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

Effect of La doping on magnetic structure in heavy fermion CeRhIn5

The magnetic structure of Ce0.9La0.1RhIn5 is measured using neutron diffraction. It is identical to the incommensurate transverse spiral for CeRhIn5, with a magnetic wave vector q_M=(1/2,1/2,0.297), a staggered moment of 0.38(2)Bohr magneton per Ce at 1.4K and a reduced Neel temperature of 2.7 K.Comment: 5 pages, 2 figures, 1 table. Conf. SCES'200

Modeling Temporal-Spatial Earthquake and Volcano Clustering at Yucca Mountain, Nevada

The proposed national high-level nuclear repository at Yucca Mountain is close to Quaternary faults and cinder cones. The frequency of these events is low, with indications of spatial and temporal clustering, making probabilistic assessments difficult. In an effort to identify the most likely intrusion sites, we based a 3D finite element model on the expectation that faulting and basalt intrusions are primarily sensitive to the magnitude and orientation of the least principal stress in extensional terranes. We found that in the absence of fault slip, variation in overburden pressure caused a stress state that preferentially favored intrusions at Crater Flat. However, when we allowed central Yucca Mountain faults to slip in the model, we found that magmatic clustering was not favored at Crater Flat or in the central Yucca Mountain block. Instead, we calculated that the stress field was most encouraging to intrusions near fault terminations, consistent with the location of the most recent volcanism at Yucca Mountain, the Lathrop Wells cone. We found this linked fault and magmatic system to be mutually reinforcing in the model in that dike inflation favored renewed fault slip

Real-time PCR assays for detection and quantification of early P. falciparum gametocyte stages

Introduction The use of reverse transcription, quantitative qRT-PCR assays for detection and quantification of late gametocyte stages has revealed the high transmission capacity of the human malaria parasite, Plasmodium falciparum. A full understanding how the parasite adjusts its transmission in response to varying in-host environmental conditions during natural infections requires simultaneous quantification of early and late gametocytes. Here, we describe qRT-PCR assays that are specific for detection and quantification of early-stage gametocytes of P. falciparum. Methods The assays are based on expression of known early gametocyte genes (pfpeg4, pfg27, pfge1, pfge3 and pfgexp5). The specificity of the qRT-PCR assays was tested using purified stage II and stage V gametocytes. These validated assays were used with qRT-PCR assays targeting late stage (pfs25) and all-stage (pfs16) gametocyte-specific transcripts to quantify gametocytes in natural P. falciparum infections and in a controlled human clinical infection study. Results The relative expression of pfpeg4, pfg27 and pfge3, but not of pfge1 and pfgexp5, was significantly higher in purified stage II compared to stage V gametocytes, indicating early gametocyte specificity. In natural infections, 71.2% of individuals had both early and late gametocyte transcripts (pfpeg4/pfg27 plus pfs25), 12.6% harboured only early gametocytes transcripts (pfpeg4/pfg27), and 15.2% had only late gametocytes transcripts (pfs25). In natural infections, the limit of detection was equivalent to 190 and 390 gametocytes/mL blood for pfpeg4 and pfg27, respectively. In infected volunteers, transcripts of pfpeg4 and pfg27 were detected shortly after the onset of blood stage infection, demonstrating the specificity of the assays. Conclusion The pfpeg4 and pfg27 qRT-PCR assays can be used specifically to quantify circulating immature gametocytes. Quantification of early gametocytes will improve understanding of epidemiological processes that modulate P. falciparum transmission and enhance the evaluation of transmission blocking interventions

Dynamical chiral symmetry breaking by a magnetic field and multi-quark interactions

Catalysis of dynamical symmetry breaking by a constant magnetic field in (3+1) dimensions is considered. We use the three flavour Nambu -- Jona-Lasinio type model with 't Hooft and eight-quark interaction terms. It is shown that the multi-quark interactions introduce new additional features to this phenomenon: (a) the local minimum of the effective potential catalyzed by the constant magnetic field is smoothed out with increasing strength of the field at the characteristic scale H~10^{19} G, (b) the multi-quark forces generate independently another local minimum associated with a larger dynamical fermion mass. This state may exist even for multi-quark interactions with a subcritical set of couplings, and is globally stable with respect to a further increase of the magnetic field.Comment: 6 pages, 3 figures, added discussion and references, version to appear in Phys.Lett.

Sensitivity of the g-mode frequencies to pulsation codes and their parameters

From the recent work of the Evolution and Seismic Tools Activity (ESTA, Lebreton et al. 2006; Monteiro et al. 2008), whose Task 2 is devoted to compare pulsational frequencies computed using most of the pulsational codes available in the asteroseismic community, the dependence of the theoretical frequencies with non-physical choices is now quite well fixed. To ensure that the accuracy of the computed frequencies is of the same order of magnitude or better than the observational errors, some requirements in the equilibrium models and the numerical resolutions of the pulsational equations must be followed. In particular, we have verified the numerical accuracy obtained with the Saclay seismic model, which is used to study the solar g-mode region (60 to 140$\mu$Hz). We have compared the results coming from the Aarhus adiabatic pulsation code (ADIPLS), with the frequencies computed with the Granada Code (GraCo) taking into account several possible choices. We have concluded that the present equilibrium models and the use of the Richardson extrapolation ensure an accuracy of the order of $0.01 \mu Hz$ in the determination of the frequencies, which is quite enough for our purposes.Comment: 10 pages, 5 figures, accepted in Solar Physic

Continuous-distribution puddle model for conduction in trilayer graphene

An insulator-to-metal transition is observed in trilayer graphene based on the temperature dependence of the resistance under different applied gate voltages. At small gate voltages the resistance decreases with increasing temperature due to the increase in carrier concentration resulting from thermal excitation of electron-hole pairs. At large gate voltages excitation of electron-hole pairs is suppressed, and the resistance increases with increasing temperature because of the enhanced electron-phonon scattering. We find that the simple model with overlapping conduction and valence bands, each with quadratic dispersion relations, is unsatisfactory. Instead, we conclude that impurities in the substrate that create local puddles of higher electron or hole densities are responsible for the residual conductivity at low temperatures. The best fit is obtained using a continuous distribution of puddles. From the fit the average of the electron and hole effective masses can be determined.Comment: 18 pages, 5 figure

Regular particle acceleration in relativistic jets

Exact solution is obtained for electromagnetic field around a conducting cylinder of infinite length and finite radius, with a periodical axial current, when the wave length is much larger than the radius of the cylinder. The solution describes simultaneously the fields in the near zone close to the cylinder, and transition to the wave zone. Proper long-wave oscillations of such cylinder are studied. The electromagnetic energy flux from the cylinder is calculated. These solutions could be applied for description of the electromagnetic field around relativistic jets from active galactic nuclei and quasars and particle acceleration inside jets.Comment: 12 pages, 1 figure. To appear in Proc. of the Workshop The Multiwavelength Approach To Unidentified Gamma Ray Sources. The University of Hong Kong - Hong Kong, China, 1-4 June 200

FIELD TOLERANCE OF SELECTED VARIETIES TO AND FUNGICIDE EFFICACY AGAINST ALTERNARIA BLIGHT OF SWEET POTATO

Alternaria blight (AB) of sweet potato ( Ipomoea batatas L. ), caused by Alternaria spp., was recently reported in South Africa, but is common in southern and eastern Africa. Elsewhere in the world, AB is controlled primarily using resistant varieties. Twenty-five sweet potato varieties/breeding lines, from different origins were assessed for tolerance to AB. The materials were planted in fields having a history of AB disease and rated for tolerance based on a General Disease Index (GDI), with the lowest scores representing tolerance, and the higher scores representing susceptibility. Variety 199062-1 had the lowest GDI value, and was the most tolerant to AB; while W119 had the highest GDI value and was the most susceptible to the disease. Other varieties/breeding lines showed a variation in GDI values between most tolerant and most susceptible. Among the fungicides tested under field conditions, the mixture azoxystrobin-difenoconazole was the most effective in reducing AB intensity. Fungicides pyraclostrobin-boscalid, unizeb, azoxystrobin-chlorothalonil and cymoxanil-mancozeb were also effective against the disease.L\u2019alternariose (AB) de la patate douce ( Ipomoea batatas L. ), maladie caus\ue9e par Alternaria spp., est une maladie nouvellement rencontr\ue9e en Afrique du Sud, mais tr\ue8s fr\ue9quemment rencontr\ue9e dans les pays au Sud et \ue0 l\u2019Est de l\u2019Afrique. Ailleurs dans le monde, l\u2019utilisation de vari\ue9t\ue9 r\ue9sistantes est la premi\ue8re mesure de lutte contre les d\ue9g\ue2ts caus\ue9s par AB. Vingt cinq vari\ue9t\ue9s de patate douce de diverses origines ont \ue9t\ue9 \ue9valu\ue9es pour leur sensibilit\ue9 \ue0 l\u2019alternariose. Le mat\ue9riel g\ue9n\ue9tique avait \ue9t\ue9 plant\ue9 dans des champs ayant une fois infect\ue9s de AB et class\ue9s tol\ue9rants en fonction de leur index g\ue9n\ue9ral de la maladie (GDI). Les plus petits scores indiquent la tolerance, tandis que les scores les plus \ue9lev\ue9s indiquent la susceptibilit\ue9. La vari\ue9t\ue9 199062-1 avait la plus petite de GDI et donc \ue9tait le plus tolerant \ue0 AB, tandis que la vari\ue9t\ue9 W119 pr\ue9sentait la valeur de GDI la plus \ue9lev\ue9e; par cons\ue9quent \ue9tait la plus susceptible de toutes les vari\ue9t\ue9s. Les autres vari\ue9t\ue9s \ue9taient diff\ue9rentes en ce qui concerne leur GDI, les valeurs de GDI variaient du plus petit au plus grand. Parmi les fongicides test\ue9s, le m\ue9lange azoxystrobin-difenoconazole \ue9tait le plus efficace. Les fongicides pyraclostrobin-boscalid, unizeb, azoxystrobin-chlorothalonil et cymoxanil-mancozeb \ue9taient aussi efficace contre l\u2019 alternariose

Disorder-to-order transition in the magnetic and electronic properties of URh_2Ge_2

We present a study of annealing effects on the physical properties of tetragonal single--crystalline URh_2Ge_2. This system, which in as-grown form was recently established as the first metallic 3D random-bond heavy-fermion spin glass, is transformed by an annealing treatment into a long-range antiferromagnetically (AFM) ordered heavy-fermion compound. The transport properties, which in the as-grown material were dominated by the structural disorder, exhibit in the annealed material signs of typical metallic behavior along the crystallographic a axis. From our study URh_2Ge_2 emerges as exemplary material highlighting the role and relevance of structural disorder for the properties of strongly correlated electron systems. We discuss the link between the magnetic and electronic behavior and how they are affected by the structural disorder.Comment: Phys. Rev. B, in print (scheduled 1 Mar 2000