Dust cloud evolution in sub-stellar atmospheres via plasma deposition and plasma sputtering

Context. In contemporary sub-stellar model atmospheres, dust growth occurs through neutral gas-phase surface chemistry. Recently, there has been a growing body of theoretical and observational evidence suggesting that ionisation processes can also occur. As a result, atmospheres are populated by regions composed of plasma, gas and dust, and the consequent influence of plasma processes on dust evolution is enhanced.Aim. This paper aims to introduce a new model of dust growth and destruction in sub-stellar atmospheres via plasma deposition and plasma sputtering.Methods. Using example sub-stellar atmospheres from DRIFT-PHOENIX, we have compared plasma deposition and sputtering timescales to those from neutral gas-phase surface chemistry to ascertain their regimes of influence. We calculated the plasma sputtering yield and discuss the circumstances where plasma sputtering dominates over deposition.Results. Within the highest dust density cloud regions, plasma deposition and sputtering dominates over neutral gas-phase surface chemistry if the degree of ionisation is ≳10−4. Loosely bound grains with surface binding energies of the order of 0.1–1 eV are susceptible to destruction through plasma sputtering for feasible degrees of ionisation and electron temperatures; whereas, strong crystalline grains with binding energies of the order 10 eV are resistant to sputtering.Conclusions. The mathematical framework outlined sets the foundation for the inclusion of plasma deposition and plasma sputtering in global dust cloud formation models of sub-stellar atmospheres

Critical velocity ionisation in substellar atmospheres

The observation of radio, X-ray and Hα emission from substellar objects indicates the presence of plasma regions and associated high-energy processes in their surrounding envelopes. This paper numerically simulates and characterises Critical Velocity Ionisation, a potential ionisation process, that can efficiently generate plasma as a result of neutral gas flows interacting with seed magnetized plasmas. By coupling a Gas-MHD interactions code (to simulate the ionisation mechanism) with a substellar global circulation model (to provide the required gas flows) we quantify the spatial extent of the resulting plasma regions, their degree of ionisation and their lifetime for a typical substellar atmosphere. It is found that the typical average ionisation fraction reached at equilibrium (where the ionisation and recombination rates are equal and opposite) ranges from 10-5 to 10-8, at pressures between 10-1 and 10-3 bar, with a trend of increasing ionisation fraction with decreasing atmospheric pressure. The ionisation fractions reached as a result of Critical Velocity Ionisation are sufficient to allow magnetic fields to couple to gas flows in the atmosphere

Understanding how patients' pain beliefs influence chronic low back pain management in Ghana: a grounded theory approach.

Chronic low back pain (CLBP) is associated with negative consequences in high and low/middle-income countries. Pain beliefs are important psychosocial factors that affect the occurrence and progression of CLBP and may be influenced by the sociocultural context and interactions with healthcare professionals (HCPs). The pain beliefs of Ghanaian patients with CLBP are unknown and the factors influencing pain beliefs in African contexts are unclear. To explore the pain beliefs of Ghanaian patients with CLBP, how they influence CLBP management/coping and to identify the mechanisms influencing them. Qualitative study using individual semistructured face-to-face interviews, situated within Straussian grounded theory principles and critical realist philosophy. Thirty patients with CLBP accessing physiotherapy at two teaching hospitals in Ghana. Participants suggested dominant biomedical/mechanical beliefs (related to CLBP causes, posture and activity, and the belief of an endpoint/cure for CLBP). Maladaptive beliefs and practices, in particular fear-avoidance beliefs, and dependence on passive management and coping, were common among participants. These beliefs and practices were mostly influenced by HCPs and sociocultural expectations/norms. Although spirituality, pacing activity and prescribed exercises were commonly mentioned by participants, other active strategies and positive beliefs were expressed by a few participants and influenced by patients' themselves. Limited physiotherapy involvement, knowledge and awareness were also reported by participants, and this appeared to be influenced by the limited physiotherapy visibility in Ghana. Participants' narratives suggested the dominant influence of HCPs and the sociocultural environment on their biomedical/mechanical beliefs. These facilitated maladaptive beliefs and adoption of passive coping and management practices. Therefore, incorporation of more positive beliefs and holistic/active strategies by Ghanaian patients and HCPs may be beneficial. Furthermore, patient empowerment and health literacy opportunities to address unhelpful CLBP/sociocultural beliefs and equip patients with management options for CLBP could be beneficial. [Abstract copyright: © Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

Chronic Low Back Pain Beliefs and Management Practices in Africa: Time for a Re-think?

Background: Chronic low back pain (CLBP) beliefs are important psychosocial risk factors affecting the occurrence and progression of CLBP. To address pain beliefs and implement recommended biopsychosocial approaches for CLBP management, an understanding of the beliefs of patients and healthcare professionals (HCPs), and also CLBP management practices, is necessary. A narrative review was conducted to explore CLBP beliefs and practices in African countries. Methods: Two systematic searches were conducted using seven databases (MEDLINE, Embase, PsychInfo, CINAHL Plus, AMED, PubMed and Web of Science) with combined variations of the terms “Management”, “Guidelines”, “Chronic Low Back Pain”, “Beliefs”, “Patients”, “Healthcare Professionals” and “Africa”. Results: Five studies and one standard treatment guideline document were included. No systematically developed African CLBP treatment guideline was found, although CLBP practices were identified in two African countries. CLBP management in African countries appears to be biomedically orientated. Only three research articles investigated the CLBP beliefs of patients in Africa, with none assessing HCP beliefs. Unhelpful CLBP beliefs (catastrophizing and fear avoidance) and biomedical thoughts about the causes of CLBP were identified. Unhelpful CLBP beliefs were associated with increased disability. Conclusions: Management practices for CLBP in African countries appear to contradict recommended biopsychosocial management guidelines by developed countries and are not sufficiently documented. Research on CLBP beliefs and CLBP management practices in Africa is lacking. To enhance the uptake of biopsychosocial approach in Africa, research around CLBP beliefs in African CLBP patients and HCPs is required

Evolution of spheroidal dust in electrically-active sub-stellar atmospheres

Context. Understanding the source of sub-stellar polarimetric observations in the optical and near-infrared is key to characterising sub-stellar objects and developing potential diagnostics for determining properties of their atmosphere. Differential scattering from a population of aligned, non-spherical dust grains is a potential source of polarization that could be used to determine geometric properties of the dust clouds.Aims. This paper addresses the problem of spheroidal growth of dust grains in electrically-activated sub-stellar atmospheres. It presents the novel application of a mechanism whereby non-spherical, elongated dust grains can be grown via plasma deposition as a consequence of the surface electric field effects of charged dust grains.Methods. We numerically solve the differential equations governing the spheroidal growth of charged dust grains via plasma deposition as a result of surface electric field effects in order to determine how the dust eccentricity and the dust particle eccentricity distribution function evolve with time. From these results we determine the effect of spheroidal dust on the observed linear polarization.Results. Numerical solutions show that e ≈ 0.94 defines a watershed eccentricity, where the eccentricity of grains with an initial eccentricity less than (greater than) this value decreases (increases) and spherical (spheroidal) growth occurs. This produces a characteristic bimodal eccentricity distribution function yielding a fractional change in the observed linear polarization of up to ≈ 0.1 corresponding to dust grains of maximal eccentricity at wavelengths of ≈ 1µm, consistent with the near infrared observational window. Order of magnitude calculations indicate that a population of aligned, spheroidal dust grains can produce degrees of polarization P ≈ O(10−2 − 1%) consistent with observed polarization signatures.Conclusions. The results presented here are relevant to the growth of non-spherical, irregularly-shaped dust grains of general geometry where non-uniform surface electric field effects of charged dust grains are significant. The model described in this paper may also be applicable to polarization from galactic dust and dust growth in magnetically confined plasmas

A Qualitative Investigation of the Psychosocial Impact of Chronic Low Back Pain in Ghana

Introduction: Chronic low back pain (CLBP) is a global health concern associated with multidimensional/biopsychosocial levels of affectation in developed countries, with holistic management requiring consideration of these factors. There has been minimal research exploring the psychosocial impact of CLBP, and the factors influencing it, in African contexts, with none in Ghana. Objectives: To explore the psychosocial impact of CLBP among patients with CLBP in Ghana. Design: Qualitative study using individual semistructured face-to-face interviews, underpinned by Straussian grounded theory principles and critical realist philosophy. Participants: Thirty patients with CLBP attending physiotherapy at two hospitals in Ghana. Results: Five categories: loss of self and roles, emotional distress, fear, stigmatisation and marginalisation, financial burden, and social support and three mechanisms: acquired biomedical/mechanical beliefs from healthcare professionals (HCPs), sociocultural beliefs and the socioeconomic impact of CLBP were derived. Conclusion: CLBP adversely affects multidimensional/biopsychosocial aspects of individuals experiencing CLBP in Ghana. This delineates the need for a biopsychosocial approach to care. There is the need for HCPs in Ghana to reassess current CLBP management strategies to address the influence of adverse HCPs biomedical inclinations on patients’ psychosocial consequences. Population-based education strategies and consideration of formal support systems for persons with disabling CLBP may also be beneficial

The evolution of electron overdensities in magnetic fields

When a neutral gas impinges on a stationary magnetized plasma an enhancement in the ionization rate occurs when the neutrals exceed a threshold velocity. This is commonly known as the critical ionization velocity effect. This process has two distinct timescales: an ion–neutral collision time and electron acceleration time. We investigate the energization of an ensemble of electrons by their self-electric field in an applied magnetic field. The evolution of the electrons is simulated under different magnetic field and density conditions. It is found that electrons can be accelerated to speeds capable of electron impact ionization for certain conditions. In the magnetically dominated case the energy distribution of the excited electrons shows that typically 1% of the electron population can exceed the initial electrostatic potential associated with the unbalanced ensemble of electrons

A Qualitative Investigation of the Psychosocial Impact of Chronic Low Back Pain in Ghana

Data availability statement: No data are available. No additional data available.Supplemental material is available online at https://bmjopen.bmj.com/content/bmjopen/13/7/e073538.full.pdf?with-ds=yes .Copyright © Author(s) (or their employer(s)) 2023. Introduction Chronic low back pain (CLBP) is a global health concern associated with multidimensional/biopsychosocial levels of affectation in developed countries, with holistic management requiring consideration of these factors. There has been minimal research exploring the psychosocial impact of CLBP, and the factors influencing it, in African contexts, with none in Ghana. Objectives To explore the psychosocial impact of CLBP among patients with CLBP in Ghana. Design Qualitative study using individual semistructured face-to-face interviews, underpinned by Straussian grounded theory principles and critical realist philosophy. Participants Thirty patients with CLBP attending physiotherapy at two hospitals in Ghana. Results Five categories: loss of self and roles, emotional distress, fear, stigmatisation and marginalisation, financial burden, and social support and three mechanisms: acquired biomedical/mechanical beliefs from healthcare professionals (HCPs), sociocultural beliefs and the socioeconomic impact of CLBP were derived. Conclusion CLBP adversely affects multidimensional/biopsychosocial aspects of individuals experiencing CLBP in Ghana. This delineates the need for a biopsychosocial approach to care. There is the need for HCPs in Ghana to reassess current CLBP management strategies to address the influence of adverse HCPs biomedical inclinations on patients' psychosocial consequences. Population-based education strategies and consideration of formal support systems for persons with disabling CLBP may also be beneficial.London South Bank Universit

Magnetized electron-positron plasmas

Electrostatic oscillations in cold electron-positron plasmas can be coupled to a propagating electromagnetic mode if the background magnetic field is inhomogeneous. Previous work considered this coupling in the quasi-linear regime, successfully simulating the electromagnetic mode. Here we present a stability analysis of the non-linear problem, perturbed from dynamical equilibrium, in order to gain some insight into the modes present in the system.Comment: Proceedings of the 363. WE-Heraeus Seminar on: Neutron Stars and Pulsars (Posters and contributed talks) Physikzentrum Bad Honnef, Germany, May.14-19, 2006, eds. W.Becker, H.H.Huang, MPE Report 291, pp.145-14