Model-checking tool support for quantitative risk analysis and design for safety

This paper is concerned with quantitative analysis of tolerance of sensor hardware failures by control system software. The aim is to help the system designer evaluate the efectiveness of risk reduction measures in the system design. This paper proposes an approach for using stochastic model checking to evaluate how likely a given sensor failure mode is to lead to a hazardous system failure, taking control logic and sensor-update timing failures into account. In particular we propose two complementary techniques: one for examining short- term consequences of component failures and the other for examining more subtle longer-term consequences (so-called hidden failures). The techniques overcome scaling issues and yield valuable insights into the relative merits of dierent design decisions. The PRISM model checker is used for stochastic analysis of Continuous Time Markov Chain (CTMC) system models. The approach is illustrated on a case study from manufacturing, involving an industrial metal Press. Although relatively simple, the Press exhibits a wide range of different behaviours, including hidden failures and subtle race conditions

Can We Efficiently Help Adults Strengthen their Relational Practice?

Human interactions across settings shape young people’s learning and development, and building adult expertise in facilitating productive interactions takes deliberate practice and reflective experience. However, relational practices are not consistently part of adult learning for those who work with youth. We describe a 2-year design study to develop the Simple Interactions Leadership Program, a professional learning workshop focused on relational practices. We refined the program across 3 iterations with library and after-school staff (with a total of 41 participants). Iterative changes included adding participant-driven “try-it-out” projects, adding external accountability features, and combining staff from the library and after-school sectors. Using artifacts and memos from workshops and participants’ reflections, we found that these features incrementally improved participants’ engagement, depth of learning, and sense of professional community—which we suggest are three central goals for related professional development efforts. As a collective youth-serving field, we need effective and scalable ways to help adults recognize and strengthen their relational practices with young people. The Simple Interactions Leadership Program offers a flexible structure for professional learning focused on building expertise in relational practice while sustaining change and improvement through continuous reflection within communities of practice

Postcardiac transplant survival in the current era in patients receiving continuous-flow left ventricular assist devices

ObjectivesContinuous-flow left ventricular assist devices have become the standard of care for patients with heart failure requiring mechanical circulatory support as a bridge to transplant. However, data on long-term post-transplant survival for these patients are limited. We evaluated the effect of continuous-flow left ventricular assist devices on postcardiac transplant survival in the current era.MethodsAll patients who received a continuous-flow left ventricular assist device as a bridge to transplant at a single center from June 2005 to September 2011 were evaluated.ResultsOf the 167 patients who received a continuous-flow left ventricular assist device as a bridge to transplant, 77 (46%) underwent cardiac transplantation, 27 died before transplantation (16%), and 63 (38%) remain listed for transplantation and continued with left ventricular assist device support. The mean age of the transplanted patients was 54.5 ± 11.9 years, 57% had an ischemic etiology, and 20% were women. The overall mean duration of left ventricular assist device support before transplantation was 310 ± 227 days (range, 67-1230 days). The mean duration of left ventricular assist device support did not change in patients who had received a left ventricular assist device in the early period of the study (2005-2008, n = 62) compared with those who had received a left ventricular assist device later (2009-2011, n = 78, 373 vs 392 days, P = NS). In addition, no difference was seen in survival between those patients supported with a left ventricular assist device for fewer than 180 days or longer than 180 days before transplantation (P = NS). The actuarial survival after transplantation at 30 days and 1, 3, and 5 years by Kaplan-Meier analysis was 98.7%, 93.0%, 91.1%, and 88.0%, respectively.ConclusionsThe short- and long-term post-transplant survival for patients bridged with a continuous-flow left ventricular assist device in the current era has been excellent. Furthermore, the duration of left ventricular assist device support did not affect post-transplant survival. The hemodynamic benefits of ventricular unloading with continuous-flow left ventricular assist devices, in addition to their durability and reduced patient morbidity, have contributed to improved post-transplant survival

Modified Bell-Plesset Effect with Compressibility: Application to Double-Shell Ignition Target Designs

The effect of spherical convergence on the fluid stability of collapsing and expanding bubbles was originally treated by Bell [Los Alamos Scientific Laboratory Report No. LA-1321 (1951)] and Plesset [J. Appl. Phys. 25, 96 (1954)]. The additional effect of fluid compressibility was also considered by Bell but was limited to the case of nonzero density on only one side of a fluid interface. A more general extension is developed which considers distinct time-dependent uniform densities on both sides of an interface in a spherically converging geometry. A modified form of the velocity potential is used that avoids an unphysical divergence at the origin [Goncharov et al., Phys. Plasmas 7, 5118 (2000); Lin et al., Phys. Fluids 14, 2925 (2002)]. Two consequences of this approach are that an instability proposed by Plesset for an expanding bubble in the limit of large interior density is now absent and application to inertial confinement fusion studies of stability becomes feasible. The model is applied to a proposed ignition double-shell target design [Amendt et al., Phys. Plasmas 9, 2221 (2002)] for the National Ignition Facility [Paisner et al., Laser Focus World 30, 75 (1994)] for studying the stability of the inner surface of an imploding high-Z inner shell. Application of the Haan [Phys. Rev. A 39, 5812 (1989)] saturation criterion suggests that ignition is possible

Is high whitefly abundance on cassava in sub-Saharan Africa driven by biological traits of a specific, cryptic Bemisia tabaci species?

In East Africa, the prevalent Bemisia tabaci whiteflies on the food security crop cassava are classified as sub-Saharan Africa (SSA) species. Economically damaging cassava whitefly populations were associated with the SSA2 species in the 1990s, but more recently, it has been to SSA1 species. To investigate whether biological traits (number of first instar nymphs, emerged adults, proportion of females in progeny and development time) of the cassava whitefly species are significant drivers of the observed field abundance, our study determined the development of SSA1 sub-group (SG) 1 (5 populations), SG2 (5 populations), SG3 (1 population) and SSA2 (1 population) on cassava and eggplant under laboratory conditions. SSA1-(SG1-SG2) and SSA2 populations’ development traits were similar. Regardless of the host plant, SSA1-SG2 populations had the highest number of first instar nymphs (60.6 ± 3.4) and emerged adults (50.9 ± 3.6), followed by SSA1-SG1 (55.5 ± 3.2 and 44.6 ± 3.3), SSA2 (45.8 ± 5.7 and 32.6 ± 5.1) and the lowest were SSA1-SG3 (34.2 ± 6.1 and 32.0 ± 7.1) populations. SSA1-SG3 population had the shortest egg–adult emergence development time (26.7 days), followed by SSA1-SG1 (29.1 days), SSA1-SG2 (29.6 days) and SSA2 (32.2 days). Regardless of the whitefly population, development time was significantly shorter on eggplant (25.1 ± 0.9 days) than cassava (34.6 ± 1.0 days). These results support that SSA1-(SG1-SG2) and SSA2 B. tabaci can become highly abundant on cassava, with their species classification alone not correlating with observed abundance and prevalence

Trends in gabapentinoid prescribing, co-prescribing of opioids and benzodiazepines, and associated deaths in Scotland

Background: Gabapentinoid drugs (gabapentin and pregabalin) are effective in neuropathic pain, which has a prevalence of ~7%. Concerns about increased prescribing have implications for patient safety, misuse, and diversion. Drug-related deaths (DRDs) have increased and toxicology often implicates gabapentinoids. We studied national and regional prescribing rates (2006–2016) and identified associated sociodemographic factors, co-prescriptions and mortality, including DRDs. Methods: National data from the Information Service Division, NHS Scotland were analysed for prescribing, sociodemographic, and mortality data from the Health Informatics Centre, University of Dundee. DRDs in which gabapentinoids were implicated were identified from National Records of Scotland and Tayside Drug Death Databases. Results: From 2006 to 2016, the number of gabapentin prescriptions in Scotland increased 4-fold (164 630 to 694 293), and pregabalin 16-fold (27 094 to 435 490). In 2016 ‘recurrent users’ (three or more prescriptions) had mean age 58.1 yr, were mostly females (62.5%), and were more likely to live in deprived areas. Of these, 60% were co-prescribed an opioid, benzodiazepine, or both (opioid 49.9%, benzodiazepine 26.8%, both 17.1%). The age-standardised death rate in those prescribed gabapentinoids was double that in the Scottish population (relative risk 2.16, 95% confidence interval 2.08–2.25). Increases in gabapentinoids contributing to cause of DRDs were reported regionally and nationally (gabapentin 23% vs 15%; pregabalin 21% vs 7%). In Tayside, gabapentinoids were implicated in 22 (39%) of DRDs, 17 (77%) of whom had not received a prescription. Conclusions: Gabapentinoid prescribing has increased dramatically since 2006, as have dangerous co-prescribing and death (including DRDs). Older people, women, and those living in deprived areas were particularly likely to receive prescriptions. Their contribution to DRDs may be more related to illegal use with diversion of prescribed medication

Whole‐genome single nucleotide polymorphism and mating compatibility studies reveal the presence of distinct species in sub‐Saharan Africa Bemisia tabaci whiteflies

In sub‐Saharan Africa cassava growing areas, two members of the Bemisia tabaci species complex termed sub‐Saharan Africa 1 (SSA1) and SSA2 have been reported as the prevalent whiteflies associated with the spread of viruses that cause cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) pandemics. At the peak of CMD pandemic in the late 1990s, SSA2 was the prevalent whitefly, although its numbers have diminished over the last two decades with the resurgence of SSA1 whiteflies. Three SSA1 subgroups (SG1 to SG3) are the predominant whiteflies in East Africa and vary in distribution and biological properties. Mating compatibility between SSA1 subgroups and SSA2 whiteflies was reported as the possible driver for the resurgence of SSA1 whiteflies. In this study, a combination of both phylogenomic methods and reciprocal crossing experiments were applied to determine species status of SSA1 subgroups and SSA2 whitefly populations. Phylogenomic analyses conducted with 26 548 205 bp whole genome single nucleotide polymorphisms (SNPs) and the full mitogenomes clustered SSA1 subgroups together and separate from SSA2 species. Mating incompatibility between SSA1 subgroups and SSA2 further demonstrated their distinctiveness from each other. Phylogenomic analyses conducted with SNPs and mitogenomes also revealed different genetic relationships among SSA1 subgroups. The former clustered SSA1‐SG1 and SSA1‐SG2 together but separate from SSA1‐SG3, while the latter clustered SSA1‐SG2 and SSA1‐SG3 together but separate from SSA1‐SG1. Mating compatibility was observed between SSA1‐SG1 and SSA1‐SG2, while incompatibility occurred between SSA1‐SG1 and SSA1‐SG3, and SSA1‐SG2 and SSA1‐SG3. Mating results among SSA1 subgroups were coherent with phylogenomics results based on SNPs but not the full mitogenomes. Furthermore, this study revealed that the secondary endosymbiont—Wolbachia—did not mediate reproductive success in the crossing assays carried out. Overall, using genome wide SNPs together with reciprocal crossings assays, this study established accurate genetic relationships among cassava‐colonizing populations, illustrating that SSA1 and SSA2 are distinct species while at least two species occur within SSA1 species