58,911 research outputs found

    Precision measurement noise asymmetry and its annual modulation as a dark matter signature

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    Dark matter may be composed of ultralight quantum fields that form macroscopic objects. As the Earth moves through the galaxy, interactions with such objects may leave transient signatures in terrestrial experiments. These signatures may be sought by analyzing correlations between multiple devices in a distributed network. However, if the objects are small (<~10^3 km) it becomes unlikely that more than one device will be affected in a given event. Such models may, however, induce an observable asymmetry in the noise distributions of precision measurement devices, such as atomic clocks. Further, an annual modulation in this asymmetry is expected. Such an analysis may be performed very simply using existing data, and would be sensitive to models with a high event rate, even if individual events cannot be resolved. For certain models, our technique extends the discovery reach beyond that of existing experiments by many orders of magnitude

    Information Systems Undergraduate Degree Project: Gaining a Better Understanding of the Final Year Project Module

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    The place of an individual project in the final year of Information Systems (IS) undergraduate degrees at UK universities is well established. In this paper we compare the final year project modules at four UK universities: the University of Brighton, the University of South Wales, University of West London and the University of Westminster. We find that the aims of the projects are similar, emphasising the application of the knowledge and skills from the taught element of their course in a complex development project, often including interactions with a real client. Although we show in this analysis that projects serve a similar purpose in the IS degree courses, the associated learning outcomes and the assessment practice varies across the institutions. We identify some gaps in the skills and abilities that are not being assessed. In further work we are planning to consult final year students undertaking their projects and their supervisors, in order to gain an understanding of how project assessment criteria are actually put to use

    Problem-formulation in a South African organization. Executive summary

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    Complex Problem Solving is an area of cognitive science that has received a good amount of attention, but theories in the field have not progressed accordingly. In general, research of problem solving has focussed on identifying preferable methods rather than on what happens when human beings confront problems in an organizational context Queseda, Kirtsch and Gomez (2005) Existing literature recognises that most organizational problems are ill-defined. Some problems can become well-defined whereas others are and remain ill-structured. For problems that can become well-defined, failure to pay attention to the area of problem definition has the potential to jeopardise the effectiveness of problem-formulation and thus the entire problem solving activity. Problem defining, a fundamental part of the problem-formulation process, is seen as the best defence against a Type III Error (trying to solve the wrong problem). Existing literature addresses possible processes for problem-formulation and recognises the importance of applying problem domain knowledge within them. However, inadequate attention is given to the possible circumstances that, within an organization, the participants do not know enough about the problem domain and do not recognise the importance of applying adequate problem domain knowledge or experience to the problem-formulation process. A case study is conducted into exactly these circumstances as they occurred and were successfully addressed within Eskom Holdings Ltd (Eskom), the national electricity utility in South Africa. The case study is a fundamental part of this research project, which explores the gap in the existing body of knowledge related to the circumstances described above and specifically to problems that can become well-defined, and provides the basis for the innovation developed herein that addresses that gap

    Nuclear-spin-dependent parity nonconservation in s-d_5/2 and s-d_3/2 transitions

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    We perform calculations of s-d_5/2 nuclear-spin-dependent parity nonconservation amplitudes for Rb, Cs, Ba+, Yb+, Fr, Ra+ and Ac++. These systems prove to be good candidates for the use in atomic experiments to extract the so-called anapole moment, a P-odd T-even nuclear moment important for the study of parity violating nuclear forces. We also extend our previous works by calculating the missed spin-dependent amplitudes for the s-d_3/2 transitions in the above systems.Comment: 8 page

    Double core polarization contribution to atomic PNC and EDM calculations

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    We present a detailed study of the effect of the double core polarization (the polarization of the core electrons due to the simultaneous action of the electric dipole and parity-violating weak fields) for amplitudes of the s-s and s-d parity non-conserving transitions in Rb, Cs, Ba +, La 2+, Tl, Fr, Ra +, Ac 2+ and Th 3+ as well as electron EDM enhancement factors for the ground states of the above neutral atoms and Au. This effect is quite large and has the potential to resolve some disagreement between calculations in the literature. It also has significant consequences for the use of experimental data in the accuracy analysis.Comment: 6 page

    Search for transient ultralight dark matter signatures with networks of precision measurement devices using a Bayesian statistics method

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    We analyze the prospects of employing a distributed global network of precision measurement devices as a dark matter and exotic physics observatory. In particular, we consider the atomic clocks of the Global Positioning System (GPS), consisting of a constellation of 32 medium-Earth orbit satellites equipped with either Cs or Rb microwave clocks and a number of Earth-based receiver stations, some of which employ highly-stable H-maser atomic clocks. High-accuracy timing data is available for almost two decades. By analyzing the satellite and terrestrial atomic clock data, it is possible to search for transient signatures of exotic physics, such as "clumpy" dark matter and dark energy, effectively transforming the GPS constellation into a 50,000km aperture sensor array. Here we characterize the noise of the GPS satellite atomic clocks, describe the search method based on Bayesian statistics, and test the method using simulated clock data. We present the projected discovery reach using our method, and demonstrate that it can surpass the existing constrains by several order of magnitude for certain models. Our method is not limited in scope to GPS or atomic clock networks, and can also be applied to other networks of precision measurement devices.Comment: See also Supplementary Information located in ancillary file

    Quantum electrodynamics corrections to energies, transition amplitudes and parity nonconservation in Rb, Cs, Ba+^+, Tl, Fr and Ra+^+

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    We use previously developed radiative potential method to calculate quantum electrodynamic (QED) corrections to energy levels and electric dipole transition amplitudes for atoms which are used for the study of the parity non-conservation (PNC) in atoms. The QED shift in energies and dipole amplitudes leads to noticeable change in the PNC amplitudes. This study compliments the previously considered QED corrections to the weak matrix elements. We demonstrate that the QED corrections due to the change in energies and dipole matrix elements are comparable in value to those due to change in weak matrix elements.Comment: 5 pages, 1 figur

    Characterisation of friction and lubrication regimes in premium tubular connections

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    A friction test rig has been developed to carry out repeated sliding friction tests for premium tubular connections. The test rig enables accurate measurement of friction in various contact regimes which are relevant to the threaded connections between tubular components. Higher load tests can simulate the contact in metal-to-metal seals under very high contact pressures by using perpendicular pin-on-pin tests. The contact in the thread loading flank under intermediate pressures can be simulated by using larger radius coupon-on-coupon tests. The measured coefficient of friction is well correlated with a lubrication parameter combining lubricant film thickness and initial surface roughness. © 2012 Elsevier Ltd. All rights reserved

    Fast-food offerings in the United States in 1986, 1991, and 2016 show large increases in food variety, portion size, dietary energy, and selected micronutrients

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    BACKGROUND US national survey data shows fast food accounted for 11% of daily caloric intake in 2007-2010. OBJECTIVE To provide a detailed assessment of changes over time in fast-food menu offerings over 30 years, including food variety (number of items as a proxy), portion size, energy, energy density, and selected micronutrients (sodium, calcium, and iron as percent daily value [%DV]), and to compare changes over time across menu categories (entrées, sides, and desserts). DESIGN Fast-food entrées, sides, and dessert menu item data for 1986, 1991, and 2016 were compiled from primary and secondary sources for 10 popular fast-food restaurants. STATISTICAL ANALYSIS Descriptive statistics were calculated. Linear mixed-effects analysis of variance was performed to examine changes over time by menu category. RESULTS From 1986 to 2016, the number of entrées, sides, and desserts for all restaurants combined increased by 226%. Portion sizes of entrées (13 g/decade) and desserts (24 g/decade), but not sides, increased significantly, and the energy (kilocalories) and sodium of items in all three menu categories increased significantly. Desserts showed the largest increase in energy (62 kcal/decade), and entrées had the largest increase in sodium (4.6% DV/decade). Calcium increased significantly in entrées (1.2%DV/decade) and to a greater extent in desserts (3.9% DV/decade), but not sides, and iron increased significantly only in desserts (1.4% DV/decade). CONCLUSIONS These results demonstrate broadly detrimental changes in fast-food restaurant offerings over a 30-year span including increasing variety, portion size, energy, and sodium content. Research is needed to identify effective strategies that may help consumers reduce energy intake from fast-food restaurants as part of measures to improve dietary-related health issues in the United States.Accepted manuscrip
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