5,723 research outputs found
Reflection high-energy electron diffraction experimental analysis of polycrystalline MgO films with grain size and orientation distributions
Analysis of biaxial texture of MgO films grown by ion-beam-assisted deposition (IBAD) has been performed using a quantitative reflection high-energy electron diffraction (RHEED) based method. MgO biaxial texture is determined by analysis of diffraction spot shapes from single RHEED images, and by measuring the width of RHEED in-plane rocking curves for MgO films grown on amorphous Si3N4 by IBAD using 750 eV Ar+ ions, at 45° incidence angle, and MgO e-beam evaporation. RHEED-based biaxial texture measurement accuracy is verified by comparison with in-plane and out-of-plane orientation distribution measurements made using transmission electron microscopy and x-ray rocking curves. In situ RHEED measurements also enable the analysis of the evolution of the biaxial texture which narrows with increasing film thickness. RHEED-based measurements of IBAD MgO biaxial texture show that the minimum in-plane orientation distribution depends on the out-of-plane orientation distribution, and indicates that the minimum obtainable in-plane orientation on distribution is 2°
UniquID: A Quest to Reconcile Identity Access Management and the Internet of Things
The Internet of Things (IoT) has caused a revolutionary paradigm shift in
computer networking. After decades of human-centered routines, where devices
were merely tools that enabled human beings to authenticate themselves and
perform activities, we are now dealing with a device-centered paradigm: the
devices themselves are actors, not just tools for people. Conventional identity
access management (IAM) frameworks were not designed to handle the challenges
of IoT. Trying to use traditional IAM systems to reconcile heterogeneous
devices and complex federations of online services (e.g., IoT sensors and cloud
computing solutions) adds a cumbersome architectural layer that can become hard
to maintain and act as a single point of failure. In this paper, we propose
UniquID, a blockchain-based solution that overcomes the need for centralized
IAM architectures while providing scalability and robustness. We also present
the experimental results of a proof-of-concept UniquID enrolment network, and
we discuss two different use-cases that show the considerable value of a
blockchain-based IAM.Comment: 15 pages, 10 figure
Data sharing: not as simple as it seems
In recent years there has been a major change on the part of funders, particularly in North America, so that data sharing is now considered to be the norm rather than the exception. We believe that data sharing is a good idea. However, we also believe that it is inappropriate to prescribe exactly when or how researchers should preserve and share data, since these issues are highly specific to each study, the nature of the data collected, who is requesting it, and what they intend to do with it. The level of ethical concern will vary according to the nature of the information, and the way in which it is collected - analyses of anonymised hospital admission records may carry a quite different ethical burden than analyses of potentially identifiable health information collected directly from the study participants. It is striking that most discussions about data sharing focus almost exclusively on issues of ownership (by the researchers or the funders) and efficiency (on the part of the funders). There is usually little discussion of the ethical issues involved in data sharing, and its implications for the study participants. Obtaining prior informed consent from the participants does not solve this problem, unless the informed consent process makes it completely clear what is being proposed, in which case most study participants would not agree. Thus, the undoubted benefits of data sharing does not remove the obligations and responsibilities that the original investigators hold for the people they invited to participate in the study
Virtual light-by-light scattering and the g factor of a bound electron
The contribution of the light-by-light diagram to the g factor of electron
and muon bound in Coulomb field is obtained. For electron in a ground state,
our results are in good agreement with the results of other authors obtained
numerically for large Z. For relatively small Z our results have essentially
higher accuracy as compared to the previous ones. For muonic atoms, the
contribution is obtained for the first time with the high accuracy in whole
region of Z.Comment: 10 pages, 3 figures, RevTe
In-situ biaxial texture analysis of MgO films during growth on amorphous substrates by ion-beam-assisted deposition
We used a kinematical electron scattering model to develop a RHEED based method for performing quantitative analysis of mosaic polycrystalline thin film in-plane and out-of-plain grain orientation distributions. RHEED based biaxial texture measurements are compared to x-ray and transmission electron microscopy measurements to establish the validity of the RHEED analysis method. MgO was grown on amorphous Si3N4 by ion beam-assisted deposition (IBAD) using 750 eV Ar+ ions and MgO e-beam evaporation. The ion/MgO flux ratio was varied between 0.66 and 0.42. In situ RHEED analysis reveals that during nucleation the out-of-plane orientation distribution is very broad (almost random), but narrows very quickly once well-oriented grains reach a critical size. Under optimal conditions a competition between selective sputtering and surface roughening yields a minimum out-of-plane texture at about 100 angstrom, which degrades with increasing film thickness. The narrowest in- plane orientation distribution (5.4 degrees FWHM) was found to be at an ion/MgO flux ratio between 0.55 and 0.51, in good agreement with previous experiments. The systematic offsets between RHEED analysis and x-ray measurements of biaxial texture, coupled with evidence that biaxial texture improves with increasing film thickness, indicates that RHEED is a superior technique for probing surface biaxial texture
Two dimensionality in quasi one-dimensional cobalt oxides
By means of muon spin rotation and relaxation (SR) techniques, we have
investigated the magnetism of quasi one-dimensional (1D) cobalt oxides
CoO (=Ca, Sr and Ba, =1, 2, 3, 5 and
), in which the 1D CoO chain is surrounded by six equally spaced
chains forming a triangular lattice in the -plane, using polycrystalline
samples, from room temperature down to 1.8 K. For the compounds with =1 - 5,
transverse field SR experiments showed the existence of a magnetic
transition below 100 K. The onset temperature of the transition () was found to decrease with ; from 100 K for =1 to 60 K for
=5. A damped muon spin oscillation was observed only in the sample with
=1 (CaCoO), whereas only a fast relaxation obtained even at 1.8
K in the other three samples. In combination with the results of susceptibility
measurements, this indicates that a two-dimensional short-range
antiferromagnetic (AF) order appears below for all
compounds with =1 - 5; but quasi-static long-range AF order formed only in
CaCoO, below 25 K. For BaCoO (=), as decreased
from 300 K, 1D ferromagnetic (F) order appeared below 53 K, and a sharp 2D AF
transition occurred at 15 K.Comment: 12 pages, 14 figures, and 2 table
Human papillomavirus vaccine and behavioural disinhibition
Objectives—We sought to identify characteristics of parents who believe in sexual disinhibition and that Pap smears can safely be stopped after females receive HPV vaccine. Methods—We surveyed 647 parents of adolescent girls living in areas of North Carolina with elevated rates of cervical cancer. We report data primarily from a survey conducted in Fall 2008. Results—Only 16% (101/647) of parents agreed that teenage girls who receive HPV vaccine may be more likely to have sex. Parents who believed in vaccine-induced sexual disinhibition were more likely to be older (OR 1.89; 95% CI 1.09, 3.26) or report conservative political views (OR 2.26; 95% CI 1.37, 3.73). Parents were less likely to believe in sexual disinhibition if they had greater knowledge about HPV vaccine (OR 0.52; 95% CI 0.32 0.85) or if their daughters had received HPV vaccine (OR 0.31; 95% CI 0.17, 0.57). While few parents (5%, 30/647) believed that women could safely stop getting regular Pap smears after receiving HPV vaccine, this belief was somewhat more common among racial and ethnic minority parents (16%) and among fathers (13%). Conclusions—Few parents believed that HPV vaccine is likely to lead to increased sexual activity among females or reduce the need for vaccinated women to have regular Pap smears in the future. Characterizing parents who hold beliefs in behavioral disinhibition is important as clinicians encountering parents in practice may desire information about this population
Foreign Object Damage in a Gas-Turbine Grade Silicon Nitride by Spherical Projectiles of Various Materials
Assessments of foreign object damage (FOD) of a commercial, gas-turbine grade, in situ toughened silicon nitride ceramic (AS800, Honeywell Ceramics Components) were made using four different projectile materials at ambient temperature. AS800 flexure target specimens rigidly supported were impacted at their centers in a velocity range from 50 to 450 m/s by spherical projectiles with a diameter of 1.59 mm. Four different projectile materials were used including hardened steel, annealed steel, silicon nitride ceramic, and brass. Post-impact strength of each target specimen impacted was determined as a function of impact velocity to appraise the severity of local impact damage. For a given impact velocity, the degree of strength degradation was greatest for ceramic balls, least for brass balls, and intermediate for annealed and hardened steel balls. For steel balls, hardened projectiles yielded more significant impact damage than annealed counterparts. The most important material parameter affecting FOD was identified as hardness of projectiles. Impact load as a function of impact velocity was quasi-statically estimated based on both impact and static indentation associated data
An ecosystem characterisation of the Bay of Bengal
This study summarises the high level drivers on ecological systems of the BOBLME. The ecological characterisation resulted in the identification of 29 subsystems. The report recommends the development of fully integrated approaches that considers human needs and the ecological system, involving stakeholders in a transparent way
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