Survey of bearded sprangletop (Leptochloa fusca spp. fasicularis) response to clomazone in California rice

Bearded sprangletop is a problematic weed in California rice production and few herbicides provide effective control. As control of bearded sprangletop has declined, grower suspicion of resistance to clomazone has increased, because of the continuous rice cropping system and herbicide dependence in the region. The objectives of this research were to confirm clomazone resistance in bearded sprangletop populations and determine the level of resistance. Seed from 21 suspected clomazone-resistant populations was collected from the California rice growing region. A greenhouse experiment was conducted to determine population sensitivity to clomazone. Clomazone was applied into the water to emerging seedlings. Plant ht and control of bearded sprangletop were recorded weekly for 3 wk, plants were then harvested, and dry weight was measured. Of the populations tested, 17 were susceptible and four (5%) were resistant to clomazone. A dose-response assay was conducted using eight doses ranging from an eighth of the full rate to 12 times the full rate. The three most resistant populations had resistant-to susceptible ratios of 1.25×, 2×, and 5× the labeled rate of clomazone. The use of clomazone in California rice production is beneficial; however, it should be used at the appropriate timing and as part of an herbicide program to prevent further development of clomazone resistance.

Detection of the stroboscopic effect by young adults varying in sensitivity

The advent of LED lighting has renewed concern about the possible visual, neurobiological, and performance and cognition effects of cyclic variations in lighting system luminous flux (temporal light modulation). The stroboscopic visibility measure (SVM) characterises the temporal light modulation signal to predict the visibility of the stroboscopic effect, one of the visual perception effects of temporal light modulation. A SVM of 1 means that the average person would detect the phenomenon 50% of the time. There is little published data describing the population sensitivity to the stroboscopic effect in relation to the SVM, and none focusing on people subject to visual stress. This experiment, conducted in parallel in Canada and France, examined stroboscopic detection for horizontal and vertical moving targets when viewed under commercially available lamps varying in SVM conditions (SVM: ∼0; ∼0.4; ∼0.9; ∼1.4; ∼3.0). As expected, stroboscopic detection scores increased with increasing SVM. For the horizontal task, average scores were lower than the expected 4/8 at ∼0.90, but increased non-linearly with higher SVMs. Stroboscopic detection scores did not differ between people low and high in pattern glare sensitivity, but people in the high-pattern glare sensitivity group reported greater annoyance in the SVM ∼1.4 and ∼3.0 conditions.

Single platelet variability governs population sensitivity and initiates intrinsic heterotypic behaviours

Droplet microfluidics combined with flow cytometry was used for high throughput single platelet function analysis. A large-scale sensitivity continuum was shown to be a general feature of human platelets from individual donors, with hypersensitive platelets coordinating significant sensitivity gains in bulk platelet populations and shown to direct aggregation in droplet-confined minimal platelet systems. Sensitivity gains scaled with agonist potency (convulxin>TRAP-14>ADP) and reduced the collagen and thrombin activation threshold required for platelet population polarization into pro-aggregatory and pro-coagulant states. The heterotypic platelet response results from an intrinsic behavioural program. The method and findings invite future discoveries into the nature of hypersensitive platelets and how community effects produce population level behaviours in health and disease.

Sensitivity of Sclerotinia sclerotiorum to strobilurin fungicides in Slovakia

Rapeseed isolates of Sclerotinia sclerotiorum (Lib.) de Bary 1884 from Nitra Region of Slovakia were investigated for their in vitro sensitivity to azoxystrobin and picoxystrobin; and determining the EC₅₀ value. The growth of S. sclerotiorum was evaluated on PDA amended with the selected fungicide´s active ingredient at 4 different concentration – 0.08, 0.83, 8.33, and 83.30 ppm. The overall mean EC₅₀ values for azoxystrobin and picoxystrobin were 2.73 ppm and 3.12 ppm respectively. Majority of isolates had a resistance factors up to 20, that suggests the shift in S. sclerotiorum population sensitivity towards the resistance.

Interpreting biological variation: seeds, populations and sensitivity thresholds

Seeds offer a unique perspective from which to view biology. An individual seed is an autonomous biological entity that must rely on its own resources (and resourcefulness) to persist after dispersal and to time its transition to germination and seedling growth to coincide with environmental opportunities for survival. At the same time, seed biology in agriculture and ecology is determined largely by the behaviours of populations of individual seeds. The percentage of seeds in a population that is in a particular state (e.g. dormant, germinated, dead) at a given time is a fundamental metric of seed biology. This duality of individual diversity underlying consistent population-wide behaviour patterns can be described quantitatively using population-based threshold (PBT) models. While conceptually simple, these models are highly flexible and can describe the wide diversity of responses of seed populations to temperature, water potential, hormones, oxygen, light, ageing and combinations of these factors. This seed behaviour is linked to respiratory rates of individual seeds, indicating that basic metabolic processes within seeds vary among individuals in accordance with PBT principles. Looking more broadly across microbial, plant and animal biology, examples of cellular diversity in hormonal sensitivity, gene expression, developmental responses and signalling abound. This variation often is termed ‘noise’, and analysis efforts are focused on extracting mean signals from this variation to understand regulatory pathways. However, extension of the PBT approach to the cellular and molecular levels suggests that population sensitivity distributions and recruitment phenomena may underlie many fundamental biological processes. Thus, concepts and quantitative approaches developed for the analysis of seed populations can be applied across biological scales from molecules to ecosystems to interpret inherent biological variation and provide mechanistic insights into the nature of biological regulatory systems.

Estimating negative likelihood ratio confidence when test sensitivity is 100%: A bootstrapping approach

Objectives Assessing high-sensitivity tests for mortal illness is crucial in emergency and critical care medicine. Estimating the 95% confidence interval (CI) of the likelihood ratio (LR) can be challenging when sample sensitivity is 100%. We aimed to develop, compare, and automate a bootstrapping method to estimate the negative LR CI when sample sensitivity is 100%. Methods The lowest population sensitivity that is most likely to yield sample sensitivity 100% is located using the binomial distribution. Random binomial samples generated using this population sensitivity are then used in the LR bootstrap. A free R program, “bootLR,” automates the process. Extensive simulations were performed to determine how often the LR bootstrap and comparator method 95% CIs cover the true population negative LR value. Finally, the 95% CI was compared for theoretical sample sizes and sensitivities approaching and including 100% using: (1) a technique of individual extremes, (2) SAS software based on the technique of Gart and Nam, (3) the Score CI (as implemented in the StatXact, SAS, and R PropCI package), and (4) the bootstrapping technique. Results The bootstrapping approach demonstrates appropriate coverage of the nominal 95% CI over a spectrum of populations and sample sizes. Considering a study of sample size 200 with 100 patients with disease, and specificity 60%, the lowest population sensitivity with median sample sensitivity 100% is 99.31%. When all 100 patients with disease test positive, the negative LR 95% CIs are: individual extremes technique (0,0.073), StatXact (0,0.064), SAS Score method (0,0.057), R PropCI (0,0.062), and bootstrap (0,0.048). Similar trends were observed for other sample sizes. Conclusions When study samples demonstrate 100% sensitivity, available methods may yield inappropriately wide negative LR CIs. An alternative bootstrapping approach and accompanying free open-source R package were developed to yield realistic estimates easily. This methodology and implementation are applicable to other binomial proportions with homogeneous responses.