Negative Group Velocity

The group velocity for pulses in an optical medium can be negative at frequencies between those of a pair of laser-pumped spectral lines. The gain medium then can amplify the leading edge of a pulse resulting in a time advance of the pulse when it exits the medium, as has been recently demonstrated in the laboratory. This effect has been called superluminal, but, as a classical analysis shows, it cannot result in signal propgation at speeds greater than that of light in vacuum.Comment: v3 adds discussion of "rephasing", and adds a figure. v4 adds references to the early history of negative group velocity, and adds a figure; thanks to Alex Grani

Are Risk Regulators Rational' Evidence from Hazardous Waste Cleanup Decisions

Using original data on the cleanup of 130 hazardous waste sites, W. Kip Viscusi of Harvard Law School and James T. Hamilton of Duke University's Sanford Institute of Public Policy examine the extent that political decisions and quantitative risk assessments influence cleanup and remediation decisions. They conclude that target risk levels chosen by regulators are largely a function of political variables and risk-perception biases. Communities with higher voter turnouts are more likely at times to have lower risks remaining after final site cleanup and to have more spent to avert expected cases of cancer. They find these political influences are most significant for the least cost-effective site cleanups and the lowest site risks. By basing its policies on an individual risk approach that does not reflect the size of the exposed population or whether the population exists at the site, the Environmental Protection Agency often fails to recognize important aspects of the overall beneficial consequences of its efforts. The mean cost per case of cancer averted at the sample of 130 EPA sites is $11.7 billion. The median cost is$418 million. These estimates use EPA conservative risk assumptions and assume no latency period. With such adjustments, the median cost rises to above $1 billion per cancer case. The most effective 5 percent of all cleanup expenditures eliminate over 99 percent of the cancer risk. Put somewhat differently, 95% of the costs are spent to address less than 1 percent of the risks.

The Ranger 4 Flight Path and Its Determination from Tracking Data

The ranger iv flight path and its determination from tracking dat

Ethnic inequalities in time to diagnosis of cancer: a systematic review

This is the final version of the article. Available from the publisher via the DOI in this record.BACKGROUND: Minimising diagnostic delays in cancer may help improve survival. Ethnic minorities have worse outcomes in some cancer types when compared to the majority; this may relate in part to differences during the diagnostic phase. Only a few British studies have specifically explored this relationship, and no synthesis of these exists. The present study aimed to systematically review evidence on ethnic inequalities in cancer diagnosis, focussing on patient and primary care intervals of diagnosis. METHODS: Six electronic databases were searched. Included studies were those conducted in the UK or elsewhere (where access to healthcare is comparable to the NHS) and those that described a time element during diagnosis. Study quality was evaluated using the Critical Appraisal Skills Programme (CASP) checklist for cohort studies and synthesis method was narrative. RESULTS: Seven of 8,520 studies retrieved by our search met the review criteria; six conducted in the UK, and one in New Zealand. Five (including one covering several sites) focused on breast cancer, one on prostate, and one on oesophagogastric cancer. The studies employed different methods of ascertainment and definition of ethnic groups and defined diagnostic delay in a non-standardised way; therefore, narrative synthesis was performed. In breast cancer, three studies reported longer diagnostic intervals among ethnic minorities and two found no evidence of differences by ethnicity. There was some evidence of longer diagnostic and referral intervals among ethnic minorities in oesophagogastric and colorectal cancers, but no evidence of this in prostate, non-Hodgkin's lymphoma, lung, and ovarian cancers. None of the studies identified shorter patient or primary care intervals in ethnic minorities. CONCLUSIONS: Existing studies provide insufficient evidence to confirm or refute ethnic inequalities in diagnostic intervals of cancer. Further studies are necessary to examine common cancer types including those frequently found in ethnic minorities (in addition to those covered here) and using current definitions of intervals in cancer diagnosis.The Policy Research Unit (PRU) in Cancer Awareness, Screening and Early Diagnosis receives funding for a research programme from the Department of Health Policy Research Programme. It is collaboration between researchers from seven institutions (Queen Mary University of London, UCL, King’s College London, London School of Hygiene and Tropical Medicine, Hull York Medical School, Durham University and Peninsula Medical School). The views expressed are those of the authors and not necessarily those of the NHS, or the Department of Health

The Benefits and Costs of Regulatory Reforms for Superfund

The current policy approach used in the Superfund program is a peculiar halfway house. EPA devotes substantial effort to identifying chemicals at a site and ascertaining their potential risks. It also assesses the costs of a range of remedies in considerable detail. However, many key elements are missing in the agency\u27s analyses. There is no explicit consideration of the size of the population at risk. Risks to a single individual have the same weight as risks to a large exposed population. Actual and hypothetical exposures to chemicals receive equal weight so that risks to a person who, in the future, may choose to live near a currently uninhabited Superfund site receive the same weight as risks to large populations that are currently involuntarily exposed.73 EPA also reports the conservative risk assessment value for each site, without focusing its policy attention on the expected risk level or most likely risk scenarios. Finally, explicit tradeoffs that balance benefits and costs do not enter remediation decisions. These problems arise in part because of decision-making constraints in the Superfund legislation and in part because of the manner in which regulators have implemented the program. Our data show that the core economic elements of the proposed regulatory reform bills would dramatically alter EPA\u27s policy choices. Put simply, the reforms would require that agency regulations maximize the net gain to society (benefits less costs) using plausible risk assumptions. Sound risk assessment and benefit-cost analysis would force wiser spending and eliminate many of the problems that decrease the overall performance of those potentially desirable regulatory efforts such as hazardous waste cleanup...Risk reform is inevitably vulnerable to becoming a vehicle for ignoring environmental hazards rather than remediating them more efficiently. As our analysis shows however, there is a wide zone within which risk reforms can improve efficiency without sacrificing human health considerations

Superfund and Real Risks

An analysis of the Superfund program represents the first systematic effort to document the character of the risks addressed by this legislation, which will in turn determine the total cleanup cost and the degree to which Superfund addresses environmental risks. This analysis is examined

Earth - venus trajectories, 1968-69, volume 4, part b

Earth-venus trajectories 1968-196

Wind-Tunnel Tests of a 0.16-Scale Model of the Douglas MX-656 Airplane at High Subsonic Speeds

Wind tunnel tests of the 0.16-scale Douglas MX-656 model were made at low and high subsonic Mach numbers to investigate the static longitudinal- and lateral stability characteristics. The tests shows that undesirable changes in longitudinal stability at the stall were apparently caused by an altered downwash pattern at the tail. The jettisonable nose fins were highly destabilizing. Compressibility effects for the test Mach numbers were not detrimental to the longitudinal- or lateral-stability characteristics

The Market Value of Reducing Cancer Risk: Hedonic Housing Prices with Changing Information

In this paper, we use housing price changes occurring after the release of a regulatory agency\u27s environmental risk information to estimate the value people place on cancer risk reduction. Using a large original data set on the repeat sales of houses, matched with detailed data on hazardous waste cancer risk and newspaper publicity, we find that housing prices respond in a rational manner to changes in information about risk. Since the new information indicated that the sites in our sample pose relatively low cancer risk, the informational release led residents to lower their risk beliefs, resulting in an average housing price increase of $56 to$87. This price change implies a statistical value per case of cancer of $4.3 million to$8.3 million, which is similar to the estimates obtained in labor market studies of the value of a statistical life. Newspaper publicity about the local sites increased housing prices, suggesting that residents perceived the news as good