In this paper we explain how the C++ code quality is managed in ATLAS using a range of tools from compile-time through to run time testing and reflect on the substantial progress made in the last two ...years largely through the use of static analysis tools such as Coverity®, an industry-standard tool which enables quality comparison with general open source C++ code. Other available code analysis tools are also discussed, as is the role of unit testing with an example of how the GoogleTest framework can be applied to our codebase.
Background: Shape coexistence in heavy nuclei poses a strong challenge to state-of-the-art nuclear models, where several competing shape minima are found close to the ground state. A classic region ...for investigating this phenomenon is in the region around Z = 82 and the neutron midshell at N = 104. Purpose: Evidence for shape coexistence has been inferred from a-decay measurements, laser spectroscopy, and in-beam measurements. While the latter allow the pattern of excited states and rotational band structures to be mapped out, a detailed understanding of shape coexistence can only come from measurements of electromagnetic matrix elements. Method: Secondary, radioactive ion beams of Rn-202 and Rn-204 were studied by means of low-energy Coulomb excitation at the REX-ISOLDE in CERN. Results: The electric-quadrupole (E2) matrix element connecting the ground state and first excited 2(1)(+) state was extracted for both Rn-202 and Rn-204, corresponding to B(E2; 2(1)(+) -> 0(1)(+)) = 29(-8)(+8) and 43(-12)(+17) W.u., respectively. Additionally, E2 matrix elements connecting the 2(1)(+) state with the 4(1)(+) and 2(2)(+) states were determined in Rn-202. No excited 0(+) states were observed in the current data set, possibly owing to a limited population of second-order processes at the currently available beam energies. Conclusions: The results are discussed in terms of collectivity and the deformation of both nuclei studied is deduced to be weak, as expected from the low-lying level-energy schemes. Comparisons are also made to state-of-the-art beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.
A description of the algorithms and the performance of the ATLAS Inner Detector trigger for LHC Run 1 are presented, as well as prospects for a redesign of the tracking algorithms in Run 2. The Inner ...Detector trigger algorithms are vital for many trigger signatures at ATLAS. The performance of the algorithms for electrons is presented. The ATLAS trigger software will be restructured from two software levels into a single stage which poses a big challenge for the trigger algorithms in terms of execution time and maintaining the physics performance. Expected future improvements in the timing and efficiencies of the Inner Detector triggers are discussed, utilising the planned merging of the current two stages of the ATLAS trigger.
In quantum mechanics, asymptotic degeneracy is often considered in the context of a particle in a symmetric double-well potential, and is the phenomenon whereby pairs of energy levels come together ...to form doubly degenerate levels in response to an increase in the separation, or depth of the two wells. Here we highlight a new kind of asymptotic degeneracy that can arise when a particle is bound to a surface formed by the intersection of two planes, when the intersection angle is greater than pi. To demonstrate this effect we consider the bound states of a charged particle subject its own 'image' potential in a highly polarizable wedge, as a function of the wedge opening angle.
Background: Shape coexistence in heavy nuclei poses a strong challenge to state-of-the-art nuclear models, where several competing shape minima are found close to the ground state. A classic region ...for investigating this phenomenon is in the region around \(Z=82\) and the neutron mid-shell at \(N=104\). Purpose: Evidence for shape coexistence has been inferred from \(\alpha\)-decay measurements, laser spectroscopy and in-beam measurements. While the latter allow the pattern of excited states and rotational band structures to be mapped out, a detailed understanding of shape coexistence can only come from measurements of electromagnetic matrix elements. Method: Secondary, radioactive ion beams of \(^{202}\)Rn and \(^{204}\)Rn were studied by means of low-energy Coulomb excitation at the REX-ISOLDE facility in CERN. Results: The electric-quadrupole (\(E2\)) matrix element connecting the ground state and first-excited \(2^{+}_{1}\) state was extracted for both \(^{202}\)Rn and \(^{204}\)Rn, corresponding to \({B(E2;2^{+}_{1} \to 2^{+}_{1})=29^{+8}_{-8}}\) W.u. and \(43^{+17}_{-12}\) W.u., respectively. Additionally, \(E2\) matrix elements connecting the \(2^{+}_{1}\) state with the \(4^{+}_{1}\) and \(2^{+}_{2}\) states were determined in \(^{202}\)Rn. No excited \(0^{+}\) states were observed in the current data set, possibly due to a limited population of second-order processes at the currently-available beam energies. Conclusions: The results are discussed in terms of collectivity and the deformation of both nuclei studied is deduced to be weak, as expected from the low-lying level-energy schemes. Comparisons are also made to state-of-the-art beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.
Abstract Here we present the design of an engineered, elastin-like protein (ELP) that is chemically modified to enable stable coatings on the surfaces of titanium-based dental and orthopaedic ...implants by novel photocrosslinking and solution processing steps. The ELP includes an extended RGD sequence to confer bio-signaling and an elastin-like sequence for mechanical stability. ELP thin films were fabricated on cp-Ti and Ti6Al4V surfaces using scalable spin and dip coating processes with photoactive covalent crosslinking through a carbene insertion mechanism. The coatings withstood procedures mimicking dental screw and hip replacement stem implantations, a key metric for clinical translation. They promoted rapid adhesion of MG63 osteoblast-like cells, with over 80% adhesion after 24 h, compared to 38% adhesion on uncoated Ti6Al4V. MG63 cells produced significantly more mineralization on ELP coatings compared to uncoated Ti6Al4V. Human bone marrow mesenchymal stem cells (hMSCs) had an earlier increase in alkaline phosphatase activity, indicating more rapid osteogenic differentiation and mineral deposition on adhesive ELP coatings. Rat tibia and femur in vivo studies demonstrated that cell-adhesive ELP-coated implants increased bone-implant contact area and interfacial strength after one week. These results suggest that ELP coatings withstand surgical implantation and promote rapid osseointegration, enabling earlier implant loading and potentially preventing micromotion that leads to aseptic loosening and premature implant failure.
We consider the information relaxation approach for calculating performance bounds for stochastic dynamic programs (DPs), following Brown et al. Brown DB, Smith JE, Sun P (2010) Information ...relaxations and duality in stochastic dynamic programs.
Oper. Res.
58(4, Part 1):785–801. This approach generates performance bounds by solving problems with relaxed nonanticipativity constraints and a penalty that punishes violations of these constraints. In this paper, we study infinite horizon DPs with discounted costs and consider applying information relaxations to reformulations of the DP. These reformulations use different state transition functions and correct for the change in state transition probabilities by multiplying by likelihood ratio factors. These reformulations can greatly simplify solutions of the information relaxations, both in leading to finite horizon subproblems and by reducing the number of states that need to be considered in these subproblems. We show that any reformulation leads to a lower bound on the optimal cost of the DP when used with an information relaxation and a penalty built from a broad class of approximate value functions. We refer to this class of approximate value functions as
subsolutions
, and this includes approximate value functions based on Lagrangian relaxations as well as those based on approximate linear programs. We show that the information relaxation approach, in theory, recovers a tight lower bound using any reformulation and is guaranteed to improve on the lower bounds from subsolutions. Finally, we apply information relaxations to an inventory control application with an autoregressive demand process, as well as dynamic service allocation in a multiclass queue. In our examples, we find that the information relaxation lower bounds are easy to calculate and are very close to the expected cost using simple heuristic policies, thereby showing that these heuristic policies are nearly optimal.
We develop a new method for pricing American options. The main practical contribution of this paper is a general algorithm for constructing upper and lower bounds on the true price of the option ...using any approximation to the option price. We show that our bounds are tight, so that if the initial approximation is close to the true price of the option, the bounds are also guaranteed to be close. We also explicitly characterize the worst-case performance of the pricing bounds. The computation of the lower bound is straightforward and relies on simulating the suboptimal exercise strategy implied by the approximate option price. The upper bound is also computed using Monte Carlo simulation. This is made feasible by the representation of the American option price as a solution of a properly defined dual minimization problem, which is the main theoretical result of this paper. Our algorithm proves to be accurate on a set of sample problems where we price call options on the maximum and the geometric mean of a collection of stocks. These numerical results suggest that our pricing method can be successfully applied to problems of practical interest.
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