Similarity between the primary and secondary air-assisted liquid jet breakup mechanism

we report an ultrafast synchrotron x-ray phase contrast imaging study of the primary breakup mechanism of a coaxial air-assisted water jet. We demonstrate that there exist great similarities in the phenomenology of primary breakup with that of the secondary breakup. Especially, a membrane-mediated breakup mechanism dominates the breakup process for a wide range of air speeds. This finding reveals the intrinsic connections of these two breakup regimes and has deep implications on the unified theoretical approach in treating the breakup mechanism of high speed liquid jet.Comment: 15 pages, 4 figure

A TETRAD-based Approach for Theory Development in Information Systems Research

Theory development and theory testing are two primary processes in social science research. Statistical methods and tools are used in various stages of these processes. Information systems researchers have employed many statistical methods and tools for theory testing. However, very few statistical approaches are known to help researchers with theory development. In this paper, we introduce TETRAD as a powerful approach to aid researchers in developing and discovering new theoretical relationships. We illustrate the TETRAD approach by re-analyzing data from two articles published in premier information systems journals. The results from the previous examples demonstrate that TETRAD is a useful tool for uncovering potential theoretical relationships, especially when prior knowledge of underlying theory bases is lacking. We demonstrate that TETRAD is an effective and powerful statistical tool that can assist researchers in the iterative process of theory development

Surface crack growth in fiber composites

The results of an experimental study of damage extension and failure in glass and graphite/epoxy laminates containing partially through-thickness surface cracks are presented. The laminates studied are divided between those containing four plies, 90/0/0/90, 15/-15/-15/15, and 45/-45/-45/45, and those containing 12-16 plies of the general configurations 0/90, + or - 45, and 0/+ or - 60. Most of the results are for surface cracks of various lengths and several depths. Stable damage extension in laminates containing surface cracks is predominantly delamination between plies, and tends to be much more extensive prior to failure than is the case with through-thickness cracks, resulting in approximately notch-insensitive behavior in most cases. A greater tendency for notch-sensitive behavior is found for 0/90 graphite/epoxy laminates for which stable damage extension is more limited. The rate of damage extension with increasing applied stress depends upon the composite system and ply configuration as well as the crack length and depth. An approximate semiempirical method is presented for estimating the growth rate of large damage-regions

Cyclic Permeability Evolution during Repose then Reactivation of Fractures and Faults

Cyclic growth and decay of permeability in fractures is explored during repeated reactivation and repose of saw‐cut fractures of Green River shale. These slide‐hold‐slide experiments are supported by measurements of fracture normal deformation and optical surface profilometry. Overall, we observe continuous permeability decay during repose (holds) and significant permeability enhancement during slow reactivation (slide). The permeability decay is accompanied by fault compaction. Both hydraulic aperture change (Δb_h) and measured compaction (Δb_s) are consistent with time‐dependent power law closure with a power exponent of ~0.2–0.4. These dual compaction magnitudes are positively correlated but Δb_h > Δb_s in late stage holds. Permeability enhancement during reactivation is typically also accompanied by fault dilation. However, we also observe some cases where hydraulic aperture change decouples from the measured deformation, conceivably driven by mobilization of wear products and influenced by the development of flow bottlenecks. Pretest and posttest surface profiles show that the surface topography of the fractures is planed down by shear removal. The shear removal is significant with initial laboratory prepared surface (~10 μm of aperture height) but less significant following consecutive reactivations (~2 μm). The flattened surfaces retain small‐scale, ~10–20 μm wavelength, roughness. Flow simulations, constrained by the surface topography and measured deformation, indicate that small‐scale roughness may control permeability at flow bottlenecks within a dominant flow channel. These results suggest cycles of permeability creation and destruction are an intrinsic component of the natural hydraulic system present in faults and fractures and provide an improved mechanistic understanding of the evolution of permeability during fault repose and reactivation

Observation of Superheating of Si at the Si/SiO2 Interface in Pulsed-laser irradiated Si Thin Films

Substantial superheating of single-crystal Si films at and near the bottom Si/SiO2 interface was observed. This was accomplished via back-side irradiation of a (100) single-crystal Si film on a quartz substrate using an excimer-laser pulse. The spatiotemporal details of the melting transition were tracked in situ using surface-side and substrate-side transient reflectance measurements, and the one-dimensional thermal profile evolution within the solid film during the heating period was numerically computed using the experimentally extracted temporal profile of the incident beam and temperature-dependent optical and thermal parameters of the materials. A simple lower-bound estimation identifies that superheating in excess of 100 K was attained within Si along the bottom (100)-Si/SiO2 interface even at moderate beam energy densities

Photochemical internalisation of a macromolecular protein toxin using a cell penetrating peptide-photosensitiser conjugate.

Photochemical internalisation (PCI) is a site-specific technique for improving cellular delivery of macromolecular drugs. In this study, a cell penetrating peptide, containing the core HIV-1 Tat 48-57 sequence, conjugated with a porphyrin photosensitiser has been shown to be effective for PCI. Herein we report an investigation of the photophysical and photobiological properties of a water soluble bioconjugate of the cationic Tat peptide with a hydrophobic tetraphenylporphyrin derivative. The cellular uptake and localisation of the amphiphilic bioconjugate was examined in the HN5 human head and neck squamous cell carcinoma cell line. Efficient cellular uptake and localisation in endo/lysosomal vesicles was found using fluorescence detection, and light-induced, rupture of the vesicles resulting in a more diffuse intracellular fluorescence distribution was observed. Conjugation of the Tat sequence with a hydrophobic porphyrin thus enables cellular delivery of an amphiphilic photosensitiser which can then localise in endo/lysosomal membranes, as required for effective PCI treatment. PCI efficacy was tested in combination with a protein toxin, saporin, and a significant reduction in cell viability was measured versus saporin or photosensitiser treatment alone. This study demonstrates that the cell penetrating peptide-photosensitiser bioconjugation strategy is a promising and versatile approach for enhancing the therapeutic potential of bioactive agents through photochemical internalisation

Analysis of cybersecurity threats in Industry 4.0: the case of intrusion detection

Nowadays, industrial control systems are experiencing a new revolution with the interconnection of the operational equipment with the Internet, and the introduction of cutting-edge technologies such as Cloud Computing or Big data within the organization. These and other technologies are paving the way to the Industry 4.0. However, the advent of these technologies, and the innovative services that are enabled by them, will also bring novel threats whose impact needs to be understood. As a result, this paper provides an analysis of the evolution of these cyber-security issues and the requirements that must be satis ed by intrusion detection defense mechanisms in this context.Springer ; Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Biomimetic three-dimensional nanocrystalline hydroxyapatite and magnetically synthesized single-walled carbon nanotube chitosan nanocomposite for bone regeneration

Owen Im1, Jian Li2, Mian Wang2, Lijie Grace Zhang2,3, Michael Keidar2,31Department of Biomedical Engineering, Duke University, Durham, NC; 2Department of Mechanical and Aerospace Engineering, 3Institute for Biomedical Engineering and Institute for Nanotechnology, The George Washington University, Washington, DC, USABackground: Many shortcomings exist in the traditional methods of treating bone defects, such as donor tissue shortages for autografts and disease transmission for allografts. The objective of this study was to design a novel three-dimensional nanostructured bone substitute based on magnetically synthesized single-walled carbon nanotubes (SWCNT), biomimetic hydrothermally treated nanocrystalline hydroxyapatite, and a biocompatible hydrogel (chitosan). Both nanocrystalline hydroxyapatite and SWCNT have a biomimetic nanostructure, excellent osteoconductivity, and high potential to improve the load-bearing capacity of hydrogels.Methods: Specifically, three-dimensional porous chitosan scaffolds with different concentrations of nanocrystalline hydroxyapatite and SWCNT were created to support the growth of human osteoblasts (bone-forming cells) using a lyophilization procedure. Two types of SWCNT were synthesized in an arc discharge with a magnetic field (B-SWCNT) and without a magnetic field (N-SWCNT) for improving bone regeneration.Results: Nanocomposites containing magnetically synthesized B-SWCNT had superior cytocompatibility properties when compared with nonmagnetically synthesized N-SWCNT. B-SWCNT have much smaller diameters and are twice as long as their nonmagnetically prepared counterparts, indicating that the dimensions of carbon nanotubes can have a substantial effect on osteoblast attachment.Conclusion: This study demonstrated that a chitosan nanocomposite with both B-SWCNT and 20% nanocrystalline hydroxyapatite could achieve a higher osteoblast density when compared with the other experimental groups, thus making this nanocomposite promising for further exploration for bone regeneration.Keywords: nanomaterials, single-walled carbon nanotube, nanocrystalline hydroxyapatite, chitosan, bone regeneration, biomimeti

Enhanced Osteogenesis of Adipose-Derived Stem Cells by Regulating Bone Morphogenetic Protein Signaling Antagonists and Agonists.

UnlabelledAlthough adipose-derived stem cells (ASCs) are an attractive cell source for bone tissue engineering, direct use of ASCs alone has had limited success in the treatment of large bone defects. Although bone morphogenetic proteins (BMPs) are believed to be the most potent osteoinductive factors to promote osteogenic differentiation of ASCs, their clinical applications require supraphysiological dosage, leading to high medical burden and adverse side effects. In the present study, we demonstrated an alternative approach that can effectively complement the BMP activity to maximize the osteogenesis of ASCs without exogenous application of BMPs by regulating levels of antagonists and agonists to BMP signaling. Treatment of ASCs with the amiloride derivative phenamil, a positive regulator of BMP signaling, combined with gene manipulation to suppress the BMP antagonist noggin, significantly enhanced osteogenic differentiation of ASCs through increased BMP-Smad signaling in vitro. Furthermore, the combination approach of noggin suppression and phenamil stimulation enhanced the BMP signaling and bone repair in a mouse calvarial defect model by adding noggin knockdown ASCs to apatite-coated poly(lactic-coglycolic acid) scaffolds loaded with phenamil. These results suggest novel complementary osteoinductive strategies that could maximize activity of the BMP pathway in ASC bone repair while reducing potential adverse effects of current BMP-based therapeutics.SignificanceAlthough stem cell-based tissue engineering strategy offers a promising alternative to repair damaged bone, direct use of stem cells alone is not adequate for challenging healing environments such as in large bone defects. This study demonstrates a novel strategy to maximize bone formation pathways in osteogenic differentiation of mesenchymal stem cells and functional bone formation by combining gene manipulation with a small molecule activator toward osteogenesis. The findings indicate promising stem cell-based therapy for treating bone defects that can effectively complement or replace current osteoinductive therapeutics