Reconstruction of inhomogeneous metric perturbations and electromagnetic four-potential in Kerr spacetime

We present a procedure that allows the construction of the metric perturbations and electromagnetic four-potential, for gravitational and electromagnetic perturbations produced by sources in Kerr spacetime. This may include, for example, the perturbations produced by a point particle or an extended object moving in orbit around a Kerr black hole. The construction is carried out in the frequency domain. Previously, Chrzanowski derived the vacuum metric perturbations and electromagnetic four-potential by applying a differential operator to a certain potential $\Psi$. Here we construct $\Psi$ for inhomogeneous perturbations, thereby allowing the application of Chrzanowski's method. We address this problem in two stages: First, for vacuum perturbations (i.e. pure gravitational or electromagnetic waves), we construct the potential from the modes of the Weyl scalars $\psi_{0}$ or $\phi_{0}$. Second, for perturbations produced by sources, we express $\Psi$ in terms of the mode functions of the source, i.e. the energy-momentum tensor $T_{\alpha \beta}$ or the electromagnetic current vector $J_{\alpha}$.Comment: 20 pages; few typos corrected and minor modifications made; accepted to Phys. Rev.

Clearing the Air on Radon Testing: The Duty of Real Estate Brokers to Protect Prospective Homebuyers

This Note recommends that the federal government create legislation that will impose a duty on real estate brokers to test homes for radon and to disclose the results to prospective purchasers. Based on a common law negligence theory, such a duty would become part of the current obligation of a real estate broker: (1) to conduct a reasonably diligent and competent search of property for sale; and (2) to disclose to prospective homebuyers all material defects affecting the value or desirability of the home. In his investigation, the broker must use the expertise and knowledge that derive from his training and experience as a professional. Initially, the Note addresses the dilemma of the homebuyer who discovers radon only after occupying the home and who has no formally defined cause of action based on common law precedent or statute. Part II traces the development of a real estate broker\u27s liability in negligence to the recently imposed duty to discover and disclose latent defects. Part III analyzes the duty to discover and disclose latent defects with respect to radon and concludes that real estate brokers should have an affirmative duty to test for radon and to disclose the results to prospective purchasers. Finally, part IV recommends legislation to protect the unwary homebuyer who otherwise would take possession of the home and suffer potential economic loss and exposure to a carcinogenic substance

The power of storytelling in social media

Tourists are increasingly connecting in online social networks (OSN) where they share content and coconstruct narratives of tourist destinations through their shared tourism experiences. The destinations give tourists a stage to act on where they perform a desirable self. Thus, their performances and performative acts reflect on how destinations are represented. This poses a challenge for destination management organisations (DMOs). They have to find ways to join the conversations of OSN users to influence perception of their destination. It is believed that DMOs ought to build alliances with tourists by empowering them to co-construct brand narratives and aligning their storytelling with DMOs’ preferred narratives. This research aims to assess the role of storytelling in mediating tourism experiences in order to identify ways for DMOs to build alliances to strengthen destination narratives. It examines a range of different storytellers and how they reinforce and undermine preferred narratives of DMOs, and how they might write different stories across different types of OSN due to their performativity. The practices and strategies DMOs adopt to strengthen storytelling in OSN are also examined

Plasma-wall interaction in ATC during high power neutral beam injection

Measurements of the elemental composition of the vacuum vessel wall surface and impurity influx into ATC during high power beam-heated discharges are combined with previous measurements of power balance and scaling laws to give a self consistent model of plasma-wall interaction in ATC. It is shown that plasma charge exchange induced desorption is the main cause of impurity influx during neutral beam injection. Impurities change the net power balance in these beam- heated discharges by approximately 15 percent. (auth

A fusion power plant without plasma-material interactions

A steady-state fusion power plant is described which avoids the deleterious plasma-material interactions found in D-T fueled tokamaks. It is based on driven p-{sup 11}B fusion in a high-beta closed-field device, the field-reversed configuration (FRC), anchored in a gas-dynamic trap (GDT). The plasma outflow on the open magnetic-field lines is cooled by radiation in the GDT, then channeled through a magnetic nozzle, promoting 3-body recombination in the expansion region. The resulting supersonic neutral exhaust stream flows through a turbine, generating electricity

Vacuum and wall problems in precursor reactor tokamaks

The Princeton Large Torus (PLT) will be completed in 1975 and two other CTR oriented toroidal plasma devices, the Poloidal Divertor Experiment (PDX) and the Tokamak Fusion Test Reactor (TFTR). are planned to be completed in 1977 and 1981. The vacuum systems of these machines must satisfy stringent requirements because of unusual operating conditions, such as, magnetic field induced strains and eddy currents, energetic particle and photon bombardment, large transient gas loads, and the use of 100 Curie quantities of tritium. In addition, novel vacuum wall surfaces and fast moving mechanical or magnetic plasma limiters will be required to minimize the influx of impurities during discharges. (auth

Changes in surface conditions with first plasma in the Princeton Large Torus (PLT)

In--situ measurements are reported of the changes in surface composition of 305 stainless steel exposed to the first plasma discharges in PLT. Auger electron spectroscopy of pre-exposure surfaces shows a multilayer coverage of carbon and a fractional monolayer coverage of oxygen. Surfaces subjected to increasing levels of plasma exposure show substantial removal of the carbon multilayer, increased fractional-monolayer coverages of oxygen and iron, and tenth-monolayer quantities of chlorine and sulfur. (auth

A Hollow Cathode Magnetron (HCM)

A new type of plasma sputtering device, named the hollow cathode magnetron (HCM), has been developed by surrounding a planar magnetron cathode with a hollow cathode structure (HCS). Operating characteristics of HCMs, current-voltage ( I-V ) curves for fixed discharge pressure and voltage-pressure ( V-p ) curves for fixed cathode current, are measured. Such characteristics are compared with their planar magnetron counterparts. New operation regimes, such as substantially lower pressures (0.3 mTorr), were discovered for HCMs. Cathode erosion profiles show marked improvement over planar magnetron in terms of material utilization. The use of HCMs for thin film deposition are discussed