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Author: Timothy Robishaw
Publisher: Universal-Publishers
ISBN: 1599426846
Category : Science
Languages : en
Pages : 173
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Book Description
According to astrophysical theory, magnetic fields should play an important role in the structure and dynamics of the interstellar medium. While astronomical observations confirm this directly, the observational record is sparse. This is because magnetic fields can only be measured via polarimetric methods, and most of these methods can only provide an indirect inference of the magnetic field strength. The Zeeman effect, however, is the only method by which in situ measurements of astrophysical magnetic fields can be made. The spectral signature of Zeeman splitting is imprinted in the circular polarization spectrum of radiation received from an astronomical source. In order to make a reliable detection at radio frequencies, one must employ careful calibrations and account for instrumental effects. We begin this dissertation by covering the fundamentals of radio spectropolarimetry. We then offer historical details regarding the Zeeman effect and its use in single-dish radio observations. We present an outline of how one accurately measures the Zeeman effect using large single-dish radio telescopes. We follow this with results from an assessment of the polarization properties of the 100 m Green Bank Telescope (GBT). We then present magnetic field detections made via the Zeeman effect from the Galactic scale to cosmological distances. We begin with GBT observations of 21 cm emission toward the Taurus Molecular Cloud (TMC) complex. Recent observations have suggested that fields stronger than 20 microgauss are located at the distance of the TMC. Our Zeeman observations rule out fields of this strength, but do show a clear +5 microgauss detection from HI emission at the velocity of the TMC. More surprisingly, we have discovered multiple detections of a line-of-sight magnetic field of strength roughly +40 microgauss in a filament near -50 km/s. We then present a windfall of detections of milligauss-strength magnetic fields in starburst galaxies. Detected by means of Zeeman splitting of 1667 MHz hydroxyl megamaser emission, these Arecibo and GBT results represent the first extragalactic Zeeman measurements to probe the field inside an external galaxy. Finally, we climb the cosmological distance ladder, and present a dramatic GBT detection of a magnetic field in a damped Lyman-alpha absorber at a redshift of 0.692. We discuss possible scenarios for the creation of an 84 microgauss field at a look-back time of 6.4 Gyr.
Author: Timothy Robishaw
Publisher: Universal-Publishers
ISBN: 1599426846
Category : Science
Languages : en
Pages : 173
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Book Description
According to astrophysical theory, magnetic fields should play an important role in the structure and dynamics of the interstellar medium. While astronomical observations confirm this directly, the observational record is sparse. This is because magnetic fields can only be measured via polarimetric methods, and most of these methods can only provide an indirect inference of the magnetic field strength. The Zeeman effect, however, is the only method by which in situ measurements of astrophysical magnetic fields can be made. The spectral signature of Zeeman splitting is imprinted in the circular polarization spectrum of radiation received from an astronomical source. In order to make a reliable detection at radio frequencies, one must employ careful calibrations and account for instrumental effects. We begin this dissertation by covering the fundamentals of radio spectropolarimetry. We then offer historical details regarding the Zeeman effect and its use in single-dish radio observations. We present an outline of how one accurately measures the Zeeman effect using large single-dish radio telescopes. We follow this with results from an assessment of the polarization properties of the 100 m Green Bank Telescope (GBT). We then present magnetic field detections made via the Zeeman effect from the Galactic scale to cosmological distances. We begin with GBT observations of 21 cm emission toward the Taurus Molecular Cloud (TMC) complex. Recent observations have suggested that fields stronger than 20 microgauss are located at the distance of the TMC. Our Zeeman observations rule out fields of this strength, but do show a clear +5 microgauss detection from HI emission at the velocity of the TMC. More surprisingly, we have discovered multiple detections of a line-of-sight magnetic field of strength roughly +40 microgauss in a filament near -50 km/s. We then present a windfall of detections of milligauss-strength magnetic fields in starburst galaxies. Detected by means of Zeeman splitting of 1667 MHz hydroxyl megamaser emission, these Arecibo and GBT results represent the first extragalactic Zeeman measurements to probe the field inside an external galaxy. Finally, we climb the cosmological distance ladder, and present a dramatic GBT detection of a magnetic field in a damped Lyman-alpha absorber at a redshift of 0.692. We discuss possible scenarios for the creation of an 84 microgauss field at a look-back time of 6.4 Gyr.
Author: J. A. Jacobs
Publisher: Cambridge University Press
ISBN: 0521450721
Category : Science
Languages : en
Pages : 357
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Book Description
This 1994 book examines how reversals of the Earth's magnetic field have played a major role in establishing plate tectonics and a geological time scale.
Author: McElhinny
Publisher: Academic Press
ISBN: 0080954634
Category : Science
Languages : en
Pages : 417
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Book Description
The Earth's Magnetic Field : Its History, Origin, and Planetary Perspective
Author: Auravana
Publisher: Travis A. Grant
ISBN:
Category : Architecture
Languages : en
Pages : 562
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Book Description
This publication is the Habitat System for a community-type society. A habitat (a.k.a., city, town) is a material-operational service environment where humans live and have their needs fulfilled. It is a service composed of interacting material objects. This habitat system standard identifies the services, technologies, components, and processes that compose a habitat service system. A habitat service system encodes and expresses humanity's decided material fulfillment services. When a decision resolves into a service, that service is specified to exist in the habitat system. Different configurations of a habitat lead to different levels and qualities of fulfillment. The coherent integration and open visualization of the habitat system is important for human requirements to be met at the local and global level through scientific planning. This standard represents the encoding of decisions into a global habitat service system with many local configurations of habitat that act together as a fulfillment platform for the whole community population. The visualization and simulation of humanity’s interconnected habitat systems is essential for maintaining a set of complex, fulfillment-oriented constructions and operations that meet human fulfillment requirements. This publication details what has been, what is, and what could be constructed in the material environment. It depicts through language and symbols, visualization, and simulation, a habitat service environment consisting of life, technology, and exploratory support services. For anything that is to be constructed in the material system, there is a written part, a drawing part, and a simulation part, which is also how the material system is sub-divided. Further, all habitats are designed and operated by means of master planning; they all have a master plan.
Author: James C. Lin
Publisher: CRC Press
ISBN: 1000218694
Category : Medical
Languages : en
Pages : 460
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Book Description
Spanning static fields to terahertz waves, this volume explores the range of consequences electromagnetic fields have on the human body. Topics discussed include essential interactions and field coupling phenomena; electric field interactions in cells, focusing on ultrashort, pulsed high-intensity fields; dosimetry or coupling of ELF fields into biological systems; and the historical developments and recent trends in numerical dosimetry. It also discusses mobile communication devices and the dosimetry of RF radiation into the human body, exposure and dosimetry associated with MRI and spectroscopy, and available data on the interaction of terahertz radiation with biological tissues, cells, organelles, and molecules.
Author: Kenneth R. Lang
Publisher: Cambridge University Press
ISBN: 110701638X
Category : Science
Languages : en
Pages : 347
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Book Description
Explains how stars are born, how they evolve and their ultimate fates, for a broad general audience.
Author: Analog Devices Inc. Analog Devices Inc. Engineeri
Publisher: Elsevier
ISBN: 0080477011
Category : Technology & Engineering
Languages : en
Pages : 976
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Book Description
This comprehensive handbook is a one-stop engineering reference. Covering data converter fundamentals, techniques, applications, and beginning with the basic theoretical elements necessary for a complete understanding of data converters, this reference covers all the latest advances in the field. This text describes in depth the theory behind and the practical design of data conversion circuits as well as describing the different architectures used in A/D and D/A converters. Details are provided on the design of high-speed ADCs, high accuracy DACs and ADCs, and sample-and-hold amplifiers. Also, this reference covers voltage sources and current reference, noise-shaping coding, and sigma-delta converters, and much more. The book’s 900-plus pages are packed with design information and application circuits, including guidelines on selecting the most suitable converters for particular applications. You’ll find the very latest information on: · Data converter fundamentals, such as key specifications, noise, sampling, and testing · Architectures and processes, including SAR, flash, pipelined, folding, and more · Practical hardware design techniques for mixed-signal systems, such as driving ADCs, buffering DAC outputs, sampling clocks, layout, interfacing, support circuits, and tools. · Data converter applications dealing with precision measurement, data acquisition, audio, display, DDS, software radio and many more. The accompanying CD-ROM provides software tools for testing and analyzing data converters as well as a searchable pdf version of the text. * Brings together a huge amount of information impossible to locate elsewhere. * Many recent advances in converter technology simply aren't covered in any other book. * A must-have design reference for any electronics design engineer or technician.
Author: Kenneth R. Lang
Publisher: Springer Science & Business Media
ISBN: 0387333657
Category : Science
Languages : en
Pages : 296
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Book Description
Written in a light and friendly style, this lavishly illustrated book introduces the Sun and its physics, and describes all aspects of the Sun’s interaction with us on Earth. The second edition of this book updates the popular text by providing comprehensive accounts of the most recent discoveries made by five modern solar spacecraft during the past decade. It contains a number of images never before seen in print. Breakthrough observations with the underground Sudbury Neutrino Observatory are also included. The new edition further provides modern interpretations of ozone depletion and global warming.
Author: ORAU Panel on Health Effects of Low-Frequency Electric and Magnetic Fields
Publisher:
ISBN:
Category : ELF electromagnetic fields
Languages : en
Pages : 392
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Book Description
Author: Hiroaki Kogure
Publisher: Artech House
ISBN: 1608071588
Category : Science
Languages : en
Pages : 293
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Book Description
Written for novice engineers and engineering students, this easy-to-comprehend resource offers you thorough introductory-level treatment of antenna analysis using electromagnetic (EM) simulators. This richly-illustrated book shows you how to use EM software to analyze and tune wireless antennas to meet specific requirements. You learn important wireless antenna design terminology and gain a detailed understanding of how antennas work. Moreover, the book offers you guidance in troubleshooting problems with wireless antenna designs. This authoritative reference also provides you with a complete overview of the many different kinds of antennas and related EM tools.
