bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dating the Volcanic Eruption at Thera
Authors: Bronk Ramsey Christopher , Manning Sturt W , Galimberti Mariagrazia 
Published: July 2016

The eruption of the volcano at Thera (Santorini) in the Aegean Sea undoubtedly had a profound influence on the civilizations of the surrounding region. The date of the eruption has been a subject of much controversy because it must be linked into the established and intricate archaeological phasings of both the prehistoric Aegean and the wider east Mediterranean. Radiocarbon dating of material from the volcanic destruction layer itself can provide some evidence for the date of the eruption, but because of the shape of the calibration curve for the relevant period, the value of such dates relies on there being no biases in the data sets. However, by dating the material from phases earlier and later than the eruption, some of the problems of the calibration data set can be circumvented and the chronology for the region can be resolved with more certainty.In this paper, we draw together the evidence we have accumulated so far, including new data on the destruction layer itself and for the preceding cultural horizon at Thera, and from associated layers at Miletos in western Turkey. Using Bayesian models to synthesize the data and to identify outliers, we conclude from the most reliable 14C evidence (and using the INTCAL98 calibration data set) that the eruption of Thera occurred between 1663 and 1599 BC.
High-Resolution AMS 14C Dating of Post-Bomb Peat Archives of Atmospheric Pollutants
Authors: Goodsite Michael E , Rom Werner , Heinemeier Jan , Lange Todd , Ooi Suat , Appleby Peter G , Shotyk William , van der Knaap W O , Lohse Christian , Hansen Torben S 
Published: July 2016

Peat deposits in Greenland and Denmark were investigated to show that high-resolution dating of these archives of atmospheric deposition can be provided for the last 50 years by radiocarbon dating using the atmospheric bomb pulse. 14C was determined in macrofossils from sequential one cm slices using accelerator mass spectrometry (AMS). Values were calibrated with a general-purpose curve derived from annually averaged atmospheric 14CO2 values in the northernmost northern hemisphere (NNH, 30°–90°N). We present a thorough review of 14C bomb-pulse data from the NNH including our own measurements made in tree rings and seeds from Arizona as well as other previously published data. We show that our general-purpose calibration curve is valid for the whole NNH producing accurate dates within 1–2 years. In consequence, 14C AMS can precisely date individual points in recent peat deposits within the range of the bomb-pulse (from the mid-1950s on). Comparing the 14C AMS results with the customary dating method for recent peat profiles by 210Pb, we show that the use of 137Cs to validate and correct 210Pb dates proves to be more problematic than previously supposed.As a unique example of our technique, we show how this chronometer can be applied to identify temporal changes in Hg concentrations from Danish and Greenland peat cores.
Bomb Radiocarbon Dating of Animal Tissues and Hair
Authors: Geyh Mebus A 
Published: July 2016

Initially, radiocarbon dating by bomb14C was used to check vintages of wine and whisky and to estimate the turnover times of carbon in various biological tissues. However, this technique has never been widely used for routine dating, although it has a wide field of application in geriatric medicine and forensic investigations. Fifteen years' experience in this field has shown the potential and limits of this technique. Taking into account the decisive biological factors, such as growth and aging, a complicated picture is obtained. Recent human bones cannot be dated with a constant precision. Despite an incomplete understanding of the process of incorporation of14C into human bones, the present dating technique is still more precise than most estimates by geriatric experts, for conventional14C dating follows that14C dates of bone collagen represent the years of the termination of puberty rather than those of death.Another application is the identification of furs of illegally hunted animals on the “Red List of threatened species” of the World Conservation Union (IUCN). For court cases, the year the animals were killed must be precisely determined. Due to the long and variable turnover time of more than one year of leather hair is the best dating material for animals.
Re-Evaluation of the Late Bronze Age and Early Iron Age Chronology of the Western Belgian Urnfields Based on 14C Dating of Cremated Bones
Authors: De Mulder Guy , van Strydonck Mark , Boudin Mathieu , Leclercq Walter , Paridaens Nicolas , Warmenbol Eugène 
Published: July 2016

The urnfields in western Belgium have been studied since the second half of the 20th century. Most of these studies, as well as the excavations themselves, date from before the last quarter of the 20th century, except for the urnfields at Velzeke and Blicquy, which were excavated recently. The chronology of these cemeteries was largely based on typochronological studies of pottery. Other funeral gifts, like bronze objects in the graves, are rather exceptional. The typochronology was worked out in a comparison with the framework of neighboring regions and central Europe. There was a need, then, for a chronology based on absolute dates. This was only possible by radiocarbon dating of the cremated bones. Tests on duplicate samples, like cremated bone in context with charcoal or 2 depositions of cremated bones within 1 urn, have shown that the results are reproducible and that there is no discrepancy between the charcoal and the cremated bone dates.The results of the 14C dating project on the cremated bones of the 2 urnfields at Velzeke and the one at Blicquy are promising. The interpretation of the occupational history of both sites at Velzeke can be revised, and the currently accepted ceramic sequence for this period needs reworking. In addition, the chronological framework of the Late Bronze Age and Early Iron Age is open for discussion. It seems plausible that the urnfield phenomenon starts earlier in western Belgium than previously expected. These dates can also contribute to the discussion about the transition from the Late Bronze Age to the Early Iron Age.
Methods of Separating Soil Carbon Pools Affect the Chemistry and Turnover Time of Isolated Fractions
Authors: Castanha Cristina , Trumbore Susan , Amundson Ronald 
Published: July 2016

A variety of physical and chemical techniques are used to fractionate soil organic matter, but detailed comparisons of the different approaches and tests of how separation methods influence the properties of isolated organic matter pools are lacking. In this case study based on A horizon samples of 2 California coniferous forests soils, we 1) evaluate the effects of root removal and ultrasonic dispersion on the properties of the <2 g cm-3 light fraction and 2) compare the properties of fractions obtained by sequential density separations of ultrasonically treated soil with those obtained by density followed by acid/base hydrolysis (Trumbore et al. 1996).A root-removal effort based on hand-picking visible roots reduced the radiocarbon content and increased the estimated turnover time of the light fraction by roughly 12%. Root-removal protocols that vary between investigators thus can potentially confound variability in carbon cycling for this fraction caused by environmental factors, such as climate. Ultrasonic dispersion did not have a clear effect on the light fraction C and N content or isotopic signature, but led to a decrease in the % C and C/N of the recovered heavy fractions, and losses of 12–19% of the total soil C to the sodium metatungstate density solution.Sequentially isolated density fractions clearly differed in mineralogy and organic matter chemistry, but natural-abundance 14C analyses indicated that distinct mineral phases did not correspond to unique C-turnover pools. Density fractions containing kaolinite group minerals alone and in combination with hydroxy-interlayered vermiculite were found to harbor both fast and slow cycling carbon. In contrast, severe chemical treatment isolated a carbon pool with the lowest overall 14C content and longest inferred mean turnover time. Overall, our results show that care must be taken when relying on physical (density) separation to isolate soil fractions with different dynamics, as the details of treatment will influence the results.
Radiocarbon Dating of Modern Peat Profiles: Pre- and Post-Bomb14C Variations in the Construction of Age-Depth Models
Authors: Goslar Tomasz , van der Knaap W O , Hicks Sheila , Andrič Maja , Czernik Justyna , Goslar Ewa , Räsänen Satu , Hyötylä Heidi 
Published: July 2016

We present studies of 9 modern (up to 400-yr-old) peat sections from Slovenia, Switzerland, Austria, Italy, and Finland. Precise radiocarbon dating of modern samples is possible due to the large bomb peak of atmospheric14C concentration in 1963 and the following rapid decline in the14C level. All the analyzed14C profiles appeared concordant with the shape of the bomb peak of atmospheric14C concentration, integrated over some time interval with a length specific to the peat section. In the peat layers covered by the bomb peak, calendar ages of individual peat samples could be determined almost immediately, with an accuracy of 2–3 yr. In the pre-bomb sections, the calendar ages of individual dated samples are determined in the form of multi-modal probability distributions of about 300 yr wide (about AD 1650–1950). However, simultaneous use of the post-bomb and pre-bomb14C dates, and lithological information, enabled the rejection of most modes of probability distributions in the pre-bomb section. In effect, precise age-depth models of the post-bomb sections have been extended back in time, into the “wiggly” part of the14C calibration curve.Our study has demonstrated that where annual resolution is concerned, tissues ofSphagnumare the only representative material for14C dating, although even samples of pureSphagnumcollected from a very thin slice of the peat section contain tissues grown in different years, so they integrate the atmospheric14C signal over a period of time. This time period (0.5–8 yr, depending on the site) seems to correlate with the peat accumulation rate, but it also depends on how the sampled peat sections were handled. When constructing age-depth models, for some peat sections we used the strategy of multi-stage14C dating. This led to a drastic reduction in the uncertainty of the age-depth models, by dating only a few additional samples in the profile.Our study is the first in which peat sections from the late pre-bomb time (AD 1900–1960) have been precisely dated at a high temporal resolution. In this time interval,14C ages of all the samples dated were younger than those derived from the atmospheric calibration curve, apparently due to the effect of integration. Evidently, the determination of calendar ages based on14C dating of single peat samples from that interval may be affected by a serious error if the possibility of integration is ignored.
Ultrafiltration: Boon or Bane?
Authors: Hüls C M , Grootes P M , Nadeau M-J 
Published: July 2016

Ultrafiltration of bone collagen, dissolved as gelatin (M ~100,000 D), has received considerable attention as a means to remove small contaminants and thus produce more reliable dates (Brown et al. 1988; Bronk Ramsey et al. 2004; Higham et al. 2006; Mellars 2006). However, comparative dating studies have raised the question whether this cleaning step itself may introduce contamination with carbon from the filters used (Bronk Ramsey et al. 2004; Brock et al. 2007; Hüls et al. 2007).Here, we present results of further ultrafiltration experiments with modern and fossil collagen samples using Vivaspin 20™ and Vivaspin 15R™ ultrafilters. Evidently, the Vivaspin 20 (VS 20) ultrafilter with a polyethersulfone (PES) membrane retains more material in the >30 kD fraction than the Vivaspin 15R (VS 15R) filter with a regenerated cellulose membrane (Hydrosat), which may be related to increased retention of proteins due to suboptimal electrostatic conditions during ultrafiltration with the PES membrane. In addition, this filter type shows clear evidence for contamination with fossil carbon, presumably from membrane fibers, in the <30 kD fraction. Radiocarbon measurements on ultrafiltrated fossil collagen seem to indicate small contributions of modern carbon via glycerin left on and within the filter membranes of both types. Although SEM pictures show film remnants on the fibrous filter structure of cleaned filter membranes, EDX analysis on the VS 20 membrane to not support the assumption this may be glycerin. Our observations indicate the risks and benefits of the use of ultrafiltration in cleaning collagen samples for 14C dating need to be further quantified, especially for the cleaning of fossil bone collagen of good quality samples.
A Review of Current Approaches in the Pretreatment of Bone for Radiocarbon Dating by AMS
Authors: Hedges R. E. M. , Van Klinken G. J. 
Published: July 2016

Although the reliability of 14C dates of bone has increased greatly since AMS methods permitted better pretreatment on smaller samples, most old, badly contaminated or severely weathered bone still give serious problems. Several groups have recently proposed improvements to sample purification methods, often supported by a number of 14C measurements. We present here an overview of these improvements. The issue is complicated by the following:
1.Different problems are presented depending on age, preservation and degree of contamination of bone.2.Methods may or may not be developed with routine application in mind.3.Determining the conditions for which any method can be regarded as reliable is not at all straightforward.
QSQs and Radio Galaxies - their Spectra and Time Variations at Radio Frequencies
Authors: Harris Beverley J. 
Published: July 2016

Accurate relative spectra for 300 radio sources from the Parkes catalogue have been measured and a statistical study made of their relation to class of optical identification and to other radio properties. Individual spectra and their time variations have also been investigated.The results support the contention that radio sources for which no identification appears on the Palomar Sky Survey prints may be galaxies more luminous at radio frequencies than those which are identified. From a study of QSOs, radio galaxies and these blank field objects, it appears (a) that with increasing radio luminosity compact components are more often found, their presence being indicated by synchrotron self-absorption at low and high frequencies, by flat, variable spectra at high frequencies, and by interplanetary scintillations; and (b) that where no compact component contributes to the spectrum at high frequencies, many spectra steepen with increasing frequency, an effect which may be more marked for the more radio luminous objects.Detailed analyses of the time variations in the compact components of 22 variable sources are generally consistent with the adiabatically expanding, uniform sphere model of Shklovsky, Kellermann, van der Laan and others. The model was modified to include relativistic expansion according to the formulae given by Rees and Simon. The results suggest that these components have evolved within months or years, have linear dimension of 0.1 to 100 pc and magnetic fields of 1 to 10−4 G. Some spectra at frequencies above 5000 MHz suggest non-adiabatic expansion which may be the result of continued injection of energy into an expanding region.
A Preliminary Study of the Classical Cepheid P-L Relation in the R, I Photometric System
Authors: Fernie J. D. 
Published: July 2016

It is pointed out that observational work on Cepheids in the R, I photometric system offers a number of advantages: the stars are generally brighter at these wavelengths and so can be more easily and accurately observed; effects of binary companions, which are usually earlier type stars, are minimized; reddening is less, can be more easily determined, and is less liable to differing extinction laws than in the UBV system; line-blanketing problems are smaller; the range in (R — I)0 is probably less than in (B — V)0, and the importance of the colour term in the P-L-C relation thus reduced.Available R, I data for classical Cepheids are gathered from the literature, and the P-L, P-C, and P-L-C relations investigated. It is found that the preliminary relations
represent the data to within ± 0.13 mag. in 〈MR〉 and ± 0.02 mag. in 〈R–I〉o.There is some indication that the intrinsic colours of EV Set, U Sgr, and S Nor are bluer than hitherto believed, conceivably due to circumstellar reddening.
9. The influence of exposure duration and trail orientation on photographic meteor spectra
Authors: Halliday I. 
Published: July 2016

The effects on photographic meteor spectra produced by an occulting shutter and by the geometric orientation of the trail with respect to the camera are considered. A Perseid meteor photographed with both an occulted and unocculted spectrograph shows that large changes in the relative intensity of spectral lines can be caused by a shutter. The strong wake spectrum of this meteor is studied and a classification of multiplets according to duration and wake intensity is presented. It is emphazised that a strong wake is produced by a coasting gas rather than by particles or droplets. The gas may coast an appreciable distance during the radiating lifetime of some multiplets.The spectrum of a bright Quadrantid meteor is used to show that long-duration multiplets are strongly enhanced when the orientation of the trail lengthens the effective path length of the wake column, i.e., the meteor is observed near its radiant. The abundance of calcium appears to be above average in this meteor.Multiple photographs of the λ5577 line of neutral oxygen have been secured showing a decay time in excess of 1·5 sec. The decay is more rapid at lower heights and it appears that the mechanism of excitation to the metastable level operates for an interval of about 0·1 sec.As more accurate photometry of meteor spectra is achieved it will be essential to give careful attention to all of these effects.
Observation des jets et concentrations de la couronne au-dessus des régions actives
Authors: Dollfus Audouin 
Published: July 2016

The ‘K-Coronameters’ in use since 1956 at Pic-du-Midi and Meudon Observatories for the study of the white-light corona were replaced in 1963 by new improved instruments.The coronal activity was continuously recorded from 1964 to 1967. The electron density in the low corona and its variation with height are summarized by curves and maps.A study is given of the corona streamers above the proton flares area in July and September 1966.
Water Vapor in Venus Determined by Airborne Observations of the 8200 Å Band
Authors: Gull Theodore R. , O'Dell C. R. , Parker R. A. R. 
Published: July 2016

The region of the 8200 Å Band of H2O was studied in spectra of Venus obtained with an echelle grating spectrograph operated at an altitude of 14.6 km in the NASA Learjet research aircraft. Taking advantage of low foreground absorption, observing at a time of velocity quadrature, differential spectroscopy with respect to lunar spectra, and spectrum averaging, we establish a value of H2O of 3 ± 20 μ for the total path over the entire disk. This value differs from earlier studies of the integrated disk but supports the low values recently derived from infrared bands and by very high spectral resolution groundbased studies.These results establish that the average value over the entire disk is quite low but allows that locally larger values may exist as reported by Barker. A more complete description of this work appeared in Icarus21 (1974), 213.
The Stability of Continental Blocks in Seismically Active Regions
Authors: Shcheglov V. P. 
Published: July 2016

In connection with the problem of continental drift some authors voice a supposition of the existence of progressive and rotational motion of continental blocks, particularly in seismically active regions. Azimuths of some terrestrial objects determined over long time intervals were used to investigate these motions. Naturally, the reliability of the result depends on the length of these intervals.The axis of the meridian instrument of Uloug-Beg Observatory in Samarkand, installed 550 years ago (1420-30) is the most ancient meridian direction on the Earth. Using measurements made by the author in 1941, 1956, and present-day observations, it was found that the direction of the axis had moved through an angle of . Allowing for observational errors in the pre-optical period one can accept a change of 5′ or per year. To ascertain if the observed change is caused by rotation of the continental block or local deformation repeated measurements of azimuths of triangulation stations first measured forty years ago were made. The results show the absence of continental block rotation in the region of Middle Asia within a possible accidental error of .
Optical observations of nonthermal galactic radio sources
Authors: Minkowski R. 
Published: July 2016

A total of 9 nonthermal sources near the plane of the Galaxy have now been definitely identified with nebulosities. The identifications are well established; positions and sizes of the nebulosities and of the sources are in satisfactory agreement. At least three types of objects can be recognized:1. Remnants of supernovae of type I.2. The Cassiopeia A source, a remnant of a supernova of type II.3. The Cygnus loop and several other large nebulosities which are most likely of similar origin. They also may be remnants of supernovae type II.The large size and the low surface brightness of these objects render their detailed investigation a difficult and time-consuming task. The true picture may emerge slowly, and conclusions drawn at an early stage of the work may have to be discarded as the investigation progresses.
Summary of IAU Symposium 176
Authors: Linsky Jeffrey L. 
Published: July 2016

This IAU Symposium 176 on the topic “Stellar Surface Structure” provided a much needed opportunity for instrumentalists, observers, and theoreticians to present their exciting new results and to preview the even more exciting future for high-resolution imaging of stellar surfaces. I will attempt a critical summary of this symposium by calling attention to those areas that will likely be very productive in the future and by discussing some important topics that have not been addressed adequately to date, such as the roles of systematic and random errors, the true nature of the solar-stellar connection, and the physical processes responsible for stellar surface structure.Lesser artists borrow, great artists steal. Igor StravinskyYou never can tell. George Bernard Shaw
The FK5: Present Status and Some Derived Results
Authors: Schwan Heiner 
Published: July 2016

Work on all parts of the FK5 is near to completion. The Basic FK5 has been published in the course of 1989 so that this catalogue is now officially released; the data have been made available to the various data centres. Work on the bright part of the FK5 Extension is finished since the end of 1988 and a tape version was sent to various institutions on request. Work on the Faint Extension is also nearly finished and the complete FK5 Extension will presumably be available on magnetic tape in a few months.Some results obtained from new observations of FK5 stars are presented. Comparisons of the FK5 with FC, NFK, FK3, FK4, GC, N30 were performed and are discussed with respect to systematic and individual accuracy. The parameters of galactic rotation and precession, and the distance to the Hyades cluster have been derived using proper motions which were obtained within the work on the FK5.