Buckling of Carbon Nanotube-Reinforced Polymer Laminated Composite Materials Subjected to Axial Compression and Shear Loadings

A multi-scale method to predict the stiffness and stability properties of carbon nanotube-reinforced laminates has been developed. This method is used in the prediction of the buckling behavior of laminated carbon nanotube-polyethylene composites formed by stacking layers of carbon nanotube-reinforced polymer with the nanotube alignment axes of each layer oriented in different directions. Linking of intrinsic, nanoscale-material definitions to finite scale-structural properties is achieved via a hierarchical approach in which the elastic properties of the reinforced layers are predicted by an equivalent continuum modeling technique. Solutions for infinitely long symmetrically laminated nanotube-reinforced laminates with simply-supported or clamped edges subjected to axial compression and shear loadings are presented. The study focuses on the influence of nanotube volume fraction, length, orientation, and functionalization on finite-scale laminate response. Results indicate that for the selected laminate configurations considered in this study, angle-ply laminates composed of aligned, non-functionalized carbon nanotube-reinforced lamina exhibit the greatest buckling resistance with 1% nanotube volume fraction of 450 nm uniformly-distributed carbon nanotubes. In addition, hybrid laminates were considered by varying either the volume fraction or nanotube length through-the-thickness of a quasi-isotropic laminate. The ratio of buckling load-to-nanotube weight percent for the hybrid laminates considered indicate the potential for increasing the buckling efficiency of nanotube-reinforced laminates by optimizing nanotube size and proportion with respect to laminate configuration

Dynamic hydrological discharge modelling for coupled climate model simulations of the last glacial cycle: the MPI-DynamicHD model version 3.0

The continually evolving large ice sheets present in the Northern Hemisphere during the last glacial cycle caused significant changes to river pathways both through directly blocking rivers and through glacial isostatic adjustment. Studies have shown these river pathway changes had a significant impact on the ocean circulation through changing the pattern of freshwater discharge into the oceans. A coupled Earth system model (ESM) simulation of the last glacial cycle thus requires a hydrological discharge model that uses a set of river pathways that evolve with Earth's changing orography while being able to reproduce the known present-day river network given the present-day orography. Here, we present a method for dynamically modelling river pathways that meets such requirements by applying predefined corrections to an evolving fine-scale orography (accounting for the changing ice sheets and isostatic rebound) each time the river directions are recalculated. The corrected orography thus produced is then used to create a set of fine-scale river pathways and these are then upscaled to a coarser scale on which an existing present-day hydrological discharge model within the JSBACH land surface model simulates the river flow. Tests show that this procedure reproduces the known present-day river network to a sufficient degree of accuracy and is able to simulate plausible paleo-river networks. It has also been shown this procedure can be run successfully multiple times as part of a transient coupled climate model simulation

Accretion-ejection connection in the young brown dwarf candidate ISO-Cha1 217

As the number of observed brown dwarf outflows is growing it is important to investigate how these outflows compare to the well studied jets from young stellar objects. A key point of comparison is the relationship between outflow and accretion activity and in particular the ratio between the mass outflow and accretion rates ($\dot{M}_{out}$/$\dot{M}_{acc}$). The brown dwarf candidate ISO-ChaI 217 was discovered by our group, as part of a spectro-astrometric study of brown dwarfs, to be driving an asymmetric outflow with the blue-shifted lobe having a position angle of $\sim$ 20$^{\circ}$. The aim here is to further investigate the properties of ISO-ChaI 217, the morphology and kinematics of its outflow, and to better constrain ($\dot{M}_{out}$/$\dot{M}_{acc}$). The outflow is spatially resolved in the $[SII]\lambda \lambda 6716,6731$ lines and is detected out to $\sim$ 1\farcs6 in the blue-shifted lobe and ~ 1" in the red-shifted lobe. The asymmetry between the two lobes is confirmed although the velocity asymmetry is less pronounced with respect to our previous study. Using thirteen different accretion tracers we measure log($\dot{M}_{acc}$) [M$_{sun}$/yr]= -10.6 $\pm$ 0.4. As it was not possible to measure the effect of extinction on the ISO-ChaI 217 outflow $\dot{M}_{out}$ was derived for a range of values of A$_{v}$, up to a value of A$_{v}$ = 2.5 mag estimated for the source extinction. The logarithm of the mass outflow ($\dot{M}_{out}$) was estimated in the range -11.7 to -11.1 for both jets combined. Thus $\dot{M}_{out}$/$\dot{M}_{acc}$ [\Msun/yr] lies below the maximum value predicted by magneto-centrifugal jet launching models. Finally, both model fitting of the Balmer decrements and spectro-astrometric analysis of the H$\alpha$ line show that the bulk of the H I emission comes from the accretion flow.Comment: accepted by Astronomy & Astrophysic

Orange IV stabilizes silk fibroin microemulsions

Silk fibroin (SF) is a natural biopolymer that has been extensively studied in various applications due to its impressive mechanical properties and biocompatibility. Recently, SF-based particles have been proposed as controlled drug delivery systems. A new and efficient method to prepare SF microemulsions (SF-MEs) was developed by oil-in-water emulsions using high-pressure homogenization to promote emulsification. During SF-ME production, the secondary structure of SF changed to a more stable conformation (from random coil to -sheets), thus allowing the formation of small and stable (140.7 ± 1.9 nm; polydispersity index, 0.25) SF microparticles (SF-MPs). The efficiency of SF-MP formation was 60%. Orange IV was used as a model compound for incorporation and release studies, although its incorporation into the SF-MEs significantly improved particle size and size distribution over at least 4 wk compared to traditional stabilizers (e.g., poloxamer 407, transcutol, Tween 80, and SDS). This should be a call of attention when using dyes as model compounds since they can influence particle properties and lead to misinterpretation of the results. Orange IV showed an incorporation efficiency of 91% and a controlled release over time. Stable SF-MP formulations, further enhanced by orange IV incorporation, provide an innovative method with potential application in pharmaceutical development due to its associated high biocompatibility and release profile.The authors thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013 and the project "BioHealth - Biotechnology and Bioengineering Approaches to Improve Health Quality," Ref. NORTE-07-0124-FEDER-000027, cofunded by the Programa Operacional Regional do Norte (ON.2 - O Novo Norte), QREN, FEDER. We would also like to acknowledge CRA - Unita di Ricerca di Apicoltura and Bachicoltura Padova (Italy) for the supply of B. mori silkworm cocoons, and Andreia Vasconcelos for technical support

Nucleocytoplasmic transport: a thermodynamic mechanism

The nuclear pore supports molecular communication between cytoplasm and nucleus in eukaryotic cells. Selective transport of proteins is mediated by soluble receptors, whose regulation by the small GTPase Ran leads to cargo accumulation in, or depletion from the nucleus, i.e., nuclear import or nuclear export. We consider the operation of this transport system by a combined analytical and experimental approach. Provocative predictions of a simple model were tested using cell-free nuclei reconstituted in Xenopus egg extract, a system well suited to quantitative studies. We found that accumulation capacity is limited, so that introduction of one import cargo leads to egress of another. Clearly, the pore per se does not determine transport directionality. Moreover, different cargo reach a similar ratio of nuclear to cytoplasmic concentration in steady-state. The model shows that this ratio should in fact be independent of the receptor-cargo affinity, though kinetics may be strongly influenced. Numerical conservation of the system components highlights a conflict between the observations and the popular concept of transport cycles. We suggest that chemical partitioning provides a framework to understand the capacity to generate concentration gradients by equilibration of the receptor-cargo intermediary.Comment: in press at HFSP Journal, vol 3 16 text pages, 1 table, 4 figures, plus Supplementary Material include

The Influence of Murine Genetic Background in Adeno-Associated Virus Transduction of the Mouse Brain

Adeno-associated virus (AAV) vectors have become an important tool for delivering therapeutic genes for a wide range of neurological diseases. AAV serotypes possess differential cellular tropism in the central nervous system. Although several AAV serotypes or mutants have been reported to transduce the brain efficiently, conflicting data occur across studies with the use of various rodent strains from different genetic backgrounds. Herein, we performed a systematic comparison of the brain transduction properties among five AAV serotypes (AAV2, 5, 7, 8, and 9) in two common rodent strains (C57BL/6J and FVB/N), following local intrastriatal injection of AAV vectors encoding enhanced green fluorescent protein (EGFP) driven by the CBh promoter. Important differences were found regarding overall cellular tropism and transduction efficiency, including contralateral transduction among the AAV serotypes and between the mouse strains. We have further found loss of NeuN-immunoreactivity and microglial activation from AAV transduction in the different mouse strains. The important strain-specific differences from our study suggest that the genetic background of the mouse may affect AAV serotype transduction properties in the brain. These data can provide valuable information about how to choose an effective AAV vector for clinical application and interpret the data obtained from preclinical studies and clinical trials

280 one-opposition near-Earth asteroids recovered by the EURONEAR with the <i>Isaac Newton</i> Telescope

Context. One-opposition near-Earth asteroids (NEAs) are growing in number, and they must be recovered to prevent loss and mismatch risk, and to improve their orbits, as they are likely to be too faint for detection in shallow surveys at future apparitions. Aims. We aimed to recover more than half of the one-opposition NEAs recommended for observations by the Minor Planet Center (MPC) using the Isaac Newton Telescope (INT) in soft-override mode and some fractions of available D-nights. During about 130 h in total between 2013 and 2016, we targeted 368 NEAs, among which 56 potentially hazardous asteroids (PHAs), observing 437 INT Wide Field Camera (WFC) fields and recovering 280 NEAs (76% of all targets). Methods. Engaging a core team of about ten students and amateurs, we used the THELI, Astrometrica, and the Find_Orb software to identify all moving objects using the blink and track-and-stack method for the faintest targets and plotting the positional uncertainty ellipse from NEODyS. Results. Most targets and recovered objects had apparent magnitudes centered around V ~ 22.8 mag, with some becoming as faint as V ~ 24 mag. One hundred and three objects (representing 28% of all targets) were recovered by EURONEAR alone by Aug. 2017. Orbital arcs were prolonged typically from a few weeks to a few years; our oldest recoveries reach 16 years. The O−C residuals for our 1854 NEA astrometric positions show that most measurements cluster closely around the origin. In addition to the recovered NEAs, 22 000 positions of about 3500 known minor planets and another 10 000 observations of about 1500 unknown objects (mostly main-belt objects) were promptly reported to the MPC by our team. Four new NEAs were discovered serendipitously in the analyzed fields and were promptly secured with the INT and other telescopes, while two more NEAs were lost due to extremely fast motion and lack of rapid follow-up time. They increase the counting to nine NEAs discovered by the EURONEAR in 2014 and 2015. Conclusions. Targeted projects to recover one-opposition NEAs are efficient in override access, especially using at least two-meter class and preferably larger field telescopes located in good sites, which appear even more efficient than the existing surveys