3,845 research outputs found

    The gravitational wave rocket

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    Einstein's equations admit solutions corresponding to photon rockets. In these a massive particle recoils because of the anisotropic emission of photons. In this paper we ask whether rocket motion can be powered only by the emission of gravitational waves. We use the double series approximation method and show that this is possible. A loss of mass and gain in momentum arise in the second approximation because of the emission of quadrupole and octupole waves.Comment: 10 pages LaTe

    Photoemission evidence for crossover from Peierls-like to Mott-like transition in highly strained VO2_2

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    We present a spectroscopic study that reveals that the metal-insulator transition of strained VO2_2 thin films may be driven towards a purely electronic transition, which does not rely on the Peierls dimerization, by the application of mechanical strain. Comparison with a moderately strained system, which does involve the lattice, demonstrates the crossover from Peierls- to Mott-like transitions

    A national certification programme for academic degrees in cyber security

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    With a growing need for cyber security skills, there has been a notable increase in the number of academic degrees targeting this topic area, at both undergraduate and postgraduate levels. However, with a widening and varied choice available to them, prospective students and employers require a means to identify academic degrees that offer appropriate and high-quality education in the subject area. This paper presents a case study of the establishment and operation of a certification programme for academic degrees in cyber security. It describes the means by which appropriate topic themes and subject areas for relevant degrees were identified and defined, leading to a certification programme that addresses degrees in general cyber security as well as notable specialisations including digital forensics and network security. The success of the programme is evidenced by 25 degrees across 19 universities having been certified to date, and a continued response to new calls for certification

    Strain dependence of bonding and hybridization across the metal-insulator transition of VO2

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    Soft x-ray spectroscopy is used to investigate the strain dependence of the metal-insulator transition of VO2. Changes in the strength of the V 3d - O 2p hybridization are observed across the transition, and are linked to the structural distortion. Furthermore, although the V-V dimerization is well-described by dynamical mean-field theory, the V-O hybridization is found to have an unexpectedly strong dependence on strain that is not predicted by band theory, emphasizing the relevance of the O ion to the physics of VO2

    Multiparametric prostate MRI quality assessment using a semi-automated PI-QUAL software program

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    The technical requirements for the acquisition of multiparametric magnetic resonance imaging (mpMRI) of the prostate have been clearly outlined in the Prostate Imaging Reporting and Data System (PI-RADS) guidelines, but there is still huge variability in image quality among centres across the world. It has been difficult to quantify what constitutes a good-quality image, and a first attempt to address this matter has been the publication of the Prostate Imaging Quality (PI-QUAL) score and its dedicated scoring sheet. This score includes the assessment of technical parameters that can be obtained from the DICOM files along with a visual evaluation of certain features on prostate MRI (e.g., anatomical structures). We retrospectively analysed the image quality of 10 scans from different vendors and magnets using a semiautomated dedicated PI-QUAL software program and compared the time needed for assessing image quality using two methods (semiautomated assessment versus manual filling of the scoring sheet). This semiautomated software is able to assess the technical parameters automatically, but the visual assessment is still performed by the radiologist. There was a significant reduction in the reporting time of prostate mpMRI quality according to PI-QUAL using the dedicated software program compared to manual filling (5'54″ versus 7'59″; p = 0.005). A semiautomated PI-QUAL software program allows the radiologist to assess the technical details related to the image quality of prostate mpMRI in a quick and reliable manner, allowing clinicians to have more confidence that the quality of mpMRI of the prostate is sufficient to determine patient care

    Quantitative motor assessment of muscular weakness in myasthenia gravis: a pilot study

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    BACKGROUND: Muscular weakness in myasthenia gravis (MG) is commonly assessed using Quantitative Myasthenia Gravis Score (QMG). More objective and quantitative measures may complement the use of clinical scales and might detect subclinical affection of muscles. We hypothesized that muscular weakness in patients with MG can be quantified with the non-invasive Quantitative Motor (Q-Motor) test for Grip Force Assessment (QGFA) and Involuntary Movement Assessment (QIMA) and that pathological findings correlate with disease severity as measured by QMG. METHODS: This was a cross-sectional pilot study investigating patients with confirmed diagnosis of MG. Data was compared to healthy controls (HC). Subjects were asked to lift a device (250 and 500 g) equipped with electromagnetic sensors that measured grip force (GF) and three-dimensional changes in position and orientation. These were used to calculate the position index (PI) and orientation index (OI) as measures for involuntary movements due to muscular weakness. RESULTS: Overall, 40 MG patients and 23 HC were included. PI and OI were significantly higher in MG patients for both weights in the dominant and non-dominant hand. Subgroup analysis revealed that patients with clinically ocular myasthenia gravis (OMG) also showed significantly higher values for PI and OI in both hands and for both weights. Disease severity correlates with QIMA performance in the non-dominant hand. CONCLUSION: Q-Motor tests and particularly QIMA may be useful objective tools for measuring motor impairment in MG and seem to detect subclinical generalized motor signs in patients with OMG. Q-Motor parameters might serve as sensitive endpoints for clinical trials in MG

    Visible light-driven H2 production over highly dispersed Ruthenia on Rutile TiO2 nanorods

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    The immobilization of miniscule quantities of RuO2 (~0.1%) onto one-dimensional (1D) TiO2 nanorods (NRs) allows H2 evolution from water under visible light irradiation. Rod-like rutile TiO2 structures, exposing preferentially (110) surfaces, are shown to be critical for the deposition of RuO2 to enable photocatalytic activity in the visible region. The superior performance is rationalized on the basis of fundamental experimental studies and theoretical calculations, demonstrating that RuO2(110) grown as 1D nanowires on rutile TiO2(110), which occurs only at extremely low loads of RuO2, leads to the formation of a heterointerface that efficiently adsorbs visible light. The surface defects, band gap narrowing, visible photoresponse, and favorable upward band bending at the heterointerface drastically facilitate the transfer and separation of photogenerated charge carriers.Peer ReviewedPostprint (published version
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