Reflection of Ultrasonic Waves by an Imperfect Diffusion Bond

The analytical treatment of the reflection of ultrasonic wave motion by a planar distribution of cracks is of interest for the nondestructive evaluation of imperfect diffusion bonds. Preliminary results for an experimental approach have been given by Hosten et al.1, for two bonded stainless steel cylinders. In practice, new high strength steel tubing has complicated the pinch welding process and placed emphasis on the integrity of the resulting weld, see Rehbein et al2, Thomas et al3. Two ultrasonic nondestructive evaluation techniques to find defects in the pinch weld and to determine weld strength have been discussed by Thomas et al.4

Ultrasonic Evaluation and Imaging of Tube Closure Welds

Tube closure welds, commonly called pinch welds, are made by solid state upset welding, where quality assurance consists of process control and geometric feature verification. Ultrasonic nondestructive evaluation demonstrated the feasibility for sorting oxide contaminated pinch welds from clean welds. Until now contaminated pinch welds could only be detected by destructive testing. Two approaches are presented in this paper. First, a study was conducted to detect the variation in the ultrasonic signal caused by interaction with the pinch weld. Correlations between the good and bad welds were accomplished with feature extraction and pattern recognition techniques. The second approach involved high resolution scanning of the pinch weld with an acoustic microscope. The acoustic microscope produced excellent color images of the weld which clearly distinguished the pre-weld cleanliness.</p

Ultrasonic Model for Solid State Weld Evaluation

Ultrasonic techniques have classified good and poor solid state welds in several studies [1,2,3]. A number of different types of solid state welds such as pinch welds, inertia welds, and diffusion bonds, have been evaluated with various ultrasonic feature extraction and pattern recognition techniques. The results of these studies have presented trends in the features needed to determine bond quality, but there is no physical explanation as to why certain features of the ultrasonic wave forms are influenced by the bond quality. An appropriate physical model that complements the experimental results would help explain the acoustic interactions measured. One model for the solid state weld is that the acoustic interaction with the bond line is controlled by the effective compliance of the interface. We have designed an experiment to examine this model. In our experiment, two blocks made from a high glass transition temperature (Tg) epoxy are joined together with a thin, lower Tg epoxy interlayer. If the temperature of the specimen is held below the Tg of the low temperature epoxy, then the interlayer compliance ratio across the interface can be changed by varying the temperature. Ultrasonic data are acquired at each temperature and, thus, each compliance ratio. This ultrasonic data can be compared with theoretical predictions from the compliance model.</p

Sexual selection predicts the rate and direction of colour divergence in a large avian radiation

Sexual selection is proposed to be a powerful driver of phenotypic evolution in animal systems. At macroevolutionary scales, sexual selection can theoretically drive both the rate and direction of phenotypic evolution, but this hypothesis remains contentious. Here, we find that differences in the rate and direction of plumage colour evolution are predicted by a proxy for sexual selection intensity (plumage dichromatism) in a large radiation of suboscine passerine birds (Tyrannida). We show that rates of plumage evolution are correlated between the sexes, but that sexual selection has a strong positive effect on male, but not female, interspecific divergence rates. Furthermore, we demonstrate that rapid male plumage divergence is biased towards carotenoid-based (red/yellow) colours widely assumed to represent honest sexual signals. Our results highlight the central role of sexual selection in driving avian colour divergence, and reveal the existence of convergent evolutionary responses of animal signalling traits under sexual selection

The Spectrin cytoskeleton regulates the Hippo signalling pathway

The Spectrin cytoskeleton is known to be polarised in epithelial cells, yet its role remains poorly understood. Here, we show that the Spectrin cytoskeleton controls Hippo signalling. In the developing Drosophila wing and eye, loss of apical Spectrins (alpha/beta-heavy dimers) produces tissue overgrowth and mis-regulation of Hippo target genes, similar to loss of Crumbs (Crb) or the FERM-domain protein Expanded (Ex). Apical beta-heavy Spectrin binds to Ex and co-localises with it at the apical membrane to antagonise Yki activity. Interestingly, in both the ovarian follicular epithelium and intestinal epithelium of Drosophila, apical Spectrins and Crb are dispensable for repression of Yki, while basolateral Spectrins (alpha/beta dimers) are essential. Finally, the Spectrin cytoskeleton is required to regulate the localisation of the Hippo pathway effector YAP in response to cell density human epithelial cells. Our findings identify both apical and basolateral Spectrins as regulators of Hippo signalling and suggest Spectrins as potential mechanosensors

Towards a general framework for predicting threat status of data-deficient species from phylogenetic, spatial and environmental information

In taxon-wide assessments of threat status many species remain not included owing to lack of data. Here, we present a novel spatial-phylogenetic statistical framework that uses a small set of readily available or derivable characteristics, including phylogenetically imputed body mass and remotely sensed human encroachment, to provide initial baseline predictions of threat status for data-deficient species. Applied to assessed mammal species worldwide, the approach effectively identifies threatened species and predicts the geographical variation in threat. For the 483 data-deficient species, the models predict highly elevated threat, with 69% ‘at-risk’ species in this set, compared with 22% among assessed species. This results in 331 additional potentially threatened mammals, with elevated conservation importance in rodents, bats and shrews, and countries like Colombia, Sulawesi and the Philippines. These findings demonstrate the future potential for combining phylogenies and remotely sensed data with species distributions to identify species and regions of conservation concern

Impact of quality of evidence on the strength of recommendations: an empirical study

<p>Abstract</p> <p>Background</p> <p>Evidence is necessary but not sufficient for decision-making, such as making recommendations by clinical practice guideline panels. However, the fundamental premise of evidence-based medicine (EBM) rests on the assumed link between the quality of evidence and "truth" and/or correctness in making guideline recommendations. If this assumption is accurate, then the quality of evidence ought to play a key role in making guideline recommendations. Surprisingly, and despite the widespread penetration of EBM in health care, there has been no empirical research to date investigating the impact of quality of evidence on the strength of recommendations made by guidelines panels.</p> <p>Methods</p> <p>The American Association of Blood Banking (AABB) has recently convened a 12 member panel to develop clinical practice guidelines (CPG) for the use of fresh-frozen plasma (FFP) for 6 different clinical indications. The panel was instructed that 4 factors should play a role in making recommendation: quality of evidence, uncertainty about the balance between desirable (benefits) and undesirable effects (harms), uncertainty or variability in values and preferences, and uncertainty about whether the intervention represents a wise use of resources (costs). Each member of the panel was asked to make his/her final judgments on the strength of recommendation and the overall quality of the body of evidence. "Voting" was anonymous and was based on the use of GRADE (Grading quality of evidence and strength of recommendations) system, which clearly distinguishes between quality of evidence and strength of recommendations.</p> <p>Results</p> <p>Despite the fact that many factors play role in formulating CPG recommendations, we show that when the quality of evidence is higher, the probability of making a strong recommendation for or against an intervention dramatically increases. Probability of making strong recommendation was 62% when evidence is "moderate", while it was only 23% and 13% when evidence was "low" or "very low", respectively.</p> <p>Conclusion</p> <p>We report the first empirical evaluation of the relationship between quality of evidence pertinent to a clinical question and strength of the corresponding guideline recommendations. Understanding the relationship between quality of evidence and probability of making (strong) recommendation has profound implications for the science of quality measurement in health care.</p

Meeting report: a hard look at the state of enamel research.

The Encouraging Novel Amelogenesis Models and Ex vivo cell Lines (ENAMEL) Development workshop was held on 23 June 2017 at the Bethesda headquarters of the National Institute of Dental and Craniofacial Research (NIDCR). Discussion topics included model organisms, stem cells/cell lines, and tissues/3D cell culture/organoids. Scientists from a number of disciplines, representing institutions from across the United States, gathered to discuss advances in our understanding of enamel, as well as future directions for the field