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Amid growing dissatisfaction with its health care system, the United States is increasingly looking abroad for insights into health system reform. In the Spring 1989 issue of Health Affairs, an analysis of a threenation survey of how Americans, Canadians, and Britons viewed the performance of their health care systems showed that, of citizens of the three countries, Americans expressed the greatest degree of dissatisfaction with their health system and Canadians the least. In addition, only Americans were so dissatisfied that they would consider adopting the type of health system found in another country. The majority of the public (61 percent) stated they would prefer the Canadian system of national health insurance, in which “the government pays most of the cost of care for everyone out of taxes, and the government sets all fees charged by doctors and hospitals” to the current U.S. system. A number of questions were raised about the results of this survey, including the following. (1) Were the findings of this three-nation survey replicable across multiple surveys and time periods, or were they a onetime, random result? (2) Are citizens of other industrialized countries as satisfied with their governments’ national health plans as Canadians or Britons are? Might not other nations with health systems similar to these have populations that are dissatisfied with their government-sponsored programs? (3) Were Canadians’ favorable attitudes toward their health system more a reflection of their optimistic and supportive views regarding their national institutions than an actual measure of their satisfaction with their universal health program? This DataWatch seeks to address these questions with recent findings from a number of international and domestic opinion surveys.

Physicians' time is under assault in the current health care system. In particular, managed care payers are reducing compensation to physicians on a discounted fee-for-service basis. More demanding consumers, complex new technologies, and increased managerial and administrative burdens are placing further constraints on physicians' time. As we look ahead, it seems likely that these pressures will intensify and transform the ways in which physicians spend their time. Physicians will play eight key roles in the future: clinical data collector, shaman, health advisor and wellness coach, knowledge navigator, proceduralist, diagnostician, physician manager, and quality assurance specialist. They will need to lead the redesign of these roles and define the ways in which they should spend their time in the health care system of the new millennium.

Guillain-Barre syndrome and its variant, Miller-Fisher syndrome, are acute, postinfectious, autoimmune neuropathies that frequently follow Campylobacter jejuni enteritis. The pathogenesis is believed to involve molecular mimicry between sialylated epitopes on C. jejuni LPSs and neural gangliosides. More than 90% of Miller-Fisher syndrome cases have serum anti-GQ1b and anti-GT1a ganglioside antibodies that may also react with other disialylated gangliosides including GD3 and GD1b. Structural studies on LPS from neuropathy-associated C. jejuni strains have revealed GT1a-like and GD3-like core oligosaccharides. To determine whether this structural mimicry results in pathogenic autoantibodies, we immunized mice with GT1a/GD3-like C. jejuni LPS and then cloned mAb’s that reacted with both the immunizing LPS and GQ1b/GT1a/GD3 gangliosides. Immunohistology demonstrated antibody binding to ganglioside-rich sites including motor nerve terminals. In ex vivo electrophysiological studies of nerve terminal function, application of antibodies either ex vivo or in vivo via passive immunization induced massive quantal release of acetylcholine, followed by neurotransmission block. This effect was complement-dependent and associated with extensive deposits of IgM and C3c at nerve terminals. These data provide strong support for the molecular mimicry hypothesis as a mechanism for the induction of cross-reactive pathogenic anti-ganglioside/LPS antibodies in postinfectious neuropathies.

We report a full-scale calculation of the third-order susceptibility, X((3)), in GaAs-AlAs superlattices. We present the frequency dependence of X((3)) and find a favorable figure of merit for near-resonant enhancement of X((3)).

We report the electronic and optical properties of very-small-period (10--30-A\r{}) Si/${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ge}}_{\mathrm{x}}$ superlattices. We present the first conduction dispersion relations (band structures) and the oscillator strengths for these systems. The magnitude of the oscillator strength associated with the transition across the fundamental superlattice gap is explained in terms of the relative importance of the strain and microscopic potential. In particular, it is found that the oscillator strength strongly reflects the relationship between the degree of momentum mixing and the corresponding wave-function overlap in real space concerning the states involved in the transition. A detailed description is given of the symmetry properties of the optical spectra in question and their relationship to the splitting of the degeneracy at the top of the valence band.

We report on an investigation of four-dimensional terminal cyclic quotient singularities which are not Gorenstein. (For simplicity, we focus on quotients by cyclic groups of prime order.) An enumeration, using a computer, of all such singularities for primes < 1600 led us to conjecture a structure theorem for these singularities (which is rather more complicated than the known structure theorem in dimension three). We discuss this conjecture and our evidence for it; we also discuss properties of the anticanonical and antibicanonical linear systems of these singularities. Introduction. The recent successes in understanding the birational geometry of algebraic varieties of dimension greater than two have focused attention on a class of singularities (called terminal singularities) which appear on the birational models which the theory selects. In dimension three, the structure of these terminal singularities is known in some detail: The terminal quotient singularities were classified, in what is now called the "terminal lemma", by several groups of people working independently (cf. [1], [2], [5], [8]), and all other three-dimensional terminal singularities were subsequently classified by work of the first author [6] and of Kollar and Shepherd-Barron [4]. Both of these classifications were based on key results of Reid [10], [11] who reduced the problem to an analysis of quotients of smooth points and double points by cyclic group actions. (A detailed account of the classification can be found in [12].) A consequence of this classification, apparently first observed by Reid [12], is that for any three-dimensional terminal singularity T, the general element of the anticanonical linear system I KT has only canonical singularities. This in turn implies that if we form the double cover of T branched on the general antibicanonical divisor D E I 2KT I, that double cover will also have only canonical singularities. At first glance, this second property appears to have no advantages over the first, but looking at things in these terms proved decisive in a slightly more global context: Kawamata [3] showed that if T is an "extremal neighborhood" of a rational curve C on a threefold, then the existence of such a divisor D globally on T is sufficient to conclude the existence of a certain kind of birational modification (a "directed flip") centered on C. The first author [7] showed that such divisors always exist, completing the proof of the Minimal Model Theorem for threefolds. (See [7] for more details.) Received August 26, 1987; revised December 17, 1987. 1980 Mathematics Subject Classification (1985 Revision). Primary 14B05; Secondary 14-04, 14J10, 14L32. *Research partially supported by the National Science Foundation. ** Current addresses. S. M.: Department of Mathematics, Faculty of Science, Nagoya University, Nagoya 464, Japan; D. R. M.: Department of Mathematics, Duke University, Durham, North Carolina 27706; I. M.: Department of Mathematics, Fordham University, Bronx, New York 10458. ? 1988 American Mathematical Society 0025-5718/88 $1.00 + $.25 per page

Clinical chemistry tests are most frequently ordered by physicians and consequently, this branch of laboratory medicine incurs substantial operational costs. This study describes an analysis of factors affecting the cost of tests in a clinical chemistry laboratory in a major teaching hospital. Results indicate that increasing automation in clinical chemistry has been associated with an alteration in the mix of tests ordered, a reduction in real labor and capital costs per test, and an increase in real cost of consumables per test. Increased use of a relatively small number of highly automated tests has contributed to increases in use and cost.

We report pseudopotential calculations of the electronic structure of strained-layer superlattices consisting of Si and ${\mathrm{Si}}_{0.5}$${\mathrm{Ge}}_{0.5}$, with periods in the range 20--140 A\r{}. In our calculation, both the effect of the microscopic crystal potential and that of the strain peculiar to the choice of ${\mathrm{Si}}_{0.75}$${\mathrm{Ge}}_{0.25}$ as a buffer layer are taken into account. The superlattice energy levels and wave functions are obtained in the wave-vector space by expanding the wave function in terms of the eigenfunctions of a bulk crystal Hamiltonian of the buffer layer. In this representation, the superlattice wave function is uniquely determined by a set of bulk wave vectors and the optical matrix elements can be obtained directly from the corresponding expansion coefficients. We assume the strain is uniform in both constituents with the lattice constant parallel to the interfaces being determined by the choice of buffer layer. Two different strain configurations are then investigated: firstly the lattice separation in directions perpendicular to the interfaces being the same as in the unstrained bulk constituents and secondly with this lattice separation as in the minimum-energy configuration. A scheme involving the nearly-free-electron model is used to deal with the absolute energies of the constituents. We find that the electron states are confined in the silicon layers, in agreement with existing experimental results. The effective confining barrier in the conduction and valence bands is strain dependent. We model the evolution of the effect of strain upon the formation of confined states and demonstrate that the position of the conduction- and valence-band levels is a sensitive function of strain and well and/or barrier widths. We calculate the optical matrix element across the fundamental superlattice gap and find that the superlattice potential enhances this optical matrix element in ultrathin layers.

The development of dynamics concepts is studied longitudinally with two groups, one between ages 12‐14 and the other from 14‐16. Data collected includes performances on APS tasks (for which there is also national data) and performance on Piagetian tasks, with interviews on tasks for selected pupils. Classroom science curriculum data was also obtained. The study can thus discuss the interaction of cognitive development and classroom experience in the development of concepts. This particular paper focuses on the APS tasks.

The purpose of this study was to obtain a numerically accurate discrete model of the effect of front aspheric soft lenses of various asphericities on the retinal illuminance profiles within the blur circles of a model eye. A computer program was developed for a model eye based on geometrical optics. The ray density was assumed to be proportional to the flux density or illumination. Retinal illuminance profiles are calculated for several values of defocus and asphericity. These results are validated by calculations based on modulation transfer functions (MTFs), observational data from contrast sensitivity and clinical results with Cals aspheric soft lenses. The results suggest that aspheric soft lenses maximize the central illuminance of blur circles and extend the range of desensitivity to retinal defocus in the eye to 4.00 D at the largest asphericity constant investigated.

Experimental archaeology has now a definite place in research and the late Paul Johnstone was a pioneer in organizing such experiments especially with boats. In our February issue we published a reconsideration of his experiment, in collaboration with Professor Marstrander, on building a hide boat. We now welcome a discussion by Mr Christensen and Dr Morrison on the recent publication The building and trials of the replica of an ancient boat: the Gokstad faering Part 1. Building the replica by Sean McGrail. 59 pp. 50 figs. Part 2. The sea trials by Eric McKee. 38 pp. 25 figs. National Maritime Museum. Maritime monographs and reports no. 11, 1974. London. Ed.

We report a pseudopotential calculation of the nonparabolicity of the conduction and valence minibands for Si-${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ge}}_{\mathrm{x}}$ strained-layer superlattices of period 10--30 A\r{}. We find that the conduction-band nonparabolicity in directions both perpendicular (z) and parallel to the interface planes is several orders of magnitude larger than that for bulk silicon and is comparable in magnitude with the value for bulk GaAs. Along the superlattice axis (z), the conduction-band nonparabolicity is dominated by virtual transitions involving the lowest conduction states and strongly reflects the energy separation between them. Since this separation depends on strain and layer widths, the magnitude of this nonparabolicity can be ``tuned'' over 2 orders of magnitude. In the valence band, and along the direction parallel to the interface planes in the conduction band, the nonparabolicity is dominated by virtual excitations across the fundamental gap. The effective masses are also presented. A comparison is given of the mechanisms determining band nonparabolicity in Si-${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ge}}_{\mathrm{x}}$, GaAs-${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Al}}_{\mathrm{x}}$As, and GaAs-${\mathrm{GaAs}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{P}}_{\mathrm{x}}$ superlattices.

We present a quantitative study of the electronic structure and zone folding in Si SiGe and Si SiSn strained layer superlattices. We find that the effect of strain is to increase the degree of electronic confinement and to enhance the optical matrix element across the fundamental superlattice gap, although this latter effect is small in the systems studied.

The authors have carried out a pseudopotential calculation of the electronic structure of a strained Si/Si0.5Ge0.5 superlattice in which the effect of strain peculiar to the choice of substrate (i.e. Si0.75Ge0.25) and that of the microscopic potential of the individual layers are fully accounted for. They report several strain-induced well confined electron states localised in the silicon layers. They find that the optical matrix element for the transition across the fundamental superlattice gap is quite small.

The communist insurrection in Malaya will be six months old by the end of this year. Two questions are frequently asked in connection with it: What is its relation to communist uprisings elsewhere in South? east Asia? And why and when did the Malayan Com? munist Party decide to resort to direct action? The answers are bound to be speculative in charac? ter, for no direct sources of information are available. The central executive committee of the Malayan Com? munist Party (MCP), its high command, has always been an ultra-secret underground body, even during the postwar period when the party was a legal organization. The party was proscribed immediately after the in? surrection and is now likely to remain so for a long time to come.

We show that the nonlinear response of a direct‐gap semiconductor superlattice is greatly enhanced when the separation of the lowest two conduction minibands approaches the magnitude of the principal gap. Two structures exhibiting this enhanced nonlinear response are described.

In this review we have tried to identify some of the management issues affecting laboratories in the past, present, and future. In particular, we have focused on the increases in utilization and cost and have attempted to demonstrate some of the factors affecting the supply and demand sides of these issues. In the absence of a price mechanism to allocate resources, alternative strategies to evaluate and regulate laboratory use were discussed. Although promise is held out by some of these approaches, they are not, in our view, fully workable at this stage. We suggest that, in the interim, sound medical direction and management of the laboratory as a production function can be of benefit in inhibiting, if not actually controlling, cost increases. In particular, we recommend concentration on the management of technology because of its crucial role in laboratory costs and utilization. Emerging trends in clinical laboratory and monitoring technologies suggest that issues relating to decentralization, quality control, and funding will have to be addressed in the near future. The prime motivation for clinical laboratory use, i.e., the generation of answers to clinical questions, seems destined to continue and expand. The challenge for practitioners, researchers, and policy-makers is to harness, evaluate, and manage the technologies that can best contribute to both medical practice and health.

Les calculs a partir d'un modele de pseudopotentiel de la structure electronique du superreseau Si 4 Ge 4 (001) sont effectues. Les spectres optiques observes sont expliques, sans l'aide de transitions indirectes, en termes de modele dans lequel le potentiel microscopique et des longueurs des liaisons dans la couche Ge sont de type volume

We have carried out full-scale pseudopotential calculations of the effect of zone-fol-ding on band structure, optical absorption and non-linear response function of semiconductor superlattices. To provide a complete picture of this phenomenon we chose to study GaAs-Gal-xAlxAs, Si-Si1-xGe and HgTe-CdTe superlattices which represent examples of the breakdown of the simple particle-in-a-box model because of Γ - X mixing, strain and relativistic effects, respectively.

Real space, high-resolution transmission electron microscopy observations of Xe confined in nanometer size faceted cavities in Al yield information on both the inert gas and the matrix in which it is confined. At room temperature, Xe in such cavities can be liquid or an fcc solid. In larger cavities, Xe within can undergo melting and recrystallization. The Al surface energy can be deduced from the largest Xe nanocrystal at 300 K by setting the corresponding calculated Laplace pressure equal to the equilibrium pressure for melting of Xe, obtained from empirical bulk compression data. These surface energy values are 1.05 J m-2 for {111} facets and 1.10 Jm-2 for {200} facets. Because of the weak interactions, these values correspond to the surface tensions for Al at 300 K.At room temperature, fluid Xe confined in small faceted cavities in aluminum has up to three ordered layers of Xe atoms at the Al interface. Conceptually in a three-dimensionally confined system of sufficiently small size, complete three-dimensional ordering of the fluid may occur. Molecular dynamics simulations have revealed that such ordering would result in fluid Xe confined to a small tetragonal volume solidifying as a body-centered cubic phase on compression.

REM sleep behavior disorder (RBD) is a parasomnia in which normal muscle atonia of REM sleep is lost. The aim of this study was to confirm if diagnostic delay exists in RBD and identify any contributing factors.A database was compiled of 49 patients with RBD seen at a tertiary referral center from 2005 to 2011 by retrospective review of referral letters and polysomnographic (PSG) reports. Patients with comorbid narcolepsy were excluded. A questionnaire was sent to investigate diagnostic delay, management, and comorbidities.Mean diagnostic delay was 8.7 ± 11 (median 4.5, IQR 1.75-11.75) years in 30 questionnaire responders. Common reasons for diagnostic delay included belief that symptoms were not serious enough to consult a doctor (59%), mild or infrequent occurrence of sleep behavior (56%), belief that symptoms may resolve (47%), and lack of knowledge of treatment options (47%). The bed partner was an important influence, with the decision to seek medical attention being made jointly by the patient and partner in 47%.This study has demonstrated the existence of significant diagnostic delay in RBD, mainly due to lack of understanding of the disorder and its treatment by patients and members of the medical profession.

We provide an overview of the exciting capabilities of the SKA in the Cradle of Life theme. With the deployment of the high frequency band 5 receivers, the phase 1 of the SKA can conduct headline science in the study of the earliest stages of grain growth in proto-planetary disks. SKA1-MID can map the 2 cm continuum emission at a resolution of 4 au in the nearest systems and therefore begin to probe the distribuion of cm-sized particles across the snow line. This frequency range will also enable deep searches for pre-biotic molecules such as amino acids from pre-stellar cores to the cold, outer regions of proto-planetary disks where cometary material forms. The lowest frequency capabilities of SKA1 can be used to examine the magnetic fields of exo-planets via their auroral radio emission. This gives unique insight into their interiors and could potentially detect exo-moons. Across the full frequency range, the SKA1 will also carry out systematic, volume-limited searches of exo-planet systems for signals from technologically advanced civilizations. The sensitivity of SKA1 means that these only need to be at the level of typical airport radar signals in the nearest systems. Hence, the SKA1 can conduct high impact science from the first steps on the road to planets and life, through areas affecting the habitability of planets, and ultimately, to whether we are alone in the Galaxy. These inspirational themes will greatly help in the effort to bring SKA1 science to a wide audience and to ensure the progression to the full SKA.

After more than 50 years of searching the skies across the electromagnetic spectrum, no evidence has yet been found for the existence of extraterrestrial life, let alone a signature that could be attributed to an intelligent and technological extraterrestrial civilisation. Proposed explanations range from the non-existence of such putative civilisations, to the likelihood that the search has barely "scratched the surface" in terms of covering the entire discovery space. The present work is premised on the latter position, and its central thesis is that most searches conducted thus far have been disadvantaged by sub-optimal design. In general, they have (1) not targeted the most appropriate signal types; (2) not targeted the region of the electromagnetic spectrum that should be preferred for interstellar communications; and (3) not consistently concentrated on the regions of the sky that hold the highest likelihood for the emergence of extraterrestrial intelligence. The very nature of past searches provides a credible explanation for the null result to date. It is impossible to predict the specific technologies and communications methodologies likely to be adopted by extraterrestrial civilisations, particularly when one considers how much older and more technologically advanced than ourselves they may be. However, beginning with a single key assumption – that energy efficiency is a concern to those wishing to transmit signals across interstellar space – this work shows how the application of fundamental principles of astrophysics and information theory can lead to meaningful constraints on the discovery space for artificial interstellar signals. It is shown why the search for extraterrestrial intelligence should focus on intentionally transmitted wideband signals occupying the upper end of the microwave range of the radio spectrum - a region largely ignored by past searches. Furthermore, searches should concentrate on the inner Galaxy rather than our own solar neighbourhood. A new signal processing algorithm is introduced for the blind detection of wideband signals of a class that is attractive for interstellar communications, offering high detection sensitivity while making minimal assumptions about the precise signal format. The findings of this thesis suggest a range of new priorities and approaches to the search for extraterrestrial intelligence, aimed at increasing its chances of success.