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The terrestrialization of life has profoundly affected the biosphere, geosphere and atmosphere, and the Geological Magazine has published key works charting the development of our understanding of this process. Integral to this understanding – and featuring in one of the Geological Magazine publications – is the Devonian Rhynie chert Konservat-Lagerstätte located in Aberdeenshire, Scotland. Here we provide a review of the work on this important early terrestrial deposit to date. We begin by highlighting contributions of note in the Geological Magazine improving understanding of terrestrialization and Palaeozoic terrestrial ecosystems. We then introduce the Rhynie chert. The review highlights its geological setting: the Caledonian context of the Rhynie Basin and its nature at the time of deposition of the cherts which host its famous fossils. There follows an introduction to the development of the half-graben in which the cherts and host sediments were deposited, the palaeoenvironment this represented and the taphonomy of the fossils themselves. We subsequently provide an overview of the mineralization and geochemistry of the deposit, and then the fossils found within the Rhynie chert. These include: six plant genera, which continue to provide significant insights into the evolution of life on land; a range of different fungi, with recent work starting to probe plant–fungus interactions; lichens, amoebae and a range of unicellular eukaryotes and prokaryotes (algae and cyanobacteria); and finally a range of both aquatic and terrestrial arthropods. Through continued study coupled with methodological advances, Rhynie fossils will continue to provide unique insights into early life on land.
We report major new insights from recent research at the Powars II Paleoindian red ocher quarry (48PL330). We salvaged more than 7,000 artifacts from Powars II between 2014 and 2016 by screening redeposited sediment from the talus slope below the intact portion of the site. Clovis artifacts dominate the diagnostic artifact assemblage, including 53 Clovis points, 33 preforms, and artifacts associated with a previously unrecognized blade core industry. We report the first radiocarbon dates from the site, determined from dating bone tools, which indicate Cody-aged use (ca. >10,000 cal BP). Further, salvage efforts discovered a previously unknown toolstone source from which many of the Clovis artifacts were produced. The Powars II Clovis points most resemble early Paleoindian points from the far Northern Plains and were likely both produced and discarded in the red ocher quarry after hunting, as evidenced by preform production and the presence of impact fractures on many used points. Given these production and discard patterns, Powars II holds some of the best evidence archaeologists currently have for Paleoindian ritualism related to hunting.
My paper on the Corpus Juris project in the first volume of this Yearbook closed by saying, in effect, “Watch this space!” At the end it told how, at the time of writing, the European Parliament and Commission had re-engaged the original team that drafted the proposals, plus some others, and constituted them as a Comité du suivi with instructions to find out how hard or easy it would be to integrate the Corpus scheme into the existing legal systems of the Member States. And it also told how the House of Lords Select Committee on the European Communities had begun to carry out a study of the Corpus project.
The use of spanwise waviness in wings has been proposed in the literature as a possible mechanism for obtaining improved aerodynamic characteristics, motivated by the tubercles that cover the leading edge of the pectoral flippers of the humpback whale. We investigate the effect of this type of waviness on the incompressible flow around infinite wings with a NACA0012 profile, using direct numerical simulations employing the spectral/hp method. Simulations were performed for Reynolds numbers of
, considering different angles of attack in both the pre-stall and post-stall regimes. The results show that the waviness can either increase or decrease the lift coefficient, depending on the particular
and flow regime. We observe that the flow around the wavy wing exhibits a tendency to remain attached behind the waviness peak, with separation restricted to the troughs, which is consistent with results from the literature. Then, we identify three important physical mechanisms in this flow. The first mechanism is the weakening of the suction peak on the sections corresponding to the waviness peaks. This characteristic had been observed in a previous investigation for a very low Reynolds number of
, and we show that this is still important even at
. As a second mechanism, the waviness has a significant effect on the stability of the separated shear layers, with transition occurring earlier for the wavy wing. In the pre-stall regime, for
, the flow around the baseline wing is completely laminar, and the earlier transition leads to a large increase in the lift coefficient, while for
, the earlier transition leads to a shortening of the separation bubble which does not lead to an increased lift coefficient. The last mechanism corresponds to a sub-harmonic behaviour, with the flow being notably different between subsequent wavelengths. This allows the wing to maintain higher lift coefficients in some portions of the span.
Cyg X-3 underwent a series of giant radio outbursts beginning on September 28, 1982 (Geldzahler et al. 1983). The flux densities at 2.7 and 8.1 GHz (11.1, 3.71 cm respectively, see Figure 1) were measured with the 2.4 km baseline of the Green Bank interferometer once every three days before October 5, 1982 (= JD 244 5248) and three times daily thereafter.
SS433 has been under intensive study for the past five years in almost all wavelength bands of the electromagnetic spectrum. This peculiar object is generally regarded (Beer 1981) as being a binary system composed of a main sequence star losing mass via Roche lobe overflow to a massive accretion disk associated with a compact object, probably a neutron star. The binary period is 13.1 days. Supercritical accretion onto the disk causes about 10−6 M⊙/year of ionised matter to be ejected in the form of jets with a relatively constant velocity of 0.26 c along the disk axis. The disk (or the inner part of it) precesses with a period of about 164 days, although there is evidence that this may not be constant. The half angle of the precession cone is ~20° and its axis lies at an angle of ~80° to the line of sight. The main sequence star loses mass at a rate of 10−4 to 10−6 M⊙/yr into a stellar wind with the result that a relatively dense environment surrounds the binary system.
In Table I we present the list of 38 celestial objects that have been observed since January 1978 at 2.7 and 8.1 GHz with the Green Bank interferometer. The sources fall naturally into three categories: radio stars, possibly Galactic sources, and extragalactic sources. SS433, Cyg X-3, and each extrgalactic source is measured several times per day while the other sources are measured once every three days. Reports on the entire program will be found in Geldzahler et al. (1983a), and on specific sources: SS433—Johnston et al. (1983a), BL Lac—Johnston et al. (1983b), Cyg X-3—Geldzahler et al. (1983b) and elsewhere in this volume), and CTA 26—Spencer et al. (1983).
The well known jet in M87 (Virgo A) has been extensively studied in the radio regime using conventional arrays with resultant resolutions in the range 0.22–1 arcsecond. We present here the results of a VLBI experiment to map the jet over its entire length (30 arcseconds) to high resolution. The observations were made in April 1984 at 1.67 GHz with a ‘World Array’ containing 18 VLBI telescopes. In addition, simultaneous observations were performed with the 6 station MERLIN array.
On 8–12 October 1981 a 5-station MkII VLBI experiment at 1660 MHz was performed using antennas at Westford, Maryland Point, Green Bank, Fort Davis, and Owens Valley. Fifteen extragalactic sources (Table 1) were observed with an average synthesized beam of roughly 10 mas. The data were processed using the NRAO correlator, globally fringe-fit, and mapped with the AIPS package. In addition to the usual self-calibration techiques, corrections were made to eliminate baseline-dependent calibration errors. Some of the sources, for example 1641+399 (3C345), display extended components not before observed at the dynamic range of the maps, which on the average is roughly 200:1.
At the lowest radio frequencies (≤30 MHz), the Earth's ionosphere transmits poorly or not at all. This relatively unexplored region of the electromagnetic spectrum is thus an area where high resolution, high sensitivity observations can open a new window for astronomical investigations. Also, extending observations down to very low frequencies brings astronomy to a fundamental physical limit where the Milky Way becomes optically thick over relatively short path lengths due to diffuse free-free absorption.
Until recently, the compact structure in 3C 395 could be described as follows (Simon et al. 1987):
(1)A bright, unresolved, flat spectrum core to the northwest. The core brightened by about 0.4 Jy between 1983.3 and 1985.4, from 0.6 Jy to 1.0 Jy.
(2)A moderately resolved component 15.8+/−0.2 mas to the southwest along P.A.I 18o. The position of this component relative to the core has changed by less than 0.2 mas in 6 years and the flux density of this component has remained roughly constant.
(3)A component which was moving rapidly away from the core towards component (2) with a proper motion of 0.64+/−0.1 mas yr−1. For 3C 395 (z=0.635), this implies (v/c)∼20c for Ho =100 km/s/Mpc and qo =0.5.
The galaxy M87 (3C274, NGC4486) contains one of the nearest jet sources in the northern hemisphere, and one of our best opportunities to study a jet in detail. We have made MkII VLBI observations of the nuclear jet at 1.66 GHz using 18 stations of the “World Array.” The array included Arecibo which greatly improved the north-south resolution. The data were global fringe fitted, and self-calibrated to remove both antenna and baseline amplitude and phase errors. The resulting map (Fig. 1) has a dynamic range of 2300:1 and reveals a very complex structure. At distances ≥50 mas from the core, the jet is resolved across its width and appears limb-brightened. The brightness centroid oscillates from side to side by an amount roughly equal to the jet's width; this may be caused by brightness variations at the edges of a limb-brightened jet. Within 50 mas of the core the opening angle (at the FWHM points) is 6.5°±0.3°; this is larger than that of the 20″ jet, and suggests there is recollimation between the pc and kpc scales. The jet is aligned within 1° of the 20″ jet. There is no evidence for a counter-jet; the jet/counter-jet brightness ratio is R≥200.
Radio-glaciological parameters from the Moore’s Bay region of the Ross Ice Shelf, Antarctica, have been measured. The thickness of the ice shelf in Moore’s Bay was measured from reflection times of radio-frequency pulses propagating vertically through the shelf and reflecting from the ocean, and is found to be 576 ± 8 m. Introducing a baseline of 543 ± 7m between radio transmitter and receiver allowed the computation of the basal reflection coefficient, R, separately from englacial loss. The depth-averaged attenuation length of the ice column, 〈L〉 is shown to depend linearly on frequency. The best fit (95% confidence level) is 〈L(ν)〉= (460±20) − (180±40)ν m (20 dB km−1), for the frequencies ν = [0.100–0.850] GHz, assuming no reflection loss. The mean electric-field reflection coefficient is (1.7 dB reflection loss) across [0.100–0.850] GHz, and is used to correct the attenuation length. Finally, the reflected power rotated into the orthogonal antenna polarization is <5% below 0.400 GHz, compatible with air propagation. The results imply that Moore’s Bay serves as an appropriate medium for the ARIANNA high-energy neutrino detector.
The WAIS (West Antarctic Ice Sheet) Divide deep ice core was recently completed to a total depth of 3405 m, ending 50 m above the bed. Investigation of the visual stratigraphy and grain characteristics indicates that the ice column at the drilling location is undisturbed by any large-scale overturning or discontinuity. The climate record developed from this core is therefore likely to be continuous and robust. Measured grain-growth rates, recrystallization characteristics, and grain-size response at climate transitions fit within current understanding. Significant impurity control on grain size is indicated from correlation analysis between impurity loading and grain size. Bubble-number densities and bubble sizes and shapes are presented through the full extent of the bubbly ice. Where bubble elongation is observed, the direction of elongation is preferentially parallel to the trace of the basal (0001) plane. Preferred crystallographic orientation of grains is present in the shallowest samples measured, and increases with depth, progressing to a vertical-girdle pattern that tightens to a vertical single-maximum fabric. This single-maximum fabric switches into multiple maxima as the grain size increases rapidly in the deepest, warmest ice. A strong dependence of the fabric on the impurity-mediated grain size is apparent in the deepest samples.
We consider the influence of a smooth three-dimensional (3-D) indentation on the instability of an incompressible boundary layer by linear and nonlinear analyses. The numerical work was complemented by an experimental study to investigate indentations of approximately
width at depths of 45 %, 52 % and 60 % of
indicates 99% boundary layer thickness. For these indentations a separation bubble confined within the indentation arises. Upstream of the indentation, spanwise-uniform Tollmien–Schlichting (TS) waves are assumed to exist, with the objective to investigate how the 3-D surface indentation modifies the 2-D TS disturbance. Numerical corroboration against experimental data reveals good quantitative agreement. Comparing the structure of the 3-D separation bubble to that created by a purely 2-D indentation, there are a number of topological changes particularly in the case of the widest indentation; more rapid amplification and modification of the upstream TS waves along the symmetry plane of the indentation is observed. For the shortest indentations, beyond a certain depth there are then no distinct topological changes of the separation bubbles and hence on flow instability. The destabilising mechanism is found to be due to the confined separation bubble and is attributed to the inflectional instability of the separated shear layer. Finally for the widest width indentation investigated (
), results of the linear analysis are compared with direct numerical simulations. A comparison with the traditional criteria of using
-factors to assess instability of properly 3-D disturbances reveals that a general indication of flow destabilisation and development of strongly nonlinear behaviour is indicated as
values are attained. However
-factors, based on linear models, can only be used to provide indications and severity of the destabilisation, since the process of disturbance breakdown to turbulence is inherently nonlinear and dependent on the magnitude and scope of the initial forcing.
A circular letter was sent out to all members of the Commission in December 1937, to which the majority have replied. While work is going on steadily in the Observatories where meridian observations are carried out, comparatively few catalogues have been published since 1935. In view of the very full report made three years ago it is only necessary to draw attention to the progress which has been made in the interval.
La centralisation au Bureau international de l’Heure des résultats d’observations de l’Opération internationale de 1933 a été très lente, puisque les dernières données attendues ont été reçues vers la fin de 1937.
Le nombre des stations ayant coopéré à l’Opération internationale et ayant transmis leurs observations à l’organisme centralisateur s’élève à soixante et onze. Ainsi qu’il a été expliqué à notre Commission mixte, lors du Congrès de l’Union géodésique et géophysique internationale tenu à Édimbourg en 1936, ces stations ont été réparties en trois groupes:
Le Ier comprenant vingt Observatoires, disposant chacun de plusieurs horloges de première classe (soit à poids sous pression et à température constantes, soit à quartz piézoélectrique);
We present preliminary results from absolutely flux-calibrated optical spectroscopy, together with 5 GHz radio flux measures of 17 symbiotic stars. The data were obtained quasi-simultaneously using the Manchester Echelle Spectrograph on the Isaac Newton Telescope, La Palma between 1988 September 20 and 24, and the Broad Band Interferometer at Jodrell Bank during 1988 October. This represents the largest sample of these stars observed in this way to date. Distances are calculated using visual extinctions and are compared with other quoted values. In general, the agreement is surprisingly good. Plots of individual line luminosities vs. radio luminosity indicate that the D-type (dusty) symbiotics (both also proto-planetary nebulae) have far higher radio luminosities than S-types (stellar) for comparable recombination and forbidden line luminosities. This may however be due to underestimation of optical line luminosities for the D-types as the circumstellar extinction contribution is uncertain. The single D’-type (cool dust, yellow secondary) lies at the low luminosity end of the S-type region. ‘Very slow novae’ in our sample lie in both groups.
The orthodox model of active galactic nuclei (AGN), as is generally accepted, is that of Rees. We have found an AGN (3C 147) which has a counter-jet much longer than the main jet. It also has an unusual sideways ejection from the nuclear region. Both of these and the 3-jet structure per se do not seem to conform with the general accepted model, and are also not explained by relativistic beaming effects. We speculate that this is due to coronal mass ejection (CME) in the accretion disk corona. Recently, we have found convincing new evidence that this is true. We have also found direct evidence of helical magnetic fields in the core region of 3C 147. These results may be of importance to the understanding of AGN.
We present MERLIN observations of the exciting X-ray transient GRS 1915+105. Previous radio observations of GRS 1915 have shown that it is a source of superluminal radio jets. The emission of anti-parallel radio knots has led to this being described as a ‘microquasar’. MERLIN observations presented here show further details of the structure. The two main features observed are a bright extension in the direction of the superluminal jet and also, an extended region of low brightness which is elongated almost at right angles to the jet. This latter feature could either be an associated nebulosity or the remains of a jet which has undergone a radical change in direction.