Rubber toughening of glass-fiber -reinforced nylon 66

Glass fibers are commonly added to thermoplastics by the process of extrusion compounding for a variety of reasons, mainly to enhance their strength and make them dimensionally stable. Since the extruder has to be flushed out each time product composition is changed, a large amount of incompatible polymeric waste is generated. This waste material is usually landfilled even though the polymers contained in it are valuable and worth being recycled. It is the drastic reduction in mechanical properties resulting from polymer incompatibility which restricts their recycling. A good strategy of recycling thermoplastics calls for separating materials from each other before utilizing them. This research deals with characterizing and rubber toughening of a post industrial glass-fiber-reinforced nylon 66 which was separated from other polymers. A virgin glass-fiber-reinforced nylon 66 was also used in order to compare its properties with those of the recycled ones.;Rubbers used in this study were Styrene-Ethylene-Butylene-Styrene and Ethylene-Propylene grafted with maleic anhydride; SEBS-g-MA and EP-g-MA. Composites of glass-fiber-reinforced nylon 66 with various rubber contents were prepared by extrusion. The pelletized extrudates were injection molded to different standard specimens for mechanical testing such as impact, tensile, and flexural. Flow properties of the composites were examined by the melt flow index and rotational viscometry. Morphology of the fractured surface of the composites was examined by scanning electron microscopy.;Elongation and impact strength of the composites were found to increase with increasing rubber content while tensile and flexural strength decrease with increasing rubber content. Elongation of the recycled material was slightly less than that of the virgin material. This is probably due to the presence of contaminants within the recycled material. The variation of rubber content with both tensile and flexural strengths was found to obey the rule of mixtures. The morphology of the fractured surfaces showed significant signs of plastic deformation such as shear bands and cavitations as rubber content increased, and this correlates well with mechanical properties which resulted in an increase in toughness of the composites when rubber content was increased. The results of this investigation clearly show the possibility of balancing strength and toughness of the material when adding rubber to a glass-fiber-reinforced nylon 66

Low latency via redundancy

Low latency is critical for interactive networked applications. But while we know how to scale systems to increase capacity, reducing latency --- especially the tail of the latency distribution --- can be much more difficult. In this paper, we argue that the use of redundancy is an effective way to convert extra capacity into reduced latency. By initiating redundant operations across diverse resources and using the first result which completes, redundancy improves a system's latency even under exceptional conditions. We study the tradeoff with added system utilization, characterizing the situations in which replicating all tasks reduces mean latency. We then demonstrate empirically that replicating all operations can result in significant mean and tail latency reduction in real-world systems including DNS queries, database servers, and packet forwarding within networks

Long-term magnetic field stability of Vega

We present new spectropolarimetric observations of the normal A-type star Vega, obtained during the summer of 2010 with NARVAL at T\'elescope Bernard Lyot (Pic du Midi Observatory). This new time-series is constituted of 615 spectra collected over 6 different nights. We use the Least-Square-Deconvolution technique to compute, from each spectrum, a mean line profile with a signal-to-noise ratio close to 20,000. After averaging all 615 polarized observations, we detect a circularly polarized Zeeman signature consistent in shape and amplitude with the signatures previously reported from our observations of 2008 and 2009. The surface magnetic geometry of the star, reconstructed using the technique of Zeeman-Doppler Imaging, agrees with the maps obtained in 2008 and 2009, showing that most recognizable features of the photospheric field of Vega are only weakly distorted by large-scale surface flows (differential rotation or meridional circulation).Comment: Proceedings of the conference "Stellar polarimetry: from birth to death", 2011 Jun 27-30, Madiso

Histological study of eyelid in Algerian locale bovine

Ten pairs of eyelids of adult, healthy cattle of the local breed from the region of Guelma, Algeria, were collected at the slaughterhouse in order to carry out research to determine the structure, the components and to make a comparison with the results of this subject in other ruminants, classical staining techniques such as Hematoxylin & eosin, Masson trichrome and silver nitrate were carried out in the histology laboratory on sections of these membranes, the studied parts were the upper eyelid and lower eyelid, medial and lateral canthus, the results observed were significant, there was a small increase in the thickness of the epidermis in the lower eyelid, and the small sebaceous glands which made the difference between the lower eyelid from local cattle, these glands originate near the basement membrane of the upper eyelids. Regarding the tarsal gland, empty its secretion onto the surface of the eyelid through a duct lined with typical stratified squamous epithelium

Magnetic field, differential rotation and activity of the hot-Jupiter hosting star HD 179949

HD 179949 is an F8V star, orbited by a giant planet at ~8 R* every 3.092514 days. The system was reported to undergo episodes of stellar activity enhancement modulated by the orbital period, interpreted as caused by Star-Planet Interactions (SPIs). One possible cause of SPIs is the large-scale magnetic field of the host star in which the close-in giant planet orbits. In this paper we present spectropolarimetric observations of HD 179949 during two observing campaigns (2009 September and 2007 June). We detect a weak large-scale magnetic field of a few Gauss at the surface of the star. The field configuration is mainly poloidal at both observing epochs. The star is found to rotate differentially, with a surface rotation shear of dOmega=0.216\pm0.061 rad/d, corresponding to equatorial and polar rotation periods of 7.62\pm0.07 and 10.3\pm0.8 d respectively. The coronal field estimated by extrapolating the surface maps resembles a dipole tilted at ~70 degrees. We also find that the chromospheric activity of HD 179949 is mainly modulated by the rotation of the star, with two clear maxima per rotation period as expected from a highly tilted magnetosphere. In September 2009, we find that the activity of HD 179949 shows hints of low amplitude fluctuations with a period close to the beat period of the system.Comment: Accepted for publication in Monthly Notices of The Royal Astronomical Societ

Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system

Since the discovery of the transiting super-Earth CoRoT-7b, several investigations have yielded different results for the number and masses of planets present in the system, mainly owing to the star's high level of activity. We re-observed CoRoT-7 in January 2012 with both HARPS and CoRoT, so that we now have the benefit of simultaneous radial-velocity and photometric data. This allows us to use the off-transit variations in the star's light curve to estimate the radial-velocity variations induced by the suppression of convective blueshift and the flux blocked by starspots. To account for activity-related effects in the radial-velocities which do not have a photometric signature, we also include an additional activity term in the radial-velocity model, which we treat as a Gaussian process with the same covariance properties (and hence the same frequency structure) as the light curve. Our model was incorporated into a Monte Carlo Markov Chain in order to make a precise determination of the orbits of CoRoT-7b and CoRoT-7c. We measure the masses of planets b and c to be 4.73 +/- 0.95 Mearth and 13.56 +/- 1.08 Mearth, respectively. The density of CoRoT-7b is (6.61 +/- 1.72)(Rp/1.58 Rearth)^(-3) g.cm^(-3), which is compatible with a rocky composition. We search for evidence of an additional planet d, identified by previous authors with a period close to 9 days. We are not able to confirm the existence of a planet with this orbital period, which is close to the second harmonic of the stellar rotation at around 7.9 days. Using Bayesian model selection we find that a model with two planets plus activity-induced variations is most favoured.Comment: Accepted 2014 July 2. Received 2014 June 30; in original form 2013 May 30 (17 pages, 9 figures

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The Sun as a planet-host star : proxies from SDO images for HARPS radial-velocity variations

RDH gratefully acknowledges STFC studentship grant number ST/J500744/1, and a grant from the John Templeton Foundation. ACC and RF acknowledge support from STFC consolidated grants numbers ST/J001651/1 and ST/M001296/1. JL acknowledges support from NASA Origins of the Solar System grant No. NNX13AH79G and from STFC grant ST/M001296/1.The Sun is the only star whose surface can be directly resolved at high resolution, and therefore constitutes an excellent test case to explore the physical origin of stellar radial-velocity (RV) variability. We present HARPS observations of sunlight scattered off the bright asteroid 4/Vesta, from which we deduced the Sun's activity-driven RV variations. In parallel, the Helioseismic and Magnetic Imager instrument on board the Solar Dynamics Observatory provided us with simultaneous high spatial resolution magnetograms, Dopplergrams and continuum images of the Sun in the Fe i 6173 Å line. We determine the RV modulation arising from the suppression of granular blueshift in magnetized regions and the flux imbalance induced by dark spots and bright faculae. The rms velocity amplitudes of these contributions are 2.40 and 0.41 m s−1, respectively, which confirms that the inhibition of convection is the dominant source of activity-induced RV variations at play, in accordance with previous studies. We find the Doppler imbalances of spot and plage regions to be only weakly anticorrelated. Light curves can thus only give incomplete predictions of convective blueshift suppression. We must instead seek proxies that track the plage coverage on the visible stellar hemisphere directly. The chromospheric flux index R′HK derived from the HARPS spectra performs poorly in this respect, possibly because of the differences in limb brightening/darkening in the chromosphere and photosphere. We also find that the activity-driven RV variations of the Sun are strongly correlated with its full-disc magnetic flux density, which may become a useful proxy for activity-related RV noise.PostprintPeer reviewe