Finite-frequency sensitivity of body waves to anisotropy based upon adjoint methods

We investigate the sensitivity of finite-frequency body-wave observables to mantle anisotropy based upon kernels calculated by combining adjoint methods and spectral-element modelling of seismic wave propagation. Anisotropy is described by 21 density-normalized elastic parameters naturally involved in asymptotic wave propagation in weakly anisotropic media. In a 1-D reference model, body-wave sensitivity to anisotropy is characterized by ‘banana–doughnut’ kernels which exhibit large, path-dependent variations and even sign changes. P-wave travel-times appear much more sensitive to certain azimuthally anisotropic parameters than to the usual isotropic parameters, suggesting that isotropic P-wave tomography could be significantly biased by coherent anisotropic structures, such as slabs. Because of shear-wave splitting, the common cross-correlation travel-time anomaly is not an appropriate observable for S waves propagating in anisotropic media. We propose two new observables for shear waves. The first observable is a generalized cross-correlation travel-time anomaly, and the second a generalized ‘splitting intensity’. Like P waves, S waves analysed based upon these observables are generally sensitive to a large number of the 21 anisotropic parameters and show significant path-dependent variations. The specific path-geometry of SKS waves results in favourable properties for imaging based upon the splitting intensity, because it is sensitive to a smaller number of anisotropic parameters, and the region which is sampled is mainly limited to the upper mantle beneath the receiver

Finite-Frequency SKS Splitting: Measurement and Sensitivity Kernels

Splitting of SKS waves caused by anisotropy may be analyzed by measuring the splitting intensity, i.e., the amplitude of the transverse signal relative to the radial signal in the SKS time window. This quantity is simply related to structural parameters. Extending the widely used cross-correlation method for measuring travel-time anomalies to anisotropic problems, we propose to measure the SKS-splitting intensity by a robust cross-correlation method that can be automated to build large high-quality datasets. For weak anisotropy, the SKS-splitting intensity is retrieved by cross-correlating the radial signal with the sum of the radial and transverse signals. The cross-correlation method is validated based upon a set of Californian seismograms. We investigate the sensitivity of the SKS-splitting intensity to general anisotropy in the mantle based upon a numerical technique (the adjoint spectral-element method) considering the full physics of wave propagation. The computations reveal a sensitivity remarkably focused on a small number of elastic parameters and on a small region of the upper mantle. These fundamental properties and the practical advantages of the measurement make the cross-correlation SKS-splitting intensity particularly well adapted for finite-frequency imaging of upper-mantle anisotropy

Adaptations To Major Curriculum Change: The Case Of Further Education Lecturers

In the late 1980s and 1990s, like other sections of the UK education system, Further Education (FE) was subjected to major institutional change. Furthermore, there were significant government interventions in the curriculum of FE colleges: the introduction of General National Vocational Qualifications (GNVQs) and subsequently of the Advanced Vocational Certificate in Education (AVCE). The introduction of GNVQs in the early 1990s involved a substantial change in the working practices of FE lecturers. Not only was there modification to the content to be taught but the roles of lecturer and student were transformed. In 2000, GNVQ was replaced by AVCE. This too involved considerable modification in the work of FE lecturers, in some respects a shift back towards the situation prior to the introduction of GNVQ, but also introducing new elements. These changes are the focus of this thesis. The fundamental character of the switch to GNVQ, and the subsequent move away from it, provide a distinctive context for exploring lecturers’ responses and adaptations to dramatic and rapid change. Understanding these is important if we are to grasp the factors shaping the implementation of curricular policies, and their effects. This case study attempts to deepen understanding of the significant factors which influence policy implementation by investigating how recent curricular reforms in FE came about, and how lecturers responded to them, on the basis of data from documents and interviews. The conclusion reached is that how a policy gets implemented will reflect previously prevailing working practices, along with practitioners’ views about the sort of education they are engaged in, about their central professional task, and about how it ought to be carried out; views which will be shaped by different career trajectories. These factors determine attitudes both towards the goals of any new policy and towards the operational procedures it imposes

Can finite-frequency effects be accounted for in ray theory surface wave tomography?

International audience[ 1] We present a series of synthetic tests showing that regional surface wave tomographies with a dense path coverage of the target region can be safely conducted under ray theory because the shortcomings of ray theory in considering finite-frequency effects can be counterbalanced by a physically-based regularization of the inversion. In particular, we show that with ray theory applied under the above conditions, it is possible to detect heterogeneities with length scales smaller than the wavelength of the data set

Forecasting overhead distribution line failures using weather data and gradient-boosted location, scale, and shape models

Overhead distribution lines play a vital role in distributing electricity, however, their freestanding nature makes them vulnerable to extreme weather conditions and resultant disruption of supply. The current UK regulation of power networks means preemptive mitigation of disruptions avoids financial penalties for distribution companies, making accurate fault predictions of direct financial importance. Here we present predictive models developed for a UK network based on gradient-boosted location, scale, and shape models, providing spatio-temporal predictions of faults based on forecast weather conditions. The models presented are based on (a) tree base learners or (b) penalised smooth and linear base learners -- leading to a Generalised Additive Model (GAM) structure, with the latter category of models providing best performance in terms of out-of-sample log-likelihood. The models are fitted to fifteen years of fault and weather data and are shown to provide good accuracy over multi-day forecast windows, giving tangible support to power restoration.Comment: 25 pages, 7 figures, based on the MSc dissertation of the primary author submitted for the MSc degree in Applied Statistics and Datamining at the University of St Andrews in 2021 -- under the supervision of the co-autho

Cultural aspect of social responsibility implementation in SMEs

Purpose: The purpose of the article is to identify cultural factors considered in the social responsibility of micro, small and medium-sized enterprises. Approach/Methodology/Design: In order to achieve the main goal, logit models were used. To assess the quality of estimated ordered logit models, the combined significance of all explanatory variables (significance of the model) and the Wald test were used. In order to identify factors shaping the CSR level, variables describing the organizational culture were adopted such as individualism-collectivism, distance to power and the level of tolerance of uncertainty. Findings: Logit models allow for the identification of the key cultural parameters that will enable maintaining consistency between them and between the socially responsible activities. In terms of the individualism-collectivism dimension, for p = 0.05 the key factor in three cultural areas are the expectations towards work. Practical Implications: The use of logit models allows managers to focus the CSR implementation process on the key cultural factors. Originality/Value: The use of logit models to identify statistically significant factors depending on the dominant, three-dimensional cultural pattern, determining the level of awareness in the dimension of internal and external stakeholders and the general level of CSR awareness in micro, small and medium-sized enterprises.peer-reviewe

Patients with a Higher Number of Periodic Limb Movements Have Higher Nocturnal Blood Pressure

There is growing evidence that periodic limb movements in sleep (PLMS) may lead to increased blood pressure (BP) values during the night. The aim of this study was to assess if patients with disordered sleep and an increased number of PLMS have higher BP values at night. We analyzed 100 polysomnographic (PSG) recordings of patients with disordered sleep, with the exclusion of sleep-related breathing disorders. Patients also registered beat-to-beat blood pressure during PSG. We compared the BP of patients with an increased number of PLMS (more than 5 PLMS per hour of sleep) during the night (examined group, n = 50) to the BP of patients with a PLMS number within the normal range (up to 5 PLMS per hour of sleep) (control group, n = 50). Patients from the examined group had significantly higher values of systolic BP during the night (119.7 mmHg vs. 113.3 mmHg, p = 0.04), sleep (119.0 mmHg vs. 113.3 mmHg, p = 0.04), and wake (122.5 mmHg vs. 117.2 mmHg, p = 0.04) periods and of diastolic BP during the night (75.5 mmHg vs. 70.6 mmHg, p = 0.04) and wake (77.6 mmHg vs. 71.5 mmHg, p = 0.01) periods. Our results suggest a relationship between the number of PLMS during the night and the values of nocturnal blood pressure. It is possible that their treatment could lower nocturnal BP in patients with sleep disorders, therefore improving their vascular risk profile

Patients with a Higher Number of Periodic Limb Movements Have Higher Nocturnal Blood Pressure

There is growing evidence that periodic limb movements in sleep (PLMS) may lead to increased blood pressure (BP) values during the night. The aim of this study was to assess if patients with disordered sleep and an increased number of PLMS have higher BP values at night. We analyzed 100 polysomnographic (PSG) recordings of patients with disordered sleep, with the exclusion of sleep-related breathing disorders. Patients also registered beat-to-beat blood pressure during PSG. We compared the BP of patients with an increased number of PLMS (more than 5 PLMS per hour of sleep) during the night (examined group, n = 50) to the BP of patients with a PLMS number within the normal range (up to 5 PLMS per hour of sleep) (control group, n = 50). Patients from the examined group had significantly higher values of systolic BP during the night (119.7 mmHg vs. 113.3 mmHg, p = 0.04), sleep (119.0 mmHg vs. 113.3 mmHg, p = 0.04), and wake (122.5 mmHg vs. 117.2 mmHg, p = 0.04) periods and of diastolic BP during the night (75.5 mmHg vs. 70.6 mmHg, p = 0.04) and wake (77.6 mmHg vs. 71.5 mmHg, p = 0.01) periods. Our results suggest a relationship between the number of PLMS during the night and the values of nocturnal blood pressure. It is possible that their treatment could lower nocturnal BP in patients with sleep disorders, therefore improving their vascular risk profile.Peer reviewe

Patients with a Higher Number of Periodic Limb Movements Have Higher Nocturnal Blood Pressure

There is growing evidence that periodic limb movements in sleep (PLMS) may lead to increased blood pressure (BP) values during the night. The aim of this study was to assess if patients with disordered sleep and an increased number of PLMS have higher BP values at night. We analyzed 100 polysomnographic (PSG) recordings of patients with disordered sleep, with the exclusion of sleep-related breathing disorders. Patients also registered beat-to-beat blood pressure during PSG. We compared the BP of patients with an increased number of PLMS (more than 5 PLMS per hour of sleep) during the night (examined group, n = 50) to the BP of patients with a PLMS number within the normal range (up to 5 PLMS per hour of sleep) (control group, n = 50). Patients from the examined group had significantly higher values of systolic BP during the night (119.7 mmHg vs. 113.3 mmHg, p = 0.04), sleep (119.0 mmHg vs. 113.3 mmHg, p = 0.04), and wake (122.5 mmHg vs. 117.2 mmHg, p = 0.04) periods and of diastolic BP during the night (75.5 mmHg vs. 70.6 mmHg, p = 0.04) and wake (77.6 mmHg vs. 71.5 mmHg, p = 0.01) periods. Our results suggest a relationship between the number of PLMS during the night and the values of nocturnal blood pressure. It is possible that their treatment could lower nocturnal BP in patients with sleep disorders, therefore improving their vascular risk profile