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J G Power

Publications and source records attributed to J G Power.

6 recordsLinked to original sources
PubMed2004

Observation of multipactor in an alumina-based dielectric-loaded accelerating structure.

We report a new regime of single-surface multipactor that was observed during high-power testing of an 11.424-GHz alumina-based dielectric-loaded accelerating structure. Previous experimental observations of single-surface multipactor on a dielectric occurred in cases for which the rf electric field was tangential and the rf power flow was normal to the dielectric surface (such as on rf windows) and found that the fraction of power absorbed at saturation is approximately 1%, independent of the incident power. In this new regime, in which strong normal and tangential rf electric fields are present and the power flow is parallel to the surface, the fraction of power absorbed at saturation is an increasing function of the incident power, and more than half of the incident power can be absorbed. A simple model is presented to explain the experimental results.

Journal Article↗
PubMed1999

Wakefield excitation in multimode structures by a train of electron bunches.

We discuss wakefield excitation and propagation in dielectric structures, particularly concentrating on the case of multiple drive beam excitation in multimoded structures. We emphasize calculations of the energy loss of the drive beam train, the amplitude of the wakefield, and the relationship between power flow and stored energy in the dielectric wakefield device. We show that for a collinear multimode structure the amplitude of the wakefield generated by a bunch train is less than or equal to the wakefield generated by a single bunch of the same total charge. Furthermore, the transformer ratio R is shown to be always less than 2, even in the multiple drive beam case.

Journal Article↗
PubMed1969

Lead poisoning in Gurkha soldiers in Hong Kong.

Investigation of an outbreak of lead-poisoning in 121 Gurkha soldiers showed that this was due to the contamination of chilli powder (cayenne pepper), a constituent of curry powder, with lead chromate. Comprehensive systems of food sampling are needed in developing communities.

Anemia↗
PubMed1968

Families in flats.

Explore the source record for details and available documents.

Child, Preschool↗
PubMedDate not supplied

Evaluating health knowledge: an alternative approach.

Health campaigns concerned with HIV and AIDS confront two important barriers: the stigmatized nature of the disease and cultural values that exacerbate the taboo nature of the information disseminated. The use of surveys in HIV and AIDS research requires respondents to provide descriptions of sexual acts and body parts as measures of their knowledge. Focus groups and interviews require respondents to speak publicly about these topics. Although many young people know about HIV and AIDS, they may not have the vocabulary to express their complete knowledge either textually or verbally. This article describes an alternative approach designed to evaluate HIV and AIDS knowledge among 587 adolescents in Mexico, where the number of official cases of AIDS has increased steadily since 1981. Participants stratified on sex and social class were required to draw modes of HIV transmission. The drawings were categorized into drawings of objects and persons, focusing on behaviors or cognitions, with a relational or contextual emphasis. The utility of this method for measuring knowledge about HIV infection and AIDS in education campaigns and evaluation research is discussed.

Acquired Immunodeficiency Syndrome↗