5,012 research outputs found

    Lithostratigraphy, sedimentation and evolution of the Volta Basin in Ghana

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    We present a revised lithostratigraphy for the Voltaian Supergroup of Ghana, based on a review of existing literature, interpretations of remotely sensed data and reconnaissance field survey of the Volta Basin. These strata thicken eastwards, to a maximum of between 5 and 6 km adjacent to the Pan-African Dahomeyide orogen. They began to accumulate some time after about 1000 Ma, along the margin of an epicontinental sea. Initial sedimentation, comprising the age-equivalent Kwahu and Bombouaka Groups, shows a cyclical mode of deposition controlled by eustatic changes in sea-level that produced a range of nearshore marine, littoral and terrestrial environments. A major erosional interval was followed by deposition of the 3–4 km thick Oti-Pendjari Group. Basal tillites and associated sandy diamictons are correlated with the Marinoan (end-Cryogenian) glaciation, indicating a maximum depositional age of about 635 Ma. The overlying cap carbonates and tuffs were deposited within a shallow epeiric sea bordered by a volcanically active rift system. The main part of the group records the transition from a rifted passive margin to a fully developed foreland basin receiving marine flysch in the form of argillaceous strata interbedded with highly immature wacke-type sandstones and conglomerates. Maximum accommodation space was developed within a foredeep adjacent to the Dahomeyide belt. Towards the end of the orogenic phase, the foredeep succession became partially inverted and then was buried under coarse terrestrial, red-bed molasse of the Obosum Group

    Space Trajectory Error Analysis Program (STEAP) for halo orbit missions. Volume 2: Programmer's manual

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    The six month effort was responsible for the development, test, conversion, and documentation of computer software for the mission analysis of missions to halo orbits about libration points in the earth-sun system. The software consisting of two programs called NOMNAL and ERRAN is part of the Space Trajectories Error Analysis Programs. The program NOMNAL targets a transfer trajectory from earth on a given launch date to a specified halo orbit on a required arrival date. Either impulsive or finite thrust insertion maneuvers into halo orbit are permitted by the program. The transfer trajectory is consistent with a realistic launch profile input by the user. The second program ERRAN conducts error analyses of the targeted transfer trajectory. Measurements including range, doppler, star-planet angles, and apparent planet diameter are processed in a Kalman-Schmidt filter to determine the trajectory knowledge uncertainty

    Particle Dark Energy

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    We explore the physics of a gas of particles interacting with a condensate that spontaneously breaks Lorentz invariance. The equation of state of this gas varies from 1/3 to less than -1 and can lead to the observed cosmic acceleration. The particles are always stable. In our particular class of models these particles are fermions with a chiral coupling to the condensate. They may behave as relativistic matter at early times, produce a brief period where they dominate the expansion with w<0 today, and behave as matter at late time. There are no small parameters in our models, which generically lead to dark energy clustering and, depending on the choice of parameters, smoothing of small scale power.Comment: 8 pages, 5 figures; minor update with added refs; version appearing in Phys. Rev.

    Chemical Abundance Study of One Red Giant Star in NGC 5694 : A Globular Cluster with Dwarf Spheroidals' Chemical Signature?

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    We report the abundance analysis of one red giant branch star in the metal-poor outer halo globular cluster NGC 5694. We obtain [Fe/H] = -1.93, based on the ionized lines, and our metallicity measurement is in good agreement with previous estimates. We find that [Ca+Ti/2Fe] and [Cu/Fe] of NGC 5694 are about 0.3 -- 0.4 dex lower than other globular clusters with similar metallicities, but similar to some LMC clusters and stars in some dwarf spheroidal galaxies. Differences persist, however, in the abundances of neutron capture elements. The unique chemical abundance pattern and the large Galactocentric distance (30 kpc) and radial velocity (-138.6 +/- 1.0 km/sec) indicate that NGC 5694 had an extragalactic origin.Comment: ApJL accepte

    The Red Horizontal-Branch Star HD 17072

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    We summarize the results of a spectroscopic analysis of HD 17072, finding it to be a metal-poor ([Fe/H] = -1.17) red horizontal-branch star with Teff = 5375 K and log g = 2.4. We also derive a radial velocity of 62.8 km s-1. It has the best determined Hipparcos trigonometric parallax among the metal-poor field horizontal-branch stars and supports the fainter luminosities for such stars found from statistical parallax and Baade-Wesselink analyses, in contradiction to the results of main-sequence fitting of metal-poor field dwarfs to globular cluster main sequences

    Intestinal Parasites In Sembalun Lawang, Lombok

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    Survey tinja telah dilakukan diantara penduduk di Kampung Sembalun Lawang, Distrik Aikinal, Lombok Timur, pada bulan Agustus 1973 untuk mengetahui angka parasit usus dan demam keong di daerah tersebut. Dari 146 penduduk yang diperiksa tinjanya ditemukan 99 persen mengandung sekurang-kurangnya satu jenis parasit usus, 85 persen dengan dua jenis atau lebih dan 40 persen dengan tiga jenis atau lebih. Tidak ditemukan bibit penyakit demam keong diantara penduduk didaerah ini. Angka infeksi dari parasit usus tersebut masing-masing adalah Ascaris lumbricoides 96 persen, Trichuris trichiura 84 persen, cacing tambang 25 persen, Entamocba coli 18 persen, Enterobius vermicularis 10 persen, lodamoeba butsehlii 3 persen, Entamoeba histolytica 1 persen dan Giardia lamblia 1 persen. Pada umumnya tidak banyak perbedaan angka infeksi dari parasit usus ini diantara golongan umur dan kelamin kecuali untuk cacing tambang dimana infeksi pada golongan laki-laki lebih banyak dari pada golongan perempuan

    Multiple Endocrine Neoplasia Type 2B: Eighteen-Year Follow-up of a Four-Generation Family

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    Seven members with multiple endocrine neoplasia type 2B from a 15-member family have been followed for 18 years. All affected had the neuroma phenotype in a distribution compatible with autosomal dominant inheritance. The phenotype features have allowed 100% initial and continuing prediction of affected versus nonaffected status in as early as 1.5 years. Among the affected: immunoreactive plasma calcitonin (iCT) concentration was high in 100%; thyroid palpation was false-negative in 71%; and thyroid scintiscan was false-negative in 83%. All had total thyroidectomy, plus lymphadenectomy in three, for bilateral medullary thyroid carcinoma (MTC) or C-cell hyperplasia (in the youngest). None has died directly from MTC. The index case died at age 68 and his son at age 32 years from complications of the syndrome. All but the youngest have continuing high iCT concentrations. No patient has had parathyroid disease. During preoperative calcium infusion, immunoreactive serum parathyroid hormone concentration declined by 35% to 84% of basal. At operation, macroscopically and microscopically normal parathyroid glands were found in all. No patient has had chemical suggestion of pheochromocytomas: at postmortem the index case had no adrenal medullary disease; his son had bilateral nodular adrenal hyperplasia; his daughter has had adrenal medullary hyperplasia and a renin-secreting juxtaglomerular tumor. Initially nonaffected members remain so

    Optical/IR from ground

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    Optical/infrared (O/IR) astronomy in the 1990's is reviewed. The following subject areas are included: research environment; science opportunities; technical development of the 1980's and opportunities for the 1990's; and ground-based O/IR astronomy outside the U.S. Recommendations are presented for: (1) large scale programs (Priority 1: a coordinated program for large O/IR telescopes); (2) medium scale programs (Priority 1: a coordinated program for high angular resolution; Priority 2: a new generation of 4-m class telescopes); (3) small scale programs (Priority 1: near-IR and optical all-sky surveys; Priority 2: a National Astrometric Facility); and (4) infrastructure issues (develop, purchase, and distribute optical CCDs and infrared arrays; a program to support large optics technology; a new generation of large filled aperture telescopes; a program to archive and disseminate astronomical databases; and a program for training new instrumentalists
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