Mosaic structure in the spines of Holopneustes porossisimus

Sea urchin spines of Holopneustes porossisimus are porous singlecrystals, with the pores being filled with a material rich in carbon,silicon, fluorine and sodium. The magnesian calcite constituting thespine is highly strained. Even though the spines appear to be singlecrystalline on a macroscopic scale, the calcitic material exhibits anextended defect network. We find dislocations as well as rotational andother, not yet identified boundaries. We also observe within spinecalcite a patterned distribution of sulphur. Both distributions, that ofthe defect network and that of sulphur resemble in their pattern to eachother and have a similar mesh size of 50 nm. We conclude from theseobservations that they arise from the growth process of the spine andaccount for the mosaicity within the spine single crystals

Hierarchical structure of marine shell biomaterials: biomechanical functionalization of calcite by brachiopods

Biologic structural materials for skeletons or teeth show a hierarchicalarchitecture, where organic macromolecules and mineral substance form ahybrid composite material with its components inter-weaved on manylength scales. On the nanostructure level brachiopods form hybridcomposite mesocrystals of calcite with occluded organic molecules. Onthe microstructure level several types of materials are produced, onwhich the electron back-scatter diffraction (EBSD) technique givesinsight in texture and architecture. We describe the calcitesingle-crystal fiber composite architecture of the secondary layerinvolving organic matrix membranes, the competitive-growth texture ofthe columnar layer and the nanostructuring of the primary layer. In theoverall skeleton the organic biopolymers provide flexibility and tensilestrength while the mineral provides a high elastic modulus, compressivestrength, hardness and resistance to abrasion. The hierarchicalcomposite architecture, from the nanostructure to the macroscopic levelprovides fracture toughness. The morphogenesis of the biomaterial as awhole and of the mineral crystals is guided by the organic matrix andmost probably involves amorphous calcium carbonate (ACC) precursors. Inthis paper we review the hierarchical architecture of rhynchonelliformbrachiopod shells, which is very distinct from mollusk nacre

Psychometric properties of the revised children’s anxiety and depression scale (RCADS) for autistic youth without co-occurring intellectual disability

Autistic youth often present with comorbid anxiety and depression yet there is a dearth of validated assessment tools. The Revised Children’s Anxiety and Depression Scale (RCADS) assesses internalizing symptoms but there is little psychometric data in autistic youth. Treatment-seeking autistic youth with anxiety or obsessive-compulsive symptoms (N = 74; age 6–14 years), and caregivers, were administered the RCADS-Parent, RCADS-Child, and assessments of internalizing, externalizing symptoms and social impairment indicative of autism. RCADS-Parent and RCADS-Child total anxiety scores demonstrated excellent internal consistency, and the six subscales demonstrated acceptable-to-good internal consistency. The RCADS-Child and Parent total anxiety scores were weakly correlated, and neither child age nor gender altered the strength of this association. Convergent validity was supported by moderate-to-strong correlations with clinician and parent-reported anxiety symptoms. Support for divergent validity was mixed. Results provide support for the RCADS-Parent and RCADS-Child as reliable, valid measures of internalizing symptoms in autistic youth

Genomic Evidence for Complex Domestication History of the Cultivated Tomato in Latin America

The process of plant domestication is often protracted, involving underexplored intermediate stages with important implications for the evolutionary trajectories of domestication traits. Previously, tomato domestication history has been thought to involve two major transitions: one from wild Solanum pimpinellifolium L. to a semidomesticated intermediate, S. lycopersicum L. var. cerasiforme (SLC) in South America, and a second transition from SLC to fully domesticated S. lycopersicum L. var. lycopersicum in Mesoamerica. In this study, we employ population genomic methods to reconstruct tomato domestication history, focusing on the evolutionary changes occurring in the intermediate stages. Our results suggest that the origin of SLC may predate domestication, and that many traits considered typical of cultivated tomatoes arose in South American SLC, but were lost or diminished once these partially domesticated forms spread northward. These traits were then likely reselected in a convergent fashion in the common cultivated tomato, prior to its expansion around the world. Based on these findings, we reveal complexities in the intermediate stage of tomato domestication and provide insight on trajectories of genes and phenotypes involved in tomato domestication syndrome. Our results also allow us to identify underexplored germplasm that harbors useful alleles for crop improvement

Expression of Integrin αvβ3 in Gliomas Correlates with Tumor Grade and Is not Restricted to Tumor Vasculature

In malignant gliomas, the integrin adhesion receptors seem to play a key role for invasive growth and angiogenesis. However, there is still a controversy about the expression and the distribution of αvβ3 integrin caused by malignancy. The aim of our study was to assess the extent and pattern of αvβ3 integrin expression within primary glioblastomas (GBMs) compared with low-grade gliomas (LGGs). Tumor samples were immunostained for the detection of αvβ3 integrin and quantified by an imaging software. The expression of αvβ3 was found to be significantly higher in GBMs than in LGGs, whereby focal strong reactivity was restricted to GBMs only. Subsequent analysis revealed that not only endothelial cells but also, to a large extent, glial tumor cells contribute to the overall amount of αvβ3 integrin in the tumors. To further analyze the integrin subunits, Western blots from histologic sections were performed, which demonstrated a significant difference in the expression of the β3 integrin subunit between GBMs and LGGs. The presented data lead to new insights in the pattern of αvβ3 integrin in gliomas and are of relevance for the inhibition of αvβ3 integrin with specific RGD peptides and interfering drugs to reduce angiogenesis and tumor growth

Searching for a Stochastic Background of Gravitational Waves with LIGO

The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed the fourth science run, S4, with significantly improved interferometer sensitivities with respect to previous runs. Using data acquired during this science run, we place a limit on the amplitude of a stochastic background of gravitational waves. For a frequency independent spectrum, the new limit is $\Omega_{\rm GW} < 6.5 \times 10^{-5}$. This is currently the most sensitive result in the frequency range 51-150 Hz, with a factor of 13 improvement over the previous LIGO result. We discuss complementarity of the new result with other constraints on a stochastic background of gravitational waves, and we investigate implications of the new result for different models of this background.Comment: 37 pages, 16 figure

Breaking AI: When Even Google Fails

In 2016, Alex Graves, Greg Wayne and others at DeepMind published a paper in Nature proposing a new model for neural networks: the differentiable neural computer (DNC) [14,25]. This model is a type of neural memory network designed so that [. . .] memory can be selectively written to as well as read, allowing iterative modification of memory content. Utilizing external memory, DeepMind’s network achieved the lowest error rate yet published on the bAbI dataset, a dataset composed of short stories followed by questions on the stories. This dataset demonstrated the DNC’s ability to reason deductively and process natural language. But the dataset itself is quite limited: it possesses only — words, all of which have at least –instances and which are in the lexicon of a small child. Moreover, each of the twenty question types in the dataset has 10,000 training examples and no question requires more than a single type of reasoning. These dataset limitations suggest that the ground breaking results published by DeepMind may mask the deep and pervasive limitations of not only the differential neural computer but also of neural networks as a whole.To push the DNC to the limits of its capabilities, we introduce it to the DREAM dataset, a dataset originally presented by Kal Sun et al [27]. This dataset is much smaller than the bAbI dataset, it contains only 10,197 questions split into fivedifferent types. Additionally, the dataset is makes use of – words, where many words have as little as – instances. While Sun et al originally publish the dataset in multiple-choice format, we train the DNC in question and answer format— whichvis comparable to the bAbI dataset and further increases the difficulty of answering correctly. We expect that— provided this dataset— the DNC will experience task failure.What we did not expect is just how pervasive that failure would be

Towards systematics of calcite biocrystals: insight from the inside

Biocrystals of calcite are frequent as they are employed by many phylae of organisms in shells, eggshells, teeth, spines or sensoric apparatus. The calcite phase in these materials occurs in a range of constitutions, from polycrystalline fabrics to “single-crystals”. We demonstrate systematics of calcite biocrystal architectures, from the hybrid composite mesocrystal fibres of brachiopod and mollusc shells, via the submillimeter-sized hybrid composite crystal aggregates formed by mesocrystal fibres with both morphological co-orientation and lattice co-oriäentation, to more complex purpose-oriented multiplex äcomposite crystals of echinoderm teeth, which feature a high degree of single-crystal-like 3D orientational correlation of microstructural elements of different morphology and composition. These systematics rely on observations by electron backscatter diffraction (EBSD) and TE