altered underwater, with short internodes and rudimentary leaf blades, and when submersion was terminated, seedlings transplanted to nursery conditions recovered a normal phenotype. Furthermore, when seedlings were detached from the seeds, the ‘resown’ seeds produced a second, normal seedling within 9 months. Concentrations of the antioxidant glutathione, which was measured as a stress marker, increased with submersion time in water. Seeds that had developed roots and shoots underwater had higher concentrations of glutathione disulphide than non-germinated seeds, suggesting that the flooding stress was more intense for seedlings than seeds, although more oxidizing cellular redox environments are also consistent with the conditions required for differentiation. Submergence underwater is recommended for storage of the recalcitrant seeds of E. stipitata for up to 1 year.
Hughes etal. (1993) have made submillimetre continuum observations of 10 IRAS selected radio-quiet quasars (RQQs). Three RQQs, I Zw 1, Mrk1014 and Mrk376, have been detected at 800 and 450μm using the 3He bolometer UKT14 on t he 15-m James Clerk Maxwell telescope. These submillimetre data, together with existing 1.3 mm observations (Chini etal. 1989) demonstrate that the measured submillimetre spectral indices, 〈αsm〉 = 3.8 ± 0.5, significantly exceed the critical theoretical limit of αsm = 2.5 predicted for the self-absorption of synchrotron emission. This result is independent of any contributions to the 100μm IRAS fluxes from cirrus emission in the host galaxies, extended circumnucl ear starformation and FIR emission from companion or confusing sources. All current non-thermal models (de Kool & Begelman 1989, Schlickeiser etal. 1991) are rejected in favour of the alternative explanation that the FIR luminosity is dominated by thermal emission from warm (45–60 K) dust grains. The submillimetre optical depth and source-size for the thermal emission cannot yet be constrained by these data and, as a result, no discrimination can be made between dust heated by an extended (> 1 kpc) starburst region or a central compact luminosity source. However ground-based imaging observations at mid-IR wavelengths and FIR photometry (60–200μm) with the KAO are currently in progress specifically to address this problem. The high gas masses (> 1010M⊙) in RQQs inferred from the submillimetre continuum observations are in agreement with the H2 masses determined from CO measurements. Alternatively the results show that the MH2/Mdust ratio measured in RQQs (∼ 370 ± 150) is consistent with that measured in spiral galaxies and ultra-luminous IRAS galaxies.
We have assembled a new sample of some of the most FIR-luminous galaxies in the Universe and have imaged them in 1.1 mm dust emission and measured their redshifts 1 < z < 4 via CO emission lines using the 32-m Large Millimeter Telescope / Gran Telescopio Milimétrico (LMT/GTM). Our sample of 31 submm galaxies (SMGs), culled from the Planck and Herschel all-sky surveys, includes 14 of the 21 most luminous galaxies known, with LFIR > 1014L⊙ and SFR > 104M⊙/yr. These extreme inferred luminosities – and multiple / extended 1.1 mm images – imply that most or all are strongly gravitationally lensed, with typical magnification μ ~ 10 × . The gravitational lensing provides two significant benefits: (1) it boosts the S/N, and (2) it allows investigation of star formation and gas processes on sub-kpc scales.
Growth increments in bivalve shells have been used in geophysics and paleoecology. However, little study has been given to the variability of increment patterns within and between shells. The variability of increment patterns is examined visually and quantitatively, with the help of a serial correlation computer program. Analyses of increment patterns of the bivalves Chione fluctifraga and Protothaca staminea (Veneridae) indicate that: 1) quantitative results complement the visual observations; 2) increments are not consistently detected during successive measurements; 3) a striking similarity exists between right and left valves of the same specimen; and 4) different specimens collected from the same natural environment do not show any one-to-one increment relationship—however, increment width trends may be present. The variation of increment patterns seen between specimens suggests caution in the use of bivalve increments in paleoecology.
Within the framework of shallow-water magnetohydrodynamics, we investigate the linear instability of horizontal shear flows, influenced by an aligned magnetic field and stratification. Various classical instability results, such as Høiland’s growth-rate bound and Howard’s semi-circle theorem, are extended to this shallow-water system for quite general flow and field profiles. In the limit of long-wavelength disturbances, a generalisation of the asymptotic analysis of Drazin & Howard (J. Fluid Mech., vol. 14, 1962, pp. 257–283) is performed, establishing that flows can be distinguished as either shear layers or jets. These possess contrasting instabilities, which are shown to be analogous to those of certain piecewise-constant velocity profiles (the vortex sheet and the rectangular jet). In both cases it is found that the magnetic field and stratification (as measured by the Froude number) are generally each stabilising, but weak instabilities can be found at arbitrarily large Froude number. With this distinction between shear layers and jets in mind, the results are extended numerically to finite wavenumber for two particular flows: the hyperbolic-tangent shear layer and the Bickley jet. For the shear layer, the instability mechanism is interpreted in terms of counter-propagating Rossby waves, thereby allowing an explication of the stabilising effects of the magnetic field and stratification. For the jet, the competition between even and odd modes is discussed, together with the existence at large Froude number of multiple modes of instability.
We describe a hybrid pixel array detector (electron microscope pixel array detector, or EMPAD) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128×128 pixel detector consists of a 500 µm thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit. The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity. A 1.1 kHz framing rate enables rapid data collection and minimizes sample drift distortions while scanning. By capturing the entire unsaturated diffraction pattern in scanning mode, one can simultaneously capture bright field, dark field, and phase contrast information, as well as being able to analyze the full scattering distribution, allowing true center of mass imaging. The scattering is recorded on an absolute scale, so that information such as local sample thickness can be directly determined. This paper describes the detector architecture, data acquisition system, and preliminary results from experiments with 80–200 keV electron beams.
At the present time the orbit of the Quadrantid meteor stream not only intersects the orbit of Earth but also passes very close to the orbit of the planet Jupiter. This causes considerable perturbations. In a series of three papers (1,2,3) the authors replaced the myriad of meteoroids in the stream by ten test particles set at equal intervals of eccentric anomaly around the orbit. The equations of motion of these particles in the solar system were solved using a standard fourth order Runge–Kutta technique with self–adjusting step lengths. The orbits of the test particles were output at ten year intervals going back from the present to the year 300 B.C. and forward into the future to the year A.D. 3780.
We have conducted 1.1 mm ALMA observations of a contiguous 105” × 50” or 1.5 arcmin2 window in the SXDF-UDS-CANDELS. We achieved a 5σ sensitivity of 0.28 mJy, giving a flat sensus of dusty star-forming galaxies with LIR ~6×1011L⊙ (if Tdust=40K) up to z ~ 10 thanks to the negative K-correction at this wavelength. We detected 5 brightest sources (S/N>6) and 18 low-significant sources (5>S/N>4; they may contain spurious detections, though). One of the 5 brightest ALMA sources (S1.1mm = 0.84 ± 0.09 mJy) is extremely faint in the WFC3 and VLT/HAWK-I images, demonstrating that a contiguous ALMA imaging survey uncovers a faint dust-obscured population invisible in the deep optical/near-infrared surveys. We find a possible [CII]-line emitter at z=5.955 or a low-z CO emitting galaxy within the field, allowing us to constrain the [CII] and/or CO luminosity functions across the history of the universe.
Citizen science monitoring programmes are making increasingly important contributions to wildlife conservation, often at spatial and temporal scales unachievable by individual or teams of researchers. They are particularly valuable in estimating population trends and management impacts, and thus informing effective conservation decisions for declining species. The quality and potential biases of citizen science data are of concern, however, and appropriate experimental design and analysis are needed to ensure that the maximum scientific value is extracted. We investigated these issues in a citizen science survey of the Endangered Carnaby's black-cockatoo Calyptorhynchus latirostris. Since 2010, citizen scientists have conducted synchronized annual counts of Carnaby's black-cockatoo at roost sites to estimate the population trend. Survey effort was substantial, with c. 150 sites surveyed by > 260 volunteers each year. Relatively few sites were occupied, however, and only 42 (16%) of the 265 sites surveyed in total accounted for 95% of all observations. Many sites were empty and survey effort was often inconsistent. Taking these issues into account, analysis showed a statistically significant decline in roost occupancy rate and a non-significant decline in the mean size of roosting flocks, with an estimated overall trend of 14% decline per annum in the number of roosting birds. We highlight three important issues for citizen science monitoring programmes: the need to maintain regular surveys of sample sites to avoid patchy data, use an appropriate model that accounts for variable survey effort, high frequency of zero counts, and sampling site turnover, and incorporate information on site characteristics to help explain variation.
We examine the roles of actuaries in UK life offices, along with trends, challenges to and opportunities for actuaries. We carry out an analysis of senior roles in life offices, a questionnaire survey and interviews with relevant senior personnel. We find that actuaries occupy many important roles in life offices and are regarded as having good industry knowledge and technical skills, especially in financial modelling. There are fewer executive directors and more non-executive directors of life offices who are actuaries compared with the position in 1990. A higher proportion of reserved roles is outsourced to consultants than was the case in 1990. Only a small number of Actuarial Function Holders are directors. Actuaries are more siloed than was the case in the past, although actuaries are well represented in the finance and risk functions of many offices. Although actuarial work in connection with the preparation for Solvency II will decline, there will be important ongoing requirements for actuaries following Solvency II implementation. We also see opportunities for actuaries in four areas: in risk management, in financial analysis and management based on Solvency II and international financial reporting standards, in connection with “big data”, and in product development and the customer proposition. There are implications for the examination syllabus, continuing professional development and research.
Films of GaN have been grown using a modified MBE method in which the active nitrogen is supplied from an RF activated plasma source. Wurtzite films grown on (0 0 1) oriented GaAs substrates show highly defective, ordered polycrystalline growth with a columnar structure; the (0 0 0 1) planes of the layers being parallel to the (0 0 1) planes of the GaAs substrate. Films grown using a coincident As flux, however, have a single crystal zinc-blende growth mode. They have better structural and optical properties. To improve the properties of the wurtzite films we have studied the growth of such films on (1 1 1)A and (1 1 1)B oriented GaAs substrates. The improved structural properties of such films, assessed using x-ray and TEM methods, correlate with better low temperature PL performance.
DX Cha (HD 104237) is a southern, optically bright Herbig Ae star with an infrared excess, that is part of a small stellar group younger than 5 Myr. We used the APEX and ASTE submillimeter telescopes in Chile to search for continuum and gas emission around this system. Using LABOCA on APEX we detect strong continuum emission around HD104237-A and system component HD104237-E. Our ASTE spectrum detects a double-peaked 12CO(3-2) line profile towards the system, typical of a rotating disk. The new data are used as constraints with MCFOST to produce a disk model that fits the entire SED as well as the observed CO line profile.
Recent numerical simulations of dynamo action resulting from rotating convection have revealed some serious problems in applying the standard picture of mean field electrodynamics at high values of the magnetic Reynolds number, and have thereby underlined the difficulties in large-scale magnetic field generation in this regime. Here we consider kinematic dynamo processes in a rotating convective layer of Boussinesq fluid with the additional influence of a large-scale horizontal velocity shear. Incorporating the shear flow enhances the dynamo growth rate and also leads to the generation of significant magnetic fields on large scales. By the technique of spectral filtering, we analyse the modes in the velocity that are principally responsible for dynamo action, and show that the magnetic field resulting from the full flow relies crucially on a range of scales in the velocity field. Filtering the flow to provide a true separation of scales between the shear and the convective flow also leads to dynamo action; however, the magnetic field in this case has a very different structure from that generated by the full velocity field. We also show that the nature of the dynamo action is broadly similar irrespective of whether the flow in the absence of shear can support dynamo action.