Orbits and phase transitions in the multifractal spectrum

We consider the one dimensional classical Ising model in a symmetric dichotomous random field. The problem is reduced to a random iterated function system for an effective field. The D_q-spectrum of the invariant measure of this effective field exhibits a sharp drop of all D_q with q < 0 at some critical strength of the random field. We introduce the concept of orbits which naturally group the points of the support of the invariant measure. We then show that the pointwise dimension at all points of an orbit has the same value and calculate it for a class of periodic orbits and their so-called offshoots as well as for generic orbits in the non-overlapping case. The sharp drop in the D_q-spectrum is analytically explained by a drastic change of the scaling properties of the measure near the points of a certain periodic orbit at a critical strength of the random field which is explicitly given. A similar drastic change near the points of a special family of periodic orbits explains a second, hitherto unnoticed transition in the D_q-spectrum. As it turns out, a decisive role in this mechanism is played by a specific offshoot. We furthermore give rigorous upper and/or lower bounds on all D_q in a wide parameter range. In most cases the numerically obtained D_q coincide with either the upper or the lower bound. The results in this paper are relevant for the understanding of random iterated function systems in the case of moderate overlap in which periodic orbits with weak singularity can play a decisive role.Comment: The article has been completely rewritten; the title has changed; a section about the typical pointwise dimension as well as several references and remarks about more general systems have been added; to appear in J. Phys. A; 25 pages, 11 figures, LaTeX2

Convolution of multifractals and the local magnetization in a random field Ising chain

The local magnetization in the one-dimensional random-field Ising model is essentially the sum of two effective fields with multifractal probability measure. The probability measure of the local magnetization is thus the convolution of two multifractals. In this paper we prove relations between the multifractal properties of two measures and the multifractal properties of their convolution. The pointwise dimension at the boundary of the support of the convolution is the sum of the pointwise dimensions at the boundary of the support of the convoluted measures and the generalized box dimensions of the convolution are bounded from above by the sum of the generalized box dimensions of the convoluted measures. The generalized box dimensions of the convolution of Cantor sets with weights can be calculated analytically for certain parameter ranges and illustrate effects we also encounter in the case of the measure of the local magnetization. Returning to the study of this measure we apply the general inequalities and present numerical approximations of the D_q-spectrum. For the first time we are able to obtain results on multifractal properties of a physical quantity in the one-dimensional random-field Ising model which in principle could be measured experimentally. The numerically generated probability densities for the local magnetization show impressively the gradual transition from a monomodal to a bimodal distribution for growing random field strength h.Comment: An error in figure 1 was corrected, small additions were made to the introduction and the conclusions, some typos were corrected, 24 pages, LaTeX2e, 9 figure

Adjustment with aphasia after stroke: study protocol for a pilot feasibility randomised controlled trial for SUpporting wellbeing through PEeR Befriending (SUPERB)

Background: Despite the high prevalence of mood problems after stroke, evidence on effective interventions particularly for those with aphasia is limited. There is a pressing need to systematically evaluate interventions aiming to improve wellbeing for people with stroke and aphasia. This study aims to evaluate the feasibility of a peer-befriending intervention. Methods/design: SUPERB is a single blind, parallel group feasibility trial of peer befriending for people with aphasia post-stroke and low levels of psychological distress. The trial includes a nested qualitative study and pilot economic evaluation and it compares usual care (n = 30) with usual care + peer befriending (n = 30). Feasibility outcomes include proportion screened who meet criteria, proportion who consent, rate of consent, number of missing/incomplete data on outcome measures, attrition rate at follow-up, potential value of conducting main trial using value of information analysis (economic evaluation), description of usual care, and treatment fidelity of peer befriending. Assessments and outcome measures (mood, wellbeing, communication, and social participation) for participants and significant others will be administered at baseline, with outcome measures re-administered at 4 and 10 months post-randomisation. Peer befrienders will complete outcome measures before training and after they have completed two cycles of befriending. The qualitative study will use semi-structured interviews of purposively sampled participants (n = 20) and significant others (n = 10) from both arms of the trial, and all peer befrienders to explore the acceptability of procedures and experiences of care. The pilot economic evaluation will utilise the European Quality of life measure (EQ-5D-5 L) and a stroke-adapted version of the Client Service Receipt Inventory (CSRI). Discussion: This study will provide information on feasibility outcomes and an initial indication of whether peer befriending is a suitable intervention to explore further in a definitive phase III randomised controlled trial. Trial registration: ClinicalTrials.gov identifier NCT02947776, registered 28th October 2016

Discontinued SEC Required Disclosures: the Value of Repairs and Maintenance Expenditures using a Variance Decomposition Approach

On December 13, 1994, the Securities and Exchange Commission (SEC) eliminated certain schedules that included repairs and maintenance (R&M) disclosures previously required in annual reports and registration statements filed with the SEC. The purpose of this research is to determine if market participants utilized R&M information when making investment decisions. Resulting from a variance decomposition approach, the findings indicate that market participants did use R&M disclosures in their investment decisions. Thus, as a possible policy implication of this research, the SEC may want to reconsider the decision to eliminate the required R&M expenditure disclosures

An exploration of UK speech and language therapists' treatment and management of functional communication disorders: A mixed‐methods online survey

Background Functional Communication Disorders (FCDs) are one specific presentation of Functional Neurological Disorder (FND). FND is characterised by neurological symptoms, such as sensory and motor symptoms, which are not explained by neurological disease. Speech and language therapists (SLTs) have expertise in managing communication disorders, including FCDs, though is not known is what clinicians do in practice to treat and manage FCDs. Aim To explore the clinical practices of SLTs who regularly manage FCDs in the UK, including the assessment and intervention approaches taken. Methods & Procedures An online survey was developed using Qualtrics software and piloted before dissemination. Participants were experienced SLTs working in the UK who managed at least three FCD referrals a year. The survey was developed with a mix of qualitative and quantitative questions. The survey was disseminated via social media and professional networks. Outcomes & Results There were 73 completed responses to the survey. Participants reported working with a range of FCDs clinically, with functional stuttering and articulation disorders seen most frequently. SLTs reported working with a wide range of multidisciplinary professionals when managing patients with FCDs, though lack of access to mental health professionals was raised as an issue. SLTs reported using a combination of formal and informal communication assessments. Interventions varied, with a wide range of psychological approaches informing treatment. Lack of specific training, evidence base and negative attitudes around functional neurological disorder (FND) were raised as ongoing issues. Conclusions & Implications Therapists encountered a wide range of FCDs as part of their clinical practice, though there was a significant disparity in the service and interventions offered. SLTs feel their input can be effective, but lack the resources, training and evidence‐based interventions to provide adequate care

Current practices and beliefs regarding supporting dating skills in rehabilitation for Traumatic Brain Injury: A survey study

Background: Relationships are important to quality of life after traumatic brain injury (TBI). However, there has been limited research into how to support dating skills or how professionals view this area. Method: An online 52-item survey was developed and sent to professionals in the UK involved in rehabilitation after TBI. Recruitment was through professional networks, special interest groups and social media. Results: 125 participants from a range of professions completed the survey. Many agreed that dating skills are important in rehabilitation (81.6%), but fewer (51.2%) reported engaging in this work. Psychologists, SLTs and OTs were identified as well placed to address dating skills. Case managers also appeared aware of this work. Participants reported using a range of activities to address dating skills, including managing disinhibited behavior and teaching interaction skills. Perceived barriers were both personal and professional, including lack of resources and feeling embarrassed. Conclusion: This study has highlighted an awareness of the importance of dating in brain injury, but professionals face multiple barriers to supporting dating skills. It is possible to draw on recommendations from related areas, including rehabilitation for cognitive communication difficulties and sexual dysfunction with further research to specifically link these areas to dating skills

Blinding participants and assessors in a feasibility randomised controlled trial of peer-befriending for people with aphasia post-stroke

Background and aims: In behavioural interventions, blinding participants to intervention versus control conditions is problematic, as is blinding assessors to participants’ group allocation. When participants are provided with information about the intervention to be tested, they will know whether they are in the intervention or the control arm of the study. This is particularly problematic in psychological interventions where people who may already be distressed or anxious are likely to become even more distressed when they realise they are in the control arm of a study. To minimise potential threats to validity and maintain lack of bias, we took a number of steps in the SUpporting well-being through PEeR-Befriending (SUPERB) feasibility trial for people with aphasia to ensure blinding. This presentation will report on these steps and evaluate their effectiveness. Methods: SUPERB is a single blind, mixed methods, parallel group phase II randomised controlled trial (RCT) comparing usual care+peer-befriending (n = 30) versus usual care (n = 30), starting at discharge from hospital. Little is known about what usual care for psychological support after stroke-aphasia constitutes, and this study will document the services the participants receive in their area for both groups. A modified two-stage consent design has been adopted (Campbell, Peters, Grant, Quilty, & Dieppe, 2005; Torgerson & Roland, 1998), as highlighted in the Medical Research Council framework for complex interventions (Craig et al., 2008). In the first stage, all participants consent to take part in a study on adjustment post-stroke and have their data collected at three time points (i.e., baseline, 4 months, and 10 months). They know they may be compared to other people in the study receiving different packages of care, but are blind to the fact that the study tests a specific intervention (peer-befriending). Following baseline assessments, participants are randomised to either usual care+peer-befriending or usual care. At this point, a second stage consent to take part in the intervention is completed with those participants allocated to the peer-befriending arm. Rate of consent at both stages is monitored. Blinded researchers (assessors) complete assessments for both groups at 4 months and 10 months. Strategies to maintain blinding of assessors include the following: the use of scripts during assessments and asking the participants not to reveal what care they have received; unblinded researcher organising post-randomisation appointments, so that assessors cannot become unblinded by partners/carers of people with aphasia revealing information; and management of the work environment (separate office space, different telephones, and no physical or electronic access to sensitive data). Instances of unblinding are recorded. Results: The trial is currently underway. Thirty-eight of 60 participants have been recruited and 27 have been randomised. The two-stage consent process has been largely successful. No instances of unblinding by participants or researchers have been recorded. Near misses (n = 4) have been recorded for the blinded researchers. These are unrelated to the assessments with participants but rather workplace factors (e.g., use of email, shared calendars, and overhearing telephone conversations). Conclusions: Blinding of participants and researchers is critical to the success of a RCT. This paper raises and discusses a range of processes including a modified two-stage consent process and careful preparation and monitoring of participants, researchers, and workplace factors – which are all important steps to reducing the possibility of unblinding