bluuebunny/crossref_metadata_2025_split huggingface dataset:
Progress of the Large Interferometer at CERGA
Authors: Labeyrie A. , Schumacher G. , Thom C. , Dugué M. , Foy F. , Foy R. , Cormier P. , Vakili F. 
Published: July 2016

SummaryThe coude beams from a pair of 1.5 meter telescopes are recombined to achieve coherent aperture synthesis. The spherical telescopes move along a 70-meter baseline, expandable to 300 meters. For the VLT, a grid of railway tracks with 2-D carriages meets the requirements for incoherent and coherent observing.Steps in the design and construction of a coherent telescope array have been described previously (Labeyrie, 1982, 1984). In 1975, it was first verified that stellar light from two telescopes could be recombined coherently. In 1978, it was decided to develop spherical mounts for 1.5-meter telescopes. Among the expected features were: 1. coude focus with only one flat mirror; 2. wheels for mobility along railway tracks; 3. structural stiffness for interferometric stability, also implying vibration amplitudes inferior to 0.1 micrometer at each reflective surface. This last and most critical requirement implies materials which have to be stiff and also damped.
A Modular Structural Design for a Spectrographical MMT
Authors: Freire Ferrero Rubens , Chevreton Michel , Felenbok Paul 
Published: July 2016

SummaryWith the aim to propose alternative solutions for Multi Mirror Telescopes, we present some ideas about a MMT for High Resolution Spectroscopy purposes. The alternative solution is intended both in technical conception and in economical costs.This possible project consider the use of a system of 36 mirrors about 1.5 meter in diameter, collecting light independently each other and transmitting the light down to the slit spectrograph by optical fibers.To reduce mirror costs and structural weight, we propose to develop the “replique” technique over light-weighted supports modelled and adjusted over a master convex mirror.Different project design for a modular hive structure are considered.
Some Possible VLT Sites in Chile
Authors: Ardeberg A. , Lindgren H. 
Published: July 2016

AbstractA report is given on the site-testing programme for a Very Large Telescope in Chile. Data are now available from seven months of investigations. Comments are made on the places which have so far seemed most attractive. Meteorological data from constant monitoring of a coastal mountain, Paranal, are presented and discussed. These data indicate an average percentage of photometric nights of around 85. Atmospheric integrated water-vapour content seems very low in the winter but relatively high in the summer. Other meteorological parameters seem favourable for astronomical observations.
Fabry-Perot Spectrographs for VLT's
Authors: Monnet Guy 
Published: July 2016

Four Reasons are advocated to stress the interest of Fabry-Perot Spec-trographs (F.P.S.) as potentially useful instruments for the future Very Large Telescopes :-Reasonably wide spectrum of Astronomical uses-Good use of Telescope area-Relative cheapness-Versatility
Considerations in Photographic Detection for Very Large Telescopes
Authors: Millikan Allan G. 
Published: July 2016

AbstractCurrent practice with four-meter reflectors is reviewed and the good match with fine-grained photographic plates of high DQE is examined. The present designs of 15-meter-class telescopes appear to point to instruments with a large flat focal plane and an image scale in the 5 arc sec/mm range. This requires an emulsion of considerably larger microcrystal size than currently used. Extension of the present emulsion type to the required grain size is not likely to be efficient; however, the use of new emulsion technologies should offer the opportunity to devise appropriate photographic detectors for use with an f/6, 5 arc sec/mm telescope. A gain in detective quantum efficiency appears possible.
Emploi de la caméra électronique grand champ avec les très grands télescopes - Extrapolation des résultats obtenus avec le télescope C.F.H.
Authors: Wlérick G. , Renard L. , Horville D. , Gex F. , Munier J.M. , Lelièvre G. , Llebaria A. , Bijaoui A. , Dubout R. , Petit M. 
Published: July 2016

Abstractthe large field Lallemand electronographic camera has proved to be an ideal receptor for bidimensional photometry with the C.F.H. 3.6 m. Telescope. It permits to measure faint stars up to about B = 25. Plates of a large variety of objects have been obtained ; for example : crowded fields such as the nearby galaxy Messier 33 ; fields where one must recognize faint galaxies from stars; objects for which a high spatial resolution is needed, such as the optical jet of Messier 87 or gravitational lenses. It is possible to predict the limits of the receptor with a very large telescope.
The 15-Meter National New Technology Telescope: an Update
Authors: Barr L.D. 
Published: July 2016

The 15-Meter National New Technology Telescope (NNTT) Program, growing out of the earlier "Next Generation Telescope" studies at Kitt Peak National Observatory, is now responding to the recently published recommendation of the Astronomy Survey Committee of the American National Academy of Sciences:"...the construction of a New Technology Telescope (NTT) [NNTT] in the 15-m class on the ground for observations in the optical and in the near- and mid-infrared regions of the spectrum (0.3-to 20µm wavelength). The design studies needed before the NNT can be constructed are of the highest priority and should be undertaken immediately."
The Penn State Spectroscopic Survey Telescope
Authors: Ramsey L.W. , Weedman D.W. 
Published: July 2016

AbstractTo map the distribution of galaxies and quasars in the universe, we desire a telescope large enough to obtain spectra to about 20th magnitude in under 20 minutes integration and which is devoted entirely to such spectroscopic survey projects in dark time. We also desire extensive bright time observing to monitor large numbers of G-M stars with high-resolution spectroscopy for many years in search of solar-like activity. These projects are suited to a telescope with a large fixed primary, assembled from many spherically figured segments. We present a design for such a telescope that consists of 73 segments, each of 0.9-m diameter and 26-m radius of curvature. Mirror blanks of this size can be cut from standard Pyrex sheets. Effective aperture of the telescope exceeds 7-m; the focal plane system can track objects for 40 minutes, and sky coverage of 48 degrees is obtained by using a fixed tilt for the primary and making the entire telescope and dome rotatable. The focal plane system is lightweight and precisely pointable because spectrographs are coupled to the focus by fiber optic cables. Off-the-shelf components and existing technology are used to keep engineering and development costs low; we must remain within a budget feasible for a university. Because the telescope will be equipped with standard, minimal instrumentation and is intended for very routine observing programs, operating costs will also be low. Hardware components are now being assembled in a laboratory to develop the focal plane control system and the mirror support system.
Cepheid Radii from Infrared Photometry
Authors: Welch D. L. , Evans Nancy Remage , Drukier G. 
Published: July 2016

AbstractWe have determined radii for Cepheids using nearinfrared K(2.2 µm) photometry and Balona’s approach to the Baade-Wesselink method of radius determination. The lower sensitivity of the K flux to temperature variations results in improved sensitivity to radius changes. We present the results of maximum-likelihood radius solutions for Cepheids with modern radial velocity curves. We point out limitations of the Balona technique as it is currently applied in the optical and suggest improvements.
Light-Curve Parameters of Northern Galactic Cepheids
Authors: Moffett Thomas J. , Barnes Thomas G. 
Published: July 2016

AbstractThe BVRI light-curve parameters of 112 galactic Cepheids are determined by Fourier analysis using over 4,000 differential photoelectric observations. This catalog is similar to Schaltenbrand and Tammann's except that it is based on a homogeneous data set and the Fourier coefficients are given.
On The Binary Nature of 89 Herculis
Authors: Arellano Ferro A. 
Published: July 2016

AbstractThe radial velocities of 89 Herculis (89 Her) between 1977 and 1981 show a clear periodicity of about 285 days. This periodic variation is interpreted as the orbital variation of 89 Her around an unseen companion. From the orbital elements no support is found for a low mass (M ~ 2Mʘ ) for 89 Her, but rather a high mass (13 < M/Mʘ < 24) is preferred.
The Quasi-Cepheid Nature of Rho Cassiopeiae
Authors: Percy John R. , Keith David 
Published: July 2016

Rho Cassiopeiae (HR 9045, HD 224014) is a bright yellow supergiant (F8pla). If it is a member of the association CAS 0B5, it has an Mv of about -9.5, and is therefore one of the most luminous yellow supergiants known (Humphreys 1978).The brightness of ρ Cas varies in two ways: (i) it undergoes semiregular cycles with amplitudes of about and time scales of about a year, perhaps due to pulsation, and (ii) in the 1940's, it faded by more than a magnitude for 660 days (Gaposchkin 1949); as a result, it is often classified as “R CrB?”. Although various writers have pointed to a dissimilarities between p Cas and the R CrB stars, it should be noted that R CrB itself undergoes semi-regular cycles as well as fadings. Thus the scientific interest of p Cas lies in the nature of its variations, their possible relationship to each other and to the mass loss and extreme luminosity of the star.
Cepheid Evolution
Authors: Becker S. A. 
Published: July 2016

AbstractA review of the phases of stellar evolution relevant to Cepheid variables of both Types I and II is presented. Type I Cepheids arise as a result of normal post-main sequence evolutionary behavior of many stars in the intermediate to massive range of stellar masses. In contrast, Type II Cepheids generally originate from low-mass stars of low metalicity which are undergoing post core helium-burning evolution. Despite great progress in the past two decades, uncertainties still remain in such areas as how to best model convective overshoot, semiconvection, stellar atmospheres, rotation, and binary evolution as well as uncertainties in important physical parameters such as the nuclear reaction rates, opacity, and mass loss rates. The potential effect of these uncertainties on stellar evolution models is discussed. Finally, comparisons between theoretical predictions and observations of Cepheid variables are presented for a number of cases. The results of these comparisons show both areas of agreement and disagreement with the latter result providing incentive for further research.
Invited Review: Cepheid Variables as Extra-Galactic Distance Indicators
Authors: Madore Barry F. 
Published: July 2016

SummaryThe role of cepheid variables in establishing the inner distance scale to nearby galaxies is discussed. Emphasis is placed on the necessity for broad wavelength coverage in attempting to account for metalliclty differences and reddening internal to the parent galaxies. In addition linear detectors are essential in minimizing the effects of any unresolved background contibution to the photometry. Recent infrared observations of Cepheids in Local Group galaxies are surveyed and all published data on extragalactic Cepheids are presented for convenient access.
Ultraviolet Spectroscopy of Cometary Comae
Authors: Feldman Paul D. 
Published: July 2016

AbstractDuring the past decade, vacuum ultraviolet spectra of over 30 comets have been obtained with theInternational Ultraviolet Explorer(IUE) satellite observatory. With few exceptions, the spectra of these comets appear to be similar, with OH and H produced by the photodissociation of water being the dominant species and emissions of C, O, S, CS and CO+2usually present. Although signs of variability of many kinds in comet spectra appear, the evidence from the ultraviolet observations suggests that all comets have the same basic chemical composition and that observed differences are due to evolution and ageing processes. The principal exception is S2, which was detected byIUEin comet IRAS-Araki-Alcock (1983 VII), but not in any other comet to date. During the 1985–86 apparition of comet Halley, ultraviolet spectra were also obtained by other spacecraft and by sounding rocket instruments, including a long-slit imaging spectrograph. Further advances await future ultraviolet observations of comets by theHubble Space Telescopeand other planned ultraviolet astronomy missions.
The Accumulation and Structure of Comets
Authors: Donn Bertram 
Published: July 2016

AbstractThe evidence for the accumulation of the terrestrial planets and comets from solid grains is reviewed briefly. The various proposals for formation of cometary nuclei are described and commented upon. With three exceptions, all hypotheses conclude or imply that a single compact object forms. It has been almost universally assumed that grain accretion produced compact aggregates as is the case with liquid drops, and that this process continued. Several hypotheses start with Goldreich-Ward-type gravitational instabilities. The collapse for this case also occurs at low velocities in the cm·s−1to m·s−1range. Experiment and theory show that under these conditions, low-density, filamentary clusters form that are fractal aggregates with a fractal dimension approximately equal to two. Agglomeration of these clusters produces larger, compressible planetesimals or cometesimals, which efficiently combine upon colliding. In order to form cometary nuclei, the initial temperature must be about 50 K and not undergo a significant temperature rise during the accumulation process. The collision process can be analyzed with some simplifying assumptions using the limited experimental data available for the compaction of low-density powders. The calculations show that accumulation will occur at low temperatures. For a more refined analysis, experiments to study impacts on low-density powders are required. Models of cometary nuclei are reviewed, and a simple model of the structure that results from the accumulation of fluffy aggregates is described.
Noble Gases in Terrestrial Planets: Evidence for Cometary Impacts?
Authors: Owen Tobias , Bar-Nun Akiva , Kleinfeld Idit 
Published: July 2016

AbstractThe possible role of comets in bringing volatiles to the inner planets is investigated by means of laboratory studies of the ability of ice to trap gases at low temperatures. The pattern of the heavy noble gases formed in the atmosphere of Venus can be explained by the impact of a planetesimal composed of ices formed in the range of 20 to 30 K. The noble gas patterns on Mars and Earth are less explicable by cometary bombardment alone.
Biological Implications of Organic Compounds in Comets
Authors: Marcus Joseph N. , Olsen Margaret A. 
Published: July 2016

AbstractOrganic chemicals — compounds that contain carbon — are the substance of life and pervade the universe. Is there a connection between comets, which are rich in prebiotic organics, and the origin of life? Current concepts of biomolecular evolution are first reviewed, including the important paradigm of catalytic RNA. At the very least, impacting comets appear to have supplied a substantial fraction of the volatile elements required for life shortly after the Earth formed. Some impacting material may even have survived chemically intact to directly provide necessary complex prebiotic organic chemicals. For life to originate and evolve in comets themselves, liquid H2O would be absolutely required: arguments for and against26Al radiogenic melting of cometary cores are presented. Cometary panspermia, if theoretically possible, is not necessary to explain the origin of life on Earth. The Halley spacecraft provide evidence against Earth-type microorganisms in this comet’s dust.
Dynamical History of the Oort Cloud
Authors: Weissman Paul R. 
Published: July 2016

AbstractDynamical studies during the past decade have resulted in an almost explosive increase in our understanding of the Oort cloud of comets, which surrounds the solar system. Cometary orbits in the cloud evolve under the complex interaction of stellar, galactic, and giant molecular cloud perturbations, as well as planetary and nongravitational perturbations when the orbits re-enter the planetary region. Evidence has continued to build for a dense, inner Oort cloud of comets which acts as a reservoir to replenish the outer cloud as comets there are stripped away. A ring of comets beyond the orbit of Neptune, which may be the source of the short-period comets, is also likely. Both the estimated number and mass of comets in the Oort cloud have grown such that the total mass may be comparable to the mass of the planets. Temporal variations in the flux of comets from the Oort cloud into the planetary region by a factor of 50% are typical, and by factors of 20 to 200 are possible. The most intense cometary “showers” may have serious implications for biological extinction events on Earth as well as for the impact history of planets and satellite systems. Comets in the Oort cloud are processed by galactic cosmic rays, heated by nearby supernovae, eroded by interstellar dust impacts, and disrupted by mutual collisions (in the inner cloud). A detailed estimate of the Oort cloud’s dynamical history is not possible because of the inability to reconstruct the Sun’s varying galactic motion over the history of the solar system, and because of uncertainty over where comets actually formed. However, it is likely that a substantial fraction of the original Oort cloud population has been lost to interstellar space. We are approaching the time when Oort clouds around other stars may be detectable, though searches to date have so far been negative.
A comprehensive phylogeography of the Hyles euphorbiae complex (Lepidoptera: Sphingidae) indicates a ‘glacial refuge belt’
Authors: Mende Michael B. , Bartel Manuela , Hundsdoerfer Anna K. 
Published: July 2016

AbstractWe test the morphology based hypothesis that the Western Palaearctic spurge hawkmoths represent two species, the Eurasian H. euphorbiae and Afro-Macaronesian H. tithymali. It has been suggested that these species merged into several hybrid swarm populations, although a mitochondrial phylogeography revealed substructure with local differentiation. We analysed a three-gene mt-dataset (889 individuals) and 12 microsatellite loci (892 individuals). Microsatellite analyses revealed an overall weak differentiation and corroborated the superordinate division into two clusters. The data indicate that the populations studied belong to only one species according to the biological species concept, refuting the opening hypothesis. A future taxonomic revision appears necessary to reflect the division into two subgroups. Ancestral mitochondrial polymorphisms are retained in H. euphorbiae, indicating gene flow within a broad ‘glacial refuge belt’ and ongoing postglacial gene flow. Diverse patterns of extensive mito-nuclear discordance in the Mediterranean and the Middle East presumably evolved by more recent processes. This discordance indicates introgression of H. tithymali-related mitochondrial haplogroups, accompanied (to a lesser degree) by nuclear alleles, into Italian and Aegean H. euphorbiae populations as recently as the late Holocene. The complex mosaic of divergence and reintegration is assumed to have been influenced by locally differing environmental barriers to gene flow.
Integrin β6 serves as an immunohistochemical marker for lymph node metastasis and promotes cell invasiveness in cholangiocarcinoma
Authors: Li Zequn , Biswas Siddhartha , Liang Benjia , Zou Xueqing , Shan Liqun , Li Yang , Fang Ruliang , Niu Jun 
Published: July 2016

AbstractCholangiocarcinoma is a devastating malignancy that is notoriously difficult to diagnose and is associated with a high mortality. Despite extensive efforts to improve the diagnosis and treatment of this neoplasm, limited progress has been made. Integrin β6 is a subtype of integrin that is expressed exclusively on the surfaces of epithelial cells and is associated with a variety of tumors. In the present study, we investigated the expression and roles of integrin β6 in cholangiocarcinoma. β6 upregulation in cholangiocarcinoma was correlated with lymph node metastasis and distant metastasis. Moreover, integrin β6 was identified as a biomarker for the diagnosis of cholangiocarcinoma and an indicator of lymph node metastasis. Integrin β6 significantly promoted the proliferation, migration and invasion of cholangiocarcinoma cells. Furthermore, integrin β6 increased Rac1-GTPase, resulting in the upregulation of metalloproteinase-9 (MMP9) and F-actin polymerization. Taken together, our results indicate that integrin β6 promotes tumor invasiveness in a Rac1-dependent manner and is a potential biomarker for tumor metastasis. Integrin β6 may help to improve the diagnostic accuracy and targeting β6 may be a novel strategy for the treatment of cholangiocarcinoma.
A new way towards high-efficiency thermally activated delayed fluorescence devices via external heavy-atom effect
Authors: Zhang Wenzhi , Jin Jiangjiang , Huang Zhi , Zhuang Shaoqing , Wang Lei 
Published: July 2016

AbstractThermally activated delayed fluorescence (TADF) mechanism is a significant method that enables the harvesting of both triplet and singlet excitons for emission. However, up to now most efforts have been devoted to dealing with the relation between singlet-triplet splitting (ΔEST) and fluorescence efficiency, while the significance of spin-orbit coupling (SOC) is usually ignored. In this contribution, a new method is developed to realize high-efficiency TADF-based devices through simple device-structure optimizations. By inserting an ultrathin external heavy-atom (EHA) perturber layer in a desired manner, it provides useful means of accelerating the T1 → S1 reverse intersystem crossing (RISC) in TADF molecules without affecting the corresponding S1 → T1 process heavily. Furthermore, this strategy also promotes the utilization of host triplets through Förster mechanism during host → guest energy transfer (ET) processes, which helps to get rid of the solely dependence upon Dexter mechanism. Based on this strategy, we have successfully raised the external quantum efficiency (EQE) in 4CzPN-based devices by nearly 38% in comparison to control devices. These findings provide keen insights into the role of EHA played in TADF-based devices, offering valuable guidelines for utilizing certain TADF dyes which possess high radiative transition rate but relatively inefficient RISC.