1,002 research outputs found

    Constraining Theories of SiO Maser Polarization: Analysis of a pipi/2 EVPA Change

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    The full theory of polarized SiO maser emission from the near-circumstellar environment of Asymptotic Giant Branch stars has been the subject of debate, with theories ranging from classical Zeeman origins to predominantly non-Zeeman anisotropic excitation or propagation effects. Features with an internal electric vector position angle (EVPA) rotation of ∼π/2\sim \pi /2 offer unique constraints on theoretical models. In this work, results are presented for one such feature that persisted across five epochs of SiO ν=1,J=1−0\nu=1, J=1-0 VLBA observations of TX Cam. We examine the fit to the predicted dependence of linear polarization and EVPA on angle (θ\theta) between the line of sight and the magnetic field against theoretical models. We also present results on the dependence of mcm_c on θ\theta and their theoretical implications. Finally, we discuss potential causes of the observed differences, and continuing work

    A quantum mechanical approach to establishing the magnetic field orientation from a maser Zeeman profile

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    Recent comparisons of magnetic field directions derived from maser Zeeman splitting with those derived from continuum source rotation measures have prompted new analysis of the propagation of the Zeeman split components, and the inferred field orientation. In order to do this, we first review differing electric field polarization conventions used in past studies. With these clearly and consistently defined, we then show that for a given Zeeman splitting spectrum, the magnetic field direction is fully determined and predictable on theoretical grounds: when a magnetic field is oriented away from the observer, the left-hand circular polarization is observed at higher frequency and the right-hand polarization at lower frequency. This is consistent with classical Lorentzian derivations. The consequent interpretation of recent measurements then raises the possibility of a reversal between the large-scale field (traced by rotation measures) and the small-scale field (traced by maser Zeeman splitting).Comment: 10 pages, 5 Figures, accepted for publication in MNRA

    The Evolving Structure of the Australian Financial System

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    During the past two or three decades structural change in the Australian financial system has been rapid. The system has grown substantially in assets and volumes of activity, has become much more open and competitive, and has undergone some significant shifts in market shares. There has also been much innovation in financial products and delivery systems. In analysing these historical trends a useful distinction can be made between two major parts of the financial system: the financial intermediaries (or credit institutions), of which banks form the largest part; and the funds managers, typified by superannuation funds and unit trusts. Although the overlaps between these two institutional groupings are increasing, their historical trends have been driven by rather different forces. Within the intermediaries sector two broad processes of change have been evident. The first involved the interaction between regulatory policy and financial innovation. Prior to the main thrust of financial deregulation in the late 1970s and early 1980s, banks lost market share to less heavily regulated institutions, a trend that eventually gave impetus to the move to deregulate. In the post-deregulation period, these trends in market share were reversed and, in the process, the system was opened to greater competition. The second main historical process has been a shift in the economics of production of banks’ traditional financial services – what is often referred to as a process of ‘unbundling’. This entails a move toward production and pricing of key products on a stand-alone basis, stimulated by the development of specialist suppliers such as mortgage managers or cash management trusts. Competition from these sources has put pressure on the traditional full-service suppliers (the banks) to cut margins and to reduce cross-subsidies. In the funds-management sector, and particularly the superannuation funds, the driving forces have been somewhat different. Policy changes in the areas of taxation and compulsory contributions have had an important impact on the structure of the industry. However, the most important factor behind the rapid growth of the industry since the early 1980s has been the high average rate of return accumulated on fund investments over that period. The available data do not yet show the increases in net new contributions to the funds expected to result from increases in compulsory contributions. Notwithstanding the historical differences between the two sectors, there have been increasing areas of overlap between them. For example, banks have become more active in funds-management business through subsidiaries, and funds-management institutions have become more active in areas of traditional bank business such as mortgage lending. These developments pose a challenge for regulators as to where are the appropriate regulatory boundaries between the different groups of institutions.

    Skeletal Evidence for Leprosy in India by the Second Millenium B.C.

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    Leprosy is a chronic infectious disease caused by _Mycobacterium leprae_ that affects almost 500,000 people worldwide^1^. The timing of first infection, geographic origin, and pattern of transmission of the disease are unknown^1-3^. Comparative genomics research has recently suggested _M. leprae_ evolved in East Africa or South Asia before spreading to Europe and the rest of the World^4-5^. The earliest accepted textual evidence indicates that leprosy existed in India by at least 600 B.C. and was known in Europe by 400 B.C.^6-7^. The earliest skeletal evidence was dated 300-200 B.C. in Egypt^8^ and Thailand^9^. Here, we report the presence of lepromatous leprosy in skeletal remains from Balathal, a Chalcolithic site (2300-1550 B.C.) in India^10-11^. A middle aged adult male skeleton demonstrates manifestations of facies leprosa and rhinomaxillary syndrome, degenerative joint disease, infectious involvement of the tibia (periostitis), and injury to the peripheral skeleton, often the result of skin anaesthesia. Paleopathological analysis indicates that lepromatous leprosy was present in India by 1800 B.C., a result which supports some translations of the Atharva Veda that reference leprosy and its treatment in hymns composed before the first millennium B.C.^12^. The presence of leprosy in Chalcolithic India suggests _M. leprae_ may have been transmitted during the second or third millennium B.C., at a time when there was substantial interaction between South Asia, West Asia, and Northeastern Africa^13^. This evidence should be impetus to look for additional skeletal and molecular evidence of leprosy in human remains from this time period in India and Africa to confirm the origin of the disease

    Backscatter-immune, polarization managed, all fiber Sagnac sensing interferometer

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    We propose a new all fiber Mach-Zehnder-Sagnac hybrid interferometer topology for precision sensing. This configuration utilizes a high coherence laser source, mitigates the effects of Rayleigh backscatter and polarization wander, while eliminating scale factor drift. We also present preliminary experimental results, using telecommunications grade single mode fiber and fiber couplers, to demonstrate its principle of operation

    Suppression of Classical and Quantum Radiation Pressure Noise via Electro-Optic Feedback

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    We present theoretical results that demonstrate a new technique to be used to improve the sensitivity of thermal noise measurements: intra-cavity intensity stabilisation. It is demonstrated that electro-optic feedback can be used to reduce intra-cavity intensity fluctuations, and the consequent radiation pressure fluctuations, by a factor of two below the quantum noise limit. We show that this is achievable in the presence of large classical intensity fluctuations on the incident laser beam. The benefits of this scheme are a consequence of the sub-Poissonian intensity statistics of the field inside a feedback loop, and the quantum non-demolition nature of radiation pressure noise as a readout system for the intra-cavity intensity fluctuations.Comment: 4 pages, 1 figur
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