The credibility of health economic models for health policy decision-making: the case of population screening for abdominal aortic aneurysm

<i>Objectives</i>: To review health economic models of population screening for abdominal aortic aneurysm (AAA) among elderly males and assess their credibility for informing decision-making. <i>Methods</i>: A literature review identified health economic models of ultrasound screening for AAA. For each model focussing on population screening in elderly males, model structure and input parameter values were critically appraised using published good practice guidelines for decision analytic models. <i>Results</i>: Twelve models published between 1989 and 2003 were identified. Converting costs to a common currency and base year, substantial variability in cost-effectiveness results were revealed. Appraisals carried out for the nine models focusing on population screening showed differences in their complexity, with the simpler models generating results most favourable to screening. Eight of the nine models incorporated two or more simplifying structural assumptions favouring screening; uncertainty surrounding these assumptions was not investigated by any model. Quality assessments on a small number of parameters revealed input values varied between models, methods used to identify and incorporate input data were often not described, and few sensitivity analyses were reported. <i>Conclusions</i>: Large variation exists in the cost-effectiveness results generated by AAA screening models. The substantial number of factors potentially contributing to such disparities means that reconciliation of model results is impossible. In addition, poor reporting of methods makes it difficult to identify the most plausible and thus most useful model of those developed

Community violence in Dar es Salaam, Tanzania: A mixed methods study

Most homicide deaths in Dar es Salaam, Tanzania (DSM) are a result of violence arising from within the community. This type of violence is commonly called, by perpetrators and victims, “mob justice”. Unilateral non-state collective violence can take four forms: lynching, vigilantism, rioting, and terrorism. The purpose of this paper is to report what leads to death by such violence in DSM. A cross-sectional mixed methods study design was used. Surveillance data were collected on all 206 victims of “mob justice” in DSM for the year 2005. Fifteen in-depth interviews were conducted with the relatives of deceased victims, a policeman, a journalist, community members, and youths who survived these types of community violence. A focus group discussion was conducted with eight youths at risk of such violence. The deceased were young adult males and differed significantly from assault victims as to age, occupation, weapon causing death, and injury site. Ninety percent were identified as: unemployed, thieves, unknowns, or street vendors. The immediate history of the deceased usually involved theft. The stated desire of community members was to live in peace; they acknowledged that murder is unlawful. Often the victims had been warned; if transgressions continued, male community members punished the individual, which led to death. Family reactions varied from relief, to confusion, and loss. Community level violence in DSM is defensive; the goal is to protect the community. It is focused on individuals, not groups; incidents can be classified along the continuum of lynching and vigilantism in which lynching is a spontaneous reaction to deviance and vigilantism is an organised activity. Decreasing the number of deviant social acts should theoretically decrease cases of lynching and vigilantism. The most humane way to decrease petty theft is through appropriate employment.Keywords: homicide; Africa; Tanzania; vigilantism; lynching; community; mo

The Spectral Action Principle in Noncommutative Geometry and the Superstring

A supersymmetric theory in two-dimensions has enough data to define a noncommutative space thus making it possible to use all tools of noncommutative geometry. In particular, we apply this to the N=1 supersymmetric non-linear sigma model and derive an expression for the generalized loop space Dirac operator, in presence of a general background, using canonical quantization. The spectral action principle is then used to determine a spectral action valid for the fluctuations of the string modes.Comment: Latex file, 13 pages. Correction to equation 47, which should read Tr| |^2 and not |Tr |^2. Final form to appear in Physics Letters

Electronic excitations and the tunneling spectra of metallic nanograins

Tunneling-induced electronic excitations in a metallic nanograin are classified in terms of {\em generations}: subspaces of excitations containing a specific number of electron-hole pairs. This yields a hierarchy of populated excited states of the nanograin that strongly depends on (a) the available electronic energy levels; and (b) the ratio between the electronic relaxation rate within the nano-grain and the bottleneck rate for tunneling transitions. To study the response of the electronic energy level structure of the nanograin to the excitations, and its signature in the tunneling spectrum, we propose a microscopic mean-field theory. Two main features emerge when considering an Al nanograin coated with Al oxide: (i) The electronic energy response fluctuates strongly in the presence of disorder, from level to level and excitation to excitation. Such fluctuations produce a dramatic sample dependence of the tunneling spectra. On the other hand, for excitations that are energetically accessible at low applied bias voltages, the magnitude of the response, reflected in the renormalization of the single-electron energy levels, is smaller than the average spacing between energy levels. (ii) If the tunneling and electronic relaxation time scales are such as to admit a significant non-equilibrium population of the excited nanoparticle states, it should be possible to realize much higher spectral densities of resonances than have been observed to date in such devices. These resonances arise from tunneling into ground-state and excited electronic energy levels, as well as from charge fluctuations present during tunneling.Comment: Submitted to the Physical Review

Reach of the Fermilab Tevatron for minimal supergravity in the region of large scalar masses

The reach of the Fermilab Tevatron for supersymmetric matter has been calculated in the framework of the minimal supergravity model in the clean trilepton channel. Previous analyses of this channel were restricted to scalar masses m_0<= 1 TeV. We extend the analysis to large values of scalar masses m_0\sim 3.5 TeV. This includes the compelling hyperbolic branch/focus point (HB/FP) region, where the superpotential \mu parameter becomes small. In this region, assuming a 5\sigma (3\sigma) signal with 10 (25) fb^{-1} of integrated luminosity, the Tevatron reach in the trilepton channel extends up to m_{1/2}\sim 190 (270) GeV independent of \tan\beta . This corresponds to a reach in terms of the gluino mass of m_{\tg}\sim 575 (750) GeV.Comment: 11 page latex file including 6 EPS figures; several typos corrected and references adde

Processing blur of conflicting stimuli during the latency and onset of accommodation

The accommodative response (AR) to changes in dioptric accommodative stimulus (AS) during the latency period and onset of accommodation was investigated. Participants monocularly observed one period of a square wave in AS, with a 2-D baseline and mean, and amplitude 1 D or 2 D; the period of the square wave ranged from 0.10 s to 1.00 s; both increases and decreases were used for the first step in AS. At periods of 0.30 s and longer, accommodation was found to respond to both levels of the stimulus. Rapid retinal monitoring appeared to be taking place for such stimuli. The amplitudes of peaks in AR did not usually depend on whether a particular level of AS occurred first or second, but for 8/40 conditions, a significant difference was found, with a stronger response when the level of AS occurred second. Null or incorrect responses were also observed in many trials, possibly linked with the natural microfluctuations of accommodation. Minimum response times to the changes in AS were observed, which increased with decreasing period of the AS. The time interval between peaks in the AR decreased with decreasing period of the AS. The findings were consistent with a parallel processing model previously proposed for saccades, where input from a later change in stimulus may enter an element of the control system when that element has finished processing an earlier change. More than one change in stimulus may therefore be passing through the multi-element control system at a time

Heavy-quark mass dependence in global PDF analyses and 3- and 4-flavour parton distributions

We study the sensitivity of our recent MSTW 2008 NLO and NNLO PDF analyses to the values of the charm- and bottom-quark masses, and we provide additional public PDF sets for a wide range of these heavy-quark masses. We quantify the impact of varying m_c and m_b on the cross sections for W, Z and Higgs production at the Tevatron and the LHC. We generate 3- and 4-flavour versions of the (5-flavour) MSTW 2008 PDFs by evolving the input PDFs and alpha_S determined from fits in the 5-flavour scheme, including the eigenvector PDF sets necessary for calculation of PDF uncertainties. As an example of their use, we study the difference in the Z total cross sections at the Tevatron and LHC in the 4- and 5-flavour schemes. Significant differences are found, illustrating the need to resum large logarithms in Q^2/m_b^2 by using the 5-flavour scheme. The 4-flavour scheme is still necessary, however, if cuts are imposed on associated (massive) b-quarks, as is the case for the experimental measurement of Z b bbar production and similar processes.Comment: 40 pages, 11 figures. Grids can be found at http://projects.hepforge.org/mstwpdf/ and in LHAPDF V5.8.4. v2: version published in EPJ

The First High-Precision Radial Velocity Search for Extra-Solar Planets

In the late 1970s and early 1980s, the introduction of solid-state, signal-generating detectors and absorption cells to impose wavelength fiducials directly on the starlight, the errors in stellar radial velocity (RV) measurements were reduced to the point where Doppler searches for planets became feasible. In 1980 we began to use a hydrogen fluoride gas cell with the CFHT coud\'{e} spectrograph and, for 12 years, monitored RVs of some 29 solar-type stars. Since extra-solar planets were expected to resemble Jupiter in both mass and orbit, we were awarded only three or four two-night observing runs each year. In 1988 we highlighted a potential planetary companion to $\gamma$ Cep (K1 IV), in 1993 one to $\beta$ Gem (K0 III), and another to $\epsilon$ Eri (K2 V) in 1992. The putative planets all resembled Jovian systems with periods and masses of 2.5 yr and 1.4 $M_{J}$, 1.6 yr and 2.6 $M_{J}$, and 6.9 yr and 0.9 $M_{J}$, respectively. All three were subsequently confirmed from more extensive data by the Texas group led by Cochran and Hatzes who derived the currently accepted orbital elements. None of the systems is simple and some still question $\epsilon$ Eri b.Comment: 23 pages, 7 figure

How are management fashions institutionalized? The role of institutional work

We explore how transitory management fashions become institutionalized. Based on the concepts of institutional entrepreneurship and institutional work, we postulate that fashionable management practices acquire permanence when they are anchored within fieldwide institutions. The building of such institutions requires various types of institutional work, including political work, technical work and cultural work. Based on a review of the empirical literature on various management fashions, we identify the actors engaging in these different types of works, and their skills. Our results suggest that the institutionalization effect is stronger if more types of institutional work are deployed and if the skill sets of the involved actors vary. We also argue that institutional construction in the case of management fashions is likely to take the form of decentralized `partaking' rather than being led by a single dominant institutional entrepreneur. We conclude with implications for the study of management fashions and the role of agency in institutionalization

Factors Associated with Nodal Pathologic Complete Response Among Breast Cancer Patients Treated with Neoadjuvant Chemotherapy: Results of CALGB 40601 (HER2+) and 40603 (Triple-Negative) (Alliance)

Background: De-escalation of axillary surgery after neoadjuvant chemotherapy (NAC) requires careful patient selection. We seek to determine predictors of nodal pathologic complete response (ypN0) among patients treated on CALGB 40601 or 40603, which tested NAC regimens in HER2+ and triple-negative breast cancer (TNBC), respectively. Patients and Methods: A total of 760 patients with stage II–III HER2+ or TNBC were analyzed. Those who had axillary surgery before NAC (N = 122), or who had missing pretreatment clinical nodal status (cN) (N = 58) or ypN status (N = 41) were excluded. The proportion of patients with ypN0 disease was estimated for those with and without breast pathologic complete response (pCR) according to pretreatment nodal status. Results: In 539 patients, the overall ypN0 rate was 76.3% (411/539) to 93.2% (245/263) in patients with breast pCR and 60.1% (166/276) with residual breast disease (RD) (P < 0.0001). For patients who were cN0 pretreatment, the ypN0 rate was 88.8% (214/241), 96.3% (104/108) with breast pCR, and 82.7% (110/133) with RD. For patients who were cN1, 66.2% (157/237) converted to ypN0, 91.7% (111/121) with breast pCR and 39.7% (46/116) with RD. For patients who were cN2/3, 65.6% (40/61) converted to ypN0, 88.2% (30/34) with breast pCR and 37.0% (10/27) with RD. On multivariable analysis, only pretreatment clinical nodal status and breast pCR/RD were associated with ypN0 status (both P < 0.0001). Conclusions: Breast pCR and pretreatment nodal status are predictive of ypN0 axillary nodal involvement, with < 5% residual nodal disease among cN0 patients who experience breast pCR. These findings support the incorporation of axillary surgery de-escalation strategies into NAC trials