A microprocessor based control system for an electric vehicle

The control system described in this thesis is a low cost system designed to control the speed of an electric vehicle by adjusting the speed of a compound wound DC motor. The speed control method developed in this system is a combination of battery tapping, for control of the armature voltage, and pulse width modulation for field control; both generated by a microprocessor. Using a microprocessor, the control system is readily adaptable to a variety of motor voltages and motor control techniques by modifying the internal firmware of the processor. Overcurrent protection is included to prolong battery and motor life. Regenerative braking is automatic upon release of the accelerator and has two levels for maximum energy recovery. A display of the remaining charge in the vehicle\u27s batteries has a continually powered memory to retain the information when the vehicle is parked. This display is also temperature compensated to reflect the characteristics of lead acid batteries over varying temperatures. The control system was installed in a test vehicle where it was debugged and evaluated

Low magnetic Prandtl number dynamos with helical forcing

We present direct numerical simulations of dynamo action in a forced Roberts flow. The behavior of the dynamo is followed as the mechanical Reynolds number is increased, starting from the laminar case until a turbulent regime is reached. The critical magnetic Reynolds for dynamo action is found, and in the turbulent flow it is observed to be nearly independent on the magnetic Prandtl number in the range from 0.3 to 0.1. Also the dependence of this threshold with the amount of mechanical helicity in the flow is studied. For the different regimes found, the configuration of the magnetic and velocity fields in the saturated steady state are discussed.Comment: 9 pages, 14 figure

Upper Airways Microbiota in Antibiotic-Naive Wheezing and Healthy Infants from the Tropics of Rural Ecuador

Background: Observations that the airway microbiome is disturbed in asthma may be confounded by the widespread use of antibiotics and inhaled steroids. We have therefore examined the oropharyngeal microbiome in early onset wheezinginfants from a rural area of tropical Ecuador where antibiotic usage is minimal and glucocorticoid usage is absent. Materials and Methods: We performed pyrosequencing of amplicons of the polymorphic bacterial 16S rRNA gene from oropharyngeal samples from 24 infants with non-infectious early onset wheezing and 24 healthy controls (average age 10.2 months). We analyzed microbial community structure and differences between cases and controls by QIIME software. Results: We obtained 76,627 high quality sequences classified into 182 operational taxonomic units (OTUs). Firmicutes was the most common and diverse phylum (71.22% of sequences) with Streptococcus being the most common genus (49.72%). Known pathogens were found significantly more often in cases of infantile wheeze compared to controls, exemplified by Haemophilus spp. (OR = 2.12, 95% Confidence Interval (CI) 1.82–2.47; P = 5.46610223) and Staphylococcus spp. (OR = 124.1, 95%CI 59.0–261.2; P = 1.876102241). Other OTUs were less common in cases than controls, notably Veillonella spp. (OR = 0.59, 95%CI = 0.56–0.62; P = 8.06610286). Discussion: The airway microbiota appeared to contain many more Streptococci than found in Western Europe and the USA. Comparisons between healthy and wheezing infants revealed a significant difference in several bacterial phylotypes that were not confounded by antibiotics or use of inhaled steroids. The increased prevalence of pathogens such as Haemophilus and Staphylococcus spp. in cases may contribute to wheezing illnesses in this age group

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

A numerical model of the VKS experiment

We present numerical simulations of the magnetic field generated by the flow of liquid sodium driven by two counter-rotating impellers (VKS experiment). Using a dynamo kinematic code in cylindrical geometry, it is shown that different magnetic modes can be generated depending on the flow configuration. While the time averaged axisymmetric mean flow generates an equatorial dipole, our simulations show that an axial field of either dipolar or quadrupolar symmetry can be generated by taking into account non-axisymmetric components of the flow. Moreover, we show that by breaking a symmetry of the flow, the magnetic field becomes oscillatory. This leads to reversals of the axial dipole polarity, involving a competition with the quadrupolar component.Comment: 6 pages, 5 figure

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.

Creation and evolution of magnetic helicity

Projecting a non-Abelian SU(2) vacuum gauge field - a pure gauge constructed from the group element U - onto a fixed (electromagnetic) direction in isospace gives rise to a nontrivial magnetic field, with nonvanishing magnetic helicity, which coincides with the winding number of U. Although the helicity is not conserved under Maxwell (vacuum) evolution, it retains one-half its initial value at infinite time.Comment: Clarifying remarks and references added; 12 pages, 1 figure using BoxedEPSF, REVTeX macros; submitted to Phys Rev D; email to [email protected]

Positive Feedback, Memory and the Predictability of Earthquakes

We review the "critical point" concept for large earthquakes and enlarge it in the framework of so-called "finite-time singularities". The singular behavior associated with accelerated seismic release is shown to result from a positive feedback of the seismic activity on its release rate. The most important mechanisms for such positive feedback are presented. We introduce and solve analytically a novel simple model of geometrical positive feedback in which the stress shadow cast by the last large earthquake is progressively fragmented by the increasing tectonic stress. Finally, we present a somewhat speculative figure that tends to support a mechanism based on the decay of stress shadows. This figure suggests that a large earthquake in Southern California of size similar to the 1812 great event is maturing.Comment: PostScript document of 18 pages + 2 eps figure

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

Nonlinear dynamo action in a precessing cylindrical container

It is numerically demonstrated by means of a magnetohydrodynamics (MHD) code that precession can trigger the dynamo effect in a cylindrical container. This result adds credit to the hypothesis that precession can be strong enough to be one of the sources of the dynamo action in some astrophysical bodies.Comment: 5 pages, 5 figures including subfigure