A study of indentation behaviour of sandwich panels supported rigidly

The indentation behaviour of sandwich panels is affected by a variation of a large number of both intrinsic and extrinsic parameters. It is thus challenging not only to identify those parameters that dominate the indentation behaviour but also to ascertain how they influence the indentation behaviour across all applications. In this work, we focus on an occurrence of incipient damage in rigidly-supported laminate-skinned sandwich panels under indentation. Sandwich panels were constructed with aluminium honeycomb core and carbon/epoxy skins of two different thicknesses and lay-ups and were tested quasi-statically using hemispherical indentor. The effects of varying the loaded skin thickness, skin lay-up, indentor diameter and panel support conditions on initial critical load and incipient damage mechanisms have been examined. We’ve found that (1) the mechanisms of incipient damage induced in all ten groups of sandwich panels were combined delamination in the loaded skin laminate and buckled honeycomb cells without debonding and there were clear indications that induced local stresses were dominated by ILS stress of the skin laminates and through-the-thickness compressive strength of aluminium honeycomb core; (2) varying the thickness of the loaded laminate skin has got a profound influence over the indentation behaviour of the sandwich panels in terms of critical load, critical indentation and initial stiffness; (3) the increase of indentor diameter had the substantial effect on the indentation behaviour of the sandwich panels; (4) varying either the lay-up of the loaded skin laminates or support conditions had very little effect on the indentation behaviour

The optical rebrightening of GRB100814A: an interplay of forward and reverse shocks?

We present a wide dataset of -ray, X-ray, UVOIR, and radio observations of the Swift GRB100814A. At the end of the slow decline phase of the X-ray and optical afterglow, this burst shows a sudden and prominent rebrightening in the optical band only, followed by a fast decay in both bands. The optical rebrightening also shows chromatic evolution. Such a puzzling behaviour cannot be explained by a single component model. We discuss other possible interpretations, and we find that a model that incorporates a long-lived reverse shock and forward shock fits the temporal and spectral properties of GRB100814 the best

An experimental study of quasi-static indentation on composite sandwich panels supported rigidly

The indentation behaviour of sandwich panels could be affected by a variation of a large number of both intrinsic and extrinsic parameters. It is thus challenging not only to identify those parameters that dominate the indentation behaviour but also to ascertain how they influence the indentation behaviour across all applications. In this work, we focus on the indentation behaviour of rigidly-supported laminate-skinned sandwich panels up to an occurrence of incipient damage. Sandwich panels were constructed with carbon/epoxy skins of two different thicknesses, each in one of two lay-ups and aluminium honeycomb core. They were tested quasi-statically using hemispherical indentor. The effects of varying the thickness of loaded skin laminates, skin laminate lay-up, indentor diameter and panel support conditions on the indentation behaviour have been examined in terms of initial critical load and incipient damage mechanisms. On a basis of the extensive examinations of obtained results, we’ve found that (1) the mechanisms of incipient damage induced in all ten groups of sandwich panels were combined delamination in the loaded skin laminate and buckled honeycomb cells without debonding and there were clear indications that induced local stresses were dominated by ILS stress of the skin laminates and through-the-thickness compressive strength of aluminium honeycomb core; (2) varying the thickness of the loaded laminate skin has got a profound influence over the indentation behaviour of the sandwich panels in terms of critical load, critical indentation and initial stiffness; (3) the increase of indentor diameter had the substantial effect on the indentation behaviour of the sandwich panels; (4) varying either the lay-up of the loaded skin laminates or support conditions had very little effect on the indentation behaviour

Mo- and W‑Based Organic Nanostructures Prepared from Bulk Crystal Isomorphs Consisted of [(CH₃CH₂)₃NH)]₂[MO₂(C₁₄H₆O₄)₂] (M = Mo, W)

Two new crystal isomorphs consisting of complexes [(CH₃CH₂)₃­NH)]₂­[MoO₂­(C₁₄H₆O₄)₂] (<b>1</b>) and [(CH₃CH₂)₃­NH)]₂­[WO₂­(C₁₄H₆O₄)₂] (<b>2</b>) have been synthesized, respectively, and from which Mo-based flexible and durable nanopipes with diameters of 16 nm and lengths of hundreds of micrometers and W-based rigid and fragile nanotubules with ununiform diameters ranging from 30 to 100 nm and lengths in tens of micrometers have been prepared separately, which revealed that the change of the metal in the coordination center of the isomorphs can result in obvious variation to their nanostructures. The crystals both exhibited multilayered structures by the piling of lamellar repeating motifs through van der Waals forces, which are formed by the parallel alignment of 1D chains through hydrogen bonds, and the 1D chains are assembled by complexes <b>1</b> and <b>2</b>, respectively, through geometrical intercalation and π–π packing. However, under grinding and ultrasonication, crystal <b>1</b> disassembled uniformly into longer and narrower nanostrips, whereas crystal <b>2</b> were broken at random into shorter and wider nanoribbons; therefore, the two lamellar nanostructures curled into different cylindrical nanospecies. The differences caused by Mo and W are the following: the Mo complex prefers to assemble into more durable one-dimensional structures along Mo–O bonds than W isomorphs; since Mo–O bonds are weaker than MoO and W–O bonds, then the weakest Mo–O bonds can be supported by the adjacent molecules through intercalation and π–π packing, which resulted in that the linkages among the Mo complexes are stronger along the Mo–O direction and hence the longer Mo-based cylindrical structure. Moreover, the flexibility of Mo-based nanopipes and the rigidity of W-based nanotubules might be attributed to that Mo possesses a lower melting point than W; therefore, Mo is softer and W is harsher

Romosozumab treatment in postmenopausal women with osteoporosis: a meta-analysis of randomized controlled trials

<p><b>Aim:</b> To conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the safety and efficacy of romosozumab in the treatment of postmenopausal osteoporosis.</p> <p><b>Method:</b> A comprehensive literature review was performed of PubMed, EMBASE, Cochrane Controlled Trials Registry, and Web of Science for RCTs. Outcome measures were changes in lumbar spine, total hip and femoral neck bone mineral density (BMD), incidence of fractures and adverse events. Six trials were finally included.</p> <p><b>Results:</b> Romosozumab resulted in a significantly lower risk of new vertebral fracture (relative risk (RR) 0.37, 95% confidence interval (CI) 0.18–0.77, <i>p</i> = 0.005, <i>n</i> = 5371), non-vertebral fracture (RR 0.78, 95% CI 0.66–0.92, <i>p</i> < 0.0001, <i>n</i> = 5635) and hip fracture (RR 0.59, 95% CI 0.44–0.79, <i>p</i> = 0.0004, <i>n</i> = 5635) compared with other therapies. The BMD was significantly increased at the lumbar spine (weighted mean difference (WMD) 13.33, 95% CI 11.41–15.25, <i>p</i> < 0.00001, <i>n</i> = 198), total hip (WMD 5.09, 95% CI 3.81–6.38, <i>p</i> < 0.00001, <i>n</i> = 184) and femoral neck (WMD 4.70, 95% CI 3.50–5.90, <i>p</i> < 0.00001, <i>n</i> = 175) compared with placebo. There was no significant difference in the incidence of adverse events in patients with romosozumab compared to other therapies (RR 1.00, 95% CI 0.98–1.02).</p> <p><b>Conclusion:</b> In postmenopausal women with osteoporosis who were at high risk for fracture, romosozumab treatment resulted in a significantly lower risk of fracture. Romosozumab 210 mg monthly showed the largest gains in BMD, and was generally well tolerated.</p

Can X-ray emission powered by a spinning-down magnetar explain some gamma-ray burst light-curve features?

Long-duration gamma-ray bursts (GRBs) are thought to be produced by the core-collapse of a rapidly rotating massive star. This event generates a highly relativistic jet and prompt gamma-ray and X-ray emission arises from internal shocks in the jet or magnetized outflows. If the stellar core does not immediately collapse to a black hole, it may form an unstable, highly magnetized millisecond pulsar or magnetar. As it spins down, the magnetar would inject energy into the jet causing a distinctive bump in the GRB light curve where the emission becomes fairly constant followed by a steep decay when the magnetar collapses. We assume that the collapse of a massive star to a magnetar can launch the initial jet. By automatically fitting the X-ray light curves of all GRBs observed by the Swift satellite, we identified a subset of bursts which have a feature in their light curves which we call an internal plateau – unusually constant emission followed by a steep decay – which may be powered by a magnetar. We use the duration and luminosity of this internal plateau to place limits on the magnetar spin period and magnetic field strength, and find that they are consistent with the most extreme predicted values for magnetars

Mo- and W‑Based Organic Nanostructures Prepared from Bulk Crystal Isomorphs Consisted of [(CH₃CH₂)₃NH)]₂[MO₂(C₁₄H₆O₄)₂] (M = Mo, W)

Two new crystal isomorphs consisting of complexes [(CH₃CH₂)₃­NH)]₂­[MoO₂­(C₁₄H₆O₄)₂] (<b>1</b>) and [(CH₃CH₂)₃­NH)]₂­[WO₂­(C₁₄H₆O₄)₂] (<b>2</b>) have been synthesized, respectively, and from which Mo-based flexible and durable nanopipes with diameters of 16 nm and lengths of hundreds of micrometers and W-based rigid and fragile nanotubules with ununiform diameters ranging from 30 to 100 nm and lengths in tens of micrometers have been prepared separately, which revealed that the change of the metal in the coordination center of the isomorphs can result in obvious variation to their nanostructures. The crystals both exhibited multilayered structures by the piling of lamellar repeating motifs through van der Waals forces, which are formed by the parallel alignment of 1D chains through hydrogen bonds, and the 1D chains are assembled by complexes <b>1</b> and <b>2</b>, respectively, through geometrical intercalation and π–π packing. However, under grinding and ultrasonication, crystal <b>1</b> disassembled uniformly into longer and narrower nanostrips, whereas crystal <b>2</b> were broken at random into shorter and wider nanoribbons; therefore, the two lamellar nanostructures curled into different cylindrical nanospecies. The differences caused by Mo and W are the following: the Mo complex prefers to assemble into more durable one-dimensional structures along Mo–O bonds than W isomorphs; since Mo–O bonds are weaker than MoO and W–O bonds, then the weakest Mo–O bonds can be supported by the adjacent molecules through intercalation and π–π packing, which resulted in that the linkages among the Mo complexes are stronger along the Mo–O direction and hence the longer Mo-based cylindrical structure. Moreover, the flexibility of Mo-based nanopipes and the rigidity of W-based nanotubules might be attributed to that Mo possesses a lower melting point than W; therefore, Mo is softer and W is harsher

Jet breaks and energetics of swift gamma-ray burst X-ray afterglows

We present a systematic temporal and spectral study of all Swift-X-ray Telescope observations of gamma-ray burst (GRB) afterglows discovered between 2005 January and 2007 December. After constructing and fitting all light curves and spectra to power-law models, we classify the components of each afterglow in terms of the canonical X-ray afterglow and test them against the closure relations of the forward shock models for a variety of parameter combinations. The closure relations are used to identify potential jet breaks with characteristics including the uniform jet model with and without lateral spreading and energy injection, and a power-law structured jet model, all with a range of parameters. With this technique, we survey the X-ray afterglows with strong evidence for jet breaks (~12% of our sample), and reveal cases of potential jet breaks that do not appear plainly from the light curve alone (another ~30%), leading to insight into the missing jet break problem. Those X-ray light curves that do not show breaks or have breaks that are not consistent with one of the jet models are explored to place limits on the times of unseen jet breaks. The distribution of jet break times ranges from a few hours to a few weeks with a median of ~1 day, similar to what was found pre-Swift. On average, Swift GRBs have lower isotropic equivalent γ-ray energies, which in turn result in lower collimation corrected γ-ray energies than those of pre-Swift GRBs. Finally, we explore the implications for GRB jet geometry and energetics

Improving and Fining of Nanostructures by Mixing W with Mo in Metal Organic Hybrid Crystal

A bialloy-like multilayered bulk single crystal consisting of [(CH₃CH₂)₃NH)]₂­[W_0.25Mo_0.75O₂­(C₁₄H₆O₄)₂] has been synthesized, from which Mo–W-mixed organic hybrid nanotubes with a diameter of about 50 nm and length from tens to hundreds of nanometers were prepared by grinding and ultrasonication. The nanotubes possess the uniformity of Mo-based nanopipes and the rigidity of W-based nanotubules and are more delicate and standardized than W-based nanotubules and shorter than Mo-based nanopipes. Furthermore, the Mo–W-mixed nanotubes are disassembled into Mo-based nanowires with a diameter of about 5 nm and lengths in tens of nanometers and W-based nanoparticles with a diameter of 6 nm, which are much finer than the nanoarchitectures produced from Mo- and W-based crystal isomorphs. This research offers two new methods: one is the improvement of nanostructures in physical properties and morphologies by bialloy-like treatment, and another is the refinement of nanostructures compared with those made from crystal isomorphs based on one kind of metal, by mixing metals in a crystal lattice

DDR2 facilitates hepatocellular carcinoma invasion and metastasis via activating ERK signaling and stabilizing SNAIL1

Background: Several studies have found that DDR2 is up-regulated in many tumor types and facilitates tumor progression. However, the role of DDR2 in hepatocellular carcinoma (HCC) progression and its downstream signaling pathways remain unclear. Methods: DDR2 expression was assessed in several cell lines and 112 pairs of HCC and matched adjacent noncancerous liver tissues. Clinical significance of DDR2 in HCC was analyzed. Phosphorylated DDR2 (p-DDR2) expression was detected by immunoblotting to evaluate its correlation with DDR2. The effect of DDR2 on HCC cell migration and invasion were examined. Cycloheximide chase experiments were performed to detect the half-life of SNAIL1. Moreover, DDR2 expression was detected by immunohistochemistry to evaluate its correlation with SNAIL1. The regulatory effect of DDR2 on ERK signaling, SNAIL1, EMT, MT1-MMP and MMP2 was confirmed by immunoblotting. The effect of type I collagen on DDR2/ERK2/SNAIL1 signaling was assessed. Results: DDR2 was more highly expressed in HCC than in non-HCC tissues. DDR2 overexpression was correlated with clinicopathological features of poor prognosis. Clinical analysis revealed that DDR2 is an independent prognostic marker for predicting overall survival and disease free survival of HCC patients. Overexpression of DDR2 is associated with p-DDR2 amplification. In vitro studies showed that DDR2 facilitates HCC cell invasion, migration and EMT via activating ERK2 and stabilizing SNAIL1. DDR2 can up-regulate MT1-MMP and MMP2 expression through ERK2/SNAIL1 signaling in HCC. Additionally, collagen I can induce DDR2/ERK2/SNAIL1 signaling activation in HCC cells. Conclusions: Our findings suggest that DDR2 plays an important role in promoting HCC cell invasion and migration, and may serve as a novel therapeutic target in HCC