2,568 research outputs found
Unravelling the nature of transitional millisecond pulsars
No full textTransitional millisecond pulsars (tMSPs) are binary systems in which there is a neutron star and a low-mass, likely non-degenerate companion star. These systems switch between states as: i) an observable radio millisecond pulsar ('RMSP state'), at which time there is no evidence for an accretion disc, and ii) a state similar to that of a low-mass X-ray binary (LMXB), in which there is an accretion disc and sometimes apparently active accretion into the neutron star magnetosphere, or even a luminous X-ray outburst ('LMXB state'). In this thesis we strive to understand the evolution and nature of the LMXB state of tMSPs; in particular, the persistent, low-luminosity, 'disc-dominated' state that they sometimes occupy. We have undertaken wide-ranging, multi-wavelength explorations of tMSPs by searching, monitoring, timing and imaging them with individual and simultaneous observations spanning the electromagnetic spectrum through Gamma-ray, X-ray, UV and radio wavelengths. This has required a wide diversity of instruments and techniques. These observations have led to significant insights into the nature of tMSPs, and in particular their persistent, low-level accretion state. Specifically, in case of the tMSP, PSR J1023+0038. We have successfully modelled its spin-down behaviour in the LMXB state and detected millisecond pulsations in its Hubble Space Telescope ultraviolet observations. To understand how representative PSR J1023+0038 is of the tMSP class, we studied the candidate tMSP 3FGL J1544-1125. We also tried to connect tMSPs and accreting millisecond X-ray pulsars by searching for radio pulsations from the prototype of this class, SAX J1808-3658
Simultaneous NICER and NuSTAR Observations of the Ultracompact X-Ray Binary 4U 1543-624
No full textWe present the first joint NuSTAR and NICER observations of the ultracompact X-ray binary (UCXB) 4U 1543−624 obtained in 2020 April. The source was at a luminosity of L0.5−50 keV = 4.9(D/7 kpc)2 × 1036 erg s−1 and showed evidence of reflected emission in the form of an O viii line, Fe K line, and Compton hump within the spectrum. We used a full reflection model, known as xillverCO, that is tailored for the atypical abundances found in UCXBs, to account for the reflected emission. We tested the emission radii of the O and Fe line components and conclude that they originate from a common disk radius in the innermost region of the accretion disk (Rin ≤ 1.07 RISCO). Assuming that the compact accretor is a neutron star (NS) and the position of the inner disk is the Alfvén radius, we placed an upper limit on the magnetic field strength to be B ≤ 0.7(D/7 kpc) × 108 G at the poles. Given the lack of pulsations detected and position of Rin, it was likely that a boundary layer region had formed between the NS surface and inner edge of the accretion disk with an extent of 1.2 km. This implies a maximum radius of the neutron star accretor of RNS ≤ 12.1 km when assuming a canonical NS mass of 1.4 M
The Middle Platonists: 80 B.C. to A.D. 220
No full textThe Middle Platonists: 80 B.C. to A.D. 220 John M. Dillon (Author), 1977 Table of Contents Preface Abbreviations 1 The Old Academy and the Themes of Middle Platonism 2 Antiochus of Ascalon: The Turn to Dogmatism 3 Platonism at Alexandria: Eudorus and Philo 4 Plutarch of Chaeroneia and the Origins of Second-Century Platonism 5 The Athenian School in the Second Century A.D. 6 The 'School of Gaius': Shadow and Substance 7 The Neopythagoreans 8 Some Loose Ends Bibliography Afterword General ..
Charles Berlitz, Author of "Doomsday," Takes Predictions
No full textCharles Berlitz, author of "Doomsday," makes predictions that life will cease after 2000 A.D
THE FOOD INDUSTRY - 2000 A.D. REVISITED
No full textWhat will be the nature of the food industry in the year 2000 A.D.? What will be the roles of retailers, wholesalers and manufacturers? The author presents his views of future food processing and distribution practices and thereby poses a challenge to the industry to maximize its opportunities for growth during the next three decades.Agribusiness,
THE FOOD INDUSTRY - 2000 A.D. REVISITED
No full textWhat will be the nature of the food industry in the year 2000 A.D.? What will be the roles of retailers, wholesalers and manufacturers? The author presents his views of future food processing and distribution practices and thereby poses a challenge to the industry to maximize its opportunities for growth during the next three decades
A study of the issues surrounding the understanding of historic military artefacts as primary source documents with particular emphasis on the sword
No full textLearning from biophysical heterogeneity: inductive use of case studies for maize cropping systems in Central America
No full textGlobal society has become conscious that efforts towards securing food production will only be successful if agricultural production increases are obtained through mechanisms that ensure active regeneration of the natural resource base. Production options should be targeted in the sense of that their suitability to improve agricultural production and maintain natural resources is evaluated prior to their introduction. Biophysical targeting evaluates production options as a function of the spatial and temporal variability of climate conditions, in interaction with soil, crop characteristics and agronomic management strategies. This thesis contributes to the development of a system-based methodology for biophysical targeting. Cropping system simulation and weather generator tools are interfaced to geographical information systems. Inductive use of two case studies - a green manure cover crop and reduced tillage with residue management - helped to develop the methodology. Insight is gained into the regional potential for and the soil and climate conditions under which successful introduction of these production options may be achieved. The resulting information supports regional stakeholders involved in agriculture in their analysis and discussion, negotiation and decision-making concerning where to implement production systems. This process can improve the supply of appropriate agricultural production practices that enhance production and conserve soil and water resources
Invitation to David Bishop from the Order of United Americans for a celebration of George Washington's birthday, February 1858
No full textThe Order of United Americans, also known as the Know-Nothings, formed in the mid-1800s to support the rights of native-born Americans over those of immigrants, and to combat what they saw as foreign influences on America. This letter is an invitation to Order member David Bishop, to a celebration in honor of George Washington's birthday. Page 1 shows the actual letter, and page 2 is the transcripts of the letter
Sarmatian Attributes in Archaeological Complexes of Catacombs Burials in Arys Culture of Southern Kazakhstan (1st Century B.C. - 3rd Century A.D.)
No full textThe publication is devoted to archaeological research of monuments of the catacomb of Arys culture of Southern Kazakhstan (1st Century B.C. - 3rd Century A.D.).
Now scientists have a complete understanding of the range and typology, periodization and chronology of monuments of this culture. There are three stages: Karaultobe (4th century B.C. - 1st century A.D.); Karatobe (1st Century B.C. - 4th century A.D.); Altintobe (4th-6th centuries A.D.). These stages are characterized by specific clusters of signs in the form of artifacts. The author also carried out the ethnic attribution of the Arys culture in association with the ancient state Kangiuj. As a result of this work, the ethnicity of the state Kangiuj was revealed: in particular, late Saka’s, Sarmatian, Huns and Kangiuj ethnic components which are relevant to archaeological complexes, were identified.
In the Arys monuments of culture the author discovered complexes of findings which associated with the Sarmatian world of Eurasia by their ethno-cultural parameters.
They include typical for the Sarmatians list of ritual action and the funerary equipment, including weapons, bronze mirrors, ritual and religious objects, signs-tamgas, jewelry (including Egyptian faience), articles in “animal”, gold-turquoise and polychrome style.
The characteristics of the burial complexes of catacombs of the Arys culture discussed in the publication and corresponding to chronological calculations and ethno-cultural interpretations, allow to speak about presence in the territory of South Kazakhstan of the Asian Sarmatians or any local branch of the Union of the Sarmatian tribes in the 1st century B.C. - 3rd century A.D
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