Did people "buy" what was "sold"? A qualitative evaluation of a contingent valuation survey information set for gains in life expectancy.

A number of stated preferences studies have estimated a monetary value for the gains in life expectancy resulting from pollution control, using a Value of a Life Year (VOLY) approach. However, life expectancy gains are a complex concept and no attempt has been made, to date, to investigate peoples' understanding of what it is they are being asked to value. Past practice has been to focus on the outcome of a policy i.e. a gain to the average person of X months', providing no details on how the individual receives, or experiences this gain, a potentially important attribute to value. This paper sets up and reports the results from a structured debriefing exercise to qualitatively investigate an alternative approach which explicitly emphasises how this gain is delivered (on-going reductions in the risk of death). We find that, for the majority of respondents, the approach is effective in communicating the on-going nature of the gain and reduces or eliminates the use of the (incorrect) heuristic that it is an 'add-on' at the end of life, in poor health. Further refinements are required, however, to communicate the cumulative nature of these risk reductions and the lack of impact on quality of life. The lesson for stated preference studies in general is that structured debriefings can be very useful, highlighting such issues as the persistence of ill-defined attributes and the difficulties that respondents may encounter setting aside their preferences over attributes of the good that should not be included in the valuation.

Bichromatic slowing and collimation to make an intense helium beam.

The bichromatic force has been used to both slow and collimate a beam of metastable 2(3)S He atoms (He*). The collimation capture range is an extraordinary +/-85 m/s corresponding to approximately 0.18 radians from our source. Both slowing and collimation were accomplished in the unprecedented short distance of approximately 5 cm each. The overall brightness increase is x3200, and there is potential for considerably more.

Heart health: treatment.

Coronary heart disease (CHD) is the single most common cause of death in England and it has been estimated that about 26 per cent of all deaths each year are caused by CHD (Department of Health 1993). In light of this, it is important that all nurses understand the current investigations and treatment available for people with CHD.

Application of risk assessment to international trade in animals and animal products.

NAFTA and GATT have specified that we must base import decisions on sound scientific information. This includes the use of risk assessment procedures to justify excluding or restricting the international movement of either live animals or products from animals. Procedures and techniques have been described for calculating the risk of almost any hazard that one can imagine. Of particular concern to animal health professionals are the risks associated with introducing known or unknown disease agents into a population of animals that has been previously free of a specific disease. Traditional risk assessment procedures calculate the probability that a disease agent transmission will occur and the cost of such an event. The responsible manager must decide on an acceptable threshold of risk. A set of criteria for determining what risk is acceptable has been developed that categorizes risks for importing animals or animal products from any region of the world based on classification of the region as negligible, slight, low, moderate, high, or unknown risk.

Measurement of force-assisted population accumulation in dark states.

Atoms can be accumulated by velocity-selective coherent population trapping (VSCPT) in dark states of very highly monovelocity, resulting in very narrow distributions. The optical pumping process that permits the population accumulation proceeds by random walk in momentum space and is of limited efficiency. Several authors have predicted that damping forces can enhance VSCPT in carefully chosen laser fields. We present corroboration of this idea with measurements showing increased efficiency for VSCPT.

Risk of introducing exotic disease through importation of animals and animal products.

Between 1870 and 1929, nine separate outbreaks of foot and mouth disease (FMD) occurred in the United States of America (USA); additional outbreaks in North America include one in Mexico (1947) and two in Canada (1870 and 1952). In 1930, the United States Congress enacted a law prohibiting importation of live ruminants or swine or fresh meat from these species into the USA from countries affected with FMD or rinderpest. Although the effect of this prohibition may be debated, the USA has remained free of FMD since its enactment. A hidden benefit of this prohibition was probably the limitation on importing other disease agents from countries of the world where FMD was present. As many regions of the world make progress towards the control and eradication of FMD, North America must take greater cognizance of other disease agents with which it has not been concerned to date, as these existed only in regions of the world affected with FMD and/or rinderpest. One of the methods of dealing with these other diseases is by using risk assessment and risk management methodologies. For risk assessment to work, however, the available management technologies must be examined, and levels of risk assigned to match the available technology. The authors explore risk analysis options for the importation of animals and animal products in a manner which will continue to protect the livestock industry in the USA. They also examine the role of veterinary biologicals as a management tool to mitigate the attendant risks.

Neuroaxonal degeneration in sheep grazing Sorghum pastures.

During the fall of 1992, 250 (10%) of 2,500 Rambouilet cross feeder lambs grazing Sorghum bicolor developed neurologic signs including weakness, ataxia, head shaking, knuckling of the fetlocks, inability to rise, and opisthotonos. One hundred fifteen (46%) of the affected lambs died. Twenty of the surviving lambs exhibited residual neurologic signs of ataxia when stressed. At the same time, 275 (25%) of 1,100 ewes grazing a nearby sudex pasture (S. sudanese x S. bicolor) gave birth to lambs that were weak and unable to rise. Newborn lambs exhibited extensor rigidity and opisthotonos when assisted to a standing position. The dystocias that occurred were due to lambs with contracted limbs (arthrogryposis). All affected lambs died or were euthanized. Histologic examination of the brains of 3 feeder lambs and 9 newborn lambs revealed similar microscopic lesions. The predominant change was the presence of focal axonal enlargements (spheroids) in the proximal segments of axons, which were restricted to the nuclei of the medulla, cerebellum, and midbrain. In addition, the spinal cord contained spheroids in the ventral horn gray matter of the 6 newborns examined. Ultrastructurally, the spheroids were composed of aggregates of neurofilaments, mitochondria, vesicular bodies, and dense bodies bounded by a thin myelin sheath. There was mild gliosis in the more severely affected animals of both groups. There was minimal Wallerian degeneration in the white matter adjacent to affected nuclei in the brain and the ventromedial and dorsolateral funiculi of the spinal cord. This is the first detailed report of Sorghum toxicity in sheep.

Instrumentation for multistep excitation of lithium atoms to Rydberg states.

We have developed a diode laser apparatus to excite Li from its ground 2S state, through 2P and 3S, to its Rydberg states with three cw diode lasers operating at λ = 671 nm, 813 nm, and 630-635 nm. A He-Ne laser at λ = 633 is sometimes used in place of the 635-nm diode laser for the last step. The output power of each of these lasers was ~1 mW. We describe our technique of locking the first two lasers on Li resonance lines by obtaining a fluorescent signal from the second decay (3S ? 2P) that is normally overpowered by a strong background of fluorescent light from the first decay (2P ? 2S). We used two balanced photodiodes to reject the strong fluorescent light without loss of collection efficiency. A rejection ratio as high as 100 has been obtained.

Beam profile flattener for Gaussian beams.

We describe a novel technique to make a Gaussian laser beam profile spatially flat. We exploit the angular dependence of the transmission of an étalon to tailor the spatial profile to the desired form. A simple analysis shows why our method works so well and how an étalon could be tuned to give the optimum results at all wavelengths. This technique has enormous advantages over other methods.

Tunable diode-laser-pumped solid state LNA laser for helium spectroscopic experiments.

We have designed, built, and tested a compact, integrated, single-mode solid state LNA laser pumped by a semiconductor laser array for exciting the He resonance line at lambda = 1.083 microm. The laser's three major components are mounted on a single aluminum base, and the diode laser and its beam shaping optics are mounted on a separate stage. This compact and stable structure provides good frequency stability and nearly pure TEM(00) transverse mode operation. The laser can be tuned around the metastable He resonance transition in a single longitudinal mode with linewidth congruent with 5 MHz using a solid, 60% coated intracavity 0.25-mm thick etalon. Saturated absorption signals on this transition have been used to measure the stability and tuning range. We have measured the properties for several crystals and calculated the expected performance characteristics to compare with the measured ones.