Acceptance Criteria for Critical Software Based on Testability Estimates and Test Results

Testability is defined as the probability that a program will fail a test, conditional on the program containing some fault. In this paper, we show that statements about the testability of a program can be more simply described in terms of assumptions on the probability distribution of the failure intensity of the program. We can thus state general acceptance conditions in clear mathematical terms using Bayesian inference. We develop two scenarios, one for software for which the reliability requirements are that the software must be completely fault-free, and another for requirements stated as an upper bound on the acceptable failure probability

Transformation of spin information into large electrical signals via carbon nanotubes

Spin electronics (spintronics) exploits the magnetic nature of the electron, and is commercially exploited in the spin valves of disc-drive read heads. There is currently widespread interest in using industrially relevant semiconductors in new types of spintronic devices based on the manipulation of spins injected into a semiconducting channel between a spin-polarized source and drain. However, the transformation of spin information into large electrical signals is limited by spin relaxation such that the magnetoresistive signals are below 1%. We overcome this long standing problem in spintronics by demonstrating large magnetoresistance effects of 61% at 5 K in devices where the non-magnetic channel is a multiwall carbon nanotube that spans a 1.5 micron gap between epitaxial electrodes of the highly spin polarized manganite La0.7Sr0.3MnO3. This improvement arises because the spin lifetime in nanotubes is long due the small spin-orbit coupling of carbon, because the high nanotube Fermi velocity permits the carrier dwell time to not significantly exceed this spin lifetime, because the manganite remains highly spin polarized up to the manganite-nanotube interface, and because the interfacial barrier is of an appropriate height. We support these latter statements regarding the interface using density functional theory calculations. The success of our experiments with such chemically and geometrically different materials should inspire adventure in materials selection for some future spintronicsComment: Content highly modified. New title, text, conclusions, figures and references. New author include

Quantum phase transitions of light

Recently, condensed matter and atomic experiments have reached a length-scale and temperature regime where new quantum collective phenomena emerge. Finding such physics in systems of photons, however, is problematic, as photons typically do not interact with each other and can be created or destroyed at will. Here, we introduce a physical system of photons that exhibits strongly correlated dynamics on a meso-scale. By adding photons to a two-dimensional array of coupled optical cavities each containing a single two-level atom in the photon-blockade regime, we form dressed states, or polaritons, that are both long-lived and strongly interacting. Our zero temperature results predict that this photonic system will undergo a characteristic Mott insulator (excitations localised on each site) to superfluid (excitations delocalised across the lattice) quantum phase transition. Each cavity's impressive photon out-coupling potential may lead to actual devices based on these quantum many-body effects, as well as observable, tunable quantum simulators. We explicitly show that such phenomena may be observable in micro-machined diamond containing nitrogen-vacancy colour centres and superconducting microwave strip-line resonators.Comment: 11 pages, 5 figures (2 in colour

Rapid tests and urine sampling techniques for the diagnosis of urinary tract infection (UTI) in children under five years: a systematic review

Background: Urinary tract infection (UTI) is one of the most common sources of infection in children under five. Prompt diagnosis and treatment is important to reduce the risk of renal scarring. Rapid, cost-effective, methods of UTI diagnosis are required as an alternative to culture. Methods: We conducted a systematic review to determine the diagnostic accuracy of rapid tests for detecting UTI in children under five years of age. Results: The evidence supports the use of dipstick positive for both leukocyte esterase and nitrite (pooled LR+ = 28.2, 95% CI: 17.3, 46.0) or microscopy positive for both pyuria and bacteriuria (pooled LR+ = 37.0, 95% CI: 11.0, 125.9) to rule in UTI. Similarly dipstick negative for both LE and nitrite (Pooled LR- = 0.20, 95% CI: 0.16, 0.26) or microscopy negative for both pyuria and bacteriuria (Pooled LR- = 0.11, 95% CI: 0.05, 0.23) can be used to rule out UTI. A test for glucose showed promise in potty-trained children. However, all studies were over 30 years old. Further evaluation of this test may be useful. Conclusion: Dipstick negative for both LE and nitrite or microscopic analysis negative for both pyuria and bacteriuria of a clean voided urine, bag, or nappy/pad specimen may reasonably be used to rule out UTI. These patients can then reasonably be excluded from further investigation, without the need for confirmatory culture. Similarly, combinations of positive tests could be used to rule in UTI, and trigger further investigation

On Schubert's Problem of Characteristics

The Schubert varieties on a flag manifold G/P give rise to a cell decomposition on G/P whose Kronecker duals, known as the Schubert classes on G/P, form an additive base of the integral cohomology of G/P. The Schubert's problem of characteristics asks to express a monomial in the Schubert classes as a linear combination in the Schubert basis. We present a unified formula expressing the characteristics of a flag manifold G/P as polynomials in the Cartan numbers of the group G. As application we develop a direct approach to our recent works on the Schubert presentation of the cohomology rings of flag manifolds G/P.Comment: 27page

Characterization of Parameters Required for Effective Use of Tamoxifen-Regulated Recombination

Conditional gene targeting using the Cre-loxp system is a well established technique in numerous in vitro and in vivo systems. Ligand regulated forms of Cre have been increasingly used in these applications in order to gain temporal and spatial control over conditional targeting. The tamoxifen-regulated Cre variant mer-Cre-mer (mCrem) is widely utilized because of its reputation for tight regulation in the absence of its tamoxifen ligand. In the DT40 chicken B cell line, we generated an mCrem-based reversible switch for conditional regulation of a transgene, and in contrast with previous work, observed significant constitutive activity of mCrem. This prompted us to use our system for analysis of the parameters governing tamoxifen-regulated mCrem recombination of a genomic target. We find that robust mCrem expression correlates with a high level of tamoxifen-independent Cre activity, while clones expressing mCrem at the limit of western blot detection exhibit extremely tight regulation. We also observe time and dose-dependent effects on mCrem activity which suggest limitations on the use of conditional targeting approaches for applications which require tight temporal coordination of Cre action within a cell population

Estimation of the incidence of genital warts and the cost of illness in Germany: A cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Human papillomavirus (HPV) is a necessary cause of cervical cancer. HPV is also responsible for benign <it>condylomata acuminata</it>, also known as genital warts. We assessed the incidence of genital warts in Germany and collected information on their management to estimate the annual cost of disease.</p> <p>Methods</p> <p>This was a multi-centre observational (cross-sectional) study of genital warts in Germany. Data were collected from gynecologists, dermatologists, and urologists seeing patients with genital warts between February and April 2005. The number of patients with new and recurrent genital warts was used to estimate the incidence in Germany. We assessed resource use for patients with genital warts seen during a two-month period as well as retrospective resource use twelve months prior to the inclusion visit through a chart review. The mean costs of treatment of patients with genital warts from third-party payer and societal perspectives were estimated, and the total annual cost of genital warts was then calculated.</p> <p>Results</p> <p>For the incidence calculation 217 specialists provided information on 848 patients and 214 specialists provided resource use data for 617 patients to assess resource consumption. The incidence of new and recurrent cases of genital warts was 113.7 and 34.7 per 100 000, respectively, for women aged 14–65 years consulting gynecologists. The highest incidence was observed in women aged 14–25 years (171.0 per 100 000) for new cases and in women aged 26–45 years (53.1 per 100 000) for recurrent cases. The sample size for males was too small to allow a meaningful estimate of the incidence. The mean direct cost per patient with new genital warts was estimated at 378 euros (95% CI: 310.8–444.9); for recurrent genital warts at 603 euros (95% CI: 436.5–814.5), and for resistant genital warts at 1,142 euros (95% CI: 639.6–1752.3). The overall cost to third-party payers was estimated at 49.0 million euros, and the total societal cost at 54.1 million euros, corresponding to an average cost per patient of 550 euros and 607 euros, respectively.</p> <p>Conclusion</p> <p>The societal burden and costs of managing and treating genital warts in Germany are considerable. A vaccination programme using the quadrivalent human papillomavirus vaccine could provide a substantial health benefit and reduce the costs associated with genital warts in Germany.</p

How does study quality affect the results of a diagnostic meta-analysis?

Background: The use of systematic literature review to inform evidence based practice in diagnostics is rapidly expanding. Although the primary diagnostic literature is extensive, studies are often of low methodological quality or poorly reported. There has been no rigorously evaluated, evidence based tool to assess the methodological quality of diagnostic studies. The primary objective of this study was to determine the extent to which variations in the quality of primary studies impact the results of a diagnostic meta-analysis and whether this differs with diagnostic test type. A secondary objective was to contribute to the evaluation of QUADAS, an evidence-based tool for the assessment of quality in diagnostic accuracy studies. Methods: This study was conducted as part of large systematic review of tests used in the diagnosis and further investigation of urinary tract infection (UTI) in children. All studies included in this review were assessed using QUADAS, an evidence-based tool for the assessment of quality in systematic reviews of diagnostic accuracy studies. The impact of individual components of QUADAS on a summary measure of diagnostic accuracy was investigated using regression analysis. The review divided the diagnosis and further investigation of UTI into the following three clinical stages: diagnosis of UTI, localisation of infection, and further investigation of the UTI. Each stage used different types of diagnostic test, which were considered to involve different quality concerns. Results: Many of the studies included in our review were poorly reported. The proportion of QUADAS items fulfilled was similar for studies in different sections of the review. However, as might be expected, the individual items fulfilled differed between the three clinical stages. Regression analysis found that different items showed a strong association with test performance for the different tests evaluated. These differences were observed both within and between the three clinical stages assessed by the review. The results of regression analyses were also affected by whether or not a weighting (by sample size) was applied. Our analysis was severely limited by the completeness of reporting and the differences between the index tests evaluated and the reference standards used to confirm diagnoses in the primary studies. Few tests were evaluated by sufficient studies to allow meaningful use of meta-analytic pooling and investigation of heterogeneity. This meant that further analysis to investigate heterogeneity could only be undertaken using a subset of studies, and that the findings are open to various interpretations. Conclusion: Further work is needed to investigate the influence of methodological quality on the results of diagnostic meta-analyses. Large data sets of well-reported primary studies are needed to address this question. Without significant improvements in the completeness of reporting of primary studies, progress in this area will be limited

Neuronal circuitry for pain processing in the dorsal horn

Neurons in the spinal dorsal horn process sensory information, which is then transmitted to several brain regions, including those responsible for pain perception. The dorsal horn provides numerous potential targets for the development of novel analgesics and is thought to undergo changes that contribute to the exaggerated pain felt after nerve injury and inflammation. Despite its obvious importance, we still know little about the neuronal circuits that process sensory information, mainly because of the heterogeneity of the various neuronal components that make up these circuits. Recent studies have begun to shed light on the neuronal organization and circuitry of this complex region

Darbepoetin alfa for treating chemotherapy-induced anemia in patients with a baseline hemoglobin level < 10 g/dL versus ≥10 g/dL: an exploratory analysis from a randomized, double-blind, active-controlled trial

<p>Abstract</p> <p>Background</p> <p>Several studies have shown that darbepoetin alfa, an erythropoiesis-stimulating agent (ESA), can reduce transfusions and increase hemoglobin (Hb) levels in patients with chemotherapy-induced anemia (CIA). Recent safety concerns, however, have prompted changes to ESA product information. In the European Union and United States, ESA therapy initiation for CIA is now recommended at a Hb level ≤10 g/dL. The present exploratory analysis examined how ESA initiation at this Hb level may impact patient care.</p> <p>Methods</p> <p>Data from a phase 3 randomized trial were retrospectively reanalyzed. CIA patients with nonmyeloid malignancies were randomized 1:1 to 500 mcg darbepoetin alfa every three weeks (Q3W) or 2.25 mcg/kg darbepoetin alfa weekly (QW) for 15 weeks. A previously published report from this trial showed Q3W dosing was non-inferior to QW dosing for reducing transfusions from week 5 to end-of-the-treatment period (EOTP). In the present analysis, outcomes were reanalyzed by baseline Hb <10 g/dL and ≥10 g/dL. Endpoints included transfusion rates, Hb outcomes, and safety profiles.</p> <p>Results</p> <p>This study reanalyzed 351 and 354 patients who initiated ESA therapy at a baseline Hb of <10 g/dL or ≥10 g/dL, respectively. From week 5 to EOTP, the estimated Kaplan-Meier transfusion incidence (Q3W vs QW) was lower in the ≥10 g/dL baseline-Hb group (14% vs 21%) compared with the <10 g/dL baseline-Hb group (36% vs 41%). By week 5, the ≥10 g/dL baseline-Hb group, but not the <10 g/dL baseline-Hb group, achieved a mean Hb ≥11 g/dL. The Kaplan-Meier estimate of percentage of patients (Q3W vs QW) who achieved Hb ≥11 g/dL from week 1 to EOTP was 90% vs 85% in the ≥10 g/dL baseline-Hb group and 54% vs 57% in the <10 g/dL baseline-Hb group. Both baseline-Hb groups maintained mean Hb levels <12 g/dL and had similar safety profiles, though more patients in the ≥10 g/dL baseline-Hb group reached the threshold Hb of ≥13 g/dL.</p> <p>Conclusion</p> <p>In this exploratory analysis, darbepoetin alfa Q3W and QW raised Hb levels and maintained mean Hb at <12 g/dL in both baseline-Hb groups. The ≥10 g/dL baseline-Hb group had fewer transfusions and faster anemia correction. Additional studies should prospectively evaluate the relationship between Hb levels at ESA initiation and outcomes.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov Identifier NCT00118638.</p