Mathematical modelling and analysis of cerebrospinal mechanics: an investigation into the parthogenesis of syringomyelia

Syringomyelia is a disease in which fluid-filled cavities, called syrinxes, form in the spinal cord causing progressive loss of sensory and motor functions. Invasive monitoring of pressure waves in the spinal subarachnoid space implicates a hydrodynamic origin. Poor treatment outcomes have led to myriad hypotheses for its pathogenesis, which unfortunately are often based on small numbers of patients due to the relative rarity of the disease. However, only recently have models begun to appear based on the principles of mechanics. One such model is the mathematically rigorous work of Carpenter and colleagues. They suggest that a pressure wave due to a cough or sneeze could form a shock-like elastic jump, which when incident at a stenosis, such as a hindbrain tonsil, would generate a transient region of high pressure within the spinal cord and lead to fluid accumulation. The salient physiological parameters of this model are reviewed from the literature and the assumptions and predictions re-evaluated from a mechanical standpoint. It is found that, while the spinal geometry does allow for elastic jumps to occur, their effects are likely to be weak and subsumed by the small amounts of damping that have been measured in the subarachnoid space. The analysis presented here does not support the elastic-jump hypothesis for syrinx formation. Furthermore, the site of maximum transpial pressure dierential due to a cough-induced pulse is most likely to be at the site of pulse origin|not, as supposed, at a distant reflection site. This suggests that there must be some other localising factor more critical to providing the necessary conditions for syrinx formation. Two coaxial tube models are developed that incorporate Darcy's law separately in the pial membrane and the spinal cord tissue. It is shown that permeability plays opposing roles in the spinal cord and pia for wave attenuation; the propagation of a pressure wave is aided by a less-permeable pia but a more-permeable spinal cord. This may have implications in a syringomyelic cord. To understand the dynamic interaction of the fluid and solid components of the spinal cord tissue Biot's theory of poroelasticity is employed. It is concluded that physiological frequencies are probably too low for poroelastic dissipation to be of signicance in such a soft and weak material as the spinal cord. Accumulating evidence in the last decade from animal studies implicates arterial pulsations in syrinx formation. In particular, Bilston and colleagues suggested that a phase difference between the pressure pulse in the spinal subarachnoid space and the perivascular spaces, due to a pathologically disturbed blood supply, could result in a net in flux of cerebrospinal fluid into the spinal cord. A lumped-parameter model is developed of the cerebrospinal system to investigate this conjecture. It is found that although this phase-lag mechanism may operate, it requires the spinal cord to have an intrinsic storage capacity due to the collapsibility of the contained venous reservoir. If this storage requirement is met then the results presented here suggest that, on mechanical grounds, a syringo-subarachnoid shunt may be a better surgical treatment option than a subarachnoid bypass for post-traumatic syringomyelia

Design of the advanced regional aircraft, the DART-75

This design analysis is intended to show the capabilities of the DART-75, a 75 passenger medium-range regional transport. Included are the detailed descriptions of the structures, performance, stability and control, weight and balance, and engine design. The design should allow for the DART to become the premier regional aircraft of the future due to some advanced features like the canard, semi-composite construction, and advanced engines

Galen, Rome and the Second Sophistic

Galen of Pergamum is principally famous for his works on anatomy, medicine and moral philosophy. He is also noted for his acerbic temperament, his affirmations of his own brilliance and his denigration of the education, morals and lifestyle of his medical opponents and of anyone who viewed differently the things that he held dear. On his arrival in Rome he used a variety of techniques reminiscent of those used by the sophists in order to establish his place amongst the social and intellectual elite both as a physician and as a philosopher. At this and later points in his career his rhetoric emphasised the quality of his Greek education which included a thorough grounding in mathematics. He also appealed to his philosophic lifestyle and to his social connections in Rome in order to differentiate himself from the general run of doctors and to promote his own agenda. In this dissertation I examine his writings with the object of testing the validity of Galen’s claims in these areas and, in the process, to come to a deeper understanding the social and intellectual environments that formed him and with which he interacted. Special attention is given to his literary and rhetorical education and his knowledge of the exact sciences.

Manually defining regions of interest when quantifying paravertebral muscles fatty infiltration from axial magnetic resonance imaging : a proposed method for the lumbar spine with anatomical cross-reference

Background: There is increasing interest in paravertebral muscle composition as a potential prognostic and diagnostic element in lumbar spine health. As a consequence, it is becoming popular to use magnetic resonance imaging (MRI) to examine muscle volume and fatty infiltration in lumbar paravertebral muscles to assess both age-related change and their clinical relevance in low back pain (LBP). A variety of imaging methods exist for both measuring key variables (fat, muscle) and for defining regions of interest, making pooled comparisons between studies difficult and rendering post-production analysis of MRIs confusing. We therefore propose and define a method as an option for use as a standardized MRI procedure for measuring lumbar paravertebral muscle composition, and to stimulate discussion towards establishing consensus for the analysis of skeletal muscle composition amongst clinician researchers. Method: In this descriptive methodological study we explain our method by providing an examination of regional lumbar morphology, followed by a detailed description of the proposed technique. Identification of paravertebral muscles and vertebral anatomy includes axial E12 sheet-plastinates from cadaveric material, combined with a series of axial MRIs that encompass sequencing commonly used for investigations of muscle quality (fat-water DIXON, T1-, and T2-weighted) to illustrate regional morphology; these images are shown for L1 and L4 levels to highlight differences in regional morphology. The method for defining regions of interest (ROI) for multifidus (MF), and erector spinae (ES) is then described. Results: Our method for defining ROIs for lumbar paravertebral muscles on axial MRIs is outlined and discussed in relation to existing literature. The method provides a foundation for standardising the quantification of muscle quality that particularly centres on examining fatty infiltration and composition. We provide recommendations relating to imaging parameters that should additionally inform a priori decisions when planning studies examining lumbar muscle tissues with MRI. Conclusions: We intend this method to provide a platform towards developing and delivering meaningful comparisons between MRI data on lumbar paravertebral muscle quality

Recent developments in male fertility evaluation, sperm cryopreservation and artificial fertilisation, and their potential application to decapod crustacean aquaculture

To maximise productivity, a better understanding of the underlying causes of subfertility that lead to inferior offspring and high mortality is imperative. In decapod crustaceans, most research has focused on female reproductive performance, with little attention given to male fertility. Paternal genetic contribution is critical to both successful embryonic and post-embryonic development. Assessment of sperm quality can be a direct method to determine male subfertility in decapods. Sperm quality parameters such as sperm concentration and morphology have traditionally been used to determine male reproductive performance, but these procedures are time-consuming and can only assess a limited number of sperm cells and males. Alternative diagnostic biomarkers used widely in humans and other mammals could be adapted to decapod crustaceans and may be more indicative of sperm fertilisation competence and male reproductive performance. These predictive biomarkers use fluorescent cellular dyes and high-throughput flow cytometry or computer-assisted sperm microscopic analysis to evaluate sperm viability, mitochondrial function, acrosome reaction and DNA fragmentation. This review examines current and advanced biomarkers to evaluate sperm quality and further explores state-of-the-art procedures of sperm cryopreservation (conventional vs. vitrification techniques) and artificial fertilisation in decapod crustaceans. Sperm freezing coupled with artificial fertilisation in decapods permits the long-term storage, controlled timing and selection of individuals for reproduction. Collectively, these tools can be applied to commercial broodstock management to improve productivity and accelerate selective breeding in the crustacean aquaculture industry

Mathematical modelling and analysis of cerebrospinal mechanics : an investigation into the parthogenesis of syringomyelia

Syringomyelia is a disease in which fluid-filled cavities, called syrinxes, form in the spinal cord causing progressive loss of sensory and motor functions. Invasive monitoring of pressure waves in the spinal subarachnoid space implicates a hydrodynamic origin. Poor treatment outcomes have led to myriad hypotheses for its pathogenesis, which unfortunately are often based on small numbers of patients due to the relative rarity of the disease. However, only recently have models begun to appear based on the principles of mechanics. One such model is the mathematically rigorous work of Carpenter and colleagues. They suggest that a pressure wave due to a cough or sneeze could form a shock-like elastic jump, which when incident at a stenosis, such as a hindbrain tonsil, would generate a transient region of high pressure within the spinal cord and lead to fluid accumulation. The salient physiological parameters of this model are reviewed from the literature and the assumptions and predictions re-evaluated from a mechanical standpoint. It is found that, while the spinal geometry does allow for elastic jumps to occur, their effects are likely to be weak and subsumed by the small amounts of damping that have been measured in the subarachnoid space. The analysis presented here does not support the elastic-jump hypothesis for syrinx formation. Furthermore, the site of maximum transpial pressure dierential due to a cough-induced pulse is most likely to be at the site of pulse origin|not, as supposed, at a distant reflection site. This suggests that there must be some other localising factor more critical to providing the necessary conditions for syrinx formation. Two coaxial tube models are developed that incorporate Darcy's law separately in the pial membrane and the spinal cord tissue. It is shown that permeability plays opposing roles in the spinal cord and pia for wave attenuation; the propagation of a pressure wave is aided by a less-permeable pia but a more-permeable spinal cord. This may have implications in a syringomyelic cord. To understand the dynamic interaction of the fluid and solid components of the spinal cord tissue Biot's theory of poroelasticity is employed. It is concluded that physiological frequencies are probably too low for poroelastic dissipation to be of signicance in such a soft and weak material as the spinal cord. Accumulating evidence in the last decade from animal studies implicates arterial pulsations in syrinx formation. In particular, Bilston and colleagues suggested that a phase difference between the pressure pulse in the spinal subarachnoid space and the perivascular spaces, due to a pathologically disturbed blood supply, could result in a net in flux of cerebrospinal fluid into the spinal cord. A lumped-parameter model is developed of the cerebrospinal system to investigate this conjecture. It is found that although this phase-lag mechanism may operate, it requires the spinal cord to have an intrinsic storage capacity due to the collapsibility of the contained venous reservoir. If this storage requirement is met then the results presented here suggest that, on mechanical grounds, a syringo-subarachnoid shunt may be a better surgical treatment option than a subarachnoid bypass for post-traumatic syringomyelia.EThOS - Electronic Theses Online ServiceUniversity of Warwick (UoW)Royal Academy of Engineering (Great Britain) (RAE)Physiological Flow Network (PFN)GBUnited Kingdo

Effect of reaction mechanism on precursor exposure time in atomic layer deposition of silicon oxide and silicon nitride

Atomic layer deposition (ALD) of highly conformal, silicon-based dielectric thin films has become necessary because of the continuing decrease in feature size in microelectronic devices. The ALD of oxides and nitrides is usually thought to be mechanistically similar, but plasma-enhanced ALD of silicon nitride is found to be problematic, while that of silicon oxide is straightforward. To find why, the ALD of silicon nitride and silicon oxide dielectric films was studied by applying ab initio methods to theoretical models for proposed surface reaction mechanisms. The thermodynamic energies for the elimination of functional groups from different silicon precursors reacting with simple model molecules were calculated using density functional theory (DFT), explaining the lower reactivity of precursors toward the deposition of silicon nitride relative to silicon oxide seen in experiments, but not explaining the trends between precursors. Using more realistic cluster models of amine and hydroxyl covered surfaces, the structures and energies were calculated of reaction pathways for chemisorption of different silicon precursors via functional group elimination, with more success. DFT calculations identified the initial physisorption step as crucial toward deposition and this step was thus used to predict the ALD reactivity of a range of amino-silane precursors, yielding good agreement with experiment. The retention of hydrogen within silicon nitride films but not in silicon oxide observed in FTIR spectra was accounted for by the theoretical calculations and helped verify the application of the model

Philosophical Foundations for Citizen Science

Citizen science is increasingly being recognized as an important approach for gathering data, addressing community needs, and creating fruitful engagement between citizens and professional scientists. Nevertheless, the implementation of citizen science projects can be hampered by a variety of barriers. Some of these are practical (e.g., lack of funding or lack of training for both professional scientists and volunteers), but others are theoretical barriers having to do with concerns about whether citizen science lives up to standards of good scientific practice. These concerns about the overall quality of citizen science are ethically significant, because it is ethically problematic to waste resources on low-quality research, and it is also problematic to denigrate or dismiss research that is of high quality. Scholarship from the philosophy of science is well-placed to address these theoretical barriers, insofar as it is fundamentally concerned about the nature of good scientific inquiry. This paper examines three important concerns: (1) the worry that citizen science is not appropriately hypothesis-driven; (2) the worry that citizen science does not generate sufficiently high-quality data or use sufficiently rigorous methods; and (3) the worry that citizen science is tainted by advocacy and is therefore not sufficiently disinterested. We show that even though some of these concerns may be relevant to specific instances of citizen science, none of these three concerns provides a compelling reason to challenge the overall quality of citizen science in principle

Thermal Sensation in Older People with and without Dementia Living in Residential Care: New Assessment Approaches to Thermal Comfort Using Infrared Thermography

The temperature of the indoor environment is important for health and wellbeing, especially at the extremes of age. The study aim was to understand the relationship between self-reported thermal sensation and extremity skin temperature in care home residents with and without dementia. The Abbreviated Mental Test (AMT) was used to discriminate residents to two categories, those with, and those without, dementia. After residents settled and further explanation of the study given (approximately 15 min), measurements included: tympanic membrane temperature, thermal sensation rating and infrared thermal mapping of non-dominant hand and forearm. Sixty-nine afebrile adults (60–101 years of age) were studied in groups of two to five, in mean ambient temperatures of 21.4–26.6 °C (median 23.6 °C). Significant differences were observed between groups; thermal sensation rating (p = 0.02), tympanic temperature (p = 0.01), fingertip skin temperature (p = 0.01) and temperature gradients; fingertip-wrist p = 0.001 and fingertip-distal forearm, p = 0.001. Residents with dementia were in significantly lower air temperatures (p = 0.001). Although equal numbers of residents per group rated the environment as ‘neutral’ (comfortable), resident ratings for ‘cool/cold’ were more frequent amongst those with dementia compared with no dementia. In parallel, extremity (hand) thermograms revealed visual temperature demarcation, variously across fingertip, wrist, and forearm commensurate with peripheral vasoconstriction. Infrared thermography provided a quantitative and qualitative method to measure and observe hand skin temperature across multiple regions of interest alongside thermal sensation self-report. As an imaging modality, infrared thermography has potential as an additional assessment technology with clinical utility to identify vulnerable residents who may be unable to communicate verbally, or reliably, their satisfaction with indoor environmental conditions

Health care system collaboration to address chronic diseases: A nationwide snapshot from state public health practitioners

INTRODUCTION: Until recently, health care systems in the United States often lacked a unified approach to prevent and manage chronic disease. Recent efforts have been made to close this gap through various calls for increased collaboration between public health and health care systems to better coordinate provision of services and programs. Currently, the extent to which the public health workforce has responded is relatively unknown. The objective of this study is to explore health care system collaboration efforts and activities among a population-based sample of state public health practitioners. METHODS: During spring 2013, a national survey was administered to state-level chronic disease public health practitioners. Respondents were asked to indicate whether or not they collaborate with health care systems. Those who reported “yes” were asked to indicate all topic areas in which they collaborate and provide qualitative examples of their collaborative work. RESULTS: A total of 759 respondents (84%) reported collaboration. Common topics of collaboration activities were tobacco, cardiovascular health, and cancer screening. More client-oriented interventions than system-wide interventions were found in the qualitative examples provided. Respondents who collaborated were also more likely to use the Community Guide, use evidence-based decision making, and work in program areas that involved secondary, rather than primary, prevention. CONCLUSION: The study findings indicate a need for greater guidance on collaboration efforts that involve system-wide and cross-system interventions. Tools such as the Community Guide and evidence-based training courses may be useful in providing such guidance