230 research outputs found
External bulb variable volume maser
A maser functioning as a frequency standard stable to one part in 10 to the 14th power includes a variable volume, constant surface area storage bulb having a fixed volume portion located in a resonant cavity from which the frequency standard is derived. A variable volume portion of the bulb, exterior to the resonant cavity, has a maximum volume on the same order of magnitude as the fixed volume bulb portion. The cavity has a length to radius ratio of at least 3:1 so that the operation is attained without the need for a feedback loop. A baffle plate, between the fixed and variable volume bulb portions, includes apertures for enabling hydrogen atoms to pass between the two bulb portions and is an electromagnetic shield that prevents coupling of the electromagnetic field of the cavity into the variable volume bulb portion
Tunable Hybridization Between Electronic States of Graphene and Physisorbed Hexacene
Non-covalent functionalization via physisorption of organic molecules
provides a scalable approach for modifying the electronic structure of graphene
while preserving its excellent carrier mobilities. Here we investigated the
physisorption of long-chain acenes, namely, hexacene and its fluorinated
derivative perfluorohexacene, on bilayer graphene for tunable graphene devices
using first principles methods. We find that the adsorption of these molecules
leads to the formation of localized states in the electronic structure of
graphene close to its Fermi level, which could be readily tuned by an external
electric field. The electric field not only creates a variable band gap as
large as 250 meV in bilayer graphene, but also strongly influences the charge
redistribution within the molecule-graphene system. This charge redistribution
is found to be weak enough not to induce strong surface doping, but strong
enough to help preserve the electronic states near the Dirac point of graphene.Comment: 17 pages, 7 figures, supporting informatio
Modelling localised fracture of reinforced concrete structures
This paper presents a robust finite element procedure for simulating the localised fracture of reinforced concrete members. In this new model the concrete member is modelled as an assembly of plain concrete, reinforcing steel bar and bond-link elements. The 4-node quadrilateral elements are used for 2D modelling of plain concrete elements, in which the extended finite element method is adopted to simulate the formation and growth of individual cracks. The reinforcing steel bars are modelled by using a 3-node beam-column element. 2-node bond-link elements are employed for modelling the interaction between plain concrete and reinforcing steel bar elements. It is evident that the nonlinear procedure proposed in this paper can properly model the formation and propagation of individual localised cracks within the reinforced concrete structures. The model presented in this paper enables the researchers and designers to access the integrity of reinforced concrete members under extreme loading conditions by using mesh independent extended finite element method.The support of the Engineering and Physical Sciences Research Council of Great Britain under Grant No. EP/I031553/1
Nanosecond time transfer via shuttle laser ranging experiment
A method is described to use a proposed shuttle laser ranging experiment to transfer time with nanosecond precision. All that need be added to the original experiment are low cost ground stations and an atomic clock on the shuttle. It is shown that global time transfer can be accomplished with 1 ns precision and transfer up to distances of 2000 km can be accomplished with better than 100 ps precision
Validation of a simplified micromodel for analysis of infilled RC frames exposed to cyclic lateral loads
An RC frame structure with masonry infill walls (‘‘framed-masonry’’) exposed
to lateral loads acts as a composite structure. Numerical simulation of framed-masonry is
difficult and generally unreliable due to many difficulties and uncertainties in its modelling.
In this paper, we reviewed the usability of an advanced non-linear FEM computer
program to accurately predict the behaviour of framed-masonry elements when exposed to
cyclic lateral loading. Numerical results are validated against the test results of framedmasonry
specimens, with and without openings. Initial simplified micromodels were calibrated
by adjustment of the input parameters within the physically justifiable borders, in
order to obtain the best correlation between the experimental and numerical results. It has
been shown that the use of simplified micromodels for the investigation of composite
masonry-infilled RC frames requires in-depth knowledge and engineering judgement in
order to be used with confidence. Modelling problems were identified and explained in
detail, which in turn offer an insight to practising engineers on how to deal with them
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Reply to: New Meta- and Mega-analyses of Magnetic Resonance Imaging Findings in Schizophrenia: Do They Really Increase Our Knowledge About the Nature of the Disease Process?
This work was supported by National Institute of Biomedical Imaging and Bioengineering Grant No. U54EB020403 (to the ENIGMA consortium)
Seafloor acoustic remote sensing with multibeam echo-sounders and bathymetric sidescan sonar systems
Anthropometric and reproductive factors and risk of esophageal and gastric cancer by subtype and subsite: results from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort
Obesity has been associated with upper gastrointestinal cancers; however, there are limited prospective data on associations by subtype/subsite. Obesity can impact hormonal factors, which have been hypothesized to play a role in these cancers. We investigated anthropometric and reproductive factors in relation to esophageal and gastric cancer by subtype and subsite for 476,160 participants from the European Prospective Investigation into Cancer and Nutrition cohort. Multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox models. During a mean follow‐up of 14 years, 220 esophageal adenocarcinomas (EA), 195 esophageal squamous cell carcinomas, 243 gastric cardia (GC) and 373 gastric noncardia (GNC) cancers were diagnosed. Body mass index (BMI) was associated with EA in men (BMI ≥30 vs. 18.5–25 kg/m2: HR = 1.94, 95% CI: 1.25–3.03) and women (HR = 2.66, 95% CI: 1.15–6.19); however, adjustment for waist‐to‐hip ratio (WHR) attenuated these associations. After mutual adjustment for BMI and HC, respectively, WHR and waist circumference (WC) were associated with EA in men (HR = 3.47, 95% CI: 1.99–6.06 for WHR >0.96 vs. 98 vs. 0.82 vs. 84 vs. 2 vs. 0) and age at first pregnancy and GNC (HR = 0.54, 95% CI: 0.32–0.91; >26 vs. <22 years); whereas bilateral ovariectomy was positively associated with GNC (HR = 1.87, 95% CI: 1.04–3.36). These findings support a role for hormonal pathways in upper gastrointestinal cancers
Anthropometric and reproductive factors and risk of esophageal and gastric cancer by subtype and subsite: results from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort
Obesity has been associated with upper gastrointestinal cancers; however, there are limited prospective data on associations by subtype/subsite. Obesity can impact hormonal factors, which have been hypothesized to play a role in these cancers. We investigated anthropometric and reproductive factors in relation to esophageal and gastric cancer by subtype and subsite for 476,160 participants from the European Prospective Investigation into Cancer and Nutrition cohort. Multivariable hazard ratios (HRs) and 95%-confidence intervals (CIs) were estimated using Cox models. During a mean follow-up of 14 years, 220 esophageal adenocarcinomas (EA), 195 esophageal squamous cell carcinomas, 243 gastric cardia (GC) and 373 gastric non-cardia (GNC) cancers were diagnosed. Body mass index (BMI) was associated with EA in men (BMI≥30 vs 18.5-25kg/m2: HR=1.94, 95%-CI: 1.25-3.03) and women (HR=2.66, 95%-CI: 1.15-6.19); however, adjustment for waist-to-hip ratio (WHR) attenuated these associations. WHR and waist circumference (WC) were associated with EA in men (HR=3.47, 95%-CI: 1.99-6.06 for WHR >0.96 vs 98 vs 0.82 vs 83 vs 2 vs 0) and age at first pregnancy and GNC (HR=0.54, 95%-CI: 0.32-0.91; >26 vsPeer reviewe
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