Dynamics of Dust Particles Released from Oort Cloud Comets and Their Contribution to Radar Meteors

The Oort Cloud Comets (OCCs), exemplified by the Great Comet of 1997 (Hale-Bopp), are occasional visitors from the heatless periphery of the solar system. Previous works hypothesized that a great majority of OCCs must physically disrupt after one or two passages through the inner solar system, where strong thermal gradients can cause phase transitions or volatile pressure buildup. Here we study the fate of small debris particles produced by OCC disruptions to determine whether the imprints of a hypothetical population of OCC meteoroids can be found in the existing meteor radar data. We find that OCC particles with diameters D<10 um are blown out from the solar system by radiation pressure, while those with D>1 um have a very low Earth-impact probability. The intermediate particle sizes, D=100 um, represent a sweet spot. About 1% of these particles orbitally evolve by Poynting-Robertson drag to reach orbits with semimajor axis a=1 AU. They are expected to produce meteors with radiants near the apex of the Earth's orbital motion. We find that the model distributions of their impact speeds and orbits provide a good match to radar observations of apex meteors, except for the eccentricity distribution, which is more skewed toward e=1 in our model. Finally, we propose an explanation for the long-standing problem in meteor science related to the relative strength of apex and helion/antihelion sources. As we show in detail, the observed trend, with the apex meteors being more prominent in observations of highly sensitive radars, can be related to orbital dynamics of particles released on the long-period orbits

The vaccinia chondroitin sulfate binding protein drives host membrane curvature to facilitate fusion

Cellular attachment of viruses determines their cell tropism and species specificity. For entry, vaccinia, the prototypic poxvirus, relies on four binding proteins and an eleven-protein entry fusion complex. The contribution of the individual virus binding proteins to virion binding orientation and membrane fusion is unclear. Here, we show that virus binding proteins guide side-on virion binding and promote curvature of the host membrane towards the virus fusion machinery to facilitate fusion. Using a membrane-bleb model system together with super-resolution and electron microscopy we find that side-bound vaccinia virions induce membrane invagination in the presence of low pH. Repression or deletion of individual binding proteins reveals that three of four contribute to binding orientation, amongst which the chondroitin sulfate binding protein, D8, is required for host membrane bending. Consistent with low-pH dependent macropinocytic entry of vaccinia, loss of D8 prevents virion-associated macropinosome membrane bending, disrupts fusion pore formation and infection. Our results show that viral binding proteins are active participants in successful virus membrane fusion and illustrate the importance of virus protein architecture for successful infection.</p

European database of explanted UHMWPE liners from total joint replacements: correlations among polymer modifications, structure, oxidation, mechanical properties and lifetime in vivo

This contribution lays the foundation for the European database of explanted UHMWPE liners from total joint replacements. Three EU countries (Czech Republic, Italy and Spain) have joined their datasets containing anonymized patient data (such as age and BMI), manufacturer data (such as information on UHMWPE crosslinking, thermal treatment and sterilization), orthopedic evaluation (such as total duration of the implant in vivo and reasons for its revision) and material characterization (such as oxidative degradation and micromechanical properties). The joined database contains more than 500 entries, exhibiting gradual growth, and it is beginning to show interesting trends, which are discussed in our contribution, including (i) strong correlations between UHMWPE oxidative degradation, degree of crystallinity and microhardness; (ii) statistically significant differences between UHMWPE liners with different types of sterilization; (iii) realistic correlations between the extent of oxidative degradation and the observed reasons for total joint replacement failures. Our final objective and task for the future is to continuously expand the database, involving researchers from other European countries, in order to create a robust tool that will contribute to the better understanding of structure–properties–performance relationships in the field of arthroplasty implants

Electromechanical strain in Bi(Zn1/2Ti1/2)O3–(Bi1/2Na1/2)TiO3–(Bi1/2K1/2)TiO3 solid solutions

Solid solutions ceramics of the Bi(Zn0.5Ti0.5)O-3-(Bi0.5K0.5)TiO3-(Bi0.5Na0.5)TiO3 ternary system for <20 mol. % BZT were created and confirmed to be single phase using x-ray diffraction. The dielectric dispersion showed decreasing T-max of the dielectric spectrum with a broadening of the transition with increasing BZT content. At 2.5BZT-40BKT-57.5BNT, a secondary transition commonly observed for morphotropic phase boundary (MPB) BNT-BKT was observed. The ferroelectric behavior of the system was characterized by a transition where the polarization hysteresis showed a severe pinching effect on remanent polarization (20.8 mu C/cm(2) at 2.5% BZT) as BZT contents was increased (P-r = 2.3 mu C/cm(2) at 20% BZT). Similarly, as the temperature increased to 175 degrees C, the remanent polarization of the 2.5% BZT composition significantly reduced to 2.1 mu C/cm(2). The onset of this transition corresponds to the lower temperature frequency dispersion observed in the dielectric spectrum. The strain hysteresis experienced analogous transition to the polarization, with a change in shape from typical ferroelectric butterfly to a complete loss of negative strain as BZT concentration increased. Maximum strain values of 0.33% were observed at 5-40-55 accompanied by a large d(33)* = 547 pm/V. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4714346]This is the publisher’s final pdf. The published article is copyrighted by American Institute of Physics and can be found at: http://jap.aip.org/.Keywords: Temperature, Perovskite, Free piezoelectric ceramics, Lead free ceramics, Morphotropic phase boundaryKeywords: Temperature, Perovskite, Free piezoelectric ceramics, Lead free ceramics, Morphotropic phase boundar

Low cross-talk optical addressing of trapped-ion qubits using a novel integrated photonic chip

Individual optical addressing in chains of trapped atomic ions requires the generation of many small, closely spaced beams with low cross-talk. Furthermore, implementing parallel operations necessitates phase, frequency, and amplitude control of each individual beam. Here, we present a scalable method for achieving all of these capabilities using a high-performance integrated photonic chip coupled to a network of optical fibre components. The chip design results in very low cross-talk between neighbouring channels even at the micrometre-scale spacing by implementing a very high refractive index contrast between the channel core and cladding. Furthermore, the photonic chip manufacturing procedure is highly flexible, allowing for the creation of devices with an arbitrary number of channels as well as non-uniform channel spacing at the chip output. We present the system used to integrate the chip within our ion trap apparatus and characterise the performance of the full individual addressing setup using a single trapped ion as a light-field sensor. Our measurements showed intensity cross-talk below ~10–3 across the chip, with minimum observed cross-talk as low as ~10–5

Human Challenge Pilot Study with Cyclospora cayetanensis

We describe a pilot study that attempted to infect human volunteers with Cyclospora cayetanensis. Seven healthy volunteers ingested an inoculum of Cyclospora oocysts (approximately 200–49,000 oocysts). The volunteers did not experience symptoms of gastroenteritis, and no oocysts were detected in any stool samples during the 16 weeks volunteers were monitored

Natural images from the birthplace of the human eye

Here we introduce a database of calibrated natural images publicly available through an easy-to-use web interface. Using a Nikon D70 digital SLR camera, we acquired about 5000 six-megapixel images of Okavango Delta of Botswana, a tropical savanna habitat similar to where the human eye is thought to have evolved. Some sequences of images were captured unsystematically while following a baboon troop, while others were designed to vary a single parameter such as aperture, object distance, time of day or position on the horizon. Images are available in the raw RGB format and in grayscale. Images are also available in units relevant to the physiology of human cone photoreceptors, where pixel values represent the expected number of photoisomerizations per second for cones sensitive to long (L), medium (M) and short (S) wavelengths. This database is distributed under a Creative Commons Attribution-Noncommercial Unported license to facilitate research in computer vision, psychophysics of perception, and visual neuroscience.Comment: Submitted to PLoS ON

Boxnep - модульный подводный робот перспективных технологий

The article discusses the relevance of the underwater vehicles are able to solve a wide range of problems. The decision puts in a basis of the research is designing a modular underwater robot. It allows to make a mounting of various equipment and testing it in the water medium. The paper deals with the concept of the robot and its characteristics

Spectroscopic signatures of youth in low-mass kinematic candidates of young moving groups

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2014 by the Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present a study of age-related spectral signatures observed in 25 young low-mass objects that we have previously determined as possible kinematic members of five young moving groups: the Local Association (Pleiades moving group, age = 20–150 Myr), the Ursa Major group (Sirius supercluster, age = 300 Myr), the Hyades supercluster (age = 600 Myr), IC 2391 supercluster (age = 35–55 Myr) and the Castor moving group (age = 200 Myr). In this paper we characterize the spectral properties of observed high- or low-resolution spectra of our kinematic members by fitting theoretical spectral distributions. We study signatures of youth, such as lithium I 6708Å, Hα emission and other age-sensitive spectroscopic signatures in order to confirm the kinematic memberships through age constraints. We find that 21 (84 per cent) targets show spectroscopic signatures of youth in agreement with the age ranges of the moving group to which membership is implied. For two further objects, age-related constraints remain difficult to determine from our analysis. In addition, we confirm two moving group kinematic candidates as brown dwarfs.Peer reviewe