Many cellular processes are driven by cytoskeletal assemblies. It remains unclear how cytoskeletal filaments and motor proteins organize into cellular scale structures and how molecular properties of cytoskeletal components affect the large-scale behaviors of these systems. Here, we investigate the self-organization of stabilized microtubules in Xenopus oocyte extracts and find that they can form macroscopic networks that spontaneously contract. We propose that these contractions are driven by the clustering of microtubule minus ends by dynein. Based on this idea, we construct an active fluid theory of network contractions, which predicts a dependence of the timescale of contraction on initial network geometry, a development of density inhomogeneities during contraction, a constant final network density, and a strong influence of dynein inhibition on the rate of contraction, all in quantitative agreement with experiments. These results demonstrate that the motor-driven clustering of filament ends is a generic mechanism leading to contraction.DOI: http://dx.doi.org/10.7554/eLife.10837.001

BACKGROUND AND OBJECTIVE:There is limited information on overweight and obesity in Saudi children and adolescents. The objective of this study was to establish the national prevalence of overweight and obesity in Saudi children and adolescents.METHODS:The 2005 Saudi reference data set was used to calculate the body mass index (BMI) for children aged 5 to 18 years. Using the 2007 WHO reference, the prevalence of overweight, obesity and severe obesity were defined as the proportion of children with a BMI standard deviation score more than +1, +2 and +3, respectively. The 2000 CDC reference was also used for comparison.RESULTS:There were 19 317 healthy children and adolescents from 5 to 18 years of age, 50.8% of whom were boys. The overall prevalence of overweight, obesity and severe obesity in all age groups was 23.1%, 9.3% and 2%, respectively. A significantly lower prevalence of overweight (23.8 vs 20.4; P<.001) and obesity (9.5 vs 5.7; P<.001) was found when the CDC reference was used.CONCLUSIONS:This report establishes baseline national prevalence rates for overweight, obesity and severe obesity in Saudi children and adolescents, indicating intermediate levels between developing and industrialized countries. Measures should be implemented to prevent further increases in the numbers of overweight school-age children and adolescents and the associated health hazards.

Public evaluation campaigns and datasets promote\ud active development in target research areas, allowing direct\ud comparison of algorithms. The second edition of the challenge\ud on Detection and Classification of Acoustic Scenes and Events\ud (DCASE 2016) has offered such an opportunity for development\ud of state-of-the-art methods, and succeeded in drawing together a\ud large number of participants from academic and industrial backgrounds.\ud In this paper, we report on the tasks and outcomes of\ud the DCASE 2016 challenge. The challenge comprised four tasks:\ud acoustic scene classification, sound event detection in synthetic\ud audio, sound event detection in real-life audio, and domestic\ud audio tagging. We present in detail each task and analyse the\ud submitted systems in terms of design and performance. We\ud observe the emergence of deep learning as the most popular\ud classification method, replacing the traditional approaches based\ud on Gaussian mixture models and support vector machines. By\ud contrast, feature representations have not changed substantially\ud throughout the years, as mel frequency-based representations\ud predominate in all tasks. The datasets created for and used in\ud DCASE 2016 are publicly available and are a valuable resource\ud for further research

Gram-negative bacteria have an outer membrane that serves as a barrier to noxious agents in the environment. This protective function is dependent on lipopolysaccharide, a large glycolipid located in the outer leaflet of the outer membrane. Lipopolysaccharide is synthesized at the cytoplasmic membrane and must be transported to the cell surface. To understand this transport process, we reconstituted membrane-to-membrane movement of lipopolysaccharide by incorporating purified inner and outer membrane transport complexes into separate proteoliposomes. Transport involved stable association between the inner and outer membrane proteoliposomes. Our results support a model in which lipopolysaccharide molecules are pushed one after the other in a PEZ dispenser-like manner across a protein bridge that connects the inner and outer membranes.