Twin-shaped CFRP-sandwich pedestrian bridge

A concept of a nature-inspired pedestrian bridge which tries to merge architectural, structural and manufacturing aspects in an optimized way is presented. The 18.0-m-span bridge is designed as an overhead spatial frame of a complex double-curved shape, which is composed of twelve modules consisting of lightweight carbon fiber-reinforced polymer (CFRP) sandwich construction. The modules are fabricated with only one mould through vacuum assisted resin infusion. The aimed visible texture and black colour of the CFRP fabrics represents an essential architectonical element. The resulting benefits and required compromises of this multi-criteria approach are discussed

Impact of a revised 25^{25}Mg(p,γ\gamma)26^{26}Al reaction rate on the operation of the Mg-Al cycle

Proton captures on Mg isotopes play an important role in the Mg-Al cycle active in stellar H-burning regions. In particular, low-energy nuclear resonances in the $^{25}$Mg(p,$\gamma$)$^{26}$Al reaction affect the production of radioactive $^{26}$Al$^{gs}$ as well as the resulting Mg/Al abundance ratio. Reliable estimations of these quantities require precise measurements of the strengths of low-energy resonances. Based on a new experimental study performed at LUNA, we provide revised rates of the $^{25}$Mg(p,$\gamma$)$^{26}$Al$^{gs}$ and the $^{25}$Mg(p,$\gamma$)$^{26}$Al$^{m}$ reactions with corresponding uncertainties. In the temperature range 50 to 150 MK, the new recommended rate of the $^{26}$Al$^{m}$ production is up to 5 times higher than previously assumed. In addition, at T$=100$ MK, the revised total reaction rate is a factor of 2 higher. Note that this is the range of temperature at which the Mg-Al cycle operates in an H-burning zone. The effects of this revision are discussed. Due to the significantly larger $^{25}$Mg(p,$\gamma$)$^{26}$Al$^{m}$ rate, the estimated production of $^{26}$Al$^{gs}$ in H-burning regions is less efficient than previously obtained. As a result, the new rates should imply a smaller contribution from Wolf-Rayet stars to the galactic $^{26}$Al budget. Similarly, we show that the AGB extra-mixing scenario does not appear able to explain the most extreme values of $^{26}$Al/$^{27}$Al, i.e. $>10^{-2}$, found in some O-rich presolar grains. Finally, the substantial increase of the total reaction rate makes the hypothesis of a self-pollution by massive AGBs a more robust explanation for the Mg-Al anticorrelation observed in Globular-Cluster stars

Metformin Enhances Cisplatin-Induced Apoptosis and Prevents Resistance to Cisplatin in Co-mutated KRAS/LKB1 NSCLC

Abstract Introduction We hypothesized that activating KRAS mutations and inactivation of the liver kinase B1 (LKB1) oncosuppressor can cooperate to sustain NSCLC aggressiveness. We also hypothesized that the growth advantage of KRAS/LKB1 co-mutated tumors could be balanced by higher sensitivity to metabolic stress conditions, such as metformin treatment, thus revealing new strategies to target this aggressive NSCLC subtype. Methods We retrospectively determined the frequency and prognostic value of KRAS/LKB1 co-mutations in tissue specimens from NSCLC patients enrolled in the TAILOR trial. We generated stable LKB1 knockdown and LKB1-overexpressing isogenic H1299 and A549 cell variants, respectively, to test the in vitro efficacy of metformin. We also investigated the effect of metformin on cisplatin-resistant CD133+ cells in NSCLC patient-derived xenografts. Results We found a trend towards worse overall survival in patients with KRAS/LKB1 co-mutated tumors as compared to KRAS-mutated ones (hazard ratio: 2.02, 95% confidence interval: 0.94–4.35, p = 0.072). In preclinical experiments, metformin produced pro-apoptotic effects and enhanced cisplatin anticancer activity specifically in KRAS/LKB1 co-mutated patient-derived xenografts. Moreover, metformin prevented the development of acquired tumor resistance to 5 consecutive cycles of cisplatin treatment (75% response rate with metformin-cisplatin as compared to 0% response rate with cisplatin), while reducing CD133+ cells. Conclusions LKB1 mutations, especially when combined with KRAS mutations, may define a specific and more aggressive NSCLC subtype. Metformin synergizes with cisplatin against KRAS/LKB1 co-mutated tumors, and may prevent or delay the onset of resistance to cisplatin by targeting CD133+ cancer stem cells. This study lays the foundations for combining metformin with standard platinum-based chemotherapy in the treatment of KRAS/LKB1 co-mutated NSCLC

Source wavelet inversion for laterally-varying scaling errors using Marchenko focusing functions

ISSN:1029-7006ISSN:1607-796

Accurate source wavelet estimation using Marchenko focusing functions

Marchenko redatuming is a powerful technique that allows retrieving Green’s functions for virtual receivers in the subsurface by calculating so-called focusing functions. One required input for the Green’s function retrieval is the surface reflection response that needs to be correctly deconvolved by the source wavelet. Deconvolving with an erroneously estimated or scaled source wavelet leads to artifacts in the redatumed wavefields and images created with redatumed data. Focusing functions can be used to correct an erroneous amplitude and phase spectrum of the source wavelet, enabling an accurate deconvolution, subsequent redatuming, and imaging. Additional events are present in the focusing functions in the case of an incorrect source wavelet amplitude spectrum, whereas an erroneous phase spectrum leads to an overall phase shift of the upgoing focusing function. Therefore, two objective functions are defined, which are minimized separately to invert for the source wavelet amplitude and phase spectrum accurately. Furthermore, optimizing focusing functions for a range of lateral focusing positions in the subsurface extends the approach, enabling inversion of laterally varying scaling errors of the source wavelet. Target-oriented images created with Marchenko redatumed data using the source scaling estimation method based on focusing functions are significantly improved compared to conventional Marchenko images with incorrectly estimated source wavelets.ISSN:0016-8033ISSN:1942-215

Eliminating time dispersion from seismic wave modeling

We derive an expression for the error introduced by the second-order accurate temporal finitedifference (FD) operator, as present in the FD, pseudospectral and spectral element methods for seismic wave modeling applied to time-invariant media. The 'time-dispersion' error speeds up the signal as a function of frequency and time step only. Time dispersion is thus independent of the propagation path, medium or spatial modeling error.We derive two transforms to either add or remove time dispersion from synthetic seismograms after a simulation. The transforms are compared to previous related work and demonstrated on wave modeling in acoustic as well as elastic media. In addition, an application to imaging is shown. The transforms enable accurate computation of synthetic seismograms at reduced cost, benefitting modeling applications in both exploration and global seismology. The Author(s) 2017. Published by Oxford University Press. All rights reserved

Self-stress distribution in large-scale cylindrical tensegrity structure

Tensegrity structures are spatial, reticulated, and lightweight structures that are composed of struts and cables. Stability is provided by the self-stress state between tensioned and compressed elements. Pure tensegrity structures are composed of straight compression struts only linkedwith cables. However, there are tensegrity systems that also include struts that are interconnected. Although the form finding of tensegrity structures has attracted a lot of attention, few studies have focused on the implementation of the concept especially on large-scale complex systems.This study explores the design and the selfstress distribution in a large-scale suspended tensegrity structure with interconnected struts. The structure is 6.2m tall and consists of stainless-steel cables and carbon fiber composite tubes. Different stress levels were introduced through cabletensioners integrated into the system and the self-stress distributions were investigated experimentally. The study revealed that the effective prestress levels were different from the nominal prestress levels since the cable-by-cable prestressing process had only local effects on the structure,i.e., the changes in the stress distribution were limited to the prestressed cable in question and cables above and below that