Challenges for the National Institute for Clinical Excellence

Rationing health care is inevitable, and NICE should inform NHS decision making. Adoption of new technologies by NHS clinicians should be informed by costs as well as effectiveness. The NHS needs better information from NICE on the equity implications of new and existing technologies. NICE appraisal should focus not only on service enhancement but also on withdrawal of existing ineffective or inefficient therapies. Giving NICE a real budget to fund its recommendations would encourage it to examine the effect of its decisions on the whole NHS

Impact of NICE guidance on laparoscopic surgery for inguinal hernias: analysis of interrupted time series

After the introduction of Bassini's procedure in the late 19th century, methods of repairing hernias changed little until the 1990s, when synthetic mesh and laparoscopic methods arrived. In contrast to the open mesh technique, laparoscopic surgery remains uncommon. In January 2001, the National Institute for Clinical Excellence (NICE) issued guidance that stated, "For repair of primary inguinal hernia, open [mesh] should be the preferred surgical procedure." We describe patterns of surgical repair of inguinal hernias and assess the impact of NICE's guidance

IMPACT OF RISK PREFERENCES ON CROP ROTATION CHOICE

Stochastic dominance analysis of five crop rotations using twenty-one years of experimental yield data returned results consistent with Pennsylvania cropping practices. The analysis incorporated yield risk, output price risk, and rotational yield effects. A rotation of two years corn and three years alfalfa hay dominated for approximately risk neutral and risk averse preferences, as did participation in government programs under the 1990 Farm Bill. Crop rotation selection appeared to impact net revenues more than the decision to participate in government programs.Crop Production/Industries, Risk and Uncertainty,

Competition and cooperation in one-dimensional stepping stone models

Cooperative mutualism is a major force driving evolution and sustaining ecosystems. Although the importance of spatial degrees of freedom and number fluctuations is well-known, their effects on mutualism are not fully understood. With range expansions of microbes in mind, we show that, even when mutualism confers a distinct selective advantage, it persists only in populations with high density and frequent migrations. When these parameters are reduced, mutualism is generically lost via a directed percolation process, with a phase diagram strongly influenced by an exceptional DP2 transition.Comment: 8 pages, 4 figure

Phase Diagrams of Quasispecies Theory with Recombination and Horizontal Gene Transfer

We consider how transfer of genetic information between individuals influences the phase diagram and mean fitness of both the Eigen and the parallel, or Crow-Kimura, models of evolution. In the absence of genetic transfer, these physical models of evolution consider the replication and point mutation of the genomes of independent individuals in a large population. A phase transition occurs, such that below a critical mutation rate an identifiable quasispecies forms. We generalize these models of quasispecies evolution to include horizontal gene transfer. We show how transfer of genetic information changes the phase diagram and mean fitness and introduces metastability in quasispecies theory, via an analytic field theoretic mapping.Comment: 5 pages, 1 figure, to appear in Physics Review Letter

Total hemispherical emissivity of very high temperature reactor (VHTR) candidate materials : Hastelloy X, Haynes 230, and Alloy 617

"July 2011"The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Title from PDF of title page (University of Missouri--Columbia, viewed on May 17, 2012).Dissertation advisor: Dr. Tushar K. GhoshVita.An experimental system was constructed in accordance with the standard ASTM C835-06 to measure the total hemispherical emissivity of structural materials of interest in Very High Temperature Reactor (VHTR) systems. The system was tested with 304 stainless steel as well as oxidized and un-oxidized nickel, and good reproducibility and agreement with the literature data was found. Emissivity of each candidate material was measured over a wide range of temperatures, with conditions that included: i) 'as received' (original sample) from the supplier; ii) increased surface roughness; iii) oxidized, and; iv) graphite coated. The emissivity of as-received materials increased with temperature for Hastelloy X (from 0.18 at 473 K to 0.28 at 1498 K), Haynes 230 (from 0.178 at 600 K to 0.235 at 1375 K), and Alloy 617 (about 0.2 at 600 K to about 0.35 at 1275 K). Oxidation was found to increase emissivity, but as there is some oxidation of these materials used in the construction of VHTRs, this represents an essentially neutral finding in terms of the safety implications in post-accident VHTR environments. However, a coating of graphite powder was shown to substantially increase emissivity, and this has strong favorable safety implications in terms of decay heat removal in post-accident VHTR environments.Includes bibliographical reference

Chains of large gaps between primes

Let $p_n$ denote the $n$-th prime, and for any $k \geq 1$ and sufficiently large $X$, define the quantity $$G_k(X) := \max_{p_{n+k} \leq X} \min( p_{n+1}-p_n, \dots, p_{n+k}-p_{n+k-1} ),$$ which measures the occurrence of chains of $k$ consecutive large gaps of primes. Recently, with Green and Konyagin, the authors showed that $$G_1(X) \gg \frac{\log X \log \log X\log\log\log\log X}{\log \log \log X}$$ for sufficiently large $X$. In this note, we combine the arguments in that paper with the Maier matrix method to show that $$G_k(X) \gg \frac{1}{k^2} \frac{\log X \log \log X\log\log\log\log X}{\log \log \log X}$$ for any fixed $k$ and sufficiently large $X$. The implied constant is effective and independent of $k$.Comment: 16 pages, no figure

Characteristics of vertical and lateral tunnel turbulence measured in air in the Langley Transonic Dynamics Tunnel

Preliminary measurements of the vertical and lateral velocity components of tunnel turbulence were obtained in the Langley Transonic Dynamics Tunnel test section using a constant-temperature anemometer equipped with a hot-film X-probe. For these tests air was the test medium. Test conditions included tunnel velocities ranging from 100 to 500 fps at atmospheric pressure. Standard deviations of turbulence velocities were determined and power spectra were computed. Unconstrained optimization was employed to determine parameter values of a general spectral model of a form similar to that used to describe atmospheric turbulence. These parameters, and others (notably break frequency and integral scale length), were determined at each test condition and compared with those of Dryden and Von Karman atmospheric turbulence spectra. When the data were discovered to be aliased, the spectral model was modified to account for and 'eliminate' the aliasing