The dynamics exhibited by systems, such as galaxies, are dominated by the isolating integrals of the motion. The most common are the energy and angular momentum integrals. The motions in a system with a full complement of isolating integrals are regular, that is, periodic or quasi-periodic. Such a system is integrable. If there is a deficiency in the number of integrals, then the motions are chaotic. There is a fundamental quantative difference in the motion, depending on the number of integrals. A technique, called Generalised Painlevé analysis, based on complex variable theory allows the user to determine if a system is integrable. Two new integrable cases of the Henon-Heiles system are presented, bringing the total number of such integrable potentials to five. It is highly probable that there are no further integrable cases of the Henon-Heiles potential. Five cases of the quartic Verhulst potential, defined by certain restrictions on the coefficients, which are found to be integrable are summarised.

Walter G, Byrne S, Griffiths O, Hunt G, Soh N, Cleary M, Duffy P, Crawford G, Krabman P, Concannon P, Malhi G. Can young people reliably rate side effects of low-dose antipsychotic medication using a self-report survey?

We analyze how the availability of internal funds affects a firm's investment. We show that under fairly standard assumptions, the relation is U-shaped: investment increases monotonically with internal funds if they are large but decreases if they are very low. We discuss the tradeoff that generates the U-shape, and argue that models predicting an always increasing relation are based on restrictive assumptions. Using a large data set, we find strong empirical support for our predictions. Our results qualify conventional wisdom about the effects of financial constraints on investment behavior, and help to explain seemingly conflicting findings in the empirical literature.

There are inherent limitations in using assessments of patient satisfaction to make inferences about the quality of medical care. Such evaluations tend to be subjective, subject to reporting biases, and difficult to interpret when they are being used to motivate and guide quality improvement efforts. Newer methods of eliciting both reports and ratings from consumers, such as the Consumer Assessment of Health Plans (CAHPS) project, can provide reliable, valid, interpretable, and actionable data about selected aspects of health care. The use of these methods and continued use of new qualitative methods, such as cognitive interviewing, should allow us to continue increasing the prominence of consumer-based information in quality assessment and improvement efforts.

We have developed a nanogrowth technology for the fabrication of periodic arrays of semiconductor nanostructures on silicon that is currently being investigated for silicon based x-ray detectors. The semiconductor nanostructures are formed by chemical synthesis in pores of a template created by the anodization of aluminum on a silicon substrate. The use of the silicon substrate allows greater control over the aluminum thin film properties, better in situ monitoring of the pore formation process, and the direct integration of nanostructure arrays with conventional silicon technology.

This paper provides a review of research issues and findings on the epidemiology of delirium. Despite the fact that research on this important geriatric syndrome has been conducted for many decades, several methodological issues make it difficult to compare findings across studies. In this paper we first discuss broadly methodological issues related to diagnosis, case-finding, and populations studied. We next review data on the occurrence and consequences of the syndrome. A discussion of the design and preliminary results of the Commonwealth-Harvard Study of Delirium in Elderly Hospitalized Patients documents both how we responded to the methodological issues outlined and how these choices influenced our findings. We conclude with a discussion of the needs for further research on the epidemiology of delirium.

Over the past several decades, numerous investigators have studied the syndrome of delirium. Researchers have relied on a number of different case finding methods to detect the syndrome. This paper provides an overview of instruments used in studies of delirium. We assess the validity and reliability of these instruments and compare the advantages and disadvantages of the different methods. We then present the rationale for the development of the Delirium Symptom Interview, an instrument constructed for use in the Commonwealth-Harvard Study of delirium in elderly hospitalized patients.

Over the years, Jay Katz has consistently emphasized the need to consider both the psychodynamic factors and more general societal forces that play a role in shaping the way individuals and society respond to patients. In their 1975 book on catastrophic diseases, Katz and Capron addressed the central question of who should have the authority to make the decisions affecting those afflicted with catastrophic diseases: a theme that appears repeatedly in the insightful writing of Katz. In The Silent World of Doctor and Patient he presents a compelling case that patients’ deasion-making is an idea alien to the ethos of medicine. He has argued frequently for the importance of patient autonomy and has showed us how important conscious, as well as unconscious, and rational, as well as irrational forces are in shaping our actions.

In his work, Dr. Katz writes primarily about how physicians and patients should interact to arrive at decisions about research and treatment. These issues are certainly salient when considering the way acquired immunodeficiency syndrome (AIDS) should be treated and how we should evaluate new therapies.

In 1984, scientists isolated a new pathogen, now called human immunodeficiency virus (HIV), that is almost certainly the etiological agent for the acquired immunodeficiency syndrome (AIDS). It has been estimated that there are between 500,000 and 1,750,000 asymptomatic, chronically HIV-infected individuals in the United States. In a remarkably short time, investigators developed a number of blood tests that indicate whether an individual is likely to be infected with this virus. These assays are now being used to test patients with symptoms suggesting AIDS or related syndromes, to screen donated blood, to evaluate individuals concerned about their infection status, and to screen new military recruits, active-duty soldiers, and ROTC students. Almost weekly, new proposals are advanced for screening different subsets of the population.