Improving estimates of the number of ‘fake’ leptons and other mis-reconstructed objects in hadron collider events: BoB’s your UNCLE

We consider current and alternative approaches to setting limits on new physics signals having backgrounds from misidentified objects; for example jets misidentified as leptons, b-jets or photons. Many ATLAS and CMS analyses have used a heuristic matrix method for estimating the background contribution from such sources. We demonstrate that the matrix method suffers from statistical shortcomings that can adversely affect its ability to set robust limits. A rigorous alternative method is discussed, and is seen to produce fake rate estimates and limits with better qualities, but is found to be too costly to use. Having investigated the nature of the approximations used to derive the matrix method, we propose a third strategy that is seen to marry the speed of the matrix method to the performance and physicality of the more rigorous approach.This is the final published version. It is available online from Springer in the Journal of High Energy Physics here: http://link.springer.com/article/10.1007/JHEP11(2014)031

Proposal for Defining a Tall Timber Building

In order to talk about ‘tall’ buildings and more particularly ‘tall, timber’ buildings, it is useful to clarify what is meant by a ‘tall’ and a ‘tall, timber’ building. This clarification facilitates both productive discussion of the subject and secures the basis on which meaningful comparisons can be made between buildings using different structural systems and materials. The historic duopoly of steel and concrete as the structural materials of tall building construction is in the process of being broken by the introduction of engineered timber and it is appropriate that this change is reflected in the language of tall building design. The approach adopted in this paper has three parts. Existing definitions and terminology for ‘tall’ buildings are explored. A study is made of the structural systems and materials of existing buildings that use structural timber and have some claim to ‘tallness’. A proposal is made for the clarification and expansion of existing criteria for tall building terminology and definitions to accommodate the use of structural timber in tall building.This is the author accepted manuscript. The final version is available from the American Society of Civil Engineers via http://dx.doi.org/10.1061/(ASCE)ST.1943-541X.000161

Biased bootstrap sampling for efficient two-sample testing

The so-called 'energy test' is a frequentist technique used in experimental particle physics to decide whether two samples are drawn from the same distribution. Its usage requires a good understanding of the distribution of the test statistic, T, under the null hypothesis. We propose a technique which allows the extreme tails of the T-distribution to be determined more efficiently than possible with present methods. This allows quick evaluation of (for example) 5-sigma confidence intervals that otherwise would have required prohibitively costly computation times or approximations to have been made. Furthermore, we comment on other ways that T computations could be sped up using established results from the statistics community. Beyond two-sample testing, the proposed biased bootstrap method may provide benefit anywhere extreme values are currently obtained with bootstrap sampling

Search for direct pair production of the top squark in all-hadronic final states in proton-proton collisions at s√=8 TeV with the ATLAS detector

The results of a search for direct pair production of the scalar partner to the top quark using an integrated luminosity of 20.1fb−1 of proton–proton collision data at √s = 8 TeV recorded with the ATLAS detector at the LHC are reported. The top squark is assumed to decay via t˜→tχ˜01 or t˜→ bχ˜±1 →bW(∗)χ˜01 , where χ˜01 (χ˜±1 ) denotes the lightest neutralino (chargino) in supersymmetric models. The search targets a fully-hadronic final state in events with four or more jets and large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits are reported in terms of the top squark and neutralino masses and as a function of the branching fraction of t˜ → tχ˜01 . For a branching fraction of 100%, top squark masses in the range 270–645 GeV are excluded for χ˜01 masses below 30 GeV. For a branching fraction of 50% to either t˜ → tχ˜01 or t˜ → bχ˜±1 , and assuming the χ˜±1 mass to be twice the χ˜01 mass, top squark masses in the range 250–550 GeV are excluded for χ˜01 masses below 60 GeV

The strength of plants: theory and experimental methods to measure the mechanical properties of stems

From the stems of agricultural crops to the structural trunks of trees, studying the mechanical behaviour of plant stems is critical for both commerce and science. Plant scientists are also increasingly relying on mechanical test data for plant phenotyping. Yet there are neither standardized methods nor systematic reviews of current methods for the testing of herbaceous stems. We discuss the architecture of plant stems and highlight important micro- and macrostructural parameters that need to be controlled and accounted for when designing test methodologies, or that need to be understood in order to explain observed mechanical behaviour. Then, we critically evaluate various methods to test structural properties of stems, including flexural bending (two-, three-, and four-point bending) and axial loading (tensile, compressive, and buckling) tests. Recommendations are made on best practices. This review is relevant to fundamental studies exploring plant biomechanics, mechanical phenotyping of plants, and the determinants of mechanical properties in cell walls, as well as to application-focused studies, such as in agro-breeding and forest management projects, aiming to understand deformation processes of stem structures. The methods explored here can also be extended to other elongated, rod-shaped organs (e.g. petioles, midribs, and even roots).This work is part of a project funded by the Leverhulme Trust (Project title: ‘Natural material innovation’). The project forms a collaboration with the Department of Applied Mathematics and Theoretical Physics, Department of Biochemistry, Department of Chemistry, and Department of Plant Sciences at the University of Cambridge

Thermal relaxation of laminated bamboo for folded shells

Laminated bamboo is emerging as a novel material in design and construction. As a natural fibre composite, it has unique mechanical properties that allow for innovations that are not possible in other materials. Here, we discuss one new application of those properties: the development of a novel bending technique using high temperature, and we explore its implications for design. We have explored the fundamental properties of laminated bamboo and its thermal relaxation asit passes the glass transition temperatures of its constituent polymers.By mechanically thinning engineered bamboo material, score lines allow precise, controlled and localised heating that promotes limited but essential elasto-plastic behaviour. Concentrated heating above the glass transition temperature induces property evolution and structural morphology changes, which results in thermal relaxation with minimal recovery and full set upon cooling.This original technology is then deployed in the design and construction of a folded plate helical shell composed of thin laminated bamboo sheets.The presented work is supported by a Leverhulme Trust Programme Grant, and EPSRC Grant EP/K023403/1

An ecological approach to understanding highly able students' experiences of their academic talent development in a Singapore school

This study seeks to understand highly able students’ experiences of their academic talent development in a Singapore school, why they choose to do what they do in their talent development, and why some students thrive in their talent development while others do not. It uses an ecological approach that highlights the central role of the overall environment as it interacts with students. A working ecological system model drawn from Bronfenbrenner’s (1979) ecological systems theory provides a framework to describe the environment of the students. Based on qualitative methodology, a case study research design was used to examine the experiences of students in an advanced talent development programme. The students belonged to the top 3 per cent of the national age cohort. The study employed semi-structured focus group interviews, individual in-depth interviews and document analysis. Thematic analysis was used to analyse the data. The findings of this study suggested that the person characteristics of students and their multi-level ecological system environments are inextricably intertwined in the talent development process. Individual characteristics affect students’ experiences and their responses to experiences and these are themselves formed through interactions with environmental conditions. Immediate settings connect directly to students through their capacity to elicit participation and progression in the talent development process. Moreover, congruent messages within overlapping immediate settings amplify the developmental effects of individual settings, thereby sustaining the talent development process. Further, more distal influences such as the systemic and structural arrangements of schooling and talent development as well as national macro factors such as meritocracy and a highly competitive education system affect students’ decisions and interactions in their immediate settings. An important implication of this study is the need to reconceptualise talent development more holistically as nurturing the life of the mind rather than have a narrow focus on nurturing elite students

Measurement of the cross-section of high transverse momentum vector bosons reconstructed as single jets and studies of jet substructure in pp collisions at √s = 7 TeV with the ATLAS detector

This paper presents a measurement of the cross-section for high transverse momentum W and Z bosons produced in pp collisions and decaying to all-hadronic final states. The data used in the analysis were recorded by the ATLAS detector at the CERN Large Hadron Collider at a centre-of-mass energy of √s = 7 TeV;{\rm Te}{\rm V}$and correspond to an integrated luminosity of$4.6\;{\rm f}{{{\rm b}}^{-1}}$. The measurement is performed by reconstructing the boosted W or Z bosons in single jets. The reconstructed jet mass is used to identify the W and Z bosons, and a jet substructure method based on energy cluster information in the jet centre-of-mass frame is used to suppress the large multi-jet background. The cross-section for events with a hadronically decaying W or Z boson, with transverse momentum${{p}_{{\rm T}}}\gt 320\;{\rm Ge}{\rm V}$and pseudorapidity$|\eta |\lt 1.9$, is measured to be${{\sigma }_{W+Z}}=8.5\pm 1.7$ pb and is compared to next-to-leading-order calculations. The selected events are further used to study jet grooming techniques

Complete genome sequences of clinical Pandoraea fibrosis isolates

Pandoraea fibrosis is a newly identified Gram-negative bacterial species that was isolated from the respiratory tract of an Australian cystic fibrosis patient. The complete assembled genome sequences of two consecutive isolates (second isolate collected 11 months after antibiotic treatment) from the same individual are presented here

Is there a subjective well-being premium in voluntary sector employment?

Previous studies have found that employment in the voluntary sector offers a so-called ‘job satisfaction premium’: despite lower salaries, voluntary sector employees are more satisfied with their jobs than workers in other sectors. This paper examines whether voluntary sector employees also experience a subjective well-being premium. Using data from the UK Annual Population Survey 2012/2013, we find that voluntary sector employees do have higher levels of subjective well-being but this subjective well-being premium is not evenly distributed between men and women. Men score higher on happiness and life satisfaction. However, women in the voluntary sector have lower levels of life satisfaction compared with their counterparts in the public sector. We discuss the implications of our findings for policy and practice in the voluntary sector in the UK