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In this work, we investigate misfit dislocations in PbTe/PbSe heteroepitaxial systems using the concurrent atomistic–continuum (CAC) method. A potential model containing the long-range Coulombic interaction and short-range Buckingham potential is developed for the system. By considering the minimum potential energy of relaxed interface structures for various initial conditions and PbTe layer thicknesses, the equilibrium structure of misfit dislocations and the dislocation spacings in PbTe/PbSe(001) heteroepitaxial thin films are obtained as a function of the PbTe layer thicknesses grown on a PbSe substrate. The critical layer thickness above which misfit dislocations inevitably form, the structure of the misfit dislocations at the interfaces, and the dependence of average dislocation spacing on PbTe layer thickness are obtained and discussed. The simulation results provide an explanation for the narrowing of the spread of the distribution of misfit dislocation spacing as layer thickness increases in PbTe/PbSe(001) heteroepitaxy.
This article contributes to the current debate about why people follow the law even when they are not subject to legal sanctions, as when there are no police and little danger of a lawsuit. Most recent scholarship in this area takes the form of norms theories, suggesting that social norms rather than laws shape behavior and that deviations from the norm are punished by either social or internal sanctions. Robert Sugden, however, proposes that order may develop “spontaneously” in the many areas of life where abiding by the rules minimizes the risk of costly confrontations with others and is thus in the interest of all parties. When this is true, the threat of little or no sanctions plays no role in regulating behavior. This article tests Sugden's theory against a simple property system, that of the California gold mines, in which individual miners held small claims subject to strict work requirements. The evidence of eyewitnesses shows that the stability of the regime did not depend on norms, but on the reasonable prediction that other claim holders would themselves stand up for their rights under the local mining code. Disputes about the rules and their application were submitted to arbitrators, whose decisions were accepted by the parties and did not need to be enforced. The California experience thus provides an example of a stable property regime for which game theory has a more satisfying explanation than do any of the norms theories.
References to Rabelais in Andrew Marvell’s prose satires against religious intolerance, The Rehearsal Transpros’d (1672–73), offer insights into the Restoration reception of Rabelaisian satire in the universities and the coffeehouses as a specifically anticlerical form of wit. But these references are either misattributed or incorrect, suggesting that Marvell may never actually have read Gargantua and Pantagruel, but rather picked up Rabelaisian anecdotes when conversing in intellectual circles in France in the mid-1650s. Critical focus on the history of reading tends to neglect the inevitable role of such conversation in literary transmission, both within a national culture and across national borders.
We study the minimum degree necessary to guarantee the existence of perfect and almost-perfect triangle-tilings in an n-vertex graph G with sublinear independence number. In this setting, we show that if δ(G) ≥ n/3 + o(n), then G has a triangle-tiling covering all but at most four vertices. Also, for every r ≥ 5, we asymptotically determine the minimum degree threshold for a perfect triangle-tiling under the additional assumptions that G is Kr-free and n is divisible by 3.
We report a case of combined severe aortic stenosis and regurgitation in a pregnant patient with a history of congenital bicuspid aortic valve. The patient presented at 22 weeks of gestation with angina and pre-syncopal symptoms. During her admission, she experienced intermittent episodes of non-sustained ventricular tachycardia and hypotension. A multi-disciplinary healthcare team was assembled to decide on the appropriate medical and surgical treatment options. At 28 weeks of gestation, the patient underwent a caesarean delivery immediately followed by a mechanical aortic valve replacement.
Anxiety is debilitating and associated with numerous mental and physical comorbidities. There is a need to identify and investigate low-risk prevention and treatment strategies. Therefore, the purpose of this study was to investigate cross-sectional and longitudinal associations between different volumes of moderate-to-vigorous physical activity (PA) and anxiety symptoms and status among older adults in Ireland.
Participants (n = 4175; 56.8% female) aged ⩾50 years completed the International PA Questionnaire (IPAQ) at baseline, and the anxiety subscale of the Hospital Anxiety and Depression Scale at baseline and follow-up (2009–2013). Participants were classified according to meeting World Health Organisation PA guidelines, and divided into IPAQ categories. Respondents without anxiety at baseline (n = 3165) were included in prospective analyses. Data were analysed in 2017.
Anxiety symptoms were significantly higher among females than males (p < 0.001). Models were adjusted for age, sex, waist circumference, social class, smoking status and pain. In cross-sectional analyses, meeting PA guidelines was associated with 9.3% (OR = 0.91, 95% confidence interval 0.78–1.06) lower odds of anxiety. Compared with the inactive group, the minimally- and very-active groups were associated with 8.4% (OR = 0.92, 0.76–1.10) and 18.8% (OR = 0.81, 0.67–0.98) lower odds of anxiety, respectively. In prospective analyses, meeting guidelines was associated with 6.3% (OR = 0.94, 0.63–1.40) reduced odds of anxiety. Compared with the inactive group, the minimally and very-active groups were associated with 43.5% (OR = 1.44, 0.89–2.32) increased, and 4.3% (OR = 0.96, 0.56–1.63) reduced odds of anxiety. The presence of pain, included in models as a covariate, was associated with a 108.7% (OR = 2.09, 1.80–2.42) increase in odds of prevalent anxiety, and a 109.7% (OR = 2.10, 1.41–3.11) increase in odds of incident anxiety.
High volumes of PA are cross-sectionally associated with lower anxiety symptoms and status, with a potential dose–response apparent. However, significant associations were not observed in prospective analyses. The low absolute number of incident anxiety cases (n = 109) potentially influenced these findings. Further, as older adults may tend to experience and/or report more somatic anxiety symptoms, and the HADS focuses primarily on cognitive symptoms, it is plausible that the HADS was not an optimal measure of anxiety symptoms in the current population.
We present a novel distributed-memory parallel implementation of the concurrent atomistic-continuum (CAC) method. Written mostly in Fortran 2008 and wrapped with a Python scripting interface, the CAC simulator in PyCAC runs in parallel using Message Passing Interface with a spatial decomposition algorithm. Built upon the underlying Fortran code, the Python interface provides a robust and versatile way for users to build system configurations, run CAC simulations, and analyze results. In this paper, following a brief introduction to the theoretical background of the CAC method, we discuss the serial algorithms of dynamic, quasistatic, and hybrid CAC, along with some programming techniques used in the code. We then illustrate the parallel algorithm, quantify the parallel scalability, and discuss some software specifications of PyCAC; more information can be found in the PyCAC user’s manual that is hosted on www.pycac.org.
This work presents the recent progress in the development of the concurrent atomistic-continuum (CAC) method for coarse-grained space- and time-resolved atomistic simulations of phonon transport. Application examples, including heat pulses propagating across grain boundaries and phase interfaces, as well as the interactions between phonons and moving dislocations, are provided to demonstrate the capabilities of CAC. The simulation results provide visual evidence and reveal the underlying physics of a variety of phenomena, including phonon focusing, wave interference, dislocation drag, interfacial Kapitza resistance caused by quasi-ballistic phonon transport, etc. A new method to quantify fluxes in transient transport processes is also introduced.
This chapter will provide you with the fundamental skills for working with children, young people and their families to promote mental health. Adolescent mental health and wellbeing are covered in more detail elsewhere in this text, but it is important to acknowledge that good mental health is an important goal from birth (and even before birth), throughout childhood and into adolescence. Some adolescent mental health disorders are adolescent limited – that is, they begin and end in the period of adolescence – but mostly mental health and mental health disorders are experienced along a continuum. Indeed, as you will learn from this chapter, temporal assessment of children's behaviours is paramount in any assessment of mental health. As children mature, their behaviours change accordingly. Behaviours that can be expected among young children should disappear as they mature, such as the inability to regulate emotions, or to experience empathy for others. It is therefore imperative that mental health and behavioural assessments are not completed in one encounter. Paediatric mental health clinicians view the child or young person as a representative of a family system. This means that the family is necessarily incorporated into every facet of care, including assessment, planning, treatment and evaluation of care. Children and young people, their parents and guardians, families, school and broader communities are all considered in the planning for optimal mental healthcare service delivery.
Children and young people are actually at high risk of mental health disorders, and in Australia 8.3 per cent of children and young people live with mild, moderate or severe mental disorders (Lawrence et al., 2016). Since the first Australian survey of children's mental health was reported in 2000, the prevalence of children's mental health disorders has been stable. The National Youth Mental Health Initiative launched by the Australian Government in 2005 (Headspace) has focused on increasing prevention and treatment services for children and young people. It seems that for children identified as having mental health disorders, the uptake of services is high. But there continues to be a need for improving the prevention and early intervention strategies and services, especially for those children and young people already experiencing mental health problems.
Until recently there have been very few measurements of the ionizing continuum in quasars. With the combination of Einstein X-ray slopes and IUE spectra for a sample of quasars, this continuum can now be better constrained. Here we take a preliminary look for relations between the shape of this continuum and the emission lines produced over the observed range of continuum properties.
The first Einstein IPC X-ray spectra of quasars had slopes similar to their infrared spectra (Elvis et al. 1986) suggesting that the infrared and x-ray continua of quasars might be two ends of a single power-law extending over at least 4 decades of the electromagnetic spectrum. In retrospect this was a bold claim based as it was on only eight quasars with limited infrared coverage. If true though it would greatly simplify the structure of the quasar continuum.
It has been proposed (e.g. Carr, Bond and Arnett 1984) that the first generation of stars may have been Very Massive Objects (VMOs, of mass above 200 M⊙) which existed at large redshifts and left a large fraction of the mass of the universe in black hole remnants which now provide the dynamical ‘dark matter’. The radiation from these stars would be present today as extragalactic background light. For stars with density parameter Ω* which convert a fraction ϵ of their rest-mass to radiation at a redshift of z, the energy density of background radiation in units of the critical density is ΩR = εΩ* / (1+z). The VMOs would be far-ultraviolet sources with effective temperatures of 105 K. If the radiation is not absorbed, the constraints provided by measurements of background radiation imply (for H =50 km/s/Mpc) that the stars cannot close the universe unless they formed at a redshift of 40 or more. To provide the dark matter (of one-tenth closure density) the optical limits imply that they must have existed at redshifts above 25.