Temperature and frequency dependence of dielectric loss of Ba(Mg1/3Ta2/3)O3 microwave ceramics

Ba(Mg_1/3Ta_2/3)O₃ ceramic possessing extremely high Q × f value of more than 300 THz at microwave frequency was developed in our previous study. It is of great interest to understand the mechanism of microwave absorption in such a practical material. In the present study we report on the temperature dependence of the dielectric loss in the Ba(Mg_1/3Ta_2/3)O₃. The mechanism of the microwave absorption is discussed using two phonons difference process. The samples were prepared by conventional solid state reaction and sintered at 1893 K in oxygen atmosphere. Dielectric properties in the microwave range were measured by Hakki & Colemann and resonant cavity methods in the temperature range of 20–300 K. Whispering gallery mode technique was used for the measurement of the dielectric properties at the millimeter wave frequency. Dielectric loss of the Ba(Mg_1/3Ta_2/3)O₃ at the microwave frequency increases with temperature between 200 and 300 K in general agreement with the theory of intrinsic dielectric loss derived from the two phonon difference process. However below 200 K, the dielectric loss has shown a distinctive behavior with a loss peak at 40 K. It was inferred that the loss peak of the Ba(Mg_1/3Ta_2/3)O₃ was caused by the local orientation polarization having dispersion at the microwave frequency.     

Photoprotection of Wood Using Polyester-Type UV-Absorbers Derived from the Reaction of 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone with Dicarboxylic Acid Anhydrides

Abstract

Polyester-type UV absorbers were created by reacting the epoxy-functionalized UV absorber 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone (HEPBP) with maleic, phthalic, or succinic anhydride. The ability of the UV absorbers to photostabilize wood was then examined. Fourier transform infra-red (FTIR) spectroscopy confirmed that HEPBP reacted with phthalic anhydride to create a polyester that preserved the UV-absorbing benzophenone group. There was less evidence that the polyester was formed when HEPBP was reacted with maleic or succinic anhydride. HEPBP-phthalic anhydride was the most effective UV absorber at photostabilising wood. This UV absorber showed increased UV absorption around 270 nm, formed a leach-resistant film at wood surfaces and was able to restrict both weight and tensile strength losses of thin wood veneers during accelerated weathering, unlike chromium trioxide and a UV absorber-hindered amine light stabilizer. We conclude that polymeric polyester-type UV absorbers show promise as a way of photostabilizing wood and briefly discuss how more effective systems could be developed in future.     

Effect of the OH Radical Scavenger Hydrogen Peroxide on Secondary Organic Aerosol Formation from α-Pinene Ozonolysis

Hydrogen peroxide (HOOH) is a potentially valuable hydroxyl radical (OH) scavenger in secondary organic aerosol experiments focused on ozonolysis yields. Here, we present results for α-pinene ozonolysis. The OH scavenging produces solely HO₂ radicals and the resulting high [HO₂]/[RO₂] ratio causes an increase in aerosol formation from α-pinene ozonolysis, compared to experiments performed with butanol OH scavengers. The majority of the increase comes in the 100 μg m^?3 volatility range, suggesting that instead of more volatile products formed under higher RO₂ conditions, less volatile, multifunctional hydroperoxides form under the high-HO₂ conditions here. This dependence on the [HO₂]/[RO₂] ratio can be parameterized in a similar fashion to the way high- and low-NO _x yields are currently treated in models.     

A Microcalorimeter Using Semiconductors as the Sensing Elements

SUMMARY

Our previous work in biochemical calorimetry has been conducted with two modified versions [1, 2] of the Calvet microcalorimeter [3, 4]. The chief features of the modified versions are the use of electroplated thermocouples, reduction in overall size of the calorimeter and equilibration time, and mode of initiating the reaction.     

A Water Surface Wave-Height Radio Telemeter

ABSTRACT

This paper discusses the evolution of a telemetric device that enables the remote measurement of surface wave height on a freshwater lake. The basic instrumentation package uses an anchored, insulated metal probe as a capacitive sensor element to determine peak wave amplitudes up to 1 m; the probe also serves as the mechanical support for a lightweight UHF radio-link antenna. The principal system design considerations and circuit details of the baseband signal processing stages are included; representative test results are documented.     

Unrealised Opportunities for Sustainable Transport: Adelaide as an Example

The case for integrated land-use and transport strategies for Australian cities is evaluated with particular reference to sustainabliity and equity values. The potential to apply such a strategy to Adelaide is explored. It is concluded that there are sufficient mainly broadacre government-owned consolodation opportunities adjoining the spinal rail network to accomodate the city's forecast population growth over the next 20 years. A mutually reinforcing program of investment in rail infrastructure and rail-oriented urban village developments is proposed.     

Pornography and Sexist Attitudes Among Heterosexuals

Using a probability‐based sample of young Danish adults and a randomized experimental design, this study investigated effects of past pornography consumption, experimental exposure to nonviolent pornography, perceived realism of pornography, and personality (i.e., agreeableness) on sexist attitudes (i.e., attitudes toward women, hostile and benevolent sexism). Further, sexual arousal mediation was assessed. Results showed that, among men, an increased past pornography consumption was significantly associated with less egalitarian attitudes toward women and more hostile sexism. Further, lower agreeableness was found to significantly predict higher sexist attitudes. Significant effects of experimental exposure to pornography were found for hostile sexism among low in agreeableness participants and for benevolent sexism among women. These experimental exposure effects were found to be mediated by sexual arousal.     

Conserving Rental Housing A Policy Analysis

Conserving the existing stock of rental housing is a key part of any policy to house low-and moderate-income people and to revitalize their neighborhoods. Local governments, with their limited resources, have growing responsibility for the conservation efforts. But they have little information about what programs actually result in better maintenance and repair of rental housing. This article, based on studies of landlords' investments in repairs to their buildings, outlines policies for shaping effective programs to conserve rental housing. It focuses on six crucial issues: how to divide public actions between those that directly support housing improvements and those that indirectly encourage rehabilitation by improving neighborhood conditions; how much assistance to provide, and where to concentrate it geographically; how to involve other private parties, especially lenders; which owners to assist; what level of rehabilitation to support for a given building; and how to balance the use of “carrots” and “sticks.”