bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiocarbon Analysis of Pinus Lagunae Tree Rings: Implications for Tropical Dendrochronology
Authors: Biondi Franco , Fessenden Julianna E
Published: July 2016

A promising species for tropical dendrochronology is Pinus lagunae, a pine tree found in Baja California Sur (Mexico) around lat 23.5°N. In 1995, we sampled a total of 27 wood cores from 13 Pinus lagunae trees in Sierra La Victoria (23°36'N, 109°56'W), just north of Sierra La Laguna, at an elevation of 1500–1600 m. Selected trees were locally dominant, but their ring-width patterns could not be crossdated. To test the hypothesis that visible growth layers in Pinus lagunae are formed annually, we measured radiocarbon amounts in individual rings by means of accelerator mass spectrometry (AMS). Twenty-three 14C measurements were used to trace the location of the 1963–64 “bomb spike” in 3 wood increment cores. By comparing the location of that δ14C extreme with the number of visible radial wood increments, it was possible to conclude that 2 cores had a number of locally absent rings, while the 3rd one included a few years with more than one growth layer. Therefore, ring-width patterns of sampled Pinus lagunae were not consistent from one tree to another, most likely because of climatic regime in combination with microsite features. While the possibility of generating Pinus lagunae tree-ring chronologies cannot entirely be ruled out, the development of dendrochronological proxy records of climate from coniferous species in tropical North America should focus on species and sites that experience a more pronounced seasonality.
Louvain Natural Radiocarbon Measurements XII
Authors: Gilot E. , Capron P. C.
Published: July 2016

The following list comprises selected measurements made in the Louvain 14C Dating Laboratory with the 0.6 L CH4 proportional counter. Details of procedure are given in previous lists. Dates are reported in terms of the Libby half-life, 5570 ± 30 years and quoted with 1σ experimental error.
Belfast Radiocarbon Dates V
Authors: Smith A. G. , Pearson G. W. , Pilcher J. R.
Published: July 2016

The dating equipment and operating conditions remain essentially as previously described. Samples in this list were counted at filling pressures equivalent to either 152 or 380 cm Hg at 20°C. Pretreatments are as given in previous lists unless otherwise specified. All wood samples were treated with sodium chlorite and dilute HCl to leave a cellulose-rich residue. Pine wood was in some cases extracted with petroleum spirit in a Soxhlet apparatus before this treatment, to remove resins.
Atomic Energy Research Institute of Korea Radiocarbon Measurements II
Authors: Yang Kyung Rin
Published: July 2016

C14 measurements of archaeologic and geochemical samples using sample synthesized benzene in a Beckman LS-100 liquid scintillation spectrometer are reported. Rather high background counting rates of ca. 8 to 9 cpm and counting efficiency of ca. 45 to 48% for 4 cc counting vial of potassium free glass are observed. The counting vial (total volume of 10 cc) is supported by an aluminum bar for geometry control. Background and standard counting rates measured during the past 17 months are listed in Tables 1 and 2, respectively. Slight seasonal variations were observed.
Glasgow University Radiocarbon Measurements VI
Authors: Farmer J. G. , Stenhouse M. J. , Baxter M. S.
Published: July 2016

The following list presents results obtained during 1970-1971 and is a continuation of research of which data have been pub. previously (Baxter et al., 1969; Ergin et al., 1970; Baxter and Walton, 1970; Harkness and Walton, 1972; Ergin et al., 1972). The major research efforts at Glasgow are aimed at evaluation of (a) natural annual C14 levels and (b) burdens and residence times of artificial C14 in the environment and human tissues. The results of these studies are presented as δC14 and Δ values based on age-corrected activities, although this correction is very small. The errors quoted are counting uncertainties only, expressed at the 1σ level. Pretreatment procedures are outlined in the text and analytical methods are essentially unchanged. Gas proportional counting of both CO2 and CH4 is employed in 2.6L and 0.5L detectors, respectively. Mass spectrometric analyses are performed to a precision of 0.1‰ (± 2σ) on a V.G. Micromass 602B stable isotope mass spectrometer.
Sydney University Natural Radiocarbon Measurements I
Authors: Gillespie R. , Polach H. A. , Temple R. B.
Published: July 2016

Preparations to establish a radiocarbon dating laboratory at the University of Sydney were made in 1970 in the Department of Physical Chemistry, to support Ph.D. studies and to supplement existing dating services in Australia to the archaeologic and geologic communities.
Institut Fondamental D'Afrique Noire Radiocarbon Dates I
Authors: Diop Cheikh Anta
Published: July 2016

We follow the same method of radiocarbon dating used in the Gif-Sur-Yvette dating laboratory. Samples are inspected and foreign material removed. Wood and charcoal samples are treated with 0.1N ammonium hydroxide and 0.1N hydrochloric acid. Shells are treated with 10% hydrochloric acid to eliminate surface contamination. Bone samples are treated with 0.1N ammonium hydroxide to remove humic acids and 10% HCl to remove inorganic carbonate and retain collagen for radiocarbon measurements. Sample CO2 is produced by combustion in oxygen. The stream of gases passes over CuO at 600°C to insure complete oxidation of C to CO2 and through traps containing, respectively, silver nitrate and sulfuric chromic acid solution for purification; barium carbonate is precipited from barium hydroxide bubblers. After filtering and drying, CO2 is liberated from barium carbonate by sulfuric acid. The CO2 is used to fill a 1.2L steel proportional counter at 740mm Hg. Age calculations are based on a 14C half-life of 5568 ± yr and 0.95 of activity of the NBS oxalic acid standard; ages are quoted in yr before 1950. Finite ages are quoted with 1σ criterion corresponding to the standard deviation based only on counting errors; the maximum age is quoted with 4 σ criterion above background.
Tallinn Radiocarbon Dates II
Authors: Punning J M , Kakum T , Rajamäe R
Published: July 2016

The following list includes samples dated in 1973. Benzene is used as the carrier of natural 14C activity as previously described (Punning et al, 1973). We used both 1-channel and 2-channel scintillation devices. The detector shield comprises 10cm lead. Around the detector we put 16 Geiger-Mueller type counters in anticoincidence circuit with output signals from detector. It decreased the average background ca 20 to 40%.
Köln Radiocarbon Dates III
Authors: im Walde Th Schulte , Freundlich J C , Schwabedissen Hermann , Taute Wolfgang
Published: July 2016

The present list contains 14G dates from archaeologic samples attributed to the European Mesolithic period from the typology of associated finds, especially microliths. Of these samples, 14 are from Germany and 6 from France.
University of Lund Radiocarbon Dates XVIII
Authors: Håkansson Sören
Published: July 2016

Most of the14C measurements reported here were made between October 1983 and October 1984. Equipment, measurement, and treatment of samples are as reported previously (R, 1968, v 10, p 36–37; 1976, v 18, p 290; 1980, v 22, p 1045).
Glassy Microspherules from Bomb Combustion of Charcoal
Authors: Burleigh Richard , Meeks Nigel
Published: July 2016

Glassy microspherules, typically 200μm or less in diameter, are well documented from a variety of terrestrial and extraterrestrial sources (Baker, 1959, p 192–198; Glass, 1969; Rost, 1969; McKay, Greenwood & Morrison, 1970; Mueller & Hinsch, 1970; Cross, 1971; O'Keefe, 1980). To these we would add the formation of microspherules of similar habit when wood charcoal is burned in a combustion bomb (Barker, Burleigh & Meeks, 1969; Burleigh, 1973, 1974; Switsur, 1973; Switsur et al, 1974) as a first step in the chemical synthesis of samples for 14C age measurement. The glassy material of these spherules originates from fusion at the high temperatures reached during the combustion, of traces of alkali-metal minerals in the charcoal and silica bodies (phytoliths) within its microstructure. Other materials commonly burned, such as bone collagen, do not yield microspherules. The age and source of the charcoal are immaterial, though different species (and perhaps other woody plant materials) may be more-or-less productive of spherules. Here we give a brief summary of the characteristics of these glassy microspherules, based on optical and scanning electron microscopy and energy-dispersive x-ray analysis.
A Computer Program for Radiocarbon Age Calibration
Authors: Stuiver Minze , Reimer Paula J
Published: July 2016

The calibration curves and tables given in this issue of RADIOCARBON form a data base ideally suited for a computerized operation. The program listed below converts a radiocarbon age and its age error os (one standard deviation) into calibrated ages (intercepts with the calibration curve), and ranges of calibrated ages that correspond to the age error. The standard deviation oC in the calibration curve is taken into account using (see Stuiver and Pearson, this issue, for details).
Developments in Sample Combustion to Carbon Dioxide, and in the Oxford AMS Carbon Dioxide Ion Source System
Authors: Hedges R. E. M. , Humm M. J. , Foreman John , Van Klinken G. J. , Bronk C. R.
Published: July 2016

We describe the operation of a commercial system as modified for preparation of CO2 for the CO2 source. AMS samples are automatically combusted in a CHN analyzer, and stable isotope measurements are made on line. We describe the performance of this equipment, with reference to yield, sample contamination, memory effect, accuracy of isotope measurement, convenience and cost. We discuss the current status of dating using the CO2 source. This is the only source in operation at Oxford, and has been in routine dating since September 1989. We assess the practicalities of operation, including the latest measurements on background, memory, sample-size requirements and operating schedules. We also describe modifications to the sputter beam optics and to the gas handling systems.
Instrumentation and Software for Low-Level Liquid Scintillation Counting Radiocarbon Dating
Authors: Sanyuan Guan , Yuanming Xie
Published: July 2016

In China, the development of 14C dating is closely related to that of liquid scintillation counting (LSC). New demands are continuously made on LSC by 14C dating, and at the same time, the development of LSC promotes 14C dating. Benzene synthesis for 14C sample preparation was first developed in China in 1974 by the 14C Laboratory of the Department of History, Peking University. This has laid the foundation for 14C dating by β counting with LS counters. Initially, we used a modified conventional LS counter. Despite its poor detection efficiency and high background, it did make a great contribution to 14C dating and LSC in China. Additional 14C laboratories were established for the fields of archaeology, geology, geography, vertebrate paleontology, marine geology and seismology, for which 14C dating is becoming an important research tool. At present, over 50 14C laboratories have been established in China; 90% of the labs use LS counters for β counting, most of which are manufactured in China. 14C dating in China has been primarily concerned with sample synthesis techniques. Since 1979, we have developed three types of LS counters. One is of conventional design; the others are with anticoincidence shielding. We describe here an anticoincidence-shielded LS counter.
Evaluation of High-Purity Synthetic Silica Vials in Active and Passive Vial Holders for Liquid Scintillation Counting of Benzene
Authors: Hogg A. G. , Noakes J. E.
Published: July 2016

We evaluate high-purity synthetic silica vials in both delrin and active plastic holders (Pico adapters™) for 14C dating, using liquid scintillation counting of benzene. We have designed synthetic silica vials in the form of simple cylinder-cells based on the standard 7-ml vial. We have also designed a delrin holder for supporting 7-ml silica or glass vials. We compare the counting efficiency and background of the silica vials with Teflon, plastic and low-K glass vials for both delrin holders and Pico adapters in the 1220 Quantulus and Packard Tri-Carb 2660 XL, fitted with a plastic detector guard. In the 1220 Quantulus, synthetic silica vials in Pico adapters have the highest figure of merit (FM), closely followed by silica in delrin holders and Teflon. In the Packard Tri-Carb 2660 XL, plastic vials in Pico adapters give the highest FM.
CalibETH: An Interactive Computer Program for the Calibration of Radiocarbon Dates
Authors: Niklaus Thomas R. , Bonani Georges , Simonius Markus , Suter Martin , Wölfli Willy
Published: July 2016

A computer program for convenient calibration of radiocarbon dates has been developed. The program has a simple user interface, which includes pull-down menus, windows and mouse support. All important information, such as calibration curves, probability density function and results, in text form, are displayed on the screen and easily can be rearranged by the user. Two versions of CalibETH, one for an IBM-PC and one for the Macintosh, are available. CalibETH runs under the graphics interface, GEM, from Digital Research, on an IBM PC.
Announcement of a Further International Intercomparison Exercise
Authors: Scott E. M. , Harkness D. D. , Miller B. F. , Cook G. T. , Baxter M. S.
Published: July 2016

Following recommendations of the Glasgow International Workshop on Intercomparison of Radiocarbon Laboratories (Scott, Long & Kra 1990), a further international intercomparison is planned. This new intercomparison is complementary to the existing IAEA intercalibration, and will make use of natural samples whose ages will be unknown to the participants. The study has been funded by the UK Research Councils (SERC and NERC), and samples will be free to all participants. We anticipate that this intercomparison will be ongoing, with distribution of samples in 1992, and presentation of the results at a later meeting. We present here details of the samples available and the time scale of the study. Briefly, we envisage that the new study will be more focused than the ICS (Scott et al. 1986), and will include natural samples in both pretreated and unpretreated forms.
Twenty-Five Years of Radiocarbon Dating Soils: Paradigm of Erring and Learning
Authors: Scharpenseel H. W. , Becker-Heidmann Peter
Published: July 2016

Soil organic matter sequesters close to three times the carbon existing totally in the living biomass and nearly the same for the total carbon in the atmosphere. Models, such as Jenkinson's or Parton's Century model, help to define soil organic matter fractions of different functions, based on residence time/14C age. Rejuvenation of soil carbon was felt to be the principal impediment to absolute soil dating, in addition to the ambiguity of the initiation point of soil formation and soil age. Recent studies, for example, of Becker-Heidmann (1989), indicate that a soil14C age of >1000 yr cannot have >0.1% rejuvenation in the total soil organic matter compartments/fractions to be possible and sustainable. Always problematic in earlier observations were agevs.depth increases, in14C profile curves showing an inflection of reduced age in the deepest samples,i.e.,from the rim of the organic matter containing epipedon. We attribute this phenomenon, in mollic horizons, to earthworm casts in the terminal part of the escape tube. Becker-Heidmann (1989) has shown, in thin layer soil profile dating, a highly significant correlation between the highest14C ages and the highest clay content. Thus, optimization of soil dating is, to a lesser degree, related to the applied extracting solvent system than to soil texture fractions. Such observations allow us to mitigate error ranges inherent in dating dynamic soil systems.
Lake Sediments from the Kashmir Himalayas: Inverted 14C Chronology and Its Implications
Authors: Kusumgar Sheela , Agrawal D. P. , Bhandari Narendra , Deshpande R. D. , Raina Alok , Sharma Chhemendra , Yadava M. G.
Published: July 2016

We have measured 14C, 210Pb and 137Cs profiles in two representative cores from Manasbal Lake, Kashmir, India. The sedimentation rate derived from 210Pb and 137Cs in the upper part of the core is in the range of 3.4 to 5.5 mm yr−1. In contrast, 14C ages show an inversion at depths >20 cm. These results are attributed to the erosion of the ubiquitous 10–20-m-thick loess mantle, based on the similarity of 14C ages of the inversion layer in the sediments and the paleosols present in the catchment area. Frequency-dependent mineral magnetic susceptibility (χfd), carbon to nitrogen ratios and pigment concentrations in the profile show a significant amount of allochthonous component in the lake deposits and support the conclusion that the 14C dates do not reflect the chronology of the in-situ lake sedimentation but episodic deposition of the surrounding loess. Thus, 14C serves as a useful tracer to understand source components of the sediments.
Sources and Transformation of Dissolved Organic Carbon in the Harp Lake Forested Catchment: The Role of Soils
Authors: Trumbore S. E. , Schiff S. L. , Aravena Ramon , Elgood Richard
Published: July 2016

The 14C content of dissolved organic carbon (DOC) in streams, soil water and groundwaters in the Harp Lake catchment in Ontario, Canada, reflect a mixture of DOC sources, including both contemporary plant material and 14C-depleted soil organic matter. The concentration and isotopic content of DOC in streams is highly variable, reflecting the complex flow path of the source water entering the streams. The characteristics of groundwater DOC are set in the soil column, either through DOC production in the deeper soil layers, or through preferential decomposition and/or sorption of 14C-enriched DOC components from percolating waters. We estimate the relative magnitudes of decomposition, transport and sorption as sinks for DOC produced in forested catchment soils.
Radiocarbon Measurements in South Pacific Ocean Waters in the Vicinity of the Subtropical Convergence Zone
Authors: Sparks R. J. , Drummond G. W. , Brailsford G. W. , Lowe D. C. , Lassey K. R. , Manning M. R. , Taylor C. B. , Wallace Gavin
Published: July 2016

Distribution profiles of radiocarbon in dissolved inorganic carbonate have been measured along two transects in the southern Pacific, east of New Zealand. Use of accelerator mass spectrometry, with its small-sample-size capability, made it possible to sample near-surface waters with a depth resolution of a few tens of meters. Sampling of deeper water was guided by salinity and temperature data transmitted by a conductivity-temperature-depth probe. The measurements, taken over the Chatham Rise, show highly structured profiles that can be correlated with known circulation patterns in this region.
Radiocarbon Dating of Fourteen Dead Sea Scrolls
Authors: Bonani Georges , Ivy Susan , Wölfli Willy , Broshi Magen , Carmi Israel , Strugnell John
Published: July 2016

The name Dead Sea Scrolls refers to some 1200 manuscripts found in caves in the hills on the western shore of the Dead Sea during the last 45 years. They range in size from small fragments to complete books from the holy scriptures (the Old Testament). The manuscripts also include uncanonized sectarian books, letters and commercial documents, written on papyrus and parchment. In only a few cases, direct information on the date of writing was found in the scrolls. In all other cases, the dating is based on indirect archaeological and paleographical evidence. To check this evidence, radiocarbon ages of 14 selected scrolls were determined using accelerator mass spectrometry. The calibrated radiocarbon ages agree well, except in one case, with the paleographic estimates or the specific dates noted on the scrolls.
Direct Radiocarbon Dating of Rock Art
Authors: Russ Jon , Hyman Marian , Rowe Marvin
Published: July 2016

In14C dating of pictographs, we use a low-temperature oxygen plasma coupled with high-vacuum techniques to selectively remove carbon-containing material in the paint without contamination from the rock substrate, even if limestone (CaCO3). In addition to one previously published measurement, we analyzed two more pictograph samples, which are in accord with archaeological inference. A sample of known age charcoal, also processed by our method, matched the control. This technique produces little mass fractionation, the maximum δ13C being 0.16‰ from the untreated sample. Limestone decomposition does not occur during our procedure. Although the technique development is in its infancy, these new results demonstrate that our non-destructive technique has great potential for producing accurate14C ages.
Differences in 14C Age Between Stratigraphically Associated Charcoal and Marine Shell from the Archaic Period Site of Kilometer 4, Southern Peru: Old Wood or Old Water?
Authors: Kennett Douglas J , Lynn Ingram B , Southon John R , Wise Karen
Published: July 2016

Consistently large differences occur in the calibrated 14C ages of stratigraphically associated shell and charcoal samples from Kilometer 4, an Archaic Period archaeological site located on the extreme south coast of Peru. A series of nine shell and charcoal samples were collected from a Late Archaic Period (~6000–4000 BP) sector of the site. After calibration, the intercepts of the charcoal dates were ~100–750 years older than the paired shell samples. Due to the hyper-arid conditions in this region that promote long-term preservation of organic material, we argue that the older charcoal dates are best explained by people using old wood for fuel during the Middle Holocene. Given this “old wood” problem, marine shell may actually be preferable to wood charcoal for dating archaeological sites in coastal desert environments as in southern Peru and Northern Chile.
AMS-14C Chronology of a Lacustrine Sequence from Lake Langano (Main Ethiopian Rift): Correction and Validation Steps in Relation with Volcanism, Lake Water and Carbon Balances
Authors: Gibert Elisabeth , Travi Yves , Massault Marc , Tiercelin Jean-Jacques , Chernet Tesfaye
Published: July 2016

Located in the Ziway-Shala Basin of the Main Ethiopian Rift, Lake Langano is part of an asymmetric half-graben, defined by a series of north-northeast-trending faults in the tectonically active zone of the rift. A 15-m deep succession of organic homogeneous muds, silts, bioclastic sands, and pyroclastic layers was cored in 1994. The definition of a certified radiocarbon chronology on these deposits required the indispensable establishment of modern hydrological and geochemical balances. The isotopic contents of the total dissolved inorganic carbon (TDIC) of surface water clearly show the influence of a deep CO2 rising along the main fault crossing the lake basin. The 5.8 pMC disequilibrium existing in 1994 with the atmosphere likely produces the aging of authigenic materials developing at the lake surface. However, with a mean residence time of ~15 years, this apparent 14C aging of Lake Langano water still integrates the 14C produced by the nuclear tests in the 1960s. Reconstructing the natural 14C activity of the lake TDIC allows for the quantification of the deep CO2 influence, and for the correction of AMS-14C datings performed along the core. The correction of the AMS-14C chronology defined on Lake Langano allows for a better understanding of paleohydrological changes at a regional scale for at least the last 12,700 cal BP.
Challenges in Radiocarbon Dating Organic Carbon in Opal-Rich Marine Sediments
Authors: Zheng Yan , Anderson Robert F , Froelich Philip N , Beck Warren , McNichol Ann P , Guilderson Thomas
Published: July 2016

We explored the reliability of radiocarbon ages obtained on organic carbon phases in opal-rich Southern Ocean sediments. Paired biogenic carbonate and total organic carbon (TOC) 14C analyses for three Southern Ocean cores showed that the TOC ages were systematically younger than the carbonate ages. Carbonate ages were consistent with oxygen isotopic and bio-stratigraphy, indicating error in TOC ages that could be explained by 5–24% of modern carbon contamination of TOC samples. Two possible sources of contamination are: 1) adsorption of atmospheric CO2 or volatile organic compounds to reactive opal surface sites, and 2) fixation of atmospheric CO2 by chemosynthetic bacteria during core storage. In an effort to reduce the modern carbon contamination, diatoms were separated from sediments, purified, and pre-oxidized by concentrated nitric and perchloric acids to permit dating of opal-intrinsic organic carbon (~0.1–0.3% by weight). 14C ages of chemically pre-oxidized opal showed a significant amount of modern carbon contamination, from 11 to 32%, indicating adsorption from the atmosphere of modern carbon onto opal surfaces that were previously cleaned by acid oxidation. Several experiments designed to eliminate the modern C contamination were attempted, but so far we have not been able to obtain a radiocarbon age on 14C-dead Southern Ocean opal-rich sediments, either bulk TOC or purified diatom opal samples, as old as our procedural blank.
Reservoir Corrections for Marine Samples from the South Atlantic Coast, Santa Catarina State, Brazil
Authors: Eastoe C J , Fish S , Fish P , Dulce Gaspar M , Long A
Published: July 2016

Coeval shell and charcoal from Santa Catarina State, Brazil, differ systematically in 14C content, indicating a reservoir effect in marine samples. For modern samples (AD 1939–2000) and archeological samples (2500–1595 BP), the mean 14C age difference between marine and atmospheric carbon is 220 ± 20 years, the marine carbon being older. For three samples dated AD 1939–1944, a distinct reservoir correction of 510 ± 10 years is also observed. The ages of archeological shell samples from Jabuticabeira may be corrected by subtracting 220 years from the apparent 14C ages.
A Simple Procedure for Evaluating Global Cosmogenic 14C Production in the Atmosphere Using Neutron Monitor Data
Authors: Lowe D C , Allan W
Published: July 2016

Radiocarbon (14C) produced by cosmogenic processes in the atmosphere reacts rapidly with atomic oxygen to form 14CO. The primary sink for this species is oxidation by the OH radical, the single most important oxidation mechanism for pollutants in the atmosphere. Hence, knowledge of the spatial and temporal distribution of 14CO allows important inferences to be made about atmospheric transport processes and the distribution of OH. Because the chemical lifetime of 14CO against OH attack is relatively short, 1–3 months, its distribution in the atmosphere should show modulations due to changes in 14C production caused by variations in the solar cycle. In this work we present a simple methodology to provide a time series of global 14C production to help interpret time series of atmospheric 14CO measurements covering the whole of solar cycle 23. We use data from neutron monitors, a readily available proxy for global 14C production, and show that an existing 6-year time series of 14CO data from Baring Head, New Zealand, tracks changes in global 14C production at the onset of solar cycle 23.
Radiocarbon Ages of Lacustrine Deposits in Volcanic Sequences of the Lomas Coloradas Area, Socorro Island, Mexico
Authors: Farmer Jack D. , Farmer Maria C. , Berger Rainer
Published: July 2016

Extensive eruptions of alkalic basalt from low-elevation fissures and vents on the southern flank of the dormant volcano, Cerro Evermann, accompanied the most recent phase of volcanic activity on Socorro Island, and created the Lomas Coloradas, a broad, gently sloping terrain comprising the southern part of the island. We obtained 14C ages of 4690 ± 270 BP (5000–5700 cal BP) and 5040 ± 460 BP (5300–6300 cal BP) from lacustrine deposits that occur within volcanic sequences of the lower Lomas Coloradas. Apparently, the sediments accumulated within a topographic depression between two scoria cones shortly after they formed. The lacustrine environment was destroyed when the cones were breached by headward erosion of adjacent stream drainages. This was followed by the eruption of a thin basaltic flow from fissures near the base of the northernmost cone. The flow moved downslope for a short distance and into the drainages that presently bound the study area on the east and west. The flow postdates development of the present drainage system and may be very recent. Our 14C data, along with historical accounts of volcanic activity over the last century, including submarine eruptions that occurred a few km west of Socorro in early 1993, underscore the high risk for explosive volcanism in this region and the need for a detailed volcanic hazards plan and seismic monitoring.
Late Pleistocene-Recent Atmospheric δ13C Record in C4 Grasses
Authors: Toolin Laurence J. , Eastoe Christopher J.
Published: July 2016

Samples of Setaria species from packrat middens, herbarium specimens and modern plants preserve a record of δ13C of atmospheric CO2 from 12,600 BP to the present. No secular trend is detected between 12,600 and 1800 BP, when the mean value of δ13C during that period was −6.5 ± 0.1‰ (the error is the standard deviation of the mean). Our value agrees with δ13C averages of pre-industrial CO2 from polar ice cores, and differs significantly from modern regional (-8.2 ± 0.1‰) and global (-7.7‰) values, which are higher because of fossil fuel burning.
Carbon Isotopic Composition of Deep Carbon Gases in an Ombrogenous Peatland, Northwestern Ontario, Canada
Authors: Aravena Ramon , Warner B. G. , Charman D. J. , Belyea L. R. , Mathur S. P. , Dinel Henri
Published: July 2016

Radiocarbon dating and carbon isotope analyses of deep peat and gases in a small ombrogenous peatland in northwestern Ontario reveals the presence of old gases at depth that are 1000–2000 yr younger than the enclosing peat. We suggest that the most likely explanation to account for this age discrepancy is the downward movement by advection of younger dissolved organic carbon for use by fermentation and methanogens bacteria. This study identifies a potentially large supply of old carbon gases in peatlands that should be considered in global carbon models of the terrestrial biosphere.
On the Artistic Situation of the Contemporary Czech Theatre (1945)
Authors: Mukařovský Jan
Published: July 2016

The world storm, which has now passed, left its marks on all areas of artistic creation. Everywhere that Fascism reached, it disturbed the internal coherence of things, and their respective relationships, in order to create a formless, passive mixture, incapable of initiative. As far as art is concerned, Fascism has proclaimed the slogan of perverse art, and declared a struggle of annihilation against such art. In praxis, however, the particular artistic methods that had been created—through the modern art that was blacklisted—remained intact, because those methods did not create a system, or express a particular artistic desire, through which an intentional artistic will could have created a gap in the totality of violence. It is natural that this state of affairs endangered not only the cohesion of the internal elements of the artistic structure, but also the consistency of the functional organization of persons and institutions serving the art. The artistic schools and movements disappeared, or were at the very least disrupted. The affiliations of creative artists with distinct associations and societies became in many instances more a matter of external circumstances than of artistic decision.
Spiral structure in external galaxies
Authors: Morgan W. W.
Published: July 2016

The need for observing at least four different categories of optical objects for a satisfactory definition of optical spiral structure is emphasized. A sequence of optical form-types for the description of spiral structure is outlined. A pronounced difference in the nature of the spiral structure of the outer and inner parts of Messier 33 is illustrated. Striking local differences between spiral arms defined by differing criteria are noted.
The distribution of dark nebulae in late-type spirals
Authors: Lynds B. T.
Published: July 2016

Seventeen Sc- galaxies have been studied in order to determine the distribution of dark nebulae within them. Hα plates were used to compare the distribution of obscuring material with the location of H II regions, and it was found that the H II regions are always tangent to or imbedded in regions of high obscuration. Sandage's conclusions are confirmed that strong, regular dust lanes exist in the central regions of these galaxies and wind outward on the inside edge of the two prominent arms. Characteristic dimensions of the dust lanes are noted, and secondary dust characteristics are described.
Density distribution and the radial velocity field in the spiral arms of M31
Authors: Einasto J. , Rümmel U.
Published: July 2016

The density distribution and the radial velocity field in the Andromeda galaxy, M 31, have been studied on the basis of the 21-cm radio-line data from Jodrell Bank and Green Bank. The true density has been obtained from the observed one by solving a two-dimensional integral equation. As the resolving power of the radio telescopes is too low to locate all spiral arms separately, optical data on the distribution of ionized hydrogen clouds have been also used. The mean radial velocities have been derived by solving a two-dimensional non-linear integral equation with the help of hydrogen densities, and a model radial velocity field.

The inner concentrations of hydrogen form two patchy ringlike structures with mean radii 30′ and 50′, the outer concentrations can be represented as fragments of two leading spiral arms.

The rotational velocity, derived from the radial velocity field, in the central region differs considerably from the velocity curves obtained by earlier authors. The difference can be explained by the fact that in this region the correction for the antenna beam width is much greater than adopted by previous investigators.
H II Regions in NGC 628, NGC 4254 and NGC 5194
Authors: Chuvaev K. , Pronik I.
Published: July 2016

Multicolour observations of galaxies are being carried out at the prime focus of the 2.6 m Schajn telescope using an image converter and 6–9 colour filters. The effective wavelengths are approximately 3600, 3730, 4400, 4680, 5090, 5280, 6090, 6600 and 7400 Å. The filters for 3730, 5090 and 6600 Å are centred on emission lines. For absolute calibration extrafocal star images are used.
Spiral structure of neutral hydrogen in our Galaxy
Authors: Kerr F. J.
Published: July 2016

This paper discusses the evidence on the hydrogen spiral structure which is available from 21-cm observations. The problems involved in deriving a hydrogen map are discussed, and one interpretation of the spiral pattern is presented. Some of the major characteristics of the H I in spiral arms are discussed, and a comparison is made between the kinematics of H I and H II.
Radio observations of some details in the H I local spiral arm
Authors: Bystrova N. V. , Gossachinsky J. V. , Egorova T. M. , Rozanov V. M. , Ryzhkov N. F.
Published: July 2016

The observations were made with the large Pulkovo radiotelescope (beamwidth 7′, bandwidth 20 and 10 kHz). Figure 1 contains our drift curves across the cluster NGC 2264. The details on them may be identified with Raimond's (1966) clouds, but the proofs for the reality of the connection between the cluster and the clouds are not very reliable. The cloud ‘b’ is believed to be connected with NGC 2264 because of their close neighborhood. But on the other side of the galactic plane in this region we have found a bright and narrow (∼1°) detail, whose middle falls exactly on the western border of the H II region around the star λ Orionis (Figure 2). Figure 3 contains the computed drift curves at different velocities for Δf = 20 kHz according to the model of the neutral hydrogen expanding envelope proposed by Wade (1957) around the H II region λ Ori. Figure 4 represents our observations. Although some details, in particular the narrow detail at the velocity −1.4 km s−1, are very similar to the calculated ones, our observations differ from Wade's model in that they do not have any velocity symmetry relative to zero; in fact the details are situated only at the positive side. This fact may eliminate one half of the proposed envelope. There is no symmetry relative to the central star and no coincidence of the velocity of the narrowest detail with the velocities of the central star and nebula.
Space distribution of interstellar dust in connection with the galactic spiral structure
Authors: Uranova T. A.
Published: July 2016

A maximum of dust density along the inner edge of the Cygnus arm is found. It seems that the same happens along the inner edges of the Perseus and the Sagittarius arms.
Questions concerning the usefulness and feasibility of large-scale stellar statistics
Authors: Seitter W.
Published: July 2016

A proposal for a cooperative effort to secure three-color photometry of all stars up to the 18th magnitude of a 10° field around the galactic equator has been made.
Particle resonance in a spiral field
Authors: Barbanis B.
Published: July 2016

Plane galactic orbits near the particle resonance of a spiral field have been calculated numerically. Besides the ring type orbits, i.e. orbits filling a ring around the galactic center, there are orbits librating near the potential maxima at the co-rotation distance (Lagrangian points). This effect tends to disrupt the spiral arms at the co-rotation distance.
Magnetic fields and spiral structure
Authors: Woltjer L.
Published: July 2016

The most valuable new information on galactic magnetic fields is derived from the study of Faraday effects in extragalactic radio sources and pulsars. The rotation of the plane of polarization of an electromagnetic wave with a wavelength of 1 m – the so called Rotation Measure RM – which traverses a medium with electron density ne (cm−3) and magnetic field intensity H (in μG) is given by
where dl is the element of length along the line of sight expressed in pc. In the case of the pulsars, the delayed arrival of the pulses at the longer wavelengths immediately yields the integrated electron density along the line of sight, that is
Dynamical Implications of Deep HST Imaging of Globular Clusters
Authors: King Ivan R.
Published: July 2016

HST observations contribute in many ways to a better understanding of the dynamical nature of globular clusters. Unprecedentedly faint photometry gives new determinations of the numbers of low-mass stars. Cluster-to-cluster differences at the faint ends of the mass functions suggest differences in dynamical evolution. Mass segregation is clearly observed, from the envelope inward to the dense cluster center. The distribution of stars in the hitherto unresolved cores gives new data with which to test theories of core collapse, and these core profiles are also sensitive to the number of unseen remnant stars and binaries at the cluster center.
The Role of Binaries in the Dynamical Evolution of the Core of a Globular Cluster
Authors: Hut Piet
Published: July 2016

The size of the core is one of the main diagnostics of the evolutionary state of a globular cluster. Much has been learned over the last few years about the behavior of the core radius during and after core collapse, under a variety of different conditions related to the presence or absence of large numbers of binaries. An overview is presented of the basic physical principles that can be used to estimate the core radius. Four different situations are discussed, and expressions are presented for the ratio rc/rh of core radius to half mass radius. The regimes are: deep collapse in the absence of primordial binaries; steady post-collapse evolution after primordial binaries have been burned up; chaotic post-collapse evolution under the same conditions; and post-collapse evolution in the presence of primordial binaries. In addition, modifications to all of these cases are indicated for the more realistic situation where effects of the galactic tidal field are taken into account.
Star Cluster Simulations on HARP
Authors: Aarseth Sverre J.
Published: July 2016

We describe some aspects of implementing star cluster simulations on HARP. The code NBODY4 employs the Hermite scheme with hierarchical block-steps for direct integration. The algorithms have been optimized for parallel processing with the eight pipeline HARP-2 delivering a peak performance of about 1.7 Gflops forN= 104particles. Hard binaries are studied by KS regularization which also uses the Hermite scheme, whereas strong interactions between 3–5 particles are treated by chain regularization. Astrophysical processes modelled include mass loss by stellar evolution, two-body tidal interaction, Roche lobe mass transfer, common envelope evolution, magnetic braking and gravitational radiation. Consistent values of stellar radii and evolution type are obtained by fast look-up. A new formulation of collision outcomes yields blue stragglers and other exotic objects. Some recent results for an open cluster model are presented.
Pulsars in Globular Clusters
Authors: Kulkarni S. R. , Anderson S. B.
Published: July 2016

Since the discovery of the first globular cluster pulsar in M28 (Lyne et al. 1987) a total of 33 pulsars have been found to reside within 13 seperate clusters. Many (but not all) of the cluster pulsars have properties similar to the millisecond pulsars in the disk: short period, binarity and low magnetic field strength. The common understanding is that these pulsars are primordial neutron stars (i.e. the remnants of massive stars in clusters) which have been spun up by accretion of matter from a companion. Therefore, in this framework, the cluster pulsars are descendents of Low Mass X-ray Binaries (LMXBs) (Alpar et al. 1982). This hypothesis is by no means accepted by all workers (e.g. Michel 1987, Ray & Kluzniak 1990, Romani 1990, Bailyn & Grindlay 1993). These workers have argued that at least some (if not all) cluster pulsars could be formed by accretion induced collapse of massive white dwarfs. In either case, it is clear from the sensitivity limits of current cluster searches, and the luminosity of field pulsars, that there are currently O(103) extant radio pulsars in the Galactic globular cluster system.

In this review, specifically targeted for astronomers working in the field of globular clusters, not pulsar astronomers, we argue that cluster pulsars have provided us with a new window into the population of long-dead massive stars and the physics of tidal capture. The precision with which pulsars can be timed has created new diagnostics: measurement of the mass distribution in the dense cores, measurement of orbital evolution on short timescales and precise determination of orbital characteristics. It is fair to say that all these diagnostics are unique, and not obtainable by other observations. Despite this, it is our assessment that the typical astronomer who works in the field of globular clusters is apparently unaware of these relevant contributions. Hopefully this review will bridge this gap. A complete copy of the review article may be found at http://astro.caltech.edu/~srk.
Diagnosing Structure and Evolution of Clusters with Neutron Star Binaries
Authors: Wijers Ralph A.M.J.
Published: July 2016

A key problem in using binaries as a tool for diagnosing cluster evolution is that the tool itself is not very well understood. The theory of binary evolution, despite real successes that can be exploited, has serious problems in many areas relevant to cluster evolution. At least as important but often neglected are connective problems, which arise when theoretical model binaries need to be related to observed classes of object, which often requires poorly understood parts of their physics which can be quite irrelevant to their bulk properties. I shall discuss these issues in general briefly, and then illustrate them with the specific example of X-ray binaries and millisecond pulsars.
Stellar Encounters in Dense Systems
Authors: Davies Melvyn B.
Published: July 2016

The number density of stars in the solar neighbourhood is sufficiently low that encounters between two stars will be extremely rare. However, in the cores of globular clusters, and glactic nuclei, number densities are sufficiently high (∼ 105 stars/pc3 in some systems) that encounter timescales can be comparable, or even less than, the age of the universe. In other words, a large fraction of the stars in these systems will have suffered from at least one close encounter or collision in their lifetime.
Properties of Globular Cluster System: Primordial or Evolutional?
Authors: Surdin Vladimir
Published: July 2016

Some observable relationships between globular cluster parameters appear as a result of long time dynamical evolution of the cluster system. These relationships are inapplicable to the studies of the globular clusters origin.
Central Densities of Star Clusters in the Magellanic Clouds
Authors: Kontizas M. , Gouliermis D. , Kontizas E.
Published: July 2016

The way star cluster systems in galaxies are forming and survive seem to depend on the relation of the central density ρ (at half mass radius) of each cluster with its galactocentric distance Rgc. It is found that this relation takes the form of:
The cluster systems of our Galaxy and of the two Magellanic Clouds, have been investigated. We have taken the cluster system of the conventional globulars of our Galaxy whereas the young and old systems of clusters in the LMC and SMC were treated separately. The radial distributions of central densities and half mass radii were found for all these systems showing a definite trend which depends on: (α) The total mass of the parent galaxy & (β) The age of the cluster system (young - old). It therefore appears that the total mass and/or the morphology of the parent galaxy plays a major role on the loci where clusters survive and form.
The Depletion of Giants in Globular Clusters
Authors: Portegies Zwart Simon F.
Published: July 2016

A significant depletion of red giants is observed in the central regions of post-collapsed globulars (Djorgovski et al., 1993) like M 15 (Stetson, 1991). A simple model shows that the depletion of red giants in the high-density cores of globular clusters can be understood in terms of mutual stellar collisions. Slightly outside the core stellar collisions are not frequent enough to explain the reduction in the observed number of red giants.
Grape-SPH Simulations of Globular Cluster Formation
Authors: Nakasato N. , Mori M. , Tujimoto T. , Mathews G. , Nomoto N.
Published: July 2016

We examine two globular cluster formation scenarios with SPH simulations, using GRAPE-3AF. First model is the spontaneous collapse, which is found to induce a disruption of the system. However, the system can survive when sufficiently high external pressure exists. Second model is the collision of the two proto-cluster clouds, which can form a bound stellar system due to efficient cooling and a burst of star formation.
Truncation of the Binary Distribution Function in Globular Cluster Formation
Authors: Vesperini E. , Chernoff D.F.
Published: July 2016

Recent observational searches suggest that the frequency of primordial binaries in globular clusters may reach ~ 10% (see Hut et al. 1992 for a review). Several different treatments conclude that primordial binaries are effective in halting core collapse, supporting the core and driving the post-core collapse expansion phase (Goodman & Hut 1989, McMillan et al. 1990, 1991, Gao et al. 1991, Heggie & Aarseth 1992, McMillan & Hut 1994). The abundance and binding energy distribution have a direct impact on observable characteristics of globular clusters such as the size of the core radius (Vesperini & Chernoff 1994). In this analysis we have investigated how the initial binary distribution function may be altered in the formation of a cluster; the key question we have addressed is whether it is possible for binaries, assumed to be primordial, to survive the birth of the cluster. A detailed description of our results is in Vesperini & Chernoff (1995).