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The first flash produced by a storm usually does not strike ground, but little has been published concerning the time after the first flash before a cloud-to-ground flash occurs, particularly for a variety of climatological regions. To begin addressing this issue, this study analyzed data from very-high-frequency (VHF) lightning mapping systems, which detect flashes of all types, and from the U.S. National Lightning Detection Network (NLDN), which identifies flash type and detects roughly 90%% of cloud-to-ground flashes overall. VHF mapping data were analyzed from three regions: north Texas, Oklahoma, and the high plains of Colorado, Kansas, and Nebraska. The percentage of storms in which a cloud-to-ground flash was detected in the first minute of lightning activity varied from 0%% in the high plains to 10%%-20%% in Oklahoma and north Texas. The distribution of delays to the first cloud-to-ground flash varied similarly. In Oklahoma and north Texas, 50%% of storms produced a cloud-to-ground flash within 5-10 min, and roughly 10%% failed to produce a cloud-to-ground flash within 1 h. In the high plains, however, it required 30 min for 50%% of storms to have produced a cloud-to-ground flash, and 20%% produced no ground flash within 1 h. The authors suggest that the reason high plains storms take longer to produce cloud-to-ground lightning is because the formation of the lower charge needed to produce most cloud-to-ground flashes is inhibited either by delaying the formation of precipitation in the mid- and lower levels of storms or by many of the storms having an inverted-polarity electrical structure. [ABSTRACT FROM AUTHOR]

Lightning in all corners of the world is monitored by one or more land- or space-based lightning locating systems (LLSs). The applications that have driven these developments are numerous and varied. This paper describes the history leading to modern LLSs that sense lightning radiation fields at multiple remote sensors, focusing on the interactions between enabling technology, scientific discovery, technical development, and uses of the data. An overview of all widely used detection and location methods is provided, including a general discussion of their relative strengths and weaknesses for various applications. The U.S. National Lightning Detection Network (NLDN) is presented as a case study, since this LLS has been providing real-time lightning information since the early 1980s, and has provided continental-scale (U.S.) information to research and operational users since 1989. This network has also undergone a series of improvements during its >20-year life in response to evolving detection technologies and expanding requirements for applications. Recent analyses of modeled and actual performance of the current NLDN are also summarized. The paper concludes with a view of the short- and long-term requirements for improved lightning measurements that are needed to address some open scientific questions and fill the needs of emerging applications. [ABSTRACT FROM AUTHOR]

The article examines the use of naval power by insurgent forces engaged in asymmetric warfare. The Confederate commerce raiders of the U.S. Civil War are cited. Successes achieved by the naval forces of the Tamil Tigers separatist movement in Sri Lanka are presented. The attack by al-Qaeda operatives on the U.S.S. Cole in a Yemeni harbor in 2000 is given. The gray area between naval guerrilla warfare and piracy is noted.

This paper uses five valuation methods to derive aggregate and per person estimates of the value of household work in the United States. Two general questions are posed: (1) what is the relationship between the aggregate estimates and the valuation method used, and (2) how do per person estimates vary by sex and earnings? The main observations of the paper are as follows: First, the aggregate value of household work is sizable regardless of the valuation method used. Second, aggregate estimates are extremely sensitive to the method of valuation. For example, the highest estimate is $475 billion greater than the lowest estimate. Third, contrary to earlier findings, opportunity cost valuation methods generally produce significantly higher estimates than market cost valuation methods. Fourth, per person estimates vary significantly by sex and level of earnings across valuation methods. Generally, market cost estimates decline as earnings rise while the reverse is true for opportunity cost estimates. [ABSTRACT FROM AUTHOR]

Gregory A. Curt's life is remembered. He was instrumental in the founding of The Oncologist, and he was the journal's founding Continuing Medical Education director. He instigated the Standard Terms of Agreement for Research Trial (START) clauses in collaboration with the National Cancer Institute. [ABSTRACT FROM AUTHOR]

Radiographic image guidance has emerged as the new paradigm for patient positioning, target localization, and external beam alignment in radiotherapy. Although widely varied in modality and method, all radiographic guidance techniques have one thing in common--they can give a significant radiation dose to the patient. As with all medical uses of ionizing radiation, the general view is that this exposure should be carefully managed. The philosophy for dose management adopted by the diagnostic imaging community is summarized by the acronym ALARA, i.e., as low as reasonably achievable. But unlike the general situation with diagnostic imaging and image-guided surgery, image-guided radiotherapy (IGRT) adds the imaging dose to an already high level of therapeutic radiation. There is furthermore an interplay between increased imaging and improved therapeutic dose conformity that suggests the possibility of optimizing rather than simply minimizing the imaging dose. For this reason, the management of imaging dose during radiotherapy is a different problem than its management during routine diagnostic or image-guided surgical procedures. The imaging dose received as part of a radiotherapy treatment has long been regarded as negligible and thus has been quantified in a fairly loose manner. On the other hand, radiation oncologists examine the therapy dose distribution in minute detail. The introduction of more intensive imaging procedures for IGRT now obligates the clinician to evaluate therapeutic and imaging doses in a more balanced manner. This task group is charged with addressing the issue of radiation dose delivered via image guidance techniques during radiotherapy. The group has developed this charge into three objectives: (1) Compile an overview of image-guidance techniques and their associated radiation dose levels, to provide the clinician using a particular set of image guidance techniques with enough data to estimate the total diagnostic dose for a specific treatment scenario, (2) identify ways to reduce the total imaging dose without sacrificing essential imaging information, and (3) recommend optimization strategies to trade off imaging dose with improvements in therapeutic dose delivery. The end goal is to enable the design of image guidance regimens that are as effective and efficient as possible.